Wall base ventilation system to treat rising damp: The influence of the size of the channels

One of the major causes of pathologies in our historic buildings is the presence of moisture, particularly rising damp. Since these constructions tended to be built near water lines, to facilitate their supply, and because their walls are mainly made of high porosity materials, the presence of rising damp is constant. Although many historic buildings in Portugal have already been the targets of interventions to eliminate pathologies, the fact is that it has not been possible to do it properly. The treatment techniques available nowadays are quite diverse but all of them have low applicability to historic constructions. Research has been carried out, in this past years, at the Department of Civil Engineering of the University of Coimbra in collaboration with Department of Civil Engineering of the Faculty of Engineering of the University of Porto to try and solve this problem. An old but poorly studied technique has been investigated experimentally and numerically in the past few years: ventilation of the base of the walls. It was experimentally validated to limestone walls 20 cm thick. Numerical investigation has been carried out in order to analyze the influence of different parameters on its efficiency. In this paper we present the results of the latest investigations that have been carried out about the influence of the size of the ventilation channel on its efficiency.     

基于Matlab的RLC阻尼振荡电路建模与仿真研究

通过建立RLC阻尼振荡电路的系统模型,得到三种不同的阻尼振荡类型及其通解的形式,利用M atlab程序对后两类阻尼振荡电路的时域和频域进行编程描述,对此两者仿真波形,证实了两种方法的有效性,同时指出了第5条临界阻尼非振荡波形失真的原因。     

强夯法加固地基的应用实践

强夯法是近些年出现的突破原来压实原理的一种地基处理方法,以石家庄大学(石电大)学生宿舍楼地基处理工程为基础,通过对有关数据的分析,探讨了其在提高地基承载力、消除地基土湿陷性方面的应用.     

离散振系的特征值组和弱阻尼的定义

给出了适合于用摄动法进行特征灵敏度计算的离散振系特征值组和弱阻尼的定义 ,并作了解释和给出了算例     

系统干扰信号分析及其抑制措施典例

干扰在测量中是一种无用信号,为了有效抑制测试过程中的干扰,必须了解干扰来源及传输途径,有针对性地选择抗干扰措施。本文从干扰信号的来源分析入手,以电机性能测试系统中抗干扰电路设计为例,通过软件仿真对信号干扰问题加以研究探讨,以期在各种不同情况下选取最恰当的抗干扰办法,获得最佳抑制效果。     

化学实验室防潮的重要性及方法

针对某些实验室环境空气湿度大的问题,对高湿度环境给仪器和化学试剂造成的影响以及从整体到局部降低实验室湿度的方法进行讨论。从而达到减少资源的浪费,提高仪器和试剂的利用率,节约实验室运行成本的目的。     

基于MATLAB的RLC阻尼振荡电路建模与仿真研究

在电路分析中经常会遇到一些阻尼振荡电路,由于这类电路在高压断路器开断能力测试、受控热核研究等许多重要的工程领域有着极为广泛的应用,因此有必要对此类电路的特性加以讨论研究。通过介绍建立数学模型的方法,对利用时域中传统的微分方程法和频域中经典的拉普拉斯变换法对电路进行了分析。最后借助于MATLAB软件对RLC电路的过渡过程进行了仿真的分析,并对其产生的误差作出了一定的解释。     

Diagnosing Decay Mechanisms at the Porta Nocera Necropolis,Pompeii: The First Step Towards Effective Preventive Conservation

ABSTRACT

Aspects of preventive conservation are central to the long-term preservation of archaeological sites such as Pompeii. Mitigating moisture ingress and its manifold effects on decay mechanisms such as salt degradation are of critical importance when planning durable conservation strategies. A suite of non-destructive techniques was used to diagnose decay mechanisms at an ancient tomb monument at the Porta Nocera Necropolis. Rising damp and salt contamination are shown to be actively contributing to on-going deterioration of the plaster surfaces. An existing shelter is shown to be inadequate in its protection. These initial results are used to inform a more in-depth, long-term survey as well as the design of a holistic preventive strategy.     

Rising moisture,salts and electrokinetic effects in ancient masonries: From laboratory testing to on-site monitoring

The investigation of capillary water rise mechanisms in old masonries is of great practical interest, as well as the investigation of the electrical effects accompanying such phenomenon. In fact, moisture presence facilitates all the decay processes in porous building materials and strongly threatens the preservation of materials in architectural heritage. Previous papers have shown that performing a correct and accurate measurement of spontaneous electric potential in masonries is very challenging due to several variables influencing these phenomena, such as materials microstructure, soluble salts nature and amount. In this paper, the influence of mortar joints on the capillary water rise and on the related electrokinetic effects was investigated on laboratory assemblies; then, the same measuring procedure was applied on site to a real XVI Cent. masonry building affected by rising damp.     

Willis环状脑动脉瘤生物数学模型的渐近解

本文研究了Willis环状脑动脉瘤的生物数学模型,在具有弱阻尼的条件下,求出了系统的渐近解,得出了在共振情形的频率响应方程,分析了频率响应曲线,以及外激动频率、振幅与共振频率、振幅之间的关系,为脑动脉瘤的肿大和破裂的研究提供了信息。