Applied Mechanics and Materials Vols. 651-653

Abstract: When depoting grain for storage, the thickness of grain mass is a vital issue for the purpose of measuring its moisture content. The measurement method is focused on microwave technology, which is to collect the electromagnetic variation data of the amplitude and phase shift from the mass.The proper thickness for the mass is about 5cm and the width is less than 1m. An antenna with a high gain and a saucer-shaped pattern is in great need. This paper provides a 8-element structured antenna array with a gain of over 17dBi, especially with a particular pattern of butterfly shape.The high gain helps to penetrate a thick grain layer, and the butterfly shaped pattern is beneficial to scan more sampling sites from the same facet.The simulation results from HFSS 14.0 are also shown in this paper. When the antenna is hanged over the grain surface at a distance,it is capable to gather more data on moisture content for a wide range of the grain mass. This antenna model really fits the needs of warehousing entry for grain.

Abstract: An improved maximum likelihood (ML) positioning algorithm in WLAN is proposed. In contrast to the previous ML and weighted k-nearest neighbor (WKNN) algorithm, additional information about RSS variation over physical space is deployed in the proposed algorithm. The RSS variation information is integrated to modify the Gaussian kernel width of the ML algorithm. Besides, the mean value for Gaussian likelihood function is modified by mean RSS value of the physical adjacent reference points. Experiments are carried in a real WLAN indoor environment and the well-known ML algorithm and weighted k-nearest neighbor (WKNN) algorithm are also compared. Experimental results show that the improved ML algorithm performs best and obtains 13.0 percent improvement than compared algorithms in the sense of mean positioning error.

Abstract: Because resistance of two-dimensional position sensitive detector's (PSD) photo surface is not absolute uniformity that its output is nonlinear. It is this feature enables the PSD difficult to measure small displacement. In order to solve this problem, BP neural network is proposed to solve the problem of PSD nonlinear correction after the study of traditional nonlinear correction method; BP neural network would have a strong ability of nonlinear mapping after training, and it can approach arbitrarily contact function by arbitrary precision, and MATLAB neural networking boxes can simulate BP neural network easily. Simulation and verification indicate that the method has a remarkable effect in solving nonlinear problems, and it can meet system requirements.

Abstract: In traditional INS/GPS integrated navigation system, whether a error state can be feedback is determined by its observability, however, in that there is no precise motion reference, it is difficult to judge whether the system is observable, therefore, which error states can be feedback is hard to determine. According to the vehicle’s maneuver’s effect on error states’ observability, a changing dimensional feedback correction method based on lever arm estimation error minimization is proposed. In the beginning phase of Kalman filtering, part of error states feedback correction was executed on a 18 dimensional error sates vector including lever arm error, this scheme runs until the difference between lever arm estimation and it’s measurement less than the setting threshold, all error states feedback correction was executed with a 15 dimensional error states model. The flying test shows that the estimation result with all error states feedback is prevail to that of part of error states feedback correction after lever arm estimation error converges. The proposed method is of great value in engineering application.

Abstract: Triangle situation is a prerequisite for the effective implementation of the towed decoy interference when combat aircraft faced with missile, which described the relative positional relationship between combat aircraft, towed decoy, and missile. However, it has been a lack of mathematical modeling, signal-level closed-loop simulation and typical scenarios that combine the use of tactics and interference effects assessment. From the perspective of how to maximize the defensive side of the performance of air defense weapon system is also an urgent need to solve the problem. On the basis of the establishment of PD seeker coherent video simulation model, by studying towed decoy signals, tactical choice, constructed loop simulation analysis to complete the process of analysis of the confrontation between the triangular situation, the relevant factors effect are quantitative assessment and gives several useful suggestions.

Abstract: Multi-frequency receivers rely on GNSS to achieve high-precision positioning, high sensitivity and other functions. GNSS signal frequencies are widely distributed around 1.1GHz to 1.6GHz. Good performance RF front-end receiver will provide high-quality acquisition and tracking environment, reducing the SER to ensure CNR. RF sampling technique is widely used in software radio for its simple structure, flexible configuration, and other advantages, but rarely used in satellite navigation, because the high signal carrier frequency and sampling rate, down-conversion based on RF sampling becomes a big challenge. So, to solve the problems of widely distributed we design three signal bands, using different local oscillator to implement signal down-conversion; to solve the problems of high sampling rate, we propose a down-conversion program of using a cascade of CIC filter’s ployphase and FIR compensation filter. Through the simulation of MATLAB after tracking tests, analysis of CNR and other indicators of programs. Ultimately, we implement the program with Verilog language on the multi-frequency GNSS receiver. The results show that this scheme can achieve digital down-conversion and stable performance of tracking loop with less consumption of resources.

Abstract: Operational meteorologists and Oceanographers rely on real-time environmental data to run their numerical prediction models, even carry on the research. The ground station network is dense and the data of good quality, but there is not enough environmental data from the oceans, particularly in data-sparse areas not covered by commercial ships reporting environmental data. A drifting ocean buoy is described. The drifter consists of three main components: a surface float, a tether assembly and a dimensionally-stable drogue. It utilizes a drag structure which follows the water mass of the ocean as it flows in the form of the ocean current, and which also has an aerodynamically shaped low wind drag mast to minimize wind induced errors in ocean current drift measurements; the drag structure also being stable and resistant to heaving (pitch and roll) so as to maintain a mast carried antenna above the water even at high sea states.

Abstract: According to the characteristics of groundwater monitoring system,such as the field work unattended, replace the battery problem,the sampling time is short and standby time is long,the method is used to extend the power of life that using the watchcircuit control system under different power state automatic switching.Considering the characteristics of the system that parameter configuration commands are complex,field sampling is diverse and the communication time is not stable,thepaper puts forward the measuresthatmulti trigger source of hardware and status word of software collaborative work together to realize the system logic control.The overall power consumption of groundwater monitoring system which introduceswatch circuit is greatly reduced. Experimental results verify the feasibility of the watch circuit and show that the watch mode will become the development direction of field monitoring industry.

Abstract: Taking Model DK-52 (Grade 0.05) multi-function three-phase electrical measuring instrument calibration device as an example, the paper describes how to evaluate the uncertainty in measurement result of indication errors in mathematical model.

Abstract: In the process of fault signal detection for large-scale circuit communication systems, with traditional methods to process detection, the fault detection method is more conservative. A fault signal detection for large-scale circuit communication system based on QRS wave group detection method is proposed. The signal to be measured is transformed appropriately in the time domain or frequency domain to strengthen or separate the QRS component, in order to suppress interference from various noise to signals, and the fault point of circuit communication system fault signal is identified, the filter is utilized as representative to process multiscale decomposition for fault signals of circuit communication systems. Experiments show that QRS wave group detection method can determine the occurrence time of the circuit system fault signal, and further estimate the nature of the fault signal, thus, the fault point of communication system fault signal is found to improve the efficiency of detection.