Variation Principles Research Articles

Abstract WP351: Perceptions of Self-management Role, Barriers, Facilitators Among Stroke Survivors: A Qualitative Study

Introduction: Stroke self-management (SM) interventions have demonstrated beneficial effects for improving function and stroke outcomes. Little is known about how and what make positive behavioral change (or not) for SM participation and adherence. Objectives: To explore, from first-time stroke survivors’ perspectives, the perceived role, facilitators and barriers of stroke SM, and how they deal with day-to-day stroke SM. Methods: This qualitative study was embedded in a randomized controlled trial aimed at investigating the effects of a stroke SM program on functional and psychosocial outcomes. All participants in this study, being involved in the intervention group of the trial, were purposively selected based on their SM behavioral change post-intervention. Maximum variation principles, including age, sex and ADL were adopted for participants’ recruitment. Interview data were audio taped, transcribed verbatim and entered into NVIVO 10 for content analysis. Results: Findings from 20 stroke informants (age range 41-85, 65% male, ADL score range 65 - 100) revealed three categories including (1) perception of stroke self-management (medical and behavioral management; role management; emotional management, stroke knowledge management), (2) facilitating factors (knowledge and skills established; fear of stroke recurrence; family, professional and peer support; and personal meaningful goals and action plan), and (3) barriers (extent of negative impact of stroke; economy-related factors; environment-related factors; and powerlessness to stroke). Conclusions: Stroke participants described approaches that facilitated their SM, and identified barriers that may be amenable to SM counseling strategies for enhancing resilience for SM participation and adherence.

Up-to-date mathematical models lines of development of information technologies in the field of numerical methods of structures strength calculations

In order to carry out reliable calculations of structures adequate to reality, in particular, for taking into account plastic resource, it is necessary to use complex program systems and build finite element models of high dimensionality. This work provides a comparison of different mathematical models, which can be used for numerical analysis. Consideration was given to basic variation principles and methods of calculating structural mechanics. Distinctive features of forming systems of equations of classical methods of structural mechanics and known numerical methods were demonstrated. Possible advantages of methods with respect to accuracy and rate of calculations were revealed. Consideration was given to possible improvements of existing mathematical models in elastoplastic domain. Possible directions of development in the field of engineering methods for calculating strength were proposed.

Connections between variation principles at the interface of wave-function and density-functional theories.

A recently proposed variation principle [N. I. Gidopoulos, Phys. Rev. A 83, 040502(R) (2011)] for the determination of Kohn-Sham effective potentials is examined and extended to arbitrary electron-interaction strengths and to mixed states. Comparisons are drawn with Lieb's convex-conjugate functional, which allows for the determination of a potential associated with a given electron density by maximization, yielding the Kohn-Sham potential for a non-interacting system. The mathematical structure of the two functionals is shown to be intrinsically related; the variation principle put forward by Gidopoulos may be expressed in terms of the Lieb functional. The equivalence between the information obtained from the two approaches is illustrated numerically by their implementation in a common framework.

The coupling effect of air-bridges on broadband spiral inductors in SiC-based MMIC technology**Project supported by the National Natural Science Foundation of China (Grant Nos. 61334002 and 61474091) and the National High Technology Research and Development Program of China (Grant No. 2015AA016801).

The coupling effect of air-bridges on broadband spiral inductors in SiC-based MMIC technology has been investigated deeply. The fabricated 1-nH spiral inductor on SiC substrate demonstrates a self-resonant frequency of 51.6 GHz, with a peak Q-fact of 12.14 at 22.1 GHz. From the S-parameters measurements, the exponential decay phenomenon is observed for L, Q-factor, and SRF with the air-bridge height decreasing, and an analytic expression is concluded to exactly fit the measured data which can be used to predict the performance of the spiral inductor. All the coefficients in the formula have specific meaning. By means of establishing the lumped model, the parasitic coupling capacitance of the air-bridge has been extracted and presents the exponential decay with the air-bridge heights decreasing which indicates that this capacitor is directly related to the coupling effect of the air-bridge. Through the electromagnetic field distribution simulation, the details of the electric field around the air-bridge have been presented which demonstrate the formation and the variation principles of the coupling effect.

EXERGIC ANALYSIS AND VARIATIONAL INEQUALITIES METHODS IN SOME FLUID MECHANIC’S PROBLEMS

Purpose. The foundations of the energetic approach for analyzing of the bodies with dissipation properties are presented in the article. Methodology. Energy resource of arbitrary body is characterized by the sum of the exergy and anergy. The first of them indicates the part of energy which can be used to perform mechanical work. The second – is a measure of the processes’ irreversibility in the interaction of such body with the others. It indicates what part of the energy dissipates into the environment as low-temperature heat and can’t be used for the mechanical work performance. The energy balance in the thermodynamic systems is the basis for the relevant variation principles formulation. The introduction of the exergy and anergy concept leads to the variation inequalities formulation. They are transformed into equality in almost non-realized case of the reverse ability and equilibrium process, or in the case of the limit equilibrium state. Conclusion. Variation inequalities can be used for the formulation of general relations, which determine the parameters of quasi-static flow of real fluid in its interaction with solid obstacles - wetted perimeter of pipe or open channel, as well as the inclusions - in the cases of unknown interaction surface. These problems in particular arise in the analysis of the erosion process and shoreline destruction it caused, river flow interaction with stones during floods in natural streams.

Evaluation of residual clearance after pre-joining and pre-joining scheme optimization in aircraft panel assembly

Purpose For the automatic drilling and riveting in panel assembly, gaps between the skin and strangers are inevitable and undesirable. At present, the determination of pre-joining schemes relies on workers’ experience, introducing excessive number and inappropriate locations of pre-joining. This paper aims to present a new method for the evaluation of residual clearances after pre-joining and the pre-joining scheme optimization, providing operation guidance for the workers in panel assembly workshop. Design/methodology/approach In this paper, an equivalent gap assembly model for pre-joining is proposed on the basis of the mechanism of variation. This model retains the essential elastic behavior of the key features during the pre-joining operation and calculates the residual clearances in the view of the potential energy. Subsequently, this method is embedded into a Pareto optimality-based genetic algorithm, and the optimal pre-joining schemes are achieved with the consideration of the total residual clearances and the permissive tolerances. Findings The equivalent gap assembly model has the capability to predict an acceptable degree of accuracy of the residual clearances and achieve the optimized pre-joining schemes with less number of pre-joining at the same level of residual clearances. Practical implications The optimized pre-joining schemes are given in the form of Pareto optimality set, and workers can select suitable results according to their inclination to the quality and efficiency. Originality/value The paper is the first to propose the equivalent gap assembly model for the pre-joining operation, which provides for the simplification of the calculation of residual clearances based on the constrained variation principles.

Numerical and experimental study of field synergy analysis in water jet impingement based on minimum entropy generation method

Most detailed reviews of field synergy principle FSP are mainly focused on numerical approaches, while validating first deduction of FSP experimentally is very rare. Therefore, an experimental analysis is carried out on a simple heated plate surface. Experiments are conducted using infrared thermal-vision system and a professional high-speed camera. The field study concerns the hydrodynamic and water jet velocity ratio based on four different configurations under relatively low jet Reynolds number ranging from 2602 to 6505 and to be optimized by FSP. New analytical equations are developed to verify experimentally the synergy between velocity streamline and temperature field as well as synergy number especially in the mid integral areas where images have clear appearance along the lateral direction of the heated plate. Laminar heat flow field synergy equation is developed based on the minimum entropy generation MEG method, and it is treated for relatively low Reynolds number in order to reduce computational effort and time cost. The new proposed laminar heat synergy optimization equation is deduced by setting irreversibility of heat transfer process under the additional assumption that constraint of thermal generation by mechanism of viscous dissipation is considered. The variation principles with respect to velocity give new Navier–Stokes equation with additional volume force, which is constructed through functional variation of Lagrange multipliers to numerically simulate convective heat transfer. Solving simultaneously the field synergy equations (Fx​, Fy​, Fz) for input constant related to viscous dissipation equal to −1.0E05 will give several synergy flow fields which are followed by gradual increase of entropy generation rate as ratio of H/D increases.

The interdisciplinary research of big data and wireless channel: A cluster-nuclei based channel model

Recently, internet stimulates the explosive progress of knowledge discovery in big volume data resource, to dig the valuable and hidden rules by computing. Simultaneously, the wireless channel measurement data reveals big volume feature, considering the massive antennas, huge bandwidth and versatile application scenarios. This article firstly presents a comprehensive survey of channel measurement and modeling research for mobile communication, especially for 5th Generation (5G) and beyond. Considering the big data research progress, then a cluster-nuclei based model is proposed, which takes advantages of both the stochastical model and deterministic model. The novel model has low complexity with the limited number of cluster-nuclei while the cluster-nuclei has the physical mapping to real propagation objects. Combining the channel properties variation principles with antenna size, frequency, mobility and scenario dug from the channel data, the proposed model can be expanded in versatile application to support future mobile research.

Evolutionary Robotics: What, Why, and Where to

Evolutionary robotics applies the selection, variation, and heredity principles of natural evolution to the design of robots with embodied intelligence. It can be considered as a subfield of robotics that aims to create more robust and adaptive robots. A pivotal feature of the evolutionary approach is that it considers the whole robot at once, and enables the exploitation of robot features in a holistic manner. Evolutionary robotics can also be seen as an innovative approach to the study of evolution based on a new kind of experimentalism. The use of robots as a substrate can help address questions that are difficult, if not impossible, to investigate through computer simulations or biological studies. In this paper we consider the main achievements of evolutionary robotics, focusing particularly on its contributions to both engineering and biology. We briefly elaborate on methodological issues, review some of the most interesting findings, and discuss important open issues and promising avenues for future work.

4D seismic data acquisition method during coal mining

In order to observe overburden media changes caused by mining processing, we take the fully-mechanized working face of the BLT coal mine in Shendong mine district as an example to develop a 4D seismic data acquisition methodology during coal mining. The 4D seismic data acquisition is implemented to collect 3D seismic data four times in different periods, such as before mining, during the mining process and after mining to observe the changes of the overburden layer during coal mining. The seismic data in the research area demonstrates that seismic waves are stronger in energy, higher in frequency and have better continuous reflectors before coal mining. However, all this is reversed after coal mining because the overburden layer has been mined, the seismic energy and frequency decrease, and reflections have more discontinuities. Comparing the records collected in the survey with those from newly mined areas and other records acquired in the same survey with the same geometry and with a long time for settling after mining, it clearly shows that the seismic reflections have stronger amplitudes and are more continuous because the media have recovered by overburden layer compaction after a long time of settling after mining. By 4D seismic acquisition, the original background investigation of the coal layers can be derived from the first records, then the layer structure changes can be monitored through the records of mining action and compaction action after mining. This method has laid the foundation for further research into the variation principles of the overburden layer under modern coal-mining conditions.

Dynamic Response Analysis of Composite Soil Nailed Wall under Earthquake

In this paper, with the help of the finite element software ADINA, an actual composite soil nailed wall was solved. The dynamic response of the composite soil nailed wall is analyzed and discussed under the EL-Centro and man-made Lanzhou accelerogram. And the variation principles of the soil nailed wall which subjected to the earthquake, and the earthquake coupled with pore pressure, are demonstrated respectively. The results of the FEM dynamic analysis can be a useful reference for engineers of the design and construction of the composite soil nailed wall.

Differentiable but exact formulation of density-functional theory.

The universal density functional F of density-functional theory is a complicated and ill-behaved function of the density-in particular, F is not differentiable, making many formal manipulations more complicated. While F has been well characterized in terms of convex analysis as forming a conjugate pair (E, F) with the ground-state energy E via the Hohenberg-Kohn and Lieb variation principles, F is nondifferentiable and subdifferentiable only on a small (but dense) subset of its domain. In this article, we apply a tool from convex analysis, Moreau-Yosida regularization, to construct, for any ε > 0, pairs of conjugate functionals ((ε)E, (ε)F) that converge to (E, F) pointwise everywhere as ε → 0(+), and such that (ε)F is (Fréchet) differentiable. For technical reasons, we limit our attention to molecular electronic systems in a finite but large box. It is noteworthy that no information is lost in the Moreau-Yosida regularization: the physical ground-state energy E(v) is exactly recoverable from the regularized ground-state energy (ε)E(v) in a simple way. All concepts and results pertaining to the original (E, F) pair have direct counterparts in results for ((ε)E, (ε)F). The Moreau-Yosida regularization therefore allows for an exact, differentiable formulation of density-functional theory. In particular, taking advantage of the differentiability of (ε)F, a rigorous formulation of Kohn-Sham theory is presented that does not suffer from the noninteracting representability problem in standard Kohn-Sham theory.

Comparison of Geodesics and Energy Variation Principles of Light Propagation

The propagation of light on a set of null paths in a pseudo-Riemannian manifold is studied using a variational principle of extremal energy. This method is compared with those based on the geodesics and Fermat principles. For the static space-time all three variational methods give the same solutions. The Fermat principle for stationary gravitational fields is identical to the principle of variation of energy of light-like particles. The approach proposed here is applied to a flat expanding space, corresponding to the LCDM-model, and generalized Godel space-time. In the first case a solution obtained by the method of energy variation coincides with the geodesic method, while in the second case they give different solutions.

A metric for dynamic routing based on variational principles

In this paper the variation principles from theoretical physics is considered that would describe the process of routing in computer networks. The total traffic which is currently served on all hops of the route has been chosen as the quantity to minimize. Universal metric function has been found for dynamic routing taking into account the packet loss effect. An attempt to derive the metric of the most popular dynamic routing protocols such as RIP, OSPF, EIGRP from universal metric was made.

Fracture Reasons and Improvements for the Running Gear of Shearers

Running traction mechanism of shearers is adopted as the analysis object in this paper. The finite element models for the elastic contact analysis between the running gears and pin-rails are created. When the gears are running, the variation principles of contact spots, contact force, and internal stress for the gears and pin-rails at the different contact positions are analyzed. The calculation results show that the maximum stress is located at the edges of the gear teeth for the different contact positions. When the teeth are loaded with the repeated large stress, cracks are produced at the tooth edges at first and then are growing. The tooth breakage is produced at last. Gear chamfers using two circulars at the tooth edges can change the location of the maximum stress and the maximum MISES stress can be reduced by 20% or more. Therefore, the fracture problem of gear teeth is solved basically.

Performance Simulation Analysis and Design of the Scale Model for the Earth Pressure Balance Shield

Referring to the Earth Pressure Balance (EPB) shield with the diameter of 6.25m, a new experiment station of EPB shield is proposed, which is loaded with mechanical structure instead of traditional soil box. The structure of the experiment model is designed for the performance analysis of the EPB shield. The mechanical loading device, which is called the soil simulator, can simulate different geological environments. The soil simulator is capable of realizing three work states, such as earth balance pressure, earth under pressure, and earth over pressure. By adopting virtual prototype technology, parametric model of the shield station is established and the co-simulation scheme is determined. Besides, the kinematic analysis as well as variation principles between the displacement and driving forces of the propulsion system are obtained, which build the foundation for optimization design and control of the shield prototype.

Dynamics of Hybrid Robot Structures Using Variational Principles

The purpose of this paper is to determine the dynamic equations for a hybrid robot structure which consists of a mobile robot named PatrolBot and a 2TR robot serial structure. The motion equations will be determined on the basis of the new concepts in advanced mechanics, such as Matrix Exponentials Algorithm and Variation Principles in Analytical Mechanics, concerning the kinetic and acceleration energy part of important scientific researches deployed by the main author.

Springback Variation Principles in Materials Forming Processes

The conceptions of springback anti-couple systems and equations are initially given. By the use of the weighted residual method to the springback anti-couple equations, the springback principles of minimum potential energy and minimum complementary energy are established. Meanwhile, the springback principle of minimum potential energy is applied to calculating springback deformations of a curved beam under the radial and circumferential forces and end bending moments.

Research on Ossicular Chain Mechanics Model

On account of the complex structure of the middle ear and that it is more difficult to carry out experiments to test the nature of the mechanical components, the relevant data is hard to obtain, which has become an obstacle restricting analysis of the middle ear mechanic. Based on spatial structure and mechanical properties of ossicular chain, the paper has established functional relationship between load and members displacement with elastic principles and variation principles, in order that experimental results will be reflected in mechanical model. In the process of solving equations, we use the experimental data of a known special point or the various components function of statistical regression method and then combine them with the time shift function, so that the analytical solution of the various components will be achieved. The correctness of equation derived in this paper is verified by comparing the experimental data. So the model has provided a convenient way to obtain date in the future research analysis.

Joint edge detection and motion estimation of cardiac MR image sequence by a phase field method

In this paper a variational framework for joint segmentation and motion estimation is employed for inspecting heart in Cine MRI sequences. A functional including Mumford–Shah segmentation and optical flow based dense motion estimation is approximated using the phase-field technique. The minimizer of the functional provides an optimum motion field and edge set by considering both spatial and temporal discontinuities. Exploiting calculus of variation principles, multiple partial differential equations associated with the Euler–Lagrange equations of the functional are extracted, first. Next, the finite element method is used to discretize the resulting PDEs for numerical solution. Several simulation runs are used to test the convergence and the parameter sensitivity of the method. It is further applied to a comprehensive set of clinical data in order to compare with conventional cascade methods. Developmental constraints are identified as memory usage and computational complexities, which may be resolved utilizing sparse matrix manipulations and similar techniques. Based on the results of this study, joint segmentation and motion estimation outperforms previously reported cascade approaches especially in segmentation. Experimental results substantiated that the proposed method extracts the motion field and the edge set more precisely in comparison with conventional cascade approaches. This superior result is the consequence of simultaneously considering the discontinuity in both motion field and image space and including consequent frames (usually five) in our joint process functional.