Consumer‐diet discrimination of δ13C and δ15N: Source‐ and feeding‐oriented patterns based on gut content analysis in a large subtropical river of China

Understanding the trophic discrimination (?¹³C and ?¹⁵N) between consumers and diets in fluvial systems remains difficult because of the variable food sources and complex predator–prey interactions from headwaters to the estuaries. Here, stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotopes in fish and invertebrates from a large subtropical river in southern China were determined to explore trophic discrimination in conjunction with a gut content analysis. The ?¹³C values showed significant differences (p < .05) among functional feeding groups, with fish, shrimp, and insect scrapers presenting higher ?¹³C values (1.20 ± 0.23‰ to 1.51 ± 0.31‰) than other groups. The ?¹⁵N values varied significantly between invertebrates (0.64 ± 0.17‰ of insect collector‐gatherers to 1.63 ± 0.36‰ of shrimp predators) and fish (1.98 ± 0.19‰ of detritivores to 2.71 ± 0.43‰ of crustaceavores) and exhibited an increasing tendency from primary to secondary consumers. A linear regression analysis revealed that the longitudinal changes in ?¹³C and ?¹⁵N were closely associated with the δ¹³C of periphyton, the δ¹⁵N of particulate organic matter (POM) in water, and the relative contribution (%) of periphyton and organic detritus to the diet composition of consumers. These results indicated that discrimination factors might not only be influenced by the isotope signatures of basal food sources but also downstream shifts in dominant food items utilized by consumers. In particular, trophic discrimination between periphyton– and detritus–based food chains, such as “epilithic diatoms–shrimp scrapers–crustaceavorous fish” and “POM–bivalves–molluscivorous fish,” displayed regionally specific patterns. When back‐calculating to the diet assimilation and trophic position in subtropical streams and rivers, we suggest using the basin‐scale ?¹³C value of 0.96 ± 0.26‰ for all consumers and ?¹⁵N values of 1.07 ± 0.32‰ for invertebrates and 2.38 ± 0.37‰ for fish.     

Quantitative method for estimating stain density in electron microscopy of conventionally prepared biological specimens

Stain density is an important parameter for optimising the quality of ultrastructural data obtained from several types of 3D electron microscopy techniques, including serial block-face electron microscopy (SBEM), and focused ion beam scanning electron microscopy (FIB-SEM). Here, we show how some straightforward measurements in the TEM can be used to determine the stain density based on a simple expression that we derive. Numbers of stain atoms per unit volume are determined from the measured ratio of the bright-field intensities from regions of the specimen that contain both pure embedding material and the embedded biological structures of interest. The determination only requires knowledge of the section thickness, which can either be estimated from the microtome setting, or from low-dose electron tomography, and the elastic scattering cross section for the heavy atoms used to stain the specimen. The method is tested on specimens of embedded blood platelets, brain tissue and liver tissue.     

地铁列车-嵌入式轨道系统动力学性能研究I：理论建模、试验分析及验证

嵌入式轨道作为一种减振降噪轨道结构型式,通常是基于城市街道路面的低地板有轨电车系统设计的,而嵌入式轨道的连续支承特性及其减振降噪优点使其在地铁中具有较好的应用前景。嵌入式轨道在地铁中应用,将面临更高运行速度、更大轴重、更复杂线路条件等挑战,地铁列车-嵌入式轨道系统的动力学行为有待研究。建立地铁列车-嵌入式轨道系统的动力学模型,模型包括轨道系统模型、列车系统模型以及轮轨相互作用模型。其中,轨道子系统为嵌入式轨道系统,是建模和研究的重点。模型考虑了TIMOSHENKO钢轨模型、等效弹簧-阻尼单元支承的柔性轨道板模型、以及钢轨周围的填充材料模型,填充材料模型采用考虑质量的黏弹性弹簧-阻尼单元来模拟以考虑填充材料的惯性、弹性和阻尼特性。在我国首例运用于地铁的嵌入式轨道试验线开展了动力学性能试验研究,基于试验分析了动力学性能并通过试验验证了动力学模型的有效性,建立的分析模型和相关结论为嵌入式轨道结构在我国地铁的应用提供了理论基础和参考。     

基于嵌入式系统的塑料挤出机温度控制器设计

设计了基于嵌入式系统的温度控制器。这种控制器是基于飞利浦半导体公司的P89LPC936微控制器、PC机和Visual C＋＋程序设计语言的基础上,实现了低成本高精度的温度控制器设计方案。实现嵌入式系统对挤出机温度进行实时控制和通过PC机对过往数据的读取以及目标温度的设定。采用模糊控制原理的温度控制算法提高了系统的稳定性和温度控制精度,在实验条件下温度波动小于1℃,成本降低50％。可以取代传统控制,满足塑料机械的控制精度、可靠性及效率工艺要求。     

基于DM270的嵌入式网络视频服务器

采用TM S320DM 270双核处理器可设计单芯片网络摄像机,这里为该处理器的ARM核设计网络视频服务器,首先完成了bootloader,移植μc-linux内核,并在内核基础上编写视频捕获驱动、DSP驱动和网络驱动,实现了流媒体协议和视频W eb服务器,为了实验本地存储,还为操作系统增加了文件系统。该服务器可同时支持16用户访问,保证视频流高质量的传输。     

PTFE/7075铝合金镶嵌型自润滑材料的摩擦学行为

采用模压／烧结工艺制备了PTFE／7075铝合金镶嵌型自润滑复合材料,在往复式摩擦磨损试验机上进行了摩擦磨损试验,用扫描电镜观察了复合材料磨损后的表面形貌,并探究了其磨损机理。结果表明:在试验条件下,稳态后摩擦温度为51℃,摩擦因数为0．087,磨损率为0．38×10-3mm3／(Nm),和非镶嵌型PTFE基复合材料相比,导热性和耐磨性大大提高,而摩擦因数无明显增加;稳定磨损阶段主要表现为粘着磨损,同时伴有轻微磨粒磨损,磨损后期局部呈现疲劳特征。     

IEC 61850控制对象状态机嵌入式软件设计及应用

对IEC 61850控制对象模型行为状态机的嵌入式多任务软件实现方法进行了研究。分析了控制对象行为状态机的现实意义和模型构建方法;结合网络环境下变电站开关操作行为规范和访问控制的应用需求,以及访问操作的多用户对多对象的特点,提出了控制对象行为状态机的实时多任务内核的实现模式,并介绍了基于μC/OS-Ⅱ操作系统的软件实现方法。     

输电线路嵌固式岩石基础抗拔试验

对湖南省某500 kV 输电线路嵌固式岩石基础进行真型试验, 根据试验结果, 分析基础承载特性和破坏机理, 采用极限平衡理论验算基础稳定性, 在综合造价分析的基础上指出嵌固式岩石基础的经济性和环保性。     

微机保护装置中PLC功能的实现和应用

提出了一种结合电力微机保护和可编程逻辑控制器(PLC)2种自动化设备各自优点的新方法,从功能实现的基础上看这2种装置有很大的相似之处,具备互相融合的条件、一定规模的可编程逻辑,从而方便用户实现现场的复杂闭锁和特殊要求。分析了2种装置的软、硬件框架和实现方案,给出了PLC平台和传统微机保护平台的差别和合并的可行性,并介绍了在微机保护装置中增加PLC功能的具体方法,所有方案都在相应平台上做过测试。最后,介绍了西门子保护的PLC功能(CFC)及其应用模式的灵活性。     

基于DSP和嵌入式系统的便携式数据采集分析装置设计

介绍了以TMS320F206数字信号处理器(DSP)和嵌入式系统为核心的便携式数据采集分析装置的设计。该装置数据采集模块可实现16路模拟量和8路开关量的同时采集。数据分析模块硬件电路以嵌入式计算机为核心,外围由译码电路、开入/开出电路组成。装置软件包括数据采集和数据分析2部分程序,数据采集程序采用TMS320C2XX标准汇编语言编程,完成数据的采集与上传,给出了程序流程图;数据分析软件采用嵌入式Linux实时多任务操作系统,给出了装置软件程序主界面及各界面功能。所设计的装置运行后,效果良好。