• 대한기계학회논문집B
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• 제25권12호
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• pp.1739-1747
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• 2001

Experimental study has been conducted to clarify the pneumatic characteristics of brake system for freight train and enhance the performance of diaphragm valve. Empty-load and diaphragm valves are installed in pneumatic brake system for freight trains of KNR (Korean National Railroad). Experiments are conducted by using freight train and diesel locomotive in operation. From the experimental results. new quick release valve shortens release time after brake application. In case of normal brake application, the release time is shortened to 34% of the original diaphragm valve. Reducing the release time of pneumatic brake system will be helpful to assure brake-release application and save maintenance efforts like wheel grinding.

• Archives of Pharmacal Research
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• 제13권4호
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• pp.293-297
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• 1990

Sustained release microspheres containing phenylpropanolamine HCI (PPA) were prepared with acrylic polymer (Eudragit RL/RS) sand hydroxypropylmethylcellulose phthalate (HPMCP) using a emulsion-solvent evaporation method. Magnesium strate was used a smoothing agent for preparation of microspheres. The microspheres obtained were very spherical and free-flowing particles. Scanning electron microscopy showed that microspheres have a smooth surface and a sponage-like internal structure. The dissolution rate of PPA from the microspheres was dependent on the pH of dissolution media. PPA showed faster relase in hP 1. 2 solution than in pH 7.4 solution due to the solubility of PPA. Therefore we prepared new microspheres containing 5% (w/v) HPMCP in order to control the release of PPA. The release rate of PPA from these new microspheres was similar in pH 1.2 and pH 7.4 solution.

• Journal of Pharmaceutical Investigation
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• 제23권4호
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• pp.207-211
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• 1993

Reservoir type devices were designed for long-term implantable drug delivery system. The reservoir type device was prepared with the polymethacrylic acid gel coated with polyurethane membrane. Release controlling agent (RCA) were employed to control drug release from devices via generation of micropores in the membranes. The polyurethane membrane functioned as a rate controlling barrier. The drug release pattern of hydrogel demonstrated zero order kinetics. The release rate of drugs could be regulated by varying hydrophobicity/hydrophilicity and content of the RCA, as well as the thickness of the polyurethane membrane. The release of drugs from this system was governed by pore mechanism via simple diffusion and osmotic pressure.

• 약학회지
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• 제41권1호
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• pp.22-29
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• 1997

Poloxamer-poly (acrylic acid) (PAA) interpenetrating polymer networks (IPNs) were prepared via matrix polymerization of acrylic acid with poloxamer prepolymer. The equilibrium s welling of poloxamer/PAA IPNs was determined in various pH medium. The swelling of poloxamer/PAA IPNs was more affected by pH difference compared with the swelling of homo PAA gel due to protonation and deprotonation of the PAA network, followed by reversible formation and dissociation of the interpolymer complex due to hydrogen bonding between acidic hydrogens and ether oxygens. Nonionic/anionic/cationic drugs were incorporated into IPN matriceds as a model drug and their release behavior was studied. Nonionic, drug revealed release patterns depending solely on pH dependent swelling kinetics. In contrast, the release of ionic drugs was significantly affected by ionic drug-polymer interaction as well as the swelling kinetics.

• Journal of Korean Dental Science
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• 제14권2호
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• pp.51-60
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• 2021

Purpose: Measuring viability of a three-dimensional in vitro organotypic human oral tissue model has been suggested as an alternative test method to the oral mucosa irritation test of oral care products. The aim of this study was to investigate the production of two different cytokines using organotypic human oral tissue model following exposure to chemicals that are commonly used in oral care products. Materials and Methods: The organotypic human oral tissues were exposed to ethanol, sodium lauryl sulphate or hydrogen peroxide for 90 minutes. Following exposure, interleukin (IL)-1α and IL-8 productions were assessed and correlated with cell viability testing as well as histology of the organotypic human oral tissues. Result: High levels of IL-8 were released from organotypic human oral tissues in all of the test and control groups without any significant differences between them. In contrast, differences were found in IL-1α release between the test and control groups. Additionally, the trend of IL-1α release corresponded to the phenotypes observed in histological analysis while different trend existed between IL-1α release and cell viability. Conclusion: The study concluded the non-specific release of IL-8 for the assessment of oral care product chemicals' toxicity, while potential of measuring IL-1α cytokine level as the possible alternative test method.

• 현장농수산연구지
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• 제16권1호
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• pp.143-154
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• 2014

Settlement of artificially released abalone, Haliotis discus hannai at the marine farming area in Jeollanam-do in 2007 was very efficient by showing the recapture of 2.0-5.2 ind./m² and the survival rate of 60-67%. The growth of shell after 1 year was highest in Hwoenggando by 75.9 mm and the lowest in Hwasan by 64.6 mm. Our result especially showed that the effect of the stock recruitment was the most efficient when abalone was released. The shell growth of the released abalone was better when sea mustard (Undaria sp.) was provided as food (shell length was up to 23.9 mm) or predators were periodically removed (shell length was up to 23.8 mm) in order to enhance the effect of the artificial release than the control group. The recapture rate was also higher than the control. However due to the difficulty of managing the release areas, it will be more efficient to release the recruited stocks after considering various biological and ecological factors such as survey of suitable release areas, stock size, release density, and health of stocks.

• Restorative Dentistry and Endodontics
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• 제29권6호
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• pp.548-552
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• 2004

본 연구는 제어방출형 근관소독제(CRD)로 부터 chlorhexidine (CHX)의 방출 속도를 제어하기 위한 3가지 polymer (chitosan, PMMA, PLGA) 의 코팅 효과를 평가하기 위함이다. 80번 paper point (Sure-EndoTM)에 20% CHX를 loading 한 후 각 군당 10개씩 4군으로 분류하였다: Group A: 폴리머를 코팅하지 않은 CRD prototype (control), Group B: chitosan-coated prototype, Group C: PMMA-coated prototype, Group D: PLGA-coated prototype. 모든 시편은 3 ml 증류수가 담긴 큐벳에 넣은 후 3, 6, 10, 20, 30, 40, 50분 마다, 1, 2, 3, 4, 5, 6시간마다 각각 10 μl 씩 채취하고, 1주일 후 다시 10 μl을 채취한 후 UV 흡광도를 이용하여 CHX의 방출 속도를 비교하였다. 실험결과 제어방출형 근관소독제로부터 CHX의 방출속도는 대조군, 키토산, PLGA, PMMA-군 순으로 천천히 일어났으며 PMMA군에서 가장 천천히 일어났다. 결론적으로 제어방출형 근관소독제 표면의 폴리머는 약물 (CHX) 방출속도를 효과적으로 제어하였다.

• 한국토양비료학회지
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• 제39권6호
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• pp.345-350
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• 2006

본 시험은 벼 종이멀칭이앙 시 적정한 완효성비료의 시용량을 구명하고자 경기도 수원에 위치한 작물과학원 벼 연구 포장 강서통에서 대안벼를 2004년 5월 28일에 중묘를 멀칭기계 이앙하였다. 시험에 사용한 완효성비료는 LCU (Latex Coated Urea, 21-7-9) 복비를 시용하였다. 피복재료는 생분해성 폴리에스터 (PES $10{\mu}m$)+재생지를 이용하여 피복하였다. 처리내용은 관행질소시비량 ($110kg\;ha^{-1}$)을 기준으로 하여 완효성비료호 기준시비량의 60%, 80%구, 100%구와 관행 및 무질소구를 두고 시험을 수행하였다. 벼 멀칭이앙 시 모의 결주율은 무피복의 관행이앙과 차이가 없었다. 잡초발생 및 방제가는 시비량이 적을수록 잡초가 다양해지고 잡초방제가가 낮아지는 경향이었다. 벼 이앙 후 일수가 진전됨에 따라서 시비량이 많을수록 초장와 경수가 크거나 많아지는 경향이었고 완효성비료 80%구의 벼 생육이 관행시비구와 차이가 없는 경향이었다. 엽색도와 토양 중 $NH_4{^+}-N$도 유사한 경향을 보였다. 따라서 수량구성요소 중 $m^2$당 이삭수의 증가로 인하여 완효성비료 80%구가 관행과 수량 차이가 없었다. 농업적 질소이용 효율은 시비량이 적을수록 증가하였다. 벼 종이멀칭이앙 시 벼 수량 및 수량구성요소, 잡초발생 및 방제가, 시비효율 등을 종합적으로 고려하여 관행질소 시비량의 80%를 완효성비료로 이앙 전에 밑거름으로 전층시비 하는 것이 알맞을 것으로 생각된다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.505-508
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• 1995

This paper suggests new hydraulic circuit to control the pressure of clutches and brakes which has several advantages than conventional hydraulic circuit in automatic transmissions. In conventional hydraulic circuit, the pressures of all friction elements are controlled by only one pressure control valve and accumlators. So, controllable range is limited and it is unable to control the friction elements independently. Therefore, we can not do the fine control of timing between apply clutch and release clutch which is needed in clutch-to clutch shifting automatic transmissions. To overcome these faults, we designed the direct-acting hydraulic circuit where one pressure control valve and pressure control solenoid valve are allocated to each friction element and control that independently. Through this structural improvement of hydraulic circuit, we can achieve elaborate aontrol to clutch pressure. Specially, We can control the timing between apply clutch and release clutch delicately which is needed in clutch-to-clutch shifting.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.577-580
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• 1995

This paper suggests direct-acting hydraulic circuit to control clutches and brakes in automatic transmission. As only one pressure control valve controls the pressure of several friction elements with accumulators in conventional hydraulic circuit, the controllable range is limited. In addition, it is difficult to control the fine timing between apply clutch and release clutch. So, we designed new method to control the pressure of clutch which uses ressure control valve and pressure control solenoid valve independently in each friction element. through this structure improvement of hydraulic circuit, we can control the pressure of clutches and brakes finely and fine timing of between apply clutch and release clutch.