为准确表征扣件弹性垫板的非线性动力学性能,将超弹性本构和线性黏弹性本构相结合,同时考虑垫板塑性,建立扣件弹性垫板非线性黏弹性-塑性本构模型;以中国高速铁路WJ-8B型扣件弹性垫板为研究对象,根据垫板的材料特性,结合各种本构模型的...为准确表征扣件弹性垫板的非线性动力学性能,将超弹性本构和线性黏弹性本构相结合,同时考虑垫板塑性,建立扣件弹性垫板非线性黏弹性-塑性本构模型;以中国高速铁路WJ-8B型扣件弹性垫板为研究对象,根据垫板的材料特性,结合各种本构模型的优缺点,分别采用Yeoh模型、Berg摩擦模型和高阶分数阶导数模型(Fraction Voigt and Maxwell model in Parallel,FVMP)对垫板的超弹性、黏弹性和塑性特性进行表征;利用配有高低温试验箱的MFT-250加载系统分别对垫板进行变温静载试验、低频大振幅试验和定频变温试验,求取各本构模型中的参数;通过前述3种试验探究温度对垫板超弹性、黏弹性和塑性的影响。结果表明:当温度高于-40℃时,垫板非线性性质较显著,且垫板所受荷载越大,位移非线性增大趋势越明显;各温度下垫板动态塑性力-位移滞回曲线主刚度与静态力学试验结果变化趋势一致;垫板储能刚度随温度降低逐渐增大,而耗能刚度则随温度降低先增后减,峰值处温度为-46℃;损耗因子在-42℃时达到峰值,约为玻璃化转变温度;非线性黏弹性-塑性模型相较于线性黏弹性-塑性模型拟合效果更好,能全面反映垫板非线性动力学特性;该组合模型可进一步嵌入车辆-轨道耦合动力学仿真平台,为车辆-轨道系统动力学性能优化、减振降噪技术研发提供模型支撑。展开更多
针对弱信号环境下全球定位系统(global position system,GPS)信号捕获问题,提出了一种基于双块零拓展(double block zero padding,DBZP)差分相干捕获算法。该算法将快速傅里叶变换(fast Fourier transform,FFT)、DBZP、差分相干及频率...针对弱信号环境下全球定位系统(global position system,GPS)信号捕获问题,提出了一种基于双块零拓展(double block zero padding,DBZP)差分相干捕获算法。该算法将快速傅里叶变换(fast Fourier transform,FFT)、DBZP、差分相干及频率误差修正等4项技术有机结合,从而有效减小了在FFT计算过程中由大多普勒频移引起的码片速率变化而造成的相关功率损失,同时也削弱了残余多普勒频率造成的功率损失。实验表明,算法能明显提高系统捕获性能,在仿真数据集下,与直接FFT差分相干算法相比,捕获灵敏度提高了约2.8dB,并在给定的积分时间及载噪比下,捕获频率误差的标准差小于20Hz;在实验数据集下,与直接FFT差分相干算法相比,捕获结果信噪比提高了约3dB。展开更多
随着汽车智能化的发展,汽车内的电子控制单元(Electronic Control Unit,ECU)数量激增,因CAN总线自身的特点,挂载在总线上的ECU缺乏必要的安全保护。为此,提出了基于物理不可克隆函数(Physical Unclonable Functions,PUF)的车载网络ECU...随着汽车智能化的发展,汽车内的电子控制单元(Electronic Control Unit,ECU)数量激增,因CAN总线自身的特点,挂载在总线上的ECU缺乏必要的安全保护。为此,提出了基于物理不可克隆函数(Physical Unclonable Functions,PUF)的车载网络ECU身份认证方案。该方案利用PUF的物理特征动态生成密钥,将身份认证划分为两个关联结合阶段,以满足车载网络实时性和安全性的双重需求。在车辆出厂前的非实时场景下,采用数字证书完成ECU间的注册。在车辆启动的实时场景下,基于认证链建立“一次一密”的快速身份认证机制。采用仿真测试对该方案的性能进行了评估,并与其他认证方案进行对比。实验结果表明,该方案可以同时满足车载网络在实时性和安全性方面的需求。展开更多
[Objective] This study aimed to investigate the effects of different padding on ammonia concentration in broiler house and growth performance and blood indi- cators of broilers. [Method] A total of 480 one-day-old 817...[Objective] This study aimed to investigate the effects of different padding on ammonia concentration in broiler house and growth performance and blood indi- cators of broilers. [Method] A total of 480 one-day-old 817 broilers were selected. They were randomly divided into four groups with different paddings, and each group was in triplicate. The weights of broilers and feed were weighed weekly. The growth performance of broilers was determined. On day 30, the ammonia concentra- tions in broiler houses were determined. On day 35, 6 broilers were randomly se- lected from each group, and their vein blood was sampled. In the sampled vein blood, the concentrations of ammonia, glucose, globulin, serum total protein and urea nitrogen were determined. [Result] There were significant differences in ammo- nia concentration among broiler houses laid with different paddings （P〈0.05）. The ammonia concentration in group 1 was significantly lower than those in group 3 and group 4 （P〈0.05）. No significant difference was found in ammonia concentrations in broiler houses between group 2 and group 3 （P〉0.05）. The ammonia concentration in group 4 was significantly higher than those in group1, group 2 and group 3 （,0〈 0.05）. There were also significant differences in blood indicators among different groups （P〈0.05）. The blood ammonia, blood glucose and serum urea nitrogen con- centrations in group 1 were significantly lower than those in other groups （P〈0.05）, the serum total protein concentration was significantly higher than those in group 3 and group 4 （P〈0.05）, and the serum globulin concentration was significantly higher than those in group 2, group 3 and group 4 （P〈0.05）. Significant differences were observed in feed intake, body weight gain and slaughter weight between different groups （P〈0.05）, but there were no significant differences in feed to grain ratio （P〉 0.05）. [Conclusion] Under the experimental conditions, the padding of Chinese medicine residue showed better effect on reducing ammonia concentration in broiler house, which was conducive to play of production potential of broilers.展开更多
文摘为准确表征扣件弹性垫板的非线性动力学性能,将超弹性本构和线性黏弹性本构相结合,同时考虑垫板塑性,建立扣件弹性垫板非线性黏弹性-塑性本构模型;以中国高速铁路WJ-8B型扣件弹性垫板为研究对象,根据垫板的材料特性,结合各种本构模型的优缺点,分别采用Yeoh模型、Berg摩擦模型和高阶分数阶导数模型(Fraction Voigt and Maxwell model in Parallel,FVMP)对垫板的超弹性、黏弹性和塑性特性进行表征;利用配有高低温试验箱的MFT-250加载系统分别对垫板进行变温静载试验、低频大振幅试验和定频变温试验,求取各本构模型中的参数;通过前述3种试验探究温度对垫板超弹性、黏弹性和塑性的影响。结果表明:当温度高于-40℃时,垫板非线性性质较显著,且垫板所受荷载越大,位移非线性增大趋势越明显;各温度下垫板动态塑性力-位移滞回曲线主刚度与静态力学试验结果变化趋势一致;垫板储能刚度随温度降低逐渐增大,而耗能刚度则随温度降低先增后减,峰值处温度为-46℃;损耗因子在-42℃时达到峰值,约为玻璃化转变温度;非线性黏弹性-塑性模型相较于线性黏弹性-塑性模型拟合效果更好,能全面反映垫板非线性动力学特性;该组合模型可进一步嵌入车辆-轨道耦合动力学仿真平台,为车辆-轨道系统动力学性能优化、减振降噪技术研发提供模型支撑。
文摘针对弱信号环境下全球定位系统(global position system,GPS)信号捕获问题,提出了一种基于双块零拓展(double block zero padding,DBZP)差分相干捕获算法。该算法将快速傅里叶变换(fast Fourier transform,FFT)、DBZP、差分相干及频率误差修正等4项技术有机结合,从而有效减小了在FFT计算过程中由大多普勒频移引起的码片速率变化而造成的相关功率损失,同时也削弱了残余多普勒频率造成的功率损失。实验表明,算法能明显提高系统捕获性能,在仿真数据集下,与直接FFT差分相干算法相比,捕获灵敏度提高了约2.8dB,并在给定的积分时间及载噪比下,捕获频率误差的标准差小于20Hz;在实验数据集下,与直接FFT差分相干算法相比,捕获结果信噪比提高了约3dB。
文摘随着汽车智能化的发展,汽车内的电子控制单元(Electronic Control Unit,ECU)数量激增,因CAN总线自身的特点,挂载在总线上的ECU缺乏必要的安全保护。为此,提出了基于物理不可克隆函数(Physical Unclonable Functions,PUF)的车载网络ECU身份认证方案。该方案利用PUF的物理特征动态生成密钥,将身份认证划分为两个关联结合阶段,以满足车载网络实时性和安全性的双重需求。在车辆出厂前的非实时场景下,采用数字证书完成ECU间的注册。在车辆启动的实时场景下,基于认证链建立“一次一密”的快速身份认证机制。采用仿真测试对该方案的性能进行了评估,并与其他认证方案进行对比。实验结果表明,该方案可以同时满足车载网络在实时性和安全性方面的需求。
基金Supported by Innovation Project for Universities and Research Institutes in Jinan City(201303053)Shandong Provincial Science and Technology Plan Project(2014GGH210001)Program of Animal Husbandry and Veterinary Bureau of Shandong Province~~
文摘[Objective] This study aimed to investigate the effects of different padding on ammonia concentration in broiler house and growth performance and blood indi- cators of broilers. [Method] A total of 480 one-day-old 817 broilers were selected. They were randomly divided into four groups with different paddings, and each group was in triplicate. The weights of broilers and feed were weighed weekly. The growth performance of broilers was determined. On day 30, the ammonia concentra- tions in broiler houses were determined. On day 35, 6 broilers were randomly se- lected from each group, and their vein blood was sampled. In the sampled vein blood, the concentrations of ammonia, glucose, globulin, serum total protein and urea nitrogen were determined. [Result] There were significant differences in ammo- nia concentration among broiler houses laid with different paddings （P〈0.05）. The ammonia concentration in group 1 was significantly lower than those in group 3 and group 4 （P〈0.05）. No significant difference was found in ammonia concentrations in broiler houses between group 2 and group 3 （P〉0.05）. The ammonia concentration in group 4 was significantly higher than those in group1, group 2 and group 3 （,0〈 0.05）. There were also significant differences in blood indicators among different groups （P〈0.05）. The blood ammonia, blood glucose and serum urea nitrogen con- centrations in group 1 were significantly lower than those in other groups （P〈0.05）, the serum total protein concentration was significantly higher than those in group 3 and group 4 （P〈0.05）, and the serum globulin concentration was significantly higher than those in group 2, group 3 and group 4 （P〈0.05）. Significant differences were observed in feed intake, body weight gain and slaughter weight between different groups （P〈0.05）, but there were no significant differences in feed to grain ratio （P〉 0.05）. [Conclusion] Under the experimental conditions, the padding of Chinese medicine residue showed better effect on reducing ammonia concentration in broiler house, which was conducive to play of production potential of broilers.
