Gradient flow approach to discrete-time envelope-constrained filterdesign via orthonormal filters

Using digital orthonormal filters and Lagrangian duality theory, the envelope-constrained (EC) filtering problem has been formulated as a dual quadratic programming (QP) problem with simple constraints. Applying the barrier-gradient and barrier-Newton methods based on the space transformation and gradient flow technique, two efficient design algorithms are constructed for solving this QP problem. An adaptive algorithm, based on the barrier-gradient algorithm, is developed to solve the EC filtering problem in a stochastic environment. The convergence properties are established in the mean and mean square error senses. To demonstrate the effectiveness of the proposed algorithms, a practical example using the Laguerre networks is solved for both the deterministic and stochastic cases     

Potentiostatic formation of porous silicon in dilute HF: Evidence that nanocrystal size is not restricted by quantum confinement

The role that applied potential has in controlling the properties of porous silicon formed on highly conductive p-type silicon in diluted HF has been investigated by studying the photoluminescence characteristics along the current-voltage curve and using high resolution transmission electron microscopy (HRTEM) evidence to support the conclusions drawn. A dramatic decrease in the average nanocrystal size was found to take place after the etching current density switched from an exponential dependence on the applied potential to a linear relationship. Importantly this event occurred prior to reaching the U_ps potential (usually consider the onset of electropolishing). This rapid decrease in particle sizes has been explained in terms of the partial formation of an oxide film. The presence of oxygen terminated porous silicon allows a trapped exciton states model to be invoked, which removes the quantum confinement restrictions on the minimum particle size. Support for the presence of a partial oxide prior to U_ps comes from both FTIR measurements and previous literature related to the location of the flat-band potential.     

Methanation of Carbon Dioxide on Ni Catalysts on Mesoporous ZrO2 Doped with Rare Earth Oxides

About 20–40 mol% Ni/ZrO₂ catalysts doped with Ce and Sm were synthesized by an ultrasound-assisted method and characterized by a number of physico-chemical methods (XRD, HR TEM, BET, XPS). It was demonstrated that the synthesized catalysts had a mesoporous structure, where ca. 10 nm size Ni nanoparticles were incorporated into the rare earth metal modified tetragonal zirconium oxide. The Ni particles formed during the reduction treatment could support the porous structure in the supports, and thus the porous properties of the catalysts were related to the Ni-loading. The maximum porous volume and size were obtained for the catalyst with a 30 mol% Ni loading, which coincidentally exhibited the highest catalytic activity for the methanation of CO₂. After an oxidation–reduction pretreatment, the catalytic activity could be further improved. The increase in the catalytic activity was attributed to the formation of additional active centers on the catalysts’ surface.     

Proposal of standards for intelligibility tests of Chinese speech

The authors propose standards for evaluating the intelligibility of coded, synthesised or distorted Chinese speech over a wired or wireless voice channel in a communication system. The standards are based on the English equivalent diagnostic rhyme test (DRT) and modified rhyme test (MRT). The relative features of Chinese phonetics are outlined and the underlying principles of choosing phonetic units for the proposed standards, the Chinese diagnostic rhyme test (CDRT) and the Chinese modified rhyme test (CMRT), are presented     

A novel improvement on nano-deposition of Ru on Pt for fuel cell applications

A new avenue for analyzing Ru deposition solution and depositing uniform nano-sized Ru structures on Pt substrates with enhanced reproducibility is shown in this work. UV–vis spectrophotometry in conjunction with electrochemical analysis shows that the deposition has a 5-day stability period between 2 and 6 days of its aging. During this stability period, UV–vis spectra showed that Ru(III) and Ru(IV) complexes of [Ru(H₂O)Cl₅]^2?, [RuH₂O(OH)₂Cl₃]^? and Ru-sulfates are in equilibrium. Electrochemical and in situ STM analysis also revealed that Ru nano-structures can be reproducibly deposited onto Pt using a diffusion control potential range of ?0.47 to ?0.32 V/MSE found in this work. The presence of both metallic Ru and Ru oxides within the deposit from XPS analysis suggests that the different Ru complexes present in the aged solution are involved in multiple parallel reduction processes for Ru deposition.     

Design of multiparameter steerable functions using cascade basisreduction

An efficient method of computing the least-squares optimal basis functions to steer any function locally is presented. The method combines the Lie group-theoretic and the singular value decomposition approaches. Its efficiency is demonstrated with the design of basis functions to steer a Gabor function under the four-parameter linear transformation group     

Gender differences in internet usage and task preferences

Although there has been much publicity about the Internet, empirical research focusing on it is still relatively sparse. Much of the existent research on the internet has been predicated upon data collected in Europe and America. To date, there is a dearth of published studies on the internet in the Asian context. This study examines gender differences in internet usage in Singapore, a small island of 650 square kilometres in south-east Asia. Data were collected on internet users via a questionnaire survey placed on the World Wide Web. 1370 usable responses were received, of which 89% were males and 11% were females. Gender differences in terms of the demographic profile of internet users, usage patterns, task preferences and factors affecting an enjoyable Internet experience are examined.     

ST Logistics: Distributing Consumer Goods in China

This paper describes the experience gained from a research collaboration between a group of researchers at the National University of Singapore and logistics executives in Sembcorp Logistics (formerly ST Logistics), in the latter's effort to develop a marketing and strategic planning software tool to enhance its third party logistics (3PL) services in China. As China opened up its economy in the late 1980s, many Western consumer goods manufacturers set up plants or formed joint ventures in China in an attempt to capture this huge market. While the production process can be easily built on the existing technologies and can be efficient costwise, the distribution process is still a challenge because of the backward nature of the infrastructure and the bureaucratic roadblocks, resulting in very high supply chain transaction costs. Consequently, most manufacturers turn to third-party logistics providers (3PLs) who have the required logistics expertise to operate in China. One of the leading 3PLs in China is Shenzhen ST-Anda Logistics (ST-Anda), a joint venture between Sembcorp Logistics and China Merchant Holdings. It has an existing pan-China network of distribution centers. Recently, to improve services to their customers, ST-Anda started planning for the expansion of their logistics distribution network. An OR/MS modeling approach was taken to help them in this venture.     

Knowledge portals in Chinese consulting firms: a task–technology fit perspective

Although knowledge management (KM) has been examined in previous research, the utilization of KM technologies is still not well understood. Hence, in this study, a model was developed to investigate the utilization of KM technologies, specifically, knowledge portals, from the task–technology fit (TTF) perspective. An empirical study was conducted in the Chinese consulting industry to test the validity of the model. The results show that knowledge tacitness, output quality, and compatibility are positively related to utilization. Utilization and compatibility are positively related to performance. TTF is more strongly related to performance than to utilization. Implications of the results are discussed.     

Polymer memories: Bistable electrical switching and device performance

As an emerging area in organic electronics, polymer memories have become an active research topic in recent years. Polymer memories based on bistable electrical switching are likely to be an alternative or supplementary technology to the conventional memory technology facing the problem in miniaturizing from micro- to nano-scale. In this article, an account of our recent work on bistable electrical switching in a series of processable electroactive polymers is given. The polymers can provide the required electronic properties within a single macromolecule for memory device applications. Bistable electrical switching phenomena arising from four processes, viz., trapping-detrapping, charge transfer, conformational change and nanocomposite redox effects, in electroactive polymers are described. In each case, three aspects of the memory effect, viz., (i) materials and structural features, (ii) conductance switching and current-voltage characteristics, and (iii) operating mechanism and electronic transitions are emphasized. Finally, the performance of these polymer memories is summarized.