Composite pulses for high fidelity population transfer in three-level systems

In this work, we propose a composite pulses scheme by modulating phases to achieve high fidelity population transfer in three-level systems. To circumvent the obstacle that not enough variables are exploited to eliminate the systematic errors in the transition probability, we put forward a cost function to find the optimal value. The cost function is independently constructed either in ensuring an accurate population of the target state, or in suppressing the population of the leakage state, or both of them. The results demonstrate that population transfer is implemented with high fidelity even when existing the deviations in the coupling coefficients. Furthermore, our composite pulses scheme can be extensible to arbitrarily long pulse sequences. As an example, we employ the composite pulses sequence for achieving the three-atom singlet state in an atom-cavity system with ultrahigh fidelity. The final singlet state shows robustness against deviations and is not seriously affected by waveform distortions. Also, the singlet state maintains a high fidelity under the decoherence environment.

Gravitational wave propagation beyond general relativity: waveform distortions and echoes

We study the cosmological propagation of gravitational waves (GWs) beyond general relativity (GR) across homogeneous and isotropic backgrounds. We consider scenarios in which GWs interact with an additional tensor field and use a parametrized phenomenological approach that generically describes their coupled equations of motion. We analyze four distinct classes of derivative and non-derivative interactions: mass, friction, velocity, and chiral. We apply the WKB formalism to account for the cosmological evolution and obtain analytical solutions to these equations. We corroborate these results by analyzing numerically the propagation of a toy GW signal. We then proceed to use the analytical results to study the modified propagation of realistic GWs from merging compact binaries, assuming that the GW signal emitted is the same as in GR. We generically find that tensor interactions lead to copies of the originally emitted GW signal, each one with its own possibly modified dispersion relation. These copies can travel coherently and interfere with each other leading to a scrambled GW signal, or propagate decoherently and lead to echoes arriving at different times at the observer that could be misidentified as independent GW events. Depending on the type of tensor interaction, the detected GW signal may exhibit amplitude and phase distortions with respect to a GW waveform in GR, as well as birefringence effects. We discuss observational probes of these tensor interactions with both individual GW events, as well as population studies for both ground- and space-based detectors.

Detecting Small Size Mass Loading Using Transversely Coupled SAW Resonator

In the detection of small size mass loading, such as a single cell, a micro droplet or an aerosol particle, the sensors with longitudinally coupled surface acoustic wave resonator (LC-SAWR) structure can hardly avoid waveform distortions. The relative size of mass loading to the sensitive surface of the detector is the main factor affecting the response of LC-SAWR. The smaller the relative size, the worse the waveform distortion. In order to avoid influences from the mass loading’s size, in this paper, a transversely coupled SAW resonator (TC-SAWR) was proposed in order to achieve high performance in sensing small size mass loadings. For the design and simulation of TC-SAWR, the two-dimensional coupling of model (2D-COM) theory and finite element method (FEM) were used in this work. In the experiment, SiO2 was deposited on the sensor’s surface as a small size mass loading. The results from simulation and experiment mutually demonstrated the advantage of TC-SAWR to conquer waveform distortion in the detection of small size mass loading.

Understanding Power Quality using IoT-based Smart Analyzers and Advanced Software Tools

Power Quality is an important topic for undergraduate electrical engineering students around the world. In addition to the theoretical contents prepared and explained by the lecturer to their students, this matter has an important practical focus. In this paper, a framework for teaching power quality in laboratories using IoT-based smart analyzers and advanced software tools is developed to provide the students the opportunity of studying real data with a high level of detail. In particular, practical lessons have been designed in such a way that the students are trained in the use of well-known commercial smart meters (like the Circutor MYeBOX 1500) or opensource systems (like the openZmeter) to acquire energy and power quality data from real world measurements and to analyze the data collected using advanced software tools (like PowerVision). The results obtained from several courses of electrical and electronic engineering show that the students acquire practical skills that allow them to reinforce their knowledge regarding power quality concepts, including harmonics, and power quality events such as voltage sag/swell, flicker, or waveform distortions. Therefore, this methodology can be applied for teaching power quality in undergraduate and graduate electrical engineering courses.

The Earth’s Correlation Wavefield: Proof of Concept, Origin and Applications

<p>We have recently shown that all features in the earthquake-coda correlogram can be explained by the similarity of seismic phases that have a common slowness for the analysed receiver pair. This includes both the features that have their equivalents in the conventional traveltime stacks, but also those that were previously unexplained. Consequently, the information contained in the correlograms – cross-correlated ground-motion time-series in a two-dimensional representation – can be used to constrain Earth’s internal structure, however, that requires a proof of concept and further investigation into the origin of the correlation wavefield. We thus first decompose relevant correlogram features into discrete constituents with respect to their arrival times and we uniquely identify contributing seismic phases to each constituent. This confirms that the correlation wavefield does not arise due to the reconstruction of body waves between the two receivers (a.k.a. Green’s function) – instead, it is dominated by the interaction of various body waves, and its features are characterised by complex sensitivity kernels.</p><p>We demonstrate that the event locations relative to the receivers alter the similarities between the body waves, and may result in significant waveform distortions and inaccuracies in arrival-time predictions. We further show that the nature of source-mechanism and energy-release dynamics are the key influencers responsible for individual correlograms equal in quality to a stack of hundreds of correlograms. In other words, a single seismic event that meets a set of criteria in the presence of multiple receivers can completely `illuminate’ the Earth’s interior. Quantitative kernel-decomposition and identification of body-wave pairs that contribute to a given feature in the correlogram, along with informed choices of seismic events, thus makes the correlation-wavefield tomography and other applications fully feasible. This has the potential to change the course of global seismology in the coming decades.</p>

Adaptive Repetitive Control of A Linear Oscillating Motor under Periodic Hydraulic Step Load

A linear oscillating motor has a direct and efficient linear motion output and is widely used in linear actuation systems. The motor is often applied to compact hybrid electrohydraulic actuators to drive a linear pump. However, the periodic switch of the rectification valve in the pump brings the hydraulic step load to the linear motor, which causes periodic oscillation waveform distortions. The distortion results in the reduction of pumping capacity. The conventional feedback proportional-integral-derivative control is applied to the pump, however, this solution cannot handle the step load as well as resolving nonlinear properties and uncertainties. In this paper, we introduce a nonlinear model to identify periodic hydraulic load. Then, the loads are broken up into a set of simple terms by Fourier series approximation. The uncertain terms and other modeling uncertainties are estimated and compensated by the practical adaptive controller. A robust control term is also developed to handle uncertain nonlinearities. The controller overcame drawbacks of conventional repetitive controllers, such as heavy memory requirements and noise sensitivity. The controller can achieve a prescribed final tracking accuracy under periodic hydraulic load via Lyapunov analysis. Finally, experimental results on the linear oscillating motor-pump are provided for validation of the effectiveness of the scheme.

Способы компенсации высших гармоник напряжения в судовых электроэнергетических системах

В статье выполнен анализ способов компенсации высших гармоник в судовой сети единой электроэнергетической системы (ЕЭЭС), в составе которой, основным потребителей электроэнергии является система электродвижения (СЭД). Рассмотрены три схемы компенсации высших гармоник, создаваемых неуправляемыми выпрямителями, входящими в состав преобразователей частоты (ПЧ). Проведено компьютерное моделирование фрагмента структуры ЕЭЭС, запатентованной фирмой Siemens , схемы 18-пульсного выпрямителя, а также схемы с двумя 12-пульсными выпрямителями. Результаты моделирования показали, что в структуре ЕЭЭС фирмы Siemens , пропульсивный трансформатор обеспечивает компенсацию только части высших гармоник, из-за чего, искажения формы напряжения в судовой сети могут быть значительными. Схема, содержащая два 12-пульсных выпрямителя, а также трехфазный трансформатор с четырьмя трехфазными обмотками, имеющими сдвиг фаз на 15 электрических градусов, показала наилучшие показатели по качеству тока, обеспечивая эффективную компенсацию 5, 7, 11, 13 гармонических составляющих тока. Предложенная схема с двумя 12-пульсными выпрямителями позволяет в составе ПЧ применить трехуровневые автономные инверторы напряжения, характеризующиеся высоким качеством тока в обмотках гребного электродвигателя.The article analyzes the methods for compensating for higher harmonics in the ship network of the unified electric power system (UEPS), in which the main electric power consumers are electric propulsion systems (EPS). Three compensation schemes for higher harmonics created by uncontrolled rectifiers that are part of frequency converters are considered. Computer simulation of a fragment of the UEPS structure patented by Siemens, an 18-pulse rectifier circuit, and also circuits with two 12-pulse rectifiers were carried out. The simulation results showed that in the Siemens UEPS structure, a propulsive transformer provides compensation for only a part of the higher harmonics, due to which, voltage waveform distortions in the ship network can be significant. The circuit, containing two 12-pulse rectifiers, as well as a three-phase transformer with four three-phase windings having a phase shift of 15 electrical degrees, showed the best current quality indicators, providing effective compensation for 5, 7, 11, 13 harmonic components of the current. The proposed circuit with two 12-pulse rectifiers allows the use of three-level autonomous voltage inverters, which are characterized by high quality current in the windings of the propeller motor, as part of the frequency converter.

Current Quality: Assessment and Standardization Aspects

Power quality issues concern absolutely all spheres of human activity, from household to economy and transportation. Standardization, monitoring, management, and coordination to ensure electromagnetic compatibility in the power supply system are the subject of constantly ongoing research in most countries. In order to attract attention to issues of the harmonic current, this study focused on the harmonic current distortions observed on the level of urban electricity users. The paper considers the aspects of consolidating terminology and structure of power quality indicators. We carefully reviewed the current and voltage waveform distortions and related harmonic components. We also summed up the power quality indicators currently used around the world as a flowchart. Based on the results of measurements of quality indicators at the existing urban infrastructure facilities, a comparative analysis with the IEEE 519-2014 standard requirements was performed. As a result of the field measurements analysis, an unsatisfactory situation in terms of harmonic current distortions was revealed; the most probable causes and consequences of poor current quality are described.

Autoencoder for ecg signal outlier processing in system of biometric authentication

A novel method for ECG signal outlier processing based on autoencoder neural networks is presented in the article. Typically, heartbeats with serious waveform distortions are treated as outliers and are skipped from the authentication pipeline. The main idea of the paper is to correct these waveform distortions rather them in order to provide the system with better statistical base. During the experiments, the optimum autoencoder architecture was selected. An open Physionet ECGID database was used to verify the proposed method. The results of the studies were compared with previous studies that considered the correction of anomalies based on a statistical approach. On the one hand, the autoencoder shows slightly lower accuracy than the statistical method, but it greatly simplifies the construction of biometric identification systems, since it does not require precise tuning of hyperparameters.