氧化镧活性的热分析研究

草酸镧热分解产物氧化镧直接水解得到反应活性高的氢氧化镧，用热重（ＴＧ）和差热分析（ＤＴＡ）研究了氧化镧的活性，方法简单且不易引进其它杂质。     

Surrogate-based modeling and dimension reduction techniques for multi-scale mechanics problems

Successful modeling and/or design of engineering systems often requires one to address the impact of multiple "design variables" on the prescribed outcome.There are often multiple,competing objectives based on which we assess the outcome of optimization.Since accurate,high fidelity models are typically time consuming and computationally expensive,comprehensive evaluations can be conducted only if an efficient framework is available.Furthermore,informed decisions of the model/hardware’s overall performance rely on an adequate understanding of the global,not local,sensitivity of the individual design variables on the objectives.The surrogate-based approach,which involves approximating the objectives as continuous functions of design variables from limited data,offers a rational framework to reduce the number of important input variables,i.e.,the dimension of a design or modeling space.In this paper,we review the fundamental issues that arise in surrogate-based analysis and optimization,highlighting concepts,methods,techniques,as well as modeling implications for mechanics problems.To aid the discussions of the issues involved,we summarize recent efforts in investigating cryogenic cavitating flows,active flow control based on dielectric barrier discharge concepts,and lithium(Li)-ion batteries.It is also stressed that many multi-scale mechanics problems can naturally benefit from the surrogate approach for "scale bridging."     

Active TLCGD control of plane asymmetric buildings under earthquake excitation

The sealed,tuned liquid column gas damper (TLCGD) with gas-spring effect extends the frequency range of application and efficiently increases the modal structural damping.Active tuned liquid column gas damper (ATLCGD) is developed for the vibration control of plane asymmetric buildings subjected to earthquake excitation,improving the performance of the passive control scheme.The active behaviour is obtained by adjusting the pressure at the end of the liquid column using a pressurised reservoir.The classical linear quadratic regulator (LQR) design is presented as a straightforward approach to optimal control.Numerical simulations indicate a significant vibration reduction of plane asymmetric buildings by active control within the strong motion of the dynamic response.     

Redox behaviour of thermally activated platinum electrodes with particular reference to operation at elevated temperature

The present work is a continuation of an earlier investigation of the effect of severe thermal pretreatment on the redox properties of platinum electrodes in aqueous media. The most interesting observation was that raising the solution temperature to ca. 75 °C resulted in a dramatic anodic response in the positive sweep at ca. 0.25 V (RHE). Such behaviour was noted earlier at room temperature but only when the thermally pretreated sample was further activated by cathodic polarization. This transition at 0.25 V was partially reversed on the negative sweep, but the cathodic process involved was subject to severe inhibition. There is independent evidence for similar behaviour for gold in aqueous acid solution. The relevance of the present results to the operation of fuel cell anodes is outlined. Received: 2 December 1999 / Accepted: 24 February 2000     

Palladium-catalyzed stereoselective synthesis of 3-(aminomethylene)-oxindoles

An efficient palladium-catalyzed protocol for the stereoselective synthesis of 3-(aminoarylmethylene)-oxindoles has been developed. In this approach, Ugi-4-component reaction adducts were used as starting materials for carbopalladative cyclization-Buchwald reaction sequences.     

On the Convergence of the Pshenichnyi-Pironneau-Polak Minimax Algorithm with an Active Set Strategy

The purpose of this technical note is to present a proof of convergence of the Pshenichnyi-Pironneau-Polak (PPP) minimax algorithm (see Algorithm 2.4.1 in Polak, Optimization: Algorithms and Consistent Approximations, Springer, [1997]), modified to use an active set strategy. This active set strategy was formally derived in Polak (Optimization: Algorithms and Consistent Approximations, Springer, [1997]) from those used in the methods of feasible directions developed by Zoutendijk (Methods of Feasible Directions, Elsevier, [1960]) and Polak (Computational Methods in Optimization: A Unified Approach, Academic, [1971]). The resulting ε-Active PPP algorithm was presented as Algorithm 2.4.34, in Polak (Optimization: Algorithms and Consistent Approximations, Springer, [1997]), without any proofs.     

Transition-Metal Thiolates: From Molecular Fragments of Sulfidic Solids to Models for Active Centers in Biomolecules

Thiolates are presently a subject of great interest in the chemistry of complexes involving transition-metal elements and soft ligands. The manifold electronic and steric capabilities offered by the monodentate ligands RS^? and the bidentate chelate ligands ^?SRS^? have been used to stabilize a broad spectrum of mononuclear, oligomeric, and polymeric complexes with new and remarkable structures and properties. Impetus has especially been provided by the synthesis of polynuclear cagelike homo- and heteroleptic metal–sulfur frameworks, which can often be regarded as “molecular fragments” of the structures of inorganic sulfides. Thiolates and mixed sulfide-thiolates of the late open- and closed-shell 3d metals (Fe, Co, Ni, Cu, Zn) and some of their homologues (Au, Cd, Hg), as well as of Mo, are of particular importance as model complexes for biologically important metal centers coordinated by sulfur. They have played an important role in increasing our understanding of the structure, bonding, and function of the reactive centers in ferredoxins, rubredoxins, nitrogenases, blue copper proteins, metallothioneins, and antiarthritic drugs.     

Mode-locked performance of hybrid soliton pulse source utilizing fiber grating external cavity lasers

Mode-locking characteristic of hybrid soliton pulse source (HSPS) utilizing linearly chirped raised-cosine flat top apodized fiber Bragg grating (FBG) is investigated by using coupled-mode equations. It is found that the fundamental repetition frequency range of HSPS is significantly extended by using linearly chirped raised-cosine flat top apodized FBG instead of linearly chirped Gaussian apodized FBG. The range of repetition frequencies over which proper mode-locking is obtained is 2-3.3 GHz with linearly chirped raised-cosine flat top apodized grating whereas this range is 2.1-2.95 GHz with linearly chirped Gaussian apodized grating.     

含随机参数的偏微分方程的自适应高斯过程求解器

对于数值求解含随机参数的偏微分方程的问题,本文基于以高斯过程为核心的求解器提出了一种自适应挑选训练数据的求解模型.该模型从极少的初始训练数据集出发训练高斯过程求解器,将参数池中预测方差指示变量最大的参数及其对应的偏微分方程的高精度解加入训练数据集中,然后重复上述过程,直到所训练出来的高斯过程求解器在测试数据集上达到所要求的精度.此外,本文还将该自适应模型在带有二维随机参数的扩散方程上进行测试,结果表明所提出的自适应选点策略有效,模型的预测准确度随着训练数据的增加而迅速提高,最终只需要40个训练数据即可在测试数据集上达到要求的精度.     

Active learning for OPM in FMF systems

Optical performance monitoring (OPM) is essential to guarantee the robust and reliable operation of few-mode fiber (FMF)-based transmission. The available OPM methods including the analytical models such as the enhanced Gaussian noise model provide high accuracy along with high computational complexity which makes them improper for real-time implementations. As an alternative approach, machine learning (ML)-based OPM removes this barrier at the cost of leveraging a large training dataset. However, generating a field or synthetic dataset for FMF-based transmission is very hard and time-consuming. As a specific ML deployment, active learning (AL) is designed to work with a small training dataset, therefore, in this paper, we employ AL for OPM in FMF-based transmission. Results indicate that the proposed AL-based OPM can properly estimate the generalized signal-to-noise ratio by using a very small training dataset and achieve the root mean squared error similar to that obtained by working on large training datasets.