Multiobjective design optimization of IGBT power modules considering power cycling and thermal cycling

Insulated-gate bipolar transistor (IGBT) power modules find widespread use in numerous power conversion applications where their reliability is of significant concern. Standard IGBT modules are fabricated for general-purpose applications while little has been designed for bespoke applications. However, conventional design of IGBTs can be improved by the multiobjective optimization technique. This paper proposes a novel design method to consider die-attachment solder failures induced by short power cycling and baseplate solder fatigue induced by the thermal cycling which are among major failure mechanisms of IGBTs. Thermal resistance is calculated analytically and the plastic work design is obtained with a high-fidelity finite-element model, which has been validated experimentally. The objective of minimizing the plastic work and constrain functions is formulated by the surrogate model. The nondominated sorting genetic algorithm-II is used to search for the Pareto-optimal solutions and the best design. The result of this combination generates an effective approach to optimize the physical structure of power electronic modules, taking account of historical environmental and operational conditions in the field.

Through the prisms of gender and power: Agency in international courtship between Colombian women and American men

Since 1999 Colombia has experienced dramatic increases in emigration, particularly the emigration of women towards the U.S. as fiancées of U.S. citizens or residents. Parallel to this trend is the increased number of websites facilitating these Colombian-American matches. This dissertation investigates the agency of Colombian women and American men who pursue romantic courtship through the services of International Marriage Brokers (IMBs) from the “Gendered Geographies of Power��� (GGP) framework of analysis. It examines how both groups’ social locations, their positioning in multiple axes of differentiation including gender, nationality and social class, affects how and why they exert their agency across and within different geographic scales. Most importantly, it investigates the role the imagination plays (imagination work) in both men and women’s agency, an aspect of the GGP framework that has been under-researched and theorized to date. The research also finds that this imagination work is promoted and cultivated in deeply gendered ways by IMBs seeking to profit off this transnational courtship. ^ Employing data collected via interviews and content analysis of IMBs’ websites, the dissertation analyzes comparatively the expectations each group (women, men and IMBs) bring to their imagination work and experiences of the courtship marketplace. A central question posed and answered in the dissertation is “What do women and men courting each other in cyberspace seek and do they find it?” The dissertation finds that the men seek “traditional” women and the women seek “liberated” less “macho” men. Ironically, the men find Colombian women who are among the most “liberated” women in their homeland but who downplay this aspect of themselves in order to strategically find a more modern man and migrate abroad where they expect to find greater personal and professional opportunities.^

Efficiency and power density improvement of grid-connected hybrid renewable energy systems utilizing high frequency-based power converters

High efficiency of power converters placed between renewable energy sources and the utility grid is required to maximize the utilization of these sources. Power quality is another aspect that requires large passive elements (inductors, capacitors) to be placed between these sources and the grid. The main objective is to develop higher-level high frequency-based power converter system (HFPCS) that optimizes the use of hybrid renewable power injected into the power grid. The HFPCS provides high efficiency, reduced size of passive components, higher levels of power density realization, lower harmonic distortion, higher reliability, and lower cost. The dynamic modeling for each part in this system is developed, simulated and tested. The steady-state performance of the grid-connected hybrid power system with battery storage is analyzed. Various types of simulations were performed and a number of algorithms were developed and tested to verify the effectiveness of the power conversion topologies. A modified hysteresis-control strategy for the rectifier and the battery charging/discharging system was developed and implemented. A voltage oriented control (VOC) scheme was developed to control the energy injected into the grid. The developed HFPCS was compared experimentally with other currently available power converters. The developed HFPCS was employed inside a microgrid system infrastructure, connecting it to the power grid to verify its power transfer capabilities and grid connectivity. Grid connectivity tests verified these power transfer capabilities of the developed converter in addition to its ability of serving the load in a shared manner. In order to investigate the performance of the developed system, an experimental setup for the HF-based hybrid generation system was constructed. We designed a board containing a digital signal processor chip on which the developed control system was embedded. The board was fabricated and experimentally tested. The system's high precision requirements were verified. Each component of the system was built and tested separately, and then the whole system was connected and tested. The simulation and experimental results confirm the effectiveness of the developed converter system for grid-connected hybrid renewable energy systems as well as for hybrid electric vehicles and other industrial applications.

A hermeneutic phenomenology of graduate education students' understandings of instructor power in a higher education classroom

Higher education is a distribution center of knowledge and economic, social, and cultural power (Cervero & Wilson, 2001). A critical approach to understanding a higher education classroom begins with recognizing the instructor's position of power and authority (Tisdell, Hanley, & Taylor, 2000). The power instructors wield exists mostly unquestioned, allowing for teaching practices that reproduce the existing societal patterns of inequity in the classroom (Brookfield, 2000). ^ The purpose of this hermeneutic phenomenological study was to explore students' experiences with the power of their instructors in a higher education classroom. A hermeneutic phenomenological study intertwines the interpretations of both the participants and the researcher about a lived experience to uncover layers of meaning because the meanings of lived experiences are usually not readily apparent (van Manen, 1990). Fifteen participants were selected using criterion, convenience, and snowball sampling. The primary data gathering method were semi-structured interviews guided by an interview protocol (Creswell, 2003). Data were interpreted using thematic reflection (van Manen, 1990). ^ Three themes emerged from data interpretation: (a) structuring of instructor-student relationships, (b) connecting power to instructor personality, and (c) learning to navigate the terrains of higher education. How interpersonal relationships were structured in a higher education classroom shaped how students perceived power in that higher education classroom. Positive relationships were described using the metaphor of family and a perceived ethic of caring and nurturing by the instructor. As participants were consistently exposed to exercises of instructor power in a higher education classroom, they attributed those exercises of power to particular instructor traits rather than systemic exercises of power. As participants progressed from undergraduate to graduate studies, they perceived the benefits of expertise in content or knowledge development as secondary to expertise in successfully navigating the social, cultural, political, and interpersonal terrains of higher education. Ultimately, participants expressed that higher education is not about what you know; it is about learning how to play the game. Implications for teaching in higher education and considerations for future research conclude the study.^

Optimization of wireless power transfer via magnetic resonance in different media

A wide range of non-destructive testing (NDT) methods for the monitoring the health of concrete structure has been studied for several years. The recent rapid evolution of wireless sensor network (WSN) technologies has resulted in the development of sensing elements that can be embedded in concrete, to monitor the health of infrastructure, collect and report valuable related data. The monitoring system can potentially decrease the high installation time and reduce maintenance cost associated with wired monitoring systems. The monitoring sensors need to operate for a long period of time, but sensors batteries have a finite life span. Hence, novel wireless powering methods must be devised. The optimization of wireless power transfer via Strongly Coupled Magnetic Resonance (SCMR) to sensors embedded in concrete is studied here. First, we analytically derive the optimal geometric parameters for transmission of power in the air. This specifically leads to the identification of the local and global optimization parameters and conditions, it was validated through electromagnetic simulations. Second, the optimum conditions were employed in the model for propagation of energy through plain and reinforced concrete at different humidity conditions, and frequencies with extended Debye's model. This analysis leads to the conclusion that SCMR can be used to efficiently power sensors in plain and reinforced concrete at different humidity levels and depth, also validated through electromagnetic simulations. The optimization of wireless power transmission via SMCR to Wearable and Implantable Medical Device (WIMD) are also explored. The optimum conditions from the analytics were used in the model for propagation of energy through different human tissues. This analysis shows that SCMR can be used to efficiently transfer power to sensors in human tissue without overheating through electromagnetic simulations, as excessive power might result in overheating of the tissue. Standard SCMR is sensitive to misalignment; both 2-loops and 3-loops SCMR with misalignment-insensitive performances are presented. The power transfer efficiencies above 50% was achieved over the complete misalignment range of 0°-90° and dramatically better than typical SCMR with efficiencies less than 10% in extreme misalignment topologies.

Through the Prisms of Gender and Power: Agency in International Courtship between Colombian Women and American Men

Since 1999 Colombia has experienced dramatic increases in emigration, particularly the emigration of women towards the U.S. as fiancées of U.S. citizens or residents. Parallel to this trend is the increased number of websites facilitating these Colombian-American matches. This dissertation investigates the agency of Colombian women and American men who pursue romantic courtship through the services of International Marriage Brokers (IMBs) from the “Gendered Geographies of Power��� (GGP) framework of analysis. It examines how both groups’ social locations, their positioning in multiple axes of differentiation including gender, nationality and social class, affects how and why they exert their agency across and within different geographic scales. Most importantly, it investigates the role the imagination plays (imagination work) in both men and women’s agency, an aspect of the GGP framework that has been under-researched and theorized to date. The research also finds that this imagination work is promoted and cultivated in deeply gendered ways by IMBs seeking to profit off this transnational courtship. Employing data collected via interviews and content analysis of IMBs’ websites, the dissertation analyzes comparatively the expectations each group (women, men and IMBs) bring to their imagination work and experiences of the courtship marketplace. A central question posed and answered in the dissertation is “What do women and men courting each other in cyberspace seek and do they find it?” The dissertation finds that the men seek “traditional” women and the women seek “liberated” less “macho” men. Ironically, the men find Colombian women who are among the most “liberated” women in their homeland but who downplay this aspect of themselves in order to strategically find a more modern man and migrate abroad where they expect to find greater personal and professional opportunities.

Use of active power filter to reduce the effects of harmonics in solid oxide fuel cells

The Solid Oxide Fuel Cell (SOFC) is a class of fuel cells that is capable of generating very high levels of power at high temperatures. SOFCs are used for stationary power generation and as Combined Heat and Power (CHP) systems. In spite of all the beneficial features of the SOFC, the propagation of ripple currents, due to nonlinear loads, is a challenging problem, as it interferes with the physical operation of the fuel cell. The purpose of this thesis is to identify the cause of ripples and attempt to eliminate or reduce the ripple propagation through the use of Active Power Filters (APF). To this end, a systematic approach to modeling the fuel cell to account for its nonlinear behavior in the presence of current ripples is presented. A model of a small fuel cell power system which consists of a fuel cell, a DC-DC converter, a single-phase inverter and a nonlinear load is developed in MATLAB/Simulink environment. The extent of ripple propagation, due to variations in load magnitude and frequency, are identified using frequency spectrum analysis. In order to reduce the effects of ripple propagation, an APF is modeled to remove ripples from the DC fuel cell current. The emphasis of this thesis is based on the idea that small fuel cell systems cannot implement large passive filters to cancel the effects of ripple propagation and hence, the compact APF topology effectively protects the fuel cell from propagating ripples and improves its electrical performance.

Pitit se rìches malere [Children are the wealth of the poor]: The Influence of Gender and Power on Choice and Uptake of Long Acting Contraceptives

Background: Haiti has the highest maternal mortality rate in the Latin American and Caribbean region. Despite the fact that Haiti has received twice as much family planning assistance as any other country in the western hemisphere, the unmet need for contraception remains particularly high. Our hypothesis is that unsuccessful efforts of family planning programs may be related to a misconstrued understanding of the complex role of gender in relationships and community in Haiti. This manuscript is one of four parts of a study that intends to examine some of these issues with a particular focus on the influence of uptake and adherence to long acting contraceptive (LAC) methods.

Methods: We conducted a three-month community-based qualitative assessment through 20 in-depth interviews in Fondwa, Haiti. Participants were divided into 4 groups of five: female users, female non-users, men and key community stakeholders.

Results: Based on the qualitative interviews, we found that main barriers included lack of access to family planning education and services and concerns regarding side effects and health risks, especially related to menstrual disruption and fears of infertility. Women have a constant pressure to remain fertile and bear children, due not only to social but also economic needs. As relationships are conceived as means for economic provision, the likelihood of uptake of irreversible methods (vasectomy and tubal ligation) was restricted by loss of fertility. Consequently, the discourse of family planning, though self-recognized in their favor, assumes women can afford not to bear children. This assumption should be questioned given the complexities of the other social determinants at play, all which affect the reproductive decisions made by Haitians.

Conclusions: Overall, our study indicated awareness surrounding contraception in the Haitian Fondwa community. Combining the substantial impact of birth spacing with the elevated yet unmet need for contraceptives in the area, it is necessary to address the intricacies of gender issues in order to implement successful programing. In Haiti not being able to bear a child poses a threat to economic and social survival, possibly explaining a dimension of the low uptake of LACs in the region, even when made available. For this reason, we believe IUDs (Intrauterine Devices) provide a suitable alternative, allowing the couple to comprehend all of the factors involved in decision making, thus decreasing the imbalances of power and knowledge prior to considering an irreversible alternative.

Method to Improve the Conversion Gain Flatness of Transformer-Coupled Mixers

A 4-10 GHz, on-chip balun based current commutating mixer is proposed. Tunable resistive feedback is used at the transconductance stage for wideband response, and interlaced stacked transformer is adopted for good balance of the balun. Measurement results show that a conversion gain of 13.5 dB, an IIP3 of 4 dBm and a noise figure of 14 dB are achieved with 5.6 mW power consumption under 1.2 V supply. The simulated amplitude and phase imbalance is within 0.9 dB and ±2◦ over the band.

Measuring the Diversity and the Integration of Film Production in Mercosur: A Social Network Analysis

Based on an original and comprehensive database of all feature fiction films produced in Mercosur between 2004 and 2012, the paper analyses whether the Mercosur film industry has evolved towards an integrated and culturally more diverse market. It provides a summary of policy opportunities in terms of integration and diversity, emphasizing the limiter role played by regional policies. It then shows that although the Mercosur film industry remains rather disintegrated, it tends to become more integrated and culturally more diverse. From a methodological point of view, the combination of Social Network Analysis and the Stirling Model opens up interesting research tracks to analyse creative industries in terms of their market integration and their cultural diversity.

Narrative Deliberation? On Storytelling as a Necessary Component of Public Deliberation

This paper deals with the place of narrative, that is, storytelling, in public deliberation. A distinction is made between weak and strong conceptions of narrative. According to the weak one, storytelling is but one rhetorical device among others with which social actors produce and convey meaning. In contrast, the strong conception holds that narrative is necessary to communicate, and argue, about topics such as the human experience of time, collective identities and the moral and ethical validity of values. The upshot of this idea is that storytelling should be a necessary component of any ideal of public deliberation. Contrary to recent work by deliberative theorists, who tend to adopt the weak conception of narrative, the author argues for embracing the strong one. The main contention of this article is that stories not only have a legitimate place in deliberation, but are even necessary to formulate certain arguments in the fi rst place; for instance, arguments drawing on historical experience. This claim, namely that narrative is constitutive of certain arguments, in the sense that, without it, said reasons cannot be articulated, is illustrated by deliberative theory’s own narrative underpinnings. Finally, certain possible objections against the strong conception of narrative are dispelled.

The making of professionals: Embedded civil society development in a transition country

The paper addresses the development of non-governmental organisations (NGOs) in transition settings. Caught in the balance of knowledge exchange and translation of ideas from abroad, organisations in turbulent setting legitimise their existence by learning through professional networks. By association, organisational actors gain acknowledgement by their sector by traversing the corridors of influence provided by international partnerships. What they learn is how to conduct themselves as agents of change in society, and how to deliver on stated missions and goals, therefore, legitimising their presence in a budding civil society at home. The paper presents a knowledge production and learning practices framework which indicates a presence of dual identity of NGOs - their “embeddedness” locally and internationally. Selected framework dimensions and qualitative case study themes are discussed with respect to the level of independence of organisational actors in the East from their partners in the West in a post-socialist context. A professional global civil society as organisations are increasingly managed in similar, professional ways (Anheier & Themudo 2002). Here knowledge “handling” and knowledge “translation” take place through partnership exchanges fostering capable and/or competitive change-inducing institutions (Czarniawska & Sevon 2005; Hwang & Suarez 2005). How professional identity presents itself in the third sector, as well as the sector’s claim to expertise, need further attention, adding to ongoing discussions on professions in institutional theory (Hwang & Powell 2005; Scott 2008; Noordegraaf 2011). A conceptual framework on the dynamic involved for the construction professional fields follows: • Multiple case analysis provides a taxonomy for understanding what is happening in knowledge transition, adaptation, and organisational learning capacity for NGOs with respect to their role in a networked civil society. With the model we can observe the types of knowledge produced and learning employed by organisations. • There are elements of professionalisation in third sector work organisational activity with respect to its accreditation, sources and routines of learning, knowledge claims, interaction with the statutory sector, recognition in cross-sector partnerships etc. • It signals that there is a dual embeddedness in the development of the sector at the core to the shaping the sector’s professional status. This is instrumental in the NGOs’ goal to gain influence as institutions, as they are only one part of a cross-sector mission to address complex societal problems The case study material highlights nuances of knowledge production and learning practices in partnerships, with dual embeddedness a main feature of the findings. This provides some clues to how professionalisation as expert-making takes shape in organisations: • Depending on the type of organisations’ purpose, over its course of development there is an increase in participation in multiple networks, as opposed to reliance on a single strategic partner for knowledge artefacts and practices; • Some types of organisations are better connected within international and national networks than others and there seem to be preferences for each depending on the area of work; • The level of interpretation or adaptation of the knowledge artefacts is related to an organisation’s embeddedness locally, in turn giving it more influence within the network of key institutions; An overreaching theme across taxonomy categories (Table 1)is “professionalisation” or developing organisational “expertise”, embodied at the individual, organisational, and sector levels. Questions relevant to the exercise of power arise: Is competence in managing a dual embeddedness signals the development of a dual identity in professionalisation? Is professionalisation in this sense a sign of organisations maturing into more capable partners to the arguably more experienced (Western) institutions, shifting the power balance? Or is becoming more professional a sign of domestication to the agenda of certain powerful stakeholders, who define the boundaries of the profession? Which dominant dynamics can be observed in a broadly-defined transition country civil society, where individual participation in the form of activism may be overtaking the traditional forms of organised development work, especially with the spread of social media?

Review of virtual power plant applications for the power system management and V2G market development

Utilization of renewable energy sources and energy storage systems is increasing with fostering new policies on energy industries. However, the increase of distributed generation hinders the reliability of power systems. In order to stabilize them, a virtual power plant emerges as a novel power grid management system. The VPP has a role to make a participation of different distributed energy resources and energy storage systems. This paper defines core technology of the VPP which are demand response and ancillary service concerning about Korea, America and Europe cases. It also suggests application solutions of the VPP to V2G market for restructuring national power industries in Korea.

The effects of transients on photospheric and chromospheric power distributions

We have observed a quiet Sun region with the Swedish 1-meter Solar Telescope (SST) equipped with CRISP Imaging SpectroPolarimeter. High-resolution, high-cadence, H-alpha line scanning images were taken to observe different layers of the solar atmosphere from the photosphere to upper chromosphere. We study the distribution of power in different period-bands at different heights. Power maps of the upper photosphere and the lower chromosphere show suppressed power surrounding the magnetic-network elements, known as "magnetic shadows". These also show enhanced power close to the photosphere, traditionally referred to as"power halos". The interaction between acoustic waves and inclined magnetic fields is generally believed to be responsible for these two effects. In this study we explore if small-scale transients can influence the distribution of power at different heights. We show that the presence of transients, like mottles, Rapid Blueshifted Excursions (RBEs) and Rapid Redshifted Excursions (RREs), can strongly influence the power-maps. The short and finite lifetime of these events strongly affects all powermaps, potentially influencing the observed power distribution. We show that Doppler-shifted transients like RBEs and RREs that occur ubiquitously, can have a dominant effect on the formation ofthe power halos in the quiet Sun. For magnetic shadows, transients like mottles do not seem to have a significant effect in the power suppression around 3 minutes and wave interaction may play a key role here. Our high cadence observations reveal that flows, waves and shocks manifest in presence of magnetic fields to form a non-linear magnetohydrodynamic system.

Power relations and good governance: a social network analysis of the evolution of the integrity in public office act in the Commonwealth of Dominica

La Banque mondiale propose la bonne gouvernance comme la stratégie visant à corriger les maux de la mauvaise gouvernance et de faciliter le développement dans les pays en développement (Carayannis, Pirzadeh, Popescu & 2012; & Hilyard Wilks 1998; Leftwich 1993; Banque mondiale, 1989). Dans cette perspective, la réforme institutionnelle et une arène de la politique publique plus inclusive sont deux stratégies critiques qui visent à établir la bonne gouvernance, selon la Banque et d’autres institutions de Bretton Woods. Le problème, c’est que beaucoup de ces pays en voie de développement ne possèdent pas l’architecture institutionnelle préalable à ces nouvelles mesures. Cette thèse étudie et explique comment un état en voie de développement, le Commonwealth de la Dominique, s’est lancé dans un projet de loi visant l’intégrité dans la fonction publique. Cette loi, la Loi sur l’intégrité dans la fonction publique (IPO) a été adoptée en 2003 et mis en œuvre en 2008. Cette thèse analyse les relations de pouvoir entre les acteurs dominants autour de évolution de la loi et donc, elle emploie une combinaison de technique de l’analyse des réseaux sociaux et de la recherche qualitative pour répondre à la question principale: Pourquoi l’État a-t-il développé et mis en œuvre la conception actuelle de la IPO (2003)? Cette question est d’autant plus significative quand nous considérons que contrairement à la recherche existante sur le sujet, l’IPO dominiquaise diverge considérablement dans la structure du l’IPO type idéal. Nous affirmons que les acteurs "rationnels," conscients de leur position structurelle dans un réseau d’acteurs, ont utilisé leurs ressources de pouvoir pour façonner l’institution afin qu’elle serve leurs intérêts et ceux et leurs alliés. De plus, nous émettons l’hypothèse que: d’abord, le choix d’une agence spécialisée contre la corruption et la conception ultérieure de cette institution reflètent les préférences des acteurs dominants qui ont participé à la création de ladite institution et la seconde, notre hypothèse rivale, les caractéristiques des modèles alternatifs d’institutions de l’intégrité publique sont celles des acteurs non dominants. Nos résultats sont mitigés. Le jeu de pouvoir a été limité à un petit groupe d’acteurs dominants qui ont cherché à utiliser la création de la loi pour assurer leur légitimité et la survie politique. Sans surprise, aucun acteur n’a avancé un modèle alternatif. Nous avons conclu donc que la loi est la conséquence d’un jeu de pouvoir partisan. Cette recherche répond à la pénurie de recherche sur la conception des institutions de l’intégrité publique, qui semblent privilégier en grande partie un biais organisationnel et structurel. De plus, en étudiant le sujet du point de vue des relations de pouvoir (le pouvoir, lui-même, vu sous l’angle actanciel et structurel), la thèse apporte de la rigueur conceptuelle, méthodologique, et analytique au discours sur la création de ces institutions par l’étude de leur genèse des perspectives tant actancielles que structurelles. En outre, les résultats renforcent notre capacité de prédire quand et avec quelle intensité un acteur déploierait ses ressources de pouvoir.