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A multi-FPGA system consists of multiple FPGAs connected by physical wires, and a circuit is partitioned to fit each FPGA and routed on the system by such physical wires. Due to the limited numbers of input/output (I/O) pins in an FPGA, however, not all signals can be transmitted between FPGAs directly. Moreover, the routing resource may not be sufficient to accommodate many cross-FPGA signals from circuit partitioning. As a result, input/output time-division multiplexing (TDM) is introduced to send a group of cross-FPGA signals in a routing channel with a timing penalty. To optimize the performance of such a system, we shall develop a simultaneous partitioning and routing algorithm considering the timing penalty caused by I/O TDM. Considering the TDM delay penalty, we propose a simultaneous partitioning and routing algorithm to remedy the insufficiency of the two-stage flow of partitioning followed by routing. Our algorithm consists of two major steps: (1) a novel routing-aware partitioning framework to obtain an initial solution considering irregular, asymmetric connections, and (2) a partition-aware routing scheme to optimize routing in each partitioning pass. Experimental results show that our proposed algorithm can achieve better timing than the classical flow.

System in Package (SiP) is an outstanding assembly technology, which integrates active dies and passive components into a single tiny module. For further miniaturization, SiP module evolves from single side molding to double side molding (DSM) structure, which can enhance the space utilization. DSM involves backside molding and grinding to reduce the package thickness as well as solder ball exposure. After grinding, solder balls in backside become non-spherical and need further reballing process to form a protruded spherical shape for package mount. In this work, a reballing ball height prediction model was proposed. Through this model, a predictable ball height and process adjustment guideline could be obtained. DSM structure with 230$\mu$ m pad opening and 290$\mu m/ 250 \mu$ m ball size were utilized in this study. For 290$\mu$ m ball size, the predicted ball protrusion height is 68.31$\mu$ m, and the experimental result is 71.43$\mu$ m in average; for 250$\mu$ m ball size, a predicted ball protrusion height is 51.24$\mu$ m, and the experimental result is 52.28$\mu$ m in average. The deviations were quite low and only 3.12$\mu$ m and 1.04$\mu$ m in above two cases, respectively. In this work, a ball protrusion height simulation model was presented and precise prediction of ball protrusion height can be obtained with 1% dimension deviation by which effective and lower cost as product development was realized.

In this paper, we propose a new pair hidden Markov model (Pair-HMM) algorithm, namely Banded Pair-HMM, which is a heuristic approach for variant calling applications. When compared to the conventional Pair-HMM, our Banded Pair-HMM can reduce the execution time at a minor cost in accuracy. In addition, a hardware accelerator is implemented using TSMC 40nm technology based on the proposed algorithm. As demonstrated later in the paper, the proposed hardware accelerator runs 4× faster than the conventional Pair-HMM hardware, and over 17,000× faster than the original Pair-HMM software.

Virtual reality (VR) and augmented reality (AR) are expected to change people’s daily life in the future, but it still faces many challenges. New advanced coding techniques like depth image based rendering (DIBR) mitigate the need to complete content by synthesizing the scene with nearby views. However, due to the limitation of wireless spectrum, delivering VR/AR content to many people doing some activities (e.g., watching sport in a stadium or seeing an exhibition in a museum) in mobile hotspot areas is still very challenging in terms of available bandwidth. In this work, we analyze how to multicast multi-view VR/AR 3D multimedia streams over multiple wireless access points (APs) to multiple users, and then propose a multi-view allocation (MVA) algorithm to improve the delivered content quality. The simulation results show that our MVA algorithm can achieve about 90% performance of the optimal solution and outperform non-DIBR and SSA model, by 48% and 25%, respectively.

Recently distributed multiple SDN controller architecture is proposed to improve the scalability of SDN architecture. Unfortunately, the state-of-art SDN controller failover mechanism, i.e., switch leader competition, did not consider the characteristics of data center network and the time cost, resource usage, and load balancing after failure. In this paper, we propose a temporal-based load adaptive SDN controller failover mechanism (TLACF) based on the temporal pattern of traffic. The results demonstrate the proposed TLACF can save up to 46% time cost of failover and 66% memory usage for state backup.

As computation-intensive tasks such as deep learning and big data analysis take advantage of GPU based accelerators, the interconnection links may become a bottleneck. In this paper, we investigate the upcoming performance bottleneck of multi-accelerator systems, as the number of accelerators equipped with single host grows. We instrumented the host PCIe fabric to measure the data transfer and compared it with the measurements from the software tool. It shows how the data transfer (P2P) helps to avoid the bottleneck on the interconnection links, but multi-GPU performance does not scale up as expected due to the control messages. We quantify the impact of host control messages with suggestions to remedy scalability bottlenecks. We also implement the proposed strategy on Lulesh to validate the concept. The result shows our strategy can save 59.86% time cost of the kernel and 13.32% PCIe H2D payload.

Software-defined networking (SDN) is a centrally managed network architecture which can flexibly allocates network resources according to current network conditions. However, since the cost of replacing all legacy switches to commercial SDN devices is not affordable to most enterprises, only a few switches can be replaced at a time. Such network architecture, combining legacy and SDN switches, is named as hybrid SDN. In this work, we formulate the hybrid SDN deployment problem as an optimization problem with resource constrains. Since this problem is NP-hard, we relax this problem to allow the use of greedy-based heuristic algorithms and propose a switch deployment strategy named HybridScore. HybridScore aims to provide the most control capacity over the network given a fixed number of switches to upgrade in hybrid SDN environment. The proposed HybridScore exploits the real traffic pattern of the network to determine the location of new SDN switches. The simulation results conducted with real-world enterprise network topology demonstrates that compared with existing strategies, our HybridScore deployment strategy improves the result by 11.28%. Moreover, compared with full SDN environment, our HybridScore provides comparable controlling capacity with only about 13% SDN switches.

Border Gateway Protocol (BGP) has been the de facto inter-domain routing protocol since it was introduced. Its destination-based routing nature, which is not able to choose a specific end-to-end AS-level route, might overload some popular peering (or inter-AS) links, while making some others underused. This could result in congestion and cause service disruption. To cope with the issue of destination-based routing of BGP, we resort to Software-Defined Networking (SDN) techniques to propose Effective Tunnel-based Multi-path BGP (ETMP-BGP), which is able to obtain the whole control of tunnel-based multi-path BGP routing in terms of AS-level routing. In ETMP-BGP, destinations provide the feedback of path quality to the source. This feedback is used to detect congestions on AS-level routes and adjust such routes accordingly in a per-source basis. That is, ETMP-BGP with SDN is able to get the AS-level global view of Internet and choose a better AS-level end-to-end BGP routing. Through simulations, our results show that ETMP-BGP could mitigate the AS-level congestions and outperforms existing BGP schemes.

Content Delivery Networks (CDNs) are able to improve user-oriented application performance through caching and anycast routing or DNS-based user mapping mechanism. With the fact that BGP is widely used for inter autonomous system (AS) routing for CDNs, there is a middle mile bottleneck problem, which cause by the nature limitation of BGP. To solve this problem, we propose an SDN-based tunnel multi-path system, CDN-Detour, which can detour the bottleneck for CDN to improve user experience.

The through-silicon-via (TSV) technology is one of the most effective approaches to fulfill the form factor, profile, performance, and 3D interconnect demand of next generation handheld and wearable electronics. This paper introduces two structures of TSV LAST technology, standard flow and short flow. The standard flow TSV LAST structure shows better warpage control performance. The short flow TSV LAST structure can shorten manufacture procedures up to 20% and reduce the cost. This paper reports two warpage control solutions: (1) low modulus and low CTE passivation material, and (2) a balance layer design that the warpage issue can be improved more than 30% and 20%, respectively.

In this paper, a mass production solution of integrated passive device utilized on radio frequency communication systems was proposed through a glass panel platform where the size could be up to 408 mm * 512 mm and provided 1-layer capacitor and 1-layer inductor for IPD design. The structure characterization of panel-based IPD was performed as well as the electrical stability and RF functional test were evaluated to show the capability reference for further applications. The panel-based process could also provide a cost effective solution on emerging production.

Magnetic resonant coupling is widely considered a promising candidate for the midrange transfer of power because of its long range and compact dimensions. This paper reports the process of designing a high-efficiency resonant wireless power transfer (RWPT) system. It discusses the optimal parameters for maintaining high power transfer efficiency with respect to distance and load variations. The design method is based on circuit theory, analytical derivation, and the use of Matlab to find the relationships of the parameters and to simulate the overall system. The analytical derivation is used for determining the average values of voltage and power in the circuit. The proposed system consists of a class E amplifier with a 6.78 MHz resonant frequency, coupling coils, and a class E rectifier. With a mutual inductance coefficient of k = 0.2, the expected efficiency is 93% for a power of 5 W.

In this paper, the discolor on back-side revealing through-silicon-via (TSV) after wafer thinning and silicon recess process was investigated with various surface analysis methods. According to the analysis results, surface discolor could be raised by Cu oxidation during Si recess process. To eliminate the discolor occurrence, a remedy with in-situ Ar-ion bombardment was proposed which plays a role of enforced surface clean in the same plasma process stage. After this modified Si recess process, surface analysis were performed to ensure a comparable result to standard process but less Cu oxidation.

The Embedded die in substrate (EDS) market has grown significantly over the past several years and it is now one of the fastest growing packaging technologies in the semiconductor industry driven by smaller form factor, better heat dissipating, low noise emission, higher levels of integration and better performance. In addition, for power management and mobile-wireless application the embedded technology had been evaluated to replace assembles fabrication not only thinner thickness but superior electrical performance. However, Embedded Die causes severe package warpage issue due to CTE mismatch happened on diffusion bond process. In this work, the three Dimensional Warpage Metrology Analyzer (3D-WMA), as a non-contact optical deformation measurement method used to measure unit package warpage behavior with different temperatures. Reducing the warpage issue of package, the parametric factors on the structure and material would be investigated. These design guides are then studied by finite element modeling to understand mechanism for warpage improvement and the dielectric material property selection is critically factoring for warpage control. The measured warpage data agrees very well with the predicted one that the maximum discrepancy is within 3%. Based on the above justification, it starts to carry out the parametric study. Initially, changed prepreg can improve the warpage 64%. Besides, Cu layer should be thick and soldermask layer should be thin. Furthermore, asymmetric structure design of cu layer and soldermask layer is another effective for warpage reduction. Impact from structural design and material property selection is studied in this paper.

In this paper, the interface adhesion and reliability between copper lead frame(C-19210) and resin prepreg material of different copper lead frame lamination pretreatment processes (CZ and brown oxide) was studied. Surface morphology, roughness, peel strength and moisture sensitivity level, MSL3, reliability tests were performed in order to investigate the performance between these pretreatment procedures. CZ (HCl/formic acid system) process for copper etching is commonly used for lamination pretreatment, but it is not suitable to create uniformity coarse surface on copper alloy material. Compare to CZ, brown oxide gives better uniformity morphology, higher Ra/s-ratio and stronger peel strength. Reliability test including precondition + MSL3 (failure rate: BO∶CZ=14∶100) and solder dipping (260, 270, 288 °C × 10 times) were performed to evaluate the bond strength.

The objective of this study was to develop a microinverter for solar power conversion systems for converting dc voltage generated by solar cells at varying voltage levels into single-phase ac power with constant voltage and constant frequency. This study proposes coupled inductors and double-boost topology architecture for maintaining a stable voltage on the output side and reducing the size and cost of the system. The Furthermore, maximum power point tracking (MPPT) control and voltage zero-crossing detection methods were implemented to operate the microinverter in grid-connected fashions. The established coupled inductors, double-boost microinverters, and solar cells with MPPT control strategy were simulated using Matlab/Simulink to demonstrate their feasibility. The simulations revealed that the prototype of a 230-W power conversion system supplied sufficient power in the stand-alone and grid connected power systems. Moreover, the rated effective output voltage was 220 V and frequency was 60 Hz.

Energy efficiency has become an important research issue for wireless sensor networks. Sensor nodes, thus, need to make use of their limited energy to keep active time as small as possible to prolong the whole network lifetime while meeting the performance requirement. In this work, we reinvestigate the overhearing problem, which occurs when an awake node overhears the transmission nearby, and this introduces unnecessary energy cost at the overhearing node. To cope with this issue and alleviate repeated sampling problem, we propose a cross-layer cluster routing and scheduling protocol, which jointly considers the properties of MAC layer, network layer, and application data of WSNs. That is, we group the nodes nearby that can communicate with the same neighbors and sense similar data into a cluster and let those nodes cooperatively prolong heir lifetime. We implement the proposed protocol on Tiny OS and do the simulations with TOSSIM. Both experimental and imulation results show that our proposed protocol can prolong the network lifetime up to 3x over ALPL and BMAC.

Employing an L-C-L filter cell to modify the asymmetrical half-bridge converter (AHBC), an AHBC with input current ripple reduction (AHBC-CRR) is proposed. In addition to having zero-voltage switching operation, low voltage stress, lossless snubbing, and voltage clamping features preserved from its predecessor, the proposed converter can shape input current waveform of AHBC to a non-pulsating fashion. Consequently, the ripple and undesired harmonic components of the input current can be significantly reduced without adding a large input filter. These characteristics make it suitable for high-input voltage high-frequency high-efficiency and low electromagnetic interference (EMI) power conversion applications. Besides the circuit analysis and design consideration, two 100-kHz converters, AHBC and AHBC-CRR, with the same specification, 300–400-V input, 24-V/10-A output, are built and tested. Several performance comparisons are made to demonstrate the superiority of the proposed converter over AHBC.

With successful deployments of commercial swarm-based P2P streaming systems, peer-to-peer streaming traffic grows rapidly in the last few years. To leverage system-wide bandwidth, peers in P2P streaming systems are expected to exchange their own data with other peers, and this is extremely vulnerable to pollution attacks, where malicious peers inject fake data blocks into the network and those fake data blocks will soon be propagated by the innocent nodes received them. Such attack leads to degradation of data delivery ratio and failure to decode the streaming data. In this paper, we propose a novel Social-Enhanced hash-based Cross-verification framework (SEC) to defense content pollution attacks. That is, the fake data is able to be rapidly identified through the SEC scheme, and thus the malicious nodes are isolated from clean peers. With the assistance of social networks, we can reinforce the resilience of our SEC scheme for multiple colluding malicious peers and improve the data availability by the AIMD-based reputation module. The results show that the SEC framework is able to provide high delivery ratio, (as well as high accuracy, low computational overhead, low communication overhead, and low delay) for fulfilling the stringent requirements of P2P live streaming systems even under a severe or dynamic environment (e.g., when the total capacity of polluters is larger than the source node capacity).

This paper is concerned with the design and implementation of a power controller for variable-speed permanent-magnet synchronous generators. In this system, ac-to-dc and dc-to-ac power converters are designed to convert single-phase, three-wire, variable-voltage and variable-frequency power generated by synchronous generator to that with constant-voltage and constant-frequency. In ac-to-dc power converter, the half-controlled, three-phase rectifier is built to implement the sequential-switching of switches in power converter; therefore, no rotor-position detector is needed for power converter connected with generators. The dc-to-ac power converter controlled by differential- and common- voltage modes is designed for a single-phase, three-wire inverter to yield balanced output voltage under unbalanced loads. A low-cost, 32-bit digital signal processor (DSP, TMS320F2808) is used to implement the combined drive system of generator with 220W capacity. Experiments are given to justify the analysis.

During recent years, the success of live swarm-based P2P streaming system has been witnessed. Nevertheless, how to design an effective mechanism for mitigating video quality degradation in a lossy network environment is still not thoroughly resolved yet. Unlike conventional client-server paradigm, there is data availability problem in swarm-based P2P streaming system. If we directly conduct the importance-first scheduling strategy (i.e. let the chunks with most distortion-rate efficiency get scheduled first) in swarm-based P2P streaming system, the serious content bottleneck for low priority chunks occurs, particularly when the population size is large. To cope with the above issue, in this work, we propose a dynamic strategy-switching approach that combines the advantages of random scheduling and importance-first scheduling. Our simulation results indicate that compared with existing approaches our approach not only provides better scheduling efficiency, but also is scalable even if population size is large.

During recent years, the success of live swarm-based P2P streaming system has been witnessed. Nevertheless, how to design an effective mechanism for mitigating video quality degradation in a lossy network environment is still not thoroughly resolved yet. Unlike conventional client-server paradigm, there is data availability problem in swarm-based P2P streaming system. If we directly conduct the importance-first scheduling strategy in swarm-based P2P streaming system, the serious content bottleneck for low priority chunks occurs, particularly when the population size is large. In this work, we propose a dynamic strategy-switching approach that combines the advantages of random scheduling and importance first scheduling to deal with the problem. Simulation results indicate that our approach not only provides better scheduling efficiency, but also is scalable even if population size is large.

During recent years, the success of live swarm-based P2P streaming system has been witnessed. Nevertheless, how to design an effective mechanism in mitigating video quality degradation in a lossy network environment is still not thoroughly resolved yet. Unlike conventional client-server paradigm, there is data availability problem in swarm-based P2P streaming system. If we directly conduct the importance-first scheduling strategy (i.e. let the chunks with most distortion-rate efficiency get scheduled first) in swarm-based P2P streaming system, the serious content bottleneck for low priority chunks occurs, particularly when the population size is large. In this paper, we first identify the unique problem and understand the rationale behind. After that, a dynamic strategy-switching approach that combines the advantages of random and importance-first scheduling strategy is proposed. Simulation results indicate that compared with existing approaches our approach not only provides better scheduling efficiency, but also is scalable even if population size is large.

The reliability study of thermal shock and damp heat tests for high-power white-light-emitting diode modules (WLEDMs) incorporating Ce:YAG doped glass, instead of conventional Ce:YAG doped silicone, as a phosphor layer is presented. The Ce:YAG doped glass as a phosphor layer is used for the glass to possess high transition temperature (T g ) of 750°C that can exhibit higher thermal stability and humidity resistance than conventional silicone. A comparison study of lumen loss, chromaticity shift, and transmittance loss of high-power WLEDWs with Ce:YAG doped glass and Ce:YAG doped silicone under thermal shock and damp heat tests was performed. The damp heat results showed that the high-power WLEDWs with Ce:YAG doped glass at 2∼8 wt% doping concentrations exhibited 67∼69%, 49∼65%, and 35∼67% better improvements than doped silicone for the lumen loss, chromaticity shift, and transmittance loss, respectively. The damp heat test demonstrated the larger improvement of glass doped in transmittance loss. The thermal shock results showed that the high-power WLEDWs with Ce:YAG doped glass at 2∼8 wt% doping concentrations exhibited 57∼68%, 53∼58%, and 58∼67% better improvements than doped silicone for the lumen loss, chromaticity shift, and transmittance loss, respectively. These results demonstrated that the Ce:YAG doped glass exhibited higher humidity resistance than the Ce:YAG doped silicone under damp heat and thermal shock tests. A better thermal stability and humidity resistance of doped glass phosphor layer may be beneficial to the many applications where the LED modules with high-power and high reliability are demanded.

The pervasive use of Peer-to-Peer (P2P) systems and the growing demand on personalization for consumers has made future business focus on the niche market instead of the mass market. The recommender system, which is able to timely select data of the interest to each individual user, has become the key to any successful business. However, currently most recommendation systems are based on a centralized architecture; nonetheless, they are not suitable for P2P environments. In this article, we propose a distributed semantic P2P overlay, which can provide music search and recommendation services by considering both of user preference and diversity of interests. We then propose a 3C hybrid recommendation procedure that adapts three traditional filtering techniques to fitting the requirements in a distributed semantic overlay. First, we choose a set of proper meta-data to represent a music object and use them to construct the characteristic-vector-based content filter. Second, a dominant attribute, which is one of the attributes in the characteristic vector of a music object, is used to build the profile of a peer. With the idea of the social network, a P2P profile-based collaborative filter is proposed. Finally, we explore the item-to-item relationship to construct a history-based cooperative filter. We use simulations and a real database called Audio Scrobbler, which tracks users’ listening habits, to evaluate the performance of the recommendation system. The results demonstrate the effectiveness of the proposed approach compared with existing recommendation systems.

High thermal stability of high-power phosphor-converted white-light-emitting diodes (PC-WLEDs) incorporating a Ce:YAG-doped glass as the phosphor layer is demonstrated. An exploring study of lumen loss, chromaticity shift, and transmittance loss of high-power PC-WLEDs with Ce:YAG-doped glass and Ce:YAG-doped silicone under thermal aging at 150°C for 500 hours was performed and compared. The results showed that the high-power PC-WLEDs with 6 wt% of Ce:YAG-doped glass exhibited 60% less lumen loss, 50% lower chromaticity (CIE) shift, and 20 % smaller transmittance loss than with the Ce:YAG-doped silicone. This clearly indicates that the Ce:YAG-doped glass exhibits higher thermal stability than the Ce:YAG-doped silicone after thermal aging. A better thermal stability of glass phosphor layer may be beneficial to the many applications where the LEDs with high-power and high reliability are demanded.

Perceptual visual quality guarantee is of vital concern for the P2P streaming system. One of challenging issues for assuring overall video quality is to design an effective media chunk scheduler. To the best of our knowledge, there is still a lack of studies on integrating video characteristics into P2P media chunk scheduler. In this work, we attempt to integrate video characteristics, i.e. rate-distortion impact, into P2P media chunk scheduler. No more “rarest-first” strategy, “rate-distortion first” strategy (RD-first) is deployed so that the chunks with larger rate-distortion score can be spread more effectively. Predictably, such a strategy can be better against video quality degradation by losing some less important chunks under a bandwidth constrained network. Moreover, to adapt for dynamic networks, we propose a hybrid available bandwidth prober. The simulation results show that received video quality can be substantially improved up to 1.7dB compared with existing P2P schedulers.

In this work, a low hysteresis surface prepared by hierarchical textures for the reduction of liquid droplet adhesion is proposed. This surface is important to provide a platform for droplet-based biological reactions with minimum surface interferences. The hierarchical textures, mimicking lotus leaf surface, were composed of two length scales (nano-/micro-textures). Hereby, a high contact angle (160°) and low hysteresis (~2.7°) was obtained and comparable to the surface properties of lotus leaf. In dynamic contact angle analysis by droplet impinging onto the surface, multi-metastable states were categorized and showed a high correlation to the multilength scale that would be noticeable for contact angle control.

This paper proposes a nanostructure-enhanced fiber-optic interferometry (NSFOI) biosensor, combining the abilities of high sensitivity, real-time monitoring and in-situ measurement for label-free immunological detection, by employing high-aspect-ratio pillar-like nanostructures on the tip of sensor surface. The nanostructure layer, fabricated by a simple etching process on resonant cavity without mask patterning, was employed not only for the improvement of the detection limit to reach 1ng/ml for rabbit-IgG (~6.7pM) due to the increase of the biomolecular binding surface, but also for the enhancement of the optical path length to enlarge the maximum magnitude of fringe shift which was approximated to 1.4nm by both experimental and theoretical results.

High-power light-emitting diodes (LEDs) modules encapsulated with different lens shapes after a thermal-aging test were studied experimentally and numerically. Samples from different manufacturers were aged at 65, 85, and 95degC under a constant driving current of 350 mA. The results showed that the optical power of the LED modules at the two view angles of plusmn (45deg~75deg) decreased more than the other view angles as the aging time increased. This was due to the reduction of radiation pattern from the corner effect of lens shape, resulted in lower output power. The simulation of the corner effect of lens shape is in good agreement with the experiment result. Results also showed that the center wavelength of the LED spectrum shift 5 nm after thermal aging 600 hours at 95degC because of degradation the lens material. The key module package related failure modes under thermal-aging may be due to the corner effect of lens shape and the degradation of the lens material. Therefore, improving the lens structure and lens material is essential to extend the operating life of the phosphor-based white LEDs modules.

When people browse the learning materials on a Web site, the sequence of content they browse might not have any particular relations. Therefore, the proposed research tries to build an intelligent agent for discovering a specific learner's interests in different knowledge fields dynamically, instead of finding the sequence of content he browses. Naive Bayesian classifier (NBC for short) is used as the approach of prospecting and analyzing learner's interests. Push technology is applied to do recommendation of new coming learning materials based on the suggestion obtained by NBC. The simulation results show the power of the proposed intelligent agent.

The high-power phosphor-based white-light-emitting diodes (LEDs) after thermal aging at 150°C and 500 hours are studied experimentally. The white-light LEDs formed by three combinations of different thicknesses and concentrations of the silicone YAG phosphor are 1 mm and 5.48%, 2mm and 3.2%, 3mm and 2.4%, respectively. The results showed that the lumen loss, chromaticity (CIE) shift, and spectrum intensity reduction in yellow YAG phosphor of the highpower white-light LEDs increased as the silicone YAG phosphor concentration increased. These were due to that the transmittance loss and the refractive index variation of the silicone YAG phosphor increased as the aging time increased and resulted in lower emission efficiency of the high-power white-light LEDs. However, the lumen loss and CIE shift did not significantly depend on the thickness of the silicone YAG phosphor. The likely cause for the transmittance reduction and refractive index variation increased is that the thermal effect increased after thermal aging. As a result, the key of high-power phosphor-based white-light LEDs module package related degradation mode under thermal aging was identified as the decay of the silicone YAG phosphor, evidenced by secondary-ion mass spectroscopy (SIMS) analyses. This study clearly indicates that in order to maintain luminous power and minimize color shift of the highpower white-light LEDs modules, a lower concentration of the YAG phosphor for use in packaging of the phosphorbased white-light LEDs modules is essential.

In this paper, we present a two-layer rate control framework for low delay video transmission based on a characteristic-based rate-quantization (R-Q) model. Specifically, with the frame-layer characteristic-based R-Q model, we are able to figure out the most appropriate quantization parameter (QP) to maintain targeted end-to-end delay by jointly considering the current buffer status, network bandwidth and the variation of bit rate of the input video source. Next, in macroblock-layer (MB), a greed-based rate-distortion (R-D) refinement of MBs approach is proposed to efficiently utilize the remaining available bit rate in order to enhance visual quality as much as possible. The experiments show that our two-layer characteristic-based rate control framework can quickly smooth out the impact of varying bit rate of video source on the buffer, meet targeted buffer delay time well, and substantially enhance the quality of the perceived video with lower computational complexity.

In this work, a novel fabrication process of self-formed polymer nanopillars by reactive ion etching (RIE) is proposed. During this one-step RIE process, polymer nanopillars were generated adjacent XPS surface analysisto glass slide that was partially covered on treated polymer of either PDMS or parylene C. The surface morphologies and water contact angles were compared for different RIE parameters of RF-power and etching time. The aspect-ratio and water contact angle of nanopillar could reach 10 and 162.6deg, respectively. Furthermore, the mechanism of this novel fabrication process was established based on the evidences of nanopillar distribution and XPS surface analysis.

In this study, a novel fabrication method of nanostructure by reactive ion etching (RIE) process on PDMS without predefinition of nanopattern is proposed. During etching process, self-formed high-aspect-ratio nanostructure was observed on PDMS surface adjacent to SiO2 area, suggested the provision of nano masks from the SiO2 residue during RIE etching. In tuning the flow rate of working gases (CF4, O2), the distribution of nanostructure can be controlled. Furthermore, it was observed that different species of nanostructures could be fabricated by the selection of mask materials (SiO2, Cu) under RIE etching.

This paper presents the design and implementation of a power control system for variable-speed, permanent-magnet synchronous generators. In this system, a three-phase, full-bridge rectifier and a single-phase, three-level inverter are proposed to convert the three-phase varying voltage and frequency generated by wind to single-phase source with constant voltage and frequency. Specifically, the output power of the overall system is adjusted by detecting the dc-link voltage as well as output voltage and current of inverter. A novel three-level dc/dc power converter is designed to charge and discharge the battery set, while fixed- voltage control method is used to supply load power when wind speed is low. The single-phase, three-level inverter operated under voltage-controlled mode by using new two-axis amplitude-lock- loop technique algorithm can provide a single-phase source with fast response, stable and low harmonic distortion power to load. The performance of the system is simulated by Matlab/Simulink. Then, a low-cost, 16-bit digital signal processor (DSP, TMS320LF2407A) is used to implement the control functions of the generation system. The experimental results for a 750 W generation system show that the output voltage and frequency can be held at 110/220 V and 60 Hz, respectively, when the speed varies from 200 to 450 rpm. The feasibility of the generation system is verified experimentally.

A novel method to modify the surface morphology of the vapor coated chlorosilane-based self assembled monolayer (SAM) on glass substrates was proposed. This so-called "interrupted-growth" process involves a combination of evaporative drying of solvent and annealing processes. Atomic force microscope measurements revealed the conglomerates of SAM molecular chains with possible multilayer rearrangements. Contact angle increment as high as 30deg was observed while hysteresis remains unaltered. The possible mechanism of conglomerates formation was proposed. The method has been successfully applied to further improve the superhydrophobicity of polydimethylsiloxane (PDMS) nanopillar-based surface.

The paper proposes and demonstrates a novel protein microarray chip with an embedded microchannel array for the delivery of protein separately. This chip system is applicable to high throughput disease diagnosis and drug screening. Demonstration in spot formations by the novel design using MEMS technology and characterization of the spot-forming process by numerical simulations are performed to illustrate the feasibility and the advantages of the presented design.

This paper investigates the influence of various levels of Sb addition on the microstructure of Sn-Ag hypoeutectic solder. To be precise, the microstructural evolution and the characteristics of Sn2.58Ag solder are studied for Sb additions of 1.75, 4.75 and 8.78wt%. The experimental results indicate that part of the Sb addition solutes into the /spl beta/-Sn matrix, while the remainder reacts with the Ag and Sn atoms to form /spl epsiv/-Ag/sub 3/(Sb,Sn) and SbSn compounds. It is noted that Ag/sub 3/(Sb,Sn) is readily formed even when the level of Sb addition is low (1.75%). This suggests that the Sb atoms are quite active in substituting some of the Sn atoms in the Ag/sub 3/Sn compound to form a nonstoichiometry compound, i.e. Ag/sub 3/(Sb,Sn). In contrast, the SbSn phase is only identified when the Sb content exceeds 4.75%. After a process of deep etching, it is observed that the morphology of the Ag/sub 3/(Sb,Sn) phase in the as-soldered condition possesses a long-strip-like appearance. However, it is shown that if the cooling rate is sufficiently slow, then the /spl beta/-Sn matrix and the Ag/sub 3/(Sb,Sn) compound tend to solidify simultaneously in the as-cast condition. A coarse laminated structure is observed and the Ag/sub 3/(Sb,Sn) phase appears platelike. This results in a substantial reduction in the strength and ductility of the solder joint. Finally, it is shown that the size of the SbSn phase remains at a constant value of ca.30 /spl mu/m for the two cooling rate conditions considered in the present investigation.

This study investigates the microstructure, intermetallic compound (IMC) morphology and shear strength of Sn4.38Ag solder joints with different percentages of Sb content. The paper also evaluates, and compares, the thermal resistance of solder joints with different Sb content by means of high temperature storage testing. In order to achieve solder joints of the size found in the BGA package, this study used pure copper wires of 1 mm diameter as substrates for hot-dipping soldering. Solders with different compositions were selected for investigation, namely Sn4.38Ag, Sn3.9Ag0.9Sb, Sn4.4Ag1.44Sb and Sn4.11Ag1.86Sb, while a Sn40Pb solder was chosen for comparison purposes. High temperature storage testing was performed after soldering, with storage temperatures of 150/spl deg/C and 200/spl deg/C, respectively, and storage times of 0, 25, 100, 228 and 625 hours, respectively. Experimental results show that most of the Sb which is added to the solder is soluted in the /spl beta/-Sn matrix, with the remainder reacting with the Sn and Ag atoms to form an /spl epsiv/-Ag/sub 3/(Sn,Sb) compound.