Distributed scheduling: a review of concepts and applications

Distributed scheduling (DS) is an approach that enables local decision makers to create schedules that consider local objectives and constraints within the boundaries of the overall system objectives. Local decisions from different parts of the system are then integrated through coordination and communication mechanisms. Distributed scheduling attracts the interest of many researchers from a variety of disciplines, such as computer science, economics, manufacturing, and service operations management. One reason is that the problems faced in this area include issues ranging from information architectures, to negotiation mechanisms, to the design of scheduling algorithms. In this paper, we provide a survey and a critical analysis of the literature on distributed scheduling. While we propose a comprehensive taxonomy that accounts for many factors related to distributed scheduling, we also analyse the body of research in which the scheduling aspect is rigorously discussed. The focus of this paper is to review the studies that concern scheduling algorithms in a distributed architecture, not, for example, protocol languages or database architectures. The contribution of this paper is twofold: to unify the literature within our scope under a common terminology and to determine the critical design factors unique to distributed scheduling and in relation to centralised scheduling.     

Polymer Carpets

The fabrication of defined polymer objects of reduced dimensions such as polymer‐coated nanoparticles (zero‐dimensional (0D)), cylindrical brushes (1D), and polymer membranes (2D), is currently the subject of intense research. In particular, ultrathin polymer membranes with high aspect ratios are being discussed as novel materials for miniaturized sensors because they would provide extraordinary sensitivity and dynamic range when sufficient mechanical stability can be combined with flexibility and chemical functionality. Unlike current approaches that rely on crosslinking of polymer layers for stabilization, this report presents the preparation of a new class of polymer material, so‐called “polymer carpets,” a freestanding polymer brush grown by surface‐initiated polymerization on a crosslinked 1‐nm‐thick monolayer. The solid‐supported, as well as freestanding, polymer carpets are found to be mechanically robust and to react instantaneously and reversibly to external stimuli by buckling. The carpet mechanics and the dramatic changes of the film properties (optical, wetting) upon chemical stimuli are investigated in detail as they allow the development of completely new integrated micro‐/nanotechnology devices.     

Exploiting the synergy between fractal dimension and lacunarity for improved texture recognition

Fractal dimension measures the geometrical complexity of images. Lacunarity being a measure of spatial heterogeneity can be used to differentiate between images that have similar fractal dimensions but different appearances. This paper presents a method to combine fractal dimension (FD) and lacunarity for better texture recognition. For the estimation of the fractal dimension an improved algorithm is presented. This algorithm uses new box-counting measure based on the statistical distribution of the gray levels of the “boxes”. Also for the lacunarity estimation, new and faster gliding-box method is proposed, which utilizes summed area tables and Levenberg-Marquardt method. Methods are tested using Brodatz texture database (complete set), a subset of the Oulu rotation invariant texture database (Brodatz subset), and UIUC texture database (partial). Results from the tests showed that combining fractal dimension and lacunarity can improve recognition of textures.     

A Bayesian approach for user aware peer-to-peer video streaming systems

Peer-to-Peer (P2P) architectures for live video streaming has attracted a significant attention from both academia and industry. P2P design enables end-hosts to relay streams to each other overcoming the scalability issue of centralized architectures. However, these systems struggle to provide a service of comparable quality to that of traditional television. Since end-hosts are controlled by users, their behavior has a strong impact on the performance of P2P streaming systems, leading to potential service disruption and low streaming quality. Thus, considering the user behavior in these systems could bring significant performance improvements. Toward this end, we propose a Bayesian network that captures all the elements making part of the user behavior or related to it. This network is built from the information found in a cross-analysis of numerous large-scale measurement campaigns, analyzing the user behavior in video streaming systems. We validate our model through intensive simulations showing that our model can learn a user behavior and is able to predict several activities helping thus in optimizing these systems for a better performance. We also propose a method based on traces collection of the same user type that accelerates the learning process of this network. Furthermore, we evaluate the performance of this model through exploring its applications and comparison with non-contextual models.     

Analysis of serial production lines: characterisation study and a new heuristic procedure for optimal buffer allocation

Buffer allocation in serial production lines is one of the important design issues, and hence it has been studied extensively in the literature. In this paper, we analyse the problem to characterise the optimal buffer allocation; specifically, we study the cases with single and multiple bottleneck stations under various experimental conditions. In addition, we develop an efficient heuristic procedure to allocate buffers in serial production lines to maximise throughput. The results of the computational experiments indicate that the proposed algorithm is very efficient in terms of both solution quality and CPU time requirements. Moreover, the characterisation study yields interesting findings that may lead to important practical implications. A comprehensive bibliography is also provided in the paper.     

Preliminary study of adsorption behavior of bovine serum albumin(BSA) protein and its effect on antibacterial and corrosion property of Ti-3Cu alloy

The adsorption behavior,antibacterial,and corrosion properties of a Ti-3Cu alloy were studied in a phosphate-buffered saline solution containing 0,1,3,and 6 g L-1 bovine serum albumin protein at 37 ℃and pH =7.4 (±0.2).The protein adsorption behavior was examined via cyclic voltammetry,secondary ions mass spectroscopy (SIMS),and angle-resolved X-ray photoelectron spectroscopy (ARXPS).The cor-rosion property was analyzed by the open circuit potential (OCP),potentiodynamic polarization (PD),and electrochemical impedance spectroscopy (EIS) examinations.The antibacterial test was conducted according to the GB/T 21510 China Standard.It was observed that the surface charge density (Q～s) was directly proportional to the amount of the adsorbed BSA protein,signifying that the protein adsorption was accompanied by the charge transfer,pointing to chemisorptions phenomena.BSA amino groups and other organic species were observed in the surface analysis examinations.It was shown that the formation of barrier complexes between the TiO2 oxide-layer and PBS solution resulted in decreasing the release of Cu-ions,which consequently reduced the antibacterial activity.On the other hand,these barrier complexes improved the corrosion resistance by increasing the charge transfer resistance and double-layer capacitance of the Ti-3Cu alloy.     

Synthesis of Ag‐NPs impregnated cellulose composite material: its possible role in wound healing and photocatalysis

Cellulose is the natural biopolymer normally used as supporting agent with enhanced applicability and properties. In present study, cellulose isolated from citrus waste is used for silver nanoparticles (Ag‐NPs) impregnation by a simple and reproducible method. The Ag‐NPs fabricated cellulose (Ag‐Cel) was characterised by powder X‐rays diffraction, Fortier transform infrared spectroscopy and scanning electron microscopy. The thermal stability was studied by thermo‐gravimetric analysis. The antibacterial activity performed by disc diffusion assay reveals good zone of inhibition against Staphylococcus aureus and Escherichia coli by Ag‐Cel as compared Ag‐NPs. The discs also displayed more than 90% reduction of S. aureus culture in broth within 150 min. The Ag‐Cel discs also demonstrated minor 2,2‐diphenyl 1‐picryl‐hydrazyl radical scavenging activity and total reducing power ability while moderate total antioxidant potential was observed. Ag‐Cel effectively degrades methylene‐blue dye up to 63.16% under sunlight irradiation in limited exposure time of 60 min. The Ag‐NPs impregnated cellulose can be effectively used in wound dressing to prevent bacterial attack and scavenger of free radicals at wound site, and also as filters for bioremediation and wastewater purification.Inspec keywords: silver, nanoparticles, particle reinforced composites, nanocomposites, filled polymers, wounds, nanomedicine, biomedical materials, photochemistry, catalysis, X‐ray diffraction, Fourier transform infrared spectra, scanning electron microscopy, thermal stability, thermal analysis, antibacterial activity, dyes, wastewater treatment, contaminated site remediation, nanofabricationOther keywords: silver nanoparticles, impregnated cellulose composite, wound healing, photocatalysis, natural biopolymer, citrus waste, powder X‐ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, thermal stability, thermo‐gravimetric analysis, antibacterial activity, disc diffusion assay, Staphylococcus aureus, Escherichia coli, inhibition zone, broth, 2,2‐diphenyl 1‐picryl‐hydrazyl radical scavenging activity, total reducing power ability, total antioxidant potential, methylene‐blue dye, sunlight irradiation, wound dressing, bacterial attack, free radical scavenger, wastewater purification, bioremediation filters, wound site, time 60 min, Ag     

A GA-based solution approach for balancing printed circuit board assembly lines

Printed circuit board (PCB) assembly lines consist of a number of different machines for mounting electronic components onto PCBs. While high-speed placement machines are employed to assemble standard components, so-called fine-pitch placement machines are used to mount complex electronic components with high precision and by use of specific nozzles. In this paper, we investigate a typical mass production environment where a single type of PCB is assembled in a line comprising high-speed as well as high-precision placement machines. The PCB assembly line balancing problem consists of assigning component feeders, each holding a specific electronic component type, and the corresponding placement operations to machines in the line so as to minimize the assembly cycle time. To solve this problem, a two-stage solution procedure based on genetic algorithm (GA) is proposed. In the first stage, component feeders are assigned to the placement machines with the objective of balancing the workload within the assembly line. A number of candidate solutions are then transmitted to the second stage, where specific machine optimization algorithms are applied to determine the feeder-slot assignment in the component magazine of the machines and the placement sequence of the various components. As a result, fine-tuned placement operation times are achieved which reflect the individual operation mode and the actual component setup of the placement machines. Finally, from the candidate solutions the one which minimizes the actual PCB assembly time is selected.     

Electric and Dielectric Properties of Cr-Ga Substituted BaM Hexaferrites for High-Frequency Applications

Single-phase Cr-Ga-substituted BaM hexaferrites with chemical formula BaCr _x Ga _x Fe_12?2x O₁₉ (x = 0.0, 0.1, 0.2, 0.3, and 0.4) are synthesized by means of a sol-gel autocombustion technique. Cold isostatic-pressing technique has been used to press the as-prepared powders into pellets. Room-temperature DC resistivity enhances with the substitution of Cr-Ga contents. The temperature dependence of the DC resistivity shows the semiconducting nature. The dielectric constant and dielectric tangent loss decrease, while AC conductivity increases with the increasing applied field frequency in the range of 1 MHz-3 GHz consistent with Koop’s theory and Maxwell-Wagner’s bi-layer model. The magnetic loss enhances, while the reflection coefficient decreases with the increase of frequency as well as with the increase of Cr-Ga contents. Owing to improved properties, these materials are potential candidates for high-frequency applications in GHz range.