Xn+Yn=Zn n≥3时无整数解

本文利用首创的互补开方法,来证明此定理。     

"生态旅游"在实践中出现严重偏差的原因和对策探析

“生态旅游”以可衡量和可控制的手段来实现真实和完整的可持续发展特性 ,因为它符合人类生存发展的长远利益 ,必将在未来的旅游业中占据主导地位。但是 ,在现阶段实践“生态旅游”的过程中 ,还存在着许多难以解决的技术问题和社会问题 ,因此执行起来就很容易出现偏差。在我国 ,“生态旅游”最大的一个偏差是 ,目光短浅地追逐眼前利益 ,旅游消费者只考虑到原始、美妙的环境中去尽情享受 ;旅游经营者只考虑利用良好的生态环境来吸引游客 ,赚取高额利润 ,在“发展旅游经济”的大旗掩护下 ,使“生态旅游”之名背离生态旅游之实 ,后果不堪设想。     

磁致冷却效应的试验装置

磁致冷却效应即磁热效应,导磁材料在磁化过程中,内部趋向于磁有序,若此时去除磁场就会使得导磁材料内部重新回到磁无序状态,这个过程需要从外界吸收大量的热量,从而达到冷却和制冷的效果。本研究搭建了一套磁致冷却测试系统,包括永磁体试验平台和Labview测温程序两部分,利用这套系统可以实现磁场—热量转化过程的直观观察和分析,可以用于相应的电磁传热学机理研究及相应的教学示范。     

一种新型高功率密度的正弦波永磁电机

A novel high power-density PMSM (permanent magnetic synchronous motor) with independent magnetic flux path for each phase is proposed in the paper.The complex mathematic model of PMSM is simplified by decoupling of magnetic flux paths between motor phases.In addition,harmonic compoments are lowered through optimum design of EMF (electric motive force) wave.Thus the ripple torque caused by EMF wave distortion is suppressed.     

Rural Communities Lacking Multi-Sector Schooling Options: Indiana’s School Choice Deserts

ABSTRACT

Despite Indiana’s school choice landscape – including private school vouchers, tax-credit scholarships, inter-district and intra-district enrollment, magnet schools, and charter schools – not all Indiana communities have reasonable access to options outside of their traditional public schools. This research explores what lack-of-reasonable access differences – defined as greater than a 30-minute one-way drive time to a choice school – exist by locale, with a focus on rural communities. Geospatial analysis is used to identify “school choice deserts” lacking multi-sector schooling options in various communities. These deserts tend to exist wholly or mostly in rural areas, although Indiana students in grades K–8 exhibit greater access levels to non-traditional schools than those in high school.     

绝对值不等式中一类问题的解法

本文就含绝对值不等式的一类参数范围问题中常见的三种情况进行了详尽的分析,并给出了多种解法,总结了解决这类问题的一般规律和方法。     

终身教育背景下的职业教育体系构建

职业教育作为“以职业为导向”的教育类型,应该是一个相对独立的完整的教育体系。在整个教育系统内,受教育者不仅可以向更高层次发展,实现“升学”愿望,也可以在不同性质的教育类型间转换角色,实现内涵式与外延式相统一的发展。终身教育背景下的职业教育体系应具有职业主导、就业为本、开放性和多样化的基本特性,具有多层立交、多向贯通;横向沟通,交叉协调;纵向衔接,多级贯通的基本功能。     

New analytical solution for the analysis and design of permanent magnet thrust bearings

On the basis of the current sheet model, a new analytical solution for permanent magnet （PM） bearings is developed. Compared with analytical methods based on the coupling energy model and the magnetic dipole model, the proposed one is more physically intuitive and convenient for engineering designers. According to the analytical model, the thrust characteristics of a novel PM thrust bearing is studied and verified by finite element analysis （FEA）. In the proposed thrust bearing configuration, the rotor is composed of stacked PM tings with alternative axial magnetization directions, and the stator with alternative radial magnetization directions while copper rings are used to separate adjacent PM rings. A prototype PM thrust bearing with the proposed configuration is designed and fabricated. The performances of the PM thrust beating are experimentally validated. It is shown that the calculation accuracy of the presented analytical solution is satisfying.     

A New Technique: Research and industrial application of a novel compound permanent magnet synchronous machine

We propose a novel kind of compound permanent magnet synchronous machine (CPMSM), which is applicable in low-speed and high-torque situations. We first explain the structure of the CPMSM. Based on theoretically deducing the calculation formulae of the CPMSM electromagnetic parameters, we analyze the operating characteristics of the CPMSM, and obtain the power-angle curves and working curves. The no-load magnetic field distribution and the cogging torque are analyzed by applying the finite element method of three-dimensional (3D) magnetic fields, to determine the no-load leakage coefficient and the wave0form of the cogging torque. Furthermore, the optimal parameters of the permanent magnet for reducing the cogging torque are determined. An important application target of the CPMSM is in direct-drive pumping units. We have installed and tested a directdrive pumping unit in an existing oil well. Test results show that the power consumption of the direct-drive pumping unit driven by CPMSM is 6 1. 1% of that of the beam-pumping unit, and that the floor space and weight are only 50% of those of a beam-pumping unit. The noise output does not exceed 58 dB in a range of 1 m around the machine when the machine is 1.5 m from the ground.     

关于创设我国永佃权立法的思考。

我国现行的农地法律制度存在着一定的历史局限性和诸多缺陷，无法有效地保证农民的利益。形成这些缺陷的原因是多方面的，最重要的是与土地承包经营权的债权性质有关。农地法律制度立法，如果完全脱离现行的土地制度，实行土地私有制或单纯建立农地使用权制度，都不能很好地解决目前土地制度立法面临的困扰。而在现行农地制度的基础上，创设一种适合中国国情的新型永佃权制度，把农村家庭联产承包责任制与永佃权制度有机地进行整合。具有极大的可行性，必将极大地调动广大农民的生产积极性，从而为本世纪大力发展农村社会生产力提供有效的制度保障。因此，有必要在邓小平理论指导下，本着与时俱进的精神，创设适合中国国情的永佃权制度。