• 환경생물
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• 제38권1호
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• pp.82-92
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• 2020

축산 폐수는 고농도의 영양염류와 중금속을 함유하고 있어, 배출될 때 수질을 악화시킨다. 기존 처리 기술과 비교하여 bioremediation은 축산 폐수 처리에 유능하다. 특히, 미세조류는 오염물질 제거에 잠재력을 가지고 있다. 본 연구에서는 Ankistrodesmus bibraianus를 이용하여 축산 폐수 내 영양염류(질소(N), 인(P))와 중금속(구리(Cu), 아연(Zn))의 제거 가능성을 평가하고, A. bibraianus의 최적 배양조건을 확립하였다. 연구결과, 최적 배양조건은 28℃, pH 7, 광주기는 14:10 h로 설정되었다. N과 P의 단일 처리구(500, 1,000, 5,000, 10,000mg L^-1)에서 제거효율은 각각 22.9~80.6%와 11.9~50.0%였다. 또한, N과 P의 복합 처리구에서 제거효율은 각각 16.4~58.3%와 7.80~49.8%였다. Cu와 Zn의 단일 처리구(10, 30, 50mg L^-1)에서 제거효율은 각각 15.5~81.5%와 6.28~34.3%였다. 유사하게, Cu와 Zn의 복합 처리구에서 제거효율은 각각 16.7~74.5%와 5.58~27.5%였다. 또한 영양염류(N 및 P)와 중금속(Cu 및 Zn)의 성장 및 제거효율을 축산 폐수에 적용할 수 있음을 나타냈다. 본 연구의 결과에 따르면 A. bibraianus는 축산 폐수 내 영양염류와 중금속 제거에 이용할 수 있을 것으로 사료된다.

• 한국소음진동공학회논문집
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• 제23권4호
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• pp.332-337
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• 2013

This paper presents a subsequent research work on the roller design of IRB(isolation roller bearing) seismic isolation device presented in Part 1 by focusing on heat treatment. The hardness and friction factor are very important factors of material and after-treatment process selection. Normally, roller bearing consists of roller and retainer. The roller gets high pressure constantly, while the retainer gets tensile and compressive stress. Therefore, sensitive material selection and heat treatment of each part is quite important. In this experimental evaluation, carbon steel, chrome special steel and others are employed and their characteristics after heat treatment are identified. Each material is prepared by refining high frequency heat treatment. The friction factor and static load capacity of manufactured material are experimentally identified and destructive test of material is processed. Optimal material and heat treatment conditions for IRB roller bearing are determined based on experiment results.

• 대한안전경영과학회지
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• 제15권4호
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• pp.123-129
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• 2013

Among various manual materials handling tasks, pushing/pulling was known to be one of the risk factors for the low back and shoulder musculoskeletal disorders (MSDs). This study was conducted to find out an optimal solution set of the handle height and distance for 4-wheel cart with two vertical handles. Ten male college students participated in the pushing force measurement experiment. The face-centered cube design, one of the central composite designs, was applied for the experiment, and the isometric voluntary pushing force was measured in 9 treatment conditions. The second order response surface model was predicted by using the pushing strength as a response variable, and the handle height and distance as independent factors. According to the 2nd order response model, the handle height and distance showed nonlinear relationship with the isometric pushing strength. To maximize the 2nd order response model (pushing force), the handle height and distance were optimized. The optimal handle height was 'xyphoid process height - stature', and the optimal handle distance was '$1.25{\times}shoulder$ width'. When calculated using the anthropometric data of the subjects of this study, the optimal handle height was $115.4{\pm}3.4$ cm, slightly higher than the elbow height, and the handle distance was $52.9{\pm}2.3$ cm.

• Membrane and Water Treatment
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• 제13권2호
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• pp.105-110
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• 2022

Al₂O₃ positively charged nanofiltration composite membrane was successfully prepared with aluminate coupling agent (ACA) as modifier, sodium bisulfite (NaHSO₃) and potassium persulfate (K₂S₂O₈) as initiator and methacryloyloxyethyl trimethylammonium chloride (DMC) as crosslinking monomer. The surface of the membrane before grafting and after polymerization were characterized by SEM and FT-IR. Three factor and three-level orthogonal experiments were designed to explore the optimal conditions for membrane preparation, and the optimal group was successfully prepared. The filtration experiments of different salt solutions were carried out, and the retention molecular weight was determined by polyethylene glycol (PEG). The results showed that the polymerization temperature had the greatest effect on the rejection rate, followed by the reaction time, and the concentration of DMC had the least effect on the rejection rate. The rejection rates of CaCl₂, MgSO₄, NaCl and Na₂SO₄ in the optimal group were 83.8%, 81.3%, 28.1% and 23.6% (average value), respectively. The molecule weight cut-off of 90% (MWCO) of the optimal group was about 460, which belongs to nanofiltration membrane.

• 한국해양공학회지
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• 제25권5호
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• pp.33-39
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• 2011

This study involved a series of experiments, which included impact tests (drop weight & Charpy) and hardness tests under various heat treatment conditions, followed by fractography observations of Normal Roll Shell steel (NRS), Abnormal Roll Shell steel (ARS), and S25C steel, in order to analyze the cause of brittle fracture and damages in Roll Shell steel. The optimal tempering temperature was characterized for ARS and NRS.

• Journal of Korean Neurosurgical Society
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• 제66권1호
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• pp.6-11
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• 2023

Spinal cord injury (SCI) has a significant negative effect on the quality of life due to permanent neurologic damage and economic burden by continuous treatment and rehabilitation. However, determining the correct approach to ensure optimal clinical outcomes can be challenging and remains highly controversial. In particular, with the introduction of the concept of early decompression in brain pathology, the discussion of the timing of decompression in SCI has emerged. In addition to that, the concept of "time is spine" has been added recently, and the mortality and complications caused by SCI have been reduced by providing timely and professional treatment to patients. However, there are many difficulties in establishing international clinical guidelines for the timing of early decompression in SCI because policies for each country and medical institution differ according to the circumstances of medical infrastructure and economic conditions in the surgical treatment of SCI. Therefore, we aim to provide a current review of timing of early decompression in patient with SCI.

• Composites Research
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• 제30권6호
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• pp.416-421
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• 2017

CFRP와 금속간의 접합공정이 개선된 구조용 접착제가 제조되었다. 구조용 접착제에 대한 경화시간, 기지재료의 표면상태 그리고 접착제의 양에 따른 최적의 접합공정 조건을 랩쉐어 실험을 통하여 파악하였다. 적합한 접합조건을 확인하기 위해 이종재료간의 접합 파단면 상태를 반사현미경을 이용하여 평가하였다. 이종재료간 접합력 향상을 위해 접착제의 개선뿐만 아니라 CFRP의 표면처리 또한 중요하였다. 구조용 접착제의 경우 180도 조건에 20분의 경화온도 조건이 최적이였으며, CFRP의 표면 처리에 따라 접합특성이 향상됨을 확인하였다. 이종재료 간 접합을 위해 구조용 접착제의 양은 $1.5{\times}10^{-3}g/mm^2$ 조건일 때 최적이었다. 접합공정의 개선 및 최적화를 통해 기존의 접착력 대비 10% 이상의 물성 강화를 나타냄을 확인하였다.

• 한국수산과학회지
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• 제54권3호
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• pp.293-297
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• 2021

Herein, two experiments were performed to determine the appropriate pH range and immersion time for organic acid-activating treatment (OAT) in a Pyropia farm. The effects of pH (0.50, 0.75, 1.00, 1.25, 1.50, 1.75, and 2.00) on the cell mortality of Pyropia yezoensis and Ulva linza thalli were tested after 20 sec of immersion under OAT. In addition, the cell mortality of the two species was estimated under various combinations of immersion time (30, 60, and 120 sec) and pH (1.00, 1.50, and 2.00). Upon 20 sec of immersion under OAT conditions, the cell mortality of P. yezoensis did not differ at any pH but that of U. linza exceeded 90% at a pH range of 0.50-1.00. P. yezoensis showed little cell mortality upon 30 sec of immersion, but its mortality exceeded 55% upon 120 sec of immersion at a pH range of 1.00-1.50. U. linza showed 67.9-100% mortality at a pH of 1.50 and 100% mortality at a pH of 1.00, regardless of the immersion time (30-120 sec). These results indicate that for the effective removal of U. linza, the optimal pH range is 1.00-1.50 and the optimal immersion time is 20-30 sec.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1992년도 한국자동제어학술회의논문집(국제학술편); KOEX, Seoul; 19-21 Oct. 1992
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• pp.208-213
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• 1992

In this paper we are concerned with optimal control problems whose costs am quadratic and whose states are governed by linear delay equations and general boundary conditions. The basic new idea of this paper is to Introduce a new class of linear operators in such a way that the state equation subject to a starting function can be viewed as an inhomogeneous boundary value problem in the new linear operator equation. In this way we avoid the usual semigroup theory treatment to the problem and use only linear operator theory.

• Biotechnology and Bioprocess Engineering:BBE
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• 제8권3호
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• pp.210-212
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• 2003

Recombinant $\beta$-glucosidase from Thermus caldophilus GK24 was easily purified partially by a heat treatment procedure, resulting in 8-fold and recovery yield of 80% from crude enzyme. When the $\beta$-glucosidase was incubated with a 80% glucose solution (w/w), gentiobiose ($\beta$1,6-glucobiose) was the major product in the reaction mixture. The optimal conditions for producing gentiobiose (11% yields of total sugar) were pH 8-9 and 7$0^{\circ}C$ for 72 h.