scholarly journals Effect of Microneedle Cross-Sectional Shape on Puncture Resistance – Investigation of Polygonal and Star-Shaped Cross Sections –

2020 ◽  
Vol 32 (2) ◽  
pp. 371-381
Author(s):  
Seiji Aoyagi ◽  
Kento Okuda ◽  
Tomokazu Takahashi ◽  
Masato Suzuki ◽  
◽  
...  
Keyword(s):  
Cross Sections ◽  
Frictional Resistance ◽  
Needle Insertion ◽  
Medical Field ◽  
Cross Sectional ◽  
Puncture Resistance ◽  
Laser Lithography ◽  
Maximum Resistance ◽  
Sharp Edges ◽  
Sectional Shape

The shape of the needle tip that is currently used in the medical field is a “lancet point,” which is a diagonally cut cylindrical pipe, further cut on both sides. The shape of the needle shank is typically cylindrical. In this paper, tip and shank shapes that differ from the standard shape are experimentally investigated for the purpose of reducing puncture resistance. Microneedles of various cross-sectional shapes, such as polygonal and star-like, were fabricated using stereo laser lithography. Before the needle penetrates the skin, sharp edges at the needle tip may be effective to generate a stress concentration on the skin, inducing a skin fracture. After the needle penetrates the skin, corners in the cross section of the needle shank may effectively reduce the frictional resistance because the contact area between the skin and needle is limited at the corners. A needle insertion experiment was conducted against an artificial skin made of polydimethylsiloxane. The puncture resistance decreased respectively for the circular needle, polygonal needle, and star-shaped needle. For the star-shaped needles, the maximum resistance decreased as the number of corners (N) decreased. For the polygonal needle, the maximum resistance increased as N increased from 3 to 5; however, there was no observable difference for N from 6 to 8. The experimental results show that a triangular star-shaped microneedle is the most effective in reducing the puncture resistance.

Automated 3D measurement of fiber cross section morphology in handsheets

2012 ◽  
Vol 27 (2) ◽  
pp. 264-269 ◽  
Author(s):  
Christian Lorbach ◽  
Ulrich Hirn ◽  
Johannes Kritzinger ◽  
Wolfgang Bauer
Keyword(s):  
Image Analysis ◽  
Cross Section ◽  
Cross Sections ◽  
Image Plane ◽  
3D Measurement ◽  
Cross Sectional ◽  
Fiber Cross Section ◽  
Fiber Wall ◽  
Sectional Shape ◽  
Cross Section Geometry

Abstract We present a method for 3D measurement of fiber cross sectional morphology from handsheets. An automated procedure is used to acquire 3D datasets of fiber cross sectional images using an automated microtome and light microscopy. The fiber cross section geometry is extracted using digital image analysis. Simple sample preparation and highly automated image acquisition and image analysis are providing an efficient tool to analyze large samples. It is demonstrated that if fibers are tilted towards the image plane the images of fiber cross sections are always larger than the true fiber cross section geometry. In our analysis the tilting angles of the fibers to the image plane are measured. The resulting fiber cross sectional images are distorted to compensate the error due to fiber tilt, restoring the true fiber cross sectional shape. We use an approximated correction, the paper provides error estimates of the approximation. Measurement results for fiber wall thickness, fiber coarseness and fiber collapse are presented for one hardwood and one softwood pulp.

scholarly journals On the effect of cross sectional shape on incipient motion and deposition of sediments in fixed bed channels

2014 ◽  
Vol 62 (1) ◽  
pp. 75-81 ◽  
Author(s):  
Mir-Jafar-Sadegh Safari ◽  
Mirali Mohammadi ◽  
Golezar Gilanizadehdizaj
Keyword(s):  
Cross Sections ◽  
Research Work ◽  
Fixed Bed ◽  
Deposition Condition ◽  
Incipient Motion ◽  
Rigid Boundary ◽  
Cross Sectional ◽  
Motion Equations ◽  
Sectional Shape ◽  
Minimum Velocity

Abstract The condition of incipient motion and deposition are of the essential issues for the study of sediment transport. This phenomenon is of great importance to hydraulic engineers for designing sewers, drainage, as well as other rigid boundary channels. This is a study carried out with the objectives of describing the effect of cross-sectional shape on incipient motion and deposition of particles in rigid boundary channels. In this research work, the experimental data given by Loveless (1992) and Mohammadi (2005) are used. On the basis of the critical velocity approach, a new incipient motion equation for a V-shaped bottom channel and incipient deposition of sediment particles equations for rigid boundary channels having circular, rectangular, and U-shaped cross sections are obtained. New equations were compared to the other incipient motion equations. The result shows that the cross-sectional shape is an important factor for defining the minimum velocity for no-deposit particles. This study also distinguishes incipient motion of particles from incipient deposition for particles. The results may be useful for designing fixed bed channels with a limited deposition condition.

Enamel Crystal Shape: History of an Idea

1987 ◽  
Vol 1 (2) ◽  
pp. 322-329 ◽  
Author(s):  
H. Warshawsky
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Cross Sections ◽  
Three Dimensional ◽  
Unit Cell ◽  
Cross Sectional ◽  
Transmission Electron ◽  
History Of ◽  
Sectional Shape ◽  
Imaging Plane

The purpose of this paper is to review evidence which casts doubt on the interpretation universally applied to hexagonal images seen in sectioned enamel. The evidence is based on two possible models to explain the hexagonal profiles seen in mammalian enamel with transmission electron microscopy. The "hexagonal ribbon" model proposes that hexagonal profiles are true cross-sections of elongated hexagonal ribbons. The "rectangular ribbon" model proposes that hexagonal profiles are caused by three-dimensional segments that are parallelepipeds contained in the Epon section. Since shadow projections of such rectangular segments give angles that are inconsistent with the hexagonal unit cell, a model based on ribbons with rhomboidal cut ends and angles of 60 and 120° is proposed. The "rhomboidal ribbon" model projects shadows with angles that are predicted by the unit cell. It is suggested that segments of such crystallites in section project as opaque hexagons on the imaging plane in routine transmission electron microscopy. Morphological observations on crystallites in sections - together with predictions from the hexagonal, rectangular, and rhomboidal ribbon models - indicate that crystallites in rat incisor enamel are flat ribbons with rhomboidal cross-sectional shape. Hexagonal images in electron micrographs of thin-sectioned enamel can result from rhomboidal-ended, parallelepiped-shaped segments of these crystallites projected and viewed as two-dimensional shadows.

A Method of Form Selection for Large Scale Structures

2002 ◽  
Author(s):  
Damiano Pasini ◽  
S. C. Burgess ◽  
D. J. Smith
Keyword(s):  
Cross Sections ◽  
Large Scale ◽  
Design Parameters ◽  
Cross Sectional ◽  
Geometrical Properties ◽  
Large Scale Structures ◽  
Shape Selection ◽  
Efficiency Parameter ◽  
Sectional Shape ◽  
Selection Of

This paper presents a new method for modelling the efficiency of large-scale structural forms. Parametric equations, which include all design parameters and also the effect of buckling, are developed. Shape transformers, envelope efficiency parameter and scaling factor are introduced to describe the geometrical properties of cross-sections and to allow interaction between form and cross-sectional shape selection. Design charts provide insight and understanding and assist the selection of different structural concepts at the preliminary stage of design.

The Interaction of Coherent Vortices With Short Flat Plates (Data Bank Contribution)

1993 ◽  
Vol 115 (4) ◽  
pp. 590-596 ◽  
Author(s):  
J. Swirydczuk ◽  
M. C. Wilder ◽  
D. P. Telionis
Keyword(s):  
Pressure Fluctuations ◽  
Data Bank ◽  
Laser Doppler Velocimeter ◽  
Flat Plates ◽  
Cross Sectional ◽  
Vortical Structures ◽  
Practical Applications ◽  
Strong Source ◽  
Sharp Edges ◽  
Sectional Shape

The interaction between a vortex and a small plate, are studied experimentally in a water tunnel using a computer-controlled laser-Doppler velocimeter. The interaction is proved to be a strong source of secondary and tertiary vorticity, the formation of which can be controlled by a selection of the plate dimensions, and cross-sectional shape. It is demonstrated that shorter plates with sharp edges are more efficient in breaking up oncoming vortical structures, while they create lower levels of secondary and tertiary vorticity. Such devices could be employed to control the amplitude of pressure fluctuations and the generation of noise in many practical applications.

scholarly journals Influence of the volute cross-sectional shape on mixed inflow turbine performances

2017 ◽  
Vol 9 (7) ◽  
pp. 168781401770817 ◽  
Author(s):  
Mohamed Amine Meghnine ◽  
Mohammad Kamal Hamidou ◽  
Mohammed Hamel
Keyword(s):  
Cross Sections ◽  
Radial Direction ◽  
Essential Element ◽  
Sectional Area ◽  
Cross Sectional ◽  
Flow Angle ◽  
Absolute Flow ◽  
Subsonic Regime ◽  
Simulation Results ◽  
Sectional Shape

The volute is an essential element in the centrifugal machines. Improving its performance is an effective way to improve the total performance of the turbine. The purpose of this study is to replace the accelerating and guiding nozzle vanes by exploring different design possibilities on the cross-sectional area convergence of the volute, since a decreasing area is then associated with expansion in the subsonic regime. The work is extended to a mixed inflow turbine using the new volute cross sections under pulsating regimes for turbocharging. The numerical simulation results show larger accelerations [Formula: see text] and lesser losses in the case of sections with flatter area in the radial direction and without vaneless space between the volute and the rotor; but this combination has an effect on the exit absolute flow angle which is less uniform.

Wind-induced instability of structures

1971 ◽  
Vol 269 (1199) ◽  
pp. 395-413 ◽  
Keyword(s):  
Wind Speed ◽  
Cross Sections ◽  
Natural Frequencies ◽  
Structural Response ◽  
Cross Sectional ◽  
Periodic Surface ◽  
Speed Range ◽  
Aerodynamic Instability ◽  
Sectional Shape ◽  
Transverse Galloping

Forms of wind-induced instability of structures are described, and two of these, typical of long bodies with bluff cross-sections, are selected for more detailed consideration. The first is vortex-induced bending oscillation, a type of resonant response to the periodic surface pressure loading caused by the discrete wake vortex street formed from the shear layers separating from the bluff cross-section. Oscillation phenomena are described, including capture of the vortex frequency by the structural response frequency over a discrete wind speed range and amplification and phase shift of the loading over this range. The second form is transverse galloping, arising from aerodynamic instability of the bluff cross-sectional shape, so that small-amplitude oscillations generate forces which increase the amplitudes to large values. Oscillation phenomena are described, including the occurrence at very nearly natural frequencies, and the relatively large amplitudes (compared to vortex-induced oscillations) increasing with wind speed beyond a critical wind speed dependent on the level o fstructural damping. Effects of body and wind parameters on both forms of oscillation are considered, and methods of analysis and suppression for susceptible structures are described. Some probable future requirements and prospects are considered.

Vulnerability of different nerves to intrafascicular injection by different needle types and at different approach angles: a mathematical model

2020 ◽  
Vol 45 (4) ◽  
pp. 306-310
Author(s):  
Margarita Sanromán-Junquera ◽  
Andre Boezaart ◽  
Yury Zasimovich ◽  
Olga C Nin ◽  
Xavier Sala-Blanch ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Cross Sections ◽  
Longitudinal Axis ◽  
Needle Insertion ◽  
Nerve Roots ◽  
Nerve Blocks ◽  
Cross Sectional ◽  
Peripheral Nerve Blocks ◽  
Microscopic Images ◽  
Insertion Angle

Background and objectivesWe assume that intrafascicular spread of a solution can only occur if a large enough portion of the distal needle orifice is placed inside the fascicle. Our aim is to present and evaluate a mathematical model that can calculate the theoretical vulnerability of fascicles, analyzing the degree of occupancy of the needle orifice in fascicular tissue by performing simulations of multiple positions that a needle orifice can take inside a cross-sectional nerve area.MethodsWe superimposed microscopic images of two routinely used nerve block needles (22-gauge, 15° needle and 22-gauge, 30° needle) over the microscopic images of cross-sections of four nerve types photographed at the same magnification. Fascicular tissue that was overlapped between 80% and 100% by a needle orifice was considered at risk to possible intrafascicular injection. The effect of three angular approaches was evaluated.ResultsThere were statistical differences between the vulnerability of fascicular tissue depending on nerve type, the bevel angle of the needle and the angle approach. Fascicular vulnerability was greater in nerve roots of the brachial plexus after using a 22-gauge 30° needle, as was choosing a 45° angle approach to the longitudinal axis of the nerve.ConclusionsOur results suggest that clinicians may want to consider needle insertion angle and bevel type as they perform peripheral nerve blocks. Furthermore, researchers may want to consider this mathematical model when estimating vulnerabilities of various nerves, needle types and angles of approach of needles to nerves.

scholarly journals Twist-to-bend ratio: an important selective factor for many rod-shaped biological structures

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Steve Wolff-Vorbeck ◽  
Max Langer ◽  
Olga Speck ◽  
Thomas Speck ◽  
Patrick Dondl
Keyword(s):  
Cross Sections ◽  
Phase Field ◽  
Material Properties ◽  
Flexural Rigidity ◽  
Torsional Rigidity ◽  
Cross Sectional ◽  
Deep Groove ◽  
Biological Structures ◽  
The Cross ◽  
Sectional Shape

AbstractMechanical optimisation plays a key role in living beings either as an immediate response of individuals or as an evolutionary adaptation of populations to changing environmental conditions. Since biological structures are the result of multifunctional evolutionary constraints, the dimensionless twist-to-bend ratio is particularly meaningful because it provides information about the ratio of flexural rigidity to torsional rigidity determined by both material properties (bending and shear modulus) and morphometric parameters (axial and polar second moment of area). The determination of the mutual contributions of material properties and structural arrangements (geometry) or their ontogenetic alteration to the overall mechanical functionality of biological structures is difficult. Numerical methods in the form of gradient flows of phase field functionals offer a means of addressing this question and of analysing the influence of the cross-sectional shape of the main load-bearing structures on the mechanical functionality. Three phase field simulations were carried out showing good agreement with the cross-sections found in selected plants: (i) U-shaped cross-sections comparable with those of Musa sp. petioles, (ii) star-shaped cross-sections with deep grooves as can be found in the lianoid wood of Condylocarpon guianense stems, and (iii) flat elliptic cross-sections with one deep groove comparable with the cross-sections of the climbing ribbon-shaped stems of Bauhinia guianensis.

scholarly journals On turbulent friction in straight ducts with complex cross-section: the wall law and the hydraulic diameter

2018 ◽  
Vol 846 ◽  
Author(s):  
Sergio Pirozzoli
Keyword(s):  
Common Duct ◽  
Frictional Resistance ◽  
Hydraulic Diameter ◽  
Effective Diameter ◽  
Regular Polygons ◽  
Rod Bundles ◽  
Cross Sectional ◽  
Turbulent Friction ◽  
Complex Cross ◽  
Sectional Shape

We develop predictive formulae for frictional resistance in ducts with complex cross-sectional shape based on the use of the log law and neglect of wall shear stress non-uniformities. The traditional hydraulic diameter naturally emerges from the analysis as the controlling length scale for common duct shapes such as triangles and regular polygons. The analysis also suggests that a new effective diameter should be used in more general cases, yielding corrections of a few percent to friction estimates based on the traditional hydraulic diameter. Fair, but consistent, predictive improvement is shown for duct geometries of practical relevance, including rectangular and annular ducts, and circular rod bundles.

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