Nobutoshi Sagawa

Dynamic Gateways: A Novel Approach to Improve Networking Performance and Availability on Parallel Servers

Parallel servers realize scalability and availability by effectively using multiple hardware resources (i.e., nodes and disks). Scalability is improved by distributing processes and data onto multiple resources; and availability is maintained by substituting a failed resource with a spare one. Dynamic Gateways extends these features to networking, by balancing the traffic among multiple connections to the network in order to improve scalability, and detours traffic around failed resources to maintain availability. This is made transparent to the clients and to applications in the server by using proxy and gratuitous ARP to control the network traffic. A performance evaluation shows that Dynamic Gateways improves the scalability (allowing the maximum networking performance to increase with increasing number of connections) and the performance (improving throughput and reducing access latency).

IC tag based traceability: system and solutions

An increasing number of companies want to improve product traceability for several reasons: to meet stricter government regulations about food and medical safety, to cope with ever-stronger consumer demands to know exactly what they are buying, and to improve and protect the companys brand value through more transparent business operations. Two aspects of traceability are technically important: (1) techniques for tracing the events associated with the goods a company handles at all necessary points of the business operation, possibly through the use of IC tags and tag readers: and (2) ways to store, manage, and use the collected logs of events either to cope with problems or to improve business processes. In this paper, we first review currently available traceability systems by considering examples from real-world situations. After that, we discuss the likely directions and possibilities of next-generation traceability systems.

Solution functions of PDEQSOL (Partial differential EQuation SOlver language) for fluid problems

No abstract available

Simulation of the eddy current in the thermal flying height control slider

This paper investigates the alternating current (AC) current induced eddy current in the thermal flying height control slider. The effects of the current frequency on the temperature rise and thermal protrusion of the slider are studied. Using the developed simulation method, the flying performance of the TFC slider at input AC current is also investigated.

SUPRA: a sampling-query optimization method for large-scale OLAP

Relational online analytical processing (ROLAP) reduces the amount of storage required for maintaining various sizes of data cubes by materializing only parts of them in a lazy evaluation manner. In ROLAP however, cube creation queries need to be issued repeatedly in order to search for useful features (i.e. rules or patterns) within large scale databases. The cube creation cost can be a bottleneck in the whole ROLAP processing. The cost of the queries can be effectively reduced by estimating the query results using samples. To maintain the accuracy of ROLAP even when using samples, the samples need to be extracted in an appropriate unit. However, conventional query optimization methods only support record based sampling and cannot be applied for complex queries that have other sampling units, such as the ones that include grouping aggregate operations. We develop a query optimization method named SUPRA that preserves the sampling unit used in random data extraction. The method is designed to preserve both the sampling unit and the randomness of the sampling operation. Using this method, typical ROLAP queries can be transformed into more efficient ones than those obtained through conventional methods.