Mechanisms of bottom boundary fluxes in a numerical model of the Shetland shelf

Across-slope bottom boundary layer (BBL) fluxes on the shelf-edge connect this region to deeper waters. Two proposed ways in which across-slope BBL fluxes can occur, in regions that have a slope current aligned to the bathymetry, are: the frictional veering of bottom currents termed the ‘Ekman drain’; and through local wind-forced downwelling (wind-driven surface Ekman flow with an associated bottom flow). We investigate the variability, magnitude and spatial scale of BBL fluxes on the Shetland shelf, which has a prominent slope current, using a high-resolution (∼ 2 km) configuration of the MITgcm model. Fluxes are analysed in the BBL at the shelf break near the 200 m isobath and are found to have a seasonal variability with high/low volume transport in winter/summer respectively. By using a multivariate regression approach, we find that the locally wind-driven Ekman transport plays no explicit role in explaining daily bottom fluxes. We can better explain the variability of the across-slope BBL flux as a linear function of the speed and across-slope component of the interior flow, corresponding to an Ekman plus mean-flow flux. We estimate that the mean-flow is a greater contributor than the Ekman flux to the BBL flux. The spatial heterogeneity of the BBL fluxes can be attributed to the mean-flow, which has a much shorter decorrelation length compared to the Ekman flux. We conclude that both the speed and direction of the interior current determines the daily BBL flux. The wind does not explicitly contribute through local downwelling, but may influence the interior current and therefore implicitly the BBL fluxes on longer timescales

Open circuit fault diagnosis for a five-level neutral point clamped inverter in a grid-connected photovoltaic system with hybrid energy storage system

Introduction. Recently, the number of high and medium voltage applications has increased dramatically. The connection between these different applications requires series-parallel combinations of power semiconductors. Multilevel converter topologies provide major advantages to these applications. In this paper, a grid-connected photovoltaic system with a hybrid energy storage system using a five-level neutral point clamped inverter is studied. Although the multilevel inverter has many advantages over the two-level inverter, it has a high probability of experiencing an open circuit fault. In this context, the five-level inverter has 24 controllable switches, one of which may experience an open circuit fault at any time. Therefore, it plays an important part in the reliability and robustness of the whole system. The novelty of this paper presents an approach to accurately detect the open circuit fault in all insulated gate bipolar transistors of a five-level neutral point clamped inverter in a photovoltaic power generation application with a hybrid energy storage system. Purpose. Before using fault-tolerant control to ensure service continuity, fault diagnosis techniques must first be used, which are the crucial phase of reliability. Methods. A detection method based on the maximum and minimum error values is proposed. These errors are calculated using the expected and measured line-to-line pole voltages. Results. The open circuit fault detection method is implemented using MATLAB/Simulink. Simulation results showed the accuracy of detecting the open circuit fault in all insulated gate bipolar transistors in a short time. Moreover, this method is adaptable to several applications and is also robust to transient regimes imposed by solar irradiation and load variations.Вступ. Останнім часом різко зросла кількість застосувань високої та середньої напруги. З’єднання між цими різними використаннями вимагає послідовно-паралельних комбінацій силових напівпровідників. Топології багаторівневих перетворювачів надають цим додаткам великі переваги. У цій статті вивчається фотоелектрична система, підключена до мережі, з гібридною системою зберігання енергії, яка використовує п’ятирівневий інвертор із фіксуванням нейтральної точки. Хоча багаторівневий інвертор має багато переваг, порівняно з дворівневим інвертором, він має високу ймовірність виникнення обриву кола. У зв’язку з цим п’ятирівневий інвертор має 24 керовані перемикачі, один з яких будь-якої миті може зіткнутися з обривом кола. Таким чином, він відіграє важливу роль у надійності та стійкості всієї системи. Новизна цієї статті являє собою підхід до точного виявлення несправності розімкнутого кола у всіх біполярних транзисторах із ізольованим затвором п’ятирівневого інвертора з фіксуванням нейтральної точки у фотоелектричних додатках для вироблення електроенергії з гібридною системою зберігання енергії. Мета. Перш ніж використовувати відмовостійкий контроль для забезпечення безперервності обслуговування, необхідно спочатку використовувати методи діагностики несправностей, які є вирішальним етапом надійності. Методи. Запропоновано метод виявлення, заснований на максимальному та мінімальному значеннях помилок. Ці помилки розраховуються з використанням очікуваних та виміряних міжфазних напруг на полюсах. Результати. Метод виявлення обриву кола реалізовано з використанням MATLAB/Simulink. Результати моделювання показали точність виявлення обриву кола у всіх біполярних транзисторах із ізольованим затвором за короткий час. Більш того, цей метод адаптується до кількох застосувань, а також стійкий до перехідних режимів, викликаних сонячним випромінюванням та змінами навантаження

Acoustical and thermodynamic study of binary mixture cyclohexane-methanol using ultrasonic interferometer at different temperatures

The ultrasonic velocity (U) mass density (ρ) and shear viscosity (η) of the binary liquid mixtures of cyclohexane-methanol have been determined experimentally in the single-phase region and over the whole composition range at temperature range (T = 321.15 to 325.15 K). The experimental measurements of these properties have been carried out at atmospheric pressure, for a constant frequency 2 MHz. From these experimental data values, various acoustic and thermodynamic parameters namely adiabatic compressibility (βs), acoustic impedance (Z), intermolecular free length (Lf), relaxation time (τ), molar volume (Vm), free volume (Vf), internal pressure (πi), attenuation (α/f2), Gibb’s energy (ΔG), and cohesive energy (CE) have been calculated. Also their excess values have been calculated. All these parameters and their excess values have been interpreted in terms of molecular interaction such as dipole-dipole and dipole induced dipole interactions through hydrogen bonding between components of binary liquid mixture

Use of lipids of Chlorella microalgae in poultry meat marinades and sauces recipes

ArticleThe aim of this study is to develop formulations and technologies for fermented poultry meat products with the addition of whey and lipid extracts obtained from Chlorella microalgae. Lyophilized microalgal biomass was obtained from cell suspensions of Chlorella sorokiniana (strain 211-8k) cultivated in a closed photobioreactor under laboratory conditions. For the cell wall disintegration, the biomass samples were homogenized using a high-speed homogenizer at 10,000 vol min-1 for 5 minutes. The lipid extraction was performed on a Sohxlet apparatus Buchi E-812 SOX with the solvent extraction system ethanol: n-hexane (1: 9). The higher fatty acids composition of the obtained microalgal lipid extracts was determined by gas chromatography with flame-ionization detection using nitrogen as a carrier gas. The ω-3 and ω-6 content represented 26.59% and 19.05% respectively, which indicates that these lipid extracts have high nutritional values. The curd whey was obtained from cow's milk of summer and winter production from 2017 to 2018 (Lomonosov district auxiliary farm, Leningrad region); and lyophilized Direct Vat Set (DVS) cultures (Ch. Hansen, Denmark). The organic acids and carbohydrate content in the serum was determined by ion-exclusion HPLC. The FD-DVS CHN-19 culture was selected to produce a serum with improved organoleptic characteristics and a lower propionic acid content (0.01 g L -1 ). To obtain an optimal ω-3 / ω-6 ratio, a phyto-additive mixture based on sunflower oil and lipid extracts from C. sorokiniana microalgae at a ratio of 5–10: 1 is proposed to be used in recipes and technologies of sauces and marinades. It is established that the use of curd whey marinades allow to increase the water-holding capacity (WHC) by 6−8% and to reduce losses during heat treatment of poultry meat from 2 to 11%