• Bulletin of the Korean Chemical Society
• /
• 제28권3호
• /
• pp.457-462
• /
• 2007

Amorphous calcium carbonate (ACC) can readily be prepared using ethanol as the reaction medium and ammonium carbonate as the source of carbon dioxide. Other additives, or any elaborate pH control are not needed to form the initial calcium carbonate precipitate. Ammonia generated from ammonium carbonate maintains the reaction medium in a neutral or weakly basic condition, retarding the crystallization of ACC, while ethanol itself inhibits the dissolution of ACC. The ACC prepared in this way provides a rare opportunity to fabricate molded biomimetic crystals in vitro, but the ACC is too fragile to be fabricated into proper shapes. The malleability of ACC is, however, greatly enhanced by incorporating poly(ethylenimine) (PEI). The ACC/PEI composite can then be fabricated, using a proper mold or template, into mechanically durable biomimetic crystals of definite shape. The ACC in the ACC/PEI composite can further be transformed into vaterite by heating under N2 atmosphere, while the native ACC simply converts into calcite.

• 대한설비공학회:학술대회논문집
• /
• 대한설비공학회 2009년도 하계학술발표대회 논문집
• /
• pp.58-63
• /
• 2009

A ground-loop heat exchanger for the ground source heat pump system is the core equipment determining the thermal performance and initial cost of the system. The size and performance of the heat exchanger is highly dependent on the ground thermal properties - the ground effective thermal conductivity, the borehole thermal resistance and the undisturbed ground temperature. Nowadays, precast concrete piles using steel reinforced precast concrete piles - energy piles - are used to reduce the installing cost of the ground-loop heat exchanger. We were carried out some tests to investigate the effects of some parameters such as borehole length, grouting materials and U-tube configuration of the energy piles. 4 concrete piles, each measuring $250mm{\sim}400mm$ in diameter and approx. 10m in length, and rigged with single spiral and 3 U-tube loop of $16mm{\times}2.3mm$ PB piping. The thermal response tests were conducted using a testing device for 4-different ground-loop heat exchangers. During the heating period, the energy piles absorb the heat of 0.89kW to 1.37kW.

• 대한설비공학회:학술대회논문집
• /
• 대한설비공학회 2009년도 하계학술발표대회 논문집
• /
• pp.1185-1190
• /
• 2009

Korea is an industrial country that overspends energy and has a policy that is more focused on a supply side. When an urban developmental program is to set up, surveys are carried out only with the respect to electricity, telecommunication, gas, and heating sources. Based on the existing survey results, the problems related to the supply side are being dealt with more importantly and the quantities of those supplies are estimated only by each energy source. The aim of this study is to provide basic information on energy consumption patterns of a diverse comsumer groups including industry, transportation, commerce, public and household to plan diverse energy policies. Through this basic information, it may be possible to analyze the energy consumption pattern by each consumer group and provide data for setting up efficient energy policies by the government. The energy consumption map that are analyzed and developed by the data obtained from Busan municipal area will be deposited and used as a part of the national energy statistics.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2005년도 추계학술대회 논문집 전기물성,응용부문
• /
• pp.93-95
• /
• 2005

VASIMR (Variable Specific Impulse Magnetoplasma Rocket: JSC, NASA)의 개념을 바탕으로 하는 K2H (KBSI-KAIST-Hanyang University)라고 이름 붙여진 우주 추진체 모사장치 (Space Propulsion Simulator)를 개발하였다. 이 장치는 헬리콘 플라즈마 소스, 이온 가열부 (ICRH: Ion Cyclotron Resonance Heating), 자기노즐 부분으로 이루어져 있다. 헬리콘 플라즈마 소스는 m=+1 형태의 Right-helical 안테나를 사용하여 발생하였다. 본 연구에서는 K2H 장치의 기본적인 설계 개념 및 초기에 발생한 헬리콘 플라즈마의 물성을 RF 보상탐침을 이용하여 측정하였다. 그 결과 900 W, 13.56 MHz rf파워를 사용하여, 아르곤 7 mTorr하에서 전자밀도 = $10^{12}-10^{13}cm-3$, 전자온도 = 4-6 eV의 헬리콘 플라즈마를 안정적으로 발생시켰다.

• 한국지열·수열에너지학회논문집
• /
• 제12권4호
• /
• pp.33-39
• /
• 2016

A ground source heat pump (GSHP) system is recommended as a heating and cooling system to solve the pending energy problem in the field of air conditioning, because it has the highest efficiency. However, higher initial construction cost works as a barrier to the promotion and dissemination of GSHP system. In this study, numerical analysis on the characteristics of high density polyethylene (HDPE) pipe with spiral inside was executed. The heat transfer and flow characteristics of it were compared with those of a conventional smooth HDPE pipe. The heat transfer coefficient and pressure drop of the spiral HDPE pipe were higher than those of the smooth HDPE pipes at the same fluid flow rate. By decreasing the flow rate, the spiral HDPE pipe represented similar values of heat transfer coefficient and pressure drop to the smooth HDPE pipe. The lower flow rate of the spiral HDPE pipe comparing with it of the smooth HDPE pipe is estimated to reduce the length of the ground loop heat exchanger.

• 한국전산유체공학회지
• /
• 제10권2호
• /
• pp.48-53
• /
• 2005

This work discusses the numerical analysis, the design and experimental test of the SMA actuator along with its capabilities and limitations. Convective heating and cooling using water actuate the SMA(Shape memory alloy) element of the actuator. The fuel such as propane, having a high energy density, is used as the energy source for the SMA actuator in order to increase power and energy density of the system, and thus in order to obviate the need for electrical power supplies such as batteries. The system is composed of a pump, valves, bellows, a heater(burner), control unit and a displacement amplification device. The experimental test of the SMA actuator system results in 150 MPa stress(force : 1560 N) with $3\%$ strain and 0.5 Hz. actuation frequency. The actuation frequency is compared with the prediction obtained from numerical analysis. For the designed SMA actuator system, the results of numerical analysis were utilized in determining design parameters and operating conditions.

• 한국전산유체공학회지
• /
• 제14권1호
• /
• pp.9-17
• /
• 2009

In this study we investigated the characteristics of fluid flow and heat transfer within a coolant passage in the cylinder head assembly of an internal combustion engine by using a commercial CFD code, CFX The complex coolant passage of the cylinder head assembly was modelled by suitable choice of a grid system and careful attention was paid in the construction of meshes near the walls where significant cooling occurs. To treat the simultaneous heating and cooling of the combustion walls we invented a methodology allowing a heat source within the solid wall and the convective cooling at the interface between the solid and the fluid. We managed to reproduce the experimental results by adjusting parameters appropriately. We have found that high temperature was concentrated at the surface of the cylinder jacket. It turned out that the effect of oil cooling from the piston head was unexpectedly significant. On the other hand the effect of cooling from the ambient air is almost negligible. The CFD method proposed in this study is believed to be useful in the early stage of the design of the engine-cooling system.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2003년도 춘계전력전자학술대회 논문집(2)
• /
• pp.499-502
• /
• 2003

This paper presents the voltage source type half bridge lossless auxiliary inductor snubber assisted series capacitor compensated resonant high frequency inverter for induction heated fixing roller in copy machines. This high-frequency inverter treated here can completely achieve zero current soft switching (ZCS) commutation for wide power regulation range under its constant frequency pulse density modulation (PDM) scheme. Its transient and steady-state operating principle is originally presented fur a constant frequency PDM control strategy under a ZCS operation commutation, together with its output effective power regulation characteristics-based on the PDM strategy. The experimental operating performances of this ZCS-PDM high frequency inverter using IGBTs are illustrated as compared with computer simulation ones. Its power losses and actual efficiency are evaluated and discussed on the basis of simulation and experimental results.

• 대한전기학회논문지:전기물성ㆍ응용부문C
• /
• 제50권1호
• /
• pp.1-5
• /
• 2001

P(VDF/TrFE) copolymer thin films with 70/30 and 80/20 mol% VDF (polyvinylidene fluoride) and TrFE (trifluoroethylene) rates were prepared by using a vapor deposition method, During thin films were prepared, the substrate temperatures were maintained at 30 $^{\circ}C$ and 120 $^{\circ}C$, and the heating source temperature was fixed at 350 $^{\circ}C$. Contary to PVDF homopolymer, P(VDF/TrFE) copolymers showed the Curie point(Tc) below the melting point. The Curie point (Tc) and the melting point of the P(VDF/TrFE) copolymers were changed as a function of substrate temperature and the VDF mol%. The Curie point and the melting point of P(VDF/TreFE) thin films decreased and increased with increasing substrate temperature, respectively. Also with increasing VDF mol%, the melting point decreased slightly, however the Curie point increased.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 1998년도 제14회 학술발표회 논문개요집
• /
• pp.27-27
• /
• 1998

진공기술의 응용과 진공환경의 이용은 더 이상 논하지 않더라도 산업 전반에 그 충요성이 점점 더 커가고 있다. 이러한 여건에도 불구하고 진공율 이용하는 system 개밟의 국산화는 수 입하는 system으$\mid$ 수에 비하여 절대적으로 부족하며, 또한 개발하는 system의 자동화는 거의 이 루어지지 않고 있으며, 자동화된 진공판련 system은 거의 대부분 수입에 의흔하고 있다. 실험 실 규모에서부터 System올 하나하나 개밭하고, 이톨 자동화하는 노력과 일이 진행됨다면 산업 응용에 있어서도 자연스럽게 자동화된 system으$\mid$ 개발이 이루어 질 것이다 .. system 자동화는 상 품수명의 단축과 이에 따른 다품종 소량을 요구하는 시장수요에 대응하고, 인력절감과 고풀짙 화로 생산성 향상의 요구에 대응하기 위하여 필요하다. 본 연 구에 서 는 e-beam evaporator로 evaporation하면 서 ion beam으로 assist하여 thin film율 제 작하는 IBAD vacuum system율 싫 계 및 제 작하고[1,2], PLC[3,떼톨 이 용하여 system 자동화톨 하였다 .. thin film 제작 process는 먼저 기본 진공상태로 만뚫고 난 뒤, e-beam evaporator로 e evaporation하면서 ion beam source로 assist하여 substrate 011 thin film율 제조한다 226;. thin film올 제 조하면서 thickness monitor로 sample의 thickness rate톨 control 하고, sample의 균얼성과 밀착 성을 고려하여 substrate톨 rotation 및 heating 할 수 있도록 싫계, 제작하였다. 양질의 박막올 제조하기 위해서 진공환경이 좋은 상태로 제공되어야 한다. 이톨 위하여 oil free operation 0 I 가 능한 dry pump와 turbo molecular pump로 고진공 배기 하였다. 진공도의 흑점은 thermal effect 툴 고려하여 cold cathode ion gauge률 사용하였고, intro chamber와 main chamber 사이에는 g gate valve톨 설치하여 벌도로 운용되도록 하였다. 이러한 process를 박막의 두께, 진공도, 시 간, 온도, 공정 동의 조건올 기훈으로 자동화한 것이다. 또한 정전과 단수에 대한 interlock 기능 도 고려하였다.하였다.