Collision with friction; Part B: Poisson’s and Stornge’s hypotheses

In Part B of this paper, planar collision theories, counterparts of the theory associated with Newton’s hypotheses described in Part A, are developed in connection with Poisson’s and Stronge’s hypotheses. First, expressions for the normal and tangential impulses, the normal and tangential velocities of separation, and the change of the system mechanical energy are written for five types of collision. These together with Routh’s semigraphical method and Coulomb’s coefficient of friction are used to show that the algebraic signs of the four parameters introduced in Part A span the same five cases of system configuration of Part A. For each, α determines the type of collision which once found allows the evaluation of the normal and tangential impulses and ultimately the changes in the motion variables. The analysis of the indicated cases shows that for Poisson’s hypothesis, a solution always exists which is unique, coherent and energy-consistent. The same applies to Stronge’s hypothesis, however, for a narrower range of application. It is thus concluded that Poisson’s hypothesis is superior as compared with Newton’s and Stronge’s hypotheses.     

Comment: collision with friction; part B: Poisson’s and Stronge’s hypotheses

For planar oblique collision with friction that opposes sliding at the contact point, this comment compares calculations of terminal relative velocity and energy dissipation obtained using the kinematic (Newton), kinetic (Poisson) and energetic (Stronge) definitions for coefficient of restitution. The kinematic and kinetic definitions yield results which are energetically inconsistent for some initial velocities when sliding stops or changes direction before separation. If initial sliding does not come to a stop before separation, the three definitions are equivalent. In general, only the energetic coefficient of restitution e _S satisfies e _S≤1.     

Dynamics of a three-module vibration-driven system with non-symmetric Coulomb’s dry friction

In the present paper, a three-module vibration-driven system moving on a rough horizontal plane is modeled to investigate the relation among the system’s steady-state motion, external Coulomb’s dry friction force and internal excitations. Each module of the system represents a vibration-driven system composed of a rigid body and a movable internal mass. Major attention is focused on the primary resonance situation that the excitation frequency is close to the first-order natural frequency of the system. In the case that the external friction is low, the internal excitation is weak and the stick–slip motion is negligible, both methods of averaging and modal superposition are employed to study the steady-state motion of the system. Through a set of algebraic equations, an approximate value of the system’s average steady-state velocity is obtained. Several numerical examples are calculated to verify the validity of the analytical results both qualitatively and quantitatively. It is seen that big quantitative errors will appear if stick–slip motions occur. Then, two mechanisms for the possible stick–slip motions are put forward, which explain the errors on the average steady-state velocity. Numerical simulations verify our analysis on the stick–slip effects and their mechanisms. Finally, to maximize the average steady-state velocity of the system, optimal control problem is studied. It is shown that, in addition to modifying the friction coefficients, the improvement of the system’s efficiency can be provided by changing the initial phase shifts among the three internal excitations.     

A maximal monotone impact law for the 3-ball Newton’s cradle

The 3-ball Newton’s cradle is used as a stepping stone to divulge the structure of impact laws. A continuous conewise linear impact law that maps the preimpact contact velocities to the postimpact contact velocities is proposed for the 3-ball Newton’s cradle. The proposed impact law is kinematically, kinetically, and energetically consistent. It reproduces the outcomes of experimental observation. Moreover, it is in accordance with the outcome of the collision of three identical linear-elastic thin rods for which the impact process is governed by the one-dimensional wave equation. The proposed impact law is shown to be nonexpansive. Therefore, the relationship between the mean contact velocity and its dual, the impulsive force, is maximal monotone. A counterexample to maximal cyclical monotonicity of this relationship allows us to conclude that no dissipation function exists for the proposed impact law.     

A Newton method for Bernoulli’s free boundary problem in three dimensions

Summary The present paper is dedicated to the numerical solution of Bernoulli’s free boundary problem in three dimensions. We reformulate the given free boundary problem as a shape optimization problem and compute the shape gradient and Hessian of the given shape functional. To approximate the shape problem we apply a Ritz–Galerkin discretization. The necessary optimality condition is resolved by Newton’s method. All information of the state equation, required for the optimization algorithm, are derived by boundary integral equations which we solve numerically by a fast wavelet Galerkin scheme. Numerical results confirm that the proposed Newton method yields an efficient algorithm to treat the considered class of problems.      

Two-Level Newton’s Method for Nonlinear Elliptic PDEs

A combination method of Newton’s method and two-level piecewise linear finite element algorithm is applied for solving second-order nonlinear elliptic partial differential equations numerically. Newton’s method is to find a finite element solution by solving $m$ Newton equations on a fine mesh. The two-level Newton’s method solves $m-1$ Newton equations on a coarse mesh and processes one Newton iteration on a fine mesh. Moreover, the optimal error estimates of Newton’s method and the two-level Newton’s method are provided to justify the efficiency of the two-level Newton’s method. If we choose $H$ such that $h=O(|\log h|^{1-2/{p}}H^2)$ for the $W^{1,p}(\Omega )$ -error estimates, the two-level Newton’s method is asymptotically as accurate as Newton’s method on the fine mesh. Meanwhile, the numerical investigations provided a sufficient support for the theoretical analysis. Finally, these investigations also proved that the proposed method is efficient for solving the nonlinear elliptic problems.     

A quantum prisoner’s dilemma cellular automaton with probabilistic updating

The effect of variable entangling on the dynamics of a spatial quantum formulation of the iterated prisoner’s dilemma game is studied in this work. The game is played in the cellular automata manner, i.e. with local and synchronous interaction. The effect of probabilistic updating is assessed in fair and unfair contests, both in the two and three parameter strategy spaces.     

Web service adaptation: A decade’s overview

With the exponential growth of communication and information technologies, adaptation has gained a significant attention as it becomes a key feature of service-based systems, allowing them to operate and evolve in highly dynamic and uncertain environments. Although several Web service standards and frameworks have been proposed and extended, existing solutions do not provide a suitable architecture, in which all aspects of monitoring and adaptation (e.g., proactive, cross-layer, and autonomic adaptation) can be expressed. In addition, the emergence of new computing environments to host and execute various types of services (Web/cloud services, big data-intensive services, mobile services, microservices, etc.) raises the need for more efficient monitoring and adaptation systems. This survey aims to bring a synthesis and a road-map to the adaptation of service-based systems. We also discuss adaptation solutions in emerging service models, such as cloud services and big services. Based on an adaptation taxonomy which we extracted from the surveyed approaches, and by identifying the main requirements and goals of service adaptation in Web, cloud and big data environments, detailed analysis and discussions, as well as the open issues, are provided.     

A novel approach to exploring company’s financial soundness: Investor’s perspective

Prediction of company’s life cycle stage change; creation of an ordered 2D map allowing to explore company’s financial soundness from a rating agency perspective; and prediction of trends of main valuation attributes usually used by investors are the main objectives of this article. The developed algorithms are based on a random forest (RF) and a nonlinear data mapping technique “t-distributed stochastic neighbor embedding”.Information from five different perspectives, namely balance, income, cash flow, stock price, and risk indicators was aggregated via proximity matrices of RF to enable exploration of company’s financial soundness from a rating agency perspective. The proposed use of information not only from companies’ financial statements but also from the stock price and risk indicators perspectives has proved useful in creating ordered 2D maps of rated companies. The companies were well ordered according to the credit risk rating assigned by the Moody’s rating agency.Results of experimental investigations substantiate that the developed models are capable of predicting short term trends of the main valuation attributes, providing valuable information for investors, with low error. The models reflect financial soundness of actions taken by company’s management team. It was also found that company’s life cycle stage change can be determined with the average accuracy of 72.7%. Bearing in mind fuzziness of the transition moment, the obtained prediction accuracy is rather encouraging.     

<Emphasis Type="Italic">A Midsummer Night’s Dream</Emphasis> (with flying robots)

Seven flying robot “fairies” joined human actors in the Texas A&;M production of William Shakespeare’s A Midsummer Night’s Dream. The production was a collaboration between the departments of Computer Science and Engineering, Electrical and Computer Engineering, and Theater Arts. The collaboration was motivated by two assertions. First, that the performing arts have principles for creating believable agents that will transfer to robots. Second, the theater is a natural testbed for evaluating the response of untrained human groups (both actors and the audience) to robots interacting with humans in shared spaces, i.e., were believable agents created? The production used two types of unmanned aerial vehicles, an AirRobot 100-b quadrotor platform about the size of a large pizza pan, and six E-flite Blade MCX palm-sized toy helicopters. The robots were used as alter egos for fairies in the play; the robots did not replace any actors, instead they were paired with them. The insertion of robots into the production was not widely advertised so the audience was the typical theatergoing demographic, not one consisting of people solely interested technology. The use of radio-controlled unmanned aerial vehicles provides insights into what types of autonomy are needed to create appropriate affective interactions with untrained human groups. The observations from the four weeks of practice and eight performances contribute (1) a taxonomy and methods for creating affect exchanges between robots and untrained human groups, (2) the importance of improvisation within robot theater, (3) insights into how untrained human groups form expectations about robots, and (4) awareness of the importance of safety and reliability as a design constraint for public engagement with robot platforms. The taxonomy captures that apparent affect can be created without explicit affective behaviors by the robot, but requires talented actors to convey the situation or express reactions. The audience’s response to robot crashes was a function of whether they had the opportunity to observe how the actors reacted to robot crashes on stage, suggesting that pre-existing expectations must be taken into account in the design of autonomy. Furthermore, it appears that the public expect robots to be more reliable (an expectation of consumer product hardening) and safe (an expectation from product liability) than the current capabilities and this may be a major challenge or even legal barrier for introducing robots into shared public spaces. These contributions are expected to inform design strategies for increasing public engagement with robot platforms through affect, and shows the value of arts-based approaches to public encounters with robots both for generating design strategies and for evaluation.     

A Closed-Form Solution to Stollery’s Problem with Damage in Utility

Stollery (Can J Econ 31(3):730–742, 1998) studied a polluting oil-extracting economy governed by a constant utility criterion. The pollution, resulted from oil use, negatively affected production and utility. Stollery provided a closed-form solution for the case where only the production function was affected by the damage. This paper offers a closed-form solution to a non-trivial example of this economy with damage in the utility function. The solution is used for the analysis of uncertainties in resource policy caused by uncertainties in reserve estimate and in the intensity of the damage.     

Production scheduling with subcontracting: the subcontractor’s pricing game

This paper studies a two-stage game with a manufacturer and a subcontractor who are faced by a production scheduling problem. The manufacturer has a set of jobs to process, a subset of which can be subcontracted to the subcontractor to reduce the tardiness cost. In the game, the subcontractor makes the first decision to ask for a unit price of his machine time to be used by the manufacturer, and then the manufacturer follows to decide which jobs to be subcontracted to process and how the production scheduling is made. We analyze the game and derive how the subcontractor can optimize the unit price to maximize his profit. We then investigate the performance of such a simple contract from the viewpoint of coordination, and propose two other contracts that can achieve coordination between the two players.     

StoryCube: supporting children’s storytelling with a tangible tool

Storytelling is one of the effective methods used in education. Computer-aided storytelling allows children to create more free-form stories and provides a large amount of story materials. Grounded in the current related works, we design a tangible interactive tool, which supports children to interact with virtual objects via a tangible way instead of the usage of mouse/keyboard. With this tool, we also develop a storytelling system called StoryCube where children are able to create a 3D story environment and accomplish story narrations through physical manipulations to different virtual characters. From a preliminary user study, we find StoryCube full of playfulness, easy to learn and use, and somehow inspire children in storytelling activities.     

A Review of “Marketing Today’s Academic Library: A Bold New Approach to Communicating with Students”

ABSTRACT

This paper contends that the potential of Usenet as an information tool is outstanding, but that librarians have been slow to realize this promise. By examining Usenet discussions, the paper looks at the issues involved in using Usenet, and discusses the notion that real information can only come from professionals. It concludes that Usenet is a valuable tool that needs to be developed, especially when determining what sources of information could best assist patrons.     

The contact problem in Lagrangian systems subject to bilateral and unilateral constraints,with or without sliding Coulomb’s friction: a tutorial

This work deals with the existence and uniqueness of the acceleration and contact forces for Lagrangian systems subject to bilateral and/or unilateral constraints with or without sliding Coulomb’s friction. Sliding friction is known to yield singularities in the system, such as Painlevé’s paradox. Our work aims at providing sufficient conditions on the parameters of the system so that singularities are avoided (i.e., the contact problem is at least solvable). To this end, the frictional problem is treated as a perturbation of the frictionless case. We provide explicit criteria, in the form of calculable upper bounds on the friction coefficients, under which the frictional contact problem is guaranteed to remain well-posed. Complementarity problems, variational inequalities, quadratic programs and inclusions in normal cones are central tools.     

Szegedy’s quantum walk with queries

When searching for a marked vertex in a graph, Szegedy’s usual search operator is defined by using the transition probability matrix of the random walk with absorbing barriers at the marked vertices. Instead of using this operator, we analyze searching with Szegedy’s quantum walk by using reflections around the marked vertices, that is, the standard form of quantum query. We show we can boost the probability to 1 of finding a marked vertex in the complete graph. Numerical simulations suggest that the success probability can be improved for other graphs, like the two-dimensional grid. We also prove that, for a certain class of graphs, we can express Szegedy’s search operator, obtained from the absorbing walk, using the standard query model.     

Matching couples with Scarf’s algorithm

In a seminal paper Phan Minh Dung (Artif. Intell. 77(2), 321–357, 1995) developed the theory of abstract argumentation frameworks (AFs), which has remained a pivotal point of reference for research in AI and argumentation ever since. This paper assesses the merits of Dung’s theory from an epistemological point of view. It argues that, despite its prominence in AI, the theory of AFs is epistemologically flawed. More specifically, abstract AFs don’t provide a normatively adequate model for the evaluation of rational, multi-proponent controversy. Different interpretations of Dung’s theory may be distinguished. Dung’s intended interpretation collides with basic principles of rational judgement suspension. The currently prevailing knowledge base interpretation ignores relevant arguments when assessing proponent positions in a debate. It is finally suggested that abstract AFs be better understood as a paraconsistent logic, rather than a theory of real argumentation.