• Proceedings of the KIPE Conference
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• 2004.07b
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• pp.479-483
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• 2004

Fuel Cell (FC) has slow response characteristic for load variation. During a load step, the inverter cannot pull more power from the fuel cell than is currently available so supplemental power must be provide by some sort of energy storage elements. In this paper, hi-directional do-dc converter for FC generation system is proposed to improve load response characteristic. The hi-directional converter interfaces the low voltage battery to the inverter dc link of FC generation system. The converter is based on a active full bridge in the primary side and on a half bridge in the secondary of a high frequency isolation transformer. The complete operating principles and simulation results in presented.

• Asian-Australasian Journal of Animal Sciences
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• v.14 no.8
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• pp.1062-1066
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• 2001

Studies were carried out on forty young bulls of the Hariana breed (around 18 months of age) selected on the basis of their dam's milk yield at the animal farm of CCS HAU, Hisar during the period 1993-1999. Since animals showed variation in capacity to work over prolonged periods, they were subjected to regimes of carting without load and with 8 qtls. of load for three hours. The study revealed that maximum change took place in the pulse rate, followed by respiration rate and rectal temperature. The mean fatigue score for pulling an empty cart ranged between 1.66 to 2.20 after two hours work, and 2.36 to 2.73 after three hours work. For a cart loaded with 8 qtls., the corresponding ranges were 2.90 to 3.36 and 3.40 to 4.10, respectively. These results indicated that the animals under experiment had the capacity to pull moderate load (8 qtls.) for about two hours without showing any serious effect on the ability to recover and soon to work again.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.219-224
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• 2009

In this study, the characteristics of pullout behavior of Pressurized light-weight steel Anchor was investigated through centrifuge model tests considering pull-out angle $0^{\circ}$ with changing undrained shearstrength(0~1, 2~4, 5~7kPa) of clay. According to the results of tests, the yield pullout load of clay ground was gradually increased up to 30% as undrained shear strength was increased. Therefore, it was known that the yield pullout load was affected by increasing the undrained shear strength, in addition, the pattern of behavior was not changed.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.03a
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• pp.413-420
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• 2002

Recent experimental research results of connection method between steel pipe pile and concrete footing are provided based on various experimental observations. It gives a shedding light toward developing better and concrete connection method for steel pipe pile at the field application. In this study, the newly developed method is tested for compressive, pull put and combination load including moment with carefully designed monitoring system. The measured data show that new method have at least equivalent or better load resistant capacities compared with those of specified method in Korea Highway Corporation design code. It is also tried to define and investigate the load transfer mechanism for new method.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.05a
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• pp.248-254
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• 2002

The most controversial topics in plasma sprayed ceramic coating system are recently mechanical properties such as bond strength, cohesive strength, toughness and so on. Determination of bond strength of coatings is one of the most important problems. In the industry, the bond strength of coating system has been estimated by Pull-off test(ASTM standard C633-79). But, without a fixed jig and specimen, it is impossible to obtain the bond strength. Therefore, it is necessary to study the critical fracture load on interface of the coating by indentation test. Because the critical fracture load plays an important role in evaluating the bond strength for plasma sprayed ceramic coating system. So, we have estimated critical fracture load in plasma sprayed ceramic coating system, and it was shown that inverse relationship between the cross-section hardness of coating and the critical fracture load(Pc). In case of the high load(1kgf, 2kgf) in $Al_{2}O_{3}+13%TiO_{2}$, it was found that the critical point(Pco), which the coating was broken on.

• Journal of Welding and Joining
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• v.18 no.5
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• pp.105-111
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• 2000

The wear behavior of thermal sprayed AlSiMg-40TiC composite coatings were studied as a function of load and sliding velocity under unlubricated conditions. Experiments were performed using a block-on-ring(WC-6wt%/Co, Hv 1500) type. The tests were carried out a various load(30∼ 125.5N) and sliding velocity(0.5∼2.0m/s). Three wear rate regions were observed in the AlSiMg-40TiC composite coatings. The wear rate in region I at low load (less then 8N( were less than 1×{TEX}$10^{-5}${/TEX}㎣/m. Low wear rates in region I resulted from the load-bearing capacity of TiC particles. The transition from region I to II occurred when the applied load exceeded the fracture and pull-out strength of the particles. The TiC fractured particles trapped between the specimen and the counterface acted as third-body abrasive wear. The subsurface layer worn surface in region II was composed of the mechanically mixed layer (MML). The wear rate increase abruptly above a critical load (region III). The high wear rate in region III was induced by frictional temperature and involves massive surface damage.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.11
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• pp.1034-1046
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• 2013

In this paper, a design of a GaN HEMT power amplifier using output matching circuit with arbitrary harmonic impedances is presented. The adopted GaN HEMT device, TGF2023-02 of TriQuint Semiconductor, was packaged in commercial package. The optimal impedances of the GaN HEMT package are extracted from load-pull simulation at package input and output reference planes. The targets of load-pull simulation are the highest output power at fundamental frequency and the highest efficiency at $2^{nd}$ and $3^{rd}$ harmonic frequencies. Because of fixture in the package, the extracted impedances shows arbitrary harmonic impedances. In order to match the optimal impedances, output matchin circuit which has 4 transmission lines is presented. Characteristic impedances and electrical lengths of the transmission lines are mathmatically calculated. The power amplfiier with $54.6{\times}40mm^2$ shows the output power of 8 W at the fundamental frequency of 2.5 GHz, the efficiency above 55 %, and harmonic suppression of above 35 dBc at the $2^{nd}$ and the $3^{rd}$ harmonics.

• Journal of Power Electronics
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• v.7 no.3
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• pp.246-256
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• 2007

In this paper, a novel type auxiliary active edge resonant snubber assisted zero current soft switching pulse modulation Single-Ended Push Pull (SEPP) series load resonant inverter using IGBT power modules is proposed for cost effective consumer high-frequency induction heating (IH) appliances. Its operating principle in steady state is described by using each switching mode's equivalent operating circuits. The new multi resonant high-frequency inverter with series load resonance and edge resonance can regulate its high frequency output power under a condition of a constant frequency zero current soft switching (ZCS) commutation principle on the basis of the asymmetrical pulse width modulation (PWM) control scheme. Brand-new consumer IH products using the proposed ZCS-PWM series load resonant SEPP high-frequency inverter using IGBTs is evaluated and discussed as compared with conventional high-frequency inverters on the basis of experimental results. In order to extend ZCS operation ranges under a low power setting PWM as well as to improve efficiency, the high frequency pulse density modulation (PDM) strategy is demonstrated for high frequency multi-resonant inverters. Its practical effectiveness is substantially proved from an application point of view.

• 전기의세계
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• v.21 no.2
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• pp.20-24
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• 1972

The transient stability of the synchronous motor is generally improved by damper winding or flywheel. However the synchronous motor at full load will be pulled out from normal operation state when the period of power failure exceeds approximately ten cycle per second. This paper studies the method of improving the stability of synchronous motor by equipping the phase slipping switch between the motor and power source. This paper shows the motor does not pull out, which results from the decrease of power angle to about 30 electrical degrees by means of the switch even when the relatively long period of power failure brings the power angle to some 150 electrical degrees.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2000.11a
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• pp.220-224
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• 2000

AlGaAs/GaAs HBT를 이용하여 1.9 GHz 대역 2단 MMIC 전력증폭기를 설계하였다. HBT의 실측 S 파라미터를 이용하여 정합회로를 설계하였으며, 목적에 따라 적절한 형태의 출력 정합 회로를 하이브리드 형태로 칩 외부에 부가할 수 있도록 설계하였다. HBT의 실측정 S 파라미터의 fitting을 통하여 비선형 등가모델을 추출하였고, load-pull 시뮬레이션으로 최대 출력 정합 임피던스를 결정하였다. 시뮬레이션 결과, 29 dBm의 출력 전력, 40 %의 전력 부가 효율, 그리고 16 dB의 전력 이득을 얻었다.