基于MATLAB的虚拟示波器设计

本文对虚拟示波器的结构进行了分析,设计出基于AVR单片机现场数据采集系统与MATLAB应用软件的虚拟示波器.文中详细给出了数据采集系统的设计、基于MATLAB仪器控制工具箱的数据通信软件的设计,以及MATLAB下波形显示程序的设计.所设计的虚拟示波器在一阶惯性电路上进行实验测试,测试结果表明该设计正确、可行.     

基于LabVIEW的虚拟示波器的构建

虚拟仪器的应用可解决高校电子测试仪器更新与投入不足的矛盾.介绍了虚拟仪器的构建方式,提出一款虚拟示波器的构建方案.以选定的硬件设备为前提,通过LabVIEW实现了该示波器的软件开发.此款虚拟示波器具有传统示波器的基本功能,并具有波形存储与回放、信号测量和频谱分析等扩展功能.实际应用表明,该虚拟示波器可以满足使用要求.     

数据采集卡和虚拟示波器系统

针对传统示波器价格昂贵,设备更新周期长的现状,结合虚拟仪器技术性能高、开发周期短等优越性,以Lab-VIEW8.6软件为平台,以计算机和基于音频芯片的数据采集卡为硬件设计了双通道虚拟示波器。虚拟示波器实质上是集前端信号采集、信号调理与传输、后端信号处理于一体的测试系统,能够完成模拟信号的采集、波形显示测量、数据处理等,在低采样频率测试场合,可以代替传统示波器,操作方便、成本低,具有一定的实用性。     

虚拟示波器的设计研究

论述用VB6开发虚拟示波器的面板设计、串行通讯、数据处理和程序设计。     

基于声卡的虚拟双踪数字存储示波器

虚拟仪器技术强大、灵活.是今后测试技术发展的趋势。本文基于虚拟仪器技术.利用声卡用于数据采集.设计了虚拟双踪数字存储示波器。经过检测.虚拟示波器能很好的显示被测波形.精度高、失真度小。     

基于多线程的测控平台虚拟示波器设计

采用C 编程语言和面向对象的方法,探讨了在VC开发环境下虚拟数字示波器的软件开发.研究了基于多线程技术的虚拟数字示波器的编程过程和技巧,结合面向汽车零部件试验的通用测控平台的硬件和软件分析,并以应用实例车辆减振器噪声测控平台验证该虚拟数字示波器的有效性.     

基于网络的分布式虚拟仪器测试系统

首先回顾了近几年虚拟仪器的发展过程，在分析了各阶段发展特点的基础上，进一步介绍了集成测试、分布式测试、分布式虚拟仪器的概念。提出一种结合分布式测试与集成测试的优点于一身的测试系统，该系统提高了测试的效率，在此基础上自行开发了分布式虚拟示波器，最后预测了基于网络信息化的虚拟仪器系统的发展方向。     

自动测试与虚拟仪器

随着计算机技术的快速发展，利用计算机代替人的繁锁劳动，已经应用到各行各业。在无线电测量领域，使用计算机和可程控的测试仪器，则能组成自动测试系统，如脉冲自动测试系统，可对示波器、示波器校准仪、脉冲发生器等进行校准和对脉冲波形进行分析。该测试系统由示波器、示波器校准仪、数字电压表、计数器、脉冲幅度标准测量装置。取样示波器、计算机、A／D与D／A转换器。显示器、打印机等仪器组成。在系统中，人们要做的工作，是利用高级语言编写程序，然后输入给计算机，计算机将高级语言程序译成计算机语言（数字代码），来管理和控…     

虚拟声波示波器设计

文章介绍了声波测井的基本原理及利用VC6．0提供的工具和组件实现虚拟声波示波器功能的方法，详细介绍了声波波形显示、声波参数显示和命令输入的程序设计方法。     

手持嵌入式设备虚拟示波器系统设计

为了增强嵌入式虚拟示波器应用程序的可移植性,该文基于嵌入式Linux系统平台和S3C2440微处理器设计了一种虚拟示波器.为了验证系统的有效性,在2种不同的手持嵌入式设备进行了仿真实验,结果表明该方案具有较好可移植性.     

The intracellular distribution of ions and water in rat liver and heart muscle

Local dry mass concentrations of intracellular compartments in rat heart muscle and liver cells were estimated by quantitative electron microscopy and X-ray microanalysis of ultrathin frozen-dried cryosections. The results were used to calculate elemental concentrations per litre of compartment water from the X-ray microanalytical data. Water fractions were between 80.3 ± 1.3% of wet weight in the decondensed chromatin and only 45.1 ± 1.7% in mitochondria of liver cells. The lowest water fraction in heart muscle cells was also found in mitochondria. The ionic concentrations found in the cytoplasm of liver cells and in the myofibrils are in accord with the electroneutrality rule and in osmotic equilibrium with the extracellular concentrations. The concentrations of Na, K, Cl and P both in the cytoplasm and in the regions of decondensed chromatin within the nuclei were found to be equal. However, in regions of condensed chromatin K⁺ concentrations were found to be much higher than expected for a Donnan distribution of ions free in solution. Most probably the activity coefficient for K⁺ is lower in the condensed chromatin than in the decondensed or in the cytoplasm. The same holds true for the A-band as compared to the I-band in heart muscle cells. A sequestration of K⁺ was measured also in the rough endoplasmic reticulum (RER) of hepatocytes. The Cl^? concentration in mitochondria both in heart muscle and liver cells has been measured far in excess of what might be expected from a Nernstian distribution. A coupled inward Cl^? transport in mitochondria must, therefore, be assumed.     

A synchrotron X-ray study of the changes occurring in the corneal stroma during processing for electron microscopy

Using a high-intensity synchrotron X-ray source, the structural changes occurring in the corneal stroma were monitored during each stage of several different processing runs for the transmission electron microscope (TEM) and scanning electron microscope (SEM). The parameters studied were interfibrillar spacing, intermolecular spacing, D-periodicity and fibril diameter. The processing schedule that produced the least changes in spacings for TEM specimens involved extended fixation in glutaraldehyde followed by low-temperature embedding in Lowicryl K4M resin. However, interfibrillar material was better preserved after embedding in LR White resin or Nanoplast. Almost every processing stage for electron microscopy produced significant changes in one or more structural parameters in the cornea. Glutaraldehyde fixation significantly increased the intermolecular spacings, while resin infiltration and resin polymerization each resulted in shrinkage of all the spacings monitored. Critical-point drying for SEM specimens resulted in considerable shrinkage in all three spacings, but was still preferable to air drying, which caused reduction in the order of the fibril packing, resulting in loss of the interfibrillar X-ray pattern. Perhaps the most drastic effect was caused by post-fixation in osmium tetroxide, which resulted in loss of the intermolecular pattern, and also increased the amount of shrinkage in the interfibrillar spacings and the D-periodicity which occurred during later stages of processing.     

Ciliary neurotrophic factor increases the survival of magnocellular vasopressin and oxytocin neurons in rat supraoptic nucleus in organotypic cultures.

Organotypic cultures of the rat hypothalamus are very useful models for the long-term study of parvocellular vasopressin (VP) neurons in the paraventricular (PVN) and suprachiasmatic (SCN) nuclei. However, they do not preserve significant numbers of VP magnocellular neurons (VP-MCNs) in either the PVN or the supraoptic nucleus (SON). Vutskits et al. [(1998) Neuroscience 87:571-582] reported that ciliary neurotrophic factor (CNTF) was a selective survival factor for rat VP-MCNs in organotypic cultures of the rat hypothalamic paraventricular nucleus (PVN). We examined the effects of CNTF on the survival of these neurons in rat and mouse SONs. CNTF (10 ng/ml) in the culture media increased the survival of VP-MCNs by 6-fold and OT-MCNs by 3-fold. In the mouse, both OT- and VP-MCNs survive very well in organotypic cultures under standard culture conditions and the addition of CNTF had no further effect. Consistent with these results, in situ hybridization showed substantially higher levels of VP- and OT-mRNA in rat PVNs and SONs in the presence of CNTF, but produced no changes in these nuclei in the mouse. The optimum period for the survival effect of CNTF on MCNs in the rat hypothalamic cultures was in the first 7-10 days of culture and this effect is maintained for at least 5 additional days if CNTF is then removed from the medium. Therefore, using CNTF in the culture media can provide an opportunity for long-term studies of rat VP- and OT-MCNs in SONs in organotypic cultures.     

Gender-related changes in the avian vasotocin system during ontogeny

The arginine vasotocin (AVT) system of the avian brain includes a sexually dimorphic part that extends from the caudal part of preoptic region through the medial part of the bed nucleus of stria terminalis (BSTm) to the lateral septum. It is composed of the parvocellular neurons located in the BSTm and the dense innervation of the medial preoptic region and lateral septum. In this part of the brain, AVT expression is stronger in males than in females in a few bird species investigated to date. This review focuses on the ontogeny of sexual differences in the vasotocinergic system of two gallinaceous species, domestic chicken and Japanese quail, and on the role of gonadal hormones in organizing during development and maintaining in adulthood these differences. Parvocellular AVT neurons become discernible in the BSTm of males and females during the second half of embryonic development. These cells undergo a profound and irreversible sexual differentiation during ontogenetic development. Recent findings demonstrate a dual role of estrogens in the organization and activation of sex differences in the AVT system. During the embryonic period of ontogeny, estrogens differentiate the AVT system in a sexually dimorphic manner in parallel with the differentiation of sexual behavior, while in adulthood estrogens, locally produced from testosterone in the male brain, activate AVT synthesis in the BSTm. The sexually dimorphic part of the AVT system is sensitive to a number of abiotic factors such as light, temperature, and water availability. It is suggested that sex dimorphic vasotocinergic systems could be implicated in processes of social recognition in various behavioral contexts.     

工程热力学中关于不可逆绝热过程的分析

指出了文献中关于不可逆绝热过程分析存在的问题,认为按照热力学第一定律闭口系统能量方程式．闭口系统绝热膨胀过程对外所作的功等于热力学能降,而非膨胀功等于热力学能降。终压相同时,可逆绝热膨胀过程对外所作的功等于膨胀功,不可逆绝热膨胀过程对外所作的功小于膨胀功,其对外所作的功仅是膨胀功的一部分．是排斥大气所作功与有用功之和,故不可逆过程对外所作的功小于可逆过程的膨胀功．而不是其“膨胀功”小于可逆过程的膨胀功。并运用反证法和算例进行了证明。     

The Ralph knife in practice

Long edge glass knives, ‘Ralph knives’, were produced in an LKB Histo KnifeMaker. The edge angles were measured by light microscopy; depending on the breaking conditions the angles varied between 12° and 58°, as measured close to the edge in the mid-portion of the knives. Hackle marks were more common in the left portion of the edge than in the middle and right portions. Some of the knives were used for cutting sections from urinary bladder tumours embedded in paraffin or in glycol methacrylate. Following microtomy the sections were allowed to stretch on a water surface; this procedure resulted in an increased width of the plastic sections, whereas the paraffin sections were not affected. The compression of the whole sections averaged 15% in the paraffin sections and 11% in the plastic sections; in both cases the compression factors were positively correlated to the angle of the knife edge. Smaller compression factors were found for the cell nuclei in the embedded tissue.     

Mechanotransduction-The relationship between gravity,cells and tensile loading in extracellular matrix

Gravity plays a central role in vertebrate development and evolution. Mechanotransduction involves the tensile tethering of veins and arteries, connections between the epidermis and dermis in skin, tensile stress concentrations that occur at tissue interfaces, cell-cell interactions, cell-collagen fiber stress transfer in extracellular matrix and fluid shear flow. While attention in the past has been directed at understanding the myriad of biochemical players associated with mechanotransduction pathways, less attention has been focused on determining the tensile mechanical behavior of tissues in vivo. Fibroblasts sit on the surface of collagen fibers in living skin and exert a retractile force on the fibers. This retractile force pulls against the tension in collagen fibers in skin. After fibroblast-collagen fiber interactions are altered either by changes in fibroblast adhesion or after formation of cancer associated fibroblasts, and changes in cell junctions, alterations in the retractive force leads to changes in mechanotransduction. The purpose of this paper is to present a model of tensile forces that occur at the fibroblast-collagen fiber interface and how these forces are important in extracellular matrix physiology in health and disease.     

Use of primary cell cultures and intact isolated glandular epithelia for X-ray microanalysis

Changes in the elemental composition of cells during isolation of glandular epithelia were studied by electron probe X-ray microanalysis. Fine chopping of rat submandibular gland followed by enzymatic treatment for 15 min caused marked increases in Na and Cl and a decrease in K concentrations in acinar cells. After enzymatic treatment for 50 min, Na, Cl and K concentrations returned to close to the control level. Mechanical disaggregation of the acinar clumps following enzymatic treatment resulted again in minor increases in Na and Cl and a marked decrease in K concentration. Exposure of isolated acini to cholinergic stimulation in vitro resulted in secretion of Cl and K from the acinar cells. Dissection of the sweat gland from human skin caused a decrease in the K/Na ratio. Incubation of the gland for 30–45 min with collagenase gave rise to a gradual decrease in the K/Na ratio. After mechanical separation of the gland into the secretory coil and reabsorptive duct, a further reduction of the K/Na ratio was seen. However, the duct cells had a much lower K/Na ratio and higher Ca concentration than the coil cells. In primary cultures, the K/Na ratios of the coil and duct cells returned to the in situ level. The elemental composition of sweat gland cells incubated in collagenase-containing medium was no different from that in cells incubated in collagenase-free medium. In the intact collagenase-isolated tissue, Cl^? secretion in the coil was elicited by carbachol but not by cAMP, whereas in the duct cells the reverse was the case. In primary cell cultures, Cl^? efflux in both coil and duct cells could be elicited by both carbachol and cAMP. In conclusion, although changes in elemental composition of gland cells during the isolation procedure occur, physiological responses can be detected. When primary cell cultures are used, it should be borne in mind that cultured cells may have physiological properties different from those of the intact tissue.     

Circadian organization and the role of the pineal in birds

All organisms exhibit significant daily rhythms in a myriad of functions from molecular levels to the level of the whole organism. Significantly, most of these rhythms will persist under constant conditions, showing that they are driven by an internal circadian clock. In birds the circadian system is composed of several interacting sites, each of which may contain a circadian clock. These sites include the pineal organ, the suprachiasmatic nucleus (SCN) of the hypothalamus, and, in some species, the eyes. Light is the most powerful entraining stimulus for circadian rhythms and, in birds, light can affect the system via three different pathways: the eyes, the pineal, and extraretinal photoreceptors located in the deep brain. Circadian pacemakers in the pineal and in the eyes of some avian species communicate with the hypothalamic pacemakers via the rhythmic synthesis and release of the hormone melatonin. Often the hypothalamic pacemakers are unable to sustain persistent rhythmicity in constant conditions in the absence of periodic melatonin input from the pineal (or eyes). It has also been proposed that pineal pacemakers may be unable to sustain rhythmicity in constant conditions without periodic neural input from the SCN. Significant variation can occur among birds in the relative roles that the pineal, the SCN, and the eyes play within the circadian system; for example, in the house sparrow pacemakers in the pineal play the predominant role, in the pigeon circadian pacemakers in both the pineal and eyes play a significant role, and in Japanese quail ocular pacemakers play the predominant role.     

Anisotropic properties of bovine nasal cartilage

To investigate the structural anisotropy in bovine septal cartilage, quantitative procedures in microscopic magnetic resonance imaging (μMRI), polarized light microscopy (PLM), and mechanical indentation were used to measure the tissue in three orthogonal planes: vertical, medial, and caudocephalic. The quantitative T2 imaging experiments in μMRI found strong anisotropy in the images of both vertical and caudocephalic planes but little anisotropy in the images from the medial plane. The PLM birefringent experiments found that the retardation values in the medial section were only about 10% of these in the vertical and caudocephalic sections and that the angle values in all three sections followed the rotation of the tissue section in the microscope stage. The stress relaxation experiments in mechanical indentation showed reduced stiffness in the medial plane compared to stiffness in either the vertical or caudocephalic planes. Collectively, the results in this project coherently indicate a marked structural anisotropy in cartilage from the nasal septum, where the long axis of the collagen fibrils is oriented in parallel with the medial axis.