Statistical energy analysis of non-resonant response of isotropic and orthotropic plates

The conventional SEA model considers only the resonant part of the structural response to an acoustic excitation. Therefore, this study investigates non-resonant responses of isotropic and orthotropic plates to acoustically induced vibrations in a reverberation chamber. A modified SEA model is introduced to predict the non-resonant plate response. The estimated non-resonant and resonant responses are then compared with those obtained experimentally, and good agreement is observed for isotropic and orthotropic plates. For an isotropic plate with a small dissipation loss factor, when the non-resonant part is ignored, the estimated response can lead to significant errors at frequencies near and above the critical frequency, while large errors may occur at frequencies below the critical frequency for an orthotropic plate with a high dissipation loss factor. The experimental study indicates that the non-resonant response component should be included in the estimated responses to enhance predictive accuracy.     

Particle Size Effects of Silicon Carbide on Wear Behavior of SiC<Subscript>p</Subscript>-Reinforced Magnesium Matrix Composites

This article investigated the particle size effect of micro-sized SiC on the tribological behavior of SiC_p-reinforced AZ91D Mg-based metal–matrix composites (MMCs). The Mg MMCs were prepared by the melt-stirring technique for wear tests. The hardness and coefficient of friction of Mg MMCs increases as particle size of SiC particle in MMCs increases, except for the hardness tendency at the region between particle size of 11 and 15 μm. The SiC_p/AZ91D MMCs exhibit superior wear resistance under lower and moderate sliding condition. However, the effects of the SiC particle reinforcements on wear resistance are not as conclusive under severe sliding condition, since the matrix of MMCs were softened at elevated temperature under such a severe condition.     

A Molecular Dynamics Study of Lubrication Rheology of Polymer Fluids

This study investigated the characteristics of lubrication rheology for polymer fluids using the molecular dynamics method. The confining potential and FENE potential were used to describe the bonding force in a polymer chain. Both Poiseuille and Couette flows were simulated and the results are presented for the density distribution, velocity profiles, slip ratio, viscosity, and relation between shear stress and shear rate. The effects of the number of molecular layers and film thickness on the rheology characteristics were also investigated.     

茅苍术挥发油化学成分的GC/MS分析

采用水蒸气蒸馏法从茅苍术中提取挥发油。试用不同类型的毛细管柱进行分析,找出最佳分析条件,用归一化法测定其百分含量,用气相色谱-质谱法对茅苍术挥发油化学成分进行鉴定。共鉴定了57个成分,占挥发油总成分的82％以上。本方法稳定可靠,重现性好,适用于中药挥发油的化学成分分析。     

Guest-host ferroelectric side-chain liquid crystalline polymeric materials with improved electro-optical properties

A ferroelectric side-chain liquid crystalline polysiloxane (FLCP) containing azobenzene dyes as guest molecules for electro-optics has been investigated. The intensity and frequency of the Goldstone mode for the FLCP were increased remarkably after doping with azobenzene dyes. Larger fluctuation of the spontaneous polarization vector in each smectic layer under an applied electric field can be brought about with the addition of a strong dipole-moment guest molecule. This leads to a larger spontaneous polarization and shorter response time. It was found that the doping of a suitable amount of a strong dipole-moment azobenzene dye in the LC phase of the FLCP is helpful for the improvement of the electro-optical properties.     

排油烟通风复合消声技术的研究

进行了排油烟噪声的频谱分析，研制出一种可防油烟雾、降噪性能好(插入损失达31．8～33．9dBA)、耐高温、使用寿命长的排油烟通风复合式消声器。该技术经过两年的实际应用证明，降噪能力强，效果稳定，解决了同时降噪和排油烟的难题，是一项值得推广的技术。     

Surface aerosol radiative forcing derived from collocated ground-based radiometric observations during PRIDE, SAFARI, and ACE-Asia

An approach is presented to estimate the surface aerosol radiative forcing by use of collocated cloud-screened narrowband spectral and thermal-offset-corrected radiometric observations during the Puerto Rico Dust Experiment 2000, South African Fire Atmosphere Research Initiative (SAFARI) 2000, and Aerosol Characterization Experiment-Asia 2001. We show that aerosol optical depths from the Multiple-Filter Rotating Shadowband Radiometer data match closely with those from the Cimel sunphotometer data for two SAFARI-2000 dates. The observed aerosol radiative forcings were interpreted on the basis of results from the Fu-Liou radiative transfer model, and, in some cases, cross checked with satellite-derived forcing parameters. Values of the aerosol radiative forcing and forcing efficiency, which quantifies the sensitivity of the surface fluxes to the aerosol optical depth, were generated on the basis of a differential technique for all three campaigns, and their scientific significance is discussed.     

Analysis of the Optimum Configuration of Roadside Units and Onboard Units in Dedicated Short-Range Communication Systems

With the aid of a simple relation, which is analogous to the radar equation, the uplink signal strength received by the receiving module of a roadside unit (RSU) and emitted from the radiation module of an onboard unit (OBU) can be described. Setting the scale of this relation arbitrarily and determining the signal strength threshold from experimental measurements, and combined with the simulation of the radiation and the receiving pattern by cosineⁿ function, the relative signal strength emitted from the OBU and received by the RSU can be calculated successfully. From this computed relative signal strength and the threshold, the influence of the RSU and OBU mounting parameters, such as the mounting angles and mounting height, on the available communication region is analyzed. The effect of windshield fading is also considered. With the help of the analysis results, an optimum RSU and OBU mounting configuration can be easily obtained. This method can be used conveniently and successfully for very short wavelengths. This includes visible light, infrared, and even submillimeter-wave ranges. For millimeter-wave and microwave systems, this method can, in some cases, also provide a rudimentary estimation     

Electronic structures of quasi-one-dimensional ferrimagnetic insulator Ca3Co2O6

The electronic structures of quasi-one-dimensional ferrimagnetic Ca₃Co₂O₆ are investigated using the generalized gradient approximation (GGA) as well as the GGA plus on-site Coulomb interaction (GGA+U) scheme. GGA+U calculations reveal that the interchain ferrimagnetic Ca₃Co₂O₆ is a Mott–Hubbard insulator rather than a metal given from GGA. In addition, we found an on-site U induced 3z²−r² orbital ordering on Co_pri sublattice which drives the intrachain ferromagnetic coupling along c-axis. Our findings suggest that strong electron-electron correlation plays an important role in Ca₃Co₂O₆.     

Shrinkage and model selection with correlated variables via weighted fusion

In this paper, we propose the weighted fusion, a new penalized regression and variable selection method for data with correlated variables. The weighted fusion can potentially incorporate information redundancy among correlated variables for estimation and variable selection. Weighted fusion is also useful when the number of predictors p is larger than the number of observations n. It allows the selection of more than n variables in a motivated way. Real data and simulation examples show that weighted fusion can improve variable selection and prediction accuracy.