• Title/Summary/Keyword: Temperature Gradient

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Numerical Study of Radial Temperature Gradient Effect on Taylor Vortices (반경방향으로의 온도구배가 Taylor Vortex에 미치는 영향에 대한 수치적 연구)

  • Kang, Chang-Woo;Yang, Kyung-Soo;Yoon, Dong-Hyeog
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.33 no.11
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    • pp.900-908
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    • 2009
  • Numerical simulation has been carried out to investigate the influence of radial temperature gradient on the Taylor Vortex flow. Varying the Grashof number, we study the detailed flow and temperature fields. The current numerical results show good agreement with the experimental results currently available. It turns out that wavy spiral vortices are generated by increasing temperature gradient. We classify flow patterns for various Grashof numbers based on the characteristics of flow fields and spiral vortices. The correlation between Grashof number with wave number shows that the spiral angle and size of Taylor vortices increase with increasing temperature gradient. Temperature gradient does not have a great influence on the heat transfer rate of the cylinder surfaces.

Detection of Mutated DNA Fragment by the Heteroduplex Analysis at the Temperature Gradient Gel (온도 기울기(temperature gradient) 젤에서 Heteroduplex Analysis 기법을 이용한 돌연변이 DNA의 검출)

  • 조용석;구미자;박귀근;박영서;강종백
    • Environmental Mutagens and Carcinogens
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    • v.18 no.2
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    • pp.83-88
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    • 1998
  • To detect the mutation in a given sequence, there are variety of methods developed by use of the gel electrophoresis. One of the methods, TGGE (Temperature Gradient Gel Electrophoresis), is a popular technique because it can detect mutations in DNA fragment with ease and at low cost. This study used 200 bp BamHI-digested DNA fragment containing the human $\varepsilon$-globin promoter which was mutated[$\varepsilon$ F1*(-141), GATA- I*(-163), and GATA-1* & $\varepsilon$F1]. This BamHI-digested DNA fragment was directly used to detect the mutated DNA fragment on 50% denaturant gel with temperature gradient of 45$^{\circ}C$ through $53^{\circ}C$. In agreement with the theoretical result of MELTSCAN program (Brossette and Wallet, 1994) the mobilities of mutated DNA fragments were shown to be nearly distinguished on the temperature gradient gel. In contrast to the above result the heteroduplex analysis under the temperature gradient condition was shown to detect the mutated DNA fragments through the heteroduplex formation between strands of mutated DNA and wild-type DNA.

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Effect of temperature gradient on track-bridge interaction

  • Kumar, Rakesh;Upadhyay, Akhil
    • Interaction and multiscale mechanics
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    • v.5 no.1
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    • pp.1-12
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    • 2012
  • Considerable longitudinal rail forces and displacements may develop in continuous welded rail (CWR) track on long-span bridges due to temperature variations. The track stability may be disturbed due to excessive relative displacements between the sleepers and ballast bed and the accompanied reduction in frictional resistance. For high-speed tracks, however, solving these problems by installing rail expansion devices in the track is not an attractive solution as these devices may cause a local disturbance of the vertical track stiffness and track geometry which will require intensive maintenance. With reference to temperature, two actions are considered by the bridge loading standards, the uniform variation in the rail and deck temperature and the temperature gradient in deck. Generally, the effect of temperature gradient has been disregarded in the interaction analysis. This paper mainly deals with the effect of temperature gradient on the track-bridge interaction with respect to the support reaction, rail stresses and stability. The study presented in this paper was not mentioned in the related codes so far.

Effect of Temperature Gradient on the Defects of Nd;YAG Single Crystal Grown by Czochralski Method (융액인상법에 의한 Nd;YAG 단결정 성장시 온도구배의 변화에 따른 결함거동)

  • 김한태;배소익;이상호;정수진
    • Journal of the Korean Ceramic Society
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    • v.34 no.10
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    • pp.1015-1020
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    • 1997
  • In the Nd;YAG crystal growth by Czochralski method, the relationship between the core formation and the solid-liquid interface was observed by controlling the temperature gradient in the furnace. When the crystal was grown along<111> direction, defects and core area were reduced as the temperature gradient increased. The optimum temperature gradient was found to be higher than 4$0^{\circ}C$/cm. The Nd3+ concentration analysis by ICP-Mass showed that the segregation coefficient was about 20% higher in the core region than core-free region, where the segregation coefficients of core region and core-free region were 0.22 and 0.18, respectively.

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An experimental and numerical study on temperature gradient and thermal stress of CFST truss girders under solar radiation

  • Peng, Guihan;Nakamura, Shozo;Zhu, Xinqun;Wu, Qingxiong;Wang, Hailiang
    • Computers and Concrete
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    • v.20 no.5
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    • pp.605-616
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    • 2017
  • Concrete filled steel tubular (CFST) composite girder is a new type of structures for bridge constructions. The existing design codes cannot be used to predict the thermal stress in the CFST truss girder structures under solar radiation. This study is to develop the temperature gradient curves for predicting thermal stress of the structure based on field and laboratory monitoring data. An in-field testing had been carried out on Ganhaizi Bridge for over two months. Thermal couples were installed at the cross section of the CFST truss girder and the continuous data was collected every 30 minutes. A typical temperature gradient mode was then extracted by comparing temperature distributions at different times. To further verify the temperature gradient mode and investigate the evolution of temperature fields, an outdoor experiment was conducted on a 1:8 scale bridge model, which was installed with both thermal couples and strain gauges. The main factors including solar radiation and ambient temperature on the different positions were studied. Laboratory results were consistent with that from the in-field data and temperature gradient curves were obtained from the in-field and laboratory data. The relationship between the strain difference at top and bottom surfaces of the concrete deck and its corresponding temperature change was also obtained and a method based on curve fitting was proposed to predict the thermal strain under elevated temperature. The thermal stress model for CFST composite girder was derived. By the proposed model, the thermal stress was obtained from the temperature gradient curves. The results using the proposed model were agreed well with that by finite element modelling.

Experimental Study on the Stimulating Effect of Commercial Moxa Combustion through the Measurement of Temperature - Focused on ascending temperature gradient and effective stimulating period - (온도 측정을 통한 상용 쑥뜸의 자극효과에 대한 실험적 연구 - 승온속도 및 유효자극기를 중심으로 -)

  • Lee, Geon-Mok;Lee, Gun-Hyee;Lee, Seung-Hoon;Yang, Myung-Bok;Go, Gi-Deok;Seo, Eun-Mi;Jang, Jong-Deok;Hwang, Byung-Chan
    • Journal of Acupuncture Research
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    • v.19 no.3
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    • pp.64-76
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    • 2002
  • Objective : The purpose of this study is to investigate the mechanism and effect of moxibustion objectively and to be used as the quantitative data for developing the new thermal stimulating treatment by observing the combustion characteristics of commercial moxaes. Methods : We have selected two types(large-size moxa A(LMA), large-size moxa B(LMB)) among large moxaes used widely in the clinic. We examined combustion times, temperatures, temperature gradients in each period during a combustion of moxa. Results : 1. The ascending temperature gradient measured in the central point of non-contacted surface was fastest, the average ascending temperature gradient of both moxaes was $0.0384^{\circ}C/sec$, $0.0123^{\circ}C/sec$ respectively, 3.1 times faster in LMA. The maximum ascending temperature gradient was also about 2.9 times faster in LMA. The time required for the maximum ascending temperature gradient from ignition was 254sec, 411sec respectively. 2. The minimum descending temperature gradient in the retaining period was $-0.0250^{\circ}C/sec$, $-0.0090^{\circ}C/sec$ respectively and the average descending temperature gradient was $-0.0160^{\circ}C/sec$, $-0.0037^{\circ}C/sec$ respectively on the non-contact surface. 3. On the basis of the non-contact surface($A_I$), the time at which the effective stimulus period began to occur was about 264sec, 796sec respectively after an ignition, the time at which the maximum temperature began to occur was about 373sec, 1323sec respectively after an ignition, and the maximum temperature was $0.9^{\circ}C$ higher in LMA. The maximum ascending temperature gradient was also about 4.2 times faster in LMA. Conclusion : It was thought that not only the figure of moxicombustion device, but also the form and size of moxa had influence on the combustion characteristics deciding the performance of stimulus seriously.

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Study of Different Radial Temperature Gradient Effect on Taylor-Couette Flow Instability (온도구배가 Taylor-Couette유동의 불안정성에 주는 영향에 관한 연구)

  • Cha, Jae-Eun;Liu, Dong;Tu, Xin Cheng;Kim, Hyoung-Bum
    • Journal of the Korean Society of Visualization
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    • v.8 no.3
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    • pp.35-40
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    • 2010
  • We have investigated different radial temperature gradient effect on the stability of Taylor-Couette flow. The radius ratio and aspect ratio of the model was 0.825 and 48, respectively. Two heating exchangers were used for generating different temperature gradient along the radial direction. The change of flow regime in the Taylor-Couette flow was studied by increasing the Reynolds number. The results showed that: as Gr is increased in helical vortex flow regime, the vortices with the same direction of convection flow increased in size, and the vortex moving velocity also increased. It is also shown that the presence of temperature gradient obviously increased the flow instability when the Richardson number is larger than 0.0045.

Effect of Temperature Gradient on the Characteristics of GaN Nanorods Grown on R-plane Sapphire Substrates (기판 주변 반응 기체와 기판 사이의 온도 차이에 따른 r-면 사파이어 기판에 성장된 길화갈륨 나노 막대의 특성 변화 연구)

  • Shin, Bo-A;Kim, Chin-Kyo
    • Journal of the Korean Vacuum Society
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    • v.18 no.1
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    • pp.44-48
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    • 2009
  • The effect of temperature gradient between the substrate and ambient gas on the structural characteristics of GaN nanorods grown on r-plane sapphire substrates by hydride vapor phase epitaxy was investigated. The density, diameter, and length strongly depended on the tempearture gradient. In addition, the cross-sectional shape of the nanorrods at the end of growth was found to be more dependedent on the temperature of a substrate itself than the temperature gradient.

Characteristic Changes of the Hydrated Sodium Silicate Depending on Heat Treatment Temperature (수화된 규산소다의 열처리 온도에 따른 물성변화)

  • Kong, Yang-Pyo;Cho, Ho-Yeon;Suhr, Dong-Soo
    • Journal of the Korean Ceramic Society
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    • v.45 no.3
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    • pp.185-189
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    • 2008
  • In order to fabricate porous ceramics, hydrated sodium silicate was synthesized by hydrothermal reaction using anhydrous sodium silicate. The microstructural and the structural characteristics of the expanded ceramics were observed depending on heat treatment temperature (550, 600, 650, $700^{\circ}C$) and then the effect of these characteristics on the compressive strength and the temperature gradient was investigated. As the heat treatment temperature was increased, the compressive strength was decreased from $0.717KN/cm^2\;(550^{\circ}C)\;to\;0.166KN/cm^2\;(700^{\circ}C)$. The temperature gradient was increased with increasing the experimental temperature regardless of the heat treatment temperature. The temperature gradient of the expanded ceramics which was heat treated at $650^{\circ}C\;was\;300^{\circ}C$. The bulk specific gravity, porosity, pore size, pore characteristics and wall thickness were varied depending on heat treatment temperature, and the compressive strength and the temperature gradient were governed by the complex effects of these factors.

Hadley Circulation Strength Change in Response to Global Warming: Statistics of Good Models

  • Son, Jun-Hyeok;Seo, Kyong-Hwan
    • Atmosphere
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    • v.26 no.4
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    • pp.665-672
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    • 2016
  • In this study, we examine future changes in the Hadley cell (HC) strength using CMIP5 climate change simulations. The current study is an extension of a previous study by Seo et al. that used all 30 available models. Here, we select 18-23 well-performing models based on their significant internal sensitivity of the interannual HC strength variation to the latitudinal temperature gradient variation. The model projections along with simple scaling analysis show that the inter-model variability in the HC strength change is a result of the inter-model spread in the meridional temperature gradient across the subtropics for both DJF and JJA, not by the tropopause height or gross static stability change. The HC strength is expected to weaken significantly during DJF, while little change is expected in the JJA HC strength. Compared to the calculations with all model members, selected model statistics increase the linear correlation between the changes in HC strength and meridional temperature gradient by 13~23%, confirming the robust sensitivity of the HC strength to the meridional temperature gradient. Two scaling equations for the selected models predict changes in HC strength better than all-member predictions. In particular, the prediction improvement in DJF is as high as 30%. The simple scaling relations successfully predict both the ensemble-mean changes and model-to-model variations in the HC strength for both seasons.