• Title/Summary/Keyword: 항력

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A Study on Compensation for Damage in Civil Litigation of Japanese Long-term Care Facilities (개호사고에서 손해배상책임에 관한 연구 -일본의 판례를 중심으로-)

  • Jeong, Da-Young
    • The Korean Society of Law and Medicine
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    • v.19 no.2
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    • pp.173-207
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    • 2018
  • Japan is a super-aged society where the proportion of the people aged over 65 is exceeded 20%. Therefore, there are many accidents that occur in long-term care facilities in Japan, and there are many civil litigations. The Japanese court has acknowledged in many cases that the long-term facility is responsible for the damage to the elderly who is injured in the facility. The cases can be divided into ① tumbling down, ② wandering, ③ suffocation, ④ bedsore, and ⑤ accidents among the facility-users. In most cases, the court found that the facility violated its obligation to protect their users. This is not only the case where the manager or the employee of the facility violates the obligation to watch and care for the elderly, but in some cases, the failure to maintain the human and material system itself is recognized. The basis for such judgment is whether the facility can predict the possibility of an accident and whether the facility has taken measures to prevent accidents. Also, the Japanese court recognizes the transfer of burden of proof in order to expedite the victims' rights. However, the liability of the facility for damages should not be so heavy that it would be hesitant to allow a person to enter the facility and make a contract.

Computational Fluid Analysis for the Otter Boards - 3 . Efficiency Analysis of the Single Cambered Otter Boards for the Various Slot Position - (전개판에 대한 수직해법 - 3 . 슬롯에 따른 단순만곡형전개판의 성능분석 -)

  • 고관서
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.27 no.4
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    • pp.278-285
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    • 1991
  • The authors propose to use the slot system in order to improve of the efficiency for the cambered otter boards. The experiment is divided into 2 parts, one is the efficiency model test, and the other is the visualization model test. The hydrodynamic characteristics of the model otter boards were tested by efficiency model test to measure the shearing, drag force of the models and visualization test using hydrogen bubble method to observe the streak-line and time-line of flow around the models, and milk spout method to observe the separation zone in the wake behind the models. This study tested for 5 models such ad without slot, slot position 0.2C, 0.4C, 0.6C and 0.8C. The results obtained are as follows: \circled1 The maximum C sub(L) of model otter board with slot position 0.6C in attack angle 27$^{\circ}$ was the highest of all models, it's value was 1.59. \circled2 In general, the L/D ratio of the one slot otter boards were 16~28% higher than otter board without slot. \circled3 The slot position 0.6C was better than any other slot position, and it's conformed by visiualization. \circled4 As to the model otter board with slot position 0.6C, flow speed of the back side was faster 1.3 to 1.7 times than in the front side. \circled5 The size of the separated zone in case of the model otter board with 0.6C was smaller than that of any other models.

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Analysis for Aerodynamic Resistance of Chrysanthemum Canopy through Wind Tunnel Test (풍동실험을 통한 국화군락의 공기유동 저항 분석)

  • Yu, In-Ho;Yun, Nam-Kyu;Cho, Myeong-Whan;Lee, In-Bok
    • Journal of Bio-Environment Control
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    • v.17 no.2
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    • pp.83-89
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    • 2008
  • A wind tunnel test was conducted at Protected Horticulture Experiment Station of National Horticultural Research Institute in Busan to find the aerodynamic resistance and quadratic resistance coefficient of chrysanthemum in greenhouse. The internal plants of the CFD model has been designed as a porous media because of the complexity of its physical shapes. Then the aerodynamic resistance value should be input for analyzing CFD model that crop is considered while the value varies by crops. In this study, the aerodynamic resistance value of chrysanthemum canopy was preliminarily found through wind tunnel test. The static pressure at windward increased as wind velocity and planting density increased. The static pressure at leeward decreased as wind velocity increased but was not significantly affected by planting density. The difference of static pressure between windward and leeward increased as wind velocity and planting density increased. The aerodynamic resistance value of chrysanthemum canopy was found to be 0.22 which will be used later as the input data of Fluent CFD model. When the planting distances were $9{\times}9\;cm$, $11{\times}11\;cm$, and $13{\times}13\;cm$, the quadratic resistance coefficients of porous media were found to be 2.22, 1.81, and 1.07, respectively. These values will be used later as the input data of CFX CFD model.

Hydrophobicity and Adhesion of SiO2/Polyurethane Nanocomposites Topcoat for Aircraft De-icing with Different Pre-curing Time (선경화 시간에 따른 항공기 De-icing용 나노실리카/폴리우레탄 복합재료 탑코트의 소수성 및 접착특성 평가)

  • Kim, Jong-Hyun;Shin, Pyeong-Su;Kwon, Dong-Jun;Park, Joung-Man
    • Composites Research
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    • v.33 no.6
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    • pp.365-370
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    • 2020
  • The icing formation at aircraft occur problems such as increasing weight of the body, fuel efficiency reduction, drag reduction, the error of sensor, and etc. The viscosity of polyurethane (PU) topcoat was measured at 60℃ in real time to set the pre-curing time. SiO2 nanoparticles were dispersed in ethanol using ultra-sonication method. The SiO2/ethanol solution was sprayed on PU topcoat that was not cured fully with different pre-curing conditions. Surface roughness of SiO2/PU nanocomposites were measured using surface roughness tester and the surface roughness data was visualized using 3D mapping. The adhesion property between SiO2 and PU topcoat was evaluated using adhesion pull-off test. The static contact angle was measured using distilled water to evaluate the hydrophobicity. Finally, the pre-curing time of PU topcoat was optimized to exhibit the hydrophobicity of SiO2/PU topcoat.

Aerodynamic Characteristics of a Tube Train (튜브 트레인 공력특성 해석)

  • Kim, Tae-Kyung;Kim, Kyu-Hong;Kwon, Hyeok-Bin
    • Proceedings of the KSR Conference
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    • 2010.06a
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    • pp.139-150
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    • 2010
  • Recently, full-scale research about a passenger tube train system is being progressed as a next-generation transportation system in Korea in light of global green technology. The Korea Railroad Research Institute (KRRI) has commenced official research on the construction of a tube train system. In this paper, we studied various parameters of the tube train system such as the internal tube pressure, blockage ratio, and operating speed through computational analysis with a symmetric and elongated vehicle. This study was about the aerodynamic characteristics of a tube train that operated under standard atmospheric pressure (open field system, viz., ground) and in various internal tube environments (varying internal tube pressure, blockage ratio, and operating speed) with the same shape and operating speed. Under these conditions, the internal tube pressure was calculated when the energy efficiency had the same value as that of the open field train depending on various combinations of the operating speed and blockage ratio (the P-D relation). In addition, the dependence of the relation between the internal tube pressure and the blockage ratio (the P-${\beta}$ relation) was shown. Besides, the dependence of the relation between the total drag and the operating speed depending on various combinations of the blockage ratio and internal tube pressure (the D-V relation) was shown. Also, we compared the total (aerodynamic) drag of a train in the open field with the total drag of a train inside a tube. Then, we calculated the limit speed of the tube train, i.e., the maximum speed, for various internal tube pressures (the V-P relation) and the critical speed that leads to shock waves under various blockage ratios, which is related to the efficiency of the tube train (the critical V-${\beta}$ relation). Those results provide guidelines for the initial design and construction of a tube train system.

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Cumulative Distributions and Flow Structure of Two-Passage Shear Coaxial Injector with Various Gas Injection Ratio (2중 유로형 전단 동축 분사기의 기체 분사율에 따른 유동 및 입도분포)

  • Lee, Inchul;Kim, Dohun;Koo, Jaye
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.37 no.7
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    • pp.675-682
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    • 2013
  • To verify the effect of inner- and outer-stage gas jets, a shear coaxial injector was designed to analyze the axial velocity profile and breakup phenomenon with an increase in the measurement distance. When the measurement position was increased to Z/d=100, the axial flow showed a fully developed shape due to the momentum transfer, aerodynamic drag effect, and viscous mixing. An inner gas injection, which induces a higher momentum flux ratio near the nozzle, produces the greater shear force on atomization than an outer gas injection. Inner- and Outer-stage gas injection do not affect the mixing between the inner and outer gas flow below Z/d=5. The experiment results showed that the main effect of liquid jet breakup was governed by the gas jet of an inner stage. As the nozzle exit of the outer-stage was located far from the liquid column, shear force and turbulence breaking up of the liquid jets do not fully affect the liquid column. In the case of an inner-stage gas injection momentum flux ratio within 0.84, with the increase in the outer gas momentum flux ratio, the SMD decreases. However, at an inner-stage gas jet momentum flux ratio over 1.38, the SMD shows the similar distribution.

CFD Analysis on the Hydro Turbine by the Existence of Blade Holes (블레이드 타공에 따른 수차의 유동해석)

  • Park, Yoo-Sin;Kim, Ki-Jung
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.18 no.10
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    • pp.675-680
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    • 2017
  • Considering that most sewage treatment facilities have a water head of less than 2.0 m and a constant flow rate, the development of a small hydro power generation device capable of maintaining stable power generation and efficiency is urgently needed. In this study, a numerical analysis using the CFD code was carried out to develop a drag force type vertical axis hydro turbine for the improvement of the production efficiency of small-scale hydro energy underlow flow velocity conditions. The blade pressure changes and internal flows were analyzed in the presence or absence of hydro turbine blade holes at a flow velocity of less than 2.0 m/s. The pressure distribution of the hydro turbine blades with holes was found to be about 5.1 % lower than that of the hydro turbine blades without holes. The analysis of the internal flow around the water tank and hydro turbine blade revealed that the flow velocity varied with the vector distribution and that the flow velocity of the hydro turbine blades with holes was 5.6 % less than that of the hydro turbine blades without holes. It is believed that forming a hole in the blade may be helpful for its structural safety.

Numerical Simulation of Flow Characteristics behind a Circular Patch of Vegetation using a Two-Dimensional Numerical Model (2차원 수치모형을 이용한 원형군락 하류의 흐름특성 수치모의)

  • Kim, Hyung Suk;Park, Moonhyeong
    • Journal of Korea Water Resources Association
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    • v.48 no.11
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    • pp.891-903
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    • 2015
  • This paper presents numerical simulations of flow around a circular patch of vegetation using a depth-averaged two-dimensional numerical model which is capable of simulating flow structure in vegetated open channel. In order to account for vegetation effect, drag force terms are included in governing equations. Numerical simulations are conducted with various solid volume fractions (SVF). Flow passes through a circular patch and low velocity region, which is called wake region, is formed downstream of the patch. When SVF is larger than 0.08, a recirculation is observed. The location of the recirculation is moved further downstream as SVF decreases. Von-$K{\acute{a}}rm{\acute{a}}n$ vortex street is developed beyond the wake region due to interaction between two shear layers induced by a circular patch of vegetation. The vortex is developed as SVF is larger than 0.08, and the location of the vortex is consistent with the maximum of turbulence kinetic energy. The location of the peak of turbulence kinetic energy is moved further downstream as SVF decreases.

Numerical Investigation of Turbulence Structure and Suspended Sediment Transport in Vegetated Open-Channel Flows (식생된 개수로에서 난류 구조와 부유사 이동 현상의 수치해석)

  • Gang, Hyeong-Sik;Choe, Seong-Uk
    • Journal of Korea Water Resources Association
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    • v.33 no.5
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    • pp.581-592
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    • 2000
  • Turbulence structure and suspended sediment transport capacity in vegetated open-channel flows are investigated numerically in the present paper. The $\textsc{k}-\;\varepsilon$ model is employed for the turbulence closure. Mean velocity and turbulence characteristics including turbulence intensity, Reynolds stress, and production and dissipation of turbulence kinetic energy are evaluated and compared with measurement data available in the literature. The numerical results show that mean velocity is diminished due to the drag provided by vegetation, which results in the reduction of turbulence intensity and Reynolds stress. For submerged vegetation, the shear at the top of vegetation dominates turbulence production, and the turbulence production within vegetation is characterized by wakes. For emergent condition, it is observed that the turbulence generation is dominated by wakes within vegetation. In general, simulated profiles compares favorably to measured data. Computed values of eddy viscosity are used to solve the conservation equation for suspended sediment, yielding sediment concentration more uniform over the depth compared with the one in the plain channel. The simulation reveals that the suspended load decreases as the vegetation density increases and the suspended load increases as the particle diameter decreases for the same vegetation density.

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A Gear Shape of a Midwater Trawl and Its Change (중층트롤의 어구형상과 그 변화)

  • Park, Hae-Hoon;Yoon, Gab-Dong
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.38 no.3
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    • pp.209-216
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    • 2002
  • How to estimate the shape of trawl net and ropes of a midwater trawl on full scale was described by implementing a three-dimensional semi-analytic treatment of a towing cable system with the field experiments obtained with the Scanmar system. The shape of trawl net from wingend to the beginning of codend was assumed to be of form $\chi$$^2$/ae$^2$+ y$^2$/be$^2$=(z - c)$^2$/c$^2$, and that of the ropes attached behind otter boards be of form yr = $A\chi$rB. In case of warp length 300m long, the volume of trawl net, the ratio of net height to net width at the mouth of the trawl net, and the inclination angle of float rope were estimated according to the change of towing speed. The volume and the distance between wingtips were increased with increasing towing speed. And the inclination angle of float (or ground) rope was slightly decreased with increasing towing speed.