OWEC(Overtopping Wave Energy Converter)는 월파된 파도를 이용한 파력발전시스템이라한다. OWEC의 성능 및 안전성은 파고, 주기 등 파도의 특성에 의해 영향을 받는다. 따라서 해역 특성에 따른 OWEC의 최적 형상과 구조안전성에 관한 연구가 필요하다. 본 연구 에서는 울릉읍 연안 해양 환경 데이터를 이용하였으며, SPH(Smoothed Particle Hydrodynamics) 입자법 해석을 통해 기존 케이슨 하부 구조에 변화를 준 모델 4개를 비교하여 월파 효율을 분석하였다. 그 결과, 하부 구조의 변경 및 경량화가 가능함을 확인하였다. 최적화 해석을 통 해 설계 하중에 내하력을 가지는 하부 구조인 새로운 트러스형 구조를 제안하였다. 이후 부재 직경 및 두께를 설계변수로 하는 사례 연구 를 통해 허용응력조건 하에서 구조 안전성의 확보를 확인하였다. 주기적인 파랑 하중을 받기 때문에 제안하는 구조의 고유 진동수와 해 당 해역의 파주기를 비교하였으며, 1년 재현 주기의 파랑을 하중으로 한 조화응답해석을 수행하였다. 제안하는 하부 구조는 동일 가진력 에서 기존 설계 대비 응답의 크기가 감소하였으며, 기존 대비 32% 이상의 중량 절감을 수행하였다.

Lithium (Li) is a key resource driving the rapid growth of the electric vehicle industry globally, with demand and prices continually on the rise. To address the limited reserves of major lithium sources such as rock and brine, research is underway on seawater Li extraction using electrodialysis and Li-ion selective membranes. Lithium lanthanum titanate (LLTO), an oxide solid electrolyte for all-solid-state batteries, is a promising Li-ion selective membrane. An important factor in enhancing its performance is employing the powder synthesis process. In this study, the LLTO powder is prepared using two synthesis methods: sol-gel reaction (SGR) and solid-state reaction (SSR). Additionally, the powder size and uniformity are compared, which are indices related to membrane performance. X-ray diffraction and scanning electron microscopy are employed for determining characterization, with crystallite size analysis through the full width at half maximum parameter for the powders prepared using the two synthetic methods. The findings reveal that the powder SGR-synthesized powder exhibits smaller and more uniform characteristics (0.68 times smaller crystal size) than its SSR counterpart. This discovery lays the groundwork for optimizing the powder manufacturing process of LLTO membranes, making them more suitable for various applications, including manufacturing high-performance membranes or mass production of membranes.

The massive amount of radioactive waste will generated during decommissioning of nuclear. Among the radioactive waste from these disposal process, 50-55 million tons of concrete waste are included. For safe disposal, it is very important to accurately analyze the concentration of radionuclides, especially 129I and 131I, contaminated concrete. 129I, a long-lived radioisotope of iodine (t1/2=1.57 × 107 y), and 131I (t1/2=8.04 d) are generated from the fission of uranium in nuclear reactors. In Korea, according to the Nuclear Safety and Security Commission (NSSC) radioactive clearance level guide, the limit for radioactive clearance level of 129I is less than 0.01 (Bq/g). Iodine can be absorbed, accumulate in organisms, and exhibit low energy emission compared with cesium, and cobalt. Therefore, it is essential to an accurately separate and analyze iodine radioactive waste. In this study, we focused on the determination of iodine in simulated cement waste form containing KI for the recovery of iodine. We performed cement waste form sieved through a different particle size (0.5 mm < ɸ < 6.35 mm). For the separation of iodine from solid samples with low iodine content, such as soil, sediment, and cement, for sample decomposition associated with solvent extraction using CHCl3 for separation of iodine from the matrix. The separation of iodine in cement waste particles was therefore carried out using an acid leaching method using KI containing cement particles. We observed that cement particle size decreased at 6.35 mm to 0.5 mm with iodine yield decrease at 0.840±0.011 to 0.582±0.010. Thus, in this study, the acid leaching method enables to determination Iodine in cement.

This research was conducted for dewatered sludge cake of industrial wastewater treatment, i.e., as the object of inorganic sludge discharged especially in iron & steel manufacturing shop which used Air drying system to reduce water content. That drying system's single-type cyclone separator was confirmed to have significantly lower separation efficiency on the conditions 20μm and below of particular size through computational fluid dynamics(CFD) analysis. However, we found out the primarily advanced value of separation efficiency on dual-type directly connected. Regarding separation efficiency on size of 10μm, the efficiency of a single-type was presented at 51.91%. On the other side, the efficiency of the dual-type was 97.88%. This advanced effect of the dual cyclone separator was checked at a demo facility of air drying equipment designed by 340m3/min of airflow on site.

노란잔산잠자리(멸종위기야생생물 II급) 약충은 내성천 일대 서식하는 것으로 알려져 있다. 2019년 3월 서식이 확인된 37개 지점의 하상 0.2㎡ 면적에서 채취한 퇴적물 입도 분석 및 개체수와의 상관관계를 분석하였다. 입도 분석 결과 ‘조립사’(500 ~ 1,000 ㎛) 52.5%, ‘극조립 사’(1,000 ~ 2,000 ㎛) 25.6%, ‘중립사’ (250 ~ 500 ㎛) 17.2%, ‘세립사’(125 ~ 250 ㎛) 3.1%, ‘극세립사’(63 ~ 125 ㎛) 1.0%, ‘실트’(63 ㎛미 만) 0.7% 순으로 나타났다. 노란잔산잠자리 약충의 개체수는 ‘극세립사’(63 ~ 125 ㎛), ‘세립사’(125 ~ 250 ㎛)와는 양의 상관관계를, ‘조립사’ (500 ~ 1.000 ㎛)와는 음의 상관관계를 나타내었다. 본 연구 결과를 통해 노란잔산잠자리 약충이 고운 모래를 서식처로 활용하고 있는 것을 확인 하였으며, 이러한 연구결과는 이후 내성천 일대 하상 환경변화 모니터링에 활용 할 수 있을 것이다.

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.

Most of the red ginseng (RG) products contain active substances derived from hot water or alcohol extraction. Since active substances of RG are divided into two two types: water-soluble and liposoluble, water or alcohol is needed as an extraction solvent and this leads the different extraction yields and components of the active substances. To overcome the limit, whole red ginseng powder can be used and consumed by consumers. In this study, the physicochemical properties and extractable active substance contents of variable-sized RG powder (158.00 μm, 8.45 μm, and 6.33 μm) were analyzed, and dispersion stability was measured to investigate the suitable size of RG powder for industrial processing. In the results, no significant difference was found from the changes in color intensity and thiobarbutric acid tests at 4°C, 25°C, and 40°C for 4 weeks. There was no significant difference on the production of antioxidants and ginsenoside among the samples (p>0.05). In dispersion stability, RG-158.00 μm was precipitated immediately, and the dispersion stabilities between RG-8.45 μm and RG-6.33 μm showed no significant difference. It implies that fine RG is suitable for the production process. With further study, it seemed that the physicochemical effects of RG particle sizes can be clearly revealed.

The properties of rice were studied, and 8 rice flour cultivars were used to study the effect of particle size on the physicochemical properties, color value, RVA viscosities, water absorption index (WAI), and water solubility index (WSI) of rice flours. The mean particle size by the 3 particle size classification of 150 mesh, 200 mesh, and 250 mesh was, 90.75 μm, 60.73 μm, 39.94 μm, respectively. Thai rice had the highest amylose content and Samkwang rice had the lowest amylose content. Protein content of rice flours prepared was decreased as the particle size of rice flour decreased. In terms of color values, the L-value and the a-value of rice flour were increased as the particle size of rice flours decreased, while the b-value was decreased as the particle size of rice flours decreased. Using a rapid visco analyzer (RVA), the initial pasting temperature of Thai rice cultivar was found to be the highest; the peak viscosities of Sunpum cultivar and Misomi cultivar, and Samkwang rice were higher than those of other rice flours. The water absorption index and water solubility index were increased as the particle size of rice flour decreased. In order to use processed rice flour for the development of processed foods, proper characteristics of the cultivars and particle size should be considered.

Particle morphology change and different experimental condition analysis during composite fabrication process by traditional ball milling with discrete element method (DEM) simulation were investigated. A simulation of the three dimensional motion of balls in a traditional ball mill for research on the grinding mechanism was carried out by DEM simulation. We studied the motion of the balls, the ball behavior energy and velocity; the forces acting on the balls were calculated using traditional ball milling as simulated by DEM. The effect of the operational variables such as the rotational speed, ball material and size on the flow velocity, collision force and total impact energy were analyzed. The results showed that increased rotation speed with interaction impact energy between balls and balls, balls and pots and walls and balls. The rotation speed increases with an increase of the impact energy. Experiments were conducted to quantify the grinding performance under the same conditions. Furthermore, the results showed that ball motion affects the particle morphology, which changed from irregular type to plate type with increasing rotation speed. The evolution was also found to depend on the impact energy increase of the grinding media. These findings are useful to understand and optimize the particle motion and grinding behavior of traditional ball mills.

최근 국내에서는 안전하고 고품질인 농산물에 대한 소비자의 선호도가 높아지고 있다. 고품질 농산물 생산과 환경오염을 줄이기 위해서는 화학비료와 같은 농자재의 과잉투입 문제를 해결하여야 하며 이를 위하여 변량시비에 관한 연구가 수행되고 있다. 변량시비용으로 널리 사용되는 원판식 입제 살포기의 경우 시비량이 변화함에 따라 살포패턴이 변화하는 문제점이 있다. 본 연구에서는 시비량 변화에 따른 살포패턴 변화 요인을 찾기 위하여 이산 요소 모델링과 고속카메라 촬영을 통하여 살포기 원판 위에서 의 입자거동을 분석하였다. 그 결과, 시비량이 증가함에 따라 원판회전 반대방향으로 비산되는 입자량 이 증가하게 되고 출구방향 조절장치의 출구 시작지점에서 빠져나가지 않고 출구 끝 부분에서 빠져나가 는 입자가 증가하여 원판 위에서 회전방향으로 더 많이 이동되어 살포되므로 살포패턴에 변화를 가져오 는 것으로 파악되었다. 이러한 문제를 해결하기 위하여 회전원판 위에 내부날개를 설치하여 회전 축 주 변에 낙하하는 입자를 원심력에 의해 출구방향 조절장치의 벽 쪽으로 강제 이동하도록 장치를 개선하여 원판 위 입자거동을 분석하였다. 그 결과, 시비량의 변화와 상관없이 회전축 주변의 입자가 출구방향 조절장치의 벽 쪽으로 이동하여 원판 위에서 회전하다가 조절장치의 출구 시작 부분에서 빠져나가 살포 되는 것으로 나타나 시비량의 변화에 따른 살포패턴의 변이가 줄어들 것으로 판단되었다. 차후, 균일한 살포패턴을 만들기 위해서 내부날개를 설치한 원판식 입제 살포기를 이용하여 다양한 시비조건에 따른 살포패턴 데이터를 수집 및 분석 하고자 한다.

In this study, we numerically analyzed flow and particle transport near the electrostatic precipitator in the tunnel according to train runs. When there was no train running, flow field was formed by a precipitator. Flow emitted from precipitator blocks the path along the tunnel, and therefore most contaminated air passes through the precipitator and can be cleaned. On the other hand, flow pattern during the train run was affected by train induced wind. A strong straight flow was generated at the front of train, and back flow was formed in the opposite line. When a train runs upward only (train start from suction section to blow section), the subway train transports contaminated particles along the tunnel. For downward train runs only case, the cleaned air reentered the contaminated section with train wind. Both train runs case showed combined flow and particle concentration pattern of both single train runs.

This study was conducted the comparative analysis on quality and rice bread process suitability properties by four particle size classification of dry-milled flours for four rice varieties. Dry-milled rice flours were prepared by dry milling and classified according to particle size using 100, 150, 200, and 250 mesh sieves. The mean particle size by four particle size classification of 60 ~ 100 mesh, 100 ~ 150 mesh, 150 ~ 200 mesh, 200 ~ 250 mesh exhibited 118.9 μm, 87.4 μm, 65.3 μm, 46.1 μm, respectively. The particle size of dry-milled rice flours was the finer, the damaged starch content was the higher (r = − 0.570*). The particle size also had significant negative correlation with the water absorption index (r = − 0.533*, r = − 0.593*), and water solubility index (r = − 0.857**, r = − 0.584*). Dry-milled rice flours with particle size of 60 ~ 70 μm, passed through 150 and 200 mesh sieves exhibited the highest specific volume of rice bread. Whereas, the dry-milled rice flour with finer particle size above 200 mesh showed the lowest specific volume of rice bread. These results will be applied as a quality standard to aid in the selection of the most suitable dry-milled rice flour for baking.

본 연구에서는 입경·비중 겸용 밭작물 곡물 선별기 개발을 위한 전 단계로서, 밭작물 곡물의 완전립과 불량립의 기하학적, 공기역학적, 마찰 특성을 측정하고, 선별기 설계에 적용하기 위한 선별 요인을 분석하였다. 측정된 곡물의 기하학적 특성 결과(길이, 폭, 두께)를 이용하여 스크린의 치수와 형상을 결정하여 선별기를 제작하여 선별시험을 한 결과 선별효율은 콩의 경우 94.7%, 커피는 92.0%, 아몬드는 74.5%, 옥수수는 90.0%로 나타났다. 측정된 곡물의 마찰 특성 결과를 이용한 고무벨트 선별 시험 결과 콩의 경우 벨트 속도 0.5 m/s, 벨트 각도 5˚ 일 때 선별효율이 88.2%로 가장 높게 나타났다. 측정된 곡물의 공기역학적 특성 결과, 종말속도는 콩의 경우 4.4∼6.0 m/s, 커피는 3.2∼4.4 m/s, 아몬드는 3.5∼5.1 m/s, 옥수수는 4.7∼6.0 m/s의 범위로 나타났다.

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.

습식분쇄의 최적조건을 얻고자 부형제 종류, 농도, 습식분쇄시 rotor speed, bead size, feed rate, 분쇄회수를 달리하여 분쇄한 결과, 부형제로는 gum arabic을 사용하여 5%의 농도로 첨가할 때 가장 좋은 분쇄효과를 나타내었다. Rotor speed를 달리하여 습식분쇄한 결과, rotor speed가 증가할수록 좋은 결과를 나타내어 4,000 rpm에서 가장 우수한 것으로 나타났다. 원료와 직접 부딪혀 분쇄를 하게 되는 bead는 0.4 mm의 크기를 사용하였을 때 가장 작은 사이즈로 분쇄되는 것으로 나타났다. 분쇄가 이루어지는 chamber내에 원료를 공급하는 비율에 따른 결과에서는 40 L/h 의 속도로 공급했을 때 가장 작은 입도분포를 보였다. 분쇄회수에 따른 영향은 횟수에 따라서는 8회 이상으로 분쇄하였을때 0.6 μm이하의 입도분포가 90% 이상으로 나타나 10회를 분쇄하였을때 가장 좋은 효과를 나타내었다. 연속운전과 비연속운전의 비교에서는 연속운전이 더 효율적이었으며 부형제 종류에 따른 영향은 gum arabic을 첨가하여 분쇄하였을때 가장 우수한 결과를 나타내었다. 따라서 적절한 농도와 종류의 부형제 사용과 rotor speed, bead size, feed rate, 용매와의 혼합비의 최적공정을 수립한 습식분쇄기술로 초미세액상칼슘의 제조가 가능하였고, 습식분쇄기술을 식품가공기술로 활용할 수 있는 가능성을 확보하였다.

Dynamic plastic deformation behavior of copper particles occurred during the cold spray processing was numerically analyzed using the finite element method. The study was to investigate the impact as well as the heat transfer phenomena, happened due to collision of the copper particle of in diameter with various initial velocities of into the copper matrix. Effective strain, temperature and their distribution were investigated for adiabatic strain and the accompanying adiabatic shear localization at the particle/substrate interface.

For precise property control of sintered products, it is important to understand accurately the packing density of the powder. We developed a packing simulation program that could make a packed bed of spherical particles having particle size distribution. In addition, the influence of the particle shape of the actual powder on the packing density was quantitatively analyzed. The predicted packing densities corresponded well to the actual data.

The decrease of the distance between particle centers due to the growth of the sinter necks can be explained by the well known two-particle model. Unfortunately this model fails to provide a comprehensive description of the processes for 3D specimens. Furthermore, there is a significant discrepancy between the calculated and the measured shrinkage because particle rearrangements are not considered. Only the recently developed analysis of the particle movements inside of 3D specimens using micro focus computed tomography (μCT), combined with photogrammetric image analysis, can deliver the necessary experimental data to improve existing sintering theories. In this work, μCT analysis was applied to spherical copper powders. Based on photogrammetric image analysis, it is possible to determine the positions of all particle centers for tracking the particles over the entire sintering process and to follow the formation and breaking of the particle bonds. In this paper, we present an in-depth analysis of the obtaine data. In the future, high resolution synchrotron radiation tomography will be utilized to obtain in-situ data and images of higher resolution.