Optimal classification methods for mapping agricultural tillage practices

The classification of agricultural tillage systems has proven challenging in the past using traditional classification methods due to the similarity of spectral reflectance signatures of soils and senescent crop residues. In this study, five classification methods were examined to determine the most suitable classification algorithm for the identification of no-till (NT) and traditional tillage (TT) cropping methods: minimum distance (MD), Mahalanobis distance, Maximum Likelihood (ML), spectral angle mapping (SAM), and the cosine of the angle concept (CAC). A Landsat ETM+ image acquired over southern Michigan and northern Indiana was used to test these classification methods. Each classification method was validated with 293 ground truth sampling locations collected commensurate with the satellite overpass. Classification accuracy was then assessed using error matrix analysis, Kappa statistics, and tests for statistical significance. The results indicate that of the classification routines examined, the two spectral angle methods were superior to the others. The cosine of the angle concept algorithm outperformed all the other classification routines for tillage practice identification and mapping, yielding an overall accuracy of 97.2% (Kappa=0.959).     

2π空间发光的理想点光源系统

为获得能在２π空间发光的理想点光源，本文提出了一种特殊光学系统，介绍了这种系统的工作原理、设计方法和设计结果。     

辐射角系数计算的边界元法

本文提出了用边界元方法计算辐射角系数。从角系数的定义式出发,运用stokes公式及边界元理论,导出了计算的基本公式。并用Basic算法语言写出计算机程序,通过四个典型算例的计算以及与精确解和其他方法计算结果加以对比,得出本法计算可靠,具有输入数据少,精度高等优点。同时指出     

对皖北地区500kV输电线路耐雷性能的研究

根据安徽电网皖电东送通道8条500 kV线路的运行情况,结合皖北地区500 kV输电线路跳闸原因,分析输电线路设备耐雷状况,提出了综合防治措施,以便改进皖北地区500 kV线路的耐雷性能,提高其安全稳定运行水平。     

挤压模障碍角作用误区

型材挤压的流动均匀性关系到制品尺寸的稳定性，目前常用的控制流动的方法是调整挤压模工作带的大小，采用先导模，扁挤压筒，开促流角，障碍角等措施。开障碍角的办法由于其自身的可操作性问题和增加阻力机理不明确，并没有广泛地应用。作者针对这一情况对障碍角的作用从模拟实验和理论角度进行了探讨，分析并指出了障碍角作用的误区。     

半不连续切屑流动速度的系统分析及切屑变形的度量

本文借助影片运动分析仪,对用高速摄影记录的钛合金切屑沿前刀面的流动规律进行了研究,并用系统分析法进行了描述,推导出能反映半不连续切屑不均匀变形过程的动态衡量参数,同时也导出了度量此种切屑塑性变形的准静态参数——等效切削比。     

多波束条带测深中的声线跟踪技术

海洋环境里声速随着盐度、温度和深度以及其他因素的变化而变化，导致声波并不沿直线传播，利用声波到达海底某区域的往返时间和声线离换能器的出射角计算该区域的海底深度时，如果采用固定声速，则必然带来误差。为提高测深精度，有必要进行声速补偿，为此，研究一种在深度方向上采用声线跟踪技术进行补偿以提高海底深度测量精度的方法，叙述了射线跟踪的基本原理，进行了计算机仿真，并利用海试数据进行了相应的处理。结果表明，依据声速的变化进行声线跟踪可以大大提高测深的精度。     

西南桦木包装材料在热处理后的润湿性能研究

通过动态接触角测量、红外光谱分析、表面粗糙度测量、扫描电镜观察和偏相关分析,研究了西南桦木的润湿性能。结果表明,木材经180℃热处理4 h后,润湿性能下降:接触角由40°增至121°,羟基和羰基数量减少,粗糙度降低;处理时间与接触角显著相关;西南桦木用作包装材料,若采用热处理,可去除有害生物,还具备疏水功能。     

Order vs. Disorder: Cholesterol and Omega-3 Phospholipids Determine Biomembrane Organization

Lipid structural diversity strongly affects biomembrane chemico-physical and structural properties in addition to membrane-associated events. At high concentrations, cholesterol increases membrane order and rigidity, while polyunsaturated lipids are reported to increase disorder and flexibility. How these different tendencies balance in composite bilayers is still controversial. In this study, electron paramagnetic resonance spectroscopy, small angle neutron scattering, and neutron reflectivity were used to investigate the structural properties of cholesterol-containing lipid bilayers in the fluid state with increasing amounts of polyunsaturated omega-3 lipids. Either the hybrid 1-stearoyl-2-docosahexaenoyl-sn-glycero-3-phosphocholine or the symmetric 1,2-docosahexaenoyl-sn-glycero-3-phosphocholine were added to the mixture of the naturally abundant 1-palmitoyl-2-oleyl-sn-glycero-3-phosphocholine and cholesterol. Our results indicate that the hybrid and the symmetric omega-3 phospholipids affect the microscopic organization of lipid bilayers differently. Cholesterol does not segregate from polyunsaturated phospholipids and, through interactions with them, is able to suppress the formation of non-lamellar structures induced by the symmetric polyunsaturated lipid. However, this order/disorder balance leads to a bilayer whose structural organization cannot be ascribed to either a liquid ordered or to a canonical liquid disordered phase, in that it displays a very loose packing of the intermediate segments of lipid chains.     

PAN基原丝预氧丝炭纤维微结构的几种新的X射线衍射散射定量表征技术

介绍几种新近开发的针对PAN基原丝、预氧丝和炭丝微结构和结构缺陷的X射线衍射与散射定量表征技术,它们是:纤维材料中柱状(椭球状)纳米取向微孔体积分数X射线小角散射定量表征方法;纤维材料中柱状(椭球状)纳米取向微孔取向角的小角散射定量表征方法;预氧丝中链状相与环化相体积分数的小角衍射定量表征方法以及炭纤维中乱层石墨相与单层石墨相的X射线广角衍射定量表征方法等。