10,583 research outputs found
A 155-mW 50-mvertices/s graphics processor with fixed-point programmable vertex shader for mobile applications
No full textA 36 mm(2) graphics processor with fixed-point programmable vertex shader is designed and implemented for portable two-dimensional (2-D) and three-dimensional (3-D) graphics applications. The graphics processor contains an ARM-10 compatible 32-bit RISC processor, a 128-bit programmable fixed-point single-instruction-multiple-data (SIMD) vertex shader, a low-power rendering engine, and a programmable frequency synthesizer (PFS). Different from conventional graphics hardware, the proposed graphics processor implements ARM-10 co-processor architecture with dual operations so that user-programmable vertex shading is possible for advanced graphics algorithms and various streaming multimedia processing in mobile applications. The circuits and architecture of the graphics processor are optimized for fixed-point operations and achieve the low power consumption with help of instruction-level power management of the vertex shader and pixel-level clock gating of the rendering engine. The PFS with a fully balanced voltage-controlled oscillator (VCO) controls the clock frequency from 8 MHz to 271 MHz continuously and adaptively for low-power modes by software. The chip shows 50 Mvertices/s and 200 Mtexels/s peak graphics performance, dissipating 155 mW in 0.18-mu m 6-metal standard CMOS logic process
A branch and bound algorithm for a production scheduling problem in an assembly system under due date constraints
No full textThis paper focuses on a production scheduling problem in a tree-structured assembly system operating on a make-to-order basis. Due dates are considered as constraints in the problem, that is, tardiness is not allowed. The objective of the problem is to minimize holding costs of final product inventory as well as work-in-process inventory. A mixed integer linear programming model is given and a branch and bound (B&B) algorithm based on a Lagrangian relaxation method is developed. In the algorithm, a subgradient method is used for obtaining good lower bounds of subproblems (or partial solutions) while a Lagrangian heuristic is used for upper bounds. Results of computational experiments on randomly generated test problems showed that the B&B algorithm found optimal solutions of problems of moderate sizes in a reasonable amount of computation time. (C) 2000 Elsevier Science B.V. All rights reserved
A systematic procedure for setting parameters in simulated annealing algorithms
No full textValues of parameters used in simulated annealing (SA) algorithms must be carefully selected since parameter values may have a significant influence on the performance of the algorithm. However, it is not easy to find good parameter values because values of a wide range have to be considered for each parameter and some parameters may be correlated with each other. In this paper, we suggest a procedure which gives good parameter values quickly without much human intervention by using the simplex method for nonlinear programming. To show the performance of the procedure, computational tests are done on a graph partitioning problem, a permutation flowshop scheduling problem and a short-term production scheduling problem. We select values for parameters needed in SA algorithms for the problems using the suggested procedure. The SA algorithms designed with this procedure are compared with existing SA algorithms in which parameter values were selected after extensive experiments. (C) 1998 Elsevier Science Ltd. All rights reserved
A heuristic algorithm for a production planning problem in an assembly system
No full textThis paper focuses on a production planning problem in an assembly system operating on a make-to-order basis. Due dates are considered as constraints in the problem, that is, tardiness is not allowed. The objective of the problem is to minimise holding costs for final product inventory as well as work-in-process inventory. A non-linear mathematical model is presented and a heuristic algorithm is developed using a solution property and a network model for defining solutions of the problem. A series of computational tests were done to compare the algorithm with a commercial planning/scheduling software and backward finite-loading methods that employ various priority rules. The results showed that the suggested algorithm outperformed the others
New titanatranes: Characterization and styrene polymerization behavior
No full textNew titanatranes containing cyclopentadienyl ligands were prepared by the reactions of various kinds of trialkanolamines with (C5Me4R)TiCl3 (Cp' = C5Me4R) in the presence of triethylamine. The X-ray analyses reveal that they exist in the monomeric form in the solid state and the Ti atom adopts essentially an eta(5) bonding posture with the Cp' ring and a tetradentate bonding mode with the trialkanolatoamine ligand via a transannular interaction from the bridgehead N atom to Ti. All compounds show very high catalytic activity for the syndiospecific polymerization of styrene in the presence of modified methylaluminoxane (MMAO) cocatalyst.We gratefully acknowledge financial
support from the Korea Science and Engineering
Foundation and the Brain Korea 21 Project
Search heuristics for a flowshop scheduling problem in a printed circuit board assembly process
No full textWe consider a scheduling problem in a factory producing printed circuit boards (PCBs). The PCB assembly process in this factory can be regarded as a flowshop which has two special characteristics: jobs have sequence dependent setup times and each job consists of a lot (batch) of identical PCBs. Because of the latter characteristic, it is possible to start a job on a following machine before the job is entirely completed on a previous machine, that is, there is time-lag between machines. In this paper, we propose several heuristics, including taboo search (TS) and simulated annealing (SA) methods, for this generalized flowshop scheduling problem with the objective of minimizing mean tardiness. We compare suggested heuristics after series of tests to find appropriate values for parameters needed for the two search algorithms, TS and SA. Results of computational tests on randomly generated test problems are reported.This research is supported by the Korean Science and Engineering Foundation (KOSEF) under grant 941-1000-015-1
Identification of transacting factors responsible for the tissue-specific expression of human glucose transporter type 2 isoform gene - Cooperative role of hepatocyte nuclear factors 1 alpha and 3 beta
No full textWe investigated transacting factors binding to the cis-element important in tissue-specific expression of the human glucose transporter type 2 isoform (GLUT2) gene. By transient transfection assay, we determined that the 227-base pair fragment upstream of the ATG start site contained promoter activity and that the region from +87 to +132 (site C) was responsible for tissue-specific expression. DNase I footprinting and electrophoretic mobility shift assay indicated that site C contained one binding site for hepatocyte nuclear factor 1 (HNF1) and two binding sites for HNF3 The mutations at positions +101 and +103, which are considered to be critical in binding HNF1 and HNF3, resulted in a 53% decrease in promoter activity, whereas the mutation of the proximal HNF3 binding site (+115 and +117) reduced promoter activity by 28%. The mutations of these four sites resulted in marked decrease (70%) in promoter activity as well as diminished bindings of HNF1 and HNF3, A to G mutation, which causes conversion of the HNF1 and HNF3 binding sequence to the NF-Y binding site, resulted in a 22% decrease in promoter activity. We identified that both HNF1 and HNF3 function as transcriptional activators in GLUTS gene expression. Coexpression of the pGL+74 (+74 to +301) construct with the HNF1 alpha and HNF3 beta expression vectors in NIH 3T3 cells showed the synergistic effect on GLUTS promoter activity compared with the expression of HNF1 alpha, HNF3 beta, or a combination of HNF1 beta and HNF3 beta. These data suggest that HNF1 alpha and HNF3 beta may be the most important players in the tissue-specific expression of the human GLUTS gene
Comparative feasibility study of a 30 MW disruptive floater solution with a 15 MW PivotBuoy and a benchmark 15 MW semi-submersible floater in the Bay of Biscay
No full textThis paper investigates the technical, life cycle, and economic feasibility of a 30 MW upscaled downwind turbine, comparing it to a 15 MW X1 Wind PivotBuoy downwind turbine and a benchmark 15 MW IEA Umaine VolturnUS-S upwind turbine in the 450 MW Sud de la Bretagne I wind farm site. The study is significant due to the rising energy demand, the potential for decreasing the levelized cost of energy with increased turbine size, and the optimized use of space. The size limit of current upwind turbine designs could be addressed using a downwind turbine solution.The research is conducted by modelling the global dynamic response of the structure using OpenFAST and computing the natural frequencies and stresses using a finite element model. A lifecycle analysis is performed to identify potential pitfalls and bottlenecks by analysing the individual lifecycle phases. The economic feasibility is assessed by simulating the annual energy production using TOPFARM and utilizing structural analysis and lifecycle assessment to quantify capital, operational, and abandonment expenditures. Based on the annual energy production and the performance indicators the levelized cost of energy is calculated.The findings indicate that while the global stability is within boundaries, the stress in members is too high with a simple scale-up of the proposed design. Bottlenecks are found in lifting operations and supply chain readiness. The levelized cost of energy and capital expenditure increased due to substructure self-weight, rendering the proposed 30 MW scale-up currently unfeasible when compared to the other two wind farms.These findings are important as they demonstrate that the 15 MW X1 Wind PivotBuoy is not scalable without design changes. The levelized cost of energy does not decrease with an increased floater solution. The 15 MW X1 Wind PivotBuoy downwind turbine seems more economically viable, making it a more interesting option for future development.Civil Engineerin
- …
