• Journal of the Korean Chemical Society
• /
• v.43 no.3
• /
• pp.307-314
• /
• 1999

Ml RNA, the RNA component of RNase P from Escherichia coli, is produced by 3' processing of pre-Ml RNA, a major primary transcript of the rnpB gene. The enzyme fraction containing the processing activity was partially purified and characterized. Since exposure of the active fraction to the high salt condition results in the inactivation of the processing activity, the processing enzyme seems to be an enzyme complex composed of multiple enzymes. The enzyme fraction loses the processing activity when treated with the chemical nuclease lead(II) ion, but regains its activity by the addition of RNA isolated from the enzyme fraction itself, suggesting that an RNA molecule(s) may be essential for the processing activity. Analysis of cleavage sites produced by the partially purified enzyme fraction also implies that the 3' processing occurs by multiple enzymes and at least in two distinct pathways.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2005.06a
• /
• pp.100-103
• /
• 2005

In this study, tool path control algorithm for aspherical surface grinding was derived and discussed. The aspherical surface actually means contact points between lens and tool. Tool positions are generally defined at the center of a tool, so there is difference between tool path and lens surface. The path was obtained from contact angle and relative position from the contact point. The angle could be calculated after differentiating an aspheric equation and complex algebraic operations. The assumption of the control algorithm was that x moves by constant velocity while z velocity varies. X was normal to the radial direction of lens, but z was tangential. The z velocities and accelerations were determined from current error and next position in each step. In the experiment, accuracy of the control algorithm was checked on a micro-precision machine. The result showed that the control error tended to be diminished when the tool diameter increased, and the error was under sub-micro level.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.24 no.10 s.181
• /
• pp.2496-2501
• /
• 2000

High speed ball end milling is attracting interest in the aerospace industry for the machining of complex 31) airfoil surfaces in nickel based superalloys, Experimental work is detailed on the effect of cutter orientation on tool life, cutting forces, chip formation, specific force and workpiece surface roughness, when high speed ball end milling nickel based supperalloy(lnconel 718). Dry cutting was performed using 8min diameter solid carbide cutters coated with either TiA1N or CrN for the workpiece mounted at an angle of 45˚ from the cutter axis. A horizontal downwards cutting orientation provided the best tool life with cut lengths~50% longer than for all other directions. Evaluation of cutting forces and associated spectrum analysis of results indicated that cutters employed in a horizontal downwards direction produced the least vibration.

• Journal of Life Science
• /
• v.33 no.2
• /
• pp.216-226
• /
• 2023

Since nylon 66, a polyamide resin, has been developed and applied to toothbrush bristles, plastic consumption has increased rapidly every year, along with the increase in the amount of plastic discarded. Among the various forms of plastic debris produced by the decomposition of plastics, microplastics with a size of less than 5 mm are widely distributed in the environment, which poses a threat not only to the environment but also to animals and humans. The pathway through which microplastics enter the human body is known as ingestion by water and food, inhalation from air, and skin contact. Microplastics introduced into the human body affect human health. Recently, food-related studies have begun to be reported among microplastics-related studies, and analyses of the presence of microplastics in processed foods, such as canned foods, dried seaweed, beverages, beer, milk, sugar, and honey, are underway. Here, we present trends in the production and consumption of plastics, the generation of microplastics, the route of human inflow and human risk, and the microplastics present in processed foods, which are limited but have recently been reported. Thus far, studies on microplastics and risk assessment in processed foods have been insufficient, but microplastics are gradually being recognized as a factor that affects the environment and food. Future studies are expected to have implications for regulations regarding microplastics present in processed foods.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.44 no.10
• /
• pp.1567-1582
• /
• 2015

The purpose of this study was to examine the status of environmentally-friendly ingredients and dietitians' perceptions toward them in order to find for improvement. Data was collected from questionnaires completed by 202 school dietitians and nutrition teachers in Chungbuk, and this data was analyzed utilizing the SPSS 20.0 program. The results obtained from this study were as follows: 'mixed grains (58.9%)' and 'eggs (36.6%)' were found to be the most used environmentally-friendly ingredients. 81.7% of the respondents said they 'never used' marine products, whereas 'fruits (43.6%)', 'pork (40.8%)', and 'fish (54.5%)' were the most preferred ingredients. Dietitians and nutrition teachers used environmentally-friendly marine products less than other ingredients, had a poor understanding about environmentally-friendly marine products, and demonstrated low reliability and belief in the necessity of the system. In order to verify the environmentally-friendly status of the ingredients, marks on the product and documents of certification were mostly used. In order to improve the supply system, a more strict tracking system in the distribution process by securing more reliable suppliers is required.

• Proceedings of the Korean Society of Dyers and Finishers Conference
• /
• 2012.03a
• /
• pp.62-62
• /
• 2012

지구온난화 및 환경오염의 영향으로 선진국을 중심으로한 환경규제가 심해지면서, 홈 텍스타일 분야에서는 세계 패션 트렌드 및 소비자 선호에 부응한 친환경 섬유소재 개발, 웰빙 시대에 적합한 기능성 및 고감성 제품개발을 통한 차별화가 요구되고 있다. 최근의 섬유산업의 동향도 인체에 무해한 천연적인 섬유소재에 많은 관심이 증대됨에 따라 개인의 건강 뿐만 아니라 환경을 생각하는 생활패턴인 친환경섬유의 개발이 새로운 트렌드로 떠오르고 있는 실정이다. 헴프는 일년생 식물로서 학명은 Cannabis sativa L.이다. 헴프섬유의 장점으로 내구성 및 내수성, 항균성 등이 우수한 것으로 보고되고 있으나 양질의 원료 확보, 세섬도 추출 기술 및 combing 기술 등의 부족으로 100% 헴프 세 번수 방적사의 제조가 어려워 주로 면섬유와의 혼합소재로 제조되어 왔다. 최근 들어, 친환경 소재로서 박테리아 성장 억제 기능을 가진 재생섬유인 Tencel 소재를 이용하여 stiff한 Hemp의 성질에 유연성을 추가하여 촉감을 개선함과 동시에, Tencel과 Hemp를 혼용함으로써 soft touch부터 harsh touch까지 혼용율에 의한 다양한 감성을 느끼게 함으로써 용도의 다양화 추구가 시도되어 왔다. Hemp의 거친 느낌을 완화시키고 Tencel의 박테리아 억제 기능과 Hemp의 항균기능, 방충, 탈취기능이 상호 보완되어 친환경적이고 위생적인 다용도 홈 인테리어 및 가구용 직물 등의 제품으로 Hemp/Tencel 복합사가 많이 사용되고 있다. 본 연구는 Hemp와 Tencel의 혼용율의 변화에 따른 복합사의 물리적 특성을 확인하기 위하여 천연복합 태번수 방적사 최적 사설계 이론을 적용하여 Hemp 섬유 혼용율에 따른 사의 물성분석을 함으로써 Hemp/Tencel 방적사 최적 공정 조건을 결정하기 위한 사설계 이론 결과와 실험결과를 비교 분석하고자 한다. 최적 천연 Hemp복합방적사 사설계의 이론화 및 사 물성 DB화 그리고 태번수 Hemp사의 물성분석 및 이들을 DB화 함으로써 가구용 직물로 많이 사용되는 친환경 Hemp 소재사의 방적성 향상을 꾀하고자 한다. 이를 위해서 제조한 방적사의 Dry heat shrinkage와 Wet heat shrinkage를 측정하여 확인하였고 인장시험기를 이용하여 Tenacity, Initial Modulus, breaking strain을 측정 분석하였다. 방적사의 표면 특성은 영상 현미경 시스템을 사용하여 ${\times}40$ 배율로 측정하여 확인하였다.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2007.05a
• /
• pp.241-245
• /
• 2007

The residual stress in axial stress in the axial direction of the steel filaments has been measured by using a method based on the combination of the focused ion beam (FIB) and high resolution strain mapping program (VIC-2D). That is, the residual stress was calculated from the measured displacement field before and after the introduction of a slot along the steel filaments. The displacement was obtained by the digital correlation analysis of high-resolution scanning electron micrographs, while the slot was introduced by FIB milling with low energy beam. The present measurement revealed that the residual stress within 8% of the magnitude was persistent in the steel filaments fabricated.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2007.05a
• /
• pp.314-317
• /
• 2007

Automotive rear subframe of aluminum tube was developed by using hydroforming process, based on the numerical analysis and physical tryouts. In the previous study, the effect of prebending was evaluated on the basis of forming limit diagram which had been obtained from free bulging, T-shape forming and cross-shape forming, using the developed tube hydroformability testing system. In order to get the sound products, appropriate internal pressure is to be imposed corresponding to the axial feeding. In this study, the loading path, the combination of internal pressure and axial feeding during the process, was optimized to ensure minimum thickness variation and dimensional accuracy, by using response surface method.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2007.05a
• /
• pp.409-412
• /
• 2007

A motorcycle helmet is the best means to protect the head of bike's driver and it is directly connected to a driver's life. Prior to producing of the helmet, it has to be passed the process of impact test to evaluate of its safety. This test evaluates peak acceleration and H.I.C (Head Injury Criteria). This paper analyzes impact test with finite element method to find the behavior of helmet during the test. Also, the effect of impact sites on the helmet was evaluated to improve the thickness distribution of the helmet.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2008.10a
• /
• pp.273-276
• /
• 2008

In this study, microstructure and distribution of alloy elements were investigated in thermo-mechanically processed C-Mn-Si transformation induced plasticity (TRIP) steels. The microstructures of TRIP steels were investigated by using advanced analysis techniques, such as three dimensional atom probe tomography (3D-APT). At first, the microstructure was observed by using TEM. TEM results revealed that microstructure of C-Mn-Si TRIP steel was composed of ferrite, bainte, and retained austenite. 3D-APT was used to characterize atomic-scale partitioning of added elements at the phase interface. In the retained austenite phase, Ti and B were enriched with C. However, there was no fluctuation of Mn and Si concentration across the interface. Through these analysis techniques, the advanced characteristics of constituent microstructure in C-Mn-Si TRIP steels were identified.