商高确实证明了勾股定理——兼论这里的“矩”不宜理解为长方形

严格遵守"矩"是古代中国的测量仪器,"矩"在古文字中的含义为"矩线",或为"磬折形",将"矩"理解为长方形(包含正方形)是不可取的.商高确实证明了一般勾股定理.古证应该是最原始、最简单的.     

物理课堂教学中的提问原则及技巧之我见

课堂教学中的提问是一门学问,更是一门艺术,它没有固定的模式,只要不断实践,不断摸索,就会提高自己的教学水平。在教学中科学地设计并恰当地进行课堂提问,可及时唤起学生的注意,创造积极的课堂气氛,激发学生的学习动机和兴趣,优化课堂结构,真正发挥教师的主导作用和学生的主体作用,从而展示教师的教学艺术,显现教师的教学魅力。本文主要从课堂提问的原则、提问的技巧这两个方面阐述一些个人的浅见。     

重力输水系统

为学习微积分的读者介绍如何将基本流体力学应用于对发展中国家非常重要的简单重力输水系统的建模。首先推导出Bernoulli方程,从而了解作为沿流线运动的流体质点压力、速度和高度之间的关系。其次,应用Bernoulli方程分析一个简单的输水系统的合力和流速。然后,对层流和湍流分别考虑分压水箱、不同直径的管道及摩擦的影响。最后,讨论在密克罗尼西亚和洪都拉斯重力输水系统的设计和安装。     

类Ne钛X射线激光输出特性实验

 在星光激光装置上, 使用X射线多层膜反射镜、铝滤片及X射线CCD探测器组成高灵敏度空间分辨探测系统, 对用预脉冲技术产生的类Ne钛单线 (J=0-1, 3p-3s跃迁)软X射线激光输出特性进行了测量。由实验得到了类Ne钛X 射线激光束近场与距靶端32mm处(准远场)强度的空间分布, 给出了该激光束在近场强度最大区域的空间尺度(FWHM)约为72μm×31μm, 以及在垂直靶面与平行靶面方向的束发散角分别约为4mrad与9mrad。     

Edge assisted epitaxy of CsPbBr3 nanoplates on Bi2O2Se nanosheets for enhanced photoresponse

Bi$_{2}$O$_{2}$Se has been proved to be a promising candidate for electronic and optoelectronic devices due to their unique physical properties. However, it is still a great challenge to construct the heterostructures with direct epitaxy of hetero semiconductor materials on Bi$_{2}$O$_{2}$Se nanosheets. Here, a two-step chemical vapor deposition (CVD) route was used to directly grow the CsPbBr$_{3}$ nanoplate-Bi$_{2}$O$_{2}$Se nanosheet heterostructures. The CsPbBr$_{3}$ nanoplates were selectively grown on the Bi$_{2}$O$_{2}$Se nanosheet along the edges, where the dangling bonds provide the nucleation sites. The epitaxial relationships between CsPbBr$_{3}$ and Bi$_{2}$O$_{2}$Se were determined as ${[200]}_{\rm Bi_{2}O_{2}Se}||{[110]}_{\rm CsPbBr_{3}}$ and ${[110]}_{\rm Bi_{2}O_{2}Se}||{[200]}_{\rm CsPbBr_{3}}$ by transmission electron microscopy characterization. The photoluminescence (PL) results reveal that the formation of heterostructures results in the remarkable PL quenching due to the type-I band arrangement at CsPbBr$_{3}$/Bi$_{2}$O$_{2}$Se interface, which was confirmed by ultraviolet photoelectron spectroscopy (UPS) and Kelvin probe measurements, and makes the photogenerated carriers transfer from CsPbBr$_{3}$ to Bi$_{2}$O$_{2}$Se. Importantly, the photodetectors based on the heterostructures exhibit a 4-time increase in the responsivity compared to those based on the pristine Bi$_{2}$O$_{2}$Se sheets, and the fast rise and decay time in microsecond. These results indicate that the direct epitaxy of the CsPbBr$_{3}$ plates on the Bi$_{2}$O$_{2}$Se sheet may improve the optoelectronic performance of Bi$_{2}$O$_{2}$Se based devices.     

一类平面五次系统的定性分析

本文研究平面五次系统（１．１），应用［４，５］的最新结果，给出了奇点Ｏ（０，０）为中心的充要条件和焦点量公式，以及（１．１）至多有一个，二个极限环的充分条件．     

关于不同分布两两NQD列的Jamison型加权乘积和的强稳定性

本文讨论了不同分布两两ＮＱＤ列的Ｊａｍｉｓｏｎ型加权乘积和的强稳定性及乘积和的Ｍａｒｃｉｎｋｉｅｗｉｃｚ型强大数律,推广并改进了Ｅｔｅｍａｄｉ［１］关于不同分布两两独立列部分和的工作及Ｍａｔｕｌａ［２］,王岳宝等［３］关于同分布两两ＮＱＤ列部分和的工作．     

On generalized hamiltonian systems

1. PreliminaryIt is well known that{1] a 8ymPlectic form is invariant along the trajectory of a Hamilto-nian system. Based on this fundamental property, certain techniques have been developed.The purpose of this paper is to extend such an approach to a wider class of dynamic systeIns,namely, genera1ized Hamiltonian systems. Our purpose is to investigate a class of dynaInicsystems, which possess a certain "geometric structure".Deflnition 1.1[1'2]. Let M be a tIlallifo1d. w E fl'(M) is call…     

Charge ordering modulations in a Bi_0.4Ca_0.6MnO₃ film with a thickness of 110 nm

The low temperature sample stage in a transmission electron microscope is used to investigate the charge ordering behaviours in a Bi 0.4 Ca 0.6 MnO 3 film with a thickness of 110 nm at 103 K.Six different types of superlattice structures are observed using the selected-area electron diffraction(SAED) technique,while three of them match well with the modulation stripes in high-resolution transmission electron microscopy(HRTEM) images.It is found that the modulation periodicity and direction are completely different in the region close to the Bi 0.4 Ca 0.6 MnO 3 /SrTiO 3 interface from those in the region a little further from the Bi 0.4 Ca 0.6 MnO 3 /SrTiO 3 interface,and the possible reasons for this are discussed.Based on the experimental results,structural models are proposed for these localized modulated structures.     

改进蚁群算法优化周期性车辆路径问题

周期性车辆路径问题(PVRP)是标准车辆路径问题(VRP)的扩展,PVRP将配送期由单一配送期延伸到T(T＞1)期,因此,PVRP需要优化每个配送期的顾客组合和配送路径。由于PVRP是一个内嵌VRP的问题,其比标准VRP问题更加复杂,难于求解。本文采用蚁群算法对PVRP进行求解,并提出采用两种改进措施——多维信息素的运用和基于扫描法的局部优化方法来提高算法的性能。最后,通过9个经典PVRP算例对该算法进行了数据实验,结果表明本文提出的改进蚁群算法求解PVRP问题是可行有效的,同时也表明两种改进措施可以显著提高算法的性能。