• Journal of the Korean Vacuum Society
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• v.12 no.2
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• pp.105-111
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• 2003

In order to find out whether a reflectron can be used as a mass selector in the gas cluster experiment, computer simulation are performed using the SIMION’ program. flight paths of energetic particles in the reflectron does not depend on their mass but energy. In the case of $(CO_2)n $ gas cluster, however, the position of clusters just after passing through the reflectron are spacially distributed with respect to the mass. The reason that the masses spacially distributes is the E/m ratio of clusters is constant, and it is the key reason that a reflectron can be used as a mass selector. Mass resolution does not depend on the cluster size and incident angle of clusters, and it is proportional to the incident position of clusters. This means that mass resolution can be enhanced by resizing the dimension of a reflectron. Therefore, it is concluded that a reflectron can be used as a mass selector with excellent mass resolution in the gas cluster experiment.

• Applied Chemistry for Engineering
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• v.18 no.4
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• pp.320-325
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• 2007

Nickel powders were prepared from an aqueous nickel acetate solution and hydrazine hydrate using diethanolamine as the nonaqueous organic solvent in the conventional and microwave synthetic method. It was investigated that microwave non-thermal effect and synthetic condition affect the preparation of nickel powders by means of X-ray diffractometry, scanning electron microscopy, thermal gravymetry analysis, and X-ray photoelectron spectroscopy analysis. Compared with the conventional synthetic method, less of aggregation, smaller particle size, and more uniform distribution of particle size were obtained in the microwave synthetic method due to the non-thermal effect of microwaves.

• Journal of the Mineralogical Society of Korea
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• v.24 no.3
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• pp.217-224
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• 2011

Removal of dissolved selenium by D. michiganensis, a iron-reducing bacterium, and effects of dissolved metal elements such as iron, sulfate, and copper were investigated. Selenide that was reduced from selenite (2 mM) by D. michiganensis was gradually removed from the aqueous medium. As the reduced selenide was combined with aqueous iron, it was precipitated as a nanoparticulate iron-selenide. Sulfate and copper negatively affected the microbial selenite reduction, and the copper was especially toxic to the bacterium, inhibiting a microbial removal of dissolved selenite. These results show that it should be carefully biotreated for a selenium-contaminated site considering in situ sulfate or copper distribution and concentration. Consequently, the formation of iron-selenide by bacteria will be an important measure for preventing a long-distance migration of selenium in the subsurface environments.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2002.11a
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• pp.36-36
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• 2002

최근 한국기계연구원에서 개발된 Mechanochemical process (MCP)는 Spray conversion 법에 의하여 나노크기의 W/Cu 복합 분말을 제조하는 방법으로서, 현재 (주)나노테크에서 산업화를 위한 시험/개발이 진행 중이다. 이 방법에 의하여 W /1 0 ~ 40wt. %Cu 조성의 초미렵 W/Cu 복합 분말의 양산화가 가능하게 됨으로써, 나노복합분말을 사용한 초미립 W/Cu 합금의 소결 제조 연구 역시 나 노태크에서 분말사업화와 동시에 수행되고 있다. 현재 Spray conversion 법으로 제조되고 있는 W/Cu 나노복합분말 및 그 소결체는 Cu의 조성범 위에 따라 민수용 및 군수용 제품으로의 적용이 시도되고 있으며, 각기 특성향상을 목표로 각 적용 분야에서 요구되는 제반 성능에 대한 검토가 이루어지고 있다. 특히 군수용의 목적으로 사용될 경우, 정적 및 동적부하상태에서 재료의 균일한 변형이 가장 중요한 특성이다. 현 개발품의 경우, 일반 W 빛 Cu 원료에 비하여 상대적으로 높은 순도의 원료를 사용하였기 때문에 분말 및 소재상태 에서의 순도가 높아서, 연성을 저하시키는 것으로 알려진 기지상내 합금원소 또는 interface 게재물 이 존재할 가능성이 매우 낮다. 또한 초미립 W 입자들과 Cu 상의 혼합도가 극대화된 상태이기 때문에 상대적으로 저옹에서도 완전치밀화된 미세조직을 얻을 수 있는데, 이는 분말상태의 균일한 미세구조를 유지할 수 있으며, 동시에 W 업자간의 과도한 neck 형성을 방지함으로써 기계적 변형시 재료의 연성 향상이 기대된다. 이러한 W/Cu 나노복합분말 소결체의 특성은 균일한 밀도분포와 동시에 과도한 동적 부하상태에서 균일한 변형이 보장되어야만 하는 특정 군수용 목적에 잘 부합하는 것으로 판단된다. 본 고에서는 상기한 W/Cu 나노복함분말을 사용하여 균일한 미세구조를 가지는 완전치밀화된 소결재를 제조하는 과정과 제조된 소결재를 향후 군수용 제품에 척용시키기 위하여 진행된 단조특성에 대한 연구결과틀을 재료의 미세구조척 관점에서 논의하였다.

• Journal of Energy Engineering
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• v.20 no.4
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• pp.338-345
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• 2011

The swirl flow applied for high efficiency and reduction of emission such as NOx, CO in a gas turbine engine makes recirculation zone by shear layer in the combustion chamber. This recirculation zone influences a decreasing flame temperature and flame length by burned gas recirculation. Also it is able to suppress from instability in lean-premixed flame. In this study, it was found that the swirl flow field was characterized as function of swirl number using PIV measurement in dump combustor. As increasing swirl number, a change of flow field was presented and recirculation zone was shifted in the nozzle exit direction. Also turbulent intensity and turbulent length scale in combustor were decreased in combustion. It has shown reduction of eddies scale with swirl number increasing.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.5
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• pp.84-91
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• 2008

Due to increasing need for better emission characteristics and lower fuel consumption rate in automotive engines, alternative fuels are drawing more attentions recently. The GTL (gas to liquid) is the one of most favored candidates. In this study, emission characteristics are compared between diesel and GTL fuel in commercial 2.0 liter diesel engine and vehicle with CRDi(Common Rail Direct injection) system. The effects of injection timings on emission and fuel consumption rate are compared at various engine speeds and loads. Noticeable reduction in HC, CO and PM emissions are observed due to higher cetane number and low sulfur and aromatic contents in GTL. On the trade-off curve of NOx and PM(Particulate matter) GTL showed much more benefits than diesel, where about 30% of PM mass decreased at the same operating conditions. On CVS 75 mode test in vehicle, GTL showed an excellent emission enhancement, in which 50% of HC, 21% of PM, and 12% of NOx engine-out emissions are decreased compared to ULSD(Ultra low sulfur diesel) fuel.

• Korean Chemical Engineering Research
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• v.55 no.1
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• pp.68-73
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• 2017

The removal of particulate matter ranging from $0.01{\mu}m{\sim}10{\mu}m$ can be performed by using membrane filters composed of fibers. Electrospinning techniques offer the production of very thin fibers with a uniform fiber diameter over conventional techniques including template synthesis, melt-blown, phase separation, etc. Air filtration will be improved with electrospun membranes due to the open pore structures, high porosity, and large surface area of the membranes. In the present study, filtration efficiency increased with pore size decrease and fiber density increase induced by carbon nanotube and the increased CA (cellulose acetate) concentration during electrospinning process.

• Journal of the Korean Ceramic Society
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• v.40 no.1
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• pp.62-68
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• 2003

Ba-ferrite particles added with Co and Ti, which were known well the additives for the control in coercivity, were synthesized by sol-gel method. In the range 90 to 120 minute reaction time, a stable sol solution which showed no change with temperature, pH, viscosity and aging time. After dried and heat treatment of sol solution, Ba-ferrite phase formed at $700^{\circ}C$ with Differential Thermal Analysis(DTA) and X-Ray Diffractometer(XRD) measurement. The crystallinity became to be better with increasing the temperature. It were showed by Scanning Electron Microscopy(SEM) that Ba-ferrite increased to particle sizes as increasing heating temperature and obtained of narrow particles size distribution. Also, magnetic characteristics of Ba-ferrite powders Co and Ti added were observed by a Vibrating Sample Magnetometer(VSM). Saturation magnetization$(M_s)$ was not much changed, however. the coercivity$(H_c)$dramatically dropped with addition of Co and Ti.

• Clean Technology
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• v.13 no.3
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• pp.208-214
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• 2007

Environmentally-friendly acrylic resin particles having the diameter between $0.1\;and\;1\;{\mu}m$ were prepared using non-aqueous dispersion (NAD) polymerization technique. The first step is to prepare the stabilizer and the next step is the NAD polymerization by dropping an acrylic monomer to stabilizer dispersed in organic media. To obtain a NAD resin with proper level of viscosity, it fumed out that stabilizers having sufficient viscosity such as 1000 cP need to be used, for which the stepwise feeding of monomer and initiator was necessary. It was necessary to put proper amount of stabilizer, but no more increase in viscosity was observed when more than that amount of stabilizer was added. Choice of proper monomers considering solubility parameter was essential to avoid the bimodal particle size distribution in the NAD resin product.

• Clean Technology
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• v.14 no.4
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• pp.256-264
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• 2008

In this study, using PBAST (poly(butylene adipate-co-succinate-co-terephthalate)) which was eco-friendly biodegradable aliphatic polyester, PBAST/PVA (poly(vinyl alcohol)) double-layered hollow microspheres were prepared with the water/oil/water multiple emulsion ($W_1/O/W_2$) method. The double-layered hollow microspheres were manufactured with the yield of 30.92% when the concentration of polymer PBAST in organic phase was 5 wt%, the concentration of PVA in inner aqueous phase was 5 wt%, the volume ratio of $W_1/O$ emulsion to outer aqueous phase was 1:4.5, and when co-surfactants that had large gap in HLB (hydrophile-lipophile balance) value were used. The bulk density of prepared hollow microsphere was 0.180 g/ml and particle size was $1.5{\sim}3\;{\mu}m$.