Thermite welding is an exceptional process that does not require additional energy supplies, resulting in welded joints that exhibit mechanical properties and conductivity equivalent to those of the parent materials. The global adoption of thermite welding is growing across various industries. However, in Korea, limited research is being conducted on the core technology of thermite welding. Currently, domestic production of thermite powder in Korea involves recycling copper oxide (CuO). Unfortunately, controlling the particle size of waste CuO poses challenges, leading to the unwanted formation of pores and cracks during thermite welding. In this study, we investigate the influence of powder particle size on thermite welding in the production of Cu-thermite powder using waste CuO. We conduct the ball milling process for 0.5–24 h using recycled CuO. The evolution of the powder shape and size is analyzed using particle size analysis and scanning electron microscopy (SEM). Furthermore, we examine the thermal reaction characteristics through differential scanning calorimetry. Additionally, the microstructures of the welded samples are observed using optical microscopy and SEM to evaluate the impact of powder particle size on weldability. Lastly, hardness measurements are performed to assess the strengths of the welded materials.

본 연구에서는 실버 파우더의 입자 크기, 즉 평균 입자 크기가 2㎛과 7㎛, 이렇게 2가지 실버 페이스트를 개발하였다. 이렇게 개 발된 실버 페이스트에 대해서 점도 및 점탄성, 경화후에 잔류용제 유무 확인을 위한 TGA측정, Strain에 따른 저항 변화 및 전극 표면 구조 변화에 대해서 검토하였다. 이러한 결과를 정리하면 Strain에 따른 저항 변화를 최소화하기 위해서는 실버 파우더의 입 자를 2㎛정도인 것이 가장 바람직함을 알 수 있었다.

To evaluate the chemical properties of the epsilon particle present as a precipitate in the high-level radioactive waste, we performed the experiments for the samples fabricated by CeO2 containing 1, 3, and 5wt%Mo, where CeO2 is used as the simulated high-level radioactive waste to replace the real one, using X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEMEDS). Moreover, to evaluate the chemical behavior of Mo epsilon particle in CeO2 at high temperature, the manufactured CeO2-1wt%Mo, CeO2-3wt%Mo, and CeO2-5wt%Mo samples were heated at 100, 300, 500, 700 and 900ºC for 7 h in a tube furnace under Ar atmosphere. In this study, the results of comprehensive analysis including the crystal structure, chemical state, and elemental distribution will be presented to verify the chemical properties for CeO2 samples containing Mo epsilon particle, depending on the Mo content and heating temperature.

The purpose of this study is to analyze the distribution characteristics of mist spray particle size by devising a rotary mist spraying device to develop the evaporative salt water desalination system. The rotary mist spraying device was consisted of a BLDC sirocco fan, a spinning fan, a fan fixed shaft and a salt water supply device etc. In this study we analyzed the characteristics of spray particle size and distribution according to the variation of sirocco fan surface roughness(Ra, μm), revolutions(rpm) and salt water flow rate(mL/min). When sirocco fan surface roughness( Ra) was in the range of 0.27~7.65 μm, the spray particle size was 0.117~1.360 μm. And then more than 90% of spray particles were found to be less than 0.50 μm. When sirocco fan surface roughness(Ra) was in the range of 12.70~22.84 μm, the spray particle size was 2.51~184.79 μm and more than 98% of spray particles were found to be less than 13.59 μm. To analyze the effect of fan rotation speed on the size and distribution of spray particles, when surface roughness Ra was fixed 0.27 μm and fan rotation speed and salt water flow rate was respectively changed at 3,800~5,600 rpm and 2.77~8.28 mL/min, spray particle size was 0.341~0.541 μm. And when salt water flow rate was 9.74 mL/min and fan rotation speed was 3,800~5,200 rpm, spray particle size was in the range of 29.29~341.46 μm and in case of 5,600 rpm more than 98.23% of spray particles were in the range of 2.51~13.59 μm.

강원지역은 우리나라의 다설지로서 복잡한 지형 때문에 강설량의 공간변동성이 크다. 특히 동풍조건에서 강설이 발생할 시 강설량의 공간적 변동을 예측하기 어렵다. 동풍조건에서는 강원지역 내 위치에 따라 대기환경조건이 다르며 이는 강설의 특성에도 영향을 줄 수 있다. 본 연구에서는 동풍 조건에서 태백산맥의 풍상측과 풍하측에서 강설의 미세 물리적 특성을 서로 비교 분석하였다. 강원지역 내 4개 관측지점을 선정하여 파시벨 수적계로 입자크기분포를 관측하였다. 얻어진 강설입자 크기 분포의 특성을 풍상측과 풍하측간 비교한 결과, 풍상측의 강설입자 크기 분포는 풍하측에 비해 넓은 분포를 가졌고 작은 강설입자의 수도 많았다. 강설입자의 수농도에 비례하는 보편특성수농도와 강설입자의 직경에 비례하는 보편특성직경 둘 다 풍상측에서 상대적으로 큰 값을 보였다. 또한, 얼음수함량과 강설강도 비교에서도 풍상측 지점에서 큰 평균값을 가졌다. 이 결과가 나타난 원인은 태백산맥 산사면에서 공기덩어리의 강제적 상승효과로 풍상측 지점 상공에 새로운 강설입자의 생성이 활발했기 때문으로 추정된다. 또한, 풍상측은 따뜻하고 습한 동풍이 불어오므로 이로 인해 지상기온이 0oC 근처에 머무르며 강한 부착과정이 일어나기 좋은 조건이다.

In this study, dry-milled rice flour from different varieties (Samgwang, Boranchan, Hanareum, Dasan, Hangaru) and different particle sizes were used to manufacture Jeung-pyun and the quality characteristics were analyzed. The Jeung-pyun produced from Samgwang, Dasan and Hangaru milled rice flour showed highly dense pores. The Jeung-pyun produced from Hanareum only showed a significant difference according to the particle size. Samgwang, Boranchan and Dasan varieties with a particle size of 150 m showed a significant decrease in volume (p<0.05). Samgwang showed the lowest pH at all particle sizes (p<0.05). The sweetness of Samgwang varieties was the highest at 3.27-3.63°Brix (p<0.05). The hardness of Jeung-pyun increased with increasing particle size (p<0.05). The highest acceptance of Jeung-pyun in terms of volume and bitter taste was observed with Hanareum at a particle size of 50 m. When the particle size was 50 m, the overall acceptance was highest for Jeung-pyun made from Samgwang followed by Hanareum. The acceptance of all the sensory characteristics was high when the particle size of rice flour was 50 m. When the appearance of Jeung-pyun was measured, Samgwang showed a dense structure and low hardness. Hanareum showed an increasing volume and springiness. Overall Samgwang and Hanareum were found to be the most suitable varieties for the production of Jeungpyun.

본 연구는 지방 대체제로 첨가된, 각기 다른 입자의 크기로 분쇄된 돈피가 유화소시지의 이화학적 성질과 저장 기간, 그리고 관능검사에 끼치는 영향을 조사하기 위해 수행되었다. 지방 대체제로 첨가된 돈피는 대조구에 첨가된 지방 12%와 동일한 수준인 지방 4%, 분쇄 돈피 8%를 T1에서는 3mm, T2에서는 5mm, T3에서는 7mm로 분쇄하여 첨가하였다. 모든 처리구들은 일반적인 냉장 온도인 4±1℃에서 0, 5, 10, 15일간 저장되며 시료로 쓰였다.첨가되는 돈피의 분쇄 입자 크기가 클수록 전단가와 경도, 검성, 씹힘성이 유의적으로 증가하였고, 전 저장구간에서 포장감량, TBARS, VBN, 씹힘성은가식권 내의 값을 유지하며 유의적으로 증가하였다. 관능검사에서는 Color에서 입자의 크기가 클수록 부정적인 영향이 있었고, Chewiness는 저장기간이 지남에 따라 유의적으로 증가하였고 입자 크기가 작을수록 유의적 으로 높은 값을 나타내었다. 실험결과 돈피를 첨가한 처리구가 대조구에 비해 Shear force, Puncture test, 관능 평가에서 우수한 평가를 받았고 저장성검사와 이화학적 성질에서도 큰 차이를 보이지 않고 모두 가식권내의 값을 유지하였다. 이는 돈피가 육가공품에서 지방이 작용하는 역할을 충분히 수행가 능하며, 좋은 평가를 얻어 지방을 대체할 수 있을 것으로 판단된다.

The demands of rice products have been steadily increasing because of their non-allergenic-functionalities. However, the use of rice flour in the gluten-free food industry has been still limited due to undesirable quality characteristics derived from the weak structural network by the lack of gluten. Therefore, there is a need to search for new approaches to enhance the structural network of gluten-free foods. In this study, zein, protein derived from corn, was applied to rice noodles as a structural network provider for sheeting and the rheological and structural properties of the rice noodles were investigated depending on the particle size of rice flour. The starch damage of the rice flours increased with decreasing particle size. The zein-rice flours with smaller particle size exhibited greater water hydration properties and pasting parameters that contributed to the increased elastic characteristics. The use of zein positively contributed to the formation of sheeted rice dough that could be successfully slit into noodle strips. The zein-rice noodles with medium particle size (100–150 mesh) had the highest breaking stress and hardness values that were correlated to the lowest cooking loss. This study thus provides a new opportunity for food industry to improve the qualities of gluten-free rice noodles by controlling particle size.

It is well known that smoking generates harmful air pollutants. With smoking in buildings as well as in the streets prohibited, the need for smoking rooms has emerged. In this study, particle and CO contamination in a 63.6 m3 smoking room was experimentally investigated using Korean tobacco. Tobacco smoking was artificially simulated using a smoking machine. The number and size distribution of particles ranging from 10-420 nm and 0.25-32 μm were measured using a Nanoscan (TSI model 3910) and a portable aerosol spectrometer (Grimm model 1.109), respectively. CO concentration was also monitored using an IAQ monitor (Graywolf IAQ-Xtra 610). Four tobaccos were simultaneously smoked in each experiment, and the experiment was repeated four times. Maximum CO concentrations of 7-10 ppm were observed and high concentrations of particles (176,000-1,115,000 particles/cm3 for 10-420 nm, 3,700-5,200 particles/cm3 for 0.25-32 μm) were also monitored. The dominant size of tobacco particles was about 100 nm in diameter.

The milling characteristics of rice using different milling methods (dry and wet) were investigated. Generally, average particle sizes of dry-milling flours were bigger than those of wet-milling flours due to low moisture content. Three theoretical models for milling, such as the Rittinger, Kick, and Bond model, were applied to characterize the milling process of rice. The wet-milling method showed higher value milling constants including Bond’s work index. Baeksulgi was used to study the effect of the milling method and particle size on rice flour’s physicochemical property (water content, color value, and texture). Moisture content and hardness of Baeksulgi were smaller as the particle size became smaller. L value of Baeksulgi was greater as the particle size became smaller. The energy requirement for the milling of grains to obtain a suitable size of particles was estimated by the grinding models. The results of our study might provide a systematic way to estimate the energy requirement to obtain a suitable particle size by milling

The purpose of this study is to validate and verify a head nose exposure inhalation system for nano particle inhalation toxicity studies. Carbon nano tube(CNT) particles were generated by a chemical vapor deposition(CVD) generator. And purchased single wall carbon nanotubes(SWCNT) and multi wall carbon nanotubes(MWCNT) were generated by an atomizer. CNT particle distribution was measured by Scanning Nano-Particle Spectrometer(SNPS) and Condensation Particle Counter(CPC). Diameter and length of MWCNT generated by CVD were 10~40 nm and 220~20 μm respectively. Particle number concentration of MWCNT generated by CVD were 1.3×105, 4.1×104, 5.6×103#/cc in high, middle, low chamber respectively. Distribution of particles which were less than 100 nm was 45%. Particle number concentration of SWCNT generated by atomizer after magnetic stirring were 8.5×106, 5.3×105, 1.1×104#/cc and after sonication 6.7×106, 4.1×105, 9.5×103#/cc in high, middle, low chambers respectively. Particle number concentration of SWCNT generated by atomizer after magnetic stirring were 6.7×106, 4.6×105, 8.6×103#/cc and after sonication 7.7×106, 5.1×105, 1.3×104#/cc in high, middle, low chambers respectively. We set up head nose exposure inhalation system to conduct a study on nano particle inhalation toxicity. There were sufficient particle number concentrations of nano particles generated in each chamber.

In this study, the porous ceramic filter was developed to be able to remove both dust and hazardous gas contained in fuel gas at high temperature. The porous ceramic filters were fabricated and used as a catalyst support. And the effects have been investigated such as the mean particle size, organic content and addition of foaming agent on the porosity, compressive strength and pressure drop of ceramic filters. With the increase of mean powder size and the organic content for the cordierite filter, the porosity was increased, but the compressive strength and pressure drop were decreased. From the results of the research, the optimum condition for the fabrication of ceramic filters could be acquired and they had the porosity of 58%, the compressive strength of 13.4 MPa and the pressure drop of 250 Pa. It was expected that this ceramic filter was able to be applied to the glass melting furnace, combustor, and dust/toxic gas removal filter.

천수만 내 어장해역과 비어장해역의 해저퇴적물에 대한 지화학적 특성을 파악하기 위하여 입도 및 유기물오염의 특성과 중금속 오염도를 평가하였다. 천수만 퇴적물은 Sand, Silt, Clay가 혼재된 퇴적 특성을 나타내었으며, 어장해역인 만내에는 세립질이 우세하고, 비어장해역인 만외는 조립질이 우세한 것으로 나타났다. 퇴적물의 유기물(COD, TOC, I.L.) 오염정도는 양식어장해역이 비양식어장해역보다 유기물 오염도가 더 심한 것으로 나타났으며, 퇴적물 총질소 농도도 양식어장이 더 높은 것으로 나타났다. 퇴적물중의 중금속 함량을 양식어장인 내측과 비양식어장인 외측과 비교해 보면, 모든 항목에서 양식어장에서 높은 평균농도를 나타내고 있었다. 퇴적물의 입도와 이화학적 성분, 중금속과의 상관성에서 평균입도, Sand, Clay는 유기물 인자와 높은 상관성을 보였고, 유기물 지표와 중금속간의 상관성도 대체적으로 높게 나타났다. 중금속 오염도의 평가에서 농축계수는 Cu를 제외한 모든 중금속 항목에서 1 이상의 값을 보여 인위적인 영향이 있는 것으로 나타났고, 중금속 과잉량은 Cd와 Cr이 0에 가까운 값을 보였으나, 나머지 항목은 높은 값을 나타내어 중금속 과잉량이 높은 것으로 나타났다. 농집지수에 의한 평가에서는 Cu, Pb, Al은 0등급의 오염되지 않은 수준이었고, Hg, Cr은 10개 이내의 자료에서 0~1등급 이상이었고, 나머지는 0등급이었다. 그리고 Cd은 18개 자료에서 0~1등급 이상을 나타내었고, As의 경우 모든 자료에서 0~1등급 이상이었다. 미국해양대기청(NOAA) 퇴적물 기준과 비교하면 모든 중금속 항목에서 ERL 이하의 오염수준을 보였고, 한국환경정책평가연구원 퇴적물 기준과 비교에서도 목표수준 이하의 농도를 나타내었다.

The characteristics of abrasive wear of the rubber matrix composites filled with nano sized silica particles were investigated at ambient temperature by pin-on-disc friction test. The range of volume fraction of silica particles tested are between 11% to 25%. The cumulative wear volume and friction coefficient of these materials on particle volume fraction were determined experimentally. The major failure mechanisms were lapping layers, deformation of matrix, ploughing, deboding of particles and microcracking by scanning electric microscopy photograph of the tested surface. The cumulative wear volume showed a tendency to increase nonlinear with increase of sliding distance. As increasing the silica particles of these composites indicated higher friction coefficient.

본 연구는 부산지역의 먼지 농도와 황사발원지의 기후학적 요소를 주기분석 함으로써 부산지역의 먼지농도 주기에 영향을 주는 기후학적 조건, 특히 황사 발생과의 관련성에 대하여 고찰하였다. 부산지역에서 관측된 먼지 농도 시계열 자료를 이용한 단일스펙트럼분석을 수행한 결과 배출량이나 강수 효과 등에 의해 나타난 일반적인 주기(1년, 7일) 이외에, 상대적으로 3-4년 주기가 우세하게 나타났으며, 먼지 농도와 부산지역의 기상자료 및 황사발원지에서의 풍속과의 교차스펙트럼 분석을 통한 주기 분석을 수행해 본 결과, 3-4년 주기일 때 먼지농도와 풍속, 기압은 양의 상관관계, 기온, 상대습도와는 각각 음의 상관관계가 나타났다. 이는 황사 발생 조건과 잘 부합되는 것으로 나타나, 3-4년의 먼지 농도 주기는 황사의 장거리 수송과 관련이 있는 것으로 판단된다. 또한 황사 발생은 발원지의 지표 상태에 따라 발생빈도가 달라지므로, 여러 기후학적 요소들 중 황사발원지에서의 강수량과의 주기 분석을 수행해 본 결과, 발원지에서의 강수량 그 자체보다는 발원지에서의 가뭄지수(EDI)의 시계열이 우리나라 먼지 농도의 3-4년 주기와 더 연관이 있는 것으로 나타났고 이는 기후학적으로 황사 발원지에서의 지표건조 특성의 변동성과 연관이 있는 것으로 나타났다.