scholarly journals Variability of the mechanical properties of bone, and its evolutionary consequences

2006 ◽  
Vol 4 (12) ◽  
pp. 127-135 ◽  
Author(s):  
John D Currey ◽  
Jonathan W Pitchford ◽  
Paul D Baxter
Keyword(s):  
Mechanical Properties ◽  
Mathematical Model ◽  
Mineral Content ◽  
Optimal Allocation ◽  
Compact Bone ◽  
Simple Mathematical Model ◽  
Trade Off ◽  
Evolutionary Consequences ◽  
Insight Into ◽  
Mechanical Phenomena

The relative variabilities (coefficient of variation (CV)) of 10 different mechanical properties of compact bone were determined from 2166 measurements. All measures of variability were made on a minimum of four specimens from any bone. Three pre-yield properties had a CV of about 12%. Six post-yield properties had CVs varying from 24 to 46%. Pre-yield properties increase as a function of mineral content, whereas post-yield properties decrease. These differences give insight into mechanical phenomena occurring at different stages during loading. Furthermore, the fact that some properties are more tightly determined than others has implications for the optimum values set by natural selection. This assertion is made more rigorous using a simple mathematical model for the evolutionarily optimal allocation in a trade-off where one property is imprecisely determined. It is argued that in general the optimum will be biased in favour of the more tightly determined properties than would be the case if all properties had the same CV.

Short Fiber Reinforcement of Elastomers

1974 ◽  
Vol 47 (5) ◽  
pp. 1074-1081 ◽  
Author(s):  
S. R. Moghe
Keyword(s):  
Experimental Data ◽  
Mechanical Properties ◽  
Mathematical Model ◽  
Fiber Orientation ◽  
Probability Distribution Function ◽  
Tensile Modulus ◽  
Short Fiber ◽  
Simple Mathematical Model ◽  
Short Fibers ◽  
Rubber Compounds

Abstract Based upon a simple mathematical model, the directional properties of elastomers mixed with uniaxially oriented short fibers are predicted. The model takes into account a probability distribution function for a number of fibers in any direction during fiber orientation. Theory is compared with experimental data on tensile modulus for a number of rubber compounds and fibers with good success. A possibility of characterizing calendering and extrusion processes in view of orientation and mechanical properties is discussed.

A Decision Support Model for Salary Structure Design

2020 ◽  
Vol 52 (3) ◽  
pp. 109-120
Author(s):  
Biniyam Asmare Kassa
Keyword(s):  
Mathematical Model ◽  
Decision Support ◽  
Structure Design ◽  
Simple Mathematical Model ◽  
Decision Support Model ◽  
External Market ◽  
Trade Off ◽  
Actual Application ◽  
Salary Structure ◽  
Market Competitiveness

This article presents a simple mathematical model for salary structure design that enhances clarity and allows for reasonable trade-off between internal equity and external market competitiveness considerations in salary structure design. Practical use of the model is illustrated with an actual application in one organization.

Insight into the basis of root growth in Arabidopsis thaliana provided by a simple mathematical model

2006 ◽  
Vol 119 (2) ◽  
pp. 85-93 ◽  
Author(s):  
Akitoshi Iwamoto ◽  
Daisuke Satoh ◽  
Masahiko Furutani ◽  
Shinichiro Maruyama ◽  
Hideaki Ohba ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Arabidopsis Thaliana ◽  
Root Growth ◽  
Simple Mathematical Model ◽  
Insight Into

scholarly journals Mechanosensitive remodeling of the bacterial flagellar motor is independent of direction of rotation

2021 ◽  
Vol 118 (15) ◽  
pp. e2024608118
Author(s):  
Navish Wadhwa ◽  
Yuhai Tu ◽  
Howard C. Berg
Keyword(s):  
Escherichia Coli ◽  
Mathematical Model ◽  
Steady State ◽  
Bacterial Motility ◽  
Flagellar Motor ◽  
Simple Mathematical Model ◽  
Output Torque ◽  
Chemical Stimuli ◽  
Bacterial Flagellar Motor ◽  
Insight Into

Motility is important for the survival and dispersal of many bacteria, and it often plays a role during infections. Regulation of bacterial motility by chemical stimuli is well studied, but recent work has added a new dimension to the problem of motility control. The bidirectional flagellar motor of the bacterium Escherichia coli recruits or releases torque-generating units (stator units) in response to changes in load. Here, we show that this mechanosensitive remodeling of the flagellar motor is independent of direction of rotation. Remodeling rate constants in clockwise rotating motors and in counterclockwise rotating motors, measured previously, fall on the same curve if plotted against torque. Increased torque decreases the off rate of stator units from the motor, thereby increasing the number of active stator units at steady state. A simple mathematical model based on observed dynamics provides quantitative insight into the underlying molecular interactions. The torque-dependent remodeling mechanism represents a robust strategy to quickly regulate output (torque) in response to changes in demand (load).

scholarly journals Global and local contributions to corneal surface curvature: a simple model

2008 ◽  
Vol 67 (1) ◽  
Author(s):  
W. F. Harris
Keyword(s):  
Mathematical Model ◽  
Simple Model ◽  
Tear Film ◽  
Surface Curvature ◽  
Simple Mathematical Model ◽  
Corneal Surface ◽  
Local Effects ◽  
Numerical Example ◽  
Global And Local ◽  
Insight Into

Variations in corneal surface powers reflect variations in the geometry of the cornea.  In particular one can regard corneal surface curvature as a combination of local and global effects.  A simple mathematical model of the cornea is presented which makes use of measurements of the curvature of the anterior and posterior surfaces to decompose the curvature into global and local contributions.  The model gives insight into the source of variations in keratometric measurements, lids and eye turn, perhaps, for global effects and the tear film, perhaps, for local effects.  The model also takes account of the thickness of the cornea.  A numerical example is presented.

The effect of pressure on the compressibility of aluminum alloys

2020 ◽  
pp. 102-107
Keyword(s):  
Mechanical Properties ◽  
Mathematical Model ◽  
Liquid Metal ◽  
Control Systems ◽  
Physical And Mechanical Properties ◽  
Reliable Data ◽  
Output Process ◽  
Automated Control ◽  
Input And Output ◽  
Crystallization Under Pressure

To obtain reliable data on the properties of liquid metal and create automated control systems, the technological process of molding with crystallization under pressure is studied. A mathematical model of the input and output process parameters is developed. It is established that the compressibility of the melt can represent the main controlled parameter influencing on the physical-mechanical properties of the final products. The obtained castings using this technology are not inferior in their physical and mechanical properties to those produced by forging or stamping.

Effect of mobility conditions on the throughput of the Wireless Body Area Network

2020 ◽  
Vol 10 ◽  
Author(s):  
Shilpa Shinde ◽  
Santosh Sonavane
Keyword(s):  
Mathematical Model ◽  
Wireless Body Area Network ◽  
Data Rate ◽  
Hand Movements ◽  
Body Area Network ◽  
Area Network ◽  
Mobility Patterns ◽  
Body Area ◽  
Insight Into ◽  
Leg Movements

Background and objective: In the Wireless Body Area Network (WBAN) sensors are placed on the human body; which has various mobility patterns like seating, walking, standing and running. This mobility typically assisted with hand and leg movements on which most of the sensors are mounted. Previous studies were largely focused on simulations of WBAN mobility without focusing much on hand and leg movements. Thus for realistic studies on performance of the WBAN, it is important to consider hand and leg movements. Thus, an objective of this paper is to investigate an effect of the mobility patterns with hand movements on the throughput of the WBAN. Method: The IEEE 802.15.6 requirements are considered for WBAN design. The WBAN with star topology is used to connect three sensors and a hub. Three types of mobility viz. standing, walking and running with backward and forward hand movements is designed for simulation purpose. The throughput analysis is carried out with the three sets of simulations with standing, walking and running conditions with the speed of 0 m/s, 0.5 m/s and 3 m/s respectively. The data rate was increased from 250 Kb to 10000 Kb with AODV protocol. It is intended to investigate the effect of the hand movements and the mobility conditions on the throughput. Simulation results are analyzed with the aid of descriptive statistics. A comparative analysis between the simulated model and a mathematical model is also introduced to get more insight into the data. Results: Simulation studies showed that as the data rate is increased, throughput is also increased for all mobility conditions however, this increasing trend was discontinuous. In the standing (static) position, the throughput is found to be higher than mobility (dynamic) condition. It is found that, the throughput is better in the running condition than the walking condition. Average values of the throughput in case of the standing condition were more than that of the dynamic conditions. To validate these results, a mathematical model is created. In the mathematical model, a same trend is observed. Conclusion: Overall, it is concluded that the throughput is decreased due to mobility of the WBAN. It is understood that mathematical models have given more insight into the simulation data and confirmed the negative effect of the mobility conditions on throughput. In the future, it is proposed to investigate effect of interference on the designed network and compare the results.

scholarly journals Mechanical Properties and Bioactivity of Poly(Lactic Acid) Composites Containing Poly(Glycolic Acid) Fiber and Hydroxyapatite Particles

Nanomaterials ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 249
Author(s):  
Han-Seung Ko ◽  
Sangwoon Lee ◽  
Doyoung Lee ◽  
Jae Young Jho
Keyword(s):  
Mechanical Properties ◽  
Lactic Acid ◽  
Flexural Strength ◽  
Interfacial Adhesion ◽  
Glycolic Acid ◽  
Compact Bone ◽  
Poly Lactic Acid ◽  
Coupling Reactions ◽  
The Poor ◽  
Human Compact Bone

To enhance the mechanical strength and bioactivity of poly(lactic acid) (PLA) to the level that can be used as a material for spinal implants, poly(glycolic acid) (PGA) fibers and hydroxyapatite (HA) were introduced as fillers to PLA composites. To improve the poor interface between HA and PLA, HA was grafted by PLA to form HA-g-PLA through coupling reactions, and mixed with PLA. The size of the HA particles in the PLA matrix was observed to be reduced from several micrometers to sub-micrometer by grafting PLA onto HA. The tensile and flexural strength of PLA/HA-g-PLA composites were increased compared with those of PLA/HA, apparently due to the better dispersion of HA and stronger interfacial adhesion between the HA and PLA matrix. We also examined the effects of the length and frequency of grafted PLA chains on the tensile strength of the composites. By the addition of unidirectionally aligned PGA fibers, the flexural strength of the composites was greatly improved to a level comparable with human compact bone. In the bioactivity tests, the growth of apatite on the surface was fastest and most uniform in the PLA/PGA fiber/HA-g-PLA composite.

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