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Study Design: Technical report. Objectives: Dural tear is one of the most common complications of endoscopic spine surgery. Although endoscopic dural repair of the durotomy area may be difficult, we successfully repaired the dural tear area using nonpenetrating clips during biportal endoscopic surgery. We introduce the surgical technique of dural repair using nonpenetrating titanium clips in biportal endoscopic spine surgery and report its clinical outcome. Methods: We retrospectively reviewed and analyzed 5 patients who were treated via primary dural repair using nonpenetrating titanium clips during biportal endoscopic lumbar surgery. The 2 methods of dural clipping and repair include 2 or 3 portals. We analyzed radiological parameters such as cerebrospinal fluid collection as well as clinical parameters, including postoperative clinical outcomes. Results: Five patients underwent biportal endoscopic dural repair using nonpenetrating clips. Incidental durotomy was successfully repaired using nonpenetrating titanium clips in all 5 patients. No cerebrospinal fluid collection was detected in the postoperative magnetic resonance images. Clinically, preoperative symptoms improved significantly after surgery ( P < .05). Conclusions: We repaired the dural tear area completely using nonpenetrating titanium vascular anastomosis clips in biportal endoscopic lumbar surgery. Dural repair via clipping method may be an effective alternative for incidental durotomy.

We investigated whether ADT use was associated with the risk of ischemic cardiovascular diseases (CVD) and cerebrovascular diseases (CrVD) in a nationwide population-based cohort. Claims data of the Health Insurance and Review Assessment system in South Korea were used. In total, 195,308 men with newly diagnosed prostate cancer between January 1, 2008 and December 31, 2017 were identified. After applying the exclusion criteria, 131,189 men were enrolled. The study cohort was divided into ADT and non-ADT groups. Study outcomes were newly developed CVD, cardiovascular intervention (CVI), and CrVD. To control for potential confounders, various cardiovascular risk factors were balanced between groups. Cox proportional hazard regression models were used to estimate adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) of events. Univariable analysis revealed that ADT was significantly associated with an increased risk of CVD and CrVD. Multivariable analysis did not reveal this association. In the propensity score matched cohort (n = 61,722), multivariable analysis demonstrated that ADT independently reduced the risk of CVD (HR 0.890; 95% CI 0.846–0.936; p

In spite of various merit of algae as biofuel, the production cost of algae is a considerable obstacle for commercialization. The concurrent development of essential technologies is needed for the cultivating, harvesting, extracting and energy transformation. The production cost of algae biofuel has still higher than that of the other commercial biofuel. The major research activity has been focused on the cultivating and the research of other processes has been done with relatively lower activity. It is difficult to separate the algae from water because of the similar magnitude of density each other. The agglomeration and extracting of algae with the hybrid technology using ultrasonic wave is rare effect of environmental hazard and also it is appropriate technology for the next generation energy resources.The present research is investigated for the effective separation of algae from water with the ultrasonics wave. The aim of the present research is focused on the establishment of optimal design of algae agg-lomeration system. For this purpose, the computational fluid dynamic analysis has been conducted in the flow field with ultrasonic wave and algae flow to clarify the mechanism of algae separation by ultrasonic wave.

A heat exchanger tube array in a heat recovery steam generator is exposed to hot exhaust gas flow that can cause flow induced vibrations, which could damage the heat exchanger tube array. The characteristics of flow induced vibration in the tube array need to be established for the structural safe operation of a heat exchanger. Several studies of the flow induced vibrations of typical heat exchangers have been conducted and the nondimensional PSD (Power Spectral Density) function with the Strouhal number, fD/U, had been derived using an experimental method. The present study examined the results of the previous experimental research on the nondimensional PSD characteristics by CFD analysis and the basis for the application of flow induced vibration to the heat recovery steam generator tube array was determined from the present CFD analysis. The present CFD analysis introduced circular cylinder tube array and calculated using unsteady laminar flow for the tube array. The characteristics of lift and drag fluctuations over the cylinder tube array was investigated. The derived nondimensional lift and drag PSD was compared with the results of the previous experimental research and the characteristics of lift and drag PSD for a circular cylinder tube array was established from the present CFD study.

Heat exchanger tube array in a heat recovery steam generator is exposed to the hot exhaust gas flow and it could cause the flow induced vibration, which could damage the heat exchanger tube array. It is needed for the structural safe operation of the heat exchanger to establish the characteristics of flow induced vibration in the tube array. The researches for the flow induced vibration of typical heat exchangers have been conducted by using single cicular tube or circular tube array and the nondimensional PSD(Power Spectral Density) function with the Strouhal number, fD/U, had been derived by experimental method. From the present study, the basis for the application of flow induced vibration to the heat recovery steam generator tube array would be prepared. For the previous mentioned purpose, the present CFD analysis introduced a single fin tube and calculated with the unsteady laminar flow over the single fin tube. The characteristics of vortex shedding and lift fluctuation over the fin tube was investigated. The derived nondimensional PSD was compared with the results of the previous experimental researches and the characteristics of lift PSD over a single fin tube was established from the present CFD study.

Heat exchanger tube array in a heat recovery steam generator is exposed to the hot exhaust gas flow and it could cause the flow induced vibration, which could damage the heat exchanger tube array. It is needed for the structural safe operation of the heat exchanger to establish the characteristics of flow induced vibration in the tube array. The researches for the flow induced vibration of typical heat exchangers have been conducted and the nondimensional PSD(Power Spectral Density) function with the Strouhal number, fD/U, had been derived by experimental method. The present study examined the results of the previous experimental researches for the nondimensional PSD characteristics by CFD analysis and the basis for the application of flow induced vibration to the heat recovery steam generator tube array would be prepared from the present CFD analysis. For the previous mentioned purpose, the present CFD analysis introduced a single circular cylinder and calculated with the unsteady laminar flow over the cylinder. The characteristics of vortex shedding and lift fluctuation over the cylinder was investigated. The derived nondimensional PSD was compared with the results of the previous experimental researches and the characteristics of lift PSD over a single circular cylinder was established from the present CFD study.

Heat exchanger tube array in a heat recovery steam generator is exposed to the hot exhaust gas flow and it could cause the flow induced vibration, which could damage the heat exchanger tube array. It is needed for the structural safe operation of the heat exchanger to establish the characteristics of flow induced vibration in the tube array. The researches for the flow induced vibration of typical heat exchangers have been conducted and the nondimensional PSD(Power Spectral Density) function with the Strouhal number, fD/U, had been derived by experimental method. The present study examined the results of the previous experimental researches for the nondimensional PSD characteristics by CFD analysis and the basis for the application of flow induced vibration to the heat recovery steam generator tube array would be prepared from the present CFD analysis. For the previous mentioned purpose, the present CFD analysis introduced a single circular cylinder and calculated with the unsteady laminar flow over the cylinder. The characteristics of vortex shedding and lift and drag fluctuation over the cylinder was investigated. The derived nondimensional PSD was compared with the results of the previous experimental researches and the characteristics of lift and drag PSD over a single circular cylinder was established from the present CFD study.

A MILD(Moderate and Intense Low oxygen Dilution) combustion, which is effective in the reduction of NOx, is considerably affected by the recirculation flow position of hot exhaust gas to the combustion furnace. A numerical analysis was accomplished to elucidate the flow characteristics in the MILD combustion incinerator for several cases with or without exhaust gas recirculation. It could be seen from the result of the present numerical study that the flow recirculation could be observed in the upper region over the vertical dividing wall for the case without exhaust gas recirculation. The optimal position of exhaust gas recirculation position was derived by the comparison of %RMS of x directional velocity for the cases with exhaust gas recirculation. The case with the exhaust gas recirculation position at the upper right of free board was the most effective with the smallest value of 57.4% RMS.

The present study used the MILD combustor, which has coaxial cylindrical tube. The outside tube of the MILD combustor corresponds to the exhaust gas passage and the inner side tube is the furnace passage. A numerical analysis was accomplished to elucidate the characteristics of exhaust gas entrainment toward the inner furnace with the changes of venturi nozzle geometrical parameters, nozzle position, nozzle gap between high pressure air nozzle and venturi nozzle, and with the change of high pressure nozzle inlet velocity. The entrainment flow rate for the case with the high pressure air nozzle attached at the exhaust gas wall has relatively small change with the change of nozzle gap. That for the case with the high pressure air nozzle exposed to the exhaust gas has monotonically increase with the change of nozzle gap. The flow rate ratio of entrainment flow rate has considerably increase tendency with relatively lower air inlet velocity, on the other hand, that with relatively higher air inlet velocity could be seen relatively small increase.

A MILD (Moderate and Intense Low oxygen Dilution) combustion, which is effective in the reduction of NOx, is considerably affected by the recirculation flow rate of hot exhaust gas to the combustion furnace. The present study used the MILD combustor, which has coaxial cylindrical tube. The outside tube of the MILD combustor corresponds to the exhaust gas passage and the inner side tube is the furnace passage. A numerical analysis was accomplished to elucidate the characteristics of exhaust gas entrainment toward the inner furnace with the changes of coanda nozzle geometrical parameters, nozzle passage gap length, nozzle passage length, nozzle angle and expansion length. The optimal configuration of coanda nozzle for the best entrainment flow rate was gap length, 0.5 mm, expansion angle, 4o and expansion length, 146 mm. The nozzle passage length was irrelevant to the exhaust gas entrainement.

The present study has been carried out to reduce the heat loss from a built in refrigerator by using reverse heat loss method to discern the region with larger heat loss. To perform this purpose, an infrared thermographic camera has been used to measure the surface temperature of the refrigerator and tried to improve the heat loss near the ice dispenser. The numerical heat transfer analysis also has been accomplished to clarify the heat transfer mechanism near the ice dispenser. The possible applicable method to reduce heat loss was increasing the curvature radius at the ice dispenser corner. The curvature radius has been changed from 0mm to 40mm to see the effect of the curvature at the corner. From the present research, the optimal curvature radius for the reduction of heat loss at the ice dispenser could be 30mm.

The present study has been carried out to analyze the effect of steam hammering on the steam piping system including the final superheater, the high pressure turbine, check valve and the first reheater by sudden stoping of main stop valve in a power plant. For the present steam hammering analysis, the well known Flowmaster software has been used to model the steam piping system and the time dependent characteristics of pressure and steam mass flow r ate has been conducted. Using the result of the unsteady pressure and steam mass flow rate, the forces acting on the elbows in the piping system has been derived. From the present analy-sis, it has been elucidated that the elbow just before the main stop valve and the elbow near the connection pipe between bypass pipe and check valve had the largest force among the elbows in the steam piping system. The structural safety diagnostics study on the elbow and the supporting structures of the steam piping system of a power plant will be conducted in the future by the present results of the forces acting on the elbow.Key words : steam hammering, steam piping system, power plant, final superheater, first reheater, main stop valve, check valve, elbow, pressure, steam mass flow rate, forceKIGAS Vol. 17, No. 2, pp 70~77, 2013 http://dx.doi.org/10.7842/kigas.2013.17.2.70(Journal of the Korean Institute of Gas)

The present paper has been accomplished to elucidate the characteristics of temperature change in a car washer heater system for removal of frost formed at the surface of a car. The previous studies had used a simplified mathematical modeling to analyse the temperature change characteristics for a car washer heater system. In the present study, an unsteady computational fluid flow and heat transfer analysis for a washer heater system has been done by using computational fluid dynamic analysis method. From the present CFD analysis, the time dependent temperature change in a car washer heater system has been analysed and derived the heating time and ejection temperature of the washer liquid to establish the optimal design basis for a washer heater system. Key Words : Washer heater system, Frost, Temperature distribution, Ejection temperature, Heating time, Thermistor * Corresponding Author : Ji-Soo Ha(Keimyung Univ.)Tel: +82-53-580-5919 email: jisooha@kmu.ac.krReceived December 14, 2012 Revised February 5, 2013 Accepted March 7, 2013

The present study has been carried out to analyze the flow characteristics in the inlet expasion duct of a heat recovery steam generator by using numerical flow analysis. The inlet of HRSG corresponds the outlet of gas turbine exit and the flow after gas turbine has strong swirl flow and turbulence. The inlet flow condition of HRSG should be included the exit flow characteristics of gas turbine. The present numerical analysis adopted the flow analysis result of gas turbine exit flow as a inlet flow condition of HRSG analysis. Because the flow characteristics in the inlet duct of the tube bank is strongly related to the performance of a HRSG, it is most important for the optimal design of HGSG to understanding the flow phenomena in the inlet duct of HRSG. From the present study, the position of breakpoint in the inlet expansion duct should be lower than the reference breakpoint position for the optimal flow uniformity before the tube bank.

The present study has been carried out to analyze the flow characteristics of a heat recovery steam generator with the change of inlet flow conditions by using numerical flow analysis. The inlet of HRSG corresponds the outlet of gas turbine exit and the flow after gas turbine has strong swirl flow and turbulence. The inlet flow condition of HRSG should be included the exit flow characteristics of gas turbine. The present numerical analysis adopted the flow analysis result of gas turbine exit flow as a inlet flow condition of HRSG analysis. The computational flow analysis result of gas turbine exit shows that the maximum axial velocity appears near circular duct wall and the maximum turbulent kinetic energy and dissipation rate exist relatively higher gradient region of axial velocity. The comparison of flow analysis will be executed with change of inlet turbulent flow condition. The first case is using the inlet turbulent properties from the result of computational analysis of gas turbine exit flow, and the second case is using the assumed turbulent intensity with the magnitude proportional to the velocity magnitude and length scale. The computational results of flow characteristics for two cases show great difference especially in the velocity field and turbulent properties. The main conclusion of the present study is that the flow inlet condition of HRSG should be included the turbulent properties for the accurate computational result of flow analysis.

This study has purpose of minimizing damage from fire incident as analyzing the fire characteristic about fire incident of multi-use hostel s, which is increasing recently. For this, CFAST, a verified analysis program for the fire incident was employed to prove the logicality of the study by comparing with a established result of the research work and working the fire simulation for an apartm ent house. On the basis of this, the study will help to improve safety of fire by analyzing the fire characteristic of Karaoke and Gosiwon which are typical model of multi-use hostels and by establishing how to deal with the fire incident. Key words: CFAST, Zone model, Fire Characteristics, Multi-use hostels †교신저자(계명대학교 기계자동차공학부, E-mail:tkkim@kmu.ac.kr, Tel: 053-580-5551)1 계명대학교 에너지환경과학과2 계명대학교 기계공학과3 인제대학교 보건안전공학과 1. 서 론 화재위험이 높은 것으로 지적되고 있는 고시원과 찜질방, 산후조리원, pc방 등의 다중이용업소의 수가 짧은 기간 동안에 급격하게 증가하고 있다. 소방방재청 집계에 의하면 노래방, 찜질방 등 다중이용업소로 신고등록 또는 허가된 업소는 2009년 기준으로 약 177,000여개 소이다.[1] 이들 업종의 특성상 지하층 영업과 실내 구조물의 다양화와 복잡함으로 인해 화재 시 많은 인명피해가 우려되고, 화재의 발생 및 확산형태도 예측하기 어려워졌다. 특히 최근에 발생한 부산 실내사격장(2009년)과 부산 영도구 노래주점(2009년) 및 용인 고시원(2008년) 등의 화재사고는 다중이용업소의 화재위험성 및 피해크기를 보여주는 대표적인 예이다. 이러한 실제 사례를 바탕으로 발생 가능한 화재를 예측하여 피해의 크기와 종류를 예측할 수 있다면 그에 대한 적절한 대처방법을 제시할 수 있게 될 것이다. 그러나 실제 화재실험은 그 위험성 때문에 현실적으로 어려운 사항이다. 이에 대한 대안으로 컴퓨

An infrared thickness measuring technique for thin film coated on the metal mold was developed and applied to thickness measuring of the artificial breast implant pack. The infrared light emitted from a metal mold itself was partly absorbed to the silicon film, and the remainder of the infrared light was transmitted through the film. The relationship between the thermal image captured by an infrared camera and the film thickness was analyzed. The thicker the film, the bigger the amount absorbed. The new infrared thickness measuring technique agreed well with the results directly measured by a microscope when applied to the artificial breast implant pack.

An examination of the condition of the flow leaving the impeller exit kinetic energy often accounts for 30-50% of the shaft work input to the compressor stage, and for energy efficiency it is important to recover as much of this as possible. This is the function of the diffuser which follows the impeller. The purpose of this study is to investigate the sensitivity of how compressor performances changes as vaned diffuser geometry is varied. Three kinds of vaned diffusers were studied and its results were compared. First vaned diffuser type is based on NACA airfoil and second is channel diffuser and third is conformal transformation of NACA65(4A10)06 airfoil. Mean-line prediction method was applied to investigate the performance and stability for three kinds of diffusers. And CFD analyses have been done for comparison and detailed interior flow pattern study. NACA65(4A10)06 airfoil showed the widest operating range and higher pressure characteristics than the others.

An aerodynamic design for centrifugal compressor which was applied to medium speed diesel engine has been done. First of all, exact compressor specifications must be defined by accurate engine system matching. This matching program has been developed. Using the meanline prediction method, geometric design and performance curves for compressor were established and verified by comparing three dimensional viscous CFD results. The deviation at the design point was about 2.3%. Combustor has been designed and manufactured for the performance test of medium speed diesel engine turbocharger. Fuel nozzle of combustor was designed and its characteristics was analyzed by PIV and PDPA test equipment. Through these results, spray characteristics were studied and flow coefficient equation was deduced.

The ventilation performance for the various venting duct arrays has been experimentally compared in the scaled model of the container hold. Most container ships have the ventilation duct system to remove effectively the condensing heat released from container refrigerator. The existing duct system is vertically installed and basically has the number of duct as many as the columns of reefer container stack. In this study, to make up for the weak points having stagnantly hot legions in the centered area of container hold for the present system, the horizontal upward jotting duct system was proposed and proved by temperature rising tests on the scaled model. In this paper, the expected flow regimes and the thermal and hydrodynamic analogies as well as the measured temperature distributions in a hold for various duct types and heat released rates are deeply discussed.

A thermal vapor compressor in which the subsonic/supersonic flow appears simultaneously, has been accurately designed through the CFD analysis for the various shape parameters such as the primary nozzle shape, converging duct shape, mixing tube diameter, and so on. The performance of the developed thermal vapor compressor has been experimentally verified to be installed in a Multi Effect Desalination(MED) plant as an important element. In this paper, the effects of each parameter are discussed on the basis of CFD results and the experimental results for various boundary conditions(motive pressure, suction pressure, and discharge pressure) are presented in compared with CFD results. The two results show a good agreement with each other within 2 % accuracy with regard to the entrainment ratio.

A thermal vapor compressor (TVC) in which the subsonic/supersonic flow appears simultaneously, has been accurately designed through the CFD analysis for the various shape parameters such as the primary nozzle shape, converging duct shape, mixing tube diameter, and so on. The performance of the developed TVD has been experimentally verified to be installed in a multi-effect desalination (MED) pilot plant. In this paper, the experimental results for various boundary conditions (motive pressure, suction pressure, and discharge pressure) are presented in comparing with CFD results. The two results show a good agreement with each other within 3.5% accuracy with regard to the entrainment ratio.

This paper presents a lightweight prefix-based routing (LPR) for content-centric networking. In CCN, every communication with the named data is based on hierarchical naming convention and forwarding decision using the longest-prefix matching mechanism. However, there are no comprehensive researches on designing a general routing protocol over such a naming hierarchy. Our LPR scheme provides a lightweight management of routing table and Forwarding Information Base (FIB) table that manage a lower number of routes enough to perform the longest-prefix matching. Also, a method is proposed to cope with connections between CCN routers in different hierarchies. We evaluate the proposed LPR against the existing routing approaches and show that it leads to less control overhead and FIB size.

The centrifugal compressor of marine engine turbocharger is composed of impeller, 1st vaneless diffuser, vaned diffuser, 2nd vaneless diffuser and volute casing. An examination of the condition of the flow leaving the impeller exit kinetic energy often accounts for 30–50% of the shaft work input to the compressor stage, and for energy efficiency it is important to recover as much of this as possible. This is the function of the diffuser which follows the impeller. Effective pressure recovery downstream of an impeller is very important to realize a centrifugal compressor with high efficiency and high pressure ratio, and an appropriate selection of a diffuser for a specific impeller is a critical step to develop the compressor accordingly. The purpose of this study is to investigate the sensitivity of how compressor performances changes as vaned diffuser geometry is varied. Three kinds of vaned diffusers were studied and its results were compared. First vaned diffuser type is based on NACA airfoil and second is channel diffuser and third is conformal transformation of NACA 65 airfoil. Mean-line prediction method was applied to investigate the performance and stability for three kinds of diffusers. And CFD analyses have been done for comparison and detailed interior flow pattern study. In this study, the off design behavior of three different type of diffuser, given by mean-line prediction, was investigated using CFD results and selected best diffuser geometry which satisfy wider operating range and higher pressure recovery than the others. The numerical results were compared with experimental data for validation.Copyright © 2006 by ASME

A fuel injection with high pressure in a medium speed diesel engine would increase the possibility of cavitation damage in the fuel injection system or secondary injection to the combustion chamber. The purpose of this study is to prevent cavitation and secondary injection in a medium speed diesel engine by modifying the design of the delivery valve and the constant pressure valve in a fuel injection system. Three-dimensional flow analyses for the fuel injection nozzle, delivery valve, constant pressure valve and spill port were performed using FLUENT S/W to calculate loss coefficients of them. Simulation of fuel injection system with loss coefficients from results of three-dimensional flow analyses were performed using FLOWMASTER2 S/W and the simulation results were compared with the experimental data. The delivery valve and constant pressure valve were modified to prevent cavitation and secondary injection and proved in the field test.

A turbocharger has been designed to fulfill the requirements of medium speed marine engines, 900 kW output power at nominal operation point. The main objective of the design was to meet the requirements of engine power and increased engine operating range. This must be achieved by improving the degree of aerodynamic efficiency and the pressure ratio. The design was performed by the two stages. First, quasi-two dimensional program code was used to determine the main geometry of the compressor. Second, the detailed geometries of compressor blade were completed by using a three dimensional fluid flow analysis. The analyzed performance results were compared with the experimental data for the verification of their validity. Also, the designed three different impeller exits allow for a substantial performance variation. Increased compression ratio and mass flow rate of new optimized impeller were 10.08 and 27.3 percent higher than those of origin impeller, respectively. This simple change of design parameter offers considerable advantages to customers when upgrading their engines.Copyright © 2005 by ASME

The centrifugal compressor design of the high-speed marine engine (500–900 kW) turbocharger has been done. Increased Higher compressed air and power density help improvement of the engine performance and power. The centrifugal compressor of the marine engine turbocharger is composed of impeller, 1st vaneless diffuser, vaned diffuser, 2nd vaneless diffuser and volute casing. The design process is achieved by three following stages. First, quasi-two dimensional code is used to determine the main geometry of the compressor. Second, three-dimensional compressible Navier-Stokes equation is applied to analyze the flow pattern and structures of the compressor blade loading. Here, among compressor impeller geometry, blade height variables are mainly changed. Smooth flow guidance has to precede and flow separation symptoms must not appear within compressor impeller. When the loading distribution is inadequate from blade hub to shroud, new curved profile should be designed to minimize the pressure loss. By analyzing the internal flow fields for the compressor impeller geometry variations, three dimensional impeller design profile has been confirmed. Compressed air pressure and mass flow rates from new optimized design were 2.7%, 27.3% higher than that of old one each other. Third, analyzed results are compared with experimental data for the verification of the present design method.Copyright © 2004 by ASME

Prediction of the ROHR (rate of heat release) and NOx production in medium-speed marine diesel engines was investigated. The subject of this paper is qualitative and quantitative evaluation of the numerical results. FIRE code v8.1 was used to examine the behavior of spray and combustion phenomena in diesel engine. Wave breakup and Zeldovich models were adopted to describe the atomization characteristics and NOx formation. The spray visualization was performed experimentally in the constant-volume high-pressure chamber to clarify numerical results on the spray characteristics of the spray angle and penetration. Time-resolved spray behaviors were captured by high-speed digital camera. The simulation results were tested with the experimental data of the real engine. Finally, with adjustment of some model constants, reasonable agreements between experimental and simulated results on the ROHR and NOx were shown.