An integrated placement and routing approach

As the feature size continues scaling down, interconnects become the major contributor of signal delay. Since interconnects are mainly determined by placement and routing, these two stages play key roles to achieve high performance. Historically, they are divided into two separate stages to make the problem tractable. Therefore, the routing information is not available during the placement process. Net models such as HPWL, are employed to approximate the routing to simplify the placement problem. However, the good placement in terms of these objectives may not be routable at all in the routing stage because different objectives are optimized in placement and routing stages. This inconsistancy makes the results obtained by the two-step optimization method far from optimal;In order to achieve high-quality placement solution and ensure the following routing, we propose an integrated placement and routing approach. In this approach, we integrate placement and routing into the same framework so that the objective optimized in placement is the same as that in routing. Since both placement and routing are very hard problems (NP-hard), we need to have very efficient algorithms so that integrating them together will not lead to intractable complexity;In this dissertation, we first develop a highly efficient placer - FastPlace 3.0 for large-scale mixed-size placement problem. Then, an efficient and effective detailed placer - FastDP is proposed to improve global placement by moving standard cells in designs. For high-degree nets in designs, we propose a novel performance-driven topology design algorithm to generate good topologies to achieve very strict timing requirement. In the routing phase, we develop two global routers, FastRoute and FastRoute 2.0. Compared to traditional global routers, they can generate better solutions and are two orders of magnitude faster. Finally, based on these efficient and high-quality placement and routing algorithms, we propose a new flow which integrates placement and routing together closely. In this flow, global routing is extensively applied to obtain the interconnect information and direct the placement process. In this way, we can get very good placement solutions with guaranteed routability

Effect of gate voltage on spin transport along α\alpha-helical protein

Recently, the chiral-induced spin selectivity in molecular systems has attracted extensive interest among the scientific communities. Here, we investigate the effect of the gate voltage on spin-selective electron transport through the $\alpha$-helical peptide/protein molecule contacted by two nonmagnetic electrodes. Based on an effective model Hamiltonian and the Landauer-B\"uttiker formula, we calculate the conductance and the spin polarization under an external electric field which is perpendicular to the helix axis of the $\alpha$-helical peptide/protein molecule. Our results indicate that both the magnitude and the direction of the gate field have a significant effect on the conductance and the spin polarization. The spin filtration efficiency can be improved by properly tuning the gate voltage, especially in the case of strong dephasing regime. And the spin polarization increases monotonically with the molecular length without the gate voltage, which is consistent with the recent experiment, and presents oscillating behavior in the presence of the gate voltage. In addition, the spin selectivity is robust against the dephasing, the on-site energy disorder, and the space angle disorder under the gate voltage. Our results could motivate further experimental and theoretical works on the chiral-based spin selectivity in molecular systems.Comment: 8 pages, 7 figure

Development and evaluation of a NFWEAV simulation model for weaving areas under non-freeway condition

The development of a microscopic digital computer simulation model representing vehicle interaction at a weaving area under non-freeway condition is presented. Weaving areas are classified into two categories: 1. Weaving caused by merging and diverging of a ramp with an arterial, 2. On/off ramps connecting an arterial with a highway. The principal characteristics of the simulation model are the following: 1) a car following and lane changing model were used to represent vehicle movements; 2) an anti-collision check algorithm was developed for all vehicle movements; 3) driver merging urgency and follower courtesy model were developed for weaving vehicles. The simulation model was validated through field observation using video taping and photogrammetry techniques Comparative analyses between field observations and model predictions are carried out for non-weaving and weaving speed, as well as non-weaving and weaving acceleration. The results indicate that there is no statistically significant difference between the field data and simulation output

functional analyses of variants of human SCO1, a mitochondrial metallochaperone

Cytochrome c oxidase (COX) is a multimeric protein complex whose enzymatic activity contributes to the generation of an electrochemical potential required to synthesize adenosine triphosphate (ATP). Synthesis of Cytochrome c Oxidase 1 (SCO1) and SCO2 are two of the many accessory factors that are required to assemble individual structural subunits of COX into a functional holoenzyme complex. Mutations in either SCO gene cause severe, early onset forms of human disease. SCO1 and SCO2 are closely related paralogues localized to the inner mitochondrial membrane. Both proteins bind copper and exhibit a thiol disulphide oxidoreductase activity. Copper is bound by a highly conserved Cysteine x x x Cysteine motif and a histidine found within a thioredoxin fold, which is contained in the C-terminal half of the protein and projects into the mitochondrial intermembrane space. Mutations in either SCO1 or SCO2 affect their ability to deliver copper to COX II and metallate its CuA site, and also result in an increased rate of copper efflux from the cell. However, the relative importance of the ability to bind and transfer copper to SCO protein function remains poorly understood. Therefore, to investigate the significance of several cysteine residues and the conserved histidine to the copper-binding properties of SCO1, I functionally characterized a series of N- and C-terminal SCO1 mutant proteins by transducing them into control and patient fibroblasts, and quantifying their phenotypic effect on COX activity. I found that the two cysteines within the soluble, N-terminal matrix domain of SCO1 are not required for protein function. Overexpression of C-terminal SCO1 mutants only affected COX activity in SCO1-2 patient fibroblasts. To further characterize the copper-binding properties of these C-terminal mutants, soluble forms of each SCO1 variant were expressed and purified from bacteria, and the amount of total bound copper and the relative abundance of Cu(I) and Cu(II) were quantified. Although these analyses suggested that one mutant, SCO1 C169H, binds significantly more Cu(I) than the wild-type protein, none of the SCO1 variants exhibited properties that furthered our understanding of the precise role of SCO1 in the biogenesis of the CuA site of COX II