Fundamental Cycle Research Articles

Eigenbasis of the evolution operator of 2-tessellable quantum walks

Staggered quantum walks on graphs are based on the concept of graph tessellation and generalize some well-known discrete-time quantum walk models. In this work, we address the class of 2-tessellable quantum walks with the goal of obtaining an eigenbasis of the evolution operator. By interpreting the evolution operator as a quantum Markov chain on an underlying multigraph, we define the concept of quantum detailed balance, which helps to obtain the eigenbasis. A subset of the eigenvectors is obtained from the eigenvectors of the double discriminant matrix of the quantum Markov chain. To obtain the remaining eigenvectors, we have to use the quantum detailed balance conditions. If the quantum Markov chain has a quantum detailed balance, there is an eigenvector for each fundamental cycle of the underlying multigraph. If the quantum Markov chain does not have a quantum detailed balance, we have to use two fundamental cycles linked by a path in order to find the remaining eigenvectors. We exemplify the process of obtaining the eigenbasis of the evolution operator using the kagome lattice (the line graph of the hexagonal lattice), which has symmetry properties that help in the calculation process.

Inter-Turn Fault Detection of Dry-Type Transformers Using Core-Leakage Fluxes

In this paper, a new technique for low-severity inter-turn fault detection under online operating conditions of dry-type transformers is proposed. The proposed methodology requires just two inexpensive flux sensors and is based on the fundamental component of the core-leakage fluxes at the transformer's outer limbs. Theoretical analysis using the proposed analytical models and experimental validation on a 10-kVA experimental prototype transformer are carried out to evaluate the performance of the proposed methodology under various fault severities. The real-time fault-detection capability of the proposed technique is also evaluated using a fabricated prototype health monitoring device, which reveals that as low as 2-turns bolted fault out of 150 turns can be detected within 3 fundamental cycles. The methodology is immune to loading and supply voltage unbalance conditions and on par with the classical differential negative sequence current based technique with an additional advantage of 78% reduction in the total number of sensors required for a three-phase three-winding transformer.

Postfault Zero-Sequence Current Injection for Open-Circuit Diode/Switch Failure in Open-End Winding PMSM Machines

This paper proposes and experimentally assesses two zero-sequence current control strategies that allow continuous operation of the three-phase dual-inverter drive using an open-end winding permanent magnet synchronous machine (PMSM) when freewheel diodes (or semiconductor switches) in either inverters fail open circuit. With an identified failure present, the proposed control strategies inject zero-sequence current to bias the phase current(s) of the faulted phase(s) such that the phase current(s) are unipolar, thereby eliminating current flow in the device(s) that have failed. Two possible injection modes are proposed. The first mode injects the minimum required zero-sequence current to bias the current in the phase that has a semiconductor open-circuit failure(s). The injected zero-sequence current varies over a fundamental cycle. This minimizes the increase in total rms currents in the phases yielding higher torque capability in fault conditions. The second mode injects a zero-sequence current that has a constant value over a fundamental cycle to bias all three-phase currents appropriately. This mode is used if more than one phase has suffered a fault. Additional thermal and current stresses resulting from both techniques were assessed and compared. A detailed electromagnetic torque model was also developed to demonstrate that the zero-sequence current does not affect the average torque output. Experimental results verify the theoretical treatment and are used to examine the advantages of techniques and show the improvement in the maximum available torque under fault conditions.

A Submodule-Capacitor Voltage Balancing Strategy for Alternative-Arm Converters in HVDC Systems

The standard alternative-arm converters (AAC) with the sweet spot or short overlap operation have faced a challenge of balancing submodule (SM) capacitor voltages, where this issue has not been paid much attention so far. In this paper, a new control strategy for the SM-capacitor voltage balancing of the AAC applied in high-voltage dc transmission systems is proposed. The suggested control technique is composed of three regulators, where a control for the average voltage of all SM capacitors, the voltage balancing among the converter arms, and the voltage balancing of the individual SM capacitor are performed. Based on the operation principle of the standard AAC, which activates only three of six converter arms simultaneously, the energy balancing of the three activated arms is performed every one sixth of the fundamental cycle by the converter common offset voltage. Band-stop filters with the central frequencies at the fundamental, second-, and third-order components of the line frequency are applied to obtain the average values of the SM capacitor voltages for the feedback controllers. The simple proportional and integral controllers are employed for this scheme and the voltages of SM capacitors are mostly balanced during the steady states and kept closely to the rating with overshoot of less than 7% under the transient conditions. The proposed control method is verified by simulation results for a 33-level AAC under both normal and fault conditions.

Geometry Aware Tori Decomposition

AbstractThis work presents a shape decomposition algorithm to partition a complex high genus surface into simple primitives, each of which is a torus. First, using a novel iterative algorithm, handle and tunnel fundamental cycles on the surface are progressively localized. Then, the problem of computing the splitting cycles that produce such a tori decomposition is posed as a min‐cut problem on the mesh's dual graph with earlier computed tunnels as source and target. The edge weights for the min‐cut problem are designed for the cut to be geometry‐aware. We present an implementation and demonstrate the results of our algorithm on numerous examples.

Contact homology and virtual fundamental cycles

We give a construction of contact homology in the sense of Eliashberg–Givental–Hofer. Specifically, we construct coherent virtual fundamental cycles on the relevant compactified moduli spaces of pseudo-holomorphic curves.

Time series analysis of mantle cycles Part I: Periodicities and correlations among seven global isotopic databases

In this study, seven isotopic databases are presented and analyzed to identify mantle and crustal episodes on a global scale by focusing on periodicity ranging from 70 to 200 million years (Myr). The databases are the largest, or among the largest, compiled for each type of data – with an objective of finding some samples from every region of every continent, to make each database as global as conceivably possible. The databases contain zircon Lu/Hf isotopic data, whole-rock Sm/Nd isotopic data, U/Pb detrital zircon ages, U/Pb igneous zircon ages, U/Pb non-zircon ages, whole-rock Re/Os isotopic data, and large igneous province ages. Part I of this study focuses on the periodicities of age histograms and geochemical averages developed from the seven databases, via spectral and cross-correlation analyses. Natural physical cycles often propagate in exact integer multiples of a fundamental cycle, referred to as harmonics. The tests show that harmonic geological cycles of ∼93.5 and ∼187 Myr have persisted throughout terrestrial history, and the cyclicities are statistically significant for U/Pb igneous zircon ages, U/Pb detrital zircon ages, U/Pb zircon-rim ages, large igneous province ages, mean εHf(t) for all samples, mean εHf(t) values for igneous-only samples, and relative abundance of mafic rocks. Equally important, cross-correlation analyses show these seven time-series are nearly synchronous (±7 Myr) with a model consisting of periodicities of 93.5 and 187 Myr. Additionally, the similarities between peaks in the 93.5 and 187 Myr mantle cycles and terminal ages of established and suspected superchrons provide a framework for predicting and testing superchron periodicity.

Minimum fundamental cycle basis of some bipartite graphs

We determine the number of cycles of different lengths in the minimum fundamental cycle basis of some bipartite graphs with centralized spanning trees. As applications, we characterize the minimum fundamental cycle basis of some (n−k)-regular balanced graphs with order 2n.

Investigation on Extending the DC Bus Utilization of a Single-Source Five-Level Inverter With Single Capacitor-Fed H-Bridge Per Phase

Enhancement of dc bus voltage utilization for a five-level inverter with single dc source and capacitor-fed H-bridge (CHB) units is investigated in this paper. A carrier-based modulation technique is used for boosting the dc bus utilization, which is established by providing detailed mathematical analysis. The five-level inverter used here is realized by cascading a CHB unit to each phase of a three-level neutral point clamped inverter. The increase in dc bus voltage utilization owes to the pole voltage redundancies offered by CHB units. The floating capacitors of H-bridge units are balanced within a quarter fundamental cycle using the switching state redundancies of pole voltage levels. The aforementioned modulation technique allows the inverter to enhance the dc bus utilization from 0.577 $\text{V}_{\text{dc}}$ to 0.63 $\text{V}_{\text{dc}}$ under unity power factor. This enhancement is obtained in the linear modulation range without increasing the dc bus voltage, and thus, the inverter can operate without the presence of low-order harmonics in its phase voltages. The strength of this paper lies in its detailed mathematical analysis for finding out the limiting modulation index and power factor condition in the light of floating capacitor voltage balancing issue. Simulation as well as experimental verification of the modulation scheme is carried out on an induction motor drive under various operating conditions. It is shown that this carrier-based modulation technique is suitable for any single source inverter topology with one CHB unit per phase.

Analysis of generalized continual-clamp and split-clamp PWM schemes for induction motor drive

Continual-clamp pulse width modulation (CCPWM) clamps each phase of a three-phase inverter to one of the two dc buses continually for \(60^{\circ }\) duration in each half of the fundamental cycle. Split-clamp pulse width modulation (SCPWM) divides the \(60^{\circ }\) clamping interval into two sub-intervals, which are not necessarily equal, and falling in two different quarter cycles. Whether continual clamp or split clamp, the positioning of the clamping interval in case of CCPWM, and the ratio of splitting the clamping interval in SCPWM – all influence the waveform quality of the inverter output. This paper derives analytically closed-form expressions for the total RMS harmonic distortion factor and torque ripple factor pertaining to CCPWM with any arbitrary position of the clamping interval (i.e., generalized CCPWM) and also corresponding to SCPWM with any arbitrary ratio of splitting of the clamping interval (i.e., generalized SCPWM). The analytical results are well supported by experimental results on 3-hp and 5-hp induction motor drives.

Efficiency of Multiple Cycles: Theoretical Study of Efficiency of Cycles

This is an eye-opening study on the overall efficiency of a jet generating motors on the basics of ambient conditions of compressor which produces high environmental condition for effective combusting. In general the efficiency of a gas turbine version of jet production is taken for studying and finding the changes of efficiency that happens on the basics of changing ambient condition on compressor. Let taking the primary and secondary compressor of modern version of gas turbine engine, for studying the variation of overall efficiency on the basics of ambient and providing physical conditions and establishing a general picture of combinations of compressor and its effects on the overall efficiency. Over here, we have two set of compressors were available for producing compression, such as low pressure and high pressure (this is based on the pressure has been used as the initial and provided by compressor, to the air molecule which present on the compressor). This can be defining the nature of the compressor. That is, if the compressor work with low pressure air as inlet and provide comparatively lower compression to the molecule, we can be defining it as the low pressure compressor. Similarly, if the compressor works comparatively high environment, it can be calling as high pressure compressor. In this study, Brayton cycle is used as the fundamental cycle for jet production.

Voltage Balancing Control of Hybrid Stacked Multicell Converters Based on Modified Phase-Shifted PWM

The hybrid stacked multicell converter (HSMC) is a competitive converter in the low-voltage high-efficiency applications. Proper modulation and voltage balancing control are important for the operation of the HSMC, which may ensure the HSMC to obtain high-quality output and low power losses. A hybrid phase-shifted PWM (PS-PWM) with the modified reference signal is developed for nine-level HSMC (9L-HSMC), and the neutral point voltage can be naturally balanced in a fundamental cycle. Based on the hybrid PS-PWM, an active voltage balancing control is put forward for the flying capacitor (FC). The voltage balancing of FC is implemented by slightly modifying the reference signals to adjust the duty cycles of the high-frequency switches symmetrically. This method does not need complex calculations, and it can be easily extended to higher level HSMC and other FC-based configurations. The simulations are carried out to validate the merits of low power losses and superior power quality. A downscale experimental platform of a 9L-HSMC is a setup to verify the effectiveness of the proposed control strategy under both the steady state and the transient states.

Total Harmonic Distortion Oriented Finite Control Set Model Predictive Control for Single-Phase Inverters

Inverters are commonly controlled to generate AC current and Total Harmonic Distortion (THD) is the core index in judging the control effect. In this paper, a THD oriented Finite Control Set Model Predictive Control (FCS MPC) scheme is proposed for the single-phase inverter, where a optimization problem is solved to obtain the switching law for realization. Different from the traditional cost function, which focuses on the instantaneous deviation of amplitude between predictive current and its reference, we redesign a cost function that is the linear combination of the current fundamental tracking error, instantaneous THD value and DC component in one fundamental cycle (for 50 Hz, it is 0.02 s). Iterative method is developed for rapid calculation of this cost function. By choosing a switching state from a FCS to minimize the cost function, a FCS MPC is finally constructed. Simulation results in Matlab/Simulink and experimental results on rapid control prototype platform show the effect of this method. Analyses illustrate that, by choosing suitable weight of the cost function, the performance of this THD oriented FCS MPC method is better than the traditional one.

Localization and classification of heartbeats using robust adaptive algorithm

Abstract Automated analysis of heart sound recordings (phonocardiograms or PCG) for classification of heart beats in noisy environments is a challenging problem. The major challenges are introduced due to inter- and intra-beat variation, spectral overlap of heart and lung sounds and noise picked from environment. This paper presents a robust algorithm for heart beat localization and classification using variable length window and peak amplitude threshold variation. The technique presented in this paper first attempts to find peaks which correspond to the fundamental heart sound cycle (FHSC) i.e. S1, S2, S1, … or fundamental heart sound period (FHSP) i.e. S1, S1, …. If FHSC/FHSP is found, an attempt is made to extend it to the whole signal. Once extended, the signal is directly labeled using systole and diastole durations. During classification, history of labels is used to counter the heart rate variations. The proposed technique is evaluated on publicly available Pascal Heart Sound Challenge dataset and reports smaller average error for localization and has high sensitivity and accuracy for heart beat classification.

The effectiveness of auditory forward collision warning alerts

The objective of this study is to evaluate the effects of auditory warning characteristics from a forward collision alert system on drivers’ avoidance behavior. A driving simulator study was designed and conducted with a pre-collision scenario that included a lead vehicle decelerating. This scenario is used to examine whether any casual relationship exists between the auditory alert characteristics and collision avoidance. The study included 192 participants across the U.S. The auditory characteristics, including fundamental frequency and duty cycle, were examined at three urgency levels. The data from the study was analyzed using Partial Least Squares (PLS) path modeling. The collision avoidance behavior was measured using two reaction times (throttle release, brake) and three response intensities (maximum brake pedal force, maximum lane deviation and response type). All tested warning alerts resulted in reduced collision rates, shorter reaction times, larger maximum brake pedal force, and larger maximum lane deviation when compared to the baseline condition without a warning. Participants were also more likely to simultaneously brake and steer when given an alert. The models illustrate that the auditory warning information has both a direct and indirect effect on occurrence of collisions, with the indirect effect playing a more important role on collision avoidance than the direct effect. The findings also showed that the low urgency level of duty cycle and high urgency level of fundamental frequency are not recommended for collision warning alerts.

The Pseudo-McMillan Degree of Implicit Transfer Functions of RLC Networks

We study the structure of a given RLC network without sources. Since the McMillan degree of the implicit network transfer function is not a suitable measure for the complexity of the network, we introduce the pseudo-McMillan degree to overcome these shortcomings. Using modified nodal analysis models, which are linked directly to the natural network topology, we show that the pseudo-McMillan degree equals the sum of the number of capacitors and inductors minus the number of fundamental loops of capacitors and fundamental cutsets of inductors; this is the number of independent dynamic elements in the network. Exploiting this representation, we derive a minimal realization of the given RLC network, that is one where the number of involved (independent) differential equations equals the pseudo-McMillan degree.

Pure sheaves and Kleinian singularities

Grothendieck proved that any locally free sheaf on a projective line over a field (uniquely) decomposes into a direct sum of line bundles. Ishii and Uehara construct an analogue of Grothendieck’s theorem for pure sheaves on the fundamental cycle of the Kleinian singularity $$A_n$$ . We first study the analogue for the other Kleinian singularities. We also study the classification of rigid pure sheaves on the reduced scheme of the fundamental cycles. The classification is related to the classification of spherical objects in a certain Calabi–Yau 2-dimensional category.

A Fast Identification Method for Rotor Flux Density Harmonics and Resulting Rotor Iron Losses of Inverter-Fed Induction Motors

Inverter-fed induction machines’ iron loss characteristics become more complicated because of the harmonics brought by pulse width modulated (PWM) voltage-source power supplies. There are two main difficulties associated with analyzing the iron loss of induction motors, i.e., the identification of rotor flux density harmonics and the accurate prediction of iron loss. In order to reveal the iron loss characteristics of the inverter-fed induction motors, especially on the rotor side, a computationally efficient rotor flux density harmonics identification method using data from a single power supply fundamental frequency cycle (supply cycle) is proposed. With the proposed identification method, the rotor iron loss characteristics of a 5.5- and a 30-kW inverter-fed induction motors are investigated. By comparing the predicted and measured iron losses of those induction motors under both sinusoidal and PWM inverter voltage supplies, the effectiveness of the proposed method is validated. Furthermore, the detailed iron loss characteristics of the two induction machines under both sinusoidal and PWM inverter voltage supplies are studied.

The MegaM@Rt2 ECSEL project: MegaModelling at Runtime – Scalable model-based framework for continuous development and runtime validation of complex systems

A major challenge for the European electronic industry is to enhance productivity by ensuring quality of development, integration and maintenance while reducing the associated costs. Model-Driven Engineering (MDE) principles and techniques have already shown promising capabilities, but they still need to scale up to support real-world scenarios implied by the full deployment and use of complex electronic components and systems. Moreover, maintaining efficient traceability, integration, and communication between two fundamental system life cycle phases (design time and runtime) is another challenge requiring the scalability of MDE. This paper presents an overview of the ECSEL 11http://www.ecsel-ju.eu/web/index.php. project entitled “MegaModelling at runtime – Scalable model-based framework for continuous development and runtime validation of complex systems” (MegaM@Rt2), whose aim is to address the above mentioned challenges facing MDE. Driven by both large and small industrial enterprises, with the support of research partners and technology providers, MegaM@Rt2 aims to deliver a framework of tools and methods for: 1) system engineering/design and continuous development, 2) related runtime analysis and 3) global models and traceability management. Diverse industrial use cases (covering strategic domains such as aeronautics, railway, construction and telecommunications) will integrate and demonstrate the validity of the MegaM@Rt2 solution. This paper provides an overview of the MegaM@Rt2 project with respect to its approach, mission, objectives as well as to its implementation details. It further introduces the consortium as well as describes the work packages and few already produced deliverables.

Switching Loss Reduction in the Three-Phase Quasi-Z-Source Inverters Utilizing Modified Space Vector Modulation Strategies

Several single-stage topologies have been introduced since kicking off the three-phase Z-source inverter (ZSI), and among these topologies, the quasi-ZSI (qZSI) is the most common one due to its simple structure and continuous input current. Furthermore, different modulation strategies, utilizing multiple reference signals, have been developed as well. However, prior art modulation methods have some demerits, such as the complexity of generating the gate signals, the increased number of switch commutations with continuous commutation at high current level during the entire fundamental cycle, and the multiple commutations at a time. Hence, this paper proposes two modified space vector modulation strategies, aimed at the reduction of the qZSI number of switch commutations at high current level for shorter periods during the fundamental cycle, i.e., reducing the switching loss, simplifying the generation of the gate signals by utilizing only three reference signals, and achieving a single-switch commutation at a time. These modulation strategies are analyzed and compared to the conventional ones, where a reduced-scale 1-kVA three-phase qZSI is designed and simulated using these different modulation strategies. Finally, the 1-kVA three-phase qZSI is implemented experimentally to validate the performance of the proposed modulation strategies and verify the reported analysis.