Effects of Freeze-Thaw Cycling on Material Properties of Cancellous Cervine Bone as Characterized by Nanoindentation

2013 ◽  
Author(s):  
Alexander K. Landauer ◽  
Philip A. Yuya ◽  
Laurel Kuxhaus
Keyword(s):  
Material Properties ◽  
Applied Load ◽  
Dynamic Testing ◽  
Small Scale ◽  
Phase Lag ◽  
Static Force ◽  
Cross Sectional ◽  
Freeze Thaw ◽  
Material Parameters ◽  
Storage And Loss Moduli

Cancellous bone is an important load-bearing component of whole bone, and due to the plate-and-rod nature of trabeculae, small-scale testing is required to measure material parameters for use in modern analytic techniques such as finite element modeling [1, 2]. These material properties are measurable via nanoindentation techniques. During nanoindentation, the indenter tip is forced into the surface of the material while the applied load and tip displacement are monitored. Using these data, along with the tip’s cross-sectional area, mechanical properties are determined. Dynamic testing quantifies viscoelastic response and can obtain material response parameters such as storage and loss moduli. During dynamic testing, a low magnitude sinusoidal force is superimposed on a constant static force. The displacement response is measured at the same frequency as the applied oscillating force, and the resulting phase lag is related to material damping [3].

Preliminary Experimental Study of SMA Knitted Actuation Architectures

Aerospace ◽  
2006 ◽  
Author(s):  
Julianna Evans ◽  
Diann Brei ◽  
Jonathan Luntz
Keyword(s):  
Experimental Study ◽  
Smart Materials ◽  
Material Properties ◽  
Geometric Parameters ◽  
Design Parameters ◽  
Static Force ◽  
Vast Array ◽  
Material Parameters ◽  
Wide Range ◽  
And Control

Nature builds an immense set of materials exhibiting a wide range of behaviors using only a small number of basic compounds. The range of materials comes about through architecture, giving functional structure to the basic materials. Analogously, a new genre of actuators can be derived from existing smart materials through architecture. This paper presents a preliminary experimental study of knitted actuation architectures that yield high strains (up to 73%) with moderate forces (tens of Newtons or more) from basic contracting smart material fibers. By different combinations of the two primary knit loops – purl and knit – a variety of behaviors can be achieved including contraction, rolling, spirals, accordions, arching, and any combination of these across the fabric. This paper catalogs several basic knit stitches and their actuated form: garter, stockinette, seed, rib and I-cord. These knitted architectures provide performance tailorability (force, strain, stiffness, and motion) by manipulation of key design parameters such as the material properties of the wire, the geometric parameters (wire diameter, loop size, and gauge), and architectural parameters (stitch type and orientation). This is demonstrated via a quasi-static force-deflection experimental study with several shape memory alloy garter prototypes with varying geometric parameters. While the basic architecture of a knit is simple, it affords a vast array of architectural combinations and control of geometrical and material parameters that generate a myriad of gross motion capabilities beyond that of current day actuation strategies.

scholarly journals Extracting viscoelastic material parameters using an atomic force microscope and static force spectroscopy

2020 ◽  
Vol 11 ◽  
pp. 922-937 ◽  
Author(s):  
Cameron H Parvini ◽  
M A S R Saadi ◽  
Santiago D Solares
Keyword(s):  
Material Properties ◽  
Mechanical Response ◽  
Loss Modulus ◽  
Force Spectroscopy ◽  
Model Parameters ◽  
Viscoelastic Response ◽  
Static Force ◽  
Critical Material ◽  
Material Parameters ◽  
Atomic Force

Atomic force microscopy (AFM) techniques have provided and continue to provide increasingly important insights into surface morphology, mechanics, and other critical material characteristics at the nanoscale. One attractive implementation involves extracting meaningful material properties, which demands physically accurate models specifically designed for AFM experimentation and simulation. The AFM community has pursued the precise quantification and extraction of rate-dependent material properties, in particular, for a significant period of time, attempting to describe the standard viscoelastic response of materials. AFM static force spectroscopy (SFS) is one approach commonly used in pursuit of this goal. It is capable of acquiring rich temporal insight into the behavior of a sample. During AFM-SFS experiments the cantilever base approaches samples with a nearly constant velocity, which is manipulated to investigate different timescales of the mechanical response. This manuscript seeks to build upon our previous work and presents an approach to extracting useful linear viscoelastic information from AFM-SFS experiments. In addition, the basis for selecting and restricting the model parameters for fitting is discussed from the perspective of applying this technique on a practical level. This work begins with a guided discussion that develops a fit function from fundamental laws, continues with conditioning a raw SFS experimental dataset, and concludes with the fit and prediction of viscoelastic response parameters such as storage modulus, loss modulus, loss angle, and compliance. These steps constitute a complete guide to leveraging AFM-SFS data to estimate key material parameters, with a series of detailed insights into both the methodology and supporting analytical choices.

SUBMERGED CITRIC ACID FERMENTATION OF SUGAR BEET MOLASSES: INCREASE IN SCALE

1955 ◽  
Vol 1 (5) ◽  
pp. 299-311 ◽  
Author(s):  
R. Steel ◽  
C. P. Lentz ◽  
S. M. Martin
Keyword(s):  
Citric Acid ◽  
Scale Up ◽  
Aeration Rate ◽  
Small Scale ◽  
Acid Fermentation ◽  
Inoculum Level ◽  
Cross Sectional ◽  
Factors Affecting ◽  
Beet Molasses ◽  
Initial Ph

Factors affecting the production of citric acid in the submerged fermentation of ferrocyanide-treated beet molasses by Aspergillus niger were studied in 2.5 and 36 liter fermenters. The small fermenters were used to determine the effects of changes in sterilization technique, phosphate supplement, ferrocyanide treatment, inoculum level, initial pH, fermentation temperature, and aeration rate. The relation between ferrocyanide concentration and inoculum level was also studied. Four different samples of molasses were fermented successfully. An average yield of 8.2% citric acid (64% conversion) was obtained from 51 small-scale fermentations. Comparable yields were obtained in the large fermenters under comparable conditions. Most of the information obtained with the small fermenters was applicable to the larger-scale fermenters, but in the latter the fermentation was significantly more stable. Aeration was the main problem in the scale-up and aeration rates approximately double those calculated on a fermenter cross-sectional area basis were required for comparable results in the large fermenters.

scholarly journals Application of a fast and efficient algorithm to assess landslide-prone areas in sensitive clays in Sweden

2015 ◽  
Vol 15 (12) ◽  
pp. 2703-2713 ◽  
Author(s):  
C. Melchiorre ◽  
A. Tryggvason
Keyword(s):  
Optimal Algorithm ◽  
Model Performance ◽  
Small Scale ◽  
Depth Information ◽  
Computationally Efficient ◽  
Cross Sectional ◽  
Bedrock Depth ◽  
The Cross ◽  
Intelligent Filtering ◽  
Filtering Procedure

Abstract. We refine and test an algorithm for landslide susceptibility assessment in areas with sensitive clays. The algorithm uses soil data and digital elevation models to identify areas which may be prone to landslides and has been applied in Sweden for several years. The algorithm is very computationally efficient and includes an intelligent filtering procedure for identifying and removing small-scale artifacts in the hazard maps produced. Where information on bedrock depth is available, this can be included in the analysis, as can information on several soil-type-based cross-sectional angle thresholds for slip. We evaluate how processing choices such as of filtering parameters, local cross-sectional angle thresholds, and inclusion of bedrock depth information affect model performance. The specific cross-sectional angle thresholds used were derived by analyzing the relationship between landslide scarps and the quick-clay susceptibility index (QCSI). We tested the algorithm in the Göta River valley. Several different verification measures were used to compare results with observed landslides and thereby identify the optimal algorithm parameters. Our results show that even though a relationship between the cross-sectional angle threshold and the QCSI could be established, no significant improvement of the overall modeling performance could be achieved by using these geographically specific, soil-based thresholds. Our results indicate that lowering the cross-sectional angle threshold from 1 : 10 (the general value used in Sweden) to 1 : 13 improves results slightly. We also show that an application of the automatic filtering procedure that removes areas initially classified as prone to landslides not only removes artifacts and makes the maps visually more appealing, but it also improves the model performance.

Large- and small-scale vortical motions in a shear layer perturbed by tabs

1999 ◽  
Vol 382 ◽  
pp. 307-329 ◽  
Author(s):  
JUDITH K. FOSS ◽  
K. B. M. Q. ZAMAN
Keyword(s):  
Shear Layer ◽  
Pitch Angle ◽  
Large Scale ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Small Scale ◽  
Streamwise Vortices ◽  
Streamwise Vorticity ◽  
Cross Sectional ◽  
Scale Population

The large- and small-scale vortical motions produced by ‘delta tabs’ in a two-stream shear layer have been studied experimentally. An increase in mixing was observed when the base of the triangular shaped tab was affixed to the trailing edge of the splitter plate and the apex was pitched at some angle with respect to the flow axis. Such an arrangement produced a pair of counter-rotating streamwise vortices. Hot-wire measurements detailed the velocity, time-averaged vorticity (Ωx) and small-scale turbulence features in the three-dimensional space downstream of the tabs. The small-scale structures, whose scale corresponds to that of the peak in the dissipation spectrum, were identified and counted using the peak-valley-counting technique. The optimal pitch angle, θ, for a single tab and the optimal spanwise spacing, S, for a multiple tab array were identified. Since the goal was to increase mixing, the optimal tab configuration was determined from two properties of the flow field: (i) the large-scale motions with the maximum Ωx, and (ii) the largest number of small-scale motions in a given time period. The peak streamwise vorticity magnitude [mid ]Ωx−max[mid ] was found to have a unique relationship with the tab pitch angle. Furthermore, for all cases examined, the overall small-scale population was found to correlate directly with [mid ]Ωx−max[mid ]. Both quantities peaked at θ≈±45°. It is interesting to note that the peak magnitude of the corresponding circulation in the cross-sectional plane occurred for θ≈±90°. For an array of tabs, the two quantities also depended on the tab spacing. An array of contiguous tabs acted as a solid deflector producing the weakest streamwise vortices and the least small-scale population. For the measurement range covered, the optimal spacing was found to be S≈1.5 tab widths.

Modeling the Inflation Response of C57BL/6 Mouse Sclera

2011 ◽  
Author(s):  
Kristin M. Myers ◽  
Thao D. Nguyen
Keyword(s):  
Material Properties ◽  
Soft Tissues ◽  
Ganglion Cells ◽  
The United States ◽  
Small Rodent ◽  
Tissue Samples ◽  
Tissue Microstructure ◽  
Material Parameters ◽  
Meaningful Material

Small rodent models have become increasingly useful to investigate how the mechanical properties of soft tissues may influence disease development. These animal models allow access to aged, diseased, or genetically-altered tissue samples, and through comparisons with wild-type or normal tissue it can be explored how each of these variables influence tissue function. The challenges to deriving meaningful material parameters for these small tissue samples include designing physiologically-relevant mechanical testing protocols and interpreting the experimental load-displacement data in an appropriate constitutive framework to quantify material parameters. This study was motivated by determining the possible role of scleral material properties in the development of glaucomatous damage to the retinal ganglion cells (RGC). Glaucoma is one of the leading causes of blindness in the United States and in the world with an estimate of 60 million people affected by this year [1]. Through exploring mouse models, the overall goal of our work is to determine the role of scleral material properties and scleral tissue microstructure in the pathogenesis of glaucoma.

Mechanical Behavior of Functionally Graded Nano-Cylinders Under Radial Pressure Based on Strain Gradient Theory

2018 ◽  
Vol 35 (4) ◽  
pp. 441-454 ◽  
Author(s):  
M. Shishesaz ◽  
M. Hosseini
Keyword(s):  
Mechanical Behavior ◽  
Strain Gradient ◽  
Material Properties ◽  
Scale Effects ◽  
Radial Pressure ◽  
Functionally Graded ◽  
High Order ◽  
Strain Gradient Theory ◽  
Small Scale ◽  
Gradient Theory

ABSTRACTIn this paper, the mechanical behavior of a functionally graded nano-cylinder under a radial pressure is investigated. Strain gradient theory is used to include the small scale effects in this analysis. The variations in material properties along the thickness direction are included based on three different models. Due to slight variations in engineering materials, the Poisson’s ratio is assumed to be constant. The governing equation and its corresponding boundary conditions are obtained using Hamilton’s principle. Due to the complexity of the governed system of differential equations, numerical methods are employed to achieve a solution. The analysis is general and can be reduced to classical elasticity if the material length scale parameters are taken to be zero. The effect of material indexn, variations in material properties and the applied internal and external pressures on the total and high-order stresses, are well examined. For the cases in which the applied external pressure at the inside (or outside) radius is zero, due to small effects in nano-cylinder, some components of the high-order radial stresses do not vanish at the boundaries. Based on the results, the material inhomogeneity indexn, as well as the selected model through which the mechanical properties may vary along the thickness, have significant effects on the radial and circumferential stresses.

scholarly journals Evaluating the influence of anxiety and depression on academic performance in high school students

2021 ◽  
Author(s):  
Waleed Ahmed Shahzad
Keyword(s):  
High School ◽  
Academic Performance ◽  
High School Students ◽  
Anxiety And Depression ◽  
Small Scale ◽  
School Students ◽  
Cross Sectional ◽  
Grade Point ◽  
Negative Effect ◽  
The Mean

The purpose of this study was to evaluate whether anxiety and depression have a negative effect on academic performance. This small-scale study assessed the relationship between these factors. A cross-sectional questionnaire survey was carried out. A randomized sample of 52 high school students based in various schools across Lahore participated in the survey. Of the participants, 32 were males and 20 were females. As a measure of anxiety and depression 14 questions from the DASS-21 were utilized (The 7 questions pertaining to the measure of stress were not included in this study). Based on the DASS-21 score obtained by the respondents they were classified under categories of normal, mild, moderate, severe and extremely severe levels of anxiety and depression. As a measure of academic performance, the Grade Point Average (GPA) of the students was obtained via the survey. The mean average GPA was calculated for all the students falling under the aforementioned categories pertaining to anxiety and depression separately and these averages were compared. It was found that the mean average GPA was highest in students falling under the categories of normal and mild levels of anxiety and depression. Whereas, mean average GPA was lower in students suffering from severe levels of anxiety and depression. These findings suggest the need to come up with methods to combat anxiety and depression in high school students as these factors impede academic performance.

scholarly journals Univariate associations between housing, management, and facility design factors and the prevalence of lameness lesions in fourteen small-scale dairy farms in Northeastern Algeria

2020 ◽  
Vol 13 (3) ◽  
pp. 570-578 ◽  
Author(s):  
Zoubida Dendani-Chadi ◽  
Khelaf Saidani ◽  
Loubna Dib ◽  
Fayçal Zeroual ◽  
Faouzi Sammar ◽  
...  
Keyword(s):  
Univariate Analysis ◽  
Indirect Costs ◽  
Dairy Farms ◽  
Site Investigation ◽  
Cross Sectional Study ◽  
Small Scale ◽  
Facility Design ◽  
Cross Sectional ◽  
Housing Management ◽  
Increased Risk

Background and Aim: This cross-sectional study aimed to analyze the associations between different types of housing, management, and facilities on the prevalence of lame, causing lesions in smallholder dairy farms in Algeria. Materials and Methods: The on-site investigation took place between December 2012 and May 2015. All cows were locomotion scored on a four-point scale, and foot lesions causing lame were diagnosed and recorded. Factors related to the farm and the cows' conditions were also assessed. The association between the possible risk factors and lame lesions was assessed using univariate analysis. Results: Of the 349 cows evaluated, 13% were lame (lameness score ≥2), with higher lameness values recorded for the hind feet than for the forefeet. Cows without lameness were classified as healthy. The two most frequent lesion diagnoses observed in lame cows were interdigital dermatitis/heel horn erosion (ID/HE; 39%) and interdigital phlegmon (IP; 35%), followed by traumatic lesions (T; 11%), digital dermatitis (DD; 8.7%), and laminitis-related diseases (L; 6.5%). The risk of being lame was increased in large herds with cows of the Holstein breed, and those in the third parity and above. Tie housing, concrete floor, concentrate feeding, zero-grazing, and the use of foot trimming occasionally were associated with increased risk for the presence of lame lesions. The region and footbathing frequency had no association with the prevalence of lame lesions (p≥0.05). Conclusion: These results have important implications; they indicate that several aspects of housing, management, and facility design are common protective factors for the prevalence of lame lesions. These factors should be maintained correctly to not only reduce the number of lame cows in these herds but also decrease the direct and indirect costs associated with cases of lameness.

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