Bifurcation analysis of a dynamic power system with SVC devices

Bifurcation analysis is a very useful tool for power system stability assessment. In this paper, detailed investigation of power system bifurcation behaviour is presented. One and two parameter bifurcation analysis are conducted on a 3-bus power system. We also examined the impact of FACTS devices on power system stability through Hopf bifurcation analysis by taking static Var compensator (SVC) as an example. A simplified first-order model of the SVC device is included in the 3-bus sample system. Real and reactive powers are used as bifurcation parameter in the analysis to compare the system oscillatory properties with and without SVC. The simulation results indicate that the linearized system model with SVC enlarge the voltage stability boundary by moving Hopf bifurcation point to higher level of loading conditions. The installation of SVC increases the dynamic stability range of the system, however complicates the Hopf bifurcation behavior of the system

A real options based method for power system planning

A deregulated electricity market is characterized with uncertainties, with both long and short terms. As one of the major long term planning issues, the transmission expansion planning (TEP) is aiming at implementing reliable and secure network support to the market participants. The TEP covers two major issues: technical assessment and financial evaluations. Traditionally, the net present value (NPV) method is the most accepted for financial evaluations, it is simple to conduct and easy to understand. Nevertheless, TEP in a deregulated market needs a more dynamic approach to incorporate a project's management flexibility, or the managerial ability to adapt in response to unpredictable market developments. The real options approach (ROA) is introduced here, which has clear advantage on counting the future course of actions that investors may take, with understandable results in monetary terms. In the case study, a Nordic test system has been testified and several scenarios are given for network expansion planning. Both the technical assessment and financial evaluation have been conducted in the case study.

Power generation investment opportunities evaluation: A comparison between net present value and real options approach

To evaluate an investment project in the competitive electricity market, there are several key factors that affects the project's value: the present value that the project could bring to investor, the possible future course of actions that investor has and the project's management flexibility. The traditional net present value (NPV) criteria has the ability to capture the present value of the project's future cash flow, but it fails to assess the value brought by market uncertainty and management flexibility. By contrast with NPV, the real options approach (ROA) method has the advantage to combining the uncertainty and flexibility in evaluation process. In this paper, a framework for using ROA to evaluate the generation investment opportunity has been proposed. By given a detailed case study, the proposed framework is compared with NPV and showing a different results

Perceptions of earnings management:the effect of national culture

Manipulating, or "managing," reported earnings is a temptation faced by every accountant and corporation around the world. This study investigates whether national culture influences perceptions of the acceptability of earnings management. Participants from eight countries evaluated 13 vignettes describing various earnings management practices (Merchant & Rockness, 1994). Our results demonstrate considerable variation in perceptions across nations to the earnings management scenarios, providing strong evidence that the practice of earnings management was not perceived similarly in all countries. Using Hofstede’s (1991) cultural indices, we find that the differences in aggregate perceptions across countries were not closely associated with any of the cultural dimensions examined. We do, however, find that perceptions of earnings manipulations involving the timing of operating decisions were associated with both the Power Distance Index and the Masculinity Index.

Role of power jitter induced by interchannel interactions in dispersion-managed lines

Collision induced power jitter is examined in dispersion-managed wavelength division-multiplexed transmission systems. The power jitter causes ’ a serious problem for a singly-periodic dispersion managed line having almost zero average dispersion, which can be reduced by applying doubly-periodic dispersion management.

Analysis of power jitter induced by interchannel interactions in dispersion-managed optical soliton transmission systems

Collision-induced power jitter is theoretically and numerically examined in dispersion-managed wavelength-division-multiplexed optical soliton transmission systems. The variational method is mainly used to develop a time efficient jitter calculation approach. The power jitter causes a serious problem for a singly periodic dispersion managed line having almost zero average dispersion, which can be reduced by applying doubly periodic dispersion management.

The Proinflammatory Environment in Potential Heart and Lung Donors: Prevalence and Impact of Donor Management and Hormonal Therapy

BACKGROUND: Brain stem death can elicit a potentially manipulable cardiotoxic proinflammatory cytokine response. We investigated the prevalence of this response, the impact of donor management with tri-iodothyronine (T3) and methylprednisolone (MP) administration, and the relationship of biomarkers to organ function and transplant suitability. METHODS: In a prospective randomized double-blinded factorially designed study of T3 and MP therapy, we measured serum levels of interleukin-1 and -6 (IL-1 and IL-6), tumor necrosis factor-alpha (TNF-alpha), C-reactive protein, and procalcitonin (PCT) levels in 79 potential heart or lung donors. Measurements were performed before and after 4 hr of algorithm-based donor management to optimize cardiorespiratory function and +/-hormone treatment. Donors were assigned to receive T3, MP, both drugs, or placebo. RESULTS: Initial IL-1 was elevated in 16% donors, IL-6 in 100%, TNF-alpha in 28%, CRP in 98%, and PCT in 87%. Overall biomarker concentrations did not change between initial and later measurements and neither T3 nor MP effected any change. Both PCT (P =0.02) and TNF-alpha (P =0.044) levels were higher in donor hearts with marginal hemodynamics at initial assessment. Higher PCT levels were related to worse cardiac index and right and left ventricular ejection fractions and a PCT level more than 2 ng x mL(-1) may attenuate any improvement in cardiac index gained by donor management. No differences were observed between initially marginal and nonmarginal donor lungs. A PCT level less than or equal to 2 ng x mL(-1) but not other biomarkers predicted transplant suitability following management. CONCLUSIONS: There is high prevalence of a proinflammatory environment in the organ donor that is not affected by tri-iodothyronine or MP therapy. High PCT and TNF-alpha levels are associated with donor heart dysfunction. (C) 2009 Lippincott Williams & Wilkins, Inc.

Reactive oxygen and nitrogen species production in cardiomyoblasts during hypoxia and reoxygenation

Hypoxia is a stress condition in which tissues are deprived of an adequate O2 supply; this may trigger cell death with pathological consequences in cardiovascular or neurodegenerative disease. Reperfusion is the restoration of an oxygenated blood supply to hypoxic tissue and can cause more cell injury. The kinetics and consequences of reactive oxygen and nitrogen species (ROS/RNS) production in cardiomyoblasts are poorly understood. The present study describes the systematic characterization of the kinetics of ROS/RNS production and their roles in cell survival and associated protection during hypoxia and hypoxia/reperfusion. H9C2 cells showed a significant loss of viability under 2% O2 for 30min hypoxia and cell death; associated with an increase in protein oxidation. After 4h, apoptosis induction under 2% O2 and 10% O2 was dependent on the production of mitochondrial superoxide (O2-•) and nitric oxide (•NO), partly from nitric oxide synthase (NOS). Both apoptotic and necrotic cell death during 2% O2 for 4h could be rescued by the mitochondrial complex I inhibitor; rotenone and NOS inhibitor; L-NAME. Both L-NAME and the NOX (NADPH oxidase) inhibitor; apocynin reduced apoptosis under 10% O2 for 4h hypoxia. The mitochondrial uncoupler; FCCP significantly reduced cell death via a O2-• dependent mechanism during 2% O2, 30min hypoxia. During hypoxia (2% O2, 4h)/ reperfusion (21% O2, 2h), metabolic activity was significantly reduced with increased production of O2-• and •NO, during hypoxia but, partially restored during reperfusion. O2-• generation during hypoxia/reperfusion was mitochondrial and NOX- dependent, whereas •NO generation depended on both NOS and non-enzymatic sources. Inhibition of NOS worsened metabolic activity during reperfusion, but did not effect this during sustained hypoxia. Nrf2 activation during 2% O2, a sustained hypoxia and reperfusion was O2-•/•NO dependent. Inhibition of NF-?B activation aggravated metabolic activity during 2% O2, 4h hypoxia. In conclusion, mitochondrial O2-•, but, not ATP depletion is the major cause of apoptotic and necrotic cell death in cardiomyoblasts under 2% O2, 4h hypoxia, whereas apoptotic cell death under 10% O2, 4h, is due to NOS-dependent •NO. The management of ROS/RNS rather than ATP is required for improved survival during hypoxia. O2-• production from mitochondria and NOS is cardiotoxic during hypoxia/reperfusion. NF-?B activation during hypoxia and NOS activation during reperfusion is cardiomyoblast protective.

An exploratory study of management accounting and control systems in a developing country

This thesis reports on the results of case studies in four commercial banks in Nigeria. The study focuses how management accounting and control systems (MCS) operate in the four banks. The study is motivated by the dearth of literature on management accounting practices in the developing world in general and in Nigeria in specific. The case study approach adopted in conducting the research was useful in exploring the dynamics of the MCS in the organisations. Data was gathered from two sources. First, semi-structured interviews were conducted with managers at the head office, regional office and branches of each bank. The participants were selected from different backgrounds and managerial levels to provide broader understanding of the operations of the MCS. Second, various internal and external documents were reviewed to provide supporting evidence for the interview results. New institutional sociology (NIS) provided the theoretical framework to understand the results. NIS provided explanations for how the MCS in the four banks were shaped by diverse external and internal factors. The key factors identified as shaping the operations of the MCS were the need to comply with the regulatory environment (coercive isomorphism), the need to maintain social and cultural support (normative isomorphism) and the need to imitate successful organisations in order to appear legitimate (mimetic isomorphism). The study also examines the interplay between the institutional forces, market forces and infra-organisational power relations. This analysis is necessary to overcome the criticism of NIS that it downplays the role of market forces, agency and intra-organisational relations. The findings of the study have implications for understanding the operations of MCS in the developing world.

The dynamics of organizational change : an analysis of power, professions and new managerialism in the case of CoastElectric

It is widely accepted that the Thatcher years and their immediate aftermath were associated with substantive social and organizational change. The privatisation programme, 'the rolling back of the State', prosecuted by the successive Conservative Governments from 1979-1997 was a central pillar of Governmental policy. This thesis seeks to engage with privatization through the of CoastElectric, a newly privatised Regional Electricity Company. This thesis contributes to the extant understanding of the dynamics of organizational change in four major ways. Firstly, the study into CoastElectric addresses the senior management decision making within the organization: in particular, it will attempt to make sense of 'why' particular decisions were made. The theoretical backdrop to this concern will draw on the concepts of normalization, cultural capital and corporate fashion. The argument presented in this thesis is that the decision-making broadly corresponded with that which could be considered to be at the vanguard of mangerialist thought. However, a detailed analysis suggested that at different junctures in CoastElectric's history there were differences in the approach to decision making that warranted further analysis. The most notable finding was that the relative levels of new managerialist cultural capital possessed by the decision-making elite had an important bearing upon whether the decision was formulated either endogenously or exogenously, with the assistance of cultural intermediaries such as management consultants. The thesis demonstrates the importance of the broader discourse of new managerialism in terms of shaping what is considered to be a 'commonsensical, rational' strategy. The second concern of this thesis is that of the process of organizational change. The study of CoastElectric attempts to provide a rich account of the dynamics of organizational change. This is realized through, first, examining the pre-existing context of the organization; second, through analyzing the power politics of change interventions. The master concepts utilised in this endeavour are that of: dividing practices, the establishment of violent hierarchies between competing discourses; symbolic violence; critical turning points; recursiveness; creative destruction; legitimation strategies and the reconstitution of subjects in the workplace.

Does stakeholder orientation matter? : empirical evidence about power and influence in local government decision-making

Despite being in the business agenda for almost thirty years, stakeholder management is still an under explored field in the public management context. The investigation presented in this doctoral thesis aims to ensure that stakeholder management is a useful technique able to raise issues about power and interests to public organisation’s strategic management processes. Stakeholder theory is tested in an exploratory study carried out with English Local Authorities whose focus is place on decision-making. The findings derive from two distinct and complementary studies: a cross-sectional survey undertaken with chief executives based on the quantitative approach and a qualitative investigation based on cross-sectional case studies and in-depth interviews of validation. While the first study aimed to produce a reliable and comprehensive list of stakeholders able to raise issues in decision-making, the second study aimed to depict the arena in which decision-making comes about. The findings indicate that local government decision-making is a multistakeholder process in which influences are exerted according to stakeholders’ power and interest. The findings also indicate that local government managers should take into account these tissues to avoid losing resources and legitimacy from its environmental supporters. Another issue raised by the investigation is related to the ethics upon which these types of relationships are based. According to the evidence gathered throughout the investigation, the formal model of accountability does not cover the whole set of stakeholders engaged in the process.