Effect of thickness on magnetic properties of single domain GdBCO bulk superconductors

To study the influence of thickness on the magnetic properties of ReBCO(Re = Y, Gd, Sm, Nd, etc.) bulk superconductors, a single domain gadolinium barium copper oxide(GdBCO) bulk superconductor fabricated by the Re + 011 top seeded infiltration growth(Re + 011 TSIG) method was continuously sliced along the bottom to obtain samples of different thickness. The levitation force and attractive force of these samples were tested at 77 K in the zero-field-cooled(ZFC)state. It is found that as the sample thickness decreases, the levitation force decreases gradually whereas the attractive force increases. This is related to the varied ability to resist the penetration of magnetic field occasioned by varying sample thickness, which are deeply revealed by combining with the characteristics of the non-ideal type-II superconductor. Further,the levitation force exhibits a trend of slow initial change followed by rapid change, which may be attributed to the growth of the sample. Measurement of the trapped field shows that a similar distribution of trapped field at the top and bottom surfaces can be achieved by removing some materials from the bottom of the bulk. These results provide a reference for meeting the actual requirements of ReBCO bulks of different thicknesses and greatly contribute to practical designs and applications.

Controlled Synthesis and Application of α-Al_2O_3 for Lu_3Al_5O_(12): Ce^(3+) Green Spherical Phosphors

Al_2O_3 powders with different morphologies,namely fibrous,sheet-like,and spherical,were prepared by the hydrothermal-thermolysis method.Subsequently,polycrystalline,transparent cerium doped lutetium aluminum garnet(Lu_3Al_5O_(12):Ce^(3+))green phosphors were synthesized by high temperature solidstate method using commercial lutetium(III)oxide,cerium(III)oxide,and as-prepared Al_2O_3 powders with different morphologies.The phases,morphologies,and photoluminescent properties of the prepared phosphors were investigated by X-ray diffraction(XRD),scanning electron microscopy(SEM),and photoluminescence spectroscopy(PL).Moreover,the influences of the morphologies ofα-Al_2O_3 on the types of crystal structure,morphologies,and photoluminescent properties of LuAG:Ce^(3+)green phosphors were investigated.The results indicated that the morphologies and particle sizes of theα-Al_2O_3 powders could be controlled by the additives and parameters.Notably,the sphericalα-Al_2O_3 powders with good dispersibility were found to be the excellent base materials of LuAG:Ce^(3+)green phosphors for white light emitting diodes.

Laser Cladding Fe-Al-Cr Coating with Enhanced Mechanical Properties

Dense Fe-Al-Cr coatings with approximately 50 μm in thickness are successfully prepared on the 1045 carbon steel substrates via a laser cladding process. Proper Cr content(5 at% Cr) will lead to decrease in the melting point, and improves the viscosity of the liquid and the nucleation rate of the molten pool, leading to refining grains of the solidification structure. As a result, the Fe-29 Al-5 Cr laser cladding layer exhibits the best hardness, plasticity properties, and wear resistance at 400 °C. Excessive Cr for the Fe-29 Al-7.5 Cr coating leads to the formation of Cr2 Al in the grain boundaries and thermal vacancies during the solidification process, resulting in inferior mechanical properties and poor tribological behavior.

Studies of a combined way of flame stability in ramjet combustor

numerical simulation was conducted to study the influence of bleeding. The Euler-Lagrange method was used to investigate the two-phase turbulent combustion flow. Standard k-ε turbulent model was adopted in the continuous phase simulation and particle-trajectory model was adopted in the dispersed phase simulation. The results demonstrates: air bleeding can improve the flow field after the strut and the stability of trapped vortex in the cavity; change of bleeding temperature has little effect on the total pressure recovery coefficient and significant effect on combustion efficiency; When fuel-air ratio changes, the combustor performs better in a lean oil state.

Enhancement of Heat-Resistance of Carbonyl Iron Particles by Coating with Silica and Consequent Changes in Electromagnetic Properties

Silica-coated carbonyl iron particles(CIPs) are fabricated with the Stober method to improve their heat-resistance and wave-absorption properties. The morphology, heat-resistance, electromagnetic properties and microwave absorption of raw-CIPs and silica-coated CIPs are investigated using a scanning electron microscope, an energy dispersive spectrometer, a thermal-gravimetric analyzer, and a network analyzer. The results show that the heat-resistance of silica-coated CIPs is better than that of raw CIPs. The reflection losses exceeding-10 dB of silica-coated CIPs are obtained in the frequency range 9.3-12.4 GHz for the absorber thickness of 2.3 mm, and the same reflection losses of uncoated CIPs reach the data in the lower frequency range for the same thickness. The enhanced microwave absorption of silica-coated CIPs can be ascribed to the combination of proper electromagnetic impedance match and the decrease of dielectric permittivity.

High-efficiency and pollution-controlling in-situ gasification chemical looping combustion system by using CO_2 instead of steam as gasification agent

Using CO_2 as gasification agent instead of steam in in-situ coal gasification chemical looping combustion(i G-CLC)power plant can eliminate energy consumption for steam generation, thus obtaining higher system efficiency. In this work, a comparative study of iG-CLC power plant using steam and CO_2 as gasification agent is concentrated on. The effects of steam to carbon ratio(S/C) and CO_2 to carbon ratio(CO_2/C) on the fuel reactor temperature,char conversion, syngas composition and CO_2 capture efficiency are separately investigated. An equilibrium carbon conversion of 88.9% is achieved in steam-based case as S/C ratio increases from 0.7 to 1.1, whereas a maximum conversion of 84.2% is obtained in CO_2-based case with CO_2/C ranging from 0.7 to 1.1. Furthermore the effects of oxygen carrier to fuel ratio(φ) on system performances are investigated. Increasing φ from 1.0 to1.4 helps to achieve char conversion from 75.9% to 88.9% in steam-based case, by contrast the char conversion can achieve 66.3%–84.2% in CO_2-based case within the same φ range. In terms of iG-CLC power plant, recycling partial CO_2 to the fuel reactor improves the overall performance. Approximately 3.9% of net power efficiency are increased in CO_2-based plant, from steam-based plant. Higher CO_2 capture efficiency and lower CO_2 emission rate are observed in CO_2-gasified iG-CLC power plant, expecting to be 90.63% and 85.18 kg·MW-1·h-1,respectively.

Coherent Control of High Harmonic Generation Driven by Metal Nanotip Photoemission

Steering ultrafast electron dynamics with well-controlled laser fields is very important for generation of intense supercontinuum radiation.It can be achieved through coherent control of the symmetry of the interaction between strong-field laser fields and a metal nanotip.We employ a scheme of two-color laser pulses combined with a weak static field to realize the control of a single quantum path to generate high harmonic generation from a single solid-state nanoemitter.Moreover,a smooth and ultrabroad supercontinuum in the extreme ultraviolet region is obtained,which can produce a single attosecond pulse.Our findings are beneficial for efficient generation of isolated sub-100 as XUV pulses from solid-state sources.

Effect of tongue clearance on hydraulic performance of double support vortex pump

In order to study influence of tongue clearance on the hydraulic performance of double support vortex pump,three dimensional flow model with symmetric variable size tongue clearance was established by changing section parameter of tongue clearance,and applied to numerically simulate the steady inner flow in a vortex pump based on fixed working conditions and impeller through ANSYS FLUENT.The numerical results show the influence of tongue channel with two sections(non-uniform and uniform sections)on flow field characteristics in vortex pump.Firstly,the variation of tongue channel section changes the vortex structure distribution in circumferential flow channel.Specifically the spiral forward vortex structure in the circumferential direction shifts to large radius side with increasing tongue width.Secondly,the circumferential velocity gradient and axial pressure gradient both diminish with the increase of the tongue section,and the inlet/outlet pressure difference and velocity distribution also reduce with increasing tongue channel section.Finally,for vortex pump with non-uniform section of tongue channel,the head diminishes and the efficiency remains constant approximately with the increase of the tongue width,while the head and the efficiency both diminish for uniform section of tongue channel.

Angle-resolved spectra of the direct above-threshold ionization of diatomic molecule in IR + XUV laser fields

The direct above-threshold ionization(ATI) of diatomic molecules in linearly-polarized infrared and extreme ultraviolet(IR+XUV) laser fields is investigated by the frequency–domain theory based on the nonperturbative quantum electrodynamics. The destructive interference fringes on the angle-resolved ATI spectra, which are closely related to the molecular structure, can be well fitted by a simple predictive formula for any alignment of the molecular axis. By comparing the direct ATI spectra for monochromatic and two-color laser fields, we found that the XUV laser field can both raise the ionization probability and the kinetic energy of the ionized electron, while the infrared(IR) laser field can broaden the energy distribution of the ionized electron. Our results demonstrate that, by using IR+XUV two-color laser fields, the angle-resolved spectra of the direct ATI can image the structural information of molecules without considering the recollision process of the ionized electron.

Analytical Higher-Order Model for Flexible and Stretchable Sensors

The stretchable sensor wrapped around a foldable airfoil or embedded inside of it has great potential for use in the monitoring of the structural status of the foldable airfoil.The design methodology is important to the development of the stretchable sensor for status monitoring on the foldable airfoil.According to the requirement of mechanical flexibility of the sensor,the combined use of a layered flexible structural formation and a strain isolation layer is implemented.An analytical higher-order model is proposed to predict the stresses of the strain-isolation layer based on the shear-lag model for the safe design of the flexible and stretchable sensors.The normal stress and shear stress equations in the constructed structure of the sensors are obtained by the proposed model.The stress distribution in the structure is investigated when bending load is applied to the structures.The numerical results show that the proposed model can predict the variation of normal stress and shear stress along the thickness of the strain-isolation(polydimethylsiloxane)layer accurately.The results by the proposed model are in good agreement with the finite element method,in which the normal stress is variable while the shear stress is invariable along the thickness direction of strain-isolation layer.The high-order model is proposed to predict the stresses of the layered structure of the flexible and stretchable sensor for monitoring the status of the foldable airfoil.

Phase Transition and Quasinormal Modes for Spherical Black Holes in 5D Gauss–Bonnet Gravity

We study the quasinormal modes(QNMs) of massless scalar perturbations to probe the van der Waals like SBH/LBH phase transition of anti-de Sitter black holes in five-dimensional(5D) Gauss–Bonnet gravity. It is found that the signature of this SBH/LBH phase transition is detected when the slopes of the QNMs frequency change drastically and differently in small and large black holes near the critical point. The obtained results further support that the QNMs can be a dynamic probe to investigate the thermodynamic properties in black holes.

Factors Affecting Box Office during Broad Spring Festival Based on Partial Least Squares Regression

The box office during the later Spring Festival shows an attractive prospect.This paper studied the factors affecting total box office during the broad Spring Festival which is from the Spring Festival to the Lantern Festival.Data of films released during the broad Spring Festival from the years 2016 to 2019 in China were gathered,and the impact of eight explanatory variables on the box office during the broad Spring Festival was empirically analyzed by partial least squares(PLS)regression with software SIMCA.The results suggest that word-of-mouth has the most positive effect on the box office during the broad Spring Festival.Later propaganda has a positive effect,while early promotion has a negative effect on the box office.Director’s influence has a positive effect,while actor’s influence does not contribute much to the box office.Length of the trailer has a negative effect.The film format of 2D or 3D doesn’t contribute much to the box office.

Review on typical applications and computational optimizations based on semiclassical methods in strong-field physics

The semiclassical method based on Feynman’s path-integral is in favor of uncovering the quantum tunneling effect,the classical trajectory description of the electron, and the quantum phase information, which can present an intuitive and transparent physical image of electron’s propagation in comparison with the ab initio time-dependent Schr ¨odinger equation.In this review, we introduce the basic theoretical concepts and development of several semiclassical methods as well as some of their applications in strong-field physics. Special emphasis is placed on extracting time delay on attosecond scale by the combination of the semiclassical method with phase of phase method. Hundreds of millions of trajectories are generally adopted to obtain a relatively high-resolution photoelectron spectrum, which would take a large amount of time. Here we also introduce several optimization approaches of the semiclassical method to overcome the time-consuming problem of violence calculation.

Technical Analysis of Green Construction Management of Large Public Buildings

With the development of the times and the improvement of the economic level,the people’s ideological consciousness has gradually changed,driven by the scientific concept of development and the concept of sustainable development,the people have been able to realize that,traditionally,the extensive economic model has led to more serious damage to the environment,and caused a certain degree of resource waste,but also endangered human health.As a result,the concept of healthy living has received more and more widespread attention.The construction industry as an important pillar of China’s economic development,but also the implementation of the concept of sustainable development in China is one of the key points for the implementation of green construction of large public buildings,it is necessary to strengthen the management of technology,so in this paper,will be the main green construction of large public buildings management technology analysis work.

Research on the Cultivation Mode of College Students'Innovation and Entrepreneurship Education under the Background of"Internet plus"

Colleges and universities are an important position to cultivate high-quality talents.In order to cultivate a group of comprehensive talents with professional skills,post practice skills and high Internet literacy for the society,it is necessary to fully combine the current“Internet plus”background and actively innovate and reform the talent cultivation mode of entrepreneurship education for college students.

A Brief Analysis of Shannxi Cuisine's English Translation-Taking Menu Translation as an Example

Dissemination of Chinese culinary culture is important for Chinese culture to go global.Shannxi,a western province of China,features abundant cuisine which is representative of Shannxi local's lifestyle.However,there are many spelling mistakes and other translation mistakes in some time-honoured Chinese restaurants5 English menu.Appropriate translation strategies,including domestication,fbreignization and Pinyin,a phonetic transcription system for Chinese characters,should be adopted to explore practical and feasible translation of the culinary culture.

Gravitational decoupling for hairy black holes in asymptotic AdS spacetimes

In this study,the gravitational decoupling approach via extended geometric deformation is utilized to generate analytical black hole solutions owing to its simplicity and effectiveness.Considering the external fields surrounding Schwarzschild AdS black holes,we derive hairy black hole solutions in asymptotic AdS spacetime,satisfying the strong and dominant energy conditions.Moreover,we find that if the black hole spacetime is a fluid system,the fluid under each of these conditions is anisotropic.