• 한국전기전자재료학회논문지
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• 제16권12호
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• pp.1150-1154
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• 2003

The voltage profile during discharge of the zinc air battery has very flat pattern until reach to end of discharge voltage. But, when zinc air battery is discharged by high current, the discharge voltage and energy becomes low. Therefore, we focused on effects of catalyst size to solve this problems by increasing active sites of oxygen reduction reaction. The size of catalyst was reduced from 27 to l${\mu}{\textrm}{m}$ and we examined average discharge voltage, capacity, energy, resistance and characteristics during GSM pulse discharge of zinc air battery with change of current density. And we also measured porosity of the cathode according to the ASTM. So we have got improvement of average discharge voltage and energy when catalyst was minimized and we have got optimum size of catalyst at 5${\mu}{\textrm}{m}$.

• 한국세라믹학회지
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• 제30권9호
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• pp.747-753
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• 1993

The investigation was carried out to study the behaviors of the pore size and porosity, the mechanical strength, the resistance to thermal spallings and slag attacks according to particle sizes of starting raw materials in porous high Alumina ceramics. This porous ceramics have been used in processing of the clean steel by the blowing of the inert gas. The required properties in the practice are the suitable pores size, the sharp pores distribution for a uniform blowing of the gas, the strong corrosion resistance to slags and molten metals and the resistance to thermal spalling. The optimized properties in porous high alumina ceramics of the specimen No. 3 was found to be the very low slag intrusion and the superior resistance to thermal spalling because of the suitable pore size of 2.5${\mu}{\textrm}{m}$, the porosity of 30% and the high sinterability.

• 한국대기환경학회지
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• 제20권3호
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• pp.361-369
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• 2004

A metal fiber bed has seldom been applied to the practical filtration process despite its excellent mechanical and chemical stability. The filter-bed used in this work was highly porous with open structure, of which apparent porosity was 80 ∼ 90%. Although pressure loss across the filter-bed was very low, separation efficiency was found to be quite high. This paper focuses on the basic filtration mechanisms of a metal filter-bed and a thin ceramic filter from fly ash for reference. The experimental parameters were face velocity, dust loading and porosity of filter-bed. Pressure drop increased with increasing face velocity and dust feeding load for both filters. It also showed that dust particles deposited in the deep flow path, finally resulting in clogging the pore channels. It thereby indicates that the dominating mechanism of the metal filter-bed would be depth filtration. Meanwhile, the thin fly ash composite filters trapped the aerated dust mainly on the surface of the filter medium, so that the instantaneously formed dust layer might cause a steep increase of pressure drop across the filtration system.

• 한국해양학회지
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• 제23권3호
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• pp.146-157
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• 1988

북서 태평양에 분포하는 반 원양성 점토의 심해저 시추 코어를 이용한 공극율, 음파전달속도, 속도 비등방성, 전기비저항, 비저항 비등방성에 대한 성질이 측정 되었다. 음파속도와 비저항은 퇴적물 깊이에 따라 증가하고 반대로 공극율은 감소한다. 깊이에 따른 속도와 비저항의 비등방성의 변화양상은 거의 비슷하다. 수평방향으로 발달된 얇고 긴 공극과 일정한 방향성을 가지고 배열하는 점토광물이 속도의 비등방성의 원인이 될 수 있음이 제시되었다.

• 한국세라믹학회지
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• 제47권5호
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• pp.365-372
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• 2010

This paper was to evaluate the influence of kiln process parameter(kiln angle, kiln rotating speed) of lightweight aggregate using waste glass and bottom ash with industrial by-products on thermal conductivity, density, water absorption, fracture load and porosity by response surface analysis. In the results of surface plot and contour plot, it has verified that kiln residence time of lightweight aggregate increase as kiln angle and rotating speed decreases. For this reason, pore size and quantity tend to increase by active reaction of forming agent. It seems to be that increase in pore size and quantity have caused decreasing density, fracture load and thermal conductivity, and increasing water absorption. In conclusion, optimization of kiln process parameter on thermal conductivity, density, water absorption, fracture load and porosity by response surface analysis are kiln angle 2.4646%, kiln rotating speed 40.7089 rpm.

• 설비공학논문집
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• 제16권7호
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• pp.623-629
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• 2004

Rapid development of electronic technology requires small size, high density packaging and high power of electronic devices, which result in more heat generation by the electronic system. Present cooling technology may not be adequate for the thermal management in the current state-of-the-art electronic equipment. Forced convective heat transfer in a channel filled with pin-fin array is studied experimentally in this paper as an alternative cool-ing scheme for a high heat-dissipating equipment. Various configurations of the pin-fin array are selected in order to find out the effect of spacing and diameter of the pin-fin on the heat transfer and pressure drop characteristics. In the low porosity region, interfacial heat transfer and pressure drop seem to show different trend compared to the conventional heat transfer process.

• Journal of Ceramic Processing Research
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• 제19권6호
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• pp.467-471
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• 2018

Diatomite powder, a naturally occurring porous raw material, was used to make ceramic materials with porosity and high strength. The sintering behavior of the diatomite powder at various sintering temperatures suggests that diatomite monoliths with a high porosity and strength can be prepared at $1100^{\circ}C$. The compressive strength of the sintered diatomite monoliths increased as the sintering temperature increased, and the molding pressure of 2 MPa and the binder of 18.6 wt.% were excellent. When the sintering temperature rises, the diatomite powder is melted, and its pores gradually disappear. SEM images show that strengthening begins with the formation of inter-particle bonds at a low sintering temperature.

• Computers and Concrete
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• 제27권3호
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• pp.269-282
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• 2021

A dynamic analytical solution for a simply supported, rectangular functionally graded plate with a porous middle layer under time-dependent load based on a refined third-order shear deformation theory with a cubic variation of in-plane displacements according to the thickness and linear/quadratic transverse displacement is presented. The solution achieved in the trigonometric series form and rests on the Green's function method. Two porosity types and their influence on material properties, and mechanical behavior are considered. The network of pores is assumed to be empty or filled with low-pressure air, and the material properties are calculated using the power-law distribution idealization. Numerical calculations have been carried out to demonstrate the accuracy of the kinematic model for the dynamic problem, the effect of porosity, thickness of porous layers, power-law index, and type of loading on the dynamic response of an imperfect functionally graded material plate.

• 한국가스학회지
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• 제18권3호
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• pp.20-30
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• 2014

비전통가스 자원을 개발하기 위해서는 저류층 암체의 치밀성을 도출하는 물성 분석이 요구된다. 특히, 치밀가스와 같은 비전통자원의 경우, 전통적인 천연가스전과 비교하여 투과도가 특징적으로 낮아서 통상적인 물성 측정 기술을 적용하기에는 한계가 있다. 이에 본 연구에서는 비정상상태에서 저투과성 암체의 물성을 측정하는 압력펄스감소법을 기반으로 실험 장치를 개발하였다. 개발된 기기는 우리나라 경상분지 치밀사암의 물성 분석에 이용되었으며, 각 시료의 투과도와 공극률을 도출하였다. 또한, 실험을 통해 얻은 자료와 이론해 모델 간의 회귀분석 결과 모두 0.96 이상의 상관계수를 나타냈으며, 개발된 장치에 대한 높은 신뢰성을 확인할 수 있었다.

• 한국치위생학회지
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• 제10권3호
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• pp.531-540
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• 2010

Objectives : In this study, following the cavity restorations with low copper conventional alloy, high copper admixed one and high copper unicompositional one, which are used the most frequently in a clinical setting at the present, to experiment the time-dependent changes of strength, bubbles were examined. Besides, to examine the detrimental effects of mercury contained in dental amalgam, the amount of mercury release was evaluated. Methods : As dental amalgams which were used herein, [BESTALOY], [Hi-Aristaloy 21] and [Sybraloy] were selected for a low-copper conventional amalgam, a high-copper admixed one and a high-copper unicompositional one in the corresponding order. The formation of bubbles and the weight ratio of mercury release were evaluated using a field emission scanning electron microscope (FE-SEM). Thus, the following results were obtained: Results : 1. The time-dependent amount of mercury release reached a statistical significance in three types of alloys, which was shown in such a descending order as [BESTALOY], [Hi-Aristaloy 21] and [Sybraloy]. 2. A low-copper conventional type, BESTALOY is a cutting type and it was found to have an increased formation of fine bubbles. In the remaining two types, [Hi-Aristaloy 21] (a high-copper admixed alloy) and [Sybraloy] (a high-copper unicompositional alloy), the time-dependent changes in the formation of bubbles was negligible. Conclusions : Accordingly, this type of mercury release from amalgam alloy denotes the difference in the weight ratio of total constituents between after 24 hours and after two weeks. But further studies are warranted to examine the amount of mercury release which is detrimental to human bodies. Besides, a low-copper conventional alloy is a cutting type and it was characterized by the abundant formation of bubbles in a time-dependent manner. This implies that the strength of amalgam is impaired, which should be considered in selecting the appropriate amalgam alloy in a clinical setting.