• 한국군사과학기술학회지
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• 제8권4호
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• pp.85-90
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• 2005

We report the phase transition temperatures of the $PbZrO_3$ perovskite nanotubes made by sol-gel template synthesis. The lead zirconate($PbZrO{_3}$) nanotubes were prepared with a chelate sol-gel of zirconium tetrabutoxide($Zr(OBu){_4}$) and leadacetate($Pb(OAc){_2}-3H_2O$). $Whatman^(r)$ anodisc membranes, with a 200nm pore size, served as the template. After removing the template in the 6M-NaOH solution, the $PbZrO{_3}$ nanotubes so far have shown an anomalous transition temperature, $123.6^{\circ}C$ as measured by DSC with a small particle size, 15.4nm determined by X-ray analysis with the aid of Scherrer's equation.

• 한국주거학회논문집
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• 제15권2호
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• pp.19-25
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• 2004

The aim of the research was to evaluate the characteristics of indoor thermal environment and thermal sensation in the traditional Ondol room. Indoor thermal factors including air temperature, operative temperature, floor surface temperature, relative humidity, PMV, OT were measured, and survey was carried out to understand subjective responses of resident's related to indoor thermal environment in Ondol room. The analysed houses are: the Chung hyo dang(the head house of Ryu family in Andong) and the Pyeung won jung(the traditional house in Yesan). The purpose of the survey was to know the relationship between resident's sensation and thermal environmental indicators such as air temperature, relative humidity, floor surface temperature, OT. The experimental results have pointed out how Ondol room may lead to comfortable and uniform indoor thermal environments.

• 한국대기환경학회:학술대회논문집
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• 한국대기환경학회 2001년도 추계학술대회 논문집
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• pp.165-166
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• 2001

HO$_2$ radical plays pivotal roles in the tropospheric $O_3$ formation chemistry. This radical oxidizes NO to NO$_2$ and thus HO$_2$ radical can lead to in-situ ozone formation. Numerous methods have been tried to measure concentrations of atmospheric HO$_2$ in gas phase. Detecting methods applied in the air are a chemical amplifier (Cantrell et al., 1996), FAGE (Fluorescence Assay with Gas Expansion) (Hard et al., 1984), and LIF (Laser-induced Fluorescence) (Stevens et al., 1994). These methods have been limited because of low sensitivity and interferences such as $O_3$, NO, and itself (Stevens et al.,1994). (omitted)

• 한국산학기술학회논문지
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• 제10권7호
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• pp.1465-1472
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• 2009

완전혼합 반응기에서 외부로의 열손실이 $CH_4/air$예혼합화염의 NOx 생성특성에 미치는 영향을 수치해석으로 검토하였다. 주요 결과로서, 단열조건에서 NOx는 체류시간에 따라 급격히 증가하는 반면에, 열손실이 고려될 때 열전 달 상수와 체류시간의 증가에 따라 NOx 저감현상이 뚜렷하게 발생하였다. 민감도 해석을 통해 열손실율이 증가함에 따라 Thermal NO 기구와 Re-burning NO 기구는 NOx 저감에 크게 기여하는 반면, Prompt NO 기구와 $N_2O$-경유 NO 기구는 오히려 NOx 증가에 기여함을 확인하였다. NOx 생성기구는 열전달 상수 및 체류시간의 변화에 따라 매우 복합한 특성을 갖지만, NOx 농도는 독립된 Thermal NO 기구에 의해 표현될 수 있었다. 이를 통해 실용 $CH_4/air$예혼합 연소기에서 NOx 농도를 예측할 수 있는 열손실율과 체류시간을 조합한 새로운 NOx 상관식이 도출되었다.

• 한국대기환경학회지
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• 제20권4호
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• pp.503-514
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• 2004

In Seoul metropolitan area, nocturnal variation of surface ozone concentrations observed at 27 monitoring sites from 1998 to 2002 showed that high ozone levels occurred frequently during the spring. Frequency distributions for nighttime ozone indicated that elevated concentrations in spring were influenced by advection of different air mass compared to other seasons. Surface wind analysis during the spring revealed that relatively strong southwesterly winds were associated with nocturnal ozone enhancement, which can be attributed to the regional transport of ozone. In order to identify the origin of nocturnal ozone enhancement in spring, 3-day backward trajectories were calculated by HYSPLIT 4 for the episode days and then classified. The results showed that NW, W, and SW flows, indicating influence of polluted air masses from the China continent, have 51% in a]1 the episode days, which suggest that the nocturnal ozone enhancement can occur under the effect of long-range transport of ozone-laden air mass on a regional scale. Case study of nocturnal ozone maxima associated with long-range transport was discussed in more detail in the light of meteorological conditions. Southwesterly synoptic flow along the outer edge of moving high-pressure system was found to be the important cause of nocturnal ozone maxima in Seoul. This flow could lead to be long-range transport of ozone that had effectively accumulated in the stagnating portion of the system located eastern coast of China. Low atmosphere soundings, backward trajectories, and elevated ozone and CO levels at the back-ground tiles gave evidence for regional effects on nocturnal ozone enhancement In Seoul.

• Asian Journal of Atmospheric Environment
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• 제2권1호
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• pp.60-67
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• 2008

The spatial limitations of urban environments in general lead to invention and design of a wide range of underground transportation systems such as subways, underground roads and paths, etc. Among them, the application of subway systems in metropolitan cities is most commonly observed to ease those confronted difficulties on this purpose. It in turn leaves passengers and workers to be exposed to indoor air potentially polluted by various sources existing in this underground environment. Specifically when considering the IAQ in a subway station, there exist many IAQ-related parameters to be counted either as individual or as integrated exposures. In this study, a model system has been developed to manage the general IAQ in a subway station. Field survey and $CO_2$ measurements were initially conducted to analyze and understand the relationship between the indoor and outdoor air quality while considering the internal pollution sources such as passengers, subway trains, etc. The measurement data were then employed for the model development with other static information. For the model development, the algorithm of simple continuity was built and applied to model the subway IAQ concerned. In this paper, the recent updated draft version of model developed will be reported and demonstrated.

• 산업경영시스템학회지
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• 제32권1호
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• pp.44-51
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• 2009

A bonded warehouse is the warehouse located in bonded area. It functions not only as a general warehouse but also as a place for managing the work related to import and export bonded goods. As a general warehouse, it uses the rack system to store the goods and the folk lift truck to move the unitized goods. The operation of the storing system closely related to the efficiency of space uses in a warehouse and vehicle working. Thus, vehicle performance measured in distance units in the ware-house could be used as one of the key performance measure in warehouse system. This paper focuses on the operation efficiency of the bonded warehouse which uses rack system for the storing and the folk lift truck for moving goods. The method of load allocation for balancing the rack uses and vehicle operation for maximizing efficiency are the specific concerns in this paper. The simulation study is conducted to find a policy for efficient vehicle operation based on balanced rack utilization, and the favorable result for the system operation would lead the usable proposal in vehicle operation.

• Journal of Electrical Engineering and information Science
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• 제2권3호
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• pp.71-76
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• 1997

A lot of experiments and analyses have been done to determine the aging mechanism of mica-epoxy composite material used for large generator stator windings in order to estimate remaining life of the generator for last decades. After degrading artificially the mica-epoxy composite material, the surface analysis is performed to analyze breakdown mechanism of insulation in air and hydrogen atmosphere; i) In the case of air atmosphere, it is observed that an aging propagation from conductor to core by partial discharge effect and the formation of cracks between layers is widely carbonized surface. ii) In case of hydrogen atmosphere, the partial discharge effect is reduced by the hydrogen pressure (4kg/$\textrm{cm}^2$). Potassium ions forming a sheet of mica is replaced by hydrogen ions, which can lead to microcracks. It is confirmed that the sizes of crack by SEM analysis are 10∼20[$\mu\textrm{m}$] in length under air, and 1∼5[$\mu\textrm{m}$] in diameter, 10∼50[$\mu\textrm{m}$] in length under hydrogen atmosphere respectively. The breakdown mechanism of sttor winding insulation materials which are composed of mica-epoxy is analyzed by the component of materials with EDS, SEM techniques. We concluded that the postassium ions of mica components are replaced by H\ulcorner, H$_3$O\ulcorner at boundary area of mica-epoxy and/or mica-mica. It is proposed that through these phenomena, the conductive layers of potassium enable creation of voids and cracks due to thermal, mechanical, electrical and environmental stresses.

• 대기
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• 제30권1호
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• pp.17-30
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• 2020

KMA performed the special observation program to provide information about severe weather and to monitor typhoon PRAPIROON using the ship which called the Gisang 1 from 29 June 2018 to 4 July 2018 (UTC). For this period, upper-air was observed 21 times with 6 hour intervals using rawinsonde in the Gisang 1. We investigated the impact of upper-air observation data from the Gisang 1 on the performance of the operational convective scale model (we called LDAPS). We conducted two experiments that used all observation data including upper-air observation data from the Gisang 1 (OPER) and without it (EXPR). For a typhoon PRAPIROON case, track forecast error of OPER was lower than EXPR until forecast 24 hours. The intensity forecast error of OPER for minimum sea level pressure was lower than EXPR until forecast 12 hours. The intensity forecast error of OPER for maximum wind speed was mostly lower than EXPR until forecast 30 hours. OPER showed good performance for typhoon forecast compared with EXPR at the early lead time. Two precipitation cases occurred in the south of the Korean peninsula due to the impact of Changma on 1 July and typhoon on 3 July. The location of main precipitation band predicted from OPER was closer to observations. As assimilating upper-air data observed in the Gisang 1 to model, it showed positive results in typhoon and precipitation cases.

• 대한인간공학회지
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• 제15권2호
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• pp.25-36
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• 1996

The purposes of the present study were: (1) to investigate aeromedical dissorders prevalent among ROK air force pilots and (2) to evaluate their detrimental effects on flight performance. The study examined the eight flight-induced disorders primarily responsible for permanent grounding and flying restrictions. According to the survey of 600 randomly selected pilots, 80.2% of the respondents have experienced low back pain, which was 20% higher than the lifetime prevalence in Swedish male workers. Bradyacusia ranked second (56.0%) resulting from continuous exposure to high aircraft noise. The cardiovascular disorders, the most common cause for permanent grounding of Canadian forces pilots, were found in 16.0% of the Korean pilots. Due to the high prevalence of the disorders, in 1993 the Korean pilots received medical treatments 10 times as many as factory workdes. Compared to the flight performance of Israeli and British pilots in wars, the flight performance of the Korean pilots was found to be inferior. Such poor performance can be attributable to the high incidence rates of disorders. Statistical analyses revealed that the aeromedical disorders were related to personal variables such as age, flight career- related factors, and fatigue. Cigarette smoking and drinking habit contributed to worsening back pain, barotitis media, and pulmonary disorders. More comprehensive research was recommended to identify health hazards, combined with intervention to minimize disorders that could lead to early termination of flight careers or excessive loss of flight time. This study further suggests that aeromedical institutions in Korean air force should be fostered more professionally and financially.