A performance study of multiprocessor task scheduling algorithms

Multiprocessor task scheduling is an important and computationally difficult problem. A large number of algorithms were proposed which represent various tradeoffs between the quality of the solution and the computational complexity and scalability of the algorithm. Previous comparison studies have frequently operated with simplifying assumptions, such as independent tasks, artificially generated problems or the assumption of zero communication delay. In this paper, we propose a comparison study with realistic assumptions. Our target problems are two well known problems of linear algebra: LU decomposition and Gauss–Jordan elimination. Both algorithms are naturally parallelizable but have heavy data dependencies. The communication delay will be explicitly considered in the comparisons. In our study, we consider nine scheduling algorithms which are frequently used to the best of our knowledge: min–min, chaining, A^*, genetic algorithms, simulated annealing, tabu search, HLFET, ISH, and DSH with task duplication. Based on experimental results, we present a detailed analysis of the scalability, advantages and disadvantages of each algorithm.

Active time scheduling for rechargeable sensor networks

Recent progress in energy harvesting technologies made it possible to build sensor networks with rechargeable nodes which target an indefinitely long operation. In these networks, the goal of energy management is to allocate the available energy such that the important performance metrics, such as the number of detected threats, are maximized. As the harvested energy is not sufficient for continuous operation, the scheduling of the active and inactive time is one of the main components of energy management. The active time scheduling protocols need to maintain the energy equilibrium of the nodes, while considering the uncertainties of the energy income, which is strongly influenced by the weather, and the energy expenditures, which are dependent on the behavior of the targets. In this paper, we describe and experimentally compare three active time scheduling protocols: (a) static active time, (b) dynamic active time based on a multi-parameter heuristic and (c) utility-based uniform sensing. We show that protocols which take into consideration the probabilistic models of the energy income and expenditure and can dynamically adapt to changes in the environment, can provide a significant performance advantage.     

Electrochemical performance and modeling of lithium‐sulfur batteries with varying carbon to sulfur ratios

Lithium‐sulfur batteries have attracted much research interest because of their high theoretical energy density and low‐cost raw materials. While the electrodes are composed of readily available materials, the processes that occur within the cell are complex, and the electrochemical performance of these batteries is very sensitive to a number of cell processing parameters. Herein, a simple electrochemical model will be used to predict, with quantitative agreement, the electrochemical properties of lithium‐sulfur cathodes with varying carbon to sulfur ratios. The discharge capacity and the polarization were very similar for the lowest sulfur loadings, while above 23.2 wt% sulfur the gravimetric capacity dropped significantly, and there was an increase in the cell polarization. In addition, a transition in the electrode morphology, from well dispersed to aggregated sulfur at the surface, will be reflected in the change in a critical model parameter demonstrating the sensitivity and functionality of even this simple model in predicting complex behavior in the lithium‐sulfur cells.     

Comparison of additive effects on the PVA/starch cryogels: Synthesis,characterization, cytotoxicity,and genotoxicity studies

The research goal of this study is to produce suitable scaffolds for tissue engineering applications. Different ratios of polyvinyl alcohol (PVA)/starch (90:10, 70:30, 50:50) and crosslinking methods have been used to prepare cryogels. Chemically crosslinked cryogels were synthesized using glutaraldehyde as the crosslinking agent. For the physically crosslinked cryogels, sodium dodecyl sulfate was used during cryogelation as the foaming agent. Chemical structure and pore morphology were demonstrated by Fourier transform infrared spectroscopy and scanning electron microscopy (SEM). Swelling ratio and degradation profile of the scaffolds were also determined. 3-(4,5-dimethylthiazoyl-2-yl)-2,5-diphenyltetrazolium bromide assay and SEM were used to investigate the biocompatibility of the scaffolds and cell morphology. Genotoxicity test was performed to show DNA fragmentation. The overall results demonstrated that PVA/starch cryogels could have potentially appealing application as scaffolds for tissue engineering applications and additives affect the architecture and characteristic properties of the cryogels.     

Radiological characterization of Cay?rhan coal-fired power plant in Turkey

Natural radioactivity of Cay?rhan lignite coal treated at Cay?rhan (Ankara, Turkey) power plant, its ash and soil samples mixed with ash in the power plant field were investigated. For comparison, soil samples were collected from a distance of 4 km south of the plant. The analysis shows that the samples include natural radionuclides such as ²²⁶Ra, ²³²Th and ⁴⁰K. The mean activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K were 57.82, 30.45 and 322.21 Bq · kg⁻¹, respectively. Obtained values shows that the average radium equivalent activity (Ra_eq), air-absorbed dose rate (D), annual effective dose (AED) and external hazard index (H_ex) for all samples are 123.9 Bq · kg⁻¹, 58.90 nGy · h⁻¹, 71.99 μSv · y⁻¹ and 0.34, respectively. The Ra_eq values of samples are lower than the limit of 370 Bq · kg⁻¹, equivalent to a γ-dose of 1.5 mSv · y⁻¹. The measured activity concentrations for these radionuclides were compared with the reported data of other countries.     

An antibacterial composite system based on multi-responsive microgels hosting monodisperse gold nanoparticles

A multi-responsive microgel having response to pH, temperature, and salt concentration was successfully prepared using a water-soluble monomer. Microgels were readily prepared from 2-(N-morpholino)ethyl methacrylate (MEMA) via emulsion polymerization using glycidyl methacrylate as a comonomer cross-linker. The morpholino groups of MEMA residues of microgels were able to give complexation with metal containing anions such as AuCl₄ ^? in acidic conditions. The reduction of aurate ions with sodium borohydride led to immobilized-gold nanoparticles (AuNP) in the microgel system. Average particle diameters of AuNPs were determined to be 10 ± 2 nm. The resulting AuNP-microgel system was examined as a nanoreactor for catalyst system and determined to be very effective in the reduction of 4-nitrophenol model reaction in aqueous media. AuNPs-microgel composite system had antibacterial properties against several Gram-positive and Gram-negative bacteria similar to amoxicillin. This P(MEMA-co-GMA) microgel is also very useful for different applications such as a host for metal nanoparticle production, a drug carrier or drug delivery system.     

Metal Organic Framework Crystals in Mixed‐Matrix Membranes: Impact of the Filler Morphology on the Gas Separation Performance

Mixed‐matrix membranes comprising NH₂‐MIL‐53(Al) and Matrimid or 6FDA‐DAM have been investigated. The metal organic framework (MOF) loading has been varied between 5 and 20 wt%, while NH₂‐MIL‐53(Al) with three different morphologies, nanoparticles, nanorods, and microneedles has been dispersed in Matrimid. The synthesized membranes have been tested in the separation of CO₂ from CH₄ in an equimolar mixture. At 3 bar and 298 K for 8 wt% MOF loading, incorporation of NH₂‐MIL‐53(Al) nanoparticles leads to the largest improvement compared to nanorods and microneedles. The incorporation of the best performing filler, i.e., NH₂‐MIL‐53(Al) nanoparticles, into the highly permeable 6FDA‐DAM has a larger effect, and the CO₂ permeability increases up to 85% with slightly lower selectivities for 20 wt% MOF loading. Specifically, these membranes have a permeability of 660 Barrer with a CO₂/CH₄ separation factor of 28, leading to a performance very close to the Robeson limit of 2008. Furthermore, a new non‐destructive technique based on Raman spectroscopy mapping is introduced to assess the homogeneity of the filler dispersion in the polymer matrix. The MOF contribution can be calculated by modeling the spectra. The determined homogeneity of the MOF filler distribution in the polymer is confirmed by focused ion beam scanning electron microscopy analysis.     

Cross-document word matching for segmentation and retrieval of Ottoman divans

Motivated by the need for the automatic indexing and analysis of huge number of documents in Ottoman divan poetry, and for discovering new knowledge to preserve and make alive this heritage, in this study we propose a novel method for segmenting and retrieving words in Ottoman divans. Documents in Ottoman are difficult to segment into words without a prior knowledge of the word. In this study, using the idea that divans have multiple copies (versions) by different writers in different writing styles, and word segmentation in some of those versions may be relatively easier to achieve than in other versions, segmentation of the versions (which are difficult, if not impossible, with traditional techniques) is performed using information carried from the simpler version. One version of a document is used as the source dataset and the other version of the same document is used as the target dataset. Words in the source dataset are automatically extracted and used as queries to be spotted in the target dataset for detecting word boundaries. We present the idea of cross-document word matching for a novel task of segmenting historical documents into words. We propose a matching scheme based on possible combinations of sequence of sub-words. We improve the performance of simple features through considering the words in a context. The method is applied on two versions of Layla and Majnun divan by Fuzuli. The results show that, the proposed word-matching-based segmentation method is promising in finding the word boundaries and in retrieving the words across documents.