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171.
叙述了DFT在连续信号谱分析中的频谱泄漏现象,分析了造成频谱泄漏的原因,讨论了一种自适应同步抽样算法.该算法利用频率跟踪技术实现采样频率的自适应调整.实验结果表明,该算法能够有效地减少频谱泄漏,在以交流电信号测量为基础的系统中具有较好的应用价值. 相似文献
172.
王波 《贵阳学院学报(自然科学版)》2017,12(2)
结合在渥太华大学工程学院研修期间的见闻,从人才培养目标、课程体系、课堂教学评价、教学理念、教学方法和手段等方面,对两国的工程教育进行了对比,并提出了一些提升新生本科院校工程人才培养质量的建议. 相似文献
173.
题目a、b、c是正实数.证明:(a5-a2 3)(b5-b2 3)(c5-c2 3)≥(a b c)3.(2004,美国数学奥林匹克)研究该题,笔者发现可以将其堆广.命题若ai∈R ,i=1,2,…,n,则∏ni=1(a2n-1i-an-1i n)≥∑ni=1ain,n∈ .证明:因为ai∈R ,i=1,2,…,n,所以,(ani-1)(an-1i-1)≥0(n∈N )a2n-1i-ani-an-1i 1≥0a2n-1i-an-1i n≥ani (n-1).记Ani=ani (n-1),则由上式知∏ni=1(a2n-1i-an-1i n)≥∏ni=1(Ani).①下面证明∏ni=1(Ani)≥∑ni=1ain.因为1=an1An1 n-1An1=an1An1 1An1 … 1An1,1=1An2 an2An2 1An2 … 1An2,1=1An3 1An3 an3An3 1An3 … 1An3,……1=1Ann … 相似文献
174.
The standardized IEEE ,802. II distributed coordination function ( DCF) provides a contention-based distributed channel access mechanism for mobile stations to share the wireless medium. However, when stations are mobile or portable units, power consumption becomes a primary issue since terminals are usually battery driven. This paper proposes an analytical model that calculates the energy efficiency of both the basic and the RTS/CTS access mechanisms of the IEEE 802. II protocol. The model is validated with simulation results using NS-2 simulation package. The effects of the network size, the average packet length, the initial contention window and maximum backoff stages on the energy efficiency of both access mechanisms are also investigated. Results show that the basic scheme has low energy efficiency at large packet length and large network size, and depends strongly on the number of stations and the backoff procedure parameters. Conversely, the RTS/CTS mechanism provides higher energy efficiency when the network size is large, and is more robust to variations in the backoff procedure parameters. 相似文献
175.
杨博 《太原大学教育学院学报》2005,23(3):25-27
从新诗否定形式要素的现象出发,在提出"声情"这一传统诗论概念的基础上,引入了"形式情绪"这一概念从心理学的角度入手分析形式情绪的自我赋形机制. 相似文献
176.
Chinese Meishan and Jiangquhai pigs are two of the most prolific pigs in the world, but their growth rate is lower than that of Duroc, Landrace and Pietrain pigs. It is suggested that growth rate is regulated by growth hormone. The objective of the current study was to analyze the porcine growth hormone (pGH) gene polymorphisms based on the polymerase chain reaction restriction fragment-length polymorphism method (PCR-RFLP) for three western meat-type breeds (Duroc, Landrace and Pietrain) and two local Chinese pigs (Meishan and Jiangquhai). Five polymorphic restriction sites were detected with the ApaI, MspI, BspI and HhaI restriction enzymes in two amplified fragments (605 bp, -119 to +486; 506 bp, +206 to +711). Breed difference was found only in the 506 bp fragment. There was no difference in allelic frequencies of BspI and HhaI restriction sites among the five breeds (P>0.05). Landrace and Meishan pigs lacked allele G3 of MspI site. The allele G3 frequency of restriction MspI site of the 506 bp fragment in Pietrain pigs was higher than that in Duroc and Jianquhai pigs (P<0.001). For ApaI site, the Meishan pigs lacked allele G1; no difference was found in allelic frequencies among Pietrain, Duroc, Landrace and Jiangquhai pigs (P>0.05). This new and rapid PCR-RFLP typing method is an attractive tool for analysis of porcine growth hormone gene restriction sites. The differences in MspI and ApaI restriction sites may explain the growth difference between the foreign meat-type breeds above mentioned and local Chinese pigs. 相似文献
177.
本文分析了生活形式在后期维特根斯坦哲学、美学中的重要性,这种重要性表现在生活形式不但是家族相似的背景,而且是语言游戏的落脚地,还是意义判断的标准。生活形式具有实践性、不可穷尽性和语言性的特点,而美的本质观正是在其中得以消解。维氏对美的本质观的消解直接或间接地影响到中国语言美学的形成。 相似文献
178.
Benny Hin Wai Yung Siu Ling Wong Man Wai Cheng Ching Sum Hui Derek Hodson 《Research in Science Education》2007,37(3):239-259
A CD-ROM consisting of videos of two lessons by different teachers demonstrating exemplary science teaching was used to elicit,
develop and track the changing conceptions of good science teaching of student teachers enrolled for the one-year Postgraduate
Diploma in Education (PGDE) at several stages during the programme. It was found that the videos acted as an effective probe
to elicit student teachers’ conceptions and had significant impact on those conceptions at different stages of the programme
through the provision of teacher models demonstrating exemplary teaching. The experience has extended novice teachers’ awareness
of alternative teaching methods and approaches not experienced in their own schooling, broadened their awareness of different
classroom situations, provided proof of existence of good practices and prompted them to reflect on their current conceptions
of good science teaching. Most importantly, the strategy of asking student teachers to watch the same videos on three separate
occasions at different times of the course was recognized by them as a crucial element in facilitating their reflection on
their changing conceptions of good science teaching.
PGDE is the standard form of pre-service teacher education in Hong Kong. It provides qualified teacher status within Hong
Kong. Student teachers enrolled for the PGDE have completed a relevant undergraduate degree. 相似文献
179.
民主政治决策的成本与收益分析 总被引:1,自引:0,他引:1
公共选择学派认为政治人的理论预设有助于政治决策领域的分析,如同经济人一样,政治人在政治决策过程中也会不断追求自身利益的最大化。政治收益大于政治成本是政治人的理性预期和根本目标。然而,在民主政治中,政治人的这种预期容易滋生滥用权力的倾向,阻碍民主政治的实现。 相似文献
180.