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排序方式: 共有768条查询结果,搜索用时 203 毫秒
11.
Alaa S. Abd-El-Aziz T. Christopher Corkery Erin K. Todd Tarek H. Afifi Guozhang Ma 《Journal of Inorganic and Organometallic Polymers》2003,13(3):113-130
The synthesis of an aromatic ether complex of cyclopentadienyliron containing two terminal aldehyde groups was achieved via metal-mediated nucleophilic aromatic substitution reactions. This dialdehyde monomer was subsequently reacted with a variety of aliphatic and aromatic diamines to produce the corresponding soluble cationic organoiron polyether-imines. These cationic organometallic polymers were characterized using IR, 1H, and 13C NMR, viscosity and thermogravimetric analysis. Viscosity measurements showed that these polymers exhibited polyelectrolyte effects in DMSO solutions. Thermogravimetric analysis showed that decoordination of the iron moieties occurred at about 300°C for polymers with aliphatic spacers in their backbones, while the cyclopentadienyliron moieties were cleaved from the polymers with aromatic spacers in their backbones at about 200°C. Photolytic demetallation of the organoiron polymers resulted in the removal of the pendent cyclopentadienyliron moieties and allowed for the isolation of their organic analogs. While the organoiron polymers were soluble in polar organic solvents, the corresponding organic polymers exhibited very limited solubilities or were insoluble. The organic polymers had glass transition temperatures between 101 and 120°C 相似文献
12.
Uniprocessor schedulability theory made great strides, in part, due to the simplicity of composing the delay of a job from
the execution times of higher-priority jobs that preempt it. In this paper, we bound the end-to-end delay of a job in a multistage
pipeline as a function of job execution times on different stages under preemptive as well as non-preemptive scheduling. We
show that the end-to-end delay is bounded by that of a single virtual “bottleneck” stage plus a small additive component. This contribution effectively transforms the pipeline into a
single stage system. The wealth of schedulability analysis techniques derived for uniprocessors can then be applied to decide
the schedulability of the pipeline. The transformation does not require imposing artificial per-stage deadlines, but rather
models the pipeline as a whole and uses the end-to-end deadlines directly in the single-stage analysis. It also does not make
assumptions on job arrival patterns or periodicity and thus can be applied to periodic and aperiodic tasks alike. We show
through simulations that this approach outperforms previous pipeline schedulability tests except for very short pipelines
or when deadlines are sufficiently large. The reason lies in the way we account for execution overlap among stages. We discuss
how previous approaches account for overlap and point out interesting differences that lead to different performance advantages
in different cases. Further, we also show that in certain cases non-preemptive scheduling can result in higher system utilization
than preemptive scheduling in pipelined systems. We hope that the pipeline delay composition rule, derived in this paper,
may be a step towards a general schedulability analysis foundation for large distributed systems.
相似文献
Tarek AbdelzaherEmail: |
13.
R. Gopi R. Sheeba K. Anguraj T. Chelladurai Haya Mesfer Alshahrani Nadhem Nemri Tarek Lamoudan 《计算机系统科学与工程》2023,44(2):1567-1582
Rapid increase in the large quantity of industrial data, Industry 4.0/5.0 poses several challenging issues such as heterogeneous data generation, data sensing and collection, real-time data processing, and high request arrival rates. The classical intrusion detection system (IDS) is not a practical solution to the Industry 4.0 environment owing to the resource limitations and complexity. To resolve these issues, this paper designs a new Chaotic Cuckoo Search Optimization Algorithm (CCSOA) with optimal wavelet kernel extreme learning machine (OWKELM) named CCSOA-OWKELM technique for IDS on the Industry 4.0 platform. The CCSOA-OWKELM technique focuses on the design of feature selection with classification approach to achieve minimum computation complexity and maximum detection accuracy. The CCSOA-OWKELM technique involves the design of CCSOA based feature selection technique, which incorporates the concepts of chaotic maps with CSOA. Besides, the OWKELM technique is applied for the intrusion detection and classification process. In addition, the OWKELM technique is derived by the hyperparameter tuning of the WKELM technique by the use of sunflower optimization (SFO) algorithm. The utilization of CCSOA for feature subset selection and SFO algorithm based hyperparameter tuning leads to better performance. In order to guarantee the supreme performance of the CCSOA-OWKELM technique, a wide range of experiments take place on two benchmark datasets and the experimental outcomes demonstrate the promising performance of the CCSOA-OWKELM technique over the recent state of art techniques. 相似文献
14.
15.
We present two new classifiers for two-class classification problems using a new Beta-SVM kernel transformation and an iterative
algorithm to concurrently select the support vectors for a support vector machine (SVM) and the hidden units for a single
hidden layer neural network to achieve a better generalization performance. To construct the classifiers, the contributing
data points are chosen on the basis of a thresholding scheme of the outputs of a single perceptron trained using all training
data samples. The chosen support vectors are used to construct a new SVM classifier that we call Beta-SVN. The number of chosen
support vectors is used to determine the structure of the hidden layer in a single hidden layer neural network that we call
Beta-NN. The Beta-SVN and Beta-NN structures produced by our method outperformed other commonly used classifiers when tested
on a 2-dimensional non-linearly separable data set. 相似文献
16.
Stabilization of uncertain sampled-data strict-feedback systems is addressed. The stability study is carried out on the Euler approximation of the exact discretized model of the plant. Firstly, a class of state-feedback controllers is developed that guarantees an input-to-state stability property for the closed-loop system. Additionally, assuming some hypotheses on the uncertain terms hold, a practical asymptotic stability property is ensured by designing an appropriate class of controllers. 相似文献
17.
Tarek Sheltami Anas Al-Roubaiey Elhadi Shakshuki Ashraf Mahmoud 《Multimedia Systems》2009,15(5):273-282
Mobile Ad-hoc NETworks (MANET) are infrastructureless networks where self-configuring mobile nodes are connected by wireless
links. Because of its decentralized operation, these nodes rely on each other to store and forward packets. Video transmission
over MANETs is more challenging than over conventional wireless networks due to rapid topology changes and lack of central
administration. Most of the proposed MANET protocols assume that all nodes are working within a cooperative and friendly network
context. However, misbehaving nodes that exhibit abnormal behaviors can disrupt the network operation and affect the network
availability by refusing to cooperate to route packets due to their selfish or malicious behavior. In this paper, we examine
the effect of packet dropping attacks on video transmission over MANETs. We also study the effects of mitigation using intrusion
detection systems to MANET in presence of video traffic. To the best of our knowledge, this is the first attempt to study
multimedia over such environments. We propose a novel intrusion detection system, which is an adaptive acknowledgment scheme
(AACK) with the ability to detect misbehaved nodes and avoid them in other transmissions. The aim of AACK scheme is to overcome
watchdog weaknesses due to collisions and limited transmission power and also to improve TWOACK scheme. To demonstrate the
performance of our proposed scheme, simulation experiments are performed. The results of our experiments show that MPEG4 is
more suitable for our simulation environment than H264 video traffic. The simulation results show that AACK scheme provides
better network performance with less overhead than other schemes; it also shows that AACK outperforms both TWOACK and watchdog
in video transmission applications in the presence of misbehaving nodes. 相似文献
18.
Mohammad Alshibli Ahmed El Sayed Elif Kongar Tarek M. Sobh Surendra M. Gupta 《Journal of Intelligent and Robotic Systems》2016,82(1):69-79
End-of-life disassembly has developed into a major research area within the sustainability paradigm, resulting in the emergence of several algorithms and structures proposing heuristics techniques such as Genetic Algorithm (GA), Ant Colony Optimization (ACO) and Neural Networks (NN). The performance of the proposed methodologies heavily depends on the accuracy and the flexibility of the algorithms to accommodate several factors such as preserving the precedence relationships during disassembly while obtaining near- optimal and optimal solutions. This paper improves a previously proposed Genetic Algorithm model for disassembly sequencing by utilizing a faster metaheuristic algorithm, Tabu search, to obtain the optimal solution. The objectives of the proposed algorithm are to minimize (1) the traveled distance by the robotic arm, (2) the number of disassembly method changes, and (3) the number of robotic arm travels by combining the identical-material components together and hence eliminating unnecessary disassembly operations. In addition to improving the quality of optimum sequence generation, a comprehensive statistical analysis comparing the previous Genetic Algorithm and the proposed Tabu Search Algorithm is also included 相似文献
19.
When multimedia information is transported over a packet-switched network, the quality of presentation can be degraded due
to network delay variation or jitter. This paper presents a dejittering scheme that can be used in the transport of MPEG-4
and MPEG-2 video to absorb any introduced network jitter, thus preserving the presentation quality of transported media streams.
The dejittering scheme is based on the statistical approximation of delay variation in the arrival times of video packets
carrying encoded clock reference values and a filtering and re-stamping mechanism. In addition, a brief overview of the MPEG-4
system is presented. 相似文献
20.
Tarek M. Sobh Abdelshakour A. Abuzneid Raul Mihali 《Journal of Intelligent and Robotic Systems》2001,31(4):355-377
General form application is a very important issue in industrial design. Prototyping a design helps in determining system parameters, ranges and in structuring better systems. Robotics is one of the industrial design fields in which prototyping is crucial for improved functionality. Developing an environment that enables optimal and flexible design using reconfigurable links, joints, actuators and sensors is essential for using robots in the education and industrial fields. We propose a PC-based software package to control, monitor, and simulate a generic 6-DOF (six degrees of freedom) robot including a spherical wrist. This package may be used as a black box for the design implementations or as a white (detailed) box for learning about the basics of robotics and simulation technology. 相似文献