Gold nanoparticles (AuNPs) decorated CNTs are promising materials for photocatalytics and biosensors. However, the synthesis of AuNPs chemically linked to the walls of MWCNTs is challenging and toxic ...products such as thionylchloride (SOCl
) or 1-ethyl-3(dimethyl-amino) propyl carbodiimide hydrochloride (EDAC) need to be used. This work reports a new approach to prepare gold nanoparticles decorated multiwalled carbon nanotubes (MWCNTs) by using cysteaminium chloride via the formation of a Zwitterionic acide-base bond. The grafting process consists of 3 mains steps: oxidation, thiolation and decoration of AuNPs on the surface of MWCNTs. The completion of each step has been verified out by both spectroscopic (Raman, UV-Vis, FT-IR) and Scanning Electron Miscroscopy (SEM). The chemical bonding states of synthesized products have been proven by X-ray photoelectron spectroscopy (XPS).
We first present a new service network design model for freight consolidation carriers, one that selects services and routes both commodities and resources needed to support the services that ...transport them, while explicitly recognizing that there are limits on how many resources are available at each terminal. We next present a solution approach that combines column generation, meta-heuristic, and exact optimization techniques to produce high-quality solutions. We demonstrate the efficacy of the approach with an extensive computational study and benchmark its performance against both a leading commercial solver and a column generation-based heuristic.
•Investigation of drought from regional climate model.•Assess ability of multiple RCMs to reproduce drought.•Standard Precipitation Index and Mann Kendall applied.•Good performance by RCMs in ...simulating drought patterns.•Useful tool for studying future changes due to climate change.
The Standardized Precipitation Index (SPI) has been computed based on the monthly precipitation for different observed and modelled datasets over the Central Highland, Vietnam during the period 1990–2005. Station data from a total of 13 stations were collected from the study region and used for benchmarking to compare gridded observation data and two regional climate models (RCMs). Various characteristics of drought across the study region were analyzed using spatial and temporal distributions, number of drought events, their frequency and their deficit. The RCMs were able to capture the SPI temporal distributions of station data fairly well. The analysis from RCMs showed close estimation for the number of drought events to station data and gridded observations. In terms of Drought Deficit and frequency, the RCMs matched the station data better than gridded observations. The drought trend was carried out using a Modified Mann–Kendall trend test which yielded no clear trends that suggested the need for longer records of data. The results also highlight uncertainties in gridded data and the need for robust station data quality and record lengths. The regional climate models proved to be appropriate tools in assessing drought over the study area as they can serve as good proxies over data sparse regions, especially in developing countries, for studying detailed climate features at sub regional and local scales.
The main aim of this article is to establish an analytical approach on the torsional postbuckling for functionally graded graphene‐reinforced composite (FG‐GRC) laminated circular cylindrical shells ...stiffened by FG‐GRC laminated stiffener system in thermal environment and subjected to torsion loads. The polymer matrixes of shell skin and stiffeners are reinforced by graphene with two graphene reinforcement directions, namely, zigzag and armchair directions. The anisotropic smeared stiffener technique for FG‐GRC stiffener system is used, and the governing equations are established based on the Donnell shell theory with von Kármán–Donnell‐type geometrical nonlinearity and the Airy's stress function. A three‐state solution of deflection is chosen and Galerkin's method is applied, the explicit forms of critical buckling torsion and expression of load‐deflection postbuckling curves relation are obtained. The effects of graphene‐reinforced composite laminated stiffeners, uniformly distributed temperature, the volume fraction of graphene of stiffened shell on the nonlinear torsional buckling behavior are numerically investigated.
In this study, the projected drought characteristics over Vietnam for the future periods of the middle (2046–2065) and end of the 21st century (2080–2099) were investigated under the Representative ...Concentration Pathway (RCP) scenarios RCP4.5 and RCP8.5. The drought characteristics (duration, severity, intensity, inter‐arrival time, and geographic extent) were estimated based on the Palmer Drought Severity Index (PDSI). The PDSI was calculated using temperature and precipitation data from six regional climate downscaling experiments and their ensemble conducted by the Coordinated Regional Climate Downscaling Experiment‐Southeast Asia (CORDEX‐SEA) project. Projected changes of drought characteristics in the future periods were determined with respect to those in the baseline period 1986–2005. Results show biases in the regional climate model (RCM) outputs, namely an underestimation of temperature and an overestimation of precipitation, which also affect the representation of drought characteristics by overestimating the PDSI. In terms of projections, substantial increases of drought duration, severity and intensity, and decreases in the inter‐arrival time are found over the Red River Delta, northern parts of the North Central sub‐region, parts of the Central Highlands and over southern Vietnam. The droughts are projected to be more widespread under scenario RCP8.5 than RCP4.5, especially in southern Vietnam. With the increasing likelihood of droughts in Vietnam as a result of climate change, sustainable water resources management should be taken into account for agriculture, natural ecosystems and social development.
Changes of ensemble drought characteristics in the mid‐future (MF) and far‐future (FF) periods under the RCP4.5 and RCP8.5 scenarios. Left to right are the mean (1) and maximum (2) of drought duration (a, in month), drought severity (b, in %), drought intensity (c, in %), and drought inter‐arrival time (d, in month)
The stability of the tunnel face during tunneling is one of the major criteria for the design and construction of the tunnel. Collapse and blowout are two modes of tunnel face failure during the ...excavation. The cover-to-diameter ratio is one of the main parameters controlling these failure modes. Several analytical solutions have been proposed to estimate the range of support pressure applied on the tunnel face to avoid both the collapse and the blowout. However, most of those models deal with homogeneous soils. This paper aims at proposing an analytical model to predict the blowout of the tunneling face of a tunnel in multi-layered soils. The derivation is based on a limit equilibrium analysis, which considers the water tCiable. The proposed model is validated against the real blowout data reported from the tunneling in the Second Heinenoord Tunnel project in the Netherlands. Then, the maximum support pressure exerted on the tunneling face is predicted as a function of the cover-to-diameter ratio, the tunnel diameter, and the water table level for five representative soils. Finally, the model is applied to an underground segment of the Hanoi Metro Line 3 project (in Vietnam) to show the role of the multi-layer aspect.
Polymer based composites as thermal management materials have become one of the most critical components in the design of modern microelectronic devices. Strategies to improve the thermal ...conductivities of the polymer composites such as introducing thermally conductive fillers into polymer matrices have received increasing interests. However, enhancements in the thermal conductivities are still limited even at high loadings of fillers, which may be due to lack of efficient heat conduction pathways. This study presents a facile and scalable method to fabricate highly thermal conductive epoxy composites possessing continuous 3D interconnected networks, which allows excellentat thermally conductive pathways throughout the epoxy matrix. Copper nanoparticles were first coated on poly (methyl methacrylate) microbeads to form Cu@PMMA by electroless-plating to prepare thermally conductive filler. Thereafter, the filler was incorporated into an epoxy matrix at different concentrations. The thermal conductivities of the composites are improved with increasing the Cu@PMMA filler content. The composites with a filler concentration of 50 wt% achieves a thermal conductivity of 3.38 W m−1 K−1, which is over 14-folds compared to the neat epoxy. In addition, the curing temperature slightly affects the thermal conductivities at filler contents lower than 30 wt%; however, it significantly enhances the thermal conductivities at filler contents higher than 30 wt%. On the other hand, increasing the weight fraction of Cu@PMMA filler retards the volume resistivities of the composites. A reduction of 11 orders of magnitude is observed for the volume resistivity of the composite loaded with 50 wt% filler (1.9 × 104 Ω·cm) when compared to that of the pure epoxy (4.5 × 1015 Ω·cm).
In this article, the vibration and nonlinear dynamic response of imperfect advanced sandwich nanocomposite plate subjected to uniformly distributed pressure has been studied using fourth-order ...Runge-Kutta and Galerkin methods. The composites are assumed to be made of a gold layer, an auxetic layer, and a piezoelectric layer. Detailed parametric studies to evaluate the effects of the geometrical dimensions, the thickness of layers, imperfections and mechanical loads on the nonlinear dynamic response and natural frequency of advanced multilayer nanocomposite plates are discussed. The accuracy of the present results is validated by comparing with others from literature.
This study aimed to analyze the Salmonella serovars, measure the minimum inhibitory concentration of antimicrobials, and examine the antimicrobial resistance genes of Salmonella isolated from 192 ...broiler flocks in Kagoshima Prefecture in Japan, from 2013 to 2016. We found that all Salmonella isolates belonged to three serovars: Salmonella Manhattan, S. Infantis, and S. Schwarzengrund. Among them, S. Schwarzengrund prevalence has recently increased annually making the main serovar. Most recovered isolates were highly resistant to streptomycin, sulfamethoxazole, and oxytetracycline. We saw the reduction of third-generation cephalosporin resistance and identified the reason of increased kanamycin resistance to be the increased number of S. Schwazengrund isolates. Among the kanamycin-resistant Salmonella isolates, aphA1 constituted the main resistance gene detected.
The durability of concrete structures strongly depends on the water and chloride penetration in cracked concrete during its service life. This work aims at modeling the damage effect of tension ...stiffening behavior on the permeability for concrete tie specimen under tensile load by a dual lattice model, which considers hydromechanical couplings. Three concrete materials, including normal strength concrete (NSC), steel fiber reinforced concretes (SFRC), and ultra high‐performance fiber reinforced concrete (UHPFRC), are considered. The hydromechanical lattice model is based on a dual element network modeling: the water transport and the mechanical response. The fiber bridging effect is considered by means of the cohesive law of Mazars. The water flow in the damaged conduit elements is proportional to the cube of the crack width, which results from the damage variable. Experimental results available in open literature for both NSC and SFRC tie specimens are used to analyze and validate the proposed model. Considering a UHPFRC tie specimen, the model well predicted the load drops due to macrocrack occurrence, load hardening, and permeability evolution. Based on the present results, the current lattice hydromechanical model is a useful tool for predicting the service life of steel bar reinforcing concrete structure with and without steel fiber reinforcement.
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