Ehrenfest’s theorem and nonclassical states of light 1. Ehrenfest’s theorem in quantum mechanics

When it was first enunciated, Ehrenfest’s Theorem provided a necessary and important link between classical mechanics and quantum mechanics. Today, the content of the theorem is understood to be a natural and immediate consequence of the equation of motion for operators when quantum mechanics is formulated in the Heisenberg picture. Nevertheless, the theorem leads to useful approximations when systems with Hamiltonians of higher than quadratic order in the dynamical variables are considered. In this two-part article, we use it to provide a convenient illustration of the differences between so-called classical and nonclassical states of radiation.     

Ehrenfest’s theorem and nonclassical states of light 2. Dynamics of Nonclassical States of Light

The states of radiation of a single frequency and polarization propagating in free space are very conveniently represented by those of a quantum mechanical simple harmonic oscillator. This fact is exploited, together with the Ehrenfest theorem, to map the time evolution of the radiation to the dynamics of the oscillator. This enables a graphical comparison of the behaviour of classical and nonclassical states of radiation.     

Aerobasics — An introduction to aeronautics 2. The atmosphere

Aircraft of all types dynamically interact with the atmosphere generate forces required for lift and propulsion. Properties of the atmosphere and their variations over geographic locations and altitude are thus relevant to aircraft flight operations. This article presents some facts about the atmosphere and indicates their relevance to flight.     

Aerobasics — An introduction to aeronautics 14. Air navigation principles

Air navigation has evolved over the last hundred years from an art into a mature science. Airplane accidents due to navigational errors are practically nonexistent. In large measure this advance has been due to radio aids to navigation which operate under all weather conditions. However in remote areas and in hostile airspaces, the radio aids may not be available and a fully self contained navigational device is required. Navigation by stars (celestial navigation) is feasible under such conditions. But the inertial navigation system (INS) is the preferred choice. In recent times, a navigational instrument based on radio communication with specially designed satellites in low Earth orbits called the global positioning system (GPS) has become popular. This article deals with the principles of these various methods of air navigation.     

Aerobasics — An introduction to aeronautics 12. Safety in aviation

Public awareness of airplane safety is very high due to the spectacular nature of airplane accidents. Partly as a result, civil airplane operations are tightly regulated at all levels from design to operation and maintenance. Scheduled airline operations have thus been able achieve a very high level of safety. In this article we quantify the safety of flight operations and indicate the design concepts like fail safety and safe life used in achieving a high level of safety. As an illustration, we consider the safety of a flight of a twin engine airplane in the event of one engine failure.     

Aerobasics — An introduction to aeronautics 15. Mini and micro airplanes

There is much current interest in small unmanned airplanes weighing about five kilograms all the way down to about 100 grams. Even such small airplanes are capable of performing useful surveillance missions in peace time and during conflicts. As these airplanes operate at very low flight speeds in the range of about 10–20 m/s, their performance is strongly affected by the low Reynolds numbers characteristic of such flight. In this article, we consider the special aerodynamic and propulsion problems associated with the flight of such small airplanes.     

论体育精神

此研究讨论了体育精神的各个方面,认为体育精神应包括人文精神、科学精神、拼搏精神、合作精神和审美精神,体育精神对人才的培养、人格的完善起着重要的作用。     

How to protect the chromosomal ends? Telomerase, chromosome stability and aging

The 2009 Nobel Prize in Physiology or Medicine was jointly awarded to three scientists — Elizabeth H Blackburn, Carol W Greider and Jack W Szostak — for their work during early 1980s and 1990s which helped unravel the molecular mechanisms of protection of chromosomal ends by telomeres and the enzyme telomerase. Their discovery has had major implications in the fields of ageing and cancer research. Blackburn and Greider are the ninth and tenth women scientist, to get this award in physiology or medicine and this is the first time that two women scientists have shared the prize.     

Unidirectional motion of vehicle on sinusoidal path Can it cause illusory forward and backward motion?

The feeling of being in motion, while observing a moving train passing nearby is a common experience. It is an example of relative motion where a stationary observer experiences an illusory motion caused by a vehicle moving in the opposite direction. It is however counter-intuitive to imagine periodic changes in the direction of relative motion, while the vehicle continues to move in one direction only. To an observer, sitting inside the moving vehicle, periodic changes in direction can lead to the illusion of being in oscillatory forward and backward relative motion. This article, using a simple mathematical model describes how the unidirectional motion of vehicle on a sinusoidal path can lead to the illusion of being in periodic forward and backward relative motion. This work has emerged out of a real life experience during a train journey on the hilly curves from Kalka to Shimla.     

Ya B Zeldovich (1914–1987) Chemist, nuclear physicist, cosmologist

Ya B Zeldovich was a pre-eminent Soviet physicist whose seminal contributions spanned many fields ranging from physical chemistry to nuclear and particle physics, and finally astrophysics and cosmology. This article attempts to convey some of the zest with which he did science and the important role he played in fostering and mentoring a whole generation of talented Soviet scientists.     

论姚鼐词

姚鼐词是作者在人生特定时期情感思想与生活状态的表达,反映了乾嘉时期社会大背景以及文人的真实心态。在艺术形式方面,姚鼐词继承浙西又有所突破,体现了浙西词派向常州词派转变的历史趋势。姚鼐词虽仅存八首,但在乾嘉词坛占有一席之地,其价值不容忽视。     

王世贞论骆宾王长歌

骆宾王是"初唐四杰"之一,其长篇歌行在唐代诗坛占有极高的地位,后人也给予其非常高的评价。明代王世贞在《艺苑卮言》中对骆宾王长歌亦有好评,虽然评价话语不多,但涉及骆宾王长歌的特征、不足以及诗歌史地位等重要问题,具有重要的诗学价值。     

禅宗自然观谫论

中国禅宗自然观具有以下四方面的理论内涵:第一,性即自然。中国禅宗把其最核心的理论范畴"性"等同于"自然",高扬人性的自然与自由,反对一切外在雕饰、权威与束缚。第二,山水皆真如。禅宗主张山水皆真如,触目皆菩提,强调在对自然的直觉观照之中契悟宇宙实相。第三,生命的自然境界。禅宗主张人与自然打成一片,追求一种自然适意的生命情调。最后,自然悟道。在修行实践上,禅宗的自然观表现为对无修无证、自然悟道修行方式的提倡。禅宗自然观对中国古代美学、艺术产生了重要影响。     

吴汝纶与严译西学

吴汝纶自幼接受传统教育,是晚清桐城派的末代宗师。严复早年留学英伦,接受西式教育,是中国近代著名的启蒙思想家。尽管吴汝纶与严复的师承关系以及受教育的经历有较大差异,但思想观念和文化认识的趋同奠定了他俩友谊关系的基础。严复拜吴汝纶为师,服膺桐城派,擅长以桐城古文译介西学。严译西学与吴汝纶的序言,可谓珠联璧合,影响深远。与其说严复请吴汝纶作序有借重其学界名望的考虑,毋宁说是吴汝纶信奉进化论而推崇严译西学。     

Faculty – Personalstrukturen an US-amerikanischen Universit?ten Ein Vergleich zwischen dem ?sterreichischen und dem US-amerikanischen System

US-amerikanische Universit?ten sind in Zeiten, in denen sich auch das Wissenschaftssystem in europ?ischen L?ndern in einem starken Wandel befindet, aus unterschiedlichen Gründen einen Vergleich wert, gelten sie doch gemeinhin als besonders leistungsf?hige Institutionen im Rahmen einer globalen Wissensgesellschaft. Jedes Bildungswesen ist ein komplexes System, und in Anbetracht seiner Systemhaftigkeit liegt es auf der Hand, dass einzelne Systemelemente aus anderen L?ndern nicht ohne weiteres übertragen oder in ein anders geartetes Ambiente eingefügt werden k?nnen. Im Folgenden werden die Personalstrukturen des US-amerikanischen und des ?sterreichischen Hochschulsystems miteinander verglichen, sie werden in ihren Vorzügen und Schw?chen analysiert und in das jeweilige institutionelle Gefüge eingebettet.     

谈德国职业教育的质量观

德国的产品质量享誉世界。从德国人对技能的追求、对质量的追求和对职教教师的要求三个层面,探讨德国"双元制"职业教育对德国产品质量的影响,以企对提升我国职业教育质量有所启示。     

Web3.0时代数字图书馆信息资源管理

基于Web3.0时代数字图书馆信息资源的特点,要求数字图书馆信息资源的管理要强化信息管理意识以建立信息资源管理体系;要能提高馆员的信息素养和专业技能;同时建立有效的数字图书馆信息资源管理评价体系。Web3.0时代数字图书馆信息资源管理能有效促进信息资源的共建共享,充分满足读者对信息资源的需求。     

秦汉财产损害赔偿制度考

损害赔偿是秦汉立法所涉及的一个重要方面,从出土的法律资料来看,主要针对财产损害赔偿,涉及赔偿的形态、范围、原则,法律还根据当时实际情况规定了几种实现方式,并在执行环节制定相应的制度,这些内容表明秦汉财产赔偿制度已形成初步的体系。秦汉财产损害赔偿法律制度,是当时社会的政治、经济、文化产物,是当时各种社会关系的直接反映,因此考察当时财产损害赔偿法律制度内容,全面分析和总结它的功能,对我们进一步深刻认识秦汉法律的真实面貌和当时的社会状况具有重要意义。     

大龙山镇留守儿童心理健康状况调查

安庆市宜秀区大龙山镇留守儿童在社交焦虑、孤独感、学习焦虑、对人焦虑、孤独倾向和恐怖倾向等六个因子上与非留守儿童有显著性差异。留守儿童的心理健康水平没有太大的性别差异,但女生的心理健康水平低于男生。建议家庭教育、学校教育和社会都要关注留守儿童心理健康的发展。     

课堂比课程更重要

课程是学校教育活动的内容及其科目设置,它只有而且必须通过师生课堂的活动才能为学生所掌握,从而转化为学生内在的知识与素质结构。所以,课堂是课程落实的最主要、最有效的场所。对于学校人才培养来说,课堂比课程更重要。这是因为从根本上说,课堂教学就是教师和学生围绕教学目的而展开的共同活动,亦即师生双方通过行为作用于课程促进学生身心发展的活动。因此,从整个教育活动来说,师生的课堂教学行为良否决定着课程实施状况好坏和教学质量的高低,最终决定着人才培养质量的优劣。