Analysis of Error Propagation from NMR-Derived Internuclear Distances into Molecular Structure ofCyclo-Pro-Gly

Analytical expressions have been derived that translate uncertainties in distance constraints (obtained from NMR investigations) into uncertainties in atom positions in the maximum likelihood (ML) structure consistent with these inputs. As a test of this approach, a comparison was made between test structures reconstructed by the new ML approach, which yields a single structure and a covariance matrix for coordinates, and those reconstructed by metric matrix distance-geometry (MMDG), which yields a family of structures that sample uncertainty space. The test structures used were 560 polyhedra, with edges of arbitrary length containing up to 50 vertices, and one polyhedron, with 100 vertices; randomized distance constraints generated from these structures were used in reconstructing the polyhedra. The uncertainties derived from the two methods showed excellent agreement, and the correlation improved, as expected, with increasingly larger numbers of MMDG structures. This agreement supports the validity of the rapid analytical ML approach, which requires the calculation of only a single structure. As a second test of the ML method, the approach was applied to the determination of uncertainties in the structure of a cyclic dipeptide,cyclo(DL-Pro-Gly) (cPG), derived from NMR cross-relaxation data. The input data were interproton distances calculated from NOEs measured for a solution of the peptide in 2:1 DMSO:H₂O at −40°C (so as to yield large negative NOEs). In order to evaluate effects of the quality of the input spectral parameters on the precision of the resulting NMR structure, information from the covalent geometry of cPG was not used in the structure calculations. Results obtained from the analytical ML approach compared favorably with those from the much slower random-walk variant of the Monte Carlo method applied to the same input data. As a third test, the ML approach was used with synthetic structural constraints for a small protein; the results indicate that it will be feasible to use this rapid method to translate uncertainties associated with a given set of distance restraints into uncertainties in atom positions in larger molecules.     

海面偶极子声场中近程运动参数估计

对海面偶极子声场提出基于单个水听器的定位算法,并设计信号处理流程和双曲线提取的Hough变换法。海试结果表明信号处理和双曲线提取具有较高增益,定位算法稳健、具有较高精度。该算法所需设备简单,运算量小,在近距离目标运动参数估计和辐射噪声测量方面具有特色。     

进一步增大主动红外夜视仪视距的途径

本文根据主动红外夜视仪的视距公式讨论了影响视距的各种因素，对进一步增大视距指明了方向。寄希望于阴极红外灵敏度获得突破性的进展；改进光源结构，提高光能利用率和减小发散角是增大视距的主要途径。     

Upper bounds for the L 1-risk of the minimum L 1-distance regression estimator

A new estimator of a regression function is introduced via minimizing the L ₁-distance between some empirical function and its theoretical counterpart plus penalty for the roughness. The L ₁-risk of the estimator is bounded from above for every sample size no matter what the dependence structure of the observed random variables is. In the case of independent errors of measurement with a common variance the estimator is shown to achieve the optimal L ₁-rate of convergence within the class of m-times differentiable functions with bounded derivatives.     

微光夜视系统新的阈值探测理论和视距探测方程研究

在对各种阈值探测理论和视距探测方程进行深入研究分析的基础上，从人眼阈值特性和微光视觉理论出发，建立微光夜视系统新的阈值探测理论模型，导出微光夜视系统新的视距综合探测方程。     

Double-diffusive magnetoconvection

This review deals principally with the interaction between double-diffusive convection and an externally imposed vertical magnetic field in a Boussinesq fluid. Both linear and nonlinear (two and three-dimensional) theories have been discussed. Double-diffusive magnetoconvection is shown to exhibit a rich variety of dynamical behaviour unimaginable in a single component system and serves as a guide to the behaviour of all triple-diffusive systems. Finally, the effects of cross-diffusion, rotation and chemical reaction on double-diffusive magnetoconvection and pattern selection have been briefly touched upon. The author felicitates Prof. D S Kothari on his eightieth birthday and dedicates this paper to him on this occasion.     

军用微光夜视系统的现状与研究

叙述三代像增强器及其相关的夜视仪和微光电视的发展现状，评定像增强器探测和识别目标的能力，探讨提高微光夜视系统作用距离的途径。     

测定核间距的不对称2D NOESY方法——1.从不对称2D NOESY峰强度求取完整的混合系数矩阵

本文提出不对称2D NOESY实验方法来测定完整的2D NOESY混合系数矩阵。理论研究表明,不对称2D NOESY实验信澡比要比传统2D NOESY的高,不对称2D NOESY峰强度矩阵是非对称的,因此可以只用不对称2D NOESY的非对角峰强度来求得完整的2D NOESY混合系数矩阵,避免测量大分子等复杂自旋系统的严重重叠的对角峰强度所引起的困难,而这是传统2D NOESY实验方法所无法作到的。本文最后应用数值模拟方法对理论研究结果进行了计算验证。     

CCD辅助测量凸透镜焦距的一种新方法

本文针对凸透镜主点及物像平面难以精确定位的问题,提出了一种以理想光学系统的物像关系为理论基础,基于高斯公式,用CCD摄像机辅助的精确测量凸透镜焦距新方法,这种方法也可以在焦距未知的情况下,求共轭距。     

Orthogonality and Disjointness in Spaces of Measures

The disjointness of measures and their Hahn–Jordan decomposition are instances of the general notion of minimal decomposition in base normed spaces. The mixing distance, a specification of a novel concept of angle in real normed vector spaces, is applied to provide a geometric interpretation of disjointness as orthogonality.