植物根与茎输水结构的研究和功能分析

本文采用树脂复型法对裸子植物红豆杉的管胞，木本单子叶植物竹和棕榈藤木质部中各种管状分子（主要是导管和管胞）的内壁结构进行了研究;采用原子力显微镜对玉米和小麦根内皮层细胞内切向壁的表面结构进行了探索性的研究;用光学显微镜并结合荧光技术对典型的旱生、中生及水生植物根内皮层的次生加厚壁进行了比较观察;同时辅以传统的组织切片法对以上研究结果做了进一步的论证。 采用树脂复型法，不仅可观察到常规解剖法所能展示的结构，而且还可清晰地观察到管状分子间具缘纹孔对等常规方法所难以显示的三维构造，并对其各项结构参数进行了定量测量。结果表明：裸子植物管胞和竹、藤管状分子具缘纹孔的内、外口比例分别约为3:1 和1:1，其它各项结构参数均存在较大差别。此外，在云南省藤和桂竹等导管内壁上还观察到瘤层结构，瘤体直径大小为200-800纳米之间。 旱生植物内皮层细胞内切向壁的闪生加厚最为明显，水生植物的加厚程度最微弱，而中生植物则介于两类植物之间。玉米内皮层细胞内切向壁的内表面起伏不平，并具有70-90纳米的“孔状”质外体结构，其频率约为2，000个/平方微米。

Mechanics of a grip system of three-key-board hydraulic tongs developed for offshore oil pipe lines

This paper carries out the analysis of mechanics of a grip system of three-key-board hydraulic tongs developed for offshore oil pipe lines which has been successfully used in oil fields in China. The main improvement of this system is that a lever frame structure is used in the structural design, which reduces greatly the stresses of the major components of the oil pipe tongs. Theoretical analysis and numerical calculation based on thirteen basic equations developed Show that the teeth board of the tongs is not easy to slip as frequently happens to other systems and is of higher reliability.

High-Strength Composite Fibers: Realizing True Potential of Carbon Nanotubes in Polymer Matrix through Continuous Reticulate Architecture and Molecular Level Couplings

Carbon nanotubes have unprecedented mechanical properties as defect-free nanoscale building blocks, but their potential has not been fully realized in composite materials due to weakness at the interfaces. Here we demonstrate that through load-transfer-favored three-dimensional architecture and molecular level couplings with polymer chains, true potential of CNTs can be realized in composites as Initially envisioned. Composite fibers with reticulate nanotube architectures show order of magnitude improvement in strength compared to randomly dispersed short CNT reinforced composites reported before. The molecular level couplings between nanotubes and polymer chains results in drastic differences in the properties of thermoset and thermoplastic composite fibers, which indicate that conventional macroscopic composite theory falls to explain the overall hybrid behavior at nanoscale.

Visual pattern recognition network: Its training algorithm and its optoelectronic architecture

A visual pattern recognition network and its training algorithm are proposed. The network constructed of a one-layer morphology network and a two-layer modified Hamming net. This visual network can implement invariant pattern recognition with respect to image translation and size projection. After supervised learning takes place, the visual network extracts image features and classifies patterns much the same as living beings do. Moreover we set up its optoelectronic architecture for real-time pattern recognition. (C) 1996 Optical Society of America