A survey and taxonomy of layout compaction algorithms

This paper presents a survey and a taxonomy of layout compaction algorithms, which are an essential part of modern symbolic layout tools employed in VLSI circuit design. Layout compaction techniques are also used in the low-end stages of silicon compilation tools and module generators. The paper addresses the main algorithms used in compaction, focusing on their implementation characteristics, performance, advantages and drawbacks. Compaction is a highly important operation to optimize the use of silicon area, achieve higher speed through wire length minimization, support technology retargeting and also allow the use of legacy layouts. Optimized cells that were developed for a fabrication process with a set of design rules have to be retargeted for a new and more compact process with a different set of design rules

A model for the fragmentation kinetics of crumpled thin sheets

As a confined thin sheet crumples, it spontaneously segments into flat facets delimited by a network of ridges. Despite the apparent disorder of this process, statistical properties of crumpled sheets exhibit striking reproducibility. Experiments have shown that the total crease length accrues logarithmically when repeatedly compacting and unfolding a sheet of paper. Here, we offer insight to this unexpected result by exploring the correspondence between crumpling and fragmentation processes. We identify a physical model for the evolution of facet area and ridge length distributions of crumpled sheets, and propose a mechanism for re-fragmentation driven by geometric frustration. This mechanism establishes a feedback loop in which the facet size distribution informs the subsequent rate of fragmentation under repeated confinement, thereby producing a new size distribution. We then demonstrate the capacity of this model to reproduce the characteristic logarithmic scaling of total crease length, thereby supplying a missing physical basis for the observed phenomenon.Comment: 11 pages, 7 figures (+ Supplemental Materials: 15 pages, 9 figures); introduced a simpler approximation to model, key results unchanged; added references, expanded supplementary information, corrected Fig. 2 and revised Figs. 4 and 7 for clearer presentation of result

Dynamics of Convective Heat and Mass Transfer in Permeable Parts of Seismofocal Zones of the Kamchatka Region and Conjugated Volcanic Arcs

This chapter considers the dynamics of convective heating of mantle and crustal rocks in the seismic focal zone of Kamchatka region and associated volcanic arcs, which are characterized by the predominance of compressive stresses and the compaction of the heterophase medium. Features of heating, determining the dynamics of metasomatic transformations and convective melting, are studied on the basis of nonisothermal hydrodynamic model of heating of lithospheric rocks above the magmatic chambers

General Geology of northern Gunung Semanggol, Bukit Merah, Taiping with emphasis on Tectono-Stratigraphic Evolution of Semanggol Formation

Previous researches of northwest Peninsular Malaysia have classified Gunung Semanggol as part of the Semanggol Formation that extends from north and south Kedah. The study presented in this paper aims to investigate the geological outcrops along the west and east face of the northern Gunung Semanggol. Data recorded during the research is used to conceptualise a sedimentary facies model, depositional settings and tectono-stratigraphic model. The methods used are geological fieldwork and laboratory works including thin section and petrography analysis. The results show that the outcrops exhibit fining upward sequence of bedded chert, and sandstone interbedded with shale, as well as some siltstone. It is postulated that the northern Gunung Semanggol was once deposited in deep marine settings that lead to deposition of bedded chert, followed by deposition of turbidite materials. The age of the northern Gunung Semanggol formation is suggested to be Permo-Triassic. The data presented in this paper are valuable in understanding the geological link between outcrops of the Semanggol Formation. It is recommended that other aspects such as biostratigraphy and geochemistry to be included in the future to gain accurate distinction between Permian and Triassic rocks formation of the northern Gunung Semanggol and the Semanggol Formation exclusively

Numerical Evaluation of Porosity Band Formation as a Mechanism for Melt Focusing at Mid-Ocean Ridges

It has been well established through various experimental and numerical studies that imposing an external shear on a system of partial melt will result in the compaction of the solid matrix and expulsion of the interstitial liquid melt; this leads to the formation of regions of contrasting high and low porosity that are commonly referred to as melt bands. An early numerical study of melt bands speculated that these structures could contribute to melt extraction at mid-ocean ridges. This thesis examines the formation of melt bands beneath mid-ocean ridges. With linear and nonlinear models similar to those from previous numerical melt band studies, melt bands are evaluated as a mechanism for lateral melt extraction using the shear geometry derived from the velocity field of the plate-driven corner flow of a mid-ocean ridge. The degree of similarity between previous numerical and experimental results has been found to be greatly influenced by the imposed rheology of the solid matrix phase. Knowing this, the numerical models in this contribution will use three different matrix shear viscosity laws: isotropic strain rate independent, isotropic strain rate dependent and anisotropic strain rate independent. The linear analysis indicates that though fast growing bands may be oriented toward the ridge axis, the bands that undergo the greatest change in porosity over time are oriented toward the lithosphere-asthenosphere boundary at the base of the plate. The nonlinear simulations produce bands with orientations similar to those found in the linear analysis, along with a great deal of unexpected porosity accumulation present on the boundaries of the model domain. These models indicate that melt bands will not likely act as high permeability melt-channeling conduits except near the lithosphere-asthenosphere boundary at the base of the plate. These models are highly sensitive to the poorly defined matrix bulk viscosity, with an increased bulk viscosity resulting in little or no development of significant band-like structures. The models are also sensitive to the initial heterogeneity, which, like the bulk viscosity, is also poorly defined; too great an initial heterogeneity results in the bands quickly surpassing the disaggregation limit for mantle rocks

Radio-Echo Sounding Over Polar Ice Masses

Peer reviewedPublisher PD

Tertiary tectonics and sedimentation history of the Sarawak basin, east Malaysia

A seismic stratigraphic study of the regional lines for the offshore Sarawak area was undertaken with the aim of understanding the tectonics and sedimentation history of the hydrocarbon prolific Sarawak Basin. The aim here is to develop a workable stratigraphic scheme, a model of the sedimentation history of the basin, a model for Tertiary tectonics, and an analysis of the subsidence history of the basin. Six unconformities have been identified within the Tertiary sedimentary succession, based on seismic reflection and well data. Some unconformities coincide with eustatic sea-level falls; others are probably tectonic in origin. An alternative stratigraphic scheme for the Sarawak Basin was developed by subdividing the whole Tertiary succession into seven sequences. Palaeoenvironment maps of the basin document the interaction of tectonics and sedimentation commencing in late Oligocene times. Deposition started with a NW-SE coastline and a broad coastal plain, almost perpendicular to the present-day coastline (NE-SW) developed during late Miocene times. The maps illustrate the likely distribution of Sarawak Basin source and reservoir rocks which will help in effective planning for future exploration in the area. The Sarawak Basin formed as a result of NW-SE trending right lateral fault movement during late Oligocene to Pliocene times. This dextral movement was responsible for creating the NW-SE coastline and divided the offshore Sarawak area into two sub-basins. Deposition and preservation of coastal plain and shallow-marine sediments continued in the eastern area while the western area remained as a 'high' until late Miocene times and subsided during late Early to Middle Miocene. The dextral strike-slip movement which controlled the evolution of the Sarawak Basin is sub-parallel to a number of lineaments elsewhere in Sarawak. The timing of movement suggests a progressive younging in an eastward direction. Basin modelling suggests that the Sarawak Basin was characterised by rapid subsidence in the early stage of basin formation with a high stretching factor and episodic movements. This suggests that the basin did not form as a foreland basin nor as a typical rift basin, but indicates a strike-slip origin. Supplementary evidence for this is provided by the findings of the regional seismic stratigraphic study, which suggests that the whole onshore area of Sarawak and northern Borneo was subjected to strike-slip tectonism during Tertiary times. The driving force may have been initiated by the lateral movement between the Sundaland and South China Continental blocks, probably due to collision between Indian and Asian plates during the Middle Tertiary, continuing with the opening of the South China Sea during the Oligocene. The end result of tectonism in the region, however, is believed to be the combination of strike-slip movements and the counter-clockwise rotation of Borneo during the Oligo-Miocene. The superiority of the proposed strike-slip tectonic model over the present subduction model is the capability to explain most of the geological phenomena, including the absence of evidence for any subduction taking place in the area. The findings of this study should contribute towards a better understanding of the tectonics of the area which will be able to provide information on the development of structural traps for hydrocarbon plays that are believed to have formed by strike-slip tectonism

Will present day glacier retreat increase volcanic activity? Stress induced by recent glacier retreat and its effect on magmatism at the Vatnajokull ice cap, Iceland

Global warming causes retreat of ice caps and ice sheets. Can melting glaciers trigger increased volcanic activity? Since 1890 the largest ice cap of Iceland, Vatnajokull, with an area of similar to 8000 km(2), has been continuously retreating losing about 10% of its mass during last century. Present-day uplift around the ice cap is as high as 25 mm/yr. We evaluate interactions between ongoing glacio-isostasy and current changes to mantle melting and crustal stresses at volcanoes underneath Vatnajokull. The modeling indicates that a substantial volume of new magma, similar to 0.014 km(3)/yr, is produced under Vatnajokull in response to current ice thinning. Ice retreat also induces significant stress changes in the elastic crust that may contribute to high seismicity, unusual focal mechanisms, and unusual magma movements in NW-Vatnajokull