Performance Optimization Criteria Research Articles

High-pressure synthesis and performance analysis of WC-cBN-MoS2 self-lubricating ceramic composites

WC-cBN-MoS2 self-lubricating ceramics were synthesized by using high pressure and high temperature sintering method. An analytical model of the self-lubricating properties has been developed to reveal the interrelationship between mechanical and self-lubricating properties. The influence of mechanical and self-lubricating properties of ceramics on the wear rate were analyzed. Self-lubricating performance optimization criterion are proposed accordingly. It was found that MoC, WS2 can be formed during sintering, which can ensure self-lubricating and low temperature sintering properties. Adhesive wear is the main wear mechanism, the extent of which varies with the content of self-lubricating components. The high modulus of elasticity is the main reason for the excellent self-lubricating and mechanical properties of composites. The well-sintered WC-cBN-MoS2 bulks present an excellent self-lubricating property with a hardness of 26.3 GPa and fracture toughness of 10.5 MPa·m1/2, which is improved at least by 52% and 46% respectively compared with the traditional self-lubricating ceramics.

A simple cross-layer mechanism for congestion control and performance enhancement in a localized multiple wireless body area networks

Commercialization of the wireless body area network (WBAN) envisions future new normal for WBAN devices coexistence in a localized area. The coexistence may allow devices to freely change positions, associate, or dissociate with the neighbours as users interact. Devices’ interaction in a stationary or mobile fashion radiates heat and also competes for the limited network resources resulting to unreliable communication and other performance challenges. Besides alarming user safety, device mobility affects network performance through topology changes, which result to recursive link disconnections, energy waste, packet delay, degraded throughput, and congestion due to excessive control messaging during route repair. In this article, we propose WBAN performance optimization criteria focusing on improving energy efficiency, network throughput, and reducing the end to end delay in multiple existence schemes. Firstly, we propose an alternative routing algorithm, whose routing decision depends on a cost function considering the parameterized residue energy to node distance ratio, link energy reliability, and specific heat absorption in addition to node sequence number and hop count as fundamental route selection metrics. Secondly, we implement congestion control adaptation in the medium access control (IEEE 802.11MAC) mechanism, which improves throughput, reduces congestion, and delay. Due to link discontinuities during mobility, we demonstrate a comparative network performance to address the effect of WBAN speed at different hello intervals. The comparative analysis show, protocol implementation with a cross-layer approach outperforms the conventional protocol without MAC adaptations in terms of energy efficiency, network throughput, and a reduced end to end delay, by an average of 0.45%, 2.8%, and 13.7%, respectively.

Low complexity robust adaptive beamforming for general-rank signal model with positive semidefinite constraint

We propose a low complexity robust beamforming method for the general-rank signal model, to combat against mismatches of the desired signal array response and the received signal covariance matrix. The proposed beamformer not only considers the norm bounded uncertainties in the desired and received signal covariance matrices, but also includes an additional positive semidefinite constraint on the desired signal covariance matrix. Based on the worst-case performance optimization criterion, a computationally simple closed-form weight vector is obtained. Simulation results verify the validity and robustness of the proposed beamforming method.

Performance optimization criterion of blast furnace stave

On the basis of a study using entransy theory, the thermal resistance and heat transfer coefficient of a blast furnace stave is defined. Combined with the pump power of the cooling water pipe, a comprehensive performance optimization criterion of a blast furnace stave is defined. The new criterion takes the overall heat transfer of the stave and the flow resistance of the water pipe into account at the same time, so as to break through the traditional evaluation mode, which only considers the local single index. The calculation method of the thermal resistance, heat transfer coefficient and comprehensive performance optimization criterion of the blast furnace stave is illustrated by an example. The performances of blast furnace staves with different pipe spacings and different pipe shapes are analyzed using the new criterion. The results show that the use of a reasonable pipe spacing can effectively optimize the performance of the blast furnace stave. When a circular pipe is replaced by an elliptical pipe with the same cross-section area, the comprehensive performance of the stave cannot be optimized. When a circular pipe is replaced by a rectangular pipe with the same cross-section area, and the ratio of the shorter and longer axis is between 0.7 and 1, the overall heat transfer performance of the cooling stave is increased, but the pump power consumption is increased significantly. The comprehensive performance of the cooling stave is not optimized. The results of this paper provide a new criterion for the reasonable evaluation and design optimization of a blast furnace stave.

Static Batch Mode Heuristic Algorithm for Mapping Independent Tasks in Computational Grid

Grid computing plays an important role in solving large-scale computational problems in a high performance computing environment. Scheduling of tasks to efficient and best suitable resource is one of the most challenging phase in grid computing systems. Grid environment reveals several challenges in efficient scheduling of complex applications because of its heterogeneity, dynamic behavior and shared resources. Scheduling of independent tasks in grid computing is dealt by a number of heuristic algorithms. This study proposes a new heuristic algorithm for mapping independent tasks in a grid environment to be assigned optimally among the available machines in a grid computing system. Due to the multi-objective nature of the grid scheduling problem, several performance measures and optimization criteria can be assumed to determine the quality of a given schedule. The metrics used here include makespan and resource utilization. This algorithm provides effective resource utilization by reducing machine idle time and minimizes makespan. This algorithm also balances load among the grid resources and produce high resource utilization with low computational complexity. The proposed algorithm is compared with other popular heuristics for performance measures.

A Survey on Radio Resource Allocation in Cognitive Radio Sensor Networks

Wireless sensor networks (WSNs) use the unlicensed industrial, scientific, and medical (ISM) band for transmissions. However, with the increasing usage and demand of these networks, the currently available ISM band does not suffice for their transmissions. This spectrum insufficiency problem has been overcome by incorporating the opportunistic spectrum access capability of cognitive radio (CR) into the existing WSN, thus giving birth to CR sensor networks (CRSNs). The sensor nodes in CRSNs depend on power sources that have limited power supply capabilities. Therefore, advanced and intelligent radio resource allocation schemes are very essential to perform dynamic and efficient spectrum allocation among sensor nodes and to optimize the energy consumption of each individual node in the network. Radio resource allocation schemes aim to ensure QoS guarantee, maximize the network lifetime, reduce the internode and internetwork interferences, etc. In this paper, we present a survey of the recent advances in radio resource allocation in CRSNs. Radio resource allocation schemes in CRSNs are classified into three major categories, i.e., centralized, cluster-based, and distributed. The schemes are further divided into several classes on the basis of performance optimization criteria that include energy efficiency, throughput maximization, QoS assurance, interference avoidance, fairness and priority consideration, and hand-off reduction. An insight into the related issues and challenges is provided, and future research directions are clearly identified.

Robust Nearfield Wideband Beamformer Design Using Worst Case Mean Performance Optimization With Passband Response Variance Constraint

Conventional wideband beamformers are known highly sensitive to gain and phase errors in microphone characteristics, especially for small-sized arrays. Recently, a robust design approach for nearfield wideband beamformers using worst case performance optimization has been proposed. However, the worst case performance optimization criterion might be overly conservative in practice, which may lead to undesired low-pass filtered distortion of target signals. In this paper, a robust design approach for nearfield wideband beamformers using the worst case mean performance optimization is proposed, which is less conservative than the existing approach. Unlike the existing robust design approaches which have no control over array response variance, the presented approach further proposes to impose the passband response variance constraint to enhance the stability of passband array response and hence to reduce the target signal distortion. Moreover, some insights into the properties of array response variance are derived, which are helpful to better understand the robustness characteristics of nearfield wideband beamformers. Design examples demonstrate the effectiveness of the proposed robust design approach.

The $n$th-Order Bias Optimality for Multichain Markov Decision Processes

In this paper, we propose a new approach to the theory of finite multichain Markov decision processes (MDPs) with different performance optimization criteria. We first propose the concept of nth-order bias; then, using the average reward and bias difference formulas derived in this paper, we develop an optimization theory for finite MDPs that covers a complete spectrum from average optimality, bias optimality, to all high-order bias optimality, in a unified way. The approach is simple, direct, natural, and intuitive; it depends neither on Laurent series expansion nor on discounted MDPs. We also propose one-phase policy iteration algorithms for bias and high-order bias optimal policies, which are more efficient than the two-phase algorithms in the literature. Furthermore, we derive high-order bias optimality equations. This research is a part of our effort in developing sensitivity-based learning and optimization theory.

Performance optimization criteria for pulsed inductive plasma acceleration

A model of pulsed inductive plasma thrusters consisting of a set of coupled circuit equations and a one-dimensional momentum equation has been nondimensionalized leading to the identification of several scaling parameters. Contour plots representing thruster performance (exhaust velocity and efficiency) were generated numerically as a function of the scaling parameters. The analysis revealed the benefits of underdamped current waveforms and led to an efficiency maximization criterion that requires the circuit's natural period to be matched to the acceleration timescale. It is also shown that the performance increases as a greater fraction of the propellant is loaded nearer to the inductive acceleration coil

USB/IP: A Transparent Device Sharing Technology over IP Network

Personal computing with affordable computers and their peripheral devices becomes more popular. To use such devices more efficiently and improve their usability, people want to share surrounding peripheral devices between computers without any modification of their own computing environments. The recent device sharing technologies in the pervasive computing area are not sufficient for the peripheral devices of personal computers because these technologies do not provide the network-transparency for applications and device drivers. In this paper, we propose USB/IP as a transparent device sharing mechanism over IP network. This advanced device sharing mechanism is based on the modern sophisticated peripheral interfaces and their supports in operating systems. By the Virtual Host Controller Interface Driver we have implemented as a peripheral bus driver, users can share diverse devices over networks without any modification in existing operating systems and applications. The experiments show that USB/IP has fairly practical I/O performance for various USB devices, including isochronous ones. We also describe the performance optimization criteria for the further improvements.

Measurement station performance optimization for testing of high efficiency variable speed drives

In efficiency measurements of high performance variable speed drives, it is necessary to perform power measurement on distorted signals with low uncertainty. This involves the adoption of a suitable equipment and an adequate measurement technique. In this paper, a measurement station for digital efficiency measurements on high and low power electrical drives is described. A systematic approach to uncertainty evaluation and a performance optimization criterion are proposed for the automatic measurement station designed for the testing of high efficiency variable speed drives.

Design considerations for the thermal accelerometer

This paper presents some design and optimization aspects of the thermal accelerometer. The design and optimization strategy is based on a one-dimensional model describing both the thermal and mechanical properties of the device. It is shown that this model is reasonably in agreement with experiments carried out on some prototype devices. The performance optimization criteria are based on the ‘maximally flat amplitude response’ from which the optimum design parameters can be calculated for a given bandwidth.