• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.1
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• pp.78-82
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• 2020

In this study, MOSFETs fabricated on Si-doped, MBE-grown β-Ga₂O₃ are demonstrated. A Si-doped Ga₂O₃ epitaxial layer was grown on a Fe-doped, semi-insulating 1.5 cm × 1 cm Ga₂O₃ substrate using molecular beam epitaxy (MBE). The fabricated devices are circular type MOSFETs with a gate length of 3 ㎛, a source-drain spacing of 20 ㎛, and a gate width of 523 ㎛. The device exhibited a good pinch-off characteristic, a high on-off drain current ratio of approximately 2.7×10⁹, and a high breakdown voltage of 1,080 V, which demonstrates the potential of Ga₂O₃ for power device applications including electric vehicles, railways, and renewable energy.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.12
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• pp.1167-1172
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• 2013

This paper presents a X-band doppler radar with high conversion gain using a self-oscillating-mixer(SOM) that oscillation and frequency mixing is realized at the same time. To improve phase noise of the SOM oscillator, a ${\lambda}/2$ slotted square patch resonator(SSPR) was proposed, which shows high Q-factor of 175.4 and the 50 % reduced circuit area compared to the conventional resonator. To implement the low power system, low biasing voltage of 1.7 V was supplied. To enhance the conversion gain of the SOM, bias circuit is configured near the pinch-off region of transistor, and the conversion gain was optimized. The output power of the proposed SOM was -3.16 dBm at 10.65 GHz. A high conversion gain of 9.48 dB was obtained whereas DC Power consumption is relatively low about 7.65 mW. The phase noise is -90.91 dBc/Hz at 100 kHz offset. The figure-of-merit(FOM) of the proposed SOM was measured as -181.8 dBc/Hz, which is supplier to other SOMs by more than about 7 dB.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.4 s.247
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• pp.357-363
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• 2006

According to the study of grasping of the human hand, it is noted that the metacarpal link of the thumb plays the key role in power grasping. Also the face of fingertip can be discriminated into five parts depending on the grasping modalities such as pinch grasp, fingertip grasp and power grasp. In this paper, the design of the anthropomorphic robot hand which has a thumb and three fingers is proposed. A difference of SKKU hand II from the previous gripperlike robot hand is that the metacarpal bone is connected between the thumb and the palm. This thumb mechanism is specially designed to get the degree of freedom which can realize flexible motions relative to objects. Based on the analysis, the hand mechanism is developed. Since the driving circuits for the hand are embedded in the hand, only the communication lines supporting CAN protocol with DC power cable are necessary as the input. A new robot is manufactured and feasibility of the hand is validated through preliminary experiments.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.11
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• pp.699-707
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• 2017

This study presents a comparative thermodynamic analysis of subcritical and transcritical organic Rankine cycles for the recovery of low-temperature heat sources considering nine substances as the working fluids. The effects of the turbine inlet pressure, source temperature, and working fluid on system performance were all investigated with respect to metrics such as the temperature distribution of the fluids and pinch point in the heat exchanger, mass flow rate, and net power production, as well as the thermal efficiency. Results show that as the turbine inlet pressure increases from the subcritical to the supercritical range, the mismatch between hot and cold streams in the heat exchanger decreases, and the net power production and thermal efficiency increase; however, the turbine size per unit power production decreases.

• Journal of Korean Orthopaedic Sports Medicine
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• v.4 no.1
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• pp.49-54
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• 2005

Purpose: Complete rupture of metacarpophalangeal ulnar collateral ligament of thumb needs surgical exploration and repair, owing to the interposition of the adductor aponeurosis (Stener lesion) which interferes in healing process. We performed arthroscopic diagnosis and treatment on ulnar collateral ligament injury of thumb and evaluated it's efficiency. Materials and Methods: Arthroscopy was perfomed on 13 patients of whom injured on complete ruture of metacarpophalangeal ulnar collateral ligament. Follow-up period was over 1 year and mean age was 35.6 years old. Ulnar collateral ligament tears and Stener lesion were diagnosed and treated by arthroscopy procedure. Results were interpreted by joint instability, pinch power, grip power and range of motion on metacarpophalangeal joint of thumb. Results: We found 5 Stener lesions in 13 cases. There was no appreciable postoperative instability. Pinch and grip power were recovered to 92%, 94% of uninjured thumb respectively. Range of motion on metacarpophalangeal joint was mean $52^{\circ}$, almost equal to uninjured thumb. Conclusions: Arthroscopic treatment in metacapophalangeal ulnar collateral ligament injury of thumb is useful method that Stener lesion can be clearly comfirmed and treated. Also soft tissue injuries can be minimized, thereby early functional recovery can be expected.

• Journal of Korean Neurosurgical Society
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• v.55 no.5
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• pp.296-299
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• 2014

We report a rare case of pronator teres syndrome in a young female patient. She reported that her right hand grip had weakened and development of tingling sensation in the first-third fingers two months previous. Thenar muscle atrophy was prominent, and hypoesthesia was also examined on median nerve territory. The pronation test and Tinel sign on the proximal forearm were positive. Severe pinch grip power weakness and production of a weak "OK" sign were also noted. Routine electromyography and nerve conduction velocity showed incomplete median neuropathy above the elbow level with severe axonal loss. Surgical treatment was performed because spontaneous recovery was not seen one month later.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.518-518
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• 2013

자외선이 생체를 파괴하거나 탄생시킬 수 있는 중요한 요소라는 것은 잘 알려져있다. 이 때문에 생체 시료를 보통 자외선 파장대인 250~350 nm보다 짧은 10 nm 영역에 있는 극자외선에 노출되었을 때 그 상호작용 및 변화를 찾아서 분석하는 것을 목표로 삼는다. 먼저 이에 대한 기초내용으로, 앞으로 활용하게 될 플라즈마 집속장치에서의 전극형태에 따른 EUV 광원의 특성을 알아보는 실험을 진행하였다. 이 실험은 집속 플라즈마 발진장치의 2가지 전극인 마테르 (Mather) 형태의 전극과, 초사이클로이달 핀치(Hypercycloidal pinch) 핀치 형태의 전극에서 발진된 극자외선(Extreme Ultraviolet : EUV) 집속 플라즈마의 전자온도와, 전자밀도, power를 분석하였다. 그리고 EUV 광원 발생장치에 Ar 가스와, Ne-Xe 가스내 환경에서 2 종류의 전극에 의해 만들어진 고밀도 플라즈마로부터 발생된 EUV의 특성을 알아보았다.

• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1606-1608
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• 1994

A performance of the torch greatly depends on the plasma gas and the cooling gas. The plasma gas constricted by the nozzle concentrates electric power and momentum, so it can eject molten metal from a cut. As an electric arc constricted in a nozzle is more constricted through thermal pinch by the cooling gas, it is possible to transfer larger thermal concentration to the workpiece. The optimized parameter value in this study was given below. Plasma gas pressure is $4[kgf/cm^2]$ and gas mass flow is $30[{\ell}/min]$. Cooling gas pressure is $6[kgf/cm^2]$ and gas mass flow is $120[{\ell}/min]$.

• Proceedings of the IEEK Conference
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• 2003.11c
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• pp.72-76
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• 2003

In this paper, active frequency doubler with broadband characteristics and unconditional stability from 6GHz to 12GHz was designed and fabricated using PHEMT. The designed frequency multiplier has a bias point near pinch-off and a proposed RC circuit between bias line and input matching network for the improvement of stability. With 0dBm input power, second harmonic of 1.7dBm at 12GHz, - 27.5dBc suppression of 6GHz fundamental, -18dBc suppression of 18GHz 3rd harmonic and the output bandwidth of 1.8GHz have been measured.

• Journal of Korean Academy of Nursing
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• v.36 no.2
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• pp.403-414
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• 2006

Purpose: The purpose of this study was to investigate the effects of constraint-induced (CI) movement using self-efficacy on U/E function of chronic hemiplegic patients. CI movement discourages the use of the unaffected U/E, combined with intensive training of the affected U/E. Method: A non-equivalent pretest-posttest design was used. Study subjects were 40 hemiplegic patients conveniently selected from 2 different community health centers. The experimental subjects participated in the CI movement program for 6 hours daily over a period of two weeks. The exercises for affected U/E consisted of warming up, main exercise and ADL practice. To encourage the participants' behaviors self-efficacy enhancing strategies were used, which included performance accomplishment, vicarious experience, verbal persuasion and emotional arousal. Result: After 2 weeks of treatment, the grip power, pinch power, wrist flexion/extension, elbow flexion, and shoulder flexion/extension were significantly higher in the experimental subjects than in the control subjects. However, there was no significant difference in hand functions of the two groups. Conclusion: The above results show that the constraint-induced movement using self-efficacy could be an effective nursing intervention for improving U/E function of chronic hemiplegic patients. Long term studies are needed to determine the lasting effects of constraint-induced movement.