• Title/Summary/Keyword: practical surface

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CRITICAL HEAT FLUX ENHANCEMENT

  • Chang, Soon-Heung;Jeong, Yong-Hoon;Shin, Byung-Soo
    • Nuclear Engineering and Technology
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    • v.38 no.8
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    • pp.753-762
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    • 2006
  • In this paper, works related to enhancement of the CHF are reviewed in terms of fundamental mechanisms and practical applications. Studies on CHF enhancement in forced convection are divided into two categories, CHF enhancement of internal flow in tubes and enhancement of CHF in the nuclear fuel bundle. Methods of enhancing the CHF of internal flows in tubes include enhancement of the swirl flow using twisted tapes, a helical coil, and a grooved surface; promotion of flow mixing using a hypervapotron; altering the characteristics of the heated surface using porous coatings and nano-fluids; and changing the surface tension of the fluid using additives such as surfactants. In the fuel bundle, mixing vanes or wire wrapped rods can be employed to enhance the CHF by changing the flow distributions. These methods can be applied to practical heat exchange systems such as nuclear reactors, fossil boilers, fusion reactors, etc.

Practical Silicon-Surface-Protection Method using Metal Layer

  • Yi, Kyungsuk;Park, Minsu;Kim, Seungjoo
    • JSTS:Journal of Semiconductor Technology and Science
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    • v.16 no.4
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    • pp.470-480
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    • 2016
  • The reversal of a silicon chip to find out its security structure is common and possible at the present time. Thanks to reversing, it is possible to use a probing attack to obtain useful information such as personal information or a cryptographic key. For this reason, security-related blocks such as DES (Data Encryption Standard), AES (Advanced Encryption Standard), and RSA (Rivest Shamir Adleman) engines should be located in the lower layer of the chip to guard against a probing attack; in this regard, the addition of a silicon-surface-protection layer onto the chip surface is a crucial protective measure. But, for manufacturers, the implementation of an additional silicon layer is burdensome, because the addition of just one layer to a chip significantly increases the overall production cost; furthermore, the chip size is increased due to the bulk of the secure logic part and routing area of the silicon protection layer. To resolve this issue, this paper proposes a practical silicon-surface-protection method using a metal layer that increases the security level of the chip while minimizing its size and cost. The proposed method uses a shift register for the alternation and variation of the metal-layer data, and the inter-connection area is removed to minimize the size and cost of the chip in a more extensive manner than related methods.

A Study of Optimization of Electrodeposited CuSnZn Alloys Electrolyte and Process

  • Hur, Jin-Young;Lee, Ho-Nyun;Lee, Hong-Kee
    • Journal of the Korean institute of surface engineering
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    • v.43 no.2
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    • pp.64-72
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    • 2010
  • CuSnZn electroplating was investigated as alternative to Ni plating. Evaluation of electrolyte and plating process was performed to control physical characteristics of the film, and to collect practical data for application. Hull-cell test was conducted for basic comparison of two commercialized products and developed product. Based on hull-cell test results, long term test of three electrolytes was performed. Various analysis on long term tested electrolyte and samples have been done. Reliable and practical data was collected using FE-SEM (FEI, Sirion), EDX (ThermoNoran SIX-200E), ICP Spectrometer (GBC Scientifi c, Integra XL), FIB (FEI, Nova600) for anlysis. Physical analysis and reliability test of the long term tested film were also carried out. Through this investigation plating time, plating speed, electrolyte composition, electrolyte metal consumption, hardness and corrosion resistance has been compared. This set of data is used to predict and control the chemical composition of the film and modify the physical characteristics of the CuSnZn alloy.

A Continuous Sliding Surface Transformed VSS by Saturation Function for MIMO Uncertain Linear Plants (다입출력 불확실 선형 플랜트를 위한 포화함수에 의한 연속 슬라이딩 면 변환 가변구조시스템)

  • Lee, Jung-Hoon
    • Journal of the Institute of Electronics and Information Engineers
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    • v.52 no.7
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    • pp.127-134
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    • 2015
  • In this note, a continuous sliding surface transformed variable structure systems by the saturation function is presented for MIMO uncertain linear plants. A discontinuous sliding surface transformed VSS is proposed theoretically. The closed loop exponential stability together with the MIMO existence condition of the sliding mode on the predetermined sliding surface is investigated. For practical applications, a continuous approximation of the discontinuous VSS is made by means of the saturation function. The discontinuity of the control input as the inherent property of the VSS is much improved in view of the practical aspects. Through a design example and simulation studies, the usefulness of the proposed continuous transformed VSS controller is verified.

Hybrid RANS and Potential Based Numerical Simulation for Self-Propulsion Performances of the Practical Container Ship

  • Kim, Jin;Kim, Kwang-Soo;Kim, Gun-Do;Park, Il-Ryong;Van, Suak-Ho
    • Journal of Ship and Ocean Technology
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    • v.10 no.4
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    • pp.1-11
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    • 2006
  • The finite volume based multi-block RANS code, WAVIS developed at MOERI is applied to the numerical self-propulsion test. WAVIS uses the cell-centered finite volume method for discretization of the governing equations. The realizable $k-{\epsilon}$ turbulence model with a wall function is employed for the turbulence closure. The free surface is captured with the two-phase level set method and body forces are used to model the effects of a propeller without resolving the detail blade flow. The propeller forces are obtained using an unsteady lifting surface method based on potential flow theory. The numerical procedure followed the self-propulsion model experiment based on the 1978 ITTC performance prediction method. The self-propulsion point is obtained iteratively through balancing the propeller thrust, the ship hull resistance and towing force that is correction for Reynolds number difference between the model and full scale. The unsteady lifting surface code is also iterated until the propeller induced velocity is converged in order to obtain the propeller force. The self-propulsion characteristics such as thrust deduction, wake fraction, propeller efficiency, and hull efficiency are compared with the experimental data of the practical container ship. The present paper shows that hybrid RANS and potential flow based numerical method is promising to predict the self-propulsion parameters of practical ships as a useful tool for the hull form and propeller design.

Development of a Practical Surface Image Velocimeter using Spatio-Temporal Images (시공간영상을 이용한 실용적인 표면영상유속계 개발)

  • Yunho Lee;Kwonkyu Yu
    • Ecology and Resilient Infrastructure
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    • v.10 no.4
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    • pp.208-216
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    • 2023
  • The purpose of this study is to present the most appropriate hardware and software configurations to produce a practical SIV (surface image velocimeter). To make a practical SIV, we constructed the system with a CCTV, a water stage gauge, and an analysis software installed on an Android board. The camera captures continuously images for 30 seconds with 2 minute intervals. And the 11-parameter projection method was used in the software that analyzes the captured images to reconstruct the exact measurement points according to the changing water stage. In addition, a spatio-temporal image construction method was developed so that the directions of the images could be arranged in the main flow direction at each measurement point. The surface image velocimeter composed of the proposed method was produced and installed at the Insu Stream, Seoul for a test site. And a result of measurement during a heavy rainfall event showed that the proposed system can measure flow discharge in proper, rapid and continuous manner.

A Study on a Hartmann Test of Optical Mirror for On-Machine Measurement of Polishing machine (광학면 연마기의 OMM을 위한 Hartmann Test 방법 연구)

  • 김옥현;이응석;오창진;김용관
    • Journal of the Korean Society for Precision Engineering
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    • v.21 no.1
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    • pp.40-45
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    • 2004
  • Recently, aspheric optical lenses and mirrors, which are harder to manufacture and measure than the conventional spherical ones, are widely used, particularly in electronic fabrication process. Generally, interferometric optical method is used for the measurement of spherical optical surface. However, the interferometric method for aspheric surface measurement is difficult because it needs a precise null corrector and strict environmental conditions such as constant temperature, humidity and vibrations. We have been studied on the manufacturing of aspheric optics to improve the surface profile accuracy and productivity using a corrective polishing process. For the corrective polishing, a practical method of On-Machine Measurement (OMM) is required. For this purpose, an optical OMM system has been studied using the Shach-Hartmann test, which is very robust to the practical polishing environment. The wavefront has been reconstructed from the measured data using the primary aberration polynomial function by the least squares fitting. The measured result of the OMM system shows that the maximum deviation is less than 200 nm for the one of commercial Fizeau interferometer Wyko 6000.

Resistance Reduction of a High Speed Small Boat by Air Lubrication

  • Jang Jin-Ho;Kim Hyo-Chul
    • Journal of Ship and Ocean Technology
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    • v.10 no.1
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    • pp.1-9
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    • 2006
  • The resistance reduction by an air lubrication effect of a large air cavity covering the hull bottom surface and the similarity relations involved have been investigated with a series of towing tank tests of three geometrically similar models. The test results of geometrically similar models have indicated that a large air cavity was formed beneath the bottom having a backward-facing step by artificially supplying air is effective for resistance reduction. The areas of air cavity and the required flow rates of air are directly related to the effective wetted surface area. The traditional extrapolation methods seem to be applicable to the estimation of the resistance in the tested range if corrections are made to account the changes in the frictional resistance caused by the changes in the effective wetted surface area. To investigate the effectiveness of air lubrication in improving the resistance performance of a practical ship, a small test boat having a backward-facing step under its bottom has been manufactured and speed trials in a river have been performed. Air has been supplied artificially into the downstream region of the bottom step to form a large air cavity covering the bottom surface. The results have confirmed the practical applicability of air lubrication for the resistance reduction of a small high-speed boat.

Algorithms for iso-surface representation of res from finite element analysis of stress (유한요소법에 의한 응력 해석 결과의 등가면 표시 알고리즘)

  • Lee, Jae Young;Lee, Young-Jin
    • Journal of the Korea Computer Graphics Society
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    • v.3 no.2
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    • pp.85-97
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    • 1997
  • This study is intended to propose methods of iso-surfaces representation in visualizing the stress distribution in 3-dimensional solids computed by finite element method, and to develop efficient algorithms related to iso-surfaces, and also to exploit the practical application to various data visualizations. This paper suggests practical methods of creating and rendering iso-surfaces, and methods of surface smoothing which removes local irregularity on the surface. Also devised in this study are various methods of rendering stress distribution with the aid of iso-surfaces. Their effectiveness and usefulness have been tested and verified through actual implementaion of a finite element analysis software and case studies using the software.

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