Computational Analysis of Active and Passive Flow Control for Backward Facing Step

The internal steady and unsteady flows with a frequency and amplitude are examined through a backward facing step (expansion ratio 2), for low Reynolds numbers (Re=400, Re=800), using the immersed boundary method. A lower part of the backward facing step is oscillating with the same frequency as the unsteady flow. The effect of the frequency, the amplitude, and the length of this oscillation is investigated. By suitable active control regulation, the recirculation lengths are reduced, and, for a percentage of the time period, no upper wall, negative velocity, region occurs. Moreover, substituting the prescriptively moving surface by a pressure responsive homogeneous membrane, the fluid–structure interaction is examined. We show that, by selecting proper values for the membrane parameters, such as membrane tension and applied external pressure, the upper wall flow separation bubble vanishes, while the lower one diminishes significantly in both the steady and the unsteady cases. Furthermore, for the time varying case, the length fluctuation of the lower wall reversed flow region is fairly contracted. The findings of the study have applications at the control of confined and external flows where separation occurs.

FOCUS SHAPING OF CYLINDRICALLY POLARIZED VORTEX BEAMS BY A LINEAR AXICON

Focus shaping of cylindrically polarized vortex beams (CPVBs) by linear axicon is studied theoretically. Vector diffraction theory has been used to derive the expressions of the light field in the focal region. It is shown that a different intensity distribution in the focal region can be obtained by adjusting the topological charge, the polarization rotation angle and the numerical aperture maximal angle. A focal spot, a dark channel and a flat-topped shapes are formed by choosing proper values of parameters. A controllable polarization state of dark channel is obtained. The different focal region shapes may find wide applications such as material processing and optical tweezers.

Optimization and Sensitivity Analysis of the Cutting Conditions in Rough, Semi-Finish and Finish Honing

Honing processes are currently employed to obtain a cross-hatched pattern on the internal surfaces of cylinders that favors oil flow in combustion engines or hydraulic cylinders. The main aim of the present paper is to optimize the machining conditions in honing processes with respect to surface roughness, material removal rate and tool wear by means of the desirability function. Five process variables are considered: grain size, density, pressure, linear speed and tangential speed. Later, a sensitivity analysis is performed to determine the effect of the variation of the importance given to each response on the results of the optimization process. In the rough and semi-finish honing steps, variations of less than 5% of the importance value do not cause substantial changes in the optimization process. On the contrary, in the finish honing step, small changes in the importance values lead to modifications in the optimization process, mainly regarding pressure. Thus, the finish honing phase is more sensitive to changes in the optimization process than the rough and the semi-finish honing phases. The present paper will help users of honing machines to select proper values for the process variables.

Influence of Water-Induced Degradation of Polytetrafluoroethylene (PTFE)-Coated Woven Fabrics Mechanical Properties

The impact of water-induced degradation on the mechanical properties of the chosen two PTFE-coated, glass threads woven fabrics is investigated in this paper. The paper begins with a survey of literature concerning the investigation and determination of coated woven fabric properties. The authors carried out the uniaxial tensile tests with an application of flat and curved grips to establish the proper values of the ultimate tensile strength and the longitudinal stiffness of groups of specimens treated with different moisture conditions. Despite the water resistance of the main materials used for fabrics manufacturing, the change of the mechanical properties caused by the influence of water immersion has been noticed. The reduction in the tensile strength resulting under waterlogged is observed in the range from 5% to 16% depending on the type of investigated coated woven fabric and direction of weft or warp.

An Ethnographic Study on the Non-Material Impacts of the Educated Youth Program

In a movement that led to over a million civilian deaths and the persecution of millions more, the Chinese Cultural Revolution mobilized all aspects of state in order to upheave traditional hierarchy and maintain a Maoist regime. During this time, under the Educated Youth Program, nearly 17 million students of varying societal backgrounds moved to rural locations to develop “proper” values and skills. Through a qualitative ethnographic case study, twelve narrative interviews conducted with participants of the program, representing multiple regions in China, were examined under the principles of thematic analysis in order to discover overarching themes about the immaterial impacts that occurred as a result of this wide-scale emigration and whether these changes were positive or negative. Data indicated that (1) because of the rural environment and hard-working people around them, many participants gained perseverance, and (2) increased interactions with those of ethnic and economic different backgrounds led to greater acceptance of others. The findings of the study suggest that the Educated Youth Program was ultimately beneficial for its participants in regards to their overall life. These results help build a more comprehensive understanding about the impacts of rural education in China through the direct incorporation of participants’ perspectives.

Hierarchical organization of the blood pressure regulation system in the human body

Цель исследования - создание на основе анализа нарушений механизмов системы регуляции артериального давления (АД) нового методологического подхода в определении эффективности антигипертензивной терапии у пациентов с гипертонической болезнью. Методика. В исследование включены данные 277 пациентов (136 мужчин, 141 женщина) с гипертонической болезнью II стадии 1-2 степени, риск II, III. Возраст пациентов 58,6±6,4 лет, давность заболевания 7,2±1,4 лет. В группу контроля вошли 57 практически здоровых лиц (25 женщин, 32 мужчины) в возрасте 52,1±4,4 года. После скрининга и получения письменного информированного согласия в виде монотерапии назначены: небиволол, лизиноприл, лозартан, индапамид, амлодипин, и нефиксированная комбинация лизиноприла и индапамида. Изучены изменения показателей АД на выделенных уровнях системы регуляции АД после 6 мес терапии. Результаты. Оценка эффективности применяемой терапии показала, что при стабилизации артериального давления у пациентов всех 6 групп на должном уровне существенные различия выявлены на интегративном уровне регуляции. При применении амлодипина, лозартана, лизиноприла, а также комбинации лизиноприла и индапамида регуляторно-адаптивные возможности организма улучшились, при лечении индапамидом - не изменились, при применении небиволола снизились. Предложена оригинальная классификация уровней регуляции (контроля) артериального давления у человека, основанная на общебиологическом принципе иерархической организации регуляции вегетативных функций. Выделены уровни: интегративный, вегетативного обеспечения (осуществляемый автономной нервной системой), органный, периферический (эндотелиально-микроциркуляторный). Заключение. Количественная оценка на интегративном уровне является универсальным показателем эффективности лечения, что открывает возможность создания методологического подхода, основанного на оценке влияния терапевтических воздействий не только на орган- или функцию-мишень, но и на состояние организма как целостной системы. Aim. To create a new methodological approach for determining the effectiveness of antihypertensive therapy in patients with arterial hypertension based on the analysis of violation of mechanisms in the blood pressure (BP) regulation system. Methods. This study included 277 patients (136 males, 141 females) with stage II, grade 1-2 hypertension, risk II, III, aged 58.6±6.4 yrs, with disease duration 7.2±1.4 yrs. The control group included 57 essentially healthy individuals (25 females, 32 males) aged 52.1±4.4 yrs. After screening and obtaining written informed consent, the following monotherapy was prescribed: nebivolol, lisinopril, losartan, indapamide, and amlodipine, plus an unfixed combination of lisinopril and indapamide. Changes in BP indexes at the predetermined levels of the BP regulation system were studied after 6 mos. of treatment. Results. Evaluation of the therapy effectiveness showed that, when BP was stabilized in all six groups at proper values, significant differences were revealed at the integrative regulatory level. When patients were treated with amlodipine, losartan, lisinopril, as well as a combination of lisinopril and indapamide, the regulatory and adaptive capabilities of the body improved. When treated with indapamide, these capabilities were unchanged, and when treated with nebivolol, these capabilities decreased. A new classification of the regulatory levels of BP control in humans is proposed. This classification is based on the general biological principle of hierarchical organization for the regulation of autonomic functions. The following levels are distinguished: integrative, autonomic support, i.e., carried out by the autonomic nervous system, organ, and peripheral, i.e., endothelial-microcirculatory. Conclusion. Quantitative assessment at the integrative level is a universal indicator of the treatment effectiveness. It makes it possible to create a methodological approach to determine possible effectiveness of treatment based on the assessed impact not only on the target organ or function, but also on the status of the body as a whole system.

Optimal Covid-19 Based PD/PID Cascaded Tracking Control for Robot Arm driven by BLDC Motor

This paper presents an efficient covid-19 optimization algorithm to find the optimal values of the PD/PID cascaded controller. The purpose of the control algorithm is to force the link shaft to follow the desired reference position with good accuracy all time. This objective should be achieved for different position/time tracks regardless of load disturbance and parameter variations. This work, simulating how the covid-19 spreads and infects to optimize the parameters of the PD/ PID control. The initial values of PD/PID controller parameters consider the zero patient, which infects new patients (other values of PD/PID controller parameters). The optimization model simulates as accurately as possible the covid-19 activity. The covid-19 has two major advantages compared to other similar strategies. First, the covid-19 parameters are already adjusted according to disease statistics to prevent designers from initializing them with arbitrary values. Second, the approach has the ability to finish after several iterations where the infected population initially grows at an exponential rate. However, after some iterations. The proposed covid-19 was investigated with well-known optimization techniques such as the genetic algorithm (GA) and Harmony Search (HS) optimization. A multi-objective function is used to allow the designer to select the desired rise time, the desired settling time, the desired overshoot, and the desired steady-state error. Several tests have been performed to investigate the obtained proper values of PD/PID controller parameters. In the first test, a step position reference had been applied. In the second test, the continuous change in position reference had been subjected to the robot arm. The results provide that the covid-19 based PD/PID controller has the best performance among other techniques. In addition, the covid-19 based PID controller can track accurately the position command compared to other techniques.

Somatometric method to Assess the Level of high schoolers’ physical Development

Aim: To develop tables to assess the physical development of high schoolers based on the interaction of total physical dimensions. materials and methods: To achieve this goal, we studied the indicators of body length, body weight and chest circumference of 7-17 years old boys (n=1111) and girls (n=1133) of secondary schools in Kyiv (Ukraine). Multiple correlation was used to calculate the interaction of indicators of total physical dimensions, and multiple regression was used to develop gender and age standards of physical development of high schoolers. Results: The tables to assess physical development of high schoolers of a certain gender and age have been developed. The tables contain body length in vertical direction and body weight or chest circumference in horizontal direction, depending on what is needed for determination: the proper values of CC or body weight. The quantitative characteristics of high schoolers with good, excessive, below average and low levels of physical development are presented. Conclusions: Rational organization of physical training of high schoolers is impossible without objective testing of the level of their physical development. Timely corresponding testing is a guarantee in preventing physical strains and health problems.

Effect of raster inclinations and part positions on mechanical properties, surface roughness and manufacturing price of printed parts produced by fused deposition method

Additive manufacturing (AM) technology has the ability to produce parts or products using data from 3D CAD models based on adding material. Fused deposition modeling (FDM) is among the most popular AM technologies wherein the plastic materials like acrylonitrile-butadiene-styrene filaments get added in the form of semi-molten plastic layers from bottom to top to produce the final product. Besides, the merits of using the FDM process, it faces challenges related to strength, dimensional accuracy, surface finish, and so on. The mechanical, tribological, and surface finish of functional parts is an essential consideration in FDM. In this work, the role of process parameters such as the part positions and raster inclinations involved in the manufacturing of parts by FDM has been evaluated experimentally to obtain the desired properties for reducing production time, the quantity of supporting material, and overall cost including maintenance costs. The study revealed that part position is a more significant parameter than the raster inclinations on the surface roughness and mechanical properties of the FDM parts. It also concludes with the proper values of part positions and raster inclinations for achieving optimal mechanical properties, roughness, and manufacturing costs to withstand operating loading conditions.

Vegetation Survival in Green Roofs without Irrigation

The implementation of green roofs as sustainable urban drainage systems provides benefits for stormwater control and the environment and is always more encouraged. In this paper, the estimation of the probability of vegetation survival without irrigation has been proposed as a guide to choose the proper values for the design parameters; in particular the growing medium thickness has been related to the average return interval of the water content at the end of the dry period. Moreover the study represents an improvement of the analytical probabilistic approach since a chain of consecutive rainfall events has been considered, in order to take into account the possibility that the storage capacity is not completely available at the beginning of each event because of the pre-filling from more than one previous rainfall as typically happens for green roofs. Finally, developed equations have been validated by means of their application to two case studies, respectively in northern and southern Italy.