The basic principle of the sawtooth-wave generator which designed by the 555 timer was analyzed briefly.The key condition that the timed capacitor must charged by constant current and discharge quickly to the well linearity sawtooth-wave generator was pointed out.In consideration of different circuit can provide constant current,three kinds of concrete methods which can generate well linearity sawtooth-wave have been put forward:bootstrap type,constant current source type,and voltage-current converter type.And their respective characteristic was analyzed,the formula to calculate the frequency of the sawtooth wave which generated by these methods was pointed out.The sawtooth wave which generated by these methods has well linearity,this was demonstrated by the experiments.
High precise pH value measurement meter is depicted.This pH value measurement meter is designed based on MSP430 MCU and pH electrode sensor,while the method of two point calibration and software temperature compensation is applied in the designed meter.This pH value measurement has the features of two point calibration,auto temperature compensation,historical data storage and real-time data transmission.The problem of low power,high precise and data transmission of the pH value measurement meter are solved.This meter has been applied in industry.
Because the detection of small target in the background of sea clutter is strongly influenced by the sea condition, this paper studies the fractal property of sea clutter in fractional Fourier transform (FRFT) domain and proposes the fractal detection method in single and high dimensions. The FRFT deduced from mathematical definition is not consistent with the self-similar properties in orders and scales. Multifractal detrended fluctuation analysis (MF-DFA) method is used to determine the fractal parameter H(q) and analyze the fractal property of the sea clutter in different situations, distances, and polarizations. In single dimension, the small target detection method is proposed based on an adaptive order. By comparing different factors of the multifractal parameters, the results show that the transform order method in sea clutter FRFT domain can detect small signals under complicated sea conditions. The detection threshold mostly increases above 200%, which is 26.3% higher than the method of time domain signal. H(q) has an obvious multifractal difference on high negative scale, the H(q)-q curve satisfies the arctangent distribution. The fitting amplitude ratios of pure sea clutter and target data are greater than 1.8 (HH) and 1.4 (VV), which provide the basis for the small target detection in sea clutter background.
From teaching practice, the author discusses how to develop the creative ideas and interest by feeling of beauty, getting models, leading imagination and divergent think, and inducing query.
In this work, a fusion algorithm is proposed for improving the accuracy and stability of passive sound source localization. Different from the traditional algorithm that contains a single-plane cross array, here, the fusion algorithm is used to overcome the position blur in the process of localization. First, the two-plane four-element cross array model is established. Based on this model, the method is defined to judge the position where the sound source is located. According to the localization principle, we derive the calculation formula of the sound source position, based on a single four-element planar array. Then, the elevation angle sine value is introduced into the coordinate formula as the weighted coefficient by analyzing the indirect measurement error, and the fusion algorithm is employed to conduct the sound source localization, based on the two-plane four-element cross array. Finally, the relationships are obtained, between the time delay estimation error, the elevation angle, the horizontal angle, and the localization performance. Besides, the validity of this algorithm is validated by measuring the ranging and direction-finding accuracy. The results show that the distance error rate is within 2%, and the angle error rate is within 3%, which means a good localization effect. The proposed algorithm is expected to be widely used in thunderstorm cloud detection for its quick measurement and high precision.
According to the phase space reconstruction theory of nonlinear system, we propose a prediction method of support vector machine based on genetic algorithm. Using the improved autocorrelation method and Grassberger-Procaccia algorithm to determine the time delay and embedding dimension of chaotic signal, the phase space reconstruction is implemented. The penalty coefficient and the kernel function parameter of support vector machine are optimized by genetic algorithm. Combined with support vector machine, single-step prediction model of the chaotic sequence is set up, so we can detect the weak signal in chaos from the prediction error (including the transient signal and periodic signal). Lorenz attractor and the data from the McMaster IPIX radar sea clutter database are used in the simulation. The proposed method can effectively detect the weak target from chaotic signal. When the signal-to-noise ratio is -89.7704 dB in the chaotic noise background, by using the new method the root mean square error can be reduced by two orders of magnitude, reaching 0.00049521, while the conventional support vector machine can reach only 0.049 under the condition of -54.60 dB.
This paper described that the angle of the certain type dump truck transmission shaft is adjusted to three de grees in order to reduce cab jitter firstly,then choosed gear-box auxiliary mounting to transmission shaft vibration.Above-mentioned means resolve the certain type dump truck cab jitter.
In this paper, detection and estimation of weak signal are presented on the basis of Least-Squares Support Vector Machine (LS-SVM), which is combined with generalized embedding window. Firstly, the embedded dimension and time delay of Lorenz system are determined by improved correlation function method, with which phase space is reconstructed. Then error forecasting model is estimated by LS-SVM with different targets like transient and periodic signals. Last, separate the weak target signal from the prediction error to compute signal-noise-ratio (SNR). As a result, there is a remarkable reduce in detection threshold and improvement in prediction precision, compared with those conventional methods, which is proved by Chen's system.
The effects of the strength of natural and recycled aggregate,practical water-to-cement ratio and nominal water-to-cement ratio on the compressive strength of concrete are studied in a quantitative manner.Experimental results show that the compressive strength of concrete is closely related not only to the water-to-cement ratio,but also to the crushing value of aggregate.Through further analysis,it is found that a good linear correlation between the compressive strength of concrete and the cement-to-water ratio and the crushing value of aggregate exists and a unified Bolomey's formula is established for concrete made with both natural and recycled aggregate.
This paper presents an enhanced approach for multiattribute decision making with interval-valued intuitionistic fuzzy assessing values for each alternative. To efficiently deal with the interval-valued intuitionistic fuzzy multiattribute decision mak
This article presents a multipath imaging system for thunderstorm developments, wherein data are three-dimensional atmospheric electric-field signals (3DAEFSs) collected with a self-made 3DAEF apparatus (3DAEFA). In this way, thunderstorms are presented in a staged and visual form. To start with, entropy-based intervals are constructed from historical AEF data, to classify denoised AEFS components, according to the entropy value of each component. Furthermore, AEFS time sequences are reconstructed with a reference to whether components within the same entropy-based interval are sequential or not, providing time information for the subsequent clustering-based spatial denoising to thunderstorm point charge coordinates. Finally, predicted value (PV) intervals, which are used to divide and then reconstruct AEFS time periods, are acquired to realize the point charge multipath imaging corresponding to periods, based on the established stacked autoencoder and the extreme gradient boosting (SAE-XGBoost) model. Empirical results demonstrate that the multipath better visualizes the whole process of thunderstorm activities. Comparisons with radar charts further confirm that the proposed system effectively images charge multipaths and provides a valid reference for visual thunderstorm monitoring.
A non‐Robertsonian wheat‐rye chromosome translocation was observed in pollen‐derived line WER‐I‐1 from the FI hybrid between M27 [a 1R(1D) substitution line] and ‘Chinese Spring’. Biochemical assays of high molecular weight glutenin subunits and gliadin components and Southern hybridization of dispersed rye repeat sequences pSc 119.2 and pSc 5.3H3 provided sufficient evidence that in WER‐1‐1, wheat chromosome pair ID was substituted by 1R chromosome pair. C‐banding and genomic in situ hybridization further revealed that the 1R chromosomes, present in WER‐I‐1, were abnormal in that the distal parts of their long arms were lost and translocated to the long arm ends of a pair of wheat chromosomes. The mode of origin of this transiocation is also discussed.
