• 한국구조물진단유지관리공학회 논문집
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• 제14권2호
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• pp.137-144
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• 2010

팽이기초에 대한 일본과 국내에서 현재까지 공통적으로 연구되고 있는 것은 팽이기초의 현장재하실험에 대한 지지력과 침하량에 주목되어 있다. 그러나 팽이기초에서 선행되어야할 연구는 공법 자체가 상재하중을 하부에 어떠한 원리로 전달되는 지에 대한 분석이 수행되어야 한다. 이에 본 연구에서는 일본에서 개발된 Top-Base Foundation과 국내에서 개발된 부양형 팽이기초의 응력전달 메커니즘을 수치해석 및 실내모형실험을 통하여 분석하였다. 팽이기초의 하중전달 메커니즘을 분석한 결과 상재하중에 대한 팽이기초 자체의 하중저감 분담률은 주로 팽이기초와 쇄석사이에서 발생하는 주면마찰력이 가장 크게 나타났다. 또한, 팽이기초의 내부응력분산효과를 포함한 Top-Base Foundation의 총 응력분산각은 $41.8^{\circ}$이며, 부양형 팽이기초의 총 응력분산각은 $44.5^{\circ}$로 산정되었다.

• Journal of the Korean Wood Science and Technology
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• 제48권6호
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• pp.869-877
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• 2020

The power consumption in the low consistency (LC) refining is an important indicator for the optimal control of the process and it is composed of the net power and the no-load power. The refining efficiency and process characterization of LC refining are directly affected by power consumption. In this paper, the effect of pulp consistency and average fiber length on the power consumption and refining efficiency were studied through the LC refining trials conducted by an experimental disc refiner. It is found that the curve of power-gap clearance can be divided into constant power section, power reduction section, and power increase section. And the no-load power and the adjustable domain of loading applied by the refining plates will increase as the increase of pulp consistency, while the increase of net power is larger than that of no-load power which makes the increasing of refining efficiency. Meanwhile, the adjustable domain of loading applied by the refining plates can be slightly improved by increasing the average fiber length, but its effect on the no-load power in the LC refining process can be neglected. The study of power consumption in LC refining is of positive significance for the proper selection of pulp properties in LC refining, in-depth exploration of refining mechanism, and energy consumption reduction in refining.

• 수산해양교육연구
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• 제18권1호
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• pp.58-64
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• 2006

In order to examine the effect of humidity on hydrogen embrittlement of STS 444 weld zone for boiler with dry and wet welding conditions, this paper was carried out the accelerated hydrogen osmosis test and the electrochemical Tafel polarization test. In 0.5M $H_2SO_4$ + 0.01M $As_20_3$ solution, this test is added to load of $1400kg/cm^2$ together with hydrogen osmosis by current of $50 {mA/cm^2}$ for 60 min.. The electrochemical Tafel polarization test was carried out in 0.5M $H_2SO_4$ + 0.01M $As_20_3$ solution. Therefore, the effect of humidity on hydrogen embrittlement of STS 444 was considered. The main results are as following: On the basis of hydrogen embrittlement mechanism, that is, integrated electrochemical polarization characteristics with the established mechanism of hydrogen embrittlement, the reduction rate of corrosion current density of weld zone in the wet weld condition is larger than in the dry condition. We can nondestructively predict the degree of hydrogen embrittlement of STS 444 weld zone for boiler through the reduction rate of electrochemical corrosion current density.

• Structural Engineering and Mechanics
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• 제58권6호
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• pp.967-988
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• 2016

Due to the significant aerodynamic interference from sub-towers and surrounding tall buildings, the wind loads and dynamic responses on main tower of three-tower connected tall building typically change especially compared with those on the isolated single tall building. This paper addresses the wind load effects and equivalent static wind loads (ESWLs) of three-tower connected tall building based on measured synchronous surface pressures in a wind tunnel. The variations of the global shape coefficients and extremum wind loads of main tower structure with or without interference effect under different wind directions are studied, pointing out the deficiency of the traditional wind loads based on the load codes for the three-tower connected tall building. The ESWLs calculation method based on elastic restoring forces is proposed, which completely contains the quasi-static item, inertia item and the coupled effect between them. Then the wind-induced displacement and acceleration responses for main tower of three-tower connected tall building in the horizontal and torsional directions are investigated, subsequently the structural basal and floor ESWLs under different return periods, wind directions and damping ratios are studied. Finally, the action mechanism of interference effect on structural wind effects is investigated. Main conclusions can provide a sientific basis for the wind-resistant design of such three-tower connected tall building.

• Wind and Structures
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• 제25권5호
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• pp.433-457
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• 2017

As a novel typical wind-sensitive structure, the wind load and wind-induced structural behaviors of super-large straight-cone cooling towers are in an urgent need to be addressed and studied. A super large straight-cone steel cooling tower (189 m high, the highest in Asia) that is under construction in Shanxi Power Plant in China was taken as an example, for which four finite element models corresponding to four structural types: the main drum; main drum + stiffening rings; main drum + stiffening rings + auxiliary rings (auxiliary rings are hinged with the main drum and the ground respectively); and main drum + stiffening rings + auxiliary rings (auxiliary rings are fixed onto the main drum and the ground respectively), were established to compare and analyze the dynamic properties and force transferring paths of different models. After that, CFD method was used to conduct numerical simulation of flow field and mean wind load around the cooling tower. Through field measurements and wind tunnel tests at home and abroad, the reliability of using CFD method for numerical simulation was confirmed. On the basis of this, the surface flow and trail characteristics of the tower at different heights were derived and the wind pressure distribution curves for the internal and external surfaces at different heights of the tower were studied. Finally, based on the calculation results of wind-induced responses of the four models, the effects of stiffening rings, auxiliary rings, and different connecting modes on the dynamic properties and wind-induced responses of the tower structure were derived and analyzed; meanwhile, the effect mechanism of internal suction on such kind of cooling tower was discussed. The study results could provide references to the structure selection and wind resistance design of such type of steel cooling towers.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1993년도 한국자동제어학술회의논문집(국내학술편); Seoul National University, Seoul; 20-22 Oct. 1993
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• pp.281-286
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• 1993

In this paper, a parallel link typed wrist is developed for robotic precision assembly. The developed wrist can make the corrective motion required for compensating lateral and tilting errors. The mechanism of this wrist is one example of a motion simulator generating 6 DOF motion in space by 6 actuators connected in paralle. To make the wrist more compact, miniature DC motors containing reduction gears and servo system were used. The parallel link architecture enables a high positioning accuracy and high nominal load capacity. In this study, inverse kinematic problem is solved by using a Denavet-Hartenberg method and a simulational result about workspace of the proposed parallel mechanism is obtained.

• 동력기계공학회지
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• 제18권6호
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• pp.174-179
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• 2014

The wear behavior of epoxy matrix composites filled with nano sized silica particles is discussed in this paper. Especially, the variation of the coefficient of friction and the specific wear rate under the various applied load and sliding velocity were investigated for these materials. Wear tests of pin-on-disc mode were carried out and followed by scanning electron microscope observations. The presence of silica filler in epoxy composites was demonstrated significant influence on the friction and wear behavior of epoxy nanocomposites. With the incorporation of silica filler into the epoxy matrix, reduction of the coefficient of friction and specific wear rate were identified. Wear mechanism was discussed by analyzing the worn surface by scanning electron microscope as well.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.697-701
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• 2007

In this paper, noise sources of a planocentric gear reducer are identified by experimental mehod. This study consider a reduction method of a noise/vibration about the gear, axle, bearing and others. Namely, the purpose of this study is to reduce a noise/vibration for a stability of the total system. Form the data to be measured through an experimental method, the problems of the gear, axle, bearing and others are examined closely, and the reducer is derived the model to be the engineering. The mechanism of the problem occurrence is examined through a parametric research about an each influence factor(Load). Lastly, the results of this study propose the model to be improved.

• Tribology and Lubricants
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• 제17권6호
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• pp.426-434
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• 2001

The hermetic reciprocating compressor driven by the BLDC motor rotating with variable speeds, is modelled and analyzed for dynamic characteristics. The governing equations of piston, connecting rod and crank-shaft of the reciprocating compression mechanism and characteristics of driving torque of the motor are obtained. Dynamic behavior of the crankshaft supported on 2 journal bearings is analyzed considering compression load and eccentric unbalance for the 4 rotating speeds of crankshaft. And. reaction forces generated from oil film in the journal bearings are analyzed under transient condition using Reynolds' equation. To take into account the dynamic characteristics depending on the variable rotating speeds, comparison on the dynamic behavior of crank-shaft is made for the 4 operating modes of the compressor. Results show that the magnitude of crankshaft locioperating on the lower rotating speeds is more larger than the higher ones due to reduction of inertia force of the reciprocating piston.

• 융합보안논문지
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• 제5권1호
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• pp.53-62
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• 2005

virus 방역 체계 관리는 network infra 구조관리, traffic 소통경로관리, 방역 zone 설정, gateway구간 방역관리이다. 본 논문은 일반적인 방역체계 구조의 성격과 취약점을 진단하고 이를 개선할 수 있는 대책으로서 개선된 방역체계를 설계하였다. 또한 설계된 방역체계와 configuration, mechanism하에서는 어느 정도의 개선효과 나타나고 있는지 분석하였다. 개선된 다단계 방역체계 하에서는 gateway 단계에서 불필요한 mail을 걸러줌으로서 server에 주는 부하는 감소하며 virus wall상의 CPU 부하의 감소와 virus 치료율의 상승으로 송신 적체 건수는 감소하고 시스템 process수는 증대하고 있다.