Utility function of TCP

Understanding the TCP congestion control mechanism from a global optimization point of view is not only important in its own right, but also crucial to the design of other transport layer traffic control protocols with provable properties. In this paper, we derive a global utility function and the corresponding optimal control law, known as TCP control law, which maximizes the global utility. The TCP control law captures the essential behaviors of TCP, including slow start, congestion avoidance, and the binary nature of congestion feedback in TCP. We find that the utility function of TCP is linear in the slow start phase and is proportional to the additive increase rate and approaches the well-known logarithm function as the data rate becomes large in the congestion avoidance phase. We also find that understanding the slow start phase with a fixed threshold is critical to the design of new transport layer control protocols to enable quality of service features. Finally, as an application, we design a Minimum Rate Guaranteed (MRG) traffic control law that shares the same utility function as the TCP control law. Our simulation study of the MRG control law indicates that it is indeed TCP friendly and can provide minimum rate guarantee as long as the percentage of network resource consumed by the MRG flows is moderately small.     

折射率非线性调制的双重光纤光栅特性

利用耦合模理论 ,系统分析了双重光纤光栅在折射率深度调制或非线性调制情况下的光谱特性。结果发现 ,在折射率非线性调制情况下 ,双重光纤光栅具有规则的多波长反射特性 ,同时 ,其反射光谱中的二次谐波也变得非常强 ,因此 ,它是一种实现多通道波分复用器、分插复用器及多波长激光器等的潜在技术。     

共轭点电荷系在静电劈形问题中的应用

根据点-面情形电像解的规律提出共轭点电荷系概念,对不同类型的共轭点电荷系在半无限大导体平面上的感应电荷总量进行了计算,并应用到有一定对称性分布的静电劈形问题中。共轭点电荷系思想对π是夹角整数倍情形时的劈形角平分面上点电荷的电像解提供了一种新的解法和思路。     

“数字信号处理”中重叠保留法的证明

重叠保留法是计算一个短序列与一个无限长序列线性卷积的有效方法。就我们所知,多数《数字信号处理》教材详细叙述了重叠保留法的步骤,有些教材还从线性卷积与循环卷积的关系出发给出了重叠保留法的原理,笔者认为这种解释不够清楚、也不够严谨。本文给出了一个较为严谨而准确的证明。     

Combined spatial-temporal energy harvesting and relay selection for cognitive wireless powered networks

In order to improve the Energy Efficiency (EE) and spectrum utilization of Cognitive Wireless Powered Networks (CWPNs), a combined spatial-temporal Energy Harvesting (EH) and relay selection scheme is proposed. In the proposed scheme, for protecting the Primary User (PU), a two-layer guard zone is set outside the PU based on the outage probability threshold of the PU. Moreover, to increase the energy of the CWPNs, the EH zone in the two-layer guard zone allows the Secondary Users (SUs) to spatially harvest energy from the Radio Frequency (RF) signals of temporally active PUs. To improve the utilization of the PU spectrum, the guard zone outside the EH zone allows for the constrained power transmission of SUs. Moreover, the relay selection transmission is designed in the transmission zone of the SU to improve the EE of the CWPNs. In addition to the EE of the CWPNs, the outage probabilities of the SU and PU are derived. The results reveal that the setting of a two-layer guard zone can effectively reduce the outage probability of the PU and improve the EE of CWPNs. Furthermore, the relay selection transmission decreases the outage probabilities of the SUs.     

国内外食品接触材料中着色剂的法规

简述了着色剂的种类及其对食品接触材料安全性的影响,重点介绍了欧盟、美国、日本和我国关于着色剂的一些法规和要求.     

香豆素类荧光增白剂的研究进展

本文探讨了荧光增白剂的作用机理,概述了合成香豆素类荧光增白剂的经典方法以及几种最新研究成果。认为功能性的香豆类化合物具有巨大的应用潜力,如何简便、高效、绿色地制备此类物质是该领域的研究热点之一。     

无锡地铁盾构区间下穿京杭大运河技术研究

结合无锡地铁2号线11标大王基站—梁溪大桥站区间盾构机下穿京杭大运河的施工经验,从盾构掘进参数选择入手,分析了盾构机过河的重难点,并提出了相应的措施,包括采取控制土仓压力值、掘进速度、刀盘转速、出土量、同步注浆量、二次注浆以及各项措施完成盾构推进,为同类工程施工提供了参考。     

Microstructural and analytical characterization of TiNχ precipitation in N+ implanted equiatomic NiTi alloys

In order to explain the improved tribological properties obtained on NiTi alloys after N⁺ implantation, complementary surface sensitive techniques (TEM, SIMS and XPS) are used to characterize an initially martensitic NiTi alloy. When the nitrogen ions are implanted at 293 K, the affected zone is fully amorphous with embedded fine disoriented TiNx (x ≈ 0.8) precipitates. At 473 K the implanted region consists of an amorphized layer and an underneath crystalline austenitic layer both containing TiN_χ precipitates. These precipitates are in epitaxy with the austenitic matrix. After implantations at 573 K and above, the implanted zone is fully austenitic with epitaxial TiNx precipitates. Post implantation annealings under 823 K do not sensibly affect the implanted element distribution but favor the evolution of TiN_χ precipitates towards the stoichiometric compound TiN. Beyond 823 K the amorphous layer crystallizes.     

Semantic-based role matching and dynamic inspection for smart access control

Multimedia Tools and Applications - In this paper, we propose a scheme of semantic-based role matching and dynamic inspection for smart access control. The basic roles are established first, and...