Numerical estimation of the piecewise constant Robin coefficient by identifying its discontinuous points

We propose a new numerical method for estimating the piecewise constant Robin coefficient in two-dimensional elliptic equation from boundary measurements. The Robin inverse problem is recast into a minimization of an output least-square formulation. A technique based on determining the discontinuous points of the unknown coefficient is suggested, and we investigate the differentiability of the solution and the objective functional with respect to the discontinuous points. Then we apply the Gauss-Newton method for reconstructing the shape of the unknown Robin coefficient. Numerical examples illustrate its efficiency and stability.     

粘土担载的钼基催化剂的制备、结构及CO加氢合成醇性能

采用溶胶凝胶法与等体积浸渍相结合制备了一系列以粘土为载体的K-Co-Mo催化剂. 采用XRD、N₂等温吸脱附、H_{26+的还原,但对Mo⁴⁺和Co²⁺的还原没有明显的影响. 催化剂经还原后,在其表面生成了一种更低价态的Mo^δ+(1<δ<4)物种,被认为是合成醇的活性中心. 与非负载催化剂相比,粘土担载的K-Co-Mo具有更高的合成醇性能. 负载型催化剂具有较高的活性物种分散度,并且其介孔结构在一定程度上延长了合成醇反应中间体的滞留时间,从而促进了低碳醇的生成. 经773 K还原的催化剂具有较高的活性,其原因可为催化剂表面具有较高含量的Mo^δ+物种.}     

Ce-Cu-Co/CNTs催化剂催化合成气制低碳醇及乙醇的研究

采用共浸渍法制备了不同Ce含量的Ce-Cu-Co/CNTs催化剂,考察了其在合成气制低碳醇反应中的催化性能,借助X射线衍射(XRD)、程序升温还原(H2-TPR)、N2吸脱附实验(BET)、透射电镜(TEM)和CO程序升温脱附(CO-TPD)对这些催化剂进行了表征.结果表明,当Ce的质量分数为3%时,低碳醇的时空收率和选择性达到最高,分别为696.4 mg?g-1?h-1和59.7%,其中乙醇占总醇的46.8%,适量Ce的添加能提高Cu物种在催化剂上的分散度和催化剂的还原性能,能显著地增加催化剂吸附CO的能力,促进合成醇活性位的形成,进而明显提高催化剂的活性和总醇的选择性.研究表明,将具有高活性和高碳链增长能力的CuCo基催化剂与碳纳米管的限域效应结合,可实现缩窄产物分布、大幅度提高乙醇选择性的目的.     

低碳醇合成Raney Cu－Co催化剂的表征

本文采用ＸＲＤ、ＸＰＳ、及Ｈ_２—ＴＰＤ技术对不同Ｃｕ／Ｃｏ比的几个ＲａｎｅｙＣｕ－Ｃｏ催化剂进行了表征．并与反应醇选择性进行了关联．结果表明：ＲａｎｅｙＣｕ－Ｃｏ催化剂均由不同Ｃｕ／Ｃｏ比的两个Ｃｕ－Ｃｏ固溶体相组成，还原（Ｈ_２，５６３Ｋ，２ｈ）前，表面除有Ｃｕ￣０和Ｃｏ￣０外，尚有少量Ｃｕ￣（＋１）和显著量的Ｃｏ￣（＋２）存在，还原后，Ｃｕ￣（＋１）几乎消失，Ｃｏ￣（＋２）仍有一定量存在，在反应温度下（５６３Ｋ），ＣＯ和ＣＯ_２均能使表面Ｃｏ￣０部分氧化，且ＣＯ_２氧化能力大于ＣＯ，而合成气（Ｈ_２／ＣＯ＝２）表现为还原的性质。三种气氛对Ｃｕ￣０无明显影响。催化剂表面Ｃｕ／Ｃｏ比高于体相Ｃｕ／Ｃｏ比，表面Ｃｕ富集显著．ＲａｎｅｙＣｕ－Ｃｏ催化剂表面有四种吸氢中心：Ｃｕ（弱吸氢中心），高配位Ｃｏ（弱吸氢中心），低配位Ｃｏ（活化吸氢中心），及强吸氢中心；对不同催化剂，表面低配位Ｃｏ中心的比例与醇选择性有一致的变化规律。基于上述结果，就ＣＯ播入中心进行了讨论。     

NODAL O（h^4）-SUPERCONVERGENCE IN 3D BY AVERAGING PIECEWISE LINEAR,BILINEAR, AND TRILINEAR FE APPROXIMATIONS

We construct and analyse a nodal O（h^4）-superconvergent FE scheme for approximating the Poisson equation with homogeneous boundary conditions in three-dimensional domains by means of piecewise trilinear functions. The scheme is based on averaging the equations that arise from FE approximations on uniform cubic, tetrahedral, and prismatic partitions. This approach presents a three-dimensional generalization of a two-dimensional averaging of linear and bilinear elements which also exhibits nodal O（h^4）-superconvergence （ultracon- vergence）. The obtained superconvergence result is illustrated by two numerical examples.     

函数的逼近及其在下半连续函数可微性中的应用

通过函数的下卷积函数列的逼近方法,在变分原理中从扰动最小值点集的“大小”入手,研究了下半连续函数的可微性。     

Higher Harmonic Operations of Submillimeter Wave Gyrotrons (Gyrotron FU Series)

Higher harmonic operation of gyrotrons is necessary to obtain high frequencies. Some gyrotrons included in the Gyrotron FU series developed at Fukui University have achieved operation at the third and even fourth harmonics of the electron cyclotron frequency. The output lies in the millimeter to submillimeter wavelength range and the output powers are several watts to several tens of watts. In this paper, the gyrotrons and the conditions under which they operate are described in detail.     

Higher spin gauge theories in any dimension

Some general properties of higher spin gauge theories are summarized, with the emphasize on the nonlinear theories in any dimension. To cite this article: M.A. Vasiliev, C. R. Physique 5 (2004).

Résumé

Des propriétés générales des théories de jauge de grands spins sont présentées, en insistant particulièrement sur les théories non-linéaires en dimensions diverses. Pour citer cet article : M.A. Vasiliev, C. R. Physique 5 (2004).