• Corrosion Science and Technology
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• 제8권3호
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• pp.110-115
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• 2009

At the onset of corrosion of steel in concrete, hydrogen ions usually evolve in the process of electrochemical reaction, thereby decreasing the pH of the pore solution, which can be buffered by cement hydration products, as being representatively illustrated by calcium hydroxide. Hence, a fall in the pH is dependent on properties of cement hydration (i.e. hydration products and degree of hydration). The present study tested acid neutralization capacity (ANC) of cementitious binders of OPC(Ordinary Portland Cement), 30% PFA(Pulverized Fuel Ash), 60% GGBS(Ground Granulated Blast Furnace Slag), 10% SF(Silica Fume) to quantify the resistance of cement matrix to a pH fall. Cement pastes were cast at 0.4 of a free W/C ratio with 1.5% chlorides by weight of binder in cast. Powder samples obtained crushed and ground specimen after 200 days of curing were diluted in still water combined with different levels of 1M nitric acid solution, ranging from 0.5 to 20 mol/kg. Then, the pH of diluted solution was monitored until any further change in the pH did not take place. It was seen that the pH of the diluted solution gradually decreased as the molar amount of nitric acid increased. At some particular values of the pH, however, a decrease in the pH was marginal, which can be expressed in the peak resistances to a pH fall in the ANC curve. The peaks occurred at the variations in the pH, depending on binder type, but commonly at about 12.5 in the pH, indicate a resistance of precipitated calcium hydroxide. The measurement of water soluble chloride at the end of test showed that the amount of free chloride was significantly increased at the pH corresponding to the peaks in the ANC curve, which may reflect the adsorption of hydration products to chlorides.

• 한국식품과학회지
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• 제25권4호
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• pp.404-406
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• 1993

시판되고 있는 초고온 멸균유의 저장 중 겔 형성을 추적하기 위하여 제품을 실온에 저장하면서 2,4,6-trinit-robenzene sulfonic acid를 이용하여 유리 아미노그룹을 정량하고 pH와 알콜 안정성을 측정하였다. 유리아미노그룹은 저장초기에 $0.94{\sim}1.11{\mu}M$이었고 $5{\sim}6$개월째에는 $1.95{\sim}2.17{\mu}M$이었으며 12개월째에는 $4.95{\sim}6.36{\mu}M$ 로 증가하였다. 시료의 pH는 저장초기에는 6.72이었고 $5{\sim}6$개월째에는 $6.49{\sim}6.55$이었으며 12개월째에는 $6.14{\sim}6.16$으로 서서히 감소하였다. 알콜시험에서 시료는 저장 $5{\sim}6$개월째부터 양성반응을 보여 카제인의 불안정성과 겔 형성의 개시를 추정케 하였다. 이상의 결과로 시판되는 초고온 멸균유의 겔 형성은 제조 후 정기적으로 몇 가지 요소들을 측정함으로써 추적될 수 있고 이 방법들은 제품의 품질관리에 도움이 될 것으로 생각된다.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1996년도 춘계학술대회
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• pp.22-26
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• 1996

In this paper, we designed 4-channel electrolyte analyzer that can measure simultaneousely the 4 electrolytes - pH, $pNa^{+}$, $pCa^{2+}$, and $pK^{+}-$ using 2-point calibration and implemented it. Developed electrolyte analyzer consists of singal processing part, actuator part and control unit for sample flow system. To implement reliable instrument, design considerations are emphasized on flow system and sample chamber that requires small sample volume and prevent air contact with sample solution. In addition to the hardware design, we developed system software which controls full measuring process. After system developed, we verified the system performance by the test measurement for pH, $pNa^{+}$, $pCa^{2+}$, and $pK^{+}$ value.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1991년도 하계학술대회 논문집
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• pp.286-291
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• 1991

Most of the failures of rotating machine are stator coil insulation failures. The insulation diagnostic testing for high voltage motors and generators are only megger test and P. I Test which is applied DC voltage until now. But it was impossible to judge insulation deterioration status of high voltage rotating machinery by above testing. In other words, even though the megger measurement values are fairly high, they used to be failed from time to time. Therefore in order to excute reliable and detailed diagnosis of insulation deterioration for rotating machinery, the tangent delta test, the alternating current test and the partial discharge test shall be applied to the insulation diagnostic testing on site.

• 한국환경농학회지
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• 제36권4호
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• pp.288-292
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• 2017

BACKGROUND: Silicon tetrachloride reacts with moisture in the atmosphere to generate hydrogen chloride, which affects the environment. Since silicon tetrachloride and its by-products are dispersed in the atmosphere in a short time after the silicon tetrachloride release into the atmosphere, it is difficult to directly assess the extent of environmental impact. In the present study, the exposure test of silicon tetrachloride or hydrogen chloride was examined in order to establish the criterion of the range affected by the silicon tetrachloride release, and the actual crops in the area exposed to silicon tetrachloride leakage were analyzed. METHODS AND RESULTS: For the experiment of exposure to silicon tetrachloride or hydrogen chloride, the leaves of red-pepper and corn were used in glass sealed containers. In the actual accident area, 59 samples from 10 different kinds of crops were collected. The pretreatment of the sample was performed by freezing and grinding, and then extracted using distilled water. The pH and concentration of chloride ($Cl^-$) ion of the extracted solution were measured using pH meter and ion chromatograph, respectively. CONCLUSION: Exposure to silicon tetrachloride caused visible damage, increasing the concentration of chloride ion, and decreasing the pH as well as hydrochloric acid. In the actual crops of the affected area, the tendency was the same as the result of the laboratory test, and the range of influence could be estimated through the concentration of $Cl^-$ ion over 2,000 mg/kg, and the correlation evaluation between the concentration of $Cl^-$ and pH. Therefore, the concentration of $Cl^-$ ion and the correlation between $Cl^-$ and pH would be considered as the factors to estimate the influence range of silicon tetrachloride release.

• Journal of Welding and Joining
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• 제15권5호
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• pp.124-133
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• 1997

Corrosion behavior of welded SWS400 steel used for bridges was studied in a range of the acid-rain environment using immersion, potentiodynamic polartization, polarization resistance, and galvanic corrosion tests. The SWS400 steel exhibited active corrosion behavior in the range of acid-rain environment, i.e. no passivation. As the results of immersion corrosion test, Tafel extrapolation method, and polarization resistance measurement, the average corrosion rats of the steels were 0.31-0.72 mm/year in the pH of 4-5, and 0.17 mm/yera in the pH 6, respectively. The steel showed a resistance to corrosion in the pH 6. The observed active behavior of SWS400 steel in chloride-containing environment indicated that the chloride ions exerts a detrimental influence on the formation of passive films. Galvanic corrosion was observed between the weld and the base metals because the weld is anodic to the base metal.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1992년도 한국자동제어학술회의논문집(국제학술편); KOEX, Seoul; 19-21 Oct. 1992
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• pp.290-295
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• 1992

Tendon driven method to drive one joint using two actuators is developed and implemented. While the method has advantages over conventional transmissions, it also has several drawbacks like tendon slack, elongation and endurability. In this paper, a compensation method of the intrinsic non-linearities of tendon is proposed to improve the performance of antagonistic tendon driven method. In this method, tendon tension measurement is prerequisite which is measured with strain gauge type tension sensor. The developed method is implemented on one link test bed with colocated and non-colocated position sensor.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2003년도 생물공학의 동향(XII)
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• pp.719-723
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• 2003

Cystan의 분산활성은 점토광물에 대한 침강속도가 완연히 느려짐을 확인하여 분산제로서의 성능이 우수함을 볼 수 있었으며, 넓은 범위의 중성 pH에서는 고르게 분산활성을 유지하는 것으로 밝혀졌다. 이는 rheological test에서도 알 수 있었는데, 여러 pH와 온도에서의 Cystan 용액의 점도측정결과 넓은 영역에서 pH 및 온도 변화에 따른 큰 차이가 없었다. Cystobacter sp. MSL-9에 의해 생산되는 Cystan은 분산활성과 안정성이 높으며 기존 화학분산제보다 환경친화적이어서 그 산업적 가치가 클 것으로 기대된다.

• 한국전기전자재료학회논문지
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• 제18권10호
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• pp.960-964
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• 2005

In this paper, we dealt with a partial discharge(PD) measurement method that has been accepted as an effective and non-destructive technique to estimate insulation performance of low-voltage electric and electronic devices. The PD measurement system Is composed of a coupling network, a low noise amplifier, and associated electronics. h shielded box Is adopted to make a better measurement environment against around noise. A low cut-off frequency of the coupling network estimated by a sinusoidal wave input was 125 kHz (-3 dB). Calibration tests on laboratory set-up have shown that the PD measurement system has a stable sensitivity of 10 mV/pC. In an application test oil a low-voltage three phase Induction motor (5 HP), we could detect 0.53 pC level of partial discharge at the applied voltage of AC 650 $V_{peak}$.

• 한국지반신소재학회논문집
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• 제18권1호
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• pp.67-77
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• 2019

그라우팅 공법은 연약지반의 보강과 방수 및 지하수위저하 또는 상승과 진동으로 인한 침하 및 부등침하로 손상된 구조물의 지지력을 높이고 차수를 목적으로 하는데 사용된다. 본 연구는 아라미드 섬유를 이용하여 그라우트재료의 압축강도를 향상시키고, 고로슬래그 미분말을 이용하여 높은 강도의 지반개량공법을 개발하는데 있다. 따라서 본 연구에서는 시멘트와 고로슬래그미 분말의 비는 100:0, 70:30, 40:60%로 고치환(50%이상)까지 확인하고, 아라미드 혼입률은 시멘트와 고로슬래그 중량의 0, 0.5, 1.0%로 증가시켜 첨가하였으며, 표면의 유제처리 비율을 0.7과 1.2%로 샌드겔을 성형하여 일축압축시험을 수행하였다. 환경성 평가는 중금속용출시험과 pH 측정을 수행하였다. 실험결과 아라미드 섬유 1%첨가 시 일축압축강도는 약 1.3배 정도 강도가 증가하였고, 6가크롬은 고로슬래그 미분말이 30% 증가할수록 중금속 용출은 약 50% 감소하였으나, pH용출시험결과, 고로슬래그 미분말이 30% 증가할수록 pH는 약 0.5 증가하는 경향을 나타났다. 향후 pH에 대한 부분은 보완이 필요할 것으로 판단된다.