scholarly journals The ultrafast snap of a finger is mediated by skin friction

2021 ◽  
Vol 18 (184) ◽  
Author(s):  
Raghav Acharya ◽  
Elio J. Challita ◽  
Mark Ilton ◽  
M. Saad Bhamla
Keyword(s):  
Mathematical Model ◽  
Energy Storage ◽  
Energy Release ◽  
Skin Friction ◽  
High Speed ◽  
Middle Finger ◽  
Professional Baseball ◽  
High Speed Imaging ◽  
Systematic Analysis

The snap of a finger has been used as a form of communication and music for millennia across human cultures. However, a systematic analysis of the dynamics of this rapid motion has not yet been performed. Using high-speed imaging and force sensors, we analyse the dynamics of the finger snap. We discover that the finger snap achieves peak angular accelerations of 1.6 × 10 6 ° s −2 in 7 ms, making it one of the fastest recorded angular accelerations the human body produces (exceeding professional baseball pitches). Our analysis reveals the central role of skin friction in mediating the snap dynamics by acting as a latch to control the resulting high velocities and accelerations. We evaluate the role of this frictional latch experimentally, by covering the thumb and middle finger with different materials to produce different friction coefficients and varying compressibility. In doing so, we reveal that the compressible, frictional latch of the finger pads likely operates in a regime optimally tuned for both friction and compression. We also develop a soft, compressible friction-based latch-mediated spring actuated model to further elucidate the key role of friction and how it interacts with a compressible latch. Our mathematical model reveals that friction plays a dual role in the finger snap, both aiding in force loading and energy storage while hindering energy release. Our work reveals how friction between surfaces can be harnessed as a tunable latch system and provides design insight towards the frictional complexity in many robotic and ultra-fast energy-release structures.

scholarly journals The ultrafast snap of a finger is mediated by skin friction

2021 ◽  
Author(s):  
Raghav Acharya ◽  
Elio J. Challita ◽  
Mark Ilton ◽  
M. Saad Bhamla
Keyword(s):  
Mathematical Model ◽  
Energy Storage ◽  
Energy Release ◽  
Skin Friction ◽  
High Speed ◽  
Middle Finger ◽  
Dual Role ◽  
High Speed Imaging ◽  
Systematic Analysis

The snap of a finger has been used as a form of communication and music for millennia across human cultures. However, a systematic analysis of the dynamics of this rapid motion has not yet been performed. Using high-speed imaging and force sensors, we analyze the dynamics of the finger snap. Our analysis reveals the central role of skin friction in mediating the snap dynamics by acting as a latch to control the resulting high velocities. We evaluate the role of this frictional latch experimentally, by covering the thumb and middle finger with different materials to produce different friction coefficients and varying compressibility. In doing so, we reveal that the compressible, frictional latch of the finger pads likely operate in a regime optimally tuned for both friction and compression. We also develop a soft, compressible friction-based latch-mediated spring actuated (LaMSA) model to further elucidate the key role of friction and how it interacts with a compressible latch. Our mathematical model reveals that friction plays a dual role in the finger snap, both aiding in force loading and energy storage while hindering energy release. Our work reveals how friction between surfaces can be harnessed as a tunable latch system and provide design insight towards the frictional complexity in many robotics and ultra-fast energy-release structures.

scholarly journals The Energy Balance in Aluminum–Copper High-Speed Collision Welding

2021 ◽  
Vol 5 (2) ◽  
pp. 62
Author(s):  
Peter Groche ◽  
Benedikt Niessen
Keyword(s):  
High Speed ◽  
Bond Formation ◽  
High Strength ◽  
Weld Interface ◽  
High Speed Imaging ◽  
Collision Zone ◽  
High Speed Collision ◽  
New Generation ◽  
Lower Limits

Collision welding is a joining technology that is based on the high-speed collision and the resulting plastic deformation of at least one joining partner. The ability to form a high-strength substance-to-substance bond between joining partners of dissimilar metals allows us to design a new generation of joints. However, the occurrence of process-specific phenomena during the high-speed collision, such as a so-called jet or wave formation in the interface, complicates the prediction of bond formation and the resulting bond properties. In this paper, the collision welding of aluminum and copper was investigated at the lower limits of the process. The experiments were performed on a model test rig and observed by high-speed imaging to determine the welding window, which was compared to the ones of similar material parings from former investigation. This allowed to deepen the understanding of the decisive mechanisms at the welding window boundaries. Furthermore, an optical and a scanning electron microscope with energy dispersive X-ray analysis were used to analyze the weld interface. The results showed the important and to date neglected role of the jet and/or the cloud of particles to extract energy from the collision zone, allowing bond formation without melting and intermetallic phases.

scholarly journals Estimasi Posisi Magnetic Levitation Ball Menggunakan Metode Akar Kuadrat Ensemble Kalman Filter (AK-EnKF)

2017 ◽  
Vol 2 (1) ◽  
pp. 45
Author(s):  
Teguh Herlambang
Keyword(s):  
Mathematical Model ◽  
Kalman Filter ◽  
Ensemble Kalman Filter ◽  
High Speed ◽  
Magnetic Levitation ◽  
Steel Ball ◽  
Electromagnetic Power ◽  
The Mathematical Model ◽  
Air Medium

The role of Magnetic Levitation Ball in an industrial world is very important, among others, as system applied to a train moving on the rail at high speed (MAGLEV). Magnetic Levitation Ball is system consisting of a ferromagnetic solid steel ball floating over The surface of air medium when supplied with electromagnetic power which is hard to predict its position, and therefore estimations is required to estimate the position, and speed of the steel ball when the electromagnetic power is supplied to the steel ball. This paper was study on application of the modification of Ensemble Kalman Filter (EnKF) method by adding Root Square at the stage of corecction called Ensemble Kalman Filter Square Root (EnKF-SR). Implemented to the mathematical model of magnetic levitation ball and speed of ferromagentic steel ball the result of the simulation of EnKF-SR using mathematical model of magnetic levitation ball showed that the error was less than 2% by generating both 200 and 300 ensembles. The least error was observed when 200 ensemble was generated at which the position error of ball was 0.018 m, and speed of the bll was 0.016 m/s and the electric current was 0.018 A.

scholarly journals Drug delivery via tattooing: Effect of needle and fluid properties

2021 ◽  
Author(s):  
Idera Lawal ◽  
Pankaj Rohilla ◽  
Jeremy Marston
Keyword(s):  
Drug Delivery ◽  
High Speed ◽  
In Vitro Study ◽  
Injection Technique ◽  
High Speed Imaging ◽  
Injection Process ◽  
Gelatin Gels ◽  
Fluid Properties

Tattooing is a commonplace practice among the general populace in which ink is deposited within dermal tissue. Typically, an array of needles punctures the skin which facilitates the delivery of a fluid within the dermis. Although, a few studies in the past have investigated the potential of tattooing as an intradermal (ID) drug injection technique, an understanding of the fluid dynamics involved in the delivery of fluid into skin is still lacking. Herein, we sought to provide insight into the process via an in vitro study. We utilize a five needle flat array (5F) with a tattoo machine to inject fluids into gelatin gels. High-speed imaging was used to visualize the injection process and estimate the amount of fluid delive red after each injection upto the 50th injection. We investigate the role of reciprocating frequency (f) of the needle array and the physical properties of the fluids on the volume (Vo) and the percentage delivery (η) after injection. In addition, we illustrate the physical mechanism of fluid infusion during tattooing, which has not been reported. An understanding of the injection process via tattooing can be useful in the development of ID tattoo injectors as drug delivery devices.

A Statistical Study of Process Variables to Optimize a High Speed Curtain Coater: Part I

TAPPI Journal ◽  
2009 ◽  
Vol 8 (1) ◽  
pp. 20-26 ◽  
Author(s):  
PEEYUSH TRIPATHI ◽  
MARGARET JOYCE ◽  
PAUL D. FLEMING ◽  
MASAHIRO SUGIHARA
Keyword(s):  
Boundary Layer ◽  
Experimental Design ◽  
High Speed ◽  
Statistical Study ◽  
Process Variables ◽  
High Speeds ◽  
The Stability ◽  
Air Removal ◽  
Removal System

Using an experimental design approach, researchers altered process parameters and material prop-erties to stabilize the curtain of a pilot curtain coater at high speeds. Part I of this paper identifies the four significant variables that influence curtain stability. The boundary layer air removal system was critical to the stability of the curtain and base sheet roughness was found to be very important. A shear thinning coating rheology and higher curtain heights improved the curtain stability at high speeds. The sizing of the base sheet affected coverage and cur-tain stability because of its effect on base sheet wettability. The role of surfactant was inconclusive. Part II of this paper will report on further optimization of curtain stability with these four variables using a D-optimal partial-facto-rial design.

The Impact of Light Polarisation on Light Field of Scenes with Multiple Reflections

2020 ◽  
pp. 108-115 ◽  
Author(s):  
Vladimir P. Budak ◽  
Anton V. Grimaylo
Keyword(s):  
Mathematical Model ◽  
Light Field ◽  
Global Illumination ◽  
Multiple Reflections ◽  
Software Environment ◽  
The Monte Carlo Method ◽  
Mueller Matrices ◽  
Volume Integration ◽  
The Impact

The article describes the role of polarisation in calculation of multiple reflections. A mathematical model of multiple reflections based on the Stokes vector for beam description and Mueller matrices for description of surface properties is presented. On the basis of this model, the global illumination equation is generalised for the polarisation case and is resolved into volume integration. This allows us to obtain an expression for the Monte Carlo method local estimates and to use them for evaluation of light distribution in the scene with consideration of polarisation. The obtained mathematical model was implemented in the software environment using the example of a scene with its surfaces having both diffuse and regular components of reflection. The results presented in the article show that the calculation difference may reach 30 % when polarisation is taken into consideration as compared to standard modelling.

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