Effects of Surface Rotation on the Phase Change Process in a 3D Complex-Shaped Cylindrical Cavity with Ventilation Ports and Installed PCM Packed Bed System during Hybrid Nanofluid Convection

The combined effects of surface rotation and using binary nanoparticles on the phase change process in a 3D complex-shaped vented cavity with ventilation ports were studied during nanofluid convection. The geometry was a double T-shaped rotating vented cavity, while hybrid nanofluid contained binary Ag–MgO nano-sized particles. One of the novelties of the study wasthat a vented cavity was first used with the phase change–packed bed (PC–PB) system during nanofluid convection. The PC–PB system contained a spherical-shaped, encapsulated PCM paraffin wax. The Galerkin weighted residual finite element method was used as the solution method. The computations were carried out for varying values of the Reynolds numbers (100 ≤ Re ≤ 500),rotational Reynolds numbers (100 ≤ Rew ≤ 500), size of the ports (0.1L1 ≤ di ≤ 0.5L1), length of the PC–PB system (0.4L1 ≤ L0 ≤ L1), and location of the PC–PB (0 ≤ yp ≤ 0.25H). In the heat transfer fluid, the nanoparticle solid volume fraction amount was taken between 0 and 0.02%. When the fluid stream (Re) and surface rotational speed increased, the phase change process became fast. Effects of surface rotation became effective for lower values of Re while at Re = 100 and Re = 500; full phase transition time (tp) was reduced by about 39.8% and 24.5%. The port size and nanoparticle addition in the base fluid had positive impacts on the phase transition, while 34.8% reduction in tp was obtained at the largest port size, though this amount was only 9.5%, with the highest nanoparticle volume fraction. The length and vertical location of the PC–PB system have impacts on the phase transition dynamics. The reduction and increment amount in the value of tp with varying location and length of the PC–PB zone became 20% and 58%. As convection in cavities with ventilation ports are relevant in many thermal energy systems, the outcomes of this study will be helpful for the initial design and optimization of many PCM-embedded systems encountered in solar power, thermal management, refrigeration, and many other systems.

LABORATORY TESTS OF A FOUR-SECTION SEED WHEEL WITH GROOVES IN THE SHAPE OF A PART OF THE ROTATION SURFACE OF A TORUS

В статье рассматривается вопрос повышения качественного показателя посева семян зерновых культур, такого как неустойчивость общего высева и результаты лабораторных исследований экспериментального высевающего аппарата, катушка которого выполнена четырехсекционной, с желобками в форме части поверхности вращения тора. При помощи использования лабораторной установки проведены лабораторные исследования экспериментального высевающего аппарата для нахождения рациональных значений его конструктивных и режимных параметров, необходимых для качественной работы. Получены графические зависимости неустойчивости общего высева от частоты вращения катушки, выполненной четырехсекционной, радиуса образующей части поверхности вращения тора и длины желобка одной секции четырехсекционной катушки. В работе представлены двухмерные сечения графической зависимости, характеризующие неустойчивость общего высева от его конструктивных и режимных параметров экспериментального высевающего аппарата, катушка которого выполнена четырехсекционной, с желобками в форме части поверхности вращения тора, частота вращения катушки, выполненной четырехсекционной, радиус образующей части поверхности вращения тора и длина желобка одной секции четырехсекционной катушки, которые обеспечивают наименьшую неустойчивость общего высева [1, 2]. The article deals with the issue of improving the quality indicator of sowing cereal seeds, such as instability of total sowing and the results of laboratory research of experimental sowing machine, the reel of which is made four-sectional, with grooves in the form of a part of the torus surface rotation. Laboratory researches of experimental sowing machine to find rational values of its design and operating parameters necessary for quality work were carried out using a laboratory set-up. The graphical dependences of instability of total seeding on frequency of rotation of the four-sectional coil, the radius of the forming part of the torus rotation surface and the groove length of one section of the four-sectional wheel were obtained. The paper presents two-dimensional cross-sections of the graphic dependence that characterize the instability of total seeding on its design and operating parameters of the experimental seeding unit, the wheel of which is made four-sectional, with grooves in the form of a part of the torus rotation surface, the rotation frequency of the four-sectional wheel, the radius of the forming part of the torus rotation surface and the groove length of one section of the four-sectional wheel, which provide the lowest instability of the total seeding [1, 2].

Locomotion of the C60-based nanomachines on graphene surfaces

We provide a comprehensive computational characterization of surface motion of two types of nanomachines with four C60 “wheels”: a flexible chassis Nanocar and a rigid chassis Nanotruck. We study the nanocars’ lateral and rotational diffusion as well as the wheels’ rolling motion on two kinds of graphene substrates—flexible single-layer graphene which may form surface ripples and an ideally flat graphene monolayer. We find that the graphene surface ripples facilitate the translational diffusion of Nanocar and Nanotruck, but have little effect on their surface rotation or the rolling of their wheels. The latter two types of motion are strongly affected by the structure of the nanomachines instead. Surface diffusion of both nanomachines occurs preferentially via a sliding mechanism whereas the rolling of the “wheels” contributes little. The axial rotation of all “wheels” is uncorrelated.

Осаждение фторполимерных покрытий на вращающиеся цилиндрические поверхности методом химического осаждения из газовой фазы, активированной горячей нитью

The Hot Wire Chemical Vapor Deposition method has been adapted to deposit fluoropolymer coatings onto rotating cylindrical surfaces with a small radius (less than 20 mm). The effect of the surface rotation frequency on the structure of a thin fluoropolymer coating deposited on it has been investigated. A significant change in the morphology of the formed fluoropolymer coating was found depending on the rotational frequency of the cylindrical surface. One more parameter has been established that makes it possible to change the structure of the formed fluoropolymer coating during the deposition process.

AGE–GENDER DIFFERENCE IN THE PERCEPTION AND MUSCLE RESPONSE THRESHOLDS OF SUPPORT SURFACE ROTATION

Proprioception while standing is important for the balance control, but the proprioception has not been investigated in the unconstrained standing conditions. The purpose of this study was to investigate the effects of age and gender on the thresholds of perception and muscle response in response to the support surface rotation. The experiment was designed so that the thresholds depend mainly on the proprioception, i.e., quasistatic condition (0.2∘/s rotation of the platform) with eyes closed. Fifty-two healthy subjects (half young and half elderly) participated in this study. A platform was developed which can be rotated in four directions. Perception threshold angle was registered from subjects’ pressing a button. Muscle response threshold angle was determined as the earlier onset of EMG in lower limb muscles. Two standing conditions (feet together and natural stance) were tested. Repeated-measures ANOVA showed that both thresholds increased with age. Post hoc tests revealed (1) that the perception threshold was greater for women than men in the elderly and (2) both thresholds of the elderly were greater for the feet-together stance than natural stance. Inferior perception sensitivity of platform rotation in elderly women may be associated with inferior performance in cortical postural control and greater fall ratio compared to elderly men, which suggests the need of proprioception trainings.

Dynamic spinal posture and pelvic position analysis using a rasterstereographic device

Background Until recently, rasterstereographic analysis of the spine was limited to static measurements. However, understanding and evaluating the motion of the spine under dynamic conditions is an important factor in the diagnosis and treatment of spinal pathologies. The aim of this study was to study the spinal posture and pelvic position under dynamic conditions and compare it to static measurements using a dynamic rasterstereographic system. Methods A total of 121 healthy volunteers (56 females; 65 males) were included in this observational study. The parameters trunk inclination, trunk imbalance, pelvic obliquity, kyphotic angle, lordotic angle, surface rotation, and lateral deviation were studied and compared under static and dynamic (1, 2, 4, 5 km/h) conditions using the system “Formetric 4D Motion®“ (DIERS International GmbH, Germany). Results Female volunteers had a higher lordotic angle than males under static conditions (p < 0.001). Trunk inclination (5.31° vs. 6.74°), vertebral kyphotic angle (42.53° vs. 39, 59°), and surface rotation (3.35° vs. 3.81°) increase under dynamic conditions (p < 0.001). Trunk inclination and lordotic angle both show significant changes during walking compared to static conditions (p < 0.001). Conclusion The spinal posture differs between females and males during standing and during walking. Rasterstereography is a valuable tool for the dynamic evaluation of spinal posture and pelvic position, which can also be used to quantify motion in the spine and therefore it has the potential to improve the understanding and treatment of spinal pathologies. Trial registration Retrospectively registered

Asteroseismic sensitivity to internal rotation along the red-giant branch

Context. Transport of angular momentum in stellar interiors is currently not well understood. Asteroseismology can provide us with estimates of internal rotation of stars and thereby advances our understanding of angular momentum transport. Aims. We can measure core-rotation rates in red-giant stars and we can place upper bounds on surface-rotation rates using measurements of dipole (l = 1) modes. Here, we aim to determine the theoretical sensitivity of modes of different spherical degree towards the surface rotation. Additionally, we aim to identify modes that can potentially add sensitivity at intermediate radii. Methods. We used asteroseismic rotational inversions to probe the internal stellar rotation profiles in red-giant models from the base of the red-giant branch up to the luminosity bump. We used the inversion method of multiplicative optimally localised averages to assess how well internal and surface rotation rates can be recovered from different mode sets and different synthetic rotation profiles. Results. We confirm that dipole mixed modes are sufficient to set constraints on the average core-rotation rates in red giants. However, surface-rotation rates estimated with only dipole mixed modes are contaminated by the core rotation. We show that the sensitivity to surface rotation decreases from the base of the red-giant branch until it reaches a minimum at 60–80% of the bump luminosity due to a glitch in the buoyancy frequency. Thereafter, a narrow range of increased surface sensitivity just below the bump luminosity exists. Quadrupole and octopole modes have more sensitivity in the outer parts of the star. To obtain accurate estimates of rotation rates at intermediate radii (i.e. a fractional radius of ∼0.4), acoustic oscillation modes with a spherical degree of l ≈ 10 are needed. Conclusions. We find a minimum and subsequent maximum in the sensitivity to the surface rotation rate in red giants below the luminosity bump. Furthermore, we show that, if observed, quadrupole and octopole modes enable us to distinguish between differential and solid body rotation in the convection zone. This will be important when investigating the transport of angular momentum between the core and the envelope.