Estimation of relative displacement of two adjacent asymmetric structures

AbstractWhen sound interacts with geometrically asymmetric structures, it experiences coupling between pressure and particle velocity, known as Willis coupling. While in most instances this phenomenon is perturbative in nature, tailored asymmetries combined with resonances can largely enhance it, enabling exotic acoustic phenomena. In these systems, Willis coupling obeys reciprocity, imposing an even symmetry of the Willis coefficients with respect to time reversal and the impinging wave vector, which translates into stringent constraints on the overall scattering response. In this work, we introduce and experimentally observe a dual form of acoustic Willis coupling, arising in geometrically symmetric structures when time-reversal symmetry is broken, for which the pressure-velocity coupling is purely odd-symmetric. We derive the conditions to maximize this effect, we experimentally verify it in a symmetric subwavelength scatterer biased by angular momentum, and we demonstrate the opportunities for sound scattering enabled by odd Willis coupling. Our study opens directions for acoustic metamaterials, with direct implications for sound control, non-reciprocal scattering, wavefront shaping and signal routing, of broad interest also for nano-optics, photonics, elasto-dynamics, and mechanics.

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Policing gentrification or policing displacement? Testing the relationship between order maintenance policing and neighbourhood change in Los Angeles

Urban Studies ◽

10.1177/0042098021993354 ◽

2021 ◽

pp. 004209802199335

Author(s):

Charles R. Collins ◽

Forrest Stuart ◽

Patrick Janulis

Keyword(s):

Los Angeles ◽

Low Income ◽

Quantitative Research ◽

Police Department ◽

Relative Displacement ◽

Simultaneous Increase ◽

Census Tracts ◽

Order Maintenance ◽

Neighbourhood Change ◽

Number Of Citations

Urban scholars increasingly contend that local police departments play a central role in facilitating neighbourhood change. Recent critics warn that ‘order maintenance’ policing and other low-level law enforcement tactics are deployed in gentrifying areas to displace ‘disorderly’ populations. Despite influential qualitative case studies, there remains scant quantitative research testing this relationship, and few studies that evaluate the link between policing, displacement and gentrification. We address this lacuna, drawing on new citation data from the Los Angeles Police Department (LAPD) and employing a measure of neighbourhood change that focuses on the displacement of low-income residents. Examining policing patterns in 978 US Census tracts in Los Angeles over four years, our analysis reveals that tracts experiencing gentrification – defined as the simultaneous increase in non-poor residents and decrease in the number of people in poverty – experience a greater number of citations compared with other tract types. Similar patterns emerge in our analysis of citations that explicitly target homelessness and extreme poverty. In post-hoc analyses, we found that Census tracts characterised by a decrease in the number of people in poverty experienced greater numbers of total police citations and of citations targeting homeless individuals, compared with other tract types. These findings carry important theoretical implications for understanding the divergent manifestations of, and potential mechanisms driving, order maintenance policing. Methodologically, we contend that police citations provide a more precise measure of order maintenance policing compared with previous studies, and that classifying neighbourhoods in terms of relative displacement of residents in poverty provides much-needed interpretive clarity.

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Josephson effect in graphene bilayers with adjustable relative displacement

Physical Review Research ◽

10.1103/physrevresearch.2.032074 ◽

2020 ◽

Vol 2 (3) ◽

Author(s):

Mohammad Alidoust ◽

Antti-Pekka Jauho ◽

Jaakko Akola

Keyword(s):

Josephson Effect ◽

Relative Displacement

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Influence of Relative Displacement on Surface Roughness in Longitudinal Turning of X37CrMoV5-1 Steel

Materials ◽

10.3390/ma14051317 ◽

2021 ◽

Vol 14 (5) ◽

pp. 1317

Author(s):

Michal Skrzyniarz ◽

Lukasz Nowakowski ◽

Edward Miko ◽

Krzysztof Borkowski

Keyword(s):

Surface Roughness ◽

Standard Deviation ◽

Surface Texture ◽

Roughness Parameter ◽

Relative Displacement ◽

Edge Radius ◽

Shaping Process ◽

Feed Value ◽

Longitudinal Turning ◽

Final Effect

The shaping process of surface texture is complicated and depends on many factors and phenomena accompanying them. This article presents the author’s test stand for the measurement of relative displacements in a tool–workpiece system during longitudinal turning. The aim of this study was to determine the influence of edge radius on the relative displacement between the tool and workpiece. The cutting process was carried out with inserts with different edge radii for X37CrMoV5-1 steel. As a result of the research, vibration charts of the tool–workpiece system were obtained. In the range of feed 0.03–0.18 mm/rev, the values of the standard deviation of relative displacements in the x-axis were obtained in the range of 0.36–0.78 μm for the insert with an edge radius of rn = 48.8 μm. As a result of the work, it was determined that for the feed value of 0.12 mm/rev for all inserts, the relative displacements are the smallest. As the final effect, the formula for forecasting the Ra roughness parameter was presented.

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Density Distribution Maps: A Novel Tool for Subcellular Distribution Analysis and Quantitative Biomedical Imaging

Sensors ◽

10.3390/s21031009 ◽

2021 ◽

Vol 21 (3) ◽

pp. 1009

Author(s):

Ilaria De Santis ◽

Michele Zanoni ◽

Chiara Arienti ◽

Alessandro Bevilacqua ◽

Anna Tesei

Keyword(s):

Density Distribution ◽

Large Scale ◽

Super Resolution ◽

Spatial Location ◽

Relative Displacement ◽

Distribution Analysis ◽

Laboratory Equipment ◽

Imaging Device ◽

Distribution Maps ◽

Super Resolution Microscopy

Subcellular spatial location is an essential descriptor of molecules biological function. Presently, super-resolution microscopy techniques enable quantification of subcellular objects distribution in fluorescence images, but they rely on instrumentation, tools and expertise not constituting a default for most of laboratories. We propose a method that allows resolving subcellular structures location by reinforcing each single pixel position with the information from surroundings. Although designed for entry-level laboratory equipment with common resolution powers, our method is independent from imaging device resolution, and thus can benefit also super-resolution microscopy. The approach permits to generate density distribution maps (DDMs) informative of both objects’ absolute location and self-relative displacement, thus practically reducing location uncertainty and increasing the accuracy of signal mapping. This work proves the capability of the DDMs to: (a) improve the informativeness of spatial distributions; (b) empower subcellular molecules distributions analysis; (c) extend their applicability beyond mere spatial object mapping. Finally, the possibility of enhancing or even disclosing latent distributions can concretely speed-up routine, large-scale and follow-up experiments, besides representing a benefit for all spatial distribution studies, independently of the image acquisition resolution. DDMaker, a Software endowed with a user-friendly Graphical User Interface (GUI), is also provided to support users in DDMs creation.

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Transient Response of Bridge Piers to Structure Separation under Near-Fault Vertical Earthquake

Applied Sciences ◽

10.3390/app11094068 ◽

2021 ◽

Vol 11 (9) ◽

pp. 4068

Author(s):

Wenjun An ◽

Guquan Song

Keyword(s):

Large Scale ◽

Bending Moment ◽

Relative Displacement ◽

Superposition Method ◽

Longitudinal Displacement ◽

Transient Wave ◽

Vibration Period ◽

Vertical Excitation ◽

Mode Superposition Method ◽

Main Girder

Given the possible separation problem caused by the double-span continuous beam bridge under the action of the vertical earthquake, considering the wave effect, the transient wave characteristic function method and the indirect mode superposition method are used to solve the response theory of the bridge structure during the earthquake. Through the example analysis, the pier bending moment changes under different vertical excitation periods and excitation amplitudes are calculated. Calculations prove that: (1) When the seismic excitation period is close to the vertical natural vibration period of the bridge, the main girder and the bridge pier may be separated; (2) When the pier has a high height, the separation has a more significant impact on the longitudinal displacement of the bridge, but the maximum relative displacement caused by the separation is random; (3) Large-scale vertical excitation will increase the number of partitions of the structure, and at the same time increase the vertical collision force between the main girder and the pier, but the effect on the longitudinal displacement of the form is uncertain; (4) When V/H exceeds a specific value, the pier will not only be damaged by bending, but will also be damaged by axial compression.

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Roller–rail parameters on the transverse vibration characteristics of super-high-speed elevators

Transactions of the Canadian Society for Mechanical Engineering ◽

10.1139/tcsme-2018-0083 ◽

2019 ◽

Vol 43 (4) ◽

pp. 535-543 ◽

Cited By ~ 2

Author(s):

Shunxin Cao ◽

Ruijun Zhang ◽

Shuohua Zhang ◽

Shuai Qiao ◽

Dongsheng Cong ◽

...

Keyword(s):

High Speed ◽

Relative Displacement ◽

Guide Rail ◽

Coupled Vibration ◽

Vibration Acceleration ◽

Vibration Model ◽

Vibration Problems ◽

Equivalent Method ◽

Relationship Of ◽

The Relationship

Interaction and wear between wheel and rail become increasingly serious with the increase in elevator speed and load. Uneven roller surface, eccentricity of rollers, and the looseness of rail brackets result in serious vibration problems of high-speed and super-high-speed elevators. Therefore, the forced vibration differential equation representing elevator guide rails is established based on Bernoulli–Euler theory, and the vibration equation of the elevator guide shoes and the car is constructed using the Darren Bell principle. Then, the coupled vibration model of guide rail, guide shoes, and car can be obtained using the relationship of force and relative displacement among these components. The roller–rail parameters are introduced into the established coupled vibration model using the model equivalent method. Then, the influence of roller–rail parameters on the horizontal vibration of super-high-speed elevator cars is investigated. Roller eccentricity and the vibration acceleration of the car present a linear correlation, with the amplitude of the car vibration acceleration increasing with the eccentricity of the roller. A nonlinear relationship exists between the surface roughness of the roller and the vibration acceleration of the car. Increased continuous loosening of the guide rail results in severe vibration of the car at the loose position of the support.

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Investigation of the Thermodynamic Properties of Anharmonic Crystals with Defects and Influence of Anharmonicity in Exafs by the Moment Method

International Journal of Modern Physics B ◽

10.1142/s0217979298000144 ◽

1998 ◽

Vol 12 (02) ◽

pp. 191-205 ◽

Cited By ~ 7

Author(s):

Vu Van Hung ◽

Nguyen Thanh Hai

Keyword(s):

Thermal Expansion ◽

Thermodynamic Properties ◽

Phase Change ◽

Specific Heat ◽

Thermal Expansion Coefficient ◽

Expansion Coefficient ◽

Moment Method ◽

Adiabatic Compressibility ◽

Relative Displacement ◽

The Moment

By the moment method established previously on the basis of the statistical mechanics, the thermodynamic properties of a strongly anharmonic face-centered and body-centered cubic crystal with point defect are considered. The thermal expansion coefficient, the specific heat Cv and Cp, the isothermal and adiabatic compressibility, etc. are calculated. Our calculated results of the thermal expansion coefficient, the specific heat Cv and Cp… of W, Nb, Au and Ag metals at various temperatures agrees well with the measured values. The anharmonic effects in extended X-ray absorption fine structure (EXAFS) in the single-shell model are considered. We have obtained a new formula for anharmonic contribution to the mean square relative displacement. The anharmonicity is proportional to the temperature and enters the phase change of EXAFS. Our calculated results of Debye–Waller factor and phase change in EXAFS of Cu at various temperatures agrees well with the measured values.

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Jet-torus connection in radio galaxies

Astronomy and Astrophysics ◽

10.1051/0004-6361/201731048 ◽

2018 ◽

Vol 609 ◽

pp. A80 ◽

Cited By ~ 9

Author(s):

C. M. Fromm ◽

M. Perucho ◽

O. Porth ◽

Z. Younsi ◽

E. Ros ◽

...

Keyword(s):

Thermal Emission ◽

Ambient Medium ◽

Galactic Nuclei ◽

Radio Galaxies ◽

Asymmetric Structures ◽

Long Baseline ◽

Volume Method ◽

Index Maps ◽

Thermal Absorption ◽

Core Shift

Context. High resolution very long baseline interferometry observations of active galactic nuclei have revealed asymmetric structures in the jets of radio galaxies. These asymmetric structures may be due to internal asymmetries in the jets or they may be induced by the different conditions in the surrounding ambient medium, including the obscuring torus, or a combination of the two. Aims. In this paper we investigate the influence of the ambient medium, including the obscuring torus, on the observed properties of jets from radio galaxies. Methods. We performed special-relativistic hydrodynamic (SRHD) simulations of over-pressured and pressure-matched jets using the special-relativistic hydrodynamics code Ratpenat, which is based on a second-order accurate finite-volume method and an approximate Riemann solver. Using a newly developed radiative transfer code to compute the electromagnetic radiation, we modelled several jets embedded in various ambient medium and torus configurations and subsequently computed the non-thermal emission produced by the jet and thermal absorption from the torus. To better compare the emission simulations with observations we produced synthetic radio maps, taking into account the properties of the observatory. Results. The detailed analysis of our simulations shows that the observed properties such as core shift could be used to distinguish between over-pressured and pressure matched jets. In addition to the properties of the jets, insights into the extent and density of the obscuring torus can be obtained from analyses of the single-dish spectrum and spectral index maps.

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