4,865 research outputs found
Network partitioning techniques based on network natural properties for power system application
No full textThis thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University, 10/04/2002.In this thesis, the problem of partitioning a network into interconnected sub-networks is addressed. The goal is to achieve a partitioning which satisfies a set of specific engineering constraints, imposed in this case, by the requirements of the decomposed state-estimation (DSE) in electrical power systems. The network-partitioning problem is classified as NP-hard problem. Although many heuristic algorithms have been proposed for its solution, these often lack directness and computational simplicity. In this thesis, three new partitioning techniques are described which (i) satisfy the DSE constraints, and (ii) simplify the NP-hard problem by using the natural graph properties of a network. The first technique is based on partitioning a spanning tree optimally using the natural property of the spanning tree branches. As with existing heuristic techniques, information on the partitioning is obtained only at the end of the partitioning process. The study of the DSE constraints leads to define conditions of an ideal balanced partitioning. This enables data on the balanced partitioning to be obtained, including the numbers of boundary nodes and cut-edges. The second partitioning technique is designed to obtain these data for a given network, by finding the minimum covering set of nodes with maximum nodal degree. Further simplification is then possible if additional graph-theoretical properties are used. A new natural property entitled the 'edge state phenomenon' is defined. The edge state phenomenon may be exploited to generate new network properties. In the third partitioning technique, two of these, the 'network external closed path' and the 'open internal paths', are used to identify the balanced partitioning, and hence to partition the network. Examples of the application of all three methods to network partitioning are provided
A HIGH-VOLTAGE DRIVING 60-GHz POWER AMPLIFIER WITH P-sat OF 13 dBm AND PAE OF 9.1% IN 90-nm CMOS FOR IEEE 802.11ad COMMUNICATION SYSTEMS
No full text[[abstract]]A high-voltage (3 V) driving 60-GHz power amplifier (PA) for direct-conversion transceiver using standard 90 nm CMOS technology is reported. The PA comprises two cascode stages with inductive load and low-impedance interstage matching, followed by a common-source output stage. To increase the saturated output power (P-sat) and power-added efficiency (PAE), the output stage adopts a two-way power dividing and combining architecture. Instead of the area-consumed Wilkinson power divider and combiner, miniature low-loss LC power divider and combiner (IL=0.536 dB @60 GHz) are used. This in turn results in further P-sat and PAE enhancement. The PA consumes 176.2 mW and achieves power gain (S-21) of 17.9 +/- 3.7 dB, input-port input reflection coefficient (S-11) of -5.8 to -7.3 dB, output-port input reflection coefficient (S-22) of -10.4 to -26.3 dB, and reverse isolation (S-12) of -56.4 to -81.7 dB for frequencies 50-60 GHz. In addition, for frequencies 50-60 GHz, the PA achieves output 1-dB compression point (OP1dB) of 6.6-7.8 dBm, P-sat of 10.6-13 dBm and maximum PAE of 9.1%, one of the best PAE results ever reported for a 60 GHz CMOS PA. These results demonstrate the proposed PA architecture is very promising for 60-GHz short-range communication system applications. (c) 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2033-2039, 2013[[note]]SC
Business Model Innovation of JF Logistics Company
No full text摘要 随着全球化经济的发展，市场竞争变得越来越复杂。信息时代使得物流供应链管理已上升到企业的战略管理高度。在这样的背景下，本文应用翁君奕老师的介观商务模式创新观点，对JF物流公司所处行业现状进行剖析，重新审视了外部客户市场以及内部自身情况，找出了JF物流公司自身的优势，并结合外部市场客户的需求，提出了“为客户提供个性化的集物流、资金流、信息流于一体的供应链物流服务”这一价值主张，并在此基础上，重新定位客户市场，创新服务产品，理顺内部管理架构和业务流程以支撑和保持这一价值主张。文中同时以例证来说明依据新价值主张所创新的服务产品给JF物流公司所带来的变化，以此说明通过商务模式创新来实行自身的战略...Abstract With the development of the global economy, the competition in market becomes more complicated. In the era of information, logistics and supply chain management is regarded as important as part of the company strategy. Under such background , the author of this essay uses the concept of “JieGuan Business Model Innovation” proposed by Professor Weng Junyi of Xiamen University, and analy...学位：管理学硕士院系专业：管理学院高级经理教育中心（EMBA项目）_管理经济学学号：X200615614
African legislators : unrepresentative power elites?
No full textAfrican legislators both resemble and differ from the societies they claim to represent in important ways. Based on a unique survey of representative samples of parliamentarians in 17 countries, we find that legislatures are representative of national publics in terms of ethnicity and religion. At the same time, compared to ordinary African citizens, African MPs possess far higher levels of education and are far more likely to be older, male and to come from professional or business backgrounds. Besides coming from higher social and economic status backgrounds, many MPs also previously held senior posts in the state and national government, or leadership positions in their political party. Does this mean that African legislators constitute a coherent, self-interested, social, economic and political ‘power elite’ detached from the interests of the voters? In the legislatures under investigation, we find little evidence of this effect. Markers of social, economic or political privilege and power overlap irregularly and in a non-cumulative way. For example, while MPs are significantly older than the average voter, we find that most African legislators are in their first term of office. Thus, far from comprising a slowly changing, cohesive and self-interested elite, characterised by overlapping and cumulative markers of social and political influence, Africa’s legislators come from a plurality of social and political backgrounds, and are relative legislative neophytes
Low-power, high-gain and low-noise CMOS distributed amplifier for UWB systems
No full text[[abstract]]A 3-10 GHz CMOS distributed amplifier (DA) with. at and low noise figure (NF) and. at and high power gain (S(21)) is demonstrated. A. at and low NF was achieved by adopting an RL terminating network for the gate transmission line, and a slightly under- damped Q-factor for the second- order NF frequency response. Besides, an. at and high S(21) was achieved by using the proposed cascade gain cell, which constitutes a cascode- stage with a low- Q RLC load and an inductive-peaking common- source stage. In the high-gain mode, the DA consumed 37.8 mW and achieved a. at and high S(21) of 20.47 +/- 0.72 dB with an average NF of 3.29 dB over the 3-10 GHz band of interest, one of the best reported NF performances for a CMOS UWB DA or low- noise amplifier. In the low- gain mode, the DA achieved S(21) of 11.03 +/- 0.98 dB and an average NF of 4.25 dB with a power dissipation (P(D)) of 6.86 mW, the lowest P(D) ever reported for a CMOS UWB DA or LNA with an average S(21) of greater than 10 dB.[[note]]SC
From 9/11 to 2011: the "War on Terror" and the onward march of executive power?
No full textBook chapter focusing on the rise of executive power from 9/11 to 2011
Support or subvert? Assessing devolution’s effect on central power during Kenya’s 2017 presidential rerun
No full textDevolution introduced new local-level political offices in order to transform Kenyan politics by reducing the high stakes around the presidential race. The controversy over the 2017 presidential election rerun, however, saw pressure on county-level politicians to support either the ruling party or opposition coalition, underlining the important intersection between national and county politics. Using a broadened definition of ‘political linkages’, this paper explores the logics shaping how and why county-level politicians responded to the rerun as they did, comparing ruling party and opposition areas. Different forms of linkage politics indicate that devolution’s effect on central power is not uniform across counties, challenging the view that devolution simply leads to a recentralisation of power. The reproduction of national partisan divides at the county level suggests that devolution’s effect on central power is contingent partly on the way that national and county political alliances intersect. Given Kenya’s fluid national electoral alliances, devolution’s effect on central power is therefore not stable and may change with each electoral cycle
Temporal and spatial variability in speakers with Parkinson's Disease and Friedreich's Ataxia
No full textSpeech variability in groups of speakers with Parkinson's disease (PD) and with Friedreich's ataxia was compared with healthy controls. Speakers repeated the same phrase 20 times at one of two rates (fast or habitual). A non-linear analysis of variability was performed which used some of the principles behind the spatio-temporal index (STI). The STI usually employs variation in lip displacement over repetitions of the same utterance and a linear analysis of such signals is conducted to represent the combined variation in spatial and temporal control. When working with patients, audio measures (here we used speech energy) are preferred over kinematics ones as they are minimally disruptive to speech. Non-linear methods allow spatial variability to be estimated separately from temporal variability. The results are tentatively interpreted as showing that PD speakers were distinguished from healthy control speakers in spatial variability and ataxic speakers were distinguished from controls in temporal variability. These findings are consistent with the speech symptoms reported for these disorders. We conclude that the non-linear analysis using the speech energy measure is worth investigating further as it is potentially revealing of the differences underlying these two pathologies
A sequential conic programming approach for the coordinated and robust design of power system stabilizers
No full textThis paper shows that conic programming is an effective tool to solve robust power system stabilizer (PSS) design problems, namely coordinated gain tuning and coordinated phase and gain tuning. Design robustness is achieved by simultaneously considering several operating scenarios. The method is implemented through a sequence of conic programming runs that define a multivariable root locus along which the eigenvalues move. Specifically, the eigenvalues corresponding to the unstable and poorly damped modes are moved to a conic sector in the left half of the s-plane, whereas the eigenvalues corresponding to the well damped modes are constrained to stay within the boundaries of this conic sector. At each step of the solution, the PSS design parameters are restricted in a trust-region such that the computation of the eigenvalue shift based on the residue method holds valid. The proposed method is demonstrated on a 68-bus test system with nine different operating conditions. Comparisons are carried out between conic programming implementations for PSS coordinated gain tuning and for simultaneous tuning of gain and phase characteristics. © 2010 IEEE.Abdel-Magid YL, 2003, IEEE T POWER SYST, V18, P1125, DOI 10.1109-TPWRS.2003.814848; Ben-Tal A, 2001, LECT MODERN CONVEX O; Boukarim GE, 2000, IEEE T POWER SYST, V15, P1287, DOI 10.1109-59.898103; Chow JH, 2000, IEEE CONTR SYST MAG, V20, P82, DOI 10.1109-37.856181; CRUZ JJ, 1997, ELECT POWER ENERGY S, V19, P519; do Bomfim ALB, 2000, IEEE T POWER SYST, V15, P163, DOI 10.1109-59.852116; Dobson I, 2001, IEEE T CIRCUITS-I, V48, P340, DOI 10.1109-81.915389; DOI A, 1984, IEEE T POWER AP SYST, V103, P1473, DOI 10.1109-TPAS.1984.318486; Ferrahi MI, 2007, EXPRESS POLYM LETT, V1, P24, DOI 10.3144-expresspolymlett.2007.5; FERRAZ JCR, 2001, P POW ENG SOC WINT M, V3, P1154; GIBBARD MJ, 1991, IEEE T POWER SYST, V6, P794, DOI 10.1109-59.76727; KUNDUR P, 1989, IEEE T POWER SYST, V4, P614, DOI 10.1109-59.193836; LARSEN EV, 1981, IEEE T POWER AP SYST, V100, P3025, DOI 10.1109-TPAS.1981.316410; Martins N., 1989, P IEEE S APPL EIG FR, P17; MITCHELL JR, 1970, IEEE T AUTOMAT CONTR, VAC15, P483, DOI 10.1109-TAC.1970.1099526; Pal B., 2005, ROBUST CONTROL POWER; Pal BC, 2002, IEE P-GENER TRANSM D, V149, P739, DOI 10.1049-ip-gtd:20020659; Pal BC, 2000, IEEE T POWER SYST, V15, P356, DOI 10.1109-59.852144; Pal BC, 2000, IEEE T POWER SYST, V15, P320, DOI 10.1109-59.852139; Pourbeik P, 1998, IEEE T POWER SYST, V13, P473, DOI 10.1109-59.667371; Rogers G., 2000, POWER SYSTEM OSCILLA; Rommes J, 2008, IEEE T POWER SYST, V23, P434, DOI [10.1109-TPWRS.2008.920050, 10.1209-TPWRS.2008.920050]; Rommes J, 2006, IEEE T POWER SYST, V21, P1471, DOI 10.1109-TPWRS.2006.881154; Rommes J, 2006, IEEE T POWER SYST, V21, P1218, DOI 10.1109-TPWRS.2006.876671; Sturm JF, 1999, OPTIM METHOD SOFTW, V11-2, P625, DOI 10.1080-10556789908805766; XU XM, 1986, P 25 IEEE C DEC CONT, V25, P713; Zanetta LC, 2005, IEEE T POWER SYST, V20, P895, DOI 10.1109-TPWRS.2005.846111; Zhang P, 2000, IEEE T POWER SYST, V15, P811, DOI 10.1109-59.867178; 1991, POWER SYSTEM TOOLBOX25232
Exploiting Sparsity in SDP Relaxations of the OPF Problem
No full textThis letter presents a framework for exploiting sparsity in primal-dual interior-point based semidefinite programming (SDP) solutions of the optimal power flow (OPF) problem. It is shown that a formulation based on positive semidefinite matrix completion results in a drastic reduction in computational effort. © 2012 IEEE.Bai XQ, 2008, INT J ELEC POWER, V30, P383, DOI 10.1016-j.ijepes.2007.12.003; Fukuda M., 2000, SIAM Journal on Optimization, V11; Gross J. L., 2006, GRAPH THEORY ITS APP; Kim S, 2011, MATH PROGRAM, V129, P33, DOI 10.1007-s10107-010-0402-6; Lavaei J, 2011, P AMER CONTR CONF, P4566; Lavaei J., IEEE T POWE IN PRESS; Lofberg J, 2009, OPTIM METHOD SOFTW, V24, P313, DOI 10.1080-10556780802553325; Sturm JF, 1999, OPTIM METHOD SOFTW, V11-2, P625, DOI 10.1080-10556789908805766; Valiente G, 2002, ALGORITHMS TREES GRA11121
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