• 대한임상전기생리학회지
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• 제8권1호
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• pp.23-29
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• 2010

Purpose : This study is to offer clinical primary data that examines the change of imaging structure and the quantitative evaluation of muscle activity on myofascial trigger points. This study examines neuromuscular physiological characteristic by comparing the differences in physical findings, pressure pain threshold, imaging, and electrophysiological characteristics in latent and active myofascial trigger points muscle and normal muscle through the following experimental procedures. Methods : The participants for the study were thirty-three adults in their twenties. We divided three groups into normal, latent and active myofascial trigger points groups by physical findings. We analyzed the results of measured pressure pain, threshold for pain, ultrasound imaging perform for structure characteristic of muscle, surface EMG according to type of muscle contraction for function of muscle contraction. Results : Significant differences were indicated in pressure pain threshold (p<0.05). Significant differences were discovered in the ultrasound imaging analysis. There were increases in muscle Echogenicity white area index (p<0.001). There were significant differences that decrease in %MVIC (p<0.05), increase in MDF (p<0.05). Conclusion : From these results, active rnyotascial trigger points muscle showed quality deterioration on ultrasound imaging and decreased function of muscle contraction, increased motor unit action potential of II type fiber, and electrophysiologically. Imaging structure and neuromuscular physiological characteristic can be diagnostic and quantitative analytical techniques for myofascial pain syndrome and a primary factor that reflected in physical therapy intervention.

• 한국수소및신에너지학회논문집
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• 제22권4호
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• pp.552-558
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• 2011

A 50 kW class rotating body type wave energy converter consisted of two floating bodies and a PTO (Power Takeoff) unit is studied. As an wave energy extractor, the body is designed to have a VLCO (Variable Liquid-Column Oscillator) having a liquid filled U-tube with air chambers. Owing to the oscillation of the liquid in the U-tube caused by the air spring effect of the air chambers, the amplitude of response of the VLCO becomes significantly amplified for a target wave period. The PTO converts the rotational moment introduced from the relative motion of the hinged bodies to an hydraulic power by means of a cylinder. A high pressure accumulator, hydraulic motor and a generator are equipped in the PTO to convert the hydraulic power to electric power. A control law for adjusting the oscillation period of the VLCO is proposed for the efficient operation of the VLCO with various wave conditions. It is found that the effect of the air spring has an important role to play in making the oscillation of the VLCO match with the ocean wave. In this way, the wave energy converter equipped with the VLCO provides the most effective mode for extracting energy from the ocean wave.

• 한국기계가공학회지
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• 제19권7호
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• pp.52-59
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• 2020

Automatic tool changers (ATCs) can be divided into drum and chain types. Drum-type ATCs contain a magazine, where the tools are mounted, and a cam gearbox, which swaps the tools via roller gear and grooved plate cams. Drum-type ATCs are advantageous in that the operating time for the tool magazine is more rapid than that of chain-type ATCs and the length of the unit is shorter. Thus, drum-type ATCs can be fabricated into various shapes and forms depending on the number of tools and the magazine size in accordance with machining center requirements and consumer demand. In particular, the price competitiveness of a machining center with a drum-type ATC is higher, while drum-type ATCs are more rigid with fewer parts, possibly reducing the need for regular servicing. This study aims to verify the structural stability and design validity of the magazine base, which is the main structure of a drum-type ATC, using finite element analysis. This study kinematically verifies the specifications of the selected drive motor and reducer and assessed the design of the cam gearbox. It also conducts a structural analysis of the roller camp, which is the core component of the cam gearbox, based on the results of the kinetodynamic analysis, thus validating the structural design.

• 한국항공우주학회지
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• 제46권5호
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• pp.393-401
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• 2018

고체 로켓 추진기관에서 우발점화를 방지하기 위해 사용하는 전자식 점화안전장치의 신뢰도 예측에 관하여 연구하였다. 신뢰도 예측을 위해 가장 먼저 점화안전장치의 주요 구성품(점화회로, 고전압 기폭관, 격벽착화기)을 정의하고, 각 구성품의 작동원리에 대해 시스템 분석을 수행하였다. 시스템 분석을 통해 선별된 입력 변수를 이용하여 각 부품의 성능 모델링을 수행하였으며, 복잡한 해석이 필요한 경우 반응표면기법을 이용하여 다항식으로 근사하였다. 마지막으로 만들어진 성능 모델링을 기반으로 몬테칼로 시뮬레이션을 적용하여 설계 신뢰도를 예측하였다.

• 한국운동역학회지
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• 제19권3호
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• pp.603-610
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• 2009

본 연구의 목적은 드롭 착지 동작 시 탄성 섬유 바지 착용이 충격력과 근육 활동에 어떠한 영향을 미치는가를 분석하는데 있다. 10명의 피험자를 대상으로 7쌍의 표면전극을 대퇴직근, 내측광근, 외측광근, 대퇴이두근, 전경골근, 내측비복근, 외측비복근에 부착하고 탄성 바지와 일반 바지를 무작위로 착용한 상태로 플랫폼에서 드롭 랜딩하였고 각 변인에 대해 대응표본 t-검증을 실시하여 통계적 유의차를 밝혔다(p< .05). 착지 구간 동안 전경골근, 대퇴이두근, 내측비복근의 평균적분 근전도치가 일반바지 착용 시 유의하게 감소되었다. 대퇴직근을 제외한 모든 근육에서 최대적분 근전도가 탄성바지 착용 집단이 높게 나타났다. 탄성바지 착용 시 신체 하지분절의 감속과 안정을 유지하기 위한 근육 동원 능력이 높아져 이러한 현상이 발생되어진 것으로 사료된다. 탄성바지 착용이 충격력과 부하율의 감소에 통계적으로 유의한 결과를 발생시키지 못하였다. 본 연구에서 사용된 탄성바지는 피험자의 하지 둘레에 적합하게 제작되어진 바지가 아니기 때문에 탄성과 압축력이 이상적으로 발생되지 못한 것으로 판단된다.

• Tribology and Lubricants
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• 제31권4호
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• pp.141-147
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• 2015

Gas foil thrust bearings (GFTBs) have attractive advantages over rolling element bearings and oil film thrust bearings, such as oil-free operation, high speed stability, and high-temperature operation. However, GFTBs have lower load carrying capacity than the other two types of bearings owing to the inherent low gas viscosity. The load carrying capacity of GFTBs depends mainly on the compliance of the foil structure and the formed hydrodynamic wedge, where the gas pressure field is generated between the top foil and the thrust runner. The load carrying capacity of the GFTBs is very important for the suitable design of oil-free turbomachinery with high performance. The aim of the present study is to identify the characteristics of the load carrying performance of GFTBs. A new test rig for the experimental measurements is designed to provide static loads up to 800 N using a pneumatic cylinder. The maximum operating speed of the driving motor is 30,000 rpm. A series of experimental tests—lift-off test, static load performance test, and maximum load capacity test—estimate the performance of a six-pad GFTB, in terms of the static load, driving torque, and temperature. The maximum load capacity is determined by increasing the static load until the driving torque rises suddenly with a sharp peak. The test results show that the torque and temperature increase linearly with the static load. The estimated maximum load capacity per unit area is approximately 80.5 kPa at a rotor speed of 25,000 rpm. The test results can be used as a design guideline for GFTBs for realizing oil-free turbomachinery.

• 한국산업융합학회 논문집
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• 제17권4호
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• pp.234-244
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• 2014

Recently it has been focused that the automobile engine has developed in a strong upward tendency for the use of the high viscosity and poorer quality fuels in achieving the high performance, fuel economy, and emission reduction. Therefore it is not easy to solve the problems between low specific fuel consumption and exhaust emission control at motor cars. In this study, it is designed and used the engine test bed which is installed with turbocharger and intercooler. In addition to equipped using CRDI by controlling injection timing with mapping modulator, it has been tested and analyzed the engine performance, combustion characteristics, and exhaust emission as operating parameters, and they were engine speeds(rpm), injection timing(bTDC), and engine load(%). From the result of an experimental analysis, peak cylinder pressure and the rate of pressure rise were increased, and the location of it was closer toward top dead center according to the increasing of engine speed and load, and with advancing injection timing. The combustion characteristics are effected by fuel injection timing due to be enhanced the mass burned fraction. Using the engine dynamometer for analyzing the engine performance, the engine torque and power have been enhanced according to advancing the fuel injection timing. In analyzing of exhaust emission, there has been a trade-off between PM and NOx with increasing of engine speed and load, and with advanced injection timing. The experimental data are shown that the formation of NOx has increased and PM, vice versa.

• 대한조선학회논문집
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• 제32권3호
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• pp.1-18
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• 1995

중력진자식과 원심진자식의 두가지 형의 소형동흡진기를 이용한 구조물 진동의 제어시스템을 개발하였다. 개발된 본 시스템은 step 및 servo motor, 소형흡진기, metor drive unit와 제어장치로 구성되어 있으며, 구조물의 진동을 수진기로 감지하고, 이 신호를 받아 소형흡진기의 기능을 최적 제어하여 구조물의 진동을 제어한다. 제어시스템의 제어성능 검증시험을 위해 상자형 강판구조물($L{\times}W{\times}H{\times}T=800mm{\times}700mm{\times}1500mm{\times}7mm$) 중량 180kg를 제작하여 시험을 수행하였으며, 실험결과 중력진자식 흡진기는 95%의 흡진성능을, 원심진자식 흡진기는 88%의 흡진성능을 가지게 됨이 확인되었다.

• 조명전기설비학회논문지
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• 제14권4호
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• pp.1-7
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• 2000

본 논문에서 원전의 핵연료 다발의 중섬자속을 측정할 수 있는 노내중성지속 감시계통의 구동모터를 제어하기 위한 스위치의 오동작 원인 분석 및 이 문제를 해결하기 위한 방안을 제시하고자 한다. 노내중성자속 감시계동은 검출기 안내관을 통해 검출기가 노심으로 삽입되거나 인출될 경우 접점선호를 발생하는 기계식 스위치레버를 장착하고 있다. 그러나 기계적인 열화나 환경적인 요인에 의해 기계식 스위치레버의 특성이 점점 변화되어 마침내 잘못된 접점신호를 발생하게 된다. 그러므로 아들 문제 해결을 위해 기계식 스위지 대선 전자식 스위치를 검출기 안내관 밖에 배치하였고, 공진효과를 이용하여 점점신호를 발생하는 회로개선과 소음 및 전기적 방해를 방지하기 위한 콘데서를 전자회로 전원 입력측에 설치하였다. 이러한 개선을 완료한 후, 여러 조건하에서 이 향상된 스위치 제어회로를 반복적으로 시험하였는데, 결국 이를 통해 원하는 접점신호를 얻게되었을 뿐 아니라 발전소 정상운전 중에 관련시스템의 주기시험을 통해서도 검출기 접점 오동작 신호가 발생되지 않음울 확인할 수 있게 되었다.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2007년도 동계학술발표대회 논문집
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• pp.606-611
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• 2007

Pulsation is an inherent phenomenon in reciprocating compressors. It interacts with piping to cause vibrations and performance problems. Indiscriminately connecting to a compressor can be dangerous and cost money in the form of broken equipment and piping, poor performance, inaccurate metering, unwanted vibration, and sometimes noise. Piping connected to a compressor can materially affect the performance and response. To minimize these detrimental effects, reciprocating compressor system should be equipped by pulsation suppression system. This study discusses pressure pulsation phenomena occurred in a reciprocating compressor system. An experiment applied air compressor unit, as pulsating pressure generator, has been done. The compressor was connected sequentially to a snubber model and pressure tank. Sensor probes were placed on the inlet and outlet pipes of snubber. Compressor was driven by a motor controlled by a frequency regulator. The experiment was conducted by adjusting the regulator at 40Hz. General information about an internal gas flow can be achieved by numerical analysis approach. Information of the velocity, pressure and turbulence kinetic energy distribution are presented in this paper. Based on this result, the design improvement might be done.