Spintronic technology and energy applications benefit greatly from the exceptional characteristics of rare-earth-based spinel chalcogenides.Examining the electrical,magnetic and thermoelectric properties of HgNd_(2)Z_...Spintronic technology and energy applications benefit greatly from the exceptional characteristics of rare-earth-based spinel chalcogenides.Examining the electrical,magnetic and thermoelectric properties of HgNd_(2)Z_(4)(Z=S,Se)in a systematic manner is essential for the strategic advancement of spin polarized current in a spintronic device.In this recent study,the WIEN2K code was employed to comprehensively analyze these properties.The calculated lattice constants,obtained using the generalized gradient approximation(GGAsol-PBE),closely match experimental findings of the similar family compounds.The examination of the stability of ferromagnetic states in the ground state involves comparing energies between anti-ferromagnetic and ferromagnetic states.Moreover,an assessment of the stability of the cubic phase in both spinels was conducted using analyses of the phonon dispersion curve,formation energy and Born stability criteria.The ductility characteristics were examined through the calculation of Poisson's and Pugh's ratios.Furthermore,details regarding the density of states,spin polarization,ex-change coupling and Curie temperature were provided to explore the characteristics associated with ferromagnetism.Potential optoelectronic applications were proposed,leveraging the direct band gaps of 1.4 and 1.0 eV for HgNd_(2)Z_(4)(Z=S,Se)respectively,within the visible spectrum.Particularly noteworthy is the effective light absorption of HgNd2Se4 in the visible range,characterized by prominent peaks that facilitate the transition of electrons from the valence band(VB)to the conduction band(CB).Additionally,the study extends to thermoelectric characteristics,determining various factors such as Seebeck coef-ficient(S),figure of merit(ZT),electrical and thermal conductivities of the evaluated spinels.展开更多
The layered PbBi_(4)Te_(7) compound is considered a promising thermoelectric material due to its unusually high electrical transport properties in ternary compound systems.However,its high carrier concentration leads ...The layered PbBi_(4)Te_(7) compound is considered a promising thermoelectric material due to its unusually high electrical transport properties in ternary compound systems.However,its high carrier concentration leads to relatively high thermal conductivity and low Seebeck coefficient,limiting the enhancement of its thermoelectric performance.In this work,we introduce Se alloying and Cu doping to synergistically regulate the thermoelectric transport properties of PbBi_(4)Te_(7).Se alloying induces strong lattice contraction and increased interlayer electron scattering,significantly reducing lattice thermal conductivity while enhancing the Seebeck coefficient.Besides,Cu doping forms interlayer electron transport channels thus optimizing carrier mobility and electrical transport properties.Cu substitution also enhances point defect scattering further suppressing phonon transport.Ultimately,the strong anharmonic structure formed by Se alloying and Cu-induced phonon scattering results in a remarkably low lattice thermal conductivity of 0.27 W m^(−1) K^(−1) at 300 K in PbBi_(4)Te_(5)Se_(2)-0.1%Cu samples.The maximum thermoelectric figure of merit(ZT_(max))is increased to 0.68,with an average thermoelectric figure of merit(ZTave)of 0.56 in the near-room temperature range(300–573 K),outperforming other typical ternary Pb-Bi-based compounds.展开更多
Half-metallic ferromagnetism,mechanical as well as thermoelectric properties for rare earth-based spinels MgHo_(2)Z_(4)(Z=S,Se)were investigated using density functional theory(DFT).Structural optimization was done wi...Half-metallic ferromagnetism,mechanical as well as thermoelectric properties for rare earth-based spinels MgHo_(2)Z_(4)(Z=S,Se)were investigated using density functional theory(DFT).Structural optimization was done with Perdew-Burke-Ehrenzorf(PBE)sol-generalized gradient approximation(GGA)to calculate the lattice constant of both spinels comparable to experimental data.In addition,Born stability criteria and negative formation energy show that our studied spinels are also structurally and dynamically stable in the cubic phase.For ferromagnetic(FM)state stability,we also calculated the energy differences among FM,antiferromagnetic(AFM),and non-magnetic(NM)states.Additionally,Curie temperatures of ferromagnetic phases were also estimated.We used Trans-Blaha improved BeckeJohnson(TB-mBJ)potential functional for electronics as well as magnetic characteristics,which lead to the consistent explanation of half-metallic ferromagnetism,representing the whole band-occupancy in material with exact detail of density of states(DOS).The stable FM state was examined in spinels due to the exchange splitting of Ho cation consisting of p-d hybridizations compatible with the result achieved for electronics band structure and DOS.Further,spin magnetic moment was explained in terms of anion,cation,and sharing charge on studied spinels.In addition,the calculated thermoelectric properties clearly show that operation range of these systems may be utilized by future experimental works for identifying the potential applications of these systems.展开更多
This study sets up two new merit functions,which are minimized for the detection of real eigenvalue and complex eigenvalue to address nonlinear eigenvalue problems.For each eigen-parameter the vector variable is solve...This study sets up two new merit functions,which are minimized for the detection of real eigenvalue and complex eigenvalue to address nonlinear eigenvalue problems.For each eigen-parameter the vector variable is solved from a nonhomogeneous linear system obtained by reducing the number of eigen-equation one less,where one of the nonzero components of the eigenvector is normalized to the unit and moves the column containing that component to the right-hand side as a nonzero input vector.1D and 2D golden section search algorithms are employed to minimize the merit functions to locate real and complex eigenvalues.Simultaneously,the real and complex eigenvectors can be computed very accurately.A simpler approach to the nonlinear eigenvalue problems is proposed,which implements a normalization condition for the uniqueness of the eigenvector into the eigenequation directly.The real eigenvalues can be computed by the fictitious time integration method(FTIM),which saves computational costs compared to the one-dimensional golden section search algorithm(1D GSSA).The simpler method is also combined with the Newton iterationmethod,which is convergent very fast.All the proposed methods are easily programmed to compute the eigenvalue and eigenvector with high accuracy and efficiency.展开更多
It is hard to simultaneously realize the high dielectric tunability and low loss for the single Ba_(0.6)Sr_(0.4)TiO_(3)(BST)dielectric film made through chemical method.Garnet structured Y_(2.80)Pr_(0.20)Fe_(5)O_(12)(...It is hard to simultaneously realize the high dielectric tunability and low loss for the single Ba_(0.6)Sr_(0.4)TiO_(3)(BST)dielectric film made through chemical method.Garnet structured Y_(2.80)Pr_(0.20)Fe_(5)O_(12)(YPrIG)ex-hibits the merits of high saturation magnetization and a much high resistivity,which are helpful for realizing magnetoelectric double tuning and suppressing the dielectric loss of BST film.In this work,Y_(2.80)Pr_(0.20)Fe_(5)O_(12)/Ba_(0.6)Sr_(0.4)TiO_(3)(YPrIG/BST)composite films were fabricated by sol-gel method.The com-posite films exhibited a low dielectric loss(0.0087),and got a magnetic tunability of 11.73%at 10 kOe and 1.44 MHz.Compared with BST film,the tunability of YPrIG/BST film was enhanced from 56.25%to 73.24%under the bias electric field of 800 kV/cm.Additionally,YPrIG/BST films exhibited an electromag-netic double adjustability.The electromagnetic tunability of YPrIG/BST composite films was as high as 80.40%at 1.44 MHz,under the DC bias electric field of 800 kV/cm and magnetic field of 10 kOe.This phenomenon can be explained in terms of the superposition effect of electric field and magnetic field.展开更多
The purpose of this paper is to present the results of investigations on quasi-one-dimensional organic crystals of tetrathiotetracene-tetracyanoquinodi- methane (TTT(TCNQ)<sub>2</sub>) from the prospective...The purpose of this paper is to present the results of investigations on quasi-one-dimensional organic crystals of tetrathiotetracene-tetracyanoquinodi- methane (TTT(TCNQ)<sub>2</sub>) from the prospective of thermoelectric applications. The calculations were performed after analytical expressions, obtained in the frame of a physical model, more detailed than the model presented earlier by authors. The main Hamiltonian of the model includes the electronic and phonon part, electron-phonon interactions and the impurity scattering term. In order to estimate the electric charge transport between the molecular chains, the physical model was upgraded to the so-called three-dimen- sional (3D) physical model. Numeric computations were performed to determine the electrical conductivity, Seebeck coefficient, thermal conductivity, thermoelectric power factor and thermoelectric figure-of-merit as a function on charge carrier concentrations, temperatures and impurity concentrations. A detailed analysis of charge-lattice interaction, consisting of the exploration of the Peierls structural transition in TCNQ molecular chains of TTT(TCNQ)<sub>2</sub> was performed. As result, the critical transition temperature was determined. The dispersion of renormalized phonons was examined in detail.展开更多
Finding binary sequences with Large SHG ratios is very important in the field of ultrafast science, biomedical optics, high-resolution microscopy and label-free imaging. In this paper, we have demonstrated the relatio...Finding binary sequences with Large SHG ratios is very important in the field of ultrafast science, biomedical optics, high-resolution microscopy and label-free imaging. In this paper, we have demonstrated the relation between the SHG contrast ratio and the traditional Merit Factor values. And in the light from known results in Merit Factor Problems, we have shown that Legendre Sequences or Jacobi Sequences, are still the best candidates to obtain binary sequences with large SHG contrast ratios. The authors also discussed the SHG behaviors on some sequences obtained from cyclotomic classes over the finite field GF (2l) .展开更多
Task-based language teaching approach(TBLTA), which lays stress on "learning by doing", gained increasing popularity in English teaching in recent years. The design of phonetic teaching calls for more emphas...Task-based language teaching approach(TBLTA), which lays stress on "learning by doing", gained increasing popularity in English teaching in recent years. The design of phonetic teaching calls for more emphasis from English educators since it is one of the basic rounds of English teaching. This paper made a trial on the utilization of TBLTA in the English phonetic teaching context and designed a TBLTA model for English phonetic teaching based on discussions about model and merits of TBLTA.展开更多
Task-based language teaching is very popular in the modern English teaching.It is based on the Task-based Syllabus. Task-based Syllabus focuses on the learners' communicative competence,which stresses learning by ...Task-based language teaching is very popular in the modern English teaching.It is based on the Task-based Syllabus. Task-based Syllabus focuses on the learners' communicative competence,which stresses learning by doing. From the theoretical assumption and definitions of the task,the paper analysizes the components of the task, then points out the merits and demerits of the syllabus. By this means the paper may give some tips to teachers and students when they use the tsk-based language teaching.展开更多
A new ultralow gate–drain charge(Q_(GD)) 4 H-SiC trench MOSFET is presented and its mechanism is investigated by simulation. The novel MOSFET features double shielding structures(DS-MOS): one is the grounded split ga...A new ultralow gate–drain charge(Q_(GD)) 4 H-SiC trench MOSFET is presented and its mechanism is investigated by simulation. The novel MOSFET features double shielding structures(DS-MOS): one is the grounded split gate(SG), the other is the P+shielding region(PSR). Both the SG and the PSR reduce the coupling effect between the gate and the drain, and transform the most part of the gate–drain capacitance(C_(GD)) into the gate–source capacitance(C_(GS)) and drain–source capacitance(C_(DS)) in series.Thus the C_(GD) is reduced and the proposed DS-MOS obtains ultralow Q_(GD). Compared with the double-trench MOSFET(DT-MOS)and the conventional trench MOSFET(CT-MOS), the proposed DS-MOS decreases the Q_(GD) by 85% and 81%, respectively.Moreover, the figure of merit(FOM), defined as the product of specific on-resistance(R_(on, sp)) and Q_(GD)(R_(on, sp)Q_(GD)), is reduced by 84% and 81%, respectively.展开更多
This paper investigates the effects of pH on stability and thermal properties of copper oxide(CuO),graphene oxide(GO),and their hybrid nanofluid(HNF)at different mixing ratios.Initially,sol-gel and Hummer’s method wa...This paper investigates the effects of pH on stability and thermal properties of copper oxide(CuO),graphene oxide(GO),and their hybrid nanofluid(HNF)at different mixing ratios.Initially,sol-gel and Hummer’s method was employed for the synthesis of CuO and GO nanoparticles(NPs),and they are characterized with various techniques.The effects of two different surfactants were analyzed on nanofluid’s(NF’s)stability at different pH values.The properties like thermal conductivity(TC)and viscosity(VST)of NFs were measured at different volume concentration(0.1 vol%to 1.0 vol%)and temperature range of 30-60℃,respectively.The TC and VST of GO/CuO(50:50)HNF are higher than that of GO/CuO(20:80).The figure of merit(FOM)is determined for the studied HNFs.The correlations were presented to calculate the TC as well as VST of HNFs.Two modern novel machine learning-based ensemble approaches were employed for predictive model development for TC and VST of considered HNFs.The comparison of prognostic models with Taylor’s diagram revealed that Bayesian optimized support vector machine(BoASVM)was superior to Bayesian optimized boosted regression trees(BoA-BRT)for both TC and VST models.展开更多
We obtained TiNiSn-based half-Heusler Hf_(x)Ti_(1-x)NiSn_(0.97)Sb_(0.03)bulks with 85%-96%relative densities via 5-min microwave synthesis and 20-min microwave sintering in sealed vacuum.The phase composition and micr...We obtained TiNiSn-based half-Heusler Hf_(x)Ti_(1-x)NiSn_(0.97)Sb_(0.03)bulks with 85%-96%relative densities via 5-min microwave synthesis and 20-min microwave sintering in sealed vacuum.The phase composition and microstructure of samples were characterized by X-ray diffractometer(XRD)and scanning electron microscopy(SEM).Thermoelectric(TE)properties were measured,i.e.,Seebeck coefficient(S),electrical resistivity(ρ),and thermal conductivity(κ)through Seebeck coefficient/resistance analysis system(S/RAs)and laser flash thermal analyzer(LFT).The results show that the nearly single phase exists after microwave sintering.The grain sizes and the number of grain boundaries decrease with increase in Hf-doping amount due to an increase in point defects.The matrix grains for Hf_(0.1)Ti_(0.9)NiSn_(0.97)Sb_(0.03)are~10μm.The nanoscle pores and precipitates are present as second phases in matrix grain.The real composition for Hf_(0.1)Ti_(0.9)NiSn_(0.97)Sb_(0.03)matrix grain is Hf_(3.51)Ti_(28.76)-Ni_(34.76)Sn_(31.55)Sb_(1.43).The variation trends of electrical resistivity,Seebeck coefficient,power factor,and thermal conductivity were analyzed in detail.The maximum figure of merit(ZT)of 0.46 is obtained for Hf_(0.1)Ti_(0.9-)NiSnSn_(0.97)Sb_(0.03)at 723 K.The innovation route exhibits advantages for predation of TE bulks when compared to the conventional methods,especially in terms of efficiency while it still maintains TE performance.展开更多
Memristor with memory properties can be applied to connection points(synapses)between cells in a cellular neural network(CNN).This paper highlights memristor crossbar-based multilayer CNN(MCM-CNN)and its application t...Memristor with memory properties can be applied to connection points(synapses)between cells in a cellular neural network(CNN).This paper highlights memristor crossbar-based multilayer CNN(MCM-CNN)and its application to edge detection.An MCM-CNN is designed by adopting a memristor crossbar composed of a pair of memristors.MCM-CNN based on the memristor crossbar with changeable weight is suitable for edge detection of a binary image and a color image considering its characteristics of programmablization and compactation.Figure of merit(FOM)is introduced to evaluate the proposed structure and several traditional edge detection operators for edge detection results.Experiment results show that the FOM of MCM-CNN is three times more than that of the traditional edge detection operators.展开更多
We investigate the sensitivity and figure of merit （FOM） of a localized surface plasmon （LSP） sensor with gold nanograting on the top of planar metallic film. The sensitivity of the localized surface plasmon senso...We investigate the sensitivity and figure of merit （FOM） of a localized surface plasmon （LSP） sensor with gold nanograting on the top of planar metallic film. The sensitivity of the localized surface plasmon sensor is 317 nm/RIU, and the FOM is predicted to be above 8, which is very high for a localized surface plasmon sensor. By employing the rigorous coupled-wave analysis （RCWA） method, we analyze the distribution of the magnetic field and find that the sensing property of our proposed system is attributed to the interactions between the localized surface plasmon around the gold nanostrips and the surface plasmon polarition on the surface of the gold planar metallic film. These findings are important for developing high FOM localized surface plasmon sensors.展开更多
A novel super-junction LDMOS with low resistance channel(LRC),named LRC-LDMOS based on the silicon-on-insulator(SOI)technology is proposed.The LRC is highly doped on the surface of the drift region,which can significa...A novel super-junction LDMOS with low resistance channel(LRC),named LRC-LDMOS based on the silicon-on-insulator(SOI)technology is proposed.The LRC is highly doped on the surface of the drift region,which can significantly reduce the specific on resistance(R^(on,sp))in forward conduction.The charge compensation between the LRC,N-pillar,and P-pillar of the super-junction are adjusted to satisfy the charge balance,which can completely deplete the whole drift,thus the breakdown voltage(BV)is enhanced in reverse blocking.The three-dimensional(3D)simulation results show that the BV and R^(on,sp)of the device can reach 253 V and 15.5 mΩ·cm^(2),respectively,and the Baliga's figure of merit(FOM=BV^(2)/R^(on,sp))of 4.1 MW/cm^(2)is achieved,breaking through the silicon limit.展开更多
基金the Deanship of Scientific Research at King Khalid University for funding this work through large group Research Project under grant number RGP2/450/44。
文摘Spintronic technology and energy applications benefit greatly from the exceptional characteristics of rare-earth-based spinel chalcogenides.Examining the electrical,magnetic and thermoelectric properties of HgNd_(2)Z_(4)(Z=S,Se)in a systematic manner is essential for the strategic advancement of spin polarized current in a spintronic device.In this recent study,the WIEN2K code was employed to comprehensively analyze these properties.The calculated lattice constants,obtained using the generalized gradient approximation(GGAsol-PBE),closely match experimental findings of the similar family compounds.The examination of the stability of ferromagnetic states in the ground state involves comparing energies between anti-ferromagnetic and ferromagnetic states.Moreover,an assessment of the stability of the cubic phase in both spinels was conducted using analyses of the phonon dispersion curve,formation energy and Born stability criteria.The ductility characteristics were examined through the calculation of Poisson's and Pugh's ratios.Furthermore,details regarding the density of states,spin polarization,ex-change coupling and Curie temperature were provided to explore the characteristics associated with ferromagnetism.Potential optoelectronic applications were proposed,leveraging the direct band gaps of 1.4 and 1.0 eV for HgNd_(2)Z_(4)(Z=S,Se)respectively,within the visible spectrum.Particularly noteworthy is the effective light absorption of HgNd2Se4 in the visible range,characterized by prominent peaks that facilitate the transition of electrons from the valence band(VB)to the conduction band(CB).Additionally,the study extends to thermoelectric characteristics,determining various factors such as Seebeck coef-ficient(S),figure of merit(ZT),electrical and thermal conductivities of the evaluated spinels.
基金financial support from the National Natural Science Foundation of China(Grant No.52172236 and No.22205032)the Fund of the State Key Laboratory of Solidification Processing in NPU(Grant No.SKLSP202314)supported by“Bairen”Program from University of Electronic Science and Technology of China.
文摘The layered PbBi_(4)Te_(7) compound is considered a promising thermoelectric material due to its unusually high electrical transport properties in ternary compound systems.However,its high carrier concentration leads to relatively high thermal conductivity and low Seebeck coefficient,limiting the enhancement of its thermoelectric performance.In this work,we introduce Se alloying and Cu doping to synergistically regulate the thermoelectric transport properties of PbBi_(4)Te_(7).Se alloying induces strong lattice contraction and increased interlayer electron scattering,significantly reducing lattice thermal conductivity while enhancing the Seebeck coefficient.Besides,Cu doping forms interlayer electron transport channels thus optimizing carrier mobility and electrical transport properties.Cu substitution also enhances point defect scattering further suppressing phonon transport.Ultimately,the strong anharmonic structure formed by Se alloying and Cu-induced phonon scattering results in a remarkably low lattice thermal conductivity of 0.27 W m^(−1) K^(−1) at 300 K in PbBi_(4)Te_(5)Se_(2)-0.1%Cu samples.The maximum thermoelectric figure of merit(ZT_(max))is increased to 0.68,with an average thermoelectric figure of merit(ZTave)of 0.56 in the near-room temperature range(300–573 K),outperforming other typical ternary Pb-Bi-based compounds.
基金the Deanship of Scientific Research at King Khalid University for funding this work through the small Groups Project under grant number(R.G.P.1/153/43)。
文摘Half-metallic ferromagnetism,mechanical as well as thermoelectric properties for rare earth-based spinels MgHo_(2)Z_(4)(Z=S,Se)were investigated using density functional theory(DFT).Structural optimization was done with Perdew-Burke-Ehrenzorf(PBE)sol-generalized gradient approximation(GGA)to calculate the lattice constant of both spinels comparable to experimental data.In addition,Born stability criteria and negative formation energy show that our studied spinels are also structurally and dynamically stable in the cubic phase.For ferromagnetic(FM)state stability,we also calculated the energy differences among FM,antiferromagnetic(AFM),and non-magnetic(NM)states.Additionally,Curie temperatures of ferromagnetic phases were also estimated.We used Trans-Blaha improved BeckeJohnson(TB-mBJ)potential functional for electronics as well as magnetic characteristics,which lead to the consistent explanation of half-metallic ferromagnetism,representing the whole band-occupancy in material with exact detail of density of states(DOS).The stable FM state was examined in spinels due to the exchange splitting of Ho cation consisting of p-d hybridizations compatible with the result achieved for electronics band structure and DOS.Further,spin magnetic moment was explained in terms of anion,cation,and sharing charge on studied spinels.In addition,the calculated thermoelectric properties clearly show that operation range of these systems may be utilized by future experimental works for identifying the potential applications of these systems.
基金the National Science and Tech-nology Council,Taiwan for their financial support(Grant Number NSTC 111-2221-E-019-048).
文摘This study sets up two new merit functions,which are minimized for the detection of real eigenvalue and complex eigenvalue to address nonlinear eigenvalue problems.For each eigen-parameter the vector variable is solved from a nonhomogeneous linear system obtained by reducing the number of eigen-equation one less,where one of the nonzero components of the eigenvector is normalized to the unit and moves the column containing that component to the right-hand side as a nonzero input vector.1D and 2D golden section search algorithms are employed to minimize the merit functions to locate real and complex eigenvalues.Simultaneously,the real and complex eigenvectors can be computed very accurately.A simpler approach to the nonlinear eigenvalue problems is proposed,which implements a normalization condition for the uniqueness of the eigenvector into the eigenequation directly.The real eigenvalues can be computed by the fictitious time integration method(FTIM),which saves computational costs compared to the one-dimensional golden section search algorithm(1D GSSA).The simpler method is also combined with the Newton iterationmethod,which is convergent very fast.All the proposed methods are easily programmed to compute the eigenvalue and eigenvector with high accuracy and efficiency.
基金supported by the National Natural Science Foundation of China(Nos.52171191,52371198)Shaanxi Key Program for International Science and Technology Coopera-tion Projects(No.2021KWZ-12)the Youth Innovation Team of Shaanxi Universities.
文摘It is hard to simultaneously realize the high dielectric tunability and low loss for the single Ba_(0.6)Sr_(0.4)TiO_(3)(BST)dielectric film made through chemical method.Garnet structured Y_(2.80)Pr_(0.20)Fe_(5)O_(12)(YPrIG)ex-hibits the merits of high saturation magnetization and a much high resistivity,which are helpful for realizing magnetoelectric double tuning and suppressing the dielectric loss of BST film.In this work,Y_(2.80)Pr_(0.20)Fe_(5)O_(12)/Ba_(0.6)Sr_(0.4)TiO_(3)(YPrIG/BST)composite films were fabricated by sol-gel method.The com-posite films exhibited a low dielectric loss(0.0087),and got a magnetic tunability of 11.73%at 10 kOe and 1.44 MHz.Compared with BST film,the tunability of YPrIG/BST film was enhanced from 56.25%to 73.24%under the bias electric field of 800 kV/cm.Additionally,YPrIG/BST films exhibited an electromag-netic double adjustability.The electromagnetic tunability of YPrIG/BST composite films was as high as 80.40%at 1.44 MHz,under the DC bias electric field of 800 kV/cm and magnetic field of 10 kOe.This phenomenon can be explained in terms of the superposition effect of electric field and magnetic field.
文摘The purpose of this paper is to present the results of investigations on quasi-one-dimensional organic crystals of tetrathiotetracene-tetracyanoquinodi- methane (TTT(TCNQ)<sub>2</sub>) from the prospective of thermoelectric applications. The calculations were performed after analytical expressions, obtained in the frame of a physical model, more detailed than the model presented earlier by authors. The main Hamiltonian of the model includes the electronic and phonon part, electron-phonon interactions and the impurity scattering term. In order to estimate the electric charge transport between the molecular chains, the physical model was upgraded to the so-called three-dimen- sional (3D) physical model. Numeric computations were performed to determine the electrical conductivity, Seebeck coefficient, thermal conductivity, thermoelectric power factor and thermoelectric figure-of-merit as a function on charge carrier concentrations, temperatures and impurity concentrations. A detailed analysis of charge-lattice interaction, consisting of the exploration of the Peierls structural transition in TCNQ molecular chains of TTT(TCNQ)<sub>2</sub> was performed. As result, the critical transition temperature was determined. The dispersion of renormalized phonons was examined in detail.
文摘Finding binary sequences with Large SHG ratios is very important in the field of ultrafast science, biomedical optics, high-resolution microscopy and label-free imaging. In this paper, we have demonstrated the relation between the SHG contrast ratio and the traditional Merit Factor values. And in the light from known results in Merit Factor Problems, we have shown that Legendre Sequences or Jacobi Sequences, are still the best candidates to obtain binary sequences with large SHG contrast ratios. The authors also discussed the SHG behaviors on some sequences obtained from cyclotomic classes over the finite field GF (2l) .
文摘Task-based language teaching approach(TBLTA), which lays stress on "learning by doing", gained increasing popularity in English teaching in recent years. The design of phonetic teaching calls for more emphasis from English educators since it is one of the basic rounds of English teaching. This paper made a trial on the utilization of TBLTA in the English phonetic teaching context and designed a TBLTA model for English phonetic teaching based on discussions about model and merits of TBLTA.
文摘Task-based language teaching is very popular in the modern English teaching.It is based on the Task-based Syllabus. Task-based Syllabus focuses on the learners' communicative competence,which stresses learning by doing. From the theoretical assumption and definitions of the task,the paper analysizes the components of the task, then points out the merits and demerits of the syllabus. By this means the paper may give some tips to teachers and students when they use the tsk-based language teaching.
基金supported by the National Key Research and Development Program of China(No.2016YFB0400502)
文摘A new ultralow gate–drain charge(Q_(GD)) 4 H-SiC trench MOSFET is presented and its mechanism is investigated by simulation. The novel MOSFET features double shielding structures(DS-MOS): one is the grounded split gate(SG), the other is the P+shielding region(PSR). Both the SG and the PSR reduce the coupling effect between the gate and the drain, and transform the most part of the gate–drain capacitance(C_(GD)) into the gate–source capacitance(C_(GS)) and drain–source capacitance(C_(DS)) in series.Thus the C_(GD) is reduced and the proposed DS-MOS obtains ultralow Q_(GD). Compared with the double-trench MOSFET(DT-MOS)and the conventional trench MOSFET(CT-MOS), the proposed DS-MOS decreases the Q_(GD) by 85% and 81%, respectively.Moreover, the figure of merit(FOM), defined as the product of specific on-resistance(R_(on, sp)) and Q_(GD)(R_(on, sp)Q_(GD)), is reduced by 84% and 81%, respectively.
文摘This paper investigates the effects of pH on stability and thermal properties of copper oxide(CuO),graphene oxide(GO),and their hybrid nanofluid(HNF)at different mixing ratios.Initially,sol-gel and Hummer’s method was employed for the synthesis of CuO and GO nanoparticles(NPs),and they are characterized with various techniques.The effects of two different surfactants were analyzed on nanofluid’s(NF’s)stability at different pH values.The properties like thermal conductivity(TC)and viscosity(VST)of NFs were measured at different volume concentration(0.1 vol%to 1.0 vol%)and temperature range of 30-60℃,respectively.The TC and VST of GO/CuO(50:50)HNF are higher than that of GO/CuO(20:80).The figure of merit(FOM)is determined for the studied HNFs.The correlations were presented to calculate the TC as well as VST of HNFs.Two modern novel machine learning-based ensemble approaches were employed for predictive model development for TC and VST of considered HNFs.The comparison of prognostic models with Taylor’s diagram revealed that Bayesian optimized support vector machine(BoASVM)was superior to Bayesian optimized boosted regression trees(BoA-BRT)for both TC and VST models.
基金financially supported by the National Natural Science Foundation of China (Nos.51574134 and 51574042)the Joint Fund between Shenyang National Laboratory for Materials Science and State Key Laboratory of Advanced Processing and Recycling of Nonferrous Metals (No.18LHPY016)Anhui University Outstanding Young Talent Support Program (Key Project) (No.gxyq ZD2017039)。
文摘We obtained TiNiSn-based half-Heusler Hf_(x)Ti_(1-x)NiSn_(0.97)Sb_(0.03)bulks with 85%-96%relative densities via 5-min microwave synthesis and 20-min microwave sintering in sealed vacuum.The phase composition and microstructure of samples were characterized by X-ray diffractometer(XRD)and scanning electron microscopy(SEM).Thermoelectric(TE)properties were measured,i.e.,Seebeck coefficient(S),electrical resistivity(ρ),and thermal conductivity(κ)through Seebeck coefficient/resistance analysis system(S/RAs)and laser flash thermal analyzer(LFT).The results show that the nearly single phase exists after microwave sintering.The grain sizes and the number of grain boundaries decrease with increase in Hf-doping amount due to an increase in point defects.The matrix grains for Hf_(0.1)Ti_(0.9)NiSn_(0.97)Sb_(0.03)are~10μm.The nanoscle pores and precipitates are present as second phases in matrix grain.The real composition for Hf_(0.1)Ti_(0.9)NiSn_(0.97)Sb_(0.03)matrix grain is Hf_(3.51)Ti_(28.76)-Ni_(34.76)Sn_(31.55)Sb_(1.43).The variation trends of electrical resistivity,Seebeck coefficient,power factor,and thermal conductivity were analyzed in detail.The maximum figure of merit(ZT)of 0.46 is obtained for Hf_(0.1)Ti_(0.9-)NiSnSn_(0.97)Sb_(0.03)at 723 K.The innovation route exhibits advantages for predation of TE bulks when compared to the conventional methods,especially in terms of efficiency while it still maintains TE performance.
基金supported by the Research Fund for International Young Scientists of the National Natural Science Foundation of China(61550110248)the Research on Fundamental Theory of Shared Intelligent Street Lamp for New Scene Service(H04W200495)+1 种基金Sichuan Science and Technology Program(2019YFG0190)the Research on Sino-Tibetan Multi-source Information Acquisition,Fusion,Data Mining and its Application(H04W170186).
文摘Memristor with memory properties can be applied to connection points(synapses)between cells in a cellular neural network(CNN).This paper highlights memristor crossbar-based multilayer CNN(MCM-CNN)and its application to edge detection.An MCM-CNN is designed by adopting a memristor crossbar composed of a pair of memristors.MCM-CNN based on the memristor crossbar with changeable weight is suitable for edge detection of a binary image and a color image considering its characteristics of programmablization and compactation.Figure of merit(FOM)is introduced to evaluate the proposed structure and several traditional edge detection operators for edge detection results.Experiment results show that the FOM of MCM-CNN is three times more than that of the traditional edge detection operators.
基金Project supported by the National Key Research Program of China(Grant No.2011ZX01015-001)
文摘We investigate the sensitivity and figure of merit （FOM） of a localized surface plasmon （LSP） sensor with gold nanograting on the top of planar metallic film. The sensitivity of the localized surface plasmon sensor is 317 nm/RIU, and the FOM is predicted to be above 8, which is very high for a localized surface plasmon sensor. By employing the rigorous coupled-wave analysis （RCWA） method, we analyze the distribution of the magnetic field and find that the sensing property of our proposed system is attributed to the interactions between the localized surface plasmon around the gold nanostrips and the surface plasmon polarition on the surface of the gold planar metallic film. These findings are important for developing high FOM localized surface plasmon sensors.
文摘A novel super-junction LDMOS with low resistance channel(LRC),named LRC-LDMOS based on the silicon-on-insulator(SOI)technology is proposed.The LRC is highly doped on the surface of the drift region,which can significantly reduce the specific on resistance(R^(on,sp))in forward conduction.The charge compensation between the LRC,N-pillar,and P-pillar of the super-junction are adjusted to satisfy the charge balance,which can completely deplete the whole drift,thus the breakdown voltage(BV)is enhanced in reverse blocking.The three-dimensional(3D)simulation results show that the BV and R^(on,sp)of the device can reach 253 V and 15.5 mΩ·cm^(2),respectively,and the Baliga's figure of merit(FOM=BV^(2)/R^(on,sp))of 4.1 MW/cm^(2)is achieved,breaking through the silicon limit.
