An approach to emulating separable graphs

A technique foremulating multicomputer interconnection networks that are based onseparable graphs (graphs having bounded degree and sublinear multicolor recursive bisectors) is presented. Efficient emulations among interconnection networks are necessary for porting programs designed for one network to another.Emulations are formalized asgraph embeddings, where the nodes (processors) of theguest graph (emulated network) are assigned to nodes of thehost graph (emulator), while the edges (communication links) of the guest are routed via paths in the host. The communication slowdown in an emulation depens on thedilation (length of the longest routing path) and thecongestion (number of paths that contend for a host edge) of the embedding. Theexpansion of the embedding (the ratio of the sizes of the host to guest) determines the inefficiency of processor utilization. Cell trees are introduced as interconnection networks whose special communication properties enable them to serve as intermediate devices in these emulations. Nodes in cell trees are organized into equinumerous parts calledcells; the cells are labeled by nodes of a complete binary tree. Communication in cell trees is restricted to two specific and distinct primitives:cell communication is confined within cells, whiletransfer communication occurs between adjacent cells. Rather than solved directly, the emulation problem for the original guest-host pair is decomposed into two independent parts: emulating the guest by the cell tree, and emulating the cell tree by the host.In emulations of separable graphs by cell trees, the node assignment that ensures small dilation is derived from the separator-based decomposition of guest graphs. The congestion-free edge routing is achieved by coordinatingglobal andlocal phases, which are based on two characteristic cell-tree communication primitives.The technique is instantiated by emulating cell trees on specific host graphs. Withshuffle-like hypercube-derivative networks as hosts new constant-expansion emulations are obtained that have both dilation and congestion logarithmic in the size of the multicolor bisector of guest graphs. These emulations are the first such to have optimal (up to constants)congestion; they provide the firstoptimal algorithm for emulating arbitrary separable graphs on shuffle-like networks. The application of the technique tohypercubes as hosts also produces optimal emulations that differ from those previously known by having smaller expansion constants.This research was supported in part by NSF Grants CCR-88-12567 and CCR-90-13184, and by the University of Massachusetts Graduate School Fellowship for the academic year 1991-92. A preliminary version of this paper was presented at the 3rd ACM Symposium on Parallel Algorithms and Architectures, July 22–24, 1991, in Hilton Head, South Carolina, USA.     

Obelix searches Internet using customer data

One major problem with purchasing through the Web is locating reliable suppliers that offer the exact product or service you need. In the usual approach, you access an indexing based search engine, specify keywords for the purchase, and initiate the search. The outcome is typically a list ranked according to keyword matches; useful, but not always helpful. Keyword matches provide only one ingredient to finding the right Web sites. The ranking should also consider the satisfaction of previous customers purchasing from those sites, customer profiles, and customer behavior. The Obelix search engine uses reconfigurable technology to apply customer satisfaction data obtained from the Internet service provider infrastructure to refine its search criteria. The Obelix system collects data about customer activities, calculates a customer satisfaction index, and updates the search engines with its findings     

Relationship between the Undrained Shear Strength, Water Content, and Mineralogical Properties of Fine-Grained Soils

The relationship between the undrained shear strength of fine-grained soils and the water content can be described with a nonlinear function in which the type of soil is determined by two parameters. It is well known that these parameters depend mainly on the mineral compositions of soils; these relationships, however, have not yet been investigated. The findings described in this paper define those mineralogical properties of soils which determine the values of both parameters. Experimentally obtained results suggest that the parameters primarily depend on the size of the clay minerals, their quantity in soil composition, and the interlayer water quantity in the expanding clay minerals. As this dependence is well defined, the parameters, and thus the undrained shear strength at different water content, can be defined from knowledge of these mineralogical soil properties.     

Theoretical and experimental investigation of cold hobbing processes in cases of cone-like punch manufacturing

Optimal tool making is of great importance for reducing costs and increasing the performance of toolsets. The dies and punches, which are basic components of any metal forming toolset, are usually produced by machining, but this technology requires relatively long manufacturing times, characterized by significant material and energy waste. By replacing machining operations or combining them with forming ones, such as cold hobbing (indenting), significant cost and time savings, as well as improvement of tool performance could be achieved. Cold hobbing could be applied to making die cavities as well as shaping punch profiles. Investigations showed that a large number of variables influence the successful application of this technique. However, there is a scarcity of literature regarding the choice of relevant process parameters for the hobbing process. With this in mind, the aim of this paper is to yield further insight into the hobbing process. Special focus will be placed on the influence of the hob geometry on the deformation process and relevant process parameters. This paper presents theoretical, numerical, and experimental investigations of a cold hobbing process in which a cone-like punch is obtained. The upper-bound method was used for metal flow analysis and optimization of hob geometry. Stress–strain distribution, workpiece geometry prediction, and load estimation were obtained with the finite element method (FEM) using Simufact.Forming 8.1 software. The results were analyzed, compared, and discussed.     

EM3: a taxonomy of heterogeneous computing systems

The field of heterogeneous computing is growing rapidly. New concepts and systems appear daily. Hence, it is important to fit each new contribution into its proper place in the puzzle called heterogeneous computing. This is possible only if an adequate taxonomy/classification exists, one that can show whether or not a new system is heterogeneous, and if so, what kind of heterogeneity it exhibits. We propose a new taxonomy that shows the relative position of each and every heterogeneous system in the overall computer systems world. The proposed taxonomy is intended to be both broad enough to encompass all existing heterogeneous systems and simple enough to be easily accepted. Consequently, our taxonomy includes only four classes of computer systems. We propose that computer systems be classified as follows: SESM (single execution mode, single machine model); SEMM (single execution mode, multiple machine models), MESM (multiple execution modes, single machine model), and MEMM (multiple execution modes, multiple machine models)     

Chromosomal location of the genetic determinants for bacteriocins produced by Lactobacillus gasseri K7

The production of similar or even identical bacteriocins by different lactic acid bacteria is not a rare event. To take advantage of this finding, genetic determinants of the Lactobacillus K7 bacteriocins were tested for putative homologies with previously described bacteriocins of the Lactobacillus acidophilus group through polymerase chain reaction (PCR). Among specific primer pairs of seven known bacteriocins, derived from their respective sequences, only acidocin LF221 A and B primers amplified fragments in chromosomal DNA of K7 strain that revealed strong similarity over small regions of LF221 bacteriocins. Treatment of Lactobacillus K7 with ethidium bromide and mitomycin C was ineffective in generating non-bacteriocinogenic derivatives and had no impact on plasmid loss either. Classification studies elucidated Lactobacillus K7 as a member of the Lactobacillus gasseri species.     

Emulating a Complex Instruction Set Computer with a Reduced Instruction Set Computer

GaAs now allows up to 30K transistors per chip. With such a limitation, can you build a 32-bit CISC on a single GaAs chip? Yes, if you build a reduced instruction set computer and emulate the 32-bit CISC on it.     

Gas–liquid mass transfer in periodically operated trickle-bed reactors: Influence of the liquid-phase physical properties and flow modulation

The influence of periodic operation on trickle-bed reactor (TBR) hydrodynamics and gas–liquid mass transfer was investigated. Two-phase pressure drop, dynamic liquid hold-up and gas–liquid mass transfer coefficient (k_La) were determined at various liquid flow rates and for different modes of liquid flow variation (increasing and decreasing liquid flow rate). The results reveal the considerable influence of type of liquid flow rate modulation on k_La values (deviations of up to 80% in k_La). Simulation studies on gas-limited reaction in a periodically operated TBR indicate that an enhancement in conversion of about 14% can be expected from an appropriate selection of the operating mode, thus clearly demonstrating the quantitative process intensification feasible through increased gas–liquid mass transfer.