• 신재생에너지
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• 제2권2호
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• pp.75-80
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• 2006

The effective thermal conductivities of $Mm(La_{0.6-0.8})Ni_{4.0}Co_{0.6}Mn_{0.2}Al_{0.2}$ [TL-492] with hydrogen and helium have been examined. Experiment results show that pressure has great influence on effective thermal conductivity in low pressure range [below 0.5 MPa]. And that influence decreases rapidly with increase of gas pressure. The reason is at low pressure, the mean free path of gas becomes greater than effective thickness of gas film which is important to the heat transfer mechanism in this research. And, carbon fibers have been used to try to enhance the poor thermal conductivity of TL-492. Three types of carbon fibers and three mass fractions have been examined and compared. Naturally, the highest effective thermal conductivity has been reached with carbon fiber which has highest thermal conductivity, and highest mass fraction. This method has acquired 4.33 times higher thermal conductivity than pure metal hydrides with quite low quantity of additives, only 0.99 wt% of carbon fiber. This is a good result comparing to other method which can reach higher effective thermal conductivity but needs much higher mass fraction of additives too.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.3079-3084
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• 2008

A fast response $CO_2$ analyzer has been developed for measuring the $CO_2$ concentration during transient condition of SI engine. The analyzer is based on the non-dispersive infrared absorption technique, electrical chopping system and water cooling system. The analyzer has good repeatability, linearity and permissible drift characteristic. Besides, it has 18ms with a response to measure the $CO_2$ concentration. The fast response $CO_2$ analyzer was applied to single cylinder SI engine and the $CO_2$ emission was examined during engine start. Simultaneously, the standard exhaust gas analyzer, which has slow response time, was used for considering the engine-out $CO_2$ characteristic. The developed analyzer showed much faster responsive characteristic than that of a standard analyzer and made cycle by cycle exhaust gas analysis possible. The transient engine operating characteristics will be estimated and the transient behaviors on engine-out emission and performance will be improved.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 동계학술발표대회 논문집
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• pp.119-124
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• 2008

Recently, focus has been drawn on natural refrigerants due to increasing concern on global warming. As a consequence, CO2 systems such as a heat pump water heater using CO2 as a refrigerant are rapidly growing on the market. Currently, rolling piston rotary compressors are widely used for CO2 heating and/or refrigeration systems. There are several ways of realizing gas compression structure. They are single stage compression with single cylinder, single stage compression with two cylinders, and two stage compression with two cylinders. In this paper, computer simulation program which was validated for a single stage rotary compressor with one cylinder has been extended for a single stage, two cylinder rotary type. Numerical investigation has been made on optimal design for the cylinder configuration using the extended simulation program. For a single stage two cylinder rotary compressor having a displacement volume of 4 cc for each cylinder, compressor efficiency has been found to be maximum when the cylinder radius and height are 31mm and 10mm, respectively.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1993년도 추계학술대회 논문집
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• pp.141-143
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• 1993

A nontoxic organic photoreceptor for near infrared light has been developed. A double layered photoreceptor using $\tau$-H$_2$Pc as the CGL was made. The CTL was formed by oxadiazole derivative dispersed in two other host polymers. This photoreceptor has a charge acceptance of -900 V when a corona charge is used, and has residual potentials of -20 V for PC, and -10 V for PVB by light irradiation.

• 한국자원식물학회지
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• 제5권1호
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• pp.31-35
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• 1992

The somatic chromosome numbers were counted to be 2n = 16 of Codonopsis lanceolata. Chromosomes 2 and 7 of Sokrisan and Koheung II has a hetero satellite on short arm. Chromosome 5 of Bakwoonsan showed homo satllite on short arms. Short arms of chromosomes 1 and 5 has homo satellite and short arms of chromosomes 2 and 7 has hetero satellite of Jilin.

• Bulletin of the Korean Chemical Society
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• 제23권6호
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• pp.803-807
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• 2002

The conversion of dimethyl ether(DME) has been carried out over $\gamma-alumina$, silica-alumina, and modified $\gamma-aluminal$ catalysts. Especially, the water effect has been investigated on purpose to develop a suitable catalyst for one-step synthesis of DME from $CO_2$ hydrgenation, The $\gamma-Al_2O_3$ modified with 1 wt% silica is more active and less deactivated by water than unmodified one. $CO_2has$ no effect on catalytic dehydration of methanol to DME.

• 한국응용곤충학회지
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• 제49권4호
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• pp.393-400
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• 2010

담배나방 알(HAs)을 기주로 사육된 명충알벌(TC)을 담배나방(HAs-HAs)과 왕담배나방(HAs-HAr) 알에, 줄알락명나방(CC) 알을 기주로 사육된 TC를 왕담배나방(CC-HAr) 알과 담배나방(CC-HAs)에, 왕담배나방(HAr) 알을 기주로 사육된 TC를 왕담배나방(HAr-HAr)과 담배나방(HAr-HAs)에 대한 기생률, 발육기간, 우회율, 번식량을 실험실 조건(온도 $25{\pm}2^{\circ}C$; 습도 50~70%; 광기간 16L-8D)에서 조사하였다. TC는 직전에 어떤 기주에 사육했는가에 따라 시험 기주에서 나타나는 발육반응이 다르다는 것을 알 수 있었으며, 흔히 직전기주와 시험기주의 크기에 의해 발육기간 우회율, 기생률, 번식량이 차이를 보였으며, 가장 큰 차이를 보인 것은 기생률과 번식량인 것으로 나타났다. 기생률은 가장 낮은 CC-HAr의 $10.1{\pm}2.05%$에서 가장 높은 HAr-HAs의 $47.0{\pm}2.09%$로 나타나 처리 간에 유의한 차이를 보였으며, 우회율에서도 유사한 경향을 보였다. 발육기간은 직전기주의 크기가 가장 작고 시험기주의 크기가 가장 큰 CC-HAr처리에서 가장 짧았다. 처리에 따른 TC의 번식량은 HAr-HAs에서 가장 높았으며($93.9{\pm}6.87$마리), 가장 낮은 처리는 CC-HAs($18.4{\pm}6.36$마리)였다.

• Computers and Concrete
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• 제3권2_3호
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• pp.79-90
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• 2006

This paper describes the results of an investigation into high mass-low velocity impact behaviour of reinforced concrete beams. Tests have been conducted on fifteen 2.7 m or 1.5 m span beams under drop-weight loads. A high-speed video camera has been used at rates of up to 4,500 frames per second in order to record the crack formation, propagation, particle spallation and scabbing. In some tests the strain in the reinforcement has been recorded using "Durham" strain gauged bars, a technique developed by Scott and Marchand (2000) in which the strain gauges are embedded in the bars, so that the strains in the reinforcement can be recorded without affecting the bond between the concrete and the reinforcement. The impact force acting on the beams has been measured using a load cell placed within the impactor. A high-speed data logging system has been used to record the impact load, strains, accelerations, etc., so that time histories can be obtained. This research has led to the development of computational techniques based on combined continuum/discontinuum methods (finite/discrete element methods) to permit the simulation of impact loaded reinforced concrete beams. The implementation has been within the software package ELFEN (2004). Beams, similar to those tested, have been analysed using ELFEN a good agreement has been obtained for both the load-time histories and the crack patterns.

• Tuberculosis and Respiratory Diseases
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• 제85권4호
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• pp.313-319
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• 2022

Environmental exposure to air pollution is known to have adverse effects on various organs. Air pollution has greater effects on the pulmonary system as the lungs are directly exposed to contaminants in the air. Here, we review the associations of air pollution with the development, morbidity, and mortality of pulmonary diseases. Short-and long-term exposure to air pollution have been shown to increase mortality risk even at concentrations below the current national guidelines. Ambient air pollution has been shown to be associated with lung cancer. Particularly long-term exposure to particulate matter with a diameter <2.5 ㎛ (PM_2.5) has been reported to be associated with lung cancer even at low concentrations. In addition, exposure to air pollution has been shown to increase the incidence risk of chronic obstructive pulmonary disease (COPD) and has been correlated with exacerbation and mortality of COPD. Air pollution has also been linked to exacerbation, mortality, and development of asthma. Exposure to nitrogen dioxide (NO₂) has been demonstrated to be related to increased mortality in patients with idiopathic pulmonary fibrosis. Additionally, air pollution increases the incidence of infectious diseases, such as pneumonia, bronchitis, and tuberculosis. Furthermore, emerging evidence supports a link between air pollution and coronavirus disease 2019 transmission, susceptibility, severity and mortality. In conclusion, the stringency of air quality guidelines should be increased and further therapeutic trials are required in patients at high risk of adverse health effects of air pollution.

• 한국주조공학회지
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• 제12권2호
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• pp.155-161
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• 1992

This study has been performed in increase the wear resistance characteristic and the mechanical properties of high Mn steel castings with an addition of Ni to $1{\sim}4%$ range. The initial structure of plastic cememtite has been possible to transform perfect austenite with watertoughening treatment. Increasing Ni content, the most wear loss has shown that ore has crushed until 100kg and decreased with increasing ore amount at ascast, the similar tendency has shown at heat treatment. Chang of hardness has shown high values that ore has been crushed until 300kg, both as cast and treatment added 2%Ni.