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Artificial intelligence (AI)-based cybersecurity services offer significant promise in many scenarios, including malware detection, content supervision, and so on. Meanwhile, many commercial and government applications have raised the need for intellectual property protection of using deep neural network (DNN). Existing studies (e.g., watermarking techniques) on intellectual property protection only aim at inserting secret information into DNNs, allowing producers to detect whether the given DNN infringes on their own copyrights. However, since the availability protection of learning models is rarely considered, the piracy model can still work with high accuracy. In this paper, a novel model locking (M-LOCK) scheme for the DNN is proposed to enhance its availability protection, where the DNN produces poor accuracy if a specific token is absent, while it maps only the tokenized inputs into correct predictions. The proposed scheme performs the verification process during the DNN inference operation, actively protecting models’ intellectual property copyright at each query. Specifically, to train the token-sensitive decision-making boundaries of DNNs, a data poisoning-based model manipulation (DPMM) method is also proposed, which minimizes the correlation between the dummy outputs and correct predictions. Extensive experiments demonstrate the proposed scheme could achieve high reliability and effectiveness across various benchmark datasets as well as typical model protection methods.

Based on the special background of transition economies, in which governments play a particularly important role in firms’ survival and development, we discuss the impact of performance shortfall on firms’ tax avoidance, which is a behavior that is considered unethical and irresponsible by the public. Drawing upon performance feedback theory and institutional theory, we propose that performance shortfall will drive firms to reduce tax avoidance to enhance their political legitimacy, thereby gaining more government support to solve current performance problems. We also argue that the relationship between performance shortfall and firms’ tax avoidance is likely nuanced and may vary by institutional logics (e.g., state-owned enterprises (SOEs)), and regional marketization degree). Specifically, we argue that SOEs will strengthen the above-mentioned relationship, and the regional marketization degree will weaken the above-mentioned relationship. After testing listed companies in China as the research object, we find that most of our theoretical views are supported by empirical evidence.

An acceleration measurement-based disturbance observer (DOB) control method is proposed to capture and eliminate transient and dramatic dynamic disturbance torque in the flexible belt-drive servo instrumentation. The essence of this method is to incorporate the acceleration difference between the motor side and the load side to implement a DOB in the dual-rate control loop. The acceleration difference is sensitive to the rate variation caused by the motor-load large span distribution. The input signal of the motor inner loop with the high bandwidth is equivalently processed to obtain the estimated motor-side acceleration. However, the observed acceleration disturbance suffers from low-frequency drift and noise accumulation, resulting in system instability under integral characteristics. Therefore the $H_{\infty }$ principle is used to ensure stronger stability and the compensator is bandpass-corrected to enhance the anti-disturbance performance in a limited bandwidth. The proposed method is experimentally validated to effectively suppress the disturbance torque after obtaining an optimal trade-off between robust stability and anti-disturbance. The error spikes and buffeting in the flexible transmission chain are further reduced compared with the conventional methods.

In this paper, a robust control based on disturbance observer is proposed to improve the tracking accuracy of the Risley prism system (RPS). Applying the flexible thin-wall ring mechanism in the RPS causes a series of tracking and pointing challenges. Disturbances such as friction, shaft deformation, and model perturbation significantly deteriorate the tracking and pointing accuracy of the RPS. Two different observer-based control methods are proposed to guarantee the tracking precision of the RPS. Moreover, the disturbance observation and compensation (DOC) performance of the proposed methods is analyzed and compared. Finally, simulation and experiment results indicate that the proposed control methods, especially the DOC-expanded state observer control mode, obtain the best performance for disturbance rejection in the RPS.

Efficiently and accurately predicting the steering ability of the bottom hole assembly (BHA) in slide drilling is a crucial yet challenging task. While the industry standard three-point geometry method is computationally efficient, it cannot capture the intricate mechanics involved in the drilling process. Conversely, utilizing the whole drill string dynamics model for simulating slide drilling provides a more comprehensive representation but involves time-consuming evaluations, making it difficult to balance precision and efficiency. This study addresses this challenge by proposing a rapid evaluation method that ensures both speed and accuracy by developing a multi-body dynamics rapid model of the slide drilling system. Based on the whole drill string model, this method incorporates two key techniques to achieve its primary objective. Firstly, it utilizes the equivalent torque model of the bit, which includes the fixed joint and the virtual rotational velocity, to replace the original revolute joint between the positive displacement motor (PDM) and the bit. Secondly, a segmentation model is established to decouple the simulation of the BHA drilling process from the drill string equilibrium process, thereby significantly reducing the slide drilling system’s degree of freedom (DOF). The proposed method offers a new approach to improving the efficiency of evaluating the steering ability of the slide drilling system while ensuring a high level of accuracy.

Purpose: The phenomenon of defamilization of family firms is gradually increasing for the growth of family firms, that is, nonfamily executives are increasingly present in the executive teams of family firms. Although previous scholars have identified various determinants of family firms' defamilization, whether and when innovation underperformance affects the decision to defamilize family firms has not been explore. This study aims to fill the aforementioned research gaps. Design/methodology/approach: This study empirically tests the theoretical view based on the data of Chinese A-share family listed companies from 2009 to 2017. Findings: The authors found that innovation underperformance drives family companies to increase the percentage of nonfamily executives in their executive teams. Further, the authors found that family firms are less willing to hire nonfamily executives with an increase in socioemotional wealth, particularly when founders of such businesses serve as directors or are major shareholders, even when they are not directors. Originality/value: This study shows that innovation underperformance and socioemotional wealth are important predictors of family firms’ defamilization decisions.

In low-Earth orbit, the already existing population of small and medium debris (between 1 cm and several dozens of cm) is a concrete threat to operational satellites. A space-based laser space debris removal (SLDR) system that can remove hazardous debris around selected space assets appears to be a flexible and effective project. To achieve high-precision tracking and emitting, the optical system of the SLDR mission includes a target-detection telescope and emitting telescope, adopting a common light path structure. The optical design results, system performance, tolerance budget, and detailed stray light control design are presented in this paper. The large-aperture off-axis two-mirror beam-narrowing system characteristics are also discussed in terms of stray light control. This paper will present the lateral-displacement (LD) setting, two-stage fore baffle design, black baffle surface selection, and opening direction of the telescope door. The results showed that the stray light elimination reaches a 10^−9 order, meeting design requirements.

In this paper, a cascade double-loop control (DLC) combined with modeling compensation methods is proposed to improve the tracking precision of the multiaperture imaging system (MAIS). The application of the flexible thin-wall ring mechanism in the coupling rotating prism (CRP) system causes a series of tracking and pointing challenges. Disturbances such as friction, shaft deformation, and model perturbation significantly deteriorate the tracking and pointing accuracy of the CRP. Two different modeling compensation methods that are interfaced with classical DLC are proposed to guarantee the tracking precision of the MAIS. Moreover, the disturbance observation and compensation performance of two different modeling compensation methods are analyzed and compared. Finally, simulation and experiment results indicate that the proposed control methods, especially model compensation based on speed close-loop control, obtain the best performance for disturbance rejection in the MAIS.

Deformable image registration (DIR) has been well explored in recent decades, and it is widely utilized in clinical tasks, especially dose warping. Nowadays, as deep learning (DL) develops rapidly, many DL-based methods were also applied in DIR. This paper reviews DL-based DIR methods in recent years and the application of DIR in dose warping. We collected and categorized the latest DL-based DIR studies. A thorough review of each category was presented, in which studies were discussed based on their supervision, advantage, and challenges. Then, we reviewed DIR-based dose warping and discussed its rationale, feasibility, successes, and difficulties. Lastly, we summarized the review on both parts and discussed their future development trend.

Boresight and jitter are two fundamental pointing errors of laser illumination systems. A triangular-scanning algorithm is proposed to estimate the direction of the boresight via a three-step maximum boresight estimation and laser beam deflection procedure. On this basis, the closed-loop laser illumination (CLLI) for non-cooperative targets is realized, and the Cramer–Rao lower bounds (CRLB) performance in the lower limit of the pointing error is analyzed. Additionally, a Monte Carlo simulation system is built, and the performance of the CLLI algorithm is analyzed. The simulation results demonstrate that the triangular-scanning algorithm has good performance and can accurately estimate the direction of the boresight to achieve CLLI. Further study shows that the simulation results agree well with theoretical estimations and approximate the CRLB at the lower limit.

Phase aberration is one of the prime factors that degrade the quality of observed images. Pupil-size diversity technology (PSDT) is a newly developed post-processing method for aberration correction and image reconstruction. However, images reconstructed using PSDT suffer from massive grains when imaging astronomical faint objects, which extremely limits its further application. In this paper, we propose an improved PSDT with embedded denoising reprocessing to overcome this drawback. Diversity raw images, generated by modulating the size of the pupil, are firstly processed by blocking-matching and 3D filtering (BM3D), a state-of-art denoising algorithm. Then, the traditional PSDT can be employed to estimate the wavefront and reconstruct a high-resolution image. Both numerical simulations and experiment demonstrations show that our proposed strategy exhibits superior performance for aberrations correction and image restoration of faint objects in view of its efficiency and robustness. Being capable of realizing high-resolution imaging with faint objects, this proposed method may have important application prospects in the fields of astronomical object detection, remote sensing, etc.

Biofilm is an important survival mode of microorganisms in nature. Biofilm culture is supposed to be a way of learning from nature to endow microorganisms with a strong tolerance. However, microorganisms possess different biofilm formation abilities, and universal scaffolds, especially edible scaffolds, suitable for fast biofilm formation are not found yet. Zein is a hydrophobic and biocompatible prolamine-rich protein from corn and is one of the most used biomacromolecules now. In this work, natural zein was utilized to produce electrospun zein nanofibrous biomaterial. The results demonstrate that edible electrospun zein nanofibrous scaffolds significantly enhance biofilm formation, where bacterial probiotics and yeasts are 0.9–1.4 Log cfu/cm2(8–25 × ) and 1.7–3.3 Log cfu/cm2(50–2000 × ) higher than the values on polystyrene plates and zein films, respectively. Gaps in biofilm formation abilities between bacteria and yeasts are narrowed from 1.7–1.8 Log cfu/cm2(50–63 × ) to 0.5–0.6 Log cfu/cm2(3–4 × ), respectively. Biofilms quickly formed on electrospun zein nanofibrous scaffolds before the occurrence of serious swelling deformation of the scaffolds. This is the first attempt to use edible electrospun fibrous scaffolds based on natural biomacromolecules for enhancing biofilm formation, crucially important for the application of probiotics and yeast in food and medical industries. Electrospun zein nanofibrous scaffolds can serve as powerful tools to enhance the biofilm formation of valuable food microorganisms and close the huge gaps in biofilm formation abilities between microorganisms, providing a convenient and universal strategy to produce biofilm-phenotyped probiotics and yeasts.

Recent work has shown that subsurface microbial communities assemble by selective survival of surface community members during sediment burial, but it remains unclear to what extent the compositions of the subsurface communities are a product of their founding population at the sediment surface or of the changing geochemical conditions during burial. Here we investigate this question for communities of sulfate-reducing microorganisms (SRMs). We collected marine sediment samples from the upper 3–5 m at four geochemically contrasting sites in the Skagerrak and Baltic Sea and measured SRM abundance (quantitative PCR of dsrB), metabolic activity (radiotracer rate measurements), and community composition (Illumina sequencing of dsrBamplicons). These data showed that SRM abundance, richness, and phylogenetic clustering as determined by the nearest taxon index peaked below the bioturbation zone and above the depth of sulfate depletion. Minimum cell-specific rates of sulfate reduction did not vary substantially between sites. SRM communities at different sites were best distinguished based on their composition of amplicon sequence variants (ASVs), while communities in different geochemical zones were best distinguished based on their composition of SRM families. This demonstrates environmental filtering of SRM communities in sediment while a site-specific fingerprint of the founding community is retained.

An essential issue for the low-noise system application of the fiber optic gyroscope (FOG) is to reduce its noise level. The relative intensity noise (RIN) of the light source is the dominant noise of the FOG when the light power on the detector reaches a certain level. The noise subtraction method is effective for RIN reduction and easy to implement in a FOG. This paper theoretically analyzes the factors that influence the result of the method and deduces the function to calculate the noise suppression ratio that can be achieved. A method that uses an optimum filter design based on the Wiener filter in the reference detector signal is proposed to improve the subtraction result. A FOG system is set up to test the feasibility of the method. The experiment results meet with the theoretical analysis, and by using the Wiener filter, the achieved noise subtraction factor reaches the limitation that restrains the optical system and detection circuit.

Fusion power shutdown system (FPSS) is a safety system to stop plasma in case of accidents or incidents. The gas injection system for the FPSS presented in this work is designed to research the flow development in a closed system. As the efficiency of the system is a crucial property, plenty of experiments are executed to get optimum parameters. In this system, the flow is driven by the pressure difference between a gas storage tank and a vacuum vessel with a source pressure. The idea is based on a constant volume system without extra source gases to guarantee rapid response and high throughput. Among them, valves and gas species are studied because their properties could influence the velocity of the fluid field. Then source pressures and volumes are emphasized to investigate the volume flow rate of the injection. The source pressure has a considerable effect on the injected volume. From the data, proper parameters are extracted to achieve the best performance of the FPSS. Finally, experimental results are used as a quantitative benchmark for simulations which can add our understanding of the inner gas flow in the pipeline. In generally, there is a good consistency and the obtained correlations will be applied in further study and design for the FPSS.

In this paper, an aberration correction method for an extended target is proposed to solve the problem of the lenslet-based plenoptic camera not imaging clearly under the influence of aberrations. We propose a light field manipulation method to improve performance of the light field imaging system. The principle of this method is that the sub-aperture images extracted from the raw light field image are offset when the light field imaging system is affected by aberrations, and the symmetrical arrangement of the sub-aperture image array is destroyed. By repairing the symmetrical arrangement of the sub-aperture image array, the influence of phase aberrations on the imaging system can be eliminated, and the resolution of the plenoptic camera can be improved. We use an image correlation algorithm to process the sub-aperture images of the plenoptic camera, calculate and compensate each sub-aperture image’s displacement caused by aberrations, and restore the symmetrical arrangement of the sub-aperture image array; then, a corrected high-resolution refocused image can be generated. In particular, this method uses only the raw light field information obtained by the plenoptic camera in a single exposure, without adding other hardware devices. Furthermore, it takes the extended target itself as the reference image, so the ideal position need not be calibrated in advance. Also, the parallax information of the sub-aperture images is retained, and the method is simple and easy to use. Numerical simulation and experimental results show that the technology proposed in this paper can work well for high-resolution imaging of a plenoptic camera with phase aberrations. This method can be potentially applied to analyze lens aberration, media-induced image distortion such as water turbulence in underwater imaging, and atmospheric turbulence in remote imaging. It may have important application prospects in the fields of astronomical object detection, remote sensing, etc.

A compact sub-nanosecond optical image amplifier is proposed and demonstrated. It is pumped by an actively Q-switched diode-pumped Nd:YAG microlaser in virtue of the optical parametric amplification (OPA) technique and quasi-phase-matching scheme. Experimental results show that the optical image gain reaches 15.4 dB under a pump intensity of 15.3  MW/cm^2. The influence of parametric fluorescence noise on the amplified image is obvious above 10 dB gain. The signal-to-noise ratio degradation of the amplifier image characterized by the noise figures is in sheer contrast with theoretical expectations. It shows that the experimental noise figure value reaches 2.2 dB, larger than the theoretical result of 0.7 dB at 15 dB gain.

Risley prisms appear to be a promising solution to high-accuracy pointing and tracking. To improve the pointing accuracy of achromatic Risley prisms, an appropriate mathematical model is established, and the forward and inverse solutions are proposed. Focusing on the sources of systematic errors, an optimization method based on a genetic algorithm is proposed to identify the parameters of the physical model, including wedge angles, refractive indexes, and installations. Finally, the experimental platform is established. The pointing accuracy and the size of the blind zone are tested to prove the validity of the method. Experimental results show that the proposed method is effective to reduce the influence of manufacturing, installation, and measurement errors. The optimized pointing accuracy has been improved significantly. Within the maximum deflection angle of 3°, the maximum pointing error is reduced from 33 arcsec to less than 1 arcsec. And the angular dynamic range is found to be greater than 43 dB, able to meet the needs of the majority of applications. In addition, the test of the blind zone shows that the optimized parameters are consistent with the actual system.

Extraneous thermal loads on the primary mirror of a large-aperture telescope directly influence the optical performance of the telescope through temperature gradients within the mirror and thermal boundary layer at the face sheet. In this paper, we propose a new thermal control system consisting of a flushing and sucking system for eliminating the excessive heat of a primary mirror. First, a 2.8 m-aperture lightweighted primary mirror is fabricated. Second, a thermo-optic analysis using finite element analysis is conducted in natural and forced convection. Finally, the optical performance denoted by Zernike polynomials with and without our proposed thermal control system is evaluated and examined. The comparative results reveal that the image quality of the primary mirror in forced convection is significantly enhanced with obvious reduction of optical surface distortion, thereby demonstrating the effectiveness of our proposed thermal control system.

The coregistration of complex image pairs is a very important step in interferometric synthetic aperture radar (InSAR) data processing. This article proposes a coregistration method based on the stochastic parallel gradient descent (SPGD) algorithm. Stochastic parallel perturbations are imposed on the translation coefficients of the polynomial coregistration model to make the performance evaluation function converge to a global extremum, which allows the translation coefficients to be obtained, and then the coregistration is achieved after resampling. Data processing of images from Kashgar and Mount Etna show that the proposed method is effective and robust. Furthermore, a series of experiments is designed to evaluate the convergence characteristics of the proposed method, which indicates that it has a stable convergence process and good robustness.

It has come to the attention of The Optical Society (OSA) that the article “Analytical solutions for Risley-prism-based tracking and pointing systems” by Qi Peng, Xinghui Wang, Ge Ren, Hongbin Chen, Lei Cao and Jihong Wang, Appl. Opt. 53, C83-C90 (2014) should not have been submitted owing to its substantial replication, without appropriate attribution, of significant elements found in the previously published paper “Closed form analytical inverse solutions for Risley-prism-based beam steering systems in different configurations” by Yajun Li, Appl. Opt. 50, 4302-4309 (2011).

The research on drillstring dynamics is necessary for improving drilling efficiency and safety. In this investigation, a multibody dynamical model for 3D full hole drillstring system is presented based on the Absolute Nodal Coordinate Formulation (ANCF). The drillstring is modeled with the ANCF beam element. The absolute nodal coordinate formulation of the beam element as well as the boundary conditions at the top-drive and drill-bit, and the contact/friction model between drillstring and wellbore are also investigated. The dynamic governing equation for full hole drillstring system is given and solved by the backward differentiation formulation (BDF) for differential algebraic equations (DAEs). The developed multibody dynamic solver is capable of analyzing full coupled vibration for the full hole drillstring system. It can play a certain role in drillstring dynamics researches and engineering applications.

Time Petri net is a model method which describes the dynamic behavior of the system by the moving of token. This paper takes location of a nursing home in Xi’an as the research object. The best position is selected by building dynamic models with time Petri net, and solving the model with Ant Colony algorithm, based on considering some factors such as public transport, health and environment. Finally, the effectiveness of the method on the selecting of location is confirmed by empirical analysis.

Thermal load is non-ignorable in the design and analysis of high precision and reliable space deployable structures. A new approach based on flexible multibody system is presented in order to investigate the thermoelastic effect on the deployment of space structure. Dynamic equations of an Euler Bernoulli beam element with transient thermal load are derived in Absolute Nodal Coordinate Formulation. The temperature distribution in the beam section is assumed as linear, which is reasonable for slender beams. The resulting generalized thermoelastic forces can be decomposed into thermal axial force and thermal bending moments, which can cause tension/compression and bending of the beam respectively. The dynamic equations of the beam element are then assembled into a flexible multibody system. Deployment analysis of a space mechanism with transient thermal load is studied with the new approach. Simulation result shows that thermoelasticity could cause static deformation of the final configuration as well as affect the external driving forces.

An efficient 3D incompatible element for the simulation of Flexible Multibody System (FMBS) is derived based on the principle of virtual work and the theory of continuum mechanics. The presented incompatible element uses absolute coordinates and internal parameters for the degrees of freedom and fixed the locking problem under the state of pure bending. Considering the geometric nonlinearities and using the Total Lagrangian Formulation, system dynamic equations are derived and then solved by the Backward Difference Formula (BDF) in conjunction with Newton-Raphson algorithm. Eigenvalue analysis and dynamic analysis of several numerical examples are presented to show the convergence of the 3D incompatible element and excellent performance in terms of accuracy and time efficiency comparing with standard linear and quadratic hexahedral elements.

Dynamic equations of viscoelastic bodies with fractional constitutive are derived base on the principle of virtual work and the theory of continuum mechanics. The three-dimensional fractional derivative viscoelastic constitutive model is implemented into the flexible multibody system (FMBS), using the 3D solid element based on the absolute nodal coordinate formulation (ANCF), which can exactly describe the geometric nonlinearities due to large rotation and large deformation. The BDF time integration scheme in conjunction with the Grünwald approximation of fractional derivative and the Newton-Raphson algorithm are used to solve the equations of motion. Several numerical examples are presented to demonstrate the use of the modeling procedure presented in this investigation and the effects of parameters in the fractional derivative model.

A new Region-based GAC (geodesic active contour) model was presented, which is the improvement of traditional GAC model. A new region-based signed pressure forces function was presented, which takes the place of the edge stopping function, and can efficiently solve the problem of segmentation of objects with weak edges or without edges. The model is implemented by level set method with a binary level set function to reduce the expensive computational cost of re-initialization of the traditional level set function. The proposed algorithm has been applied to images of different modalities with promising results, which are better than that of traditional GAC model and C-V model.

In this Letter, we report a Golay3 sparse-aperture telescope newly built in the Key Laboratory of Optical Engineering, Chinese Academy of Sciences and present the experimental results of enhanced resolution. The telescope consisting of 3 collector telescopes of 127 mm diameter can achieve a theoretical resolution corresponding to a monolithic aperture of 245 mm diameter. It is shown by the experimental results that the resolution is improved to 3.33 μrad with respect to the diffraction limit of 6.07 μrad for a single aperture using the Rayleigh criteria at 632 nm. The compact optical configuration and cophasing approach are also described.