Study of the longitudinal distribution of power generated in a random distributed feedback Raman fibre laser with unidirectional pumping

The longitudinal distribution of the Stokes-component power in a Raman fibre laser with a random distributed feedback and unidirectional pumping is measured. The fibre parameters (linear loss and Rayleigh backscattering coefficient) are calculated based on the distributions obtained. A numerical model is developed to describe the lasing power distribution. The simulation results are in good agreement with the experimental data. © 2012 Kvantovaya Elektronika and Turpion Ltd.

Biomass fast pyrolysis energy balance of a 1kg/h test rig

The present paper offers a methodological approach towards the estimation and definition of enthalpies constituting an energy balance around a fast pyrolysis experiment conducted in a laboratory scale fluid bed with a capacity of 1 kg/ h. Pure N2 was used as fluidization medium at atmospheric pressure and the operating temperature (∼500°C) was adjusted with electrical resistors. The biomass feedstock type that was used was beech wood. An effort was made to achieve a satisfying 92.5% retrieval of products (dry basis mass balance) with the differences mainly attributed to loss of some bio-oil constituents into the quenching medium, ISOPAR™. The chemical enthalpy recovery for bio-oil, char and permanent gases is calculated 64.6%, 14.5% and 7.1%, respectively. All the energy losses from the experimental unit into the environment, namely the pyrolyser, cooling unit etc. are discussed and compared to the heat of fast pyrolysis that was calculated at 1123.5 kJ per kg of beech wood. This only represents 2.4% of the biomass total enthalpy or 6.5% its HHV basis. For the estimation of some important thermo-physical properties such as heat capacity and density, it was found that using data based on the identified compounds from the GC/MS analysis is very close to the reference values despite the small fraction of the bio-oil components detected. The methodology and results can help as a starting point for the proper design of fast pyrolysis experiments, pilot and/or industrial scale plants.

Message passing for distributed optimisation of power allocation with renewable resources

The increase in renewable energy generators introduced into the electricity grid is putting pressure on its stability and management as predictions of renewable energy sources cannot be accurate or fully controlled. This, with the additional pressure of fluctuations in demand, presents a problem more complex than the current methods of controlling electricity distribution were designed for. A global approximate and distributed optimisation method for power allocation that accommodates uncertainties and volatility is suggested and analysed. It is based on a probabilistic method known as message passing [1], which has deep links to statistical physics methodology. This principled method of optimisation is based on local calculations and inherently accommodates uncertainties; it is of modest computational complexity and provides good approximate solutions.We consider uncertainty and fluctuations drawn from a Gaussian distribution and incorporate them into the message-passing algorithm. We see the effect that increasing uncertainty has on the transmission cost and how the placement of volatile nodes within a grid, such as renewable generators or consumers, effects it.

School desegregation in Broward County, Florida, 1970--1998: A historical study of power

This is a historical case study on school desegregation and power in Broward County, Florida from 1970 to 1998. The purpose of this study is to describe, explain and analyze types of power used by the School Board of Broward County, Florida and community activists, in their efforts to influence desegregation decisions from 1970 to 1998. In addition, this study explains who benefited and who won from the School Board's desegregation decisions and who governed those decisions? ^ A historical case study approach was used as the method for conducting this study. Data sources included 11 interviews of individuals who were involved in school desegregation issues as either School Board officials or community activists and 10 archival data sources. ^ The theoretical models of Russell, Galbraith, Wartenberg and Domhoff were used to determine the different types of power techniques used by School Board officials and community activists and to answer the questions: who benefited and who won from the School Board's desegregation decisions and who governed those policies and practices? ^ The primary beneficiaries of school desegregation policies and practices in Broward County were: white, affluent communities and the builders, developers, realtors and other businesses in the western suburban communities. All of the data sources indicated that the black community did not benefit from the School Board's desegregation policies. ^ The primary power techniques used by School Board officials to influence desegregation policies and practices was “power over opinions” and compensation. These power techniques were manifested by the School Board publicly disputing the allegations raised by community activists and by compensating those who supported and promoted the School Board's desegregation policies and practices. ^ The power techniques primarily used by community activists were coercive force and “power over opinions.” They effectively used these power techniques to change the School Board's policies and practices they felt were detrimental to black children and the black community. ^ Based on the analysis of the qualitative data, it can be concluded that black children did not benefit from school desegregation in Broward County, Florida and the community continues to suffer residual effects from past desegregation policies and practices. ^

History and evolutionary trajectory of the Iranian nuclear program

What actors and processes at what levels of analysis and through what mechanisms have pushed Iran's nuclear program (INP) towards being designated as a proliferation threat (securitization)? What actors and processes at what levels of analysis and through what mechanisms have pushed Iran's nuclear program away from being designated as an existential threat (de-securitization)? What has been the overall balance of power and interaction dynamics of these opposing forces over the last half-century and what is their most likely future trajectory? ^ Iran's nuclear story can be told as the unfolding of constant interaction between state and non-state forces of "nuclear securitization" and "nuclear de-securitization." Tracking the crisscrossing interaction between these different securitizing and de-securitizing actors in a historical context constitutes the central task of this project. ^ A careful tracing of "security events" on different analytical levels reveals the broad contours of the evolutionary trajectory of INP and its possible future path(s). Out of this theoretically conscious historical narrative, one can make informed observations about the overall thrust of INP along the securitization - de-securitization continuum. ^ The main contributions of this work are three fold: First, it brings a fresh theoretical perspective on Iran's proliferation behavior by utilizing the "securitization" theory tracing the initial indications of the threat designation of INP all the way back to the mid 1970s. Second, it gives a solid and thematically grounded historical texture to INP by providing an intimate engagement with the persons, processes, and events of Tehran's nuclear pursuit over half a century. Third, it demonstrates how INP has interacted with and even at times transformed the NPT as the keystone of the non-proliferation regime, and how it has affected and injected urgency to the international discourse on nuclear proliferation specifically in the Middle East.^

Development of physics-based models and design optimization of power electronic conversion systems

The main objective for physics based modeling of the power converter components is to design the whole converter with respect to physical and operational constraints. Therefore, all the elements and components of the energy conversion system are modeled numerically and combined together to achieve the whole system behavioral model. Previously proposed high frequency (HF) models of power converters are based on circuit models that are only related to the parasitic inner parameters of the power devices and the connections between the components. This dissertation aims to obtain appropriate physics-based models for power conversion systems, which not only can represent the steady state behavior of the components, but also can predict their high frequency characteristics. The developed physics-based model would represent the physical device with a high level of accuracy in predicting its operating condition. The proposed physics-based model enables us to accurately develop components such as; effective EMI filters, switching algorithms and circuit topologies [7]. One of the applications of the developed modeling technique is design of new sets of topologies for high-frequency, high efficiency converters for variable speed drives. The main advantage of the modeling method, presented in this dissertation, is the practical design of an inverter for high power applications with the ability to overcome the blocking voltage limitations of available power semiconductor devices. Another advantage is selection of the best matching topology with inherent reduction of switching losses which can be utilized to improve the overall efficiency. The physics-based modeling approach, in this dissertation, makes it possible to design any power electronic conversion system to meet electromagnetic standards and design constraints. This includes physical characteristics such as; decreasing the size and weight of the package, optimized interactions with the neighboring components and higher power density. In addition, the electromagnetic behaviors and signatures can be evaluated including the study of conducted and radiated EMI interactions in addition to the design of attenuation measures and enclosures.

Effects of Simulated Drought on the Carbon Balance of Everglades Short-Hydroperiod Marsh

Hydrology drives the carbon balance of wetlands by controlling the uptake and release of CO2 and CH4. Longer dry periods in between heavier precipitation events predicted for the Everglades region, may alter the stability of large carbon pools in this wetland's ecosystems. To determine the effects of drought on CO2 fluxes and CH4 emissions, we simulated changes in hydroperiod with three scenarios that differed in the onset rate of drought (gradual, intermediate, and rapid transition into drought) on 18 freshwater wetland monoliths collected from an Everglades short-hydroperiod marsh. Simulated drought, regardless of the onset rate, resulted in higher net CO2 losses net ecosystem exchange (NEE) over the 22-week manipulation. Drought caused extensive vegetation dieback, increased ecosystem respiration (Reco), and reduced carbon uptake gross ecosystem exchange (GEE). Photosynthetic potential measured by reflective indices (photochemical reflectance index, water index, normalized phaeophytinization index, and the normalized difference vegetation index) indicated that water stress limited GEE and inhibited Reco. As a result of drought-induced dieback, NEE did not offset methane production during periods of inundation. The average ratio of net CH4 to NEE over the study period was 0.06, surpassing the 100-year greenhouse warming compensation point for CH4 (0.04). Drought-induced diebacks of sawgrass (C3) led to the establishment of the invasive species torpedograss (C4) when water was resupplied. These changes in the structure and function indicate that freshwater marsh ecosystems can become a net source of CO2 and CH4 to the atmosphere, even following an extended drought. Future changes in precipitation patterns and drought occurrence/duration can change the carbon storage capacity of freshwater marshes from sinks to sources of carbon to the atmosphere. Therefore, climate change will impact the carbon storage capacity of freshwater marshes by influencing water availability and the potential for positive feedbacks on radiative forcing.

Physics-based modeling of power system components for the evaluation of low-frequency radiated electromagnetic fields

The low-frequency electromagnetic compatibility (EMC) is an increasingly important aspect in the design of practical systems to ensure the functional safety and reliability of complex products. The opportunities for using numerical techniques to predict and analyze system's EMC are therefore of considerable interest in many industries. As the first phase of study, a proper model, including all the details of the component, was required. Therefore, the advances in EMC modeling were studied with classifying analytical and numerical models. The selected model was finite element (FE) modeling, coupled with the distributed network method, to generate the model of the converter's components and obtain the frequency behavioral model of the converter. The method has the ability to reveal the behavior of parasitic elements and higher resonances, which have critical impacts in studying EMI problems. For the EMC and signature studies of the machine drives, the equivalent source modeling was studied. Considering the details of the multi-machine environment, including actual models, some innovation in equivalent source modeling was performed to decrease the simulation time dramatically. Several models were designed in this study and the voltage current cube model and wire model have the best result. The GA-based PSO method is used as the optimization process. Superposition and suppression of the fields in coupling the components were also studied and verified. The simulation time of the equivalent model is 80-100 times lower than the detailed model. All tests were verified experimentally. As the application of EMC and signature study, the fault diagnosis and condition monitoring of an induction motor drive was developed using radiated fields. In addition to experimental tests, the 3DFE analysis was coupled with circuit-based software to implement the incipient fault cases. The identification was implemented using ANN for seventy various faulty cases. The simulation results were verified experimentally. Finally, the identification of the types of power components were implemented. The results show that it is possible to identify the type of components, as well as the faulty components, by comparing the amplitudes of their stray field harmonics. The identification using the stray fields is nondestructive and can be used for the setups that cannot go offline and be dismantled

Feasts of power : how food reveals Eve's influential role in John Milton's epic poem, "Paradise Lost"

This writing explores how food in Paradise Lost reflects Eve's power in the story of man's (and woman's) fall from grace. Critics often emphasize Adam in Paradise Lost; however, I challenge the notion of the first man as the most influential character of the poem. By examining Eve's role and her abilities with food, one sees the first woman as a well-rounded, complete being, albeit the first to succumb to temptation. Notwithstanding her transgression, -- certainly no trivial act of disobedience -- Eve should be viewed at least as Adam's equal, if not his superior. Her uncanny understanding of matters related to food points to skills Adam does not enjoy, and even Milton acknowledges Eve's importance in this arena. By studying the food in this epic, we see Eve sheds much light on all the other elements of Paradise Lost, and her personal strengths become obvious.

China's Building of a Blue-Water Fleet

In recent years the People’s Republic of China has begun to exhibit a more aggressive naval policy as a result of its decision to switch its naval force from a primarily green-water fleet (coastal) to a blue-water fleet (expeditionary) (“China’s New,” n.d.). This decision has brought China to loggerheads not only with other local East and South Asian powers such as India and Japan, but also with the predominant blue-water power of the world, the United States, that sees its supremacy threatened (“When Grand,” n.d.). Why would China embark on a route that would pit it against the world naval superpower, the United States, which has a huge lead on China in terms of naval blue-water power? Why would China try to challenge and match the U.S. Navy’s eleven aircraft carriers (“The World’s,” n.d.)? What could compel China to embark on a plan that would so disrupt the balance of power in the waters around Asia? To fully understand the Chinese government’s decision, one must first look at Chinese import figures and Chinese trade routes.

School desegregation in Broward County, Florida 1970-1998 : a historical study of power

This is a historical case study on school desegregation and power in Broward County, Florida from 1970 to 1998. The purpose of this study is to describe, explain and analyze types of power used by the School Board of Broward County, Florida and community activists, in their efforts to influence desegregation decisions from 1970 to 1998. In addition, this study explains who benefited and who won from the School Board's desegregation decisions and who governed those decisions? A historical case study approach was used as the method for conducting this study. Data sources included 11 interviews of individuals who were involved in school desegregation issues as either School Board officials or community activists and 10 archival data sources. The theoretical models of Russell, Galbraith, Wartenberg and Domhoff were used to determine the different types of power techniques used by School Board officials and community activists and to answer the questions: who benefited and who won from the School Board's desegregation decisions and who governed those policies and practices? The primary beneficiaries of school desegregation policies and practices in Broward County were: white, affluent communities and the builders, developers, realtors and other businesses in the western suburban communities. All of the data sources indicated that the black community did not benefit from the School Board's desegregation policies. The primary power techniques used by School Board officials to influence desegregation policies and practices was "power over opinions" and compensation. These power techniques were manifested by the School Board publicly disputing the allegations raised by community activists and by compensating those who supported and promoted the School Board's desegregation policies and practices. The power techniques primarily used by community activists were coercive force and "power over opinions." They effectively used these power techniques to change the School Board's policies and practices they felt were detrimental to black children and the black community. Based on the analysis of the qualitative data, it can be concluded that black children did not benefit from school desegregation in Broward County, Florida and the community continues to suffer residual effects from past desegregation policies and practices.

Cascade failure analysis of power grid using new load distribution law and node removal rule

The work is supported in part by NSFC (Grant no. 61172070), IRT of Shaanxi Province (2013KCT-04), EPSRC (Grant no.Ep/1032606/1).

Cascade failure analysis of power grid using new load distribution law and node removal rule

The work is supported in part by NSFC (Grant no. 61172070), IRT of Shaanxi Province (2013KCT-04), EPSRC (Grant no.Ep/1032606/1).

From ‘poor parenting’ to micro-management:coalition governance and the sponsorship of arm’s-length bodies in the United Kingdom, 2010–13

The delegation of public tasks to arm’s-length bodies remains a central feature of contemporary reform agendas within both developed and developing countries. The role and capacity of political and administrative principals (i.e. ministers and departments of state) to control the vast network of arm’s-length bodies for which they are formally responsible is therefore a critical issue within and beyond academe. In the run-up to the 2010 General Election in the United Kingdom, the ‘quango conundrum’ emerged as an important theme and all three major parties committed themselves to shift the balance of power back towards ministers and sponsor departments. This article presents the results of the first major research project to track and examine the subsequent reform process. It reveals a stark shift in internal control relationships from the pre-election ‘poor parenting’ model to a far tighter internal situation that is now the focus of complaints by arm’s-length bodies of micro-management. This shift in the balance of power and how it was achieved offers new insights into the interplay between different forms of governance and has significant theoretical and comparative relevance. Points for practitioners: For professionals working in the field of arm’s-length governance, the article offers three key insights. First, that a well-resourced core executive is critical to directing reform given the challenges of implementing reform in a context of austerity. Second, that those implementing reform will also need to take into account the diverse consequences of centrally imposed reform likely to result in different departments with different approaches to arm’s-length governance. Third, that reforming arm’s-length governance can affect the quality of relationships, and those working in the field will need to mitigate these less tangible challenges to ensure success.