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1.
A synchronizer is a compiler that transforms a program designed to run in a synchronous network into a program that runs in an asynchronous network. The behavior of a simple synchronizer, which also represents a basic mechanism for distributed computing and for the analysis of marked graphs, was studied by S. Even and S. Rajsbaum (1990) under the assumption that message transmission delays and processing times are constant. We study the behavior of the simple synchronizer when processing times and transmission delays are random. The main performance measure is the rate of a network, i.e., the average number of computational steps executed by a processor in the network per unit time. We analyze the effect of the topology and the probability distributions of the random variables on the behavior of the network. For random variables with exponential distribution, we provide tight (i.e., attainable) bounds and study the effect of a bottleneck processor on the rate 相似文献
2.
Phase diagrams for oil/methanol/ether mixtures 总被引:4,自引:4,他引:4
David G. B. Boocock Samir K. Konar Hanif Sidi 《Journal of the American Oil Chemists' Society》1996,73(10):1247-1251
One-phase transmethylations of vegetable oils with methanol to form methyl esters occur considerably faster than conventional
two-phase reactions. Addition of simple ethers is an efficient method for producing a single phase. Ternary phase diagrams
have been determined at 23°C for oil/methanol/ether mixtures; these are useful when applying the one-phase method across a
wide range of conditions. Soybean, canola, palm, and coconut oils were used in combination with five ethers, namely, tetrahydrofuran
(THF), 1,4-dioxane (DO), diethyl ether (DE), diisopropyl ether (DI), andtert-butyl methyl ether (TBM). All five ethers can produce miscibility for all methanol/oil compositions. The ether/methanol volumetric
ratios required for miscibility at a methanol/soybean or canola oil volumetric ratio of 0.20 (5.4 molar ratio) at 23°C are:
THF, 1.15; DO, 1.60; DE, 1.38 DI, 1.57; and TBM, 1.57. For THF, this results in one-phase mixtures that contain 65 vol% oil.
Soybean and canola oil form identical diagrams. Palm oil requires slightly less ether at the lower methanol concentrations,
but coconut oil requires considerably less across the whole concentration range. Acid-catalyzed reactions, when performed
at the boiling point of the most volatile component, require less ether than predicted from the diagrams. 相似文献
3.
Rachid El-Azouzi Francesco De Pellegrini Habib B.A. Sidi Vijay Kamble 《Computer Networks》2013,57(4):1003-1018
In this paper, we apply evolutionary games to non-cooperative forwarding control in Delay Tolerant Networks (DTNs). The main focus is on mechanisms to rule the participation of the relays to the delivery of messages in DTNs. Thus, we express the success probability as a function of the competition that takes place within a large population of mobiles, and we characterize the effect of reward-based mechanisms on the performance of such systems. Devices acting as active relays, in fact, sacrifice part of their batteries in order to support message replication and thus increase the probability to reach the destination. In our scheme, a relay can choose the strategy by which they participate to the message relaying. A mobile that participates receives a unit of reward based on the reward mechanism selected by the network. A utility function is introduced as the difference between the expected reward and the energy cost, i.e., the cost spent by the relay to sustain forwarding operations. We show how the evolution dynamics and the equilibrium behavior (called Evolutionary Stable Strategy – ESS) are influenced by the characteristics of inter contact time, energy expenditure and pricing characteristics.We extend our analysis to mechanisms that the system can introduce in order to have the message delivered to the destination with high probability within a given deadline and under energy constraints which bound the number of released copies per message. Finally, we apply our findings in order to devise decentralized forwarding algorithms that are rooted in the theory of stochastic approximations. Thus, we demonstrate that the ESS can be attained without complete knowledge of the system state and letting the source monitor number of released copies per message only. We provide extensive numerical results to validate the proposed scheme. 相似文献
4.
Data transformation is the core process in migrating database from relational database to NoSQL database such as column-oriented database. However,
there is no standard guideline for data transformation from relational database to
NoSQL database. A number of schema transformation techniques have been proposed to improve data transformation process and resulted better query processing
time when compared to the relational database query processing time. However,
these approaches produced redundant tables in the resulted schema that in turn
consume large unnecessary storage size and produce high query processing time
due to the generated schema with redundant column families in the transformed
column-oriented database. In this paper, an efficient data transformation technique
from relational database to column-oriented database is proposed. The proposed
schema transformation technique is based on the combination of denormalization
approach, data access pattern and multiple-nested schema. In order to validate the
proposed work, the proposed technique is implemented by transforming data from
MySQL database to HBase database. A benchmark transformation technique is
also performed in which the query processing time and the storage size are compared. Based on the experimental results, the proposed transformation technique
showed significant improvement in terms query processing time and storage space
usage due to the reduced number of column families in the column-oriented
database. 相似文献
5.
Active Sites Engineering toward Superior Carbon‐Based Oxygen Reduction Catalysts via Confinement Pyrolysis 下载免费PDF全文
Sidi Wang Qun He Changda Wang Hongliang Jiang Chuanqiang Wu Shuangming Chen Guobin Zhang Li Song 《Small (Weinheim an der Bergstrasse, Germany)》2018,14(19)
Developing efficient and low‐cost defective carbon‐based catalysts for the oxygen reduction reaction (ORR) is essential to metal–air batteries and fuel cells. Active sites engineering toward these catalysts is highly desirable but challenging to realize boosted catalytic performance. Herein, a sandwich‐like confinement route to achieve the controllable regulation of active sites for carbon‐based catalysts is reported. In particular, three distinct catalysts including metal‐free N‐doped carbon (NC), single Co atoms dispersed NC (Co–N–C), and Co nanoparticles‐contained Co–N–C (Co/Co–N–C) are controllably realized and clearly identified by synchrotron radiation‐based X‐ray spectroscopy. Electrochemical measurements suggest that the Co/Co–N–C catalyst delivers optimized ORR performance due to the rich Co–Nx active sites and their synergistic effect with metallic Co nanoparticles. This work provides deep insight for rationally designing efficient ORR catalyst based on active sites engineering. 相似文献
6.
Avram Sidi 《Journal of scientific computing》2007,31(3):391-417
Variable transformations for numerical integration have been used for improving the accuracy of the trapezoidal rule. Specifically,
one first transforms the integral via a variable transformation that maps [0,1] to itself, and then approximates the resulting transformed integral by the trapezoidal rule. In this work, we propose a new class of symmetric and nonsymmetric variable transformations which
we denote , where r and s are positive scalars assigned by the user. A simple representative of this class is . We show that, in case , or but has algebraic (endpoint) singularities at x = 0 and/or x = 1, the trapezoidal rule on the transformed integral produces exceptionally high accuracies for special values of r and s. In particular, when and we employ , the error in the approximation is (i) O(h
r
) for arbitrary r and (ii) O(h
2r
) if r is a positive odd integer at least 3, h being the integration step. We illustrate the use of these transformations and the accompanying theory with numerical examples.
相似文献
7.
数据库是计算机智能决策支持系统的核心。文章介绍了智能数据库设计系统的结构,并以农作物中的水稻作物数据库为例,提出了具体的设计方法,分析了智能数据库管理的功能。 相似文献
8.
9.
Noriah Bidin Siti Radhiana Azni Shumaila Islam Mundzir Abdullah M. Fakaruddin Sidi Ahmad Ganesan Krishnan A. Rahman Johari M. Aizat A. Bakar Nur Syahirah Sahidan NurFatin Musa M. Farizuddin Salebi Naqiuddin Razali Mohd Marsin Sanagi 《International Journal of Hydrogen Energy》2017,42(26):16325-16332
Hydrogen production via water electrolysis was studied under the effect of magnetic and optical field. A diode solid state laser at blue, green and red were utilized as optical field source. Magnetic bar was employed as external magnetic field. The green laser has shown a greatest effect in hydrogen production due to its non-absorbance properties in the water. Thus its intensity of electrical field is high enough to dissociation of hydronium and hydroxide ions during orientation toward polarization of water. The potential to break the autoprotolysis and generate the auto-ionization is the mechanism of optical field to reveal the hydrogen production in water electrolysis. The magnetic field effect is more dominant to enhance the hydrogen production. The diamagnetic property of water has repelled the present of magnetic in water. Consequently the water splitting occurs due to the repulsive force induced by the external magnetic field. The magnetic distributed more homogenous in the water to involve more density of water molecule. As a result hydrogen production due to magnetic field is higher in comparison to optical field. However the combination both fields have generated superior effect whereby the hydrogen yields nine times higher in comparison to conventional water electrolysis. 相似文献
10.