Effect Of Thermal Environment Research Articles

Developmental temperature affects phenotypic means and variability: A meta‐analysis of fish data

AbstractFishes are sensitive to their thermal environment and face an uncertain future in a warming world. Theoretically, populations in novel environments might express greater levels of phenotypic variability to increase the chance of surviving—and eventually thriving—in the new conditions. Most research on the effect of the early thermal environment in fish species focuses on average phenotypic effects rather than phenotypic variability, but to understand how fishes will respond to rising temperatures we need to consider both the average response of the population, as well as the breadth of individual responses. Here we present the first meta‐analysis on the effects of developmental temperature in fishes. Using data from 43 species and over 6,000 individual fish, we show that a change in developmental temperature induces a significant change in phenotypic means and variability, but differently depending on whether the temperature is increased or decreased. Decreases in temperature (cool environments) showed a significant decrease in phenotypic means and no change in phenotypic variability. Increases in temperature (warm environments) showed a non‐significant increase in phenotypic means and a marginally significant increase in phenotypic variability. Larger increases in temperature saw greater increases in phenotypic variability, but no increase in the mean phenotypic response. Together, our results suggest that fishes exhibit both directed and stochastic developmental plasticity in response to warming temperatures, which could facilitate or accelerate adaptation to a changing environment.

Mean skin temperature estimated from 3 measuring points can predict sleeping thermal sensation

Sensory input from the skin appears to be of crucial importance in the regulation of sleep but there has been limited research on human skin temperature during sleep. The present study was undertaken to validate calculation of the mean skin temperature (MST) of sleeping subjects from measurements at only three locations: forehead, chest, and foot, by means of an analysis of skin temperature data obtained from four human experiments that investigated the effects of thermal environment on the sleep quality and thermal comfort of a total of 64 sleeping subjects. The results show that skin temperatures were more evenly distributed across the body surface of sleeping subjects than they are when subjects are awake. The skin temperature of the forehead was highly correlated with thermal sensation in long-term measurements. MST values calculated using the three-point method were found to predict thermal sensation while sleeping better than those calculated using the normally accepted Hardy and Dubois's seven-point method. The validity, convenience and reliability of this approach, which also causes less sleep disturbance, makes it a suitable choice for obtaining estimates of mean skin temperature in sleep studies.

Thermal buckling and forced vibration characteristics of a porous GNP reinforced nanocomposite cylindrical shell

In this research, thermal buckling and forced vibration characteristics of the imperfect composite cylindrical nanoshell reinforced with graphene nanoplatelets (GNP) in thermal environments are presented. Halpin–Tsai nanomechanical model is used to determine the material properties of each layer. The size-dependent effects of GNPRC nanoshell is analyzed using modified couple stress theory. For the first time, in the present study, porous functionally graded multilayer couple stress (FMCS) parameter which changes along the thickness is considered. The novelty of the current study is to consider the effects of porosity, GNPRC, FMCS and thermal environment on the resonance frequencies, thermal buckling and dynamic deflections of a nanoshell using FMCS parameter. The governing equations and boundary conditions are developed using Hamilton’s principle and solved by an analytical method. The results show that, porosity, GNP distribution pattern, modified couple stress parameter, length to radius ratio, mode number and the effect of thermal environment have an important role on the resonance frequencies, relative frequency change, thermal buckling, and dynamic deflections of the porous GNPRC cylindrical nanoshell using FMCS parameter. The results of current study can be useful in the field of materials science, micro-electro-mechanical systems and nano electromechanical systems such as microactuators and microsensors.

Hazardous characteristics of charge and discharge of lithium-ion batteries under adiabatic environment and hot environment

The 18,650 lithium-ion battery was charged and discharged at different rates, first in an environment with heat source, and then in one with heat-insulation, to study the effects of different thermal environments on the thermal behavior of lithium batteries. In the case of charging and discharging in adiabatic environments, the battery did not have thermal runaway, and the maximum temperature and temperature rise rate increased with the increase of the charging and discharging rates. During the 4 C discharge process, the resistance increased due to the action of the Positive Temperature Coefficient (PTC) element, and the loop current decreased, which made the highest temperature lower than that in the 3 C discharge process. In the presence of an external heat source, when charged and discharged at different rates, the battery was thermally out of control. The thermal runaway behavior of the battery during charging was a large amount of gas leakage. At the time of discharge, due to the high initial State of Charge (SOC), at the 0.5 C, 1 C, 2 C rates, there was thermal runaway following a large amount of gas leakage. The same phenomenon also occurred at the 3 C, 4 C rates, but without continuous combustion. In the environment of external heat source, results showed that the thermal runaway heat release was always greater in the charge process than in the discharge process. With the increase of the charge and discharge currents, the battery power before and after the thermal runaway remained almost the same. Therefore, the ratio of the thermal runaway heat release in the charge process to that in the discharge process kept increasing and finally approached 1.

CFD study with consideration of the surrounding buildings using a through-wall unit air conditioning system

In order to select the operation patterns of a through-wall unit (TWU) according to the air conditioning needs of the ocupants, it is necessary to confirm the indoor thermal environment and natural ventilation effects by the operation patterns. CFD analysis was performed utilizing Building Information Modeling (BIM) and the outdoor fan characteristics of a TWU by a full-scale performance experiments. It was confirmed that the airside economizer mode using the outdoor fan on an improved TWU supplies a sufficient ventilation rate of about 4.5 ACPH to the office and it can provide a good indoor thermal environment during no wind conditions. In addition, CFD analysis using the night-time cool breeze mode with consideration of the surrounding buildings was conducted. As a whole, a good indoor environment of about 26 to 27°C could be obtained with about 3 ACPH ventilation and a cool breeze effect. It was confirmed that by conducting precise analysis on the whole building, a stable effect was obtained, regardless of the difference in building height and wind direction.

Vibration, Buckling and Deflection Analysis of Cracked Thin Magneto Electro Elastic Plate Under Thermal Environment

The Magneto-Electro-Elastic (MEE) material exhibits pyroelectric and pyromagnetic effects under thermal environment. The effects of such pyroelectric and pyromagnetic behavior on vibration, buckling and deflection analysis of partially cracked thin MEE plate is presented and discussed in this paper. The aim of the study is to develop an analytical model for the vibration and geometrically linear thermal buckling analysis of cracked MEE plate based on the classical plate theory (CPT). The line spring model (LSM) is modified for the crack terms to accommodate the effect of electric and magnetic field rigidities, whereas the effect of thermal environment is accommodated in the form of thermal moment and in-plane forces. A classical relation for thermal buckling phenomenon of cracked MEE plate is also proposed. The governing equation for cracked MEE plate has also been solved to get central deflection which shows an important phenomenon of shift in primary resonance due to crack and temperature rise. The results evaluated for natural frequencies as affected by crack length, plate aspect ratio and critical buckling temperature are presented for first four modes of vibration. The obtained results reveal that the fundamental frequency of the cracked plate decreases with increase in temperature and crack length. Furthermore the variation of the critical buckling temperature with plate aspect ratio and crack length is also established for different modes of vibration.

Nonlinear dynamic buckling of full-filled fluid sandwich FGM circular cylinder shells

This paper is concerned with the nonlinear dynamic buckling of sandwich functionally graded circular cylinder shells filled with fluid. Governing equations are derived using the classical shell theory and the geometrical nonlinearity in von Karman–Donnell sense is taken into account. Solutions of the problem are established by using Galerkin's method and Runge–Kutta method. Effects of thermal environment, geometric parameters, volume fraction index $ k $ and fluid on dynamic critical loads of shells are investigated.

Effect of Fluid–Structure Interaction on Vibration and Deflection Analysis of Generally Orthotropic Submerged Micro-plate with Crack Under Thermal Environment: An Analytical Approach

To develop a new analytical model for vibration analysis of cracked-submerged orthotropic micro-plate affected by fibre orientation and thermal environment. The proposed analytical model is based on Kirchhoff’s classical thin plate theory and the size effect is introduced using the modified couple stress theory. Effect of crack is deduced using appropriate crack compliance coefficients based on line spring model while the effect of thermal environment is introduced in terms of thermal in-plane moments and forces. The coupling of shear and normal stresses for fibre orientation is represented using the coefficient of mutual influence. The fluid forces associated with its inertial effects are added in the governing differential equation to incorporate the fluid–structure interaction effect. The results are presented for frequency response as affected by different fibre orientation, crack length, crack location, level of submergence, temperature variation and material length-scale parameter for simply supported boundary condition. Furthermore, to study the phenomenon of shifting of primary resonance in a cracked micro-plate, the classical relations for central deflection of plate is also proposed. The results show that the fundamental frequency of micro-plate decreases by the presence of crack and thermal environment and this decrease in frequency is further intensified by the presence of surrounding fluid medium in present study. Another important conclusion is that with increase in temperature variation the reduction in frequency at 45° of fibre orientation is less when compared to 0 and 90° for both intact and cracked orthotropic plates.

Nonlinear Thermo-Mechanical Stability Analysis of Eccentrically Spiral Stiffened Sandwich Functionally Graded Cylindrical Shells Subjected to External Pressure

A new analytical approach to investigate the nonlinear buckling and postbuckling of the sandwich functionally graded circular cylindrical shells reinforced by ring and stringer or spiral stiffeners subjected to external pressure is presented in this paper. By employing the Donnell shell theory, the geometrical nonlinearity in Von Kármán sense and developed Lekhnitskii’s smeared stiffener technique, the governing equations of sandwich functionally graded circular cylindrical shells are derived. Resulting equations are solved by applying the Galerkin method to obtain the explicit expression of critical buckling external pressure load and postbuckling load–deflection curve. Effects of spiral stiffeners, thermal environment, external pressure, and geometrical parameters on nonlinear buckling behavior of sandwich functionally graded circular cylindrical shells are shown in numerical results.

Effects of thermal environment on elderly in urban and rural houses during heating season in a severe cold region of China

In this study, field measurements on the indoor living environments of elderly people were conducted to assess residential forms, heating methods, physical parameters, and thermal sensations in five urban and ten rural houses in Heilongjiang Province, China, in January 2017. The results indicated that urban houses used regional centralized heating systems in all the functional rooms, whereas rural houses used decentralized heating systems in only bedrooms and kitchens. Rural houses were less airtight than urban houses. Urban houses had continuous centralized heating and, thus, were warmer with steadier indoor temperatures than rural houses with decentralized heating. Additionally, the elderly in rural areas frequently encountered large temperature differences (weekly average = 28.9 °C) between the indoors and outdoors, due to the outdoor toilet location. The daily amplitude of indoor temperature variations experienced by rural elderly was 8.0 °C, which was 2.2 °C higher than experienced by urban elderly. Moreover, most rural elderly did not express discomfort for indoor thermal environments despite living in colder rooms, since they wore thicker clothing and had lower comfort expectations. In addition, the rural elderly indicated strong adaptability to lower temperatures as suggested by their predicted mean vote, which was significantly lower than the thermal sensation vote.

Investigating the effect of indoor thermal environment on occupants’ mental workload and task performance using electroencephalogram

Workers' performance in indoor offices can be greatly affected by the thermal condition of the environment. However, this effect can be difficult to quantify, especially when the thermal stress is a moderate increase or decrease in temperature and the work productivity cannot be directly measured. Subjects' high motivation to perform well under experimental conditions also causes difficulties in comparing their performance in different thermal environments. In order to overcome these limitations, this paper proposes a method to investigate the effect of the indoor thermal conditions on occupants' performance by studying occupants' mental workload measured by the electroencephalography (EEG) when they perform standardized cognitive tasks. An experiment integrating EEG mental workload measurement and cognitive tasks was implemented on 15 subjects. EEG data were collected while subjects were performing four cognitive tasks on computers. Based on previous studies, we propose a mental workload index calculated from the frontal theta and parietal alpha frequency band power. Within-subject comparisons were performed to investigate whether subjects' mental workload is statistically different under three different thermal environments, representing thermal sensations of slightly cool, neutral, and slightly warm. The results show that the effect of thermal environment varies across different individuals. By comparing the mental workload index among different thermal environments, we found that the slightly warm environment resulted in a relatively higher mental workload than the other two environments to achieve the same performance. The study provides promising insights into how the thermal environment influences occupants’ performance by affecting their mental workload from the neurophysiological perspective.

Thermal environment and strain energy related micro-model for properties of carbon nanotubes

In this paper, a molecular structural mechanics model is proposed to study the effect of thermal environment on elastic properties of carbon nanotubes. The covalent bonds are traded as a truss in this new model. The influence of the temperature on Young’s modulus and shear modulus of both armchair and zigzag carbon nanotubes are investigated. According to the principle of elastic theory, a temperature-dependent continuum shell model of strain energy density is also established. The strain energy density of single-walled carbon nanotubes (SWCNTs) decreases with the increase of temperature. The Young's modulus of SWCNTs increases with the increase of tube diameter, but decreases with the increase of temperature. The temperature-dependent modulus of SWCNTs has a similar trend of change with multi-walled carbon nanotubes (MWCNTs), but MWCNTs are more sensitive to the wall thickness.

Rigid-flexible-thermal analysis of planar composite solar array with clearance joint considering torsional spring, latch mechanism and attitude controller

This paper establishes a thermal-structural coupling model of planar spacecraft system with large flexible composite solar array under nodal coordinate formulation and absolute nodal coordinate formulation framework. Perfect revolute joint is adopted as connection type to give the different influences from fixed constraint used in previous researches, and consequently, torsional spring, latch mechanism, and attitude controller are involved into the spacecraft system. Imperfect revolute joint is further introduced to investigate the coupling effects of thermal load, adjustment motion, and joint clearance on dynamics of the system, including spacecraft attitude, solar panel responses, and wear prediction. Results of six comparison models (with or without clearance joint, considering thermal environment, or adjustment motion, and considering both these two conditions) show that the coupling effect of thermal environment and overall motion brings dramatic and unmanageable shock to the system with clearance joint, that is no longer can be seen as a simple superposition of each single condition effect like the system with ideal joint, although the suspension damper property of clearance joint can weaken thermal-induced vibration or motion induced vibration separately. For a period after attitude adjustment, wear depth of the system subjected to solar radiation is two orders of magnitude lager than that of the system without considering thermal environment. Joint clearance and thermal environment should be considered both; for on-orbit spacecraft system, the coupling effects of them are significant and non-ignorable for relevant mechanism design and performance analysis.

Effect of Thermal Environment on Vibration Analysis of Partially Cracked Thin Isotropic Plate Submerged in Fluid

Based on a non classical plate theory, an analytical model is proposed for the first time to analyze free vibration problem of partially cracked thin isotropic submerged plate in the presence of thermal environment. The governing equation for the cracked plate is derived using the Kirchhoff’s thin plate theory and the modified couple stress theory. The crack terms are formulated using simplified line spring model whereas the effect of thermal environment is introduced using thermal moments and in-plane forces. The influence of fluidic medium is incorporated in governing equation in form fluids forces associated with inertial effects of its surrounding fluids. Applying the Galerkin’s method, the derived governing equation of motion is reformulated into well known Duffing equation. The governing equation for cracked isotropic plate has also been solved to get central deflection which shows an important phenomenon of shift in primary resonance due to crack, temperature rise and internal material length scale parameter. To demonstrate the accuracy of the present model, few comparison studies are carried out with the published literature. The variation in natural frequency of the cracked plate with uniform rise in temperature is studied considering various parameters such as crack length, fluid level and internal material length scale parameter. Furthermore the variation of the natural frequency with plate thickness is also established.

Strongly robust approach for temperature monitoring of power cable joint

This study aims to monitor the temperature inside power cable joint, with strong robustness to variable thermal environments and uncertain thermal parameters of the joint. The model consists of two sequential steps, radial-direction temperature inversion in the cable and axial-direction temperature inversion in the conductor. The former part was improved by coating the cable with a heat insulated layer, whereas the latter one was optimised through a proper parameter selection. Afterwards, an outdoor cable joint temperature-rise test was carried out and the temperature obtained from the proposed approach agrees well with the measured one. With the great change in ambient temperature and wind speed during the test, the model accuracy remains almost constant, and this is due to the heat insulated layer and low sensitivity coefficient of the algorithm. Besides, if the thermal conductivity and volumetric specific heat of waterproof compound in cable joint are assumed to increase by nearly five times, the maximum changes in temperature monitoring are only 1.4 and 0.4°C, respectively. The results indicate that this approach can effectively overcome the effects of variable thermal environments and thermal parameter dispersion in joint, thus promoting practical applications in temperature monitoring for cable joints.

Spatial differentiation of urban wind and thermal environment in different grid sizes

Due to rapid urbanization, China's urban morphology has undergone tremendous changes, resulting in an increased urban heat island (UHI) effect and negative impact of thermal environment, especially in summer. Studying the scale effect between urban wind and thermal environment can provide the best scale for the wind environment planning on mitigating UHI effect. Taking Dalian as an example, using multi-source data, a nonlinear correlation analysis was used to analyze the correlation between the frontal area index (FAI) and land 77uuyyhsurface temperature (LST) under different grids. The results show that first, FAI is sensitive to grid-size changes. When the grid size increases from 25 × 25 m to 150 × 150 m with a step size of 25 m, in July, the numbers of grids with FAI > 1 are 19,992, 1538, 153, 20, 4, and 0 (0%) accounting for 2.106%, 0.645%, 0.081%, 0.019%, 0.006%, and 0% of the total, respectively. In September, the numbers of grids with FAI > 1 are 17,633, 1643, 164, 22, 8, and 0, accounting for 1.849%, 0.689%, 0.155%, 0.037%, 0.021%, and 0% of the total, respectively. When the grid size is greater than or equal to 150 × 150 m, there is no grid with FAI > 1. Second, the most effective grid size to study the relationship between FAI and LST is 25 m. When the grid size increases from 25 m to 300 m with a step size of 25 m, the correlation between FAI and LST shows a significant decrease. When the grid size is 25 m, the correlation is the strongest.

Vibration and deflection analysis of thin cracked and submerged orthotropic plate under thermal environment using strain gradient theory

Based on a non-classical plate theory, a nonlinear analytical model is proposed to analyze transverse vibration of thin partially cracked and submerged orthotropic plate in the presence of thermal environment. The governing equation for the cracked plate is derived using the Kirchhoff’s thin plate theory in conjunction with the strain gradient theory of elasticity. The effect of centrally located surface crack is deduced using appropriate crack compliance coefficients based on the simplified line spring model, whereas the effect of thermal environment is introduced using moments and in-plane forces. The influence of fluidic medium is incorporated in the governing equation in the form of fluid forces associated with its inertial effects. The equation has been solved by transforming the lateral deflection in terms of modal functions. The shift in primary resonance due to crack, length scale parameter and temperature has also been derived with central deflection. To demonstrate the accuracy of the present model, a few comparison studies are carried out with the published literature. The variation in fundamental frequency of the cracked plate is studied considering various parameters such as crack length, plate thickness, level of submergence, temperature and length scale parameter. It has been concluded that the frequency is affected by crack length, temperature and level of submergence. A comparison has also been made for the results obtained from the classical plate theory and Strain gradient theory. Furthermore, the variation in frequency response and peak amplitude of the cracked plate is studied using method of multiple scales to show the phenomenon of bending hardening or softening as affected by level of submergence, temperature, crack length and length scale parameter .

Dephasing in a Molecular Junction Viewed from a Time-Dependent and a Time-Independent Perspective

The current through a molecular junction can be determined numerically in a multitude of ways. Some of these methods like the Landauer scheme are only valid for coherent transport and the steady state regime while other schemes are able to treat time-dependent electronic currents across molecular junctions subject to fluctuating environments. In time-independent formalisms, the effect of thermal environments can be introduced in several ways. Here we focus on the vibronic dephasing model within a Green’s function approach. This time-independent scheme is contrasted with the time-dependent nonequilibrium Green’s function (TD-NEGF) approach in which the effect of the thermal environment manifests itself in fluctuating site energies. It is found that the time-averaged results of the TD-NEGF approach agree excellently with those from the vibronic model. This numerical comparison helps us to better understand the connection between these different pure dephasing schemes, which both have advantages and specific...

Effect of nozzle thermal environment on the ablation rate of the throat inserts of solid rocket motors

Effect of nozzle thermal environment on the ablation rate of the throat inserts of solid rocket motors

Geometric phase for a two-level atom immersed in a thermal bath in the global monopole space–time

In the framework of open quantum systems, and combining with the quantum field theory in curved space–time, we study the geometric phase for a static two-level atom immersed in a thermal bath of a massless scalar field in the background of global monopole space–time. We show that the correction to geometric phase of the atom results from combined effects of both thermal radiation of the thermal bath at finite temperature and the topological property of global monopole. We also discuss the modified geometric phases for this two-level atom purely due to thermal fluctuation of the thermal bath at an effective temperature in Minkowski space–time and also purely resulting from the effect of global monopole space–time. In addition, the numerical results of correction to the geometric phase induced by the effects of thermal environment and the global monopole is presented and discussed. It is clearly seen that the corrections depend crucially on the temperature T of environment and the position r of the atom relative to the global monopole.