Search

We show a superplastic diffusion bonding method to join metallic glasses (MGs) via high-speed heating at 2000 K/min taking a timescale of the order of microseconds to milliseconds at ambient pressure because the minimum viscosity of supercooled liquid drastically decreases as the heating rate increases. The results show strong metallic bonds are formed but the amorphous structure is still maintained. Finally, we establish a general equation containing the involved parameters for high-speed heating bonding. This method provides a new path to join MGs rapidly and benefits for improving the critical size of MGs.

In human information, visual information accounts for about 60%. Image is the main way for humans to obtain visual information. Image binarization is an important technique in image pre-processing. It has important applications in pattern recognition, optical character recognition, and medical imaging. This paper first introduces the research background, basic principle, elements, algorithm flow, advantages, and disadvantages of bee colony algorithm. To solve the problem that artificial bee colony algorithm is easy to fall into local optimum, this paper proposes an adaptive cauchy mutation artificial bee colony algorithm. This algorithm introduces adaptive factors to expand the search range of bee colony and uses the characteristics of Cauchy distribution to search the global, which improves the universality of bee colony search. Then using stochastic process theory, the adaptive Cauchy mutation artificial bee colony algorithm is analysed theoretically, and the convergence of the algorithm has demonstrated. Finally, we can use Matlab to implement the artificial bee colony algorithm, and we can optimize the Griewank function and Sphere function. In addition, this paper has successfully used in image multi-threshold feature retrieval. Compared with the conventional methods, it shows that the method is more accurate.

Three flywheel energy-stored impulse motor-generators (MGs) are used in the power supply system of HL-2A tokamak to produce short high-voltage or high-current pulse of desired parameters that are usually used for magnetic field coils and auxiliary heating equipment loads. The operation changing of these loads will cause disturbances in generator’s terminal voltage and the remarkable drop in MG’s rotating speed. This paper describes the implementation of an excitation controller using LabVIEW and CompactRIO for a 125-MVA impulse MG in power supply system of HL-2A/2M. Both a staged control strategy and digital PID algorithm built in LabVIEW are applied to the excitation controller that runs preciously in a 1-ms cycle to achieve voltage feedback control. The excitation controller, composed mainly of host computer and CompactRIO embedded reconfigurable system, is available to restore and stabilize terminal voltage in accordance with the desired voltage curves set by operators when pulsed loads and motor speed change quickly. It also implements real-time monitoring of the working condition and some electrical parameters of excitation system and communicates with central control system via Ethernet to either download discharge control files at time interval between two impulse discharges or upload waveform data generated in control process after a pulsed discharge. Engineering experiment results show that the use of excitation controller improves the voltage stiffness of the power supply system and provides the effective control of generator’s terminal voltage under the management of central control system.

Due to the toxicity and carcinogenicity, antimony and its compounds have been included as priority pollutants by Environmental Protection Agency of the United States (USEPA) and the European Union (EU). The removal methods of antimony need to be further studied. In this study, nZVI/Fe3O4 nanocomposites were synthesized, characterized, and applied to remove Sb(III). The nZVI/Fe3O4 nanocomposites before and after reaction with Sb(III) were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), vibrating sample magnetometry (VSM), and X-ray photoelectron spectroscopy (XPS). nZVI/Fe3O4 nanocomposites have a maximum Sb(III) adsorption capacity of 87.6 mg/g at pH 7.0. The removal of Sb(III) was a complex process including surface adsorption and oxidation. The removal of Sb(III) mainly involved three processes: (1) most Sb(III) was adsorbed on the surface of nZVI/Fe3O4 nanocomposites; (2) part of Sb(III) was rapidly oxidized to less toxic Sb(V); and (3) the generated Sb(V) was further adsorbed on the surface of nZVI/Fe3O4 nanocomposites. The nZVI/Fe3O4 nanocomposites can be separated from solution with an external magnet. The high Sb(III) removal efficiency and rapid separability of nZVI/Fe3O4 nanocomposites exhibited the great potential for the removal of Sb(III) from wastewater.

In this work, we introduced a method for capturing aqueous drop based on a patterned substrate in space. Through the manipulation test of a colloidal drop, it could be verified that this patterned substrate had excellent control ability for aqueous drop in microgravity condition. The confinement mechanism of this substrate was clarified, which showed that drops with different volume could be pinned and attracted at a given area on the substrate. The confinement capability was related to the gravity effect, and the patterned substrate could confine aqueous drops with larger volume under microgravity than in normal gravity. With advantages of simple operation and strong capability to control large drops, this technique exhibited the wide application prospect in the fields of fluid management, biosensing, and pharmacy in microgravity condition in the future.

The perception layer of Internet of Things (IOT) consists of various sensors. It is the source of the IOT to identify objects and collect information. Information fusion collected from multi-sensor has been widely used in various fields, such as intelligent industry, intelligent agriculture, intelligent transportation, and intelligent environmental protection. In this paper, multi-sensor image fusion, multispectral (MS) and panchromatic (PAN) images, is studied, and the fused images are used in target detection, recognition, and classification. However, traditional methods based on an injection model generally consider the MS images as a whole to compute the spectral weights. They ignore the local information of MS images and produce some spectral distortions, because for different objects, the spectral response will be different. Therefore, we propose a novel multi-sensor image fusion based on application layer of IOT (IFIOT) to preserve the spectral information of MS images. In this method, local homogeneous areas are found first by superpixel segmentation. Due to good properties of superpixel, the homogeneous areas are uniform and contain only one kind of object. Then, we estimate the spectral weights for different bands on the homogeneous area. The injection gain has an important influence on fusion results. Therefore, we adaptively compute the gain coefficients by minimizing the error between the spectral degraded MS and PAN images. Finally, after the injection of spatial details obtaining from the PAN image, fused images are produced. Experimental results reveal that the IFIOT method can give good fusion results and the spectral information is preserved well.

This paper aims to effectively preserve the spatial and spectral information of hyperspectral (HS) images. For this purpose, the author proposed a new image fusion method based on coupled tensor decomposition (CTD). First, the wanted high spatial resolution HS (HRHS) images were decomposed into the core tensor and basis matrices. Assuming that the basis matrices can be calculated from low spatial resolution HS (LRHS) images, the core tensor was estimated from the high spatial resolution multispectral (HRMS) images based on the relationship between HRHS and HRMS images. Finally, the HRHS images were obtained by reconstructing the core tensor with basis matrices. Owing to the good properties of tensor, the proposed method achieved better fusion results on different data sets than those of the contrastive methods. The research findings shed new light on hyperspectral pansharpening.

The coating is applied to prevent corrosion on the surface of ships or marine structures, and the thickness of the coating affects its anti-corrosion effect. As a result, non-destructive testing (NDT) is required to measure coating thickness, and ultrasonic NDT is a convenient and quick way to measure the thickness of underwater coatings. However, the offshore coating’s energy attenuation and absorption rates are high, the ultrasonic pulse echo test is difficult, and the testing environment is harsh. Because of the coating’s high attenuation, the distance of the optimal water delay line designed based on the reflection coefficient of the vertically incident wave is used. To accurately measure the thickness of the coating material, TOF of the reflected echo on the time-domain waveform was evaluated. The experimental results show that, when compared to caliper measurements, the coating thickness measured by the proposed method has a lower error and can be used for accurate measurement. The use of ultrasonic water immersion measurement is almost limitless in terms of size, location, and material of the object to be measured, and it is expected to be used to measure the thickness of the surface coating of ships or marine structures in the water.

Metals which are widely used in many types of industries are usually subjected to fatigue and surface corrosion. There is a demand to detect the surface damage caused by fatigue and corrosion at an early stage to ensure the structural integrity. In this paper, a novel nonlinear ultrasonic technique based on the measure of third-order combined harmonic generation, is proposed to detect and locate the surface damage in 6061 aluminum alloy. Third-order combined harmonic generation caused by non-collinear mixing of one longitudinal wave and one transverse wave at different frequencies, is firstly analyzed and experimentally observed. An experimental procedure of nonlinear scanning is proposed for the damage detection and location by checking the variation of frequency nonlinear response. The correlations of nonlinear frequency mixing responses and surface damage in the specimens are obtained. Results show that the nonlinear response caused by fatigue damage and surface corrosion can be identified and located by this method. In addition, this approach can exclude the nonlinearity induced by the instruments and simplify the signal processing.

Targeting the autophagy process is considered to be a promising new strategy for drug treatment of ovarian cancer. α-Tomatine, a steroidal alkaloid extracted, is mainly isolated from leaves, roots and immature green tomatoes. α-Tomatine has biological activities such as anticancer, antioxidative and anti-inflammatory. The study aimed to explore the effects of α-tomatine on proliferation, apoptosis and autophagy and the underlying mechanisms in ovarian cancer Skov3 cells. After treatment with different concentrations of α-tomatine (0, 0.75, 1 and 1.5 μM) in Skov3 cells for 24 h, proliferation was determined by the CCK-8 assay, and apoptosis was detected by flow cytometric analysis. Autophagy in cells was determined by the number of fluorescent spots using confocal fluorescence microscopy after mRFP-GFP-LC3 transfection. The relationship between autophagy and apoptosis was proved by Beclin-1 overexpression. The protein expression levels were tested by western blotting. The results demonstrated that α-tomatine effectively repressed proliferation, exerted a proapoptotic effect and inhibited early-stage autophagy in Skov3 cells in a dose- and time-dependent manner. Additionally, Beclin-1 overexpression significantly suppressed α-tomatine-treated apoptosis in Skov3 cells, indicating that α-tomatine inhibits autophagy to induce apoptosis. We also found α-tomatine inhibited the protein expression levels of PI3K/Akt/mTOR signaling pathway. However, the autophagy inhibition of α-tomatine could be reversed obviously by Beclin-1 overexpression. Taken together, α-tomatine inhibited autophagy through Beclin-1. Our study suggests that α-tomatine, as a novel early-stage autophagy inhibitor, might be a potential drug for further treatment of ovarian cancer by inhibiting proliferation and promoting apoptosis.

Supercooled large droplets widely exist in clouds, which have poor aerodynamic follow-up and strong dynamic characteristics, making the relevant experiments and numerical simulation more difficult. Splash is the main influencing factor of droplet collection efficiency, and it is easier to be recorded and quantified. In the LEWICE model, little or no splash happened around stagnation point. Focus on this problem, an improved large droplet splashing model is proposed based on the idea of minimum mass loss ratio. In the numerical simulation part, the advantages and disadvantages of the proposed model are analyzed by comparing with several classical splashing models and experimental data. Based on the experimental data of airfoil MS317, the validity of the model is verified. Moreover, airfoil NACA23012 and ARJ cruise configuration are chosen to obtain the droplet collection efficiency, which shows the feasibility of the proposed model.

In this study, a facile water-soluble fluorescence sensor 2-((2-hydroxybenzylidene)-amino)-2-(hydroxymethyl)propane-1,3-diol (ST) was synthesized via one-step reaction, and its fluorescence sensing performance for Al3+ both in aqueous solution and on paper substrate was evaluated. The results showed that ST exhibited an specific fluorescence "turn-on" response to Al3+ over other cations in aqueous solution as well as on the test paper. The limit of detection was found to be 3.2×10-7M, which revealed that the obtained Schiff-base based fluorescence chemosensor ST possessed a great potential for the rapid, quantitative and qualitative detection of Al3+.

It has been shown that the use of frequency mixing response has some unique advantages over the nonlinear ultrasonic technique based on the higher harmonic generation, such as frequency selectivity, which can intentionally avoid receiving unexpected harmonic components induced by the instrumental systems. In addition, the feature of spatial selectivity of scanning wave mixing technique can readily be used to locate the region of damage. In this paper, frequency mixing response induced by the collinear interaction of two primary Lamb wave modes with different frequencies in an isotropic and homogenous plate is theoretically analyzed and experimentally observed. The second- and third-order combined harmonics generated by the collinear wave mixing of two primary Lamb waves propagating in a given specimen are analyzed, and meanwhile the existences of the combined harmonics at some specific frequencies are predicted. An experimental procedure is proposed to measure the combined harmonics that are induced by the collinear cross-interaction of the two specific primary Lamb wave modes at some given frequencies. The theoretical analysis and experimental observation provide a clear physical insight into the frequency mixing response induced by the collinear cross-interaction of two primary ultrasonic Lamb wave modes. Considering the difficulty for experimental verification for theoretical predictions in a systematic manner, characteristics of nonlinear frequency response for Lamb waves mixing are also examined numerically in this paper. Results indicate that the synchronism and symmetric property of selection of primary Lamb wave mode pair significantly affect the generation of combined harmonic waves at mixing frequencies. These numerical investigations clearly illustrate the physical process and nonlinear feature of Lamb waves mixing. It is shown that the controllable potential of mode pair selection for Lamb waves mixing, which is of practical significance for nonlinear acoustic scanning in large specimen.

Sepsis is still a severe health problem worldwide with high morbidity and mortality. Blood bacterial culture remains the gold standard for the detection of pathogenic bacteria in bloodstream infections, but it is time-consuming, and both the sophisticated equipment and well-trained personnel are required. Immunoassays and genetic diagnosis are expensive and limited to specificity and sensitivity. Aptamers are single-stranded deoxyribonucleic acid (ssDNA) and ribonucleic acid (RNA) oligonucleotide or peptide sequence generated in vitro based on the binding affinity of aptamer-target by a process known as Systematic Evolution of Ligands by Exponential Enrichment (SELEX). By taking several advantages over monoclonal antibodies and other conventional small-molecule therapeutics, such as high specificity and affinity, negligible batch-to-batch variation, flexible modification and production, thermal stability, low immunogenicity and lack of toxicity, aptamers are presently becoming promising novel diagnostic and therapeutic agents. This review describes the prospective application of aptamerbased laboratory diagnostic assays and therapeutics for pathogenic bacteria and toxins in bloodstream infections.

Understanding and manipulating the non-Hermitian optical property based on coherent atomic gases is of great importance and has attracted much theoretical and experimental attentions. Advancing this study to the nonlinear optics regime is highly desirable due to its importance in fundamental physics and potential applications. In this work, we propose to realize a tunable electromagnetically induced grating (EIG) with parity-time ($\mathcal{PT}$) symmetry in a cold gas of Rydberg atoms, where interatomic interactions between Rydberg states are mapped to strong and long-range optical interactions, and investigate nonlinear light diffractions in this system. We show that for far-field diffraction, laser beams incident upon the $\mathcal{PT}$-symmetric EIG display distinctive asymmetric diffraction fringes, which can be actively manipulated through tuning the gain-absorption coefficient of the EIG, the incident intensity of the laser beam, and the nonlocality provided by Rydberg atoms. For near-field diffraction, the nonlinear Talbot diffraction carpets emerge and can be modulated by $\mathcal{PT}$ symmetry in the presence of strong nonlocal interactions, allowing the realization of controllable optical self-imaging. The results are not only imperative for the study of non-Hermitian nonlinear optics but also useful for characterizing the interatomic interaction in Rydberg gases and for designing new optical devices useful in optical information processing and transmission.

Drought and nitrogen (N) addition have been shown to affect tree hydraulic traits, but few studies have been made on their interactions across species with different wood types or leaf forms. We examined the responses of hydraulic conductance and xylem anatomical traits of Quercus mongolica (ring porous with simple leaves), Fraxinus mandshurica (ring porous with compound leaves) and Tilia amurensis (diffuse porous with simple leaves) to drought, N addition and their interactions. Drought stress decreased current-year xylem-specific conductivity in stems (Ksx) and leaf hydraulic conductance (Kleaf ), but N addition affected Ksx and Kleaf differently among species and watering regimes. These divergent effects were associated with different responses of anatomical traits and leaf forms. Higher mean vessel diameter in stems and lower vessel density in leaves were observed with N addition. The three-way interactive effects of drought, N addition and tree species were significant for most values of anatomical traits. These results were also reflected in large differences in vessel diameter and density among species with different wood types or leaf forms. The two-way interactive effects of drought and N addition were significant on Kleaf and predawn water potential, but not Ksx, indicating that leaves were more sensitive than stems to a combination of drought stress and N addition. Our results provide mechanistic insight into the variable responses of xylem water transport to the interactions of drought and N availability.

Drying droplets on solid substrates has always formed a nonuniform and disordered "coffee ring" stain, which has a great negative effect on the application of inject printing and colloidal assembly. We obtain a macrouniform and micro-ordered pattern through evaporation of a colloidal droplet resting on a liquid substrate. The evaporative convection and the capillary forces were responsible for the formation of the ordered structures, which assembled into a monolayer pattern at the liquid-air interface under the action of the weak capillary flow and shrinkage of the triple line. The central bump deposits with disordered particle stacking on the liquid-liquid interface could be attributed to the fast meeting of the descending particles (gravitational sedimentation) and ascending liquid-liquid interface; they would scatter on the ordered monolayer structure and form the final uniform pattern.

Generating quantum entanglement in large systems on time scales much shorter than the coherence time is key to powerful quantum simulation and computation. Trapped ions are among the most accurately controlled and best isolated quantum systems with low-error entanglement gates operated via the vibrational motion of a few-ion crystal within tens of microseconds. To exceed the level of complexity tractable by classical computers the main challenge is to realise fast entanglement operations in large ion crystals. The strong dipole-dipole interactions in polar molecule and Rydberg atom systems allow much faster entangling gates, yet stable state-independent confinement comparable with trapped ions needs to be demonstrated in these systems. Here, we combine the benefits of these approaches: we report a $700\,\mathrm{ns}$ two-ion entangling gate which utilises the strong dipolar interaction between trapped Rydberg ions and produce a Bell state with $78\%$ fidelity. The sources of gate error are identified and a total error below $0.2\%$ is predicted for experimentally-achievable parameters. Furthermore, we predict that residual coupling to motional modes contributes $\sim 10^{-4}$ gate error in a large ion crystal of 100 ions. This provides a new avenue to significantly speed up and scale up trapped ion quantum computers and simulators., 23 pages, 7 figures

Supplemental Digital Content is available in the text, Backgrounds: Previous investigations yielded inconsistent results for the associations between pancreatic cancer (PC) risk and genetic polymorphisms. The study aimed to perform a systematic review and meta-analysis of studies exploring association of some genetic polymorphisms and PC risk. Methods: We systematically searched on PubMed and Web of Science for association of genetic polymorphisms and PC risk published from 1969 to January 2019. We computed the multivariate odd ratio (OR) and 95% confidence intervals (CI), comparing different genetic types. Results: The present meta-analysis showed significant associations between deoxyribonucleic acid (DNA) repair gene (X-ray repair cross-complementing group 1 (XRCC1) Arg399GIn and Arg194Trp, excision repair cross complementation 1 (ERCC1) rs11615 and rs3212986, ERCC2 rs13181) polymorphisms and PC risk. Conclusions: Because of the limited sample size and ethnicity enrolled in the present meta-analysis, further larger scaled studies should be performed to demonstrate the association.

Aiming at the practicability of license plate recognition, a robust license plate recognition system is designed. Firstly, Sobel-Color algorithm is proposed to locate license plate based on Sobel edge and color features, and combined with MSER algorithm, a reliable license plate location method is designed to obtain candidate license plate regions, and then the SVM algorithm is used to judge them. Finally, a license plate character segmentation algorithm is designed according to the license plate characteristics, which can segment the characters of the license plate correctly, and effectively remove the false characters of the edge of the license plate. According to the characteristics of the license plate characters, the LeNet-5 depth network model is improved, and then the improved LeNet-5 network is used to recognize the license plate characters. The normal condition test, harsh condition test and efficiency test of the license plate recognition system are carried out. The experimental results show that the method of license plate location and license plate judgment has high reliability, and the license plate character recognition has high accuracy. Therefore, the designed license plate recognition system has good robustness and practicability.

We introduce a simple model system to study synchronization theoretically in quantum oscillators that are not just in limit-cycle states, but rather display a more complex bistable dynamics. Our oscillator model is purely dissipative, with a two-photon gain balanced by single- and three-photon loss processes. When the gain rate is low, loss processes dominate and the oscillator has a very low photon occupation number. In contrast, for large gain rates, the oscillator is driven into a limit-cycle state where photon numbers can become large. The bistability emerges between these limiting cases with a region of coexistence of limit-cycle and low-occupation states. Although an individual oscillator has no preferred phase, when two of them are coupled together a relative phase preference is generated which can indicate synchronization of the dynamics. We find that the form and strength of the relative phase preference varies widely depending on the dynamical states of the oscillators. In the limit-cycle regime, the phase distribution is $\pi$-periodic with peaks at $0$ and $\pi$, whilst in the low-occupation regime $\pi$-periodic phase distributions can be produced with peaks at $\pi/2$ and $3\pi/2$. Tuning the coupled system between these two regimes reveals a region where the relative phase distribution has $\pi/2$-periodicity., Comment: 12 pages, 6 figures

We introduce a scheme to entangle Rydberg ions in a linear ion crystal, using the high electric polarizability of the Rydberg electronic states in combination with mutual Coulomb coupling of ions that establishes common modes of motion. After laser-initialization of ions to a superposition of ground- and Rydberg-state, the entanglement operation is driven purely by applying a voltage pulse that shuttles the ion crystal back and forth. This operation can achieve entanglement on a sub-$\mu$s timescale, more than two orders of magnitude faster than typical gate operations driven by continuous-wave lasers. Our analysis shows that the fidelity achieved with this protocol can exceed $99.9\%$ with experimentally achievable parameters., Comment: 8 pages, 4 figures

The use of an acoustic nonlinear response has been accepted as a promising alternative for the assessment of micro-structural damage in metallic solids. However, the full mechanism of the acoustic nonlinear response caused by the material micro-damages is quite complex and not yet well understood. In this paper, the effect of material microstructural evolution on acoustic nonlinear response of ultrasonic waves is investigated in rolled copper and brass. Microstructural evolution in the specimens is artificially controlled by cold rolling and annealing treatments. The correlations of acoustic nonlinear responses of ultrasonic waves in the specimens corresponding to the microstructural changes are obtained experimentally. To eliminate the influence of attenuation, which was induced by microstructural changes in specimens, experimentally-measured nonlinear parameters are corrected by an attenuation correction term. An obvious decrease of nonlinearity with the increase of grain size is found in the study. In addition, the influences of material micro-damages introduced by cold rolling on the acoustic nonlinear response in specimens are compared with the ones of grain boundaries controlled by heat treatment in specimens. The experimental results show that the degradation of material mechanical properties is not always accompanied by the increase of acoustic nonlinearity generated. It suggested that the nonlinear ultrasonic technique can be used to effectively characterize the material degradations, under the condition that the variations of grain sizes in the specimens under different damage states are negligible.

This study aimed to screen DNA aptamers against the signal molecule C4-HSL of the rhl system for the inhibition of biofilm formation of Pseudomonas aeruginosa using an improved systematic evolution of ligand by exponential enrichment (SELEX) method based on a structure-switching fluorescent activating bead. The aptamers against the C4-HSL with a high affinity and specifity were successfully obtained and evaluated in real-time by this method. Results of biofilm inhibition experiments in vitro showed that the biofilm formation of P. aeruginosa was efficiently reduced to about 1/3 by the aptamers compared with that of the groups without the aptamers. Independent secondary structure simulation and computer-aided tertiary structure prediction (3dRNA) showed that the aptamers contained a highly conserved Y-shaped structural unit. Therefore, this study benefits the search for new methods for the detection and treatment of P. aeruginosa biofilm formation.

The use of ultrasonic guided wave, which has been widely accepted as a conventional, screening NDE tool to overcome the inaccessibility of large scale structural integrities is now being extended to early stage damage detection in conjunction with its nonlinear features for more precise material characterization. The status of guided wave based NDE is evolved from detecting geometric defects to monitoring strength related ones. Combining guided wave based NDE schemes with its nonlinearity is challenging due to the existence of multiple modes, the dispersive manner and the need of proper mode tuning. In this paper, some key concepts for the success will be introduced along with recent accomplishments including nonlinear guided wave imaging and application to composites.

The manipulation of liquid drops could be very promising in space applications, such as fluid management, heat exchangers, life support systems, etc. Colloidal material box is one of a subsystem and payload of SJ-10 satellite, which was designed for studying the aqueous drop control and colloidal assembling in space. Based on space experiment platform (colloid material box), we have carried out the drop manipulation experiment in space successfully by using the hydrophilic/hydrophobic patterned surface technique, and the mechanism of the drop wetting and control on the patterned substrate during drop evaporation have been further studied. In addition, the drying process of the constrained colloidal drops on the patterned surface has been investigated. Through analyzing deposition patterns of both sessile and pendant droplets, we found that the deposition morphology is the result of competition and cooperation interactions of the free setting, the interface shrinkage and the outward capillary flow. Two different regimes for the relative motion between the particles and the interface was proposed: the pursuit regime (sessile droplet) and the meeting regime (pendant droplet), which furthered the theory of particles deposition in drying droplet.

Collective excitations (spinwaves) of long-lived atomic hyperfine states can be synthesized into a Bose-Hubbard model in momentum space. We explore many-body ground states and dynamics of a two-leg momentum-space lattice formed by two coupled hyperfine states. Essential ingredients of this setting are a staggered artificial magnetic field engineered by lasers that couple the spinwave states, and a state-dependent long-range interaction, which is induced by laser-dressing a hyperfine state to a Rydberg state. The Rydberg dressed two-body interaction gives rise to a state-dependent blockade in momentum space, and can amplify staggered flux induced anti-chiral edge currents in the many-body ground state in the presence of magnetic flux. When the Rydberg dressing is applied to both hyperfine states, exotic sliding insulating and superfluid/supersolid phases emerge. Due to the Rydberg dressed long-range interaction, spinwaves slide along a leg of the momentum-space lattice without costing energy. Our study paves a route to the quantum simulation of topological phases and exotic dynamics with interacting spinwaves of atomic hyperfine states in momentum-space lattice., Comment: 5 pages, 4 figrures, with Supplemental Material, accepted by Phys. Rev. Lett

Nonlinear guided wave has been recognized as a potential means to characterize the state of material microstructures in solids. However, nonlinear guided wave approaches based on second harmonic generation or combined harmonic generation induced by counter-directional wave mixing, are applicable only under the condition that transmitters and receivers are placed at two different ends of the tested structures. These approaches are not effective for characterization of the structures with only one accessible end. In this paper, modeling of the backward combined harmonic at difference frequency induced by one-way mixing of two primary co-directional guided waves is investigated in a circular pipe, where the transmitters and receivers are placed at the same end of the pipe. The backward combined harmonic, generated at difference frequency and propagating in the direction opposite to that of two primary co-directional guided waves, is successfully observed numerically. A strong frequency mixing response characterized by a cumulative growth effect of the generated backward combined harmonic is demonstrated. The use of the generated backward combined harmonic for localized material degradation characterization and location is numerically examined in the given pipe. The obtained results indicate that the use of the backward combined harmonic can locate and characterize the localized material degradations in the given pipe by controlling the mixing zone of two primary co-directional guided waves. This study provides a promising means for characterization of localized degradations in pipes.

The curved composite structures are popularly used in the aerospace field for their superior properties. Complexity of structure and geometry generally limit the inspection or monitoring effect of different types of defects in the curved composite structure. A feasible damage probabilistic tomography algorithm combined with ultrasonic guided wave technology is necessary to be developed for the structural health monitoring of curved composite structures. In this paper, defect zones in a curved composite structure are characterized using the modified probabilistic tomography (MPT) method and fusion of damage index (DI). The MPT with the defect shape factor βM at each damage-impaired path and hybrid DI schemes are proposed to indicate the location and propagation of defect zones in tested sample. The feasibility of proposed approaches is verified on the curved carbon/epoxy composite structure, experimentally. The results show that the MPT and fusion DI methods successfully represent the extension of defect zones in a quantitative manner. It is suggested that the accuracy and reliability of localization results of the MPT algorithm is better than those obtained by the probabilistic tomography (PT) algorithm with the averaged β.

Fractional operators are the main tools to describe diffusion problems on fractal objects. This paper first shows the equivalence between conformable fractional derivative and fractal derivative, and then investigates various models for the diffusion on fractal objects by the conformable fractional derivative and its generalized form. The recommended models are solved by the mesh-free physics-informed neural network method with high computational effectiveness and universality.

The propagation characteristics of feature guided waves (FGWs) in topographical waveguides, such as welded joints, have been widely investigated. However, most of these investigations analyzed linear acoustic characteristics. Considering the high sensitivity of nonlinear ultrasonic techniques in the nondestructive evaluation of microscopic defects in materials, such as identifying micro-defects at an early stage, it is particularly relevant to investigate the nonlinear acoustic response of FGWs in topographical waveguides. In this paper, we use a theoretical analysis and numerical simulation to investigate the second-harmonic generation (SHG) of FGWs in a welded joint. The theoretical framework is firstly expounded based on the reciprocity relation and modal expansion with the nonlinear semi-analytical finite element (SAFE) method and perfectly matched layers. Numerical models are implemented to predict the effect of SHG of FGWs in a welded joint. Two families of FGW propagation in a welded joint are analyzed. The results obtained demonstrate that mode conversion and the cumulative effect of the generated second harmonics can be observed in the welded joint. This investigation provides new physical insights into SHG for FGW propagation.

Snowpack in winter is very sensitive to climate change, and may in turn induce complex effects on terrestrial biochemistry processes. Here we synthesized the results from 49 papers based on snow depth manipulation experiments and conducted a meta-analysis to evaluate the general response of 9 variables related to terrestrial carbon pools and dynamics to the altered snowpack depth. Our meta-analysis results indicated that increasing snowpack depth significantly increased litter biomass (+18.4%), MBC (+18.2%) and CO2 emission (+15.5%), and significantly decreased litter C: N ratio (−5.8%) and total soil carbon (−28.5%) under snow addition manipulation, but did not significantly affect fine root biomass, MBC: MBN ratio and soil dissolved organic carbon (DOC). However, increasing snowpack depth only significantly altered litter C: N ratio (+11.2%) under snow removal manipulation. The different responses between snow addition and removal were possibly related to the higher soil temperature and moisture under snow addition than under snow removal manipulation experiments. In addition, the effect of increasing snowpack depth on CH4 flux was not significant, presumably because all these studies were compiled from snow-removal experiments. These results are useful for a better understanding of the effects of altered snowpack on terrestrial carbon cycling under climate change scenarios.

To study the self-assembly behavior of colloidal spheres in the solid/liquid interface and elucidate the mechanism of liquid crystal phase transition under microgravity, a Colloidal Material Box (CMB) was designed which consists of three modules: (i) colloidal evaporation experimental module, made up of a sample management unit, an injection management unit and an optical observation unit; (ii) liquid crystal phase transition experimental module, including a sample management unit and an optical observation unit; (iii) electronic control module. The following two experimental plans will be performed inside the CMB aboard the SJ-10 satellite in space. (i) Self-assembly of colloidal spheres (with and without Au shell) induced by droplet evaporation, allowing observation of the dynamic process of the colloidal spheres within the droplet and the change of the droplet outer profile during evaporation; (ii) Phase behavior of Mg2Al LDHs suspensions in microgravity. The experimental results will be the first experimental observations of depositing ordered colloidal crystals and their self-assembly behavior under microgravity, and will illustrate the influence of gravity on liquid crystal phase transition.

The use of guided wave tomography has become an attractive alternative to convert ultrasonic wave raw data to visualized results for quantitative signal interpretation. For more accurate life prediction and efficient management strategies for critical structural components, there is a demand of imaging micro-damages in early stage. However, there is rarely investigation on guided wave tomographic imaging of micro-defects. One of the reasons for this might be that it becomes challenging to monitor tiny signal difference coefficient in a reliable manner for wave propagation in the specimens with micro-damages. Nonlinear acoustic signal whose frequency differs from that of the input signal can be found in the specimens with micro-damages. Therefore, the combination of guided wave tomography and nonlinear acoustic response induced by micro-damages could be a feasibility study for imaging micro-damages. In this paper, the nonlinear Rayleigh surface wave tomographic method is investigated to locate and size micro-corrosive defect region in an isotropic solid media. The variations of acoustic nonlinear responses of ultrasonic waves in the specimens with and without defects are used in guided wave tomographic algorithm to construct the images. The comparisons between images obtained by experimental signals and real defect region induced by hydrogen corrosion are presented in this paper. Results show that the images of defect regions with different shape, size and location are successfully obtained by this novel technique, while there is no visualized result constructed by conventional linear ultrasonic tomographic one. The present approach shows a potential for inspecting, locating and imaging micro-defects by nonlinear Rayleigh surface wave tomography.

Coal liquefaction residues with a high content of nitrogen were used to prepare N-doped activated carbon as a catalyst of the oxygen reduction reaction (ORR). N-Doped activated carbon materials prepared at 900 °C (AC-900) exhibited a large specific surface area of 3130 m2 g−1 and a small average pore size of 1.91 nm. AC-900 also displayed more edges on the surface and higher N-doped contents of pyridinic-N and graphitic-N, which enhanced the conductivity and created more catalytic active sites. Electrochemical tests showed for AC-900 a half-peak current density of −2.11 mA cm−2 at a potential of −0.17 V, which was only 63 mV lower than that of the commercial Pt/C (20%) catalyst. As much as 85.1% of the initial current density for AC-900 was maintained during the course of a stability test lasting 20000 s compared with a value of 82.1% for the commercial Pt/C (20%) catalyst. Low-cost N-doped activated carbon should not only be an efficient non-precious catalyst for the ORR in alkaline fuel cells but also offer a porous carbon precursor for the further preparation of compound catalysts.

In this work, thiol-functionalized MnFe2O4-MCM-41 (MnFe2O4-MCM-41-SH) was applied to remove Sb(III) from wastewater. Superparamagnetic MnFe2O4 nanoparticles were incorporated onto the thiol-functionalized MCM-41, which not only solved the aggregation problem of MnFe2O4 nanoparticles and the difficulty in separation of MCM-41, but also improved adsorption efficiency for Sb(III). The removal of Sb(III) by MnFe2O4-MCM-41-SH was investigated through batch experiments. The research results showed excellent adsorption performance and re-usability of MnFe2O4-MCM-41-SH. According to the Langmuir isotherm model, the maximum adsorption capacity of Sb(III) by MnFe2O4-MCM-41-SH is 164.8 mg/g. The Sb(III) removal efficiency was around 89.1% in the fifth cycle by MnFe2O4-MCM-41-SH with desorption treatment. On the basis of X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy, the Sb(III) removal mechanism was discussed. The reaction mechanism between Sb(III) and MnFe2O4-MCM-41-SH was complex, involving surface adsorption, oxidation, and reduction. In view of magnetic property and the high removal efficiency of Sb(III), MnFe2O4-MCM-41-SH is a promising adsorbent for Sb(III).