• 한국세라믹학회지
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• 제41권11호
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• pp.851-857
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• 2004

전기로 제강분진(EAF dust)이 첨가된 규산염 유리, 붕규산염 유리 그리고 납규산염 유리 내의 중금속 안정화 특성을 독성용출 시험법(TCLP)으로 조사하였다. 또한 XRD와 FT-IR 방법을 통하여 EAF dust 첨가량에 따른 유리의 구조변화가 TCLP 결과에 미치는 영향을 고찰하였다. 모유리에 EAE dust를 30 wt%까지 첨가하여도 규산염 유리, 붕규산염 유리, 납규산염 유리 계열의 시편 모두 결정화가 발생되지 않고 비정질을 나타내었다. TCLP법에 의한 유리시편의 중금속 용출량은 EAF dust의 첨가량과 함께 증가되었다. 중금속 용출이 가장 적은 시편은 규산염 유리 계열이었으며 납규산염 유리 계열의 시편은 붕규산염 유리 계열에 비해 중금속 용출량이 상대적으로 적었다. 단, 납규산염 유리 계열 모유리 조성에 포함되어 있는 납의 영향으로 Pb용출은 납규산염 유리 계열시편에서 가장 많았다. Oxygen/network former ratio 값을 이용하여 같은 계열 시편 간의 화학적 내구성을 비교할 수 있었으나 다른 계열 시편 간에는 적절치 않았다. EAF dust가 첨가되면 규산염 유리 계열의 시편에서는 유리구조 내 Si-O-Si 대칭성이 감소되고 비가교 산소가 증가되어 유리의 구조를 약화시키고 화학적 내구성을 감소시켰다 붕규산염 유리 계열 시편에서 EAF dust가 첨가되면 tetraborate group이 diborate group으로 변화되고 2차원 층상구조인 pyre-와 ortho-borate도 형성되어 결국 구조약화를 가져왔다. 3가지 계열의 유리조성 중에서 EAF dust내의 중금속들을 안정화하는데 가장 적합한 것은 규산염 유리 계열의 시편으로 판단되었다.

• 한국결정학회지
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• 제16권2호
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• pp.75-80
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• 2005

[ $LiK_{1-x}Rb_{x}SO_{4}(x=0.1,\;0.2)$ ]의 결정을 313K에서 수용액법으로 성장시켰다. 결정구조는 X-ray 회절법을 이용하여 동일한 공간군 $P6_{3}(#173)$에서 수행되었다. 동일한 대칭성을 가진 두 화합물은 각각 3회 회전축에 위치하고 있는 Li과 $SO_{4}^{2-}$ 이온들이 서로 무한히 연결된 3차원적 그물구조를 형성하고 있고, 6회 회전축에 위치하고 있는 K와 Rb원자들은 각각 12개와 15개의 O 원자들과 배위를 이루고 있다. K와 Rb의 점유도는(0.91 : 0.09), (0.77 : 0.23)으로 정밀화 하였을 때 가장 안정된 상태에 도달하였다.

• 대한기계학회논문집A
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• 제26권5호
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• pp.914-923
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• 2002

Recently, there has been considerable interest in micro gyroscopes made of silicon chips. It can be applied to many micro-electro-mechanical systems (MEMS): devices for stabilization, general rate control, directional pointing, autopilot systems, and missile control. This paper shows how the mechanical design of the gyroscope can be done using axiomatic design, followed by the application of the Taguchi robust design method to determine the dimensions of the parts so as to accommodate the dimensional variations introduced during manufacturing. Functional requirements are defined twofold. One is that the natural frequencies should have fixed values, and the other is that the system should be robust to large tolerances. According to the Independence Axiom, design parameters are classified into a few groups. Then, the detailed design process is performed fellowing the sequence indicated by the design matrix. The dimensions of the structure are determined to have constant values fur the difference of frequencies without consideration of the tolerances. It is noted that the Taguchi concept is utilized as a unit process of the entire axiomatic approach.

• Journal of Advanced Marine Engineering and Technology
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• 제35권7호
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• pp.957-965
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• 2011

The wakes of a cylindrical body have been investigated. The cylindrical body was attached with a thin film. The film is made of silicon with configurations of 50mm(W) ${\times}$ 150mm(L) ${\times}$ 0.3mm(T). The cylinder wakes have been measured with PIV experiments under the conditions with and without the thin film. The diameter of the installed cylinder body is 30mm and the Reynolds numbers are 2730, 6160 and 9750 with the diameter. The measurement system consists of an Ar-ion laser(6W), a high speed camera(1024 ${\times}$ 992 pixel, 500fps) and a host computer. FFT analyses have been carried out using the velocity vectors obtained by PIV measurements at the point X/D=1.52 and Z/D=0.52. For understanding the three-dimensional flow structures, a new Volumetric PTV(particle tracking velocimetry) has been constructed, in which the same four high-resolution cameras have been used. It has been verified that the flexible film suppresses or damps the vortices separated from the cylinder body, which makes the cylinder's wakes stable. With increase of Re numbers the intensity of the dominant frequency of the wakes become smaller.

• 한국안전학회지
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• 제27권1호
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• pp.20-25
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• 2012

The purpose of the study is to assess the extinguishing concentration of inert gases in engine nacelle fire. The experiment was performed with a two dimensional rectangular bluff body stabilized flames, where the fuel was ejected to counter flow and co-flow against an oxidizer stream. Two inert gases, $CO_2$ and $N_2$, were used for extinguishing agent in the oxidizer and methane was used for fuel. The main experimental parameters were the direction of injecting fuel, the kinds of agent and the velocity ratio between air and fuel streams, which controlled the mixing characteristic near bluff body and the strength of recirculation zone in the downstream. The result shows the flame structure and the mode were strongly dependent with fuel/air ratio and the fuel jet direction. For both flow configurations, the extinguishing concentration of $CO_2$ was smaller than the $N_2$ because of the large heat capacity of $CO_2$. However, the concentration of inert gasesat blowout was much smaller than those in the cup burner and coflow jet diffusion flames, which implies that the extinction mechanism of bluff body stabilized flames was mainly due to the aerodynamic aspect. Compared to co-flow fuel injection, the extinguishing concentration of inert gases under counter flow configuration was lower. The effect of direction might result from the mixing characteristic and strength of recirculation zonearound a bluff body. More details should be investigated for the characteristic of recirculation zone in the wake of bluff body using the LES(Large Eddy Simulation).

• 한국항공우주학회지
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• 제32권6호
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• pp.110-116
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• 2004

고주파 연소불안정을 억제/방지하기 위해서는 가장 먼저 로켓엔진 연소기 내에서 나타나는 음향학적 특성을 파악하여야 하며, 수동안정화기구의 장착에 따른 음향안정성 여분을 정량적으로 비교/평가하는 것이 필수적이다. 본 연구에서는 기존의 실험적 평가방법을 대체할 수 있는 3차원 음향 해석코드를 개발하였으며, KSR-III 엔진 개발과정을 통해 수행되었던 상온음향 시험결과와 비교를 통해 신뢰도를 검증하였다. 연소기내의 주파수 응답특성을 잘 예측하였으며, 특히 배플 장착에 따른 음향감쇠효과를 정량적으로 나타내는 감쇠인 자비와 공진주파수 변이에 대해 실험결과와 일치하는 결과를 나타내었다. 따라서 향후 수동안정화기구를 설계/해석하는데 있어 유용하게 활용할 수 있을 뿐 아니라, 연소안정화와 관련된 다양한 연구에 폭넓게 활용될 수 있을 것으로 판단된다.

• Journal of Microbiology and Biotechnology
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• 제29권11호
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• pp.1830-1840
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• 2019

Loliolide is one of the most ubiquitous monoterpenoid compounds found in algae, and its potential therapeutic effect on various dermatological conditions via agent-induced biological functions, including anti-oxidative and anti-apoptotic properties, was demonstrated. Here, we investigated the effects of loliolide on hair growth in dermal papilla (DP) cells, the main components regulating hair growth and loss conditions. For this purpose, we used a three-dimensional (3D) DP spheroid model that mimics the in vivo hair follicle system. Biochemical assays showed that low doses of loliolide increased the viability and size of 3D DP spheroids in a dose-dependent manner. This result correlated with increases in expression levels of hair growth-related autocrine factors including VEGF, IGF-1, and KGF. Immunoblotting and luciferase-reporter assays further revealed that loliolide induced AKT phosphorylation, and this effect led to stabilization of β-catenin, which plays a crucial role in the hair-inductive properties of DP cells. Further experiments showed that loliolide increased the expression levels of the DP signature genes, ALP, BMP2, VCAN, and HEY1. Furthermore, conditioned media from loliolide-treated DP spheroids significantly enhanced proliferation and the expression of hair growth regulatory genes in keratinocytes. These results suggested that loliolide could function in the hair growth inductivity of DP cells via the AKT/β-catenin signaling pathway.

• Journal of Korean Neurosurgical Society
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• 제44권1호
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• pp.15-18
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• 2008

Objective : C2 laminar screw fixation is considered as an excellent alternative to Magerl's transfacetal approach or Harms construct for the atlantoaxial stabilization. However, to our knowledge, there is no report on the feasibility of the new approach to Korean population. We investigated morphometric parameters of the dorsal arch of the C2 to provide the quantitative data for the feasibility of laminar screw fixation. Methods : One-hundred-and-two patients' cervical computed tomography had been reconstructed and investigated on the anatomical parameters related with C2 laminar screw placement. Sixty patients were male and forty-two patients were female. Measurements included the laminar thickness and slope, spino-laminar angle, and maximal screw length. Results : Ages ranged from 20 to 81 and the mean age was 48.4. Mean laminar thickness was 5.7 mm (${\pm}1.0$) (5.8 mm in male and 5.4 mm in female). Fifty-one patients (50%) had a laminar thickness smaller than 5.5 mm at least unilaterally, therefore the patients were considered as inappropriate candidates for the laminar screw fixation in the smaller side of the laminae. Mean value of maximal length of screw was 33.3 mm (34.3 mm in male and 31.9 mm in female). Mean spino-laminar angle was $43.2^{\circ}$ and mean slope angle was $32.9^{\circ}$. Conclusion : Half of patients had inappropriate laminar profiles to accommodate a 3.5 mm screw in at least one side of the axis. The three-dimensional computed tomography reconstruction is mandatory for the preoperative assessment for the feasibility of the C2 lamina.

• 보존과학회지
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• 제24권
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• pp.57-66
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• 2008

출토 부분탄화 목제유물은 물성이 다른 부위가 공존하는 것에 의해 박리와 변형이 일어나기 쉬운 것으로 오래전부터 보고되어 왔지만, 실험연구 등을 통한 연구성과는 많지 않았다. 이번 실험에서는 당알코올법과 일반적으로 널리 사용되고 있는 친수성 수지인 Pdyethyleneglycol(PEG)법을 비교 대상 처리법으로 설정하였다. 중량변화율과 수축변화율, 전자현미경(SEM)관찰에 의한 목재조직의 변화양상을 검토한 결과 PEG4000법은 80%이상 농도까지 단계적 함침이 필요하며 Sugar Alcohol(S A)법은 40%농도 함침에서부터 안정적인 양상을 보여 단기간 함침의 가능성을 나타냈다. 본 연구에 사용한 판상 부분 탄화재의 변형은 주로 미탄화부의 수축에 의한 현상으로 생각되며 PEG4000법의 경우 최종 함침농도가 20%, 40%, 60%에서, S A법은 20%농도에 함침한 샘플에서 목재세포조직의 수축이 확인되었다.

• Journal of Microbiology and Biotechnology
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• 제22권1호
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• pp.34-45
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• 2012

A thermophilic Bacillus stearothermophilus F1 produces an extremely thermostable serine protease. The F1 protease sequence was used to predict its three-dimensional (3D) structure to provide better insights into the relationship between the protein structure and biological function and to identify opportunities for protein engineering. The final model was evaluated to ensure its accuracy using three independent methods: Procheck, Verify3D, and Errat. The predicted 3D structure of F1 protease was compared with the crystal structure of serine proteases from mesophilic bacteria and archaea, and led to the identification of features that were related to protein stabilization. Higher thermostability correlated with an increased number of residues that were involved in ion pairs or networks of ion pairs. Therefore, the mutants W200R and D58S were designed using site-directed mutagenesis to investigate F1 protease stability. The effects of addition and disruption of ion pair networks on the activity and various stabilities of mutant F1 proteases were compared with those of the wild-type F1 protease.