Causes of Building Failures

Causes of Building Failures Building failure can be some part of building cracking occur, more seriously will bring building collapse. Building collapse will carry the risk of human injure or deaths. For example, buildings and structures all around start falling. This causes many people to get hurt, many of them fatally, because of the impact of falling material. Or, in high rise buildings, people themselves might fall from higher floor, thus, getting hurt, due to the impact of fall. Buildings with glass-facades are especially dangerous, as, glass being brittle would tend to crack with smallest deformation of the frame. And, worse, glass being very heavy has a very high impact on hitting somebody. And then, glass shards have a tendency to go inside the skin and cause damage to internal organs (Sanjay Churiwala and Naveen Gabrani n.d.). In addition, building collapse results in property damage and functionality inadequate. It also needs to spent time on clean-up, repair, cost losses and so on to get the facility up and running again. Building that causes fail may due to numerous of reasons that may not be easy predict before or during the construction. The analysis shows the general causes of building tend to failure that include unwise land-use and defective in designs which are arise at pre-construction phase and those construction and operational error which arise at during construction phase. Errors appear from pre-construction and during construction phase has the greatest potential influence on a projects final outcome. Building failure may occur due to three parties involved Consultant, Contractor and Developer/ Owner. The Consultants and Contractors had given insufficient of control and supervision of site operation and the quality control. More that, owner also is the one who are required to give cooperate and any assistance with Consultants and Contractors to completed the construction project. According to Mohammed Azad Hossain (2009), such errors ultimately lead to a situation, which may involve such failures, which are related to excavation and equipment, inappropriate sequencing, not enough temporary support; unnecessary structure weight; untimely taking away of shoring or formwork; and non-conformance to design objectives. Problem Statement and Research Question Failures have been found in various types of the buildings. Failure in buildings built any time the last 25 years, some as recently as the last couple of year (Steve 2008). A total of 225 building failure in Unites States and the result show that the building failure of low rise building constitutes about 63% of all cases, followed by multi-storey building as a distant second and this has been established by Kumalasari Wardhana and Fabian C.Hadipriono (2003). Building tend fail are depending on materials, designs, environmental conditions, method of construction and which the building is put of the use to, etc. Sultan Mizan Zainal Abidin Stadium is a new multi- purpose stadium in Kuala Terengganu, Malaysia which was constructed by South Korean construction firm. On July 3, 2009, a major part of the roof construction collapsed. The major cause such stadium collapsed has been identified are failure by design and materials used, rush development and under-supervised. Aims and Objectives The aim in this dissertation is to study and analyse the building failure and to find out the factor that causing building failure by three parties involved in construction industries. The objectives are: To study the factor that caused building failure by Contractor. To undertake the factor that caused building failure by Consultant; and To determine the factor that caused building failure by Developer/ Owner. Scope of Study The scope of study emphasizes on the building failure and factors that causing by three parties involved in Construction industries which are Consultant, Contractor and Developer/ Owner. Research Methodology Research Methodology is the way in which the research objectives can be questioned. There are two types of research strategies, which are quantitative and qualitative research. Quantitative research is highlight in the collection and analysis of data. This research based on testing of theories and to look for whether the theories are true. For the qualitative research, it approaches seek to gain insights and understand peoples awareness. The understandings, opinions, views, etc. of people are investigate which collect from survey questionnaires and document review. Primary Data Source Survey Questionnaires In this proposal, Survey Questionnaires will be used to collect all the opinions, views, etc. This method is the more accurate since as the first hand information collected from original research. The survey questionnaire form will be distributed form to 50 people who are random citizens and the purpose to investigate the major factor of building failure causing by three parties involved in construction industries. The survey questionnaire form will be set out in closed-ended question format for respondent to select the answer. That mean the closed-ended is the limit respondents answers to the survey, such as choosing either yes/no, true/false, or multiple choices. More that, the recommendation to reduce such failure in construction industries are also be conducted by survey questionnaire. Secondary Data Source The research undertakes a review of all literature which known as secondary research method that is selection of available related documents on the topic, which contain information, ideas, data and evidence written from a particular standpoint to fulfil certain aim or express certain views on the nature of the topic (Chris 2003, p.1-2). In this proposal, the information sources and obtains can be from reference book which are from Library College and National Library. Beside, information also can be obtained from article and journal that were related to cause failure of the building. Electronic sources such as internet website from Google can helped to found the information which required in this research, and etc. Dissertation Contents For this study dissertation report involved 5 chapters. The general description of each chapter as follow: Chapter 1 Introduction The first chapter is the introduction of the dissertation. The contents in this chapter include Project title, background of the research problem, problem statement and research question, aim and objectives, scope of study, research methodology of the study and dissertation contents. Chapter 2 Literature Review In this chapter two is the literature review. It will review on the selection criteria of building failure which in discussed for failure of building, factor that causes of failure by primary parties involved in construction industry. Chapter 3 Research Methodology Chapter three is includes the research methodologies and to provide the rationale for the method adopted in this dissertation project. Then methods used to research are literature review on journal, reference book, etc., survey questionnaire, and case study. Chapter 4 Research Findings Chapter four is the discussion and result analysis. The data collected and interpret from research method adopted, identify and analysis it, then present and explain the findings. The data present will in a table, chart, diagram, and essay form. Chapter 5 Conclusions and Recommendations The last chapter will be the conclusions and recommendations. The achievement of research objectives, recommendations and limitation of the research will be record in this chapter. References Tunku Abdul Rahman (TAR) College Harvard Referencing system will be using in the research. This Harvard Referencing system is a standard practice at all institution of higher learning including Tunku Abdul Rahman (TAR) College. Project Plan and Schedule The table below is the Project Plan and Schedule of the research proposal project. CHAPTER 2: LITERATURE REVIEW Basic of Building Failure in Construction Industries Definition of Building Failure Building Failure is refers to the member within structure or component or structure itself which are loss of load carrying capacity. More on the time initiated of building failure is when material stressed to its strength limit and fails to withstand the stresses imposed upon it. The failure will expose itself by crack or breaking, occur permanently deformed, becoming bending and more seriously may collapse (Wikipedia 2012). Calvert (2002) notes the buildings, like all structures, are designed to support certain loads without deforming excessively. The loads are the weights of people and objects, the weight of rain and snow and the pressure of wind and load of the building itself. With buildings of a few floors, strength generally accompanies sufficient rigidity, and the design is mainly that of a roof that will keep the weather out while spanning large open spaces. With tall buildings of many floors, the roof is a minor matter, and the support of the weight of the building itself is the main consideration. Like long bridges, tall buildings are subject to catastrophic collapse. The loads can divide into two parts which called live loads and dead load. Live loads are the weight of temporarily attached to; it can produce by like people, machinery and equipment, furniture, appliances, etc. of the building or other structure. But do not including the material that utilized in construction or environmental loads or anything permanently attached to it such as wind load, snow load, rain load, earthquake load, flood load, or dead load (N.A.N.d.). The case effects of machinery, equipment, furniture, appliances concentration, deflections or cracks must be considered and to determine the necessary proper intensity of design to considering those effects. Dead load is a fix load in a structure such as a bridge, building, or machine that is the weight from members itself, the supported structure itself, and permanent attachments equipment or accessories that apply in the building (Merriam-Webster, Incorporated 2012). The item that considered of dead load include construction material that use to build or make up the building such as beams, columns, floor systems, ceiling systems, wall systems, doors, windows, floor coverings, wall coverings, cabinets, and the like. Besides, the item considered of permanently attached equipment or accessories such as heating and ventilating systems, electrical trays, piping, etc. In the other way round that the item is not considered to dead load are the things as movable. That item like shelving, desks, chairs, beds, chests, books, copiers, stored items, or anything else that can be moved around during the life of the structure. The feature of dead load shows that they are the weight of final structure . This is creates a bit difficult for the design Engineer since in order to design the building, the Engineer must need to know the weight of the structure. Besides, the engineer also needs the accurately define the weights of the final structure. At the beginning of design process, the weight of the structural element and the framing are all unknown. So more of time to solution this kind of difficult position is the design Engineer often involves iteration where an educated guess is needed as to where design will finish, the dead loads is based on estimate, select the structure members that based on the estimated loads, dead loads is need to recomputed, then continue the cycle until all the member sizes do not change (T. Bartlett Quimby 2007). The aim of the structures are designed is to achieved the requested function of creation, ensuring the structures could be applied all of the loads, and sufficient safety of structures is obtain. In the properly designed system, it will prevent a local failure cause immediate and gradual failure of the complete building. The ultimate failure strength of a material or structural element is taken carefully consideration in the structural engineering and structural design to prevent failure (Finn 2009). As Aggeliki (2009) notes in his articles, if that are unexpected loads are applied, one of the factor of safety is needed to link into the design analysis to prevent building failure. Nowadays, building codes have improved and expressively to reduce the structural collapses, but it still cannot essential completely prevent the structural failures. Even though the structural failure is become less, but the results still are disastrous. Until now the engineers are still insistently searchi ng the method to reduce structural failures by introduce to proper building standards and other safety requirements. Lastly, reducing of human error, carrying out proper hazard identification, and using suitable maintenance procedures for the structures is the chance can be minimized of structural failure (Suvo 2009). Type of Building Failure The term of defect is defined as the premature failure of structure and the results cause from improper or substandard engineering, manufacture, design, application and installation. In another way, the term failure can described as the system breakdown or unable to function at all, breakdown in the operation, quality, or appearance of structure, component or material. Therefore those are different meaning in term of defect with the term failure. So, the following table show some of that various type of building failure (James and Ransom 2007, p.8): Failure Type Example Aesthetic failure Concrete or render cause crazing or shrinkage cracking. Flaking and peeling of paintwork. Staining and soiling of the finishes. Functional failure Caused sagging of the floors. Leaks in elements such as roofs, walls and floors Failure of materials Chemical attack of rendering or concrete, mortar or brick. Fungal are attack of the timber. Metals are corrosion. System failure of components and elements Carbonation of concrete. Leading to corrosion of reinforcement and subsequent cracking and spalling of concrete members. Structural failure Subsidence which caused downward movement of a building and caused by below ground factors such as desiccation of clay soil. Settlement which also caused downward movement and caused by overloading. Non- structural failure Cracking and deboning of plaster. Tenting, deboning and bubbling of floor coverings. Roof tiles and slates are delamination. Reversible failure Jamming of door and windows since of moisture intake by these components. Usually in winter or summer, the wood will be dry out and door and window will become unstuck. Irreversible failure Chemical reaction (sulphate attack) on mortar or rendering. Excessive distortion in beam, column or wall owing to structural movement. Primary Parties Involved in Construction Industries Definition Lawrence (2003, p.1-2) indicated that, The management of construction is an enterprise that involves many people with diverse interests, talents and backgrounds. The owner, the design professional and the contractor comprise the primary triad of parties, but others, such as subcontractors, material suppliers, and bankers, insurance and bonding companies, attorneys and public agency officials, are vital elements of the project team whose interrelated roles must be coordinated to assure a successful project. In this part will concern the duties and responsibilities of the primary parties such as the building contractor, consultants, and Developer/ Owner on the construction project. The primary focus here is on the building contractor who are to carries the lead duties and responsibility for the on-site installation work or sometimes off- site as well and all of the associated planning and follows up. At the same time, also to understand the duties and responsibility for other people an d organisations participate to success the project. Definition of Building Contractor According to Exforsys Inc. (2010), In the Construction industries, the contractor also can calls as the project engineer or project manager. The contractor is the one an individual who engages in the planning, developing and coordinating of activities in the construction project. The contractor also is the one to supervise the construction and to ensure all necessary measures must be taken in the result of completed finished product. More important is notwithstanding that possible delays due to bad weather or building causes any emergencies, contractor needs to sure that construction work finish are met the deadlines and try do the best of prevent causing any delay. The General contractor is employed by the developer/owner, and may also advice of the Architect to the developer/owner. Contractor must first assess the project-specific documents (referred to as tender documents). In during of the construction stage, contractor required to visit the site since it will help to get a better understanding of the project. He may handle the work on residential dwellings, commercial buildings or infrastructure, such as roads, bridges or schools. As the contractor, working hours are more the time is irregular, since any sudden problems that may arise at the construction site and constructor must be available at all times to resolve that problem. Besides, the contractor may need to calculate the price, as also called an estimate. Contractor required providing the approximate price with considers the cost of materials and equipment as well as the cost of labour to the owner for the project. The General Contractors Duties and Responsibilities That is many duties and Responsibilities that building contractor must be fully complete on day to day in order to ensure the construction project is completed smoothly and in a timely and correct manner. More about that, building contractor also need to ensure the project complete by price specified in the contract. Building contractor to construct the construction project must be according to the designers plans and specifications. Firstly, the duty of the building contractor is require implementing a plan and direct in which to carry out all the aspects of construction project. This is from hiring the workers to developing the contraction project and follow the step-by-step timeline that the project from start until end. In addition to implementing the construction plan, the building contractor is responsible for hiring, supervising, firing employees who are under the specific construction project with the contractor. For example, building contractor including design and worker selection or appoint as to hires specialized subcontractors to perform all or portions of the construction work, managing personnel on site, providing site surveying and engineering on site, etc. As a supervisor on construction project to supervising the employees, the building contractor must be regard to the workers and also take care of payslip. Ensure engage in hire someone to do work for the contractor. Obtaining the materials for the project also is the one of responsible for the building contractor. For instance, Contractor is the one to providing all of the labour, material, equipment (such as engineering vehicles and tools) and services necessary in the construction project. Since construction projects must be up to the contractor to acquire goods to build the structures, if not, cannot complete without the necessary building materials. Another duty of the building contractor is to applying for building permits from relevant department (local authorities). At before want start to construct the building, it must be acquire all necessary licenses and permits from relevant entities so that the building project just can begin. Since there are many regulation that the building contractor must be follow which relate to these documents which each building in order to engage in construction. The building contractor must complete the project which agrees with all laws, rules and regulations. The building contractor need to research about relevant regulations and laws that are related to the construction process. There are many laws such as different state have their different own law. Those laws will state that when, where and how a building contractor and his crew should build in certain areas. So, the building contractor must be recognized and followed in order to complete the project in a law-abiding manner. Another specific duty of the building contractor is budget issues. The building contractor may require planning all aspects of a construction project which including establish a budget for the construction project. That budget must be follow by the building contractor as closely as possible. For the example that budget will allow the building contractor to gain supplies, hire workers and finish the construction in a cost-efficient manner. That must be taken in serious matter which building contractor to following budgets and his/her should be care with or to ensure that the project will be completed as what was aspiration in the beginning of plan. From the beginning to end of the construction process, reviewing the progress and implementing any changes along the way also is another item which relate to the responsible of a building contractor. The building contractor needs to follow closely of the specific building project and necessary to make any changes when he/she deems fit to do so (Exforsys Inc. 2010). Lastly, the working hours of building contractor are irregular. Those emergencies and surprises may arise which relate to the project and it may occur on-site and sometimes off-site as well. So, as the building contractor must be assistance with an emergency issue available at all times and to resolve that problem. On the Wikipedia (2012) provided that, In the during construction phase, the building contractor is also responsible for providing temporary utilities on site like equipment, tool, formwork and etc., securing the property, control the quality assurance, managing personnel on site, providing site surveying and engineering on site, disposing of or recycling construction waste, monitoring master program (schedules) and cash flows, maintaining accurate records and etc. Besides, he/she should day-to-day go to the site and specialize and oversee of a construction site or the progress of a particular building task, such as plumbing, heating or electrical wiring. He or She also require to management of the vendors and trades. The building contractor should be done to prevent any oblation either the safety of the workers or the quality of the work. The contractor is has fully responsibility to complete and the purpose to achieving the quality level and for safety that required in the documents. The building contractor may also be involved in the training of the owners personnel in the operation of the building systems and may be provide some maintenance after construction is complete. It is important that the contractors has an obligation to get satisfy the minimum requirements of the drawings and specifications from the Architect. In the bidding process, the owner will asks for the lowest possible price to perform and that only those things are absolutely required by the drawings and specifications. Thus, the contractor is need obligated to satisfy those minimum requirements and no more. Of course, the owner is always free to require additional performance by change order. In the design / bid / build method, the owner only contract with the contractor. In the case, the contractor has no any contract with the designer. Then the contractors is required responsibility to comply any requirements of the contract with the owner. All efforts by contractor are essential to prevent the structural failure as it causes dangers to human life and property. There are the numerous of causes for a structural failure, and there is a requirement for a proper analysis of all the factors before construction (N.A, N.D). Definition of Consultants Who are the consultants? The consultants can be the design consultants, cost and contract consultants, land surveyors, etc. The design consultants usually comprises of the architect, civil and structural engineers, mechanical and electrical engineers and other specialist designers, such as interior designers, landscape architects, lighting specialists, town planners, etc. Design consultants as a designer of the project in the area he/ she is specialized in. They also as a facilitator of clients need and project brief. Besides, they as an advisor to the client on matters are relating to design and on statutory requirements and by- laws relating to the project. The cost and contract consultant can be the quantity surveyors. The quantity surveyors usually act as the cost and contract consultant for a project. The General Consultants Duties and Responsibilities In the following are shows the duties and the responsibilities of both which are design consultants and cost and contract consultant. Design Consultants Carrying out design works in their areas of specialization. Ensuring design works are properly coordinated with fellow consultants. Ensuring design complies with the requirements of the authorities, and with the by- laws. Choosing appropriate systems and materials, and making sure design for the elements of the works is kept within the cost plan. Notifying and advising the client on any necessary design changes due to unforeseen circumstances. Ensuring that design works are carried out within the time frame as set out in the programme. Conducting field observations to ensure that the contractor carries out the works as per the specifications and design. Contract documents include a budget, specifications, any general and special conditions prepared by a design professional such as an architect. Cost and Contract Consultant Responsible for study of the economics and financial implication of a construction project. Preliminary cost preparation and estimating. Cost plan preparation and cost studies. Contract documentation and administration preparation. Evaluation of contractors tenders. Cash flow forecast and post contract coat monitoring. Valuation of Variations. Preparation of periodic cost report for the client. Evaluation and settlement of contractors claim. Settlement of contractual disputes. Definition of Developer/Owner The developer/owner is the party who wishes to have a project constructed and pays for it. The developer/owner can be an individual, a business enterprise or an organization, and it can be both private and public. Developer/Owner is the key master to the construction production process. In addition, when initiate a construction project, developer/owner have a right to selecting project timing, priorities, cost limits, specific requirement, and determine the contractual methods. There are two type of developer/owner which are well informed and know nothing. Developer/Owner who are well informed mean know what they want and take decisive steps to achieve it. Another are know nothing mean the developer/owner need guidance to formulate their wishes and match them to the available budget. The General Developer/Owner Duties and Responsibilities Basically the duties and responsibilities of the developer/owner in a project can be under the following: Providing the clients brief and clarity of brief. Financing the project, i.e. they pay for the project. Ensure safety, health and environment aspects of the project are complied with in accordance with the legislation as laid down by DOSH and the Department of Environment. Make sure smooth incorporation and prevent disruption takes place. Avoidance of interruption to professional advisors job. Building Failure Caused by Primary Parties General Adel Abdulaziz Al Barrak (1993) postulates that, the construction business is the much higher level of competitors than any other business. As the result showing that, construction business has very high risks could lead to failure are exposed than any other business. Therefore, to determine cases of failure should be studied and such cases should be avoided in order to reduce that number of failure. The construction business need to more attention to treat the weak point. In the section will study the various building failure that cases by primary Parties involved in construction industries. There are three parties involved, namely, developer/ owner, consultant, and contractor. The relationship between these parties is adversarial since different parties has different goals they want to meet and each party goals that will has arisen conflict with the other parties goals. For the instances, the developer/ owner want the project be low cost to expend and result in good quality. But t his will reduce the profit that contractor gain. Besides, as the consultant, he/she wants the project is much more attractive and safe. In this circumstance, it may cause both the contractor and the developer/ owner spend more money or extra cost on the project. Except on this relation among parties, which still have more any other reason could be a major source of building failure. Building Failure Caused by Contractor More commonly factor that strong influence in the contractors failures in the project or building are lack of experience, poor labour productivity, bad management decisions, lack clearly assigning the responsibility and authority, recruiting multinationals, neglect, frauds, lack of control or supervision system, and lack of communication system. Lack of Experience That is important the building contractor must have the experience in the construction project. Contractor is the person who is daily to manage the activities process on the construction site. Besides, the building contractor also as field supervision to supervising all hiring worker on site. If the building contractor does not have experience, he may not to solve any problem arise from construction site. Dr. Sadi Assaf (2004) indicated that, the owner should try to employer a higher degree qualified working team in the company because that may able to maximize the usage of the companys resources and avoid any waste resources occur. The working team employer by owner mean should have good experience in the same line of work. As the more experienced building contractor in the project should be able to demonstrating knowledge of, propose a wide array of options, and have the experience with a variety of products, materials and techniques. Little or no experience of the building contractor is the most common cause the project or building failure. That is very difficult if the contractor resign at the halfway through the project, since the new contractor employ by the owner need to take over the work that where ex-contractor left off. For instance, the second contractor may not familiar to use the materials or techniques that first contractor have used. In addition, the second contractor may not at the same way that first contractor wishes to did, unless there are very specific drawings are provided (McCaleb Construction Inc, 2012). Poor Labour Productivity Poor labour productivity also mean as poor workmanship in construction industries. Poor workmanship is the actual that cause of construction either in defect or failure

Angry men analysis

In the beginning of the movie, Jury number 1 seems to be an â€Å"emergent leader† (An emergent leader gradually achieves leadership by interacting with group members and contributing to the achievement of the group's goal, page 113). From the start he has started folding papers for voting, and the other Jurors seem to follow him. When he said we would like to get started, they all gather on the table. The type of leadership he is showing is â€Å"democratic† (a democratic leader promotes the interests of group members and practices social equality, page 117).He asks for input from the other Jurors on how they should do the discussion. Pretty much he is the one controlling the flow of the discussion. He is also an â€Å"initiator† (Proposes ideas and suggestions; provides direction for the group; gets the group started, page 58). When the group Just came back from break he said, â€Å"Now let's get started. Who wants to start it off? † However, during the movie Henry Found seems to starting to take over gradually by leading the group of â€Å"not guilty'. He looks more like the emergent leader towards the end of the movie.During the discussion, some of the Jurors are acting as â€Å"deserter† (Withdraws from the group; appears â€Å"above it all† and bored or annoyed with the discussion; remains aloof or stops contributing, page 61) by playing games, left the room, even the group leader Our no. L) was about to desert the group because he feels that the group thinks that his way of doing things is not right. The juror that wants to leave the discussion because he wants to watch a game almost â€Å"deserts† the discussion by changing his vote to â€Å"not guilty' so that the discussion would end earlier.Toward the middle of the discussion, one of the Jurors was taking totes and trying to build up a solid fact from the discussion while the other Jurors are talking. He was doing an â€Å"analytical listening†, which focuses on evaluating and forming appropriate opinions about a message. It requires critical thinking and analysis (page 193). The climate changes moderately throughout the film. It starts off with a good climate, then it gets tighter when the Jurors start arguing until even some of them feels that the other is being insensible. Nonverbal communications† (message components other than words that generate meaning, page 163) that were shown in the discussion are for example, Jurors playing games hill the others are talking, throwing papers, etc. As for verbal communication (focuses on how you use words and language, page 163), there are changes in vocal tone by the Jurors that were aggravated by some other Jurors that changed their mind to â€Å"not guilty'. The Conflict starting at the beginning of the movie when the jurors were trying to answer the question, â€Å"Is the suspect guilty? † .Henry Found decided to go against the other 11 Jurors by voting â€Å" not guilty' for the suspect. This raised a â€Å"substantive conflict† (Occurs when a member disagrees about issues, ideas, decisions, actions or goals†, page 211). The group does not like that decision, so the goal cannot be reached. Henry Found was very strong in his vote, so then emerged â€Å"hidden agenda† (A hidden agenda occurs when a member's private goal conflicts with the group's goals, page 38) from the group to try to convince Henry to change his vote because some of them want to go home, and the other thinks that it is too obvious and sticks to their decisions.Henrys conflict style is â€Å"compromise conflict style† (a middle ground approach that involves conceding some goals in order to achieve others, page 218), this works well because if you use compromise conflict Tyler, you are not saying that the other person is wrong, but saying that he has a point, but there is more to it. In the movie when somebody says â€Å"the kid ran away becaus e he is afraid to get caught†, he would reply with â€Å"let's say the kid really ran away †¦ Then he would say his reasoning. In the middle of the movie, there was a â€Å"procedural conflict† (disagreement among group members about the method or process the group uses in its attempt to accomplish a goal, page 212). When a Juror suggested for another vote, one other Juror wanted an open ballot instead of a vote. Toward the middle of the discussion, there are basically two groups that were formed in there, which are the â€Å"guilty' group and the â€Å"not guilty' group.The â€Å"not guilty' group reached â€Å"performing stage†, where all members are fully engaged and eager to work (page 32). They all work together to try to put all the evidence together to see exactly if the testimonies from witnesses are true. Juror no. 3 (the one that said â€Å"not guilty' the last) is very â€Å"aggressive† (acts in their own self-interest at the expense o f others. They are critical, insensitive, combative, and even abusive, page 68). He hoots most of the time, and even gets angry to some of the other Jurors.His conflict style looks like a â€Å"competition conflict style† (group member are more concerned with their own goals than the group†, page 217), because I feel like his pride is a bit in the way of him choosing â€Å"not guilty'. The Juror that has a cold in the beginning of the movie is has â€Å"prejudice† (negative attitudes about other people that are based on faulty and inflexible stereotypes. Prejudices about an individual or culture group often arise when we have little or no direct experience with that person, page 81) award people who grew in slums.He said that he knows everything about those who grows in slums, that they are aggressive, and does not even speak good English. He mentioned those even without knowing the person he is talking about. During the discussion, some of the members wanted vo tes to see how they are doing so far. This expresses a â€Å"sense of progress†. It is difficult for members to stay motivated throughout the life of the group when they have no idea whether the group is making progress toward its goal (page 147). One of the Jurors even asked for an open ballot to see who is still voting for â€Å"not guilty'.

Apush Ap Test Release Essay Topics Guide

Apush Ap Test Release Essay Topics Guide As you pay for homework, we provide those options free of charge. It took us some opportunity to discover the proper answer to Release. There are lots of score calculators out there, therefore it can be challenging to understand which ones to trust. The absolute most important thing to keep in mind about any APUSH score calculator is that it's an estimate. This opens up lots of possibilities for you! The notion is extremely simple behind it. Consider the brief answer as a chance for you to do more of the historical thinking work which you have prepared to do. I have to admit this clue isn't so simple. The New Fuss About Apush Ap Test Release Essay Topics Score calculators are an excellent way to motivate you whenever you're studying for your AP exams. One of the best ways to think about the average AP US History it is to consider a multi-year trend. Well, if you receive a perfect score you will certainly get a 5 on the exam. You cannot pass this kind of exam in general without preparation and thorough knowledge in the area of the U.S. History. Practice questions that mimic the actual exam are a significant part being prepared for test day. This document comprises a lot of DBQs from previous versions of the AP test. It should take a minumum of one year to get ready for this exam. The more compact S cassettes utilize the exact form factor as Betamax. An APUSH calculator can provide you a great idea of where you will likely score on the exam. There's additionally a mechanical key which allows a video tape recorder to spot which format was inserted. Learn more about the way score calculators work and the way to discover the best ones. Gossip, Deception and Apush Ap Test Release Essay Topics Our customer support will gladly tell you whether there are any special offers at the present time, in addition to make sure you are getting the very best service our business can deliver. They are rather useful serving as an introduction to an intriguing topic, but are not too professional in the feeling they rather attempt to catch the interest of the audience rather than presenting detailed info on this issue. We'll deal with them, and for an affordable price, as we understand that students typically don't have a great deal of money to spare. However, you can be certain that you're getting a fine work for the price tag you're paying. There's, obviously, a limit on the range of pages even our very best writers can produce with a pressing deadline, but usually, we figure out how to satisfy all the clients seeking urgent assistance. Things You Should Know About Apush Ap Test Release Essay Topics The following suggestions will provide you a better grasp about how to compose an APUSH essay or what things to anticipate from it. Generally, it's always a great notion to take an SAT Subject Test right after you finish v in the matter. Attempt to analyze the topic and begin writing your pla n. The Basics of Apush Ap Test Release Essay Topics As you ought to be aware that schools like Dartmouth are likely to phase the exams out later on. It expects a specific level of advanced understanding of larger trends associated with racial tension in US History and when and the way the responses of unique groups to legislative changes played out. Only a few of students get perfect scores annually. They lead busy lives and often forget about an upcoming deadline. Select your responses carefully.

Protection from Harm Abuse - Essay Case Study

Throughout this work I will relate to a case study. I will provide a definition of abuse using both sociological and psychological perspectives to contribute to our understanding of the causes of abuse. I will define the types, indicators, signs and symptoms of abuse and its impact on families and individuals, identifying factors relevant to the case study, recognising and explaining current legislation making reference to Government reports/inquiries and research into failures to protect from harm and abuse. I will consider the policies and procedures that my work place use and I will identify some statutory and voluntary agencies and their roles in supporting those affected by abuse, relating specifically to the abuse of children.†¦show more content†¦Ã¢â‚¬Å"A sexual invasion of the body by force, an incursion into the private, personal inner space without consent. . . . constitutes a deliberate violation of emotional, physical and rational integrity and is a hostile, degrading act of violence that deserves the name of rape† (Brownmiller, S p377) The five most common social service workers will likely see are: Physical Abuse, Emotional Abuse, Sexual Abuse, Neglect and Financial Abuse. Physical abuse is causing bodily harm it may involve hitting, shaking, throwing, poisoning, burning or scalding, drowning or suffocating or excessive discipline or family violence, use of restraints or imprisonment, denial or misuse of medication, physical aids and adaptations or when the carer feigns ill-health of a child. Some signs and indicators may be physical (several injuries in various stages of healing, repeated injuries or accidents over a period of time, injuries that form a shape like the object used to injure (buckle, hand, iron, teeth, cigarette burns), or death. Behavioural indicators include (negative self-image, deserving punishment, no recall how injuries occurred, offer inconsistent explanations, wary of others and reluctance to go home) Physical abuse can be seen in relation to John Burn (60). He claimed no recollection to a black-eye and urged for his son not to be informed, although it is important not to cast assumptions. Emotional abuse is persistent neglect with severe effects on a child’sShow MoreRelatedThe Australian Code Of Ethics For Social Work1591 Words   |  7 Pagesparticipation was particularly concerning especially after the insensitive research practices involving human subjects in Nazi Germany during the WW2. The abuses led to the establishment of the Nuremberg Code, which highlighted a number of key principles that continues to remain the foundation of any human research (Sherlock 2010, p.2). This essay will demonstrate the importance the importance of adhering to ethical principles in research process, especially around vulnerable groups in particular theRead MoreThe Australian Code Of Ethics For Social Work1581 Words   |  7 Pagesparticipation was particularly concerning especially a fter the insensitive research practices involving human subjects in Nazi Germany during the WW2. The abuses led to the establishment of the Nuremberg Code, which highlighted a number of key principles that continues to remain the foundation of any human research (Sherlock 2010, p.2). This essay will demonstrate the importance of adhering to ethical principles in research process, especially around vulnerable groups in particular the refugees. ConcentratingRead MoreSafeguarding And Promoting The Welfare Of The Child1154 Words   |  5 Pagespromoting the welfare of the child’ which by definition is the process of protecting children from abuse or neglect, preventing impairment of their health and development.’ (DfES 2005a, p11). Working together to safeguard children (HM Government 2005a p 19) state child protection as â€Å"the activity which is undertaken to protect specific children who are suffering or at risk of suffering significant harm’’.The DfE S (2005) have emphasised in their current legislation that ‘safeguarding and promotingRead MoreHnc Social Care Essay4439 Words   |  18 Pagesprocessed and include appropriate references both in main essay through acknowledgement using the author surname and date of publication and detailed as a full reference in an end list attached to the back of your work. Please visit the power point on the moodle for further information as to the correct technique to use. In addition lecturers and library staff will help you with this. Make note of the word count assigned to each essay and try to stay within the set number. If you are notRead MoreDomestic Violence On Women : Implications For Child Protection Essay1142 Words   |  5 PagesDomestic Violence on Women: Implications for Child Protection Introduction Intimate Partner Violence (IPV) is a worldwide social problem whose perpetrators include men as well as women (Anderson, 2002; Archer, 2000, 2002; Brown, 2004; Capaldi, Kim, Shortt, 2007; Capaldi Owen, 2001; Hamberger Potente, 1994; Straus Gelles, 1986, as cited in Ali Naylor, 2013). For the purpose of this essay, I will discuss IPV faced by women and perpetuated by men, referring to it as domestic violence (DV)Read MoreThe History Of Social Work Practice1530 Words   |  7 PagesIn this essay I will be giving a brief introduction to the history of social work practice, by introducing the laws that contributed to its development. Explaining how the sub divisions divide into specialism s within the variety of social work settings, using both public and private sectors to show understanding. Also, demonstrate knowledge of different legislation that has been introduced to social work practice over the past 25 years and why it is used in particular areas. Then to finalise usingRead MoreCauses And Effects Of Child Abuse1565 Words   |  7 Pagesand effects of child abuse, suggestions to assist victims and punishment for abusers. Each year, nearly a million children are determined by child protective services to be the victims of abuse and/or neglect in this/country, while many more are at risk. The majority of victims suffer from neglect, but some children also endure the effects of physical, psychological, or sexual abuse. Child abuse results in several social, emotional and psychological problems. This essay will discuss the causesRead MoreThe Main Difficulties With Multi Agency Partnerships1541 Words   |  7 Pagessafeguarding children? Discuss with reference to social science literature and official reports. Safeguarding children can best be described as an action taken to promote the welfare of children and protect them from harm, this involves protecting children from abuse and maltreatment and preventing harm to children’s health or development. (NSPCC, 2016). Multi-agency partnerships in safeguarding children look to identify the goals, circumstances and needs of children, agencies must agree with both the contributionRead MoreEssay on Bioethics1696 Words   |  7 Pagesboy with pus from a diseased cow. The list goes on, and such experiments continue even until today. nbsp;nbsp;nbsp;nbsp;nbsp;Nowadays these experiments would be ethically and legally unacceptable. Nevertheless, there have been clear documented cases of abuse in recent times. An example of this is the experiments conducted by Nazi doctors on prisoners in the concentration camps during the Holocaust. nbsp;nbsp;nbsp;nbsp;nbsp;Does this mean that since there is potential for abuse, all experimentationRead MoreSafeguard Methods Used to Protect Vulnerable People.1716 Words   |  7 PagesIn this essay, I will examine a case study with four individual service users; Mr D, Mr R, Ms M and Ms P who are all described as vulnerable adults with learning disabilities, how and why these disabilities have lead to the service users being regarded as vulnerable. For this reason, I would define what learning disability is and the effects it may have on the individual service users. I would use the labelling theory in this concept to explain my knowledge and understanding of vulnerability. I

The Technological Accessibility And Socioeconomic Mobility...

I remember travelling to the resort and marvelling at the engineering feat of the Cayo Santa Maria (CSM) causeway in Cuba. The design of the causeway functioned as a method of connecting small parchments of man-made land to the larger archipelagos. Despite the devastation of Hurricane Katrina in ‘08, the causeway remained portionately intact. During my visit in ‘11, however, the causeway was noted for its damages bridges still in need of further repair1. The causeway itself (for the most part) is unlit. Due to (prior) partisan economic sanctions against Cuba, the CSM is a main artery for tourist flow being the major route to the resort(s). The main archipelago sponsors twelve hotels, the first built in ‘01, is quite incredible, considering the limitations placed on the technological accessibility and socioeconomic mobility of Cuban workers. While traversing on the CSM causeway, I distinctly thought of the abundance of people travelling Cuba’s main highway bef orehand. I had asked the guide, (foolishly,) ‘Where are they going?’ -- ’To work’. It was considered a privilege, I learned, to be able to work on the archipelagos—at least you wouldn’t have to walk to work2. A walk that took the workers half of their day. The CSM causeway is very narrow, a two-lane 48 km stretch, I was curious to how the resort workers (unable to walk the causeway) made it to work. Transportation being expensive, not primarily vehicle ownership but public transportation, again, how do they commute? DidShow MoreRelatedThe Technological Accessibility And Socioeconomic Mobility Of Cuban Workers947 Words   |  4 Pagesconsidering the limitations placed on the technological accessibility and socioeconomic mobility of Cuban workers. While traversing on the CSM causeway, I distinctly thought of the abundance of people travelling Cuba’s main highway earlier. I had asked the guide, (foolishly,) ‘Where are they going?â €™ -- ’To work’. It was considered a privilege, I learned, to be able to work on the archipelagos—at least you wouldn’t have to walk to work2. A walk that took the workers half of their day. The CSM causeway isRead MoreOne Significant Change That Has Occurred in the World Between 1900 and 2005. Explain the Impact This Change Has Made on Our Lives and Why It Is an Important Change.163893 Words   |  656 Pages 2 †¢ INTRODUCTION of two epochs we routinely set apart as centuries suggests the need for flexibility in demarcating phases of world history, and for determining beginnings and endings that accord with major shifts in political and socioeconomic circumstances and dynamics rather than standard but arbitrary chronological break points. In the decades that followed the Great War, the victorious European powers appeared to have restored, even expanded, their global political and economicRead MoreStephen P. Robbins Timothy A. Judge (2011) Organizational Behaviour 15th Edition New Jersey: Prentice Hall393164 Words   |  1573 PagesPractices? 30 Point/Counterpoint Lost in Translation? 31 Questions for Review 32 Experiential Exercise Workforce Diversity 32 Ethical Dilemma Jekyll and Hyde 33 Case Incident 1 â€Å"Lessons for ‘Undercover’ Bosses† 34 Case Incident 2 Era of the Disposable Worker? 35 vii viii CONTENTS 2 2 The Individual Diversity in Organizations 39 Diversity 40 Demographic Characteristics of the U.S. Workforce 41 †¢ Levels of Diversity 42 †¢ Discrimination 42 Biographical Characteristics 44 Age 44 †¢Read MoreMarketing Management 14th Edition Test Bank Kotler Test Bank173911 Words   |  696 Pagesagents that display, sell, or deliver the physical product or service(s) to the buyer or user. Answer: TRUE Page Ref: 11 Objective: 3 Difficulty: Easy 96) The task environment of a firm consists of demographic, economic, natural, and technological environments, as well as the political-legal system and the social-cultural arena. Answer: FALSE Page Ref: 11 Objective: 3 AACSB: Analytic skills Difficulty: Moderate 97) Regulation of industries has created greater competition and

Pro Terrorist Torture Free Essays

September 11, 2001, is a moment frozen in time. It was on this day that the world seemed to stop turning, and its course would never be the same again. It was the day of the largest organized attack on American citizens that took the lives of 2,976 innocent everyday people (attention grabber). We will write a custom essay sample on Pro Terrorist Torture or any similar topic only for you Order Now It not only destroyed buildings, it destroyed lives. Not only the innocent lives of the thousands murdered in the burning buildings were destroyed, but the lives of their families were destroyed, and their hearts became filled with hurt and loss. As a result of this unthinkable attack on our country, the lives of thousands of American Soldiers and their families would soon be affected as well The war that 9/11 spun Americans and the rest of the world into was not a regular war in a regular country with regular soldiers. This war was one in which our brave men and women took on a radical religious band of terrorists who hide in caves, hide behind women and children, and strap bombs to themselves just to harm and terrorize others. These people continue to threaten American safety and liberty each and every day and were responsible for the most bloodshed on American soil in a single act of war. These people want nothing more than to harm innocent people and their families and will stop at nothing to do so. So when these terrorists who wear no uniforms and claim no country are captured, some argue that they deserve to be treated humanely. The fact is, they have information that could save thousands of American lives. However, they are so passionate about their cause; such information is not easily obtained. Therefore, the United States has the right to torture prisoners of war (suspected terrorists) in order to acquire vital information that is required to protect our country and its citizens. Terrorists are not regular soldiers in a regular war. They do not even merit POW (prisoner of war) status as stated by the Geneva Convention passed by the United Nations and approved by the Supreme Court. Colin Powell stated that â€Å"bestowing POW status on detainees who do not meet the clear requirements of the Geneva Convention would undermine the rule of law giving equal protections and privileges to all combatants regardless to their respect to the law. † This is not a regular war because we are not fighting against a country; we are fighting religious extremists. Terrorists are not part of an organized military, have no uniforms, and do not represent a country or legitimate state, and therefore, are not protected nor deserved to be rotected under the Geneva Convention. Despite the agreed Geneva Convention, this nine-year war has resulted in different opinions on how protocol should be run halfway across the globe in our country. A very prominent issue between politicians today is the issue of torture. Torture sounds like a horrible word, and when spoken the thought of inhumane treatment, pain, and misery come to mind. But there are different forms and types of torture th at are not so cruel. The United States has been accused of using a form of torture on suspected terrorists known as stress and duress. But this form of torture is, as defined by the Supreme Court, neither inappropriate nor inhumane by any means. (establish credibility/ source #2, quote supreme court) â€Å"Stress and duress is a form of torture that includes: psychological and physical pressure on suspects through methods such as sleep deprivation, covering head with hood to cause disorientation, and pinning prisoners in uncomfortable positions for hours. † This is considered a form of torture. It is sad to think that American citizens who are more worried about being politically correct than the safety of our country and their friends and neighbors are speaking out against these insignificant pushes that soldiers perform on prisoners of war. Videos come out from Iraq and Afghanistan of terrorists slowly cutting off the heads of our brave men and women protecting freedom. It is odd to think that terrorists decapitate and inhumanely kill and murder our soldiers and there is fuss when our soldiers keep a terrorist with American blood on his hands deprived of sleep for a week. It is nice to know that our country still cares about and supports our men and women in uniform. As stated by a poll conducted by Rasmussen (source #3): â€Å"58% of U. S. voters say water boarding and other aggressive interrogation techniques should be used to gain information from the terrorist who attempted to bomb an airline on Christmas Day. † (Rasmussen) T hat means that over half of our nation supports interrogation methods that are more severe than the methods that others in this country are upset about. Also, the military is not torturing terrorists just to torture them because they do not like them or want revenge. Terrorists are being â€Å"tortured† for information such as future plots, hiding places, sources of weapons, etcetera that is needed to simply protect our men and women overseas and our citizens who call this great country home. Some opposition goes so far as to demand American rights for terrorists who want to kill Americans and who hate this country. A Counsel member for Human Rights Watch, Katherine Bierman, (cite source #4) is quoted saying â€Å"If you’re going to sentence them, there has to be a fair trial [this] amounts to nothing more extravagant than giving the defendant the chance to defend himself, not forcing him to incriminate himself and insuring he’s not tortured– the elements of what an ordinary citizen would consider a fair trial. † (quoted in Katel 6) There are many scary and utterly ridiculous elements in this quote. First, as established above, â€Å"torture† is not being used on suspected terrorists– they are using stress and duress to extract information. Secondly, terrorists openly express their hate for this country and say they are proud of their actions; none have incriminated themselves by nothing more than the truth. A terrorist is not going to bluntly admit to something he/she did not do, even if he was severely tortured which they are not. Government documentation, the definition of the word torture, and 58% of our nation can prove that. Not to mention, a trial is costly. To fly a terrorist to our country to have a so-called â€Å"fair trial† is ridiculous and costs the people of this nation hard earned money to have this man put on trial. Not only is it costly, but it brings him/her into the country that his leaders and fellow terrorists spilt blood in. It is not only ethically incorrect to pay American money for these terrorists to have American rights; it is unconstitutional to not give someone a fair trial. Can someone realistically say that a terrorist will receive a fair trial in the country he tried to commit terrorist acts against? What jury of American citizens would find this man innocent? What judge will set him free? And even if by some horrible miracle this murderer is set free- what happens to him? Does he freely walk our streets, or do our citizens spend yet more money to fly this man back home so he can go back to plotting against us? Finally these are not ordinary citizens, let alone even citizens. By no means does a foreign murderer against our citizens get the luxury of the rights he would have if he were a citizen. As stated by an American General Tommy Franks (source citation) , â€Å"I don’t want a soldier when he kicks down a door in a hut in Afghanistan searching for Osama bin Laden to have to worry about whether when he does so and questions the individuals he finds inside who may or may not be bin Laden’s body guards, or even the individual himself- he’s got to advise them of their rights before he takes a statement† (quoted in Katel 6). â€Å"If you are intentionally inflicting pain on someone, then you are torturing them period,† (Masci 5) Human Rights leaders declare. But the politically correct opposition fails to determine the definition of pain. Pain is defined in the dictionary as (source dictionary) â€Å"the acutely unpleasant physical discomfort experienced by somebody who is violently struck, injured, or ill. † When a linebacker sacks the quarterback in a football game and puts the quarterback out of the game for a little bit with a rolled ankle, did he torture him? Or when children are playing dodge ball at school and a child is given a bloody nose, did the child who threw it torture the other child? Absolutely not. My point? Torture is inhumane treatment that causes severe and sometimes permanent damage to another human being through psychological threats and physical beatings, not by sleep deprivation. There is a difference between torture and inhumane treatment. Causing someone stress or discomfort is not torture. Terrorists are a serious threat to our nation, citizens, beliefs, and safety. They do not deserve our rights, trials, and should be â€Å"tortured† by means of stress which is considered humane. The United States will not stoop to our enemy’s level and cruelly and brutally torture our prisoners of war. The time of war is not the time to be politically correct, but the time to take a step back and look at the big picture, the one in which our country has the right to freedom win the war on terror so the world will be a safer place. It is up to us to maintain and protect our freedom and safety. These are the facts, and these are the views of opinions from both sides of this fragile issue. Now you know, and it is important as American citizens to be informed and aware so we can elect people that will do the right thing in our eyes and defend freedom in the way you see it best. Works Cited Barber, Ben. â€Å"The POW Predicament. The American Legion. 1  Aug. 2002:  (pg 1). Career and Technical Education,  ProQuest. Canyon Ridge High School Library. 17 Feb. 2010. lt; http://proquest. umi. com Katel, Peter, and Kenneth Jost. â€Å"Treatment of Detainees. † CQ Researcher 16: 29 (25 Aug 2006): 673-696. (pg6) CQ Researcher Online. 17 Feb. 2010 . Masci, David, and Patrick Marshall. â€Å"Civil Liberties in Wartime. † CQ Researcher 11: 43 (14 Dec 2001): 1017-1040. CQ Researcher. 17 Feb. 2010 . Masci, David. â€Å"Torture. † CQ Researcher. 13: 15 (18 April 2003): 345-368. (pg 3, 4,5) CQ Researcher. 17 Feb. 2010. http://library. cqpress. com/cqresearcher/cqresrre2003041800 How to cite Pro Terrorist Torture, Papers

Basic Electronics free essay sample

The p-n junction is a homojunction between a p-type and an n-type semiconductor. It acts as a diode, which can serve in electronics as a rectifier, logic gate, voltage regulator (Zener diode), switching or tuner (varactor diode); and in optoelectronics as a light-emitting diode (LED), laser diode, photodetector, or solar cell. In a relatively simplified view of semiconductor materials, we can envision a semiconductor as having two types of charge carriers-holes and free electrons which travel in opposite directions when the semiconductor is subject to an external electric field, giving rise to a net flow of current in the direction of the electric field. Figure 1 illustrates the concept. A p-n junction consists of a p-type and n-type section of the same semiconductor materials in metallurgical contact. The p-type region has an abundance of holes (majority carriers) and a few mobile electrons (minority carriers); the n-type region has an abundance of mobile electrons and a few holes (Fig. 2). Both charge carriers are in continuous random thermal motion in all directions. Fig. 2. Energy levels and carrier concentrations for a p-type and n-type semiconductor before contact. 1 When a section of p-type material and a section of n-type material are brought in contact to form a pn junction, a number of interesting properties arise. The pn junction forms the basis of the semiconductor diode. Electrons and holes diffuse from areas of high concentration toward areas of low concentration. Thus, electrons diffuse from the n-region to the p-region. , leaving behind positively charged ionized donor atoms. In the p-region the electrons recombine with the abundant holes. Similarly, holes diffuse from the p-region into the n-region, leaving behind negatively charged ionized acceptor atoms. In the n-region the holes recombine with the abundant mobile electrons. This diffusion process does not continue indefinitely, however, because it causes a disruption of the charge balance in the two regions. As a result, a narrow region on both sides of the junction becomes nearly depleted of the mobile charge carriers. This region is called the depletion layer. It contains only the fixed charges (positive ions on the n-side and negative ions on the p-side). The thickness of the depletion layer in each region is inversely proportional to the concentration of dopants in the region. The net effect is that, the depletion region sees a separation of charge, giving rise to an electric field pointing from the n side to the p side. The fixed charges create an electric field in the depletion layer that points from the n-side towards the p-side of the junction. The charge separation therefore causes a contact potential (also known as built-in potential) to exist at the junction. This built-in field obstructs the diffusion of further mobile carriers through the junction region. An equilibrium condition is established that results in a net contact potential difference Vo between the two sides of the depletion layer, with the n-side exhibiting a higher potential than the p-side. This contact potential is typically on the order of a few tenths of a volt and depends on the material (about 0. 5 to 0. 7 V for silicon). The built-in potential provides a lower potential energy for an electron on the n-side relative to the p-side. As a result, the energy bands bend as shown in Fig. 3. In thermal equilibrium there is only a single Fermi function for the entire structure so that the Fermi levels in the p- and the n-regions must align. No net current flows across the junction. The currents associated with the diffusion and built-in field (drift current) cancel for both the electrons and holes. Fig. 3. A p-n junction in the Thermal equilibrium at T gt; 0? K. The depletion-layer, energy-band diagram, and concentrations (on a logarithmic scale) of the mobile electrons n(x) and holes p(x) are shown as a functions of the position x. The built-in potential difference V corresponds to the energy eV where e is the electron charge. 0 0 2 The Biased p-n Junction An externally applied potential will alter the potential difference between the p- and n-regions. This in turn will modify the flow of majority carriers, so that the junction can be used as a â€Å"gate†. If the junction is forward biased by applying a positive voltage V to the p-region (Fig. 4), its potential is increased with respect to the n-region, so that an electric field is produced in a direction opposite to that of the built-in field. The presence of the external bias voltage causes a departure from equilibrium and a misalignment of the Fermi levels in the p- and n-regions, as well as in the depletion layer. The presence of the two Fermi levels in the depletion layer, Efc and Efv represents a state of quasi-equilibrium. Fig. 4. Energy band diagram and carrier concentrations for a forward-biased p-n junction. In effect, then, if one were to connect the two terminals of the p-n junction to form a closed circuit, two currents would be present. First, a small current, called reverse saturation current, is, exists because of the presence of the contact potential and the associated electric field. In addition, it also happens that holes and free electrons with sufficient thermal energy can cross the junction. This current across the junction flows opposite to the reverse saturation current and is called diffusion current. Of course, if a hole from the p side enters, it is quite likely that it will quickly recombine with one of the n-type carriers on the n side. (Fig. 4) The net effect of the forward bias is to reduce the height of the potential-energy hill by an amount eV. The majority carrier current turns out to increase by an exponential factor exp(eV/kT). So that the net current becomes i = isexp(eV/kT) – is, where is is nearly a constant. The excess majority carrier holes and electrons that enter the n and p regions, respectively, become minority carriers and recombine with the local majority carriers. To explain the mechanism of reverse conduction, one needs to visualize the phenomenon of avalanche breakdown. When a very large negative bias is applied to the p-n junction, sufficient energy is imparted to charge carriers that reverse current can flow, well beyond the normal reverse, saturation current. In addition, because of the large electric field, electrons are energized to such levels that if they collide with other charge carriers at a lower energy level, some of their energy is transferred to the carriers with low energy, 4 and these can now contribute to the reverse conduction process, as well. This process is called impact ionization. Now, these new carriers may also have enough energy to energize other lowenergy electrons by impact ionization, so that once a sufficiently high reverse bias is provided, this process of conduction takes place very much like an avalanche: a single electron can ionize several others. Fig. 6. The reverse breakdown region The phenomenon of Zener breakdown is related to avalanche breakdown. It is usually achieved by means of heavily doped regions in the neighbourhood of the metal-semiconductor junction (the ohmic contact) . The high density of charge carriers provides the means for a substantial reverse breakdown current to be sustained at a much lower specific voltage than normal diode, at a nearly constant reverse bias known as the Zener voltage, Vz. This phenomenon is very useful in applications where one would like to hold some load voltage constant for example, in voltage regulators. The response time of a p-n junction to a dynamic (ac) applied voltage is determined by solving the set of differential equations governing the processes of electrons and hole diffusion, drift (under the influence of the built-in and external electric fields), and recombination. These effects are important for determining the speed at which the diode can be operated. They may be conveniently modeled by two capacitances, a junction capacitance and diffusion capacitance, in parallel with an ideal diode. The junction capacitance for the time necessary to change the fixed positive and negative charges stored in the depletion layer when the applied voltage changes. The thickness l of the depletion layer turns out to be proportional to v(Vo-V); it therefore increases under the reverse-bias conditions (negative V) and decreases under the forward-bias conditions (positive V). The junction capacitance C=ЄA/l (where A is the area of the junction) is therefore inversely proportional to v(VoV). The junction capacitance of a reverse-biased diode is smaller (and the RC response time is therefore shorter) than that of a forward-biased diode. The dependence of C on V is used to make voltage-variable capacitors (varactors). 5 Experiment l(a) : i-v characteristics of a semiconductor diode Procedure Connect the diode according to the circuit diagram as shown in Fig. 8. Fig 8 Vary the voltage V on the power supply between 0-30V. Alternately, the second concept is that the blocking action of an inductor stops the a. c. portion while the d. c. portion passes without much attenuation. Note: For filtering, large capacitance (hundreds to tens of hundreds microfarad) is needed. These are generally electrolytic capacitors, which consist of a repeating sandwich of aluminum sheets and a conducting paste, rolled into a cylinder for miminmun size. The aluminum sheets are polarized to form thin layers of aluminum oxide, a dielectric insulating material. The thinner the the dielectric the higher the capacitance will be.