Cloud Computing has become a well-known primitive nowadays; many researchers and companies are embracing this fascinating technology with feverish haste. In the meantime, security and privacy challenges are brought forward while the number of cloud storage user increases expeditiously. In this work, we conduct an in-depth survey on recent research activities of cloud storage security in association with cloud computing. After an overview of the cloud storage system and its security problem, we focus on the key security requirement triad, i.e., data integrity, data confidentiality, and availability. For each of the three security objectives, we discuss the new unique challenges faced by the cloud storage services, summarize key issues discussed in the current literature, examine, and compare the existing and emerging approaches proposed to meet those new challenges, and point out possible extensions and futuristic research opportunities. The goal of our paper is to provide a state-of-the-art knowledge to new researchers who would like to join this exciting new field.

This paper analyzes the effect of the anisotropy of single crystal silicon on the frequency split of the vibrating ring gyroscope, operated in the n = 2 wineglass mode. Firstly, the elastic properties including elastic matrices and orthotropic elasticity values of (100) and (111) silicon wafers were calculated using the direction cosines of transformed coordinate systems. The (111) wafer was found to be in-plane isotropic. Then, the frequency splits of the n = 2 mode ring gyroscopes of two wafers were simulated using the calculated elastic properties. The simulation results show that the frequency split of the (100) ring gyroscope is far larger than that of the (111) ring gyroscope. Finally, experimental verifications were carried out on the micro-gyroscopes fabricated using deep dry silicon on glass technology. The experimental results are sufficiently in agreement with those of the simulation. Although the single crystal silicon is anisotropic, all the results show that compared with the (100) ring gyroscope, the frequency split of the ring gyroscope fabricated using the (111) wafer is less affected by the crystal direction, which demonstrates that the (111) wafer is more suitable for use in silicon ring gyroscopes as it is possible to get a lower frequency split.

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With the rapid development and widespread adoption of wireless sensor networks (WSNs), security has become an increasingly prominent problem. How to establish a session key in node communication is a challenging task for WSNs. Considering the limitations in WSNs, such as low computing capacity, small memory, power supply limitations and price, we propose an efficient identity-based key management (IBKM) scheme, which exploits the Bloom filter to authenticate the communication sensor node with storage efficiency. The security analysis shows that IBKM can prevent several attacks effectively with acceptable computation and communication overhead.

An automatic mode-matching method for MEMS (Micro-electromechanical Systems) disk resonator gyroscopes (DRGs) based on virtual Coriolis force is presented in this paper. For this mode-matching method, the additional tuning electrodes are not required to be designed, which simplifies the structure design. By using the quadratic relationship between the driving voltage and the electrostatic force, the virtual Coriolis force is obtained by applying an AC voltage whose frequency is half of the driving mode resonant frequency to the sense electrode. The phase difference between the virtual Coriolis force and the sense output signal is used for mode-matching. The structural characteristics and electrode distribution of the DRG are briefly introduced. Moreover, the mode-matching theories of the DRG are studied in detail. The scheme of the mode-matching control system is proposed. Simultaneously, the feasibility and effectiveness of the mode-matching method are verified by system simulation. The experimental results show that under the control of mode-matching at room temperature, the bias instability is reduced from 30.7575 • /h to 2.8331 • /h, and the Angle Random Walk (ARW) decreases from 1.0208 • / √ h to 0.0524 • / √ h. Compared with the mode mismatch condition, the ARW is improved by 19.48 times.Micromachines 2020, 11, 210 2 of 22 Therefore, the mode-matching technology improves the bias stability and mechanical sensitivity of MEMS gyroscopes by eliminating the frequency split between the driving mode and the sensing mode, which has attracted significant attention from researchers [19][20][21]. Furthermore, some frequency modification techniques are proposed. Laser finishing, ion beam milling, and selective deposition mass loading reduce frequency split [22,23]. However, these methods are often used to change the dynamic characteristics of the sensor permanently, and this type of tuning is inflexible and time-consuming. The tuning control is limited and can only be achieved offline.Electrostatic tuning is usually used for mode-matching, which can provide more flexibility and real-time realization [24][25][26][27][28][29]. The mode-matching process based on phase-locked loop (PLL) takes advantage of the phase delay of 90 • between the quadrature input and output of the sensing mode. This feature is used in [27] to achieve mode-matching and to adjust the tuning voltage using PLL technology. The amplitude-frequency characteristic refers to the maximum amplitude of the quadrature response signal during mode-matching [28]. However, in these methods, the signal from the Coriolis demodulation channel is used to control the frequency tuning voltage. Therefore, the angular velocity can only be measured if the tuning voltage is fixed, and the matching loop is disconnected after mode-matching. Thus, these methods cannot achieve real-time mode-matching. However, in practical applications, the frequency split of the vibratory mode changes with changes in environmental parameters [29]. Therefore, such one-time matching methods a...

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With the wide adoption of wireless sensor network (WSN), security problems emerge as a challenging issue because of the limited computational power and energy of the sensor nodes. Furthermore, the deployment of WSN in the hostile area with a large number of nodes also poses a threat. In this paper, we proposed a new efficient key management scheme based on Elliptic Curve Cryptography (ECC) and AVL tree for large scale WSNs. In our scheme the Elliptic Curve Paillier Encryption (ECPE) cryptography is adopted for communication and the AVL tree is used to store the neighbors' ID and public key. The number of keys used in our scheme is smaller than the proposed schemes as we store these keys using AVL tree to shorten the search time. Regular key updates are also designed to further improve the security of the whole network. Our scheme has a good scalability where the node addition and deletion are supported. Experimental results and analysis show our scheme can significantly reduce the energy consumed by the node and reduce the memory and computational overhead.

Coriolis vibratory gyroscopes (CVGs) with circular micro-resonators, such as hemispherical, ring, and disk resonators, exhibit excellent performances and have extraordinary potential. This paper discusses a generalized lumped mass model for both 3D and planar circular micro-resonators, establishing the relationship between the modal effective mass, the modal equivalent force, and the point displacement of the resonator. The point displacement description of a continuous circular resonator’s motion is defined from the view of capacitance measurement. The modal effective mass is, consequently, determined by the kinetic and the potential energy of the structure and is computed with numerical simulations. Moreover, the modal equivalent force, which can be theoretically calculated for any configuration of discrete electrodes, is deduced by using the concept of force density and the force distribution function. By utilizing the lumped mass model in this paper, the stiffness softening, the mode tuning, and the quadrature correction of the micro-resonators are investigated in detail. The theoretical model is verified by both the finite element method (FEM) and the experiments.