Almost k-wise independence versus k-wise independence

We say that a distribution over {0,1}ⁿ is (ε,k)-wise independent if its restriction to every k coordinates results in a distribution that is ε-close to the uniform distribution. A natural question regarding (ε,k)-wise independent distributions is how close they are to some k-wise independent distribution. We show that there exist (ε,k)-wise independent distributions whose statistical distance is at least n^O(k)·ε from any k-wise independent distribution. In addition, we show that for any (ε,k)-wise independent distribution there exists some k-wise independent distribution, whose statistical distance is n^O(k)·ε.     

Measurement of photon beam backscatter from collimators to the beam monitor chamber using target-current-pulse-counting and telescope techniques

Backscattered radiation (BSR) arising from field-defining collimators and entering the beam monitor chamber (BMC) may contribute to observed variations in medical linear accelerator photon beam output with collimator setting. Measuring the magnitude of such contributions for particular accelerators under specified operating conditions is therefore important when attempting to understand and model accelerator head scatter. The present work was conducted to confirm some backscatter measurements for collimating jaws reported previously and to extend these to include other accelerators and a multileaf collimator (MLC). BSR reaching the BMC from the jaws of Clinac 600C, 2100C and 2300CD accelerators and from an MLC on the 2300CD was investigated using both target-current-pulse-counting and telescope methods. Our measurements show that for the Clinac 600C BSR-dependent output variations are negligible. However, for the 2100C and 2300CD BSR-dependent relative output increased in an almost linear fashion, by up to 2.4% for 15 and 18 MV beams, and by up to 1.7% for 6 MV beams, as the field size varied from 5 x 5 cm2 to 40 x 40 cm2. The magnitude of BSR dependent upon collimator location in the head, as expected, thereby contributing to the collimator exchange effect. An earlier study at our centre using the telescope method had reported higher BSR levels. This discrepancy was resolved when corrections for telescope block and room scatter, previously assumed negligible, were made.     

Fuzzy reliability analysis of nanocomposite ZnO beams using hybrid analytical-intelligent method

A hybrid analytical-intelligent approach is proposed for fuzzy reliability analysis of the composite beams reinforced by zinc oxide (ZnO) nanoparticle. The fuzzy reliability index corresponding to buckling failure mode of nanocomposite beam under thickness-direction external voltage is computed based on three-levels: (1) fuzzy analysis, (2) reliability analysis and (3) analytical buckling analysis. In fuzzy analysis level, an improved gravitational search algorithm has been applied to determine uncertainty interval for membership levels of reliability index. The adaptive formulation with a dynamical self-adjusting process is used for reliability analysis level based on conjugate first-order reliability method (FORM). The self-adjusting term in conjugate sensitivity vector is used to satisfy the sufficient descent condition for controlling instability of FORM formula while the proposed conjugate scalar factor is computed less than the original conjugate FORM, thus it may be provided with the efficient results for the convex problem. The new and previous sensitivity vectors obtained by conjugate and steepest descent vectors dynamically adjusted the proposed conjugate factor. In the buckling analysis level, an exponential theory in conjunction with the method of energy is utilized. Fuzzy random variables including applied voltage, the volume fraction of ZnO, thickness of beam, spring constant and shear constant of the foundation are considered in studied nanocomposite beam. Survey results indicated that the proposed method can provide stable and acceptable fuzzy membership functions for parametric study. Moreover, the ratio of length to thickness and spring constant of foundation are the more sensitive parameters which affect fuzzy reliability index significantly.

     

Preparation,Properties and Applications of the Hybrid Organic/Inorganic Nanocomposite Based on Nanoporous Carbon Matrix

Journal of Inorganic and Organometallic Polymers and Materials - Nanoporous carbon matrix was prepared by the sol–gel process from pyrogallol-formaldehyde (PF) mixtures in water using picric...     

Evaluation of Polyester Resin as a New Compatibilizer for SBR/PVC Blends

A polyester (PE) based on the glycolyzed products of PET was prepared and added in different concentrations to a series of SBR/PVC blends. The addition of the polyester showed that all properties of SBR/PVC blends were improved by incorporation of PE. Highest mechanical strength values were obtained at a polyester concentration of 7.5 phr. Thermal analysis as well as dynamic mechanical properties of SBR/PVC blends after the addition of 7.5 and 10 phr polyester indicated one single glass transition temperature. The dielectric losses (?") were analyzed in the frequency domains in the two terms of Fröhlich related to the Maxwell Wagner effect and the orientation of the aggregates caused by the movement of the main chain. The permittivity (?') values were found to increase by increasing the polyester content. This increase was followed by a decrease in the ?" up to a 7.5 phr polyester content after which no pronounced change was noticed.     

Hierarchical inversion‐based output tracking control for uncertain autonomous underwater vehicles using extended Kalman filter

In this study, a hierarchical inversion‐based output tracking controller (HIOTC) is developed for an autonomous underwater vehicle (AUV) subject to random uncertainties (e.g., current disturbances, unmodeled dynamics, and parameter variations) and noises (e.g., process and measurement noises). The proposed HIOTC respectively utilizes a combination of feedforward and feedback controls in a hierarchical structure based on the kinematic and dynamic models of the system. Moreover, to obtain uncontaminated or unavailable states for implementing the proposed control law, the extended Kalman filter (EKF) is employed to estimate the system states. Then, the position outputs, orientation, and velocity of the AUV are reached with guaranteed asymptotic stability. The robustness of the proposed HIOTC is verified through injection of random uncertainties into the system model. The closed‐loop stability of the proposed individual subsystems is respectively guaranteed to have uniformly ultimately bounded (UUB) performance based on the Lyapunov stability criteria. In addition, the asymptotic tracking of the overall system is demonstrated using Barbalat's lemma. Finally, the feasibility and effectiveness of the proposed control scheme are evaluated through computer simulations and it is shown that the overall system achieves good asymptotic tracking performance.     

Composite web QoS with workflow conditional pathways using bounded sets

In our previous work (Dillon and Mansour 2009), a stochastic reliability model of atomic web services was proposed. Using the well-known classic two-state bounded set technique, we developed a service-oriented model that dynamically calculates the reliability of composite web services with rollback recovery (Mansour and Dillon in IEEE Trans Serv Comput 4(4), 2011). In order to improve the Quality of Service, fault tolerance techniques have been introduced using recovery block adaptation. Our workflow was based on series-parallel structures that constitute parts of existing structures. It is worth mentioning that major service-oriented systems contain larger and more complex structures than the simple series and parallel ones. This is a limitation in our previous approach. In order to consider more realistic service-oriented systems, other main structures, such as AND, XOR and Loop, should be included into our model. In this article, our previous structures are generalized to include AND, XOR and Loops. In addition to generalized structures, we extended the existing two-state bounded set technique to include three-state systems. This extension was especially motivated by XOR-based structures. A comparative study between bounded set techniques and a new stochastic model is also presented. Our simulation results accurately reflect the performance of the new proposed model and confirm our theoretical studies. Furthermore, Monte Carlos simulations were performed and the results obtained clearly validate our stochastic model.     

Robust tracking design based on adaptive fuzzy control of uncertain nonlinear MIMO systems with time delayed states

It is proposed here to use a robust tracking design based on adaptive fuzzy control technique to control a class of multi-input-multi-output (MIMO) nonlinear systems with time delayed uncertainty in which each uncertainty is assumed to be bounded by an unknown gain. This technique will overcome modeling inaccuracies, such as drag and friction losses, effect of time delayed uncertainty, as well as parameter uncertainties. The proposed control law is based on indirect adaptive fuzzy control. A fuzzy model is used to approximate the dynamics of the nonlinear MIMO system; then, two on-line estimation schemes are developed to overcome the nonlinearities and identify the gains of the delayed state uncertainties, simultaneously. The advantage of employing an adaptive fuzzy system is the use of linear analytical results instead of estimating nonlinear system functions with an online update law. The adaptive fuzzy scheme uses a Variable Structure (VS) scheme to resolve the system uncertainties, time delayed uncertainty and the external disturbances such that H_∞ tracking performance is achieved. The control laws are derived based on a Lyapunov criterion and the Riccati-inequality such that all states of the system are uniformly ultimately bounded (UUB). Therefore, the effect can be reduced to any prescribed level to achieve H _∞ tracking performance. A two-connected inverted pendulums system on carts and a two-degree-of-freedom mass-spring-damper system are used to validate the performance of the proposed fuzzy technique for the control of MIMO nonlinear systems.     

一种基于数据流跟踪的无线传感网能量模型及网络优化

提出了一种基于数据流跟踪的能量模型,通过跟踪数据流在网络中的整个过程来计算全网的能量消耗,是一种不受网络结构限制的普遍适用的能量模型;在此基础上.建立了基于能耗的网络优化模型,针对链式和簇式结构进行了拓扑、功率和路由方面的优化设计,仿真结果证明了理论分析的正确性.     

Disaster Monitoring of Satellite Image Processing Using Progressive Image Classification

The analysis of remote sensing image areas is needed for climate detection and management, especially for monitoring flood disasters in critical environments and applications. Satellites are mostly used to detect disasters on Earth, and they have advantages in capturing Earth images. Using the control technique, Earth images can be used to obtain detailed terrain information. Since the acquisition of satellite and aerial imagery, this system has been able to detect floods, and with increasing convenience, flood detection has become more desirable in the last few years. In this paper, a Big Data Set-based Progressive Image Classification Algorithm (PICA) system is introduced to implement an image processing technique, detect disasters, and determine results with the help of the PICA, which allows disaster analysis to be extracted more effectively. The PICA is essential to overcoming strong shadows, for proper access to disaster characteristics to false positives by operators, and to false predictions that affect the impact of the disaster. The PICA creates tailoring and adjustments obtained from satellite images before training and post-disaster aerial image data patches. Two types of proposed PICA systems detect disasters faster and more accurately (95.6%).