The paper reports an adaptive-network-based fuzzy inference system for the measurement of axial strain using long-period fiber grating sensors. The long-period fiber grating sensor supports optical resonances, which are sensitive to the change of axial strain. The axial strain can be quantified based on the wavelength shift and amplitude changes of the optical resonance. To improve the accuracy of axial strain quantification, this paper proposes the adaptive-network-based fuzzy inference system model. The adaptive-network-based fuzzy inference system model is trained using the strain data measured with long-period fiber grating sensors. The parameters of the membership functions used in the adaptive-network-based fuzzy inference system are set adaptively. In the adaptive-network-based fuzzy inference system–based method, the maximum relative error was found to be 1.5%, which is about one-ninth of that when the data fitting method was used. The R-squared statistics using the adaptive-network-based fuzzy inference system model is 0.9872, while that using the linear fitting algorithm is 0.8815. Compared with the conventional data fitting methods, the proposed approach is highly adaptive and versatile with the capability of improving the accuracy of strain quantification.
The cylindrical illusion device with isotropic and homogeneous materials is studied deeply based on the Mie scattering theory. The formula for illusion of core-shell structure is derived in the quasistatic approximation. Whether the inner core is a dielectric or PEC material, it can be equivalent to a certain target cylinder after wrapping a properly designed shell. We investigate what range of permittivity of the shell may be possible to achieve a target, which can provide convenient and intuitive design charts for an approximate design a core-shell illusion device. It is found that the number for the thickness of the shell is zero, one or two when the permittivities of the target and the shell take a variety of parameters. Moreover, the physical insights into the parameters' distribution are explained by analyzing the electric dipole moments in each part of the core-shell structure. It is interesting to see that a double negative material can be equivalently achieved by a PEC core coated with a positive magnetic material, which may offer a new design approach for the realization of double negative materials. The scattering widths and full-wave simulations are given to verify correctness of the proposed method.
Abstract The illusion device developed from the scattering cancellation employs very simple homogeneous and isotropic materials, but this device is only valid for electrically small objects. In this paper, we prove that the illusion device optimized by genetic algorithm can be applied to large-scale occasions. For an electrically small target, an optimized core–shell illusion device can achieve better illusion effect than the analytical design based on the scattering cancellation. With the increase of the device size, the ability of the single-layered shell to manipulate the scattering is very limited. For a moderate-size target, two optimized multi-layered examples are presented: one is to make a dielectric cylinder appear as another dielectric target, and the other is to make a conducting cylinder behave like a double-negative-material target. The full-wave simulations are carried out to visualize the similar field distributions of the target and the optimized multi-layered design. This optimized design greatly widens the size application range of the illusion device and can also improve the illusion performance with simple material parameters.
This paper presents the design of one dimensional broadband phase shifters based on a new class of negative refraction index transmission line. The proposed phase shifter here consists of conventional microstrip line and Negative Refraction Index (NRI) transmission line (TL) in which ideal operational amplifiers are applied to form the periodically loaded negative-impedance-converted inductors and capacitors. It is demonstrated that variations in inductors and capacitors can produce arbitrary phase shifts while maintaining the same overall length. Also, the NRI-TL is non-dispersive so that the new phase shifter can be used in many new broadband devices.
Abstract This study proposes a long‐period fibre grating (LPFG) curvature estimation method based on random forest regression (RFR) to address the shortcomings of the existing curvature evaluation method, namely, polynomial fitting; these shortcomings cause difficulty in achieving adequate model regularity and application universality. The resonant wavelength and resonant peak amplitude of the LPFG are used as input variables in this method to develop an RFR model for curvature estimation, allowing for accurate curvature prediction of the sample. The results show that the RFR‐based LPFG curvature prediction model can better characterise the input–output regression relationship than back‐propagation neural networks. The average R 2 value of the RFR model is 0.9826, and the actual measured curvature value is highly correlated with the model predicted curvature value. Compared to that exhibited by back‐propagation neural networks, the RFR model exhibits higher accuracy for curvature estimation, with average values of 0.1314 and 0.1173 for root mean square and mean absolute errors, respectively. This method can provide a more comprehensive theoretical basis for the application of robot learning in the curvature measurement of LPFG and has practical value.
The new scheme of using a long period grating for simultaneous discriminating measurement of temperature and strain is proposed. The scheme is based on the long period grating's spectrum characteristics. The spectrum is composed of multiple and different loss peak. The resonant wavelength of the first and fourth-order loss peak with different temperature and strain sensitivity was selected in this experiment. The wavelength shift resulting from parameter variation can be obtained by observing its corresponding spectrum. The temperature was acquired by a study on the temperature characteristic of a LPG. The strain sensitivity was obtained by the research on the strain characteristic of a LPG. The standard matrix equation was set up and solved according to the corresponding parameter. The authors know by calculating the standard matrix equation that the cross-sensitivity has little influence on the measurement of the parameter. As the effect of cross-sensitivity is lower than the resolution of the LPG in this case, we can eliminate the deviation due to the cross-sensitive by appropriate compensation. The errors of temperature and strain were calculated to be +/- 0.92 degrees C and +/- 22 microepsilon respectively. The cross-sensitivity between temperature and strain was decreased and the measuring precision of the system was improved by using this scheme in which a single long period grating was used to test two measurands. By comparison between the applied and the calculated temperature and strain of a LPG, the experiment results showed that the methods are feasible. The experimental system is small and the cost is relatively low. The experimental device is simple and practical and has good application prospect.
The idea and strategy of training applied talents in local colleges and universities is analyzed in this paper.It is necessary to strengthen the research on the social needs of applied professionals and study the training standards for undergraduate applied talents.The talent training model is needed to reform by clarifying the orientation of schools.Establishing the application oriented curriculum system based on disciplines, strengthening the construction of teachers, and reforming the talent training model are some main strategies of cultivating talents.It is important to develop a talent training program that meets the characteristics of the university and improve the quality of applied talents.1.
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