Inspired by the compound eyes of insects, many multi-aperture optical imaging systems have been proposed to improve the imaging quality, e.g., to yield a high-resolution image or an image with a large field-of-view. Previous research has reviewed existing multi-aperture optical imaging systems, but few papers emphasize the light field acquisition model which is essential to bridge the gap between configuration design and application. In this paper, we review typical multi-aperture optical imaging systems (i.e., artificial compound eye, light field camera, and camera array), and then summarize general mathematical light field acquisition models for different configurations. These mathematical models provide methods for calculating the key indexes of a specific multi-aperture optical imaging system, such as the field-of-view and sub-image overlap ratio. The mathematical tools simplify the quantitative design and evaluation of imaging systems for researchers.
Traditional high performance computing (HPC) systems provide a standard preset environment to support scientific computation. However, HPC development needs to provide support for more and more diverse applications, such as artificial intelligence and big data. The standard preset environment can no longer meet these diverse requirements. If users still run these emerging applications on HPC systems, they need to manually maintain the specific dependencies (libraries, environment variables, and so on) of their applications. This increases the development and deployment burden for users. Moreover, the multi-user mode brings about privacy problems among users. Containers like Docker and Singularity can encapsulate the job’s execution environment, but in a highly customized HPC system, cross-environment application deployment of Docker and Singularity is limited. The introduction of container images also imposes a maintenance burden on system administrators. Facing the above-mentioned problems, in this paper we propose a self-deployed execution environment (SDEE) for HPC. SDEE combines the advantages of traditional virtualization and modern containers. SDEE provides an isolated and customizable environment (similar to a virtual machine) to the user. The user is the root user in this environment. The user develops and debugs the application and deploys its special dependencies in this environment. Then the user can load the job to compute nodes directly through the traditional HPC job management system. The job and its dependencies are analyzed, packaged, deployed, and executed automatically. This process enables transparent and rapid job deployment, which not only reduces the burden on users, but also protects user privacy. Experiments show that the overhead introduced by SDEE is negligible and lower than those of both Docker and Singularity.
To ensure the reliability and availability of data, redundancy strategies are always required for distributed storage systems. Erasure coding, one of the representative redundancy strategies, has the advantage of low storage overhead, which facilitates its employment in distributed storage systems. Among the various erasure coding schemes, XOR-based erasure codes are becoming popular due to their high computing speed. When a single-node failure occurs in such coding schemes, a process called data recovery takes place to retrieve the failed node’s lost data from surviving nodes. However, data transmission during the data recovery process usually requires a considerable amount of time. Current research has focused mainly on reducing the amount of data needed for data recovery to reduce the time required for data transmission, but it has encountered problems such as significant complexity and local optima. In this paper, we propose a random search recovery algorithm, named SA-RSR, to speed up single-node failure recovery of XOR-based erasure codes. SA-RSR uses a simulated annealing technique to search for an optimal recovery solution that reads and transmits a minimum amount of data. In addition, this search process can be done in polynomial time. We evaluate SA-RSR with a variety of XOR-based erasure codes in simulations and in a real storage system, Ceph. Experimental results in Ceph show that SA-RSR reduces the amount of data required for recovery by up to 30.0% and improves the performance of data recovery by up to 20.36% compared to the conventional recovery method.
For group signature (GS) supporting membership revocation, verifier-local revocation (VLR) mechanism seems to be a more flexible choice, because it requires only that verifiers download up-to-date revocation information for signature verification, and the signers are not involved. As a post-quantum secure cryptographic counterpart of classical number-theoretic cryptographic constructions, the first lattice-based VLR group signature (VLR-GS) was introduced by Langlois et al. (2014). However, none of the contemporary lattice-based VLR-GS schemes provide backward unlinkability (BU), which is an important property to ensure that previously issued signatures remain anonymous and unlinkable even after the corresponding signer (i.e., member) is revoked. In this study, we introduce the first lattice-based VLR-GS scheme with BU security (VLR-GS-BU), and thus resolve a prominent open problem posed by previous works. Our new scheme enjoys an O(log N) factor saving for bit-sizes of the group public-key (GPK) and the member’s signing secret-key, and it is free of any public-key encryption. In the random oracle model, our scheme is proven secure under two well-known hardness assumptions of the short integer solution (SIS) problem and learning with errors (LWE) problem.
Many traditional applications can be refined thanks to the development of blockchain technology. One of these services is non-repudiation, in which participants in a communication process cannot deny their involvement. Due to the vulnerabilities of the non-repudiation protocols, one of the parties involved in the communication can often avoid non-repudiation rules and obtain the expected information to the detriment of the interests of the other party, resulting in adverse effects. This paper studies the fairness guarantee quantitatively through probabilistic model checking. E-fairness is measured by modeling the protocol in probabilistic timed automata and verifying the appropriate property specified in the probabilistic computation tree logic. Furthermore, our analysis proposes insight for choosing suitable values for different parameters associated with the protocol so that a certain degree of fairness can be obtained. Therefore, the reverse question—for a certain degree of fairness ε, how can the protocol parameters be specified to ensure fairness—is answered.
The affine formation tracking problem for fixed-wing unmanned aerial vehicles (UAVs) is considered in this paper, where fixed-wing UAVs are modeled as unicycle-type agents with asymmetrical speed constraints. A group of UAVs are required to generate and track a time-varying target formation obtained by affinely transforming a nominal formation. To handle this problem, a distributed control law based on stress matrix is proposed under the leader-follower control scheme. It is proved, theoretically, that followers can converge to the desired positions and achieve affine transformations while tracking diverse trajectories. Furthermore, a saturated control strategy is proposed to meet the speed constraints of fixed-wing UAVs, and numerical simulations are executed to verify the effectiveness of our proposed affine formation tracking control strategy in improving maneuverability.
This paper presents a sensor-guided gait-synchronization system to help potential unilateral knee-injured people walk normally with a weight-supported lower-extremity-exoskeleton (LEE). This relieves the body weight loading on the knee-injured leg and synchronizes its motion with that of the healthy leg during the swing phase of walking. The sensor-guided gait-synchronization system is integrated with a body sensor network designed to sense the motion/gait of the healthy leg. Guided by the measured joint-angle trajectories, the motorized hip joint lifts the links during walking and synchronizes the knee-injured gait with the healthy gait by a half-cycle delay. The effectiveness of the LEE is illustrated experimentally. We compare the measured joint-angle trajectories between the healthy and knee-injured legs, the simulated knee forces, and the human-exoskeleton interaction forces. The results indicate that the motorized hip-controlled LEE can synchronize the motion/gait of the combined body-weight-supported LEE and injured leg with that of the healthy leg.
Low-angle estimation for very high frequency (VHF) radar is a difficult problem due to the multipath effect in the radar field, especially in complex scenarios where the reflection condition is unknown. To deal with this problem, we propose an algorithm of target height and multipath attenuation joint estimation. The amplitude of the surface reflection coefficient is estimated by the characteristic of the data itself, and it is assumed that there is no reflected signal when the amplitude is very small. The phase of the surface reflection coefficient and the phase difference between the direct and reflected signals are searched as the same part, and this represents the multipath phase attenuation. The Cramer-Rao bound of the proposed algorithm is also derived. Finally, computer simulations and real data processing results show that the proposed algorithm has good estimation performance under complex scenarios and works well with only one snapshot.
We present a new counter-based Wallace-tree (CBW) 8×8 multiplier. The multiplier’s counters are implemented with a new hybrid full adder (FA) cell, which is based on the transmission gate (TG) technique. The proposed FA, TG-based AND gate, and hybrid half adder (HA) generate M:3 (4≤M≤7) digital counters with the ability to save at least 50% area occupation. Simulations by 90 nm technology prove the superiority of the proposed FA and digital counters under different conditions over the state-of-the-art designs. By using the proposed cells, the CBW multiplier exhibits high driving capability, low power consumption, and high speed. The CBW multiplier has a 0.0147 mm2 die area in a pad. The post-layout extraction proves the accuracy of experimental implementation. An image blending mechanism is proposed, in which a direct interface between MATLAB and HSPICE is used to evaluate the presented CBW multiplier in image processing applications. The peak signal-to-noise ratio (PSNR) and structural similarity index metric (SSIM) are calculated as image quality parameters, and the results confirm that the presented CBW multiplier can be used as an alternative to designs in the literature.