This paper describes the manufacturing process of tilting pad gas bearing with a diameter of 5 mm and a length of 0.5-1 mm for power MEMS (Micro Electomechanical Systems) applications. The bearing compacts with nanopowder feedstock were prepared by Ni-metal mold with 2-mold system using LIGA process. The effect of the manufacturing conditions on sintering properties of nanopowder gas bearing was investigated. In this work, Fe-45 wt%Ni nanopowder with an average diameter of 30-50 nm size was used as starting material. After mixing the nanopowder and the wax-based binders, the amount of powder was controlled to obtain the certain mixing ratio. The nanopowder bearing compacts were sintered with 1-2 hr holding time under hydrogen atmospheres and under temperatures of to . Finally, the critical batch of mixed powder system was found to be 70% particle fraction in total volume. The maximum density of the sintered bearing specimen was about 94% of theoretical density.

가로 및 교차로에 설치된 단순입체시설의 현행 분석기법은 시설을 이용하는 주교통류를 분석대상에 포함시키지 않고 있어 불합리한 도로 및 신호운영을 유도하여 엇갈림현상, 병목현상과 같은 도로의 혼잡을 야기한다. 이러한 여건에도 불구하고 단순 입체시설을 이용하는 교통류 분석기법의 연구가 거의 수행된 바 없다. 또한 개략적으로 제시되어 있는 설정기준 역시 여러 가지 도로 및 교통조건을 반영하지 못하고 있는 실정으로, 단순입체시설이 포함된 교차로분석 시 지체도가 과소 추정되는 경향이 있다. 그러므로 본 연구는 도시내 입체시설의 효과를 파악하기 위한 선행과정으로서 대상시설의 효과를 파악할 수 있도록 입체시설의 분석기법을 개발하고 분석교차점의 적정간격을 응용하는데 그 목적이 있다. 본 연구는 다음과 같이 수행하였다. (1) 기존 분석기법의 문제점 제기, (2) 새로운 분석기법의 정립, (3) 사례지역의 적용 및 비교검정, (4) 분합류구간의 적정간격에 대한 민감도 분석을 수행한다. 연구결과, 본 연구에서 제시한 분석기법은 기존 분석기법의 모호한 부분을 명확히 하고 합리적인 결과를 추정할 수 있었다. 또한 그 분석기법을 응용하여 분합류구간에 대한 적정간격을 추정한 결과, 본선에서는 65m, 측도에서는 45m로 나타나 최소한 그 이상의 위치에 접속지점을 설치하는 것이 타당하다고 판단된다. 본 연구의 수행으로 얻어지는 가치는 다음과 같다. (1) 당해 시설에 대한 선행연구 또는 분석방법이 없었으므로 대상시설물로 인한 파급효과를 파악할 수 있다. (2) 본 연구의 분석기법은 기존 교차로의 분석방법을 차용함으로써 새로운 분석방법을 숙지하지 않아도 용이한 분석이 가능하다. (3) 본 연구에서 제시한 분석기법에 의하면 기존에 제외된 통과교통량을 포함시켜 분석할 수 있다. 이러한 방법을 통해 교차로 및 가로분석 시에 현황과 동떨어질 수 있는 결과에 대한 오류를 최소화할 수 있다. (4) 새로운 분석기법을 이용하면 신설 또는 기존 시설물에 대한 문제점을 도출하여 도로운영 및 신호운영 등의 개선방안을 제시할 수 있다.

Spills of M/V Hebei Spirit on 7th December 2007 caused a seriously damage to the ecosystem of Korean coast. Of these, microbial communities (i.e., attached benthic micro-algae) were reported to be sentive to the environmental change so it can be used for ecological risk assessment. Our experiment was designed to examine the ecological risk assessments for oil pollutant using benthic attached algal community on the artificial substrates of acrylic plates. Field monitoring in the culture system was conducted in Jangmok Bay. The abundances of attached micro-algae on artificial substrates gradually increased with increasing of sampling times. Among them, diatoms were the most important colonizer of coastal water, with the genera Cylindrotheca and Navicular most abundant. In particular, developed the culture system has correctly measured qualitative and quantitative abundance of attached micro-algae because same acrylic plates as artificial substrates were used. Thus, this culture system may be directly applied to the ecological risk experiments of microbial community structure from oil pollutants.

This study was conducted to determine the micro-hotspot for bird habitats in Yeongheung Island. We analyzed the spatio-temporal changes in the distribution based on species diversity, species richness at the 13 focal areas, which was classified in five categories depending on the types of habitats, using Analysis of Variance Test for four years (2006~2009). The distribution of birds was different depending on areas, seasons but not years. The forests of two areas of 13 areas were determined as the micro-hospot in three season (spring, summer, autumn), which is consistent for 4 years. This study provides the new analytical method that habitats for birds are systematically characterized through micro-hotspot using the spatio-temporal analysis.

This paper presents a new type of optical silicon accelerometer using deep reactive ion etching (DRIE) and micro-stereolithography technology. Optical silicon accelerometer is based on a mass suspended by four vertical beams. A vertical shutter at the end of the mass can only moves along the sensing axis in the optical path between two single-mode optical fibers. The shutter modulates intensity of light from a laser diode reaching a photo detector. With the DRIE technique for (100) silicon, it is possible to etch a vertical shutter and beam. This ensures low sensitivity to accelerations that are not along the sensing axis. The microstructure for sensor packaging and optical fiber fixing was fabricated using micro stereolithography technology. Designed sensors are two types and each resonant frequency is about 15 kHz and 5 kHz.

MAO(Micro-Arc Oxidation) method was used to make surface on 6063 Al specimen. This study was focused on an influence of voltage, density of electrolyte and a period of treatment on the change of surface microstructure by using SEM(Scanning Electron Microscope), EDS(Energy Dispersive X-ray Spectroscopy). The microstructure shows higher roughness and thicker oxidized layer with increase of voltage and maintaining period of treatment. The density of electrolyte affected a formation of more dense surface and increase of a oxidized layer.

This study describes a hydrogen embrittlement evaluation of the subsurface zone in 590DP steel by micro-Vickers hardness measurement. The 590DP steel was designed to use in high-strength thin steel sheets as automotive materials. The test specimens were fabricated to 5 series varying the chemical composition through the process of casting and rolling. Electrochemical hydrogen charging was conducted on each specimen with varying current densities and charging times. The relationship between the embrittlement and hydrogen charging conditions was established by investigating the metallography. The micro-Vickers hardness was measured to evaluate the hydrogen embrittlement of the subsurface zone in addition to the microscopic investigation. The micro-Vickers hardness increased with the charging time at the surface. However, the changing ratio and maximum variation of hardness with depth were nearly the same value for each test specimen under the current density of 150 mA/cm2 and charging time of 50 hours. Consequently, it appears that hydrogen embrittlement in 590DP steel can be evaluated by micro-Vickers hardness measurement.

Zinc oxide nanoparticles (nZnO) are used in a various range, including ceramic manufacture, photocatalysis, UV filters, and the food industry. However, little is known about the effects of micro- and nano-particles during mouse embryo organogenesis. To determine whether ZnO affects size-dependent anomalies during embryonic organogenesis, mouse embryos were cultured for two days with 300 ug/ml micro ZnO (mZnO;80±25 μm) and nZnO (< 100 nm) and the developmental changes were then investigated. Quantity of Zn by inductively coupled plasma mass spectrometry analysis, and expression patterns of various antioxidant enzymes in the embryos were investigated. Embryos exposed to mZnO or nZnO exhibited severe retardation of growth and development. In embryos exposed to mZnO and nZnO, yolk sac diameter, crown-rump length, and head length were significantly diminished. The morphological parameters, including yolk sac circulation, allantois, flexion, heart, hindbrain, midbrain, forebrain, otic system, optic system, branchial bars, maxillary process, mandibular process, olfactory system, caudal neural tube, forelimb, hindlimb, and somites in mZnO and nZnO-treated groups were significantly decreased. Zn absorption of the nZnO-treated group was significantly higher than that of the mZnO-treated group. Significantly decreased levels of CuZn-SOD, Mn-SOD, cGPx, and PHGPx mRNA were observed in the ZnO-treated group. In addition, antioxidant enzyme mRNA expressions of the nZnO group were significantly diminished, less than those of the mZnO treated group. These findings indicate that 300 ug/ml ZnO showed abnormality and nZnO may have a more severe effect than mZnO in developing embryos.

The effect of heat treatment on the micro-structures and the mechanical properties of 0.002% boron added low carbon steel was investigated. The tensile strength reached the peak at about 880-890˚C with the rising quenching temperature and then the hardness decreased sharply, but the tensile strength hardly decreased. The tensile and yield strength decreased and the total elongation increased with a rising tempering temperature, but the tensile and yield strength sharply fell and the total elongation prominently increased from above a 400-450˚C tempering temperature. Tempered martensite embrittlement (TME) was observed at tempering condition of 350-400˚C. In the condition of quenching at 890˚C and tempering at 350˚C, the boron precipitates were observed as Fe-C-B and BN together. The hardness decreased in proportion to the tempering temperature untill 350˚C and dropped sharply above 400˚C regardless of the quenching temperature.

The relative viscosity was measured at different filler loadings for a cycloaliphatic epoxy resin and hexahydro-4-methylphthalic anhydride hardener system filled with micro/nano hybrid silica. Various empirical models were fitted to the experimental data and a fitting parameter such as critical filler fractions (φmax) was estimated. Among the models, the Zhang-Evans model gave the best fit to the viscosity data. For all the silica loadings used, ln (relative viscosity) varied linearly with filler loadings. Using the Zhang-Evans model and the linearity characteristics of the viscosity change, simple methods to predict the relative viscosity below φmax are presented in this work. The predicted viscosity values from the two methods at hybrid silica fractions of φ = 0.086 and 0.1506 were confirmed for a micro:nano = 1:1 hybrid filler. As a result, the difference between measured and predicted values was less than 11%, indicating that the proposed predicting methods are in good agreement with the experiment.

Information technology devices, such as cellular phones, MP3s and so on, due to restrictions of space, require thin and small micro-speakers to generate sound. The reduction of the size of micro-speakers has resulted in the decrease of sound quality, due to such factors as frequency range and sound pressure level. In this study, the acoustical properties of oval microspeakers has been studied as a function of pattern shape on the diaphragm. The other conditions of micro-speakers, except for the pattern, was not changed. When the pattern is present on the diaphragm and the shape of pattern was a whirlwind, the resonance frequency was reduced due to the decrease of tensile strength of diaphragm. The patterns presented in the semi-minor axis of diaphragm did not effect a change of resonance frequency. However, increasing the number of patterns in the semimajor axis of diaphragm became a reason for the decrease of resonance frequency on edge side. When the depth of pattern on edge side was increased, the resonance frequency was decreased due to reduction of geometrical stiffness. If the height of edge and dome were increased, the resonance frequency and geometrical stiffness rapidly increased. After reaching the maximum values, they began to decrease with the continuous increase of height.

Micro bubbles are widely used in many cases such as agriculture, fishery, skin care, prevention of water pollution. A high pressure compressor which is one of part of a micro bubble generating system is needed to generate these micro bubbles. The purpose of this research is the development of a high pressure compressor which is achieve following conditions; discharge flow 0.6ℓ/min, maximum air flow 2ℓ/min, discharge pressure 5bar. To achieve these conditions, we optimized the geometry of cylinder and piston, clearance volume, compression ratio, power of operating motor experimentally. Moreover, we minimized the compressor which is the biggest part of a micro bubble generating system so that we could minimized the size of entire system.

This paper analyzes the main factors affecting user selection of a small-sum electronic payment system using survey data of 396 users. Several findings emerge. First, users consider three pillars and eight factors in adopting a new system : system feature

The methods for determining the diffusion parameters for the diffusion of d-limonene, a major volatile compound of orange juice, through a multi-layered food packaging material and predicting its absorption into the packaging material have been investigated. The packaging material used was the 1.5-mm thick multi-layered packaging material composed of high impact polystyrene (HIPS), polyvinylidene chloride (PVDC), and low density polyethylene (LDPE). Orange juice was placed in a cell where volatiles were absorbed in the sample package and kept at 23±2oC for 72 hr. The d-limonene absorbed in a 1.5-mm thick multi-layered food packaging material was analyzed by a solid phase micro-extraction (SPME). The absorption parameters for the absorption of d-limonene in the packaging material were determined and absorption of d-limonene into the packaging material was predicted using absorption storage data. The SPME desorption at 60oC for 1 hr resulted in the most sensitive and reproducible results. The diffusion coefficients of d-limonene in the packaging material and the partition coefficient at 23±2oC were approximately 1-2×10-12m2/s and 0.03, respectively. The absorption profile no earlier than 30 hr was fit well by a model derived from the Fick’s law.

High strength sheet steels for automobile are seriously compromised by hydrogen embrittlement. This issue has been continuously studied, but the field of interest, which lies between microstructural characteristics and hydrogen behavior with hydrogen charging, has not yet been thoroughly investigated. This study was done to investigate the behavior of hydrogen according to the hydrogen volume fraction on 590MPa grade DP steels, which are developed under hydrogen charging conditions as high strength sheet steels for automobiles. The penetration depths and the mechanical properties, according to charging conditions, were investigated through the distribution of micro-hardness and the microstructural observation of the subsurface zone. It was found that the amount of hydrogen trapping in 590MPa DP steels was related to the austenite volume fraction. It was confirmed that the distribution of micro-hardnesses according to the depth of the subsurface zone under the free surface showed the relationship of the depth of the hydrogen saturation between the charging conditions.

Electrical discharge machining (EDM) is an attractive machining technique but it requires electrically conductive ceramic materials. In this study, Alumina matrix composites reinforced with CNTs were fabricated through CNT purification, mixing, compaction and spark plasma sintering (SPS) processes. nanocomposites with the different CNT concentrations were synthesized. The mechanical and electrical characteristics of /CNTs composites were examined in order to apply the materials to the EDM process. In addition, micro-EDM using wire electrical discharge grinding (WEDG) was conducted under the various EDM parameters to investigate the machining characteristics of machined hole by Field Emission Scanning Electron Microscope (FE-SEM). The results show that /CNTs 10%Vol. was more suitable than the other materials because high conductivity and large discharge energy caused violent sparks resulting in bad machining accuracy and surface quality.

In fabricating plasma display panels, the photolithographic process is used to form patterns of barrier ribs with high accuracy and high aspect ratio. It is important in the photolithographic process to control the refractive index of the photosensitive paste. The composition of this paste for photolithography is based on the B2O3-SiO2-Al2O3 glass system, including additives of alkali oxides and rare earth oxides. In this work, we investigated the density, structure and refractive index of glasses based on the B2O3-SiO2-Al2O3 system with the addition of Li2O, K2O, Na2O, CaO, SrO, and MgO. The refractive index of the glasses containing K2O, Na2O and CaO was similar to that of the [BO3] fraction while that of the SrO, MgO and Li2O containing glasses were not correlated with the coordination fraction. The coordination number of the boron atoms was measured by MAS NMR. The refractive index increased with a decrease of molar volume due to the increase in the number of non-bridging oxygen atoms and the polarizability. The lowest refractive index (1.485) in this study was that of the B2O3-SiO2-Al2O3-K2O glass system due to the larger ionic radius of K+. Based on our results, it has been determined that the refractive index of the B2O3-SiO2-Al2O3 system should be controlled by the addition of alkali oxides and alkali earth oxides for proper formation of the photosensitive paste.

A study was conducted to determine the effects of the cattle manure (CM) application on the botanical composition and micro-mineral contents (Fe, Mn, Cu, Zn) of grazing pasture at the experimental field of Livestock Division, Subtropical Animal Experiment Station, National Institute of Animal Science from year 2003 to 2005. The experiment was arranged in a randomized complete block design with three replications. The treatment consisted of T1: 100% chemical fertilizer (CF 100%), T2: 50% CF +50% CM, T3: 25% CF +75% CM, T4: 100% cattle manure (CM 100%), T5: 100% CM (1st yr.)+ 100% CF (2nd yr.) + 100% CM (3rd yr.), T6: 100% CM (1st yr.)+ 100% CF (2nd yr.)+ 100% CF (3rd yr.). The botanical composition of grassland for grass, legumes, and weeds showed that the rate of legumes was increased in all treatments. The weeds rate in T4 was the highest in comparison to the other treatments. For micro-mineral contents T5 showed the highest average Fe contents of 262.08 ppm and T1 showed the lowest (199.20 ppm). Mn contents was the highest in T1 among the other treatments. Zn contents was the highest in T3 as compared with other treatments. Cu contents was the highest in T6 as compared with other treatments. The results of this experiments indicated that micro-mineral contents of change was effect of legumes increased than treatment