Correlations for the ignition delay times of hydrogen/air mixtures

Correlations for the ignition delay times of hydrogen/air mixtures were developed using the method of High Dimensional Model Representation (HDMR).The hydrogen/air ignition delay times for initial conditions over a wide range of temperatures from 800 to 1600 K,pressures from 0.1 to 100 atm,and equivalence ratios from 0.2 to 10 were first calculated utilizing the full chemical mechanism.Correlations were then developed based on these ignition delay times.Two forms of correlations were constructed:the first one is an overall general model covering the whole range of the initial conditions;while the second one is a piecewise correlation model valid for initial conditions within different sub-domains.The performance of these correlations was studied through comparison with results from the full chemical mechanism as well as experimental data.It was shown that these correlations work well over the whole range of initial conditions and that the accuracy can be significantly improved by using different piecewise correlations for different sub-domains.Therefore,piecewise correlations can be used as an effective replacement for the full mechanism when the prediction of chemical time scale is needed in certain combustion modeling.     

Skin collagen fiber-based radar absorbing materials

By using skin collagen fiber (CF) as raw material,Schiff base structure containing CF (Sa-CF) was synthesized through CF-salicylaldehyde reaction.Then a novel radar absorbing material (Fe-Sa-CF) was prepared by chelating reaction between Sa-CF and Fe 3+.The coaxial transmission and reflection method was used to analyze the complex permittivity and complex magnetic permeability of these CF-based materials,and the radar cross section (RCS) method was used to investigate their radar absorbing properties in the frequency range of 1.0-18.0 GHz.Experimental results indicated that the conductivity of CF increased from initial 1.08×10-11 to 2.86×10-6 S/cm after being transferred into Fe-Sa-CF,and its dielectric loss tangent (tanδ) in the frequency range of 1.0-17.0 GHz also increased.These facts suggest that the Fe-Sa-CF is electric-loss type radar absorbing material.In the frequency range of 3.0-18.0 GHz,Sa-CF (1.0 mm in thickness) exhibited somewhat radar absorbing property with maximum radar reflection loss (RL) of-4.73 dB.As for Fe-Sa-CF,the absorbing bandwidth was broadened,and the absorbing intensity significantly increased in the frequency range of 1.0-18.0 GHz where a maximum radar RL of-9.23 dB was observed.In addition,the radar absorbing intensity of Fe-Sa-CF can be further improved by increasing membrane thickness.When the thickness reached to 2.0 mm,the RL values of Fe-Sa-CF were-15.0-18.0 dB in the frequency range of 7.0-18.0 GHz.Consequently,a kind of novel radar absorbing material can be prepared by chemical modification of collagen fiber,which is characterized by thin thickness,low density,broad absorption bandwidth and high absorption intensity.     

Quantum key distribution using four-level particles

We present a quantum key distribution protocol based on four-level particle entanglement. Furthermore, a controlled quantum key distribution protocol is proposed using three four-level particles. We show that the two protocols are secure.     

Role of Tip60 tumor suppressor in DNA repair pathway

To prevent the damage caused by DNA strand breaks, eukaryotic cells have evolved a series of highly conserved DNA repair mechanisms. The ubiquitously expressed acetyltransferase, Tip60, plays a central role in ATM (ataxia-telangiectasia mutated) activation which is involved in DNA repair. Recent work uncovered a new mechanism of ATM activation mediated by Tip60 and demonstrated that histone methylation, specifically, trimethylation of histone H3, is a key factor in the process. Here, we review the current understanding of how Tip60 is activated and how it activates ATM in response to DNA damage.     

乳酸膨润土及其在聚乳酸材料中的应用

为扩展聚乳酸的应用范围,用乳酸与碱性钙基膨润土反应制备出剥离型乳酸膨润土,并用该材料与聚乳酸通过氯仿溶液铸膜法制备出聚乳酸/乳酸膨润土复合膜.用扫描电镜(SEM)观察膜的形态,万能力学试验机测定膜的拉伸强度和断裂伸长率,差示扫描量热法(DSC)和热重分析(TGA)研究膜的热性能.测试结果表明,添加1％的乳酸膨润土以剥离...     

基于优化肌电特征的无声语音信号识别

提出了一种基于遗传算法(GA)和fisher投影的最佳可鉴别基的求解方法.将原始特征向量向着最佳可鉴别基投影可得到具有最佳可分性的新的特征向量.从颧肌和二腹肌前腹的皮肤表面检测无声发出6个汉语元音的表面肌电信号(SEMG),以该肌电信号的AR模型系数、倒谱系数和美尔倒谱系数作为原始特征向量.使用遗传算法找出了原始特征的次优组合,并组成新的特征向量.将GA找出的次优特征向量向着fisher最佳可鉴别基投影可得到最佳鉴别特征向量.最后用改进的BP神经网络作为分类器得到了较好的识别效果.     

含单轴媒质和多层金属栅的多层介质结构电磁散射分析

应用有限元法结合Floquet定理分析含单轴媒质和多层金属栅周期性结构的多层有耗介质结构的电磁散射特性.首先对单层单轴媒质和带有单层金属栅的介质平板的反射系数进行了计算,数值结果与文献报道结果一致,验证了理论模型与计算程序的正确性.在此基础上,计算了含单轴媒质和三层金属栅结构的多层介质平板的散射参数.数值结果表明,该方法可有效地分析含单轴媒质的多层介质中任意形状周期结构的散射特性.     

基于蒙特卡洛仿真的液压系统动态可靠性

由于传统可靠性分析方法侧重于系统静态结构的描述,难以反映系统的动态运行过程,所以采用蒙特卡洛仿真方法研究液压系统的动态可靠性特征,重点计算液压元件故障服从不同分布、元件维修后故障率服从不同分布条件下液压系统可靠性指标的变化.仿真结果表明:修复如新时,不同分布对系统动态可靠性指标影响较小;修复如旧时,不同分布对系统动态可靠性指标影响较大.以可靠性仿真数据为基础,给出液压系统预防性维修策略.     

机器人足球训练中视觉感知与动作执行同步机制

主要研究RoboCup训练中球员视觉感知与动作执行同步的技术.在全面分析RoboCup现有同步方法存在问题的基础上,提出一种动态的视角调整方法,即通过对球员视角宽度的调整控制视觉信息到达的时刻,结合动作指令发送的特殊策略,实现球员向服务器发送指令时机的优化,以达到最佳同步效果.关于球员视角宽度动态切换的实现,具体包括:基于增强视觉检测的视角切换与分类视角动态切换2种方法.对比实验证实了该同步技术的优越性.     

松香型成核透明剂在聚丙烯中增透效果的研究

实验研究了松香型成核剂在聚丙烯(PP)中成核增透效果的影响因素,并通过偏光显微镜(PLM)和差热扫描量热分析(DSC)探讨了其中原因.