Academic literature on the topic 'Temperature sensitivity phenomenon'
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Journal articles on the topic "Temperature sensitivity phenomenon"
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Zhu, Zhi-Wu, Yue Ma, Hai-Dong Zhang, Wei-Dong Song, and Yuan-Chao Gan. "Evaluation of thermal effects and strain-rate sensitivity in frozen soil." Thermal Science 18, no. 5 (2014): 1631–36. http://dx.doi.org/10.2298/tsci1405631z.
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Temperature variation is one important factor that affects the dynamic mechanical properties of frozen soil under impact loading. Thermal damage is a collective phenomenon that can be caused by temperature variation. This paper investigates the effects of thermal damage on strain course. A split Hopkinson pressure bar was employed to investigate the dynamic mechanical characteristics of frozen soil at different temperatures and different strain rates. The stress-strain curves were obtained under impact loading. The compressive strength of frozen soil showed a negative temperature sensitivity and positive strain-rate trend. Specifically, the strength of frozen soil increased with decreasing temperatures and increasing strain rates.
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Cole, Nancy L. "Temperature sensitivity of herpes simplex virus type 1 is a tissue-dependent phenomenon." Archives of Virology 127, no. 1-4 (March 1992): 49–63. http://dx.doi.org/10.1007/bf01309574.
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Okojie, Robert S., Dorothy Lukco, Vu Nguyen, and Ender Savrun. "Demonstration of SiC Pressure Sensors at 750 °C." Additional Conferences (Device Packaging, HiTEC, HiTEN, and CICMT) 2014, HITEC (January 1, 2014): 000028–32. http://dx.doi.org/10.4071/hitec-ta21.
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We report the first demonstration of MEMS-based 4H-SiC piezoresistive pressure sensors tested at 750 °C and in the process confirmed the existence of strain sensitivity recovery with increasing temperature above 400 °C, eventually achieving near or up to 100 % of the room temperature values at 750 °C. This strain sensitivity recovery phenomenon in 4H-SiC is uncharacteristic of the well-known monotonic decrease in strain sensitivity with increasing temperature in silicon piezoresistors. For the three sensors tested, the room temperature full-scale output (FSO) at 200 psig ranged between 29 and 36 mV. Although the FSO at 400 °C dropped by about 60 %, full recovery was achieved at 750 °C. This result will allow the operation of SiC pressure sensors at higher temperatures, thereby permitting deeper insertion into the engine combustion chamber to improve the accurate quantification of combustor dynamics.
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Zhang, Zhen, M. A. Cuddihy, and F. P. E. Dunne. "On rate-dependent polycrystal deformation: the temperature sensitivity of cold dwell fatigue." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 471, no. 2181 (September 2015): 20150214. http://dx.doi.org/10.1098/rspa.2015.0214.
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A temperature and rate-dependent crystal plasticity framework has been used to examine the temperature sensitivity of stress relaxation, creep and load shedding in model Ti-6Al polycrystal behaviour under dwell fatigue conditions. A temperature close to 120°C is found to lead to the strongest stress redistribution and load shedding, resulting from the coupling between crystallographic slip rate and slip system dislocation hardening. For temperatures in excess of about 230°C, grain-level load shedding from soft to hard grains diminishes because of the more rapid stress relaxation, leading ultimately to the diminution of the load shedding and hence, it is argued, the elimination of the dwell debit. Under conditions of cyclic stress dwell, at temperatures between 20°C and 230°C for which load shedding occurs, the rate-dependent accumulation of local slip by ratcheting is shown to lead to the progressive cycle-by-cycle redistribution of stress from soft to hard grains. This phenomenon is termed cyclic load shedding since it also depends on the material's creep response, but develops over and above the well-known dwell load shedding, thus providing an additional rationale for the incubation of facet nucleation.
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Yan, Dong Ming, and Wei Xu. "Strain-Rate Sensitivity of Concrete: Influence of Temperature." Advanced Materials Research 243-249 (May 2011): 453–56. http://dx.doi.org/10.4028/www.scientific.net/amr.243-249.453.
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Knowledge about the dynamic properties of concrete is vital to the design and safety evaluation of large-scale concrete structures subjected to seismic excitation. There are many factors affecting the dynamic properties of concrete such as moisture content and temperature. Though a lot of concrete structures have been designed to withstand low temperature, research on the strain-rate sensitivity of concrete under low temperature condition is still very limited so far. In this study, both tensile and compressive experiments were carried out to investigate the influence of temperature on the rate-dependent characteristics of concrete. Tensile experiments of dumbbell-shaped specimens were carried out on a MTS810 testing machine and compressive tests on cubic specimens were performed using a servo-hydraulic testing machine. Specimens at two types of temperature, room temperature 20oC and low temperature -30oC, were characterized. The strain rate varied over a wide range. It was concluded from the test data that the strengths of specimens at both types of temperature tended to increase as strain rate increased. Temperature had slight influence on the rate-sensitive behavior of concrete when concrete specimens were dry; however, test on saturated specimens indicated that the role of temperature on the mechanical behavior of concrete subject to dynamic loading was very significant. This phenomenon may be attributed to the state of free water in concrete.
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Wang, Xiaoxue, Yuguo Li, Xinyan Yang, Pak Chan, Janet Nichol, and Qinglan Li. "The Street Air Warming Phenomenon in a High-Rise Compact City." Atmosphere 9, no. 10 (October 16, 2018): 402. http://dx.doi.org/10.3390/atmos9100402.
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The street thermal environment is important for thermal comfort, urban climate and pollutant dispersion. A 24-h vehicle traverse study was conducted over the Kowloon Peninsula of Hong Kong in summer, with each measurement period consisting of 2–3 full days. The data covered a total of 158 loops in 198 h along the route on sunny days. The measured data were averaged by three methods (direct average, FFT filter and interpolated by the piecewise cubic Hermite interpolation). The average street air temperatures were found to be 1–3 °C higher than those recorded at nearby fixed weather stations. The street warming phenomenon observed in the study has substantial implications as usually urban heat island (UHI) intensity is estimated from measurement at fixed weather stations, and therefore the UHI intensity in the built areas of the city may have been underestimated. This significant difference is of interest for studies on outdoor air temperature, thermal comfort, urban environment and pollutant dispersion. The differences were simulated by an improved one-dimensional temperature model (ZERO-CAT) using different urban morphology parameters. The model can correct the underestimation of street air temperature. Further sensitivity studies show that the building arrangement in the daytime and nighttime plays different roles for air temperature in the street. City designers can choose different parameters based on their purpose.
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Brown, Ross D., Marilyn G. Hughes, and David A. Robinson. "Characterizing the long-term variability of snow-cover extent over the interior of North America." Annals of Glaciology 21 (1995): 45–50. http://dx.doi.org/10.3189/s0260305500015585.
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Historical and reconstructed snow-cover data show evidence of a gradual increase in snow cover over the continental interior of North America (NA) during much of the 20th century, primarily in response to increasing snowfall. A rapid decrease in Canadian-prairies snow cover after 1970 is not observed over the Great Plains. Analysis of snow-cover-climate relationships revealed systematic increases in the sensitivity of snow cover to Northern Hemisphere (NH) temperatures over the 1940-65 period. This change is mainly due to an increase in snowfall-temperature sensitivity during this period. Seasonal analysis revealed that the observed increase in snow-cover and snowfall temperature sensitivity is primarily a spring phenomenon. A marked increase in the importance of the spring period is observed around 1960, which coincides with a well-documented change in atmospheric circulation over NA. The post-1960 period is characterized by a significant inverse relationship between snow cover and hemispheric air temperature over the Canadian prairies and northern Great Plains regions.
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Brown, Ross D., Marilyn G. Hughes, and David A. Robinson. "Characterizing the long-term variability of snow-cover extent over the interior of North America." Annals of Glaciology 21 (1995): 45–50. http://dx.doi.org/10.1017/s0260305500015585.
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Historical and reconstructed snow-cover data show evidence of a gradual increase in snow cover over the continental interior of North America (NA) during much of the 20th century, primarily in response to increasing snowfall. A rapid decrease in Canadian-prairies snow cover after 1970 is not observed over the Great Plains. Analysis of snow-cover-climate relationships revealed systematic increases in the sensitivity of snow cover to Northern Hemisphere (NH) temperatures over the 1940-65 period. This change is mainly due to an increase in snowfall-temperature sensitivity during this period. Seasonal analysis revealed that the observed increase in snow-cover and snowfall temperature sensitivity is primarily a spring phenomenon. A marked increase in the importance of the spring period is observed around 1960, which coincides with a well-documented change in atmospheric circulation over NA. The post-1960 period is characterized by a significant inverse relationship between snow cover and hemispheric air temperature over the Canadian prairies and northern Great Plains regions.
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Shinohara, Ryuichiro, Yoji Tanaka, Ariyo Kanno, and Kazuo Matsushige. "Relative impacts of increases of solar radiation and air temperature on the temperature of surface water in a shallow, eutrophic lake." Hydrology Research 52, no. 4 (July 14, 2021): 916–26. http://dx.doi.org/10.2166/nh.2021.148.
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Abstract We monitored lake surface water temperatures from 1992 to 2019 in Lake Kasumigaura, a shallow lake in Japan. We hypothesized that increases of shortwave radiation had increased surface water temperatures and heat fluxes more than had the increases of air temperature. We used the heat flux analyses and the sensitivity analyses to test the hypothesis. The fluxes of solar radiation gradually increased during the study period in a manner consistent with the phenomenon of global brightening. The increase was especially apparent in the spring. The rate of increase of surface water temperature was especially significant in May. Air temperature did not significantly increase in May, but it increased significantly in June (0.40 °C decade−1). A sensitivity analysis of the heat fluxes at the lake surface (shortwave radiation, longwave radiation, latent heat flux, and sensible heat flux) revealed that surface water temperature was more sensitive to changes of shortwave radiation than to air temperature during the spring. Although other factors such as inflows of groundwater and river water may also have impacted surface water temperatures, the increase of solar radiation appeared to be the major factor responsible for the increase of surface water temperature during the spring in Lake Kasumigaura.
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Sarnowski, Michał, Karol Kowalski, Jan Król, and Piotr Radziszewski. "Influence of Overheating Phenomenon on Bitumen and Asphalt Mixture Properties." Materials 12, no. 4 (February 18, 2019): 610. http://dx.doi.org/10.3390/ma12040610.
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In the course of manufacturing, transport and installation, road bitumens and asphalt mixtures can be exposed to the impact of elevated process temperatures exceeding 240 °C. This mainly applies to the mixtures used for road pavements and bridge deck insulation during adverse weather conditions. The heating process should not change the basic and rheological properties of binders and the asphalt mixtures that to a degree cause the degradation of asphalt pavement durability. The work involved analyzing the properties of non-modified bitumens and SBS polymer modified bitumens, heated at temperatures of 200 °C, 250 °C and 300 °C for 1 h. Next, the asphalt mixtures were heated in the same temperatures. Based on the developed Overheating Degradation Index (ODI) it was demonstrated that polymer-modified bitumens were characterized by higher overheating sensitivity A(ODI) than non-modified bitumens, which was confirmed by mixture test results. Overheating limit temperatures T(ODI) were determined, which in the case of polymer-modified bitumens are up to 20 °C lower than for non-modified bitumens. When the temperature increases above T(ODI), loss of viscoelastic properties occurs in the material which causes, among other effects, a loss of resistance to fatigue cracking.
Book chapters on the topic "Temperature sensitivity phenomenon"
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Juurola, E., T. Vesala, T. Aalto, T. Markkanen, and P. Hari. "On Importance of Physical Phenomena in the Temperature Dependence of Photosynthesis -A Sensitivity Analysis." In Photosynthesis: Mechanisms and Effects, 3495–98. Dordrecht: Springer Netherlands, 1998. http://dx.doi.org/10.1007/978-94-011-3953-3_816.
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Smith, Raymond C., and Xiaojun Yuan. "The Quasi-Quintennial Timescale—Synthesis." In Climate Variability and Ecosystem Response in Long-Term Ecological Research Sites. Oxford University Press, 2003. http://dx.doi.org/10.1093/oso/9780195150599.003.0020.
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The El Nino–Southern Oscillation (ENSO) is one of the most important contributors to interannual variability on Earth (Diaz and Markgraf 2000). It is an aperiodic phenomenon that tends to reoccur within the range of 2 to 7 years, and it is manifest by the alternation of extreme warm (El Niño) and cold (La Niña) events. There is also evidence (Allen 2000) that the aperiodic ENSO phenomenon must be considered in conjunction with climate fluctuations at decadal to multidecadal time frames that may modulate ENSO’s lower frequency variability. Numerous studies show global climatic impacts associated with the ENSO phenomenon. Further, there is considerable evidence to indicate that ENSO impacts the climate of both middle and high latitudes, and a recent analysis (figure S.1, discussed below) provides a global picture of warm versus cold ENSO conditions. Consequently, it is not surprising that many LTER sites, from the Arctic to Antarctic, show evidence of ENSO-related fluctuations in environmental variables. The quasi-quintennial timescale of variability is second only to seasonal variability in driving worldwide weather patterns. Consequently, an important theme in part II is the worldwide influence of ENSO-related climate variability and the teleconnected spatial patterns of this variability. Also, a common theme for several ecosystems discussed in this section is their high sensitivity to small climatic changes that are subsequently amplified and cascaded through the system. For example, the narrow temperature threshold for an ice-to-water phase change may create a pronounced nonlinear ecosystem response to what is a relatively small temperature shift (as demonstrated for the McMurdo Dry Valleys). Or alternatively, this narrow temperature threshold may shift a sea ice–dominated ecosystem (Palmer LTER) to a more oceanic marine ecosystem by reducing the seasonality and magnitude of the sea ice habitat. Such nonlinear amplifications of small climatic changes can increase the ecological response and make it more detectable within the natural background of variability. We explore these themes here. To illustrate the global footprint of ENSO variability, composites of yearly averaged El Niño and La Niña conditions for surface air temperature (SAT) and sea surface temperature (SST, Reynolds and Smith 1994) were generated.
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Ammer, Kurt. "The sensitivity of infrared imaging for diagnosing Raynaud’s phenomenon is dependent on the method of temperature extraction from thermal images." In Infrared Imaging. IOP Publishing, 2014. http://dx.doi.org/10.1088/978-0-7503-1143-4ch16.
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Tsiaras, Stefanos. "Exploring the Impact of Tourism to the Sustainable Development of Mountain Regions." In Sustainable Tourism, 437–53. IGI Global, 2019. http://dx.doi.org/10.4018/978-1-5225-7504-7.ch024.
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Sustainable development is difficult to be achieved in mountain regions because of their sensitivity to climate change. The rapid development of mountain tourism worldwide during the last years makes the goal for sustainable mountain tourism even more challenging. Key factor to the development of mountain tourism in Europe was the function of ski centres. According to the spirit of the Brundtland Report ski centres are not in general sustainable, because they may have economic benefits but they negatively affect the other two pillars of sustainability: environment and society. The present paper focuses on a ski resort in Greece, attempting to assess the impact of mountain tourism on the sustainable development of the area. Ski resorts played a crucial role to the bloom of mountain tourism in Greece. Its evolution is a relatively recent phenomenon which has been affected by the economic crisis that afflicts the country in the past years. Demographic data compared with tourism indicators were used to assess the environmental impact of tourism in the area. Moreover, meteorological data were used in order to examine the correlation of climatic conditions and the number of visitors. The results show that the ski centre in Elatohori despite the economic benefits has a major environmental impact, especially because of the increased carbon emissions caused by the visitors of the area. Additionally, the climatic conditions (precipitation and temperature, especially the absolute maximum air temperature) affect the number of visitors.
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Adeniyi, Mayowa. "Impacts of Environmental Stressors on Autonomic Nervous System." In Autonomic Nervous System [Working Title]. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.101842.
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Stress can be described as the perception of discomforts physically, psychologically, or physico-psychologically. During stress, the perceived discomfort indicates there is a deviation from homeostasis. In stress, there is a nonspecific physiological response to stressors, a group of stress-inducing phenomena. Stress-inducing phenomena can be defined as environmental insults, such as perturbed levels of light, temperature, chemicals, ambient oxygen, and noise. Response to stress occurs via the chemical messenger-mediated sympathetic nervous system including the autonomic-adrenal axis. Furthermore, the chemical messenger-mediated sympathetic nervous system determines nonhormonal effects which are often devised as general stress markers. Examples of general stress markers include changes in heart rate, heart rate variability, blood pressure, body temperature, blood glucose, baroreflex sensitivity, among others.
Conference papers on the topic "Temperature sensitivity phenomenon"
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Wei, Xiangyu, Wenhua Zhang, and Yingchun Zhao. "Feasibility Study on Power Ramp Test Under Atmospheric Pressure and Ordinary Temperature." In 2022 29th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/icone29-93417.
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Abstract Pellet-to-cladding mechanical interaction is an important physical phenomenon during reactor power change as well as a multi-phenomenal fuel rod failure mechanism involving stress, strain and material irradiation properties. In order to avoid the failure caused by PCMI, a large number of power ramp tests have been carried out by international organizations over the past decades. The typical way of power ramp test in a high temperature and pressure loop requires stringent test capabilities and high test costs. The key parameters of the PCMI phenomena are stress and strain of cladding, which are generally chosen as the evaluation indicators of PCMI. If it is possible to simulate the pellet-to-cladding contact state, i.e. the gap between pellet and cladding under basic irradiation power level in atmospheric pressure and ordinary temperature environment, then the high stress and strain state of the cladding during the subsequent power ramp test could also be simulated in the same environment, which means lower test costs and test loop requirements. Therefore, a sensitivity analysis using the fuel rod performance analysis code RoPE, was carried out on factors such as initial pellet-to-cladding gap and fuel densification in the power ramp test rod design. By adapting the manufacturing parameters of the test rod and coolant conditions, the high stress and strain state of the cladding could be simulated in the test environment at normal temperature and pressure. The sensitivity analysis provides a theoretical basis for conducting power ramp tests in an atmospheric pressure and ordinary temperature loop.
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Gokulakrishnan, P., M. S. Klassen, and R. J. Roby. "Development of Detailed Kinetic Mechanism to Study Low Temperature Ignition Phenomenon of Kerosene." In ASME Turbo Expo 2005: Power for Land, Sea, and Air. ASMEDC, 2005. http://dx.doi.org/10.1115/gt2005-68268.
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The objective of this work is to develop a detailed kinetic mechanism for low temperature kerosene oxidation, which is essential to predict premature auto-ignition of liquid fuels in gas turbines and cool flame behavior in hydrocarbon reformers for fuel cells. Kerosene, a fractional distillate of petroleum known by its generic term, is comprised of a wide range of aviation fuel grades such as Jet A, Jet-4, JP-8 etc, with a chemical composition varying from higher order n-alkanes to complex aromatics. Thus, developing a detailed kinetic mechanism to represent actual kerosene is not only cumbersome but also computationally intensive to implement. Therefore, very often a surrogate mixture with known chemical composition is devised to study kerosene oxidation. In this work, a hierarchical structure of the kerosene mechanism with approximately 1400 reactions of 550 species is developed using a surrogate mixture of n-decane, n-propylcyclohexane and n-propylbenzene to represent major components of kerosene, namely n-alkanes, cyclo-alkanes and aromatics, respectively. Since a major portion of the kerosene consists of very reactive n-alkanes rather than the less reactive ring structures, the low temperature oxidation kinetics is predominantly dictated by n-alkanes. Thus, the modeling effort is mainly focused on developing a low temperature mechanism for n-decane. The low-temperature oxidation of the individual fuel of the surrogate mixture, especially n-decane, was fairly well-characterized experimentally in shock-tubes and flow-reactors, and hence, the mechanism is validated against the available experimental measurements. With the objective of achieving a more comprehensive mechanism, the model validation is extended to include target data for wide range of conditions including high pressure and high temperature experimental data available in the literature. The model predictions of the kerosene mechanism were compared to the available experimental data on ignition delay time as well as the reactivity species profiles of different aviation grade fuels obtained in flow reactors. The predictions of the kerosene mechanism agree with the experimental data fairly well especially at low to intermediate temperature regimes. A sensitivity analysis was performed to identify the rate-limiting steps at low, intermediate and high temperatures. It was observed that reactions involving ketohydroperoxides and hydrogen-peroxides are the most important reactions at low and intermediate temperatures, respectively.
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Chen, Q., and H. K. Chia. "Pipe-in-Pipe Walking: Understanding the Mechanism, Evaluating and Mitigating the Phenomenon." In ASME 2010 29th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2010. http://dx.doi.org/10.1115/omae2010-20058.
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This paper addresses the walking phenomenon of pipe-in-pipe system, which can cause the cumulative axial displacement, leading to the potential failures of tie-ins or risers. The main mechanism that drives the pipe-in-pipe walking is the nonlinear spacer-pipe friction (between the inner pipe and outer pipe) and pipe-soil friction, together with thermal transients along the pipe-in-pipe system during start-up and shutdown. Sensitivity studies are also performed by investigating the effect of variation in spacer-pipe friction coefficient, pipe-soil friction coefficient, transient temperature profile and internal pressure through detailed finite element simulation with Abaqus. The paper also presents some methods to mitigate the pipe-in-pipe walking and some advantages of selecting pipe-in-pipe system in deepwater development.
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Ammer, K. "The sensitivity of infrared imaging for diagnosing Raynaud´s phenomenon and for Thoracic Outlet Syndrome is depended on the method of temperature extraction from thermal images." In 2008 Quantitative InfraRed Thermography. QIRT Council, 2008. http://dx.doi.org/10.21611/qirt.2008.03_01_17.
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Wu, Huanchun, Xinming Meng, Yaolei Han, Yanwei Zhang, and Qunjia Peng. "Effect of Surface Machining on Stress Corrosion Cracking Sensitivity of 304L and 316L Austenite Stainless Steel." In 2022 29th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/icone29-90466.
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Abstract 304L/316L austenitic stainless steels (SSs) often used for main pipe of PWR nuclear power plant. Surface machining has a significant effect on microstructure and residual stress of SS, which further affects its stress corrosion cracking (SCC) sensitivity. The present study results show that, the SCC sensitivity of machined specimens increases significantly tested in 300 °C high temperature and high pressure water environment by the slow strain rate tensile test (SSRT). It increased from less than 10% of polished specimens to 20–30% of machined specimen for SCC sensitivity. It was found that the machined specimen showed as cleavage cracking, while the polished specimen was shown as ductile cracking with obviously fracture necking phenomenon. The mechanism of SCC of two kinds of SSs materials focused on the deformation layer of machined specimen was analysed, and the model of SCC initiation caused by nanocrystalline layer was established.
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Kang, Hyung Seok, Sang Baik Kim, Min-Hwan Kim, and Hee Cheon No. "CFD Prediction for an Overpressure Buildup Phenomenon of SRI Hydrogen Test in an Open Space." In ASME-JSME-KSME 2011 Joint Fluids Engineering Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/ajk2011-18002.
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A computational fluid dynamics (CFD) calculation for a hydrogen explosion test with a complicated obstacle tube geometry of pitch 21.3mm and diameter 99.1mm at a stoichiometric condition was performed to establish a CFD analysis method for a hypothetical hydrogen explosion accident between a very high temperature reactor (VHTR) and a hydrogen production facility. We developed a spark ignition model to simulate high ignition energy of 40J induced by an electric device for 2 ms in the hydrogen explosion based on an energy conservation law. We performed a sensitivity calculation by varying a constant value of the eddy dissipation model (EDM), a time step size, and a cell length size around the obstacle tube to evaluate an effect of each factor on the flame propagation and overpressure buildup phenomenon. The CFD results of the flame front time of arrival (TOA) and overpressure were compared with those of the test data. The comparison results showed that the spark ignition model with a radius of 6 cm, a pressure of 105.7 kPa, a temperature of 1000 K, a turbulent mixing time of 2 ms, and an assumption of the 10% product mass fraction can reasonably initiate the hydrogen flame propagation in the CFD calculation. As for the CFD analysis method, the EDM constants of A = 10 and B = 0.8, the time step size of 0.01 ms, the cell length of 1 cm around the obstacle tube predicted the measured flame front TOA and peak overpressure with an error range of about 27.8% and 53.3%, respectively. Therefore, it is known that the CFD analysis with the EDM may be used as an accurate evaluation tool to provide the 3-dimesnional information of the flame front TOA and overpressure buildup phenomenon if the CFD analysis method is properly chosen.
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Nie, Jia-xi, Zhen-hao Lin, Jiao-shan Hao, Yong-bing Jiang, Zhi-jiang Jin, and Jin-yuan Qian. "Research on Fluid Dynamics and Thermal Characteristics in Hydraulic Valves by Thermal-Fluid-Solid Coupling Method." In ASME 2022 Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/fedsm2022-86878.
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Abstract Hydraulic valve is used as an important hydraulic component, playing a vital role in fluid power transmission and control systems. When the phenomenon of sticking of valve core occurs, it may seriously decrease the accuracy and sensitivity of the hydraulic valve. Micro-deformation is one of the most common faults causing the valve core sticking, which is due to the thermal load. Therefore, studying the mechanism of valve core sticking caused by thermal fluid is of great significance. In this paper, the fluid dynamics in hydraulic valves and the temperature characteristics of valve core are analyzed based on the thermal-fluid-solid coupling method. Results show that the jet angle (θ) will decrease with the increase of opening degree (k), and the maximum velocity and temperature increase with the increase of the opening degree. By loading the temperature field into the thermal analysis as a boundary condition, it shows that the temperature of the U-throttle groove increases with the increase of the opening degree. In addition, with the increase of opening degree, the maximum thermal deformation increases and the contact pressure between valve core and valve body also increases. This work has a certain reference value for researching and improving the phenomenon of valve core stuck in hydraulic valve.
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EricksonKirk, Mark T., and Terry L. Dickson. "The Sensitivity of Risk-Informed Reactor Structural Integrity Analysis Results to Various Interpretations of Warm Pre-Stress." In ASME 2009 Pressure Vessels and Piping Conference. ASMEDC, 2009. http://dx.doi.org/10.1115/pvp2009-77127.
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Warm pre-stress, or WPS, is a phenomenon by which the apparent fracture toughness of ferritic steel can be elevated in the fracture mode transition if crack is first “pre-stressed” at an elevated temperature. Taking proper account of WPS is important to the accurate modeling of the postulated accident scenarios that, collectively, are referred to as pressurized thermal shock, and to the accurate modeling of routine cool-down transients. For both accident and routine cool-downs the transients begin at the reactor operating temperature (approximately 290°C for pressurized water reactors in the United States) and proceed to colder temperatures as time advances. The probabilistic fracture mechanics code FAVOR, which is being used by the NRC to provide the technical basis for risk-informed revisions of 10 CFR 50.61 and 10 CFR 50 Appendix G, adopts a model of WPS as part of its fracture driving force module. In this paper we assess the conservatism inherent to the FAVOR WPS model relative to a best-estimate WPS model constructed using data recently produced by the European Commission “SMILE” project and published by Moinereau and colleagues. Assessments of the conservatisms inherent to the so-called “conservative principle” WPS model, and also to a classic LEFM model that does not credit WPS are also made. The data presented herein demonstrate that, for an integrated analysis of PTS risk, the FAVOR and conservative principle WPS models both over-estimate the vessel failure risk by a factor of between 2 and 3× relative to the best estimate model. Our examination of the effect of WPS models on the predictions of individual transients reveals that for the severe transients that dominate risk there is little difference (usually less than 4×) between the conditional probabilities of crack initiation and of through wall cracking predicted by the different WPS models. There are considerable differences in the predictions of the various WPS and non-WPS models for low severity transients, however, the contribution of these transients to the total risk of vessel failure is small.
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Journaix, Richard, Loïc Ancian, and Rémi Salanon. "Use of PVDF Wires As Sensors for Non Intrusive Pressure Measurement." In ASME 2018 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/pvp2018-84651.
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One of the most challenging aspects when performing on-site piping troubleshooting is to obtain the most pertinent information possible regarding piping behavior: acceleration, stress, pressure levels, etc. This last parameter is always difficult to obtain because when pressure taps are available on the line, they are rarely in the area of interest. PVDF (PolyVinyliDene Fluoride) wire makes it possible to perform non-intrusive pressure measurements but needs to be calibrated in order to have a good representation of phenomenon occurring inside the pipe. After development of a dedicated calibrator and calculation of the fluid/structure coupling coefficient, VibraTec is able to assess PVDF sensor sensitivity according to client’s installation characteristics. Non-intrusive measurements provide a good accuracy regarding phenomenon amplitude and frequency localization even though some temperature restrictions apply to PVDF measurements. Although PVDF sensors seem to be simple to implement, particular attention must be paid during installation as this has a direct influence on the PVDF response.
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Ba, Wei, Longgang Liu, and Hong Liu. "Aero-Thermal Coupled Predictive Model for Preliminary Gas Turbine Blade Cooling Analysis." In ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/gt2018-75089.
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The turbine inlet temperature has been increasing over the years to improve gas turbine efficiency and specific power. Blade cooling technology is essential to keep component temperatures below their critical value, and this makes the aero-thermal coupled phenomenon more significant. Blade life assessment is closely related to blade metal temperature distribution and gradients, and blade cooling analysis is always considered starting from the preliminary design stage. However, traditional blade cooling analysis for preliminary design is always based on external boundary conditions determined by experience, which affects the prediction accuracy as the interaction effect between the main flow and coolant is not considered. In this paper, an aero-thermal coupled blade cooling model is further developed by combining the improved streamline curvature method with a one-dimensional thermo-fluid network. This model is capable of predicting blade surface temperature distribution and internal coolant flow conditions in the preliminary phase of blade cooling design with a limited amount of input information. Experimental data for the NASA C3X profile with film cooling was selected for validation. In addition, a sensitivity analysis was performed on different film cooling mass flow rates to demonstrate the model flexibility for different boundary conditions.