• Title/Summary/Keyword: Time-Dependent Behaviors

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Analysis of Stress Relaxation Behaviors of Geosynthetics (지오신세틱스의 응력완화거동 해석)

  • Jeon, Han-Yong
    • Journal of the Korean Geosynthetics Society
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    • v.5 no.3
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    • pp.31-36
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    • 2006
  • In this study, stress relaxation behaviors of nonwoven geotextile and geomembrane which have protection, filtration and drainage, water barrier functions, respectively were examined. 'Theory of transition phenomen' was applied to interpretate the stress relaxation behaviors of two geosynthetics. The initial and later relaxation times for stress relaxation behaviors of geosynthetics were derived from the constitutive equations. The initial relaxation behaviors of these geosynthetics were dependent on the additional strains and were especially faster with temperature. Finally, both relaxation times of geosynthetics were shorter with additional strain and temperature and the reduction of relaxation times of nonwoven geotextile were larger than those of geomembrane.

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Analysis of Stress Relaxation Behaviors of Geosynthetics (토목 합성재료의 응력완화 거동 해석)

  • Jeon, Han-Yong;Park, Young-Mok;Chung, Jin-Gyo
    • Journal of the Korean Geosynthetics Society
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    • v.3 no.4
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    • pp.21-27
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    • 2004
  • Stress relaxation behaviors of nonwoven geotextile and geomembrane which have protection, filtration and drainage, water barrier functions, respectively were analyzed. 'Theory of transition phenomena' was applied to interpretate the stress relaxation behaviors of two geosynthetics. The initial and later relaxation times for stress relaxation behaviors of geosynthetics were derived from the constitutive equations. The initial relaxation behaviors of these geosynthetics were dependent on the additional strains and were especially faster with temperature. Finally, both relaxation times of geosynthetics were shorter with additional strain and temperature.

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Effect of Rice Lipid and Protein on Rheological Characteristics of Gelatinized Rice Flour Solutions (쌀의 지방과 단백질이 쌀가루 호화액의 리올리지 특성에 미치는 영향)

  • 이영순;김인호;김현정;이상효;이현유;박광희
    • Journal of the Korean Society of Food Science and Nutrition
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    • v.28 no.6
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    • pp.1293-1297
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    • 1999
  • Effect of rice protein and lipid on rheological properties of gelatinized rice flour solutions(4%) with three rice varieties(Dongjin, Jinmi, Tamjin) known for varying taste of cooked rice was investigated with Haake viscometer. The rheological behaviors of all rice flour solutions were illustrated by Herschel Bulkley equation and exhibited pseudoplastic behavior with yield stress. When rice flour solutions treated with protease and dithiothreitol, there was decreased in flow behavior index value. Flow behavior index was decreased by dealbumin and deglutelin rice flour solutions among deprotein groups. The Jinmi rice flour solutions exhibited slightly lower consistency index than Dongjin and Tamjin. Defatted rice flour solutions exhibited lower consistency index than rice flour solutions, while dealbumin, deglutelin rice flour solutions exhibited high consistency index. Protease treated rice flour solutions exhibited increase in Dongjin and Tamjin. The yield stress was increased in sequence eating quality. Yield stress of defatted rice flour solutions was decreased, while deglutelin and rice starch flour solutions was increased. The time dependent charac teristics of all rice flour solutions appeared forming hysteresis loop and thixotropic behavior showed. The time dependent characteristics was appeared in sequence eating quality. Rice starch and deglutelin flour solutions appeared greatly time dependent characteristics, but defatted rice flour solutions appeared very little.

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A Study on Characteristics of Indoor- Air-Quality in Interior Space Equipped with System Air-Conditioner (시스템 에어컨 설치 공간의 실내공기질 특성에 관한 연구)

  • Lee, Sang-Won;Kim, Jong-Min;Yeum, Seung-Won;Cho, Dae-Gun;Choi, Jae-Boong;Kim, Seok-Woo
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.20 no.5
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    • pp.304-313
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    • 2008
  • This paper investigates the indoor-air-quality (IAQ) characteristics of the interior space equipped with system air-conditioner. The behaviors of individual variables such as temperature, humidity and concentration of carbon dioxide ($CO_2$) that influence on IAQ of the interior space were characterized under various cooling conditions by numerical and experimental studies. The numerical analysis predicting the temperature behavior of the interior space was conducted, and its results showed a good agreement with the experimental ones. The $CO_2$ concentration and humidity were measured and their time dependent behaviors were monitored and analyzed. From the results, it was found that there existed the differences of the time-dependent behaviors of IAQ variables according to the locations. In addition, it is demonstrated that the large discharge angle of $45^{\circ}$ made the temperature profile more irregular and the high discharge flow of 5.34 m/s produced similar temperature profiles at three different sensing locations. Finally, the humidity of interior space was less sensitive to the changes of the air cooling conditions than the case of temperature and the $CO_2$ concentration increase mainly depended on the number of individuals inside the space.

A Study on Behaviors of Prestressed Bridge Girders Made Continuous (연속화된 Prestress 거더교의 거동연구)

  • 구민세;최인식;김진헌
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2002.10a
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    • pp.396-403
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    • 2002
  • To eliminate deck joints, continuous span bridges are becoming an attractive option. Defferent continuty methods and construction sequences have different time-dependent effects on the behavior of the bridge system. This paper is carried out to evaluate the restraint moments generated at interior span of bridges constructed with full-span prestessed concrete bridge. Especially, effects of creep and shrinkage between ACI209-95 and Eurocode 2 are compared in this paper. Time-dependent effects in prestressed concrete bridges include creep and shrinkage of concrete. Creep due to prestress makes the girders camber up and cause positive restraint moments. The most significant effect of shrinkage in continuous bridges is the differential shrinkage that occurs because of the difference in type and age of girder and deck concrete. Differential shrinkage between the precast girder and the deck typically causes negative res03int moments.

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Response of angle-ply laminated cylindrical shells with surface-bonded piezoelectric layers

  • Wang, Haojie;Yan, Wei;Li, Chunyang
    • Structural Engineering and Mechanics
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    • v.76 no.5
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    • pp.599-611
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    • 2020
  • A state-space method is developed to investigate the time-dependent behaviors of an angle-ply cylindrical shell in cylindrical bending with surface-bonded piezoelectric layers. Both the interfacial diffusion and sliding are considered to describe the properties of the imperfect interfaces. Particularly, a matrix reduction technique is adopted to establish the transfer relations between the elastic and piezoelectric layers of the laminated shell. Very different from our previous paper, in which an approximate numerical technique, i.e. power series expansion method, is used to deal with the time-dependent problems, the exact solutions are derived in the present analysis based on the piezoelasticity equations without any assumptions. Numerical results are finally obtained and the effects of imperfect interfaces on the electro-mechanical responses of the laminated shell are discussed.

PHASE ANALYSIS FOR THE PREDATOR-PREY SYSTEMS WITH PREY DENSITY DEPENDENT RESPONSE

  • Chang, Jeongwook;Shim, Seong-A
    • The Pure and Applied Mathematics
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    • v.25 no.4
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    • pp.345-355
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    • 2018
  • This paper looks into phase plane behavior of the solution near the positive steady-state for the system with prey density dependent response functions. The positive invariance and boundedness property of the solution to the objective model are proved. The existence result of a positive steady-state and asymptotic analysis near the positive constant equilibrium for the objective system are of interest. The results of phase plane analysis for the system are proved by observing the asymptotic properties of the solutions. Also some numerical analysis results for the behaviors of the solutions in time are provided.

A GN-based modified model for size-dependent coupled thermoelasticity analysis in nano scale, considering nonlocality in heat conduction and elasticity: An analytical solution for a nano beam with energy dissipation

  • Hosseini, Seyed Mahmoud
    • Structural Engineering and Mechanics
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    • v.73 no.3
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    • pp.287-302
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    • 2020
  • This investigation deals with a size-dependent coupled thermoelasticity analysis based on Green-Naghdi (GN) theory in nano scale using a new modified nonlocal model of heat conduction, which is based on the GN theory and nonlocal Eringen theory of elasticity. In the analysis based on the proposed model, the nonlocality is taken into account in both heat conduction and elasticity. The governing equations including the equations of motion and the energy balance equation are derived using the proposed model in a nano beam resonator. An analytical solution is proposed for the problem using the Laplace transform technique and Talbot technique for inversion to time domain. It is assumed that the nano beam is subjected to sinusoidal thermal shock loading, which is applied on the one of beam ends. The transient behaviors of fields' quantities such as lateral deflection and temperature are studied in detail. Also, the effects of small scale parameter on the dynamic behaviors of lateral deflection and temperature are obtained and assessed for the problem. The proposed GN-based model, analytical solution and data are verified and also compared with reported data obtained from GN coupled thermoelasticity analysis without considering the nonlocality in heat conduction in a nano beam.

Small and Large Deformation Rheological Behaviors of Commercial Hot Pepper-Soybean Pastes

  • Choi, Su-Jin;Kang, Kyoung-Mo;Yoo, Byoung-Seung
    • Food Science and Biotechnology
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    • v.15 no.6
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    • pp.871-876
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    • 2006
  • Rheological behavior of commercial hot pepper-soybean paste (HPSP) was evaluated in small amplitude oscillatory and steady shear tests. Storage modulus (G'), loss modulus (G"), and complex viscosity (${\eta}^*$) as a function of angular frequency (${\omega}$), and shear stress (${\sigma}$) as a function of shear rate (${\gamma}$) data were obtained for 5 commercial HPSP samples. HPSP samples at $25^{\circ}C$ exhibited a non-Newtonian, shear-thinning flow behavior with high yield stresses and their flow behaviors were described by power law, Casson, and Herschel-Bulkley models. Time-dependent flow properties were also described by the Weltman, Hahn, and Figoni & Shoemaker models. Apparent viscosity over the temperature range of $5-35^{\circ}C$ obeyed the Arrhenius temperature relationship with activation energies (Ea) ranging 18.3-20.1 kJ/mol. Magnitudes of G' and G" increased with an increase in ${\omega}$, while ${\eta}^*$ decreased. G' values were higher than G" over the most of the frequency range (0.63-63 rad/sec), showing that they were frequency dependent. Steady shear viscosity and complex viscosity of the commercial HPSP did not fit the Cox-Merz rule.

HEAT-UP AND COOL-DOWN TEMPERATURE-DEPENDENT HYDRIDE REORIENTATION BEHAVIORS IN ZIRCONIUM ALLOY CLADDING TUBES

  • Won, Ju-Jin;Kim, Myeong-Su;Kim, Kyu-Tae
    • Nuclear Engineering and Technology
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    • v.46 no.5
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    • pp.681-688
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    • 2014
  • Hydride reorientation behaviors of PWR cladding tubes under typical interim dry storage conditions were investigated with the use of as-received 250 and 485ppm hydrogen-charged Zr-Nb alloy cladding tubes. In order to evaluate the effect of typical cool-down processes on the radial hydride precipitation, two terminal heat-up temperatures of 300 and $400^{\circ}C$, as well as two terminal cool-down temperatures of 200 and $300^{\circ}C$, were considered. In addition, two cooling rates of 2.5 and $8.0^{\circ}C/min$ during the cool-down processes were taken into account along with zero stress or a tensile hoop stress of 150MPa. It was found that the 250ppm hydrogen-charged specimen experiencing the higher terminal heat-up temperature and the lower terminal cool-down temperature generated the highest number of radial hydrides during the cool-down process under 150MPa hoop tensile stress, which may be explained by terminal solid hydrogen solubilities for precipitation, and dissolution and remaining circumferential hydrides at the terminal heat-up temperatures. In addition, the slower cool-down rate generates the larger number of radial hydrides due to a cooling rate-dependent, longer residence time at a relatively high temperature that can accelerate the radial hydride nucleation and growth.