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In situ g-C3N4@ZnO nanocomposites (with 0, 1, 3, 5, and 7 wt.% of g-C3N4 in nanocomposite) were synthesized via a one-pot hydrothermal method using precursors of urea, zinc nitrate hexahydrate, and hexamethylenetetramine. The g-C3N4@ZnO nanocomposites were characterized by X-ray diffraction, scanning electron microscope, diffuse reflectance spectroscopy, and photoluminescence spectroscopy. The photocatalyst activity of g-C3N4@ZnO nanocomposites was evaluated via methylene blue degradation experiment under visible light irradiation. The g-C3N4@ZnO nanocomposites showed an enhancement in photocatalytic activity in comparison to pure ZnO which increased with the g-C3N4 content (1, 3, 5, and 7 wt.%) in nanocomposites. The photocatalytic activity reached the highest efficiency of 96.8% when the content of g-C3N4 was 7.0 wt.%. Nanocomposite having 7.0 wt.% of g-C3N4 also showed good recyclability with degradation efficiency higher than 90% even in the 4th use. The improvement of photocatalytic activity could be attributed to the adsorption ability and effective separation of electron-hole pairs between g-C3N4 and ZnO. This work implies a simple method to in situ prepare the nanocomposite material of g-C3N4 and semiconductors oxide for photocatalyst applications with high efficiency and good recyclability.

Co-packaging of optics and electronics for data center switches has been proposed to reduce system-level power consumption by minimizing power-hungry electrical interconnects. Co-packaging optical components near high-temperature electronics, however, can diminish their performance and reliability. Moreover, limitations of the switch environment, such as restricted footprint, power, and number of fiber attachments can limit practical co-packaging implementations. Here, we study four architectures for co-packaged optical interfaces using either single- or multi-wavelength light sources that can be either external to or integrated with the optical interfaces. We model the temperature- and current-dependent performance and reliability of the sources and calculate the link budget for switch bandwidths up to 102.4 Tb/s. We compare architectures based on coherent and direct detection and find that all coherent detection architectures support 102.4 Tb/s switching with over 13 dB link budget, while most direct detection architectures scale to 51.2 Tb/s or 102.4 Tb/s switching with link budgets less than 5 dB. In addition, we demonstrate that external-source architectures require wavelength-division multiplexing at lower switch bandwidths and consequently have link budgets 1-5 dB lower than integrated source architectures. Further, we demonstrate that higher-power lasers can scale external architectures to 102.4 Tb/s switching with over 4 dB link budgets. Finally, for 51.2 Tb/s switching, we show that a reduction in integrated source temperature improves link budgets by 2-4 dB and direct detection external-source architectures can achieve greater than 5 dB link budget with fewer than 300 fiber attachments.

In this study, a weight-control bender element system has been developed to investigate the impact of matric suction equalization on the measurement of small strain shear modulus (Gmax) during an air-drying process. The setup employed is capable of measuring the shear wave velocity and the corresponding Gmax of the soil sample in either an open system in which the soil sample evaporates freely or in a closed system that allows the process of matric suction equalization. The comparison between measurements of Gmax in the open and closed systems revealed underestimations of Gmax when matric suction equalization was ignored due to the nonuniform distribution of water content across the sample cross-sectional area. This study also investigated the time required for matric suction equalization tse to be established for samples with different sizes. The experimental results indicated two main mechanisms driving the matric suction equalization in a closed system during an air-drying process, namely the hydraulic flow of water and the flow of vapour. While the former played the key role when the micropores were still saturated at the high range of water content, effects of the latter increased and finally dominated when more air invaded the micropores at lower water contents.

We introduce a graphene-based nanofluidic cell that facilitates in-situ imaging of liquid samples via transmission electron microscopy. The cell combines the benefits of graphene liquid cells – nam...

The photocatalytic activity of the ZnO NRs/CuO composite film was investigated by using both experimental and numerical methods. The ZnO NRs/CuO composite film exhibits significantly enlarge absorption range to visible-light and suppress the recombination rate of the photogenerated electron-hole pairs, which can be well utilized as a photocatalyst. The ZnO NRs/CuO composite film also presents good stability, and reusability, and durability for photo-decomposition purpose. The optimal ZnO NRs/CuO composite film contains 1μ-thick of CuO film and 10 nm-thick of ZnO NRs film. The donor concentration in ZnO NRs film should be lower than 1016 cm−3. The short circuit current density of the optimal composite film is 25.8 mA/cm2 resulting in the calculated pseudo-order rate constant of 1.85 s−1. The enhancement in degradation efficiency of this composite film is attributed to the inner electric field and large effective surface area of ZnO NRs film.

The paper discusses the main disadvantages of strip and underground mining methods and possibilities of eliminating the disadvantages through introducing a combined technology of coal deposit mining. Combined coal mining technology is the method comprising elements of several geotechnologies, for example, underground and strip mining, as well as, possibly, underwater mining, borehole and other techniques of deposit mining. The combined coal mining technology provides for unified layout for opening, development, production and processing of reserves for the whole LoM on the basis of general technological solutions made in advance. Such complex solutions for opening and development of deposit reserves within the opencast and underground mining contour allows minimizing the volume of openings and reducing the time for commissioning, investment costs, as well as decreasing the costs for aerage, drainage, rock mass hauling and land reclamation. Substantiation of deposit opening options should comprehensively take into account technical, organizational, and economic factors [34–37]. Analysis of the options as exemplified by the Makar’evskoe coal deposit development in Kuzbass allows to conclude that the combined method is promising and promotes increasing optimal volumes of coal production, while reducing the deposit development time by about 15 %, and increase the net present value compared to underground and opencast mining options more than 5 times.

Published in IFAC-PapersOnLine, 54(11):55-60, 2021; International audience; The problem of reducing vibrations during continuous hot-dip galvanizing process is addressed. Using the finite difference method the concerned part of the steel production line is modeled by a state space version of the axially moving strip equation which takes into account disturbances that may affect its efficient functioning. The synthesis of an appropriate control law for this process aims to reduce the impact of these disturbances and its implementation requires a definition of the position and the number of the sensor/actuator allowing an optimal reduction. Some numerical simulation of the steel strip behavior are presented and discussed for different sources of vibrations with and without a control system.

Rock burst represents a very dangerous phenomenon in deep underground mining, as well as for underground structures in unfavourable conditions (great depth, high horizontal stress, proximity of major tectonic structures, etc.). The rock burst problem relates to the natural and mining conditions of the rock mass. The evaluation of rock burst is becoming increasingly important as mining activities reach greater depths. In the literature, rock burst assessment challenge was tackled by many researchers using various methods. However, no study providing review and comparison of different rock burst assessment methods is available. In this paper, rock burst classification is briefly summarized. This includes a classification based on rock burst type, and another classification based on rock burst severity. As an important method for rock burst prevention, some novel energy-absorbing bolts were developed. These bolts demonstrate constant resistance under both static and shock loads and large elongation ability enabling them to withstand large deformations of rock masses under rock burst-prone conditions. Among the novel energy absorbing bolts, Modified Cone Bolt (MCB) and Constant Resistance at Large Deformation (CRLD) Bolt are selected to be presented in this paper.

The present article proposes an efficient method for damage assessment of structures with incomplete and noisy modal data using model reduction method and Lightning Attachment Procedure Opt...

Mineral demand rapidly increases; as a result, underground mining activities gradually dig into the earth’s crust to deeper levels. For instance, the depth of coal mines has reached 1500 m, whereas the depth of mines for nonferrous metals has already achieved around 4500 m. Deep mining faces a number of technical and environmental challenges, first of all, great rock mass stresses, high temperature and long winding distance. The traditional technologies are hardly capable to provide the development and extraction efficiency and safety. That is why the need in developing and implementation of new modern mining technologies arose. In roadheading, TBM (tunnelboring machine) method is gradually introduced. A TBM combines the functions of rock breaking, support installation, mucking and conveying rock. In mining industry, smart mining based on mechanized and automated mining methods is successfully implemented at coal mines. Besides, a technical concept of fluidized mining for deepseated mineral resources (6000 m and more) was proposed. This paper presents the review of the current global status of deep mining and highlights some of the newest technological achievements in roadheading and the mineral extraction processes.

We present here an effective scheme for image denoising based on total variation regularization. The proposed scheme allows to efficiently remove Poisson noise as well as Gaussian noise simultaneously with the help of a new kind of data fidelity term, suitable for the mixed Poisson - Gaussian noise model. The results show that the algorithm corresponding to our new scheme outperforms the existing methods for mixed Poisson - Gaussian noise removal.

The exploration of new catalysts for the vapor-liquid-solid (VLS) synthesis of one-dimensional (1-D) materials promises to yield new morphologies and functionality. Here, we show, for the model ZnO system, that this possible using a semiconductor (Ge) catalyst. In particular, two unusual morphologies are described: twisted nanowires and twisted nanotubes, in addition to the usual straight nanowires. The twisted nanotubes show large hollow cores and surprisingly high twisting rates (up to 9o/{\mu}m), which cannot be easily explained through the Eshelby twist model. A combination of ex situ and in situ transmission electron microscopy measurements suggest that the hollow core results from a competition between growth and etching at the Ge-ZnO interface during synthesis. The twisting rate is consistent with a softening of elastic rigidity. These results indicate that the use of unconventional, nonmetallic catalysts provide opportunities to synthesize unusual oxide structures with potentially useful properties., Comment: 27 pages, 5 figures

The Earth Surface Mineral Dust Source Investigation, EMIT, is planned to operate from the International Space Station starting no earlier than the fall of 2021. EMIT will use visible to short wavelength infrared imaging spectroscopy to determine the mineral composition of the arid land dust source regions of the Earth to advance our knowledge of the radiative forcing effect of these aerosols. Mineral dust emitted into the atmosphere under high wind conditions is an element of the Earth system with many impacts to the Earth’s energy balance, atmosphere, surface, and oceans. The Earth’s mineral dust cycle with source, transport, and deposition phases are studied with advanced Earth System Models. Because the chemical composition, optical and surface properties of soil particles vary strongly with the mineral composition of the source, these models require knowledge of surface soil mineral dust source composition to accurately understand dust impacts on the Earth system now and in the future. At present, compositional knowledge of the Earth’s mineral dust source regions from existing data sets is uncertain as a result of limited measurements. EMIT will use spectroscopically-derived surface mineral composition to update the prescribed boundary conditions for state-of-the-art Earth System Models. The EMIT-initialized models will be used to investigate the impact of direct radiative forcing in the Earth system that depends strongly on the composition of the mineral dust aerosols emitted into the atmosphere. These new measurements and related products will be used to address the EMIT science objectives and made available to the science community for additional investigations. An overview of the EMIT science, development, and mission is presented in this paper.

Fill compaction in the construction of Geosynthetic Reinforced Soil (GRS) mass is typically performed by operating a vibratory or roller compactor, which in turns imposed a compaction load in direction perpendicular to the wall face. The compaction process resulted in the development of the so-called compaction-induced stress (CIS), which may subsequently increase the stiffness and strength of the fill material. Compaction process is normally simulated using one of the following compaction procedures&mdash, (i) a uniformly distributed load acting on the top surface of each soil lift, (ii) a uniformly distributed load acting on the top and bottom surface of each soil lift, and (iii) a moving strip load with different width. Uncertainties such as compaction procedures, compaction and surcharge loads led to the disparity in studying the mechanism of GRS mass. This paper aimed to study the impact of compaction load, compaction procedure, surcharge load and CIS on the stress-deformation behavior of GRS mass via the simulation of a 2 m high Soil Geosynthetic Composite (SGC) mass and a 6 m high GRS mass. The results were examined in terms of reinforcement strains, wall lateral displacements, and net CIS. Results from the analysis show the important impacts of compaction conditions on the stress-deformation behavior of SGC mass and the CIS.

The atomic structure at the interface between two-dimensional (2D) and three-dimensional (3D) materials influences properties such as contact resistance, photo-response, and high-frequency electrical performance. Moir\'e engineering is yet to be utilized for tailoring this 2D/3D interface, despite its success in enabling correlated physics at 2D/2D interfaces. Using epitaxially aligned MoS2/Au{111} as a model system, we demonstrate the use of advanced scanning transmission electron microscopy (STEM) combined with a geometric convolution technique in imaging the crystallographic 32 A moir\'e pattern at the 2D/3D interface. This moir\'e period is often hidden in conventional electron microscopy, where the Au structure is seen in projection. We show, via ab initio electronic structure calculations, that charge density is modulated according to the moir\'e period, illustrating the potential for (opto-)electronic moir\'e engineering at the 2D/3D interface. Our work presents a general pathway to directly image periodic modulation at interfaces using this combination of emerging microscopy techniques., Comment: 14 pages and 5 figures

The effects of ambient humidity and temperature on the NO2 sensing characteristics of WS2/graphene aerogel (WS2/GA) composite are investigated. In order to probe the gas sensing performances of WS2/GA, the sensor is fabricated by integrating WS2/GA with a microfabricated two-electrode device. The WS2/GA is characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and nitrogen porosimetry. This hybrid nanomaterial is found to improve the selectivity to NO2, compared to control graphene and WS2 aerogels. The NO2 sensing performance of the WS2/GA-based sensors is investigated under different relative humidities (0–60%), and ambient temperatures (room temperature (RT) to 180 °C). In all cases, the sensors exhibit p-type behavior. In dry atmosphere, faster response and better recovery are obtained with increasing temperature, reaching optimum sensing performance around 180 °C. At room temperature, interestingly, humidity is found helpful for enhancing the response and recovery of the sensor to NO2. Detection limits in the range of 10–15 ppb NO2 were determined. A possible gas sensing mechanism for this composite aerogel is proposed.

International audience; This article presents a new configuration for multiphase induction-heating (IH) systems and their control schemes. Instead of using separate voltage inverters to supply the required current to the inductors in each phase, we specifically configured the inverters to reduce the number of power switches. A modification of the inverter-setting parameters ensured the proper operation of the system. We obtained the best references through a specific optimization procedure and tested several solutions for neutral current minimization, including a new arrangement of the coils. In addition, proportional-resonant (PR) controllers allowed us to achieve current control in the different phases. We developed the application on a reduced-power, three-phase coupled resonant test bench, which provided simulation and experimental results.

The gas sensing characteristics of porous tungsten disulfide (WS 2 ) aerogel are investigated. The sensor is fabricated by integrating WS 2 aerogel onto a low power polycrystalline silicon microheater platform to provide control over the operating temperature. The WS 2 aerogel is characterized by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and thermal gravimetric analysis. The sensing performances of the WS 2 aerogel-based sensor to NO 2 , O 2 , NH 3 , H 2 , and humidity are investigated, indicating a p-type behavior. The optimum sensing temperature is found to be about 250 °C, when considering sensitivity, power consumption and response time. The role of O 2 in the sensor performance is probed and is found to be helpful for enhancing the sensitivity and recovery of the sensor in H 2 , humidity and NH 3 .

This paper presents a new analytical expression intended to accurately evaluate the leakage inductance of transformers in the step-up DC-DC conveter in the high frequency range in which the behavior of the magnetic field within the windings is altered. Unlike conventional expressions, which usually overestimate the leakage inductance at higher frequencies, this expression accounts for high frequency behavior of the magnetic field and provides high accuracy when operating at high frequencies. These high accuracy and applicability makes the derived expression of interest for designers to avoid time consuming finite element simulations without compromising with accuracy. The expression is validated by 2-D FEMM simulation, as well as by measurement.

A simple and versatile strategy is presented for the localized on-chip synthesis of an ordered metal oxide hollow sphere array directly on a low power microheater platform to form a closely integrated miniaturized gas sensor. Selective microheater surface modification through fluorinated monolayer self-assembly and its subsequent microheater-induced thermal decomposition enables the position-controlled deposition of an ordered two-dimensional colloidal sphere array, which serves as a sacrificial template for metal oxide growth via homogeneous chemical precipitation; this strategy ensures control in both the morphology and placement of the sensing material on only the active heated area of the microheater platform, providing a major advantage over other methods of presynthesized nanomaterial integration via suspension coating or printing. A fabricated tin oxide hollow sphere-based sensor shows high sensitivity (6.5 ppb detection limit) and selectivity toward formaldehyde, and extremely fast response (1.8 s) and recovery (5.4 s) times. This flexible and scalable method can be used to fabricate high performance miniaturized gas sensors with a variety of hollow nanostructured metal oxides for a range of applications, including combining multiple metal oxides for superior sensitivity and tunable selectivity.

This study reported a hierarchically ordered porous Ni-based cathode of a solid oxide electrolysis cell to realise stable CO2 electrolysis without the need of safe gas. The Ni/(Y2O3)0.08(ZrO2)0.92 (YSZ) cathode support has a microchannel structure, which enabled efficient catalyst delivery to the reaction zone between the cathode and the electrolyte and resulted in facilitated gas diffusion through straight channels instead of the tortuous pores intrinsic to conventional porous electrodes. A catalyst network covering a Ni/YSZ scaffold reduced electrode polarisation resistance, prevented carbon formation and suppressed Ni oxidation. The facilitated gas diffusion diminished or eliminated concentration polarisation and carbon formation due to CO accumulation in the reaction zone. The novel hierarchical structure enables stable CO2 electrolysis over conventional Ni-based cathodes with low capital and operational costs.

Organic-inorganic halide perovskite materials have emerged as attractive alternatives to conventional solar cell building blocks. Their high light absorption coefficients and long diffusion lengths suggest high power conversion efficiencies, and indeed perovskite-based single bandgap and tandem solar cell designs have yielded impressive performances. One approach to further enhance solar spectrum utilization is the graded bandgap, but this has not been previously achieved for perovskites. In this study, we demonstrate graded bandgap perovskite solar cells with steady-state conversion efficiencies averaging 18.4%, with a best of 21.7%, all without reflective coatings. An analysis of the experimental data yields high fill factors of ∼75% and high short-circuit current densities up to 42.1 mA cm

The main objective of this study is to develop and compare hybrid Artificial Intelligence (AI) approaches, namely Adaptive Network-based Fuzzy Inference System (ANFIS) optimized by Genetic Algorithm (GAANFIS) and Particle Swarm Optimization (PSOANFIS) and Support Vector Machine (SVM) for predicting the Marshall Stability (MS) of Stone Matrix Asphalt (SMA) materials. Other important properties of the SMA, namely Marshall Flow (MF) and Marshall Quotient (MQ) were also predicted using the best model found. With that goal, the SMA samples were fabricated in a local laboratory and used to generate datasets for the modeling. The considered input parameters were coarse and fine aggregates, bitumen content and cellulose. The predicted targets were Marshall Parameters such as MS, MF and MQ. Models performance assessment was evaluated thanks to criteria such as Root Mean Squared Error (RMSE), Mean Absolute Error (MAE) and correlation coefficient (R). A Monte Carlo approach with 1000 simulations was used to deduce the statistical results to assess the performance of the three proposed AI models. The results showed that the SVM is the best predictor regarding the converged statistical criteria and probability density functions of RMSE, MAE and R. The results of this study represent a contribution towards the selection of a suitable AI approach to quickly and accurately determine the Marshall Parameters of SMA mixtures.

The quasi-one-dimensional linear chain compound HfTe3 is experimentally and theoretically explored in the few- to single-chain limit. Confining the material within the hollow core of carbon nanotubes allows isolation of the chains and prevents the rapid oxidation which plagues even bulk HfTe3. High-resolution transmission electron microscopy combined with density functional theory calculations reveals that, once the triple-chain limit is reached, the normally parallel chains spiral about each other, and simultaneously a short-wavelength trigonal anti-prismatic rocking distortion occurs that opens a significant energy gap. This results in a size-driven metal-insulator transition., Comment: 20 pages, 9 images

We present a neural pipeline approach that performs named entity recognition (NER) and concept indexing (CI), which links them to concept unique identifiers (CUIs) in a knowledge base, for the PharmaCoNER shared task on pharmaceutical drugs and chemical entities. We proposed a neural NER model that captures the surrounding semantic information of a given sequence by capturing the forward- and backward-context of bidirectional LSTM (Bi-LSTM) output of a target span using contextual span representation-based exhaustive approach. The NER model enumerates all possible spans as potential entity mentions and classify them into entity types or no entity with deep neural networks. For representing span, we compare several different neural network architectures and their ensembling for the NER model. We then perform dictionary matching for CI and, if there is no matching, we further compute similarity scores between a mention and CUIs using entity embeddings to assign the CUI with the highest score to the mention. We evaluate our approach on the two sub-tasks in the shared task. Among the five submitted runs, the best run for each sub-task achieved the F-score of 86.76% on Sub-task 1 (NER) and the F-score of 79.97% (strict) on Sub-task 2 (CI).

A MoS2/graphene hybrid aerogel synthesized with two-dimensional MoS2 sheets coating a high surface area graphene aerogel scaffold is characterized and used for ultrasensitive NO2 detection. The combination of graphene and MoS2 leads to improved sensing properties with the graphene scaffold providing high specific surface area and high electrical and thermal conductivity and the single to few-layer MoS2 sheets providing high sensitivity and selectivity to NO2. The hybrid aerogel is integrated onto a low-power microheater platform to probe the gas sensing performance. At room temperature, the sensor exhibits an ultralow detection limit of 50 ppb NO2. By heating the material to 200 °C, the response and recovery times to reach 90% of the final signal decrease to

© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. A high-surface-area, highly crystalline boron nitride aerogel synthesized with nonhazardous reactants has been loaded with crystalline platinum nanoparticles to form a novel nanomaterial that exhibits many advantages for use in a catalytic gas sensing application. The platinum nanoparticle-loaded boron nitride aerogel integrated onto a microheater platform allows for calorimetric propane detection. The boron nitride aerogel exhibits thermal stability up to 900°C and supports disperse platinum nanoparticles, with no sintering observed after 24 h of high-temperature testing. The high thermal conductivity and low density of the boron nitride aerogel result in an order of magnitude faster response and recovery times (

Stone Mastic Asphalt (SMA) is a tough, stable, rut-resistant mixture that takes advantage of the stone-to-stone contact to provide strength and durability for the material. Besides, the warm mix asphalt (WMA) technology allows reducing emissions and energy consumption by reducing the production temperature by 30–50 °C, compared to conventional hot mix asphalt technology (HMA). The dynamic modulus |E*| has been acknowledged as a vital material property in the mechanistic-empirical design and analysis and further reflects the strains and displacements of such layered pavement structures. The objective of this study is twofold, aiming at favoring the potential use of SMA with WMA technique. To this aim, first, laboratory tests were conducted to compare the performance of SMA and HMA through the dynamic modulus. Second, an advanced hybrid artificial intelligence technique to accurately predict the dynamic modulus of asphalt mixtures was developed. This hybrid model (ANN-TLBO) was based on an Artificial Neural Network (ANN) algorithm and Teaching Learning Based Optimization (TLBO) technique. A database containing the as-obtained experimental tests (96 data) was used for the development and assessment of the ANN-TLBO model. The experimental results showed that SMA mixtures exhibited higher values of the dynamic modulus |E*| than HMA, and the WMA technology increased the dynamic modulus values compared with the hot technology. Furthermore, the proposed hybrid algorithm could successfully predict the dynamic modulus with remarkable values of R2 of 0.989 and 0.985 for the training and testing datasets, respectively. Lastly, the effects of temperature and frequency on the dynamic modulus were evaluated and discussed.

Controlling the size and shape of nanopores in two-dimensional materials is a key challenge in applications such as DNA sequencing, sieving, and quantum emission in artificial atoms. We here experimentally and theoretically investigate triangular vacancies in (unconventional) Bernal-stacked AB-h-BN formed using a high-energy electron beam. Due to the geometric configuration of AB-h-BN, triangular pores in different layers are aligned, and their sizes are controlled by the duration of the electron irradiation. Interlayer covalent bonding at the vacancy edge is not favored, as opposed to what occurs in the more common AA′-stacked BN. A variety of monolayer, concentric, and bilayer pores in the bilayer AB-h-BN are observed in high-resolution transmission electron microscopy and characterized using ab initio simulations. Bilayer pores in AB-h-BN are commonly formed and grow without breaking the bilayer character. Nanopores in AB-h-BN exhibit a wide range of electronic properties, ranging from half-metallic to non-magnetic and magnetic semiconductors. Therefore, because of the controllability of the pore size, the electronic structure is also highly controllable in these systems and can potentially be tuned for particular applications.

Problems in surrounding rock displacement, roadway deformation and complex support are the hallmarks of the long wall mining system. Such problems seriously affect the safety and efficient production of coal mines. To control the deformation of the rocks around the roadway next to the goaf, to reduce the support pressure, in Vietnamese underground mines often leave supporting coal pillars. Identification of a reasonable design for roadway supporting pillars by a numerical simulation study was conducted under the geological and technical foundation of I-10- 2 working faces at the Khe Cham coal mine, Vietnam . The characteristics of stress and pressure distribution of roof layers on coal pillars are modeled under different pillar widths. The results show a great linear increase of the vertical stress on the narrow coal pillar and as the width of the coal pillar increases, the area of the elastic core area also increases and the level of stress increase tends to be stable without any apparent uptrend. Coal pillar deformation decreases with increasing coal pillar width, but it leads to large coal loss and waste of resources. Therefore, with the current supporting solutions to increase the stability of the coal pillar, the size range of a coal pillar is determined to be 6-8 m through numerical simulation. The conclusions obtained may provide a certain reference number to choose the logical location of the furnace lines under similar geological conditions.

We demonstrate the fabrication of individual nanopores in hexagonal boron nitride (h-BN) with atomically precise control of the pore shape and size. Previous methods of pore production in other 2D materials typically create pores with irregular geometry and imprecise diameters. In contrast, other studies have shown that with careful control of electron irradiation, defects in h-BN grow with pristine zig-zag edges at quantized triangular sizes, but they have failed to demonstrate production and control of isolated defects. In this work, we combine these techniques to yield a method in which we can create individual size-quantized triangular nanopores through an h-BN sheet. The pores are created using the electron beam of a conventional transmission electron microscope; which can strip away multiple layers of h-BN exposing single-layer regions, introduce single vacancies, and preferentially grow vacancies only in the single-layer region. We further demonstrate how the geometry of these pores can be altered beyond triangular by changing beam conditions. Precisely size- and geometry-tuned nanopores could find application in molecular sensing, DNA sequencing, water desalination, and molecular separation.

We report on bottom-up synthesis of graphene nanoribbons inside boron nitride nanotubes, using coronene molecules as building blocks. The synthesized ribbons are one or two coronene molecules wide, ...

We have systematically investigated the magnetic saturation process for Co/Pt multilayers with perpendicular magnetic anisotropy by using the first-order reversal-curve (FORC) technique. We find that even for a field that apparently is higher than the major-loop saturation field, some microscopically not-yet-annihilated domains still remain. The true saturation on a microscopic scale field is found to be about 1.5 to 2.5 times greater than the macroscopicall-determined majorloop saturation field. Not-yet-annihilated domains are observed to be exponentially reduced with respect to the applied magnetic field.

A lot of systems are basically developed on DC-DC or DC-AC converters including electronic switches such as MOS or bipolar transistors. The limits of efficiency are quickly reached when high output voltages and high input currents are needed. This work presents a new high-efficiency-high-step-up based on push-pull DC-DC converter integrating recovery stages dedicated to smart HVDC distributed architecture in PV solar energy production systems. Appropriate duty cycle ratio assumes that the recovery stage work with parallel charge and discharge to achieve high step-up voltage gain. Besides, the voltage stress on the main switch is reduced with a passive clamp circuit and thus, low on-state resistance Rdson of the main switch can be adopted to reduce conduction losses. Thus, the efficiency of a basic DC-HVDC converter dedicated to renewable energy production can be further improved with such topology. A prototype converter is developed, and experimentally tested for validation.

Author(s): Gilbert, SM; Pham, T; Dogan, M; Oh, S; Shevitski, B; Schumm, G; Liu, S; Ercius, P; Aloni, S; Cohen, ML; Zettl, A | Abstract: The relative orientation of successive sheets, i.e. the stacking sequence, in layered 2D materials is central to the electronic, thermal, and mechanical properties of the material. Often different stacking sequences have comparable cohesive energy, leading to alternative stable crystal structures. Here we theoretically and experimentally explore different stacking sequences in the van der Waals bonded material hexagonal boron nitride (h-BN). We examine the total energy, electronic bandgap, and dielectric response tensor for five distinct high symmetry stacking sequences for both bulk and bilayer forms of h-BN. Two sequences, the generally assumed AA′ sequence and the relatively unknown (for h-BN) AB (Bernal) sequence, are predicted to have comparably low energy. We present a scalable modified chemical vapor deposition method that produces large flakes of virtually pure AB stacked h-BN; this new material complements the generally available AA′ stacked h-BN.

One dimensional boron nitride (BN) nanomaterials with a high aspect ratio are of great interest due to their unique properties and potential applications. However, BN nanomaterials are generally difficult to synthesize. Here, we describe the creation of arrays of vertically aligned pure BN nanofibers and BN coated carbon nanofibers, fabricated on-chip via a straightforward template-assisted chemical conversion reaction. The template, a glassy carbon nanofiber array, is produced by plasma processing of conventional photoresists. The method is highly controllable, patternable, and scalable, and the final arrays can be fabricated over large areas with a controlled fiber length. We characterize the electron field emission properties of the BN-coated carbon nanofiber array and find a large field enhancement factor, low turn-on voltage, and good stability. The outstanding field emission performance results from the small tip size and high aspect ratio of the nanofiber as well as the high chemical stability and high thermal conductivity of the BN coating.

In longwall mining where use frame support and control roof by full caving; rocks could impact the support, damage some its details and reduce support’s longevity. Using waste, elastic, and deformable capability materials (like old truck tires) not only reduce impulse which impact the support fatally and increase support’s longevity, but also contribute to protect the environment.

Comprehensive studies were conducted using measuring stations to measure the rock pressure and displacements of the roof rocks in the mine workings adjacent to the face when extracting medium thick inclined coal seams with the use of longwall (seam 6 at the Quang Hanh mine of Quang Ninh coal basin, Vietnam). The results of the study show that the displacement of the roof rock on the parallel roadway increases sharply at a distance of 1 to 12 m to the face, varies from 20 to 40 mm when the mining depth of the coal seam is 200 m and the maximum rock pressure on the haulage roadway supports is located at a distance of 3–8 m ahead of the face and is from 14 to 16 tons ranges.

The potential of micro and nano electromechanical systems (M and NEMS) has expanded due to advances in materials and fabrication processes. A wide variety of materials are now being pursued and deployed for M and NEMS including silicon carbide (SiC), III–V materials, thin-film piezoelectric and ferroelectric, electro-optical and 2D atomic crystals such as graphene, hexagonal boron nitride (h-BN), and molybdenum disulfide (MoS₂). The miniaturization, functionality and low-power operation offered by these types of devices are attractive for many application areas including physical sciences, medical, space and military uses, where exposure to radiation is a reliability consideration. Understanding the impact of radiation on these materials and devices is necessary for applications in radiation environments., Defense Threat Reduction Agency (DTRA) (Grant HDTRA1-15-1-0027), Defense Threat Reduction Agency (DTRA) (Grant HDTRA1-15-1-0035), Defense Threat Reduction Agency (DTRA) (Grant HDTRA1-15-1-0036), Defense Threat Reduction Agency (DTRA) (Grant HDTRA1-15-1-0039), Defense Threat Reduction Agency (DTRA) (Grant HDTRA1-15-1-0060)

This paper presents a new configuration of multi-phase induction heating system and its control scheme. Instead of using separate voltage inverters to supply the required currents in the inductors in each phase, the inverters will be arranged in a special configuration in order to reduce the number of power switches. A modification in the setting parameters of the formers will make sure the best operation of the system. Optimal references are obtained through a specific optimization procedure and several solutions are tested for neutral current minimization, including a new arrangement of the coils. In addition, current control in the different phases is achieved thanks to proportional-resonant controllers. The application is currently developed on a reduced power 3-phase coupled resonant test bench from which simulation and experimental results are provided.

The atomic structure, stability, and dynamics of defects in hexagonal boron nitride (h-BN) are investigated using an aberration-corrected transmission electron microscope operated at 80 kV between room temperature and 1000 °C. At temperatures above 700 °C, parallelogram- and hexagon-shaped defects with zigzag edges become prominent, in contrast to the triangular defects typically observed at lower temperatures. The appearance of 120° corners at defect vertices indicates the coexistence of both N- and B-terminated zigzag edges in the same defect. In situ dynamics studies show that the hexagonal holes grow by electron-induced sputtering of B-N chains, and that at high temperatures these chains can migrate from one defect corner to another. We complement the experiments with first-principles calculation which consider the thermal equilibrium formation energy of different defect configurations. It is shown that, below a critical defect size, hexagonal defects have the lowest formation energy and therefore are the more-stable configuration, and triangular defects are energetically metastable but can be "frozen in" under experimental conditions. We also discuss the possible contributions of several dynamic processes to the temperature-dependent defect formation.

We present a facile wet-chemistry method for efficient metal filling of the hollow inner cores of boron nitride nanotubes (BNNTs). The fillers conform to the cross-section of the tube cavity and extend in length from a few nm to hundreds of nm. The methodology is robust and is demonstrated for noble metals (Au, Pt, Pd, and Ag), transition metals (Co), and post-transition elements (In). Transmission electron microscopy and related electron spectroscopy confirm the composition and morphology of the filler nanoparticles. Up to 60% of BNNTs of a given preparation batch have some degree of metal encapsulation, and individual tubes can have up to 10% of their core volume filled during initial loading. The growth, movement, and fusing of metal nanoparticles within the BNNTs are also examined.

Nature Materials 16, 522–525 (2017); published online 7 November 2016; retracted after print 20 December 2017. The authors of the study are retracting this Letter due to concerns about the reproducibility of the photovoltaic architecture performance presented, and with the interpretation of the dataincluded in the manuscript and Supplementary Information.

We demonstrate a new strategy to tune the density of graphene aerogels. This facile method is capable of producing graphene aerogels over a wide density range without compromising the morphology or quality of the material. Perylenetetracarboxylic acid dianydride serves as a sacrificial filler material that can be thermally decomposed to yield a graphene aerogel with tunable density.

International audience; This paper presents a predictive control scheme, based on the receding horizon optimalcontrol (RHOC) approach with zero terminal constraint, to guarantee the closed-loop stabilityof linear 2 × 2 hyperbolic systems with boundary control. The extension of this control schemeto networks of such hyperbolic systems is also considered. The boundary control problem is firstreformulated in the abstract form for which the optimal control with terminal constraint was wellstudied. These results are then used in the RHOC scheme to give a complete proof of stability of theclosed-loop system. For the implementation, the calculus of variations is used to derive the adjointstate which is then discretized and solved together with the state to obtain the optimal control.The analysis is applied to open-channel hydraulic systems in cases of single pool and multipoolsin cascade. Finally, simulations are carried out to illustrate the effectiveness of the here-proposedapproach.

Correction for ‘Nanoscale structure and superhydrophobicity of sp2-bonded boron nitride aerogels’ by Thang Pham et al., Nanoscale, 2015, 7, 10449–10458.

International audience; Identical domain concepts reified in different metamodelling projects may be named, represented and connected differently. It turns out that a transformation defined for a particular metamodel cannot be directly used for another metamodel. To tackle this problem, we propose a process for automatically adapting legacy transformations. Such a transformation is adapted to the new metamodel that has a slightly different representation in comparison with the original one, while the transformation intention is preserved. To this end, we first introduce a Domain Specific Language (DSL) that allows users to describe the intended correspondences between elements of two metamodels. Then we provide an adaptation engine using these user-defined correspondences to adapt the transformation automatically. We also propose a graph-based typing relation that enables safe adaptations. Our approach has been prototyped with MOMENT2 and can be used with any framework based on the same graph transformation paradigm.