Body Collisions Research Articles

Career readiness: Finding a place for health and safety education.

Studies have identified gaps in health and safety knowledge and work practices of vocational students in the United States and abroad. Little is known about what, how, when, or if health and safety are taught and if the teaching that takes place is effective. Faculty skilled in their technical area may lack knowledge related to health and safety and pedagogy. This knowledge gap is compounded by a deficiency or absence of high-quality safety and health resources for vocational and technical college faculty, the use of outdated and often inaccurate information, and lack of any standardized assessment of knowledge and skills. To identify these knowledge gaps, we conducted group interviews with auto body collision technology and machine tool technology faculty at two colleges. Most instructors reported a rapid transition from technical trade worker or business owner into their faculty role, with little support or education related to teaching. No instructor used a defined health and safety curriculum and materials or could describe the breadth safety skills required for their profession. Instructors tested and evaluated health- and safety-related skills on an ad hoc basis and said that workers and employers were ultimately responsible for job health and safety. Standardized health and safety training is needed nationally and should be progressive and integrated with career-specific educational programs. It should ensure that students obtain knowledge and understanding of how to apply the principles of safety and health and communicate with employers about health- and safety-related issues.

Mesosiderite formation on asteroid 4 Vesta by a hit-and-run collision

Collision and disruption processes of proto-planetary bodies in the early solar system are key to understanding the genesis of diverse types of main-belt asteroids. Mesosiderites are stony-iron meteorites that formed by mixing of howardite-eucrite-diogenite-like crust and molten core materials and provide unique insights into the catastrophic break-up of differentiated asteroids. However, the enigmatic formation process and the poorly constrained timing of metal-silicate mixing complicate the assignment to potential parent bodies. Here we report high-precision uranium-lead dating of mesosiderite zircons by isotope dilution thermal ionization mass spectrometry, revealing initial crust formation 4,558.5 +/- 2.1 million years ago and metal-silicate mixing at 4,525.39 +/- 0.85 million years. The two distinct ages coincide with the timing of crust formation and a large-scale reheating event on the eucrite parent body, likely the asteroid Vesta. This chronological coincidence corroborates that Vesta is the parent body of mesosiderite silicates. Mesosiderite formation on Vesta can be explained by a hit-and-run collision 4,525.4 million years ago that caused the thick crust observed by NASA's Dawn mission and explains the missing olivine in mesosiderites, howardite-eucrite-diogenite meteorites, and vestoids.

On the theory of collisions of elastic bodies

This paper investigates the dynamic contact problem. In particular, there are considered two methods for determining the reduction coefficient, which is an integral energy characteristic of the impact process.It is shown that the value of this coefficient, obtained in the presence of the influence of Rayleigh surface waves, is closer to its value which is obtained experimentally.

Particle-scale computational approaches to model dry and saturated granular flows of non-Brownian, non-cohesive, and non-spherical rigid bodies

We discuss methods to compute the flow of non-Brownian, non-cohesive, and non-spherical rigid bodies immersed in a single homogeneous fluid. We address both the case of negligible effect of the surrounding fluid corresponding to dry granular flows in which the dynamics of rigid bodies is controlled by gravity and collisions only, and the case of non-negligible effect of the surrounding fluid in which rigid bodies not only exchange momentum by collisions but also by two-way coupling with the surrounding fluid flow. We review the common computational methods to compute rigid body collisions and the two-way interaction of rigid bodies with the surrounding fluid flow. We specifically discuss the extension or applicability of these methods to non-spherical rigid bodies.

CRASHWORTHINESS ANALYSIS OF THE STRUCTURE OF METRO VEHICLES CONSTRUCTED FROM TYPICAL MATERIALS AND THE LUMPED PARAMETER MODEL OF FRONTAL IMPACT

This paper establishes a Finite Element (FE) model of a rigid barrier impact of a single vehicle constructed from carbon steel, stainless steel, and aluminum alloy, which are three typical materials used in metro vehicle car body structures. The different responses of the three materials during the collision are compared. According to the energy absorption, velocity, deformation and collision force flow characteristics of each vehicle, the relationship between the energy absorption ratio of the vehicle body and the energy absorption ratio of its key components is proposed. Based on the collision force flow distribution proportion of each component, the causes of the key components’ deformation are analysed in detail. The internal relationship between the deformation, energy absorption and impact force of the key components involved in a car body collision is elucidated. By determining the characteristic parameters describing the vehicle’s dynamic stiffness, a metro vehicle frontal impact model using lumped parameters is established that provides a simple and efficient conceptual design method for railway train safety design. These research results can be used to guide the design of railway trains for structural crashworthiness.

Artist's Statement: The Alchemy of Intimacy: The Photography of Cara Judea Alhadeff, PhD

Artist's Statement: The Alchemy of IntimacyThe Photography of Cara Judea Alhadeff, PhD Cara J. Alhadeff (bio) I develop my photographic scenarios by finding natural and architectural sites that I juxtapose to human gestures and psychological states. I then choreograph narratives within these environments. Although the photographs are consciously constructed, the relationships are born out of an improvised collaboration in which the physics of touch, gravity, and balance establish an unfolding performance. My photographic performers simultaneously splay their bodies like a smear, echo, trace of memory, and compress themselves into the present moment. The photograph exposes the viewer to what is unfolding in front of the camera; nothing is manipulated during the analogue developing or printing process. Although I am a photographer, I don't see my work as strictly photographic, but as sculptural, performative, cinematic. Collaborating with artists, activists, and scholars from multiple disciplines is critical to my working process. I arrange space, objects, and bodies (including my own) in such a way as to blur the lines that separate them. This luminescent excess inhabits both the domestic and the animalistic. Characters become hybrids of machine and animal that populate dreamlike worlds. The quotidian in relation to the sensual spectacle sets up a ritualistic narrative—a strewn collision of bodies and space is simultaneously purposeful and haphazard. Through a carnal visual language, these polymorphic bodies are engaged in ambiguous ceremonies. I explore the body as a membrane between sensuality and restraint, surrender and resistance. My intention is to disrupt the distinction between the interior and exterior of both psychological and physical experiences. Images illuminate a call and response between anxiety and beauty: anxiety in the moment of recognizing the familiar within the unfamiliar, beauty in the moment of responsiveness to our undeniable connectedness, yet clinging to a separate identification. I explore this web as a [End Page 272] process of multi-layered storytelling in which ambiguity is not a lack of clarity but a multiplicity of clarities. Click for larger view View full resolution Fig 1. Self-Spain #4. Analog Color Print, 44 × 44.″ Photograph Shot: 2008, Fundación Valparaiso, Residency, Playa de Mojácar, Spain. The following elliptical stories further expand my photographic scenarios. These include my childhood pilgrimage to Romanesque cathedrals throughout France and Le Museé Picasso, early intimacies as a teenager working on a biological farm and as a beekeeper in the French Pyrenees and Béja, Tunisia, and numerous censorship incidents. 1977. Boulder Imbibing the articulated muscularity of Michelangelo's David coincided with the chaos of my parents' divorce. This collision offered me my first conscious taste of the power of vulnerability, beauty, and the naked human body. As an art historian, my father had an acute appreciation of the nude in art—in particular, the male nude. His preoccupation with developing his own ideal body led us to the university gym. He would frequently take me with him to lift weights. I remember hiding at the age of five in the tall yellow lockers in the men's locker-room—eagerly peeking out to see college students pumping iron, showering, parading around in all their magnificence. Primed by my father's art historical pontifications about the eroticized nobility of the male form, I conflated these sneaker-wearing, muscle-bound, towel-less men with Michelangelo's idealized marble statue of David that I had seen the previous year in Florence. The same year, my artist mother collaborated with Nancy Spanier Dance Theater of Colorado. I can still feel the exhilarating sense of curiosity and awe as two topless female dancers strode majestically across the stage wearing undulating pleated pantaloons and the Egyptian funerary portrait masks that my mother had made for the performance. These Faiyum-like headdresses were mesmerizing portraits of the deceased, like those painted on sarcophagi—a spectacular image of the living soul for the dead to take to the afterlife. The dancers' naked breasts and the sumptuous flow of pantaloons draped around their bodies, floating across the stage with stylized determination and purpose, set in motion an uncanny, raw intensity that continues to influence my vision of gesturing into consciousness, life in constant flux. 1980. Paris I find home the first...

Analytical solution of the elastic impact problem for a cone over a half-space

Using the main provisions of the theory of H. Hertz on the mechanical impact of solids, the dynamic interaction of an elastic cone with an elastic half-space bounded by a flat surface is considered. The case is investigated when the axis of the cone of rotation is perpendicular to the boundary of the half-space, and the initial point of contact of the bodies is the vertex of the cone. To describe the local deformations of bodies in the zone of their interaction, the well-known solution of the axisymmetric static contact problem of the theory of elasticity, constructed by I. Ya. Shtaermann, is used. The problem of the collision of bodies is reduced to a second-order differential equation with quadratic nonlinearity. Two forms of analytical solution of this nonlinear Cauchy problem are obtained. The first uses the Ateb-sine, and the second uses the elliptical cosine. The equivalence of the obtained forms of solutions is established, that is, the possibility of replacing one form with another. To calculate the values of the Ateb-sine using the linear interpolation method, a special table is presented, and an analytical approximation by its elementary functions is proposed. The consistency of the results to which these two methods of approximate calculation of the Ateb-sine values are shown is shown. An approximate formula for calculating the values of the elliptic cosine is also derived and its reliability is confirmed. As a result of solving the impact problem, formulas were obtained that describe the change over time: the convergence of the centers of mass of the bodies, the forces of impact interaction, the radius of the circular contact area and the contact pressure. It is noted that the pressure is infinite in the center of the site, where the top of the cone is in contact with the half-space. The results are compared, to which two analytical forms of the solution result and numerical computer integration of the differential equation of compression of bodies subjected to impact. Established a good agreement of numerical results obtained in different ways. The effect of the taper angle on the main parameters of the dynamic interaction of bodies is investigated. It is shown that an increase in the angle of a solution of a conical body, which strikes, leads to a decrease in the maximum dynamic compression of bodies and the duration of their interaction, as well as to an increase in the maximum impact force, with a constant value of its momentum. A numerical example of calculation is given, where steel is taken as the material of a conical body, and rubber is used as the material of a fixed half-space. Problems of this type arise when calculating the parameters of impact of a piece of mineral raw materials on rubber-lined rolls of the vibration classifier.

Three-dimensional Simulation on Collision Response of Ships

In order to enhance the realism and fidelity of the navigation simulator in ship collision response simulation, a technical solution for adding the Bullet physics engine to the three-dimensional visual simulation of the navigation simulator is proposed. Using rigid body dynamics theory, collision dynamics and energy conservation law to establish a three-dimensional collision mechanics model of ships. In the collision response phase, the Gauss-Seidel iterative algorithm is used to solve the real-time six-degree-of-freedom position and attitude parameters of the ship during the collision process, and the rendering update is synchronized in the 3D view. Experiments show that the scheme is feasible, and it can render ship collision scenes in real time and stably, and the collision process conforms to objective physical laws, which effectively improves the realism and fidelity of ship collision simulation in navigation simulator.

The extended theory of elastic bodies collision

У роботі проводиться дослідженні залежності сили динамічної взаємодії твердих тіл під час удару від місцевого стиснення, що отримана відповідно до розширеної теорії удару. Результати теоретичного дослідження порівнюються із результатами експерименту, що проведений раніше іншими авторами. Можна зробити висновок, що результати, які отримані за розширеною теорією, якісно краще узгоджуються із даними експерименту, ніж результати отримані за класичною теорією Г. Герца.

“Intrusions into the Human Body”: Quarantining Disease, Restraining Bodies, and Mapping the Affective in State Discourses

The recent explosion of post-apocalyptic visions of zombie outbreaks, plague, and bio-engineered super viruses reveals the preoccupation that exists about the potential for future disaster and its link to our conceptions of health, the body, and the public good. Born from this same historical conjuncture, The New York State Public Health Manual: A Guide for Attorneys, Judges, and Public Health Professionals , published in 2011, outlines the powers of the state of New York during a time of catastrophe; i.e. plague, outbreak, natural disaster. This particular legal guide demonstrates a current manifestation of biopower and the affective potential States hope to capture and control that emanate from the collision and interaction of bodies. States harness affect through various ways, and in this particular study, through a text that mobilizes fear and the ever-present potential of a threat, ultimately justifying draconian social measures in the name of “public safety”. Written texts provide a rich context in which to critique and better situate State policies within larger frameworks of discipline and control. States and bodies are inextricably connected to each other, and analyzing public policies help better contextualize these links specifically.

Health and Safety Education in Auto Body Collision and Machine Tool Technology Programs in Vocational Colleges: Challenges and Opportunities.

Collision repair, machining, and metal manufacturing are industries with a large percentage of small businesses whose owners face unique challenges implementing health and safety regulatory requirements. Previous research found that 72% of collision repair technicians and 47% of machinists attended some classes or graduated from vocational colleges. Although health and safety is a mandatory part of the curricula for post-secondary vocational education, little is known about what, how, and when health and safety is taught and if teaching is effective. Surveys and discussion groups were used to evaluate health and safety education in two vocational colleges in Minnesota. Six instructors and 76 students in collision repair, and 6 instructors and 130 students in machine tool technology programs participated. Instructors had no formal training in health and safety, few teaching materials, and lacked opportunities to learn about safety in their trade. Teaching was unscripted and heavily influenced by each instructor's™ industry experience, knowledge, perceptions and attitude towards safety, with little or no guidance from school administration, or safety professionals. Student survey results show that graduates have significant gaps in safety and health knowledge. Standardized trade-specific curricula and instructor training are needed to ensure students receive adequate health and safety education.

Stability of periodic orbits in no-slip billiards

Rigid bodies collision maps in dimension-two, under a natural set of physical requirements, can be classified into two types: the standard specular reflection map and a second which we call, after Broomhead and Gutkin, no-slip. This leads to the study of no-slip billiards—planar billiard systems in which the moving particle is a disc (with rotationally symmetric mass distribution) whose translational and rotational velocities can both change after collisions with the boundary of the billiard domain.This paper, which continues the investigation initiated in Cox and Feres (2017 Dynamical Systems, Ergodic Theory, and Probability: in Memory of Chernov (Providence, RI: American Mathematical Society), is mainly focused on the issue of stability of periodic orbits in no-slip planar billiards. We prove Lyapunov stability of periodic orbits in polygonal billiards of this kind and, for general billiards domains, we obtain curvature thresholds for linear stability at commonly occurring period-2 orbits. More specifically, we prove that: (i) for billiard domains in the plane having piecewise smooth boundary and at least one corner of inner angle less than π, no-slip billiard maps admit elliptic period-2 orbits; (ii) polygonal no-slip billiards under this same corner angle condition always contain small invariant neighborhoods of the periodic point on which, up to smooth conjugacy, orbits of the return map lie on concentric circles; in particular the system cannot be ergodic with respect to the canonical invariant billiard measure; (iii) the no-slip version of the Sinai billiard must contain linearly stable periodic orbits of period 2 and, more generally, we obtain a curvature threshold at which the period-2 orbits go from being hyperbolic to being elliptic; (iv) finally, we make a number of observations concerning periodic orbits in wedge and triangular billiards. Our linear stability results extend those of Wojtkowski for the no-slip Sinai billiard.

An analytical dynamics approach for mechanical systems involving a single frictional contact using b-geometry

This study focuses on the development of a new formulation, which describes the dynamics of a class of mechanical systems involving a single contact with friction. The whole process is performed within the general framework of analytical dynamics. At the same time, the efforts are assisted and enhanced by employing some fundamental tools of differential geometry. This provides a strong theoretical foundation, allowing for a systematic and consistent application of Newton's law of motion to systems possessing configuration manifolds with boundary. The manifold boundary is first defined by using the unilateral constraint representing the contact event. Then, it is shown that the corresponding contact phase takes place inside a thin layer near this boundary, where the dominant dynamics is described by a suitable set of three ordinary differential equations. The explicit appearance of time in the formulation introduces a short but finite time scale, which permits the consideration of contact of any combination of mechanical bodies, including rigid and discretized deformable bodies. Finally, the study concludes with presentation of a selected set of examples. In all cases, emphasis is put on illustrating the basic steps of the analysis as well as on capturing and investigating phenomena arising during central or eccentric collision of bodies.

The effect of moisture on friction coefficient of fabrics used on taekwondo personal protective equipment

The purpose of this study was to investigate the friction characteristics of different fabrics used in personal protective equipment worn during competition and matches. During vigorous taekwondo activity, sweat, movement, and body collisions may cause personal protective equipment to slide from its original position and accordingly fail to protect the athletes effectively. Therefore, a thorough study investigating the friction characteristics among different fabrics used in personal protective equipment and its effect on the skin is needed. This study is intended to be helpful for the athletes in the selection of appropriate personal protective equipment fabrics. Universal Nano + Micro + Macro Materials Tester was used in friction tests between six different personal protective equipment fabrics and the dorsum forearm skin to obtain the coefficients of kinetic friction and static friction. The results indicated that PVC faux leather showed better anti-skid performance under dry conditions. Under wet conditions, however, the friction coefficient of PVC faux leather decreased significantly due to lubrication, and thus lowered the anti-skid performance. In addition, the friction coefficient of fabrics with better water absorption or drainage capacity showed greater adhesion with the increasing of skin hydration. In particular, 100% polyester weft-knitted fabric showed better anti-skid performance under wet conditions. The result of this study provides a good reference in the selection and design of Taekwondo personal protective equipment for athletes, coaches, and manufacturers.

Differential Inverse Kinematics of a Redundant 4R Exoskeleton Shoulder Joint.

Most active upper-extremity rehabilitation exoskeleton designs incorporate a three sequential rotational shoulder joint with orthogonal axes. This kind of joint has poor conditioning close to singular configurations when all joint axes become coplanar, which reduces its effective range of motion. We investigate an alternative approach of using a redundant non-orthogonal 4R shoulder joint. By inspecting the behavior of the possible nullspace motions, a new method is devised to resolve the redundancy in the differential inverse kinematics (IK) problem. A 1D nullspace global attraction method is used, instead of naive nullspace projection, to guarantee proper convergence. The design of the exoskeleton and the proposed IK method ensure good conditioning, avoid collisions with the human head, arm and trunk, can reach the entire human workspace, and outperforms conventional 3R orthogonal exoskeleton designs in terms of lower joint velocities and no body collisions.

Interactions between nitrogen and oxygen molecules studied by gas-phase NMR spectroscopy

Gas-phase 14N and 15N NMR studies of nitrogen and synthetic air pressurized up to 300 bar were performed. It was found that the magnetic shielding of an isolated N2 molecule, σ0(N) = −63.4(2) ppm, is in good agreement with the results of ab initio calculations. The binary N2-O2 interactions contribute to shielding an order of the magnitude larger than the N2-N2 pairs. For nitrogen the three body collisions become observable by NMR for pressure higher than 200 bar and the appropriate coefficient can be practically assigned to the interaction between one molecule of N2 and a pair of O2 molecules.

Catastrophic disruptions as the origin of bilobate comets

Several comets observed at close range have bilobate shapes 1 , including comet 67P/Churyumov–Gerasimenko (67P/C–G), which was imaged by the European Space Agency’s Rosetta mission2,3. Bilobate comets are thought to be primordial because they are rich in supervolatiles (for example, N2 and CO) and have a low bulk density, which implies that their formation requires a very low-speed accretion of two bodies. However, slow accretion does not only occur during the primordial phase of the Solar System; it can also occur at later epochs as part of the reaccumulation process resulting from the collisional disruption of a larger body 4 , so this cannot directly constrain the age of bilobate comets. Here, we show by numerical simulation that 67P/C–G and other elongated or bilobate comets can be formed in the wake of catastrophic collisional disruptions of larger bodies while maintaining their volatiles and low density throughout the process. Since this process can occur at any epoch of our Solar System’s history, from early on through to the present day 5 , there is no need for these objects to be formed primordially. These findings indicate that observed prominent geological features, such as pits and stratified surface layers4,5, may not be primordial. This paper puts into question the standard scenario of a primordial formation for bilobate comets. The authors show that bilobate comets can retain their properties even if they form through collisions of larger bodies, which can happen at any time.

Transient Air-Water Flow and Air Demand following an Opening Outlet Gate

In Sweden, the dam-safety guidelines call for an overhaul of many existing bottom outlets. During the opening of an outlet gate, understanding the transient air-water flow is essential for its safe operation, especially under submerged tailwater conditions. Three-dimensional CFD simulations are undertaken to examine air-water flow behaviors at both free and submerged outflows. The gate, hoisted by wire ropes and powered by AC, opens at a constant speed. A mesh is adapted to follow the gate movement. At the free outflow, the CFD simulations and model tests agree well in terms of outlet discharge capacity. Larger air vents lead to more air supply; the increment becomes, however, limited if the vent area is larger than 10 m2. At the submerged outflow, a hydraulic jump builds up in the conduit when the gate reaches approximately 45% of its full opening. The discharge is affected by the tailwater and slightly by the flow with the hydraulic jump. The flow features strong turbulent mixing of air and water, with build-up and break-up of air pockets and collisions of defragmented water bodies. The air demand rate is several times as much as required by steady-state hydraulic jump with free surface.

МЕХАНИКА СТОЛКНОВЕНИЙ ТВЕРДЫХ ТЕЛ: ВЛИЯНИЕ ТРЕНИЯ И АДГЕЗИИ. II. ЧИСЛЕННОЕ МОДЕЛИРОВАНИЕ

This paper is the second part of the review on the physics of two-particle collisions of solids. The first one describes theoretical and experimental works on collisions of elastic and elastic-plastic solid bodies in the case when the energy dissipation is caused by the inner or interface friction, plasticity, adhesion, or some other damping mechanisms. In this second part, we concentrate on the case of collisions of elastic particles. Results of the analytical and numerical modelling within the dimensionality reduction (MDR) method are presented. MDR allows describing a three-dimensional contact by a reduction to an equivalent problem in a one-dimensional space. We consider three cases: a collision between bodies without slipping (equivalent to an infinite coefficient of friction), with a finite coefficient of friction in the interface, and with the presence of adhesion, which is described in the JKR limit. In all the considered cases, proper dimensionless variables have been identified which fully characterize the collision process, and the functions determining the transformation of the state before the impact into the state after the impact has been determined numerically. By using these dimensionless variables, it is possible to calculate the velocity components and the angular velocity, and hence the trajectory of the ball after the collision, in case if analogous parameters are known before the collision. Theoretical results are compared with the available results, the experimental data show agree well with the experiments.

About the impact of a viscoelastic on a fixed semi-space

The impact interaction of a viscoelastic body bounded by a quadratic paraboloid in the contact zone with an absolutely rigid fixed half-space having a flat boundary surface is considered. We have introduced the assumption that the force of resistance to the deformation of a body that hits depends not only on its elastic characteristics, but also on the square of the velocity of its center of mass. Additionally, the well-known dependences of G. Hertz on the distribution of contact deformations and dynamic pressure were used. Under these assumptions, the first integral of a non-linear differential equation of motion of the second order is expressed in elementary functions. In the same functions, the expression for the maxima was obtained: dynamic compression, impact force, dimensions of the elliptical contact area, pressure at the center of this area. An extremum study has established that with a viscoelastic impact, the maxima of the impact force and contact pressure can be reached not at the end of the body compression phase, but somewhat earlier during this process. A condition is derived when the maxima of the forces of viscoelastic and elastic impacts are the same. It is related to the coefficient of viscosity and the square of the velocity of the collision of bodies. It is shown that at the end of the compression stage, the impact force and the contact pressure during viscoelastic impact can be significantly less than the maximum, as well as those that the theory of impact of perfectly elastic bodies leads to. A compact formula for calculating the coefficient of speed recovery with a direct central impact is derived. It is shown that it depends on the coefficients of viscosity for compression and decompression and on the square of the velocity of collision of bodies. With the increase of this value, the speed recovery coefficient decreases. The duration in time of the stages of compression and expansion are represented by improper convergent integrals of the second kind, which are not expressed analytically in terms of known functions. The integrands in them have an algebraic singularity in the series 1/2. Therefore, it is recommended to single out the singular part in quadratures and integrate it analytically, and calculate the regular part on a computer. Examples of calculations are given and a comparative analysis of numerical results is carried out.