Making path selection faster: a routing algorithm for ONoC.

Optical network-on-chip (ONoC) is an effective communication architecture to realize high performance and energy efficiency. Diverse routing algorithms are proposed to avoid the congestion, tolerate the faults, and reduce the insertion loss or energy consumption. However, existing algorithms did not consider the characteristic optical circuit-switching of ONoC, which aggravates the network congestion and degrades the associated performance severely. In this paper, by exploiting congestion prediction technique, we propose a new routing algorithm for ONoC, named loophole-routing, to improve the success rate of path-setup and decrease the latency. We use the congestion prediction technique to analyze the latency and predict the port condition caused by the network congestion. Theoretical analysis and experimental results of different synthetic traffic patterns show that the loophole-routing improves network latency over XY routing and OE-turn routing by 15.56%, 25.71%, 18.92%, 66.67% and 42.86% under uniform, hotspot1, hotspot2, transpose2 and transpose3 traffic patterns while improving the saturation throughput by 31.43%, 34.33%, 35.29%, 67.86% and 99.5% under uniform, hotspot1, hotspot2, transpose2 and transpose3 traffic patterns on average than XY routing. In addition, our proposed loophole-routing has the benefits of high path diversity and adaptive degree and low computing complexity and overhead and the potential to make fault-tolerant path selection.

Structural, Electronic, and Optical Properties of Hexagonal XC6 (X=N, P, As, and Sb) Monolayers.

Based on first-principles calculations, a novel family of two-dimensional (2D) IV-V compounds, XC6 (X=N, P, As and Sb), is proposed. These compounds exhibit excellent stability, as determined from the cohesive energies, phonon dispersion analysis, ab initio molecular dynamics (AIMD) simulations, and mechanical properties. In this type of structure, the carbon atom is sp2 hybridized, whereas the X (N, P, As and Sb) atom is nonplanar sp3 hybridized with one 2pz orbital filled with lone pair electrons. NC6 , PC6 , AsC6 and SbC6 monolayers are intrinsic indirect semiconductors with wide bandgaps of 2.02, 2.36, 2.77, and 2.85 eV (based on HSE06 calculations), respectively. After applying mechanical strain, PC6 , AsC6 and SbC6 monolayers can be transformed from indirect to direct semiconductors. The appropriate bandgaps and well-located band edge positions make XC6 monolayers potential materials for photocatalytic water splitting. XC6 family members also have high absorption coefficients (∼105  cm-1 ) in the ultraviolet region and higher electron mobilities (∼103  cm2  V-1 s-1 ) than many known 2D semiconductors.

Effects of multiplication layers on dark current components of InGaAs/InP avalanche photodiodes.

Based on results from the Silvaco Atlas device simulation software, a separate absorption grading charge multiplication InGaAs/InP avalanche photodiode has been modeled. The Shockley-Read-Hall current, avalanche amplification current, trap-assisted tunneling current, and band-to-band direct tunneling current are combined and considered as the dark current. Individual components of the dark current have been obtained separately through numerical simulation. Due to the multiplication effect, the influence of the multiplication layer on the dark current components has been studied. The simulation results are analyzed based on semiconductor physics knowledge. The conclusions presented provide some theoretical guidance for the optimum design of avalanche photodiodes.

Permutation Matrix Encryption Based Ultralightweight Secure RFID Scheme in Internet of Vehicles.

Radio frequency identification (RFID) is a kind of non-contact automatic identification technology. The Internet of Vehicles (IoV) is a derivative of the Internet of Things (IoT), and RFID technology has become one of the key technologies of IoV. Due to the open wireless communication environment in RFID system, the RFID system is easy to be exposed to various malicious attacks, which may result in privacy disclosure. The provision of privacy protection for users is a prerequisite for the wide acceptance of the IoV. In this paper, we discuss the privacy problem of the RFID system in the IoV and present a lightweight RFID authentication scheme based on permutation matrix encryption, which can resist some typical attacks and ensure the user's personal privacy and location privacy. The fast certification speed of the scheme and the low cost of the tag is in line with the high-speed certification requirement in the Internet of vehicles. In this thesis, the specific application scenarios of the proposed RFID authentication scheme in the IoV is also discussed.

EARS-DM: Efficient Auto Correction Retrieval Scheme for Data Management in Edge Computing.

Edge computing is an extension of cloud computing that enables messages to be acquired and processed at low cost. Many terminal devices are being deployed in the edge network to sense and deal with the massive data. By migrating part of the computing tasks from the original cloud computing model to the edge device, the message is running on computing resources close to the data source. The edge computing model can effectively reduce the pressure on the cloud computing center and lower the network bandwidth consumption. However, the security and privacy issues in edge computing are worth noting. In this paper, we propose an efficient auto-correction retrieval scheme for data management in edge computing, named EARS-DM. With automatic error correction for the query keywords instead of similar words extension, EARS-DM can tolerate spelling mistakes and reduce the complexity of index storage space. By the combination of TF-IDF value of keywords and the syntactic weight of query keywords, keywords who are more important will obtain higher relevance scores. We construct an R-tree index building with the encrypted keywords and the children nodes of which are the encrypted identifier FID and Bloom filter BF of files who contain this keyword. The secure index will be uploaded to the edge computing and the search phrase will be performed by the edge computing which is close to the data source. Then EDs sort the matching encrypted file identifier FID by relevance scores and upload them to the cloud server (CS). Performance analysis with actual data indicated that our scheme is efficient and accurate.

MedBlock: Efficient and Secure Medical Data Sharing Via Blockchain.

With the development of electronic information technology, electronic medical records (EMRs) have been a common way to store the patients' data in hospitals. They are stored in different hospitals' databases, even for the same patient. Therefore, it is difficult to construct a summarized EMR for one patient from multiple hospital databases due to the security and privacy concerns. Meanwhile, current EMRs systems lack a standard data management and sharing policy, making it difficult for pharmaceutical scientists to develop precise medicines based on data obtained under different policies. To solve the above problems, we proposed a blockchain-based information management system, MedBlock, to handle patients' information. In this scheme, the distributed ledger of MedBlock allows the efficient EMRs access and EMRs retrieval. The improved consensus mechanism achieves consensus of EMRs without large energy consumption and network congestion. In addition, MedBlock also exhibits high information security combining the customized access control protocols and symmetric cryptography. MedBlock can play an important role in the sensitive medical information sharing.

A Secure and Verifiable Outsourced Access Control Scheme in Fog-Cloud Computing.

With the rapid development of big data and Internet of things (IOT), the number of networking devices and data volume are increasing dramatically. Fog computing, which extends cloud computing to the edge of the network can effectively solve the bottleneck problems of data transmission and data storage. However, security and privacy challenges are also arising in the fog-cloud computing environment. Ciphertext-policy attribute-based encryption (CP-ABE) can be adopted to realize data access control in fog-cloud computing systems. In this paper, we propose a verifiable outsourced multi-authority access control scheme, named VO-MAACS. In our construction, most encryption and decryption computations are outsourced to fog devices and the computation results can be verified by using our verification method. Meanwhile, to address the revocation issue, we design an efficient user and attribute revocation method for it. Finally, analysis and simulation results show that our scheme is both secure and highly efficient.

Two novel silicon phases with direct band gaps.

Due to its abundance, silicon is the preferred solar-cell material despite the fact that many silicon allotropes have indirect band gaps. Elemental silicon has a large impact on the economy of the modern world and is of fundamental importance in the technological field, particularly in the solar cell industry. Looking for direct band gap silicon is still an important field in material science. Based on density function theory with the ultrasoft pseudopotential scheme in the frame of the local density approximation and the generalized gradient approximation, we have systematically studied the structural stability, absorption spectra, electronic, optical and mechanical properties and minimum thermal conductivity of two novel silicon phases, Cm-32 silicon and P21/m silicon. These are both thermally, dynamically and mechanically stable. The absorption spectra of Cm-32 silicon and P21/m silicon exhibit significant overlap with the solar spectrum and thus, excellent photovoltaic efficiency with great improvements over Fd3[combining macron]m Si. These two novel Si structures with direct band gaps could be applied in single p-n junction thin-film solar cells or tandem photovoltaic devices.

Optical interconnection network for parallel access to multi-rank memory in future computing systems.

With the number of cores increasing, there is an emerging need for a high-bandwidth low-latency interconnection network, serving core-to-memory communication. In this paper, aiming at the goal of simultaneous access to multi-rank memory, we propose an optical interconnection network for core-to-memory communication. In the proposed network, the wavelength usage is delicately arranged so that cores can communicate with different ranks at the same time and broadcast for flow control can be achieved. A distributed memory controller architecture that works in a pipeline mode is also designed for efficient optical communication and transaction address processes. The scaling method and wavelength assignment for the proposed network are investigated. Compared with traditional electronic bus-based core-to-memory communication, the simulation results based on the PARSEC benchmark show that the bandwidth enhancement and latency reduction are apparent.

Average BER of subcarrier intensity modulated free space optical systems over the exponentiated Weibull fading channels.

The average bit error rate (BER) for binary phase-shift keying (BPSK) modulation in free-space optical (FSO) links over turbulence atmosphere modeled by the exponentiated Weibull (EW) distribution is investigated in detail. The effects of aperture averaging on the average BERs for BPSK modulation under weak-to-strong turbulence conditions are studied. The average BERs of EW distribution are compared with Lognormal (LN) and Gamma-Gamma (GG) distributions in weak and strong turbulence atmosphere, respectively. The outage probability is also obtained for different turbulence strengths and receiver aperture sizes. The analytical results deduced by the generalized Gauss-Laguerre quadrature rule are verified by the Monte Carlo simulation. This work is helpful for the design of receivers for FSO communication systems.

Dark current suppression of MgZnO metal-semiconductor-metal solar-blind ultraviolet photodetector by asymmetric electrode structures.

The application of asymmetric Schottky barrier and electrode area in an MgZnO metal-semiconductor-metal (MSM) solar-blind ultraviolet photodetector has been investigated by a physical-based numerical model in which the electron mobility is obtained by an ensemble Monte Carlo simulation combined with first principle calculations using the density functional theory. Compared with the experimental data of symmetric and asymmetric MSM structures based on ZnO substrate, the validity of this model is verified. The asymmetric Schottky barrier and electrode area devices exhibit reductions of 20 times and 1.3 times on dark current, respectively, without apparent photocurrent scarification. The plots of photo-to-dark current ratio (PDR) indicate that the asymmetric MgZnO MSM structure has better dark current characteristic than that of the symmetric one.

Ultra-High Frequency Self-Focusing Ultrasonic Sensors With Half-Concave Geometry for Visualization of Mouse Brain Atrophy.

Ultra-high frequency (>100 MHz) acoustic waves feature biocompatibility and high sensitivity and allow biomedical imaging and acoustic tweezers. Primarily, excellent spatial resolution and broad bandwidth at ultra-high frequency is the goal for pathological research and cell selection at the cellular level. Here, we propose an efficient approach to visualize mouse brain atrophy by self-focused ultrasonic sensors at ultra-high frequency with ultra-broad bandwidth. The numerical models of geometry and theoretically predicted acoustic parameters for half-concave piezoelectric elements are calculated by the differential method, which agrees with measured results (lateral resolution: 24 µm, and bandwidth: 115% at -6 dB). Compared with the brain slices of 2-month-old mouse, the atrophy visualization of the 6-month-old mouse brain was realized by C-mode imaging with an acoustic microscopy system, which is a potential prospect for diagnosis and treatment of Alzheimer's disease (AD) combined with neuroscience. Meanwhile, the acoustic properties of the brain slices were quantitatively measured by the acoustic microscopy. These encouraging results demonstrate the promising application for high-resolution imaging in vitro biological tissue with ultra-high frequency self-focusing ultrasonic sensors.

Engineering Multiphase Phase Transitions for Exceptional Electrocaloric Performance and Ultraweak Electrostrictive Response in Ferroelectrics.

In the pursuit of eco-friendly alternatives for refrigeration technology, electrocaloric materials have emerged as promising candidates for efficient solid-state refrigeration due to their high efficiency and integrability. However, current advancements in electrocaloric effects (ECEs) are often constrained by high temperatures and elevated electric fields (E-field), limiting practical applicability. Informed by phase-field simulation, this study introduces a (1-x)Pb(Yb1/2Nb1/2)O3-xPb(Mg1/3Nb2/3)O3 system, strategically engineered to incorporate highly ordered YN and disordered MN mixtures. The synergistic interplay between E-field/temperature-induced polarization reorientation and cation shift initiates multiple ferroelectric-antiferroelectric-paraelectric phase transitions. Our results demonstrate that under a moderate E-field of 50 kV cm-1, the x = 0.22 composition achieves remarkable performance with a giant temperature change (ΔT) of 3.48 K, a robust ECE strength (ΔT/ΔE) of 0.095 K cm kV-1, and a wide temperature span (Tspan) of 38 °C. Notably, the disrupted lattice structure contributes to ultralow electrostrains below 0.008%, with an average electrostrictive coefficient Q33 of 0.007 m4 C-2. The significantly weakened electrostrictive activity favors enhancing the performance stability of subsequent devices. This work introduces an innovative strategy for developing robust electrocaloric materials, offering substantial ΔT and low electrostrains, presenting promising advancements in ECE applications with an extended lifetime.

0.36BiScO3-0.64PbTiO3/Epoxy 1-3-2 High- Temperature Composite Ultrasonic Transducer for Nondestructive Testing Applications.

The development of high-temperature nondestructive testing (NDT) requires ultrasonic transducers with good temperature resistance and high sensitivity for improved detection efficiency. Piezoelectric composite can improve the performance of transducers because of its high electromechanical coupling coefficient and adjustable acoustic impedance. In this study, 1-3-2 composites and 1-3-2 high-temperature composite ultrasonic transducers (HTCUTs) based on 0.36BiScO3-0.64PbTiO3 (BSPT), which is preferred piezoelectric materials at 200 ° C- 300 ° C, and high-temperature epoxy with a center frequency of 6 MHz were designed and fabricated. From 25 ° C to 250 ° C, 1-3-2 composites show a higher electromechanical coupling coefficient kt especially at high temperatures (~0.53 at 25 ° C and ~0.64 at 250 ° C) than monolithic BSPT (~0.5). The signal of the pulse-echo response of 1-3-2 HTCUTs is distinguishable up to 250 ° C and remains stable ( [Formula: see text] mV) below 150 ° C, exhibiting higher sensitivity (improved by 7 dB) than that of monolithic BSPT high-temperature ultrasonic transducers (HTUTs). Bandwidth has been greatly enhanced especially at high temperatures (~103% at 250 ° C) compared with that of monolithic BSPT HTUTs (~30% at 250 ° C). To verify the excellent performance, B-mode scanning imaging measurement of a stepped steel block and defect location detection of a steel block was performed, showing the potential for high-temperature NDT applications.

Acoustic hologram-induced virtual in vivo enhanced waveguide (AH-VIEW).

Optical imaging and phototherapy in deep tissues face notable challenges due to light scattering. We use encoded acoustic holograms to generate three-dimensional acoustic fields within the target medium, enabling instantaneous and robust modulation of the volumetric refractive index, thereby noninvasively controlling the trajectory of light. Through this approach, we achieved a remarkable 24.3% increase in tissue heating rate in vitro photothermal effect tests on porcine skin. In vivo photoacoustic imaging of mouse brain vasculature exhibits an improved signal-to-noise ratio through the intact scalp and skull. These findings demonstrate that our strategy can effectively suppress light scattering in complex biological tissues by inducing low-angle scattering, achieving an effective depth reaching the millimeter scale. The versatility of this strategy extends its potential applications to neuroscience, lithography, and additive manufacturing.

An omni-directional optical antenna and its beam control method based on the EC-KPA algorithm for mobile FSO.

In order to ensure the communication link stability in mobile FSO system, a new omni-directional optical antenna is designed. Being aimed at discontinuous tracking, a novel beam control method based on the error correction Kalman prediction algorithm (EC-KPA) is proposed. The comparison of EC-KPA and the conventional Kalman prediction algorithm (KPA) is given. Numerical simulations about beam control method are carried out. The results show that the prediction accuracy of EC-KPA is improved about 77% than that of KPA in Gaussian noise situation, and that the increase is up to 12.92 times in strong noise situation. Therefore, the beam control method is feasible, and this optical antenna can meet the demands of fast mobile FSO.

Steady-state characteristics and transient response of MgZnO-based metal-semiconductor-metal solar-blind ultraviolet photodetector with three types of electrode structures.

Detailed studies of MgZnO-based metal-semiconductor-metal (MSM) solar-blind ultraviolet photodetector with different electrode structures are performed. A two-dimensional physical model is established based on the Poisson's equation and time-dependent continuity equations, which is verified by our experimental data of conventional electrode MSM detector. The steady-state characteristics and transient response of semicircular and triangular electrode MSM detectors are also investigated by this model. Compared with the conventional electrode, semicircular and triangular electrode devices exhibit a substantial improvement on the photocurrent. At a bias of 10 V, the steady-state saturated photocurrents for semicircular and triangular electrode devices are 14.69 nA and 24.37 nA respectively, corresponding to a 20.5% and 100% increase over the conventional electrode detector. Meanwhile, the transient peak photocurrents reach 31.38 nA and 52.09 nA respectively, both of which are notably larger than that of conventional device.

Analysis of SiC/Si Heterojunction Band Energy and Interface State Characteristics for SiC/Si VDMOS.

SiC/Si and GaN/Si heterojunction technology has been widely used in power semiconductor devices, and SiC/Si VDMOS and GaN/Si VDMOS were proposed in our previous paper. Based on existing research, breakdown point transfer technology (BPT) was used to optimize SiC/Si VDMOS. Simulation results showed that the BV of the SiC/Si heterojunction VDMOS was considerably increased from 259 V to 1144 V, and Ron,sp decreased from 18.2 mΩ·cm2 to 6.03 mΩ·cm2 compared with Si VDMOS. In order to analyze the characteristics of the SiC/Si heterojunction structure deeply, the influence of the interface state characteristics of the SiC/Si heterojunction on the electrical parameters of VDMOS was analyzed, including electric field characteristics, blocking characteristics, output characteristics, and transfer characteristics. In addition, the influence of the interface state of the SiC/Si heterojunction on energy band characteristics was analyzed. The results showed that with an increase in the interfacial charge (acceptor) concentration, the p-type trap layer was introduced into the interface of the SiC/Si heterojunction, energy increased slightly, and the barrier height difference at the heterojunction increased, resulting in an increase in BV. At the same time, since the barrier height became higher, electrons did not flow easily, so Ron,sp increased. On the contrary, when a charge (donor) was introduced at the interface of the SiC/Si heterojunction, the number of electrons in the channel increased, resulting in an increase in the electron current, which is conducive to the flow of electrons, resulting in a decrease in Ron,sp. The energy band and other characteristics of devices with temperature were simulated at different temperatures. Finally, the effects of SiC/Si heterojunction interface states on interface capacitances and switching performances of VDMOS devices were also discussed.

GaN/Si Heterojunction VDMOS with High Breakdown Voltage and Low Specific On-Resistance.

A novel VDMOS with the GaN/Si heterojunction (GaN/Si VDMOS) is proposed in this letter to optimize the breakdown voltage (BV) and the specific on-resistance (Ron,sp) by Breakdown Point Transfer (BPT), which transfers the breakdown point from the high-electric-field region to the low-electric-field region and improves the BV compared with conventional Si VDMOS. The results of the TCAD simulation show that the optimized BV of the proposed GaN/Si VDMOS increases from 374 V to 2029 V compared with the conventional Si VDMOS with the same drift region length of 20 µm, and the Ron,sp of 17.2 mΩ·cm2 is lower than 36.5 mΩ·cm2 for the conventional Si VDMOS. Due to the introduction of the GaN/Si heterojunction, the breakdown point is transferred by BPT from the higher-electric-field region with the largest radius of curvature to the low-electric-field region. The interfacial state effects of the GaN/Si are analyzed to guide the fabrication of the GaN/Si heterojunction MOSFETs.

ALBSNN: ultra-low latency adaptive local binary spiking neural network with accuracy loss estimator.

Spiking neural network (SNN) is a brain-inspired model with more spatio-temporal information processing capacity and computational energy efficiency. However, with the increasing depth of SNNs, the memory problem caused by the weights of SNNs has gradually attracted attention. In this study, we propose an ultra-low latency adaptive local binary spiking neural network (ALBSNN) with accuracy loss estimators, which dynamically selects the network layers to be binarized to ensure a balance between quantization degree and classification accuracy by evaluating the error caused by the binarized weights during the network learning process. At the same time, to accelerate the training speed of the network, the global average pooling (GAP) layer is introduced to replace the fully connected layers by combining convolution and pooling. Finally, to further reduce the error caused by the binary weight, we propose binary weight optimization (BWO), which updates the overall weight by directly adjusting the binary weight. This method further reduces the loss of the network that reaches the training bottleneck. The combination of the above methods balances the network's quantization and recognition ability, enabling the network to maintain the recognition capability equivalent to the full precision network and reduce the storage space by more than 20%. So, SNNs can use a small number of time steps to obtain better recognition accuracy. In the extreme case of using only a one-time step, we still can achieve 93.39, 92.12, and 69.55% testing accuracy on three traditional static datasets, Fashion- MNIST, CIFAR-10, and CIFAR-100, respectively. At the same time, we evaluate our method on neuromorphic N-MNIST, CIFAR10-DVS, and IBM DVS128 Gesture datasets and achieve advanced accuracy in SNN with binary weights. Our network has greater advantages in terms of storage resources and training time.