Variation Of Temperature Field Research Articles

Experimental research on characteristics of temperature field distribution of mild moxibustion and sparrow-pecking moxibustion

To explore the temperature field distribution and variation rules during treatment with mild moxibustion and sparrow-pecking moxibustion of TCM. Six healthy subjects were selected. Mild moxibustion and sparrow-pecking moxibustion were exerted at Zusanli (ST 36) respectively, for 25 min. Using infrared thermal imaging instrument, the temperature field distribution was measured during moxibustion at Zusanli (ST 36). The simulated thermometer was adopted to measure the temperature field distribution during moxibustion at the imitated cortex. At 20 min of mild moxibustion and sparrow-pecking moxibustion, the temperature field distribution generated by moxibustion was observed at the imitated cortex and Zusanli (ST 36) separately. The temperature values were collected at the sites 0.7, 2.1 and 3.5 cm far from the center of the moxibustion-exerted places successively, and then the characteristics of temperature field distribution and variation rules were compared between different moxibustion methods at the imitated cortex and Zusanli (ST 36). At 20 min of mild moxibustion and sparrow-pecking moxibustion at Zusanli (ST 36), the temperature field distribution focused on the center of moxibustion-exerted site and the temperature was reduced to all directions and illustrated as a curved surface graph, whereas, the temperature field distribution at the imitated cortex was consistent with that at Zusanli (ST 36). With mild moxibustion, the temperature field was distributed uniformly along the longitudinal temperature gradient; whereas, with sparrow-pecking moxibustion, the longitudinal temperature of the temperature field was greatly different, in which, the maximum temperature and the average temperature were higher than those with mild moxibustion respectively and the first time up to the peak value of sparrow-pecking moxibustion was shorter than that with mild moxibustion. The thermal transfer was presented at the non-moxibustion exerted areas during the moxibustion experiment at Zusanli (ST 36). A distance feature is presented in the temperature field measured by simulated thermometer and generated under suspension moxibustion at Zusanli (ST 36). The warm stimulation effect of sparrow-pecking moxibustion is much more obvious at the moxibustion-exerted center as compared with mild moxibustion and the area of warm stimulation generated by sparrow-pecking moxibustion is more concentrated as compared with mild moxibustion. The radiation energy produced by suspension moxibustion is scattered and attenuated in skin tissue, resulting in a certain temperature gradient in the temperature field. The warm stimulation generated at skin surface by moxibustion has a warming-dredging effect.

Study on characteristics of temperature field in cargo tank during heating of cargo oil

In order to avoid the difficulties of unloading due to natural cooling and solidification of cargo oil in the process of shipping, the cargo oil is heated and insulated. In this paper, based on the heat transfer theory, and the fluid dynamics software FLUENT was used to establish a three-dimensional scale model to simulate the actual heating process of the cargo oil in the oil tank, and the change law of the temperature field of the cargo oil in the oil tank was calculated and analyzed.The results show that the temperature of cargo oil is approximately proportional to the heating time. During the heating process of the cargo oil, the rise of the temperature of the cargo oil leads to the increase of oil fluidity, and the oil above the heat source flows upward along the bulkhead, resulting in vortexes of different sizes. In the same heating time, the external temperature difference is 40 K, the oil temperature rise difference is 1.5 K. The variation of temperature field in the heating process of cargo oil is of engineering significance to improve heating efficiency, reduce operating cost and reduce environmental pollution.

Investigation of the tool influence function neighborhood effect in atmospheric pressure plasma processing based on an innovative reverse analysis method.

Ultra precision optical surfaces can be efficiently manufactured using a computer-controlled optical surfacing (CCOS) process. Based on the chemical reaction, atmospheric pressure plasma processing (APPP) is a promising deterministic CCOS technique and has great application prospect for the figuring processing as well as freeform generation. However, the plasma jet also works as the heat source, leading to the variation of substrate temperature field. This way, the tool influence function (TIF) is continuously changed, which leads to the nonlinear removal characteristic. Especially, it becomes much more complex when considering the neighboring dwell points, because they are thermally interacted. The conventional time-variant TIF model cannot accurately describe the practical TIF changes. In this paper, an innovative reverse analysis method is proposed to derive the practical TIF changes in APPP. First, the special problem of the TIF neighborhood effect is pointed out. The limitation of the conventional TIF model is analyzed with the assisted thermal model. Then, an innovative reverse analysis method is presented to derive the TIF changes from the practical removal, which is demonstrated with the simulation. Further, the proposed method is applied to the analysis of the TIF changes in APPP. To verify its feasibility, the experimental validation is undertaken, which proves its capability of deriving complex TIF changes.

Analysis of time-dependent heat transfer with periodic excitation in microscale systems

• Analytical, experimental and numerical study of heat transfer on microscale. • Time-dependent temperature distribution with periodic excitation. • Penetration depth at which the periodic-thermal excitations are still noticeable. • A round impinging water jet used to cool a surface heated by pulsing laser. • System reaction for time scales and material properties typical for micro-systems. This study investigates time-dependent heat transfer with periodic excitation in micro-scale systems. Specifically, this study sheds light on time and length scales relevant to periodic heat transfer in micro systems. First, a system's substrate is modeled as a slab of finite thickness, in which the heat conduction equation is solved analytically for a periodic temperature boundary condition over the entire range of transient-periodic process. Using the analytical solutions, the system reaction in time is characterized for time scales and material properties typical for micro-systems. A “penetration depth” is defined as a parameter which indicates the maximum distance from the periodically-heated boundary/surface at which the periodic-thermal excitations are still noticeable. Then, as a case study, an experimental device is examined that uses a round, impinging water jet to cool a surface heated by pulsing laser. Finally, a three-dimensional numerical simulation, validated versus experiments, is used to elucidate the system's expected thermal behavior, including spatial and temporal temperature field variation, relevant time scales for measurements, and the spatial distribution of the heat transfer coefficient. It is demonstrated that the analytical findings can serve to characterize the real behavior rather accurately. The findings can assist in the design of systems with unsteady heating, and in future studies aiming at understanding more complex physically-driven transient phenomena, like flow boiling in micro-systems.

Fine tunability of optical gain characteristics of InGaAs/GaAsSb/InAlAs nano-heterostructure under combined effect of field and temperature

The high optical gain of InGaAs/GaAsSb/InAlAs nano-scale heterostructure has motivated us for its further study under variable temperature and electric field. The presented work is devoted to show the impact of variable temperature and electric field on optical gain characteristics of InGaAs/GaAsSb/InAlAs nano-scale heterostructure which has been assumed to grow on lattice matched GaAs substrate. A six band k.p approach has been utilized to optimize the heterostructure in terms of carrier's wavefunctions, local carriers' density in conduction and valence band and dispersion curves followed by calculating momentum matrix elements and the optical gain spectra. According to the calculation results, the increasing range of temperature (having range of 100–300 K at the interval of 50 K) can control the peak gain significantly (6070 cm−1 to 4470 cm−1) with the red shift in wavelength; while enhanced order of electric field at room temperature can control the gain slightly (4470 cm−1 to ~4150 cm−1) with fine red shift in wavelength. The results achieved in this work will definitely prove the method of controlling the gain characteristics as excellent; and the heterostructure studied will be suitable in design of tunable NIR (near infrared) light sources.

Temporal Klein Model for Particle-Pair Creation

This work considers the creation of electron-positron pairs from intense electric fields in vacuum, for arbitrary temporal field variations. These processes can be useful to study quantum vacuum effects with ultra-intense lasers. We use the quantized Dirac field to explore the temporal Klein model. This model is based on a vector potential discontinuity in time, in contrast with the traditional model based on a scalar potential discontinuity in space. We also extend the model by introducing a finite time-scale for potential variations. This allows us to study the transition from a singular electric field spike, with infinitesimal duration, to the opposite case of a static field where the Schwinger formula would apply. The present results are intrinsically non-perturbative. Explicit expressions for pair-creation as a function of the potential time-scales are derived. This work explores the spacetime symmetry associated with pair creation in vacuum: the space symmetry breaking of the old Klein paradox model, in contrast with the time symmetry breaking of the temporal Klein model.

Demonstration of a trapped-ion atomic clock in space

Atomic clocks, which lock the frequency of an oscillator to the extremely stable quantized energy levels of atoms, are essential for navigation applications such as deep space exploration1 and global navigation satellite systems2, and are useful toolswith which to address questions in fundamental physics3-6. Such satellite systems use precise measurement of signal propagation times determined by atomic clocks, together with propagation speed, to calculate position. Although space atomic clocks with low instability are an enabling technology for global navigation, they have not yet been applied to deep space navigation and have seen only limited application to space-based fundamental physics, owing to performance constraints imposed by the rigours of space operation7. Methods of electromagnetically trapping and cooling ions have revolutionized atomic clock performance8-13. Terrestrial trapped-ion clocks operating in the optical domain have achieved orders-of-magnitude improvements in performance over their predecessors and have become a key component in national metrology laboratory research programmes13, but transporting this new technology into space has remained challenging. Here we show the results from a trapped-ion atomic clock operating in space. On the ground, NASA's Deep Space Atomic Clock demonstrated a short-term fractional frequency stability of 1.5×10-13/τ1/2 (where τ is the averaging time)14. Launched in 2019, the clock has operated for more than 12months in space and demonstrated there a long-term stability of 3×10-15 at 23days (no drift removal), and an estimated drift of 3.0(0.7)×10-16 per day. Each of these exceeds current space clock performance by up to an order of magnitude15-17. The Deep Space Atomic Clock is particularly amenable to the space environment because of its low sensitivity to variations in radiation, temperature and magnetic fields. This level of space clock performance will enable one-way navigation in which signal delay times are measured in situ, making near-real-time navigation of deep space probes possible18.

Transport current and magnetization of Bi-2212 wires above liquid Helium temperature for cryogen-free applications

Since the discovery of high temperature superconductors, a possible cryogen-free scenario has always been wished. Nowadays, liquid Helium is running out, and it is likely that the cooling by will be a large part of the costs of any superconducting system. Bi-2212 wires at temperature higher than 4.2 K still show a very high irreversibility field and thus a deep investigation of their properties in such a range of temperature is very useful in order to assess the applicability in high field cryogen-free magnets. Here electrical transport and magnetic properties characterization at variable temperature and magnetic field on our “GDG—processed” wires are reported together with a well-described original approach to calculate the irreversibility field Hirr. This study is devoted to provide reference data on the behaviour of the only isotropic wire for high field application with an eye to the performances at temperatures above 4.2 K.

Flow Rate Measurement of Production Profile Logging Using Thermal Method

This paper presents a kind of thermal flow meter designed to measure downhole fluid flow at production profile logging. A computational fluid dynamics model is established to study the variation of temperature field in Downhole Thermal Flow Meter with medium and input power. The relation curve between heating power and fluid velocity and heating time is determined. According to the theoretical research, the experimental prototype of downhole thermal flow meter is designed and manufactured, and the dynamic experimental research is carried out on the multiphase flow simulation experimental device. The results show that when the power of the heating wire is constant, the temperature of the liquid around the heating wire decreases with the increase of the flow rate, and the resolution of the instrument is obvious when the flow rate is less than 20 m3/d. When the flow rate is constant, the greater the power of the heating wire, the more obvious the response characteristics of the instrument. It has a good response in the whole single-phase oil and single-phase water environment. The research of theoretical and dynamic experimental shows that it is feasible to use downhole thermal flow meter to measure downhole flow. This method will provide a new idea for the measurement of flow in production profile.

Experiment study and refined modeling of temperature field of steel-concrete composite beam bridges

The temperature field and its effect are important issues related to the design and construction of bridges. For steel–concrete composite bridges, the huge difference in thermal performance between steel and concrete makes the temperature field distribution and variation more complicated. In this paper, an indoor baking lamp radiation experiment with controllable parameters is carried out on a group of two steel–concrete composite beam specimens for the study of temperature field. The temperature time-history and distribution laws of the specimen during heating and cooling process are observed and analyzed. Furthermore, a refined numerical model of the solar temperature field of the composite bridge is established and verified by the baking lamp radiation experiment. The proposed refined numerical model of the temperature field of the steel–concrete composite bridge realizes the temperature field analysis of various cross-sections of composite bridges and can automatically consider the shielding effect of the flange on the web, providing a useful tool for the modeling of and analysis of the temperature field of composite bridges.

An enriched finite element method for efficient solutions of transient heat diffusion problems with multiple heat sources

We propose an efficient formulation using the framework of Generalized Finite Element Method (GFEM) for the solutions of transient heat diffusion problems having multiple heat sources in the solution domain. The purpose here is to use minimal computational resources and rely on coarse mesh grids to capture the sharp variations of temperature field. We use Gaussian functions of global nature to enrich the GFEM approximation space which ensure efficient solution in the whole solution domain. To capture steep thermal gradients at multiple locations, a multiplicity of enrichment functions is used and the peaks of enrichment functions are centred at the cores of heat sources. The advantage of this approach is that no further degrees of freedom (DOFs) are added to capture the solution at multiple locations. Besides, the enrichment functions are time-independent; the temporal variation of temperature is embedded in the definition of the enrichment functions. This formulation requires the assembly of system matrix once and only the right-hand side of the system of equations is updated at subsequent time steps which results in a significant reduction in the overall computational time. We consider problems in two-dimensional (2D) and three-dimensional (3D) domains to show the effectiveness of the proposed approach. A reduction of more than 95% in DOFs and more than 80% in computational time is achieved as compared to the h-version of finite element method.

Modelling of vibrations of rotating nanoscale beams surrounded by a magnetic field and subjected to a harmonic thermal field using a state-space approach

In this study, a mathematical model for rotating thermal nanobeams is presented. A system of equations is derived that describes the thermoelastic behaviour of rotating nanoscale beams. The proposed model is based on Eringen’s nonlocal elasticity theory, Euler–Bernoulli's assumptions, and generalized thermoelasticity with two different phase lags. The nanoscale beam material is completely surrounded by an axial magnetic field and exposed to a time-dependent variable temperature field. The Laplace transform in the state-space approach is employed to solve the problem studied. Because of the difficulty in finding the inversion of the Laplace transforms, it was obtained numerically using one of the techniques based on the technique of the Fourier series expansion. The significance of different parameters such as the rotational angular velocity, nonlocal parameter, temperature change, and magnetic field on the nanobeam response has been investigated. Moreover, the results obtained are verified with the corresponding results from the literature.

Experimental investigation on the thermophysical properties of low concentration magnetic colloidal suspensions (nanofluids) with the variations in temperature & magnetic field

The experiments are conducted to investigate the effect of temperature, magnetic field, and nanoparticles on the effective thermophysical properties (thermal conductivity, viscosity and density) of the magnetic nanofluids. The Fe3O4 magnetic nanoparticles are dispersed in the water at various concentrations and the resulted suspensions are assessed in the temperature range 10–70°C and under the presence of an external magnetic field range from 0 to 750 Gauss. The different parameters have observed the significant effects on the thermal conductivity, viscosity and density of these colloidal suspensions. The experiments have revealed that the thermal conductivity is enhanced with nanoparticle concentration, temperature and magnetic field. The new empirical correlations using Buckingham-Pi theorem and analytical approach have been proposed and discussed comprehensively for the effective thermal conductivity for such magnetic suspensions under the presence of a magnetic field. The viscosity of the colloidal suspension is shown significant enhancement with nanoparticle concentration and decrement with increasing temperature. The empirical correlation for the viscosity is reported and elucidates the temperature dependence of the viscosity. However, the density for these suspensions shows only a trivial enhancement with concentrations.

Admittance spectroscopy of dopants implanted in silicon and impurity state-induced AC magnetoresistance effect

A silicon structure doped with Ga using ion implantation has been investigated by admittance spectroscopy. It has been established that the presence of the Ga impurity, along with the B one, in the silicon structure leads to the appearance of the second peak in the temperature dependence of the real part of the impedance (admittance). Moreover, switching-on a magnetic field parallel to the sample plane shifts the singularities in the temperature curve to the high-temperature region. This results in the manifestation of both the positive and negative magnetoresistance effect upon temperature and magnetic field variation. It has been found by the standard admittance spectroscopy analysis of the impedance data that the energy structure of the investigated sample includes two interfacial energy levels ES1(0) = 42 meV and ES2(0) = 69.4 meV. As expected, these energies are consistent with the energies of B and Ga dopants. In a magnetic field, these levels increase by 3 meV for B and 2 meV for Ga, which induces the magnetoresistance effect. It has been demonstrated that the interfacial state-induced magnetoresistance effect can be tuned by ion implantation and dopant selection.

Simulations of micropolar nanofluid-equipped natural convective-driven flow in a cavity

PurposeThis paper aims to focus on the natural convective flow analysis of micropolar nanofluid fluid in a rectangular vertical container. A heated source is placed in the lower wall to generate the internal flow. In further assumptions, the left/right wall are kept cool, while the upper and lower remaining portions are insulated. Free convection prevails in the regime because of thermal difference in-between the lower warmer and upper colder region.Design/methodology/approachThe physical setup owns mathematical framework in-terms of non-linear partial differential equations. For the solution purpose of the differential system, finite volume method is adopted. The interesting features of the flow along with thermal transportation involve both translational and rotational movement of fluid particles.FindingsPerforming the simulations towards flow controlling variables the outputs are put together in contour maps and line graphs. It is indicated that the variations in flow profile mass concentration and temperature field augments at higher Rayleigh parameter because of stronger buoyancy effects. Higher viscosity coefficient implies decrease in flow and thermal transportation. Further, the average heat transfer rate also grows by increasing both the Rayleigh parameter and heated source length.Originality/valueTo the best of the authors’ knowledge, no such study has been addressed yet. Further, the results are validated by comparing with previously published work.

Longitudinal wave analysis of infinite length piezoelectric circular rod based on temperature effect

Piezoelectric elements have been commonly used because of their wide applications in sensors, transducers, and some micro intelligent structures. However, in the fields of aviation, aerospace, and automation, some relevant equipment works in a harsh environment and is susceptible to the temperature change, thereby leading its performances to be greatly affected. Therefore, the problem of nonlinear wave relating to piezoelectric circular rods in different temperature fields is studied by modeling and numerical analysis. Firstly, based on the theory of finite deformation, we take infinite piezoelectric circular rod as a research object and consider the effects of transverse inertia and equivalent Poisson's ratio under the thermoelectric coupling action. Using the Hamilton principle and introducing the Euler equation, the longitudinal wave equation of piezoelectric circular rod is obtained. Secondly, Jacobi elliptic cosine function and Jacobi elliptic sine function expansion method are used to solve the wave equation of the piezoelectric circular rod, and the solitary wave solution and the exact periodic solution of the wave equation are obtained. It is found that the periodic solution can be reduced into a solitary wave solution under certain conditions, and it is proved theoretically that there may be solitary wave stably propagating in a piezoelectric circular rod. Finally, the dispersion curves of different wave velocity ratios and the curves about influences of temperature field on the waveform, amplitude and wave number of the piezoelectric rod are obtained by Matlab. The numerical results show that the wave velocity decreases with the increase of temperature when the wave velocity ratio is constant. Given the temperature is constant, it can be found that with the increase of the ratio, the amplitude of solitary wave gradually increases while the wavelength gradually decreases. In addition, the images obtained show that although temperature change can cause the characteristics of solitary waves to change, the solitary waves are always symmetrical bell shaped waves in the propagation process, reflecting the stability characteristics under the combined action of nonlinear and dispersion effects. Therefore, the variation of temperature field can influence and control some propagation characteristics of solitary waves. Moreover, the wave theory has been widely used in the nondestructive testing of structures and the improving of information transmission quality due to its special stability.

玉龙雪山地区地表三维温度场时空变化分析

玉龙雪山地区地表三维温度场时空变化分析

Influence of Polarization-Maintaining Fibers on Azimuth Transmission Under Variable Temperature and Electric Field

Influence of Polarization-Maintaining Fibers on Azimuth Transmission Under Variable Temperature and Electric Field

Temperature Field Variation Law of Low Exothermic Polymer Grouting Material in Repairing Void Damage of Frozen Soil Subgrade

In this study, the self‐developed grouting mold was used to study the heat release characteristics of different density polymer grouting material under different temperature conditions. The spatial distribution characteristics of the frozen soil subgrade temperature field under the effect of polymer grouting repair were analyzed. Further, the rules governing the temperature change of a frozen soil subgrade monitoring point under the effect of polymer grouting repair were studied. The heat transfer mechanism of polymer grouting material in frozen soil subgrade was revealed. The results showed that in the void region of the frozen soil subgrade, a discontinuity zone appeared in the temperature field distribution isotherm due to the effect of voids; this zone exhibited a layered radioactive distribution along the two sides of the void area. Furthermore, during the exothermic stage of the curing reaction, the temperature distribution isotherms changed from a layered radioactive distribution to a ring distribution that decreased from the inside to outside. During the natural cooling process, the peripheral temperature of the ring isotherm first decreased and a negative temperature ring‐shaped isotherm gradually formed. Finally, the upper boundary of the influence of the heat energy released by the curing reaction on the frozen soil subgrade temperature field was determined to be 30 cm, and the lower boundary was 20 cm.

Study on temporal and spatial variation of temperature field in horizontal freezing and thawing settlement

Artificial freezing method is commonly used in underground engineering excavation, such as mine, foundation pit and subway. The problem of post-construction thaw settlement has attracted more and more attention, but it is difficult to calculate the development law of thaw temperature field of complex frozen curtain by analytical method. Therefore, this paper adopts numerical method to study this problem. In this paper, taking the horizontal freezing construction of a subway connecting passage as an example, the development law of temperature field in the melting process is analyzed, and the results are basically consistent with the measured data. As a general means, numerical simulation is feasible to simulate the development law of temperature field in horizontal melting of complex curtain. The results of this paper can be used to guide the design and construction of artificial freezing.