Bounding inconsistency using a novel threshold metric for dead reckoning update packet generation

Human-to-human interaction across distributed applications requires that sufficient consistency be maintained among participants in the face of network characteristics such as latency and limited bandwidth. The level of inconsistency arising from the network is proportional to the network delay, and thus a function of bandwidth consumption. Distributed simulation has often used a bandwidth reduction technique known as dead reckoning that combines approximation and estimation in the communication of entity movement to reduce network traffic, and thus improve consistency. However, unless carefully tuned to application and network characteristics, such an approach can introduce more inconsistency than it avoids. The key tuning metric is the distance threshold. This paper questions the suitability of the standard distance threshold as a metric for use in the dead reckoning scheme. Using a model relating entity path curvature and inconsistency, a major performance related limitation of the distance threshold technique is highlighted. We then propose an alternative time—space threshold criterion. The time—space threshold is demonstrated, through simulation, to perform better for low curvature movement. However, it too has a limitation. Based on this, we further propose a novel hybrid scheme. Through simulation and live trials, this scheme is shown to perform well across a range of curvature values, and places bounds on both the spatial and absolute inconsistency arising from dead reckoning

Exploring the use of local consistency measures as thresholds for dead reckoning update packet generation

Human-to-human interaction across distributed applications requires that sufficient consistency be maintained among participants in the face of network characteristics such as latency and limited bandwidth. Techniques and approaches for reducing bandwidth usage can minimize network delays by reducing the network traffic and therefore better exploiting available bandwidth. However, these approaches induce inconsistencies within the level of human perception. Dead reckoning is a well-known technique for reducing the number of update packets transmitted between participating nodes. It employs a distance threshold for deciding when to generate update packets. This paper questions the use of such a distance threshold in the context of absolute consistency and it highlights a major drawback with such a technique. An alternative threshold criterion based on time and distance is examined and it is compared to the distance only threshold. A drawback with this proposed technique is also identified and a hybrid threshold criterion is then proposed. However, the trade-off between spatial and temporal inconsistency remains

A first report on electromigration studies at a model copper-aluminum railgun contact

10A) was necessary to produce the large current densities typically found in railguns, and was able to simulate the skin effect on both the Cu rails and Al armature under static, long-term testing conditions. In this method, the effects of electromigration were discerned clearly, in dissociation from various movement related damage phenomena. The aluminum from the armature quickly reached its melting point via Joule heating due to high contact resistance at the armature-rail contact. Once liquid aluminum was formed, it rapidly migrated along the copper rail towards the negative terminal. This transport of liquid aluminum along the copper rails was attributed to electromigration of the liquid under the influence of the direct electric field. Once the aluminum began to be transported along the rail towards the cathode terminal, it alloyed with the copper rails and the resistance steadily increased in the circuit. Electromigration is shown to be a contributing factor to the degradation of aluminum armatures performance and copper rails lifespan in the railgun.http://archive.org/details/afirstreportonel109452511Approved for public release; distribution is unlimited

Quantum Monte Carlo Simulation of the High-Pressure Molecular-Atomic Crossover in Fluid Hydrogen

A first-order liquid-liquid phase transition in high-pressure hydrogen between molecular and atomic fluid phases has been predicted in computer simulations using ab initio molecular dynamics approaches. However, experiments indicate that molecular dissociation may occur through a continuous crossover rather than a first-order transition. Here we study the nature of molecular dissociation in fluid hydrogen using an alternative simulation technique in which electronic correlation is computed within quantum Monte Carlo, the so-called Coupled Electron Ion Monte Carlo (CEIMC) method. We find no evidence for a first-order liquid-liquid phase transition.Comment: 4 pages, 5 figures; content changed; accepted for publication in Phys. Rev. Let

Radiative corrections in processes at the SSC

We discuss radiative corrections for interactions in the SSC environment. Based on the theory of Yennie, Frautschi and Suura, we develop appropriate Monte Carlo event generators to compute the background electromagnetic radiation. Our results indicate that multiple-photon effects must be taken into account in the study of SSC physics such as Higgs decay.Comment: UTHEP-92-0901, 15 pages (incl. 3 figures), LaTeX (Talk presented at the XXXII Cracow School of Theoretical Physics, Zakopane, June 1992