scholarly journals Rotational Doppler cooling and heating

2021 ◽  
Vol 7 (2) ◽  
pp. eabd6705
Author(s):  
Deng Pan ◽  
Hongxing Xu ◽  
F. Javier García de Abajo
Keyword(s):  
Rotational Motion ◽  
Chiral Symmetry Breaking ◽  
Strong Dependence ◽  
Translational Motion ◽  
Particle Morphology ◽  
Laser Cool ◽  
Solid Particles ◽  
Linearly Polarized ◽  
Geometrically Constrained ◽  
Doppler Cooling

Doppler cooling is a widely used technique to laser cool atoms, molecules, and nanoparticles by exploiting the Doppler shift associated with translational motion. The rotational Doppler effect arising from rotational coordinate transformation should similarly enable optical manipulation of the rotational motion of nanosystems. Here, we show that rotational Doppler cooling and heating (RDC and RDH) effects embody rich and unexplored physics, including an unexpected strong dependence on particle morphology. For geometrically constrained particles, cooling and heating are observed at red- or blue-detuned laser frequencies relative to particle resonances. In contrast, for nanosystems that can be modeled as solid particles, RDH appears close to resonant illumination, while detuned frequencies produce cooling of rotation. We further predict that RDH can lead to optomechanical spontaneous chiral symmetry breaking, where an achiral particle under linearly polarized illumination starts spontaneously rotating. Our results open up new exciting possibilities to control the rotational motion of nanosystems.

Contamination of the intake air of internal combustion engines of motor vehicles

2021 ◽  
Vol 70 (2) ◽  
pp. 35-64
Author(s):  
Sebastian Dominik Dziubak
Keyword(s):  
Air Pollution ◽  
Internal Combustion Engines ◽  
Strong Dependence ◽  
Road Dust ◽  
Volcanic Eruptions ◽  
Internal Combustion ◽  
Solid Particles ◽  
Dust Concentration ◽  
Combustion Engines ◽  
Atmospheric Air

The paper presents the composition of atmospheric air as a mixture of gases that make up the solid and variable components, and the definitions of air pollutants are referenced. Gaseous and solid pollutants (dust) of the atmospheric air have been defined. Dusts were divided according to various criteria and their properties were given. Exemplary courses of immission of the fraction of solid particles are given, indicating a strong dependence of the immission on the seasons, days of the week and day and night. The sources and characteristics of artificial and natural pollutants in the atmospheric air are presented. It has been shown that the main sources of anthropogenic pollution in addition to industry and the automotive industry. Cars are a source of gaseous and particulate pollutants PM, and they also emit pollution from brake and clutch lining wear, as well as from tire and road wear. The main sources of natural air pollution were discussed, including volcanic eruptions, fires in landfills, forests, steppes and sand storms, as well as mineral dust (road dust) carried from the ground by vehicles. The properties of road dust are discussed: chemical and fractional composition, density, dust concentration in the air. It has been shown that the two basic components of the dust, silica and corundum, whose share in dust reaches 95%, also have the highest hardness, which may have a decisive influence on the wear of engine components. Various valuesof dust concentration in the air were presented depending on the type and condition of the ground and the conditions of use of vehicles. Keywords: mechanical engineering, internal combustion engines, air pollution sources, road dust

Electro-optical property of polymerized liquid crystal devices using linearly polarized UV irradiation

2021 ◽  
Author(s):  
Masahiro Ito ◽  
Kazuma Kajiwara ◽  
Kohki Takatoh
Keyword(s):  
Liquid Crystal ◽  
Uv Light ◽  
Strong Dependence ◽  
Fast Response ◽  
Alignment Layer ◽  
Liquid Crystal Devices ◽  
Decay Times ◽  
Linearly Polarized ◽  
Reactive Mesogens ◽  
Strong Anchoring

Abstract Display characteristics have a fairly strong dependence on the configuration of the liquid crystal (LC) molecules and interactions between the LC molecules and the alignment layer surface. To obtain LC devices with a fast response, the usage of reactive mesogens (RMs) have been studied. RMs polymerize in the vicinity of the alignment layer. We assessed the effectiveness of linearly polarized UV light for polymer formation. Three kinds of UV light, namely (i)non-polarized (ii)parallel to, and (iii)perpendicular to the rubbing direction, were used to irradiate LC cells with RM concentrations of 5wt% and 10wt%. For both RM concentrations, LC devices using LPUV parallel to the rubbing direction yielded the shortest decay times. SEM observation revealed that the fibrils polymerized linearly in the same direction on using LPUV parallel to the rubbing direction. The decay time was presumably shortened by the strong anchoring force and high alignment ability of the linear fibrils.

scholarly journals Probing roto-translational diffusion of small anisotropic colloidal particles with a bright-field microscope

2021 ◽  
Vol 44 (4) ◽  
Author(s):  
Fabio Giavazzi ◽  
Antara Pal ◽  
Roberto Cerbino
Keyword(s):  
Particle Size ◽  
Rotational Motion ◽  
Colloidal Particles ◽  
Aqueous Suspension ◽  
Translational Motion ◽  
Translational Diffusion ◽  
Experimental Demonstration ◽  
Bright Field ◽  
Microscopic Scale ◽  
Bright Field Microscopy

Abstract Soft and biological materials are often composed of elementary constituents exhibiting an incessant roto-translational motion at the microscopic scale. Tracking this motion with a bright-field microscope becomes increasingly challenging when the particle size becomes smaller than the microscope resolution, a case which is frequently encountered. Here we demonstrate squared-gradient differential dynamic microscopy (SG-DDM) as a tool to successfully use bright-field microscopy to extract the roto-translational dynamics of small anisotropic colloidal particles, whose rotational motion cannot be tracked accurately in direct space. We provide analytical justification and experimental demonstration of the method by successful application to an aqueous suspension of peanut-shaped particles. Graphic abstract

scholarly journals Diffusion in the aqueous compartment.

1984 ◽  
Vol 99 (1) ◽  
pp. 180s-187s ◽  
Author(s):  
A M Mastro ◽  
A D Keith
Keyword(s):  
Rotational Motion ◽  
Spin Label ◽  
Mammalian Cells ◽  
Translational Motion ◽  
Diffusion Constant ◽  
Rotational Correlation Time ◽  
Model Systems ◽  
Quiescent Cells ◽  
Spin Resonance ◽  
In Cells

Measurements of diffusion of molecules in cells can provide information about cytoplasmic viscosity and structure. In a series of studies electron-spin resonance was used to measure the diffusion of a small spin label in the aqueous cytoplasm of mammalian cells. Translational and rotational motion were determined from the same spectra. Based on measurements made in model systems, it was hypothesized that calculations of the apparent viscosity of the cytoplasm from both rotational and translational motion would distinguish between the effects of viscosity and structure on diffusion. The diffusion constant measured in several cell lines averaged 3.3 X 10(-6) cm2/s. It was greater in growing cells and in cells treated with cytochalasin B than in quiescent cells. The viscosity of the cytoplasm calculated from the translational diffusion constant or the rotational correlation time was 2.0-3.0 centipoise, about two to three times that of the spin label in water. Therefore, over the dimensions measured by the technique, 50-100 A, solvent viscosity appears to be the major determinant of particle movement in cells under physiologic conditions. However, when cells were subjected to hypertonic conditions, the translational motion of the spin label decreased threefold, whereas the rotational motion changed by less than 20%. These data suggest that the decrease in cell volume under hypertonic conditions is accompanied by an increase in cytoplasmic barriers and a decrease in the space between existing cytoplasmic components without a significant increase in viscosity in the aqueous phase. In addition, a comparison of reported diffusion values of a variety of molecules in water and in cells indicates that cytoplasmic structure plays an important role in the diffusion of proteins such as bovine serum albumin.

On the Motion of Solid Spheres Falling Through Viscous Fluids in Vertical and Inclined Tubes

1992 ◽  
Vol 114 (1) ◽  
pp. 2-11 ◽  
Author(s):  
Joseph A. C. Humphrey ◽  
Hiroyuki Murata
Keyword(s):  
Inclination Angle ◽  
Rotational Motion ◽  
Lift Force ◽  
Tube Wall ◽  
Translational Motion ◽  
Creeping Flow ◽  
Viscous Fluids ◽  
Rotation Direction ◽  
Concentric Spheres ◽  
Inclined Tube

Little is known about the rotational motion of spheres falling through viscous fluids in inclined tubes. Most studies have investigated translational and rotational motions in vertical tubes. These works show that in creeping flow a sphere’s translational and rotational velocities are independent. Rotation is predicted and observed for eccentric spheres while concentric spheres fall without rotation. Experiments were performed by us with steel spheres of radius r falling through glycerine in a tube of variable inclination angle and of radius R such that r/R = 0.882, 0.757, 0.442. For the cases involving two or three spheres falling together various modes of motion were observed. Especially interesting was the finding that the rotation direction of a sphere gradually changes from positive (opposite to downhill rolling) to negative (in the sense of downhill rolling) as the tube inclination angle is increased. This is allowed by the inertia-induced lift force which maintains a sphere at a very small but finite distance from the inclined tube wall. However, by further increasing the inclination angle the lift force eventually becomes smaller than the apparent weight of the sphere which, upon finally contacting the tube wall, descends by rolling along it. Examination of our findings in the light of earlier results for vertical and inclined tubes suggests that, through its effect on sphere eccentricity, inertia indirectly affects the rotational motion of a falling sphere when Rep10−3 but it does not significantly affect the translational motion when Rep<1. None of the inclined tube studies performed to date has been completely devoid of inertia-induced lift effects.

scholarly journals ISAR Autofocus Imaging Algorithm for Maneuvering Targets Based on Phase Retrieval and Keystone Transform

2019 ◽  
Vol 2019 ◽  
pp. 1-11 ◽  
Author(s):  
Hongyin Shi ◽  
Ting Yang ◽  
Yue Liu ◽  
Jingjing Si
Keyword(s):  
Rotational Motion ◽  
Phase Retrieval ◽  
Translational Motion ◽  
Retrieval Algorithm ◽  
Imaging Method ◽  
Keystone Transform ◽  
Maneuvering Targets ◽  
Coherent Integration ◽  
Motion Parameters ◽  
Phase Retrieval Algorithm

In the current scenario of high-range resolution radar and noncooperative target, the rotational motion parameters of the target are unknown and migration through resolution cells (MTRC) is apparent in the obtained inverse synthetic aperture radar (ISAR)images, in both slant-range and cross-range directions. In the case of the high-speed maneuvering target with a small value of rotation, the phase retrieval algorithm can be applied to compensate for the translational motion to form an autofocusing image. However, when the target has a relatively large rotation angle during the coherent integration time, phase retrieval method cannot get an acceptable image for viewing and analysis as the location of the scatterer will not be true due to the Doppler shift imposed by the target’s rotational motion. In this paper, a novel ISAR imaging method for maneuvering targets based on phase retrieval and keystone transform is proposed, which can effectively solve the above problems. First, the keystone transform is used to solve the MTRC effects caused by the rotation component. Next, phase errors caused by the remaining translational motion will be removed by employing phase retrieval algorithm, allowing the scatterers are always kept in their range cells. Finally, the Doppler frequency shifts of scatterers will be time invariant in the phase of the received signal. Furthermore, this approach does not need to estimate the motion parameters of the target, which simplifies the processing steps. The simulated results demonstrate the validity of this method.

FLIGHT SIMULATIONS OF A TWO-DIMENSIONAL FLAPPING WING BY THE IB-LBM

2013 ◽  
Vol 25 (01) ◽  
pp. 1340020 ◽  
Author(s):  
YUSUKE KIMURA ◽  
KOSUKE SUZUKI ◽  
TAKAJI INAMURO
Keyword(s):  
Rotational Motion ◽  
Lattice Boltzmann ◽  
Translational Motion ◽  
Reynolds Numbers ◽  
Flapping Wings ◽  
Immersed Boundary ◽  
High Reynolds ◽  
The Stability ◽  
Boltzmann Method ◽  
Flight Simulations

The stability of flight by flapping wings is investigated by using the immersed boundary-lattice Boltzmann method (IB-LBM). First, the rotational motion with an initial small disturbance is computed, and it is found that the rotational motion is unstable for high Reynolds numbers. Second, we show simple ways to control the rotational and translational motion by bending or flapping the tip of the wing.

A Dynamic Model of a Concentric LADD Actuator

1983 ◽  
Vol 105 (3) ◽  
pp. 157-164 ◽  
Author(s):  
K. L. Pottebaum ◽  
J. J. Beaman
Keyword(s):  
Dynamic Model ◽  
Rotational Motion ◽  
Dynamic Models ◽  
Translational Motion ◽  
Bond Graph ◽  
Second Order ◽  
Sixth Order ◽  
Order Model ◽  
Lumped Parameter ◽  
Elasticity Effects

A LADD actuator is a device capable of converting rotational motion to translational motion and has potential for use in manipulators, robotics, and prosthetics. Two low order lumped parameter dynamic models of a concentric LADD actuator have been formulated and experimentally verified. The sixth order model includes elasticity effects while the second order model does not. Both of these models are presented in bond graph terminology in order to ease their use in overall system models.

scholarly journals Numerical Simulation of Fluid Flows in Rotary Discs

2020 ◽  
Author(s):  
Dragan Mandić ◽  
◽  
◽  
Keyword(s):  
Rotational Motion ◽  
Initial Conditions ◽  
Translational Motion ◽  
Fluid Motion ◽  
Fluid Flows ◽  
Fluid Stream ◽  
Rotary Disk ◽  
Complex Fluid ◽  
Flow Diagrams ◽  
Rotating Bodies

The object of this paper is to model the complex fluid motion that is caused by the rotational motion of rotary disks. In doing so, the rotary disk occupied a normal or parallel position with respect to the fluid flow axis. Various designs of rotary bodies were also applied, with the introduction of fluid through the central opening inside the impeller of the rotating bodies and with the introduction of fluid on the outer surfaces of these impellers (surfaces limited by the largest diameters of the rotary discs). During the modeling, different initial conditions for different structures and positions of rotating bodies were adopted. For each individual stream, flow diagrams are given through a cylindrical fluid stream whose translational motion is complicated by the rotational motion of the friction disks in its flow. The results obtained give a clear picture of the disturbances and changes in the front of the fluid motion wave which can be used as a necessary experience in the design of circulating technological systems.

Dry Deposition of Atmospheric Aerosols: Approaches, Observations, and Mechanisms

2021 ◽  
Vol 72 (1) ◽  
Author(s):  
Delphine K. Farmer ◽  
Erin K. Boedicker ◽  
Holly M. DeBolt
Keyword(s):  
Atmospheric Aerosols ◽  
Dry Deposition ◽  
Strong Dependence ◽  
Solid Particles ◽  
Annual Review ◽  
Publication Date ◽  
New Techniques ◽  
Radiative Balance ◽  
Aerosol Sources ◽  
Aerosol Instrumentation

Aerosols are liquid or solid particles suspended in the atmosphere, typically with diameters on the order of nanometers to microns. These particles impact air quality and the radiative balance of the planet. Dry deposition is a key process for the removal of aerosols from the atmosphere and plays an important role in controlling the lifetime of atmospheric aerosols. Dry deposition is driven by turbulence and shows a strong dependence on particle size. This review summarizes the mechanisms behind aerosol dry deposition, including measurement approaches, field observations, and modeling studies. We identify several gaps in the literature, including deposition over the cryosphere (i.e., snow and ice surfaces) and the ocean; in addition, we highlight new techniques to measure black carbon fluxes. While recent advances in aerosol instrumentation have enhanced our understanding of aerosol sources and chemistry, dry deposition and other loss processes remain poorly investigated. Expected final online publication date for the Annual Review of Physical Chemistry, Volume 72 is April 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

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