• Title/Summary/Keyword: Poor-contact

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Printability Improvement of Hanji (한지의 인쇄적성 향상)

  • Hyun Kyung-Su;Kim Min-Jung;Lee Myoung-Ku
    • Journal of Korea Technical Association of The Pulp and Paper Industry
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    • v.37 no.4 s.112
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    • pp.52-59
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    • 2005
  • Most of printing paper market today have been occupied by western paper and some machine-made Hanji used don't show the characteristic advantages for traditional hand-made Hanji. Although hand-made Hanji has an aesthetic and qualitative value, it has limited uses because of poor printability as printing paper. Unlike western paper, conventional Hanji cannot be used as Printing paper because it is impossible to make the clear formation of printed dot and to develop a high level of sizing and picking problem occurs during printing. Improvements of physical and optical properties such as roughness, smoothness, air permeability, contact angle, opacity, and paper gloss as well as sizing level were accomplished through internal and surface sizing and calendering, which made the paper better suited for printing and decreased problems during printing.

Evaluation of Friction Torque for a Turbopump Ball Bearing (터보펌프 볼 베어링의 마찰 토크 평가)

  • Jeon, Seong-Min;Kwak, Hyun-Duck;Kim, Jin-Han
    • Tribology and Lubricants
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    • v.27 no.1
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    • pp.25-33
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    • 2011
  • Rolling contact ball bearings are utilized almost exclusively for liquid propellant rocket engine turbopump. Turbopump ball bearings are required to endure high speed and high load for a poor lubricated condition in cryogenic environment. To evaluate bearing heat generation performance, friction torque is investigated as a function of rotation speed, bearing load and cooling flow rate through an experimental study using water coolants. Radial and axial loads are simultaneously applied to the test bearing by gas pressurized cylinder rod. Endurance performance of bearing has been also verified under the bearing required load for operating condition during total accumulated test time 2,100 sec.

A Study on the Thermal Characteristics Depending on Poor Contact of Wire Connection Part in Terminal Block (단자대 전선접속개소의 접촉불량에 따른 발열특성에 관한 연구)

  • Park, Sang-Min;Jee, Seung-Wook;Kim, Si-Kuk;Lee, Chun-Ha
    • Proceedings of the Korea Institute of Fire Science and Engineering Conference
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    • 2011.11a
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    • pp.48-51
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    • 2011
  • 본 논문은 나사조임 단자대 내에 접속되는 전선의 접촉불량에 따른 발열특성을 분석하고자 단자대 접속개소의 조임토크를 KS C 2625에서 규정한 정상조임토크와 인위적인 불량조임토크를 변수로 설정하여 조임토크의 크기별로 동일한 부하를 인가한 후, 열화상카메라를 이용하여 접속불량에 따른 발열특성을 비교 분석하였다.

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Transverse Flow and Process Modeling on the Polymer Composite with 3-Dimensionally Stitched Woven Fabric

  • Lee, Geon-Woong;Lee, Sang-Soo;Park, Min;Kim, Junkyung;Soonho Lim
    • Macromolecular Research
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    • v.10 no.4
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    • pp.194-203
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    • 2002
  • In resin infusion process(RIP), the fiber and the resin are in contact with each other for an impregnation step and often results in flow-induced defects such as poor fiber wetting and void formation. Resin flow characteristics in transverse direction and process modeling for woven fabric were studied, and the process modeling was applied to the manufacturing of hybrid composite materials. This study also considered the compressibility of woven fabrics in a series of compression force, and it was fitted well to an elastic model equation. Void formation was varied with the processing conditions in the stage of manufacturing composites using RIP. It was concluded from this study that proper combination of pressure build-up and dynamic heating condition makes important factor for flow-induced composite processing.

Study on the Improvement of the Reliability of Al-Cu Connections in Power Distribution Systems (송배전용 Al-Cu접속 금구의 신뢰도 향상일 관한 연구(I) 알루미늄 및 동의 부식 특성)

  • Ha, Yoon-Cheol;Bae, Jeong-Hyo;Kim, Dae-Kyeong;Ha, Tae-Hyun;Lee, Hyun-Goo
    • Proceedings of the KIEE Conference
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    • 2003.07a
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    • pp.488-490
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    • 2003
  • As aluminum becomes more widely used in power distribution systems, so the corrosion caused by bimetallic contacts of aluminum and copper becomes more serious problem. In particular, the poor contact of the commonly used compression type bimetal connections may bring about the disastrous interruption of the power supply resulted from the increased corrosion within the joints, which is accelerated by the permeation of water and electrolyte into the interface. In this paper, the corrosion characteristics of aluminum and copper are investigated to improve the reliability of Al-Cu connectons.

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Improvement in Interfacial Performances of Silicone Rubber by Oxygen Plasma Treatment

  • Lee, Ki-Taek;Seo, Yu-Jin;Huh, Chang-Su
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2005.07a
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    • pp.232-233
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    • 2005
  • The Surface of semi-conductive silicone rubber was treated by oxygen plasma to improve adhesion and electric performance in joints between insulating and semi-conductive silicone materials. Surface characterizations were assessed using contact angle measurement and Fourier transform infrared spectroscope (FTIR). Adhesion level was understood from T-peel tests between plasma treated semi-conductive and insulating material. Electrical breakdown strength was measured to understand the charge of electrical performance. From the results, the oxygen plasma treatment produces a significant increase in function group of containing oxygen which can be mainly ascribed to the creation of carbonyl groups on the silicone surface from the strength were improved. Therefore it is concluded then plasma treatment leads to decrease voids originating form poor adhesive, and the improve the adhesion in silicone interface. So we could obtain higher electrical design level of silicone material used for electrical apparatus using oxygen plasma treatment.

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Study on the Air-bearing Stage Driven by Linear Induction Motors (선형 유도기 구동 방식 공기 베어링 스테이지에 관한 연구)

  • Jung, Kwang-Suk;Shim, Ki-Bon
    • Journal of the Korean Society for Precision Engineering
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    • v.27 no.6
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    • pp.39-46
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    • 2010
  • Linear induction motor is adopted as an actuator of the planar stage. An inherently poor characteristic at zero or ultra-low speed zone of the induction motor is remarkably improved due to a recent development of power electronic semiconductor technology and a spatial vector control theory. At present, a servo response speed of the induction motor reaches 90 percent of one of PM synchronous or BLDC motor. Specially, as a secondary of the induction motor can be constructed using uniform conducting sheets, there is no periodic force ripple as in PM motors. So, the induction motor can be superior to another driving means under a certain condition. This paper discusses the overall development procedure of non-contact planar stage with a big workspace using linear induction motors.

Manufacturing of High-Performance Double Layered Tube with Corrugated Internal Pattern via the Hydroforming Process (액압 성형을 이용한 내부복합파형 고효율 이중관 제조 기술)

  • Han, S. W.;Kim, D. Y.;Moon, Y. H.
    • Transactions of Materials Processing
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    • v.31 no.3
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    • pp.143-150
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    • 2022
  • The purpose of this study was to investigate an innovative hydroforming process for the cost-effective manufacturing of double layered tube with circumferentially corrugated patterns. Conventional double pipe heat exchanger has relatively poor heat transfer efficiency because of the limited contact area resulting from the concentrically arranged simple cylindrical structure. As a promising alternative to enhance heat transfer efficiency, double layered tube with corrugated internal pattern was considered in this study. To fabricate corrugated inner tube, innovative tube hydroforming system was developed. The customized loading paths were established using the simulated forming pressure and contracting stroke at various bar diameters. Experimentally obtained cross-sectional profiles were analyzed to evaluate the reliability and applicability of the hydroformed tube with various patterns. The results demonstrate that the proposed hydroforming process can be a feasible alternative for manufacturing high-performance double-tube heat exchangers.

A Study on the Spectacles Wearing State of High School Students (고등학생들의 안경착용에 관한 연구)

  • Doo, Ha-Young;Sim, Sang-Hyun
    • Journal of Korean Ophthalmic Optics Society
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    • v.5 no.1
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    • pp.107-116
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    • 2000
  • This study is of investigation of refraction error, spectacles and contact lenses wearing state, visual acuity test, ophthalmologic common sense and vision care, using questionnaire study for 850 male and female high school students in Kunsan and Chongup City, Cheolla North Province. The results are as follows: 1. Among the 823 answerers, emmetropia is 18%, myopia is 55.1%, and hyperopia is 7%, respectively. 2. Among the 837 answerers, 381 students(45.5%) wear spectacles or contact lenses. Among the 381 students who wear spectacles or contact lenses, 78% wear only spectacles, 4% wear only contact lenses and 18% wears spectacles sometimes or contact lenses sometimes. 3. The places where the answerers had visual acuity test to wear spectacles or contact lenses are optical shop(64.7%), hospital(28.3%), unchecked(4.2%) and the others(2.7%). The places where the answerers had visual acuity test to change their spectacles or contact lenses are optical shop(82%), hospital(28.3%), unchecked(6.6%) and the others(1.9%). 4. As for the period of visual acuity test, from 6 months to one year is 54.1%, within 6 months is 9.2%, from one year to two years is 29.5%, and more than two years is 7.2%. 5. The contact lens wearers purchased their contact lenses at optical shops(94%) and at hospital(6%). 6. The reasons why they like wearing contact lenses are their appearance(51.2%), convenience in physical excercise(23.l%), lighter weight than spectacles(9.8%) and the others(15.7%). 7. As for the spectacles frame they like, plastic frame is 24.4%, gold or silver plated frame is 43.4%, coloured frame is 32.1%. 8. As for the considerations in choosing spectacles frame, their design is 37%, their quality is 36%, their price is 14.7% and their brand is 12.5%. 9. As for the period for changing spectacles, 10.5% is within 6 months, 57.3% is 6months to 1 year, 22.4% is 1 year to 2 months and 9.6% is more than 2 years. 10. There is a false fact, in Korea, that even though one has his poor eyesight, not wearing custom is helpful for the eyesight recovery. As for their conviction of the false fact, 10.5% of the answerers have 100% conviction, 22.5% of them have 22.5% conviction, 49.5% of them have 50% conviction and 17.5% of them don't have any conviction. 11. 48.5% of the answerers are interested in their vision care while 51.5% of them are not interested at all. As for the way of vision care, the vision-care way to keep enough distant when they are watching TV, when they are using computers and when they are reading, is 49% while the vision-care way such as hypogastric breathing or eye massage is 11%. And alimentotherapy is 4% and the rest who are not interested in vision care is 36%. 12. When they come to an age, the students who want vision correction operation are 45.9% while the students who do not want it are 27%. The students who do not have any idea about the operation are 27.1%

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Analysis of Problems of Food Service Establishments Contributing to Food Poisoning Outbreaks Discovered through the Epidemiological Studies of Some Outbreaks (식중독 발생의 사례 통해 본 집단급식의 문제접 분석)

  • 김종규
    • Journal of Food Hygiene and Safety
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    • v.12 no.3
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    • pp.240-253
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    • 1997
  • The main problems contributing to food poisoning outbreaks in institutional settings and a home were reviewed and analyzed through the epidemiological investigations of food poisoning. The major documented factors included improper holding temperatures, inadequate cooking, poor personal hygiene, cross-contamination and contaminated equipment, food from unsafe sources, failure to follow food hygiene policies, and lack of education, training, monitoring and superivision. Usually more than one factor contributed to the development of an outbreak. (1) Use of improper holding temperatures was the single most important factor contributing to food poisoning. They included improper cooling, allowing a laps of time (12 hours or more) between preparing food and eating it, improper hot holding, and inadequate or improper thawing. Food thermometers were not used in most of the instances. (2) In inadequate cooking, the core temperature of food during and after cooking had not been measured, and routine monitoring was limited to recording the temperature of plated meals. Compared with conventional methods of cooking, microwave ovens did not protect against food poisoning as effectively. Centralized food preparation potentially increased the risk of food poisoning outbreaks. (3) Poor personal hygiene both at the individual level (improper handwashing and lack of proper hygienic practices) and at the institutional level (poor general sanitization) increased the risk of transmission. Person to person transmission of enteric pathogens through direct contact and via fomites has been noted in several instances. (4) Obtaining food from unsafe sources was a risk factor in outbreaks of food poisoning. Food risks were high when food was grown or harvested from contaminated areas. Possibilities included contamination in the field, in transport, at the retail site, or at the time it was prepared for serving. (5) Cross-contamination and inadequate cleaning/handling of equipment became potential vehicles of food poisoning. Failure to separate cooked food from raw food was also a risk factor. (6) Failure to follow food hygiene policies also provided opportunities for outbreaks of food poisoning. It included improper hygienic practices during food preparation, neglect of personnel policies (involvement of symptomatic workers in food preparation), poor results on routine inspections, and disregarding the results and recommendations of an inspection. (7) Lack of formal and in-service education, training, monitoring, and supervision of food handlers or supervisors were critical and perhaps neglected elements in occurrences of food poisoning.

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