• 연구논문집
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• 통권29호
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• pp.185-194
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• 1999

The shape and thickness distribution according to the pressure-time curve were carried out using the FEM and experiment. Also, mechanical properties were investigated. The square cup parts have been formed with pressure-time curve generated by result of analysis. The tensile strength and elongation have been investigated according to applied pressure conditions using the tensile test specimen obtained from the superplastic formed cup. We can use to predict the shape of formed part under the applied pressure using the FEM analysis. In the case of optimum pressure condition, the thickness distribution and mechanical properties were improved. From this study, we can find the important of optimum pressure-time condition. We have investigated about the forming of airplane part and fuel tank for motorcycle. If the applied load used in boundary conditions was appropriate, the simulation result coincides with the formed part. However, it is very difficult to define the pressure condition in complicated shape. Thus, it is need to develop the optimum pressure condition for superplastic forming.

• 한국의류산업학회지
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• 제19권5호
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• pp.602-607
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• 2017

This study was undertaken to compare the gait characteristics between the Korean elderly and young adults, we measured the plantar pressure and contact time of gait with barefoot along a walkway at their preferred walking speed. The results indicate that older people exhibited significantly less plantar pressure than young adult in all 3 regions (FF, MF and RF) and significantly less time % on the initial contact phase (ICP), forefoot push-off phase (FFPOP) and significantly more % forefoot contact phase (FFCP) and foot flat phase (FFP). The converted plantar pressure value to percentage, it showed more pressure in forefoot (FF) in the elderly person than the young adults. It could be explained that the forward shifting in plantar pressure are associated with a more flexed posture of elderly such as actual stabilizing fearrelated adaptations. Longer total foot contact time in the elderly means that the old people show the decreased gait velocity. In other words, lower velocity was found to be associated with pre-existing fear of falling. With longer contact time and slower stepping movement, the elderly become more unstable. With these findings, it could be confirmed that there were significant changes in foot characteristics which contribute to alter the plantar pressure and contact time during gait with advancing age. Further research is required to establish possible links to risk of falling and development of footwear in the elderly adults.

• Journal of Welding and Joining
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• 제8권4호
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• pp.20-26
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• 1990

In this study, to make research on its optimum condition in friction weld when the heating pressure is change during 1.6 to 3.0 $kgf/mm^2$, the experiment was performed with metal bearing under various condition; 1600 r.p.m spindile speed, 0.6 $kgf/mm^2$ preheating pressure, upset pressure 2.6 $kgf/mm^2$, 0.5 seconds preheating time, 1.7 seconds heating time, water and air was ejected 6 $kgf/mm^2$ into the bushing. On the basis of the experimental results, the following conclusion are drawn; 1) At the area of weld interface, the heardness is shown the maximum value and heat-affected zone about 0.5mm both sides. 2) Bending strength is shown the optimum heating pressure 2.4 kgf/mm. 3) With the approach of the flash, Sn is increased only 2 mm in A-alloy structure.

• 한국인터넷방송통신학회논문지
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• 제18권4호
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• pp.161-168
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• 2018

고혈압은 현대 주요 성인병이며 기존의 혈압계로는 실시간 혈압 측정 및 원격 모니터링이 어렵다. 그러나 실시간 혈압 모니터링 u-헬스케어 시스템은 효과적인 건강관리가 가능하도록 해준다. 실시간 혈압 모니터링을 위해 본 논문에서는 손목형 혈압계, 스마트폰 및 u-헬스케어 서버로 구성된 실시간 혈압 모니터링 u-헬스케어 시스템의 구조를 제시한다. 그리고 손목형 혈압계의 하드웨어 설계를 위한 주요 핵심 기능인 맥파검출 아날로그 회로 구성과 손목형 혈압계를 구성하는 디지털 하드웨어 구성을 제시한다. 또한 이들 하드웨어 시스템을 동작시키는 소프트웨어 개발을 위한 UML 분석방법과 소프트웨어 설계를 위한 플로우차트와 화면 설계를 보여준다. 따라서 본 논문에서 제시한 설계방법은 실시간 모니터링 u-헬스케어 시스템 구현에 매유 유용하게 활용될 수 있을 것으로 기대된다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2009년도 정보 및 제어 심포지움 논문집
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• pp.138-140
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• 2009

Hemorrhage shock occupies high rate in trauma patient's mortality and blood pressure is the variance that judges early diagnosis and the effect of remedy. Systolic blood pressure is related to pulse transit time(PTT). PTT means the time that is required to flow from the heart to peripheral artery. PTT is influenced from the length, cross section and stiffness of the blood vessels. It is hard to evaluate the correlation between systolic blood pressure and PTT because they are variable in human body. In this paper, we evaluated the correlation between the systolic blood pressure and PTT in normal and hemorrhage states using standardized rat. PTT is defined as the time differences between the R peak and the peak of pulse wave. The analyzed time differences of ECG and blood pressure are analyzed every 5minutes for 30 seconds when there is before and after bleeding. Before bleeding, systolic blood pressure and PTT are steadily preserved but when the bleeding comes started, systolic blood pressure is declined. However PTT was increased and decreased. Under the circumstance that the standardized rat is controlled by age, the length of the blood vessels, and any disease, it shows that PTT measurement using systolic blood pressure of bleeding is impossible.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.355-356
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• 2002

The dielectric permittance and the dielectric loss factor of several lubricating oils were measured at frequencies from 100 Hz to 1.5 MHz. The measurements were carried out under atmospheric pressure as a function of temperature and under fixed temperature as a function of pressure. Temperature and pressure dependence of dielectric relaxation time were investigated. The temperature dependence of relaxation time obeyed the Vogel-Fulcher-Tammann (VFT) law. We modified the VFT equation in order to express the dielectric relaxation time as a function of temperature and pressure. Furthermore. by taking into consideration the similarity of the temperature and pressure dependence between dielectric relaxation and mechanical relaxation. the prediction of high-pressure viscosity were conducted. The predicted results were compared with the viscosity data obtained from the falling-sphere type viscometer.

• 교육심리연구
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• 제31권3호
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• pp.389-408
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• 2017

이 연구는 대학생의 시간압박감과 자유재량시간이 성별에 따라 차이가 있는지와 주관적 안녕감과 어떤 관계가 있는지를 밝히는데 목적을 두고 있다. 이를 위하여 부산 경남지역의 대학생 493명을 대상으로 시간압박감, 자유재량시간, 주관적 안녕감(삶의 만족도, 긍정정서, 부정정서)검사를 실시하여 다음과 같은 결과를 도출하였다. 첫째, 대학생의 시간압박감, 긍정정서, 부정정서는 성별에 따라 유의미한 차이를 보였다. 시간압박감와 부정정서는 여자 대학생이 높은 것으로 나타났고, 긍정정서는 남자 대학생이 높은 것으로 나타났다. 하지만 대학생의 자유재량시간과 삶의 만족도는 성별에 따라 차이가 없는 것으로 나타났다. 둘째, 대학생의 시간압박감은 삶의 만족도와는 부적 상관을 가졌으나 부정정서와 정적 상관을 보였다. 대학생의 자유재량시간은 삶의 만족도와는 정적 상관을 가졌으나 부정정서와 부적 상관을 보였다. 하지만 대학생의 시간압박감과 자유재량시간은 긍정정서와 상관이 없는 것으로 나타났다. 셋째, 회귀분석 결과 대학생의 시간압박감은 이들의 삶의 만족도와 부정정서를 유의하게 설명하였으나, 자유재량시간은 통계적으로 유의한 설명력이 없었다. 이와 같은 연구결과는 대학생의 주관적 안녕감을 증진시키기 위해서는 자유재량시간을 늘이기 보다는 시간압박감을 낮출 필요가 있으며, 남녀의 차이를 고려할 필요가 있음을 시사한다.

• 대한기계학회논문집A
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• 제21권3호
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• pp.485-501
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• 1997

Pressure control is possible driving a simple ON/OFF 3-way valve of hydraulic servo system by pulse width modulation signal. But the pressure varies according to the duty ratio and carrier frequency and repeated on-off action induces pressure fluctuation. So equations for mean pressure and ripple amplitude are theoretically derived as a function of on/off time, the system parameters which decide the pressure characteristics are arranged and they are verified by experimental study. As the result selection criteria for the major design parameters are established and the basic strategy to suppress the unnecessary fluctuation can be provided for a hydraulic pressure control system using these type of valves.

• 한국정보시스템학회지:정보시스템연구
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• 제18권3호
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• pp.155-181
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• 2009

Modern persons should do many activities during limited time. In such situation, people feel time pressure because they think that time is short. Time pressure affects negatively several factors such as satisfaction and intention to use through perceived time cost. Ubiquity, an mobile service's characteristic in which users can use desired information or services in anywhere and anytime, would let users feel free from time pressure. This study examines the relationship between perceived time and intention to use and the moderating effect of ubiquity. We performed a survey for users of DMB service, a representative mobile service. Using Partial Least Square, we tested hypotheses. The results suggest that time pressure influences positively perceived time cost and that perceived time cost affects negatively satisfaction but not enjoyment. And the results show that there are the significant positive relationships between enjoyment and intention to use and between satisfaction and intention to use. Finally, the moderating effects of ubiquity on the relationships between perceived time cost and enjoyment and between perceived time cost and satisfaction was found to be positive and significant. We suggests implications basing on the results.

• Structural Engineering and Mechanics
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• 제13권3호
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• pp.329-343
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• 2002

In this research, the dynamic stability of an orthotropic elastic conical shell, with elasticity moduli and density varying in the thickness direction, subject to a uniform external pressure which is a power function of time, has been studied. After giving the fundamental relations, the dynamic stability and compatibility equations of a nonhomogeneous elastic orthotropic conical shell, subject to a uniform external pressure, have been derived. Applying Galerkin's method, these equations have been transformed to a pair of time dependent differential equations with variable coefficients. These differential equations are solved using the method given by Sachenkov and Baktieva (1978). Thus, general formulas have been obtained for the dynamic and static critical external pressures and the pertinent wave numbers, critical time, critical pressure impulse and dynamic factor. Finally, carrying out some computations, the effects of the nonhomogeneity, the loading speed, the variation of the semi-vertex angle and the power of time in the external pressure expression on the critical parameters have been studied.