Influence of hydrodynamics on many-particle diffusion in 2D colloidal suspensions

We study many-particle diffusion in 2D colloidal suspensions with full hydrodynamic interactions through a novel mesoscopic simulation technique. We focus on the behaviour of the effective scaled tracer and collective diffusion coefficients $D_T(\rho) / D_0$ and $D_C(\rho) / D_0$, where $D_0$ is the single-particle diffusion coefficient, as a function of the density of the colloids $\rho$. At low Schmidt numbers $Sc={\cal O}(1)$, we find that hydrodynamics has essentially no effect on the behaviour of $D_T(\rho)/D_0$. At larger $Sc$, $D_T(\rho)/D_0$ is enhanced at all densities, although the differences compared to the case without hydrodynamics are minor. The collective diffusion coefficient, on the other hand, is much more strongly coupled to hydrodynamical conservation laws and is distinctly different from the purely dissipative case

Exact Chiral Spin Liquids and Mean-Field Perturbations of Gamma Matrix Models on the Ruby Lattice

We theoretically study an exactly solvable Gamma matrix generalization of the Kitaev spin model on the ruby lattice, which is a honeycomb lattice with "expanded" vertices and links. We find this model displays an exceptionally rich phase diagram that includes: (i) gapless phases with stable spin fermi surfaces, (ii) gapless phases with low-energy Dirac cones and quadratic band touching points, and (iii) gapped phases with finite Chern numbers possessing the values {\pm}4,{\pm}3,{\pm}2 and {\pm}1. The model is then generalized to include Ising-like interactions that break the exact solvability of the model in a controlled manner. When these terms are dominant, they lead to a trivial Ising ordered phase which is shown to be adiabatically connected to a large coupling limit of the exactly solvable phase. In the limit when these interactions are weak, we treat them within mean-field theory and present the resulting phase diagrams. We discuss the nature of the transitions between various phases. Our results highlight the richness of possible ground states in closely related magnetic systems.Comment: 9 pages, 9 figure

Core Polarization Effect in the Polarization Cross Section of Atomic Lithium

Purpose. The paper continues the authors’ studies devoted to transients in three-phase five-limb transformers. The main purpose of the work is to propose a method of evaluating model parameters, which cover transformer operations in saturation. This purpose is achieved by using the concept of the model reversibility.Methodology. The method of obtaining model parameters employs magnetic transformer model and is based on the idea of the model reversibility. The solution is found by equating input reluctances seen from the terminals of the innermost and outermost windings to the reluctances of the corresponding windings on air.Findings. The modeling of GIC events represented in the paper is the most accurate ever obtained for three-phase, five-leg transformers. The model is validated by close agreement of the predicted values and waveforms of the phase currents and reactive power with those measured in tests performed on two 400 MVA transformers connected back-to-back and to a 400 kV power network. The validity of the model was verified at 75 and 200 A dc currents in the transformer neutral. It is shown that the model is a reliable tool in evaluating inrush currents.Originality. The originality and advantage of the method proposed is its ability to determine the model parameters without fitting to experimental data obtained in regimes with highly saturated core. The method ensures the reversibility of the three-winding transformer model that is its correct behavior regardless of which winding is energized.Practical value. The practical value and significance of the paper is caused by the fact that the model proposed is a simple and reliable tool for power system studies. As a practically important example, time domain response of transformer subjected to geomagnetically induced currents (GIC) is analyzed and compared with results of a comprehensive field experiment.Цель работы. Статья продолжает исследования авторов, посвященные переходным процессам в трехфазных пятистержневых трансформаторах. Главная цель работы − предложить методику расчета параметров модели, охватывающих работу трансформатора с насыщенным сердечником. Эта цель достигается использованием концепции обратимости модели.Методы исследования. Расчет параметров модели выполняется с использованием магнитной схемы замещения трансформатора и основан на идее ее обратимости. Решение находится путем приравнивания входных магнитных сопротивлений, определяемых со стороны внутренней и внешней обмоток, и магнитных сопротивлений этих обмоток на воздухе.Полученные результаты. Точность моделирования процессов при наличии ГИТ превышает точность известных моделей трехфазных пятистержневых трансформаторов. Адекватность модели подтверждается близостью предсказанных фазных токов и потребляемой реактивной мощности, к соответствующим величинам, измененным в эксперименте на двух 400 MBA трансформаторах, подключенных к энергосистеме с напряжением 410 кВ. Обоснованность модели проверена при постоянных токах в нейтрали силой 75 и 200 А. Показана применимость модели для оценки бросков тока включения.Научная новизна. Оригинальность и новизна предложенного метода состоит в возможности определять параметры модели без использования экспериментальных данных, полученных при насыщенном сердечнике. Метод обеспечивает обратимость модели трехобмоточного трансформатора, то есть ее правильное поведение при возбуждении любой обмотки устройства.Практическая ценность. Практическая ценность и значение статьи обусловлено тем, что предложенная модель трансформатора является простым и надежным инструментом для исследования электрических сетей. В качестве практически важного результата, показано правильное предсказание моделью временного отклика трансформатора, наблюдаемого в эксперименте.Мета роботи. Стаття продовжує дослідження авторів, присвячені перехідним процесам в трифазних п’ятистрижневих трансформаторах. Головна мета роботи − запропонувати методику розрахунку параметрів моделі, що охоплюють роботу трансформатора з насиченим осердям. Ця мета досягається шляхом використанням концепції оберненості моделі.Методи дослідження. Розрахунок параметрів моделі виконується з використанням магнітної схеми заміщення трансформатора і побудований на юдеї її оберненості. Рішення знаходиться шляхом прирівнювання вхідних магнітних опорів, розрахованих з боку внутрішньої і зовнішньої обмоток, і магнітних опорів цих обмоток у повітрі.Отримані результати. Точність моделювання процесів в присутності ГІТ перевищує точність відомих моделей трифазних п’ятистрижневих трансформаторів. Адекватність моделі підтверджується близькістю прогнозованих фазних струмів і споживаної реактивної потужності, до відповідних величин, виміряним в експерименті на двох 400 МВА трансформаторах, які були під’єднані до енергосистеми напругою 410 кВ. Обґрунтованість моделі перевірена при постійних струмах в нейтралі силою 75 і 200 А. Показано застосовність моделі для оцінки кидків струму включення.Наукова новизна. Оригінальність і новизна методу полягає в можливості визначати параметри моделі без використання експериментальних даних, що отримані при насиченому осерді. Метод забезпечує оберненість моделі триобмоточного трансформатора, тобто її коректну поведінку при збудженні будь якої з обмоток.Практична цінність. Практична цінність і значимість статті обумовлені тим, що запропонована модель трансформатора являє собою простий і надійний інструмент для дослідження електричних систем. В якості практично важливого результату, показано правильне прогнозування моделлю часового відгуку трансформатора, що спостерігався в експерименті

Detailed plan for the COMET WP3 initial research activity - list of research projects and goals, participants and timing

Detailed plan for the COMET Work Package (WP) 3

Beryllium melting and erosion on the upper dump plates in JET during three ITER-like wall campaigns

Data on erosion and melting of beryllium upper limiter tiles, so-called dump plates (DP), are presented for all three campaigns in the JET tokamak with the ITER-like wall. High-resolution images of the upper wall of JET show clear signs of flash melting on the ridge of the roofshaped tiles. The melt layers move in the poloidal direction from the inboard to the outboard tile, ending on the last DP tile with an upward going waterfall-like melt structure. Melting was caused mainly by unmitigated plasma disruptions. During three ILW campaigns, around 15% of all 12376 plasma pulses were catalogued as disruptions. Thermocouple data from the upper dump plates tiles showed a reduction in energy delivered by disruptions with fewer extreme events in the third campaign, ILW-3, in comparison to ILW-1 and ILW-2. The total Be erosion assessed via precision weighing of tiles retrieved from JET during shutdowns indicated the increasing mass loss across campaigns of up to 0.6 g from a single tile. The mass of splashed melted Be on the upper walls was also estimated using the high-resolution images of wall components taken after each campaign. The results agree with the total material loss estimated by tile weighing (similar to 130 g). Morphological and structural analysis performed on Be melt layers revealed a multilayer structure of re-solidified material composed mainly of Be and BeO with some heavy metal impurities Ni, Fe, W. IBA analysis performed across the affected tile ridge in both poloidal and toroidal direction revealed a low D concentration, in the range 1-4 x 10(17) D atoms cm(-2).Peer reviewe

Influence of surface morphology on erosion of plasma-facing components in H-mode plasmas of ASDEX Upgrade

Net erosion of plasma-facing materials was investigated at the low-field-side (outer) strike-point area of the ASDEX Upgrade (AUG) divertor during H-mode discharges with small and frequent ELMs. To this end, Au and Mo marker samples with different surface morphologies and geometries were exposed to plasmas using the DIMII divertor manipulator. The results were compared to existing erosion and deposition patterns from various Land H-mode experiments, in the latter case the main difference was the size and frequency of the ELMs. We noticed that increasing surface roughness reduces net erosion but less than what is the case in L-mode. On the other hand, net-erosion rates in H-mode are generally 2–5 times higher than the corresponding L-mode values, in addition to which exposure in H-mode conditions results in strong local variations in the poloidal and toroidal erosion/deposition profiles. The latter observation we associate with the large migration length, on the order of several cm, of the eroded material, resulting in strong competition between erosion and re-deposition processes especially at poloidal distances > 50 mm from the strike point. Considerable net erosion was measured throughout the analysed poloidal region unlike in L-mode where the main erosion peak occurs in the vicinity of the strike point. We attribute this qualitative difference to the slow decay lengths of the plasma flux and electron temperature in the applied H-mode scenario. Both erosion and deposition require detailed analyses at the microscopic scale and the deposition patterns may be drastically different for heavy and light impurities. Generally, the rougher the surface the more material will accumulate on locally shadowed regions behind protruding surface features. However, rough surfaces also exhibit more non-uniformities in the quality or even integrity of marker coatings produced on them, thus complicating the analyses of the experimental data. We conclude that local plasma parameters have a huge impact on the PFC erosion rates and, besides incident plasma flux, surface morphology and its temporal evolution have to be taken into account for quantitative estimates of erosion rates and PFC lifetime under reactor-relevant conditions

Gastroschisis in Finland 1993 to 2014-Increasing Prevalence, High Rates of Abortion, and Survival: A Population-Based Study

Introduction The study aims to assess the changes in prevalence and mortality of gastroschisis, and to identify associated anomalies.Materials and Methods It is a population-based nationwide study. All gastroschisis cases were identified in the Finnish Register of Congenital Malformations and the Care Register for Health Care from 1993 to 2014 including live births, stillbirths, and terminations of pregnancy due to fetal anomalies. Associated anomalies were recorded, and analyzed, and prevalence and infant mortality were calculated.Results There were 320 cases of gastroschisis; 235 (73%) live births, 16 (5%) stillbirths, and 69 (22%) terminations of pregnancy. Live birth prevalence of gastroschisis in Finland was lower than generally reported (1.73 in 10,000). However, due to relatively high rates of abortion, our total prevalence of 2.57/10,000 was similar with other reports. The most common risk factor was young maternal age. Babies with gastroschisis were born prematurely, on average on the 36th week and most are delivered by caesarean section. There was a significant increasing trend in live birth prevalence (p = 0.0018). Overall infant mortality was 7.7% (18/235), 7.2% (16/222) in simple gastroschisis and 15% (2/13) in complex gastroschisis. Associated anomalies were rare both in aborted fetuses and neonates, and there was only one case with a chromosomal abnormality.Conclusion Gastroschisis is usually an isolated anomaly with increasing birth prevalence and excellent survival rates. Regardless of the good prognosis, the abortion rates in Finland are higher than previously reported, and we hypothesize this to be due to lack of appropriate antenatal counselling.</p

Detection of Chern numbers and entanglement in topological two-species systems through subsystem winding numbers

Topological invariants, such as the Chern number, characterize topological phases of matter. Here we provide a method to detect Chern numbers in systems with two distinct species of fermion, such as spins, orbitals or several atomic states. We analytically show that the Chern number can be decomposed as a sum of component specific winding numbers, which are themselves physically observable. We apply this method to two systems, the quantum spin Hall insulator and a staggered topological superconductor, and show that (spin) Chern numbers are accurately reproduced. The measurements required for constructing the component winding numbers also enable one to probe the entanglement spectrum with respect to component partitions. Our method is particularly suited to experiments with cold atoms in optical lattices where time-of-flight images can give direct access to the relevant observables