• Title/Summary/Keyword: Radiation stability

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A Numerical Study of Opposed Nonpremixed Tubular Flames with Radiative Heat Loss (복사열손실이 있는 비예혼합 튜브형 화염에 관한 수치 해석적 연구)

  • Bak, Hyun Su;Yoo, Chun Sang
    • 한국연소학회:학술대회논문집
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    • 2015.12a
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    • pp.247-250
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    • 2015
  • The characteristics of opposed nonpremixed tubular flames with radiation heat loss are investigated using linear stability analysis and 2-D numerical simulations. Two extinction limits, as the $Damk{\ddot{o}}hler$ number is small or large, are confirmed using finite difference method with a simple continuation method. It is verified that the results of linear stability analysis predict the number of flame cells and the critical Da starting cellular instability or amplification of temperature near both extinction limits with good resolution.

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Instability Analysis of Counterflow Diffusion Flames with Radiation Heat Loss (복사 열손실을 받는 대향류 확산화염의 불안정성 해석)

  • Lee, Su-Ryong
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.36 no.8
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    • pp.857-864
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    • 2012
  • A linear stability analysis of a diffusion flame with radiation heat loss is performed to identify linearly unstable conditions for the Damk$\ddot{o}$hler number and radiation intensity. We adopt a counterflow diffusion flame with unity Lewis number as a model. Near the kinetic limit extinction regime, the growth rates of disturbances always have real eigenvalues, and a neutral stability condition perfectly falls into the quasi-steady extinction. However, near the radiative limit extinction regime, the eigenvalues are complex, which implies pulsating instability. A stable limit cycle occurs when the temperatures of the pulsating flame exceed the maximum temperature of the steady-state flame with real positive eigenvalues. If the instantaneous temperature of the pulsating flame is below the maximum temperature, the flame cannot recover and goes to extinction. The neutral stability curve of the radiation-induced instability is plotted over a broad range of radiation intensities.

Investigation of Influence of Pulse-periodical Laser Radiation Power on Stability of Liquid-metal Contacts between Powder Particles during Selective Laser Sintering

  • Beljavin, K.E.;Minko, D.V.;Bykov, R.P.;Kuznechik, O.O.
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • 2006.09a
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    • pp.518-519
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    • 2006
  • A connection between pulse-periodical laser radiation power and stability of liquid-metal contacts between powder particles during selective laser sintering (SLS) is determined based on analysis solving the problem of stability of liquid column in the gravity and capillary forces field. On the grounds of obtained relationships the optimization of pulse-periodical laser radiation power and SLS-process duration is realized, that allows to produce voluminous powder porous materials with pre-determined physical and mechanical properties and surface geometry. Results of metallographic investigations of powder porous materials of titanium powder produced with technological regimes calculated by means of obtained relationships are given in the work

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Evaluation of Image Quality and Stability of Radiation Output according to Change in Tube Voltage and Sensitivity when Abdomen and Pelvis Examination of Digital Radiography (DR) (디지털 방사선 시스템(DR)의 복부와 골반부 검사 시 관전압과 감도 변화에 따른 영상 화질과 방사선 출력의 안정성 평가)

  • Hwang, Jun-Ho;Yang, Hyung-Jin;Choi, Ji-An;Lee, Kyung-Bae
    • The Journal of the Korea Contents Association
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    • v.19 no.12
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    • pp.517-526
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    • 2019
  • The purpose of this study is to find the optimal method for clinical application by analyzing image quality and radiation output according to parameter combination when using the Automatic Exposure Control (AEC). The experimental method combines 70, 81 kVp with sensitivity S200, S400, S800 and S1000 of the Automatic Exposure Control for Entrance Surface Dose (ESD), current volume, Signal to Noise Ratio (SNR), Contrast to Noise Ratio (CNR), Time-to-Radiation Dose Curve in abdomen and pelvis. And then, image quality and radiation output stability were evaluated. As a results, Entrance Surface Dose, current volume, Signal to Noise Ratio, Contrast to Noise Ratio decreased as the tube voltage and sensitivity were set higher. In addition, the higher tube voltage and sensitivity, the Time-to-Radiation Dose Curve showed a poor output stability. In conclusion, the higher the combination of tube voltage and sensitivity in the use of Automatic Exposure Control, the more problems can be seen in image quality and stability of the radiation output. Therefore, a relatively low combination of tube voltage and sensitivity showed that the image quality and radiation output stability could be optimized by minimizing the error range that would occur when the detector recognized a combination of parameters.

Combined Effect of Gamma Irradiation and Silk Peptide on the Radio-sensitivity of Bacteria and Storage Stability of Ready-to-eat Hamburger Patty (감마선 조사와 실크 펩타이드 병용처리가 세균의 방사선 감수성 및 햄버거 패티의 저장 안정성에 미치는 영향)

  • Kim, Jae-Hun;Park, Jin-Gyu;Song, Beom-Seok;Lee, Ju-Woon;Kim, Wang-Geun;Hwang, Young-Jeong;Byun, Myung-Woo
    • Food Science and Preservation
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    • v.14 no.5
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    • pp.481-486
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    • 2007
  • This study was conducted to evaluate the combined effect of gamma irradiation and silk peptide on the radiosensitivity of bacteria and the storage stability of ready-to-eat hamburger patty. The $D_{10}$ values obtained for Escherichia coli, Listeria ivanovii, Salmonella typhimurium and Clostridium sporogenes by gamma irradiation were 0.25, 0.50, 0.55 and 1.35 kGy, respectively. The inactivation rate of S. typhimurium ($D_{10}=0.53kGy$) inoculated into hamburger patty with 5%(w/w) silk peptide was reduced 6% compared with the control $D_{10}=0.558kGy$). In acceleration storage at $30^{\circ}C$, microorganisms were not observed in samples irradiated with 7 kGy or 10 kGy during storage. However the irradiation at 5 kGy was insufficient to sterilize the contaminated microorganisms in hamburger patty regardless of the addition of silk peptide (5%). These results indicate that the combined treatment of gamma-irradiation and silk peptide admixture could be helpful to ensure storage stability of ready-to-eat hamburger patty, by controlling the preliminary microbial load.

Combined Effect of Heat Treatment and Gamma Irradiation on the Shelf-Stability and Quality of Packaged Kimchi during Accelerated Storage Condition (가열 및 감마선 조사 병용처리가 가속저장 포장 김치의 저장안정성 및 품질에 미치는 영향)

  • Kim, Mi-Jung;Park, Jin-Gyu;Kim, Jae-Hun;Park, Jae-Nam;Lee, Hyun-Joo;Kim, Wang-Geun;Lee, Ju-Woon;Byun, Myung-Woo
    • Food Science and Preservation
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    • v.13 no.5
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    • pp.531-537
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    • 2006
  • This study was conducted to evaluate the combined effect of heating and gamma irradiation on the shelf-stability and quality of kimchi during storage at $35^{\circ}C$. The optimum condition for heat treatment of kimchi was considered at $60^{\circ}C$ for 30 min. Irradiation after kent treatment was effective to inhibit the growth of microorganisms and prevent the quality change of kimchi during storage. In particular, microorganisms of kimchi co-treated with heat and 20 kGy-irradiation were not detected and sensory scores of that were the highest after storage at $35^{\circ}C$ for 14 days. Therefore, combination treatment of heat and irradiation was considered as the effective method to improve the shelf-stability of kimchi in the accelerated condition.

Improvements in Storage Stability of Undaria pinnatifida after Gamma Irradiation (감마선 조사에 의한 미역의 저장성 개선)

  • Kim, Hyun-Joo;Choi, Jong-Il;Kim, Jae-Hun;Chun, Byung-Soo;Ahn, Dong-Hyun;Kim, Gwang-Hoon;Byun, Myung-Woo;Lee, Ju-Woon
    • Food Science and Preservation
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    • v.16 no.4
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    • pp.590-593
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    • 2009
  • The effect of gamma irradiation on the storage stability of Undaria pinnatifida was investigated. A three-log reduction in total aerobic bacteria in U. pinnatifida samples was obtained by irradiation with 3 kGy. During storage for 2 weeks, the viable counts of microorganisms in non-irradiated U. pinnatifida increased to 6 log CFU/g. However, irradiation of U. pinnatifida by 5 kGy eliminated microorganisms. The Hunter $L^{\ast}-value$ of U. pinnatifida was slightly increased after 5 kGy of irradiation. The hardness properties of U. pinnatifida decreased during storage, but were not changed by irradiation with up to 3 kGy. These results indicate that low-dose irradiation (3 kGy) could be effective for improvement of the storage stability of U. pinnatifida.

A Study on the Improvement of the Thermal Stability of a Commercial Polyethylene Separator for Lithium Secondary Battery by an Electron Beam Irradiation (전자선 조사에 의한 리튬 이차전지용 상용 폴리에틸렌 분리막의 내열성 향상에 관한 연구)

  • Sohn, Joon-Yong;Lim, Jong-Soo;Gwon, Sung-Jin;Shin, Jun-Hwa;Choi, Jae-Hak;Nho, Young-Chang
    • Polymer(Korea)
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    • v.32 no.6
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    • pp.598-602
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    • 2008
  • In this study we prepared crosslinked separators with the improved thermal stability by irradiating a commercial polyethylene (PE) separator for lithium secondary battery with an electron beam, and the thermal and mechanical properties of the prepared separators were evaluated as a function of the absorption dose. The thermal shrinkage of electron beam irradiated separator was decreased with increasing absorption dose. As a result of the shutdown behavior using an AC impedance, it was observed that the irradiated separator had the better shutdown function than the unirradiated separator. The modulus of the irradiated separator was enhanced as the absorption dose was increased, while the tensile strength and the break elongation of the irradiated separator were decreased.

Effect of D-(+)-Glucose on the Stability of Polyvinyl Alcohol Fricke Hydrogel Three-Dimensional Dosimeter for Radiotherapy

  • Yang, Yuejiao;Chen, Jie;Yang, Liming;Chen, Bin;Sheng, Zhenmei;Luo, Wenyun;Sui, Guoping;Lu, Xun;Chen, Jianxin
    • Nuclear Engineering and Technology
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    • v.48 no.3
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    • pp.608-612
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    • 2016
  • D-(+)-glucose (Glc) was added to the original Fricke polyvinyl alcohol-glutaraldehyde-xylenol orange (FPGX) hydrogel dosimeter system to make a more stable FPGX hydrogel three-dimensional dosimeter in this paper. Polyvinyl alcohol was used as a substrate, which was combined with Fricke solution. Various concentrations of Glc were tested with linear relevant fitting for optimal hydrogel production conditions. The effects of various formulations on the stability and sensitivity of dosimeters were evaluated. The results indicated that D-(+)-Glc, as a free radical scavenger, had a great effect on stabilizing the dose response related to absorbency and reducing the auto-oxidization of ferrous ions. A careful doping with Glc could slow down the color change of the dosimeter before and after radiation without any effect on the sensitivity of the dosimeter.

The Otimization of Laser System for Photodynamic Therapy of Malignancies (악성종양의 광역학적 치료를 위한 레이저 시스템의 최적화)

  • 임현수;김주옥;황인경
    • Journal of the Institute of Electronics Engineers of Korea SC
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    • v.41 no.6
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    • pp.51-60
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    • 2004
  • In this paper, we optimized the PDT laser system to improve the therapy effects of malignancies. In order to optimize, the variation of laser output and specific wavelength shift have to reduced. To improve the PDT therapy clinician require the diverse radiation mode which irradiate the tumor surface. Continuous wave mode that general application may causes tissue thermal damage not only to tumor tissue, but also to normal tissue. In this paper, therefore, we suggested new technique for radiation method to improved PDT effects and prevented to the thermal effects for the tissue. In the experimental we verified the stability of wavelength, laser output stability and proved the reduced thermal effects to the tissue using the pulse & burst radiation modes in vitro.