Mechanism design with rotational and positioning calibrations for double-sided structure replication

This study is designing a mechanism with functions of rotational and positioning calibrations. This mechanism was applied to a hot embossing mold used for replications of double-sided structure. The hot embossed product was measured for double sided structures. The rotational and positioning alignment errors for both sides were measured by using a microscope. According to the results, the errors were calibrated wit this mechanism. The positioning and rotational resolutions of this mechanism are 40 μm and 0.5°, respectively. The results show that the mechanism has acceptable calibration accuracy. The average calibration accuracy for X-axis, Y-axis and C-axis were 92.5, 91.75 and 98.67 %, respectively. The small errors were induced by the large temperature difference between upper die and lower die during rapid cooling of a hot embossing process.     

Optimization of the finite production rate model with scrap,rework and stochastic machine breakdown

This study employs mathematical modeling along with a recursive searching algorithm to determine the optimal run time for an imperfect finite production rate model with scrap, rework, and stochastic machine breakdown. In real-life manufacturing systems, generation of defective items and machine breakdown are inevitable. The objective of this paper is to address these issues and to be able to derive the optimal production run time. It is assumed that the proposed manufacturing system produces defective items randomly, a portion of them is considered to be scrap, and the other portion can be repaired through rework. Further, the proposed system is subject to random breakdown and when it occurs, the abort/resume (AR) policy is adopted. Under such an inventory control policy, the production of the interrupted lot will be resumed immediately when machine is fixed and restored. Mathematical modeling along with a recursive searching algorithm is used for deriving the replenishment policy for such a realistic production system.     

Exploring and mitigating social loafing in online communities

The motivation to share members’ knowledge is critical to an online community’s survival and success. Previous research has established that knowledge sharing intentions are based on group cohesion. Several studies also suggested that social loafing behavior will seriously corrode group cohesion. Therefore, social loafing is a key obstacle to fostering online community development. Although substantial studies have been performed on the critical factors that affect social loafing in the learning group, those on online communities are still lacking. By integrating two perspectives, social capital and perceived risk, a richer understanding of social loafing behavior can be gained. In the research model, social ties and perceived risk have been driven by anonymity, offline activities, knowledge quality, and media richness. Social ties and perceived risk are hypothesized to affect social loafing in the online community, which, in turn, is hypothesized as negatively affecting group cohesion. Data collected from 323 online users in online communities provide support for the proposed model. The study shows that social loafing is a significant negative predictor of the users’ group cohesion. The study also shows that social ties and perceived risk are important components of social loafing. Anonymity, offline activities, knowledge quality, and media richness all have strong effects on social ties and perceived risk in the online community. Implications for theory and practice and suggestions for future research are discussed.     

Intra-supply chain system with multiple sales locations and quality assurance

The emergence of the global economy has transformed the interdepartmental nature of a transnational enterprise into a highly collaborative oriented team. This transformation enables the enterprise to lower its transaction and coordination costs and increase its competitive advantage in the global market. This study investigates such a so-called intra-supply chain system that exists in present-day transnational firms, wherein a single production unit manufactures products to meet the demands of multiple regional sales offices and incorporates quality assurance in its production. The objective of the present study is to determine an optimal production quantity and shipment policy that minimizes the integrated production–inventory–delivery costs for the intra-supply chain system. In this study, considerations related to a product’s quality assurance include inspection for quality, rework of defective items and failure in rework. Delivery of the finished products starts when quality of the entire production lot is assured. Multi-shipment policy is used to synchronously transport finished items to multiple locations for satisfying customer demands in each cycle. Mathematical modeling along with Hessian matrix equations is employed to solve the proposed intra-supply chain system. A numerical example with a discussion and cost-benefit analysis of outsourcing work to an external distributor is presented to demonstrate the practical applicability of the obtained results.     

An efficient scheduling algorithm for scalable video streaming over P2P networks

During recent years, the Internet has witnessed rapid advancement in peer-to-peer (P2P) media streaming. In these applications, an important issue has been the block scheduling problem, which deals with how each node requests the media data blocks from its neighbors. In most streaming systems, peers are likely to have heterogeneous upload/download bandwidths, leading to the fact that different peers probably perceive different streaming quality. Layered (or scalable) streaming in P2P networks has recently been proposed to address the heterogeneity of the network environment. In this paper, we propose a novel block scheduling scheme that is aimed to address the P2P layered video streaming. We define a soft priority function for each block to be requested by a node in accordance with the block’s significance for video playback. The priority function is unique in that it strikes good balance between different factors, which makes the priority of a block well represent the relative importance of the block over a wide variation of block size between different layers. The block scheduling problem is then transformed to an optimization problem that maximizes the priority sum of the delivered video blocks. We develop both centralized and distributed scheduling algorithms for the problem. Simulation of two popular scalability types has been conducted to evaluate the performance of the algorithms. The simulation results show that the proposed algorithm is effective in terms of bandwidth utilization and video quality.     

Virtual Sample Processing: Extending the Reach of Multimedia

Traditional multimedia systems deal with only a few basic media: text, graphics, audio and video. However, many other types of media, such as ultrasound, infrared and RF signals, can be represented by streams of data samples and processed within multimedia applications. In this paper, we introduce some of these new media domains and identify interesting opportunities enabled by their software-based processing. We also describe our SpectrumWare testbed for experimenting with these new media types and report on our experience to date.We believe that the time has come to broaden the scope of multimedia to include any form of sampled information. Advances in processor and analog-to-digital conversion technology have brought raw sample streams within the grasp of desktop computers and media processing systems. Coupling these new media types with software-based processing allows the construction of virtual devices that can handle different sample sources, modify their behavior based on information extracted from the media, and transform information between media domains.     

A stability-guaranteed integral sliding disturbance observer for systems suffering from disturbances with bounded first time derivatives

This paper presents an integral sliding disturbance observer (I-SDOB) to compensate for unknown disturbances for a class of nonlinear systems. To guarantee the existence of a sliding mode for disturbance estimation, the proposed I-SDOB needs only a small switching gain compared with conventional sliding disturbance observers, which leads to further alleviation of chatter. Moreover, the stability analysis of the controller-observer system is given based on the Lyapunov theory. Applications of the proposed scheme to a two-link robotic manipulator have been conducted, and experimental results confirm the effectiveness of the proposed scheme.     

Comparative study of hot embossed micro structures fabricated by laboratory and commercial environments

 Hot embossed microstructures fabricated by laboratory and commercial environments have been studied. The laboratory process uses silicon with micropyramid patterns as the mold insert. Fine replication by using Polymethyl Methacrylate (PMMA) has been achieved. The commercial process uses electroplated nickel as the mold insert. Polyvinyl Chloride (PVC), which has a lower glass transition point than PMMA, has been used as the raw material. Fabrication results show that the laboratory process, although taking about 2 hours long per run, can successfully replicate microstructures. The commercial process which takes only 1 minute per run may be fine tuned for good replication. Atomic Force Microscope (AFM) has been used to analyze the fabricated microstructures. It is found that the root mean square (r.m.s.) roughness of PMMA is about 4 nm and that of PVC is about 10–15 nm. Defects including voids and bumps on both PMMA and PVC films have been found. Received: 25 August 1997/Accepted: 22 September 1997     

Applying fuzzy neural network to estimate software development effort

The ability to accurately and consistently estimate software development efforts is required by the project managers in planning and conducting software development activities. Since software effort drivers are vague and uncertain, software effort estimates, especially in the early stages of the development life cycle, are prone to a certain degree of estimation errors. A software effort estimation model which adopts a fuzzy inference method provides a solution to fit the uncertain and vague properties of software effort drivers. The present paper proposes a fuzzy neural network (FNN) approach for embedding artificial neural network into fuzzy inference processes in order to derive the software effort estimates. Artificial neural network is utilized to determine the significant fuzzy rules in fuzzy inference processes. We demonstrated our approach by using the 63 historical project data in the well-known COCOMO model. Empirical results showed that applying FNN for software effort estimates resulted in slightly smaller mean magnitude of relative error (MMRE) and probability of a project having a relative error of less than or equal to 0.25 (Pred(0.25)) as compared with the results obtained by just using artificial neural network and the original model. The proposed model can also provide objective fuzzy effort estimation rule sets by adopting the learning mechanism of the artificial neural network.     

Spontaneous deposition of gold nanoparticle nanocomposite on polymer surfaces through sol-gel chemistry

A aminosilica nanocomposite layer containing a monolayer of gold nanoparticles (d = 18-22 nm) with a well-defined spacing was spontaneously deposited on an unmodified polystyrene surface via a sol-gel reaction when the reduction reaction was carried out under 1:8 molar ratio (gold(III):aminosilane). The amount of aminosilica and spacing between gold nanoparticles were found to be a function of the aminosilane:water molar ratio, which contributes to the plasmonic property of the films with its absorption wavelength ranging between 701 and 548 nm. Furthermore, the nanocomposite film that consists of a monolayer of nanoparticles in aminosilica has also been deposited on the surface of polystyrene beads. This core-shell structure was found capable of storing electrostatic charges and forming a well-separated 2D array.