Time-Delay Switch Attack on Networked Control Systems, Effects and Countermeasures

In recent years, the security of networked control systems (NCSs) has been an important challenge for many researchers. Although the security schemes for networked control systems have advanced in the past several years, there have been many acknowledged cyber attacks. As a result, this dissertation proposes the use of a novel time-delay switch (TDS) attack by introducing time delays into the dynamics of NCSs. Such an attack has devastating effects on NCSs if prevention techniques and countermeasures are not considered in the design of these systems. To overcome the stability issue caused by TDS attacks, this dissertation proposes a new detector to track TDS attacks in real time. This method relies on an estimator that will estimate and track time delays introduced by a hacker. Once a detector obtains the maximum tolerable time delay of a plant’s optimal controller (for which the plant remains secure and stable), it issues an alarm signal and directs the system to its alarm state. In the alarm state, the plant operates under the control of an emergency controller that can be local or networked to the plant and remains in this stable mode until the networked control system state is restored. In another effort, this dissertation evaluates different control methods to find out which one is more stable when under a TDS attack than others. Also, a novel, simple and effective controller is proposed to thwart TDS attacks on the sensing loop (SL). The modified controller controls the system under a TDS attack. Also, the time-delay estimator will track time delays introduced by a hacker using a modified model reference-based control with an indirect supervisor and a modified least mean square (LMS) minimization technique. Furthermore, here, the demonstration proves that the cryptographic solutions are ineffective in the recovery from TDS attacks. A cryptography-free TDS recovery (CF-TDSR) communication protocol enhancement is introduced to leverage the adaptive channel redundancy techniques, along with a novel state estimator to detect and assist in the recovery of the destabilizing effects of TDS attacks. The conclusion shows how the CF-TDSR ensures the control stability of linear time invariant systems

Orbital Polarization in Relativistic Density Functional Theory

The description of the magnetic properties of interacting many-particle systems has been one of the most important goals of physics. The problem is to derive the magnetic properties of such systems from quantum mechanical principles. It is well understood that the magnetization in an atom described by quantum numbers, spin (S), orbital (L), and total angular momentum (J) of its electrons. A set of guidelines, known as Hund's rules, discovered by Friedrich Hermann Hunds help us to determine the quantum numbers for the ground states of free atoms. The question ``to which extent are Hund's rules applicable on different systems such as molecules and solids?'' is still on the agenda. The main problem is that of finding the ground state of the considered system. Density functional theory (DFT) methods apparently are the most widely spread self-consistent methods to investigate the ground state properties. This is due to their high computational efficiency and very good accuracy. In the framework of DFT, usually the total energy is decomposed into kinetic energy, Coulomb energy, and a term called the exchange-correlation energy. Taking into account the relativistic kinetic energy leads to direct and indirect relativistic effects on the electronic structure of a solid. The most pronounced direct effect (although not the biggest in magnitude) is the spin-orbit splitting of band states. A well-known indirect relativistic effect is the change of screening of valence electrons from the nuclear charge by inner-shell electrons. One can ask that how relativistic effects come into play in ordinary density functional theory. Of course ordinary density functional theory does not include those effect. Four-current density functional theory (CDFT), the quantum electrodynamic version of the Hohenberg-Kohn theory is a powerful tool to treat relativistic effects. Although it is principally designed for systems in strong magnetic fields, CDFT can also be applied in situations where currents are present without external magnetic fields. As already pointed out by Rajagopal and Callaway (1973), the most natural way to incorporate magnetism into DFT is the generalization to CDFT. These authors, however, treated its most simple approximation, the spin density functional theory (SDFT), which keeps the spin current only and neglects completely correlation effects of orbital currents. By using the Kohn-Sham-Dirac (KSD) equation, spin-orbit coupling is introduced kinematically. The part of the orbital magnetism that is a consequence of Hund's second rule coupling is absent in this theory and there is not any more a one-to-one mapping of spin densities onto external fields. In solids, in particular in metals, the importance of Hund's second rule coupling (orbital polarization) and Hund's third rule (spin-orbit coupling) is usually interchanged in comparison to atoms. Thus, in applications of the relativistic CDFT to solids, the usual way has been to keep the spin-orbit coupling in the KSD equation (an extension to ordinary Kohn-Sham (KS) equation) and to neglect the orbital contribution to the total current density and approximate exchange-correlation energy functional with spin density only. This scheme includes a spontaneous exchange and correlation spin polarization. Orbital polarization, on the other hand, comes into play not as a correlation effect but also as an effect due to the interplay of spin polarization and spin-orbit coupling: In the presence of both couplings, time reversal symmetry is broken and a non-zero orbital current density may occur. Application of this scheme to 3d and 4f magnets yields orbital moments that are smaller than related experimental values by typically a factor of two. Orbital magnetism in a solid is strongly influenced by the ligand field, originating from the structural environment and geometry of the solid. The orbital moments in a solid with cubic symmetry are expected to be quenched if spin-orbit coupling is neglected. However, spin-orbit coupling induces orbital moments, accordingly. The relativistic nature of the spin-orbit coupling requires orbital magnetism to be treated within QED, and the treatment of QED in solids is possible in the frame of current density functional theory. The kinematic spin-orbit coupling is accounted for in many DFT calculations of magnetic systems within the LSDA. However, a strong deviation of the LSDA orbital moments from experiment is found in such approaches. To avoid such deviations, orbital polarization corrections would be desirable. In this Thesis, those corrections have been investigated in the framework of CDFT. After a short review for CDFT in Chapter 2, in Chapter 3, an "ad hoc" OP correction term (OPB) suggested by Brooks and Eriksson is given. This correction in some cases gives quite reasonable corrections to orbital moments of magnetic materials. Another OP correction (OPE), which has been introduced recently, was derived from the CDFT in the non-relativistic limit. Unfortunately, the program can only incompletely be carried through, as there are reasonable but uncontrolled approximations to be made in two steps of the derivation. Nevertheless, the result is quite close to the "ad hoc"ansatz. The calculated OPE energies for 3d and 4f free ions are in qualitative agreement with OPB energies. In Chapter 4, both corrections are implemented in the FPLO scheme to calculate orbital moments in solids. We found that both OPB and OPE corrections implemented in FPLO method, yield reasonably well the orbital magnetic moments of bcc Fe, hcp Co and fcc Ni compared with experiment. In Chapter 5, the effect of spin-orbit coupling and orbital polarization corrections on the spin and orbital magnetism of full-Heusler alloys is investigated by means of local spin density calculations. It is demonstrated, that OP corrections are needed to explain the experimental orbital moments. Model calculations employing one ligand field parameter yield the correct order of magnitude of the orbital moments, but do not account for its quantitative composition dependence. The spin-orbit coupling reduces the degree of spin polarization of the density of states at Fermi level by a few percent. We have shown that the orbital polarization corrections do not change significantly the spin polarization degree at the Fermi level. We also provide arguments that Co2FeSi might not be a half-metal as suggested by recent experiments. In Chapter 6, to understand recent XMCD data for Co impurities in gold, the electronic structure of Co impurities inside gold has been calculated in the framework of local spin density approximation. The orbital and spin magnetic moment have been evaluated. In agreement with experimental findings, the orbital moment is enhanced with respect to Co metal. On the other hand, internal relaxations are found to reduce the orbital moment considerably, whereas the spin moment is less affected. Both OPB and OPE yield a large orbital moment for Co impurities. However, those calculated orbital moments are almost by a factor of two larger than the experimental values. We also found that the orbital magnetic moment of Co may strongly depend on pressure

Sensorimotor control: computing the immediate future from the delayed present

Background The predictive nature of the primate sensorimotor systems, for example the smooth pursuit system and their ability to compensate for long delays have been proven by many physiological experiments. However, few theoretical models have tried to explain these facts comprehensively. Here, we propose a sensorimotor learning and control model that can be used to (1) predict the dynamics of variable time delays and current and future sensory states from delayed sensory information; (2) learn new sensorimotor realities; and (3) control a motor system in real time. Results This paper proposed a new time-delay estimation method and developed a computational model for a predictive control solution of a sensorimotor control system under time delay. Simulation experiments are used to demonstrate how the proposed model can explain a sensorimotor system?s ability to compensate for delays during online learning and control. To further illustrate the benefits of the proposed time-delay estimation method and predictive control in sensorimotor systems a simulation of the horizontal Vestibulo-Ocular Reflex (hVOR) system is presented. Without the proposed time-delay estimation and prediction, the hVOR can be unstable and could be affected by high frequency oscillations. These oscillations are reminiscent of a fast correction mechanism, e.g., a saccade to compensate for the hVOR delays. Comparing results of the proposed model with those in literature, it is clear that the hVOR system with impaired time-delay estimation or impaired sensory state predictor can mimic certain outcomes of sensorimotor diseases. Even more, if the control of hVOR is augmented with the proposed time-delay estimator and the predictor for eye position relative to the head, then hVOR control system can be stabilized. Conclusions Three claims with varying degrees of experimental support are proposed in this paper. Firstly, the brain or any sensorimotor system has time-delay estimation circuits for the various sensorimotor control systems. Secondly, the brain continuously estimates current/future sensory states from the previously sensed states. Thirdly, the brain uses predicted sensory states to perform optimal motor control

Immunohistochemical comparison of E-cadherin expression in oral lichen planus with and without dysplasia

Objectives E-cadherin is a transmembrane glycoprotein, which is responsible for cell adhesion and its expression decreases in dysplastic lesions. This study aimed to assess the expression of this marker in oral lichen planus (OLP) with and without dysplasia to assess its potential for use as a predictor of malignant transformation.Methods This descriptive, cross-sectional study was conducted on 44 OLP specimens using immunohistochemistry (IHC) by streptavidin- biotin technique. For this purpose, E-cadherin antibody was used and the intensity score (IS), proportional score (PS) and total score (TS) were calculated. Data were analyzed using SPSS version 21. The relationship between the intensity of expression of E-cadherin and dysplastic changes was assessed using the Mann Whitney U test. P < 0.05 was considered significant.Results The TS of E-cadherin expression was 3 to 6 and 3 in the superficial and deep layers of 100% of specimens with dysplasia, respectively. The TS of E-cadherin expression was 3 to 6 in the superficial layer of 82.5% of specimens and 3 in deep layers of 81.2% of specimens without dysplasia. According to the Mann Whitney U test, the expression of E-cadherin in the superficial (P = 0.90) and deep (P = 0.35) layers was not significantly different between the two groups of OLP with and without dysplasia.Conclusion No significant difference was found in the expression of E-cadherin in OLP specimens with and without dysplasia. It may be concluded that in contrast to other preneoplastic lesions, dysplastic changes of OLP do not follow other malignant transformation patterns in the oral mucosa

Examining the implementation of competency-based approach to increase the efficiency in Zahedan University of Medical Sciences

Today, intense competition and technological change upsurges the increasing pressure on organizations and their different ways of increasing the productivity of their workforces; this is what makes competency the most important part of a competitive environment. This study was designed to see whether implementing a competency-based performance management system resolve the problems that were inherent in the previous job-based system. Therefore, the aim of this study was to collect data from behavioral event interviews and methods of data analysis; and by presenting questionnaires to the experts and managers, our results were acquired about the role of merit in improving the efficiency and effectiveness. The results showed that all individuals confirmed that competency is the key elements of increasing the efficiency and productivity and they should be applied in all organization for designing and developing the competency –based orientations

An analysis of human resource strategic planning in Zahedan University of Medical Sciences by applying SWOT model

Nowadays, one of the most significant elements of organizations' success depends on the role played by human resources in such a way that organizations without motivated and energetic human resources are changing into a inefficient and inactive organization. In recent years, human resources assumed a pivotal position in organizations and is considered as a strategic factor in administering organization. The present research is conducted to develop optimal strategies of human resources in one of the country's organizations. The research data were collected through questionnaires, interviews with managers and experts of the organization as well as studying available reports. In order to develop strategies of human resource SWOT, analysis methods were used. Also, Delphi test was used from the initial steps till developing strategies. In the analysis of the research results, there were10 internal positive points (strengths) against 12 negative points and also we observed 7 external positive effects (opportunities) against 9 negative effects (threats). However, we observed a total of 17 positive points (strengths and opportunities) against 21 negative points (weaknesses and threats) as limitation and bottleneck. In the process of entering human resources, the organization under study has a good condition in terms of internal and external factors and is above average level. In the process of output and preserving human resources, the organization is not in a good condition in terms of external factors and is lower than average level; therefore, it is recommended that the organization emphasize aggressive strategies in the process of entering human resources and emphasize defensive strategies in the processes of preserving and output. The findings of the research indicate that the organization in question can improve its performance and functionality by successful implementation of the proposed strategies. According to SWOT model, the graph is curved toward strengths and opportunities; i.e. SO. Therefore our strategies should be SO or maximum or competitive-aggressive

An analysis of human resource strategic planning in Zahedan University of Medical Sciences by applying SWOT model

Nowadays, one of the most significant elements of organizations' success depends on the role played by human resources in such a way that organizations without motivated and energetic human resources are changing into a inefficient and inactive organization. In recent years, human resources assumed a pivotal position in organizations and is considered as a strategic factor in administering organization. The present research is conducted to develop optimal strategies of human resources in one of the country's organizations. The research data were collected through questionnaires, interviews with managers and experts of the organization as well as studying available reports. In order to develop strategies of human resource SWOT, analysis methods were used. Also, Delphi test was used from the initial steps till developing strategies. In the analysis of the research results, there were10 internal positive points (strengths) against 12 negative points and also we observed 7 external positive effects (opportunities) against 9 negative effects (threats). However, we observed a total of 17 positive points (strengths and opportunities) against 21 negative points (weaknesses and threats) as limitation and bottleneck. In the process of entering human resources, the organization under study has a good condition in terms of internal and external factors and is above average level. In the process of output and preserving human resources, the organization is not in a good condition in terms of external factors and is lower than average level; therefore, it is recommended that the organization emphasize aggressive strategies in the process of entering human resources and emphasize defensive strategies in the processes of preserving and output. The findings of the research indicate that the organization in question can improve its performance and functionality by successful implementation of the proposed strategies. According to SWOT model, the graph is curved toward strengths and opportunities; i.e. SO. Therefore our strategies should be SO or maximum or competitive-aggressive

An analysis of human resource strategic planning in Zahedan University of Medical Sciences by applying SWOT model

Nowadays, one of the most significant elements of organizations' success depends on the role played by human resources in such a way that organizations without motivated and energetic human resources are changing into a inefficient and inactive organization. In recent years, human resources assumed a pivotal position in organizations and is considered as a strategic factor in administering organization. The present research is conducted to develop optimal strategies of human resources in one of the country's organizations. The research data were collected through questionnaires, interviews with managers and experts of the organization as well as studying available reports. In order to develop strategies of human resource SWOT, analysis methods were used. Also, Delphi test was used from the initial steps till developing strategies. In the analysis of the research results, there were10 internal positive points (strengths) against 12 negative points and also we observed 7 external positive effects (opportunities) against 9 negative effects (threats). However, we observed a total of 17 positive points (strengths and opportunities) against 21 negative points (weaknesses and threats) as limitation and bottleneck. In the process of entering human resources, the organization under study has a good condition in terms of internal and external factors and is above average level. In the process of output and preserving human resources, the organization is not in a good condition in terms of external factors and is lower than average level; therefore, it is recommended that the organization emphasize aggressive strategies in the process of entering human resources and emphasize defensive strategies in the processes of preserving and output. The findings of the research indicate that the organization in question can improve its performance and functionality by successful implementation of the proposed strategies. According to SWOT model, the graph is curved toward strengths and opportunities; i.e. SO. Therefore our strategies should be SO or maximum or competitive-aggressive