The precise modification of redox species on the inner and outer surfaces of hollow nanostructures is relevant in catalysis, surface science, and nanotechnology, but has proven difficult to achieve. ...Herein, we develop a facile approach to specifically fabricate Pt and Co3O4 nanoparticles (NPs) onto the interior and exterior surface of hollow carbon nitride spheres (HCNS), respectively, to promote the surface redox functions of the polymer semiconductors. The photocatalytic water splitting activities of HCNS with spatially separated oxidation and reduction centers at their nanodomains were enhanced. The origin of the enhanced activity was attributed to the spatially separated reactive sites for the evolution of H2 and O2 and also to the unidirectional migration of the electron and hole on the Janus surfaces, thereby preventing the unwanted reverse reaction of water splitting and decreasing charge recombination.
Interior design: A hollow conjugated carbon nitride semiconductor nanosphere with Pt and Co3O4 nanoparticles on the interior and exterior surfaces, respectively, has been prepared by a precise nanofabrication technology. The nanoparticle co‐catalysts enable the Janus hollow structure to photocatalyze water splitting by promoting charge separation and inhibiting the unwanted reverse reaction.
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The constrained control of unmanned aerial vehicles (UAVs) is a challenging task due to their nonlinear and underactuacted dynamics. This brief focuses on the position control of a quadrotor UAV with ...state and input constraints using an inner-outer loop control structure. The outer loop generates a saturated thrust, and the reference roll and pitch angles, while the inner loop is designed to follow these reference angles using a traditional PID controller. Assuming perfect inner loop tracking, the outer loop nested saturation controller guarantees global asymptotic stability for output regulation and tracking. The effect of nonideal inner loop tracking on closed-loop stability is analyzed. The proposed method is experimentally validated on an indoor quadrotor platform.
Carbon‐based catalysts have demonstrated great potential for the aerobic oxidative dehydrogenation reaction (ODH). However, its widespread application is retarded by the unavoidable deactivation ...owing to the appearance of coking or combustion under ODH conditions. The synthesis and characterization of porous structure of BCN nanosheets as well as their application as a novel catalyst for ODH is reported. Such BCN nanosheets consist of hybridized, randomly distributed domains of h‐BN and C phases, where C, B, and N were confirmed to covalent bond in the graphene‐like layers. Our studies reveal that BCN exhibits both high activity and selectivity in oxidative dehydrogenation of ethylbenzene to styrene, as well as excellent oxidation resistance. The discovery of such a simple chemical process to synthesize highly active BCN allows the possibility of carbocatalysis to be explored.
The porous structure of two‐dimension BCN nanosheets, consisting of hybridized h‐BN and C domains, were constructed for aerobic oxidative dehydrogenation reactions. The high porosity, novel pore structure, and abundant oxygen‐containing functional groups endow the BCN with more active sites.
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With the advent of cloud computing, data owners are motivated to outsource their complex data management systems from local sites to the commercial public cloud for great flexibility and economic ...savings. But for protecting data privacy, sensitive data have to be encrypted before outsourcing, which obsoletes traditional data utilization based on plaintext keyword search. Thus, enabling an encrypted cloud data search service is of paramount importance. Considering the large number of data users and documents in the cloud, it is necessary to allow multiple keywords in the search request and return documents in the order of their relevance to these keywords. Related works on searchable encryption focus on single keyword search or Boolean keyword search, and rarely sort the search results. In this paper, for the first time, we define and solve the challenging problem of privacy-preserving multi-keyword ranked search over encrypted data in cloud computing (MRSE). We establish a set of strict privacy requirements for such a secure cloud data utilization system. Among various multi-keyword semantics, we choose the efficient similarity measure of "coordinate matching," i.e., as many matches as possible, to capture the relevance of data documents to the search query. We further use "inner product similarity" to quantitatively evaluate such similarity measure. We first propose a basic idea for the MRSE based on secure inner product computation, and then give two significantly improved MRSE schemes to achieve various stringent privacy requirements in two different threat models. To improve search experience of the data search service, we further extend these two schemes to support more search semantics. Thorough analysis investigating privacy and efficiency guarantees of proposed schemes is given. Experiments on the real-world data set further show proposed schemes indeed introduce low overhead on computation and communication.
Cloud computing economically enables the paradigm of data service outsourcing. However, to protect data privacy, sensitive cloud data have to be encrypted before outsourced to the commercial public ...cloud, which makes effective data utilization service a very challenging task. Although traditional searchable encryption techniques allow users to securely search over encrypted data through keywords, they support only Boolean search and are not yet sufficient to meet the effective data utilization need that is inherently demanded by large number of users and huge amount of data files in cloud. In this paper, we define and solve the problem of secure ranked keyword search over encrypted cloud data. Ranked search greatly enhances system usability by enabling search result relevance ranking instead of sending undifferentiated results, and further ensures the file retrieval accuracy. Specifically, we explore the statistical measure approach, i.e., relevance score, from information retrieval to build a secure searchable index, and develop a one-to-many order-preserving mapping technique to properly protect those sensitive score information. The resulting design is able to facilitate efficient server-side ranking without losing keyword privacy. Thorough analysis shows that our proposed solution enjoys "as-strong-as-possible" security guarantee compared to previous searchable encryption schemes, while correctly realizing the goal of ranked keyword search. Extensive experimental results demonstrate the efficiency of the proposed solution.
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•Reduced graphene oxide based flexible aerogel was fabricated successfully.•Underwater superoleophobic aerogel exhibited anti-fouling/self-cleaning property.•Fluorinated aerogel was ...superhydrophobic with high stability under corrosive media.•All mentioned aerogels exhibited efficient oil/water separation behavior.
In recent years, reduced graphene oxide (rGO) has attracted wide attention from researchers due to its excellent physicochemical properties and rich surface chemistry. Inspired by the innate adhesive property of dopamine, a facile and environmentally-friendly approach was developed to fabricate reduced graphene oxide/polydopamine composite aerogel reinforced by chitosan and modified by 1H,1H,2H,2H-perfluorodecanethiol (PFDT). During the preparation process, a polydopamine (PDA) film was first anchored on reduced graphene oxide (rGO) nanosheets via dopamine self-polymerization. By means of hydrothermal treatment, immersion and freeze-drying process, rGO nanosheets modified by PDA were self-assembled into a 3D porous structure, and the chitosan/reduced graphene oxide composite aerogel (CGA) was synthesized. Subsequently, PFDT reacted with PDA film to fabricate perfluorinated superhydrophobic polydopamine/chitosan/reduced graphene oxide composite aerogel (fCGA). The CGA possesses super-amphiphilicity in air and superoleophobicity underwater, while fCGA exhibits superhydrophobicity. Both of them have oil/water separation behavior, indicating that the aerogels are promising materials for the treatment of oil-spill accidents and oily wastewater.
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The paper proposes the method of uniform flow loading the improved consensus algorithm to achieve obstacle avoidance for multi‐UAV with 3‐D formation. In view of that the flow function is generally ...only applicable to two dimensional flow field, dimension reduction is to treat multi‐UAV formation as each UAV flows around along the circular surface of the projected cylinder of spherical obstacle at its different heights. To formation guaranteeing the smooth realization of obstacle avoidance of multi‐UAV formation centered on the leader, it is used the tactics of virtually expanding the radius of these static or moving equivalent cylindrical obstacles to reserve a certain space. The innovation of this strategy is to further reduce the possibility of collision between UAV formation and the edge of obstacles, meanwhile the problem of multi‐UAV formation avoiding obstacles is transformed into the problem of collision avoidance navigation for the leader treated as a particle. It is considered collision avoidance for multi‐UAV formation under three scenarios assumed are the most common situations, and the simulation experimental results of these scenarios are demonstrated on the validity of the designed experiments based on these algorithms.
Every multi‐UAV formation and spherical obstacle are wrapped into an equivalent infinite cylinder along the z axis, and each UAV flows around along the circular surface of the projected cylinder of spherical obstacle or of multi‐UAV formation at its different heights based on the approach of combining with the consensus algorithm and uniform flow. To formation guaranteeing the smooth realization of obstacle avoidance of multi‐UAV formation centered on the leader, it is used the tactics of virtually expanding the radius of these static or moving equivalent cylindrical obstacles to reserve a certain space. It is considered collision avoidance for multi‐UAV formation under three scenarios assumed are the most common situations, and the simulation experimental results of these scenarios are demonstrated on the validity of the designed experiments based on these algorithms.
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As a novel two-dimensional carbon material, graphene has fine potential applications in the fields of electron transfer agent and supercapacitor material for its excellent electronic and optical ...property. However, the challenge is to synthesize graphene in a bulk quantity. In this paper, graphite oxide was prepared from natural flake graphite by Hummers’ method through liquid oxidization, and the reduced graphene oxide was obtained by chemical reduction of graphene oxide using NH3·H2O aqueous solution and hydrazine hydrate. The raw material graphite, graphite oxide, and reduced graphene oxide were characterized by X-ray diffraction (XRD), attenuated total reflectance-infrared spectroscopy (ATR-IR), and field emission scanning electron microscope (SEM). The results indicated that the distance spacing of graphite oxide was longer than that of graphite and the crystal structure of graphite was changed. The flake graphite was oxidized to graphite oxide and lots of oxygen-containing groups were found in the graphite oxide. In the morphologies of samples, fold structure was found on both the surface and the edge of reduced graphene oxide.
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A Phase-Decomposition-Based PSInSAR Processing Method Cao, Ning; Lee, Hyongki; Jung, Hahn Chul
IEEE transactions on geoscience and remote sensing,
2016-Feb., 2016-2-00, 20160201, Volume:
54, Issue:
2
Journal Article
Peer reviewed
A phase-decomposition-based persistent scatterer (PS) InSAR (PD-PSInSAR) method is developed in this paper to improve coherence and spatial density of measurement points (MPs). In order to improve PS ...network density, a distributed scatterer (DS) has been utilized in some advanced PSInSAR process, such as SqueeSAR. In addition to the conventional DS that consists of independent small scatterers with a uniform scattering mechanism, processing the DSs dominated by two or more scattering mechanisms is a promising way to improve MP density. Estimating phases from DS with multiple scattering mechanisms is difficult for many DS algorithms because of the interference between different scattering mechanisms. Recently, a covariance-matrix-decomposition-based method, which is named Component extrAction and sElection SAR (CAESAR), is proposed to extract different scattering components from the analysis of the covariance matrix. Instead of using a covariance matrix, the PD-PSInSAR in this study is developed to perform eigendecomposition on a coherence matrix, in order to estimate the phases corresponding to the different scattering mechanisms, and then to implement these estimated phases in a conventional PSInSAR process. The major benefit of using a coherence matrix rather than a covariance matrix is to compensate the amplitude unbalances among SAR images. A detailed study of comparison among SqueeSAR, CAESAR, and PD-PSInSAR is also performed in this study. It has been found that these three methods share very similar mathematic forms with different weight values. The PD-PSInSAR method is implemented to estimate land deformation over the greater Houston area using Envisat ASAR images, which verifies that the proposed method can detect more MPs and provide better coherences.
Highlights
The traditional and novel etching methods are summarized and compared, especially fluorine-free method. The methods for accelerating exfoliation of Ti
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C
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T
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are classified.
The energy ...storage mechanisms of Ti
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in different electrolytes are compared. Based on energy storage mechanisms, the influencing factors of morphology and surface functional groups are discussed.
In response to the problems of the Ti
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, strategies for improving capacitance from structure modulation to composite structure construction are summarized and compared.
Ti
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, a novel two-dimensional layer material, is widely used as electrode materials of supercapacitor due to its good metal conductivity, redox reaction active surface, and so on. However, there are many challenges to be addressed which impede Ti
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obtaining the ideal specific capacitance, such as restacking, re-crushing, and oxidation of titanium. Recently, many advances have been proposed to enhance capacitance performance of Ti
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T
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. In this review, recent strategies for improving specific capacitance are summarized and compared, for example, film formation, surface modification, and composite method. Furthermore, in order to comprehend the mechanism of those efforts, this review analyzes the energy storage performance in different electrolytes and influencing factors. This review is expected to predict redouble research direction of Ti
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materials in supercapacitors.
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