• Title/Summary/Keyword: Variable Resistance

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Synthesis and Evaluation of Variable Temperature-Electrical Resistance Materials Coated on Metallic Bipolar Plates (온도 의존성 가변 저항 발열체로 표면 처리된 금속 분리판 제조 및 평가)

  • Jung, Hye-Mi;Noh, Jung-Hun;Im, Se-Joon;Lee, Jong Hyun;Ahn, Byung Ki;Um, Sukkee
    • 한국신재생에너지학회:학술대회논문집
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    • 2010.11a
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    • pp.73.1-73.1
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    • 2010
  • For the successful cold starting of a fuel cell engine, either internal of external heat supply must be made to overcome the formation of ice from water below the freezing point of water. In the present study, switchable vanadium oxide compounds as variable temperature-electrical resistance materials onto the surface of flat metallic bipolar plates have been prepared by a dip-coating technique via an aqueous sol-gel method. Subsequently, the chemical composition and micro-structure of the polycrystalline solid thin films were analyzed by X-ray diffraction, X-ray fluorescence spectroscopy, and field emission scanning electron microscopy. In addition, it was carefully measured electrical resistance hysteresis loop over a temperature range from $-20^{\circ}C$ to $80^{\circ}C$ using the four-point probe method. The experimental results revealed that the thin films was mainly composed of Karelianite $V_2O_3$ which acts as negative temperature coefficient materials. Also, it was found that thermal dissipation rate of the vanadium oxide thin films partially satisfy about 50% saving of the substantial amount of energy required for ice melting at $-20^{\circ}C$. Moreover, electrical resistances of the vanadium-based materials converge on an extremely small value similar to that of pure flat metallic bipolar plates at higher temperature, i.e. $T{\geq}40^{\circ}C$. As a consequence, experimental studies proved that it is possible to apply the variable temperature-electrical resistance material based on vanadium oxides for the cold starting enhancement of a fuel cell vehicle and minimize parasitic power loss and eliminate any necessity for external equipment for heat supply in freezing conditions.

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A Variable-Gain Low-Voltage LNA MMIC Based on Control of Feedback Resistance for Wireless LAN Applications (피드백 저항 제어에 의한 무선랜용 가변이득 저전압구동 저잡음 증폭기 MMIC)

  • Kim Keun Hwan;Yoon Kyung Sik;Hwang In Gab
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.29 no.10A
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    • pp.1223-1229
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    • 2004
  • A variable-gain low-voltage low noise amplifier MMIC operating at 5GHz frequency band is designed and implemented using the ETRI 0.5$\mu\textrm{m}$ GaAs MESFET library process. This low noise amplifier is designed to have the variable gain for adaptive antenna array combined in HIPERLAN/2. The feedback circuit of a resistor and channel resistance controlled by the gate voltage of enhancement MESFET is proposed for the variable-gain low noise amplifier consisted of cascaded two stages. The fabricated variable gain amplifier exhibits 5.5GHz center frequency, 14.7dB small signal gain, 10.6dB input return loss, 10.7dB output return loss, 14.4dB variable gain, and 2.98dB noise figure at V$\_$DD/=1.5V, V$\_$GGl/=0.4V, and V$\_$GG2/=0.5V. This low noise amplifier also shows-19.7dBm input PldB, -10dBm IIP3, 52.6dB SFDR, and 9.5mW power consumption.

A Study on the Factors Affecting the Adoption of Cloud Computing Service:Focused on the Technology Acceptance Model(TAM) and Resistance (개인사용자 중심의 클라우드서비스의 수용에 영향을 미치는 요인에 관한 연구:기술수용모형(TAM)과 저항을 중심으로)

  • Park, Yoonseo;Kim, Yongsik
    • Journal of Information Technology Services
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    • v.12 no.4
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    • pp.1-23
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    • 2013
  • This study examines whether key characteristics of cloud computing services would affect the intention of use for personalized cloud computing services. The research model was generated based on Technology Acceptance Model (TAM) with resistance variable, and verified statistically by undertaking a survey about the perception of personal users. As the results of this analysis, we could find the structural relationship among the factors affecting adoption of the cloud computing service. We found that the expectation of ubiquity as a representative function of the cloud computing service meaningfully affected the perceived ease of use and resistance, and that the relativeness with existing services also meaningfully affected the perceived ease of use, but not the resistance. In addition, the moderating effects of use experience in the path leading from the perceived ease of use and resistance to the intention of use were identified. This study will provide diverse implications for the companies providing personalized cloud computing services.

A Study on Balanced -type Oseillating Mole-Drainer(III)-Model Test for Draft Force, Torque, Power and Moment (평행식 진동탄환 암거 천공기의 연구(III)-견인력, 토크, 동력 및 모멘크에 관한 모형시험-)

  • 김용환
    • Journal of Biosystems Engineering
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    • v.1 no.1
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    • pp.1-6
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    • 1976
  • This paper is the third one of the study on balanced type oscillating mole-drainer, the first one was presented in No 9. Gyeongsang College Report and the second one in Vol. 17, No.4 of the KSAE. In the first part of this study, the characteristics of traction forces between the nonoscillating earth working equipments and oscillating ones was compared. A model of the balanced type oscillating mole-drainer, which composed of a mechanism that may reduce the machine vibration, was designed following the dimensional analysis and similitude technique. The model test was carried out to clarify the balancing mechanism of the oscillating parts and other parts of the machine. In the light of the results from the model tests, a prototype machine was made for experimental purpose. Results from the field test by a reported in the near future. In the second report, the model tests were carried out under the same soil conditions, i.e, . oscillating frequency, running velocity, and oscillating amplitude, etc. It was clear that use of balanced type oscillating model could substantially reduce the vibration of the whole system of the machine, when compared with the nonoscillating type model. In this paper(the third report), results of investigation on the traction force, power requirement, and moment. etc, is presented. Analysis of variance technique was used for analyzing the effect of the frequency, amplitude, and running velocity on the draft force, torque, power requirements, and moments. The results obtained from the model tests are as follows, 1) By practicing a balanced-type oscillating mole-drainer, it was possible to reduce the traction resistance by 55.1-61. 2 percent of traction resistance, however, was 1.75 - 1.95 times greater than the value of resistance which was induced by use of a mole-drainer with single bullet. The resistance of rear shank against soil was considered as a main causing factor of the above results. 2) As the oscillation frequency was increased, the traction resistance was decreased. Considering on the effect of oscillation the greater the amplitude, and the slower the running velocity was, the greater the reduction ratio of traction resistance was. 3) The ratio of the traction resistance of oscillating mole-drainer to that of non-oscillating one could be represented as a function of dimensionless variable (V/$Af$). The results from the tests were well agreed with the reported results from the experim ents on oscillation plow or hoe. 4) By taking a lower value of (V/$Af$), reducing the traction resistance was possible. This fact meant, however, that the efficiency of mole drain practice would be lower. 5) It was experimentally confirmed under the same condition of soil that the variable (R/$rD1^3$) could be represented as a function of a variable($V^2/gD$) when a non\ulcornerocillating mole-drainer was used. 6) When a oscillating mole-drainer was used, the variable(R/$rD_1^{3}$) could be represented as a function of two variables ($v^2/gD_1$) and (V^2/gD_1$). 7) The torque was not affected by a change of frequency. However, a relation of proportionality existed between torque and amplitude, running velocity, and ratio of bullet diameter. When a balanced type oscillating mole-drainer with two bullets was used, torque was increased by 52.8-78. 4 percent and total power requirement was also increased. 8) Total power requirement was increased linearly in accordance with the increasing frequency, 41.96 percent of total power was used for oscillating action. The magnitude of total power requirement was 1. 8-9. 4 times greater than that of a non-oscillating mechanism. In the view point of power requirement, it was not advisable to increase the frequency, amplitude, running velocity, and ratio of bullet diameter at the same time. 9) Only the positive moment occured in the rear shank. Change of the diameter of a rear bullet, could not affect the balancing against the soil resistance. It was necessary for rear bullet to have a large resistance against soil only when the rear bullet was in backward motion. 10) Within an extent of the experimental base, optimum limits for several design factors were A=0.5cm, $f$=22.5Hz, V=O. 05m/sec, and $\lambda$=1.0 By adapting these values traction resistance was reduced by 40 percent and vibration acceleration wa s reduced by 60 percent. Even though the total , power requirements for operating a balanced type oscillation mechanism was greater ~than that of non-oscillating one, using a oscillating mechanism would be more effective. Because a balanced type oscillating mechanism is used, tractive resistance will be reduced and then the lighter . tractive equipment could be used.

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A Sliding Mode Control for an Engine Mount Using Magneto-Rheological Fluid (MR유체를 이용한 엔진마운트의 슬라이딩모드제어)

  • 이동길;안영공;정석권;양보석
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2001.11b
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    • pp.1144-1149
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    • 2001
  • In this paper, a sliding mode controller of a fluid engine mount using MR (Magneto-Rheological) fluid was discussed When the MR fluid is applied to a fluid mount, resistance of MR fluid can be controlled by electro-magnetic valve installed in the inertia track. Since the rheological property of the MR fluid shows a function of shear rate, the damping characteristics of the mount will be change according to the frequency. Changing an applied magnetic field to the valve changes the property of the mount, such as the resistance of the MR fluid, the notch and the resonant frequencies due to the fluid passing, quantity of the fluid passing, the effective piston area of the volumetric damping and stiffness. Therefore, the fluid mount using MR fluid can be regarded as a variable structure system The sliding mode control known well as a particular type of variable structure control was introduced in this study. The sliding mode control, which has inherent robustness, is also expected to improve the control performance in the engine mount The sliding mode controller for the mount formatted by taking into account the response property with a time constant to MR fluid and the variable mount property. The motion equations of the fluid mount are derived from Newton's law of motion and used in numerical simulation. Numerical simulations illustrate the effectiveness of the sliding mode controller.

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정보시스템 사용에 대한 내부통제 효과성이 정보역량에 미치는 영향에 관한 연구

  • Lee, Jae-Beom;Kim, Sang-Su;Im, Byeong-U
    • 한국경영정보학회:학술대회논문집
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    • 2007.11a
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    • pp.117-122
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    • 2007
  • Recently, as the management environments are changing rapidly and the uncertainty is becoming larger, the needs of internal control for management and IS become stronger. In order to construct a new internal control system for IS, it is necessary to evaluate the former research of the system. This study emphasizes the importance of effective internal control system, presents a conceptual framework for the preceding factors to consider, and verifies empirically the framework. This study sets the organization citizenship behavior, IS innovation resistance, and IT capability from the viewpoint of Socio-Technical system as the preceding factors for the effectiveness of internal control system. A research model, affecting the above factors on IS capability as a mediating variable of the internal control effectiveness for the use of IS, is set up. PLS-Graph 3.0 is used to verify the model. We found that the internal control effectiveness have affirmative effect on information capability, a surrogate variable of the IS effectiveness and a mediation effect is meaningful.

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A Study on the Fundamental Performance of Electric-driven Bollard (전동식 볼라드의 기본 성능에 관한 연구)

  • Park, Tae-Joon;Jung, Byeong-Gyu;Song, Jun-Ho;Lee, Kee-Man
    • Proceedings of the KAIS Fall Conference
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    • 2011.12b
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    • pp.385-388
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    • 2011
  • This study is about development of remote controlled bollard using the BLDC motor mechatronics theory. A bollard is composed of the sensor part and the control part. The sensor part is consisted of sensors that detect the locations of a bollard. The role of the control part are adjusting motor speed and power through variable resistance. In order to confirm required performance, The speed of decent and ascent of the bollard, the time and the RPM of BLDC motor were tested according to the variable resistance and the load.

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Load Relaxation and Creep Transition Behavior of a Spray Cast Hypereutectic Al-Si Based Alloy (분무 주조 과공정 Al-Si계 합금의 응력이완 및 Creep 천이 거동)

  • Kim M. S.;Bang W.;Park W. J.;Chang Y. W.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2005.05a
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    • pp.176-179
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    • 2005
  • Spray casting of hypereutectic Al-Si based alloy has been reported to provide distinct advantages over ingot metallurgy (IM) or rapid solidification/powder metallurgy (RS/PM) process in terms of microstructure refinement. Hypereutectic Al-Si based alloys have been regarded attractive for automotive and aerospace application, due to high specific strength, good wear resistance, low coefficient of thermal expansion, high thermal stability, and good creep resistance. In this study, hypereutectic Al-25Si-2.0Cu-1.0Mg alloy was prepared by OSPREY spray casting process. High temperature deformation behavior of the hypereutectic Al-Si based alloy has been investigated by applying the internal variable theory proposed by Chang et al. The change of strain rate sensitivity and Creep transition were analyzed by using the load relaxation test and constant creep test.

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Study on Estimate of Window Condensation performance Due to Temperature Depreciation Ratio (표면 온도 저하율에 따른 창호부 결로성능 예측에 관한 연구)

  • Sung, Uk-Joo;Cho, Soo;Jang, Cheul-Yong;Lee, Jin-Seong;Peak, Sang-Hun
    • Proceedings of the SAREK Conference
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    • 2006.06a
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    • pp.1255-1260
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    • 2006
  • This present study analyzed temperature depreciation ratio of window inside surface by KS F 2295 'Procedure for determining fenestration product condensation resistance values'. it estimated window indoor surface condensation due to variable environmental condition. Performance of condensation resistance by using temperature depreciation ratio until applied Low-e and Ar glazing improved about 45% from 24 mm clear. Temperature depreciation ratio by KS F 2295 considers analytic index of window condensation due to variable boundary condition.

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Study of the Constant Current Fuzzy Control System Design using CRS Algorithm during Inverter DC Resistance Spot Welding Process (인버터 DC 저항점용접 공정에서 CRS 알고리즘을 이용한 정전류 퍼지 제어시스템 설계에 관한 연구)

  • Park, Hyoung-Jin;Park, Pyeong-Won;Yu, Ji-Young;Kim, Dong-Cheol;Kang, Mun-Jin;Rhee, Se-Hun
    • Journal of Welding and Joining
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    • v.28 no.6
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    • pp.76-83
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    • 2010
  • The purpose of this study is to propose a method to decide near-optimal settings of the constant current fuzzy control parameters using a controlled random search. This method tries to find the near-optimal settings of the constant current fuzzy control parameters through experiments. It has an advantage of being able to carry out searches in the search domain which includes some irregular points. The method suggested in this study was used to determine the fuzzy control parameters by which the desired welding current were formed during inverter DC resistance spot welding. The output variable was the ITAE (integral of time multiplied by the absolute error). This output variable was determined according to the input variables, which are the GE, GDE, and GDU. This study described how to obtained near-optimal welding current condition over a wide search space conducting a relatively small number of experiments.