• International Journal of Railway
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• 제3권3호
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• pp.106-112
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• 2010

Accidents at level crossing have large portion on train accidents, and causes economical loss by train delay and operational interruption. Various safety equipments are employed to reduce the accident at level crossing, but existing warning device, and crossing barrier are simple train-oriented protection equipments. In this paper, intelligent railway level crossing system is proposed to prevent and reduce accidents. For train driver's prompt action, image of level crossing and obstacle warning message are continuously provided to train driver through wireless communication in level crossing control zone. Obstacle warning messages, which are extracted by computer vision processing of captured image at level crossing, are recognized by train driver through message color, flickering and warning sound. It helps train driver to decide how to take an action. Meanwhile, for vehicle driver's attention, location and speed of approaching train are given to roadside equipments. We identified the effect of proposed system through test installation at Sea train and Airport level crossing of Yeong-dong line.

• 천문학회보
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• 제36권1호
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• pp.55.2-55.2
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• 2011

Many astrophysical high energy phenomena involve relativistic flows. We describe codes for adiabatic and isothermal flows in relativistic regimes. For adiabatic flows, we employ an equation of state (EOS) which is simple and yet approximates very closely the EOS of the single-component perfect gas. For isothermal flows, we use an EOS of constant sound speed. We present the eigenstructures of relativistic hydrodynamics which can be used to build numerical codes, and discuss the calculation of primitive variables from conservative ones for both adiabatic and isothermal flows. The shock tube tests show differences between the two flows.

• 정보기술과데이타베이스저널
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• 제7권1호
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• pp.67-82
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• 2000

In this paper we have developed a message transfer protocol, CMP, which improves MSP's message processing capability. The proposed method has taken into account document classification to improve the efficiency of message processing. The difference between the conventional MSP and CMP has been addressed. The CMP's performance has been shown by various experiments including number, alphabet, Korean letter, Chinese letter, music sound and compression file transmission. And security capability of both protocols has been compared based on the specification of FIPS 140-2. The CMP's overall performance is shown to be superior to that of MSP on the processing speed in the performance perspective and on the function of cryptographic module interface and cryptographic key management in the security perspective respectively.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 추계학술대회논문집 II
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• pp.1242-1248
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• 2001

In this paper, the process of development of resilient sleepers, which improves the train safety, passenger comport and reduces the noise and vibration, is presented. To determine the required material properties of elastic pad, static and dynamic simulations are performed and is applied in manufacturing. Lateral resistance and durability characteristics of the resilient sleepers are experimentally investigated. From the experiment results, it is investigated that the displacement is less for sleeper with elastic pad than that in ordinary PC form. However, the lateral resistance is investigated little less -for sleeper with elastic pad than ordinary PC form. These results indicate that the elastic pad can reduce possibility of rail-corrugations and thus resulting in the reduction of maintenance costs.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 추계학술대회논문집
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• pp.782-785
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• 2004

In the Well-being age, many people use a city park for rest deeply think and constitutional walk. The city park is located at near side by traffic road in urban. Citizens are not satisfied with it's fuction as a haven of peace due to road traffic noise. Thus, this study is for a research on the actual noise condition of a city park in Nowon go. This study uses a prediction method called ASJ-model in order to calculate PWLs of road traffic noise. Using calculated PWLs, noise levels in a park are predicted and compared with measured values.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.70.4-70
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• 2001

Advances of the computer system and the high-speed network have made it possible to popularize the multimedia services among various applications in the internet. In addition, the number of the users and the kinds of multimedia services have been increasing day by day. Thus, this paper presents an internet live-broadcasting server system to accelerate these trends. The developed system facilitates creating or joining the broadcasting with just such basic components as PC camera and sound card. Also, it guarantees the scalability that the channels could be dynamically expanded as the population of users rapidly increases. The clustered streaming servers are generically managed by the CSM ...

• Journal of the Korean Physical Society
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• 제73권12호
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• pp.1849-1854
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• 2018

The present study aims to investigate the feasibility of using a simple nonlinear acoustic method for the assessment of bone status and osteoporosis in trabecular bone. Correlations of linear and nonlinear ultrasound parameters with the apparent bone density were obtained in 32 bovine femoral trabecular bone samples. Highly significant positive correlations were observed between the apparent bone density and the two linear ultrasound parameters, the speed of sound (SOS) and the normalized broadband ultrasound attenuation (nBUA), with Spearman's correlation coefficients of r = 0.85 and 0.77. In contrast, the apparent bone density was found to be negatively correlated with the nonlinear ultrasound parameter introduced in the present study, the logarithmic difference between the power spectrum levels of the fundamental frequency and the second harmonic (PSL1-PSL2), with the highest correlation coefficient of r = -0.92. These results suggest that the PSL1-PSL2, in addition to the SOS and the nBUA, may be useful for the assessment of bone status and osteoporosis.

• 한국분무공학회지
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• 제26권4호
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• pp.182-188
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• 2021

In this paper, using a transfer function-based analytical model, major factors influencing the acoustics and combustion instability in a two-stage duct system composed of a nozzle and a combustor were derived and their quantitative effects were evaluated. From the acoustic analysis, it was confirmed that the change in reflection coefficient and mean flow could have a great influence on the instability growth rate, and the area ratio and speed of sound ratio between the nozzle and the combustor are also key parameters to determine combustion instability as well as flame transfer functions.

• 대한설비공학회지:설비저널
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• 제16권5호
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• pp.477-483
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• 1987

A FORTRAN code has been developed to calculate thermodynamic properties of 12 kinds of refrigerants. Input variables are temperature and pressure or temperature only depending on the saturation. The program output properties are specific volume, saturation pressure, enthalpy, entropy, specific heats and speed of sound. Sample calculations show that output properties are in very good agreements with thermodynamic tables and charts.

• Korean Journal of Radiology
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• 제23권1호
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• pp.13-29
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• 2022

Nonalcoholic fatty liver disease, characterized by excessive accumulation of fat in the liver, is the most common chronic liver disease worldwide. The current standard for the detection of hepatic steatosis is liver biopsy; however, it is limited by invasiveness and sampling errors. Accordingly, MR spectroscopy and proton density fat fraction obtained with MRI have been accepted as non-invasive modalities for quantifying hepatic steatosis. Recently, various quantitative ultrasonography techniques have been developed and validated for the quantification of hepatic steatosis. These techniques measure various acoustic parameters, including attenuation coefficient, backscatter coefficient and speckle statistics, speed of sound, and shear wave elastography metrics. In this article, we introduce several representative quantitative ultrasonography techniques and their diagnostic value for the detection of hepatic steatosis.