A general stability analysis on regional and national voting schemes against noise—why is an electoral college more stable than a direct popular election?

By discarding the previous restrictive weak average distribution assumption on region sizes, we have developed a new general probabilistic model on the regional voting (known as “direct popular voting” in political science) and the national voting (typically, the electoral college), where we regard the percentage of a candidate's supporters in the nation as the probability of a voter voting for the candidate. Our analysis demonstrates that the regional voting is always more stable than the national voting, and that the stability margin of the regional voting always increases as the size of such partitioned regions decreases down to a certain critical value of region size, beyond which the stability margin starts to decrease, asymptoting to a national voting level where the size of the partitioned regions approaches the unit of voting cell so that the improved stability of the regional voting by localizing the effects of noise into a restricted number of smaller effective areas will not be effective. Our stability analysis remains valid over the entire range in size of the partitioned regions for regional voting. We show that the regional voting asymptotes to the national voting in two extreme limiting cases, when the region size decreases to a voting cell size and when the region size increases to the size of the nation.     

分布式拉曼放大器在长距离传输系统中的应用

讨论了分布式拉曼放大器在长距离传输系统中的应用,介绍了它的大动态范围特性、掉波特性、级联特性和应用于不同的传输光纤时的测量结果。     

基于噪声抑制的电机结构设计与工艺优化比较研究

介绍电机噪声的分类及其产生的机理与原因。基于噪声抑制，对电机结构设计与制造工艺进行优化比较．从而择优选用。     

Data analysis with fuzzy clustering methods

An encompassing, self-contained introduction to the foundations of the broad field of fuzzy clustering is presented. The fuzzy cluster partitions are introduced with special emphasis on the interpretation of the two most encountered types of gradual cluster assignments: the fuzzy and the possibilistic membership degrees. A systematic overview of present fuzzy clustering methods is provided, highlighting the underlying ideas of the different approaches. The class of objective function-based methods, the family of alternating cluster estimation algorithms, and the fuzzy maximum likelihood estimation scheme are discussed. The latter is a fuzzy relative of the well-known expectation maximization algorithm and it is compared to its counterpart in statistical clustering. Related issues are considered, concluding with references to selected developments in the area.     

A physical-based noise macromodel for fast simulation of switching noise generation

Efficient prediction of the substrate noise generated by large digital sections is currently a major challenge in System-on-a-Chip design. A macromodel to accurately and efficiently predict the substrate noise generated by digital standard cells is presented. The macromodel is generated from identification of the physical elements relevant to noise generation. Techniques to directly or indirectly compute the values of the elements in the cell macromodel are proposed. Using this macromodel, prediction of the noise generated by large digital sections can be easily done following a methodology based on high-level logic simulation. As a first step to validation, the macromodel accuracy is demonstrated in some circuits consisting of a reduced number of gates.     

Dynamic Coupling Effects in Frictional Geomaterials—Stochastic Resonance

Nonlinear, dynamic coupling effects and the manifestation of stochastic resonance are explored in the context of frictional geomaterials. The first experiment is designed to study a single interface between two mineral surfaces. Results demonstrate that as the amplitude of the driving signal approaches the threshold of static frictional resistance, the noise level required to cause slippage decreases and the peak output signal-to-noise ratio increases, inducing stochastic resonance. The second experimental study is conducted with sand specimens. While the classical signature of stochastic resonance is not observed in these multiinterface systems, nonlinear energy coupling effects appear. The effect of signal interaction through the nonlinear behavior of the medium is further studied by simultaneously exciting the specimen with two sinusoidal signals of different frequencies. The output response at the frequency of the primary driving signal increases as the amplitude of the secondary “noise” signal increases. Coupling increases as the driving signal brings the specimen to its nonlinear regime. The results highlight the interaction between friction and vibration in geomaterials, and suggest potential implications to experimental studies, construction operations, and dynamic phenomena such as seismic response and landslides.     

Vegetation height estimation from Shuttle Radar Topography Mission and National Elevation Datasets

A study was conducted to determine the feasibility of obtaining estimates of vegetation canopy height from digital elevation data collected during the 2000 Shuttle Radar Topography Mission (SRTM). The SRTM sensor mapped 80% of the Earth's land mass with a C-band Interferometric Synthetic Aperture Radar (InSAR) instrument, producing the most complete digital surface map of Earth. Due to the relatively short wavelength (5.6 cm) of the SRTM instrument, the majority of incoming electromagnetic energy is reflected by scatterers located within the vegetation canopy at heights well above the “bald-Earth” surface. Interferometric SAR theory provides a basis for properly identifying and accounting for the dependence of this scattering phase center height on both instrument and target characteristics, including relative and absolute vertical error and vegetation structural attributes.An investigation to quantify the magnitude of the vertical error component was conducted using SRTM data from two vegetation-free areas in Iowa and North Dakota, revealing absolute errors of −4.0 and −1.1 m, respectively. It was also shown that the relative vertical error due to phase noise can be reduced significantly through sample averaging. The relative error range for the Iowa site was reduced from 13 to 4 m and for the North Dakota site from 7 to 3 m after averaging of 50 samples. Following error reduction, it was demonstrated that the SRTM elevation data can be successfully correlated via linear regression models with ground-measured canopy heights acquired during the general mission timeframe from test sites located in Georgia and California. Prior to outlier removal and phase noise reduction, initial adjusted r² values for the Georgia and California sites were 0.15 and 0.20, respectively. Following outlier analysis and averaging of at least 20 SRTM pixels per observation, adjusted r² values for the Georgia and California sites improved to 0.79 (rmse=1.1 m) and 0.75 (rmse=4.5 m), respectively. An independent validation of a novel bin-based modeling strategy designed for reducing phase noise in sample plot data confirmed both the robustness of the California model (adjusted r²=0.74) as well as the capacity of the binning strategy to produce stable models suitable for inversion (validated rmse=4.1 m). The results suggest that a minimum mapping unit of approximately 1.8 ha is appropriate for SRTM-based vegetation canopy height mapping.     

基于FPGA的CCD驱动模块设计

本文针对天文观测项目中导星的需求,使用全帧型的CCD探测器KAF-3200,完成了导星CCD相机的驱动模块设计。在介绍CCD芯片KAF-3200的基础上,通过使用FPGA和超低噪声的LDO实现了CCD芯片的时序电路和偏压电路,并通过示波器、ADC采样等方法对该设计进行了多次测试。测试表明该设计有着高速、低噪声、低功耗的优点,满足设计需求,并且为CCD的驱动设计提供了一种新的思路。     

A Determination of the Ratio of the Zinc Freezing Point to the Tin Freezing Point by Noise Thermometry

A Johnson-noise thermometer (JNT) has been used with a quantized voltage noise source (QVNS), as a calculable reference to determine the ratio of temperatures near the Zn freezing point to those near the Sn freezing point. The temperatures are derived in a series of separate measurements comparing the synthesized noise power from the QVNS with that of Johnson noise from a known resistance. The synthesized noise power is digitally programed to match the thermal noise powers at both temperatures and provides the principle means of scaling the temperatures. This produces a relatively flat spectrum for the ratio of spectral noise densities, which is close to unity in the low-frequency limit. The data are analyzed as relative spectral ratios over the 4.8 to 450 kHz range averaged over a 3.2 kHz bandwidth. A three-parameter model is used to account for differences in time constants that are inherently temperature dependent. A drift effect of approximately −6 μK·K⁻¹ per day is observed in the results, and an empirical correction is applied to yield a relative difference in temperature ratios of −11.5 ± 43 μK·K⁻¹ with respect to the ratio of temperatures assigned on the International Temperature Scale of 1990 (ITS-90). When these noise thermometry results are combined with results from acoustic gas thermometry at temperatures near the Sn freezing point, a value of T − T ₉₀ = 7 ± 30 mK for the Zn freezing point is derived.     

Three-Dimensional Electromechanical Impedance Model for Multiple Piezoceramic Transducers—Structure Interaction

In the last few decades, piezoceramic (PZT) transducers have been extensively used either as actuators or as sensors in the vibration and noise control of aero, civil, and mechanical (ACM) systems. Only in the last decade, PZT transducers have been used in the electromechanical impedance (EMI) models as both sensor and actuator for the structural health monitoring of ACM systems. In the EMI models, the PZT transducers are generally surface bonded to the host structure and are then subjected to one-dimensional (1D) voltage to interrogate the structure for the desired frequency range. The interrogation results in the prediction of electromechanical admittance signatures. These signatures serve as indicators of the health/integrity of the structure. However, the existing single PZT–structure interaction models consider the PZT transducer to be negligible in mass and thus ignored. Moreover, they impose restrictions on the PZT shape, size, and isotropy. This paper presents a novel semianalytical multiple three-dimensional PZT–structure interaction model which considers the “mass” of the PZT transducers, and the transducers are subjected to parallel (1D) sinusoidal voltage. Further, the model does not impose restriction on the shape (square or rectangular), size (thin or thick), and electrical properties (isotropic or anisotropic) of PZT. The derived model is also experimentally verified using lab-sized aluminum plate. As it is generic, the model is expected to be applicable for the nondestructive evaluation of most ACM systems.