• 한국공작기계학회논문집
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• 제11권2호
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• pp.71-79
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• 2002

In this paper, an oil hydraulic pipeline is terminated by both rotary sinusoidal flow generator at upstream oriffice at down stream. The pulsating pressure wave from generated by the rotary sinusoidal flow generator, is measured by using sensor. In the analysis of this paper, a component of the fundamental frequency is obtained by using Laplace transformation.. The experimental and analytical results make clear that (1) viscosity is significant role in hydraulic pipe. (2) When pulsating frequency is matched with the natural frequency, resonance frequency occured periodically. According to the study proposed here, dynamic pressure in a circular oil pipe is expressed in propagation of pressure wave with respect to frequency and Bessel function. The resonance at oil temperature $20^{\circ}$$0^{\circ}C$ in this study. The abrupt change of gain value is due to effect of resonance frequency. The results of experiment are compared with the calculated results, and agreement of both results is fairly good.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.1784-1787
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• 2005

In this paper, proportional modulator which controls the second pressure of the pneumatic system was studied and proportional operating of modulator was gotten by two digital valves that have a fast dynamic characteristics and were controlled by PWM operating method. In order to more precision pressure control, this modulator consist of not only high speed two digital valves but also pressure sensor, measurement equipment and controller having a microprocessing function. In this study, for the development of the new proportional modulator, various research such as PWM control method, test equipment manufacturing, testing and evaluation were accomplished.

• 센서학회지
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• 제10권6호
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• pp.304-309
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• 2001

콘크리트 구조물의 내부 변형률을 측정할 수 있는 광섬유 간섭계 센서가 개발되어졌다. 광섬유 간섭계 센서는 11 mm 길이의 광섬유 Fabry-Perot 간섭계를 2 mm 지름의 스텐레스 강관 내부에 접착제로 고정하여 만들었다. 제작된 변형률 센서들은 $100{\times}100{\times}500\;mm^3$ 크기의 콘크리트 구조물 내부에 삽입되어 외부에서 구조물에 압력을 인가했을 때 구조물 내부의 변형률을 측정하였다. 센서들의 출력은 변형률 변화에 따라 선형적으로 변화하였다. 이를 바탕으로 실제 교량에 적용하여 변형률 센서의 광출력 특성을 살펴본 결과 우수한 변형 감지 특성을 보였으며, 실제 구조물에서 원거리측정에 이용도 가능하였다.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2002년도 제24회 KOSCO SYMPOSIUM 논문집
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• pp.140-146
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• 2002

The tulip-inversion of flames in half-open tubes was investigated experimentally. Experiments was carried out in tubes with various shapes. The image of a flame propagation were pictured by HICCD(High speed intensified CCD) and the dynamic pressure of tubes was measured by a piezo pressure sensor. By analyzing the images of the flame propagation, we found the time and the distance for the occurrence of tulip-inversion. Regardless of the shapes of tubes, time of tulip-inversion are similar and inversely proportional to the burning velocity. But distances have different tendency. In a straight tube, the distance of tulip-inversion increases when the burning velocity increases. But in a converging tube, the distance of tulip-inversion decreases when a burning velocity increases. And the distance of tulip-inversion in a converging tube is much smaller than the distance of tulip-inversion in a straight tube. These results are caused by the deceleration of a flame when the diameter of a hole in open-side of a tube is small. The deceleration causes little effect on the time of tulip-inversion.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.1231-1234
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• 2003

Pneumatic servo valve which is widely applied in industrial world is advanced technology compounded with electric, electronic and machine. And It is consist of Linear Force Motor. Spool Commutation Mechanism and Microprocessor. In this study, we accomplished test method of Linear Force motor test, Static characteristic test, Dynamic characteristic test for KS(Koran industrial standard) of Pneumatic servo valve. we accomplished study about the main item of Static characteristic test which is related to unload flow characteristic test. And Dynamic characteristic test was step input test and frequency response test. Specially about frequency response test, There was a difficulty resulting from the time delay problem caused by the basic compressibility of air. In order to solve the problem in this study. we proposed two methods. First, displacement of the servo valve spool was directly measured by using a laser sensor. Second, method of calculating control flow by measuring pressure and temperature of chamber.

• 전력전자학회논문지
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• 제13권3호
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• pp.171-178
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• 2008

본 논문에서는 압력예측기법과 직접 순시토크 제어기법을 통한 유압펌프용 SRM의 압력제어 구동시스템을 제안하였다. 일반적으로 유압 펌프 시스템은 유압센서의 응답성으로 인하여 제어시스템의 시지연이 비교적 길어지게 되며, 이러한 시간지연은 PI 또는 PID 제어 구조에서 장시간의 진동과 불안정화를 만들기 쉽다. 본 논문에서는 시간 지연문제를 해결하고 리플이 없는 압력제어를 위하여 스미스 예측기(simth predictor)를 통한 지연보상과 직접 순시토크제어기법(Direct Instantaneous Torque, 이하 DITC)을 적용하였다. 제안된 제어 방식은 펌프와 센서간의 기구적 문제에 의한 지연문제 해결과 안정성을 확보하고, 펌프 압력제어의 동특성을 향상시키며 전류(轉流, commutation) 구간에서 균일한 토크를 발생시켜 토크 리플을 억제하기 위함이다. 제안된 제어방식은 시뮬레이션과 실험을 통하여 효용성을 검증하였다.

• 센서학회지
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• 제18권2호
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• pp.147-153
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• 2009

A thermal flow sensor has been fabricated and characterized, consisting of a center resistive heater surrounded by two upstream and one downstream temperature sensing resistors. The heater and temperature sensing resistors are fabricated from nitrogen-doped(n-type) polycrystalline silicon carbide(poly-SiC) deposited by LPCVD(low pressure chemical vapor deposition) on LPCVD silicon nitride films on a Si substrate. Cavities were etched into the Si substrate from the front side to create suspended silicon nitride membranes carrying the poly-SiC elements. One upstream sensor is located $50{\mu}m$ from the heater and has a sensitivity of $0.73{\Omega}$/sccm with ${\sim}15\;ms$ rise time in a dynamic range of 1000 sccm. N-type poly-SiC has a linear negative temperature coefficient and a TCR(temperature coefficient of resistance) of $-1.24{\times}10^{-3}/^{\circ}C$ from room temperature to $100^{\circ}C$.

• 한국전문물리치료학회지
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• 제12권2호
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• pp.1-10
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• 2005

Pressure ulcers are serious complications of tissue damage that can develop in patients with diminished pain sensation and diminished mobility. Pressure ulcers can result in irreversible tissue damage caused by ischemia resulting from external loading. There are many intrinsic and extrinsic contributors to the problem, including interface tissue pressure, shear, temperature, moisture, hygiene, nutrition, tissue tolerance, sensory and motor dysfunction, disease and infection, posture, and body support systems. The purposes of this study were to investigate the relationship between buttock interface pressure and seating position, wheelchair propulsion speed. Seated-interface pressure was measured using the Force Sensing Array pressure mapping system. Twenty subjects propelled wheelchair handrim on a motor-driven treadmill at different velocities (40, 60, 80 m/min) and seating position used recline ($100^{\circ}$, $110^{\circ}$, $120^{\circ}$) with a wheelchair simulator. Interface pressure consists of average (mean of the pressure sensor values) and maximum pressure (highest individual sensor value). The results of this study were as follows; No significant correlation in maximum/average pressure was found between a static position and a 40 m/min wheelchair propulsion (p>.05). However, a significant increase in maximum/average pressure were identified between conditions of a static position and 60 m/min, and 80 m/min wheelchair propulsion (p<.05). No significant correlation in maximum pressure were found between a $90^{\circ}$ recline (neutral position) and a $100^{\circ}$, $110^{\circ}$, or $120^{\circ}$ recline of the wheelchair back (p>.05). No significant difference in average pressure was found between conditions of a $90^{\circ}$ recline and both a $100^{\circ}$ and $110^{\circ}$ recline of wheelchair back. However, a significant reduction in average pressure was identified between conditions of a $90^{\circ}$ and $120^{\circ}$ recline of wheelchair back (p<.05). This study has shown some interesting results that reclining the seat by $120^{\circ}$ reduced average interface pressure, including the reduction or prevention in edema. And interface pressure was greater during dynamic wheelchair propulsion compared with static seating. Therefore, the optimal seating position and seating system ought to provide postural control and pressure relief. We need an education on optimal seating position and a suitable propulsion speeds for wheelchair users.

• 한국추진공학회지
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• 제17권1호
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• pp.89-96
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• 2013

산화제 과잉 예연소기의 연소안정성을 알아보기 위하여 예연소기의 각 부위에서 압력을 측정하였다. 압력측정은 정압센서와 동압센서를 모두 이용하여 이루어졌다. 이 때 사용된 정압센서와 동압센서의 해상도는 각각 최고 1000 Hz와 25,600 Hz이다. 예연소기의 정격압은 200 bar이나 위험을 줄이기 위하여 초기에는 80 bar로 낮추어 시험을 하였고 안정성이 확인된 이후 200 bar 시험을 실시하였다. 또한 모든 시험에서 점화충격을 줄이기 위하여 저압점화 후 연소압을 정격압력까지 올리는 2단 점화를 사용하였다. 시험은 최대 약 10초가량 실시되었으며 메인모드 진입 이후에는 연소압에 큰 변화 보이지 않았다. 연소압의 측정결과는 FFT를 통해 좀 더 심도 있게 분석되었으며 그 결과 예연소기의 연소안정성을 해할 만한 주파수의 커플링은 발견되지 않았다. 따라서 현재 개발되고 있는 예연소기는 향후 다단 연소사이클 엔진 연구에 활용할 수 있을 것으로 기대한다.

• 산업경영시스템학회지
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• 제41권3호
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• pp.108-114
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• 2018

One of the most performed action in daily life is standing up from sitting position. As the population of the world is aging at the high rates, people may face problems with reduced muscle strength as well as psychological changes. This can lead elderly people having difficulties with standing up from chair. Now, with the aging trend worldwide, products are being developed that can support the lives of the elderly. This study examines the distribution of hip pressure in relation to the seating positions of the standing assistance seats under development to prevent standing up accidents in older adults. The currently developing standing assistant chair designed to tilt to a maximum angle of 25 degrees. At over $25^{\circ}$, design considers that older people are at risk of thrown back out of that force and that the forces exerted on their arms and legs can be a significant burden to older people. By considering danger of higher than $25^{\circ}$ for older people which is experimented in the basis of static capturing approach in previous papers, it is experimented people with age group of 20~60 on $0^{\circ}$ to $25^{\circ}$ tilting angle on the basis of dynamic capturing method in order to pick convenient angle of inclination. Moreover, tried to find the optimum angle by comparing the hip pressure distribution when seated at the edge of the seat and at the center of the seat with the pressure distribution sensor.