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61.
62.
Quantitative analyses of flow and stage data, remote sensing and geographic information systems analysis, and field studies were used to assess the impact of dams and diversions on the point bar habitat of the Sacramento Valley Tiger Beetle (Cicindela hirticollis abrupta). The reaches of interest include sites of known historic populations of C. h. abrupta along the Sacramento River from approximately 8 km north of Colusa southward to the confluence with the Feather River and along the Feather River between Yuba City and its confluence with the Sacramento River. The results from this study show that construction of two major dams has altered flows such that prolonged and increased flows during summer, fall, and early winter have most likely disrupted life cycles, flooded larvae, drowned overwintering adults and led to high mortality. Additionally, habitat availability has decreased over time because point bars have decreased in number and area causing increased distances between populations and isolation of populations. Moreover, point bar armouring, channel scouring, altered flows, redirected flows through weirs, and lithologic controls have produced a bimodal distribution of mean grain sizes in the Sacramento River in which the more northern bars contain gravel deposits and more southern bars possess fine sands. These conditions negatively alter moisture retention and sediment compaction and, consequently, burrowing conditions needed by this tiger beetle. Additionally, more stabilized flows (reduced variability) and increased fine‐grained deposition have enabled development and encroachment of vegetation onto the sand bars. Finally, human stresses, such as foot traffic and vehicular traffic may have interfered with burrowing, ovipositing, and foraging. The combination of these stress factors has most likely led to a reduction in source populations and, ultimately, the apparent extirpation of the entire metapopulation. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
63.
成形磨削中砂轮修整精度的研究 总被引:6,自引:1,他引:5
成形磨削一般采用金刚石笔来修整所需要的砂轮形状,金刚石笔在安装中的位置误差将影响被加工工件的精度,本文对此误差的大小进行了分析。 相似文献
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65.
Sven Beyer Christian Jacobi Daniel Kröning Dirk Leinenbach Wolfgang J. Paul 《International Journal on Software Tools for Technology Transfer (STTT)》2006,8(4-5):411-430
In the verified architecture microprocessor (VAMP) project we have designed, functionally verified, and synthesized a processor
with full DLX instruction set, delayed branch, Tomasulo scheduler, maskable nested precise interrupts, pipelined fully IEEE
compatible dual precision floating point unit with variable latency, and separate instruction and data caches. The verification
has been carried out in the theorem proving system PVS. The processor has been implemented on a Xilinx FPGA.
A shorter version of this article with the title “Instantiating uninterpreted functional units and memory system: functional
verification of the VAMP” appeared in [8]. The work reported here was done while all the authors were with Saarland University. 相似文献
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68.
稳定主槽是当前黄河下游河道治理的关键。窄深河槽具有很强的泄洪能力与输沙能力,是主槽整治追求的目标。黄河下游均是顺直微弯河道,河道水流最基本的主导机理是沿着阻力最小的方向流动,走直路、走近路,主槽整治设计流路应以顺直为上策。当前有必要对微弯整治方案进行再认识,实现对其否定之否定的提高。控制性弯道整治、对口丁坝整治、节点整治都属于双岸整治的范畴,对双岸整治的方向应予肯定。今后的整治应从微弯整治向节点整治发展,逐步过渡到以节点整治为主,最终达到稳定河势流路、高效排洪输沙之目的。 相似文献
69.
唐德修 《成都纺织高等专科学校学报》2007,24(3):13-15
科学焚烧处理垃圾法具有占地少,场地易选择,时间短,减量化显著,无害化彻底以及回收余热供发电供热等优点.其处理设备和控制系统是保证科学焚烧处理垃圾成功,并带来巨大经济效益的关键.鉴于此,文章对科学焚烧垃圾系统设计作了比较详细的介绍. 相似文献
70.
《Petroleum Science and Technology》2007,25(7):915-923
Polymer modified bitumen (PMB) is used in various construction applications, especially in motorways. The aim of this study is to improve features of 60/70 penetration grade, modified bitumen used on highways. Increasing the sensitivity to temperature and oxidation resistance are very important points for the modified bitumen. This condition was provided by reacting the carboxylic acid groups in asphaltene with the reactive ethylene terpolymer to form ester. Reactive ethylene terpolymer (RETP) and ethylene terpolymer (ETP) manufactured by DuPont USA were used as additives in this study. Infrared Spectrophotometer (IR) graphics and optical pictures of the modified bitumen have been examined. It has been observed that the softening point has increased on the other hand, the penetration and ductility values have decreased according to the test results. 相似文献