As indoor air cleaners have large sizes and high air flow rates, the test methods for particle cleaning capacity need to be reconsidered because the prescribed test chamber size becomes relatively smaller. In this study, air flow rate of air cleaners compared to test chamber size (Q/V) has been investigated by comparing the short-circuit factor which indicates the air mixed condition in the test chamber. The test method of Korea Air Cleaning Association (KACA) has been analysed and compared to that of Association of Home Appliance Manufacturers (AHAM) for clean air delivery rate (CADR) of two household air conditioners equipped with air cleaners having a maximum air flow rate of 15 m³/min in terms of initial particle concentrations, neutralized/non-charged particles, delay time before acquiring initial particle concentration, sampling positions. Constant short-circuit factor of about 0.9 was obtained in the range of Q/V less than 0.73 min^-1. CADR based on KACA test method was somewhat dependent on initial particle concentrations, delay time before acquiring initial concentration, sampling positions. However, CADR based on AHAM test method was less dependent. Two or three minutes of delay time before acquiring initial concentration was necessary to reduce the variation of CADR according to initial particle concentration and sampling position.

The effect of particle size distribution on green and sintered properties of Fe-Cr-Mo prealloy powder was investigated in this study. For the study, prealloyed Fe-Cr-Mo powders with different particle sizes were mixed as various ratios and cold compacted at various pressure and sintered at for 30 min, atmosphere in the continuous sintering furnace. The results shows that the powders with large particle size distribution have high compressibility and low ejection force. However the green strength are much less than those with small particle size distribution. Tensile prperties of the sintered specimes with large particles size also have high strength and elongation.

Particle collection efficiency and air cleaning capacity were tested for the two-stage electrostatic precipitator for use in indoor air cleaning systems. A wire-plate type ionizer was used as a particle charger and a dielectric film consisted of polypropylene (or polyethylene) coated metals and zigzagged metal electrodes was used as a particle collector in the electrostatic precipitator. Both particle collection efficiency and air cleaning capacity increased as increasing the applied voltage on the charger and the collector, and furthermore, as increasing the collector film width (i.e. collection area). Air cleaning capacities estimated by the product of particle collection efficiency and air flow rate were quite well consistent with the experimental ones with a proportional constant of 0.964. Ozone concentrations emitted from the charger at the applied voltages of 5.0 and 5.2 kV were less than 0.05 ppm, indoor ozone standards of UL 867-2002, KS C 9314 and SPS-KACA002-132. For the air flow rate of 11.7 m³/min, the applied floor area of 48.2 m² could be obtained when 5.2 kV and 6.0 kV were applied on the ionizer and the collector, respectively and the collector of two 15 mm polyethylene dielectric films was used.

Al/AlN composites were synthesized by mechanical alloying using process control agents(PCAs). Three different PCAs which contain N element, were examined to see the effectiveness of ball-milling and the nitridation during sintering. Among examined PCAs, was the most effective to facilitate ball-milling and to form nitrides during a subsequent sintering. By a proper control of ball-milling and sintering, we could obtained surface-hardened Al-based composites.

nanowires were synthesized by a hydrothermal reaction of metallic Y with aqueous solution of LiOH. The morphology and the size of the nanowires changed with varying the volume of the LiOH solution inside the autoclave. nanowires transformed to by a subsequent heat-treatment without morphological change. By a proper control of hydrothermal reaction parameter and heat-treatment, the yield of pure nanowires up to 97% was attained.

The ultrafine titanium carbonitride () particles below 100 nm in mean size, including various carbon and nitrogen contents (x=0.55~0.9, y=0.1~0.5), were successfully synthesized by new Mg-thermal reduction process. Nanostructured sub-stoichiometric titanium carbide () particles were initially produced by the magnesium reduction of gaseous at and post heat treatments in vacuum were performed for 2 hrs to remove residual magnesium and magnesium chloride mixed with . Finally, well C/N-controled phases were successfully produced by nitrification heat treatment under normal gas atmosphere at for 2 hrs. The values of purity, mean particle size and oxygen content of produced particles were about 99.3%, 100 nm and 0.2 wt.%, respectively.

본 연구는 2008년 6월부터 2009년 3월까지 남한강 지류인 복하천과 달천의 이화학적 수질 및 부착규조를 이용한 생물학적 수질평가를 하였다. 그 결과 복하천은 영양염의 총인이 0.041~0.886 mg·L-1 총질소가 0.336~10.532 mg·L-1의 범위로 매우 높게 나타났으며, BOD의 농도도 일부지점을 제외하고 2~5 mg·L-1의 범위로 수질이 다소 오염

The ultrafine titanium carbonitride particles () below 100nm in mean size were successfully synthesized by Mg-thermal reduction process. The nanostructured sub-stoichiometric titanium carbide () particles were produced by the magnesium reduction at 1123K of gaseous and the heat treatments in vacuum were performed for five hours to remove residual magnesium and magnesium chloride mixed with . And final phase was obtained by nitrification under normal gas at 1373K for 2 hrs. The purity of produced particles was above 99.3% and the oxygen contents below 0.2 wt%. We investigated in particular the effects of the temperatures in vacuum treatment on the particle refinement of final product.

Test methods of Korea Air Cleaning Association (KACA) and Association of Home Appliance Manufacturers (AHAM) for particle cleaning capacity performance of an indoor air cleaner were compared in terms of the conditions of the test particle generation, the range of particle measurement and the calculation methods for particle cleaning capacity, and types of the test particles. The performance test was conducted in a 30 m³ chamber with the same test specimen and the test particles of each test were generated until the number concentration of 0.3 ㎛ particles reached 2.2 × 108 #/m³. The performance test results showed that the cleaning capacity with the particles of higher surface area and volume density, regardless of the type of test particles, was higher than with those of lower and the capacity from calculation with 0.3～1 ㎛ particles was higher than with 0.3 ㎛ particles. Moreover, the cleaning capacity with the calculation of KACA method was lower than with that of AHAM method in spite of using the same test specimen.

The densification behavior of Al-20Si-5.5Fe-1.2Mg-0.5Mn powders was investigated through micro-structure analysis of sintered specimens. The specimens sintered in vacuum or in high purity (99.999%) nitrogen showed porous near-surface microstructures. The densification of near-surface part was enhanced by means of ultra-high purity (99.9999%) nitrogen atmosphere. The relationship between slow densification and oxide surfaces of Al alloy powders was discussed. And the effects of Mg addition, nitrogen gas, and humidity on densification were discussed. In addition, the rapid growth of primary Si crystals above the critical temperature was reported.

The hypereutectic Al-20 wt%Si powders including some amount of Cu, Fe, Mg, Mn were prepared by a gas atomization process. In order to get highly densified Al-Si bulk specimens, the as-atomized and sieved powders were extruded at , Microstructure and tensile properties of the extruded Al-Si alloys were investigated in this study. Relative density of the extruded samples was over 98%. Ultimate tensile strength (UTS) in stress-strain curves of the extruded powders increased after T6 heat treatments. Elongation of the samples was also increased from 1.4% to 3.2%. The fracture surfaces of the tested pieces showed a fine microstructure and the average grain size was about

알루미늄 분말야금부품은 철계 분말부품에 비해 가볍고 알루미늄 주조부품에 비해 우수한 기계적 물성을 갖는다. 단, 상대적으로 비싼 가격이 이 부품의 응용을 제약하는 장벽이었으나 최근의 환경과 에너지 문제에 대한 세계적인 관심은 이를 극복할 수 있는 계기를 제공하고 있다. 선진국은 이미 일본을 중심으로 1990년대부터 알루미늄 분말부품에 대한 기술개발을 진행하였고 현재는 다양한 상용 부품을 판매하고 있으며 조만간 그 판매량이 크게 증가할 것으로 예상된다.

The purpose of this paper is to cross-culturally analyze the meaning of 'love' in Korean and American pop lyrics of 1980's. Pointing out that the information provided by dictionaries is not sufficient to understand the cultural meaning of 'love', the corpus analytic method of semantic prosody is introduced as it is explicated by Hunston (2002). Using this semantic prosody technique, three different sets of pop lyrics are analyzed with WordSmith Tools software. The three data sets, one Korean and two American, represent 150 pop lyrics. Specifically, these texts are analyzed in terms of distribution patterns of 'love' in the lyrics. First, the modification pattern of 'love' is investigated. It is found that the Korean data is significantly skewed toward negative expressions, producing negative semantic prosody of 'love', while the American data which reflect American culture is overwhelmingly skewed toward positive expressions, producing positive semantic prosody. That is, Koreans experience 'love' in a fairly negative terms in their pop music, while Americans basically treat it positively. Interestingly, the American pop lyrics popular with the Korean public show in-between characteristics. Next, the predication patterns of 'love' are investigated when it plays the role of subject NP. The result again shows that these two cultures define 'love' drastically differently in their pop music. In sum, the semantic prosody technique proved to be useful as an analytic method for cross-cultural studies.

A high efficiency roll-type electret polypropylene (PP) filter with an external electric field was developed and its particle collection efficiency and air cleaning capacity was investigated in a room when applied to an air cleaner having a fan. To enhance air cleaning performance of the cleaner, a wire-plate type ionizer was installed in front of the filter to enhance electric field to filter and one side of the filter was embossed by press of a pattern with a lot of circular projection. Performance test results showed that the newly developed electret PP filter with an ionizer becomes an appropriate filter to be applied to indoor air cleaner due to its low pressure drop and high air cleaning performance.

Ozone has become a significant pollutant not only outdoors but also indoors. The ozone emission test was conducted for the sum of forty five air cleaners selected in the online shops and department stores. Negative ion emission test was also conducted for the selected fifteen ones which had the function to generate negative ions. Filter-type and complex type air cleaners emitted ozone less than 0.05 ppm, the standard of indoor ozone emission of air cleaner. Wet type ones emitted no ozone. In the case of ionizer type, 66.7% in the nine ones emitted ozone about 1.4~10 times larger than 0.05ppm. Most of air cleaners used a pin corona discharge emitted large amount of ozone. Those which used carbon fiber emitted little ozone in spite of generating a lot of negative ions.