11,827 research outputs found
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A new partitioning approach for layout synthesis from register-transfer netlists
Most of the IC today are described and documented using heiarchical netlists. In addition to gates, latches, and flip-flops, these netlists include sliceable register-transfer components such as registers, counters, adders, ALUs, shifters, register files, and multiplexers. Usually, these components are decomposed into basic gates, latches, and flip-flops, and are laid out using standard cells. The standard cell architecture requires excessive routing area, and does not exploit the bit-sliced nature of register-transfer components. In this paper, we present a new sliced-layout architecture to alleviate the preceding problems. We also describe partitioning algorithms that are used to generate the floorplan for this layout architecture. The partitioning algorithms not only select the best suited layout style for each component, but also consider critical paths, I/O pin locations, and connections between blocks. This approach improves the overall area utilization and minimizes the total wire length
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SLAM : an automated structure to layout synthesis system
SLAM is a structure to layout synthesis system. It incorporates parameterisable bit-sliced and glue-logic generators to produce high density layout. In this paper, we describe a sliced layout architecture and SLAM system. In addition, we present partitioning algorithms for generating the floorplan for such an architecture. The algorithms partition the netlist into component sets best suited for different layout styles such as bit-sliced or strip-oriented logic. Each group is partitioned further into clusters to achieve better area utilization. Several experiments demonstrate that highly dense layouts can be achieved by using these algorithms with the sliced layout architecture
Investigation of the bi-drifting subpulses of radio pulsar B1839-04 utilising the open-source data-analysis project PSRSALSA
The usefulness and versatility of the PSRSALSA open-source pulsar
data-analysis project is demonstrated through an analysis of the radio pulsar
B1839-04. This study focuses on the phenomenon of bi-drifting, an effect where
the drift direction of subpulses is systematically different in different pulse
profile components. Bi-drifting is extremely rare in the pulsar population.
Various tools in PSRSALSA, including those allowing quantification of
periodicities in the subpulse modulation, their flux distribution, and
polarization properties, are exploited to obtain a comprehensive picture of the
radio properties of PSR B1839-04. In particular, the second harmonic in the
fluctuation spectra of the subpulse modulation is exploited to convincingly
demonstrate the existence of bi-drifting. Bi-drifting is confirmed with a
completely independent method allowing the average modulation cycle to be
determined. Polarization measurements were used to obtain a robust constraint
on the magnetic inclination angle of less than 35 deg. Two distinct emission
modes are discovered to be operating, with periodic subpulse modulation being
present only during the weaker mode. Despite the variability of the modulation
cycle and interruption by mode-changes, the modulation pattern responsible for
the bi-drifting is strictly phase locked over a timescale of years such that
the variability is identical in the different components. The phase locking
implies that a single physical origin is responsible for both drift directions.
Phase locking is hard to explain for many models, including those specifically
proposed in the literature to explain bi-drifting, and they are therefore shown
to be implausible. It is argued that within the framework of circulating
beamlets, bi-drifting could occur if the circulation were severely distorted,
possibly by distortions in the magnetic field.Comment: 16 pages, 9 figures, accepted for publication in A&
Direct strain and elastic energy evaluation in rolled-up semiconductor tubes by x-ray micro-diffraction
We depict the use of x-ray diffraction as a tool to directly probe the strain
status in rolled-up semiconductor tubes. By employing continuum elasticity
theory and a simple model we are able to simulate quantitatively the strain
relaxation in perfect crystalline III-V semiconductor bi- and multilayers as
well as in rolled-up layers with dislocations. The reduction in the local
elastic energy is evaluated for each case. Limitations of the technique and
theoretical model are discussed in detail.Comment: 32 pages (single column), 9 figures, 39 reference
Preliminary Solar Sail Design and Fabrication Assessment: Spinning Sail Blade, Square Sail Sheet
Blade design aspects most affecting producibility and means of measurement and control of length, scallop, fullness and straightness requirements and tolerances were extensively considered. Alternate designs of the panel seams and edge reinforcing members are believed to offer advantages of seam integrity, producibility, reliability, cost and weight. Approaches to and requirements for highly specialized metalizing methods, processes and equipment were studied and identified. Alternate methods of sail blade fabrication and related special machinery, tooling, fixtures and trade offs were examined. A preferred and recommended approach is also described. Quality control plans, inspection procedures, flow charts and special test equipment associated with the preferred manufacturing method were analyzed and are discussed
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Synthesis from VHDL : Rockwell-counter case study
This report describes the design process and synthesis tools used in the UC Irvine CADLAB design environment to design a representative benchmark. The steps taken and rationale used in each stage of the design process are discussed. The benchmark is initially described using a VHDL behavioral description; results produced by each intermediate tool are presented, showing the system flow and integration of tools. The final silicon layout is performed in 3 micron CMOS technology
Chance and Necessity in Evolution: Lessons from RNA
The relationship between sequences and secondary structures or shapes in RNA
exhibits robust statistical properties summarized by three notions: (1) the
notion of a typical shape (that among all sequences of fixed length certain
shapes are realized much more frequently than others), (2) the notion of shape
space covering (that all typical shapes are realized in a small neighborhood of
any random sequence), and (3) the notion of a neutral network (that sequences
folding into the same typical shape form networks that percolate through
sequence space). Neutral networks loosen the requirements on the mutation rate
for selection to remain effective. The original (genotypic) error threshold has
to be reformulated in terms of a phenotypic error threshold. With regard to
adaptation, neutrality has two seemingly contradictory effects: It acts as a
buffer against mutations ensuring that a phenotype is preserved. Yet it is
deeply enabling, because it permits evolutionary change to occur by allowing
the sequence context to vary silently until a single point mutation can become
phenotypically consequential. Neutrality also influences predictability of
adaptive trajectories in seemingly contradictory ways. On the one hand it
increases the uncertainty of their genotypic trace. At the same time neutrality
structures the access from one shape to another, thereby inducing a topology
among RNA shapes which permits a distinction between continuous and
discontinuous shape transformations. To the extent that adaptive trajectories
must undergo such transformations, their phenotypic trace becomes more
predictable.Comment: 37 pages, 14 figures; 1998 CNLS conference; high quality figures at
http://www.santafe.edu/~walte
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