This work presents a general method for the synthesis of any open-circuit transfer function, which is expressed as a rational function with real coefficients. It is shown that such functions can be realized by using two distributed RC elements (modified by active units if necessary), one negative impedance converter and one lumped capacitor. The distributed RC element used here is a three-layer structure, a pure dielectric sandwiched in between a perfect conductor and a resistive film.
Palm fiber weaving is a traditional handicraft of Han nationality, and Wangcang palm fiber weaving is one of the important birthplaces and inheritance places of palm fiber weaving. Based on the analysis of the present situation of Wangcang brown knitting, combined with contemporary technology and modern marketing, this paper explores the inheritance and development method of modern brown knitting technology, so as to better protect traditional skills and carry forward brown knitting culture.
An iterative algorithm for precisely reconstructing the complex amplitude of a laser beam based on a radial shearing interferometer is proposed. First, the complex amplitude of the modulation function that includes the test beam’s information is obtained from a cyclic radial shearing interferogram by the Fourier filtering method. Then the complex amplitude of the modulation function is used to estimate the complex amplitude of the laser output with a successive iterative process. The simulations and real experimental results show the performance of the proposed iteration method of beam complex amplitude reconstruction.
Traditionally, the most precise way to get the mutual inductance value is by a calculable mutual inductor. Here a new approach of measuring the mutual inductance at low frequency with compensation method is described. The mutual inductance is traced to the value of the frequency and resistance directly. The measurement uncertainty is 0.1 ppm and could be improved further.
The application of high-speed real-time data acquisition is becoming increasingly wide spread in industrial field, and its measurement accuracy is also increasing. The closed-loop test system of sine wave signal is constructed by the RIGOL’s DG1022 dual-channel signal source, DS1102C oscilloscope and PCI7489 multifunctional data acquisition card. Three kinds of timing methods, such as Visual Basics (VB) Timer control, multimedia timer function timing and query performance frequency function timing method, were carried out a series of comparative experiments. This paper analyzes the correlation characteristics of the measured voltage peak data, which includes mean value, variance, standard deviation, range, mutation system, deviation, kurtosis and so on, and then finds out the influence rules of software timing error on data acquisition and measurement accuracy. In the high-speed data acquisition, the repeatability error can be reduced from 84.22% to 0.62%, which provides scientific basis and reference for selecting software timing method in different test environment.
To investigate the recovery effect of natural self-healing of freeze-thaw damage of cementitious material-poor hydraulic concrete, we carried out a natural self-healing test for hydraulic concrete damaged by up to 200 rapid freeze-thaw cycles. The self-healing effect of macro-mechanical properties of hydraulic concrete damaged by freeze-thaw cycles was quantitatively characterized by the recovery rate of the specimens which underwent different numbers of freeze-thaw cycles then continued the standard curing to 28 days. Next, the microscopic properties of damaged hydraulic concrete after self-healing were further investigated by combining XRD, SEM and nitrogen adsorption tests. Finally, a prediction model of recovery rate of macro-mechanical properties was established by using the microscopic pore test results. The results showed that, when the hydraulic concrete undergoes the damage of different freeze-thaw cycles and continues to standard curing for 28d, the concrete specimens manifest natural self-healing to some extent even if damaged by up to 200 freeze-thaw cycles.
The paper proposes a type of symmetrical flexure hinge displacement amplification mechanism, which is based on the differential lever to effectively improve the displacement output stroke of the PZT and reduce the additional displacement. In addition to describes the working principle of the differential displacement amplification, it establishes the semi-model of the micro-displacement amplification mechanism according to the symmetrical structure. The stiffness, displacement loss, and natural frequency of the amplification mechanism are simulated by finite element analysis (FEA). Simultaneously, build the mathematical model of amplification ratio to obtain the optimal driving frequency when the natural frequency is 930.58 Hz. The maximum output displacement of the designed mechanism is 313.05 µm and the amplification ratio is 6.50. Due to the symmetrical structure, the output additional displacement of the whole amplification mechanism is small.It provides a scientific basis for further improving the positioning accuracy of the micro/nano drive control system.
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