• Korean Chemical Engineering Research
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• 제52권3호
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• pp.355-359
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• 2014

최근 목질계, 미세조류, 해양 거대조류 등의 재생가능한 자원으로부터 생산된 많은 화학물질들이 화학산업에 도입되고 있다. 키틴/키토산은 지구상에서 두 번째로 풍부한 자원이며, 게, 새우, 곤충과 같은 갑각류의 껍질로부터 얻을 수 있다. 본 연구에서는 키토산으로부터 levulinic acid의 생산을 위하여 고온 산 가수분해와 실험계획법을 적용하여 반응온도, 촉매량, 반응시간의 반응조건을 최적화 하였다. 결과적으로 반응온도와 촉매농도는 높을수록 levulinic acid의 생성이 증가하였고, 반응시간은 일정시간 이후에는 크게 영향을 미치지 못하였다. 최적 반응조건을 조사한 결과, 반응온도 $175^{\circ}C$, 촉매농도 2.4%, 그리고 반응시간 40.7분의 조건에서 2.7 g/L의 levulinic acid를 얻었다.

• 한국해양공학회지
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• 제21권5호
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• pp.55-60
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• 2007

Bellows are mechanical components which prevent the damage of system by absorption of the vibration and the displacement of axle and radial direction. Thermal piping system is expanded by the fluid of the high temperature from the heat engine inside. At this time, bellows prevent the damage of the piping due to the thermal expansion. Recently, design of bellows is required to fit some other operational environments which are not suggested in the E.J.M.A code book. And it is difficult to produce and to maintain bellows of high temperature and high pressure bemuse of its complicated shape and this causes the manufacturing cost to rise. The objective of this study is to determine optimum shape of bellows which can endure in the high temperature and high pressure. The maximum stress has an effect on the fatigue life of bellows, therefore it needs to be minimized. This study attempts to find a shape which minimizes the stress occurring in the bellows by the design of experiment. The model used in this study is not presented in the E.J.M.A code book, therefore, from the result of design of experiment we find the factors which give effects on the characteristic value and we presents the recession model using the RSM, which can predict the characteristic values depending on the change of factor values.

• 대한전자공학회논문지SP
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• 제41권5호
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• pp.251-258
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• 2004

본 논문은 디지털 카메라로 획득된 실영상에서 카메라의 응답분포의 특성을 이용하여 광원의 색도값을 추정하는 방법을 제안한다. 광휘도 영역을 이용하는 방법은 물체의 표면에 의한 색과 광원에 의한 색이 일정하게 변하는 특징을 이용하여 광원의 색도값을 추정한다. 일반적인 디지털 카메라 영상의 경우, 광휘도 영역의 화소들은 실영상에서 야기되는 광원의 기하학적 불균일성, 카메라에 의한 양자화 오차 및 CCD 센서의 불균일한 특성들을 포함하는 값이다. 그러므로 전처리 과정이 없는 카메라의 응답을 이용하여 광원을 추정한 결과, 정확한 광원의 색도값 추정이 어려웠다. 따라서 이 문제를 해결하기 위해서 본 논문에서는 카메라의 응답 특성을 조사하고, 광휘도 영역에서 Mahalanobis distance를 이용하여 화소들을 선택함으로써, 광원 추정의 정확성을 높이고자 하였다. 카메라 응답에서 Mahalanobis distance의 사용함으로써 광휘도 영역에서 분포된 화소들 중에서 유효한 화소들을 선택하는 것이 가능하다. 선택된 화소들을 주성분 분석 과정을 이용하여 r-g 좌표계에서 직선을 만들었으며, 그 직선들의 교차점으로부터 광원의 색도값을 추정하였다. 제안한 방법을 이용하여 다양한 실영상에서 실험한 결과 기존의 방법에 비해 광원 추정에 대한 오차가 감소함을 확인하였다.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제44권2호
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• pp.59-65
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• 2018

Objectives: This study aimed to optimize the thread depth and pitch of a recently designed dental implant to provide uniform stress distribution by means of a response surface optimization method available in finite element (FE) software. The sensitivity of simulation to different mechanical parameters was also evaluated. Materials and Methods: A three-dimensional model of a tapered dental implant with micro-threads in the upper area and V-shaped threads in the rest of the body was modeled and analyzed using finite element analysis (FEA). An axial load of 100 N was applied to the top of the implants. The model was optimized for thread depth and pitch to determine the optimal stress distribution. In this analysis, micro-threads had 0.25 to 0.3 mm depth and 0.27 to 0.33 mm pitch, and V-shaped threads had 0.405 to 0.495 mm depth and 0.66 to 0.8 mm pitch. Results: The optimized depth and pitch were 0.307 and 0.286 mm for micro-threads and 0.405 and 0.808 mm for V-shaped threads, respectively. In this design, the most effective parameters on stress distribution were the depth and pitch of the micro-threads based on sensitivity analysis results. Conclusion: Based on the results of this study, the optimal implant design has micro-threads with 0.307 and 0.286 mm depth and pitch, respectively, in the upper area and V-shaped threads with 0.405 and 0.808 mm depth and pitch in the rest of the body. These results indicate that micro-thread parameters have a greater effect on stress and strain values.

• Journal of Periodontal and Implant Science
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• 제25권2호
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• pp.192-209
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• 1995

The purpose of this study was to evaluate drug-loaded biodegradable membranes for guided tissue regeneration(GTR). The membranes were made by coating mesh of polyglycolic acid(PGA) with polylactic acid(PLA) containing 10% flurbiprofen or tetracycline. The thickness of membrane was $150{\pm}30{\mu}m$, and the pore size of surface was about $8{\mu}m$ in diameter. The release of drugs from the membrane was measured in vitro. Cytotoxity test for the membrane was performed by gingival fibroblast cell culture, and the tissue response was observed after implant of membrane into the dorsal skin of the rat for 8 wks. Ability to guided tissue regeneration of membranes were tested by measuring new bone in the calvarial defects(5mm in diameter) of the rat for 5 weeks. The amount of flurbiprofen and tetracycline released from membrane were about 30-60% during 7 days. Minimal cytotoxity was observed in the membrane except 20% drug containing membrane. In histologic finding of rat dorsal skin, many inflammatory cells were observed around e-PTFE, polyglactin 910 and PLAPGA membrane after 1 or 2 weeks. PLA-PGA membrane was perforated by connective tissue after 4 or 6 weeks, and divided as a segment at 8 weeks. In bone regeneration guiding potential test, tetracycline loaded membrane was most effective (p

• 대한치과보철학회지
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• 제46권6호
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• pp.602-609
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• 2008

STATEMENT OF PROBLEM: Loss of the marginal bone to the first thread have been accepted but continuous effort have been made to reduce this bone loss by varying implant design and surface texture. PURPOSE: This animal study has examined the histomorphometric variations between implants with micro-thread, micro-grooved and turned surfaced neck designs. MATERIAL AND METHODS: Four mongrel dogs have been used the premolars removed and left to heal for three months. One of each implant systems with turned neck, micro-thread and micro-grooved were placed according to the manufacturers’protocol and left submerged for 8 and 12 weeks. These were then harvested for histological examination. RESULTS: The histologically all samples were successfully ossointegrated and active bone remodelling adjacent to implants. With the micro-grooved implants 0.40 mm and 0.26 mm of the marginal bone level changes were observed at 8 and 12 weeks respectively. The micro-threaded implants had changes of 0.79 mm and 0.56 mm at 8 and 12 weeks respectably. The turned neck designed implants had marginal bone level changes of 1.61 mm and 1.63 mm in 8 and 12 weeks specimens. A complex soft tissue arrangement could be observed against micro-threaded and micro-grooved implant surfaces. CONCLUSION: Within the limitations of this study, it could be concluded that implants with micro-grooved had the least and the turned neck designed implants had the most changes in the marginal bone level. The textured implant surfaces affect soft tissue responses.

• 생물정신의학
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• 제11권1호
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• pp.40-48
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• 2004

Objective:Event-related potentials(ERPs) are electrical changes recorded at the surface of the scalp in response to stimulus presentation, and their latency and amplitude change according to cognitive processes. Through past studies of the auditory ERP in schizophrenia, the P300 has been reported to be statistically smaller and delayed in schizophrenia than comparison groups. However, studies of the visual ERP have not been systematically examined. The present study was designed to investigate the visual P300 in patients with schizophrenia and normal controls and to compare the pattern of P300 between them. Methods:The subjects were composed of patients(N=22) with schizophrenia by DSM-IV and normal controls(N=22). The visual ERPs were measured by the visual continuous performance test. P300 amplitude and latency measured on 5 scalp electrodes(Fz, Cz, Pz, $T_7$, $T_8$) were compared between patients and controls. Results:The P300 latencies measured on Fz, Cz, Pz, and $T_7$ electrodes were significantly longer in patients than controls(p<0.05). The P300 amplitudes in patients were smaller than controls. However, the difference between them was not statistically significant. Conclusion:Analysis of the visual ERPs showed that the P300 latency is significantly delayed and the P300 amplitude is slightly smaller in patients than controls. These results are similar to established studies of the auditory P300 in schizophrenia.

• 대한기계학회논문집A
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• 제35권10호
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• pp.1273-1279
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• 2011

자동차 압축기는 연비 개선효과를 위해 가변 사판형 압축기를 사용한다. 가변 사판의 회전 토크와 피스톤에 작용하는 압력은 사판의 형상과 변형에 중요한 영향을 미친다. 본 논문은 Chebyshev 직교다항식과 최적화 기법을 이용하여 가변 사판의 최적 형상을 결정하였다. 사판의 설계 요구사항은 정상 운전상태에서 최대 응력과 변형을 최소화하면서 체적을 감소시키는 것이다. 직교배열표, 분산분석과 반응표면최적화 방법은 최적 설계변수를 결정하고 주효과를 찾는데 사용하였다. 최적설계 결과로부터, 사판의 유의한 설계변수를 확인하고 이의 최적해와 설계요구조건 만족에 대한 유용성을 설명하였다.

• 한국수산과학회지
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• 제45권3호
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• pp.232-237
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• 2012

Snow crab Chionoecetes japonicus cooker effluent (SCCE) is a processing byproduct that is produced in large quantities during snow crab processing. However, it is typically discarded due to the lack of a suitable application or used only as a seasoning following simple concentration. We performed a series of studies to make crab-like flavorings (CFs) from SCCE using response surface methodology and reaction flavor technology. To develop material for CFs, taste compounds in the precipitate of SCCE (PSCCE) and the enzymatic hydrolysate of PSCCE (EHSCCE) were analyzed. The content of free amino acids in EHSCCE was 21.6 times higher than that in PSCCE. The major compounds in PSCCE were arginine, glycine, taurine, alanine and sarcosine in that order; leucine, phenylalanine, arginine, valine and lysine were the major compounds in EHSCCE. Six nucleotides and related compounds were identified in EHSCCE. Hypoxanthine ($40.3{\mu}g/100g$) was the most abundant, followed by 5'-GMP ($22.9{\mu}g/100g$), ADP ($22.5{\mu}g/100g$), AMP ($21.0 {\mu}g/100g$), inosine ($3.6{\mu}g/100g$) and 5'-IMP ($2.3{\mu}g/100g$).

• Fisheries and Aquatic Sciences
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• 제18권1호
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• pp.51-56
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• 2015

A 8-week trial was conducted to evaluate the effects of photoperiod manipulation on the growth performance and hematological parameters of juvenile Caspian roach, Rutilus rutilus caspicus (average weight $1.46{\pm}0.12g$ mean${\pm}$SD) reared under five photoperiods (24 h Light, 24L; 18 h Light & 6 h Dark, 18L:6D; 12 h Light & 12 h Dark, 12L:12D; 6 h Light & 18 h Dark, 6L:18D; 24 h Dark, 24D) with constant light intensity 1,500 lx on the water surface. Triplicate of 20 fish were allocated into each of 15 fiberglass tanks of 50 L capacity and they were fed three times per day with the commercial feed (SFK, Co., Sari - Iran) contains 50.0% protein and 10.5% lipid. At the end of experimental period, final body weight, weight gain and specific growth rates of fish exposed to 24L were significantly higher than those of fish exposed to 12L:12D, 6L:18D and 24D (P < 0.05). Red blood cell and hemoglobin of fish exposed to 24L were significantly higher than those of fish exposed to 24D. No significant difference observed in hematocrit, white blood cell and plasma glucose among the different treatments groups. Therefore, these results demonstrated that the growth performance of juvenile Caspian roach can be significantly stimulated by using 24L and 18L:6D photoperiods without any measurable significant stress response such as plasma glucose concentration.