小学生数学学习常见误区及解决对策研究---以《平行四边形面积》为例

《平行四边形面积》一课,在小学数学几何图形的教学中既是重点也是难点.小学生学习平行四边形面积时,常见误区主要是:误用计算公式为领边相乘、拉伸和割补后的长方形变化问题、斜而长的平行四边形转化问题、公式误用底不对应高问题、等底等高和面积相等的平行四边形的差异等问题.通过分析上述误区,提出割补法、拉伸平行四边形木架、平行四边形对外做高、计算有两条高的平行四边形面积、画图对比说明等对策研究.     

基于小学数学核心素养培养的"鸡兔同笼"教学策略探究

核心素养的培养是当下基础教育的关键问题."鸡兔同笼"自身的历史文化内涵,解题方面的多元化以及每种解法背后蕴含的数学思想方法都是培养学生核心素养的重要载体.文章基于小学数学核心素养的培养,结合鸡兔同笼问题的解决,具体从选择蕴含核心素养的教学内容、在有效参与中实现一题多解、在深度探究中解决鸡兔同笼类实际问题等三个方面进行了解读分析,以期为小学数学核心素养的培养提供实践经验.     

Approximation schemes for single‐machine scheduling with a fixed maintenance activity to minimize the total amount of late work

We consider the problem of scheduling n independent and simultaneously available jobs without preemption on a single machine, where the machine has a fixed maintenance activity. The objective is to find the optimal job sequence to minimize the total amount of late work, where the late work of a job is the amount of processing of the job that is performed after its due date. We first discuss the approximability of the problem. We then develop two pseudo‐polynomial dynamic programming algorithms and a fully polynomial‐time approximation scheme for the problem. Finally, we conduct extensive numerical studies to evaluate the performance of the proposed algorithms. © 2016 Wiley Periodicals, Inc. Naval Research Logistics 63: 172–183, 2016     

Level workforce planning for multistage transfer lines

In this article, we define two different workforce leveling objectives for serial transfer lines. Each job is to be processed on each transfer station for c time periods (e.g., hours). We assume that the number of workers needed to complete each operation of a job in precisely c periods is given. Jobs transfer forward synchronously after every production cycle (i.e., c periods). We study two leveling objectives: maximin workforce size () and min range (R). Leveling objectives produce schedules where the cumulative number of workers needed in all stations of a transfer line does not experience dramatic changes from one production cycle to the next. For and a two‐station system, we develop a fast polynomial algorithm. The range problem is known to be NP‐complete. For the two‐station system, we develop a very fast optimal algorithm that uses a tight lower bound and an efficient procedure for finding complementary Hamiltonian cycles in bipartite graphs. Via a computational experiment, we demonstrate that range schedules are superior because not only do they limit the workforce fluctuations from one production cycle to the next, but they also do so with a minor increase in the total workforce size. We extend our results to the m‐station system and develop heuristic algorithms. We find that these heuristics work poorly for min range (R), which indicates that special structural properties of the m‐station problem need to be identified before we can develop efficient algorithms. © 2016 Wiley Periodicals, Inc. Naval Research Logistics 63: 577–590, 2016     

喷嘴结构对高压水射流影响及结构参数优化设计

喷嘴是产生高压水射流的关键部件,其结构形式对射流动力学性能有很大影响。以圆柱形喷嘴为对象,进行喷嘴结构对高压水射流的影响分析及结构参数优化设计。采用两相流计算流体力学模型进行喷嘴内外的射流流场分析。为节省计算资源,在优化设计时引入Kriging代理模型替代计算流体力学模型。分别采用改进的非劣分类遗传算法和基于分解的多目标进化算法进行单目标和多目标优化设计。研究结果表明:直线型喷嘴总体性能较优,凹型喷嘴的次之,凸型喷嘴性能最差。以直线型喷嘴为设计对象,以射流初始段长度和流量为目标,得到了单目标和多目标优化设计结果。单目标优化时,两个指标较基准外形分别提高14.71%和27.56%。多目标优化时,优化得到的半锥角处于[15.4°,89.8°]区间内。运用代理模型和进化算法的全局优化方法在进行喷嘴的优化设计时是有效的。     

关于我国发展新型固定翼舰载机的几点建议

随着我国航母事业的发展,舰载机研发与制造产业得到了相应的发展。但是由于我国舰载机研发与制造产业起步晚,舰载机在技术性能等方面相比于西方国家还存在一定差距。文章以美国F-35"闪电Ⅱ"飞机研发历程为依据,对我国发展新型固定翼舰载机在设计、研发和维护等方面提出了建议,总结了值得我国研发人员借鉴的经验和教训。     

谈公安现役部队专业技术干部竞争激励机制建设

当前,公安现役部队专业技术干部人才队伍竞争激励机制建设还存在评审机制需要完善、奖惩机制不健全、制度建设针对性不强等突出问题,所以,必须创新管理理念,建立和完善专业技术干部人才队伍建设机制。重点是完善专业技术干部人才队伍选拔使用机制,建立具有公安现役部队特色的专业技术干部评价机制,构建公安现役部队专业技术干部成长的长效激励机制。     

基于MDA的C~4ISR系统分析设计方法

先进的分析设计方法是提高C4ISR系统开发质量的有效手段。基于软件领域的MDA思想,提出了基于MDA的C4ISR系统分析设计方法,研究了其开发过程和关键技术。该方法实现以模型为基础的系统开发与优化,通过不同阶段模型的转化演进来推进系统的分析设计,有利于提高系统的设计质量,并支持模型重用。     

共产国际与中共应对皖南事变军事方针的调整

自抗日战争进入战略相持阶段到皖南事变发生后的1个月间,中共中央面对国民党顽固派制造的一系列反共摩擦,对各种复杂因素进行综合判断,采取了适当的应对措施,维护了抗日民族统一战线的完整,军事措施是其中一个重要方面。在这一方面,中共中央从对国民党顽固派采取攻势防御战略到皖南事变前夕采取的拖延方针,再到皖南事变之后军事守势方针的确立,都受到共产国际观点的影响。     

一种新的伪码调相与线性调频组合脉冲压缩信号性能分析研究

介绍了伪码调相与线性调频组合而成的新的脉冲压缩信号,给出了信号的表达式,详细推导了发射信号的模糊函数,分析了其时频域特性。理论和仿真分析表明,这种组合波形在高分辨力、抗干扰、低截获能力等方面都显示出独特的优越性。