Academic literature on the topic 'Maximum temperature difference'
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Journal articles on the topic "Maximum temperature difference"
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Драбкин, И. А. "Холодильный коэффициент составной охлаждающей термоэлектрической ветви". Физика и техника полупроводников 53, № 5 (2019): 685. http://dx.doi.org/10.21883/ftp.2019.05.47563.21.
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AbstractOne of the main energy characteristics of a cooling leg is the maximum available temperature difference (Δ T _max). Its increase indicates an increase in the coefficient of performance (COP) at all temperatures. The use of a segmented leg makes it possible to increase the Δ T _max value; however, the maximum available COP increases only at large temperature differences, whereas at small temperature differences the maximum available COP is even smaller than in a simple leg.
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Vikhor, L. N., and L. I. Anatychuk. "Theoretical evaluation of maximum temperature difference in segmented thermoelectric coolers." Applied Thermal Engineering 26, no. 14-15 (2006): 1692–96. http://dx.doi.org/10.1016/j.applthermaleng.2005.11.009.
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KESETYANINGSIH, Tri Wulandari, Sri ANDARINI, Sudarto SUDARTO, and Henny PRAMOEDYO. "The Minimum-Maximum Weather Temperature Difference Effect on Dengue Incidence in Sleman Regency of Yogyakarta, Indonesia." Walailak Journal of Science and Technology (WJST) 15, no. 5 (2018): 387–96. http://dx.doi.org/10.48048/wjst.2018.2277.
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Dengue is a viral disease, transmitted by Aedes aegypti, and is still a big problem in tropical areas, including Indonesia, where the temperatures are relatively warm and suitable for vector mosquito life. In the dry season, the day and night temperature differences are quite sharp and, at that time, the number of dengue cases is low. In this study, the difference between day and night temperature is referred to as daily temperature fluctuation and represented by the maximum and minimum temperature difference in each month. The research was conducted in Sleman Regency, Yogyakarta Province, Indonesia, as an endemic area, and the data were collected from 4 endemic areas in Sleman; Gamping, Godean, Sleman, and Depok districts. The data collected were quantitative with serial data retrospective. Secondary data of monthly dengue incidence in the years 2008 - 2013 were obtained from the Regency Health Office and used as a dependent variable. Monthly minimum and maximum temperatures in the same periods were obtained from the Agency of Meteorology, Climatology, and Geophysics. The differences between the minimum and maximum temperatures were calculated, to be used as independent variable data, and represented the different day and night temperatures of the month. Data were analyzed by using linear regressions to determine the influence of fluctuating temperature on the incidence of dengue. Results show that fluctuating temperature affected dengue incidence in the districts of Godean (p = 0.000; R2 = 0.207) and Gamping (p = 0.006; R2 = 0.125), but did not affect it in Sleman (p = 0.164) or Depok (p = 0.075). The data suggests that fluctuating temperature affected dengue incidence with powers of 20.7 % in Godean and 12.5 % in Gamping.
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Hermansson, Åke. "Simulation Model for Calculating Pavement Temperatures Including Maximum Temperature." Transportation Research Record: Journal of the Transportation Research Board 1699, no. 1 (2000): 134–41. http://dx.doi.org/10.3141/1699-19.
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A simulation model has been developed to calculate the temperatures of asphalt concrete during summer. Input data to the simulation model are hourly values for solar radiation, air temperature, and wind velocity. Longwave radiation incident to and outgoing from the pavement surface is calculated from the air and pavement surface temperatures, respectively. The portion of the incident shortwave radiation absorbed by the pavement surface is calculated from the albedo of the surface. By means of a finite difference approximation of the heat transfer equation, the temperatures are calculated under the surface. Apart from radiation and heat transfer, convection losses from the pavement surface are also calculated depending on wind velocity, air temperature, and surface temperature. The formulas used for the calculation of radiation and the simulation model as a whole are validated by comparison with measurements, showing good agreement. A method for the calculation of direct solar radiation from a clear sky, at an arbitrary location and time, is used to create input data to the simulation model in order to calculate maximum pavement temperatures. The formulas used with Superpave to calculate maximum pavement temperatures are based on the assumption that there is an equilibrium when a maximum temperature is reached. Such an equilibrium assumption can be strongly questioned, and its consequences are discussed.
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Bakker, P., and H. Renssen. "Last Interglacial model-data mismatch of thermal maximum temperatures partially explained." Climate of the Past Discussions 10, no. 1 (2014): 739–60. http://dx.doi.org/10.5194/cpd-10-739-2014.
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Abstract. The timing of the Last Interglacial (LIG) thermal maximum is highly uncertain. Compilations of maximum LIG temperatures are therefore based on the assumption that maximum warmth occurred synchronously across the globe. Although known to be an oversimplification, the impact of this assumption on temperature estimates has yet to be assessed. We use the LIG temperature evolutions simulated by 9 different climate models to investigate whether the assumption of synchronicity results in a sizeable overestimation of LIG thermal maximum temperatures. We find that for annual temperatures, the overestimation is small, strongly model-dependent (global mean 0.4 ± 0.3 °C) and cannot explain the recently published 0.67 °C difference between simulated and reconstructed LIG thermal maximum temperatures. However, if one takes into consideration that temperature proxies are possibly biased towards summer, the overestimation of the LIG thermal maximum based on warmest month temperatures is non-negligible (global mean 1.1 ± 0.4 °C) and can at least partly explain the 0.67 °C global model-data difference.
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Di-Giovanni, F., P. G. Kevan, and G. É. Caron. "Estimating the timing of maximum pollen release from jack pine (Pinus banksiana Lamb.) in northern Ontario." Forestry Chronicle 72, no. 2 (1996): 166–69. http://dx.doi.org/10.5558/tfc72166-2.
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A practical heat sum method was validated for estimating the date of maximal pollen release of jack pine (Pinus banksiana Lamb.) in northern Ontario. The base temperature and start date that minimized differences between estimated and observed maximum pollen release dates were sought. Heat sums were calculated for all data sets (n = 26) for a range of base temperatures (1 to 20 °C) and start dates (January 1 to maximum pollen release). The best combination was a start date at Julian day 107 and base temperature at 4 °C. The heat sum to maximum pollen release was 288.58 degree days and the average difference between estimated and observed was 2.75 days. Recommendations for operational testing are made. Key words: heat sum, phenology, Piuns banksiana Lamb., temperature, pollen, dehiscence, contamination, seed orchard
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Lin, Chun Jing, Si Chuan Xu, Guo Feng Chang, and Zhao Li. "Thermal Characteristic Analysis of Rectangular and Large-Capacity Lithium-Ion Power Batteries." Advanced Materials Research 1044-1045 (October 2014): 448–56. http://dx.doi.org/10.4028/www.scientific.net/amr.1044-1045.448.
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Operating temperature and thermal uniformity have great effect on the performance, cycle life and safety of lithium-ion power batteries. In order to investigate the surface temperature change and distribution of a large-capacity and rectangular LiFePO4/C power battery, this paper conducts experiments on charging and discharging a battery module and cell at different current rates and various ambient temperatures. Results of thermalcouple-measurement show that temperature rising rates at different temperatures during charge and discharge change in accordance with the variation tendency of the resistance at different state of charge (SOC) and oprating temperatures. Under elevated ambient temperatures, the temperature excurtion and maximum temperature difference of the module are all smaller. Under the same ambient temperature, battery temperature at the end moment of discharge increases and the temperature uniformity of the module deteriorate at higher discharging rate. Temperature excurtion over the same time period is in a relationship of a standard quadratic function with the discharge current. Results of the thermal infrared imaging tests show that the maximum surface temperature differences at different discharging currents of 20A, 40A, and 80A are all above 5°C under natral convection heat transfer. The temperature of the lower part is higher than that of the upper part, while that of the central area is the highest. In a comprehensive charging and discharging scheme, the tendency of maximum surface temperature difference changes in accordance with that of the average surface temperature.
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Bartoszuk, Marian, and Wit Grzesik. "Numerical Prediction of the Interface Temperature Using Updated Finite Difference Approach." Advanced Materials Research 223 (April 2011): 231–39. http://dx.doi.org/10.4028/www.scientific.net/amr.223.231.
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This investigation is devoted to the heat flow problem occurring in dry orthogonal machining of a C45 medium carbon steel performed with uncoated single-point carbide tools. Finite Difference Approach (FDA) is applied to predict the variations of temperature distribution, and both average and maximum temperatures at the tool-chip interface, resulting from differentiating the heat flux configuration, and additionally the changes of thermal resistance along the tool-chip contact length. Moreover, some realistic computing errors due to possible measuring variations of the tool-chip contact length and the density and dimension of heat source on the shear plane were assessed and considered as input data in simulations. Finally, the measured values of temperatures using natural tool-work thermocouples have confirmed that the models proposed predict acceptably the average interface temperatures and estimate their maximum values for carbide tools.
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Xuan, X. C., K. C. Ng, C. Yap, and H. T. Chua. "The maximum temperature difference and polar characteristic of two-stage thermoelectric coolers." Cryogenics 42, no. 5 (2002): 273–78. http://dx.doi.org/10.1016/s0011-2275(02)00035-8.
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Morisaki, Takafumi, Takeshi Yasunaga, and Yasuyuki Ikegami. "Heat Source Temperature Difference and Maximum Power of Multi-stage Rankine Cycle." Proceedings of the Thermal Engineering Conference 2016 (2016): D214. http://dx.doi.org/10.1299/jsmeted.2016.d214.
Full textDissertations / Theses on the topic "Maximum temperature difference"
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Ali, Haider Adel Ali, and Ziad Namir Abdeljawad. "THERMAL MANAGEMENT TECHNOLOGIES OF LITHIUM-ION BATTERIES APPLIED FOR STATIONARY ENERGY STORAGE SYSTEMS : Investigation on the thermal behavior of Lithium-ion batteries." Thesis, Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-48904.
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Batteries are promising sources of green and sustainable energy that have been widely used in various applications. Lithium-ion batteries (LIBs) have an important role in the energy storage sector due to its high specific energy and energy density relative to other rechargeable batteries. The main challenges for keeping the LIBs to work under safe conditions, and at high performance are strongly related to the battery thermal management. In this study, a critical literature review is first carried out to present the technology development status of the battery thermal management system (BTMS) based on air and liquid cooling for the application of battery energy storage systems (BESS). It was found that more attention has paid to the BTMS for electrical vehicle (EV) applications than for stationary BESS. Even though the active forced air cooling is the most commonly used method for stationary BESS, limited technical information is available. Liquid cooling has widely been used in EV applications with different system configurations and cooling patterns; nevertheless, the application for BESS is hard to find in literature.To ensure and analyze the performance of air and liquid cooling system, a battery and thermal model developed to be used for modeling of BTMS. The models are based on the car company BMW EV battery pack, which using Nickel Manganese Cobalt Oxide (NMC) prismatic lithium-ion cell. Both air and liquid cooling have been studied to evaluate the thermal performance of LIBs under the two cooling systems.According to the result, the air and liquid cooling are capable of maintaining BESS under safe operation conditions, but with considering some limits. The air-cooling is more suitable for low surrounding temperature or at low charging/discharge rate (C-rate), while liquid cooling enables BESS to operate at higher C-rates and higher surrounding temperatures. However, the requirement on the maximum temperature difference within a cell will limits the application of liquid cooling in some discharge cases at high C-rate. Finally, this work suggests that specific attention should be paid to the pack design. The design of the BMW pack is compact, which makes the air-cooling performance less efficient because of the air circulation inside the pack is low and liquid cooling is more suitable for this type of compact battery pack.
Books on the topic "Maximum temperature difference"
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Liu, Xiaodong, and Libin Yan. Elevation-Dependent Climate Change in the Tibetan Plateau. Oxford University Press, 2017. http://dx.doi.org/10.1093/acrefore/9780190228620.013.593.
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As a unique and high gigantic plateau, the Tibetan Plateau (TP) is sensitive and vulnerable to global climate change, and its climate change tendencies and the corresponding impact on regional ecosystems and water resources can provide an early alarm for global and mid-latitude climate changes. Growing evidence suggests that the TP has experienced more significant warming than its surrounding areas during past decades, especially at elevations higher than 4 km. Greater warming at higher elevations than at lower elevations has been reported in several major mountainous regions on earth, and this interesting phenomenon is known as elevation-dependent climate change, or elevation-dependent warming (EDW).At the beginning of the 21st century, Chinese scholars first noticed that the TP had experienced significant warming since the mid-1950s, especially in winter, and that the latest warming period in the TP occurred earlier than enhanced global warming since the 1970s. The Chinese also first reported that the warming rates increased with the elevation in the TP and its neighborhood, and the TP was one of the most sensitive areas to global climate change. Later, additional studies, using more and longer observations from meteorological stations and satellites, shed light on the detailed characteristics of EDW in terms of mean, minimum, and maximum temperatures and in different seasons. For example, it was found that the daily minimum temperature showed the most evident EDW in comparison to the mean and daily maximum temperatures, and EDW is more significant in winter than in other seasons. The mean daily minimum and maximum temperatures also maintained increasing trends in the context of EDW. Despite a global warming hiatus since the turn of the 21st century, the TP exhibited persistent warming from 2001 to 2012.Although EDW has been demonstrated by more and more observations and modeling studies, the underlying mechanisms for EDW are not entirely clear owing to sparse, discontinuous, and insufficient observations of climate change processes. Based on limited observations and model simulations, several factors and their combinations have been proposed to be responsible for EDW, including the snow-albedo feedback, cloud-radiation effects, water vapor and radiative fluxes, and aerosols forcing. At present, however, various explanations of the mechanisms for EDW are mainly derived from model-based research, lacking more solid observational evidence. Therefore, to comprehensively understand the mechanisms of EDW, a more extensive and multiple-perspective climate monitoring system is urgently needed in the areas of the TP with high elevations and complex terrains.High-elevation climate change may have resulted in a series of environmental consequences, such as vegetation changes, permafrost melting, and glacier shrinkage, in mountainous areas. In particular, the glacial retreat could alter the headwater environments on the TP and the hydrometeorological characteristics of several major rivers in Asia, threatening the water supply for the people living in the adjacent countries. Taking into account the climate-model projections that the warming trend will continue over the TP in the coming decades, this region’s climate change and the relevant environmental consequences should be of great concern to both scientists and the general public.
Book chapters on the topic "Maximum temperature difference"
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Tesfaye, Argaw, and Arragaw Alemayehu. "Climate Change and Variability on Food Security of Rural Household: Central Highlands, Ethiopia." In African Handbook of Climate Change Adaptation. Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-45106-6_188.
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AbstractThis chapter analyzes the impact of climate change and variability on food security of rural households in the central highlands of Ethiopia taking Basona Werana district as a case study site. Data were obtained from 123 households selected using simple random sampling from three agro ecological zones. Key informant interviews and focus group discussion (FDG) were used to supplement the data obtained from household survey. The monthly rainfall and temperature data are for 56 points of 10 × 10 km grids reconstructed from weather stations and meteorological satellite observations, which cover the period between 1983 and 2016. Standardized rainfall anomaly (SRA), linear regression (LR), and coefficient of variation (CV) are used to examine inter-annual and intra-annual variability of rainfall. Annual and seasonal rainfalls show decreasing trends over the period of observation. The decreasing trends in annual and March–May (Belg) rainfall totals exhibit statically significant decreasing trends at p = 0.05 level. Kiremt (June–September) shows statically significant decreasing trends at p = 0.1 level. Mean annual maximum and minimum temperatures show statically significant increasing trends at p = 0.05 level. More than 80% of households perceived that the climate is changing and their livelihoods (crop and livestock production) are impacted. The district belongs to one of the most vulnerable areas to climate change and variability in the country where large proportions of households (62%) are under different food insecurity classes. Results suggest that local level investigations are useful in developing context-specific climate change adaptation.
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Mbwambo, Naza A., and Emma T. Liwenga. "Cassava as an adaptation crop to climate variability and change in coastal areas of Tanzania: a case of the Mkuranga district." In Climate change impacts and sustainability: ecosystems of Tanzania. CABI, 2020. http://dx.doi.org/10.1079/9781789242966.0023.
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Abstract This study was carried out in two villages, Kizapala and Kazole, of the Mkuranga District, in the Coast Region of Tanzania. The objective of the study was to establish the role of cassava as an adaptation crop to the changing climate and household food security. Primary data were obtained using household questionnaires and different participatory rural appraisal (PRA) techniques which included focus group discussions (FGDs), key informants and expert meetings. Secondary data were collected through a literature review, whereas temperature and rainfall data from 1984 to 2014 was obtained from the Tanzania Meteorological Agency (TMA). In each village, a sample size of 10% of all households was interviewed. Findings showed that 96% of respondents from Kazole village and 90% from Kizapala linked climate change with major climatic extreme events such as prolonged droughts and occasional abnormal floods. Analysis of temperature data for the last 30 years (1984-2014) revealed that temperature had significantly risen by a correlation coefficient of R<sup>2</sup> = 0.4936 for maximum and R<sup>2</sup> = 0.777 for minimum temperature. The field survey results closely correlated with findings from the analysis of TMA rainfall and temperature data. Findings revealed a decline in crop production which resulted in food shortages and livelihood insecurity in the study villages. The respondents in both villages consider cassava as a crop that is least affected by climate and environmental extremes, thus serves to ensure food availability and security in their households. As a result, growing cassava should be considered as an adaptation strategy to climate change and variability now and in the future. Improving cassava production, processing, marketing and value chain infrastructures is, therefore, crucial for enhancing sustainable adaptation in the district.
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Noji, H., and F. Furusawa. "Differences of Microstructural and Superconducting Properties of Bi-2212 Thick Films by a Variation of the Maximum Temperature During Melt-Solidification with and without Bi2Al4O9." In Advances in Superconductivity XII. Springer Japan, 2000. http://dx.doi.org/10.1007/978-4-431-66877-0_204.
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Sahli, Youcef, Bariza Zitouni, and Ben Moussa Hocine. "Three-Dimensional Numerical Study of Overheating of Two Intermediate Temperature P-AS-SOFC Geometrical Configurations." In Hydrogen Fuel Cell Technology for Stationary Applications. IGI Global, 2021. http://dx.doi.org/10.4018/978-1-7998-4945-2.ch008.
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The purpose of this work is to perform a three-dimensional and stationary numerical study of the heat transfer phenomenon in the planar anode-supported solid oxide fuel cells operating at intermediate temperature (IT-P-AS-SOFC). With particular interest to evaluate and localize the maximum and minimum temperatures in a single cell during their stable operation according to two geometrical configuration types, repetition, and symmetry of the cell stages to determine the best configuration that minimizes and produces more homogeneous thermal stresses and logically improves their lifetime and performance. The considered heat sources are mainly due to electrical overpotentials (Ohm, activation, and concentration). The results are obtained according to a FORTRAN code based on the proposed model that is numerically modeled using the finite difference method. From the obtained result analysis, the achieved temperature values by IT-P-AS-SOFC with cell stages repetition are greater than obtained by IT-P-AS-SOFC with cell stages symmetry.
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Liu, Shuting, Yingguang Li, Yingxiang Shen, and Yee Mey Goh. "A Multi-Zoned Self-Resistance Electric Heating Method for Curing Irregular Fiber Reinforced Composite Parts." In Advances in Transdisciplinary Engineering. IOS Press, 2021. http://dx.doi.org/10.3233/atde210028.
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Fibre Reinforced Polymers (FRP) have been widely applied in various industries due to their outstanding properties. As a promising curing technology for FRP parts, the self-resistance electric (SRE) heating method has attracted plenty of attention. However, it is difficult for the SRE heating method to uniformly cure the FRP parts with irregular structures. In this paper, a multi-zoned SRE heating method is proposed, in which the FRP part is divided into several heating zones and the temperature of each zone is regulated independently. A multi-channel electrical voltage control system is developed to realise the multi-zoned SRE heating of a wing-shaped FRP part, in which a rapid zone-based temperature control responsiveness is achieved, and the maximum temperature difference is reduced from 60 °C to less than 10 °C, reaching 2.5 °C at its best. This work presents an alternative for the high efficiency and energy-saving curing process of FRP parts.
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Dolman, Han. "The Physics of Radiation." In Biogeochemical Cycles and Climate. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780198779308.003.0004.
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This chapter discusses radiation, radiative transfer and the greenhouse effect. It starts by analysing radiation from a blackbody, identifying the key difference between shortwave radiation from the Sun and longwave radiation from Earth. It then describes the Planck function, which calculates the intensity of radiation emitted by a blackbody; the Stefan–Boltzmann law, which shows how changing the temperature of a blackbody affects the rate at which it emits radiation; Wien’s law, which calculates the wavelength of maximum emission; and Kirchhoff’s law of emission and absorption. These are then used to show the effect of increasing longwave-absorbing gases in the troposphere on the lower tropospheric temperature: the greenhouse gas effect. The chapter then describes the aspects of scattering, emission and absorption that are needed to understand the interaction of radiation with greenhouse gases. The chapter concludes by discussing radiative forcing and showing the current estimate of Earth’s energy balance.
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Sanchis-Sánchez, Enrique, Rosario Salvador-Palmer, Pilar Codoñer-Franch, et al. "Clinical Applications." In Disruptive Technology. IGI Global, 2020. http://dx.doi.org/10.4018/978-1-5225-9273-0.ch015.
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The study of the diagnostic accuracy of Infrared Thermal Imaging in the diagnosis of orthopaedic injuries in childhood has been motivated by the high incidence of these injuries throughout the world, being one of the most common reasons for urgent medical consultation. Diagnosis of musculoskeletal injuries usually involves radiography, but this exposes children without fractures to unnecessary ionising radiation. This chapter assesses whether infrared thermography could provide a viable alternative in cases of trauma. To evaluate the accuracy of this technique new thermographic variables have been added to those commonly analysed, such as the extent of the injury and the difference in the size of the area that is at an equal temperature or higher than the maximum temperature of the healthy area. Non-linear cataloguing methods (decision tree models) have also been applied. With the protocol presented, infrared thermal imaging had a sensitivity of 0.91, a specificity of 0.88 and a negative predictive value of 0.95 for diagnosing musculoskeletal injuries.
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Sanchis-Sánchez, Enrique, Rosario Salvador-Palmer, Pilar Codoñer-Franch, et al. "Clinical Applications." In Innovative Research in Thermal Imaging for Biology and Medicine. IGI Global, 2017. http://dx.doi.org/10.4018/978-1-5225-2072-6.ch003.
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The study of the diagnostic accuracy of Infrared Thermal Imaging in the diagnosis of orthopaedic injuries in childhood has been motivated by the high incidence of these injuries throughout the world, being one of the most common reasons for urgent medical consultation. Diagnosis of musculoskeletal injuries usually involves radiography, but this exposes children without fractures to unnecessary ionising radiation. This chapter assesses whether infrared thermography could provide a viable alternative in cases of trauma. To evaluate the accuracy of this technique new thermographic variables have been added to those commonly analysed, such as the extent of the injury and the difference in the size of the area that is at an equal temperature or higher than the maximum temperature of the healthy area. Non-linear cataloguing methods (decision tree models) have also been applied. With the protocol presented, infrared thermal imaging had a sensitivity of 0.91, a specificity of 0.88 and a negative predictive value of 0.95 for diagnosing musculoskeletal injuries.
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Barkouch, Yassir, Sana El Fadeli, Mohyeddine El Khadiri, Abdelaziz Ait Melloul, and Alain Pineau. "Study of the Effect of Climate Changes on the Well Water Contamination by Some Heavy Metals at a Mining Extract Region in Marrakech City, Morocco." In Advances in Environmental Engineering and Green Technologies. IGI Global, 2019. http://dx.doi.org/10.4018/978-1-5225-7775-1.ch007.
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Seasonal variation on chemical parameters of well water at Draa Lasfar region (Marrakech, Morocco) was studied. A total of 144 samples were collected between 2012 and 2013 and were analyzed for temperature (T°), pH, total hardness (TH), chemical oxygen demand (COD), nitrates, Cd, Pb, and Zn. Significant difference between seasons was observed for these parameters. Highest temperature (28.72±3.16) was recorded during summer. COD and Zn concentration was recorded maximum during summer (167.25±31.05 mg/l, 131.4±12.0 µg/l respectively). Highest nitrates (2.67±0.75 mg/l) concentrations were recorded during spring. Highest Pb (632.14±82.54 µg/l) and Cd (1.93±0.36 µg/l) concentrations were recorded during winter. Alternating seasons can be likened to small-scale climate change. Therefore, the impacts of this change on quality of water resources include particularly the modification of parameters values. The main drawn conclusion is that a degradation trend of well water quality in the context of climate change can lead to an increase of at-risk situations related to potential health impact.
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Avery, William H., and Chih Wu. "Closed-Cycle OTEC Systems." In Renewable Energy from the Ocean. Oxford University Press, 1994. http://dx.doi.org/10.1093/oso/9780195071993.003.0011.
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The Rankine closed cycle is a process in which beat is used to evaporate a fluid at constant pressure in a “boiler” or evaporator, from which the vapor enters a piston engine or turbine and expands doing work. The vapor exhaust then enters a vessel where heat is transferred from the vapor to a cooling fluid, causing the vapor to condense to a liquid, which is pumped back to the evaporator to complete the cycle. A layout of the plantship shown in Fig. 1-2. The basic cycle comprises four steps, as shown in the pressure-volume (p—V) diagram of Fig. 4-1. 1. Starting at point a, heat is added to the working fluid in the boiler until the temperature reaches the boiling point at the design pressure, represented by point b. 2. With further heat addition, the liquid vaporizes at constant temperature and pressure, increasing in volume to point c. 3. The high-pressure vapor enters the piston or turbine and expands adiabatically to point d. 4. The low-pressure vapor enters the condenser and, with heat removal at constant pressure, is cooled and liquefied, returning to its original volume at point a. The work done by the cycle is the area enclosed by the points a,b,c,d,a. This is equal to Hc–Hd, where H is the enthalpy of the fluid at the indicated point. The heat transferred in the process is Hc–Ha Thus the efficiency, defined as the ratio of work to heat used, is: . . . efficiency(η)=Hc–Hd/Hc–Ha (4.1.1) . . . Carnot showed that if the heat-engine cycle was conducted so that equilibrium conditions were maintained in the process, that the efficiency was determined solely by the ratio of the temperatures of the working fluid in the evaporator and the condenser. . . . η=TE–Tc/TE (4.1.2) . . . The maximum Carnot efficiency can be attained only for a cycle in which thermal equilibrium exists in each phase of the process; however, for power to be generated a temperature difference must exist between the working fluid in the evaporator and the warm-water heat source, and between the working fluid in the condenser and the cold-water heat sink.
Conference papers on the topic "Maximum temperature difference"
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Yao, Yue, Xiao Lei, and Zhigang Guo. "Experiment Research on the Maximum Temperature Difference during Concrete Hydration of Box Girder Bridge Construction." In First International Conference on Information Sciences, Machinery, Materials and Energy. Atlantis Press, 2015. http://dx.doi.org/10.2991/icismme-15.2015.108.
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Bar-Meir, Genick. "The Maximum Temperature and Second Law Analysis of the Shock Tube." In ASME 2012 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/imece2012-85765.
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The shock tube is a device that is used to obtain high temperatures for a very short time. The core driving force is pressured gas which is allowed to flow to a low pressure chamber, and thus achieve a high temperature. This device has been in use since the 1940s. Initially, the shock tube was used to study detonation. Later, it was used to study chemical reactions, complex flow phenomena, and several industrial applications. Several researchers suggested methods to increase the temperature. However, there is no study on the maximum potential temperature. This investigation was prompted by several industrial applications in different industries such as printing, automobile, and manufacturing. The maximum temperature analysis is conceptually similar to the analysis of the maximum work which can be obtained when two bodies with a different temperature are brought into contact. Here, the semi–equilibrium actually creates the maximum temperature difference. This study solves for the maximum temperature and hence renders a guide on how the different parameters affect the maximum temperature. This study indicates that the typical efficiency of typical shock tube is 3–5%.
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Jia, Yi, and Pablo D. Quinones. "Gear Surface Temperature Monitoring." In ASME 2003 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/detc2003/ptg-48128.
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Frictional heating from rolling and sliding contacts of gear teeth is of extreme importance for monitoring the health of a gear transmission under its continuing operation. The surface temperature holds the critical information about a gear’s health condition. A new power circulating gear test rig with a multichannel computer data acquisition system has been built to develop various sensor technologies for surface temperature evaluation of gear teeth. In this paper, the surface temperature monitoring of gear tooth will be presented by using miniature thermocouples. Five miniature type-K thermocouples of 125 μm in diameter have been embedded underneath the tooth surface of a spur gear, and real-time surface temperature variations from a wide range of operating conditions were measured. The various effects of load, rotating speed, and meshing point on the surface temperature are discussed. The results attained in this study indicate that the maximum temperature rise occurs on the dedendum, close to the dedendum circle, and the maximum surface temperature difference at the various contact points along the tooth profile was 13°C. Among the various temperature monitoring techniques, the thermocouple is a very reliable and practical mean for gear health monitoring.
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Shrivastava, Devashish, and Tim Ameel. "A General Analytical Approach for Defining Effectiveness in Ideal Two Fluid Heat Exchangers." In ASME 2002 International Mechanical Engineering Congress and Exposition. ASMEDC, 2002. http://dx.doi.org/10.1115/imece2002-33142.
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A general analytical development, based on the first and second laws of thermodynamics, is used to define the maximum possible heat transfer in an ideal two-fluid exchanger as well as the maximum possible temperature differences for both fluid streams. It is shown that the conventional expression for the maximum possible heat transfer in ideal two-fluid heat exchangers is a special case of the general expressions. The application of both the first and second laws of thermodynamics in defining the maximum possible heat transfer and maximum possible temperature difference provides only one expression (instead of two different expressions) for either stream which is a measure of both thermal and temperature effectiveness of the particular stream. Differences between the conventional and proposed effectiveness values are presented as functions of the capacity ratio and NTU. These data are used to demonstrate the advantages of the new definitions for maximum heat transfer and maximum temperature difference in ideal two-fluid heat exchangers.
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Li, Xunfeng, Lifang Zheng, Li Wang, and Quan Ji. "Numerical Study of Temperature Field in BEPCII Interaction Region." In ASME 2008 2nd International Conference on Energy Sustainability collocated with the Heat Transfer, Fluids Engineering, and 3rd Energy Nanotechnology Conferences. ASMEDC, 2008. http://dx.doi.org/10.1115/es2008-54146.
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The temperature field of the beam pipe was calculated at the maximum heat loads and designed flow rates of the cooling liquids. The maximum difference between the predicted and measured temperature on the outer surface of the beam pipe was found to be 0.6 K. In addition, the temperature field between the beam pipe and the inner barrel of the main drift chamber (MDC) was calculated assuming natural convection heat transfer of the air in the enclosed cavity under three different conditions. The results of the calculation showed that only the use of insulation covers on the transition sections of the beam pipe keeps the temperature of the inner barrel in the range of 293.0±1.0 K. The thermal conductivity of the heat insulators under the heat insulation covers must be less than 0.5 W/(m·K).
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Koeppel, Brian J., Kevin Lai, and Moe A. Khaleel. "Effect of Geometry and Operating Parameters on Simulated SOFC Stack Temperature Uniformity." In ASME 2011 9th International Conference on Fuel Cell Science, Engineering and Technology collocated with ASME 2011 5th International Conference on Energy Sustainability. ASMEDC, 2011. http://dx.doi.org/10.1115/fuelcell2011-54803.
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A uniform temperature field is desirable in the solid oxide fuel cell stack to avoid local hot regions that contribute to material degradation, thermal stresses, or very high current densities. Various geometric and operational design changes were simulated by numerical modeling of co-flow and counter-flow multi-cell stacks, and the effects on stack maximum temperature, stack temperature difference, and maximum cell temperature difference were characterized. The results showed that 11–17% methane fuel composition for on-cell steam reforming and a reduced reforming rate of 25–50% of the nominal rate was beneficial for a more uniform temperature field. Fuel exhaust recycling up to 30% was shown to provide lower temperature differences for reforming fuel in the co-flow stack, but counter-flow stacks with hydrogen fuel showed higher temperature differences. Cells with large aspect ratios showed a more uniform temperature response due to either the strong influence of the inlet gas temperatures or the greater thermal exchange with the furnace boundary condition. Improved lateral heat spreading with thicker interconnects was demonstrated, but greater improvements towards a uniform thermal field for the same amount of interconnect mass could be achieved using thicker heat spreader plates appropriately distributed along the stack height.
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Ji, Fang, Xiaomei Wang, Guide Deng, Jingliang Feng, and Haifeng Liang. "Effect of the Shapes of Diversion Umbrellas on Temperature Field in a Large Spherical Tank During Heat Treatment Processes." In ASME 2015 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/pvp2015-45362.
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Internal combustion method is widely used to reduce residual stress of large spherical tanks in China, when post weld heat treatment of the spherical tanks is required. During the heat treatment processes diversion umbrellas set in the spherical tanks can be utilized to drop the maximal difference of wall temperatures of the spherical tanks. Numerical simulation based on Fluent software was carried out to study the effect of an A-shaped diversion umbrella and three V-shaped diversion umbrellas with different angles on internal flow and wall temperatures of a 10000 m3 spherical tank. The results show that the V-shaped diversion umbrellas have better performance than the A-shaped one, but the angles of the V-shaped diversion umbrellas from 100° to 140° have little effect on maximum wall temperature differences of the spherical tank during the heat preservation stage of the heat treatment processes.
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Xu, Junxiu, Ming Ding, Changqi Yan, and Guangming Fan. "Experimental Study on Natural Convection Heat Transfer Outside Tube Bundle in Space Under Low Temperature Difference." In 2020 International Conference on Nuclear Engineering collocated with the ASME 2020 Power Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/icone2020-16109.
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Abstract The Passive Residual Heat Removal System (PRHRS) is very important for the safety of the heating reactor after shutdown. PRHRS is a natural circulation system driven by density difference, therefore, the heat transfer performance of the Passive Residual Heat Removal Heat Exchanger (PRHR HX) has a great impact to the heat transfer efficiency of PRHRS. However, the most research object of PRHR HX is the C-shape heat exchanger at present, which located in In-containment Refueling Water Storage Tank (IRWST). This heat exchanger is mainly used for the PRHRS of nuclear power plants. In the swimming pool-type low-temperature heating reactor (SPLTHR), the PRHR HX is placed in the reactor pool, which the pressure and temperature of the reactor pool are relatively low, and the outside heat transfer mode of tube bundle is mainly natural convection heat transfer. In this study, a miniaturized single-phase pool water cooling system was built to investigate the natural convective heat transfer coefficient of the heat exchanger under the large space and low temperature conditions. The experimental data had been compared with several correlations. The results show that the predicted value of Yang correlation is the closest to the experimental data, which the maximum deviation is about 11%.
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Araya Go´mez, Pablo E., and Miles Greiner. "2D Natural Convection and Radiation Heat Transfer Simulations of a PWR Fuel Assembly Within a Constant Temperature Support Structure." In ASME 2006 Pressure Vessels and Piping/ICPVT-11 Conference. ASMEDC, 2006. http://dx.doi.org/10.1115/pvp2006-icpvt-11-93332.
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Two-dimensional simulations of steady natural convection and radiation heat transfer for a 14×14 pressurized water reactor (PWR) spent nuclear fuel assembly within a square basket tube of a typical transport package were conducted using a commercial computational fluid dynamics package. The assembly is composed of 176 heat generating fuel rods and 5 larger guide tubes. The maximum cladding temperature was determined for a range of assembly heat generation rates and uniform basket wall temperatures, with both helium and nitrogen backfill gases. The results are compared with those from earlier simulations of a 7×7 boiling water reactor (BWR). Natural convection/radiation simulations exhibited measurably lower cladding temperatures only when nitrogen is the backfill gas and the wall temperature is below 100°C. The reduction in temperature is larger for the PWR assembly than it was for the BWR. For nitrogen backfill, a ten percent increase in the cladding emissivity (whose value is not well characterized) causes a 4.7% reduction in the maximum cladding to wall temperature difference in the PWR, compared to 4.3% in the BWR at a basket wall temperature of 400°C. Helium backfill exhibits reductions of 2.8% and 3.1% for PWR and BWR respectively. Simulations were performed in which each guide tube was replaced with four heat generating fuel rods, to give a homogeneous array. They show that the maximum cladding to wall temperature difference versus total heat generation within the assembly is not sensitive to this geometric variation.
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Yan, Yi, Menggang Wen, and Yun Li. "FEM Analysis and Preload Evaluation of Bolted Joints Subject to Low Temperature." In ASME 2015 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/pvp2015-45209.
Full textAbstract:
Bolted joints are broadly used in various industrial products. Especially in chemical engineering, the reliability of bolted joints can have a significant influence on the safety of chemical systems. In some fields, such as liquefied natural gas (LNG) industry, equipment usually works in low temperature (−162°C). Different materials with various thermal expansion rates are usually used in bolted joints; Therefore the preload and stress distribution of bolted joints in low temperature can change apparently due to the different axial and radial thermal deformation. If the preload design in normal temperature is inappropriate, the bolted joints may either encounter relaxation or over-tightening in working temperature. In this study, a theoretical analysis is proposed in order to evaluate the appropriate preload selection of bolted joints work in low temperature. FE analysis is made to examine the accuracy of the theoretical formula. The result shows that the error is less than 10% in most cases. The stress distribution on the bolt thread region is studied and the result shows that the maximum tensile stress on the bolt thread region is much higher than in non-thread region. Availability and safety should be both considered in preload selection of bolted joints working in low temperature. Finally the effect of radial thermal deformation difference is discussed when the thermal expansion rate difference is high. The effect of radial thermal deformation difference should not be neglected in some cases.
Reports on the topic "Maximum temperature difference"
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Ruosteenoja, Kimmo. Applicability of CMIP6 models for building climate projections for northern Europe. Finnish Meteorological Institute, 2021. http://dx.doi.org/10.35614/isbn.9789523361416.
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In this report, we have evaluated the performance of nearly 40 global climate models (GCMs) participating in Phase 6 of the Coupled Model Intercomparison Project (CMIP6). The focus is on the northern European area, but the ability to simulate southern European and global climate is discussed as well. Model evaluation was started with a technical control; completely unrealistic values in the GCM output files were identified by seeking the absolute minimum and maximum values. In this stage, one GCM was rejected totally, and furthermore individual output files from two other GCMs. In evaluating the remaining GCMs, the primary tool was the Model Climate Performance Index (MCPI) that combines RMS errors calculated for the different climate variables into one index. The index takes into account both the seasonal and spatial variations in climatological means. Here, MCPI was calculated for the period 1981—2010 by comparing GCM output with the ERA-Interim reanalyses. Climate variables explored in the evaluation were the surface air temperature, precipitation, sea level air pressure and incoming solar radiation at the surface. Besides MCPI, we studied RMS errors in the seasonal course of the spatial means by examining each climate variable separately. Furthermore, the evaluation procedure considered model performance in simulating past trends in the global-mean temperature, the compatibility of future responses to different greenhouse-gas scenarios and the number of available scenario runs. Daily minimum and maximum temperatures were likewise explored in a qualitative sense, but owing to the non-existence of data from multiple GCMs, these variables were not incorporated in the quantitative validation. Four of the 37 GCMs that had passed the initial technical check were regarded as wholly unusable for scenario calculations: in two GCMs the responses to the different greenhouse gas scenarios were contradictory and in two other GCMs data were missing from one of the four key climate variables. Moreover, to reduce inter-GCM dependencies, no more than two variants of any individual GCM were included; this led to an abandonment of one GCM. The remaining 32 GCMs were divided into three quality classes according to the assessed performance. The users of model data can utilize this grading to select a subset of GCMs to be used in elaborating climate projections for Finland or adjacent areas. Annual-mean temperature and precipitation projections for Finland proved to be nearly identical regardless of whether they were derived from the entire ensemble or by ignoring models that had obtained the lowest scores. Solar radiation projections were somewhat more sensitive.
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Bowles, David, Michael Williams, Hope Dodd, et al. Protocol for monitoring aquatic invertebrates of small streams in the Heartland Inventory & Monitoring Network: Version 2.1. National Park Service, 2021. http://dx.doi.org/10.36967/nrr-2284622.
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The Heartland Inventory and Monitoring Network (HTLN) is a component of the National Park Service’s (NPS) strategy to improve park management through greater reliance on scientific information. The purposes of this program are to design and implement long-term ecological monitoring and provide information for park managers to evaluate the integrity of park ecosystems and better understand ecosystem processes. Concerns over declining surface water quality have led to the development of various monitoring approaches to assess stream water quality. Freshwater streams in network parks are threatened by numerous stressors, most of which originate outside park boundaries. Stream condition and ecosystem health are dependent on processes occurring in the entire watershed as well as riparian and floodplain areas; therefore, they cannot be manipulated independently of this interrelationship. Land use activities—such as timber management, landfills, grazing, confined animal feeding operations, urbanization, stream channelization, removal of riparian vegetation and gravel, and mineral and metals mining—threaten stream quality. Accordingly, the framework for this aquatic monitoring is directed towards maintaining the ecological integrity of the streams in those parks. Invertebrates are an important tool for understanding and detecting changes in ecosystem integrity, and they can be used to reflect cumulative impacts that cannot otherwise be detected through traditional water quality monitoring. The broad diversity of invertebrate species occurring in aquatic systems similarly demonstrates a broad range of responses to different environmental stressors. Benthic invertebrates are sensitive to the wide variety of impacts that influence Ozark streams. Benthic invertebrate community structure can be quantified to reflect stream integrity in several ways, including the absence of pollution sensitive taxa, dominance by a particular taxon combined with low overall taxa richness, or appreciable shifts in community composition relative to reference condition. Furthermore, changes in the diversity and community structure of benthic invertebrates are relatively simple to communicate to resource managers and the public. To assess the natural and anthropo-genic processes influencing invertebrate communities, this protocol has been designed to incorporate the spatial relationship of benthic invertebrates with their local habitat including substrate size and embeddedness, and water quality parameters (temperature, dissolved oxygen, pH, specific conductance, and turbidity). Rigid quality control and quality assurance are used to ensure maximum data integrity. Detailed standard operating procedures (SOPs) and supporting information are associated with this protocol.