Internal electric field modulation by copper vacancy concentration of cuprous sulfide nanosheets for enhanced selective CO_(2) photoreduction

Although the internal electric field(IEF)of photocatalysts is acknowledged as a potent driving force for photocharge separation,modulating the IEF intensity to achieve enhanced photocatalytic performances remains a challenge.Herein,cuprous sulfide nanosheets with different Cu vacancy concentration were employed to study IEF modulation and corresponding direct charge transfer.Among the samples,Cu_(1.8)S nanosheets possessed intensified IEF intensity compared with those of Cu_(2)S and Cu_(1.95)S nanosheets,suggesting that an enhanced IEF intensity could be achieved by introducing more Cu vacancies.This intensified IEF of Cu_(1.8)S nanosheets induced numerous photogenerated electrons to migrate to its surface,and the dissociative electrons were then captured by Cu vacancies,resulting in efficient charge separation spatially.In addition,the Cu vacancies on Cu_(1.8)S nanosheets accumulated electrons as active sites to lower the energy barrier of rate-determining step of CO_(2)photoreduction,leading to the selective conversion of CO_(2)to CO.Herein,the manipulation of IEF intensity through Cu vacancy concentration regulation of cuprous sulfide photocatalysts for efficient charge separation has been discussed,providing a scientific strategy to rationally improve photocata lytic performances for solar energy conversion.

Distribution of Electrical Field Energy for Conversion of Methane to C_2 Hydrocarbons via Dissymmetrical Electric Field Enhanced Plasma

Direct conversion of methane into C2 hydrocarbons through alternating current electric field enhanced plasma was studied under room temperature, atmospheric pressure and low power conditions. The distribution of electrical field intensity and distribution of energy were calculated with software that was developed by us according to the charge simulation method. The results indicated that the energy of tip of electrode was 0.36 J/mm^3 and it was higher than the methane dissociation energy （0.0553 J/mm^3）. The methane located at this area can be activated easily. The higher-energy particles produced by dissociation collided with molecules around them and initiated consecutive reactions between free radicals and molecules. The method was proved to be valided and could be taken as a basis for the electrical field study concerned.

Effect of Electric Field Intensity on the Morphology of Magnetic-field-assisted Electrospinning PVP Nanofibers

Polyvinylpyrrolidone （PVP） nanofibers were processed by magnetic-field-assisted electrospinning （MFAES） technique. Since electric field intensity was one of the most important parameters influencing fiber morphology, the research aimed to study how electric field intensity affects fiber morphology in MFAES technique. The experimental results revealed that the distribution of diameter widened while the average diameter of PVP fibers decreased and the degree of the alignment reduced with the increase of electric field intensity. However, the fibers would be conglutinated together when the electric field intensity was too low. Also, the increase of working distance made the average diameter and the degree of the alignment increase slightly under the same electric field intensity, but the fibers could be partially curved instead of being fully straight if the working distance was too long. It was also indicated that maintaining the electric field intensity at 1 kV/cm With the voltage-distance combinations of 12 kV-12 cm （for 12wt% PVP） and 15 kV-15 cm （for 14wt% PVP） among all other combinations would result in the optimal alignment as well as a narrow size distribution of the fibers.

Lorentz Transformation Leads to Invariance of the Difference between the Electric and Magnetic Field Intensity

In course of a direct calculation we demonstrate the activity of parameters of the Lorentz transformation entering the original electric and magnetic field vectors E and H. The validity of the transformation is shown with the aid of the relation E 2- H2 = E'2- H'2 which holds for any suitable pair of the vectors E, H and E', H'. No special geometry of the vector pairs entering (E, H) and (E ', H') is assumed. The only limit applied in the paper concerns the velocity ratio betweeen v and c which should be smaller than unity.

Heat transfer model for microwave hot in-place recycling of asphalt pavements

In order to solve for temperature fields in microwave heating for recycling asphalt mixtures, a two-dimensional heat transfer model for the asphalt mixtures within the heating range is built based on the theory of unsteady heat conduction. Four onedimensional heat transfer models are established for the asphalt mixtures outside the heating range, which are simplified into four half-infinite solids. The intensity of the radiation electric field is calculated through experiment by using heating water loads. It is suggested that the mathematical model of boundary conditions can be established in two ways, which are theoretical deduction and experimental reverse. The actual temperature field is achieved by fitting temperatures of different positions collected in the heating experiment. The simulant temperature field, which is solved with the Matlab PDE toolbox, is in good agreement with the actual temperature field. The results indicate that the proposed models have high precision and can be directly used to calculate the temperature distribution of asphalt pavements.

A Kinetic Model of Dielectric Ageing

A kinetic model of dielectric ageing is presented. The central finding of this investigation is that there is a power-law relationship between the local electric field concentration and the rate of defect-tip initiated conducting crack growth. By applying such a power-law conducting crack growth rate expression to the evaluation of the life of solid dielectrics, the empirical classical ageing law of insulation materials can be derived theoretically as a lobical result. All the results are universal and agree with the experimental data of oxide films.

ANTI-PLANE SHEAR CRACK IN A FUNCTIONALLY GRADIENT PIEZOELECTRIC MATERIAL

The main objective of this paper is to study the singular natureof the crack-tip stress and electric displacement field in afunctionally gradient piezoelectric medium having materialcoefficients with a discontinuous derivative. The problem isconsidered for the simplest possible loading and geometry, namely,the anti-plane shear stress and electric displacement in -plane oftwo bonded half spaces in which the crack is parallel to theinterface.

Numerical Study of Temperature and Electric Field Effects on the Total Optical Absorption Coefficient in the Presence of Optical Inter-Conduction-Subband Transitions in InGaN/GaN Single Parabolic Quantum Wells

In this paper,we theoretically investigate the total optical coefficient(TOAC)considering 1S-2P and 2S-2P conduction subband transitions in a single parabolic quantum well(SPQW)with an on-center hydrogen-like impurity.Within the framework of the effective-mass approximation,the Schrödinger equation is solved numerically to obtain the eigenvalues and their corresponding eigenvectors using the finite difference method.The calculations are performed for finite confinement potential height,taking into account the dielectric and effective mass mismatches between GaN and InGaN materials under the considered electric field and temperature effects.The temperature dependence of the effective mass,dielectric constant and band gap energy are obtained accordingly.On the one hand,the results show that a significant shift is produced with the variation of both the temperature and the intensity of the electric field.On the other hand,the absorption spectrum is shifted to lower energies with increasing both electric field strength and temperature.Moreover,its amplitude is enhanced with an increase in the intensity of the electric field,and show a slight drop with increasing temperature for the two optical transitions considered.The results show that such parameters can be used to adjust the optical properties of single parabolic Quantum Well for solar cell applications.

Dynamic anti-plane interaction between an impermeable crack and a circular cavity in an infinite piezoelectric medium

Wave propagation in an infinite elastic piezoelectric medium with a circular cavity and an impermeable crack subjected to steady-state anti-plane shearing was studied based on Green's function and the crack-division technique.Theoretical solutions were derived for the whole elastic displacement and electric potential field in the interaction between the circular cavity and the impermeable crack.Expressions were obtained on the dynamic stress concentration factor(DSCF) at the cavity's edge,the dynamic stress intensity factor(DSIF) and the dynamic electric displacement intensity factor(DEDIF) at the crack tip.Numerical solutions were performed and plotted with different incident wave numbers,parameters of piezoelectric materials and geometries of the structure.Finally,some of the calculation results were compared with the case of dynamic anti-plane interaction of a permeable crack and a circular cavity in an infinite piezoelectric medium.This paper can provide a valuable reference for the design of piezoelectric actuators and sensors widely used in marine structures.

ELECTRO-ELASTIC GREEN'S FUNCTIONS FOR APIEZOELECTRIC HALF-SPACE ANDTHEIR APPLICATION

In this paper, as is studied are the electro-elastic solutions for a piezoelectric halfspace subjected Io a line force, a line charge and a line dislocation, i. e.. Green sfunclions on the basis of Stroh formalism and the concept of analytical continuation,explicit expressions for Green's functions are derived. As a direct application of theresults obtained, an infinite piezoelectric solid containing a semi-infinite crack isexammed. Attention iffocused on the stress and electric displacement fields of a cracktip. The stress and electric displacement intensity .factors are given explicitly.

Electromagnetic Environmental Impact of 500-kV Double -Circuit Transmission Lines

The strength of the power frequency electric intensity and magnetic field of the 500-kV double circuit transmission lines was calculated by using the equivalent charge method and the Ampere's Law, and the environmental impact factors of the fields were evaluated. By optimizing the phase sequence, the frequency electric intensity and magnetic field strength can be reduced. Within a distance of 25 m from the center of the transmission line, the power frequency electric intensity and magnetic field strength fall off sharply with the distance increase. Finally, the best phase sequence and the minimum ground clearance of the transmission lines were obtained to meet the requirements of the least impact on envionment.

TRANSIENT RESPONSE OF A CRACKED PIEZOELECTRIC STRIP UNDER ARBITRARY ELECTRO:MECHANICAL IMPACT

By using the well-developed integral transform methodology, the dynamic response of stress and electric displacement around a finite crack in an infinite piezoelectric strip are investigated under arbitrary dynamic anti-plane loads. The dynamic stress intensity factors and electric displacement are obtained analytically. It is shown that the dynamic crack-tip stress and electric field still have a square-root singularity. Numerical computations for the dynamic stress intensity factor show that the electric load has a significant influence on the dynamic response of stress field. The higher the ratio of the crack length to the width of the strip, the higher the peak value of the dynamic stress intensity factor is. On the other hand, the dynamic response of the electric field is determined solely by the applied electric load. The electric field will promote or retard the propagation of the crack depending on the time elapse since the application of the external electro-mechanical loads. (Author abstract) 9 Refs.

Analytical Solution for the Reissner-Sagoci Problem of a Piezoelectric Half-Space

In this paper,a transversely isotropic piezoelectric half-space with the isotropy axis parallel to the z-axis is considered under rotation on a rigid circular disk bonded to the surface of the piezoelectric medium.This is a type of Reissner-Sagoci mixed boundary value problem.By utilizing the Hankel transform,the mixed boundary value problem is simplified into solving a pair of dual integral equations.Full-field analytical expressions for displacement,stresses,and electric displacement inside the half-space are obtained.The shear stresses and electric displacement on the surface are found to be singular at the edge of the rigid circular disk,and the stress intensity factors and electric displacement intensity factor are defined.Numerical results show that material properties and geometric size have significant effects on displacement,shear stresses,and electric displacement.

Electric Field Distribution of Soluble Salt Deposition on the Surface of Insulators in Railway Overhead Lines

Different constituents of soluble salts have different effects on the insulation performance of insulators.To study the electric field distribution of soluble salt deposition on the surface of high-speed railway insulators,a two-dimensional model of the cantilever insulator electrostatic field and constant-current field with soluble salt deposition is constructed.The simulation results indicate that the relative dielectric constant of dry pollution is the main factor that affects the electric field distribution on the surface of the insulator.The electric field intensity is arranged in the following order:CaSO_(4)>KNO_(3)>NaNO_(3)>K_(2)SO_(4)>NaCl>MgSO_(4),and the conductivity of each dirty liquid in the wet state becomes a key factor affecting the electric field distribution,which is specifically shown as sodium chloride>nitrate>sulfate.The simulation results are compared with existing test results to verify that they were correct.It is also found that the electric field intensity of the insulator with good hydrophobicity is slightly greater than that of the insulator without hydrophobicity.The results provide a theoretical basis for the classification of regional pollution levels and the testing of insulator contamination in the laboratory.

Hot-carrier reliability in OPTVLD-LDMOS

An improved structure that eliminates hot-carrier effects（HCE） in optimum variation lateral doping （OPTVLD） LDMOS is proposed.A formula is proposed showing that the surface electric field intensity of the conventional structure is strong enough to make a hot-carrier injected into oxide.However,the proposed structure effectively reduces the maximum surface electric field from 268 to 100 kV/cm and can be realized without changing any process,and thereby reduces HCE significantly.