1,443 research outputs found
A Computational Framework Towards the Tele-Rehabilitation of Balance Control Skills
No full textMobility has been one of the most impacted aspects of human life due to the spread of the COVID-19 pandemic. Home confinement, the lack of access to physical rehabilitation, and prolonged immobilization of COVID-19-positive patients within hospitals are three major factors that affected the mobility of the general population world-wide. Balance is one key indicator to monitor the possible movement disorders that may arise both during the COVID-19 pandemic and in the coming future post-COVID-19. A systematic quantification of the balance performance in the general population is essential for preventing the appearance and progression of certain diseases (e.g., cardiovascular, neurodegenerative, and musculoskeletal), as well as for assessing the therapeutic outcomes of prescribed physical exercises for elderly and pathological patients. Current research on clinical exercises and associated outcome measures of balance is still far from reaching a consensus on a “golden standard” practice. Moreover, patients are often reluctant or unable to follow prescribed exercises, because of overcrowded facilities, lack of reliable and safe transportation, or stay-at-home orders due to the current pandemic. A novel balance assessment methodology, in combination with a home-care technology, can overcome these limitations. This paper presents a computational framework for the in-home quantitative assessment of balance control skills. Novel outcome measures of balance performance are implemented in the design of rehabilitation exercises with customized and quantifiable training goals. Using this framework in conjunction with a portable technology, physicians can treat and diagnose patients remotely, with reduced time and costs and a highly customized approach. The methodology proposed in this research can support the development of innovative technologies for smart and connected home-care solutions for physical therapy rehabilitation
An agent-specific stochastic model of generalized reaching task difficulty
No full textThe ability of an agent to accomplish a trajectory during a certain motor task depends on the fit between external (environment) and internal (agent) constraints, also known as affordance. A model of difficulty for a generalized reaching motor task is proposed as an affordance-related measure, as perceived by a specific agent for a given environment and task. By extending the information-based Index of Difficulty of a trajectory, a stochastic model of difficulty is formulated based on the observed variability of spatial trajectories executed by a given agent during a repetitive motor task. The model is tested on an experimental walking dataset available in the literature, where the repetitive stride movement of differently aged subjects (14 “old” subjects aged 50-73; 20 “young” subjects aged 21-37) at multiple speed conditions (comfortable, ~30% faster, ~30% slower) is analyzed. Reduced trajectory variability in older as compared to younger adults results in a higher Index of Difficulty (slower: +24%, p < 0.0125; faster: +38%, p < 0.002) which is interpreted in this context as reduced affordance. The model overcomes the limits of existing difficulty measures by capturing the stochastic dependency of task difficulty on a subject’s age and average speed. This model provides a benchmarking tool for motor performance in biomechanics and ergonomics applications
The analogue of grad-div stabilization in DG methods for incompressible flows: Limiting behavior and extension to tensor-product meshes
No full textSchroeder, Philipp W./0000-0001-7644-4693WOS: 000442638700037grad-div stabilization is a classical remedy in conforming mixed finite element methods for incompressible flow problems, for mitigating velocity errors that are sometimes called poor mass conservation. Such errors arise due to the relaxation of the divergence constraint in classical mixed methods, and are excited whenever the spatial discretization has to deal with comparably large and complicated pressures. In this contribution, an analogue of grad-div stabilization for Discontinuous Galerkin methods is studied. Here, the key is the penalization of the jumps of the normal velocities over facets of the triangulation, which controls the measure-valued part of the distributional divergence of the discrete velocity solution. Our contribution is twofold: first, we characterize the limit for arbitrarily large penalization parameters, which shows that the stabilized nonconforming Discontinuous Galerkin methods remain robust and accurate in this limit; second, we extend these ideas to the case of non-simplicial meshes; here, broken grad-div stabilization must be used in addition to the normal velocity jump penalization, in order to get the desired pressure robustness effect. The analysis is performed for the Stokes equations, and more complex flows and Crouzeix-Raviart elements are considered in numerical examples that also show the relevance of the theory in practical settings. (C) 2018 Elsevier B.V. All rights reserved.German Academic Exchange Service (DAAD)Deutscher Akademischer Austausch Dienst (DAAD); program "Research Grants for Doctoral Candidates and Young Academics and Scientists", 2017/18 [57299291]; National Science FoundationNational Science Foundation (NSF) [DMS1522191]; U.S. ArmyUnited States Department of Defense [65294-MA]The authors would especially like to thank Christoph Lehrenfeld for several related fruitful discussions on stabilization and hybridization and the invaluable help he provided in using the finite element library NGSolve in the context of this work. Mine Akbas acknowledges support from the German Academic Exchange Service (DAAD) with the program "Research Grants for Doctoral Candidates and Young Academics and Scientists", 2017/18 (57299291). The third author was supported by National Science Foundation grant DMS1522191 and U.S. Army grant 65294-MA
A multi-level multi-label text classification dataset of 19th century Ottoman and Russian literary and critical texts
No full textThis paper introduces a multi-level, multi-label text classification dataset comprising over 3000 documents. The dataset features literary and critical texts from 19th-century Ottoman Turkish and Russian. It is the first study to apply large language models (LLMs) to this dataset, sourced from prominent literary periodicals of the era. The texts have been meticulously organized and labeled. This was done according to a taxonomic framework that takes into account both their structural and semantic attributes. Articles are categorized and tagged with bibliometric metadata by human experts. We present baseline classification results using a classical bag-of-words (BoW) naive Bayes model and three modern LLMs: multilingual BERT, Falcon, and Llama-v2. We found that in certain cases, Bag of Words (BoW) outperforms Large Language Models (LLMs), emphasizing the need for additional research, especially in low-resource language settings. This dataset is expected to be a valuable resource for researchers in natural language processing and machine learning, especially for historical and low-resource languages. The dataset is publicly available
State-Space Characterization of Balance Capabilities in Biped Systems with Segmented Feet
No full textThe human ability of keeping balance during various locomotion tasks is attributed to our capability of withstanding complex interactions with the environment and coordinating whole-body movements. Despite this, several stability analysis methods are limited by the use of overly simplified biped and foot structures and corresponding contact models. As a result, existing stability criteria tend to be overly restrictive and do not represent the full balance capabilities of complex biped systems. The proposed methodology allows for the characterization of the balance capabilities of general biped models (ranging from reduced-order to whole-body) with segmented feet. Limits of dynamic balance are evaluated by the Boundary of Balance (BoB) and the associated novel balance indicators, both formulated in the Center of Mass (COM) state space. Intermittent heel, flat, and toe contacts are enabled by a contact model that maps discrete contact modes into corresponding center of pressure constraints. For demonstration purposes, the BoB and balance indicators are evaluated for a whole-body biped model with segmented feet representative of the human-like standing posture in the sagittal plane. The BoB is numerically constructed as the set of maximum allowable COM perturbations that the biped can sustain along a prescribed direction. For each point of the BoB, a constrained trajectory optimization algorithm generates the biped’s whole-body trajectory as it recovers from extreme COM velocity perturbations in the anterior–posterior direction. Balance capabilities for the cases of flat and segmented feet are compared, demonstrating the functional role the foot model plays in the limits of postural balance. The state-space evaluation of the BoB and balance indicators allows for a direct comparison between the proposed balance benchmark and existing stability criteria based on reduced-order models [e.g., Linear Inverted Pendulum (LIP)] and their associated stability metrics [e.g., Margin of Stability (MOS)]. The proposed characterization of balance capabilities provides an important benchmarking framework for the stability of general biped/foot systems
The Effect of Electrolytes on the Interaction of C. I. Reactive Orange 16-Tetradecyltrimethylammonium Bromide
No full textThe aim of this study is to investigate the interaction of a cationic surfactant tetradecyltrimethyl ammonium bromide (TTAB) on the electronic absorption spectra of azo dye Reactive Orange 16 (RO16) and to observe the effects of the kind and concentration of electrolytes on these interactions by means of UV-Vis spectroscopy in submicellar and micellar concentration range at a certain temperature (303 K). TTAB affects the electronic absorption spectra of dye solution that is dye-surfactant interaction results into formation of complex and therefore, a decrease in maximum absorption spectra (1.577 at 494 nm). The electrolyte anions cause an increase on the absorbance of TTAB-RO16 ion-pair complex in the following order: Br- > Cl- > SO42- > NO3- > CN- and also for cations; Na+ > K+ > NH4+ > Mg2+. The increase or decrease on absorption spectra of RO16-TTAB solution depends on concentration range of the electrolyte added.Trakya UniversityH. Akbas gratefully acknowledges the financial support of the Trakya University Research Fund
Effects of Electrolytes on Interfacial and Micelle Properties of C.I. Reactive Orange 16 - Dodecylpyridinium Chloride Binary System
No full textThe effect of electrolytes on the interaction between the anionic dye C.I. Reactive Orange 16 and the cationic surfactant dodecylpyridinium chloride was investigated using surface tension measurement in a certain concentration range. The influence of the concentration of electrolyte on critical micelle concentration (CMC) values was observed in the following order; 0.1 M NaCl > 0.5 M NaCl > 1.0 M NaCl. Also, the influence of the electrolyte cations was observed as Na+ > Mg2+ > K+. An increase on CMC values of dye-surfactant solution with increasing electrolyte concentration is explained as charge screening and also the decrease in these values for higher concentration of electrolyte is attributed to the change of micelle shape. Furthermore this change is due to ionic polarizability, valency and hydrated radius. Using Rubingh's regular solution theory, the values of micellar interaction parameters (beta), were found as negative in all studied mixtures.Trakya University [TUBAP-659]H. Akbas greatefuly acknowledges the financial support of the Trakya University Research Fund (TUBAP-659)
Seismic response mitigation of elevated tanks by HDRB and FPS isolation systems
No full textThe aim of the paper is to evaluate the effectiveness of two isolation systems for the seismic protection
of elevated steel storage tanks: High Damping Rubber Bearings (HDRB) and Friction Pendulum (FPS)
isolators. As a case study, an elevated tank which collapsed during the Kocaeli Earthquake in 1999 at Habas
Pharmaceutics plant in Turkey has been studied. A time-history analysis is conducted using lumped mass
model to demonstrate the high base shear demand and inevitable collapse of support columns due to the
insufficient shear strength. A proper design of HDRB and FPS isolator and a complete non-linear analysis of
the isolated tanks prove the high effectiveness of both isolation systems for reducing the response of the
tank. Results revealed that the tank with the FPS provides better performance compared to HDRB in terms
of the isolation displacement convective base shear demands
Seismic behavior of liquid storage tanks with 2D and 3D base isolation systems
No full textIn past major earthquakes (1994 Northridge, 1995 Kobe, Chi-Chi 1999, Kocaeli 1999), significant damages occurred in the liquid storage tanks. The basic failure patterns were observed to be the buckling of the tank wall and uplift of the anchorage system. The damages in the industrial facilities and nuclear power plants have caused the spread of toxic substances to the environment and significant fires. Seismic isolation can be used in liquid storage tanks to decouple the structure and decrease the structural demand in the superstructure in case of ground shaking. Previous studies on the use of seismic isolation systems on liquid storage tanks show that an isolation system reduces the impulsive response but might slightly increase the convective one. There is still a lack of understanding of the seismic response of seismically isolated liquid storage tanks considering the fluid-structure interaction. In this study, one broad tank, one medium tank, and one slender tank are selected and designed. Two- and three-dimensional elastomeric bearings are used as seismic isolation systems. The seismic performance of the tanks is then investigated through nonlinear dynamic time-history analyses. The effectiveness of each seismic isolation system on tanks’ performance was investigated. Isolator tension forces, modal analysis results, hydrodynamic stresses, strains, sloshing heights and base shear forces of the tanks are compared. The results show that the total base shear is lower in 3D-isolators compared to 2D-isolators. Even though the tank wall stresses, and strains are slightly higher in 3D-isolators, they are more efficient to prevent the tension problem
Dynamic traffic signal control using a nonlinear coupled oscillators approach
No full textTraditional signal control systems use prestored timing plans that have been developed offline using historic data. These systems are not responsive to dynamical demand changes of traffic and may deteriorate in performance over time. Dynamic traffic signal control systems can adapt to actual traffic conditions, coping with complex flow patterns and unpredictable variations. They seek continuous optimal system performance. The main goal of this paper is to design a methodology for control of arterial traffic flows. To fulfill this goal, the nonlinear coupled oscillators model is adapted to the traffic signal system of a two-way arterial road. The control methodology is based on measurements of the microscopic occupancy parameters for incoming flows at intersections that have a four-way geometrical structure with four-green splits. The desired signal parameters such as cycle times, green splits, and offsets are adjusted dynamically according to local traffic data. Thus, the desired signal patterns are self-organized through the mutual interactions among the signals. The numerical and case study simulation results demonstrate the effectiveness of the control methodology under the dynamical demand changes of traffic
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