• 대한환경공학회지
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• 제39권10호
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• pp.549-555
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• 2017

본 연구는 오존용해탱크 구조에 따라 마이크로오존버블의 분포, 에너지 소비, 수처리 효율이 어떻게 변하는지를 알아보고자 하였다. 오존용해탱크 내부의 격판은 압력의 변화, 전단력, 선회유동을 발생시키고 이는 버블 직경의 크기에 변화를 준다. 버블 직경의 크기는 내부의 격판에 따라 10.5%까지 차이가 났다. 오존 버블 직경의 변화는 에너지 소비와 관련이 깊다. 오존 버블이 작아질수록 버블생성에너지는 높아지지만 용존 효율이 올라가면서 오존생산에너지는 줄어들게 된다. 따라서 버블생성에너지와 오존생산에너지의 합이 최소인 마이크로오존버블을 생성하는 오존용해탱크를 선정하여야 한다. 동일한 양의 오존가스을 방류수에 주입하기 위해 소비된 에너지는 내부의 격판에 따라 2.5%까지 차이가 났다. 하지만 수처리 효율까지 고려한다면 오존용해탱크 선정 조건이 달라진다. 오존 버블이 작아질수록 증가하는 자유라디칼이 수처리에 매우 효율적이기 때문이다. 동일한 오존주입농도에서도 내부의 격판에 따라 수처리 효율이 10.4%까지 차이가 났다. 따라서 수처리 효율과 에너지 효율을 고려하여 합리적인 마이크로오존버블을 생성하는 오존용해탱크 구조에 대하여 연구하였다.

• Bulletin of the Korean Chemical Society
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• 제35권6호
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• pp.1713-1719
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• 2014

1FSD is a 28-residue designed protein with a ${\beta}{\beta}{\alpha}$ motif. Since this protein displays most essential features of protein structures in such a small size, this model protein can be an outstanding system for evaluating the balance in the propensity of the secondary structures and the quality of all-atom protein force fields. Particularly, this protein would be difficult to fold to its correct native structure without establishing proper balances between the secondary structure elements in all-atom energy functions. In this work, a series of the recently optimized five amber protein force fields [$ff03^*$, $f99sb^*$-ildn, ff99sb-${\phi}^{\prime}$-ildn, ff99sb-nmr1-ildn, ff99sb-${\Phi}{\Psi}$(G24, CS)-ildn] were investigated for the simulations of 1FSD using a conventional molecular dynamics (MD) and a biased-exchange meta-dynamics (BEMD) methods. Among those tested force fields, we found that ff99sb-nmr1-ildn and ff99sb-${\Phi}{\Psi}$(G24, CS)-ildn are promising in that both force fields can locate the native state of 1FSD with a high accuracy (backbone rmsd ${\leq}1.7{\AA}$) in the global free energy minimum basin with a reasonable energetics conforming to a previous circular dichroism (CD) experiment. Furthermore, both force fields led to a common set of two distinct folding pathways with a heterogeneous nature of the transition state to the folding. We anticipate that these force fields are reasonably well balanced, thereby transferable to many other protein folds.

• Elastomers and Composites
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• 제36권1호
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• pp.44-51
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• 2001

카본블랙의 화학적 표면개질에 따른 영향을 조사하기 위해 3종류 화학약품(KOH, $H_3PO_4$, 벤젠)을 이용하여 카본블랙 표면을 처리하였으며, 이를 함유한 스티렌-부타디엔 고무(SBR)의 가황특성과 기계적 특성을 조사하였다. 산(HCB)이나 염기(KCB)로 표면 처리할 경우 표면 자유에너지의 증가가 관찰된 반면, 벤젠(BCB)의 경우 미세한 증가만이 관찰되었다. London 비극성 성분은 BCB가 가장 높았다. 각 표면처리 카본블랙을 함유한 SBR 컴파운드의 가황반응의 빠르기는 KCB-SBR>BCB-SBR>VCB- SBR(무처리)>HCB-SBR의 순으로 나타났다. 일반적으로 가교도를 나타내는 가황곡선상의 최대토오크와 최소토오크의 차이는 VCB-SBR, KCB-SBR, HCB-SBR에 비해 BCB-SBR이 높은 값을 나타내었다. BCB-SBR과 KCB-SBR의 경우 인장특성과 동적기계적 특성이 증진되었다. 표면자유에너지 중 London 비극성 요소와 기계적 특성간에는 비례관계가 있음이 확인되었다.

• Korean Journal of Radiology
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• 제22권2호
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• pp.179-188
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• 2021

Objective: This study aimed to prospectively compare the efficacy, safety, and mid-term outcomes of dual-switching monopolar (DSM) radiofrequency ablation (RFA) to those of conventional single-switching monopolar (SSM) RFA in the treatment of hepatocellular carcinoma (HCC). Materials and Methods: This single-center, two-arm, parallel-group, randomized controlled study was approved by the Institutional Review Board. Written informed consent was obtained from all patients upon enrollment. A total of 80 patients with 94 HCC nodules were randomized into either the DSM-RFA group or SSM-RFA group in a 1:1 ratio, using a blocked randomization method (block size 2). The primary endpoint was the minimum diameter of the ablation zone per unit time. The secondary endpoints included other technical parameters, complication rate, technique efficacy, and 2-year clinical outcomes. Results: Significantly higher ablation energy per unit time was delivered to the DSM-RFA group than to the SSM-RFA group (1.7 ± 0.2 kcal/min vs. 1.2 ± 0.3 kcal/min; p < 0.001). However, no significant differences were observed between the two groups for the analyzed variables, including primary endpoint, regarding size of the ablation zone and ablation time. Major complication rates were 4.9% in the DSM-RFA group and 2.6% in the SSM-RFA group (p = 1.000). The 2-year local tumor progression (LTP) rates of the HCC nodules treated using DSM-RFA and SSM-RFA were 8.5% and 4.7%, respectively (p = 0.316). The 2-year LTP-free survival rates of patients in the DSM-RFA and SSM-RFA groups were 90.0% and 94.4%, respectively (p = 0.331), and the 2-year recurrence-free survival rates were 54.9% and 75.7%, respectively (p = 0.265). Conclusion: Although DSM-RFA using a separable clustered electrode delivers higher ablation energy than SSM-RFA, its effectiveness failed to show superiority over SSM-RFA in the treatment of HCC.

• 한국정밀공학회지
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• 제19권5호
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• pp.149-158
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• 2002

Recently, the minimum line width shows a tendency to decrease and the multi-level increases in semiconductor. Therefore, a planarization technique is needed and chemical mechanical polishing(CMP) is considered as one of the most suitable process. CMP accomplishes a high polishing performance and a global planarization of high quality. However there are several defects in CMF, such as micro-scratches, abrasive contaminations and non-uniformity of polished wafer edges. Wet etching process including spin-etching can eliminate the defects of CMP. It uses abrasive-free chemical solution instead of slurry. On this study, ILD(Interlayer-Dielectric) was removed by CMP and wet etching process using DHF(Diluted HF) in order to investigate the possibility of planrization by wet etching mechanism. In the thin film wafer, the results were evaluated from the viewpoint of material removal rate(MRR) and within wafer non-uniformity(WIWNU). And the pattern step heights were also compared for the purpose of planarity characterization of the patterned wafer. Moreover, Chemical polishing process which is the wet etching process with mechanical energy was introduced and evaluated for examining the characteristics of planarization.

• Advances in aircraft and spacecraft science
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• 제3권2호
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• pp.113-148
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• 2016

In a whole variety of higher order plate theories existing in the literature no consideration is given to the transverse normal strain / deformation effects on flexural response when these higher order theories are applied to shear flexible composite plates in view of minimizing the number of unknown variables. The objective of this study is to carry out cylindrical bending of simply supported laminated composite and sandwich plates using sinusoidal shear and normal deformation plate theory. The most important feature of the present theory is that it includes the effects of transverse normal strain/deformation. The displacement field of the presented theory is built upon classical plate theory and uses sine and cosine functions in terms of thickness coordinate to include the effects of shear deformation and transverse normal strain. The theory accounts for realistic variation of the transverse shear stress through the thickness and satisfies the shear stress free conditions at the top and bottom surfaces of the plate without using the problem dependent shear correction factor. Governing equations and boundary conditions of the theory are obtained using the principle of minimum potential energy. The accuracy of the proposed theory is examined for several configurations of laminates under various static loadings. Some problems are presented for the first time in this paper which can become the base for future research. For the comparison purpose, the numerical results are also generated by using higher order shear deformation theory of Reddy, first-order shear deformation plate theory of Mindlin and classical plate theory. The numerical results show that the present theory provides displacements and stresses very accurately as compared to those obtained by using other theories.

• Nuclear Engineering and Technology
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• 제48권6호
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• pp.1396-1403
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• 2016

In this study, fast-curing shielding materials were prepared with a two-component polyurethane matrix and a filler material of PbO through a one-step, laboratory-scale method. With an increase in the filler content, viscosity increased. However, the two components showed a small difference. Curing time decreased as the filler content increased. The minimum tack-free time of 27 s was obtained at a filler content of 70 wt%. Tensile strength and compressive strength initially increased and then decreased as the filler content increased. Even when the filler content reached 60 wt%, mechanical properties were still greater than those of the matrix. Cohesional strength decreased as the filler content increased. However, cohesional strength was still greater than 100 kPa at a filler content of 60 wt%. The ${\gamma}$-ray-shielding properties increased with the increase in the filler content, and composite thickness could be increased to improve the shielding performance when the energy of ${\gamma}$-rays was high. When the filler content was 60 wt%, the composite showed excellent comprehensive properties.

• 한국정보전자통신기술학회논문지
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• 제12권2호
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• pp.142-149
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• 2019

전기자동차를 무선으로 충전하기 위하여서는 전기에너지를 전송하기 위한 코일이 꼭 필요하다. 코일의 형태는 기본적인 원형 코일에서부터 두 코일 간의 커플링 효과를 높이기 위한 DD 형상의 코일 등 여러 종류가 있다. 하지만 코일 간 커플링이 좋은 DD 형상의 코일은 송수신 측 전력변환장치의 구조가 복잡해지는 단점이 있어 사용에 제한이 있다. 본 논문에서는 자유공간에서 2개의 코일을 이용하여 무선으로 전력을 전송할 때 제작이 편리한 스파이럴 인덕터의 인덕턴스 값을 계산하고 적절한 크기의 인턱터를 설계하는 방법을 제시하였다. 공진기에서 XLm 값이 부하저항 값과 비슷하여질 때 bifurcation 현상이 나타나므로, 이 현상이 덜 일어나도록 XLm 값을 최소부하저항 값과 같도록 선택하여 공진기에 필요한 인덕턴스 값을 계산하였다. 계산된 인덕턴스 값을 스파이럴 인덕터로 구현하기 위하여 스파이럴 인덕터에서 인덕턴스 값과 인턱터의 크기, 턴 수, 총 코일 길이와의 관계를 알아보았다. 또한, 두 개의 코일의 수평 이격에 따른 결합계수 k 값의 변화를 알아본 후 적절한 인덕터를 선정하였다.

• Tribology and Lubricants
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• 제40권1호
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• pp.17-23
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• 2024

This study analyzes the thermal effects on the performance of an air foil thrust bearing (AFTB) using COMSOL Multiphysics to approximate actual bearing behavior under real conditions. An AFTB is a sliding-thrust bearing that uses air as a lubricant to support the axial load. The AFTB consists of top and bump foils and supports the rotating disk through the hydrodynamic pressure generated by the wedge effect from the inclined surface of the top foil and the elastic deformation of the bump foils, similar to a spring. The use of air as a lubricant has some advantages such as low friction loss and less heat generation, enabling air bearings to be widely used in high-speed rotating systems. However, even in AFTB, the effects of energy loss due to viscosity at high speeds, interface frictional heat, and thermal deformation of the foil caused by temperature increase cannot be ignored. Foil deformation derived from the thermal effect influences the minimum decay in film thickness and enhances the film pressure. For these reasons, performance analyses of isothermal AFTBs have shown few discrepancies with real bearing behavior. To account for this phenomenon, a thermal-fluid-structure analysis is conducted to describe the combined mechanics. Results show that the load capacity under the thermal effect is slightly higher than that obtained from isothermal analysis. In addition, the push and pull effects on the top foil and bump foil-free edges can be simulated. The differences between the isothermal and thermal behaviors are discussed.

• 농업과학연구
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• 제8권1호
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• pp.44-50
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• 1981

한국재래산양(韓國在來山羊)에 대(對)한 단백질(蛋白質)의 요구량(要求量)을 구명(究明)하기 위(爲)하여 생체종별(生體種別)로 단백질(蛋白質)의 급여수준(給與水準)에 차이(差異)를 두고 질소(窒素)의 축적율(蓄積率)을 측정(測定)하였고 혈청(血淸)의 단백질(蛋白質) 및 요소(尿素)의 함량(含量)을 조사(調査) 분석(分析)한 결과(結果)는 다음과 같다. l. 생후(生後) 8개월령(個月令)의 생체중(生體重) 14kg의 빈산양(牝山羊)에 대(對)하여 무단백질사료(無蛋白質飼料)를 급여(給與)하여 측정(測定)한 내인성요질소량(內因性尿窒素量)은 1일(日) 평균(平均) 1.29g이었으며, 내인성(內因性) 분질소량(糞窒素量)은 1.27g이었다. 따라서 1일(日) 최소(最少) 단백질(蛋白質) 요구량(要求量)은 22g이다. 2. 기온(氣溫)이 영하(零下) $10^{\circ}C$이하(以下)로 하강(下降)할때는 단백질수준(蛋白質水準)을 20%로 급여(給與)하여도 질소축적율(窒素蓄積率)이 부(負)를 나타내므로 energy의 소모량(消耗量)이 많은 것으로 추측(推測)된다. 3. 생체중(生體重) 20kg의 임신(姙娠)한 빈산양(牝山羊)의 질소(窒素) 축적율(蓄積率)은 17~20%로서 성장중(成長中)인 산양(山羊)에 비(比)하여 낮았다. 4. 혈청(血淸)의 단백질(蛋白質) 및 요소함량(尿素含量)은 단백질(蛋白質) 급여수준(給與水準)의 저하(低下)에 따라서 현저(顯著)하게 저하(低下)되었다.