Industrial control network (ICN) is characterized by real-time responsiveness and reliability, which plays a key role in increasing production speed, rational and efficient processing, and managing the production process. Despite tremendous advantages, ICN inevitably struggles with some challenges, such as malicious user intrusion and hacker attack. To detect malicious intrusions in ICN, intrusion detection systems have been deployed. However, in ICN, network traffic data is equipped with characteristics of large scale, irregularity, multiple features, temporal correlation and high dimensionality, which greatly affect the efficiency and performance. To properly solve the above problems, we design a new intrusion detection method for ICN. Specifically, we first design a novel neural network model called associative recurrent network (ARN), which can properly handle the relationship between past moment hidden state and current moment information. Then, we adopt ARN to design a new intrusion detection method that can efficiently and accurately detect malicious intrusions in ICN. Subsequently, we demonstrate the high efficiency of our proposed method through theoretical computational complexity analysis. Finally, we develop a prototype implementation to evaluate the accuracy. The experimental results prove that our proposed method has sate-of-the-art performance on both the ICN dataset SWaT and the conventional network traffic dataset UNSW-NB15. The accuracies on the SWaT dataset and the UNSW-NB15 dataset reach 95.48% and 97.61%, respectively.
When the actual displacement of viscous damper exceeds the stroke limit, excessive pounding force may be generated, resulting in damage to the damper. To address this issue, a novel viscous damper with variable stiffness, simple processing, and good economy is proposed. First, the load-displacement relation of the novel viscous damper is established through theoretical analysis and experimental studies. Second, numerical simulations and a series of parametric analyses are conducted to analyze the pounding mitigation effect of the proposed damper. Third, real-time hybrid simulation (RTHS) for considering the pounding effect of the novel viscous damper is presented. Finally, design recommendations for the pounding mitigation design of the novel viscous damper are given. The results show that the novel viscous damper effectively reduces the amplitudes of the pounding force and acceleration by 25% and 24%, respectively. The Fourier power of acceleration decreases in the region from 0.6 Hz to 3.3 Hz. The results of RTHS demonstrate that the real-time hybrid testing system can effectively simulate the pounding effect of the proposed damper. However, the normalized error peak value of velocity between RTHS and the reference result exceeds 10%, indicating that the proposed damper considering the pounding effect imposes new requirements to the real-time hybrid testing method.
A novel shaking table substructure testing method that includes interaction forces determined by actuator forces and shaking table dynamic parameters is proposed and validated. The seismic performance of a storage tank that incorporates soil-structure interactions is investigated by the method proposed in this article. The experimental results show that the proposed shaking table substructure testing method is an efficient alternative method of evaluating the seismic performance of a storage tank that incorporates soil-structure interactions. The experimental results show that the influence of the soil-structure interactions increases as the stiffness of the foundation soil decreases, which was demonstrated by the results showing that the displacement and acceleration responses of the storage tank decrease as the stiffness of the foundation soil decreases. Moreover, the influence of the soil-structure interactions increases as the liquid height increases, which was illustrated by the decreased displacement responses of the storage tank with increases in the liquid height. The maximum acceleration response of the storage tank occurred at the liquid surface height.
In this paper, a digital precision assembly method is proposed to solve the problem that the assembly quality of piston accumulator sealing pair is not controllable. To solve this problem, the assembly-force prediction model of the sealing structures was established, and a finite element nonlinear simulation method was adopted to simulate the assembly process of the sealing pair. The influence of friction coefficient, tolerances and other factors on the assembly-force was analyzed by combining simulation and practical application, and the envelope range of the assembly-force curves of the X-shape sealing ring and the polytetrafluoroethylene (PTFE) retaining ring was obtained under various influencing factors. By comparing the quantified assembly-force collected in the actual assembly process of automated press-fitting equipment and the envelope range, the assembly quality of the sealing structure in the assembly process can be judged in real-time.
Real-time hybrid simulation (RTHS) has become a recognized methodology for isolating and testing complex, rate-dependent structural components and devices to understand their behavior and to evaluate their ability to improve the performance of structures exposed to severe dynamic loading. Although RTHS is efficient in its utilization of equipment and space compared with conventional testing techniques, the laboratory resources may not always be available in a single testing facility to conduct large-scale experiments. Consequently, distributed systems, capable of connecting multiple RTHS setups located at several geographically distributed facilities through appropriate information exchange, become desirable. This study presents a distributed RTHS (dRTHS) platform that enables the integration of geographically distributed physical and numerical components across the Internet. The essential capabilities needed to establish such a dRTHS platform are discussed, including the communication architecture, network components, and connection reliability. One significant challenge for conducting successful dRTHS is sustaining real-time communication between test sites. To accommodate realistic network delays due to variations in the Internet service, a Smith predictor-based delay compensation algorithm that includes a network time delay estimator is developed. A series of numerical and experimental studies is conducted to verify the platform and to quantify the impact of uncertainties present in a typical distributed system. Through an evaluation of the results, it is demonstrated that dRTHS is feasible for coupling laboratory capabilities and is a viable alternative to traditional testing techniques.
The temperature coefficients of remanence and coercivity of Sm 2 Co 17 magnets are optimized by Dy 88 Cu 12 liquid phase doping. Dy 88 Cu 12 alloy and Sm 0.6 Gd 0.1 Dy 0.3 (Co 0.695 Fe 0.2 Cu 0.08 Zr 0.025 ) 7.8 alloy is chosen as the liquid phase and main phase, respectively. With different Dy 88 Cu 12 addition, several Sm 2 Co 17 magnets with spin-reorientation-transition cell boundary phase were prepared. The thermal stability indicates that all the magnets possess low remanence temperature coefficient above room temperature with minor Dy 88 Cu 12 alloy doping, while the positive coercivity temperature coefficient phenomenon appears. It is conducive to optimize the temperature coefficients of remanence and coercivity in Sm 2 Co 17 magnets synchronously. The magnet with 6 wt.% Dy 88 Cu 12 doping depicted best magnetic properties of B r =7.796 kGs, H cj =8.03 kOe, ( BH ) max = 13.45 MGOe, α (RT-100°C) ≈ 0.0072%/°C, β (RT-100°C) ≈ 0.0274%/°C. The coercivity temperature coefficient is an order of magnitude lower than no liquid phase doped.
Recently, SmCo5 was found to be capable of forming amorphous shear bands to induce dislocation-free plastic deformation at large strains. The formation of shear band is energetically more favorable compared to cracking and the small density variation in shear bands is not likely to induce high local stress that assists crack opening. However, the related mechanism of crystalline-to-amorphous transition during shear-band formation at the atomic level remains unclear. In this paper, the shear deformation of SmCo5 is investigated by molecular dynamics simulations and we discuss the behavior of shear-band formation by exploring the atomic packing in the interfacial zone between crystal matrix and shear band. The stress-strain curves of SmCo5 show anisotropy with respect to formation of amorphous shear band. The analysis of atomic packing indicates that the behavior of Sm is critical to the atomistic amorphization path and thus accounts for the mechanical anisotropy of the material. Temperature calculations show that the material is not subject to shear melting during deformation that would otherwise lead to embrittlement.
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