Influence Of Thermal Environment Research Articles

Influence of Thermal Environment on College Students’ Learning Performance in Hot Overhead Spaces in China

Influence of Thermal Environment on College Students’ Learning Performance in Hot Overhead Spaces in China

Simulation of metal fatigue crack analysis based on thermal environment numerical analysis in street metal sculpture design process

With the popularity of urban public art, metal materials are easily affected by environmental factors in practical applications, especially the influence of thermal environment on metal fatigue, which often leads to cracks in sculptures, affecting their service life and safety. Through the numerical analysis of thermal environment, the fatigue crack generation mechanism of street metal sculpture in the process of use is deeply discussed in order to provide theoretical support and practical guidance for sculpture design. The finite element analysis method is used to simulate the stress distribution of metal sculpture under different thermal conditions. By setting a variety of conditions such as ambient temperature and humidity, the corresponding thermodynamic model is established, and the fatigue properties of metal materials are evaluated comprehensively. The numerical model is calibrated with experimental data to improve the accuracy of the simulation. It is found that the change of thermal environment significantly affects the internal stress distribution of metal sculpture, and then affects the generation of fatigue cracks. At high temperature, the fatigue limit of the material is reduced, which leads to more cracks. Under the condition of sudden temperature change, the stress concentration of the material is more obvious, and the fatigue life of the metal is significantly shortened.

Nonlinear vibration analysis of a double curved shallow sandwich shell in which the core made of three-phase nanocomposite and the two-outer layer of electromagnetic materials

This paper investigates the nonlinear vibrations of a double curved shallow sandwich shell with a three-phase nanocomposite core and two outer electromagnetic layers considering the thermal environment's influence. Relying on the Halpin–Tsai model, the core is assumed to be made of some composite plies incorporating three constituents: carbon nanotubes (CNTs) or graphene nanoplatelets (GPLs) as nanocomposites, fibers and polymeric matrix (resin). Governing equations calculating the nonlinear vibration of the double curved shallow shell were obtained by combining Reddy's first-order shear deformation theory (FSDT) and the Von Kármán geometrical nonlinearity. Later, this system of equations is transformed into the nonlinear ordinary differential expressions by utilizing the Galerkin procedure. Thus, the effects of material properties, temperature, geometrical properties, elastic foundations to the frequency of linear and nonlinear free vibration, and amplitude–frequency relations of the double curved shallow sandwich shell were discussed. The results demonstrate that the free vibration frequency of the shell increases if the magnetic field enhances, whereas that decreases when the voltage expands in both models as CNTs and GPLs. Simultaneously, the shallow shell has a better ability to force load compared to a plate with the same dimensions. These outcomes can make a profit in the design and manufacturing of new smart structures applied in energy harvesting, and medicine.

Analysis of thermal comfort and threshold range of airflow supply parameters for different types of work in humid-heat coal mines

For the purpose of investigating the effects of various factors as to the thermal comfort of miners, obtaining the most comfortable threshold range of air supply parameters. Five types of jobs with moderate and light labor intensity were selected for the study. The effects of labor intensity, environmental parameters and thermal resistance of clothing on the thermal comfort of miners were analyzed using PMV-PPD index, air motion and temperature difference. Under the same environment, moderate manual workers showed more satisfactory thermal comfort than light manual workers. In a humid and hot mine, the degree of influence of environmental parameters on thermal comfort of workers is ranked as: temperature > humidity > wind speed. Considering the influence of thermal environment and dust on people, the temperature of 27–30 °C, humidity of 40–50% and wind speed of 1.5–2.5 m/s are an optimal combination of ventilation parameters that can simultaneously satisfy human comfort and low energy consumption. The worker can compensate the temperature by adjusting the heat resistance value of the garment. 0.38–2.12clo clothing thermal resistance value, can compensate the temperature range of 27–30 °C. These findings can provide a reference for reducing energy consumption and improving human thermal comfort.

Dissipative dynamics of magnons under the influence of thermal environment: Bunched, antibunched and coherent magnons

We consider a system consisting of magnons in an isotropic ferromagnet interacting with a thermal reservoir and proceed to investigate the dissipative dynamics of the magnons under various physical conditions. We show how bunched, antibunched and coherent magnons can be realized by manipulating the thermal reservoir, a driving field as well as the initial state of the system. Our results show that when the system is initiated with the thermal state, the magnons do not obtain nonclassical properties, while for Schrödinger cat states, the magnons acquire nonclassical characteristics. Besides, the magnon blockade phenomenon is observed after the onset of interaction especially when the system is initialized with the nonclassical states, i.e., the odd Schrödinger cat state. However, the classical magnons prevail in the steady state regime. This work provides theoretical support for the realization of quantum–classical transitions in real magnonic systems and may be fruitful for designing the single-magnon sources.

Variable stiffness composite laminated beams - nonlinear free flexural vibration behavior using a sinusoidal based shear flexible structural theory accounting for Poisson’s effect

In the present work, formulation for the nonlinear free vibrational behavior of laminated variable stiffness composite beams with curvilinear fibers is made incorporating sinusoidal function for representing the transverse shear flexibility, geometrical nonlinearity, and accounting for Poisson’s effect through the constitutive equation for analyzing beams with general composite lay-up. Applying Hamilton’s principle combining with a finite element approach based on three-noded C1 beam element, the governing equations are formed through matrices. The solutions for the developed governing equations are evaluated iteratively by introducing eigenvalue analysis and the results are viewed through the frequency–amplitude relationship. A large number of design parameters like curvilinear fiber angles in a layer, number of layers, lay-up sequence, thickness ratio, etc. is assumed to visualize the nonlinear free vibration characteristics of VSCL beams. Also, for the practical situation, the influence of thermal environment and restraint elastically against beam ends rotation, to accommodate other than classical boundary conditions, hybrid beam (consisting of constant and variable stiffness layers) on the non-linear free vibrational behavior is presented.

Influence of thermal environment on metallographic structure characteristics of the electric arc bead pattern

Electrical apparatuses are prone to arc, which generally causes a fire, even an explosion hazard, when a flammable gas mixture is present, especially during industrial processes. Terrible fire scenes are challenging for fire investigations. In this work, by performing a simultaneous thermal analysis test we simulated a fire environment and found that as the oxygen concentration decreased, the oxidation/exothermic peak temperature of ‘cause’ bead became higher, but the melting temperature was unaffected. Results indicated that the bead pattern underwent oxidation at approximately 831 °C, melting initiated at approximately 1060 °C, and the pattern then disappeared. The melted pattern grain changes were divided into three critical temperature stages: Approximately 600 °C, the onset temperature at which the melted pattern grains began to be equiaxed; approximately 831 °C, at which the grains were interspersed with oxygen-containing material; and 831–1060 °C, when the grains disappeared, which is a criterion for identifying electrical fires. However, the boundaries remained throughout the thermal environment process. Moreover, the bead pattern demonstrated three metallographic regions: Deep layer (Region I), the intermediate layer (Region Ⅱ), and surface layer (Region Ⅲ). Region I was the most thermally sensitive, in which equiaxed crystals first appeared. Region Ⅲ was the thermal reaction lag zone, in which the typical branching crystals finally disappeared, and Region Ⅱ was intermediate between Regions I and Ⅲ. The results may help fire investigators determine the fire scene temperature stages and provide support for fire evidence extraction.

Axisymmetric vibrations of temperature-dependent functionally graded moderately thick circular plates with two-dimensional material and temperature distribution

In the present paper, free vibration analysis of bi-directional functionally graded circular plates subjected to two-dimensional temperature variation has been presented on the basis of first-order shear deformation theory. The mechanical properties of the plate material are assumed to be temperature-dependent and graded in thickness as well as radial direction. Using the thermal boundary conditions of the plate, the exact solution of two-dimensional heat conduction equation has been obtained by separation of variables technique. The thermoelastic equilibrium equations and equations of motion for such plate have been derived from an energy-based Hamilton’s principle. The generalized differential quadrature method has been applied to compute the numerical values for thermally induced displacements and natural frequencies. MATLAB has been used to obtain these values for clamped and simply supported plates. The influence of thermal environment together with various plate parameters such as power-law index, heterogeneity parameter and density parameter on the natural frequencies has been investigated for the first three modes. The results obtained herein for some special cases are in good agreement with those obtained by other numerical methods. Three-dimensional mode shapes for specified plates have been illustrated.

Influence of Thermal Environment on Simulation State of Abrasion Tester and Compensation Method

Abrasive testing machine can effectively evaluate the wearability of sealed coatings for aircraft engines. High temperature, high speed and harsh working conditions have brought difficulties to the development of testing machines, At the same time, it brings motion error to the test machine feed system. This paper analyzes the error brought by the high temperature environment to the feeding system of the testing machine, and proposes an evaluation and compensation method. Through experimental verification, the method can effectively eliminate the experimental error caused by temperature and evaluate the wearability of the seal coating. Laid the foundation of research and provided accurate test evaluation conditions.

Stability and dynamic analysis of partially cracked thin orthotropic microplates under thermal environment: an analytical approach

An analytical model is proposed to analyze the vibration and buckling problem of partially cracked thin orthotropic microplate in the presence of thermal environment. The differential governing equation for the cracked plate is derived using the classical plate theory in conjunction with the strain gradient theory of elasticity. The crack is modeled using appropriate crack compliance coefficients based on the simplified line spring model. The influence of thermal environment is incorporated in governing equation in form thermal moments and in-plane compressive forces. The governing equation for cracked plate has been solved analytically to get fundamental frequency and central deflection of plate. To demonstrate the accuracy of the present model, few comparison studies are carried out with the published literature. The stability and dynamic characteristics of the cracked plate are studied considering various parameters such as crack length, plate thickness, change in temperature, and internal length scale of microstructure. It has been concluded that the frequency and deflection are affected by crack length, temperature, and internal length scale of microstructure. Furthermore, to study the buckling behavior of cracked plate, the classical relations for critical buckling load and critical buckling temperature is also proposed considering the effect of crack length, temperature, and internal length scale of microstructure.

Impact response and energy absorption of functionally graded foam under temperature gradient environment

As an effective strategy to enhance the energy absorption and impact resistance capacities of foam materials, density-gradient design has been widely proposed as a viable solution. However, the influence of thermal environment on the impact response and energy absorption of functionally graded foam still remains unclear. In the present paper, an analytical model based on the double shock wave theory is presented to examine the impact performance of density-graded foam rods under temperature gradient environments. A density-graded foam with one end supported and the other end struck by a block of mass is presented to evaluate their impact performances. Both the positive and negative density-gradient models with power-law profiles along the axial direction of the foam rod are considered. The proposed theoretical representation is validated against several previous models, including a finite element (FE) simulation. It is demonstrated that the temperature gradient may lead to transformations in the deformation pattern for the positive and negative density-graded foams. Moreover, the temperature gradient can enlarge the impact resistance property in most cases and can reduce the energy absorption capacity of density-graded foams.

Influence of thermal environment on occipital EEG signal amplitude in sedentary activities

Even in sedentary activities, the workload is justifying more accurate studies about its impact on human beings mainly when related to different temperature and humidity conditions. One of these impacts is related to mental activity, which can be studied by the amplitude of Alpha and Beta waves. This study aims to evaluate brain activity in the occipital lobe from the amplitude of the EEG signal (Alpha and Beta waves) and to relate it to different conditions of temperature and relative humidity (RH) in sedentary tasks. Tests were performed under four different conditions (22°C-40%RH, 22°C-80%RH, 32°C-40%RH and 32°C, 80%RH) with 30 volunteers from which 15 were validated. Results suggest that both temperature and humidity influence the amplitude of the EEG signal (Alpha and Beta waves) in both hemispheres. The greatest amplitudes were found whenever environmental temperature and/or relative humidity values were higher. The results are in agreement with other authors.

Effect of crack location on vibration analysis of cracked FGM plate under thermal environment

In the present work, the effect of crack location on the fundamental frequency of functionally graded thin rectangular plate is presented under the influence of thermal environment. The proposed new analytical model is developed using Kirchhoff’s classical plate theory and the crack terms are induced using the well known simplified line spring model (LSM). Thermal moments and in-plane compressive forces are considered to incorporate the effect of thermal environment. The solution for governing equation is obtained using Galerkin's method. The fundamental frequency of the FGM plate as affected by crack length, crack location, uniform rise in temperature and gradient index is presented for simply supported boundary condition. It is found that the results obtained for natural frequencies are significantly affected by rise in temperature, crack length and its location.

Nonlinear magneto-electro-thermo-mechanical response of layered magnetoelectric composites: theoretical and experimental approach

Composite structures exhibiting magnetoelectric (ME) coupling behavior have applications in various fields such as energy harvesting, sensors and actuators. ME coupling behavior is considered to occur by transfer of strain through bonding of the constituent phases of the ME composite. Here, the influence of thermal environment on the constitutive behavior of ferroic phases was examined, firstly by conducting experiments at various temperatures. To mimic the constitutive behavior of ferroic phases, constitutive models were built based on a thermodynamic framework. In order to account for thermal effects, appropriate functions were introduced to the formulation. Model parameters were chosen based on experimental data and simulation studies were performed. The obtained results were found to be in agreement with the experiments. Additionally, an attempt was made to capture the mechanical, electrical, magnetic and ME coupling behavior of composites. To capture the response of ME composites, a homogenization technique was employed along with the proposed constitutive relation for the constituent phases of an ME composite.

A-41 夏期の寝室温熱環境が高齢者と若齢者の終夜睡眠に与える影響

A-41 夏期の寝室温熱環境が高齢者と若齢者の終夜睡眠に与える影響

Influences of thermal environment on fish growth.

Thermoregulation in ectothermic animals is influenced by the ability to effectively respond to thermal variations. While it is known that ectotherms are affected by thermal changes, it remains unknown whether physiological and/or metabolic traits are impacted by modifications to the thermal environment. Our research provides key evidence that fish ectotherms are highly influenced by thermal variability during development, which leads to important modifications at several metabolic levels (e.g., growth trajectories, microstructural alterations, muscle injuries, and molecular mechanisms). In Atlantic salmon (Salmo salar), a wide thermal range (ΔT 6.4°C) during development (posthatch larvae to juveniles) was associated with increases in key thermal performance measures for survival and growth trajectory. Other metabolic traits were also significantly influenced, such as size, muscle cellularity, and molecular growth regulators possibly affected by adaptive processes. In contrast, a restricted thermal range (ΔT 1.4°C) was detrimental to growth, survival, and cellular microstructure as muscle growth could not keep pace with increased metabolic demands. These findings provide a possible basic explanation for the effects of thermal environment during growth. In conclusion, our results highlight the key role of thermal range amplitude on survival and on interactions with major metabolism‐regulating processes that have positive adaptive effects for organisms.

Free vibration of functionally graded quadrilateral microplates in thermal environment

As a first attempt, the influences of thermal environment together with the geometrical parameters and material properties on the free vibration characteristics of the functionally graded (FG) quadrilateral microplates are investigated. The governing equations are based on the modified strain gradient theory (MSGT) together with the first-order shear deformation theory (FSDT) of plates. Both the temperature dependence of the material properties and the initial thermal stresses are included in the mathematical modeling of the problem. The Chebyshev–Ritz method is employed to extract the free vibration eigenvalue equations from the higher-order governing equations. Chebyshev polynomials in conjunction with suitable boundary functions are used as the admissible functions of the Ritz method to handle the microplates with different set of boundary conditions. After demonstrating the fast rate of convergence and the accuracy of the method, the effects of the temperature rise, length scale parameters, material gradient index, and the length-to-thickness ratio, on the free vibration behaviors of skew and symmetric trapezoidal microplates subjected to different boundary conditions are studied.

Thermal effect on free vibration of functionally graded truncated conical shell panels

The influences of thermal environment on the free vibration characteristics of functionally graded (FG) truncated conical panels are investigated based on the first-order shear deformation theory (FSDT). By taking into account both the temperature dependence of material properties, which are assumed to be graded in the thickness direction, and the initial thermal stresses, the equations of motion and the related boundary conditions are derived using Hamilton's principle. The differential quadrature method (DQM) is employed to discretize the equations of motion subjected to any types of classical boundary conditions. After studying the convergence of the method, its accuracy is demonstrated by solving different examples in the limit cases. Then, the effects of the temperature dependence of the material properties and the initial thermal stresses together with the material graded index and the geometrical parameters on the free vibration of the FG truncated conical panels are investigated. It is shown that in addition to the temperature dependence of material properties, the initial thermal stresses have significant effects on the vibrational characteristics of the FG conical shell panels and cannot be ignored.

Investigation on interlaminar shear stresses in laminated composite beam under thermal and mechanical loading

In the present study, the combined effects of thermal and mechanical loadings on the interlaminar shear stresses of both moderately thin and thick composite laminated beams are numerically analyzed. The finite element modelling of laminated composite beams and analysis of interlaminar stresses are performed using the commercially available software package MSC NASTRAN/PATRAN. The validity of the finite element analysis (FEA) is demonstrated by comparing the experimental test results obtained due to mechanical loadings under the influence of thermal environment with those derived using the present FEA. Various parametric studies are also performed to investigate the effect of thermal loading on interlaminar stresses generated in symmetric, anti-symmetric, asymmetric, unidirectional, cross-ply, and balanced composite laminated beams of different stacking sequences with identical mechanical loadings and various boundary conditions. It is shown that the elevated thermal environment lead to higher interlaminar shear stresses varying with the stacking sequence, length to thickness ratio, ply orientations under identical mechanical loading and boundary conditions of the composite laminated beams. It is realized that the magnitude of the interlaminar stresses along xz plane is always much higher than those of along yz plane irrespective of the ply-orientation, length to thickness ratios and boundary conditions of the composite laminated beams. It is also observed that the effect of thermal environment on the interlaminar shear stresses in carbon-epoxy fiber reinforced composite laminated beams are increasing in the order of symmetric cross-ply laminate, unidirectional laminate, asymmetric cross-ply laminate and anti-symmetric laminate. The interlaminar shear stresses are higher in thinner composite laminated beams compared to that in thicker composite laminated beams under all environmental temperatures irrespective of the laminate stacking sequence, ply-orientation and boundary conditions.

Computable negativity in two-mode squeezing subject to dissipation

We study a system of two bosonic fields subject to two-mode squeezing in the presence of dissipation. We find the Lie algebra governing the dynamics of the problem and use the Wei-Norman method to determine the solutions. Using this scheme we arrive at a closed form expression for an infinitely dimensional density operator which we use to calculate the degree of entanglement (quantified by Horodeckis' negativity) between the modes. We compare our result to the known continuous variable entanglement measures. We analyse the conditions for entanglement generation and the influence of thermal environments on the state formed. The problem is relevant, in particular, for understanding of quantum dynamics of coupled optical and/or mechanical modes in optomechanical and nanomechanical systems.