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太阳风中的Alfven波耗散与电子和质子温度分布问题
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作者 肖池阶 宋礼庭 《空间科学学报》 CAS CSCD 北大核心 1998年第4期296-300,共5页
根据动力论Alfven波耗散机制,详细计算了动力论Alfven波衰减的能量分配给质子和电子的比率.初步解释了高速太阳风中质子温度比电子温度高的事实,定性说明了r<10Rs时电子快速冷却的原因.
关键词 动力论Alfven波 高速太阳风 质子温度 电子温度
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Influences of Structure Disorder and Temperature on Properties of Proton Conductivity in Hydrogen-Bond Molecular Systems 被引量:1
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作者 PANG Xiao-Feng YU Jia-Feng 《Communications in Theoretical Physics》 SCIE CAS CSCD 2007年第2期235-243,共9页
The dynamic properties of proton conductivity along hydrogen-bonded molecular systems, for example, ice crystal, with structure disorder or damping and finite temperatures exposed in an externally applied electric-fie... The dynamic properties of proton conductivity along hydrogen-bonded molecular systems, for example, ice crystal, with structure disorder or damping and finite temperatures exposed in an externally applied electric-field have been numerically studied by Runge-Kutta way in our soliton model. The results obtained show that the proton-soliton is very robust against the structure disorder including the fluctuation of the force constant and disorder in the sequence of masses and thermal perturbation and damping of medium, the velocity of its conductivity increases with increasing of the externally applied electric-field and decreasing of the damping coefficient of medium, but the proton-soliton disperses for quite great fluctuation of the "force constant and damping coefficient. In the numerical simulation we find that the proton-soliton in our model is thermally stable in a large region of temperature of T ≤ 273 K under influences of damping and externally applied electric-field in ice crvstal. This shows that our model is available and appropriate to ice. 展开更多
关键词 proton conductivity structure disorder temperature hydrogen bonded system
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Dynamic Thermal Model and Temperature Control of Proton Exchange Membrane Fuel Cell Stack 被引量:5
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作者 邵庆龙 卫东 +1 位作者 曹广益 朱新坚 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2005年第2期218-224,共7页
A dynamic thermal transfer model of a proton exchange membrane fuel cell (PEMFC) stack is developed based on energy conservation in order to reach better temperature control of PEMFC stack. Considering its uncertain p... A dynamic thermal transfer model of a proton exchange membrane fuel cell (PEMFC) stack is developed based on energy conservation in order to reach better temperature control of PEMFC stack. Considering its uncertain parameters and disturbance, we propose a robust adaptive controller based on backstepping algorithm of Lyaponov function. Numerical simulations indicate the validity of the proposed controller. 展开更多
关键词 proton exchange membrane fuel cell stack dynamic thermal transfer model temperature control
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Nonlinear Predictive Control for PEMFC Stack Operation Temperature
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作者 李曦 曹广益 朱新坚 《Journal of Shanghai Jiaotong university(Science)》 EI 2005年第2期157-159,共3页
Operating temperature of proton exchange membrane fuel cell stack should be controlled within a special range. The input-output data and operating experiences were used to establish a PEMFC stack model and operating t... Operating temperature of proton exchange membrane fuel cell stack should be controlled within a special range. The input-output data and operating experiences were used to establish a PEMFC stack model and operating temperature control system. A nonlinear predictive control algorithm based on fuzzy model was presented for a family of complex system with severe nonlinearity such as PEMFC. Based on the obtained fuzzy model, a discrete optimization of the control action was carried out according to the principle of Branch and Bound method. The test results demonstrate the effectiveness and advantage of this approach. 展开更多
关键词 proton exchange membrane fuel cell (PEMFC) nonlinear predictive control operation temperature
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Oxidative Degradation of Soda Lignin Assisted by Microwave Irradiation 被引量:16
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作者 欧阳新平 林再雄 +2 位作者 邓永红 杨东杰 邱学青 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2010年第4期695-702,共8页
The effects of oxidant dosage,oxidation temperature and time on the degradation of soda lignin by hydrogen peroxide with and without the presence of microwave irradiation were investigated.It is found that the oxidati... The effects of oxidant dosage,oxidation temperature and time on the degradation of soda lignin by hydrogen peroxide with and without the presence of microwave irradiation were investigated.It is found that the oxidative degradation of lignin includes the cleavage of ether bond inβ-O-4 structure,the partial destruction of aromatic ring,and the re-condensation of the degraded lignin.Compared to the conventionally heated oxidation of lignin,the microwave irradiation efficiently facilitates the degradation of the lignin with high molecular weight and the re-condensation of that with low molecular weight at a low oxidant dosage,low oxidation temperature,or a short oxidation time,which leads to the formation of the degraded lignin with narrower molecular weight distribution and lower molecular weight.Additionally,the lignin degraded in the presence of microwave irradiation has the characteristics of higher content of phenolic hydroxyl group,lower content of methoxyl group,and lower degree of condensation,which enhances the reactivity of lignin.Therefore,the oxidative degradation of lignin assisted by microwave irradiation may be a new pretreatment approach for efficiently utilizing the soda lignin. 展开更多
关键词 OXIDATION DEGRADATION soda lignin microwave irradiation
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Swelling properties and molecular simulation of PNIPA porous hydrogels 被引量:1
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作者 李智慧 刘文涛 +6 位作者 李中原 段翔远 高旭静 李蕴才 杨明成 何素芹 朱诚身 《Journal of Central South University》 SCIE EI CAS 2013年第5期1161-1172,共12页
A series of porous intelligent hydrogels, which exhibited appropriate lower critical solution temperature (LCST) and fast response behavior, were synthesized by radiation method. The structure and surface morphology o... A series of porous intelligent hydrogels, which exhibited appropriate lower critical solution temperature (LCST) and fast response behavior, were synthesized by radiation method. The structure and surface morphology of hydrogels were examined by the infrared radiation and the scanning electron microscopy, respectively. The influences of the content of crosslinking agent and relative molecular mass of polyethylene glycol (PEG) on the swelling properties of hydrogels were discussed. The molecular mechanics simulations were performed to investigate the phase transformation mechanism of poly(N-isopropyl acrylamide) (PNIPA) hydrogel. The results show that macropores are observed in hydrogels, whereas hydrogels prepared without using PEG have a dense surface. LCST of hydrogels increases with the increase of relative molecular mass of PEG. The swelling mechanism of PNIPA porous hydrogels follows non-Fickian diffusion model. The theoretical maximum water absorption S∞ is approximately consistent with experimental value according to the second-order kinetics model established by Schott. The molecule chains of PNIPA hydrogel begin folding and curling, resulting in volume shrinkage at 305 K. There are much intramolecular nonbonding interactions in molecule chains of hydrogels. The porous hydrogels are expected to be applied in the field of artificial intelligence material. 展开更多
关键词 poly(N-isopropyl acrylamide) RADIATION swelling properties molecular simulation
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Density functional theory study of active sites and reaction mechanism of ORR on Pt surfaces under anhydrous conditions 被引量:1
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作者 Guangdong Liu Huiqiu Deng +1 位作者 Jeffrey Greeley Zhenhua Zeng 《Chinese Journal of Catalysis》 SCIE EI CAS CSCD 2022年第12期3126-3133,共8页
Identifying active sites and catalytic mechanism of the oxygen reduction reaction under anhydrous conditions are crucial for the development of next generation proton exchange membrane fuel cells(PEMFCs)operated at a ... Identifying active sites and catalytic mechanism of the oxygen reduction reaction under anhydrous conditions are crucial for the development of next generation proton exchange membrane fuel cells(PEMFCs)operated at a temperature>100℃.Here,by employing density functional theory calculations,we studied ORR on flat and stepped Pt(111)surfaces with both(110)and(100)type of steps.We found that,in contrast to ORR under hydrous conditions,(111)terrace sites are not active for ORR under anhydrous conditions,because of weakened binding of ORR intermediates induced by O*accumulation on the surface.On the other hand,step edges,which are generally not active for ORR under hydrous conditions,are predicted to be the active sites for ORR under anhydrous conditions.Among them,(110)type step edge with a unique configuration of accumulated O stabilizes O_(2)adsorption and facilitates O_(2)dissociation,which lead an overpotential<0.4 V.To improve ORR catalysts in high-temperature PEMFCs,it is desirable to maximize(110)step edge sites that present between two(111)facets of nanoparticles. 展开更多
关键词 Oxygen reduction Active site Anhydrous condition High-temperature PEMFCs Density functional theory
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Chiral Phase Transition at Finite Isospin Density in Linear Sigma Model
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作者 SHUSong LIJia-Rong 《Communications in Theoretical Physics》 SCIE CAS CSCD 2005年第3期487-492,共6页
Using the linear sigma model, we have introduced the pion isospin chemical potential. The chiral phase transition is studied at finite temperatures and finite isospin densities. We have studied the μ - T phase diagra... Using the linear sigma model, we have introduced the pion isospin chemical potential. The chiral phase transition is studied at finite temperatures and finite isospin densities. We have studied the μ - T phase diagram for the chiral phase transition and found the transition cannot happen below a certain low temperature because of the BoseEinstein condensation in this system. Above that temperature, the chiral phase transition is studied by the isotherms of pressure versus density. We indicate that the transition, in the chiral limit, is a first-order transition from a low-density phase to a high-density phase like a gas-liquid phase transition. 展开更多
关键词 finite temperature field theory nuclear matter chiral symmetries
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Temperature-triggered Protein Adsorption and Desorption on Temperature-responsive PNIPAAm-grafted-silica:Molecular Dynamics Simulation and Experimental Validation 被引量:2
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作者 康锴 卢滇楠 刘铮 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2012年第2期284-293,共10页
Poly(N-isopropylacrylamide)(PNIPAAm) grafted onto silica,which may be used for reverse phase chromatography(RPC),was simulated and synthesized for protein separation with temperature-triggered adsorption and desorptio... Poly(N-isopropylacrylamide)(PNIPAAm) grafted onto silica,which may be used for reverse phase chromatography(RPC),was simulated and synthesized for protein separation with temperature-triggered adsorption and desorption.Molecular dynamics simulation at an all-atom level was performed to illustrate the adsorption/desorption behavior of cytochrome c,the model protein,on PNIPAAm-grafted-silica,a temperature responsive adsorbent.At a temperature above the lower critical solution temperature(LCST),the PNIPAAm chains aggregate on the silica surface,forming a hydrophobic surface that is favorable for the hydrophobic adsorption of cytochrome c,which has a high exposure of hydrophobic patches.At temperatures below the LCST,the PNIPAAm chains stretch,forming hydrophilic surface due to hydrogen bonding between PNIPAAm and surrounding water.Desorption of cytochrome c on the PNIPAAm-grafted-silica surface occurs as a result of competition with water,which forms hydrogen bonds with the protein.The conformational transitions of both cytochrome c and PNIPAAm are monitored,providing molecular insight into this temperature-responsive RPC technique.PNIPAAm-grafted-silica beads were synthesized and used for the adsorption and desorption of cytochrome c at approximately 313 K and 290 K,respectively.The experimental results validate the molecular dynamics simulation.In comparison to conventional RPC,using temperature as a driving force for RPC reduces the risk of protein denaturation caused by exposure to chaotropic solvents.Moreover,it simplifies the separation process by avoiding the buffer exchange operations between the steps. 展开更多
关键词 reverse phase chromatography PNIPAAm-grafted-silica cytochrome c molecular dynamics simulation atom transfer radical polymerization (ATRP)
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Salinization:the ultimate threat to temperate lakes,with particular reference to Southeastern Wisconsin(USA)
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作者 Jeffrey A.THORNTON Thomas M.SLAWSKI Hebin LIN 《Chinese Journal of Oceanology and Limnology》 SCIE CAS CSCD 2015年第6期1461-1475,共15页
Many lakes in Southeastern Wisconsin(the metropolitan-Milwaukee area) are gradually becoming increasingly "salty".While these waterbodies would not be considered presently to be saline lakes,there has been a... Many lakes in Southeastern Wisconsin(the metropolitan-Milwaukee area) are gradually becoming increasingly "salty".While these waterbodies would not be considered presently to be saline lakes,there has been a rapid increase in the chloride concentrations in most of these lakes over the last 30 years,with the lakes increasing from a mean chloride concentration of about 19 mg/L to over 100 mg/L in some cases.While ecological impacts can be expected when chloride values exceed 250 mg/L,the rate of increase presents a basis for concern,especially since the underlying geology of the region is based on limestone/dolomite which is deficient in chlorides.Thus,the origin of the chlorides is anthropogenic:human and industrial wastewaters(treatment of which has effected improvements in trophic status but has not affected other water-borne contaminants) and winter de-icing practices based upon large quantities of sodium chloride are major contributors to the increasing concentrations of chloride in the region's waterways.Without taking remedial measures,the rate of salinization is expected to continue to increase,resulting,ultimately,in the alteration of the freshwater systems in the region. 展开更多
关键词 SALINIZATION temperate lakes chloride concentrations salt management
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太阳风
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作者 程学军 《中学物理教学参考》 1996年第8期48-48,共1页
太阳风广东省惠阳市崇雅中学程学军1.什么是"太阳风""太阳风"是太阳连续不断地向宇宙空间辐射出的稳定的粒子流.2."太阳风"的观测在1962年,美国的"水手二号"卫星在宇宙中观测到太阳连续不断地向外辐射等离子体,证实... 太阳风广东省惠阳市崇雅中学程学军1.什么是"太阳风""太阳风"是太阳连续不断地向宇宙空间辐射出的稳定的粒子流.2."太阳风"的观测在1962年,美国的"水手二号"卫星在宇宙中观测到太阳连续不断地向外辐射等离子体,证实了太阳风的存在,有力地说明了日地空... 展开更多
关键词 太阳风 质子温度 太阳活动 太阳物理学 日冕 带电粒子 地球磁场 太阳大气 动力学模型 行星际磁场
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Observational connection between local high-temperature phenomena within magnetic clouds and the Sun 被引量:2
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作者 WANG JieMin FENG HengQiang 《Science China Earth Sciences》 SCIE EI CAS CSCD 2016年第5期1051-1056,共6页
Magnetic clouds(MCs) frequently show abnormal high-ionization states of heavy ions. The abnormal high-charge distributions are related to the coronal temperature of their source regions. We examined the plasma and mag... Magnetic clouds(MCs) frequently show abnormal high-ionization states of heavy ions. The abnormal high-charge distributions are related to the coronal temperature of their source regions. We examined the plasma and magnetic field data of 74 MCs observed by the Advanced Composition Explorer from February 1998 to December 2008. We determined that 14 of the 74 events showed local high-temperature phenomena. We analyzed the correlation between proton temperature and O7/O6ratio(or high mean Fe charge state ?Fe?) within the local high-temperature regions in the 14 MCs. Results show that proton temperature and O7/O6 ratio(or high mean Fe charge state) had good correlations in nine MCs, but had no evident correlation in the other five MCs. The local high-temperature phenomena within the nine MCs have resulted from the Sun. 展开更多
关键词 Magnetic cloud Ion ionization state High temperature proton
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A naive toy model of dark matter:Fermion sea
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作者 ZHANG YuJie 《Science China(Physics,Mechanics & Astronomy)》 SCIE EI CAS 2011年第6期1178-1178,共1页
A naive toy model that the fermion sea offers the dark matter density is discussed here.If the fermion sea fills the total space and the temperature equals the temperature of CMB,we can get the mass of the fermion is ... A naive toy model that the fermion sea offers the dark matter density is discussed here.If the fermion sea fills the total space and the temperature equals the temperature of CMB,we can get the mass of the fermion is about 4.7×10 38 kg (0.026 eV). 展开更多
关键词 dark matter fermion sea CMB temperature
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Vector Meson Mass in Finite Density and Temperature Lattice QCD
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作者 王睿 陈莹 +6 位作者 宫明 刘川 刘玉斌 刘朝峰 马建平 孟祥飞 张剑波 《Communications in Theoretical Physics》 SCIE CAS CSCD 2015年第5期559-564,共6页
Vector meson mass values are studied at finite chemical potential and temperature in lattice QCD with lattice size of 24 × 122× 6 using two flavors of staggered quarks. The investigation focuses on the chang... Vector meson mass values are studied at finite chemical potential and temperature in lattice QCD with lattice size of 24 × 122× 6 using two flavors of staggered quarks. The investigation focuses on the change of the vector meson mass in the critical region close to T c with two different types of chemical potentials switched on: the isoscalar chemical potential μS and its isovector counterpart μV. It is found that the vector meson mass increases in the QGP phase with both chemical potentials and decreases with μS in the confinement phase. 展开更多
关键词 lattice QCD numerical simulation vector meson
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Surface properties of encapsulating hydrophobic nanoparticles regulate the main phase transition temperature of lipid bilayers: A simulation study 被引量:3
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作者 Xubo Lin Ning Gu 《Nano Research》 SCIE EI CAS CSCD 2014年第8期1195-1204,共10页
The main phase transition temperature of a lipid membrane, which is vital for its biomedical applications such as controllable drug release, can be regulated by encapsulating hydrophobic nanoparticles into the membran... The main phase transition temperature of a lipid membrane, which is vital for its biomedical applications such as controllable drug release, can be regulated by encapsulating hydrophobic nanoparticles into the membrane. However, the exact relationship between surface properties of the encapsulating nanoparticles and the main phase transition temperature of a lipid membrane is far from clear. In the present work we performed coarse-grained molecular dynamics simulations to meet this end. The results show the surface roughness of nanoparticles and the density of surface-modifying molecules on the nanoparticles are responsible for the regulation. Increasing the surface roughness of the nanoparticles increases the main phase transition temperature of the lipid membrane, whereas it can be decreased in a nonlinear way via increasing the density of surface-modifying molecules on the nanoparticles. The results may provide insights for understanding recent experimental studies and promote the applications of nanoparticles in controllable drug release by regulating the main phase transition temperature of lipid vesicles. 展开更多
关键词 lipid bilayer phase transition NANOPARTICLE surface roughness density surface molecules
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Fe3O4-nanoparticle-decorated TiO2 nanofiber hierarchical heterostructures with improved lithium-ion battery performance over wide temperature range 被引量:2
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作者 Hengguo Wang Guangsheng Wang +3 位作者 Shuang Yuan Delong Ma Yang Li Yu Zhang 《Nano Research》 SCIE EI CAS CSCD 2015年第5期1659-1668,共10页
A facile strategy was designed for the fabrication of Fe3O4-nanoparticle- decorated TiO2 nanofiber hierarchical heterostructures (FTHs) by combining the versatility of the electrospinning technique and the hydrother... A facile strategy was designed for the fabrication of Fe3O4-nanoparticle- decorated TiO2 nanofiber hierarchical heterostructures (FTHs) by combining the versatility of the electrospinning technique and the hydrothermal growth method. The hierarchical architecture of Fe3O4 nanoparticles decorated on TiO2 nanofibers enables the successful integration of the binary composite into batteries to address structural stability and low capacity. In the resulting unique architecture of FTHs, the 1D heterostructures relieve the strain caused by severe volume changes of Fe3O4 during numerous charge-discharge cycles, and thus suppress the degradation of the electrode material. As a result, FTHs show excellent performance including higher reversible capacity, excellent cycle life, and good rate performance over a wide temperature range owing to the synergistic effect of the binary composition of TiO2 and Fe304 and the unique features of the hierarchical nanofibers. 展开更多
关键词 hierarchical heterostructures wide temperature range electrochemical performance lithium-ion batteries
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Influence of temperature and LO phonon on the effective mass of bipolarons in polar semiconductor quantum dots
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作者 辛伟 高忠明 +1 位作者 韩超 额尔敦朝鲁 《Optoelectronics Letters》 EI 2012年第6期477-480,共4页
The temperature and LO phonon effects of the bipolaron in polar semiconductor quantum dots (QDs) are studied by using the Tokuda modified linear-combination operator method and the Lee-Low-Pines variational method. ... The temperature and LO phonon effects of the bipolaron in polar semiconductor quantum dots (QDs) are studied by using the Tokuda modified linear-combination operator method and the Lee-Low-Pines variational method. The expressions for the mean number ofLO phonons and the effective mass of the bipolaron are derived. Numerical results show that the mean number of LO phonons of the bipolaron decreases with increasing the temperature and the relative distance r between two electrons, but increases with increasing the electron-phonon coupling strength a The effective mass of the bipolaron M* increases rapidly with increasing the relative distance r between two electrons when r is smaller, and it reaches a maximum at r ≈ 4.05rp, while after that, 34* decreases slowly with increasing r. The effective mass of the bipolaron M' decreases with increasing the temperature. The electron-phonon coupling strength a markedly influences the changes of mean number of LO phonons and the effective mass M* with the relative distance r and the temperature parameter y. 展开更多
关键词 Electron correlations ELECTRON phonon interactions Semiconductor quantum dots
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Donor Binding Energy in GaAs/Ga_(1-x) Al_xAs Quantum Well:the Laser Field and Temperature Effects
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作者 危书义 侯文秀 +1 位作者 陈晓阳 夏从新 《Communications in Theoretical Physics》 SCIE CAS CSCD 2013年第7期124-128,共5页
Based on the effective-mass approximation theory and variational method, the laser field and temperature effects on the ground-state donor binding energy in the GaAsflGa1-x AlxAs quantum well (QW) are investigated. ... Based on the effective-mass approximation theory and variational method, the laser field and temperature effects on the ground-state donor binding energy in the GaAsflGa1-x AlxAs quantum well (QW) are investigated. Numerical results show that the donor binding energy depends on the impurity position, laser parameter, temperature, Al composition, and well width. The donor binding energy is decreased when the laser field and temperature are increased in the QW for any impurity position and QW parameter case. Moreover, the laser field has an obvious influence on the donor binding energy of impurity located at the vicinity of the QW center. In addition, our results also show that the donor binding energy decreases (or increases) as the well width (or AI composition x) increases in the QW. 展开更多
关键词 laser field TEMPERATURE impurity states
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