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圆锥曲线中的几何最值和参数取值范围问题实属一类问题,解决的方法是统一的,往往是代数、三角、几何等多方面知识的渗透和综合,函数、方程、不等式、转化、归纳、分类讨论等多种思想的交叉运用,以及换元、数形结合、三角代换等多种方法技巧的灵活运用,考查学生观察、分析、综合构造、创新等多方面的结合思维能力,是历届联赛考查的重点内容之一. 相似文献
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圆锥曲线中的几何最值和参数取值范围问题实属一类问题,解决的方法是统一的,往往是代数、三角、几何等多方面知识的渗透和综合,函数、方程、不等式、转化、归纳、分类讨论等多种思想的交叉运用,以及换元、数形结合、三角代换等多种方法技巧的灵活运用,考查学生观察、分析、综合构造、创新等多方面的结合思维能力,是历届联赛考查的重点内容之一.例1(1995年全国高中数学联赛题)给定曲线族2(2sinθ-cosθ 3)x2-(8sinθ cosθ 1)y=0(θ为参数),求该曲线族在直线y=2x上所截得的弦长的最大值.分析曲线族和直线y=2x都过原点,设曲线族与直线y=2x的另… 相似文献
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Hydrophobic nanochannel self-assembled by amphipathic Janus particles confined in aqueous nano-space 下载免费PDF全文
Hydrophobic nanochannel plays a significant role in many physical, biological, and geological phenomena and exhibits impressive applications due to both its ubiquitous distribution and great ability to transport hydrophobic molecules,including various oils and gases. Based on theoretical modeling, we herein reveal that the amphipathic Janus nanoparticles have a large probability to self-assemble into uninterrupted hydrophobic nanochannels inside the aqueous nano-space, although there are large portions of the Janus nanoparticles to be hydrophilic. The key to this observation is the attractions between the hydrophobic regimes on neighboring amphipathic Janus particles through hydrophobic interaction in aqueous nano-space. More surprisingly, the permeation efficiency of hydrophobic molecules through the uninterrupted hydrophobic channel in Janus particles aggregate is even higher than that in the aggregate of hydrophobic particles. We note that the proposed amphipathic Janus particles can be transported to the appropriate positions by the water since the hydrophilic regimes still remain a strong particle–water interaction. We also note that most natural subsurface rocks are not completely hydrophobic or hydrophilic but have complex surfaces with inhomogeneous wetting property. Our work therefore provides a detailed molecular level understanding of the formation of underground strata as well as the new insight for constructing the artificial hydrophobic channels for various applications, such as the design of proppants to enhance the recovery of the unconventional oil/gas. 相似文献
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多种燃料多级燃烧的燃气热力性质简捷算法 总被引:2,自引:0,他引:2
文献[1]给出了计算烃型燃料C_8H_(16)燃烧产物热力性质的方法,文献[2]把它推广到C-H-O-N′-S类型任意燃料。本文在上述基础上,推出能计算多种任意C-H-O-N′-S类型的气体、液体或固体燃料(含不可燃组分)混烧或多级燃烧后的燃气热力性质的简捷方法。 相似文献
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本文应用变工况的折合参数相似理论和因次分析原理,确定燃气轮机功热并供装置标定试验的试验工况原则,并提出简捷合理的修正方法。具体推导多结合较复杂的分轴燃气轮机与排气全燃型锅炉联合的功热并供系统进行。对工程实践有一定实用价值。 相似文献
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氢氧联合循环——设计点及变工况初步分析 总被引:1,自引:0,他引:1
一、前言 氢氧完全反应生成物是水蒸汽,膨胀过程包括了部分底循环,可以没有常规联合循环中燃机排气放热与蒸汽吸热过程,这是氢氧循环提出的出发点,也是此循环的最大优点。氢氧反应放出的大量能量除提高生成物温度外,还加热底部循环工质,加热方式分为直接混合式加热和面式加热两种。本文着重讨论以上两种氢氧联合循环的性能。 相似文献
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