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The present study provides a wideband high-gain monopulse antenna based on a dielectric lens operating in X- and Ku-bands, in which a wideband dielectric lens is designed and employed to fulfill the radiation pattern and bandwidth necessities of a monopulse antenna. The proposed configuration has four horns allowing for the simultaneous creation of $\Delta $ and $\Sigma $ designs in two perpendicular planes. The main advantages of the proposed dielectric lens are low cost, lightweight, and easy fabrication using 3-D printing technology. The measurement findings show that the peak gain of the sum pattern is 28.9 dBi with a peak aperture efficiency of 60% over the desired frequency bandwidth. The suggested design can produce a simultaneous sum and two distinct difference patterns in orthogonal planes, meeting the rigorous demands for speed and accuracy in tracking applications.

This paper proposes a non-contact current measurement method for three-phase rectangular busbars based on TMR (tunneling magneto-resistance) sensors, due to their advantages of large dynamic range, wide bandwidth, light weight, and easy installation. A non-contact current sensor composed of only three TMR sensors is developed and the TMR sensors are respectively placed at a location with a certain distance from the surface of each rectangular busbar to measure the magnetic fields generated by the busbar currents. To calibrate the developed current sensor, i.e., to establish the relationship between the magnetic fields measured by the TMR sensors and the currents flowing in the three-phase rectangular busbars, we designed a thyristor-controlled resistive load as a calibrator, which is connected to a downstream branch of the distribution cabinet. By switching the resistive load, a calibration current, which can be identified from the background current, is generated in one rectangular busbar and its value is measured at the location of the calibrator, and transmitted wirelessly to the location of the TMR sensors. A new and robust method is proposed to extract the voltage components, corresponding to the calibration current, from the voltage waveforms of the TMR sensors. By calculating the proportional coefficients between the calibration currents and the extracted voltage components, online calibration of the current sensor is achieved. We designed and implemented a current measurement system consisting of a current sensor using TMR sensors, a thyristor-controlled resistive load for current sensor calibration, and a data acquisition circuit based on a multi-channel analog-to-digital converter (ADC). Current measurement experiments were performed in a practical distribution cabinet installed in our laboratory. Compared to the measurement results using a commercial current probe with an accuracy of 1%, the relative error of the measured currents in RMS is less than 2.5% and the phase error is less than 1°, while the nonlinearity error of the current sensor is better than 0.8%.

As one of the most basic electric quantities in a power system, voltage plays an important role in many fields such as condition monitoring and fault diagnosis. The construction and development of the smart grid cannot be separated from the reform and progress of the advanced sensing and measurement technology. Noncontact voltage measurement technology, as one of the important technologies, has many advantages such as no electrical contact, low insulation requirements, easy installation, and great potential in improving the panoramic perception ability of the power system. In this paper, a noncontact measurement method of the power line voltage based on capacitive coupling principle is proposed, which realizes the reliable measurement of the line voltage waveform. First, the principle of the noncontact voltage measurement method is introduced, which mainly includes self-calibration and online measurement of the sensor. The high-frequency voltage signal is injected into the capacitive coupling network of the sensor to implement the self-calibration of the sensor. Then, the digital integration method is used to integrate the output signal of the sensor to measure the line voltage waveform. Second, the noncontact voltage sensor prototype and signal processing circuit are designed. Finally, the test platform of the line voltage measurement is built, and the measurement test of 220 V/50 Hz line voltage waveform is carried out. The test results show the relative amplitude error of the voltage measured by the sensor is less than 2.5%, the maximum phase error less than 2° at 50 Hz, and the linearity better than 0.5%. The frequency response experiment shows that the system has almost constant gain in the frequency range of 50-1800 Hz, and the phase error reaches a maximum of 2.8°C at a frequency of 1800 Hz. [ABSTRACT FROM AUTHOR]

Treating peat soil foundations around Dianchi Lake and Erhai Lake in Yunnan is a complex problem in practical engineering projects. Peat soil solely reinforced with ordinary cement (OPC) does not satisfy demand. This study aims to solidify soil to achieve better mechanical properties. The preparation of peat soil incorporates a humic acid (HA) reagent into cohesive soil, and cement and ultra-fine cement (UFC) are mixed by stirring to prepare cement soil samples. They are then immersed in fulvic acid (FA) solution to simulate cement soil in the actual environment. X-ray diffraction (XRD), mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM), and pores and cracks analysis system (PCAS) tests are used to study the impact of the UFC on the microscopic pore structure of cement soil in a peat soil environment. The unconfined compressive strength (UCS) test is used for verification. The microscopic test results indicate that incorporating UFC enhances the specimen’s micropore structure. The XRD test results show the presence of C–S–H, C–A–S–H, and C–A–H. SEM and PCAS tests show that the UFC proportion increases by between 0% and 10%, and the percentage reduction in the macropore volume is the largest, at 38.84%. When the UFC admixture is 30%, the cumulative reduction in the percentage of macropore volume reaches 71.55%. The MIP test results show that the cumulative volume greater than 10 µm in pore size decreases from 7.68% to 0.17% with an increase in the UFC proportion. The UCS test results show that the maximum strength growth of cement soil is 12.99% when the UFC admixture is 0–10%. Incorporating UFC to form a compound curing agent solves the problem of the traditional reinforcement treatment of peat soil foundation being undesirable and decreases the amount of cement. This study provides practical guidance for reducing carbon emissions in actual projects.

Many peat soils are distributed around plateau lakes, and the reinforcement of peat soils with high organic matter content by ordinary cement cannot meet the actual engineering requirements. In order to obtain better mechanical properties and durability of the reinforcement, this experiment prepared peat soil by mixing humic acid reagent into the alluvial clay soil with low organic matter content. The cement soil samples were prepared by adding cement and ultrafine cement (UFC) by stirring method; the samples were then soaked in fulvic acid solution to simulate the cement soil in the peat soil environment. Using the unconfined compressive strength (UCS) test, scanning electron microscope (SEM) test, and pores and cracks analysis system (PCAS) test, the effect of UFC content change on cement soil’s humic acid erosion resistance was explored, and the optimal UFC content range was sought. The results of the UCS test show that with an increase in immersion time, the strength curves of cement soil samples gradually increase to the peak strength and then decrease. Significant differences in the time correspond to the peak strength, and the overall presentation is two processes: the strength enhancement stage and the corrosion stage of the sample. The incorporation of UFC makes the cement soil in the peat soil environment exhibit excellent corrosion resistance, and the optimal UFC content is 10%. The results of the SEM and PCAS tests show that the microstructure of cement soil after immersion time exceeds 90 days, increases with an increase in immersion time, and its structural connectivity gradually weakens. The excellent characteristics of UFC particles, such as small particle size, narrow particle size distribution, fast hydration reaction rate, high hydration degree, and many hydration products, weakened the adverse effects of humic acid on the cement soil structure to a certain extent. Therefore, although the number of macropores increases, they are not connected. It still presents a relatively compact honeycomb overall structure, which correlates well with the UCS results.

The organic soil is widely distributed around Dianchi Lake in Kunming, which is rich in the humic group (HG). In order to explore the effect of HG on the strength development of organic soil, this paper adopts the method of adding humic acid (HA) reagent into the undisturbed cohesive soil (blending method) and soaking it in fulvic acid (FA) solution (steeping method) to simulate the organic soil. Then, the effect of HG on soil is analyzed by the unconfined compressive strength (UCS) and the scanning electron microscope (SEM) tests. The UCS test shows that HA can significantly reduce the UCS of the samples, and it continues to decrease with the increase of the HA reagent content. FA can substantially enhance the UCS of the samples, which continues to increase with the concentration of FA solution (decreasing the pH value). Under each HG condition, the steeping of FA can significantly increase the UCS of the sample when the content of the HA reagent is less than 10%, and the growth rate of the UCS decreases when it is greater than 10%. With the increase of steeping age, the UCS of the 5% HA samples continued to increase and gradually became stable, and when the content of the HA reagent is more than 5%, the UCS curve first increases and then decreases. The SEM test shows that adding HA reagent can significantly increase the pore size, improve the connectivity between the pores, and weaken the connection of the soil structure. The steeping of FA can reduce the pore size, weaken the connectivity between the pores, and strengthen the connection of the sample structure.

The disposal of soil containing humic acid (HA) poses an increasingly difficult problem for geotechnical environmental engineering. In this study, the unconfined compressive strength (UCS) test of cement-soil with different HA contents is conducted to analyze the effect of HA on the strength of cement-soil. Mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM), and X-ray diffraction (XRD) experiments reveal the effective mechanism of HA on the strength of cement-soil from the microscopic level. The results show that the strength of cement-soil decreases gradually with the increase of HA content. The failure mode of cement-soil slightly changed from brittle failure to plastic failure. The microscopic test shows that the incorporation of HA will lead to the apparent enlargement of the pores in the cement-soil. The large pores in the sample increase, the small micropores decrease, and the structure tends to be loose and overhead. The increased HA content added will significantly reduce the cement hydration products and destroy the cementation of the hydration products.

The formation shear-wave (S-wave)’s velocity information around a borehole is of great importance in evaluating borehole stability, reflecting fluid invasion, and selecting perforation positions. Dipole acoustic logging is an effective method for determining a formation S-wave’s velocity radial profile around the borehole. Currently, the formation S-wave’s radial-profile inversion methods are mainly based on the impacts of radial velocity changes of formations outside the borehole on the dispersion characteristics of dipole waveforms, without considering the impacts of an acoustic tool on the dispersion curves in the inversion methods. Accordingly, the inversion accuracy is greatly impacted in practical data-processing applications. In this paper, a novel inversion algorithm, which introduces equivalent-tool theory into the shear-velocity radial profile constrained-inversion method, is proposed to obtain the S-wave’s slowness radial profile. Based on the equivalent-tool theory, the acoustic tool can be modeled using two parameters, radius and elastic modulus. The tool’s impact on the dipole waveform’s dispersion is eliminated first by using the equivalent-tool theory. Then, the corrected dispersion curve is used to carry out the constrained inversion processing. The results of this processing on the simulation data and the real logging data show the validity of the proposed algorithm.