新型语法分析器构造的研究

文中阐述了语法分析器构造的研究现状和构造过程中存在的问题;在讨论向前看多个符号必要性的基础上,分析了向前看多个符号的新型语法分析器构造方法;指出了语法分析器构造研究中待解决的若干问题。     

基于XGBoost的Ebay网上拍卖最终成交价格预测

对成交价格进行预测,旨在获得Ebay拍卖品的价格动态,使买卖双方更好地进行交易.将价格区间进行多分类划分和多次最优参数选择,建立极端梯度提升(XGBoost,eXtreme Gradient Boosting)模型,并与最优逻辑斯蒂回归模型比较,使用平均准确率作为模型的评估指标.经比较发现XGBoost模型达到90.5...     

试论企业财务管理

财务管理工作是现代企业中的一个庞大而严密的管理系统，从会计核算、财务信息、财务分析、财务管理、财务理财、财务评价等6个层面对企业如何开展财务管理工作进行了论述。     

分子生物学技术在浸矿微生物研究中的应用

分子生物学技术在浸矿微生物的研究中发挥着举足轻重的作用。总结了一些先进分子生物学技术在浸矿微生物鉴定和浸矿微生物基因工程育种两方面的应用情况,包括16S rRNA和16S rDNA基因序列分析技术、实时定量PCR技术、限制性片段长度多态性分析技术、荧光原位杂交技术、变性梯度凝胶电泳和温度梯度凝胶电泳技术、基因间隔序列分析技术、浸矿微生物质粒载体研究、外源基因导入浸矿微生物方法研究等。     

Generation of hydrogen from aluminum and water - Effect of metal oxide nanocrystals and water quality

Metal Oxides nanocrystals such as TiO₂, Co₃O₄, Cr₂O₃, Fe₂O_3, Mn₂O₃, NiO, CuO and ZnO were used as modifiers on the metallic aluminum (Al) powders for the production of hydrogen in deionized water or tap water at room temperature. In particular, the influences of TiO₂ nanocrystals with various crystal sizes on the production of hydrogen from the reaction in tap water under ambient condition were investigated in details. It was found that hydrogen was barely generated from metal Al powders in tap water at 25-45 °C but significantly produced in deionized water above 35 °C without any modifiers. TiO₂, Co₃O₄, and Cr₂O₃ nanocrystals were very effective to promote hydrogen generation from the reaction of Al and deionized water at 25 °C. In addition, while other oxide nanocrystals were ineffective to promote hydrogen generation in tap water, TiO₂ nanocrystals (P90, ∼14 nm in diameter) were found to be highly effective in facilitating the production of hydrogen from the reaction of Al with tap water, comparable to the well-known γ-Al₂O₃. The production of hydrogen over time was found to be dependent on the passive layer of metal Al, where Al(OH)₃ plays an important role during reaction. Pitting is proposed as the major mechanism behind the production of hydrogen in the nanocrystals TiO₂ (P90)-modified Al/tap water system, which is thought to be originated from point defects, and differ considerably from the uniform corrosion model.     

Single-step flash-heat synthesis of red phosphorus/graphene flame-retardant composite as flexible anodes for sodium-ion batteries

Nano Research - Red phosphorus (RP) has attracted considerable attention as the anode for high-performance Na-ion batteries, owing to its low cost and high theoretical specific capacity of ∼...     

Differences between beginning and advanced design students in analogical reasoning during idea generation: evidence from eye movements

Cognition, Technology & Work - In existing studies about analogical reasoning during idea generation in design, there is lack in quantitative and objective evidences showing the relationship...     

Architecture design and implementation of image based autonomous car: THUNDER-1

Autonomous driving with high velocity is a research hotspot which challenges the scientists and engineers all over the world. This paper proposes a scheme of indoor autonomous car based on ROS which combines the method of Deep Learning using Convolutional Neural Network (CNN) with statistical approach using liDAR images and achieves a robust obstacle avoidance rate in cruise mode. In addition, the design and implementation of autonomous car are also presented in detail which involves the design of Software Framework, Hector Simultaneously Localization and Mapping (Hector SLAM) by Teleoperation, Autonomous Exploration, Path Plan, Pose Estimation, Command Processing, and Data Recording (Co- collection). what’s more, the schemes of outdoor autonomous car, communication, and security are also discussed. Finally, all functional modules are integrated in nVidia Jetson TX1.

     

Rail fatigue crack propagation in high-speed wheel/rail rolling contact

Railway Engineering Science - To study the wheel/rail rolling contact fatigue of high-speed trains, we obtain the distribution of contact forces between wheel and rail by introducing the...     

用灵敏值确定纯β核素的液闪测量效率

纯β核素液闪测量技术应用广泛,实际工作中往往需要确定核素的测量效率;但除~3H、~(14)C等半衰期较长的核素外,多无系列猝灭标准源,给工作带来很多不便。本文根据国外有关方面研究,做了以~3H标准源为基准、通过理论计算求出其它纯β核素在均相条件下的测量效率和猝灭校正曲线,进而求得放射性的活度。本方法使用简便、结果可靠,实用性强。