基于成像光通信的时间-空间扩频混合光码分多址编码方案

为了在成像光通信中充分利用时间和空间两种频带资源,以成像光通信为基础,提出一种利用二维光正交Pattern码结合时域扩频实现光码分多址(OCDMA)编码的新方案。分析在该方案中存在的多址干扰噪声,并给出了噪声的概率密度函数,然后讨论由多址噪声引起的误码率与判决门限、用户数、码长积和码重积之间的关系。在相同的码容量下与时域扩频光码分多址编码和空间扩频光码分多址编码方案相比,该方案能降低对相关器件性能(时域码片数量和空间像素规模)的要求,而且还可获得更小的误码率。最后给出编码解码的光学实现方案。     

Relativistic Motion with Linear Dissipation

A general formalism for obtaining the Lagrangian and Hamiltonian for a one-dimensional dissipative system is developed. The formalism is illustrated by applying it to the case of a relativistic particle with linear dissipation. The relativistic wave equation is solved for a free particle with linear dissipation. PACS Numbers: 45.20.Jj, 03.65.Pm     

A new “one flask” preparation of 2-alkylamino-4-chloroquinazolines from ortho aminobenzonitriles and phosgeniminium salts

Phosgeniminium salts $\text{7}$ react easily with ortho amino-benzonitriles $\text{6}$ to give, selectively and quantitatively the corresponding 2-dialkylamino-4-chloroquinazolines $\text{5}$.     

Trapping quasiminimizing submanifolds in spaces of negative curvature

LetM be a Hadamard manifold with all sectional curvatures bounded above by some negative constant. A well-known lemma essentially due to M. Morse states that every quasigeodesic segment inM lies within an a priori bounded distance from the geodesic arc connecting its endpoints. In this paper we establish an analogue of this fact for quasiminimizing surfaces in all dimensions and codimensions; the only additional requirement is that the sectional curvatures ofM be bounded from below as well. We apply this estimate to obtain new solutions to the asymptotic Plateau problem in various settings. The second author was supported by the Swiss National Science Foundation and enjoyed the hospitality of the University of Bonn. The collaboration between the authors was facilitated by the program GADGET II.     

Groups with three real valued irreducible characters

We obtain strong restrictions on the structure of a Sylow 2-subgroup of a group with at most three real valued irreducible characters. This extends results of Iwasaki, who studied groups with at most two real valued irreducible characters. This research was partially supported by the Spanish Ministerio de Educación y Ciencia, MTM2004-06067-C02-01 and MTM2004-04665, and the FEDER. The first author was also supported by the Programa Ramón y Cajal and the Generalitat Valenciana.     

Transmission-System Design

This paper describes some of the complexities of designing high-pressure gas-transmission systems. The contribution of OR to efficient gas-transmission-system design is discussed. A new network design program is described to illustrate the benefits of models to system design and plant selection.     

共面光路在等待型转镜高速摄影机中实现同时分幅扫描

根据胶片图象形式的不同,转镜相机可分为两类,即扫描摄影机和分幅摄影机。由于它们各有利弊,因此,最好的方法是能用一台摄影机,同时得到现象的扫描和分幅图象。国际上有美国的330A型相机,但它采用空间光路,三面体铍转镜及整体充氦技术,这就给技术、工艺带来许多困难。本文根据我国的具体情况,提出了一种新颖方案来同时实现分幅、扫描,它包括以下内容: 采用两层共面光路可实现同时分幅扫描。研究了几种可能的等待形式,以尽量减少整体尺寸,入口角,增大光力,提高象质。同时,进行了结构优选,对空间光路的实现方式作了比较研究,给出了光学系统的设计参数。 实验中,首先采用了高强度铝合金六面体转镜。用弹性力学理论,对六面体铝转镜的强度及变形进行了精确计算,证明其变形量仅为同样回转半径三面体铍转镜的1.45倍,边缘线速度达816m/s。此外,对铝转镜进行了强度及变形实验,实验结果表明:其性能与理论相符,满足役计要求。 采用了国内较成熟的真空球罩技术,与充氦气相比,大大降低了成本。     

Are heavy-fermion metals Fermi liquids?

We present the results of specific-heat and resistivity measurements as a function of temperature, magnetic field and hydrostatic pressure on the Kondo lattice CeNi₂Ge₂, the heavy-fermion superconductors CeCu₂Si₂ and UBe₁₃ as well as the low-carrier-density system Yb₄As₃. “Non-Fermi-liquid” effects in the low-temperature normalstate properties of the three former systems are consistent with the existence of a “nearby” quantum critical point, presumably of antiferromagnetic type. Yb₄As₃, though showing the outward appearance of a Landau-type heavy-fermion metal, behaves very differently, i.e. as an extreme two-fluid system.     

New nickel(II) chloride-morpholine complexes

The compounds [NiCl₂(Morph)₃(H₂O)₂] and [NiCl₂(Morph)₃] have been prepared by treating NiCl₂·6H₂O with morpholine (Mo