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To solve the problems of frequent network link jitter and high bit error rate is the development direction of power grid communication technology. Therefore, a multi-channel data stream transmission method of Internet of things in power systems based on big data analysis is proposed. The data stream matching method based on big data stability mechanism is constructed by using data stream matching method to match the data stream to be transmitted and improve the anti-noise performance of the transmission process; the multichannel model of data stream transmission is constructed, and the matched data stream is transmitted by the multi-channel model; the big data analysis technology is used to process the data stream transmission process and improve the transmission performance of the model; the adaptive multi-channel equalization control method of sampling decision is used to realize the equalization design of data stream transmission channel, optimize the model transmission process, and reduce the bit error rate of transmission. Experimental results show that this method has better channel equalization performance; the link jitter frequency of this method is low, and it has better transmission stability; the lowest bit error rate can reach 0%, and the reliability of data stream transmission is high.

Radiation detection material is a central component of nuclear technology finding applications in many critical fields. Developing a highly radiation-sensitive material that shows a facilely detectable response to ultra-low dosage of radiation is a long-term research target and remains to be a challenge. Previously reported most optimal chemical radiation dosimeter can detect low-dosage X- and γ-ray radiations down to 10−4 Gy. We document here a new photoresponsive coordination polymer showing upgraded radiation detection capabilities with the detection limit on the radiation dose one order of magnitude lower than the previous record. The radiation induced photoluminescence quenching process was elucidated by multiple spectroscopic characterizations.

Human arm/hand gestures capturing and recognition provide an intelligent and convenient way for use in application from human-machine interface (HMI) and human-computer interaction (HCI) to human-robot interaction (HRI). As human gestures constitute a powerful inter-human communication modality, they can be considered as well an intuitive and convenient mean for the communication between human and machines. This paper presents a novel real-time static and dynamic human gesture capturing and recognition method designed using flexible wearable data band/data glove, which are designed based on three/ten stretchable strain sensors respectively. The wearable data bands and data gloves are worn by human arm/hand to ensure that the sensors are accurately attached to the human joints for accurate measurement of joints movements of shoulders joints, elbows joints, wrists joints, metacarpal and proximal joints of fingers. In this work, a new idea of real-time static and dynamic human gesture capturing and recognition is introduced and developed based on the radial basis function neural network (RBFNN). Dynamic time warping (DTW) is used to select dynamic behavior candidates and also to recognize gestures by comparing the observed records with a series of pre-recorded reference data patterns. The solution deals simultaneously with static and dynamic gestures as well as with multiple joints within the interest space. The experimental results of human arm/hand static gestures and dynamic gestures capturing and recognition verify the effectiveness of the proposed methods.

For the first time, we report intense X-ray scintillation enabled by a series of isotypic lanthanide (Eu and Tb) based metal-organic frameworks, initially showing a very efficient X-ray to visible light luminescence conversion. By systematic adjusting of the molar ratio of Eu3+ and Tb3+ in the same MOF structure as a traditional strategy for color-tuning in lanthanide-based photoluminescent materials, linear multicolor visualization of X-ray radiation from red to green can be facilely achieved, providing a new class of scintillating materials with continuous color tunability that can be customized for desired purposes. Moreover, these lanthanide-organic framework based scintillators exhibit excellent radiation resistance and humidity stability, in comparison with the state of the art and commercially-available X-ray scintillator, CsI:Tl.

Activity around transmission lines after bird nesting poses a threat to the safe operation of the power grid. Identifying bird nests in transmission lines and towers is the key to preventing wading bird failures. With the development and change of deep learning and patrol mode, the accuracy and speed of bird's nest recognition algorithm are challenged. To address this challenge, this paper presents a bird's nest location recognition method based on YOLOv4-tiny. YOLOv4-tiny, a lightweight version of YOLOv4, consists of a backbone network, FPN, and YOLO head with 13×13 and 26×262 prediction scales. The YOLOv4-tiny algorithm extracts the features of the input bird's nest image data to realize the positioning recognition of the bird's nest. This paper chooses the open source Darknet framework as a tool, which combines Loss and AP curves in the visualization training process. The results show that the model accuracy of YOLOv4-tiny algorithm can reach 77.20%, and the inference speed on the edge computing platform Jetson Xavier NX can reach up to 50.39 FPS. The method proposed in this paper can meet the requirements of real-time target detection in both speed and accuracy, and has a good application prospect.

Searching for new green phosphors featured with a narrow band, small Stokes-shift, high thermal stability, and decent chemical resistance is critical for white light emitting diodes (LEDs) in liqui...

Objective: Non-alcoholic fatty liver disease (NAFLD) is a serious health threat worldwide. The aim of this study was to comprehensively describe the metabolic and immunologic characteristics of NAFLD, and to explore potential therapeutic drug targets for NAFLD.Methods: Six NAFLD datasets were downloaded from the Gene Expression Omnibus (GEO) database, including GSE48452, GSE63067, GSE66676, GSE89632, GSE24807, and GSE37031. The datasets we then used to identify and analyze genes that were differentially expressed in samples from patients with NAFLD and normal subjects, followed by analysis of the metabolic and immunologic characteristics of patients with NAFLD. We also identified potential therapeutic drugs for NAFLD using the Connectivity Map (CMAP) database. Moreover, we constructed a prediction model using minimum depth random forest analysis and screened for potential therapeutic targets. Finally, therapeutic targets were verified in a fatty liver model stimulated by palmitic acid (PA).Results: A total of 1,358 differentially expressed genes (DEGs) were obtained, which were mainly enriched in carbohydrate metabolism, lipid metabolism, and other metabolic pathways. Immune infiltration analysis showed that memory B cells, regulatory T cells and M1 macrophage were significantly up-regulated, while T cells follicular helper were down regulated in NAFLD. These may provide a reference for the immune-metabolism interaction in the pathogenesis of NAFLD. Digoxin and helveticoside were identified as potential therapeutic drugs for NAFLD via the CMAP database. In addition, a five-gene prediction model based on minimum depth random forest analysis was constructed, and the receiver operating characteristic (ROC) curves of both training and validation set reached 1. The five candidate therapeutic targets were ENO3, CXCL10, INHBE, LRRC31, and OPTN. Moreover, the efficiency of hepatocyte adipogenesis decreased after OPTN knockout, confirming the potential use of OPTN as a new therapeutic target for NAFLD.Conclusion: This study provides a deeper insight into the molecular pathogenesis of NAFLD. We used five key genes to construct a diagnostic model with a strong predictive effect. Therefore, these five key genes may play an important role in the diagnosis and treatment of NAFLD, particularly those with increased OPTN expression.

Background: Acute mountain sickness (AMS) is the effect when people accessing high altitude in a short period of time. As a cyclooxygenase (COX) inhibitor, ibuprofen could alleviate the symptoms of AMS. However, whether it can prevent AMS or not is still controversial. It is necessary to perform a meta-analysis to evaluate the role of ibuprofen in AMS prophylaxis. Methods: PubMed, EMBASE, Medline, ISI Web of Science, Cochrane Library, China National Knowledge Infrastructure (CNKI) will be searched for the relevant published studies that explored the value of ibuprofen in AMS prophylaxis from inception to October 2020. The data will be independently extracted by 2 researchers. Risk of bias will be evaluated based on Cochrane risk of bias assessment tool. Heterogeneity among the included studies will be evaluated by χ2 and I2 values. The meta-analysis was conducted by RevMan software version 5.3. Results: This study will evaluate the role of ibuprofen in AMS prophylaxis. Conclusion: This study will summarize the current evidence of ibuprofen in AMS prophylaxis, which could further guide the recommendation in prevention of AMS. Open Science Framework (OSF) registration number: October 8, 2020. osf.io/n3mjt.

3D printing of amorphous and crystalline ceramics is of paramount importance for the fabrication of a wide range of devices with applications across different technology fields. Printed ceramics are remarkably enabled by the sol–gel synthesis method in conjunction with continuous filament direct ink writing. During printing, multiple processes contribute to the evolution of inks including shape retention, chemical conversion, solidification, and microstructure formation. Traditionally, depending on the ink composition and printing environment, several mechanisms have been associated with the shape retention and solidification of 3D printed structures: gelation, rapid solvent evaporation, energy-driven phase transformation, and chemical-driven phase transformation. Understanding the fundamental differences between these mechanisms becomes key since they strongly influence the spatiotemporal evolution of the materials, as the out-of-equilibrium processes inherent to the extrusion, relaxation, and solidification of printed materials have significant effects on the materials properties. In this work, we investigate the shape retention mechanism and the hydrolysis-induced material conversion and microstructure formation during the 3D printing of a water reactive sol–gel ink that transforms into titanium dioxide-based ceramic. This study aims at identifying characteristic mechanisms associated with the material transformation, establishing connections between the microstructure development and the timescales associated with solidification under operando 3D-printing conditions. The investigation of this material’s out-of-equilibrium pathways under processing conditions is enabled by time-resolved coherent X-ray scattering, providing simultaneous access to temporospatially resolved microstructural and dynamics information. Furthermore, we explore X-ray speckle tracking as a tool to resolve deformations of the microstructure in a printed filament associated with the deposition of consecutive filaments. Through this work, we aim at providing a fundamental understanding of the relationships behind these transformative processes in 3D printing and their timescales as the basis for achieving unprecedented control over printed materials microstructure.

Driving mechanism is an important part of the flapping-wing UAV. However, in the flight experiments, the driving mechanism failed several times which led to unexpected flight interruptions. This was because that the uneven wear in the hinge of the connecting rod and the crank was significantly serious, which was the main problem affecting flight stability. To solve the above problem, a multi-body dynamic model with clearance hinge is established, considering that the hinge of the connecting rod and the crank has clearance. The bushing is divided into multiple sections along the circumference, and the distance from each section to the axis is parameterized. The contact-impact force model is established between the connecting rod and each section of the bushing. In addition, the concept of wear cycle is introduced, and the wear depths under different wear cycles are iteratively calculated based on the Archard’s wear model. Finally, by analyzing the contact stresses between each section of the bushing and the crank under different wear cycles, the law of uneven wear of the bushing is obtained. The wear model in this paper is estimated to provide guidance for the life prediction and optimization design of the flapping wing driving mechanism.

The main scientific goal of the LHAASO WFCTA experiment is to measure the cosmic ray energy spectra and composition from 10 TeV to 1 EeV. Cherenkov photons in the extensive air shower measured by the SiPM camera of Cherenkov telescopes can be used to reconstruct the cosmic ray energy. The absolute calibration of the camera is a crucial step to achieve the accurate measurement of the cosmic ray energy spectrum. A multi-wavelength cylindrical illuminator based on LEDs is developed and mounted inside the telescope to calibrate and monitor the camera, and the illuminator’s stability is better than 0.5% under the temperature variation from -26 to 26 ° C. A portable probe with a single photoelectron resolution of 21.6% is developed. After calibration by National Institute of Metrology, China (NIM), the probe is taken to the LHAASO site to measure the absolute photon density of the cylindrical illuminator inside the telescope. Based on the illuminator with known photon density, the photon conversion factor of the camera can be calibrated, and the overall calibration uncertainty is less than 2.6%.

The control of phonon propagation in nanoparticle arrays is one of the new frontiers of nanotechnology, potentially enabling the discovery of materials with unknown functionalities for potential innovative applications. The exploration of the terahertz window appears quite promising as phonons in this range are the leading carriers of heat transport in insulators and their control is the key to implement devices for heat flow management. Unfortunately, this scientific field is still in its infancy and even a basic topic such as the influence of floating nanoparticles on the terahertz phonon propagation of a colloidal suspension still eludes a firm answer. Shedding some light on this topic is the main motivation of the present work, which focuses an Inelastic X-Ray Scattering (IXS) measurements on a dilute suspension of Au nano-spheres in water. Measured spectra showed a non-trivial and unexpected shape displaying multiple inelastic features that, based on a Bayesian inference analysis, we assign to phonon modes propagating throughout the nanoparticle interior. Surprisingly, the spectra bear no evidence of propagating modes, which are known to dominate the spectrum of pure water, owing to the scattering that these modes suffer from the sparse nanoparticles in suspension. In perspective, this finding may inspire simple routes to manipulate high-frequency acoustic propagation in hybrid - liquid and solid- materials.

The selenium dioxide was used as the precursor to synthesize wide-size-ranged CdSe quantum dots (2.4-5.7 nm) via hot-injection route. The CdSe quantum dots are featured with high crystalline, monodisperse, zinc blende structure and wide emission region (530-635 nm). In order to improve the stability and quantum yield, a phosphine-free single-molecular precursor approach is used to obtain CdSe/CdS core/shell quantum dots. The CdSe/CdS quantum dots are highly fluorescent with quantum yield up to 65%, and persist the good monodispersity and high crystallinity. Moreover, the quantum dots white light-emitting-diodes are fabricated by using the resultant red emission core/shell quantum dots and Y3Al5O12:Ce3+ yellow phosphors as color-conversion layers on a blue InGaN chip. The prepared light-emitting-diodes show good performance with CIE-1931 coordinated of (0.3583, 0.3349), an Ra of 92.9, and a Tc of 4410 K at 20 mA, which indicate that the combination of red-emission QDs and yellow phophors as a promising approach to obtain warm WLEDs with good color rendering.

We report the crossover of the coefficient of thermal expansion (CTE) from positive to negative by withdrawing the excess fluorines in ReO3-type TiZrF7−x (x = 0, 0.5 and 1) compounds. The average volumetric CTE between 300 K and 623 K changes from 8.07 ppm K−1 for x = 0, to 0.66 ppm K−1 for x = 0.5 and finally to −6.09 ppm K−1 for x = 1. After withdrawing the excess fluorines, the lattice expands and the edge-sharing polyhedra partially transform to corner-sharing ones, which enhances the transverse vibrations of fluorines and thus accounts for the crossover of CTE. Moreover, these compounds are narrow-gap semiconductors with the energy gap decreasing with x. NTE may also be achievable in other fluorine-excess cubic fluorides by removing the excess fluorines, which opens up a new avenue for exploring the NTE in fluorides.

A new technique is presented to allow the measurement of weakly scattering samples despite a high-background environment. Coherent interference between the sample and a nanofabricated ‘amplifier’ structure generates a strong interference scattering pattern, which can be analyzed using angular correlation functions to reconstruct the sample’s symmetry., Small-angle X-ray scattering (SAXS) often includes an unwanted background, which increases the required measurement time to resolve the sample structure. This is undesirable in all experiments, and may make measurement of dynamic or radiation-sensitive samples impossible. Here, we demonstrate a new technique, applicable when the scattering signal is background-dominated, which reduces the requisite exposure time. Our method consists of exploiting coherent interference between a sample with a designed strongly scattering ‘amplifier’. A modified angular correlation function is used to extract the symmetry of the interference term; that is, the scattering arising from the interference between the amplifier and the sample. This enables reconstruction of the sample’s symmetry, despite the sample scattering itself being well below the intensity of background scattering. Thus, coherent amplification is used to generate a strong scattering term (well above background), from which sample scattering is inferred. We validate this method using lithographically defined test samples.

A facile synthesis of aqueous CdZnTe quantum dots (QDs) incorporated in CaCO3 matrix is demonstrated, providing a new type of solid-state light conversion material. Highly luminescent CdZnTe QDs were firstly synthesized using CdCl2, ZnCl2 and Te as precursors and 3-Mercaptopropionic acid (MPA) as ligand. Then CdZnTe QDs were incorporated into CaCO3 matrix through a co-precipitation method. Due to the protection of the tight matrix, the resulting CdZnTe QDs/CaCO3 composites exhibit good photostability and processability as well as high photoluminescence properties. A white light-emitting diode (WLED) applying the composites as a red color conversion layer was also fabricated, which showed excellent performance including a Commission Internationale de I'eclairage (CIE) color coordinate of (0.3662, 0.3396), a high color rendering index (Ra) of 92.7 and a low correlated color temperature (Tc) of 4146 K under 20 mA forward-bias current, suggesting the promising application of the composites in solid-state lighting systems.

Owing to their ultrahigh sensitivity, crack-based flexible strain sensors have garnered considerable attention in recent years. In this study, a practical, and reliable chemical bonding-based dip-coating method is proposed to fabricate high sensitivity and high stability crack-based flexible strain sensor with dual hydrogen bond-assisted structure. The strain sensor has a sandwich structure, which is composed of graphene nanoplatelets (GNPs)/poly (sodium-p-styrenesulfonate) (PSS) conductive layer, ultra-violet (UV) adhesive substrate layer, and UV adhesive covering layer. The fabrication process, principle of dual hydrogen bond-assisted structure, strain sensing mechanism, and various properties of the proposed sensor are examined. It is demonstrated that the cracks and the dual hydrogen bond-assisted structure facilitate a practical strain sensor with high sensitivity (gauge factor of 19.65 in the strain range of 0–30%), long-term stability (over 10,000 cycles), good linearity, negligible drift, fast response time (~50 ms), and low detection limit (0.10%). Meanwhile, the proposed crack-based flexible strain sensor can be used as a wearable device, which can be directly mounted on human skin to monitor tiny human motions and writing behavior. Consequently, it exhibits immense potential for wearable applications including artificial skin, human-machine interfaces, and medical healthcare.

Hybrid white LEDs were constructed by leveraging a combination of CdSe/ZnS core/shell QDs and YAG: Ce³⁺ phosphors. The CdSe/ZnS core/shell QDs were synthesized by a two-step process in which CdSe QDs were first prepared via a hot-injection method, followed by ZnS coating through a facile single-molecular precursor approach. The resultant red-emitting CdSe/ZnS QDs showed decent fluorescent quantum yielding (36%). The resultant hybrid white LEDs--that based on CdSe/ZnS QDs and solid-state-reaction-processed YAG: Ce³⁺ phosphors--showed good luminescence properties, including bright warm light, a high color rendering index of 91.3, a low color temperature of 4965 K and a luminous efficiency of 44.22 lm/W. Moreover, increased luminous intensity has been observed in the presence of increased forward current without luminescence saturation, promising an ideal approach to construct warm-white LEDs with excellent color rendering properties.

Additive printing techniques are regarded as revolutionary and versatile methods of advanced device manufacturing, stemming from the possibility to pattern materials on a custom-based approach and the potential to create novel microstructures and achieve new functionalities. Despite these advantages, the inherent anisotropy of the printing process is a source of property gradients within the printed materials, often associated with variable and/or poor performance. Up to date, the evolutionary pathways associated with printing have largely remained unaddressed, mainly owing to the difficulty to study the transformations induced in the material during processing. Time-resolved coherent X-ray scattering techniques, such as X-ray photon correlation spectroscopy, enable the in situ study of transient nanoscale and mesoscale states in a large variety of materials, including amorphous ones, by directly accessing the most relevant timescales and length scales of their nanoscale and mesoscale dynamics, self-assembly, and mesostructure evolution. We conduct in operando studies of continuous-flow direct writing with colloidal inks, focusing on how the ink formulation and ink-substrate interactions affect the processes that determine the macroscopic properties of the printed materials. We find fundamental differences in the ink structural relaxations emerging from the primary colloid properties (monodisperse versus aggregated colloids) and the substrates surface energy and mechanical properties. Our work helps to reveal and quantify the basic science governing the evolution of 3D-printed materials during processing, ultimately improving engineering criteria for the design of printable materials.

There is an increasing demand for flexible and wearable strain sensors for the potential applications in wearable monitor, including human activities, human-machine interfaces and master devices for teleoperated robotic system, etc. Herein, we propose a highly stretchable strain sensor developed by structured single-walled carbon nanotube /carbon black (SWCNTs/CB) networks for wearable monitor. The fabrication process, strain sensing mechanism and characterization of the sandwich-structured strain sensor were systematacially investigated. The results show that the sandwich-structured strain sensor has high stretchability of strain up to 160%, a sensitivity with the gauge factor (GF) approximate 1.04, as well as high stability and reproducibility of 1000 repeated stretching/releasing cycles. Furthermore, bending of elbow and knee was recorded, demonstrating that the highly stretchable strain sensor could have promising applications in flexible and wearable devices for human motion monitoring.

Vertically aligned nanowire arrays (NWAs) of semiconductor materials, combined with the merits of the large surface-to-volume ratio and low reflectance induced by light scattering and trapping, have attracted growing interests in the fabrication of high-performance optoelectronic nano-devices due to their exceptional geometrical structure and device architecture. However, an inexpensive synthesis of II–VI group semiconductor NWAs, e.g. CdS, CdSe NWAs, especially their heterostructures, is still a great challenge, and the devices (photodetector, field emitter, etc.) based on these NWA heterostructures have therefore been rarely studied. Here, we report a new method of synthesizing high-quality vertical CdS NWAs which heteroepitaxially grow on CdSe single-crystalline sheets (SCSs). The CdS NWA/CdSe SCS heterostructures as a whole are designed and fabricated into novel photodetectors via E-beam lithography. The obtained photodetectors exhibit excellent performance with high photosensitivity, responsivity, and external quantum efficiency, alongside fast response speed, and wide range response spectrum. Additionally, field-emission data of these vertically tapered CdS NWAs on CdSe SCS show enhanced properties with low turn-on field, high enhancement factor, and good stability. The results indicate that the synthesized CdS NWA/CdSe SCS heterostructure is a good candidate for broadband (ultraviolet-visible) photodetectors and field-emitters.

A formalism is described which enables the simulation or fitting of small-angle scattering data (X-ray or neutron) for periodic heterogeneous lattices of arbitrary nano-objects. Generality is maximized by allowing for particle mixtures, anisotropic nano-objects and definable orientations of nano-objects within the unit cell. The model is elaborated by including a variety of kinds of disorder relevant to self-assembling systems: finite grain size, polydispersity in particle properties, positional and orientation disorder of particles, and substitutional or vacancy defects within the lattice. The applicability of the approach is demonstrated by fitting experimental X-ray scattering data. In particular, the article provides examples of superlattices self-assembled from isotropic and anisotropic nanoparticles which interact through complementary DNA coronas.

Survivability strengthening/vulnerability reduction designs have become one of the most important design disciplines of military aircraft now. Due to progressiveness and complexity of modern combat aircraft, the existing vulnerability modeling and computation methods cannot meet the current engineering application requirements. Therefore, a vulnerability modeling and computation method based on product structure and CATIA is proposed in sufficient consideration of the design characteristics of modern combat aircraft. This method directly constructs the aircraft vulnerability model by CATIA or the digital model database, and manages all the product components of the vulnerability model via aircraft product structure. Using CAA second development, the detailed operations and computation methods of vulnerability analysis are integrated into CATIA software environment. Comprehensive assessment data and visual kill probability Iso-contours can also be presented, which meet the vulnerability analysis requirements of modern combat aircraft effectively. The intact vulnerability model of one hypothetical aircraft is constructed, and the effects of redundant technology to the aircraft vulnerability are assessed, which validate the engineering practicality of the method.

A new structure nonvolatile memory, with large conductance switching (on/off ratio > 106), has been constructed from a p-ZnS nanoribbon (NR)/n-Si heterojunction. The p-type ZnS NRs were obtained using cuprous sulfide (Cu2S) as the Cu dopant. Excellent Ohmic contact to p-type ZnS NRs was achieved by using a Cu/Au bilayer electrode, which contributed to the formation of the thin Cu2S interfacial layer between the electrode and the NR, as confirmed from the combined X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) analysis. These devices exhibit a stable and reproducible hysteresis and excellent memory characteristics with a long retention time of 1 × 105 s and good endurance >6 months at room temperature. The electrical switching behavior could be attributed to the charge trapping and detrapping in interface states at the junction. The approach could potentially provide a viable way to create new advanced nonvolatile memory devices with simple structure and to fabricate large conductance switching and large-capacity data storage.

In this paper, the characteristics of the kinetic reliability of space four-links mechanism are analyzed and the relationship between the kinetic accuracy and wear clearances in joints is explored, using Advanced First Order and Second Moment (AFOSM) method and Monte-Carlo Simulation (MCS). The Archard wear model is applied to analyze the increasing wear clearances in joints; and the function between the joint clearance and the equivalent length of links is built; then the kinetic accuracy of the space four-links mechanism with the increase of wear clearances is analyzed. Finally a demonstrative application is given, illustrating the reliability degradation of kinetic accuracy with the increase of wear clearances, and AFOSM has much higher computational efficiency compared with MCS. Besides, the influence of the contact forces in joints to the kinetic accuracy of space four-links mechanism is analyzed, with instructive results for the design of space four-links mechanism in engineering applications.

The gear door lock system (GDLS) is a mechanism with multi-failure modes. It often leads to a large error when ignoring the correlation between failure modes. Copula theory in this work is applied to research the correlation between two failure modes. A dynamic simulation model is constructed to acquire the joint statistics characteristics of the two failure modes. Gumbel and Clayton Copula functions are chosen to establish the reliability model respectively, which shows that the single Copula model cannot fully capture the tail dependence. To solve the problem, a mixed Copula function is constructed. The minimum squared Euclidean distance is adopted to estimate the parameters of the reliability models. It shows that the result of mixed Copula model is the closest to that of the Monte Carlo simulation, and it presents the relative error is at least 46% lower than the single Copula.

A set of new data analysis software tools have been developed for the study of structural dynamics of materials using coherent scattering and photon correlation techniques. The new software tools can readily process high-throughput, multidimensional data, enabling studies of slow and fast dynamics of materials using X-ray Speckle Visibility Spectroscopy and X-ray Photon Correlation Spectroscopy techniques. They support a wide range of user expertise, from novice to developer, and are available in Scikit-beam python package which is available at https://github.com/scikit-beam/scikit-beam.

Photoluminescence quenching of colloidal CdSe core/shell quantum dots (QDs) with CdS, ZnS and CdS/CdZnS/ZnS shells in the presence of hole-transporting materials (HTMs) is studied by means of steady-state and time-resolved photoluminescence spectroscopy. Static quenching is surprisingly found to play an even more important role in the PL quenching process than the dynamic one originating from a hole transfer from QDs to HTMs. The static quenching efficiency of the QDs with single CdS shells of 3 and 6 monolayers is much larger than that of the QDs with a multilayer CdS/CdZnS/ZnS shell. The experimental results are important for understanding the control of the static quenching pathways in QDs by using multishell structures.

c2D transition metal dichalcogenides (TMDCs)-based heterostructures have been demonstrated to achieve superior light absorption and photovoltaic effects theoretically and experimentally, making them extremely attractive for realizing optoelectronic devices. In this work, a vertical multilayered n-MoS2/n-silicon homotype heterojunction is fabricated, which takes advantage of multilayered MoS2 grown in situ directly on plane silicon. Electrical characterization reveals that the resultant device exhibits high sensitivity to visible-near-infrared light with responsivity up to 11.9 A W(-1). Notably, the photodetector shows high-speed response time of ≈ 30.5 µs/71.6 µs and capability to work under higher pulsed light irradiation approaching 100 kHz. The high response speed could be attributed to a good quality of the multilayer MoS2 , as well as in situ device fabrication process. These findings suggest that the multilayered MoS2 /Si homotype heterojunction have great potential application in the field of visible-near-infrared detection and might be used as elements for construction of high-speed integrated optoelectronic sensor circuitry.

We used DNA self-assembly methods to fabricate a series of core-shell gold nanoparticle-DNA-colloidal quantum dot (AuNP-DNA-Qdot) nanoclusters with satellite-like architecture to modulate optical (photoluminescence) response. By varying the intercomponent distance through the DNA linker length designs, we demonstrate precise tuning of the plasmon-exciton interaction and the optical behavior of the nanoclusters from regimes characterized by photoluminescence quenching to photoluminescence enhancement. The combination of detailed X-ray scattering probing with photoluminescence intensity and lifetime studies revealed the relation between the cluster structure and its optical output. Compared to conventional light-harvesting systems like conjugated polymers and multichromophoric dendrimers, the proposed nanoclusters bring enhanced flexibility in controlling the optical behavior toward a desired application, and they can be regarded as controllable optical switches via the optically pumped color.

We demonstrated a flexible and reversibly deformable radio-frequency antenna based on SWCNTs/PANI/Lycra conductive fabric and semipermeable film for wireless wearable communications applications. The conductive fabric fabricated by using the 'dip and dry' process exhibits good flexibility, electrical stability, stretchability and mechanical properties, and a high electrical conductivity (with low sheet resistance of ~35 Ω/sq) was obtained based on the SWCNTs/PANI synergistic conductive network. The morphology of the semipermeable film was investigated to further illustrate the waterproof breathable features. Meanwhile, the modeling, fabrication procedure and radiating properties of the radio-frequency textile antenna worked at 2.45 GHz were systematically illustrated. The measured reflection coefficient, VSWR and the −10 dB bandwidth is ~−18.6 dB, 1.58 and ~270 MHz respectively, which agreed well with the simulation results. Furthermore, the results indicate that the design methodology for the radio-frequency textile antenna could have promising applications in flexible and reversibly deformable antennas for wearable wireless communications systems.

Flexible, stretchable, and wearable strain sensors have attracted significant attention for their potential applications in human movement detection and recognition. Here, we report a highly stretchable and flexible strain sensor based on a single-walled carbon nanotube (SWCNTs)/carbon black (CB) synergistic conductive network. The fabrication, synergistic conductive mechanism, and characterization of the sandwich-structured strain sensor were investigated. The experimental results show that the device exhibits high stretchability (120%), excellent flexibility, fast response (~60 ms), temperature independence, and superior stability and reproducibility during ~1100 stretching/releasing cycles. Furthermore, human activities such as the bending of a finger or elbow and gestures were monitored and recognized based on the strain sensor, indicating that the stretchable strain sensor based on the SWCNTs/CB synergistic conductive network could have promising applications in flexible and wearable devices for human motion monitoring.

An attempt was made to investigate the effect of the target orientation on pointing performance. An experiment was accomplished in which 10 subjects performed three-dimensional aiming tasks under the manipulation of target orientation, distance to target and direction to target. Results show that target orientation affects the duration of three-dimensional movements significantly. As a result, the conventional movement model did not satisfactorily explain the variance in the movement times produced. The conventional model was employed by incorporating an oriented parameter into the model. The modified model was shown to better fit the data than the conventional model, in terms of r2 between the measured movement time and the value predicted by model fit.

Nonvolatile resistive switching has been observed for the first time in CdSe nanowire (NW)/Au Schottky barrier diodes, where a Schottky contact electrode and an Ohmic contact electrode were formed at the Au/CdSe NW and CdSe NW/In interfaces, respectively. The CdSe NWs Schottky devices were found to possess multibit storage ability in an individual nanowire, and exhibited excellent memory characteristics, with a resistance on/off ratio exceeding four orders of magnitude, a long retention time of over 10(4) s and a lower operating voltage of 2 V. By replacing the SiO(2)/Si substrate with a poly ethylene terephthalate substrate, flexible and transparent memory devices with superior stability under strain were realized. The resistive switching of CdSe NW/Au Schottky devices is understood by electron trapping and detrapping in the interfacial oxide layer. Our findings provide a viable way to create new functional high-density nonvolatile multibit memory devices compatible with simple processing techniques for normal one-dimensional nanomaterials.

Silicon based optoelectronic integration is restricted by its poor optoelectronic properties arising from the indirect band structure. Here, by combining silicon with another promising optoelectronic material, the CdS nanoribbon (NR), devices with heterojunction structure were constructed. The CdS NRs were also doped with gallium to improve their n-type conductivity. A host of nano-optoelectronic devices, including light emitting diodes, photovoltaic devices, and photodetectors, were successfully constructed on the basis of the CdS:Ga NR/Si heterojunctions. They all exhibited excellent device performances as regards high stability, high efficiency, and fast response speed. It is expected that the CdS NR/Si heterojunctions will have great potential for future applications of Si based optoelectronic integration.

In the past several years, the alert correlation methods have been advocated to discover high-level attack scenarios by correlating the low-level alerts. The causal correlation method based on prerequisites and consequences has great advantages in the process of correlating alerts. But it must depend on complicated background knowledge base and has some limits in discovering new attacks. The cluster can aggregate the relational alerts by computing the similarity between alert attributes, as well as can discover new and simple high-level attacks. However, it is difficult to establish the attribute weights in the similarity membership function of two alerts and the threshold of classification similarity value. In order to solve the problem, the quantum-behaved particle swarm optimization algorithm is used to optimize the weights and similarity value. In view of the advantages and disadvantages of cluster and correlation, this paper uses improved cluster algorithm to optimize correlation in the process of attack detection. The experimental results on LLS DDoS1.0 prove that the method proposed is useful and effective.

This paper studies conductive mechanism of the new pressure-sensitive conductive composite based on flexible tactile sensing, believes that conductive mechanism of the composite within percolation zone gives priority to quantum tunnel effect theory. Starting from the quantum tunnel effect theory it studies the relationship between pressure and resistance, and piezoresistive model could be established by using the quantum tunnel effect. Based on theory and experiment, through the analysis and research on the conductive characteristics of such new sensitive material with different content conductive fillers, the conductive mechanism could be obtained within the pressure sensitive range, which provides theoretical foundation for the study of such new flexible tactile sensing material. It also discusses the influence mechanism of the temperature to the conductivity of the pressure-sensitive conductive composite. Positive temperature coefficient (PTC) and negative temperature coefficient (NTC) characteristics of the pressure-sensitive conductive silicon rubber will appear in the heating process of one sample, which provides reference for the practical application of such new sensitive material. Whereas there is still a certain distance between the performances of the above flexible material compared with the requirements of sensor sensitive materials, therefore, this paper further studies the modification function of nano-SiO2 by adopting the special nature of nano materials. Since nowadays, the study on nanoparticles modified materials and nano materials' mechanical behavior is only in the early stage, which only detects the external manifestations of mechanical phenomena, far from the study on its internal mechanism [13]. Therefore, this paper mainly conducts experimental study and measurement on modification of pressure-sensitive conductive rubber after the addition of nano-SiO2 materials. The results show that the unique properties of nano-SiO2, the mechanical properties of pressure-sensitive conductive rubber, temperature performance and stability are significantly improved. As for the modified composites, we can improve the technical indicators of the produced tactile sensors to meet the requirement of tactile sensing. Further more, the compounding of nanoparticles and polymer modifies the heat-resistant and ageing resistance, and improves the properties of shock resistance and anti-fatigue. Flexible tactile sensor material, presented in this chapter, has both good tactile sensing function and flexibility, its preparation method is simple. Flexible tactile sensor based on this material can measure various tactile information of contact surface, which is expected to provide a new way of thinking and research methods of the flexible tactile sensor.

Nowadays, it becomes more and more important to construct high-level attack scenarios from low-level intrusion alerts reported by intrusion detection systems (IDSs). Some methods have been presented to resolve this problem. These methods have different strengths. However, they also have different limitations. In order to build complicated attack processes accurately, this paper uses cluster and correlation techniques to construct high-level attack scenarios. Fuzzy cluster algorithm based on the similarity of attack attributes is proposed to classify alerts generated by IDSs. And then in every alert class, alert correlation method based on prerequisites and consequences of attacks is used to construct attack scenarios. Finally, to get whole attack graphs, this paper hypothesizes and reasons about attacks possibly missed based on the equality constrain and casual relation between intrusion alerts. The experimental results on LLS DDOS2.0 prove that the method is useful and effective.

Due to various network intrusions, network security has always been a main concern of the network administrator. However, nowadays traditional security tools like IDSs, firewalls etc cannot play the roles of effective defense mechanisms. Instead, they only generate elementary alerts to form alert flooding and they often have high false alerts rates. Moreover due to their weak collaboration-awareness, they cannot detect large distributed attacks such as a DDoS attack. In this paper, we present an efficient and effective model for collaborative alerts analyzing. Our system enhances the alert verification using assets? contextual information. By applying alert fusion and using a precisely defined knowledge base in the correlation phase, it also provides a method to get general and synthetic alerts from the large volume of elementary alerts. Moreover, this system is able to reconstruct the attack scenarios for multi-step attacks. Experiments show the system can effectively distinguish false positives, detect and predicate large-scale attacks in their early stage.

For the purpose of reducing redundant alerts and false alerts as well as recognizing complicated attack scenarios, a multilevel model of alert fusion is presented. This model fuses alerts layer upon layer through primary alert reduction, alert verification, alert clustering and alert correlation. In order to construct accurate and complete attack sensors, in the phase of alert clustering, this paper proposes alert correlation method based on the similarity between alert attributes as well as based on prerequisites and consequences of attacks. The experimental results show that the model is effective and efficient in fusing large numbers of alerts.

Effects of a prepulse on gamma-ray radiation have been investigated experimentally using 150-fs laser pulses at an irradiance of I lambda(2) similar to 5X10(15) W cm(-2)mu m(2) focused on copper targets. The fraction of high energy photons (>100 keV) has been found to be greatly enhanced by introducing an 8% prepulse at 70 ps before the main pulse. Measurements have shown that a hot electron temperature as high as 83 keV has been produced at such a modest irradiance.

A novel fast electron beam emitting along the surface of a target irradiated by intense laser pulses is observed. The beam is found to appear only when the plasma density scale length is small. Numerical simulations reveal that the electron beam is formed due to the confinement of the surface quasistatic electromagnetic fields. The results are of interest for potential applications of fast electron beams and deep understanding of the cone-target physics in the fast ignition related experiments.

Sb-doped p-type ZnTe nanoribbons (NRs) and Ga-doped n-type CdSe NRs were synthesized via a co-thermal evaporation method in a horizontal tube furnace, respectively. Crossbar heterojunction diode (HD) devices were constructed from p-ZnTe:Sb NRs and n-CdSe NRs by a convenient route. The p-ZnTe/n-CdSe NR HD device exhibits a significant rectification characteristic with a rectification ratio up to 103 within ±5 V and a low turn-on voltage of 2.6 V. Photoresponse analysis reveals that such HD devices were highly sensitive to light illumination with excellent stability, reproducibility and fast response speeds of 37/118 μs at reverse bias voltage. It is expected that such HD devices will have great potential applications in electronic and optoelectronic devices in the future.

A low-intensity ultraviolet photodetector (PD), with a gain as high as ∼2.4 × 106, has been successfully constructed based on gallium (Ga) doped zinc sulfide (ZnS) nanoribbons (NRs). The device exhibits excellent photoconductive properties upon a bias voltage as low as ∼0.01 V in terms of high sensitivity to UV light with an intensity of 1 μW cm−2 (corresponding to an incident power of 10−14 W), relatively fast response times of ∼3.2 ms, and an extremely high detectivity of ∼1.3 × 1019 cm Hz1/2 W−1. The high gain and fast response time are attributed to the excellent ohmic contact obtained by using a high quality ITO electrode and having a carrier mobility as high as 130 cm2 V−1 s−1, which was confirmed from the back-gate field effect transistors. These results show that the single-crystalline n-type ZnS:Ga NRs will have potential applications in future high-performance low-intensity ultraviolet photodetectors.

Composition-controllable ternary CdSe(x)S(1-x) quantum dots (QDs) with multiple emission colors were obtained via a hot-injection-like method at a relatively low injection temperature (230 ° C) in octadecene. Then highly fluorescent CdSe(x)S(1-x)/ZnS core/shell (CS) QDs were synthesized by a facile single-molecular precursor approach. The fluorescent quantum yield of the resulting green (λ(em) = 523 nm), yellow (λ(em) = 565 nm) and red (λ(em) = 621 nm) emission of CS QDs in toluene reached up to 85%, 55% and 39%, respectively. Moreover, a QDs white light-emitting diode (QDs-WLED) was fabricated by hybridizing green-, yellow- and red-emitting CdSe(x)S(1-x)/ZnS CS QDs/epoxy composites on a blue InGaN chip. The resulting four-band RYGB QDs-WLED showed good performance with CIE-1931 coordinates of (0.4137, 0.3955), an R(a) of 81, and a T(c) of 3360 K at 30 mA, which indicated the combination of multiple-color QDs with high fluorescence QYs in LEDs as a promising approach to obtain warm WLEDs with good color rendering.

Ag-doped p-type ZnS nanoribbons (NRs) with a high hole concentration of 5.1 × 1018 cm−3 and high carrier mobility of 154.0 cm2 V−2 s−1 were synthesized by using silver sulfide (Ag2S) as the Ag source. Excellent ohmic contact to p-ZnS NR with specific contact resistivity as low as 5.6 × 10−7 Ω cm2 was achieved by using bilayer Cu (4 nm)–Au electrode, which according to the depth profiling X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) analysis can help to form a thin Cu2S interfacial layer between the electrode. Based on the high quality ZnS NRs and achievement on ohmic contact, p–n photodiodes have been constructed from the p-ZnS nanoribbon (NR)–n-Si heterojunction with a response speed as high as ∼48 μs (rise time). Furthermore, the device also exhibits stable optoelectrical properties with high sensitivity to UV-visible-NIR light and an enhancement of responsivities of 1.1 × 103 AW−1 for 254 nm under a reverse bias of 0.5 V. These generality of the above results shows that the p-ZnS NR–n-Si heterojunction will have potential applications in future high-performance photodetectors.