The fourier transformations of positive distributions on lorentz groupSO (3, 1)

With the aid of Plancherel-Godement Theorem, we prove that every positive distributionT onSO (3, 1) which is bi-invariant underSO(3) corresponds to a measure μ on ω=∝σC|s(2-s)>=0∝, and μ can be decomposed intoμ=μ ₁+μ ₂, whereμ ₁ is a bounded measure on 0<=s<=2 andμ ₂ is slowly increasing measure on (sχC|Re(s)=1)} Foundation item: Supported by the National Natural Science Foundation of China (19871065) and Hua Cheng Mathematics Science Foundation. Biography: Zhu Li (1976-), male, Graduate student, research interest: partial differential equation     

Effects of anions on the biosorption of microelement cations by macroalga <Emphasis Type="Italic">Enteromorpha prolifera</Emphasis> in single- and multi-metal systems

The results of research on the effects of anions on the biosorption of microelement cations by the edible marine macroalga Enteromorpha prolifera in singleand multi-metal systems are discussed in this paper. It was shown that the maximum biosorption capacity (qmax) in a single-metal system of Co(II) ions decreased in the following sequence: Cl- (46.0 mg g-1) > SO42- (42.8 mg g-1) > NO3- (41.9 mg g-1). In multi-metal systems, in which the ratios of Cl-, NO3-, and SO42- were 0:0:4, 1:1:2, 3:0:1, and 4:0:0, there were clear differences among the biosorption capacities. In all the examined systems (other than the 0:0:4 system), inhibition of the binding of microelement cations by the macroalga was observed. In all the systems, the highest value of qmax was obtained for Cu(II) cations; the value ranged from 31.9 mg g-1 in 0:0:4 (SO42- only) to 18.2 mg g-1 in 4:0:0 (Cl-only).     

Doping effect on thermoelectric properties of nonstoichiometric AgSbTe<Subscript>2</Subscript> compounds

Nonstoichiometric ternary thermoelectric materials Ag_0.84Sb_1.15M_0.01Te_2.16 (M=Ce, Yb, Cu) were prepared by a direct melt-quench and hot press process. The carrier concentration of all the samples increased after doping. Thermoelectric properties, namely electrical conductivity, Seebeck coefficient, and thermal conductivity, were measured from 300 to 673 K. The phase transition occurring at about 418 K representing the phase transition from β-Ag₂Te to α-Ag₂Te influenced the electrical transport properties. The electrical conductivities of Ce and Yb doped samples increased after doping from 1.9×10⁴ to 2.5×10⁴ and 2.3×10⁴ S·m⁻¹, respectively, at 673 K. Also, at room temperature, the Seebeck coefficient of the Ce doped sample relatively increased corresponding to the high carrier concentration due to the changes in the band structure. However, all the thermal conductivities increased after doping at low temperature. Because of the higher thermal conductivity, the dimensionless figure of merit ZT of these doped samples has not been improved.     

Luminescent Cu doped CdTe nanocrystals via cation exchange of Cu7Te5 nanocubes: From undoped to doped emission

In II-VI group, the doping in CdTe nanocrystals (NCs) is more difficult than other chalcogenides. In this communication, CdTe nanocrystals containing Cu impurities were carefully synthesized based on controlled reverse cation exchange process between as-prepared Cu₇Te₅ nanocubes and Cd²⁺ ions. By well-defined Cu₇Te₅ nanocubes, the obtained CdTe NCs kept the original morphology. The concentration of Cu impurities in CdTe NCs was controlled by the regulation such reverse cation exchange. Additionally, the regulation from band gap (BG) photoluminescence (PL) to the coexistence of the bandgap emission, dopant emission, and surface-state emission was realized. This tailoring from undoped to doped emission in the case of Cu impurities is helpful to study the Cu related doping in telluride NCs.     

La_(1-x)Ca_xMnO_3的电子结构与磁有序研究

采用DV-Xa分子轨道法计算了不同掺杂浓度的立方结构钙钛矿La_(1-x)Ca_xMnO_3体系的电子结构,分析了体系磁电特性随钙浓度变化的特征.结果表明:自旋相关的锰3d—氧2p轨道杂化出现在整个体系中.未掺杂体系具有金属型导电性,费米能级处多数自旋子带的态密度高于少数子带.随着掺杂浓度的提高,体系发生金属-半金属相变.与此同时,锰离子磁矩单调降低,与3d带自旋交换劈裂的变化规律一致.掺杂的钙提高了锰3d和氧2p电子波函数的交迭,加强了Mn-O-Mn超交换作用,使CaMnO3呈现G型反铁磁态.LaMnO_3中锰3d和氧2p波函数的交迭最弱,呈铁磁有序.     

Transition-metal-doped Fe2O3 nanoparticles for oxygen evolution reaction

Hematite(α-Fe_2O_3)has been extensively studied as a promising photocatalyst,with the capacity to split water under visible light.To tune its electronic structure and improve the performance for oxygen evolution reaction(OER),high-quality single crystals ofα-Fe_2O_3nanoparticles were synthesized and doped by various transition metals(M=V,Cr,Mn,Zn,Co,Ni,Cu,Nb,Mo,Ti)by a molten-salt flux method.Optical,electronic and catalytic properties of transition-metal-dopedα-Fe_2O_3(TM-dopedα-Fe_2O_3)have been systematically investigated.Cobalt has been identified as the best dopant forα-Fe_2O_3,reducing the OER overpotential by 0.16 V with respect to the undoped.     

交叉轧制对TA1钛箔材组织和性能的影响

采用光学显微镜和室温拉伸试验研究了交叉轧制对TA1钛箔材组织和性能的影响。结果表明：交叉轧制后,晶粒尺寸减小,组织更加均匀。拉伸测试表明：采用交叉轧制后,塑性升高,强度、各向异性和横向屈强比均显著降低。屈服强度与晶粒尺寸的关系遵循Hall—Petch公式。交叉轧制后,σ₀值显著降低,K值为正值。普通轧制后,σ₀值较高,K值都为负值。     

退火温度对N掺杂MgZnO薄膜光电性能的影响

采用射频磁控溅射技术, 用氮气作为掺杂源, 在石英基片上生长N掺杂Mg_xZn_1-xO薄膜, 并将薄膜分别在550,600,650,700 ℃真空中进行热退火处理. 结果表明: 晶体质量随退火温度的升高而提高; 薄膜中Mg和Zn的原子比发生了变化; Raman光谱中位于272,642 cm^-1处的振动峰逐渐消失; 室温光致发光光谱中薄膜的紫外激子发射峰变强, 且发生峰移; 随着退火温度的升高, 薄膜的导电类型发生转变, 当退火温度为600 ℃时, 薄膜呈最佳的p型导电性质.     

Isotope effect of the stereodynamics in the reactions F+HCl→HF+Cl and F+DCl→DF+Cl

Using a new ground-state ab initio potential energy surface reported by Deskevich et al., the product polarizations in the reactions F+HCl→HF+Cl and F+DCl→DF+Cl were studied by employing the quasi-classical trajectory method. At a collision energy of 10 kcal/mol, the four generalized polarization-dependent differential cross-sections (2π/σ)(dσ₀₀/dω _t ), (2π/σ)(dσ₂₀/dω _t ), (2π/σ)(dσ₂₂₊/dω _t ) and (2π/σ)(dσ₂₁₋/dω _t ) were calculated in the center-of-mass frame. The distribution of the angle between k and j′, P(θ _r ), the distribution of the dihedral angle denoting the k-k′-j′ correlation, P(φ _r ), and the angular distribution of the product rotational vectors in the form of polar plots P(θ _r , φ _r ) were also calculated. The evident influence of isotope substitution on the product polarization is revealed. This effect may result from the different mass factors of the two reactions.     

Retrieving dry snow density with SIR-C polarimetric SAR data

For a given incidence angle at the snow surface, a greater snow density causes a greater change in the incidence angle at the snow-ground interface; for a given snow density, however, a larger incidence angle at the snow surface results in a greater change in the refractive angle in the snow layer, by comparing the difference of incidence angle at the snow-ground interface and the air-snow interface with different snow density. Algorithm for estimating dry snow density used backscattering measurements with polarimetric SAR at L-band frequency is developed based on simulation of the surface backscattering componentsσ ^g _hh andσ ^g _vv using the IEM model and regression analysis. The comparison of the estimated snow density from SAR L-band images with that from field measurements during the SIR-C/X-SAR overpass shows root means square error of 0.050 g/cm³. It shows that this algorithm can be accurately used to estimate dry snow density distribution.     

12-硼钨酸钾掺杂聚苯胺的制备、表征和性能简

以过硫酸铵为氧化剂,采用化学氧化聚合法制备了12-硼钨酸钾（K5 BW12 O40·nH2O）与盐酸共掺杂的聚苯胺材料。通过傅里叶红外光谱分析、X射线衍射分析和电导率测试等手段研究了12-硼钨酸钾与苯胺单体的质量比（X）对掺杂聚苯胺结构和性能的影响,同时结合循环伏安测试研究了材料的电化学性质。结果表明,在掺杂过程中[BW12 O40]5-作为对阴离子进入到聚苯胺链上,其含量随着犡的增大而增多。进入分子链上的[BW12 O40]5-阴离子会影响材料分子链排列的有序程度,进而影响材料的导电性能。合成的新材料可作为新型的电化学活性材料。     

SnO2中空球和纳米粒子结构的光谱对比分析

以SnCl4.5H2O作为锡源,采用共沉淀法制备SnO_2纳米粒子,以碳球为模板制备了SnO_2中空球。对产物进行了TGA,XRD,TEM,EDX表征,以检测产物的微观结构和形貌为纯SnO_2样品金红石结构。与SnO_2纳米粒子相比,SnO_2中空球结构具有较大的比表面积,因此在表面产生大量的氧空位,造成中空球结构的禁带宽度较小,拉曼光谱中四方金红石的固有模式Eg和A1g发生蓝移现象,SnO_2中空球的PL光谱强度比纳米粒子要强。     

一类包含σ紧空间和可分空间的拓扑空间

定义*σ紧空间的概念，讨论*σ紧空间的一些性质以及*σ紧性与*Lindelo(e)性。c，c，c与可分性之间的关系。结合点可数基讨论了一些空间的某些性质。     

High-pressure synthesis and properties of CeO2-ZrO2 solid solution

Using nanoparticles of CeO₂ and ZrO₂ prepared by the chemical precipitation method as starting materials, the singlephase cubic Ce_0.5Zr_0.5O₂ solid solution (cCe_0.5Zr_0.5O₂) has been synthesized under 3.1 GPa at 1073 K for the first time. The structure of the c-Ce_0.5Zr_0.5O₂ has not been changed before and after annealing at 773 K for 1 h. Only an unknown EPR signal (g =1.990) has been observed in the c-Ce_0.5Zr_0.5O₂ and not varied after annealing at 773 K for 1 h, which exhibited that there exists no Ce³⁺ in the c-Ce_0.5Zr_0.5O₂ and the Ce⁴⁺ has not been reduced into Ce³⁺ after annealing. The transport mechanism is ionic for the c-Ce_0.5Zr_0.5O₂. The bulk conductivity (σ =1.2 ×10⁻⁵ S/cm at 823 K, σ=2.1 × 10⁻³ S/cm at 1123 K) is the same as that of CeO₂, but smaller than that of Y₂O₃-stabilized ZrO₂. A marked curvature at T = 823 K has been observed in the Arrhenius plot of the bulk conductivity. The activation energy below 823 K is lower than that above 823 K, and the reason has been discussed.     

氮对光催化性能的影响:TiO_2纳米球和纳米线对比研究

使用阳极氧化和氨气退火N化的方法制备了N掺杂的TiO2纳米球薄膜和纳米线薄膜.经过N掺杂TiO2纳米线薄膜与未掺杂纳米线可见光区的光吸收强度相差不大,能带宽度从未掺杂样品的3.2eV缩小为3.1eV.TiO2纳米球薄膜在可见光区的光吸收显著增强,能带宽度由未掺杂样品的3.2eV缩小为2.8eV,同时纳米球生长被抑制,其直径约为50nm,明显小于未掺杂TiO2样品的100mn.在可见光照射TiO2氮掺杂纳米线薄膜和纳米球薄膜降解4h后,溶液中亚甲基蓝的浓度分别降至45%和44%,N掺杂样品获得了优异的可见光光催化活性.研究表明N掺杂导致的O空穴浓度增加和能带宽度有效减小是其可见光区光催化活性增强的主要原因.     

Description of mechanism function about dehydration of cobalt oxalate dihydrate by multiple rates isotemperature method

0　IntroductionThetechnologyofthermalanalysishasbeenwidelyusedinthestudyofthermalbehaviorandthermalcharacterofsolidstatereaction ,theprimaryintentionofthermalanalysiskineticsistoestablishseparatevaluesofapparentactivationenergyE ,themostprobablemechanism g(α)andthepre exponentialfactorA ,meanwhilethedeterminationofg(α)hasgraduallybeenthefocusofthisfield .Inthisfield ,therearemostlygeneralkineticsmethodsused presently ,suchasCoats Redfern’s[1 ] integralmethod ,Achar’s[2 \〗differentialmet…     

Effect of Pd doping on the acetone-sensing properties of NdFeO<Subscript>3</Subscript>

The acetone-sensing properties of the undoped and Pd doped perovskite-type oxides NdFeO₃ were investigated from room temperature to 400°C. The perovskite-type NdFeO₃ was synthesized by a sol-gel method, and the dopants Pd with the content from 1wt% to 5wt% were implanted into NdFeO₃ nanoparticles by thermal diffusion. X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques show that NdFeO₃ is an orthorhombic structure with the average particle size of about 40 nm. A giant acetone-sensing response of 675.7 is observed when the Pd content in NdFeO₃ powders is about 3wt%. The response and recovery time of the sensor to the 5×10⁻⁴ acetone gas are 16 and 1 s, respectively. At the same time, it performs a good selectivity to acetone gas and may be a new promising material candidate for the acetone-sensor development.     

Secular variations in geomagnetic Field caused by the fluctuations in the fluid flow in the outer-core

The theoretical spatial power spectrum of a dipole located at ( r0, θ60, φ0) can be fitted by a straight line in logarithmic scale when n is larger than 2. Based on the spherical harmonic coefficients of geomagnetic field during 1900-1995, the depth( r0) of source-layer of every 5a is calculated. The results show that r0 decreased from 1900 to 1960; abruptly changed from 1945 to 1950 related to some kind of disturbance; decreased again from 1960 to 1975; increased from 1975 to 1985; and kept stable after 1985. Then the mean energy density (MED) of each year is induced to its corresponding r0. We find that MED of dipole field kept nearly unchanged from 1900 to 1960. While, MED of non-dipole field increased. The change of r0 coinciding with the geomagnetic secular variation, impulse and length-of-day happened around 1970, suggesting that the change of r0 may be related to the impulse. The variation in the fluid flow in the outer-core caused by the core-mantle coupling is a plausible candidate in explaining the changes in geomagnetic Jerk, length-of-day, and r0.     

Effects of Ce, Y, and Sm doping on the thermoelectric properties of Bi2Te3 alloy

Nanopowders of elements doped Bi2Te3thermoelectric alloy R0.2Bi1.8Te3(R Ce,Y and Sm)were synthesized by the hydrothermal method.The nanopowders were hot-pressed into pellets and their thermoelectric properties were investigated.The results show that Ce,Y,and Sm doping has signifcant effects on the morphologies of the synthesized nanopowders and thermoelectric properties.Among the doping elements,Ce doping is a superiority dopant.Although the electrical conductivity and Seebeck coeffcient are not improved much by Ce doping,the thermal conductivity is supressed greatly.As a result the fgure of merit(ZT) of Ce0.2Bi1.8Te3is improved and reaches 1.29 at 398 K,which is higher than the Bi2Te3ingots made by the traditional zone-melting method