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To design an automatic harvesting machine for hydroponic lettuce (Lactuca sativa L.), physical and mechanical properties of hydroponic lettuce were investigated and analyzed. Moisture content of stem, root and leaf, geometric characteristics, pulling force, and root cutting force were studied for harvesting hydroponic lettuce. The pulling force was examined by a tensile experiment, while the root cutting force was investigated by a shear experiment on the electronic universal testing machine. The moisture content of hydroponic lettuce was obtained by direct drying. Experiment data were processed using regression analysis and mathematical statistics method. A regression equation and the law of numerical distribution were obtained. The results showed that the geometric size of different hydroponic lettuce had little difference, and the distribution of physical parameters was concentrated. Moisture content was found statistically similar in stem and root (around 91%), while the highest moisture content was found in the leaf of 95.73%. The root cutting force decrease with the increase of cutting speed and decrease with the cutting position move downward. The minimum average root cutting force in the experiment was 1.41 N. The average pulling force was 13 N. This study provides adequate theoretical support for the design of the automatic harvesting machine of hydroponic lettuce.

To prove the theory that meteorological factors, especially winter drying events, usually affect trees by inducing water and energy imbalance, systematic studies of winter drying damage to Ligustrum lucidum trees in Shandong, China in 2018 were performed by analyzing digital and thermal images of the trees and integrating the results with meteorological and geostatistical analysis and the results of osmotic stress tests in saturated sucrose solution. The results indicate that sap water can not only be transported upward with assistance from cohesion-tension force, but also can be turned back from the terminals of leaves and branches under the inverse pulling force. Under extreme conditions during winter drying events, the breakage of sap water column and reduction of the terminal tissues or organs occur. Similar “∧”-shaped leaf symptoms can also be induced by freezing, summer drought and osmotic stress. The results support the theory of transpiration surface reduction characterized by unity of freezing and drying. Therefore, severe damage to juvenile plants of Ligustrum lucidum under these conditions may be caused by the combined effects of low temperature, drought, strong irradiation and saline soil as well as by the sensitive status of the plants.

The paper presents a model for predicting pulling forces during pulling back phase in horizontal directional drilling (HDD) projects. The analytical method follows the method proposed by Polak et al. (2007) and expands it in three aspects: (1) the surrounding soil is described by Winkler model and it constitutes an elastic support for pipe during pulling back, (2) the non-Newtonian properties of slurry is considered and (3) the resistance exerted on drill string is considered and the pulling force at rig is calculated. Components of the pulling force are calculated considering the effect of pipe-soil interaction in cross section and the coefficient of chock effect, which can be calculated using the finite element analysis is defined to indicate the clamping effect of soil on the pipe. A computer program PipeForce Version1 was compiled according to the given method. A comparison of HDD experimental data and predictions of pulling forces are presented.

Background External ventricular drain (EVD) dislodgement is common and leads to significant morbidity and mortality. Many securement techniques to prevent this are described. There are, however, no objective studies comparing them. This study aimed to determine the most secure method of securing an EVD. Methods A survey was distributed through the British Neurosurgical Trainee Research Collaborative to determine common EVD securement methods and select techniques for testing. Securement methods were tested in a pig cadaver model. Peak pull force before EVD failure was measured. Failure was defined as catheter displacement 1 cm from the insertion site, catheter fracture, or suture fracture. Results Twenty-three neurosurgical units responded. Five basic EVD securement methods were in common use. These were tested in isolation and in combination so that in total 15 common methods were tested. The most secure method was a triple construct, consisting of an anchoring suture, sutures around a coil of the catheter, and either a soft plastic flange (25.85 N, 95% confidence interval 24.95 N–26.75 N) or a hard plastic flange (29.05 N, 95% confidence interval 25.69 N–32.41 N). Of the individual methods, single anchoring sutures, soft flanges, VentriFix, and staples were found to be the least secure, whereas multiple sutures and hard flanges were the most secure. Conclusions An anchoring suture followed by a coil of the catheter and finally a flange is the most secure method for securing EVDs. This simple technique can withstand up to 8.2 times the force of a single anchoring suture, is easily used, and decreases the likelihood of EVD dislodgement and associated complications.

A review of computational modelling and simulation of pultrusion processes is presented including such aspects as: resin flow and pressure distribution in a forming die; impregnation of reinforcing fibers; heat transfer and resin reaction; pulling force, stresses and strains development; methods for numerical optimization of the process. Development of models provides deeper knowledge concerning the mechanisms behind the process as well as the influence of constituent materials’ properties and manufacturing parameters. Consequently, accelerated development of pultrusion process, allowing for the manufacturing of geometrically complex profiles is promoted.

During dynamic compaction , frequent heavy load unloading impacts are the main reasons for crane structural damage. To address this problem, a new method to reduce the unloading impact for a crane is discussed. Firstly, through the energy method, an expression for the energy consumption of the unloader that has been ignored before is established and a mathematical model describing the key parameters of the unloader is obtained. Secondly, a force controlled unloader is designed to convert the pulling force control of the wire rope that suspends the heavy hammer into its own hydraulic control. Thirdly, a rigid-flexible coupling model of a crawler crane used for dynamic compaction is built to predict the relationship between the unloading time and the dynamic response. Finally, a new unloader that slowly releases heavy hammer in the air under gravity has been developed and the experimental result proves the feasibility of flexible unloader.

Reinforcement of elevated subgrades, embankments, or slopes is a focus of highway construction projects. In this study, a new negative-Poisson's-ratio geobelt (NPRG) is developed to facilitate such reinforcements. Herein, the NPRG design and manufacturing process are described in detail. Additionally, tensile tests, pull-out tests, and numerical simulations to test the negative-Poisson’s-ratio effect and mechanical behavior of the NPRG in soil are reported. The results show that the NPRG shell structures are lifted by the core structure under tension, thereby expanding the NPRG cross-section. Hence, a negative-Poisson's-ratio effect is generated. Further results show that the negative-Poisson's-ratio effect of the NPRG only appears when the axial strain exceeds 1.2% or 1.6% (from the test and numerical simulation, respectively). Moreover, with 300 kPa as the boundary, the NPRG peak pulling force first increases and then decreases with increasing upper pressure. Finally, the negative-Poisson's-ratio effect of the NPRG disturbs the surrounding soil. Simultaneously, the NPRG cross-sectional expansion makes it more closely integrated with the surrounding soil, thereby, improving the reinforcement effect.

Older adults exhibit reductions in push-off power that are often attributed to deficits in plantarflexor force-generating capacity. However, growing evidence suggests that the foot may also contribute to push-off power during walking. Thus, age-related changes in foot structure and function may contribute to altered foot mechanics and ultimately reduced push-off power. The purpose of this paper was to quantify age-related differences in foot mechanical work during walking across a range of speeds and at a single fixed speed with varied demands for push-off power. 9 young and 10 older adults walked at 1.0, 1.2, and 1.4 m/s, and at 1.2 m/s with an aiding or impeding horizontal pulling force equal to 5% BW. We calculated foot work in Visual3D using a unified deformable foot model, accounting for contributions of structures distal to the hindfoot's center-of-mass. Older adults walked while performing less positive foot work and more negative net foot work (p 0.05). Further, we found that the effect of age on mechanical work performed by the foot and the ankle-foot complex increased with increased locomotor demand (p 0.05). Our findings suggest that during walking, age-related differences in foot mechanics may contribute to reduced push-off intensity via greater energy loss from distal foot structures, particularly during walking tasks with a greater demand for foot power generation. These findings are the first step in understanding the role of the foot in push-off power deficits in older adults and may serve as a roadmap for developing future low-cost mobility interventions.

This work is motivated by the need for prediction of pulling forces during pulling back phase in the horizontal directional drilling (HDD) installations for steel or polyethylene pipe. Six current prediction models are reviewed and components of pulling force resistance used in calculations are discussed. Two HDD installations are used to evaluate the accuracies of six models, including a 1816.2 m steel pipe crossing of the Yangtze River, Nanjing, China, and a 200 m polyethylene pipe installation at the University of Waterloo, Waterloo, Canada. Comparison of the results show that Driscopipe method and Drillpath method underestimate the maximum pulling forces in both steel pipe and polyethylene pipe cases, ASTM F 1962 method underestimates the maximum pulling force in steel pipe case while PRCI method and NEN 3650 method overestimate the maximum pulling force in polyethylene case, PRCI method, NEN 3650 method and developed PipeForce method are suitable for steel pipe case, ASTM F 1962 method and the PipeForce method are acceptable for polyethylene pipe case.

The translocation behavior of preformed particle gel (PPG) in porous media is crucial for its application in enhanced oil recovery. By means of non-equilibrium molecular dynamics simulation, the translocation mechanism of PPG confined in different silica nanopores were investigated. The influence of surface chemistry and chemical heterogeneity of silica nanopore on the translocation process was revealed. As the degree of surface hydroxylation increases and the heterogeneity decreases, the pulling force needed to drive PPG decreases. We infer that the nanopore’s surface (i.e. surface chemistry and heterogeneity) affects the translocation of PPG indirectly by forming different hydration layers.

Enterprise eco-development is one of the effective ways to resolve the conflicts between resources exploitation and environment protection, and to realize sustainable development. A sound understanding of enterprise ecological motivation is a prerequisite and foundation of promoting enterprise ecologicalization. This study analyzes the level of eco-development of 12 resources-based enterprises in the Pan-Qaidam economic pilot area so as to determine influential motivators and to identify their eco-development paths using the entropy TOPSIS method. The results show that the level of motivation is generally low and uneven among the 12 enterprises. Enterprise ownership affects enterprise ecological motivation in the pulling force of eco-culture only. The top three motivators are the leading-force of government, the driving force of science and technology, and the pulling force of market. The remaining important motivation factors are mostly internal, including the driving force of enterprise innovation, the guiding force of eco-culture, and the induced force of interest, even though internal motivation is weaker than external motivation. In general, the 12 enterprises have an uneven distribution in their level of eco-development. The majority of them (8) fall into the type I model (weak internal and external motivation) of development, with 3 and 1 in the type II (weak internal but strong external motivation) and type III (strong internal but weak external motivation) models, respectively, without any in type IV (strong internal and external motivation). This situation can be remedied through four recommendations.

Mechanical force regulates the formation and growth of cell-cell junctions. Cadherin is a prominent homotypic cell adhesion molecule that plays a crucial role in establishment of intercellular adhesion. It is known that the transmitted force through the cadherin-mediated junctions directly correlates with the growth and enlargement of the junctions. In this paper, we propose a physical model for the structural evolution of cell-cell junctions subjected to pulling tractions, using the Bell-Dembo-Bongard thermodynamic model. Cadherins have multiple adhesive states and may establish slip or catch bonds depending on the Ca 2+ concentration. We conducted a comparative study between the force-dependent behavior of clusters of slip and catch bonds. The results show that the clusters of catch bonds feature some hallmarks of cell mechanotransduction in response to the pulling traction. This is a passive thermodynamic response and is entirely controlled by the effect of mechanical work of the pulling force on the free energy landscape of the junction., 11 pages, 12 figures, 2 tables

Statement of problem Clinical studies comparing the retention values of milled denture bases with those of conventionally processed denture bases are lacking. Purpose The purpose of this clinical study was to compare the retention values of conventional heat-polymerized denture bases with those of digitally milled maxillary denture bases. Material and methods Twenty individuals with completely edentulous maxillary arches participated in this study. Definitive polyvinyl siloxane impressions were scanned (iSeries; Dental Wings), and the standard tessellation language files were sent to Global Dental Science for the fabrication of a computer-aided design and computer-aided manufacturing (CAD-CAM) milled denture base (group MB) (AvaDent). The impression was then poured to obtain a definitive cast that was used to fabricate a heat-polymerized acrylic resin denture base resin (group HB). A custom-designed testing device was used to measure denture retention (N). Each denture base was subjected to a vertical pulling force by using an advanced digital force gauge 3 times at 10-minute intervals. The average retention of the 2 fabrication methods was compared using repeated ANOVA (α=.05). Results Significantly increased retention was observed for the milled denture bases compared with that of the conventional heat-polymerized denture bases ( P Conclusions The retention offered by milled complete denture bases from prepolymerized poly(methyl methacrylate) resin was significantly higher than that offered by conventional heat- polymerized denture bases.

In many biological materials, the interfacial behaviour between constituents such as protein and minerals greatly contributes to the overall mechanical behaviour. However, the governing mechanisms, in particular at small material length scales, have not been clearly understood. This paper presents a molecular dynamics (MD) study of the mechanical behaviour of osteopontin (OPN) and hydroxyapatite (HA) interfaces under different geometrical constraints. The results indicate that some OPN residues are attracted to the HA layers during loading. The formation of new interfacial bonds leads to a stick-slip type motion of the OPN peptides along the HA surfaces, resulting in high pulling force and energy dissipation. The attractive interaction energy and energy dissipation generally increase with reducing the gap distance between the HA layers, demonstrating a significant nano-scale constraint effect.

Improving machine performance and optimum energy usage are great importance in mechanized agriculture. The purpose of the study was to assess the tractor driving system including rear-wheel drive (RWD), four-wheel drive (4WD) and front-wheel drive (FWD) effect on the tractor performance and its fuel use during tillage operation. Then the field experiments were conducted to investigate the effect of driving system type. Moreover the tire inflation pressure of 170, 200, and 230 kPa, ballast weights of 0, 60, and 120 kg, and pulling force of 2, 6, and 10 kN on the Goldoni tractor performance were examined. The results indicated that the 4WD system had more impact on the rolling resistance than other factors. The trend of draft force represented that using the 4WD system allows achieving a higher pulling force without exceeding the allowable slip. In comparison, the FWD and RWD systems exceeded the allowable slip of the 6–10 kN draft force. At a pulling force of 2 kN, the minimum fuel consumption was corresponded to the RWD system while the maximum fuel consumption corresponded to the 4WD system. But in the pulling force of 10 kN, the situation was different and the type of driving system had a significant effect on reducing fuel consumption and the minimum fuel consumption was achieved for the 4WD system.

Trigeminal neuralgia is featured by episodic and severe unilateral facial pain triggered usually by innocuous cutaneous stimuli.1-4 Microvascular decompression (MVD) is a safe and effective treatment for cases refractory to medical treatment caused by neurovascular conflicts.1,5-7 This Video 1 demonstrates MVD using arachnoid membrane and petrosal dura to transpose dual offending arteries. Informed consent was obtained from the patient for publication of this operative video. The patient was a 64-year-old woman with refractory right trigeminal neuralgia (V2 territory). Preoperative magnetic resonance imaging demonstrated simultaneous conflict between the right trigeminal nerve (TN) and superior cerebellar (SCA) and anterior inferior cerebellar arteries (AICA). Due to progressive and refractory symptoms, MVD was indicated, with aid of neurophysiologic monitoring. A right retrosigmoid approach was employed and after exposure of the TN root, both AICA and SCA were identified conflicting with the nerve. The AICA was displaced inferolaterally and attached to the petrosal dura between the VII/VIII and IX cranial nerves using a USP #0 silk thread. The SCA was mobilized into a fissure created in the lateral pontomesencephalic arachnoid membrane and fixed with shredded Teflon (polytetrafluoroethylene). Another piece of Teflon was positioned between the TN and the proximal segment of AICA to lighten the pulling force from the thread. Postoperative imaging demonstrated no signs of cerebellar contusion or hemorrhage. The patient presented complete resolution of her pain, and no neurologic deficits were observed. We demonstrate MVD with 2 different transposition techniques that can be considered for trigeminal neuralgia with dual offending arteries (AICA, SCA).

Objective The objective of this study was to investigate the mechanics of ventricular anchor for heart valve repair or replacement. Methods Thirteen anchors were designed based on six geometric parameters of the anchor teeth: width, thickness, root length, radius of curvature, tip angle, and tip length. Finite element method was applied to simulate the process of the anchor compressing into a sheath. The Von-Mises strain, peak pulling force, and bite depth were evaluated. An experiment was performed to validate the simulation. Results The maximum Von-Mises strain was at the contact region of the anchor in a sheath where the teeth were compressed against one another and were distorted. The maximum strain increased with an increase in tooth width, thickness, radius of curvature and tip angle. The peak pulling force increased as tooth thickness and width increased, and radius of curvature decreased. Both the radial and axial bite depths increased with an increase in the tip length at the tip length≥3 ​mm. The radial bite depth increased with an increase in the radius of curvature. Conclusion 1) the maximum strain depends primarily on the tooth width, thickness, radius of curvature and tip angle; 2) the peak pulling force depends primarily on the tooth width, thickness, radius of curvature; 3) the axial bite depth depends primarily on the tip length at the tip length≥3 ​mm. The radial bite depth depends on the radius of curvature and the tip length at the tip length >3 ​mm. The study provides guidance for ventricular anchor design.

A bearingless induction motor (BIM) is a new type of motor with non-contact rotor suspension and negligible friction loss. One major imperfection of this motor is that its performance highly depends on the rotor slot width. This paper attempts to solve this problem by using a combined analytical method and finite element analysis method (FEM). Firstly, the influence on the motor starting characteristics is revealed by analytical method and verified by finite element simulation. Secondly, using the fast Fourier transform (FFT), the effect on the radial harmonic magnetic field distribution of air gap is analyzed. Meanwhile, the impact on the motor load performance is calculated. Thirdly, the relationship among the rotor slot width, the suspension force and the unbalanced magnetic pull force is explored. Finally, the simulation and experimental results show that the BIM designed by the combined analytical method and finite element calculation can not only obtain good torque characteristics and suspension performance but also has less load loss and a better accuracy in its mathematical model. This paper provides a theoretical basis and means for further design optimization of this type of motor.

In this paper the out of die ultraviolet (UV) cured pultrusion for manufacturing impact automotive energy absorbing parts has been analysed. Aspects such as the UV source, pultrusion process variables and final mechanical and physical properties of the pultruted parts have been studied. The measured maximum pulling force in the die was approximately 80 N. The parts cured with high intensity UV LED sources present low void concentration and almost no expansion at the exit of the die. The parts cured with the traditional UV arc lamp have an expansion of 20% of the expected thickness and hence, high void concentration. The less expansion at the exit of the die is translated into an improvement of 26% in the interlaminar properties and in 8% in the energy absorbing capability of the UV LED cured parts.

The mechanics of belt friction before the state of gross slip is considered. The variation of the belt force within the contact region is evaluated based on the assumption of gradual growth of slip from the pull-end to the hold-end of the belt, as the pull force increases towards its Euler's value. The local pressure and friction forces exerted by the belt on the cylinder are also determined. Both flat and V-shaped belts are considered. The total pressure and friction forces are evaluated at an arbitrary stage of slip growth. They are neither proportional nor orthogonal to each other, unless the state of gross slip is reached throughout the contact range.

In ultraviolet nanoimprint lithography (UV-NIL), adhesion between the UV curable resin and the stamp is one of the most significant factors affecting successful pattern transfer. Therefore, the adhesion properties of UV curable resins used in UV-NIL must be properly understood. In this study, a simple and novel method is proposed for evaluating the adhesion properties of UV curable resin, using a specially-designed adhesion tester. Using this method, the pull-off tests between a stamp and a UV curable resin for UV-NIL was conducted, and the effects of UV-NIL process conditions on adhesion properties were investigated. PAK-01 was used as the UV curable resin for UV-NIL and a counterpart was a fused silica lens as the stamp. The pull-off forces between the PAK-01 and the lens were measured for various hold times, pulling force rates and relative humidities, and the effects of these process conditions on the pull-off force were examined. The pulling force rate and the relative humidity were found to have a strong influence on the pull-off force. The pull-off force increased as the pulling force rate increased, but decreased as the relative humidity increased. In contrast, the effect of hold time on the pull-off force was insignificant.

Atlantic cod (Gadus morhua) bite at netting materials in sea-cages, which is known to weaken and destroy net materials, contribute to the formation of net holes and lead to escapes. We determined the lateral pulling forces applied to nets through biting by cod in a laboratory set-up. A sensor for automatic logging of the lateral pulling force was used to obtain data for over 1000 undisturbed, objectively collected biting events. Lateral pull force varied between cod of different size (180 and 610 g) and different net types, ranging from 0.9 to 9.4 N. Further, pull forces were on average 1.5–2.5 times stronger during lengthy biting events compared to single, brief bites. Maximum lateral pulling forces exerted by 610 g cod were similar to their body weight in air, while 180 g fish were able to pull with a force equivalent to twice their own weight in air. All recorded lateral pull strengths significantly exceeded the known force needed to break single nylon fibres of the netting material. Our results advance understanding of mechanisms and forces involved when cod interact with sea-cage nets and provide important baseline data for the design and production of more bite-resistant netting.

Piezo ion channels mediate the conversion of mechanical touch into electrical signals and are critical for the organism's responsiveness to mechanical forces. How Piezos detect mechanical stimuli is unknown.The apparent mechanical sensitivity of Piezo1 varies substantially across cellular environments, stimulating methods and protocols, raising the fundamental questions of what precise physical stimulus activates the channel and how its stimulus sensitivity is regulated. Here, we measured Piezo1 currents evoked by membrane stretch, while simultaneously visualizing and measuring membrane geometry. Building on this approach, we developed protocols to minimize resting membrane curvature and tension prior to probing Piezo activity. We find that Piezo1 responds to lateral membrane tension with high sensitivity as compared to other mechanically activated channels and that resting tension can drive channel inactivation, thereby tuning overall mechanical sensitivity of Piezo1. Our results explain how Piezo1 can function efficiently and with adaptable sensitivity as a sensor of mechanical stimulation in diverse cellular contexts.The next step in understanding the mechanism of Piezo activation would be the identification of structures within Piezos that detect a mechanical stimulus and that mediate channel inactivation. We hypothesized that specific structures within Piezos are highly sensitive to localized application of force, whereas others are less sensitive in comparison. To test this hypothesis, we developed a novel method, where we apply highly localized force to specific protein domains and simultaneously measure ion channel activity upon pressure-clamp stimulation. For this, we label specific domains within Piezos with magnetic nanoparticles and use an external magnetic field to generate a precise mechanical force that is highly localized. Simultaneously, we measure Piezo-activation electrophysiologically. With this approach we have identified domains that are sensitive to application of localized magnetic pulling force and other domains that are completely insensitive to the same force.

With the rapid development of advanced microelectronic packaging technologies, research on fine-pitch wire bonding with improved reliability is driven by demands for smaller form factors and higher performance. In this study, thermosonic wire bonding process with a 20 μm wire for fine-pitch interconnection is described. To strengthen stitch bonds made in a gold–silver bonding system when the bonding temperature is as low as 150 °C, ball bumps (security bump) are placed on top of the stitch bonds. The ball–stitch bond and bump forming parameters are optimized using a design of experiment (DOE) method. A comparison of pull test results for stitch bonds with and without security bumps shows a substantial increase of the stitch pull force (PF) due to the use of security bonds. By varying the relative position of the security bumps to the stitch bonds via wedge shift offset (WSO), a WSO window ranging from 15 to 27 μm results in stitch PF higher than 7 gf, which is equivalent to an increase in average stitch PF of 118%.

The current study determined the maximal voluntary isometric forces for a variety of finger pulling tasks. Twenty healthy females, with no history of upper extremity injuries, were asked to use the fingers from their dominant hands and apply their maximal voluntary pull forces for seven conditions that varied in the number of fingers, force application location and interface characteristics. All conditions were tested with and without the use of a glove. However, there was no significant effect of wearing a glove. As expected, the maximum force increased with the number of fingers used and decreased when forces were applied on the finger tip instead of the first distal inter-phalangeal joint. Maximum forces ranged from 59.5 ± 21.4 N when using the index finger tip on a thin ring, to 268.7 ± 77.2 N when using all four fingers on a straight bar. Relevance to industry Many industrial tasks require pulling with the finger(s). The current study provides a set of maximal finger pull force values that can be used to set force limits that will contribute to protecting worker health and safety and insuring manufacturing quality.

A pulling force device is used to carry out monthly performance tests on 12 judo athletes of the Olympic Center Linz, Austria. The variation of a friction brake simulates the resistance of the opponent in the throwing technique Seoi-Nage. By measuring force and velocity, the parameters F max , t ( F max ) , d F max and v max are calculated using LabView. A synchronous 3D motion analysis in Peak Motus shows the quality of movement in more detail. The relevant investigations comprise the 3D position of center of mass, ankle and shoulder; knee and elbow angle, body axis as well as trunk rotation.

A manual guided vehicle (MGV) is used to handle heavy materials in thin film transistor-liquid crystal display (TFT-LCD) manufacturing clean rooms. This study focuses on evaluating the force exertions and muscle activities in MGV operations. The independent variables include gender, force direction, handle height, load handled and wheel diameter of the MGV. The results show the force direction, handle height and load handling effects are significant in most measures except for F(ending) (the peak force required to stop the MGV) and the EMG of the anterior deltoid. The wheel diameter had a significant effect on F(initial) (the peak force required to move the MGV) and F(ending) responses. Gender did not significantly effect any measures. Moreover, the pushing and pulling force is less at 115cm handle height than at 101.5cm and 88cm handle heights. Using 15.3cm (6 inch) diameter wheels requires less force than 20.3cm (8 inch) diameter wheels because the two front wheels are fixed and the two rear wheels are rotatable. The design implications are discussed.

Nowadays, Pneumatic Artificial Muscle (PAM) has become one of the most widely-used fluid-power actuators which yields remarkable muscle-like properties such as high force to weight ratio, soft and flexible structure, minimal compressed-air consumption and low cost. To obtain optimum design and usage, it is necessary to understand mechanical behaviors of the PAM. In this study, the proposed models are experimentally derived to describe mechanical behaviors of the PAMs. The experimental results show a non-linear relationship between contraction as well as air pressure within the PAMs and a pulling force of the PAMs. Three different sizes of PAMs available in industry are studied for empirical modeling and simulation. The case studies are presented to verify close agreement on the simulated results to the experimental results when the PAMs perform under various loads.

An agricultural worker has to exert push/pull force in the horizontal plane while operating many farm tools and equipment. However, very little data are available on push/pull strength of agricultural workers. A study was therefore carried out to collect these data on male as well as female agricultural workers. A strength measurement setup developed at CIAE, Bhopal was used for the purpose. Data were collected on 920 subjects from different parts of Madhya Pradesh State in central India of which 604 were male and 316 were female agricultural workers. The mean age, stature and weight of the male subjects were 29.6 ± 8.9 years, 1646 ± 59 mm and 51.4 ± 6.5 kg whereas for female subjects the values were 32.6 ± 8.1 years, 1512 ± 52 mm and 45.3 ± 7.2 kg, respectively. The isometric push/pull strength of male subjects was higher than that of female subjects. The mean values for isometric push and pull strength in a standing posture with both hands (in the horizontal plane) were 253.8 ± 52.8 N and 234.2 ± 43.0 N, respectively for male subjects and 183.1 ± 35.6 N and 185.1 ± 30.8 N, respectively for female subjects. Weight of the subjects indicated a positive correlation with isometric push/pull strength. The 5th percentile push and pull strength values were 167.0 N and 163.5 N, respectively for male subjects and 124.4 N and 134.4 N, respectively for female subjects. These values can be used to set limits in the design of manually operated farm tools and equipment as well as for manual materials handling activities involving pushing/pulling, depending on the frequency of movement. Relevance to industry The strength values and design criteria presented in this paper may be used for setting limits for design of manually operated tools and equipment involving push/pull activities in agriculture as well as in other industrial jobs.

Radial drilling technology, of which the jet bit is the key device, is a research focus in the field of oil drilling and production. This paper establishes mechanical equations for jet bits and analyzes the hydroseal of backward jets in bottom holes. Meanwhile this paper establishes a mechanical equation for a high pressure hose and analyzes the axial force distribution. Laboratory experiments indicate that the flow rate, the angle between the backward nozzle axis and the jet bit axis, and the hole diameter are the major influencing factors; the generation of the pulling force is mainly due to the inlet pressure of the jet bit; the backward jets can significantly increase not only the pulling force but also the stability of jet bits. The pulling force would reach 8,376 N under experimental conditions, which can steadily pull the high-pressure hose forward.

The so-called peel test, in which a thin plate bonded to a substrate is subjected to an inclined pulling force, has been widely used to characterise the bond behaviour of adhesives. This paper presents an analytical solution for the interfacial normal and shear stresses in such a peel test to provide an improved understanding of its underlying mechanism. An approximate closed-form solution is also presented. The effect of the peel angle (i.e. the angle between the applied force and the substrate) on the interfacial stresses is discussed. Apart from being a widely used test for quantifying adhesive characteristics, the process of debonding in a peel test resembles that of intermediate flexural-shear or shear crack induced debonding in flexurally strengthened RC members, where a relative vertical displacement exists between the two sides of the crack, leading to an angle between the external plate and the concrete substrate. Therefore, the results of this study also offer some insight into the latter failure mode which is very important in the flexural strengthening design of RC members.

Recent imaging studies revealed that neocortical neurons undergo multiple modes of migration, but their earliest morphologies and behaviors remain unclear. We found that some neurons generated at the ventricular surface initially adopt a pin-like morphology and generally lack a leading process. During abventricular nuclear movement, their centrosomes are localized to the ventricular endfoot. Their detachment from the germinal zone is accomplished by retraction of the ventricular process, which is frequently accompanied by an adventricular somal movement, suggesting that a pulling force within the process might function to contract the cell. Subsequently, they become multipolar upon entry into the subventricular zone.

Thioredoxins (Trx) are a class of enzymes, which catalyze the reduction of disulphide bonds between two cysteine residues, commonly found in proteins. An experimental investigation into the reaction mechanisms employed by various species of Trx was carried out by Perez-Jimenez et al. using single molecule force-clamp spectroscopy. The experiment involved applying a pulling force along the disulfide bond of the protein substrate, and measuring the rate of the Trx-catalyzed reduction as a function of the pulling force. One interesting finding of the experiment was that some forms of thioredoxin exhibit a biphasic relationship for reduction rate as a function of force magnitude. For this project, a mathematical model of this system was created, which employs a Smoluchowski formalism in the vein of Agmon-Hopfied or Sumi-Markus models. The model describes the time evolution of the probability distribution function of the protein's configuration within a space defined as the internal protein coordinate, as it diffuses over a potential which distorts under the applied force, while losing probability density to the Bell model type “sink” term, which is also a function of the applied force, representing reactants going to products (disulphide bond cleavage). By numerically solving the Smoluchowski equation and integrating the resulting surface over both time and the protein coordinate to calculate lifetime for increasing values of applied force, the model successfully reproduced the experimentally observed values for disulphide bond reduction rate as a function of applied force. Parameterizing the Smoluchowski equation to fit the experimentally measured data points provided a means of drawing insights into a physical interpretation of the model including the relationship between degree of biphasic behavior and the distance along the reaction coordinate from the bottom of the reactant well to the top of the transition state.

A generalized JKR model is established for non-slipping adhesive contact between two dissimilar elastic spheres subjected to a pair of pulling forces and a mismatch strain. We discuss the full elastic solution to the problem as well as the so-called non-oscillatory solution in which tension and shear tractions along the contact interface is decoupled from each other. The model indicates that the mismatch strain has significant effect on the contact area and the pull-off process. Under a finite pulling force, a pair of adhering spheres is predicted to break apart spontaneously at a critical mismatch strain. This study suggests an adhesion mediated deformation sensing mechanism by which cells and molecules can detect mechanical signals in the environment via adhesive interactions.

In the processing of the bottom-exposure stereolithography system, the curing photopolymer will connect to the resin tank as well as the upper layer. After the exposure of each layer, the forming platform has to be levered up and resin can flow into the gap between the completed layers and the resin tank. During the pulling up stage, the cured layer might not levitate together with the above layers but break and stay on the bottom of the resin tank. In order to conquer the pulling failure, a great amount of over curing is necessary to gain enough bonding force between the new exposure layer and the above layers. This over curing will cause decline of accuracy. In this paper, a super elastic intermediate material has been introduced to minimize the pulling force. The super elastic and shear strength property can help to break the vacuum between the new exposure layer and the resin tank. By the reduction of the pulling force, the amount of over curing requirement can also be reduced. Formulation of the cured forming shape and the pulling force has been proposed. The result shows that only area size is important. Hence, the pulling force can be predicted and used in on-line monitoring of the fabrication process.

The aim of the study was to examine the effect of articaine hydrochloride (AH) on the healing of surgical wounds and to compare healing with that of lidocaine.Forty rats were used in this study. The rats were randomly separated into 4 groups. Three groups were given 2% lidocaine, 4% AH, or injectable saline, and the fourth was a control group. Skin specimens underwent the breaking strength test (BST) and histologic examination at 1 week after the surgical procedure. The skin specimens of the rats were subjected to a pulling force of 10 mm/min across the incision line. The strength value at the moment of breaking in the tissue was expressed in Newtons. Histologic examination was performed as well, and wound healing was graded.Both the histologic grade and BST values in the lidocaine and AH groups were significantly lower than those of the control and saline groups (P.01). Similarly, the histologic and BST values of the AH and lidocaine groups were statistically significant (P.05, P.001). Some necrotic regions were observed at the incision region in 2 samples from the AH group.The results of the study showed that AH is as safe a local anesthetic agent as lidocaine from the standpoint of wound response.

Variously known as “Bent pultrusion”, “3D pultrusion”, or “Post-Die Manipulation”, this is a method of pultrusion where the cure process takes place outside the die. This results in very low pulling forces and the ability to manipulate the shape of the pultrudate during formation. In the normal pultrusion process continuous thermoset resin coated fibres are pulled through a long heated die. Since the resin is cured within the die the pulling force required could be significant, consequently current process machines are large and expensive. The finished pultrudate is also limited to continuous straight profiles of constant cross-section. In the feasibility study work described in this paper, the process of curing relies primarily on irradiating the resin-coated fibres with ultra-violet (UV) light, as the profile exits the die. The die therefore, is only required to impart a profile, and strip excess resin from the fibre/resin bundle. The pulling force is thus very much reduced lowering the capital cost of the plant. The pultrudate can be manipulated after it exits the die and before the resin matrix has fully cured to produce a product with controlled variation in curvature.

We consider a vesicle, bound on one side to a pipette and sticking on the other side to a flat plate. When a pulling force f is applied to the pipette, the radius R c of the contact patch decreases, and jumps to zero at a critical value of the force. We present here an extension of the Evans theory for these processes. Then we discuss the dynamics of separation for two distinct cases: (a) nonspecific adhesion; and (b) specific adhesion induced by mobile proteins. To cite this article: F. Brochard-Wyart, P.-G. de Gennes, C. R. Physique 4 (2003).

A compensatory stepping response is a commonly used strategy in recovering balance control after a postural perturbation. Unlike gait initiation, the compensatory stepping often occurs without an anticipatory postural adjustment (APA), in which body weight is shifted to the swing leg first and then back to the stance leg prior to foot lifting. In postural perturbation studies using a moving platforms stepping responses without an APA were found to have shorter latency to foot lifting than trials with an APA. We studied stepping responses of healthy young adults under postural perturbation of a pulling force impulse on the subject's waist. In contrast to previous studies, the latency of foot lifting was found in the current study to be shorter in the trials with an APA than trials without an APA. Furthermore, greater amplitude of an APA was associated with a shorter latency of foot lifting. Response with an APA of large amplitude may indicate high level of determinant for foot lifting. A pause as to whether or not to initiate/complete a stepping response is suggested to be partially the cause of delayed foot lifting in trials without an APA or with small amplitude of the APA.

We present a novel ultrasonic wire-to-wire bonding method for bonding two micrometer-thick metal wires together. A special jig and an industrial wire bonder perform the bonding. This wire-to-wire bonding is the core unit process to produce space tether for the Electric Solar Wind Sail. The proposed method was validated experimentally with 38 bonds where a [email protected] and a [email protected] by diameter Al wires that were first bonded together after which the bond was pull tested. The measured average pull force was (74+/-15)mN whereas the lowest pull force value was 40mN. The results show that wire-to-wire bonds of sufficient strength can be produced for the Electric Solar Wind Sail tether application. Tether manufacturing was demonstrated with a separate test where a 1.4m long tether was produced featuring more than 100 wire-to-wire bonds.

Objective. Compare the mechanical load on the low back and shoulders during pushing and pulling a two-wheeled container with the load during lifting and carrying the same amount of waste. Background. Only little is known about risk factors and mechanical loads during push/pull operations. Design. A complete 23 factor push/pull experiment. A two-wheeled container with 25 or 50 kg was pushed in front of and pulled behind the body by seven waste collectors. Further, the same subjects lifted and carried a paper bag and a dustbin both loaded with 7 and 25 kg. Method. All operations were video recorded and the push/pull force was measured by means of a three-dimensional force transducer. Peak Motus and Watbak software were used for digitising and calculation of torque at L4/L5 and the shoulder joints and compression and shear forces at L4/L5. Results. During pushing and pulling the compression at L4/L5 is from 605 to 1445 N. The extension torque at L4/L5 produced by the push/pull force is counteracted by the forward leaning of the upper body. The shear force is below 202 N in all situations. The torque at the shoulders is between 1 and 38 Nm. Conclusion. In the present experiments the torques at the low back and the shoulders are low during pushing and pulling. No relation exists between the size of the external force and the torque at the low back and the shoulder. Relevance Pushing and pulling are common in many workplaces and have often replaced lifting and carrying situations. This has emphasised the need for more knowledge of the internal mechanical load on the body during these activities.

An alternative model for predicting adequate operating parameters of a continuous, metal matrix composite production process is developed. Predictions from the model are compared with a previous model and with experimental results. The fiber tow molten metal interaction is described as flow through a parallel, cylindrical fiber array (PCA) in the new model. The predicted critical pulling velocity, pulling force and the pressure gradient are self-consistent with experimentally measured parameters within 1%. The PCA model is expected to provide a useful design and operating tool for fabrication of metal matrix composite wire.

This paper presents a new technique to predict forces and deformations of pipes installed underground by horizontal directional drilling (HDD). The proposed technique consists of several models each describing different aspects of mechanics of HDD. It allows prediction of the shape of the pipe in the borepath. Based on the pipe shape, shape of the borepath and pipe stiffness, the contact forces between the pipe and the borepath are calculated. The contact forces cause friction and thus axial pulling force is induced to equilibrate the frictional forces and the weight of the pipe. The analytical model is used to study the stresses and strains on two pipes that were tested in the field. The theoretical results are compared with the strains measured in the field.

Objectives: To measure in vitro the direction and force of applied loads applied by clinicians when using both a conventional slow surgical handpiece (CH) and an ultrasonic chisel (USC) for cutting bone. Study design: Five clinicians were asked to cut bovine bone using either an USC or a CH. The bone was placed on a force measurement system that could measure both longitudinal and downward loads. The rate of cut was calculated over a fixed time-period and the depth of cut measured using a penetratometer. Results: The magnitude of the longitudinal forces generated varied between 1.48 and 3.22 N (USC) and 0.04 and 4.56 N (CH). The CH had a pulling force directed towards the operator. Both instruments produced a similar range of downward forces although there was intra- and inter-operator variability. The rate of cut varied in a similar manner, however, the CH produced a significantly greater depth of cut ( p Conclusions: The force measurement system demonstrated differences in the way clinicians used the USC and CH instruments to cut bone. Of the two cutting methods investigated, the rotary bur is more efficient than the ultrasonic chisel. An ultrasonic chisel does cut bone in a different manner from a conventional bur and clinicians may require training before using it clinically.

Summary The in vivo tissue isolation technique presented here allows localization of tissue tension within contractile roots, and thus, localization of a potential to shorten. Tissue strips of the stele, inner cortex, and outer root parts no longer have shortening potential after isolation. However, defined tissue strips of middle cortical cells shorten immediately after isolation by 10–30%. This starts when root swelling appears (zone II/I), and continues up to root zone (III). The ability to contract seems to be limited to the expanded cells, which finally collapse. Thus, changes in the longitudinal cell dimension of these expanded cells does not occur in fixed roots. However, pressure to shorten affects the inner and outer root tissues, which shorten passively. Innermost cell layers of the root cortex show partial dissolution of middle lamellar material, and thus, cell wall bubbles appear. In older roots (after contraction), cells of the inner cortex often become disconnected from each other and the inner cortex separates from the outer root parts. Quantitative comparison of cells before and after root contraction shows that the inner cortical cells become shorter by half. On the basis of ‘shortening potential’, an alternative model of the mechanism of root contraction is presented. In this ‘pneumodel’, the active, middle cortical cells function like expanded ‘elastic bands’, and a small drop in cell pressure causes the expanded cell walls to lose their elastic tension, resulting in them shortening. This shortening creates a pulling force, which eventually effects underground movement.

A movable lug wheel was tested in a soil bin test apparatus to determine its traction performance and to measure the soil reaction forces on its lugs. Similar tests were also conducted using a fixed lug wheel. The effects of the lug motion pattern, lug spacing and horizontal load on pull and lift forces were studied. From the experiments it is confirmed that the movable action of the lug plate could generate superior pull and lift forces in comparison with the fixed lug wheel. Among the test wheels, lug motion pattern-2 generated the highest pull and lift forces. Within the range of the test conditions, there was no significant difference in pull and lift forces of the lug plate between the test lug wheels with 12 lugs and 15 lugs at the same level of horizontal and vertical loads. The increase of horizontal load up to 200 N generally increased the pull force and generated smaller rolling resistance before the lug left the soil, but did not increase the lift force significantly. The patterns of pull force, lift force and drawbar pull generated under a constant slip were slightly different from those under a constant horizontal load. Finally, the results were also elucidated by their actual lug trajectories in soil.

In order to clarify characteristics of a new mechanism called a movable lug, a model of a single movable lug equipped with an L-shaped force transducer has been developed. The soil reaction forces (normal and tangential) on a flat single movable lug, a curved single movable lug and a fixed lug were measured on wet sandy loam soil in the laboratory soil bin test. These measured forces then were converted to lug pull and lift forces. The pull and lift forces obtained by the flat movable lug with 45° lug inclination angle and the curved movable lug were higher than those of the fixed lug. It was observed that the lift force of the fixed lug achieved its peak and dropped earlier than those of the movable lugs. However, the peaks of pull and lift forces of the flat and curved movable lugs were almost the same. The flat movable lug with 45° lug inclination angle generated a slightly higher peak of pull force than those with 30° and 60° lug inclination angles. However, the higher lug inclination angle produced, the lower peak of lift force. It was observed that the pull and lift forces increased as the sinkage increased. In contrast to the flat movable lug with 45° lug inclination angle, the curved movable lug produced greater lift force especially at high sinkage. The increase in lug slip from 5% to 25 and 50% caused an increase in the peaks of pull and lift forces. The soil moisture content affected the lug forces significantly.

Pull-out resistance has been evaluated using pull-out tests on geogrids in soils. Both field and laboratory pull-out tests were carried out in order not only to make clear the pull-out mechanism but also to determine the parameters for design and analysis of the reinforced soil structures. When the geogrid in the soil is subjected to a pulling force, the geogrid is pulled out of the soil as the grid itself elongates. In order to evaluate the pull-out resistance, two elevation methods which are called ‘Mobilizing Process Method’ and ‘Average Resistance Method’ are newly defined. These are implemented using the test results. Recommendations for laboratory pull-out tests are also proposed.