• Journal of the korean Society of Automotive Engineers
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• v.2 no.1
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• pp.21-31
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• 1980

Two phase boundary layer equations of laminar filmwise condensation are solved by an approximate integral method under the following condition; saturated vapour flows vertically downward over a cooled surface of uniform temperature, the condensate film is so thin that the inertia and convection terms are neglected. The following conclusions are drawn under the above assumptions. 1. free convection In case of the linear temperature profile in a liquid film, numerical results for the average coefficients of heat transfer may be expressed as N $u_{m}$=4/3,(G $r_{l}$ /4.H)$^{1}$4/ and in case of the quadratic profile, numerical results may be expressed as N $u_{m}$=2/1.682,(G $r_{l}$ /H)$^{1}$4/. 2. Forced convection When the temperature profile is assumed to be linear in a liquid film, numerical results fir the average heat transfer coefficients may be expressed as N $u_{m}$=(A, R $e_{l}$ /H)$^{1}$2/. This expression is compared with the experimental results hitherto reported; For theoretical Nusselt number (N $u_{m}$)$_{th}$<2*10$^{4}$, the experimental Nusselt number (N $u_{m}$)$_{exp}$ is on the average larger than theoretical Nusselt number (N $u_{m}$)$_{th}$ by 30%. For (N $u_{m}$)$_{th}$>2*10$^{4}$, experimental Nusselt number (N $u_{m}$)$_{exp}$ is about 1.6 times as large as theoretical Nusselt number (N $u_{m}$)$_{th}$. These large deviation may be caused by the presence of turbulence in the liquid film. In case of the quadratic temperature profile in a liquid film, numerical results for the average coefficients of heat transfer may be expressed as N $u_{m}$'=(2,A,Re/H)$^{1}$2/. This formular shows that theoretical Nusselt number (N $u_{m}$)$_{th}$ is larger than experimental Nusselt number (N $u_{m}$)$_{exp}$ by 60%. It is speculated that when the temperature difference between cooled surface and saturated vapour is small, temperature profile in a liquid film is quadratic.quadratic.. quadratic.quadratic..atic..

• Wind and Structures
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• v.39 no.1
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• pp.31-45
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• 2024

This paper examines the flow characteristics around an inclined prism with a U-shaped cross-section ("U-profile") and investigates the connection between the flow and flow-induced vibrations. The study employs a combined approach that involves wind tunnel experiments and computational fluid dynamics (CFD) using an unsteady Reynolds-averaged Navier-Stokes (RANS) turbulence model. Distinct vortex formation patterns are observed in the flow field surrounding the stationary inclined profile. When the cavity of the profile faces away from the incoming flow, large vortices develop behind the profile. Conversely, when the cavity is oriented towards the oncoming flow, these vortices form within the cavity. Notably, due to the slow movement of these large vortices through the cavity, the frequency at which vortices are shed in the negative inclination case is lower compared to the positive inclination, where they form in the wake. Wind tunnel experiments reveal an intermittent transition between the two vortex formation patterns at zero inclination. Large vortices sporadically emerge both in the cavity and behind the profile. The simulation results demonstrate that when these large vortices occur at a frequency close to the structure's natural frequency, they induce prominent pitch vibrations. This phenomenon is also sought after and presented in coupled vibration experiments. Additionally, the simulations indicate that when the natural frequency of the structure is considerably lower than the vortex shedding frequency, this type of vibration can be observed.

• The KIPS Transactions:PartC
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• v.17C no.2
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• pp.135-144
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• 2010

U-City pursues personalized service by collecting contexts through sensors located over the city and presenting the service automatically depending not on the user's request but on the situations that are needed. To provide the personalized service, however, contexts collected through various sensors are needed, and they include private information. Therefore, it is important to keep a balance between the convenience by presenting service and protecting private information. In this paper, we classify and grade person's various contexts requested in the personalized service environment. Based on these, we make decisions on whether to present the service or not by profile-matching between user profile and service profile. Also, we propose an efficient privacy-protection management scheme to encrypt transmitted private information and to control key distribution.

• Journal of Institute of Control, Robotics and Systems
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• v.17 no.3
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• pp.199-205
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• 2011

This paper presents an algorithm capable of detecting free space for the autonomous vehicle navigation. The algorithm consists of two main steps: 1) estimation of longitudinal profile of road, 2) detection of free space. The estimation of longitudinal profile of road is detection of v-line in v-disparity image which is corresponded to road slope, using v-disparity image and hough transform, Dijkstra algorithm. To detect free space, we detect u-line in u-disparity image which is a boundary line between free space and obstacle's region, using u-disparity image and dynamic programming. Free space is decided by detected v-line and u-line. The proposed algorithm is proven to be successful through experiments under various traffic scenarios.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.6
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• pp.1365-1369
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• 2013

Recently, the Personal Health Device(PHD) that measures various biometric data easily are highlighted for ensuring portability, scalability and interoperability among the device as well as needs for a standardization of managing information measured by. In this paper, we'd like to propose u-healthcare monitoring system that measure biometric data(Oxygen saturation, Body weight, ECG and Blood pressure) by PHD featured with transferring data into devices such as smartphone using Bluetooth Health Device Profile(HDP) based on the ISO/IEEE 11073.

• Proceedings of the Korean Information Science Society Conference
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• 2003.10b
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• pp.430-432
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• 2003

카메라를 내장한 휴대용 단말기의 보급과 인터넷 및 무선 네트워크의 급속한 확산으로 유비쿼터스 컴퓨팅 환경을 구체화한 새로운 서비스들이 등장하고 있다. 본 논문에서는 4개 분야의 학제간 공동연구를 통해 기존 PC 기반의 인터넷 컴퓨팅 환경에서 적용하기 어려웠던 U-Campus 서비스를 제안한다. 이는 UTOPIA 프로젝트의 일부로서 휴대용 단말기와 이미지 기반 센서인 컬러코드를 이용한 유비쿼터스 컴퓨팅형 캠퍼스 서비스이다. 현재 테스트 베드를 구축하고 U-Profile. U-Messaging 및 U-Campus Tour Guide 서비스를 제공하고 있다. 학생. 교수. 교직원 및 학교 방문자들은 U-Campus환경 하에서 다양한 정보를 PDA, 휴대전화, 스마트폰 등 휴대용 단말기를 통해서 언제, 어디서나 자연스럽게 제공 받을 수 있다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.05a
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• pp.392-394
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• 2013

최근 u-Healthcare 서비스에서 다양한 생체정보를 간편하게 측정하는 개인건강기기(PHD)와 측정된 정보를 전송하고 수집하기 위한 표준의 필요성이 제품 간의 이식성, 확장성, 상호 운영성을 보장하기 위해 크게 대두되고 있다. 개인건강기기에서 측정된 생체정보(산소포화도, 몸무게, 심전도, 혈압 등)를 ISO/IEEE 11073 기반인 Bluetooth Health Device Profile을 이용해서 스마트폰으로 실시간 모니터링 할 수 있는 시스템을 설계한다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.857-860
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• 1996

The area of gear dynamics has recently been the focus of many studies. A new tooth profile modification was proposed by author for reducing vibration and noise of involute gears. A comparative dynamic analysis of the gear drive with the involute tooth and the modified tooth profile(using cubic splines) is performed to the unuformal transmission error reduces the gear vibration and noise due to less dynamic tooth load variation during the meshing cycle. This work also include a gear design process by the meaning of a practical approach, such as Win95 based simulation program with all using basic geardesign variables. Especially this program enables gear designers to dynamic analysis based on G.U.I.

• Journal of Intelligence and Information Systems
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• v.16 no.1
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• pp.57-69
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• 2010

The ubiquitous transportation system environments make it possible to collect each vehicle's position and velocity data and to perform more sophisticated traffic flow management at individual vehicle or platoon level through V2V and V2I communication. It is necessary to develop a new data processing methodology to take advantage of the ubiquitous transportation system environments. This paper proposed to build 3-dimension data profiles to maintain the detailed traffic flow information contained in the individual vehicles' data and at the same time to keep the profiles from the meaningless fluctuations. Also methods to build the platoon profile and the shock wave speed profile are proposed, which have not been possible under ITS(Intelligent Transportation System) environments.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.29 no.6
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• pp.279-285
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• 2017

In general, the power law and logarithmic profile are commonly used as flow vertical velocity profile model. However, since the parameters of profile vary with characteristics of coastal environment, it is necessary to estimate these values from measured data using regression analysis. In this paper, we estimated the power law exponent (n), friction velocity ($u^*$) and roughness length ($z_0$) of logarithmic profile by analyzing measured tidal current data that are averaged at a interval of 30 min. In the results of analysis, power law exponent (n) was estimated to be about 10.75 during flood and about 9.3 during ebb. Meanwhile, $u^*$ of logarithmic profile was estimated to be about 0.084 m/s, 0.105 m/s during flood and ebb, respectively. Also, $z_0$ was estimated to be 0.004 m and 0.006 m, respectively.