Transition Of Motions Research Articles

Высокоточные представления Ван-дер-Ваальсовских взаимодействий

This paper considers the interactions between two and three fullerenes using the methods of molecular dynamics. The results show that at a time step of one femtosecond, very high calculation accuracy can be achieved regarding the kinematic and energy parameters of the interaction. Thus, the details associated with the symmetry of the relative opposition of molecular objects are revealed, and the features and nature of the transition of two-dimensional motions of interacting objects into three-dimensional interaction of fullerenes are clarified, in particular, the interaction with the formation of a kinematic pair. The role of the initial spin of the fullerenes, which disables the transition of kinematic energy from the reservoir of translational energy into rotational energy, is also identified. This makes the formation of a kinematic pair impossible. In the general case, the triple collision of fullerenes is a complex process, in which, even in the special case of plane approximation, three phases can be distinguished: initial planar motion, multi-sheet spatial interaction of three objects, and a double spiral of interacting molecules with the linear motion of the discarded fullerene.

Simulation of aircraft multi-axis acceleration in a four-axis Human Centrifuge System

High G-accelerations produced during Aircraft Combat Manoeuvres (ACMs) can adversely affect the physiological and psychological conditions of aircrew and deteriorate their performance. Human Centrifuge Systems (HCSs) provide an effective G-acceleration training tool to prepare and increase the G-tolerance of aircrew. Though highly capable HCSs are available, they are yet to be fully optimised to accurately and reliably recreate the G-vectors produced by ACMs. Optimisation steps to achieve this improvement involve the configurational structure, motion capability, and motion control of HCSs. To improve the motion capability and control of HCSs, the relationship between aircraft G-vectors and HCS G-vectors should be profoundly investigated. This work analyses the G-vectors of common ACMs and the corresponding G-vectors as well as kinematics of an active four Degree-of-Freedom (DoF) HCS. The mathematical models of an aircraft and HCS kinematics are developed using rigid body equations of motion through Newton-Euler method. The relationship between aircraft G-vectors and HCS G-vectors is established using inverse kinematics with an optimal solver. The outcomes of this study show that an active four-DoF HCS with gondola roll, pitch, and yaw rotation can replicate the G-vectors of common ACMs with small discrepancies. The largest error between the reference and achieved G-vectors occurred along the local z-axis of the HCS gondola during the transition of roll, pitch, and yaw motions of the gondola to the required angle replicating the G-vectors of the ACMs. The tracing errors are not significant; hence they can be mitigated with an optimal control technique. The presented outcomes will provide an essential step in identifying the optimal design and refined requirements for an HCS to efficiently replicate aircraft G-vectors. The applied methodology is easily adaptable to HCS with different structures and DoFs.

DYNAMICS OF A BODY UNDER THE IMPULSE FORCE AND WITH OSCILLATION LIMITER

The paper investigates the dynamics of a body under a piecewise constant periodic force with an arbitrary duty cycle and in the presence of an oscillation limiter. The mathematical model is a strongly nonlinear non-autonomous dynamical system with a truncated phase space along one of the phase coordinates. Using the point mapping method for strongly nonlinear (vibro-impact) dynamical systems, equations for two-dimensional Poincare map are obtained in the form of explicit analytical formulas. The relations obtained for Poincare map made it possible to effectively study the rearrangements of arbitrarily complex periodic motions with both a finite and an infinite number of fixed points, depending on the change in the parameters of the dynamical system. This allowed us to represent for the first time an analytical form of the equations that define in the parameter space the boundaries of the existence and stability domain of periodic motions with an infinite number of fixed points on the Poincare surface (corresponds to the infinitely impact mode of motion). The numerical experiments presented in the paper using a software product developed in the C++ language made it possible to present bifurcation diagrams that clearly demonstrate the ranges of parameter values with chaotic motion modes of the body. A scenario for the emergence of chaos has been established. The transition of body motions with a change in the overload parameter from periodic motion modes to chaos is carried out according to the period doubling. Comparison of numerical analysis with analytical results for different sets of parameters of the system under study (overload parameter) showed their good agreement.

Low-Frequency Raman Spectroscopy as an Avenue to Determine the Transition Temperature of β- and γ-Relaxation in Pharmaceutical Glasses.

In an earlier investigation, low-frequency Raman (LFR) spectroscopy was shown to detect the transition temperature of the β-relaxation (Tβ) in both amorphous celecoxib and various celecoxib amorphous solid dispersions [Be̅rziņš, K. Mol. Pharmaceutics 2021, 18(10), 3882-3893]. In this study, we further investigated the application of this technique to determine Tβ, an important parameter for estimating crystallization potency of amorphous drugs. Alongside commercially available amorphous drugs (zafirlukast and valsartan disodium salt), differently melt-quenched samples of cimetidine were also analyzed. Overall, the variable-temperature LFR measurements allowed for an easy access to the desired information, including the even lesser transition of the tertiary relaxation motions (Tγ). Thus, the obtained results not only highlighted the sensitivity, but also the practical usefulness of this technique to elucidate (subtle) changes in molecular dynamics within amorphous pharmaceutical systems.

An individual prediction model of the pre-loading motion for operator and backhoe pairs

The autonomous dump truck must judge whether the backhoe is ready for loading the sediment for smooth and safe cooperation with the human-operated backhoes. Analyzing time-series data of the human-operated backhoe loading motion is an effective method to build a prediction model. The transition of several primitive motions enables us to predict the timing when the backhoe starts loading. However, in transition modeling, manually selecting the appropriate primitive motions in the pre-loading motions requires considerable effort. In addition, a robust loading prediction is required for sensor layout changes in the installations of them. Here, we propose a BP-HMM-based prediction method of the pre-loading motion. The algorithm automatically finds the transition of several primitive motions from time-series data and its annotation labels. The selection of three angular velocities as features of the BP-HMM increases the robustness of the prediction method. The proposed method built a suitable prediction model for three different combinations of operators and backhoes. The prediction method was robust for sensor layout changes, and showed an accuracy of 100%. The proposed prediction method contributes to the automation of earthmoving work by enabling smooth cooperation between autonomous dump trucks and human-operated backhoe.

Trifluorinated Keto-Enol Tautomeric Switch in Probing Domain Rotation of a G Protein-Coupled Receptor.

Conformational dynamics and transitions of biologically active molecules are pivotal for understanding the physiological responses they elicit. In the case of receptor activation, there are major implications elucidating disease mechanisms and drug discovery innovation. Yet, incorporation of these factors into drug screening systems remains challenging in part due to the lack of suitable approaches to include them. Here, we present a novel strategy to probe the GPCR domain rotation by utilizing the 19fluorine signal variability of a trifluorinated keto-enol (TFKE) chemical equilibrium. The method takes advantage of the high sensitivity of the TFKE tautomerism toward microenvironmental changes resulting from receptor conformational transitions upon ligand binding. We validated the method using the adenosine A2AR receptor as a model system in which the TFKE was attached to two sites exhibiting opposing motions upon ligand binding, namely, V229C6.31 on transmembrane domain VI (TM6) and A289C7.54 on TM7. Our results demonstrated that the TFKE switch was an excellent reporter for the domain rotation and could be used to study the conformational transition and dynamics of relative domain motions. Although further studies are needed in order to establish a quantitative relationship between the rotational angle and the population distribution of different components in a particular system, the research presented here provides a foundation for its application in studying receptor domain rotation and dynamics, which could be useful in drug screening efforts.

The role of visual angle in pattern phase transition of collective motions

Abundant collective motion patterns of animal groups have different kinds of functions like migration, predator avoidance and foraging. To explore the phase transition mechanism behind such charming collective behaviors, some self-propelled particle models have been proposed, most of which however have isotropic inter-particle interactions and hence could not reproduce sophisticated natural collective patterns. As a remedy, this letter develops an anisotropic self-propelled particle model. By slightly tweaking the vision range and inter-particle attraction, the proposed model demonstrate transitions between four distinct collective motion patterns, i.e., torus, dumbbell, twist, and worm. To investigate more insightfully into the phase transition nature, quantitative analysis is carried out, revealing the relationship of visual angle-based inter-agent interactions and abundant pattern transitions existing in large numbers of natural, social and artificial grouping behaviors. From the industrial application point of view, the present study can help adjust the formation of multiple unmanned systems by simply tweaking a couple of vision-related parameters in their models.

Dynamics of a vibro-impact system by the global analysis method in parameter-state space

The global analysis method in parameter-state space for achieving both the distribution and the transition rule of periodic motions and the distribution rule of the multiple motions coexistence of the vibro-impact system is developed. A nonlinear dynamic model in a system of vibro-impact with asymmetric clearances is researched by the new method. Three grazing motions and relevant conditions have been discussed. The distribution and the transition rule of periodic motions are analyzed. The influence of the grazing and saddle-node bifurcation during the change in the left and the right gaps are demonstrated. The distribution of subharmonic motions is illustrated. The coexistence of multiple motions which exist at the junction of periodic motions within the motion-sensitive areas is researched by the global analysis method in parameter-state space, and the distributions of periodic motions and the multiple motions coexistence are illustrated. The transition of the multiple motions coexistence with the guide of the global distribution of the motions is further analyzed by the evolution of the attractors and the corresponding attracting domains. The results contribute a lot to the study of the transition and the control of the motions.

Dynamical heterogeneities of cold 2D Yukawa liquids

Dynamical heterogeneities of 2D liquid dusty plasmas at different temperatures are investigated systematically using Langevin dynamical simulations. From the simulated trajectories, various heterogeneity measures have been calculated, such as the distance matrix, the averaged squared displacement, the non-Gaussian parameter, and the four-point susceptibility. It is found that, for 2D Yukawa liquids, both spatial and temporal heterogeneities in dynamics are more severe at a lower temperature near the melting point. For various temperatures, the calculated non-Gaussian parameter of 2D Yukawa liquids contains two peaks at different times, indicating the most heterogeneous dynamics, which are attributed to the transition of different motions and the α relaxation time, respectively. In the diffusive motion, the most heterogeneous dynamics for a colder Yukawa liquid happen more slowly, as indicated by both the non-Gaussian parameter and the four-point susceptibility.

Global Behavior of a Vibro-Impact System With Multiple Nonsmooth Mechanical Factors

A nonlinear mechanical model of a vibro-impact system influenced by double nonsmooth mechanical factors that combine elastic and rigid impact is described. The theoretical solutions to judge the periodic motion stability of the system are presented, and three different “gazing” motions and the corresponding conditions are described. The transition and coupling of periodic motions by the nonsmooth mechanical factors are demonstrated. The formation mechanism of sticking motion, chattering motion, and the periodic cavity by the influence of gazing bifurcation are analyzed. The coexistence of periodic motions and the extreme sensitivity of the initial value within the high frequency region are studied. The distribution of the attractor and the corresponding attracting domain corresponding to different periodic motions are also studied.

Dynamical Transition of Collective Motions in Dry Proteins.

Water is widely assumed to be essential for protein dynamics and function. In particular, the well-documented "dynamical" transition at ∼200 K, at which the protein changes from a rigid, nonfunctional form to a flexible, functional state, as detected in hydrogenated protein by incoherent neutron scattering, requires hydration. Here, we report on coherent neutron scattering experiments on perdeuterated proteins and reveal that a transition occurs in dry proteins at the same temperature resulting primarily from the collective heavy-atom motions. The dynamical transition discovered is intrinsic to the energy landscape of dry proteins.

Tensile test simulation of high-carbon steel by discrete element method

Purpose – The tensile test is one of the fundamental experiments used to evaluate material properties. Simulating a tensile test can be a replacement of experiments to determine mechanical parameters of a continuous material. The paper aims to discuss these issues. Design/methodology/approach – This research uses a new approach to model a tensile test of a high-carbon steel on the basis of discrete element method (DEM). In this research, the tensile test specimen was created by using a DEM packing theory. The particle-particle bond model was used to establish the internal forces of the tensile test specimen. The particle-particle bond model was first tested by performing two-particle tensile test, then was adopted to simulate tensile tests of the high-carbon steel by using 3,678 particles. Findings – This research has successfully revealed the relationships between the DEM parameters and mechanical parameters by modelling a tensile test. The parametric study demonstrates that the particle physical radius, particle contact radius and bond disc radius can significantly influence ultimate stress and Young’s modulus of the specimen, whereas they slightly impact elongation at fracture. Increasing the normal and shear stiffness, the critical normal and shear stiffness can enable the increase of ultimate stress, however, up to maximum values. Research limitations/implications – To improve the particle-particle bond model to simulate a tensile test for high-carbon steel, the damping factors for compensating energy loss from transition of particle motions and failure of bonds are required. Practical implications – This work reinforces the knowledge of applying DEM to model continuous materials. Originality/value – This research illustrates a new approach to model a tensile test of a high-carbon steel on the basis of DEM.

채널 유동 내 유연한 캡슐의 관성 이동과 움직임

We explored the dynamic motions and the lateral equilibrium positions of an elastic capsule in channel flow at moderate Reynolds number varying Re, aspect ratio, size ratio, membrane stretching and bending coefficient. The transition of tank-treading/swinging to tumbling motion was observed in the simulations and the transition of dynamic motions for capsules resulted in different trend of the variation in the lateral equilibrium positions. Though other conditions were similar, the capsule with tumbling motion migrated closer to the wall than that with tank-treading motion.

Parallel Motion Simulation of Large‐Scale Real‐Time Crowd in a Hierarchical Environmental Model

This paper presents a parallel real‐time crowd simulation method based on a hierarchical environmental model. A dynamical model of the complex environment should be constructed to simulate the state transition and propagation of individual motions. By modeling of a virtual environment where virtual crowds reside, we employ different parallel methods on a topological layer, a path layer and a perceptual layer. We propose a parallel motion path matching method based on the path layer and a parallel crowd simulation method based on the perceptual layer. The large‐scale real‐time crowd simulation becomes possible with these methods. Numerical experiments are carried out to demonstrate the methods and results.

Supramolecular Bola-Like Ferroelectric: 4-Methoxyanilinium Tetrafluoroborate-18-crown-6

Molecular motion is one of the structural foundations for the development of functional molecular materials such as artificial motors and molecular ferroelectrics. Herein, we show that pendulum-like motion of the terminal group of a molecule causes a ferroelectric phase transition. Complex 4-methoxyanilinium tetrafluoroborate-18-crown-6 ([C(7)H(10)NO(18-crown-6)](+)[BF(4)](-), 1) shows a second-order ferroelectric phase transition at 127 K, together with an abrupt dielectric anomaly, Debye-type relaxation behavior, and the symmetry breaking confirmed by temperature dependence of second harmonic generation effect. The origin of the polarization is due to the order-disorder transition of the pendulum-like motions of the terminal para-methyl group of the 4-methoxyanilinium guest cation; that is, the freezing of pendulum motion at low temperature forces significant orientational motions of the guest molecules and thus induces the formation of the ferroelectric phase. The supramolecular bola-like ferroelectric is distinct from the precedent ferroelectrics and will open a new avenue for the design of polar functional materials.

Resonance bifurcation of a three-degree-of-freedom vibratory system with symmetrical rigid stops

Abstract A three-degree-of-freedom vibratory system impacting symmetrical rigid stops is considered. Dynamics of the vibroimpact system is studied by use of a mapping derived from the equations of motion, supplemented by transition conditions at the instants of impacts. Two-parameter bifurcations of fixed points in the vibroimpact system, associated with 1 : 3 strong resonance, are analyzed. Neimark–Sacker bifurcations of period-1 double-impact symmetrical orbits, near 1 : 3 resonance point, are found, and the transition of quasi-periodic impact motions to unstable period-3 six-impact motions, are obtained numerically. The results conform to 1 : 3 resonance bifurcation theory of maps available. More complicated “tire-like” quasi-periodic attractor and torus bifurcation associated with the transition of the closed invariant curve to torus, near 1 : 3 resonance point, are found to exist in the nonlinear system. The results imply that there exist possibly more complicated bifurcation sequences near 1 : 3 resonance points of nonlinear dynamical systems.

Measurement of(∂P∂T)Vand Related Properties in Solidified Gases. III. SolidD2

Measurements in solid ${\mathrm{D}}_{2}$ of pressure changes with temperature and para concentration are reported, and related thermodynamic properties are calculated. The study covers both the hcp and cubic phases in the temperature range $0.4<~T<~4.2$ K and para concentration range $0.02<~c<~0.90$. The measurements were carried out with a capacitance strain gauge capable of resolving pressure changes of 2\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}5}$ bar. Two types of study were made. (a) The pressure changes accompanying the phase transition were determined as a function of $c$, and the hysteresis was studied as a function of the number of cyclings through the transition. (b) The quantity ${(\frac{\ensuremath{\partial}P}{\ensuremath{\partial}T})}_{V}$ was obtained in the cubic and hcp phases as a function of $T$ and $c$. The results were analyzed in terms of separate contributions from the lattice and from the rotation of the paradeuterium molecules ($p$-${\mathrm{D}}_{2}$, lowest rotational level $J=1$). The molecular rotation was assumed to be quenched by the electric quadrupole-quadrupole (EQQ) interaction, and all other effects such as those due to crystal-line field were neglected. The EQQ interaction parameter $\ensuremath{\Gamma}$ was determined experimentally. The results from (a) extend the phase diagram to low para concentrations and show that the transition from the hcp to the cubic phase does not take place below $c=0.55$. The data from thermal cyclings, when analyzed in conjunction with corresponding data from x-ray diffraction, indicate that the changes in pressure (and in other thermodynamic properties) are due mainly to the order-disorder transition of the rotational motions and not to the crystalline phase change per se. The results from (b) give values of $\frac{{\ensuremath{\Gamma}}_{\mathrm{eff}(\mathrm{pair})}}{{k}_{B}}=1.05\ifmmode\pm\else\textpm\fi{}0.07$ K and $\frac{{\ensuremath{\Gamma}}_{\mathrm{eff}(c=1)}}{{k}_{B}}=0.93\ifmmode\pm\else\textpm\fi{}0.05$ K for low and high concentrations of $p$-${\mathrm{D}}_{2}$, respectively. For a rigid lattice, the theoretical value is $\frac{{\ensuremath{\Gamma}}_{0}}{{k}_{B}}=1.20$ K. A comparison is made with values of $\frac{\ensuremath{\Gamma}}{{k}_{B}}$ from a previous determination and with those predicted by the theory of Harris, which takes into account quantum effects in the solid. Anomalies in ${(\frac{\ensuremath{\partial}P}{\ensuremath{\partial}T})}_{V}$ at very low $p$-${\mathrm{D}}_{2}$ concentrations are observed, but are not explained. The entropy of the rotational motion of the $J=1$ state is calculated above 0.4 K and is found to approach $R\mathrm{ln}3$ per mole of $p$-${\mathrm{D}}_{2}$ for $c>~0.6$.