基于误差流理论的金工实习课程教学体系的思考

基于“误差流理论”的理论和方法,将金工实习中“培养和提高学生的动手能力和工程素质”视为在有限的时间和空间内应给予学生的“能力流”,结合具体的“创新大赛”或“卓越学子”计划,将金工实习课程中的车、铣、钳、铸、数控等学习环节转达为“能力”,进行量化和升华之后,通过数学模型、适应性分析,最终为学生学习环节的合理搭建、能力提高,提供可量化的评价.     

Hybrid ants-like search algorithms for P2P media streaming distribution in ad hoc networks

Media streaming delivery in wireless ad hoc networks is challenging due to the stringent resource restrictions,po-tential high loss rate and the decentralized architecture. To support long and high-quality streams,one viable approach is that a media stream is partitioned into segments,and then the segments are replicated in a network and served in a peer-to-peer(P2P) fashion. However,the searching strategy for segments is one key problem with the approach. This paper proposes a hybrid ants-like search algorithm(HASA) for P2P media streaming distribution in ad hoc networks. It takes the advantages of random walks and ants-like algorithms for searching in unstructured P2P networks,such as low transmitting latency,less jitter times,and low unnecessary traffic. We quantify the performance of our scheme in terms of response time,jitter times,and network messages for media streaming distribution. Simulation results showed that it can effectively improve the search efficiency for P2P media streaming distribution in ad hoc networks.     

消除误区 求解木牛流马——兼评木牛流马研制现状

木牛流马制作于汉中勉县的黄沙。木牛流马由诸葛亮创意、构思,蒲元参与研制,可能还有其人参与了制作。民间有传说诸葛亮从其妻处获得木牛流马的设计。《南史》和宋人对木牛流马的记载对后世的影响极大,造成的误解也大。木牛流马运行的道路不是蜀道。用木牛运粮走的是"出祁山"的道路,用流马运粮走的是褒斜道,都不是蜀中的金牛道、剑阁道。木牛运行道路是诸葛亮北伐"出祁山"的路线以西北方向迂回道路为主,道路相对平坦。流马运粮所走的是褒斜栈道,比较宽阔、平缓,有一定起伏。人们对小说《三国演义》中描述的木牛流马存在误解。今人对木牛流马研制的主要成果有:范文澜先生认为木牛是独轮车,流马是四轮车;刘先洲先生提出木牛流马是鹿车(独轮车)的改进;陈从周、陆敬严先生认为木牛流马是独特的独轮车;谭良啸、方北辰先生先后提出木牛流马是两种规格不同的四轮车;王湔先生复制的四足迈步型木牛流马;赵彬、向国富先生的杠杆单摆型木牛。从物理学的原理评今人研制的木牛流马:车轮滚动型——古代运载物资的最佳形式;杠杆驱动型——构造合理而相距真实甚远;四足迈步型——不靠谱的机械步行器。研究、复制必须以《作木牛流马法》为依据。诸葛亮的木牛、流马一是制作不会太花费精力、财力、人力;二是一定能负重,载重量应符合要求;三是关于行进速度,必须把握,这是研制木牛流马的一个突破口之一;四是既然名曰"木牛流马",应该以木构件为主,结构不会太复杂,构件加工难度不会太高。这也是研究和复制木牛流马的方向及条件。     

回家

我闭上了眼睛,缓缓吸气,胸脯慢慢鼓起,双肩也向上紧紧收耸,然后重重呼出那口气,睁开双眼,心底传来一个声音;终于回家了。1月1日,下午三点多钟,我关掉电脑,跑到露台,用手机群发了一条短信:普天同庆,我写完了     

心淌流韶

总有那么一些感动,在黎明,在子夜,在每个沉思默想中绽放。有唏嘘,有欣慰,亦有伤怀。     

Nearest neighbor search algorithm based on multiple background grids for fluid simulation

The core of smoothed particle hydrodynamics (SPH) is the nearest neighbor search subroutine. In this paper, a nearest neighbor search algorithm which is based on multiple background grids and support variable smooth length is introduced. Through tested on lid driven cavity flow, it is clear that this method can provide high accuracy. Analysis and experiments have been made on its parallelism, and the results show that this method has better parallelism and with adding processors its accuracy become higher, thus it achieves that efficiency grows in pace with accuracy.     

科学玩出来

拯救钞票你能把压在两个啤酒瓶之间的钞票"救"出来吗?不过,手不能碰到酒瓶哦。工具百宝箱髴两个空啤酒瓶髵一张钞票在桌上放一个啤酒瓶,将钞票放在一个啤酒瓶的瓶口上,然后再在上面倒扣一个同样的啤酒瓶。捏住钞票的一端,使钞票与桌面保持水平。一只手扶住下面的瓶子,另一只手捏住钞票,迅速抽出。     

外加纵向磁场对TIG电弧的影响

试验研究表明外加纵向磁场对电弧的电流密度、等离子流力有很大影响。本对其变化规律及原因进行了分析和研究。