Narrow Results

In this paper we investigate the problem of designing load balancing protocols in distributed systems involving self-interested participants. These participants have their own requirements and objectives and no a-priori motivation for cooperation. Their selfish behavior may lead to poor performance and inefficiency. To address this problem we design a load balancing mechanism with verification that provides incentives to participants to report their true parameters and follow the given algorithm. We prove that our load balancing mechanism is truthful (i.e., agents will be better off by reporting their true parameters) and satisfies the voluntary participation condition (i.e., truthful agents never incur a loss). We present a simulation study to show the performance of our load balancing mechanism.

Although supply disruption is ubiquitous because of natural or man-made disasters, many firms still use the price-only reverse auction (only the cost is considered) to make purchase decisions. We first study the suppliers’ equilibrium bidding strategies and the buyer’s expected revenue under the first- and second-price price-only reverse auctions when the suppliers are unreliable and have private information on their costs and disruption probabilities. We show that the two auctions are equivalent and not efficient. Then we propose two easily implementable reverse auctions, namely the first-price and second-price format announced penalty reverse auction (APRA), and show that the “revenue equivalence principle” holds, i.e., the two auctions generate the same ex ante expected profit to the buyer. We further show that the two reverse auctions are efficient and “truth telling” is the suppliers’ dominant strategy in the second-price format APRA. We conduct numerical studies to assess the impacts of some parameters on the bidding strategies, the buyer’s profit and social profit.

There have recently been extensive studies on proportional response protocol, which is motivated by the successful BitTorrent system for file sharing over a P2P network. The proportional response protocol has been proved to be strategy-proof against weight cheating attacks and edge cheating attacks, in order to allocate a single type of resource on P2P networks. This strategy-proof property holds due to an elegant combinatorial structure: the bottleneck decomposition of the underlying network structure, and the utility function, defined as the total resources that one agent receives from its neighbors. However, Sybil attacks, under which an agent may form several fictitious players and split its resource among them, have been shown as a more difficult attack to defend against, and thus a strategic agent playing Sybil attacks may result in personal gain.

Previous efforts have been made to show that an agent may generate a gain, but with limited gains by Sybil attacks on several special networks, including trees, cliques, and rings. This paper is the first to study the agent’s incentives by adopting a Sybil attack on general networks. The main contribution is to prove that any agent cannot obtain more than three times as much as the revenue when it plays honestly.

In this study, theoretical super screen vibration analysis has been carried out to predict the dynamic characteristics of interactive waste particles. The vibrating screen is modeled of three assemblies such as screen, wastes guide, and supported screen. Then materials (or particles) of different size is to be separated by using the eccentric vibrator and classifying tilt plates. In processing separation mechanism, much lighter construction wastes (wood, Styrofoam, etc) and heavier materials are separated by staying time delay in a super screen. The design results, separation screen were able to know that small and larger particles are conspicuous difference each motion character according to trajectory particles, and small particles raise the probability in classifying tilt plates.

Coalitional power in multistage processes is modeled using effectivity frames, which link an effectivity function to every possible state of the world. Effectivity frames are general enough to capture, e.g., what groups of agents can bring about in extensive games of perfect and almost perfect information. Coalition Logic is used to describe effectivity frames, and the question of generating an extensive game satisfying a given specification is formulated as a satisfiability problem in Coalition Logic. Using this logical reformulation, we show that the complexity of this implementation problem depends on two parameters: For coalitional specifications, the problem is shown to be PSPACE-complete. For individual specifications on the other hand, i.e., for specifications which only refer to the powers of individual agents, generating an implementation with perfect information is PSPACE-complete, whereas generating an implementation with almost perfect information is NP-complete.

This article explains a simulation of the Co-Author Model (CAM) applied in strategic alliance setting where firms use and optimize their network resources. To understand its process casualty better, I explain the model's mechanisms in terms of its interactive dynamics and resulting equilibrium structure. Classified as a Boolean network with two inputs, CAM's dynamics cause a biased equilibrium structure that could then be explained by the Simmelian tie and the completion of structure through structural balance. These explanations not only could answer the criticism that a simulation model is merely a toy model without much realism but could also explain and give insights to both substantive theory and methodology development in strategic alliance research. The results include the effect of a third party, the embeddedness of firms in their alliances, and the real-world implications of the "frozen web": a phenomenon drawn parallel to the financial crisis beginning in 2007.

We study a system in which N agents have to decide between two strategies θ_i(i ∈ 1 … N), for defection or cooperation, when interacting with other n agents (either spatial neighbors or randomly chosen ones). After each round, they update their strategy responding nonlinearly to two different information sources: (i) the payoff a_i(θ_i, f_i) received from the strategic interaction with their n counterparts, (ii) the fraction f_i of cooperators in this interaction. For the latter response, we assume social herding, i.e., agents adopt their strategy based on the frequencies of the different strategies in their neighborhood, without taking into account the consequences of this decision. We note that f_i already determines the payoff, so there is no additional information assumed. A parameter ζ defines to what level agents take the two different information sources into account. For the strategic interaction, we assume a Prisoner's Dilemma game, i.e., one in which defection is the evolutionary stable strategy. However, if the additional dimension of social herding is taken into account, we find instead a stable outcome where cooperators are the majority. By means of agent-based computer simulations and analytical investigations, we evaluate the critical conditions for this transition toward cooperation. We find that, in addition to a high degree of social herding, there has to be a nonlinear response to the fraction of cooperators. We argue that the transition to cooperation in our model is based on less information, i.e., on agents which are not informed about the payoff matrix, and therefore rely on just observing the strategy of others, to adopt it. By designing the right mechanisms to respond to this information, the transition to cooperation can be remarkably enhanced. Our results are obtained in an evolutionary PD game with fixed payoffs and a fixed four-player neighborhood, where agents follow a stochastic better response dynamics.

Systems design utilizes top-down and bottom-up approaches to influence social or economic systems such that a desired outcome is obtained. We characterize different approaches like network controllability, network interventions, nudging and mechanism design and discuss the problems involved. We argue that systems design cannot be reduced to solving complex optimization problems.

In our multi-agent model, agents generate wealth from repeated interactions for which a prisoner’s dilemma payoff matrix is assumed. Their gains are taxed by a government at a rate $\alpha$. The resulting budget is spent to cover administrative costs and to pay a bonus to cooperative agents, which can be identified correctly only with a probability $p$. Agents decide at each time step to choose either cooperation or defection based on different information. In the local scenario, they compare their potential gains from both strategies. In the global scenario, they compare the gains of the cooperative and defective subpopulations. We derive analytical expressions for the critical bonus needed to make cooperation as attractive as defection. We show that for the local scenario the government can establish only a medium level of cooperation because the critical bonus increases with the level of cooperation. In the global scenario, instead full cooperation can be achieved once the cold-start problem is solved because the critical bonus decreases with the level of cooperation. This allows to lower the tax rate, while maintaining high cooperation.

In this paper, the problem of multi-attribute procurement auction of divisible goods is investigated, and an optimal mechanism of multi-attribute auction, which enables negotiation on several attributes in addition to the price of a divisible good, is designed. First, several important assumptions of multi-attribute procurement auctions of divisible goods are given, and the buyer's utility function and the supplier's utility function are defined. Then, a set of sufficient conditions for feasible multi-attribute auction mechanism are given. Based on these conditions, an optimal model of multi-attribute procurement auction whose goal is to maximize the buyer's expected utility, is established. By solving this model, the optimal allocation strategies are obtained. Third, the properties of the optimal multi-attribute auction are discussed. Finally, a multi-attribute auction example about the steam coal procurement is given to show how to implement the optimal multi-attribute auction mechanism.

Quantum strategies have been successfully applied to game theory for years. However, as a reverse problem of game theory, the theory of mechanism design is ignored by physicists. In this paper, the theory of mechanism design is generalized to a quantum domain. The main result is that by virtue of a quantum mechanism, agents who satisfy a certain condition can combat "bad" social choice rules instead of being restricted by the traditional mechanism design theory.

Artificial torso is a fundamental part of humanoid robots with special features for mimicking human performance. In this paper, a novel torso design is presented with cable-driven vertebra-based solution, as inspired by human anatomy. Whereas the anatomy of the human torso and their joints are indeed very complex, a formulation for basic functioning of the humanoid torso has been developed. The structure is introduced by describing its main characteristics and performance starting from its kinematics up to design constrains. The design is presented with numerical results of dynamic simulation and FEM analysis with the aim of testing the feasibility of the proposed solution and characterizing its operation performance.

A new torso structure for a humanoid robot has been proposed. The structural characteristics and functions of human torso have been considered to gain inspirations for design purposes. The proposed torso structure consists of six revolute units divided into two basic categories connected in a serial chain mechanism. The proposed torso structure shows more advantages compared to traditional humanoid robots in terms of high degrees of freedom (DOFs), high stiffness, self-locking capabilities, as well as easy-to-control features. Bionic optimization design based on objective function method has been implemented on structural design for better motion performances. A 3D model has been elaborated and simulated in SolidWorks and ADAMS environments for structural design and kinematic simulation purposes, respectively. Simulation results show that the new bionic torso structure is able to well imitate movements of human torso.

Grasp planning and motion synthesis for dexterous manipulation tasks are traditionally done given a pre-existing kinematic model for the robotic hand. In this paper, we introduce a framework for automatically designing hand topologies best suited for manipulation tasks given high-level objectives as input. Our pipeline is capable of building custom hand designs around specific manipulation tasks based on high-level user input. Our framework comprises of a sequence of trajectory optimizations chained together to translate a sequence of objective poses into an optimized hand mechanism along with a physically feasible motion plan involving both the constructed hand and the object. We demonstrate the feasibility of this approach by synthesizing a series of hand designs optimized to perform specified in-hand manipulation tasks of varying difficulty. We extend our original pipeline³² to accommodate the construction of hands suitable for multiple distinct manipulation tasks as well as provide an in depth discussion of the effects of each non-trivial optimization term.

The robots with humanoid hands can take the place of humans in carrying objects and using tools efficiently in different situations. This paper presents a novel hydraulic-driven robotic hand named the WLRH-II (the second-generation wheel-legged robot humanoid hand) which bears heavy load and has strong robustness. This paper focuses on the design of humanoid hand driving and transmission mechanisms, kinematic and static analyses. First, the linkage mechanism is proposed according to the particle swarm optimization algorithm. Then, the kinematics and the statics of WLRH-II are analyzed in grasp state. In addition, the hydraulic servo control method is used to control the position of a hand through angle feedback. Finally, position tracking and load experiments are completed to verify the reasonableness and effectiveness of the control. The robotic hand can grasp objects of 30kg with 2.85-kg self-weight. The WLRH-II has a high load/self-weight ratio of 10.55 in this paper, which is rare in similar humanoid robotic hands.

In some countries, it is common that initial public offerings (IPOs) are preceded by forward ("when-issued") trading of the shares; in the US, such trading is prohibited. We analyze the effect of when-issued trading on the pricing and allocation of IPO shares. We demonstrate that the optimal selling mechanism in the presence of when-issued trading differs qualitatively from the optimal mechanism if such trading is prohibited. Furthermore we show that trading rules in the when-issued market can be designed so that allowing when-issued trading results in an increase in expected issue proceeds.

Let $p$, $p(I)$, $\varrho$ and $p(M)$ denote, respectively, the current stock price, the future stock price that is conditioned on information, the minimum stock market tick size and the realized future stock price. Formal theoretical proofs in this study show modeling of stock returns in continuous time induces stock returns that have parameterization as gambles over lotteries. Stock returns have parameterization as gambles because in the presence of fairness of formation of $p<[p+\varrho ]<p(I)$, regardless arrival of liquidity and speculative trades feasibly induces $p(M)<p<p(I)$. Evolution of ‘(conditional) trade imbalances’ as random walks is shown to be a necessary and sufficient condition for parameterization of stock returns as gambles over lotteries. Suppose, on the contrary, a resort to modeling of stock returns in discrete time. The formal theory arrives at two dichotomous sufficiency conditions, which predict directionality and sizes of price changes, and facilitate evolution of stock returns as random walks. In presence of the two dichotomous conditions, fairness of formation of $p<[p+\varrho ]<p(I)$ necessarily induces, regardless of arrival of liquidity and speculative trades, $p(M)\ge [p+\varrho ]$. Risk is parameterized by $p_t(M)>p_t(I)>[p_t+\varrho ]$, because all else constant, an inversion of the perturbing conditionally positive trade imbalance induces $p_{t+1}(M)<p_t(M)$. Whereas then, $p_{t+1}(M)<p_t(M)$ has parameterization as ‘materialization of risk’, always, it is $p_t(M)>p_t(I)$ that is statistic for risk; risk, as such is well parameterized, that is, does not coincide with its materialization (note that whereas volatility is statistic for risk, it is not a statistic for materialization of risk; a statistic for risk necessarily is robust to non-materialization of risk). Given modeling in continuous time does not facilitate either of the two sufficiency conditions, always, risk has parameterization as the probability that $p_{t+1}(M)<p_t(M)$. Since risk, as such coincides qualitatively with its materialization, it is not well parameterized. Given study findings parameterize general equilibrium, formal theoretical predictions have characterization as axiomatic statements, as opposed to propositional (parameter-dependent) statements.

We study repeated games in which players observe a public outcome that imperfectly signals the actions played. We provide conditions guaranteeing that any feasible, individually rational payoff vector of the stage game can arise as a perfect equilibrium of the repeated game with sufficiently little discounting. The central condition requires that there exist action profiles with the property that, for any two players, no two deviations—one by each player—give rise to the same probability distribution over public outcomes. The results apply to principal-agent, partnership, oligopoly, and mechanismdesign models, and to one-shot games with transferable utilities.

This paper proposed a new gravity compensation system which is suitable for the lower extremity rehabilitation therapy. The proposed system can compensate the gravitational moments exerting on the leg joints perfectly using the passive mechanical elements. In contrast with the previous systems, the proposed gravity compensation mechanisms are wholly embedded in the link body, so that the system is safer and well-suited to the wearable equipment. The feasibility of the gravity proposed mechanisms is confirmed through the experiments using an actual equipment. The effectiveness of the system as a lower extremity rehabilitation equipment is examined through computer simulations for the bending and stretching exercises.

A speaker wishes to persuade a listener to accept a certain request. The conditions under which the request is justified, from the listener's point of view, depend on the values of two aspects. The values of the aspects are known only to the speaker and the listener can check the value of at most one. A mechanism specifies a set of messages that the speaker can send and a rule that determines the listener's response, namely, which aspect he checks and whether he accepts or rejects the speaker's request. We study mechanisms that maximize the probability that the listener accepts the request when it is justified and rejects the request when it is unjustified, given that the speaker maximizes the probability that his request is accepted. We show that a simple optimal mechanism exists and can be found by solving a linear programming problem in which the set of constraints is derived from what we call the L-principle.