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As a typical IV-VI compound, SnTe has aroused widely attentions in the thermoelectric community due its similar crystal and band structures with PbTe. However, both the large number of inherent Sn vacancies and high thermal conductivity result in inferior thermoelectric performance in intrinsic SnTe over a broad temperature. In this work, we successfully improved those disadvantages of SnTe via stepwisely Pb heavily alloying and then In doping. A significantly wide fraction of Pb into SnTe (0–50%) achieves multiple effects: (a) the carrier concentration of SnTe is reduced through decreasing Sn vacancies via alloying high solution Pb atoms in the matrix; (b) the band structure is optimized through promoting the convergence of the two valence bands, simultaneously enhancing the Seebeck coefficient; (c) HAADF-STEM coupled with EDS results illustrate that guest Pb atoms randomly and uniformly occupied Sn atomic sites in the matrix, concurrently strengthening the phonon scattering. Furthermore, we introduced indium into Sn0.6Pb0.4Te system to create resonant states further enlarging the power factors at low-medium temperature. The integration of bands convergence and DOS distortion achieves a considerably high ZTave of ∼0.67 over the wide temperature range of 300–823 K in (Sn0.6Pb0.4)0.995In0.005Te sample.

Only 0.1% of the acoustic energy can transmit across the water-air interface because of the huge acoustic impedance mismatch. Enhancing acoustic transmission across the water-air interface is of great significance for sonar communications and sensing. However, due to the interface instability and subwavelength characteristics of acoustic metamaterials, wide-angle intermediate-frequency (10 kHz-100 kHz) water-air acoustic transmission remains a great challenge. Here, we demonstrate that the lotus leaf is a natural low-cost acoustic transmission metasurface, namely, the lotus acoustic metasurface (LAM). Experiments demonstrate the LAM can enhance the acoustic transmission across the water-air interface, with an energy transmission coefficient of about 40% at 28 kHz. Furthermore, by fabricating artificial LAMs, the operating frequencies can be flexibly adjusted. Also, the LAM allows a wide-angle water-to-air acoustic transmission. It will enable various promising applications, such as detecting and imaging underwater objects from the air, communicating between ocean and atmosphere, reducing ocean noises, etc.

Using Martian resource to construct a site on Mars is a superior choice to instead of transporting all the construction materials from Earth to the Mas with incredibly high cost. This study proposes a developed Martian concrete composed of sulfur and magnetite, heated by microwave to meet the energy-poor environment on Mars. A lattice Boltzmann model is developed to determine the optimal microwave power and heating time for Martian concrete casting. The compressive strength and microstructure of Martian concrete casted by microwave are measured by test. Finally, a 3D printed device is conceived to prepare Martian concrete and the four-layered specimen is casted to simulate the 3D print process. The results indicate that the compressive strength of Martian concrete casted by microwave can reach 1.78 kgf/mm2 (17.44 MPa) on earth, which is corresponding to 4.62 kgf/mm2 on Mars. Since the heating rate of magnetite under microwave is very high, if possible, the low microwave power and long heating time should be chosen to reduce the temperature gradient in matrix and reduce the possibility of sulfur matrix boiling. In addition, the strength of four-layered (simulated 3D printed) Martian concrete can reach 1.21 kgf/mm2 (11.86 MPa) on earth, which is corresponding to 3.15 kgf/mm2 on Mars.

Chemical durability of lanthanide zirconates (A2Zr2O7) (A = La-Yb) under near-field environments is important for evaluating their application as potential nuclear waste forms. In this work, A2Zr2O7 (A = La-Yb) are synthesized by spark plasma sintering with controlled microstructure and their chemical durability are evaluated in a nitric acid solution (pH = 1). Scanning transmission electron microscopy analysis reveals an amorphous passivation film either enriched with Zr or lanthanide. The complex chemistry of the passivation films can be correlated with a transition in corrosion mechanisms from a preferential release of lanthanide in La2Zr2O7 to a preferential release of Zr in Er2Zr2O7 and Yb2Zr2O7. These results suggest a dominant mechanism of incongruent dissolution and surface reorganization for the formation of passivation films. Strong correlations are identified between the leaching rates and cation ionic size, ionic potential, electronegativity differences between A-site cation and Zr, and bonding valence sum of oxygen, suggesting important impacts of structural and bonding characteristics in controlling chemical durability of lanthanide zirconates.

Thermoelectric materials transfer heat and electrical energy, being useful for power generation or cooling applications. Many of these materials have narrow bandgaps, especially for cooling applications where this property has been seen as particularly important for enhancing the thermoelectric properties. We developed SnSe crystals with a wide bandgap Eg ~ 33 kBT with attractive thermoelectric properties through Pb alloying. The momentum and energy multiband alignment promoted by Pb alloying resulted in an ultra-high power factor ~75 μWcm–1K–2 at 300 K, and a ZTave ~ 1.90. We show that a 31-pair thermoelectric device can produce a power generation efficiency ~4.4% and a cooling ΔTmax ~ 45.7 K. These results demonstrate that wide bandgap compounds can be used for thermoelectric cooling applications.

Marine structures are inevitably influenced by parametric perturbations as well as multiple external loadings. Among these loadings, earthquake is generally more destructive and unpredictable than others. It is significant to develop effective active control schemes to guarantee the safety, stability, and integrity of marine structures subject to earthquakes and parametric perturbations. In this paper, the problem of networked [Formula: see text] robust damping control is addressed to stabilize a marine structure subject to earthquakes. First, in consideration of perturbations of the structure parameters, an uncertain model of the networked marine structure under earthquakes is presented. Second, a robust networked [Formula: see text] control scheme is presented to suppress seismic responses of the structure. By using stability theory of time-delay systems, several sufficient conditions on robust stability of the networked marine structure system are obtained, and the linear matrix inequality methods are utilized to solve the gain matrix of the controller. Finally, simulation indicates that compared with the traditional robust [Formula: see text] control and the proposed networked [Formula: see text] control, the seismic responses amplitudes of the marine structure under the two controllers are almost the same, while the latter is more economic than the former.

Incentive mechanism design has aroused extensive attention for crowdsourcing applications in recent years. Most research assumes that participants are already in the system and aware of the existence of crowdsourcing tasks. Whereas in real-life scenarios without this assumption, it is more effective to leverage incentive tree mechanisms that incentivize both users’ direct contributions and solicitations to other users. Although such mechanisms have been investigated, we are the first to propose budget-balanced incentive tree mechanisms, called generalized lottrees , which require the total payout to be equal to the announced budget, while guaranteeing several desirable properties including continuing contribution incentive , continuing solicitation incentive , value proportional to contribution , unprofitable solicitor bypassing , and unprofitable Sybil attack . Moreover, three types of generalized lottree mechanisms, 1-Pachira , $K$ K -Pachira and Sharing-Pachira , are presented for supporting diversified requirements. A solid theoretical guideline on the mechanism selection is provided based on the Cumulative Prospect Theory. Both extensive simulations and realistic experiments with 82 users are conducted to confirm our theoretical analysis.

An advanced method called internal electromagnetic stirring (I-EMS) was investigated to resolve the engineering problems like coarse-grain, inhomogeneous structure and macrosegregation. The electromagnetic stirrer functioned with internal-cooling was inserted in the melt during DC casting. In this study, a round billet of 2219 alloy DC cast with a diameter of 880mm under I-EMS process condition was produced, and its structure and composition distribution were comparatively characterized. The results show that the mean grain size decreased from the range of 872, 1023, 332 μm to the range of 317, 438, 271 μm at different billet positions with I-EMS. I-EMS consequently produce superior grain refinement and homogeneity. The effect of I-EMS on the grain-refinement and macrosegregation was also discussed.

Due to significant differences in imaging mechanisms between multimodal images, registration methods have difficulty in achieving the ideal effect in terms of time consumption and matching precision. Therefore, this paper puts forward a rapid and robust method for multimodal image registration by exploiting local edge information. The method is based on the framework of SURF and can simultaneously achieve real time and accuracy. Due to the unpredictability of multimodal images’ textures, the local edge descriptor is built based on the edge histogram of neighborhood around keypoints. Moreover, in order to increase the robustness of the whole algorithm and maintain the SURF’s fast characteristic, saliency assessment of keypoints and the concept of self-similar factor are presented and introduced. Experimental results show that the proposed method achieves higher precision and consumes less time than other multimodality registration methods. In addition, the robustness and stability of the method are also demonstrated in the presence of image blurring, rotation, noise, and luminance variations.

SnSe crystals have been discovered as one of the most efficient thermoelectric materials due to their remarkable thermal and electrical transports. But the polycrystalline SnSe possesses much lower performance especially for the low carrier mobility and electrical conductivity. We firstly attempted to explain and verify the difference in the electrical conductivity as a function of temperature between p-type crystalline and polycrystalline SnSe by considering the grain boundary effects in the polycrystalline samples. On the basis of 2% Na doping to optimize the carrier concentration, the carrier mobility is improved by further introducing In, leading to enhanced carrier mobility from 3 to 9 cm2·V−1·s−1 in polycrystalline SnSe. Moreover, In doping introduces extra resonant levels in SnSe, which increases the density of states near Fermi level and leads to an enhanced band effective mass. Large Seebeck coefficient of ~ 205 μV·K−1 at 300 K and maximum power factor of ~ 7.5 μW·cm−1·K−2 at 773 K can be obtained in the Sn0.975Na0.02In0.005Se sample, leading to a competitively high dimensionless figure of merit (ZT) value exceeding 1.1 at 773 K. 晶体 SnSe 由于出色的电声传输性能, 不断表现出优异的热电特性。但是, 相对于晶体, 多晶 SnSe 的电导率和载流子迁移率呈现数量级的降低。首先, 我们试图通过考虑多晶样品中晶界的影响来解释 p 型晶体 SnSe 和多晶 SnSe 的电导率随温度变化的差异。通过掺杂 2% 的 Na 来优化多晶 SnSe 的载流子浓度, 在此基础上引入 In 提高了基体的载流子迁移率, 样品的室温迁移率由 3 cm2·V-1·s-1增加到 9 cm2·V-1·s-1。此外, 通过在多晶 SnSe 中掺杂 In 引入了额外的共振能级, 增加了费米能级附近的态密度, 提高了能带有效质量 。引入 In 之后, Sn0.975Na0.02In0.005Se样品在 300 K 时的塞贝克系数从 ~ 137提高到 ~ 205 μ V·K-1, 在 773 K 时的最大功率因子从 ~ 3.9提 高到 ~ 7.5 μ W·cm-1·K-2, 使热电优值 (ZT) 在 773 K 时超过了 1.1

Nanophotonic devices, composed of metals, dielectrics, or semiconductors, enable precise and high-spatial-resolution manipulation of electromagnetic waves by leveraging diverse light–matter interaction mechanisms at subwavelength length scales. Their compact size, light weight, versatile functionality and unprecedented performance are rapidly revolutionizing how optical devices and systems are constructed across the infrared, visible, and ultraviolet spectra. Here, we review recent advances and future opportunities of nanophotonic elements operating in the ultraviolet spectral region, which include plasmonic devices, optical metamaterials, and optical metasurfaces. We discuss their working principles, material platforms, fabrication, and characterization techniques, followed by representative device applications across various interdisciplinary areas such as imaging, sensing and spectroscopy. We conclude this review by elaborating on future opportunities and challenges for ultraviolet nanophotonic devices.

Super-fine L10-FePt nanoparticles (NPs) with high ordering degree were successfully prepared by a modified two-step sintering method, which includes low-temperature pre-sintering, and the high magnetic field (HMF) assisted post-sintering processes. The particle size of the L10-FePt NPs was obviously refined by lowering the sintering temperature. By applying the HMF during the post-sintering process, the fine size characteristics of L10-FePt NPs were retained, and the ordering degree was significantly improved. The L10-FePt NPs with sizes of about 4.5 nm, ordering degree of 0.940, and coercivity of 22.01 kOe were obtained by this two-step sintering under a magnetic field of 12 T. The mechanism investigation of HMF enhancing the ordering degree indicates that the HMF enhances lattice distortion and magnetization energy (Zeeman energy). The enhanced lattice distortions cause high stress existing in the lattice, which can effectively promote the disordered-order transition. When the magnetic field reaches to 3 T, the Zeeman energy of the NPs is higher than the thermal disturbing energy of the NPs, and the magnetization effect is stronger. Therefore, the HMF (higher than 3 T) can obviously improve the disorder-order transition by lowering the energy barrier and accelerating the orderly diffusions of atoms. The HMF is a promising assistant to synthesize the L10-phase NPs with both of high ordering degree and super-fine size.

Possessing inherently low thermal conductivity, BiSbSe3 is a promising thermoelectric material for medium temperature. Therefore, to substantially optimize the thermoelectric performance of BiSbSe3, researchers mainly focus on the strategies to improve its electrical transport properties. Among these strongly coupled thermoelectric parameters, carrier concentration and effective mass are two intrinsic variables to decisively affect the electrical transport properties. In this work, Cl as a donor dopant is effective to provide extra electrons in n-type BiSbSe3, and the carrier concentration and effective mass can be well optimized simultaneously with increasing Cl content owing to the multiple conduction bands in BiSbSe3. What’s more, maximum weighted mobility ∼53 cm2 V−1 s−1 is obtained in Cl-doped BiSbSe3, which contributes to a largely enhanced power factor ∼4.8 μW cm−1 K-2 at room temperature and outperforms other halogen-doped BiSbSe3 samples. Finally, combining the significantly enhanced power factor and maintained low thermal conductivity, a maximum ZT ∼1.0 is achieved in Cl-doped BiSbSe3 at 800 K.

Multicomponent pyrochlore solid solutions with and without uranium incorporation were fabricated and their thermal-mechanical properties were characterized. Multicomponent pyrochlore solid solutions without uranium exhibit comparable thermal conductivity and higher mechanical strength compared to baseline single component rare-earth titanate pyrochlore (A2Ti2O7). Uranium incorporation reduces hardness as compared with single component compositions. High entropy pyrochlore with uranium displays the highest thermal conductivity within multicomponent pyrochlore solid solutions with significantly better mechanical properties than UO2. The measured thermal conductivity correlates well with A-site cation mixing entropy and a modified size disorder parameter, and thus the size disorder and mixing entropy could be good indicators for predicting thermal conductivity of multicomponent pyrochlore solid solutions. This work opens up the possibility of designing multicomponent oxide solid solutions by controlling their chemical disorder/mixing entropy to achieve acceptable thermal-mechanical properties, desired radiation and corrosion performance for potential nuclear waste form and inert matrix fuel applications.

While neural-network-based lossy image compression methods have shown impressive performance, most of them output a fixed-length coding using a trained-specific network. However, it is essential to support the variable-length compression or meet a target rate with a high-coding performance in practice. This paper steps forward the neural-network-based image compression method, making it possible for a single network model to generate variable compression rates. Our network model combines an auto-encoder (AE) and a generative adversarial network (GAN) for generative compression. We introduce a noise interference mechanism to train the feature representation produced by the encoder, making the feature nodes training controllable and distributed from top to bottom according to their importance in feature expression. Based on this importance distribution, the latent nodes are quantized into bits and the variable-length compression can be achieved by discarding bits of those less-important feature nodes to meet the compression target. We propose several noise interference methods, and the experiments confirm the feasibility of method Random-add and Dropout in controllable learning. Further experiments illustrate that our compression method can not only achieve variable-length compression but also can recover high-quality compressed images at extremely low bit rates, outperforming that with a fixed rate.

Baseflow is crucial to maintaining river flow during low-rainfall periods. The baseflow estimation is important to water supply and ecological environmental protection in the Yellow River Basin (YRB), China. This paper comprehensively assessed the applicability of four single-parameter digital filtering, recursive digital filtering, and HYSEP (streamflow hydrograph separation) methods across four typical catchments in the Yellow River Basin: the Zuli River Basin, the Kuye River Basin, the Tuwei River Basin, and the Jingle sub-basin. We also investigated annual and monthly variations in baseflow. We found the standard deviation and coefficient of variation of baseflow index through recursive digital filter were relatively small. And the baseflow process line was smoother and more reasonable in typical year and typical storm-flood events, which conformed to the damping and hysteresis effect of the underlying surface. Thus the recursive digital filter method had the best performance, which was recommended for baseflow separation in the YRB. The estimated baseflow index of typical basins were between 0.354 and 0.502. In addition, inter-annual baseflow showed a decreasing trend and intra-annual baseflow was characterized by uneven distribution, which was subject to the characteristics of each basin. HIGHLIGHTS The evolution of baseflow in the typical catchments in the YRB was investigated by various methods.; The recursive digital filter method is an effective method for baseflow separation in the YRB.

This paper addresses a fault accommodation issue for flexible hypersonic vehicles by the static output feedback. Firstly, a longitudinal dynamics for hypersonic vehicles is established in the ODE-b...

Mobility models, which reproduce traces with basic crowd mobility patterns, are crucial for realistic mobile network simulation and performance evaluation of the planning strategies used for urban networks (such as transit network, communication network, and crowdsensing network). However, trajectories generated by traditional models are often perceived as not realistic for urban context or lack of scalability and universality. This article presents a data-driven trajectory generating technique, named as TraG, that produces synthetic trajectories with the help of some real-world trajectories. Our technique can automatically extract the context features and statistical mobility features, which characterize the mobility of a specific urban crowd from the input empirical traces and, then, regenerate more trajectories based on demand. Moreover, we also summarize the power-law scale correlation of crowd mobility based on four real-world open datasets, including public bicycle traces in New York City and Washington, D.C., taxicab traces in San Francisco and Shenzhen. Finally, we validate the proposed TraG model via the continuous San Francisco taxicab traces, and the result demonstrates that the trajectories simulated by TraG not only inherit the fundamental statistical features of crowd mobility from real traces, but also reflect the features of urban context.

The unique microstructure of biomaterials provides inspiration in materials structure design and performance breakthroughs. Here we prepared a MoAlB reinforced Al matrix composites with laminated structure and strong interfacial bonding. This work mainly focuses on the relationship between tribological properties of the MoAlB/Al laminated composites and the MoAlB layer orientation. The results show that the tribological properties of the composites deeply depend on the relation of sliding direction VS. the MoAlB layer orientation, while the dependency gradually decreases with the MoAlB content increasing. The friction coefficient and wear rate of the composites can be decreased by 55.5% and 95.1%, lower than those of pure Al, when 15 vol% MoAlB reinforcement is added. The friction and wear mechanisms of the MoAlB/Al laminated composites are proposed, and the outstanding tribological properties are ascribed to the formation of tribochemical worn film and different stress states caused by the laminated structure.

In this article, a systematic fault diagnosability evaluation, including fault detectability and isolability, is established in a quantitative manner for two-dimensional systems. With ingenious data formulation, a parity relation of two-dimensional systems is first established, then the Kullback-Leibler divergence is employed as the key measure for the diagnosability analysis based on the established parity relation. The basic idea is to quantify the distribution differences among each fault scenario-related system dynamic behavior. Explicit necessary and sufficient condition for fault diagnosability is further derived based on the appropriately introduced definitions corresponding to the two directions evolving system properties. Finally, the effectiveness of the proposed method is verified by two examples.

NdFeB magnetic nanoparticles with a main phase of Nd2Fe14B have successfully been synthesized. The preparation includes the following processes. First, the NdFeB intermediate was synthesized by a wet-chemical method. The NdFeB intermediate was annealed at 800 °C, which resulted in the formation of an NdFeB oxide. Then, the NdFeB oxide was reduced into NdFeB nanoparticles by a second-step reduction annealing with a CaH2 reductant. The second-step reduction annealing temperature was a key factor in preparing the NdFeB nanoparticles. A lower reduction temperature of 900 °C could not completely reduce the NdFeB oxide into Nd2Fe14B. There were some residual unreduced nonmagnetic phases in the prepared materials, which resulted in obvious decreases of coercivity. A sufficiently high second-stage reduction temperature resulted in an increased reduction, and more of the Nd2Fe14B phase could be obtained. In this work, nanoparticles with a uniform morphology and an increased Nd2Fe14B phase could be obtained at an optimum reduction temperature of 940 °C, achieving a high coercivity of 5.4 kOe.

The metallic engineering structures were commonly covered and protected by the anti-corrosion coatings. The early corrosion under the coatings and at the defects was concealed. Once the corrosion was visible to the naked eye, it indicated that the corrosion has developed seriously. Therefore, it was practical significant to detect the early corrosion of the metal under the coatings and at the defects. The formation of iron ions and anodic acidification were the characteristics of local corrosion process. Based on this fact, iron ions and protons responsive fluorescent on-off probes Rhodamine B Acylhydrazone (RBA) were prepared for the detection of corrosion. In the prepared supramolecules of RBA/LDHs, RBA intercalated and was loaded between layered double hydroxide (LDHs) to protect RBA from premature exposure to corrosive environment and fluorescence quenching. When corrosive Cl− was presented, the RBA loaded by LDHs exchanged with Cl− in corrosive environment, and RBA was released, and Cl− intercalated and was loaded between layers of LDHs. Therefore, the response to corrosion factors and release of RBA were realized, and was accompanied by the capture of Cl− and treatment of corrosion region. In the epoxy coatings, RBA/LDHs indicated the occurrence of corrosion and accurately locate the corrosion site and coating defects in form of fluorescence. Simultaneously, the sheet morphology and dispersion distribution of RBA/LDHs enhanced the shielding performance of the coatings.

To address the increasingly serious parking pain, numerous mobile Apps have emerged to help drivers to find a convenient parking spot with various auxiliary information. However, the phenomenon of "multiple cars chasing the same spot" still exists, especially for on-street parking. Existing reservation-based resource allocation solutions could address the parking competition issue to some extent, but it is impractical to treat all spots as reservable resources. This paper first conducts a qualitative investigation based on the online survey data, which identifies diversified parking requirements involving i) reserved users, who request guaranteed spots with a reservation fee, ii) normal users, who request non-guaranteed spots with a "best-effort" service, and iii) external users, who do not use any guidance service. To this end, we design the D2Park system for diversified demand-aware parking guidance services. We formulate the problem as a novel Heterogeneous-Agent Dynamic Resource Allocation (HADRA) problem, which considers both current and future parking demands, and different constraints for diversified requirements. Two main modules are used in the system: 1) multi-step parking prediction, which makes multi-step parking inflow and occupancy rate predictions given the current parking events data and external factors; and 2) diversified parking guidance, which integrates the cooperation-based and competition-based resource allocation mechanisms based on a model predictive control framework to achieve a better performance balance among different user groups. Extensive experiments with a four-month real-world on-street parking dataset from the Chinese city Shenzhen demonstrate the effectiveness and efficiency of D2Park.

Recently, low-cost and environmentally friendly materials have attracted increasing attention in the thermoelectric community. SnS2 as a sister compound of SnS with abundant and nontoxic elements e...

All-dielectric nanostructures have attracted attention for highly efficient light manipulation. Higher Q-factor Fano resonance can be excited due to the rich phenomenology of optical modes supported by high-index dielectric materials with low intrinsic material loss, including both electric and magnetic multipolar Mie resonances. So far, there have been few studies done on the sensing with Fano-resonant all-dielectric resonator nanostructures. Here, an all-dielectric self-referenced optical sensor is numerically demonstrated based on Si quadrumers and mirror-symmetric 1-D photonic crystals (1DPCs) hybridstructure, operating at the infrared wavelength range with higher sensing performance and much more stable reference signal. Magnetic Fano resonance and Fabry-Perot resonance were combined into such a hybridstructure for the first time. The influences of the gap distance, including Δx and Δy , on the coupling effects between the Si nanodimers along the polarization direction and the 1DPCs are systematically discussed. The sensing performance has been numerically investigated in different analytes with the sensitivity and figure of merit (FOM) of 760 nm/RIU and 1515 RIU−1 respectively, which paves the way to be a much more sensitive detection of small refractive index changes in an unstable environment and suggests potential applications in biological and chemical sensing.

Profile-cast provides a novel data dissemination paradigm in mobile opportunistic networks, allowing messages to be disseminated to nodes based on their profiles rather than network identities. Profile-cast has attracted increasing attention, but most of existing algorithms cannot account for some scenarios where multiple attributes need to be considered simultaneously in a profile. We focus on the multi-attribute profile-cast (MapCast) paradigm, where the node’s profile is represented by a multi-dimensional vector, which may contain multiple attributes of the node such as its behavior, interest, social information, etc. First, we consider a scenario with a fixed source node. We construct a message dissemination tree using the node encounter history. Then we propose a dissemination tree based MapCast algorithm, which adapts a heuristic search algorithm to select relay nodes so that the destination node can receive the message as soon as possible and the network has a low overhead. Second, we consider a more complex scenario with unfixed source nodes. In this scenario, the concept of group profile is defined, and a new high-efficient algorithm, group-profile based MapCast (G-MapCast), is proposed to limit the scope of message forwarding to the nodes whose profile or group profile satisfies certain delivery conditions. To further reduce the network overhead, we propose a network coding based MapCast algorithm on the basis of G-MapCast. Finally, we provide simulation results based on two real human contact datasets and verify the effectiveness and superiority of our algorithms.

Low temperature selective catalytic reduction (SCR) catalysts were prepared by using acetic acid modified fly ash (ACFA) and TiO2 with the loading of Mn-Ce. The powder catalysts were characterized by BET, XRD and SEM. The effects of Mn-Ce molar ratio on the NO conversion of SCR catalyst were investigated under different atmospheres of N 2 and CO2, respectively. The 8% Mn-Ce/ACFA-TiO2 catalyst with Mn-Ce molar ratio of 1:1 showed good performance of NO conversion at 300 °C, 84.28% in N 2 atmosphere and 74.29% in CO2 atmosphere. N 2 O was observed in the experiments of 8% Mn/ACFA-TiO2, 95.3 ppm in N 2 atmosphere and 103.6 ppm in CO 2 atmosphere, respectively.

We investigate the topological edge modes in a rhombic waveguide array with imaginary coupling, which is realized by incorporating auxiliary waveguide between the coupled waveguides. By suitably tuning both real and imaginary couplings to generate an effective π flux, a non-Hermitian analog of Aharonov-Bohm (AB) cage is formed as the band structures become flat and coalesce into third-order exceptional points (EPs). We show the array can support gapped topological edge modes, which can be explained by mapping the system Hamiltonian into the square root of an anti-parity-time (PT) -symmetric waveguide array. In contrast to the linear power increase of bulk modes, the propagation of edge modes can be conserved or exponentially amplified depending on which termination is initially excited. Our study provides a promising way to realizing robust light propagation.

Natural geological structures in rock (e.g., joints, weakness planes, defects) play a vital role in the stability of tunnels and underground operations during construction. We investigated the failure characteristics of a deep circular tunnel in a rock mass with multiple weakness planes using a 2D combined finite element method/discrete element method (FEM/DEM). Conventional triaxial compression tests were performed on typical hard rock (marble) specimens under a range of confinement stress conditions to validate the rationale and accuracy of the proposed numerical approach. Parametric analysis was subsequently conducted to investigate the influence of inclination angle, and length on the crack propagation behavior, failure mode, energy evolution, and displacement distribution of the surrounding rock. The results show that the inclination angle strongly affects tunnel stability, and the failure intensity and damage range increase with increasing inclination angle and then decrease. The dynamic disasters are more likely with increasing weak plane length. Shearing and sliding along multiple weak planes are also consistently accompanied by kinetic energy fluctuations and surges after unloading, which implies a potentially violent dynamic response around a deeply-buried tunnel. Interactions between slabbing and shearing near the excavation boundaries are also discussed. The results presented here provide important insight into deep tunnel failure in hard rock influenced by both unloading disturbance and tectonic activation.

A novel epoxy composite with flame retardance and fire resistance was prepared by adding silicate glass frit (SGF) and ammonium polyphosphate (APP) into the epoxy resin. In the combustion test, epoxy composites displayed obvious flame retardance feature, showing much lower heat release rate, total heat release and total smoke production than epoxy resin. The composite residue formed at 900 °C had a flexural strength of 19.05 MPa. In addition, possible mechanisms for the phase separation and crystallization reactions at high temperatures were also investigated in detail through thermogravimetric analyzer, X-ray diffraction, X-ray photoelectron spectrometer, and scanning electron microscopy. It was suggested that phosphorus element tends to migrate to the surface of the composite residue during firing process, and sodium element from SGF is selectively combined with the phosphorus element to obtain crystalline phases. With this unique phase separation and crystallization reactions, the fire resistance of the epoxy composite was significantly improved.

This paper develops a new fault-tolerant control scheme for a coupled rigid-flexible system to handle control-matched uncertain faults, using backstepping based sliding mode control technique. The system dynamics is modeled by an Euler-Bernoulli beam-ODE (EBB-ODE) system. A distinct model refinement is utilized to map this EBB-ODE cascade into a Schrodinger-like PDE-ODE cascade. In order to surmount the obstacles when deriving the kernels in a one-step backstepping control design, a distinct backstepping control procedure is employed by constructing an exponentially stable target system with arbitrary decay rate. Based on the relative degrees of the selected sliding mode surfaces, a novel fault-tolerant controller is developed to drive faulty boundaries to zero in finite time and to avoid chattering effectively. A modified Lyapunov-based Riesz basis frame is adopted to prove the exponential stability and the well-posedness of closed-loop system. A numerical simulation is presented to validate the effectiveness of the developed control scheme.

Room-temperature self-healing and self-growing of the exoskeleton with aligned structures in insects has few analogs in synthetic materials. Insect cuticle, such as elytra in beetles, with a typical lightweight lamellar structure, has shown this capability, which is attributed to the accumulation of phenol oxidase with polyphenol and amine-rich compounds in the hard cuticle. In this study, laminar-structure-based intelligence is imitated by incorporating adaptable and growable pyrogallol (PG)-borax dynamic-covalent bonds into a poly(acrylamide)-clay network. The events that lead to crack formation and water accumulation quickly trigger the deprotection of PG. Subsequently, atmospheric O2, as a regeneration source, activates PG oxidative self-polymerization. Multiple permanent and dynamic cross-links, with the involvement of the sacrificed borax, and initiation of a series of intelligent responses occur. The fabricated composites with an aligned lamellar structure exhibit outstanding characteristics, such as air/water-triggered superstrong adhesion, self-repairing, self-sealing and resealing, and reprocessing. Moreover, the strategy endows the composites with a self-growing capability, which leads to a 4- to 10-fold increase in its strength in an outdoor climate (up to 51 MPa). This study could lead to advances in the development of air/water-responsive composite materials for applications such as adaptive barriers.

In this work we investigated the thermoelectric transport behaviors of p-type PbS and n-type PbS with an emphasis on its contrasting electronic band structures. We found that the Seebeck coefficients of p-type PbS increased faster with rising temperature than that of n-type PbS with the same carrier concentration. The Density functional theory (DFT) calculation of the energy band structure of PbS as a function of temperature illustrates a significant contribution from multiple valence bands in K-doped p-type PbS. This work revealed one important information that manipulating electronic bands is also suitable in developing high-performance PbS thermoelectric systems.

In order to improve the accuracy of semiconductor wafer virtual metrology, and overcome the physical metrology delay of wafer acceptance test, a virtual physical vapor deposition metrology method based on combination of tree-based ensemble models is proposed to conduct online virtual metrology on semiconductor wafer electrical parameters, and use hyperparameter optimization technique to perform model optimization and to achieve real-time alarm on process deviation. This combination of tree-based ensemble model combines Bagging, Boosting, and Stacking techniques. First, based on 4 types of base learner, Random Forest, Extra-Trees, XGBoost, and lightGBM, preliminary virtual metrology is performed on wafer PVD process, and then transforms the predict results of the 4 base learners into meta feature vector as the input of meta learner lightGBM to perform further virtual metrology. The Sequential model-based optimization algorithm is used to improve the accuracy of virtual metrology. First, the initial hyperparameter of the sequential model-based optimization is initialized by using random sampling, then the combination model is approximated by the surrogate model of tree-structured Parzen estimator, and the recommended hyperparameters is obtained by using EI (Expected Improvement), and then the optimized combination model is obtained. Finally, the superiority of the method proposed in this paper is verified by studying the results comparing to the common virtual metrology methods on the PVD process. The experiment shows the result of resistivity metrology using the combination of tree-based ensemble models in the PVD process is significantly better than LASSO regression, partial least squares regression(PLSR), support vector machine(SVR), Gaussian process regression(GPR) and artificial neural network regression(ANN).

This paper considers a fault-tolerant control and vibration suppression problem of flexible spacecraft. The attitude dynamics is modeled by an interconnected system, in which the rigid part and the flexible part are coupled with each other. Such a model allows us to use the interconnected system approach to analyze the flexible spacecraft. Both distributed and decentralized observer-based fault-tolerant control schemes are developed, under which the closed-loop stability of flexible spacecraft can be ensured by using the cycle-small-gain theorem. Compared with the traditional method, this paper considers the faults occurred not only in the rigid parts, but also in the flexible parts. In addition, the application of the interconnected system approach simplifies the system model of flexible spacecraft, thereby the difficulty of theoretical analysis and engineering practice of fault-tolerant control of flexible spacecraft are greatly reduced. Simulation results show the effectiveness of the proposed methods and the comparison of different fault-tolerant control approach.

A Mach-Zehnder interferometer (MZI) based on two spherical structures is proposed and temperature and humidity are measured simultaneously. The device is fabricated by inserting two spherical structures into a single mode optical fiber (SMF). The results of the experiment indicate that the temperature sensitivities are 0.079 nm/°C and 0.090 nm/°C from 10 °C to 60 °C, respectively. When the humidity changes from 30% to 70%, the humidity sensitivities are 0.148 nm/%RH and 0.06 nm/%RH, respectively. Therefore, temperature and humidity are measured simultaneously by the sensitive matrix. The new structure is demonstrated to be a particularly useful approach to detect temperature and humidity.

In this paper, Ge0.94Bi0.06Te was firstly fabricated by mechanical alloying. Compared with the Ge0.94Bi0.06Te sample prepared by the melting process, the maximum ZT achieved an improvement from 1.4 to 1.8. The thermoelectric performance of Ge0.94Bi0.06Te can be improved through suppressing Ge vacancies and refining grains via mechanical alloying. Further introducing nano-SiC into the matrix of Ge0.94Bi0.06Te improves thermoelectric performance by increasing Seebeck coefficient and reducing thermal conductivity. Meanwhile, the mechanical properties including the microhardness and Young's modulus are also enhanced by dispersing nano-SiC. Consequently, a maximum ZT ~ 2.1 at 723 K was achieved in GeTe-based materials.

Camouflage is critical for many living organisms to survive in the natural world and has stimulated applications, such as optical cloaking and military affairs. However, most applications adopt crypsis-type camouflage that prevents the organisms from being detected by matching the environment, which is challenging to realize the large angle-of-view and broadband operation at optical frequencies. Here, as inspired by nature's system of masquerade, we demonstrate an optical masquerade, being detected but not recognized, with perturbative metasurfaces that could camouflage an object into another unrelated one under the oblique (±69°) illumination of visible light with an ∼160 nm bandwidth. Predicted by the perturbation theory, the dielectric metastructures encircling a pistol-shaped object have a thin layer of nanodisk array, which can suppress the electromagnetic resonances of nanomodes for mimicking the transmitted intensity and phase of the camouflaged object. We also exhibit that optical masquerade is an invasive, environment-independent, object-unlimited, and material-extendable camouflage, which might benefit optical security, anticounterfeiting, and encoding.

The existing modulation classification method using instantaneous features is poor for low SNRs, and the high-order cumulant features-based modulation recognition algorithm is only applicable to so...

A layered composite structural model with an outer wear-resistant layer of high-silicon aluminum alloy and an inner layer of ultra-high strength aluminum alloy is designed. A scaling brake drum part with layered composite was prepared by semi-solid precision forming process. The effects of process parameters such as casting temperature, specific pressure, solid layer temperature and heattreatment system on the composite interface were investigated. The results show that the casting temperature and solid layer temperature had a great influence on the interface recombination. The high forming specific pressure could effectively restrain the growth of secondary dendritesof the composite, and the proper heat treatment process could improve the morphology of the composite interface. A scaling brake drum component with A390/7050 layered composite structure was well prepared under optimal conditions.

Compared with SBR latex, waterborne epoxy resin has obvious advantages. The cured epoxy resin emulsified asphalt material has stronger mechanical properties, but it is less used in asphalt modification applications. Aiming at this problem, this paper uses waterborne epoxy resin as the modified material of emulsified asphalt, and carries out performance characterization and road performance evaluation of waterborne epoxy resin modified emulsified asphalt and its mixture under different dosages. Fluorescence microscopic analysis of waterborne epoxy asphalt with a content of 8wt%, 15wt%, 30wt%, and 50wt%, respectively, shows that the resin content should not exceed 30wt% to ensure the performance of asphalt. The bonding properties of SBR modified emulsified asphalt and waterborne epoxy resin modified emulsified asphalt with different dosages at 20 °C and 60 °C were analyzed. The results show that the tensile strength and oblique shear of waterborne epoxy modified emulsified asphalt. The strength is higher than SBR modified emulsified asphalt, and its high temperature resistance is better than SBR modified emulsified asphalt material. The road performance analysis was carried out on the mixture prepared by the aqueous epoxy modified emulsified asphalt with the content of 0wt%, 8wt%, 15wt% and 30wt% respectively. The results show that with the increase of waterborne epoxy content, the Marshall stability, splitting strength and high temperature rutting resistance of the mixture increase more obviously. The freeze-thaw splitting strength of the waterborne epoxy resin mixture is 13% higher than that of the pure emulsified asphalt mixture, and the splitting strength is also significantly improved. Due to the high stiffness of the waterborne epoxy resin after curing, the maximum bending strain of the mixture is reduced, and the recommended dosage is not more than 30% by weight. On the whole, the introduction of waterborne epoxy resin could greatly improve the strength and road performance of the asphalt, and could be used as a proper road repair material.

To obtain fine microstructure and homogeneous distribution of alloying elements in the large-sized billet, the internal electromagnetic stirring as a new electromagnetic stirring method was proposed and utilized for the preparation of Ф508 mm 7050 aluminum alloy billet. The results demonstrate that the internal electromagnetic stirring could refine the microstructure and second phase, and alleviated the macrosegregation significantly. The grain size at the edge, 1/2 radius, and center of the billet decreased to 180 μm, 175 μm, and 185 μm, respectively. Moreover, the relative macrosegregation of Zn, Mg, and Cu at the edge and center decreased to 3.9% and 2.8%, 2.3% and 1.6%, 4.1% and 2.5%, respectively.

Large-sized 2219 aluminum alloy ingot has wide application prospect in aerospace and military fields. Severe defects, such as coarse grain, the inhomogeneity of structure and macrosegregation occurred in large-sized aluminum ingot produced by normal DC casting. The application of a single magnetic field in DC casting process cannot solve these defects. In this paper, a new method with the combination of electromagnetic fields imposed on bulk melt treatment during DC casting was proposed. And a φ508 mm ingot of 2219 aluminum alloy was prepared in this method. Compared with the normal DC casting, the effect of the combined electromagnetic fields on the microstructure and properties was studied. The experimental results demonstrate that the application of the combined electromagnetic fields significantly refines the grains, and the grain size distribution on the cross section of the ingot tends to be more uniform as well as the mechanical properties are significantly improved. The microstructure and grain size distribution can be significantly affected by different combined electromagnetic fields. It is considered that the appropriate combined electromagnetic fields parameters play an important role in controlling the homogeneity of large-sized ingots.

To compare the clinical efficacy between ‘warming-unblocking needling technique’ and reinforcing method by twirling in treating knee osteoarthritis (KOA) due to deficiency of liver and kidney. A total of 72 patients with KOA were divided into a warming-unblocking group and a reinforcing group by complete randomized method, with 36 cases in each group. Xuehai (SP 10), Heding (EX-LE 2), Liangqiu (ST 34), Neixiyan (EX-LE 4), Xizhong (Extra), Dubi (ST 35), Yinlingquan (SP 9), Zusanli (ST 36) and Yanglingquan (GB 34) were the main points in both groups. Taichong (LR 3), Taixi (KI 3) and Sanyinjiao (SP 6) were the combined points. ‘Warming-unblocking needling technique’ was applied in the warming-unblocking group, and reinforcing method by twirling was applied in the reinforcing group. The treatments were performed once a day, 10 times as a treatment course, at a 2-day interval between two courses, for 3 courses in total. The scores of Western Ontario and McMaster Universities osteoarthritis index (WOMAC) in the two groups were observed before and after the treatment, and the clinical efficacy was compared. After treatment, the total effective rate was 94.3% in the warming-unblocking group and 87.9% in the reinforcing group, and the difference between the two groups was statistically significant (P

Herein, we offer a simple but crucial case for rational design and syntheses of infrared nonlinear optical (NLO) materials by employing state-of-art AgGaS2 as a parent model. On the basis of inheri...

This paper presents a study on the trajectory planning of optical polishing based on an optimized implementation of dwell time to improve the polishing quality and efficiency of optical surfaces. The large-scale, sparse, and ill-posed linear equation solution is transformed into a quadratic programming problem with boundary constraint, and the monotone projection gradient method is adopted to obtain an optimal dwell time solution by considering its fluctuation characteristic. Then, parametric polishing paths are constructed using cubic B-spline curves to guarantee one-to-one correspondence between each curve segment and dwell time of a removal spot. Finally, an interpolation process of polishing trajectory is proposed on the basis of the equal–proportional feed rate adjustment strategy to improve the implementation accuracy of dwell time. Simulation and experimental results show that the proposed dwell time algorithm and spline interpolation method can considerably improve the solution accuracy of dwell time and the convergence rate of the form error during polishing. These results provide important scientific basis and technical support for the high-efficiency and high-precision polishing of large-aperture aspheric optical surfaces.

Eco-friendly tin sulfide (SnS) has attracted increasing attention in the thermoelectric community because of its elemental abundance and analogous crystal structure to SnSe as a new thermoelectric material. However, so far no high dimensionless thermoelectric figure of merit ZT > 1 was reported in SnS polycrystals. This work found an effective strategy for enhancing the thermoelectric performance of p-type polycrystalline SnS by Ag doping and vacancy engineering, leading to three orders of magnitude increase in carrier concentration and optimized effective mass and carrier mobility. As a result of the enhanced electrical conductivity, three times higher power factor ∼3.85 μW/cm K2 at 877 K is realized in Sn0.995Ag0.005S sample. Interestingly, nanostructuring with Ag nano-precipitates were formed in the Ag-doped SnS sample. Moreover, with introducing Sn vacancies in the crystal structure of Sn0.995-vacAg0.005S, the power factor further enhanced to ∼4.25 μW/cm K2. In addition to the low-frequency phonons scattering by Ag nano-precipitates, dislocations strengthens the scattering of mid-frequency phonon, leading to an ultralow lattice thermal conductivity < 0.5 W/m K above 800 K and a record high ZT up to 1.1 at 877 K in Sn0.99Ag0.005S polycrystals. Keywords: Thermoelectric tin sulfide, Spark plasma sintering, Nanoprecipitation, Dislocation

MnOx-CeO2 (denoted as Mn–Ce) nanorod and MnOx-CeO2 nanooctahedra catalysts were synthesized by the hydrothermal method and were used for selective catalytic reduction of NO with NH3. The catalytic performance tests showed that the NO removal efficiency of CeO2 catalysts was obviously improved after loading MnOx. The structure and properties of catalysts had been characterized by SEM、TEM、XRD、BET、XPS、H2-TPR、NH3-TPD and in situ DRIFTS. It was found that Mn–Ce catalyst were of uniform core-shell structure, higher concentrations of Mn4+ and Ce3+, better reducibility, the increase of weak acid sites. The results of in situ DRIFTS indicated that the NH3-SCR reaction should obey the E–R mechanism. Moreover, the promotion effect and mechanism of MnOx doped CeO2 was demonstrated, which improved the catalytic activity of Mn–Ce catalysts.

Coal-bed methane (CBM) is a new type of clean energy, which is abundant in China. Rational development and use of CBM can not only reduce the occurrence of mine disasters but also alleviate energy shortages. However, the “high storage capacity and low-permeability” characteristics of China’s CBM have hindered the realization of industrialized CBM production. To study the effect of microwave radiation on the permeability of coal reservoirs, a seepage experiment under different stress and microwave radiation conditions was carried out by using the seepage experiment system of gas-bearing coal under microwave radiation developed by the authors. The relationship among different microwave powers, different irradiation times, different energy inputs, and coal permeability was explored. The results show that the microwave power effect and the temperature effect promote coal permeability. Under microwave radiation, the relationship between permeability and effective stress followed a negative exponential function, and all R-squared values were greater than 0.97. The permeability increased monotonically with increasing microwave power and irradiation time, and the linear fitting slope of the rate of increase in the low-effective-stress area was greater than in the high-effective-stress area. Under the same energy input, permeability increased with rising microwave power. The peak temperature of the coal sample also increased with increasing power. When the microwave power increased to a certain range, the permeability growth of the coal sample was the greatest, and the temperature gradient of the coal-sample temperature field was the steepest. The coal sample experienced the optimum microwave radiation power under the action of microwaves to achieve the permeability enhancement effect of microwaves on the coal sample. The experimental results provide a theoretical reference for applying microwave radiation technology in coal-bed methane extraction.

This paper presents a GPU based parallel implementation for the non-uniform illumination image restoration method, which uses a retinex based algorithm to decompose the original image into brightness and reflectance components, and adjusts the brightness value through an adaptive gamma correction and nonparametric mapping to achieve the restoration. Specifically, we parallelize the improved retinex algorithm on GPU to extract the brightness value of each pixel. After that, the probability of different brightness range is counted through each block to the entire image to reduce the competition of memory access. Finally, we use two different parallel reduce methods to calculate the probability density and cumulative density of brightness value and generate the mapping curve. The experiment conducted on three different GPUs and two CPUs with different resolution images shows that our method can process a 1024 × 2048 image in 1.024 ms on RTX2080Ti, indicates a great potential for real-time application.