Deep Learning Prediction for Rotational Speed of Turbine in Oscillating Water Column-Type Wave Energy Converter

This study uses deep learning algorithms to predict the rotational speed of the turbine generator in an oscillating water column-type wave energy converter (OWC-WEC). The effective control and operation of OWC-WECs remain a challenge due to the variation in the input wave energy and the significantly high peak-to-average power ratio. Therefore, the rated power control of OWC-WECs is essential for increasing the operating time and power output. The existing rated power control method is based on the instantaneous rotational speed of the turbine generator. However, due to physical limitations, such as the valve operating time, a more refined rated power control method is required. Therefore, we propose a method that applies a deep learning algorithm. Our method predicts the instantaneous rotational speed of the turbine generator and the rated power control is performed based on the prediction. This enables precise control through the operation of the high-speed safety valve before the energy input exceeds the rated value. The prediction performances for various algorithms, such as a multi-layer perceptron (MLP), recurrent neural network (RNN), long short-term memory (LSTM), and convolutional neural network (CNN), are compared. In addition, the prediction performance of each algorithm as a function of the input datasets is investigated using various error evaluation methods. For the training datasets, the operation data from an OWC-WEC west of Jeju in South Korea is used. The analysis demonstrates that LSTM exhibits the most accurate prediction of the instantaneous rotational speed of a turbine generator and CNN has visible advantages when the data correlation is low.

Experimental and numerical investigation of different geometrical parameters in a centrifugal blood pump

Purpose Due to the importance of public health and economics, cardiovascular disease has become one of the most important debates and challenges for scientists. However, few studies have been done to address this challenge. The main objective of this document is to provide an optimal model to improve the performance of the left ventricular assist device and reduce costs. In this way, in the present study, the experimental and numerical procedures were developed to analyze the effects of the geometrical features and operational parameters on the performance of a centrifugal blood pump (CBP). Methods In order to achieve this aim, first, experimental tests were carried out to study the influence of the working fluid temperature and the rotational speed on the CBP. Subsequently, the performance of the CBP was assessed using computational fluid dynamics (CFD), and comparison was made against the experimental data. In addition, the influence of mounting an inducer on the overall performance of CBP was also investigated. Results Good agreement between the CFD and the data was obtained. The CFD results showed that increasing the fluid temperature and rotational speed leads to an increase in the hydraulic efficiency, pressure difference, and power. In addition, the reduction of the pressure difference and hydraulic efficiency with increasing the surface roughness was observed. While mounting an inducer on the pump did not significantly impact its overall performance, the highest value of the wall shear stress dropped moderately on the impeller and, therefore, unveiled the possibility of improving the performance of such designs.

Parametric optimization of friction stir welding process parameters of dissimilar welded joints using grey relational analysis and desirability function approach

Purpose The main purpose of the present work is to study the multi response optimization of dissimilar friction stir welding (FSW) process parameters using Taguchi-based grey relational analysis and desirability function approach (DFA). Design/methodology/approach The welded sheets were fabricated as per Taguchi orthogonal array design. The effects of tool rotational speed, transverse speed and tool tilt angle process parameters on ultimate tensile strength and hardness were analyzed using grey relational analysis, and DFA and optimum parameters combination was determined. Findings The tensile strength and hardness values were evaluated from the welded joints. The optimum values of process parameters were estimated through grey relational analysis and DFA methods. Similar kind of optimum levels of process parameters were obtained through two optimization approaches as tool rotational speed of 1150 rpm, transverse speed of 24 mm/min and tool tilt angle of 2° are the best process parameters combination for maximizing both the tensile strength and hardness. Through these studies, it was confirmed that grey relational analysis and DFA methods can be used to find the multi response optimum values of FSW process parameters. Research limitations/implications In the present study, the FSW is performed with L9 orthogonal array design with three process parameters such as tool rotational speed, transverse speed and tilt angle and three levels. Practical implications Aluminium alloys are widely using in automotive and aerospace industries due to holding a high strength to weight property. Originality/value Very limited work had been carried out on multi objective optimization techniques such as grey relational analysis and DFA on friction stir welded joints made with dissimilar aluminium alloys sheets.

An experimental performance comparison of Newtonian and non-Newtonian fluids on a centrifugal blood pump

The use of substitute fluid with similar rheological properties instead of blood is important due to ethical concerns and high blood volume consumption in pump performance test before clinical applications. The performance of a centrifugal blood pump with hydrodynamic journal bearing is experimentally tested using Newtonian 40% aqueous glycerin solution (GS) and non-Newtonian aqueous xanthan gum solution of 600 ppm (XGS) as working fluids. Experiments are performed at four different rotational speeds which are 2700, 3000, 3300, and 3600 rpm; experiments using GS reach between 8.5% and 37.2% higher head curve than experiments using the XGS for every rotational speed. It was observed that as the rotational speed and flow rate increase, the head curve difference between GS and XGS decreases. This result can be attributed to the friction reduction effect when using XGS in experiments at high rotation speed and high flow rate. Moreover, due to different fluid viscosities, differences in hydraulic efficiency were observed for both fluids. This study reveals that the use of Newtonian fluids as working fluids is not sufficient to determine the actual performance of a blood pump, and the performance effects of non-Newtonian fluids are remarkably important in pump performance optimizations.

Influence of tool rotational speed on the evolution of microstructure and mechanical properties of precipitation-hardened Aluminium 6061 butt joint during friction stir welding

The present investigation intends to interpret the effect of tool rotational speed on the mechanical properties and microstructural evolution in Aluminium 6061-T6 alloy during friction stir welding. A higher value of tool rotation produces more hardness at the nugget zone, which is attributed to the higher intensity of reprecipitation at higher rpm, revealed by transmission electron microscopy. The nugget zone is revealed as a nearly precipitate-free region, while the thermo-mechanically affected zone contains coarse precipitates, deformed and dynamically recovered grains with a few recrystallized grains. Significant reduction in grain size in the stirred zone is also a key finding. The observations depict the dependence of microstructure, and thus mechanical behaviour on tool rotational speed. A specific combination of process parameters has been determined from experiments, which corresponds to the maximum joint efficiency.

An Evaluation of Optimal Friction Stir Welding Factors (FSWF) For Yellow Brass 405-20

Friction stir welding (FSW) is a green, environmentally amicable, and solid-state joining technology. FSW can successfully weld a wide range of materials (similar/dissimilar parent materials) including aluminum, copper, steel, different alloys from these materials, plastics, composites. FSW of brass has already been accomplished by fewer researchers. In this research, yellow brass 405-20 is, therefore, welded with FSW that was never welded before. In this study, tool material utilized was M2 HSS that was also novel. Effect of two friction stir weld factors (FSWF), rotational speed (RS) and traverse speed (TS), was found on three output parameters i.e., weld temperature, weld strength and weld hardness. Weld temperature developed, was found to be 63.72% of melting point of base metal. A significant improvement in friction stir weld strength (FSWS) was also measured that was found to be 106.37% of the base brass strength. Finally, weld hardness was measured which was found to be 87.80% of original brass hardness. Based on main effects, optimal FSW factors were found to be 1450 rpm and 60 mm/min resulting interestingly in optimal temperature, optimal weld strength, and optimal hardness. Rotational speed (RS) was found to be significant to affect the weld temperature only at the friction stir weld zone (FSWZ) with the highest percent contribution (PCR) of 65.69%. However, PCR of transverse speed was found to be maximum for affecting weld strength as compared to its PCR towards both weld temperature and weld hardness. Current study was also deepened by microscopic investigation.

Elastic Material Damage of Rotational Atherectomy and Orbital Atherectomy: An in Vitro Assessment

PurposeRotational atherectomy (RA) and orbital atherectomy (OA) are effective procedures for severe calcified coronary artery disease. Nonetheless, vessel perforation remains an adverse complication of these procedures. This study aimed to evaluate factors affecting elastic material damage caused by RA and OA.MethodsAn in vitro assessment was conducted in which the damage to the rubber latex, an elastic material, after RA was evaluated under various conditions, including burr rotational speed (100,000–220,000 rotations per minute), approaching curve, burr size (1.25 mm, 1.75 mm, and 2.0 mm), and fluid viscosity (water and low-molecular weight dextran). Similarly, the rubber latex damage after OA was evaluated in the same experimental system under various conditions, including crown rotational speed, approaching curve, and fluid viscosity.ResultsIn RA, the rubber latex was damaged at lower rotational speeds (p = 0.003), tighter approaching curves (p < 0.0001), and lower fluid viscosity (p = 0.03). In OA, the rubber latex was generally severely damaged.ConclusionA higher rotational speed, coaxial approach for the wall, and higher viscosity contributed to lesser elastic material damage in RA. The safety mechanism for elastic material in OA proved less effective.

Investigation of the disperse composition and strength of granules of instant drinks

В условиях высокой занятости населения возникает необходимость развития более сбалансированного питания. Одним из таких продуктов могут выступать инстантированные напитки на основе плодово-ягодного сырья. Подавляющее большинство таких продуктов на рынке представлено в виде многокомпонентного гранулятора с заданными показателями качества. При производстве таких продуктов используются грануляторы различного типа, однако для малых производств, которые могут быстро переориентироваться на выпуск новой продукции, более перспективными являются грануляторы периодического действия, например, роторные смесители-грануляторы. Однако при анализе получаемого дисперсного состава было выявлено, что продукт имеет нестабильный гранулометрический состав. В работе исследовались дисперсный состав и прочность гранулированного продукта, полученного в роторном смесителе-грануляторе. В результате литературно-патентного обзора была предложена модернизация известного гранулятора и определен дисперсный состав получаемых гранул. В результате проведенных исследований было выявлено, что гранулометрический состав готовой продукции стал более стабилен по сравнению с прототипом оборудования. При анализе прочности получаемых гранул не было выявлено существенного изменения, однако была выявлена зависимость прочности на раздавливание от частоты вращения рабочих органов, так при увеличении частоты вращения лопасти выше 2000 мин-1 наблюдался рост прочности гранул. Также при увеличении частоты вращения происходит рост мелкодисперсной фракции в готовой продукции. Обработка полученных результатов исследований позволила получить экспериментально статистическую модель зависимости среднемедианного размера получаемых гранул от режимных параметров и свойств связующего раствора. In conditions of high employment of the population, it becomes necessary to develop more balanced nutrition. One of the types of such foods can be instantized drinks based on fruit and berry raw materials. An overwhelming majority of these foods on the market are presented in the form of a multicomponent granules with specified quality indicators. When manufacturing such foods granulators of different types are used, however, for minor productions that can be quickly reorientated to the release of new foodstuffs, periodical activity granulators are more promising, for example, rotary mixers-granulators. However, when analyzing the resulting dispersed composition, it was revealed that the foodstuff has an unstable particle size distribution. The work investigated the dispersed composition and strength of the granular staff obtained in a rotary mixer-granulator. As a result of the literature and patent review, the modernization of the well-known granulator was proposed and the dispersed composition of the resulting granules was determined. As a result of the research carried out, it was revealed that the granulometric composition of the finished staff became stabler in comparison with the prototype of the equipment. When analyzing the strength of the granules obtained, no significant change was revealed, however, the dependence of the crushing strength of the working bodies’ rotational speed was revealed, so, with an increase in the blade’s rotational speed over 2000 RPM, an increase in the strength of the granules was observed. Also, with an increase in the rotational speed, an increase in the fine fraction in the product finished occurs. The processing of the research results obtained made it possible to obtain an experimental statistical model of the dependence of the average median size of the granules obtained on the operating parameters and the properties of the binder solution.

Split-Plot I-Optimal Design Optimisation of Combined Oil-Based and Friction Stir Rotation-Assisted Heating in SPIF of Ti-6Al-4V Titanium Alloy Sheet under Variable Oil Pressure

The aim of this paper is to determine the optimal input parameters for the process in order to ensure the maximum formable wall angle is obtained in a conical frustum with a varying wall angle fabricated using Single Point Incremental Forming (SPIF). The test material was 0.8-mm-thick Ti-6Al-4V titanium alloy sheets, and the test used a tungsten carbide tool with a rounded tip with a radius of 4 mm. Complete workpieces were heated using hot oil with a temperature of about 200 °C, and in addition, the high rotation speed of the forming tool generated an amount of friction heat. The input parameters were tool rotational speed, feed rate, step size, and tool rotation direction. Various oil pressures were used to improve both the accuracy of the components formed and the friction heating process. On the basis of calculations performed by means of the response surface methodology, split-plot I-optimal design responses were obtained by means of polynomial regression models. Models were fitted using REstricted Maximum Likelihood (REML), and p-values are derived using the Kenward–Roger approximation. Observation of the fracture surface of Ti-6Al-4V drawpieces showed that the destruction is as a result of ductile fracture mode. Tool rotational speed and step size are the most significant factors that affect the axial force, followed by feed rate. It was also found that step size is the most significant factor that affects the in-plane SPIF force.

Effect of Rotational Speed on Static and Fatigue Properties of Rotary Friction Welded Dissimilar AA7075/AA5083 Aluminium Alloy Joints

In this work, rotary friction welding processes of dissimilar AA7075/AA5083 aluminium alloy rods with the diameter of 15 mm were performed at varying rotational speeds, typically 370 to 2500 rpm. The aim of this research is to improve mechanical properties, in particular, strength and fatigue performance of the weld joints. Several experiments including macro and microstructural examinations, Vickers microhardness measurements, tensile tests, fatigue tests and residual stress measurements were carried out. Results showed that at higher rotational speeds, typically 540 rpm or above, the dissimilar AA7075/AA5083 rotary friction weld joints revealed a static fracture in the AA5083 base metal side, indicating that the joint efficiency is more than 100%. It seemed that the best weld joint was achieved at the rotational speed of 1200 rpm, in which the friction heat was sufficient to form metallurgical bonding without causing excessive flash and burn-off. In such a condition, the fatigue strength of the weld joint was slightly higher than AA5083 base metal, but it was lower than AA7075 base metal. It was confirmed that the crack origin is observed at the interface followed by fatigue crack growth towards AA5083 side, and the growth of crack seemed to be controlled by microstructure and residual stress.