一类求解抛物型方程侧边值问题的最优滤波方法

该文考虑一类特殊的抛物型方程侧边值问题,即一类含有对流项的非标准逆热传导问题. 给定在x=1处的温度测量值来确定区间(0,1)上的未知解u(x, t). 这是一类不适定问题,即问题的解(如果解存在)不连续依赖于数据.为了求解这一问题, 必须采用某些正则化技巧. 该文给出了一种最优滤波方法, 使得问题的真实解和近似解之间的误差估计达到了Hölder型最优. 同时还证明了问题的解在x=0处的收敛性.     

氩氧流量比对CeOx-SnOx膜微观结构及光学性能的影响

采用磁控反应共溅射的方法,以金属Ce和Sn为金属源,成功地制备出CeOx-SnOx薄膜.利用扫描电子显微镜(SEM)、X射线衍射(XRD)、透射电子显微镜(TEM)和X射线光电子能谱(XPS)等测试手段对薄膜的结构、表面形貌及成分进行了分析和表征.结果表明薄膜以岛状模式生长,随氩氧比降低,结晶性增强,出现CeO2和SnO相.此外,利用紫外-可见分光光度计对薄膜的光学性能进行了研究,测试结果表明薄膜对紫外光有极强的吸收作用.当氩氧流量比为3∶1时,紫外光平均透过率仅为5.80;,而可见光平均透过率为81.48;.     

Effect of Sulfonation Degree on Performance of Proton Exchange Membranes for Direct Methanol Fuel Cells

A series of proton exchange membranes based on sulfonated polyarylene ether ketones(SPAEKs) was used to study the effect of sulfonation degree on proton conductivity, methanol permeation and performance of direct methanol fuel cells(DMFCs). Dependences of physical characteristics of the membranes, i. e., proton conductivity, water uptake, swelling ratio, methanol permeability and ion exchange capacity(IEC) were systematically studied. Both methanol permeability and proton conductivity of the SPAEK membrane grow rapidly as the increase in sulfonation degree since methanol molecules and protons share the same transfer channel. However,the methanol permeability plays more important role comparing to proton conductivity. As a result, the SPAEK membrane with a medium sulfonation degree(60%) was found to yield the best performance in a DMFC due to the acquirement of balanced conductivity and methanol permeability.     

Synthesis and structure of 1-[(3-hydroxybenzo[<Emphasis Type="Italic">b</Emphasis>]thiophen-2-yl)methylidene]-3-oxo-5-phenyl-1-pyrazolidinium-2-ide

Potentially tautomeric azomethine imine, 1-[(3-hydroxybenzo[b]thiophen-2-yl)methylidene]-3-oxo-5-phenyl-1-pyrazolidinium-2-ide has been prepared. According to X-ray diffraction, ¹H, ¹³C, and ¹⁵N NMR and electronic spectroscopy, the compound exists as 3-hydroxybenzothiophene structure containing intermolecular hydrogen bond between the hydroxy group and the carbonyl oxygen of the pyrazolidone ring in crystal state. Quantum chemical calculations predict the possibility of OH and NH tautomeric forms.     

Hybird Membrane with High Proton Conductivity and Selectivity Based on SPEEK for Direct Methanol Fuel Cells

Composite membranes based on sulfonated silica/sulfonated poly(ether ether ketone)(SPEEK) were prepared by means of sol-gel method so as to gain a high conductivity and reasonable methanol permeability.The sulfonated silica is generated in situ via the hydrolysis of sulfonated 3-anminopropyl triethoxysilane(KH550) synthesized newly from 3-aminopropyl triethoxysilane and 1,4-butane sultone.The membrane with a silica mass fraction of 5% exhibits a conductivity of 0.187 S/cm at 80 °C and a methanol coefficient with 9.72×10-7 cm2/s.The composite membranes show improved condutive ability and better selectivity that can be promisingly used in direct methanol fuel cell.     

KF/Al2O3催化合成2-甲基-3-(3,4-亚甲二氧基苯基)丙烯醛

缩合;催化剂;洋茉莉醛;KF/Al2O3催化合成2-甲基-3-(3;4-亚甲二氧基苯基)丙烯醛     

用广角X光衍射测定不同晶型间规聚苯乙烯结晶度

多晶型;用广角X光衍射测定不同晶型间规聚苯乙烯结晶度     

Effects of Heat Treatment on the Crystallization Behavior of Poly(3-alkylthiophenes)

IntroductionPoly( 3- alkylthiophenes) ( P3ATs) ,as a newkind of soluble,fusible and processable conductivepolymers,have attracted a great interest and muchattention ofchemistsand physicists[1,2 ] . Ithas beenwidely accepted that P3ATs can form similarlayered structures with alkyl side chains beingoriented in the lateral a- axis direction[3— 6] .Moreover,when the number of the carbon atoms inthe alkyl side chains is more than1 0 ,some orderlyarrangements of the side chains will occur between…     

Effect of electrolyte cations on the charge transfer in films of prussian blue

Charge transfer in films of Prussian blue is studied by cyclic voltammetry and chronoamperometry at potentials of first (PB/PW) and second (PB/PY) redox processes in solutions of potassium, cesium, and ammonium nitrates (pH 4.0). The current relaxation following a film perturbation by a small-amplitude voltage pulse is analyzed with theoretical relationships obtained earlier for the charge transfer in redox polymers. Parameters, characterizing the charge transfer rate (formal diffusion coefficient, instantaneous current), are calculated and analyzed as a function of the film oxidation state and the supporting-electrolyte nature     

Preconcentration of arsenic(V) as molybdoarsenic heteropoly acid by dynamic sorption

The sorption of molybdoarsenic heteropoly acid (MAA) and its ion pair with tri-n-octylamine (TOA) on sorbents of different nature and hydrophobic filters has been studied. It is demonstrated that MAA is efficiently extracted on the polyacrylate sorbent Amberlyte XAD-8; the distribution coefficient of arsenic is 1 x 10⁴ cm³/g for the sorption from 0.35-1.5 M H₂SO₄. Conditions of the quantitative extraction of MAA in the presence of TOA on thin-layer cellulose triacetate filters are found. A procedure is proposed for the sorption-X-ray fluorescence determination of arsenic in potable water. The detection limit of arsenic is 10 Μg/L for the sorption from 100 mL of a solution.