Degradation of starch by incubation with rumen fluid. A comparison of different starch sources

The degradability of starch from various feedstuffs was investigated in vitro by incubation of 500-mg amounts in 50 ml of a 3:1 rumen fluid/buffer solution at 39°C for 6 h. The rumen fluid was obtained from one of three cows fed on hay or hay and concentrate. The degree of degradation after 6 h incubation varied strongly for the 23 feedstuffs investigated. The degradation of starch from the same feedstuff in rumen fluid from a hay-fed cow was significantly lower than in rumen fluid from a concentrate-fed cow. It seemed that differences in degradability between feedstuffs were not determined by the ration of the donor cow, but merely by the properties of the starch. Processed feedstuffs showed a higher degradation of their starch than the unprocessed feedstuffs, independent of the ration of the donor cow. Particle size influenced degradation, but not of the starch of tapioca meal. A fairly constant ranking in degradability between the various feedstuffs was found. Fermentation of mixtures of feedstuffs showed about the same rate of degradation as found for the single products. Only when great differences in the degree of degradability existed was the degradation of the total starch enhanced. The time of collection of rumen fluid strongly influenced the in-vitro degradation of starch.     

步进电动机加速控制算法研究及仿真

针对步进电动机在启动、停止时,会出现启动失步、堵转以及超程或冲击大等现象,提出了指数加减速算法和S形曲线加减速算法。首先建立了步进电动机的数学模型和传递函数。鉴于加速启动和减速停止过程是对称的,故笔者仅研究分析了对步进电动机启动阶段进行加速控制的过程。介绍了指数加减速算法和S形曲线加减速算法原理和设计方法,并应用Matlab实现了系统设计与仿真。最后对指数加速控制和S形曲线加速控制的仿真结果进行对比分析,结果表明:与指数加减速算法相比,S形曲线加速控制方法速度过渡光滑,具有更好的动、静态性能,且易于调整和改进。     

单电子隧道结隧穿特性研究与仿真

基于单电子隧道结电压特征公式[1],借助Matlab拟合其隧穿特性曲线,给出了时不变和时变偏置电流作用下的I-V特性震荡曲线,并就仿真结果进行分析,将该模型应用于单电子盒进行仿真验证,出现了明显的库仑台阶,仿真曲线印证了理论分析结果.利用Matab强大的计算功能进行单电子器件特性仿真对单电子器件的应用研究有重要意义.     

冲激引信超窄脉冲源的研究

主要对冲激引信中的超窄脉冲源在以下几方面进行详细讨论：冲激脉冲源的核心器件(阶跃恢复二极管)特性，等效电路、冲激脉冲源电路组成与原理，以及一种冲激脉冲源的工程实现；另外，对微分脉冲源原理也进行了简要介绍。超窄脉冲源的研究成果为冲激引信原理性试验提供了基础，也为目标冲激响应特征的测试提供了手段。     

Amplifying Nanoparticle Targeting Performance to Tumor via Diels–Alder Cycloaddition

Traditional targeting approach utilizing biological ligands has to face the problems of limited receptors and tumor heterogeneity. Herein, a two‐step tumor‐targeting and therapy strategy based on inverse electron‐demand [4+2] Diels–Alder cycloaddition (iEDDA) is described. Owing to the unique acidic tumor microenvironment, an intravenous injection of tetrazine modified pH (low) insertion peptide could efficiently target and incorporate onto various cell surfaces in tumor tissue, such as cancer cells, vascular endothelial cells, and tumor‐associated fibroblasts. The “receptor‐like” tetrazine groups with a large amount and homogeneous intratumoral distribution could then serve as the baits to greatly amplify the tumor‐targeting ability of indocyanine green (ICG)‐loaded and trans‐cyclooctene (TCO)‐conjugated human serum albumin (HSA) nanoparticles (TCO‐HSA‐ICG NPs) via iEDDA after the second intravenous injection. Compared with the passive enhanced permeability and retention (EPR) effect and traditional active targeting approaches, the targeting performance and photothermal therapeutic effect based on the two‐step strategy are significantly enhanced, while no notable toxicity is observed. As acidity is a characteristic of solid tumor, the two‐step strategy can serve as a universal and promising modality for safe and high‐performance nanoparticle‐based antitumor therapy.     

一种机动目标调频步进雷达成像算法

针对低信噪比下机动目标的调频步进雷达成像问题,提出基于Radon-分数阶模糊函数(RFRAF)的方法进行积累成像的方法.在分析了机动目标的调频步进雷达回波信号特征的基础上,将目标回波信号在RFRAF域进行匹配和积累,通过峰值搜索出目标的运动参数,并构建补偿函数实现机动目标运动补偿,从而获得目标精确ISAR像.计算机仿真结果进一步表明了该方法能在低信噪比下稳健成像.     

基于AVR单片机的图书录入系统

介绍一种AVR单片机在图书录入系统中的应用,对系统的软件和硬件设计做了说明。本设计以高性能、低功耗的8位AVR微处理器ATmega32L为核心,通过控制步进电机实现执行机构的移动、定位等功能,对书籍进行自动翻页、拍照,适用于有收藏价值、书况不好的书籍的电子图像录入保存。     

CMA算法盲均衡性能分析

由于受多径传输和有限带宽的影响,无线信道不可避免地存在码间干扰和信道间干扰.盲均衡技术是一种不需要训练序列就能补偿信道畸变的新兴自适应均衡技术.文中从Bussgang类盲均衡原理出发,讨论了属于Bussgang类的CMA盲均衡算法,并利用Simulink对算法进行了仿真.从仿真结果可看出步长对算法收敛性能和精度的影响,步长越小,收敛速度越慢,但稳态误差越小;反之亦然.     

高效率小型化行波管的二次谐波抑制

以罗埃大信号理论为基础，利用两节螺距具有正负变化的双跳变输出电路对提高宽带行波管效率的二次谐波抑制问题进行了模拟。对输出电路的跳变位置和跳变螺距进行了详细研究。模拟与测试结果证明：采用双跳变输出线路，在低频端二次谐波受到很大抑制，正向基波分量得到明显增强，在宽频带(6—18GHz)范围内，获得了均衡的饱和功率输出。     

微弱电容信号的离散频率测试方法及其硬件电路的实现

硅微惯性器件的微弱电容信号检测一直是微机械研究领域的重要问题,其检测方法及集成电路的实现已成为制约微惯性器件发展的一个重要因素。利用频率信号抗干扰性好的特点将微弱电容信号转换成频率信号,提出了一种利用离散频率测试的方法对加速度信号进行测试,使得所测加速度可以通过各离散频率点与步长频率的倍数关系直接读出,并通过硬件电路实现了该方法,对实验结果进行了验证,与理论仿真结果很相符。