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The electronic structures and the magnetic properties of Fe doped GaSb have been investigated by the first-principles calculation based on the framework of the generalized gradient approximation (GGA) and GGA+ U schemes. The calculated results indicated that Fe atoms tend to form the anti-ferromagnetic (AFM) coupling with the nearest-neighbor positions preferentially. Compared with the anti-ferromagnetic coupling, the ferromagnetic interactions occurred at the second nearest-neighbor and third nearest-neighbor sites have a bigger superiority energetically. The effect of strong electron correlation at Fe- d orbit taking on the magnetic properties predicted by GGA+ U approach demonstrated that the ferromagnetic (FM) coupling between the Fe ions is even stronger in consideration of the strong electron correlation effect. The ferromagnetism in Fe doped GaSb system predicted by our investigation implied that the doping of Fe into GaSb can be as a vital routine for manufacturing the FM semiconductors with higher Curie temperature.

Intravascular optical coherence tomography (IVOCT) has been widely used in clinical coronary artery intervention field. Owing to defocus and contrast agent absorption effects, the intensity fluctuation caused by imaging catheter locating at an eccentric position significantly influence the quality of IVOCT imaging and even plaque type identification. In this paper, we present a novel method to compensate intensity fluctuation caused by defocus and contrast agent absorption in IVOCT imaging. We construct a principle model of IVOCT intensity signal based on defocus function and contrast agent absorption. By measuring the parameters of defocus function and contrast agent absorption, we compensate intensity fluctuation of each A-line caused by defocus and contrast agent absorption effects in IVOCT imaging. In clinical imaging, the proposed method improve the quality of IVOCT images and is helpful for plaque type identification. The average signal to noise ratio (SNR) of 200 images after compensation increase 6.5 dB than that before compensation.

To explore the effects of joint inclination angle and the size on the mechanical properties and failure process of rock-like specimens, a series of uniaxial compression tests were carried out on rock-like specimens.The specimens are consist of two sizes and contain three parallel joints with various inclination angles. During testing, the variation characteristics of apparent strain field of specimens is recorded by digital image correlation (DIC) system. Testing results reveal the uniaxial compression strength of the specimen decreases gradually with the joint inclination increases from 0° to 60°, while increasing gradually with the joint inclination increases from 60° to 90°. In addition, the peak compression strength of the large-size specimens is obviously lower than that of the small-size specimen when the joint inclination angle is 0°~30°. By contrast, the peak compression strength of the large-size specimens is the same as that of the small-size specimen when the angle is 30°~60°, approximately. But, the peak compression strength of large-size specimen is obviously higher than that of small-size specimen when the joint inclination angle is between 60° and 90°. Finally, five different types of cracks are observed in this work, i.e., tensile crack,airfoil tension crack,pull-shear mixing crack,secondary crack and far field tensile crack.

Monitoring of farmland pests is an important prerequisite to sprinkle agriculture in a timely and appropriate manner, which provide an important guarantee for agricultural production. This paper presents a method for obtaining the dynamic characteristics of pests in farmland based on machine vision. First, the pests and the background images are segmented by color feature and thresholding methods. Then, the shape features and the number of pests were obtained by Gaussian filtering. Finally, the quantity of pest motion is obtained by frame-to-frame differencing method. The experimental results show that the accuracy rate of the experimental sample is 99%. It can provide quantitative information of pest activity for plant protection personnel. This system can also be applied in large-scale crop pest monitoring.

A low-noise and fast preamplifier is needed for the new boron-coated multiwire proportional chamber (MWPC) neutron detector with a delay line readout system to improve position resolution. A transimpedance preamplifier with a rise time of 30ns, a signal-to-noise ratio higher than 40dB, and an automatic gain control function are designed to meet the aforementioned requirements. On the other hand, we also compare it to commercial preamplifiers. Then, the advantages and disadvantages of commercial and in-house preamplifiers are analyzed. The preamplifier is used and tested on a MWPC neutron detector, and results are presented.

A marine seismic prospecting system is a kind of data acquisition and transmission system with large-scale coverage and synchronous multi-node acquisition. In this kind of system, data transmission is a fundamental and difficult technique. In this paper, a high-speed data-transmission method is proposed, its implications and limitations are discussed, and conclusions are drawn. The method we propose has obvious advantages over traditional techniques with respect to long-distance operation, high speed, and real-time transmission. A marine seismic system with four streamers, each 6000 m long and capable of supporting up to 1920 channels, was designed and built based on this method. The effective transmission baud rate of this system was found to reach up to 240 Mbps, while the minimum sampling interval time was as short as 0.25 ms. This system was found to achieve a good synchronization: 83 ns. Laboratory and in situ experiments showed that this marine-prospecting system could work correctly and robustly, which verifies the feasibility and validity of the method proposed in this paper. In addition to the marine seismic applications, this method can also be used in land seismic applications and certain other transmission applications such as environmental or engineering monitoring systems.

Hydrogen fuel produced by photovoltaic-eletrolyzer system is a solution to solve problem of global warming, air pollution and fossil fuel crisis. The efficiency of photovoltaic-electrolyzer system can be promoted by the optimal matching between photovoltaic modules and electrolyzer. Based on experimental test and mathematical model, a certain series–parallel connection of photovoltaic cells is determined to match with electrolyzer. The aim is to match the voltage and the maximum power output of the photovoltaic modules to the operating voltage of the electrolyzer. So some auxiliaries such as DC-DC converter, maximum power point (MPP) tracking unit can be omitted. Therefore, the cost and resistances in the circuit are greatly reduced.

In order to improve the accuracy of the fiber Bragg grating demodulation system,a denoising processing and filtering analysis method based on empirical mode decomposition is proposed.The intrinsic mode functions obtained by EMD are derived into signal component dominanting modes and noise component dominanting modes.Denoising can be achieved by reconstructing the signal using the modes reflecting the main structures of the signal.The experimental results show that the output signal of demodulation system can achieve identitfying the location of central wavelength and the Bragg wavelength shift accurately.The output spectrum has the features of less distortion and higher SNR.The curve fitting of temperature shows that the fitting linearity is 0.998,and the accuracy of demodulation system is greatly improved.

The instability of the pillar was discussed based on the potential energy principle and the cusp catastrophe theory, and a simplified mechanical model of the pillar was established considering the mining effect. The necessary-sufficient conditions, the jump value of displacement of pillar and the released energy expressions were deduced. The results show that the instability of the pillar is related to the properties of the rock, the external force and the relative stiffness of the elastic area to the plastic area. The instability of system is like to occur with the enlarging of the softening area or the decreasing of E/λ. The calculation done shows that the estimated results correspond to practical experience.

A detailed analysis of mode II stress intensity factors(SIFs) for the double edge cracked Brazilian disk subjected to different diametral compression is presented using a weight function method. The model II SIFs at crack tips can be obtained by simply calculating an integral of the product of mode II weight function and the shear stress on the prospective crack faces of uncracked disk loaded by a diametral compression. A semi-analytical formula for the calculation of normalized mode II SIF, fII, is derived for different crack lengths (from 0.1 to 0.7) and inclination angles (from 10° to 75°) with respect to loading direction. Comparison between the obtained results and finite element method solutions shows that the weight function method is of high precision. Combined with the authors’ previous work on mode I fracture analysis, the new specimen geometry can be used to study fracture through any combination of mode I and mode II loading by a simple alignment of the crack relative to the diameter of compression loading, and to obtain pure mode II crack extension. Another advantage of this specimen geometry is that it is available directly from rock core and is also easy to fabricate.

An automatic clock synchronization method implemented in a field programmable gate array (FPGA) is proposed in this paper. It is developed for the clock system which will be applied in the end-cap time of flight (ETOF) upgrade of the Beijing Spectrometer (BESIII). In this design, an FPGA is used to automatically monitor the synchronization circuit and deal with signals coming from the external clock synchronization circuit. By testing different delay time of the detection signal and analyzing the signal state returned, the synchronization windows can be found automatically by the FPGA. The new clock system not only retains low clock jitter which is less than 20ps root mean square (RMS), but also demonstrates automatic synchronization to the beam bunches. So far, the clock auto-synchronizing function has been working successfully under a series of tests. It will greatly simplify the system initialization and maintenance in the future.

This paper deals with two of the most important and difficult aspects of portable planar broadband antennas: the ground plane effects and measurements. To minimize the ground plane effects, optimized slots are created on the ground plane to limit the current flow hence the ground plane effects, which is demonstrated to be a simple but effective approach. For the antenna measurement, our focus is on how to measure the antenna radiation efficiency accurately and efficiently. Two of the latest methods, reverberation chamber and source stirred chamber/cap methods, are employed and discussed. Both numerical and experimental results are presented to aid our analyses and discussions.

This paper presents a feedback predistortion technique for power amplifiers based on amplitude and phase signal processing to correct distortion in RF power amplifiers (PAs). By employing input and output signals of the power amplifier, the changes of the amplitude and phase caused by the nonlinear PA are compared in this technique. Furthermore, adjustable voltage controlled variable attenuator (VVA) and voltage controlled variable phase shifter (VVP) are used to achieve the purpose of predistortion compensation. The simulation results show that the third-order intermodulation distortion (IMD3) suppression of over 20dB may be achieved over bandwidth of 1 MHz at 2.14GHz. The results also show an adjacent channel leakage ratio (ACLR) improvement of about 8dB for realistic wideband code-division multiple access (WCDMA) signal. This method is a promising technique for rectifying the nonlinearity of PAs.

Under current business environment, product development becomes an important way for a firm to enhance its competitive power. Yet in practice, most product development project fail. This paper tries to discover the key elements for its success or failure by way of survey investigation, whose conclusion can be categorized into 6 issues, i.e. organization management, knowledge management, product development and information technology, project planning, project control, operation capacity integration.

Supplier selection is a critical issue in information systems(IS) outsourcing decision, and it is a difficult problem which includes both tangible and intangible factors. Besides cost and benefit analysis, some intangible factors such as risk also need to be considered. In this paper, a multi-objective programming model is proposed to help outsourcers to select IS providers. This model considers cost and risk factor simultaneously in distribution of modules among candidate suppliers to minimize the total cost and failure rate. Then according to the difficulty of solving of this complicated nonlinear integer programming model, a modified hybrid algorithm is proposed to obtain the most preferred non-dominated solution. This algorithm is a hybrid algorithm combining genetic algorithm and particle swarm algorithm. Finally, a numerical example shows the effectiveness and feasibility of the model, and proved the convergence of the hybrid algorithm.