• 유변학
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• 제11권2호
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• pp.82-90
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• 1999

전기유변 유체(electorheological fluid)는 전기장이 가해지면 아주 짧은 시간에 유변 물성이 급격히 변하며 그 응답이 반복적으로 수행될 수 있는 유체이다. 전기유변 유체는 전기장의 세기에 따라 면찰 응력(shear stress)과 점도의 크기를 조절할 수 있고, 짧은 응답시간은 빠른 제어를 요하는 분야에 효과적으로 이용될 수 있지만, 낮은 항복 응력, 조업 온도 범위의 제한성, 전력 소비에 의한 열적 불안정성, 그 외에도 응집, 침전 등의 단점이 있다. 특히, 이 유체가 갖는 항복 응력의 크기와 그 성질은 실제 장치에 응용하는데 중요한 특성이다. 이러한 문제점을 해결하기 위해 면찰 유동(shear flow)이 아닌 압착 유동(squeezing flow)을 고려하게 되었고, 이 유동 하에서의 전기유변 유체의 거동을 이해하기 위해 본 연구에서는 전기유변 유체의 압착 유동에 대한 동적 수치모사를 수행하였다. 고립된 사슬 구조에 대한 수치모사를 통하여 사슬의 위치와 압착 속도를 변화 시키면서 이에 따른 수력학적 힘과 정전기적 힘의 효과를 예측하였으며, 이를 토대로 많은 사슬을 포함한 현탁액 모델에 대한 수치모사를 수행하였다. 그 결과 실험에서 관찰할 수 있는 수직 응력의 증가와 초기 항복 응력의 존재를 확인하였고, 수직 응력의 효과적인 제어는 수력학적 힘과 정전기적 힘 간의 최적화된 조건에서 얻어질 수 있음을 예측하였다. 이러한 수치모사의 개발을 통해 압착 유동을 이용한 전기유변 유체의 응용에 대한 이론적인 토대를 마련하였고, 향후 보다 깊은 이해를 위한 기반을 구축할 수 있었다.

• 드라이브 ㆍ 컨트롤
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• 제10권1호
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• pp.7-13
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• 2013

Port size 80mm or above large-flow type solenoid valves are extensively used in dust collector and power plants. These multi-stage solenoid valve have few problem. first, multi-solenoid valves are almost depend on imports and there are weak in the brine environment and the low energy efficiency. Because these problem, increased the necessity of research on the development of large flow and high pressure type solenoid valves. In this study, describe the design method of multi-stage solenoid test bench and confirm the influence valve performance on several parameter such as diaphragm orifice diameter. At first, each part has modeled by AMESim simulation tool and combining them. This AMESim virtual multi-stage solenoid valve found influence valve performance on the valve parameter. Finally developed the multi-stage solenoid valve and verified that performance on experimental result.

• 대한기계학회논문집
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• 제18권6호
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• pp.1559-1566
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• 1994

Using the finite element method, the contact force, contact band width and temperature distribution of lip seals analyzed for the interference including some nonlinearities such as material nonlinearity, geometrical nonlinearity and nonlinear contact boundary condition. The calculated results showed that the contact stress concentrated on the contact zone between the garter spring and the rubber toward the flex side, the contact edge of lip seals. The high contact forces due to the increased interference separate the sealing gap between the lip edge and the rotating shaft. This may lead to leak the sealed oil.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.757-761
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• 2009

Axial-flow cyclone separator cluster can be used for a dust removal device inside a heating, ventilation, and air conditioning(HVAC) system of subway station. In this study, 3-dimensional computational fluid dynamics(CFD) analysis was performed to compare single unit axial-flow cyclone with couple unit axial-flow cyclone cluster. It is shown that the performance of cyclone separator is not influenced by number of single units but influenced by ability of single unit.

• 한국자동차공학회논문집
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• 제5권3호
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• pp.47-53
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• 1997

The importance of intake system can not be overstressed in the recent heavy duty commercial vehicle design. The basic requirements of intake system are to have less flow resistance and better air cleaning performance which have direct effects on the performance and service life of engine. In order to improve the performance of engine intake system, the flow phenomena in the intake system should be fully understood. With readily availble CFD code, the numerical analysis becomes the more reliable tools for flow optimization in recent design work. In this research, flow field in the intake system was analyzed by STAR-CD, the 3-D computational fluid dynamics code. Especially, the flow inside of air cleaner was thoroughly analyzed. Pressure distribution and velocity profile in the air cleaner and intake duct was obtained. Having the dust seperated from incoming air at the expense of less pressure drop is the ultimate goal for the research.

• 한국가시화정보학회지
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• 제18권3호
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• pp.90-95
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• 2020

The purpose of this study is to numerically evaluate the collection performance of an ultra-small Lapple cyclone separator for 1~10 ㎛ particles introduced at flow rate of 10 L/min. The numerical evaluation reveals that a static pressure drop occurs more dominantly inside of the cyclone separator than at the inlet and the vortex finder. Also a fluid flow in the cyclone separator is confirmed to have a helical structure heading upward in the center of cyclone separator and downward in the vicinity of wall. The investigation on dust collection efficiency of the Lapple cyclone separator shows that particles of 4~8 ㎛ diameters are collected at very lower efficiency than other sizes. Then, the cut-point diameter of the cyclone separator is 1.48 ㎛.

• 드라이브 ㆍ 컨트롤
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• 제17권4호
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• pp.15-22
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• 2020

With the need for efficient maintenance technology to reduce maintenance costs for steel bridges, repainting robots are being developed to automate the work in narrow and poor bridge spaces. The repainting robot is equipped with a blasting module to remove paint layers and contaminants. This study developed a prototype monitoring module to be mounted on the repainting robot. The monitoring module analyzes the condition of the painting surface through a camera installed in the front, guides the direction of movement of the robot, and provides the operator with a video to check the working status after blasting through a camera installed in the back. Various image visibility enhancement technologies were applied to the monitoring module to overcome worksite challenges where incomplete lighting and dust occurs.

• 드라이브 ㆍ 컨트롤
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• 제19권1호
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• pp.8-15
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• 2022

The demand for the re-painting of steel bridges is increasing, but surface treatment is still centered on human resources for on-site re-painting processes. Worker safety accidents continue to occur because the work is performed in a narrow space. Recently, PS balls with excellent surface treatment have been used for blasting, but the working environment is poor due to the large amount of dust generated. In this study, an effective surface treatment method using impeller blasting equipment was developed. The correlation between steel ball size, impeller rotation speed, and exposure time was studied to optimize the efficiency of the surface treatment.

• 한국농공학회논문집
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• 제63권5호
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• pp.63-71
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• 2021

Windbreak forests, which have a windproof effect against strong winds, are known to be effective in reducing the spread of odors and dust emitted from livestock farms. The effect of reducing the spread of odors and dust can be estimated through numerical models such as computational fluid dynamics, which require aerodynamic coefficients of the windbreaks for accurate prediction of their performance. In this study, we aimed to evaluate the aerodynamic coefficients, Co, C₁, C₂, and α, of two windbreaks, Thuja occidentalis and a mesh net, through wind tunnel experiments. The aerodynamic coefficients were derived by the relation between the incoming wind speed and the pressure loss due to the windbreaks which was measured by differential pressure sensors. In order to estimate the change in the aerodynamic coefficient concerning various leaf density, the experiments were conducted repeatedly by removing the leaves gradually in various stages. The results showed that the power law regression model more suitable for coefficient evaluation compared to the Darcy-Forchheimer model.

• BMB Reports
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• 제54권3호
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• pp.182-187
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• 2021

Leukotriene B4 (LTB4) is a lipid mediator of inflammation that is generated from arachidonic acid via the 5-lipoxygenase pathway. Previous studies have reported that the receptors of LTB4, BLT1, and BLT2 play mediatory roles in the allergic airway inflammation induced by ovalbumin (OVA). However, considering that house dust mites (HDMs) are the most prevalent allergen and well-known risk factor for asthmatic allergies, we are interested in elucidating the contributory roles of BLT1/2 in HDM-induced allergic airway inflammation. Our aim in this study was to investigate whether BLT1/2 play any roles in HDM-induced allergic airway inflammation. In this study, we observed that the levels of ligands for BLT1/2 [LTB4 and 12(S)-HETE (12(S)-hydroxyeicosatetraenoic acid)] were significantly increased in bronchoalveolar lavage fluid (BALF) after HDM challenge. Blockade of BLT1 or BLT2 as well as of 5-lipoxygenase (5-LO) or 12-lipoxygenase (12-LO) markedly suppressed the production of TH2 cytokines (IL-4, IL-5, and IL-13) and alleviated lung inflammation and mucus secretion in an HDM-induced eosinophilic airway-inflammation mouse model. Together, these results indicate that the 5-/12-LO-BLT1/2 cascade plays a role in HDM-induced airway inflammation by mediating the production of TH2 cytokines. Our findings suggest that BLT1/2 may be a potential therapeutic target for patients with HDM-induced allergic asthma.