生物质成型机成型模孔内表面摩擦力分形预测

选择2种模孔材料,利用粗糙仪测出其表面形貌,提取轮廓数据,采用尺码法计算出表面分形参数D和G,再基于经典接触公式和M-B分形接触模型建立成型模孔内表面滑动摩擦力分形预测模型并进行模拟,最后利用摩擦磨损试验台进行验证。结果表明:当环模模孔内表面的粗糙度Ra值3.428μm时(45钢),D值为1.373,G值为1.55×10^(-6) m;而当其Ra值为4.002μm时(40Cr),D值为1.359,G值为0.82×10^(-6) m;摩擦力随真实接触面积的增加呈增大趋势,单位摩擦力随真实接触面积的增加呈减小趋势;在Ar<Arc时,摩擦力增大速度较快,单位摩擦力减小速度较快;在Ar>Arc时,摩擦力增幅较平缓,单位摩擦力降幅较平缓。经实验验证,摩擦力模拟结果比试验结果略高,且随真实接触面积的增大,摩擦力的模拟值正逐渐接近实验值,模型预测较准确。

Comparison on Winter Wheat Yield Estimating Models Based on Radarsat-2 and HJ Satellite in Huaihe River Region

The establishment of crop yield estimating model based on microwave and optical satellite images can conduct the mutual verification of the accuracy of the reported crop yield and the precision of the estimating model. With Shou County and Huaiyuan County of Anhui Province as the experimental fields of winter wheat producing areas, the linear winter wheat yield estimating models were established by adopting backscattering coefficient and Normalized Difference Vegetation Index（NDVI） based on images from the synthetic aperture radar（SAR）—RDARSAT-2 and HJ satellite photographed in mid-April and early May, 2014, and then comparisons were conducted on the accuracy of the yield estimating models. The accuracies of the yield estimating models established using co-polarized（HH） and cross-polarized（HV） modes of SAR in Jiangou Town, Shou County were 68.37% and 74.01%, respectively, while the accuracies in Longkang Town, Huaiyuan County were 63.10%and 69.10%, respectively. Accuracies of yield estimating models established by HJ satellite data were 69.52% and 66.43% in Shou County and Huaiyuan County, respectively. Accuracies of winter yield estimating model based on HJ satellite data and that based on SAR were closed, and the yield difference of winter wheat in the lodging region was analyzed in detail. The model results laid the foundation and accumulated experience for the verification, parameters correction and promotion of the winter wheat yield estimating model.

In-situ synthesized mesoporous TiO_2-B/anatase microparticles:Improved anodes for lithium ion batteries

Mesoporous TiO_2-B/anatase microparticles have been in-situ synthesized from K_2Ti_2O_5 without template.The TiO_2-B phase around the particle surface accelerates the diffusion of charges through the interface,while the anatase phase in the core maintains the capacity stability.The heterojunction interface between the main polymorph of anatase and the trace of TiO_2-B exhibits promising lithium ion battery performance.This trace of 5%(by mass) TiO_2-B determined by Raman spectra brings the first discharge capacity of this material to 247 mA · h ·g^(-1),giving 20%improvement compared to the anatase counterpart Stability testing at 1 C reveals that the capacity maintains at 171 mA·h·^(-1),which is better than 162 mA·h·g^(-1) for single phase anatase or 159 mA·h·g^(-1) for TiO_2-B.The mesoporous TiO_2-B/anatase rnicroparticles also show superior rate performance with 100 mA·h·g^(-1) at 40 C,increased by nearly 25%as compared to pure anatase.This opens a possibility of a general design route,which can be applied to other metal oxide electrode materials for rechargeable batteries and supercapacitors.

Quantitative Assessment of Remotely Sensed Global Surface Models Using Various Land Classes Produced from Landsat Data in Istanbul

Digital elevation model （DEM） is the most popular product for three-dimensional （3D） digital representation of bare Earth surface and can be produced by many techniques with different characteristics and ground sampling distances （GSD）. Space-borne opti- cal and synthetic aperture radar （SAR） imaging are two of the most preferred and modern techniques for DEM generation. Using them, global DEMs that cover almost entire Earth are produced with low cost and time saving processing. In this study, we aimed to assess the Satellite pour robservation de la Terre-5 （SPOT-5）, High Resolution Stereoscopic （HRS）, the Advanced Space-borne Thermal Emission and Reflection Radiometer （ASTER）, and the Shuttle Radar Topography Mission （SRTM） C-band global DEMs, produced with space-borne optical and SAR imaging. For the assessment, a reference DEM derived from 1 ： 1000 scaled digital photogrammetric maps was used. The study is performed in 100 km2 study area in Istanbul including various land classes such as open land, forest, built-up land, scrub and rough terrain obtained from Landsat data. The analyses were realized considering three vertical accuracy types as fundamental, supplemental, and consolidated, defined by national digital elevation program （NDEP） of USA. The results showed that, vertical accuracy of SRTM C-band DEM is better than optical models in all three accuracy types despite having the largest grid spacing. The result of SPOT-5 HRS DEM is very close by SRTM and superior in comparison with ASTER models.

Simulation Study on SAR Images of the Oceanic Internal Waves

Based on the research of Lynett and Liu, the horizontal fully two-dimensional, depth-integrated model for the internal wave propagation is re-deduced. By combining this model with the M4S model, the propagation process of the internal waves is simulated in Synthetic Aperture Radar （SAR） images. The simulation results clearly show the bottom effects during the propagation such as fission and isobaths-parallelized propagation direction. This simulation procedure can lay the foundation for the quantitative interpretation of internal waves from fully two-dimensional SAR images.

Synthetic aperture radar imaging based on attributed scatter model using sparse recovery techniques

The sparse recovery algorithms formulate synthetic aperture radar （SAR） imaging problem in terms of sparse representation （SR） of a small number of strong scatters＇ positions among a much large number of potential scatters＇ positions, and provide an effective approach to improve the SAR image resolution. Based on the attributed scatter center model, several experiments were performed with different practical considerations to evaluate the performance of five representative SR techniques, namely, sparse Bayesian learning （SBL）, fast Bayesian matching pursuit （FBMP）, smoothed 10 norm method （SL0）, sparse reconstruction by separable approximation （SpaRSA）, fast iterative shrinkage-thresholding algorithm （FISTA）, and the parameter settings in five SR algorithms were discussed. In different situations, the performances of these algorithms were also discussed. Through the comparison of MSE and failure rate in each algorithm simulation, FBMP and SpaRSA are found suitable for dealing with problems in the SAR imaging based on attributed scattering center model. Although the SBL is time-consuming, it always get better performance when related to failure rate and high SNR.

Estimation of tropical cyclone parameters and wind fields from SAR images

The traditional method of Synthetic Aperture Radar(SAR)wind field retrieval is based on an empirical relation between the near surface winds and the normalized radar backscatter cross section to estimate wind speeds,where this relation is called the geophysical model function(GMF).However,the accuracy rapidly decreases due to the impact of rainfall on the measurement of SAR and the saturation of backscattered intensity under the condition of tropical cyclone.Because of no available instrument synchronously monitoring rain rate on the satellite platform of SAR,we have to derive the precipitation of the SAR observation time from non-simultaneous passive microwave observations of rain in combination with geostationary IR images,and then use the model of rain correction to remove the impact of rain on SAR wind field measurements.For the saturation of radar backscatter cross section in high wind speed conditions,we develop an approach to estimate tropical cyclone parameters and wind fields based on the improved Holland model and the SAR image features of tropical cyclone.To retrieve the low-to-moderate wind speed,the wind direction of tropical cyclone is estimated from the SAR image using wavelet analysis.And then the maximum wind speed and the central pressure of tropical cyclone are calculated by a least square minimization of the difference between the improved Holland model and the low-to-moderate wind speed retrieved from SAR.In addition,wind fields are estimated from the improved Holland model using the above-mentioned parameters of tropical cyclone as input.To evaluate the accuracy of our approach,the SAR images of typhoon Aere,typhoon Khanun,and hurricane Ophelia are used to estimate tropical cyclone parameters and wind fields,which are compared with the best track data and reanalyzed wind fields of the Joint Typhoon Warning Center(JTWC)and the Hurricane Research Division(HRD).The results indicate that the tropical cyclone center,maximum wind speed,and central pressure are generally consistent with the best track data,and wind fields agree well with reanalyzed data from HRD.

Focusing Azimuth-Invariant Bistatic Synthetic Aperture Radar Data Based on a Polynomial Model

In this paper,a focusing approach is presented to widen the use of efficient monostatic imaging algorithms for azimuth-invariant bistatic synthetic aperture radar(SAR) data.The bistatic range history is modeled by a polynomial of azimuth time.Using this model,an analytic form of the signal spectrum in the 2D frequency domain is derived,and a simple single-valued relation between the transmitter and receive ranges is established.In this way,a lot of monostatic image formation algorithms can be extended for the bistatic SAR data,and a bistatic chirp scaling algorithm is developed as an application of the new approach.This algorithm can be used to process the azimuth-invariant bistatic configuration where the transmitter and receiver platforms are moving on parallel tracks with the same velocity.In addition,some simulation results are given to demonstrate the validity of the proposed approach.

Determining the oil weighting factor of oil-water emulsion based on the fractional Weierstrass scattering model

The formation of oil-water emulsion often occurs when oil is spilled into the ocean. Oil weighting factor of oil-water emulsion is one of the most important parameters for emergent oil-spill microwave monitoring. A new method is proposed here to evaluate the oil weighting factor based on fractional Weierstrass scattering model. By using the proposed method, we analyze the Uninhabited Aerial Vehicle Synthetic Aperture Radar(UAVSAR) L-band fully polarimetric data acquired during 2010 Deepwater Horizon oil spill disaster event in the Gulf of Mexico. The result shows that our method performs well in evaluating oil weighting factor of oil-covered area.