Regardless of whether the global navigation satellite system (GNSS)/inertial navigation system (INS) is integrated or the INS operates independently during GNSS outages, the stochastic error of the ...inertial sensor has an important impact on the navigation performance. The structure of stochastic error in low-cost inertial sensors is quite complex; therefore, it is difficult to identify and separate errors in the spectral domain using classical stochastic error methods such as the Allan variance (AV) method and power spectral density (PSD) analysis. However, a recently proposed estimation, based on generalized wavelet moment estimation (GMWM), is applied to the stochastic error modeling of inertial sensors, giving significant advantages. Focusing on the online implementation of GMWM and its integration within a general navigation filter, this paper proposes an algorithm for online stochastic error calibration of inertial sensors in urban cities. We further develop the autonomous stochastic error model by constructing a complete stochastic error model and determining model ranking criterion. Then, a detecting module is designed to work together with the autonomous stochastic error model as feedback for the INS/GNSS integration. Finally, two experiments are conducted to compare the positioning performance of this algorithm with other classical methods. The results validate the capability of this algorithm to improve navigation accuracy and achieve the online realization of complex stochastic models.
Weakly supervised object detection is an interesting yet challenging research topic in computer vision community, which aims at learning object models to localize and detect the corresponding objects ...of interest only under the supervision of image-level annotation. For addressing this problem, this paper establishes a novel weakly supervised learning framework to leverage both the instance-level prior-knowledge and the image-level prior-knowledge based on a novel collaborative self-paced curriculum learning (C-SPCL) regime. Under the weak supervision, C-SPCL can leverage helpful prior-knowledge throughout the whole learning process and collaborate the instance-level confidence inference with the image-level confidence inference in a robust way. Comprehensive experiments on benchmark datasets demonstrate the superior capacity of the proposed C-SPCL regime and the proposed whole framework as compared with state-of-the-art methods along this research line.
In this paper, we present a column-and-constraint generation algorithm to solve two-stage robust optimization problems. Compared with existing Benders-style cutting plane methods, the ...column-and-constraint generation algorithm is a general procedure with a unified approach to deal with optimality and feasibility. A computational study on a two-stage robust location-transportation problem shows that it performs an order of magnitude faster.
We consider a system where a massive multiple-input multiple-output (MIMO) base station (BS) transmits information and energy to multiple energy harvesting receivers. Each receiver has no power ...source and needs to harvest sufficient energy in order to decode its message from the received signal. Under either the power splitting mode or the time switching mode at the receivers, we consider two design problems. One is to maximize the minimum transmission rate among all receivers and the other is to optimize the system energy efficiency (EE) through jointly designing the power allocation proportions at the BS and the power splitting (or time switching) factors at the receivers. The optimal solutions to these problems are obtained either in terms of closed-form expressions or efficient algorithms by leveraging the asymptotic channel orthogonality and hardening effects of massive MIMO. The simulation results indicate that the power splitting mode outperforms the time switching mode in terms of both the minimum transmission rate and the system EE.
•Ionic liquid was covalently immobilized onto cellulose microspheres via radiation method.•ILFC had practicality, reusability and selectivity for Cr(VI) removal.•ILFC exhibited good adsorption ...performance toward Cr(VI) in column.
Combining the advantages of both cellulose and ionic liquid, ionic liquid functionalized cellulose (ILFC) as adsorbent was prepared through radiation grafting glycidyl methacrylate onto cellulose microsphere following by reaction with ionic liquid 1-aminopropyl-3-methyl imidazolium nitrate. Its adsorption properties towards Cr(VI) were investigated in batch and column experiments. In batch experiments, the adsorption kinetics was well fitted with pseudo-second-order mode with equilibrium time of 2 h and the adsorption capacity reached 181.8 mg/g at pH 2 calculated from Langmuir model. In fixed column, both Yoon-Nelson and Thomas models gave satisfactory fit to experimental data and breakthrough curves, and equilibrium adsorption capacity calculated by Thomas model was 161.0 mg/g. Moreover, ILFC exhibited high selectivity towards Cr(VI) even in synthetic chrome-plating wastewater. Besides, adsorption/desorption test revealed ILFC can be regenerated and reused several times without obvious decrease in adsorbed amount. The adsorption process was demonstrated to anion exchange-reduction mechanism via XPS analysis.
Chiral materials have been widely present in people's lives, and their in-depth application research is underway. Generally, the circularly polarized light obtained from nonpolarized light through ...filters would result in brightness loss. Scientists have found that chirality can be introduced into organic compounds to obtain circularly polarized luminescence (CPL). Chiral compounds with CPL properties have attracted great attention and interest in recent years for their wide potential applications in 3D information displays, quantum communication, spintronics information storage, CPL lasers, nonlinear optics, biological probes and other fields. It is worth noting that helicene derivatives with twisted extended π-conjugated molecular structures could exhibit special helical chirality and excellent CPL properties. A chiral helix has also proven to be a valuable structural design for exploring small organic molecules with CPL. This review summarizes the recent development of CPL based on helicene derivatives.
This review summarizes the recent research progress of helicenes and their derivatives with circularly polarized luminescence properties.
Fluoroalkylation reactions in aqueous media: a review Song, Hai-Xia; Han, Qiu-Yan; Zhao, Cheng-Long ...
Green chemistry : an international journal and green chemistry resource : GC,
2018, Letnik:
2, Številka:
8
Journal Article
Recenzirano
This review highlights the progress of aqueous fluoroalkylation over the past few decades. Fluorine-containing functionalities are important design elements in new pharmaceuticals, agrochemicals, and ...functional materials, due to their unique effects on the physical, chemical, and/or biological properties of a molecule. Because the environmental concerns are receiving increasing attention in organic synthesis, the development of methods for the mild, environment-friendly, and efficient incorporation of fluorinated or fluoroalkylated groups into the target molecules is of broad interest. At the early stage, most of the fluoroalkylation reactions and their variants were thought in principle to be hydrophobic. Recently, the environment-benign fluoroalkylation reactions by taming nucleophilic, radical, or electrophilic fluoroalkylation reagents in water or in the presence of water have been explored, building a new prospect for green chemistry. The use of significant catalytic systems and/or the newly developed reagents is the key to the success of these reactions. Water is used as a (co)solvent and/or a reactant in aqueous fluoroalkylation, including trifluoromethylation, difluoromethylation, monofluoromethylation, trifluoroethylation, perfluoroalkylation, trifluoromethylthiolation, and other conversions, under environment-friendly conditions. Although great accomplishments have been achieved, they are just the tip of the iceberg with a wide scope for improvement. This review will draw great attention and inspire more contributions in the development of new aqueous fluoroalkylation reactions.
Recent advances in aqueous fluoroalkylation using various fluoroalkylation reagents are summarized in this review.
Vanishing point is an important geometric element in sports video. In this paper, a new calibration algorithm is proposed by using the algebraic and geometric properties of vanishing points, which ...resolves the three main problems of the traditional camera calibration technology based on vanishing points: (1) calibrating camera with varied focal length; (2) screening out outliers from a set of images; (3) estimation of distortion coefficients. The principal line passes through the principal point, and the algebraic relationship between it and the vanishing points is deduced. Using the geometry feature of the principal line, problems (1) and (2) can be easily solved. The linear relationship between the point and the line is used to estimate the distortion coefficient under the condition of obtaining the principal point. Simulation and real experiments show the validity and robustness of the proposed algorithm, and satisfactory results can be obtained by solving the above three problems.
WiFi fingerprinting-based indoor positioning system (IPS) using received signal strength (RSS) has been considered to be one solution for indoor positioning. However, there are two major bottlenecks ...that hamper its large-scale implementation. One widely recognized problem is the construction of a proper fingerprint database with high efficiency and accuracy. Second is to improve the online positioning accuracy on the basis of the fingerprint database. To address these issues comprehensively, this paper proposes a novel system-Digital navigation center IPS (DncIPS), an IPS that enables automatic online radio map construction, and step-by-step positioning, aiming for the high-accuracy RSS estimation and high-precision positioning. DncIPS can capture WiFi data packets transmitted in WiFi traffic so that they obtain the MAC addresses, frequency, and RSS of any WiFi access point (AP) at any point. DncIPS uses Gaussian process regression model based on a fireworks algorithm to approximate the RSS distribution of an indoor environment and to estimate the location of APs increasing the flexibility of DncIPS work environment. This system also consists of a coarse localizer detecting the outliers and dividing clustering area and a fine localizer followed to improve the online positioning accuracy. Extensive experiments results indicate the proposed system DncIPS leads to improvement on radio map updating and localization accuracy.
Despite a well‐developed and growing body of work in Cu catalysis, the potential of Cu to serve as a photocatalyst remains underexplored. Reported herein is the first example of visible‐light‐induced ...Cu‐catalyzed decarboxylative C(sp3)−H alkylation of glycine for preparing α‐alkylated unnatural α‐amino acids. It merits mentioning that the mild conditions and the good functional‐group tolerance allow the modification of peptides using this method. The mechanistic studies revealed that a radical–radical coupling pathway is involved in the reaction.
Out of the clear blue: The title reaction was developed for preparing α‐alkylated non‐natural α‐amino acids by transformation of glycine moieties. Mild conditions and good functional‐group tolerance allow the modification of peptides using this method. Mechanistic studies revealed that a radical–radical coupling pathway is involved in the reaction.
