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Failures in hydraulic systems in offshore wind turbines represent an enormous challenge for manufacturers and operators, as the pitch system statistically is one of the subsystems contributing the most to the downtime of the turbines, which is the case for both electrical and hydraulic pitch systems. However, the complex failure mechanisms of the various different hydraulic components mean that, typically, the critical components of hydraulic systems must be tested to better understand the failure mechanisms. Nonetheless, conventional testing procedures are lengthy and costly. Accelerated testing plays a critical role as it can mimic hydraulic system failure mechanisms in a shorter period. However, the lack of standardized test methods and detailed knowledge about the failure-accelerating effects complicates the process. Therefore, this paper offers a comprehensive examination of approaches applicable to conducting accelerated tests on hydraulic systems. It identifies and discusses five primary component types or sub-components related to the acceleration of testing in hydraulic systems: pumps, cylinders, seals, valves, and hoses. Each section references studies that delve into accelerated testing methodologies for these individual components. Furthermore, within each component, a concise overview of the current techniques is provided, followed by a discussion and summary based on the state of the art.

This article is devoted to the study of a class of reaction-advection-diffusion equations of the form u t − Δ u + β (y) u x = f (t , u) in cylinders, where f is a tristable or multistable nonlinearity satisfying f (⋅ , 0) = f (⋅ , 1) = 0. We establish the alternative of wave solutions, that is, either there is a unique, asymptotically stable periodic traveling wave connecting 0 to 1 directly, or there is a unique propagating terrace connecting 0 to 1. Under the assumption that all wave speeds in propagating terrace are not equal to each other, we further obtain that the propagating terrace is asymptotically stable if it exists. Moreover, the sufficient and necessary conditions for the existence of periodic traveling waves connecting 0 to 1 are given respectively. Our arguments are based on the parabolic maximum principle, sliding method and the super- and sub-solution method. [ABSTRACT FROM AUTHOR]

Failures in hydraulic systems in offshore wind turbines represent an enormous challenge for manufacturers and operators, as the pitch system statistically is one of the subsystems contributing the most to the downtime of the turbines, which is the case for both electrical and hydraulic pitch systems. However, the complex failure mechanisms of the various different hydraulic components mean that, typically, the critical components of hydraulic systems must be tested to better understand the failure mechanisms. Nonetheless, conventional testing procedures are lengthy and costly. Accelerated testing plays a critical role as it can mimic hydraulic system failure mechanisms in a shorter period. However, the lack of standardized test methods and detailed knowledge about the failure-accelerating effects complicates the process. Therefore, this paper offers a comprehensive examination of approaches applicable to conducting accelerated tests on hydraulic systems. It identifies and discusses five primary component types or sub-components related to the acceleration of testing in hydraulic systems: pumps, cylinders, seals, valves, and hoses. Each section references studies that delve into accelerated testing methodologies for these individual components. Furthermore, within each component, a concise overview of the current techniques is provided, followed by a discussion and summary based on the state of the art. [ABSTRACT FROM AUTHOR]

Floating breakwaters (FBs) are frequently used to protect marinas, fisheries, or other bodies of water subject to wave attacks of moderate intensity. New forms of FBs are frequently introduced and investigated in the literature as a consequence of technological advancements. In particular, a new possibility is offered by High-Density Polyethylene (HDPE) by extruding pipes of large diameters (e.g., 2.5 m in diameter) and with virtually no limit in length (hundreds of meters). By connecting two or three such pipes in a vertical layout, a novel low-cost floating breakwater with deep draft is devised. This note investigates numerically and experimentally the efficiency of this type of multi-cylindrical FBs in evaluating different geometries and aims at finding design guidelines. Due to the extraordinary length of the breakwater, the investigation is carried out in two dimensions. The 2D numerical model is based on the solution of the rigid body motion in the frequency domain, where the hydrodynamic forces are evaluated (thanks to a linear potential flow model), and the mooring forces do not include dynamic effects nor drag on the lines. The numerical predictions are compared to the results of a 1:10 scale experimental investigation. An atypical shape of the wave transmission ( k t ) curve is found, with a very low minimum in correspondence with the heave resonance frequency. The results essentially point out the influence of the position of the gravity center, the stiffness, and the mutual distance among cylinders on k t . [ABSTRACT FROM AUTHOR]

As part of the research carried out in the field of processing systems and the production process of oil-hydraulic cylinders of large dimensions and power, the specifics of fluid power transmission, in the functioning of hydropower facilities, were analyzed. The research also includes the optimization of the physical–mathematical model of non-stationary processes, which take place inside the chamber of a large hydrocylinder. In parallel with the definition of the optimization model, the work parameters that affect the process of fluid flow and piston movement were determined. The operating and technological construction parameters of the hydraulic cylinder, which most significantly affect the operation of the hydraulic cylinder, were defined, and the observed parameters were optimized, based on which a prototype with improved characteristics compared to existing solutions was realized. [ABSTRACT FROM AUTHOR]

In the present paper, the dynamic behaviors of a bubble collapsing at the symmetrical positions of the double cylinders within a narrow gap are qualitatively and quantitatively investigated. Using a high-speed photographic technique, the morphological evolution of a bubble near the double cylinders in a two-dimensional flow field is explored and qualitatively demonstrated. The mechanism by which the position of the bubble affects its dynamics is revealed. At the symmetrical position of the double cylinders, the bubble's dimensionless abscissa shows significant impacts on the collapse behaviors, and its increase weakens the bubble deformation and strengthens the centroid movement. [ABSTRACT FROM AUTHOR]

Floating breakwaters (FBs) are frequently used to protect marinas, fisheries, or other bodies of water subject to wave attacks of moderate intensity. New forms of FBs are frequently introduced and investigated in the literature as a consequence of technological advancements. In particular, a new possibility is offered by High-Density Polyethylene (HDPE) by extruding pipes of large diameters (e.g., 2.5 m in diameter) and with virtually no limit in length (hundreds of meters). By connecting two or three such pipes in a vertical layout, a novel low-cost floating breakwater with deep draft is devised. This note investigates numerically and experimentally the efficiency of this type of multi-cylindrical FBs in evaluating different geometries and aims at finding design guidelines. Due to the extraordinary length of the breakwater, the investigation is carried out in two dimensions. The 2D numerical model is based on the solution of the rigid body motion in the frequency domain, where the hydrodynamic forces are evaluated (thanks to a linear potential flow model), and the mooring forces do not include dynamic effects nor drag on the lines. The numerical predictions are compared to the results of a 1:10 scale experimental investigation. An atypical shape of the wave transmission (kt) curve is found, with a very low minimum in correspondence with the heave resonance frequency. The results essentially point out the influence of the position of the gravity center, the stiffness, and the mutual distance among cylinders on kt.

As part of the research carried out in the field of processing systems and the production process of oil-hydraulic cylinders of large dimensions and power, the specifics of fluid power transmission, in the functioning of hydropower facilities, were analyzed. The research also includes the optimization of the physical–mathematical model of non-stationary processes, which take place inside the chamber of a large hydrocylinder. In parallel with the definition of the optimization model, the work parameters that affect the process of fluid flow and piston movement were determined. The operating and technological construction parameters of the hydraulic cylinder, which most significantly affect the operation of the hydraulic cylinder, were defined, and the observed parameters were optimized, based on which a prototype with improved characteristics compared to existing solutions was realized.

In the present paper, the dynamic behaviors of a bubble collapsing at the symmetrical positions of the double cylinders within a narrow gap are qualitatively and quantitatively investigated. Using a high-speed photographic technique, the morphological evolution of a bubble near the double cylinders in a two-dimensional flow field is explored and qualitatively demonstrated. The mechanism by which the position of the bubble affects its dynamics is revealed. At the symmetrical position of the double cylinders, the bubble’s dimensionless abscissa shows significant impacts on the collapse behaviors, and its increase weakens the bubble deformation and strengthens the centroid movement.

This article deals with two activities of the Lithuanian Science Society (LSS, 1907-1938) and the history of the folklore collections it accumulated. Its members encouraged people to record folk songs, fairytales, stories, riddles, and other forms of folklore, and they tried to gather in one place all the older manuscripts that contained folklore. This way, the LSS's folklore archive was formed at the beginning of the twentieth century. In 1908, Eduard Wolter, a member of the LSS, made the first folklore sound recordings with a phonograph apparatus. The chair of the Society, Jonas Basanavičius, knew about the Phonogram Archives of Vienna and Berlin; therefore, he encouraged the establishment of such an archive in Vilnius. Another idea of the LSS, initiated by Mykolas Biržiška, was to gather all the songs in one place and to publish a national songbook. Unfortunately, these goals were visionary and utopian for this period of cultural development in Lithuania. In this study, the birth of these ideas and the path to their realisation are chronologically reviewed. The author discusses the reasons why they were not accomplished in the first part of the twentieth century, and gives explanations for why they were successfully implemented in the second part of the twentieth - beginning of the twenty-first centuries. The historical-political context as well as the actual digitisation of intangible heritage archives help clarify the process. [ABSTRACT FROM AUTHOR]

Impact tests are the most common tests for high-strength materials. These tests not only specify the rigidity of the component but also determine the life expectancy of a machine part. Therefore, it is important to test various machine components for using different impact analyses. In this work, a single plate made of steel is impacted by two cylinders at each end also made of steel. The analysis was carried out using the Dynamic Analysis module of ANSYS Workbench.The distance between the cylinders is kept constant for simplified analysis. Also, the impact velocity was kept the same for the two cylinders. Furthermore, a plate of epoxy carbon UD (395 GPa) was also simulated for deformation, stress, and strain. The analysis yields the reaction of the steel plate and epoxy carbon UD (395GPa) prepreg material when impacted by two cylinders simultaneously. The deformation, stress, and strain simulation results show the effect of impact on the plate. [ABSTRACT FROM AUTHOR]

This paper documents the 2D numerical study of magnetohydrodynamic unsteady natural convective heat transfer in a circular enclosure with four heating cylinders in both the horizontal and the vertical mid-plane. The fluid is an incompressible Newtonian fluid. The main transport equations based on the conservation of mass, momentum, and energy are calculated and solved using a finite element numerical solver with the following parameter ranges: dimensionless distance between cylinders S = 0.05–0.29, Rayleigh number R a = 10 3 – 10 6 , and Hartmann number for Ha = 0–120. COMSOL Multiphysics, a numerical simulation program, was used to solve the governing equations. It was demonstrated that for lower Ra values, heat transfer through an applied magnetic field is unaffected for a specific S value because the mechanism of transport is diffusion, whereas for larger Ra, there is a complex interaction among magnetic field and physical thermal properties. The features of the heat transfer rate are determined by the interaction. The Nusselt number virtually stays constant as Ha rises at smaller Ra. However, at high Ra, the Nusselt number initially declines with Ha and thereafter essentially stays constant, and at high Ra values, the switch from conduction to convective heat transfer takes place. Additionally, Nu rises slightly with S at increasing Ra. [ABSTRACT FROM AUTHOR]

In additive manufacturing, geometric shape deviations are built through statistical deviation models. Nonetheless, the resource constraints limit the manufacturers to test shapes. However, in addition to the power, the simplicity of the deviation models has been demonstrated with illustrative cases for in-plane deviation modelling for regular pentagon, irregular octagon as well as straight edges in free-form shapes utilizing only data and models for single regular pentagon and cylinders. Bayesian deviation models, built for geometric shapes, provide a better fit on the data and help in achieving better predictive accuracy. The main aim of this study is to assess the effect of the error distribution, generally assumed as the normal, and evaluate its impact on the deviation model. In particular, we consider Laplace, logistic, Cauchy, and exponential distributions for the errors. It is shown that logistic distribution provides better alternative error distribution for deviation models as compared to the normal distribution.

The present study aims to investigate the dominant frequency ranges of a cylinder free to vibrate transversally to the flow positioned in the first, the second or in both positions of the tandem assembly for L/D = 1.26, 1.4, 1.6, and 3.52 with the increase in the flow velocity. Accelerometers and hot wire anemometers were the experimental tools applied in this study. The range of study encompassed the reduced velocity with values from 6 to 72 and Reynolds number from 7.1 × 103 to 2.4 × 104. Fourier transform, continuous wavelet transform, magnitude-square coherence, and wavelet coherence were applied to analyze the cylinder acceleration results for all L/D and wake velocity values studied. The results show that the amplitudes of vibration are below 1.5% of the diameter for all the cases, except for the lower L/D, where the amplitude increases. The first cylinder free to vibrate presents the highest amplitudes observed. Fourier and continuous wavelet analysis showed high energy associated with the two natural frequencies of the system and a third frequency, which may be associated with the flow excitation. In the second cylinder free to vibrate, energy spreads across the monitored spectrum, justifying the smaller amplitudes but the energy level increases with increasing L/D and may be associated with wake-induced vibration. The cases with both cylinders free to vibrate show that the relation between the assembly parameters of each cylinder is relevant to the vibration response and the excitation frequency range. The results showed that even with a clear excitation in a higher frequency, the main energy in the vibration signals is in the natural frequency range.

Inverse problems for line sources radiating inside a homogeneous magneto-dielectric cylinder are investigated. The developed algorithms concern the determination of the location and the current of each source. These algorithms are mostly analytical and are based on proper exploitation of the moments obtained by integrating the product of the total field on the cylindrical boundary with complex exponential functions. The information on the unknown parameters of the problem is encoded in these moments, and hence all parameters can be recovered by means of relatively simple explicit expressions. The cases of one and two sources are considered and analyzed. Under certain conditions, the permittivity and permeability of the cylinder are also recovered. The results from two types of numerical experiments are presented: (i) for a single source, the effect of noise on the boundary data is studied, (ii) for two sources, the pertinent nonlinear system of equations is solved numerically and the accuracy of the derived solution is discussed. [ABSTRACT FROM AUTHOR]

During a national lockdown and curfew, most concrete projects are left without curing; therefore, the building elements need to be strengthened. An effective strengthening method is the use of post-tensioned metal strip (PTMS), which is a relatively new method. In this study, the effectiveness of PTMS in strengthening cylindrical samples without curing was tested. Fifteen cylinders were cast, 12 of which were left without curing for 28 days. Three samples that did not undergo strengthening were used as control samples. The remaining specimens were strengthened using one, two, three, and 5 layers of PTMS. To compare the strengths of the cylinders, three cylinders from the same batch were prepared and cured for 28 days. We found that the compressive strength of the cylinders increased by 39%, 57%, 84%, and 125% when the samples were strengthened using one, two, three, and full layers of PTMS, respectively. Additionally, the failure of the cylinders became ductile as the number of layers increased. [ABSTRACT FROM AUTHOR]

This study is a systematic review of research on heat transfer analysis in cavities and aims to provide a comprehensive understanding of flow and heat transfer performance in various kinds of cavities with or without the presence of fins, obstacles, cylinders, and baffles. The study also examines the effects of different forces, such as magnetic force, buoyancy force, and thermophoresis effect on heat transfer in cavities. This study also focuses on different types of fluids, such as air, water, nanofluids, and hybrid nanofluids in cavities. Moreover, this review deals with aspects of flow and heat transfer phenomena for only single-phase flows. It discusses various validation techniques used in numerical studies and the different types and sizes of mesh used by researchers. The study is a comprehensive review of 297 research articles, mostly published since 2000, and covers the current progress in the area of heat transfer analysis in cavities. The literature review in this study shows that cavities with obstacles such as fins and rotating cylinders have a significant impact on enhancing heat transfer. Additionally, it is found that the use of nanofluids and hybrid nanofluids has a greater effect on enhancing heat transfer. Lastly, the study suggests future research directions in the field of heat transfer in cavities. This study's findings have significant implications for a range of areas, including electronic cooling, energy storage systems, solar thermal technologies, and nuclear reactor systems. [ABSTRACT FROM AUTHOR]

This paper presents an investigation on predicting natural frequency of functionally graded carbon nanotube-reinforced composite (FG-CNTRC) cylinders in similitude. To solve the problem of non-scalability caused by the thickness and material distribution, the energy similitude correction method, a novel similitude approach proposed by the author in recent years, is applied to derive the similitude relationship. With the similitude relationship, a brief predictive formula of natural frequency is derived, which reveals the inherent law of natural frequency varying with radius-to-thickness ratio; and the natural frequency of FG-CNTRC cylinders with arbitrary radius-to-thickness ratio can be predicted by two or three models with known frequency. Through numerical cases of various FG-CNTRC cylinders with different volume fractions, distribution patterns of CNTs and edge-to-radius ratios, the results with high accuracy verify the correctness and wide applicability of the derived formula. [ABSTRACT FROM AUTHOR]

Oxygen is used extensively in illnesses involving respiratory system. In emergencies such as the one created by the flare of Covid-19, oxygen consumption has increased tremendously. This article aims to improve our understanding about the medical oxygen, its production (air separation unit, pressure swing adsorption, oxygen concentrators), the supply chain, storage methods, and the final delivery system to the patient. This article also provides a comprehensive review on the additions in the medical infrastructure during the time of oxygen crisis in India along with the introduction of certain novel approaches towards oxygen production and conservation. We aim to minimize the panic among our readers by giving them an insight about the course behind the oxygen supply in that oxygen mask.

The goal of this investigation is to carry out a comprehensive analysis of hydrodynamic forces, with particular attention being paid to the power-law fluid flow across cylinders and presence gap considerations. With the assistance of the Galerkin finite element method (GFEM), the discretization of the two-dimensional system of non-linear partial differential equations was successfully completed. The research is carried out with a significant variance of the flow behavior index n from .3 to 1.7, gap aspects Gp from 0 .0 to .3, and fixed Reynolds number Re 20. To obtain an extremely accurate solution, first, a coarse hybrid computational mesh needs to be developed, and then, more refinement must take place. The selection of the best possible case can be determined by comparing flow patterns, coefficients of drag and lift, and cylinder gaps. The shear-thickening behavior of fluids has a substantially greater influence on the drag characteristics than either the Newtonian or the shear-thinning behavior of fluids do. In addition to this, the shear-thickening action causes the upstream obstacle’s drag coefficient to increase because the gap spacing becomes more widespread.

Multiple scattering of parallel cylinders with arbitrary cross section is computed using the T-matrix of each single scatterer and the general translational matrix for cylindrical waves. Usually, the recommended golden rule to compute the translational matrix is Graf’s addition theorem. However, this approach cannot be properly implemented for some geometries, such as in a two-cylinder case when the center of one of them falls within the minimum circular cylinder that circumscribes the other one. In order to overcome this limitation, a transformation between cylindrical waves and plane waves, followed by propagation of the latter, is proposed. The new approach succeeds due to an adequate truncation of the evanescent plane wave spectrum. This strategy is demonstrated by studying the scattering of three infinite elliptic metallic cylinders for different electrical sizes and observing the convergence of the results as a function of the truncated spectrum. Finally, to conclusively show the interest and applicability of the approach, two more complex problems are treated: a group of infinite elliptic metallic cylinders where two different sizes are combined and a practical real-life filter in substrate integrated waveguide (SIW) technology, including several groups of rectangular dielectric cylinders. [ABSTRACT FROM AUTHOR]

Inverse problems for line sources radiating inside a homogeneous magneto-dielectric cylinder are investigated. The developed algorithms concern the determination of the location and the current of each source. These algorithms are mostly analytical and are based on proper exploitation of the moments obtained by integrating the product of the total field on the cylindrical boundary with complex exponential functions. The information on the unknown parameters of the problem is encoded in these moments, and hence all parameters can be recovered by means of relatively simple explicit expressions. The cases of one and two sources are considered and analyzed. Under certain conditions, the permittivity and permeability of the cylinder are also recovered. The results from two types of numerical experiments are presented: (i) for a single source, the effect of noise on the boundary data is studied, (ii) for two sources, the pertinent nonlinear system of equations is solved numerically and the accuracy of the derived solution is discussed.

The aim of this study was to evaluate the performance of the new Ingenuity TF model PET / CT system installed at cedt-CIMEQ, based on the implementation of latest international standards. Measurements were made following NEMA NU2-2012 and manufacturer's indications. The tests carried out were: energy resolution; timing resolution; spatial resolution; sensitivity; scatter fraction, counts loss, and random measurements; relative count rate error and image quality. The estimated energy and timing resolutions were 55,3 keV and 529 ps respectively. The results showed an average spatial resolution of 5.17 mm and an average absolute sensitivity of 8,26 cps / kBq. The maximum NECR peak was 119,09 kcps at 20,65 kBq / mL, while the maximum of the true count rates was 361,43 kcps at the concentration of 31,78 kBq / mL. Scatter fraction at NECR peak was 35,2% and relative error of accuracy of corrections had a maximum value of 9%. In the images obtained in the image quality test, all spheres were observed and no artifacts were found. The PET / CT Ingenuity TF System installed at cedt-CIMEQ shows physical performance similar or higher to other last generation scanners for all the parameters determined with the NEMA NU2-2012. [ABSTRACT FROM AUTHOR]

Oxygen is used extensively in illnesses involving respiratory system. In emergencies such as the one created by the flare of Covid-19, oxygen consumption has increased tremendously. This article aims to improve our understanding about the medical oxygen, its production (air separation unit, pressure swing adsorption, oxygen concentrators), the supply chain, storage methods, and the final delivery system to the patient. This article also provides a comprehensive review on the additions in the medical infrastructure during the time of oxygen crisis in India along with the introduction of certain novel approaches towards oxygen production and conservation. We aim to minimize the panic among our readers by giving them an insight about the course behind the oxygen supply in that oxygen mask. [ABSTRACT FROM AUTHOR]

Intersection formulae of Croton type for general geometric probes are well known in integral geometry. For the special case of cylinders with non necessarily convex direktrix, however, no equivalent formula seems to exist in the literature. We derive such formula resorting to motion invariant probability elements associated with test systems, instead of using a traditional approach. Because cylinders are seldom used as probes in stereological practice, however, this note is mainly of a theoretical nature.

The present numerical study investigates unsteady natural convection heat transfer within a square-shaped porous confinement with four heated cylinders. Simulations are performed for different cylinder spacings by arranging the cylinders along the enclosure diagonals in a rectangular array for different Darcy numbers (Da) and Rayleigh numbers (Ra). The positions of cylinders within the enclosure are limited to 0.3 ≤ S (= sH /L = sV /L) ≤ 0.6 and for each rectangular array computations were performed for 103 ≤ Ra ≤ 106 and 10−4 ≤ Da ≤ 10−2. Results reveal that conduction mode heat transfer dominates within the enclosure at Ra ≤ 104 irrespective of Da, whereas for Da = 10−3, 10−2, convective heat transfer prevails for high Ra (105, 106) values. With the increase in Ra up to Ra ≥ 105, the temperature and flow fields lose symmetry about the vertical centerline of the enclosure. For Ra = 106 and Da = 10−2 the change in time-averaged Nusselt number Nut with cylinder spacing is insignificant for all cylinders, whereas for Da = 10−3 Nut at the lower cylinders decreases slightly between S = 0.3 and 0.4 and then increases slightly up to S = 0.6.

This study is a systematic review of research on heat transfer analysis in cavities and aims to provide a comprehensive understanding of flow and heat transfer performance in various kinds of cavities with or without the presence of fins, obstacles, cylinders, and baffles. The study also examines the effects of different forces, such as magnetic force, buoyancy force, and thermophoresis effect on heat transfer in cavities. This study also focuses on different types of fluids, such as air, water, nanofluids, and hybrid nanofluids in cavities. Moreover, this review deals with aspects of flow and heat transfer phenomena for only single-phase flows. It discusses various validation techniques used in numerical studies and the different types and sizes of mesh used by researchers. The study is a comprehensive review of 297 research articles, mostly published since 2000, and covers the current progress in the area of heat transfer analysis in cavities. The literature review in this study shows that cavities with obstacles such as fins and rotating cylinders have a significant impact on enhancing heat transfer. Additionally, it is found that the use of nanofluids and hybrid nanofluids has a greater effect on enhancing heat transfer. Lastly, the study suggests future research directions in the field of heat transfer in cavities. This study’s findings have significant implications for a range of areas, including electronic cooling, energy storage systems, solar thermal technologies, and nuclear reactor systems.

In additive manufacturing, geometric shape deviations are built through statistical deviation models. Nonetheless, the resource constraints limit the manufacturers to test shapes. However, in addition to the power, the simplicity of the deviation models has been demonstrated with illustrative cases for in-plane deviation modelling for regular pentagon, irregular octagon as well as straight edges in free-form shapes utilizing only data and models for single regular pentagon and cylinders. Bayesian deviation models, built for geometric shapes, provide a better fit on the data and help in achieving better predictive accuracy. The main aim of this study is to assess the effect of the error distribution, generally assumed as the normal, and evaluate its impact on the deviation model. In particular, we consider Laplace, logistic, Cauchy, and exponential distributions for the errors. It is shown that logistic distribution provides better alternative error distribution for deviation models as compared to the normal distribution. [ABSTRACT FROM AUTHOR]

The studies of the classical cops and robber problem are generally aimed at determining the minimum number of cops needed to capture the robber, and proposing algorithms for the capture. This paper is a contribution to this problem, directed to two-dimensional grids, cylinders (i. e., grids with toroidal closure in one dimension), and tori, with a new extension to using teams of any number of cops. We discuss some new features of the problem and propose a new solution to the capture problem on grids that was already solved under a different approach, and then give efficient capture algorithms on cylinders and tori making use of these features. We examine the effect of using teams of any number k of cops and give efficient algorithms for this case, evaluating lower and upper bounds on the capture time t k , and compute the minimum value of k needed for any given capture time. To this aim we extend the concept of work w k = k · t k of an algorithm, inherited from parallel processing, and study a possible speed-up phenomenon using larger teams of cops. [ABSTRACT FROM AUTHOR]

The determination of the concrete modulus of elasticity (MOE) plays a crucial role in the analysis and design of structural reinforced and prestressed concrete elements. Various empirical MOE prediction equations have been developed for UHPC. However, most of the existing models have been typically calibrated or developed based on data from one type of UHPC and material tests only. As such, no previous work looked at the MOE prediction equations validity at a large-scale structural level and for the different range of UHPC mixtures that span from economic or non-proprietary lower-end mixtures to robust carbon nanofiber (CNF)-enhanced and high-end mixtures. This research fills this knowledge gap by revisiting the topic of UHPC MOE prediction equations using exclusive companion datasets of materials and full-scale structural tests that also incorporate, for the first time, four different types of UHPC mixtures. In this study, MOE values are estimated from experimentally determined axial stiffness of 22 full-scale UHPC columns with varying cross-sections in conjunction with hundreds of cylinders. The study first compared cylinders and columns-based MOE values, then used the extensive experimental datasets to assess recent and relevant UHPC MOE prediction equations, including what has been proposed for the AASHTO UHPC Structural Design Guide. The results show that while some of the existing prediction models are accurate for traditional UHPC mixtures, all models consistently underestimate MOE for CNF-enhanced UHPC and overestimate it for economic UHPC mixtures with local sand and cement. The paper concludes with a recommendation to account for UHPC mixture type and proposes new modifications for adopting MOE prediction equations for all types of UHPC. • Comprehensive experimental materials and structural UHPC testing. • Results cover three classes of UHPC: Traditional, CNF-enhanced, and economic mixtures with locally sourced materials. • Assess MOE prediction equations, including AASHTO equation, different classes of UHPC using materials and structural data. • Propose new modifications and equations for accurate MOE estimation for three distinct classes of UHPC. [ABSTRACT FROM AUTHOR]

In the paper we study encoding of the fractional part of a real number with an infinite alphabet (set of digits) coinciding with the set of non-negative integers. The geometry of this encoding is generated by Q3-representation of real numbers, which is a generalization of the classical ternary representation. The new representation has infinite alphabet, zero redundant and can be efficiently used to specify mathematical objects with fractal properties. We have been studied the functions preserving the "tails"of ̅Q3-representation of numbers and the set of such functions, some metric problems and some problems of the probability which are connected with Q3-representation. [ABSTRACT FROM AUTHOR]

Laser metal deposition (LMD) is extensively used for repairing and remanufacturing mechanical components. Amongst these components, the vast majority comprise of cylindrical and planar geometries. In recent remanufacturing work, it is a challenge to generate a deposition tool-path directly from point cloud data of a damaged surface. Additionally, the acquisition of high resolution point cloud data that is necessary to carry out a high precision repair presents another problem since it is a time-consuming process. Hence, this paper explores a novel approach for tool-path generation for the repair of cylindrical components directly from point clouds via LMD technology. The presented method discounts the surface reconstruction and registration steps and directly generates tool-path from the damaged point cloud data. In this paper, a comparison is drawn between the traditional framework of reverse engineering and the proposed approach. Following, a tool-path generation method is presented, which incorporates enhancing the resolution or information density of the point cloud data. Finally, the results are validated through a robot laser cladding system (RLCS), which carries out autonomous repair based on the tool-path algorithm. The proposed method is demonstrated to repair a cylindrical fixed bend. [ABSTRACT FROM AUTHOR]

The potential for acoustic metamaterials to provide a breakthrough in sound attenuation has been unlocked in recent times due to advancements in additive manufacturing techniques. These materials allow the targeting of specific frequencies for sound attenuation. To date acoustic metamaterials have not been experimentally tested in an automotive silencer for performance enhancement. This study investigates the effect of acoustic metamaterials within a representative automotive silencer. These results are then compared with commonly used techniques in the silencer industry to gauge the effectiveness of the acoustic metamaterials. COMSOL simulations were used to validate the developed test rig and were compared to experimental results which were obtained using the two-load transmission loss test method. Through this testing method, the implementation of the acoustic labyrinthine DENORMS cylinder proved to be the most significant improvement in transmission loss within the silencer, with an increase in transmission loss of 40 dB at 1500 Hz. It was also found that the traditional hard wall internal baffle silencer performance can be improved by replacing it with a DENORMS internal baffle. Acoustic metamaterials have potential as a novel method for automotive companies to attenuate sound of specific frequencies. [ABSTRACT FROM AUTHOR]