一种基于多标定体融合的超宽带虚拟孔径雷达系统校正方法

系统校正技术是影响超宽带(Ultra Wide Band,UWB)虚拟孔径雷达(Virtual Aperture Radar,VAR)对浅埋弱小目标穿地探测效果的重要因素,系统的超宽带特性及多通道不一致性使得常规高频窄带雷达基于单一标定体的校正方法不再适用,该文在对系统误差、标定体及地雷电磁特性分析的基础上,提出了多标定体-分频段融合的多通道校正方法,利用多个标定体对不同频段分别校正,该方法有效地校正了系统误差,提高了成像质量,实测数据验证了方法的有效性。

关节式坐标测量机标定体的结构仿真设计

利用ANSYS有限元分析软件对提出的新型标定体的具体结构进行了仿真,对标定体的主要结构部分——底座与杆件分别进行了主要误差源的误差仿真分析;通过对不同结构参数的标定体杆件数据进行分析,从而对标定体的具体结构进行了优化并确定了误差范围。

基于钢珠填充标定弹体容积的新研究方法

本文研究基于钢珠填充标定弹体的容积的新方法,通过分析以钢珠与水分别作为填充物时获取的实验数据,得到填充钢珠的重量与弹体容积之间的换算公式,并得到该公式的计算值与测量值的无显著性差异,最大误差为0.18067%,以及单次实验结果的可信度为80%等结论。

基于误差隔离的触发式测头预行程标定方法

触发式测头是在机测量系统的主要组成部分,其预行程会计入测量结果从而影响测量精度,因此有必要对其在实际工况下的预行程进行标定并补偿。在分析预行程产生原因的基础上,提出了一种全新的预行程定量标定方法,它通过在实际工况下检测探针与工件接触状况及接触时刻与测头触发时刻之间工件相对测头位移变化而标定出预行程,有效避免了机床伺服系统误差、机床几何及运动误差、探针测球圆度误差、标定体制造误差等因素对标定结果精确性的影响。标定了某高精密测头在实际工况下的预行程,并依据标定结果,完成了触发式测头预行程补偿实验。补偿结果表明,该标定方法实施简单、可行有效,标定精度高。

节理几何参数对岩体力学特征的影响

岩体作为由完整岩块和节理组成的离散介质,其力学行为主要取决于节理的几何和力学特征,探明节理对岩体力学行为的影响具有重要的学术价值和工程意义。利用PFC2D软件,建立了人工合成岩体模型(SRM),研究了单轴压缩条件下节理几何参数对岩体力学强度指标和破坏模式等岩体力学特征的影响。通过正交实验分析,探讨了各节理几何参数对岩体强度指标的显著性影响。结果表明:当节理倾角为10°~50°时,节理长度、节理倾角、节理间距以及岩桥长度对岩体单轴压缩强度和弹性模量具有显著影响;当节理倾角为50°~90°时,岩桥长度对岩体单轴压缩强度和弹性模量的影响不明显;节理阶梯角在整个节理倾角范围内对岩体的单轴压缩强度和弹性模量没有显著影响。岩体破坏模式主要受节理倾角和节理阶梯角影响。研究结果可为岩体工程稳定性分析及支护方案设计提供借鉴。

Physiological Character and Gene Mapping in a New Green-revertible Albino Mutant in Rice

A green-revertible albino mutant-Qiufeng M was found from the japonica rice （Oryza sativa L. ssp. japonica） Qiufeng in the field. The first three leaves of the mutant were albino with some green. The leaf color became pale green since the fourth leaf and the glume had the same phenomenon as the first three leaves. The measuring data of the pigment content confirmed the visually observed results. It truly had a remarkable changing process in the leaf color in Qiufeng M. Comparison of the main agronomic characters between Qiufeng and Qiufeng M indicated that the neck length and grain weight showed significant difference at the 1% level, and other characters were not different. Genetic analysis showed that the green-revertible albino trait was controlled by a single recessive nucleic gene. Using 209 recessive mutant individuals in the F2 population derived from the cross Pei＇ai 64S × Qiufeng M, a gene, tentatively named gra（t）, was located between the SSR markers of RM475 and RM2-22 on the long arm of chromosome 2. The genetic distance were 17.3 cM and 2.9 cM respectively.

Isolation and Chromosomal Mapping of a Corn B Chromosome Specific RAPDs

B染色体存在于多种动植物中 ,具有很多独特的性状。B染色体与正常染色体在DNA组成方面十分相似 ,寻找B染色体特异序列一直是B染色体研究的难点和热点。通过对含有和不含有B染色体的两种玉米 (ZeamaysL .)基因组进行了RAPD分析 ,筛选到一个B染色体特异性分子标记B480。该标记与玉米的自主复制起始序列ARS1和ARS2同源 ,特别是该序列中的 2 5bp出现在多种模式生物基因组中。FISH的结果显示 。

Optimization on Identification Standards and Artificial Inoculation Methods In Vitro on Resistance to Chrysanthemum White Rust

[Objective] This research aimed at exploring an effective way for inoculation and identification of chrysanthemum white rust under controlled conditions. [Method] By combining the observation methods with the naked eye and under optical microscope, we had established the identification standards for chrysanthemum white rust with six classifications and optimized artificial inoculation methods in vitro. [Result] The results showed that bottled cuttings identification method and petri dished leaves identification method both can be used for identification in vitro of chrysanthemum white rust, bottled cuttings identification method had shown better effects than petri dished leaves identification method, and was supposed to be best artificial inoculation and identification method in vitro. [Conclusion] This research had provided a scientific method for safe and effective researches on chrysanthemum white rust, in order to control the occurrence and diffusion of this quarantine disease.

基于图像质量优化的锥束CT几何校正法

为了解决CBCT图像中因机械误差所导致的几何伪影的问题,提出一种基于图像质量优化的锥束CT几何校正方法。本方法通过引入CBCT图像几何伪影的评价指数,将评价指数作为衡量几何伪影严重程度的目标函数,通过迭代修正标定模体上标记点的坐标,进而达到校正几何参数和消除CBCT图像几何伪影的目的。仿真实验结果显示:CBCT系统的几何参数误差由19.07%降到2.21%,图像中的几何伪影明显减少;在真实实验数据中,该方法有效消除CBCT图像的几何伪影。本方法降低了标定模体加工误差对校正精度的影响,同时大幅度降标定模体的制作成本。

锥束X-CT系统四椭圆法获取全几何参数的研究

锥束CT具有成像质量高、低辐射、操作简单等优点,近几年得到迅速发展。锥束CT几何参数的精确获取是得到高质量图像的关键因素。针对FDK算法要求的条件以及现有的几何参数获取方法,本文提出了一种基于四椭圆快速获取全参数的方法。首先介绍了锥束CT中的关键参数,然后提出了四椭圆全参数获取原理并设计出通用标定模体。本标定模体可用于任何锥角不同的锥束CT系统。通过标定模体在空间的几何关系获取系统中所有几何参数。最后针对该方法进行了实验论证,结果表明,本方法获取的几何参数精度高。综上所述,可证实该算法具有一定的工程实用价值。

Greedy calibration method for binocular camera system via characteristic homography matrix

A plane-based and linear camera calibration technique without considering lens distortion is proposed in a greedy and intuitive framework for the binocular camera system. Characteristic homography matrix and consistency constraints in close range are employed in this calibration. First, in order to calculate the internal geometries of the cameras, total least-square fitting as a robust tool for the geometrical cost function is exploited to recover the accurate principal point of each camera from all the characteristic lines of the homography matrices for all model planes. Secondly, generic prior knowledge of the aspect ratio of pixel cells is incorporated into the system to obtain the exact principal length in each camera. Thirdly, extrinsic geometries are accurately computed for all planar patterns with respect to each monocular camera. Finally, the rigid displacement between binocular cameras can be obtained by imposing the consistency constraints in 3-space geometry. Both simulation and real image experimental results indicate that reasonably reliable results can be obtained by this technique. And the proposed method is sufficient for applications where high precision is not required and can be easily performed by common computer users who are not experts in computer vision.

STUDY OF NON-CONTACT MEASUREMENT OF FREE-FORM SURFACES

A non contact three dimensional measurement method is presented in this paper.This system consists of a laser triangulation probe,a probe head and a coordinate measuring machine (CMM).The measurement principle of the system is discussed,and a system calibration method employing a reference ball is proposed.The geometric model involving four frames is established to calculate the data points based on the reading of the laser probe and position information from the CMM.A measuring experiment for gesso free form surface using this system is carried out.

基于体标定追迹法的光场PIV权系数计算方法

针对光场粒子图像测速(PIV)技术中介质折射率变化及镜头畸变等因素而导致权系数计算误差较大的问题,提出一种基于体标定追迹技术的光场PIV权系数计算方法。该方法首先通过体标定方法建立空间物点与微透镜之间的映射关系,然后利用光线追迹技术计算控制体内的离散体素对像素的权系数,最后将该方法计算的权系数与直接追迹法计算的结果进行比较,并对标定板特征点的空间位置进行重建实验研究。实验结果表明,体标定追迹法计算出的权系数与直接追迹法的计算结果高度吻合;重建获得的标定板特征点在横向和深度方向上的位置误差分别小于0.002 mm和0.250 mm。

Principle of Coordinates Acquisition Based on Single Camera

The principle and accuracy of 3-D coordinates acquisition using one single camera and the Aided Measuring Probe(AMP) are discussed in this paper. Using one single camera and one AMP which has several embedded targets and one tip with known coordinates, the single camera′s orientation and location can be calculated. After orientation, the global coordinate system is obtained. During measurement, the camera is fixed firstly, then the AMP is held and the feature point is touched.The camera is triggered lastly. The position and orientation of the AMP are therefore calculated from the size and position of its image on the sensor. Since the tip point of AMP has known relation with the embedded targets, the feature point can be measured. Tests show that the accuracy of length measurement is 0.2 mm and accuracy for flatness measurement in XSY-plane is 0.1 mm.

The Study of Using Near-infrared Diffuse Reflectance Spectroscopy Rapid Identify Wheat Drought Resistance-Ⅱ

[Objective] The aim was to build an evaluation method rapidly identifying wheat drought tolerance with near infrared diffuse reflectance spectroscopy. [Method] In the research, 36 wheat varieties in 2007-2009 were chosen and drought-tolerance degrees of wheat were graded and identified according to Winter-wheat Drought Tol- erance Evaluation Technical Standards （GB/T 21127-2007）, and harvest wheat grains underwent spectrum collection, with a full-spectrum analyzer, to establish a database. [Result] Based on qualitative analysis and full-spectrum correlation research, the coef- ficient of determination （RSQ） and cross-validation coefficient of determination （1-VR） were concluded at 0.697 5 and 0.600 2, showing near-infrared diffuse reflectance spectroscopy is of significant differences among wheat varieties and of significant or extremely significant correlation with drought-tolerance indices. [Conclusion] The re- search indicates that to evaluate drought-tolerance of wheat with near-infrared diffuse reflectance spectroscopy is a rapid and feasible way, which is simple, convenient without damages on grains, and of practical values for construction wheat drought-tol- erance evaluation index system and identification of breeding materials.

Vulnerability of Large City and Its Implication in Urban Planning: A Perspective of Intra-urban Structure

Vulnerability is a new field and analytical tool in the study of urban safety. Analysis and assessment of vulnerability provide a new basis for urban planning. This study constructed a quantitative index system for assessing vulnerability, based on the city′s sensitivity and emergency response capacity. City size, density, and spatial form influence a city′s sensitivity to crises and risks, to which vulnerability is positively related. Levels of socio-economic development, infrastructures, and emergency management contribute to a city′s emergency response capacity, with which vulnerability is inversely associated. Vulnerability of 19 large Chinese cities was assessed. Harbin and Shenzhen demonstrated the highest and lowest vulnerability among 19 cities, while Beijing, Shanghai and Guangzhou ranked the 5th, the 9th and the 12th. Spatially, northern cities tended to be more vulnerable than southern cities. And the differences in vulnerability among cities were explored based on cities′ physical geography conditions, level of socioeconomic development, infrastructures, regional status, history of disaster, history of urban planning and development, government policies, etc.

A Survey on Smart Collaborative Identifier Networks

The current Internet architecture was designed on the basis of a triple bindings model, which could meet the needs of the early Internet. However, with the tremendous growth of the Internet and the continuous innovations of applications, the triple bindings(namely, control/data binding, resource/location binding and user/network binding) have given rise to many problems for the Internet, such as scalability, mobility, and security. In order to solve these problems, many network techniques have been developed. Besides, novel future Internet architectures including Information-Centric Networks and Software-Defined Networks have emerged. However, these architectures only partially decouple the triple bindings. To completely separate the triple bindings, Smart Collaborative Identifier Networks(SINET) is proposed. There have been many research efforts on SINET, which built the foundation of SINET being a promising future Internet. In this paper, we comprehensively introduce SINET and these related research works. We start by introducing the motivation for SINET, explain its fundamental concepts and how it can make a difference. Next, we present in details the design principles of every layer in SINET, explaining how it can decouple the triple bindings and solve the problems of the current Internet. Finally, we discuss the state-of-theart challenges in SINET. We investigate the ongoing research works and commercial products in SINET, with aspects such as scalability, mobility, security and reliability.

Comparison Among Depths of Penetration of Different Targets Subjected to Rigid Projectile Impact

The ratios of depth of penetration (DOP) of different targets under the same penetration condition was investigated according to the dimensionless formula of DOP of different targets penetrated by a non-deformable projectile.Results show that various targets may be equivalent to each other.The applicable range of the equivalence and the feasibility of targets substitution were discussed by integrating the available test data.

Experiment study of optimization on prediction index gases of coal spontaneous combustion

The coal of Anyuan Mine has the characteristic of easy spontaneous combustion. Conventional method is difficult to predict it. Coal samples from this mine were tested in laboratory. The data obtained from laboratory determination were initialized for the value which was defined as "K". The ratio of each index gas and value of "K", and the ratio of combination index gases and value of "K", were analyzed simultaneously. The research results show that for this coal mine, if there is carbon monoxide in the gas sample, the phenomenon of oxidation and temperature rising for coal exists in this mine; if there is C_2H_4 in the gas sample, the temperature of coal perhaps exceeds 130 °C. If the coal temperature is between 35 °C and 130 °C, prediction and forecast for coal spontaneous combustion depend on the value of Φ(CO)/K mainly; if the temperature of coal is between 130 °C and 300 °C, prediction and forecast for coal spontaneous combustion depend on the value of Φ(C_2H_6)/Φ(C_2H_2) and Φ(C_2H_6)/K. The research results provide experimental basis for the prediction of coal spontaneous combustion in Anyuan coal mine, and have better guidance on safe production of this coal mine.

Study on Excess Thermodynamic Parameters and Theoretical Estimation of Ultrasonic Velocity Using Scaled Particle Theory in Binary Liquid Mixtures of 2-Methyl-2-propanol and Nitriles at Different Temperatures

Density, ρ, ultrasonic speed, u, and viscosity, η, of binary mixtures of 2-methyl-2-propanol (2M2P) with acetonitrile (AN), propionitrile (PN) and butyronitrile (BN) including those of pure liquids are measured over the entire composition range at temperatures 298.15, 303.15 and 308.15 K. From these experimental data, the excess available volume, E a V , excess free volume, E f V , excess isothermal compressibility, E T β , excess thermal expansion coefficient, E α , and excess internal pressure, E i π , are calculated. The variation of these properties with composition and temperature are discussed in terms of molecular interactions between unlike molecules of the mixtures. It is found that the values of E a V , E f V , E T β and E α are positive and those of E i π are negative for all the mixtures at each temperature studied, indicating the presence of weak interactions between 2M2P and AN/PN/BN molecules. The variations of E a V , E f V , E T β , E α and E i π values with composition indicate that the interactions in these mixtures follow the order: AN<PN<BN, i.e., the 2M2P-nitrile interaction decreases with the increase of alkyl chain length in these nitrile molecules. In addition, the theoretical ultrasonic velocity is calculated using the scaled particle theory and compared with the experimental values.