• 한국대기환경학회지
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• 제30권4호
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• pp.362-377
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• 2014

Polycyclic aromatic hydrocarbons (PAHs) have been of particular concern since they are present both in the vapor and particulate phases in ambient air. In this study, a simple method was applied to determine the vapor phase PAHs, and the performance of the new method was evaluated with a conventional method. The simple method was based on adsorption sampling and thermal desorption with GC/MS analysis, which is generally applied to the determination of volatile organic compounds (VOCs) in the air. A combination of Carbotrap (300 mg) and Carbotrap-C (100 mg) sorbents was used as the adsorbent. Target compounds included two rings PAHs such as naphthalene, acenaphthylene, and acenaphthene. Among them, naphthalene was listed as one of the main HAPs together with a number of VOCs in petroleum refining industries in the USA. For comparison purposes, a method based on adsorption sampling and solvent extraction with GC/MS analysis was adopted, which is in principle same as the NIOSH 5515 method. The performance of the adsorption sampling and thermal desorption method was evaluated with respect to repeatabilities, detection limits, linearities, and storage stabilities for target compounds. The analytical repeatabilities of standard samples are all within 20%. Lower detection limits was estimated to be less than 0.1 ppbv. In the results from comparison studies between two methods for real air samples. Although the correlation coefficients were more than 0.9, a systematic difference between the two groups was revealed by the paired t-test (${\alpha}$=0.05). Concentrations of two-rings PAHs determined by adsorption and thermal desorption method consistently higher than those by solvent extraction method. The difference was caused by not only the poor sampling efficiencies of XAD-2 for target PAHs and but also sample losses during the solvent extraction and concentration procedure. This implies that the levels of lower molecular PAHs tend to be underestimated when determined by a conventional PAH method utilizing XAD-2 (and/or PUF) sampling and solvent extraction method. The adsorption sampling and thermal desorption with GC analysis is very simple, rapid, and reliable for lower-molecular weight PAHs. In addition, the method can be used for the measurement of VOCs in the air simultaneously. Therefore, we recommend that the determination of naphthalene, the most volatile PAH, will be better when it is measured by a VOC method instead of a conventional PAH method from a viewpoint of accuracy.

• 한국인쇄학회지
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• 제28권1호
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• pp.15-24
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• 2010

Photovoltaic solar cells are all in the incident because they are not converted into electrical energy, high-efficiency solar cells in order to reduce the loss of elements must be. Significant factor in the loss of solar cells, optical loss and electrical loss can be divided into. Optical losses occur when the sun will be joined on the surface of the reflection, the shadow loss due to electrodes, and the losses are in the solar wavelengths. Commercialization is currently the most common solar cells on the front of the light incident on the electrode is formed. Therefore, the shadow caused by the electrode to cover the dead area of the sun, due to factors that hinder the absorption of sunlight which is shadowing them and conversion efficiency of solar cells is the inhibition factor. These barriers to eliminate the electrode linewidth reduces the shadowing to reduce, but simply of the electrode line width is reduced electrode area by reducing the series resistance elevates this because to improve the electrode Aspect ratio(height/width) to increase Ag development of paste is required. In this study, aspect ratio of screen-printing method to increase the electrode Ag paste composition of the binder for the characterization of rheology in the shadow of the electrode by reducing the optical loss of the photoelectric conversion efficiency of solar cells to boost the performance measures was. Properties and printability of the paste, the binder resin sintered characteristics that affect the thermal properties are excellent with a good screen printability acrylic resin, ethyl cellulose, using a resin were evaluated. Prepared paste rheology properties, was formed to evaluate the electrode conductivity and aspect ratio.

• Advances in aircraft and spacecraft science
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• 제2권2호
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• pp.169-182
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• 2015

Aeronautics engine cooling is one of the biggest problems that engineers have tried to solve since the beginning of human flight. Systems like radiators should solve this purpose and they have been studied extensively and various solutions have been found to aid the heat dissipation in the engine zone. Special interest has been given to air coolers in order to guide the air flow on engine and lower the high temperatures achieved by the engine in flow conditions. The aircraft companies need faster and faster tools to design their solutions so the development of tools that allow to quickly assess the effectiveness of an cooling system is appreciated. This paper tries to develop a methodology capable of providing such support to companies by means of some application examples. In this work the development of a new methodology for the analysis and the design of oil cooling systems for aerospace applications is presented. The aim is to speed up the simulation of the oil cooling devices in different operative conditions in order to establish the effectiveness and the critical aspects of these devices. Steady turbulent flow simulations are carried out considering the air as ideal-gas with a constant-averaged specific heat. The heat exchanger is simulated using porous media models. The numerical model is first tested on Piaggio P180 considering the pressure losses and temperature increases within the heat exchanger in the several operative data available for this device. In particular, thermal power transferred to cooling air is assumed equal to that nominal of real heat exchanger and the pressure losses are reproduced setting the viscous and internal resistance coefficients of the porous media numerical model. To account for turbulence, the k-${\omega}$ SST model is considered with Low- Re correction enabled. Some applications are then shown for this methodology while final results are shown in terms of pressure, temperature contours and streamlines.

• Elastomers and Composites
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• 제40권3호
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• pp.166-173
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• 2005

본 논문에서는 세가지 종류의 경화제 (D-230, G-5022 및 HN-2200)를 사용하여 열화가 에폭시 접착제의 질량변화 및 흡수량에 미치는 영향을 고찰하였다. 경화된 시편의 열적 및 기계적 특성은 유리전이온도와 전단강도 측정을 통하여 알아보았다. 실험 결과, D-230와 HN-2200를 경화제로 사용하였을 경우 열화 시간이 시스템의 질량 변화에 영향을 주지 않았으며, G-5022를 경화제로 사용하였을 경우 시스템의 질량은 열화 시간에 따라 현저하게 감소하였다. 열화 이전의 DGEBA/G-5022 시편을 제외하고 모든 시편의 흡수량은 시간에 따라 점차 증가하였다. 또한, DGEBA/HN-2200 시스템이 제일 높은 $T_g$ 값을 나타내었으며, 이는 경화된 시스템이 지방족 고리를 함유한 3차원 네트워크 구조를 형성한 것으로 판단된다. 에폭시 수지의 접착강토는 열화 시간에 따라 점차 증가하였으며, 이는 에폭시 수지의 경화도 증가와 보다 발달된 3차원 네트워크 구조의 형성에 기인한다. 또한, 내수 실험 후 열화 전후의 모든 시편의 유리전 이온도와 전단접착강도는 흡수시간에 따라 감소하였다.

• Nuclear Engineering and Technology
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• 제50권3호
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• pp.356-367
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• 2018

A series of tests dedicated to station blackout (SBO) accident scenarios have been recently performed at the $Prim{\ddot{a}}rkreislauf-Versuchsanlage$ (primary coolant loop test facility; PKL) facility in the framework of the OECD/NEA PKL-3 project. These investigations address current safety issues related to beyond design basis accident transients with significant core heat up. This work presents a detailed analysis using the best estimate thermal-hydraulic code TRACE (v5.0 Patch4) of different SBO scenarios conducted at the PKL facility; failures of high- and low-pressure safety injection systems together with steam generator (SG) feedwater supply are considered, thus calling for adequate accident management actions and timely implementation of alternative emergency cooling procedures to prevent core meltdown. The presented analysis evaluates the capability of the applied TRACE model of the PKL facility to correctly capture the sequences of events in the different SBO scenarios, namely the SBO tests H2.1, H2.2 run 1 and H2.2 run 2, including symmetric or asymmetric secondary side depressurization, primary side depressurization, accumulator (ACC) injection in the cold legs and secondary side feeding with mobile pump and/or primary side emergency core coolant injection from the fuel pool cooling pump. This study is focused specifically on the prediction of the core exit temperature, which drives the execution of the most relevant accident management actions. This work presents, in particular, the key improvements made to the TRACE model that helped to improve the code predictions, including the modeling of dynamical heat losses, the nodalization of SGs' heat exchanger tubes and the ACCs. Another relevant aspect of this work is to evaluate how well the model simulations of the three different scenarios qualitatively and quantitatively capture the trends and results exhibited by the actual experiments. For instance, how the number of SGs considered for secondary side depressurization affects the heat transfer from primary side; how the discharge capacity of the pressurizer relief valve affects the dynamics of the transient; how ACC initial pressure and nitrogen release affect the grace time between ACC injection and subsequent core heat up; and how well the alternative feeding modes of the secondary and/or primary side with mobile injection pumps affect core quenching and ensure stable long-term core cooling under controlled boiling conditions.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2003년도 추계학술발표강연 및 논문개요집
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• pp.137-137
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• 2003

Optical amplificator have been used to compensate the losses in the optical signal transmission and processing. Today, there has been increasing demand for the very low cost optical amplifier. Sol-gel offers considerable potential both low cost manufacture, and for great flexibility in materials composition and structure. In addition, the sol-gel process is a very attractive method for producing porous materials with controlled structure. In this work, we present the potoluminescence properties of Er doped A1$_2$O$_3$/SiO$_2$ films. Erbium doped alumina nano sol was prepared by Al(NO$_3$)$_3$.9$H_2O$ and Er(NO$_3$)$_3$.5$H_2O$ through hydrolysis and peptization, and then GPS (3-Glycidoxypropyltrimethoxysilane) was added into Er doped alumina nano sol for organic- inorganic hybridization. Er doped A1$_2$O$_3$/SiO$_2$ film was obtained by spin coating, dip coating and thermal treatment from 30$0^{\circ}C$~120$0^{\circ}C$, and there were crack-free after thermal treatment. The thickness of film was measured SEM, and the porosity of film was characterized by BET and TGA. The crystal phase of Er doped A1$_2$O$_3$/SiO$_2$ were determined by XRD. Finally, the photoluminescence properties of Er doped A1$_2$O$_3$/SiO$_2$ films will be discuss with the consideration of porosity and crystallity.

• Journal of Biosystems Engineering
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• 제38권4호
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• pp.287-294
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• 2013

Purpose: Greenhouses for a protected horticulture covered with a plastic or glass are easy to have weakness in a heat loss by deterioration, damage, poor construction, and so on. To grasp the vulnerable points of heat loss of the greenhouses is important for heating energy saving. In this study, an on-site heat loss audit and energy consulting system were developed for an efficient energy usage of a greenhouse. Method: Developed system was mounted with infrared thermal and visual cameras to grasp the heat loss from the greenhouse quickly and exactly, and a trial calculation program of heating load of greenhouse to provide farmers with the information of heating energy usage. Results: Developed system could print out the reports about the locations and causes of the heat losses and improvement methods made up by an operator. The mounted trial calculation program could print out the information of the period heating load and fuel cost according to the conditions of greenhouse and cultivation. The program also mounted the databases of the information on the 13 horticultural energy saving technologies developed by the Korea Rural Development Administration and simple economic analysis sub-program to predict the payback period of the technologies. Conclusion: The developed system was expected to be used as the basic equipment for an instructors of district Agricultural Technology and Extension Centers to conduct the energy consulting service for the farmers within the jurisdiction.

• 한국농공학회지
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• 제29권4호
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• pp.132-141
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• 1987

The objective of the study was to obtain the compressive the tensile and the fleniril strengthes, thermal resistance, chemical resistance and fire resistance of the reclaimed plastic corcrete in order to investigate the feasibility as a new construction material This reclaimed plastic concrete is a compositive material which is composed of sand and blend of 50% of LDPE(Low density polyethylene) and 50% of HDPE (High density polyethylene) which are inexpensive and easy to reclaim. The results obtained in the study are summarized as follows: 1. As the binder content ranging from 20 to 40 % increase, the compresie, the splitting tensile and the flexural strengthes were increased. The compressive strenzth of the specimen tested was the highest and flexural strength the next and tensile strength the lowest 2. The compressive, the tensile and flexural strengthes of specimens made of fine sand were higher than those of coarse sand. The compressive, the tensile and the flexural strengthes of specimens made of high pressure molding were higher than those of low pressure molding. 3.In comparison with different additives, the specimens with carbon black was excellent and B. H. T. good and ferric oxide poor for thermal resistance. 4. In relationship between the flexural strength with varying temperature from -23$^{\circ}C$ to 80$^{\circ}C$. The flexural strengthes were decreared as temperature increased at 25 %, 30 % and 35 % of binder contents, respectively. Especially at 60$^{\circ}C$, the flexural strength was significantly decreased. 5. The decrement of flexural strengthes and the weight losses after 7 days immersion in acid or alkali solutions were not significant. 6. Fire resistance of the reclaimed plastic concrete was not significantly influenced by the contents of sand. However, the fire resistance of the reclaimed plastic concrete was depend upon melting and ignition properties of the binder itself. Therefore. a proper selection of the binder and the fire retardant are recommended in arder to improve fire resistance of the reclaimed plastic concrete.

• 한국자동차공학회논문집
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• 제15권1호
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• pp.193-200
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• 2007

Natural gas is one of the most promising alternatives to gasoline and diesel fuels because of its lower harmful emissions, including $CO_2$, and high thermal efficiency. In particular, natural gas is seen as an alternative fuel for heavy-duty Diesel Engines because of the lower resulting emissions of PM, $CO_2$ and $NO_x$. Almost all CNG vehicles use the PFI-type Engine. However, PFI-type CNG Engines have a lower brake horse power, because of reduced volumetric efficiency and lower burning speed. This is a result of gaseous charge and the time losses increase as compared with the DI-type. This study was conducted to investigate the effect of injection conditions (early injection mode, late injection mode) on the combustion phenomena and performances in the or CNG Engine. A DI Diesel Engine with the same specifications used in a previous study was modified to a DI CNG Engine, and injection pressure was constantly kept at 60bar by a two-stage pressure-reducing type regulator. In this study, excess air ratios were varied from 1.0 to the lean limit, at the load conditions 50% throttle open rate and 1700rpm. The combustion characteristics of the or CNG Engine - such as in-cylinder pressure, indicated thermal efficiency, cycle-by-cycle variation, combustion duration and emissions - were investigated. Through this method, it was possible to verify that the combustion duration, the lean limit and the emissions were improved by control of injection timing and the stratified mixture conditions. And combustion duration is affected by not only excess air ratio, injection timing and position of piston but gas flow condition.

• 생물환경조절학회지
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• 제8권2호
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• pp.136-146
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• 1999

본 연구에서는 동절기 시설원예용 하우스의 열환경, 난방방식별 에너지 소비 특성, 하우스내 열이동 프로세스자 난방효율에 대해서 중점적으로 검토하였다. 동절기 하우스의 벽체, 지붕을 통해 손실되는 관류열량을 정량적으로 계산하므로서, 하우스의 단열계획 및 난방에너지 절약을 유도할 수 있는 기초데이터를 제시하였다. 난방방식별 실내외 온도차와 에너지 소비량과의 관계를 정량적으로 도출하므로서, 쾌적성, 경제성을 고려한 최적의 하우스 난방방식 선정과 난방기 운용의 효율화를 유도하기 위한 기초자료를 제시하였다 난방방식별 실내외 온도차와 에너지 소비량과의 관계로부터 도출된 결과는 심야전력 난방이 온풍난방에 비해 난방효율이 현저히 높은 것으로 나타났다. 덕트 주변의 수평 및 연직방향으로 다수의 열전대를 설치하여 온풍 난방시 덕트주변의 작물에 미칠 수 있는 고온피해 발생 가능성을 검토하였으나, 약 1$^{\circ}C$이내의 비교적 균일한 온도가 계측되므로서, 온풍에 의한 주변작물의 고온피해는 관측되지 않았다. 덕트 길이방향으로 일정간격마다 덕트내부에 열전대를 설치하여 덕트길이에 따른 온도하강 추이를 검토한 결과, 덕트 단위길이당 0.5~0.8$^{\circ}C$의 온도강하가 계측되었다.