Single-body Model Research Articles

Work and heat of a quantum system far from its equilibrium state

In this paper, we give a computational approach of work and heat for any quantum systems. We use the strategy that the part of energy exchange with the von Neumann entropy unchanging is defined as work, and the part with the von Neumann entropy changing is defined as heat. We define the work and heat and they are formulated. This method is suitable for the study of any quantum systems (not only bipartite quantum systems, but also single-body, and multi-body quantum systems). As examples, firstly we investigate a bipartite model whose dynamics can be rigorously solved by using the Bloch equation, and secondly, we study two single-body models by using the numerical method of master equation of Redfield form.

Design, microstructure, and mechanical property of negative Poisson's ratio porous structure fabricated by LPBF of AlCoCrFeNi2.1 eutectic high-entropy-alloy

Negative Poisson's ratio (NPR) materials are a type of structural materials that show an atypical deformation response. In general, metal-based porous materials with NPR do not have good mechanical properties due to the substrate's limited yield strength and plasticity, as the NPR behavior is unlikely to play a continuous role in the deformation. AlCoCrFeNi2.1, a eutectic high-entropy alloy (EHEA) with high yield strength and high ductility was used to fabricate the NPR structures by laser powder bed fusion (LPBF) to enhance the structures mechanical properties and NPR behavior. Structures with four different sets of structural parameters were designed for this study. The microstructure and mechanical properties of AlCoCrFeNi2.1 EHEA, synthesized by LPBF were studied, and the strength and energy absorption effect of NPR porous structure materials were investigated by static and dynamic compression experiments. Research showed the large number of inter-phase interfaces provided by the nano-scale cellular eutectic microstructure effectively restrict dislocation movement, thereby enhancing the strength and toughness of this EHEA alloy, endowing it with superior impact resistance, fracture resistance, and mechanical energy absorption. The compressive performance and the mechanical energy absorption capacity of the 3D EHEA-based NPR porous structure strongly depend on the inclination angle Ф between the thick rod and the horizontal direction in the 2D single-body model design. The strength and energy absorption of the structure with a high inclination angle of 75° material are both higher than those of the structure with a low inclination angle of 45° by almost a factor of two.

High-Frequency Noise Peaks in Mo/Au Superconducting Transition-Edge Sensor Microcalorimeters

The measured noise in Mo/Au transition-edge sensor (TES) microcalorimeters produced at NASA has recently been shown to be well described by a two-body electro-thermal model with a finite thermal conductance between the X-ray absorber and the TES. In this article, we present observations of a high-frequency peak in the measured current noise in some of these devices. The peak is associated with an oscillatory component of the TES response that is not predicted in a single-body model but can be qualitatively described by the two-body model.

A Multibody Model of Tilt-Rotor Aircraft Based on Kane’s Method

A tilt-rotor aircraft can switch between two flight configurations (the helicopter configuration and the fixed-wing plane configuration) by tilting its rotors. In the process of rotor tilting, the nacelles which drive the rotors tilt together with the rotors. Because the mass of the nacelles cannot be ignored compared to the mass of the whole aircraft, the tilting of the nacelles is a coupling motion of the body and the nacelles. In order to better character the aircraft dynamics during the nacelle tilting, a multibody model is established in this paper. In this multibody model, Kane’s method is used to build a dynamic model of a tilt-rotor aircraft. The generalized rates are used to describe the movement of the body and the nacelles (with rotors). The generalized active forces and generalized inertial forces of both the body and the nacelles (with rotors) are obtained, respectively, and the first-order differential equations of the generalized rates are obtained. The longitudinal trim of the XV-15 aircraft is calculated according to the single-body model and our multibody model, in this paper, and the results verify the correctness of the multibody model. In the process of nacelle inclination angle command tracking, the multibody model can provide more information about the disturbance torque of the nacelle than the single-body model, and model inversion control based on the proposed multibody model can obtain a better tracking result than a PID control method only using nacelle angle feedback information.

Soft soil track interaction modeling in single rigid body tracked vehicle models

Single rigid body models are often used for fast simulation of tracked vehicle dynamics on soft soils. Modeling of soil-track interaction forces is the key modeling aspect here. Accuracy of the soil-track interaction model depends on calculation of soil deformation in track contact patch and modeling of soil resistive response to this deformation. An algorithmic method to calculate soft soil deformation at points in track contact patch, during spatial motion simulation using single body models of tracked vehicles, is discussed here. Improved calculations of shear displacement distribution in the track contact patch compared to existing methods, and realistically modeling plastically deformable nature of soil in the sinkage direction in single body modeling of tracked vehicle, are the novel contributions of this paper. Results of spatial motion simulation from a single body model using the proposed method and from a higher degree of freedom multibody model are compared for motion over flat and uneven terrains. Single body modeling of tracked vehicle using the proposed method affords quicker results with sufficient accuracy when compared to those obtained from the multibody model.

Modelling a short-wake meteor as a single or fragmenting body

An attempt is made to model a meteor observed with the Canadian Automated Meteor Observatory tracking system using a single body model. This meteor showed only very faint wake, implying that fragmentation was not important. Previous attempts to model the meteor with models of fragmenting meteors had overpredicted the amount of wake seen. A single-body, non-homogeneous ablation code was developed, but proved unsuccessful at matching the observed light curve of the meteor, even after a thorough search of parameter space. A model of a meteoroid fragmenting in many small bursts of small fragments was developed in an attempt to match both the light curve and the observed wake, and it succeeded in producing a qualitative fit to the light curve and to the high-resolution wake.

A Comparative Analysis of Edge Detection Methods in Magnetic Data

Many edge detection methods, based on horizontal and vertical derivatives, have been introduced to provide us with intuitive information about the horizontal distribution of a subsurface anomalous body. Understanding the characteristics of each edge detection method is important for selecting an optimized method. In order to compare the characteristics of the individual methods, this study applied each method to synthetic magnetic data created using homogeneous prisms with different sizes, the numbers of bodies, and spacings between them. Seven edge detection methods were comprehensively and quantitatively analyzed: the total horizontal derivative (HD), the vertical derivative (VD), the 3D analytic signal (AS), the title derivative (TD), the theta map (TM), the horizontal derivative of tilt angle (HTD), and the normalized total horizontal derivative (NHD). HD and VD showed average good performance for a single-body model, but failed to detect multiple bodies. AS traced the edge for a single-body model comparatively well, but it was unable to detect an angulated corner and multiple bodies at the same time. TD and TM performed well in delineating the edges of shallower and larger bodies, but they showed relatively poor performance for deeper and smaller bodies. In contrast, they had a significant advantage in detecting the edges of multiple bodies. HTD showed poor performance in tracing close bodies since it was sensitive to an interference effect. NHD showed great performance under an appropriate window.

An integrated dynamic model of ocean mining system and fast simulation of its longitudinal reciprocating motion

An integrated dynamic model of China’s deep ocean mining system is developed and the fast simulation analysis of its longitudinal reciprocating motion operation processes is achieved. The seafloor tracked miner is built as a three-dimensional single-body model with six-degree-of-freedom. The track-terrain interaction is modeled by partitioning the track-terrain interface into a certain number of mesh elements with three mutually perpendicular forces, including the normal force, the longitudinal shear force and the lateral shear force, acting on the center point of each mesh element. The hydrodynamic force of the miner is considered and applied. By considering the operational safety and collection efficiency, two new mining paths for the miner on the seafloor are proposed, which can be simulated with the established single-body dynamic model of the miner. The pipeline subsystem is built as a three-dimensional multi-body discrete element model, which is divided into rigid elements linked by flexible connectors. The flexible connector without mass is represented by six spring-damper elements. The external hydrodynamic forces of the ocean current from the longitudinal and lateral directions are both considered and modeled based on the Morison formula and applied to the mass center of each corresponding discrete rigid element. The mining ship is simplified and represented by a general kinematic point, whose heave motion induced by the ocean waves and the longitudinal and lateral towing motions are considered and applied. By integrating the single-body dynamic model of the miner and the multi-body discrete element dynamic model of the pipeline, and defining the kinematic equations of the mining ship, the integrated dynamic model of the total deep ocean mining system is formed. The longitudinal reciprocating motion operation modes of the total mining system, which combine the active straight-line and turning motions of the miner and the ship, and the passive towed motions of the pipeline, are proposed and simulated with the developed 3D dynamic model. Some critical simulation results are obtained and analyzed, such as the motion trajectories of key subsystems, the velocities of the buoyancy modules and the interaction forces between subsystems, which in a way can provide important theoretical basis and useful technical reference for the practical deep ocean mining system analysis, operation and control.

Steering Control for Rollover Avoidance of Heavy Vehicles

The aim of this paper is to develop an active steering assistance system to avoid the rollover of heavy vehicles (HV). The proposed approach is applied on a single body model of HV presented in this paper. An estimator based on the high-order sliding mode observer is developed to estimate the vehicle dynamics, such as lateral acceleration limit and center height of gravity. Lateral position and lateral speed are controlled using a twisting algorithm to ensure the stability of the vehicle and avoid accidents. At the same time, the identification of unsprung masses and suspension stiffness parameters of the model have been computed to increase the robustness of the method. Some simulation and experimental results are given to show the quality of the proposed concept.

A MODEL OF SINGLE AND FRAGMENTING METEOROID INTERACTION WITH ISOTHERMAL AND NON-ISOTHERMAL ATMOSPHERE

The basic equations of physical theory of meteors are considered without the assumption of atmospheric isothermality. Analytical solutions are found in the case of single and fragmenting meteoroids, the fragmentation process being modeled in terms of the statistical theory of strength (Weibull, 1939). The comparison against a classical solution is made for the single body model. The comparisons against the observations and gross-fragmentation model results are made for a fragmenting meteoroid. An example of parametric investigations based on the obtained solutions is provided.

점착성 연약지반 주행차량의 동적거동 연구

Abstract : This paper concerns about a study on dynamic responses of tracked vehicle on soft cohesive soil.For dynamic analyses of tracked vehicle, two different models were adopted, i.e. a single-body model and amulti-body model. The single-body vehicle model was assumed as a rigid body with 6-dof. The multi-bodyvehicle was modeled by using a commercial software, RecurDyn-LM. For the both models properties ofcohesive soft soil were modeled by means of three relationships: pressure to sinkage, shear displacement toshear stress, and shear displacement to dynamic sinkage. Traveling performances of the two tracked vehiclemodels were compared through dynamic analyses in time domain.Key words : (Tracked vehicle), 3 (3D unsteady analysis), (cohesive soil model), / (shear displacement/stress), (Multi-body), (Single-body) 1. . , . (Hayasi 1975; Kitano and Tyorzaki 1976; Kitanoand Kuma 1977; Baladi and Rohani 1978; Bode 1991;Murakami et al. 1992; Zhang 1995; Tran et al. 2002;Hong et al. 2002). . . . , .  , (Degree of freedom) . .

Meteoroid Properties from Photographic Records of Meteors and Fireballs

Statistical criteria based on the single-body theory enabled the distinction of different composition groups of meteoroids in the past. The new single-body model proposed by Pecina and Ceplecha (1983, 1984) is capable of determining the individual values of ablation coefficients, which has proved to be a better tool for separating meteoroids of different ablation properties. However, a significant fraction of fireballs exhibit a time-dependence of residuals, when the single-body model is applied to their photographic observations. This was recently explained by assuming sudden fragmentation at a point (gross-fragmentation). The proposed gross-fragmentation model was checked in exceptional cases, when splitting of a fireball was directly visible on the photographs. The new fragmentation model was then applied to the best photographic records of Prairie Network fireballs (PN). Least-squares fit of computed to observed distances along a meteoroid trajectory determines uniquely the ablation coefficient, the shape-density coefficient, the position of the gross-fragmentation point and the amount of fragmented material relative to the main body mass. This enabled not only a better classification according to ablation coefficient (composition groups), but also a recognition of different strength categories according to dynamic pressure at the fragmentation point. Except for composition groups (types) I, II, IIIA, IIIB, each meteoroid with precise photographic data on its fireball can be classified as NF (no-fragmenting), 1F (with one point of fragmentation) and MF (with many points of fragmentation). The fragmenting meteoroids (1F and MF) can moreover be sorted into several categories (a, b, c, d, e) according to dynamic pressure at the fragmentation point. Thus the classification became two dimensional, separating meteoroid composition from structure. Values of ablation coefficients and bulk-densities were revised using this model. The amount of fragmented mass relatively to the main body was also determined. Typical sudden fragmentation for almost half of all fragmenting meteoroids is equivalent to stripping away slightly more than half of the mass.

Photoelectric analysis of asteroid 216 Kleopatra: Implications for its shape

In some recent theoretical papers it has been suggested that gravitationally bound “rubble piles” in hydrostatic equilibrium possibly exist among the asteroids. For a higher-than-critical value of the angular momentum acquired by such a body, the instability phenomena can produce fission into a binary system. S. J. Weidenschilling [ Icarus 44, 807–809 (1980)] suggested that 216 Kleopatra may represent a binary asteroid, since it has a large light curve amplitude (1.3–1.4 mag). In this paper new observations of Kleopatra are presented, suggesting the equal plausibility of the single triaxial ellipsoid model. Namely, when phase and aspect effects are taken into account, the actual maximum amplitude is reduced to about 0.9 mag at 90° of aspect which is close to the value predicted by theory for the instability limit. Moreover, multiple-scattering effects [M. Poutanen, E. Bowell, and K. Lumme, Bull. Amer. Astron. Soc. 13, 725 (1981)] can reduce the axial ratio a/ b even more. If the single-body model is adopted, the density of Kleopatra should be on the order of 1.7 g/cm 3. This low value seems reasonable for “rubble pile” models.