For the case of infinitely large apertures the followiug probability distributions are derived in this paper: the probability of finding a ray at the nth lens at a distance r from the axis, the probability of finding ...
详细信息
For the case of infinitely large apertures the followiug probability distributions are derived in this paper: the probability of finding a ray at the nth lens at a distance r from the axis, the probability of finding a ray with an amplitude A at lens n, the cumulative probability of finding a ray with a displacement less than r and the cumulative probability of finding a ray with an amplitude less than A. The case of lenses with finite apertures was explored with the help of computer simulated experiments whose results are given. These experiments show that the probability distributions for the ray amplitudes which were derived for infinite apertures are still useful even in the case of lenses with finite apertures as long as the probability of losing the ray is less than 20 percent.
We present private secure coded computation that ensures both the master's privacy and data security against the workers, where the master aims to compute a function of its private data and a specific data in a li...
详细信息
We present private secure coded computation that ensures both the master's privacy and data security against the workers, where the master aims to compute a function of its private data and a specific data in a library exclusively owned by the external workers. For privacy, the master should conceal the index of the specific data in the library against the workers. For security, the master should encrypt its private data. As an achievable scheme, we propose private secure polynomial codes and compare the proposed scheme with private polynomial codes in private coded computation and the optimal scheme of robust private information retrieval (RPIR).
Coded computation has attracted great interests as a promising technique to cope with straggling computing nodes in mobile edge computing (MEC) networks. Contrary to the existing coded computation schemes developed wi...
详细信息
Coded computation has attracted great interests as a promising technique to cope with straggling computing nodes in mobile edge computing (MEC) networks. Contrary to the existing coded computation schemes developed with a fixed network topology, this paper studies a MDS coded computation for random networks. Specifically, we put forth maximum distance separable (MDS) coded task offloading and investigate its MDS coded computing gain by deriving the average successful retrieval probability with stochastic geometry in random wireless edge computing networks, where it encodes the original task into multiple equal and small sized MDS coded sub-tasks and offloads their subset to edge computing nodes for computation. We also identify a tradeoff between the latency in processing a sub-task at an edge node and the minimal number of edge nodes required to retrieve the original task output, according to the size of MDS coded sub-tasks. To efficiently control the tradeoff, we determine the desirable size of MDS coded sub-tasks in a semi-closed form to maximize the average successful retrieval probability for regime 1 and regime 2 networks, which correspond to the cases that communication latency is negligible compared to computation latency and that computation latency is negligible compared to communication latency, respectively, and develop an efficient algorithm with low search complexity for a general environment. Our numerical results reveal that the proposed scheme outperforms the other conventional task offloading schemes such as partial task offloading and replication task offloading in terms of average successful retrieval probability.
The National Fusion Collaboratory (NFC) project was created to advance scientific understanding and innovation in magnetic fusion research by enabling more efficient use of existing experimental facilities through mor...
详细信息
The National Fusion Collaboratory (NFC) project was created to advance scientific understanding and innovation in magnetic fusion research by enabling more efficient use of existing experimental facilities through more effective integration of experiment, theory, and modeling. To achieve this objective, NFC introduced the concept of "network services", which build on top of computational Grids, and provide Fusion codes, together with their maintenance and hardware resources as a service to the community. This mode of operation requires the development of new authorization and enforcement capabilities. In addition, the nature of Fusion experiments places strident quality of service requirements on codes run during the experimental cycle. In this paper, we describe Grid computing requirements of the Fusion community, and present our first experiments in meeting those requirements. Published by Elsevier Science B.V.
A water-loaded, indirectly cooled wavegnide antenna with a small aperture size (2 x 5.5 cm/sup 2/) has been developed for local hyperthermia applications. The operation frequency is 432 MHz. The indirect cooling is ac...
详细信息
A water-loaded, indirectly cooled wavegnide antenna with a small aperture size (2 x 5.5 cm/sup 2/) has been developed for local hyperthermia applications. The operation frequency is 432 MHz. The indirect cooling is achieved by circulating water in an external chamber having common walls with the waveguide, and good thermal and electrical stability is achieved for radiation powers up to 100 W. The water loading provides a good coupling of the radiated power into tissue. The observed variations in standing wave ratios and the concentration of the specific absorption rates (SAR's) are found to be satisfactory for localized superficial hyperthermia treatments. The matching of the water-loaded antenna into the power generator requires special attention because of two possible matting conditions corresponding to high- and low-power dissipations inside the antenna cavity. SAR distributions inside tissues have been computed and compared with thermographic measurements performed in phantoms. Preliminary results of trials in Wistar rats transplanted with Walker sarcoma are also reported.
This note reports an interesting kind of partition, called an s-partition, for a natural number n. Each cell in an s-partition has an element of the form 2(r) - 1. We give a recurrence relation to enumerate all s-part...
详细信息
This note reports an interesting kind of partition, called an s-partition, for a natural number n. Each cell in an s-partition has an element of the form 2(r) - 1. We give a recurrence relation to enumerate all s-partitions of it and also derive an upper bound on the number of possible s-partitions. We define a relation of domination to get a lexical order on s-partitions and show that a unique partition, called d-partition, dominates all other s-partitions of n. A d-partition has the smallest cardinality of O(log n) and can be generated in O(log n) steps. A d-partition may have a potential application in cryptography as we demonstrate its use in a distributed algorithm to compute a(n) mod m, a key computation intensive step in many cryptographic algorithms. (C) 1999 Elsevier Science B.V. All rights reserved.
Given a set of nodes in a distributed system, a coterie is a collection of subsets of the set of nodes such that any two subsets have a nonempty intersection and are not properly contained in one another. A subset of ...
详细信息
Given a set of nodes in a distributed system, a coterie is a collection of subsets of the set of nodes such that any two subsets have a nonempty intersection and are not properly contained in one another. A subset of nodes in a coterie is called a quorum. Coteries may be used to implement a distributed mutual exclusion algorithm which gracefully tolerates node and communication line failures. Two types of coteries exist: dominated and nondominated. In this paper, we introduce an algorithm, called the join algorithm, which takes nonempty coteries, as input, and returns a new, larger coterie. The new coterie is called a composite coterie. We prove that a composite coterie is nondominated if and only if the input coteries are nondominated. Using the algorithm, dominated or nondominated coteries may be easily constructed for a large number of nodes. Then, we present an efficient method for determining whether a given set of nodes contains a quorum of a composite coterie. The test does not require that the quorums of a composite coterie be computed in advance. As an example, we generalize tree coteries, using the join algorithm, and prove that tree coteries are nondominated. Finally, we show that the join algorithm may be used to generate read and write quorums which may be used by a replica control protocol.
Ultrahigh Q, X-band resonators, used in a frequency discriminator for stabilization of a low-noise signal generator, can provide a means of obtaining significant reduction in phase noise levels. Resonator unloaded Qs ...
详细信息
Ultrahigh Q, X-band resonators, used in a frequency discriminator for stabilization of a low-noise signal generator, can provide a means of obtaining significant reduction in phase noise levels. Resonator unloaded Qs on the order of 500 K can be obtained in a sapphire dielectric resonator (DR) operating on a low-order (i.e., TE01) mode at 77 K and employing high-temperature superconducting (HTS) films installed in the DR enclosure covers. Rigorous analysis for the determination of resonator frequency, modes, and unloaded Q have been carried out using mode matching techniques. Trade-off studies have been performed to select resonator dimensions for the optimum mode yielding highest unloaded Q and widest spurious mode separation. Field distributions within the resonator have been computed to enable practical excitation of the required mode. The results of both analysis and prototype device evaluation experiments are compared for resonators fabricated using enclosures consisting of conventional, metal sidewalls and covers employing high-temperature superconducting films as a function of cover (i.e., HTS film) conductivity.
Electromagnetic Fields (EMFs) have been studied and used for a long time. The past decades have seen a tremendous increase of applications of EMF in daily life. A particularly prevalent application is formed by wirele...
详细信息
Electromagnetic Fields (EMFs) have been studied and used for a long time. The past decades have seen a tremendous increase of applications of EMF in daily life. A particularly prevalent application is formed by wireless personal communication devices, e.g., mobile phones with currently more than five billion users worldwide. Large efforts have been expended to develop tools and methods that can be used to design EMF systems, to manage their performance, capabilities, quality, efficiency, compatibility, as well as to ensure that they comply with safety standards. Taking advantage of improvements in computer performance, efficient numerical methods continue to be developed that are being used to predict or characterize the EMF. In addition, particularly significant advances in software implementation and in experimental setups and techniques have 'been achieved during the past 15 years. Today, computers are capable of handling physically and electrically large problems, almost without limitations, thanks to distributed computing.
A pair of closely spaced dielectric prisms used as an adjustable bidirectional coupler has been discussed by a number of investigators. In its simplest form this device permits an adjustable arbitrary distribution of ...
详细信息
A pair of closely spaced dielectric prisms used as an adjustable bidirectional coupler has been discussed by a number of investigators. In its simplest form this device permits an adjustable arbitrary distribution of power output in two directions at right angles to one another. Reflections from the external air-dielectric interfaces change the power distribution from the theoretically computed values and resuft in power output in a third direction. This paper describes a theoretical calculation of the power transmission in all four directions taking into account reflections at all interfaces. Experimental data recorded at 35 Gc exhibit very good agreement with predicted results.
暂无评论