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961.
Long lines of periodic hole structures were produced on a gold film, a glass slide and polystyrene by laser ablation using interfering femtosecond lasers split by a transmission grating. An optical system comprising a cylindrical lens added to an imaging system with a transmission grating was used to obtain the interference of two beams along a long length, and high laser fluence was used to achieve laser ablation. The separation of each hole was 6.25 m, and the total length of the structure produced reached 6 mm, which is longest periodic structure produced by a shot of femtosecond laser. PACS 42.62.-b; 07.60.Ly; 42.40.Eq 相似文献
962.
963.
In modern magnetic resonance imaging (MRI), patients are exposed to strong, nonuniform static magnetic fields outside the central imaging region, in which the movement of the body may be able to induce electric currents in tissues which could be possibly harmful. This paper presents theoretical investigations into the spatial distribution of induced electric fields and currents in the patient when moving into the MRI scanner and also for head motion at various positions in the magnet. The numerical calculations are based on an efficient, quasi-static, finite-difference scheme and an anatomically realistic, full-body, male model. 3D field profiles from an actively shielded 4T magnet system are used and the body model projected through the field profile with a range of velocities. The simulation shows that it possible to induce electric fields/currents near the level of physiological significance under some circumstances and provides insight into the spatial characteristics of the induced fields. The results are extrapolated to very high field strengths and tabulated data shows the expected induced currents and fields with both movement velocity and field strength. 相似文献
964.
Guoen Hu 《Journal of Mathematical Analysis and Applications》2003,283(2):351-361
boundedness is considered for the commutator of higher-dimensional Marcinkiewicz integral. Some conditions implying the and the boundedness for the commutator of the Marcinkiewicz integral are obtained. 相似文献
965.
We study a processing system comprised of parallel queues, whose individual service rates are specified by a global service mode (configuration). The issue is how to switch the system between various possible service modes, so as to maximize its throughput and maintain stability under the most workload-intensive input traffic traces (arrival processes). Stability preserves the job inflow–outflow balance at each queue on the traffic traces. Two key families of service policies are shown to maximize throughput, under the mild condition that traffic traces have long-term average workload rates. In the first family of cone policies, the service mode is chosen based on the system backlog state belonging to a corresponding cone. Two distinct policy classes of that nature are investigated, MaxProduct and FastEmpty. In the second family of batch policies (BatchAdapt), jobs are collectively scheduled over adaptively chosen horizons, according to an asymptotically optimal, robust schedule. The issues of nonpreemptive job processing and non-negligible switching times between service modes are addressed. The analysis is extended to cover feed-forward networks of such processing systems/nodes. The approach taken unifies and generalizes prior studies, by developing a general trace-based modeling framework (sample-path approach) for addressing the queueing stability problem. It treats the queueing structure as a deterministic dynamical system and analyzes directly its evolution trajectories. It does not require any probabilistic superstructure, which is typically used in previous approaches. Probability can be superposed later to address finer performance questions (e.g., delay). The throughput maximization problem is seen to be primarily of structural nature. The developed methodology appears to have broader applicability to other queueing systems. 相似文献
966.
Lp(Rm × Rn) boundedness is considered for the multiple Marcinkiewicz integral. Some size conditions implying the LP(Rm × Rn) boundedness of the multiple Marcinkiewicz integral for some fixed 1 < p <∞ are obtained. 相似文献
967.
Sharp Function Estimates and Weighted Norm Inequalities for Multilinear Singular Integral Operators 总被引:1,自引:0,他引:1
A sharp function estimate is established for multilinear singularintegral operators. As applications, some weighted norm inequalitiesare obtained for such operators. 2000 Mathematics Subject Classification42B20. 相似文献
968.
Gejza Jenca Sylvia Pulmannová 《Proceedings of the American Mathematical Society》2003,131(9):2663-2671
We prove that for every orthocomplete effect algebra the center of forms a complete Boolean algebra. As a consequence, every orthocomplete atomic effect algebra is a direct product of irreducible ones.
969.
Qing-xuYan Hui-chaoZou De-xingFeng 《应用数学学报(英文版)》2003,19(2):239-246
In this paper, the stabilization problem of nonuniform Timoshenko beam by some nonlinear boundary feedback controls is considered. By virtue of nonlinear semigroup theory, energy-perturbed approach and exponential multiplier method, it is shown that the vibration of the beam under the proposed control actiondecays exponentially or in negative power of time t as t→∞. 相似文献
970.
H.-P. Butzmann 《Applied Categorical Structures》2001,9(4):365-368
In this paper we construct complete, regular convergence vector spaces E and F such that c(E,F), the space of all continuous linear mappings from E to F, endowed with the continuous convergence structure, is not complete. 相似文献