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Abstract Recently, the development trend of large capacity generator has gradually shifted from electrical excitation generator to permanent magnet generator (PMG). As a result, the large capacity high‐speed permanent magnet generator (HSPMG) with high power density and high efficiency have received widespread attention. This paper aims to analyse the loss optimization of novel large capacity HSPMG under multi‐operating conditions. In terms of the parameter requirements, a 2.5 MW and 7000 rpm HSPMG is designed. To verify the accuracy of simulation model and the rationality of generator design, the output characteristics of large capacity HSPMG which has been combined with prototype experimental data are calculated under both no‐load and load conditions. Based on the load power characteristics of large capacity HSPMG, the optimization range of the magnetization angle under multi‐operating conditions is explored. By analysing the no‐load back electromotive force (EMF) and loss characteristics of large capacity HSPMG, the optimal magnetization angle that corresponds to the minimum loss under three conditions is obtained. The correctness of the analysis and optimization method is verified by comparing the loss distribution and electromagnetic results before and after the optimization. The research results provide a reference for the multi‐operating characteristics analysis and loss optimization of large capacity HSPMG.

Recently, the development trend of large capacity generator has gradually shifted from electrical excitation generator to permanent magnet generator (PMG). As a result, the large capacity high‐speed permanent magnet generator (HSPMG) with high power density and high efficiency have received widespread attention. This paper aims to analyse the loss optimization of novel large capacity HSPMG under multi‐operating conditions. In terms of the parameter requirements, a 2.5 MW and 7000 rpm HSPMG is designed. To verify the accuracy of simulation model and the rationality of generator design, the output characteristics of large capacity HSPMG which has been combined with prototype experimental data are calculated under both no‐load and load conditions. Based on the load power characteristics of large capacity HSPMG, the optimization range of the magnetization angle under multi‐operating conditions is explored. By analysing the no‐load back electromotive force (EMF) and loss characteristics of large capacity HSPMG, the optimal magnetization angle that corresponds to the minimum loss under three conditions is obtained. The correctness of the analysis and optimization method is verified by comparing the loss distribution and electromagnetic results before and after the optimization. The research results provide a reference for the multi‐operating characteristics analysis and loss optimization of large capacity HSPMG. [ABSTRACT FROM AUTHOR]

The hiding capacity of the current information hiding field has reached a relatively high level, which can hide two color images into one color image. In order to explore a larger hidden capacity, an information hiding scheme based on an improved FCdDNet is proposed, which can hide large-size color images into small-size color images. An improved FCdDNet network is used as the main structure shared by the hidden network and the extraction network. These two networks promote and improve each other during the confrontation training process and are used in pairs. It can be seen that the proposed scheme achieves a larger information hiding capacity, and the hidden information is four times larger than the scale of the carrier image. At the same time, the visual effect after hiding is guaranteed, and the image extracted from the hidden image also has a high degree of restoration. The scheme can be applied to image authentication, secret image transmission, and other fields. [ABSTRACT FROM AUTHOR]

Aprotic lithium‐oxygen (Li–O2) batteries hardly cycle at the condition of high area capacity for realizing their high energy density, because the unconducive lithium peroxide (Li2O2) discharge product limits the electron transfer between electrode and O2/Li2O2. Here, it is demonstrated that one of redox mediator (RM), triethylene glycol bis‐2,2,6,6‐tetramethylpiperidin‐1‐oxyl radical (D‐TEMPO), can be effectively used to promote the electron transfer between electrode and Li2O2, which the shuttle effect of RM can be cooperatively inhibited by regulating the size of RM and the thickness of ion‐selective membrane. As a result, the Li–O2 battery coupled with double cathodes, D‐TEMPO, and ion‐selective membrane can be stably operated for 46 days at a capacity of 5 mAh cm−2. The concept in this work provides the cooperative design of a stable solution‐mediated pathway for high‐capacity Li–O2 battery with long cycle stability. [ABSTRACT FROM AUTHOR]

Miniaturized energy storage devices with superior performance and compatibility with facile fabrication are highly desired in smart microelectronics. Typical fabrication techniques are generally based on powder printing or active material deposition, which restrict the reaction rate due to the limited optimization of electron transport. Herein, we proposed a new strategy for the construction of high-rate Ni-Zn microbatteries based on a 3D hierarchical porous nickel (Ni) microcathode. With sufficient reaction sites from the hierarchical porous structure as well as excellent electrical conductivity from the superficial Ni-based activated layer, this Ni-based microcathode is featured with fast-reaction capability. By virtue of facile electrochemical treatment, the fabricated microcathode realized an excellent rate performance (over 90% capacity retention when the current density increased from 1 to 20 mA cm−2). Furthermore, the assembled Ni-Zn microbattery achieved a rate current of up to 40 mA cm−2 with a capacity retention of 76.9%. Additionally, the high reactivity of the Ni-Zn microbattery is also durable in 2000 cycles. This 3D hierarchical porous Ni microcathode, as well as the activation strategy, provides a facile route for the construction of microcathodes and enriches high-performance output units for integrated microelectronics. [ABSTRACT FROM AUTHOR]

Single pixel imaging as an alternative to traditional imaging methods, has attracted extensive attention in various research fields. Metasurfaces with subwavelength unit cells and compact footprint can be used as a substitute for traditional optical elements. In this work, we propose a single pixel imaging scheme based on metasurface composed of photon sieves, where spatial modulation is realized through shifting. Spatial multiplexing capability is demonstrated by this shifting mode, which can obtain more patterns in limited space and greatly increase the mask capacity. Benefited from the simple structure and easy manufacture of photon sieves, large capacity metasurface can be manufactured. Meanwhile, metasurfaces can simplify the single pixel imaging system, leading to the system miniaturization and integration. In addition, numerical and optical experiments prove that our proposal can operate at the range from the entire visible light to near-infrared light. Such scheme provides a new way for single pixel imaging and would be applied in microscopic imaging, dynamic imaging, hyperspectral imaging, and so on.

With the challenge of space size in urban densely populated areas and the increase in power demand, three-phase coaxial high temperature superconducting (HTS) cable has an attractive prospect in its compact structure and low loss. In order to minimize the proximity-effect among conductors of the same phase when the layers per phase increase, a new structure of cable composed of many three-phase groups is proposed, which decomposes the superconducting layers into many magnetically independent three-phase groups. Each three-phase group contains three-phase conductors composed of one or two layers per phase. The ac losses between the proposed and conventional HTS cables are compared by means of an analytical solution. The result shows that the new architecture greatly reduces the ac loss, and the efficiency of reducing loss is enhanced with the increase of layers. Therefore, the proposed cable is expected to replace the copper cables in some mid- or low-voltage levels and high-current conditions. [ABSTRACT FROM AUTHOR]

Miniaturized energy storage devices with superior performance and compatibility with facile fabrication are highly desired in smart microelectronics. Typical fabrication techniques are generally based on powder printing or active material deposition, which restrict the reaction rate due to the limited optimization of electron transport. Herein, we proposed a new strategy for the construction of high-rate Ni-Zn microbatteries based on a 3D hierarchical porous nickel (Ni) microcathode. With sufficient reaction sites from the hierarchical porous structure as well as excellent electrical conductivity from the superficial Ni-based activated layer, this Ni-based microcathode is featured with fast-reaction capability. By virtue of facile electrochemical treatment, the fabricated microcathode realized an excellent rate performance (over 90% capacity retention when the current density increased from 1 to 20 mA cm−2). Furthermore, the assembled Ni-Zn microbattery achieved a rate current of up to 40 mA cm−2 with a capacity retention of 76.9%. Additionally, the high reactivity of the Ni-Zn microbattery is also durable in 2000 cycles. This 3D hierarchical porous Ni microcathode, as well as the activation strategy, provides a facile route for the construction of microcathodes and enriches high-performance output units for integrated microelectronics.

The “Phase-Hopping” AC-AC frequency conversion technology proposed on the basis of traditional technology has the advantages of no circulating current, no dead zone and output frequency that can be improved to close to the power frequency. However, the research on this technology at present is still limited to the low voltage level, and problems such as low system capacity and high harmonic wave still exist, which cannot be applied in practice. To this end, a three-phase series-connected six-fold “phase-hopping” AC-AC frequency conversion main circuit is designed on the basis of traditional series-connected multiple technology, which addresses the voltage withstanding problem of thyristors, reduces harmonic content and enlarges system capacity, and the circuit is simulated by MATLAB. Furthermore, a single-phase series-connected six-fold “phase-hopping” AC-AC frequency conversion experiment platform is set up, which includes the key main circuit and the trigger circuit and improves its synchronous detection circuit. The simulation and experimental results are consistent with the theoretical analysis. In view of the technical transformation of “phase-hopping” AC-AC frequency conversion of common high-voltage and large-capacity pump station motors, the main circuit is designed, the model selection of thyristor is conducted, and the cost estimation of frequency converter is carried out. The analysis shows that the system has a high cost performance, thus it can be seen that this technology has a broad practical application prospect.

In practice, most audio files such as MP3 and AAC are stored and transmitted in the form of compressed files, which can serve as the cover in audio steganography. Currently, the prevailing audio steganography methods are not ideal because of the drawbacks. Some are characterized by low capacity while others are irreversible. In this paper, we propose a method to embed secret messages in MP3 encoding. Our strategy is to hide the information by Huffman table transformation. We extract secret information by analyzing side information. Experimental results show that our method can greatly improve the steganographic capacity with low distortion and high security. Meanwhile, it featured with higher decoding rate and reversible over some state-of-the-art methods.

Saliva as a sample matrix has been an attractive alternative for the detection of SARS-CoV-2. However, due to potential variability in collection and processing steps, evaluating a proposed workflow amongst the local population is recommended. Here, we aim to validate the collection and treatment of human saliva as a direct specimen for RT-qPCR-based detection of SARS-CoV-2 in Indonesia. We demonstrated that SARS-CoV-2 target genes were detected in saliva specimens and remained stable for five days either refrigerated or stored at room temperature. The method of processing saliva specimens described in this report bypasses the need for an RNA-extraction process, thereby reducing the cost, time, and manpower required for processing samples. The developed method was tested across nine commercial kits, including the benchmark, to demonstrate its wide applicability on multiple existing workflows. Our developed method achieved an 86% overall agreement rate compared to paired nasopharyngeal and oropharyngeal swab specimens (NPOP). With the assistance of a saliva sampling device, the collection was found to be more convenient for individuals and improved the overall agreement rate to 97%. [ABSTRACT FROM AUTHOR]

This article presents a successful design of a three-phase large capacity line-start permanent magnet synchro nous motor (LSPMSM) developed for industrial applications. A hybrid rotor containing both slotted solid steels and cage bars is included in the designed LSPMSM to enhance the motor starting and synchronizing abilities. A salient rotor periphery making air-gap length, which maximizes at the quadrature axis and minimizes at the direct axis, is employed to reduce the harmonics of air-gap flux density and motor losses. The implementation of a genetic algorithm coupled with a neural network optimizes the rotor-periphery saliency ratio and other crucial dimensions for further performance improvement. Finite-element analyses highlight the advantages of the designed LSPMSM by comparing its performance indexes with those of a conventional cage-rotor LSPMSM. The effectiveness of the designed motor is validated by a series of prototype tests. [ABSTRACT FROM AUTHOR]

Abstract Sodium ion batteries have attracted special research interests world widely for large-scale electrical stationary applications due to the abundant reserve and wide distribution of Na element. However, most cathodes suffer from limited capacity, poor rate capability or inferior cycling stability, which cannot meet the requirements of high-performance sodium ion batteries. Thus, developing cathode materials with improved capacity, rate and cycling performance is in urgent demand. Herein, we design a series of Na 2 Ru 1-x Mn x O 3 using both cationic and anionic redox activities to achieve high capacity. Mn-doped Na 2 RuO 3 has been found to be capable of enhancing the oxygen redox activity, raising the redox potential, preventing the generation of spinel phase and moisture-sensitive phase upon charge process, facilitating charge transfer kinetics and suppressing the O3→P3 phase transition in a long cycle. As a result, Na 2 Ru 0.8 Mn 0.2 O 3 exhibits outstanding electrochemical performance by delivering a large capacity of over 90 mAh g−1 for long cycling of 1000 times at a high rate of 5 C. This study provides a prototype of high-performance ion-doped Na-rich cathode and could encourage scientists to explore more Na 2 MM'O 3 materials for ultrafast sodium ion batteries with large capacity and superlong cycle life. Graphical abstract Image 1 Highlights • A novel O3-type of cathode material was designed for high-performance SIBs. • The cathode shows excellent rate capability and high energy density (471 Wh kg−1). • The cathode mitigates O3→P3 phase transition upon cycling. • The cathode owns long-term cycling durability after 1000 cycles at ultrahigh rate. [ABSTRACT FROM AUTHOR]

Based on characteristics of instantaneously, large capacity and miniaturization of digital image acquisition and processing technology, a real-time video image acquisition and processing circuit system was designed，FPGA was used as the center of controlling the whole system and the center of processing image data. With DDR2 SDRAM the core component of high speed storage module, and CMOS 7670 the video image acquisition device. Through the Quratus II and Modelsim software for edge detection algorithm and the control process, each module of the hardware design and simulation, the realization of the video images from the collection and storage to the treating and display, which shows smooth, clear and real-time.

The histogram watermark, which performs watermark embedding by slightly modifying the histogram of the original image, has been a hot research topic in information hiding technology due to the superiority of its pixel modification during the watermark embedding process, which is independent of the pixel position. This property makes the histogram-based watermark strong resistant to geometric attacks, such as cropping attack, crossed attack, rotation attack, etc. In this paper, we propose a large capacity histogram-based robust watermarking algorithm based on three consecutive bins for the first time. In our scheme, we divide the shape of three consecutive bins into eight cases. According to these cases, we embed Information Number 0, 1, 2, 3, 4, 5, 6, or 7, respectively. The embedded information capacity reaches one bit per bin (bpb), and the amount of embedded information is equal to 200% of the previous existing algorithms. Experimental results show that the new algorithm not only has a large capacity of embedding information, but also has strong robustness to geometric attacks, as well as common image processing operations. [ABSTRACT FROM AUTHOR]

Reversible information hiding plays an important roles in the field of privacy protection. In this paper, a new reversible information hiding scheme is proposed which supports the direct operation in homomorphic encrypted domain. The proposed “Joint Hiding and Tracing, JHT” tactics and the “3 Level Integrity Authentication Scheme” devote to piracy tracing and integrity authentication. To enhance security, the Paillier homomorphic encryption and Arnold technology are employed. Furthermore, we present the dual region division tactics including Data/Signature region division and Texture/Smooth region division. Data/Signature region division is to circumvent conflicts, and Texture/Smooth region division is fit well with the human visual characteristics. Besides, neighboring quadratic optimization approach is presented to eliminate the smooth/texture isolated islands in the texture/smooth regions. In addition, Extended Integer Transform and position image are developed to achieve reversibility and circumvent overflow/underflow problems. Experimental results confirm the efficient of the proposed scheme, and demonstrate it not only realizes privacy protection, integrity authentication and piracy tracing, but also holds the characteristics of higher security, larger capacity and better restoration quality. [ABSTRACT FROM AUTHOR]

Accurate characterization of the heat generation behavior of a battery is crucial to a good design of its thermal management system. Concerning the thermal properties, much attention has been paid to small-sized batteries such as the 18650- or button-type and little information is available for large-capacity Li-ion prismatic cells under adiabatic conditions. In this work, heat generation of a commercial 40 Ah prismatic LiFePO 4 /C battery is evaluated using an accelerating rate calorimeter under an adiabatic condition. The battery cell is charged or discharged at an initial temperature from −12.5 to 40 °C and a current rate from 0.2C to 2C. The experiment results show that heat generated in the battery is highly dependent on its operating temperature, state of charge and current rate. Internal resistance and entropy coefficient of the battery cell are also determined by the Hybrid Pulse Power Characterization method and potentiometric method, respectively. Relationship between the internal resistance and the heat generation behavior is highlighted. Entropy coefficient and volumetric heat generation rate of the battery cell obtained in this work are compared with those of other Li-ion batteries reported in literature. [ABSTRACT FROM AUTHOR]

Abstract: Polymer binders with high ion and electron conductivities are prepared by assembling ionic polymers (polyethylene oxide and polyethylenimine) onto the electrically conducting polymer poly(3,4‐ethylenedioxythiophene): poly(styrenesulfonate) chains. Crosslinking, chemical reductions, and electrostatics increase the modulus of the binders and maintain the integrity of the anode. The polymer binder shows lithium‐ion diffusivity and electron conductivity that are 14 and 90 times higher than those of the widely used carboxymethyl cellulose (with acetylene black) binder, respectively. The silicon anode with the polymer binder has a high reversible capacity of over 2000 mA h g−1 after 500 cycles at a current density of 1.0 A g−1 and maintains a superior capacity of 1500 mA h g−1 at a high current density of 8.0 A g−1. [ABSTRACT FROM AUTHOR]

The moored three-float line absorber WEC M4 has been developed to optimise power capture through experiments and linear diffraction modelling. With the progression down wave from small to medium to large floats, the device heads naturally into the wave direction. The bow and mid floats are rigidly connected by a beam and a beam from the stern float is connected to the hinge point above the mid float for power take off (PTO). Increasing the bow to mid float spacing to be more than 50% greater than the mid to stern float spacing has been found to improve power capture. To increase power capture further and potentially reduce electricity generation cost the number of mid floats and stern floats is increased while maintaining a single bow float for mooring connection. The bow and mid floats still form a rigid body while the stern floats may respond independently. A time domain linear diffraction model based on Cummins method has been applied to configurations of 121, 123, 132, 133, and 134 floats where the numbers indicate the number of floats: bow, mid, stern. This shows how power capture is increased while response remains similar. We only consider uni-directional (long-crested) waves with narrow band width typical of swell. By considering scatter diagrams for various offshore sites capacities may range from 3.7 MW to 17.3 MW for the eight float system with a capacity factor of 1/3 while the cost of electricity assuming capital cost to be a fixed multiple of steel cost is reduced from that for the three-float system. [ABSTRACT FROM AUTHOR]

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Image steganography is a technique for hiding secret data within a cover image and thus making the data immune to typical steganalysis attacks. Recently, there is a great concern about color distortion in most commonly used color-based image steganography methods. To address this issue, we first propose a steganography method that hides secret images in grayscale image and creates a color image. Specifically, we design a colorable information hiding mechanism to convert the image steganography task to gray-to-color conversion. In addition, we exploit the invertible neural network to realize image hiding and recovering in the forward and backward propagation, respectively. Meanwhile, we develop a perceptual loss function to effectively improve the quality of the stego image for increasing steganography security. Experiments indicate that the proposed method outperforms other state-of-the-art image steganography on secret image recovery, embedding capacity, and steganography security over different datasets. [ABSTRACT FROM AUTHOR]

Large-capacity information encryption has attracted significant interest in the information age. The diversity and controllability of spectra have positioned them to be widely applied for information encryption. Current spectra-based information encryption methods commonly rely on either spectral alteration induced by external stimuli or the utilization of narrowband channels within spectra. However, these methods encounter a common challenge in attaining both high security and large capacity simultaneously. To address these issues, we propose a multiple-channel information encryption system based on quantum dot (QD) absorption spectra. The diversity of QD absorption spectra and their broadband features ensure that the encrypted spectra can hardly be decrypted without knowing the correct channel matrix. Meanwhile, the large capacity is realized through the combination of multiple QD spectral channels with a theoretical maximum capacity of 24.0 bits in a single spectrum. In order to optimize the performance of our proposed system, the selection principle of the channel matrix is established to achieve the rapid identification of the optimal channel matrix in several milliseconds. The additivity of QD spectral channels and the consistency of QD spectra are also explored to minimize the impact of errors on information decryption. Furthermore, two spectral encryption scenarios of spatial pattern and spectral pattern are applied to demonstrate the feasibility, showcasing their ability to achieve both a high level of security and large capacity. Owing to the advantages offered by QD spectra, the QD spectra-based information system exhibits excellent potential for broader applications in information storage, authentication, and computing.