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A facile approach has been adopted for coating cross-linked polystyrene (PS) shells on the surface of Fe3O4 magnetic clusters using reflux-precipitation polymerization (RPP). Treating the PS shell with chlorosulfonic acid yields magnetic composite particles with acid functionality. By adjusting the amount and proportion of monomers (styrene and divinylbenzene), the obtained magnetic composite particle solid acid (MPM-5S) exhibits a saturation magnetization value of 18 emu/g, a specific surface area of 243 m2/g and an acid density of 2.113 mmol/g. The MPM-5S magnetic solid acid catalyst was evaluated for esterification of oleic acid with methanol to prepare biodiesel. Under mild conditions, the conversion of oleic acid reached 91%, which was much higher than the catalytic activity of Amberlyst-15 and close to the catalytic activity of concentrated H2SO4. The solid acid catalyst can be recovered by magnetic separation and reused three times maintaining over 95% of its initial catalytic activity. Additionally, the solid acid can be used to catalyze the dehydration of fructose to 5-hydroxymethylfurfural.

A novel multidimensional hashing scheme, named the Exclusive Grouped Spatial Hashing (EGSH), which compresses repetitive spatial data into several compact tables while retaining efficient random access, is presented. EGSH represents a multi-level hashing without any losses. Moreover, EGSH compresses a group of repetitive elements into the same entry of the hash tables, while it uses a coverage table to mark the corresponding hash tables of the compressed data. Although, prior hashing work is related to hash collisions mitigation, here a full use of these collisions is obtained and therefore the spatial data compression rate is improved. The performance of exclusive grouped spatial hashing is presented in 2D and 3D graphic examples.

The detection and sensing of trace iron(III) ions is a crucial but challenging task. Herein, we report a facile strategy to build carbazole-based copolymer latexes and films via semi-continuous emulsion copolymerization for the selective detection of iron(III) ions. Carbazole-decorated styrene–acrylic copolymer latexes were synthesized by the copolymerization of styrene, acrylates, and N-vinylcarbazole (NVCz) under mild conditions. The effects of the comonomer composition on emulsion copolymerization and the properties of the copolymer latexes/films were studied. The obtained copolymer latexes exhibit homogeneous spheres through regulating the NVCz content from 0 to 5 wt%. Notably, the copolymers exhibited the characteristic emission of carbazole in both latex and solution form, and the emission intensity can be easily tuned by varying the NVCz content. Surprisingly, higher carbazole content led to differences in the excitation and emission peaks of the latex and solution, resulting from the formation of an excimer in the latex. Moreover, the fluorescence of the latex and film can be selectively and effectively quenched by trace amounts of iron(III) ions in aqueous media. The limits of detection (LODs) of the copolymer latex and film were 1.90 and 1.71 μM, respectively. These results illustrate that the carbazole-decorated styrene–acrylic copolymer prepared employing a facile, inexpensive, scalable and environment-friendly procedure can be used to fabricate high-performance photoelectric devices and high-efficiency fluorescent sensors.

We demonstrate an environmentally friendly one-step soap-free emulsion polymerization strategy to develop fluorescent carbazole-based copolymer monodisperse microspheres for highly sensitive and selective detection of Fe3+ . The copolymer microspheres feature a stable spherical morphology with a narrow size distribution through regulating N-vinylcarbazole (NVCz) content (1.25-10.0 wt.%). Notably, the as-made microspheres exhibit a strong luminescence, tunable emission intensity and specific surface areas. Interestingly, the fluorescence of the copolymer microspheres can be selectively quenched by trace amounts of Fe3+ due to the oxidation of carbazole, and the quenching fluorescence can be facilely recovered by reduction with NaBH4 . Its excellent sensing performance is shown in terms of high sensitivity (low limit of detection, 1.3 μm), excellent selectivity, and rapid response rate, due to the porous nature of the copolymer microspheres. These results illustrate the copolymer microspheres obtained by simple preparative procedure without using expensive or toxic raw materials would serve as a high performance sensor for highly selective and recyclable detection of Fe3+ in aqueous medium.

Counting the cardinality of flows for massive high-speed traffic over sliding windows is still a challenging work under time and space constrains, but plays a key role in many network applications, such as traffic management and routing optimization in software defined network. In this paper, we propose a novel data structure (called LRU-Sketch) to address the problem. The significant contributions are as follows. 1) The proposed data structure adapts a well-known probabilistic sketch to sliding window model; 2) By using the least-recently used (LRU) replacement policy, we design a highly time-efficient algorithm for timely forgetting stale information, which takes constant (O(1)) time per time slot; 3) Moreover, a further memory-reducing schema is given at a cost of very little loss of accuracy; 4) Comprehensive experiments, performed on two real IP trace files, confirm that the proposed schema attains high accuracy and high time efficiency.

The prepared Ti:MgAl2O4 crystal samples were annealed at different temperature for 24 h in an air atmosphere, and then the transmission spectra, emission spectra, excitation spectra and photoluminescence decay curve were recorded. Furthermore, electron spin resonance of annealed samples were measured at 130 K. It is found that the absorption bands disappeared and the fluorescence intensity increased after annealed at 1200 °C. And when the annealing temperature is up to 1400 °C, the intensity of fluorescence emission was reduced significantly. These results are related to the oxidation of Ti3+ to Ti4+ and the increase of the disorder of cations. The shortening of fluorescence lifetime of the annealed samples may be related to the decrease or disappearance of oxygen vacancies.

This letter proposes a graph-based satellite handover framework for the low earth orbit (LEO) satellite communication networks. In order to maintain the connection with the communicating counterpart, the user has to switch between consecutive satellites covering the very user. A directed graph with covering period of the satellite as its node, and the link representing the possible handover between two overlapping periods, is calculated in advance, and then, the satellite handover process can be viewed as finding a path in the directed graph. By setting the link weight according to different handover criterions, the graph-based framework can support a variety of satellite handover strategies, which shows the improved flexibility over the existing research. The application of the framework to find the shortest handover path conducted on two typical LEO satellite networks, viz., Iridium and Globalstar, also corroborates the effectiveness of the proposed handover framework.

Estimating the cardinality of data streams over a sliding window is an important problem in many applications, such as network traffic monitoring, web access log analysis and database. The problem becomes more difficult in large-scale data streams when time and space complexity is taken into account. In this paper, we present a novel randomized data structure to address the problem. The significant contributions are as follows: (1) A space-efficient counter vector sketch (CVS) are proposed, which extends the well-known bitmap sketch to sliding window settings. (2) Based on the CVS, a random update mechanism is introduced, whereby a small fixed number of entries are randomly chosen from CVS in a step and then updated. This means that the update procedure just costs constant time. (3) Furthermore, estimating cardinality by CVS just needs one-pass scan of the data. (4) Finally, a theoretical analysis is given to show the accuracy of CVS-based estimators. Our comprehensive experiments confirm that the CVS-based schema attains high accuracy, and demonstate its time efficiency in comparison with the Timestamp Vector (TSV) and the auxiliary indexing method.

A dual reciprocity multiwavelet Galerkin method is developed for the solution of Poisson׳s equation in this paper, which combines the dual reciprocity boundary element method (DRBEM) and the multiwavelet Galerkin method (MGM). The DRBEM is used to transform the domain integral in the boundary element formulation of Poisson׳s equation into the boundary of the domain, which is based on compactly supported positive definite radial basis function. Then, the MGM is employed for solving the resulting boundary integral equation, in which Alpert multiwavelets are employed to construct the trial and test functions of Galerkin variational formulation. Because of the use of multiwavelets, the resulting system matrix can be approximated by a sparse matrix. Compared to the DRBEM based on radial basis functions, the present method reduces the memory spaces and computational costs of the system matrix significantly. Numerical results show the efficiency of the present method.

Real-time video stitching can build a wider field of view for surveillance, which faces a compromise between stitching speed and visual quality. A fast and robust real-time surveillance video stitching method is proposed to deal with the ghosting effect caused by moving objects and misalignments caused by background change or slight camera shift through automatic updating. By stitching key frames, parameters such as pix mapping table, stitching seams and blending weights are calculated, and most of subsequent frames are directly blended with CUDA acceleration based on the pre-calculated stitching parameters. Fast and effective algorithms are designed to detect the change of stitching seam and background during the whole stitching process, which determines whether to update the stitching seam or recalculate stitching parameters. Experiments show that this method can robustly and automatically solve the ghosting and misalignments to improve visual quality and achieve satisfactory real-time performance.

In our previous study, a series of experiments had been conducted by applying different pressure depletion rates in a 1 m long sand-pack. In this study, numerical simulation models are built to simulate the lab tests, for both gas/oil production data and pressure distribution along the sand-pack in heavy oil/methane system. Two different simulation models are used: (1) equilibrium black oil model with two sets of gas/oil relative permeability curves; (2) a four-component nonequilibrium kinetic model. Good matching results on production data are obtained by applying black oil model. However, this black oil model cannot be used to match pressure distribution along the sand-pack. This result suggests the description of foamy oil behavior by applying equilibrium black oil model is incomplete. For better characterization, a four-component nonequilibrium kinetic model is developed aiming to match production data and pressure distribution simultaneously. Two reactions are applied in the simulation to capture gas bubbles status. Good matching results for production data and pressure distribution are simultaneously obtained by considering low gas relative permeability and kinetic reactions. Simulation studies indicate that higher pressure drop rate would cause stronger foamy oil flow, but the exceed pressure drop rate could shorten lifetime of foamy oil flow. This work is the first study to match production data and pressure distribution and provides a methodology to characterize foamy oil flow behavior in porous media for a heavy oil/methane system.

Gratefulness is Chinese traditional virtue, which gives Chinese the power to go upper ,encourages Chinese to understand others, having a important meaning to cultivate personal character, perfect the life meaning. In addition to this, it is necessary to build the harmonious camp and society. However, at present as a necessary part of the students’ education in university, it is also weak. There is no delay to strengthen the gratefulness education. This dissertation aims at probing into the reasons of loss of gratitude feeling, thereafter puts forward the countermeasures for this issue.

Having gone through many generations of inheritance and development, Chinese paintings have become world′s artistic and cultural treasure. Chinese culture has influenced the world for thousands of years with its art, philosophy, technology, food, medicine and performing arts. In this article, it is discussed that painting and calligraphy is from fountain, between the traditional culture and traditional art, which impresses the soul of the Chinese traditional culture.

This paper presents a method for incremental updating on consumer electronic devices, called differential compression based on Dijkstra algorithm (DDIFF). It describes the similarities between the old and new versions as a directed weighted graph. In the graph, the shortest path between the start and end vertices corresponds to the minimal delta. As a result, the delta-encoding problem is reduced to the single-source shortest path problem. Experiments show that the proposed method is feasible, and average data transmission saving is as high as 69.3%. In comparison with the existing methods, DDIFF constructs the minimal patch, and the patch costs less time to apply1.

We explore using perfect spatial hashing to store octrees efficiently while needing no explicit parent-to-child pointers. Specifically, we design a new linkless hierarchical structure – one that encodes the absolute locations of the subdivided nodes using specific tokens and packs these nodes into hash tables using perfect hashing. Whereas prior methods have overhead in space and time due to the unused links and chain of the indirection pointers, our linkless hierarchical structure has lower storage requirements and has an efficient random accessibility on the GPUs. The performance of our scheme is demonstrated on different 2D/3D datasets together with some classical algorithms.

Pr,Yb,Ho:GYTO polycrystalline powders with various Y3+ doping concentration were synthesized by the solid-state method. Their structures were determined by the Rietveld refinement to X-ray powder diffraction. The optical spectra of Pr,Yb,Ho:GYTO polycrystalline powders were investigated by absorption and emission measurements at room temperature. With the increase of doping concentration of Y3+, the photoluminescence emission peaks related to 5I6→5I7 show a red shift from 2908 nm to 2915 nm, and a fluorescence emission with the center of 2911 nm was observed when Y3+ doping concentration is 47 at%. The 1200 nm and 2000 nm infrared emissions were also surveyed. Lifetime measurement indicates that the deactivator Pr3+ ions can efficiently decrease the lifetime of the lower level 5I7 of Ho3+. Furthermore, energy-transfer mechanism between in Y3+-Ho3+-Pr3+ was also studied and analyzed.

A series of novel near-infrared (NIR) luminescent linear copolymers, PCzLnQL2 (Cz = carbazole; Ln = Er, Nd, and Yb; Q = 8-hydroxyquinoline; L = 8-hydroxyquinoline, 5-[(carbazole-9-yl)methyl]-8-hydroxyquinoline and 2-thenoyltrifluoroacetone) covalently linked with Ln-complexes were synthesized and characterized. The obtained copolymers exhibit appropriate molecular weight, good solubility-processability and thermal stability for PLEDs application. The photophysical properties of the copolymers were studied by UV-vis absorption, steady state and transient fluorescence spectra. Monitoring the characteristic emission of the corresponding Ln3+, the copolymers show a broad excitation band extending from UV light to the region of visible light. Upon excitation with UV-vis light, the copolymers display high efficient near-infrared (NIR) luminescence of the corresponding Ln3+. Effects of N-vinylcarbazole segments and ligands on the NIR-luminescence of Ln3+ were investigated carefully. The results indicate that the NVK segments are not only used as light-harvesting groups, but also as a barrier to form a special microenvironment for the Ln-complex moieties. The three ligands can sensitize the three lanthanide ions, but the sensitized efficiency is not identical. Based on the observed luminescence phenomena and the reported energy transfer theories, the energy transfer mechanism for the NIR-luminescence of the copolymers was also investigated, which will provide a rule for designing perfect NIR-luminescence materials.

Two novel salenAlQ-complex monomers and the corresponding copolymers are synthesized and characterized by 1H NMR, 13C NMR, FT-IR spectroscopy, and elemental analysis. The properties of the copolymers are investigated by gel permeation chromatography (GPC), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), cyclic voltammetry (CV), UV–vis absorption and photoluminescence (PL) spectra. The results indicate that the copolymers exhibit appropriate molecular weight, good solubility-processability, perfect thermal stability, and improved hole-transporting performance. Particularly, since two ligands (salen and quinoline) coordinate with aluminum ions simultaneously, the copolymers exhibit exciting photoluminescence phenomenons. The solution emission is mainly salen-centered, while the solid emission is mainly quinoline-centered. In addition, the PL emission intensities, efficiencies and decay lifetimes of the copolymers are higher than those of the corresponding monomers. These results demonstrate that the incorporated NVK segments are used as multiple roles (hole-transport group, light-harvesting groups and luminescence protection) in the copolymers.