• Journal of Industrial and Engineering Chemistry
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• 제67권
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• pp.373-379
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• 2018

A transparent, freestanding Porous Aromatic Framework-97 (PAF-97) membrane was successfully synthesized via a one-step acid-catalyzed reaction. Due to the introduction of ether groups, the obtained PAF-97 membrane possesses enhanced structural flexibility, thus increasing the flexibility of the resulting membrane. This is proofed by the fact that the feeding pressure of the membrane reaches as high as 5.5 bar during the separation of gas mixtures. The Young's moduli of the membrane were 6.615 GPa and 11.11 GPa, either in a dry or hydrated state respectively. To be highlighted, under a feeding pressure of 3.6 bar, the PAF-97 membrane rendered the permeance values of $2.90{\times}10^{-7}$, $1.29{\times}10^{-8}mol\;m^{-2}s^{-1}Pa^{-1}$ for $CO_2$ and $CH_4$, respectively, with a $CO_2/CH_4$ permselectivity of 22.48.

• Nuclear Engineering and Technology
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• 제53권5호
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• pp.1436-1445
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• 2021

To obtain the dynamic characteristics of reactor secondary circuit under transient conditions, the system analysis program was developed in this study, where dynamic models of secondary circuit were established. The heat transfer process and the mechanical energy transfer process are modularized. Models of main equipment were built, including main turbine, condenser, steam pipe and feedwater system. The established models were verified by design value. The simulation of the secondary circuit system was conducted based on the verified models. The system response and characteristics were investigated based on the parameter transients under emergency shutdown and overload. Various operating conditions like turbine emergency shutdown and overspeed, condenser high water level, ejector failures were studied. The secondary circuit system ensures sufficient design margin to withstand the pressure and flow fluctuations. The adjustment of exhaust valve group could maintain the system pressure within a safe range, at the expense of steam quality. The condenser could rapidly take out most heat to avoid overpressure.

• 한국음향학회지
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• 제24권4호
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• pp.194-201
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• 2005

국제적으로 음향$\cdot$초음파$\cdot$진동분야의 정밀계측 필요성이 점차 강조되고 있기 때문에 1998년도에 국제도량형위원회(CIPM; International Committee for Weights and Measures) 산하에 음향$\cdot$초음파$\cdot$진동 자문위원회 (CCAUV; Consultative Committee for Acoustics, Ultrasound and Vibration)가 신설되어 활동을 시작하였다. 그 첫 번째 사업의 하나가 1999년부터 시작된 음향분야의 1" 표준 마이크로폰에 대한 핵심측정표준 국제비교 (Key Comparison)이다. 1" 표준 마이크로폰 핵심측정표준 국제비교는 1999년 4월부터 2001년 4월까지 진행되었으며 한국표준과학연구원을 포함한 12개 국가표준기관이 참여하였다. 주관기관 (pilot lab.)은 영국의 National Physical Laboratory (NPL)이 맡았다. 이동용 표준기는 IEC 61094-1에 명시된 1" 표준 음압형 마이크로폰 (LS1P Microphone; Laboratory Standard 1" Pressure Type Microphone) 두 개이며 교정 주파수 범위는 63 Hz부터 8 kHz까지이다. 본 논문에서는 최종 보고서에 수록된 분석 결과를 요약하여 정리하였다.

• Geomechanics and Engineering
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• 제29권1호
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• pp.91-97
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• 2022

The cohesive non-swelling soil (CNS) cushion technology has been widely applied in the subgrade and slope improvement at expansive soil regions. However, the mechanism of the inhibition effect of the CNS layer on expansive soil (ES) has not been fully understood. We performed four outdoor model tests to further understand the inhibition effect, including different kinds of upper layer and thickness, under the unidirectional seepage condition. The swelling deformation, soil pressure, and electrical resistivity were constantly monitored during the saturation process. It is found that when a CNS layer covered the ES layer, the swelling deformation and electrical resistivity of the ES layer decreased significantly, especially the upper part. The inhibition effect of the CNS layer increases with the increase of CNS thickness. The distribution of vertical and lateral soil pressure also changed with the covering of a CNS layer. The electrical resistivity can be an effective index to describe the swelling deformation of ES layer and analyze the inhibition effect of the CNS layer. Overall, the CNS deadweight and the ion migration are the major factors that inhibit the swelling deformation of expansive soil.

• Structural Engineering and Mechanics
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• 제74권2호
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• pp.297-311
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• 2020

The main purpose of this study is to analyze the effects of external pressure on the vibration and buckling of functionally graded (FG) spherical panels resting of elastic medium. The material characteristics of the FG sphere continuously vary through the thickness direction based on the power-law rule. In accordance with first-order shear deformation shell theory and by the use of Ritz formulation the governing equations are presented. In this regard, the beam functions are applied in two-dimensions for different sets of boundary supports. The Winkler and Pasternak models of elastic foundations are also taken into account. In order to show the validity and applicability of the presented formulation, various comparison studies are given. Furthermore, a diverse range of numerical results is reported to check the impacts of geometrical and material parameters along with external pressure on the vibration and buckling analysis of FG spherical panels.

• Membrane and Water Treatment
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• 제6권6호
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• pp.513-524
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• 2015

In this study, the effects of the angles of spacer filaments and the different feed Reynolds number on the fluid flow behavior have been investigated. Three-dimensional computational fluid dynamics (CFD) study is carried out for fluid flow through rectangular channels within different angles ($30^{\circ}$, $40^{\circ}$, $50^{\circ}$, $60^{\circ}$, $70^{\circ}$, $80^{\circ}$, $90^{\circ}$, $100^{\circ}$, $110^{\circ}$, $120^{\circ}$, respectively) between two filaments of spacer for membrane modules. The results show that the feed Reynolds number and the angles of spacer filaments have an important influence on pressure drop. While the feed Reynolds number is fixed, the optimal angle of spacer should be between $80^{\circ}$ to $90^{\circ}$, because the pressure drop is not only relatively small, but also high flow rate region expanded significantly with the increase of the angles between $80^{\circ}$ to $90^{\circ}$.The Contours of velocities and change of the average shear stress with the different angle of spacer filaments confirm the conclusion.

• 한국가시화정보학회지
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• 제16권1호
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• pp.42-47
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• 2018

A needle-free injector is one of the new non-invasive players in impregnating the biological barriers. It is considered as the next phase in drug delivery and therapeutic applications. One of the major fields of application is in skin remodeling procedures. Although many studies were carried out in understanding the principle in the needle-free injection procedure, fewer studies were done with the aim of therapeutic applications. In the present study, we tried to identify key parameters that affect the jet divergence and peak stagnation pressure on the skin surface in a conventional needle-free injector for skin treatment. A summary of the working principle and effect of the key parameters are presented.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.663-664
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• 2006

Sintered Ti(C,N)-based cermets were treated with hot isostatic pressing (HIP) at different nitrogen pressures. The tribological properties of the treated cermets have been evaluated. The results show that a hard near-surface area rich in TiN formed after HIP treatment. The cermets treated at higher pressure had a relatively lower friction coefficient and specific wear rate. In all cases the microhardness of treated cermets is higher than that without HIP natridation. The wear mechanisms of cermets were hard particle flaking-off and ploughing. It was also found that the HIP natridation is well-suited for improving the tribological properties of cermets.

• International Journal of Naval Architecture and Ocean Engineering
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• 제11권1호
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• pp.285-293
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• 2019

In the present paper, model tests of suppressing sloshing fitted with two perforated floating plates are carried out. The study involves identification of system performance such as the suppression and the solidity ratio. Three different solidity ratios of perforated plates have been tried out as potential positive slosh damping devices. A series of painstaking experiments have been conducted in a rigid rectangular tank on six degrees of freedom motion platform under roll harmonic excitation. Comparison of the clean tank shows that the three types of perforated plates are all effective on damping the run-up and impact pressure along the bulkhead. The parametric study indicates that the perforated plate with the median solidity ratio is the most optimal one in suppressing sloshing among three configurations.

• Wind and Structures
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• 제21권2호
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• pp.183-202
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• 2015

Experiments on two-dimensional rectangular prisms with various side ratios (B/D=2, 3, and 4, where B is the along-wind dimension, and D is the across-wind dimension) and rounded corners (R/D=0%, 5%, 10%, and 15%, where R is the corner radius) are reported in this study. The tests were conducted in low-turbulence uniform flow to measure the wind pressures on the surfaces of 12 models for Reynolds numbers ranging from $1.1{\times}10^5$ to $6.8{\times}10^5$. The aerodynamic force coefficients were obtained by integrating the wind pressure coefficients around the model surface. Experimental results of wind pressure distributions, aerodynamic force coefficients, and Strouhal numbers are presented for the 12 models. The mechanisms of the Reynolds number effects are revealed by analyzing the variations of wind pressure distributions. The sensitivity of aerodynamic behavior to the Reynolds number increases with increasing side ratio or rounded corner ratio for rectangular prisms. In addition, the variations of the mean pressure distributions and the pressure correlations on the side surfaces of rectangular prisms with the rounded corner ratio are analyzed at $Re=3.4{\times}10^5$.