Natural Coordinates Research Articles

Construction of a risk assessment and prediction model for athlete doping use based on bioinformatics

A suitable approach to identifying doping behavior among athletes is to use advanced techniques. Bioinformatics can analyze large biological databases. It has potential approaches for mapping out decision models. Doping substances can severely distort an athlete’s biomechanical performance. For example, stimulants may enhance short-term power output but disrupt the natural rhythm and coordination of muscle contractions, leading to imbalanced forces and increased risk of musculoskeletal injuries. This abnormal biomechanical loading can affect joint stability and movement efficiency. n training, doping gives a false impression of enhanced capacity. Athletes might overtrain, ignoring proper recovery periods. Their bodies, under the influence of doping, can’t follow the normal adaptive process of training, leading to a breakdown in the physiological systems. Recovery is also hampered. Doping can disrupt the body’s hormonal and metabolic balance, slowing down tissue repair and regeneration. Genetic predispositions, which might make an athlete more receptive to doping’s effects, along with lower recovery rates and high competitive stress levels, are identified as key doping risk factors. Bioinformatics collects multi-source data like genomic profiles, hormone levels, and metabolic markers. Advanced tools analyze these to expose patterns and correlations related to doping risks. Machine learning trains a prediction model using historical doping data and biological signatures. Validated via simulations and real-world tests, it predicts doping risks. Sports authorities can use the resulting risk matrix to detect potential dopers early, promoting clean sports.

Co‐Simulation Interface Model Reduction for Large‐Scale Coupled Simulations

ABSTRACTThe paper presents a novel approach for reducing the co‐simulation interface representation between multiple large‐scale models. The methodology leverages model order reduction through component mode synthesis in some specific small deformation flexible multibody formulations that yield a constant transformation matrix between Cartesian coordinates and general multibody coordinates, such as the flexible natural coordinates formulation or the generalized component mode synthesis. The constant transformation matrix stemming from these techniques is further modified using modified Gram–Schmidt orthonormalization and the effective independence methodology to create a constant interface model reduction matrix. This matrix effectively connects a minimal set of interface nodes to the entire nodal domain, while simultaneously projecting the forces acting on the entire nodal domain onto the interface nodes. Notably, the proposed methodology scales the size of the required co‐simulation interface representation with the considered set of mode shapes rather than the size of the numerical finite element mesh. This co‐simulation interface model reduction strategy not only renders large distributed load models compatible with the Functional Mock‐Up Interface but also extends its applicability to any structural model beyond the flexible multibody scope, provided that deformations remain relatively small. Numerical validation with a simply supported beam, connected to springs at each node, demonstrates that the interface model reduction error is significantly smaller than the co‐simulation error. This suggests that substantial interface model reduction can be achieved without compromising accuracy. Moreover, additional numerical validation performed with a rotor‐drum model showcases the versatility and scalability of the proposed approach, particularly in addressing dynamic structural systems.

Uma Nova Generalização dos Ternos Pitagóricos

In this work, we revisit the Pythagorean equation and its solutions with natural coordinates, called Pythagorean triples, as well as some of its well-known generalizations. Moreover, we realize a study on the solutions with natural coordinates of a quadratic equation that extends the Pythagorean equation, obtaining expressions that allow us to characterize algebraically these solutions and present a new generalization of the Pythagorean triples.

QSLE-v1.0: A New Software Package for the Calculation of Coupled Quantum-Classical Dynamics in Condensed Phases Based on a Stochastic Approach.

Recently, a stochastic version of the quantum-classical Liouville equation has been proposed [Campeggio, J.; Cortivo, R.; Zerbetto, M. J. Chem. Phys. 2023, 158, 244104], to compute the coupled quantum-classical dynamics of molecules in condensed phases. The approach, called quantum-stochastic Liouville equation (QSLE), is based on coupling the time evolution of electronic states to a stochastic description of the relevant (classical) nuclear coordinates. Natural internal coordinates are used, i.e., bond lengths, bond angles, and dihedral angles. The approach is tailored to directly propagate the populations of the electronic states over time, based on a classical Fokker-Planck equation for the nuclear degrees of freedom coupled to a master equation for the jumps among the electronic states. The QSLE is a multiscale approach requiring many ingredients to be assembled in order to carry out the numerical solution. To make the approach accessible, a software package that handles the main (and most cumbersome) details of the numerical workflow has been implemented into the software package QSLE-v1.0, which is introduced in the present paper. Here, it is considered the case of one torsional nuclear coordinate and two nonadiabatic electronic potential energy surfaces. This is a very basic model for interpreting photoisomerization or charge transfer phenomena, but despite its simplicity, it can be applied even in complex systems where the relevant quantum/classical parts affecting the phenomena under study are highly localized. A sand-box model system for describing photoisomerization processes is reported to demonstrate the usage of the software package. QSLE-v1.0 is open source and distributed under the GPLv2.0 license.

Dynamics modeling and analysis of a down-hole drill string multibody system based on the absolute coordinate formulation

Abstract Drilling system dynamics is the basis of studying the interaction between components in drilling process, which needs to solve many difficult problems such as geometric nonlinear dynamics of drill string, contact between drill string and wellbore, solving timeliness and so on. The existing research on establishing dynamic unit of local drilling tool structure has low solution efficiency, and it is difficult to meet the requirements of directional trajectory control and drilling speed increase analysis efficiently. Dynamics model of a downhole drill string system is established by using the multibody system dynamics method in this study. The natural coordinate formulation and the absolute nodal coordinate formulation are adopted to describe the rigid parts and the flexible beams, respectively. The presented model can be used to analyze the dynamic characteristics of the drill string system and the interaction between the drill string and the environment such as the wellbore and rocks in the drilling process. Finally, through comparative analysis with on-site test data, the correctness of the multibody dynamic model of the drill string system established in this paper was preliminarily verified.

Stability Conditions and Stiffness Variability of General Tensegrity Systems with Kinematic Joints

Abstract Tensegrity systems represent promising candidate mechanisms with in-situ stiffness variability through changing the cables' prestress levels. However, prestress-based stiffness behaviors of tensegrity systems with arbitrary kinematic joints have not been analyzed systematically. This paper adopts the natural absolute coordinates for static modeling of tensegrity systems consisting of rigid members and tension elements. Then, a generic stiffness analysis method is developed to formulate the reduced-basis tangent stiffness matrix, which is found to include three parts: positive semi-definite material and geometric stiffness matrices, and an indefinite constraint stiffness matrix. Based on these findings, a systematic stability-checking procedure is derived to determine prestress and super stability, which are qualitative indicators of the softening and stiffening effects in different tensegrity systems. Then, we proceed to quantify the range of prestress-based stiffness variability by formulating semidefinite programming problems that numerically pinpoint the maximum and zero stiffness points. Furthermore, this paper reveals the composable nature of multiple self-stress states, enabling the composability of stiffness properties in mechanism designs. Several numerical examples verify the efficacy and versatility of the proposed method and demonstrate interesting stiffness behaviors of tensegrity systems with kinematic joints.

Dynamics for rigid–flexible coupled solar panel multibody system composed of composite laminated plates

Composite laminates are widely employed in the fabrication of solar panels in modern spacecraft engineering because of their superior durability, mechanical qualities, and cost-effectiveness. This research is dedicated to multibody system dynamics modeling of composite laminate solar panels, specifically the coupling system between the rigid main body and the flexible solar panels. In this study, the rigid body is modeled using the natural coordinate formulation (NCF), and for the flexible solar panel, the absolute nodal coordinate formulation (ANCF) with a 36-DOF reduced-order composite thin shell element is used to accurately capture the coupling effect of the solar panel under large motion and deformation. Compared to a 48-DOF fully parameterized thick plate element, this method efficiently avoids shear locking and improves numerical solution convergence efficiency. Based on the Kirchhoff theory and the constitutive relationship of composite laminates, a dynamic model of the multibody system is developed, taking into account the rigid-flexible coupling effect and the kinematic constraints. This work thoroughly discusses the dynamic behavior of solar panel deployment using a comparative analysis of numerical simulation and virtual prototype simulation, and the accuracy is verified. The findings indicate that the flexible characteristics and fiber orientation of composite laminates have a significant impact on the dynamic response of solar panels during deployment. Furthermore, the bang-bang attitude controller is designed, and the difference in dynamic response between the two modeling methods in controlled and uncontrolled states is studied, providing an important theoretical foundation and technical support for solar panel design and analysis.

Evaluation of Coupled Human–Natural System Coordination in Xinjiang and Analysis of Obstacle Factors

The coupling and coordination of humans and natural systems, as the core of geographical research, is an important issue that social development needs to confront and explore. The study of the coupling and coordination of the human–natural system in Xinjiang, as well as the obstacles, is of great significance for its ecological environment and social development. This study establishes a multidimensional index system for the coupling of the human–natural system in Xinjiang. The comprehensive evaluation index and coupling coordination degree of the human–natural system from 2013 to 2020 were calculated, using weighted methods and a coupling coordination evaluation model. The main obstacles to the development of coupling and coordination in Xinjiang were identified, with the aid of a barrier model. The study indicates: (1) the human–natural system composed of ecological environment, urban–rural livability, cultural characteristics, civil harmony, and green development reflects the comprehensive development level of Xinjiang; (2) from 2013 to 2020, the sustainable development of the human–natural system in Xinjiang was good, with an upward trend in the evaluation index; (3) from 2013 to 2020, the level of coupling and coordination of the human–natural system in Xinjiang improved, transitioning from low to high levels; (4) from 2013 to 2020, the main factors impeding the coordinated development of the human–natural system changed. In addition to urban–rural differences and water resource conditions, medical conditions and carbon emissions also became major influencing factors on the coupling and coordination degree of the human–natural system in arid regions. Therefore, the research on the coupling and coordination relationship of the human–natural system and the analysis of obstacles in Xinjiang can provide scientific basis for the high-quality sustainable development and the construction of a beautiful Xinjiang.

Steady-State Rotary Periodic Solutions of Rigid and Flexible Mechanisms With Large Spatial Rotations Using the Incremental Harmonic Balance Method for Differential-Algebraic Equations

Abstract Steady-state rotary periodic responses of mechanisms lead to stress cycling in flexible structures or connecting joints, which in turn can result in structural fatigue. A general approach is developed to study rotary periodic solutions of rigid and flexible mechanisms with large spatial rotations based on the incremental harmonic balance (IHB) method. The challenge in analyzing such dynamic systems emanates from the noncommutativity of the spatial rotation and the nonsuperposition nature of the rotational coordinates. The generally used rotational coordinates, such as Euler angles, cannot be expanded into Fourier series, which prevents direct usage of the IHB method. To overcome the problem, the natural coordinates method and absolute nodal coordinate formulation (ANCF) are used herein for the dynamic modeling of the rigid and flexible bodies, respectively. The absolute positions and gradients are used as generalized coordinates, and rotational coordinates are naturally avoided. Equations of motions of the system are differential-algebraic equations (DAEs), and they are solved by the IHB method to obtain the steady-state rotary periodic solutions. The effectiveness of the proposed approach is verified by the simulation of rigid and flexible examples with spatial rotations. The approach is general and robust, and it has the potential to be further extended for other extensive multibody dynamic systems.

Movement-Based Prosthesis Control with Angular Trajectory Is Getting Closer to Natural Arm Coordination.

Traditional myoelectric controls of trans-humeral prostheses fail to provide intuitive coordination of the necessary degrees of freedom. We previously showed that by using artificial neural network predictions to reconstruct distal joints, based on the shoulder posture and movement goals (i.e., position and orientation of the targeted object), participants were able to position and orient an avatar hand to grasp objects with natural arm performances. However, this control involved rapid and unintended prosthesis movements at each modification of the movement goal, impractical for real-life scenarios. Here, we eliminate this abrupt change using novel methods based on an angular trajectory, determined from the speed of stump movement and the gap between the current and the 'goal' distal configurations. These new controls are tested offline and online (i.e., involving participants-in-the-loop) and compared to performances obtained with a natural control. Despite a slight increase in movement time, the new controls allowed twelve valid participants and six participants with trans-humeral limb loss to reach objects at various positions and orientations without prior training. Furthermore, no usability or workload degradation was perceived by participants with upper limb disabilities. The good performances achieved highlight the potential acceptability and effectiveness of those controls for our target population.

HeadShift: Head Pointing with Dynamic Control-Display Gain

Head pointing is widely used for hands-free input in head-mounted displays (HMDs). The primary role of head movement in an HMD is to control the viewport based on absolute mapping of head rotation to the 3D environment. Head pointing is conventionally supported by the same 1:1 mapping of input with a cursor fixed in the centre of the view, but this requires exaggerated head movement and limits input granularity. In this work, we propose to adopt dynamic gain to improve ergonomics and precision, and introduce the HeadShift technique. The design of HeadShift is grounded in natural eye-head coordination to manage control of the viewport and the cursor at different speeds. We evaluated HeadShift in a Fitts’ Law experiment and on three different applications in VR, finding the technique to reduce error rate and effort. The findings are significant as they show that gain can be adopted effectively for head pointing while ensuring that the cursor is maintained within a comfortable eye-in-head viewing range.

Using differential-algebraic equations and natural coordinates for modelling and simulating cable-driven parallel robots

This paper proposes a comprehensive approach to the dynamic modelling of Cable-Driven Parallel Robots (CDPRs) by means of Differential-Algebraic Equations (DAEs). CDPRs are usually modelled through a minimal set of Ordinary Differential Equations (ODEs), often by making some simplification or just focusing on the unconstrained platform/end-effector dynamics. The alternative use of redundant DAEs provides several benefits since several non-ideal properties and peculiar operations of CDPRs can be easily and accurately modelled. To provide a comprehensive modelling frame, the typical components of a CDPR with rigid cables are here discussed and modelled by exploiting the concept of DAEs, which use redundant coordinates and embed kinematic constraints in the algebraic part of the equations. Through such advantageous features, it is possible to model swivelling guiding pulleys with non-negligible dimensions and mass. The use of rheonomous constraints is proposed as well, to represent in a simple way the effect of the movable exit-points, that are widely adopted in reconfigurable CDPRs. Finally, the use of Natural Coordinates is proposed for representing spatial end-effectors and modelling some challenging operations such as its overturning or the picking of heavy objects. Numerical simulations and the comparison with the results provided by a benchmark software are shown to demonstrate the accuracy and the computational efficiency of the proposed approach.

Bioinspired Heterocoordination in Adaptable Cobalt Metal-Organic Framework for DNA Epigenetic Modification Detection.

Metal-organic frameworks (MOFs) show unique advantages in simulating the dynamics and fidelity of natural coordination. Inspired by zinc finger protein, a second linker was introduced to affect the homogeneous MOF system and thus facilitate the emergence of diverse functionalities. Under the systematic identification of 12 MOF species (i.e., metal ions, linkers) and 6 second linkers (trigger), a dissipative system consisting of Co-BDC-NO2 and o-phenylenediamine (oPD) was screened out, which can rapidly and in situ generate a high photothermal complex (η = 36.9%). Meanwhile, both the carboxylation of epigenetic modifications and metal ion (Fe3+, Ni2+, Cu2+, Zn2+, Co2+ and Mn2+) screening were utilized to improve the local coordination environment so that the adaptable Co-MOF growth on the DNA strand was realized. Thus, epigenetic modification information on DNA was converted to an amplified metal ion signal, and then oPD was further introduced to generate bimodal dissipative signals by which a simple, high-sensitivity detection strategy of 5-hydroxymethylcytosine (LOD = 0.02%) and 5-formylcytosine (LOD = 0.025‰) was developed. The strategy provides one low-cost method (< 0.01 $/sample) for quantifying global epigenetic modifications, which greatly promotes epigenetic modification-based early disease diagnosis. This work also proposes a general heterocoordination design concept for molecular recognition and signal transduction, opening a new MOF-based sensing paradigm.

Effects of different deployment strategies on the dynamic characteristics of bidirectional solar array

Based on natural coordinate method, a multi-rigid-body dynamic model of a bidirectional solar array is established. A typical solar array composed of a spacecraft main-body, a yoke, three main solar panels and two side solar panels is utilized as a demonstration case. Three deployment strategies have been designed for bidirectional solar array. Different deployment strategies are evaluated by analysing the attitude and kinetic energy of the spacecraft main-body, angular velocities of deployable components and constraint forces. The simulation results reveal that the strategy of the side panels to be deployed synchronously after the main panels are locked allows the solar arrays to reach a steady state more quickly after entering orbit. The analysis results in this paper can be utilized to aid in the engineering design of solar array deployment.

Nearest Vector Control Method Applied to an MMC for PV Generation

This paper proposes a new and simplified Nearest Vector Control (NVC) modulation technique for a grid-connected photovoltaic (PV) system using a Modular Multilevel Converter (MMC). Compared to the Nearest Level Control (NLC) technique, which defines three independent states for the three phases of medium to large four-wire multilevel converters, NVC offers a more coordinated behavior for three-wire converters. The proposed scheme is easy to implement, and it simplifies the understanding of using vectors when detecting the vector of the converter nearest to a given reference. Because it uses natural coordinates, namely, ab, bc and ca, the proposed method is easier to understand and more useful for further developments. Compared with earlier NVC methods, this approach offers full independence of the number of levels at the converter and it can readily accommodate changes in the number of levels, with no need for lookup tables or artificial coordinate transformations. The proposed NVC method was implemented on a 16-cell MMC used for PV generation and then it was compared to NLC, leading to a smaller and more consistent low-order harmonic distortion, requiring about the same complexity of implementation. Furthermore, in comparison to NLC, when applying the proposed NVC modulation, a behavior more insensitive to changes in the grid voltage was found, the most hazardous odd harmonics from the 5th to the 19th were reduced, and a consistent reduction of about 25 dB was achieved on the 5th and 7th harmonics. The newly proposed method is supported by simulations and experimental results with constant and sharply changing solar irradiance, leaving or removing the 100 Hz component of the MMC circulating currents.

Research on Deployment Process Dynamics and Vibration for Replaceable Interface Mast

The mast of the rover is a device used to carry precision instruments such as cameras on the rover, and its performance directly affects the working quality of these devices. The replaceable interface mast can effectively solve the problems of a single structure and poor maintenance of ordinary masts, so we study the deployment process dynamics properties and vibration for replaceable interface mast. Firstly, we analyzed the spatial motion of the reconfigurable rigid body module by the absolute node coordinate method and the natural coordinate method, and established the dynamic equation of the interface, the reconfigurable module without external constraints. Then, we established a dynamic model of the mast system deployment process. We analyzed the dynamic behavior of the replaceable interface mast and studied and compared the differences in the deployment behavior of the replaceable interface mast under different system configurations, flexible interface geometric parameters, and different driving rules. Finally, we built a model of the mast system and experimentally analyzed the deployment process of the replaceable interface mast. Using numerical solution and experimental verification, we proved that the established dynamic model of the mast system can correctly analyze the deployment behavior dynamics of the replaceable interface mast, and the study can provide a reference for the design and behavior analysis of the mast system.

Learning to Assist Bimanual Teleoperation Using Interval Type-2 Polynomial Fuzzy Inference

Assisting humans in collaborative tasks is a promising application for robots, however effective assistance remains challenging. In this paper, we propose a method for providing intuitive robotic assistance based on learning from human natural limb coordination. To encode coupling between multiple-limb motions, we use a novel interval type-2 (IT2) polynomial fuzzy inference for modeling trajectory adaptation. The associated polynomial coefficients are estimated using a modified recursive least-square with a dynamic forgetting factor. We propose to employ a Gaussian process to produce robust human motion predictions, and thus address the uncertainty and measurement noise of the system caused by interactive environments. Experimental results on two types of interaction tasks demonstrate the effectiveness of this approach, which achieves high accuracy in predicting assistive limb motion and enables humans to perform bimanual tasks using only one limb.

Deployment dynamics and experiments of a tendon-actuated flexible manipulator

The quantity of space debris on Earth orbit has escalated tremendously in recent years, presenting a significant hazard to human space operations. It is urgent to develop effective measures to capture and remove various space debris. For this purpose, this paper presents a tendon-actuated flexible deployable manipulator. The flexible manipulator consists of several deployable units connected by Cardan joints and actuated by tendons. Compared with the present technologies for capturing space debris such as rigid robotic arm or flying net, this flexible manipulator is deployable, reusable, lightweight and applicable to the capture of large space debris. In order to investigate its deployment dynamics, an accurate dynamic model of the flexible manipulator is established based on the natural coordinate formulation (NCF) and the absolute nodal coordinate formulation (ANCF). Subsequently, numerical simulations are carried out to study the effects of system parameters and the base satellite on its deployment dynamics. Finally, ground experiments for both deployment and bending of the flexible manipulator are conducted to verify its effectiveness and feasibility.

Affirmations of Ecosystem: The Ecotopian Bio-Network in Vedic Eco-Narratives

Objective: The present study focuses on the interconnectivity of all life as reflected in Vedic literature. The affirmation of ecosystem, natural balance and bio-network transpires somewhat very naturally in ancient Indian Classical literature the Vedas. It chants the sacredness of the ecological designs and the natural coordination of human beings and the ecosystem. Method: Literature review and the analysis of the Vedic Mantras relating to the contemporary present-day contexts. Results and Discussion: The study discusses and reveals the pieces of evidence of ecological poetry of peace between human beings and their natural surroundings in Vedic literature. Human understanding of nature as sacred builds an individual’s attitude on how one perceives and preserves the nature around an ecosystem. Human bonding and decoding of the semiotics of nature need to be holistic and non-discriminatory. This is an attempt to rejuvenate the degree of blessedness which we attribute to ecology, devoted to our overall moral and ethical being. The paper inclines towards a study that endeavours vital enquiry into the possible borders of human inventiveness and receptiveness. This is an exploration of the use of poetic spontaneity by the human race to figure out human bonding to the ecology and the earth. It illustrates that Vedic eco-poetry marvellous sequencing that admires the search for esthetic exquisiteness, methodical pragmatism and connotation in human interactions with nature. Conclusion: The study presents connectivity in Vedic Eco poetry drawing it to contemporary concepts of Sustainability and concluding with education for sustainable development. Originality and Value: Vedic narratives are the ethno-eco-poetry of nature and human nature. It reflects this co-existence as a celebration of life. It reveals harmony and natural interconnectivity as well as the interdependence of all living entities and nature.

Dynamics of reconfiguration and assembly of a stacked satellite system

Separation and reconfiguration of stacked satellites in orbit is an effective method for constructing large space structures. This paper investigates the dynamics of a stacked satellite system (SSS) during the separation and reconfiguration process. Firstly, the dynamic model of the SSS is established via the natural coordinate formulation (NCF) to conveniently handle the time-varying constraints between satellites. Then, the separation and reconfiguration strategies are proposed for the SSS including the reconstruction step between two configurations. To ensure collision-free satellite assembly, a proportional differential (PD) controller combined with a potential function is introduced. Additionally, a docking mechanism is designed, considering collision force constraints during satellite docking assembly. Finally, several numerical simulations are conducted to demonstrate the effectiveness of the separation and assembly strategies.