scholarly journals Migration Behavior of Low-Density Particles in Lab-on-a-Disc Devices: Effect of Walls

Micromachines ◽  
2021 ◽  
Vol 12 (9) ◽  
pp. 1032
Author(s):  
Vyacheslav R. Misko ◽  
Agata Kryj ◽  
Aude-Muriel Tamandjo Ngansop ◽  
Sogol Yazdani ◽  
Matthieu Briet ◽  
...  
Keyword(s):  
Centrifugal Force ◽  
Radial Direction ◽  
Tangential Direction ◽  
Equation Of Motion ◽  
Model System ◽  
Migration Behavior ◽  
Angular Rotation ◽  
System Of Particles ◽  
Euler Force ◽  
Lateral Walls

The effect of the lateral walls of a Lab-On-a-Disc device on the dynamics of a model system of particles with a density lower than that of the solvent (modelling parasites eggs) is analyzed theoretically and experimentally. In the absence of lateral walls, a particle always moves in the direction of the centrifugal force, while its trajectory is deflected in the tangential direction by the inertial Coriolis and Euler forces. Lateral walls, depending on the angle forming with the radial direction, can guide the particle either in the same or in the opposite direction to the centrifugal force, thus resulting in unusual particle trajectories including zig-zag or backwards particle motion. The effect is pronounced in the case of short operation times when the acceleration of the angular rotation, and thus the Euler force, is considerable. The predicted unusual motion is demonstrated by numerically solving the equation of motion in the presence of lateral walls and verified in the experiment with particles of density lower than that of the solvent. Our analysis is useful for design and operational considerations of Lab-On-a-Disc devices aiming for or involving (bio)particle handling.

Cell grouping and primary wall generations in the cambial zone, xylem, and phloem in Pinus

1968 ◽  
Vol 16 (2) ◽  
pp. 177 ◽  
Author(s):  
A Mahmood
Keyword(s):  
Cell Division ◽  
Mother Cell ◽  
Secondary Wall ◽  
Radial Direction ◽  
Cell Plate ◽  
Tangential Direction ◽  
Primary Wall ◽  
Photographic Evidence ◽  
Secondary Wall Deposition ◽  
Cambial Zone

The use of the term cambium, or equivalent terms, in modern literature is discussed. The term cambial zone adopted in this paper includes the cambial initial and the dividing and enlarging cells. The tissue mother cell produced at each division of the initial produces a group of four cells in xylem or two cells in phloem. Theoretical constructs have been made for xylem and phloem production by associating the concepts that xylem and phloem are produced in alternate series of initial divisions and that a new primary wall is deposited around each daughter protoplast at each cell division. Correlations are derived from the theoretical constructs for the thickness of primary wall layers lying in the tangential direction and of those lying in the radial direction at progressive histological levels. Deductions from theoretical constructs are made when the initial is producing xylem, when it changes its polarity from xylem to phloem production, and when the reverse change occurs. Most of the theoretical deductions are supported by photographic evidence. The chief point of this study is the demonstration of generations (multiplicity) of primary parental walls. The term intercellular material proposed in this paper includes the cell plate plus any remnants of ancestral primary walls between the current primary walls surrounding the adjacent protoplasts. This term is still applicable to cells where secondary wall deposition is taking place or has been completed.

scholarly journals Physical properties of sessile oak (quercus petraea l) used by the wood industry in Kosovo

2020 ◽  
Vol 2 (7) ◽  
pp. 278-285
Author(s):  
Rrahim Sejdiu ◽  
Florit Hoxha ◽  
Bujar Jashari ◽  
Lulzim Idrizi
Keyword(s):  
Specific Gravity ◽  
Moisture Content ◽  
Physical Properties ◽  
Radial Direction ◽  
Tangential Direction ◽  
Quercus Petraea ◽  
Sessile Oak ◽  
Content Ratio ◽  
Wet Condition ◽  
Shrinkage Coefficient

The paper shows some physical properties of sessile oak obtained in Kosovo regions. In the study are shown: wood shrinkage, specific gravity, shrinkage coefficient for 1% change of moisture content, ratio of shrinkage in tangential and radial direction etc. The amount of volumetric shrinkage of sessile oak is 15.95%, heartwood part has an average shrinkage 15.41% in The shrinkage of sapwood part is 17.56%. Specific gravity at: wet condition: (1.013gr/cm3); 12% (0.853gr/cm3) and 0% (0.826gr/cm3) of moisture content. Specific gravity of heartwood at: wet condition (1.05gr/cm3); 12% (0.88gr/cm3); 0% (0.85gr/cm3). The specific gravity of sapwood at: wet condition (0.91gr/cm3); 12% (0.77gr/cm3); 0% (0.748gr/cm3). The ratio of average shrinkage between tangential and radial cutting direction is 1.71%. This ratio was significantly higher in sapwood than heartwood. Coefficient of shrinkage (changing 1% of moisture content) in the radial direction is 0.00196, and 0.00323 in tangential direction.  

Dynamics of a Continuous System With Clearance and Motion Limiting Stops

1999 ◽  
Author(s):  
P. Metallidis ◽  
S. Natsiavas
Keyword(s):  
Piecewise Linear ◽  
Research Work ◽  
Continuous System ◽  
Continuous Model ◽  
Equation Of Motion ◽  
Model System ◽  
Periodic Motions ◽  
System Parameters ◽  
Rigid Rods ◽  
The Stability

Abstract The present study generalises previous research work on the dynamics of discrete oscillators with piecewise linear characteristics and investigates the response of a continuous model system with clearance and motion-limiting constraints. More specifically, in the first part of this work, an analysis is presented for determining exact periodic response of a periodically excited deformable rod, whose motion is constrained by a flexible obstacle. This methodology is based on the exact solution form obtained within response intervals where the system parameters remain constant and its behavior is governed by a linear equation of motion. The unknowns of the problem are subsequently determined by imposing an appropriate set of periodicity and matching conditions. The analytical part is complemented by a suitable method for determining the stability properties of the located periodic motions. In the second part of the study, the analysis is applied to several cases in order to investigate the effect of the system parameters on its dynamics. Special emphasis is placed on comparing these results with results obtained for similar but rigid rods. Finally, direct integration of the equation of motion in selected areas reveals the existence of motions, which are more complicated than the periodic motions determined analytically.

Material point method simulations of transverse fracture in wood with realistic morphologies

Holzforschung ◽  
2007 ◽  
Vol 61 (4) ◽  
pp. 375-381 ◽  
Author(s):  
John A. Nairn
Keyword(s):  
Crack Propagation ◽  
Radial Direction ◽  
Material Point Method ◽  
Tangential Direction ◽  
Solid Wood ◽  
Material Point ◽  
Point Method ◽  
Complex Geometries ◽  
Transverse Fracture ◽  
Material Points

Abstract A new numerical method called the material point method (MPM) is well suited for modeling problems with complex geometries and with crack propagation in arbitrary directions. In this paper, these features of MPM were used to simulate transverse fracture in solid wood. The simulations were run on the scale of growth rings. The ease with which MPM handles complex geometries was helpful for modeling realistic morphologies of earlywood and latewood. Because MPM discretizes a body into material points, it was possible to go directly from a digital image of wood to a numerical model by assigning the location and properties of material points based on the intensity or color of pixels in an image. Because the description of cracks in MPM is meshless, it can handle a variety of crack propagation and direction criteria and can simulate complex crack paths that are a consequence of the morphology of the specimen. MPM simulations were run for cracks in the radial direction, the tangential direction, and at two angles to the radial direction. The specimens were loaded by axial displacement or by wedge opening. The MPM simulations fully included contact effects during wedge loading. Finally, the potential for coupling such simulations to new experiments as a tool for characterization of wood is discussed.

Mechanical Model of Non-Magnetic Particles Centrifugal Separation in Magnetic Fluid

2013 ◽  
Vol 820 ◽  
pp. 225-228
Author(s):  
Tong Li ◽  
Jing Tao Wei ◽  
Ji Li
Keyword(s):  
Centrifugal Force ◽  
Magnetic Fluid ◽  
Mechanical Model ◽  
Radial Direction ◽  
Magnetic Particles ◽  
Axial Direction ◽  
Separation Mechanism ◽  
Centrifugal Separation

It is difficult to sort fine non-magnetic particles only by the buoyancy of magnetic fluid. Therefore, based on the magneto hydrostatic separation, the centrifugal separation under the condition of centrifugal force would be an effective method to improve the efficiency. By establishing the mechanical model of centrifugal separation in magnetic fluid, this paper analyzes the kinematical equations of non-magnetic particles in three directionstangential direction, radial direction, and axial direction, and then theoretically explores the separation mechanism of this method.

Experimental Investigation of Water Soaked Wood at Uniaxial and Biaxial States of Stress

1995 ◽  
Vol 48 (10) ◽  
pp. 684-688 ◽  
Author(s):  
M. Kowal ◽  
S. J. Kowalski
Keyword(s):  
Experimental Investigation ◽  
Stress State ◽  
Moisture Content ◽  
Radial Direction ◽  
Tangential Direction ◽  
Biaxial Stress ◽  
Growth Rings ◽  
Significant Difference ◽  
Free Swelling

It is possible to observe a significant difference in swelling strains of unstressed and stressed water soaked wood. This paper points out that the swelling strains depend not only on the magnitude of stress in wood but also on the kind of stress state. Our main aim is to investigate the relation between various states of stress and the swelling strains in water soaked wood. Three different states of stress are studied: tension in the radial direction, compression in the tangential direction with respect to the growth rings, and both these stresses acting together (biaxial stress). Some weighty conclusions follow from the investigations. The main one is that, although the mechanical strains alone are negligibly small compared to the free swelling strains, the coupled mechanical-swelling strains, being a function of the stress state and the moisture content, have a great significance in total strains of water soaked wood.

Fabrication of Metal-Based Functionally Graded Grinding Wheel by a Centrifugal Mixed-Powder Method

2012 ◽  
Vol 706-709 ◽  
pp. 661-666 ◽  
Author(s):  
Eri Miura-Fujiwara ◽  
Hisashi Sato ◽  
Motoko Yamada ◽  
Yoshimi Watanabe
Keyword(s):  
Centrifugal Force ◽  
Alloy System ◽  
Functionally Graded ◽  
Grinding Wheel ◽  
Migration Behavior ◽  
Mixed Powder ◽  
Cross Sectional ◽  
Diamond Grinding Wheel ◽  
Powder Method ◽  
Diamond Grinding

Metal-bonded diamond grinding wheel was fabricated by a centrifugal mixed-powder method. The centrifugal mixed-powder method is a novel and effective casting process to obtain functionally graded material (FGM). At the beginning, we performed fundamental experiments using Al-Si alloy system for the purpose of knowing the migration behavior of mixed-powder under centrifugal force. Al-Si hypereutectic alloyed-powder or mixed-powder of Al and Si particles was placed into the mold, and then Al molten metal was cast under a centrifugal force. Cross sectional microstructure observation and quantitative analysis of Si content were conducted using an electron probe microanalyzer. Amount of Si decreased with receding from a mixed-powder region. Si concentration gradient in the sample fabricated Al-Si powder was smaller than the one fabricated using mixed-powder of Al and Si particles. Subsequently, φ 20 mm Cu/diamond grinding wheel was fabricated by the casting method. Graded diamond distribution was successfully obtained.

Tooth Cutting Method of Face Gear by Using CNC-Hobbing Machine

1992 ◽  
Author(s):  
Harumi Ishii ◽  
Shigeyoshi Nagata
Keyword(s):  
Processing Time ◽  
General Type ◽  
Radial Direction ◽  
Tangential Direction ◽  
View Point ◽  
Face Gear ◽  
Cutting Method ◽  
Cutting Resistance ◽  
Latent Ability ◽  
Tooth Cutting

Abstract At present, the research on a gear having special tooth profile a using CNC hobbing machine have been making progress. However, the method of tooth cutting with using CNC hobbing machine is not used the full for an inherent ability of itself. From the aforementioned view point, we have tried to test cut a face gear which is used an inherent latent ability of the CNC hobbing machine. The unipurpose device has been manufactured for the purpose of improving aforementioned defects of conventional tooth cutting method. Then we have used a fly tool instead of an unipurpose hob cutter. In general, a helicon gear has been cut by unipurpose hob cutter, giving vertical feed with using general type hobbing machine. In this way, not only the tooth roughness decreases, but also processing time increases for the tooth cutting because the size of cut has to be made very small due to heavy cutting resistance. In our research, the unipurpose device is attached to the CNC hobbing machine. Then a fly tool already located on the final point of full depth, translates along the tangential direction of the gear from an appointed position in the radial direction. In this way, we can expect the cutting resistance to be reduced during manufacture. Also the tooth roughness will be improved.

CENTRIFUGAL IMPULSE AS COORDINATE IN THE TABARROKIAN FORMULATION

1995 ◽  
Vol 19 (3) ◽  
pp. 261-269
Author(s):  
F.P.J. Rimrott ◽  
W.M. Szczygielski
Keyword(s):  
Kinetic Energy ◽  
Potential Energy ◽  
Centrifugal Force ◽  
Nonholonomic Constraint ◽  
Lagrange Equation ◽  
Equations Of Motion ◽  
Essential Elements ◽  
Model System ◽  
The Other ◽  
Generalized Displacements

While the well-known conventional Lagrange equation, based on kinetic coenergy and potential energy, uses generalized displacements of the inertia (mass) elements of a system as coordinates, the complementary alternative or Tabarrok formulation, is based on kinetic energy and potential coenergy, and uses as coordinates the generalized impulses of the system’s force (spring) elements. A model system specifically selected to be as simple as possible, yet to contain all essential elements for an illustration of the application of the Tabarrokian approach for the case where a centrifugal force is present, has been devised to show that the centrifugal impulse appears as additional coordinate for the complementary Lagrangian, and that the system turns out to be non-Tabarrokian. It is then shown that the centrifugal impulse is related to the other impulse coordinates by a nonholonomic constraint. Eventually the compatibility equations of motion for the model system are obtained.

Studies about the Influence Factors on Ultrasonic Velocity of Domestic Red Pine

2006 ◽  
Vol 321-323 ◽  
pp. 1177-1181 ◽  
Author(s):  
So Ra Han ◽  
Chun Young Park ◽  
Young Geun Eom ◽  
Jun Jae Lee
Keyword(s):  
Ultrasonic Velocity ◽  
Radial Direction ◽  
Influence Factors ◽  
Tangential Direction ◽  
Red Pine ◽  
Normal Wood ◽  
Reaction Wood ◽  
Decayed Wood ◽  
Effect Factors ◽  
Factors Influencing

This research was carried out to grasp the factors influencing to the ultrasonic velocity to improve the efficiency of the ultrasonic wave test using as the method of NDE of wood. However, it was difficult to detect the defect of wood accurately, because ultrasonic velocity is influenced by various factors. So, some effect factors, which were not concerned with decay, were confirmed at first. Therefore, in this research, we tried to find the factors which affect on the natural characters and the ultrasonic velocity at decayed wood, additionally, we tried an anatomic experiment and analyze. As a result of research, the velocity at radial direction was faster than that at tangential direction and the ultrasonic velocity at immature wood and reaction wood was slower than that at normal wood. And the ultrasonic velocity was more the slower at bigger the length of decay and reduction of weight.

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