• Advances in nano research
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• 제16권5호
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• pp.459-472
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• 2024

Nanotechnology is a popular field in the construction industry due to its multiple functions. It mitigates CO₂ emissions and enhances the desirable properties of concrete by replacing small amounts of cement with supplements. This study assess the sustainability impact of using two different nanoparticles partially replacing the cement with 0.3%, 0.6%, 1.0% of nano silica (NS) and 0.03%, 0.045%, 0.06% of Multi-Walled Carbon Nanotubes (MWCNT) in the green concrete mix developement. Nano-sized fragments at the atomic scale tends to modify the properties of concrete. Concrete may increase its strength, durability by adding nanocomposite materials, which will decrease the amount of nano and micropores in structural parts. The strength of the structural elements can be greatly improved and allowing them to withstand higher loads and resist deformation. It improved durability properties by 64.8% in water absorption, 56.4% in acid attack, 78.1% in sulphate attack, and 53.4% in chloride attack. There was an improvement in compressive strength of 37% and split tensile strength of 90%. SEM, FTIR, and XRD investigations have used to look at the microstructural characteristics of nanoconcrete dictated the microstructure characteristics may be made more consistent and dense by adding nanocomposite materials.

• 식품과학과 산업
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• 제50권2호
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• pp.2-11
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• 2017

소비자들의 전반적인 생활환경 향상에 따른 웰빙 라이프 추구에 따라 소비자는 맛뿐만 아니라 식품의 질적인 측면 또한 중요시하게 되었으며, 이에 따라 안전한 식품 섭취에 대한 요구가 확대되었다. 또한 가공 곡류 등의 저장 식품에서의 해충의 피해가 빈번히 일어나며, 이는 식중독 유발 등 인체에 위해를 가할 수 있다는 보고가 계속 됨에 따라 이에 대한 해결 방안이 필요하다는 목소리가 커지고 있는 실정이다. 따라서 전 세계적으로 식품에의 해충 오염 원인을 파악하고 이에 대한 해결 방안을 제시하기 위한 연구들이 지속적으로 진행되고 있으나 궁극적인 해결 방안이 제시되지 않고 있는 실정이며, 특히 방충 식품 포장재 개발 연구에 뒤따른 실질적인 상용화는 상당히 미흡한 실정이다. 따라서 식품 업계에서는 식품포장 본연의 목적을 충실히 만족하며 기능성 포장으로서 해충의 침입을 방지하는 합리적인 방충 포장재 개발기술을 발전시키는데에 총력을 기울여야 할 것이다. 더불어 앞으로 산학연의 협력하에 저장해충을 방지할 수 있는 안전성이 입증된 적합한 방충 물질 탐색에 관한 연구는 물론, 실제 산업에도 도입시킬 수 있도록 경제성을 갖춘 포장재 개발에 대한 연구가 활발히 이루어져야 할 것이다.

• 한국생산제조학회지
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• 제19권2호
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• pp.163-170
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• 2010

We have studied on welding dissimilar materials of cold-reduced carbon steel sheet and stainless steel sheet together by using laser beam. It is well known that stainless steel is so strong againt rust and heat, while cold-reduced carbon steel is widely used in various parts of industry. In this research we have performed some experiments to know the possibility of welding dissimilar materials using laser beam by adjusting the power output of 3kW laser. Other conditions of the experiments were as follows : the welding speed was varied in the range between 2m/min and 7m/min, argon gas and helium gas were used as shield gas, the flow value of shield gas was ranged between $10{\ell}/min$ and $30{\ell}/min$, and the gap of two materials was ranged between 0mm and 0.3mm. In order to ascertain of the welded surface, we have done the tensile strength testing, the hardness testing and the microscope observation. As a result, we have found that tensile strength was the highest at the condition of the welding speed of 4, the flow value of $20{\ell}/min$, the gap of two materials 0, and the use of helium gas. Above testings have also showed that the tensile strength was generally satisfactory since the penetration of welding was almost complete due to the thinness of the materials. In addition, the formation of the welded area was excellent when it had the highest tensile strength.

• 한국안전학회지
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• 제1권1호
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• pp.51-59
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• 1986

This study was conducted to analyse the exact causes of occupational accidents in Korean construction industry and to contribute to the accident prevention programs. The results and conclusions of the field survey are as follows ： 1) The accidents caused by hazardous conditions are 96 percent, and those by unsafe acts are 97.3 percent. The accidents caused simultaneously by two categories are nore than 96 percent. 2) The injured workers who were employed less than 3 months are 71.1 percent. Safety training for newly recruited workers should be required. 3) More than 40 percent of all accidents were occurred in the morning and more than 30 percent were in summer. Required caution should be paid for the time and season. 4) Fracture, cut/laceration/puncture and multiple injuries in the lower extremeties, upper entremeties and head as well as many kinds of injuries by the fall from elevation mainly occurred. Safety. shoes, safety gloves, safety helmets, safety glasses, face shields and safity belts should be used 5) As the sources of injuries, each of building/structure and materials is one third of all sources, and machinery is a quarter. 6) The use of hazardous methods/procedures, defects of agencies and inadequate guarding of builing/structure, materials' and machinery mainly caused the accident types, such as s truck by, struck against, fall from elevation, and fall on same level. Such a hazardous conditiion should not be used and be correctet 7) The unsafe acts, such as improper use of hands or body parts, the operation or working at unsafe speed and improper use of equipment mainly caused accidents. Safety training for the control of such a unsafe acts should be strengthened.

• 소성∙가공
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• 제17권2호
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• pp.124-129
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• 2008

Net shape forging technologies give many effects into the costs and qualities for the finished products. So, the studies to reduce the additional machining amount are very important in forging industry. Specially, there are two main topics in cold forging industry, such as, tool life and precision forging. In this study, new forging technique was proposed to eliminate the machining process for fixing up the length and improve the lead accuracy of gear. The luck-up hub is manufactured through many processes, such as upsetting, piercing and direct extrusion. The gear is formed in direct extrusion process; however, lead accuracy of the gear is over allowance limit. Therefore, the additional sizing process must be added. In this study, process design for closed-die forging of a lock-up hub used for a component of automobile transmission was made using three-dimensional finite element simulations, and the strain distributions and velocity distributions are investigated through the post processor. The rigid-plastic finite-element method for back pressure forging has been used in order to reduce development time and die cost. Using the FEM simulation, we found the optimum value of back pressure. The prototypes of lock-up hub parts were forged into the net-shape. In the experiment, lead precision of tooth are measured by the CCMM(Contact Coordinate Measuring Machine). The dimensional accuracy of forged part was improved up to the 40% when back press was applied.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2015년도 추계학술대회
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• pp.208-210
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• 2015

최근 중국 천진항에서 발생한 폭발사고로 인하여 위험물에 대해 규제가 강화되고 있다. 이는 국내에서 수출되는 화학제품에도 영향을 주어 국제기준과 상이한 부분까지도 충족해야만 수입통관이 가능한 규제가 되었다. 2004년부터 국제적으로 강제화 된 위험물 운송규정(IMDG Code)을 준수하여 위험물을 수출하고 있는 국내 산업계에도 상당한 피해가 되고 있으나 중국정부의 요구에 따라야만 통관이 가능하기 때문에 물류의 효율성 측면에서 많은 어려움이 가중 되었다. 국내에서도 안전한 위험물 관리 필요성이 대두되고 있지만 단편적인 임시방편의 정책은 오히려 경제적 비용 손실과 불필요한 규제 가중으로 연결되기 되기 때문에 장기적으로 안전한 동시에 효율적인 위험물 관리방안을 찾아야만 국내 화학산업의 지속적인 성장이 가능하다.

• 한국안전학회지
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• 제38권3호
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• pp.10-19
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• 2023

Fall accidents account for the highest accident fatality rate in the construction industry. In addition, wearing and using a safety belt is the most realistic and important preventive measure to reduce fall accidents. Safety belts are protective devices worn by individual workers; they prevent workers from falling and allow for time to rescue the workers. However, the legal standards for safety belts only stipulate the materials, specifications, and strength of parts; there is no provision for an auxiliary rope fixing method to fix the safety belts safely. Due to this reason, workers in industrial sites arbitrarily fix and use the auxiliary rope. Currently, the most used method to fix the auxiliary rope is to tie a knot, which significantly lowers the strength of the material compared to the standard strength. Moreover, many construction sites are located outdoors, so the strength of the materials used in the auxiliary rope is inevitably reduced due to various external environmental conditions. Therefore, to solve this problem, this study was conducted to evaluate the strength of the material of the auxiliary rope for fixing the safety belt and the knot-tying method for the auxiliary rope. In this study, the exposure conditions for the effects of temperature and moisture were set to reflect the characteristics of the construction industry. The results of this study are expected to be used for standards establishment and the safe use of the auxiliary rope for safety belts in actual field applications.

• Journal of Welding and Joining
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• 제34권1호
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• pp.21-25
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• 2016

The automotive vehicle is made through the following processes such as press shop, welding shop, paint shop, and general assembly. Among them, the most important process to determine the quality of the car body is the welding process. Generally, more than 400 pressed panels are welded to make BIW (Body In White) by using the RSW (Resistance Spot Welding) and GMAW (Gas Metal Arc Welding). Recently, as the needs of light-weight material due to the $CO_2$ emission issue and fuel efficiency, new joining technologies for aluminum, CFRP (Carbon Fiber Reinforced Plastic) and etc. are needed. Aluminum parts are assembled by the spot welding, clinching, and SPR (Self Piercing Rivet) and friction stir welding process. Structural adhesive boning is another main joining method for light-weight materials. For example, one piece aluminum shock absorber housing part is made by die casting process and is assembled with conventional steel part by SPR and adhesive bond. Another way to reduce the amount of the car body weight is to use AHSS (Advanced High Strength Steel) panel including hot stamping boron alloyed steel. As the new materials are introduced to car body joining, productivity and quality have become more critical. Productivity improvement technology and adaptive welding control are essential technology for the future manufacturing environment.

• Elastomers and Composites
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• 제47권1호
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• pp.65-74
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• 2012

최근 전세계적으로 자원 고갈로 인한 에너지 절약과 환경 문제에 관한 규제 강화는 환경 친화적인 소재 개발의 필요성을 가속화시키고 있다. 이러한 추세는 자동차 산업을 포함한 운송 산업도 예외가 아니다. 또한, 기본적으로 단순히 성능이 좋으면서도 값이 저렴한 제품이 아니라, 소비자와 사회의 요구에 부합되는 고기능성 소재의 개발이 필요하다. 이에 부합하는 소재로는 최근 운송 수단의 경량화를 위하여 많은 연구가 진행중인 탄소섬유 복합재료라할 수 있다. 최근 탄소섬유 복합재료는 자동차의 경량화를 위해 차체 및 부품 등 다양한 부분에 적용됨에 따라 그 수요는 크게 증가하고 있고, 차량에 적용시 차체 중량감소에 따른 제동, 조향, 내구 및 연비향상과 이에 따른 에너지 절약 및 이산화탄소 배출을 최소화 하는 장점을 갖는다. 따라서, 본고에서는 자동차의 경량화를 위한 탄소섬유 복합재료의 필요성과 더불어 탄소섬유 복합재료의 기술동향과 나아가야 할 방향에 대하여 살펴보도록 하겠다.

• 비파괴검사학회지
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• 제23권2호
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• pp.148-155
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• 2003

저방사화 페라이트강인 JLF는 핵융합로의 블랑켓과 같은 열교환기의 재료로써 유용한 재료이다. 이 재료의 광범위한 적용을 위해서는 JLF강과 다른 재료와의 접합기술의 개발이 중요하다. 최근 두 이종재료간의 접합에는 마찰용접이 많이 이용되고 있으며 본 연구에서도 JLF강과 STS304 간의 마찰용접에 의한 용접특성을 평가하였으며 특히 비파괴기법중의 하나인 음향방출 기법을 이용하여 두 이종재료간의 용접특성 및 최적의 용접조건을 평가하였다. 음향방출 파라미터중의 하나인 카운트와 사상수 등이 최적용접조건 및 용접품질을 평가하는데 유효한 파라미터들이었다.