A circuit for measuring the real component of an impedance

Measurement Techniques -     

Phase-meter method of measuring total microwave impedance

Translated from Izmeritel'naya Tekhnika, No. 2, pp. 45–47, February, 1991.     

Dynamic pressurization method for measuring permeability and modulus: I. theory

The permeability of a saturated porous body can be determined from the kinetics of dilatation resulting from a change in pressure in the surrounding bath. This method was previously applied to aerogels [Gross J, Scherer GW (2003) J Non-Cryst Solids 325, 34–47]. The theory is here extended to allow for the compressibility of the solid phase, so that the method can be applied to more rigid materials, such as concrete. A viscoelastic analysis indicates that creep of the sample will have a small effect on the measured permeability for cementitious materials, in most cases. However, the effect of entrapped air in the pore liquid is shown to have a drastic effect on the relaxation behavior, so it is essential to reduce the air content below ∼0.1 volume %. For samples without entrapped air, a simple result is obtained that is tested in a companion paper.An erratum to this article can be found at     

一种测定单向纤维增强陶瓷基复合材料组分"原位"弹性模量的方法

提出了一种将细观分析和宏观实验相结合的方法以测量纤维陶瓷基复合材料组分"原位"弹性模量, 即利用混合率和Evans等导出的加载后卸载-再加载应力-应变曲线迟滞回环和组分材料力学性能之间的关系, 反解出纤维的原位模量。将此方法成功地应用于C/SiC复合材料, 初步结果表明此方法是行之有效的, 还表明C/SiC复合材料中纤维的原位弹性模量有明显下降。      

Dynamic pressurization method for measuring permeability and modulus: II. cementitious materials

In a companion paper, the theory behind a novel method for measuring permeability and bulk modulus is derived. The new method is termed ‘dynamic pressurization’ (DP). In this paper, an apparatus for the new method is described, and the test procedure is applied to cement pastes and concretes. The test involves rapidly applying a hydrostatic pressure to a saturated cylinder, then measuring the time-dependent deformation response of the material. The test is found to be repeatable, and the fitting function described in the companion paper is found to adequately fit the measured data. The measured permeability of the cement pastes compares well to measured values on identical materials using a different technique. The measured bulk moduli of the solid phase of the hardened cement pastes and concretes obtained in the DP test are in the range of expected values based on literature values for the Young’s moduli of clinker and hydration products.

---

Résumé Dans le premier article de cette série, la théorie à la base d’une nouvelle méthode de mesure par ‘pressurisation dynamique’ (PD) de la perméabilité et du module de déformation a été présentée. Dans cet article, un appareil permettant de réaliser cette nouvelle procédure expérimentale est décrit. Des examples d’application de cet essai à des éprouvettes de pate de ciment et de béton sont également donnés. La technique consiste à appliquer, sur un court laps de temps, une pression hydrostatique sur un cylindre saturé et de suivre l’évolution de la déformation du matériau en fonction du temps. Les résultats démontrent que l’essai est reproductible. De plus, les données confirment la validité de la fonction de relaxation identifiée dans le premier papier de cette série. Les résultats démontrent qu’il existe une bonne corrélation entre les valeurs de perméabilité mesurées pour des pates de ciment avec la nouvelle méthode et celles obtenues pour des matériaux similaires en utilisant une technique différente. Les modules de déformation mesurés pour le squelette solide de pates et de bétons durcis avec la méthode “PD” correspondent aux valeurs publiées dans la documentation scientifiques pour les modules de Young du clinker et des hydrates du ciment.

     

New approach to making instruments for measuring the electrical impedance of biological tissues

A new approach to the construction of instruments for measuring the electrical impedance of biological tissues is substantiated. The crux of the method is in the use of an electrical power generator for producing the electrical regime. Consideration is given to problems in the implementation of electrical power generators. Translated from Izmeritel'naya Tekhnika, No. 2, pp. 59–61, February, 1996.     

回热器声阻抗特性的直接测量法─—传递函数法

报告了一种直接测量回热器声阻抗特性的传递函数法。将实验管内的声波分解成入射波和反射波，通过两个不同位置上的传感器所测得的压力波之比，以及两个位置上反射波与入射波声压之间的简单传递函数关系，确定实验段入出口处的复反射因子，再由复反射因子确定实验段入出口处的压力波动和流量波动，从而得到实验段的阻抗特性。同时报告了理论分析和实验测量得到的简单管道阻抗特性的对比。结果表明，这种直接测量方法是可靠的。     

Optical method for measuring optical rotation angle and refractive index of chiral solution

Based on the phenomena of Brewster's angle and the principles of common-path heterodyne interferometry, we present an optical method for measuring the optical rotation angle and the refractive index of a chiral solution simultaneously in one optical configuration. A heterodyne light beam and a circularly polarized heterodyne light beam are separately guided to project onto the interface of a semicircle glass and a chiral solution. One of the beams is transmitted through the solution, and the other is reflected near Brewster's angle at the interface. Then the two beams pass through polarization components respectively for interference. The phase differences of the two interference signals used to determine the rotation angle and the refractive index become very high with the proper azimuth angles of some polarization components, hence achieving an accurate rotational angle and a refractive index. The feasibility of the measuring method was demonstrated by our experimental results. This method should bear the merits of high accuracy, short sample medium length, and simpler operational endeavor.