Software‐defined networking approach for enhanced evolved packet core network

The evolved packet core (EPC) network is the mobile network standardized by the 3rd Generation Partnership Project and represents the recent evolution of mobile networks providing high‐speed data rates and on‐demand connectivity services. Software‐defined networking (SDN) is recently gaining momentum in network research as a new generation networking technique. An SDN‐based EPC is expected to introduce gains to the EPC control plane architecture in terms of simplified, and perhaps even software‐based, vendor independent infrastructure nodes. In this paper, we propose a novel SDN‐based EPC architecture along with the protocol‐level detailed implementation and provide a mechanism for identifying information fields exchanged between SDN‐EPC entities that maintains correct functionality with minimal impact on the conventional design. Furthermore, we present the first comprehensive network performance evaluation for the SDN‐based EPC versus the conventional EPC and provide a comparative analysis of 2 networks performances identifying potential bottlenecks and performance issues. The evaluation focuses on 2 network control operations, namely, the S1‐handover and registration operations, taking into account several factors, and assessing performance metrics such as end‐to‐end delay (E2ED) for completion of the respective control operation, and EPC nodes utilization figures.     

限流用BaTiO3系PTC陶瓷的制备及影响因素

介绍了以钛酸四丁酯和自制高纯醋酸钡为主要原料,采用溶胶–凝胶一步法(sol-gel)制备限流用BaTiO3系PTC陶瓷材料的工艺路线,用正交实验法研究了Ti/Ba,Pb,Ca,Y,Mn等组分因素对PTC陶瓷材料性能的影响。优化确定了PTC陶瓷材料的较佳组成。在基方固溶体化学组成,原材料选择和复合添加物的改性,特别是烧结工艺等方面做了细致的工作。最终获得了居里温度(tC)100℃,室温电阻率(r25) ≤20 ·cm,升阻比(Rmax / Rmin)>105,温度系数(aR)≥15% /℃,耐电压(Vb)≥190 V·mm1的PTC陶瓷材料。     

格栅翼组合体的超音速气动特性研究

介绍了超音速下格栅翼组合体的气动特性实验研究情况 .通过对两种格栅翼翼身组合体气动力实验结果的分析 ,以及与平板翼翼身组合体气动力数据的比较 ,阐述了格栅翼的气动特性 .结果显示格栅翼的阻力比平板翼的大 ,网格数越多阻力越大 ,在 M=2 .52 1 0时 ,斜置密网格格栅翼的升力大于平板翼的升力 ,削尖格栅翼的边框可以显著地减少格栅翼的阻力     

电控柴油机实时智能诊断系统实验研究

开发了电控柴油机实时智能诊断系统，并对该系统的仿真实验和台架实验的方法、步骤和路线进行了详细地论述，实验结果表明：系统能正确报警并能正确地输出故障结果，其输出结果与实际故障现象相吻合，故障判断正确率达到89％，说明设计的系统实验操作规程是可行的。     

大庆油田射孔完井过程中的油层保护技术

室内实验研究可知,射孔完井过程中油层的伤害主要是射孔压实带和射孔液的伤害。射孔压实带伤害程度较大,渗透率伤害率高达60.0%～80.0%;射孔液伤害程度相对较小,室内实验岩心渗透率伤害率在30%～36%之间。综述了大庆油田目前射孔完井过程中的油层技术,主要有负压射孔和采用射孔保护液,取得了较好的油层保护效果,采用负压射孔技术单井产能提高幅度20%～30%,采用优质射孔液单井产能提高幅度为20%左右。     

冲击电压校准器的实验验证

本文介绍的是用来校验冲击峰值电压表的标准仪器——冲击电压校准器的实验验证方法的原理及实用试验线路,分析了实验误差。     

An improved BEM model for the power curve prediction of stall‐regulated wind turbines

Blade element momentum (BEM) theory is the standard computational technique for the prediction of power curves of wind turbines; it is based on the two‐dimensional aerodynamic properties of aerofoil blade elements and some corrections accounting for three‐dimensional wing aerodynamics. Although most BEM models yield acceptable results for low‐wind and pitch‐controlled regimes where the local angles of attack are small, no generally accepted model exists up to date that consistently predicts the power curve in the stall regime for a variety of blade properties and operating conditions. In this article we present a modified BEM model which satisfactorily reproduces the power curves of four experimental wind turbines reported in the literature, using no free fit parameters. Since these four experimental cases comprehend a great variety of conditions (wind tunnel vs field experiments, different air densities) and blade parameters (no twist and no taper, no taper but twist, both twist and taper, different aerofoil families), it is believed that our model represents a useful working tool for the aerodynamic design of stall‐regulated wind turbines. Copyright © 2004 John Wiley & Sons, Ltd.     

台阶式溢流坝跌落水流时压强特性研究

当台阶均一的台阶式溢流坝在跌落水流流态时,台阶面上的脉动压力主要由跌落水舌影响,台阶水平面上压强均大于竖直面。由于水舌掺气,时均负压主要集中在台阶竖直面自台阶凸角至台阶凹角3 4的台阶高度范围内;受到跌落水舌在台阶水平面上的冲击,时均正压则主要集中在台阶水平面凸角水舌跌落处附近。台阶竖直面上的脉动压强强度远小于台阶水平面,而台阶水平面上的脉动压强强度则集中于水舌跌落处。     

CCD组件靶面脏斑成因分析及解决方法

通过三项试验,找到了CCD摄像机组件靶面脏斑形成的原因。潮湿的自然环境、温度变化和运输振动三个因素促成CCD组件机壳内的水汽吸附灰尘,凝聚到芯片靶面上形成脏斑。提出了解决脏斑问题的具体方法。通过在CCD组件的装配、包装过程中采取针对性措施来保证密封性能,这样就能在存储和运输过程中避开空气中的灰尘、水汽等脏斑源,靶面上就不会因受潮而产生脏斑。采取这些措施后,在后续产品中脏斑问题得到了彻底解决。     

整数阶Jerk混沌吸引子及其实现

以整数阶Jerk系统为例,提出了一种基于DSP Builder和FPGA的数字离散混沌系统解决方法.同时设计了相应的模拟硬件电路,并分别给出了硬件实验结果.实验结果表明,利用产生的实验结果与模拟电路产生的结果基本一致,证实了该方法的可行性,这为混沌系统的数字实现提供了新的思路.