• 한국진공학회지
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• 제21권3호
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• pp.171-177
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• 2012

본 연구에서는 Mn을 첨가시킨 $LiNbO_3$ 단 결정을 기술하는 스핀 해밀토니언으로 계의 고유치를 구하고, 이를 이용하여 자기 감수성을 온도 의존성으로 조사하였다. 선형응답이론에 기초한 Argyres-Sigel의 투영연산자 방법을 이용하여 계의 자체 에너지함수를 유효한 항까지 계산하였다. 초 미세구조 효과를 고려한 온도 의존성의 역 자기 감수성은 온도의 증가에 따라 그 효과가 더욱 크게 나타나는 것으로 조사되었다. 자체에너지 함수의 실수 부분인 선 너비는 온도의 증가에 따라 감소하는데 이는 온도의 증가로 인해 $Nb^{5+}$와 $Li^+$ 이온들이 산소 층과 다른 인접한 산소 층 쪽으로 이동하기 때문인 것으로 보인다.

• 한국컴퓨터정보학회논문지
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• 제13권6호
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• pp.137-145
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• 2008

대형 무선 센서 네트워크(WSNs)는 일반적으로 수백에서 수천 개의 센서 노드들로 구성되어 있다. 이러한 대형 WSNs는 비용 및 에너지를 고려한 에너지 효율성뿐만 아니라 네트워크의 유지 및 관리가 요구된다. 사용자는 효율적인 시스템을 통해서 사용자 수준의 센싱 서비스 품질을 제공받을 수 있어야 한다. 이 네트워크에서 사용자에게 제공되는 결과 데이터의 품질은 이벤트 검출에 관련된 센서들의 개수가 결정적인 역할을 한다. 그러므로 사용자 요구 품질에 적합한 QoS를 제공할 수 있는 네트워크 프로토콜은 일부 센서 노드들에서 에러가 발생하더라고 전체 시스템 성능에 영향을 주지 않으면서, 동시에 에너지 소비가 최소화되도록 설계되어야 한다. 본 논문에서 제안된 프로토콜은 LEACH(Low Energy Adaptive Clustering Hierarchy) 프로토콜을 기반으로 하며, 지속적인 감시가 요구되는 대형 네트워크에 적합한 역할 기반의 자가 구성 프로토콜을 제안하였다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.1315-1318
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• 2003

In this paper, a neural network based approach using a self-organizing feature map is proposed for the segmentation of X ray images. A number of algorithms based on such approaches as histogram analysis, region growing, edge detection and pixel classification have been proposed for segmentation of general images. However, few approaches have been applied to X ray image segmentation because of blur of the X ray image and vagueness of its edge, which are inherent properties of X ray images. To this end, we develop a new model based on the neural network to detect objects in a given X ray image. The new model utilizes Mumford-Shah functional incorporating with a modified adaptive SOFM. Although Mumford-Shah model is an active contour model not based on the gradient of the image for finding edges in image, it has some limitation to accurately represent object images. To avoid this criticism, we utilize an adaptive self organizing feature map developed earlier by the authors.[1] It's learning rule is derived from Mumford-Shah energy function and the boundary of blurred and vague X ray image. The evolution of the neural network is shown to well segment and represent. To demonstrate the performance of the proposed method, segmentation of an industrial part is solved and the experimental results are discussed in detail.

• 한국디지털건축인테리어학회논문집
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• 제13권2호
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• pp.5-16
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• 2013

With regard to the new town developments which have supplied lots of houses in a short period of time in Korea this study aims to evaluation and finding out problems of the developments finally to suggest the direction. A new town's competitiveness model set in the previous paper takes a role of research frame to recognize the problems and to show the direction. The model explains that new town's competitiveness is composed of 4 factors; Self-sufficiency, Innovativenss, Identity and Sustainability. Problems of the developments are as follows; incongruity of spatial structure especially in the capital region, deficiency of self-sufficiency resulted from single-use development, restriction on mixed development by a number of regulations in capital region, low business value, grand scale of land compensation, house oriented planning guidance, unfair share of infrastructure fee, and physical structure depending mainly on fossil energy. Based on this recognition this study conclusively suggests corresponding direction such as role performance as a means of urban growth management, promotion of quality of life by accumulating social capital, introduction of socially sustainable management program for the new towns, discovery and creation of town's value, reexamination of self-sufficiency's meaning or target, selective deregulation of metropolitan development, institutional strategy for cost reduction, changeover from house index to urban function oriented index, and pursuit of low-carbon green town.

• Steel and Composite Structures
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• 제51권3호
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• pp.289-304
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• 2024

The seismic performance of traditional steel frame-shear wall structures was significantly improved by the application of self-centering steel-reinforced concrete (SRC) wall-panel structures in the steel frames. This novel resilience functionality can rapidly restore the structure after an earthquake. The presented steel frame with steel-reinforced concrete self-centering wall-panel structures (SF-SCW) was validated, indicating its excellent seismic performance. The seismic design method based on bear capacity cannot correctly predict the elastic-plastic performance of the structure, especially certain weak floors that might be caused by a major fracture. A four-level seismic performance index, including intact function, continued utilization, life safety, and near-collapse, was established to achieve the ideal failure mode. The seismic design method, based on structural displacement, was proposed by considering performance objectives of the different seismic action levels. The pushover analysis of a six-floor SF-SCW structure was carried out under the proposed design method and the results showed that this six-floor structure could achieve the predicted failure mode.

• 대한기계학회논문집B
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• 제35권3호
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• pp.309-319
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• 2011

질소 희석된 프로판 부상화염에서 열손실에 의한 자기진동을 기초로 화염안정화선도를 도출하기 위하여 노즐직경 0.3 mm, 1.0 mm에서 실험적 연구를 수행하였다. 예혼합화염에서 확산화염으로의 전도 열손실에 의한 자기진동 및 매연 복사에 의한 자기진동을 관찰하였다. 0.1 Hz보다 낮은 주파수 성향을 띄는 열손실에 의한 자기진동은 제안된 메커니즘에 의해 잘 묘사되었고 반면 매연복사에 의한 자기진동은 O(0.1 Hz)의 주파수 범위를 나타내었으며 제안된 메커니즘은 항온항습실 실험을 통해 입증하였다. 질소 희석된 프로판 부상화염에서 관찰된 열손실에 의한 자기진동의 특성화는 관련된 변수 및 스트라훌 수에 의해 잘 묘사되었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.1246-1247
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• 2008

With recent advanced in portable electric devices, wireless sensor, MEMS and bio-Mechanics device, the new typed power supply, not conventional battery but self-powered energy source is needed. Particularly, the system that harvests from their environments are interests for use in self powered devices. For very low powered devices, environmental energy may be enough to use power source. Therefore, in other to made piezoelectric energy harvesting device, PMN-PZT thick film was formed by the screen printing method on the Ag/Pd coated alumina substrate. The layer was 8 layers and slurry where a-terpineol, ethycellulose, ferro B-75001 as Vehicle, PMN-PZT powder used are fabricated by ball mill. The output power quality was be also investigated by changing the load resistance, weight and frequency. The made piezoelectric energy harvesting device was resulted from the conditions of 33$k{\Omega}$, 0.25g, 197Hz respectively. The thick film was prepared at the condition of 2.75Vrms, and its power was 230${\mu} W$ and its thickness was 56${mu}m$. The piezoelectric energy harvesting device output voltage was increased, when the load weight, load resistance was increasing and resonance frequency was diminishing. The other side, resonance frequency was diminished, when the weight was increasing. And output power was continuously it changed by load resistance, output voltage, weight and resonance frequency.

• Molecules and Cells
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• 제46권12호
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• pp.727-735
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• 2023

Stem cells require high amounts of energy to replicate their genome and organelles and differentiate into numerous cell types. Therefore, metabolic stress has a major impact on stem cell fate determination, including self-renewal, quiescence, and differentiation. Lysosomes are catabolic organelles that influence stem cell function and fate by regulating the degradation of intracellular components and maintaining cellular homeostasis in response to metabolic stress. Lysosomal functions altered by metabolic stress are tightly regulated by the transcription factor EB (TFEB) and TFE3, critical regulators of lysosomal gene expression. Therefore, understanding the regulatory mechanism of TFEB-mediated lysosomal function may provide some insight into stem cell fate determination under metabolic stress. In this review, we summarize the molecular mechanism of TFEB/TFE3 in modulating stem cell lysosomal function and then elucidate the role of TFEB/TFE3-mediated transcriptional activity in the determination of stem cell fate under metabolic stress.

• Nuclear Engineering and Technology
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• 제27권3호
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• pp.317-326
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• 1995

증기발생기의 수위제어시스템에 대해 특히 저출력시 수위제어의 문제점을 분석고찰하고 퍼지제어기 법을 기반으로 한 안정되고도 신속한 수위제어에 관한 연구가 주로 수행되었다. 문제해결의 한 방안으로서, 중요 제어변수임에도 불구하고 저출력운전시 저유량구간의 추정불량으로 인해 사용할 수 없는 유량신호를 대신하여 밸브개도를 이용한 대체정보를 채용하였으며 또한 소속함수크기의 유동적인 조정방법을 이용하여 수위오차가 크게 발생한 과도상태시에는 신속한 수위회복이 이루어지도록 하였다. 실제운전환경에서 제시된 제어기를 튜닝 하기 위한 방법으로서 제어성능지수 및 decent method를 이용한 소속함수의 self-tuning 기법을 제시하였다. 원자력 연구소의 연수원에 설치된 교육훈련용 시뮬레이터에서 수행된 실험결과는 제시된 제어기 및 튜닝방법의 안정되고 우수한 성능구현 및 실질적 인 유용성을 보여주고 있다.

• Structural Engineering and Mechanics
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• 제46권4호
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• pp.549-569
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• 2013

A passive control using flaps will be an alternative solution for flutter stability and buffeting response of a long suspension bridge. This method not only enables a lightweight economic stiffening girder without an additional stiffness for aerodynamic stability but also avoid the problems from the malfunctions of control systems and energy supply system of an active control by winglets and flaps. A time domain approach for predicting the coupled flutter and buffeting response of bridge deck with flaps is investigated. First, the flutter derivatives of bridge deck and flaps are found by experiment. Next, the derivation of time domain model of self-excited forces and control forces of sectional model is reported by using the rational function approximation. Finally, the effectiveness of passive flap control is investigated by the numerical simulation. The results show that the passive control by using flaps can increase the flutter speed and decrease the buffeting response. The experiment results are matched with numerical ones.