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Search Results: 1 - 10 of 14238 matches for " 戴漂漂 "
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传粉动物多样性的保护与农业景观传粉服务的提升
,张旭珠,刘云慧,*,*
生物多样性 , 2015,
Abstract: ?传粉动物为许多植物尤其是作物提供了重要的传粉服务,在保障全球粮食安全和人类福祉、缓冲气候变化对作物产量的影响等方面都发挥着重要的作用。然而来自全球土地利用变化、化学农药使用、外来物种入侵及气候变化等的威胁,导致传粉动物的多样性下降并造成了依赖动物传粉的作物产量和品质的下降。针对这一情况,作者提出了农业景观传粉动物多样性保护和利用的3种主要途径:(1)改善生产管理,例如减少化学农药的使用、适当地采取有机种植;(2)促进景观多样性,包括创建适宜野生传粉者的半自然生境、保护高价值的自然生境、作物多样化、合理配置资源和生境的空间分布;(3)加强对本土传粉动物的保护和开发利用。文章最后提出,为进一步提升传粉服务,还需加强对传粉者的生物学特征、传粉服务的需求与供给现状、影响传粉动物多样性和传粉服务的农作措施和景观因素等方面的研究。
农业景观害虫控制生境管理及植物配置方法
,张旭珠,肖晨子,张 鑫,宇振荣,刘云慧
中国生态农业学报 , 2015,
Abstract: 集约化农业生产过程中,化学农药所带来的大量环境问题日益引起关注。为减少农药的投入及其所产生的环境负效应,生物防治害虫的方法在国内外得到了更多的关注与发展。生境管理是一种有利于天敌群落发展,而不利于害虫种群增长的保护性生物防治方法,其实质是通过为自然天敌提供诸如花蜜、替代猎物或寄主、躲避不利干扰的庇护所等资源,将农业景观中天敌的害虫控制服务和功能最大化,或者通过构建不适宜害虫取食和繁殖的环境条件起到抑制或阻碍害虫发展的作用。本文在参阅国内外文献的基础上,阐述了生境管理控制害虫的机理,并总结国外生物防治的实践经验以及近些年国内外的相关研究,概括提出田间尺度上害虫生物防治的非作物生境及作物生境的建设和植物配置方法,为通过生境管理提升农业景观中害虫生物防治生态系统服务提供参考。
一种改性塔罗油染料分散剂的制备及其性能研究
,刘明华,郭佳
福州大学学报(自然科学版) , 2011,
Abstract: 以塔罗油为原料合成高效染料分散剂,其制备工艺为:塔罗油经过氧化氢预处理后,以高锰酸钾为催化剂,以甲醛和亚硫酸钠混合物为磺化剂进行磺化反应,制备改性塔罗油染料分散剂,并将其应用于还原橄榄T染料,进行分散性能及耐热稳定性研究.结果表明,当磺化时间为3.5 h,原料与磺化剂质量比为1∶3,预处理剂质量分数为4.0%,磺化温度为120℃,预处理时间为25 min,催化剂质量分数为0.2%时,所制备的分散剂的分散等级可达4.3级,其在130℃下能保持较好的耐热稳定性能,分散等级仍可达4.0级.
北京大学图书馆学系函授专修科一九八三年继续招生

图书情报工作 , 1982,
Abstract: ?为加速培养图书馆专门人才,经教育部批准,北京大学图书馆学系函授专修科定于一九八二年冬季在北京、天津、沈阳、大连、长春、哈尔滨、成都等七个城市招收一九八三年级新生。
新加坡英语:语言迁移与华文元素
Singlish: Linguistic Transfer and Chinese Elements
 [PDF]

卫平
Advances in Social Sciences (ASS) , 2012, DOI: 10.12677/ASS.2012.12004
Abstract: 作为众多英语变体中的一种,新加坡英语与英、美等所谓标准英语明显不同,主要原因在于受普通话、广东话、闽南话、海南话、客家话以及马来语、泰米尔语的影响。本文从新加坡英语中的语音、词汇、语法等方面探究具有华语和中华文化元素的新加坡英语及其语言迁移的深层机理。
As one of English varieties, Singlish differs from British or American English as it is heavily in- fluenced by Chinese in particular, Malay, and Tamil in general. There are varied factors of linguistic transfer in terms of phonology, vocabulary, sentence pattern, and grammar. This paper attempts to delve into the transfer of Chinese elements in the formation and development of Singlish.
江苏省谷物类农产品竞争力:基于2001~2010年的实证分析
The Competitiveness of the Cereal Products in Jiangsu Province: Empirical Analysis Based on the Data from 2001 to 2010
 [PDF]

, 王洪亮
World Economic Research (WER) , 2013, DOI: 10.12677/WER.2013.24005
Abstract:

加入WTO以后,江苏省谷物类农产品贸易出现了新特征。本文采用贸易竞争力指数(TC)、类显示比较优势指数(LRCA)、国际市场占有率指数(MS)对江苏省谷物类农产品的国际竞争力进行了分析,并建立计量经济模型对影响谷物类农产品贸易竞争力因素,包括粮食作物播种面积、农民家庭人均农业收入、汇率、CPI指数进行了实证分析。结果表明,江苏谷物类农产品贸易的比较优势正在消失,国际市场占有率逐渐降低,竞争力不断减弱。在此基础上本文提出提高江苏谷物类农产品竞争力的对策与建议。
 After the entry to WTO, the trade of cereal products in Jiangsu Province shows some new features. This article adopts the indexes of TC, LRCA, MS to analyze the international competitiveness of cereal products of Jiangsu. The article also analyzes some factors which affect the trade competitiveness of cereal products, including crop area, per farming income in farm family, the exchange rate, CPI, by establishing an econometric model. The result shows that the comparative advantage in Jiangsu cereal products is disappearing, the share of international market is gradually reducing, and the competitiveness is diminishing. Based on the analysis, the article puts forward some suggestions to improve the competitiveness of cereal products of Jiangsu.

矿渣微粉对水泥耐久性能影响的研究
Influence of Ground Slag on Durability of Cement
 [PDF]

银所
Hans Journal of Civil Engineering (HJCE) , 2015, DOI: 10.12677/HJCE.2015.46034
Abstract: 矿渣微粉具有一定的水化活性,掺入水泥浆体后能够明显提高水泥抗化学侵蚀性能,抗干缩,抗碳化,抗冻性等耐久性能,提高幅度基本可以达到10%左右;利用SEM,TG-DTA,XRD,压汞孔分析等方法对水泥水化物进行分析,结果表明:矿渣微粉能够吸收水泥水化产物Ca(OH)2生成C-S-H凝胶,导致降低孔径,优化孔结构,从而提高水泥石的密实度,从而改善水泥的各项性能。
Experiment of cement with ground slag shows that ground slag can improve the properties of ce-ment such as coefficient of resistance to chemical corrosion, dry shrinkage, and carbonation coef-ficient, freezing and thawing resistance by 10%. The microstructure-analysis by using SEM, TG- DTA, XRD and MIP shows that the ground slag can absorb the productions of hydrating cement: Ca(OH)2, and C-S-H gel is formed, which can refine the distribution of pore structure and increase the density of cement-stone, therefore improving the durability.
小型化高性能带状线型滤波器的研究
A Research of Bandpass Filter with Miniaturization and High Performance Based on Stripline Configuration
 [PDF]

刘毅, 永胜
Applied Physics (APP) , 2016, DOI: 10.12677/APP.2016.61002
Abstract:
随着科技的不断进步,现代通信技术对设备的要求愈来愈高,对于微波滤波器这一重要的射频元器件在小型化与高性能方面的要求也越来越严格。而基于LTCC技术的带状线型微波滤波器正好满足了这些需求,逐渐成为了微波元器件研究的热点之一。本文实现了一种基于LTCC技术的小型化高性能带状线滤波器设计的实现方法,工艺上采取的LTCC技术大大缩小了滤波器的尺寸。借助电路仿真并在电磁场三维仿真软件上进行优化,实物测试结果与仿真结果很好的吻合,中心频率为2800 MHz,带宽为200 MHz,在2600 MHz频率上的衰减优于33 dB,在3020 MHz频率上的衰减优于25 dB,尺寸仅为4.8 mm × 4.2 mm × 1.5 mm。
With the continuous progress of technology, modern communication technology has increasingly demand for high-level equipment; the situation of the microwave filter as one of the essential components in microwave module is the same case. Multilayer microwave filter which is based on the LTCC technology meets these requirements and is becoming one of the hot research fields. A method for the section of stripline configuration bandpass filter with miniaturization and high performance is proposed. In order to ensure its miniaturization, this filter is based on the LTCC technology which is advance in the world. Using the circuit simulation and 3D simulation software to optimize and simulate, the measured results of the filter satisfy its performance requirement. The centre frequency of the BPF is at 2800 MHz and its bandwidth is 200 MHz; at 2600 MHz the stop-band attenuation needs to be more than 33 dB and at 3020 MHz is more than 20 dB. Its size of the fabricated filter is only 4.8 mm × 4.2 mm × 1.5 mm.
LTCC微型巴伦设计
Design of a Miniature Balun Based on LTCC
 [PDF]

孙超, 永胜
Applied Physics (APP) , 2016, DOI: 10.12677/APP.2016.63006
Abstract:
本文提出了一种基于LTCC (低温共烧陶瓷)技术的微型巴伦的设计与实现方法。此种巴伦采用Marchand型结构,运用LTCC多层三维立体集成技术,通过宽边耦合的螺旋型结构实现1/4波长耦合线,大大减小了巴伦的实际体积。随后通过带状线末端电容加载技术的改进型结构,近一步缩小了耦合线长,实现了结构的微型化。最终设计的巴伦工作频带1.5~3 GHz,具有插损小,幅度平坦性好,相位一致性高的优点,巴伦尺寸为2.5 mm × 3 mm × 1.2 mm。文章讨论了该巴伦工作原理、微型化的设计思路、三维结构,最后给出了设计的仿真和测试结果,两者一致性较好。
A method of designing and implementing a miniature LTCC balun is proposed in this paper. This kind of balun is based on the structure of Marchand microstrip balun in order to realize the mi-niaturization. LTCC multilayer 3D technology, broadband coupling spiral stripline and loading terminal capacitors structure have been used to achieve quarter-wave coupling line to reduce the size. The operation frequency ranges from 1 GHz to 3 GHz with the advantages of low insertion loss, well amplitude balance and strong phase consistency. The dimension was only 2.5 mm × 3 mm × 1.2 mm. The operation principle, design thoughts of miniaturization and the structure of balun were discussed in this paper. At last, the results from the simulation and those from the measurement are in good agreement.
一种小型化LTCC集总巴伦设计
Design of a Miniaturized LTCC Lumped Balun
 [PDF]

王鑫, 永胜
Hans Journal of Wireless Communications (HJWC) , 2016, DOI: 10.12677/HJWC.2016.62007
Abstract:
本文提出了一种基于LTCC技术的集总巴伦的设计与实现方法。该小型化集总巴伦由简易LC巴伦结构改进而成,利用ADS软件进行电路仿真以及HFSS软件三维建模设计。性能测试结果表明:测量结果数据与仿真结果基本一致,该巴伦的标称中心频率为70 MHz,频带宽20 MHz,通带内插入损耗小于4.7 dB,两端口相位差大于172?,尺寸仅为2.5 mm × 1.5 mm × 1 mm。完全能够满足当今通信设备日益小型化的要求。
This paper presented a design and realization method of lumped balun based on the LTCC tech-nology, which was derived from simple LC balun and designed by ADS circuit simulation and the HFSS software to optimize the 3D modeling. The measured results agree with the simulated data basically, the center frequency of balun sample is 70 MHz, the bandwidth is 20 MHz, the insertion loss of the pass band is less than 4.7 dB, the phase difference between the two output ports is more than 172?, the size is only 2.5 mm × 1.5 mm × 1 mm. The balun can totally be used in miniaturized mobile communication equipment.
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