Influence of the Structure of Seersucker Woven Fabrics on their Friction Properties

Friction is defined as a force resisting a relative motion between two bodies in contact. The friction of a fabric on itself or on another fabric influences significantly a fabric’s performance and user’s utility comfort, especially the so-called sensorial comfort. Generally, the coefficient of friction is determined for a given pair of materials. The aim of the present work was to investigate the influence of the structure of the seersucker woven fabrics on their frictional properties. Three variants of the seersucker woven fabrics of different repeat of the seersucker effect were the objects of the investigations. Three measuring elements were applied: made of aluminum and steel and covered with silicone. The obtained results confirmed the influence of the pattern of the seersucker effect on the values of friction coefficient. It was also stated that there are differences between the friction coefficients measured in the warp and weft directions of the seersucker woven fabrics. Values of friction coefficient between the seersucker woven fabrics and measuring elements were the highest for the measuring element covered by silicone. These values were several times higher than the values of friction coefficient measured using the measuring elements made of aluminum and steel.

Gas flow measuring system using signal processing on the basis of entropy estimations

Purpose. To increase the accuracy of gas flow measurement in tachometric transducers based on the improvement of structural, hardware and algorithmic support of information and measuring systems. Methodology. The gas consumption value is determined by the parameters of information and measurement signals. Sensor signals interacting with the environment are traditionally processed on the basis of amplitude and frequency methods. The research methodology is based on the information theory, methods of statistical and spectral analysis, digital signal processing, the theory of gas dynamics, based on mathematical modeling in a computational experiment, as well as the theory of errors and measurement results uncertainty. The statistical characteristics of the measuring signals of the converter presented in the unitary basis are studied. Findings. The conducted research resulted in development of an information-measuring system to control the sensitivity threshold of the transducers of the primary volume and the volume of gas consumption based on the developed primary transducer, which allows providing relative standard uncertainty of cost determination within 0.5%. A special processor has been developed to calculate the entropy estimates of signal information. Originality. For the first time, a method for the formation and processing of information-measuring signals, which is based on the use of pressure pulsations due to the movement of the measuring element of the converter in the toroidal measuring cell, is proposed. Implementation of the measuring element of a spherical converter, whose density is almost commensurable with the density of the controlled medium is offered. Practical value. The proposed method allows providing a lower sensitivity threshold compared to the industrial implementation of tachometric type transducers.

Technique of Performance Improvement of the Microprocessor-Based Protection Measuring Element

The technique is proposed to improve the performance of the measuring element of microprocessor-based protection and its implementation is considered at the software level. Two factors mainly influence on the performance of the measuring elements of microprocessorbased protection of electrical installations. The first one is associated with the appearance of aperiodic and harmonic components in the measured signals due to transients and nonlinearity of the electrical installation elements, and the second–with the inertia of information processing algorithms, in particular–with analog and digital filtering. This leads to the fact that the signal determining time at the output of the measuring element is delayed to unacceptable values that in some cases makes the high-speed protection of electrical equipment ineffective. To solve this problem, it is proposed to form the output signal of the measuring element in the form of special equivalent signals, which are a function of the pre-calculated correction factor and orthogonal components of the controlled signal. In the MatLab-Simulink dynamic modeling environment a mathematical model of the developed measuring element has been implemented, as well as a model of the elements of the power system. Checking the functioning of the model of the measuring element was carried out with the use of 2 types of test effects, viz. a sinusoidal signal with a frequency of 50 Hz (idealized effect), as well as a signal close to the real secondary current of the current transformer in case of short circuit. Computational experiments carried out in relation to the current measuring element using harmonic and close-to-real test effects made it possible to reveal a significant (up to 2 times) increase in the performance of the proposed measuring element as compared to existing ones based on the implementation of the discrete Fourier transform.

Characterization study of As and Se in pyrites from two historic mines in British Columbia

Arsenic (As) and selenium (Se) can be toxic if they occur as soluble species at elevated concentrations. One process that can mobilize these elements into the environment is the oxidation of As- and Se-containing pyrites. This study presents the initial mineralogical (XRD, SEM-EDS, LA-ICP-MS, and synchrotron micro-XRF and micro-XANES) characterization of As- and Se-pyrites from two historic mines in British Columbia, the Sullivan Mine and the Sunro Mine. Results show that As occurs in some of the pyrites from the Sullivan Mine; comparison of the micro-XANES measurements to published data suggests As substitutes for sulphur. Selenium is detected in pyrites from the Sunro Mine but this Se is slightly more oxidized than measured in previous studies on Se-pyrite and further investigation of these samples is required. Results from this characterization study will be incorporated into the next phase of research measuring element mobilization after oxidation reactions to identify the effects of As or Se substitution on these reactions.

Model and Simulation Studies of the Method for Optimization of Dynamic Properties of Tachometric Anemometers

Mechanical tachometric anemometers, based on the phenomenon of the exchange of momentum between the flow and rotating measuring element, represent an important class of instruments used in flow metrology. In particular, they are used in meteorological and ventilation measurements. Mechanical anemometers with rotating measuring element are, however, known for their drawback related to their poor dynamic properties resulting from relatively large dimensions and mechanical inertia of the measuring element. In these instruments, the phenomenon of overestimating the measured average velocity caused by the inertia of the rotor takes place. Optimization of the dynamics of the measurement process, as well as the estimation and minimization of the measurement uncertainty, can be performed based on mathematical model of anemometer. In this study, a new, original concept of optimization of dynamic properties of tachometric anemometers is proposed, and the results of model and simulation studies are presented. The new concept of measuring instrument is based on the use of feedback and active control of the rotor. The new method was tested using model research, where two types of flow velocity excitations were applied: sinusoidal and rectangular. The tests carried out showed that the developed method allows for minimization of the dynamic uncertainty of the measurement and minimizes the phenomenon of average flow velocity overestimation occurring in time-varying flows. It has been shown that the use of optimization system allows for approximately tenfold reduction of the error of average velocity measurement in the case of pulsating flows. In addition, the optimization systems allow for anemometer’s transmission bandwidth to be extended about a hundred times. This creates new application possibilities for these instruments and allows for a large reduction of measurement uncertainty.