Concept Of Structural Control Research Articles

Total network controllability analysis discovers explainable drugs for Covid-19 treatment

BackgroundThe active pursuit of network medicine for drug repurposing, particularly for combating Covid-19, has stimulated interest in the concept of structural controllability in cellular networks. We sought to extend this theory, focusing on the defense rather than control of the cell against viral infections. Accordingly, we extended structural controllability to total structural controllability and introduced the concept of control hubs. Perturbing any control hub may render the cell uncontrollable by exogenous stimuli like viral infections, so control hubs are ideal drug targets.ResultsWe developed an efficient algorithm to identify all control hubs, applying it to a largest homogeneous network of human protein interactions, including interactions between human and SARS-CoV-2 proteins. Our method recognized 65 druggable control hubs with enriched antiviral functions. Utilizing these hubs, we categorized potential drugs into four groups: antiviral and anti-inflammatory agents, drugs acting on the central nervous system, dietary supplements, and compounds enhancing immunity. An exemplification of our approach’s effectiveness, Fostamatinib, a drug initially developed for chronic immune thrombocytopenia, is now in clinical trials for treating Covid-19. Preclinical trial data demonstrated that Fostamatinib could reduce mortality rates, ICU stay length, and disease severity in Covid-19 patients.ConclusionsOur findings confirm the efficacy of our novel strategy that leverages control hubs as drug targets. This approach provides insights into the molecular mechanisms of potential therapeutics for Covid-19, making it a valuable tool for interpretable drug discovery. Our new approach is general and applicable to repurposing drugs for other diseases.

A new perspective into torsional inelastic response of actively controlled irregular multistorey buildings

The nonlinear dynamics of irregular structures is influenced by both local and global torsional effects. In order to capture the inelastic structural response, the concept of plastic hinges is one of the most used tools due to its numerical efficiency. However, the combined effect of bending and torsion into the inelastic domain is scarcely illustrated in literature. In this paper, the recently developed 3D Force Analogy Method is augmented with an algorithm to consider axial force – biaxial bending moment –torque interaction. A structure having both plan and elevation irregularities is considered as a case study to illustrate the benefits of the proposed algorithm. The structural control concept is further implemented in the attempt to improve structural performance of irregular structures. A non-commercial Matlab/Simulink code is developed for the scopes of this paper.

Seismic Performance of H-Shaped Steel Column with Replaceable Slip Friction Joints

Based on the concept of structural damage control, a beam-through steel frame system with continuous columns was constructed. Replaceable connectors were set at both ends of an H-shaped steel column to connect the beam with high-strength bolts. In this study, three specimens were designed and fabricated, that is, a standard H-shaped column, an H-shaped column with replaceable connectors at the bottom of the column, and an H-shaped column with replaceable connectors at both ends. Low-circumferential reciprocal loading tests were carried out to analyse the influence of the location of replaceable slip friction joints on the seismic performance of steel columns. Results showed that the H-shaped steel column with replaceable slip friction joints at both ends slipped during the loading process, as expected. The test hysteresis curve was full, and the skeleton curve did not drop significantly; thus, the column demonstrated satisfactory seismic performance. The steel column was not significantly damaged or deformed, and connectors could be reset and replaced after an earthquake to achieve post-earthquake repair. The effect of the thickness of the horizontal limbs of the connectors on the seismic performance of the H-shaped column with replaceable connectors at both ends was analysed using finite element simulation. The results revealed that the reasonable setting of the thickness of the horizontal limbs of the connectors can ensure the frictional energy dissipation capacity of the connectors and achieve the expected damage control.

Control on Pt-containing ordered honeycomb mesoporous nanostructures via self-assembly of block copolymer

Control on the mesoporous nanostructures with uniform-sized and well-arranged mesopores can provide enhanced surface areas and mechanical properties, which are preferred for the development of energies, sensors, and electro-optical devices. Herein, Pt-containing ordered honeycomb (Pt/OHC) nanocomposites with regularly arranged mesopores were synthesized via self-assembly of polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) block copolymers (BCPs), following mechanism study of morphological evolution, concept of structural control, potential in catalyst application, and exploration of various metals. Particularly, it was found that the self-assembly of BCP directed the ordered arrangement of the mesopores, whereas the P4VP blocks incorporated Pt and precisely positioned it on the pore walls and on the outer surface of the honeycomb matrix. Mono- to multi-layered Pt/OHCs could be generated by controlling the thicknesses of the self-assembled pristine templates, and the average diameters of the mesopores could be varied from 12 nm to 40 nm by tuning the PS:P4VP block mass ratios. The obtained Pt/OHC demonstrated promising application as electrocatalysts in hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR), for which an overpotential of 39 mV at current density of 10 mA/cm2 (η10) and a high half wave potential (E1/2) of 0.87 V (vs. RHE), respectively, were observed in acidic media. In addition, the strategy developed here could be expanded for other metals, such as Au and Ir, to be incorporated into the ordered honeycomb matrix, providing a robust method to synthesize metal-containing mesoporous nanomaterials. With this work, we aim to offer an insight of designing ordered mesoporous nanocomposites, a concept of control over the mesoporous nanostructures, and a potential for their application in electrocatalysts.

WITHDRAWN:Control on Pt-Containing Ordered Honeycomb Mesoporous Nanostructures via Self-Assembly of Block Copolymer

Control on the mesoporous nanostructures with uniform-sized and well-arranged mesopores can provide enhanced surface areas and mechanical properties, which are preferred for the development of energies, sensors, and electro-optical devices. Herein, Pt-containing ordered honeycomb (Pt/OHC) nanocomposites with regularly arranged mesopores were synthesized via self-assembly of polystyrene- block -poly(4-vinylpyridine) (PS- b -P4VP) block copolymers (BCPs), following mechanism study of morphological evolution, concept of structural control, potential in catalyst application, and exploration of various metals. Particularly, it was found that the self-assembly of BCP directed the ordered arrangement of the mesopores, whereas the PVP blocks incorporated Pt and precisely positioned it on the pore walls and on the outer surface of the honeycomb matrix. Mono- to multi-layered Pt/OHCs could be generated by controlling the thicknesses of the self-assembled pristine templates, and the average diameters of the mesopores could be varied from 12 nm to 40 nm by tuning the PS:P4VP block mass ratios. The obtained Pt/OHC demonstrated promising application as electrocatalysts in hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR), for which an overpotential of 39 mV at current density of 10 mA/cm 2 (η 10 ) and a high half wave potential ( E 1/2 ) of 0.87 V (vs. RHE), respectively, were observed in acidic media. In addition, the strategy developed here could be expanded for other metals, such as Au and Ir, to be incorporated into the ordered honeycomb matrix, providing a robust method to synthesize metal-containing mesoporous nanomaterials. With this work, we aim to offer an insight of designing ordered mesoporous nanocomposites, a concept of control over the mesoporous nanostructures, and a potential for their application in electrocatalysts. Pt-containing ordered honeycomb (Pt/OHC) nanocomposites were synthesized via self-assembly of PS- b -P4VP block copolymers (BCPs), following mechanism study of morphological evolution, concept of structural control, potential in electrocatalyst application, and exploration of various metals. With this work, we aim to offer some insights in designing and controlling on the mesoporous nanostructures and to provide a facile method to synthesize mesoporous metallic nanocomposites with advanced performance for potential application in electrocatalysts.

Structural Target Controllability of Brain Networks in Dementia.

Controlling the dynamics of large-scale neural circuits might play an important role in aberrant cognitive functioning as found in Alzheimer's disease (AD). Analyzing the disease trajectory changes is of critical relevance when we want to get an understanding of the neurodegenerative disease evolution. Advanced control theory offers a multitude of techniques and concepts that can be easily translated into the dynamic processes governing disease evolution at the patient level, treatment response evaluation and revealing some central mechanisms in brain connectomic networks that drive alterations in these diseases. Two types of controllability - the modal and average controllability - have been applied in brain research to provide the mechanistic explanation of how the brain operates in different cognitive states. In this paper, we apply the concept of target controllability to structural (MRI) connectivity graphs for control (CN), mild cognitive impairment (MCI) and Alzheimer's disease (AD) subjects. In target controllability, only a subset of the network states are steered towards a desired objective. We show the graph-theoretic necessary and sufficient conditions for the structural target controllability of the above-mentioned brain networks and demonstrate that only local topological information is needed for its verification. Certain areas of the brain and corresponding to nodes in the brain network graphs can act as drivers and move the system (brain) into specific states of action. We select first the drivers that ensures the controllability of these networks and since they do not represent the smallest set, we employ the concept of structural target controllability to determine those nodes that can steer a collection of states being representative for the transitions between CN, MCI and AD networks. Our results applied on structural brain networks in dementia suggest that this novel technique can accurately describe the different node roles in controlling trajectories of brain networks and being relevant for disease evolution.

A Graphical Characterization of Structurally Controllable Linear Systems With Dependent Parameters

One version of the concept of structural controllability defined for single-input systems by Lin and subsequently generalized to multi-input systems by others, states that a parameterized matrix pair $(A, B)$ whose nonzero entries are distinct parameters, is structurally controllable if values can be assigned to the parameters which cause the resulting matrix pair to be controllable. In this paper the concept of structural controllability is broadened to allow for the possibility that a parameter may appear in more than one location in the pair $(A, B)$. Subject to a certain condition on the parameterization called the "binary assumption", an explicit graph-theoretic characterization of such matrix pairs is derived.

NetControl4BioMed: a pipeline for biomedical data acquisition and analysis of network controllability

BackgroundNetwork controllability focuses on discovering combinations of external interventions that can drive a biological system to a desired configuration. In practice, this approach translates into finding a combined multi-drug therapy in order to induce a desired response from a cell; this can lead to developments of novel therapeutic approaches for systemic diseases like cancer.ResultWe develop a novel bioinformatics data analysis pipeline called NetControl4BioMed based on the concept of target structural control of linear networks. Our pipeline generates novel molecular interaction networks by combining pathway data from various public databases starting from the user’s query. The pipeline then identifies a set of nodes that is enough to control a given, user-defined set of disease-specific essential proteins in the network, i.e., it is able to induce a change in their configuration from any initial state to any final state. We provide both the source code of the pipeline as well as an online web-service based on this pipeline http://combio.abo.fi/nc/net_control/remote_call.php.ConclusionThe pipeline can be used by researchers for controlling and better understanding of molecular interaction networks through combinatorial multi-drug therapies, for more efficient therapeutic approaches and personalised medicine.

Deployment behavior control using cables and bi-shape memory alloy convex tape booms

This study aims to demonstrate the synchronous and stable deployment of a newly proposed boom system that consists of cables, a rotary damper, and shape memory alloy with a memorized convex tape shape. Through a shaft, a rotary damper is connected to a reel, and cables wound around the reel are connected to the shape memory alloy boom tips. The deployed part consists of bi-shape memory alloy convex tape booms in which two shape memory alloy convex tapes are combined to form a convex lens cross section, and the outside of the bi-shape memory alloy convex tape is wrapped by a sheet-type heater and polyimide film. The boom is deployed using only the shape recovery force of the shape memory alloy. By installing cables and a rotary damper, the deployment behavior of each boom is controlled, and each boom is deployed synchronously owing to the resistance force of the damper to a leading deploy boom. Moreover, the structural stiffness control concept of the proposed shape memory alloy bi-convex tape boom is discussed considering that Young’s modulus becomes almost half in the martensitic phase.

Predictive Smooth Variable Structure Filter for Attitude Synchronization Estimation During Satellite Formation Flying

In this paper, a novel predictive smooth variable structure filter (PSVSF) is presented for attitude synchronization during satellite formation flying (SFF). The strategy is proposed based on variable structure control concept and applies to any nonlinear system with modeling errors. Because the modeling errors in the PSVSF are not restricted to Gaussian noise only, the technique can deal with various kinds of uncertainties, parameter variations, or noises. It also has low computational burden; therefore, it is more general than other nonlinear estimation methods. Sufficient conditions to analyze the stability and characteristics of the PSVSF are presented. Simulations are performed to demonstrate the accuracy, robustness, and stability of the proposed PSVSF for the attitude synchronization estimation of the SFF system.

PERFORMANCE EVALUATION OF LEAD RUBBER ISOLATORS UNDER SEISMIC LOADS

Earthquake is the natural phenomenon that occurs due to sudden movement of the earth surface, releasing tremendous amount of energy which proves to be a curse to the structural integrity and hence to the mankind. In order to safeguard the structural integrity, from the past few decades’ ductility method has been adopted. Ductility method ensures the life safety but structural integrity is not ensured. Hence in order to enhance the structural safety, many structural control concepts have been developed in recent times. Base isolation, Seismic damper etc are some of the structural control concepts which are being used widely nowadays. Base isolation is a passive type of energy dissipation system in which the superstructure and substructure are decoupled by a rubber media known as isolators. The basic principle behind the base isolation system is to elongate the fundamental period of the structure; thereafter the seismic energy transmitted to the structure will be significantly reduced. Thus the superstructure acts as a rigid body and damages to the non-structural elements are also reduced. In the present study, a G+10 reinforced concrete structure is considered, 4 x 4 bays, 5 m in both directions. Non-linear time history analysis of the building is carried out by using SAP2000 computer package. Analysis is carried out for time history records of zone V (confirming to BIS) and El-Centro (N-S component).

Unscented predictive variable structure filter for satellite attitude estimation with model errors when using low precision sensors

For the satellite attitude estimation problem, the serious model errors always exist and hider the estimation performance of the Attitude Determination and Control System (ACDS), especially for a small satellite with low precision sensors. To deal with this problem, a new algorithm for the attitude estimation, referred to as the unscented predictive variable structure filter (UPVSF) is presented. This strategy is proposed based on the variable structure control concept and unscented transform (UT) sampling method. It can be implemented in real time with an ability to estimate the model errors on-line, in order to improve the state estimation precision. In addition, the model errors in this filter are not restricted only to the Gaussian noises; therefore, it has the advantages to deal with the various kinds of model errors or noises. It is anticipated that the UT sampling strategy can further enhance the robustness and accuracy of the novel UPVSF. Numerical simulations show that the proposed UPVSF is more effective and robustness in dealing with the model errors and low precision sensors compared with the traditional unscented Kalman filter (UKF).

Adaptive Predictive Variable Structure Filter for Attitude Synchronization Estimation

In this paper, a novel Predictive Variable Structure Filter (PVSF) and its adaptive deformation (APVSF) are presented for attitude synchronisation during Satellite Formation Flying (SFF). The PVSF is proposed based on the variable structure control concept and applied to any nonlinear system with model errors. The model errors in the PVSF need not satisfy the assumption of Gaussian white noise; therefore, it has advantages in dealing with various kinds of uncertainties, parameter variations or noises. Then, the APVSF is also presented to adjust the smoothing boundary layer of PVSF by minimising the Mean-Square Error (MSE). Simulations are performed to demonstrate the accuracy, robustness, and stability of the proposed methodologies for the attitude synchronisation estimation of the SFF system.

Minimal set of nodes to control the dynamics of biological neuronal networks

Controlling the dynamics of biological neuronal network (BNNs) is of great importance for both understanding the brain and for developing means to control brain disease related aberrant activity. In the last decade, the relationship among node properties, network structure and network dynamics has become clearer and several neuron and network properties could be used to control the network dynamics. Designing appropriate control inputs would require selective manipulation of the control variable in each node. However, the large size of BNNs and scarcity of resources do not allow control of all individual nodes by external means. Therefore, there is a need to identify a much smaller number of influential nodes that are sufficient to drive the activity dynamics of the entire BNN to a desired state. Here, we used the concept of structural controllability [1] to identify a small set of influential nodes, control nodes, for synthetic and experimental networks. The later includes large-scale connectivity of macaque cortical regions [2], meso-scale connectome of a mouse brain [3] and the neuronal connectivity of C. elegans [4]. We investigated the effect of random and systematic edge pruning on the number of these control nodes. Moreover, We showed that there is a power law or exponential dependence between the number of control nodes and the average degree of many networks. Finally, we used a simplified network of the basal ganglia to qualitatively show that few control nodes can indeed drive the network dynamics to a desired state. While every sub-network could be used as a control node or sensor, each node is different in terms of the required stimulation pattern, stimulation energy and time to reach the desired dynamical state.

Reduction of Structural Vibrations by Passive and Semiactively Controlled Friction Dampers

Reduction of structural vibrations is of major interest in mechanical engineering for lowering sound emission of vibrating structures, improving accuracy of machines, and increasing structure durability. Besides optimization of the mechanical design or various types of passive damping treatments, active structural vibration control concepts are efficient means to reduce unwanted vibrations. In this contribution, two different semiactive control concepts for vibration reduction are proposed that adapt to the normal force of attached friction dampers. Thereby, semiactive control concepts generally possess the advantage over active control in that the closed loop is intrinsically stable and that less energy is required for the actuation than in active control. In the chosen experimental implementation, a piezoelectric stack actuator is used to apply adjustable normal forces between a structure and an attached friction damper. Simulation and experimental results of a benchmark structure with passive and semiactively controlled friction dampers are compared for stationary narrowband excitation. For simulations of the control performance, transient simulations must be employed to predict the achieved vibration damping. It is well known that transient simulation of systems with friction and normal contact requires excessive computational power due to the nonlinear constitutive laws and the high contact stiffnesses involved. However, commercial finite-element codes do not allow simulating feedback control in a general way. As a remedy, a special simulation framework is developed which allows efficiently modeling interfaces with friction and normal contact by appropriate constitutive laws which are implemented by contact elements in a finite-element model. Furthermore, special model reduction techniques using a substructuring approach are employed for faster simulation.

Concept of Locomotion Mobile Undercarriage Structure Control for the Path Tracking

The article deals with the proposal structure of undercarriages mobile robot GTR 2010 control. Functional model of the undercarriages mobile robot GTR2010 should be able to carry out active tracking of desired path for achieving a goal and get over obstacles in unstructured environments.

Variable Structure System with Sliding Mode Controller

This paper describes the application of sliding mode variable structure control (SMVSC) concept for DC motor position control. A mathematical procedure for determining the values of the gains of variable structure system (VSS) controller (a, P) and the slope of switching line (c) are mentioned and obtained mathematically but optimized values, also, achieved by using MATLAB/Simulink design optimization toolbox - signal constraint by applying gradient descent optimization method. The proposed control scheme is derived, simulated and tested thoroughly by using MATLAB/Simulink package software Ver. 7.10/Version 7.5 (R2010a) respectively. The control-system schematics are given and sample results are shown for three types of controllers (Proportional (P), three terms PID and sliding mode variable structure controllers). The SMVSC simulation should be of interest to design engineers who wish to demonstrate and investigate sophisticated position-control methods and their applications. This simulation may also serve as a basis for further applications of SMVSC in other engineering fields.

The Application of Resettable Device to Semi-Active Tuned Mass Damper Building Systems for Multi-level Seismic Hazard Mitigation

An innovative multi-story Semi-Active Tuned Mass Damper (SATMD) building system is proposed to control seismic response of existing structures. The application of adding new stories as large tuned mass and semi-active (SA) resettable actuators as central features of the control scheme is derived. For the effective control of the structures, the optimal tuning parameters are considered for the large mass ratio, for which a previously proposed equation is used and the practical optimal stiffness is allocated to the actuator stiffness and rubber bearing stiffness. A two-degree-of freedom (2-DOF) model is adopted to verify the principal efficiency of the suggested structural control concept. The simulations for this study utilizes the three ground motions, from SAC project, having probability of exceedance of 50% in 50 years, 10% in 50 years, and 2% in 50 years for the Los Angeles region. 12-story moment resisting frames, which are modified as '12+2' and '12+4' story structures, are investigated to assess the viability and effectiveness of the system that aims to reduce the response of the buildings to earthquakes. The control ability of the SATMD scheme is compared to that of an uncontrolled and an ideal Passive Tuned Mass Damper (PTMD) building system. From the performance results of suggested '12+2' and '12+4' story retrofitting case studies, SATMD systems shows significant promise for application of structural control where extra stories might be added.

Experimental investigation of different active noise control concepts applied to a passenger car equipped with an active windshield

The main purpose of this work is the implementation and experimental investigation of different active structural acoustic control (ASAC) concepts for the reduction of interior noise in an automobile passenger compartment. For the control experiments, a medium-class test car was used, which had been equipped with an active windshield. The active windshield consists of the serial-production laminated glass pane augmented with piezoceramic patch-transducers applied to the blackened rim of the windshield. A multi-reference test provided measurement data for the identification of a local discrete-time state-space model (SSM). The subsequent acquisition of frequency response functions (FRF) by way of using the same actuators but measuring on a much finer grid provided the database for the formulation of a least-squares problem to derive a global system model. Based on the local and global discrete-time SSMs, different controllers were designed and experimentally realized. The comparison of the vibration levels in open- and closed-loop showed a global reduction of 5–7dB in the acoustically relevant frequency band containing the second and third structural resonance of the windshield system. The occurrence of complex operational deflection shapes (ODS) was identified as the main limitation concerning the disturbance rejection of the active system. The acoustic performance of the ASAC system is reflected in a reduction up to 15dB in sound pressure level (SPL).

Influence of time delay and saturation capacity to the response of controlled structures under earthquake excitations

During the last thirty years many structural control concepts have been proposed for the reduction of the structural response caused by earthquake excitations. Their research and implementation in practice have shown that seismic control of structures has a lot of potential but also many limitations. In this paper the importance of two practical issues, time delay and saturation effect, on the performance of controlled structures, is discussed. Their influence, both separately and in interaction, on the response of structures controlled by a modified pole placement algorithm is investigated. Characteristic buildings controlled by this algorithm and subjected to dynamic loads, such as harmonic signals and actual seismic events, are analyzed for a range of levels of time delay and saturation capacity of the control devices. The response reduction surfaces for the combined influence of time delay and force saturation of the controlled buildings are obtained. Conclusions regarding the choice of the control system and the desired properties of the control devices are drawn.