Minimum energy states of the plasma pinch in standard and Hall magnetohydrodynamics

Axisymmetric relaxed states of a cylindrical plasma column are found analytically in both standard and Hall magnetohydrodynamics (MHD) by complete minimization of energy with constraints imposed by invariants inherent in corresponding models. It is shown that the relaxed state in Hall MHD is the force-free magnetic field with uniform axial flow and/or rigid azimuthal rotation. The relaxed states in standard MHD are more complex due to the coupling between velocity and magnetic field. Application of these states for reversed-field pinches (RFP) is discussed

Wild horse optimization algorithm implementation in 7-level packed U-cell multilevel inverter to mitigate total harmonic distortion

Introduction. Multilevel inverters (MLIs) are a popular industrial and, more especially, renewable energy application solution. This is because of its appetite for filters, low distortion class, and capacity to provide a multilayer output voltage that resembles a pure sine waveform. The novelty is in applying the wild horse optimization algorithm (WHOA) to adjust the sinusoidal pulse width modulation (SPWM) technique by producing the optimal reference signal parameters in a new multilevel inverter architecture known as the packed U-cell multilevel inverter (PUC-MLI). Purpose. This study helps with the idea of new inverter architecture and a modified pulse width modulation (MPWM) method to make the multilevel inverter smaller, cheaper, and with less total harmonic distortion (THD). Methods. We use the proposed approach to control a 7-level, single-phase PUC-MLI. The WHOA is used to discover the optimal parameters of the additional reference sine signal after being compared with SPWM to evaluate its performance in harmonic reduction. The simulation’s outcome was validated by building a PUC-MLI prototype. Results. Experimental results and simulations validate the effectiveness of the suggested approach. The WHOA-improved MPWM approach achieves a significant reduction in THD on the PUC-MLI output voltage, as indicated by the results. Practical value. THD in MLI output voltage will be reduced without spending any cost. The suggested solution works with many MLI topologies with varying output voltage levels. References 20, tables 6, figures 12.Вступ. Багаторівневі інвертори (MLIs) є популярним рішенням для застосування у промисловості та, особливо, у відновлюваних джерелах енергії. Це пов’язано з його потребою у фільтрах, низьким класом спотворень та здатністю забезпечувати багатошарову вихідну напругу, що нагадує чистий синусоїдальний сигнал. Новизна полягає у застосуванні алгоритму оптимізації «дикого коня» (WHOA) для налаштування методу синусоїдальної широтно-імпульсної модуляції (SPWM) шляхом створення оптимальних параметрів опорного сигналу в новій архітектурі, відомої як упакований багаторівневий інвертор U-подібного типу (PUC-MLI). Мета. Це дослідження допомагає реалізувати ідею нової архітектури інвертора та модифікованого методу широтно-імпульсної модуляції (MPWM), що дозволяє зробити багаторівневий інвертор меншим, дешевшим і з меншим загальним гармонічним спотворенням (THD). Методи. Ми використовуємо запропонований підхід для керування 7-рівневим однофазним PUC-MLI. WHOA використовується для визначення оптимальних параметрів додаткового еталонного синусоїдального сигналу після порівняння зі SPWM для оцінки його ефективності зниження гармонік. Результати моделювання були підтверджені створенням прототипу PUC-MLI. Результати. Експериментальні результати та моделювання підтверджують ефективність запропонованого підходу. Удосконалений WHOA підхід MPWM дозволяє досягти значного зниження THD вихідної напруги PUC-MLI, про що свідчать результати. Практична цінність. THD вихідної напруги MLI буде знижено без будь-яких витрат. Пропоноване рішення працює з багатьма топологіями MLI з різними рівнями вихідної напруги. Бібл. 20, табл. 6, рис. 12

Exponential Renormalization II: Bogoliubov's R-operation and momentum subtraction schemes

This article aims at advancing the recently introduced exponential method for renormalisation in perturbative quantum field theory. It is shown that this new procedure provides a meaningful recursive scheme in the context of the algebraic and group theoretical approach to renormalisation. In particular, we describe in detail a Hopf algebraic formulation of Bogoliubov's classical R-operation and counterterm recursion in the context of momentum subtraction schemes. This approach allows us to propose an algebraic classification of different subtraction schemes. Our results shed light on the peculiar algebraic role played by the degrees of Taylor jet expansions, especially the notion of minimal subtraction and oversubtractions.Comment: revised versio

Composition-Diamond lemma for λ\lambda-differential associative algebras with multiple operators

In this paper, we establish the Composition-Diamond lemma for $\lambda$-differential associative algebras over a field $K$ with multiple operators. As applications, we obtain Gr\"{o}bner-Shirshov bases of free $\lambda$-differential Rota-Baxter algebras. In particular, linear bases of free $\lambda$-differential Rota-Baxter algebras are obtained and consequently, the free $\lambda$-differential Rota-Baxter algebras are constructed by words

On CSP and the Algebraic Theory of Effects

We consider CSP from the point of view of the algebraic theory of effects, which classifies operations as effect constructors or effect deconstructors; it also provides a link with functional programming, being a refinement of Moggi's seminal monadic point of view. There is a natural algebraic theory of the constructors whose free algebra functor is Moggi's monad; we illustrate this by characterising free and initial algebras in terms of two versions of the stable failures model of CSP, one more general than the other. Deconstructors are dealt with as homomorphisms to (possibly non-free) algebras. One can view CSP's action and choice operators as constructors and the rest, such as concealment and concurrency, as deconstructors. Carrying this programme out results in taking deterministic external choice as constructor rather than general external choice. However, binary deconstructors, such as the CSP concurrency operator, provide unresolved difficulties. We conclude by presenting a combination of CSP with Moggi's computational {\lambda}-calculus, in which the operators, including concurrency, are polymorphic. While the paper mainly concerns CSP, it ought to be possible to carry over similar ideas to other process calculi

Optimal discrete stopping times for reliability growth tests

Often, the duration of a reliability growth development test is specified in advance and the decision to terminate or continue testing is conducted at discrete time intervals. These features are normally not captured by reliability growth models. This paper adapts a standard reliability growth model to determine the optimal time for which to plan to terminate testing. The underlying stochastic process is developed from an Order Statistic argument with Bayesian inference used to estimate the number of faults within the design and classical inference procedures used to assess the rate of fault detection. Inference procedures within this framework are explored where it is shown the Maximum Likelihood Estimators possess a small bias and converges to the Minimum Variance Unbiased Estimator after few tests for designs with moderate number of faults. It is shown that the Likelihood function can be bimodal when there is conflict between the observed rate of fault detection and the prior distribution describing the number of faults in the design. An illustrative example is provided

The effects of arm movement on reaction time in patients with latent and active upper trapezius myofascial trigger point

Background: Myofascial pain syndrome is a significant source of mechanical pain. The aim of this study was to investigate the effects of arm movement on reaction time in females with latent and active upper trapezius myofascial trigger point. Methods: In this interventional study, a convenience sample of fifteen women with one active MTP, fifteen women with one latent MTP in the upper trapezius, and fifteen normal healthy women were participated. Participants were asked to stand for 10 seconds in an erect standing position. Muscle reaction times were recorded including anterior deltoid (AD), cervical paraspinal (CP) lumbar paraspinal (LP), both of upper trapezius (UT), sternocleidomastoid (SCM) and medial head of gastrocnemius (GcM). Participants were asked to flex their arms in response to a sound stimulus preceded by a warning sound stimulus. Data were analyzed using one-way ANOVA Test. Results: There was significant differences in motor time and reaction time between active and control groups (p<0.05) except for GcM. There was no significant difference in motor time between active and passive groups except for UT without MTP and SCM (p<0.05). Also, there were no significant differences in motor times between latent MTP and control groups. Furthermore, there was no significant difference in premotor times between the three groups. Conclusion: The present study shows that patients with active MTP need more time to react to stimulus, but patients with latent MTP are similar to healthy subjects in the reaction time. Patients with active MTP had less compatibility with environmental stimulations, and they responded to a specific stimulation with variability in Surface Electromyography (SEMG)