• 한국항공우주학회지
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• 제38권11호
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• pp.1130-1135
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• 2010

착륙장치는 완충장치를 이용하여 항공기 착륙 시의 충격을 흡수하는 역할을 한다. 다양한 종류의 완충장치가 존재하나, 완충효율 측면에서 가장 우수한 것은 유공압 방식이다. 착륙장치의 완충 성능은 반드시 낙하시험을 통해 입증하여야 하며, 이는 미 군사규격, 미연방 항공규정 등에서 공통적으로 요구하는 있는 사항이다. 이 논문에서는 낙하시험을 위한 설비 구성, 시험 절차 및 결과분석 방법을 실제 낙하시험 사례와 함께 제시한다.

• 한국주거학회:학술대회논문집
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• 한국주거학회 2008년도 춘계학술발표대회 논문집
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• pp.281-284
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• 2008

The purposes of this study were to make clear the present condition of indoor thermal environment in apartment units and to analyze the relation of the living factors with indoor thermal elements. The field surveys consisted of measurements on physical elements and observations on living factors and interview on resident's subjective responses were carried out in 20 apartment units. The field surveys were carried out during the $January{\sim}March$ 2007. Measuring elements were air temperature, globe temperature, and relative humidity. As results, the averages of indoor temperature each houses were $21.2{\sim}27.2^{\circ}C$, the number of houses exceed the comfort zone were 4. The averages of globe temperature each houses were $21.3{\sim}27.5^{\circ}C$, 6 houses exceeded the comfort zone. The means of relative humidity were $19.5{\sim}58.8%$, relatively dry condition. The clothing value of residents were $0.39{\sim}0.89$ clo(average 0.68 clo). The average of thermal sensation ratings each room were $4.2{\sim}4.8$, 'neutral'$\sim$'slightly warm'. The results of regression analysis on relations of living factors with the thermal elements are as follow; ventilation time(outdoor air exchange), door opening time with balcony, and gas cooker use time had significant effect on indoor temperature.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.531-536
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• 2004

In-arm type hydropeumatic suspension unit(ISU) is an equipment of armed tracked vehicle to absorb impact load and vibration from the irregular ground. During the operation of ISU, main piston moves forward and backward and oil flowing through damper transmits the external impact load to floating piston. Heat is generated in ISU by the oil pressure drop through the damper orifice and the friction between cylinder wall and two pistons. On the other hand, internal heat dissipatis outside via heat convection. Occurrence of high temperature can deteriorate durability of major components and basic function of ISU. And, it can cause fatal problem in the ISU life time and the sealing performance of piston rings. As well, the spring constant change of nitrogen gas that is caused by the temperature rise exerts the negative effect to the vehicle stability. Therefore, in this paper, we analyze the heat transfer analysis of the entire ISU unit, by finite element method, with the outside flow velocities 8m/s and 10m/s.

• 한국생산제조학회지
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• 제23권5호
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• pp.478-484
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• 2014

Ultrasonic atomic force microscopy(Ultrasonic-AFM) can be used to obtain images of the elastic properties of a subsurface and to evaluate the elastic properties by measuring the contact resonance frequency. When a tip is in contact with the sample, it is necessary to understand the cantilever behavior and the tip-sample interaction for the quantitative and reliable analysis. Therefore, precise analysis models that can accurately simulate the tip-sample contact are required; these can serve as good references for predicting the contact resonance frequency. In this study, modal analyses of the first four modes were performed to calculate the contact resonance frequency by using a spring model, and the deformed shapes of the cantilever were visualized at each mode. We presented the contact characteristics of the cantilever with a variety of contact conditions by applying the contact area, contact material thickness, and material properties as the parameters for the FEM analysis.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 추계학술대회논문집
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• pp.967-971
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• 2004

Today, as the demands for home appliances are increasing, the understanding of noise and vibration characteristics have become more important. It is hard to control its vibration and noise characteristics, because its mechanical structure is very complex. In this study a model of reciprocating compressor is developed. Spring, frame, and LDT are modeled as flexible body, and the other parts are modeled as rigid. FEM model of frame is simplified in order to save the simulation time. We validated the simple model by comparing their natural frequencies and mode shapes. Motor torque is applied to a rotor, and the piston is subjected to a gas pressure. The vibrational characteristics of compressor is analyzed with LS-DYNA. Its results are compared with the simulation results of rigid body frame. The effect of LDT is also studied by comparing the vibration of frame with the results of simulation with no LDT.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.419-426
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• 2008

As pulse detonation engine(PDE) does not need compression mechanisms such as compressors because self-sustained detonation waves are able to compress propellant gases by their incident shock waves, the PDE can have a simple straight-tube structure. In this study, we propose an autonomous driving valve system of the PDE, which fill premixed gases into the PDE tubes at high frequency with high mass flow rate. The proposed valve is composed of only three parts: a piston, a cylinder, and a spring. This valve system can produce intermittent flow at high mass flow rate, and also can keep stable reciprocal motion by using the propellant-gas enthalpy. When the cylinder content product is assumed to be constant, experimental results of the mass flow rate were approximately equal to the calculation model. We confirmed the autonomous driving valve performance by experiments, and concluded that this extremely simple valve with no electrical power and controller can be used as the PDE propellant supply system.

• Asian Journal of Atmospheric Environment
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• 제6권4호
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• pp.288-303
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• 2012

In this study, real time measurements of particle number size distribution in urban Gwangju, coastal Taean, and industrial Yeosu in Korea were conducted in 2008 to understand the occurrence of ultrafine particle (UFP) (<100 nm) events, the variation of its concentration among different sampling sites, and UFP formation pathways. Also, to investigate seasonal and long-term variation of the UFP number concentration, data were collected for the period of 5 years (2007, 2008, 2010, 2011, and 2012) in urban Gwangju. Photochemical and combustion events were found to be responsible for the formation of UFP in the urban Gwangju site, whereas only photochemical event led to the formation of UFP in the coastal Taean site. The highest UFP concentration was found in industrial Yeosu (the average UFP number fractions were 79, 59 and 58% in Yeosu, Gwangju, and Taean, respectively), suggesting that high amount of gas pollutants (e.g., $NO_2$, $SO_2$, and volatile organic carbon (VOC)) emitted from industries and their photochemical reaction contributed for the elevated UFP concentration in the industrial Yeosu site. The UFP fraction also showed a seasonal variation with the peak value in spring (61.5, 54.5, 50.5, and 40.7% in spring, fall, summer, and winter, respectively) at urban Gwangju. Annual average UFP number concentrations in urban Gwangju were $5.53{\times}10^3\;cm^{-3}$, $4.68{\times}10^3\;cm^{-3}$, $5.32{\times}10^3\;cm^{-3}$, $3.99{\times}10^3\;cm^{-3}$, and $2.16{\times}10^3\;cm^{-3}$ in the year 2007, 2008, 2010, 2011, and 2012, respectively. Comparison of the annual average UFP number concentration with urban sites in other countries showed that the UFP concentrations of the Korean sites were lower than those in other urban cities, probably due to lower source strength in the current site. TEM/EDS analysis for the size-selected UFPs showed that the UFPs were classified into various types having different chemical species. Carbonaceous particles were observed in both combustion (soot and organics) and photochemical events (sulfate and organics). In the photochemical event, an internal mixture of organic species and ammonium sulfate/bisulfate was identified. Also, internal mixtures of aged Na-rich and organic species, aged Ca-rich particles, and doughnut shaped K-containing particles with elemental composition of a strong C with minor O, S, and K-likely to be originated from biomass burning nearby agricultural area, were observed. In addition, fly ash particles were also observed in the combustion event, not in the photochemical event.

• 한국환경농학회지
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• 제3권2호
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• pp.30-36
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• 1984

수종(數種)의 과실채소류(果實菜蔬類)에 대(對)한 유기린계(有機燐系) 살충제들의 잔유량(殘留量)을 조사(調査)한 결과(結果)는 다음과 같다. 1) 채소류(菜蔬類)(무우, 배추, 오이, 토마토)에서 diazinon의 검출률(檢出率)은 20%, 검출범위(檢出範圍)는 부검출(不檢出)${\sim}0.020ppm$ 이었으며, 검출시료(檢出試料)의 평균(平均)은 0.004ppm이었다. DEP는 검출률(檢出率)이 52.5%, 검출범위(檢出範圍)는 부검출(不檢出)${\sim}0.273ppm$이었으며, 검출시료(檢出試料)의 평균(平均)은 0.096ppm 이었다. Malathion의 검출률(檢出率)은 15%이며 검출범위(檢出範圍)는 부검출(不檢出)${\sim}0.038ppm$이고 검출시료(檢出試料)의 평균(平均)은 0.021ppm 이었다. 2) 고추에서는 EPN은 전시료(全試料)에서 부검출(不檢出) 되었으며, PAP는 1점(點)의 시료(試料)에서만 0.006ppm으로 검출(檢出)되었다. 3) 포도에서의 PAP는 검출률(檢出率)이 20%이고 검출범위(檢出範圍)는 부검출(不檢出)${\sim}0.008ppm$ 이었으며 검출시료(檢出試料)의 평균(平均)은 0.006ppm 이었다. EPN은 전시료(全試料)에서 부검출(不檢出)되었으며 MEP의 검출률(檢出率)은 20%, 검출범위(檢出範圍)는 부검출(不檢出)${\sim}0.007ppm$이며 검출시료(檢出試料)의 평균(平均)은 0.005ppm이었다. 4) 복숭아에서 EPN은 전시료(全試料)에서 부검출(不檢出)이었고, demeton-methyl은 검출률(檢出率)이 30%, 검출범위(檢出範圍)는 부검출(不檢出)${\sim}0.047ppm$이였으며, 검출시료(檢出試料)의 평균(平均)은 0.032ppm이었다. parathion은 1점(點)의 시료(試料)에서만 0.003ppm으로 검출(檢出)되었다. 5) 본(本) 조사결과(調査結果)에서 대상농작물(對象農作物)인 국내생산(國內生産) 과실채(果實菜) 소중(蔬中) 유기린계(有機燐系) 농약(農藥)의 잔유량(殘留量)은 국내외(國內外)의 잔류허용기준(殘留許容基準)에 훨씬 미달(未達)되는 수준(水準)이었으며 그 잔유량(殘留量)도 세정(洗淨)이나 조리과정(調理過程)에서 상당한 량(量)이 제거(除去)될 것으로 생각되므로 실제(實際)로 인체내(人體內)에 섭취(攝取)되는 잔유농약(殘留農藥)의 량(量)은 극소(極小)한 것으로 판단(判斷)된다.

• 한국지반공학회논문집
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• 제31권9호
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• pp.53-68
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• 2015

매설가스배관의 내진설계에서 종방향 변형률은 중요한 평가 요소이다. 일반적으로 지진파를 조화파로 단순화하며 이의 파장은 토층의 주기와 전단파 속도의 곱으로 계산하여 매설관의 응답을 계산하는 경험적 설계방법이 널리 사용되지만 이의 정확성이 평가된 사례가 없다. 본 연구에서는 1차원 지반응답해석을 수행하여 매설심도에서의 변위-시간 이력을 추출하였으며, 이를 적용한 시간이력해석을 수행하여 매설관의 응답을 평가하였다. 매설관과 지반의 상호작용은 3차원 쉘-스프링 모델을 사용하여 모사하였다. 시간이력해석으로 계산된 결과는 설계방법과 비교하여 이의 정확성을 평가하였다. 비교 결과, 파장을 예측하기 위해서는 지반응답해석을 수행해야 하는 것으로 나타났다. 토층의 고유주기는 가속도의 탁월주기를 예측하는 데에는 활용될 수 있으나 변위의 탁월주기를 예측할 수 없는 것으로 나타났다. 반면, 파장에 대한 정확한 정보가 제공될 경우, 조화파에 대하여 제시된 해석해는 정확도가 높으며 설계에 적용 가능한 것으로 나타났다. 본 연구 대상이 동시베리아 지역에 적용될 매설가스관이라 동시베리아 지역의 대표 주상도를 해석 에 사용하였지만 본 연구의 결론은 기타 모든 지역에 적용 가능하며 가스관뿐만 아니라 상수도관 등 다양한 매설관에 적용 가능하다.

• 한국산학기술학회논문지
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• 제11권7호
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• pp.2719-2726
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• 2010

본 연구는 포항지역 환경오염물질의 보건 환경 위해성 평가를 위한 기초연구의 일환이며, 이를 위하여 포항시에 소재한 지역대기자동측정 자료를 이용하여 연별, 계절별 $PM_10$ 농도분포에 대한 현황, 기상특성 및 오염물질 농도분포 분석을 수행하였고, 대기확산 모델(CALPUFF)을 이용하여 농도분포 특성에 대해 정성적, 정량적으로 확인하였다. 포항지역의 $PM_10$ 농도분포를 확인한 결과, 포항지역의 계절별 $PM_10$ 평균농도는 봄($75.7{\mu}g/m^3$)>여름($56.8{\mu}g/m^3$)>겨울($53.6{\mu}g/m^3$) >가을($52.7{\mu}g/m^3$) 순으로 봄에는 빈번히 발생하는 황사의 영향으로 높은 농도를 나타내었다. 포항지역 오염원별 $PM_10$ 배출량은 점오염원 62%>이동오염원 33%>면오염원 5% 순이며, 점오염원 중 전체 97%가 철강산업인 제철제강업에서 발생되었다. 포항지역은 $PM_10$의 영향을 많이 받고 있는 지역으로 포항철강공단지역에 대한 환경오염물질 원인배출원에 대한 감시체계의 보완 및 집중관리와 함께 포항지역 주민의 건강 보호를 위하여 보건 및 환경에 악영향을 미치는 위해인자 및 오염물질을 원천적으로 차단하는 작업이 지속적으로 수행되어야 할 시점이다.