排序方式： 共有141条查询结果，搜索用时 15 毫秒
11.
A simple channel estimator for space-time coded orthogonal frequency division multiplexing (OFDM) systems in rapid fading channels is proposed. The channels at the training bauds are estimated using the EM (expectation-maximization) algorithm, while the channels at the data bauds are estimated based on the method for modelling the time-varying channel as the linear combination of several time-invariant "Doppler channels". Computer simulations showed that this estimator outperforms the decision-directed tracking in rapid fading channels and that the performance of this method can be improved by iteration. 相似文献
12.
民营企业在经历了原始积累和快速发展阶段后，正处于第二次飞跃阶段。民营企业涉足的领域不断扩大，资本及技术含量大为提高，对融资及金融服务在规模和方式上均有了更高的要求。本文主要通过对台州市路桥区民营企业融资情况的调查和分析，探讨民营企业在融资渠道、融资方式等方面所面临的问题。 相似文献
13.
M-ZSM-5分子筛的结构及催化性能研究进展 总被引：3，自引：0，他引：3
探究了ZSM-5分子筛的晶体结构、孔结构及酸性质：对通过离子变换对其表面进行优化以提高催化活性方面的研究工作进行了阐述；对Cu-ZSM-5分子筛上NO直接催化分解反应提出了：4CuO=2Cu20＋02，2Cu2O＋4NO=4CuO＋2N2＋O2的反应机理。 相似文献
14.
自愈环是SDH组网最常用的结构方案,本论文探讨了几种自愈环的原理,分析其各自的特点及应用场合,着重研究了各种自愈环的容量,得出了复用段保护环信道利用率要大大高于通道保护倒换环的结论,并且论述了如何根据网络所处层次、业务分布等原因灵活使用各种自愈环。 相似文献
15.
Refining and Extending the Business Model With Information Technology: Dell Computer Corporation 总被引：7，自引：0，他引：7
The exceptional performance of Dell Computer in recent years illustrates an innovative response to a fundamental competitive factor in the personal computer industry - the value of time. This article shows how Dell's strategies of direct sales and build-to-order production have proven successful in minimizing inventory and bringing new products to market quickly, enabling it to increase market share and achieve high returns on investment. The Dell case illustrates how one business model may have inherent advantages under particular market conditions, but it also shows the importance of execution in exploiting those advantages. In particular, Dell's use of information technology (IT) has been vital to executing both elements of its business model - direct sales and build-to-order - and provides valuable insights into how IT can be applied to achieve speed and flexibility in an industry in which time is critical. Many of the insights gained from this case can be applied more generally to other time-dependent industries, suggesting that the findings from the Dell case will have implications for a growing number of companies and industries in the future. 相似文献
16.
【目的】 了解我国医学期刊微信视频号运营现状,探究现存问题并提出建议,为更多医学期刊发展微信视频号提供思路。【方法】 采用网络搜索法对《中文核心期刊要目总览(2020版)》收录的医药、卫生类期刊名称进行检索,获取期刊开通微信视频号的情况、信息资料、运营情况等相关数据进行统计整理、分析,总结问题并提出有效发展策略。【结果】 医学期刊微信视频号存在开通率低、信息资料不完善、运营意识不强、推送规划不够、平台活跃度不高、渠道引流不足等问题。【结论】 医学期刊在微信视频号领域具有较大发展空间,建议充分发挥新型视频媒介优势及自身学科优势,积极投身微信视频号,重视平台建设,提高运营意识,构建推送体系,并注重用户互动性及多渠道引流,提升微信视频号的传播能力。 相似文献
17.
Oh and LaRose (2016) contended that problem severity and channel publicness shape support seekers’ goals, time spent composing messages, and the sophistication of those messages. The current study seeks to replicate and extend Oh and LaRose’s study to produce a more accurate understanding of the factors that influence the sophistication of support-seeking messages online. Support seekers’ goals varied according to the severity of a stressor and the publicness of a channel, and the amount of time people spent composing a message influenced its sophistication. We extend the original study by examining associations that were not initially tested. Time spent composing messages mediated the influence of problem severity on the quality of people’s messages, and this effect was moderated by channel publicness. 相似文献
18.
19.
从SAN技术特点和数字图书馆的数字资源永久保存战略出发，阐述了SAN作为存储系统的优势，并通过实际的物理模型，给出了基于FC—SAN的数字资源永久保存方案。 相似文献
20.
奉国和 《现代图书情报技术》2006,1(5):74-76
运用有限状态图设计图书馆语音自动应答系统, 以弥补图书馆现有系统的不足，实现以读者为中心的新型信息服务模式，使图书馆的信息服务在广度、深度、效率等方面都有较大的提高。 相似文献