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761.
Abstract. The problem is that of determining the parameters in a trigonometric polynomial when it is observed with added stationary noise. The frequencies, in particular, must be determined and the situation especially considered is that where these are close together. A similar problem arises if an angular frequency is close to zero or π. The method of estimation is the maximization of the regression sum of squares as a function of the unknown frequencies. In the asymptotic theory, the closely adjacent frequencies are separated by an amount that is of the order T-1 , where T is the length of the series. Simulations show that this asymptotic treatment gives a better approximation in cases where the separation is of this magnitude than that obtained by treating the frequencies as fixed. 相似文献
762.
We describe a compiler and run-time system that allow data-parallel programs to execute on a network of heterogeneous UNIX workstations. The programming language supported is Dataparallel C, a SIMD language with virtual processors and a global name space. This parallel programming environment allows the user to take advantage of the power of multiple workstations without adding any message-passing calls to the source program. Because the performance of Individual workstations in a multi-user environment may change during the execution of a Dataparallel C program, the run-time system automatically performs dynamic load balancing. We present experimental results that demonstrate the usefulness of dynamic load-balancing In a multi-user environment These results suggest that initially allocating the same amount of work to each processor and letting the dynamic load balancing algorithm adjust the load during program execution yields very good performance. Hence neither the compiler nor the run-time system need a priori knowledge of the speeds of the machines that will participate in a program execution. 相似文献
763.
Identifying changes in the nanoscopic domain is a key challenge in the physicochemical sciences, where great interest is on sensing complex processes that involve cellular biochemical reactions, chemical heterogeneities, contact forces, and other interfacial phenomena. This has stimulated the development of diverse materials that allow subtle nanoscopic environments to be "seen". The challenge in the nano-domain has always been the ability to sense changes on the minute scale and rapidly transduce the information out for macroscopical observation. Ideally, materials should inform when processes are occurring. Recently, new systems that leverage established concepts with fluorescence- and plasmonic-based sensing have been devised, which has reinvigorated the domain, where functional polymers coupled in specific architectures to transducing motifs allow for a new basis of messenger materials to be realized. The key aspect in this regard is that the polymers allow for sensing to be achieved only when they are carefully coupled to the amplification system. In this perspective, the role of specific functional polymer architectures for the realization of nano-to-macro sensing of subtle nano-messengers is discussed and where the exciting field of messenger materials is seen moving forward is pointed out. 相似文献