3-Dimensional Force Curve and Dissipation Model Acquisition Using the Spectral Inversion Method in Tapping Mode AFM

2011 ◽  
Author(s):  
Jeffrey C. Williams ◽  
Santiago D. Solares
Keyword(s):  
Excitation Amplitude ◽  
Analytical Models ◽  
Inversion Method ◽  
Total Force ◽  
Experimental Conditions ◽  
3 Dimensional ◽  
Select Group ◽  
Feasible Range ◽  
Dissipation Model ◽  
Constant Quality

Atomic force microscopy (AFM) has been a field driving at exploring nanoscale surfaces and measuring both topography as well as material properties. One of the phenomena that has attracted significant interest is tip-sample dissipation, which was initially investigated by Cleveland and coworkers [Appl. Phys. Lett. 72, 2613–2615 (1998)]. In this paper we expand on that work by developing a method to map the total conservative and non-conservative forces simultaneously in space and as a function of relative tip-sample velocity. This is accomplished through Fourier analysis performed on the response of a torsional harmonic cantilever (THC) probe, previously developed by Sahin and coworkers [Nature Nanotechnology 2, 507–514 (2007)]. The effect of a select group of AFM parameters (cantilever resonant frequency, force constant, quality factor, amplitude set point and excitation amplitude) is simulated in a feasible range of experimental conditions, which maximizes the spatial and velocity range of the oscillating tip, such that useful maps of the total force as a function of tip velocity and position can be acquired. We analyze the observed trends and propose an approach to acquire analytical models of the local tip-sample dissipative and conservative forces.

scholarly journals Comparison of Bite Force in Patients After Treatment of Mandibular Fractures With 3-Dimensional Locking Miniplate and Standard Miniplates

2019 ◽  
Vol 1 (1) ◽  
pp. 7-10
Author(s):  
Gaurav Singh ◽  
Madan Mishra ◽  
Amit Gaur ◽  
Dhritiman Pathak
Keyword(s):  
Treatment Strategies ◽  
Bite Force ◽  
Mandibular Fractures ◽  
Time Intervals ◽  
Experimental Conditions ◽  
3 Dimensional ◽  
The Mean ◽  
Group 2 ◽  
Drilling Conditions ◽  
Group 1

Background: Fractures of the mandible can be studied and described in anatomic terms, functional considerations, treatment strategies, and outcome measures. The performance of any fixation system depends on multiple factors including plate adaptation, screw placement, bone quality, drilling conditions, and postoperative patient compliance. Bite force assesses masticatory muscle function under clinical and experimental conditions. Method: 30 patients with isolated, noncomminuted mandibular fractures were randomly divided into two equal groups. Group 1 patients were treated using 3-dimensional locking miniplates and group 2 patients were treated with standard miniplates. The bite forces were recorded at definite time intervals: preoperatively, and second week, sixth week, third month, and sixth month postoperatively. Result: At 6 weeks postoperative, 3 month postoperative, and 6 month postoperative, the mean bite force was found to be significantly higher among group 1 patients as compared to those in group 2 in all the sites. While at 2 week postoperative, the mean bite force was found to be significantly higher in Group 2 as compared to Group 1 at incisor region. Conclusion: The overall results of the present study show better performance in bite force for the 3-dimensional locking miniplate when compared with standard miniplates.

Stochastic Stability of a Universal-Joint Driven Torsional System

1999 ◽  
Author(s):  
S. F. Asokanthan ◽  
Xiao-Hui Wang
Keyword(s):  
Lyapunov Exponent ◽  
Excitation Frequency ◽  
Excitation Amplitude ◽  
Angular Speed ◽  
Analytical Models ◽  
Largest Lyapunov Exponent ◽  
Deterministic Case ◽  
Speed Fluctuation ◽  
The Difference ◽  
The Stability

Abstract Torsional instabilities in a two-degree-of-freedom system driven by a Hooke’s joint due to random input angular speed fluctuation are investigated. Linearised analytical models are used for calculating the largest Lyapunov exponent. Instability behaviour is then characterised by examining the sign of this exponent. Conditions for the onset of instability via sub-harmonic parametric resonances has been shown to coincide with those for the deterministic case. However, the onset of instability via sum as well as the difference type combination resonance is found to be different from that of the deterministic case. The instability conditions for the system under input angular speed fluctuation have been presented graphically in the excitation frequency-excitation amplitude-top Lyapunov exponent space. Predictions for the deterministic and the stochastic cases are compared. The effect of fluctuation probability density as well as that of inertia loads on the stability behaviour of the system has been examined.

scholarly journals Spastic diparetic does not directly affect the capacity to ascend and descend access ramps: three-dimensional analysis

2017 ◽  
Vol 30 (3) ◽  
pp. 537-547 ◽  
Author(s):  
Tainá Ribas Mélo ◽  
Ana Tereza Bittencourt Guimarães ◽  
Vera Lúcia Israel
Keyword(s):  
Imaging System ◽  
Three Dimensional ◽  
Control Group ◽  
Initial Contact ◽  
Experimental Conditions ◽  
3 Dimensional ◽  
Flexion Extension ◽  
Posterior Trunk ◽  
Hip Flexion ◽  
Study Participants

Abstract Introduction: Diplegic children have difficulties in gait and therefore ramps are used as strategies of accessibility. Objective: The present study investigated the influence of an inclined surface (ascending and descending) on the kinematic characteristics during gait of the diplegic group (DG) when compared to typically developing children of the control group (CG). Methods: Study participants included 20 children (10 with DG and 10 CG) matched by age, which were evaluated in three experimental conditions (horizontal and inclined ascending and inclined descending surfaces of 7º) through an optoelectronic imaging system. Results: Among the linear kinematic variables, only step width differed among groups, however, without influence of the surface. The foot height differed among the groups only in the descending phase, where DG had greater difficulty in raising the foot. The 3-dimensional gait analyses could not provide more evidences of differences in kinematics variables, especially in transverse plane, between DG and CG, but provide some evidence to support that hip range of motion (ROM) during the gait cycle, hip flexion-extension in initial contact, knee ROM and the 2nd anterior-posterior trunk peak amplitude of the DG were influenced on descent by their flexor pattern. Conclusion: The DG was most affected by the inclination plane than CG especially on descent. Although a hip and knee flexor pattern is evident for DG on inclination of 7º, this angle is accessible since it allows independent gait functional activity.

Quantitative Analysis of Precipitate Compositions in an Al-Li-Mg-Cu Alloy Using Atom Probe Tomography

2010 ◽  
Vol 654-656 ◽  
pp. 914-917 ◽  
Author(s):  
Xiang Yuan Xiong ◽  
Stavroula Moutsos ◽  
Russell King ◽  
Barry C. Muddle
Keyword(s):  
Quantitative Analysis ◽  
Aluminium Alloy ◽  
Atom Probe Tomography ◽  
Lithium Concentration ◽  
Stoichiometric Composition ◽  
Atom Probe ◽  
Field Evaporation ◽  
Experimental Conditions ◽  
3 Dimensional ◽  
Cu Alloy

The composition of  precipitates in aluminium alloy 8090 has been analysed using a 3 dimensional atom probe with fast data acquisition rates. The effects of experimental conditions for the quantitative atom probe analysis have been examined in detail. The results show that i) lithium is prone to preferential DC field evaporation at temperatures > 25K and with a pulse fraction < 20%; ii) the lithium concentration of  precipitates can vary from precipitate to precipitate, ranging from 19.1 to 25.3 at.%, and iii) the stoichiometric composition of the  phase can be obtained provided that the probing temperature is  25K and pulse fraction is  20%.

Temporal Gating for the Optimization of Laser-Induced Breakdown Spectroscopy Detection and Analysis of Toxic Metals

2001 ◽  
Vol 55 (10) ◽  
pp. 1312-1319 ◽  
Author(s):  
Brian T. Fisher ◽  
Howard A. Johnsen ◽  
Steven G. Buckley ◽  
David W. Hahn
Keyword(s):  
Toxic Metals ◽  
Delay Time ◽  
Atomic Emission ◽  
Metal Species ◽  
Laser Induced Breakdown Spectroscopy ◽  
Experimental Conditions ◽  
Breakdown Spectroscopy ◽  
Select Group ◽  
Delay Times ◽  
Laser Induced Breakdown

Optimal temporal gating for laser-induced breakdown spectroscopy (LIBS) analysis was investigated for a select group of toxic metals, namely the Resource Conservation and Recovery Act (RCRA) metals arsenic, beryllium, cadmium, chromium, lead, and mercury. The differing rates of decay between the continuum plasma emission and the atomic emission were used as a means to maximize the signal-to-noise ratio of the atomic emission lines for these six metal species. Detection windows were investigated corresponding to delay times from 2 to 50 μs following the plasma-initiating laser pulse. For the current experimental conditions, it is concluded that the relatively short delay time of 12 μs is optimal for the detection of arsenic, beryllium, cadmium, and mercury, while a longer delay time of 50 μs is optimal for the detection of chromium and lead. The reduced atomic emission intensity at relatively long delay times is compensated for by the use of long detector gate widths. Estimated detection limits are reported for the six metal species based on the optimized temporal gating and ensemble averaging of multiple laser pulses, and the implications for simultaneous metals monitoring are discussed.

scholarly journals Spatiotemporal Analysis of Multichannel EEG: CARTOOL

2011 ◽  
Vol 2011 ◽  
pp. 1-15 ◽  
Author(s):  
Denis Brunet ◽  
Micah M. Murray ◽  
Christoph M. Michel
Keyword(s):  
Electric Fields ◽  
Spatiotemporal Analysis ◽  
Temporal Segmentation ◽  
Source Imaging ◽  
Experimental Conditions ◽  
Topographic Analysis ◽  
3 Dimensional ◽  
Inverse Solutions ◽  
Electroencephalogram Eeg ◽  
Multichannel Eeg

This paper describes methods to analyze the brain's electric fields recorded with multichannel Electroencephalogram (EEG) and demonstrates their implementation in the software CARTOOL. It focuses on the analysis of the spatial properties of these fields and on quantitative assessment of changes of field topographies across time, experimental conditions, or populations. Topographic analyses are advantageous because they are reference independents and thus render statistically unambiguous results. Neurophysiologically, differences in topography directly indicate changes in the configuration of the active neuronal sources in the brain. We describe global measures of field strength and field similarities, temporal segmentation based on topographic variations, topographic analysis in the frequency domain, topographic statistical analysis, and source imaging based on distributed inverse solutions. All analysis methods are implemented in a freely available academic software package called CARTOOL. Besides providing these analysis tools, CARTOOL is particularly designed to visualize the data and the analysis results using 3-dimensional display routines that allow rapid manipulation and animation of 3D images. CARTOOL therefore is a helpful tool for researchers as well as for clinicians to interpret multichannel EEG and evoked potentials in a global, comprehensive, and unambiguous way.

The Mechanism for Ultrananocrystalline Diamond Growth: Experimental and Theoretical Studies

2006 ◽  
Vol 956 ◽  
Author(s):  
Paul William May ◽  
Yuri A. Mankelevich
Keyword(s):  
Growth Rate ◽  
Crystal Size ◽  
Calculated Data ◽  
Chemical Vapor ◽  
Diamond Growth ◽  
Experimental Conditions ◽  
3 Dimensional ◽  
Ultrananocrystalline Diamond ◽  
Hot Filament ◽  
Experimental And Theoretical Studies

ABSTRACTAr/CH4/H2 gas mixtures have been used to deposit microcrystalline diamond, nanocrystalline diamond and ultrananocrystalline diamond films using hot filament chemical vapor deposition. A 3-dimensional computer model was used to calculate the gas phase composition for the experimental conditions at all positions within the reactor. Using the experimental and calculated data, we show that the observed film morphology, growth rate, and across-sample uniformity can be rationalized using a model based on competition between H atoms, CH3 radicals and other C1 radical species reacting with dangling bonds on the surface. Proposed formulae for growth rate and average crystal size are tested on both our own and published experimental data for Ar/CH4/H2 and conventional 1%CH4/H2 mixtures, respectively.

Static and Dynamic Characterization of a Bump-Type Foil Bearing Structure

2006 ◽  
Vol 129 (1) ◽  
pp. 75-83 ◽  
Author(s):  
Sébastien Le Lez ◽  
Mihai Arghir ◽  
Jean Frene
Keyword(s):  
Dynamic Stiffness ◽  
Excitation Amplitude ◽  
Analytical Models ◽  
Stick Slip ◽  
Equivalent Viscous Damping ◽  
Foil Bearings ◽  
Commercial Code ◽  
Transient Simulations ◽  
Static And Dynamic Loads ◽  
Stiffness And Damping

The performance of gas foil bearings (GFBs) relies on a coupling between a thin gas film and an elastic structure with dissipative characteristics. Because of the mechanical complexity of the structure, the evaluation of its stiffness and damping is still largely inaccurate if not arbitrary. The goal of this paper is to improve the understanding of the behavior of the bump-type FB structure under static and dynamic loads. The structure was modeled with finite elements by using a commercial code. The code employed the large displacements theory and took into account the friction between the bumps and the support and between the bumps and the deformable top foil. Static simulations enabled the estimation of the static stiffness of each bump of a strip. These simulations evidence a lack of reliable analytical models that can be easily implemented in a FB prediction code. The models found in the literature tend to overestimate the foil flexibility because most of them do not consider the interactions between bumps that seem to be highly important. The transient simulations allowed the estimation of the dynamic stiffness and the damping of a single bump of the FB structure. The presence of stick slip in the structure is evidenced, and hysteretic plots are obtained. The energy dissipation due to Coulomb friction is quantified in function of materials, excitation amplitude, and frequency. Some energetic considerations allow the calculation of the equivalent viscous damping coefficient, and the results are related to experimental data found in literature. The influence of the number of bumps is also briefly addressed.

Vibro-Impact Interaction of Ships With Ice

2008 ◽  
Author(s):  
I. F. Grace ◽  
R. A. Ibrahim
Keyword(s):  
Initial Conditions ◽  
Excitation Amplitude ◽  
Basins Of Attraction ◽  
Analytical Models ◽  
Safe Operation ◽  
Rigid Barrier ◽  
Impact Interaction ◽  
Different Response ◽  
Motion Period ◽  
Impact Motion

Impact dynamic interaction of ships with solid ice or stationary rigid structures is a serious problem that affects the safe operation and navigation in arctic regions. The purpose of this study is to present two analytical models of impact interaction between ship roll dynamics and one-side rigid barrier. These models are the phenomenological modeling represented by a power law in stiffness and damping forces, and Zhuravlev non-smooth coordinate transformation. Extensive numerical simulations are carried out for all initial conditions covered by the ship grazing orbit for different values of excitation amplitude and frequencies of external wave roll moment. The basins of attraction of safe operation are obtained and reveal the coexistence of different response regimes such non-impact periodic oscillations, modulation impact motion, period added impact oscillations, chaotic impact motion and unbounded rotational motion. The results are summarized in the bifurcation diagram in terms of response amplitude-excitation amplitude plane.

scholarly journals Deep spectral learning for label-free optical imaging oximetry with uncertainty quantification

2019 ◽  
Vol 8 (1) ◽  
Author(s):  
Rongrong Liu ◽  
Shiyi Cheng ◽  
Lei Tian ◽  
Ji Yi
Keyword(s):  
Optical Imaging ◽  
Uncertainty Quantification ◽  
Analytical Models ◽  
Label Free ◽  
Blood Oxygen Saturation ◽  
Experimental Conditions ◽  
Spectral Learning ◽  
Traditional Approaches ◽  
Mean Square Errors

AbstractMeasurement of blood oxygen saturation (sO2) by optical imaging oximetry provides invaluable insight into local tissue functions and metabolism. Despite different embodiments and modalities, all label-free optical-imaging oximetry techniques utilize the same principle of sO2-dependent spectral contrast from haemoglobin. Traditional approaches for quantifying sO2 often rely on analytical models that are fitted by the spectral measurements. These approaches in practice suffer from uncertainties due to biological variability, tissue geometry, light scattering, systemic spectral bias, and variations in the experimental conditions. Here, we propose a new data-driven approach, termed deep spectral learning (DSL), to achieve oximetry that is highly robust to experimental variations and, more importantly, able to provide uncertainty quantification for each sO2 prediction. To demonstrate the robustness and generalizability of DSL, we analyse data from two visible light optical coherence tomography (vis-OCT) setups across two separate in vivo experiments on rat retinas. Predictions made by DSL are highly adaptive to experimental variabilities as well as the depth-dependent backscattering spectra. Two neural-network-based models are tested and compared with the traditional least-squares fitting (LSF) method. The DSL-predicted sO2 shows significantly lower mean-square errors than those of the LSF. For the first time, we have demonstrated en face maps of retinal oximetry along with a pixel-wise confidence assessment. Our DSL overcomes several limitations of traditional approaches and provides a more flexible, robust, and reliable deep learning approach for in vivo non-invasive label-free optical oximetry.

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