• 분석과학
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• 제18권4호
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• pp.292-297
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• 2005

붕산수를 중성자 조사하였을 때 발생하는 화학특성 변화를 측정하였다. 붕산 용액의 pH는 조사시간과 붕산농도가 증가할수록 감소하였다. 물의 방사분해물인 과산화수소는 붕산농도에 비례하였고 조사시간에는 반비례하였다. 기체 방사분해물인 수소와 산소기체는 당량비로 생성되었다. $^{10}B(n{\cdot}{\alpha})^7Li$ 핵반응으로 생성된 Li과 조사시간과의 상관관계는 낮은 붕산 농도범위에서는 좋지 않았으나 높은 농도범위에서는 비례성이 다소 좋아지는 현상을 발견하였다.

• Corrosion Science and Technology
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• 제4권3호
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• pp.75-80
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• 2005

This work dealt with the evaluation of galvanic corrosion rate in a corrosion cell having annular gap of 0.5 mm between carbon steel 1018 and alloy 600 as a function of temperature and boron concentration. Temperature and boron concentration were ranged from 110 to 300 $^{\circ}C$ and 2000~10000 ppm, respectively. After the operating temperature of the corrosion cell where the electrolyte was injected was attained at setting temperature, galvanic coupling was made and at the same time galvanic current was measured. The galvanic corrosion rate decreased with time, which was described by corrosion product such as protective film as well as boric acid deposit formed on the carbon steel with time. From the galvanic current obtained as a function of temperature and boron concentration, it was found that the galvanic corrosion rate decreased with temperaturewhilethe corrosionrate increasedwith boronconcentration. The experimental resultsobtained from galvanic corrosion measurement were explained by adhesive property of corrosion product such as protective film, boric acid deposit formed on the carbon steel wall and dehydration of boric acid to be slightlysolubleboric acid phase.Moreoverthe galvaniccorrosionrate calculatedusing initialgalvaniccoupling current instead of steady state coupling current was remarked, which could give us relatively closer galvanic corrosion rate to real pressurized water reactor.

• Membrane and Water Treatment
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• 제10권3호
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• pp.201-206
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• 2019

In this study, we performed an electrowinning process for effective removal of metals (Cu and Ni) in solution and their recovery as solid forms. A complete removal of Cu and Ni (1,000 mg/L) was observed during four times recycling test, indicating that our electrowinning system can ensure the efficient metal removal with high stability and durability. In addition, we investigated effect of operation parameters (i.e., concentration of boric acid only for Ni, variation of pH, concentration of electrolyte ($H_2SO_4$), and cell voltage) on the efficiency of metal removal (Cu and Ni) during the electrowinning. The addition of boric acid significantly enhanced removal efficiency of Ni as the concentration of boric acid increased up to 10 g/L. Compared to negligible pH effect (pH 1, 2, and 4) on the Cu removal, we observed the increase in removal efficiency of Ni as the pH increased from 1 to 4. The electrolyte concentration did not significantly influence the removal of Cu and Ni in this study. We also obtained great removal rates of Cu and Ni at 2.5 V and 4.0 V, which were much faster than those at lower voltages. Finally, almost 99% of each Cu and Ni (1,000 mg/L) was selectively removed from the mixture of metals by adjusting pH and addition of boric acid after the completion of Cu removal. The findings in this study can provide a fundamental knowledge about effect of important parameters on the efficiency of metal recovery during the electrowinning.

• 한국재료학회지
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• 제16권3호
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• pp.163-167
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• 2006

The transition of europium-doped gadolinium oxide phosphor to gadolinium borate phosphor with the concentration of boron in the spray pyrolysis was investigated. The particles prepared from spray solution below 10 wt% boric acid of prepared phosphor had crystal structure of $Gd_2O_3:Eu$ phosphor, in which the crystallinity of the particles decreased with increasing the boron concentration. A single phase $GdBO_3:Eu$ phosphor particles were prepared from spray solution above 50 wt% boric acid of prepared phosphor. The phosphor particles prepared from spray solution with 20 wt% boric acid of prepared phosphor had no XRD peaks of $Gd_2O_3:Eu$ and $GdBO_3:Eu$ Therefore the phosphor particles prepared from spray solution with 20 wt% boric acid of prepared phosphor had the lowest photoluminescence intensity under ultraviolet and vacuum ultraviolet. $GdBO_3:Eu$ and $Gd_2O_3:Eu$ phosphor particles prepared from spray solutions with proper concentrations of boric acid had good photoluminescence intensity under vacuum ultraviolet. The morphology of the phosphor particles were strongly affected by the concentrations of boric acid added into spray solution.

• Nuclear Engineering and Technology
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• 제52권9호
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• pp.1939-1944
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• 2020

Pool boiling heat transfer of a copper microporous coating was experimentally studied in borated water with a concentration of boric acid from 0.0 to 5.0 vol percent (vol%) to determine the effect of boric acid on boiling heat transfer in water. A high-temperature, thermally conductive microporous coating (HTCMC) was created by sintering copper powder with an average particle size of 67 ㎛ onto a 1 cm × 1 cm plain copper surface with a coating thickness of ~300 ㎛ within a furnace in a vacuum environment. The tests showed that the nucleate boiling heat transfer coefficient (NBHT) of HTCMC became slightly less enhanced as the concentration of boric acid increased but the NBHT coefficient values were still significantly higher than those of the plain surface. The critical heat flux (CHF) values from 0 to 1.0 vol% were maintained at ~2,000 kW/㎡, and then, they gradually decreased down to ~1,700 kW/㎡ as the concentration increased further to 5.0 vol%. It is believed that the micro-scale pores of the HTCMC were partially blocked by the high boric acid concentration during the nucleate boiling such that the small bubbles were not effectively created using the HTCMC reentrant cavities as the boric acid concentration increased.

• Nuclear Engineering and Technology
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• 제52권3호
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• pp.538-543
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• 2020

Boric acid is used as a coolant for pressurized-water reactors, and the degree of burnup is controlled by the concentration of boric acid. Therefore, accurate measurement of the concentration of boric acid is an important factor in reactor safety. An improved system was proposed for the accurate determination of boron concentration. A new boron-concentration measurement technique, called multisensitive detection, was developed to improve the measurement accuracy of boron meters. In previous studies, laboratory-scale experiments were performed based on different sensitivity detectors, confirming a 65% better accuracy than conventional single-detector boron meters. Based on these experimental results, an experimental system simulating the coolant-circulation environment in the reactor was constructed; accuracy analysis of the boron meter with a multisensitivity detector was performed at the actual coolant pressure and temperature. In this study, the boron concentration conversion equation was derived from the calibration test, and the accuracy of the boron concentration conversion equation was examined through a repeatability test. Through the experiment, it was confirmed that the accuracy was up to 87.5% higher than the conventional single-detector boron meter.

• Nuclear Engineering and Technology
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• 제52권11호
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• pp.2607-2612
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• 2020

The present work was aimed to show the possibility of using hydrogel (acrylic/boric acid) for evaluation of the neutron radiation shielding. The influence of acrylic acid concentration, different gamma doses and relative contents of boric acid were studied. The physical properties and the thermomechanical stability of the studied samples were investigated. The shielding property of the composite for neutron was tested by Pu-Be neutron source (5 Ci) under room temperature. The neutron fluence rates and gamma fluxes were measured using a stilbene organic scintillator. The macroscopic effective removal cross-section Σ_R (cm^-1) of fast neutrons and total attenuation coefficient μ (cm^-1) of gamma rays has been studied experimentally. The transmission parameters, the relaxation length (??) and the half-value layer (HVL) were obtained. The obtained results indicated that the addition of boric acid to acrylic acid tends to increase the macroscopic effective removal cross-section Σ_R (cm^-1) to 0.141 compared to 0.094 of ordinary concrete.

• 한국지하수토양환경학회지:지하수토양환경
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• 제9권4호
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• pp.8-14
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• 2004

카드뮴과 크롬으로 오염된 토양에 EDTA 와 붕산 혼합용출제를 주입하는 토양수세법(Soil flushing)을 적용 시 최적운전조건을 결정하기 위해서 여러 가지 반응조건에서 카드뮴과 크롬의 제거효율을 측정하였다. 카드뮴의 제거효율은 EDTA 농도가 0.001M에서 0.1M로 증가하면서 $73.2\%$에서 $98.5\%$로 $25.3\%$증가하였으며, 크롬의 제거효율은 붕산의 농도가 0.001M에서 0.1M로 증가하면서 $59.2\%$에서 $100\%$로 $40.8\%$가 증가하였다. 서로 다른 특성을 갖고 있는 카드뮴과 크롬 오염토양에 pH가 3,5,7로 조정된 0.005M EDTA 와 0.005M 붕산 혼합용출제를 주입하여 제거효율을 측정한 결과 카드뮴의 제거효율은 pH가 3에서 7로 증가함에 따라 $92.4\%$에서 $80.9\%$로 감소하였으며, 크롬의 제거효율은 pH 5에서 $70.4\%$로 가장 높았다. pH 5에서 EDTA&붕산 혼합용출제의 농도비를 변화시키면서 카드뮴의 제거효율을 측정한 결과 [EDTA]:[붕산]=0.01M:0.1M에서 가장 효율적이며, 크롬의 제거효율은 [붕산] 주입농도가 0.1M이상일 때 가장 효율적인 것으로 조사되었다. 광산지역과 산업지역에서 채취한 실제오염토양에 적용한 실험에서도 비슷한 결과를 얻었다.

• Journal of Plant Biotechnology
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• 제34권4호
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• pp.339-346
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• 2007

식물화분발아는 수분수정을 통한 식물의 종자형성과 식물개체의 지속적 세대유지를 위한 중요한 요소이다. 따라서, 본 연구에서는 boric acid를 이용하여 형질전환 하지 않은 (NT) 식물과 항암활성 (anti-colorectal cancer mAb CO17-1A, anti-breast cancer mAb BR55) 혹은 항바이러스 활성을 갖는 항체 (anti-rabies virus mAb57)의 유전인자를 발현하는 형질전환식물 간의 in vitro pollen germination과 Pollen tube growth의 차이를 알아보았다. Boric acid의 화분발아에 미치는 영향을 보기 위하여 0, 5, 10, 15, 20, $40{\mu}g/mL$의 농도를 갖는 발아용액 (germination buffer)을 담배식물 화분에 처리하여 pollen germination rate을 본 결과 $20{\mu}g/mL$에서 가장 높게 발아율 (49.5%)을 보였다. Boric acid ($20{\mu}g/mL$)에 대해 형질전환식물과 NT 식물에서 화분발아율을 관찰한 결과, boric acid를 처리하지 않은 화분에 비해 형질전환여부에 관계없이 발아율이 3-10배 증가하였다. 또한, boric acid $20{\mu}g/mL$농도에서 형질전환식물과 NT 식물의 pollen tube length의 성장률이 가장 높게 나타났다. 시간 별로 형질전환 식물들의 Pollen tube length를 확인 한 결과, germination buffer ($20{\mu}g/mL$)를 처리하고 난 후 3시간까지 가장 빠른 성장률을 보였으며, 3시간 후에는 그 성장률이 둔화됨을 확인하였다. Western blot를 이용하여 식물의 화분과 잎에서 황체유전자 단백질 발현을 확인하였다. 화분과 잎에서의 발현을 비교해 본 결과, 잎에서 항체의 안정한 발현을 확인하였다. 본 연구결과를 통해 $20{\mu}g/mL$의 boric acid가 항체발현 형질전환담배식물의 in vitro pollen germination을 보기 위해 가장 적절한 농도라는 것을 제시하였다. 궁극적으로 의료용 항체유전자를 발현하는 형질전환식물의 in vitro pollen germination viability를 확인함으로써 형질전환식물의 화분의 안정적인 수분수정이 이루어질 수 있음을 간접적으로 제시하였다.

• Nuclear Engineering and Technology
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• 제43권3호
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• pp.195-204
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• 2011

The effects on pool boiling heat transfer of aqueous solutions of boric acid ($H_3BO_3$) and sodium chloride (NaCl) as working fluids have been studied. Borated and NaCl water were prepared by dissolving 0.5~5% volume concentration of boric acid and NaCl in distilled-deionized water. The pool boiling tests were conducted using $1{\times}1\;cm^2$ flat heaters at 1 atm. The critical heat flux (CHF) dramatically increased compared to boiling pure water. At the end of boiling tests it was observed that particles of boric acid and NaCl had deposited and formed a coating on the heater surface. The CHF enhancement and surface modification during boiling tests were very similar to those obtained from boiling with nanofluids. Additional experiments were carried out to investigate the reliability of the additives deposition in pure water. The boric acid and NaCl coatings disappeared after repeated boiling tests on the same surface due to the soluble nature of the coatings, thus CHF enhancement no longer existed. These results demonstrate that not only insoluble nanoparticles but also soluble salts can be deposited during boiling process and the deposited layer is solely responsible for significant CHF enhancement.