• 소성∙가공
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• 제25권4호
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• pp.248-253
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• 2016

Induction hardening process of tubular drive shaft for automobile is simulated by combining the thermal, mechanical, electro-magnetic and metallurgical analysis models. Various material properties for each analysis model are obtained in a consistent way via material properties calculation software, JMatPro^®. To consider the scanning process of induction heating, boundary element method is adopted for electro-magnetic field calculation. The distribution of temperature, stress and phase volume fraction are tracked out through the whole process and the effect of scanning velocity is reviewed. The analysis result shows that the critical principal stress is developed at the phase boundary where martensite is formed.

• 설비공학논문집
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• 제11권1호
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• pp.125-132
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• 1999

Studies are being done to replace conventional refrigerants with alternatives that have low or no ozone depletion and greenhouse warming Potentials, yet possess appropriate pro perties for a refrigeration cycle. To achieve this goal, a consistent set of thermodynamic properties of the working fluid is required. A common problem with the possible alternative refrigerants is that sufficient experimental data do not exist, thus making it difficult to develp complete equations of state that can predict properties in all regions including the vapor-liquid equilibrium. One solution is the use of the generalized equation of state correlations that can predict thermodynamic properties with a minimum number of characteristic parameters. Characteristic parameters required for the generalized equation of state are, in general, critical temperature, critical pressure, critical volume and normal boiling temperature. In this study, estimation of these characteristic parameters of refrigerants by group contribution method is developed.

• Journal of Advanced Marine Engineering and Technology
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• 제23권5호
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• pp.662-670
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• 1999

A numerical prediction was performed to clarify the air motion in the cylinder of an axisymmet-ric four-stroke reciprocating engine at its intake and compression stage. A scheme of finite volume method is used for the calculation. Modified $k-{\varepsilon}$ turbulence model is adopted and wall function is applied to the grids near the wall. The predicted mean velocity and rms velocity profiles showed a reasonable agreement with an available experimental data at its intake and compression stage. The predicted in-cylinder flow fields show that a strong turbulent twin vortex structure is pro-duced during induction but it commences to decay rapidly around inlet valve closure. The mean velocity continues to fall to a low level during compression but the turbulence intensity attains an approximate constant level.

• 한국안전학회지
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• 제7권3호
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• pp.66-72
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• 1992

An experimental study was carried out to analyse the explosion characteristics of flammable gas-air mixtures. Used flammable gases were hydrogen, methane, acethylene, ethylene and pro-pane, explosion Pressure, explosoin pressure rising rate, and flame propagation velocity were measured experimentaly. The maximum explosion pressure and rising rate of flammmalbe gas air mixtures were appeared at the range of slightly higher concentration than the stoichiometric concentration. Initial pressure before explosion was controlled from 0.6 to 2.0kg/cm absolutly. Explosion pressure was increased with increment of the initial pressure, and the relationship between initial pressure and explosion pressure was Pe = KPi. The effect of vessel size on explosion characteristics was also analysed In this experiment. Explosion pressure was increased with in-creasing the vessel size, otherwise explosion pressure rising rate was decreased. When we locate a dummy material in vessel explosion pressure was decreased with increasing the dummy volume but exlosion pressure rising rate was increased.

• International Journal of Air-Conditioning and Refrigeration
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• 제11권1호
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• pp.10-16
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• 2003

The present study performs an experimental measurement on transient thermal response of an air-conditioned space by a variable air volume (VAV) system with a PI(pro-portional-integral) control logic. A thermal chamber with a PI controlled VAV unit is constructed to verify the previously suggested stratified multi-zone model. The effects of thermal parameters and control parameters such as supply air temperature and PI control factor are investigated by implementing the thermal chamber test. The experimental results obtained show that transient behavior of the air-conditioned space-temperature is in good accordance with the simulation results of the stratified thermal model.

• International Journal of Internet, Broadcasting and Communication
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• 제13권2호
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• pp.14-19
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• 2021

Aim of this research was to investigate the effects of Digital Elevation Model (DEM) for sensitivity analysis with two types of DEMs: 1 to 24,000 and 1 to 250,000 DEM. Another emphasis was given to the development of methodology for processing DEMs to create ArcGIS Pro and GRASS layers. This was done while developing water quality system modeling using DEMs which were used to model hydrological processes and SWAT model. Sensitivity analysis with DEMs resulted in different runoff volumes in the model simulation. Runoff volume was higher for the 1:24,000 DEM than 1:250,000 DEM, probably due to the finer resolution and slope which increased the estimated runoff from the watershed. Certainly the DEMs were factors in precision of the simulations and it was obvious during sensitivity analysis that DEMs had significant effect on runoff volumes. We suggest, however, that additional comparative research could be conducted involving more parameters such as soil and hydrologic parameters to provide insight into the overall physical system which the SWAT model represents.

• 한국항공운항학회지
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• 제27권1호
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• pp.20-25
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• 2019

To prepare for the ever-increasing demand for air transport, airport operators should be well aware of the timing of the saturation of the facility and increase the capacity of the airport through extension or extension. The capacity of an airport is determined by the smallest value of the facilities that make up the airport, but it is generally customary to determine the capacity of the costly and time-consuming runway as a whole for the airport. For analyzing the capacity of the runway capacity, the study used the most accurate microscopic air traffic simulation, Simmod-PRO, to analyze the saturation time of three runways currently in Incheon International Airport's operation, and calculate the appropriate time for operation of the 4th runway. The study also calculate the relocation of Airport's high-speed exit taxiway for analyzing the increasing of capacity.

• Korean Journal of Radiology
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• 제24권4호
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• pp.294-304
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• 2023

Objective: We aimed to investigate whether image standardization using deep learning-based computed tomography (CT) image conversion would improve the performance of deep learning-based automated hepatic segmentation across various reconstruction methods. Materials and Methods: We collected contrast-enhanced dual-energy CT of the abdomen that was obtained using various reconstruction methods, including filtered back projection, iterative reconstruction, optimum contrast, and monoenergetic images with 40, 60, and 80 keV. A deep learning based image conversion algorithm was developed to standardize the CT images using 142 CT examinations (128 for training and 14 for tuning). A separate set of 43 CT examinations from 42 patients (mean age, 10.1 years) was used as the test data. A commercial software program (MEDIP PRO v2.0.0.0, MEDICALIP Co. Ltd.) based on 2D U-NET was used to create liver segmentation masks with liver volume. The original 80 keV images were used as the ground truth. We used the paired t-test to compare the segmentation performance in the Dice similarity coefficient (DSC) and difference ratio of the liver volume relative to the ground truth volume before and after image standardization. The concordance correlation coefficient (CCC) was used to assess the agreement between the segmented liver volume and ground-truth volume. Results: The original CT images showed variable and poor segmentation performances. The standardized images achieved significantly higher DSCs for liver segmentation than the original images (DSC [original, 5.40%-91.27%] vs. [standardized, 93.16%-96.74%], all P < 0.001). The difference ratio of liver volume also decreased significantly after image conversion (original, 9.84%-91.37% vs. standardized, 1.99%-4.41%). In all protocols, CCCs improved after image conversion (original, -0.006-0.964 vs. standardized, 0.990-0.998). Conclusion: Deep learning-based CT image standardization can improve the performance of automated hepatic segmentation using CT images reconstructed using various methods. Deep learning-based CT image conversion may have the potential to improve the generalizability of the segmentation network.

• 보건행정학회지
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• 제6권1호
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• pp.110-143
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• 1996

The purpose of this study is to assess the extent of inequality in health outcomes and the distribution of health services according to health need under National Health Insurance System in Korea. For the empirical analysis, data were collected through an interview survey during one month of October, 1994. Interview were conducted with a total of 10, 875 of the employees and the self-employed selected through cluster, systematic sampling. The major findings of this research are as follows: 1. The analysis of the differentials in morbidity rates by socio-economic group showed that health inequality in the pro-higher groups existed in all self-reported morbidity indicators. 2. The findings of the conventional use measures showed that the lower socio-economic groups had more ambulatory and inpatient services than the higher groups. In contrast to the level of the medical care utilization, however, the higher socio-economic groups were more likely to use the high-quality source of care in terms of their treatment place compared to the lower groups. 3. By using the need-based use measures, the results were different from each use-disability ration indicator. Using the use-disability ration measured by physician visits per 100 restricted-activity days in the population, it was found that there was no evidence favoring the higher socio-economic groups. In contrast, the use-disability ration based on physician visits per a chronic patient in one year displayed that there was remarkable relative difference by income group as well as the evidence of the pro-higher income groups. 4. The results of logistic regression analysis and two-stage estimation method indicated that although the utilization is significantly affected by type and duration of insurance coverage, the use or nonuse of service and the volume of physician care consumed is determined by health need and demographic characteristics rater than economic status. In sum, these findings suggest that physician service is equitably distributed according to health need under national health insurance system in Korea. As there were some evidences of inequality including the differential in physician visits of chronic patients by income group, however, the government should strengthen the activities to guarantee the equity of health services utilization.

• 한국방사선학회논문지
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• 제2권1호
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• pp.5-10
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• 2008

본 연구에서는 PDA 기반의 블루투스를 이용한 무선통신 방사선 측정 장치를 개발하였다. 제안하는 시스템은 방사선 측정 센서로 GM (Geiger-Mueller) 계수관을 이용하는 Vernier사의 Student Radiation Monitor, 데이터 획득을 위한 모듈로는 Vernier사의 LabPro, 데이터의 무선전송을 위하여 Initium사의 최대 30미터까지 블루투스 통신이 가능한 Promi-SD 101, 데이터의 저장과 디스플레이에는 운영체계로 Pocket PC 2003이 내장된 HP사의 5550으로 구성하였다. 방사선측정센서로 GM 계수관을 이용하였으므로 방사선 에너지 측정은 불가능하고 카운트 양과 카운트율을 측정할 수 있다. PC를 이용한 시스템의 자연방사선 계측치와 PDA를 이용한 시스템의 자연방사선 계측치를 비교한 결과, 제안하는 시스템은 자료의 왜곡 없이 송수신이 이루어지고 있음을 확인하였다.