• Environmental Engineering Research
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• 제18권3호
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• pp.163-168
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• 2013

In this study, an innovative media, iron mixed ceramic pellet (IMCP) has been developed for arsenic (As) removal from groundwater. A porous, solid-phase IMCP (2-3 mm) was manufactured by combining clay soil, rice bran, and Fe(0) powder at $600^{\circ}C$. Both the As(III) and As(V) adsorption characteristics of IMCP were studied in several batch experiments. Structural analysis of the IMCP was conducted using X-ray absorption fine structure (XAFS) analysis to understand the mechanism of As removal. The adsorption of As was found to be dependent on pH, and exhibited strong adsorption of both As(III) and As(V) at pH 5-7. The adsorption process was described to follow a pseudo-second-order reaction, and the adsorption rate of As(V) was greater than that of As(III). The adsorption data were fit well with both Freundlich and Langmuir isotherm models. The maximum adsorption capacities of As(III) and As(V) from the Langmuir isotherm were found to be 4.0 and 4.5 mg/g, respectively. Phosphorus in the water had an adverse effect on both As(III) and As(V) adsorption. Scanning electron microscopy results revealed that iron(III) oxides/hydroxides are aggregated on the surface of IMCP. XAFS analysis showed a partial oxidation of As(III) and adsorption of As(V) onto the iron oxide in the IMCP.

• 한국정보처리학회논문지
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• 제6권1호
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• pp.115-122
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• 1999

본 논문에서는 VSAT 위성 통신의 안전성을 위해 변형 Yacobi 방식과 변형 Diffie-Hellman 키분배 방식을 제안한다. 제안된 변형 DH 방식은 세션키로 키센터에서 발급한 비밀키로 사용하지 않으며 수시로 변경할 수 있다. 또한 변형 Yacobi 방식도 세션키가 키센터에서 발급한 비밀키에 독립적이며 안전성을 이산대수 문제와 큰 소수의 인수분해의 어려움에 바탕을 두고 있다. 제안된 방식은 VSAT 위성통신의 특성상 키 센터를 중심국의 망관리 및 운영부로 두고 가입자를 VSAT 단말로 하여 시뮬레이션 했으며 여기서 모듈러 연산을 위해 몽고메리 알고리즘을, 해시 함수로 MD5를 각각 이용했다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.1366-1371
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• 2003

Molecular dynamics (MD) simulations are conducted to investigate the thermophysical characteristics and the stability of liquid threads for various conditions. A cylindrical thread in the simulation domain is made of Lennard-Jones molecules. The surface tension of liquid threads can be determined from local densities, local normal and transverse components of the pressure force. In order to understand the effects of thread radii on surface tensions, the Tolman equation is modified on the basis of the cylindrical coordinates for prediction of surface tensions. Surface tensions calculated from the MD simulation agree with the prediction from the modified Tolman equation. In addition, surface tensions decrease linearly with increasing system temperature. For a binary system, the surface tension decreased linearly compared to that for a pure system with increasing binary ratio of solute molecules which have relatively large value of the affinity coefficient. For a fixed binary ratio, the surface tension increased slightly with the affinity coefficient and the maximum value appear around where the affinity coefficient is 1.5 and decreased rapidly for upper value of 1.5. In addition, the critical wavelengths of perturbations are proven to be directly proportional to the equimolar dividing radii of the liquid threads.

• Computers and Concrete
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• 제19권5호
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• pp.515-526
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• 2017

Recent trend is to use the lightweight concrete in the construction industry because it has several advantages over normal weight concrete. The Lightweight concrete can be produced from the industrial waste materials. In South East Asian region, researchers are very keen to use the waste materials such as oil palm shell (OPS) and palm oil clinker (POC) from the palm oil producing industries. Extensive research has been done on lightweight concrete using OPS or POC over the last three decades. In this paper the aggregate properties of OPS and POC are plotted in conjunction with mechanical and structural behavior of OPS concrete (OPSC) and POC concrete (POCC). Recent investigation on the use of crushed OPS shows that OPSC can be produced to medium and high strength concrete. The density of OPSC and POCC is around 20-25% lower than normal weight concrete. Generally, mechanical properties of OPSC and POCC are comparable with other types of lightweight aggregate concrete. It can be concluded from the previous study that OPSC and POCC have the noteworthy potential as a structural lightweight concrete.

• 대한치과마취과학회지
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• 제8권2호
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• pp.118-121
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• 2008

Background: This retrospective study aims to describe the airway management and to search predictive parameter for difficult intubation in 700 patients undergoing oromaxillary surgery. Methods: The medical records of 700 patients undergone oromaxillary surgery were reviewed for airway management during perioperative period. The cases of difficult intubation were selected and those radiologic findings were reviewed. The mandibular depth (MD), mandibular length (ML), thyromental distance (TMD) were measured. Results: In 41 cases difficult intubation were recorded in anesthetic record. The grade of Cormack and Lehane was III in 36 patients and IV in 5 cases. The MD of difficult intubation cases was $4.2{\pm}3.2\;cm$. The ML of difficult intubation cases was $10.1{\pm}3.8\;cm$. The TMD of difficult intubation cases was $5.9{\pm}4.3\;cm$. Under the fiberoptic guided awake intubation was undertaken in 75 patient. In none of the cases was failed nasotracheal intubation. Conclusions: The patients undergoing oromaxillar surgery have a potentially difficult airway but, if managed properly during perioperative preiod, morbidity and mortality can be reduced or avoided. The radiologic findings were poor predict for difficult intubation. The fiberoptic guided awake intubation is a safe alternative to direct laryngoscopic intubation.

• 한국동물위생학회지
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• 제20권4호
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• pp.331-338
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• 1997

The purpose of this study was to establish early diagnosis for bovine virus diarrhea-mucosal disease(BVD-MD) Two Holstein among 22 breeding cows were shown ulcer in the mouth and watery diarrhea. Diarrheal feces and ulcerous lesion of the mouth from 2 cows were sampled for detection of viral antigen. BVD virus was isolated by inoculation of the samples to MDBK cells, and the cytopathic effects were observed in cultured MDBK cells which inoculated with virus isolates from the feces. Viral antigens were detected in the feces and ulceruous lesion by immunogold staining. The serum neutralization titers were shown 1 : 64 or greater in 8 blood samples by using BVD virus (NADL strain). By the RT-PCR, using reverse primer 5'-ACTCCATGTGCCATGTACAG-3', forward primer 5'-ACTCCATGTGCCATGTACAG-3', 285 base pair band specific to BVD virus was detected. In conclusions, the results of above tests which executed using the diarrheal feces and ulcerous lesion of the mouth and the isolates were conformed as BVD virus.

• 멤브레인
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• 제25권3호
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• pp.216-222
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• 2015

막증류(membrane distillation, MD)용 분리막의 장기 내구성능에 영향을 미치는 인자인 소수성 분리막의 젖음 현상에 대한 평가 지표로 사용되는 액체투과압력(liquid entry pressure, LEP) 측정 방법을 최적화하였다. PE (polyethylene) 분리막 및 PVDF (polyvinylidene di-fluoride) 중공사 분리막의 LEP를 측정하기 위하여 20 wt%의 고농도 염수를 제조하여 원수로 사용하고 투과수의 전도도를 모니터링하였다. PE와 PVDF 중공사 분리막의 신뢰성 있는 LEP 측정을 위해서는 5 min 이상의 holing time을 두고 주입 압력을 증가시켜야 하며, 증류수 수조의 물량대비 분리막의 면적비 또한 $10m^2/m^3$ 이상으로 부여되어야 함을 확인하였다.

• Reproductive and Developmental Biology
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• 제36권2호
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• pp.103-108
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• 2012

Anestrus is one of the most important production limiting disorders in dairy buffaloes and its underlying causes have been a current topic of studies. The objectives of this study were to explore the causes of anestrus in buffaloes with the application of ultrasonography. Two examinations were performed by transrectal ultrasonography at 12 days apart in buffalo cows that were not seen in oestrus at 60 or more days postpartum. As high as 54.5% buffaloes had silent ovulation and 45.5% suffered from the true anestrus with ovarian dysfunction. The duration of anestrus after calving was 60~90, 91~120, 121~180 and 181~365 days in 27%, 32%, 18% and 23% buffalo cows, respectively. Treatment with prostaglandin of cyclic buffalo cows with a corpus luteum (72.7%) resulted in higher estrous rate as compared with close observation of estrus (23.1%) by the farmer (p=0.021). Acyclic buffalo cows without any corpus luteum on ovaries were successfully treated with gonadotropin releasing hormone (70%), resulting in higher estrous detection rate than those treated with a vitamin-mineral mixture (20%) (p=0.035). In conclusion, poor heat detection due to silent ovulation is the most important cause of apparent anoestrus in buffaloes; however the percentage of the true anestrous is also quite high in postpartum buffaloes.

• 대한화학회지
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• 제57권5호
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• pp.554-559
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• 2013

본 연구에서는 ${\beta}$-D-glucopyranose 분자의 hydroxymethyl group의 두 torsion angle의 변화에 따른 포텐셜 에너지의 변화를 진공 상태와 implicit water 상태에서 연구하였으며 이를 통해 Solvation Energy가 구조에 미치는 영향에 대해서 알아보았다. 계산에 사용한 프로그램은 AMBER package였으며, force field는 GLYCAM_06을 사용하였다. Solvation model은 Hawkins, Cramer, Truhlar 등이 제안한 generalized Born model을 사용하였다. 계산 결과, methyl hydroxyl group 내의 hydroxyl group이 고리구조의 hydroxyl group과 강한 수소결합이 가능한 영역에서 많은 변화가 일어났다. 이를 통해 solvation effect로 인해서 수소 결합의 중요성이 감소했다는 결론을 내렸다.

• Membrane and Water Treatment
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• 제6권6호
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• pp.451-476
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• 2015

Membrane distillation (MD), which can utilize low-grade thermal energy, has been extensively studied for desalination. By incorporating solar thermal energy, the solar membrane distillation desalination system (SMDDS) is a potential technology for resolving the energy and water resource problems. Small-scale SMDDS (s-SMDDS) is an attractive and viable option for the production of fresh water for small communities in remote arid areas. The minimum-cost design and operation of s-SMDDS are determined by a systematic method, which involves a pseudo steady state approach for equipment sizing and the dynamic optimization using overall system mathematical models. The s-SMDDS employing three MD configurations, including the air gap (AGMD), direct contact (DCMD) and vacuum (VMD) types, are optimized. The membrane area of each system is $11.5m^2$. The AGMD system operated for 500 kg/day water production rate gives the lowest unit cost of $5.92/m^3$. The performance ratio and recovery ratio are 0.85 and 4.07%, respectively. For the commercial membrane employed in this study, the increase of membrane mass transfer coefficient up to two times is beneficial for cost reduction and the reduction of membrane heat transfer coefficient only affects the cost of the DCMD system.