H ∞ Optimal control

Our aim in this paper is to develop a new approach for solving the H ^∞ optimal control problem where the feedback arrangement takes the form of a linear fractional transformation. The paper is in two parts. In Part 1, a basic kind of model-matching problem is considered: given rational matrices M(s) and N(s), the H ^∞-norm of an error function defined as E(s)=M(s) – N(s)Q(s) is minimized (or bounded) subject to E(s) and Q(s) being stable. Closed-form state-space characterizations are obtained for both E(s) and Q(s). The results established here will be used in Part 2 of the paper (Hung 1989) to solve the H ^∞ optimal control problem.     

Object relevance weight pattern mining for activity recognition and segmentation

Monitoring daily activities of a person has many potential benefits in pervasive computing. These include providing proactive support for the elderly and monitoring anomalous behaviors. A typical approach in existing research on activity detection is to construct sequence-based models of low-level activity features based on the order of object usage. However, these models have poor accuracy, require many parameters to estimate, and demand excessive computational effort. Many other supervised learning approaches have been proposed but they all suffer from poor scalability due to the manual labeling involved in the training process. In this paper, we simplify the activity modeling process by relying on the relevance weights of objects as the basis of activity discrimination rather than on sequence information. For each activity, we mine the web to extract the most relevant objects according to their normalized usage frequency. We develop a KeyExtract algorithm for activity recognition and two algorithms, MaxGap and MaxGain, for activity segmentation with linear time complexities. Simulation results indicate that our proposed algorithms achieve high accuracy in the presence of different noise levels indicating their good potential in real-world deployment.     

Viscous heating in nanoscale shear driven liquid flows

Three-dimensional Molecular Dynamics (MD) simulations of heat and momentum transport in liquid Argon filled shear-driven nano-channels are performed using 6–12 Lennard–Jones potential interactions. Work done by the viscous stresses heats the fluid, which is dissipated through the channel walls, maintained at isothermal conditions through a recently developed interactive thermal wall model. Shear driven nano-flows for weak wetting surfaces (ε _wf /ε ≤ 0.6) are investigated. Spatial variations in the fluid density, kinematic viscosity, shear- and energy dissipation rates are presented. Temperature profiles in the nano-channel are obtained as a function of the surface wettability, shear rate and the intermolecular stiffness of wall molecules. The energy dissipation rate is almost a constant for ε _wf /ε ≤ 0.6, which results in parabolic temperature profiles in the domain with temperature jumps due to the well known Kapitza resistance at the liquid/solid interfaces. Using the energy dissipation rates predicted by MD simulations and the continuum energy equation subjected to the temperature jump boundary conditions developed in [Kim et al. Journal of Chemical Physics, 129, 174701, 2008b], we obtain analytical solutions for the temperature profiles, which agree well with the MD results.     

Configurable AC electroosmotic generated in-plane microvortices and pumping flow in microchannels

This paper proposes the patterned AC electroosmotic flows (AC-EOF) by simply grouping discrete electrodes together to form various electrode configurations for generation of in-plane microvortices with clockwise/counter-clockwise rotation, and pumping flow in a microchannel. The rotational direction of in-plane microvortices and pumping flow direction can be controlled using the same electrode pattern by simple switching of the voltages on the electrodes. Microparticle image velocimetry (μPIV) was used to characterize the flow fields of the generated in-plane microvortices and pumping flow. The rotational strength of microvortices and flow rates of pumping flows were found to increase with the increase of the applied voltages, and an optimal value was achieved at an appropriately applied frequency. Moreover, the dependency of the applied voltages, frequencies, and the heights of the measured planes on the rotational strength of in-plane microvortices between the interdigitated and discrete electrode configurations were examined. The discrepancy in electrode geometry results in a small performance reduction, whereas it can be compensated for the ability of switching the rotational direction of in-plane microvortices using the same device. The configurable in-plane microvortices and pumping flow in microchannels provide the potential for micromixing applications and for the integration into a lab-on-a-chip system.     

LED数码管计数控制方式编程技巧三则

本文介绍了用C语言程序实现LED数码管计数显示控制的方法与技巧。     

Discovering patterns of online purchasing behaviour and a new‐product‐launch strategy

Spurred by rapid development of computers and Internet technology, online shopping is gradually overtaking in‐store shopping, because of advantages such as convenience, more choice of products or services etc. Online stores must devote a great deal of time and resources to locating and attracting new customers. Growing a customer base requires first understanding customers and then providing the products or services they need, thus encouraging customers to purchase more. This paper develops a system to analyse customers’ purchasing behaviour and track shifts in their interests. Customers’ purchasing behaviour is measured using proposed standard product loyalty status and standard brand loyalty status. Using these metrics, together with the preference map established for each customer, a marketing specialist can easily locate potential customers to target when a company launches a new product. The new‐product‐launch strategy proposed in this paper can be used to create a list of potential customers for a product being launched under a variety of conditions. A prototype system has been built to test the feasibility of the proposed new‐product‐launch strategy. The result shows almost 40% of potential customers respond to the recommendation positively.     

On the design of online synchronous assessments in a synchronous cyber classroom

Online learning has been rapidly developing in the last decade. However, there is very little literature available about the actual adoption of online synchronous assessment approaches and any guidelines for effective assessment design and implementation. This paper aims at designing and evaluating the possibility of applying online synchronous assessments in a formal credit course. Relying on the four dimensions of knowledge taxonomy, this paper describes four different online synchronous assessments for conducting a formal mid‐term exam, including synchronous quiz, synchronous practicum, synchronous essay and synchronous oral assessments. The designs were implemented and evaluated in a synchronous cyber classroom for an online credit course. This study identified the challenges and potential issues while conducting the online synchronous assessments, including (1) the extent of monitoring and cheating; (2) the lack of suitable software tools specifically for supporting online synchronous assessments; and (3) the need for a variety of online synchronous assessment methods for different subject matter. This paper concludes with some possible solutions, such as a short time limit for answering questions and a well analysed need of a software tool, to address all the issues.     

Combining fuzzy weight average with fuzzy inference system for material substitution selection in electric industry

Material selection is a very important issue for an electronics company as it includes many qualitative or quantification factors. The material selection problem is associated with design and manufacturing problems which have been widely investigated. This study develops a hybrid fuzzy decision-making model which combines the fuzzy weight average (FWA) with the fuzzy inference system (FIS) for material substitution selection in the electronics industry. FWA is employed to select a substitute material in an uncertain environment, while FIS is used for reasoning purposes. FWA with α-cuts arithmetic (FWA_α-cut) is a popularly technology in decision-making problems. However, FWA_α-cut may result in the following unanticipated situations: (1) unclear decision situations; (2) undecided results expressed by fuzzy membership functions; and (3) high computational complexity. Therefore, a fuzzy weight average with the weakest t-norm (FWA_Tω) is designed as an alternative method for group decision making. In contrast to traditional FWA methods, FWA_Tω obtains more visible fuzzy results for decision makers with lower computational complexity, and can provide exacter estimation by the weakest t-norm operations in uncertain environment. Thus, the proposed hybrid fuzzy decision-making model imitates an expert’s experiences and can estimate substitution purchasing in various statuses. A real material substitution selection case is employed to examine the feasibility of the proposed model; experimental results reveal that the proposed model performs better than the traditional FWA model in coping with material substitution selection problems.     

A novel automatic virtual metrology system architecture for TFT-LCD industry based on main memory database

The semiconductor and thin-film-transistor–liquid-crystal-display (TFT-LCD) industries widely value Automatic Virtual Metrology System (AVMS). AVMS needs to handle a large volume of VM-related data, which may cause poor internal database performance. In general, AVMS adopts efficient but expensive commercial database management systems (DBMSs) to yield good AVMS performance. This usually makes the AVMS construction cost very high. Therefore, the industries require a novel AVMS architecture with lower cost and greater efficiency in database. This paper proposes a novel AVMS architecture based on Main Memory Database (MMDB) technology. Specifically, the MMDB is used to improve the performance bottlenecks of the current Disk Resident Database (DRDB). Also, we design automatic data-backup and automatic data-query sources integration mechanisms to effectively relieve rapidly increased data volume in the original AVMS architecture. In addition, the novel AVMS architecture adopts a free commercial MMDB to significantly reduce total system cost. Integrated testing results show that the proposed AVMS architecture and developed technologies can enable the AVMS to have better data-storage efficiency, superior data-query performance, and lower database cost. The proposed AVMS architecture and research results in this paper can be a useful reference for TFT-LCD manufacturing companies in constructing their own AVM systems. The proposed AVMS architecture can also be applied in the semiconductor and solar-cell industries.     

Executing mobile applications on the cloud: Framework and issues

Modern mobile devices, such as smartphones and tablets, have made many pervasive computing dreams come true. Still, many mobile applications do not perform well due to the shortage of resources for computation, data storage, network bandwidth, and battery capacity. While such applications can be re-designed with client–server models to benefit from cloud services, the users are no longer in full control of the application, which has become a serious concern for data security and privacy. In addition, the collaboration between a mobile device and a cloud server poses complex performance issues associated with the exchange of application state, synchronization of data, network condition, etc. In this work, a novel mobile cloud execution framework is proposed to execute mobile applications in a cloud-based virtualized execution environment controlled by mobile applications and users, with encryption and isolation to protect against eavesdropping from cloud providers. Under this framework, several efficient schemes have been developed to deal with technical issues for migrating applications and synchronizing data between execution environments. The communication issues are also addressed in the virtualization execution environment with probabilistic communication Quality-of-Service (QoS) technique to support timely application migration.