Inertia emulation control strategy for VSC-HVDC transmission systems

There is concern that the levels of inertia in power systems may decrease in the future, due to increased levels of energy being provided from renewable sources, which typically have little or no inertia. Voltage source converters (VSC) used in high voltage direct current (HVDC) transmission applications are often deliberately controlled in order to de-couple transients to prevent propagation of instability between interconnected systems. However, this can deny much needed support during transients that would otherwise be available from system inertia provided by rotating plant

Dynamics of quantum entanglement in the reservoir with memory effects

The non-Markovian dynamics of quantum entanglement is studied by the Shabani-Lidar master equation when one of entangled quantum systems is coupled to a local reservoir with memory effects. The completely positive reduced dynamical map can be constructed in the Kraus representation. Quantum entanglement decays more slowly in the non-Markovian environment. The decoherence time for quantum entanglement can be markedly increased by the change of the memory kernel. It is found out that the entanglement sudden death between quantum systems and entanglement sudden birth between the system and reservoir occur at different instants.Comment: 14 pages, 3 figure

A detailed study of giant pulses from PSR B1937-1-21 using the Large European Array for Pulsars

Contains fulltext : 202558.pdf (Publisher’s version ) (Open Access

Comparing temporal patterns in body condition of ringed seals living within their core geographic range with those living at the edge

Ecological theory suggests that demographic responses by populations to environmental change vary depending on whether individuals inhabit central or peripheral regions within the species’ geographic range. Here, we tested this prediction by comparing a population of ringed seals Pusa hispida located at high latitudes as part of their core range (core) with a population located at the southern extremity of their range (peripheral). First, we compared the two regions’ environmental trends in timing of sea-ice breakup and freeze-up, open-water duration and the North Atlantic Oscillation (NAO). We found that the core region shifted to progressively warmer conditions in the early 1990s; whereas, in the peripheral region, the warming trend shifted in 1999 to one with no warming trend but high inter-annual variability. Next, we examined how body condition, inferred from blubber depth, responded to temporal changes in sea-ice and climatic variables – variables that have been shown to influence ringed seal demography. Core seals displayed minimal seasonal changes in body condition; whereas peripheral seals displayed a 20–60% amplitude seasonal change in body condition with a phase shift to earlier initiation of fat accumulation and loss. Finally, we tested for interannual differences and found that both core and peripheral seals responded similarly with decreased body condition following more positive NAO. Environmental variables influenced body condition in opposite directions between the two regions with core seals declining in body condition with later spring breakup and shorter open-water duration, whereas peripheral seals showed opposite relationships. Seals living at the core likely benefit from an evolved match between adaptation and environmental variation resulting in dampened seasonal and interannual fluctuations in body condition. Knowledge of how different populations respond to environmental change depending on geographic location within a species range can assist in anticipating population specific responses to climate warming

Unified Solutions on Plastic Limit Internal Pressure for Metallic Elbows

With consideration of the intermediate principal stress and different strength values in tension and compression, the plastic analysis of metallic elbows under internal pressure is conducted based on the unified strength theory. The unified solutions for elbows with constant and variable wall thickness values, and those with a local thinning are derived. Parametric studies are carried out to investigate the dependence between the unified strength theory parameter, tension-compression ratio, bending coefficient, and wall thickness. Comparing the theoretical results and the experimental data, a good agreement was observed. The results obtained show that the unified solutions are versatile in the theoretical analysis of metallic elbows and can be reduced to many existing results. The latent potentialities of metallic elbows are fully achieved due to considering the intermediate principal stress. The unified solutions have an important practical value for the optimum design and engineering application of metallic elbows.На базе комплексной теории прочности проанализирована пластичность металлического колена при внутреннем давлении с учетом промежуточного главного напряжения и различной прочности при растяжении и сжатии. Получены комплексные решения для колен с одинаковой и разной толщиной стенок и локальным утонением. С целью изучения влияния параметра комплексной теории прочности, степени растяжения–сжатия, коэффициента изгиба и толщины стенок проведено параметрическое исследование. Сравнительный анализ расчетных и экспериментальных данных показал хорошее их соответствие. Установлено, что при расчете металлических колен комплексные решения многофункциональны, о чем свидетельствуют полученные результаты. Учет промежуточного главного напряжения позволил выявить скрытые потенциальные возможности металлических колен. Комплексные решения имеют важное практическое значение для оптимального проектирования и технического применения металлических колен.На базі комплексної теорії міцності проаналізовано пластичність металічного коліна при внутрішньому тиску з урахуванням проміжного головного напруження і різної міцності при розтязі і стиску. Отримано комплексні розв’язки для колін, що мають одинакову і різну товщину стінок і локальне стоншення. Із метою вивчення впливу параметра комплексної теорії міцності, ступеня розтягу–стиску, коефіцієнта згину і товщини стінок проведено параметричне дослідження. Порівняльний аналіз розрахункових і експериментальних даних показав хорошу їх відповідність. Установлено, що при розрахунку металічних колін комплексні розв’язки є багатофункціональними, про що свідчать отримані дані. Урахування проміжного головного напруження сприяло вивченню прихованих потенційних можливостей металічних колін. Комплексні розв’язки мають важливе практичне значення для оптимального проектування і технічного використання металічних колін

Azimuthal asymmetries in lepton-pair production at a fixed-target experiment using the LHC beams (AFTER)

A multi-purpose fixed-target experiment using the proton and lead-ion beams of the LHC was recently proposed by Brodsky, Fleuret, Hadjidakis and Lansberg, and here we concentrate our study on some issues related to the spin physics part of this project (referred to as AFTER). We study the nucleon spin structure through $pp$ and $pd$ processes with a fixed-target experiment using the LHC proton beams, for the kinematical region with 7 TeV proton beams at the energy in center-of-mass frame of two nucleons $\sqrt{s}=115$ GeV. We calculate and estimate the $\cos2\phi$ azimuthal asymmetries of unpolarized $pp$ and $pd$ dilepton production processes in the Drell--Yan continuum region and at the $Z$-pole. We also calculate the $\sin(2\phi-\phi_S)$, $\sin(2\phi+\phi_S)$ and $\sin2\phi$ azimuthal asymmetries of $pp$ and $pd$ dilepton production processes with the target proton and deuteron longitudinally or transversally polarized in the Drell--Yan continuum region and around $Z$ resonances region. We conclude that it is feasible to measure these azimuthal asymmetries, consequently the three-dimensional or transverse momentum dependent parton distribution functions (3dPDFs or TMDs), at this new AFTER facility.Comment: 15 pages, 40 figures. Version accepted for publication in EPJ

Gaussian Tunneling Model of c-Axis Twist Josephson Junctions

We calculate the critical current density $J^J_c$ for c-axis Josephson tunneling between identical high temperature superconductors twisted an angle $\phi_0$ about the c-axis. We model the tunneling matrix element squared as a Gaussian in the change of wavevector q parallel to the junction, $<|t({\bf q})|^2>\propto\exp(-{\bf q}^2a^2/2\pi^2\sigma^2)$. The $J^J_c(\phi_0)/J^J_c(0)$ obtained for the s- and extended-s-wave order parameters (OP's) are consistent with the Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ data of Li {\it et al.}, but only for strongly incoherent tunneling, $\sigma^2\ge0.25$. A $d_{x^2-y^2}$-wave OP is always inconsistent with the data. In addition, we show that the apparent conventional sum rule violation observed by Basov et al. might be understandable in terms of incoherent c-axis tunneling, provided that the OP is not $d_{x^2-y^2}$-wave.Comment: 6 pages, 6 figure

Anomaly analysis of Hawking radiation from Kaluza-Klein black hole with squashed horizon

Considering gravitational and gauge anomalies at the horizon, a new method that to derive Hawking radiations from black holes has been developed by Wilczek et al. In this paper, we apply this method to non-rotating and rotating Kaluza-Klein black holes with squashed horizon, respectively. For the rotating case, we found that, after the dimensional reduction, an effective U(1) gauge field is generated by an angular isometry. The results show that the gauge current and energy-momentum tensor fluxes are exactly equivalent to Hawking radiation from the event horizon.Comment: 15 pages, no figures, the improved version, accepted by Eur. Phys. J.