Xiangzhen Zhang

• Huazhong University of Science and Technology

In this paper, a three-dimensional mathematical model has been developed to describe the fluid flow and heat transfer process in a weld pool in plasma arc welding using the lattice Boltzmann method. A combined equivalent heat source model is established to consider the key-holing effect. The computational efficiency is greatly improved by using par...

In this paper, phase change material(PCM) structures were testing, then Hot disk method is used to measure the thermal conductivity, specific heat capacity is obtained by comparison measurement, phase change properties is obtained by DSC, PSCP method is used to study the phase change process in restricted space and internal. The result show that: t...

A two dimensional numerical model has been developed to simulate the weld pool behaviors during stationary plasma arc welding (PAW) process with Lattice Boitzmann Method (LBM), especially focusing on the heat transfer and fluid flow with phase change. Based on the energy distribution of practical PAW, the combined heat source model has been improve...

Heat conduction of double-walled carbon nanotubes (DWCNTs) with interstitial additional carbon atoms was investigated using molecular dynamics (MD) simulation method. The interaction between carbon atoms was described by the Adaptive Intermolecular Reactive Empirical Bond Order (AIREBO) Potential. The related phonon density of states (DOS) was anal...

A mesoporous silica substrate consists of uniformly distributed and unconnected spherical pores. Since the pore diameter is less than the characteristic wavelength of thermal radiation, near-field radiative heat transfer cannot be ignored. In this paper, near-field radiation across a spherical pore in mesoporous silica was simulated by employing th...

We investigated thermal transport and thermal rectification in the boron nitride nanoribbons (BNNRs) with triangular vacancy defects in series, by using non-equilibrium molecular dynamics simulation. The analysis was performed on the related phonon wave-packet. Furthermore, the orthogonal test was carried out to compare factors such as the number a...

According to the structure and process characteristics of large-capacity coke oven with multiple-point heat supply, a 3-D mathematical model was established to describe the flow, combustion and heat transfer process in coupled coking and combustion chambers. The numerical solution was obtained. The impacts of multiple-point heat supply on the cokin...

The nanoparticles are easily to aggregate because of high surface energy and non-saturability of single particle. The formation of clustering is self-sustainable, limits the application of nanomaterials. The clustering effect on nanoparticle melting behavior is investigated via molecular dynamics simulations in this paper. Results indicate that a d...

The thermal conductivity of carbon nanopeapods (CNPs) is studied using the linear response Green-Kubo (GK) theory and equilibrium molecular dynamic simulation method in this paper. The interactions of C-C bonding are described by AIREBO potential, and the nonbonding interactions are assumed by Lennard-Jones (L-J) potential. The results show that, C...

A three dimensional mathematical model was proposed to describe the heat transfer and molten flow in plasma arc welding (PAW) process with keyholing effect considered. In the model, a novel dynamic heat source model was constructed by a Gaussian heat flux at the top surface and a developing conical heat source at the lower part. The heat source mod...

In this paper, molecular dynamics simulation was performed to predict the thermal conductivities of ordered mesoporous α-Al2O3. A kind of porous structure was proposed to guarantee the electrical neutrality. Based on the Matsui potential, the nonequilibrium molecular dynamics method adapted by Müller-Plathe was used to calculate the lattice thermal...

According to the structure and process characteristics of regenerator in coking oven, a three dimension mathematical model was built to describe the flowing process in the flue and ramp area, the model was numerical solved and the law of the gas flow in regenerator was revealed, the pressure, flow distribution of the oulet in the flue and ramp area...

The reconstruction of 3D heat transfer model is established based on the analysis of physiological structure of the head. The temperature distribution within the brain is calculated using numerical method. Given the variation of physiological function during fever, we find that the main influencing factors of the temperature distribution are metabo...

Conductive polymers polyaniline (PANI) and polypyrrole (PPy) loaded mesoporous silica (SBA-15) composites are prepared and characterized. The one-dimensional reference bar method and the relevant devices to measure the thermal conductivity are introduced and established. The equivalent pore diameter is proposed to characterize the mesostructures of...

A three dimensional numerical model has been developed to simulate the plasma arc welding (PAW) process, featuring a modified compound volumetric heat source together with enhanced heat transfer, phase change and fluid flows in the melten weld pool driven mainly by surface tension. The new heat source, which can reasonably characterize the keyhole...

Though coking industry is highly energy-consuming and heavily air-pollutant, it has tremendous potential of energy saving and emission reduction. Based on the material balance and heat balance calculation, thermal efficiency of coke oven was calculated and energy consumption of coke oven was analyzed. To make full use of waste heat of coke ovens, s...

In the preparation process of carbon nanotubes, various point defects inevitably come into being in the lattice structures. The defects strongly affect the thermal transport properties of carbon nanotubes. Thermal conduction in carbon nanotube is simulated by using nonequilibrium molecular dynamics method with reactive bond order (REBO) potential....

The theoretical investigation on thermal conductivity of silica nanoparticles was carried out using the relaxation-time method based on Callaway model. Then a model was established to obtain the effective thermal conductivity of the silica-nanoparticle-packed powder by coupling the conduction, radiation in nanopores and contact thermal resistance....

To describe fluid flow, combustion and heat transfer in coke oven, a three-dimensional transient mathematical model with coupled coking and combustion chambers was developed and solved numerically. The calculated central temperature of the coke was compared with measured data. Three different evaporation models were compared. Effects of operational...

In this paper, the mesoporous structural unit of MCM-41 is established first and the equilibrium molecular dynamics (EMD) numerical simulation is performed to obtain the shell thermal conductivity of MCM-41. Then, based on one-dimensional heat transfer analysis, the analytical expression for effective thermal conductivity of MCM-41 is obtained by c...

Based on the analysis of biological heat transfer process for the esophageal cancer local hyperthermia with metal stent and Pennes bio-heat transfer equation, the three-dimension heat transfer model has been established to calculate the transient temperature distribution using the finite element method. The simulation results were in good agreement...

In order to investigate the influence of coupling effect between the temperature gradient and concentration gradient on the diffusion process of magnetic nanoparticles and heat transfer process in tumor, a coupling mathematical model for heat and mass transfer was established based on phenomenological laws in non-equilibrium thermodynamics. The the...

The three-dimensional steady laminar flow of an incompressible non-Newtonian power-law fluid over a rotating infinite disk with heat transfer was studied. The governing partial differential equations, including the continuity equation, the momentum equation and the energy equation, were transformed to ordinary differential equations by utilizing th...

A mathematical model was established to describe complicated heat and mass transport processes in a 90 m-long alumina clinker rotary kiln. The effects of heat absorption and release induced by sintering on the temperature distribution in the rotary kiln were studied by using the chemical dynamics method. It is suggested that the reaction between al...

This work is focused on the steady boundary layer flow and heat transfer near the stagnation point of plane and axisymmetric bodies towards a stretching sheet. The analytical solutions of the velocity and temperature distributions are obtained for the various values of the ratio of free stream velocity and stretching velocity, heat source parameter...

The thermal conductivity of doped carbon nanotubes is investigated by nonequilibrium molecular dynamical simulations. The analysis contains the influencing factors of the atom type, defect density, ambient temperature, the chirality and the length. The results show that the doped boron, nitrogen and potassium atoms leading to the overall thermal co...

The metallurgical nature of production flow was compared between aluminum and iron & steel under structural characteristics of current production flow and energy utilization states in the aluminum industry. The production flow was divided into process sections. The energy structure and energy dissipation disciplines of the aluminum industry were sy...

A mathematical model was developed for a 60 t · h-1 alumina clinker rotary kiln on the comprehensive consideration of the effects of heat transfer and mass transport processes. The model was utilized to study the impact of the moisture content of feeding slurry on the thermal process in the rotary kiln, and to analyze the clinker sintering method b...

Convective heat transfer in metal-foam filled three-dimensional rectangular channels was experimentally and numerically studied. Non-dimensional Darcy and Reynolds number based on the permeability were introduced. And the empirical equations describing convective heat transfer in foam-filled channel were finally obtained. The effects of pore struct...

Based on the present situation of research on the on-line refinery technology and its application in China, the refinery gas distribution in a molten aluminum purifying reactor on the base of the on-line MINT technology was simulated in an Euler-Euler multiphase flow model. Three incidence angles of molten aluminum were used to calculate multiphase...

An incompressible laminar flow in a semi-infinite porous channel with expanding or contracting walls is considered. Following the self-similarity transformation, the Navier-Stokes equations are reduced to a fourth-order non-linear differential equation. The resulting equation is then solved asymptotically for large suction Reynolds number. The infl...

The analytical approximate solution for Marangoni convection is which is induced by variation of surface tension along the liquid of finite thickness presented. The surface tension changes with the variety of temperature. The Marangoni convection boundary layer problem is solved by an efficient transformation and asymptotic expansion technique. The...

A simplified geometrical model of high porosity open-cell metal foams was constructed. A related expression of effective thermal conductivity of the metal foams was derived on the base of the analogy between thermal and electrical resistance at the scale of unit pore. The correlation was further modified by existing experimental data. In addition,...

Marangoni convection induced by surface tension gradient along the liquid of finite thickness was researched. It is assumed that the surface tension is a quadratic function of temperature, the under surface temperature is constant, and the super surface temperature is a linear function of horizontal distance. The Marangoni convection boundary layer...

A mathematical model that considers both microheat and mass transfer and macrotransport phenomena is presented to investigate the unidirectional solidification of a binary NH4Cl-H2O solution. It is shown that the solidus and liquidus locations predicted by the numerical coupling calculation are close to the experimental data. The variation of solut...

In the light of such problems as a big overshoot and a high oscillation frequency etc. currently existing in the temperature control of a heating furnace, on the basis of the development of intelligent control theory and by combining the expert, fuzzy and neural network control in the above control theory with PID (Proportional-Integral-Differentia...

By an efficient transformation, asymptotic expansion and Pade approximant technique, the analytical approximate solution for boundary layer flow problem with the power law velocity is presented. The results were compared with the numerical ones in the literature for different velocity parameters. The associated transfer mechanism is analyzed in det...

A long-standing thermal transport problem is the analytical determination of the effective thermal conductivity in composite materials. Based on the thermal resistance model and integration method, two theoretical expressions for the effective thermal conductivity in two-phase composite materials in which the dispersed phase consists of spheres or...

The coke descending behavior in a CDQ cooling shaft is studied experimentally by means of a tracing method with a digital camera. For three different blast-caps, the law of coke flow is studied under five conditions of coke charge. The experimental results show that, for the sake of the uniformity of the coke burden descending, a blast-cap with ell...

Based on the anatomic data and fractal theory, the vascular tree model of forearms similar to actual vessel was established, and then the 3D heat transfer model of forearms based on the actual vessel anatomic structure was created. The model was analyzed and investigated with finite element method to explore the influential factors such as dimensio...

In this article, a numerical model that considers not only the micro heat and mass transfer but also two-dimensional macro scale momentum, energy and species transport is presented to investigate the unidirectional solidification of a binary NH 4Cl-H 2O solution. Further analysis is made to discuss the effect of convection on the growth of crystals...

The coke descent in the cold model of CDQ cooling chamber was studied by means of tracing method with digital camera. For three different blast-cups, the law of coke descent was studied under five conditions of coke charging. The results showed that, elliptical blast-cup cross is better than low or high located circular blast-cups; coke charge patt...

A mathematical model has been built to numerically predict the thermal history of thin slab during CSP (compact strip process) rolling. To estimate the temperature distribution in the slab more accurately, the mathematical model combines heat transfer in the slab, in the roll, and at the roll-slab interface during bite. The numerical results agree...

A steady-state, two-dimensional numerical model has been used to describe coupled liquid steel's turbulent flow and heat transfer with solidification for Fe-C binary alloy in a crystallizer of inverse casting. The solid-liquid phase change phenomena have been modeled by using continuum formulations and considering the mushy zone as porous media. Th...

A theoretical analysis for the laminar boundary layer flow of a non-Newtonian fluid on a continuous moving flat plate with surface strong suction/blowing is made. The types of potential flows necessary for similar solutions to the boundary layer are determined and both analytical and numerical solutions are presented. It is shown that the solution...

Bifurcation solutions are numerically presented for reverse flow boundary layer equations with special suction/injection by utilizing similarity transformation and shooting technique. The results indicate that both superior solution and inferior solution are noticeable. The skin friction and shear stress for the superior solution decrease with the...

A suitable similarity transformation is introduced to reduce the laminar boundary layer equations of power law fluids to a class of singular nonlinear two-point boundary value problems. The skin friction and shear stress distributions for boundary layer flow over a moving flat plate are investigated by utilizing the shooting technique. Results indi...

The stratigraphic variations in nannoflora observed in the two deep-sea cores recovered from the offshore Western Australia revealed a sequence of paleoceanographic changes for the last 250 kyr. The dominance of small placolith taxa in the upper-photic flora indicates continuous mild upwelling for the isotope stages 7-5 in this region. The most imp...

Spectroscopic and laser-pumped laser studies of Nd3+-doped LiKYF5 and LiKGdF5 are reported. The optical absorption and photoluminescence spectra are strongly polarised, the sense of polarisation of the , absorption near 800 nm being opposite to that of the laser emission near 1.05 μ. At ambient temperature (∼ 300 K) the luminescence decay times of...

© 1997 Optical Society of America

Nd3+ doped Sr5(PO4)3F, or Nd:SFAP, has been demonstrated1-3 to be an efficient, low threshold material for 945 nm, 1.059 µm and 1.328 µm laser operation originating from the three transitions between 4F3/2 and 4I9/2, 4I11/2, 4I13/2 manifolds, respectively. Nonlinear frequency conversion techniques have been applied to generate blue2, green4, orange...

Lamp‐pumped laser performance of Nd³⁺‐doped strontium fluorapatite, Sr 5 (PO 4 ) 3 F or S‐FAP, has been characterized and compared with that of Nd³⁺‐doped yttrium aluminum garnet (YAG) at both 1.06 and 1.3 μm. Nd³⁺:S‐FAP was found to exhibit lower thresholds and lower slope efficiencies than Nd³⁺:YAG. The...

Simultaneous lasing at 1.059 and 1.328 µm has been demonstrated in Nd3+ doped strontium fluorapatite, Sr5(PO4)3F or S-FAP, in lamp-pumped operation. More than 1 joule of pulsed output energy has been achieved at each laser line. 589 nm laser emission has been demonstrated through the sum-fiequency generation of these two wavelengths.

A room temperature, diode-laser-pumped 945 nm laser has been demonstrated in Nd3+ doped Sr5(PO4)3F. Blue laser emission at 472.5 nm has been demonstrated via the intracavity second harmonic generation of this wavelength.

The luminescence properties of Cr³⁺ ions and the energy transfer between Cr³⁺ and Nd³⁺ ions have been studied quantitatively in yttrium aluminum garnet (YAG). The energy level diagram and the emission spectrum of ⁴T 2 →⁴A 2 transition of Cr³⁺ ions were calculated in this crystal usin...

Strong blue emissions have been observed in fluoride crystals, such as ${\mathrm{LiYF}}_{4}$, ${\mathrm{BaY}}_{2}$${\mathrm{F}}_{8}$, and ${\mathrm{KYF}}_{4}$, codoped with ${\mathrm{Tm}}^{3+}$ and ${\mathrm{Yb}}^{3+}$ when excited into the ${\mathrm{Tm}}^{3+}$ $^{3}$${\mathit{F}}_{4}$ state at $\sim${}780 nm. Energy transfer from ${\mathrm{Tm}}^{3...

Lasing of Nd3+ ions in different crystallographic sites of KYF4 has been demonstrated to occur at different wavelengths. Low threshold, high efficiency lasing performance at 1041 and 1302 nm were achieved under selective pumping conditions. The stimulated emission cross section at 1041.2 nm was estimated to be 2.6×10−19 cm2 and the radiative lifeti...

High slope efficiency and low threshold laser performance have been achieved for both long pulsed and cw operation at 1.065 μm in Nd³⁺‐doped strontium fluorovanadate crystal, Nd³⁺:Sr 5 (VO 4 ) 3 F, when pumped by narrow band pulsed Cr:LiSAF and cw Ti:sapphire lasers. However, there are inequivalent Nd³⁺ sites in the...

High efficiency, low threshold laser performance of Nd³⁺ doped Sr 5 (PO 4 ) 3 F, or S‐FAP, crystals has been demonstrated. Its performance and properties compared with commercially available Nd:YVO 4 indicate that Nd:S‐FAP is an outstanding medium for diode pumped laser applications at both 1.059 and 1.328 μm.

Systematic investigations of the effect of self-absorption on the dynamic and steady-state spectroscopic properties in ruby have been carried out at different temperatures (from approximately 130 to 500 K) using a long, pink laser rod. At about 140 K,the lengthening of decay times of the R lines reached a maximum and then decreased with increasing...

Temperature and Yb3+ Concentration dependences of the Ho3+ to Yb3+ energy transfer process in KYF4 are reported. The energy transfer rate from Ho3+ to Yb3+ increases as T4 at low temperatures and depends quadratically on Yb3+ concentration. The results are explained by a one-phonon-assisted nonradiative energy transfer process with an electric dipo...

The effect on Nd3+ Stark levels of substituting Gd for Y in YLiF4, KLiYF5, and YVO4 laser crystals is slight, as demonstrated in our spectra and in our best-fit crystal-field parameters. Gd-based crystals maintain the spectral properties of Y-based crystals while allowing for larger Nd concentrations.

Citation P. Hong, X. X. Zhang, G. Loutts, R. E. Peale, H. Weidner, M. Bass, B. H. T. Chai, S. A. Payne, L. D. DeLoach, L. K. Smith, and W. F. Krupke, "Lasing and Spectroscopic Characteristics of a New Nd Laser Crystal - Strontium Fluorovanadate," in Advanced Solid State Lasers, T. Fan and B. Chai, eds., Vol. 20 of OSA Proceedings Series (Optica...

Citation B. H. T. Chai, G. Loutts, J. Lefaucheur, X. X. Zhang, P. Hong, M. Bass, I. A. Shcherbakov, and A. I. Zagumennyi, "Comparison of Laser Performance of Nd-Doped YVO4, GdVO4, Ca5(PO4)3F, Sr5(PO4) 3F and Sr5(VO4)3F," in Advanced Solid State Lasers, T. Fan and B. Chai, eds., Vol. 20 of OSA Proceedings Series (Optical Society of America, 1994...

The article presents a report on the low threshold, high efficiency lasing of calcium fluorapatite crystals (FAP) doped with Nd3+. The FAP crystals were grown using the Czoralski method. The pulsed and continuous wave laser pumping were analyzed using Ti:sapphire laser for cw pumping and Cr:LiSAF laser to achieve pulse excitation. The pulsed slope...

Lattice vibrations of oriented GdLiF4 and YLiF4 single crystals are studied by polarized Raman spectroscopy. The Raman spectra show identical symmetry properties in both materials implying that the vibrational modes of the new laser crystal GdLiF4 have the same irreducible representation of the point group as in YLiF4. The substitution of Gd3+ for...

Upconversion laser can potentially provide light sources in the blue-green region.

Energy transfer from Ho³⁺ to Yb³⁺ has been demonstrated in fluoride crystals such as KYF 4 , BaY 2 F 8 , and LiYF 4 . This transfer was found to occur above a certain temperature and its efficiency increases with temperature. It accounts for the thermal quenching of green emission from upconverted Ho³⁺ and partly ex...

Cr⁴⁺‐doped Y 2 SiO 5 and Ca 2 Al 2 SiO 7 have been investigated as broadband, solid state saturable absorbers. Saturation properties in the near infrared as well as a demonstration of tunable, passive Q switching of a flash‐lamp pumped Cr:LiSAF laser are discussed.

A comprehensive investigation on the spectroscopic properties and laser performance of Nd³⁺ doped GdLiF 4 (GLF), a new laser crystal, is reported. Our high resolution absorption and emission spectra for GLF are nearly identical to those of Nd:LiYF 4 (YLF), a well known laser crystal, strongly suggesting that the two crystals are isostruc...

Laser action of Nd³⁺ doped GdLiF 4 (GLF) has been demonstrated for both pulsed and cw laser pumped operation. A slope efficiency of 60% was obtained in either manner of operation. The spectroscopic properties and laser performance of Nd:GLF are very similar to those of Nd:YLF. GLF, on the other hand, can be doped with much higher Nd<sup>...

Citation X. X. Zhang, M. Bass, J. Lefaucheur, A. Pham, A. B. Villaverde, and B. H. T. Chai, "Laser Performance of a New Laser Crystal - Nd:GdLiF4," in Advanced Solid State Lasers, A. Pinto and T. Fan, eds., OSA Proceedings Series (Optical Society of America, 1993), paper NL2. http://www.opticsinfobase.org/abstract.cfm?URI=ASSL-1993-NL2

A recent comparison of Yb, Ho upconversion energy transfer in different fluoride crystals has been performed[1]. The purpose was to demonstrate the promise of Yb,Ho:KYF 4 as a green upconversion laser as compared with similarly doped BaY 2 F 8 (BYF) and YLiF 4 (YLF). We compare here high resolution, low temperature absorption spectra for the three...

Recently, there is a renewed interest in obtaining short wavelength solid state lasers through upconversion schemes. Yb sensitized upconversion energy transfer is specially attractive for this purpose because of the ability of high power InGaAs diode lasers to pump Yb. Yb, Ho upconversion energy transfer is relatively simple compared to upconversio...

We have found that the Yb → Ho upconversion process in KYF 4 (KYF) is much more efficient than in either BaY 2 F 8 or YLiF 4 [1] under the same doping conditions. Long lifetime, low phonon energy, weak self-absorption, and some other unique spectroscopic features make KYF a promising host for an Yb, Ho upconversion green laser. In order to optimize...

The spectroscopy and lasing properties of several Cr ⁴⁺ doped crystals and glasses are presented. Included is a discussion of the intensity dependence of the broad band, Cr ⁴⁺ absorption.

Laser action in Cr⁴⁺ doped yttrium‐orthosilicate Cr⁴⁺:Y 2 SiO 5 cooled to 77 K was demonstrated for the first time with 1064 and 532 nm pumping from a pulsed Nd:YAG laser and broad band ( 840 nm) pumping from a Q‐switched Cr:LiSAF laser.

Laser action in Cr4+ doped yttrium-orthosilicate Cr : Y2SiOg (Cr:YSO) cooled to 77 OK was demonstrated for the f irst time with 1064nm and 532nm pumping from a pulsed Nd:YAG laser and broadband (@ 840nm) pumping from a Q-switched Cr:LiSAF laser.

Spectroscopic studies of Cr4+ ions in different hosts are reported. Absorption and fluorescente spectra of Cr:Y2Si05,the newest member of the Cr4+ doped laser crystals are presented. Low temperature luminescence data in the near inf rared (NIR) has shown evidence of two types of emissions from both Cr:Y2Si05 and Cr:Ca2A12SiO7 in the 1200 nm band. T...

The effective phonon density of states of MgO: V2+ is obtained from the emission vibronic structure of the V2+ impurity ion under the assumption that the vibronic transition is mainly a single-phonon process. The validity for doing so is supported by the consistent fitting of the temperature dependences of the width and the shift of the zero-phonon...

The temperature dependences of lifetimes and absolute intensities of the single-ion and pair lines of heavily doped ruby are given. Thermalization of the R and N levels is seen above ≈ 100 K, as shown by the identical lifetimes for all emissions. Both the R and N intensities and lifetimes increase with increasing temperature above this thermalizati...