The importance of introducing a waiting time for Lattice Monte Carlo simulations of a polymer translocation process

For a standard Lattice Monte Carlo (LMC) simulation of a random walker subject to a bias, it is impossible to obtain both a correct mean velocity and diffusion coefficient. To correct this, a modified LMC algorithm has been developed where the introduction of a probability of remaining in the current state allows for a distribution of intervals between jumps. In this paper, we demonstrate the impact of this modification for a first-passage problem: the translocation of a polymer through a nanopore. We find that while either approach yields the correct mean first-passage time, the incorporation of a waiting time is necessary to obtain the correct spread of times.     

GF(2~N)上线性化多项式根的存在性

给出了判断有限域上某元素为线性化多项式根的方法。在此基础上,将线性化多项式根的求解问题归结为有限域上简单方程的求解,使得可以方便地用计算机求解线性化多项式的根。     

Virtual Triangulation Sensor Development, Behavior Simulation and CAR Integration Applied to Robotic Arc-Welding

Background: An increasing number of industrial robots are being programmed using CAR (Computer Aided Robotics). Sensor guidance offers a means of coping with frequent product changes in manufacturing systems. However, sensors increase the uncertainty and to preserve system robustness, a tool is needed that makes it possible to understand a sensor guided robot system before and during its actual operation in real life.Scope: A virtual sensor is developed and integrated in a CAR hosted environment. The real sensor is of a type commonly used in the arc-welding industry and uses a triangulation method for depth measurements. The sensor is validated both statically and dynamically by matching it with a real sensor through measurements in setups and by comparing a welding application performed in a real and a virtual work-cell created with a CAR application. The experimental results successfully validates its performance. In this context, a virtual sensor is a software model of a physical sensor with similar characteristics, using geometrical and/or process specific data from a computerized model of a real work-cell.     

On the optimal design of the shape of a buckled elastic beam

Analysis of stability, post-buckling bending and vibrations is performed for a beam (a spring element) having an optimal shape. A buckled pin-jointed spring element of a constant thickness and variable width is considered. The optimal shape of this beam is suggested to provide a uniform distribution of maximum bending stresses in its buckled equilibrium configuration for a given value of a supercritical axial force. Sensitivities of a critical force and a buckling mode to variations of the shape of a beam are calculated. A dependence of the static lateral deflection upon an axial force is analysed. Nonlinear equations of large-amplitude oscillations are derived by a use of the Hamilton principle. The natural frequencies of a spring element, compressed by a supercritical force are calculated. Received April 29, 1999     

A path following problem for a class of non-holonomic control systems with noise

This paper deals with a path following problem for a system affected by noise and proposes a dynamic inversion-based controller that makes use of the error between the real position and a suitable path location. An estimate of such error is given in terms of the noise bounds, showing the practical stability of the closed loop system. The results presented in this article apply to a subclass of Chaplygin control systems which includes several common mechanical systems. As an example the developed strategy has been applied to maneuver a kinematic model of a system moving in a 3-dimensional space in such a way that a point located at a positive distance from its center of geometry is driven towards a given path.     

Error estimate for quasistatic history-dependent contact model

In this paper we consider a mathematical model which describes a quasistatic process for a viscoelastic body in contact with an obstacle or a foundation. The variational formulation of the problem is in the form of a system coupling a nonlinear integral equation with a history-dependent hemivariational inequality. We establish a fully discrete scheme of the abstract problem and derive a result on error estimate.     

A hybrid system approach for supporting digital libraries

A digital library (DL) consists of a database which contains library information and a user interface which provides a visual window for users to search relevant information stored in the database. Thus, an abstract structure of a digital library can be defined as a combination of a special purpose database and a user-friendly interface. This paper addresses one of the fundamental aspects of such a combination. This is the formal data structure for linking an object oriented database with hypermedia to support digital libraries. It is important to establish a formal structure for a digital library in order to efficiently maintain different types of library information. This article discusses how to build an object oriented hybrid system to support digital libraries. In particular, we focus on the discussion of a general purpose data model for digital libraries and the design of the corresponding hypermedia interface. The significant features of this research are, first, a formalized data model to define a digital library system structure; second, a practical approach to manage the global schema of a library system; and finally, a design strategy to integrate hypermedia with databases to support a wide range of application areas. Received: 15 December 1997 / Revised: June 1999     

A Combined Feedforward–Feedback Control Strategy for Improving the Dynamics of a Flexible Mechanism

Modern high-speed mechanisms often experience undesirable vibrations,which may render a required accuracy unattainable or, even worse, leadto a failure of the whole process. Instead of suppressing the vibrationby a stiffer design, active control methods may greatly improve thesystem performance and lead the way to a reduction of the mechanism'sweight.We investigate a four-bar-linkage mechanism and show that byintroducing an additional degree of freedom for a controlled actuatorand providing a suitable control strategy, the dynamically inducedinaccuracies can be substantially reduced and new reference paths bedescribed. The modeling of the four-bar-linkage mechanism as a hybridmultibody system and the modeling of the complete system including theactuator is briefly explained. From the combined feedforward–feedbackoptimal control approach presented in [11], a time-varying outputcontrol law is derived that leads to a very good system performancefor both a regulating and a tracking problem. The experimental resultsshow the effectiveness of the applied control strategies.     

On the equivalence between small-step and big-step abstract machines: a simple application of lightweight fusion

We show how Ohori and Sasano's recent lightweight fusion by fixed-point promotion provides a simple way to prove the equivalence of the two standard styles of specification of abstract machines: (1) in small-step form, as a state-transition function together with a ‘driver loop’, i.e., a function implementing the iteration of this transition function; and (2) in big-step form, as a tail-recursive function that directly maps a given configuration to a final state, if any. The equivalence hinges on our observation that for abstract machines, fusing a small-step specification yields a big-step specification. We illustrate this observation here with a recognizer for Dyck words, the CEK machine, and Krivine's machine with call/cc.The need for such a simple proof is motivated by our current work on small-step abstract machines as obtained by refocusing a function implementing a reduction semantics (a syntactic correspondence), and big-step abstract machines as obtained by CPS-transforming and then defunctionalizing a function implementing a big-step semantics (a functional correspondence).     

A case study of a difficult refinement: a fast dictionary for a spell-checking program

We present a difficult refinement of a dictionary for a spell-checker. It represents a realistic problem and shows how a calculational approach using a relation known as a coupling invariant can improve the process of refinement over the conventional posit-and-prove approach. The paper concludes with a brief discussion of the advantages of the approach we adopt. We also hope that the paper will contribute a difficult refinement to the rather sparse corpus of such case studies in the literature—especially those using the calculational approach.     

Towards Ontology-driven Knowledge Synthesis for Heterogeneous Information Systems

Information integration enables delivery of the right information to the right user in a timely manner giving manufacturers a competitive edge in today’s global manufacturing market. However, as enterprise information is usually aggregated from a variety of heterogeneous information sources, without using an adequate integration framework it is difficult to extract pertinent information and apply current knowledge to assessing production situations and making informed decisions. This paper investigates a method of facilitating knowledge synthesis in a distributed computing environment. A formal model of domain ontology and knowledge base is presented, which aims at providing a vehicle for representing information and knowledge using a common shared semantics in a given application domain. As a result, a common knowledge representation based architecture is proposed, creating a foundation for establishing a systematic approach for ease of knowledge synthesis in a manufacturing environment     

Discernibility matrix simplification for constructing attribute reducts

This paper proposes a reduct construction method based on discernibility matrix simplification. The method works in a similar way to the classical Gaussian elimination method for solving a system of linear equations. Elementary matrix simplification operations are introduced. Each operation transforms a matrix into a simpler form. By applying these operations a finite number of times, one can transform a discernibility matrix into one of its minimum (i.e., the simplest) forms. Elements of a minimum discernibility matrix are either the empty set or singleton subsets, in which the union derives a reduct. With respect to an ordering of attributes, which is either computed based on a certain measure of attributes or directly given by a user, two heuristic reduct construction algorithms are presented. One algorithm attempts to exclude unimportant attributes from a reduct, and the other attempts to include important attributes in a reduct.     

A GA-Tabu algorithm for scheduling in-line steppers in low-yield scenarios

This paper presents a scheduling algorithm for an in-line stepper in low-yield scenarios, which mostly appear in cases when new process/production is introduced. An in-line stepper is a bottleneck machine in a semiconductor fab. Its interior comprises a sequence of chambers, while its exterior is a dock equipped with several ports. The transportation unit for entry of each port is a job (a group of wafers), while that for each chamber is a piece of wafer. This transportation incompatibility may lead to a capacity-loss, in particular in low-yield scenarios. Such a capacity-loss could be alleviated by effective scheduling. The proposed scheduling algorithm, called GA-Tabu, is a combination of a genetic algorithm (GA) and a tabu search technique. Numerical experiments indicate that the GA-Tabu algorithm outperforms seven benchmark ones. In particular, the GA-Tabu algorithm outperforms a prior GA both in solution quality and computation efforts.     

Logical foundations of multilevel databases

In this paper, we propose a formal model for multilevel databases. This model aims at being a generic model, that is it can be interpreted for any kind of database (relational, object-oriented …). Our model has three layers. The first layer corresponds to a model for a non-protected database. The second layer corresponds to a model for a multilevel database. In this second layer, we propose a list of theorems that must be respected in order to build a secure multilevel database. We also propose a new solution to manage cover stories without using the ambiguous technique of polyinstantiation. The third layer corresponds to a model for a MultiView database, that is, a database that provides at each security level a consistent view of the multilevel database. Finally, as an illustration, we interpret our 3-layer model in the case of an object-oriented database.     

Universal characteristic decomposition of radical differential ideals

We call a differential ideal universally characterizable, if it is characterizable w.r.t. any ranking on partial derivatives. We propose a factorization-free algorithm that represents a radical differential ideal as a finite intersection of universally characterizable ideals. The algorithm also constructs a universal characteristic set for each universally characterizable component, i.e., a finite set of differential polynomials that contains a characterizing set of the ideal w.r.t. any ranking. As a part of the proposed algorithm, the following problem of satisfiability by a ranking is efficiently solved: given a finite set of differential polynomials with a derivative selected in each polynomial, determine whether there exists a ranking w.r.t. which the selected derivatives are leading derivatives and, if so, construct such a ranking.     

A Simulation Model of the Price Bargaining Rules in Vertical Relationships

This paper analyzes the dynamics of the price and quantity bargaining betweenfour agents, in a current industrial structure, with a special attention tothe price bargaining. The structure combines a bilateral monopoly in a marketfor inputs, and a duopoly in a final market. After a simplified presentationof a model which proposes equilibrium solutions to the bargaining, we presentthe protocol and the results of an experiment whose objective is twofold. Thefirst one is to test the assumptions of the model. The second one is toidentify behavioral models and bargaining rules for a work of simulation. Theexperimental results do not confirm the solutions of the theoretical model,which predicted a Nash solution for the price bargaining, and used the cournotconjecture in the quantity bargaining. A detailed analysis of the resultsleads to some observations useful to parameterize a simulation model. Thesimulation runs a systematic analysis of the dynamics of the bargaining rulesin this structure.     

Performance study of a water ramjet engine

A performance study of a water ramjet engine is described.The engine is powered by the reaction of a magnesium-based propellant and ingested water.In this study,a solid propellant,which consisted of a large percentage of magnesium,a binder and a small amount of oxidant,was used as a hydro reactive fuel.Cold water was injected into the combustion chamber as a main oxidant.A scaled-down experimental engine was tested in a direct-connect ground testing system to characterize the factors influencing the engine ...     

Multiple threshold perceptron

As a natural generalization of the linear perceptron with a single threshold element, we define a multiple threshold perceptron which learns a particular type of piecewise linear discriminant set of functions, namely those that are describable by a set of parallel hyperplanes. We also suggest a learning method in the form of an error-correction procedure, and a kind of gradient method that seeks the minimum of a rational criterion function. Experimental results show that the proposed procedure is effective.     

Sensor Placement for Sensing Coverage and Data Precision in Wireless Sensor Networks

We present a novel paradigm of sensor placement concerning data precision and estimation. Multiple abstract sensors are used to measure a quantity of a moving target in the scenario of a wireless sensor network. These sensors can cooperate with each other to obtain a precise estimate of the quantity in a real-time manner. We consider a problem on planning a minimum-cost scheme of sensor placement with desired data precision and resource consumption. Measured data is modeled as a Gaussian random variable with a changeable variance. A gird model is used to approximate the problem. We solve the problem with a heuristic algorithm using branch-and-bound method and tabu search. Our experiments demonstrate that the algorithm is correct in a certain tolerance, and it is also efficient and scalable.     

Design of switched linear systems in the presence of actuator saturation and L-infinity disturbances

This paper considers the problem of disturbance tolerance/rejection of a switched system resulting from a family of linear systems subject to actuator saturation and L-infinity disturbances. For a given set of linear feedback gains, a given switching scheme and a given bound on the L-infinity norm of the disturbances, conditions are established, in terms of linear or bilinear matrix inequalities, under which a set of a certain form is invariant for a given switched linear system in the presence of actuator saturation and L-infinity disturbances, and the closed-loop system possesses a certain level of disturbance rejection capability. With these conditions, the design of feedback gains and switching scheme can be formulated and solved as constrained optimization problems. Disturbance tolerance is measured by the largest bound on the disturbances for which the trajectories starting from a given set remain bounded. Disturbance rejection is measured either by the L-infinity norm of the system output or by the system’s ability to steer its state into and/or keep it within a small neighborhood of the origin. In the event that all systems in the family are identical, the switched system reduces to a single system under a switching feedback law. Simulation results show that such a single system under a switching feedback law could have stronger disturbance tolerance/rejection capability than a single linear feedback law can.