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981.
The goal of this study is to model the data from the experiments of nanoparticle filtration performed at the Particle Technology
Lab, University of Minnesota and at the 3M Company. Comparison shows that the experimental data for filter efficiency are
bounded by the values computed from theoretical expressions which do not consider thermal rebound. Therefore thermal rebound
in the tested filter media is not detected down to 3 nm particles in the present analysis. The efficiency measured experimentally
is in good agreement with the theoretical expression by Stechkina (1966, Dokl. Acad. Nauk SSSR 167, 1327) when the Pectlet
number Pe is larger than 100; it agrees well with the theoretical expression by Kirsch and Stechkina (1978, Fundamentals of Aerosol
Science. Wiley, New York) when Pe is of the order of unit. We develop an empirical power law model for the efficiency depending on the Peclet number, which
leads to satisfactory agreement with experimental results. 相似文献
982.
Based on the well-known electron coherent tunneling phenomenon, by simulation, a photonic tunneling filter fabricated in an
optical waveguide is proposed. The Bragg grating structure is applied as the photonic barrier. Two photonic barriers confine
a coherent resonance cavity or photon-quantum-well. We report an asymmetric-barrier structure with opposite phase. In this
configuration, the central tunneling wavelength is exactly the same as the Bragg wavelength of the grating, independent of
the photon-quantum-well dimension. The photon-quantum-well length can be adjusted to make the tunneling peak interval fall
to a desired spacing. The photon barrier length is responsible for the filter bandwidth. As an application, an asymmetric
grating photon tunneling filter with International Telecommunication Union grid is demonstrated. 相似文献
983.
Chunhui Yao Wenmei Zhang Liping Han Runbo Ma 《International Journal of Infrared and Millimeter Waves》2007,28(10):859-863
A novel miniature ultra-wideband (UWB) bandpass filter with coplanar waveguide (CPW) fed is proposed. The size of the filter
is reduced largely because of combining the wideband couple gap and parallel-coupled CPW line (not cascading multiple resonator),
and the length of realized filter is only 0.42 λ
g0
(λ
g0
is the guiding wavelength at central frequency). The measured insertion loss is less than 2.0 dB, and the group delay variation
is less than 0.2 ns within the UWB passband. Basic agreement between the simulated and measured results has been achieved. 相似文献
984.
Thermally poled fused silica with periodic interdigital electrodes can induce second-order optical nonlinear effects and generate
a band-pass filter with characteristics for microwave application. The filter has a center frequency of ∼2.5 GHz, 3 dB bandwidth
of ∼300MHz, and insertion loss of −5.15 dB. 相似文献
985.
A Bayesian tutorial for data assimilation 总被引:1,自引:0,他引:1
Data assimilation is the process by which observational data are fused with scientific information. The Bayesian paradigm provides a coherent probabilistic approach for combining information, and thus is an appropriate framework for data assimilation. Viewing data assimilation as a problem in Bayesian statistics is not new. However, the field of Bayesian statistics is rapidly evolving and new approaches for model construction and sampling have been utilized recently in a wide variety of disciplines to combine information. This article includes a brief introduction to Bayesian methods. Paying particular attention to data assimilation, we review linkages to optimal interpolation, kriging, Kalman filtering, smoothing, and variational analysis. Discussion is provided concerning Monte Carlo methods for implementing Bayesian analysis, including importance sampling, particle filtering, ensemble Kalman filtering, and Markov chain Monte Carlo sampling. Finally, hierarchical Bayesian modeling is reviewed. We indicate how this approach can be used to incorporate significant physically based prior information into statistical models, thereby accounting for uncertainty. The approach is illustrated in a simplified advection–diffusion model. 相似文献
986.
Investigation on stability of directionally solidified CBr4-C2Cl6 lamellar eutectic by using multiphase field simulation
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With the multiphase field method, the stability of lamellar basic state is investigated during the directional solidification of eutectic alloy CBr4-C2Cl6. A great number of lamellar patterns observed in experiments are simulated, and a stability diagram for lamellar pattern selections is presented. The simulated growth behaviours of these patterns are found to be qualitatively consistent with Karma et al's numerical calculations and experimental results. The formation of the primary instability is attributed to the destabilization of solute boundary layer. 相似文献
987.
988.
二维异质结光子晶体中含近邻点缺陷的弯曲波导的可调谐滤波特性 总被引:1,自引:0,他引:1
应用时域有限差分(FDTD)法,对光在二维异质结光子晶体中含两个近邻点缺陷直角弯曲波导的传输特性进行了数值模拟研究。计算结果表明,具有特定本征共振频率的光子晶体微腔(点缺陷),可将在其邻近波导中传播的相同频率成分的光波"引入"到微腔中。"引入"的频率依赖于异质结光子晶体弯曲波导和微腔的参量,从而能够实现调变"引入"频率。通过改变点缺陷周围介质材料(液晶)的折射率或相关介质柱半径,可分别实现约31 nm或12 nm的波长调谐范围。计算结果为光通信中的调谐、上/下载滤波器,提供了一条新的设计思路和依据。 相似文献
989.
We propose and demonstrate a simple technique to stabilize the frequencies of multiple semiconductor lasers simultaneously using a Fabry-Perot etalon filter and a digital signal processing. Unlike other stabilization techniques, the proposed technique could stabilize DFB lasers using only one digital feedback control loop. The result shows that the proposed technique could maintain the frequency stability of 16 DFB lasers within ±150 MHz. 相似文献
990.
A novel packet format with non-return-to-zero (NRZ) label and duobinary carrier-suppressed return-to-zero (DCS-RZ) payload is proposed for optical packet switching networks.NRZ label is followed by DCS-RZ payload with a certain guard time.The spectra of the low-rate NRZ label locate around the optical carrier frequency where some parts of the corresponding spectra of the high-rate DCS-RZ payload have been suppressed due to DCS-RZ modulation.At the switching node,the label or payload extraction can be realized simply through an optical bandpass or notch filter respectively.The feasibility of the scheme is verified by the simulation on the famous photonic design platform designed by Virtual Photonics Inc.(VPI).The effects of optical filter bandwidth on the received signal quality are discussed by analyzing bit error rate(BER)and contrast ratio performances. 相似文献