Browsing by Subject "DESIGN"

Now showing 1 - 4 of 4
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    A Modular Multilevel Series/Parallel Converter for a Wide Frequency Range Operation
    (IEEE Transactions on Power Electronics, 2019-10-01) Li, Z; Ricardo Lizana, F; Yu, Z; Sha, S; Peterchev, AV; Goetz, SM
    When providing ac output, modular multilevel converters (MMCs) experience power fluctuation in the phase arms. The power fluctuation causes voltage ripple on the module capacitors, which grows with the output power and inversely to the output frequency. Thus, low-frequency operations of MMCs, e.g., for motor drives, require injecting common-mode voltages and circulating currents, and strict dc voltage output relative to ground is impossible. To address this problem, this paper introduces a novel module topology that allows parallel module connectivity in addition to the series and bypass states. The parallel state directly transfers power across the modules and arms to cancel the power fluctuations and hence suppresses the capacitor voltage ripple. The proposed series/parallel converter can operate at a wide frequency range down to dc without common-mode voltages or circulating currents; it also allows sensorless operation and full utilization of the components at higher output frequencies. We present detailed simulation and experiment results to characterize the advantages and limitations of the proposed solution.
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    Chains of Love? Global Production and the Firm-Level Diffusion of Labor Standards
    (American Journal of Political Science, 2018-07-01) Malesky, EJ; Mosley, L
    ©2018, Midwest Political Science Association Under what conditions does the global economy serve as a means for the diffusion of labor standards and practices? We anticipate variation among internationally engaged firms in their propensity to improve labor standards. Upgrading is most likely when a firm's products exhibit significant cross-market differences in markups, making accessing high-standards overseas markets particularly profitable. Additionally, upgrading is more likely when lead firms attach a high salience to labor standards. Therefore, while participation in global production induces “trading up” behaviors among firms overall, the effect strength varies across industries. We test our expectations via a survey experiment, which queries foreign firms operating in Vietnam about their willingness to invest in labor-related upgrading. We find strong evidence for the effect of markups on upgrading choices and suggestive evidence for the saliency mechanism.
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    Estimating willingness to pay: Do health and environmental researchers have different methodological standards?
    (Applied Economics, 2013-06-01) Özdemir, S; Johnson, FR
    Health and environmental economists have been employing Stated-Preference (SP) methods such as conjoint analysis or contingent valuation to estimate the monetary value of public health interventions and environmental goods and services. However, the quality of data and the validity of results are sensitive to a number of decisions researchers make. The aim of this study is to compare the degree of the current consensus among active researchers in the rapidly evolving area of SP methods in health and environmental valuation. We surveyed researchers who have published manuscripts on SP methods in the last 10 years. Researchers were presented with hypothetical SP studies with different attributes. They were first asked which study they would recommend to use to inform policy decisions, and then asked which study has better-quality. Our results show that good-practice SP methods vary among study features and among researchers with different amounts and kinds of research experience. Although health researchers had specific preferences on which study features were better, their quality judgements were not very consistent with their judgements about the acceptability of studies for policy analysis. On the other hand, environmental researchers had similar preferences over the study attributes for the two types of questions. © 2012 Copyright Taylor and Francis Group, LLC.
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    Lessons learned when innovations go awry: a baseline description of a behavioral trial-the Enhancing Fitness in Older Overweight Veterans with Impaired Fasting Glucose study.
    (Translational behavioral medicine, 2011-11) Hall, KS; Pieper, CF; Edelman, DE; Yancy Jr, WS; Green, JB; Lum, H; Peterson, MJ; Sloane, R; Cowper, PA; Bosworth, HB; Huffman, KM; Cavanaugh, JT; Chapman, JG; Pearson, MP; Howard, TA; Ekelund, CC; McCraw, BL; Burrell, JB; Taylor, GA; Morey, MC
    Individuals diagnosed with impaired glucose tolerance (i.e., prediabetes) are at increased risk for developing diabetes. We proposed a clinical trial with a novel adaptive randomization designed to examine the impact of a home-based physical activity (PA) counseling intervention on metabolic risk in prediabetic elders. This manuscript details the lessons learned relative to recruitment, study design, and implementation of a 12-month randomized controlled PA counseling trial. A detailed discussion on how we responded to unforeseen challenges is provided. A total of 302 older patients with prediabetes were randomly assigned to either PA counseling or usual care. A novel adaptive design that reallocated counseling intensity based on self-report of adherence to PA was initiated but revised when rates of non-response were lower than projected. This study presents baseline participant characteristics and discusses unwelcome adaptations to a highly innovative study design to increase PA and enhance glucose metabolism when the best-laid plans went awry.