• Economic and Environmental Geology
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• v.50 no.3
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• pp.215-224
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• 2017

Arsenic (As) is known to be the most toxic element and frequently detected in groundwater environment. Inorganic As exists as arsenite [As(III)] and arsenate [As(V)] in reduced and oxidized environments, respectively. It has been reported that the toxicity of arsenite is much higher than that of arsenate and furthermore arsenite shows relatively higher mobility in aqueous environments. For this reason, there have been numerous researches on the process for oxidation of arsenite to arsenate to reduce the toxicity of arsenic. In particular, photooxidation has been considered to be simple, economical, and efficient to attain such goal. This study was conducted to evaluate the applicability of naturally-occurring goethite as a photocatalyst to substitute for $TiO_2$ which has been mostly used in the photooxidation processes so far. In addition, the effects of several factors on the overall performance of arsenite photocatalytic oxidation process were evaluated. The results show that the efficiency of the process was affected by total concentration of dissolved cations rather than by the kind of those cations and also the relatively higher pH conditions seemed to be more favorable to the process. In the case of coexistence of arsenite and arsenate, the removal tendency by adsorption onto goethite appeared to be different between arsenite and arsenate due to their different affinities with goethite, but any effect on the photocatalytic oxidation of arsenite was not observed. In terms of effect of humic acid on the process, it is likely that the higher concentration of humic acid reduced the overall performance of the arsenite photocatalytic oxidation as a result of competing interaction of activated oxygen species, such as hydroxyl and superoxide radicals, with arsenite and humic acid. In addition, it is revealed that the injection of oxygen gas improved the process because oxygen contributes to arsenite oxidation as an electron acceptor. Based on the results of the study, consequently, the photocatalytic oxidation of aqueous arsenite using goethite seems to be greatly feasible with the optimization of process.

• Korean Journal of Soil Science and Fertilizer
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• v.40 no.4
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• pp.242-248
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• 2007

To find a feasibility of utilization of food waste slurry (FWS) generated during composting, FWS was combined with pig manure slurry (PMS) in various ratios and the change of nutrient contents and offensive odor of the combined slurries before and after fermentation were studied. The initial pH was 7.67 for PMS and 8.45 for FWS. However, during the fermentation, pH increased in the combined slurries with the higher FWS rate among the treatments while decreased in thosewith higher PMS rate. EC of each slurry sample showed that the difference among combined slurry samples has been reduced during fermentation and became stabilized in $21{\sim}23dS\;m^{-1}$ after 180 days. After 180 days fermentation, total nitrogen (T-N) decreased. T-N of mixture with a half and more FWS decreased up to 0.1%, less than the critical level (0.3%). The contents of O.M., T-N, phosphorus, calcium and magnesium decreased with fermentation while those of potash and salinity increased. From initial fermentation until 30 days, a lot of $NH_3$, as an offensive odor, was produced. However, it decreased steadily, except in higher PMS rate. In terms of producing $50{\mu}g\;ml^{-1}$ of $NH_3$, the top layer took 30 days after fertilization with FWS only, 45 days for utilized treatment with F75 (25 % of PMS), 75 days for utilized with F50 (50%) and F25 (75%) and 90 days for PMS only, respectively. $RNH_2$ also had similar trend with $NH_3$ but it was produced continuously as long fermentation proceeded. In terms of $RNH_2$, the decrease in concentration up to $50{\mu}g\;ml^{-1}$ were; 45 days for FWS only(F100), 105 days for F75 utilization, 120 daysfor F50, 165 days for F25, respectively. ethyl mercaptan was produced in PMS until 180 days after fertilization but it was not produced in FWS. Sensory tests as an integrated test of offensive odor were also done. FWS showed lower than 1 after 30 days from initial fermentation, while PMS had still offensive odor even up to 180 days from initial fermentation. It is probably affected by the continuous production of ethyl mercaptan and amines. However, considering in decrease T-N content caused by volatilization while offensive odor intensity according to official standard of fertilizer is lower than 2. Further study on controlling offensive odor needs to be done.

• Journal of the Mineralogical Society of Korea
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• v.21 no.1
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• pp.37-44
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• 2008

This study was performed to synthesize Na-A type zeolite with melting slag from the Mapo incineration site and recycle the zeolite as an environmental remediation agent. The melting slag used had a favorable composition containing 26.6% $SiO_2$, 10.9% $Al_2O_3$ and 2.7% $Na_2O$ for zeolite synthesis although there were high contents of iron oxides, including 19.6% $Fe_2O_3$ and 18.9% FeO, which had been used as a flux for the melting. It was confirmed that the Na-A type zeolite could be successfully synthesized at $80^{\circ}C$ and $SiO_2/Al_2O_3\;=\;0.80{\sim}1.96$. The cation exchange capacities (CEC) of the zeolites was determined to be about 220 cmol/kg leveled off at the synthetic time more than 10hrs. The adsorption capacities of zeolite to heavy metals (Cd, Cu, Mn and Pb) were high except for As arid Cr. It was also confirmed through the Eh and pH analysis that As and Cr existed in the forms of $HAsO_4^{2-}$ and $CrO_4^{2-}$. The low absorption rates of zeolite for As and Cr are attributed to the fact that the pore size ($4\;{\AA}$) of Na-A type is smaller than those of $HAsO_4^{2-}$ and $CrO_4^{2-}$ ions ($4\;{\AA}$ ionic radii and $8\;{\AA}$ diameter).

• Korean Journal of Poultry Science
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• v.36 no.1
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• pp.47-55
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• 2009

This study was carried out to investigate the effects of spider-derived protease [Arazyme (AZ)] supplementation on egg production, egg quality, cecal microflora and viscosity of intestinal contents in laying hens at the late production. A total of two hundred, 59-wks-old, Hy-Line Brown layers were divided into four groups, placed into 5 replicates per group (50 birds per group) and fed one of four diets containing 0.05, 0.075 or 0.1% AZ or control for 5 wks. The results showed that egg weight in group fed the diet containing 0.05% AZ was significantly higher than those of other groups (P<0.05). There were no significant differences in egg interior and eggshell qualities among the groups. The serum parameters such as total cholesterol, the levels of GOT and GPT were not influenced by AZ feeding. There were no significant differences in the cecal number of total microbes, Coliforms and lactic acid bacteria among the groups. The viscosity and ammonia concentration of intestinal contents in the groups fed AZ were significantly reduced compared to those of the control (P<0.05). In conclusion, laying hens fed AZ supplemented diet improved egg weight as compared with that of control. In addition, the AZ supplemented diet reduced the viscosity and ammonia concentration of intestinal contents, reflecting a significant feed enzyme effect.

• Journal of the Korean Society of Food Science and Nutrition
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• v.42 no.7
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• pp.1103-1108
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• 2013

This study was conducted in order to determine the effect of autoclave and microwave treatments on cookies. Wheat dough was treated in an autoclave (30 min), a microwave (1 min), and both autoclave and microwave (30 min/1 min). The treated dough was baked or non-baked and cookies quality was assessed. The pH, moisture content, color, and texture were measured, and sensory evaluation was performed. The pH showed a slight increase when dough was treated in a microwave (before baking) and decreased in both the autoclave and autoclave/microwave (after baking) treatments. The moisture content showed a significant increase, compared to the control, in autoclave treatments. Regarding surface color of cookies, lightness was decreased in all treatments and redness was higher compared with the control, except for microwave (before baking), and yellowness was lower compared to the control, except for microwave treatment (after baking). Hardness, gumminess, chewiness, and shear force showed a significant increase when dough was treated in an autoclave/microwave (after baking) compared to the control. In the sensory evaluation, color, taste, texture, shape, and overall preference of cookies treated with an autoclave/microwave (after baking) showed a low score. These results suggest that autoclaving and microwaving may reduce the quality of bread and that preparation of countermeasures is necessary.

• Korean Chemical Engineering Research
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• v.50 no.1
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• pp.18-24
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• 2012

Lignocellulose is difficult to hydrolyze due to the presence of lignin and the technology developed for cellulose fermentation to ethanol is not yet economically viable. However, recent advances in the extremely new field of biotechnology for the ethanol production are making it possible to use of Agriculture residual biomass, e.q., Barley straw, because of their several superior aspects as Agriculture residual biomass; low lignin, high contents of carbohydrates. Barley straw consists of 39.78% cellulose (glucose), 22.56% hemicelluloses and 19.27% lignin. Pretreatment of barley straw using NaOH pretreatment solutions concentration with 2%, temperature $85^{\circ}C$ and reaction times 1 hr were investigates. $NH_4OH$ pretreatment condition was solutions concentration with 15%, temperature $60^{\circ}C$, and reaction times 24hr were investigates. Furthermore, enzymatic saccharification using cellulose at $50^{\circ}C$, pH 4.8, 180 rpm for conversion of cellulose contained in barley straw to monomeric sugar. The pretreatment of barley straw using NaOH and $NH_4OH$ can significantly improve enzymatic saccharification of barley straw by extract more lignin and increasing its accessibility to hydrolytic enzymes. The result showed NaOH pretreatment extracted yield of lignin was 24.15%. $NH_4OH$ pretreatment extracted yield of lignin was 29.09%. Shaccharification of barley straw pretreatment by NaOH for 72hr and pH 4.8 result in maximum glucose concentration 15.39g/L (58.40%) and by $NH_4OH$ for 72hr and pH 4.8 result in maximum glucose concentration 16.01g/L (64.78%).

• Journal of Radiation Protection and Research
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• v.15 no.1
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• pp.9-13
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• 1990

1959년 한국원자력연구소가 창립됨과 동시에 &Health Physics&, 즉 보건물리라고 하는 명칭과 조직이 탄생되어, 방사선안전관리의 실무와 보건물리의 연구가 시작되었다. 최초 10년간은 선진제국의 보건물리분야의 연구와 기술을 추적하여 우리나라의 방사선안전관리 기술의 기초를 다지는 시기로서 개인방사선모니터링기술, 환경방사선(능) 모니터링기술 및 방사선방어용계측기기의 교정기술 개발에 중점을 두고 연구개발이 추진되었으며, TRIGA Mark-II 연구용원자로의 가동에 따라 원자로 생체차폐체의 건전성 검증에 관한 유익한 방사선량 측정자료도 얻게 되었다. 즉 이 기간은 방사선안전관리의 체제정비 및 기초기술 확립에 노력한 기간이었다. 1970년대는 원자력 연구개발에 대한 기본방향과 정책의 변경등으로 보건물리 연구조직은 방사선안전관리, 환경연구 그리고 방사화학분야로 분산되었으며, 그로인하여 연구개발활동은 거의 정체되어 겨우 방사선안전관리 실무만이 그 명맥을 유지하였다. 그 결과 우리나라 방사선안전관리 및 그와 관련된 연구개발의 기반이 흔들리게 되었으나, 그러한 환경하에서도 방사선량측정평가기술, 방사선차폐설계기술 및 원자로사고시 피폭선량평가기술의 선진화에 필요한 지식을 얻었으며, 방사선 안전관리에 유익한 실무경험도 축적하게 되었다. 1980년대는 통합된 원자력 연구개발체제의 구축으로 방사선작업종사자 및 일반공중의 피폭저감화 기술개발에 필요한 각종 최신기술을 도입하였고, 관리업무에 있어서도 측정의 정확도와 신뢰성향상 및 새로운 관리기술의 개발에 많은 노력을 한 결과, 유익한성과를 얻게된 기간이다. 특히, 이 기간은 방사선안전관리기술의 선진화를 위한 지식이 축적되어 90년대의 방사선안전관리기술자립화를 위한 전환기로서, 이와같이 축적된 기술은 원자력의 평화적 이용에 크게 기여할 것으로 기대된다.서 dithiothreitol를 투여한 군에서는 우라늄단독투여군에 비해 cretinine의 배설이 상당히 증가하였다(P<0.05). 6. 우라늄오염에 의한 신장의 소견에 있어 우라늄단독투여군은 근위곡세뇨관상피의 공포화 및 종창, microvilli와 brush border의 손실, 세뇨관 상피의 괴사가 관찰되었으며, 간장의 충혈, 중심성 괴사 및 모세관 확장증도 관찰되었다. 그리고 sodium bicarbonate와 생리적 식염수를 병행투여한 군과 우라늄을 투여하고 30분이 지나서 dithiothreitol를 투여한 군에서는 우라늄 단독투여군에 비해 높은 방호효과가 관찰되었으나 다른 실험군에서는 큰 효과가 없는 것으로 나타났다. 결론적으로 우라늄의 체내오염시에는 sodium bicarbonate와 생리적 식염수를 가능한 빨리 병행투여하거나 dithiothreitol을 체내오염후 30분이 지나서 투여하는 방법이 우라늄오염에 대한 제염에 매우 유효할 것으로 생각되며, 특히 우라늄에 의한 인체장해를 유의하게 경감시켜줄 것으로 사료되었다.내의 어떤 부위와도 관계가 되는 것으로 간주되는데 이것이 $(^3H)$ QNB가 $(^3H)$ NMS보다 높은 최대 결합능력 $(B_{max})$을 나타낼 이유이다. (b) 두 종류의 다른 제제에서 우리는 같은 양상의 결과를 관찰하었기에 결점이 많은 homogenates 제제보다는 intact cell aggregates 제제를 수용체 연구에 대한 새로운 실험모형(experiment model)으로 사용할 수 있는 가능성을 제시하고자 한다.$가 38.8%로 가장 많고, 그 다음이 ${\ulcorner}$l9세(歲)이후${\lrcorner}$가 25.2%로서 전체

• The Journal of the Acoustical Society of Korea
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• v.39 no.5
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• pp.379-389
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• 2020

In this study, the flow and noise performances of high-speed fan motor unit for cordless vacuum cleaner is improved by optimizing the impeller which drives the suction air through flow passage of the cordless vacuum cleaner. Firstly, the unsteady incompressible Reynolds averaged Navier-Stokes (RANS) equations are solved to investigate the flow through the fan motor unit using the computational fluid dynamics techniques. Based on flow field results, the Ffowcs-Williams and Hawkings (FW-H) integral equation is used to predict flow noise radiated from the impeller. Predicted results are compared to the measured ones, which confirms the validity of the numerical method used. It is found that the strong vortex is formed around the mid-chord region of the main blades where the blade curvature change rapidly. Given that vortex acts as a loss for flow and a noise source for noise, impeller blade is redesigned to suppress the identified vortex. The response surface method using two factors is employed to determine the optimum inlet and outlet sweep angles for maximum flow rate and minimum noise. Further analysis of finally selected design confirms the improved flow and noise performance.

• Journal of the Korea Concrete Institute
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• v.13 no.4
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• pp.336-345
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• 2001

The construction of underwater structures has been increased, but underwater concrete hassome problems of quality deterioration and contamination around in-situ of civil and architecture; therefore, new materials and methods for them are demanded. In this paper in-situ application of underwater antiwashout concrete which is manufactured for trio purpose of not only decreasing suspended solids and the heat of hydration but also increasing long term strength was studied. In the case of mock-up test(Ⅰ), when underwater antiwashout concrete, whose slump flow was 58 cm, was placed in the mock-up test at a speed of 24 ㎥/hr, it took about a minute to flow to the side wall, and the surface was maintained at horizontal level. In this case, compressive strength of the core specimens in each section was higher than the standard design compressive strength of 240 kgf/㎠. In the case of mock-up test(II), pH value and suspended solids of high strength underwater antiwashout concrete were 10.0∼11.0 and 51 mg/ℓ at 30 minutes later, initial and final setting time were about 30, 37 hr, and the slump flow of that was 53$\pm$2 cm. In the placement at a speed of 27 ㎥/hr, there was no large difference in flowing velocity, with or without reinforcement and flowing slope was maintained at horizontal level. In this case, compressive strength and elastic modulus of the core specimens somewhat decreased as flowing distance was far : however, those of central area showed the highest value.

• Journal of Animal Environmental Science
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• v.13 no.3
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• pp.171-178
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• 2007

This study was carried out to investigate the effect of microbial complex diets on improvement of air quality in finishing pig building. Ammonia and hydrogen sulfide concentrations were significantly(p<0.05) decreased by dietary supplementation of 0.1% level of microbial complex compared with those of control according to the time in the finishing pig building. Characteristics of piggery liquid slurry that total nitrogen and $NH_3-N$ of treatment were reduced relatively compared with those of control, and were decreased depending on the time. In conclusion, the result obtained from this study suggest that the dietary supplementation of microbial complex for finishing pigs may improve environment in the finishing pig building.