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This article provides a comprehensive analysis of calcaneal apophysitis, or Sever's disease, a major cause of heel pain in children. This overuse injury stems from repetitive mechanical stress on the calcaneal apophysis, often intensified by rapid growth spurts and high physical activity. It is particularly prevalent among young athletes involved in sports with repetitive impact. The condition's pathophysiology involves microtrauma and inflammation at the calcaneus's secondary ossification center due to traction forces from the Achilles tendon. Diagnosis is primarily clinical while imaging is used to rule out other conditions. Symptoms include localized heel pain and tenderness, worsened by activity. Risk factors encompass intrinsic elements like limited ankle dorsiflexion and foot alignment issues, and extrinsic factors such as intense physical activity. Management mainly involves conservative treatments: rest, NSAIDs, stretching exercises, and orthotics. Physical therapy and proper footwear are also effective. Prevention focuses on maintaining a healthy weight, adequate rest, supportive footwear, low-impact activities, and regular stretching to reduce re-injury risk.

The paper proposes that the phonological make-up of segments is influenced by the activity of the constraint *Hydra, which penalizes the presence of more than one headed element per one phonological expression. *Hydra influences the shape of the inventories and the phonological behaviour of nasal vowels in languages such as French and Brazilian Portuguese. At the same time, the behaviour of nasal vowels in Yoruba shows that *Hydra a violable constraint. In Polish, the high ranking of *Hydra proves necessary to account for the absence of Surface Velar Palatalization before the front nasal vowel /ɛ/. It also allows us to formulate a unified account of the 1st Velar and Anterior Palatalization, which have very different structural descriptions but take place before the same set of derivational affixes.

Bearings are commonly employed in various types of rotating machineries. Their properties indisputably influence the overall performance and time of maintenance-free operation of the mechanical systems in which they are used to support the shafts. Consequently, much effort is considered to provide reliable bearings’ solution and develop new methods and technical tools for measurement and possibly modification of the operational characteristics of the above-mentioned parts. In reference, the concept of a smart bearing is developed as providing the means for real-time passive and active control of the bearings’ behavior as well as different types of smart materials are used to enhance their characteristics. The current study deals with an applications of structural components made of shape memory alloys to gas foil bearings (GFB). The paper presents and discusses the results of experimental tests conducted for the bearing’s prototype to characterize the efficiency of thermally-induced modifications of geometric properties of one of the crucial parts of the investigated GFB.

Essential parts of rotating machineries are supporting nodes, i.e., bearing systems. They assure required rotational degrees of freedom and feature desired load carrying capacity. Following the specificity of a technical solution considered, various types of bearings may be taken into account to effectively address the requirements regarding the speed and load. Specifically, gas foil bearings (GFB) are used in high-speed and lightly-loaded rotating machineries, e.g., auxiliary power units. In fact, they can operate up to several hundreds of thousands rpm, also for a wide temperature range. The current work reports an application of piezoelectric composites to control operation of a GFB. The authors present the developed bearing’s prototype installation which is equipped with a specialized multifunctional structural component that advantageously allows to both characterize GFB’s operational parameters and modify them. The experimental results confirm the usability of the proposed actively-controlled configuration of a GFB.

Ground tests of the attitude control system of small satellites can be performed with a test stand that simulates torque free rotations. It consists of a floating platform mounted on a spherical frictionless air bearing joint and equipped with a balancing system that removes the gravity torque acting upon the system. An important design requirement of such platforms is its reduced weight and inertia. In this work we propose an original lightweight 3D printed floating platform made of polylactide (PLA). The utilization of plastic for structural elements is a novelty for this kind of devices, but it also introduces some challenging aspects. Indeed, the reduced stiffness of PLA, when compared with aluminum commonly used in these applications, negatively affects the balancing process. Nonetheless, thanks to the peculiar design we adopted, the platform shows high performance in terms of structural rigidity and balancing accuracy. Experiments evidence that the platform is able to reduce gravity torques to a few tens of micro Newton meters and a residual offset between the center of mass and center of rotation of about 10 micro meters. These values agree with those of solutions presented in the literature.

The paper presents an approach to efficiently detect local defect resonances (LDRs) in solids with localized defects. The 3D scanning laser Doppler vibrometry (3D SLDV) technique is applied to acquire vibration responses on the surface of a test sample due to a broadband vibration excitation applied by a piezoceramic transducer and modal shaker. Based on the response signals and known excitation, the frequency characteristics for individual response points are determined. The proposed algorithm then processes these characteristics to extract both out-of-plane and in-plane LDRs. Identification is based on calculating the ratio between local vibration levels and the mean vibration level of the structure as a background. The proposed procedure is verified on simulated data obtained from finite element (FE) simulations and validated experimentally for an equivalent test scenario. The obtained results confirmed the effectiveness of the method in identifying in-plane and out-of-plane LDRs for both numerical and experimental data. The results of this study are important for damage detection techniques utilizing LDRs to enhance the efficiency of detection.

The following content refers to the thermal aspects of Gas Foil Bearing (GFB). The GFBs are the subgroup of journal bearings, for which lubrication is provided by air, instead of ‘traditional’ lubricants like oil, graces etc. Gas Foil Bearings offer specific features unachievable for traditional bearings. GFB can operate with rotating speed up to several dozens of krpm in extreme temperature up to hundreds of Celsius degrees. However due to their specific construction, GFBs are prone to specific thermal issues which complicate their design process. Until now, many tools, mainly based on numerical models were developed. Their effectiveness is evaluated based on experimental data. Due to the high complexity of GFB’s structure, the temperature measurement is a challenging task and so far, no reliable simple technique was proposed. There is still a need for developing reliable measurement techniques, allowing for precise temperature measurement. This paper presents the novel approach to temperature measurement of the GFBs compliant structure. The unique concept of foil with integrated sensors was presented and described in detail.

It is possible to detect damage in structures based only on vision-system-based assessment of their deformation shape under load. There is, however, a gap between available methods designed to detect damage in beam-like structures and engineering needs for monitoring structures of many different shapes. In this article, a new Aligned Marker Space method of morphing vision data is introduced. The method allows damage detection of any engineering object with one fixed support as if it were a cantilever beam. The paper also presents a new fusion technique to combine the results of several damage-detection methods for an increase in accuracy and sensitivity. The methods are tested based on numerical simulation of various structures, a blender-based simulation, and a set of practical experiments in which crane structures are subjected to damage of different sizes and locations. The optimization of damage detection methods’ metaparemeters is performed using an evolutionary algorithm designed to find the Pareto front of the solutions. The assessment of the influence of different factors, like camera position, damage position, or repetition of the experiment, is provided.

Modern approaches dedicated to controlling the operation of gas foil bearings require advanced measurement techniques to comprehensively investigate the bearings’ thermal and thermomechanical properties. Their successful long-term maintenance with constant operational characteristics may be feasible only when the allowed thermal and mechanical regimes are rigorously kept. Hence, an adequate acquisition of experimental readings for the critical physical quantities should be conducted to track the actual condition of the bearing. The above-stated demand has motivated the authors of this present work to perform the thermomechanical characterization of the prototype installation of a gas foil bearing, applying a specialized sensing foil. This so-called top foil is a component of the structural part of the bearing’s supporting layer and composed of a superalloy, Inconel 625. The strain and temperature distributions were identified based on the readings from the strain gauges and integrated thermocouples mounted on the top foil. The measurements’ results were obtained for the experiments that represent the arbitrarily selected operational conditions of the tested bearing. Specifically, the considered measurement scenario relates to the operation at a nominal rotational speed, i.e., during the stable process, as well as to the run-up and run-out stages. The main objectives of the work are: (a) experimental proof for the described functionalities of the designed and manufactured specialized sensing foil that allow for the application of a novel approach to the bearing’s characterization, and (b) qualitative investigation of the relation between the mechanical and thermal properties of the tested bearing, using the measurements conducted with the newly proposed technical solution.

Structural health monitoring systems that employ vision data are under constant development. Generating synthetic vision data is an actual issue. It allows, for example, for obtention of additional data for machine learning techniques or predicting the result of observations using a vision system with a reduced number of experiments. A random speckle pattern (RSP) fixed on the surface of the observed structure is usually used in measurements. The determination of displacements of its areas using digital image correlation (DIC) methods allows for extracting the structure’s deformation in both static and dynamic cases. An RSP modeling methodology for synthetic image generation is developed within this paper. The proposed approach combines the finite element modeling technique and simulation results with the Blender graphics environment to generate video sequences of the mechanical structure with deformable RSP attached to it. The comparative analysis showed high compliance of the displacement between the synthetic images processed with the DIC method and numerical data.

Owing to high competition in e-commerce, customers may prefer sites that ensure that good user experience (UX) and website aesthetics are one of its qualities. The method of presenting items seems crucial for gaining and maintaining user attention. We conducted a task-based user eye-tracking study with n = 30 participants to examine two variants of an online fashion store: one based on aesthetic rules and one defying them. The following aspects of item presentation were considered: height and width the ratio of product photos, website colors, rounded borders, text visibility, spacing between elements, and smooth animation. We investigated their relationship to user attention by analyzing gaze fixation, tracking user interest, and conducting a supplementary survey. Experimental results showed that owing to following the rules of aesthetics in interface design in the presented fashion shopping scenario, elements such as the recommendation area and product highlights had a significant positive impact on customer attention.

E-commerce shop owners often want to attract user attention to a specific product to enhance the chances of sales, to cross-sell, or up-sell. The way of presenting a recommended item is as important as the recommendation algorithms are to gain that attention. In this study, we examined the following types of highlights: background, shadow, animation, and border, as well as the position of the item in a 5 × 2 grid in a furniture online store, and their relationships with user fixations and user interest. We wanted to verify the effects highlighting had on attracting user attention. Various levels of intensity were considered for each highlight: low, medium, and strong. Methods used for data collection were both implicit and explicit: eye tracking, tracking cart’s contents, and a supplementary survey. Experimental results showed that a low-intensity background highlight should be the first-choice solution to best attract user attention in the presented shopping scenario, resulting in the best fixation times and most users’ selections. However, in the case of the highest-intensity animations, highlighting seemed to have negative effects; despite successful attempts to attract eyesight and a long fixation time, users did not add the highlighted products to cart.

This article presents an experimental study carried out on a rotor operating on two foil bearings. One of the bearings was built in a way to measure the temperature and deformation of the top foil of the foil bearing. The dynamic performance of the two bearing journals is presented herein using the vibration trajectories and journal positions in the foil bearing sleeve. Based on these results, a method for predicting the temperature distribution on the top foil was developed. Then, the correlations between the temperature distribution and the operating parameters of the bearing journal were illustrated. It has been observed that the symmetry of the temperature distribution on the top foil depends on the eccentricity of the rotor operation. The shape and size of the vibration trajectory had no significant effect on the temperature value in the bearing, unlike the position of the journal in the bearing. The process of loss of the gas lubricating film was observed, which provides insight into the phenomena that occur during the first few seconds of rotor operation. The areas in the bearing from which fresh air had been drawn into the gap between the journal and the top foil were also determined.

Maintenance of adequate thermal properties is critical for correct operation of a gas foil bearing. In this work, the authors present the results of the experimentally conducted thermal characterization of a prototype installation of the bearing. A novel method of temperature identification, based on integrated thermocouples readings, has been employed to determine the thermal properties of the specialized sensing top foil mounted in the tested bearing. Two measurement campaigns have been subsequently completed, applying freely-suspended and two-node support configurations, to gather complementary knowledge regarding the bearing’s operation. Apart from the rotational speed and temperature field measurements, the authors have also studied the friction torque and the shaft’s journal trajectories based on its radial displacements. The temporal courses for the above-mentioned quantities have enabled inference on the effects present during run-up, run-out and stable state operation at a constant speed. As confirmed, the applied distribution of the integrated sensors allows for temperature readings on the entire outer surface of the foil, and therefore, provides useful data for the bearing characterization. The work is concluded with presentation of the recommended directions regarding future improvements of the proposed measurement technique and more comprehensive study of the bearing’s characteristics.

This paper presents the use of laser vibrometer measurements to detect and locate damage in a metal plate. An algorithm based on local spatial filters was selected, and for the purpose of comparison, the fault location was also determined based on the wavelet analysis of mode shapes. The research was carried out first on the created finite element model of aluminum plate, where two kinds of damage of increasing size and temperature change were simulated. After obtaining positive results, a laboratory experiment was carried out, which consisted of measuring the vibration of the aluminum plate with the laser vibrometer in undamaged condition, at increased temperatures, and with various damage scenarios. The conclusions of the laboratory experiment confirm the damage detection capabilities of the methods but question their damage localization potential.

Much information can be derived from operational deflection shapes of vibrating structures and the magnification of their motion. However, the acquisition of deflection shapes usually requires a manual definition of an object’s points of interest, while general motion magnification is computationally inefficient. We propose easy extraction of operational deflection shapes straight from vision data by analyzing and processing optical flow information from the video and then, based on these graphs, morphing source data to magnify the shape of deflection. We introduce several processing routines for automatic masking of the optical flow data and frame-wise information fusion. The method is tested based on data acquired both in numerical simulations and real-life experiments in which cantilever beams were subjected to excitation around their natural frequencies.

Computer vision is a frequently used approach in static and dynamic measurements of various mechanical structures. Sometimes, however, conducting a large number of experiments is time-consuming and may require significant financial and human resources. On the contrary, the authors propose a simulation approach for performing experiments to synthetically generate vision data. Synthetic images of mechanical structures subjected to loads are generated in the following way. The finite element method is adopted to compute deformations of the studied structure, and next, the Blender graphics program is used to render images presenting that structure. As a result of the proposed approach, it is possible to obtain synthetic images that reliably reflect static and dynamic experiments. This paper presents the results of the application of the proposed approach in the analysis of a complex-shaped structure for which experimental validation was carried out. In addition, the second example of the process of 3D reconstruction of the examined structure (in a multicamera system) is provided. The results for the structure with damage (cantilever beam) are also presented. The obtained results allow concluding that the proposed approach reliably imitates the images captured during real experiments. In addition, the method can become a tool supporting the vision system configuration process before conducting final experimental research.

The paper discusses a perspective of the usage of various types of smart materials to enhance the operational properties of Gas Foil Bearings. The authors, referring to the current investigation on thermomechanical characteristics of the above-mentioned bearing type, have focused on the concept of using Shape Memory Alloys, Piezoelectric Transducers, Thermoelectric Modules and Thermocouples to improve both mechanical and thermal behavior of the bearings. Based on the available literature and the authors’ experience, the present work provides an overview of the known and perspective applications of smart materials to Gas Foil Bearings. In particular, a discussion on their capabilities, limitations and effectiveness is conducted, taking into account the unique characteristics and requirements of the studied type of bearings.

Recommendation systems play an important role in e-commerce turnover by presenting personalized recommendations. Due to the vast amount of marketing content online, users are less susceptible to these suggestions. In addition to the accuracy of a recommendation, its presentation, layout, and other visual aspects can improve its effectiveness. This study evaluates the visual aspects of recommender interfaces. Vertical and horizontal recommendation layouts are tested, along with different visual intensity levels of item presentation, and conclusions obtained with a number of popular machine learning methods are discussed. Results from the implicit feedback study of the effectiveness of recommending interfaces for four major e-commerce websites are presented. Two different methods of observing user behavior were used, i.e., eye-tracking and document object model (DOM) implicit event tracking in the browser, which allowed collecting a large amount of data related to user activity and physical parameters of recommending interfaces. Results have been analyzed in order to compare the reliability and applicability of both methods. Observations made with eye tracking and event tracking led to similar results regarding recommendation interface evaluation. In general, vertical interfaces showed higher effectiveness compared to horizontal ones, with the first and second positions working best, and the worse performance of horizontal interfaces probably being connected with banner blindness. Neural networks provided the best modeling results of the recommendation-driven purchase (RDP) phenomenon.

Recommender systems play a vital role in e-commerce by increasing the likelihood of transactions and improving sales thanks to presenting personal recommendations. Due to the marketing habituation effect, users are less and less responsive to this type of content. Visual recommendation presentation, in particular the recommendation zone layout can influence the effectiveness of a recommendation. This study examines human–computer interactions for vertical, horizonal, and mixed layouts of recommending interfaces of four major e-commerce stores, and is based on our document object model events-based behavior analysis tool. Results from this implicit feedback study are presented and analyzed, showing that vertical recommendation zones attracted more attention than horizontal ones.

Numerical simulations of the pantograph-catenary dynamic interaction allow for assessment of the current collection quality provided by this subsystem at the design stage of the pantograph or the catenary system. In this paper, the authors present numerical results of simulations of the dynamic interaction between a pantograph and a catenary. Adopted catenary and pantograph models are consistent with the reference model presented in the EN 50318:2002 document, which describes the validation procedure of the simulation for the dynamic interaction between pantograph and overhead contact line. Authors have used the Finite Element Method to analyze this complex system. Ten catenary spans of simple catenary (one messenger wire and one contact wire) are modelled, each of them is 60m long. The pre-sag of the catenary is 0mm and the model of the catenary includes the stagger which equals ±200mm. The pantograph model consists of lumped masses which are connected each other with spring-damper elements. First, the static initial configuration is obtained (under gravity and tensioning loads), after which the dynamic transient simulation is conducted. Obtained results for the contact force and uplifts at supports are within the reference ranges presented in the EN 50318:2002 document, therefore it can be considered that the adopted model correctly reproduces the dynamic behaviour of the pantograph-catenary dynamic interaction.

The paper discusses the issue of perception of portable interactive multimedia guides by the museum visitors. Data from a total of 993 questionnaires, filled out by the visitors of three oceanographic museums from the South Baltic region (in Gdynia, Klaipeda and Stralsund), where interactive multimedia guides were implemented as part of the BalticMuseums 2.0 Plus international project, were analyzed. The results clearly indicate a very good visitor rating of this form of guided tours, and additionally identify, among others, the main reasons for choosing this form of guided tours, groups of users, which, in the opinion of visitors, may be particularly interested in e-guides, and types of content, which they expect to receive in the e-guides.

Mechanical properties of the components of a pantograph’s slider suspension system have large influence on the quality of pantograph-catenary interaction. In the paper the authors present the results of their experimental research on the springs that are used in the pantograph being currently in operation in Europe. Static and dynamic tests were performed, which were aimed at determining the stiffness and damping coefficients respectively. Subsequently, the procedure for automated numerical model building for the pantograph’s springs was prepared employing the Python programming language and the MSC Marc solver. When a spring model is build (accordingly to the geometric properties of the springs used in tests), the elaborated algorithm iteratively tunes the material properties and computes static and dynamic load-cases, making direct reference to the experimental procedure. After completing several iterations the numerical model is finally validated, and proper material properties, as the Young modulus and the coefficients of Rayleigh damping model, are found. Then, the obtained model can be used to determine the damping and stiffness coefficients for springs characterizing various diameters, wire diameters, numbers of turns, etc. The presented modelling tool is useful for determining the pantograph sliders suspension characteristics.

Bearings are commonly employed in various types of rotating machineries. Their properties indisputably influence the overall performance and time of maintenance-free operation of the mechanical systems in which they are used to support the shafts. Consequently, much effort is considered to provide reliable bearings' solution and develop new methods and technical tools for measurement and possibly modification of the operational characteristics of the above-mentioned parts. In reference, the concept of a smart bearing is developed as providing the means for real-time passive and active control of the bearings' behavior as well as different types of smart materials are used to enhance their characteristics. The current study deals with an application of structural components made of shape memory alloys to gas foil bearings (GFB). The paper presents and discusses the results of experimental tests conducted for the bearing's prototype to characterize the efficiency of thermally-induced modifications of geometric properties of one of the crucial parts of the investigated GFB. [ABSTRACT FROM AUTHOR]

There is a need for modelling various phenomena present in a pantograph-catenary structure, (e.g. wave propagation and its reflections, friction, aerodynamic and electromagnetic forces), which allows for a more reliable study on the dynamic behaviours of a railway pantograph, particularly in the case of high-speed trains. Hence, the creation a complex pantograph-catenary multi-domain model should help to effectively meet the above-mentioned requirements. The work presents a co-simulation approach to investigate the pantograph-catenary dynamic interaction. The elaborated co-simulation algorithm assumes data exchange between multibody models of a pantograph and finite element model of a catenary. The presented approach explores multi-domain phenomena that have an influence on the pantograph-catenary interaction. The nonlinear finite element catenary model takes into account the slackening of droppers, relatively large displacements and contact with the pantograph’s slider, while the multibody model of the pantograph considers friction forces and suspension springs. Additionally, aerodynamic forces caused by wind acting on the pantograph were computed using the fluid structure interaction method and implemented in the dynamic simulation. The influence on the pantograph-catenary interaction caused by electromagnetic force acting on the pantograph was investigated, along with the influence of the locomotive’s vertical vibrations and tilt.

Essential parts of rotating machineries are supporting nodes, i.e., bearing systems. They assure required rotational degrees of freedom and feature desired load carrying capacity. Following the specificity of a technical solution considered, various types of bearings may be taken into account to effectively address the requirements regarding the speed and load. Specifically, gas foil bearings (GFB) are used in high-speed and lightlyloaded rotating machineries, e.g., auxiliary power units. In fact, they can operate up to several hundreds of thousands rpm, also for a wide temperature range. The current work reports an application of piezoelectric composites to control operation of a GFB. The authors present the developed bearing's prototype installation which is equipped with a specialized multifunctional structural component that advantageously allows to both characterize GFB's operational parameters and modify them. The experimental results confirm the usability of the proposed activelycontrolled configuration of a GFB. [ABSTRACT FROM AUTHOR]

Ground tests of the attitude control system of small satellites can be performed with a test stand that simulates torque free rotations. It consists of a floating platform mounted on a spherical frictionless air bearing joint and equipped with a balancing system that removes the gravity torque acting upon the system. An important design requirement of such platforms is its reduced weight and inertia. In this work we propose an original lightweight 3D printed floating platform made of polylactide (PLA). The utilization of plastic for structural elements is a novelty for this kind of devices, but it also introduces some challenging aspects. Indeed, the reduced stiffness of PLA, when compared with aluminum commonly used in these applications, negatively affects the balancing process. Nonetheless, thanks to the peculiar design we adopted, the platform shows high performance in terms of structural rigidity and balancing accuracy. Experiments evidence that the platform is able to reduce gravity torques to a few tens of micro-Newton meters and a residual offset between the center of mass and center of rotation of about 10 micro meters. These values agree with those of solutions presented in the literature. [ABSTRACT FROM AUTHOR]

The goal of this study is to present high quality features usable for modeling the churn phenomenin in the telecommunications industry. This paper presents the process of identifying churn factors based on real-world data coming from one the biggest Polish telecommunications operator. The feature extraction and construction techniques are used to create preliminary sets of variables potentially describing the churn phenomenon. Variables describing subscriber demographics, contract conditions and contract usage details have been extracted for two consequent six-month periods. In the next steps, correlation and collinearity analysis were employed in order to select the best variables – candidates for churn prediction. As a final result only most promising variables were presented. Those results can be used to extend data gathered by telecommunications providers, and enhance the set of features applied in churn modeling. [ABSTRACT FROM AUTHOR]

The following content refers to the thermal aspects of Gas Foil Bearing (GFB). The GFBs are the subgroup of journal bearings, for which lubrication is provided by air, instead of ‘traditional’ lubricants like oil, graces etc. Gas Foil Bearings offer specific features unachievable for traditional bearings. GFB can operate with rotating speed up to several dozens of krpm in extreme temperature up to hundreds of Celsius degrees. However due to their specific construction, GFBs are prone to specific thermal issues which complicate their design process. Until now, many tools, mainly based on numerical models were developed. Their effectiveness is evaluated based on experimental data. Due to the high complexity of GFB’s structure, the temperature measurement is a challenging task and so far, no reliable simple technique was proposed. There is still a need for developing reliable measurement techniques, allowing for precise temperature measurement. This paper presents the novel approach to temperature measurement of the GFBs compliant structure. The unique concept of foil with integrated sensors was presented and described in detail. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to perform a multi-criteria evaluation of selected European Union member states in Central Europe with regard to the use of information and communication technologies (ICT) in enterprises in 2017. The analytic network process (ANP) methodology and k-means clustering were used. Basing on data obtained from Eurostat, ICT attributes were selected and the network of criteria was built. The preferences for main criteria were extracted from empirical data for each analyzed country (each decision variant). The obtained priority values reflected strengths of the analyzed regions. The preferences for sub-criteria were determined basing on that the criteria describing the newest fields of ICT development (e-commerce and e-business in general) are considered most important. With regard to that, the multi-criteria analysis showed that Slovenia and Austria were leaders in Central Europe in 2017, and the worst-performing country was Poland, preceded by Hungary. The results of the study can be used to generalize about the level of ICT development of each country. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to investigate how a study group consisting of 85 participants interact with selected online stores and how the interactions correlate with interest in products for each store. This work uses a quantitative research methodology involving a dedicated tool for implicit monitoring of human-website interaction, instrumented for selected stores and registering product interest for the benefit of recommender systems. One of the findings was that to predict product interest it seems a good idea to start with monitoring scrolling activities, mouse usage and time spent on a website and its sections. Rich product information played a crucial role in shaping user interest. For all stores in the study, a misclassification rate of 28.7% was achieved in a CART model, while modeling for particular stores, it varied from 39.3% to 24.8%, and we feel that it reflected different page layouts in stores. Models built to represent individual behavior patterns of most active study participants varied in terms of misclassification rates from 17% to 26%, and the analysis suggested that individual preference modeling could be considered for recommender systems, in particular for key customers or customer groups. The study leads to insights into online store user behavior and product interest prediction, and as a result to possible implications for recommender systems design, including ergonomics optimization and interaction personalization. [ABSTRACT FROM AUTHOR]

The paper presents an approach to efficiently detect local defect resonances (LDRs) in solids with localized defects. The 3D scanning laser Doppler vibrometry (3D SLDV) technique is applied to acquire vibration responses on the surface of a test sample due to a broadband vibration excitation applied by a piezoceramic transducer and modal shaker. Based on the response signals and known excitation, the frequency characteristics for individual response points are determined. The proposed algorithm then processes these characteristics to extract both out-of-plane and in-plane LDRs. Identification is based on calculating the ratio between local vibration levels and the mean vibration level of the structure as a background. The proposed procedure is verified on simulated data obtained from finite element (FE) simulations and validated experimentally for an equivalent test scenario. The obtained results confirmed the effectiveness of the method in identifying in-plane and out-of-plane LDRs for both numerical and experimental data. The results of this study are important for damage detection techniques utilizing LDRs to enhance the efficiency of detection.

Modern approaches dedicated to controlling the operation of gas foil bearings require advanced measurement techniques to comprehensively investigate the bearings' thermal and thermomechanical properties. Their successful long-term maintenance with constant operational characteristics may be feasible only when the allowed thermal and mechanical regimes are rigorously kept. Hence, an adequate acquisition of experimental readings for the critical physical quantities should be conducted to track the actual condition of the bearing. The above-stated demand has motivated the authors of this present work to perform the thermomechanical characterization of the prototype installation of a gas foil bearing, applying a specialized sensing foil. This so-called top foil is a component of the structural part of the bearing's supporting layer and composed of a superalloy, Inconel 625. The strain and temperature distributions were identified based on the readings from the strain gauges and integrated thermocouples mounted on the top foil. The measurements' results were obtained for the experiments that represent the arbitrarily selected operational conditions of the tested bearing. Specifically, the considered measurement scenario relates to the operation at a nominal rotational speed, i.e., during the stable process, as well as to the run-up and run-out stages. The main objectives of the work are: (a) experimental proof for the described functionalities of the designed and manufactured specialized sensing foil that allow for the application of a novel approach to the bearing's characterization, and (b) qualitative investigation of the relation between the mechanical and thermal properties of the tested bearing, using the measurements conducted with the newly proposed technical solution.

It is possible to detect damage in structures based only on vision-system-based assessment of their deformation shape under load. There is, however, a gap between available methods designed to detect damage in beam-like structures and engineering needs for monitoring structures of many different shapes. In this article, a new Aligned Marker Space method of morphing vision data is introduced. The method allows damage detection of any engineering object with one fixed support as if it were a cantilever beam. The paper also presents a new fusion technique to combine the results of several damage-detection methods for an increase in accuracy and sensitivity. The methods are tested based on numerical simulation of various structures, a blender-based simulation, and a set of practical experiments in which crane structures are subjected to damage of different sizes and locations. The optimization of damage detection methods' metaparemeters is performed using an evolutionary algorithm designed to find the Pareto front of the solutions. The assessment of the influence of different factors, like camera position, damage position, or repetition of the experiment, is provided.

Structural health monitoring systems that employ vision data are under constant development. Generating synthetic vision data is an actual issue. It allows, for example, for obtention of additional data for machine learning techniques or predicting the result of observations using a vision system with a reduced number of experiments. A random speckle pattern (RSP) fixed on the surface of the observed structure is usually used in measurements. The determination of displacements of its areas using digital image correlation (DIC) methods allows for extracting the structure's deformation in both static and dynamic cases. An RSP modeling methodology for synthetic image generation is developed within this paper. The proposed approach combines the finite element modeling technique and simulation results with the Blender graphics environment to generate video sequences of the mechanical structure with deformable RSP attached to it. The comparative analysis showed high compliance of the displacement between the synthetic images processed with the DIC method and numerical data.

Maintenance of adequate thermal properties is critical for correct operation of a gas foil bearing. In this work, the authors present the results of the experimentally conducted thermal characterization of a prototype installation of the bearing. A novel method of temperature identification, based on integrated thermocouples readings, has been employed to determine the thermal properties of the specialized sensing top foil mounted in the tested bearing. Two measurement campaigns have been subsequently completed, applying freely-suspended and two-node support configurations, to gather complementary knowledge regarding the bearing's operation. Apart from the rotational speed and temperature field measurements, the authors have also studied the friction torque and the shaft's journal trajectories based on its radial displacements. The temporal courses for the above-mentioned quantities have enabled inference on the effects present during run-up, run-out and stable state operation at a constant speed. As confirmed, the applied distribution of the integrated sensors allows for temperature readings on the entire outer surface of the foil, and therefore, provides useful data for the bearing characterization. The work is concluded with presentation of the recommended directions regarding future improvements of the proposed measurement technique and more comprehensive study of the bearing's characteristics.

Much information can be derived from operational deflection shapes of vibrating structures and the magnification of their motion. However, the acquisition of deflection shapes usually requires a manual definition of an object's points of interest, while general motion magnification is computationally inefficient. We propose easy extraction of operational deflection shapes straight from vision data by analyzing and processing optical flow information from the video and then, based on these graphs, morphing source data to magnify the shape of deflection. We introduce several processing routines for automatic masking of the optical flow data and frame-wise information fusion. The method is tested based on data acquired both in numerical simulations and real-life experiments in which cantilever beams were subjected to excitation around their natural frequencies.

Computer vision is a frequently used approach in static and dynamic measurements of various mechanical structures. Sometimes, however, conducting a large number of experiments is time-consuming and may require significant financial and human resources. On the contrary, the authors propose a simulation approach for performing experiments to synthetically generate vision data. Synthetic images of mechanical structures subjected to loads are generated in the following way. The finite element method is adopted to compute deformations of the studied structure, and next, the Blender graphics program is used to render images presenting that structure. As a result of the proposed approach, it is possible to obtain synthetic images that reliably reflect static and dynamic experiments. This paper presents the results of the application of the proposed approach in the analysis of a complex-shaped structure for which experimental validation was carried out. In addition, the second example of the process of 3D reconstruction of the examined structure (in a multicamera system) is provided. The results for the structure with damage (cantilever beam) are also presented. The obtained results allow concluding that the proposed approach reliably imitates the images captured during real experiments. In addition, the method can become a tool supporting the vision system configuration process before conducting final experimental research.