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Workflow computing has become an essential part of many scientific and engineering fields, while workflow scheduling has long been a well-known NP-complete research problem. Major previous works can be classified into two categories: heuristic-based and guided random-search-based workflow scheduling methods. Monte Carlo Tree Search (MCTS) is a recently proposed search methodology with great success in AI research on game playing, such as Computer Go. However, researchers found that MCTS also has potential application in many other domains, including combinatorial optimization, task scheduling, planning, and so on. In this paper, we present a new workflow scheduling approach based on MCTS, which is still a rarely explored direction. Several new mechanisms are developed for the major steps in MCTS to improve workflow execution schedules further. Experimental results show that our approach outperforms previous methods significantly in terms of execution makespan. [ABSTRACT FROM AUTHOR]

Resource allocation is vital for improving system performance in big data processing. The resource demand for various applications can be heterogeneous in cloud computing. Therefore, a resource gap occurs while some resource capacities are exhausted and other resource capacities on the same server are still available. This phenomenon is more apparent when the computing resources are more heterogeneous. Previous resource-allocation algorithms paid limited attention to this situation. When such an algorithm is applied to a server with heterogeneous resources, resource allocation may result in considerable resource wastage for the available but unused resources. To reduce resource wastage, a resource-allocation algorithm, called the minimizing resource gap (MRG) algorithm, for heterogeneous resources is proposed in this study. In MRG, the gap between resource usages for each server in cloud computing and the resource demands among various applications are considered. When an application is launched, MRG calculates resource usage and allocates resources to the server with the minimized usage gap to reduce the amount of available but unused resources. To demonstrate MRG performance, the MRG algorithm was implemented in Apache Spark. CPU- and memory-intensive applications were applied as benchmarks with different resource demands. Experimental results proved the superiority of the proposed MRG approach for improving the system utilization to reduce the overall completion time by up to 24.7% for heterogeneous servers in cloud computing. [ABSTRACT FROM AUTHOR]

This paper presents our experimental studies on improving the speed of solving nonogram puzzles. Our approach is based on the algorithm developed by Wu et al. A puzzle solving program, named LalaFrogKK, implementing the algorithm has won several nonogram tournaments since 2011. The algorithm consists of three major parts: propagation based on line solving, fully probing, and backtracking. Fully probing, running before backtracking, contributes to solving a nonogram puzzle in two ways. The first is to paint more pixels after propagation. The second is testing each unpainted pixel for providing backtracking with more accurate guidance when choosing pixels to guess. However, we found that different probing sequences can lead to significant differences in the numbers of painted pixels after fully probing. Therefore, in this paper, we investigate into the effects of different fully probing sequences, and propose several new fully probing mechanisms. Experimental results show that the new mechanisms can significantly outperform the original fully probing method. One of the new fully probing mechanisms achieves a speedup of more than two times in solving nonogram puzzles. [ABSTRACT FROM AUTHOR]

Nonogram is a typical two-dimensional logical puzzle game in which each pixel involves two constraints associated to the intersecting row and column. The recently proposed approaches can efficiently solve many puzzles via logical deduction based on the 2-SAT formulas. This paper proposes a set of new logical properties for inferencing the consistent and inverse relations among pixels. We show that the pixels with consistent (or inverse) relation must be painted to a same (or an opposite) color in the solution puzzle. Consequently, the pixels can be aggregated into groups, thereby the space of search tree of the Nonogram backtracking algorithm can be reduced. [ABSTRACT FROM AUTHOR]

Summary: This paper presents a Platform of Extensible Workflow Simulation Service (Pewss), which we have developed to provide a cloud service for aiding research work in workflow scheduling. The simulation has been a major tool for performance evaluation and comparison in workflow scheduling research. However, researchers usually have to develop their own simulation programs with limited functionality, simply outputting summarized performance results. Pewss has been developed for easing and improving current practices in conducting performance simulations during studying of existing workflow scheduling algorithms or designing of new scheduling algorithms. Pewss has been designed based on the Software as a Service (SaaS) model, adopting a multiuser Web‐based client/server architecture. Conducting simulation experiments on Pewss, researchers simply have to implement the scheduling algorithm under study instead of a whole simulation environment, allowing them to focus on their research work without spending unnecessary efforts on the simulation implementation details. Pewss provides the visualization of a workflow execution schedule based on simulation results, offering a convenient way for researchers to gain an insight into the effectiveness, characteristics, and performance bottleneck of scheduling algorithms. As a multiuser environment, Pewss also provides functionality for researchers to facilitate comparative performance analysis and collaborative research works effectively. Pewss has been used in our research work on task‐parallel workflow scheduling and has been planned to be extended to support other types of workflow scheduling research problems, eg, mixed‐parallel workflows. [ABSTRACT FROM AUTHOR]

Parallel computation has been widely applied in a variety of large-scale scientific and engineering applications. Many studies indicate that exploiting both task and data parallelisms, i.e. mixed-parallel workflows, to solve large computational problems can get better efficacy compared with either pure task parallelism or pure data parallelism. Scheduling traditional workflows of pure task parallelism on parallel systems has long been known to be an NP-complete problem. Mixed-parallel workflow scheduling has to deal with an additional challenging issue of processor allocation. In this paper, we explore the processor allocation issue in scheduling mixed-parallel workflows of moldable tasks, called M-task, and propose an Iterative Allocation Expanding and Shrinking (IAES) approach. Compared to previous approaches, our IAES has two distinguishing features. The first is allocating more processors to the tasks on allocated critical paths for effectively reducing the makespan of workflow execution. The second is allowing the processor allocation of an M-task to shrink during the iterative procedure, resulting in a more flexible and effective process for finding better allocation. The proposed IAES approach has been evaluated with a series of simulation experiments and compared to several well-known previous methods, including CPR, CPA, MCPA, and MCPA2. The experimental results indicate that our IAES approach outperforms those previous methods significantly in most situations, especially when nodes of the same layer in a workflow might have unequal workloads. [ABSTRACT FROM AUTHOR]

This paper proposes a novel nonisolated single-switch cascaded high step-up converter. The converter consists of coupled inductors, a clamp circuit, and cascaded capacitors to achieve high step-up voltage output. Only one switch is used in the proposed converter; the switch can reduce cost efficiently and simplify the control of the proposed converter. The converter also possesses an energy-recycle mechanism for recycling the spike energy of a leakage inductor. In addition, a clamp circuit is used to reduce voltage-stress across the switch, and a cascaded design is used to reduce voltage-stress across diodes and output capacitor. Thus, the proposed converter can select a low-voltage stress switch for reducing circuit loss and improving the efficiency of the converter. Finally, in this study, a 400-W nonisolated cascaded high step-up converter was implemented, of which the input and output voltages are 48 and 400 V, respectively. A microcontroller dsPIC30F4011 was used to control the converter and verify system effects and feasibility. The maximum efficiency of the proposed converter is 95% and the efficiency under a full load is 93%. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper presents a novel bidirectional DC-to-DC converter charge/discharge controller for solar energy illumination system. The bidirectional converter architecture integrates the synchronous rectification Single Ended Primary Inductor Converter (SEPIC) converter and an active clamp flyback converter. In addition to fully use the properties of the shared components and compensate for the shortcomings of conventional two-stage illumination systems, the proposed system has the advantages of soft-switching, simple structure, and high efficiency. During daytime, a SEPIC converter with synchronous rectification function was used to charge the lead acid battery through three-stage charging and maximum power point tracking. At night, the battery discharges, driving and dimming high-brightness LEDs using the active clamp flyback converter. Finally, a solar energy illumination system with both a 160 W charge/discharge controller and an 80 W LED driver was implemented to verify the feasibility and practicality of the proposed system. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper presents the design of a smart household environment illumination dimming-control. The control can be operated using either an Android App or a computer using either Wi-Fi or Zigbee to connect to a Database Management System (DBMS). The DBMS can synchronize with a central controller in order to achieve simple and convenient dimming-control of the user's home illumination. In this paper, a linear dimming scheme was adopted to reduce the light gleaming. In order to achieve suitable variations in the illumination environment, a highly-efficient three-color LED was used as the light source. This paper covers the designs of six environment illumination controls for users who can deliver the control states to the central controller and mobile phone. A 24 V DC power supply was designed in this system and can collocate with the DC/DC converter to form a power module suitable for general home use. The interface of the proposed environment illumination control is clear and simple; one can verify that the design presented in this paper possesses very high practicability from the experimental results. [ABSTRACT FROM PUBLISHER]

We conducted a chronoamperometric study to observe the electrochemical behaviors of the nucleation mechanism of electrodeposited Cu(In,Al)Se 2 films. A change from instantaneous nucleation to progressive nucleation was observed by increasing the copper concentration. SEM and EDS analyses demonstrated that the surface morphologies and chemical compositions of precursor and post-annealed Cu(In,Al)Se 2 films were influenced by the nucleation mechanism. They exhibited that Cu(In,Al)Se 2 films had roughly cauliflower-like and triangular structures with Cu-poor composition at the instantaneous nucleation mechanism, whereas smooth and round structures with Cu-rich composition at the progressive nucleation mechanism. Additionally, the quality, growth orientation, composition phase, and optical energy band gap of Cu(In,Al)Se 2 films were examined using X-ray diffraction (XRD) patterns, Raman spectra, and ( αhν ) 2 vs. hν plots (UV–vis). Thereafter, the performances of rudimentary Cu(In,Al)Se 2 solar cells fabricated at various copper concentrations were discussed, the conversion efficiency of electrodeposited Cu(In,Al)Se 2 solar cells were unpublished in previous literatures. Our studies demonstrated that the performances of Cu(In,Al)Se 2 solar cells were significantly related to the surface morphology and composition of Cu(In,Al)Se 2 absorber layer. The highest conversion efficiency of Cu(In,Al)Se 2 solar cells fabricated at a 2-mM copper concentration was 1.96% with open-circuit voltage, short-circuit current, fill factor, R sh and R s values of 0.189 V, 29.21 mA/cm 2 , 35.4%, 125 Ω and 2.82 Ω, respectively. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, the cyclic voltammetric studies were used to realize the element's reduction potential and chemical reaction mechanism for presuming the formation routes of quaternary Cu(In,Al)Se2 crystals. Thereafter, the prior adjustment of deposited potential from −0.6V to −1.0V can be identified a suitable potential as co-electrodeposition. The material characteristics of Cu(In,Al)Se2 films are dominated by the percentage of aluminum content. Thus, the influence of aluminum and indium concentrations in solutions on the percentage composition, surface morphology, structural and crystal properties, and optical energy band gap of Cu(In,Al)Se2 films were investigated. Energy dispersive X-ray spectroscopy (EDS) indicated that the ratio of Al to (Al+In) in Cu(In,Al)Se2 films varied from 0.21 to 0.42 when adjusting aluminum and indium concentrations in solutions. Scanning electron microscopy (SEM) shows that the surface morphology changed from round-like structures into cauliflower-like structures and became rough when the aluminum concentration increased and indium concentration decreased in solutions. X-ray diffraction (XRD) patterns revealed three preferred growth orientations along the (112), (204/220), and (116/312) planes for all species. The (αhυ)2 versus hυ plots (UV–Visible) shows that the optical energy band gap of the Cu(In,Al)Se2 films can be successfully controlled from 1.17eV to 1.48eV by adjusting the aluminum and indium concentrations. Furthermore, the shift of the (112) peak in the XRD patterns and variation of optical band gap are evidence that the incorporation of aluminum atoms into the crystallitic CuInSe2 forms Cu(In,Al)Se2 crystals. [Copyright &y& Elsevier]

This paper proposes waiting ratio as a basis in evaluating various scheduling methods for dynamic workloads consisting of multi-processor jobs on parallel computers. We evaluate commonly used methods as well as several methods proposed in this paper by simulation studies. The results indicate that some commonly used methods do not improve the waiting ratios as expected by intuition, while some methods proposed in this paper do greatly improve waiting ratios more than 10 times for some workload data, promising in leading to more reasonable waiting time and better user's satisfaction. [ABSTRACT FROM AUTHOR]

Recently, the superior and continuously improving cost-performance ratio of commodity hardware and software has made PC clustering a popular alternative for high-performance computing in both academic institutes and industrial organizations. The purpose of this work is to use PC clusters to solve a weather-prediction model in parallel mode, and the result also will be compared with those obtained on some conventional parallel platforms such as the Fujitsu VPP300, IBM SP2 (160 and 120 MHz), and HP SPP2200. Techniques of domain decomposition and data communication are used to exploit parallelism of the model. Interprocessor data communication is done by the Message Passing Interface communication library routines. Two versions of the parallel codes, one with longitude decomposition and the other with latitude decomposition, are tested and compared. Speedups of the parallel weather model on these machines with various numbers of processors show that substantial reductions in computation time can be achieved as compared with sequential runs. [ABSTRACT FROM AUTHOR]

With the notion of virtual servers, peers participating in a heterogeneous, structured peer-to-peer (P2P) network may host different numbers of virtual servers, and by migrating virtual servers, peers can balance their loads proportional to their capacities. The existing and decentralized load balance algorithms designed for the heterogeneous, structured P2P networks either explicitly construct auxiliary networks to manipulate global information or implicitly demand the P2P substrates organized in a hierarchical fashion. Without relying on any auxiliary networks and independent of the geometry of the P2P substrates, we present, in this paper, a novel load balancing algorithm that is unique in that each participating peer is based on the partial knowledge of the system to estimate the probability distributions of the capacities of peers and the loads of virtual servers, resulting in imperfect knowledge of the system state. With the imperfect system state, peers can compute their expected loads and reallocate their loads in parallel. Through extensive simulations, we compare our proposal to prior load balancing algorithms. [ABSTRACT FROM AUTHOR]