• 한국재료학회지
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• 제27권10호
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• pp.513-517
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• 2017

An optimum route to fabricate a hybrid-structured W powder composed of nano and micro size powders was investigated. The mixture of nano and micro W powders was prepared by a ball milling and hydrogen reduction process for $WO_3$ and W powders. Microstructural observation for the ball-milled powder mixtures revealed that the nano-sized $WO_3$ particles were homogeneously distributed on the surface of large W powders. The reduction behavior of $WO_3$ powder was analyzed by a temperature programmed reduction method with different heating rates in Ar-10% $H_2$ atmosphere. The activation energies for the reduction of $WO_3$, estimated by the slope of the Kissinger plot from the amount of reaction peak shift with heating rates, were measured as 117.4 kJ/mol and 94.6 kJ/mol depending on reduction steps from $WO_3$ to $WO_2$ and from $WO_2$ to W, respectively. SEM and XRD analysis for the hydrogen-reduced powder mixture showed that the nano-sized W particles were well distributed on the surface of the micro-sized W powders.

• 한국분말재료학회지
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• 제23권4호
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• pp.303-306
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• 2016

An optimum route to synthesize Ti-Mo system powders is investigated by analyzing the effect of the heat treatment atmosphere on the formation of the reaction phase by dehydrogenation and hydrogen reduction of ball-milled $TiH_2-MoO_3$ powder mixtures. Homogeneous powder mixtures with refined particles are prepared by ball milling for 24 h. XRD analysis of the heat-treated powder in a hydrogen atmosphere shows $TiH_2$ and $MoO_3$ peaks in the initial powders as well as the peaks corresponding to the reaction phase species, such as $TiH_{0.7}$, TiO, $MoO_2$, Mo. In contrast, powder mixtures heated in an argon atmosphere are composed of Ti, TiO, Mo and $MoO_3$ phases. The formation of reaction phases dependent on the atmosphere is explained by the partial pressure of $H_2$ and the reaction temperature, based on thermodynamic considerations for the dehydrogenation reaction of $TiH_2$ and the reduction behavior of $MoO_3$.

• The Korean Journal of Pain
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• 제12권1호
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• pp.48-53
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• 1999

Background: Despite the popularity of epidural bupivacaine-morphine infusions for postoperative pain management, the optimum concentrations and dosages of bupivacaine have not been determined. At present, due to the disadvantages conferred by intense motor block and the increased risk of toxicity, many trials focus on reducing bupivacaine concentration and thus the evaluation of concentrations less than 0.1% may be warranted. Methods: Forty patients having epiduro-general anesthesia for hysterectomy were randomly assigned to one of two study groups. As a mean of postoperative pain control, all received 2 mg of epidural morphine bolusly 1 hr before the end of surgery and continuous epidural infusion was started using a two-day Infusor containing 4 mg of morphine in 100 ml of 0.125% bupivacaine (Group 0.125B, n=20) or 100 ml of 0.0625% bupivacaine (Group 0.0625B, n=20). Study endpoints included visual analog scales (VAS) for pain during rest and movement, sensory change and motor blockade. They were assessed at 2, 4, 8, 16, 24, 32, 40 and 48 hrs postoperatively. Results: For VAS during rest, no significance could be found between two groups over the course of study. But for VAS during movement, the 0.125B group showed more satisfactory results especially during early postoperative periods. For the incidence of complications, the 0.125B group revealed greater frequency of sensory change (25.0%) and motor blockade (10.0%) compared with the 0.0625B group. Conclusion: This study suggests that 0.0625% bupivacaine with morphine via epidural route was sufficient for pain control during rest but it was not satisfactory during movement especially in early postoperative periods. We also recommend that careful attention to motor blockade should be paid when using 0.125% bupivacaine.

• Journal of Pharmaceutical Investigation
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• 제26권3호
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• pp.169-174
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• 1996

Inclusion complexes of diclofenac sodium with ${\beta}-cyclodextrin$ were prepared in aqueous solution, alkaline solution and solid phase. The interaction of diclofenac sodium with ${\beta}-cyclodextrin$ in pH 9.0 alkaline solution was evaluated by the solubility method and the instrumental analysis such as thermal analysis, infrared spectroscopy, X-ray diffractometry. The solubility of diclofenac sodium was increased linearly with the increase in the concentration of ${\beta}-cyclodextrin$up to 0.15 mol and showed that the aqueous solubility rate of diclofenac sodium was significantly increased by complex with ${\beta}-cyclodextrin$. The optimum composition of this complex was one molecule of ${\beta}-cyclodextrin$ included 1.59 molecular weight of diclofenac sodium as a guest molecule. The pharmacokinetic parameters of the diclofenac sodium and the complex with ${\beta}-cyclodextrin$ were studied in rats by oral route. $T_{max}$ between drug alone and inclusion complex showed significant difference to be 120 minute and 20 minute respectively. Both of $C_{max}$ and AUC of inclusion complex was about 40% higher than drug alone. It is estimated from the data in this study that complexation of diclofenac sodium with ${\beta}-cyclodextrin$ increased the absorption rate and improved the bioavalability of the diclofenac sodium by the formation of a water-soluble complexes.

• 지질공학
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• 제17권4호
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• pp.555-566
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• 2007

일반적으로 국내에서 터널의 지보 설계를 위한 암반분류법으로는 RMR 분류가 사용된다. 터널 시공 중 예비조사계획을 보온하고 노선을 따른 연속적인 지반 정보를 획득하기 위해 막장관찰과 동시에 RMR을 통한 암반분류가 시행된다. 하지만 국내 터널 시공 여건 상 조사를 위한 충분한 시간이 보장되지 않으며, 때로는 막장에서의 직접 관찰이 불가능 한 경우가 많다. 따라서 본 연구에서는 RMR 항목 중 상대적으로 조사 시간이 길며 세밀한 관찰이 요구되는 RQD와 불연속면 상태 항목의 배점을 추정하기 위한 선형회귀분석을 수행하였으며, 그 결과 최적 회귀식을 산정 하였다. 또한 기존 연구에서 고려하지 않은 지질조건을 반영하기 위해, 퇴적암, 천매암, 화강암을 기반으로 하는 터널의 데이터를 각각 구분하여 분석하였다. 추정을 위한 변수로는 다른 RMR 항목을 대상으로 선정하였으며, 이들 간의 선형회귀분석을 통해 최종 회귀식을 산정하였다.

• 한국재료학회지
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• 제20권10호
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• pp.508-512
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• 2010

The optimum route to fabricate nano-sized Fe-50 wt% Co and hydrogen-reduction behavior of calcined Fe-/Conitrate was investigated. The powder mixture of metal oxides was prepared by solution mixing and calcination of Fe-/Co-nitrate. A DTA-TG and microstructural analysis revealed that the nitrates mixture by the calcination at $300^{\circ}C$ for 2 h was changed to Fe-oxide/$Co_3O_4$ composite powders with an average particle size of 100 nm. The reduction behavior of the calcined powders was analyzed by DTA-TG in a hydrogen atmosphere. The composite powders of Fe-oxide and Co3O4 changed to a Fe-Co phase with an average particle size of 40 nm in the temperature range of $260-420^{\circ}C$. In the TG analysis, a two-step reduction process relating to the presence of Fe3O4 and a CoO phase as the intermediate phase was observed. The hydrogen-reduction kinetics of the Fe-oxide/Co3O4 composite powders was evaluated by the amount of peak shift with heating rates in TG. The activation energies for the reduction, estimated by the slope of the Kissinger plot, were 96 kJ/mol in the peak temperature range of $231-297^{\circ}C$ and 83 kJ/mol of $290-390^{\circ}C$, respectively. The reported activation energy of 70.4-94.4 kJ/mol for the reduction of Fe- and Co-oxides is in reasonable agreement with the measured value in this study.

• 한국재료학회지
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• 제30권2호
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• pp.61-67
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• 2020

BiFeO₃ with perovskite structure is a well-known material that has both ferroelectric and antiferromagnetic properties called multiferroics. However, leaky electrical properties and difficulty of controlling stoichiometry due to Bi volatility and difficulty of obtaining high relative density due to high dependency on the ceramic process are issues for BiFeO₃ applications. In this work we investigated the sintering behavior of samples with different stoichiometries and sintering conditions. To understand the optimum sintering conditions, nonstoichiometric Bi_1±xFeO_3±δ ceramics and Ti-doped Bi_1.03Fe_1-4x/3Ti_xO₃ ceramics were synthesized by a conventional solid-state route. Dense single phase BiFeO₃ ceramics were successfully fabricated using a two-step sintering and quenching process. The effects of Bi volatility on microstructure were determined by Bi-excess and Ti doping. Bi-excess increased grain size, and Ti doping increased sintering temperature and decreased grain size. It should be noted that Ti-doping suppressed Bi volatility and stabilized the BiFeO₃ phase.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2003년도 춘계학술대회 논문집
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• pp.321-325
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• 2003

지형에 대한 입체적인 조감도의 작성기술은 여러 건설공사의 계획수립과 설계를 위하여 매우 중요한 요소로 활용될 수가 있다. 본 연구에서는 원격탐지된 위성영상을 이용하여 기존의 수치지형도와의 결합을 통한 3차원 영상 지도의 제작을 시도하여 다차원적인 분석이 가능한 입체 영상 조감도를 작성하였다. 이를 위하여 정밀 GCP에 의한 정사투영된 영상 및 등고선으로부터 생성된 DEM의 결합으로 3차원 지형분석이 가능한 지형의 입체화를 실험하여 건설공사 예정지역의 도로 노선의 연계에 의한 입체적인 접근이 가능한 3차원 조감도를 제작할 수 있는 기술을 개발하였다. 이러한 입체 영상 조감도의 작성에 의한 다각적인 지형분석이 가능하도록 하였고, 건설공사 예정 지역의 실시간 방식으로 가상적인 접근이 가능한 연구결과를 얻어냄으로써 균형적인 국토개발 및 건설분야에서의 다양한 활용을 유도할 수 있었다.

• 한국정보통신학회논문지
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• 제23권9호
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• pp.1025-1031
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• 2019

본 연구는 선박용 해수펌프를 ML 기반으로 한 알고리즘을 구현하여 효율적으로 운용할 수 있는 PCS를 제안한다. PCS가 탑재된 2척의 선박에서 해수온도, RPM, 전력 소모 데이터를 취득하여 회귀 분석법으로 분석하고, 새로운 알고리즘을 제시한다. 제시하는 알고리즘을 적용하였을 때 Ship A는 PCS를 적용하지 않았을 때 대비하여 약 36%를 절감하였고, 특정 해역온도인 $19{\sim}27^{\circ}C$와 $32^{\circ}C$ 이상의 해역에서 ML 기반의 알고리즘이 Ship A의 PCS보다 약 1% 더 절감하였다. Ship B는 PCS를 적용하지 않았을 때 대비하여 약 50%를 절감하였고, 특정 해역온도인 $19^{\circ}C$ 이상의 해역에서 Ship B의 PCS보다 약 2%더 절감하였다. 도출된 데이터를 이용하여 최적의 펌프 속도와 항로를 제안할 수 있다. 추가적으로, 취득 데이터의 추세를 활용하여 효율이 낮아졌을 시에 펌프의 성능이나 MGPS의 소제 시기를 유추할 수 있다.

• Membrane and Water Treatment
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• 제12권1호
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• pp.43-49
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• 2021

The Commercial polymeric membranes like Polysulfone (PSF), Polyvinylidene difluoride (PVDF) and Polyacrylonitrile (PAN) which are an integral part of water purification investigation were chosen for the shockwave (SW) exposure experiment. These membranes were prepared by blending polymer (wt. %) / DMF (solvent) followed by phase-inversion casting technique. Shockwaves are generated by using Reddy Tube lab module (Table-top Shocktube) with range of pressure (1.5, 2.5 and 5 bar). Understanding the changes in membrane before and after shock wave treatment by parameters, i.e., pure water flux (PWF), rejection (%), porosity, surface roughness (AFM), morphology (SEM) and contact angle which can significantly affect the membrane's performance. Flux values PSf membranes shows increase, 465 (pristine) to 524 (1.5wt%) LMH at 50 Psi pressure and similar enhancement was observed at 100Psi (625 to 696 LMH). Porosity also shows improvement from 73.6% to 76.84% for 15wt% PSf membranes. It was observed that membranes made of polymers such as PAN and PSF (of high w/w %) exhibits some resistance against shockwaves impact and are stable compared to other membranes. Shockwave pressure of up to 1.5 bar was sufficient enough to change properties which are crucial for performance. Membranes exposed to a maximum pressure of 5 bar completely scratched the surface and with minimum pressure of 1.5bar is optimum enough to improve the water flux and other parameters. Initial results proved that SW may be suitable alternative route to minimize/control membrane fouling and improve efficiency.