DC fault isolation study of bidirectional dual active bridge DC/DC converter for DC transmission grid application

Fast isolation and detection of DC faults is currently a limiting factor in high power DC transmission grid development. Recent research has shown that the role of DC/DC converters is becoming increasingly important in solving various DC grid challenges such as voltage stepping, galvanic isolation and power regulation. This paper focuses on an additional important feature of bidirectional dual active bridge (DAB) DC-DC converters which make it attractive for future DC grids; it's inherent fault isolation capability which does not need control intervention to limit fault current in case of the most severe DC faults. Detailed analytical, simulation and experimental study are performed by subjecting the converter to DC short circuit faults at its DC voltage terminals. The results obtained have shown significant advantage of DAB where fault current is less than rated current during the fault duration. Thus no control action is necessary from the non-faulted bridge to limit fault current and no external DC circuit breakers are required. This advantage makes DAB converter feasible for DC grid integration

Reactive power minimization of dual active bridge DC/DC converter with triple phase shift control using neural network

Reactive power flow increases dual active bridge (DAB) converter RMS current leading to an increase in conduction losses especially in high power applications. This paper proposes a new optimized triple phase shift (TPS) switching algorithm that minimizes the total reactive power of the converter. The algorithm iteratively searches for TPS control variables that satisfy the desired active power flow while selecting the operating mode with minimum reactive power consumption. This is valid for the whole range of converter operation. The iterative algorithm is run offline for the entire active power range (-1pu to 1pu) and the resulting data is used to train an open loop artificial neural network controller to reduce computational time and memory allocation necessary to store the data generated. To validate the accuracy of the proposed controller, a 500-MW 300kV/100kV DAB model is simulated in Matlab/Simulink, as a potential application for DAB in DC grids

Industrial Terrorism and the Unmaking of New Deal Labor Law

The passage of the Wagner (National Labor Relations) Act of 1935 represented an unprecedented effort to guarantee American workers basic labor rights--the rights to organize unions, to provoke meaningful collective bargaining, and to strike. Previous attempts by workers and government administrators to realize these rights in the workplace met with extraordinary, often violent, resistance from powerful industrial employers, whose repressive measures were described by government officials as a system of industrial terrorism. Although labor scholars have acknowledged these practices and paid some attention to the way they initially frustrated labor rights and influenced the jurisprudence and politics of labor relations in the late 1930s and early 1940s, the literature has neither adequately described the extent and intensity of this phenomenon nor fully explored its effects. This Article remedies that shortcoming. Focusing on three industries where the practice of industrial terrorism was especially well developed and its influence especially pronounced, this Article shows how the practitioners of industrial terrorism and their allies in Congress were able to turn the legacy of violence and disorder, which they authored by their violent resistance to the Wagner Act, into the basis of an extraordinary counterattack on labor rights. It shows how this attack culminated in 1947 with the enactment of the profoundly reactionary Taft-Hartley Act and remade the landscape of American labor relations

Hair histology as a tool for forensic identification of some domestic animal species

Animal hair examination at a criminal scene may provide valuable information in forensic investigations. However, local reference databases for animal hair identification are rare. In the present study, we provide differential histological analysis of hair of some domestic animals in Upper Egypt. For this purpose, guard hair of large ruminants (buffalo, camel and cow), small ruminants (sheep and goat), equine (horse and donkey) and canine (dog and cat) were collected and comparative analysis was performed by light microscopy. Based on the hair cuticle scale pattern, type and diameter of the medulla, and the pigmentation, characteristic differential features of each animal species were identified. The cuticle scale pattern was imbricate in all tested animals except in donkey, in which coronal scales were identified. The cuticle scale margin type, shape and the distance in between were characteristic for each animal species. The hair medulla was continuous in most of the tested animal species with the exception of sheep, in which fragmental medulla was detected. The diameter of the hair medulla and the margins differ according to the animal species. Hair shaft pigmentation were not detected in all tested animals with the exception of camel and buffalo, in which granules and streak-like pigmentation were detected. In conclusion, the present study provides a first-step towards preparation of a complete local reference database for animal hair identification that can be used in forensic investigations.Comment: 8 pages, 3 Figure

The Indian Community and Its Economic Activity in Zanzibar During the 19th Century

The Indians were considered the main category working in trade in Zanzibar during the reign of Sultan Saeed Bin Sultan, the founder of the modern state of Zanzibar (1806-1856). The Indian traders got the appreciation and respect of Saeed Bin Sultan and they were allowed to work in trade in the region and he treated them as local traders in order to establish a commercial empire. Hence most of the Indian traders came during his rule, and in 1835, as the case with others, they came with the seasonal wind. The Indian traders were Muslims and Hindu, but they didn't consider Zanzibar as their homeland, they used to travel to India and come back. Among them, the Moslem Bahara became prominent, most of them were rich traders, who lived in Zanzibar and took it as their homeland. The Indian traders succeeded in supporting the economics of Zanzibar and financing the Arab commercial projects and developing the internal trade. Some of them succeeded in possessing large farms of cloves. And because of their commercial activity and their economic status they succeeded in establishing an excellent social position and they taught their children reading and writing. On the other side Britain encouraged the Indians to migrate to Eastern Africa because of its need for the technical Indian working class and handcraft to make use of their experience. Hence the important role of the Indian merchants in the trade of Eastern Africa came