Application of Vortex Generators to Remove Heat Trapped in Closed Channels

The utilization of vortex generators to increase heat transfer from cylinders installed inside a duct is investigated.In particular,a channel containing eight cylinders with volumetric heat sources is considered for different values of the Reynolds number.The effective possibility to use vortex generators with different sizes to increase heat transfer and,consequently,reduce the surface temperature of the cylinders is examined.Also,the amount of pressure drop inside the channel due to the presence of vortex generators is considered and compared with the cases without vortex generators.The results show that although the addition of generators increases the pressure drop,it strongly contributes to increase the heat transfer coefficient inside the duct(up to 80–90%).

Role of compositional changes on thermal,magnetic,and mechanical properties of Fe-P-C-based amorphous alloys

This work aimed to tune the comprehensive properties of Fe-P-C-based amorphous system through investigating the role of microalloying process on the crystallization behavior,glass forming ability(GFA),soft magnetic features,and mechanical properties.Considering minor addition of elements into the system,it was found that the simultaneous microalloying of Ni and Co leads to the highest GFA,which was due to the optimization of compositional heterogeneity and creation of near-eutectic composition.Moreover,the FeCoNiCuPC amorphous alloy exhibited the best anelastic/viscoplastic behavior under the nanoindentation test,which was owing to the intensified structural fluctuations in the system.However,the improved plasticity by the extra Cu addition comes at the expense of magnetic properties,so that the saturation magnetization of this alloying system is significantly decreased compared to the FeCoPC amorphous alloy with the highest soft magnetic properties.In total,the results indicated that a combination of added elemental constitutes,i.e.,Fe69Co5Ni5Cu1P13C7 composition,provides an optimized state for the comprehensive properties in the alloying system.

Influence of Physical Activity on Concentration of Macro-and Microelements in Physically Active Students＇ Hair

The aim of the work is to evaluate the influence of physical activity character on concentration of macro-and microelements in hair of physically active students. 127 students of I-IV year of Physical Education program at Lithuanian University of Educational Sciences participated in the research, aged from 20 to 24. They were split into three groups. The first （I） group （n = 48） consisted of endurance sport athletes （skiers, biathlon athletes, middle and long distance runners, rowers and cyclists）. The second group （II） （n = 61） was made up of the basketball, football, handball and volleyball players. The third group （III） consisted of combat sports （wrestling and boxing） athletes （n = 18）. For establishing the concentration of macro- and microelements in hair, x-ray fluorescence method was applied, using CEP-1 ELVAX （MP.MN 3730-2011） device. The results showed that the hair of the students of Physical Education program, practicing endurance sports possessed more calcium, copper, manganese in comparison to the athletes practicing other sports. Concentration of the main elements--zinc, iron, selenium and chromium in the hair of combat sports representatives was statistically significant. Concentration of potassium was also the greatest in this group of the investigated. However, this group of athletes also possessed the greatest values of toxic elements （plumbum, arsenic） in their hair, comparing to the athletes of endurance sport and players. In their hair, hydrargyrum concentration was significantly greater comparing to the values of this element in players＇ hair. The greatest mean values of cadmium were established in players＇ hair.

Implementation of the Concept of Energy and Technological Compliance of Components in the Technology of Fluorocomposites

Structural and technological aspects of obtaining and processing functional composite materials based on PTFE(polytetrafluoroethylene)are considered.It is shown that,due to the features of the molecular structure of the matrix polymer,within the framework of the traditional technological paradigm,prerequisites are created for the implementation of a structural paradox,which manifests itself in a decrease in the parameters of the stress-strain and tribological characteristics of composites with an increase in the degree of filling.Within the framework of the concept of multilevel modification,methodological approaches to the implementation of the energy and technological compliance of components,which reduce the negative impact of the structural paradox,are considered.

Head-related transfer function–reserved time-frequency masking for robust binaural sound source localization

Various time-frequency(T-F)masks are being applied to sound source localization tasks.Moreover,deep learning has dramatically advanced T-F mask estimation.However,existing masks are usually designed for speech separation tasks and are suitable only for single-channel signals.A novel complex-valued T-F mask is proposed that reserves the head-related transfer function(HRTF),customized for binaural sound source localization.In addition,because the convolutional neural network that is exploited to estimate the proposed mask takes binaural spectral information as the input and output,accurate binaural cues can be preserved.Compared with conventional T-F masks that emphasize single speech source–dominated T-F units,HRTFreserved masks eliminate the speech component while keeping the direct propagation path.Thus,the estimated HRTF is capable of extracting more reliable localization features for the final direction of arrival estimation.Hence,binaural sound source localization guided by the proposed T-F mask is robust under noisy and reverberant acoustic environments.The experimental results demonstrate that the new T-F mask is superior to conventional T-F masks and lead to the better performance of sound source localization in adverse environments.

Binaural sound source localization based on weighted template matching

In robot binaural sound source localization(SSL),locating the direction of the sound source accurately in the shortest time is important.It refers to the algorithm complexity,but even more to the shortest duration of the required signal.A novel binaural SSL method based on feature and frequency weighting is proposed.More specifically,in the training stage,the direction-related interaural cross-correlation function(CCF)and interaural intensity difference(IID)in each frequency band are calculated under noiseless conditions,which are considered the templates.In the testing stage,first the cosine similarities between the CCF and IID of the test signal and templates are calculated in all features and frequency bands.Then,the direction likelihood can be obtained by weighting the similarities.Finally,the direction with maximum likelihood is specified as the direction of the sound source.Experiments were carried out on CIPIC dataset subject 003 with different noises in the noisex-92 dataset and demonstrated that the method can accurately locate the sound source with a short signal duration.

Improving the transition capability of the low-voltage wind turbine in the sub-synchronous state using a fuzzy controller

The main problem of wind turbines is associated with induction generators in their power supply during short circuits in the grid.In this research,a new method is presented for the uninterrupted operation of a wind turbine equipped with an induction generator fed on both sides of feeding during network errors.Wind farms equipped with a doubly-fed induction generator(DFIG)require two abilities to allow system operators to increase proficiency.These capabilities include fault ride-through and synchronization of output force fluctuations,especially when these generators generate significant electrical power.A MATLAB®software environment has been used to evaluate and improve the performance of these turbines.A fuzzy complement(FC)controller is used to improve the performance of the DFIG.The results demonstrate that this controller limits the operation of the turbine current and voltage in the short-circuit mode well.Regarding results obtained from comparing two different modes,it can be said that ripple is 4%in the FC mode,while this parameter is equal to 10%for the proportional-integral controller.