Effects Of Changes In Length Research Articles

Effects of Electrodes Layout and Filler Scale on Percolation Threshold and Piezoresistivity Performances of a Cementitious-Based Geocomposite

An extensive experimental study was conducted to investigate the co-effects of surface area and distance between electrodes as well as filler scales on the percolation threshold of piezoresistive cement-stabilised sand. In this route, the electrical resistivity of numerous specimens of different sizes and composed of different content of carbon-based conductive fillers was measured, including carbon nanotubes (CNTs), graphene nanoplatelets (GNPs), and carbon fibres (CFs) with different aspect ratios. In addition, the numerical relations between the electrical percolation threshold and matrix dimensions were expressed for different conductive fillers. Furthermore, the electrical percolation threshold of two large-scale specimens with different shapes (a 10 × 10 × 85 cm3 beam, and a 15 cm size cube) were predicted through numerical relations, and their piezoresistivity performances were investigated under compression cyclic loading (cube) and flexural cyclic loading (beam). The mechanical properties of the specimens were also evaluated. The results showed that the changes in the length, width, and thickness of the matrix surrounded between electrodes had a significant effect on the electrical percolation threshold. However, the effects of length changes on the percolation threshold were greater than the width and thickness changes. Generally, increasing the aspect ratio of the conductive fillers caused a reduction in the electrical percolation threshold of the cementitious geocomposite. The appropriate piezoresistivity response of the large-scale specimens composed of filler content equal to their percolation threshold (obtained by the numerical relation presented in this study) showed the adequacy of the results in terms of threshold dosage prediction and self-sensing geocomposite design. The results of this study addressed a crucial factor for the design of self-sensing composites and pave the way for the development of field-applicable, smart, cementitious geocomposite.

Elongated styloid process: literature review and morphometric data on a collection of dried skulls

The styloid process is a subtle process of variable length that originates from the petrous part of temporal bone . From the process originate three muscles: the stylopharyngeus,the styloglossus, the stylohyoideus and two ligaments :stylohyoid and stylomandibular . The styled process of the temporal bone has a variable length as demonstrated for studies conducted in three-dimensional computed tomography or dental panoramic three-dimensional scanning,and in dried skulls The normal length of the styloid process is particularly important to establish for the relations of closeness with vascular and nervous structures and their possible compression by an elongated styloid process.Several studies have focused on the effects of changes in length and course of the styloid process, highlighting the relations of the carotid artery and the glossopharyngeal nerve to explain cerebrovascular symptoms or Eagle’s syndrome characterized by neck pain and dysphagia .However the association for the abnormal length of styloid process and Eagle’s syndrome is not always present and many cases are asymptomatic. In the present study we propose a review of the studies performed with different in vivo radiological techniques and on dried skull collections on the normal and pathological length of the stiloyd process and on its association with the Eagle’s syndrome. We also present a morphometric study carried out in dried skulls of our museum collection.The results are discussed in light of the possible variations in the muscular and ligamentous structures consequent to the elongation of the styloid process.

Dynamic Finite-Element analysis of a soft bending actuator

Compliance is both a blessing and a curse in the soft robotics field. Increased flexibility comes with serious challenges in the dynamic modeling of compliant manipulators. Soft bending actuators, with their widespread application in rehabilitative, locomotive, and manipulative robotics, are no exception. Dynamic modeling of these actuators is specifically important, as it directly affects the design criteria. In other words, the effect of geometrical features on different aspects of dynamic response such as natural frequencies or magnitude and phase responses should be investigated. Since analytical modeling of their dynamic response is extremely challenging due to the high nonlinearity of both their geometrical and material features, the Finite-Element method is regarded as a proper technique to model these actuators and gain more insight into their dynamical behavior. This study presents a Finite-Element model to describe the dynamic behavior of a pneumatically-driven soft bending actuator, including an analysis of its natural frequencies and response shape. Since inflation of the actuator impacts its structural stiffness and geometrical domain, its effect is studied on the first five natural frequencies by modeling it as a prestress. The proposed model has been scripted and analyzed in ABAQUS, regarding its hyperelastic material behavior, and then is verified experimentally by comparing the numerical analysis data with the results obtained from the bending behavior of a fabricated prototype in different frequencies. In addition to a favorable match between model and test data, a design platform is presented regarding the effect of changes in length and different thicknesses on the bending angle and curvature. Moreover, it is discovered that the geometrical features of the actuator do not endanger the assumption that its bending shape has a constant curvature. In fact, this assumption is only valid in low-frequency applications.

Analysis of quantum effects of fine scaling on the axial buckling of MWCNTs based on the density functional theory and molecular mechanics method

In this paper, quantum and molecular mechanics are used to study the quantum effects of fine scaling on the buckling strength of multi-walled carbon nanotubes under axial loading, as well as the effects of changes in length, diameter, chirality, wall number and length-to-diameter ratio of the structure. To this end, the total potential energy of the system is calculated with the consideration of both bond stretching and bond angular variations. The density functional theory along with the generalized gradient approximation function is used to obtain the relevant elastic constants of the nanotubes. An excellent agreement is found between the present numerical results and those found in the literature which confirms the validity as well as the accuracy of the present closed-form solution. The results show that in the effective longitudinal range for quantum effects of fine scaling, any change that leads to a change in the size of the structure has significant effects on the buckling strength of the structure. By increasing the diameter due to the increase in the number of walls or chirality and increasing the length of the structure, the critical buckling strength experiences a decreasing trend and this decrease is highly dependent on the increasing of the diameter due to the increase in the number of walls. In addition, zigzag multi-walled carbon nanotubes are more resistant than armchair multi-walled nanotubes, and the critical buckling strain of multi-walled carbon nanotubes with different chiralities is in the range of zigzag and armchair nanotubes. In other words, it can be said that quantum effects of fine scaling cause more buckling strengthening of the structure against external axial loads and with each longitudinal change that reduces the quantum effects of fine scaling, the strength of the structure decreases sharply.

Torsional buckling analysis of MWCNTs considering quantum effects of fine scaling based on DFT and molecular mechanics method

In this paper, quantum and molecular mechanics are used to study the quantum effects of fine scaling on the buckling strength of multi-walled carbon nanotubes (MWCNTs), as well as the effects of changes in length, diameter, chirality, wall number and length-to-diameter ratio of the structure under torsional loading. To this end, the total potential energy of the system is calculated with the consideration of both bond stretching and bond angular variations. The density functional theory (DFT) along with the generalized gradient approximation (GGA) function is used to obtain the relevant elastic constants of the nanotubes. The study shows that the quantum effects of fine scaling cause more buckling strength of the structure against external torsional loadings. Also, with any longitudinal change as well as the changes in the structural arrangement that reduce the quantum effects of fine scaling, the strength of the structure decreases sharply.

A Weldless Approach for Thermocouple Fabrication Through Direct Ink Writing Technique

Thermocouples are abundantly used for temperature measurement in various applications because of their availability and reliability. In this research two different materials, carbon a semiconductor and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT: PSS), an organic conductive polymer with silver as a common electrode were used to fabricate thermocouples through a weldless direct ink writing technique. Two different lengths were chosen for thermocouples to validate the effect of change in length on the performance of thermocouples. Each of the printed thermocouples is characterized and the sensitivity of thermocouples also known as the Seebeck coefficient are determined in a temperature range of up to 140°C. The Seebeck coefficients are found to be 16.6-17 μV/°C for PEDOT:PSS/Silver thermocouples and 15-17.8 μV/°C for carbon/silver thermocouples. These values are comparable to the recently reported numbers for the combination of the said materials. Furthermore, it was found that the Seebeck coefficient is not only material dependent but also influenced by the electrical properties of the printed thermocouples. Each type of printed thermocouple exhibits a stable and linear response towards the temperature change and is comparable to commercially available K-type thermocouple, however, the Seebeck coefficient reported is low when compared to K-type thermocouples due to material differences. Another key finding is the quick response and recovery time of the printed thermocouples as compared to sheath K-type thermocouples.

Experimental characterization of longitudinal mechanical properties of clear timber: Random spatial variability and size effects

In this study, an experimental campaign was conducted to characterize the length effect on the elasticity and tensile strength of clear spruce wood parallel to the grain direction. Four groups of specimens of different lengths, cut from the same log, were tested under the same conditions under longitudinal tensile loading. The cross-sectional area of the specimens was selected as being constant and sufficiently small to exclude the effect of variations of the properties in the transverse direction. Local deformations along the lengths of the specimens were recorded during the tests in order to characterize the spatial variability of the elastic modulus. A connection between the mesostructure of the clear wood and its local elastic modulus was observed. Statistics concerning the elastic modulus, strength and strain to failure and the effect of length change on these properties were extracted. The strength statistics were also used to examine the accuracy of the classical Weibull size effect law. The correlations between the strength, the elasticity and the density were obtained. The results show a variability of approximately 20% in the local elastic modulus. Also, the variability of the effective elastic modulus decreases with increasing length. The mean value of the strength has an upper bound when the length approaches zero, in contrast to the Weibull law, while its variability remains virtually unchanged for different lengths.

Fabrication and Experimental Analysis on L/D Ratio of Vortex Tube

Now-a-days, the first and foremost important quality of any research or development is its eco-friendly nature. As we know environment safety has become an important aspect of the industries and people in common. Vortex tube is also known as non-conventional cooling device that will produce cold air and hot air when we passed compressed air from compressor without causing any harm to the nature. In vortex tube, when a compressed air from compressor is tangentially passed into vortex chamber a free and forced vortex flow will be generated which will be divide into two air streams i.e., one has lower temperature than inlet temperature and other one has higher temperature than inlet temperature. It can be used for any type of spot cooling application. In this research an attempt is made to fabricate and test a simple vortex tube. The effect of change in length and diameter of vortex tube i.e., (L/D) ratio is investigated and presented in this paper.

Model studies on cellular reinforced fly ash walls

In India, thermal power stations produce enormous quantity of fly ash as a byproduct of combustion. It requires huge disposal area and creates environmental problems. In India, where land to population ratio is too small, acquiring huge area of land for the disposal of fly ash is not easy. The utilization of fly ash and its disposal in an environment friendly manner is a foremost concern for developing country like India. In the present study, a series of model experiments were carried out for proper utilization of fly ash as an alternative backfill material in the cellular reinforced fly ash wall. Locally available waste plastic water bottles were used to prepare the cellular reinforcement. The diameter of bottles used for cellular reinforcement is 50 mm and with varying heights of 10 and 20 mm. The effect of change in length and spacing of the cellular reinforcement on the horizontal displacement of full height facing panel and settlement of the backfill were studied. For all the types of reinforcement cases, the variation in length and spacing of the reinforcement showed significant effect on the horizontal displacement of facing panel and on settlement of the backfill. The cellular reinforcement of height 20 mm showed better performance over 10 mm height cellular reinforcement.

Modelling, Simulation and Control of a Foldable Stair Mechanism with a Linear Actuation Technique

In places where there is a space restriction, a foldable stair can be used. In accordance with this, we have simulated a mechanism in which the unfolding and folding of the stair is due to the linear motion of the slider at one end. The effect of the change in length of connecting rod that converts linear motion to rotary motion is to be analyzed. Here we consider 10 different lengths of the connecting rod. The force needed to move the slider is measured using MSC ADAMSTM software in each of these cases. Then a linear actuation circuit for the slider using a double acting cylinder is designed and simulated using Festo FluidSIMTM software. Thus in this paper we present the effect of change in length of the connecting rod by considering the force needed for actuation and the linear distance to be moved by it.

Behavior of Cellular-Reinforced Fly-Ash Walls under Strip Loading

AbstractIn India, pulverized coal is used at thermal power stations as a fuel to generate electricity, thereby producing enormous quantities of fly ash. The amount of fly ash has been increased with the increasing demand of electric utilities. The utilization of fly ash and its disposal in an environmentally friendly manner is a foremost concern for developing countries like India. In this present study, with the aim of proper utilization of fly ash, a series of model experiments was conducted by using fly ash as a backfill material in a cellular-reinforced fly-ash wall subjected to strip loading. Two different types of locally available waste water bottles were used to make cellular reinforcements. The reinforcements were laid in two different patterns, mattress and strip. This paper studies and presents the effects of changes in length, spacing, coverage ratio, and dimensions of the cellular reinforcements on the horizontal displacement behavior of a full height facing panel and on the settlement of bac...

Light scattering calculations exploring sensitivity of depolarization ratio to shape changes II Single rod-shaped vegetative bacteria in air

In article I of this series, calculations and graphs of the depolarization ratio, D(Theta,lambda)=1-<S22>/<S11>, for light scattered from an ensemble of single-aerosolized Bacillus spores using the discrete dipole approximation (DDA) (sometimes also called the coupled dipole approximation) were presented. The Sij in these papers denote the appropriate Mueller matrix elements. We compare graphs for different size parameters for both D(Theta,lambda) and the ratio R34(Theta,lambda)=<S34>/<S11>. The ratio R34(Theta,lambda) was shown previously to be sensitive to diameters of rod-shaped and spherical bacteria suspended in liquids. The present paper isolates the effect of length changes and shows that R34(Theta,lambda) is not very sensitive to these changes, but D(Theta,lambda) is sensitive to length changes when the aspect ratio becomes small enough. In the present article, we extend our analysis to vegetative bacteria which, because of their high percentage of water, generally have a substantially lower index of refraction than spores. The parameters used for the calculations were chosen to simulate values previously measured for log-phase Escherichia coli. Each individual E. coli bacterium appears microscopically approximately like a right-circular cylinder, capped smoothly at each end by a hemisphere of the same diameter. With the present model we focus particular attention on determining the effect, if any, of length changes on the graphs of D(Theta,lambda) and R34(Theta,lambda). We study what happens to these two functions when the diameters of the bacteria remain constant and their basic shape remains that of a capped cylinder, but with total length changed by reducing the length of the cylindrical part of each cell. This approach also allows a test of the model, since the limiting case as the length of the cylindrical part approaches zero is exactly a sphere, which is known to give a value identically equal to zero for D(Theta,lambda) but not for R34(Theta,lambda).

Effects of Length Changes on Force Produced by Ca2+ and ADP-Activated Myofibrils along the Ascending Limb of the Force-Length Relation

Isometric forces produced by skeletal muscles are higher after stretch and smaller after shortening. A few studies investigating these length-dependent changes in force were conducted on the ascending limb of the force-length (FL) relation, showing conflicting results with elusive mechanisms. The purposes of this study were: (i) to evaluate the effects of muscle stretching and shortening on forces along the ascending limb of the FL relation, (ii) to evaluate if sarcomere length dispersion changes after the imposed length changes, and (iii) to assess if cross-bridges play a role in the length-induced force changes. Rabbit psoas myofibrils were attached between two pre-calibrated micro-needles, and their images were projected into a photodiode array for measurements of individual sarcomere length (SL). Myofibrils were activated by Ca2+ or ADP - the later induces cross-bridge attachment to actin independently of Ca2+. After activation myofibrils were subjected to three stretches or shortenings (∼4%SL), with isometric periods allowed between length changes so that force would achieve a steady-state. Forces of ADP-activated myofibrils were greater (7-8%) than those of Ca2+-activated myofibrils at corresponding SLs (range: 2.2-2.4μm) after shortening, but forces were similar after stretch. Forces were greater (26% with ADP and 15% with Ca2+, SL: 2.2μm) after stretch than after shortening. Sarcomere dispersion was similar after stretch or shortening in Ca2+ and ADP-activated myofibrils. The results suggest that stretching and shortening affects isometric forces on the ascending limb of the FL relation through different mechanisms, and are not associated with SL dispersion. While cross-bridges seem to be involved in force depression, they are likely not involved in force enhancement.

Epimuscular myofascial force transmission occurs in the rat between the deep flexor muscles and their antagonistic muscles

The goal of the present study was to test the hypothesis that epimuscular myofascial force transmission occurs between deep flexor muscles of the rat and their antagonists: previously unstudied mechanical effects of length changes of deep flexors on the anterior crural muscles (i.e., extensor digitorum longus (EDL), as well as tibialis anterior and extensor hallucis longus muscle complex (TA + EHL) and peroneal (PER) muscles were assessed experimentally. These muscles or muscle groups were kept at constant length, whereas, distal length changes were imposed on deep flexor (DF) muscles before performing isometric contractions. Distal forces of all muscle-tendon complexes were measured simultaneously, in addition to EDL proximal force. Distal lengthening of DF caused substantial significant effects on its antagonistic muscles: (1) increase in proximal EDL total force (maximally 19.2%), (2) decrease in distal EDL total (maximally 8.4%) and passive (maximally 49%) forces, (3) variable proximo-distal total force differences indicating net proximally directed epimuscular myofascial loads acting on EDL at lower DF lengths and net distally directed loads at higher DF lengths, (4) decrease in TA + EHL total (maximally 50%) and passive (maximally 66.5%) forces and (5) decrease in PER total force (maximally 51.3%). It is concluded that substantial inter-antagonistic epimuscular myofascial force transmission occurs between deep flexor, anterior crural and peroneal muscles. In the light of our present results and recently reported evidence on inter-antagonistic interaction between anterior crural, peroneal and triceps surae muscles, we concluded that epimuscular myofascial force transmission is capable of causing major effects within the entire lower leg of the rat. Implications of such large scale myofascial force transmission are discussed and expected to be crucial to muscle function in healthy, as well as pathological conditions.

Attitude and orbit error in n-dimensional spaces

This paper focuses on the theoretical aspects associated with the definition of error for Special Orthogonal and General Linear transformations, in any dimensional space, real or complex, including both Euclidean and Riemannian spaces. In particular, we show that the orbit error can be described by a complex number with phase representing the orbit orientation error and modulus describing the orbit shape error. We also show that the angle between two quaternions has a specific geometrical meaning. More specifically, the QR decomposition allows us to see a General Linear transformation as a combination of two subsequent effects: a dilation and a rigid rotation. This decomposition is also applied to the Lorentz transformations, highlighting the relativity effects of length change and coordinate axes bending.

筋音図を用いた関節角度による筋活動変化の検討(J05-3 ライフサポート(3),J05 ライフサポート)

This study was designed to examine the effects of length changes in ankle dorsiflexor, tibialis anterior, on the muscular activities, using the mechanomyogram (MMG), electromyogram (EMG) force output during isometric ramp contractions. The relationships between the root-mean-squared amplitude (RMS) of the MMG and relative force (% MVC) in the dorsiflexed ankle and plantarflexed ankle were markedly different from those in the neutral positioned ankle. Although the RMS amplitude of EMG in the dorsiflexed ankle demonstrated the wide difference from those in the neutral positioned ankle, those in the plantarflexed ankle showed the almost same pattern as in the neutral positioned ankle. These changes in EMG and MMG would suggest that the changes in length of muscle probably influence the muscle activation pattern during isometric ramp contraction.

Myofascial force transmission between a single muscle head and adjacent tissues: length effects of head III of rat EDL.

Force transmission from muscle fibers via the connective tissue network (i.e., myofascial force transmission) is an important determinant of muscle function. This study investigates the role of myofascial pathways for force transmission from multitendoned extensor digitorum longus (EDL) muscle within an intact anterior crural compartment. Effects of length changes exclusively of head III of rat EDL muscle (EDL III) on myofascial force transmission were assessed. EDL III was lengthened at the distal tendon. For different lengths of EDL III, isometric forces were measured at the distal tendon of EDL III, as well as at the proximal tendon of whole EDL and at the distal tendons of tibialis anterior and extensor hallucis longus (TA+EHL) muscles. Lengthening of EDL III caused high changes in force exerted at the distal tendon of EDL III (from 0 to 1.03 +/- 0.07 N). In contrast, only minor changes were found in force exerted at the proximal EDL tendon (from 2.37 +/- 0.09 to 2.53 +/- 0.10 N). Increasing the length of EDL III decreased TA+EHL force significantly (by 7%, i.e., from 5.62 +/- 0.27 to 5.22 +/- 0.32 N). These results show that force is transmitted between EDL III and adjacent tissues via myofascial pathways. Optimal force exerted at the distal tendon of EDL III (1.03 +/- 0.07 N) was more than twice the force expected on the basis of the physiological cross-sectional area of EDL III muscle fibers (0.42 N). Therefore, a substantial fraction of this force must originate from sources other than EDL III. It is concluded that myofascial pathways play an important role in force transmission from multitendoned muscles.

Pedicle screw salvage: the effect of depth and diameter on pull-out strength: a biomechanical study

Objectives: To investigate the effects of change in length, diameter, length and diameter on axial pull-out strengths of revisional pedicle screws and determine the best method of salvage for failed pedicle screws. Methods: We used pedilen rigid foam (equivalent to the average bone mineral density of lumbar vertebrae in cadavers as measured by quantitative computerized tomography) and Synergy pedicle screws with 1.8 mm threads. All variables but the length and diameter were kept constant during insertion of the pedicle screws. Ten different pull-out tests were performed in each of the five groups, using an Instron Model 1195 universal test machine. In the first group, screws 6.5 mm x 40 mm in size were used to draw reference values. In the remaining groups, insertion and removal of 6.5 mm x 40 mm screws was succeeded by insertion of pedicle screws of (i) the same size (6.5 mm x 40 mm), (ii) increased length (6.5 mm x 45 mm), (iii) increased diameter (7.0 mm x 40 mm), and (iv) increased length and diameter (7.0 mm x 45 mm), respectively. Pull-out strengths and load versus time curves were recorded. Results were evaluated using SPSS program and Student’s t-test. Results: The average pull-out strength decreased by 26% after substitution of the pedicle screw for one of the same size. Conversely, pull-out strengths increased by 15%, 33%, and 49% as the length, the diameter, and the length and diameter of the salvage screws increased, respectively. Differences in pull-out strengths between groups were highly significant (p<0.0001). Conclusion: Substitution of the previous pedicle screw for one of the same size would be a major mistake. Pedicle salvage using screws with increased length and diameter seems to be the most appropriate solution in restoring the strength of mechanical fixation.

Changing practice and costs of carotid endarterectomy in Toronto, Canada.

During our annual audits of carotid endarterectomy (CEA) in Toronto metropolitan hospitals, we have been aware of major changes in the practice of this operation in recent years. To evaluate the effect of changing practice on costs of carotid endarterectomy, we have therefore compared the effects of changes in length of stay, complication rates, and other variables on cost during the last 3 years for which we have complete data. We evaluated 757 consecutive patients, of whom 600 had CEA procedures in 3 teaching hospitals, and 190 procedures in 2 community hospitals in metropolitan Toronto. We estimated costs using a specially designed computer program, Transitional System Incorporated, including surgical complications, in patients admitted between January 1994 and December 1996. There was a significant decrease in length of stay in both groups of hospitals, mainly due to preoperative outpatient evaluation but also due to lower complication rates, which probably reflect an increase in asymptomatic surgery in both hospital groups. Costs fell from approximately $8000 per procedure to $5000 in asymptomatic patients and from approximately $10,000 to $7000 in symptomatic patients (Can $). Major changes in the management of patients undergoing CEA have resulted in a significant decrease in both length of hospital stay and utilization of postoperative intensive care. At the same time, complication rates have significantly fallen, although our mortality and morbidity figures remain slightly higher than those from published multicenter trials. Future changes in surgical practice in Canada, including noninvasive carotid imaging, should produce even lower costs within the next few years.

Extensibility of the actin and myosin filaments in various states of skeletal muscle as studied by X-ray diffraction.

The effects of length changes applied to resting, contracting and rigor muscles on the reflection spacings of the X-ray diffraction patterns were summarized. The spacing changes of the actin- and myosin-based meridional reflections as a function of tension relative to an isometric tension of active muscle (P0) were linear and almost identical in the active and rigor states, showing that the extension of both filaments is Hookenian and does not depend upon the states of muscle. In addition to their length changes caused by tension generation, there are small but significant length changes of both filaments due purely to activation of muscle. The actin and myosin filaments are elongated by approximately 0.36% and approximately 0.43%, respectively under the maximum active tension. The results indicate that a large part of the sarcomere compliance of an active muscle is caused by the extensibility of the myofilaments. Inspection of the behavior of the meridional and layer-line reflection spacings reveals that there is a close relationship between the extensibility and helical twisting of the actin filaments under active and passive forces. The extension caused by tension is associated with an unwinding of right-handed helices following the actin monomers in the filament. At the pointed end of the filament could rotate anticlockwise through one fifth the complete turn during contraction.