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Developing high energy density lithium-sulfur (Li–S) batteries mainly relies on the design of the electrode matrix which can accommodate high sulfur loading and still remain high utilization of active materials. Herein, a 3D hierarchical graphitic carbon foam supported graphene@Mo2C (GCF-G@Mo2C) heterostructure is introduced as a freestanding electrode for Li–S batteries with a facile and cost-effective method. The N-doped carbon foam wrapped by graphene sheets with agaric-like porous structure could promote fast electron and ion transport, meanwhile effectively anchor the polysulfides through physical confinement and chemical adsorption by strongly polar-polar interactions. More importantly, the Mo2C nanoparticles can act as the chemical anchoring center to provide strong polysulfide adsorption, as testified by experimental data and first-principle calculations. Moreover, the catalytic effect of Mo2C also accelerates the redox kinetics of polysulfide conversion, contributing to enhanced rate performance. As a result, the cell with GCF-G@Mo2C displays an initial capacity as high as 862 mAh g−1 and a retained capacity of 597 mAh g−1 after 600 cycles with only 0.051% capacity fade per cycle at 1C rate, presenting good cycling stability. In addition, the GCF-G@Mo2C substrate with high sulfur content (70 ​wt%) and sulfur loading (10.5 ​mg ​cm−2) achieves an ultra-high areal capacity of 12.6 mAh cm−2 at 0.1 ​C, offering a competitive cathode for high-performance Li–S batteries.

With the development of laser technology, high power diode lasers have found the increasing various applications in many fields, including industry, advanced manufacturing, aerospace, Lidar and medical systems etc.. The near field non-linearity (Smile) and lasing uniformity of emitters for high power diode laser arrays are critical to high reliable optically coupled modules and laser heads in a cladding system. In order to obtain the lower smile and higher lasing uniformity, two CTEmatched substrates (Copper Tungsten-CuW) are employed to bond a single GaAs-based diode laser array with the cavity length of 2mm on a Micro Channel Cooler (MCC) using Gold-Tin hard solder. This double-CuW MCC-packaged structure is called DMCC which enables a diode laser array bonded on a CuW/MCC/CuW structure with all AuSn solder. Structural optimization has been carried out to reduce the thermal stress and smile for this package. Simulation results indicate that the smile and thermal stress is lowered 0.24μm and 16MPa, respectively. According to the simulation results, single bar DMCC-packaged diode lasers with lower Smile value are fabricated and characterized. The experimental results show that the ratio of Smile (average smile ~0.87μm) l1μm is ~71% and higher ~19% than that of conventional structure (average smile ~1.2μm). Importantly, the quantity ratio of lasing emitters (≥46 emitters) in a diode laser array is significantly raised from ~62% to 85% after the optimization of CuW submount.

High-salinity organic wastewater usually consists of diverse highly concentrated ions such as Na+, Ca2+ and Al3+ etc., which may significantly influence the fouling propensity when membrane technique is employed for contaminants removal. The current work investigated the effects of high salinity especially high-concentration Na+, Ca2+ and Al3+ on UF fouling characteristics, where 2 M Na+ and 0.5–1.0 M Ca2+ or Al3+ were applied according to the general composition of high-salinity wastewater. The results demonstrated that the presence of high-concentration Na+ alone benefited the ultrafiltration of bovine serum albumin (BSA) solution, but posed adverse effects on the ultrafiltration of humic acid (HA) solution. Further addition of Ca2+ or Al3+ on the basis of Na+ was found to aggravate the development of BSA fouling. Such differentiated behaviors were further elucidated by the comprehensive fouling characterizations in terms of foulant properties, specific resistances, filtration modelling and fouling layer observations. Correlation analysis suggested that irreversible fouling had strong relationship with Al3+ addition, while reversible fouling seemed to be primarily influenced by foulant size. Meanwhile, membrane rejection in the presence of various salts remarkably decreased, which was negatively correlated with zeta potential. Consequently, this study should shed light on the membrane fouling formation for treating high-salinity organic wastewater using membrane techniques.

Hypothesis Transfer of chemical-vapor-deposition (CVD) grown monolayer graphene from one substrate to another requires a transfer agent. The transfer agent usually needs to be removed by washing with organic solvent such as acetone or high temperature annealing, which is harmful to the structure integrity and intrinsic property of a graphene film. Here, we propose the use of camphor as a transfer agent to transfer monolayer graphene onto a target dielectric substrate, which bypasses these demanding steps and only needs the common alcohol solvent rinsing. Experiments To facilitate a crack-free graphene transfer, the proposed approach allows the camphor supported polycrystalline graphene to be rationally fastened with a thickened and solidified edge bead (i.e. camphor oil-filled boundary). A layer of camphor was first deposited onto a graphene/copper surface. The backside copper substrate was then etched away, whilst the camphor/graphene bilayer was placed onto a SiO2/Si substrate. Finally, the camphor remaining on the camphor/graphene/SiO2/Si sublimed into a vapor. The graphene/SiO2 stack was then examined by microscopic, spectral and electrical characterization. Findings The results of our examination suggest that the proposed method can guarantee a clean and damage-free graphene transfer. This method is particularly attractive in the application area for nano/micro-electronics, where it provides CVD-grown graphene the ability to be used on wide varieties of substrates that are sensitive to organic solvents and high temperature.

Direct membrane filtration (DMF) is a promising alternative secondary wastewater treatment process in Iceland, where biological treatment is not effective due to low strength wastewater nature and low temperature. This study aims to investigate membrane fouling mechanisms and mitigation approaches during DMF of municipal wastewater using a crossflow membrane filtration system integrated with an optical coherence tomography (OCT) imaging system. During DMF of wastewater, it was observed that intermediate pore blocking was dominant during the early stage of fouling, followed by cake filtration. Multi-filtration cycles were performed under different conditions, and the results revealed that (1) elevating flushing water temperature from 25 to 50 °C greatly reduced the intermediate pore blocking constant accompanied with a decreased physically-irreversible fouling; (2) increasing both filtration and flushing crossflow velocities did not influence the pore blocking constant, but caused a lower cake filtration constant with reducing both physically-reversible and irreversible fouling; (3) extending filtration-flushing duration interval appeared to slightly lower the pore blocking constant; (4) with extending filtration cycles, a shift of reversible fouling to irreversible fouling was noticed and associated with the compression of the tightly attached cake layer that was not readily removed by periodical flushing. A combination of periodical physical flushing with short term chemical-enhanced cleaning was employed and sustainable long-term operation of DMF was achieved. Furthermore, the foulants autopsy indicated that biofouling combined with organic/inorganic fouling influenced the cake fouling development. This work was supported by the University of Iceland Research Fund.

For current 905nm pulsed laser diode(PLD) for LiDAR applications, most of them are single channel chips each with a power range of 75W-120W designed for scanning multiple single points. In this work, kilowatt 905nm light source based on eight channel 905nm PLD mini-bars had been designed and packaged using flip chip bonding technology. A series of kilowatt 905nm PLD modules were fabricated and characterized. The maximum output power of 982W limited by the pulse driver was obtained for the first time under the condition of 100V@5ns,100kHz at room temperature. The spectral width of FWHM and FW90%E was 5.1nm and 7.2nm, respectively. The far field divergence test data indicated that the fast axis divergence@1/e2 and slow axis divergence@1/e2 was 0.38°and 27.59°, respectively. In the future, the fast axis divergence@1/e2 and the slow axis FoV can be designed and optimized for any particular LiDAR system.

A high peak power annularly-stacked laser diode pump has been designed and manufactured for a solid state laser (SSL), which is constructed by 12 single annular stacks composed of 3-bar laser diode (LD) submodules. High peak power and high wavelength uniformity have been considered. Macro channel cooling has been used during the operation of the annular stacks, at typical coolant flow rate of 2L/min. Heat dissipation and stress of a single annular stack have been simulated by finite element software, which shows high temperature uniformity of 3-bar submodules (plus or minus 0.5℃) and low package stress (11.8MP). The peak power of the annularly stacked laser diode pump has reached 234kW at a peak current of 450A or less. A high uniformity of centroid wavelength (802 plus or minus1nm) with a full width at half maximum (FWHM) of 4nm has been measured. More than 24 million shots have been verified for the 3-bar LD submodules.

Carbon nanotubes (CNTs) have been widely studied because of their potential applications. The increasing applications of CNTs and less known of their environmental fates rise concerns about their safety. In this study, the biotransformation of multi-walled carbon nanotubes (MWCNTs) by Labrys sp. WJW was investigated. Within 16 days, qPCR analysis showed that cell numbers increased 4.92 ± 0.36 folds using 100 mg/L MWCNTs as the sole carbon source. The biotransformation of MWCNTs, which led to morphology and functional group change, was evidenced by transmission electron microscopy and X-ray photoelectron spectroscopy analyses. Raman spectra illustrated that more defects and disordered carbon appeared on MWCNTs during incubation. The underlying biotransformation mechanism of MWCNTs through an extracellular bacterial Fenton-like reaction was demonstrated. In this bacteria-mediated reaction, the OH production was induced by reduction of H2O2 involved a continuous cycle of Fe(II)/Fe(III). Bacterial biotransformation of MWCNTs will provide new insights into the understanding of CNTs bioremediation processes.

Carbon nanomaterials (CNs), which gain heightened attention as novel materials, are increasingly incorporated into daily products and thus are released into the environment. Limited research on CNs environmental fates lags their industry growth, only few bacteria have been confirmed to biotransform CNs and the mechanism behind has not been revealed yet. In this study, four types of commercial CNs, i.e. graphene oxide (GO), reduced graphene oxide (RGO), single walled carbon nanotubes (SWCNTs), and oxidized (carboxylated) SWCNTs, were selected for investigation. The biotransformation of CNs by Labrys sp. WJW, which could grow with these CNs as the sole carbon source, was investigated. The bacterial transformation was proved by qPCR, transmission electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, liquid chromatography/time-of-flight/mass spectrometry, and gas chromatograph-mass spectrometry analyses. The biotransformation resulted in morphology change, defect increase and functional group change of these CNs. Furthermore, the underlying mechanism of CNs biodegradation mediated by extracellular Fenton-like reaction was demonstrated. In this reaction, the OH production was mediated by reduction of H2O2 involved a continuous cycle of Fe(II)/Fe(III). These findings reveal a novel degradation mechanism of microorganism towards high molecular weight substrate, which will provide a new insight into the environmental fate of CNs and the guidance for their safer use.

Graphene quantum dots (GQDs) were prepared by the pyrolysis of citric acid (CA), which were used for the loading of hydrophilic cytarabine (Cyt), an anti-cancer drug, and then wrapped with chitosan (CS) gels for the encapsulation of the loaded Cyt. The fluorescent stability of GQDs was significantly enhanced in the presence of CS, which might be attributed to the inhibited agglomeration of GQDs by the CS gels. In addition, the burst release of Cyt from the developed carrier was also effectively relieved by the CS coating. Since the incorporation of Cyt into GQDs was achieved by amidation reaction, the delivery of Cyt from the carrier was pH-sensitive due to the hydrolysis of the amido linkage between GQDs and Cyt in acidic medium.

We propose a mechanism to generate a single intense circularly polarized attosecond x-ray pulse from the interaction of a circularly polarized relativistic few-cycle laser pulse with an ultrathin foil at normal incidence. Analytical modeling and particle-in-cell simulation demonstrate that a huge charge-separation field can be produced when all the electrons are displaced from the target by the incident laser, resulting in a high-quality relativistic electron mirror that propagates against the tail of the laser pulse. The latter is efficiently reflected as well as compressed into an attosecond pulse that is also circularly polarized.

Graphene oxide (GO) is a new type of nanomaterial with unique physicochemical properties and diverse applications, whereas it poses potential risk to human and environment. By screening from natural soil exposed to GO in the laboratory, we successfully obtained a novel bacterium, Labrys sp. WJW, which was able to use GO as the sole carbon source for growth. Within 8 days, cell numbers increased 16.76 ± 3.21 folds using 100 mg/L GO as the carbon source by qPCR analysis. The bacterial biodegradation which resulted in formation of holes and functional group changes of GO was proved by Raman spectroscopy, atomic force microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy analyses. Aromatic intermediates with structures of benzoic acid and phenol were identified using gas chromatograph-mass spectrometry and liquid chromatography/time-of-flight/mass spectrometry. Combination of genomic and proteomic analyses were performed to explore the proteins associated with GO degradation. A total of 644 proteins were significantly shifted. Bioinformatics analysis indicated that part of the up-regulated proteins were related to oxidation, ring cleavage and intermediates transmembrane processes, and GO was supposed to be degraded to benzoate and further degraded for downstream processes. This study enriches our understanding and provides new insights into the environmental fate of GO.

Two-dimensional (2D) white-light-emitting hybrid perovskites (WHPs) are promising active materials for single-component white-light-emitting diodes (WLEDs) driven by UV. However, the reported WHPs exhibit low quantum yields (≤9%) and low color rendering index (CRI) values less than 85, which does not satisfy the demand of solid-state lighting applications. In this work, we report a series of mixed-halide 2D layered WHPs (C6H5C2H4NH3)2PbBrxCl4–x (0 < x < 4) obtained from the phenethylammonium cation. Unlike the reported WHPs including (C6H5C2H4NH3)2PbCl4, the mixed-halide perovskites display morphology-dependent white emission for the different extents of self-absorption. Additionally, the amount of Br has a huge influence on the photophysical properties of mixed-halide WHPs. With the increasing content of Br, the quantum yields of WHPs increase gradually from 0.2 to 16.9%, accompanied by tunable color temperatures ranging from 4000 K (“warm” white light) to 7000 K (“cold” white light). When applied to the...

Exploring earth-abundant electrocatalysts with high activity and low-cost for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is vital to energy harvesting and storage, such as fuel cell and effective overall water splitting. Herein, novel heterostructures (Ni3S2/VS2) without nitrogen (N) and with N doping are reported as superior electrocatalysts for the OER and HER, respectively. The heterostructure without doping shows enhanced OER performance with an extremely low overpotential (227mV at 10 mA/cm(2)) due to increased active sites and fantastic interfaces as well as unique structure. Moreover, N-doped Ni3S2/VS2 (N-Ni3S2/VS2) shows high electrocatalytic HER performance with a low HER overpotential (151 mV at 10 mA/cm(2)), because the N-doping greatly improves conductivity and increases large amounts of catalytic active sites. Finally, we construct a two-electrode electrolyzer system (Ni3S2/VS2//N-Ni3S2/VS2) and it achieves a current density of 10 mA/cm(2) at a low cell voltage of 1.648 V. Our findings demonstrate that structure design and doping can effectively improve the catalytic activities of nanomaterials for OER and HER. (C) 2018 Elsevier Ltd. All rights reserved.

Two series of dual-core star-shaped polyfluorenes (DC-TPAs and DC-SBFs) based on a small quantity of green-emitting phenylmaleimide cores and a good deal of non-emissive cores were prepared by a one-pot Suzuki reaction. Triphenylamine (TPA) and 9,9-spirobifluorene (SBF) are employed as the non-emissive cores to construct DC-SBFs and DC-TPAs, respectively. Due to the π-conjugation extended by the fluorene units, the phenylmaleimide core displays a yellow emission which contributes to the white emission with the blue-emitting polyfluorene arms. DC-SBFs with four arms exhibit a better protection for emissive cores and a higher energy transfer efficiency than DC-TPAs with three arms. Consequently, the quantum yield of white emission of the polymers in the film was improved by changing TPA into SBF as the non-emissive core, reaching 0.80 for DC-SBF03. Additionally, the electrons and holes can be transported smoothly in DC-SBFs. A very high electroluminescent efficiency was obtained for DC-SBF03 with a maximum luminous efficiency of 17.4 cd A−1, power efficiency of 10.9 lm W−1 and external quantum efficiency of 6.2% when applied in the solution-processing white polymeric light-emitting devices (WPLEDs) with a LiF/Al cathode. The results denote that the non-emissive core plays a key role in the performance of the star-shaped single white polymers. It provides another way to improve the efficiencies of WPLEDs by designing simple non-emissive cores of the dual-core polymers, and avoiding the complicated synthesis of fluorophores.

Functional graphene quantum dots (IL-GQDs) are synthesized by electrochemical exfoliation in a one-pot process. Ionic liquid in the mixed solution (water/acetonitrile) is used as the electrolyte, w...

Direct membrane filtration (DMF) has recently gained attention as an alternative secondary biological wastewater treatment process. This study evaluated direct microfiltration (MF) and ultrafiltration (UF) performance and cleaning protocols during crossflow DMF of primary municipal wastewater effluent. Several types of MF and UF membranes were examined by threshold flux determination, and two types of membranes (MF, 0.08 μm; UF, 100 kDa) were chosen for exploring membrane fouling mechanisms at different feed pressures via both fouling resistance analysis and optical coherence tomography (OCT) observation. The results revealed that both MF and UF displayed three-stage fouling behaviors, i.e., initial intermediate pore blocking followed by two-stage cake filtration. Increasing feed pressure from 8 kPa to 50 kPa could accelerate physically reversible fouling rate (consistent with simulated cake filtration constant). During physical flushing, the cake layer was more readily removed from the UF membrane; while residual porous cake layer was present on the MF membrane, regardless of the feed pressure. With extending filtration-cleaning cycle, shortening filtration duration and elevating cleaning solution temperature to from 25 °C to 50 °C benefited for irreversible fouling alleviation. At 50 °C, the geothermal water performed similar cleaning behaviors as clean water, facilitating lower reversible and irreversible fouling than the geothermal brine. This study shed light on the feasibility of using high temperature geothermal water for periodic physical cleaning during DMF of wastewater under Icelandic scenario. Economic Development Board (EDB) This work was supported by the University of Iceland Research Fund. The Student Innovation Fund from Rannís in Iceland was acknowledged for providing summer research grant to Dagmar Olafsd ´ ottir. The Economic Development Board (EDB) of Singapore is acknowledged for funding the Singapore MembraneTechnology Centre (SMTC) , Nanyang Technological University.

China has become the global largest country in application of new energy vehicles (NEVs) and installed capacity of lithium-ion batteries (LIBs). However, the contradiction between the demand and supply of nickel used as the typical critical resource for manufacturing LIBs, is ever-increasing aggravated especially under the tendency of cobalt-free nickel-rich. This research, hereby, predicts the nickel recycling potential from end-of-life NEVs under three sales growth scenarios by linear regression and Weibull distribution, and investigates the role of recovered nickel during closing nickel loop quantitatively. It is predicted that China's NEVs sales can achieve approximately 3800 thousand units, and the quantities of end-of-life NEVs can reach 2300 thousand units under the higher growth rate (HGR) in 2030. If the spent nickel-bearing batteries (NBBs) can be fully recycled, 44.5 Mt of nickel can be recovered, which will account for nearly one third of the total demand for manufacturing NBBs. The results indicate that the recovered nickel from spent NBBs can play a vital role during closing nickel loop in the industry of NEVs in China.

Enriched macro/mesoporous graphitic-C3N4 (g-C3N4) micro-rods (CNRs) are prepared by direct calcination of reflux treated ethylene diphosphonic acid-melamine complex fiber network. The optimized phosphorous doped CNRs (P-CNRs) exhibit a high hydrogen-evolution rate of 4960 μmol h−1 g−1 (5.5 times that of pristine g-C3N4) with a remarkable recycling stability. The significantly enhanced performance is found to be attributed to the intentionally designed morphology and electronic properties of P-CNRs. This distinctive hierarchical architecture of CNRs enhances the light scattering, and provides a high specific surface area and thus more catalytically active sites. The P doping of g-C3N4 greatly increases the visible light absorption, narrows the band gap. It also results in a boost in the density state of the conduction band as revealed by the electron paramagnetic resonance (EPR) spectra. The strong visible light emission quenching, observed from the photoluminescence of P-CNRs and photocurrent measurements, implies an enhanced charge transfer/separation process. This work presents a very simple and direct method of designing and developing high-performance visible light driven catalysts for hydrogen production.

To improve the copper bioleaching efficiency from waste printed circuit board (WPCB) by Acidithiobacillus ferrooxidans ( A. ferrooxidans ), a novel simplified material (nitrogen-doped carbon nanotubes (NCNTs) modified electrode) was used in this paper. Experiments mainly including the exploration of NCNTs optimal concentration and recycling effect of NCNTs modified electrode were investigated. The variations of pH, ORP, Fe 2+ concentration and Cu 2+ concentration were studied in detail, and the mechanism of the modified electrode was also analyzed in this study. Conclusions were obtained that the optimal experimental conditions were: bacteria inoculation 10%, initial pH 2.0, WPCB powder 1 g, solid/liquid (w/v) ratio 1/50, temperature 28 °C, rotational speed 125 r/min and modified electrode 2.5 mg/cm 2 . The copper bioleaching rate reached 99% after 9 days reaction, and it was 20% higher than that of the group which was only added A. ferrooxidans. With the analysis of XRD, the precipitate formed (NH 4 )Fe 3 (SO 4 ) 2 (OH) 6 at the end of the reaction, and the modified electrode didn’t affect the formation of the yellow precipitate. Meanwhile, the modified electrode could be recycled, and the positive effect wasn’t weakened obviously on these processes. The results may provide a reference for enhancing the copper bioleaching efficiency from WPCBs and expand the application of NCNTs in hydrometallurgy field.

Exploration of enhancing bioleaching percent of copper from waste printed circuit board (WPCB) has received an increasing attention in recent years. This research explored the catalytic effect of graphene in bioleaching copper from WPCB by Acidithiobacillus ferrooxidans ( A. ferrooxidans ). Series of experiments were investigated, such as compatibility test between A. ferrooxidans and graphene, optimal dosage test of graphene, test of orthogonal experiment design, mechanism analysis of graphene, and recycling experiment of used graphene. Conclusions were obtained that graphene had a good compatibility with A. ferrooxidans , and it could catalyze the bioleaching reaction when added with appropriate dosage of graphene. The optimal dosage of graphene was 0.04 g in 50 ml culture solution, and 84% of copper was leached after five days bioleaching, while only 74% of copper was leached without adding graphene. The optimal condition of bioleaching copper was WPCB 10 g L − 1 , initial pH 2.5, bacterial activation time 4 days, and FeSO 4 ·7H 2 O 40 g L − 1 , about 91.8% of copper was leached. The mechanism analysis of graphene indicated that the transformation between Fe 2 + and Fe 3 + was actuated by A. ferrooxidans and graphene in these reactions, and both of FeCl 3 ·6H 2 O and KFe(SO 4 ) 2 (OH) 6 were generated in bioleaching process. The catalytic ability of bioleaching copper wasn't weakened by treating with 40% HNO 3 , and graphene could recycle and reuse in these reactions. Our experimental results shows that the catalysis of graphene in bioleaching copper from WPCB by A. ferrooxidans is promising.

An efficient nitrate/HCl chemical exfoliation system for rapid production of MoS 2 and WS 2 nanosheets were presented here. After exfoliation in the NaNO 3 /HCl solution with the assistant of ultrasonication, MoS 2 and WS 2 nanosheets were produced with yields of 58% and 52%, respectively. The morphologies and crystallinity of MoS 2 and WS 2 nanosheets were characterized by transmission electron microscopy, atomic force microscopy and X-ray diffraction spectroscopy. This efficient exfoliation method is based on the synergy effects of surface etching, insertion of ions and eruption of gas bubbles. The MoS 2 and WS 2 nanosheets exhibited improved catalytic activity toward the oxygen-reduction reaction.

High power QCW diode laser stacks have been widely used in pumping applications for years. Different package structures of diode laser stacks are applied for pumping the cylindrical rod crystal, such as modular G-Stack, horizontal, vertical and annular arrays. Annular array is preferred in pumping of QCW mode with low duty cycle and short pulse width, due to the advantage of compact structural size, uniform light beam distribution and convenient electric connection. However, the development of annular diode laser array using hard solder is difficult because of the complex bonding process of diode laser on annular heatsink with conventional bonding fixture. Furthermore the stress and thermal behavior is yet to be well studied on the annular diode laser array. In this work, a sophisticated annular diode laser array was developed using hard solder. Optimized structure and thermal design were conducted to achieve uniform light beam distribution and good heat dissipation. Stress release structure of diode laser stack is applied to reduce the risk of chip crack and deviation of spatial spectrum. The annular diode laser array consists of 44 bars in a ring, with the peak output power of each bar over 500W. The maximum output power of each bar reaches 673 W.

Reduction of the customers’ exposure risk of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in the retail buildings, i.e., supermarkets and small shops where residents purchase daily necessities is of prime importance during pandemic. In this study, the main influencing factors of the exposure risk of SARS-CoV-2, namely the occupant density, dwell time, and fresh air volume per person, were on-sited measured in 5 supermarkets and 21 small shops in Shenzhen, China. The small shops with an occupant area per person of 4.7 m2/per presented a more crowded environment than the supermarkets with an occupant area per person of 18.8 m2/per. The average dwell time of customers in the supermarkets linearly increased with the floor area and its probability distribution was fitted well by the Gamma distribution with a shape parameter of 3.0. The average dwell time of customers in the supermarkets was relatively longer than the combination of five types of small shops. In addition, the measured average outdoor air change rate of the small shops by natural ventilation was 10.7 h−1, while that of the supermarkets by mechanical ventilation was only 0.7 h−1. Correspondingly, the CO2 concentration in the small shops was 100–150 ppm lower than the supermarkets. The small shops provided an average fresh air volume per person of 216 m3/(h·per), far exceeding the supermarkets with a value of 95 m3/(h·per).

To improve the recovery of valuable metals (Li, Co, Ni, and Mn) from the cathode material of waste lithium-ion batteries (LIBs), a mechanochemical reduction technique is proposed in this research. The cathode material was mechanochemically ball milled with various reductive agents as a pretreatment and then subjected to a chemical leaching process for the recovery of valuable metals. The influence of mechanochemical ball milling parameters and leaching conditions on metals recovery, and the changes in physicochemical properties of cathode materials before and after mechanochemical ball milling were investigated. The results show that Zinc (Zn) powder was an effective co-grinding reagent forimproving the recovery of valuable metals from cathode materials. The crystal structure of the cathode material gradually shifted to an amorphous state with an increase in ball milling speed and time. Mn(IV) and Co(III) in the cathode material were mechanochemically reduced to Mn(III) and Co(II) after co-grinding with Zn, which was beneficial to their leaching. The activation energies of Ni and Co decreased from 30.47 KJ/mol and 31.99 KJ/mol to 5.58 KJ/mol and 7.15 KJ/mol, respectively. The leaching rates of Li, Ni, Co, and Mn increased from 72.0%, 42.5%, 31.2%, and 15.2% to 99.9%, 96.2%, 94.3%, and 91.0% under the optimum conditions of a cathode material to Zn powder mass ratio of 7:3, a rotational speed of 500 rpm, a milling time of 2 h, and a ball-to-powder mass ratio of 19: 1. This research presents a highly efficient and feasible approach for recovering valuable metals from waste LIBs.

The generation and transport of fast electrons play an important role in intense laser interaction with dense plasma. Here, we experimentally study fast electron generation using a planar aluminum target obliquely irradiated at a large incident angle by an ultrashort high-temporal-contrast relativistic laser pulse. Simulations show that for near-relativistic laser intensities, s-polarized lasers above a certain energy threshold can generate energetic electrons ( }}\,{\text{500}}\;{\text{keV}}$?> E e > 500 keV ) with a high yield, which is different from the case of low laser contrast. It is also shown that the most energetic electrons are emitted along the target’s surface and accelerated to high energies. The key features of the acceleration regimes of lasers with different polarizations are also given.

Introduction: This meta-analysis aims to assess the effectiveness and safety of warm acupuncture therapy for treating Primary sciatica. Methods: The following 9 databases will be search from their inception to December 6, 2020: MEDLINE, EMBASE, the Cochrane Central Register of Controlled Trials (CENTRAL), the Chinese Biomedical Literature Database (CBM), the Chinese Medical Current Content (CMCC), the Wan-Fang Database and the China National Knowledge Infrastructure (CNKI). Randomized controlled trials (RCTs) of warm acupuncture for treating Primary sciatica, Chinese or Japanese without restriction of publication status will be included. Two researchers will independently undertake study selection, extraction of data and assessment of study quality. Meta-analysis will be conducted after screening of studies. Data will be analyzed using risk ratio for dichotomous data, and standardized mean difference or weighted mean difference for continuous data. Dissemination: This meta-analysis will be disseminated electronically through a peer-reviewed publication or conference presentations. Conclusion: This study will provide evidence to judge whether warm acupuncture Trial registration number: INPLASY2020120109.

The emerging soft robots have attracted increasing interests and gotten rapidly developed, but it is still challenging to substantially promote their response speed and work density. In addition, the wireless way to conveniently trigger the devices, especially for the centimeter‐scale ones, is highly desired. Herein, the multistimuli‐responsive insect‐scale soft robotics is reported based on a super‐aligned VO2 nanowire arrays (NAs)/carbon nanotube (CNT) bimorph film, comprehensively addressing aforementioned problems. The as‐prepared VO2 NA/CNT bimorph shows improved actuation performance, anisotropic behavior, rapid response to various stimuli (heat, light, and electricity), and multiple movement modes (bending and torsion). Consequently, diverse untethered, insect‐scale soft robots, serving as biomimetic crawler, lifter, gripper, wing of flying robots, torsional robot, and so on are successfully demonstrated. The findings provide an effective strategy to develop high‐performance macroscopic mechanical devices by assembling functional nanostructures.

Particles suspended within feed flow or added into membrane-filtration systems may behave as foulant or fouling mitigation agent. The fine boundary between these two roles warrant attention to promote the beneficial role of particles and avoid their undermining impact. The particle back-transport phenomenon is first elucidated, then the four possible enhancing roles of particles in membrane-filtration systems are discussed, namely, mechanical scouring, as adsorbents of organic foulants, as coagulants to form porous flocs, and as dynamic membranes to protect the primary membrane matrix. Process variables governing such phenomena and possible adverse effects that need to be mitigated are also summarized. Finally, future research directions are recommended based on the understanding accumulated, namely, hybridization of the various beneficial roles, development of customized particles, and more understanding/optimization of the energy – fouling mitigation tradeoff. Economic Development Board (EDB) Ministry of Education (MOE) The authors gratefully acknowledge the financial support from the Singapore Ministry of Education Academic Research Funds Tier 2 (MOE2014-T2-2-074; ARC16/15) and Tier 1 (2015-T1-001-023; RG7/15), the GSK (GlaxoSmithKline) -EDB (Economic Development Board, Singapore) Trust Fund, the Joint Singapore-Germany Research Project Fund (SGP-PROG3-019). The Singapore Membrane Technology Center acknowledges funding support from the Singapore Economic Development Board.

Transfer method of chemically vapor deposition graphene is an appealing issue to realize its application as flexible and transparent electrodes. A universal stamping method to transfer as grown graphene from copper onto different flexible and transparent polymers (FTPs) reported here ensures simple, robust, rapid, clean and low-cost. This method relies on coating ethylene vinyl acetate (EVA) onto the as grown graphene, binding EVA coated graphene/Cu with FTPs and delamination by hydrogen bubbling process, which is analogous to the method used by stamping process where ink carries the imprint of the object onto any materials. The fate of the stamping method depends on how strongly the adhesion of EVA coated graphene/Cu with target FTPs. Interestingly, we have found that the thin film of EVA/graphene/Cu can only bind strongly with the FTPs of less than 25 µm in thickness and lower glass transition temperature value to the EVA while wide range of other FTPs are considered upon surface engineering to enhance the binding strength between FTPs and EVA. What’s more, the electrical performance was investigated with a demonstration of triboelectric nanogenerators which confirmed the reliability of graphene transfer onto the FTPs and prospect for the development of flexible and transparent electronics.

Cold cathode fluorescent lamps (CCFLs), with mercury as their essential component, were widely used as backlight in liquid crystal display (LCD) appliances before 2008. Since 2008, the mercury-free light emitting diode started to be used as a substitute for CCFLs and the replacement finished in about 2014. Nowadays, CCFLs are obsolete products from the viewpoint of manufacture but they are important as waste. In recent years, large amounts of CCFLs are flowing to waste phase for treatment and this has become a major issue in most countries. To better understand and control the risk of CCFLs, the stock of mercury in CCFLs, its flow to waste phase and mercury emission with the life cycle of CCFLs in mainland China were estimated in this study. Results showed that there was 15.2 tons of mercury stocked in CCFLs in main LCD appliances (i.e., LCD televisions, LCD monitors, and laptop monitors) from 2003–2015. CCFLs and mercury started to flow to waste phase around the year 2007 and will likely peak in 2018 with an annual flow of 324.8 million units and 1.5 tons respectively, then will likely decline dramatically till 2030. Dismantling and production were the two main life stages of CCFLs with mercury vapor release, during which approximately 2.1 tons and 1.2 tons of mercury were released to the atmosphere respectively. The research also indicates that mercury recycling in specialized facilities was another life stage with high mercury emission risk in which the processes of shredding, separation, and residue disposal are inevitably accompanied by mercury release.

A flexible gamma-ray radiation source based on the resonant laser-plasma wakefield wiggler is proposed. The wiggler is achieved by inducing centroid oscillations of a short laser pulse in a plasma channel. Electrons (self-)injected in such a wakefield experience both oscillations due to the transverse electric fields and energy gain due to the longitudinal electric field. The oscillations are significantly enhanced when the laser pulse centroid oscillations are in resonance with the electron betatron oscillations, extending the radiation spectrum to the gamma-ray range. The polarization of the radiation can be easily controlled by adjusting the injection of the laser pulse into the plasma channel.

High power diode lasers (HPDLs) offer the highest wall-plug efficiency, highest specific power (power-to-weight ratio), arguably the lowest cost and highest reliability among all laser types. However, the poor beam quality of commercially HPDLs is the main bottleneck limiting their direct applications requiring high brightness at least in one dimension. In order to expand the applications of HPDLs, beam shaping and optical design are essential. In this work, we report the recent progresses on maximizing applications of HPDLs by synergizing diode laser light source and beam shaping micro-optics. Successful examples of matching of diode laser light sources and beam shaping micro-optics driving new applications are presented.

Water condensation and precipitation induced by 22-TW 800-nm laser pulses at 1 Hz in an open cloud chamber were investigated in a time-resolved manner. Two parts of precipitation in two independent periods of time were observed directly following each laser shot. One part started around the filament zone at t < 500 μs and ended at t ≅ 1.5 ms after the arrival of the femtosecond laser pulse. The other following the laser-induced energetic air motion (turbulence), started at t ≅ 20 ms and ended at t ≅ 120 ms. Meanwhile, the phase transitions of large-size condensation droplets with diameters of 400–500 μm from liquid to solid (ice) in a cold area (T < −30 °C) were captured at t ≅ 20 ms.

A new plasma channel undulator concept based on the wakefields generated by short intense laser pulse undergoing centroid oscillations inside parabolic plasma channel is presented. The period of such an undulator is proportional to the Rayleigh length of the laser pulse and can be in the submillimeter range, while its strength can reach unity. Two-dimensional particle-in-cell simulations of the laser pulse propagation and wakefields are presented. Spontaneous radiation produced by the electron beam inside the plasma undulator is calculated.

Ag 3 PO 4 possesses high photocatalytic activity under visible light, but its application is limited by photogenerated charges recombination, photocorrosion as well as consumption of noble Ag. It is of great interesting to develop new Ag 3 PO 4 -based photocatalysts with high charges separation efficiency, good stability and low content of Ag. In this paper, we report a novel Ag 3 PO 4 /TiO 2 /reduced graphene oxide (Ag 3 PO 4 /TiO 2 /rGO) photocatalyst. It exhibits advantages on both the microstructure and the charges separation. The microstructure shows that TiO 2 spheres of hundreds of nanometers in size are decorated with dense nano-sized Ag 3 PO 4 to form pinecone-liked particles, which are enwrapped by rGO sheets. This novel structure effectively prevents aggregation of nano-sized Ag 3 PO 4 , which not only suppresses the charges recombination in Ag 3 PO 4 but also significantly reduces the content of Ag. Ag 3 PO 4 /TiO 2 /rGO also favors separation of photogenerated charges owing to its two pathways for charges transportation, i.e., the electrons in Ag 3 PO 4 can be transferred to rGO, while the holes in Ag 3 PO 4 can be transferred to TiO 2 . The dual-pathway for charges separation as well as the pinecone-liked Ag 3 PO 4 /TiO 2 microstructure ultimately leads to enhanced photocatalytic activity and stability of Ag 3 PO 4 /TiO 2 /rGO. The photocatalytic performance varies with different contents of Ag 3 PO 4 in the composites, because low content of Ag 3 PO 4 induces weak light absorption while excess Ag 3 PO 4 results in serious charges recombination due to the aggregation of Ag 3 PO 4 nanoparticles. In this work, Ag 3 PO 4 /TiO 2 /rGO with weight ratio of Ag 3 PO 4 against TiO 2 /rGO equals to 0.6 exhibits the highest photocatalytic activity. The percentage of Ag in this composite is around 29 wt%, much lower than 77 wt% in pure Ag 3 PO 4 .

Artificial rainmaking is in strong demand especially in arid regions. Traditional methods of seeding various Cloud Condensation Nuclei (CCN) into the clouds are costly and not environment friendly. Possible solutions based on ionization were proposed more than 100 years ago but there is still a lack of convincing verification or evidence. In this report, we demonstrated for the first time the condensation and precipitation (or snowfall) induced by a corona discharge inside a cloud chamber. Ionic wind was found to have played a more significant role than ions as extra CCN. In comparison with another newly emerging femtosecond laser filamentation ionization method, the snow precipitation induced by the corona discharge has about 4 orders of magnitude higher wall-plug efficiency under similar conditions.

High power diode lasers have been widely used in many fields. To meet the requirements of high power and high reliability, passively cooled single bar CS-packaged diode lasers must be robust to withstand thermal fatigue and operate long lifetime. In this work, a novel complete indium-free double-side cooling technology has been applied to package passively cooled high power diode lasers. Thermal behavior of hard solder CS-package diode lasers with different packaging structures was simulated and analyzed. Based on these results, the device structure and packaging process of double-side cooled CS-packaged diode lasers were optimized. A series of CW 200W 940nm high power diode lasers were developed and fabricated using hard solder bonding technology. The performance of the CW 200W 940nm high power diode lasers, such as output power, spectrum, thermal resistance, near field, far field, smile, lifetime, etc., is characterized and analyzed.

High power diode laser arrays have found increasing applications in the field of pumping solid-state lasers and fiber lasers. Due to the thermal crosstalk across diode laser arrays and non-uniformity of local flow rate within microchannel cooler, junction temperature distribution becomes inhomogeneous, consequently leading to spectrum broadening and large beam divergence of diode laser pumping sources. In this work, an analytical method and numerical heat transfer based on finite volume method were employed to optimize the inner structure of microchannel cooler so as to obtain low thermal resistance and uniform junction temperature distribution for the diode laser arrays. Three-dimensional numerical models were developed to study the fluid flow and heat transfer of copper stacked microchannel coolers with different dimensions and arrangements of inner channels and fins. More uniform junction temperature distribution of diode laser array package could be achieved by self-heating compensation with specific coolant covering width. These results could provide significant guidance for the design of microchannel coolers of high power diode laser arrays for better performance.

The solid state laser relies on the laser diode (LD) pumping array. Typically for high peak power quasi-CW (QCW) operation, both energy output per pulse and long term reliability are critical. With the improved bonding technique, specially Indium-free bonded diode laser bars, most of the device failures were caused by failure within laser diode itself (wearout failure), which are induced from dark line defect (DLD), bulk failure, point defect generation, facet mirror damage and etc. Measuring the reliability of LD under QCW condition will take a rather long time. Alternatively, an accelerating model could be a quicker way to estimate the LD life time under QCW operation. In this report, diode laser bars were mounted on micro channel cooler (MCC) and operated under QCW condition with different current densities and junction temperature (T j ). The junction temperature is varied by modulating pulse width and repetition frequency. The major concern here is the power degradation due to the facet failure. Reliability models of QCW and its corresponding failures are studied. In conclusion, QCW accelerated life-time model is discussed, with a few variable parameters. The model is compared with CW model to find their relationship.

Scientific reports 7(1), 16884 (2017). doi:10.1038/s41598-017-16971-5, Published by Nature Publishing Group, London

SnSbAg 0.1 -reduced graphene oxide (RGO) composite anode materials are synthesised via chemical reduction. The structure, morphology and electrochemical performance of the synthesised materials are characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy, Raman spectrometry, galvanostatic charge-discharge and cyclic voltammetry techniques. The large surface area, excellent conductivity and mechanical properties of the graphene reduce the agglomeration of alloy particles, buffer the stress of volume change and lower the powdering rate of particles, to enhance the inner transportation of Li + between the electrodes and the electrolyte. The SnSbAg 0.1 -10%RGO composite anode materials exhibit a better electrochemical performance and cycle life than other alloy anode composite materials, demonstrating a capacity of 605.1 mAh g −1 after 100 cycles and an average capacity attenuation rate of 0.16% from the 2 nd cycle to the 100 th cycle. The discharge capacity remain 538 mAh g −1 after 200 cycles, retaining 74.3% of its capacity compared to the 2 nd cycle and therefore exhibiting an excellent electrochemical performance

Carbon nanotube (CNT) has been proved to be a kind of novel support for enzyme immobilization. In this study, we tried to find the relationship between conformation and catalytic performance of immobilized enzyme. Two C C bond hydrolases BphD and MfphA were immobilized on CNTs (SWCNT and MWCNT) via physical adsorption and covalent attachment. Among the conjugates, the immobilized BphD on chemically functionalized SWCNT (BphD-CSWCNT) retained the highest catalytic efficiency ( k cat / K m value) compared to free BphD (92.9%). On the other hand, when MfphA bound to pristine SWCNT (MfphA-SWCNT), it was completely inactive. Time-resolved fluorescence spectrum indicated the formation of static ground complexes during the immobilization processes. Circular dichroism (CD) showed that the secondary structures of immobilized enzymes changed in varying degrees. In order to investigate the inhibition mechanism of MfphA by SWCNT, molecular dynamics simulation was employed to analyze the adsorption process, binding sites and time evolution of substrate tunnels. The results showed that the preferred binding sites (Trp201 and Met81) of MfphA for SWCNT blocked the main substrate access tunnel, thus making the enzyme inactive. The “tunnel-block” should be a novel possible inhibition mechanism for enzyme-nanotube conjugate.

Single-electrode mode triboelectric nanogenerator (TENG), as an emerging and efficient sustainable power source, is highly sought to develop a low-cost fabrication process for the mass production at the commercial level. In this paper, we report an easy protocol for the fabrication of graphite coated paper (GCP) based electrode along with its application in highly flexible single electrode mode TENG for converting waste environmental energy to electricity. This GCP exhibits an excellent flexibility and hydrophobicity with sheet resistance of ~1.5 kΩ sq−1. GCP-TENG is made up of polytetrafluoroethylene film tape, as the triboelectric layer, and GCP, as the conductive single electrode as well as its roll to roll fabrication was demonstrated. By efficiently harvesting hand tapping energy, GCP-TENG can generate a maximum open-circuit voltage up to ~320 V and a maximum short-circuit current density of ~0.8 μA cm−2, sufficient for charging capacitors and power Light-emitting diodes (LEDs) and Liquid crystal displays (LCDs) with rectifying circuits. We also demonstrated that GCP-TENG can efficiently work when adjoined with the skin of Pig leading to an effective harvesting of energy from the physical motion of animal. To indicate the universal usage of GCP-TENG, a wide range of common materials, such as paper, polyethylene terephthalate (PET), wood, polymethyl methacrylate (PMMA) and fabrics like cotton and nylon, concluded in effective electrical outputs when contacted with GCP-TENG. The widespread mechanical energy in nature associated with wind and water energy can be directly harvested by GCP-TENG, thus, it can be a promising sustainable tool for obtaining waste environmental energy from our daily activities, e.g., skin-touch actuated electronics, wearable/patchable self-powered sensory system, etc.

Laser light trapping in cavities in near-critical density plasmas is studied by two-dimensional particle-in-cell simulation. The laser ponderomotive force can create in the plasma a vacuum cavity bounded by a thin overcritical-density wall. The laser light is self-consistently trapped as a half-cycle electromagnetic wave in the form of an oscillon-caviton structure until it is slowly depleted through interaction with the cavity wall. When the near-critical density plasma contains a preformed cavity, laser light can become a standing wave in the latter. The trapped light is characterized as multi-peak structure. The overdense plasma wall around the self-generated and preformed cavities induced by the laser ponderomotive force is found to be crucial for pulse trapping. Once this wall forms, the trapped pulse can hardly penetrate.

Adsorptions of dimethyl phthalate (DMP) on carbon nanotubes (CNTs) in aqueous phase at various pH and temperatures were studied. The increase in pH results in the increase in adsorption coefficient. The adsorption is governed by the π-π electron interaction which is affected by the changes in pH of the medium. The outer diameter of the CNTs greatly influences the adsorption behavior of CNT for DMP. Under the same working temperature, the adsorption capacity of CNTs for DMP is inversely related to the average outer diameter of the CNT: single-walled SWCNT (1.4 nm)>multi-walled MWCNT10 (9.4 nm)>MWCNT30 (27.8 nm)>MWCNT40 (42.7 nm). The larger surface area of CNTs provides many active sites for adsorption of DMP molecules. The Freundlich model can describe well the adsorption isotherms of DMP on CNTs. The thermodynamic parameters of standard free energy, standard enthalpy (ΔH), and standard entropy changes are determined, showing that the adsorption of DMP on CNTs is an endothermic and spontaneous reaction. T...

The adsorption and desorption of dimethyl phthalate (DMP) on five types of carbon nanotubes (CNTs) were studied in the absence and presence of 50 mg/L copper(II) (Cu 2+ ) ion. The adsorption and desorption data are well described by the Freundlich model and the first-order two-compartment model, respectively. The adsorption capacity of CNTs for DMP is inversely related to the average outer diameter of the CNTs. The surface acidic functional groups of CNTs increases in the order of lactones 2+ ions. The adsorption coefficient increases in pH 3–6 and is nearly the same at pH > 6 for all CNTs. The presence of Cu 2+ ions decreases the amounts of desorbed DMP from CNTs, inferring that Cu 2+ ions could suppress the DMP desorption from CNTs and reduce DMP toxicity to our environment.

A unified picture of femtosecond laser induced precipitation in a cloud chamber is proposed. Among the three principal consequences of filamentation from the point of view of thermodynamics, namely, generation of chemicals, shock waves and thermal air flow motion (due to convection), the last one turns out to be the principal cause. Much of the filament induced chemicals would stick onto the existing background CCN’s (Cloud Condensation Nuclei) through collision making the latter more active. Strong mixing of air having a large temperature gradient would result in supersaturation in which the background CCN’s would grow efficiently into water/ice/snow. This conclusion was supported by two independent experiments using pure heating or a fan to imitate the laser-induced thermal effect or the strong air flow motion, respectively. Without the assistance of any shock wave and chemical CCN’s arising from laser filament, condensation and precipitation occurred. Meanwhile we believe that latent heat release during condensation /precipitation would enhance the air flow for mixing.

The high power diode lasers have been widely used in many fields. In this work, a sophisticated high power and high performance horizontal array of diode laser stacks have been developed and fabricated with high duty cycle using hard solder bonding technology. CTE-matched submount and Gold Tin (AuSn) hard solder are used for bonding the diode laser bar to achieve the performances of anti-thermal fatigue, higher reliability and longer lifetime. This array consists of 30 bars with the expected optical output peak power of 6000W. By means of numerical simulation and analytical results, the diode laser bars are aligned on suitable positions along the water cooled cooler in order to achieve the uniform wavelength with narrow spectrum and accurate central wavelength. The performance of the horizontal array, such as output power, spectrum, thermal resistance, life time, etc., is characterized and analyzed.