본 논문에서는 표적의 레이다 반사면적 기여도 분석을 통한 전파흡수체 적용에 대한 레이다 반사면적 감소 효과와 최신 전파흡수체 기술인 메타물질을 적용한 레이다 반사면적 감소 효과를 고찰하였다. 레이다 반사면적 해석은 모형선 모델로 진행하였고, 레이다 반사면적 기여도 분석을 통하여 전파흡수체와 메타물질의 레이다 반사면적 평균값 감소 효과를 확인하였다.

Nd-Fe-B permanent magnets have been used in a wide variety of applications because of their high magnetic flux density. So, demand for neodymium has been increasing in worldwide. In this study, an electrowinning process was performed in LiF-NdF3-Nd2O3 high temperature molten salts. However, a corrosion resistant material for use in the molten salt must be found for stable operation because of the harsh corrosion environment of the electrowinning process. Therefore, for this paper, boron nitride(BN), aluminum nitride(AlN), and silicon nitride(Si3N4) were selected as protective and structural materials in the high temperature electrolyte. To investigate the characteristics of BN, AlN, and Si3N4, in molten salts, materials were immersed in the molten salts for 24, 72, 120, and 192 hours. Also, surface condition and stability were investigated by SEM and EDS and corrosion products were calculated by HSC chemistry. As a result, among BN, AlN, and Si3N4, AlN was found to show the best protective material properties.

In this study, the effect of temperature effect of the rubber matrix filled with nano sized silica particles composites with silica volume fraction of 19–25% was investigated by the Charpy impact test. The Charpy impact test was conducted in the temperature range from –40°C to 0°C. The critical energy release rate GIC of the rubber matrix composites filled with nano sized silica particles was considerably affected by temperature and it was shown that the maximum value was appeared at higher temperature between temperature tested and it was shown that the value of GIC increases as temperature tested increases. The major fracture mechanisms were matrix deformation, silica particle debonding and delamination, microcrack between particles and matrix, and/or pull out between particles and matrix which is ascertained by SEM photographs of Charpy impact surfaces fracture.

이 연구는 식생기반재돌망태기슭막이의 녹화효과를 분석하였다. 식생기반재돌망태기슭막이 시공 후 20일 경과 후 식생이 발아하기 시작하였으며, 봄의 피복율은 약 20%를 나타내었다. 여름에는 피복율이 약 65%로 나타났으며, 출현종은 파종한 목본인 낭아초, 참싸리 모두 출현 하였으며, 초본으로는 벌노랑이, 자운영, 수레국화, 기생초, 코스모스 등 5종이 출현하였다. 이때 침입식생은 개망초, 새, 벼룩자리, 버들잎엉겅퀴, 미국자리공, 망초, 미국가막사리, 민들 레, 아까시나무, 찔레, 물쑥, 매듭풀, 자귀나무, 바랭이, 쇠무릅 등 15종이었다. 가을에는 피 복율이 약 82%로 나타났으며, 출현종은 6종, 침임식생은 5종으로 나타났다. 또한 식생기반재 돌망태기슭막이와 전석기슭막이, 식생낭기슭막이를 비교한 결과, 식생기반재돌망태기슭막이만 녹화효과가 나타났다.

We designed a series of polymers as antifouling coating materials containing hydrophilic moiety such as polyethylene glycol (PEG) and mussel-inspired dopamine and/or hydrophobic moiety such as polyhedral oligomeric silsesquioxane (POSS) and plant-based cardanol moiety. We changed the molar composition of the hydrophilic and hydrophobic moieties in the copolymers and polymer shape (star- vs. linear-shaped polymer) and polymer morphology (block- vs. random copolymer) in order to compare fouling behaviors. These polymer coated membranes exhibited noticeably higher fouling resistance than the bare polysulfone (PSf) ultrafiltration membrane during filtration experiments. We believe that our results will provide insight into the synthesis and fabrication of multi-functional membranes for water treatment applications.

PURPOSES : The purpose of this study is to develop a deicing pavement system using carbon fiber or graphite with high electrical conductivity and thermal conductivity. METHODS: Based on literature reviews, in general, conventional concrete does not exhibit electrical and thermal conductivity. In order to achieve a new physical property, experiments were conducted by adding graphite and carbon fiber to a mortar specimen. RESULTS: The result of the laboratory experiment indicates that the addition of graphite can significantly reduce the compressive strength and improve the thermal conductivity of concrete. In the case of carbon fiber, however, the compressive strength of the concrete is slightly increased, whereas, the thermal conductivity is slightly decreased against the plain mortar irrespective of the length of the carbon fiber. In addition, a mixture of the graphite and carbon fiber can greatly improve the degree of heating test. CONCLUSIONS : Various properties of cement mortar change with the use of carbon fiber or graphite. To enhance the conductivity of concrete for deicing during winter, both carbon fiber and graphite are required to be used simultaneously.

This study was conducted to increase the shelf life of peeled-garlic by edible coating material such as carboxymethyl cellulose(CMC) with sodium benzoate, citric acid and lecithin. Peeled-garlic were stored in a storage chamber at 25℃ and were taken at regular intervals for analysis. The changes in weight loss, colour change, browning, decaying loss and texture of the coated samples with storage time were investigated in comparison with the uncoated samples to determine the delay in the deterioration time of the samples. The coatings contributed to a lower reduction in weight loss. The coatings decreased the browning and decaying loss loses in comparisonto the uncoated peeled-garlic. It was possible to extend the storage period with lower weight loss until 32 days by coating peeled-garlic surfaces with emulsions containing CMC. It was found that the emulsion prepared using the mixture of lecithin, CMC, citric acid, sodium benzoate and water was suitable for the coating of peeled-garlic.

The purpose of this study was to investigate the odor arising from the Cheong-ju industrial complex area for odor materials confirmation, and to predict the impact of the odor in the residential area using the CALPUFF Model. Among the odor causing substances in the area with a rising number of collective complaints due to odor, methyl sulfide, acetaldehyde, propionaldehyde, n-buthylaldehyde, n-valeraldehyde and styrene were detected. Odor causing substances detected in the area surrounding the industrial complex include ammonia, hydrogen sulfide, n-buthylaldehyde, toluene, xylene, benzene and styrene. Using the CALPUFF Model, it was predicted that 1hr average was 3.981~7.553 OU/m3 and 24hr average was 1.753~2.359 OU/m3. In terms of odor intensity, the predicted 1hr average was 0.6~0.9 and the 24hr average was 0.2~0.4.

The present study is undertaken to evaluate the effect of volume fraction on the results of Charpy impact test for the rubber matrix filled with nano sized silica particles composites. The Charpy impact tests are conducted in the temperature range 0°C and –10°C. The range of volume fraction of silica particles tested are between 11% to 25%. The critical energy release rate GIC of the rubber matrix composites filled with nano sized silica particles is affected by silica volume fraction and it is shown that the value of GIC decreases as volume fraction increases. In regions close to the initial crack tip, fracture processes such as matrix deformation, silica particle debonding and delamination, and/or pull out between particles and matrix which is ascertained by SEM photographs of Charpy impact fracture surfaces.

In this study, to confirm the effect of alloying elements on the phase transformation and conditions of the friction stir process, we processed two materials, SS400 and SM45C steels, by a friction stir process (FSP) under various conditions. We analyzed the mechanical properties and microstructure of the friction stir processed zone of SS400 and SM45C steels processed under 400RPM - 100mm/min conditions. We detected no macro (tunnel defect) or micro (void, micro crack) defects in the specimens. The grain refinement in the specimens occurred by dynamic recrystallization and stirring. The microstructure at the friction stir processed zone of the SS400 specimen consisted of an α-phase. On the other hand, the microstructure at the friction stir processed zone of the SM45 specimen consisted of an α-phase, Fe3C and martensite due to a high cooling rate and high carbon content. Furthermore, the hardness and impact absorption energy of the friction stir processed zone were higher than those of base metals. The hardness and impact absorption energy of FSPed SM45C were higher than that of FSPed SS400. Our results confirmed the effect of alloying elements on the phase transformation and mechanical properties of the friction stir processed zone.

Experiments for catch and cluster analysis on the catch by gillnet for the Pacific herring were conducted using traditional nylon net (PA) and developing biodegradable net (PBS) with different monofilaments of #2 (=0.23 mm) and #3 (=0.28 mm) in diameter between 2011 and 2012, and of #2, #2.5 and #3 in 2013 in the eastern coastal waters of Samcheok, Korea. The total catch during the experiments was 3,337kg in weight and 16,757 individuals in number. Though the catch ratio of the Pacific herring in 2011 and 2012 was 97.4% and 98.7%, respectively, that of the Pacific herring in 2013 was 73.6% as the biggest and followed by goldeye rockfish (8.6%), black edged sculpin (8.4%), atka mackerel (7.2%) and Alaska cod (1.0%). The ANOVA analysis on the total catch in relation to net material showed that there was not statistically significant difference at the 5% level between nylon net (PA) and biodegradable net (PBS) (p=0.91). With the cluster analysis on the catch in relation to net material (PA, PBS) and twine thick (#2, #3), it showed the influence of net material on the catch was greater than that of twine diameter in this experiment. From the test of homogeneity on the catch by the gillnet with PA and PBS in which several species were caught in 2013, there was not statistically significant homogeneity in relation to net material (p<0.005). That meant the traditional gillnet of nylon (PA) was more efficient than the biodegradable (PBS) gillnet to catch several kinds of fish, however the PBS gillnet was better than the PA gillnet to catch the target Pacific herring.

Graphite can be classified into natural graphite from mines and artificial graphite. Due to its outstanding properties such as light weight, thermal resistance, electrical conductivity, thermal conductivity, chemical stability, and high-temperature strength, artificial graphite is used across various industries in powder form and bulk form. Artificial graphite of powder form is usually used as anode materials for secondary cells, while artificial graphite of bulk form is used in steelmaking electrode bars, nuclear reactor moderators, silicon ingots for semiconductors, and manufacturing equipment. This study defines artificial graphite as bulk graphite, and provides an overview of bulk graphite manufacturing, including isotropic and anisotropic materials, molding methods, and heat treatment.

태양전지는 태양복사에너지를 반도체의 광전효과를 통해 전기에너지로 변환시키는 친환경 에너지변환장치를 의미한다. 수분을 포함하는 다양한 화학물질들에 대한 높은 차단성을 갖는 다층형 필름인 백시트는 태양전지의 중요한 요소이다. 대표적인 백시트는 polyvinyl fluoride (PVF)와 poly(ethylene terephthalate) (PET)의 다층필름으로 구성된다. PVF는 높은 내후성을 가지는 반면, 가격이 상대적으로 비싼 단점을 보인다. 따라서, 백시트의 제조가격을 낮출 수 있으면서, 동시에 실제 태양전지모듈에 적용할만한 수명특성을 만족시킬 수 있는 대체소재의 개발이 필수적이다. 본 연구에서는 일정수준의 결정성을 갖는 PET 필름을 PVF 필름 대신 사용하였다. 그러나, PET 소재는 다양한 pH 조건에서 trans-esterification 및 가수분해에 의해 분해될 수 있기 때문에, 태양전지의 구동조건에서 PET의 분해거동을 이해할 필요가 있다. 단시간 내 화학적 분해거동을 평가하기 위해서, 가속화된 PET 분해실험 프로토콜이 개발되었다. 마지막으로, 제안 개념의 효용성은 태양전지모듈의 장기운전성능 평가를 통해 확인하였다.

In order to prepare anode materials for high power lithium ion secondary batteries, carbon composites were fabricated with a mixture of petroleum pitch and coke (PC) and a mixture of petroleum pitch, coke, and natural graphite (PCNG). Although natural graphite has a good reversible capacity, it has disadvantages of a sharp decrease in capacity during high rate charging and potential plateaus. This may cause difficulties in perceiving the capacity variations as a function of electrical potential. The coke anodes have advantages without potential plateaus and a high rate capability, but they have a low reversible capacity. With PC anode composites, the petroleum pitch/cokes mixture at 1:4 with heat treatment at 1000 oC (PC14-1000C) showed relatively high electrochemical properties. With PC-NG anode composites, the proper graphite contents were determined at 10~30 wt.%. The composites with a given content of natural graphite and remaining content of various petroleum pitch/cokes mixtures at 1:4~4:1 mass ratios were heated at 800~1200 oC. By increasing the content of petroleum pitch, reversible capacity increased, but a high rate capability decreased. For a given composition of carbonaceous composite, the discharge rate capability improved but the reversible capacity decreased with an increase in heat treatment temperature. The carbonaceous composites fabricated with a mixture of 30 wt.% natural graphite and 70 wt.% petroleum pitch/cokes mixture at 1:4 mass ratio and heat treated at 1000 oC showed relatively high electrochemical properties, of which the reversible capacity, initial efficiency, discharge rate capability (retention of discharge capacity in 10 C/0.2 C), and charge capacity at 5 C were 330 mAh/g, 79 %, 80 %, and 60 mAh/g, respectively.

본 연구는 고추 논 비가림 재배시 피복 재료가 생육, 수량 및 dehydrogenase 활성 등에 미치는 영향을 구명하고자 충북 괴산군 농가포장에서 2012년부터 2013년까지 2년간 수행하였다. ‘독야청청(신젠타종묘)’ 품종을 사용하였으며, 멀칭용 피복 재료는 배색비닐, 흑색비닐, 생분해필름, 부직포 등 4처리를 하였다. 1. 피복 재료에 따른 고추의 초장, 주경장, 분지수, 엽장, 엽폭은 통계적인 유의성을 나타내지 않았다. 2. 고추 재배기간 지온은 오전 7시경에 가장 낮았고, 오후 5 ~ 6시경에 가장 높았다. 지온은 배색비닐, 흑색비닐, 생분해 필름, 부직포 순으로 높았다. 3. 생분해필름은 정식 후 60일부터 분해가 시작되었고, 정식 후 120일에는 80% 분해되었다. 4. 피복 재료에 따른 생과중과 건조중은 처리간에 유의성을 나타내지 않았다. 5. ASTA 값은 생분해필름에서 44.6으로 가장 높았고, 배색필름, 흑색필름, 부직포 순으로 높았다. 6. 정식 후 120일의 dehydrogenase 활성은 생분해필름>부직포 >흑색필름 >배색필름 순으로 높았다. 7. 토양 biomass C 함량은 정식 후 80일보다 정식 후 120일에 더 높았다. 8. 피복 재료에 따른 역병, 진딧물류, 담배나방, 응애류, 총채벌레류, 담배가루이의 발생 양상은 차이가 없었다. 결론적으로, 고추 논 재배시 멀칭용 피복 재료에 따른 생육과 수량은 차이를 나타내지 않았다. 생분해필름이 dehydrogenase 활성과 biomass C 함량이 높아 친환경적이고 필름 수거 노력이 필요하지 않아 노동력 절감할 수 있다. 따라서, 생분해필름을 영농에 활용을 적극적으로 검토해야 시점이며, 이러한 결과들은 관련 분야 산업의 활성화에 기여할 것으로 생각된다.

Ti alloys are extensively used in high-technology application because of their strength, oxidation resistance at high temperature. However, Ti alloys tend to be classified very difficult to cut material. In this paper, The powder synthesis, spark plasma sintering (SPS), bulk material properties such as electrical conductivity and thermal conductivity are systematically examined on Ti2AlN and Ti2AlC materials having most light-weight and oxidation resistance among the MAX phases. The bulk samples mainly consisted of Ti2AlN and Ti2AlC materials with density close to theoretical value were synthesized by a SPS method. Machining characteristics such as machining time, surface quality are analyzed with measurement of voltage and current waveform according to machining condition of micro-electrical discharge machining with micro-channel shape.

The finite element stress analysis of large sized rectangular water tank structures made of stainless steel materials is carried out for various combined load cases. The combined load cases for a large size of 5,000ton are further determined using the specification(KS B　6283) established from the Korean Standards Association. The changed water capacity due to the size of reservoirs could be heavily dependent for evaluating seismic effects, especially for large reservoirs. For the better numerical efficiency, the rectangular panels are modelled using the ANSYS ADPL module. The numerical results obtained for different load cases mainly show the effect of the interactions between the different load combination and other various parameters, for example, the water capacity, and different stainless steel materials. The structural performance for various load combinations is also evaluated.

단감을 재배하는 농가에서 저장성을 향상 시킬 수 있는 값싸고 쉬운 방법을 개발하기 위해 본 연구를 수행 했다. 농가 관행 LDPE 포장재 내에 동봉할 수 있는 천연소재(대나무활성숯, 왕겨숯, 겔라이트)를 선발하여 상온과 저온환경에서 가용성 고형물 함량, 경도, 식미, 부패도, 연화도의 변화를 1주일 또는 2주일 간격으로 조사 하였다. 대나무활성숯을 동봉한 LDPE 포장 방법이 단순 LDPE 포장 방법 보다 저장성 및 품질을 을 좋게 유지하였다. 대나무활성숯을 동봉한 LDPE 포장 방법은 관행 농법 농가와 유기 농법 농가 모두에서 장기 저장 시 그리고 유통 중 온도변화 시 저장성을 향상 시킬수 있는 값싸고, 손쉬운 방법으로 활용할 수 있을 것으로 판단된다.