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101.
Dah-Jing Jwo 《计算机、材料和连续体(英文)》2020,65(2):993-1014
The Global Positioning System (GPS) offers the interferometer for attitude
determination by processing the carrier phase observables. By using carrier phase
observables, the relative positioning is obtained in centimeter level. GPS interferometry
has been firstly used in precise static relative positioning, and thereafter in kinematic
positioning. The carrier phase differential GPS based on interferometer principles can
solve for the antenna baseline vector, defined as the vector between the antenna
designated master and one of the slave antennas, connected to a rigid body. Determining
the unknown baseline vectors between the antennas sits at the heart of GPS-based attitude
determination. The conventional solution of the baseline vectors based on least-squares
approach is inherently noisy, which results in the noisy attitude solutions. In this article,
the complementary Kalman filter (CKF) is employed for solving the baseline vector in
the attitude determination mechanism to improve the performance, where the receiversatellite double differenced observable was utilized as the measurement. By using the
carrier phase observables, the relative positioning is obtained in centimeter level.
Employing the CKF provides several advantages, such as accuracy improvement,
reliability enhancement, and real-time assurance. Simulation results based on the
conventional method where the least-squares approach is involved, and the proposed
method where the CKF is involved are compared and discussed. 相似文献
102.
Agricultural culture is a productive activity about education and management.
It aims at high efficiency and high quality, uses technology as its means, and takes nature
as its carrier. Agricultural cultural resources are the product of the rapid development of
modern economy. It promotes the development of the national economy and profoundly
affects people's production and life. DEA model, also known as data envelope analysis
method, is an algorithm that uses multiple data decision units for input and output
training to obtain the final model. This article explains the concept and basic
characteristics of agricultural culture. Through questionnaire surveys and expert
interviews, we collected development data, screened human, material, and financial data,
and calculated information on economic and social resources. On this basis, this paper
establishes the evaluation index of agricultural culture based on DEA model. Then,
through empirical analysis from a specific perspective, it can be concluded that
increasing human, material and financial input can achieve economic and social benefits. Generally speaking, cultural investment can promote the development of the industry.
The research results of this paper laid a theoretical foundation for the development of
agricultural culture, and put forward a development model focusing on technology
development, improving investment efficiency, and investing in material resources. 相似文献
103.
The multi-purpose forensics is an important tool for forge image detection. In
this paper, we propose a universal feature set for the multi-purpose forensics which is
capable of simultaneously identifying several typical image manipulations, including
spatial low-pass Gaussian blurring, median filtering, re-sampling, and JPEG
compression. To eliminate the influences caused by diverse image contents on the
effectiveness and robustness of the feature, a residual group which contains several highpass filtered residuals is introduced. The partial correlation coefficient is exploited from
the residual group to purely measure neighborhood correlations in a linear way. Besides
that, we also combine autoregressive coefficient and transition probability to form the
proposed composite feature which is used to measure how manipulations change the
neighborhood relationships in both linear and non-linear way. After a series of dimension
reductions, the proposed feature set can accelerate the training and testing for the multipurpose forensics. The proposed feature set is then fed into a multi-classifier to train a
multi-purpose detector. Experimental results show that the proposed detector can identify several typical image manipulations, and is superior to the complicated deep CNN-based
methods in terms of detection accuracy and time efficiency for JPEG compressed image
with low resolution. 相似文献
104.
The application of deep learning in the field of object detection has
experienced much progress. However, due to the domain shift problem, applying an
off-the-shelf detector to another domain leads to a significant performance drop. A
large number of ground truth labels are required when using another domain to train
models, demanding a large amount of human and financial resources. In order to avoid
excessive resource requirements and performance drop caused by domain shift, this
paper proposes a new domain adaptive approach to cross-domain vehicle detection. Our
approach improves the cross-domain vehicle detection model from image space and
feature space. We employ objectives of the generative adversarial network and cycle
consistency loss for image style transfer in image space. For feature space, we align
feature distributions between the source domain and the target domain to improve the
detection accuracy. Experiments are carried out using the method with two different
datasets, proving that this technique effectively improves the accuracy of vehicle
detection in the target domain. 相似文献
105.
Massive Open Online Course (MOOC) has become a popular way of online
learning used across the world by millions of people. Meanwhile, a vast amount of
information has been collected from the MOOC learners and institutions. Based on the
educational data, a lot of researches have been investigated for the prediction of the
MOOC learner’s final grade. However, there are still two problems in this research field.
The first problem is how to select the most proper features to improve the prediction
accuracy, and the second problem is how to use or modify the data mining algorithms for
a better analysis of the MOOC data. In order to solve these two problems, an improved
random forests method is proposed in this paper. First, a hybrid indicator is defined to
measure the importance of the features, and a rule is further established for the feature
selection; then, a Clustering-Synthetic Minority Over-sampling Technique (SMOTE) is
embedded into the traditional random forests algorithm to solve the class imbalance
problem. In experiment part, we verify the performance of the proposed method by using
the Canvas Network Person-Course (CNPC) dataset. Furthermore, four well-known
prediction methods have been applied for comparison, where the superiority of our
method has been proved. 相似文献
106.
朱伟婧 《信息安全与通信保密》2020,(5):102-113
美国当前在大数据方面全球领先。2010年奥巴马将发展大数据上升为国家战略,建立了一系列负责大数据的专门机构,发布大量相关战略性文件和法令。大数据在美国各个领域得到广泛应用,并基本成体系。当前我国大数据发展取得进步但仍存在问题,借鉴美国大数据战略的具体做法可为完善我国大数据战略提供较好的参考价值。 相似文献
107.
To deal with uncertainty of the spectral distribution, we consider minimax interpolation and extrapolation problems in Lp for stationary processes. The interpolation and extrapolation problems can be regarded as a linear approximation problem on the unit disk in the complex plane. Although the robust one-step-ahead predictor and interpolator has already been considered separately in the previous literature, we give two conditions for the uncertainty class to find the minimax interpolator and extrapolator in the general framework from both the point of view of the observation set and the point of view of evaluation on the interpolation and extrapolation error under the Lp-norm. We show that there exists a minimax interpolator and extrapolator for the class of spectral densities ε-contaminated by unknown spectral densities under our conditions. When the uncertainty class contains spectral distribution functions which are not absolutely continuous to the Lebesgue measure, we show that there exists an approximate interpolator and extrapolator in Lp such that its maximal interpolation and extrapolation error is arbitrarily close to the minimax error when the spectral distributions have densities. Our results are applicable to the stationary harmonizable stable processes. 相似文献
108.
Disperse dyes are poorly water-soluble and difficult to stably disperse in an aqueous medium, which greatly limits their application in dyeing synthetic fibers. Micronization can solve this problem. Herein, a facile way to prepare stable aqueous nanodispersions of disperse dye (C.I. disperse yellow 54) is presented by combining high-gravity antisolvent precipitation in a rotating packed bed (RPB) with spray drying. The as-prepared product had an average particle size of 120 nm, which could be readily redispersed in water. Compared with raw dye, the wettability and dispersibility of disperse dye nanoparticles were remarkably improved. Furthermore, the dyeing properties of the nanodispersions were obviously better than those of the commercial dye, which was micronized by ball milling. 相似文献
109.
Anne Hofmann Stefanie Wienkoop Snke Harder Fabian Bartlog Sabine Lüthje 《International journal of molecular sciences》2020,21(22)
Flooding induces low-oxygen environments (hypoxia or anoxia) that lead to energy disruption and an imbalance of reactive oxygen species (ROS) production and scavenging enzymes in plants. The influence of hypoxia on roots of hydroponically grown maize (Zea mays L.) plants was investigated. Gene expression (RNA Seq and RT-qPCR) and proteome (LC–MS/MS and 2D-PAGE) analyses were used to determine the alterations in soluble and membrane-bound class III peroxidases under hypoxia. Gel-free peroxidase analyses of plasma membrane-bound proteins showed an increased abundance of ZmPrx03, ZmPrx24, ZmPrx81, and ZmPr85 in stressed samples. Furthermore, RT-qPCR analyses of the corresponding peroxidase genes revealed an increased expression. These peroxidases could be separated with 2D-PAGE and identified by mass spectrometry. An increased abundance of ZmPrx03 and ZmPrx85 was determined. Further peroxidases were identified in detergent-insoluble membranes. Co-regulation with a respiratory burst oxidase homolog (Rboh) and key enzymes of the phenylpropanoid pathway indicates a function of the peroxidases in membrane protection, aerenchyma formation, and cell wall remodeling under hypoxia. This hypothesis was supported by the following: (i) an elevated level of hydrogen peroxide and aerenchyma formation; (ii) an increased guaiacol peroxidase activity in membrane fractions of stressed samples, whereas a decrease was observed in soluble fractions; and (iii) alterations in lignified cells, cellulose, and suberin in root cross-sections. 相似文献
110.
A new, partially discontinuous architecture is proposed to improve the mechanical performance of pseudo-ductile, unidirectional (UD) interlayer carbon/glass hybrid composites. The concept was successfully demonstrated in different laminates with high strength and high modulus carbon and S-glass epoxy UD prepregs. The novel hybrid architecture provided pseudo-ductile tensile stress–strain responses with a linear initial part followed by a wide plateau and a second linear part, all connected by smooth transitions. The best hybrid configuration showed 60% improvement in modulus compared to pure glass, 860 MPa plateau stress and 2% pseudo-ductile strain. The initial modulus, the plateau stress and the overall tensile stress–strain response of each specimen configuration were predicted accurately. 相似文献