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Kitae Jang,Kwangho Kim,Hwan Yong Kim,강상혁 대한토목학회 2018 KSCE Journal of Civil Engineering Vol.22 No.4
This study investigates the relationship between urban built environment and traffic crash occurrences in San Diego County byemploying a multi-level Poisson regression model. This model is intended to address the so-called ‘Modifiable Areal Unit Problem’by properly capturing the spatial correlations that might exist among crash occurrences within or across zones specified for dataaggregation. A preliminary inspection based on a geographic information system reveals that the crash occurrences of TrafficAnalysis Zones (TAZs) tend to show similar spatial pattern if they belong to the same city. This observation motivated us toincorporate hierarchical random components into a Poisson regression model to complement its systematic components (i.e. explanatory variables) related to socio-demographic characteristics, travel characteristics, or urban built environment. This approachturns out to improve the model’s explanatory power in assessing the relationship between urban built environment and traffic crashoccurrences while controlling other variables. A key finding from this study is that crash occurrences of individual TAZs tend todecrease with the expansion of their urban portion.
Exergy Analysis of On / Off Controlled Heat Pump
Kitae Jang,Kwanwoo Nam,Sangkwon Jeong 대한설비공학회 1999 International Journal Of Air-Conditioning and Refr Vol.7 No.-
A multi-type heat pump controls the mass flow rate of the working fluid to cope with variable heat loads when it is under dynamic load condition. This paper describes the exergy analysis associated with the unsteady response of a heat pump. First, a basic heat pump cycle is examined at a steady state to show the general trends of exergy variations in each process of the cycle. Entropy generation issue for the heat exchangers is discussed to optimize the heat pump cycle. Secondly, the performance of the inverter-driven heat pump is compared to that of the conventional one when the heat load is variable. Thirdly, the exergy destruction rate of the heat pump with On/Off operation is calculated by simulating the thermodynamic states of the working fluid in the condenser and the evaporator. The inefficiency of On/Off operation during the transient period is Quantitatively described by the exergy analysis.
장기태(Kitae Jang),정상권(Sangkwon Jeong) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.11
In the present study, the compression process in scroll compressor was simulated in consideration of<br/> flow leakage and heat transfer. Tangential and radial leakages of the refrigerant between the scrolls<br/> were considered as nozzle flow. The experiment was first conducted with a scroll compressor for<br/> automobile air conditioning system and R134a as a refrigerant. Temperature and pressure were<br/> measured at the suction and discharge ports of the compressor to determine the thermodynamic states<br/> of the refrigerant flow. Temperature distribution of the scroll with the involute angle was also measured<br/> by thermocouples that were installed inside the scroll. Measured temperature distribution was compared<br/> with the numerical results. From this result, the thermal effect of mechanical contact was found to be<br/> important in heat transfer of the compression process.
Kitae Kim,Sangkyung Choen,Jaewoo Hwang,Moonjung Jang,Junghee Yoon,Mincheol Choi 한국임상수의학회 2018 한국임상수의학회지 Vol.35 No.6
A 7-year-old intact female Shih-Tzu with chylothorax was presented. Percutaneous popliteal computedtomographic lymphangiography was performed to evaluate the thoracic duct and seek any potential cause of chylothorax. Despite two attempts, visualization of the thoracic duct failed and perianal subcutaneous computed tomographiclymphangiography with injection of iodinated, nonionic water-soluble contrast medium (0.6 ml/kg) was performed. Asingle branch of intact thoracic duct and dilated and tortuous lymphatics were detected. It was diagnosed as idiopathicchylothorax. Perianal subcutaneous lymphangiography is considered a less-invasive, easy and reliable method tovisualize lymphatics in patients with chylothorax.