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Airborne radar plays a crucial role in detecting aerial targets, but its detection capability can be significantly affected by strong ground clutter when operating in down-looking mode. The range-Doppler (RD) results of ground clutter in airborne radar may overlap the range-Doppler results of the targets, causing target occlusion and rendering them undetectable. In addition to target detection, accurate extraction of target parameters is also of great importance. Due to the high-speed movement of the airborne platform, targets may exhibit range-Doppler ambiguity, necessitating the use of appropriate methods to resolve the range-Doppler ambiguity. Aiming at the problem of target occlusion by clutter with range-Doppler two-dimensional ambiguity during airborne radar down-looking target detection, this paper conducts a study on the detection of airborne radar down-looking targets based on orthogonal signals combined with pulse repetition frequency (PRF) staggered transmission. An optimization method is employed to design multiple sets of PRF values, aiming to reduce the radar blind zone. The range-Doppler two-dimensional ambiguity of targets is resolved using multiple sets of PRF, and coherent processing is performed on the corresponding echoes using the transmission intervals, maximizing the utilization of radar transmission energy. This approach enhances the signal-to-noise ratio (SNR) and improves the detection performance and parameter estimation accuracy, particularly for low SNR targets. The superiority of the proposed approach is demonstrated through simulation experiments.

In order to improve the operation efficiency of the innovation and entrepreneurship integration system of college students, this document proposes to formulate and implement the innovation and entrepreneurship integration system of college students based on “Internet technology.” The web front end is implemented by Django technology, the back end is developed by Apache server pycharm, the database is written in Python, and the database is MySQL. The system meets the expected objectives of implementing, monitoring, and managing innovation and entrepreneurship projects. How the system realizes the functions of repeated comparison projects, easy tracking projects, and fast search, and how managers can make progress at any time. By creating different account function permissions, the system realizes the login, declaration, management, and other functions required by the users of the innovation and entrepreneurship project management system. It is very suitable for college students to improve the project application, information review, and application process. At the same time, it is helpful to supervise and select teachers and greatly improve management efficiency. The test results show that the minimum values of 30, 80, and 150 simulated users in the system performance test are 4, 5, and 7, respectively. The maximum users of the system performance test model are 30, 80, 150, 64, 284, and 398. The system performance tests are taken under the conditions of 30, 80, and 150 user bandwidth, with the results of 113/min, 104/min, and 90/min. The system basically meets the daily work management standards and fully achieves the expected system design goals. The development and use of this system are related to the development of college students’ innovation and entrepreneurship project management and have a clear reference for the development of innovation and entrepreneurship project management systems similar to manage workflow in the future.

Phase adjustment with the autofocus process is essential to inverse synthetic aperture radar (ISAR) imagery of manoeuvring targets. Conventional parametric and non-parametric autofocus methods usually degrade in front of error model mismatch and noise interference. Especially, the target manoeuvre also induces higher order phases that have the spatial-variant characteristic. In this study, a range-dependent semi-parametric autofocus algorithm for ISAR imagery is proposed. The range-variant phase is modelled semi-parametrically with a discrete cosine transform kernel. Implemented by the maximum sharpness optimisation, the algorithm well adapts to complex phase forms and enhances the robustness to strong noise. Accelerated solver to the optimisation is also introduced. Simulation and real data experiments confirm the advantages of the range-dependent semi-parametric autofocus algorithm compared with conventional algorithms.

Millimeter-wave (MMW) radar hand gesture recognition technology is becoming important in many electronic device control applications. Currently, most existing approaches utilize the radical and micro-Doppler features from single-channel MMW radar, which ignores the different importance of the information contained in the micro-Doppler feature background or target areas. In this paper, we propose an algorithm for hand gesture recognition jointly using multi-channel signatures. The algorithm blends the information of both micro-Doppler features and instantaneous angles (azimuth and elevation) to accomplish hand gesture recognition performed with the convolutional neural network (CNN). To have a better features fusion and make CNN focus on the most important target signal regions and suppress the unnecessary noise areas, we apply the channel and spatial attention-based feature refinement modules. We also employ gesture movement mechanism-based data augmentation for more effective training to alleviate potential overfitting. Extensive experiments demonstrate the effectiveness and superiorities of the proposed algorithm. This method achieves a correct classification rate of 96.61%, approximately 5% higher than that of the single-channel-based recognition strategy as measured based on MMW radar datasets.

Robust estimation of frequency hopping radar signal parameters is the key to achieving stable jam in frequency hopping communication. In order to deal with the poor noise resistance performance of conventional time-frequency analysis based parameter estimation method under low signal-noise-ratio conditions. A robust method is proposed in this paper for frequency hopping radar waveform parameters estimation. The method is performed in time domain. Firstly, the pulse repetition interval of the received radar signal is extracted by matching filtering, which is used as the window length to divide the signal into multiple frames. The coherent integration process is performed on the multi-frame signal to increase the signal-noise-ratio, which effectively ensures the robustness of the algorithm under low signal-noise-ratio conditions. Secondly, the short-time Fourier transform is used to realize the rough estimation of the frequency hopping number, which reduces the range of subsequent hopping counts and reduces the amount of algorithm calculation. Finally, an accurate estimation of the waveform parameters including frequency hopping sequence, hop duration, frequency hopping interval and carrier frequency is realized. Simulation experiments verify the effectiveness of the algorithm and the robustness under various signal-noise-ratio conditions.

Over the past 30 years, human disturbance and habitat fragmentation have severely endangered the survival of common wild rice (Oryza rufipogon Griff.) in China. A better understanding of the genetic structure of O. rufipogon populations will therefore be useful for the development of conservation strategies. We examined the diversity and genetic structure of natural O. rufipogon populations at the national, provincial, and local levels using simple sequence repeat (SSR) markers. Twenty representative populations from sites across China showed high levels of genetic variability, and approximately 44% of the total genetic variation was among populations. At the local level, we studied fourteen populations in Guangxi Province and four populations in Jiangxi Province. Populations from similar ecosystems showed less genetic differentiation, and local environmental conditions rather than geographic distance appeared to have influenced gene flow during population genetic evolution. We identified a triangular area, including northern Hainan, southern Guangdong, and southwestern Guangxi, as the genetic diversity center of O. rufipogon in China, and we proposed that this area should be given priority during the development of ex situ and in situ conservation strategies. Populations from less common ecosystem types should also be given priority for in situ conservation.

This paper presents the results of a centrifuge model test performed to study the behavior of a plumb-pile-supported wharf under yard-heaped loads. A bent composed of a slab, girders, and s...

Near-surface scattered waves (NSWs) are the main noise in seismic data in areas with a complex near surface and can be divided into surface-to-surface scattered waves and body-to-surface scattered waves. We have developed a method for NSW enhancement that uses modified source-receiver interferometry. The method consists of two parts. First, deconvolutional intersource interferometry is used to cancel the common raypath of seismic waves from a near-surface scatterer to the common receiver and the receiver function. Second, convolutional interreceiver interferometry is used to compensate the common raypath of seismic waves from the common source to the near-surface scatterer and the source function. For an isotropic point scatterer near the earth’s surface in modified source-receiver interferometry, a body-to-surface scattered wave can be reconstructed by constructive interference not only among three body-to-surface scattered waves but also among a body-to-surface scattered wave and two surface-to-surface scattered waves; a surface-to-surface scattered wave can be reconstructed by constructive interference not only among three surface-to-surface scattered waves but also among a surface-to-surface scattered wave and two body-to-surface scattered waves. According to stationary phase analysis based on the superposition principle, we have developed a so-called dual-wheel driving configuration of modified source-receiver interferometry for enhancing NSWs in the data of conventional seismic exploration. The main advantages of the scheme are that (1) it can be used to enhance NSWs without the need for any a priori knowledge of topography and near-surface velocity, (2) it can be used to reconstruct NSWs from real sources to real receivers, including 3D near-surface side-scattered waves, and (3) it can be applied to conventional seismic data with finite-frequency bandwidth, spatially limited and sparse arrays, different source and receiver functions, and static correction. Numerically simulated data and field seismic data are used to demonstrate the feasibility and effectiveness of the scheme.

An adaptive identification method is introduced to estimate unknown parameters of a multivariate dynamical model using a state variable. The unknown parameters may or may not appear in the evolution equation of the variable explicitly. The method aimed to solve the parameter identification problem when only one state variable of the model is available, in the case we assume that the differentiations and integrals of the variable are available, which are defined as the measurements of the variable, the circuit design are used to explain the physical means of the measurements. Previously adaptive identification methods do not work in the case of one state variable. This method seeks appropriate measurements of the variable for synchronization. The synchronization observers then are constructed for the measurements and they can extract the unknown parameters out of these measurements accurately. The identification convergence is proved by using Lyapunov second theorem and Kalman-Yakubovic lemma. Numerical simulations are presented for Lorenz chaotic model. The simulation results prove the efficiency of the proposed method.

Mercury (Hg) is toxic and can affect human health through soil entering food chain. Spinach absorb easily heavy metals. Corn stover biochar can improve soil structure and physicochemical property. This study wanted to establish a Hg-corn stover biochar-soil-spinach model including 1 control group (without HgCl2 and corn stover biochar) and 24 treatment groups (with HgCl2 or/and corn stover biochar). Hg concentration was 0, 1, 2, 4, and 6 mg kg−1, respectively. Corn stover biochar contents were 0%, 1%, 3%, 5%, and 7% w/w, respectively. The results showed that residual Hg concentrations was the largest and water soluble and exchangeable Hg as well as carbonate bound Hg concentrations were the lowest among five Hg forms. Hg concentrations in four Hg treatment groups were higher than the control group in dose-dependent manner. The deposition of 6 mg kg−1 Hg was the highest. Corn stover biochar decreased Hg migration from soil to leaching solution and spinach, and passivation effect of 7% concentration of corn stover biochar was the best. Besides, corn stover biochar relieved the increase of methyl Hg caused by Hg in soil. Moreover, Hg concentration in roots was the highest and Hg concentration in stems was the lowest in spinach. Furthermore, Hg absorbed by roots was more than the sum of Hg absorbed by stems and leaves. In addition, we also found that the measured soil Hg concentrations were coincided with the predicted soil Hg concentrations under 1, 2, and 4 mg kg−1 Hg concentrations, except 2 mg kg−1 Hg at 7% C. Under 6 mg kg−1 Hg concentration, measured soil Hg concentrations was lower than that of the predicted soil Hg concentrations. Taken together, our findings indicated that corn stover biochar can increase edible safety of spinach by immobilizing Hg in soil and be used as an organic amendment.

This paper deals with the stability and dynamic evolution of a sliding pipe conveying fluid in the three-dimensional sense. The pipe is assumed to slide out from a fixed channel so that its free end is moving at the same time, a problem often associated with instabilities in applications of aerial refueling operation. To tackle this problem, the nonlinear governing equations of motion are derived by using the Hamilton’s principle and then reduced to a set of ordinary differential equations by the Galerkin’s method. A parametric study is performed to explore the transient vibration responses of the pipe for different values of flow velocity and sliding rate. Various dynamic behaviors are detected for the pipe in sliding and conveying fluid. The results show that 3-D oscillations of the pipe occur when the flow velocity exceeds a certain value, which can be affected by the sliding rate. For various flow velocities, the evolution of the dynamic characteristics of the sliding pipe can be classified into three typical types of motion. When at low flow velocity, the pipe is mainly subjected to a single type of 3-D motion. When the flow speed increases to high values, multi-type of 3-D motion consisting of three typical types occurs on the pipe. In addition, the pipe can display planar motions, transferring from one plane to the other. The result presented herein is helpful to understand the stabilities and dynamic behaviors of sliding-pipe systems used in aerial refueling applications.

Coniothyrium minitans is an important mycoparasite of Sclerotinia sclerotiorum. In addition, it also produces small amounts of antifungal substances. ZS-1TN1812, an abnormal mutant, was originally screened from a T-DNA insertional library. This mutant showed abnormal growth phenotype and could significantly inhibit the growth of S. sclerotiorum when dual-cultured on a PDA plate. When spraying the filtrate of ZS-1TN1812 on the leaves of rapeseed, S. sclerotiorum infection was significantly inhibited, suggesting that the antifungal substances produced by this mutant were effective on rapeseed leaves. The thermo-tolerant antifungal substances could specifically suppress the growth of S. sclerotiorum, but could not significantly suppress the growth of another fungus, Colletotrichum higginsianum. However, C. higginsianum was more sensitive to proteinous antibiotics than S. sclerotiorum. The T-DNA insertion in ZS-1TN1812 activated the expression of CmSIT1, a gene involved in siderophore-mediated iron transport. It was also determined that mutant ZS-1TN1812 produced hypha with high iron levels. In the wild-type strain ZS-1, CmSIT1 was expressed only when in contact with S. sclerotiorum, and consistent overexpression of CmSIT1 showed similar phenotypes as ZS-1TN1812. Therefore, activated expression of CmSIT1 leads to the enhanced antifungal ability, and CmSIT1 is a potential gene for improving the control ability of C. minitans.

We report a facile impregnation–solvothermal method for the preparation of mesoporous TiO2(B) nanowires (TNWs(B)) supporting with Fe2O3 nanoparticles (NPs). Open tunnel and porous structure of TNWs(B) provided a confined micro-environment for the stabilization of well-dispersed nanoparticles. The intact fibrous morphology structure, high crystallinity and porosity were remained for TNWs(B) after supporting by nanoparticles. UV−visible DRS analysis indicated that the loading of Fe2O3 on TNWs(B) promoted light harvesting ability and further extended the absorption range. The photocatalytic experiments showed that Fe2O3/TNWs(B) had remarkable catalytic activity for photochemical oxidation of organic pollutants Direct Red 4BS in presence of H2O2 and exhibited excellent tolerance with respect to organic matter poisoning, which was attributed to favorable synergetic effect of Fe2O3 NPs and TNWs(B) support. Compared with P25, the composite material taking the advantage of fibrous morphology was more easily separated from reaction system simply by sedimentation. Moreover, the greatest interest of our finding would be exploring that impregnation duration had significant effect on size and location of NPs supported on TNWs(B). When impregnation duration time was higher than 12 h, NPs with d

A novel photocatalytic membrane reactor (PMR) system was reported by the usage of TiO 2 nanotube (TNT) photocatalysts and microfiltration (MF) membranes. TNTs were prepared by hydrothermal method and the optimal preparation conditions were determined. Results showed that prepared TNT had good photocatalytic activity which was 2.5 times higher than that of P25 in reactive brilliant blue X-BR degradation. Due to its one-dimensional structure, the membrane flux in TNT separation was also 4–5 times higher than P25 no matter what kind of membrane was applied. Surface morphology analysis predicted less membrane fouling and better recycling in TNT PMR system.

This paper presents an asymptotic analysis of a stochastic logistic population model with nonlinear diffusion term. The classical probability method is applied to obtain the criteria of asymptotic behavior for the considered model. The numerical simulations validate the efficiency of the theory analysis.

In order to solve the inconsistency in seismic data resulting from the lateral variation of the quality factors in the near-surface and shallow strata, in view of the features of stable symbol reflected events existed in seismic data, the relative quality factors estimation based on symbol events is proposed. With the lateral stability of the symbol events as target, the method computes the integrated relative quality factors of the near-surface and shallow strata above the symbol events. Inverse Q filtering based on the quality factors can effectively eliminate the energy striping phenomenon in seismic profile resulting from the lateral variation of quality factors, and improve the lateral consistency of seismic data.

Palmitoleic acid (16:1delta9), an unusual monounsaturated fatty acid, is highly valued for human nutrition, medication and industry. Plant oils containing large amounts of palmitoleic acid are the ideal resource for biodiesel production. To increase accumulation of palmitoleic acid in plant tissues, we used a yeast (Saccharomyees cerevisiae) acyl-CoA-delta9 desaturase (Scdelta9D) for cytosol- and plastid-targeting expression in tobacco (Nicotiana tabacum L.). By doing this, we also studied the effects of the subcellular-targeted expression of this enzyme on lipid synthesis and metabolism in plant system. Compared to the wild type and vector control plants, the contents of monounsaturated palmitoleic (16:1delta9) and cis-vaccenic (18:1delta11) were significantly enhanced in the Scdelta9D-transgenic leaves whereas the levels of saturated palmitic acid (16:0) and polyunsaturated linoleic (18:2) and linolenic (18:3) acids were reduced in the transgenics. Notably, the contents of 16:1delta9 and 18:1delta11 in the Scdelta9D plastidal-expressed leaves were 2.7 and 1.9 folds of that in the cytosolic-expressed tissues. Statistical analysis appeared a negative correlation coefficient between 16:0 and 16:1delta9 levels. Our data indicate that yeast cytosolic acyl-CoA-delta9 desaturase can convert palmitic (16:0) into palmitoleic acid (16:1delta9) in high plant cells. Moreover, this effect of the enzyme is stronger with the plastid-targeted expression than the cytosol-target expression. The present study developed a new strategy for high accumulation of omega-7 fatty acids (16:1delta9 andl8:1delta11) in plant tissues by protein engineering of acyl-CoA-delta9 desaturase. The findings would particularly benefit the metabolic assembly of the lipid biosynthesis pathway in the large-biomass vegetative organs such as tobacco leaves for the production of high-quality biodiesel.

Based on a practical engineering, the effects of soil-structure interactions on the dynamic characteristics of the high-piled wharf were investigated, and the influences of different soil-structure constraint styles and initial earth stress on the calculation of dynamic parameters were also studied. The results of the study were the following: (a) the soil-structure interactions should be considered when analyzing the dynamic characteristics of the high-piled wharf; (b) the soil-structure constraint styles would influence the calculation of dynamic parameters, and soil-structure constrained by contact elements was recommended; (c) the consideration of initial earth stress would increase the frequency of the high-piled wharf and had much greater influences on high order, so the soil initial earth stress should be considered when performing the modal analysis of soil-wharf.