• Journal of Electrochemical Science and Technology
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• 제12권4호
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• pp.440-452
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• 2021

Enhancement of durability and reduction of maintenance cost of concrete, with the implementation of various approaches, has always been a matter of concern to researchers. The integration of pozzolans as a substitute for cement into the concrete is one of the most desirable technique. Silica fume (SF) and colloidal nanosilica (CS) have received a great deal of interest from researchers with their significant performance in improving the durability of concrete. The synergistic role of the micro and nano-silica particles in improving the main characteristics of cemented materials needs to be investigated. This work aims to examine the utility of partial substitution of cement by SF and CS in binary and ternary blends in the improvement of the durability characteristics linked to resistance for electrochemical corrosion using electrical resistivity and half-cell potential analysis and chloride penetration trough rapid chloride penetration test. Furthermore, the effects of this silica mixture on the compressive strength of concrete under normal and aggressive environment have also been investigated. Based on the maximum compression strength of the concrete, the optimal cement substituent ratios have been obtained as 12% SF and 1.5% CS for binary blends. The optimal CS and SF combination mixing ratios has been obtained as 1.0% and 12% respectively for ternary blends. The ternary blends with substitution of cement by optimal percentage of CS and SF exhibited decreased rate for electrochemical corrosion. The strength and durability studies were found in consistence with the microstructural analysis signifying the beneficiary role of CS and SF in upgrading the performance of concrete.

• International Journal of Precision Engineering and Manufacturing
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• 제9권3호
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• pp.82-84
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• 2008

A surface encoder based on the Half-shaded square pattern (HSSP) is presented. The HSSP working as reference grid is composed of the straight lines which are easy to be fabricated and make measuring time short. Since the periodic cell is separated in ON/OFF by the $45^{\circ}$ straight line, the duration from the starting point of scanning to the first rising edge and the duty cycle of the pulse train vary with respect to the position of the starting point. And the relationship between X and Y position and the duration, and duty cycle is described in the simple linear equation. Therefore, it is possible to measure X and Y position with the measured duration and duty cycle without calculating load. Through the test set-up, the feasibility of the proposed surface encoder was verified. Also the future works for improvement of performance were suggested.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제53권4호
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• pp.218-224
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• 2004

We present a miniature Direct Methanol Fuel Cell (micro-DMFC) using platinum sputtered microcolumn electrodes with a limited amount of fuel. We use the microcolumn electrode in order to improve the power density of the micro-DMFC that consists of two electrodes and polymer electrolyte. We also design the built-in fuel chamber in the anode for the portable electronics applications. We design and fabricate both microcolumn and planar electrodes, having an identical projective area of 5mm${\times}$5mm. The diffusion current density of the microcolumn electrode is 1.73 times higher than that of the planar electrode at electrode potential of 1.1V in the half-cell test. The micro-DMFC based on the microcolumn electrodes shows the maximum power of 10.8$\pm$7.54㎼(43.23$\pm$0.16㎼/$\textrm{cm}^2$) at the projective area of 5mm${\times}$5mm, while the planar electrode micro-DMFC shows the maximum power of 0.81$\pm$0.42㎼(3.24$\pm$1.68㎼/$\textrm{cm}^2$) at the same projective area. The micro-DMFC based on the microcolumn electrodes shows 13 times higher power density that the micro-DMFC based on the planar electrodes does.

• Progress in Superconductivity
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• 제6권1호
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• pp.7-12
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• 2004

Due to the very fast switching speed of Josephson junctions, superconductive digital circuit has been a very good candidate fur future electronic devices. High-speed and Low-power microprocessor can be developed with Josephson junctions. As a part of an effort to develop superconductive microprocessor, we have designed an RSFQ 4-bit ALU (Arithmetic Logic Unit) in a pipelined structure. To make the circuit work faster, we used a forward clocking scheme. This required a careful design of timing between clock and data pulses in ALU. The RSFQ 1-bit block of ALU used in this work consisted of three DC current driven SFQ switches and a half-adder. We successfully tested the half adder cell at clock frequency up to 20 GHz. The switches were commutating output ports of the half adder to produce AND, OR, XOR, or ADD functions. For a high-speed test, we attached switches at the input ports to control the high-speed input data by low-frequency pattern generators. The output in this measurement was an eye-diagram. Using this setup, 1-bit block of ALU was successfully tested up to 40 GHz. An RSFQ 4-bit ALU was fabricated and tested. The circuit worked at 5 GHz. The circuit size of the 4-bit ALU was 3 mm ${\times}$ 1.5 mm, fitting in a 5 mm ${\times}$ 5 mm chip.

• 한국임상수의학회지
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• 제13권1호
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• pp.81-86
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• 1996

Systemic lupus erythematosus in a dog, suspected systemic lupus erythematosus in a dog, and autoimmune thrombocytopenic purpura hemmorrhagica in a dog are reported. A fice-year old, female Chihuahua (Case 1) showed initially hemorrhagic diathesis and purpura hemorrhagica. Afterward, it showed polymyositis and polyarthritis. LE-cell was demonstrated on LE-cell preparation trom blood. Systemic lupus erythematosus was diagnosed. This reponded well to the immunosuppressants, but developed iatrogenic Cushing syndrome and steroid hepatopathy. A two-and-half-year old, male toy poodle (Case 2) had chief complaint of red urine. Occult blood test for the urine sediment. This did not respond at all to antibiotics and carbazochrome, which is one of systemic coagulants. LE-cell was demonstrated on LE-cell preparation from blood. This responded relatively well to immunosupressants such as prenisolone, azathioprine and cyclophosphamide. systemic lupus erythematosus is suspected. A nine-year-and-three-month old, female Maltese (Case 3), which had history of congestive heart failure and ovariohysterectomy showed purpura hemorrhagica in the skin of chest. This had severe thrombocytopenia and leukocytosis. As prednisolone was administered before immunological examination or demonstration of LE-cell, it was impossible to diagnose whether purpura hemorrhagica developed as a member of systemic lupus erythematosus or independent of systemic lupus erythematosus. This responded well to prednisolone, and so autoimmune thrombocytopenic purpura hemorrhagica was diagnosed.

• 한국건설순환자원학회논문집
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• 제5권2호
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• pp.113-120
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• 2017

HCP 측정법은 철근부식을 판단하는 비파괴 시험으로 현장에서 효과적으로 사용되고 있다. 본 연구는 실내실험을 통하여 촉진부식실험을 수행하고 건조 상태에서 측정된 HCP 측정값과 부식량의 상관성을 분석하는 연구이다. 이를 위해 4가지 피복두께와 3가지 물-시멘트비를 가진 시멘트 모르타르 시편을 제조하여 6시간, 18시간, 42시간동안 20V의 전압을 가하여 ICM에 의한 촉진실험을 수행하였다. 분석결과 피복두께의 감소, 물-시멘트비의 증가, 촉진부식시간의 증가에 따라 부식량이 증가하였으며, 측정된 HCP 값과는 선형적인 관계를 나타내었다. HCP를 사용하여 부식량을 평가하기 위해서는 전체 부식량을 비교하는 것보다, 일정수준의 HCP 값을 선정하고 이에 따라 부식량을 평가하는 것이 높은 결정계수를 얻는 합리적인 방법으로 평가되었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계 학술발표회 논문집(II)
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• pp.201-204
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• 2006

It should be noted that the critical chloride threshold level is not considered to be a unique value for all conditions. This value is dependent on concrete mix proportions, cement type and constituents, presence of admixtures, environmental factors, reinforcement surface conditions, and other factors. In this study, the accelerated corrosion test for reinforcing steel was conducted by electrochemical and cyclic wet and dry seawater method, respectively and during the test, corrosion monitoring by half-cell potential method was carried out to detect the time to initiation of corrosion for individual test specimen. For this purpose, lollypop and right hexahedron test specimens were made for 31%, 42%, and 50% of W/C, respectively, and then the accelerated corrosion test for reinforcing steel was executed. It was observed from the test that the time to initiation of corrosion was found to be different with the water-cement ratio and accelerated corrosion test method, respectively and the critical chloride threshold values were found to range from 0.91 to $1.47kg/m^3$.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1991년도 하계학술대회 논문집
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• pp.846-849
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• 1991

This paper reports the principle, system confiquration, test results of optical voltage sensor using quartz pockels cell. The Pockels effect of quartz material is used for designing optical voltage sensor. The quarts material has very high half-wave voltage, so, it can be applied to measure high voltage level. Experimental results show that the optical voltage sensor has excellent linear characteristics within the applied AC voltage of 1200V.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(II)
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• pp.245-248
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• 2005

It should be noted that the critical chloride threshold level is not considered to be a unique value for all conditions. This value is dependent on concrete mixture proportions, cement type and constituents, presence of admixtures, environmental factors, steel reinforcement surface. conditions, and other factors. In this study, the accelerated corrosion test for reinforcing steel was conducted by electrochemical and cyclic wet and dry seawater method, respectively and during the test, corrosion monitoring by half cell potential method was carried out to estimate the chloride corrosion threshold value when corrosion for reinforcing steel in concrete was perceived. For this purpose, lollypop and right hexahedron test specimens were made for 31.4$\%$, 41.5$\%$ and 49.7$\%$ of w/c, respectively and then the accelerated corrosion test for reinforcing steel was executed. It was observed from the test that the time to initiation of corrosion was found to be different with water-cement ratio and accelerated corrosion test method, respectively and the chloride corrosion threshold value was found to range from 0.91 to 1.43 kg/$m^{3}$.

• 한국동물위생학회지
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• 제14권2호
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• pp.87-103
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• 1991

The somatic cell counts SCC and bacteria counts were done by D milk plant, P milk plant, S milk plant and Inch'${\v{\times}}n$ Vet. Serv. Lab from 1987 to 1990 with Coulter counter, Fossomatic 90, Bactoscan, Rolling ball viscometer and Resazurin reduction test. The results were summarized as follows 1. In the distribution of SCC of the bulk herd milk, D milk plant from Nov. 1989 to Oct. 1990 remarks 80.2% on the range below 500, 000, 14.5% ranging from 1, 000, 000 to 1, 500, 000, 1.2% ranging from 1, 500, 000 to 2, 000, 000, 0.69% ranging from 2, 000, 000 to 3, 000, 000, 0.71% on the range over 3, 000, 000. P milk plant remarks 237, 000 in the first half year and 251, 000 in the second half year in 1990 year. S milk plant remarks annual average of 335, 000 in 1987, 273, 000 in 1988 and 262, 000 in 1989. The individual record of Inch'${\v{\times}}n$ Vet. Serv Lab. remarks 79.35% and 80.2% below 500, 000 8.30% and 7.40% from 500, 000 to 1, 000, 000, 2.37% and 3.2% from 1, 000, 000 to 1, 500, 000, 2.77% and 2.30% from 1, 500, 000 to 2, 000, 000, 1.67% and 2.00% from 2, 000, 000 to 3, 000, 000, 5.53% and 4.40% over 3, 000, 000 in 1989 and 1990, respectively. The grade distirbution of SCC is as follows: D milk plant shows 1st grade-80.20%, 2nd grade-l6.5% and 3rd grade-3.30%. And P milk plant shows all 1st grade. S milk plant shows 87.30%, 8.6% and 4.1% in 1987 and 91.90%, 6.1% and 2.0% in 1988, and 92.40%, 6.1% and l.5% in 1989 on the 1st, 2nd and 3rd grade respectively. 2. The distribution of bacteria P milk plant reached 15.123 in 1st half year and 21.515 in 2nd half year. Also, S milk plant reached 81.5%, 12.5%, 6.0% in 1987, and 86.20%, 9.70%, 4.1% in 1988, and 86.2%, 10.8%, 3.0% in 1989 respectively for 1st, 2nd and 3rd grade. 3. The regional SCC distribution in D milk plant shows 1, 540, 000 in three regions and 714, 000 in one region. And monthly SCC distribution shows 671, 000 in December and 1, 165, 000 in June. 4. As a result of the individual SCC test, 9 times for 16 cows in “I”farm(1986-1988), and 6 times for 13 cows in“D”farm(1987-1988) No.3, 5, 9, 14 cows in“I”farm showed the high SCC beyond 1, 000, 000 over 4-5times. 5. If the SCC over 300, 000 reach 40%, the national producing quality of milk can be reduced by 87, 600M /I annually and in the sum of money, it should be about 35.5 billion Won. 6. The difference between high group and low group for SCC in D milk plant reached over 1, 000, 000. In case that the difference reaches 1, 000, 000 in the farm bulk milk at a farm breeding 20 cows which produce 20kg milk per day, it was estimate that the annual difference of producing quantity and sum of money respectively should be reached 26, 280kg in milk and 10, 643, 400 Won in income.