Asymptotic state behaviour and its modeling for saturated sand

A new double hardening elasto-plastic model is proposed in this paper based on the existing unified hardening model (UH model). By assuming that there is part coupling effect between the plastic volumetric strain and plastic shear strain, hardening parameters consisting of a coupled and an uncoupled components are adopted in this model. A unique feature of this model is that it can describe not only the conventional drained and undrained behaviors of soil, but also the stress-strain relationships of soil under partially drained conditions which can be volumetric compression or dilation. Adopting the asymptotic state concept, simple equations for estimating the limiting stress ratio under undrained or earth pressure at rest (i.e. K ₀) conditions are derived. The new model is relatively simple to be adopted in practice for two reasons. First, the same soil parameters as in Cam-clay model are used except the addition of one extra parameter, the stress ratio at the characteristic state. Second, all the parameters can be determined using conventional triaxial compression tests. Supported by the National Natural Science Foundation of China (Grant Nos. 10672010 and 50479001) and the National Earthquake Science Item (Grant No. 200808076)     

凹凸棒石粘土悬浮液的悬浮性研究

研究了凹凸棒石粘土尺寸、悬浮液浓度、分散时间等因素对凹凸棒石粘土水和乙醇悬浮液悬浮性的影响,试验结果表明:凹凸棒石粘土水悬浮液的悬浮性显著高于乙醇悬浮液的悬浮性;水悬浮液中凹凸棒石粘土长度在38μm和71μm之间对悬浮性影响不大;使用50 W功率的超声波发生器分别分散10 min和15 min可以使凹凸棒石粘土分别在水和乙醇介质中充分分散;悬浮剂浓度为5 g/150 mL时水悬浮液的悬浮性最好。     

Relay selection with feedback beamforming information through designed sector sweep report frame for mmWave WPANs

This paper proposes a novel relay selection strategy based on the feedback beamforming （BF） information through designed sector sweep （SSW） report frame for millimeter-wave （mmWave） wireless personal networks （WPANs）. First, an SSW report frame compatible with IEEE 802.11ad standard is designed. Second, an approach collecting instantaneous channel state information （CSI） overheard during BF is devised. Third, with the aim of minimizing the outage probability and maximizing the overall network throughput capacity, the optimal relay selection issue for non-line-of-sight （NLoS） links is formulated as a bipartite graph, and Kuhn Munkres （KM） algorithm is provided to resolve it. Both theoretical analysis and simulation results show, with CSI considering NLoS conditions and selected relays according to the overall network throughput capacity maximization principle, the improvements achieved over opportunistic relay selection strategy in terms of overall network throughput capacity and outage probability with minimal modifications to IEEE 802.1lad.     

Design of a broadband dielectric resonator antenna and its application in low sensitivity frequency beam‐scanning array with wide scanning angle and suppressed sidelobes

In this paper, a broadband dielectric resonator antenna (DRA) with a simple H‐slot feeding structure is proposed. The broad bandwidth (~45%) and uni‐directional radiation enable this DRA suitable to work as a radiation element in the construction of a beam‐scanning array with not only low frequency sensitivity which is important for accurate angle estimation of in‐coming targets, but also a wide scanning range. Moreover, stable coupling coefficients are established around all the above three resonances with respect to its corresponding feeding line, ensuring a low sidelobe level (SLL) across the whole operating frequency range. In order to realize such a DRA, a latticed rectangular structure is utilized to generate the lower two resonances, while the upper resonance is generated by its H‐shaped feeding slot. The shape of the latticed dielectric resonator is also modified according to a 3‐D printed fixing structure for an accurate installation. A 20‐element beam‐scanning prototype is demonstrated and manufactured. The range of scanning angle is from ?36° to +13° within the bandwidth of 10 to 16 GHz, corresponding to a frequency sensitivity of only 122.5 MHz/^o. The achieved SLL are smaller than 19 dB for all scanning beams. The above performance indicates that, this array is very suitable for near‐range radar systems requiring an accurate angle estimation.     

Satellite-Based Water Quality Mapping from Sequential Simulation with Parameter Outlier Removal

The satellite-based regression model provides the data model that identifies water quality for inland and coastal waters. However, the satellite regression usually depends on the selection of observation, satellite data, and model type. A resampling simulation technique, such as sequential simulation using geographically weighted regression (GWR simulation), can be applied in generating multiple realizations for water quality estimation to reduce the sampling effect and consider spatial heterogeneity. Traditional models often result in considerable underestimation in extreme observations. The GWR simulation provides the best goodness of fit and spatial varying relationship between observed water quality and remote sensing considering parameter outlier and noise removal for parameter stability. This simulation model can increase the sampling diversity from various observations and reduce the neighboring effects of observations using outlier and noise removal. The model that handles spatial uncertainty and heterogeneity is a novel tool for inferring the characteristics of water quality from a series of sample subsets.

     

基于FRFT的LFM信号的检测及其参数估计

针对LFM信号的检测及参数估计等问题,先对现有的检测方法如Wigner-Ville、FRFT等进行研究,在FRFT变换的基础上提出基于预判法与FRFT变换相结合的算法。通过仿真分析,验证了该方法能有效对L F M信号的参数进行估计,同时降低了计算量。     

Influence of static pre-loading on the dynamic bending strength of concrete with particle element modeling

Experimental tests show that static pre-loading has a significant effect on the dynamic strength of concrete.Based on meso-scale particle element model,numerical simulations of dynamic bending tests with pre-loading are performed.Complete stress–strain relationships are then obtained.Significant increase in dynamic strength is found when the pre-loadings are imposed within the elastic limit of concrete.However,when the imposition of pre-loadings reaches the plastic or softening range,dynamic strengths may gradually decrease along with the increase in pre-loadings.The distribution of energy components and the failure modes are discussed to explain the mechanisms of the phenomena.     

Evaluation research on applicability of rapid iodide migration test

The applicability of the rapid iodide migration test was systematically studied. Comparative experimental tests of different test conditions, including several external voltages, test durations, concrete ages and mixing proportions, were carried out to make clear the transport behaviors of iodide under parallel electric fields. Numerical simulations were also done using the finite element method to found the correlation between chloride and iodide transport behaviors. The test and numerical results show that the chloride transport behaviors of RIM and RCM tests have a good correlation under the several conditions used in the present paper. Moreover, the influence of external conditions （external voltages, test durations） on the test results is small. Thus, it can be concluded that the RIM method is available to determine the chloride penetration resistance of the chloride-eroded structural concrete.     

6CrW2Si钢渗碳后热轧形变制作冷剪刀的研究

6CrW2Si钢渗碳后经热轧形变可使渗层碳梯度平缓,碳化物分布均匀,消除了表层网状碳化物;淬火后可得到细的马氏体组织,并使残余奥氏体量减少;回火后硬度为HRC60～62。分析认为,可以用热轧形变量大小控制渗碳层的碳梯度。该工艺用于金属冷剪刀上使用寿命提高一倍。     

现代织构分析的进展

本文系统阐述了材料现代织构分析的进展。