• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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• pp.649-652
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• 2008

유리는 흔히 재활용되어 사용되는 것이 일반적이나 유리를 재활용하기 위하여 파쇄 및 분쇄하는 과정에서 유리 미분말이 발생하게 된다. 이러한 폐유리 미분말은 대부분 매립에 의존하고 있으며, 구성성분은 SiO$_2$가 73%, Al$_2$O$_3$가 16%로 중합반응에 필요한 성분이 다량으로 포함되어 있어 플라이애시보다 중합반응에 필요한 원소를 다량 포함하고 있다. 본 연구에서는 플라이애시 100% 사용 모르타르에 폐유리 미분말을 5$\sim$15% 혼합한 시멘트 ZERO 모르타르의 유동성 및 압축강도를 검토하였다. 플로우실험결과 폐유리 미분말의 혼합률은 작업성에 영향을 미치지 않는 것으로 나타났다. 압축강도 실험결과 폐유리 미분말을 5% 혼합한 경우 재령 28일 압축강도가 약 6%정도 상승하였으나 폐유리 미분말을 10% 혼합한 경우에는 기준배합과 동일하고, 15%를 혼합한 경우 약 6% 정도의 압축강도가 감소하였다. 이상의 결과를 요약하면, 폐유리 미분말을 사용할 경우 5$\sim$10%를 혼합 사용하는 것이 가장 적절할 것으로 사료된다.

• 대한기계학회논문집
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• 제17권6호
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• pp.1465-1477
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• 1993

본 연구에서는 분말혼합체의 특성인 항복응력을 포함한 Generalized Newtonian Fluid의 구성 방정식을 도입하고 미끄럼현상을 고려한 신소재의 사출성형 충전과정 해석용 CAE(computer aided engineering)시스템을 개발하였다. 수치모사를 위한 수치해석방법으로는, 유한요소법(finite element method)과 유한차분법(finite difference method)을 함께 사용하였다. 유한요소법과 검사체적법(control volume technique) 을 병용하여 유동의 진행을 수치모사 하였으며, 유한차분법을 사용하여 온도분포를 계산하였다.

• 한국분말재료학회지
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• 제21권3호
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• pp.215-221
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• 2014

Translucent alumina is a potential candidate for high temperature application as a replacement of the glass or polymer. Recently, due to the increasing demand of high power light emitting diode (LED), there is a growing interest in the translucent alumina. Since the translucent property is very sensitive to the internal defect, such as voids inside or abnormal grain growth of sintered alumina, it is important to fabricate the defect-free product through the fabrication process. Powder injection molding (PIM) has been commonly applied for the fabrication of complex shaped products. Among the many parameters of PIM, the flowability of powder/binder mixture becomes more significant especially for the shape of the cavity with thin thickness. Two different positions of the gate were applied during PIM using the disc type of die. The binder was removed by solvent extraction method and the brown compact was sintered at $1750^{\circ}C$ for 3 hours in a vacuum. The flowability was also simulated using moldflow (MPI 6.0) with two different types of gate. The effect of the flowability of powder/binder mixture on the microstructure of the sintered specimen was studied with the analysis of the simulation result.

• 한국재료학회지
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• 제23권2호
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• pp.104-111
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• 2013

In this study, GaN powders were synthesized from gallium oxide-hydroxide (GaOOH) through an ammonification process in an $NH_3$ flow with the variation of $B_2O_3$ additives within a temperature range of $300-1050^{\circ}C$. The additive effect of $B_2O_3$ on the hexagonal phase GaN powder synthesis route was examined by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier transformation infrared transmission (FTIR) spectroscopy. With increasing the mol% of $B_2O_3$ additive in the GaOOH precursor powder, the transition temperature and the activation energy for GaN powder formation increased while the GaN synthesis limit-time ($t_c$) shortened. The XPS results showed that Boron compounds of $B_2O_3$ and BN coexisted in the synthesized GaN powders. From the FTIR spectra, we were able to confirm that the GaN powder consisted of an amorphous or cubic phase $B_2O_3$ due to bond formation between B and O and the amorphous phase BN due to B-N bonds. The GaN powder synthesized from GaOOH and $B_2O_3$ mixed powder by an ammonification route through ${\beta}-Ga_2O_3$ intermediate state. During the ammonification process, boron compounds of $B_2O_3$ and BN coated ${\beta}-Ga_2O_3$ and GaN particles limited further nitridation processes.

• 한국분말재료학회지
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• 제29권6호
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• pp.459-467
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• 2022

Soft magnetic powder materials are used throughout industries such as motors and power converters. When manufacturing Fe-based soft magnetic composites, the size and shape of the soft magnetic powder and the microstructure in the powder are closely related to the magnetic properties. In this study, Fe-Si-Al-P alloy powders were manufactured using various manufacturing process parameter sets, and the process parameters of the vacuum induction melt gas atomization process were set as melt temperature, atomization gas pressure, and gas flow rate. Process variable data that records are converted into 6 types of data for each powder recovery section. Process variable data that recorded minute changes were converted into 6 types of data and used as input variables. As output variables, a total of 6 types were designated by measuring the particle size, flowability, apparent density, and sphericity of the manufactured powders according to the process variable conditions. The sensitivity of the input and output variables was analyzed through the Pearson correlation coefficient, and a total of 6 powder characteristics were analyzed by artificial neural network model. The prediction results were compared with the results through linear regression analysis and response surface methodology, respectively.

• Laboraroty Animal Research
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• 제33권2호
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• pp.105-113
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• 2017

insenosides from Panax ginseng are well known for their diverse pharmacological effects including antithrombotic activity. Since adventitious roots of mountain ginseng (ARMG) also contain various ginsenosides, blood flow-improving effects of the dried powder and extract of ARMG were investigated. Rats were orally administered with dried powder (PARMG) or ethanol extract (EARMG) of ARMG (125, 250 or 500 mg/kg) or aspirin (30 mg/kg, a reference control) for 3 weeks. Forty min after the final administration, carotid arterial thrombosis was induced by applying a 70% $FeCl_3$-soaked filter paper outside the arterial wall for 5 min, and the blood flow was monitored with a laser Doppler probe. Both PARMG and EARMG delayed the $FeCl_3$-induced arterial occlusion in a dose-dependent manner, doubling the occlusion time at high doses. In mechanism studies, a high concentration of EARMG inhibited platelet aggregation induced by collagen in vitro. In addition, EARMG improved the blood lipid profiles, decreasing triglyceride and cholesterol levels. Although additional action mechanisms remain to be clarified, it is suggested that ARMG containing high amount of ginsenosides such as $Rg_3$ improves blood flow not only by inhibiting oxidative thrombosis, but also by modifying blood lipid profiles.

• 한국산업융합학회 논문집
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• 제6권1호
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• pp.49-56
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• 2003

Based on the flow patterns of cylindrical vessel, the flow patterns of conical vessel, spherical vessel, rectangular vessel and cylindrical vessel with baffles were visualized by a trace method using aluminum powder. In addition, the correlations of the critical circulating frequency for mixing were derived from the experimental results. The conical and spherical vessels which have circular cross sections were same effective as cylindrical vessel for the shake mixing due to developing the rotational flow. Both a rectangular vessel and a cylindrical vessel with baffles should not be adapted for shake mixing because of not developing rotational flows in these type of vessels.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집B
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• pp.381-384
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• 2000

Relationships between biochemical phenomena and hemodynamics on human endothelial cells are very important to study the mechanism of atherosclerotic formation and development. The objective of this study is to investigate the flow phenomena around the endothelial cell model by the PIV experiment. The microscopic images of endothelial cells were acquired by a CCD camera to fabricate the shape of endothelial cell. The cell models were fabricated by using a photoforming process. Two consecutive particle images were captured by the CCD camera for the image processing. Conifer powder as the tracing particles was added to water to visualize the flow field. The cross-correlation method was applied fer the image processing of the flow visualization. Pressure and wall shear stress variations on the surfaces of the endothelial cells were calculated to investigate the effects of hemodynamic forces on the morphological changes.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2006년도 전기학술대회논문집
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• pp.321-322
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• 2006

Industrial agitators are used in various industrial fields where they are necessary to intimately mix two reactants in a short period of time. However, despite their widespread use, complex unsteady flow characteristics of industrial agitators are not systematically investigated. The present study alms for clarify unsteady flow characteristics induced by various impellers in a tank. Impellers are pitched blade turbine(PBT) types, Screw type and Rushton turbine type. In this study flow characteristics of the impeller using CFD. The rotating speed of impellers fixed about 100RPM. These three types of Impeller show that typical flow characteristics of axial turbine and suitable for mixing powder

• 대한기계학회논문집B
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• 제23권7호
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• pp.820-830
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• 1999

The coupled turbulent flow and solidification is considered in a typical slab continuous easting process using commercial program FIDAP. Standard $k-{\varepsilon}$ turbulence model is modified to decay turbulent viscosity in the mushy zone and laminar viscosity is set to a sufficiently large value at the solid region. This coupled turbulent flow and solidification model also contains thermal contact resistance due to the mold powder and air gap between the strand and mold using an effective thermal conductivity. From the computed flow pattern, the trajectory of inclusion particles was calculated. The comparison between the predicted and experimental solidified shell thickness shows a good agreement.