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Space cameras play a pivotal role in various fields, such as astronomical exploration. When operating in orbit, these cameras encounter the relative motion between the target and the camera during the exposure, resulting in image motion, which affects the imaging quality. Therefore, it is necessary to compensate for this image motion. This paper investigates the in-orbit image motion compensation (IMC) method for space cameras with a long integration time based on a two-axis pointing platform. Firstly, the mechanical design of the camera is introduced. Secondly, the in-orbit IMC model for the camera is analyzed, and the angular motion needed for compensating for the image motion by the two-axis pointing platform are derived. Factors influencing the compensation accuracy are also analyzed. The effectiveness of the IMC model is verified through simulations. Finally, the in-orbit experimental results indicate that the energy concentration of the target star images obtained exceeded 70%, demonstrating excellent performance in space cameras and effectively enhancing imaging quality using IMC technology. [ABSTRACT FROM AUTHOR]

Barrier-function-based adaptive fast-terminal sliding-mode control approaches have been devised to enhance the precision of speed regulation of permanent magnet synchronous motors (PMSMs). Firstly, the speed loop utilizes fast-terminal sliding-mode control, which contributes to a faster convergence rate and enhances the robustness of the system. By adopting this control technique, the system can quickly reach the desired speed setpoint and effectively handle disturbances. Secondly, an adaptive law based on the barrier function is employed to adjust the control gain adaptively. The proposed adaptive law considers the magnitude of the disturbance and effectively mitigates chattering resulting from excessive switching gain. Unlike conventional control methods, the design of the adaptive fast-terminal sliding-mode control does not require attaining the upper limit of the lumped disturbances. Experimental results are presented to validate the proposed approach. These results demonstrate that the proposed method outperforms the conventional terminal sliding mode control technique in terms of handling both external and internal disturbances. [ABSTRACT FROM AUTHOR]

The Fourth Industrial Revolution, also known as Industrial 4.0, has greatly accelerated inter-connectivity and smart automation in industrial control systems (ICSs), which has introduced new challenges to their security. With the fast growth of the Internet of Things and the advent of 5G/6G, the collaboration of Artificial Intelligence (Al) and the Internet of Things (loT) in ICSs has also introduced lots of security issues as it highly relies on advanced communication and networking techniques. Frequent ICS security incidents have demonstrated that attackers have the ability to stealthily breach the current system defenses and cause catastrophic effects to ICSs. Thankfully, trusted computing technology, which has been a popular research topic in the field of information security in recent years, offers distinct advantages when applied to ICSs. In this paper, we first analyze the vulnerabilities of ICSs and the limitations of existing protection technologies. Then, we introduce the concept of trusted computing and present a security framework for ICSs based on Trusted Computing 3.0. Finally, we discuss potential future research directions. [ABSTRACT FROM AUTHOR]

With the rapid development of the Industrial Internet of Things (IIoT), programmable logic controllers (PLCs) are becoming increasingly intelligent, leading to improved productivity. However, this also brings about a growing number of security vulnerabilities. As a result, efficiently identifying potential security vulnerabilities in PLCs has become a crucial research topic for security researchers. This article proposes a method for fuzzing industrial proprietary protocols to effectively identify security vulnerabilities in PLCs' proprietary protocols. The aim of this study is to develop a protocol fuzzing approach that can uncover security vulnerabilities in PLCs' proprietary protocols. To achieve this, the article presents a protocol structure parsing algorithm specifically designed for PLC proprietary protocols, utilizing information theory. Additionally, a fuzzing case generation algorithm based on genetic algorithms is introduced to select test cases that adhere to the format specifications of the proprietary protocol while exhibiting a high degree of mutation. The research methodology consists of several steps. Firstly, the proposed protocol structure parsing algorithm is used to analyze two known industrial protocols, namely Modbus TCP and S7Comm. The parsing results obtained from the algorithm are then compared with the correct results to validate its effectiveness. Next, the protocol structure parsing algorithm is applied to analyze the proprietary protocol formats of two PLC models. Finally, based on the analysis results, the PLCs are subjected to fuzzing. Overall, the proposed protocol fuzzing approach, incorporating the protocol structure parsing algorithm and the fuzzing case generation algorithm, successfully identifies two denial-of-service vulnerabilities in the PLCs' proprietary protocols. Notably, one of these vulnerabilities is a zero-day vulnerability, indicating that it was previously unknown and undisclosed. [ABSTRACT FROM AUTHOR]

For space target images captured by a sky-based visible light camera, various conditions are influenced by the imaging system itself and the observation environment; these conditions include uneven image background intensity, complex noise, stray light composition, and diverse target forms. A mean wavelet transform algorithm is proposed. This algorithm initially performs mean filtering and wavelet transform filtering on the noise-containing space target images and then performs a wavelet inverse transform on the filtered results to generate the final image. The experimental results show that our algorithm has good denoising performance and can effectively maintain the image details. [ABSTRACT FROM AUTHOR]

The tensile creep of Al-5Cu-0.8Mg-0.15Zr-0.2Sc(-0.5Ag) was tested at 150–250 °C and 125–350 MPa, and the effect of Ag on the high-temperature creep of Al-Cu-Mg alloys was discussed. After the addition of Ag, the high-temperature creep performances of the alloy were significantly improved at 150 °C/300 MPa and 200 °C/(150 MPa, 175 MPa). Then, constitutive relational models of the alloy during high-temperature creep were built, and the activation energy was calculated to be 136.65 and 104.06 KJ/mol. Based on the thermal deformation mechanism maps, the high-temperature creep mechanism of the alloy was predicted. After the addition of Ag, the creep mechanism of the alloy at 150 °C transitioned from lattice diffusion control to grain boundary diffusion control. At 250 °C, the mechanism was still controlled by grain boundary slip, but as the stress index increased and after Ag was added, the alloy fractures lead to the formation of dimples, thus improving the high-temperature creep performance. [ABSTRACT FROM AUTHOR]

Tensile experiments were conducted for Al-7.0Zn-2.5Mg-2.0Cu-0.1Zr-0.2Sc alloy in different aging states (18 h, 24 h, 36 h) with temperature environments including room temperature, −10 °C and −30 °C. Comparative studies were made on the evolution of the precipitate phase in alloys at three kinds of aging times and the evolution of tensile properties in alloys under different ambient temperatures. The findings showed that the precipitates in Al-7.0Zn-2.5Mg-2.0Cu-0.1Zr-0.2Sc alloy were mainly in the GP zone after the solution + aging treatment η' phase, the secondary Al3 (Sc, Zr) phase and the θ' (Al2Cu) phase. As the aging time was prolonged, the η' phase gradually grew and the PFZ gradually widened. At the three test temperatures, the tensile strength (TS) and yield strength (YS) of the alloys both showed a trend of first increasing before decreasing with the extension of aging time, while the elongation (A) and section shrinkage (Z) showed a decreasing trend. As the test temperature decreased, the TS and YS of the alloys increased and the A and Z of the alloys decreased. At room temperature, alloys showed a ductile fracture mode, which changed to mixed ductile and brittle fracture with decreasing test temperature. [ABSTRACT FROM AUTHOR]

In recent years, with the upgrading of the attack technology, stealthy DoS jamming attacks have become the primary factor to threaten the security of Industrial Cyber-Physical Systems (ICPS). Considering the complex industrial scenarios of ICPS, which are influenced by a variety of external and internal interference, a H ∞ controller designing problem is studied in this paper for an ICPS which deploys a hybrid-triggered mechanism (HTM) in the wireless channel encountering stealthy DoS jamming attacks. By employing a compensation mechanism which is employed in the controller to mitigate the impacts of attacks, external disturbance, limited channel capacity, wireless channel noise, we establish a closed-loop system and prove the closed-loop system is mean square exponentially stable and can achieve the desired H ∞ disturbance rejection level theoretically. Finally, simulation examples are used to demonstrate effectiveness of the proposed H ∞ controller. [ABSTRACT FROM AUTHOR]

To guarantee that a spectrometer can obtain effective solar spectral data, it is important that the two-dimensional turntable that carries the spectrometer tracks the sun with high accuracy for long time periods, such that the sun is always near the center of the field of view of the spectrometer. However, there is an offset lag problem for the tracking sensor, leading to an increase in the sun-tracking error and inaccuracies in solar spectrum data. To mitigate this problem, an on-axis tracking control algorithm—based on the orbital motion model—is proposed in this paper. First, the sun-tracking model of the spectrometer is established based on the coordinate transformation method, and the analytical relationship between the adjustment angle of the turntable and the solar vector in the orbit system is given by means of the inverse kinematics solution of the target model. Then, the predictive filtering algorithm of the target model is derived to acquire the target position, based on which, the on-axis tracking control algorithm of the spectrometer system is realized to compensate the offset lag and increase the sun-tracking accuracy. Finally, the simulation analysis and experimental verification were performed under the actual working conditions of an orbit. The simulation results demonstrate that the root-mean-square (RMS) of the target position deviation decreased from 2.08″ to 0.77″ after prediction filtering, and the RMS of the tracking error decreased from 7.14″ to 0.97″. The RMS of an orbit's sun-tracking error decreased from 5.72″ to 1.43″ in the ground test. The simulation and experimental results verify that the algorithm proposed in this paper can improve the tracking accuracy of the spectrometer, providing a reference for the design of a spectrometer in orbit. [ABSTRACT FROM AUTHOR]

The quasi-static and low cycle fatigue tests of extruded 7075 Al alloy (Φ200 mm) were investigated in three directions: the extrusion direction (ED), the radial direction (RD), and 45° with ED (45°). Grain morphology analysis, texture measurement, and fatigue fracture characterization were conducted to discuss the relationship between microstructure and mechanical properties. The experimental results showed that the ED specimen had higher ultimate tensile strength (UTS) and low cycle fatigue (LCF) properties, which were mainly attributed to the following three causes. First, the grain boundaries (GBs) had an obvious effect on the crack growth. The number of GBs in the three directions was different due to the shape of the grains elongated along the ED. Second, the sharp <111> texture and the small Schmidt factor along the ED explained the higher ultimate tensile strength (UTS) of the ED specimens. Third, fatigue fracture observation showed that the ED specimen had a narrow fatigue striation spacing, which indicated that the plastic deformation of the ED specimen was the smallest in each cycle. In addition, two fatigue prediction models were established to predict the LCF life of extruded 7075 Al alloy, based on the life response behavior of the three directions under different strains. [ABSTRACT FROM AUTHOR]

The rotating backward extrusion (RBE) process, as a new severe plastic deformation (SPD) process, is based on conventional backward extrusion and rotation, which meets the requirement of modern industrial development with its high performance and production efficiency. However, there is little research on the microstructure evolution and texture modification of the RBE process. Thus, in this study, the effect of different rotating revolutions, e.g., n = 5, n = 10, and n = 50, on the microstructure and texture development for the RBE process based on the AZ80 magnesium (Mg) alloy were investigated at 653 K. The results disclose that the rotating revolution is an influencing processing parameter on the deformation of the RBE process. The grain refining ability is enhanced with the increase of the rotating revolutions, and the minimum grain size of the cup bottom, shearing zone, and cup wall can reach to 16.7 μm, 15.6 μm, and 13.0 μm, respectively, under the condition of n = 50. Furthermore, with the increase in the rotating revolutions, the microstructure of the alloy becomes more uniform and the proportion of dynamic recrystallization (DRX) is also increased. The maximum DRX fractions of the sample for the cup bottom and cup wall are 95.4% and 86.8%, respectively, at n = 50. The DRX mechanism of the RBE process is determined by the continuous DRX and discontinuous DRX. In addition, the texture can be significant weakened during the RBE process, especially at the cup bottom, where the maximum pole intensity can be reduced from 17.6 at n = 10 to 6.5 at n = 50, which can be attributed to the higher proportion of new DRXed grains whose orientations are more random compared with the deformed grains. [ABSTRACT FROM AUTHOR]

High-performance control of inertial stabilization imaging sensors (ISISs) is always challenging because of the complex nonlinearities induced by friction, mass imbalance, and external disturbances. To overcome this problem, a terminal sliding mode controller (TSMC) based on a novel exponential reaching law (NERL) method with a high-order terminal sliding mode observer (HOTSMO) is suggested. First, the TSMC based on NERL is adopted to improve system performance. The NERL incorporates the power term and switching gain term of the system state variables into the conventional exponential reaching law, and the convergent speed of the TSMC is accelerated. Then, an HOTSMO is designed, which considers the speed and lumped disturbances of the system as the observation object. The estimated disturbance is then provided as a compensation for the controller, which enhances the disturbance rejection ability of the system. Comparative simulation and experimental results show that the proposed method achieves the best tracking performance and the strongest robustness than PID and the traditional TSMC methods. [ABSTRACT FROM AUTHOR]

The current work systematically investigated the microstructure, texture evolution, and mechanical properties of MDFed Mg-13Gd-4Y-2Zn-0.5Zr (wt%) alloy (GWZ) on the condition of high and low temperature cycle deformation. The high and low temperature cycle deformation was proposed on the basis of the conventional multi-directional forging (MDF) at decreasing temperature and annealing treatment. As a new method, it was aimed to timely uniform the microstructure and strengthen magnesium (Mg) matrix during the deformation process. A low accumulative strain of 3 after 1 pass resulted in a bimodal microstructure with undynamic recrystallized (unDRXed) regions and dynamic recrystallized (DRXed) grains, while a high accumulative strain of 12 after 4 passes lead to a homogeneous microstructure with fine DRXed grains. According to the experimental results, it indicated that the average grain size of 63 μm after homogenization treatment at 520 was refined remarkably to 5.20 μm after 4 passes at 420 °C through high and low temperature cycle deformation. The area fraction of DRXed grains was increased to 98.4%, which can be regarded as achieving complete DRX after 4 passes. The grain refinement was mainly caused by particle stimulation nucleation (PSN) and mechanism. As the MDF passes and accumulative strain increased, the basal texture was weakened and transformed from a strong basal texture to a random distribution gradually. Compared with conventional MDF at decreasing temperature, the mechanical properties were enhanced effectively. After 4 passes, the ultimate tensile strength (UTS), tensile yield strength (TYS), and failure elongation (FE) were 405 MPa, 305 MPa, and 13.1%, respectively. [ABSTRACT FROM AUTHOR]

The effects of repetitive upsetting extrusion under different starting temperatures on the microstructure and texture of GWZK124 alloy were investigated. The results clearly showed that the particles and second phases induced dynamic recrystallization (DRX), which can be explained by the particle-stimulated nucleation (PSN) mechanism. It was shown that grain refinement during repetitive upsetting extrusion (RUE) is dominated by a complicated combination of continuous dynamic recrystallization and discontinuous dynamic recrystallization. The RUEed alloys under different starting temperatures exhibited a bimodal microstructure comprising fine DRXed grains with weak texture and coarse deformed grains with strong texture. The DRXed grains could weaken the texture. As the RUE starting temperature decreased, the average grain size increased and the volume fraction of DRXed grains decreased. [ABSTRACT FROM AUTHOR]

Repetitive upsetting extrusion (RUE) was applied to the as-homogenized Mg-12.0Gd-4.5Y-2Zn-0.4Zr (wt %) alloy at 773 K. The microstructure evolution of the alloy during RUE was investigated. The results indicated that almost all Mg5(Gd,Y,Zn) phases and fine-lamellar long-period stacking-ordered (LPSO) phases were dissolved into the matrix after homogenization treatment at 793 K for 16 h. After one RUE pass, dynamic recrystallization (DRX) occurred. During subsequent RUE passes (from one to three passes), average volume fractions of DRXed grains increased from 43.9% to 65.8%, and that of fine-lamellar and block-shaped LPSO phases gradually decreased. All samples exhibited a typical bimodal microstructure consisting of some initial grains containing fine-lamellar LPSO phases, but consisting mostly of fine-DRXed grains with a mean grain size of 6 μm. Because of an increase in the accumulated strains, the coarse grains were substituted with fine-DRXed grains, the grains were gradually refined, and the microstructure distribution became more homogeneous. [ABSTRACT FROM AUTHOR]

The low-cycle fatigue behavior of Al-9Si-4Cu-0.4Mg-0.3Sc alloy with different casting states was investigated by performing low-cycle fatigue tests and by means of observations and analysis with a scanning electron microscope (SEM) and a transmission electron microscope (TEM). It was found that the metal-mold cast and die-cast Al-9Si-4Cu-0.4Mg-0.3Sc alloys exhibited the cyclic stress response of strain hardening under all imposed total strain amplitudes. The cyclic deformation resistance and fatigue life of the metal-mold cast Al-9Si-4Cu-0.4Mg-0.3Sc alloy were lower than those of the die-cast Al-9Si-4Cu-0.4Mg-0.3Sc alloy. The plastic strain and elastic strain amplitudes of the metal-mold cast and die-cast Al-9Si-4Cu-0.4Mg-0.3Sc alloys were linearly related to the number of reversals to failure, which obeyed the Coffin-Manson and Basquin formulas, respectively. The results of TEM observation revealed that at all imposed total strain amplitudes, the cyclic deformation mechanisms of the metal-mold cast and die-cast Al-9Si-4Cu-0.4Mg-0.3Sc alloys were planar slip and wavy slip at the lower and higher strain amplitudes, respectively.

Geniposide (GE) is the main bioactive component of Gardeniae Fructus. The hepatotoxicity of geniposide limited clinical application. In order to get a new geniposide derivative that has less hepatotoxicity and still possesses the antidepressant activity, a new C-1 hydroxyl methylation derivative named methyl genipin (MG) was synthesized from geniposide. In the present study, we demonstrated that MG did not increase the liver index, alanine aminotransferase (ALT) and aspirate aminotransferase (AST). Histopathological examination suggested that no toxic damages were observed in rats treated orally with MG (0.72 mmol/kg). More importantly, a 7-day treatment with MG at 0.13, 0.26, and 0.52 mmol/kg/day could reduce the duration of immobility. It showed that the antidepressant-like effects of MG were similar to GE in the tail suspension test and the forced swim test. Furthermore, we found MG could be detected in the brain homogenate of mice treated orally with MG 0.52 mmol/kg/day for 1 day by HPLC. The area under the curve (AUC) of MG in the brain homogenate was enhanced to 21.7 times that of GE. The brain amount and distribution speed of MG were improved significantly after oral administration. This study demonstrated that MG possessed the antidepressant effects and could cross the blood-brain barrier, but had less hepatotoxicity.