In this study, the failure characteristic of the center floor of a front-wheel drive vehicle was investigated according to material. UHSS, Al6061-T6, CFRP, and CFRP-Al were used as materials. As the analysis condition, a fixed support was applied to the rear surface of the center floor and a forced displacement of 2 mm/sec was applied to the front surface. As the result, when comparing with the equivalent stress and strain energy according to the material, it was found that UHSS, Al6061-T6, CFRP, and CFRP-Al were higher in the order. Also, when comparing with the equivalent strain due to the material, it was shown that the equivalent strain was high in the order of Al6061-T6, UHSS, CFRP and CFRP-Al. As for the damage characteristic of the center floor according to the material, it was found that the highest structural stability was obtained when UHSS was used. However, it was found that it was good to utilize Al6061-T6 in order to acquire the structural stability along with the structure with the lighter weight.

The method of evaluating the forming limit of sheet metal is using the forming limit diagram(FLD), and the test method for measuring forming limit curve(FLC) is ISO standardized. On the other hand, in the case of metal bulk materials, it was confirmed that the forming limit was defined by using various predictive models based on the ductile fracture theory. However it did not show a constant forming limit (limit damage value) depending on the shape of the specimen. Therefore, a study was conducted on the derivation of the triaxial stress curve to predict the fracture of the material for various stress triaxiality, not the existing limit damage value.

본 논문에서는 열린 셀 구조의 3차원 마이크로 엮임 재료에 대해서 다양한 전산 시뮬레이션을 수행하고 재료의 특성을 수치적으로 분석하였다. 엮임 재료에 대한 수치 해석의 정확도를 높이기 위해서 각 축 방향별 와이어 사이의 간격을 6개의 변수로 매개화 하였으며, 기존의 정육면체 대신에 사면체의 요소로 바꾸어 엮임 재료의 기하학적 형상을 더 사실적으로 구현하였다. 개선된 수치모델에 대해서 상용 프로그램을 이용해 기계적, 열역학적, 유체역학적 해석을 수행하였으며, 그 정확도를 검증하기 위해서 기존의 실험 결과와 비교하였다. 또한 x 및 y 방향으로 와이어 간격을 변화시켜 가며, 3차원 엮임 재료의 여러 물성치에 대한 파라메트릭 테스트를 수행하였으며, 물성치의 변화 경향 및 민감도를 살펴보았다. 이를 통해서 3차원 엮임 재료의 물성치 사이의 상관관계를 애슈비 차트와 함께 살펴보았으며, 기존의 벌크 형태의 금속 재료와는 다른 재료 특성들로 인해 그 활용도가 높을 것으로 기대한다.

The carbon anode material for lithium-ion battery was prepared by pyrolysis fuel oil and waste polyethylene terephthalate (PET) additive. The pitch was synthesized as a medium material for carbon anode by heat treatment. The waste PET additive improved the softening point and thermal stability of the pitch. La and Lc of the anode material (heat-treated pitch) increased at higher treatment temperature but decreased by waste PET additive. The electric capacity was evaluated based on effects of defective cavity and developed graphite interlayer, respectively. When the La and Lc of the anode material decreased, the electric capacity by cavity increased based on defective graphite structure. Therefore, the addition of waste PET causes the improved capacity by the cavity. The anode material which has a high efficiency (over 95%) and C-rate (95%, 2 C/0.1 C) was obtained by controlling the process of heat treatment and PET addition. The mechanism of lithium-ion insertion was discussed based on effects of defective cavity and developed graphite interlayer.

We reported the synthesis of dendrite-like carbon nanotube-confined polymeric sulfur composite by modifying the surface of carbon nanotubes (CNTs) with trithiocyanuric acid (TTCA) and then copolymerizing with sulfur. DSC results show the successfully formation of robust chemical bonds between sulfur and TTCA modified CNTs, which effectively avoid the dissolution of polysulfide when used as cathodes for lithium–sulfur batteries. The composite with a high sulfur content of 78 wt% exhibits an initial charge capacity of 698 mAh g− 1 and the residual capacity of 553 mAh g− 1 after 1000 cycles at a rate of 1 C.

In relation to the development of automatic discharging and grinding system producing eco-friendly composite fertilizer raw materials, the performance test was proceeded. and We had obtained the following results. 1. Of the evaluation items set as performance indicators for this technology development, the “grinding capacity” of the composite fertilizer roll mill is higher than the current market-sufficient performance (1500kg/hr) of 1800kg/hr.For “grind particle size”, results of less than 1.8 mm on average were obtained, which is smaller than market-sufficient performance (average less than 2 mm). 2. As a result of the evaluation of “1batch 400kg discharge time”, the results of less than 10min/1bach were obtained, which is shorter than the market satisfaction performance (15min/1bach).

Natural gas is the most realistic fuel among eco-friendly fuels. Natural gas production is limited, and in Korea, it is supplied and utilized in the form of liquefied natural gas (LNG). In the case of LNG, the vaporization point is 163 degrees below zero, so ordinary metal cannot be used due to its brittleness. The International Maritime Organization (IMO) defines metals that can be used in the IGC Code, and is used for storage containers, transportation containers, etc. based on the metals. Welding is essential in the manufacture of large structures such as LNG storage tanks. In this study, weldability studies related to cryogenic materials were conducted. In Part I of this study, high-manganese steel and part II were studied for two types of stainless steel (STS304L, STS316L), and in Part III, aluminum (AL5083). During laser welding, the shape of the Bead on Plate (BOP) was analyzed, and a total of nine cases were analyzed using laser power and welding speed as variables. It was confirmed that the penetration and the width of the welding width were linearly proportional to the amount of heat input. Based on this study, it is possible to conduct a follow-up study to find the optimal welding conditions for butt welding and fillet welding.

As the part of efforts to respond to the environmental pollution, the demand for clean energy is increasing. Natural gas is one of the most realistic alternatives, and interest in the storage and transportation containers to utilize the natural gas is growing. The production area of ​​natural gas is limited, and in Korea, it is imported in the form of liquefied natural gas. LNG is a cryogenic state with a vaporization point of -163°C, so the ordinary metal cannot be used due to its brittleness. The international maritime organization (IMO) defines the metals that can handle LNG in the IGC Code, and the research is ongoing. This study was a preliminary study to check the weldability of related metals and confirmed the shape of bead on plate (BOP) during the laser welding for each material. In part I, a study was conducted on the high manganese steel, and in part II, a study was conducted on the materials of STS304L and STS316L among the stainless steel. Based on this study, it can be used as an optimal welding condition for the butt and fillet welding.

As demand for eco-friendly energy increases, demand for natural gas and Liquefied natural gas (LNG) storage technologies continues to increase. LNG is a cryogenic environment with a temperature of -163°C, so ordinary metals cannot be used due to brittleness. Accordingly, IGC Code designates the cryogenic materials such as Invar, STS304L, Al5083-0, and High Manganese Steel. For fabricating those materials, research on welding possibility is the most important. Thus this study focused on the possibility of laser welding of the cryogenic materials. The weldability of High Manganese Steel was researched in this paper, the shape and the dimensions of the beads after bead on plate (BOP) welding were observed. The experiment was conducted on a total of 25 cases with laser power and welding speed of 5 cases each, and the width, height, and penetration of the beads were confirmed. It was confirmed that the paramenter of bead increased linearly with the laser power, and the paramenters of bead increased linearly with decreasing welding speed. Based on this study, high manganese steel can be applied in various industries by applying it to butt welding.

본 연구에서는 국내 유통중인 가정간편식 샤브샤브 밀키트를 원료별(쇠고기, 숙주, 쌈추, 새송이버섯, 배추, 단호 박)로 구분하여 미생물 오염도를 알아보기 위해 일반세균수(total aerobic bacteria), 대장균군(coliform)/대장균(E. coli), 효모 및 진균류(fungi), 황색포도상구균(S. aureus), 및 바실러스세레우스(B. cereus)에 대한 정량적 분석을 실시하였다. 아울러, 살모넬라(Salmonella spp.)와 리스테리아 모노사이토제네스(L. monocytogenes)에 대한 정성적 분석을 실시하였다. 샤브샤브 밀키트 원료의 일반세균수(총균 수)는 3.98-6.50 log CFU/g로 검출되었다. 특히, 쇠고기의 경우 6 log CFU/g 이상의 균이 검출되었으며 숙주, 단호박, 배추의 경우 5 log CFU/g 이상의 균이 검출되었다. 진균류 (곰팡이/효모)의 오염도는 2.78-3.52 log CFU/g 수준으로 검출되었다. 대장균군은 일반세균수와 마찬가지로 쇠고기에서 3.28 log CFU/g으로 가장 높게 검출되었으며 기타 신선야채류의 경우 2 log CFU/g 수준으로 검출되었다. 대장균은 6가지 원료 모두에서 검출되지 않았다. S. aureus 는 쇠고기와 쌈추를 제외한 숙주, 배추, 새송이버섯, 단호박에서 1.33-1.71 log CFU/g의 수준으로 검출되었다. B. cereus는 쌈추를 제외한 모든 원료에서 1.15-2.01 log CFU/g 의 수준으로 검출되었다. L. monocytogenes는 새송이버섯을 제외하곤 모든 원료에서 25-50%의 양성검출을 보였고 Salmonella는 모든 원료에서 음성으로 나타났다. 본 연구 결과의 종합적 분석시, 쇠고기 원료에서 일반세균수와 대장균군 기준치를 초과하였고 황색포도상구균과 바실러스 세레우스는 대부분의 원료에서 식품안전을 위협할만한 위험한 수준은 아니었으나 검출되었고 저온성식중독균인 리스테리아모노사이토제네스 역시 일부 원료에서 양성을 보였기 때문에 본 제품의 원료별 생산단계에서의 살균·소독의 적절한 공정과 섭취시 충분한 열처리를 통해 잔존미 생물을 사멸하는 것이 긴요하다. 또한 조리기구 및 조리 종사원 손에 의해 최종 식품을 공정하면서 미생물이 전 파될 가능성이 있으므로 최종 식품의 안전성을 확보하기 위해 오염된 접촉면에 의한 교차오염을 최소화하며, 개인위생수준의 개선, 조리기기의 분리사용과 세척 및 소독을 통한 조리기기의 청결유지가 무엇보다도 중요하다. 아울러 본 연구의 미생물오염수준 자료는 가정간편식밀키트의 미생물위해평가(Microbial Risk Assessment) 의 기초자료로 활용될 수 있을 것으로 사료된다.

In this study, air scouring cleaning was selected and applied among 5 small blocks (S1~S5) in domestic S cities to analyze the cleaning effect of particles causing discoloration. In order to identify the cleaning effect, 10 locations were selected as water quality investigation point, such as the stagnant or water mains ends. Removal of solids, variation of particle components, weight and concentration were analyzed. And the level of the cleanness of the surface inside water mains using endoscope was investigated. As a result of analysis, the solids discharged after cleaning were mainly sand and gravel, pieces related to pipe materials, and corrosion products. As a result of analyzing the concentrated particles of the filter before and after cleaning, it was found that the change in discoloration on the filter was large. In addition, as a result of comparing the weight and the concentration of the particles, it was found that the particles causing discoloration were significantly removed after cleaning. From the results of the endoscopy, it was confirmed that most of the precipitated and accumulated dark yellow discoloration matters inside water mains were removed through cleaning. Therefore, it seems that the particles causing discoloration in water decreased after cleaning. Therefore, it is expected that, if properly cleaning was applied, matters that cause discoloration can be removed from the water mains, and customer's complaints can also be reduced through water quality improvement.

초음파 탐상은 다양한 콘크리트 구조물의 비파괴검사에서 활용된다. 본 연구에서는 골재형상을 고려한 골재-모르타르 모델 생성과 초음파 전파 해석을 수행하였다. 실제 골재형상을 반영하기 위해 이미지처리를 통한 골재-모르타르 단면으로부터 모르타르와 골재 영역을 파악하고, 영역 경계형상을 보존하면서 격자를 생성하는 기법을 개발하였다. 개발된 기법에서는 모든 격자가 4각형으로 생성된다. 골재-모르타르 모델을 통해 초음파 전파 해석을 수행하였고 모델을 반무한체로 간주하기 위해 CALM 기반 경계흡수 조건을 적용하였다. 골재 및 결함을 포함한 이미지로부터 격자를 생성한 뒤, 결함 영역에 포함된 격자를 제거하여 공극결함을 모사하였다. 본격적인 결함탐지 전 선행 해석을 통해 모델 동특성을 고려한 적절한 가진 주파수를 결정 및 가진 신호형상을 설계하였다. 이후 case 별 초음파 전파 해석을 통해 신호를 획득하고 신호 에너지 맵핑 작업을 통해 내부 결함을 가시화 하였다. 가시화 결과, 골재에 의한 다수 반사 및 산란현상이 관찰되지만 결함부에서 신호 에너지는 가장 높게 나타났으며 모든 해석 case에서 결함위치 추정이 가능하였다. 또한 균열의 경우 형상파악도 가능하였다.