Walker Type Research Articles

Improved modularity and new features in ipie: Toward even larger AFQMC calculations on CPUs and GPUs at zero and finite temperatures.

ipie is a Python-based auxiliary-field quantum Monte Carlo (AFQMC) package that has undergone substantial improvements since its initial release [Malone et al., J. Chem. Theory Comput. 19(1), 109-121 (2023)]. This paper outlines the improved modularity and new capabilities implemented in ipie. We highlight the ease of incorporating different trial and walker types and the seamless integration of ipie with external libraries. We enable distributed Hamiltonian simulations of large systems that otherwise would not fit on a single central processing unit node or graphics processing unit (GPU) card. This development enabled us to compute the interaction energy of a benzene dimer with 84 electrons and 1512 orbitals with multi-GPUs. Using CUDA and cupy for NVIDIA GPUs, ipie supports GPU-accelerated multi-slater determinant trial wavefunctions [Huang et al. arXiv:2406.08314 (2024)] to enable efficient and highly accurate simulations of large-scale systems. This allows for near-exact ground state energies of multi-reference clusters, [Cu2O2]2+ and [Fe2S2(SCH3)4]2-. We also describe implementations of free projection AFQMC, finite temperature AFQMC, AFQMC for electron-phonon systems, and automatic differentiation in AFQMC for calculating physical properties. These advancements position ipie as a leading platform for AFQMC research in quantum chemistry, facilitating more complex and ambitious computational method development and their applications.

Circumstances of falls among older adult walker users in long-term care and the associated walker design deficits

ABSTRACT Falls are the leading cause of fatal and non-fatal injuries in older adults. Walkers are often used by and prescribed to this population to reduce fall risk, however, walker users and walker non-users alike experience similar fall incidence rates. The role of walkers in preventing falls is unclear as some studies suggest walkers may be a fall-inciting factor. The purpose of this study was to analyze walker deficits by evaluating the circumstances and causes of falls in older adult walker users residing in long-term care facilities. Videos capturing 34 real-life falls involving wheeled walkers (rollators and two-wheeled walkers) in two retirement facilities were analyzed for 3 themes: walker type, fall direction, and activity at the time of fall. A frequency analysis of these themes was performed to determine common fall mechanisms. The results of this study suggest two-wheeled walker and rollator users most often fall sideways while turning and backward during weight transfer, respectively. Poor maneuverability, lateral stability, and wheel velocity control of the walkers contributed to the falls. Device improvements addressing these areas of deficiency may be necessary to mitigate falls occurring in older adult walker users.

Transverse domain wall dynamics in hybrid piezoelectric/ferromagnetic devices

This work investigates the static and dynamic features of transverse domain walls in a magnetostrictive, linear elastic isotropic ferromagnetic material under the action of magnetic field (axial and transverse) and electric current. The investigation is done in the framework of the extended Landau–Lifshitz–Gilbert equation by taking into account the effects of stresses induced by a piezoelectric actuator and Rashba spin‐orbit torque caused by structural inversion asymmetry. First, we obtain the expression of magnetization orientation into the two faraway domains, then characterize the static magnetization profile under the action of magnetoelastic and transverse magnetic fields. Next, we introduce a trial function (Schryer and Walker type). After that, by adopting the small angle approximation formalism, we derive the explicit expression of key quantities such as propagating transverse domain wall profile, excitation angle, transverse domain wall velocity, mobility, and displacement. Finally, we present the numerical illustrations of derived analytical results and find that they are in qualitatively good agreement with the recent numerical simulations and experimental observations.

A technical note on percutaneous fixation of trapezium fracture under gravitational traction

Trapezium fractures rarely present as isolated fractures and warrant anatomical fixation to minimize post-traumatic arthritis. Fixation techniques reported include open approach to trapezium fracture and fixation, percutaneous fixation under image intensifier guidance or percutaneous arthroscopic fixation under gravitational traction. We have reported a novel method of percutaneous fixation of a trapezium Walker type IV coronal split fractures under gravitational traction and per-operative image intensifier guidance. Two percutaneous headless differential pitch screws were used for fixation, which was off-loaded using an inter-metacarpal K-wire. Patient was discharged on the same day with a light-weight cast. The fixation yielded acceptable reduction of the articular surface as confirmed by radiographs. The cast and off-loading K-wire were removed at four weeks post-surgery and hand therapy was commenced. 3-month review showed optimal radiological healing with excellent return to function without pain. In conclusion, using gravitational traction can allow percutaneous fixation of trapezium fractures with excellent results and also make an otherwise complex procedure simpler. Level of EvidenceIV.

Dynamics, interference effects, and multistability in a Lorenz-like system of a classical wave-particle entity in a periodic potential.

A classical wave-particle entity (WPE) can be realized experimentally as a droplet walking on the free surface of a vertically vibrating liquid bath, with the droplet's horizontal walking motion guided by its self-generated wave field. These self-propelled WPEs have been shown to exhibit analogs of several quantum and optical phenomena. Using an idealized theoretical model that takes the form of a Lorenz-like system, we theoretically and numerically explore the dynamics of such a one-dimensional WPE in a sinusoidal potential. We find steady states of the system that correspond to a stationary WPE as well as a rich array of unsteady motions, such as back-and-forth oscillating walkers, runaway oscillating walkers, and various types of irregular walkers. In the parameter space formed by the dimensionless parameters of the applied sinusoidal potential, we observe patterns of alternating unsteady behaviors suggesting interference effects. Additionally, in certain regions of the parameter space, we also identify multistability in the particle's long-term behavior that depends on the initial conditions. We make analogies between the identified behaviors in the WPE system and Bragg's reflection of light as well as electron motion in crystals.

Cosmological tests of the osculating Barthel–Kropina dark energy model

We further investigate the dark energy model based on the Finsler geometry inspired osculating Barthel–Kropina cosmology. The Barthel–Kropina cosmological approach is based on the introduction of a Barthel connection in an osculating Finsler geometry, with the connection having the property that it is the Levi-Civita connection of a Riemannian metric. From the generalized Friedmann equations of the Barthel–Kropina model, obtained by assuming that the background Riemannian metric is of the Friedmann–Lemaitre–Robertson–Walker type, an effective geometric dark energy component can be generated, with the effective, geometric type pressure, satisfying a linear barotropic type equation of state. The cosmological tests, and comparisons with observational data of this dark energy model are considered in detail. To constrain the Barthel–Kropina model parameters, and the parameter of the equation of state, we use 57 Hubble data points, and the Pantheon Supernovae Type Ia data sample. The st statistical analysis is performed by using Markov Chain Monte Carlo (MCMC) simulations. A detailed comparison with the standard Lambda CDM model is also performed, with the Akaike information criterion (AIC), and the Bayesian information criterion (BIC) used as the two model selection tools. The statefinder diagnostics consisting of jerk and snap parameters, and the Om(z) diagnostics are also considered for the comparative study of the Barthel–Kropina and Lambda CDM cosmologies. Our results indicate that the Barthel–Kropina dark energy model gives a good description of the observational data, and thus it can be considered a viable alternative of the Lambda CDM model.

Applications of AHP, FAHP, BWM, Entropy, and CRITIC Methods in Electrohydraulic Forming Process Parametric Evaluation for Automotive Panels Using the 1100 Aluminum Alloy Sheets

Although multicriteria selection methods are flexible and extensively used in machining, less attention has been paid to their comprehensive test performance in the electrohydraulic forming process. In this study, five new applications of multicriteria selection methods are proposed to analyze available parameters in the electrohydraulic forming process and select parameters best suited for further analysis and improvement of the process. The analyzed parameters are the stand-off distance, electrode gap, voltage, and medium, while the multicriteria methods are the AHP, FAHP, BMW, entropy, and CRITIC. The proposed methods were demonstrated on experimental data from the literature utilizing an impulse magnetizer system (walker type). For each method, the prioritized parametric results were obtained. All the methods assign the first position to the medium as a parameter with consensus on the voltage parameter has the worst (lowest) value of weights in all the methods. The weights of the medium parameter for the best results are 0.5030 (AHP method), 0.5600 (FAHP method), 0.5230 (best-worst method), 0.4090 (entropy method), and 0.5000 (CRITIC method). The worst parameter for all the methods is the voltage of 0.0320 (FAHP method). The results obtained from the proposed applications were compared with one another and found to be effective for multicriteria selection decisions. This article offers new methods to establish the parametric values of the electrohydraulic forming process for machining composites made of AA1100 sheets.

Comparison of anterior and posterior wheeled walkers based on body weight support in improving gait function a subjects with spinal cord injury: A case study.

The majority of people with muscle weakness or paralysis lose their ability to walk and require various assistive devices like a walker to walk. Although various studies have examined the effect of different types of anterior and posterior walkers on different walking variables, so far no studies compare anterior versus posterior walker on forces and torques applied to the lower extremities. This paper presents a novel approach of using a passive saddle-assistive device (S-AD) to investigate the effect of this device on the torques of the joints. To measure the effectiveness of the device, a volunteer with spinal cord injury (SCI) participated to walk in four modes; including the use of a standard walker, anterior, and posterior mobility S-AD with and without body weight support, in the gait laboratory. The forces and torques applied to the lower and upper limbs were measured and examined. The result demonstrated a reduction in the vertical force on the lower limb in the anterior S-AD in supporting the patient's weight compared to the standard walker up to 42.8% and to the posterior S-AD with weight support up to 12%. According to the results, the anterior S-AD has a greater effect compared to posterior S-AD and standard walkers on lower and upper limb torque and forces during walking of a SCI patient while using knee ankle-foot orthoses.

Spin correlation functions, Ramus-like identities, and enumeration of constrained lattice walks and plane partitions

Relations between the mean values of distributions of flipped spins on periodic Heisenberg XX chain and some aspects of enumerative combinatorics are discussed. The Bethe vectors, which are the state-vectors of the model, are considered both as on- and off-shell. It is this approach that makes it possible to represent and to study the correlation functions in the form of non-intersecting nests of lattice walks and related plane partitions. We distinguish between two types of walkers, namely lock step models and random turns. Of particular interest is the connection of random turns walks and a circulant matrix. The determinantal representation for the norm-trace generating function of plane partitions with fixed height of diagonal parts is obtained as the expectation of the generating exponential over off-shell N-particle Bethe states. The asymptotics of the dynamical mean value of the generating exponential is calculated in the double scaling limit provided that the evolution parameter is large. It is shown that the amplitudes of the leading asymptotics depend on the number of diagonally constrained plane partitions.

Advances in Electrochemiluminescence Biosensors Based on DNA Walkers.

Mediated by Watson-Crick base-pairing principle, DNA can be used to construct multi-functional molecular machines, such as DNA walkers, tweezers, logic gates and motors. It is noteworthy that DNA walkers with the advantages of programmability and diverse structures within the micro-nano scale have attracted intense attention in the field of biosensing, bioimaging, drug delivery, and genetic diagnosis. DNA walkers are comprised of driving power, walking strands and the tracks. The driving power acts as an external stimulus and the tracks as a platform for the walking strands to move autonomously. Under the specific external stimulus as driving power, such as strand displacement strategies, enzymatic reactions and environmental condition stimulus, DNA walkers could realize the generation and amplification of signals. Electrochemiluminescence (ECL) biosensors, combining ECL technology and bio-identification strategies, exhibit the virtue of high sensitivity, wide linear response range and low background interference. Recently, the construction of DNA walker-based ECL biosensors can amplify the targets and signals via multiple identification and recycles, achieving ultrasensitive detection for diverse targets. Herein, this review systematically summarizes the construction of different types of DNA walkers and their applications in ECL biosensors. Ultimately, this review summarizes and discusses the prospects for DNA walkers.

Dark energy and accelerating cosmological evolution from osculating Barthel–Kropina geometry

Finsler geometry is an important extension of Riemann geometry, in which each point of the spacetime manifold is associated with an arbitrary internal variable. Two interesting Finsler geometries with many physical applications are the Randers and Kropina type geometries. A subclass of Finsler geometries is represented by the osculating Finsler spaces, in which the internal variable is a function of the base manifold coordinates only. In an osculating Finsler geometry, we introduce the Barthel connection, with the remarkable property that it is the Levi–Civita connection of a Riemannian metric. In the present work we consider the gravitational and cosmological implications of a Barthel–Kropina type geometry. We assume that in this geometry the Ricci type curvatures are related to the matter energy–momentum tensor by the standard Einstein equations. The generalized Friedmann equations in the Barthel–Kropina geometry are obtained by considering that the background Riemannian metric is of Friedmann–Lemaitre–Robertson–Walker type. The matter energy balance equation is also derived. The cosmological properties of the model are investigated in detail, and it is shown that the model admits a de Sitter type solution and that an effective dark energy component can also be generated. Several cosmological solutions are also obtained by numerically integrating the generalized Friedmann equations. A comparison of two specific classes of models with the observational data and with the standard Lambda CDM model is also performed, and it is found that the Barthel–Kropina type models give a satisfactory description of the observations.

Development of a Caterpillar-Type Walker for the Elderly People

A walker assists elderly people with age-related reduced walking ability and helps to improve stability and balance ability. However, if the general-type walker (GTW) is used on an uneven, obstacle, or sloped terrain, it may cause excessive muscle use and falls. Therefore, in this study, we developed a caterpillar-type walker (CTW) that elderly people can safely use in various terrains. Twelve elderly who were able to walk normally participated in the study. The activity of upper and lower extremity muscles, the number of obstacles overcome, and walking speed was compared and analyzed when using two types of walkers in uneven terrain, obstacle terrain, and sloped terrain. In addition, satisfaction with the use of these walkers was evaluated. When CTW was used, the activity of the muscles of the upper and lower extremities was significantly reduced compared to the use of GTW on all terrains. The walker developed in this study overcame obstacles of all heights, but the GTW failed to overcome obstacles starting from the 2 cm section. In terms of walking speed, when the CTW was used, the walking speed was higher than that of the GTW in uneven terrain and obstacle terrain. In satisfaction, there were significant differences in safety, durability, simplicity of use, comfort, and effectiveness. Through these results, it was confirmed that the CTW can efficiently and safely assist the elderly in walking on uneven terrain, obstacle terrain, and inclined terrain.

Effects of assistive devices on postural control following a balance disturbance along the anterior-posterior direction.

Assistive devices provide balance and stability to those who require a greater base of support, especially during ambulation or in tasks essential to functional daily living. In ambulatory assistive device use, center of pressure (COP) movement as one of the measurements of postural control is a factor when assessing fall risk, with an overall goal of maintaining postural equilibrium. There is a lack of research on assistive devices, such as walkers, regarding measurable outcome variables related to fall risk. The purpose of this study was to determine how much the postural control in single limb stance during a balance perturbance is affected by utilizing three different walker types designed to promote stability: the standard walker, the front-wheeled walker with straight wheels and the front-wheeled walker with caster wheels. Is postural sway control in single limb stance during a balance perturbance affected by walker type? Twenty-three healthy adults participated and gave consent. The NeuroCom® SMART EquiTest® system was utilized to simulate forward falls. Subjects stood on the system's force plate, which was tipped backwards quickly, forcing subjects to attempt to maintain balance. Each participant experienced 18 simulated perturbations, during which they were asked to maintain balance while using one of three walkers in single-limb stance. Each trial was completed using random assignment of three different walker types. Leg dominance of the stance leg was also randomized for each trial. The type of walker and the leg dominance in the standing limb significantly affected postural control in a balance perturbance in the A-P direction. The walker type significantly affected the COP maximum displacement in anterior-posterior (AP) direction. However, the leg dominance significantly affected COP maximum displacement in AP and medio-lateral (ML) directions and COP velocity in AP direction. The findings suggest that when fully grounded, a standard walker is more stable than the front-wheeled walker. However, this does not indicate that the standard walker is more stable than other types of walkers when it is being picked up and moved forward during normal use.

Cosmological evolution and dark energy in osculating Barthel\u2013Randers geometry

We consider the cosmological evolution in an osculating point Barthel–Randers type geometry, in which to each point of the space-time manifold an arbitrary point vector field is associated. This Finsler type geometry is assumed to describe the physical properties of the gravitational field, as well as the cosmological dynamics. For the Barthel–Randers geometry the connection is given by the Levi-Civita connection of the associated Riemann metric. The generalized Friedmann equations in the Barthel–Randers geometry are obtained by considering that the background Riemannian metric in the Randers line element is of Friedmann–Lemaitre–Robertson–Walker type. The matter energy balance equation is derived, and it is interpreted from the point of view of the thermodynamics of irreversible processes in the presence of particle creation. The cosmological properties of the model are investigated in detail, and it is shown that the model admits a de Sitter type solution, and that an effective cosmological constant can also be generated. Several exact cosmological solutions are also obtained. A comparison of three specific models with the observational data and with the standard Lambda CDM model is also performed by fitting the observed values of the Hubble parameter, with the models giving a satisfactory description of the observations.

Pengembangan Desain Walker Fleksibel Bagi Lansia

The health condition of the elderly generally has decreased which can cause several physical and mental problems. Elderly aged over 70 years or 60 years who have health problems are categorized as high risk elderly. In carrying out their daily activities inside the house or outside the house, such as going to the mosque, garden, etc., they usually use a equipment called a walker. The types of walkers on the market still have limitations, so they need to be developed in a flexible walker design. The stages used in the flexible walker design development research are compiling a list of requirements, determining reference concepts, developing alternative concepts, selecting concepts, and analyzing techniques and postures for the selected design.
 The selected concept has specifications, namely the front pedestal functions as a fixed leg or wheeled leg, the arm of the walker holder can be adjusted up and down by 150 mm in height, has a seat that can be folded, and the walker can be folded. In addition, the results of stress analysis on the critical component, namely the main fulcrum, obtained safe criteria where the maximum stress value that occurs is 7.35x106 N/m2 is given still below the yield strength value of the brass material 3.5x108 N/m2. Posture analysis using the RULA method in standing and sitting positions obtained an average final score of 2 in the acceptable category for walker users..

Flow parsing and biological motion

Flow parsing is a way to estimate the direction of scene-relative motion of independently moving objects during self-motion of the observer. So far, this has been tested for simple geometric shapes such as dots or bars. Whether further cues such as prior knowledge about typical directions of an object’s movement, e.g., typical human motion, are considered in the estimations is currently unclear. Here, we adjudicated between the theory that the direction of scene-relative motion of humans is estimated exclusively by flow parsing, just like for simple geometric objects, and the theory that prior knowledge about biological motion affects estimation of perceived direction of scene-relative motion of humans. We placed a human point-light walker in optic flow fields that simulated forward motion of the observer. We introduced conflicts between biological features of the walker (i.e., facing and articulation) and the direction of scene-relative motion. We investigated whether perceived direction of scene-relative motion was biased towards biological features and compared the results to perceived direction of scene-relative motion of scrambled walkers and dot clouds. We found that for humans the perceived direction of scene-relative motion was biased towards biological features. Additionally, we found larger flow parsing gain for humans compared to the other walker types. This indicates that flow parsing is not the only visual mechanism relevant for estimating the direction of scene-relative motion of independently moving objects during self-motion: observers also rely on prior knowledge about typical object motion, such as typical facing and articulation of humans.

Symmetry restriction and its application to gravity

In the Hamiltonian formulation, it is not a priori clear whether a symmetric configuration will keep its symmetry during evolution. In this paper, we give precise requirements of when this is the case and propose a symmetry restriction to the phase space of the symmetric variables. This can often ease computation, especially when transcending from the infinite dimensional phase space of a field theory to a possibly finite dimensional subspace. We will demonstrate this in the case of gravity. A prominent example is the restriction of full general relativity in its Hamiltonian formulation to the cosmological configurations of Robertson–Walker type. We will demonstrate our procedure in this setting and extend it to examples that appear useful in certain approaches to quantum gravity.

Design and analysis of walker with sit to stand assistance

A walker that can provide sit-to-stand assistance to the user. As the sit-to-stand motion can define the functional independence of a person, it must be considered as an important parameter in life. Currently, various types of walkers are available from traditional to smart walkers, some walkers are developed specially according to the requirement or disability of the patient. But the main problem while using the traditional walker is that the user or the patient has to lift the walker and place it forward so that he can walk this requires a considerable amount of energy of the upper extremity of a user and because of that the patient can get easily tired or feel fatigued neither the traditional walker can help the user with such kind of problem, nor the technological advance smart walkers could help. Thus, there is a requirement of a simple cost-effective walker which can address the problem. This paper provides in detail the design and analysis of such a walker.

A Linear Inchworm Piezomotor with a New Configuration: Design Considerations, Fabrication and Characterization

The new technologies of precise positioning systems with high speed and accuracy have been in the focus of attention in the recent years. In this research, a one-axis walker type inchworm piezomotor has been designed, modeled, manufactured and characterized. Simple design, simple manufacturing and assembly processes, low manufacturing cost and also high speed and stroke are advantages of this piezomotor. This system consists of three piezoelectric actuators, which installed into the clamps and feeder sets, and a guideway. The geometrical parameters with a high impact on the stiffness have been realized and modeled by the finite element method to ensure the proper functioning of the piezomotor. The motor dimensions are 55 × 23.1 × 15 mm3 which can provide a large movement range inside the guideway. The simulation analysis and experimental tests have been carried out to characterize the piezomotor. Based on the shape mode analysis, the maximum operating frequency of the piezomtor has been determined. Also, the Von-Mises stress analysis has been employed to predict the structural behavior of the motor. Finally, the experimental tests have been conducted to illustrate the piezomotor characteristics such as step pitch, speed, and operating frequency.

Wave function of the photon in a curved spacetime

It is known that the classical variables are replaced by operators for the dynamics of the electromagnetic field, thus the second quantization is traditionally used. There is a significant question in modern theoretical physics area: “Why is there no fully developed first-quantized theory of photons?” In the present work, we argue that a photon wave function can be obtained if one uses the massless Duffin-Kemmer-Petiau (mDKP) equation. Thus, we focus on exact solutions of the mDKP equation the Robertson–Walker type spacetime via the Teleparallel Theory (TPT) of Gravity. The mDKP equation is generally known as the spinor formulation of the photons. We also focus on solutions of the Maxwell equations (MEs) to verify the equivalence between the mDKP and the ME formulations of the photons. It is shown that photons present an oscillatory behavior.