2,969 research outputs found
Comment on ``Validity of certain soft-photon amplitudes''
The criteria suggested by Welsh and Fearing (nucl-th/9606040) to judge the
validity of certain soft-photon amplitudes are examined. We comment on aspects
of their analysis which lead to incorrect conclusions about published
amplitudes and point out important criteria which were omitted from their
analysis.Comment: 6 pages plus 1 postscript figure, Revte
Reduced 30% scanning time 3D multiplexer integrated circuit applied to large array format 20KHZ frequency inkjet print heads
Enhancement of the number and array density of nozzles within an inkjet head
chip is one of the keys to raise the printing speed and printing resolutions.
However, traditional 2D architecture of driving circuits can not meet the
requirement for high scanning speed and low data accessing points when nozzle
numbers greater than 1000. This paper proposes a novel architecture of
high-selection-speed three-dimensional data registration for inkjet
applications. With the configuration of three-dimensional data registration,
the number of data accessing points as well as the scanning lines can be
greatly reduced for large array inkjet printheads with nozzles numbering more
than 1000. This IC (Integrated Circuit) architecture involves three-dimensional
multiplexing with the provision of a gating transistor for each ink firing
resistor, where ink firing resistors are triggered only by the selection of
their associated gating transistors. Three signals: selection (S), address (A),
and power supply (P), are employed together to activate a nozzle for droplet
ejection. The smart printhead controller has been designed by a 0.35 um CMOS
process with a total circuit area, 2500 x 500 microm2, which is 80% of the
cirucuit area by 2D configuration for 1000 nozzles. Experiment results
demonstrate the functionality of the fabricated IC in operation, signal
transmission and a potential to control more than 1000 nozzles with only 31
data access points and reduced 30% scanning time.Comment: Submitted on behalf of EDA Publishing Association
(http://irevues.inist.fr/EDA-Publishing
Interaction between a normal shock wave and a turbulent boundary layer at high transonic speeds. Part 1: Pressure distribution. Part 2: Wall shear stress. Part 3: Simplified formulas for the prediction of surface pressures and skin friction
An asymptotic description is derived for the interaction between a shock wave and a turbulent boundary layer in transonic flow, for a particular limiting case. The dimensionless difference between the external flow velocity and critical sound speed is taken to be much smaller than one, but large in comparison with the dimensionless friction velocity. The basic results are derived for a flat plate, and corrections for longitudinal wall curvature and for flow in a circular pipe are also shown. Solutions are given for the wall pressure distribution and the shape of the shock wave. Solutions for the wall shear stress are obtained, and a criterion for incipient separation is derived. Simplified solutions for both the wall pressure and skin friction distributions in the interaction region are given. These results are presented in a form suitable for use in computer programs
Three dimensional viscous analysis of a hypersonic inlet
The flow fields in supersonic/hypersonic inlets are currently being studied at NASA Lewis Research Center using 2- and 3-D full Navier-Stokes and Parabolized Navier-Stokes solvers. These tools have been used to analyze the flow through the McDonnell Douglas Option 2 inlet which has been tested at Calspan in support of the National Aerospace Plane Program. Comparisons between the computational and experimental results are presented. These comparisons lead to better overall understanding of the complex flows present in this class of inlets. The aspects of the flow field emphasized in this work are the 3-D effects, the transition from laminar to turbulent flow, and the strong nonuniformities generated within the inlet
Previously Unidentified Changes in Renal Cell Carcinoma Gene Expression Identified by Parametric Analysis of Microarray Data
BACKGROUND. Renal cell carcinoma is a common malignancy that often presents as a metastatic-disease for which there are no effective treatments. To gain insights into the mechanism of renal cell carcinogenesis, a number of genome-wide expression profiling studies have been performed. Surprisingly, there is very poor agreement among these studies as to which genes are differentially regulated. To better understand this lack of agreement we profiled renal cell tumor gene expression using genome-wide microarrays (45,000 probe sets) and compare our analysis to previous microarray studies. METHODS. We hybridized total RNA isolated from renal cell tumors and adjacent normal tissue to Affymetrix U133A and U133B arrays. We removed samples with technical defects and removed probesets that failed to exhibit sequence-specific hybridization in any of the samples. We detected differential gene expression in the resulting dataset with parametric methods and identified keywords that are overrepresented in the differentially expressed genes with the Fisher-exact test. RESULTS. We identify 1,234 genes that are more than three-fold changed in renal tumors by t-test, 800 of which have not been previously reported to be altered in renal cell tumors. Of the only 37 genes that have been identified as being differentially expressed in three or more of five previous microarray studies of renal tumor gene expression, our analysis finds 33 of these genes (89%). A key to the sensitivity and power of our analysis is filtering out defective samples and genes that are not reliably detected. CONCLUSIONS. The widespread use of sample-wise voting schemes for detecting differential expression that do not control for false positives likely account for the poor overlap among previous studies. Among the many genes we identified using parametric methods that were not previously reported as being differentially expressed in renal cell tumors are several oncogenes and tumor suppressor genes that likely play important roles in renal cell carcinogenesis. This highlights the need for rigorous statistical approaches in microarray studies.National Institutes of Healt
Anatomy of the Soft-Photon Approximation in Hadron-Hadron Bremsstrahlung
A modified Low procedure for constructing soft-photon amplitudes has been
used to derive two general soft-photon amplitudes, a two-s-two-t special
amplitude and a two-u-two-t special amplitude
, where s, t and u are the Mandelstam variables.
depends only on the elastic T-matrix evaluated at four sets
of (s,t) fixed by the requirement that the amplitude be free of derivatives
(T/s and /or T/). Likewise
depends only on the elastic T-matrix evaluated at four sets
of (u,t). In deriving these amplitudes, we impose the condition that
and reduce to and
, respectively, their tree level approximations. The
amplitude represents photon emission from a sum of
one-particle t-channel exchange diagrams and one-particle s-channel exchange
diagrams, while the amplitude represents photon
emission from a sum of one-particle t-channel exchange diagrams and
one-particle u-channel exchange diagrams. The precise expressions for
and are determined by using the
radiation decomposition identities of Brodsky and Brown. We point out that it
is theoretically impossible to describe all bremsstrahlung processes by using
only a single class of soft-photon amplitudes. At least two different classes
are required: the amplitudes which depend on s and t or the amplitudes which
depend on u and t. When resonance effects are important, the amplitude
, not , should be used. For processes with
strong u-channel exchange effects, the amplitude should be
the first choice.Comment: 49 pages report # LA-UR-92-270
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