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Landslides are considered to be a significant risk to life and property all over the world in general and in Vietnam in particular. Spatial prediction of landslides is required to reduce the landsl...

In December 2016, the first bus rapid transit (BRT) service in Vietnam was introduced in an urban area of Hanoi, the capital, with a 14.7-km route. This study empirically investigates the impacts of introducing the Hanoi BRT service on the travel behaviors of commuters using public transportation services. A quasi-experimental approach is employed with difference-in-differences and propensity score matching to identify the impacts on commuters’ travel time, acceptable walking distance to the nearest stop, and modal share of public transportation. Interviews with public transportation users were conducted to collect data in June 2018, and 501 valid responses were obtained. Respondents were asked about their travel behaviors and perceptions regarding public transportation before and after the BRT introduction. The study assumes a treatment group containing commuters currently using the BRT service and a control group containing those currently using standard bus services. The estimation results reveal that the introduction of the Hanoi BRT service had significantly positive impacts on improving travel time efficiency, increasing the acceptable walking distance to the nearest stop, and encouraging commuters to use more public transportation in their daily journeys.

We report the parameter values of the model dielectric function ( $$\varepsilon = \varepsilon_{1} + i\varepsilon_{2}$$ ) of SnS0.52Se0.48 in the spectral range from 0.74 to 6.42 eV and the temperature range from 27 to 350 K. An analytic representation, obtained using the Tauc–Lorentz (TL) dispersion model, allows interpolation of the parameters with respect to both energy and temperature. We used reported experimental spectra as the basis of our approach and verified that the TL model can parameterize the model dielectric function so as to reproduce the experimental data well and yield values of the dielectric function and the refractive index at arbitrary temperatures that are useful for device applications.

We present the principal components of the dielectric tensor for α-SnSe biaxial single crystal in the spectral range from 0.74 to 6.42 eV at room temperature (300 K) using spectroscopic ellipsometry. Aspnes’ first-order approximation method was applied to obtain approximated pseudodielectric response from the pseudodielectric tensor measured at an angle of incidence of ϕ = 68.8°. Multilayer calculations were then performed to extract the pure dielectric tensor without surface roughness artifacts. The Tauc–Lorentz model was applied to describe the critical point structures, and the optical constants along the principal axes of biaxial α-SnSe single crystal can be now calculated at arbitrary wavelength for device applications.

We report the dielectric function e = e1 + ie2 and the critical point (CP) energies of the orthorhombic SnS0.52Se0.48 alloy for the zigzag (a)and thearmchair(6) directions in the spectral energy range from 0.74 to 6.42 eV and the temperature range from 27 to 350 K using spectroscopic ellipsometry. The CP energies were determined from the 2nd derivative spectra by using the standard analytic method. We observed sharpenings and blue-shifts of the CPs with decreasing temperature. We found thirteen and twelve CPs for the a-and the b-directions, respectively, at the lowest temperature while only eight and nine CPs were detected at room temperature. Also, an exciton effect was observed only in the armchair direction at low temperatures. The temperature dependences of the CP energies were determined by fitting the data to a phenomenological expression that contain the Bose-Einstein statistical factor and the temperature coefficient to describe the electron-phonon interaction.

Here, we report parameter values for the model dielectric function (e = e1 + ie2) of the SnSxSe1−x alloy in the spectral range from 0.74 to 6.4 eV and the composition range 0 ≤; x ≤ 1 by using the Tauc-Lorentz (TL) model. The experimentally reported dielectric function data for SnSxSe1−x along the zigzag (a) and the armchair (b) directions were borrowed from a previous study for selected compositions. We successfully reproduced the asymmetric nature of the dielectric function with TL lineshapes. The e data are parameterized by using six and seven TL components for the zigzag and the armchair directions, respectively. The obtained parameters at several compositions were fit with cubic polynomials, which can be used to determine the dielectric function and the refractive index as continuous functions of the energy and the composition. Our results will be useful for optoelectronic device design based on SnSxSe1−x materials.

The GaAsxSb1−x; alloys are particularly promising materials for near-infrared light-emitting diode and detector devices. The optical properties, such as the dielectric function, complex refractive index, and absorption coefficient, are needed to properly design and understand semiconductor devices. Here, we report a method to obtain the optical properties of GaAsxSb1−x for the energy range from 1.5 to 6 eV and for an As composition from 0 to 1 at arbitrary wavelengths and compositions. The parameterization of the dielectric function of GaAsxSb1−x for specific compositions at x = 0, 0.183, 0.397, 0.528, 0.8, and 1 were realized by using the dielectric function parametric model.

In this paper, a broadband metamaterial microwave absorber is designed, simulated and measured. Differently from the traditional method which is only based on unit cell boundary conditions, we carried out full-wave finite integration simulations using full-sized configurations. Starting from an elementary unit cell structure, four kinds of coding metamaterial blocks, 2 × 2, 3 × 3, 4 × 4 and 6 × 6 blocks were optimized and then used as building blocks (meta-block) for the construction of numerous 12 × 12 topologies with a realistic size scale. We found the broadband absorption response in the frequency range 16 GHz to 33 GHz, in good agreement with the equivalent medium theory prediction and experimental observation. Considering various applications of metamaterials or metamaterial absorbers in the electromagnetic wave processing, including the radars or satellite communications, requires the frequency in the range up to 40 GHz. Our study could be useful to guide experimental work. Furthermore, compared to the straightforward approach that represents the metamaterials configurations as 12 × 12 matrices of random binary bits (0 and 1), our new approach achieves significant gains in the broadband absorption. Our method also may be applied to the full-sized structures with arbitrary dimensions, and thus provide a useful tool in the design of metamaterials with specific desired frequency ranges.

Methylmercury (MeHg) is one of the most potent neurotoxins. It is produced in nature through the methylation of inorganic divalent mercury (HgII) by phylogenetically diverse anaerobic microbes. The mechanistic understanding of the processes that govern the extent of bacterial export of MeHg, its bioaccumulation, and bio-toxicity depends on accurate quantification of its species, especially its complexation with low molecular mass thiols; organometallic complexes that are difficult to detect and measure in natural conditions. Here, we report the development of a novel analytical method based on liquid chromatography tandem mass spectrometry (LC-MS/MS) to determine 13 MeHg complexes with important thiol compounds which have been observed in the environment and in biological systems. By using online preconcentration via solid phase extraction (SPE), the method offers picomolar (12–530 pM) detection limits, the lowest reported so far for the determination of MeHg compounds. Among three different SPE materials, a weak cation exchange phase showed the best efficiency at a low pH of 2.5. We further report the presence of MeHg-cysteine, MeHg-cysteamine, MeHg-penicillamine, MeHg-cysteinylglycine, and MeHg-glutamylcysteine as the predominant MeHg–thiol complexes in the extracellular milieu of an important HgII methylating bacterium, Geobacter sulfurreducens PCA, exposed to 100 nM of HgII. Electronic supplementary material The online version of this article (10.1007/s00216-020-02389-y) contains supplementary material, which is available to authorized users.

Construction of hybrid three-dimensional (3D) hierarchical nanostructures via self-assembly of organic and inorganic compounds have recently attracted immense interest from scientists due to their unique properties and promise in a large range of applications. In this article, hybrid flower structures were successfully constructed by self-assembly an antibiotic, kanamycin, with Cu2+. The flower-like morphology was observed by scanning electron microscopy, to be approximately 4 µm in diameter and about 10 nm in thickness. FTIR spectroscopy and X-ray diffraction confirmed the antibiotic-inorganic hybrid structure was uniform composition, and showed crystallinity due to ordered self-assembly. The hybrid flowers showed high photocatalytic activity towards degradation of methyl blue during 240 minutes under visible light irradiation. A possible mechanism of photocatalytic activity was also proposed, that exposes the inherent advantages in using antibiotic-inorganic hybrid flowers as photocatalysts, where self-assembly can be used to generate active, high surface area structures for photodegradation of pollutants.

A series of microporous Zn doped Fe3O4 spheres were successfully fabricated by a simple method. The characteristic of the obtained products was studied using the X-ray diffraction (XRD), Ra...

In this work, we reported synthesis of a novel magnetically separable g-C3N4/Zn doped Fe3O4 composite (g-CN/ZnFe) by a simple polyol thermal method. The characteristics of the as-prepared composite was checked by XRD, SEM, TEM, XPS, PL technologies. The optimized weight ratio of g-C3N4 and Zn doped Fe3O4 was investigated. In addition, the photocatalytic activities of the composite products were checked by degradation of Cephalexin (CEX) under visible light. The results showed that g-CN/ZnFe composite with an added 20% g-C3N4 exhibited the highest photocatalytic activity for cephalexin under visible light irradiation. The improved photocatalytic activity of 20% g-CN/ZnFe can be ascribed to the low combination rate of photoinduced electron/hole pairs. Especially, g-CN/ZnFe can be recovered easily by using an external magnetic field and has the high stability after six runs. These properties of the g-CN/ZnFe as-prepared composite could be a promising photocatalyst for the degradation of pharmaceutical contaminants.

We report the pseudodielectric functions and the critical points of GaAsxSb1−x ternary alloy films. Data were obtained by performing spectroscopic ellipsometry on 1-μm-thick films grown on (001) GaAs by using molecular beam epitaxy. Artifacts from surface contaminants, including oxide overlayers, were minimized by using in-situ chemical cleaning, leading to accurate representations of the bulk dielectric responses of these materials. We determined the energies of the E1, E1+Δ1, E′0, E′0+Δ′0, E2, E′2, and E′1 critical points from numerically calculated second energy derivatives, as well as their compositional dependences by using lineshape fitting.

An analytic expression of the dielectric function of monolayer molybdenum disulfide (MoS2) e = e1 + ie2 is presented for energies from 1.4 to 6.0 eV and temperatures from 35 to 350 K. The dielectric function parametric model is used to express e as a sum of polynomials, which naturally includes asymmetry of critical-point lineshapes. The temperature dependence is achieved by fitting model parameters. In this way, the dielectric function of MoS2 for arbitrary temperature can be calculated. We observed the fundamental absorption peak, which occurs at the K point of the Brillouin zone. These results are expected to be useful in designing and understanding applied-device technologies based on monolayer MoS2.

We report the temperature dependence of the dielectric function ε = ε1 + iε2 and critical point (CP) energies of biaxial α-SnS in the spectral energy region from 0.74 to 6.42 eV and temperatures from 27 to 350 K using spectroscopic ellipsometry. Bulk SnS was grown by temperature gradient method. Dielectric response functions were obtained using multilayer calculations to remove artifacts due to surface roughness. We observe sharpening and blue-shifting of CPs with decreasing temperature. A strong exciton effect is detected only in the armchair direction at low temperature. New CPs are observed at low temperature that cannot be detected at room temperature. The temperature dependences of the CP energies were determined by fitting the data to the phenomenological expression that contains the Bose–Einstein statistical factor and the temperature coefficient for describing the electron–phonon interaction.

Guaranteeing safety is crucial for autonomous robotic agents. Formal methods such as model checking show great potential to provide guarantees on agent and multi-agent systems. However, as robotic agents often work in open, dynamic and unstructured environments, achieving high-fidelity environment models is non-trivial. Most verification approaches for agents focus on checking the internal reasoning logic without considering operating environments or focus on a specific type of environments such as grid-based or graph-based environments. In this paper we propose a framework to model and verify the decision making of autonomous robotic agents against assumptions on environments. The framework focuses on making a clear separation between agent modeling and environment modeling, as well as providing formalism to specify agent’s decision making and assumptions on environments. As the first demonstration of this ongoing research, we provide an example of using the framework to verify an autonomous UAV agent performing pylon inspection.

International audience; This paper proposed an efficient model predictive control strategy for a three-level T-type inverter connected to a doubly fed induction generator. A dynamic model is utilized to track the power reference, preserve the DC-link voltage balancing and reduce the inverter switching frequency and common-mode voltage. Unlike the traditional finite control set model predictive control, the stability of the closed-loop system and computational burden reduction are concurrently accomplished as the main contribution to the proposed strategy. At each sampling period, the proposed algorithm only considers the candidate control inputs which satisfy the stability condition taken from a suitable control Lyapunov function for evaluating the optimization problem. Due to model uncertainties and discrete set control input voltages, an attractivity set is employed to determine the stability and converge of the system. Therefore, the lower computation time of the optimization problem is the potential benefit compared with the conventional method. Simulation investigation with different operating conditions of a 2 MW wind turbine is carried out by MATLAB/Simulink. The achieved results confirm the stability guarantees while reducing the computational burden and obtaining the same control performances in comparison with the conventional method.

Unmanned Aerial Vehicles (UAVs) have become useful tools in industries. In this paper, we verify the behavior of an autonomous UAV executing an inspection task. More specifically, we look into the use of the knowledge base system IDP as a verification tool. We propose an approach for the modeling and verification of the safety-critical UAV and its environment in IDP. The methodology and modeling choices that are beneficial for the performance of the verification task and the readability of the model are denoted. We identify the need for discrete domains and investigate the consequences. Verification is successfully achieved using both Bounded Model Checking (BMC) and Invariant Checking (IC). ispartof: pages:315-326 ispartof: Advances in Practical Applications of Agents, Multi-Agent Systems, and Trustworthiness. The PAAMS Collection vol:12092 pages:315-326 ispartof: International Conference on Practical Applications of Agents and Multi-Agent Systems location:L'Aquila, Italy - online date:7 Oct - 9 Oct 2020 status: published

When producing a numerical control (NC) program for a 5-axis CNC machine (the so-called milling robot) to mill a sculptural surface, a constant feed rate value is usually assigned based on programmer’s experiences. For this reason, the feed rate in most of NC programs is often not optimized, it is much lower than maximum reachable value. To increase the productivity of the machining process, the feed rate in NC programs for the milling robots need to be maximized. This paper proposes a new feed rate optimization model, of which the objective function and all the kinematic constraints are transformed and expressed explicitly in a parametric domain which is commonly used in the tool path generation process performed by current CAM systems. Thus, the optimal feed rate values along a parametric tool path can be computed in an effective and simplified manner. Numerical examples demonstrate the effectiveness of the proposed method.

We report the facile synthesis of colloidal Si@Au and Si@Ag nanoparticles (NPs) through nanosecond IR laser plasma-mediated reduction of 0.03 mM aqueous solutions of chloroauric acid (HAuCl4) and silver nitrate (AgNO3) at different laser intensities on the surface of Si NPs during the ablation of the silicon wafer. The resulting hybrid colloidal NPs were analysed by UV–vis transmission spectroscopy, dynamic light scattering, scanning electron microscopy, energy-dispersive x-ray and x-ray photoelectron spectroscopy.

Natural laterite can be regarded as a strong adsorbent due to its special structure and composition. In this study, the laterite was modified by manganese oxide (MnO2) to create a new good adsorbent for treating phosphate and fluoride in water environment. Under the optimized conditions of the adsorbent dose (pH 6, temperature 20°C, and the contact time 180 min), laterite, doped manganese, with diameter of grains from 0.1 to 0.5 mm has maximum adsorption capacity of 31.25 mg/g and 10.99 mg/g for phosphate and fluoride, respectively. The characteristics of the manganese doping laterite were confirmed using various techniques like SEM, BET, XRD, EDX. The adsorption process of the material was investigated by both kinetic models (pseudo-first and second orders) and isotherm models (Freundlich and Langmuir). This new material was tested for treatment of wastewater taken from the superphosphate fertilizer factory, with the results obtained showing high potential for application in reality.

The dielectric function $${\boldsymbol{\varepsilon }}{\boldsymbol{=}}{{\boldsymbol{\varepsilon }}}_{{\bf{1}}}{\boldsymbol{+}}{\bf{i}}{{\boldsymbol{\varepsilon }}}_{{\bf{2}}}$$ ε = ε 1 + i ε 2 of monolayer molybdenum diselenide (MoSe2) is obtained and analyzed at temperatures from 31 to 300 K and at energies from 0.74 to 6.42 eV. The sample is a large-area, partially discontinuous monolayer (submonolayer) film of MoSe2 grown on a sapphire substrate by selenization of pulsed laser deposited MoO3 film. Morphological and optical characterizations verified the excellent quality of the film. The MoSe2 data were analyzed using the effective medium approximation, which treats the film and bare substrate regions as a single layer. Second derivatives of ε with respect to energy were numerically calculated and analyzed with standard lineshapes to extract accurate critical-point (CP) energies. We find only 6 CPs for monolayer MoSe2 at room temperature. At cryogenic temperatures 6 additional structures are resolved. The separations in the B- and C-excitonic peaks are also observed. All structures blue-shift and sharpen with decreasing temperature as a result of the reducing lattice constant and electron-phonon interactions. The temperature dependences of the CP energies were determined by fitting the data to the phenomenological expression that contains the Bose-Einstein statistical factor and the temperature coefficient.

Direct photoelectrochemical (PEC) water splitting using solar energy offers a potential pathway to produce a clean, renewable, and sustainable source of hydrogen fuel. Herein, the TiO2/graphene nanocomposite for PEC water splitting was prepared by a combination of the drop-cast deposition of graphene nanosheets and the sputtering deposition of TiO2 films. The surface morphology, crystalline phase, and optical properties were investigated by Scanning electron microscopy, Raman spectroscopy, and Ultraviolet–visible spectroscopy. The results showed that the thermal treatment process and the combination with graphene nanosheets could effectively enhance PEC water oxidation of TiO2 photocatalyst. This enhancement could attribute to efficient charge transfer from TiO2 to graphene and the porous graphene framework.

Microfluidic devices have been extensively applied for many applications including, but not limited to bio-chemical sensors, micro fuel cell, micro controllable lens, micro cell sorting and chapping devices and microreactors. In this study, microfluidic devices were designed, fabricated and used as a microreactor for synthesis of zero-valent iron nanosheets (ZVIns) by reducing Fe(II) ions in ethanol solution with a reducing agent. The Computational Fluid Dynamics simulation using Ansys Fluent Software was employed to study the mixing process for optimization of ZVIns synthesis conditions via microfluidic device. The prepared ZVIns was characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) mapping, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR) and magnetic measurements. The ZVIns showed a top layer of the structural flower-like ZVIns clusters with average diameter of 1 µm and a beneath layer of uniform petal-like nanosheets with the thickness of

Recently, many methods have been developed to efficiently eliminate oil spills due to its long-term harmful effects on marine life and human health. Expanded graphite (EG) has been considered as an excellent platform to remove contaminated oil from aqueous solution through a facile adsorption route. As an innovative approach, the decoration of magnetic components, namely, MnFe2O4, into graphite layers was taken into account for facilitating phase separation under magnetic field which resulted into an easy collection of the used adsorbents in a large scale. The expanded graphite/manganese ferrite composites were prepared from Vietnamese graphite flakes via a two-stage process. Characterization was performed using Scanning Electron Microscope (SEM), Fourier-Transform Infrared Spectroscopy (FTIR), X-Ray Powder Diffraction (XRD), Vibrating Sample Magnetometer (VSM), Energy-Dispersive X-ray (EDS), and nitrogen adsorption/desorption analysis. The adsorption behavior of EG-MnFe2O4 for widespread used heavy oils, including diesel oil and crude oil, was investigated under the effects of adsorption conditions, i.e., contact time, loaded oil dosage, and salinity of mixing oil and water. The obtained results showed successful incorporation of MnFe2O4 into graphite sheets and no considerable change on the worm-like structure of EG. The results also showed that incorporated manganese ferrites enhanced the magnetism EG up to 16 emu/g, which made the recovery of used adsorbent conveniently. The EG-MnFe2O4 adsorbents exhibited the strong adsorption ability toward diesel oil (32.20 &plusmn, 0.46 g DO/g EG) and crude oil (33.07 &plusmn, 0.33 g CO/g EG). In brief, EG-MnFe2O4 material provides a potential and promising platform with high performance for oil spill removal.

We numerically and experimentally investigate a broadband, polarization-independent and wide-incident-angle metamaterial perfect absorber (MPA) based on conductive polymer. By optimizing the electrical conductivity of the polymer, a 16.7 GHz broadband MPA is observed with the absorptivity greater than 80% for both transverse magnetic and electric polarization. The measurement results performed in the range 8-18 GHz show a diametrical concatenation with simulation results and theoretical analysis. The absorption mechanism is explained by demonstrating the influence of polymer conductivity on the dissipated power, the equivalent impedance, and the induced electric field. Our work may contribute to further studies on broadband MPA using for various applications.

A simple, low-cost, and environmentally friendly approach was proposed for preparing high thermal conductivity nanofluids containing graphene oxide (GO) by using the solution plasma exfoliation (SPE) technique from graphite electrode of recycled battery core. The average length and thickness of GO were determined to be and 1.5 μm and 3.3 nm corresponding to 8–10 layers, respectively. The nanofluids containing 1 vol% GO exhibited a good stability and highest thermal conductivity of 0.786 W.m−1.K−1 which is about 31% enhancement in the thermal conductivity compared to the water-based fluid. The interfacial thermal resistance (RK) and the thermal conductivity interfacial layer (ki) between GO and base fluid were found to be 56 × 10−8 m2 K W−1 and 8.5 W m−1 K−1, respectively.

We investigate analytically the anisotropic dielectric properties of single-crystal α-SnS near the fundamental absorption edge by considering atomic orbitals. Most striking is the excitonic feature in the armchair- (b-) axis direction, which is particularly prominent at low temperatures. To determine the origin of this anisotropy, we perform first-principles calculations using the GW0 Bethe–Salpeter equation including the electron–hole interaction. The results show that the anisotropic dielectric characteristics are a direct result of the natural anisotropy of p orbitals. In particular, this dominant excitonic feature originates from the py orbital at the saddle point in the Γ–Y region.

We present a simple method to achieve a multiband perfect metamaterial absorber for use in the K band by applying defects to the absorber structure. Open boundary conditions with an excitation port are used for simulation of the whole considered structure. A defect was then introduced into the structure to obtain multiband absorption. Two perfect absorption peaks were observed at 19.8 GHz and 23.1 GHz for the structure with a defect of 2 × 2 unit cells. The multiple resonance frequencies could be tuned by varying the defect dimensions. In addition, it was found that the absorber structure is insensitive to the polarization angle of the incident electromagnetic wave over a wide range due to the symmetry of the configuration. This represents a simpler method to create a multifrequency absorber compared with previous works. To the best of our knowledge, this is the first study considering the influence of structural defects on the absorption frequencies of a metamaterial absorber.

Wooden fences are applied as a nature-based solution to support mangrove restoration along mangrove coasts in general and the Mekong Delta coast in particular. The simple structure uses vertical bamboo poles as a frame to store horizontal bamboo and tree branches (brushwood). Fence resistance is quantitatively determined by the drag coefficient exerted by the fence material on the flow, however, the behaviour of drag is predictable only when the arrangement of the cylinders is homogeneous. Therefore, for more arbitrary arrangements, the Darcy&ndash, Forchheimer equations need to be considered. In this study, the law of fluid flow was applied by forcing a constant flow of water through the fence material and measuring the loss of hydraulic pressure over a fence thickness. Fences, mainly using bamboo sticks, were installed with model-scale and full-scale diameters applying two main arrangements, inhomogeneous and staggered. Our empirical findings led to several conclusions. The bulk drag coefficient ( C D &macr, ) is influenced by the flow regime represented by Reynolds number. The drag coefficient decreases with the increase of the porosity, which strongly depends on fence arrangements. Finally, the Forchheimer coefficients can be linked to the drag coefficient through a related porosity parameter at high turbulent conditions. The staggered arrangement is well-predicted by the Ergun-relations for the Darcy&ndash, Forchheimer coefficients when an inhomogeneous arrangement with equal porosity and diameter leads to a large drag and flow resistance.

To enhance the effectiveness of TiO2 as a photocatalyst, it was believed that the drawbacks of the large bandgap and the rapid electron-hole recombination can be overcome by coupling TiO2 with plasmonic metal nanoparticles. The incorporation of the nanoparticles onto the TiO2 surface requires a suitable procedure to achieve the proper particle adhesion. In this work, we propose a simple, clean, and effective surface activation of TiO2 using plasma enhanced wet chemical surface treatment. Under only 5 minutes of plasma treatment in a 3% NH3/3% H2O2 solution, gold nanoparticles were found better adhered onto the TiO2 surface. Hence, the methylene blue degradation rate of the Au/TiO2 under sunlight treated was improved by a factor of 3.25 times in comparison to non-treated Au/TiO2 and by 13 times in comparison to the bare rutile TiO2.

The complex dielectric function ɛ = ɛ1 + iɛ2 of monolayer tungsten disulfide (WS2) is investigated for the energy range from 1.5 to 6.0 eV and temperatures from 41 to 300 K. Measurements were performed under ultra-high vacuum conditions to avoid degradation and overlayer contamination. Fourteen critical-point (CP) energies were observed and their origins in Brillouin-zone were identified by band structure calculations. At low temperature the A and B excitonic peaks split into four CPs, which is understood as the neutral and charged exciton states of monolayer WS2. At low temperatures the CP energies show blue shifts with enhanced structure due to the reduction of electron-phonon interaction. The temperature dependence of these data was obtained by a phenomenological expression with Bose-Einstein statistical factor.

The use of nano-additives is widely recognized as a cheap and effective pathway to improve the performance of lubrication by minimizing the energy loss from friction and wear, especially in diesel engines. In this work, a simple and scalable protocol was proposed to fabricate a graphene additive to improve the engine lubricant oil. Graphene nanoplates (GNPs) were obtained by a one-step chemical exfoliation of natural graphite and were successfully modified with a surfactant and an organic compound to obtain a modified GNP additive, that can be facilely dispersed in lubricant oil. The GNPs and modified GNP additive were characterized using scanning electron microscopy, X-ray diffraction, atomic force microscopy, Raman spectroscopy, and Fourier-transform infrared spectroscopy. The prepared GNPs had wrinkled and crumpled structures with a diameter of 10&ndash, 30 &micro, m and a thickness of less than 15 nm. After modification, the GNP surfaces were uniformly covered with the organic compound. The addition of the modified GNP additive to the engine lubricant oil significantly enhanced the friction and antiwear performance. The highest reduction of 35% was determined for the wear scar diameter with a GNP additive concentration of approximately 0.05%. The mechanism for lubrication enhancement by graphene additives was also briefly discussed.

We report a model dielectric function, e = e1 + ie2, of MoSe2 from 1 to 6.42 eV with which the optical property of a MoSe2 monolayer can be calculated at arbitrary temperatures from 31 to 300 K for potential application for device designs based on this material. Analytic representations, performed with the dielectric-function parametric model, allow interpolation with respect to both energy and temperature. We used reported spectrum data [Park et al., Sci. Rep. 8(1), 3173 (2018)] as the basis of our approach, verifying that the parameterized model dielectric function can reproduce the experimental data at various temperatures and can also produce the dielectric function (and the refractive index) at arbitrary temperatures.

Metamaterial full-sized absorber structures are numerically and experimentally investigated in GHz region and then examined in THz frequency. By manipulating monitoring the number and the position of the defect elements in conventional unit cells, the optimal integrative absorber structures are generated. The proposed structures provide an ultra-broadband absorbance in the operating frequency. The good agreement between simulation, measurement and theoretical analysis is observed with a 5 GHz-bandwidth corresponding to the absorption of 95%. In particular, we extrapolate the concept to THz region and demonstrate that, the method can be applied to increase the bandwidth of the metamaterial absorber to 5 THz, while maintaining the other characteristics. This structure can be applied to improve the performance of telecommunication systems such as micro-antenna, micro-electromagnetic transmitters and apply to imaging and sensing fields.

Recently, deep learning and particularly, Convolutional Neural Network (CNN), has become predominant in many application fields, including visual image classification. In an applicative context of detecting areas with hazard of dengue fever, we propose a classification framework using deep neural networks on a limited dataset of images showing urban sites. For this purpose, we have to face multiple research issues: (i) small number of training data; (ii) images belonging to multiple classes; (iii) non-mutually exclusive classes. Our framework overcomes those issues by combining different techniques including data augmentation and multi-scale/region-based classification, in order to extract the most discriminative information from the data. Experiment results present our framework performance using several CNN architectures with different parameter sets, without and with transfer learning. Then, we analyze the effect of data augmentation and multiscale region based classification. Finally, we show that adding a classification weighting scheme allows the global framework to obtain more than 90% average precision for our classification task.

Polychlorinated benzenes (PCBzs) including penta- and hexachlorobenzene can be unintentionally formed from thermal processes in different industrial activities, and very little information is available on the contamination and emission characteristics of these new persistent organic pollutants from industries in Vietnam. In this study, contamination of PCBzs (including penta- and hexachlorobenzene, named PeCBz and HCB, respectively) and PCBs (including CB-28, 52, 101, 153, 138, 180) in fly ash, bottom ash and soil from combustion processes of waste incineration, metallurgy (steel making and zinc production) and cement production from several provinces in the Northern Vietnam, including Hai Duong, Hanoi, Bac Ninh, Hai Phong and Thai Nguyen, was preliminary investigated. The PCBzs concentrations in fly ash, bottom ash and soil ranged from 2.7 to 100 ng g(-1), from 2.7 to 159 ng g(-1) and from 0.28 to 33.9 ng g(-1), respectively. Relatively high residues of PeCBz in fly ash and bottom ash from municipal waste incinerators in some provinces from the Northern Vietnam were encountered. Total PCBs concentrations ranged from 18.0 to 8260 ng g(-1), from 1.0 to 10600 ng g(-1) and from 14.5 to 130 ng g(-1) for the fly ash, bottom ash and soil, respectively. Daily intakes of PeCBz, HCB and PCBs through soil ingestion and dermal exposure estimated for children ranged 0.33-9.93 (mean 3.14), 0.39-21.1 (mean 4.9) and 6.09-1530 ng/kg bw/day (mean 346), respectively; and these intakes were about 4.7-5.4 times higher than those estimated for adult. The intakes of PeCBz and HCB were relatively low, while those for PCBs exceeded WHO TDI for some samples.

In this paper we present the use of linear programming to systematically create control software for choreographed UAVs. This application requires the control of multiple UAVs where each UAV follows a predefined trajectory while simultaneously maintaining safety properties, such as keeping a safe distance between each other and geofencing. Modeling and incorporating safety requirements into the movement behavior of UAVs is the main motivation of our research. First, we describe an approach where the movement behavior of each UAV is formulated as a linear program. Second, we compare and analyze two different modeling techniques to implement the safe distance and geofencing requirements. Our approach was validated by doing experiments with Parrot Bebop UAVs. Besides being tested in the laboratory, our approach was validated in real life conditions in more than 30 performances of a dance show where five UAVs perform choreographed movements as part of the show introduction. ispartof: pages:326-335 ispartof: International Conference on Unmanned Aircraft Systems pages:326-335 ispartof: International Conference on Unmanned Aircraft Systems location:Miami, FL, USA date:13 Jun - 16 Jun 2017 status: published

Lanthanum has been doped onto the surface of the natural Pyrolusite for simultaneous removal of phosphate and fluoride in aqueous solution. The adsorbent characterization of the materials was observed by the SEM, BET, and XRD techniques. The dynamics and isotherms models of fluoride and phosphate adsorption, with respect to pH, pHPZC, adsorbent dose, and effect of coexisting ions, were studied. The results showed that lanthanum doped Pyrolusite ore (LDPO) relatively highly adsorbed amount of phosphate and fluoride from aqueous solution. Phosphate and fluoride removal efficiencies of LDPO are approximately 97% and 95%, respectively. Pseudo-first order for kinetic studies of phosphate and fluoride removal of the LDPO was observed with high correlations for fluoride but weak correlations for phosphate. However, pseudo-second order for kinetic studies was high correlation for both phosphate and fluoride. The phosphate and fluoride adsorption capacities of the LDPO significantly decreased with the existence of coions (sulfate, chloride, and nitrate) in the aqueous solution.

Trajectory planning using Mixed Integer Linear Programming (MILP) is a powerful approach because vehicle dynamics and other constraints can be taken into account. However, it is currently severely limited by poor scalability. This paper presents a new approach which improves the scalability regarding the amount of obstacles and the distance between the start and goal positions. While previous approaches hit computational limits when the problem contains tens of obstacles, our approach can handle tens of thousands of polygonal obstacles successfully on a typical consumer computer. This performance is achieved by dividing the problem into many smaller MILP subproblems using two sets of heuristics. Each subproblem models a small part of the trajectory. The subproblems are solved in sequence, gradually building the desired trajectory. The first set of heuristics generate each subproblem in a way that minimizes its difficulty, while preserving stability. The second set of heuristics select a limited amount obstacles to be modeled in each subproblem, while preserving consistency. To demonstrate that this approach can scale enough to be useful in real, complex environments, it has been tested on maps of two cities with trajectories spanning over several kilometers. ispartof: pages:1-6 ispartof: 2017 European Conference on Mobile Robots (ECMR) pages:1-6 ispartof: The European Conference on Mobile Robotics location:Paris, France date:6 Sep - 8 Sep 2017 status: published

We propose a new broadband metamaterial perfect absorber (MPA) based on structure of metallic dishes in the THz region. It demonstrated that the coupling interaction between the central dish and adjacent dishes leads to absorption characteristics. By optimizing the geometrical structure, the bandwidth is gained up to 1.0[Formula: see text]THz with absorption better than 90%. The mechanism of the absorption results was explained by induced current, magnetic and electric distributions. Furthermore, LC equivalent circuit was used to elucidate resonant frequencies. The obtained results can provide a general guideline for fabricating broadband MPA.

Hybrid plasmonic-dielectric material were fabricated by micro-discharge through water sols of sub-micrometer-sized diamonds mixed with HAuCl4 acid. Primary characterization of their deposits on a silicon wafer surface by means of electron microscopy and energy-dispersive x-ray spectroscopy indicate close proximity of gold nanoparticles and diamond particles, which is supported by photoluminescence studies demonstrating strong – almost two-fold – damping of diamond luminescence owing to the attachment of gold nanoparticles. UV-near IR spectroscopy of their sols consistently exhibits small red spectral shifts for the fabricated nanomaterial, comparing to bare gold nanoparticles.

International audience; We present a new system for video auto tagging which aims at correcting the tags provided by users for videos uploaded on the Internet. Unlike most existing systems, in our proposal, we do not use the questionable textual information nor any supervised learning system to perform a tag propagation. We propose to compare directly the visual content of the videos described by different sets of features such as Bag-Of-visual-Words or frequent patterns built from them. We then propose an original tag correction strategy based on the frequency of the tags in the visual neighborhood of the videos. Experiments on a Youtube corpus show that our method can effectively improve the existing tags and that frequent patterns are useful to construct accurate visual features.

The research on magnetic resonances in typical meta-atoms has led to the discovery of electromagnetic metamaterials (MMs). These new materials played a crucial role in achieving extraordinary phenomena as well as promised potential applications. In this paper, we numerically and experimentally investigated two different MM effects: the absorption and the negative refraction, which induced by magnetic resonances in a symmetric structure. The meta-atom sandwich model that includes two parallel flat rings separated by an insulating slab was designed. Firstly, three resonances in sub-wavelength range were demonstrated, revealing the negative permittivity and permeability effects. Notably, negative refractive index (NRI) was gained at the third-gap resonance, resulting from superposition of the rest of the electric resonance and the magnetic one accompanied by multi-plasmon. Moreover, the manipulation of the structural parameters could control the NRI behavior and, interestingly, a nearly perfect absorption peak arises in shallow sub-wavelength regime.

We present the results of research on fast relaxation dynamics in the electronic excitation of silver nanoparticles synthesized in the presence of carboxylated amine complexons (NTA, Na2EDTA, DTPA) without any reductant or polymeric stabilizer. Unusual transient absorption dynamics in these objects after femtosecond laser irradiation was found, manifesting as the appearance of an additional long-lived bleaching band. The effect may be assigned to the inhomogeneous and porous shell of silver nanoparticles synthesized by such a procedure, as the consequence of a partial fragmentation of this shell due to heating under femtosecond laser excitation of plasmonic nanoparticles and subsequent electron–phonon energy relaxation.

We present novel resonant modes at the THz regime in a structure combining conventional metamaterial absorber (MA) with a cavity (MAC). The well-known structure consisting of three individual layers of periodic metallic dishes on the top, a dielectric layer in the middle, and a metallic film in the bottom is used, and the cavity is formed on the top layer by changing the geometry of the metallic dishes. MACs with various cavity parameters are designed and their absorption characteristics, such as magnetic field distribution, surface current, and power loss density at resonant frequencies of the designed structure, are numerically investigated. Resonant effects in this work may find applications in THz tunable and broadband MA, and our investigation on the dependence of the absorption frequency and absorption intensity on the geometric cavity of the designed structure will provide a general guideline for MAC design.