Multistage fracturing technology has been used to enhance tight hydrocarbon resource recovery.Determining the proper well spacing and fracturing strategy is crucial for generating a complex fracture network that facil...Multistage fracturing technology has been used to enhance tight hydrocarbon resource recovery.Determining the proper well spacing and fracturing strategy is crucial for generating a complex fracture network that facilitates oil and gas flow in reservoirs.The stress-shadow effect that occurs between multiple wells significantly affects the development of fracture networks in reservoirs.However,the quantification of the stress-shadow effect and its influence on fracture networks has not been satisfactorily resolved because of the difficulties in detecting and identifying fracture propagation and reorientation in reservoirs.In this study,based on the geological information from the Shengli oilfield,we applied a hybrid finite element-discrete element method to analyze engineering-scale three-dimensional fracture propagation and reorientation by altering well spacings and fracturing strategies.The results indicate that the fracturing area generated by the synchronous fracturing scheme is much smaller than those generated by the sequential and alternative schemes.An alternative hydrofracturing scheme is optimal with respect to fracturing area.The stress-blind area was defined to quantify the mechanical disturbance between adjacent wells.Our study improves the understanding of the effect of fracturing schemes on fracture networks and the impact of independent factors contributing to stress-shadow effects.展开更多
The practical application of emerging rechargeable aqueous zinc(Zn)batteries is challenged by the poor reversibility and cycling stability of Zn anodes,primarily due to parasitic side reactions.While numerous strategi...The practical application of emerging rechargeable aqueous zinc(Zn)batteries is challenged by the poor reversibility and cycling stability of Zn anodes,primarily due to parasitic side reactions.While numerous strategies have been proposed,balancing the suppression of side reactions with the maintenance of fast Zn plating/stripping kinetics remains a significant challenge.In this study,sucrose,a sterically-hindered organic molecule with abundant hydroxyl groups,is employed to suppress the side reactions and maintain the moderate kinetics of Zn plating/stripping by modulating the hydrogen bond network without altering the Zn^(2+)solvation structure.Its steric hindrance effect further impedes the lateral diffusion of Zn atoms on the electrode surface within the electric double layer,effectively mitigating dendrite growth and stabilizing the electrodeposition process.Consequently,the formulated Suc/ZnSO_(4)electrolyte achieves a remarkably Coulombic efficiency of 99.90% over 2600 cycles at 3 mA cm^(-2)for 1 mAh cm^(-2)in Zn‖Cu cells.The enhanced Zn anode reversibility leads to excellent cycling stability in Zn‖LiFePO_(4)cells and Zn‖β-MnO_(2)cells.This study underscores the potential of sterically-hindered organic molecule strategies to enhance Zn anode stability while maintaining favorable Zn deposition/stripping dynamics in aqueous Zn batteries.展开更多
Double pipe heat exchangers(DPHEs)are normally utilized in various manufacturing uses owing to their simple design and low maintenance requirements.For that,performance enhancement by improved heat transfer is ongoing...Double pipe heat exchangers(DPHEs)are normally utilized in various manufacturing uses owing to their simple design and low maintenance requirements.For that,performance enhancement by improved heat transfer is ongoing.Air injections are a good strategy for enhancing the thermal performance of the DPHE.In the present work,the influence of air bubble injection in a DPHE was experimentally investigated,and the system’s hydrothermal performance improvement parameters were evaluated.Two modes were designed,manufactured,and used to conduct the experiments.The first mode was conducted with no air injection,named a single phase mode,while in the second mode,air was injected into the annulus of DPHE throughout different perforated rings on the side of the annular.Three different ring types were used and coded as R-1,R-2,and R-3,with an added case of insertion of the three rings inside the annulus.The airflow rate was fixed at 1.5 LPM with a 25○C inlet temperature.Also,the hot water rate in the inner pipe was maintained continuously at 3 LPM with a controlled 70○C temperature at the inlet.Five different cold water flow rates,3,3.5,4,4.5,and 5 LPM,in the annulus,were considered with a controlled inlet temperature at 17○C.Additionally,the effectiveness of the heat exchanger,the number of transfer units(NTU),and the overall heat transfer were predicted and considered for performance evaluation and comparison.The outcomes proved that the injection of air and the bubbly flow creation in the heat exchanger’s hot side is an effective method to strengthen the DPHE performance.Moreover,the total heat transfer coefficient was enhanced by 41%in R-1,58.8%in R-2,and 40.1%in R-3 at 4 LPM of cold water.The optimal ring,which yielded the most improvement,was R-2,achieving a 65%improvement in NTU,with a maximum enhancement in effectiveness of 56%.展开更多
Synergistic effects of layered double hydroxide （LDH） with intumescent flame retardanct （IFR） of phosphorusnitrogen （NP） compound in the polypropylene/ethylene-propylene-diene/IFR/LDH （PP/EPDM/IFR/LDH） nanocom...Synergistic effects of layered double hydroxide （LDH） with intumescent flame retardanct （IFR） of phosphorusnitrogen （NP） compound in the polypropylene/ethylene-propylene-diene/IFR/LDH （PP/EPDM/IFR/LDH） nanocomposites and related properties were studied by X-ray diffraction （XRD）, transmission electron microscopy （TEM）, scanning electron microscopy （SEM）, limiting oxygen index （LOI）, UL-94 test, cone calorimeter test （CCT） and thermo-gravimetric analysis （TGA）. The XRD and TEM results show that the intercalated and/or exfoliated nanocomposites can be obtained by direct melt-intercalation of PP/EPDM into modified LDH and that LDH can promote the IFR additive NP to disperse more homogeneously in the polymer matrix. The SEM results provide positive evidence that more compact charred layers can be obtained from the PP/EPDM/NP/LDH sample than those from the PP/EPDM/LDH and PP/EPDM/NP samples during burning. The LOI and UL-94 rating tests show that the synergetic effects of LDH with NP can effectively increase the flame retardant properties of the PP/EPDM/NP/LDH samples. The data from the CCT and TGA tests indicate that the PP/EPDM/NP/LDH samples apparently decrease the HRR and MLR values and thus enhance the flame retardant properties and have better thermal stability than the PP/EPDM/LDH and PP/EPDM/NP samples.展开更多
Supported Ir catalysts were prepared using layered double hydrotalcite‐like materials,such as Mg_(3)Al_(1-x)Fe_(x),containing Fe and Al species in varying amounts as supports.These Ir catalysts were applied for the s...Supported Ir catalysts were prepared using layered double hydrotalcite‐like materials,such as Mg_(3)Al_(1-x)Fe_(x),containing Fe and Al species in varying amounts as supports.These Ir catalysts were applied for the selective hydrogenation of cinnamaldehyde(CAL).When x was changed from 0(Ir/Mg_(3)Al)to 1(Ir/Mg_(3)Fe),the rate of CAL hydrogenation reached a maximum at approximately x=0.25,while the selectivity to unsaturated alcohol,i.e.,cinnamyl alcohol,monotonously increased from 44.9%to 80.3%.Meanwhile,the size of the supported Ir particles did not change significantly with x,remaining at 1.7-0.2 nm,as determined by transmission electron microscopy.The chemical state of Ir and Fe species in the Ir/Mg3Al1-xFex catalysts was examined by temperature programmed reduction by H2 and X‐ray photoelectron spectroscopy.The surface of the supported Ir particles was also examined through the in‐situ diffuse reflectance infrared Fourier‐transform of a probe molecule of CO.On the basis of these characterization results,the effects of Fe doping to Mg_(3)Al on the structural and catalytic properties of Ir particles in selective CAL hydrogenation were discussed.The significant factors are the electron transfer from Fe2+in the Mg_(3)Al_(1–x)Fex support to the dispersed Ir particles and the surface geometry.展开更多
Solar energy is replacing more and more traditional sources of energy because of the fact that it’s also fighting about global warming. This study is based on exergy analysis of a double-effect series flow absorption...Solar energy is replacing more and more traditional sources of energy because of the fact that it’s also fighting about global warming. This study is based on exergy analysis of a double-effect series flow absorption refrigeration system powered by solar energy in Ngaoundere. The simulation is done on the basis of a half hourly analysis for the first time, from 6.30 AM to 6.30 PM, using water-lithium bromide as working pair. The main parameters for the performance of an absorption cycle, which are the COP and the ECOP, have been analyzed and the results show that this two parameters increase while increasing the temperature of the main generator. The exergy loss of each component of the system and the total exergy loss of the system have been analyzed and their effectiveness calculated, using the first and second law of thermodynamics. The highest exergy loss occurs in the main generator GI and in the absorber, making these components more important in an absorption cycle. This analysis is based on a mathematical model using FORTRAN?language. The results obtained may be useful for the optimization of solar absorption refrigeration systems.展开更多
The aim of this paper is to investigate the effect of nitrite intercalated Mg-Al layered double hydroxides(Mg-Al LDH-NO_(2))on mortar durability under the coexisting environment of Cl−and SO_(4)^(2-).Cl−and SO_(4)^(2-...The aim of this paper is to investigate the effect of nitrite intercalated Mg-Al layered double hydroxides(Mg-Al LDH-NO_(2))on mortar durability under the coexisting environment of Cl−and SO_(4)^(2-).Cl−and SO_(4)^(2-) binding properties of Mg-Al LDH-NO_(2) in simulated concrete pore solutions,Cl−and SO_(4)^(2-) diffusion properties of mortars with Mg-Al LDHNO 2 were examined.The steel corrosion and resistance of mortar against SO_(4)^(2-) attack were also evaluated.The results indicate that Mg-Al LDH-NO_(2) can effectively adsorb the Cl−and SO_(4)^(2-) in simulated concrete pore solution,and inhibit the diffusion of Cl−and SO_(4)^(2-) into cement mortars.The presence of SO_(4)^(2-) can greatly affect the uptake amount of Cl−,and there is a coupled effect of Cl−and SO_(4)^(2-) on their penetration into mortar specimens.In addition,Mg-Al LDH-NO_(2) can greatly upgrade the resistance of mortars against SO_(4)^(2-) attack and well prevent the steel from corrosion.However,Cl−will aggravate the SO_(4)^(2-) attack and SO_(4)^(2-) can initially decrease and then increase the steel corrosion.展开更多
The ordered double perovskites, Sr2-xLaxMnMoO6, were prepared by sol-gel reaction. Structural, magnetic, and electrical properties were investigated for a series of ordered double perovskites Sr2- x Lax MnMoO6 （0 ≤...The ordered double perovskites, Sr2-xLaxMnMoO6, were prepared by sol-gel reaction. Structural, magnetic, and electrical properties were investigated for a series of ordered double perovskites Sr2- x Lax MnMoO6 （0 ≤ x ≤ 1 ）. The compounds have a monoclinic structure （space group P21/n） and the cell volume expands monotonically with La doping. The Tc and the magnetic moment rise and the cusp-like transition temperature below which the magnetic frustration occurs shifts to high temperature as x increases. With La doping, electrical resistivity of Sr2-x LaxMnMoO6 decreases only at low doping levels （x ≤0.2）; while at high doping levels （0.8≤x ≤1）, electrical resistivity tends to increase greatly. The resuits suggest that the competition between band filling effect and steric effect coexists in the whole doping range, and the formation of ferrimagnetic interactions is not simply at the expense of antiferromagnetic interactions.展开更多
Huanglian Jiedu decoction （HLJDD） has been shown to improve cerebral blood flow, and reduce lipid peroxidation damage to the brain and its energy metabolism. The present study was designed to observe the cerebroprot...Huanglian Jiedu decoction （HLJDD） has been shown to improve cerebral blood flow, and reduce lipid peroxidation damage to the brain and its energy metabolism. The present study was designed to observe the cerebroprotective effect of HL.JDD on an Alzheimer＇s disease rodent model, presenilin-1/amyloid protein precursor double transgenic mice. HLJDD reduced serum interleukin-6 and interleukin-113 levels, decreased [3-amyloid precursor protein gene and senile plaque expression, resisted oxidation, and reduced free radical-induced injury, thereby improving the learning and memory of these mice. Moreover, HLJDD at 433 mg/kg per day exhibited better effects compared with that at 865 or 216 mg/kg per day, and donepezil hydrochloride at 30 mg/kg per day. Thus, these results suggest that HLJDD may have protective effects against Alzheimer＇s disease.展开更多
In the framework of the functional integral formalism, we calculate the effective potential of the double sine-Gordon (DsG) model up to the second order with an optimized expansion and the Coleman's normal-orderin...In the framework of the functional integral formalism, we calculate the effective potential of the double sine-Gordon (DsG) model up to the second order with an optimized expansion and the Coleman's normal-ordering prescription. Within the range of convergence, we make a comparison among the classicaland the effective potential of the first and second order. The numerical analysis shows that the DsG post-Gaussian EP possesses some fine global properties and makes a substantial and a concordant quantum correction to the features of the classical potential.展开更多
Using an equation-of-motion technique, we theoretically study the Kondo-Fano effect in the T-shaped double quantum dots coupled to two ferromagnetic leads by the Anderson Hamiltonian. We calculate the density of state...Using an equation-of-motion technique, we theoretically study the Kondo-Fano effect in the T-shaped double quantum dots coupled to two ferromagnetic leads by the Anderson Hamiltonian. We calculate the density of states in this system by solving Green function. Our results reveal that the density of states show some noticeable characteristics not only depending upon the interdot coupling tab, the energy level eal of the side coupled quantum dot QDb, and the relative angle θ of magnetic moment M, but also the asymmetry parameter a in ferromagnetic leads and so on. All these parameters greatly influence the density of states of the eentral quantum dot QDa. This system is a possible candidate for spin valve transistors and may have potential applications in the spintronies.展开更多
Understanding the microscopic structure and thermodynamic properties of electrode/electrolyte interfaces is central to the rational design of electric-double-layer capacitors(EDLCs).Whereas practical applications ofte...Understanding the microscopic structure and thermodynamic properties of electrode/electrolyte interfaces is central to the rational design of electric-double-layer capacitors(EDLCs).Whereas practical applications often entail electrodes with complicated pore structures,theoretical studies are mostly restricted to EDLCs of simple geometry such as planar or slit pores ignoring the curvature effects of the electrode surface.Significant gaps exist regarding the EDLC performance and the interfacial structure.Herein the classical density functional theory(CDFT)is used to study the capacitance and interfacial behavior of spherical electric double layers within a coarse-grained model.The capacitive performance is associated with electrode curvature,surface potential,and electrolyte concentration and can be correlated with a regression-tree(RT)model.The combination of CDFT with machine-learning methods provides a promising quantitative framework useful for the computational screening of porous electrodes and novel electrolytes.展开更多
The electrical characteristics of a double-gate armchair silicene nanoribbon field-effect-transistor （DG ASiNR FET） are thoroughly investigated by using a ballistic quantum transport model based on non-equilibrium G...The electrical characteristics of a double-gate armchair silicene nanoribbon field-effect-transistor （DG ASiNR FET） are thoroughly investigated by using a ballistic quantum transport model based on non-equilibrium Green＇s function （NEGF） approach self-consistently coupled with a three-dimensional （3D） Poisson equation. We evaluate the influence of variation in uniaxial tensile strain, ribbon temperature and oxide thickness on the on-off current ratio, subthreshold swing, transconductance and the delay time of a 12-nm-length ultranarrow ASiNR FET. A novel two-parameter strain mag- nitude and temperature-dependent model is presented for designing an optimized device possessing balanced amelioration of all the electrical parameters. We demonstrate that employing HfO2 as the gate insulator can be a favorable choice and simultaneous use of it with proper combination of temperature and strain magnitude can achieve better device performance. Furthermore, a general model power （GMP） is derived which explicitly provides the electron effective mass as a function of the bandgap of a hydrogen passivated ASiNR under strain.展开更多
1 Introduction In recent years porous carbons have been widely used in many fields such as energy storage(Mc Creery,2008;Liu et al,2009;Ho et al,2014;Yang et al,2015),adsorption,wastewater treatment,air purification
The struetural effect of the conjugative system(C)with carbonyl-imino bridges has been studied.The results show that:In the conjugated system(C),there is no electronic absorption peak attributable to the whole system,...The struetural effect of the conjugative system(C)with carbonyl-imino bridges has been studied.The results show that:In the conjugated system(C),there is no electronic absorption peak attributable to the whole system,but there are three π-π* bands each nt which displays chacactecistics of its own independently.These indicate that the two bridges-carbonyl-and-imino-can block the tlanSmlSSion of the conjngative polarization of the whole system,so as to form three segments,this is verified by means of chemical synthesis and degradation.展开更多
A parallel-coupled double quantum dot （PCDQD） system with two multi-quantum dot chains is designed. Conductance versus Fermi energy level is investigated utilizing the non-equilibrium Green＇s function approach. If ...A parallel-coupled double quantum dot （PCDQD） system with two multi-quantum dot chains is designed. Conductance versus Fermi energy level is investigated utilizing the non-equilibrium Green＇s function approach. If two quantum dots are added on each side of the PCDQD system, additional Breit Wigner and Fano resonances occur in the conductance spectra. If quantum dots are added on one side of the system, small Fano resonances can be observed in the conductance spectra. Adjusting the number of side-coupled quantum dots, the anti-resonance bands emerge at different positions, which makes the system applicable as a quantum switching device. Moreover, the I-V characteristic curve presents the step characteristic and the width of the step decreases with increasing the number of side-coupled quantum dots.展开更多
The double-double (or tetrad) effect of low molecular lanthanide complexes has been reportedsince the effect was discovered by Fidelis and Siekierski.However,so far no description concerning thedouble-double effect of...The double-double (or tetrad) effect of low molecular lanthanide complexes has been reportedsince the effect was discovered by Fidelis and Siekierski.However,so far no description concerning thedouble-double effect of macromolecular lanthanide complexes has been published in literature.We have been successful in preparing lanthanide complexes with styrene-acrylic acid copolymer,someof which exhibite high activitiest in butadiene polymerization.It was found that the complexes showedthe double-double effect as they were characterized.In the present paper,the SAAC·Ln IR spectra whichcharacterize the double-double effect have been discussed in detail.展开更多
The mathematic model of heat transfer through ventilated double glazing was verified with the measured data,which were from a test chamber equipped with glass face temperature,solar radiation,ambient temperature,and w...The mathematic model of heat transfer through ventilated double glazing was verified with the measured data,which were from a test chamber equipped with glass face temperature,solar radiation,ambient temperature,and wind speed measurement facility.After the model validation,the double-skin facade assessment was carried out through simulation with ESP-r software integrating thermal simulation and air low net work module.The air flow situation in the air gap was analyzed on the basis of the hourly air velocity simulation data within typical winter week,summer week,spring week and autumn week.The differences of chimney effect in different seasons were discussed,and the thermal loads resulted from the ventilated and unventilated double skin facade were presented.展开更多
Electric double-layer field effect experiments were performed on ultrathin films of La0.325Pr0.3Ca0.375MnO3, which is noted for its micrometer-scale phase separation. A clear change of resistance up to 220% was observ...Electric double-layer field effect experiments were performed on ultrathin films of La0.325Pr0.3Ca0.375MnO3, which is noted for its micrometer-scale phase separation. A clear change of resistance up to 220% was observed and the characteristic metal-insulator transition temperature Tp was also shifted. The changes of both the resistance and Tp, suggest that the electric field induced not only tuning of the carrier density but also rebalancing of the phase separation states. The change of the charge-ordered insulating phase fraction was estimated to be temperature dependent, and a maximum of 16% was achieved in the phase separation regime. This tuning effect was partially irreversible, which might be due to an oxygen vacancy migration that is driven by the huge applied electric field.展开更多
A stacked lateral double-diffused metal–oxide–semiconductor field-effect transistor(LDMOS) with enhanced depletion effect by surface substrate is proposed(ST-LDMOS), which is compatible with the traditional CMOS pro...A stacked lateral double-diffused metal–oxide–semiconductor field-effect transistor(LDMOS) with enhanced depletion effect by surface substrate is proposed(ST-LDMOS), which is compatible with the traditional CMOS processes. The new stacked structure is characterized by double substrates and surface dielectric trenches(SDT). The drift region is separated by the P-buried layer to form two vertically parallel devices. The doping concentration of the drift region is increased benefiting from the enhanced auxiliary depletion effect of the double substrates, leading to a lower specific on-resistance(Ron,sp). Multiple electric field peaks appear at the corners of the SDT, which improves the lateral electric field distribution and the breakdown voltage(BV). Compared to a conventional LDMOS(C-LDMOS), the BV in the ST-LDMOS increases from 259 V to 459 V, an improvement of 77.22%. The Ron,sp decreases from 39.62 m?·cm^2 to 23.24 m?·cm^2 and the Baliga's figure of merit(FOM) of is 9.07 MW/cm^2.展开更多
基金supported in part by the National Key Research and Development Project of China(No.2022YFC3004602)in part by the National Natural Science Foundation of China(Nos.52121003 and 52342403).
文摘Multistage fracturing technology has been used to enhance tight hydrocarbon resource recovery.Determining the proper well spacing and fracturing strategy is crucial for generating a complex fracture network that facilitates oil and gas flow in reservoirs.The stress-shadow effect that occurs between multiple wells significantly affects the development of fracture networks in reservoirs.However,the quantification of the stress-shadow effect and its influence on fracture networks has not been satisfactorily resolved because of the difficulties in detecting and identifying fracture propagation and reorientation in reservoirs.In this study,based on the geological information from the Shengli oilfield,we applied a hybrid finite element-discrete element method to analyze engineering-scale three-dimensional fracture propagation and reorientation by altering well spacings and fracturing strategies.The results indicate that the fracturing area generated by the synchronous fracturing scheme is much smaller than those generated by the sequential and alternative schemes.An alternative hydrofracturing scheme is optimal with respect to fracturing area.The stress-blind area was defined to quantify the mechanical disturbance between adjacent wells.Our study improves the understanding of the effect of fracturing schemes on fracture networks and the impact of independent factors contributing to stress-shadow effects.
基金funded by the National Key Research and Development Program of China(2022YFB2404500)the Shenzhen Outstanding Talents Training Fund(01090100002)the National Natural Science Foundation of China(52201280)。
文摘The practical application of emerging rechargeable aqueous zinc(Zn)batteries is challenged by the poor reversibility and cycling stability of Zn anodes,primarily due to parasitic side reactions.While numerous strategies have been proposed,balancing the suppression of side reactions with the maintenance of fast Zn plating/stripping kinetics remains a significant challenge.In this study,sucrose,a sterically-hindered organic molecule with abundant hydroxyl groups,is employed to suppress the side reactions and maintain the moderate kinetics of Zn plating/stripping by modulating the hydrogen bond network without altering the Zn^(2+)solvation structure.Its steric hindrance effect further impedes the lateral diffusion of Zn atoms on the electrode surface within the electric double layer,effectively mitigating dendrite growth and stabilizing the electrodeposition process.Consequently,the formulated Suc/ZnSO_(4)electrolyte achieves a remarkably Coulombic efficiency of 99.90% over 2600 cycles at 3 mA cm^(-2)for 1 mAh cm^(-2)in Zn‖Cu cells.The enhanced Zn anode reversibility leads to excellent cycling stability in Zn‖LiFePO_(4)cells and Zn‖β-MnO_(2)cells.This study underscores the potential of sterically-hindered organic molecule strategies to enhance Zn anode stability while maintaining favorable Zn deposition/stripping dynamics in aqueous Zn batteries.
文摘Double pipe heat exchangers(DPHEs)are normally utilized in various manufacturing uses owing to their simple design and low maintenance requirements.For that,performance enhancement by improved heat transfer is ongoing.Air injections are a good strategy for enhancing the thermal performance of the DPHE.In the present work,the influence of air bubble injection in a DPHE was experimentally investigated,and the system’s hydrothermal performance improvement parameters were evaluated.Two modes were designed,manufactured,and used to conduct the experiments.The first mode was conducted with no air injection,named a single phase mode,while in the second mode,air was injected into the annulus of DPHE throughout different perforated rings on the side of the annular.Three different ring types were used and coded as R-1,R-2,and R-3,with an added case of insertion of the three rings inside the annulus.The airflow rate was fixed at 1.5 LPM with a 25○C inlet temperature.Also,the hot water rate in the inner pipe was maintained continuously at 3 LPM with a controlled 70○C temperature at the inlet.Five different cold water flow rates,3,3.5,4,4.5,and 5 LPM,in the annulus,were considered with a controlled inlet temperature at 17○C.Additionally,the effectiveness of the heat exchanger,the number of transfer units(NTU),and the overall heat transfer were predicted and considered for performance evaluation and comparison.The outcomes proved that the injection of air and the bubbly flow creation in the heat exchanger’s hot side is an effective method to strengthen the DPHE performance.Moreover,the total heat transfer coefficient was enhanced by 41%in R-1,58.8%in R-2,and 40.1%in R-3 at 4 LPM of cold water.The optimal ring,which yielded the most improvement,was R-2,achieving a 65%improvement in NTU,with a maximum enhancement in effectiveness of 56%.
文摘Synergistic effects of layered double hydroxide （LDH） with intumescent flame retardanct （IFR） of phosphorusnitrogen （NP） compound in the polypropylene/ethylene-propylene-diene/IFR/LDH （PP/EPDM/IFR/LDH） nanocomposites and related properties were studied by X-ray diffraction （XRD）, transmission electron microscopy （TEM）, scanning electron microscopy （SEM）, limiting oxygen index （LOI）, UL-94 test, cone calorimeter test （CCT） and thermo-gravimetric analysis （TGA）. The XRD and TEM results show that the intercalated and/or exfoliated nanocomposites can be obtained by direct melt-intercalation of PP/EPDM into modified LDH and that LDH can promote the IFR additive NP to disperse more homogeneously in the polymer matrix. The SEM results provide positive evidence that more compact charred layers can be obtained from the PP/EPDM/NP/LDH sample than those from the PP/EPDM/LDH and PP/EPDM/NP samples during burning. The LOI and UL-94 rating tests show that the synergetic effects of LDH with NP can effectively increase the flame retardant properties of the PP/EPDM/NP/LDH samples. The data from the CCT and TGA tests indicate that the PP/EPDM/NP/LDH samples apparently decrease the HRR and MLR values and thus enhance the flame retardant properties and have better thermal stability than the PP/EPDM/LDH and PP/EPDM/NP samples.
文摘Supported Ir catalysts were prepared using layered double hydrotalcite‐like materials,such as Mg_(3)Al_(1-x)Fe_(x),containing Fe and Al species in varying amounts as supports.These Ir catalysts were applied for the selective hydrogenation of cinnamaldehyde(CAL).When x was changed from 0(Ir/Mg_(3)Al)to 1(Ir/Mg_(3)Fe),the rate of CAL hydrogenation reached a maximum at approximately x=0.25,while the selectivity to unsaturated alcohol,i.e.,cinnamyl alcohol,monotonously increased from 44.9%to 80.3%.Meanwhile,the size of the supported Ir particles did not change significantly with x,remaining at 1.7-0.2 nm,as determined by transmission electron microscopy.The chemical state of Ir and Fe species in the Ir/Mg3Al1-xFex catalysts was examined by temperature programmed reduction by H2 and X‐ray photoelectron spectroscopy.The surface of the supported Ir particles was also examined through the in‐situ diffuse reflectance infrared Fourier‐transform of a probe molecule of CO.On the basis of these characterization results,the effects of Fe doping to Mg_(3)Al on the structural and catalytic properties of Ir particles in selective CAL hydrogenation were discussed.The significant factors are the electron transfer from Fe2+in the Mg_(3)Al_(1–x)Fex support to the dispersed Ir particles and the surface geometry.
文摘Solar energy is replacing more and more traditional sources of energy because of the fact that it’s also fighting about global warming. This study is based on exergy analysis of a double-effect series flow absorption refrigeration system powered by solar energy in Ngaoundere. The simulation is done on the basis of a half hourly analysis for the first time, from 6.30 AM to 6.30 PM, using water-lithium bromide as working pair. The main parameters for the performance of an absorption cycle, which are the COP and the ECOP, have been analyzed and the results show that this two parameters increase while increasing the temperature of the main generator. The exergy loss of each component of the system and the total exergy loss of the system have been analyzed and their effectiveness calculated, using the first and second law of thermodynamics. The highest exergy loss occurs in the main generator GI and in the absorber, making these components more important in an absorption cycle. This analysis is based on a mathematical model using FORTRAN?language. The results obtained may be useful for the optimization of solar absorption refrigeration systems.
基金Project(51478164)supported by the National Natural Science Foundation of ChinaProject(BK20181306)supported by Natural Science Foundation of Jiangsu Province,China。
文摘The aim of this paper is to investigate the effect of nitrite intercalated Mg-Al layered double hydroxides(Mg-Al LDH-NO_(2))on mortar durability under the coexisting environment of Cl−and SO_(4)^(2-).Cl−and SO_(4)^(2-) binding properties of Mg-Al LDH-NO_(2) in simulated concrete pore solutions,Cl−and SO_(4)^(2-) diffusion properties of mortars with Mg-Al LDHNO 2 were examined.The steel corrosion and resistance of mortar against SO_(4)^(2-) attack were also evaluated.The results indicate that Mg-Al LDH-NO_(2) can effectively adsorb the Cl−and SO_(4)^(2-) in simulated concrete pore solution,and inhibit the diffusion of Cl−and SO_(4)^(2-) into cement mortars.The presence of SO_(4)^(2-) can greatly affect the uptake amount of Cl−,and there is a coupled effect of Cl−and SO_(4)^(2-) on their penetration into mortar specimens.In addition,Mg-Al LDH-NO_(2) can greatly upgrade the resistance of mortars against SO_(4)^(2-) attack and well prevent the steel from corrosion.However,Cl−will aggravate the SO_(4)^(2-) attack and SO_(4)^(2-) can initially decrease and then increase the steel corrosion.
基金Project supported bythe National Natural Science Foundation of China (50073024 ,90101001) the Special Funds for MajorState Basic Research Projects (G1999064800) +1 种基金the Project fromthe Chinese Academy of Sciences (KJCX2-SW-H07) the In-ternational Collaboration Project from Changchun City ,China (04-03GH268)
文摘The ordered double perovskites, Sr2-xLaxMnMoO6, were prepared by sol-gel reaction. Structural, magnetic, and electrical properties were investigated for a series of ordered double perovskites Sr2- x Lax MnMoO6 （0 ≤ x ≤ 1 ）. The compounds have a monoclinic structure （space group P21/n） and the cell volume expands monotonically with La doping. The Tc and the magnetic moment rise and the cusp-like transition temperature below which the magnetic frustration occurs shifts to high temperature as x increases. With La doping, electrical resistivity of Sr2-x LaxMnMoO6 decreases only at low doping levels （x ≤0.2）; while at high doping levels （0.8≤x ≤1）, electrical resistivity tends to increase greatly. The resuits suggest that the competition between band filling effect and steric effect coexists in the whole doping range, and the formation of ferrimagnetic interactions is not simply at the expense of antiferromagnetic interactions.
基金the Natural Science Foundation of Hubei Province, No. 2007ABA060
文摘Huanglian Jiedu decoction （HLJDD） has been shown to improve cerebral blood flow, and reduce lipid peroxidation damage to the brain and its energy metabolism. The present study was designed to observe the cerebroprotective effect of HL.JDD on an Alzheimer＇s disease rodent model, presenilin-1/amyloid protein precursor double transgenic mice. HLJDD reduced serum interleukin-6 and interleukin-113 levels, decreased [3-amyloid precursor protein gene and senile plaque expression, resisted oxidation, and reduced free radical-induced injury, thereby improving the learning and memory of these mice. Moreover, HLJDD at 433 mg/kg per day exhibited better effects compared with that at 865 or 216 mg/kg per day, and donepezil hydrochloride at 30 mg/kg per day. Thus, these results suggest that HLJDD may have protective effects against Alzheimer＇s disease.
文摘In the framework of the functional integral formalism, we calculate the effective potential of the double sine-Gordon (DsG) model up to the second order with an optimized expansion and the Coleman's normal-ordering prescription. Within the range of convergence, we make a comparison among the classicaland the effective potential of the first and second order. The numerical analysis shows that the DsG post-Gaussian EP possesses some fine global properties and makes a substantial and a concordant quantum correction to the features of the classical potential.
基金Supported by the Scientific Research Fund of Southwest Petroleum University
文摘Using an equation-of-motion technique, we theoretically study the Kondo-Fano effect in the T-shaped double quantum dots coupled to two ferromagnetic leads by the Anderson Hamiltonian. We calculate the density of states in this system by solving Green function. Our results reveal that the density of states show some noticeable characteristics not only depending upon the interdot coupling tab, the energy level eal of the side coupled quantum dot QDb, and the relative angle θ of magnetic moment M, but also the asymmetry parameter a in ferromagnetic leads and so on. All these parameters greatly influence the density of states of the eentral quantum dot QDa. This system is a possible candidate for spin valve transistors and may have potential applications in the spintronies.
基金sponsored by the National Natural Science Foundation of China(Nos.91834301,21908053,and 21808055)Shanghai Sailing Program(19YF1411700)financial support from the Fluid Interface Reactions,Structures and Transport(FIRST)Center,an Energy Frontier Research Center funded by the U.S.Department of Energy,Office of Basic Energy Sciences。
文摘Understanding the microscopic structure and thermodynamic properties of electrode/electrolyte interfaces is central to the rational design of electric-double-layer capacitors(EDLCs).Whereas practical applications often entail electrodes with complicated pore structures,theoretical studies are mostly restricted to EDLCs of simple geometry such as planar or slit pores ignoring the curvature effects of the electrode surface.Significant gaps exist regarding the EDLC performance and the interfacial structure.Herein the classical density functional theory(CDFT)is used to study the capacitance and interfacial behavior of spherical electric double layers within a coarse-grained model.The capacitive performance is associated with electrode curvature,surface potential,and electrolyte concentration and can be correlated with a regression-tree(RT)model.The combination of CDFT with machine-learning methods provides a promising quantitative framework useful for the computational screening of porous electrodes and novel electrolytes.
文摘The electrical characteristics of a double-gate armchair silicene nanoribbon field-effect-transistor （DG ASiNR FET） are thoroughly investigated by using a ballistic quantum transport model based on non-equilibrium Green＇s function （NEGF） approach self-consistently coupled with a three-dimensional （3D） Poisson equation. We evaluate the influence of variation in uniaxial tensile strain, ribbon temperature and oxide thickness on the on-off current ratio, subthreshold swing, transconductance and the delay time of a 12-nm-length ultranarrow ASiNR FET. A novel two-parameter strain mag- nitude and temperature-dependent model is presented for designing an optimized device possessing balanced amelioration of all the electrical parameters. We demonstrate that employing HfO2 as the gate insulator can be a favorable choice and simultaneous use of it with proper combination of temperature and strain magnitude can achieve better device performance. Furthermore, a general model power （GMP） is derived which explicitly provides the electron effective mass as a function of the bandgap of a hydrogen passivated ASiNR under strain.
基金financial support from the National Natural Science Foundation of China (51274015)National Program on Key Basic Research Project (973 Program) (2014CB846000)Test Fund of Peking University
文摘1 Introduction In recent years porous carbons have been widely used in many fields such as energy storage(Mc Creery,2008;Liu et al,2009;Ho et al,2014;Yang et al,2015),adsorption,wastewater treatment,air purification
文摘The struetural effect of the conjugative system(C)with carbonyl-imino bridges has been studied.The results show that:In the conjugated system(C),there is no electronic absorption peak attributable to the whole system,but there are three π-π* bands each nt which displays chacactecistics of its own independently.These indicate that the two bridges-carbonyl-and-imino-can block the tlanSmlSSion of the conjngative polarization of the whole system,so as to form three segments,this is verified by means of chemical synthesis and degradation.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11447132 and 11504042the Chongqing Science and Technology Commission Project under Grant Nos cstc2014jcyj A00032 and cstc2016jcyj A1158the Scientific Research Project for Advanced Talents of Yangtze Normal University under Grant No 2017KYQD09
文摘A parallel-coupled double quantum dot （PCDQD） system with two multi-quantum dot chains is designed. Conductance versus Fermi energy level is investigated utilizing the non-equilibrium Green＇s function approach. If two quantum dots are added on each side of the PCDQD system, additional Breit Wigner and Fano resonances occur in the conductance spectra. If quantum dots are added on one side of the system, small Fano resonances can be observed in the conductance spectra. Adjusting the number of side-coupled quantum dots, the anti-resonance bands emerge at different positions, which makes the system applicable as a quantum switching device. Moreover, the I-V characteristic curve presents the step characteristic and the width of the step decreases with increasing the number of side-coupled quantum dots.
基金The project supported by the National Natural Science Foundation of China
文摘The double-double (or tetrad) effect of low molecular lanthanide complexes has been reportedsince the effect was discovered by Fidelis and Siekierski.However,so far no description concerning thedouble-double effect of macromolecular lanthanide complexes has been published in literature.We have been successful in preparing lanthanide complexes with styrene-acrylic acid copolymer,someof which exhibite high activitiest in butadiene polymerization.It was found that the complexes showedthe double-double effect as they were characterized.In the present paper,the SAAC·Ln IR spectra whichcharacterize the double-double effect have been discussed in detail.
基金Supported by Shanghai Science and Technology Supporting Program(08DZ1203500)City University of Hong Kong(7002004)+1 种基金Shanghai Local University Fund(071605124)Undergraduates Education Fund for University of Shanghai
文摘The mathematic model of heat transfer through ventilated double glazing was verified with the measured data,which were from a test chamber equipped with glass face temperature,solar radiation,ambient temperature,and wind speed measurement facility.After the model validation,the double-skin facade assessment was carried out through simulation with ESP-r software integrating thermal simulation and air low net work module.The air flow situation in the air gap was analyzed on the basis of the hourly air velocity simulation data within typical winter week,summer week,spring week and autumn week.The differences of chimney effect in different seasons were discussed,and the thermal loads resulted from the ventilated and unventilated double skin facade were presented.
基金supported by the National Basic Research Program of China(Grant Nos.2011CBA00106 and 2014CB921401)the National Natural Science Foundation of China(Grant Nos.11174342,9131208,and 11374344)
文摘Electric double-layer field effect experiments were performed on ultrathin films of La0.325Pr0.3Ca0.375MnO3, which is noted for its micrometer-scale phase separation. A clear change of resistance up to 220% was observed and the characteristic metal-insulator transition temperature Tp was also shifted. The changes of both the resistance and Tp, suggest that the electric field induced not only tuning of the carrier density but also rebalancing of the phase separation states. The change of the charge-ordered insulating phase fraction was estimated to be temperature dependent, and a maximum of 16% was achieved in the phase separation regime. This tuning effect was partially irreversible, which might be due to an oxygen vacancy migration that is driven by the huge applied electric field.
基金supported by the National Natural Science Foundation of China(Grant No.61464003)the Guangxi Natural Science Foundation,China(Grant Nos.2015GXNSFAA139300 and 2018JJA170010)
文摘A stacked lateral double-diffused metal–oxide–semiconductor field-effect transistor(LDMOS) with enhanced depletion effect by surface substrate is proposed(ST-LDMOS), which is compatible with the traditional CMOS processes. The new stacked structure is characterized by double substrates and surface dielectric trenches(SDT). The drift region is separated by the P-buried layer to form two vertically parallel devices. The doping concentration of the drift region is increased benefiting from the enhanced auxiliary depletion effect of the double substrates, leading to a lower specific on-resistance(Ron,sp). Multiple electric field peaks appear at the corners of the SDT, which improves the lateral electric field distribution and the breakdown voltage(BV). Compared to a conventional LDMOS(C-LDMOS), the BV in the ST-LDMOS increases from 259 V to 459 V, an improvement of 77.22%. The Ron,sp decreases from 39.62 m?·cm^2 to 23.24 m?·cm^2 and the Baliga's figure of merit(FOM) of is 9.07 MW/cm^2.
