• 동력기계공학회지
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• 제17권4호
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• pp.139-146
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• 2013

Because the magnetic bearing supports levitating body without contact, wear, noise and vibration, it is very useful to high revolution machinery. In this paper we selected ATmega 128, a less expensive and widely used micro controller, for control the magnetic bearing system. And we selected the sampling time and the control gain of PID controller through trial-and-error. The control program of the one board controller utilized lookup table to reduce calculation time, and bit shifting for the integer calculation in instead of floating point calculation. As the results, the controller carried out relatively high speed PID control on sampling time 0.25 ms. At last the rotation test for the magnetic bearing system was carried out by 3 phase induction motor and air turbine.

• Journal of Contemporary Eastern Asia
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• 제11권2호
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• pp.61-75
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• 2012

The historical turbulence between China and Japan started from the First Sino-Japanese War in 1895, and culminated in Japan's invasion of China during World War Two (the Second Sino-Japanese War) between 1937 and 1945. A series of wars caused huge human and material losses in both countries, and both experienced comprehensive transformations during and after the wars. The impact of this historical turbulence is so long-lasting that it still influences both countries' social psyche. Moreover, it continues casting a long shadow upon the current Sino-Japanese relations. The recent turbulence in Sino-Japanese relations partly stems from the historical turbulence. It is much less violent but can also be emotional and worrisome. It started from the early 1980s (the Japanese history textbook controversy in 1982 and the 1985 anti-Japanese student protests in China), and culminated in the anti-Japanese mass demonstrations in multiple Chinese cities in 2005 (Bush 2010; Gries 2005; Reilly 2012; Stockmann 2010; Weiss 2008). In addition to dramatic demonstrations on streets, there are also other forms of movements, such as war reparations movements, in which Chinese war victims demand reparations from the Japanese state and companies (Rose 2005; Xu and Fine 2010; Xu and Pu 2010). Although the tension has existed for many years and surfaced from time to time, the eruption of the nationwide anti-Japanese movements in China in 2005 still shocked many outside observers. Many scholars have tried to explain the anti-Japanese sentiment within current Chinese society that underlies and drives these social movements. Through careful reexamination of the existing literature, this article proposes an explanation for the anti-Japanese sentiment from a perspective that stresses the shifting state-society interaction in China's Japan policy. Specifically, the totalitarian Chinese state's neglect and suppression of genuine social concerns regarding Japan in earlier years, followed by a relatively liberalized state that tolerates societal participation in Sino-Japanese relations, are an importance source of the anti-Japanese sentiment recently observed in China.

• 한국철도학회논문집
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• 제15권4호
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• pp.334-342
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• 2012

유라시아 대륙에는 다양한 궤간이 존재하고 있다. 이런 차이는 서로 다른 궤간의 접속점에서 화물을 환적하거나 혹은 차량 운행 조립체를 교환하여야 하는 등 철도수송 시스템의 운영에 많은 영향을 준다. 그러므로, 철도 수송 시스템의 효율성은 복잡한 하역 및 교환 기술에 관련된 궤간 극복 방법에 매우 의존한다. 본 논문은 대륙철도 연결을 통한 국제 화물 수송에서 발생되는 1520/1435mm 궤간차이를 극복하기 위한 철도 수송 시스템의 효율성 평가를 목적으로 하였다. 먼저 궤간 변경지점에서 현재 수행되고 있는 수송 시스템을 간략하게 설명하고, 교환 기술에 대한 사전 분석을 수행하였다. LCC 모델에 기초하여 리프트에 의한 대차교환 방식과 자동궤간가변 시스템의 효율성을 비교평가 하였다.

• Animal cells and systems
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• 제9권3호
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• pp.153-160
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• 2005

Most living organisms exhibit the circadian rhythm in their physiology and behavior. Recent identification of several clock genes in mammals has led to the molecular understanding of how these components generate and maintain the circadian rhythm. Many reports have implicated the photic induction of either mPer1 or mPer2 in the hypothalamic region called the suprachiasmatic nucleus (SCN) to phase shift the brain clock. It is now established that peripheral tissues other than the brain also express these clock genes and that the clock machinery in these tissues work in a similar way to the SCN clock. To determine the role of the two canonical clock genes, mPer1 and mPer2, in the peripheral clock shift, stable HEK293EcR cell lines that can be induced and stably express these proteins were prepared. By regulating the expression of these proteins, it could be shown that induction of the clock genes, either mPer1 or mPer2 alone is not sufficient to cause clock phase shifting in these cells. Our real-time PCR analysis on these cells indicates that the induction of mPER proteins dampens the expression of the clock-specific transcription factor mBmal1. Altogether, our present data suggest that mPer1 and mPer2 may not function in clock shift or take part in differential roles on the peripheral circadian clock.

• 비파괴검사학회지
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• 제21권2호
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• pp.189-196
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• 2001

광탄성법은 전체적인 응력장 해석을 위하여 가장 많이 사용되는 방법중의 하나이다. 광탄성법에서 주응력의 차이와 방향은 등색선과 등경선으로 나타난다. 재래식 방법으로는 주응력 방향은 평면 편광기의 편광자와 검광자를 동시에 회전시켜 수작업으로 측정하며, 이를 타디보간법이라 한다. 이러한 방법은 전체적인 응력장 해석시 매우 번거로우며 많은 시간이 걸린다. 재래식 광탄성법에서는 광탄성 프린지로부터 등경선을 분리시킬 수 없다. 본 연구에서는 광탄성이론을 Jones행렬로 나타내고 4단계와 8단계의 위상이동법에 대해서 기술하였다. 컴퓨터시뮬레이션을 통하여 압축하중을 받는 원형디스크의 광탄성 프린지로부터 등경선과 등색선을 분리시킬 수 있는 시험을 하였다. 디스크의 프린지는 응력-광 법칙에 의하여 생성하였다. 8단계 위상이동법으로 얻은 등경선과 등색선의 크기를 이론으로 계산한 값과 비교하였다. 컴퓨터 시뮬레이션으로부터 광탄성 프린지로부터 등경선과 등색선을 분리시킬 수 있는 가능성을 예시하였다.

• 한국산학기술학회논문지
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• 제19권4호
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• pp.85-92
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• 2018

수요관리를 통해 전기요금을 절감할 수 있다. 부하의 수요 관리 방법 중 하나로 ESS를 설치해 수요가 높은 시간대의 부하를 수요가 낮은 시간대로 옮기는 peak shifting을 사용함으로써 최대 부하를 낮추고 전력량 요금을 절감할 수 있다. 전기요금은 계약 용량 당 기본요금과 전력량 요금으로 이루어져있다. 전력량 요금을 최소화하기 위한 최적화 수행시 목적함수는 선형식으로 표현할 수 있으며, 기본 요금 최소화를 위한 목적함수는 이차식으로 표현할 수 있다. 선형식으로 표현된 목적함수에서는 ESS PCS(Power Conversion System)의 충, 방전 효율이 다른 경우를 다룰 수 없기 때문에 본 논문에서 충, 방전 효율이 다른 경우의 영향을 반영하고 혼합정수계획법(MILP, Mixed Integer Linear Programming)을 이용할 수 있는 정식을 제시하였다. 혼합정수계획법을 사용한 정식에서는 사전에 정해진 최대 부하 절감율에 대해 전기요금 최소화를 수행하게 되지만 최대 부하 절감과 전기요금 절감을 동시에 고려하기 위해서는 이차 계획법을 사용하는 것이 유용하다. 본 논문에서는 각 최적화 방법에 대한 장, 단점을 도시철도 변전소에 대한 시뮬레이션 결과를 정량적으로 비교분석하여 ESS 설비계획수립에 적합한 최적화 방법을 선택할 수 있는 근거를 제시하였다.

• Structural Engineering and Mechanics
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• 제55권5호
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• pp.1055-1086
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• 2015

The dynamic response of two-dimensional unbounded domain on the rigid bedrock in the time domain is numerically obtained. It is realized by the modified scaled boundary finite element method (SBFEM) in which the original scaling center is replaced by a scaling line. The formulation bases on expanding dynamic stiffness by using the continued fraction approach. The solution converges rapidly over the whole time range along with the order of the continued fraction increases. In addition, the method is suitable for large scale systems. The numerical method is employed which is a combination of the time domain SBFEM for far field and the finite element method used for near field. By using the continued fraction solution and introducing auxiliary variables, the equation of motion of unbounded domain is built. Applying the spectral shifting technique, the virtual modes of motion equation are eliminated. Standard procedure in structural dynamic is directly applicable for time domain problem. Since the coefficient matrixes of equation are banded and symmetric, the equation can be solved efficiently by using the direct time domain integration method. Numerical examples demonstrate the increased robustness, accuracy and superiority of the proposed method. The suitability of proposed method for time domain simulations of complex systems is also demonstrated.

• 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.

• Corrosion Science and Technology
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• 제4권4호
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• pp.147-154
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• 2005

The creep resistance of geogrids is one of the most significant long-term safety characteristics used as the reinforcement in slopes and embankments. The failure of geogrids is defined as creep strain greater than 10%. In this study, the accelerated creep tests were applied to polyester geogrids at various loading levels of 30, 50% of the yield strengths and temperatures using newly designed test equipment. Also, the new test equipment permitted the creep testing at or above glass transition temperature($T_g$) of 75, 80, $85^{\circ}C$. The time-dependent creep behaviors were observed at various temperatures and loading levels. And then the creep curves were shifted and superposed in the time axis by applying time-temperature supposition principles. The shifting factors(AFs) were obtained using WLF equation. In predicting the lifetimes of geogrids, the underlying distribution for failure times were determined based on identification of the failure mechanism. The results confirmed that the failure distribution of geogrids followed Weibull distribution with increasing failure rate and the lifetimes of geogrids were close to 100 years which was required service life in the field with 1.75 of reduction factor of safety. Using the newly designed equipment, the creep test of geogrids was found to be highly accelerated. Furthermore, the time-temperature superposition with the newly designed test equipment was shown to be effective in predicting the lifetimes of geogrids with shorter test times and can be applied to the other geosynthetics.

• 생명과학회지
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• 제16권7호
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• pp.1097-1103
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• 2006

Community structure varies not only in space but also in time. We stand in one position which located at Sinhung-ri, Sacheon-ci and observe the flora of area as time passes. This area begins after disturbance on sites where organisms are already present like secondary succession. In 2001, there are invaded by Trapa japonica, Salvinia natans, and Potamogon cristatus. Four or five years later, this abandoned areas support of clover, pine, and oak, resulting in a shifting pattern of species dominance and diversity through time. Patterns of community structure such as species composition and ecological diversity have shown through seasons and five years, that is the topic of this study. The values of turnover (TO) were changes through time intervals at three regions. The gradual and seemingly directional change in the structure of the community through time from aquatic like to field. Thus, we can observe the process of secondary succession at Sinhung-ri in the very short time.