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Josephson Voltage Metrology for Watt Balance Experiments at NIST

Tang Y.-H.

Measurement Automation Monitoring

2016

Vol. 62, No. 2

42--45

The Planck constant, h, is one of the seven fundamental constants proposed to redefine the SI. It has been measured by the watt balance experiments since the 1980s. In its early days, the watt balance experiment played a vital role in determining the Josephson constant KJ-90 which was adopted internationally on January 1, 1990. The development of Josephson technology, especially the implementation of the Programmable Josephson Voltage Standard (PJVS) in voltage metrology has improved the uncertainty of voltage measurement in the watt balance experiment by more than two orders of magnitude. The Josephson voltage measurement in the watt balance experiment plays an important role in the proposed SI redefinition based on a set of fundamental constants. This paper will describe a brief history from the original NIST-1 watt balance in 1980s up to the most recent development of the NIST-4 watt balance. We will also discuss the role of voltage metrology in the watt balance experiments and the impact of the SI redefinition to the voltage metrology in the future.

Opportunity Cost Model of the Task Scheduling in Heterogeneous Systems

Zhang B.-D., Tang Y.-H., Wu J.-J., Xu S.

Przegląd Elektrotechniczny

2012

R. 88, nr 9b

177-180

With the micro-electronics technology has encountered a bottleneck, adding heterogeneous core has become the primary means of increasing processor speed. However, how to assign heterogeneous processor to maximize the performance becomes an urgent problem. The problem has been proved to be NP-complete problem, i.e. it cannot find the optimal solution in polynomial time. This article draws on the idea of the economy, given the concept of opportunity cost in heterogeneous systems, and were analyzed by the opportunity cost model for task scheduling on heterogeneous systems. On this basis, draw the basic principles of a number of task scheduling. Theory and simulation results show that the task assignment algorithm to achieve the desired performance.

Przy projektowaniu układów mikroelektronicznych niejednorodny rdzeń umożliwia zwiększenie szybkości procesora. W artykule przedstawiono ideę uwzględnienia modelu kosztów do projektowania kolejności zadań w systemie niejednorodnym.