IMPROVED SYNTHETIC APERTURE SONAR MOTION COMPENSATION COMBINED DPCA WITH SUB-APERTURE IMAGE CORRELATION

Estimation precision of Displaced Phase Center Algorithm(DPCA) is affected by the number of displaced phase center pairs,the bandwidth of transmitting signal and many other factors.Detailed analysis is made on DPCA's estimation precision.Analysis results show that the directional vector estimation precision of DPCA is low,which will produce accumulating errors when phase cen-ters' track is estimated.Because of this reason,DPCA suffers from accumulating errors seriously.To overcome this problem,a method combining DPCA with Sub Aperture Image Correlation(SAIC) is presented.Large synthetic aperture is divided into sub-apertures.Micro errors in sub-aperture are estimated by DPCA and compensated to raw echo data.Bulk errors between sub-apertures are esti-mated by SAIC and compensated directly to sub-aperture images.After that,sub-aperture images are directly used to generate ultimate SAS image.The method is applied to the lake-trial dataset of a 20 kHz SAS prototype system.Results show the method can successfully remove the accumulating error and produce a better SAS image.

基于双基模型的多接收阵合成孔径声纳CS成像算法

针对多接收阵合成孔径声纳(SAS)的传统快速成像方法较难实现高阶空变系统误差补偿的问题,将多接收阵SAS看成多个双基地声纳的组合,并利用根式的等价变换和泰勒级数方法,提出了一种充分考虑"停-走-停"近似的多接收阵SAS线频调变标成像算法。基于多接收阵SAS方位空不变和距离空变特性,在二维空域内研究了距离延迟误差,结果表明,基于双基模型的成像方法能够满足合成孔径高分辨成像。仿真和实测数据处理结果进一步验证了该方法的有效性。

Reproductive Tract Infections—A Main Factor Influencing Women’s Mental Status: Comparison on Depression and Anxiety between Naxi Women with and without RTIs

Objectives 1） To explore the relationship between RTIs and mental status of Naxi women; 2） to compare the differences of depression ＆ anxiety between Naxi women who have and not have RTIs; and 3） to put forward some suggestions for improving Naxi women＇s reproductive health in psychological point of view. Methods A cross-sectional survey was adopted, 280 married Naxi female volunteers who aged above 20 years old were selected by cluster random sampling from the two selected villages of Lugufu Township of Yanyuan county in Sichuan. Two self-reporting scales, CES-D and SAS were used for assessment of depression and anxiety of the subjects. Results The facts of mental status of Sichuan Naxi women brook no optimism. Among 280 Naxi reproductive age women who were investigated in current study, only 74 （26.4%） have no depression symptoms, and 116 （41.4%） have no anxiety symptoms. For the study population, the average total scores （TS） of CES-D was 20.1, and the average total index scores （TIS） of SAS was 50.2, and both of them were above a minimum value doubted to have symptoms. There were big differences of both average TS of CES-D and TIS of SAS between Naxi women who have and not have RTIs. Further analysis revealed that RTI was a main risk factor influencing women＇s mental status （OR = 16. 043 for depression, and OR = 12.954 for anxiety）. In addition, Naxi women＇s depression and anxiety were related to order births （≤2, OR=3.149, 95% CI： 1.228, 8.076）, sex debut was younger （≤17, OR=3.043, 95% CI： 1.895, 4.884）, and multiple pregnancy （≥ 3, OR=2.728, 95% CI： 1.990, 4.173）, etc. Conclusion For improving Naxi women＇s mental status, a pressing matter of the moment is for local medical persons to gain the knowledge about mental health and the diagnosis and treatment levels of psychological disorders. At the same time, pssychological counselling should become a main activity of reproductive health services.

Preparation and characteristics of nano-crystalline Cu-Ce-Zr-O composite oxides via a green route: supercritical anti-solvent process

The nano-crystalline Cu-Ce-Zr-O composite oxides were successfully prepared by the supercritical anti-solvent （SAS） process. The physicochemical properties and catalytic performances were investigated by X-ray diffraction （XRD）, Raman spectroscopy, H2 temperature-programmed reduction （H2 -TPR）, oxygen storage capacity （OSC） measurement and catalytic activity evaluation. It was found that Cu2＋ ions incorporated into CeO2 -ZrO2 lattice to form Cu-Ce-Zr-O solid solution associated with the formation of oxygen vacancies. The Cu-Ce-Zr-O catalysts prepared via the SAS process with the Cu content 2.63 mol.% showed the highest OSC index of 636.9 μmol/g. Compared with the samples prepared by impregnation method, Cu doping using SAS process could improve the dispersion of Cu2＋ in the composite oxide, enhance the interaction between Cu2＋ and CeO2-ZrO2 , improve the reducibility of catalyst, and thus improve the OSC performance and increase the catalytic activity for CO oxidation at low temperature.

Scale adaptive simulation of vortex structures past a square cylinder

The scale adaptive simulation（SAS） turbulence model is evaluated on a turbulent flow past a square cylinder using the open-source CFD package OpenF OAM 2.3.0. Two and three-dimensional simulations are performed to determine global quantities like drag and lift coefficients and Strouhal number in addition to mean and fluctuating velocity profiles in the recirculation and wake regions. SAS model is evaluated against the Shear Stress Transport k-ω（SST） model and also compared with previously reported results based on DES, LES and DNS turbulence approaches. Results show that global quantities along with mean velocity profiles are well-captured by 2-D SAS model. The 3-D SAS model also succeeded in providing comparable results with recently published DES study on Reynolds shear stress and velocity fluctuation components using about 12 times lower computational cost. It is shown that large values of the SAS model constant result in too dissipative behavior, so that proper calibration of the SAS model constant for different turbulent flows is vital.

Numerical investigation of drag force on flow through circular array of cylinders

A 2-D model for flow through a circular patch with an array of vertical circular cylinders in a channel is established using the Navier-Stokes equations with a hybrid RANS/LES turbulence model-the Scale Adaptive Simulation （SAS） model. The applica- bility of the model is first validated by test cases where experimental data are available for comparison with the computed results. It is verified that the present model can predict well the average velocity and turbulence structure. The drag force and drag coefficient are then calculated using the present model for a number of cases with different solid volume fractions, cylinder Reynolds numbers and patch diameters. It is shown that the drag coefficient increases with increasing solid volume fraction, but decreases with increa- sing Reynolds number. However, the drag coefficient is independent of the diameter of circular batch when the solid volume fraction and Reynolds number are kept constant.

Hollow nano-particles formation for CuO-CeO2-ZrO2 via a supercritical anti-solvent process

Hollow CuO-CeO2-ZrO2nano-particles were prepared with supercritical anti-solvent apparatus by using methanol as sol-vent and supercritical carbon dioxide as anti-solvent. Two key factors （i.e., pressure and temperature） were investigated to explore the effects of catalyst structure and physic-chemical properties （i.e., morphology, reducing property, oxygen storage capacity and specific surface area）. The resulting materials were characterized with X-ray diffraction （XRD）, high resolution transmission electron micros-copy （HRTEM）, Brunauer-Emmett-Teller （BET）,hydrogen temperature programmed reduction （H2-TPR） and oxygen storage capac-ity （OSC） measurement, respectively. The experimental results showed that lower temperatures promoted production of hollow struc-ture nano-particulates. The particle morphology also changed significantly, i.e. the solid construction was first transferred to hollow structure then back to solid construction. The optimal conditions for obtaining hollow nano-particles were determined at 45 °C, 18.0–24.0 MPa.

High precision mode of subaperture stitching for optical surfaces measurement

Subaperture stitching （SAS） provides us with an attractive way of extending the effective aperture and dynamic range of phase measuring interferometers. Accuracy of stitching algorithm becomes the key factor in the SAS technology. In this paper, the basic principle of SAS was introduced and four modes of SAS were discussed. The stitching experiments were done through the SSI-300 workstation designed and developed indepen- dently. There were several comparisons between the four different stitching methods and the measurement of full aperture. The results suggest that the global error averaging mode with reference of subaperture near optic axis is of high precision.