• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.4
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• pp.129-136
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• 2010

This study is to investigate experimentally the engineering characteristics of cement mortar according to the replacement method and contents of recycled aggregate powder (RP) by collecting the recycled aggregate powder with the maximum size of below 0.08 mm and 0.15 mm. then, the results of the study can be summarized as follows. The flow of flesh mortar represented a trend in decreasing while the recycled aggregate powder was substituted as it is compared with that of plain. In addition, in case of correlation between tests, it appeared that the correlation between flow and ring flow is big. In the case of the characteristics of hardened mortar, the strength showed more improvements as the RP was substituted to aggregate than the case, which is substituted to aggregate. In addition, it was verified that the results in which the RP was substituted to aggregate by 5% represented similar values to that of the plain according to the passage of age.

• Journal of the Korean Society for Heat Treatment
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• v.25 no.1
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• pp.6-13
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• 2012

HVOF thermal spray coating of 80%WC-CoFe powder is one of the most promising candidate for the replacement of the traditional hard chrome plating and hard ceramics coating because of the environmental problem of the very toxic $Cr^{6+}$ known as carcinogen by chrome plating and the brittleness of ceramics coatings. 80%WC-CoFe powder was coated by HVOF thermal spraying for the study of durability improvement of the high speed spindle such as air bearing spindle. The coating procedure was designed by the Taguchi program, including 4 parameters of hydrogen and oxygen flow rates, powder feed rate and spray distance. The surface properties of the 80%WC-CoFe powder coating were investigated roughness, hardness and porosity. The optimal condition for thermal spray has been ensured by the relationship between the spary parameters and the hardness of the coatings. The optimal coating process obtained by Taguchi program is the process of oxygen flow rate 34 FRM, hydrogen flow rate 57 FRM, powder feed rate 35 g/min and spray distance 8 inch. The coating cross-sectional structure was observed scanning electron microscope before chemical etching. Estimation of coating porosity was performed using metallugical image analysis. The Friction and wear behaviors of HVOF WC-CoFe coating prepared by OCP are investigated by reciprocating sliding wear test at $25^{\circ}C$ and $450^{\circ}C$. Friction coefficients (FC) of coating decreases as sliding surface temperature increases from $25^{\circ}C$ to $450^{\circ}C$.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.748-753
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• 2001

The objective of the present study is to visualize the pulsatile flow fields by using three-dimensional computer simulation and the PIV system. A closed flow loop system was built for the steady and unsteady experiments. The Harvard pulsatile pump was used to generate the pulsatile pressure and velocity waveforms. Conifer powder as the tracing particles was added to water to visualize the flow field. Two consecutive particle images were captured by a CCO camera for the image processing at several cross section. The range validation and the area interpolation methods were used to obtain the final velocity vectors with high accuracy. The finite volume predictions were used to analyze three-dimensional flow patterns in the bifurcation model. The results of the PIV experiment and the computer simulation are in good agreement and the results show the recirculation zones and formation of the paired secondary flow distal to the apex of the bifurcated model. The results also show that the branch flow is pushed strongly to the inner wall due to the inertial force effect and helical motions are generated as the flow proceeds toward the outer wall.

• Journal of the East Asian Society of Dietary Life
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• v.19 no.2
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• pp.247-255
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• 2009

This study examined the quality characteristics of brown sauce prepared with rice powder in place of wheat flour, which is the commonly used thickener. With regard to the general components, as the level of rice powder increased and its ratio in the stock increased, moisture decreased and crude protein, lipid, and ash increased. Reducing sugar content was 4.72% in the control group, and as the mixing ratio of stock to rice powder increased from 100:5 (S1) to 100:13 (S5) in the rice powder-added groups, reducing sugar content increased from 3.94% to 4.82%, respectively. In terms of Hunter's color values, as more rice power was added to the beurre mani$\acute{e}$, L, a, and b values increased. Thus, a sauce of a light brown color was appropriately made. For consistency, as more rice powder beurre mani? was inserted into the analyzer, flow was reduced and viscosity significantly increased. The pH of the control (CS) was 4.94, and there were no significant differences between the control and the rice powder-added groups. In sensory evaluations, color presented its highest score as 6.47 when the mixing ratio of stock to beurre mani$\acute{e}$ was 100:7 (S2). S2 also received the highest score for flavor at 6.32. Viscosity was highest in the control (CS) at 6.26, and was not significantly different from the 100:7 (S2) or 100:9 (S3) groups. Finally, the S2 group had the highest scores for taste (6.21) and overall-acceptability (6.30). In correlation analyses between the sensory characteristics, overall-acceptability as well as the color, flavor, viscosity, and taste of the brown sauce all presented comparatively high positive correlations, in which overall-acceptability and color had the highest correlation.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.649-652
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• 2008

Glass is often recycled. In order to recycle, glass is crushed and ground. During this process, glass powder is generated. Most of this scrap glass powder is disposed in landfills. The glass powder, consisting of 73% SiO$_2$ and 16% Al$_2$O$_3$, is richer in components necessary for polymerization than fly ash. In this study, the fluidity and compressive strength of cement zero mortar were investigated, where cement zero mortar was prepared by mixing 5$\sim$15% of glass powder with 100% fly ash mortar. Result of flow test concluded that workability was not affected by adding the powder. After aging for 28 days, the compressive strength increased by approximately 6% with 5% addition of scrap glass powder. With 10% addition, the strength remained the same. In case of 15% addition, the compressive strength decreased by approximately 6%. To summarize the results, 5$\sim$10% addition of scrap glass powder is considered to be most appropriate.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.6
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• pp.1465-1477
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• 1993

Powder Injection Molding(PM) is an advanced and complicated technology for manufacturing ceramic or metal products making use of a conventional injection molding process, which is generally used for plastic products. Among many technologies involved in the successful PIM, injection molding process is one of the key steps to form a desired shape out of powder/binder mixtures. Thus, it is of great importance to have a numerical tool to predict the powder injection molding filling process. In this regard, a finite element analysis system has been developed for numerical simulations of filling process of powder injection molding. Powder/polymer mixtures during the filling pro cess of injection molding can be rheologically characterized as Non-Newtonian fluids with a so called yield phenomena and have a peculiar feature of apparent slip phenomena on the wall boundaries surrounding mold cavity. Therefore, in the present study, a physical modeling of the filling process of powder/polymer mixtures was developed to take into account both the yield stress and slip phenomena and a finite element formulation was developed accordingly. The numerical analysis scheme for filling simulation is accomplished by combining a finite element method with control volume technique to simulate the movement of flow front and a finite difference method to calculate the temperature distribution. The present study presents the modeling, numerical scheme and some numerical analysis results showing the effect of the yield stress and slip phenomena.

• Journal of Powder Materials
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• v.21 no.3
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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.

• Korean Journal of Materials Research
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• v.23 no.2
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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.

• Journal of Powder Materials
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• v.29 no.6
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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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• v.33 no.2
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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.