• Korean Journal of Materials Research
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• v.30 no.5
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• pp.223-230
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• 2020

As a case study on aspect ratio behavior, Kaolin, zeolite, TiO₂, pozzolan and diatomaceous earth minerals are investigated using wet milling with 0.3 mm media. The grinding process using small media of 0.3 pai is suitable for current work processing applications. Primary particles with average particle size distribution D₅₀, ~6 ㎛ are shifted to submicron size, D₅₀ ~0.6 ㎛ after grinding. Grinding of particles is characterized by various size parameters such as sphericity as geometric shape, equivalent diameter, and average particle size distribution. Herein, we systematically provide an overview of factors affecting the primary particle size reduction. Energy consumption for grinding is determined using classical grinding laws, including Rittinger's and Kick's laws. Submicron size is obtained at maximum frictional shear stress. Alterations in properties of wettability, heat resistance, thermal conductivity, and adhesion increase with increasing particle surface area. In the comparison of the aspect ratio of the submicron powder, the air heat conductivity and the total heat release amount increase 68 % and 2 times, respectively.

• Nuclear Engineering and Technology
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• v.34 no.1
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• pp.60-67
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• 2002

The effects of ball-milling time(0 ~4 hrs) have been investigated on the change of powder characteristics, compaction behavior (compaction pressure range : 200 ~400MPa) and sinterability (1700'c in Ha atmosphere) of two different UO$_2$ powders (ex-ADU and ex-AUC) prepared by the wet process. It is observed that, while the ex-ADU UO$_2$ was little affected, the ex-AUC UO$_2$ was largely affected by the ball-milling treatment. This may be attributed to the characteristics of particle size formed during the preparation step, i.e.., the former has a small average size of about 1.0${\mu}{\textrm}{m}$, while the latter has a relatively large average size of about 301n. It appeared that the effective size reduction by ball-milling treatment is limited to the particle size larger than l${\mu}{\textrm}{m}$, and to the extent of maximum decrease in size of about 0.5tn. In the case of ex-AUC UO$_2$, it is observed that the particle size decreased with ball-milling time and green density and sintered density of the pellets prepared from ball-milled powder increased compared with those of pellets prepared from the as-received powder under the same conditions. This may be attributed mainly to the fine particles formed during the ball-milling treatment.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.9 no.1
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• pp.31-40
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• 2006

This paper describes the results of a series of field experiments which are carried out to assess the reduction effect of railroad vibration by utilizing waste tires. The ground vibration due to train service is measured in Honam Railroad line and Kyongbu Railroad line to assess the ground vibration with the domestic railroad line and train type before field model test. From the results of these tests, frequency on train service is presented from 5Hz to 100Hz and a range of excellence frequency is presented to be about from 20Hz to 40Hz in the domestic railroad line. Also, plate bearing tests are conducted to evaluate the variation of bearing capacity with different thickness of the waste tire layer and the fill layer. Finally, field model test is performed by using tire chips ($5cm{\times}5cm$ in size) as a reduction material of railroad vibration. The reduction effect of railroad vibration by utilizing waste tires increases with increasing the thickness of the waste tire layer and the frequency of the vibration source. The results of this experimental study was shown that the waste tire can be used for reduction of the railroad vibration.

• Fisheries and Aquatic Sciences
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• v.18 no.3
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• pp.325-332
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• 2015

An active stimulating method for juvenile fishes to drive escaping from mesh of the codend was examined by shaking canvas in the bottom trawl followed by shrimp beam trawl. Field fishing trials by a bottom trawl were carried out between the Geomoondo and Jejudo in west of South sea, Korea by conver-net methods to examine the effect on the reduction of juvenile fish as a discard catch by generating a shaking movement of the codend using two pieces of asymmetrical semi-circular canvas. The mean period of the shaking motion with the round canvas was 10-15 s, and the range of amplitude as a vertical depth change was up to 0.4-0.6 m when towing speed 3.4-4.3 k't as estimated by peak event analysis. The escape rate of juvenile fish in conver-net by total juvenile bycatch (codend and cover-net) in 14 trials increased from 20% in a steady codend to 34% using a shaking codend in the bottom trawl, while the marketing catch or total bycatch was similar between steady and shaking cod ends. There was no difference in the body size of the fish and species composition between the steady and shaking cod ends. Above results demonstrate a new method for bycatch reduction actually up to 18% using an active stimulating device, although further experiments are needed to increase an effective shaking motion of the codend in amplitude and period for more bycatch reduction.

• Journal of the Korean Home Economics Association
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• v.36 no.6
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• pp.85-94
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• 1998

In this study we tested the physiological influence on human-body according to clothing pressure with reduction rate and varied posture using three kinds of belt with different width. The width of belts were 2.5cm, 3.5cm and 4.5cm, and reduction rates of belts were 0%, 2.5% and 5% of the subject/s waist size respectively. the measured postures were standing state and sitting stste in the chair. The reasults are as follows; 1. Clothing pressure was high in the order of Side part>Front part>Back part and the rate fo change in the side part was highest, according to the reductio rate of belts. The more the width of belt was wide, the less the clothing pressure was small, and this kind of phenomenon could be explained by "The Principle of the power". 2. Both the rate of reduction of belt and the change of average skin temperature in accordance with the width of belt is small, however, the more the width of belts is wider and the reduction rate is bigger, the more the skin temperature at the waist part is increased. 3. The blood pressure and pulse was influenced when the width of belt was narrow and the reduction rate was high. 4. A sense restraining was much influenced by the width of belt, especially when the width of belts was wide, the significant difference was permitted.permitted.

• Archives of Plastic Surgery
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• v.37 no.2
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• pp.169-174
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• 2010

Purpose: Reduction mammaplasty is a procedure with a relatively high patient satisfaction rate, however, associated scarring around the areola can be a serious problem. This study proposes a new modification of the breast reduction procedure by means of an inframammary incision alone. Methods: The breast is marked out preoperatively with standing position. Under the general anesthesia, an inframammary incision of approximately 7 - 8 cm is done. The subcutaneous plane is made in the lower pole of the breast, then the subglandular plane is entered and a sharp dissection is made up to 2 cm below the areola. The breast is mobilized from the chest wall and a cone-shaped parenchyme is removed in en-block except from the retroareolar central part. The remaining both pillars are gathered together with absorbable sutures and the base of the gland is narrowed to project the breast forward. The wound is closed in a layered fashion and taping of the breast mound is applied to redistribute the breast skin. Results: 21 patients (36 breasts) underwent this procedure from December 2004 to December 2009. Average follow up was 9 months (ranged from 6 months to 12 months). No major complication occurred. Most patients were pleased with the breast size, shape, and scars. However, 2 patients complained their hypertrophic scars which were corrected by revision. Conclusion: This technique is a simple approach to mild to moderate breast reduction through an inframammary incision alone. And, this technique provides an option with minimal complications and invisible scarring, which is especially important in the young patient group.

• Journal of Powder Materials
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• v.18 no.3
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• pp.244-249
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• 2011

Spherical nanosized cobalt powder with an average size of 150-400 nm was successfully prepared at room temperature from cobalt sulfate heptahydrate ($CoSO_4{\cdot}7H_2O$). Wet chemical reduction method was adopted to synthesize nano cobalt powder and hypophosphorous acid ($H_3PO_2$) was used as reduction agent. Both the HCP and the FCC Co phase were developed while $CoSO_4{\cdot}7H_2O$ concentration ranged from 0.7 M to 1.1 M. Secondary phase such as $Co(OH)_2$ and $CO_3O_4$ were also observed. Peaks for the crystalline Co phase having HCP and FCC structure crystallized as increasing the concentration of $H_3PO_2$, indicating that the amount of reduction agent was enough to reduce $Co(OH)_2$. Consequently, a homogeneous Co phase could be developed without second phase when the $H_3PO_2/CoSO_4{\cdot}7H_2O$ ratio exceeded 7.

• Korean Journal of Materials Research
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• v.13 no.9
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• pp.631-634
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• 2003

To fabricate W-Cu nanocomposite powder, $WO_3$-CuO powder mixture was high-energetically ball-milled and subsequently hydrogen-reduced. The effect of ball-milling on the hydrogen-reduction behavior of$ WO_3$-CuO was investigated with non-isothermal hygrometric analysis during hydrogen-reduction. Increasing the ball-milling time, the reduction peak temperatures of humidity curves were shifted to low temperature. It was considered that the reduction temperature should be decreased because the specific surface area of each oxide considerably increased with increasing the ball-milling time. In case of ball-milling for 0 h, $WO_3$and CuO were independently hydrogen-reduced and W particles were nucleated on the surface of Cu adjacent to W by CVT. However, in case of ball-milling for 50 h, the aggregates of about 200-300 nm were observed. W particles of size below 30-50 nm were homogeneously distributed with Cu in the aggregates.

• Journal of Powder Materials
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• v.20 no.3
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• pp.174-179
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• 2013

The study on the fabrication of iron powder from forging scales using hydrogen gas has been conducted on the effect of hydrogen partial pressure, temperature, and reactive time. The mechanism for the reduction of iron oxides was proposed with various steps, and it was found that reduction pattern might be different depending on temperature. The iron content in the scale and reduction ratio of oxygen were both increased with increasing reactive time at 0.1atm of hydrogen partial pressure. On the other hand, for over 30 minutes at 0.5 atm of hydrogen partial pressure, the values were found to be almost same. In the long run, iron metallic powder was obtained with over 90% of iron content and an average size of its powder was observed to be about $100{\mu}m$.

• Transactions of the Korean hydrogen and new energy society
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• v.30 no.6
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• pp.549-555
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• 2019

Electrocatalysis of oxygen reduction reaction (ORR) using Pt nanoparticles or bimetal on carabon was studied. Currently, the best catalyst is platinum, which is a limited resource and expensive to commercialize. In this paper, we investigated the cheaper and more active electrocatalysts by making Pt nanoparticles and adding 3D transition metal such as copper. Electrocatalysts were obtained by chemical reduction based on ethylene glycol solutions. Elemental analysis and particle size were confirmed by XRD and TEM. The electrochemical surface area (ECSA) and activity of the catalyst were determined by electrochemical techniques such as cyclic voltammetry and linear sweep voltammetry method. The commercialized Pt support on carbon (Pt/C, JM), synthesis Pt/C and synthesis Pt3Cu1 alloy nanoparticles supported on carbon were compared. We confirmed that the synthesized Pt3-Cu1/C has high electrochemical performance than commercial Pt/C. It is expected to develop an electrocatalyst with high activity at low price by increasing the oxygen reduction reaction rate of the fuel cell.