• Bulletin of the Korean Chemical Society
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• 제17권12호
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• pp.1161-1164
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• 1996

• 한국학교보건학회지
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• 제8권2호
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• pp.315-326
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• 1995

This study was performed to find variables which affect oral health care of infants. The subjects were 439 infants and their mothers who live in suburban area. Oral examinations for the infants were conducted and the questionnairs were given to infants' mothers. Toothbrushing frequency, oral hygiene score, the percentage of filled teeth among decayed teeth, and dental treatment experience of infants were used as dependent variable, respectively. Demographic, socio-economic variables and the other variables which might affect oral health care of infants were used as independent variables. Correlation analysis and analysis of variance were used for the independent variables of toothbrushing frequency, oral hygiene score, and the percentage of filled teeth among decayed teeth of infant. Chi-Square and Student's t-test were used for the dependent variables of dental treatment experience of infant. The obtained results were as follows; 1. Toothbrushing frequency of mother and internal locus of oral control of mother were the factors which affect toothbrusing frequency of infants. 2. Oral health belief of mother was the factor which affect oral hygiene score of infants. 3. Age of infant was the factor which affect the percentage of filled teeth among decayed teeth. 4. Age of infant and educational level of infant's mother were the factors which affect the infants' consumption of dental treatment.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1999년도 봄 학술발표회 논문집
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• pp.121-128
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• 1999

This paper presents a time domain method for soil-structure interaction analysis for seismic loadings. It is based on the finite element formulation incorporating analytical frequency-dependent infinite elements for the far field soil. The dynamic stiffness matrices of the far field region formulated using the present method in frequency domain can be easily transformed into the corresponding matrices in time domain. At first, the equivalent earthquake forces are evaluated along the interface between the near and the far fields from the free-field response analysis carried out in frequency domain, and the results are transformed into the time domain. An efficient procedure is developed for the convolution integrals to evaluate the interaction force along the interface, which depends on the response on the interface at the past time instances as well as the concurrent instance. Then, the dynamic responses are obtained for the equivalent earthquake force and the interaction force using Newmark direct integration technique. Since the response analysis is carried out in time domain, it can be easily extended to the nonlinear analysis. Example analysis has been carried out to verify the present method in a multi-layered half-space.

• 동력기계공학회지
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• 제12권6호
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• pp.50-55
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• 2008

In general, the swing motion of the crane is controlled and suppressed by activating the trolley motion. In many papers reported by us, we suggested a new type of anti-sway control system of the crane. In the proposed control system, a small auxiliary mass(moving-mass) is installed on the spreader and the swing motion is controlled by moving the auxiliary mass. The actuator reaction against the auxiliary mass applies inertial control forces to the container in order to reduce the swing motion in the desired manner. Futhermore the measuring systems based on image sensor have been proposed also. To obtain the robustness for our control system, $H_{\infty}$ based control techniques and other approach have been applied to suppress swing motion. As well known, the robust control technologies based on $H_{\infty}$ control need complicated and difficult process. In the result, the obtained closed-loop system becomes to high order system which may give us many difficulties to apply it to the real plants. Therefore, we introduce an easy approach which is based on LQ control theory. In this approach, we introduce the frequency dependent weighting matrices which give the system filters to shape frequency characteristics of the controlled system and guarantee the control performance.

• 전자공학회논문지T
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• 제36T권2호
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• pp.63-69
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• 1999

이전에 여러가지 주파수영역 해석법에 의해 핀라인의 주파수 종속 특성이 해석되었다. 그러나 본 논문에서 제시된 시간영역 TLM법은 핀라인의 주파수영역 해를 얻기 위한 또 다른 독립된 해석법이다. 이와 같은 알고리즘을 이용하여 해석된 구조는 WR-62 도파관에 내재된 단방향 핀라인이며 Huygen의 산란 모델 특성에 근거한 대칭압축노드가 사용되었다. TLM 결과로부터 시간영역 데이타를 퓨리어 변환함에 의해 단방향 핀라인의 주파수 종속 산란 파라메터가 계산되었다. 수치해석 결과는 다른 논문과 잘 일치하며 따라서 제안된 방법의 타당성과 유용성을 입증하였다.

• 전기전자학회논문지
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• 제22권3호
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• pp.780-785
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• 2018

본 논문에서는 tunable RF 기기에 적용이 가능한 $HfO_2$ 강유전체를 활용하여 metal-ferroelectric-metal (MFM) 커패시터를 구현하였으며 마이크로파 대역주파수 까지 전압에 따른 커패시턴스 tunability 특성을 고찰 하였다. 1kHz부터 5GHz 대역에 이르기까지 광범위한 범위의 커패시턴스-전압 특성을 분석하였으며 커패시턴스 tunability는 500 MHz 이상의 주파수에서 2.5 GHz 대역까지 ~3 %의 tunability가 유지되는 것을 확인 하여 마이크로파 주파수 대역에서 ALD $HfO_2$기반 전자 제어 가변 커패시터의 사용 가능성을 입증하였다.

• 한국컴퓨터정보학회논문지
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• 제8권2호
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• pp.88-96
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• 2003

마이크로스트립 라인은 마이크로웨이브와 밀리미터웨이브 집적회로에 있어서 가장 필수적인 소자 중의 하나이다. 그동안 여러 가지 주파수 영역 해석법에 의해 이러한 마이크로스트립 라인의 주파수 종속특성이 해석되었다. 하지만 본 논문에서 제시된 3차원 TLM법은 마이크로스트립 라인의 주파수 영역 해를 얻기 위한 또 다른 독립적인 해석법이다. 이러한 TLM 알고리즘을 이용하여 해석된 구조는 스텝 불연속 마이크로스트립 라인이며 대칭압축노드가 사용되었다. 수치해석 과정을 거쳐 시간 영역 데이터를 퓨리어 변환함으로써 스텝 불연속 마이크로스트립 라인의 주파수 종속 산란 파라메터가 계산되었다. 시간 영역 TLM 해석 결과로부터 이와 같은 수치해석법이 스텝 불연속 마이크로스트립 라인과 같이 복잡한 구조를 모델링하는데 있어 효율적인 방법임을 보였다.

• 한국인터넷방송통신학회논문지
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• 제18권2호
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• pp.63-72
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• 2018

본 논문에서는 동종 또는 이종 무선시스템에 대해 최소결합손실 기반의 주파수 조정을 위한 이론적 모델링 및 계산 결과를 제시한다. 주파수 조정에 핵심 변수들인 시스템 특성, 전파전파 모델, 가용율 및 보호비, 주파수의존제거 또는 인접채널간섭비, 변별각을 고찰하고, 각각에 대해 수치계산 결과를 도출한다. 주파수 조정의 절차를 보이기 위해 도심 또는 부도심에서 간섭원 이동기지국과 피해 고정무선시스템 간의 간섭전력을 분석하며, 가정한 양 시스템 특성에 대해 변별각 및 거리의 함수로 최대허용간섭전력과 간섭 영향을 비교한다. 제시된 방법은 다양한 무선시스템의 주파수 조정에 필요한 상호 공존 또는 양립성을 위한 기술적 분석에 활용이 클 것으로 판단된다.

• The Korean Journal of Physiology
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• 제23권2호
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• pp.329-337
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• 1989

Cardiac muscles show stimulation frequency-dependent tension changes i.e. Bowditch phenomenon and Woodworth phenomenon, the former is an increase of tension with the increase of stimulation frequency, whereas the latter is an increase of tension with a decrease of stimulation frequency. Bowditch phenomenon is seen in the range of frequency 1.0 cps and above, and Woodworth phenomenon below the frequency 1.0 cps in the most of mammalian cardiac atrium. To throw some light on the possible mechanism of both phenomena in rat atrium, influences of drugs affecting $Ca^{2+}$ influx through the plasma membrane $(verapamil,\;La^{3+},\;norepinephrine)$ and $Ca^{2+}$ release from sarcoplasmic reticulum (SR) on frequency-tension curve were studied. The results obtained are summarized as follows: 1) At low temperature $(27.5^{\circ}C)$, both Bowditch and Woodworth phenomenon were demonstrated. But Bowditch phenomenon disappeared at the temperature above $(32.5^{\circ}C)$. 2) At $(27.5^{\circ}C)$, in the presence of verapamil, a $Ca^{2+}$ channel blocker, a time course of change in the frequency-tension was studied. It was found that Bowditch phenomenon was affected before the Woodworth phenomenon, then the former was completely disappeared. At $(32.5^{\circ}C)$, where no Bow-ditch is seen in normal atrial muscle, Bowditch phenomenon was reappeared by an administration of norepinephrine suggesting again that slow inward current of such as $Ca^{2+}$ channel is closely related to Bowditch phenomenon. 3) At $27.5^{\circ}C$, in the presence of $La^{3+}$, although tensions were decreased at all stimulation frequencies, Bowditch and Woodworth phenomenon were still demonstrated. However in the presence of both $La^{3+}$ and verapamil, Bowditch phenomena was disappeared suggesting that $La^{3+}$ is less effective in blocking $Ca^{2+}$ channel than verapamil. 4) At $27.5^{\circ}C$, in the presence of ryanodine, an inhibitor of calcium release from SR, Woodworth phenomenon was disappeared, which was consistent with previous reports of others, suggesting that $Ca^{2+}$ release from SR is closely related to Woodworth phenomenon. From the above findings, it may be concluded that Bowditch phenomenon is dependent on the magnitude of $Ca^{2+}$ influx through slow channel and Woodworth phenomenon is dependent on the amount of $Ca^{2+}$ stored in SR.

• 한국항해항만학회지
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• 제38권1호
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• pp.29-37
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• 2014

본 논문에서는 무어링윈치시스템 제어를 위한 제어계 설계법에 대해 고찰하고 있다. 특히 무어링윈치의 동적운전이 로우프에 부가하는 급격한 부하변동을 억제함으로써 로우프 피로하중을 감소시키고 선박운동제어에 있어서의 바람직한 제어성능을 달성할 수 있도록 하는 제어기 설계법을 제안하고 있다. 최적제어이론에 기반하여, 평가함수에 주어지는 중량행렬(weighting matrix)에 주파수 특성을 부여함으로써, 고주파 모드가 포함된 제어입력이 불안전한 특성을 여기시키지 않도록 하는 것이 제어기 설계 목표이며, 이것은 곧 로우프에 급격한 부하변동을 발생시키지 않게 되는 결과를 얻게 된다. 설계된 제어기는 저차이면서도 외란에 대한 강인성 뿐 만 아니라 제어성능 또한 보장하는 유용한 기법이며 시뮬레이션 및 실험을 통해 그 유효성을 검증하고 있다.