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A high efficiency 200W Adaptor with new voltage-current driven synchronous rectfier (전압전류 혼합 구동방식의 동기정류기를 이용한 200W급 고효율 AC Adaptor에 관한 연구)

  • Won, Ki-Sik;Lee, Darl-Woo;Ahn, Tae-Young;Kim, Sung-Cheol;Jang, Chan-Gyu;Kim, Young-Joo
    • Proceedings of the KIEE Conference
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    • 2005.10c
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    • pp.182-185
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    • 2005
  • This paper presents a new voltage current driven method for the synchronous rectifier (SR) in a flyback topology. The proposed synchronous rectfier of voltage-current driven can operate at wide load range with high efficiency. The gate voltage of FET in the synchronous rectifier is easily controlled by resistor ratio. regardless of line and load fluctuation. The 200W (l2V/17A) prototype is built and achiveved efficiency as high as 90% at 4A, 93.2% at 7A and full load.

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R&D Intensity and Market Structure (R&D집약도와 시장구조)

  • Kim, Byung-Woo
    • Journal of Technology Innovation
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    • v.12 no.3
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    • pp.97-109
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    • 2004
  • According to "structure-conduct-performance" paradigm in IO, market structure (concentration) determines conduct (R&D investments), and conduct yields market performance (ratio of price to marginal cost). Previous empirical studies on Schumpeter Mark I, II assumed that the explanatory variable (market structure) and the disturbance are uncorrelated in the R&D equation. In this situation, Ordinary Least Squares (OLS) estimates of the structural parameters are inconsistent, because the endogeneous variables (R&D and market structure) can be determined simultaneously. So, in this study, full information (or system methods) estimation is used to test Schumpeter hypothesis since joint estimation can as well bring efficiency gains in the seemingly uncorrelated regressions (SUR) setting.

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Design of Noncircular Gears for Wire EDM (비원형 기어의 와이어 방전가공을 위한 설계)

  • Lee, Sung-Chul
    • Tribology and Lubricants
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    • v.24 no.5
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    • pp.221-227
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    • 2008
  • This paper presents a step-by-step design of noncircular gears. From the diagram of angular velocity ratio of a noncircular gear pair, the pitch curves of the two mating gears are determined, and the perimeter of the pitch curve has been divided into equal-length segments by the number of teeth. A master tooth profile, which is a composite curve of circular arcs that represents involute, has been introduced. A noncircular gear pair has been designed by imposing the master tooth on the divided points of the pitch curve, and a full fillet has been achieved between neighbour teeth. Thus, the whole profile of the noncircular gear is a composite curve of arcs only, and consequently NC codes for wire EDM can be easily generated.

Seismic Stability and Fatigue Performance Test of Lead Rubber Bearings (납-적층고무받침의 지진안정성 및 피로거동 실험)

  • Cho, Chang-Beck;Kwahk, Im-Jong;Kim, Young-Jin;Kwark, Jong-Won;Cho, Hae-Jin
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • 2006.03a
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    • pp.537-544
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    • 2006
  • In this study, performance level evaluation tests have been actually performed on laminated rubber seismic isolation bearings (LRB) made in Korea. To provide basic data for setting up fabrication criteria and performance evaluation criteria three real scale LRB were tested and the test results were analysised. Accordingly, a large capacity test device has been designed and manufactured to implement the tests. The device selected for evaluation is a circular LRB actually applied in bridges. Evaluation tests were conducted using full-scale LRB with diameter of 851mm in the rubber part and total height of 215mm of which the effective horizontal stiffness and equivalent damping ratio have been measured during the experiments.

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Wind loads on industrial solar panel arrays and supporting roof structure

  • Wood, Graeme S.;Denoon, Roy O.;Kwok, Kenny C.S.
    • Wind and Structures
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    • v.4 no.6
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    • pp.481-494
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    • 2001
  • Wind tunnel pressure tests were conducted on a 1:100 scale model of a large industrial building with solar panels mounted parallel to the flat roof. The model form was chosen to have the same aspect ratio as the Texas Tech University test building. Pressures were simultaneously measured on the roof, and on the topside and underside of the solar panel, the latter two combining to produce a nett panel pressure. For the configurations tested, varying both the lateral spacing between the panels and the height of the panels above the roof surface had little influence on the measured pressures, except at the leading edge. The orientation of the panels with respect to the wind flow and the proximity of the panels to the leading edge had a greater effect on the measured pressure distributions. The pressure coefficients are compared against the results for the roof with no panels attached. The model results with no panels attached agreed well with full-scale results from the Texas Tech test building.

Cyclic load testing and numerical modeling of concrete columns with substandard seismic details

  • Marefat, Mohammad S.;Khanmohammadi, Mohammad;Bahrani, Mohammad K.;Goli, Ali
    • Computers and Concrete
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    • v.2 no.5
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    • pp.367-380
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    • 2005
  • Recent earthquakes have shown that many of existing buildings in Iran sustain heavy damage due to defective seismic details. To assess vulnerability of one common type of buildings, which consists of low rise framed concrete structures, three defective and three standard columns have been tested under reversed cyclic load. The substandard specimens suffered in average 37% loss of strength and 45% loss of energy dissipation capacity relative to standard specimens, and this was mainly due to less lateral and longitudinal reinforcement and insufficient sectional dimensions. A relationship has been developed to introduce variation of plastic length under increasing displacement amplitude. At ultimate state, the length of plastic hinge is almost equal to full depth of section. Using calibrated hysteresis models, the response of different specimens under two earthquakes has been analyzed. The analysis indicated that the ratio between displacement demand and capacity of standard specimens is about unity and that of deficient ones is about 1.7.

Rationally modeling collapse due to bending and external pressure in pipelines

  • Nogueira, Andre C.
    • Earthquakes and Structures
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    • v.3 no.3_4
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    • pp.473-494
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    • 2012
  • The capacity of pipelines to resist collapse under external pressure and bending moment is a major aspect of deepwater pipeline design. Existing design codes present interaction equations that quantify pipeline capacities under such loadings, although reasonably accurate, are based on empirical data fitting of the bending strain, and assumed simplistic interaction with external pressure collapse. The rational model for collapse of deepwater pipelines, which are relatively thick with a diameter-to-thickness ratio less than 40, provides a unique theoretical basis since it is derived from first principles such as force equilibrium and compatibility equations. This paper presents the rational model methodology and compares predicted results and recently published full scale experimental data on the subject. Predictive capabilities of the rational model are shown to be excellent. The methodology is extended for the problem of pipeline collapse under point load, longitudinal bending and external pressure. Due to its rational derivation and excellent prediction capabilities, it is recommended that design codes adopt the rational model methodology.

Clinical Significance of Ultrasonographic Assessment for Small Intestinal Layer in Cats

  • Kim, Young-hwan;Kim, Sung-yong;Hwang, Tae-sung;Lim, Jong-su;Jung, Dong-in;Lee, Hee-chun
    • Journal of Veterinary Clinics
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    • v.36 no.4
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    • pp.225-228
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    • 2019
  • Inflammatory bowel disease and alimentary lymphoma are common gastrointestinal disorder in cats. More recently, ultrasonographic features associated with feline alimentary lymphoma has been recognized as a diffuse thickening of muscular layer of small intestine. We investigated correlation between thickening of muscular layer of small intestine and such disease. We found a significantly increased thickness of the muscular layer of small intestine in cats with lymphoma or IBD compared with healthy cats. When a muscularis to submucosa ratio > 1 and regional lymphadenopathy were found during ultrasonography on cats with gastrointestinal signs, full-thickness biopsy could be recommended to make sure presence confirmation of inflammatory bowel disease or alimentary lymphoma.

Behavior of full-scale prestressed pile-deck connections for wharves under cyclic loading

  • Blandon, Carlos A.;Krier, Christopher J.;Restrepo, Jose I.
    • Earthquakes and Structures
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    • v.16 no.4
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    • pp.455-468
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    • 2019
  • The behavior of pile-deck connections of pile-supported marginal wharfs subjected to earthquake loading is of key importance to ensure a good performance of this type of structures. Two precast-pretensioned pile-deck connections used in the construction of pile-supported marginal wharfs were tested under cyclic loading. The first is a connection with simple reinforcement details and light steel ratio developed for use where moderate pile-deck rotation demands are expected in the wharf. The second is specifically developed to sustain the large rotation, shear force and bending moment demands, as required for the shortest piles in a marginal wharf. Data obtained from the test program is used in the paper to calibrate an equivalent plastic hinge length that can be incorporated into nonlinear analysis models of these structures when prestressed pile-deck connections with duct embedded dowels are used.

Simple Power Allocation Scheme for Data Rate Fairness in NOMA Systems (비직교 다중 접속 시스템에서 전송률 공정성을 위한 단순한 전력 할당 기법)

  • Lee, In-Ho
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.24 no.9
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    • pp.1241-1244
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    • 2020
  • In this paper, we consider a downlink non-orthogonal multiple access system with a base station and N mobile stations, where we assume that instantaneous channel state information (CSI) is available at the base station. A power allocation scheme is proposed to achieve perfect fairness, which means equal data rates for all mobile stations. However, the power allocation scheme using full CSI requires high complexity. Hence, a simple power allocation scheme with low complexity is proposed by using high signal-to-noise power ratio (SNR) approximation. The simple power allocation scheme can achieve perfect fairness only for high SNR. However, it needs only the best CSI and the simple procedure to obtain power allocation coefficients. From simulation results, we show that the simple power allocation scheme provides remarkable fairness performance at high SNR.