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A digital twin (DT) system is a virtual system that can provide a comprehensive description of a real physical system. The DT system continuously receives data from physical sensors and user input information and provides information feedback to the physical system. It is an emerging technology that utilizes an advanced Internet of Things (IoT) to connect different objects, which is in high demand in various industries and its research literature is growing exponentially. Traditional physical systems provide data support for the monitoring of physical objects such as buildings through digital modeling techniques, data acquisition tools, human computer interfaces, and building information models (BIM). However, DT can offer much more than data presentation. DT uses the received data to perform operations such as analysis, prediction, and simulation, and finally transmits the analysis results to the physical system as feedback. Compared with other physical systems, DT has the characteristics of bidirectional data exchange and real-time autonomous management. The plant factory control system based on digital twin technology continuously measures the power consumption of electrical equipment through the sensors of the physical system and makes the corresponding virtual color-coded gradient map based on the obtained data. The darker the virtual device is, the more power it currently requires, and just based on the shade of color gives the user a very intuitive idea of the current power usage of the electronic device. There has been extensive research on digital twin technology, but there are few studies on implementing plant factories based on digital twin technology. This paper proposes the idea of combining digital twin technology with plant factories to provide research directions for future smart agriculture. It proves that smart agricultural production with sustainability can also benefit from this idea.

Developing a ferroelectric tunnel junction with a robust polarization reversal is essential for errorless data storage, but it remains challenging since the second-order phase transition dominates the reversal and introduces intermediate states. This investigation has proposed a charge-gradient-induced ferroelectricity, which is featured with the first-order phase transition. As an order parameter, a charge-gradient-induced polarization is achieved by modulation of stoichiometric oxygen along the Bi

In a wireless sensor network, the sensor nodes transmit the acquired information to the server through the data transmission link. On the serverside, the data are processed, fused, and expressed to serve the user. Sensor deployment is a key factor related to the stability and security of wireless networks. This article uses environmental changes to drive related technologies to deploy wireless sensors. In this article, environmental change-driven means that through certain deployment cost model assumptions and problem descriptions, network deployment is artificially divided into two stages: initial deployment and redeployment. In the deployment phase, by referring to the idea of virtual force, a new sensor deployment algorithm is proposed in the redeployment phase, which can well solve the stability- and security-related issues encountered in agricultural wireless sensor networks. In this algorithm, the moving distance of the mobile receiver and the average coverage of the network are calculated based on the virtual force, the direction, and the number of adjacent clusters. Finally, the algorithm model was simulated in MATLAB, and the feasibility of the algorithm was verified by analyzing the event coverage and the moving distance of nodes. The final simulation results show that the algorithm proposed in this paper can achieve better performance than existing algorithms in terms of average coverage and moving distance.

We exploit a high-performing resistive-type trace oxygen sensor based on 2D high-mobility semiconducting Bi2 O2 Se nanoplates. Scanning tunneling microscopy combined with first-principle calculations confirms an amorphous Se atomic layer formed on the surface of 2D Bi2 O2 Se exposed to oxygen, which contributes to larger specific surface area and abundant active adsorption sites. Such 2D Bi2 O2 Se oxygen sensors have remarkable oxygen-adsorption induced variations of carrier density/mobility, and exhibit an ultrahigh sensitivity featuring minimum detection limit of 0.25 ppm, long-term stability, high durativity, and wide-range response to concentration up to 400 ppm at room temperature. 2D Bi2 O2 Se arrayed sensors integrated in parallel form are found to possess an oxygen detection minimum of sub-0.25 ppm ascribed to an enhanced signal-to-noise ratio. These advanced sensor characteristics involving ease integration show 2D Bi2 O2 Se is an ideal candidate for trace oxygen detection.

The formation of heterojunction within solid‐state devices enables them with eventually high performances, but provides a challenge for material synthesis and device fabrication because strict conditions such as lattice match are needed. Herein, we show a facile method to fabricate a van der Waals (vdW) heterojunction between two‐dimensional (2D) bismuth oxyselenide (Bi2O2Se) and graphene, during which the graphene is directly transferred to the Bi2O2Se and served as a low‐contract‐resistant electrode with small work function mismatch (~50 meV). As an optoelectronic device, the Bi2O2Se/graphene vdW heterojunction allows for the efficient sensing toward 1200‐nm incident laser. Regarding the application of field‐effect transistors (FETs), the short‐channel (50 nm) sample can be synthesized by utilizing these two 2D materials (ie, channel: Bi2O2Se; drain/source terminal: graphene) and the n‐type characteristic can be observed with the accordant field modulation. It is confirmed that we show a simple way to prepare the vdW heterojunction which is aiming to the high‐performance applications among optoelectronics and FETs.

Superlattice photonic crystals (SPhCs) possess considerable potentials as building blocks for constructing high-performance devices because of their great flexibilities in optical manipulation. From the prospective of practical applications, scalable fabrication of SPhCs with large-area uniformity and precise geometrical controllability has been considered as one prerequisite but still remains a challenge. In this work, we developed an anodic aluminum oxide template-guided approach to realize Ni SPhCs with the maximum area (~500 mm2) ever reported. By virtue of the dual-pore self-alignment effect arising from the periodic anodization electric fields, uniform structures over large areas were obtained for Ni SPhCs. Meanwhile, the geometrical parameters for every array of nanopores in terms of pore depth, size, and morphology can be independently controlled due to the sequential pore-opening. Based on the experimental observation about the geometrical dependence of the light absorption for Ni dual-pore SPhCs, we further fabricated Ni SPhCs with simultaneously-shaped nanopores and nanoconcaves, which not only simplified the fabrication process but also achieved omnidirectional stably-strong (~95%) light absorption spectra. Optical simulations elucidated that surface plasmon resonance and cavity resonance are responsible for the strong light trapping. Notably, the fabrication technique is applicable to Ni SPhCs with different periodicities, leading to spectrally programmable light absorption spectra. With Ni SPhCs as solar absorber, the water evaporation efficiency of a solar steam generation system and the open circuit voltage of a solar thermoelectric generator demonstrated 2.3 and 2.5 times improvement, respectively.

Soil salinity and alkalinity is an important index concerned by planting industry. In order to meet the demand of long-term observation of soil salinity and alkalinity in precision agriculture and eco-environmental protection, and to solve the current pain points of long sampling period and high cost of soil salinity measurement, this paper designs and implements an online monitoring system for soil salinity alkalinity in tideland in the Yangtze River Delta for crop planting and soil remediation. This system uses solar power supply system and maintenance-free digital sensor, which can be arranged in monitoring area for a long time to collect soil temperature, humidity and salinity data. The collected data can be stored in SD card locally and transmitted to cloud server in real time through 4G network. Up to now, the system has been running stably for nearly two years under the condition of unattended and maintenance free. More than 30000 soil salinity data have been collected from 5 monitoring points, which can be used for long-term observation of the interaction between salinity and plant growth, so as to improve the soil and improve the quality of agriculture products.

We exploit a high-performing resistive-type trace oxygen sensor based on 2D high-mobility semiconducting Bi

At the mesoscopic level of commercial lithium ion battery (LIB), it is widely believed that the poor contacts between current collector (CC) and electrode materials (EM) lead to weak adhesions and large interfacial electric resistances. However, systematic quantitative analyses of the influence of the interfacial properties of CC are still scarce. Here, we built a model interface between CC and electrode materials by directly growing hierarchical graphene films on commercial Al foil CC, and we performed systematic quantitative studies of the interfacial properties therein. Our results show that the interfacial electric resistance dominates, i.e. ∼2 orders of magnitude higher than that of electrode materials. The interfacial resistance could be eliminated by hierarchical graphene interlayer. Cathode on CC with eliminated interfacial resistance could deliver much improved power density outputs. Our work quantifies the mesoscopic factors influencing the battery performance and offers practical guidelines of boosting the performance of LIBs and beyond.

The fast development of high-resolution electron microscopy (EM) demands a background-noise-free substrate to support the specimens, where atomically thin graphene membranes can serve as an ideal candidate. Yet the preparation of robust and ultraclean graphene EM grids remains challenging. Here we present a polymer- and transfer-free direct-etching method for batch fabrication of robust ultraclean graphene grids through membrane tension modulation. Loading samples on such graphene grids enables the detection of single metal atoms and atomic-resolution imaging of the iron core of ferritin molecules at both room- and cryo-temperature. The same kind of hydrophilic graphene grid allows the formation of ultrathin vitrified ice layer embedded most protein particles at the graphene-water interface, which facilitates cryo-EM 3D reconstruction of archaea 20S proteasomes at a record high resolution of ~2.36 Å. Our results demonstrate the significant improvements in image quality using the graphene grids and expand the scope of EM imaging., High-resolution electron microscopy requires robust and noise-free substrates to support the specimens. Here, the authors present a polymer- and transfer-free direct-etching method for fabrication of graphene grids with ultraclean surfaces and demonstrate cryo-EM at record high resolution.

With the increasing of depth and complexity of the convolutional neural network, parameter dimensionality and volume of computing have greatly restricted its applications. Based on the SqueezeNet network structure, this study introduces a block convolution and uses channel shuffle between blocks to alleviate the information jam. The method is aimed at reducing the dimensionality of parameters of in an original network structure and improving the efficiency of network operation. The verification performance of the ORL dataset shows that the classification accuracy and convergence efficiency are not reduced or even slightly improved when the network parameters are reduced, which supports the validity of block convolution in structure lightweight. Moreover, using a classic CIFAR-10 dataset, this network decreases parameter dimensionality while accelerating computational processing, with excellent convergence stability and efficiency when the network accuracy is only reduced by 1.3%.

It is a widely used strategy to enhance gas sensor sensitivity by improving its surface area, but this process, including bonding the sensing block into a device substrate, needs complex manipulations. This work shows a concept of creating adsorption active sites, in which an SnO2 layer (6.85 nm thin) is directly coated on a triangle array substrate to be of an ensemble of triangular convex adsorption active sites (TCAASs). The resultant SnO2 gas sensors, with TCAAS periods ranging from 289 to 1154 nm, exhibit an adsorption-active-site-dependent sensitivity and present a low detection limit of around 6 ppm ethanol gas at room temperature. By characterizations of Kelvin force microscopy, a large surface potential variation exists on these adsorption active sites after introducing ethanol gas, distinctly showing a local adsorption enhancement. These results confirm that the creation of adsorption active sites can efficiently increase surface adsorption of a sensor to realize its sensitive gas-sensing.

Electrocatalysts for oxygen reduction and/or evolution are key components for proton-exchange membrane fuel cells (PEMFCs) and water electrolysis. However, the slow kinetics of oxygen reduction and/or evolution reactions largely hampers the efficiencies of PEMFCs and water electrolysis. Highly efficient electrocatalysts for oxygen reduction and evolution reactions must meet three requirements: (i) rapid transport of electrons, ions, and products of the reaction; (ii) sufficient catalysts/reactants contact area; and (iii) good intrinsic activity. Nanostructuration of electrocatalysts provides an effective approach to overcome the slow kinetics because nanostructured electrocatalysts with rational design can not only provide sufficient active sites but also promote intrinsic activity of electrocatalysts as well as possess the ability of rapid transport of electrons, ions, and products of the reaction. Especially, electrocatalysts in the form of one-dimensional nanostructures (1D-Nano) such as nanowires (NWs) and nanotubes (NTs) have shown significant advantages, such as high surface area, rapid electron and mass transfer, low vulnerability to dissolution, Ostwald ripening, and aggregation, for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). In this review, we summarize different strategies for fabricating 1D nanostructure-based electrocatalysts (1D-NanoECs), which are categorized into template-free and template-assisted strategies, and emphasis has been placed on anodic aluminum oxide template–assisted strategies. Then, recent advances of 1D-NanoECs for ORR and OER applications are summarized. Finally, future challenges and opportunities about 1D-NanoECs are discussed.

High sensitivity imposes strict requirements on a sensing platform, for which nanostructured arrays are promising candidates. The template-assisted method is an effective strategy to prepare various nanostructured arrays, which are widely developed for different sensing applications. Herein, nanostructured array based sensing platforms prepared from four widely used templates, a colloidal monolayer, anodic aluminum oxide, block copolymer, and a nanoimprint mold, are reviewed. In a series of sensing applications (e.g., biosensing and gas sensing), the resulting nanostructure-array-based platforms are high sensitive owing to their advanced morphology features: 1) high-density alignment of arrayed nanostructures, 2) high surface-to-volume ratio, and 3) convex-rich morphology. In surface-enhanced Raman spectroscopy (SERS) applications, noble-metal particle arrays with high-density alignment produce an enhanced SERS signal owing to a strong concentration of plasmonic resonance on the substrate. To sense biomolecules in solution and gaseous molecules, arrays with a high surface-to-volume ratio or convex-rich morphology can sensitively respond to changes in the environment. Moreover, the nanostructure-array-based sensing platforms are divided into three types (0D, 1D, and 3D nanostructured arrays) to demonstrate the morphological origin of the sensing performances.

Adsorption-induced change of carrier density is presently dominating inorganic semiconductor gas sensing, which is usually operated at a high temperature. Besides carrier density, other carrier characteristics might also play a critical role in gas sensing. Here, we show that carrier mobility can be an efficient parameter to dominate gas sensing, by which room-temperature gas sensing of inorganic semiconductors is realized via a carrier mobility-dominated gas-sensing (CMDGS) mode. To demonstrate CMDGS, we design and prepare a gas sensor based on a regular array of SnO2 nanorods on a bottom film. It is found that the key for determining the gas-sensing mode is adjusting the length of the arrayed nanorods. With the change in the nanorod length from 340 to 40 nm, the gas-sensing behavior changes from the conventional carrier-density mode to a complete carrier-mobility mode. Moreover, compared to the carrier density-dominating gas sensing, the proposed CMDGS mode enhances the sensor sensitivity. CMDGS proves to be an emerging gas-sensing mode for designing inorganic semiconductor gas sensors with high performances at room temperature.

Plasmonic nanostructures have been widely incorporated into different semiconductor materials to improve solar energy conversion. An important point is how to manipulate the incident light so that more light can be efficiently scattered and absorbed within the semiconductors. Here, by using a tunable three-dimensional Au pillar/truncated-pyramid (PTP) array as a plasmonic coupler, a superior optical absorption of about 95% within a wide wavelength range is demonstrated from an assembled CdS/Au PTP photoanode. Based on incident photon to current efficiency measurements and the corresponding finite difference time domain simulations, it is concluded that the enhancement is mainly attributed to an appropriate spectral complementation between surface plasmon resonance modes and photonic modes in the Au PTP structure over the operational spectrum. Because both of them are wavelength-dependent, the Au PTP profile and CdS thickness are further adjusted to take full advantage of the complementary effect, and subsequently, an angle-independent photocurrent with an enhancement of about 400% was obtained. The designed plasmonic PTP nanostructure of Au is highly robust, and it could be easily extended to other plasmonic metals equipped with semiconductor thin films for photovoltaic and photoelectrochemical cells.

We propose a method for reconstructing a 3D point cloud of the organ model based on optical flow and take the 3D cardiovascular model reconstruction as an example. This optical-flow distribution based 3D point cloud reconstruction method is divided into four steps. Firstly, we employ the Coey filter to remove the noise points and improve the resolution of the raw images. Secondly, we implement the Shi-Tomasi method to extract the feature points from these filtered images. Thirdly, we remove the redundancy in the feature point set by the optical flow distributions. Finally, we converted the obtained feature points from 2D to 3D through the optical flow distribution and then reconstructed a 3D point cloud of the medical organ. With the help of our 3D representation, doctors and patients can view the 3D medical models on the Web. The final result on the Web shows the proposed method is feasible and superior. Published version

In recent years, efficient and accurate detection of fruit quality has become an important means of non-destructive testing of fruit quality. In order to solve the problems of cost, efficiency and accuracy in the non-destructive testing of yellow peach quality. This paper proposes a new method for simultaneous detection of yellow peach hyperspectral multiple quality parameters. This method uses the method of extracting and recombining wavelengths at equal intervals in the full-band spectrum instead of the characteristic wavelength selection method. It can make the hyperspectral image contain all-band spectral information. This method uses 3D-CNN to replace the original regression modelling method, which improves the accuracy of model prediction. This method uses the shared network convolutional layer method to perform multi-task learning on the sugar content and hardness of yellow peaches, and finally realizes the simultaneous detection of multiple quality parameters of yellow peaches.

It is a widely used strategy to enhance gas sensor sensitivity by improving its surface area, but this process, including bonding the sensing block into a device substrate, needs complex manipulations. This work shows a concept of creating adsorption active sites, in which an SnO

For the construction of a resistive-type gas-sensor, it is usually required for a sensing film to be fabricated on a non-conductive substrate. The in situ construction of a sensor by subjecting the substrate to an electrodeposition method is impossible and there have been no related reports on this. Herein, taking the in situ construction of a SnO2 film sensor as an example, a novel electrodeposition-based method was introduced. A conductive graphite coating was firstly fabricated on the non-conductive substrate for the implementation of the electrodeposition, and then a calcining process was employed. The conductive pristine graphite coating was found to become non-conductive after being calcined for more than 70 min at 500 °C, resulting in the final electrodeposited film being able to work as a sensing film. Some important parameters related to the sensing performances, including the formation, the conductivity, the electrodeposition time, the calcining time and the working temperature, were systematically studied. Under the optimal conditions, the SnO2 film sensor exhibited high sensitivity, a fast response and recovery, and long-term stability in the detection of ethanol gas with concentrations ranging between 1–100 ppm. The electrodeposition-based method is reproducible, mass-productive and general. It is therefore practical and promising for the construction of various semiconductor film sensors.

In this study, CdS nanoparticles were directly grown on the surfaces of chitosan microspheres (CM) via photochemical method with irradiation from an 8 W ultraviolet (UV) lamp. The nanoparticles exhibited an almost spherical shape, were closely arranged, and were immobilised on the microspheres because of the induction of the amino and hydroxyl groups of the chitosan. The CM-immobilised CdS nanoparticles showed higher activity and easier recyclability than pure CdS particles obtained in the same conditions when used in the decolourisation of methyl orange (MO) under UV–vis light. The experiments proved that the photodegradation of MO was mainly caused by the oxidisation of superoxide radicals ( O2−) generated by the reaction between the electrons and the adsorbed O2. The functional groups of CM may prevent the recombination of electron/holes and effectively promote photocatalytic reactions. This photochemical method is new, general, and promising for the immobilisation of catalyst particles on polymer microspheres, which results in enhanced activity.

Atomically thin oxychalcogenides have been attracting intensive attention for their fascinating fundamental properties and application prospects. Bi2 O2 Se, a representative of layered oxychalcogenides, has emerged as an air-stable high-mobility 2D semiconductor that holds great promise for next-generation electronics. The preparation and device fabrication of high-quality Bi2 O2 Se crystals down to a few atomic layers remains a great challenge at present. Here, molecular beam epitaxy (MBE) of atomically thin Bi2 O2 Se films down to monolayer on SrTiO3 (001) substrate is achieved by co-evaporating Bi and Se precursors in oxygen atmosphere. The interfacial atomic arrangements of MBE-grown Bi2 O2 Se/SrTiO3 are unambiguously revealed, showing an atomically sharp interface and atom-to-atom alignment. Importantly, the electronic band structures of one-unit-cell (1-UC) thick Bi2 O2 Se films are observed by angle-resolved photoemission spectroscopy (ARPES), showing low effective mass of ≈0.15 m0 and bandgap of ≈0.8 eV. These results may be constructive to the synthesis of other 2D oxychalcogenides and investigation of novel physical properties.

A new general method for the fabrication of a reduced graphene oxide (rGO)-based ordered monolayer macroporous film composed of a layer of closely arranged pores is introduced. Assisted by the polystyrene microsphere monolayer colloid crystal by a simple solution-heated method, pure rGO, rGO-SnO2, rGO-Fe2O3, and rGO-NiO composite monolayer ordered porous films were examplarily constructed on the curved surface of a ceramic tube widely used in gas sensors. The rGO-oxide composite porous films could exhibit much better sensing performances than those of the corresponding pure oxide films and the composite films without the ordered porous structures in detecting ethanol gas. The enhancement mechanisms induced by distinctive rGO-oxide heterojunctions and porous structures as well as the effects of the rGO content and the pore-size on the sensitivity of the composite films were systematically analyzed and discussed. This study opens up a kind of construction method for an rGO-based composite film gas sensor with uniform surface structures and high performance.

A new graphene-based composite structure, monolayer-ordered macroporous film composed of a layer of orderly arranged macropores, was reported. As an example, SnO2-reduced graphite oxide monolayer-ordered macroporous film was fabricated on a ceramic tube substrate under the irradiation of ultra-violet light (UV), by taking the latex microsphere two-dimensional colloid crystal as a template. Graphite oxide sheets dispersed in SnSO4 aqueous solution exhibited excellent affinity with template microspheres and were in situ incorporated into the pore walls during UV-induced growth of SnO2. The growing and the as-formed SnO2, just like other photocatalytic semiconductor, could be excited to produce electrons and holes under UV irradiation. Electrons reduced GO and holes adsorbed corresponding negative ions, which changed the properties of the composite film. This film was directly used as gas-sensor and was able to display high sensitivity in detecting ethanol gas. More interestingly, on the basis of SnO2-induced photochemical behaviours, this sensor demonstrated tunable sensitivity when UV irradiation time was controlled during the fabrication process and post in water, respectively. This study provides efficient ways of conducting the in situ fabrication of a semiconductor-reduced graphite oxide film device with uniform surface structure and controllable properties.

A new graphene-based composite structure, monolayer-ordered macroporous film composed of a layer of orderly arranged macropores, was reported. As an example, SnO2-reduced graphite oxide monolayer-ordered macroporous film was fabricated on a ceramic tube substrate under the irradiation of ultra-violet light (UV), by taking the latex microsphere two-dimensional colloid crystal as a template. Graphite oxide sheets dispersed in SnSO4 aqueous solution exhibited excellent affinity with template microspheres and were in situ incorporated into the pore walls during UV-induced growth of SnO2. The growing and the as-formed SnO2, just like other photocatalytic semiconductor, could be excited to produce electrons and holes under UV irradiation. Electrons reduced GO and holes adsorbed corresponding negative ions, which changed the properties of the composite film. This film was directly used as gas-sensor and was able to display high sensitivity in detecting ethanol gas. More interestingly, on the basis of SnO2-induced photochemical behaviours, this sensor demonstrated tunable sensitivity when UV irradiation time was controlled during the fabrication process and post in water, respectively. This study provides efficient ways of conducting the in situ fabrication of a semiconductor-reduced graphite oxide film device with uniform surface structure and controllable properties.

A new photochemistry-based method was introduced for fabricating SnO2 monolayer ordered porous films with size-tunable surface pores on ceramic tubes used for gas sensors. The growth of the spherical pore walls was controlled by two times irradiation of the ultraviolet light using polystyrene microsphere two-dimensional colloidal crystal as a template. The surface pore size of the final obtained porous films was well tuned by changing the second irradiation time rather than replacing the template microspheres. The monolayer ordered porous films on the tubes were directly used, for the first time, as gas sensors. The sensitivity of the sensor depended on the surface pore size and was carefully analyzed by ethanol gas detection. The sensor also exhibited short response-recovery time and long-term stability at lower than 300 °C in practical applications. Therefore, this study opens up a kind of construction method for gas sensors, provides a new strategy for controlling the surface pore size of the monolayer ordered porous film, and introduces a new type of sensitivity-controllable gas sensor.

In this paper, through the research on two-dimensional bar codes of food source tracking; a set of traceability tracking system was designed based on the two bar coding algorithm and decoding algorithms. This system could generate PDF417 code based on food production, logistics and transport, supermarket and other storage information. Consumers could identify PDF417 code through a client based on B/S architecture so that a simple process of food traceability has been completed.