• International Journal of Computer Science & Network Security
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• 제24권6호
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• pp.171-179
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• 2024

Decentralized energy production without greenhouse gas emissions from renewable energy sources despite their advantage and environmental impact suffers from the problem of intermittent and fluctuating supply depending on weather conditions. To overcome this problem, energy storage is essential to enable reliable and continuous supply of the load. Hydrogen is one of the most promising energy storage solutions because it is easily transportable and can be used as fuel or as a raw material for the production of other chemicals.In this article, we will focus on hydrogen energy storage techniques using photovoltaic systems. We will review the different types of hydrogen storage structuresfor several applications, including residential and commercial buildings, as well as industry and transportation (electric vehicles using PEFMC fuel cells).

• 한국지진공학회논문집
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• 제11권2호
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• pp.81-94
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• 2007

지진시 발생하는 지반 액상화 현상은 지진피해예측시 가장 중용하게 평가해야 하는 항목으로 실내에서 액상화 현상을 시뮬레이션하는 경우, 불규칙성의 지진을 제어하기 어려운 이유로 등가반복형태의 정현파 또는 쐐기파를 이용하는 것이 통상적이었다. 그러나, 90년대 이후 컴퓨터의 발달과 함께한 신호처리 및 제어기술의 급속한 발전은 동역학분야에서의 실험연구에 큰 도움을 주었으며 지반진동분야의 경우, 진동대 및 원심모형기와 같은 대형지진모의시험에서 실지진하중을 이용한 연구사례들이 증가되고 있는 실정이다. 국내에서도 실지진하중재하가 가능한 요소시험결과에 대한 연구사례가 발표되는 등 이에 관한 연구가 활발하게 진행되고 있으며 특히, 실지진하중 시험결과로부터 실지진하중하에서의 과잉간극수압의 변화가 정현하중시험에서의 결과와 큰 차이를 보이고 있다는 분석결과가 발표되어 현재까지 지반동역학분야에서 지진하중의 불규칙성을 크게 고려하지 않았던 통상적 가정사항들이 문제점으로 대두되어 관심을 집중시키고 있다. 본 연구에서는 등가의 정현파 및 쐐기파와 증가형태의 쐐기파, 그리고 실지진파 등 다양한 진동하중을 재하할 수 있는 삼축압축시험기를 이용하여 기존의 유효응력개념에서 사용하는 과잉간극수압관련 매개변수인 소성일, 전단소성 변형률 상각궤도, 그리고 액상화 상태전환선의 기울기를 비교분석하였으며 하중변화에 따른 토립자의 변형과 간극수압의 변화를 상세분석하였다. 연구결과, 토립자의 변형, 간극수의 동적흐름, 동적흐름 속도수두의 압력수두로의 전환, 그리고 과잉간극수압의 증가로 표현되는 새로운 개념의 액상화 발생이론을 제안하였으며 그 타당성 검토를 위해 과잉간극수압과 동적흐름의 압력수두(흐름속도의 제곱값)와의 상관관계를 비교하였다.

• 농업과학연구
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• 제37권1호
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• pp.105-112
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• 2010

The objective of this study is to develop a standardized model for analyzing water balances in large scaled water basin by considering agricultural water districts, and to evaluate the hydrological feasibility of applying this model to several water districts such as Nonbul, Geumbok, Daejeon 1, Daejeon 2, and Cheonggang in Geum river basin. Ten types of stream network were considered in developed model. Using this model, streamflows were simulated by major stations and water balances were analyzed by water districts. Simulated streamflows and measured streamflows were compared at check stations such as Gapcheon and Bugang stations in which Nash and Schcliffe's model efficiencies were 0.633, 0.902, respectively. This results showed its applicabilities to national water resources plan, rural water development plan, and total maximum daily load plan in Korea.

• 세라미스트
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• 제22권3호
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• pp.230-242
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• 2019

Functional ceramics are widely utilized in a variety of application fields such as structural materials, sensors, energy devices, purification filter and etc due to their high strength, stability and chemical activity. With the breakthrough development of nanotechnology, many researchers have studied new types of nanomaterials including nanoparticle, nanorod, nanowire and nanoplate to realize high-performance ceramics. Especially several groups have focused on the 3D nanostructured ceramics because of their large surface area, efficient load transfer, ultra-fast ion diffusion and superior electrical (or thermal) conductivity. In this review, we introduce the reported fabrication strategies of the 3D nanostructured and functional ceramics, also summarized the 3D nanostructured ceramic based high-performance applications containing photocatalysts, structural materials, energy harvesting and storage devices.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제3B권1호
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• pp.16-22
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• 2003

This paper presents an application of an impedance boundary condition to 3D vector finite element analysis of a multi-port cylidrical microwave cavity using Snell's law. Computing memory benefits and computing time reduction are obtained from this method compared with the conventional finite element method(FEM). To verify the method, a high permittivity scatterer in free space is analyzed and compared with the results of conventional (FEM). In addition, this method has been analyzed several types of cavities, including water load, to demonstrate the validity and accuracy of the program.

• 기술발표회
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• 통권2006호
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• pp.220-231
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• 2006

Debris flows are a natural hazard which looks like a combination of flood, land and rock slide. Large rainfall in July 2006 produced several large scale debris flows and many small debris flows that resulted in loss of life and considerable property and highway damage, as was widely reported in the national media. The hazard "debris flow" is still insufficiently researched Furthermore debris flows are very hard to predict. In this paper, a general over view of the debris flow problems along the highway, a generic way for the design and dimensioning of flexible barrier systems will be presented. A brief description of the various unique barrier types will be provided, too. The future for these barrier concepts looks promising because these barriers represent the state of art for such applications and are superior to many other available options.

• Ocean Systems Engineering
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• 제1권4호
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• pp.297-315
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• 2011

New applications of streamlined Autonomous Underwater Vehicles require an AUV capable of completing missions with both high-speed straight-line runs and slow maneuvers or station keeping tasks. At low, or zero, forward speeds, the AUV's control surfaces become ineffective. To improve an AUV's low speed maneuverability, while maintaining a low drag profile, through-body tunnel thrusters have become a popular addition to modern AUV systems. The effect of forward vehicle motion and sideslip on these types of thrusters is not well understood. In order to characterize these effects and to adapt existing tunnel thruster models to include them, an experimental system was constructed. This system includes a transverse tunnel thruster mounted in a streamlined AUV. A 6-axis load cell mounted internally was used to measure the thrust directly. The AUV was mounted in Memorial University of Newfoundland's tow tank, and several tests were run to characterize the effect of vehicle motion on the transient and steady state thruster performance. Finally, a thruster model was modified to include these effects.

• 한국철도학회논문집
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• 제8권2호
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• pp.195-201
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• 2005

Mode II interlaminar fracture behaviors of carbon fabric/epoxy composites, which are applicable to tilting train carbodies, was investigated by the ENF (End notched flexure) test. The specimens were made of CF3327 plain woven fabric with epoxy and a starter delamination at one end was made by inserting Teflon film with the thickness of 12.5$mu$m or 25.0$mu$m. The equation for mode II interlaminar fracture toughness was suggested based on the effective crack length from the compliance of load-displacement curve. Mode II interlaminar fracture toughness was evaluated for several types of the specimens. Also crack propagating behaviors and fracture surfaces were examined through an optical travelling scope and a scanning electron microscope.

• Tribology and Lubricants
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• 제18권5호
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• pp.364-370
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• 2002

In this paper, numerical analyses were undertaken to calculate the static and dynamic performances of step-pocket, inward pumping spiral grooved, outward pumping spiral grooved and herringbone grooved bearings. For each bearing, optimal values for various design parameters were obtained to maximize the load capacity and the stiffness and bearing performances were calculated. The optimized performances of these bearings were compared to conclude that the performance of step-pocket bearing is better than the other bearings.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2006년도 춘계학술대회 논문집
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• pp.288-291
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• 2006

Piercing or blanking process is widely used to manufacture most of lead frame parts, but it is difficult to analyze the real process by the actual shape through progressive dies. In this paper several stages in progressive punching are modeled by 2D and 3D configurations using $DEFORM^{TM}$ 2D/ 3D code. During the progressive stage some state variables and deformed configurations are analyzed in each model. There are three stages in the process, the deformations at each stage are cumulative. The advantages and disadvantages of these two type modeling are discussed and analyzed. The experiments are performed as a working material copper alloy through manufactured die. Computed results in load by two types are compared to experiments.