Question-asking strategies for Horn clause systems

An expert system applies the deduction rules in its knowledge base to a set of initial data to reach a conclusion. When the initial data are insufficient, the expert system may ask the user for additional information. This paper analyzes effectiveness and efficiency of question-asking strategies in expert systems with Horn clause knowledge bases. An effective strategy reaches a conclusion after asking as few questions as possible. An efficient strategy can be computed quickly. We prove that effective strategies are, unfortunately, not efficient. However, we present a somewhat less effective but very efficient strategy. It employs an algorithm which simultaneously performs deduction and question selection in log-linear time.Supported in part by NSF grant DMS-8513970.     

A cost effective fault-tolerant scheme for RAIDs

The rapid progress in mass storage technology has made it possible for designers to implement large data storage systems for a variety of applications.One of the efficient ways to build large storage systems is to use RAIDs only when one error occurs .But in large RAIDs systems ,the fault probability will increase when the number of disks increases ,and the use of disks with big storage capacity will cause the recovering time to prolong,thus the probability of the second disk‘‘‘‘‘‘‘‘s fault will incerease Therefore,it is necessary to develop methods to recover data when two or more errors have occurred In this paper,a fault tolerant scheme is proposed based on extended Reed-Solomon code,a recovery procedure is designed to correct up to two errors which is implemented by software and hardware together,and the scheme is verified by computer simulation,In this scheme,only two redundant disks are used to recover up to two disks‘‘‘‘‘‘‘‘ fault .The encoding and decoding methods,and the implementation based on software and hardware are described.The application of the scheme in software RAIDs that are builit in cluster computers are also described .Compared with the existing methods such as EVENODD and DH ,the proposed scheme has distinct improvement in implementation and redundancy.     

Inference flexibility in Horn clause knowledge bases and the simplex method

This paper shows that the basis matrix inverse of the linear program associated with a propositional Horn clause knowledge base provides a proof structure of inference by forward chaining. The basis matrix inverse indicates how each assertion determines the others and is itself determined by the others. This tabulated proof structure provides a convenient way of making inference transparent and flexible.     

Optimal cost effective design of hybrid hardware redundant systems

In many critical applications of digital systems, fault tolerance has been an essential architectural attribute for achieving high reliability. We address the problem of designing an optimal hybrid hardware redundant system. The designer of a system is always confronted with the problem of trading off reliability against cost. On the one hand, it is essential to provide for each vital module of the system as many spare units as possible in order to ensure high reliability. On the other hand, it is essential not to have an excessively costly, heavy or bulky system. In this paper we determine the optimal number of spare units which minimizes the expected total system cost. A numerical example is provided to illustrate the methods.     

An Inplementation of Pure Horn Clause Logic Programming in a Reduction System

Many reduction systems have been presented for implementing functional programming languages.We propose here an extension of a reduction architecture to realize a kind of logic programming-pure Horn clause logic programming.This is an attempt to approach amalgamation of the two important programming paradigms.     

A distortion cost modification strategy for adaptive pentary steganography

In this paper, a pentary steganography scheme is proposed employing the multi-layered STCs, which takes the embedding interactions into consideration. First, based on the definition of local correlation for the four-neighborhood, we link the modification direction of the central pixel with that of its four-neighborhood. Secondly, a modification degree strategy (MDS) is proposed to adjust the costs of the pixels dynamically. And the cost of pixels is assigned utilizing the MDS, which divides the process of distortion calculation into two steps of initializing and updating distortion cost. Finally, the scheme is obtained incorporating the MDS with the existing adaptive scheme S-UNIWARD of pentary version. Experimental results show that the proposed scheme is capable of providing large capacity, and has a better performance than adaptive steganography scheme S-UNIWARD of pentary version in resisting the SRM and maxSRMd2 detection when the payload is larger than 0.5 bpp. Also, the strategy could be combined with other adaptive steganography schemes of pentary version. Besides, the proposed scheme outperforms some ternary adaptive schemes with both feature sets SRM and maxSRMd2 when the payload is from 0.05bpp to 0.5bpp.     

A data mining-constraint satisfaction optimization problem for cost effective classification

We propose a data mining-constraint satisfaction optimization problem (DM–CSOP) where it is desired to maximize the number of correct classifications at a lowest possible information acquisition cost. We show that the problem can be formulated as a set of several binary variable knapsack optimization problems, which are solved sequentially. We propose a heuristic hybrid simulated annealing and gradient-descent artificial neural network (ANN) procedure to solve the DM-CSOP. Using a real-world heart disease data set, we show that the proposed hybrid procedure provides a low-cost and high-quality solution when compared to a traditional ANN classification approach.     

A three-phase energy-saving strategy for cloud storage systems

In the running process of cloud data center, the idle data nodes will generate a large amount of unnecessary energy consumption. Furthermore, the resource misallocation will also cause a great waste of energy. This paper proposes a three-phase energy-saving strategy named TPES in order to save energy and operational costs for cloud suppliers. The three phases are replica management based on variable replication factor, cluster reconfiguration according to the optimal total costs and state transition based on observed and predicted workloads. These three phases save energy for the system at different levels which enhance the adaptability of our strategy. We evaluate our strategy using the expanded CloudSim toolkit and the results show that the proposed strategy achieves better energy reduction under different conditions in comparison with the existing schemes.     

A client-assisted interval caching strategy for video-on-demand systems

In a Video-on-Demand (VoD) system, in order to guarantee smooth playback of a video stream, sufficient resources (such as disk I/O (Input/Output) bandwidth, network bandwidth) have to be reserved in advance. Thus, given limited resources, the number of simultaneous streams can be supported by a video server is restricted. Due to the mechanical nature, the I/O subsystem is generally the performance bottleneck of a VoD system, and there have been a number of caching algorithms to overcome the disk bandwidth limitation. In this paper, we propose a novel caching strategy, referred to as client-assisted interval caching (CIC) scheme, to balance the requirements of I/O bandwidth and cache capacity in a cost-effective way. The CIC scheme tends to use the cache memory available in clients to serve the first few blocks of streams so as to dramatically reduce the demand on the I/O bandwidth of the server. Our objective is to maximize the number of requests that can be supported by the system and minimize the overall system cost. Simulations are carried out to study the performance of our proposed strategy under various conditions. The experimental results show the superior of CIC scheme to the tradition Interval Caching (IC) scheme, with respect to request accepted ratio and average servicing cost per stream.     

A practical control strategy for servo-pneumatic actuator systems

A practical control strategy with a simple controller structure is proposed for servo-pneumatic cylinder actuator systems. Theoretical analysis reveals that the acceleration of the piston indirectly represents the cylinder chamber pressure difference so it is possible to employ acceleration feedback instead of pressure feedback in the construction of servo-pneumatic actuator control systems. The main features of the control strategy developed in the paper are (1) using acceleration feedback to improve the stability of the system; and (2) introducing time-delay minimisation and optimised null offset compensation to address the problem of time delay and dead zone, which are mainly caused by the compressibility of air and friction. The experimental studies have been conducted using an asymmetric pneumatic cylinder system and the results show that the system performance has been much improved when compared with a conventional PID controller.     

A cost effective on-site fault diagnosis method for home appliance rotor failures

Microsystem Technologies - Rotating components are one of the most important machine parts used in many industrial applications. Rotating machine commonly used in homes has a washing machine, which...     

A two-stage model for cost effective part family and machine cell formation

This research presents, implements and tests a two-stage procedure for cost effective part family and machine cell formation. First, the problem is formulated as a mixed integer mathematical model for simultaneous machine grouping and part family assignment. This model, which we refer to as the single-stage model, considers the cost trade-offs of cell configuration, machine procurement and salvage, subcontracting, inter-cell movement, and capital investment, all of which reflect the significance of real life planning aspects. To alleviate the computational burden of this single-stage model, we decompose it into two stages: the first stage is a heuristic for machine cell and part family formations; the second stage integrates the heuristic method with a mathematical program to optimize the various cost aspects. The efficacy of the proposed models is shown through a number of example problems. The results show that the two-stage procedure is powerful in the planing stages of large-size problems where the cost aspects are crucial.     

A cost‐effective sparse communication strategy for networked linear control systems: an SVD‐based approach

In networked control, there is often an incentive to communicate only what is absolutely necessary to achieve the desired performance goals. This is true to both the downlink (between a control base station and actuators) and the uplink (between the sensors and base station). Here, we present a strategy aimed at this problem based on a singular value decomposition of the Hessian of the quadratic performance index generally considered in Model Predictive Control. The singular vectors are employed to generate an orthonormal basis function expansion of the unconstrained solution to the finite horizon optimal control problem. These are preloaded into each actuator and each sensor. On the downlink, the actuators are informed, in real‐time, about which basis functions they should use. On the uplink, after a ‘burn in period’, the sensors need only communicate when their response departs from that pre‐calculated for the given basis functions. We show that this strategy facilitates communication in both the downlink and uplink in a cost‐effective fashion. We also show that the strategy can be modified so that input constraints are satisfied. We illustrate the proposed results by applying them to a simulation of the cross direction control of a paper machine. Potential extensions and other applications of the proposed strategy are also discussed. Copyright © 2014 John Wiley & Sons, Ltd.     

A simulation framework for technical systems life cycle cost analysis

This paper deals with the construction of a simulation framework for technical systems life cycle cost (LCC) analysis. It also deals with the concept of software reuse in event-based simulation, since the framework involves simulation of all cost generating activities related to a technical system, from its planning and acquisition phases until its final discard. The basic principles of object-oriented programming and simulation software efficiency, reuse, extensibility and evolvability are analyzed and the concepts of computational reflection and frameworks are explored. Finally, the framework is described in detail and its extension points, based on the inheritance mechanism, are shown.     

一种基于效益的多机器人避碰协调策略

多移动机器人系统在完成同时定位和地图构建SLAM任务时,机器人之间常常存在相互碰撞的问题,而这种碰撞的避免又不同于一般的避障,因为避障问题中的障碍物一般是不动的。为了解决机器人之间的避碰问题,提出了一种基于效益的多机器人避碰协调策略。该策略以提高多机器人系统探索效率为主,确定机器人通过交叉路口的顺序。同时考虑了动态协调避碰的情况,给出了确定机器人通过交叉路口顺序的算法。通过机器人在交叉路口实现避碰协调算法的仿真示例,对该方法的避碰协调过程进行了说明,并对仿真结果进行了分析,同时对仿真中机器人和目标位置的空间关系给出了合理的假设。     

A sharing-oriented design strategy for networked knowledge organization systems

Designers of networked knowledge organization systems often follow a service-oriented design strategy, assuming an organizational model where one party outsources clearly delineated business processes to another party. But the logic of outsourcing is a poor fit for some knowledge organization practices. When knowledge organization is understood as a process of exchange among peers, a sharing-oriented design strategy makes more sense. As an example of a sharing-oriented strategy for designing networked knowledge organization systems, we describe the design of the PeriodO period gazetteer. We analyze the PeriodO data model, its representation using JavaScript Object Notation-Linked Data, and the management of changes to the PeriodO dataset. We conclude by discussing why a sharing-oriented design strategy is appropriate for organizing scholarly knowledge.     

A new fragment re-allocation strategy for NoSQL database systems

NoSQL databases are famed for the characteristics of high scalability, high availability, and high fault-tolerance. So NoSQL databases are used in a lot of applications. The data partitioning strategy and fragment allocation strategy directly affect NoSQL database systems’ performance. The data partition strategy of large, global databases is performed by horizontally, vertically partitioning or combination of both. In the general way the system scatters the related fragments as possible to improve operations’ parallel degree. But the operations are usually not very complicated in some applications, and an operation may access to more than one fragment. At the same time, those fragments which have to be accessed by an operation may interact with each other. The general allocation strategies will increase system’s communication cost during operations execution over sites. In order to improve those applications’ performance and enable NoSQL database systems to work efficiently, these applications’ fragments have to be allocated in a reasonable way that can reduce the communication cost i.e., to minimize the total volume of data transmitted during operations execution over sites. A strategy of clustering fragments based on hypergraph is proposed, which can cluster fragments which were accessed together in most operations to the same cluster. Themethod uses a weighted hypergraph to represent the fragments’ access pattern of operations. A hypergraph partitioning algorithmis used to cluster fragments in our strategy. This method can reduce the amount of sites that an operation has to span. So it can reduce the communication cost over sites. Experimental results confirm that the proposed technique will effectively contribute in solving fragments re-allocation problem in a specific application environment of NoSQL database system.