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Harvesting multi-frequency sound energy from environmental noise is a meaningful topic to supply energy for potential devices. In this work, we constructed an array of Helmholtz resonators (HRs) with cross-linked polypropylene (IXPP) ferroelectret films on the inner walls of HR cavities, whose resonant frequencies range from 300 to 800 Hz and quasi-static piezoelectric coefficient d33 is 230 pC/N. The energy harvesting performance of IXPP films is investigated, both theoretically and experimentally, in a single HR with various sizes, showing the high energy conversion capability close to the resonant frequencies of HRs, e.g., 337, 375, 445, 522, 588, 661, 739, 782, and 795 Hz, in the experiment. By putting one, two, three, and four samples of nine different sized HRs in series connection in order, we measured the average output power of 3.16, 5.31, 7.36, and 8.66 nW at the resonant frequencies. It shows that the output power of IXPP films has been significantly improved at multiple frequencies by series connection of IXPP films. In parallel, the optimal electrical resistance increases in a quasilinear way compared to the number of HRs. These results are helpful for designing efficient sound energy harvesters in the broadband frequency range.

It make traditional geophysical exploration method to adapt new requirement such as resolution of meter-level, error of depth = 5% and marking border of target and geological interface that a lot of construction of geotechnical projects and preventing geological disaster projects. Due to hard research of scientific workers for twenty years, several methods and technology can meet the requirement and some methods would get breakthrough and some also get some progress. About 10 methods will be introduced in this paper such as Landsonar, Differential electric sounding(DES), C-1 and so on, meanwhile, development direction of some methods will be introduced such as geological radar.

To eliminate the influence of the inconsistency on the cycle life and the available capacity of the battery pack, and improve the balancing speed, a novel inductor-based layered bidirectional equalizer (IBLBE) is proposed. The equalizer is composed of the bottom balancing circuits and the upper balancing circuits, and the two layer circuits both consist of a plurality of balancing sub-circuits, which allow the dynamic adjustment of equalization path and equalization threshold. The battery string is modularized by layered balancing circuits to realize fast active equalization, especially for long battery strings. By controlling the bottom balancing circuits, the individual cells can be balanced in each module. At the same time, the equalization between battery modules can be realized by controlling the upper balancing circuits. Simulation and experimental results demonstrate that the proposed equalizer can achieve fast active equalization for a long battery string, and has the characteristics of multi balancing path, large balancing current and high accuracy. The advantages of the proposed equalizer are further verified by a comparison with existing active equalizer.

In recent years, with the increase of aging population and physical disabilities, more attentions have been paid on studies of the lower extremity exoskeleton. It is a man-machine integration device and fusion of multi-subject technology. This article will discuss on mathematical modeling and PID control on exoskeleton. Firstly, the law of human gait and leg structure is studied in details. On this basis and combining the robotics, the freedom and the structure parameters of exoskeleton can be designed. Secondly, by using the D-H model, the mathematical model will be established to analyze the relationship between the pose and motion. Thirdly, by using Lagrange equation, a dynamic model which is to study the relationship between the torque and motion is established. Finally, a modern simulation tool called SimMechanics is used to set up the kinematics model. PID control is used in the article. The sine wave response has been analyzed to earn feasibility results.

Pointing at the defect of Space Frequency Algorithm in abstracting detail information used in Regional Feature Self-Adaptive Image Fusion Algorithm, an improved Spatial Frequency Algorithm is proposed. Firstly, the histogram specification is used to adjust pixel values of the infrared image. Secondly, the multi-scale decomposition is performed on visible image and the adjusted infrared image using Contourlet transform. Finally, low-frequency sub-band is fused using a rule based on Regional Energy rather than the simple weighted sum method. Other sub-bands are fused using the Improve Spatial Frequency rule. The experimental results show that the proposed method preserves more details of the visible image and obtains clear target information in the infrared image. A better effect is achieved compared to the reference article.

To eliminate the influence of the inconsistency on the cycle life and the available capacity of battery packs, and improve the balancing speed, a novel inductor-based layered bidirectional equalizer (IBLBE) is proposed. The equalizer is composed of two layers of balancing circuits connected in parallel. Each layer contains multiple balancing sub-circuits based on buck-boost converters. These balancing sub-circuits can equalize the corresponding cells simultaneously, and allow the dynamic adjustment of equalization path and equalization threshold. Analysis and simulation results demonstrate the IBLBE has a higher level balancing speed than other equalizers based on switched-capacitor or switched-inductor converters, and reduces the balancing time by 30% compared to existing inductor-based parallel architecture equalizers (PAEs). Experimental results are presented to validate the analysis and effectiveness of the proposed equalizer.

Fisheye lenses have the advantages of short focal length and large field of view. However, by using the “non-similar” imaging principle, they artificially introduce a large barrel distortion. In order to improve the quality of the images correction of distortion is required. This article analyzes the polar distortion correction model, raised a simple distortion coefficient calibration method and the use of bilinear interpolation method for gray level interpolation. Compared to other methods, this method is easier to reinforce and achieves high accuracy, and it can be easily implemented in the hardware system. At the end of the paper we introduced a device correction for a fisheye CCD camera. Based on the original data, a distortion correction model is established. In order to minimize the error, the correction was divided into three sections, and the image is well recovered.

Most existing test system for infrared focal plane arrays are dedicated, it costly and the application value are limited. A test method for infrared focal plane arrays is introduced in this paper, and test system includes driving circuit, control module, data acquiring and processing circuit, video synthesis module and the PC software based on LabVIEW is established, which measures the key parameters such as responsivity, NETD, non-effective pixels and nonhomogeneity of the conventional polysilicon uncooled infrared focal plane arrays, generate testing report automatically at last. The simple and reliable test system adapted to many devices with different resolution and package, possess excellent universal property and practical value at very low cost.

A novel mechanical anti-aliasing filtering fibre-optic hydrophone with a cylindrical Helmholtz resonator is constructed and tested. The experimental results show that the hydrophone has a function of low-pass filtering. The low frequency acoustic sensitivity is about −160 dB (1 rad/μPa), and the response curve has a resonance determined by the Helmholtz resonator. Theoretical and experimental results both show that the resonant frequency moves towards high frequency with the increasing orifice diameters. The sensitivity attenuation of high frequency is larger than 10 dB. This new fibre-optic hydrophone is a prototype device for a class of sensors used to eliminate the aliasing in future sonar systems.

A novel pseudo working-point control measurement scheme for the acoustic sensitivity of interferometric fiber-optic hydrophones is described and demonstrated. The measurement principle is introduced in detail. An experimental system, which interrogates an interferometric fiber-optic hydrophone with this method, is designed. The acoustic pressure phase sensitivity of the fiber-optic hydrophone is measured over the frequency range of 20-2500 Hz. The measured acoustic sensitivity is about -156.5 dB re 1 rad/μPa with a fluctuation lower than ±2 dB, which is in good agreement with the results obtained by the method of phase generated carrier. The experimental results testify the validity of this new method which has the advantages of no electric elements in the sensing head, the simplicity of signal processing, and wide working bandwidth.

A single-pass high-gain 1.9 μm fiber gas laser, based on vibrational stimulated Raman scattering in a hydrogen-filled hollow core photonic crystal fiber, is reported. Efficient conversion to the first-order vibrational Stokes wave of 1907 nm is obtained in a low loss negative curvature hollow core fiber with a length of 6.5 m, which is filled with high pressure hydrogen pumped with a linearly polarized 1064 nm microchip pulse laser. The maximum power conversion efficiency, which is more than 27% at 2.3 MPa hydrogen pressure, and a quantum conversion efficiency of 48% are achieved. The maximum laser average power is about 10 mW,and the maximum peak power is more than 2000 W. It provides a potentially effective method to obtain broadly tunable mid-IR fiber lasers of high power and narrow linewidth.

We numerically calculated the coherence properties of the supercontinuum based on the definition of complex degree of mutual coherence, and obtained the spectral broadening of the pump pulse and the coherence properties of the generated supercontinuum under different pump powers. The results showed that the dominant underlying mechanisms of the spectral broadening are soliton self-frequency shift and dispersive wave generation when the pump wavelength located in the anomalous dispersion region of photonic crystal fiber. While the coherence properties are affected by the modulation instability which amplifies the stochastic noise of the pump pulse, thus the generated frequency components have stochastic phases and amplitudes, which induces the degradation of the coherence of the supercontinuum. The gain of modulation instability increases with the increasing of the pump power, and the effect of the noise on the supercontinuum will become greater which degrades the coherence properties. Low pump power is required to obtain high coherent supercontinuum, and suitable pump power should be adjusted to get wide bandwidth and high coherent supercontinuum.