Industrial control systems control and supervise our most important and critical infrastructures, such as power utilities, clean water plants and nuclear plants, as well as the manufacturing industries at the base of our economy. These systems are currently undergoing a transformation driven by the Industry 4.0 evolution, characterized by increased connectivity and flexibility. Consequently, the cybersecurity threat landscape for industrial control systems is evolving as well. Current strategies used for access control within industrial control systems are relatively rudimentary. It is evident that some of the emerging cybersecurity threats related to Industry 4.0 could be better mitigated using more fine-grained access control policies. In this article we discuss and describe a number of access control strategies that could be used within manufacturing systems. We evaluate the strategies in a simulation experiment, using a number of attack-scenarios. Moreover, a method is outlined for automatic policy-generation based on engineering-data, which is aligned with one of the best performing strategies.

Abstract This paper describes influences of heat input on geometry of GMAW fillet welds of unalloyed steel with thicknesses of 8 mm. Welding current and speed are varied, as parameters influencing heat input, while weld size, reinforcement, penetration, dilution and weld asymmetry are considered as geometry properties. All of them are obtained through measurements on macro-sections. Influence of heat input on geometry is presented through the model based on regression analysis.

This paper analyses Disturbance Observer- (DOb-) based robust force control systems in the discrete-time domain. The robust force controller is implemented using velocity and acceleration measurements. A DOb is employed in an inner-loop to achieve robustness, and another DOb, viz. Reaction Force Observer (RFOb), is employed in an outer-loop to estimate interaction forces and improve the performance of force control. First, the inner-loop is analysed. It is shown that the DOb works as a phase-lead/lag compensator tuned by the nominal design parameters in the inner-loop. The phase margin of the inner-loop controller and the bandwidth of the velocity-based (i.e., conventional) DOb are constrained not only by noise-sensitivity but also by the waterbed effect. This explains why we observe unstable responses as the bandwidth of the conventional DOb increases in practice. To eliminate the design constraint due to the waterbed effect, this paper proposes an acceleration-based DOb. Then, the robust force controller is analysed. It is shown that the design parameters of the RFOb have a notable effect on the stability of the robust force control system. For example, the robust force controller has a non-minimum phase zero (zeros) when the RFOb is not properly tuned. This may cause severe stability and performance problems when conducting force control applications. By using the stability and robustness analyses, this paper proposes new design tools which enable one to synthesize a high-performance robust force control system. Simulations and experiments are presented to validate the proposed analysis and synthesis methods.

This paper introduces a novel control approach for Doubly-Fed Induction Generator (DFIG) operating in island mode based on the cascaded control structure with disturbance estimation. The control of the DFIG is a challenging task due to its inherent nonlinearity, fast dynamics, and unpredictable disturbances acting on the system. The proposed control structure involves a nominal controller for plant and disturbance observer (DOB) in each of the inner and outer control loop. The first-order disturbance observers are designed to estimate the time-varying and unknown disturbances. With disturbance estimation, the nominal linear dynamics is obtained in both loops. This enables the same approach for designing controllers for the inner and outer loop which significantly simplifies implementation. The controllers are designed based on the demanded error dynamics and ensure stable operation of the system, while proposed DOBs estimate disturbances including external load. Finally, the effectiveness and quality of the proposed control structure were verified through numerical simulations in terms of external disturbances rejection and closed-loop tracking performance.

In this paper, the tradeoff between spectrum efficiency (SE) and energy efficiency (EE) is investigated in terms of interference management and power allocation for heterogeneous networks (HetNets) with non-orthogonal multiple access (NOMA). The EE and SE tradeoff is modeled as a multi-objective problem (MOP) under the maximum power and quality of service (QoS) constraints, which is non-convex. The MOP is relaxed into a convex single objective problem (SOP) by adopting a weighted sum strategy with the hypograph transformation. The SOP is solved in two steps. In the first step, we propose a power allocation technique based on non-cooperative (NC) game for EE and SE in NOMA HetNets. In the proposed NC game, the macro base station (MBS) and the small BSs (SBSs) compete with an equal priority in order to optimize their transmit powers towards maximizing the weighted sum of SE and EE. In the second step, a closed-form formula is proposed to control the power allocated to users taking into account both QoS constraint and successive interference cancellation (SIC) condition. From simulations, the proposed technique can, in some dedicated settings, considerably improve the tradeoff between EE and SE over conventional techniques.

......................................................................................................................... 6 Introduction .................................................................................................................... 7 Theory ............................................................................................................................ 9 Computational Details and Methodology .......................................................................... 13 Results and Discussion Gibbs Reaction Energies ...................................................................................... 16 Dipoles and First Hyperpolarizabilities ................................................................... 22 Gibbs Activation Energies and Thermal Half-Lives ................................................. 25 Wiberg Indices .................................................................................................... 29 Conclusions .................................................................................................................. 33 References .................................................................................................................... 34

The aim of this study is to investigate how various elements of digital content impact the behavioural engagement of the content’s users in the setting of Southeast Europe, which has recently experienced turbulence in its political and social interrelationships. Using the stimulus-organism-response (S-O-R) theory we develop a model that considers two types of stimuli: digital content tone (consisting of positive and negative valence) and digital content substance, as well as two types of behavioural responses: opens and clicks on the content. Research is conducted in six countries over a period of three years, investigating objective users’ behavioural indicators for a regional newsletter. The results show digital content tone impacts users’ response in terms of opens and that this effect differs across the region. Furthermore, we show that the digital content substance is significantly related to number of clicks on the newsletter content and that this effect is curvilinear for the number of news features and number of calls, while it is positive and linear for the stakeholder/keywords mentions. Theoretical and managerial implications of the study are elaborated and discussed.