the mixing characteristics of a slurry transport column have been investigated by residence time distribution measurements in a pilot plant scale cold flow unit. the column (3 m high, 0.15 m ID) simulates a slurry rea...
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the mixing characteristics of a slurry transport column have been investigated by residence time distribution measurements in a pilot plant scale cold flow unit. the column (3 m high, 0.15 m ID) simulates a slurry reactor design proposed for the paraffin-olefin alkylation process with zeolite catalysts. the experimental results show that high levels of mixing are achieved in the bottom zone of the column through an especially designed slurry distributor, while the overall column response can approach the desired well-mixed behavior at sufficiently high recycle ratios. the effect of various process parameters, such as the paraffin-to-olefin ratio, the catalyst holdup, and the product recycle ratio, on the slurry reactor performance were investigated by computer simulation using a literature kinetic scheme for alkylation with zeolite catalysts. the simulation results suggest that mixing inside the reactor must be further enhanced by additional means, e.g., stagewise addition of olefin, if the catalyst holdup is not to exceed the upper limit for Newtonian behavior. (C) 1999 Elsevier Science Ltd. All rights reserved.
A software package is introduced to aid in the teaching of courses in parallel processing, particularly topics such as software distributed shared memory, memory consistency models, and synchronization mechanisms. the...
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CORBA applications can transparently use service instances running on the client's machine, on the local-area network, or across the Internet. Standard CORBA services help the application locate service instances,...
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CORBA applications can transparently use service instances running on the client's machine, on the local-area network, or across the Internet. Standard CORBA services help the application locate service instances, but do not provide a mechanism to identify service instances that will give good performance. the performanceBroker executes performance test suites on application service instances and selects service instances that will give superior application performance. the Broker weights performance test results according to client-specified criteria to choose the service instances that will provide the best application performance and allocates those service instances to clients. Tests with a distributed ray tracing application show that service instances chosen by the performanceBroker give better performancethan service instances chosen by round-robin or random selection in local-area network and Internet environments.
the paper presents a computerarchitecture Learning and Knowledge Assessment System named the CALKAS. It is a software tool aimed to be used for teaching computerarchitecture and organization. It offers the knowledge...
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Modern scientific computing involves organizing, moving, visualizing, and analyzing massive amounts of data at multiple sites around the world. the technologies, the middleware services, and the architectures that are...
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Modern scientific computing involves organizing, moving, visualizing, and analyzing massive amounts of data at multiple sites around the world. the technologies, the middleware services, and the architectures that are used to build useful high-speed, wide area distributed systems, constitute the field of data intensive computing. In this paper we will describe an architecture for data intensive applications where we use a high-speed distributed data cache as a common element for all of the sources and sinks of data. this cache-based approach provides standard interfaces to a large, application-oriented, distributed, on-line, transient storage system. We describe our implementation of this cache, how we have made it `network aware,' and how we do dynamic load balancing based on the current network conditions. We also show large increases in application throughput by access to knowledge of the network conditions.
CrispORB is a highperformance CORBA that enables low-latency request delivery among cluster nodes connected with System Area Network(SAN) and provides a communication infrastructure for large-scale and high-volume cl...
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CrispORB is a highperformance CORBA that enables low-latency request delivery among cluster nodes connected with System Area Network(SAN) and provides a communication infrastructure for large-scale and high-volume cluster system construction with distributed object-oriented components. Compared with standard IIOP ORBs, CrispORB is be able to reduce the protocol overhead using a System Area Network with intelligent functions for efficient data transfer. CrispORB preserves language mapping specified by COBRA/OMG standards so that component programs written for conventional CORBA could be used without rewriting. CrispORB can manage both SAN and TCP/IP simultaneously, which means the cluster node can communicate with clients via the Internet and with other nodes on the cluster using SAN. Components need not be aware of lower connections because CrispORB selects the transport between SAN and TCP/IP automatically. We selected the VI architecture to use SAN's communication functions, which are proposed as an industrial standard API for SAN. CrispORB will be portable onto various types of SANs. We have integrated VIA buffer management and CDR(Common Data Representation) format processing to reduce data movement cost. CrispORB was developed based on INTERSTAGE/ObjectDirector (Fujitsu's CORBA product) and Synfinity-O(Fujitsu's SAN).
this article describes a new re-configurable architecture design suitable for highperformance signal processing applications. the main benefits beside re-configurability are high computation performance, robustness a...
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Applications designed to execute on `computational grids' frequently require the simultaneous co-allocation of multiple resources in order to meet performance requirements. For example, several computers and netwo...
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Applications designed to execute on `computational grids' frequently require the simultaneous co-allocation of multiple resources in order to meet performance requirements. For example, several computers and network elements may be required in order to achieve real-time reconstruction of experimental data, while a large numerical simulation may require simultaneous access to multiple supercomputers. Motivated by these concerns, we have developed a general resource management architecture for Grid environments, in which resource co-allocation is an integral component. In this paper, we examine the co-allocation problem in detail and present mechanisms that allow an application to guide resource selection during the co-allocation process;these mechanisms address issues relating to the allocation, monitoring, control, and configuration of distributed computations. We describe the implementation of co-allocators based on these mechanisms and present the results of microbenchmark studies and large-scale application experiments that provide insights into the costs and practical utility of our techniques.
Withthe increasing number of scientific applications manipulating huge amounts of data, effective data management is an increasingly important problem. Unfortunately, so far the solutions to this data management prob...
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Withthe increasing number of scientific applications manipulating huge amounts of data, effective data management is an increasingly important problem. Unfortunately, so far the solutions to this data management problem either require deep understanding of specific storage architectures and file layouts (as in high-performance file systems) or produce unsatisfactory I/O performance in exchange for ease-of-use and portability (as in relational DBMSs). In this paper we present a new environment which is built around an active meta-data management system (MDMS). the key components of our three-tiered architecture are user application, the MDMS, and a hierarchical storage system (HSS). Our environment overcomes the performance problems of pure database-oriented solutions, while maintaining their advantages in terms of ease-of-use and portability. the high levels of performance are achieved by the MDMS, withthe aid of user-specified directives. Our environment supports a simple, easy-to-use yet powerful user interface, leaving the task of choosing appropriate I/O techniques to the MDMS. We discuss the importance of an active MDMS and show how the three components, namely application, the MDMS, and the HSS, fit together. We also report performance numbers from our initial implementation and illustrate that significant improvements are made possible without undue programming effort.
the project is a digital architectural visualization of an individual's physiological data in real time. It is both a probing and representational system that brings together science and art through architectural ...
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