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231.
Chandrasekhar Das 《IIE Transactions》1978,10(2):217-219
This paper solves the reorder point inventory model under two constraints: safety stock is nonnegative, and the fraction of backorders does not exceed a given limit. The solution procedure modifies a noniterative approach due to Simpson in order to achieve better accuracy and wider applicability of the results. A formula for the implied cost of a fixed service level is also developed. 相似文献
232.
Lunardi L.M. Chandrasekhar S. Gnauck A.H. Burrus C.A. Hamm R.A. Sulhoff J.W. Zyskind J.L. 《Photonics Technology Letters, IEEE》1995,7(2):182-184
A very high sensitivity, high speed, fiber-pigtailed photoreceiver module is described. The OEIC photoreceiver, composed of a p-i-n photodetector monolithically integrated with an InP-InGaAs heterojunction bipolar transistor (HBT)-based transimpedance amplifier, has measured sensitivity of -20 dBm and -17.6 dBm for data rates of 10 and 12 Gb/s, respectively, at a bit error rate of 1×10-9. These results are the best ever reported for an OEIC photoreceiver at these speeds. In an optical transmission experiment with a low noise erbium-doped fiber amplifier (EDFA) preceding the OEIC photoreceiver, the measured sensitivities were -35.2 and -32 dBm at 10 and 12 Gb/s respectively 相似文献
233.
234.
This paper outlines a simple, fast, and accurate method for automatically locating the nipple on digitized mammograms that have been segmented to reveal the skin-air interface. If the average gradient of the intensity is computed in the direction normal to the interface and directed inside the breast, it is found that there is a sudden and distinct change in this parameter close to the nipple. A nipple in profile is located between two successive maxima of this parameter; otherwise, it is near the global maximum. Specifically, the nipple is located midway between a successive maximum and minimum of the derivative of the average intensity gradient; these being local turning points for a nipple in profile and global otherwise. The method has been tested on 24 images, including both oblique and cranio-caudal views, from two digital mammogram databases. For 23 of the images (96%), the rms error was less than 1 mm at image resolutions of 400 microns and 420 microns per pixel. Because of its simplicity, and because it is based both on the observed behavior of mammographic tissue intensities and on geometry, this method has the potential to become a generic method for locating the nipple on mammograms. 相似文献
235.
NDDO-based (AM1) configuration interaction (CI) calculations have been used to calculate the wavelength and oscillator strengths of electronic absorptions in organic molecules and the results used in a sum-over-states treatment to calculate second-order hyperpolarizabilities. The results for both spectra and hyperpolarizabilities are of acceptable quality as long as a suitable CI-expansion is used. We have found that using an active space of eight electrons in eight orbitals and including all single and pair-double excitations in the CI leads to results that agree well with experiment and that do not change significantly with increasing active space for most organic molecules. Calculated second-order hyperpolarizabilities using this type of CI within a sum-over-states calculation appear to be of useful accuracy. 相似文献
236.
Joyner C.H. Chandrasekhar S. Sulhoff J.W. Dentai A.G. 《Photonics Technology Letters, IEEE》1992,4(9):1006-1009
The authors investigate selective epitaxy through SiO2 masks of varied geometry with the goal of making planar photonic integrated circuits. The InGaAs/InP, InGaAsP/InP, and InGaAs/InGaAsP MQW material systems are studied with atmospheric and 100-torr MOVPE. Extremely large bandgap shifts (136 meV) can be achieved, more than enough to allow construction of lasers, modulators, and low-loss waveguides in a single plane 相似文献
237.
Samelis A. Pavlidis D. Chandrasekhar S. Lunardi L.M. Rios J. 《Electron Devices, IEEE Transactions on》1996,43(12):2053-2061
A large-signal model for InP/InGaAs-based single HBTs incorporating soft-breakdown effects to the LIBRA Gummel-Poon (GP) model is developed and its validity is established from DC to microwave frequencies and over a wide range of input excitation levels. The large-signal characteristics of a cascode InP-based transimpedance optoelectronic preamplifier employing such devices are studied. Gain compression for the preamplifier was found to take place at an input power level of -20 dBm. Input power excitation varying from -65 to -5 dBm results in a degradation of the amplifier transimpedance gain of the order of 3 dBn. Experimental and theoretical characteristics are presented for the InP-based HBTs and transimpedance amplifier. Self-biasing effects are suggested as possible origin of the transimpedance variations with input power 相似文献
238.
239.
Starting with the initial aim of reconnaissance technical developments in remote sensing have progressed sufficiently for
the large-scale realisation of practical benefits. During the eighties a number of countries will have remote sensing satellite
systems in operation. There are however a few technical, legal, political and economic issues that still remain unresolved.
The resolution of these issues would facilitate practical applications especially in developing countries. Apart from the
purely technical and economic issues such as the ability to compare data from two different satellites, the cost of the data
etc one of the major hurdles in the application of this technology is the establishment of an international regime governing
the activities of states in remote sensing. This is particularly important in view of the link between surveillance and remote
sensing. Even though discussions have been going on for quite some time at the United Nations, the prospects of reaching agreement
remain bleak.
The main problems precluding agreement are national security, commercial and sovereignty concerns of the developed and developing
countries. The key issues relate to the right of countries to conduct remote sensing over other countries, the right of countries
collecting remote sensing data (over other countries) to distribute this data freely and the modalities of how the “sensitivity”
aspects of remote sensing for surveillance and economic espionage can be reconciled with a legal regime that emphasises international
cooperation. A critical analysis of existing international space law seems to indicate that there are two kinds of remote
sensing—passive and active. In passive remote sensing the satellite sensor detects the sun-reflected or self-emitted radiation
from objects on the ground. In active remote sensing a pulse of electromagnetic radiation is transmited from the satellite
and its reflectance or scattering by objects on the earth’s surface is measured. A strict reading of existing legal principles
on space seem to imply that passive sensing is legal while active sensing could be interpreted as violating the sovereignty
of the sensed state. Agreement on remote sensing can be reached if a resolution or a range of resolutions can be defined to
discriminate between “sensitive” and “non-sensitive” data.
The only international agreement in this area between the USSR and a group of nine socialist countries uses a resolution limit
of 50m. Available information on the subject seems to indicate that the range is from 25–50 m.
One other aspect dealt with relates to the use of satellite data for verification of arms control measures, for crisis monitoring
and the prospects of setting up an International Satellite Monitoring Agency (ISMA). It appears that the huge expense that this would entail would be justified only if theISMA can monitor the superpowers and the arms race between them. 相似文献
240.
Jayram Moorkanikara Nageswaran Andrew Felch Ashok Chandrasekhar Nikil Dutt Richard Granger Alex Nicolau Alex Veidenbaum 《International journal of parallel programming》2009,37(4):345-369
Even though computing systems have increased the number of transistors, the switching speed, and the number of processors,
most programs exhibit limited speedup due to the serial dependencies of existing algorithms. Analysis of intrinsically parallel
systems such as brain circuitry have led to the identification of novel architecture designs, and also new algorithms than
can exploit the features of modern multiprocessor systems. In this article we describe the details of a brain derived vision
(BDV) algorithm that is derived from the anatomical structure, and physiological operating principles of thalamo-cortical
brain circuits. We show that many characteristics of the BDV algorithm lend themselves to implementation on IBM CELL architecture,
and yield impressive speedups that equal or exceed the performance of specialized solutions such as FPGAs. Mapping this algorithm
to the IBM CELL is non-trivial, and we suggest various approaches to deal with parallelism, task granularity, communication,
and memory locality. We also show that a cluster of three PS3s (or more) containing IBM CELL processors provides a promising
platform for brain derived algorithms, exhibiting speedup of more than 140 × over a desktop PC implementation, and thus enabling
real-time object recognition for robotic systems. 相似文献