• 폴리머
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• 제25권3호
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• pp.441-449
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• 2001

폴리페닐렌 에테르(PPE)/폴리아미드(PA)를 근간으로 하는 블렌드를 상용화하기 위하여 부타디엔 고무에 스티렌이 그라프트된 공중합체 (g-BS)를 합성하고 여기에 폴리아미드의 말단기인 아민기와 반응성이 높은 무수말레인산기를 그라프트시킨 g-BS*를 도입하여 블렌드의 형태학과 기계적 성질의 변화를 조사하고 상용화제로서의 성능을 평가하였다. 폴리아미드 연속상에 분산되어 있는 PPE상의 크기와 이에 따른 기계적 성질의 변화는 사용된 g-BS의 구조와 관능기의 함량과 밀접한 관계를 나타내었다. 블렌드의 내열성과 내충격성의 균형을 위하여 g-BS성분을 PPE상에 내재시키는 것이 중요하고, 이러한 상구조의 형성은 g-BS에 포함된 폴리스티렌의 함량과 분자량이 적절하게 유지될 때 가능하였다. 고무함량과 그라프트된 폴리스티렌의 분자량이 일정하게 고정된 상태에서, g-BS*에 존재하는 무수말레인산의 함량이 낮거나, 고무입자의 크기가 커질 경우에는 연속상과 분산상의 계면 보강이 효과적으로 이루어지지 못하여 기계적 성질이 저하되었다. 본 연구에서 적용한 g-BS*를 사용하면, 폴리페닐렌 에테르에 관능기를 도입하여 상용화하는 기존의 방법과 동등한 정도의 물성이 달성될 수 있으며, 자연 색상이 보다 우수한 수지의 제조가 가능함을 확인하였다.

• 생물환경조절학회지
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• 제18권3호
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• pp.200-207
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• 2009

This study was conducted to analyze the variations of air temperature, relative humidity and pressure in a low pressure chamber for plant growth. The low pressure chamber was composed of an acrylic cylinder, a stainless plate, a mass flow controller, an elastomer pressure controller, a read-out-box, a vacuum pump, and sensors of air temperature, relative humidity, and pressure. The pressure leakage in the low pressure chamber was greatly affected by the material and connection method of tubes. The leakage rate in the low pressure chamber with the welding of the stainless tubes and a plate decreased by $0.21kPa{\cdot}h^{-1}$, whereas the leakage in the low pressure chamber with teflon tube and rubber O-ring was given by $1.03kPa{\cdot}h^{-1}$. Pressure in the low pressure chamber was sensitively fluctuated by the air temperature inside the chamber. An elastomer pressure controller was installed to keep the pressure in the low pressure chamber at a setting value. However, inside relative humidity at dark period increased to saturation level.. Two levels (25 and 50kPa) of pressure and two levels (500 and 1,000sccm) of mass flow rate were provided to investigate the effect of low pressure and mass flow rate on relative humidity inside the chamber. It was concluded that low setting value of pressure and high mass flow rate of mixed gas were the effective methods to control the pressure and to suppress the excessive rise of relative humidity inside the chamber.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 The 6th International Symposium of East Asian Resources Recycling Technology
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• pp.230-235
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• 2001

There are more than 15 millions cars or motors in Taiwan. According to the statistics from Environmental Protection Administration, the number of resulting scrap tires are near 110 thousand tons each year. The tire recycle programs in Taiwan were first conducted in 1989 and executed by ROC Scrap Tire Foundation. However, the current efficiency of the tire recycling industry still needs to be improved to minimize the environmental problem or fire hazards caused by scrap tires storage. Ten major tire-recycling factories are surveyed in this study. The investigations include the source of scrap tire, the shredding process, the market of products, the management of wastes disposal, and the difficulties of these sectors. As the varieties of the shredding machines of the recycle factories, there are three kinds of final products which include powder, granular, and chips. The wastes, wires and fibers, produced by the shredding process are the major problems fur all the factories. The percentage of the wire and fiber removal from rubbers still needs to be increased. The best approaches found in this study to increase the efficiency of scrap tire recycling processes are proposed which include the improvement of magnetic separation system fiber/rubber separation system and the minimization of waste disposal. A categorized standard of the processing outputs is suggested as a reference for the decision-making of the tire-recycling factories.

• Safety and Health at Work
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• 제2권3호
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• pp.290-300
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• 2011

Objectives: There is limited data regarding the toxicity of methylcyclohexane, despite its wide use in rubber adhesives, paint diluents, and cleansing agents. This study aimed to verify the toxicity and influence on the reproductive system of methylcyclohexane after its repeated injection in Sprague Dawley (SD) rats. Methods: Methylcyclohexane was injected subcutaneously into male and female SD rats once a day, five times a week, for 13 weeks at different doses (0, 10, 100, and 1,000 mg/kg/day) for each group. The toxicity of testing material was verified by observing the change in body and organ weight, hematological change, pathological findings, and effect on the reproductive system at each different concentration. Results: In the 1,000 mg/kg/day group, there were cases of animal deaths. In animals that survived, hematological changes, including a decrease in the red blood cell count, were observed. A considerable weight gain or loss and pathological abnormalities in the liver, kidney, and other organs were found. However, the 10 and 100 mg/kg/day groups did not cause deaths or other specific abnormalities. In terms of reproductive toxicity, there were changes in hormone levels, including a significant decrease in hormones such as estradiol and progesterone (p < 0.001) in male animals. Menstrual cycle change for female animals did not show concentration dependency. Conclusion: When injected repeatedly for 13 weeks, methylcyclohexane proved to be toxic for the liver, heart, and kidney at a high dose. The absolute toxic dose was 1,000 mg/kg/day, while the no observed adverse effect level was less than 100 mg/kg/day. The substance exerted little influence on the reproductive system.

• 대한치과마취과학회지
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• 제10권1호
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• pp.54-57
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• 2010

Foreign body aspiration (FBA) into the tracheobronchial tree could be life threatening requiringprompt intervention. Any objects placed in the oral cavity put patients at a risk of aspirating or swallowing the objects slipped or broken by physical injuries. Here, we report a case of 30 yr old patient with FBA during gold crown replacement was successfully treated with the use of the flexible bronchoscope. Case: A 30 yr old woman was admitted to Seoul National Dental Hospitalfor an amalgam restoration. She was scheduled to gold crown restoration for replacement of the damaged amalgam at #37 site. After performing crown lengthening procedure, the aspiration of gold crown occurred during the cementation of the crown. After aspiration, the patients complained of the subjective distress of respiration. Chest radiograph revealed that gold crown was enlodged to the left bronchus. Flexible fiberoptics was inserted to the bronchus to remove the aspirated crown. Fiberoptic assisted removal of the aspiratedcrown was successfully performed. After removal, there was no radiopaque material in the left bronchus on follow-up chest radiograph. Discussion: When aspiration of dental materials occurs, flexible fiberoptic can be used in the treatment of FBA. It is also very useful to take preventive management such as rubber dam, application of dental floss in dental procedure where there is high likelihood of FBA.

• 대한치과보철학회지
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• 제35권4호
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• pp.719-741
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• 1997

This study was undertaken to compare by Atomic Force Microscope the effects of various finishing and polishing instruments on surface roughness of filling and veneering composite resins. Seven composite resins were studied : Silux Plus (3M Dental Products, U.S.A.), Charisma (Heraeus Kulzer, Germany), Prisma THP (L.D.Caulk, Dentsply, U.S.A.), Photoclearfil (Kuraray, Japan), Cesead (Kuraray, Japan), Thermoresin LC (GC, Japan), Artglass (Heraeus Kulzer, Germany). Samples were placed and polymerized in holes (2mm thick and 8.5mm in diameter) machined in Teflon mold under glass plate, ensuring excess of material and moulded to shape with polyester matrix strip. Except control group (Polyester matrix strip), all experimental groups were finished and polishied under manufacturer's instructions. The finishing and polishing procedure were : carbide bur (E.T carbide set 4159, Komet, Germany), diamond bur (composite resin polishing bur set, GC, Japan), aluminum-oxide disc (Sof-Lex Pop-On, 3M Dental Products, U.S.A.), diamond-particle disc (Dia-Finish, Renfert Germany), white stone bur & rubber point( composite finishing kit, EDENTA, Swiss), respectively. Each specimens were evaluated for the surface roughness with Atomic Force Microscope (AutoProbe CP, Park Scientific Instruments, U.S.A.) under contact mode and constant height mode. The results as follows : 1. Except Thermoresin LC, all experimental composite resin groups showed more rougher than control group after finishing and polishing(p<0.1). 2. A surface as smooth as control group was obtained by $Al_{2}O_{3}$ disc all filling composite resin groups except Charisma and all veneering composite resin groups except Thermoresin LC(p<0.05). 3. In case of Thermoresin LC, there were no statistically significant differences before and after finishing and polishing(p>0.1). 4. Carbide bur, diamond bur showed rough surfaces in all composite resin groups, so these were inappropriate for the final polishing instruments.

• Journal of Biosystems Engineering
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• 제30권4호
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• pp.220-228
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• 2005

This study was conducted to investigate the main factors that contain a rotating velocity ratio between wheel and conveyor belt, a tilt angle of conveyor belt and a rotating velocity of a dick cutter for mechanization of Chinese leek harvest. In the survey on the cultivation of Chinese leek, row spacing of 350 m and cutting height of 10 mm from the ground were set up for field tests. Test equipment was designed to cut, pick up and convey Chinese leek one row by one row. From the results of material tests, pick-up height of conveyor belt was set up at $60\~90m$ from the bottom, and the strain and stress at rupture of Chinese leek was 0.487 m/m and 0.01078 MPa. An elastic coefficient of the rubber (Neoprene) of conveyor belts was 1.1077 under the strain of 0.3 nym. from the results of field tests, the tilt angle of conveyor belt was the range of $25^{\circ}\~30^{\circ}$ under consideration far space of container, the velocity ratio between vehicle and conveying belt was 1 to 2.4~1.7 at 0.1~0.3 m/s of vehicle, and optimum rotating velocity of the disk cutter was 34.8 m/s or more under consideration for soil friction.

• 한국화재소방학회논문지
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• 제25권4호
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• pp.35-41
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• 2011

연기독성생성물로 인한 인명피해가 주요한 화재피해로 보고되고 있다. 화재로 인한 연기독성을 평가하기 위해 국내외의 다양한 시험이 있으며, 국내에서는 KS F 2271의 가스유해성시험으로 건축마감재료의 유해성을 평가하고 있다. 현행 가스유해성시험은 발연가스를 설치류(실험용 흰 쥐)에 노출시켜 행동시간을 측정하여 연소가스 독성을 평가한다. 본 연구에서는 가연성 고분자소재(우레탄 및 고무바닥재)를 대상으로 가스유해성시험을 수행하고 이때 발생되는 가스를 FT-IR로 정량분석하였다. 정량분석결과는 BS6853에서 규정하는 기준값과 비교하여 독성지수(R)를 산정하였다. 동물시험과 독성지수의 상대적 비교를 통해 두 시험법의 상관성을 분석하여 다양한 독성평가를 시도하고자 하였다.

• 한국농공학회지
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• 제17권1호
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• pp.3702-3711
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• 1975

This study was originated to investigate the imparired parts of the mist and dust blowers and intended to analyze the causes of their failures by the use of the Weibull probability paper. By the use of the paper, the parts which were needed to change the design, the force of the urgency, the mean time between failures of the parts and the basic causes of the troubles could be predicted. The survey showed that the following parts got out of order: (A) flexible rubber hose, (B) blowing fan, (C) lead valve, (D) piston ring. (E) crank main bearing, (F) coil in magneto and (G) needle valve in carburettor. The analysis of the survey indicated that the parts G, C, E and D were belonged to "wear-out failure", and that the mean time between failures became shorter in order as indicated above. To insure longer lives of those parts, it would be necessary to change the design and the material and to upgrade operators mechanical technique of the mist and dust blower. The failure of the parts A, B and F was classified as "randomfailure", and they did not seem to be the "wear-out" at that time. The parts B and F was evaluated as "initial failure". Quality controls and operating tests by the producer. and the operational training for users should be strengthened so as to eliminate these failures. Were the failures only in the parts A, C, D, E, F and G, it could be said that the "reliability" of the mist and dust blower would fall to 10 percent in the second year, and 50 percent of the mist and dust blowers would fail in all parts A, C, D, E, F and G before the blower would have control insect and disease in 58.2 hectares. The use of the Weibull probability paper for analyzing failures of the mist and dust blowers was effective in that it analyzed failure in the relationship between strength of the parts and users actual circumstanoes.

• 에너지공학
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• 제28권4호
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• pp.42-47
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• 2019

본 연구에는 유화제, 살충제, 첨가제, 고무 가황 촉진제, 부식 억제제제 및 염료 생산의 원재료 등으로 다양하게 사용되고 있는 디노말부틸아민(di-n-buthylamine)을 선정하여 연소특성치를 측정하였다. 디노말부틸아민의 인화점은 밀폐식 Setaflash와 Pensky-Martens 그리고 개방식 Tag, Cleveland 장치로 측정하였고, 연소점은 개방식 장치를 이용하였다. 최소자연발화온도(AIT)는 ASTM 659E를 사용하였다. 그리고 디노말부틸아민의 폭발한계는 측정된 인화점을 이용하여 예측하였다. Setaflash와 Pensky-Martens에 의한 인화점은 38 ℃와 43 ℃로 측정되었고, Tag와 Cleveland는 각각 48로 동일하게 측정되었다. 디노말부틸아민의 AIT는 247 ℃로 측정되었다. Setaflash에서 측정된 인화점에 의한 폭발하한계는 0.69 vol%, 상한계는 7.7 vol%로 계산되었다. 본 연구에서 제시한 인화점 측정과 폭발한계의 예측 방법은 다른 가연성액체의 화재 및 폭발특성 연구에 활용이 가능하다.