关键词： 掌上电脑   厂家   消费型   市场容量   移动计算   笔记本电脑   笔记本计算机  

摘要： 亚洲经济的滑坡导致了整个PC市场的疲软,但这并没有影响掌上电脑在这个世界中燃起新的烽火。在9月举行的1998中国计算机世界展览会上,联想集团推出了国内第一台掌上电脑,在整整四天的时间里抓住了观众的目光,成了专业人士和普通百姓共同关注的焦点。 掌上电脑,顾名思义,是“口袋般大小、一掌可握”的微型电脑,国外许多专业人士仍然把它称做一种PDA(个人数字助

摘要： NMR chemical shift calculations at the SOS-DFPT/PW91/[7s6p2d/5s4pld/3s]//B3LYP/6-31G(d) level of theory were used to describe the trimesitylsilylium cation 1, recently synthesized in benzene solution and investigated by NMR spectroscopy. The conformation of cation 1 is characterized by mesityl rings rotated by 47 degrees in a propeller-like form. Contrary to other silylium cations investigated, cation 1 forms a weak Van der Waals complex 3 with benzene rather than a Wheland sigma-complex. The calculated Si-29 NMR chemical shifts for 1 and 3 are 226 and 227 ppm, compared to the experimental value of 225.5 ppm. The agreement between calculated and measured NMR chemical shifts provides evidence that cation 1 presents the first free silylium cation synthesized. (C) 1997 Elsevier Science B.V.

关键词： PORTABLE computers  

摘要： Reports on developments concerning mobile computer manufacturers as of October 27, 1997. Symbol Technologies Inc.'s plan to sell its own version of PalmPilot; International Business Machines Corp.'s preparations for a new line of disk drives for laptop computers; Palmtop computer from Hewlett-Packard Co.

关键词： bismuth compounds   photoconductivity   carrier lifetime   photorefractive materials   carrier mobility   holography  

摘要： The plane shift between the pattern of light onto a photorefractive crystal and the resulting hologram at the very beginning of the recording process in two-wave mixing is analyzed and measured as a function of the applied electric field. These data allow one to compute the diffusion length of photoexcited charge carriers and to evaluate the actual electric field inside the crystal. A diffusion length of 0.14 mu m is measured in a nominally undoped photorefractive Bi12TiO20 crystal using a 532 nm wavelength laser illumination, in agreement with results obtained from other methods. (C) 1997 American Institute of Physics. [S0003-6951(97)02243-2].

关键词： 移动计算技术   笔记本电脑   微机   便携式  

关键词： 移动计算机网络   网络协议   协议结构  

摘要： 本文研究了移动计算机网的动态寻址和移动透明性问题，提出了基于归属名字服务器和拜访名字服务器的移动管理方案．归属名字服务器存有移动台的归属地址和当前地址等信息．拜访名字服务器存有进入其所在子网移动台的寻址信息，并在移动台离开后延缓两倍分组寿命的时间再删除其寻址信息，既避免频繁地交互移动管理信息，又不用担心寻址信息过时．本文给出了移动计算机网络的协议结构，可支持有连接和无连接通信．

关键词： Timing circuits  

摘要： Vector clocks have been used to capture causal dependencies between processes in distributed computing systems. Vector clocks are not suitable for mobile computing systems due to (i) lack of scalability: its size is equal to the number of nodes, and (ii) its inability to cope with fluctuations in the number of nodes. This paper presents two efficient alternatives to vector clock, namely, sets of dependency sequences, and hierarchical clock. Both the alternatives are scalable and are immune to fluctuations in the number of nodes in the system.

关键词： MOBILE computing  

摘要： Reports on developments in the mobile computing segment of the computer industry in the United States during the week of September 22, 1997. Breakdown of laptop losses in 1996; International Business Machines' introduction of a wireless device that lets users surf the World Wide Web; European vendors' support of a wideband, wireless multimedia technology specification under consideration by the European Union.

关键词： 锂离子蓄电池   锂离子电池   正极材料   锂金属   高分子固体电解质   体积能量密度   负极材料   电解液   薄膜锂电池   移动计算  

摘要： 一、市场呼唤高能高密小型化电池 自十九世纪中叶发明一次性干电池和蓄电池以来,电池已被广泛应用于军事、工业、民用等各个领域。100多年来,从锰干电池、碱锰电池等一次性电池,铅蓄电池和镍镉蓄电等二次电池到水银电池、锂一次性电池、锂离子蓄电池、镍氢蓄电池,随着技术进步,几枯几荣,电池产业已发展成庞大的家族,种类繁多、新品层出不穷,许多十九世纪发明的电池现在仍在使用。

关键词： 笔记本电脑   台式   电脑市场   移动计算   占领市场   市场综述   中国市场   计算机   厂商   内存  

摘要： 一、前言在台式机日益降价的今天,笔记本电脑是否能够继续“玉树临风,卓而不群”保持高价位的贵族形象呢?面对NC、PDA的潜在威胁,笔记本电脑如何有效地占领市场呢?虽然全球台式机市场的增长速度放缓,