Estimation of turbulence in fan-rotor wakes for broadband noise prediction during acoustic preliminary design

When calculating broadband fan noise caused by rotor-stator wake interaction analytically, information about the airflow, particularly about the turbulence in the rotor wakes, is necessary. During the pre-design phase, two-dimensional streamline methods are commonly used. These provide only general flow quantities like mean-flow velocities or total-pressure losses. Turbulent parameters such as turbulent kinetic energy and turbulent integral length scale need to be deduced from these quantities. There are several models mentioned in the literature which correlate the wake size with the wake turbulence. But they usually comprise calibration factors that need to be assessed empirically by numerical simulations or measurements. The contribution of the paper is to present an updated semi-empirical model for rotor-wake turbulence quantities, derived on the basis of an extensive comparison of the model with measurements and numerical simulations on four different turbofan stages. A recalibration of the empirical factors improved the noise prediction by 8 dB, reaching an accuracy of 2 dB. In addition, it is shown, that the endwall flow is responsible for large variance in the noise prediction, and may have a contribution of up to 2 dB to the overall sound power

Поражение центральной нервной системы листериозной этиологии (клинический случай)

Introduction. This report of Listeria monocytogenes infection with the involvment of central nervous system is important due to the increased frequency either in adults or children as well as the usually severe course and high mortality in generalized forms, especially with the CNS involvement. The demonstration of this clinical case, especialy the features of structural changes in the CNS with MRI in the disease’s dynamics, reflects the complexity of differential diagnosis and the evaluation of therapy effectiveness.Purpose of the study. To present a clinical case of CNS lesion in a 7-year-old child, the causative factor of which was listeria infection, with a detailed description of structural changes in the CNS using MRI studies.Material and methods. There is a clinical observation of a patient (child) with a diagnosis of listeriosis, secondary generalized form, extremely severe clinical course, with lesions of the central nervous system (meningoencephalitis). A series of magnetic resonance imaging studies of the brain in dynamics against the background of treatment are analyzed. Structural changes were assessed using multiparameter MRI of the brain using the following modes: T1-weighted, T2-weighted, Flair, T1-weighted with contrast, diffusionweighted and diffusion tensor imaging (DWI / DTI), susceptibility weighted imaging (SWI), MR perfusion, MR angiography.Results. The revealed structural changes in the brain during dynamic MRI examination, as well as their correlation with the data of anamnesis and clinical and laboratory data, made it possible to confirm meningoencephalitis, as well as to evaluate and make adjustments to the treatment.Conclusion. The described clinical case, the features of the course of the disease and MRI changes, suggest that dynamic MRI research is of great importance in identifying and assessing (including dynamics) structural changes in the brain substance in patients with neurological disorders in infectious diseases. The obtained data can be used by the attending physicians to assess and correct the ongoing therapy, to determine the required amount of rehabilitation. Введение. Учитывая рост заболеваемости листериозной инфекцией, в том числе и среди детей, тяжесть течения и высокую летальность при генерализованных формах, особенно с вовлечением центральной нервной системы (ЦНС), а также сложность дифференциальной диагностики и недостаточную эффективность терапии, авторами продемонстрирован клинический случай вторично-генерализованной листериозной инфекции с  поражением ЦНС и  крайне тяжелым течением у  ребенка 7 лет, в котором раскрыты особенности структурных изменений в ЦНС при МРТ в динамике заболевания.Цель исследования. Представить клинический случай поражения ЦНС у ребенка 7 лет, причинно-значимым фактором которого являлась листериозная инфекция, с детальным описанием структурных изменений в ЦНС с помощью МР-исследования.Материал и  методы. Представлено клиническое наблюдение пациента (ребенка) с  диагнозом «Листериоз, вторичногенерализованная форма, крайне тяжелое течение, с поражением ЦНС (менингоэнцефалит)». Проанализированы серии магнитно-резонансных исследований головного мозга в динамике на фоне проводимого лечения. Оценка структурных изменений проводилась с помощью мультипараметрической МРТ головного мозга с использованием режимов: Т1-ВИ, Т2-ВИ, Flair, Т1-ВИ с контрастированием, diffusion-weighted and diffusion tensor imaging (DWI/DTI), susceptibility weighted imaging (SWI), МР-перфузии, МР-ангиографии.Результаты. Выявленные структурные изменения головного мозга при динамическом МР-исследовании, а также их корреляция с данными анамнеза, клинической и лабораторной картинами позволили подтвердить менингоэнцефалит, а также оценить и внести коррективы в проводимое лечение.Заключение. Описанный клинический случай, особенности течения заболевания и МРТ-изменений, позволяют предположить, что динамическое МР-исследование имеет большое значение в выявлении и оценке (в том числе динамики) структурных изменений вещества головного мозга у пациентов с неврологическими нарушениями при инфекционных заболеваниях. Полученные данные могут быть использованы лечащими врачами для оценки и  коррекции проводимой терапии, определения необходимого объема реабилитации.

Показатели фракционной анизотропии вещества головного мозга у здоровых детей: когортное исследование

INTRODUCTION: Diffusion-tensor magnetic resonance imaging (DT-MRI) is currently a well studied and applied in clinical practice technique. An important advantage of this technique is the measurement of fractional anisotropy (FA) values, which make it possible to quantify changes in brain matter. The authors are aware of publications on the study of FА values among children in small groups including only a part of ages. This work presents study of FA among large amount of examined children and notes values of FA for most of the significant structures of the brain in subjects from 4 months to 18 years of age.OBJECTIVE: Analysis of the FА values of the anatomical structures of the brain in children of different age groups who did not reveal changes in the brain matter during multiparametric MRI, in order to further study the processes of development and myelination of brain structures, as well as the use of these values in clinical practice as reference values in the analysis of pathology.MATERIALS AND METHODS: 153 patients aged from 4 months to 18 years were examined. MRI of brain was performed on the recommendation of the attending physician in accordance with clinical indications in case of suspected infection in the paranasal sinuses and neurological complaints, without focal symptoms. Distribution of examined children by age groups was: up to 1 year (infant age) — 6 children (3.9%); from 1 year to 3 years (early childhood) — 14 children (9.15%); from 3 to 7 years old (preschool age) — 39 children (25.5%); older than 7 years (school age and older) — 94 children (61.45%). Distribution of the examined by gender: male children — 82 (53.6%); female — 71 (46.4%). DT-MRI was applied to all patients with measurement of diffusion in 15 directions, and then FА values were measured in 21 areas of the white and gray matter of the brain. The regions of interest (ROI) were arranged in accordance with the zones of the ASPECTS and PC-ASPECTS scales adapted for the purposes of this study. Statistics: processing of the received data was carried out using application programs: Microsoft Excel, Statistica 10 with an assessment of the normality of the distribution of values and the use of parametric and nonparametric criteria.RESULTS: The highest mean numerical values of FA for all groups of children were found in the white matter along neural pathways: 0.66±0.04 for the internal capsule; 0.68±0.05 — in the white matter of the midbrain; 0.64±0.08 — at the level of the pons; 0.69±0.04 — in the cerebellar peduncles. The FA indices in the white matter of other anatomical regions are slightly lower: 0.50±0.08 — for white matter at the M4 level according to ASPECTS; 0.52±0.08 — in the occipital lobe at the level of the basal ganglia; 0.54±0.05 — in the temporal lobe. The lowest FA values appeared in the gray matter: 0.16±0.04 — in the caudate nucleus; 0.12±0.04 — in the gray matter at the M4 level according to ASPECTS. The most pronounced differences in FA in children of early childhood and school age appeared in the ROI located in the white matter of the cerebral cortex: in the area of M5 0.46±0.05 versus 0.54±0.05, respectively; in the area of M1 0.43±0.06 versus 0.51±0.06, respectively. At the same time, differences in FA in children of early childhood and school age in ROI located in the white matter at the level of stem structures are less pronounced: at the level of the pons 0.6±0.07 versus 0.64±0.07, respectively; at the level of the cerebellar peduncles 0.68±0.04 versus 0.69±0.04, respectively. These numerical indicators illustrate and additionally confirm the known ideas about the development and formation of neural pathways and about the processes of their myelination. They also reflect the known data on the structural and functional differences between the gray and white matter of the brain. A significant increase of the FА values in children older than 7 years was determined in comparison with groups of younger children in the white matter of the cortical structures of the brain. At the same time, there are no significant age-related differences of FА in the region of brainstem. It was also found that in preschoolers, compared with children from 1 to 3 years old, white matter FА increases in the region of the caudate nucleus and midbrain.CONCLUSION: The obtained normative values of FА can later be widely used in clinical practice as reference ones when performing DT-MRI and assessing neuroinfectious and other pathological changes in the brain matter in children. The revealed differences in age groups indicate an earlier development of brainstem structures, while the subcortical-cortical areas of the cerebral hemispheres develop and myelinate over a longer time.ВВЕДЕНИЕ: Диффузионно-тензорная магнитно-резонансная томография (ДТ-МРТ) на данный момент является изученной и применяемой в клинической практике методикой. Важное преимущество данной методики — измерение показателей фракционной анизотропии (ФА), позволяющих количественно оценить изменения в  веществе головного мозга (ГМ). Авторам известны работы по исследованию значений ФА в педиатрической практике на небольших выборках и с учетом только части возрастных групп. Данная работа приводит крупную выборку пациентов и отмечает числовые показатели ФА для большинства значимых структур ГМ у обследуемых с 4 мес до 18 лет.ЦЕЛЬ: Анализ показателей ФА анатомических структур ГМ у детей различных возрастных групп, у которых не выявлено изменений вещества ГМ при мультипараметрической МРТ, с целью дальнейшего изучения процессов развития и миелинизации структур головного мозга, а также применения данных значений в клинической практике как референсных при анализе патологии.МАТЕРИАЛЫ И МЕТОДЫ: Были обследованы 153 пациента в возрасте от 4 мес до 18 лет. МРТ ГМ выполнялась по рекомендации лечащего врача в соответствии с клиническими показаниями при подозрении на инфекционный процесс в околоносовых пазухах и неврологических жалобах, без очаговой симптоматики. По возрастным группам распределение составило: до 1 года (грудной возраст) — 6 детей (3,9%); от 1 года до 3 лет (ранний детский возраст) — 14 детей (9,15%); от 3 до 7 лет (дошкольный возраст) — 39 детей (25,5%); старше 7 лет (школьный возраст и старше) — 94 ребенка (61,45%). Распределение обследованных по полу: дети мужского пола — 82 (53,6%); женского пола — 71 (46,4%). Всем пациентам выполнялась ДТ-МРТ с измерением диффузии в 15 направлениях, затем были измерены показатели ФА в 21 области белого и серого вещества ГМ. Расстановка областей интереса (ОИ/ROI) проводилась в соответствии с адаптированными под цели данного исследования зонами шкал ASPECTS и PC-ASPECTS. Статистика: обработка полученных данных проводилась с помощью прикладных программ: Microsoft Excel, Statistica 10 с оценкой нормальности распределения значений и использованием параметрических и непараметрических критериев.РЕЗУЛЬТАТЫ: Наиболее высокие средние численные показатели ФА для всех групп детей были выявлены в белом веществе по ходу проводящих путей ГМ: во внутренней капсуле — 0,66±0,04; в белом веществе среднего мозга — 0,68±0,05; на уровне варолиева моста — 0,64±0,08; в ножках мозжечка — 0,69±0,04. Несколько ниже показатели ФА в белом веществе других анатомических областей: в белом веществе на уровне М4 по ASPECTS — 0,50±0,08; в затылочной доле на уровне базальных ганглиев — 0,52±0,08; в височной доле — 0,54±0,05. Самые низкие показатели ФА отмечены в сером веществе: в хвостатом ядре — 0,16±0,04; в сером веществе на уровне М4 по ASPECTS — 0,12±0,04. Наиболее выражены различия ФА у детей раннего детского и школьного возраста в ОИ, расположенных в белом веществе коры больших полушарий: в области M5 — 0,46±0,05 против 0,54±0,05 соответственно; в области M1 — 0,43±0,06 против 0,51±0,06 соответственно. В то же время различия по ФА у детей раннего детского и школьного возраста в ОИ, расположенных в белом веществе на уровне стволовых структур, выражены меньше: на уровне варолиева моста — 0,6±0,07 против 0,64±0,07 соответственно; на уровне ножек мозжечка — 0,68±0,04 против 0,69±0,04 соответственно. Данные числовые показатели иллюстрируют и дополнительно подтверждают известные представления о развитии и формировании проводящих путей и о процессах их миелинизации. Также они отражают известные данные о структурных и функциональных различиях серого и белого вещества ГМ.ОБСУЖДЕНИЕ: Определено достоверное повышение показателей ФА у детей старше 7 лет в сравнении с группами детей меньшего возраста в белом веществе корковых структур ГМ. При этом в области стволовых структур достоверных возрастных различий ФА нет. Также было выявлено, что у дошкольников в сравнении с детьми от 1 до 3 лет ФА белого вещества повышается в области хвостатого ядра и среднего мозга.ЗАКЛЮЧЕНИЕ: Полученные нормативные числовые значения ФА в дальнейшем могут быть широко применимы в клинической практике в качестве референсных при выполнении ДТ-МРТ и оценки как нейроинфекционных, так и других патологических изменений вещества ГМ у детей. Выявленные различия в возрастных группах свидетельствуют о более раннем развитии стволовых структур ГМ, в то время как субкортикально-кортикальные области больших полушарий развиваются и миелинизируются в течение более длительного времени

Field-circuit modelling of an advanced welding transformer with two parallel rectifiers

The new topology of three-winding welding transformer is proposed. Each secondary winding is connected in parallel through the separate bridge rectifier to the welding arc. The main feature of the proposed device is parallel working of two secondary windings with different rated voltage. The advantage is nonlinear transformation ratio of current that provides unprecedented power efficiency. The self- and mutual leakage inductances, which are important in power conversion, are calculated by 2D FEA model. The operational current of the device is modelled numerically via P-Spice simulator. The proposed topology is up to 30% more power effective than conventional welding transformer provided that the leakage inductances of primary and secondary windings are correctly fitted. This transformer is used for manual arc welding

Field-circuit modelling of an advanced welding transformer with two parallel rectifiers

The new topology of three-winding welding transformer is proposed. Each secondary winding is connected in parallel through the separate bridge rectifier to the welding arc. The main feature of the proposed device is parallel working of two secondary windings with different rated voltage. The advantage is nonlinear transformation ratio of current that provides unprecedented power efficiency. The self- and mutual leakage inductances, which are important in power conversion, are calculated by 2D FEA model. The operational current of the device is modelled numerically via P-Spice simulator. The proposed topology is up to 30% more power effective than conventional welding transformer provided that the leakage inductances of primary and secondary windings are correctly fitted. This transformer is used for manual arc welding

La1-x A ' xCo1-yFe (y) O-3 +/-delta (A ' = Ce,Sr) catalysts for the flameless combustion of methane

A set of La1-x A' (x) Co1-y Fe (y) O-3 +/-delta samples (A'= Ce,Sr; x= 0.1, 0.4, y= 0, 0.5, 0.8, 1) was prepared by means of the sol-gel citrate method and characterised through X-ray diffraction (XRD), N-2 adsorption/desorption and temperature programmed desorption-reduction (TPD-TPR). Their activity for the catalytic flameless combustion of methane was tested and the results interpreted focusing on the effect of doping at A and/or B position. It was found that Ce doping of lanthanum ferrite catalysts could suppress suprafacial activity and slightly enhance intrafacial activity, due to the change of oxygen mobility. However, catalytic activity seems independent of the type of electronic conductivity (p- or n-type), the activity of an analogously Sr-doped sample being similar to that of the Ce-doped one. Mixed B-metal composition can help in modulating both oxygen mobility and catalyst stability under reducing reaction conditions. High Fe content allows to optimise this last parameter. However, depression of oxygen mobility and hence of activity has to be prevented by proper doping at A-position

Preparation and sintering of Ce(1-x)Gd(x)O(2-x/2) nanopowders and their electrochemical and EPR charaterization

Different Ce1-xGdxO(4-x)/2 (x = 0.1; 0.2) samples were analysed by EPR spectroscopy at different temperatures to select the doping level which minimises the occurrence of electronic conductivity. On the base of EPR results analysis, the optimal composition of the nanopowder was selected, and several nanopowders were produced by different chemical processes. The different nanopowders obtained are sintered at high temperature to prepare a high density ceramic materials (\uf072rel \uf0b3 96%). Finally, the electrochemical and microstructural properties of those samples were studied

The potential of electromyography, diagnostic transcranial magnetic stimulation, and multiparametric magnetic resonance imaging in the combinatory assessment of facial nerve disorders: a literature review and clinical case series

Facial neuropathy (FN) is a complex multicausal problem that, with a seemingly obvious clinical picture, might be challenging to diagnose. Up to 5% of FN cases could be caused by neoplastic or otogenic processes, necessitating an interdisciplinary approach to its treatment by various specialties and in some cases a surgical intervention. In addition, in the early stages of FN, it is difficult to predict its outcomes. Therefore, beyond usual neurological exam and widely used electromyography (EMG), other additional diagnostic tools are used to ensure extended diagnosis, including cancer awareness. In this paper we have analyzed the principles, role and value of computed tomography, magnetic resonance imaging (MRI), diagnostic transcranial magnetic stimulation combined with EMG, and ultrasound assessment with a high-frequency linear transducer in acute FN. We present our own clinical cases of pediatric patients with FN, who were assessed with EMG and multiparametric MRI including diffusion tensor imaging. These cases illustrate both the abnormalities found in the typical course of Bell's palsy, as well as the abnormalities in neoplasm-associated FN that clinically fully mimic the Bell's palsy. Based on the world experience in multiparametric MRI, including the use of extended protocols in the Pediatric Research and Clinical Center for Infectious Diseases, in case of suspected FN, the most important are high-resolution structural submillimeter sequences based on the gradient echo (SSFP) and diffusion tensor imaging (DTI). Measurement and assessment of fractional anisotropy at the motor nuclei of the facial nerves in the pons look promising for further research. The paper is the first to describe a modified combination diagnostic approach to Bell's palsy with the use of diagnostic transcranial magnetic stimulation with round coil, supramaximal stimulation with identification of the motor evoked response threshold (minimal inducer power to register a reproducible evoked motor response of 50-100 mV in amplitude) in the occipito-parietal area of the ipsilateral muscle