Doing research Paper Example | Topics and Well Written Essays - 500 words

Doing - Research Paper Example A personal assessment of my skills and knowledge shows that even though I possess some level of competence to get the idea through, there remains a major aspect of my study that needs to be improved. This is because the need to go about this research and complete it according to the required objectives demand an interrelated level of skills and knowledge that are tied around a self empowered motivation to get an issue of concern, investigated to the latter. There will therefore be additional skills in interpersonal relation, communication skills, as well as data collection and handling skills to ensure that the project is carried out to its logical conclusion. I also need to revamp my knowledge in marine safety in general and boat yard safety in specific. Without an overall understanding of marine safety and boat yard safety to be specific, working on this research area will be like treating stomach ache by placing a plaster on the tummy. This is because the core or depth of the problem will not be reached. Most times, people working in the marine area have been identified to have their own peculiarities and depths of issues that affect and undermine their safety, security and general wellbeing. It is only when a researcher has an adequate level of knowledge on these that the best forms of interventions can be identified for them. As part of finding out about boat yard safety, specific aspects of learning such as causes of risk, risk factors, effects of risk, and solutions to marine risks must all be considered. The original idea of the research shall be changed significantly in this new project. It would be noted that the original idea laid emphasis on employee and employer forum. As far as the original ideas are concerned, there is one major deficiency that may hinder its feasibility. This is the absence of prove of

Rationale Essay Example | Topics and Well Written Essays - 250 words

Rationale - Essay Example s with specialized skill set, I have the advantage and prerequisites and can sign up for the course immediately, with the potentialities knocking at my door. As such after applying proper thought I have opted for, among others, the following group of subjects: Foundations of Leadership, Consumer Behavior, Principles of Marketing and Business & Economic History of the US. Foundations of Leadership and Principles of Marketing and Business & Economic History of the US should be of immense help to me in bettering my career prospectus. After graduation, I wish to join some multinational organization as a Marketing Executive to get exposed to the ground realties of marketing and interacting with the customers. My concentration is marketing/advertising for the sports industry with a coaching minor. I foresee immense scope for development of sports good industry. After getting sufficient marketing experience, I have plans to establish my own small scale unit to manufacture sports goods. Leadership is a quality needed most in every area, private as well as public relations. To me, educational and career advancement are alternative beats of the same heart and the degree in Bachelor of Science with major in Integrative Studies lays the foundation for a professional career. The sampling of several disciplines will provide to me a well-rounded education. By working in a multinational organization as stated above, and by gaining practical marketing experience, I am sure that I will be able to succeed in my business venture of establishing a sports goods manufacturing

Ideology and work choices Essay Example for Free

Ideology and work choices Essay Labour laws come from a body of administrative rulings, laws and regulations that are meant to address the legal rights and restrictions of workers and their organizations/ employers. These laws help in improving the relationship between employers, trade unions and employees. Since the 19th century, labour rights have been playing a crucial role in the development of the industrial revolution both socially and economically. These labour laws arose due to the inequality that existed between employees and employees especially when it came to workers’ demands for better conditions like health, safety and wages and employers’ demands for reduced labour costs. Therefore, labour laws are meant to e fair to both parties (employers and employees) thus, they are both a product and a component of different struggles between different interests in society. (Plowman, and Preston, 2005) Overview On 7th December 2005, the Australian Government under Prime Minister John Howard secured passage through the Australian parliament of Workplace Relations Amendment Act 2005. This legislation will greatly affect the conduct of Australian industrial relations. It will also greatly influence the way that the rules that regulate employment relationship in Australia are made and implemented. However, a complete analysis of these reforms has not been made. (Bray et al 2005) The reason why these reforms had to be made was to ensure that the loopholes and strategies that unions had developed since the Workplace Relations Act 1996 were closed off. The Australian labor party identified industrial relations gaps between what it and Howard’s government stood for. The labor’s policy platform focused on four major things: encourage family friendly workplaces, improving job security, assist parties to avoid and resolve disputes (ALP 2004) and restore the right to bargain collectively. In the 1970s, the Australian economic capacity was greatly diminished by adverse trade movements and oil price shocks. This forced the successive governments to introduce a range of reforms meant to enhance the competitiveness of Australian industries in international markets. These reforms comprised reduction in tariffs, floatation of the Australian dollar and abolition of most foreign exchange controls which increased Australia’s openness to foreign competition. Significant changes started being introduced to Australia’s workplace relations from the 1990s. These legislative reforms were meant to maintain a strong safety net for workers while at the same time provide a greater flexibility and choice for employers and workers at workplace level. It was until March 2008 that the government of Australia introduced transitional measures that phased out many concrete provisions in the workplace provisions laws (Workplace Relations Act 1996, Workplace Relations Amendment/Work Choices Act 2005 and Workplace Relations Amendment Act 2007). Ideology and work choices. It should be clearly noted that the prime minister and other members of his government have denied that their policies are not ideological. General philosophy Rather than employers and employees being stuck in an adversarial system, the government wants to put up a system that will allow them to determine their own conditions of working by looking into their common interests. (Andrews 2005b, p. 7). Therefore, a contract between an employee and an employer is seen as a meeting of minds between two partners who are equal and an agreement will only occur when both parties agree with the terms of the contract. In contrast to the pluralist perspective, the general philosophy fails to recognize that inequality of power is central feature of employment relationship. Role of employees. With this new act, provided the employees (Workers) are given the right leadership, the right incentives and the right opportunities, they will be in a position to work very closely with the management Impact on the parties and the rule making processes. In this section we shall critically look at the impact of that these reforms will have on the major actors in the Australian industrial relations. Role of the state In the last 20 years, the government of Australia has seen far greater reliance on market forces than state regulation. However, with the national competition policy as a catalyst, both state and federal governments have embraced deregulation of product markets, government owned enterprises have also been privatized and a private-sector management practice is being used in public sector organizations. (Bray et al. 2005) The narrowing of the state regulation can be seen in the shrinking role of awards and the new modest employment protections offered by the Fair Pay of Australia. Rule making process From chapter 8 of Bray et al. (2005), the four main forms of rule making in Australia are: managerial prerogative, individual contracting, collective bargaining and awards. With the Work Choices act, collective bargaining and award making will decline while managerial prerogative and individual contracting will expand significantly. The reforms here favor employers in many ways. Most employers will be able to gain significant capacity to practice improved bargaining power in their dealings with employees and unions and managerial prerogatives (Bray and Waring 2006). The changes in rule making have been encouraged as the government members have confirmed that economic success depends on freeing employers and employees from the restrictions of the old system. Awards This act has reduced the number of matters from 20 to 16 and this has helped in simplifying the awards. The award clauses that have been removed relate to: Jury service, long service leave, superannuation and notice of termination. However some federal awards that provide kind entitlements like leave arrangements will not be removed from the awards as they are deemed as preserved award entitlements. Management The Work Choices act will bring the Australian managerial sector more freedom to manage their businesses as they see fit. This is because there will be less state regulation of the employment relationship and they will not be forced by unions to collectively bargain over wages and working conditions. With this new freedom the Australian managers will be in a position to lead to more efficient enterprises, more jobs and a more competitive national economy. Many companies will also be capable of pursuing innovation/ quality-enhancement and business strategies. Unions. In chapter six of Bray et al. there is a trace of the historical evolution of unions as a form of employee representation in Australia. It was seen that membership and the power of trade unions had greatly declined from the beginning of the 1990s. This decline was brought about by many reasons. One of them was the increasingly hostile role of management and the impact of government policies that were not sympathetic. These harsh circumstances may be conducive to attracting new members and stimulated a new collective strength. However strategic differences over the union response to work Choices show great differences in ideologies within the Australian labour movement and the labour movements of other countries. Only time will tell where the union movement will go and what the real outcomes will be. Conclusion. The measures brought about by the Work Choices reforms are far reaching. This is because they represent a major break from the past in many ways. Firstly, their consequences to the constitution promise to be very big. Secondly, despite the much opposition it has faced, these reforms will help introduce new institutions by spelling an end to those institutions that have dominated Australian industrial institutions for very many years. They will also change the process by which the rules of employment relationships are made in Australia. In addition, market forces, individual contracting and managerial prerogative are going to gain a new ascendancy. According to Howard’s government and business supporters, these reforms are also inevitable as they are necessary in driving productivity and reducing unemployment and will also guarantee competitiveness. It is also important that any conclusions be left speculative and uncertain since public opinion can fail and political climate can drastically change. References: Andrews, K. (200b) ‘Where do we want workplace relations to be in five years time? ’ speech to Committee for Economic Development of Australia, Federation Square, Melbourne, retrieved on 15th March. Bray, M and Waring, P (2006) ‘The rise of managerial prerogative under the Howard government’, Australian Bulletin of Labour (in press). Bray, M. and Walsh, P. (1998), ‘Different paths to neo liberalism Comparing Australia and New Zealand’, Industrial Relations, Vol. 37, No. 3. Pp. 358-87. Bray, M. , Deery, S. , Walsh, J. and Waring, P. (2005) Industrial relations, 3rd edn, McGraw-Hill Irwin, Sydney. Plowman, D. and Preston, A. (2005) ‘The new industrial relations: portents for the lowly paid’, Journal of Australian Political Economy, No. 56, Dec, pp. 224-42

Load Flow Analysis For Electricity Supply Engineering Essay

Load Flow Analysis For Electricity Supply Engineering Essay Power flow studies, commonly referred to as load flow, are essential of power system analysis and design. Load flow studies are necessary for planning, economic operation, scheduling and exchange of power between utilities. Load flow study is also required for many other analyses such as transient stability, dynamic stability, contingency and state estimation. Network equations can be formulated in a variety of forms. However, node voltage method is commonly used for power system analysis. The network equations which are in the nodal admittance form results in complex linear simultaneous algebraic equations in terms of node currents. The load flow results give the bus voltage magnitude and phase angles and hence the power flow through the transmission lines, line losses and power injection at all the buses. 1.1 BUS Classification Four quantities are associated with each bus. These are voltage magnitude, phase angle ÃŽÂ ´, real power P and reactive power Q. In a load flow study, two out of four quantities are specified and the remaining two quantities are to be obtained through the solutions of equations. The system buses are generally classified into three categories. Slack bus: Also known as swing bus and taken as reference where the magnitude and phase angle of the voltage are specified. This bus provides the additional real and reactive power to supply the transmission losses, since there are unknown until the final solution is obtained. Load buses: Also know as PQ bus. At these buses the real and reactive powers are specified. The magnitude and phase angle of the bus voltage are unknown until the final solution is obtained. Voltage controlled buses: Also known as generator buses or regulated buses or P- buses. At these buses, the real power and voltage magnitude are specified. The phase angles of the voltages and the reactive power are unknown until the final solution is obtained. The limits on the value of reactive power are also specified. The following table summarizes the above discussion: 1.2 BUS Admittance Matrix In order to obtain the bus-voltage equations, consider the sample 4-bus power system as shown in Fig. 1.1 1.1 The impedance diagram of sample 4-bus power system For simplicity resistances of the lines are neglected and the impedances shown in Fig.1.1 are expressed in per-unit on a common MVA base. Now impedances are converted to admittance, i.e, = 1.1 Fig.1.2 shows the admittance diagram and transformation to current sources and injects currents at buses 1 and 2 respectively. Node 0 (normally ground) is taken as reference. 1.2 the admittance diagram of 1.1 Applying KCL to the independent nodes 1,2,3,4 we have Rearranging the above equations, we get Let, The node equations reduce to Note that ,in Fig.1.2, there is no connection between bus 1 and bus 4, so Above equations can be written in matrix form, 1.2 or in general 1.3 Where vevtor of the injected currents (the current is positive when flowing into the bus and negative when flowing out of the bus) admittance matrix. Diagonal element of Y matrix is known as self-admittance or driving point admittance, i.e. 1.4 Off-diagonal element of y matrix is known as transfer admittance or mutual admittance, i.e. 1.5 can be obtained from equation (1.3), i.e. 1.6 From Fig.1.2, elements of Y matrix can be written as: So 1.3 BUS Loading Equations Consider i-th bus of a power system as shown in Fig.7.4. transmission lines are represented by their equivalent à Ã¢â€š ¬ models. is the total charging admittance at bus i. Fig 1.4: i-th bus of a power system Net injected current into the bus I can be written as : 1.7 Let us define 1.8 Or 1.9 The real and reactive power injected at bus is is 1.10 From equations 7.9 and 7.10 we get 1.11 1.12 1.4 BUS Impedance Matrix The bus impedance matrix for en t 1T nodes can be written as Unlike the bus admittance matrix, the bus impedance matrix cannot be formed by simple examination of the network circuit. The bus impedance matrix can be formed by the following methods: à ¢- Inversion of the admittance matrix à ¢- By open circuit testing à ¢- By step-by-step formation à ¢- From graph theory Direct inversion of the Y matrix is rarely implemented in computer applications. Certain assumptions in forming the bus impedance matrix are: 1. The passive network can be shown within a closed perimeter, (Fig.1.3). It includes the impedances of all the circuit components, transmission lines, loads, transformers, cables, and generators. The nodes of interest are brought out of the bounded network, and it is excited by a unit generated voltage Fig.1.3 Representation of a network as passive elements with loads and faults excluded. The nodes of interest are pulled out of the network and unit voltage is applied at the common node. 2. The network is passive in the sense that no circulating currents flow in the network. Also, the load currents are negligible with respect to the fault currents. For any currents to flow an external path (a fault or load) must exist. 3. All terminals marked 0 are at the same potential. All generators have the same voltage magnitude and phase angle and are replaced by one equivalent generator connected between 0 and a node. For fault current calculations a unit voltage is assumed 1.5 POWER IN AC CIRCUITS The concepts of instantaneous power, average power, apparent power, and reactive power are fundamental and are briefly discussed here. Consider lumped impedance Z, excited by a sinusoidal voltage E (1.13) (1.14) The first term is the average time-dependent power, when the voltage and current waveforms consist only of fundamental components. The second term is the magnitude of power swing. Equation (1.2) can be written as (1.15) The first term is the power actually exhausted in the circuit and the second term is power exchanged between the source and circuit, but not exhausted in the circuit. The active power is measured in watts and is defined as (1.16) The reactive power is measured in var and is defined as: (1.17) These relationships are shown in Fig. 1.4; cosÃŽÂ ¸ is called the power factor (PF) of the circuit, and ÃŽÂ ¸ is the power factor angle. The apparent power in VA is given by (1.18) The power factor angle is generally defined as (1.19) If cosÃŽÂ ¸=1, Q=0. Such a load is a unity power factor load. Except for a small percentage of loads, i.e., resistance heating and incandescent lighting, the industrial, commercial, or residential loads operate at lagging power factor. As the electrical equipment is rated on a kVA basis, a lower power factor derates the equipment and limits its capacity to supply active power loads. The reactive power flow and control is one important aspect of power flow. The importance of power factor (reactive power) control can be broadly stated as: à ¢- Improvement in the active power handling capability of transmission lines. à ¢- Improvement in voltage stability limits. à ¢- Increasing capability of existing systems: the improvement in power factor for release of a certain per unit kVA capacity can be calculated from Eq. (10.6): where PFimp is improved power factor, PFext is existing power factor, and kVAava is kVA made available as per unit of existing kVA. à ¢- Reduction in losses: the active power losses are reduced as these are proportional to the square of the current. With PF improvement, the current per unit for the same active power delivery is reduced. The loss reduction is given by the expression: Where Lossred is reduction in losses in per unit with improvement in power factor from PFext to PFimp. An improvement of power factor from 0.7 to 0.9 reduces the losses by 39.5% à ¢- . Improvement of transmission line regulation: the power factor improvement improves the line regulation by reducing the voltage drops on load flow. All these concepts may not be immediately clear and are further developed. Fig 1.4 1.5.1 Complex Power If the voltage vector is expressed as A t jB and the current vector as C t jD, then by convention the volt-ampe`res in ac circuits are vectorially expressed as E= (A +jB) (C- jD) = AC +BD +j(BC-AD) = P+ jQ (1.20) where P = AC t BD is the active power and Q BC _ AD is the reactive power; I_ is the conjugate of I. This convention makes the imaginary part representing reactive power negative for the leading current and positive for the lagging current. This is the convention used by power system engineers. If a conjugate of voltage, instead of current, is used, the reactive power of the leading current becomes positive. The power factor is given by cosÃŽÂ ¸= (1.21) 1.5.2 Conservation of Energy The conservation of energy concept (Tellegens theorem) is based on Kirchoff laws and states that the power generated by the network is equal to the power consumed by the network (inclusive of load demand and losses). If i1; i2; i3; . . . ; in are the currents and v1; v2; v3; . . . ; vn the voltages of n single-port elements connected in any manner: (1.22) This is an obvious conclusion. Also, in a linear system of passive elements, the complex power, active power, and reactive power should summate to zero: (1.23) (1.24) (1.25) 1.6 POWER FLOW IN A NODAL BRANCH The modeling of transmission lines is unique in the sense that capacitance plays a significant role and cannot be ignored, except for short lines of length less than approximately 50 miles (80 km). Let us consider power flow over a short transmission line. As there are no shunt elements, the line can be modeled by its series resistance and reactance, load, and terminal conditions. Such a system may be called a nodal branch in load flow or a two-port network. The sum of the sending end and receiving end active and reactive powers in a nodal branch is not zero, due to losses in the series admittance Ysr (Fig. 1.5). Let us define Ysr, the admittance of the series elements= j or Z= zl= l(+j)= + =1/Ysr, where l is the length of the line. The sending end power is = Where is conjugate.This gives where sending end voltage is Vs and, at the receiving end: If is neglected: where ÃŽÂ ´ in the difference between the sending end and receiving end voltage vector angles= (. For small values of delta, the reactive power equation can be written as Fig1.5 Power flow over a two-port line. where is the voltage drop. For a short line it is Therefore, the transfer of real power depends on the angle ÃŽÂ ´, called the transmission angle, and the relative magnitudes of the sending and receiving end voltages. As these voltages will be maintained close to the rated voltages, it is mainly a function of ÃŽÂ ´. The maximum power transfer occurs at ÃŽÂ ´=90(steady-state stability limit). The reactive power flows is in the direction of lower voltage and it is independent of ÃŽÂ ´. The following conclusions can be drawn: 1. For small resistance of the line, the real power flow is proportional to sin ÃŽÂ ´. It is a maximum at ÃŽÂ ´=90ËÅ ¡. For stability considerations the value is restricted to below ÃŽÂ ´=90ËÅ ¡. The real power transfer rises with the rise in the transmission voltage. 2. The reactive power flow is proportional to the voltage drop in the line, and is independent of ÃŽÂ ´. The receiving end voltage falls with increase in reactive power demand. 2.1 Practical Load Flow The requirements for load flow calculations vary over a wide area, from small industrial systems to large automated systems for planning, security, reactive power compensation, control, and on-line management. The essential requirements are: à ¢- High speed, especially important for large systems à ¢- Convergence characteristics, which are of major consideration for large systems, and the capability to handle ill-conditioned systems. à ¢- Ease of modifications and simplicity. i.e. adding, deleting, and changing system components, generator outputs, loads, and bus types. à ¢- Storage requirement, which becomes of consideration for large systems The size of the program in terms of number of buses and lines is important. Practically, all programs will have data reading and editing libraries, capabilities of manipulating system variables, adding or deleting system components, generation, capacitors, or slack buses. Programs have integrated databases, i.e., the impedance data for short-circuit or load flow calculations need not be entered twice, and graphic user interfaces. Which type of algorithm will give the speediest results and converge easily is difficult to predict precisely. Table.2.1 shows a comparison of earlier Z and Y matrix methods. Most programs will incorporate more than one solution method. While the Gauss-Seidel method with acceleration is still an option for smaller systems, for large systems some form of the NR decoupled method and fast load-flow algorithm are commonly used, especially for optimal power flow studies. Speed can be accelerated by optimal ordering .In fast decoupled load flow the convergence is geometric, and less than five iterations are required for practical accuraci es. If differentials are calculated efficiently the speed of the fast decoupled method can be even five times that of the NR method. Fast decoupled load flow is employed in optimization studies and in contingency evaluation for system security. The preparations of data, load types, extent of system to be modeled and specific problems to be studied are identified as a first step. The data entry can be divided into four main categories: bus data, branch data, transformers and phase shifters, and generation and load data. Shunt admittances, i.e., switched capacitors and reactors in required steps, are represented as fixed admittances. Apart from voltages on the buses, the study will give branch power flows; identify transformer taps, phase-shifter angles, loading of generators and capacitors, power flow from swing buses, load demand, power factors, system losses, and overloaded system components. No. Compared parameter Y matrix Z matrix Remarks 1 Digital computer memory requirements Small Large Sparse matrix techniques easily applied to Y matrix 2 Preliminary calculations Small Large Software programs can basically operate from the same data input 3 Convergence characteristics Slow, may not converge at all Strong Both methods may slow down on large systems 4 System modifications Easy Slightly difficult See text 2.2 Y-Matrix Method The Y-matrix iterative methods were the very first to be applied to load flow calculations on the early generation of digital computers. This required minimum storage, however, may not converge on some load flow problems. This deficiency in Y-matrix methods led to Z-matrix methods, which had a better convergence, but required more storage and slowed down on large systems. Some buses may be designated as PQ buses while the others are designated as PV buses. At a PV bus the generator active power output is known and the voltage regulator controls the voltage to a specified value by varying the reactive power output from the generator. There is an upper and lower bound on the generator reactive power output depending on its rating, and for the specified bus voltage, these bounds should not be violated. If the calculated reactive power exceeds generator Qmax, then Qmax is set equal to Q. If the calculated reactive power is lower than the generator Qmin, then Q is set equal to Qmin. At a PQ bus, neither the current, nor the voltage is known, except that the load demand is known. A mixed bus may have generation and also directly connected loads. The characteristics of these three types of buses are shown in Table 2-1. Bus type Known variable Unknown variable PQ Active and reactive power Current and voltage PV Active power and voltage Current and reactive power Swing Voltage Current, active and reactive power 2.2.1 GAUSS AND GAUSS-SEIDEL Y-MATRIX METHODS The principal of Jacobi iteration is shown in Fig. 2.1. The program starts by setting initial values of voltages, generally equal to the voltage at the swing bus. In a well-designed power system, voltages are close to rated values and in the absence of a better estimate all the voltages can be set equal to 1 per unit. From node power constraint, the currents are known and substituting back into the Y-matrix equations, a better estimate of voltages is obtained. These new values of voltages are used to find new values of currents. The iteration is continued until the required tolerance on power flows is obtained. This is diagrammatically illustrated in Fig. 2.1. Starting from an initial estimate of, the final value of x* is obtained through a number of iterations. The basic flow chart of the iteration process is shown in Fig. 2.2 Fig2.1 Illustration of numerical iterative process for final value of a function Fig. 2.2 Flow chart of basic iterative process of Jacobi-type iterations 2.2.2 Gauss Iterative Technique Consider that n linear equations in n unknowns () are given. The a coefficients and b dependent variables are known: à ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦. These equations can be written as à ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦. (2.1) An initial value for each of the independent variables is assumed. Let these values be denoted by The initial values are estimated as à ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦. These are substituted into Eq. (2.1), giving à ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦. These new values of are substituted into the next iteration. In general, at the k-th iteration: à ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦. 2.2.3 Gauss-Seidel Y-Matrix Method In load flow calculations the system equations can be written in terms of current, voltage, or power at the k-th node. We know that the matrix equation in terms of unknown voltages, using the bus admittance matrix for n+ 1 node, is Although the currents entering the nodes from generators and loads are not known, these can be written in terms of P, Q, and V: The convention of the current and power flow is important. Currents entering the nodes are considered positive, and thus the power into the node is also positive. A load draws power out of the node and thus the active power and inductive vars are entered as:-p j (-Q) =-p + j Q. The current is then (-P + j Q)/. The nodal equal of current at the k-th node becomes: In general, for the k-th node: (2.2) The k-th bus voltage at r + 1 iteration can be written as (2.3) The voltage at the k-th node has been written in terms of itself and the other voltages. The first equation involving the swing bus is omitted, as the voltage at the swing bus is already specified in magnitude and phase angle. The Gauss-Seidel procedure can be summarized for PQ buses in the following steps: 1: Initial phasor values of load voltages are assumed, the swing bus voltage is known, and the controlled bus voltage at generator buses can be specified. Though an initial estimate of the phasor angles of the voltages will accelerate the final solution, it is not necessary and the iterations can be started with zero degree phase angles or the same phase angle as the swing bus. A flat voltage start assumes 1 + j0 voltages at all buses, except the voltage at the swing bus, which is fixed. 2: Based on the initial voltages, the voltage at a bus in the first iteration is calculated using Eq. (2.2) 3: The estimate of the voltage at bus 2 is refined by repeatedly finding new values of by substituting the value of into the right-hand side of the equation. 4: The voltages at bus 3 are calculated using the latest value of found in step 3 and similarly for other buses in the system. This completes one iteration. The iteration process is repeated for the entire network till the specified convergence is obtained. A generator bus is treated differently; the voltage to be controlled at the bus is specified and the generator voltage regulator varies the reactive power output of the generator within its reactive power capability limits to regulate the bus voltage: where stands for the imaginary part of the equation. The revised value of is found by substituting the most updated value of voltages: For a PV bus the upper and lower limits of var generation to hold the bus voltage constant are also given. The calculated reactive power is checked for the specified limits: If the calculated reactive power falls within the specified limits, the new value of voltage is calculated using the specified voltage magnitude and. This new value of voltage is made equal to the specified voltage to calculate the new phase angle. If the calculated reactive power is outside the specified limits, then, This means that the specified limits are not exceeded and beyond the reactive power bounds, the PV bus is treated like a PQ bus. A flow chart is shown in Fig. 2.3 2.3 Newton-Rapson Method Newton-Raphson method is an iterative method which approximates the set of non-linear simultaneous equations to a set of linear equations using Taylors series expansion and the terms are restricted to first order approximation. 2.3.1 Simultaneous Equations The Taylor series is applied to n nonlinear equations in n unknowns, à ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦. As a first approximation, the unknowns represented by the initial values can be substituted into the above equations, where are the first estimates of n unknowns. On transposing Where is abbreviated as The original nonlinear equations have been reduced to linear equations in The subsequent approximations are à ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦Ãƒ ¢Ã¢â€š ¬Ã‚ ¦ Or in matrix form: The matrix of partial derivatives is called a Jacobian matrix. This result is written as This means that determination of unknowns requires inversion of the Jacobian 2.3.2 Rectangular Form of Newton-Rapson Method of Load Flow The power flow equation at a PQ node is Voltage can be written as: Thus, the power is ] ] Equating the real and imaginary parts, the active and reactive power at a PQ node is: where and are functions of and . Starting from the initial values, new values are found which differ from the initial values by and (First iteration) (First iteration) For a PV node (generator bus) voltage and power are specified. The reactive power equation is replaced by a voltage equation: 2.3.3 Polar Form of Jacobian Matrix The voltage equation can be written in polar form: Thus the power is Equating real and imaginary terms: The Jacobian in polar form for the same four-bus system is The slack bus has no equation, because the active and reactive power at this bus is unspecified and the voltage is specified. At PV bus 4, the reactive power is unspecified and there is no corresponding equation for this bus in terms of the variable. The partial derivatives can be calculated as follows: 2.3.4 Calculation Procedure of Newton-Raphson Method The procedure is summarized in the following steps, and flow charts are shown in Figs 2.4 and 2.5 à ¢- Bus admittance matrix is formed. à ¢- Initial values of voltages and phase angles are assumed for the load (PQ) buses. Phase angles are assumed for PV buses. Normally, the bus voltages are set equal to the slack bus voltage, and phase angles are assumed equal to 0ËÅ ¡, i.e., a flat start. à ¢- Active and reactive powers, P and Q, are calculated for each load bus à ¢- P and Q can, therefore, be calculated on the basis of the given power at the buses à ¢- For PV buses, the exact reactive power are not specified, but its limits are known. If the calculated value of the reactive power is within limits, only P is calculated. If the calculated value of reactive power is beyond the specified limits, then an appropriate limit is imposed and Q is also calculated by subtracting the calculated value of the reactive power from the maximum specified limit. The bus under consideration is now treated as a PQ (load) bus. à ¢- The elements of the Jacobian matrix are calculated à ¢- This gives and à ¢- Using the new values ofand, the new values of voltages and phase angles are calculated. à ¢- The next iteration is started with these new values of voltage magnitudes and phase angles. à ¢- The procedure is continued until the required tolerance is achieved. This is generally 0.1kW and 0.1 kvar. Fig 2.4 Flow chart for NR method of load flow for PQ buses. Fig.2.5Flow chart for NR method of load flow for PV buses 2.3.5 Impact Loads and Motor Starting Load flow presents a frozen picture of the distribution system at a given instant, depending on the load demand. While no idea of the transients in the system for a sudden change in load application or rejection or loss of a generator or tie-line can be obtained, a steady-state picture is presented for the specified loading conditions. Each of these transient events can be simulated as the initial starting condition, and the load flow study rerun as for the steady-state case. Suppose a generator is suddenly tripped. Assuming that the system is stable after this occurrence, we can calculate the redistribution of loads and bus voltages by running the load flow calculations afresh, with generator 4 omitted. Similarly, the effect of an outage of a tie-line, transformer, or other system component can be studied. Table 2-2 Representation of Load Models in Load Flow 3. Conclusion Load flow is a solution of the steady-state operating conditions of a power system. It presents a frozen picture of a scenario with a given set of conditions and constraints. This can be a limitation, as the power systems operations are dynamic. In an industrial distribution system the load demand for a specific process can be predicted fairly accurately and a few load flow calculations will adequately describe the system. For bulk power supply, the load demand from hour to hour is uncertain, and winter and summer load flow situations, though typical, are not adequate. A moving picture scenario could be created from static snapshots, but it is rarely adequate in large systems having thousands of controls and constraints. Thus, the spectrum of load flow (power flow) embraces a large area of calculations, from calculating the voltage profiles and power flows in small systems to problems of on-line energy management and optimization strategies in interconnected large power systems. By the load flow studies which performed using digital computer simulations. I have a main idea of how a power networks power flow calculation operation, planning, running, and development of control strategies. Applied to large systems for optimization, security, and stability, the algorithms become complex and involved. While the study I have done above just a small part of the research and I think the treatment of load flow, and finally optimal power flow, will unfold in my following study.

J. D. Salinger :: Biography Biographies Essays

J. D. Salinger Biographer Ian Hamilton notes that J. D. Salinger has been notoriously "famous for not wanting to be famous" (4). Born in New York in 1919 and still living today, Salinger leads a rather reclusive lifestyle, choosing to avoid the general attentions of the press, and thus making his life a difficult subject for study. His work, however, has been cherished and studied for many years. He has published many works of fiction both in book form and in magazines such as the New Yorker and Esquire. One of his most intriguing novels is Franny and Zooey, which is actually composed of two short stories bearing those names. It is one of several of Salinger's works involving the Glass family, specifically Franny and her brother Zachary, known in the family as Zooey. "Franny" relates the manner in which she arrives by train to spend an afternoon with her boyfriend Lane, whom she has not seen for some time. Lane is by nature a repressive person, one who, waiting for a train, intentionally tries to "empty his face of all expression that might quite simply, perhaps even beautifully, reveal how he felt about the arriving person" (7). It beautifully and honestly illustrates the nature of their relationship, which is far less than perfect. In the wake of the suicide of her brother Seymour (which readers can learn more about in "A Perfect Day for Bananafish" included in Nine Stories'), Franny searches for spiritual meaning in her life. Her tool in this quest is a book entitled The Way of a Pilgrim, and in following the teachings of this book, she begins to consider the lack of meaning in some of her relationships, which, in this story, alienates Lane. The majority of the story focuses on their dinner conversation, and the tension which develops between the couple is well handled by Salinger; for example, when Franny begins acting strangely, Lane "looked at her, then exhaled an overly expressive stream of smoke down at his plate. 'This is going to be a real little doll of a weekend,' he said" (24). Eventually, out of mental exhaustion, Franny passes out in the restaurant, "Zooey" picks up where "Franny" leaves off; she has been sick as a result of her increasing self-neglect. The reader meets Zooey, who spends the greater part of the story discussing with Franny her condition. Franny reveals the main point of The Way of a Pilgrim, which is to repeat the Jesus Prayer incessantly until it becomes as natural and constant a bodily process as breathing.

Silas Marner :: essays research papers

In the book Silas Marner, written by George Elliot, many important themes are presented. It deals with things such as greed, prejudice, superstition, love, isolation and others. All the characters have different traits and all fit in to these themes. Prejudice is the most prevalent theme, in this book. All of the people in Ravelo were extremely prejudice against outsiders. Here are three characters that were victims of prejudice. First, there’s Slilas Marner, an old miser. His only joy in life is to sit at home and count his money. He moved to a town called Ravelo from his hometown of Lantern Yard. He was forced to do so because the people of Lantern Yard falsely accused him of a crime. When Silas arrived in Ravelo, the people looked at him as if he was inhuman. Silas suffered from epileptic fits. Also he liked to stay indoors and count his money. The towns’ people thought that these were signs that he consorted with the devil. When Silas’ money was stolen one night, he went to the Rainbow, a neighborhood hang out, to report the crime. After that episode, the towns’ people started to come around a little and began to talk with Silas on occasion. Dolly Winthrop was one of these people, and actually became good friends with Silas. When Eppie came along to Silas, people didn’t think he would be a suitable parent. Dolly stood up for Silas and said that he would make a fine paren t. Just because Silas was a little eccentric, people looked down upon him as though he was not good enough for them to be around. Then there was Molly. She was Godfrey Cass’ wife. She was to be kept secret from everyone, especially Squire Cass. If he ever found out that Godfrey had been married to her all along he would disown him. Molly was addicted to opium; therefore she was not worthy enough to be married to Godfrey Cass â€Å"the good son†. Molly had a daughter by Godfrey, who was also to be kept a secret. When molly overdosed on New Years Eve, the baby fell out of he arms and wandered in to Silas’ house. The light drew her in. When he later found her sitting by the hearth of the fire, he decided that he would keep her and name her Eppie after his sister. Finally there’s the peddler who was accused of stealing Silas’ money.

Article Critique Essay

The thought that peer exclusion is correlated with children’s classroom achievements and adjustment has been hypothesized since the 1930’s. Much research and empirical evidence for such hypotheses have since been collected, and seem to agree with the premise of the correlation. Peer acceptance is the main measurement of this study. In contrast with other types of peer relationships, peer group acceptance, or rejection, is strongly connected with academic readiness and achievement. This article focuses on peer sentiments and its effect on children’s adjustment. It differs from past studies in that its approach is to measure non-observable feelings about classmates, rather than only the observable interactions. The article begins by outlining past research, and developing a premise for the study from those previous studies. The main study that this research builds upon is that of a 2001 study by Eric S. Buhs and Gary W. Ladd, who also conduct this study along with Sarah L. Herald. The premise of the study, based on the 2001 study, is that once classmates express negative feelings and actions upon a peer, those feelings and actions act as a visible marker for further rejection by the larger peer group, and the rejected child as well; as a result, the rejected peers are flagged by their peers, and are left out of classroom interactions, and as a consequence, the rejected child’s learning is impacted ultimately leading to lower levels of achievement (Buhs, Ladd, and Herald, 2006, p. 2). The prior 2001 study found that â€Å"early peer rejection was negatively related to later achievement and that this association was partially mediated through peer maltreatment and declining classroom participation, respectively† (Buhs et al. , 2006, p. 2). The authors developed a hypothesis that built upon their previous study. Their hypothesis was stated as, â€Å"it was hypothesized that prolonged peer maltreatment increases the probability that children will disengage from classrooms (or the school context) and that increasing disengagement impairs children’s achievement. Thus, it was predicted that longer rather than shorter histories of peer maltreatment, after controlling for contemporary exclusion or abuse, would mediate the link between early peer rejection and later classroom disengagement† (Buhs et al. , 2006, p. 3). The authors further state that their purpose for conducting this study was to bridge the gap between the limitations of the previous study (it was only a one year study that attempted to predict students future outcomes) by conducting a more comprehensive longitudinal study over a six year period (kindergarten through fifth grade). Methodology The research study constructed six variables to measure the children with. They include, peer group acceptance/rejection, peer exclusion, peer abuse, classroom participation, school avoidance, and achievement. Peer group acceptance/rejection was conceptualized to mean â€Å"the extent to which individuals were liked/ disliked by classroom peers,† and operationalized by sociometric ratings that were collected from peers during kindergarten. One problem with this operationalization is the ability to comprehensively scale the true feelings of one peer toward another, especially during younger years. Scales, questionnaires, and observations might be too incomplete to capture the true meaning behind the dynamics of peer to peer interactions. Another issue is of how to evaluate separate peer groups. Many times classrooms encompass only a selection of developed peer groupings throughout the grade, and might be unfairly balanced toward one group. An example of groupings would be defined by the terms, â€Å"popular,† â€Å"punk,† or â€Å"nerds. † The research might be biased toward one group, if only because they were over represented in a class room. The variable Peer Exclusion was conceptualized as â€Å"the extent to which children were the target of peers’ nonaggressive rejecting behaviors, including behaviors such as ignoring, avoiding, or refusing to associate with them in the classroom context† (Buhs et al. , 2006, p. 3). The Variable Peer Abuse—the second form of peer mistreatment—was conceptualized to mean â€Å"the extent to which children were recipients of classmate’s aggressive and harassing behaviors† (Buhs et al. , 2006, p. 3). These two variables contained indicators to distinguish between chronic peer abuse, and situational peer abuse. Again, the issue that arises is the effectiveness of these measures. The interactions between childhood peers are complex, and can change daily. The variables Classroom Participation, and School Avoidance were used to measure disengagement from the classroom environment. A large issue with this is how to distinguish individuals who might be avoiding class as an outcome of separate circumstances. If poor participation and avoidance was only observed from the angle of peer interactions, then this view is biased toward the study. The study is seeking a correlation, and if outside factors aren’t controlled for, then they will biasly effect the results of their study. A child’s family life, neighborhood, economic status, innate ability, among other factors, could influence all of the variables that this study examines. The last variable, Achievement, was defined as â€Å"the accuracy with which children could solve progressively more advanced reading, mathematics, and spelling problems on an individualized achievement test† (Buhs et al. , 2006, p. 4). The issue that comes to mind with this variable is the way it uses tests to gauge â€Å"achievement†. Some students fare better on tests than others, while some students take time to develop adequate test taking skills. Another problem is how to control for separate curriculums in different classrooms, and the quality of what is being taught. Data (From the text) Buhs et al. , 2006, p. 5 Participants The data used in this investigation were gathered from a total sample of 380 children (190 girls These children were followed longitudinally from age 5 (kindergarten) to age 11 (fifth grade31 kindergarten class rooms across 10 schools, and by the fifth-grade data collection period, children were in 162 different classrooms across 32 schools. The sample contained nearly equal proportions of families from urban, suburban, or rural midwestern communities, and the sample’s ethnic composition was 17. 4% African American, 77. 1% Caucasian, 1. 6% Hispanic, and 3. 9% â€Å"other. † Family incomes were distributed as follows: 10. 9% of the sample reported total household incomes from $0 to $10,000, 10. 9% reported incomes from $10,000 to $20,000, 12. 6% reported incomes from $20,000 to $30,000, 12. 6% from $30,000 to $40,000, 12. 9% from $40,000 to $50,000, and 40. 3% reported incomes above $50,000. Results The study reports it’s results as, â€Å"peer group rejection is predictive of a range of chronic, negative peer behaviors that may alter both the social environment of the classroom and children’s adaptive responses within that context across the elementary school years. † (Buhs et al. , 2006, p. 11). It suggests that the facet of peer exclusion leading to reduced participation, and ultimately delayed achievements needs further study. It goes on to say that with further study, and thus more knowledge, an empirically based intervention program can be developed. Conclusion It can be argued that to have a complete understanding of the ever evolving and complex world of the social interactions in a school environment is close to impossible. The authors came into their study with a set premise, and expectations of the outcomes, and have seemed to found what they were searching for. The question becomes, how valid are the author’s findings, and can they be applied in a general manner across learning environments. I believe studies that look at complex interactions between children over several years, such as this study, might have too many outside interactionary forces that could effect the data and results. Works Cited Buhs, Eric S. , Ladd, Gary W. , and Herald, Sarah L. (2006). Peer Exclusion and Victimization: Processes That Mediate the Relation Between Peer Group Rejection and Children’s Classroom Engagement and Achievement?. journal of Educational Psychology 2006, Vol. 98, No. 1, 1–13.