• Journal of Sensor Science and Technology
• /
• v.9 no.5
• /
• pp.380-388
• /
• 2000

The finite element analysis of a micro turbine was made to investigate safety margin of its operating condition for the high aspect ratio nickel micro turbine blades fabricated by conventional LIGA-like method. From our study, we found that the fabricated turbine could not exceed its yield strength even if the pressure difference between inlet and outlet of turbine blade was about 44kPa, and the correlation of friction coefficient and the maximum stress, caused by contact friction between outer diameter of shaft and inner diameter of turbine blade, was somewhat reciprocal. The maximum stress was decreased with the increasing contact friction, when turbine blade was in its state of rotation. By the results of our study, we conclude that it is possible to fabricate metal micro turbine more easily han surface micromachining technology and to operate with no risk of metal structure's damage, which is caused by yield strength, if the operating condition with the design of micro turbine itself are optimized. It is useful to adopt other applications which have the contact problems between a moving part and the fixed one in micro structures.

• Korean Journal of Food Science and Technology
• /
• v.46 no.3
• /
• pp.364-368
• /
• 2014

This study investigated the antioxidant activity of onion peels extracted from onion byproducts by hot water treatment. Hot water extraction of freeze dried onion peel powder was analyzed for total polyphenol content, 2,2'-diphenyl-1-picryllhydrazyl (DPPH), and 2,2'-azino-bis(3-ehtylbenzothiazoline-6-sulphonic acid) (ABTS) radical scavenging activities, reducing power, oxygen radical absorbance capacity (ORAC). Total polyphenol content was the highest (233.90 mg/g) in onion peel extract mix with ethanol (OPME-1). The DPPH radical scavenging activity ($IC_{50}$), reducing power, and ORAC obtainbed from onion peel extract mix with ethanol precipitation (OPMPE-1) were the highest at 1.15 mg/mL, 1.69 $A_{700}$, and $318,509{\mu}M\;TE/mL$, respectively. The ABTS radical scavenging activity was the highest at 432.78 mg amino acids (AA) eq/g in the OPM. The results of this study suggest that onion peel extracts have marked antioxidant activity, which can have significant health benefits.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.9 no.5
• /
• pp.590-597
• /
• 1985

A recursive geometric adaptive control method to compensate for machining straightness error in the finished surface due to tool deflection and guideway error generated by end milling process is developed. The relationship between the tool deflection and the feedrate is modeled by a modified Taylor's tool life equation. Without a priori knowledge on the variations off cutting parameters, time varying parameters are then estimated by an exponentially windowed recursive least squares method with only post-process measurements of the straightness error. The location error is controlled by shifting the milling bed in the direction perpendicular to the finished surface and adding a certain amount of feedrate with respect to the tool deflection model before cutting. The waviness error is compensated by adjusting the feedrate during machining. Experimental results show that location error is controlled within a range of fixturing error of the bed on the guideway and that about 60% reduction in the waviness error can be achieved within a few steps of parameter adaption under wide operating ranges of cutting conditions even if the parameters do not converge to fixed values.

• Journal of the Society of Naval Architects of Korea
• /
• v.34 no.1
• /
• pp.122-129
• /
• 1997

Thermo-elastic-plastic analyses used in solving plate forming process are often computationally expensive. To obtain an optimal process of line heating typically requires numerous iterations between the simulation and a finite element analysis. This process often becomes prohibitive due to the amount of computer time required for numerical simulation of line heating process. Therefore, a new techniques that could significantly reduce the computer time required to solve a complex analysis problem would be beneficial. In this paper, we considered factors that influence the bending effect by line heating and developed inference engine by using the concept of artificial neural network. To verify the validity of the neural network, we used results obtained from numerical analysis. We trained the neural network with the data made from numerical analysis and experiments varying the structure of neural network, in other words varying the number of hidden layers and the number of neurons in each hidden layers. From that we concluded that if the number of neurons in each hidden layers is large enough neural network having two hidden layers can be trained easily and errors between exact value and results obtained from trained network are not so large. Consequently, if there are enough number of training pairs, artificial neural network can infer similar results. Based on the numerical results, we applied the artificial neural network technique to deal with mechanical behavior of line heating at simulation stage effectively.

• Korean Journal of Food Science and Technology
• /
• v.32 no.2
• /
• pp.323-327
• /
• 2000

Microwave-assisted process (2,450MHz), which is known as a more environmental-friendly process with economic advantages than the current extraction methods, was investigated to pre-establish the extraction conditions for soluble ginseng components used for the processing of ginseng products. The extractions of soluble ginseng components showed optimum conditions, such as 60 mesh in particle size, 1 : 10 (g/mL) in the sample to solvent ratio, and less than 100 watts in energy efficiency. Under these conditions using along with 60% ethanol for 5 min, the overall yield of ginseng extracts was about 83%. Most soluble components including saponins were extracted by repeating five times of microwave-assisted extraction.

• Korean Journal of Optics and Photonics
• /
• v.17 no.5
• /
• pp.437-446
• /
• 2006

A fabrication method fur high-aspect-ratio microchannels in stainless steel using laser-assisted thermochemical wet etching is reported in this paper. The fabrication of deep microchannels with an aspect ratio over ten is realized by applying a multiple etching process with an optimization of process conditions. The cross-sectional profile of the microchannels can be adjusted between rectangular and triangular shapes by properly controlling laser power and etchant concentration. Excellent dimensional uniformity is achieved among the channels with little heat-affected area. Microchannels with a width ranging from 15 to $50{\mu}m$ can be fabricated with an aspect ratio of ten and a pitch of 150 m or smaller. The effects of process variables such as laser power, scan speed, and etchant concentration on the fabrication results, including etch width, depth, and cross-sectional profile are closely examined.

• Proceedings of the Korean Society of Dyers and Finishers Conference
• /
• 2011.03a
• /
• pp.108-108
• /
• 2011

PLA 즉 폴리유산섬유는 옥수수를 발효하여 글루코오스(포도당)상태를 만든 후 젖산(유산, Lactic acid)으로 만들고 이것을 탈수, 축합반응시켜 polylactic acid로 만든 것이다. 생분해성이 있으므로 저탄소, 녹색성장의 모토를 대변하는 소재라는 이점이 있다. 구조는 에스테르기의 반복단위를 가지는 소수성 섬유로 벤젠환은 없으나 그 외 구조는 폴리에스테르와 비슷하며, 에스테르기가 존재하므로 분산염료와 수소결합하여 염착된다. 그러나 PLA는 융점이 $170^{\circ}C$, Tg $57^{\circ}C$로 내열성이 낮아서 염색온도, 열처리온도, 다림질에 제약이 있으며, 알칼리에 약한 단점이 있다. 따라서 PLA섬유는 낮은 염착량, 내알칼리성, 염착온도 때문에 염색 및 후가공 단계에 많은 사전 실험을 통한 조건 설정이 필요한 까다로운 섬유이다. 본 연구에서는 (주)휴비스의 PLA원사로 제직한 직물(경사:DTY 75/72SD, 위사:DTY 100/72SD, 조직:DOBBY) 생지에 대하여 열처리 시 장력의 유무, 온도, 시간에 따른 폭의 변화를 측정하여 수축률을 알아보았다. 또한, PLA직물을 온도별로 정련한 후 열처리하여 인열강도 측정을 통해 최적 전처리 조건을 조사하였다. 실험결과, PLA생지를 무장력 상태에서 열처리 시 수축이 심하게 일어나고, 장력이 주어져도 열처리 온도에 따라 수축의 정도에 차이가 나타났다. 열처리 시간은 30, 60, 90, 120초로 주었으나 큰 편차는 없었고, 경사가 위사보다 수축 정도가 더 컸으며, $130^{\circ}C$에서는 전체적으로 수축이 심하였다. 생지의 정련에는 인산에스테르계 정련제와 약알칼리인 탄산나트륨으로 조액하여 60, 70, 80, $90^{\circ}C$에서 10분간 처리한 후, Lab. tenter(Mathis, LTE)를 이용하여 110, 120, $130^{\circ}C$에서 30, 60, 90, 120초간 열처리한 다음, KS K 0535 펜듈럼법에 의거하여 인열강도를 측정하였다. 그 결과, 상기 정련온도에서는 인열강도에 영향을 주지 않았으나, 열처리 온도가 $130^{\circ}C$일 때 현저한 강도의 저하를 나타내었다. 실험조건 하에서 가장 적절한 열처리 조건은 $110^{\circ}C$, 60초로 사료된다. 따라서 PLA의 약한 내열성과 내알칼리성 실험결과, 강도나 수축 등 물성변화가 일어나지 않도록 열처리 온도의 제어에 주의가 필요함을 확인할 수 있었다. 실제 섬유가공 작업현장에서는 일반적으로 열처리기가 $180^{\circ}C$이상의 고온으로 고정된 경우가 많은데, 작업자들에게 PLA소재에 대한 사전주의 및 공정변경에 대한 주지가 요구된다.

• Food Science and Preservation
• /
• v.22 no.6
• /
• pp.851-858
• /
• 2015

This study was designed to improve the sensory characteristics and mitigate the bitter taste of Platycodon gradiflorum. It was aimed at investigating the qualitative properties of fermented P. gradiflorum after repeated steaming and drying treatments. P. gradiflorum was heated for 2 hr at $95^{\circ}C$, being the first and third treatments compared afterwards. Lactobacillus plantarum, at a concentration of 10%, was used as starter culture. As a result, the third steaming process and the addition of starter improved the physical and chemical properties of P. gradiflorum i.e., crude saponin and total polyphenol contents increased significantly. Moreover, P. gradiflorum steamed three times and fermented by L. plantarum showed the higher overall preference score. Our results indicated that the three-time steaming and drying was an effective manufacturing process for the production of high-quality fermented P. gradiflorum. Lactic acid-fermented P. gradiflorum also could have a potential use as a valuable resource for the development of functional products.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.13 no.2
• /
• pp.307-315
• /
• 1989

In recent years, the fatigue design method by analysis for the mechanical components and the welded structures has much increased, instead of the fatigue design method by rule that has been widely used from the past days. When a fatigue design is conducted by that method, the basic informations, fatigue life curves are mainly obtained from the results of the strain controlled low cycle fatigue test. From these point of views, the low cycle fatigue test is coming to be given a much importance lately. In this paper, the strain controlled low cycle fatigue properties at room temperature in air environment were investigated for the low carbon forged steel, SF45A, and the rolled steel for the welded structure, SM 41B. Throughout the test, strain ratio, R, was maintained constant with the fully reversed condition, -1. As the experimental results, the cyclic stress-strain behaviours of the test materials were different each other, but the low cycle fatigue life-time of them appeared to show little difference in the region of this test conditions.

• Korean Journal of Poultry Science
• /
• v.46 no.1
• /
• pp.39-46
• /
• 2019

This study was conducted to investigate the effect of dietary bee venom on serum characteristics, antioxidant activity, and hepatic fatty acid composition in broiler chickens. A group of 875 one-day-old feather-sexed male broiler chicks were randomly allocated to five treatments with seven replicates (25 birds/replicate) for three weeks. A corn-soybean meal-based diet was used as the basal diet. Five dietary treatments were compared: 1) basal diet, 2) basal diet containing $10{\mu}g/kg$ of bee venom powder, 3) basal diet containing $50{\mu}g/kg$ of bee venom powder, 4) basal diet containing $100{\mu}g/kg$ of bee venom powder, and 5) basal diet containing $500{\mu}g/kg$ of bee venom powder. At 21 days, one bird per pen was slaughtered by asphyxiation in $CO_2$ gas, and blood was collected to measure serum characteristics and antioxidant activity. In addition, the liver was excised to measure the concentration of malondialdehyde and determine fatty acid composition. Increasing dietary bee venom in the diet failed to affect most serum parameters except for triglyceride and non-esterified fatty acids. Dietary bee venom inclusion quadratically increased the concentration of stearic acid (P<0.05), but decreased palmitoleic acid, oleic acid, linoleic acid, mono-unsaturated fatty acids, and poly-unsaturated fatty acids. Finally, dietary bee venom tended to lower hepatic malondialdehyde contents quadratically (P=0.054). In conclusion, our study revealed that dietary bee venom improved antioxidant capacity and affected fatty acid metabolism in broiler chickens.