An asynchronous protocol for virtual factory simulation on shared memory multiprocessor systems

The development of parallel simulation technology is seen as an enabler for the implementation of the virtual factory concept, the integrated simulation of all the systems in a factory. One important parallel simulation protocol, the asynchronous deadlock avoidance algorithm proposed by Chandy, Misra, and Bryant, has usually been discussed in the context of distributed memory systems. Also, null messages have normally been associated with this approach for deadlock avoidance. This paper presents a new implementation of the CMB protocol designed for shared memory multiprocessor systems. We have successfully used this protocol, which we call the CMB-SMP protocol, to achieve useful speedups in a manufacturing simulation application, despite the fine granularity of event processing. The implementation eliminates the need for sending null messages, without causing deadlock in the simulation. Double buffering is also used to reduce the overhead of buffer locking. It is shown that the CMB-SMP protocol outperforms a synchronous super-step protocol in terms of the speedups achieved. The paper also discusses the cache behaviour of the CMB-SMP protocol implementation since cache misses are very expensive with today's high clock speed processors.     

On virtual pathwidth of virtual graphs of a virtual link

The geometric representation of a knot is not too dissimilar from a graph and this interaction has helped mathematicians to solve many problems. In this paper, we apply graph theory tools to study the classification of virtual knots and links. We define virtual planar graphs and compute virtual path width of an associated graph of a virtual link. We show that the virtual path width of an associated graph is equal to the virtual bridge number of a pseudo prime knot.     

Technological endowments in entrepreneurial partnerships

This paper discusses a novel argument to interpret the importance of thinking of collaborative partnerships in pre-competitive agreements. To do so, we adopt a dynamic iterative process to model technology diffusion between the partners of an agreement. We find that the success of an agreement of a given length hinges around identifying the suitable efficient combinations of the initial technological endowments of partners. As the time horizon of the agreement expands, the probability of identifying a suitable partner decreases, thus justifying the prevalence of short-horizon R&D agreements.     

Modelling the benefits of information sharing-based partnerships in a two-level supply chain

This paper presents a study aimed at quantifying the benefits of information sharing-based supply chain partnerships. We derive the optimal inventory policies for the manufacturer and the retailer in a two-level decentralized supply chain under different information sharing scenarios. We show that increasing information sharing among the members in a decentralized supply chain will lead to Pareto improvement in the performance of the entire chain. Specifically, the manufacturer can obtain benefits in terms of reductions in inventory levels and cost savings.     

Non-cooperative investment in partnerships and their termination

This paper investigates how partners (firms or husband and wife) should invest into an uncertain stock that provides a common good, when to stop investments and when to end their partnership. The assumption of lumpy investments leads to a real option problem which is solved for the cooperative and non-cooperative solutions. Yet despite the analytical solution, numerical means are necessary to investigate economic consequences: strong incentives to free ride under competition even turning one of the options—to stop investment at high stock levels—into one of a negative value; in contrast, divorce remains a positively valued option.     

Contract design for risk sharing partnerships in manufacturing

The development of extensive partnerships with suppliers has become a characteristic of manufacturing, particularly in the aircraft and automobile industries. This paper considers the development of appropriate contracts that enable market risks to be shared between the lead manufacturer and the partners. It is shown that it is usually appropriate to have threshold contracts, i.e., contracts where a partner only shares in profits if sales exceed a value determined by risk tolerance and target return. The value of having financial partners as well as manufacturing partners is demonstrated, although it is also shown that financial partner contributions to the project should be limited. We also consider the situation where partners have pre-existing commitments to other projects, perhaps with competitors. The producers sales may be correlated with the partners profits on pre-existing commitments so the impact on contract structure is explored. It is shown that even if a partner had preexisting commitments whose profit is positively correlated with product sales then it is often beneficial to use such a partner.     

Storage administration in a virtual memory Simula system

The run time storage administration of a planned Simula system for PDP-10 is described with emphasis on record formats, record relationships and optimizations for the virtual memory organization. A parametrized garbage collector for variable size records in virtual memory is outlined.     

Alliances, partnerships and the Banzhaf semivalue

The coordination of strategies in a cooperative game, when some players decide to act together, is the basis of the partnership notion. Nevertheless, in some situations, it may be more convenient to form an effective coalition or alliance. In this work, we consider the Banzhaf semivalue and use it to discuss the convenience to form either partnerships or alliances, especially in simple games. Throughout the paper, some mathematical properties of the Banzhaf semivalue, in relation with the partnership formation, are derived.     

The virtual mass of a sphere in a suspension of spherical particles

The problem of the virtual mass of a sphere, moving in an ideal incompressible fluid when there are other identical spherical particles of arbitrary mass present is considered. A solution is constructed for the velocity potential of the fluid in the form of the superposition of perturbation fields, introduced into the flow by each of the particles. The perturbation fields are obtained in the form of functional series, the coefficients of which are mutually consistent by a defined system of equations. An explicit expression is obtained for the hydrodynamic force acting on the sphere in the form of a function of the coordinates of all the particles. A simple analytical dependence of the mean value of the force and the virtual mass of the sphere on the particle-to-fluid density ratio in a first approximation of the volume fraction of the dispersed phase is obtained for a statistically uniform distribution of the dispersed particles in the suspension, using the procedure of averaging over their different possible configurations in space.     

Sustaining long-term supply chain partnerships using price-only contracts

In this paper, we study how an informal, long-term relationship between a manufacturer and a retailer performs in turbulent market environments characterized by uncertain demand. We show that the long-term partnership based on repeated interaction is sustainable under price-only contracts when the supply chain partners are sufficiently patient. That is, the channel can be coordinated over a long time horizon when the factor whereby the members discount the future value of this trusting relationship is sufficiently high. Second, above the minimum discount factor, a range of wholesale prices exists that can sustain the long-term partnership, and there are different possible profit divisions between the two players. Third, when the market is turbulent, i.e., either the expected demand or the demand variance changes from period to period according to a probabilistic law, it is typically less possible to sustain the long-term partnership in a booming market or in a market with low demand variability. Finally, obtaining more information about future market fluctuation may not help the supply chain to sustain the long-term partnership, due to partners’ strategic considerations. With the availability of the market signal, total supply chain profits increase, but the retailer may even be worse-off.     

Scheduling tasks and communications on a virtual distributed system

A set of tasks has to be scheduled on identical parallel processors subject to precedence constraints and small communication delays. A polynomial algorithm is known to exist if task duplication is allowed and the number of available processors is not limited. However the problem of communications scheduling is not taken into account. In this paper, we prove that this algorithm also never saturates communication channels and always delivers messages on time, if slightly stronger constraints are imposed on the tasks.     

Construction of factory schedules using reverse simulation

A real-world, multi-stage, industrial scheduling problem is presented. An algorithm is described that converts a sequence of jobs into a complete schedule. Backward simulation is used to determine minimum storage requirements when scheduling each job, and to calculate the minimum amount of delay required. Combining this algorithm with a metaheuristic, such as simulated annealing, results in an effective algorithm for schedule optimization.     

Optimal product design using a colony of virtual ants

The optimal product design problem, where the “best” mix of product features are formulated into an ideal offering, is formulated using ant colony optimization (ACO). Here, algorithms based on the behavior of social insects are applied to a consumer decision model designed to guide new product decisions and to allow planning and evaluation of product offering scenarios.     

Evaluating focused factory benefits with queuing theory

In this paper, we study the benefits of a focused factory using lead-time as a performance measure. Specifically, we model a production process, using multi-class (multiple product types), general interarrival and processing time distributions with multiple machines (GI/G/c) queuing models for deriving each product’s mean lead-time. We also perform simulations for estimating the standard deviation of lead times. There are two product types: a standard and a customized product. The customized product has a more variable demand pattern than the standard product, and also requires additional processing time (setup and run time) in its production process. We assume that management is willing to sacrifice the lead-time performance of the customized product in favor of improved performance for the standard product. The paper shows that focusing the factory is more attractive for plants operating at higher utilization, and manufacturing products that have higher processing time and demand variability differentials between product types.     

The average virtual waiting time as a measure of performance

Under weak conditions the average virtual waiting time converges exponentially fast to its limit. For this reason this quantity has been suggested as a measure of performance for queueing systems. We consider theM/G/1 queue and provide estimation and limiting behaviour of the index of exponential decay.