- Journal Details
- First Published
- 07 Mar 2008
- Publication timeframe
- 6 times per year
- Open Access
Page range: 1 - 10
Currently, electricity is treated as commodity that should be delivered from a distributor to a consumer with a certain quality. The power quality is defined by the set of measures with specific limit values. One of the basic measures is the Total Harmonic Distortion (THD), which allows to assess the level of the voltage distortion. The measurement of THD ratio should be carried out in accordance with the normative specification. It is assumed that this requirement is met by class A power quality analyzers. Currently, measures are taken to monitor power quality in a large number of measurement points with the use of smart energy meters that are part of the Advanced Metering Infrastructure (AMI). The paper presents the problem of THD ratio measurement by AMI meters if voltage fluctuations occur. In such situation, inconsistency in measurement results of AMI meters and class A power quality analyzers occurs. The problem is presented on the basis of laboratory study results in which disturbances in power grid are recreated.
- Total Harmonic Distortion (THD)
- power quality
- voltage distortion
- voltage fluctuation
- AMI smart energy meters
- Open Access
A Measurement Method of Determining the Power Supply Parameters for the Optimal Operation of a Synchronous Motor
Page range: 11 - 16
The article presents a measurement method for determining the power supply parameters for the optimal operation of a synchronous motor, i.e. operation with minimal losses in the entire load range. The measurement strategy is based on the search for the minimum sum of the power supplied to the excitation circuit and the stator circuit for the assumed load torque values. The process of searching for the minimum sum of power can be significantly shortened and simplified by using a network parameter meter. The research confirmed the usefulness of the proposed method for determining the optimal operation parameters of a synchronous motor. The tested motor was a machine with a cylindrical rotor, but the developed method will also be applicable to synchronous machines with salient pole rotors.
- Synchronous motor
- measurement method
- loss minimization
- optimal operations
- optimal power supply parameters
- Open Access
Design of Distributed Fusion Predictor and Filter without Feedback for Nonlinear System with Correlated Noises and Random Parameter Matrices
Page range: 17 - 31
This work presents distributed predictor and filter without feedback for nonlinear stochastic uncertain system with correlated noises. Firstly, for the problem that the process noise and measurement noise are correlated, the two-step prediction theorem based on projection theorem is used to replace the one-step prediction theorem, and the two-step prediction value of a single sensor is obtained. Secondly, the two-step prediction value of each sensor state is used as the measurement information to modify the distributed fusion predictor to obtain the distributed fusion prediction value. Then, according to the projection theorem, the prediction value of distributed fusion is used as measurement information to modify the filtering value of distributed fusion. Finally, the Cubature Kalman filter (CKF) algorithm is used to implement the algorithm proposed in this paper. By comparison with existing methods, the algorithm proposed in this paper solves the problem that existing methods cannot handle state estimation and prediction problems for nonlinear multi-sensor stochastic uncertain systems with correlated noises.
- nonlinear stochastic uncertain system
- distributed fusion
- state estimation
- Open Access
Page range: 32 - 43
Phase methods of measuring physical quantities and phase measuring equipment are widely used in various fields of science and technology. The article proposes a signal processing methodology based on a combination of the discrete Hilbert transform (DHT) and deterministic, as well as statistical methods of phase measurement. This methodology makes it possible to more fully use the information resource of the measuring signal phase in a wide range of the signal-to-noise ratio. It can be used both in computerized measurement and testing systems, as well as in the processing of measurement data. The benefits of the DHT are considered. The possibility of using statistics of directional data for phase measurements is shown. Circular statistics, such as the mean ring value, circular variance and the resulting vector length, were proposed for use in the phase measurements. Some examples of the use of this methodology in measurements and non-destructive testing are given.
- signal processing
- phase measurement
- discrete Hilbert transform
- circular statistics
- Open Access
Vectorcardiographic Ventricular Gradient with Constituents, and Myocardial Action Potential Parameter Distribution
Page range: 44 - 49
Theoretical grounds of integral vectors of ventricular depolarization and repolarization and their sum, i.e., the spatial ventricular gradient, have been studied. A systematic description and biophysical interpretation of these parameters are presented based on the distribution of cardiomyocyte action potential parameters in the inhomogeneous bidomain model of the myocardium. Recent medical studies have shown high efficiency and predictive value of the ventricular gradient, its constituents and related parameters, such as the angle between the con-stituents, the acceleration of repolarization, etc. Simple examples for a myocardial strip clarify the relationship between the action potential parameters and the resulting ventricular gradient. An explanation with graphic illustration is given for the very informative decartogram of repolarization acceleration. The results obtained here are useful in the modeling of vectorcardiograms for various pathological conditions of the heart ventricles and for various characteristics of the cardiomyocyte action potential, which determine its shape.
- dipole electrocardiotopography
- ventricular gradient
- action potential of cardiomyocytes
- bidomain model of the myocardium
- Open Access
Page range: 50 - 57
Objectives: Brace treatment in children with pectus carinatum has become the method of choice during the last decade. The authors evaluate the role of anthropometric measurements in diagnostic and treatment processes.
Methods: A prospective study, analysing a compressive brace treatment for pectus carinatum, performed between January 2018 and September 2020. Demographic data, anthropometric dimensions and indexes of the chest, data connected to an orthosis usage, as well as ongoing treatment outcomes were analysed.
Results: Forty-seven consecutive patients aged between 10 to 18 years with pectus carinatum were prescribed a compressive brace. Thirtynine of them (83 %) reached clinically positive results while wearing the orthosis for 6 ± 3 months. An improvement in the sagittal chest diameter was 0.5 cm – 2.8 cm (mean 1.0 cm ± 0.5 cm) and an improvement of the Thoracic Index was 0.8 % – 25.1 % (6.4 % ± 4.5 %) by using the brace on average for (6 ± 2) hours a day.
Conclusion: Clinical anthropometric measurements can evaluate the dimensions of chest wall and treatment progress in patients with pectus carinatum precisely and thus replace the need for more complex examinations requiring X-rays.
- pectus carinatum
- compressive bracing
- anthropometric measurements
- Thoracic Index