2,584 research outputs found
An FES-assisted gait training system for hemiplegic stroke patients based on inertial sensors
Online identification and nonlinear control of the electrically stimulated quadriceps muscle
A new approach for estimating nonlinear models of the electrically stimulated quadriceps muscle group under nonisometric conditions is investigated. The model can be used for designing controlled neuro-prostheses. In order to identify the muscle dynamics (stimulation pulsewidth-active knee moment relation) from discrete-time angle measurements only, a hybrid model structure is postulated for the shank-quadriceps dynamics. The model consists of a relatively well known time-invariant passive component and an uncertain time-variant active component. Rigid body dynamics, described by the Equation of Motion (EoM), and passive joint properties form the time-invariant part. The actuator, i.e. the electrically stimulated muscle group, represents the uncertain time-varying section. A recursive algorithm is outlined for identifying online the stimulated quadriceps muscle group. The algorithm requires EoM and passive joint characteristics to be known a priori. The muscle dynamics represent the product of a continuous-time nonlinear activation dynamics and a nonlinear static contraction function described by a Normalised Radial Basis Function (NRBF) network which has knee-joint angle and angular velocity as input arguments. An Extended Kalman Filter (EKF) approach is chosen to estimate muscle dynamics parameters and to obtain full state estimates of the shank-quadriceps dynamics simultaneously. The latter is important for implementing state feedback controllers. A nonlinear state feedback controller using the backstepping method is explicitly designed whereas the model was identified a priori using the developed identification procedure
Polaron and bipolaron dispersion curves in one dimension for intermediate coupling
Bipolaron energies are calculated as a function of wave vector by a
variational method of Gurari appropriate for weak or intermediate coupling
strengths, for a model with electron-phonon interactions independent of phonon
wave vectors and a short-ranged Coulomb repulsion. It is assumed that the bare
electrons have a constant effective mass. A two-parameter trial function is
taken for the relative motion of the two electrons in the bipolaron. Energies
of bipolarons are compared with those of two single polarons as a function of
wave vector for various parameter values. Results for effective masses at the
zone center are also obtained. Comparison is made with data of other authors
for bipolarons in the Hubbard-Holstein model, which differs mainly from the
present model in that it has a tight-binding band structure for the bare
electrons.Comment: 11 pages including six figures. Physical Review B, to be publishe
A multi-stage machine learning model on diagnosis of esophageal manometry
High-resolution manometry (HRM) is the primary procedure used to diagnose
esophageal motility disorders. Its interpretation and classification includes
an initial evaluation of swallow-level outcomes and then derivation of a
study-level diagnosis based on Chicago Classification (CC), using a tree-like
algorithm. This diagnostic approach on motility disordered using HRM was
mirrored using a multi-stage modeling framework developed using a combination
of various machine learning approaches. Specifically, the framework includes
deep-learning models at the swallow-level stage and feature-based machine
learning models at the study-level stage. In the swallow-level stage, three
models based on convolutional neural networks (CNNs) were developed to predict
swallow type, swallow pressurization, and integrated relaxation pressure (IRP).
At the study-level stage, model selection from families of the
expert-knowledge-based rule models, xgboost models and artificial neural
network(ANN) models were conducted, with the latter two model designed and
augmented with motivation from the export knowledge. A simple model-agnostic
strategy of model balancing motivated by Bayesian principles was utilized,
which gave rise to model averaging weighted by precision scores. The averaged
(blended) models and individual models were compared and evaluated, of which
the best performance on test dataset is 0.81 in top-1 prediction, 0.92 in top-2
predictions. This is the first artificial-intelligence-style model to
automatically predict CC diagnosis of HRM study from raw multi-swallow data.
Moreover, the proposed modeling framework could be easily extended to
multi-modal tasks, such as diagnosis of esophageal patients based on clinical
data from both HRM and functional luminal imaging probe panometry (FLIP)
Rural continental aerosol properties and processes observed during the Hohenpeissenberg Aerosol Characterization Experiment (HAZE2002)
International audienceDetailed investigations of the chemical and microphysical properties of rural continental aerosols were performed during the HAZE2002 experiment, which was conducted in May 2002 at the Meteorological Observatory Hohenpeissenberg (DWD) in Southern Germany. Online measurements included: Size-resolved chemical composition of submicron particles; total particle number concentrations and size distributions over the diameter range of 3 nm to 9 ?m; gas-phase concentration of monoterpenes, CO, O3, OH, and H2SO4. Filter sampling and offline analytical techniques were used to determine: Fine particle mass (PM2.5), organic, elemental and total carbon in PM2.5 (OC2.5, EC2.5, TC2.5), and selected organic compounds (dicarboxylic acids, polycyclic aromatic hydrocarbons, proteins). Overall, the non-refractory components of submicron particles detected by aerosol mass spectrometry (PM1, 6.6Ā±5.4 ?g m?3, arithmetic mean and standard deviation) accounted for ~62% of PM2.5 determined by filter gravimetry (10.6Ā±4.7 ?g m?3). The relative proportions of non-refractory submicron particle components were: (23Ā±39)% ammonium nitrate, (27Ā±23)% ammonium sulfate, and (50Ā±40)% organics (OM1). OM1 was closely correlated with PM1 (r2=0.9) indicating a near-constant ratio of non-refractory organics and inorganics. The average ratio of OM1 to OC2.5 was 2.1Ā±1.4, indicating a high proportion of heteroelements in the organic fraction of the sampled rural aerosol. This is consistent with the high ratio of oxygenated organic aerosol (OOA) over hydrocarbon-like organic aerosol (HOA) inferred from the AMS results (4:1), and also with the high abundance of proteins (~3%) indicating a high proportion of primary biological material (~30%) in PM2.5. This finding was confirmed by low abundance of PAHs (?3) and EC (?3) in PM2.5 and detection of several secondary organic aerosol compounds (dicarboxylic acids) and their precursors (monoterpenes). New particle formation was observed almost every day with particle number concentrations exceeding 104 cm?3 (nighttime background level 1000?2000 cm?3). Closer inspection of two major events indicated that the observed nucleation agrees with ternary H2SO4/H2O/NH3 nucleation and that condensation of both organic and inorganic species contributed to particle growth
Establishment and Persistence of Yellow-Flowered Alfalfa No-Till Interseeded into Crested Wheatgrass Stands
Crested wheatgrass [Agropyron cristatum (L.) Gaertn., A. desertorum
(Fisch. ex Link) Schult., and related taxa] often exists
in near monoculture stands in the northern Great Plains.
Introducing locally adapted yellow-flowered alfalfa [Medicago
sativa L. subsp. falcata (L.) Arcang.] would complement crested
wheatgrass. Our objective was to evaluate effects of seeding
date, clethodim {(E) -2-[1-[[(3-chloro-2-propenyl)oxy]imino]
propyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one}
sod suppression, and seeding rate on initial establishment and
stand persistence of Falcata, a predominantly yellow-flowered
alfalfa, no-till interseeded into crested wheatgrass. Research was
initiated in August 2008 at Newcastle, WY; Hettinger, ND;
Fruitdale, SD; and Buffalo, SD. Effects of treatment factors on
plant frequency during initial establishment were influenced by
site environments. Late summer and spring were suitable seeding
dates. Clethodim sod suppression increased seedling frequency
in most cases. Seedling frequency increased as seeding
rate increased from 0.56 to 7.84 kg pure live seed (PLS) haā1.
Specific seeding dates, clethodim sod suppression, and high
seeding rates did not greatly improve initial establishment when
site environments were poor. Residual effects of seeding date
and sod suppression post establishment were not significant
at most locations, but seeding rate effects were evident. Initial
establishment and persistence of Falcata alfalfa was successful at
Newcastle, indicating that interseeding in late summer or spring
using low seeding rates (ā¤3.36 kg PLS haā1) without clethodim
can be effective. Assessing grass canopy cover, soil texture, and
management (e.g., haying) is necessary to determine the suitability
of crested wheatgrass sites for interseeding
Creation of Coatings by Temperature-Controlled Polymer Deposition
In this paper, the results of the recent studies on application of lower critical solution temperature (LCST) phenomena of polymer solutions to the surface modification of flat and spherical substrates are reported. It was found that a controlled polymer deposition can be achieved upon prevailing of the LCST, a peculiar surface topology of polymer coating and particles those remarkably effective in stabilizing pigment dispersiions. Second, the finding is that the temperature induces polymer deposition as the coprecipitation of a finely dispersed component on the substrate surface. That goes along with the polymer deposition after exceeding of the LCST which in turn allows for the tailored surface modification of pigments in that particulate additiives can be incorporated into the surface modifying coating
Metabolite analysis for the comparison of irrigated and non-irrigated field grown tomato of varying genotype
Interactive decision support in hepatic surgery
BACKGROUND: Hepatic surgery is characterized by complicated operations with a significant peri- and postoperative risk for the patient. We developed a web-based, high-granular research database for comprehensive documentation of all relevant variables to evaluate new surgical techniques. METHODS: To integrate this research system into the clinical setting, we designed an interactive decision support component. The objective is to provide relevant information for the surgeon and the patient to assess preoperatively the risk of a specific surgical procedure. Based on five established predictors of patient outcomes, the risk assessment tool searches for similar cases in the database and aggregates the information to estimate the risk for an individual patient. RESULTS: The physician can verify the analysis and exclude manually non-matching cases according to his expertise. The analysis is visualized by means of a Kaplan-Meier plot. To evaluate the decision support component we analyzed data on 165 patients diagnosed with hepatocellular carcinoma (period 1996ā2000). The similarity search provides a two-peak distribution indicating there are groups of similar patients and singular cases which are quite different to the average. The results of the risk estimation are consistent with the observed survival data, but must be interpreted with caution because of the limited number of matching reference cases. CONCLUSION: Critical issues for the decision support system are clinical integration, a transparent and reliable knowledge base and user feedback
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