| 1. |
- Churilov, Alexander, et al.
(författare)
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Mathematical model of non-basal testosterone regulation in the male by pulse modulated feedback
- 2009
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Ingår i: Automatica. - : Elsevier BV. - 0005-1098 .- 1873-2836. ; 45:1, s. 78-85
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Tidskriftsartikel (refereegranskat)abstract
- A parsimonious mathematical model of pulse modulated regulation of non-basal testosterone secretion in the male is developed. The model is of the third differential order, reflecting the three most significant hormones in the regulation loop, but is yet shown to be capable of sustaining periodic solutions with one or two pulses of gonadotropin-releasing hormone (GnRH) in each period. Lack of stable periodic solutions is otherwise a main shortcoming of existing low-order hormone regulation models. Existence and stability of periodic solutions are studied. The periodic mode with two GnRH pulses in the least period has not been described in medical literature, but is found to explain experimental data well.
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| 2. |
- Abdalmoaty, Mohamed, 1986-, et al.
(författare)
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Continuous Time-Delay Estimation From Sampled Measurements
- 2023
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Ingår i: IFAC-PapersOnLine. - : Elsevier. - 2405-8963. ; 56:2, s. 6982-6987
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Tidskriftsartikel (refereegranskat)abstract
- An algorithm for continuous time-delay estimation from sampled output data and a known input of finite energy is presented. The continuous time-delay modeling allows for the estimation of subsample delays. The proposed estimation algorithm consists of two steps. First, the continuous Laguerre spectrum of the output (delayed) signal is estimated from discretetime (sampled) noisy measurements. Second, an estimate of the delay value is obtained via a Laguerre domain model using a continuous-time description of the input. The second step of the algorithm is shown to be intrinsically biased, the bias sources are established, and the bias itself is modeled. The proposed delay estimation approach is compared in a Monte-Carlo simulation with state-of-the-art methods implemented in time, frequency, and Laguerre domain demonstrating comparable or higher accuracy in the considered scenario.
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| 3. |
- Abdalmoaty, Mohamed, 1986-, et al.
(författare)
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Noise reduction in Laguerre-domain discrete delay estimation
- 2022
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Ingår i: 2022 IEEE 61st Conference on Decision and Control (CDC). - : Institute of Electrical and Electronics Engineers (IEEE). - 9781665467612 - 9781665467605 - 9781665467629 ; , s. 6254-6259
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Konferensbidrag (refereegranskat)abstract
- This paper introduces a stochastic framework for a recently proposed discrete-time delay estimation method in Laguerre-domain, i.e. with the delay block input and output signals being represented by the corresponding Laguerre series. A novel Laguerre-domain disturbance model allowing the involved signals to be square-summable sequences is devised. The relation to two commonly used time-domain disturbance models is clarified. Furthermore, by forming the input signal in a certain way, the signal shape of an additive output disturbance can be estimated and utilized for noise reduction. It is demonstrated that a significant improvement in the delay estimation error is achieved when the noise sequence is correlated. The noise reduction approach is applicable to other Laguerre-domain problems than pure delay estimation.
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| 4. |
- Aghanavesi, Somayeh, 1981-, et al.
(författare)
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A multiple motion sensors index for motor state quantification in Parkinson's disease
- 2020
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Ingår i: Computer Methods and Programs in Biomedicine. - : Elsevier BV. - 0169-2607 .- 1872-7565. ; 189
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Tidskriftsartikel (refereegranskat)abstract
- Aim: To construct a Treatment Response Index from Multiple Sensors (TRIMS) for quantification of motor state in patients with Parkinson's disease (PD) during a single levodopa dose. Another aim was to compare TRIMS to sensor indexes derived from individual motor tasks. Method: Nineteen PD patients performed three motor tests including leg agility, pronation-supination movement of hands, and walking in a clinic while wearing inertial measurement unit sensors on their wrists and ankles. They performed the tests repeatedly before and after taking 150% of their individual oral levodopa-carbidopa equivalent morning dose.Three neurologists blinded to treatment status, viewed patients’ videos and rated their motor symptoms, dyskinesia, overall motor state based on selected items of Unified PD Rating Scale (UPDRS) part III, Dyskinesia scale, and Treatment Response Scale (TRS). To build TRIMS, out of initially 178 extracted features from upper- and lower-limbs data, 39 features were selected by stepwise regression method and were used as input to support vector machines to be mapped to mean reference TRS scores using 10-fold cross-validation method. Test-retest reliability, responsiveness to medication, and correlation to TRS as well as other UPDRS items were evaluated for TRIMS. Results: The correlation of TRIMS with TRS was 0.93. TRIMS had good test-retest reliability (ICC = 0.83). Responsiveness of the TRIMS to medication was good compared to TRS indicating its power in capturing the treatment effects. TRIMS was highly correlated to dyskinesia (R = 0.85), bradykinesia (R = 0.84) and gait (R = 0.79) UPDRS items. Correlation of sensor index from the upper-limb to TRS was 0.89. Conclusion: Using the fusion of upper- and lower-limbs sensor data to construct TRIMS provided accurate PD motor states estimation and responsive to treatment. In addition, quantification of upper-limb sensor data during walking test provided strong results. © 2019
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| 5. |
- Albaba, Adnan, et al.
(författare)
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Online Model-Based Beat-by-beat Heart Rate Estimation
- 2020
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Ingår i: 2020 American Control Conference (ACC). - 9781538682661 - 9781538682678 - 9781538682654 ; , s. 539-544
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Konferensbidrag (refereegranskat)abstract
- A method for estimating the instantaneous heart rate (HR) using the morphological features of one electrocardiogram (ECG) cycle (beat) at a time is proposed. This work is not aimed at introducing an alternative way for HR estimation, but rather illustrates the utility of model-based ECG analysis in online individualized monitoring of the heart function. The HR estimation problem is reduced to fitting one parameter, whose value is related to the nine parameters of a realistic nonlinear model of the ECG and estimated from data by nonlinear least-squares optimization. The method feasibility is evaluated on synthetic ECG signals as well as signals acquired from MIT-BIH databases at Physionet website. Moreover, the performance of the method was tested under realistic free-moving conditions using a wearable ECG and HR monitor with encouraging results.
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| 6. |
- Albaba, Adnan, et al.
(författare)
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Patient-Specific Electrocardiogram Monitoring by Model-Based Stochastic Anomaly Detection
- 2020
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Ingår i: 2020 European Control Conference (ECC). - 9783907144022 - 9781728188133 ; , s. 735-740
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Konferensbidrag (refereegranskat)abstract
- A novel model-based method for patient-specific detection of deformed electrocardiogram (ECG) beats is proposed and tested. Five parameters of a patient-specific nonlinear ECG model are estimated from data by nonlinear least-squares optimization. The normal variability of the model parameters is captured by estimated probability density functions. A binary classifier, based on stochastic anomaly detection methods, along with a pre-tuned classification threshold, is employed for detecting the abnormal ECG beats. We demonstrate the utility of the proposed approach by validating it on annotated arrhythmia data recorded under clinical conditions.
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| 7. |
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| 8. |
- Bro, Viktor, 1991-, et al.
(författare)
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Continuous and discrete Volterra-Laguerre models with delay for modeling of smooth pursuit eye movements
- 2023
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Ingår i: IEEE Transactions on Biomedical Engineering. - : IEEE. - 0018-9294 .- 1558-2531. ; 70:1, s. 97-104
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Tidskriftsartikel (refereegranskat)abstract
- The mathematical modeling of the human smooth pursuit system from eye-tracking data is considered. Recently developed algorithms for the estimation of Volterra-Laguerre (VL) models with explicit time delay are applied in continuous and discrete time formulations to experimental data collected from Parkinsonian patients in different medication states and healthy controls. The discrete VL model with an explicit time delay and the method for its estimation are first introduced in this paper. The estimated parameters of a second-order VL model are shown to capture the ocular dynamics both in health and disease. The possibility of including the estimated time delay, along with the VL kernel parameters, into the set of the model parameters is explored. The results obtained in continuous VL modeling are compared with those in discrete time to discern the effects due to the sampling enforced by the eye tracker used for data acquisition.
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| 9. |
- Bro, Viktor, et al.
(författare)
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Continuous and Discrete Volterra-Laguerre Models with Explicit Time Delay
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Ingår i: Automatica. - 0005-1098 .- 1873-2836.
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Tidskriftsartikel (refereegranskat)abstract
- This paper solves the problem of estimating the time delay in a smooth nonlinear system modeled by a Volterra model (VM), along with the delay-free dynamics captured by the convolution operators. VMs with explicit time delay, whose convolution kernels are represented as series of Laguerre functions, are considered in continuous and discrete-time. Since a VM with a time delay is linear in the kernel parameters, the proposed modeling approach, on the one hand, allows for the use of efficient linear sparse estimation techniques and, on the other hand, extends the applicability of Volterra-Laguerre models (VLM) to a broader class of nonlinear systems. Hinging on recent progress in Laguerre domain modeling of linear time-delay systems, analytical expressions for the projections of kernels with a delayed argument on the Laguerre basis are obtained, featuring special kinds of polynomials that arise due to the presence of time delay. The mathematical modeling problem of the human smooth pursuit system from eye-tracking data illustrates the practical utility of the acquired theoretical results.
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| 10. |
- Bro, Viktor, et al.
(författare)
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Laguerre-domain Modeling and Identification of Linear Discrete-time Delay Systems
- 2020
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Ingår i: IFAC PapersOnline. - : ELSEVIER. - 2405-8963. ; , s. 939-944
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Konferensbidrag (refereegranskat)abstract
- A closed-form Laguerre-domain representation of discrete linear time-invariant systems with constant input time delay is derived. It is shown to be useful in a I-2 -> I-2 system identification setup (with I-2 denoting square-summables signals) often arising in biomedical applications, where the experimental protocol does not allow for persistent excitation of the system dynamics. The utility of the proposed system representation is demonstrated on a problem of drug kinetics estimation from clinical data.
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