Dendrimer-encapsulated metal nanoparticles: synthesis, characterization, and applications to catalysis

This Account reports the synthesis and characterization of dendrimer-encapsulated metal nanoparticles and their applications to catalysis. These materials are prepared by sequestering metal ions within dendrimers followed by chemical reduction to yield the corresponding zerovalent metal nanoparticle. The size of such particles depends on the number of metal ions initially loaded into the dendrimer. Intradendrimer hydrogenation and carbon-carbon coupling reactions in water, organic solvents, biphasic fluorous/organic solvents, and supercritical CO2 are also described.     

Interleaved Traffic Splitting: A promising technique to solve False Timeout

In this paper, we analyze the False Timeout (FTO) problem that TCP flows suffered in OBS networks and propose Interleaved Traffic Splitting (ITS) to solve the problem. We show that the collision loss of ACK bursts may also cause FTO, which has been neglected by previous researchers. As TCP Sack is designed to recover from multiple packet losses, we find that a Sack flow can recover its data transmission without triggering retransmission timeout if packet loss is not too severe. This suggests limiting the number of packets carried by a single burst. In ITS, this is achieved by carrying out a parallel, interleaved burst assembly process at each ingress OBS edge router. We show that ITS tackles the FTO problem caused by the loss of both data and ACK bursts. Unlike other existing approaches, the ITS scheme requires only modification to the assembly/de-assembly mechanisms implemented at the edge routers. It does not add complexities to the network management or the router design. In this paper, both analytical and simulation results are presented to demonstrate the performance improvement of ITS. Our analysis further shows that the use of two parallel bursts is optimum for ITS.     

La(Ni,Sn)5+x (x=0～0.35)贮氢合金的晶体结构与电化学性能

系统研究了La(Ni,Sn)_5+x（x=0~0.35) 无Co贮氢合金的化学计量比对其晶体结构及电化学性能的影响.X射线衍射分析仪（XRD）分析表明，上述合金均为单相CaCu₅结构.但在过计量比(x>0)合金的结构中，有部分1a位置元素（La）的原子被沿c轴定向排列的Ni-Ni“哑铃”对所替代，且其替代La原子的分数随x的增大而增多，从而导致合金晶胞的c轴及c/a比值明显增大，晶胞体积有所减小，并显著降低了合金的吸氢体积膨胀率.电化学测试表明，增大x值可使合金的循环稳定性得到显著提高，但也使合金的最大放电容量和高倍率放电性能有所降低.研究发现，由于合金的化学计量比增大会使其结构中含有较多的Ni-Ni“哑铃”对，合金的抗吸氢粉化能力得到了明显的改善，从而使合金在充放电过程中的反应比表面积有所减小、腐蚀速率得到抑制、循环稳定性得到显著提高.但合金反应比表面积的减小也导致了电极反应的速率的减小，从而使其高倍率放电性能有所降低.     

COMPLEXITY RELAXATION OF THE TENSOR PRODUCT MODEL TRANSFORMATION FOR HIGHER DIMENSIONAL PROBLEMS

The Tensor Product (TP) model transformation method was proposed recently as an automated gateway between a class of non‐linear models and linear matrix inequality based control design. The core of the TP model transformation is the higher order singular value decomposition of a large sized tensor, which requires high computational power that is usually outside of a regular computer capacity in cases of higher dimensionality. This disadvantage restricts the utilization of the TP model transformation to models having smaller dimensionality. The aim of this paper is to propose a computationally relaxed version of the TP model transformation. The paper also presents a 6 dimensional example to show the effectiveness of the modified transformation.     

A comparative study on heuristic algorithms for generating fuzzydecision trees

Fuzzy decision tree induction is an important way of learning from examples with fuzzy representation. Since the construction of optimal fuzzy decision tree is NP-hard, the research on heuristic algorithms is necessary. In this paper, three heuristic algorithms for generating fuzzy decision trees are analyzed and compared. One of them is proposed by the authors. The comparisons are twofold. One is the analytic comparison based on expanded attribute selection and reasoning mechanism; the other is the experimental comparison based on the size of generated trees and learning accuracy. The purpose of this study is to explore comparative strengths and weaknesses of the three heuristics and to show some useful guidelines on how to choose an appropriate heuristic for a particular problem.     

Effect of the reaction bath temperature in a fixed-bed reactor for oxidation of oxylene over V2O5/TiO2 catalysts

The effects of the reaction variables in the operation of a fixed-bed reactor for oxidation ofo-xylene over V₂O₅/TiO₂ catalysts were studied experimentally using a bench reactor. Reaction temperature, feed flow rate and feed concentration ofo-xylene were found to have significant effects on the product distribution and the temperature profile in the reactor. Drastic enhancements ofo-xylene oxidation reaction were observed at some conditions, which was ascribed to the effect of heat accumulated in the bed and indicated a possible way to increase the productivity in the industrial condition. This paper was presented at the 8th APCChE (Asia Pacific Confederation of Chemical Engineering) Congress held at Seoul between August 16 and 19, 1999.     

Intravascular lymphomatosis: a case presenting with encephalomyelitis and reactive haemophagocytic syndrome diagnosed by renal biopsy

OBJECTIVE: To determine the frequency of characteristics associated with unprotected heterosexual intercourse in HIV infected adults in an urban area. DESIGN: Retrospective comparison of sexual risk transmission behaviour between HIV infected men and women from a drug treatment site and between women from the drug site and HIV infected women from an urban medical centre. METHODS: HIV infected women and men were asked questions on sexual behaviour for a 1 year period before enrollment. The outcome variable was heterosexual risk behaviour (HRB) defined as having vaginal sex at least once in the previous year and not always using condoms. RESULTS: 73% of the drug clinic females, 72% of the drug clinic males, and 42% of the medical centre female engaged in HRB. Using logistic regression analysis, women and men in drug treatment engaged in similar rates of HRB; however, women in drug treatment were four times (95% CI = 2.0-8.3) more likely to engage in HRB risk behaviour than women from the medical centre. CONCLUSION: The data suggest that a surprisingly large portion of HIV infected patients under treatment engaged in HRB, especially former drug users. Without specifically targeted interventions, the heterosexual spread of HIV in urban areas will continue to be a serious problem.     

A non-trial-and-error method for lag-lead compensator design

A universal design chart for lag-lead compensators is given. This chart allows compensators to be designed without trial-and-error while meeting four specifications: steady-state error; phase margin; gain margin; and gain (or phase) crossover frequency     

Using function approximation to analyze the sensitivity of MLP withantisymmetric squashing activation function

Sensitivity analysis on a neural network is mainly investigated after the network has been designed and trained. Very few have considered this as a critical issue prior to network design. Piche's statistical method (1992, 1995) is useful for multilayer perceptron (MLP) design, but too severe limitations are imposed on both input and weight perturbations. This paper attempts to generalize Piche's method by deriving an universal expression of MLP sensitivity for antisymmetric squashing activation functions, without any restriction on input and output perturbations. Experimental results which are based on, a three-layer MLP with 30 nodes per layer agree closely with our theoretical investigations. The effects of the network design parameters such as the number of layers, the number of neurons per layer, and the chosen activation function are analyzed, and they provide useful information for network design decision-making. Based on the sensitivity analysis of MLP, we present a network design method for a given application to determine the network structure and estimate the permitted weight range for network training.     

先进栅叠层的在线光谱分析法

量测平台的复杂性和光学原理上的局限性制约着测量系统的应用，直到真空紫外光谱反射仪的出现，这种状况才得到改变。