On periodic resource scheduling for continuous-media databases

The Enhanced Pay-Per-View (EPPV) model for providing continuous-media services associates with each continuous-media clip a display frequency that depends on the clip's popularity. The aim is to increase the number of clients that can be serviced concurrently beyond the capacity limitations of available resources, while guaranteeing a constraint on the response time. This is achieved by sharing periodic continuous-media streams among multiple clients. The EPPV model offers a number of advantages over other data-sharing schemes (e.g., batching), which make it more attractive to large-scale service providers. In this paper, we provide a comprehensive study of the resource-scheduling problems associated with supporting EPPV for continuous-media clips with (possibly) different display rates, frequencies, and lengths. Our main objective is to maximize the amount of disk bandwidth that is effectively scheduled under the given data layout and storage constraints. Our formulation gives rise to -hard combinatorial optimization problems that fall within the realm of hard real-time scheduling theory. Given the intractability of the problems, we propose novel heuristic solutions with polynomial-time complexity. We also present preliminary experimental results for the average case behavior of the proposed scheduling schemes and examine how they compare to each other under different workloads. A major contribution of our work is the introduction of a robust scheduling framework that, we believe, can provide solutions for a variety of realistic EPPV resource-scheduling scenarios, as well as any scheduling problem involving regular, periodic use of a shared resource. Based on this framework, we propose various interesting research directions for extending the results presented in this paper. Received June 9, 1998 / Accepted October 13, 1998     

Galling resistance and wear mechanisms – cold work tool materials sliding against carbon steel sheets

One of the major causes for tool failure in sheet metal forming is transfer and accumulation of adhered sheet material to the tool surfaces, generally referred to as galling. In the present work, the galling resistance of several tool materials was investigated against two-phase ferritic-martensitic carbon steel under dry sliding test conditions. Tribological evaluation was carried out at different contact pressures by using a slider-on-flat-surface (SOFS) tribometer. For all selected test conditions, a consistent ranking of the materials was obtained with best performance observed for nitrogen alloyed powder metallurgy tool steel. Worst galling resistance was observed by nodular cast iron.     

The Popov criterion and the inverse Nyquist method†

Kosonbrock's inverse Nyquist array (I.N.A.) theory for linear multivariable control Bystema with constant feedback elements is extended, to include systems lip to m nonlinear feedback elements, where the system has m inputs and m outputs. This extension is achieved by considering the Popov criterion for the most general case and through two further theorems. It shows that, as in the ease of Rosenbrock's I.N.A. theory, when certain auxiliary conditions are met with the help of suitable controllers, the design of multivariable controllers containing many non-linear feedbacks, can be based on the m frequency response loci corresponding to the diagonal entries of the open-loop inverse transfer function matrix. This leads to a simple design technique identical to the I.N.A. design method, suitable for use with a computer-aided design facility which permits a designer to use his intuitive understanding of transfer functions based on classical theory. The I.N.A. theory has been extended by Rosenbrock to cover systems having non-linear, time-varying feedback elements very recently.     

Particle-based simulation of the interaction between fluid and knitwear

We present a particle-based method to simulate and visualize the interaction of knitwear with fluids. The knitwear is modeled using spring-mass systems and the fluid is modeled using the smoothed particle hydrodynamics method. Two-way coupling is achieved by considering surface tension, capillary, and interparticle forces between the fluid and knitwear. The simulation of fluid and knitwear particles is performed on the graphics processing unit. Photorealistic rendering of knitwear and fluid is achieved by using a hardware-accelerated rasterization-based rendering technique. Our method is able to simulate and visualize the macro- and microstructure of free-form knitwear and reflective and refractive characteristics of the fluid surface.     

Propagation dynamics of ultra-short high-power laser pulses in air: supercontinuum generation and transverse ring formation

Numerical and semi-analytical results of the propagation of high-power ultra-short near IR laser pulses propagating in ionizing air are presented.     

The Drop Weight Test Revisited: Characterization of the Crushability of Hot Sinter and Validation of the Approach with Natural Rocks

The crushing behaviour of sinter from blast furnace operations is known to depend on its temperature. In order to characterize it, hot sinter was subject to single particle tests in a very basic drop weight tester. Additionally, a laboratory jaw crusher was sacrificed to work the same feed material. As the results regarding net energy input were not consistent, two common rocks were tested in comparison with both the drop weight and the jaw crusher. Although some discrepancies remained, the results with the rocks can basically be considered as consistent. This investigation illustrates some of the difficulties that can arise when established test methods are applied on material with deviant properties.