Plane Parallel Research Articles

Inertial wave super-attractor in a truncated elliptic cone

We consider inertial waves propagating in a fluid contained in a non-axisymmetric three-dimensional rotating cavity. We focus on the particular case of a fluid enclosed inside a truncated cone or frustum, which is the volume that lies between two horizontal parallel planes cutting an upright cone. While this geometry has been studied in the past, we generalise it by breaking its axisymmetry and consider the case of a truncated elliptic cone for which the horizontal sections are elliptic instead of circular. The problem is first tackled using ray tracing, where local wave packets are geometrically propagated and reflected within the closed volume without attenuation. We complement these results with a local asymptotic analysis and numerical simulations of the original linear viscous problem. We show that the attractors, well known in two dimensional or axisymmetric domains, can be trapped in a particular plane in three dimensions provided that the axisymmetry of the domain is broken. Contrary to previous examples of attractors in three-dimensional domains, all rays converge towards the same limit cycle regardless of initial conditions, and it is localised in the bulk of the fluid.

Effect of stroke plane inclination on the hovering aerodynamic performance of tandem flapping foils.

The four-winged form of dragonfly and damselfly allows them to fly with great agility and endurance, which are accomplished by independently controlling the kinematics of each wing. In this study, we performed numerical simulations of two tandem airfoils oscillating along an inclined stroke plane atRe=157. We investigated the effects of the stroke plane angle (β)of forefoil and hindfoil on the aerodynamic performance of dragonflies (or damselflies) hovering flight. Simulations were conducted for parallel and non-parallel stroke planes of forefoil and hindfoil oscillating with three phase differences:ϕ=0o,90oand180o. For parallel stroke planes, the results show that the total lift increases withβ, whereas the total thrust decreases in same condition. In addition, the total lift and thrust decrease with an increase inϕ. The forefoil performance is affected by the flow induced by hindfoil's leading-edge vortices, and the hindfoil interactions with forefoil's wake vortices significantly affect the hindfoil's performance. The findings demonstrate that non-parallel stroke planes exert detrimental effects on the total lift forϕ=0oand90o. However, forϕ=180o, the lift augmentation of 46% is obtained in the case where the forefoil stroke plane angle is smaller than the hindfoil. The results obtained during this investigation can help in optimizing the wing kinematics during the micro air vehicles development.

Study of flow resistance coefficients acting on regular non-spherical particles in simple shear flow at moderate Reynolds numbers

This contribution is devoted to the study of the aerodynamic characteristics of non-spherical particles of definite regular shape, such as prolate and oblate ellipsoids as well as cylinders, immersed in a locally linear shear flow. The flow resistance coefficients of drag, lift and pitching torque are computed by means of the Particle Resolved Direct Numerical Simulation (PR-DNS) technique for such shapes as function of the Reynolds number Re. The parameter space comprises particle aspect ratio, AR, fluid spin ratio, ζ, and particle orientation angle, α. The Reynolds numbers of interest are in the intermediate range 1≤Re≤100, common in industrial and environmental processes. To properly understand and explain the obtained results, the role of the friction and pressure contributions to total flow coefficients is analyzed in detail for the different cases, allowing the differences between the considered shapes to be pointed out. On the other hand, the behavior of the pressure and skin friction coefficients in the particle plane of symmetry parallel to the flow is investigated as a function of the previous parameters (shape, AR, ζ, α), which provides further insights into the features of the shear flow around the non-spherical particles at finite Re. Finally, the influence of the shear flow magnitude and incidence angle on the location of the center of aerodynamic force is devised for the three shapes considered as function of Reynolds number and particle aspect ratio. It is expected that the information generated in this work will be useful for researchers to enhance the modeling of non-spherical particles immersed in non-uniform flows.

Parallels in Cartography: Standard, Equidistantly Mapped and True Length Parallels

In the literature on map projections, we regularly encounter the name standard parallel or standard parallels. However, it is obvious that a unique definition of a standard parallel is not universally accepted. To fully clarify the meaning of standard parallels, the author proposes the notion of equidistantly mapped parallels, which has not been common in the literature so far. Equidistantly mapped parallels can be in the direction of the parallel or in the direction of the meridian. Here, it is shown that every standard parallel is also an equidistantly mapped parallel, but that the reverse need not be true. If the parallel is mapped equidistantly in the direction of the parallel, then its length in the projection plane is equal to the length of that parallel on the sphere. The opposite does not have to be true, i.e., if the length of the image of the parallel in the projection plane is equal to the length of the parallel on the sphere, this does not mean that the parallel was mapped equidistantly. In addition to standard and equidistant parallels, the concept of parallels of true length also appears in the theory of map projections. They should also be distinguished from standard and equidistant parallels.

Enhanced surface flashover performance of oriented hexagonal boron nitride composites via anisotropic charge transportation

AbstractSurface flashover is a crucial issue for the miniaturisation of electronic facilities in military, industrial, and aerospace engineering. The oriented hexagonal boron nitride (hBN) composites, due to excellent thermal and electrical insulating properties, show a potential application in high‐voltage power equipment, while the surface flashover performance of hBN composites dependent on oriented hBN texture is rarely reported. The effects of hBN orientation and contents on the surface flashover performances of oriented hBN composites are investigated. The isothermal surface potential decay of the oriented hBN composites was also studied. It is found that the charge transportation could be adjusted by the hBN orientation, thus regulating surface flashover strength. The DC flashover voltage of the in‐plane oriented hBN composites with a thickness of 15 μm reached the maximum of 27.6 kV at the hBN loading of 20 wt%, 14.5% higher than that of the pure resin. The carrier mobility of out‐of‐plane oriented hBN composites is about three times greater than that of the in‐plane oriented composites, indicating that the charges are easily transported along the hBN basal plane. The larger carrier mobility causes charge dissipation in composites near the electrode at the hBN basal plane parallel to the axis of electrodes and inhibits the distortion of the surface electric field on the composites, thus enhancing the surface flashover. Consequently, developing oriented insulators for high‐voltage applications and enabling an optimum insulation design would be beneficial because of the compactness and high reliability of power apparatus for use in power grids.

The effect of background information and motion speed on the performance of TTC estimation

BackgroundIn previous studies, most research on motion perception have been conducted under background-free condition when the stimulus moved in a plane parallel to the observer. In real-life situations, people’s perception of the motion state of objects is usually done under different visual noise. Based on the occlusion paradigm, this study aimed to investigate whether different background information and motion speed affect the trend and accuracy of time-to-collision (TTC) estimation when stimuli move in a plane parallel to the observer.MethodsThirty five college students (mean age = 20.94, SD = 2.95, range = 18-28 years) participated in experiment 1, and used a 2 (background orientation: horizontal, vertical) × 3 (motion speed: slow, medium, fast) design to explore the effect of different line segment orientations and motion speed on TTC estimation performance; 36 college students (mean age = 20.81, SD = 2.82, range = 18-28 years) participated in experiment 2, and used a 2 (background dimension: two-dimensional background, three-dimensional background) × 3 (motion speed: slow, medium, fast) design to explore the effect of different background dimensions and motion speed on the performance of TTC estimation. The data were analyzed using SPSS 25.0.ResultsThe results revealed that: (1) The TTC was underestimated for the slow speed condition and overestimated for the medium and fast speed conditions. (2) The highest accuracy of TTC estimation was obtained for the fast condition. (3) The TTC were overestimated for the vertical background condition and underestimated for the horizontal background condition. (4) Compared to the two-dimensional background, the TTC was overestimated in the three-dimensional background.ConclusionsObject motion speed affected the TTC estimation performance, and different background information affected the TTC estimation performance when the object moved in a plane parallel to the observer. Meanwhile, the impact of background orientation and motion speed showed significant interactions.

Examining laminar, non-stationary viscoelastic fluid flow between two parallel planes

The generalized Maxwell model is used to handle problems involving the unsteady flow of a viscoelastic fluid in a flat channel under the effect of a constant pressure gradient. Formulas for fluid flow, velocity distribution, and other hydrodynamic characteristics were found. Transient processes during unsteady flow of a viscoelastic fluid in a flat channel are investigated based on the discovered formulas. The analysis’s conclusions demonstrated that, at small Debord number values, the procedures of changing a viscoelastic fluid’s properties from an unstable to a stationary state essentially don’t differ from those of a Newtonian fluid. Exceeding the Debord number relatively unity, it has been established that the process of transition of a viscoelastic fluid from an unsteady state to a stationary state is of a wave nature, in contrast to the transition process of a Newtonian fluid, and the transition time is several times longer than that of a Newtonian fluid. It was also discovered that perturbed processes can arise during the transition. These disturbances occurring in unsteady flows of a viscoelastic fluid can be stabilized by mixing the Newtonian fluid within it. The implementation of this property is important in preventing technical failures or malfunctions.

Устойчивость трансляционных колебаний зажатой капли маловязкой жидкости

The study investigates oscillatory dynamics of a drop of a low-viscosity liquid surrounded by another liquid under translational low-amplitude vibration influence. A drop of equilibrium cylindrical shape is sandwiched between parallel solid planes. The contact angles are straight and constant, the contact lines of the three media slide freely along the surface of the plates. At the droplet–surrounding liquid interface, a thin viscous boundary layer is taken into account. Natural and forced oscillations of the drop are considered. In the main order of expansion in terms of small amplitude of vibrations, the natural frequencies of oscillations of an inviscid cylindrical drop were obtained. In the first order of expansion, a correction to the frequency was found, caused by energy dissipation in the viscous boundary layer. The stability of forced oscillations with respect to small disturbances was studied. Parametric resonance occurred when the synchronism condition was met: the vibration frequency was equal to the sum of the frequencies of two adjacent modes of natural oscillations. An expression describing the resonant regions was found. It is shown that low viscosity leads to the appearance of a vibration amplitude threshold and a shift in the instability region when compared with zero viscosity.

Local structure of convex surfaces

A point on the surface of a convex body and a supporting plane to the body at this point are under consideration. A plane parallel to this supporting plane and cutting off part of the surface is drawn. The limiting behaviour of the cut-off part of the surface as the cutting plane approaches the point in question is investigated. More precisely, the limiting behavior of the appropriately normalized surface area measure in $S^2$ generated by this part of the surface is studied. The cases when the point is regular and singular (a conical or a ridge point) are considered. The supporting plane can be positioned in different ways with respect to the tangent cone at the point: its intersection with the cone can be a vertex, a line (if a ridge point is considered), a plane angle (which can degenerate into a ray or a half-plane), or a plane (if the point is regular and, correspondingly, the cone degenerates into a half-space). In the case when the intersection is a ray, the plane can be tangent (in a one- or two-sided manner) or not tangent to the cone. It turns out that the limiting behaviour of the measure can be different. In the case when the intersection of the supporting plane and the cone is a vertex or in the case of a (one- or two-sided) tangency, the weak limit always exists and is uniquely determined by the plane and the cone. In the case when the intersection is a line or a ray with no tangency, there may be no limit at all. In this case all possible weak partial limits are characterized. Bibliography: 13 titles.

Corpus callosum agenesis: a review

The corpus callosum (CC) connects the two brain hemispheres through axonal fiber tissues, being important for the functional integration of sensory, motor, visuomotor and cognitive processes, in addition to processing and management of social and emotional stimuli. Agenesis of the corpus callosum (ACC) is a congenital brain malformation defined by anatomy (complete or partial absence of the corpus callosum), rarely occurring in isolation and is a specific and relatively easy to detect phenotypic marker for developmental disorders. The prevalence of ACC in the general population is extremely variable and probably underestimated due to the asymptomatic course, the usual range is 0.020–0.025%, in individuals with neurodevelopmental impairment this defect has a prevalence of 1 to 3%. Etiology that varies, from maternal alcohol consumption, to prenatal infections, chromosomal errors or genetic mutations. Fetal alcohol syndrome (FAS) is the most important non-genetic congenital cause of ACC, with an incidence of approximately 7% in FAS cases, but the most frequent cause of ACC are genetic mutations related to axonal guidance pathways, ciliary development, cell adhesion, proliferation, differentiation and migration. Patients with ACC can be divided into three groups: the first including individuals with “syndromic” ACC who commonly present severe neurocognitive deficiency that obscures the deficiencies directly caused by the absence of CC generally associating cerebral malformations, non-cerebral structural defects, altered patterns of growth and development, in addition to progressive neurological symptoms and sensory impairment; the second presents with neurodevelopmental diseases in which ACC has been suggested to play a role; and the final includes patients with isolated complete or partial ACC who remain neurologically asymptomatic and have normal intelligence, however, in-depth neuropsychological screening can often reveal mild behavioral and cognitive deficits. In recent decades, magnetic resonance imaging (MRI) has been implemented, a tool that has increased the recognition of fetal diagnosis, which is performed in three planes and is useful in identifying associated anomalies. The use of MRI is essential and must be done together with a complementary fetal ultrasound exam, with the midsagittal plane parallel to the CC being ideal for evaluation. Multiplanar fetal neurosonography is the best imaging test to evaluate the fetus from the 20th week of gestation onwards. Most brain abnormalities remain undiagnosed until midway through the first trimester, and may go undetected due to small fetal brain structures. Between the 11th and 13th weeks, ultrasound can highlight changes that are incompatible with life. Multiplanar neurosonography is indicated in the middle of the first trimester of pregnancy, including non-axial plane scanning. The sonographer's knowledge of fetal anatomy and sonoembryology results in early diagnosis.

Photon energy dependence of photoneutron production from heavy targets

The double differential cross-sections (DDXs) of photoneutron production via the photonuclear reaction on tantalum, tungsten, and bismuth for 13 and 17 MeV linearly polarized photon beams were measured using the time-of-flight method at the NewSUBARU-BL01 facility. Polarized photons were obtained by the Laser Compton backscattering (LCS) technique. Two distinct components were observed on the spectra: the lowenergy component up to 4 MeV and the high-energy above 4 MeV. The angular distribution of the low-energy component was isotropic, whereas the high-energy was distributed anisotropically and influenced by the angle between direction of photon polarization and neutron emission, especially for 17 MeV photon energy. These phenomena were similar to those of 197Au target observed in the previous studies. The low-energy neutron distributions at 13 and 17 MeV photon energies were almost identical for all three targets. The DDX energy integration was calculated and compared among the three targets for two-photon energies. Given the horizontal polarization (plane parallel to the x-axis) of the incident photons, the emission angles of 90° on the x-axis and y-axis recorded the maximum and minimum photoneutron yield, respectively. The differences between these two positions were minor for 181Ta and natW at 13 MeV photon energy and noticeable for other cases. An underestimation of the TENDL nuclear data library was observed on the photoneutron DDXs compared to the experimental results for 181Ta and 209Bi.

DROPLET SIZE DISTRIBUTION VARIATION OF PENDENT FIRE SPRINKLER SPRAY DEPENDING ON THE MEASUREMENT LOCATION

Droplet size of sprinkler sprays is related to the rate of evaporation and penetration of a fire plume. However, sprinkler sprays have various droplet sizes even at one location. Therefore, it is essential to examine the droplet size distribution depending on the location to predict the fire suppression performance of the sprinkler spray. To examine the droplet size distribution of spray from a pendent sprinkler head, acrylic plates were installed around the sprinkler head and a gap was made on one side of the wall. A charge-coupled device camera was installed to capture the droplet images both on a plane parallel to the sprinkler frame arm and on a plane perpendicular to the frame arm. Droplet information was obtained by deriving the image from the brightness and gradient images extracted from the original image. Large droplets, exceeding 1.5 mm in diameter, were observed in the mainstream of the spray. The probability of observing small droplets decreased as the droplets moved downstream. Spherical droplets were observed in the mainstream of the frame arm direction, while nonspherical droplets were observed in the perpendicular direction to the frame arm because of high velocity. The number-based cumulative distribution function (CDFs) fitted using the Rosin-Rammler distribution function provided the best fitting results. The volume CDFs fitted using the Rosin-Rammler distribution function yielded acceptable adjusted R<sup>2</sup> values. In this case, the coefficient m related to D<sub>v50</sub> and the coefficient n related to the width of the distribution increased with increasing radial and vertical locations.

Investigation of flow characteristics and velocity fields of excited two parallel plane jets

An experimental investigation was conducted to study the flow characteristics and velocity fields of excited two parallel plane jets. The experiments were carried out at a jet Reynolds number of 200. A loudspeaker system was used to create the jets pulsation and to vary the intensity of jet pulsations at a constant excitation frequency of 40 Hz. A hot-wire anemometer was used to measure the velocities of the jets as they exited. The flow patterns were visualized using a laser-light sheet technique combined with smoke flow visualization. The jet spread widths were determined from images taken with a long-exposure method using binary edge detection. A particle image velocimetry measurement technique was used to render the flow field behaviors of the parallel jets. The introduction of jet pulsation by the speaker led to the roll-up of coherent vortices along the shear layers of the jets. These vortices became more prominent as the intensity of jet pulsations increased. These coherent vortices broke apart into turbulent eddies, resulting in wider jet spread with higher pulsation intensities. Two counter-rotating vortices were detected at the jet exit. These vortices moved closer to the jet exits as the jet pulsation intensity was increased. The intensity of turbulence and the presence of vortices were both influenced by the magnitude of the jet pulsation. Greater jet pulsation led to higher turbulence levels, a more pronounced vorticity field, and a more efficient transfer of momentum, consequently enhancing the mixing process.

SRANS Simulation on a Helical-Segmented Finned Tube Bank

A numerical simulation on a six-row helical-segmented finned tube in a staggered layout is performed with the Reynolds Averaged Navier-Stokes (RANS) approach. The turbulence effect is represented with the k-ε RNG model, and a fixed temperature in each tube row considers the inside fluid temperature. The tube bank is represented by a small finned tube bank and a single interacted module. The small finned tube bank considers symmetry conditions on the sides of the computational domain. The single interacted module considers periodic boundary conditions for velocity, pressure, and temperature. Both simulations are compared to develop the basis of complex simulations such as repetitive finned tube modules. Average values on parallel planes to the streamwise direction for velocities, pressures, and temperatures are compared in both simulations. The comparative analyses show deviations lower than 11% for the velocity field, 12% for the pressure field, and 10% single for the temperature field. Therefore, results show an appropriate flow representation with periodic boundary conditions.

Over 6 μm thick MOCVD-grown low-background carrier density (1015 cm−3) high-mobility (010) β-Ga2O3 drift layers

This work reports high carrier mobilities and growth rates simultaneously in low unintentionally doped (UID) (1015 cm−3) metalorganic chemical vapor deposition (MOCVD)-grown thick β-Ga2O3 epitaxial drift layers, with thicknesses reaching up to 6.3 μm, using triethylgallium (TEGa) as a precursor. Record-high room temperature Hall mobilities of 187–190 cm2/V s were measured for background carrier density values of 2.4–3.5 × 1015 cm−3 grown at a rate of 2.2 μm/h. A controlled background carrier density scaling from 3.3 × 1016 to 2.4 × 1015 cm−3 is demonstrated, without the use of intentional dopant gases such as silane, by controlling the growth rate and O2/TEGa ratio. Films show smooth surface morphologies of 0.8–3.8 nm RMS roughness for film thicknesses of 1.24–6.3 μm. Vertical Ni Schottky barrier diodes (SBDs) fabricated on UID MOCVD material were compared with those fabricated on hydride vapor phase epitaxy material, revealing superior material and device characteristics. MOCVD SBDs on a 6.3 μm thick epitaxial layer show a uniform charge vs depth profile of ∼ 2.4 × 1015 cm−3, an estimated μdrift of 132 cm2/V s, breakdown voltage (VBR) close to 1.2 kV, and a surface parallel plane field of 2.05 MV/cm without any electric field management—setting record-high parameters for any MOCVD-grown β-Ga2O3 vertical diode to date.

МЕТОД ПОБУДОВИ ПЛОСКОЇ КАРТИ НАВКОЛИШНЬОГО ПРОСТОРУ ДЛЯ МОБІЛЬНОЇ РОБОТИЗОВАНОЇ СИСТЕМИ

The paper proposes a method of building a local map of a mobile robot, which allows determining the position of objects in space with the help of a laser range finder. In addition, the accuracy parameters of the specified method of building an environment map were analyzed, which allows for the formation of requirements for hardware for controlling a mobile robot. It is assumed that the initial map is known and during the work (the movement of the robot) it is only clarified and supplemented. The main sensors used are odometers (wheel speed sensors) and a laser scanning range finder (lidar), which measures the distance to obstacles in a plane parallel to the plane of the robot's movement. Scanning rangefinders in machine vision systems form in this case a two-dimensional picture of the surrounding space. The final result of laser scanning is the determined spatial coordinates of the points of obstacles. The collection of laser beam reflection points forms an irregular grid with a large number of such points. According to these data, a digital model of the surface space in the form of a regular grid can be obtained by a mathematical method, after camera refinement. Insurmountable obstacles mean only projecting obstacles that fall into the field of view of the rangefinder (that is, have a height not less than the height of the rangefinder installation). It is proposed to sort the measured current points on a known map. Changes may have occurred since the creation of the v-home map (the map may be out of date). It is necessary not only to make these changes to the map, but also not to miss the old known obstacles, which are remeasured in the process. The proposed method of constructing the map works well only in a normal environment, that is, in the case when the angular dimensions of obstacles are several times greater than the angular resolution of the rangefinder. In the presence of a large number of small obstacles, the speed of the method drops sharply and errors during map construction increase. The great advantage of the method is that the number of saved points is always known - it is the number of curve segments multiplied by three.

Achieving exceptional work-hardening capability of additively-manufactured multiphase Fe-Mn alloys via multiple deformation mechanisms

Laser-powder-bed-fusion (LPBF) fabricated Fe-Mn biodegradable alloys provide an attractive prospect for orthopedic applications due to their good tensile strength and high degradation rate. Nevertheless, the ε-martensite and heterogeneous microstructures produced by the LPBF processing often lead to premature failure of alloys. Herein, we report a LPBFed multiphase Fe-18Mn alloy (γ-austenite, ε-martensite, and α-ferrite) fabricated from pre-alloyed powders. After annealing at 650 °C, the alloy with a uniform microstructure displays a high 1 GPa tensile strength, a good fracture elongation of 16 %, and an extremely high work-hardening rate of 8500 MPa. The work-hardening rate is higher than that reported in most Fe-Mn steels and Fe-based high entropy alloys. The grain size of a few hundred nanometers provided the excess Gibbs free energy, resulting in an increase in the stacking fault energy (SFE) to 23.9 mJ/m2. The multiple deformation mechanisms, i.e., SFs, the martensitic transformation (γ → ε → α') and nano-deformation twins (DTs), were sequentially activated. We elucidate such unique work-hardening capability, originating from the interaction between the DTs, SFs and transformed martensite. Besides a high-density of dislocations were accumulated between parallel planar defects, the cooperative deformation of the soft and hard phases provided continuous hardening. Our findings highlight the exceptional work-hardening capability of additively-manufactured Fe-Mn alloys achieved by a multiphase material exhibiting multiple deformation mechanisms. The work also provides a straightforward approach for the development of stable-implanted Fe-based bone substitutes.

The effect of pharyngeal structures on the severity of obstructive sleep apnea.

Obstructive sleep apnea (OSA) is characterized by complete or partial cessation of breathing during sleep. The tongue is suggested as a possible anatomical site causing airway obstruction. However, the role of other pharyngeal structures in the development of OSA remains unclear. We designed a study using both the apnea-hypopnea index (AHI) and the oxygen saturation measurements to assess the severity of OSA. We aimed to identify critical anatomical structures of the upper airway that correlate with the severity of OSA and toevaluate the utility of magnetic resonance imaging (MRI) markers to detect possible OSA inpatients without overt symptoms. The study included participants referred to the neurology outpatient clinic from the check-up unit. Participants were grouped as controls, mild, moderate, or severe OSA according to the AHI. A cranial MRI with a field of view (FOV) encompassing the upper airway structures was obtained from all participants. The areas of the tongue and the uvula were measured on the sagittal images by drawing the boundaries of the tissues manually. The posterior air space (PAS) area was evaluated from regions of interest in five parallel planes. Of 105 participants, 30 were controls, 27 had mild, 25 had moderate, and 23 had severe OSA.The moderate and severe OSA groups did not differ in oxygen saturation levels during sleep. Therefore, patients withmoderate and severe OSA were combined into one group (moderate/severe OSA). The area of the tongue was significantly larger in the moderate/severe OSA group compared to the control group. Both the tongue and the uvula areas showed a significant positive correlation with the AHI. Our findings suggest that the tongue and uvula have prominent roles in the severity of OSAS. It may be useful to measure these structures with MRI to screen for at-risk individuals without overt OSA symptoms.

Natural born cullers? How hunters police the more-than-human right to the city

Urban areas are a messy more-than-human interface for humans and synanthropic wildlife. Norms for what constitutes a ‘problem’ animal to be culled, a displaced animal to be rescued, or a species nuisance whom one simply has to let live, are undergoing rapid change. We investigate the changing expectations that municipal hunters experience that they have from society in relation to managing problem wildlife in cities. Adding to the literature on the constitution of ‘problem’ animals in human environments, we show what happens to these animals in the practical sense, and what informs this decision. Our point of departure is to ask by what rationales hunters consider lethal interventions in urban nature to be legitimate, and which they find to be morally problematic. In a discussion, we reflect on what this says about, and means for, multispecies coexistence. Through interviews and go-along participant observation with 32 municipal hunters in Sweden, we show how municipal hunters wrestle with growing unease about new custodial roles they are expected to inhabit, as facilitators of the natural order, as garbage collectors of society for unwanted wildlife, and as enforcers of an interspecies code of conduct for the city. Based on this analysis, we discuss the relative standing of reparative, sacrificial, aesthetic, goodwill, practical, categorical and situational rationales for culling. This paints a picture of hunters as more conflicted about their control of urban nature, in challenge with the stereotypical idea of the professional hunter as a ‘natural born culler’. It also shows a city of parallel planes of multispecies coexistence, where some species and animals get a pass more than others.

A Unified Real-Time Motion Generation Algorithm for Approximate Position Analysis of Planar N-Bar Mechanisms

Abstract This paper presents a novel real-time kinematic simulation algorithm for planar N-bar linkage mechanisms, both single- and multi-degrees-of-freedom, comprising revolute and/or prismatic joints and actuators. A key feature of this algorithm is a reinterpretation technique that transforms prismatic elements into a combination of revolute joint and links. This gives rise to a unified system of geometric constraints and a general-purpose solver which adapts to the complexity of the mechanism. The solver requires only two types of methods—fast dyadic decomposition and relatively slower optimization-based—to simulate all types of planar mechanisms. From an implementation point of view, this algorithm simplifies programming without requiring handling of different types of mechanisms. This versatile algorithm can handle serial, parallel, and hybrid planar mechanisms with varying degrees-of-freedom and joint types. Additionally, this paper presents an estimation of simulation time and structural complexity, shedding light on computational demands. Demonstrative examples showcase the practicality of this method.