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排序方式: 共有235条查询结果,搜索用时 15 毫秒
1.
The harmonic balance method is a technique for the numerical solution of nonlinear analog circuits operating in a periodic, or quasi-periodic, steady-state regime. The method can be used to efficiently derive the continuous-wave response of numerous nonlinear microwave components including amplifiers, mixers, and oscillators. Its efficiency derives from imposing a predetermined steady-state form for the circuit response onto the nonlinear equations representing the network, and solving for the set of unknown coefficients in the response equation. Its attractiveness for nonlinear microwave applications results from its speed and ability to simply represent the dispersive, distributed elements that are common at high frequencies. The last decade has seen the development and application of harmonic balance techniques to model analog circuits, particularly microwave circuits. The first part of this paper reviews the fundamental achievements made during this time. The second part covers the extension of the method to quasi-periodic regimes, optimization analysis, and practical application. A critical assessment of the various types of harmonic balance techniques is given. The different sampling and Fourier transform methods are compared, and numerical speed and precision results are given enabling a quantitative analysis of the merits of the major variants of the harmonic balance technique. Examples of designs which have been modeled using the harmonic balance technique and built both in hybrid and MMIC form are presented. 相似文献
2.
Water extracts of giant foxtail grass inhibited germination and radicle elongation of loblolly pine seed in a laboratory test. Most of the toxic effects came from extracts of dried foxtail tops, with lesser amounts from fresh tops and roots. Soil texture affected the phytotoxicity of the extracts. Eight chemical compounds known to be phytotoxins inSetaria were identified in extracts of foxtail leaves but could not be found in soil samples under the leaves. 相似文献
3.
Multiple forms of a symbol-digit substitution task were used to provide a componential analysis of age differences in coding task performance. The results demonstrated age differences in feature encoding, memory, and visual search. A 2nd experiment was conducted with young adults to investigate a sensory deficit as a locus of age differences. The spatial contrast sensitivity deficit of older adults was simulated on forms by applying a digital filter. Persons in the age-simulated contrast condition performed worse than those in the normal contrast condition. The stimulus degradation effect was linked to visual search speed. The study illustrates the utility of componential analysis and offers direct support for the hypothesis that sensory deficits affect performance on tasks used to assess intelligence (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
4.
Stephen Gilmore L��szl�� G?nczy Nora Koch Philip Mayer Mirco Tribastone D��niel Varr�� 《Software and Systems Modeling》2011,10(3):287-311
Systems based on the service-oriented architecture (SOA) principles have become an important cornerstone of the development
of enterprise-scale software applications. They are characterized by separating functions into distinct software units, called
services, which can be published, requested and dynamically combined in the production of business applications. Service-oriented
systems (SOSs) promise high flexibility, improved maintainability, and simple re-use of functionality. Achieving these properties
requires an understanding not only of the individual artifacts of the system but also their integration. In this context,
non-functional aspects play an important role and should be analyzed and modeled as early as possible in the development cycle.
In this paper, we discuss modeling of non-functional aspects of service-oriented systems, and the use of these models for
analysis and deployment. Our contribution in this paper is threefold. First, we show how services and service compositions
may be modeled in UML by using a profile for SOA (UML4SOA) and how non-functional properties of service-oriented systems can
be represented using the non-functional extension of UML4SOA (UML4SOA-NFP) and the MARTE profile. This enables modeling of
performance, security and reliable messaging. Second, we discuss formal analysis of models which respect this design, in particular
we consider performance estimates and reliability analysis using the stochastically timed process algebra PEPA as the underlying
analytical engine. Last but not least, our models are the source for the application of deployment mechanisms which comprise
model-to-model and model-to-text transformations implemented in the framework VIATRA. All techniques presented in this work
are illustrated by a running example from an eUniversity case study. 相似文献
5.
The prospect for improving the success of ab initio zeolite structure investigations with electron diffraction data is evaluated. First of all, the quality of intensities obtained by precession electron diffraction at small hollow cone illumination angles is evaluated for seven representative materials: ITQ-1, ITQ-7, ITQ-29, ZSM-5, ZSM-10, mordenite, and MCM-68. It is clear that, for most examples, an appreciable fraction of a secondary scattering perturbation is removed by precession at small angles. In one case, ZSM-10, it can also be argued that precession diffraction produces a dramatically improved 'kinematical' data set. There seems to no real support for application of a Lorentz correction to these data and there is no reason to expect for any of these samples that a two-beam dynamical scattering relationship between structure factor amplitude and observed intensity should be valid. Removal of secondary scattering by the precession mode appears to facilitate ab initio structure analysis. Most zeolite structures investigated could be solved by maximum entropy and likelihood phasing via error-correcting codes when precession data were used. Examples include the projected structure of mordenite that could not be determined from selected area data alone. One anomaly is the case of ZSM-5, where the best structure determination in projection is made from selected area diffraction data. In a control study, the zonal structure of SSZ-48 could be determined from selected area diffraction data by either maximum entropy and likelihood or traditional direct methods. While the maximum entropy and likelihood approach enjoys some advantages over traditional direct methods (non-dependence on predicted phase invariant sums), some effort must be made to improve the figures of merit used to identify potential structure solutions. 相似文献
6.
Decision making within many organizations is becoming increasingly complex and difficult to manage. This article describes a technique called "Responsibility Charting" which can be used as a basis for understanding and improving decision making, and for enhancing the quality of communication within an organization. The authors present a case study to illustrate the types of analyses possible with this technique. 相似文献
7.
Bowfield A Barrett DA Alexander MR Ortori CA Rutten FM Salter TL Gilmore IS Bradley JW 《The Review of scientific instruments》2012,83(6):063503
The authors report on a modified micro-plasma assisted desorption/ionisation (PADI) device which creates plasma through the breakdown of ambient air rather than utilising an independent noble gas flow. This new micro-PADI device is used as an ion source for ambient mass spectrometry to analyse species released from the surfaces of polytetrafluoroethylene, and generic ibuprofen and paracetamol tablets through remote activation of the surface by the plasma. The mass spectra from these surfaces compare favourably to those produced by a PADI device constructed using an earlier design and confirm that the new ion source is an effective device which can be used to achieve ambient mass spectrometry with improved spatial resolution. 相似文献
8.
Jack Gilmore 《集成电路应用》2009,(10):36-38
新一代无变压器技术降低了电力集成商(integrators)和公用电力事业机构的系统复杂性,针对两种最常见的大型光伏安装项目——大楼逆变器直接连接项目和用于并网发电输电的公用安装项目,该技术最大限度地提高了其电力传输能力。 相似文献
9.
Kamal J. K. Gandhi Daniel W. Gilmore Robert A. Haack Steven A. Katovich Steven J. Krauth William J. Mattson John C. Zasada Steven J. Seybold 《Journal of chemical ecology》2009,35(12):1384-1410
From 2000 through 2003 we used semiochemical-baited traps in northeastern Minnesota, USA, to assess changes in assemblages
of subcortical forest insects after a catastrophic wind storm in 1999 and subsequent (1999–2000) fuel-reduction activities
(salvage-logging and prescribed-burning). We determined the regional efficacy of fifteen semiochemical blends (pheromones
and kairomones) as attractants for target and non-target subcortical insect species (Coleoptera: Anthribidae, Buprestidae,
Cerambycidae, Cleridae, Cucujidae, Curculionidae, Histeridae, Nemonychidae, Salpingidae, Scolytidae, Tenebrionidae, and Hymenoptera:
Siricidae). During the four summers, we trapped 86,471 subcortical insects (143 species) in baited and unbaited Lindgren funnel
traps, and 500 beetles (44 species) in baited and unbaited pitfall traps. We report 23 new state collection records of subcortical
insects from Minnesota. Trap catches of subcortical insects were greatest in the wind-disturbed areas 2 years after the event,
and declined thereafter. Similar trends were observed for subcortical insects in the burned areas. Both wind-disturbance and
burning increased the subcortical insect species richness and diversity on the landscape. The subcortical insect species compositions
of the salvaged and burned forest areas differed from those of the undisturbed and wind-disturbed areas. Trap catches of subcortical
insects in response to semiochemical treatments also varied with year of sampling and land-area treatment. The greatest diversity
of subcortical beetle species was in traps baited with attractants for the scolytids, Dendroctonus valens [(+)-α-pinene and (−)-β-pinene] and Dryocoetes spp. [exo-brevicomin and (−)-α-pinene], perhaps reflecting the generic nature of the baits. The most distinct species compositions
were collected in response to the woodborer and Dendroctonus simplex baits, whereas the species compositions in traps with the D. valens and Dryocoetes spp. baits, and the unbaited funnel trap were the most similar. The variation in trap catch with time and across landscapes
suggests that the responses of subcortical insects to semiochemicals are more complex than previously appreciated. 相似文献
10.
Regenerative converter for PWM AC drives 总被引:1,自引:0,他引:1
Braun D.H. Gilmore T.P. Maslowski W.A. 《Industry Applications, IEEE Transactions on》1994,30(5):1176-1184
Since the PWM induction motor drive has become the industrial drive of choice, applications involving four-quadrant operation for AC drives have become more common. To satisfy such applications, a regenerative AC/DC converter that is robust is needed to allow bidirectional power flow between the load and power distribution system. A robust technology that is well understood is the 6 SCR converter operating in the inverting mode. However, the typical 6 SCR converter will either limit the maximum DC bus voltage or require a step-up transformer. The proposed regenerative converter allows the SCR power structure to operate as a synchronous line commutator, while a two-transistor series/shunt chopper, with a power resistor, controls the regenerative power flow, and offers an emergency braking capability. In addition, SCR commutation is accomplished by the line voltage and diversion of bus current. Both simulation and experimental results are given 相似文献