Comparison of numerical and analytical solutions for fly casting dynamics

This paper presents an approximate analytical model of the dynamics of a tapered fly line during a standard overhead cast. During casting, the line forms a nonlinear propagating wave that is frequently referred to as a ‘loop’ by fly casters. The geometry of the loop is described by three distinct parts: a straight bottom segment (attached to a stationary fly rod), a semi-circular segment that is propagating (i.e. the loop), and a straight top segment that is also propagating, (i.e. the traveling line). A fly (particle) is attached at the end of the traveling line. A work-energy balance yields the velocity of the fly as a function of the length of the traveling line. For a uniform fly line (level line), a closed-form solution is found, while for a tapered fly line, the solution is obtained by quadrature. A critical loop diameter arises in the analysis, and it determines whether the final velocity of the fly is greater or lesser than the initial velocity of the traveling line. The analytical solutions are critically compared against numerical solutions of a general model for fly line dynamics that relaxes many of the assumptions employed in the analytical model. The agreement between the two solutions remains close during the loop propagation phase, provided a significant amount of fly line remains in the traveling line. However, as the traveling line vanishes and the loop ‘turns over’, the two solutions diverge abruptly due to the many simplifying assumptions employed in the analytical model.     

《哈姆莱特》与《苍蝇》的艺术特点之比较

莎士比亚的《哈姆莱特》和萨特的《苍蝇》都是广有影响的世界名剧.虽然它们的诞生相隔了三个半世纪,两位作者又分属不同的国家和民族,然而,这两部杰作在艺术上却表现出许多相同或相似的特点.本文拟从古老题材反映现实人生、塑造人物的非凡功力、深刻的哲理和寓意、“境遇剧”理论、封闭式结构、复杂的冲突等相同或相似的方面,以及一些差异,进行了简要的比较,以期表明西方文学的一脉相承和两个伟大艺术家在表现人类心灵和艺术表现生活方面的感应和相通.     

汉字起源观念的文化审思

汉字起源的研究误解甚多 ,人们多以为汉字的历史是从甲骨文开始 ,其实 ,甲骨文不是中国最早的文字 ,也不是当时的主流文字 ,更不是当时中华文化的先进代表 ,相反却是那时一种职业性的落后的“变文” ;甲骨———金文———竹简书没有先后的继承关系 ,它们只是书刻文字材料的进化过程 ;汉字的起源不是考古学的问题 ,是心理学的问题 ,是人类文化学的问题。我们不能将文字与书写文字的物质材料等同起来     

An artificial neural network approach for prediction of long-term strength properties of steel fiber reinforced concrete containing fly ash

In this study, an artificial neural network （ANN） model for studying the strength properties of steel fiber reinforced concrete （SFRC） containing fly ash was devised. The mixtures were prepared with 0 wt%, 15 wt%, and 30 wt% of fly ash, at 0 vol.%, 0.5 vol.%, 1.0 vol.% and 1.5 vol.% of fiber, respectively. After being cured under the standard conditions for 7, 28, 90 and 365 d, the specimens of each mixture were tested to determine the corresponding compressive and flexural strengths. The pa- rameters such as the amounts of cement, fly ash replacement, sand, gravel, steel fiber, and the age of samples were selected as input variables, while the compressive and flexural strengths of the concrete were chosen as the output variables. The back propagation learning algorithm with three different variants, namely the Levenberg-Marquardt （LM）, scaled conjugate gradient （SCG） and Fletcher-Powell conjugate gradient （CGF） algorithms were used in the network so that the best approach can be found. The results obtained from the model and the experiments were compared, and it was found that the suitable algorithm is the LM algorithm. Furthermore, the analysis of variance （ANOVA） method was used to determine how importantly the experimental parameters affect the strength of these mixtures.     

浅论先秦时期百家争鸣中的音乐思想

本文系统介绍了先秦时期诸子百家的音乐思想，着重阐述了诸子百家在音乐思想方面具有保守和进步的两面性问题，并对各家音乐思想对当今社会的影响作了简要评价。     

论《苍蝇》中所体现的自由选择理论

《苍蝇》是存在主义哲学家萨特的代表作之一,萨特在文中借鉴神话传说抽象而又全面地表述了自己的哲学观点-自由选择理论,这一理论包含三个相互联系又相互帝l约的方面。其中责任现的提出是对萨特早期绝对自由选择理论的矫正,从而对20世纪西方文学乃至西方社会都产生巨大的影响。     

沛公"与樊哙……步走"辨析

本文针对人们对《鸿门宴》一文中沛公"与樊哙……步走"的不同理解,从考证"与"字入手,探讨对这段文字的正确解读.认为:文中的"与"字,既不是连词,也不是名词或介词,而是一个含有使令意义的动词,其词义相当于现代汉语的"让"或"使".因此,这段文字既不能解读为沛公"和樊哙……徒步逃跑",也不能解读为沛公"党与樊哙……徒步逃跑",而应当解读为沛公"让樊哙……跑步跟随".只有这样解读,才符合文章的原意.     

人性化教育还是克隆人养殖——《别让我走》中海尔森教育体制失败原因解析

石黑一雄小说《别让我走》中的克隆人培育机构海尔森是叙述者的回忆焦点,也是评论者分析的热点。小说中机构负责人解释了海尔森的关闭原因——受到大众关注与反对,但这并非其失败的根本原因。本文认为海尔森披着"人性化"的外衣,却以"非人道"的方式对待学生;将学生的灵魂与肉体二元对立,使其思维意识的发展囿于待宰割的身体,冷漠地在学生中造成对不存在的未来无望的期待和困惑。文章揭示出"人性化"的教育目的和"非人道"的操控手段之间、培养克隆人的灵魂与提供器官移植的供体之间的悖论性,才是其失败的真正原因。     

基于“让学引思”的小学数学教学探讨

在新课程改革背景下,教与学关系的转变,教师与学生的变化,成为创新教学模式的主要出发点。在小学数学教学改革中,“让学引思”的引入,要求教师让渡学习主动权,启发学生思考,而这对于优化教师教学行为,让学生获得学习主动权,促进学生主动发展、全面发展具有重要意义。基于此,本文从新课程改革的背景出发,简要分析“让学引思”的基本内容,并结合小学数学教学实际对“让学引思”的实践方法进行简要探究。     

《孔雀东南飞》主题驳议与新探

《孔雀东南飞》是一首脍炙人口的中国古代叙事长诗。这里对以往学史认定该诗的“反封建”主题提出质疑,并从创作、编纂和接受三个角度分析论证了该诗主题的定位问题,认为“讴歌爱情”才是本诗的主旨所在。