• Title/Summary/Keyword: release rate

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Analysis of Heat Quantity in CNG Direct Injection Bomb(1) : Homogeneous Charge (CNG 직접분사식 연소기에서의 열량해석(1) :균질급기)

  • 최승환;전충환;장영준
    • Transactions of the Korean Society of Automotive Engineers
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    • v.12 no.2
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    • pp.17-23
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    • 2004
  • A cylindrical constant volume combustion bomb is used to investigate the combustion characteristics and to analyze the heat quantity of homogeneous charge methane-air mixture under various initial pressures, excess air ratios and ignition times. As the overall pressure increase, the values of maximum combustion pressure, maximum heat release rate and cumulative heat release have been increased. But it is not very meaningful to compare with some values such as maximum combustion pressure, maximum heat release rate and cumulative heat release for different overall pressure due to the different heat energy of supplied fuel. So the each value is needed to be compared with normalized value, which is divided by the entered fuel energy. To analyze the heat quantity, some definitions including the CHR ratio, the UHC ratio and the HL ratio are needed and are calculated. As the overall pressure increase, the CHR ratios and the UHC ratios have been decreased, while the HL ratios have been increased. The CHR ratio of 300 ms has the higher value than that of 10000ms, and the HL ratios of 300 ms have a lower value.

Study of stability and evolution indexes of gobs under unloading effect in the deep mines

  • Fu, Jianxin;Song, Wei-Dong;Tan, Yu-Ye
    • Geomechanics and Engineering
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    • v.14 no.5
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    • pp.439-451
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    • 2018
  • The stress path characteristics of surrounding rock in the formation of gob were analysed and the unloading was solved. Taking Chengchao Iron Mine as the engineering background, the model for analysing the instability of deep gob was established based on the mechanism of stress relief in deep mining. The energy evolution law was investigated by introducing the local energy release rate index (LERR), and the energy criterion of instability of surrounding rock was established based on the cusp catastrophe theory. The results showed that the evolution equation of the local energy release energy of the surrounding rock was quartic function with one unknown and the release rate increased gradually during the mining. The calculation results showed that the gob was stable. The LERR per unit volume of the bottom structure was relatively smaller, which mean the stability was better. The LERR distribution showed that there was main energy release in the horizontal direction and energy concentration in the vertical direction which meet the characteristics of deep mining. In summary, this model could effectively calculate the stability of surrounding rock in the formation of gob. The LERR could reflect the dynamic process of energy release, transfer and dissipation which provided an important reference for the study of the stability of deep mined out area.

Prediction of Phosphorus Transport from Sediment and Development of Phophorus Control Technology - I. Prediction of Phosphorus Transport from Sediment (저질토로부터의 인의 용출거동 예측 및 제어기술 개발 - I. 저질토로부터의 인의 용출거동 예측)

  • Lee, Jung-Yub;Kang, Seon-Hong
    • Journal of Korean Society of Water and Wastewater
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    • v.13 no.2
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    • pp.89-94
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    • 1999
  • In this study small glass columns with 2.5cm inner diameter and 24.5cm length were used as many as the sample numbers to study the effects of initial pH, temperature, dissolved oxygen concentration, and sediment depth on the release of phosphorus from lake sediment. No phosphorus release occurred at $10^{\circ}C$ with all pHs, and release rate at $25^{\circ}C$ was higher than that at $35^{\circ}C$ with pH 4 and reverse trends were observed at pH 7 and 10. Under all conditions, DO concentrations were decreased and equilibrium was obtained after 4-8 days when phosphorus release started and the Do concentrations were less than 1 mg/l. Sediment depth had little effect on phosphorus release rate. It was found that relation between released SRP(Soluble Reactive Phosphorus) concentration and time was zero order reaction and reaction rate coefficients were obtained. The amount of phosphorus release from lake sediment can be predicted by considering these k values.

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Ignition and Heat Release Rate of Wood-based Materials in Cone Calorimeter Tests

  • Park, Joo-Saeng;Lee, Jun-Jae
    • Journal of the Korean Wood Science and Technology
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    • v.36 no.2
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    • pp.1-8
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    • 2008
  • This study was performed to evaluate the burning characteristics of wood-based materials and the effect of surface treatment of fire retardant using cone calorimeter. Four types of wood-based materials, such as Plywood, Oriented Strand Board (OSB), Particle Board (PB) and Medium Density Fiberboard (MDF), were tested at a constant heat flux of $50kW/m^2$ to investigate the time to ignition, mass loss rate, heat release rate, effective heat of combustion, etc. In addition, each type of wood-based material was tested at the same heat flux after fire retardant treatment on the surface to evaluate the effect of this treatment on the burning characteristics. The surface treatment of fire retardant, by the amount of $110g/m^2$, delayed the time to ignition almost twice. However, it was indicated that heat release rate, mass loss rate, and effective heat of combustion were not significantly affected by fire retardants treatment for all types of wood-based materials.

Controlled Release of Tamsulosin from Enteric Coated Sustained-Release Matrices with Aqueous Microchannels (수성미세채널을 형성하는 서방성 매트릭스 장용정을 이용한 탐스로신의 방출제어)

  • Lee, Ki-Bong;Choi, Sung-Up;Jeon, Hong-Ryeol;Lee, Bong-Sang;Kim, Hyun-Il;Lee, Jae-Hwi;Choi, Young-Wook
    • Journal of Pharmaceutical Investigation
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    • v.34 no.6
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    • pp.471-475
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    • 2004
  • Tamsulosin has been frequently used for the treatment of benign prostatic hyperplasia. To avoid dose-dependent side effects of tamsulosin upon oral administration, the development of sustained-release delivery system is required, that can maintain therapeutic drug levels for a longer period of time. The aim of this study was therefore to formulate sustained-release tamsulosin matrix tablets and assess their formulation variables. We designed enteric coated sustained-release tamsulosin matrices to fulfill above statement. Aqueous microchannels in the enteric film need to be formed in order to obtain tamsulosin release even in an acidic environment such as gastric region. In the sustained-release tamsulosin matrix, low viscosity hydroxypropylmethylcellulose was used as a rate controller. Povidone K30 was also added to the matrices to facilitate water uptake so that a decrease in the release rate of tamsulosin as time elapses was prevented, possibly leading to pseudo zero-order release of the drug. The matrices were enteric-coated with hydroxypropylmethylcellulose phthalate (HPMCP), along with povidone K30 as an aqueous microchannel former. With the aqueous microchannels formed within the enteric film, tamsulosin could be released in an acidic condition. The release of tamsulosin decreased with increasing thickness of HPMCP membrane while the release rates of tamsulosin from those having different HPMCP thickness in pH 7.2 aqueous media were not considerably different, indicating that the enteric film was promptly dissolved at pH 7.2. These results clearly suggest that the sustained-release oral delivery system for tamsulosin could be designed with satisfying drug release profile approved by the KFDA.

Provider's Behavior Change after the Public Release of the Information on the Cesarean Section Rate (제왕절개 분만율 공표 후 요양기관의 분만행태 변화)

  • 고수경;신순애;김기영;김창엽
    • Health Policy and Management
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    • v.11 no.3
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    • pp.121-150
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    • 2001
  • This study was conducted to investigate provider's behavior change after releasing the information on the Cesarean section rate. Claims data filed at the National Health Insurance Corporation was used for this analysis and the focus of this study was the change of cesarean rate after the public disclosure of information. Average rates of the year 1999 and 2000 were compared, on the institutional basis, and range and coefficient of variation were estimated. For the last decade, Cesarean section rate has been increased dramatically. Clinical or demographic factors could not adequately explain the increase. Instead, nonclinical factors, such as financial incentive, physician's convenience, practice characteristics, etc., were more significant in explaining the increasing rate. Providers' behavior was significantly affected by the public release of information: after the release, average rate was decreased by 10.2%, and variations were also decreased. In particular, the extent of decrease was explained mainly by nonclinical factor rather than clinical ones. The results suggest that disseminating practice information to providers and consumers could contribute to reducing unnecessary medical service.

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Controlled Release of Isonicontinic Acid Hydrazide from the Membrane-Coated Tablet

  • Kim, Ki-Man;Kim, Shin-Keun
    • Archives of Pharmacal Research
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    • v.8 no.1
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    • pp.7-14
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    • 1985
  • Membrane-coated tablet of isonicotinic acid hydrazide (INAH) which releases INAH at the zero-order kinetics was deveoped. It consisted of a soluble tablet core surrounded by a porous membrane which controls the diffusion rate. Tablet cores were prepared by compressing granules of INAH and polyvinyl chloride (PVC) dissolved in methyl ethyl ketone in which micronized sucrose were suspended. Diffusion rate of INAH from the tablet through the membrane was constant until the loaded INAH in the core was almost released. The rate was independent of pH of the dissolution medium. Water-soluble sucrose particles behaved as a poreproducing material in the water-insoluble PVC film coat. The pH independency of the rate was probably due to the high solubility of INAH in the water of wide pH range. The diffusion rate of INAH could be controlled by chnaging the composition of the membrane or the coat weight. This membrane-coated INAH tablet seemed to be a powerful candidate for the controlled release drug delivery system (DDS) of INAH or other highly watersoluble drugs.

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Effects of Hydrophilic Additives on the Release Rate of Protein Drugs (단백질 약물 방출속도에 미치는 친수성 첨가제의 영향)

  • Kwon, Young-Kwan;Kim, Ji-Hyeon;Yoo, Young-Je
    • KSBB Journal
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    • v.22 no.4
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    • pp.213-217
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    • 2007
  • It has been reported that hydrophobic additives generally decrease the release rate of protein drugs from drug delivery systems (DDS) and hydrophilic additives increase the release rate. In many cases, however, the addition of hydrophilic molecule is necessary for improving the stability of protein drugs. In the present work, the effects of hydrophilic additives on the release profiles, and micelle formation of protein drug formulations were investigated to develop a novel method for protein drug delivery. For model protein drug, bovine serum albumin (BSA) was employed and several hydrophilic additives were used in the release experiments. Hydrophilic additive D-sorbitol showed the lower release rates of BSA than other hydrophobic additives due to the gel strengthening ability of the additive and the optimum concentration of D-sorbitol was 3 w/v % for the retarded release rate. In addition, it was found that the addition of D-sorbitol was very effective for obtaining homogeneous and stable DDS. The results were discussed in terms of the micelle formation and the micelle structure, i.e., the differences in gel structure and the distribution of drugs in micelles.

Controlled Release and Stabilization of Cefaclor from Alginate-based Matrices for Oral Delivery Design

  • Bak, So-Im;Lee, Jue-Yeon;Song, Hye-Won;Hwang, Jeong-Hyo;Lee, Seung-Jin
    • Journal of Pharmaceutical Investigation
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    • v.32 no.4
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    • pp.327-330
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    • 2002
  • Alginate based polymeric matrices were designed for controlled release and stabilization of cefaclor in gastrointestinal fluid. Cefaclor is known to be acid stable and subjected to be degraded at neutral and alkaline pHs. In order to achieve an effective release profile of cefaclor in gastrointestinal tract, a particular strategy in dosage form design should be required from the view point of maintaining its activity. The amphiphilic nature of cefaclor allowed its controlled release using ionic polymers based on ionic interaction between the drug and polymers. The thrust of this study was to develop a technique that delivers cefaclor keeping effective release rate in the intestinal tract. Considering the fast degradation of cefaclor in the intestinal fluid, the matrices were designed to release surplus amount of cefaclor. The alginate based matrices demonstrated increase in release rate in the simulated intestinal fluid, which was favorable to compensate the degraded portion of cefaclor. In addition, stabilization of cefaclor in the intestinal fluid was obtained by employing citric acid that provides an local acidic environment. The matrices might be valuably used for the development of an oral cefaclor dosage form.

Evaluation of Hydrocortisone Sustained-Release Suppositories Prepared with Eudragit-Polyethylene Glycol Solid Matrix (유드라짓 및 폴리에틸렌글리콜 고체 매트릭스로 제조한 히드로코르티손 좌제의 서방성 평가)

  • Han, Kun;Kim, Hak-Hyung
    • Journal of Pharmaceutical Investigation
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    • v.20 no.1
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    • pp.13-18
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    • 1990
  • Hydrocortisone (HC) sustained-release suppositories were prepared by using a solid matrix of methacrylic acid-methacrylic acid methyl ester copolymer $(Eudragit\;L_{100}^{R}:\;EL)$ as a poorly water soluble carrier and polyethylene glycole 1540 (PEG) as an water soluble carrier. HC release rate was controlled by complexation with ${\beta}-cyclodextrin$ $({\beta}-CyD)$ which was confirmed by X-ray diffractometry, IR-spectroscopy and differential scanning calorimetry. Release rate of HC from the EL-PEG matrix suppositories decreased with increase of EL contents. The release rale from $HC-{\beta}-CyD$ complex decreased in the following order: $HC-{\beta}-CyD/PEG$ > HC/PEG > $HC-{\beta}-CyD/EL_{10%}-PEG$ > $HC/EL_{10%}-PEG$ > $HC-{\beta}-CyD/EL_{15%}-PEG$ > $HC/EL_{15%}-PEG$ > $HC-{\beta}-CyD/EL_{20%}-PEG$ > $HC/EL_{20%}-PEG$. The crystallinity of HC in polymer matrix was identified using X-ray diffractometer and the surface of matrix suppositories after release test was examined by scanning electron microscopy. The sustained release of HC from these matrix suppositories was attributed to the network structure of EL.

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