The Experts below are selected from a list of 100227 Experts worldwide ranked by ideXlab platform
R.i. Macdonald - One of the best experts on this subject based on the ideXlab platform.
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Modeling of optoelectronic switch with PIN photodiode and GaAs MESFET transmission gate
IEEE Transactions on Electron Devices, 1996Co-Authors: R.i. MacdonaldAbstract:A broadband and high-Isolation optoelectronic switch, which consists of a PIN photodiode and a GaAs MESFET in common gate configuration as a transmission gate, was theoretically and experimentally investigated. An analytical model has been developed to calculate the Isolation Level of the switch. The influences on the Isolation Level from different device parameters were studied. Experimental results obtained using commercial components validate the operation of the proposed switch. Measured Isolation of 70 dB at 300 kHz and 55 dB up to 1.0 GHz were achieved. Good agreement has been obtained between the measured and calculated results and therefore the model developed has been validated.
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Analysis and experimental demonstration of a very high Isolation optoelectronic switch with p‐i‐n photodiode and GaAs mesfet transmission gate
Microwave and Optical Technology Letters, 1995Co-Authors: R.i. MacdonaldAbstract:An optoelectronic switch with very high Isolation and bandwidth from dc to microwave frequency range is demonstrated both theoretically and experimentally. The switch consists of a p-i-n photodiode and a GaAs MESFET in a common gate configuration as a transmission gate. An analytical expression is derived to calculate the Isolation Level of the switch. Measured Isolation Levels of 70 dB at 300 KHz and 55 dB up to 1.0 GHz were obtained for the proposed optoelectronic switch. © 1995 John Wiley & Sons, Inc.
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Very high Isolation optoelectronic switch using PIN-PD and GaAs MESFET transmission gate
1994 IEEE MTT-S International Microwave Symposium Digest (Cat. No.94CH3389-4), 1994Co-Authors: R.i. MacdonaldAbstract:A novel broadband optoelectronic switch is demonstrated experimentally with very high Isolation. The switch consists of a switching PIN photodiode followed by a GaAs MESFET in common gate configuration as a transmission gate. Isolation Level higher than 70.0 dB at DC and 55.0 dB at 1.0 GHz was obtained, respectively.
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An optoelectronic switching matrix with high Isolation
Journal of Lightwave Technology, 1992Co-Authors: M. Veilleux, R.i. MacdonaldAbstract:A high-Isolation (60 dB) 10*10 optoelectronic switch matrix with surface-depleted photoconductive crosspoints is reported. The device is designed for a bandwidth greater than 1 GHz and an Isolation Level greater than 60 dB. Ten 1.8-GHz channels are supported with 0-dB insertion loss and >125 dB/Hz dynamic range. The novel crosspoints require reliability improvement because they are unstable. >
J Gonzalez R De Mendivil - One of the best experts on this subject based on the ideXlab platform.
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SIRC, a multiple Isolation Level protocol for middleware-based data replication
2007 22nd international symposium on computer and information sciences, 2007Co-Authors: R. Salinas, J. M. Bernabé-gisbert, José Enrique Armendáriz-iñigo, Francesc D. Muñoz-escoí, J Gonzalez R De MendivilAbstract:One of the weaknesses of database replication protocols, compared to centralized DBMSs, is that they are unable to manage concurrent execution of transactions at different Isolation Levels. In the last years, some theoretical works related to this research line have appeared but none of them has proposed and implemented a real replication protocol with support to multiple Isolation Levels. This paper takes advantage of our MADIS middleware and one of its implemented Snapshot Isolation protocols to design and implement SIRC, a protocol that is able to execute concurrently both generalized snapshot Isolation (GSI) and generalized loose read committed (GLRC) transactions. We have also made a performance analysis to show how this kind of protocols can improve the system performance and decrease the transaction abortion rate in applications that do not require the strictest Isolation Level in every transaction.
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managing transaction conflicts in middleware based database replication architectures
Symposium on Reliable Distributed Systems, 2006Co-Authors: F Munozesco, J Placivera, M I Ruizfuertes, Luis Irunbriz, H Decker, Jose Enrique Armendarizinigo, J Gonzalez R De MendivilAbstract:Database replication protocols need to detect, block or abort part of conflicting transactions. A possible solution is to check their writesets (and also their readsets in case a serialisable Isolation Level is requested), which however burdens the consumption of CPU time. This gets even worse when the replication support is provided by a middleware, since there is no direct DBMS support in that layer. We propose and discuss the use of the concurrency control support of the local DBMS for detecting conflicts between local transactions and writesets of remote transactions. This allows to simplify many database replication protocols and to enhance their performance.
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SRDS - Managing Transaction Conflicts in Middleware-based Database Replication Architectures
2006 25th IEEE Symposium on Reliable Distributed Systems (SRDS'06), 2006Co-Authors: F. D. Munoz-esco ´, H Decker, J. Pla-civera, M. I. Ruiz-fuertes, Luis Irún-briz, José Enrique Armendáriz-iñigo, J Gonzalez R De MendivilAbstract:Database replication protocols need to detect, block or abort part of conflicting transactions. A possible solution is to check their writesets (and also their readsets in case a serialisable Isolation Level is requested), which however burdens the consumption of CPU time. This gets even worse when the replication support is provided by a middleware, since there is no direct DBMS support in that layer. We propose and discuss the use of the concurrency control support of the local DBMS for detecting conflicts between local transactions and writesets of remote transactions. This allows to simplify many database replication protocols and to enhance their performance.
Philip M. Lewis - One of the best experts on this subject based on the ideXlab platform.
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Correct execution of transactions at different Isolation Levels
IEEE Transactions on Knowledge and Data Engineering, 2004Co-Authors: Arthur J. Bernstein, Philip M. LewisAbstract:Many transaction processing applications execute at Isolation Levels lower than SERIALIZABLE in order to increase throughput and reduce response time. However, the resulting schedules might not be serializable and, hence, not necessarily correct. The semantics of a particular application determines whether that application will run correctly at a lower Level and, in practice, it appears that many applications do. The decision to choose an Isolation Level at which to run an application and the analysis of the correctness of the resulting execution is usually done informally. We develop a formal technique to analyze and reason about the correctness of the execution of an application at Isolation Levels other than SERIALIZABLE. We use a new notion of correctness, semantic correctness, a criterion weaker than serializability, to investigate correctness. In particular, for each Isolation Level, we prove a condition under which the execution of transactions at that Level will be semantically correct. In addition to the ANSI/ISO Isolation Levels of READ UNCOMMITTED, READ COMMITTED, and REPEATABLE READ, we also prove a condition for correct execution at the READ-COMMITTED with first-committer-wins and at SNAPSHOT Isolation. We assume that different transactions in the same application can be executing at different Levels, but that each transaction is executing at least at READ UNCOMMITTED.
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ICDE - Semantic conditions for correctness at different Isolation Levels
Proceedings of 16th International Conference on Data Engineering (Cat. No.00CB37073), 1Co-Authors: Arthur J. Bernstein, Philip M. LewisAbstract:Many transaction processing applications execute at Isolation Levels lower than serializable in order to increase throughput and reduce response time. The problem is that non-serializable schedules are not guaranteed to be correct for all applications. The semantics of a particular application determines whether that application will run correctly at a lower Isolation Level, and in practice it appears that many applications do. Unfortunately, we know of an analysis technique that has been developed to test an application for its correctness at a particular Level. Apparently decisions of this nature are made on an informal basis. In this paper we describe such a technique in a formal way. We use a new definition of correctness, semantic correctness, which is weaker than serializability, to investigate the correctness of such executions. For each Isolation Level, we prove a condition under which transactions that execute at that Level will be semantically correct. In addition to the ANSI/ISO Isolation Levels of read uncommitted, read committed, and repeatable read, we also prove a condition for correct execution at the read committed with first-committer-wins (a variation of read committed) and at the snapshot Isolation Level. We assume that different transactions can be executing at different Isolation Levels, but that each transaction is executing at least at the read uncommitted Level.
Makoto Ando - One of the best experts on this subject based on the ideXlab platform.
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A Small Package With 46-dB Isolation Between Tx and Rx Antennas Suitable for 60-GHz WPAN Module
IEEE Transactions on Microwave Theory and Techniques, 2012Co-Authors: Ryosuke Suga, Yasutake Hirachi, Jiro Hirokawa, Hiroshi Nakano, Makoto AndoAbstract:A small package suitable for the mobile terminals of the 60-GHz wireless personal area network is proposed. Two antennas for Tx and Rx are integrated in the package. The antenna provides the end-fire radiation from the side face of the substrate. The package is mounted on the edge of a printed circuit board by using the ball grid array assembly. The antenna is composed of a post-wall waveguide and a slab waveguide with metal sidewalls. The gain and beamwidth are determined by the size of the slab waveguide. The sidewalls are for the design of the beamwidth in the -plane and for realizing the high Isolation between Tx and Rx antennas. The beamwidths of the fabricated antenna were measured to be 47° and 46° in the - and -plane at 60 GHz, respectively. The gain more than 7.8 dBi was measured in the frequency range from 59 to 66 GHz. The package was fabricated for the evaluation of the Isolation. The measured average Isolation Level between Tx and Rx antenna was 46.0 dB in the frequency range above. The antenna characteristics and Isolation Level are sufficient for the 60-GHz WPAN system.
Arthur J. Bernstein - One of the best experts on this subject based on the ideXlab platform.
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Correct execution of transactions at different Isolation Levels
IEEE Transactions on Knowledge and Data Engineering, 2004Co-Authors: Arthur J. Bernstein, Philip M. LewisAbstract:Many transaction processing applications execute at Isolation Levels lower than SERIALIZABLE in order to increase throughput and reduce response time. However, the resulting schedules might not be serializable and, hence, not necessarily correct. The semantics of a particular application determines whether that application will run correctly at a lower Level and, in practice, it appears that many applications do. The decision to choose an Isolation Level at which to run an application and the analysis of the correctness of the resulting execution is usually done informally. We develop a formal technique to analyze and reason about the correctness of the execution of an application at Isolation Levels other than SERIALIZABLE. We use a new notion of correctness, semantic correctness, a criterion weaker than serializability, to investigate correctness. In particular, for each Isolation Level, we prove a condition under which the execution of transactions at that Level will be semantically correct. In addition to the ANSI/ISO Isolation Levels of READ UNCOMMITTED, READ COMMITTED, and REPEATABLE READ, we also prove a condition for correct execution at the READ-COMMITTED with first-committer-wins and at SNAPSHOT Isolation. We assume that different transactions in the same application can be executing at different Levels, but that each transaction is executing at least at READ UNCOMMITTED.
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Semantic correctness of transactions and workflows
2002Co-Authors: Arthur J. BernsteinAbstract:Serializability is the correctness criterion generally used in the literature to determine a schedule's correctness. Such a criterion is clearly inappropriate, however, in determining the correctness of schedules that are produced when an application is run at an Isolation Level lower than SERIALIZABLE since such schedules might no longer be serializable. In this dissertation, using semantic-correctness criterion, we prove a condition for each Isolation Level under which transactions that execute at that Level will be semantically correct. We also apply the semantic-correctness theory to automatic workflow verification and generation problems. In particular, we propose a new workflow model that allows one to: (1) automatically check if the desired outcome of a workflow can be produced by its actual implementation, (2) automatically synthesize a workflow implementation from a workflow specification and a given task library. Finally, we present several preliminary theoretical results for the completeness of a task library and the realizability of a workflow postcondition.
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ICDE - Semantic conditions for correctness at different Isolation Levels
Proceedings of 16th International Conference on Data Engineering (Cat. No.00CB37073), 1Co-Authors: Arthur J. Bernstein, Philip M. LewisAbstract:Many transaction processing applications execute at Isolation Levels lower than serializable in order to increase throughput and reduce response time. The problem is that non-serializable schedules are not guaranteed to be correct for all applications. The semantics of a particular application determines whether that application will run correctly at a lower Isolation Level, and in practice it appears that many applications do. Unfortunately, we know of an analysis technique that has been developed to test an application for its correctness at a particular Level. Apparently decisions of this nature are made on an informal basis. In this paper we describe such a technique in a formal way. We use a new definition of correctness, semantic correctness, which is weaker than serializability, to investigate the correctness of such executions. For each Isolation Level, we prove a condition under which transactions that execute at that Level will be semantically correct. In addition to the ANSI/ISO Isolation Levels of read uncommitted, read committed, and repeatable read, we also prove a condition for correct execution at the read committed with first-committer-wins (a variation of read committed) and at the snapshot Isolation Level. We assume that different transactions can be executing at different Isolation Levels, but that each transaction is executing at least at the read uncommitted Level.
