• Journal of the Korean Geographical Society
• /
• v.36 no.3
• /
• pp.329-341
• /
• 2001

The purpose of this study focused on the distribution of crimes in Cheongju City. This study emphasized the characteristics of place and spatial pattern of crime in Central Business District(CBD). The crime core areas were delineated and explained through land-use based on fieldwork and GIS analysis For this aim. the police crime data of Cheongju Dongbu(east). Seobu(west) for 1998 were collected In which 3.909 indictable or similar offenses were reported. In this study, Included climes are murder. rape, robbery. arson, theft, burglary, assault and vandalism. Because theme crimes are related with site-specific crime. As a result. land-use patterns are often related to specific type of offenses. The climes in Cheongju City were concentrated in the CBD Most crimes were assaults and thefts Crime areas can be classified by the age of the offender Around Chungang and Pungmul Market in the CBD. the offender＇s ages were 30-50 dominantly Assaults and thefts were concentrated in Songan-gil(street). which is a place teen-ages and youngsters meet frequently The result of the buffering analysis with roads, explained 40% of crime within a 30m buffer area( including both sides) of a principal road The rest of the climes mainly occurred in the vicinity of narrow streets and alleys.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.20 no.2
• /
• pp.95-105
• /
• 1987

Traditional sea Eel pots can be divided into two groups such as bamboo and plastic pots, however they are nearly same in a shape with one entrance and fishing efficiency, except their materials. Very few yet have been studied on their catching methods or catching mechanisms at the view point of behavior. Accordingly, we have designed tubular pots in order to fill up faults of traditional fishing gear construction and behaviors of sea eel. The suitable tubular pots was decided by comparative experiments in the water tank and the fishing efficiency was compared through the field experiments. The results obtained are as follows : 1. The differences between traditional plastic pots and improved tubular pots are firstly two entrances in both ends of tube without holes, secondly flapper nets are fixed at the end of each cone, and thirdly a bait bag is fixed at the center of pot. 2. The standard size of the suitable tubular pot is: $$Tube\;:\;\phi\;12\~13{\times}L80\;cm$$, $$Cone\;:\;Inside\;ring\;\phi6{\times}D5\;cm$$, Flapper : L10 cm. 3. The fishing efficiency of tubular rots is 2.3 times better than that of plastic pots.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.24 no.7
• /
• pp.957-966
• /
• 2000

The effect of rotation on the discharge coefficient of orifices with various length-to-diameter ratios and two different inlet corner radii was studied. Length-to-diameter ratios of the orifices range from 0.2 to 10, while the inlet shapes are square edged, or round edges of radius-to-diameter ratio of 0.5. From the experiment, we found that rotational discharge coefficient and Rotation number, when based on ideal exit velocity of the orifice considering momentum transfer from the rotor, describe the effect of rotation very well. In this study, the discharge coefficients of rotating orifices are shown to behave similar to those of the well-known non-rotating orifices. For both rotating and non-rotating orifices, the discharge coefficients increase with the length-to-diameter ratio until a maximum is reached. The flow reattachments in the relatively short orifices are responsible for the increase. The coefficient then decreases with the length-to-diameter ratio due to the friction loss along the orifice bore. The length-to-diameter ratio that yields maximum discharge coefficient, however, increases with the Rotation number because the increased flow-approaching angle requires larger length-to-diameter ratio for complete reattachment. The length-to-diameter ratio for complete reattachment is shorter for round edged orifices than that of square edged orifices by about a unit length-to-diameter ratio.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.16 no.6
• /
• pp.3722-3730
• /
• 2015

The performance improvement of a small centrifugal compressor for waste water treatment has been conducted by the design change of vaneless diffuser and volute casing. Existing two compressors use a common impeller, but the width and length of the vaneless diffuser and the cross-sectional shape of the volute casing are different, respectively. Based on the experiment of the existing two compressors and their CFD results, the design of the vaneless diffuser and the volute casing has been changed. It was found that the strength of the interaction among the volute tongues, the vaneless diffusers and the impellers of two existing/one improved compressors, was affected by the cross-sectional area and inlet radial length of the volute casing including system losses' change. The efficiency of the impeller with one existing design was increased as the decrease of the width of the vaneless diffuser, but losses at the diffuser were accumulated. In conclusion, approximately 2.88%p efficiency increase at the design point of the new compressor with the improved design has been confirmed by CFD analysis results.

• Proceedings of the KSR Conference
• /
• 2008.11b
• /
• pp.66-72
• /
• 2008

In this study, transient 3D numerical simulations were performed to analyze the characteristics of fire driven flow for smoke ventilation system operating conditions in the deeply underground subway station. The smoke flow patterns were compared and discussed under smoke fan operating mode and off mode in the platform. Soongsil Univ. station(line number 7)was chosen for simulation which was the one of the deepest underground subway stations in the each lines of Seoul. The geometry for model is 365m in length include railway, 23.5m for width, 47m for depth. Therefore 10,000,000 structured grids were used for fire simulation. The parallel computational method for fast calculation was employed to compute the heat and mass transfer eqn's with 6 CPUs(Intel 3.0GHz Dual CPU, 12Cores) of the linux clustering machine. The fire driven flow was simulated with using FDS code in which LES method was applied. The Heat release rate was 10MW and The Ultrafast model was applied for the growing model of the fire source.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.40 no.1
• /
• pp.37-46
• /
• 2004

In order to increase fishing efficiencies of the fyke net used in the coast of Jeju Island, water tank experiment was caried out entering and escaping behavior using nets that were reduced to 1/20 of the size of the full scale fyke net and were improved to have antrance structure, and mackerel Scomber japonicus as experimental fish. The results of measurement are as follows : 1. Fish school behavior in the main net was showed two different patterns : swimming in a circle in the right space of the main net and swimming back and forth in ellipse in the right and left space. 2. The swimming speed of mackerel school was 23.9. 12.6 and 32.0cm/sec in the center space, right space of main net and in the mouth 3. The entering rate of fish school was 40% in net with 35cm length of the upper and funnel net in the mouth of fyke model net and 49% in conventional type fyke model net. 4. The escaping rate of fish school was 10% in net with 35cm length of the upper and funnel net in the mouth of fyke model net and 69% in conventional type fyke model net. 5. The remain rate of fish school was 90% in net with 35cm length of the upper and funnel net in the mouth of fyke model net and 31% in conventional type fyke model net.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2008.06a
• /
• pp.294-294
• /
• 2008

동시 증발 증착법 화합물의 구성원자를 독립적으로 증발시켜서 기판에 증착하는 방법이다. 각 물질은 온도에 따른 증기압을 가지는데 각 물질의 온도를 조절하여 증착률을 조절한다. 보트에서 떠난 원자가 기판에 도달할 확률은 챔버의 진공도, 보토와 기판과의 거리 등에 의하여 영향을 받는다. 진공도가 나쁠수록, 보트와 기판과의 거리가 멀수록 기판에 도달할 확률이 떨어진다. 동시증발 증착법을 이용한 SmBCO 초전도층 증착에서 각 물질의 기판에 도달하는 원자비를 조절하기 위하여 QCM(증착률 측정장치), QCM 가이드를 사용하였다. QCM sensor 입구에 튜브형태의 QCM 가이드를 설치하고 QCM 가이드가 특정한 물질의 증발보트를 향하도록 배치하였다. 따라서 각 보트에서 떠난 원자들은 특정한 QCM sensor에 도달하게 되고 결국 3원소(Sm, Ba, Cu)의 증착률의 비를 조절함으로써 조성비를 조절할 수 있게 된다. QCM 증착률의 비와 실제 조성비는 여러 가지 변수에 의하여 영향을 받는 다. 대표적인 변수는 챔버의 진공도, QCM 가이드의 직경 및 길이, QCM 센서와 보트와의 거리 등이 있다. 진공도가 높을수록 특정 보트에서 떠난 원자들이 QCM 가이드 입구에 도달할 확률이 낮아지고, QCM 가이드의 직경이 좁을수록 가이드 내벽에 흡착될 확률이 높아진다. 또한 QCM센서와 보트와의 거리가 멀수록 챔버내 잔류가스의 원자들과 충돌확률이 높아지므로 도달확률이 줄어들게 된다. 동시 증발 증확법에서 조성비의 재현성을 높이기 위해서는 매회 증착실험에서 진공도가 일정해야 하며, QCM 가이드와 보트와의 거리를 되도록 최소화 하고, QCM 직경을 크게 하는 것이 유리하다.

• Journal of Energy Engineering
• /
• v.17 no.2
• /
• pp.116-123
• /
• 2008

In order to study the heat transfer, effectiveness and pressure drop of an internal heat exchanger (IHX) for $CO_2$, heat pump under heating condition, the experiment and numerical analysis were performed. Four kinds of IHXs were used. The section-by-section method and Hardy-Cross method were used for the numerical analysis. The effects of IHX on the flow rate of refrigerant, the IHX length, the operating condition of a gas-cooler and an evaporator and the type of IHXs were investigated. With increasing the flow rate, the heat transfer rate increased about 25%. The heat transfer of the micro-channel tube was larger about 100% than that of the coaxial tube. With increasing the IHX length, the heat transfer rate decreased. The low-side pressure drop was larger compared with that of the high-side. And the pressure drop of the microchannel tube was larger about 100% than that of the coaxial tube. With increasing the high-side temperature and decreasing the low-side temperature, the heat transfer rate increased about 3%. From this study, we can see that new correlation on $CO_2$ heat transfer characteristics and tube type is necessary.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.40 no.4
• /
• pp.227-236
• /
• 2016

In the present experimental study, the effect of gas- and liquid-injected methods on the formation of bubble and liquid slug at the merging micro T-junction of a square microchannel with dimensions $600{\mu}m{\times}600{\mu}m$ was investigated. Nitrogen and water were used as test fluids. The superficial velocities of the liquid and gas were in the range of 0.05 - 1 m/s, and 0.1 - 1 m/s, respectively, where the Taylor flow was observed. The bubble length, liquid slug length, bubble velocity, and bubble generation frequency were measured by analyzing the images captured using a high-speed camera. Under similar inlet superficial velocity conditions, in the case of gas injection to the main channel at the merging T-junction (T_gas-liquid), the lengths of the bubble and liquid slug were longer, and the bubble generation frequency was lower than in the case of liquid injection to the main channel at the merging T-junction (T_liquid-gas). On the other hand, in both cases, the bubble velocity was almost the same. The previous correlation proposed using experimental data for T_liquid-gas had predicted the present experimental data of bubble length, bubble velocity, liquid slug length, and bubble generation frequency for T_gas-liquid to be ~24%, ~9%, ~39%, ~55%, respectively.

• Fire Science and Engineering
• /
• v.22 no.3
• /
• pp.272-277
• /
• 2008

This study is performed for propose that exactly equivalent length of TBP in the applied at water-based fire protection system. For predict the measuring position of equivalent length, we determined the measuring position using the FVM about pressure drop of TBP. For the reckon of the exact about measured value we compared with the result of FVM and we knew the similar value each other. Using the results we proposed the friction loss measuring position that inlet of main dirction is 20 times of appellation diameter in main pipe, outlet of main dirction is 10 times of appellation diameter in main pipe and outlet of branched direction is 20 times of appellation diameter.