共查询到19条相似文献,搜索用时 93 毫秒
1.
2.
3.
4.
5.
6.
7.
高超声速技术是未来航空航天领域的制高点,具有重要的战略性和前瞻性意义。文章采用文献计量/综述、国内外官方机构/权威网站调研等方法对全球高超声速技术发展态势进行分析。研究发现,针对高超声速技术的研究主要集中在军事领域,其中动力推进技术、制导与控制技术、新型材料和热防护技术等是该领域的研究重点方向。通过梳理各国研发态势发现,未来涉及高超声速武器研发的相关核心技术仍是研究的重点,同时各国正加快优先布局高超声速防御系统,加强与合作国在技术研发、联合防空和导弹防御等方面的合作,以提升地区防御力和威慑力。 相似文献
8.
在物质密度测量中,由于有些物质具有可溶性,有些物质具有吸水性,特别是有些物质为小粒状吸水性固体,体积测量是一个难以解决的问题.文章提出了一种测量物质密度的新方法,利用气体比热容比测定仪,即可测量可溶性物质的体积、还可测量吸水性物质的体积,特别是可以测量小粒状吸水性固体的体积.体积测出后,再利用天平称量物质的质量,就可测... 相似文献
9.
10.
制备了一个简易绝热型热量计,并用此热量计实测了7种非均相电解质水溶液在5~60℃范围内不同温度区间的比热容,提出了比热容与温度的经验关联式。关联式的计算值和实验值的平均相对偏差均小于1%。热量计采用标准物质正庚烷标定,装置的测量精度为0.9%。 相似文献
11.
Thomas M. Gardner 《Journal of The Franklin Institute》1905,159(3):199-215
A paper showing that no simple relationship exists between the values of adiabatic exponents and specific, latent or total heats. Algebraic and graphical methods of determination are used. Tables of average and instantaneous values of n, with their corresponding sheets of curves, are given for steam, carbon disulphide, ether, carbon tetrachloride and acetone. Surfaces having intantaneous exponent, pressure and quality values on coordinate axes are shown. 相似文献
12.
针对标准的BP神经网络对于声音信号识别率不高的问题,提出了一种用粒子群算法(PSO)优化BP神经网络的算法,建立了声音信号识别模型。PSO优化BP神经网络主要是用PSO来优化BP神经网络的初始权值和闽值,然后通过训练BP神经网络得到识别模型的最优解,优化后的神经网络具有误判率小、反应速度快等特点。在实验中把标准的BP神经网络和PSO优化后的BP神经网络用于八种异常声音的MFCC特征量和差分MFCC特征量识别,结果表明:在声音信号的识别系统中采用PSO优化BP神经网络的算法提高了系统的识别性能,达到了系统设计的目的。 相似文献
13.
Arthur K. Doolittle 《Journal of The Franklin Institute》1973,295(3):217-237
A volume—entropy—energy (VSE) equation of state, unlike a PVT equation of state, can be used to calculate “all conceivable” thermodynamic quantities, including specific heats, without supplemental calorimetric data. A VSE equation for liquids, based on simple theoretical concepts, is proposed and, in this paper, applied specifically to n-heptane. This equation of state requires only ten arbitrary parameters, seven of which may be calculated from data at but three temperatures, e.g., 25°, 50° and the normal boiling point. It yields calculated values of many thermodynamic properties nearly as accurate as the best experimental data, from a few degrees above the melting temperature all the way to the critical temperature. PVT equations of state of comparable accuracy over such broad ranges would require at least as many parameters, as well as supplemental calorimetric data, to calculate many thermodynamic quantities that are obtainable directly from our VSE equation. 相似文献
14.
Countries around the world have had to respond to the COVID-19 outbreak with limited information and confronting many uncertainties. Their ability to be agile and adaptive has been stressed, particularly in regard to the timing of policy measures, the level of decision centralization, the autonomy of decisions and the balance between change and stability. In this contribution we use our observations of responses to COVID-19 to reflect on agility and adaptive governance and provide tools to evaluate it after the dust has settled. Whereas agility relates mainly to the speed of response within given structures, adaptivity implies system-level changes throughout government. Existing institutional structures and tools can enable adaptivity and agility, which can be complimentary approaches. However, agility sometimes conflicts with adaptability. Our analysis points to the paradoxical nature of adaptive governance. Indeed, successful adaptive governance calls for both decision speed and sound analysis, for both centralized and decentralized decision-making, for both innovation and bureaucracy, and both science and politics. 相似文献
15.
整体思想是数学解题中一个极其重要而有效的策略,也是提高解题速度的有效途径。本文结合教学实践,通过具体实例,探讨了如何运用整体思想来提高解题速度。 相似文献
16.
虽然我国政府时风险投资业的税收政幕不断地做出完善。但是还存在相应的税收法律机制不健全;风险投资机构并没有相应税收优惠;政策偏重于行业性及地域性,缺乏公平;缺乏针对内资风险投资机构的税收优惠等问题。通过借鉴美国等发达国家税收优惠政策.提出了优化我国风险投资税收政策的建议。 相似文献
17.
An automated, disk-based, enzyme-linked immunosorbent assay (ELISA) system is presented in this work. Magnetic beads were used as the antibody carriers to improve the assay sensitivity and shorten the reaction time. The magnetic module integrated on the system is capable of controlling the magnetic beads to either move in the incubation stage or immobilize at a specific location during washing stage. This controlling mechanism utilizes a passive controlling approach so that it can be performed through disk spinning without the need of active control from external devices. The movement of the magnetic beads was investigated and the optimal rotational speed was found to be related to the ratio of the processing time to the cycle time of the magnetic beads. Comparing to ELISA conducted on microtiter plates, similar test results could be achieved by the disk-based ELISA but the entire protocol can be finished automatically within 45 min with much less reagent consumption. 相似文献
18.