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Publications in other journals ranked by Ministry of Science and Higher Education
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Affiliation to IPPT PAN

1.Graczykowski C., Faraj R., Development of control systems for fluid-based adaptive impact absorbers, MECHANICAL SYSTEMS AND SIGNAL PROCESSING, ISSN: 0888-3270, DOI: 10.1016/j.ymssp.2018.12.006, Vol.122, No.2019, pp.622-641, 2019
Graczykowski C., Faraj R., Development of control systems for fluid-based adaptive impact absorbers, MECHANICAL SYSTEMS AND SIGNAL PROCESSING, ISSN: 0888-3270, DOI: 10.1016/j.ymssp.2018.12.006, Vol.122, No.2019, pp.622-641, 2019

Abstract:
The paper presents development, evaluation and comparison of various control systems for adaptive fluid-based absorbers serving for absorption of the impact loading. The investigations concern two competitive approaches: i) standard control systems with single determination of the optimal system path based on identified impact conditions, and ii) newly-developed control systems with on-line determination and update of the system path during the process. It is revealed that low robustness of the standard control systems to imprecise impact identification and unknown disturbances results from the assumed path-determination approach and utilized simple path-tracking methods. The proposed solution to this problem is application of the innovative control systems, which utilize Automatic Path Finding and Automatic Path Update algorithms based on full kinematic feedback as well as Hybrid Path Tracking method dedicated for fluid-based absorbers. The introduced approach to absorber control is used to develop three different self-adaptive systems of increasing complexity and robustness. The favourable capabilities of proposed systems including no need for impact identification, high robustness against force disturbances and reduction of leakages influence are proved. Detailed discussion is presented using the illustrative example of single-chamber adaptive pneumatic shock-absorber mitigating impact loading.

Keywords:
Adaptive Impact Absorption, Automatic Path Finding, Automatic Path Update, Full kinematic feedback, Hybrid Path Tracking, Self-adaptive system, Pneumatic shock-absorber

2.Bajkowski J.M., Dyniewicz B., Gębik-Wrona M., Bajkowski J., Bajer C.I., Reduction of the vibration amplitudes of a harmonically excited sandwich beam with controllable core, MECHANICAL SYSTEMS AND SIGNAL PROCESSING, ISSN: 0888-3270, DOI: 10.1016/j.ymssp.2019.04.024, Vol.129, pp.54-69, 2019
Bajkowski J.M., Dyniewicz B., Gębik-Wrona M., Bajkowski J., Bajer C.I., Reduction of the vibration amplitudes of a harmonically excited sandwich beam with controllable core, MECHANICAL SYSTEMS AND SIGNAL PROCESSING, ISSN: 0888-3270, DOI: 10.1016/j.ymssp.2019.04.024, Vol.129, pp.54-69, 2019

Abstract:
We consider a theoretical analysis and experimental test of a sandwich beam, with a core layer made of controllable material that can change its properties over time. We show that this dynamically excited beam can be sequentially controlled to obtain higher amplitude attenuation and resistance to the amplitude growth in resonant ranges than when the smart beam parameters are constant over time. Numerical simulations were performed to study the possibility of shifting beam vibration frequency towards ranges distant from resonance. An experimental study on a layered beam consisting of two steel bars with a pneumatically controlled core made of pressurized granular material was considered. A simplified control was performed to detune the beam from the resonance frequencies and reduce the vibrations by 30% in simulations and 10% in experiment.

Keywords:
Smart material, Granular structures, Structural control, Semi-active control, Layered beam

3.Tauzowski P., Błachowski B., Lógó J., Functor-oriented topology optimization of elasto-plastic structures, Advances in Engineering Software, ISSN: 0965-9978, DOI: 10.1016/j.advengsoft.2019.102690, Vol.135, pp.1-11, 2019
Tauzowski P., Błachowski B., Lógó J., Functor-oriented topology optimization of elasto-plastic structures, Advances in Engineering Software, ISSN: 0965-9978, DOI: 10.1016/j.advengsoft.2019.102690, Vol.135, pp.1-11, 2019

Abstract:
The paper deals with a novel approach to development of optimality criteria based finite element code for topology optimization of elasto-plastic structures. The novelty of this work is related to the concept of function object called functor and its application to efficient FE code development. First, the general problem of topology optimization under stress constraints is briefly formulated. Then, the programming aspects of topology optimization using traditional object-oriented and functor based programming are discussed. The advantages of the functor based approach are related to simplicity of designing the FE code architecture and reusability of this code. In particular the metric known as 'Lack of cohesion of methods' is useful in comparing these two different paradigms. Finally, the paper is also illustrated with numerical examples of topology optimization using the proposed methodology.

Keywords:
Topology optimization, Function object, Functor programming, Optimal design, Elasto-plastic structures, Finite element programming

4.Wasilewski M., Pisarski D., Bajer C.I., Adaptive optimal control for seismically excited structures, Automation in Construction, ISSN: 0926-5805, DOI: 10.1016/j.autcon.2019.102885, Vol.106, pp.1-18, 2019
Wasilewski M., Pisarski D., Bajer C.I., Adaptive optimal control for seismically excited structures, Automation in Construction, ISSN: 0926-5805, DOI: 10.1016/j.autcon.2019.102885, Vol.106, pp.1-18, 2019

Abstract:
A novel adaptive control for structures subjected to seismic excitation is presented. The aim of the control is to provide a high stabilizing performance involving a limited computational burden while allowing for frequent update of the control decision to cope with the changes in the excitation characteristics. Consequently, the control is based on a computationally efficient solution to the infinite-horizon linear optimal control problem, which employs the autoregressive model for excitation signals and the alpha-shift method for a performance index. Based on numerical simulations involving an actively controlled 20-story building subjected to different earthquake scenarios, we demonstrate that the adaptive control outperforms the standard LQG and H∞ regulators. Our analysis of the controller's computational complexity has confirmed that the presented method can be successfully implemented in large-scale structures that are equipped with active control devices. Our follow up research will validate the performance of the designed control on a real environment platform and we will design an adaptive controller to mitigate vibration in semi-active structures.

Keywords:
adaptive control, structural control, autoregressive model, vibration, optimal stabilization

5.Chikahiro Y., Ario I., Pawłowski P., Graczykowski C., Holnicki-Szulc J., Optimization of reinforcement layout of scissor-type bridge using differential evolution algorithm, Computer-Aided Civil and Infrastructure Engineering, ISSN: 1093-9687, DOI: 10.1111/mice.12432, pp.1-16, 2019
Chikahiro Y., Ario I., Pawłowski P., Graczykowski C., Holnicki-Szulc J., Optimization of reinforcement layout of scissor-type bridge using differential evolution algorithm, Computer-Aided Civil and Infrastructure Engineering, ISSN: 1093-9687, DOI: 10.1111/mice.12432, pp.1-16, 2019

Abstract:
Scissors mechanisms are commonly used in safety engineering during the construction of temporary structures, owing to their inherent advantages of foldability, transformability, and reusability.We effectively utilized these scissors mechanism features to develop a lightweight, deployable emergency Mobile Bridge (MB) based on optimization, and control of the folding structure. Here, we discuss the problems of optimal reinforcement layout for the MB by formulating and solving three optimization problems, namely: (a) the load capacity maximization problem, (b) the weight minimization problem, and (c) coupling the load capacity maximization problem and the weight minimization problem. The potential benefits resulting from the application of reinforcement were evaluated using a combination of finite element analysis and an optimization algorithm based on the differential evolution method. The results demonstrate the significant positive influence of the additional reinforcing members. In particular, the limit load was increased by over 10 times, while the weight was decreased to approximately half. The proposed methodology enabled the development of a substantially improved version of the MB characterized by a higher load capacity and lower weight in comparison to the initial bridge design.

6.Zawidzki M., Jankowski Ł., Multiobjective optimization of modular structures: Weight versus geometric versatility in a Truss-Z system, Computer-Aided Civil and Infrastructure Engineering, ISSN: 1093-9687, DOI: 10.1111/mice.12478, Vol.34, No.11, pp.1026-1040, 2019
Zawidzki M., Jankowski Ł., Multiobjective optimization of modular structures: Weight versus geometric versatility in a Truss-Z system, Computer-Aided Civil and Infrastructure Engineering, ISSN: 1093-9687, DOI: 10.1111/mice.12478, Vol.34, No.11, pp.1026-1040, 2019

Abstract:
This paper proposes an approach for multicriterial optimization of modular structures with respect to their structural and geometrical properties. The approach is tested using the quickly deployable and reconfigurable modular ramp system Truss-Z intended for pedestrian traffic. The focus is on modular structures composed of a moderate number of relatively complex modules, which feature an irregular, noncuboidal geometry. Such modules can be assembled into a variety of geometrically different configurations which do not adhere to any predefined spatial grid; their global geometry can be treated as free-form and determined in situ during construction. The optimization variables represent local-level geometrical and structural properties of a single module. The Pareto front is used to balance between two kinds of objectives. The geometrical objective quantifies the ability of the modules to generate geometrically versatile global structures that are well-suited to comply with spatial constraints of real construction sites. The structural objective is formalized in analogy to the minimum weight problem with upper bound constraints imposed on the von Mises stress and the Euler buckling load ratio. A two-level optimization scheme is employed with NSGA-II at the top level and a simulated annealing with adaptive neighborhood at the lower level.

Keywords:
modular structures, multicriterial optimization, shape optimization, sizing optimization, NSGA-II, simulated annealing with adaptive neighborhood

7.Knor G., Jaskulski R., Glinicki M.A., Holnicki-Szulc J., Numerical identification of the thermal properties of early age concrete using inverse heat transfer problem, INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER, ISSN: 0017-9310, DOI: 10.1007/s00231-018-2504-2, Vol.55, No.4, pp.1215-1227, 2019
Knor G., Jaskulski R., Glinicki M.A., Holnicki-Szulc J., Numerical identification of the thermal properties of early age concrete using inverse heat transfer problem, INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER, ISSN: 0017-9310, DOI: 10.1007/s00231-018-2504-2, Vol.55, No.4, pp.1215-1227, 2019

Abstract:
The procedure of numerical identification of thermophysical properties of concrete during its hardening is presented. Heat of cement hydration, thermal conductivity and specific heat are determined for purpose of modelling temperature evolution in massive concrete elements. The developed method is based on point temperature measurements in a cylindrical mould and the numerical solution of the inverse heat transfer problem by means of direct search optimization algorithm. The determined thermal characteristics of concrete are not constant and depend on the maturity of concrete. The procedure was verified on set of concrete mixes designed with Portland cement CEM I 42.5R and Portland-slag cement CEM II/B-S 32.5 N. Calcareous fly ash was also used for partial replacement of cement in the mixtures. The obtained results have been compared with experimentally measured temperature in concrete and a fair agreement has been found.

8.Pisarski D., Myśliński A., Suboptimal distributed state-feedback control of semi-active vibrating systems, JOURNAL OF SOUND AND VIBRATION, ISSN: 0022-460X, DOI: 10.1016/j.jsv.2018.12.009, Vol.443, pp.637-651, 2019
Pisarski D., Myśliński A., Suboptimal distributed state-feedback control of semi-active vibrating systems, JOURNAL OF SOUND AND VIBRATION, ISSN: 0022-460X, DOI: 10.1016/j.jsv.2018.12.009, Vol.443, pp.637-651, 2019

Abstract:
A novel semi-active control method for mitigating structural vibration is studied. The method relies on distributed state information patterns and the solution to a suboptimal control problem that aims at replicating the switched structures of the optimal open-loop stabilizing controls. The optimality conditions and the method of solution of the suboptimal problem are discussed. The performance of this method is examined by means of numerical experiments performed for a double cantilever system equipped with a set of semi-active elastomers with controlled viscoelastic properties. The experiments were carried out for different controller architectures and a series of initial conditions. In terms of the assumed objectives, the proposed distributed control strategy significantly outperforms the passive damping strategies and is competitive with a standard centralized control. The proposed approach is general to a class of bilinear control systems concerned with smart structural elements. The practical aspects of the designed distributed controller are highlighted.

Keywords:
distributed control, optimal control, bilinear system, stabilization, semi-active structure

9.Meissner M., Wiśniewski K., Influence of room modes on low-frequency transients: Theoretical modeling and numerical predictions, JOURNAL OF SOUND AND VIBRATION, ISSN: 0022-460X, DOI: 10.1016/j.jsv.2019.02.012, Vol.448, pp.19-33, 2019
Meissner M., Wiśniewski K., Influence of room modes on low-frequency transients: Theoretical modeling and numerical predictions, JOURNAL OF SOUND AND VIBRATION, ISSN: 0022-460X, DOI: 10.1016/j.jsv.2019.02.012, Vol.448, pp.19-33, 2019

Abstract:
In the low-frequency range, a sound reproduction in enclosures is strongly influenced by excited room modes. While the spectral impact of acoustic modes on a room response is well recognized, there is no sufficient knowledge on how these modes affects transients. In the paper this issue has been examined theoretically and numerically for a room excited by a tone burst by using a modal expansion method supported by a computer implementation. To quantify a temporal accuracy of a sound reproduction, the new metrics referred to as the tone burst reproduction error was introduced. The basis for determining this quantity was a deviation between the tone burst amplitude and the amplitude of a sound pressure computed via the Hilbert transform. A numerical simulation was performed for an irregularly shaped enclosure having a form of two-room coupled system. Calculation results have proved that a high inaccuracy of a tone burst reproduction occurs at receiving points corresponding to sharp dips in a distribution of the steady-state sound pressure level. This is because in these points an amplitude of transient sound is much bigger than a tone burst amplitude. It was discovered that strong narrow peaks in the tone burst reproduction error are located at centers of vortices in the active sound intensity vector field. An influence of a sound damping in a room on a reproduction of a tone burst was also examined and it was found that a substantial increase in a wall sound absorption does not significantly improves a tone burst reproduction because it does not eliminate sharp dips in a distribution of the steady-state sound pressure level.

Keywords:
room acoustics, room modes, transients, tone burst, discrete Hilbert transform, sound intensity vector field

10.Faraj R., Graczykowski C., Hybrid Prediction Control for self-adaptive fluid-based shock-absorbers, JOURNAL OF SOUND AND VIBRATION, ISSN: 0022-460X, DOI: 10.1016/j.jsv.2019.02.022, Vol.449, pp.427-446, 2019
Faraj R., Graczykowski C., Hybrid Prediction Control for self-adaptive fluid-based shock-absorbers, JOURNAL OF SOUND AND VIBRATION, ISSN: 0022-460X, DOI: 10.1016/j.jsv.2019.02.022, Vol.449, pp.427-446, 2019

Abstract:
The paper covers detailed discussion on novel control system developed for adaptive fluidbased shock-absorbers serving for mitigation of unknown impact excitations. In order to provide complete independence of the control system from the loading conditions, the Hybrid Prediction Control (HPC) was elaborated. The proposed method is an extension of previously introduced kinematic feedback control which ensures optimal path finding, tracking and path update in case of high disturbance or sudden change of loading conditions. Implementation of the presented control system allows to obtain self-adaptive fluid-based absorbers providing robust impact mitigation. In contrast to previously developed methods of Adaptive Impact Absorption, the proposed control strategy does not require prior knowledge of impact excitation or its preliminary identification. The independence of applied control system from parameters of impact loading results in the capability of automatic path correction in the case of disturbance occurrence and readaptation to a number of subsequent impacts. The successful operation of the selfadaptive system is investigated with the use of numerical examples involving doublechamber pneumatic shock-absorber equipped with controllable valve. Efficiency of the HPC is proved by comparison with passive absorber as well as device equipped with adaptive and optimal control modules.

Keywords:
Hybrid Prediction Control, kinematic feedback control, Adaptive Impact Absorption, unknown impact mitigation, self-adaptive system

11.An Y., Chatzi E., Sim S., Laflamme S., Błachowski B., Ou J., Recent progress and future trends on damage identification methods for bridge structures, STRUCTURAL CONTROL AND HEALTH MONITORING, ISSN: 1545-2255, DOI: 10.1002/stc.2416, Vol.e2416, pp.1-30, 2019
An Y., Chatzi E., Sim S., Laflamme S., Błachowski B., Ou J., Recent progress and future trends on damage identification methods for bridge structures, STRUCTURAL CONTROL AND HEALTH MONITORING, ISSN: 1545-2255, DOI: 10.1002/stc.2416, Vol.e2416, pp.1-30, 2019

Abstract:
Damage identification forms a key objective in structural health monitoring. Several state-of-the-art review papers regarding progress in this field up to 2011 have been published. This paper summarizes the recent progress between 2011 and 2017 in the area of damage identification methods for bridge structures. This paper is organized based on the classification of bridge infrastructure in terms of fundamental structural systems, namely, beam bridges, truss bridges, arch bridges, cable-stayed bridges, and suspension bridges. The overview includes theoretical developments, enhanced simulation attempts, laboratory-scale implementations, full-scale validation, and the summary for each type of bridges. Based on the offered review, some challenges, suggestions, and future trends in damage identification are proposed. The work can be served as a basis for both academics and practitioners, who seek to implement damage identification methods in next-generation structural health monitoring systems.

Keywords:
arch bridge, beam bridge, cable‐stayed bridge, damage identification, suspension bridge, truss bridge

12.Faraj R., Jankowski Ł., Graczykowski C., Holnicki-Szulc J., Can the inerter be a successful shock-absorber? The case of a ball-screw inerter with a variable thread lead, Journal of the Franklin Institute, ISSN: 0016-0032, DOI: 10.1016/j.jfranklin.2019.04.012, Vol.356, No.14, pp.7855-7872, 2019
Faraj R., Jankowski Ł., Graczykowski C., Holnicki-Szulc J., Can the inerter be a successful shock-absorber? The case of a ball-screw inerter with a variable thread lead, Journal of the Franklin Institute, ISSN: 0016-0032, DOI: 10.1016/j.jfranklin.2019.04.012, Vol.356, No.14, pp.7855-7872, 2019

Abstract:
This paper investigates an application of a ball-screw inerter for mitigation of impact loadings. The problem of impact absorption is to provide a minimum reaction force that optimally decelerates and eventually stops an impacting object within the available absorber stroke. It significantly differs from vibration mitigation problems which are typical application of inerters. The paper demonstrates that the optimum absorption can be achieved by fully passive means. For known values of the object mass and inerter parameters, the obtained solution is independent of the impact velocity. The optimum passive absorption is achieved by employing a variable thread lead. As a result, two force components emerge, the typical inertance-related force and a damping-like term, and sum up to provide the optimum constant deceleration force. This result is relatively unique: conventional absorbers do not provide a constant force even with complex active control systems. Finally, an optimization problem is formulated to reduce the influence of process uncertainties (range of possible mass values, unknown friction). The results are verified and analyzed in a numerical example.

13.Dyniewicz B., Bajer C.I., Kuttler K.L., Shillor M., Vibrations of a Gao beam subjected to a moving mass, Nonlinear Analysis: Real World Applications, ISSN: 1468-1218, DOI: 10.1016/j.nonrwa.2019.05.007, Vol.50, pp.342-364, 2019
Dyniewicz B., Bajer C.I., Kuttler K.L., Shillor M., Vibrations of a Gao beam subjected to a moving mass, Nonlinear Analysis: Real World Applications, ISSN: 1468-1218, DOI: 10.1016/j.nonrwa.2019.05.007, Vol.50, pp.342-364, 2019

Abstract:
This paper models, analyzes and simulates the vibrations of a nonlinear Gao beam that is subjected to a moving mass or a massless point-force. Such problems arise naturally in transportation systems such as trains or trams. The dynamics of the system as the mass or the force move on the beam are investigated numerically in the cases when the vibrations are about a buckled state, and in the cases when the mass is positive or vanishes. The simulations are compared to those of the Euler–Bernoulli linear beam and the differences are highlighted. It is seen that the linear beam may be used only when the loads are small, while the Gao beam allows for moderate loads. The simulations are based on a time-marching finite elements algorithm for the model that has been developed and implemented. The results of representative and interesting computer simulations are depicted. The existence of weak solutions of the model is established using a variational formulation of the problem and results about variational set-inclusions.

Keywords:
Dynamic vibrations, Buckling of a Gao beam, Moving point-load

14.Wasilewski M., Pisarski D., Konowrocki R., Bajer C.I., A new efficient adaptive control of torsional vibrations induced by switched nonlinear disturbances, INTERNATIONAL JOURNAL OF APPLIED MATHEMATICS AND COMPUTER SCIENCE , ISSN: 1641-876X, DOI: 10.2478/amcs-2019-0021, Vol.29, No.2, pp.285-303, 2019
Wasilewski M., Pisarski D., Konowrocki R., Bajer C.I., A new efficient adaptive control of torsional vibrations induced by switched nonlinear disturbances, INTERNATIONAL JOURNAL OF APPLIED MATHEMATICS AND COMPUTER SCIENCE , ISSN: 1641-876X, DOI: 10.2478/amcs-2019-0021, Vol.29, No.2, pp.285-303, 2019

Abstract:
Torsional vibrations induced in drilling systems are detrimental to the condition of the machine and to the effectiveness of the engineering process. The cause of vibrations is a nonlinear and unknown friction between a drill string and the environment, containing jumps in its characteristics. Nonlinear behaviour of the friction coefficient results in self-excited vibration and causes undesirable stick-slip oscillations. The aim of this paper is to present a novel adaptive technique of controlling vibrating systems. The scheme is based on the linear quadratic regulator and uses direct measurements of the friction torque to synthesize its linear dynamic approximation. This approach allows generating a control law that takes into account the impact of the friction on the system dynamics and optimally steers the system to the desired trajectory. The controller’s performance is examined via numerical simulations of the stabilization of the drilling system. The proposed solution outperforms the comparative LQG regulator in terms of the minimization of the assumed cost functional and the overall stability of the control system under the nonlinear disturbance.

Keywords:
vibration control, adaptive control, linear-quadratic-regulator, drilling control

15.Nowak Ł.J., Nowak K.M., Perceptual audio processing stethoscope, JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA, ISSN: 0001-4966, DOI: 10.1121/1.5126226, Vol.146, No.3, pp.1769-1773, 2019
Nowak Ł.J., Nowak K.M., Perceptual audio processing stethoscope, JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA, ISSN: 0001-4966, DOI: 10.1121/1.5126226, Vol.146, No.3, pp.1769-1773, 2019

Abstract:
Stethoscopes are used to transmit body sounds related to various physiological processes to ears of a physician, providing basic or supportive information for eventual diagnosis. Unfavorably, the dominant frequency components of most of the auscultation signals are localized close to the lower frequency limits of the human auditory system, restricting the achievable selectivity and specificity. The present study introduces an approach that aims at overcoming the existing limitations. A signal processing scheme utilizing knock rejection, dynamic compressor, and pseudo-stereo synthesizer blocks is described, along with hardware implementation and results of the initial subjective evaluation.

16.Szmidt T., Pisarski D., Konowrocki R., Semi-active stabilisation of a pipe conveying fluid using eddy-current dampers: state-feedback control design,experimental validation, MECCANICA, ISSN: 0025-6455, DOI: 10.1007/s11012-019-00988-3, Vol.54, No.6, pp.761-777, 2019
Szmidt T., Pisarski D., Konowrocki R., Semi-active stabilisation of a pipe conveying fluid using eddy-current dampers: state-feedback control design,experimental validation, MECCANICA, ISSN: 0025-6455, DOI: 10.1007/s11012-019-00988-3, Vol.54, No.6, pp.761-777, 2019

Abstract:
An application of electromagnetic devices of the motional type (i.e. eddy-current dampers) to improve the dynamic stability of a cantilever pipe discharging fluid is proposed. When the flow velocity reaches a critical value, this system loses stability through the flutter. A contactless damping device is used. This actuator is made of a conducting plate attached to the pipe that moves together with it within the perpendicular magnetic field that is generated by the controlled electromagnets. During the motion the eddy currents in the plate and a resultant drag force of a viscous character are generated. First, an optimal control problem that aims to stabilise the system with the optimal rate of decrease of the system’s energy is posed and solved. Then a state-feedback parametrization of the obtained optimal control, which can be used in a closed-loop scheme is proposed. The effectiveness of the designed optimal controller is validated by making a comparison with the corresponding passive solutions on the specially designed and constructed experimental test stand of a pipe conveying air.

Keywords:
fluid–structure interaction, electromagnetic device, eddy-current damper, optimal control, stabilisation, smart structure

17.Zieliński T.G., Chevillotte F., Deckers E., Sound absorption of plates with micro-slits backed with air cavities: Analytical estimations, numerical calculations and experimental validations, APPLIED ACOUSTICS, ISSN: 0003-682X, DOI: 10.1016/j.apacoust.2018.11.026, Vol.146, pp.261-279, 2019
Zieliński T.G., Chevillotte F., Deckers E., Sound absorption of plates with micro-slits backed with air cavities: Analytical estimations, numerical calculations and experimental validations, APPLIED ACOUSTICS, ISSN: 0003-682X, DOI: 10.1016/j.apacoust.2018.11.026, Vol.146, pp.261-279, 2019

Abstract:
This work discusses many practical and some theoretical aspects concerning modelling and design of plates with micro-slits, involving multi-scale calculations based on microstructure. To this end, useful mathematical reductions are demonstrated, and numerical computations are compared with possible analytical estimations. The numerical and analytical approaches are used to calculate the transport parameters for complex micro-perforated (micro-slotted) plates, which allow to determine the effective properties of the equivalent fluid, so that at the macro-scale level the plate can be treated as a specific layer of acoustic fluid. In that way, the sound absorption of micro-slotted plates backed with air cavities can be determined by solving a multi-layer system of Helmholtz equations. Two such examples are presented in the paper and validated experimentally. The first plate has narrow slits precisely cut out using a traditional technique, while the second plate - with an original micro-perforated pattern - is 3D-printed.

Keywords:
Micro-slotted plates, Micro-perforated plates, Sound absorption, Microstructure-based modelling, 3D-printing

18.Nowak Ł.J., Nowak K.M., An experimental study on the role and function of the diaphragm in modern acoustic stethoscopes, APPLIED ACOUSTICS, ISSN: 0003-682X, DOI: 10.1016/j.apacoust.2019.05.009, Vol.155, pp.24-31, 2019
Nowak Ł.J., Nowak K.M., An experimental study on the role and function of the diaphragm in modern acoustic stethoscopes, APPLIED ACOUSTICS, ISSN: 0003-682X, DOI: 10.1016/j.apacoust.2019.05.009, Vol.155, pp.24-31, 2019

Abstract:
Vibrations of a diaphragm of an acoustic stethoscope in contact with a body of an auscultated patient are the source of the sound transmitted to the ears of a physician performing examination. Mechanical properties of a diaphragm can thus significantly affect the parameters of the transmitted bioacoustic signals. However, the exact relation remains mostly unclear, as the underlying phenomena involve complex effects of acoustic coupling between the diaphragm and the body of a patient. The present study introduces a detailed methodology for determining vibroacoustic behavior of a diaphragm of a stethoscope during a heart auscultation. A laser Doppler vibrometer is used to measure the velocity of vibrations at various points on the surface of a diaphragm during the examination. Synchronized recordings of electrocardiography signals are used for segmentation. Representative data sets are selected and analyzed for various kinds of diaphragms. The results show significant differences in vibration velocity levels and their distribution across the surfaces of the considered structures, but no significant filtering effects.

Keywords:
Acoustic medical diagnostics, Stethoscopes, Diaphragms, Auscultation

19.Hou J., Wang P., Jing T., Jankowski Ł., Experimental Study for Damage Identification of Storage Tanks by Adding Virtual Masses, SENSORS, ISSN: 1424-8220, DOI: 10.3390/s19020220, Vol.19, No.2, pp.220-1-17, 2019
Hou J., Wang P., Jing T., Jankowski Ł., Experimental Study for Damage Identification of Storage Tanks by Adding Virtual Masses, SENSORS, ISSN: 1424-8220, DOI: 10.3390/s19020220, Vol.19, No.2, pp.220-1-17, 2019

Abstract:
This research proposes a damage identification approach for storage tanks that is based on adding virtual masses. First, the frequency response function of a structure with additional virtual masses is deduced based on the Virtual Distortion Method (VDM). Subsequently, a Finite Element (FE) model of a storage tank is established to verify the proposed method; the relation between the added virtual masses and the sensitivity of the virtual structure is analyzed to determine the optimal mass and the corresponding frequency with the highest sensitivity with respect to potential damages. Thereupon, the damage can be localized and quantified by comparing the damage factors of substructures. Finally, an experimental study is conducted on a storage tank. The results confirm that the proposed method is feasible and practical, and that it can be applied for damage identification of storage tanks.

Keywords:
damage identification, storage tanks, sensitivity analysis, frequency

20.Hou J., Li Z., Zhang Q., Zhou R., Jankowski Ł., Optimal Placement of Virtual Masses for Structural Damage Identification, SENSORS, ISSN: 1424-8220, DOI: 10.3390/s19020340, Vol.19, No.2, pp.340-1-18, 2019
Hou J., Li Z., Zhang Q., Zhou R., Jankowski Ł., Optimal Placement of Virtual Masses for Structural Damage Identification, SENSORS, ISSN: 1424-8220, DOI: 10.3390/s19020340, Vol.19, No.2, pp.340-1-18, 2019

Abstract:
Adding virtual masses to a structure is an efficient way to generate a large number of natural frequencies for damage identification. The influence of a virtual mass can be expressed by Virtual Distortion Method (VDM) using the response measured by a sensor at the involved point. The proper placement of the virtual masses can improve the accuracy of damage identification, therefore the problem of their optimal placement is studied in this paper. Firstly, the damage sensitivity matrix of the structure with added virtual masses is built. The Volumetric Maximum Criterion of the sensitivity matrix is established to ensure the mutual independence of measurement points for the optimization of mass placement. Secondly, a method of sensitivity analysis and error analysis is proposed to determine the values of the virtual masses, and then an improved version of the Particle Swarm Optimization (PSO) algorithm is proposed for placement optimization of the virtual masses. Finally, the optimized placement is used to identify the damage of structures. The effectiveness of the proposed method is verified by a numerical simulation of a simply supported beam structure and a truss structure.

Keywords:
damage identification, sensor optimization, Virtual Distortion Method (VDM), Particle Swarm Optimization (PSO) algorithm, sensitivity

21.Szolc T., Falkowski K., Henzel M., Kurnyta-Mazurek P., Determination of parameters for a design of the stable electro-dynamic passive magnetic support of a high-speed flexible rotor, BULLETIN OF THE POLISH ACADEMY OF SCIENCES: TECHNICAL SCIENCES, ISSN: 0239-7528, DOI: 10.24425/bpas.2018.125719, Vol.67, No.1, pp.91-105, 2019
Szolc T., Falkowski K., Henzel M., Kurnyta-Mazurek P., Determination of parameters for a design of the stable electro-dynamic passive magnetic support of a high-speed flexible rotor, BULLETIN OF THE POLISH ACADEMY OF SCIENCES: TECHNICAL SCIENCES, ISSN: 0239-7528, DOI: 10.24425/bpas.2018.125719, Vol.67, No.1, pp.91-105, 2019

Abstract:
Electro-dynamic passive magnetic bearings are now viewed as a feasible option when looking for support for high-speed rotors. Nevertheless, because of the skew-symmetrical visco-elastic properties of such bearings, they are prone to operational instability. In order to avoid this, the paper proposes the addition of external damping into the newly designed vibrating laboratory rotor-shaft system. This may be achieved by means of using simple passive dampers that would be found among the components of the electro-dynamic bearing housings along with magnetic dampers, which satisfy the operational principles of active magnetic bearings. Theoretical investigations are going to be conducted by means of a structural computer model of the rotor-shaft under construction, which will take into consideration its actual dimensions and material properties. The additional damping magnitudes required to stabilize the most sensitive lateral eigenmodes of the object under consideration have been determined by means of the Routh-Hurwitz stability criterion.

Keywords:
rotor-dynamics, electrodynamic passive magnetic bearings, flexible rotor-shaft, active magnetic damper, stability analysis

22.Popławski B., Mikułowski G., Pisarski D., Wiszowaty R., Jankowski Ł., Optimum actuator placement for damping of vibrations using the Prestress-Accumulation Release control approach , SMART STRUCTURES AND SYSTEMS, ISSN: 1738-1584, DOI: 10.12989/sss.2019.24.1.027, Vol.24, No.1, pp.27-35, 2019
Popławski B., Mikułowski G., Pisarski D., Wiszowaty R., Jankowski Ł., Optimum actuator placement for damping of vibrations using the Prestress-Accumulation Release control approach , SMART STRUCTURES AND SYSTEMS, ISSN: 1738-1584, DOI: 10.12989/sss.2019.24.1.027, Vol.24, No.1, pp.27-35, 2019

Abstract:
This paper proposes a quantitative criterion for optimization of actuator placement for the Prestress–Accumulation Release (PAR) strategy of mitigation of vibrations. The PAR strategy is a recently developed semi-active control approach that relies on controlled redistribution of vibration energy into high-order modes, which are high-frequency and thus effectively dissipated by means of the natural mechanisms of material damping. The energy transfer is achieved by a controlled temporary removal of selected structural constraints. This paper considers a short-time decoupling of rotational degrees of freedom in a frame node so that the bending moments temporarily cease to be transferred between the involved beams. We propose and test a quantitative criterion for placement of such actuators. The criterion is based on local modal strain energy that can be released into high-order modes. The numerical time complexity is linear with respect to the number of actuators and potential placements, which facilitates quick analysis in case of large structures.

Keywords:
semi-active control, damping of vibrations, actuator placement, smart structures, prestress-accumulation release (PAR)

23.Hou J., Wang S., Zhang Q., Jankowski Ł., An Improved Objective Function for Modal-Based Damage Identification Using Substructural Virtual Distortion Method, Applied Sciences, ISSN: 2076-3417, DOI: 10.3390/app9050971, Vol.9, No.5, pp.1-17, 2019
Hou J., Wang S., Zhang Q., Jankowski Ł., An Improved Objective Function for Modal-Based Damage Identification Using Substructural Virtual Distortion Method, Applied Sciences, ISSN: 2076-3417, DOI: 10.3390/app9050971, Vol.9, No.5, pp.1-17, 2019

Abstract:
Damage identification based on modal parameters is an important approach in structural health monitoring (SHM). Generally, traditional objective functions used for damage identification minimize the mismatch between measured modal parameters and the parameters obtained from the finite element (FE) model. However, during the optimization process, the repetitive calculation of structural modes is usually time-consuming and inefficient, especially for large-scale structures. In this paper, an improved objective function is proposed based on certain characteristics of the peaks of the frequency response function (FRF). Traditional objective functions contain terms that quantify modal shapes and/or natural frequencies. Here, it is proposed to replace them by the FRF of the FE model, which allows the repeated full modal analysis to be avoided and thus increases the computational efficiency. Moreover, the efficiency is further enhanced by employing the substructural virtual distortion method (SVDM), which allows the frequency response of the FE model of the damaged structure to be quickly computed without the costly re-analysis of the entire damaged structure. Finally, the effectiveness of the proposed method is verified using an eight-story frame structure model under several damage cases. The damage location and extent of each substructure can be identified accurately with 5% white Gaussian noise, and the optimization efficiency is greatly improved compared with the method using a traditional objective function.

Keywords:
structural health monitoring (SHM), damage identification, substructure, virtual distortion method (VDM), frequency response

24.Szmidt T., Pisarski D., Konowrocki R., Awietjan S., Boczkowska A., Adaptive Damping of a Double-Beam Structure Based on Magnetorheological Elastomer, SHOCK AND VIBRATION, ISSN: 1070-9622, DOI: 10.1155/2019/8526179, Vol.2019, No.8526179, pp.1-16, 2019
Szmidt T., Pisarski D., Konowrocki R., Awietjan S., Boczkowska A., Adaptive Damping of a Double-Beam Structure Based on Magnetorheological Elastomer, SHOCK AND VIBRATION, ISSN: 1070-9622, DOI: 10.1155/2019/8526179, Vol.2019, No.8526179, pp.1-16, 2019

Abstract:
A method of vibration reduction based on activation of an MRE block that couples twin cantilever beams at their free ends is investigated. Four types of magnetorheological elastomers have been manufactured, and their rheological properties in a range of magnetic field intensities are established. Free vibrations of several double-beam structures with controllable damping members made of these MREs are investigated, and a method of semiactive control of such structures is proposed. The effects of compression of the elastomers and alignment of the magnets used to activate them are reported. The mathematical modeling of the system is verified experimentally.

Keywords:
adaptive damping, double-Beam structure, magnetorheological elastomer, mathematical modeling, vibration damping

25.Błachowski B., Modal Sensitivity Based Sensor Placement for Damage Identification Under Sparsity Constraint, Periodica Polytechnica Civil Engineering, ISSN: 0553-6626, DOI: 10.3311/PPci.13888, pp.1-14, 2019
Błachowski B., Modal Sensitivity Based Sensor Placement for Damage Identification Under Sparsity Constraint, Periodica Polytechnica Civil Engineering, ISSN: 0553-6626, DOI: 10.3311/PPci.13888, pp.1-14, 2019

Abstract:
The present study deals with a comprehensive approach for damage identification of spatial truss structures. The novelty of the proposed approach consists of a three-level analysis. First, sensitivity of assumed modal characteristics is calculated. Second, natural frequency sensitivity is used to determine hardly identifiable structural parameters and mode shape sensitivity is applied to select damage-sensitive locations of sensors. Third, two sparsity constrained optimization algorithms are tested towards efficient identification of applied damage scenarios. These two algorithms are based on ℓ1-norm minimization and non-negative least square (NNLS) solution. Performances of both proposed algorithms have been compared in two realistic case studies: the first one concerned a three-dimensional truss girder with 61 structural parameters and the second one was devoted to an upper-deck arch bridge composed of 416 steel members.

Keywords:
sensor placement, damage identification, ℓ1-norm minimization, sparsity constrained optimization

26.Szklarski J., Białek Ł., Szałas A., Paraconsistent Reasoning in Cops and Robber Game with Uncertain Information: A Simulation-Based Analysis, International Journal of Uncertainty, Fuzziness and Knowledge-Based Systems, ISSN: 0218-4885, DOI: 10.1142/S021848851950020X, Vol.27, No.3, pp.429-455, 2019
Szklarski J., Białek Ł., Szałas A., Paraconsistent Reasoning in Cops and Robber Game with Uncertain Information: A Simulation-Based Analysis, International Journal of Uncertainty, Fuzziness and Knowledge-Based Systems, ISSN: 0218-4885, DOI: 10.1142/S021848851950020X, Vol.27, No.3, pp.429-455, 2019

Abstract:
We apply a non-classical four-valued logic in the process of reasoning regarding strategies for cops in a modified game of “Cops and Robber” played on a graph. We extend the game by introducing uncertainty in a form of random failures of detecting devices. This is realized by allowing that a robber can be detected in a node only with the given probability PA. Additionally, with the probability PF , cops can be given a false-positive, i.e., they are informed that the robber is located at some node, whereas it is located somewhere else. Consequently, non-zero PF introduces a measurement noise into the system. All the cops have access to information provided by the detectors and can communicate with each other, so they can coordinate the search. By adjusting the number of detectors, PA, and PF we can achieve a smooth transition between the two well-known variants of the game: “with fully visible robber” and “with invisible robber”. We compare a simple probabilistic strategy for cops with the non-parametric strategy based on reasoning with a four-valued paraconsistent logic. It is shown that this novel approach leads to a good performance, as measured by the required mean catch-time. We conclude that this type of reasoning can be applied in real-world applications where there is no knowledge about the underlying source of errors which is particularly useful in robotics.

Keywords:
reasoning under uncertainty, non-classical logics, four-valued logic, paraconsistent reasoning, cops and robber game, multi-robotic systems