基于NTP的网络时间服务器校准方法探讨

为了解决基于NTP的网络时间服务器校准问题,对其展开校准项目和校准方法的探讨,给出了NTP同步偏差、定时准确度和定时稳定度等校准项目并结合实验详细阐述了两种NTP同步偏差的校准方法,实验结果表明,采用直接测量法的NTP同步偏差为10.25μs,不确定度为62.08μs(k=2);采用比较法的NTP同步偏差为139.75μs,不确定度为6.36ms(k=2).     

同时含有稀土元素La Ce Pr Nd的材料的电子探针定量分析方法

研制了稀土六硼化物单晶LaB_6、CeB_6、PrB_6和NdB_6电子探针分析标样。根据X-射线峰位表和实测的特征X-射线谱,考察分析了La、Ce、Pr和Nd元素谱线之间的干扰情况,发现分析谱线PrLα_1受到L_αLβ_1线严重的干扰。以混合稀土金属为试样,采用扣除谱线重叠强度的背底非对称测量等方法对L_n、Ce、Pr和Nd进行了电子探针定量分析,其结果与荧光X-射线光谱分析结果符合较好。     

EFFECT OF RARE EARTH ADDITIONS ON THE IMPACT FRACTURE OF Cr18Nil8Si2 STEEL

<正> Cr 18 Ni 18 Si 2钢经热处理后的低温冲击断口,其中加稀土的为穿晶断口,而未加稀土的为混合型断口。 试验用钢用高频感应炉冶炼,锭重20kg,锻成15×15mm方棒,再加工成冲击试样。其化学成分如下。稀土的加入是将一号混合稀土合金缚在钢棒上插入熔池。     

基于SVR模型预测超薄浮法玻璃气泡数量的研究

针对超薄浮法玻璃生产过程存在反馈滞后大、生产复杂、产品质量难以精确控制的情况以及气泡质量缺陷严重影响产品应用的问题,本文采用SVR模型对超薄浮法玻璃气泡数量进行预测,结合实际生产数据对模型进行验证,并探究熔化时滞时间以及特征属性对模型精度的影响,采用Relief-F算法结合实际建模结果筛选出对气泡产生有影响的重要特征属性.研究结果表明,SVR模型能精确预测玻璃气泡数量,为后续生产提供决策支持;熔窑池底温度与熔窑碹顶温度对超薄浮法玻璃生产中气泡的产生有较大影响.     

Zr替代Ti对Ti19．5V40Mn16．2Cr9．8Ni14．5合金的影响Ⅱ：电化学性能

在对合金微观结构和储氢性能研究的基础上，详细考察了少量Zr取代Ti对Ti19．5V40Mn16．2Cr9．8Ni14．5合金电化学性能的影响。通过观察电极的充放电行为，并结合EIS及多种极化曲线的分析结果，发现少量Zr对Ti的取代能够显著提高合金电极的实际电化学容量和循环稳定性，而且还能在一定程度上改善合金的电极动力学性能。对于这些性能的改善，从合金微观结构方面进行了解释。     

Solving cell formation and task scheduling in cellular manufacturing system by discrete bacteria foraging algorithm

We consider a joint decision model of cell formation and task scheduling in cellular manufacturing system under dual-resource constrained (DRC) setting. On one hand, machines and workers are multi-functional and/or multi-skilled, and they are grouped into workstations and cells. On the other hand, there is a processing sequence among operations of the parts which needs to be dispatched to the desirable workstations for processing. Inter-cell movements of parts can reduce the processing times and the makespan but will increase the inter-cell material handling costs. The objective of the problem is to minimise the material handling costs as well as the fixed and operating costs of machines and workers. Due to the NP-hardness of the problem, we propose an efficient discrete bacteria foraging algorithm (DBFA) with elaborately designed solution representation and bacteria evolution operators to solve the proposed problem. We tested our algorithm using randomly generated instances with different sizes and settings by comparing with the original bacteria foraging algorithm and a genetic algorithm. Our results show that the proposed DBFA has better performance than the two compared algorithms with the same running time.     

一种针对资源受限应用的改进PMF-FFT捕获方法

无线传感网中节点普遍受资源、成本的限制,使得节点间通信受计算复杂度和载波频偏的影响.传统的部分相关和FFT分析(PMF-FFT)捕获方法满足不了资源受限的要求.提出一种改进的PMF-FFT捕获方法(IPMF-FFT),通过时分复用FFT运算减少FFT点数从而节省资源,并对其捕获的抗噪声性能、抗频偏能力以及资源消耗进行分析.通过仿真结果看出在抗噪声、抗频偏能力相同的基础上,提出的IPMF-FFT捕获方法比传统PMF-FFT方法减少了大量的FFT点数,节省了资源.     

An effective scheduling scheme for multi-hop multicast in wireless mesh networks

With the utilization of concurrent transmission strategy, a throughput-enhanced scheduling scheme is devised for multicast service in wireless multi-hop mesh networks. Since the performance of a multicast mechanism is constrained in a wireless setting due to the interference among local wireless transmissions, the interference relationships are first characterized by introducing a graph transformation method. Based on the graph transformation, the multicast scheduling problem is converted to the graph coloring problem, and then a capacity greedy algorithm is designed to provide concurrent transmission scheduling so that the demanded multicast transmission rate can be achieved. Moreover, the necessary and sufficient conditions of multicast schedulable feasibility are derived. Through corresponding simulations, it is shown that the proposed strategy can enhance the throughput of wireless multi-hop multicast systems significantly.     

一类具有有界控制器的多重时变滞后系统的指数稳定性

考虑了一类具有多重时变滞后和有界控制器的不确定动力系统的鲁棒指数稳定性问题.匹配一个无记忆的控制器,确保存在一个吸收域.我们所考虑的这类系统的解收敛于一个给定的球.球的半径和指数收敛率可以任意选择.     

Effects of Magnetic Heat Treatment on Magnetostiction Properties of Tb0.3 Dy0.7 Fe1.95 Alloy

The effects of magnetic heat treatment on magnetostriction properties of Tb0.3Dy0.7Fe1.95 alloy were investigated.The directionally solidified alloy was heated to various temperatures near Curie temperature TC in vacuum, kept for a certain time under the application of magnetic field and then cooled to room temperature.The magnetostriction coefficient was measured by a resistance strain gage.The crystal structure was analyzed by X-ray diffraction (XRD).The experimental results show that the magnetostriction coefficient obviously increases and the grains orientations along the axis changed somewhat as the field of 1 T vertical to axis of the rod-shaped specimen is applied for 5 min at the heating temperature slightly lower than TC.