Search

Hierarchical architectures consisting of two-dimensional (2D) nanostructures are of great interest for potential use in recent year. Here, we report the successful synthesis of four hierarchical tungsten oxide flower-like architectures via a simple yet facile hydrothermal method. The as-prepared WO 3 ·H 2 O hierarchical architectures are in fact assembled with numerous nanosheets or nanoplates. Through a comprehensive characterization of microstructures and morphologies of the as-prepared products, we find that petal thickness is a key factor for affecting gas-sensing performances. We further propose a possible growth mechanism for the four flower-like architectures. Moreover, gas-sensing measurements showed that the well-defined sheet-flower WO 3 ·H 2 O hierarchical architectures exhibited the excellent gas-sensing properties to ethanol owing to their largest amount of thin petal structures and pores. [ABSTRACT FROM AUTHOR]

Hollow spheres are usually fabricated by hard template methods or soft template methods with soft surfactants, which is quiet tedious and time-consuming. In this paper, NiO hollow spheres with fluffy surface were successfully synthesized by a facile hydrothermal method and subsequent calcination, where bubbles acted as the template. NiO hollow spheres exhibited excellent gas sensing performances, which results from its hollow structure and high specific surface area. In addition, a possible evolution mechanism of NiO hollow spheres was proposed based on experimental results. [ABSTRACT FROM AUTHOR]

Nanorod arrays possess a large surface area due to the orderly arrangement of monomers, and thus are considered as an ideal microstructure to be utilized in the interface-related process such as the gas-sensing reaction. But their adoption is plagued by the complicated synthesis route in which the substrate is usually necessary. Here we propose a substrate-free fabrication of WO 3 nanorod arrays through the facile hydrothermal method. Subsequent measurements testify the superior NH 3 -sensing property of WO 3 nanorod arrays. The corresponding response is as high as 8.3 at a concentration of 50 ppm and a temperature of 200 °C, surpassing other WO 3 -based NH 3 sensors reported. [ABSTRACT FROM AUTHOR]

In present work, a novel coral rock-like ZnO with porous structure was successfully synthesized via a solvothermal method and subsequent calcination. We were surprise to find that such ZnO nanostructure exhibited super high gas response to ethanol, which was attributed to the novel coral rock-like structure with porous nature, leading to effective gas diffusion and sufficient surface chemical reaction during sensing measurement. [ABSTRACT FROM AUTHOR]

NO 2 is an oxidizing gas, which is considered to be the most dangerous and most toxic gas that should be controlled. Because of the advantages of high sensitivity, selectivity, stability and fast response/recovery speed, the chemical resistance sensor is used as a NO 2 gas sensor. This article reviews the NO 2 gas sensor based on metal oxides. Firstly, the hazards of NO 2 and the major disadvantages of chemiresistive sensors based on metal oxides were discussed. Then, different sensitive materials of chemical resistance sensors were discussed, including metal oxides (MO), conductive polymers and carbon-based materials. Finally, the NO 2 gas sensors based on metal oxide (including ZnO, NiO, CuO, SnO 2 , WO 3) were discussed from the aspects of morphology, preparation method, modification, doping and composite. [ABSTRACT FROM AUTHOR]

The monodisperse hexagonal WO 3 (h-WO 3 ) nanowires were synthesized using hydrothermal treatment through the acidification of Na 2 WO 4 · 2H 2 O by addition of K 2 SO 4 and Na 2 SO 4 . The obtained products were characterized using X-ray powder diffraction, field emission scanning electron microscopy and transmission electron microscopy. It showed a high crystallinity and good dispersity of nanowire structure with the exposure of < 200 > crystal facets. Based on h-WO 3 products, thin film sensors were prepared. The gas-sensing properties to various concentrations (10, 20, 50, 100, and 200 ppm) of ethanol and formaldehyde were investigated. The h-WO3 nanowires exhibited high responses to both ethanol and formaldehyde gas. The sensor exhibited remarkably good response and fast response/recovery time, which were as short as 6–8 s. A possible reason for the influence of oxide structure on the sensing properties of thin film sensors is proposed. This work shows great potential for the preparation of 1D h-WO 3 nanostructures and their application in the detection of toxic gases. [ABSTRACT FROM AUTHOR]

Monodisperse hexagonal tungsten oxide (h-WO 3 ) nanowires were novelly prepared on a large scale by the hydrothermal method with the assistance of K 2 SO 4 and Na 2 SO 4 . The morphologies and structures of the nanowires were characterized by X-ray diffraction (XRD), focused ion beam scanning electron microscopy (FIB-SEM) and high-resolution transmission electron microscopy (TEM). These nanowires with a diameter of 80 nm and high crystallinity are especially bundles-like structure, which are growth from primary particles with same growth direction of [001] and the exposure to 〈200〉 facets. These primary nanoparticles are believed to have a crystal structure of hexagonal prism morphology. Based on the TEM characterizations and crystal structure analyses, the morphology evolvement and is given and the growth mechanism is discussed. This research is potentially applied to controlled synthesis 1D semiconductor oxides through hydrothermal route. [ABSTRACT FROM AUTHOR]

Hollow electrospun V 2 O 5 and Au/V 2 O 5 nanotubes have been successfully synthesized by combining emulsion electrospinning (EE) and post calcination treatment. Immiscible polyvinyl pyrrolidone (PVP)/metal salts/dimethylformamide (DMF) solution and polystyrene (PS)/DMF solution are chosen for the EE to form PS@(PVP/metal salts) core-sheath nanofibers, in which PS nanorods were formed and encapsulated within in the PVP/metal salts nanofibers owing to the stretching forces and de-emulsified force during the electrospinning. Excellent sensitivity and rapid response–recovery behaviors against ethanol have been successfully achieved based on our hollow ceramic (V 2 O 5 and Au/V 2 O 5 ) nanotubes. [ABSTRACT FROM AUTHOR]

Novel urchinlike hexagonal WO 3 microspheres have been fabricated by a facile hydrothermal method in the presence of K 2 SO 4 . Morphology analysis reveals that the as-synthesized WO 3 microstructures are assembled by numerous one-dimensional nanorods. Based on comparative studies, a possible formation mechanism is proposed in detail. What’s more, gas-sensing measurement indicates that the well-defined urchinelike WO 3 microspheres exhibit excellent gas sensing properties. [ABSTRACT FROM AUTHOR]

The ignition delay times of methane/air mixture diluted by N 2 and CO 2 were experimentally measured in a chemical shock tube. The experiments were performed over the temperature range of 1300–2100 K, pressure range of 0.1–1.0 MPa, equivalence ratio range of 0.5–2.0 and for the dilution coefficients of 0%, 20% and 50%. The results suggest that a linear relationship exists between the reciprocal of temperature and the logarithm of the ignition delay times. Meanwhile, with ignition temperature and pressure increasing, the measured ignition delay times of methane/air mixture are decreasing. Furthermore, an increase in the dilution coefficient of N 2 or CO 2 results in increasing ignition delays and the inhibition effect of CO 2 on methane/air mixture ignition is stronger than that of N 2 . Simulated ignition delays of methane/air mixture using three kinetic models were compared to the experimental data. Results show that GRI_3.0 mechanism gives the best prediction on ignition delays of methane/air mixture and it was selected to identify the effects of N 2 and CO 2 on ignition delays and the key elementary reactions in the ignition chemistry of methane/air mixture. Comparisons of the calculated ignition delays with the experimental data of methane/air mixture diluted by N 2 and CO 2 show excellent agreement, and sensitivity coefficients of chain branching reactions which promote mixture ignition decrease with increasing dilution coefficient of N 2 or CO 2 . [ABSTRACT FROM AUTHOR]

We study pressure and flow-rate fluctuations in microchannels, where the flow rate is supplied by a syringe pump. We demonstrate that the pressure fluctuations are induced by the flow-rate fluctuations coming from mechanical oscillations of the pump motor. Also, we provide a mathematical model of the effect of the frequency of the pump on the normalized amplitude of pressure fluctuations and introduce a dimensionless parameter incorporating pump frequency, channel geometry and mechanical properties that can be used to predict the performance of different microfluidic device configurations. The normalized amplitude of pressure fluctuations decreases as the frequency of the pump increases and the elasticity of the channel material decreases. The mathematical model is verified experimentally over a range of typical operating conditions and possible applications are discussed. [ABSTRACT FROM AUTHOR]

Because of the abnormal vasculature, most growing solid tumors contain regions that experience either acute or chronic hypoxia. However, tumor cells can maintain a high glycolytic rate even when there is enough oxygen supply. Hypoxia-inducible factors (HIFs) play crucial role in the response of tumor cells to this distinct microenvironment by shifting energy production from mitochondria towards glycolysis. In this review, we focus on the metabolism of tumor cell survival in hypoxic microenvironments. Furthermore, we also emphasize the mechanisms by which hypoxia and HIFs regulate tumor metabolism. [ABSTRACT FROM AUTHOR]

A quadratically constrained minimum dispersion (QCMD) beamformer that is robust against model uncertainties is devised for non-Gaussian signals. Different from the minimum variance based beamformers, the QCMD beamformer minimizes the \ellp-norm (p\geq 1) of the output while constraining the magnitude response of any steering vector within a spherical uncertainty set to exceed unity. A gradient projection algorithmic framework is proposed to efficiently solve the resulting convex optimization problem instead of directly applying the standard optimization algorithm which has a high computational complexity. In each iteration, the gradient projection updates the solution along the gradient direction and projects it back to the constraint set. Importantly, a closed-form expression of the projection onto the constraint set is derived, which only needs a low complexity of \cal O(M) with M being the sensor number. Therefore, the proposed algorithm is much faster and simpler to implement compared with the standard method. In addition, the robust constant modulus beamformer (RCMB) is also discussed as a special case of the QCMD beamformer. Simulation results demonstrate the efficiency of the gradient projection algorithm and superiority of the QCMD beamformer over several representative robust beamformers, indicating that it can approach the optimal performance bound. [ABSTRACT FROM PUBLISHER]

Valve-closing analysis is used to obtain the optimal valve-closing scheme in maintenance of water distribution networks, which is significant for water supply security. A new pipeline analysis model, unit-valve graph, is presented based on the traditional node-link graph model, which has much less features and concise topology. As a pseudo-dual graph of the original node-link graph, the unit-valve graph classifies the network regions isolated by valves as vertexes, and takes valves as edges. An efficient isolated unit constructing algorithm is designed based on the node-link graph, which helps to build the unit-valve graph. Further more, an efficient valve closing algorithm based on the unit-valve graph is developed. Experimental results show that the new algorithm has a remarkable advantage in terms of efficiency compared with the traditional algorithm and get a correct valve closing scheme even in the case of multi point construction. [ABSTRACT FROM AUTHOR]

This article presents an improved parallel Raster Processing Library - pRPL version 2.0. Since the release of version 1.0, a series of modifications has been made in pRPL to improve its usability, flexibility, and performance. While retaining some of the key features of pRPL, the new version has gained several new features: (1) a new Data Manager class has been added for integrated data management, and to facilitate data decomposition, assignment mapping, data distribution, Transition execution, and load-balancing; (2) a GDAL-based raster data I/ O mechanism has been added to support various geospatial raster data formats, and provide centralized and pseudo parallel I/ O modes; and (3) a static load-balancing mode and a dynamic load-balancing mode using the task-farming technique are provided. A parallel zonal statistics tool and a parallel Cellular Automata model were developed to demonstrate the usability and performance of pRPL 2.0. The experiments using the California datasets showed that the performance altered when different pRPL options (i.e. load-balancing mode, I/ O mode and writer mode) were used for different algorithms, datasets, and varying numbers of processes. [ABSTRACT FROM AUTHOR]

In this paper, methacrylated γ-PGA (mPGA) precursor was synthesized via reaction between γ-PGA and glycidyl methacrylate (GMA). Hydrogels from this precursor were prepared under 365 nm ultraviolet irradiation. The swelling behavior and mechanical properties were studied in detail as functions of the degree of substitution (DS), precursor concentration, and environmental pH. Results showed that the crosslink density, swelling kinetics and mechanical properties of the hdyrogel could be tailored by adjusting the DS and concentration of the precursor as well as the environmental pH. Three-dimensional photo-encapsulation of swine cartilage chondrocytes and Live/Dead assay proved the cytocompatibility of the hydrogel. [ABSTRACT FROM AUTHOR]

Abstract: With the increasing attentions in exploiting natural additives for food industry, the mucilage isolated from the young fronds of Asplenium australasicum (J. Sm.) Hook under diverse extraction conditions was investigated for their physicochemical properties. It was observed that the yields of the mucilage were generally raised with increasing citric acid concentration, extraction temperature and time. Chemical analysis revealed that the mucilage was composed mainly of anionic polysaccharides and proteins (4.7–20.7%), depending on the extraction conditions. Furthermore, in comparison with some commercial food hydrocolloids reported in the literatures, A. australasicum mucilage showed significant surface activity, as evidenced by a pronounced reduction (about 29–36%) on the surface tension of water and excellent emulsion stability in a model oil-in-water type emulsion. The surface tension of A. australasicum mucilage solution decreased with increasing mucilage concentration to a certain point (0.075–0.1%), but remained fairly constant as the mucilage concentration was further increased up to 0.5%. Moreover, the emulsifying activity of A. australasicum mucilage was pH and oil/water volume ratio dependent. These results suggest that the acid-extracted mucilage from the young fronds of A. australasicum is a potential natural thickener and emulsification stabilizer. [Copyright &y& Elsevier]

• The addition of Zr promotes the δ-ferrite formation in 12Cr steels, and steels with 2 wt.% Zr have a fully ferrite. • The strength decreased and the ductility increased as an increase in the Zr content. • The fine Laves phases precipitate on grain boundary in 12Cr steels with 2 wt.% Zr. The effect of Zr in the range of 0–∼1.36 wt.% on the microstructure and mechanical properties of 12Cr ferritic/martensitic steels was investigated. The steels were prepared by melting and hot rolling, then normalized at 1050 °C for 30 min and tempered at 760 °C for 90 min. The steels with 0–∼0.11 wt.% Zr had a mixture of martensite and ferrite, while the steels with ∼1.36 wt.% Zr showed fully ferrite. The area fraction of the ferrite phase in steels increases as an increase in the Zr content, which indicates that Zr is a ferrite forming alloy element in steels. The precipitates in steels with 0–∼0.11 wt.% Zr were mainly distributed along martensitic lath boundary and ferritic/martensitic interface. The coarser precipitates distributed at the ferrite/martensite interface were M 23 C 6 carbides and obey Kurdjumov-Sachs orientation relationship, namely (110) α-Fe //(111) M23C6 and [-111] α-Fe //[011] M23C6. There were two kinds of precipitates in the steels containing ∼1.36 wt.% Zr. The coarser precipitates, which distributed randomly, were Zr-rich (Fe, Zr) compounds. The Laves phases found in smaller precipitates were distributed at the grain boundary. Tensile tests showed that the strength decreased and the ductility increased as an increase in the Zr content. The steels with 0–∼0.11 wt.% Zr demonstrated a superior strength balance, of which the tensile strength and elongation at room temperature were 750–830 MPa and 19%–22%, respectively. At the elevated temperature (600 °C), the tensile strength of the steels decreased to 390–450 MPa and the elongation of steels increased to 27%–34%. [ABSTRACT FROM AUTHOR]

• Four-point bending tests on eight DSTBs with different inner steel tube shapes, PBL types and arrangements. • Slip became prominent after yielding of steel tube bottom surface. • Specimens with square steel tubes had higher load capacities than circular tubes. • Specimens with foams between PBLs had the maximum slips. Hybrid fiber-reinforced polymer (FRP)-concrete-steel double-skin tubular beams (DSTBs) have a very ductile load–deflection response but may experience a relatively large slip between the concrete and the inner steel tube. Perfobond (PBL) shear connectors, which have a perforated steel plate with transverse reinforcing bars passing through the perforations, are widely used to enhance the bond performance between the concrete and the steel section for composite beams. In this study, for the first time, PBLs are employed in hybrid DSTBs to tackle the excessive slip problem. Four-point bending tests are performed on eight hybrid DSTBs with two cross-sectional shapes of inner steel tubes, two types of PBL plates, and four different PBL arrangements. Results identify that a typical load–deflection curve consists of three segments: an initial linear segment up to the yielding of steel tube bottom surface, a hardening segment, and an almost flat load plateau segment. The slips between concrete and steel tubes increase in a faster rate when yielding occurs at steel tube bottom surface. Overall, specimens with PBLs placed along the full span have the smallest slips (around 0.2 mm), whereas maximum slips occur for specimens with foams inserted at the spacings between PBLs (i.e., 2.33 and 0.59 mm for specimens with a circular and a square steel inner tube respectively). PBL shear connectors have efficiently reduced the slip, when comparing with the results of some hybrid DSTBs in previous studies. [ABSTRACT FROM AUTHOR]

In a T-junction microdroplet generator, as monodisperse droplets are formed for the droplet digital polymerase chain reaction (PCR), a mathematical model which can describe the nonlinear relation of droplet generation under pressure-driven microfluidic flows is established. For various viscosity of the fluids, the relation between the droplet length and the driving-pressure ratio is measured at a low capillary number (Ca < 0.01) of droplet generation. It can be observed that the droplet length varies nonlinearly with the driving-pressure ratio for a specific geometry of the T-junction. In particular, the relation between the droplet length and the driving-pressure ratio is tested experimentally for different geometries of the T-junctions. At low capillary numbers, the nonlinear relation between the droplet length and the driving-pressure ratio is basically determined by the geometrical parameters of the T-junction. Most importantly, a closed-loop control droplet microfluidic system is demonstrated, and the size of the droplets can be controlled more accurately by pressure-driven flows. The control precision of the droplet size is quantitatively studied for a wide range of typical conditions of droplet generation. In particular, the relative standard deviation of the droplet size for various flow conditions is less than 2%, which is of great importance for improving the detection accuracy of nucleic acid based on the droplet digital PCR. [ABSTRACT FROM AUTHOR]

Nanoneedle-assembled hierarchical and nanosheet-assembled hierarchical NiO nanoflowers were successfully synthesized via a facile hydrothermal method and subsequent calcination. And we proposed their growth mechanisms and the influences on gas-sensing properties. The results indicated that the gas sensing properties of NiO nanocrystals can be dramatically enhanced by tailoring the nanoscale building blocks. In addition, it was surprisingly noticed that the nanoneedle-assembled hierarchical NiO structures exhibited quicker gas response and recovery than the nanosheet-assembled ones. While nanosheet-assembled hierarchical NiO nanoflowers demonstrated higher gas response towards ethanol. [ABSTRACT FROM AUTHOR]

Novel sparse-type and close-type NiO nanoflowers have been controllably synthesized via hydrothermal process assisted with CTAB and SDS, respectively. The sensing performance of the close-type NiO was superior to the other, which benefits from the following factors: In the close-type nanoflower, (1) the architecture is more porous and closer; (2) more nanojunctions between adjacent nanosheets are formed; (3) abundant micro reaction rooms are assembled by nanosheets; (4) the thickness of nanosheets are much smaller than twice Debye length. [ABSTRACT FROM AUTHOR]

Background: Artificial nerve scaffold can be used as a promising alternative to autologous nerve grafts to enhance the repair of peripheral nerve defects. However, current nerve scaffolds lack efficient microstructure and neurotrophic support. Methods: Microsphere–Scaffold composite was developed by incorporating chitosan microspheres loaded with nerve growth factor (NGF–CMSs) into collagen-chitosan scaffolds (CCH) with longitudinally oriented microchannels (NGF–CMSs/CCH). The morphological characterizations, in vitro release kinetics study, neurite outgrowth assay, and bioactivity assay were evaluated. After that, a 15-mm-long sciatic nerve gap in rats was bridged by the NGF–CMSs/CCH, CCH physically absorbed NGF (NGF/CCH), CCH or nerve autograft. 16 weeks after implantation, electrophysiology, fluoro-gold retrograde tracing, and nerve morphometry were performed. Results: The NGF–CMSs were evenly distributed throughout the longitudinally oriented microchannels of the scaffold. The NGF–CMSs/CCH was capable of sustained release of bioactive NGF within 28 days as compared with others in vitro. In vivo animal study demonstrated that the outcomes of NGF–CMSs/CCH were better than those of NGF/CCH or CCH. Conclusion: Our findings suggest that incorporation of NGF–CMSs into the CCH may be a promising tool in the repair of peripheral nerve defects. [ABSTRACT FROM AUTHOR]

Abstract: The use of detailed chemical reaction mechanisms of kerosene is still very limited in analyzing the combustion process in the combustion chamber of the aircraft engine. In this work, a new reduced chemical kinetic mechanism for fuel n-decane, which selected as a surrogate fuel for kerosene, containing 210 elemental reactions (including 92 reversible reactions and 26 irreversible reactions) and 50 species was developed, and the ignition and combustion characteristics of this fuel in both shock tube and flat-flame burner were kinetic simulated using this reduced reaction mechanism. Moreover, the computed results were validated by experimental data. The calculated values of ignition delay times at pressures of 12, 50bar and equivalence ratio is 1.0, 2.0, respectively, and the main reactants and main products mole fractions using this reduced reaction mechanism agree well with experimental data. The combustion processes in the individual flame tube of a heavy duty gas turbine combustor were simulated by coupling this reduced reaction mechanism of surrogate fuel n-decane and one step reaction mechanism of surrogate fuel C12H23 into the computational fluid dynamics software. It was found that this reduced reaction mechanism is shown clear advantages in simulating the ignition and combustion processes in the individual flame tube over the one step reaction mechanism. [Copyright &y& Elsevier]

Currently, many universities are using traditional manual way to purchase reagents and consumptive materials, which cause long procurement cycle and high procurement costs. Therefore, it is necessary to centralize procurement of reagents and consumptive materials with the help of network. From innovating traditional procurement mode and improving procurement management, using the method of centralized bidding and e-commerce procurement, we can shorten procurement cycle, reduce procurement costs, and achieve maximum benefit. The centralized procurement network of reagents and consumptive materials which according to centralized procurement management process of universities has established a management information system and centralized procurement system. The user orders online goods and setting the time and place of delivery that can reduce the cost of procurement and improve purchasing efficiency, avoid all sorts of integrity risk and also provide data for users to use reagent consumables, then the reagents and consumptive materials purchase, use and disposal can be scientific, networked and fine management. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, sub-micron porous WO3 spheres with uniform size were firstly prepared by the hydrolysis of WCl6 using carbon microspheres as templates in the hydrothermal system and the following heating treatment. The carbon template, precursor, and the final products were characterized by XRD, SEM, TEM and BET analysis. The as-prepared sub-micron porous WO3 spheres had a large diameter of about 200nm, which is critically determined by the size of carbon templates and WO3·H2O/C precursor. In addition, these porous spheres have a large porosity and exhibit high gas sensitivity to alcohol in different concentrations. The facile preparation method and the improved properties derived from the porous spheres structures are significant in the synthesis and future applications of functional nanomaterials. [Copyright &y& Elsevier]

Abstract: WO3 H2O with different morphologies were synthesized through hydrothermal method by adding different surfactants. The effect of surfactants on tailing morphology was investigated through XRD and SEM analyses in detail and the possible formation mechanism was discussed. Furthermore, the gas-sensing performances of obtained samples to ethanol were investigated. The results revealed that the WO3 H2O with the hierarchical architectures assembled by nanosheets shows the highest response to ethanol among four kinds of the nanostructures WO3. These results on the preparation, mechanism and gas sensing properties of WO3 H2O nanostructures hold great potential for the syntheses of oxide materials with novel nanostructures and their applications. [Copyright &y& Elsevier]

Abstract: We have synthesized undoped and Ti-doped SnO2 spheres with a facile yet efficient hydrothermal approach and investigated their microstructures and gas sensing response to carbon monoxide, focusing especially on the impact of Ti doping. We find that gas response of SnO2 is enhanced significantly by doping, the origin of which is clarified in light of a proposed adsorption model. Through a combination of systematic measurements with density-functional-theory calculations, we discuss the enhancement mechanism of the gas-sensing function arising from the doping. [Copyright &y& Elsevier]

To resolve the difficult problem of soft tissue segmentation of MRI images of the segmentation of the multi target region of interest in the MRI images with complex targets and fuzzy boundary, this paper proposed a novel MRI image segmentation method, based on anisotropic diffusion and spatial fuzzy C-means clustering (SFCM). It preprocessed the images using the nonlinear and anisotropic diffusion, resolving the problem of weakening the image details while removing the noise. It designed space function combining with the neighborhood space, improving traditional FCM objective function. It used the spatial information of the image to achieve the accurate classification of every object in image was an effective solution to the isolated area correctly classified. After that, it obtained complete and continuous segmented regions. Finally, it utilized the fitting curve of histogram to initialize the classification number and the initial cluster centers, accelerating the algorithm iterative to the optimal solution, and also reducing the run time. The experiments show that the possibility of find a best solution is improved by introducing the method of MRI image segmentation method based on anisotropic diffusion and spatial FCM, so as to the processing of MRI images segmentation which has overlapped grayscale, discontinuous objects and fuzzy boundary. [ABSTRACT FROM AUTHOR]

Abstract: Materials with hierarchical architectures often exhibit novel functional properties. In this paper, the hierarchical SnO2 flower-like architecture, consisting of numerous aggregative nanosheets was successfully synthesized via a facile hydrothermal method and subsequent calcination. The structures and morphologies of this hierarchical architecture were characterized in detail by means of powder X-ray diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM). Further comparative experiments show that the sodium citrate was benefit to promote the growth of SnO2 nanosheets and accelerate the assembling of nanosheets into flower-like architecture, the PEG provided nucleation sites and made the nanoflowers grow uniformly and separated. Moreover, a possible growth mechanism of the flower-like architectures was proposed. The non-trivial behavior of flower-like SnO2 may be driven by the properties of grain boundaries. [Copyright &y& Elsevier]

Monodisperse WO3·H2O square nanoplates were obtained under hydrothermal conditions with the assistance of malic acid. The morphologies and structures of the plates are characterized by the analyses of XRD, SEM and TEM. In addition, the growth mechanism of the plate-like tungsten oxides has been primarily discussed and the schematic model and crystal structure have been given out. These WO3·H2O nanoplates are revealed as orthorhombic crystal structure with exposure (010) facet. It is proved that malic acid will preferable absorb on the (010) facets during the crystal growth, leading to the growth along the crystal direction [100] and [001], and further determining the formation of plate-like WO3·H2O. This research is of great significance in the preparations, characterizations and applications of various 2D semiconductor metal oxides. [ABSTRACT FROM AUTHOR]

Abstract: We successfully synthesized variant hierarchical assembled flower-like SnO2 via a simple hydrothermal technique and subsequent calcination. The structures and morphologies of the 3D nanostructures were investigated by means of powder X-ray diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM). The formation mechanism of these materials were proposed in detail. The gas-sensing performances of the as-prepared SnO2 were investigated towards ethanol. It is noted that the flower-sheet SnO2 sensor displayed particular response to the target gas, rendering SnO2 as a potential gas-sensing material for a broad range of future sensor applications. [Copyright &y& Elsevier]

Abstract: Morphology plays an important role in the properties of nanomaterials. We successfully synthesized three new SnO2 morphologies, nanocorals, nanofragments and nanograss, via a simple hydrothermal method with surfactant additives. The final products were characterized by field-emission scanning electron microscopy and X-ray diffraction. We found that the surfactants played a critical role in the synthesis of different SnO2 nanostructures. In particular, when poly(ethylene glycol) was added as a surfactant, a unique grass-like structure was obtained. The mechanism of formation for this novel structure is discussed. The gas-sensing performance of all the products was investigated. The results show that the nanograss morphology had a superior gas response to formaldehyde than the other morphologies. [Copyright &y& Elsevier]

To improve predicting accuracy further, this paper modified original Pareto dominance relation among the candidate solutions, and proposed a new method named d-Pareto dominance prediction using nearest neighbor. Combined with the characteristics of multi-objective optimization, it described the framework of d-Pareto and the conclusion that a d-Pareto dominance prediction could obtain a lower average prediction error rate comparing with Pareto demonstrated dominance prediction. Besides, it also explored the interaction between d-Pareto dominance prediction and multi-objective evolutionary algorithms. Experiments on several classic MOPs were conducted and the simulation results show that prediction of d-Pareto dominance is feasible and effective. [ABSTRACT FROM AUTHOR]

Abstract: Direction-of-arrival (DOA) estimation is a central problem in array processing and has a variety of applications. In this paper, a new algorithm for finding DOAs of multiple temporally correlated signals is devised. The proposed approach is based on the joint diagonalization structure of a set of spatio-temporal correlation matrices. Unlike the subspace-based DOA estimators, it is not necessary to estimate the noise or signal subspace explicitly. Moreover, the proposed method can provide the spatial spectrum and estimate the DOAs even when the number of sources is not known a priori. Interestingly, it is revealed that the well-known MUSIC method is a special case of our algorithm. Simulation results validate that the developed approach is superior to conventional DOA estimators in terms of resolution capability, estimation accuracy, and robustness against array model errors. [Copyright &y& Elsevier]

For quantitative-based and relationship-based embedding methods can not resist brightness enhancement and common attacks respectively, this paper proposed a hybrid quantization and relationship color image watermarking algorithm. Firstly, it subdivided each component of the color image to non-overlapping blocks of size 8x8 and performed 1-level discrete wavelet transform (DWT) for each selected block by using a key, and then did singular value decomposition (SVD) on the low and high frequency sub-band, respectively. Finally, the biggest singular value of low and high frequency sub-band exploited quantification and relationship method to embed preprocessed watermarking, respectively. Experimental results show that the proposed algorithm has low complexity and good transparency. Compared with other algorithms, it has better robustness performance. [ABSTRACT FROM AUTHOR]

A family of algorithms, named \ell p-MUSIC, for direction-of-arrival (DOA) estimation in impulsive noise is proposed. The \ell p-MUSIC estimator adopts the \ell p-norm (1\leq p< 2) of the residual fitting error matrix as the objective function for subspace decomposition, rather than the Frobenius norm that is used in the conventional MUSIC method. Although the matrix \ell p-norm minimization based subspace decomposition will lead to a nonconvex optimization problem, two iterative algorithms are designed for achieving efficient solutions. The first algorithm is the iteratively reweighted singular value decomposition (IR-SVD), where the SVD of a reweighted data matrix is performed in each iteration. The second algorithm solves the nonconvex matrix \ell p-norm minimization by alternating convex optimization. Two complex-valued Newton's methods with optimal step size in each iteration are devised to solve the resulting convex problem. The convergence of the iterative procedure is also proved. Numerical results verify that the \ell p-MUSIC methodology outperforms the standard MUSIC scheme and several existing outlier-resistant DOA estimation approaches in terms of resolution capability and estimation accuracy. [ABSTRACT FROM PUBLISHER]

Soil polarization is a new concept which describes the deviation of soil properties of planted pure forest from its original equilibrium status toward an extreme condition due to long-term growth or continuous planting of single tree species. It is thought to be one fundamental obstacle of the development of forest. In order to investigate the effect of litter decomposition on soil polarization of planted forests in the hilly area of Loess Plateau, China, humus soil and litter (leaf litter and fine roots) were sampled in three typical coniferous forests, and 4 treatments as "soil +leaf litter" "soil + roots" "soil+ leaf litter + roots" and CK were set for laboratory incubation experiment in this research. The results showed that polarizations of different properties were variable, in both direction and degree, after the incubation with litters. Based on analyzing the polarization ratios by PCA (principal component analysis) method, the results of comprehensive soil properties is showed as follows: both of leaf litter and roots resulted in negative polarization in the Platycladus orientalis and Larix principis-rupprechtii forest soil, conversely, as for the Pinus tabulaeformis forest soil, both of leaf litter and roots resulted in positive polarization. When leaf litter and roots mixed-together with the soil, the interaction sequence is P. tabulaeformis (2.329)P. orientalis(-0.916)L. principis-rupprechtii (-1.413). In general, P. tabulaeformis litter is more beneficial for soil properties than the other two plants after incubation. [ABSTRACT FROM AUTHOR]

Abstract: NiO nanowires with high aspect ratio and dispersive distribution have been synthesized by a hydrothermal reaction of NiCl2 with Na2C2O4 and H2O in the simultaneous presence of ethylene glycol (EG) and polyethylene glycol (PEG). Then the products were obtained by the subsequent annealing at 400°C in air. The effect of –OH from EG and –O– from PEG in the formation of nanowires was discussed. And the gas sensing properties of the as-prepared NiO nanowires toward ethanol were investigated. A novel formation mechanism of nanowires was presented and the NiO nanowires were proved to have an excellent gas sensing performance. [Copyright &y& Elsevier]

Wood-leaf separation from terrestrial laser scanning (TLS) is a crucial prerequisite for quantifying many biophysical properties and understanding ecological functions. In this study, we propose a novel multi-directional collaborative convolutional neural network (MDC-Net) that takes the original 3D coordinates and useful features from prior knowledge (prior features) as input, and outputs the semantic labels of TLS point clouds. The MDC-Net contains two key units: (1) a multi-directional neighborhood construction (MDNC) unit to obtain more representative neighbors and enable directionally aware feature encoding in the subsequent local feature extraction, to mitigate occlusion effects; (2) a collaborative feature encoding (CFE) unit is introduced to incorporate useful features from prior knowledge into the network through a collaborative cross coding to enhance the discrimination for thin structures (e.g. small branches and leaf). The MDC-Net is evaluated on five plots from forests in Guangxi, China, with different branch architectures and leaf distributions. Experimental results showed that the MDC-Net achieved an OA of 0.973 and a mIoU of 0.821 and outperformed other related methods. We believe the MDC-Net would facilitate the usage of TLS in ecology studies for quantifying tree size and morphology and thus promote the development of relevant ecological applications. [ABSTRACT FROM AUTHOR]

A method for highly sensitive determination of trace antimony was proposed by using cobalt ion enhanced photochemical vapor generation (PCVG) for sample introduction into atomic fluorescence spectrometry (AFS) or inductively coupled plasma-mass spectrometry (ICP-MS) for elemental detection. During the PCVG process, the sample introduction efficiency of Sb could be significantly improved by addition of 5 mg L−1 Co2+ in the mixed acid medium of 10% (v/v) formic acid and 20% (v/v) acetic acid, with a final 12-fold and 133-fold enhancement of AFS and ICP-MS intensity, respectively. The experimental conditions including enhancement ions, acid medium, UV irradiation, working gas as well as potential interference were investigated in detail. Under the optimal experimental conditions, the limit of detection (LOD) for Sb was 0.05 and 0.001 μg L−1 by using AFS and ICP-MS determination, respectively. The method was successfully used for analysis of real water samples, with satisfactory recoveries of 92–94%. Cobalt ion enhanced photochemical vapor generation was utilized for highly sensitive determination of antimony by atomic fluorescence spectrometry and inductively coupled plasma-mass spectrometry. [Display omitted] • Cobalt ions enhanced the photochemical vapor generation (PCVG) of antimony in medium of formic acid and acetic acid. • High efficiency of PCVG ensured high detection sensitivity for Sb with atomic fluorescence spectrometry or ICP-MS. • The accuracy and utility were validated by successfully analyzing real water samples for trace antimony. [ABSTRACT FROM AUTHOR]

Based on the first-principles method of density functional theory (DFT), the adsorption properties, bond strength and electronic structure of two sulfur-containing compounds (H 2 S and CH 3 SH) in oil and natural gas were analyzed by means of adsorption energy, partial density of states (PDOS) and charge difference density. The adsorption energy of H 2 S and CH 3 SH molecules on the LB site of Fe (110) surface is the lowest. Their adsorption energies are −2.88 eV and −3.13 eV, respectively. When the H 2 S symmetry axis is perpendicular to the surface, the S–H bond is easy to break. The generated S atom is firmly adsorbed on the hollow site. The results of partial density of states show that the hybrid conjugation peaks of the three adsorbed species appear on the substrate surface, and new bonds are formed between the surface molecules and the iron substrate. The charge around the three adsorbates is redistributed, and the order of interaction size between these molecules and the Fe (110) surface is S > CH 3 SH > H 2 S. This also shows that in oil and gas, H 2 S, CH 3 SH and S atoms generated after dissociation are very easy to adsorb on the surface of iron pipes, which directly affects the accuracy of the determination of sulfide gas in oil and natural gas. • The adsorption of H 2 S and CH 3 SH on four highly symmetric sites of Fe (110) surface is calculated. • The adsorption configurations of hydrogen sulfide and methyl mercaptan on Fe (110) surface were constructed. • The adsorption structure, adsorption energy, bonding and the change of electronic structure were discussed in detail. • The H 2 S molecules adsorbed horizontally are easy to dissociate. [ABSTRACT FROM AUTHOR]

In order to acquire the hysteretic behavior of the asymmetrical composite joints with concrete-filled steel tube (CFST) columns and unequal high steel beams, 36 full-scale composite joints were designed, and the CFST hoop coefficient (ξ), axial compression ratio (n0), concrete cube compressive strength (fcuk), steel tube strength (fyk), beam, and column section size were taken as the main control parameters. Based on nonlinear constitutive models of concrete and the double broken-line stress-hardening constitutive model of steel, and by introducing the symmetric contact element and multi-point constraint (MPC), reduced-scale composite joints were simulated by ABAQUS software. By comparing with the test curves, the rationality of the modeling method was verified. The influence of various parameters on the seismic performance of the full-scale asymmetrical composite joints was investigated. The results show that with the increasing of fcuk, the peak load (Pmax) and ductility of the specimens gradually increased. With the increasing of n0, the Pmax of the specimens gradually increases firstly and then gradually decreases after reaching a peak point. The composite joints have good energy dissipation capacity and the characteristic of stiffness degradation. The oblique struts force mechanism in the full-scale asymmetrical composite joint domain is proposed. By introducing influence coefficients ( ξ 1 and ξ 2 ), the expression of shear bearing capacity of composite joints is obtained by statistical regression, which can provide theoretical support for the seismic design of asymmetrical composite joints. [ABSTRACT FROM AUTHOR]

• Precise control of the droplet size is of significant importance for the applications of droplet microfluidic systems. • In a T-junction microdroplet generator, for both low and high capillary numbers of droplet formation, the relation between the droplet length and the flow-rate ratio of the fluids is measured experimentally. • More importantly, based on the closed-loop control droplet microfluidic system, precise control of the droplet size can be achieved for both low and high capillary numbers of monodisperse droplet formation. In a T-junction microdroplet generator, the relation between the droplet length and the flow-rate ratio of the immiscible fluids is studied experimentally at both low and high capillary numbers. In particular, different geometries of the T-junctions are designed for monodisperse droplet formation, and the droplet length as a function of the flow-rate ratio is measured for various viscosity of the fluids. It is observed that there is a linear relation between the droplet length and the flow-rate ratio at a low capillary number(C a ⩽ 0.1), while the droplet length is varying nonlinearly with the flow-rate ratio at a high capillary number(0.1 ⩽ C a ⩽ 1.0). More importantly, by using the feedback control of the droplet size, a closed-loop control droplet microfluidic system is demonstrated. Especially, by choosing specific control method, good agreements are shown between the predicted and the measured droplet size for a wide range of the capillary numbers of monodisperse droplet production. [ABSTRACT FROM AUTHOR]

Unprecedented urbanization in China has directly resulted in residential vacancies, which has seriously stunted sustainable development, a part of China's new-type urbanization plan. Understanding the various types and mixes of residential vacancies is critical for the advancement of our knowledge of speculative urbanism and for devising vacancy-mitigation policies, but this issue remains insufficiently studied. Using municipal water consumption data, this study proposes a feasible and general-purpose framework for providing innovative insights into the variability in residential vacancies at the household level and the mixture of residential vacancies at the building level. This framework was applied to the city of Changshu, China, and four categories of vacant residences at the household level were identified: seasonally vacant residences, long-term vacant residences, newly built residences and occasionally vacant residences. The first category is closely related to tourism and seasonal industries, while the last three exhibit a Matthew effect. In addition to revealing significant and intensifying spatial clustering and three patterns of changes in vacancy mixtures (i.e., emergence, disappearance, and increases or decreases), the results identify particular types of vacant residences at the building level (e.g., extremely low-entropy long-term multihousehold buildings). The insights from this study can contribute to devising customized policies for alleviating residential vacancies. • The proposed framework reveals variability in and mixtures among residential vacancies using municipal water consumption. • The document representations of vacant residences are extracted based on the vacant residence corpus and Doc2Vec method. • Four categories of vacant residences at the household level are identified using the Doc2Vec and K-means++ methods. • Seasonally vacant residences are closely related to tourism and seasonal industries. • Long-term, newly built and occasionally vacant residences exhibit a Matthew effect. [ABSTRACT FROM AUTHOR]

[Display omitted] • The heat-sensitive hydrogel loaded with PRC is used to achieve the goal of multiple intratumoral treatments with one injection. • Prussian blue nanoparticles are used be nanozyme to improve the tumor hypoxic microenvironment. • Both in vitro and in vivo experiments, the PRC demonstrated excellent effects of anti-cancer combination thermoradiotherapy (PTT-RT), good stability and biocompatibility. Hypoxia in local tumors leads to the failure or resistance of radiotherapy (RT) and high-dose RT will cause systemic reactions and local radiation damage. As a non-chemotherapeutic intervention, photothermal therapy (PTT) can remove tumor tissues through thermal ablation as well as effectively improve the microenvironment of hypoxic cells. Therefore, the combined use of PTT and RT (thermoradiotherapy) has urgently become an efficient treatment. In this work, by encapsulating prussian blue (PB) nanoparticles in agarose hydrogel, we developed an injectable hybrid light-controlled hydrogel system as a PB reservoir and release controller (PRC) which can realize single injection and multiple treatments in vivo. Under the irradiation of 808 nm near-infrared (NIR) laser, PB nanoparticles convert laser energy into heat energy, causing degradation of agarose hydrogel and the release of PB nanoparticles. Due to the excellent photothermal properties of PB, photothermal treatment in the NIR Biological Windows can greatly enhance the sensitivity of tumor cells to RT. Meanwhile, PB nanoparticles can also be a nanozyme to drive the decomposition of endogenous hydrogen peroxide (H 2 O 2), and then generate oxygen (O 2) to improve the tumor hypoxic microenvironment, achieving the further enhancement of the radiation sensitivity. Notably, this study is the first design to utilize hydrogel for thermoradiotherapy. Both in vitro and in vivo experiments, the PRC demonstrated excellent effects of PTT-RT, good stability and biocompatibility, indicating our nanoplatform promote the development of anti-cancer combination thermoradiotherapy with greater clinical significance. [ABSTRACT FROM AUTHOR]

SUMMARY This paper presents the analytical layer-element method to analyze the consolidation of saturated multi-layered soils caused by a point sink by considering the anisotropy of permeability. Starting from the governing equations of the problem, the solutions of displacements and stresses for a single soil layer are obtained in the Laplace-Hankel transformed domain. Then, the analytical layer-element method is utilized to further derive the solutions for the saturated multi-layered soils in the transformed domain by combining with the boundary conditions of the soil system and continuity conditions between adjacent layers. The actual solutions in the physical domain can be acquired by the inversion of Laplace-Hankel transform. Numerical results are carried out to show the accuracy and stability of the proposed method and evaluate the influence of sink depth and anisotropic permeability on excess pore pressure and surface settlement. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Acoustic channel estimation is an important problem in various applications. Unlike many existing channel estimation techniques that need known probe or training signals, this paper develops a blind multipath channel identification algorithm. The proposed approach is based on the single-input multiple-output model and exploits the sparse multichannel structure. Three sparse representation algorithms, namely, matching pursuit, orthogonal matching pursuit, and basis pursuit, are applied to the blind sparse identification problem. Compared with the classical least squares approach to blind multichannel estimation, the proposed scheme does not require that the channel order be exactly determined and it is robust to channel order selection. Moreover, the ill-conditioning induced by the large delay spread is overcome by the sparse constraint. Simulation results for deconvolution of both underwater and room acoustic channels confirm the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

Abstract: The structural, adsorptive and electronic properties of H2 adsorption on SnO2–F (110) surface are investigated by first-principles calculation. The results show that the F-doped (110) surface is more reducible than that of undoped SnO2 surfaces, which is mainly attributed to formation of the surface states and larger charges transfer between H2 molecule and the F-doped (110) surface. This simulation mechanism may provide the instruction to further explore the SnO2-based sensing materials. [Copyright &y& Elsevier]

Abstract: New morphologies often play an important role in deciding the properties of nanomaterials. In current study, we synthesize various types of low dimensional SnO2 nanostructure materials using a simple hydrothermal process. We find that the SnO2 nanorods, nanowires and nanosheets show higher gas response as well as lower operating temperature as compared to that of nanospheres. In addition, the obtained nanosheets SnO2 are found to show best sensing performances owing to the largest surface area and porous structure providing many quick passages to absorb and desorb gas, suggesting that the gas sensing properties of nanocrystals can be significantly improved by tailoring the shape and morphology of nanocrystals. Such an unexpected morphology holds substantial promise for rendering low dimensional nano-SnO2 as a potential gas sensing material for future sensor application. [Copyright &y& Elsevier]