Specimen Height Research Articles

Impact of anaesthesia mode on evaluation of LEEP specimen dimensions

ObjectivesTo study the influence of anaesthesia (local by cervical block vs. general or spinal anaesthesia) on height and volume of resection specimens in case of conization treatment for cervical intraepithelial neoplasia (CIN). MethodsProspective observational study of all patients who underwent a first treatment by loop electrosurgical excision procedure (LEEP) for CIN. Height of fresh resection specimens was first measured by the operator and then by the pathologist after formaldehyde fixation. Volume of fresh specimens was measured in a measuring cylinder by fluid displacement. ResultsOne hundred patients were included and 35% of LEEP were performed under local anaesthesia. There was a significant difference in height of specimens depending on anaesthesia mode: after fixation, the average height was 11.2mm in the general or spinal anaesthesia group vs. 8.8mm in the local anaesthesia group (P=0.002). There was also a difference in terms of volume depending on anaesthesia mode: 1.6mL in local anaesthesia group vs. 2.3mm in general and spinal anaesthesia group (P=0.01). ConclusionsAnaesthesia mode has an impact on height and volume of LEEP specimens. In our experience, local anaesthesia could reduce LEEP specimen height.

Dimension-controlled formation of crease patterns on soft solids

Soft solids such as PDMS or silicone are widely needed in many advanced applications such as flexible electronics and medical engineering. The ability to control the structure and properties of the surface of soft solids provides new opportunities in these applications. In particular, mechanical loading induced elastic instability is a convenient method to control the surface morphology. The critical strain at which the crease nucleates is experimentally measured under plane strain conditions, and is found to be consistent with that predicted by nonlinear large deformation theory of creases. Under compressive loading, we find that silicone undergoes a transition of creasing pattern from a single channeling or double channeling crease to an unchanneling crease, depending on the specimen's width and height. Finite element simulations are performed to better understand the underlying mechanism of creasing, wherein a relationship between the depth and spacing of the creases is established. It is found to be in good agreement with the experimental data obtained.

Adaptation of Broadband Simple Shear Device for Constant Volume and Stress-Controlled Testing

Abstract We adapted an existing digitally controlled simple shear device, originally designed for drained testing with strain-control, to perform constant height testing under strain- or stress-controlled conditions. The re-designed system provided PID control of horizontal displacements or loads coupled with either vertical force or displacement control (for drained and constant-volume testing, respectively). The new system had substantially similar horizontal displacement control capabilities as the previous system. The tracking error under stress-controlled loading depends on amplitude and frequency of the load; however, its value was almost the same as errors in strain-controlled tests for common shear strain/stress amplitudes. High-precision vertical control was achieved during constant height testing in two respects: (1) height change was small (less than 0.05 % of the specimen height for large shear-strain tests), even at high frequencies; and (2) top cap rocking was small, with the vertical displacements due to rocking at the specimen edge being half or less than average changes in specimen height.

Vibratory Compaction of Base Course Aggregates

The focus of this paper is on laboratory compaction of unbound granular base course material for road pavement construction. The primary variables evaluated in this research were particle size distribution and dry density. This research addresses the applicability of current laboratory compaction techniques and outlines the changes needed to minimize the gap between laboratory and field compaction. The target density achieved in laboratory studies with the New Zealand standard test methodology, which is then used to target field compaction levels, is often too high to realistically achieve in the field. It was found that there is a ratio of maximum aggregate average least dimension (ALD) to specimen diameter and specimen height that must be adhered to when using laboratory testing as a means to evaluate, design, or construct pavement base course layers. In addition, the power input of laboratory vibratory hammers used for compaction must be controlled to minimize aggregate degradation, especially for test molds that do not satisfy the minimum diameter to ALD ratio. The ultimate goal of laboratory compaction should be to accurately simulate field compaction and provide realistic targets that can be achieved in the field. If unrealistic field compaction density targets are specified, then overcompaction can occur and cause aggregate breakdown. The research concluded that changes are required for test standards to better reflect field conditions, such as less lateral constraint, and better reflect achievable target field densities.

Impact effect of superimposed ultrasonic vibration on material characteristics in compression tests

Abstract Conventional ultrasonic-assisted forming in macro scale has been studied widely for decades. However, ultrasonic dynamic impact effect, which only occurs in micro-scale, has never been studied thoroughly. The purpose of this study is to investigate and identify the influencing parameters of amplitude and vibration time for the ultrasonic-induced stress reduction considering dynamic impact effect. As the first step for the purpose, commercially pure aluminum 1100 with specimen size of 2 mm in diameter and height were selected for ultrasonic-assisted compression tests with varying amplitude and press speed. Ultrasonic-induced stress reduction was evaluated and the contour shape of deformed specimens was compared to obtain the effect of ultrasonic vibration on material deformation. The results showed that, ultrasonic dynamic impact effect was the dominating mechanism for stress reduction in compression condition, the stress reduction which caused was nearly 5 times of the sum by stress superposition and acoustic softening. The ratio of amplitude to specimen height is identified as an influencing index for occurrence of ultrasonic dynamic impact effect, for which the critical value equals to half of yield strain. The findings showed promising prospect of ultrasonic vibration in micro-forming, which helped to provide a basis to understand the underlying mechanism of ultrasonic-assisted micro-forming and design the process in next step.

Acetabular rim length: an anatomical study to determine reasonable graft sizes for labral reconstruction.

The purpose of this article is to determine normative values for the length of the acetabular rim and detect differences between gender, age, ethnicity, height and leg length. Six measurements were taken on the acetabular rim of 143 cadaveric skeleton specimens (286 acetabula) using a coordinate-measuring device: circumferential (excluding acetabular notch), anterior inferior iliac spine (AIIS)-anterior, AIIS-posterior, 12–3 o’clock, 12–9 o’clock and 11–5 o’clock. Museum specimen height data and leg length data from a previous study were recorded for 109 of 143 specimens. Intraclass correlation coefficients were calculated. Student t-tests compared mean values. Multiple regression analysis was used to determine the relationship between acetabular rim length and gender, age, ethnicity, height and leg length. The average acetabular rim length in males for circumferential, AIIS-anterior, AIIS-posterior, 12–3, 12–9 and 11–5 o’clock were 15.8, 4.2, 11.7, 4.9, 4.7 and 9.5 cm, respectively; and for females: 13.7, 3.7, 10.0, 4.3, 4.1 and 8.3 cm, respectively. Intraclass correlation coefficients were 0.953, 0.930, 0.958, 0.857, 0.913 and 0.951, respectively, for each measurement. All six measurements were significantly larger for males (P < 0.001). Multiple regression analysis demonstrated a significant relationship between gender and rim length for all six measurements (P < 0.001) and between height and leg length and acetabular rim length for five of the six measurements exclusive of AIIS-anterior (P < 0.001). No significant trends between age or ethnicity and rim length were found. Average acetabular rim lengths were established. The acetabular rim is significantly longer in males and correlates with height and leg length. Age and ethnicity do not appear to be significant predictors of acetabular rim length. Normative values for acetabular rim lengths may assist in hip preservation surgery.

Numerical study on the influence of cross-sectional shape on strength and deformation behaviors of rocks under uniaxial compression

Cross-sectional shape effect, which has not been well studied, is one of the geometry effects that influence rock laboratory test results. In order to investigate the influence of cross-sectional shape on the strength and deformation behaviors of rocks, a comprehensive numerical experiment is carried out to simulate the deformation responses of circular, square, and rectangular cross-sectionally shaped specimens in uniaxial compression. The validity of the numerical model is first examined by comparing the uniaxial compressive strengths (UCS) of cylinder and square prism specimens obtained from the numerical modeling with these obtained in laboratory tests. Both the numerical modeling and laboratory test results show that the cross-sectional shape has a very small influence on the UCS of rocks. However, the numerical results show that the cross-sectional shape affects the post-peak behaviors of rocks considerably. It is also concluded that hoop tension contributes little to affecting rock strength. It is revealed through the numerical study that in the laboratory tests because the square prism specimens with a slenderness (defined by specimen height divided by specimen width) the same as that of a cylinder specimen have an equivalent diameter larger than that of the cylinder specimens, a slightly higher strength of the square prism specimens is thus observed. It is suggested to use the equivalent diameter of a non-circular cross-section to define the slenderness of a specimen to present laboratory test and numerical simulation results consistently.

Fractal crushing of carbonate sands under impact loading

Carbonate sands are widely used in coastal engineering for foundation and embankment. Impact loading could be encountered during driving piles or compacting foundations, which could lead to large grain crushing and changes in grain size distribution. Fractal grading and crushing of carbonate sands were investigated through impact loading tests. The fractal grading uplifted as grains crushed. The fractal dimension and mean diameter decreased with decreasing the specimen height or increasing the input work, while the grain crushing increased with decreasing the specimen height or increasing the input work. It was observed from the test results that the fractal grading of carbonate sand under impact loadings could be intrinsically pertaining to the grain crushing.

A study on fatigue fracture at double and tapered cantilever beam specimens bonded with aluminum foams

Abstract In this study, the models of simple double cantilever beam (DCB) and tapered double cantilever beam (TDCB) were designed to analyze the fracture behavior of the aluminum foam. The fracture behaviors of composite materials exhibit similar trends. The energy release rate increases as the crack length increases and the specimen height decreases. The bonding force influences the adhesive joints of structure. The DCB and TDCB model can be applied generally to the structure with complex configuration. An aluminum foam model has been constructed by using the configuration of DCB and TDCB models in this study. This paper studies the fracture characteristics of specimens due to two kinds of configurations by comparing with the experimental results of DCB and TDCB specimens for mode 1. This study aims to apply fracture toughness to the design of adhesive joints.

Effects of specimen height on the acoustic emission rate value ‘a’ for cement mortar

In order to study the size effect on the AE rate ‘a’ value, three kinds of mix ratios were set up by different particle sizes and water cement ratios, 45 cement mortar specimens with five different heights were tested under axial compression. And the whole damage processes were monitored by full-digital acoustic emission acquisition system, followed by an analysis of mechanical behavior and AE activity. The experimental results show that the height of the cement specimen has significant effects on the compressive strength and the acoustic emission rate ‘a’ value, but a slight effect on the accumulated AE hits number, which is analyzed from aspects of failure process of cement mortar specimens.

Investigation of kinematic behavior and earth pressure development of geogrid reinforced soil walls

Abstract Geogrid reinforced soil is an advanced composite material that is widely used for the construction of retaining walls as frequently needed in transportation structures. Most standards and proposed design methods have included a beneficial effect of geogrid reinforcement on the earth pressure that acts on the facing of a retaining wall. However, field measurements at applications often show much lower deformations and stresses as estimated from the design. This indicates a certain improvement potential for the design of geogrid reinforced soil structures and thereby for the general acceptance of geogrid reinforced soil. Therefore, at RWTH Aachen University model tests with geogrid reinforced soil retaining walls have been carried out. The design of the developed test apparatus allows the determination of various parameters, such as the determination of the earth pressure distribution at the facing, geogrid connection loads at the facing and specimen deformations throughout the whole cross section of the test wall. This article deals with the results of parametric studies focusing on the reduction of the active earth pressure in geogrid reinforced retaining structures due to geogrids with varying reinforcement ratio, i.e. number of reinforcement layers per specimen height, and reinforcement stiffness. A reduction of the earth pressure due to a surface load was apparent already underneath the topmost reinforcement layer. This effect was observed for both, structures with and without a facing connection of the reinforcement. With increasing reinforcement ratio, the sliding soil wedges decreased in size and only an unconfined soil area, beneath a developing soil arch in between two reinforcement layers, caused a horizontal earth pressure on the facing. All observations were merged to formulate a mechanical model idea that is presented at the end of this article.

The Impact of Posture on the Mechanical Properties of a Functional Spinal Unit During Cyclic Compressive Loading.

To assess how posture affects the transmission of mechanical energy up the spinal column during vibration, 18 porcine functional spinal units (FSUs) were exposed to a sinusoidal force (1500 ± 1200 N) at 5 Hz for 120 min in either a flexed, extended, or neutral posture. Force and FSU height were measured continuously throughout the collection. From these data, specimen height loss, dynamic stiffness, hysteresis, and parameters from a standard linear solid (SLS) model were determined and analyzed for differences between postures. Posture had an influence on all of these parameters. In extension, the FSU had higher dynamic stiffness values than when neutral or flexed (p < 0.0001). In flexion, the FSU had higher hysteresis than both an extended or neutral posture (p < 0.0001). Height loss was greatest in a flexed posture and smallest in an extended posture (p < 0.0001). In extension, the series spring element in the SLS model had a stiffness value higher than both flexed and neutral posture conditions, whereas the stiffness in the parallel spring was the same between extension and neutral (p < 0.01), both higher than in flexion. Viscosity coefficients were highest in extension compared to both flexed and neutral (p < 0.01). Based on these results, it was determined that posture had a significant influence in determining the mechanical properties of the spine when exposed to cyclic compressive loading.

Polymerization stress of experimental composites containing random short glass fibers

ObjectiveTo test the null hypotheses that (1) the replacement of particles by short fibers does not affect polymerization stress (PS), flexural modulus (FM) or volumetric shrinkage (VS) of experimental composites and (2) PS is not affected by specimen thickness. MethodsThree experimental composites were prepared, each containing similar mass fractions of BisGMA and TEGDMA and 60 vol% of fillers, being 0%, 3% or 6% constituted by 1.6-mm long glass fibers and the remaining by 1μm glass particles. PS (n=5) was tested in a high compliance system, using two specimen heights (1.5mm and 4.0mm). VS and maximum shrinkage rate were obtained in a mercury dilatometer (n=3). FM was tested in three-point bending (n=10). As an additional control, a commercial composite (Filtek Z250, 3M ESPE) was tested. Data were recorded 10min after the onset of photoactivation and analyzed by ANOVA/Tukey test (FM only) and Kruskal–Wallis (alpha: 5%). ResultsAt both specimen heights, the composite with 3% of fibers presented significantly higher PS than the controls (which showed similar PS values). Replacing 6% of particles by fibers did not increase PS significantly. FM was reduced in the presence of fibers, and 6% of fibers led to a decrease in VS. Shrinkage rate was not affected by the fibers. SignificanceReplacing 3vol% of particles by fibers resulted in significantly higher PS, which was associated to a decrease in FM compared to the control. PS was not affected by specimen height for any of the tested materials.

Analysis of simple shear tests with cell pressure confinement

ABSTRACTThe high cost of offshore infrastructure provides continuous encouragement for optimisation of design practices. Development of a more rational method to interpret results from simple shear tests with cell pressure confinement can reduce costs and improve reliability of offshore infrastructure. This paper addresses a commonly overlooked issue affecting design parameter selection: specimen shape varies from right cylinder to oblique cylinder after loading along a single shearing direction. Thus, horizontal stresses are not always equal to the cell pressure and their magnitude varies throughout the specimen’s lateral surface. An analysis is proposed that accounts for changing specimen geometry and lateral surface area during shearing and for the actual effect of cell pressure during testing. The analysis also describes how the intermediate principal stress can be assessed. Test results for medium dense silica sand are interpreted following de Josselin de Jong’s alternative shearing mechanism hypothesis. Conventional interpretation methods yield conservative design parameters for this soil. Failure states develop when the intermediate principal effective stress is halfway between major and minor principal effective stresses. Typical results for the soil tested show equipment performance meets standard direct simple shear requirements for shear strain rate, vertical stress and specimen height control.

Preload substantially influences the intervertebral disc stiffness in loading–unloading cycles of compression

Disc hydration is controlled by fluid imbibition and exudation and hence by applied load magnitude and history, internal osmotic pressure and disc conditions. It affects both the internal load distribution and external load-bearing of a disc while variations therein give rise to the disc time-dependent characteristics. This study aimed to evaluate the effect of changes in compression preload magnitude on the disc axial cyclic compression stiffness under physiological loading.After 20h of free hydration, effects of various preload magnitudes (no preload, 0.06 and 0.28MPa, applied for eight hours) and disc-bone preparation conditions on disc height and axial stiffness were investigated using 36 disc-bone and 24 isolated disc (without bony endplates) bovine specimens. After preloading, specimens were subjected to ten loading/unloading cycles each of 7.5min compression at 0.5MPa followed by 7.5min at 0.06MPa.Under 0.06MPa preload, the specimen height losses during high loading periods of cyclic loading were greater than corresponding height recoveries during low loading phases. This resulted in a progressive reduction in the specimen height and increase in its stiffness. Differences between disc height losses in high cyclic loads and between stiffness in both load increase and release phases were significant for 0 and 0.06MPa vs. 0.28MPa preload.Results highlight the significant role of disc preload magnitude/history and hence disc height and hydration on disc stiffness in loading/unloading and disc height loss in loading periods. Proper preconditioning and hence hydration level should be achieved if recovery in height loss similar to in vivo conditions is expected.

U-노치 및 균열을 갖는 보의 응력집중계수 및 응력확대계수

Abstract : The stress concentration factors and stress intensity factors for a simple beam and a cantilever are analyzed by using finite element method and phtoelasticity. Using the analyzed results, the estimated graphs on stress concentration factors and stress intensity factors are obtained. To analyze stress concentration factors of notch, the dimensionless notch length H(height of specimen)/h=1.1~2 and dimensionless gap space r(radius at the notch tip)/h=0.1~0.5 are used. where h=H-c and c is the notch length. As the notch gap length increases and the gap decreases, the stress concentration factors increase. Stress concentration factors of a simple beam are greater than those of a cantilever beam. However, actually, the maximum stress values under a load, a notch length and a gap occur more greatly in the cantilever beam than in the simple beam. To analyze stress intensity factors, the normalized crack length (crack length)/H=0.2~0.5 is used. As the length of the crack increases, the normalized stress intensity factors increase. The stress intensity factors under a constant load and a crack length occur more greatly in the cantilever beam than in the simple beam.

Is intervertebral disc pressure linked to herniation?: An in-vitro study using a porcine model

Approximately 40% of low back pain cases have been attributed to internal disc disruption. This disruption mechanism may be linked to intradiscal pressure changes, since mechanical loading directly affects the pressure and the stresses that the inner annulus fibrosus experiences. The objective of this study was to characterize cycle-varying changes in four dependent measures (intradiscal pressure, flexion–extension moments, specimen height loss, and specimen rotation angle) using a cyclic flexion–extension (CFE) loading protocol known to induce internal disc disruption. A novel bore-screw pressure sensor system was used to instrument 14 porcine functional spinal units. The CFE loading protocol consisted of 3600 cycles of flexion–extension range of motion (average 18.30 (SD 3.76) degrees) at 1Hz with 1500N of compressive load. On average, intradiscal pressure and specimen height decreased by 47% and 62%, respectively, and peak moments increased by 102%. From 900 to 2100 cycles, all variables exhibited significant changes between successive time points, except for the specimen posture at maximum pressure, which demonstrated a significant shift towards flexion limit after 2700 cycles. There were no further changes in pressure range after 2100 cycles, whereas peak moments and height loss were significantly different from prior time points throughout the CFE protocol. Twelve of the 14 specimens showed partial herniation; however, injury type was not significantly correlated to any of the dependent measures. Although change in pressure was not predictive of damage type, the increase in pressure range seen during this protocol supports the premise that repetitive combined loading (i.e., radial compression, tension and shear) imposes damage to the inner annulus fibrosus, and its failure mechanism may be linked to fatigue.

Anatomical study of the internal thoracic arteries; implications for use in coronary artery bypass graft surgery.

The feasibility of coronary artery bypass grafting using an internal thoracic artery (ITA) depends on the length of the graft with respect to the optimal route to reach the coronary target. The goal of this study was to assess the gain in length afforded by skeletonization and to evaluate the lengths of different pathways of the ITAs to the left coronary arteries. The left and right ITAs were dissected out from 20 specimens and measured before and after skeletonization. Distance between the origin of the right ITA and the base of the left atrial appendage, corresponding to the proximal circumflex artery, was measured for both the transverse pericardial sinus and preaortic routes. Skeletonization gave a significant gain of length for both ITAs. Analysis showed no significant correlation between the ITA length and the height, weight, and BMI of specimens. We found no association between the length of the sternum and the length of skeletonized RITA or LITA. The anterior route of the skeletonized right ITA was shorter than the transverse pericardial sinus route in 18 cases. The average length to the circumflex artery territory was 132.8±23.5mm in front of the aorta and 150.5±18.8 through the transverse pericardial sinus with a gain of length of 17.7mm (p<0.0001). Skeletonization gave significant gains in length of both ITAs. The preaortic route for the skeletonized right ITA toward the circumflex territory was shorter than the transverse pericardial sinus route in 90% of cases.

Numerical Simulation of Motion Rules of Coarse Aggregates in the Compaction Process

Abstract Three-dimensional digital aggregate particles with irregular shapes were fabricated by truncating spheres with the randomly created cutting planes using the particle flow code in three-dimensions (PFC3D) to investigate their rules of motion during the compaction process. The digital specimen of aggregate mixture with the same gradation and shape characteristics of real aggregates was developed. Specimen were compacted with static pressure in PFC3D. The axial stress on particles, average motion displacement range (AMDR), and translational velocity of each particle were analyzed in the compaction process under different displacements. The results indicate that both axial stress and mean contact-force on particles increases with compacting displacements. Aggregates located at different specimen heights show great differences in AMDR on vertical and horizontal orientation. At the same height of specimen, the AMDR on vertical orientation is greater than that of horizontal orientation and has a positive correlation with compacting displacement. However, the AMDR on horizontal orientation has a poor correlation with compacting displacement. Translational velocity of particle does not show an obvious relationship with the compacting displacement and the height of specimen. This study presented some cues for a further understanding of the compaction mechanism of asphalt mixture.

Configurational phases in elastic foams under lengthscale-free punching

We carry out experiments with brick-like specimens of elastic open-cell (EOC) foams of three relative densities. Individual specimens may be “tall” (height = width = depth) or “short” (2height=width=depth). We place each specimen on a supporting plate and use a lengthscale-free (wedge-shaped or conical) punch to apply forces downward along the specimen's height. Regardless of the type of specimen, the force–penetration curves remain linear, for the wedge-shaped punch, or quadratic, for the conical punch, up to a sizable penetration commensurate with the smallest lengthscale of the specimen. After that there is an abrupt, all-but-discontinuous change in stiffness: if the specimen is tall, the stiffness drops; if the specimen is short, the stiffness shoots up. To analyze these curious experimental results, we posit that EOC foams can be found in either of two configurational phases, here termed the low-strain phase and the high-strain phase, which share a two-dimensional interface (a surface of strain discontinuity). The analysis may be outlined as follows. In the first part of an experiment, there obtains a “similarity regime” in which the penetration of the punch and the radius of the interface are the only prevailing lengthscales (because the punch is lengthscale free). In this case, it is possible to show that the force–penetration curve must be linear, or quadratic, depending on whether the punch be wedge-shaped or conical, respectively. This prediction of the analysis is consistent with the experiments. In time, the similarity regime breaks down when the interface reaches one of the specimen's boundaries distal to the tip of the punch. If the specimen is tall, the soft, stress-free lateral boundary is reached first, and the stiffness must drop; if the specimen is short, the hard boundary in contact with the supporting plate is reached first, and the stiffness must shoot up. These predictions too are consistent with the experiments. To provide direct empirical evidence of the interface, we use a digital-image correlation method. Lastly, we run computational simulations of all the experiments, using finite elements and the skeleton-and-bubble model of EOC foams. The computational results are in good accord with the experimental ones, and they allow us to carry out a detailed validation of the analysis. Our findings evince the cardinal role of configurational phases in the mechanics of EOC foams.