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"modern issues"
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Voltage regulation in LV grids by coordinated volt-var control strategies
The increasing penetration level of photovoltaic (PV) power generation in low voltage (LV) networks results in voltage rise issues, particularly at the end of the feeders. In order to mitigate this problem, several strategies, such as grid reinforcement, transformer tap change, demand-side management, active power curtailment, and reactive power optimization methods, show their contribution to voltage support, yet still limited. This paper proposes a coordinated volt-var control architecture between the LV distribution transformer and solar inverters to optimize the PV power penetration level in a representative LV network in Bornholm Island using a multi-objective genetic algorithm. The approach is to increase the reactive power contribution of the inverters closest to the transformer during overvoltage conditions. Two standard reactive power control concepts, cosφ(P) and Q(U), are simulated and compared in terms of network power losses and voltage level along the feeder. As a practical implementation, a reconfigurable hardware is used for developing a testing platform based on real-time measurements to regulate the reactive power level. The proposed testing platform has been developed within PVNET.dk project, which targets to study the approaches for large PV power integration into the network, without the need of reinforcement.
Journal Article
A self-learning TLBO based dynamic economic/environmental dispatch considering multiple plug-in electric vehicle loads
Economic and environmental load dispatch aims to determine the amount of electricity generated from power plants to meet load demand while minimizing fossil fuel costs and air pollution emissions subject to operational and licensing requirements. These two scheduling problems are commonly formulated with non-smooth cost functions respectively considering various effects and constraints, such as the valve point effect, power balance and ramp rate limits. The expected increase in plug-in electric vehicles is likely to see a significant impact on the power system due to high charging power consumption and significant uncertainty in charging times. In this paper, multiple electric vehicle charging profiles are comparatively integrated into a 24-hour load demand in an economic and environment dispatch model. Self-learning teaching-learning based optimization (TLBO) is employed to solve the non-convex non-linear dispatch problems. Numerical results on well-known benchmark functions, as well as test systems with different scales of generation units show the significance of the new scheduling method.
Journal Article
A review on applications of heuristic optimization algorithms for optimal power flow in modern power systems
Optimal power flow (OPF) is one of the key tools for optimal operation and planning of modern power systems. Due to the high complexity with continuous and discrete control variables, modern heuristic optimization algorithms (HOAs) have been widely employed for the solution of OPF. This paper provides an overview of the latest applications of advanced HOAs in OPF problems. The most frequently applied HOAs for solving the OPF problem in recent years are covered and briefly introduced, including genetic algorithm (GA), differential evolution (DE), particle swarm optimization (PSO), and evolutionary programming (EP), etc.
Journal Article
Imperial Rejuvenations
In recent years scholars have argued that “rejuvenation” took distinctively modern forms as a specific set of surgical procedures intended to realize sexual potency and libidinal enhancement, as well as anti-aging medicine and cosmetic body projects. However, this article underlines the earlier, imperial dimensions of rejuvenation as a set of modern, state-sponsored practices taking shape outside Europe. An important turning point in the modern history of rejuvenation was a shift around 1830 in thinking about “the tropics,” as scientists who identified heat as accelerating the process of aging rejected the possibility of acclimatization in hot zones. Because racial vitality supposedly diminished more quickly in the tropics, the older ideal of the grizzled, mature colonial soldier fell into decline, and rethinking the globe in racial-climatological terms made youth an essential corequisite of empire. Military commanders confronted the need to rejuvenate armies by recruiting soldiers at younger ages. Together with medical experts, they responded to fears of racial-climatological impotence by developing a range of strategies—from troop rotation to the development of hill stations—which scaled up rejuvenation to the level of entire population groups. Focusing on strategies elaborated in Asia to address this problem, this article shows how ideas about youth, time, geography, and modernity gave rise to spaces and networks designed to slow or reverse the aging process, or in other words to achieve “imperial rejuvenation” well before rejuvenation became a buzzword in late nineteenth-century Europe.
Journal Article
Mapping Modern Rejuvenation
The desire to conquer old age is as old as humanity itself, yet the pursuit of youthfulness acquired a fiercer urgency with the rise of post-Enlightenment conceptions of youth as a redemptive social force. This introductory essay widens the circle of what constitutes modern rejuvenation by moving beyond the standard focus on anti-aging medicine and lays out the historiographical and methodological stakes of conceptualizing rejuvenation more broadly. Its main contention is that rejuvenation can serve as an analytical linchpin to reveal unrecognized connections between various historically specific projects of regeneration and repair that were comprised in individual flesh-and-blood as well as in imagined collective bodies such as nations and empires.
Journal Article
Shadow mothers
Shadow Mothers shines new light on an aspect of contemporary motherhood often hidden from view: the need for paid childcare by women returning to the workforce, and the complex bonds mothers forge with the “shadow mothers” they hire. Cameron Lynne Macdonald illuminates both sides of an unequal and complicated relationship. Based on in-depth interviews with professional women and childcare providers— immigrant and American-born nannies as well as European au pairs—Shadow Mothers locates the roots of individual skirmishes between mothers and their childcare providers in broader cultural and social tensions. Macdonald argues that these conflicts arise from unrealistic ideals about mothering and inflexible career paths and work schedules, as well as from the devaluation of paid care work.
eBook
البيتكوين وحكم التعامل بها في الفقه الإسلامي
لقد أثارت عملة البيتكوين في العصر الحديث ضجة كبيرة في الأوساط الفقهية والقانونية؛ باعتبارها نازلة من نوازل العصر، وقد هدفت هذه الدراسة إلى بحث هذه النازلة من منظورها الفقهي بطريقة علمية متخصصة، وتكونت هذه الدراسة من مقدمة، ومبحثين، وخاتمة، أما المقدمة: فقد اشتملت على أهمية الدراسة، ومنهج البحث، والدراسات السابقة، وخطة البحث، المبحث الأول: وقد اشتمل على تعريف البيتكوين، ونشأتها، وخصائصها، ومميزاتها، وعيوبها، وكيفية الحصول عليها، المبحث الثاني: واشتمل على تعريف العملة، وبيان وظائفها، وحكم التعامل بعملة البيتكوين، وأما الخاتمة: فقد اشتملت على أهم نتائج البحث.
Journal Article
Soft Rejuvenation
In this article we draw together the histories of rejuvenation and cosmetic use in order to examine discourses of “soft rejuvenation” in the late nineteenth and early twentieth centuries. While rejuvenation has typically been considered in relation to transnational medicalized attempts to restore youthful vitality and virility, we suggest that the logic of rejuvenation was feminized through the promotion of cosmetic and daily self-care regimens in this period. Drawing on material from British, American, and Canadian contexts relating to beauty and hygiene, we suggest that daily practices of caring for and disciplining the white female body, especially through cosmetic use, were legitimated, in part, using the rhetoric of rejuvenation. The article considers how the transnational, the modern, and the propagation of whiteness in the early twentieth century were mobilized in these ideas of how daily bodily work could preserve the (white) youthful face and body, which was understood to embody health and vigor. This discourse was significant for young women, who were subject to male control over their bodies as they began to be employed in nontraditional workplaces; however, we also argue that these cosmetic practices can be understood as a component of girls’ and women’s own self-fashioning of modern identities.
Journal Article
Rubble and Rebirth
This article weaves together different postwar moments in the first half of the twentieth century to investigate how rejuvenationist narratives of a “fresh start” helped societies across the divides of geography and ideology to recuperate from the ravages of war. Apart from initiating boys and girls into ideologically specific and gendered regimes of citizenship, the older generation crafted reverse rites of passage to absolve themselves of responsibility for violent conflicts that had resulted in unspeakable death and suffering. Youth organizations became key sites for making young bodies useful to the dual task of regenerating war-torn nations and exonerating those whose actions had contributed to war in the first place. The need for acquitting the old was particularly pressing in light of disputes about who was to blame for the loss of young lives—disputes that often carried the tonality of ageism rather than party politics. If recapturing the innocence of youth became tantamount to deflecting questions of guilt and accountability, then bonding with youth allowed powerful men (less so women) who bore the scars of struggle to engage in deliberate acts of erasure. The disremembering of age and history endowed the ruling classes with seemingly innocuous possibilities, especially the possibility to acquire a clean slate on which to forge new collective identities within the redemptive framework of youth. Just as history is distorted by memory, rejuvenation opened up new futures while giving license to forgetting troubling pasts.
Journal Article