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Market Power and Policy in the U.S. Dairy Industry
Daniel A. Sumner,안병일 경상대학교 농업생명과학연구원 2008 농업생명과학연구 Vol.42 No.2
This paper discusses several aspects of the linkage between U.S. dairy policies and imperfect competition in dairy industry. Some key facts about the U.S. dairy industry as well as the products, marketing channels and potential for imperfect competition in each of several dairy products markets are discussed. This paper outlines the issues and considers some specific topics in the relation between dairy policy and market power or imperfect competition. This paper It is suggesteds that market power may be found among several players in several dairy markets.
Agricultural Commodity Programs in the United States: Reform, Reversal and WTO Implications
( Daniel A. Sumner ),( Jung Sup Choi ) 한국농촌경제연구원 2000 Journal of Rural Development Vol.23 No.2
American farm programs have gradually evolved over decades, and the FAIR Act continued the significant changes in form of the subsidy by reducing the effects on production. The large recent payments to U.S farmers continue to affect trade somewhat. But, these payments should not limit progress in the new WTO agricultural round if it focuses on border measures. For this WTO round, the U.S. could facilitate liberal trade by proposing the elimination of agricultural tariffs, export subsidies, and export taxes or embargoes. Limits on the use of anti-dumping duties or barriers to block import surges, reform of rules related to countervailing duties, and keeping science-based Sanitary and Phytosanitary rules are also vital to facilitate progress in negotiations.
Wind loading of a finite prism: aspect ratio, incidence and boundary layer thickness effects
Herman Heng,David Sumner 한국풍공학회 2020 Wind and Structures, An International Journal (WAS Vol.31 No.3
A systematic set of low-speed wind tunnel experiments was performed at Re = 6.5×104 and 1.1×105 to study the mean wind loading experienced by surface-mounted finite-height square prisms for different aspect ratios, incidence angles, and boundary layer thicknesses. The aspect ratio of the prism was varied from AR = 1 to 11 in small increments and the incidence angle was changed from α = 0° to 45° in increments of 1°. Two different boundary layer thicknesses were used: a thin boundary layer with δ/D = 0.8 and a thick boundary layer with δ/D = 2.0–2.2. The mean drag and lift coefficients were strong functions of AR, α, and δ/D, while the Strouhal number was mostly influenced by α. The critical incidence angle, at which the prism experiences minimum drag, maximum lift, and highest vortex shedding frequency, increased with AR, converged to a value of αc = 18° ± 2° once AR was sufficiently high, and was relatively insensitive to changes in δ/D. A local maximum value of mean drag coefficient was identified for higher-AR prisms at low α. The overall behaviour of the force coefficients and Strouhal number with AR suggests the possibility of three flow regimes.
김윤식,Daniel A. Sumner 한국농촌경제연구원 2006 농촌경제 Vol.29 No.4
*Research Fellow, Korea Rural Economic Institute, Seoul, Korea.**Professor, Department Of Agricultural And Resource Economics, University Of California At Davis, And Director Of The Agricultural Issue Center.攀攀
Yun Zhang,Yongping Gao,Jing Li,Mark Sumner 전력전자학회 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.2
A wide-voltage-conversion range bidirectional DC-DC converter is proposed in this paper. The topology is comprised of one typical LC energy storage component and a special common grounded asymmetric H-bridge with four active power switches/anti-parallel diodes. The narrow output PWM voltage is generated from the voltage difference between two normal (wider) output PWM voltages from the asymmetric H-bridge with duty cycles close to 0.5. The equivalent switching frequency of the output PWM voltage is double the actual switching frequency, and a wide step-down/step-up ratio range is achieved. A 300W prototype has been constructed to validate the feasibility and effectiveness of the proposed bidirectional converter between the variable low voltage side (24V~48V) and the constant high voltage side (200V). The slave active power switches allow VS turn-on and turn-off without requiring any extra hardware. The maximum conversion efficiency is 94.7% in the step-down mode and 93.5% in the step-up mode. Therefore, the proposed bidirectional topology with a common ground is suitable for energy storage systems such as renewable power generation systems and electric vehicles with a hybrid energy source.