Effect of non-uniform temperature gradient and magnetic field on onset of Marangoni convection heated from below by a constant heat flux

This paper investigates the effect of non-uniform temperature gradient and magnetic field on Marangoni convection in a horizontal fluid layer heated from below and cooled from above with a constant heat flux. A linear stability analysis is performed. The influence of various parameters on the convection onset is analyzed. Six non-uniform basic temperature profiles are considered, and some general conclusions about their desta- bilizing effects are presented.

Skin Temperature and Body Surface Section in Non-Uniform and Asymmetric Outdoor Thermal Environment

In indoor environments and shady outdoor environments, there is little influence of short-wavelength solar radiation, so a strikingly non-uniform and asymmetric environment is not formed. In outdoor sunny environment, however, shaded areas occur even for the same site of the body, and a remarkable difference in skin temperature is considered to occur under the influence of the short-wavelength solar radiation. The purpose of this study is to clarify the influence of the non-uniform and asymmetric thermal radiation of short-wavelength solar radiation in outdoor environment on the division of the body surface section and the calculation of the mean skin temperature. The skin temperature of the front of the coronal surface, which was facing the sun and where the body received direct short-wavelength solar radiation, and the skin temperature of the rear of the coronal surface, which was in the shadow and did not receive direct short-wavelength solar radiation were respectively measured. The feet, upper arm, forearm, hand and lower leg, which are susceptible to short-wavelength solar radiation in a standing posture, had a noticeable difference in skin temperature between sites in the sun and in shade. The mean skin temperature of sites facing the sun was significantly higher than the mean skin temperature of those in the shade.

Effect of Non-Uniform Temperature Gradient on the Onset of Rayleigh-Bénard Electro Convection in a Micropolar Fluid

The effects of electric field and non-uniform basic temperature gradient on the onset of Rayleigh-Bénard convection in a micropolar fluid are studied using the Galerkin technique. The eigenvalues are obtained for free-free, rigid-free and rigid-rigid velocity boundary combinations and for isothermal and/or adiabatic temperature boundaries. The microrotation is assumed to vanish at the boundaries. A linear stability analysis is performed. The influence of various micropolar fluid parameters and electric Rayleigh number on the onset of convection has been analyzed. One linear and five non-uniform temperature profiles are considered and their comparative influence on onset is discussed.

Effect of Non-Uniform Basic Temperature Gradient on the Onset of Rayleigh-Bénard-Marangoni Electro-Convectionin a Micropolar Fluid

The effects of electric field and non-uniform basic temperature gradient on the onset of Rayleigh-Bénard-Marangoni convection in a micropolar fluid are studied using the Galerkin technique. The eigenvalues are obtained for an upper free/adiabatic and lower rigid/isothermal boundaries. The microrotation is assumed to vanish at the boundaries. A linear stability analysis is performed. The influence of various micropolar fluid parameters and electric Rayleigh number on the onset of convection has been analysed. Six different non-uniform temperature profiles are considered and their comparative influence on onset is discussed.

Influence of Non-uniform Elevated Temperature on the Structural Stability and Strength of Gypsum-Sheathed Cold-Formed Steel Beam Channel Members

The objective of this paper is to computationally explore the structural stability and strength of gypsum-protected CFS(cold-formed steel)beam channel sections under non-uniform elevated temperatures when exposed to standard fire on one side of the panel and subjected to pure bending.When a CFS member is subjected to fire(or thermal gradients)its material properties change-but this change happens around the cross-section and along the length creating a member which is potentially non-uniform and unsymmetrical in its response even if the apparent geometry is uniform and symmetric.Computational finite element models were analyzed in ABAQUS to establish steady-state thermal gradients of interest.Existing test data were utilized to develop the temperature dependence of the stress-strain response.The time-dependent temperature distribution on the cross-sections obtained from heat transfer analysis was later used in the stability and collapse analyses.The stability of the models was explored to characterize how local,distortional,and global buckling of the member evolves under both uniform and non-uniform temperature distributions.Finally,collapse simulations were performed to characterize the strength under pure bending and explore directly the evolution of strength under the influence of non-uniform temperature.

Simulation studies of multi-line line-of-sight tunable-diode-laser absorption spectroscopy performance in measuring temperature probability distribution function

Line-of-sight tunable-diode-laser absorption spectroscopy（LOS-TDLAS） with multiple absorption lines is introduced for non-uniform temperature measurement. Temperature binning method combined with Gauss–Seidel iteration method is used to measure temperature probability distribution function（PDF） along the line-of-sight（LOS）. Through 100 simulated measurements, the variation of measurement accuracy is investigated with the number of absorption lines, the number of temperature bins and the magnitude of temperature non-uniformity. A field model with 2-T temperature distribution and15 well-selected absorption lines are used for the simulation study. The Gauss–Seidel iteration method is discussed for its reliability. The investigation result about the variation of measurement accuracy with the number of temperature bins is different from the previous research results.

New acoustic system for continuous measurement of river discharge and water temperature

In many cases, river discharge is indirectly estimated from water level or streamflow velocity near the water surface. However, these methods have limited applicability. In this study, an innovative system, the fluvial acoustic tomography system （FATS）, was used for continuous discharge measurement. Transducers with a central frequency of 30 kHz were installed diagonally across the river. The system＇s significant functions include accurate measurement of the travel time of the transmission signal using a GPS clock and the attainment of a high signal-to-noise ratio as a result of modulation of the signal by the 10th order M-sequence. In addition, FATS is small and lightweight, and its power consumption is low. Operating in unsteady streamflow, FATS successfully measured the cross-sectional average velocity. The agreement between FATS and acoustic Doppler current profilers （ADCPs） on water discharge was satisfactory. Moreover, the temporal variation of the cross-sectional average temperature deduced from the sound speed of FATS was similar to that measured by a temperature sensor near the bank.

Improving tree health assessment accuracy at low temperatures:considering the effect of trunk ice content on electrical resistance and stress wave tomography

Accurate decay detection and health assessment of trees at low temperatures is an important issue for forest management and ecology in cold areas.Low temperature ice formation on tree health assessment is unknown.Because electric resistance tomography and stress wave tomography are two widely used methods for the detection of tree decay,this study investigated the effect of ice content on trunk electrical resistance and stress wave velocity to improve tree health assessment accuracy.Moisture content,trunk electrical resistance and stress wave velocity using time domain reflectometry were carried out on Larix gmelinii and Populus simonii.Ice content is based on moisture content data.The ice content of both species showed a trend of increasing and then decreasing.This was opposite with ambient temperatures.With the decrease of temperatures,daily average ice content increased,but the range narrowed gradually and both electrical resistance and stress wave velocity increased.Both increased rapidly near 0℃,mainly caused by ice formation(phase change and freezing of free water)in live trees.In addition,both are positively correlated with ice content.The results suggest that ice content should be considered for improving the accuracy of tree decay detection and health evaluation using electric resistance tomography and stress wave velocity methods under low temperatures.

DYNAMICAL FORMATION OF CAVITY FOR COMPOSED THERMAL HYPERELASTIC SPHERES IN NONUNIFORM TEMPERATURE FIELDS

Dynamical formation and growth of compressible thermal-hyperelastic Gent-Thomas cavity in a sphere composed of two inmaterials were discussed under the case of a non-uniform temperature field and the surface dead loading. The mathematical model was first presented based on the dynamical theory of finite deformations. An exact differential relation between the void radius and surface load was obtained by using the variable transformation method. By numerical computation, critical loads and cavitation growth curves were obtained for different temperatures. The influence of the temperature and material parameters of the composed sphere on the void formation and growth was considered and compared with those for static analysis. The results show that the cavity occurs stiddenly with a finite radius and its evolvement with time displays a non-linear periodic vibration and that the critical load decreases with the increase of temperature and also the dynamical critical load is lower than the static critical load under the same conditions.

Experimental Study on Occupant's Thermal Responses under the Non-uniform Conditions in Vehicle Cabin during the Heating Period

The existing investigations on thermal comfort mostly focus on the thermal environment conditions, especially of the air-flow field and the temperature distributions in vehicle cabin. Less attention appears to direct to the thermal comfort or thermal sensation of occupants, even to the relationship between thermal conditions and thermal sensation. In this paper, a series of experiments were designed and conducted for understanding the non-uniform conditions and the occupant＇s thermal responses in vehicle cabin during the heating period. To accurately assess the transient temperature distribution in cabin in common daily condition, the air temperature at a number of positions is measured in a full size vehicle cabin under natural winter environment in South China by using a discrete thermocouples network. The occupant body is divided into nine segments, the skin temperature at each segment and the occupant＇s local thermal sensation at the head, body, upper limb and lower limb are monitored continuously. The skin temperature is observed by using a discrete thermocouples network, and the local thermal sensation is evaluated by using a seven-point thermal comfort survey questionnaire proposed by American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc（ASHRAE） Standard. The relationship between the skin temperature and the thermal sensation is discussed and regressed by statistics method. The results show that the interior air temperature is highly non-uniform over the vehicle cabin. The locations where the occupants sit have a significant effect on the occupant＇s thermal responses, including the skin temperature and the thermal sensation. The skin temperaWa-e and thermal sensation are quite different between body segments due to the effect of non-uniform conditions, clothing resistance, and the human thermal regulating system. A quantitative relationship between the thermal sensation and the skin temperature at each body segment of occupant in real life traffic is presented. The investigation result indicates that the skin temperature is a robust index to evaluate the thermal sensation. Applying the skin temperature to designing and controlling parameters of the heating, ventilation and air conditioning（HVAC） system may benefit the thermal comfort and reducing energy consumption.

Improved Non-uniformity Correction Method for Uncooled Microbolometer

The uncooled microbolometer has a severe temperature requirement for non-uniformity correction. An improved two-point non-uniformity correction method is proposed, which can operate in wider uniform substrate temperatures. This method can control the bias voltage of MOS transistors by memory and DAC to meet two restrictions about responsivity and offset before traditional two-point calibration is implemented. The simulation results seem that this non-uniformity correction can work at uniform substrate temperature with fluctuant range of 4K.

Benchmark evaluation of tomographic algorithms for simultaneous reconstruction of temperature and volume fraction fields of soot and metal-oxide nanoparticles in non-uniform flames

With the growing applications of nanofluid flame, the monitoring and controlling of its combustion process is of paramount importance. Thus, it is necessary to develop diagnosing methods which can simultaneously image important parameters such as temperature and volume fractions of soot, metal-oxide nanoparticles. Tomographic emission spectroscopy is an effective method which has been proposed for this purpose. However, the inversion process was only reported with least-squares QR decomposition(LSQR) so far and there are numerous well-established reconstruction algorithms which have not been utilized yet.Thus, this work aims to perform systematic comparative studies on several representative algorithms for the inversion process. In the simulative studies, algorithms including Tikhonov regularization, algebraic reconstruction technique(ART), LSQR,Landweber algorithm, maximum likelihood expectation maximization(MLEM), and ordered subset expectation maximization(OSEM) were discussed. The effects of the number of iterations, the signal-to-noise ratio, and the number of projections and the calibration error in projection angles on the performance of the algorithms were investigated. Advice on selecting the suitable algorithms under different application conditions is then provided according to the extensive numerical studies.

Research on temperature field of non-uniform heat source model in surface grinding by cup wheel

To address the problems of thermal damage to a workpiece surface caused by the instantaneous high temperature during grinding and the difficulty in monitoring temperature in real time,the temperature field in the case of composite surface grinding by a cup wheel is studied.In order to predict the grinding temperature,considering material removal and grinding force distribution,a nonuniform heat source model with different function distributions in the circumferential and radial directions in the cylindrical coordinate system is first proposed;then,the analytical model is deduced and the numerical model of the temperature field is established based on the heat source model.The validation experiments for grinding temperature field are carried out using a high-definition infrared thermal imager and an artificial thermocouple.Compared to the temperature field based on the uniform heat source model,the results based on the non-uniform heat source model are in better agreement with the actual temperature field,and the temperature prediction error is reduced from approximately 23% to 6%.Thus,the present study provides a more accurate theoretical basis for preventing bums in cup wheel surface grinding.

Non-uniform operative temperature distribution characteristics and heat-source-controlled core-area range of local heating radiators

Heating the whole space,which is currently used in northern China,leads to high energy consumption and substantial pollution.A transition to local heating has the potential to help address this problem.In this paper,the effects of radiator-related parameters(position,power,and size)and room-related parameters(aspect ratio and height)on local heating were studied.Two evaluation indices,the effective coefficient of operative temperature(OTEC)and the effective coefficient of local heating(LHEC),were proposed.In addition,the heat source-control core-area(HSCCA)was proposed,and the effect range of heat sources in the space was evaluated by the attenuation of operative temperature.The findings demonstrated that the radiator position has a greater influence on local heating than size.When the position of the radiator was changed from"close to the inner wall"to"close to the outer wall",the LHEC(the interior one-quarter of room is a local heating zone)was found to decrease by 73%.The size of the radiator,which is close to the inner wall,doubled or quadrupled,and the LHEC increased by 9%and 18%.Moreover,rooms with a larger aspect ratio or small room height were found to be the most optimal for local heating applications.The area of the HSCCA decreased as the position of the radiator approached the outer wall.The findings of this study can be used as a design reference for the radiator when the heating mode changes from"full-space heating"to"local heating".

Possible Impact of Spatial and Temporal Non-Uniformity in Land Surface Temperature Data on Trend Estimation

The present work investigates possible impact of the non-uniformity in observed land surface temperature on trend estimation, based on Climatic Research Unit （CRU） Temperature Version 4 （CRUTEM4） monthly temperature data-sets from 1900 to 2012. The CRU land temperature data exhibit remarkable non-uniformity in spatial and temporal features. The data are characterized by an uneven spatial distribution of missing records and station density, and dis-play a significant increase of available sites around 1950. Considering the impact of missing data, the trends seem to be more stable and reliable when estimated based on data with 〈 40% missing percent, compared to the data with above 40% missing percent. Mean absolute error （MAE） between data with 〈 40% missing percent and global data is only 0.011℃ （0.014℃） for 1900-50 （1951-2012）. The associated trend estimated by reliable data is 0.087℃ decade^-1 （0.186℃ decade^-l） for 1900-50 （1951-2012）, almost the same as the trend of the global data. However, due to non-uniform spatial distribution of missing data, the global signal seems mainly coming from the regions with good data coverage, especially for the period 1900-50. This is also confirmed by an extreme test conducted with the records in the United States and Africa. In addition, the influences of spatial and temporal non-uniform features in observation data on trend estimation are significant for the areas with poor data coverage, such as Africa, while insig-nificant for the countries with good data coverage, such as the United States.

Mulching broad ridges with a woven polypropylene fabric increases the growth and yield of young pear trees ‘Yuluxiang' in the North China Plain

Unlike traditional ridging, mulching broad ridges with a woven polypropylene fabric (WPF) can reduce soil evaporation during the drought season and avoid long saturation time in the root zone of pear trees during the rainy season. In this study, field experiments were conducted from 2017 to 2020 in a pear orchard in the North China Plain to investigate the effects of mulching broad ridges (0.3 m in height and 2 m in width) with WPF on soil temperature and moisture, nitrogen leaching, vegetative and reproductive growth of young pear trees(Pyrus bretschneideri Rehd.‘Yuluxiang’). The experiments involved two treatments, namely, control (traditional no-ridge planting without mulching) and mulching broad ridges with WPF (RM treatment). The results showed that the RM treatment increased soil moisture and temperature and decreased nitrogen leaching, resulting in vigorous growth of the young pear trees. Moreover, the RM treatment increased the tree trunk cross-sectional area and height of the young pear trees by 37%and 8%in 2020, respectively. The nitrate nitrogen content at the soil layer depth of 0-30 cm was significantly higher in the RM than that in control. Furthermore, the RM treatment significantly increased the fruit yield due to larger tree size. In addition, compared with control, significantly higher fruit soluble solid content of RM treatment was detected in 2020. High precipitation (423 mm) occurred during fruit enlargement stage in 2020, RM treatment decreased the rainfall infiltration in the ridge and the soil moisture in root region, resulting in the improvement of fruit quality, compared with control.Therefore, mulching broad ridges with WPF can be implemented to increase soil moisture during drought season, soil temperature, and nitrate nitrogen content, thereby improving the growth and fruit yield of young pear trees. Additionally, it can reduce soil moisture in the root zone during the rainy season and improve the fruit quality of the trees. Finally, it can reduce nitrate nitrogen leaching, thereby reducing environmental pollution.

Non-uniform thermal behavior of single-layer spherical reticulated shell structures considering time-variant environmental factors: analysis and design

Contrary to conventional design methods that assume uniform and slow temperature changes tied to atmospheric conditions,single-layer spherical reticulated shells undergo significant non-uniform and time-variant temperature variations due to dynamic environmental coupling.These differences can affect structural performance and pose safety risks.Here,a systematic numerical method was developed and applied to simulate long-term temperature variations in such a structure under real environmental conditions,revealing its non-uniform distribution characteristics and time-variant regularity.A simplified design method for non-uniform thermal loads,accounting for time-variant environmental factors,was theoretically derived and validated through experiments and simulations.The maximum deviation and mean error rate between calculated and tested results were 6.1℃ and 3.7%,respectively.Calculated temperature fields aligned with simulated ones,with deviations under 6.0℃.Using the design method,non-uniform thermal effects of the structure are analyzed.Maximum member stress and nodal displacement under non-uniform thermal loads reached 119.3 MPa and 19.7 mm,representing increases of 167.5%and 169.9%,respectively,compared to uniform thermal loads.The impacts of healing construction time on non-uniform thermal effects were evaluated,resulting in construction recommendations.The methodologies and conclusions presented here can serve as valuable references for the thermal design,construction,and control of single-layer spherical reticulated shells or similar structures.

Design of a DC Busbar for the ITER PF Converter

The DC busbar is an important component for the ITER PF converter module to connect the converter and the reactor. This paper analyzes different cross-sections and different thermodynamic properties under natural-cooling and water-cooling conditions, and simulation is carried out by the software of the finite element method （FEM）. The result of the analysis shows that the water-cooling method is the better choice for the DC busbar.

Parametric Selection and Continual Combination of Building Surface

A method to reparametrize G retional curve to obtain a C^1 curve is given. A practical G^1 continual connective between adjacent NURUS patches along common guadratic boundary curve is presented in this paper, and a specific algorithm for control points and weights of NURBS patches is discussed.

Accurate Determination for the Energy & Temperature Dependence of Electron Capture CrossSection of Si-SiO_2 Interface States Using a New Method

A new technique for accurate determination of the electron and hole capture cross-sections of interface states at the insulator-semiconductor interface has been developed through measuring the initial time variation in the carrier filling capacitance transient, and full consideration is given to the charge-potential feedback effect on carrier capture process. A simplified calculation of the effect is also given. The interface states have been investigated with this technique at the Si-SiO_2 interface in an n-type Si MOS diode. The results show that the electron capture cross-section strongly depends on both temperature and energy.