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A gallium nitride (GaN) boundary conduction mode (BCM) dual-boost ac–dc converter for low-voltage electromagnetic energy harvesting (EH) is presented in this article. The μ W-to-mW EH system is very susceptible to any tiny losses from power converters, interconnections, and system parasitic. To have better utilizations of harvested energy, an output power enhanced power conversion design is proposed. First, impedance matching is satisfied between electromagnetic generator and ac–dc converter to achieve maximum delivered power. The ac–dc converter is designed under BCM for constant input impedance. EH's winding inductance is employed as the boost inductor in the ac–dc converter. A codesign principle for converter on -time with electromagnetic generator's winding characteristics is revealed. Second, power transistors in EH low-voltage conversion are optimized to realize high efficiency. Power transistors’ low-voltage switching characteristics are significantly different from high-voltage situation with no or little miller plateau region. Low-voltage power transistors are compared from both device characteristics and calculated power loss to provide device selection guidance. A GaN-based dual-boost ac–dc converter under BCM operation with constant on -time controller is designed in this article to provide 3.3 V output for a 500-Ω load resistor. It achieves peak efficiency of 82.4% for open-loop operation at 0.6 V/100 Hz input and peak efficiency of 72.3% for close-loop operation at 0.75 V/100 Hz.

Medicine has been a great beneficiary of the nanotechnology revolution. Nanotechnology involves the synthesis of functional materials with at least one size dimension between 1 and 100 nm. Advances in the field have enabled the synthesis of bio-nanoparticles that can interface with physiological systems to modulate fundamental cellular processes. One example of a diverse acting nanoparticle-based therapeutic is synthetic high-density lipoprotein (HDL) nanoparticles (NP), which have great potential for treating diseases of the ocular surface. Our group has developed a spherical HDL NP using a gold nanoparticle core. HDL NPs: (i) closely mimic the physical and chemical features of natural HDLs; (ii) contain apoA-I; (iii) bind with high-affinity to SR-B1, which is the major receptor through which HDL modulates cell cholesterol metabolism and controls the selective uptake of HDL cargo into cells; (iv) are non-toxic to cells and tissues; and (v) can be chemically engineered to display nearly any surface or core composition desired. With respect to the ocular surface, topical application of HDL NPs accelerates re-epithelization of the cornea following wounding, attenuates inflammation resulting from chemical burns and/or other stresses, and effectively delivers microRNAs with biological activity to corneal cells and tissues. HDL NPs will be the foundation of a new class of topical eye drops with great translational potential and exemplify the impact that nanoparticles can have in medicine.

The high-temperature deformation behavior of the as-forged TC17 titanium alloy was studied based on the results of thermal compression simulation tests. Additionally, the effects of strain rate, temperature and true strain on the flow stress were analyzed using orthogonal experimentation and variance analysis. The results indicated that all deformation parameters exerted significant influence on flow stress, with temperature and strain having the largest and least influence, respectively. Thereafter, a constitutive equation based on modified nonlinear regression was proposed. The error analysis results showed that the flow stress of the as-forged TC17 alloy could be predicted by the obtained constitutive equation. The effect of deformation parameters on the microstructure was investigated by EBSD and TEM.

This article investigates modeling and control approaches to optimize the efficiency and power factor for discontinuous conduction mode boost power factor correction converters. First, with detailed consideration of parasitics and GaN HEMT transients, the input and output charges of the converter are exactly derived, where the rate forms the comprehensive charge rate (CCR) model. Second, based on the CCR model, the overall efficiency is derived. Since the overall efficiency is only related to the input voltage, output voltage, and switching on -time, an optimal on -time is calculated to achieve the maximum efficiency. Furthermore, with the optimal on -time, a maximum efficiency average current (MEAC) controller is proposed to regulate the input current while maintaining the maximum efficiency. With the predefined optimal on -time, a switching cycle modulation method is adopted to regulate the input current as sinusoid, which improves the power factor to unity. Finally, effectiveness of the MEAC control strategy is verified by simulations and experiments. Compared with conventional constant on -time control, it achieves an optimized efficiency and power factor over a large operation range.

A novel “time-segmented” transient analysis approach is proposed in this article for resonant gate driver (RGD) with triaspect optimization. RGD is a more advanced solution in high-frequency and high-power-density applications than the conventional gate driver (CGD). RGD will achieve lower gate driver loss, faster driving speed, and better SiC switching characteristics. However, the majority of current works on RGD only focused on gate driver loss and ignored its effect on power transistors’ switching behavior. The characteristics of RGD are not well understood and modeled due to the ignorance of nonlinear components, such as power transistor’s nonlinear input capacitor and nonlinear resonant intervals, and driving resistances. All of those result in false estimation of switching time and energy, which will cause underdesign of gate driver power supply and overdesign of resonant inductor. To fully investigate the potential of RGD, a “time-segmented” analysis approach proposed in this article utilizes the second-order equivalent circuit with actual switching transients. Different equivalent input capacitors are adopted for each segment. The impacts of the resonant inductor and gate resistor are studied. An optimized resonant inductor design is summarized by considering the three aspects mentioned earlier. Based on these, a full-bridge series RGD is designed for SiC power transistors. Compared with CGD, RGD can realize a 25% reduction in power consumption and 75.5% faster driving time. The designed RGD also improves SiC’s di / dt and dv / dt up to 32%.

Event-B is a formal modeling language that is very suitable for software engineering, but it lacks the ability of modeling time. Researchers have proposed some methods for modeling time constraints in Event-B. The limitations with existing methods are that, first of all, the existing research work lacks a systematic time refinement framework based on Event-B; secondly, the existing methods only model time in the Event-B framework and cannot be smoothly converted to automata-based models such as timed automata that facilitate the verification of time properties. These limitations make it more difficult to model and verify real-time systems with Event-B because it is very time-consuming to prove time properties in the Event-B framework. In this paper, we firstly proposed a systematic time refinement framework to express and refine time constraints in Event-B. Secondly, we also proposed various vertical refinement patterns and horizontal extension patterns to guide modelers to refine the Event-B real-time model step by step. Finally, we use a real-time system case to demonstrate the practicality of our method. The experimental results show that the proposed method can make the real-time system modeling in Event-B more convenient and the models are easier to convert to the timed automata model, thereby facilitating the verification of various time properties.

Recent approaches for predicting layouts from 360 $$^{\circ }$$ panoramas produce excellent results. These approaches build on a common framework consisting of three steps: a pre-processing step based on edge-based alignment, prediction of layout elements, and a post-processing step by fitting a 3D layout to the layout elements. Until now, it has been difficult to compare the methods due to multiple different design decisions, such as the encoding network (e.g., SegNet or ResNet), type of elements predicted (e.g., corners, wall/floor boundaries, or semantic segmentation), or method of fitting the 3D layout. To address this challenge, we summarize and describe the common framework, the variants, and the impact of the design decisions. For a complete evaluation, we also propose extended annotations for the Matterport3D dataset (Chang et al.: Matterport3d: learning from rgb-d data in indoor environments. arXiv:1709.06158 , 2017), and introduce two depth-based evaluation metrics.

In this paper, microstructure characterization of friction stir welding (FSW) joint of 7055-T6 aluminum alloy was performed via scanning electron microscope, electron backscatter diffraction, and transmission electron microscope technology. The nanomechanical behavior of FSW joint was systematically studied using nanoindentation technique. The relationship between microstructure and nanomechanical behavior was established and the nano-hardness and microhardness were analyzed. The results show that FSW led to grain refinement of aluminum alloy and continuous dynamic recrystallization and geometric dynamic recrystallization were the primary mechanisms of grain refinement. The precipitated phase dissolved and coarsened during FSW, which led to a decrease in the microhardness of the joint. The nano-hardness of each zone of the joint displayed indentation size effect. The creep behavior at room temperature conformed to the Voigt model, and dislocation glide was the primary creep mechanism. The stir zone (SZ) and thermo-mechanically affected zone (TMAZ) had high nano-hardness and elastic modulus, while TMAZ and heat-affected zone (HAZ) had high creep resistance at room temperature. The nanomechanical behavior was mainly affected by precipitation in the grain interior.

Friction stir lap welding (FSLW) was employed to weld dissimilar joints of zirconium and stainless steel for the first time. The microstructure, evolution mechanism of intermetallic compounds (IMCs) and mechanical properties of joint were investigated. Discontinuous dynamic recrystallization (DDRX) and continuous dynamic recrystallization (CDRX) occurred in zirconium, while DDRX occurred in stainless steel during FSLW. The formation sequence of IMCs at the interface was FeZr3, FeZr2, Fe2Zr, and Fe23Zr6. The crack nucleated at the hook zone on the advancing side (HookAS), and IMCs in the Zr/SS mixed zone accelerated crack propagation. The fracture surface exhibited ductile-brittle mixed fracture characteristic.

A bulk pure Al sample was prepared through cold spray-friction stir processing composite additive manufacturing (CFAM). The microstructure is uniform, and consists of fine and equiaxed recrystallized grains with an average grain size of 4.4 μm. Continuous and discontinuous dynamic recrystallizations are primary recrystallization mechanisms. The ultimate tensile strength and elongation are 87 MPa and 60.3%, respectively, with the fracture mode being ductile. The order of contribution of strengthening mechanisms for the CFAM sample, from highest to lowest, is fine grain strengthening, dislocation strengthening, and grain orientation strengthening.

Lack of directional bonding between two-dimensional crystals like graphene or monolayer transition metal dichalcogenides provides unusual freedom in the selection of components for vertical van der Waals heterostructures. However, even for identical layers, their stacking, in particular the relative angle between their crystallographic directions, modifies properties of the structure. We demonstrate that the interatomic coupling between two two-dimensional crystals can be determined from angle-resolved photoemission spectra of a trilayer structure with one aligned and one twisted interface. Each of the interfaces provides complementary information and together they enable self-consistent determination of the coupling. We parametrise interatomic coupling for carbon atoms by studying twisted trilayer graphene and show that the result can be applied to structures with different twists and number of layers. Our approach demonstrates how to extract fundamental information about interlayer coupling in a stack of two-dimensional crystals and can be applied to many other van der Waals interfaces., Here, the authors show that the interatomic coupling between two layers of a 2D crystal can be determined by studying the angle-resolved photoemission spectra of a trilayer structure with one aligned and one twisted interface, and obtain the inter-atomic coupling for carbon atoms in twisted trilayer graphene.

Friction stir processing (FSP) is a new severe plastic deformation technique where microstructure refinement, homogenization, and densification occur simultaneously. In this study, the microstructure and superplastic deformation behavior of AZ80 magnesium alloy prepared by FSP were investigated. FSP led to remarkable grain refinement and modification of texture for AZ80 magnesium alloy. A maximum elongation of 606% was obtained at 3 × 10−4 s−1 and 350 ℃. When superplastic deformation was conducted at 3 × 10-3 s−1 and 300 ℃, or at 1 × 10-4 s−1 and 400 ℃, the superplasticity was relatively lower, thus exhibiting a lower strain rate sensitivity. The coarsening of both grains and β-Mg17Al12 precipitates deteriorated superplastic elongation. Applied deformation promoted the premature dissolution of β precipitates at 400 ℃ during superplastic deformation. Moreover, superplastic deformation weakened and spread the basal texture. Although the activation of prismatic and pyramidal slips is beneficial for superplastic deformation, grain boundary sliding is the main superplastic deformation mechanism.

Aiming at the defects of large-scale large scale wireless sensor network data processing network traffic and high task latency, a data collection scheme of mobile node based on discrete elastic collision optimization algorithm and adaptive block compression sensing is proposed. Firstly, by analyzing the relationship between the network partitioning and the node deployment, an adaptive block compressed sensing data collection strategy is proposed to realize sensor node based on adaptive network block compressed sensing data collection. Designing mobile node data acquisition path planning strategy and multiple mobile nodes The collaborative computer system adopts the fitness value constraint transformation processing technology and the parallel discrete elastic collision optimization algorithm to achieve the purpose of balancing network node energy consumption and reducing data processing task delay. Finally, the simulation results show that the data collection scheme can effectively realize high-efficiency processing of large-scale sensor network data, and reduce network traffic and network task delay, and better balance network node energy consumption.

Aiming to design stable nanocrystalline (NC) materials, so far, it has been proposed to construct nanostructure stability maps in terms of thermodynamic parameters, while kinetic stabilization has seldom been considered, despite the synergy of thermodynamics and kinetics. Consequently, the thermodynamically stabilized NC materials may be easily subjected to grain growth at high temperatures due to the weakly kinetic stabilization. Starting from the thermo-kinetic synergy, a stabilization criterion is proposed as a function of intrinsic solute parameters (e.g. the activation energy for bulk diffusion and the segregation enthalpy), intrinsic solvent parameters (e.g. the intrinsic activation energy for GB migration and the GB energy) and processing parameters (e.g. the grain size, the temperature and the solute concentration). Using first-principles calculations for a series of combinations between fifty-one substitutional alloying atoms as solute atoms and Fe atom as fixed solvent atom, it is shown that the thermal stability neither simply increases with increasing the segregation enthalpy as expected by thermodynamic stabilization, nor monotonically increases with increasing the activation energy for bulk diffusion as described by kinetic stabilization. By combination of thermodynamic and kinetic contributions, the current stabilization criterion evaluates quantitatively the thermal stability, thus permitting convenient comparisons among NC materials involved by various combinations of the solute atoms, the solvent atoms, or the processing conditions. Validity of this thermo-kinetic stabilization criterion has been tested by current experiment results of Fe-Y alloy and previously published data of Fe-Ni, Fe-Cr, Fe-Zr and Fe-Ag alloys, etc., which opens a new window for designing NC materials with sufficiently high thermal stability and sufficiently small grain size.

Gallium nitride (GaN) high-electron-mobility transistor (HEMT) has the advantages of high switching speed and low ON-resistance, which make it widely used in high-frequency applications to realize high power density. Triangular current mode (TCM) modulation has been used in GaN-based converters to simultaneously achieve high power density and high efficiency through full-range zero voltage switching (ZVS). However, as switching frequency increases, the effect of dead time becomes more significant. Meanwhile, because of the junction capacitors of GaN HEMTs, the optimum dead time changes greatly with the turn-off current. Inappropriate dead time will induce extra loss that goes against the further improvement of power density. In order to minimize the dead-time loss in GaN HEMT-based TCM converter, this article proposes a strategy of adaptive dead-time control. An accurate turn-off transient model is proposed to calculate optimal dead time with consideration of the nonlinear capacitors. Based on this model, a loss model is established to evaluate the effect of dead time involving the short circuit in dead time. A new method of drive signal generation in TCM is proposed to increase the accuracy of dead-time control and reduce the current ripple. By reusing the detection signal in TCM, the adaptive dead-time control is realized without extra sensors. The proposed model is verified by a dual-pulse test, which shows the maximum error between the calculated and the experimental turn-off time is below 3 ns. The proposed adaptive dead-time control is implemented in a GaN HEMT-based boost converter. The experimental results show that the adaptive dead-time control can improve the efficiency over all operation conditions compared with using the fixed dead time, and the total loss is reduced by 26.7% at 800-W load and 70.8% at 50-W load.

Recently, physically unclonable functions (PUFs) have received considerable attention from the research community due to their potential use in security mechanisms for applications such as the Internet of things (IoT). The concept generally employs the fabrication variability and naturally embedded randomness of device characteristics for secure identification. This approach complements and improves upon the conventional cryptographic security algorithms by covering their vulnerability against counterfeiting, cloning attacks, and physical hijacking. In this work, we propose a new identification/authentication mechanism based on a specific implementation of optical PUFs based on electrochemically formed dendritic patterns . Dendritic tags are built by growing unique, complex, and unclonable nano-scaled metallic patterns on highly nonreactive substrates using electrolyte solutions. Dendritic patterns with 3D surfaces are technically impossible to reproduce, hence they can be used as the fingerprints of objects. Current optical PUF-based identification mechanisms rely on image processing methods that require high-complexity computations and massive storage and communication capacity to store and exchange high-resolution image databases in large-scale networks. To address these issues, we propose a light-weight identification algorithm that converts the images of dendritic patterns into representative graphs and uses a graph-matching approach for device identification. More specifically, we develop a probabilistic graph matching algorithm that makes linkages between the similar feature points in the test and reference graphs while considering the consistency of their local subgraphs. The proposed method demonstrates a high level of accuracy in the presence of imaging artifacts, noise, and skew compared to existing image-based algorithms. The computational complexity of the algorithm grows linearly with the number of extracted feature points and is therefore suitable for large-scale networks.

Magnesium (Mg) alloys have been extensively used in various fields, such as aerospace, automobile, electronics, and biomedical industries, due to their high specific strength and stiffness, excellent vibration absorption, electromagnetic shielding effect, good machinability, and recyclability. Friction stir processing (FSP) is a severe plastic deformation technique, based on the principle of friction stir welding. In addition to introducing the basic principle and advantages of FSP, this paper reviews the studies of FSP in the modification of the cast structure, superplastic deformation behavior, preparation of fine-grained Mg alloys and Mg-based surface composites, and additive manufacturing. FSP not only refines, homogenizes, and densifies the microstructure, but also eliminates the cast microstructure defects, breaks up the brittle and network-like phases, and prepares fine-grained, ultrafine-, and nano-grained Mg alloys. Indeed, FSP significantly improves the comprehensive mechanical properties of the alloys and achieves low-temperature and/or high strain rate superplasticity. Furthermore, FSP can produce particle- and fiber-reinforced Mg-based surface composites. As a promising additive manufacturing technique of light metals, FSP enables the additive manufacturing of Mg alloys. Finally, we prospect the future research direction and application with friction stir processed Mg alloys.

Checkerboard patterns with black rectangles can be derived from quad meshes with orthogonal diagonals. First, we present an initial theoretical analysis of these quad meshes. The analysis reveals many possible applications in geometry processing and also motivates the numerical optimization for aesthetic and functional checkerboard pattern design. Second, we describe an optimization algorithm that transforms initial 2D and 3D quad meshes into quad meshes with orthogonal diagonals. Third, we present a 2D checkerboard pattern design framework based on integer programming inspired by the logo design of the 2020 Olympic games. Our results show a variety of 2D and 3D checkerboard patterns that can be derived from 2D or 3D quad meshes with orthogonal diagonals.

Friction stir processing (FSP), as a new kind of severe plastic deformation technique, can refine and homogenize the microstructure of metallic material. In this study, the effect of FSP on the microstructure and mechanical properties of pure Zr was investigated using electron backscatter diffraction analysis, microhardness and room-temperature tensile testing. The fine-grained (FG) structure with an average grain size of ~ 5.3 μm was obtained in the processed zone, where the average microhardness was ~ 198 HV, 1.6 times higher than that of base metal. Furthermore, tensile property of FG pure Zr exhibited obvious anisotropy owing to strong texture. Both grain size and texture had a significant effect on strength and ductility of FG pure Zr. High yield strength (248 MPa) and ultimate tensile strength (483 MPa), as well as good uniform elongation (10%) were achieved, which demonstrated that FSP was an effective method to fabricate bulk FG pure Zr with high strength and good ductility.

In this paper, the influence of temperature on the bonding strength of aluminum alloy joints under the full temperature field is studied. Based on the service temperature range of vehicle bonding structures, the failure strength of aluminum alloy joints at different temperature points, namely −40 °C, −20 °C, 0 °C, 25 °C (RT), 40 °C, 60 °C and 80 °C, is tested. The results showed that compared with the failure strength of the adhesive at −40 °C, it decreased by 47.69% and 68.15% at RT and 80°C, respectively, the Young’s modulus of the adhesive decreased by 57.63% and 75.42% at RT and 80°C, respectively, with the increase of temperature, the young’s modulus, tensile strength and failure strain of the adhesive decreased. In addition, the failure strength of aluminum alloy joints varied with temperature. To be specific, the stiffness of joints decreased gradually from 25 °C to 80 °C and increased gradually from −40 °C. Based on the failure strength data of bonded joints at different temperature points, the secondary stress failure criteria of bonded joints at different temperatures were obtained. Then, the surface function of failure criteria under the full temperature field was established to provide reference for failure prediction of bonded structures under different temperatures and stresses.

Surface Fermi arcs (SFAs), the unique open Fermi-surfaces (FSs) discovered recently in topological Weyl semimetals (TWSs), are unlike closed FSs in conventional materials and can give rise to many exotic phenomena, such as anomalous SFA-mediated quantum oscillations, chiral magnetic effects, three-dimensional quantum Hall effect, non-local voltage generation and anomalous electromagnetic wave transmission. Here, by using in-situ surface decoration, we demonstrate successful manipulation of the shape, size and even the connections of SFAs in a model TWS, NbAs, and observe their evolution that leads to an unusual topological Lifshitz transition not caused by the change of the carrier concentration. The phase transition teleports the SFAs between different parts of the surface Brillouin zone. Despite the dramatic surface evolution, the existence of SFAs is robust and each SFA remains tied to a pair of Weyl points of opposite chirality, as dictated by the bulk topology., Surface Fermi arcs (SFAs) are characteristic features of a topological Weyl semimetal but there is no easy way to manipulate them so far. Here, the authors report manipulation of the shape, size and connections of SFAs in a Weyl semimetal NbAs, leading to an unusual topological Lifshitz transition.

Complexes of proteins are central to certain cellular processes. Investigated in this paper is the three-coupled fourth-order nonlinear Schrodinger system, which is used for describing the alpha he...

In this study, the effects of slag on the properties of lightweight cement-treated soils (LCS) immersed in sodium sulfate solutions were studied. The mechanical properties of the samples after immersions were evaluated by unconfined compressive strength. Microstructural properties were investigated by using X-ray diffraction (XRD) and scanning electronic microscopy (SEM). The results show the LCS can resist sodium sulfate corrosion, and the content of slag affects the internal pore structure of the material, thus affecting the strength and thermal conductivity after corrosion. When the slag content is 10% by weight of cement, the mechanical and thermal property of the LCS after corrosion was the best.

RNA modification has recently been proposed to play important roles in biological regulation. The detection and quantification of RNA modifications generally are challenging tasks since most of the modifications exist in low abundance in vivo. Here we developed an on-line trapping/capillary hydrophilic-interaction liquid chromatography/electrospray ionization-mass spectrometry (on-line trapping/cHILIC/MS) method for sensitive and simultaneous quantification of RNA modifications of N6-methyladenosine (m6A) and 5-methylcytosine (5-mC) from human blood. The hydrophilic organic-silica hybrid monolith was prepared using sol-gel combined with “thiol-ene” click reaction for the separation of nucleosides. A poly(MAA-co-EGDMA) monolithic capillary was used as the on-line trapping column. With the developed on-line trapping/cHILIC/MS analytical platform, the detection limits of m6A and 5-mC can reach to 0.06 fmol and 0.10 fmol. We then investigated the contents of m6A and 5-mC in human blood RNA from healthy persons at the age of 6–14 and 60–68 years. Our results showed that both m6A and 5-mC contents were significantly decreased in elder persons, suggesting the RNA modifications of m6A and 5-mC are correlated to aging.

Spinal cord injury (SCI) routinely causes the immediate loss and disruption of neurons followed by complicated secondary injuries, including inflammation, oxidative stress, and dense glial scar formation. Inhibitory factors in the lesion scar and poor intrinsic neural regeneration capacity restrict functional recovery after injury. Minocycline, which has neuroprotective activity, can alleviate secondary injury, but the long-term administration of this drug may cause toxicity. Polysialic acid (PSA) is a large cell-surface carbohydrate that is critical for central nervous system development and is capable of promoting precursor cell migration, axon path finding, and synaptic remodeling; thus, PSA plays a vital role in tissue repair and regeneration. Here, we developed a PSA-based minocycline-loaded nanodrug delivery system (PSM) for the synergistic therapy of spinal cord injury. The prepared PSM exerted marked anti-inflammatory and neuroprotective activities both in vitro and in vivo. The administration of PSM could significantly protect neurons and myelin sheaths from damage, reduce the formation of glial scar, recruit endogenous neural stem cells to the lesion site, and promote the regeneration of neurons and the extension of long axons throughout the glial scar, thereby largely improving the locomotor function of SCI rats and exerting a superior therapeutic effect. The findings might provide a novel strategy for SCI synergistic therapy and the utilization of PSA in other central nervous system diseases.

The industrial effluents discharge including heavy metals drain into the river, which has given rise to many problems of hazarding aquatic ecosystems and human health. Biosorption serves as the adsorption of heavy metals onto a natural adsorbent, it is becoming a potential alternative for toxic metals removal from industrial effluents in the last decades. The objectives of present research were to investigate the biosorption behaviors and the mechanisms of copper (Cu), zinc (Zn), cadmium (Cd) and chromium (Cr) ions, respectively onto foxtail millet shell as a new natural biosorbent in aqueous solution. The effects of pH (2.0–6.0), contact time (5.0–240.0 min), initial metal ions concentration (25.0–300.0 mg/L), particle size (0.25–2.0 mm) and biosorbent dosage (1.0–6.0 g/L) on the adsorption efficiency of the target metals using foxtail millet shell were evaluated in batch experiments. The models of isotherms and kinetics were used to assess the removal behaviors of Cu, Zn, Cd and Cr ions from aqueous solution by foxtail millet shell. The results showed that the best fitting equilibrium isotherm models for Cu, Zn, Cd and Cr ions were Freundlich (Cu and Zn) and Langmuir (Cd and Cr), respectively under the proper adsorption conditions. The maximum biosorption capacities were 11.89, 10.59, 12.48 and 11.70 mg g−1 of Cu, Zn, Cd and Cr, respectively by terms of Langmuir model. The kinetics of biosoption the target metal ions processes were best explained by pseudo-second-order kinetic model. Furthermore, pseudo-second-order and intraparticle diffusion models were cooperative mechanism during the whole biosorption. In addition, the pores on the surface of the shell were covered and then became smooth after biosorption through Scanning electron microscope (SEM) revealed, which demonstrated that the target metal ions were adsorbed by foxtail millet shell. The results of Energy dispersive spectrometer (EDS) further gave evidences that Cu, Zn, Cd and Cr ions were adsorbed onto surface of the adsorbent, respectively. Analysis of Fourier transform infrared spectroscopy (FTIR) demonstrated that various functional groups, such as C—H, C˭O, C˭C, C—O, O—S—O and Si—O groups were engaged in the interaction between foxtail millet shell and Cu, Zn, Cd and Cr ions. This paper provided evidences that foxtail millet shell was a potential and efficient biosorbent on removal of Cu, Zn, Cd and Cr ions from aqueous solutions, due to its high biosorption availability, capacity and low cost.

Cloud computing is a type of Internet-based computing that provides shared computing resources and data on demand. To support the massive cloud services, a data center is built with thousands of servers and switches connected by a communication network called a data center network (DCN). Along with the development of virtualization, the data center manager conducts virtual machine (VM) resizing and live migrations to adjust the allocation of VMs and improve the server utilization. However, compared to VM resizing, live migrations can negatively impact the performance of the system depending on the amount of transferred data and the path length. In this paper, we propose an online resource allocation algorithm using VM consolidation to achieve energy efficiency and reduce service-level agreement (SLA) violations of data centers while considering the power usage of servers, the number of migrations, and the path length of migrations in DCNs. Compared to the state-of-the-art mechanism, the proposed algorithm successfully reduces the power consumption, the number of migrations, and the path length of migrations for a dynamic cloud service.

Integrated electronic design project which allows students to carry out engineering design based on theoretical knowledge is one of the most important basic courses in electronic and information engineering majors in universities. Based on the analysis of existing issues, this article explores some reforms of the course in combination with the demands of talents in the electronic information industry. Explorations and reforms of integrated electronic design project are mainly focus on reforming the teaching content, reforming teaching method, strengthening the cultivation of students' comprehensive ability, reforming assessment method of student, and strengthening the construction of teacher team.

A new master-and-slave resonant tank switch approach is proposed to realize narrow switching frequency range and whole range zero voltage switching (ZVS) for series-parallel resonant converter (LCC) with wide operation range. A systematic switch strategy employing paralleled series capacitor (C s ) tanks is fully explored. A master resonant tank is firstly derived based on converter actual operation range. A series of slave resonant tanks are derived using geometric progressions, as 1/2i. The voltage gain is divided into different pieces and different resonant tanks are employed. The switching frequency range maintained similar for each segments. A 5kW SiC LCC converter is built to demonstrate the proposed concept. Three resonant tanks with C s of 5nF, 10nF and 20nF are adopted respectively. With single resonant tank of C s equaling to 20nF, switching frequency need to be adjusted from 280 kHz to 470 kHz for gain range from 0.3-1.05. With the proposed master-and-slave tank switch technique, switching range is shrink to the 390 kHz to 470 kHz for the same gain range by adopting two slave tanks. A 58% reduction of frequency range is achieved.

Launching ultrashort femtosecond photoacoustic pulses with multi-terahertz bandwidth will find broad applications from fundamental acoustics in 2D materials and THz-acoustic and phonon spectroscopy to nondestructive detection in opaque materials with a sub-nanometer resolution. Here we report the generation of ultra-short 344 fs photoacoustic pulses with a 2.1 THz bandwidth from interfacial two-dimensional electron gas using optical femtosecond excitation. A comparison with simulation supports the dominant contribution of hot electron pressure and the ultrafast electron relaxation to produce pulsewidth shorter than the acoustic transit time across the electron wavefunction. Our simulation further indicates the possibility to generate

A PCB integrated GaN gate driver module is proposed to realize fast driving and protection with highly concise system architecture. The PCB based air-coil coupled inductor is adopted as current sensor for ultra-large bandwidth and very compact size. The over-current protection approach proposed in this paper contains only three function blocks enabling very fast response. Low voltage GaN power transistors are used in gate driver circuit. The proposed driver module has the advantages of high speed, prompted response, and low driver loss. This module can also be further integrated with power switch on the same substrate.

When the Agile Earth Observation Satellite(AEOS) observes ground target points, the properties of the ground target points often change, which requires the satellite to effectively re-plan its mission in a short time. In order to solve the problem of mission re-planning of the AEOS, an improved genetic algorithm is proposed in this paper. Firstly, the fitness function to be optimized is established according to the satellite's constraints. The benefits of the satellite observation, the constraints of the satellite and the invariant target points included in the re-planned observation sequence is considered in this fitness function. These constraints mainly include time constraints, energy constraints, satellite orbital dynamic constraints, and so on. Secondly, considering the problems faced in the mission re-planning process, such as the satellite's need to complete the mission re-planning in a short time, and the constraints it faces, etc., the Adaptive Mutation Genetic Algorithm(AMGA) is proposed in this paper. Finally, simulation experiments verify that AMGA can complete mission re-planning while meeting various constraints, and that AMGA meets the fast and accurate requirements for solving mission re-planning problems.

A compact and efficient self-powered micro-power system, composing of energy harvesting unit and electric power conversion unit is the most promising candidate to support widely distributed information equipment to overcome the constraints of wired and portable power supply. However, current works fail to provide an integrated and optimized system, which suffer from large attenuation loss. Thus, the output power is too micro for board applications with unsatisfied efficiency. To overcome those problems, this paper proposes a novel PCB integrated self-powered micro-electric generator for vehicle engine vibration harvesting. The generator windings and power conversion unit are implemented on same PCB substrate. The micro-generator has the output of ± 2341.85mV AC at 52.3Hz. An all GaN high frequency dual-boost AC-DC converter with boundary conduction mode is employed with impedance matching for maximum power transferring. It also utilizes the output inductance of micro-generator as boost inductor and sensing inductor. The peak output efficiency of the converter reaches to 83% at 3.3V/21.35mW output, which is much higher than state-of-art.

Resonant gate drive (RGD) is the more efficient solution to drive SiC MOSFETs at high switching frequencies with effective gate driver energy saving. It adjusts driving characteristics from RC step response to RLC resonant response at the risk of reduced power transistors’ switching speed and increased switching loss. Resonant inductor becomes the most important component in RGD design and is mutually restraint for gate driver loss reduction and power transistor switching characteristics improvement. Current studies on RGD vaguely uses MOSFET input capacitor (Ciss) from datasheet or total gate charge (Qg) to analyze driver characteristics. The non-linear feature brought by MOSFET miller capacitor is completely ignored, which leads to un-optimized resonant inductor selection and poor understanding in RGD influence on MOSFET switching behaviors. To overcome these issues, a novel time segmented methodology is proposed to provide comprehensive analysis of RGD and understand its impacts on different aspects. The driving loss and SiC switching speed co-optimized series resonant gate driver is demonstrated with 25.5% saving on gate driver loss and 44.4% improvement in driving speed at 200 kHz switching frequency.

Public safety may be endangered by events that could lead to huge losses including human life, injuries or property damage, such as crime or disaster. In addition, there are some factors that affect public safety, such as the ratio of temporary residents, per capita GDP, etc. This paper aims at integrating Non-discretionary variable in data envelopment analysis (DEA-NDSC) and analytic hierarchy process (AHP) to evaluate the public safety of cities in China. The proposed AHP/DEA methodology uses the AHP to determine the weights of criteria to assess each item under each criterion, and the DEA-NDSC method to evaluate the efficiency of safety services. A cities’ case of public safety perception is employed to illustrate the proposed method. The results show that the method can effectively and reasonably evaluate the public safety of the city. This research also offers a simple enough and applicable approach to a number of multiple criteria decision making problems.

Two-dimensional numerical simulation is performed with the open-source program AMROC to study the effects of transverse jets (act as fluidic obstacles within a detonation tube) on the flame acceleration and deflagration to detonation transition (DDT). The slot transverse jets have been studied and compared with conventional solid obstacles in tubes. The jet initial parameters, such as mixture composition, stagnation temperature, pressure and mass flow rate, are investigated. The results demonstrate that a hydrogen-oxygen-argon reactive fluidic obstacle leads to the shortest DDT distance and time compared with solid obstacles and fluidic obstacles composed of pure oxygen or argon. The fluidic obstacles can induce more vorticities to accelerate flame propagation. The DDT distance and time decrease with the jet initial temperature, pressure and mass flow rate rise, while a high jet initial stagnation temperature is counterproductive to shorting DDT distance and time. The local static pressure rise plays an important role in flame acceleration when increasing the initial pressure of the fluidic obstacle. Higher jet pressure and a wider jet induce more compression waves, which can make the initial flame front more unstable and accelerate the flame as well.

Pulse generator in an ultrasound system produces electrical pulsing signals to drive piezoelectric transducer, which causes mechanical vibration of the crystals and generates sound waves. Different from conventional imaging short pulses, high-power ultrasonic system for therapeutic applications requires MHz pulses bursts of up to tens of milliseconds. The capability of switching high voltage (±90 V) at multi-MHz, delivering effective power efficiently, is crucial for practical systems. The advantages of low device loss at high switching frequency, and high power density make gallium nitride (GaN) high electron mobility transistors better devices than traditional silicon (Si) MOSFETs in such system. The GaN-based high-frequency transformer push–pull inverter presented in this paper is capable to produce high energy pulsating output with burst pulse length up to 50 ms and bipolar pulse amplitude of 180 Vpp. The maximum pulse frequency can be up to 10 MHz. The peak output power is 90 W with power density of 50.85 W/in2. The peak power for all the 128 pulser channels reaches up to 11.5 KW with average power of 192 W. This is the highest output power for pulse drivers that have been reported. A novel power transistor based RF switch circuit is also proposed in this design as the interface between image signal, high power signal, and return signal.

A more accurate miller capacitor model is proposed in this paper to achieve precise SiC switching characteristic prediction for high frequency and high power density designs. The SPICE models of power transistors are either not provided or fail to represent parasitic capacitor accurately, which will lead to poor estimation of device switching loss. For SiC transistor used in this paper, LTSPICE simulation shows up to 53.7% mismatch in miller capacitor compared with measurement data provided in datasheet. Accurate switching loss prediction will help to use SiC more effectively and thermally optimized in high frequency, high power density systems. The physical mechanism of miller capacitor reflects an internal cascaded configuration of a fixed capacitor with a voltage depended capacitor. The voltage depended capacitance is further influenced by different doping concentrations in vertical power MOSFET and can be splitted into four stages. Based upon these, the Segmented-and-Cascaded miller capacitor approximation method is proposed. It shows descent agreement with datasheet C-V curve of less than 15% mismatch, which is three times less than SiC SPICE model. Experimental results using double pulse test circuit are provided to verify the proposed miller capacitor model. The maximum mismatches under hard switching at 500V are 9.5% for dv/dt and 8.4% for di/dt.

We present a framework to generate mesh patterns that consist of a hybrid of both triangles and quads. Given a 3D surface, the generated patterns fit the surface boundaries and curvatures. Such regular and near regular triangle-quad hybrid meshes provide two key advantages: first, novel-looking polygonal patterns achieved by mixing different arrangements of triangles and quads together; second, a finer discretization of angle deficits than utilizing triangles or quads alone. Users have controls over the generated patterns in global and local levels. We demonstrate applications of our approach in architectural geometry and pattern design on surfaces.

The preparation of various types of miktoarm star polymers with precisely controlled structures (A2B, ABC, AB2C2, etc.) has made significant progress due to the considerable advances in the synthetic strategies, including multistep protections/deprotections, orthogonality, and integration of different polymerization techniques. However, compared to the well-developed synthesis methodologies, the investigations on miktoarm star copolymers as drug delivery vehicles remain relatively unexplored, especially for the relationship of their branched structures and properties as drug delivery systems. To elucidate this structure–property relationship of amphiphilic miktoarm star polymers, we prepared four different amphiphilic miktoarm star copolymers with the respectively identical molecular weights (MWs) of hydrophilic and hydrophobic moieties but different star structures using heteroinitiators that were synthesized by protection/deprotection strategies for integrated ring-opening polymerization of hydrophobic ...

LCC high voltage generator is widely adopted for X-ray beam excitation and control. It has the requirement of wide load range, fast transients, high efficiency and reduced system size. Therefore, SiC based high voltage generator switching at 2X-3X of current frequency will be a better option. Accurate prediction of SiC switching characteristics as well as comprehensive switching behavior evaluation are important prerequisites for thermally optimized and efficient SiC system design. This paper proposed on a novel miller capacitor modeling approach: Segmented-and-Cascaded approach. The mismatch between modeled capacitor curve and measurements data from datasheet is within 15%, which is three times as less as the SPICE model. A comprehensive switching characterization is also revealed. The hard turn on loss is $157.7\boldsymbol{\mu} \mathbf{J}$ at 500V/40A and will be significantly reduced under ZVS-ON. The turn off energy loss under hard switching is $48.1\boldsymbol{\mu} \mathbf{J}$ at 500V/40A. It is reduced to $4.43\boldsymbol{\mu} \mathbf{J}$ with 3.2nF snubber capacitor at soft turn off. Good consistency is observed of predicted data vs. measurements with maximum deviation of 17.2%. SiC power transistor with ZVS turn on and soft turn off has the lowest switching loss of $9.12\boldsymbol{\mu} \mathbf{J}$ . Therefore, designing the LCC inverter at switching frequency higher than resonant frequency will achieve both high efficiency and high power density.

Developing the formal model based on the Event-B design pattern is an excellent method to improve the development efficiency of the embedded control system and improve the reusability of the formal model. However, the instantiation of the Event-B design pattern requires the manual writing of a large number of model codes, which brings a great deal of learning cost and coding burden to the engineering staff. In this paper, we propose a modelling approach for formal development of control systems based on the application of iUML-B state machine patterns to model the four synchronization patterns of the typical control system. Then, we use the instantiation of iUML-B pattern state machine to establish a typical multilevel control system's Event-B model. The simulation results show that the event trace of the model obtained using our method is the same as that of the corresponding model obtained using the traditional Event-B design pattern. Compared with the traditional Event-B design pattern method, our method can greatly reduce the manual coding burden in the modelling process. The system model expressed using the iUML-B pattern state machine can be easily mapped to the labelled transition system so as to verify the behavioural properties of the model.

Polymeric prodrugs with precisely controlled drug loading content (DLC) and rapid intracellular destabilization generally require complicated chemistry that hinders large-scale manufacture. For this purpose, we reported in this study a facile construction of reduction-sensitive amphiphilic polyprodrugs with an anticancer drug, 10-hydroxycamptothecin (HCPT), and a hydrophilic poly(ethylene oxide) (PEG) moiety as the alternating building blocks of the multiblock copolymer using Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAc) click coupling between azide-SS-HCPT-SS-azide and alkyne-PEG-alkyne. Adoption of PEGs with two different molecular weights (MWs) of 400 and 1450 Da (PEG400 and PEG1450) afforded two polyprodrugs with different DLCs. Both formulations can self-assemble into spherical micelles with hydrodynamic diameter smaller than 200 nm, and exhibit glutathione (GSH)-triggered degradation for promoted drug release. A further comparison study revealed that the PEG1450-based polyprodrug is a better formulation than the analogue constructed from PEG400 in terms of in vitro drug release behaviors, and cytotoxicity. This work thus provides a facile yet efficient strategy toward polymeric prodrugs with precisely controlled DLC and reduction-triggered degradation for enhanced anticancer drug delivery.

A polyvinylpyrrolidone (PVP)/polyacrylic acid (PAA) layer-by-layer (LbL) assembled composite coating with a multilayer structure for the corrosion protection of AZ31 magnesium alloy was prepared by a novel spin-casting method. The microstructure and composition of this coating were investigated by means of SEM, XRD and FT-IR measurements. Moreover, electrochemical, immersion and scratch tests in vitro were performed to measure the corrosion performance and the adhesion strength. These results indicated that the (PVP/PAA)10 composite coating with defect-free, dense and uniform morphologies could be successfully deposited on the surface of magnesium alloy. The coating had excellent corrosion resistance and adhesion strength.

In Event-B, people need to use control variables to constrain the order of events, which is a time-consuming and error-prone process. This paper presents a method of combining labeled transition system and iUML-B to complete the behavior modeling of system, which is more convenient and practical for engineers who are accustomed to using the automaton to build a system behavior model. First, we use labeled transition system to establish the behavior model of the system. Then we simulate and verify the event traces of the labeled transition system behavior model. Finally, we convert labeled transition system model into iUML-B state machine and use it to generate the corresponding control flow model. We use Abrial’s bounded retransmission protocol to demonstrate the practicality of our approach. The simulation results show that the system behavior model generated by the iUML-B state machine has the same event trace as the corresponding labeled transition system model.

A micro-arc oxidation (MAO)/zinc stearate (ZnSA) composite coating was fabricated via MAO processing and subsequent sealing with electrodeposition of a superhydrophobic ZnSA. The surface morphologies, chemical composition and corrosion resistance of the coatings were investigated using field-emission scanning electron microscopy, Fourier transform infrared, X-ray diffraction and electrochemical and hydrogen evolution measurements. Results indicated that the MAO coating was efficiently sealed by the following superhydrophobic ZnSA coating. The MAO/ZnSA composite coating significantly enhanced the corrosion resistance of Mg alloy Mg-4Li-1Ca due to its superhydrophobic function. Additionally, corrosion mechanism was suggested and discussed for the composite coating.

Silk is very promising in the field of biomaterials as a natural biomacromolecule. Silk protein can be made into various forms of materials, including hydrogels. However, silk protein-based hydrogels have not attracted much attention due to its weak mechanical properties. Here, we report high water content silk protein-based hydrogels with tunable elasticity which were fabricated through Ru(II) mediated photochemically cross-linking tyrosine residues in regenerated silk protein. The regenerated silk protein was characterized by Fourier transform infrared spectroscopy (FTIR). The gelation kinetics of the silk protein was studied by rheology measurements. The compressive mechanical properties of the silk protein-based hydrogels was investigated using compressive tests and dynamic mechanical analysis (DMA). Compressive modulus of the hydrogels reached 349±64 MPa at 15 % strain. The fabricated silk protein-based hydrogels were also characterized by Scanning electron microscopy (SEM), revealing an interconnected porous network structure, typical of hydrogels, with an average pore size of approximately 130 μm. Finally, biocompatibility of the silk protein-based hydrogels was demonstrated through cell culture studies using a human fibroblast cell line, HFL1. The reported silk protein-based hydrogels represent a promising candidate for biomaterial applications.

A crosslinked ciprofloxacin (CIP) and polymethyltrimethoxysilane (PMTMS) with an inner micro-arc oxidation (MAO) coating was designed to improve the corrosion resistance and antibacterial property of magnesium alloy AZ31. Surface morphology and roughness of the obtained coating were characterized through scanning electron microscopy (SEM) and three-dimensional surface profilometry. Structural components and chemical compositions of the composite coatings were detected via Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectrometry (EDS). Corrosion resistance of the coatings was investigated by means of electrochemical impedance spectroscopy (EIS), potentiodynamic polarization curves and hydrogen evolution measurements. Cytocompatibility and antibacterial performance of the coatings were probed using in vitro cytotoxicity tests (MTT), live/dead cell staining and plate counting method. Results indicate that the MAO/CIP-PMTMS coating possesses enhanced corrosion resistance, antibacterial ability and cytocompatibility. It provides a way to effectively curb the sudden release and short release period of drugs, due to the reversible esterification reaction between -COOH in CIP and Si-OH in PMTMS during the coating formation and degradation process. And it holds a great potential in the applications of medical devices and bone implant materials.

Nowadays, with respect to the nonlinear birefringent optical fibers, efforts have been put into investigating the coupled nonlinear Schrodinger (NLS) systems. In this paper, symbolic computation on...