Offset Directions Research Articles

Numerical simulations of the effect of lateral malleolus fracture malunion on ankle biomechanics: Different offset directions and offsets

IntroductionAnkle fractures account for approximately 10 % of all fractures. Approximately 5–68 % of patients with ankle fractures may suffer from malunion. Besides, suboptimal reduction of fracture fragments can affect the biomechanics of the ankle joint, ultimately leading to damage to the ankle joint. However, there are certain controversies over the conclusion of previous cadaveric studies. MethodsIn this study, a three-dimensional model of the ankle joint was established based on CT image data. In addition, the effects of backward offset (1–2 mm) and outward offset (0.5–1 mm) of the fracture fragment on the contact area, contact pressure, and ligament force of the ankle joint were investigated via the finite element method. Moreover, lateral malleolus fracture malunion in five ankle positions (neutral, 10° dorsiflexion, 10° plantarflexion, 20° dorsiflexion, and 20° plantarflexion) was investigated. ResultsThis model predicted an overall increased contact area in the ankle joint in patients with lateral malleolus fracture malunion compared with the normal ankle joint. The results demonstrated that the outward offset had a more significant effect than the backward one. The larger the dorsiflexion-plantarflexion angle, the more pronounced the effect of malunion. Further, an outward offset can cause the fibula to lose its function. ConclusionPost-traumatic osteoarthritis occurs under the action of unaccustomed cartilage forces due to altered tibial talar joint contact patterns, rather than increased contact pressure reported in previous studies. Malunion leads to an increase or decrease in force on the affected ligament, while the cause of malunion can be envisioned based on a decrease in the force on the ligaments.

Posture and Dynamics Analysis of Hydraulic Support with Joint Clearance under Impact Load

A hydraulic support is one of the key pieces of equipment in a fully mechanized coal-mining face. The shaft is seriously worn due to repeated support shifting in coal-mining operations, and the hydraulic support bears a large amount of impact load in the support process, leading to a threat to its dynamic stability. In order to study the impact load on the posture and dynamics of a hydraulic support, and considering the joint clearance of the hydraulic-support hinge point, based on the dynamics software Adams, the equivalent variable-stiffness damping system is used to replace the column, and the impact analysis model of the hydraulic support with joint clearance is established. The roof pressure is vertically applied to the load balance area of the top beam by static load, and the impact load is vertically applied to the top beam downward. Based on the above model, considering the different distributions of joint clearance, research about the influence of joint clearance on the posture and dynamic characteristics of the hydraulic support is carried out. The results show that when there is joint clearance on both sides of the hydraulic support, when the top beam bears the impact load, the X-axis PMR (position movement ratio) at different positions of the top beam is more than 80%, and the forward-tilt posture is obvious. When the hydraulic support has only unilateral clearance, the front end of the top beam bears the impact load, and the front end of the top beam moves laterally, while the rear end of the top beam mainly moves longitudinally. When the end of the top beam bears the impact load, the vertical PMR of the top beam is less than 1%. When the impact load acts on the side with joint clearance, the top beam has a certain degree of lateral offset, and the offset directions on both sides of the top beam are inconsistent. At this time, the top beam presents a torsional-bearing posture. When the front end of the top beam is loaded, the mechanical curve of each hinge point is higher than the rear-end load. For the hinge point on the side without clearance, the maximum load-fluctuation coefficient reaches 1.04, while for the hinge point on the side with clearance, the minimum load is 0 kN, which will mean some hinge points cannot to play a supporting role. The analysis results will be helpful to research hydraulic supports considering joint clearance.

Sensitivity to Hand Offsets and Related Behavior in Virtual Environments over Time

This work explored how users’ sensitivity to offsets in their avatars’ virtual hands changes as they gain exposure to virtual reality. We conducted an experiment using a two-alternative forced choice (2-AFC) design over the course of 4 weeks, split into four sessions. The trials in each session had a variety of eight offset distances paired with eight offset directions (across a two-dimensional plane). While we did not find evidence that users became more sensitive to the offsets over time, we did find evidence of behavioral changes. Specifically, participants’ head–hand coordination and completion time varied significantly as the sessions went on. We discuss the implications of both results and how they could influence our understanding of long-term calibration for perception-action coordination in virtual environments.

Direction-Discriminating torsion sensor based on optical fiber Mach-Zehnder interferometer

Optical fiber torsion sensors play a pivotal role in artificial intelligence, construction engineering, structural health monitoring and other fields. Research on low cost, simple structures and measurement methods has become a priority for researchers. Here, we propose an intensity-modulated and direction-recognizing torsion sensor based on two mode fiber with a sandwich structure, that serves as a mode interferometer formed by fundamental modes LP01 and second order core modes LP11 excited by means of offset fusion splicing. The capacity of intensity modulation and torsional direction recognition comes from the antisymmetric phase of fiber mode, which makes the sensor work like Marius’ law. The antisymmetric phase of the LP11 mode leads to an asymmetric transmission spectrum, whose direction enables the sensor to distinguish the torsion direction. Peaks and troughs in the measured spectrum interchange when the torsion direction is reversed. The initial angle between two offset directions enables control of the zero-crossing point within in the twisting range. The torsion sensitivity reaches 364%/(rad/cm) with a measurement accuracy of ± 0.22 rad/m.

A model-based strategy for quadruped running with differentiated fore- and hind-leg morphologies

This article introduces a model-based strategy for a quadruped robot with differentiated fore- and hind-leg ground reaction force patterns to generate animal-like running behavior. The proposed model comprises a rigid body and two eccentric spring-loaded inverted pendulum (eSLIP) legs with dampers. The eSLIP model extends the traditional SLIP model by adding a bar to offset the spring direction. The proposed two-leg eSLIP (TL-eSLIP) model’s fore- and hind legs were designed to have the same offset magnitude but in opposite offset directions, producing different braking and thrusting force patterns. The TL-eSLIP model’s reference leg trajectories were designed based on the fixed-point motion of the eSLIP model. Additionally, the legs were clock torque-controlled to modulate leg motion and stabilize the model to follow its natural dynamics. The model’s equations for motion were derived, and the model’s dynamic behavior was simulated and analyzed. The simulation results indicate that the model with leg offsets and in either trotting or pronking has differentiated leg force patterns, and it is more stable and has larger basins of attraction than the model without leg offsets. A quadruped robot was built for experimental validation. The experimental results demonstrate that the robot with differentiated legs ran with differentiated ground reaction force patterns and ran more stably than another robot with the same leg morphology.

Investigating thermostat sensor offset impacts on operating performance and thermal comfort of three different HVAC systems in Wuhan, China

For heating, ventilation and air-conditioning systems (HVACs), their operating performance depends largely on sensors and their accurate measurements. Various types of faults are inevitable to sensors amounted in HVACs during the system lifespan, which eventually makes system deviated from the normal operation. To explore sensor fault impacts on different HVACs, the thermostat offset fault was taken as an example. For the same office building in Wuhan, this study compared its influences on operational performance of three HVACs including the ground source heat pump (GSHP) system, the variable refrigerant flow (VRF) system and the chiller + boiler (CB) system. The three HVACs were simulated simultaneously by EnergyPlus for the same target building with same outdoor meteorological environment to make a relatively fair comparison. The thermostat offset fault was introduced into the three HVACs with bias amplitudes ranging from −5–5 °C at the interval of 1 °C. Further, the fault impacts were quantitatively analyzed from three aspects in terms of system energy consumption, operating performance and indoor thermal comfort. Results indicated that the thermostat offset fault with different bias amplitudes and offset directions have different impacts on the three systems. Compared with the other two systems, GSHP is less affected by the introduced thermostat offset fault.

Approximation of generalized offset surfaces by bicubic splines

We present an approximation problem of surfaces of a generalized offset surface with offset variable distances and directions. Such approximating surface fits some given data points and minimizes a Sobolev’s semi-norm of order 3. The study of the new results, from a mathematical point of view, carefully establishing the proof of the convergence between the generalized offset surface and its approximating spline in an adequate parametric bicubic spline space. Moreover, the approximating spline function is computed and an estimation of the relative error is introduced. Finally, some numerical and graphic examples are shown in order to prove the useful and the effectiveness of our method.

Shoulder muscle activity in off-axis pushing and pulling tasks

Workspace design can often dictate the muscular efforts required to perform work, impacting injury risk. Within many environments, industrial workers often use sub-maximal forces in offset directions in to accomplish job tasks. The purpose of this research was to develop methods to estimate shoulder muscle activation during seated, static, sub-maximal exertions in off-axis (non-cardinal) directions. Surface EMG signals were recorded from 14 upper extremity muscles in 20 right-handed university aged, right-handed males (age: 22 ± 3 years, weight: 77.5 ± 11.1 kg, height 179.0 ± 7.0 cm) participated in this study. Each participant performed 60 submaximal exertions (40N) directed at 4 off-axis phase angles of 45° (45°, 135°, 225°, and 315°) in 3 planes (frontal, sagittal, and transverse) in 5 hand locations within a right handed reach envelope. The influence of hand location and force direction on muscle activity was evaluated with a forced-entry stepwise regression model. The ability of previously published on-axis prediction equations to predict muscle activity during these off-axis exertions was also evaluated. Within each muscle, activity levels were affected by both hand location and three-dimensional force direction and activation levels ranged from <1 to 37 %MVE. For each force direction there were 75 predictive equations selected and used, and the specific equation that best predicted activation depended on the muscle, exertion direction and hand location evaluated. This work assists ergonomic workplace design to minimize muscle demands during commonly performed off-axis exertions. These estimated demands can be employed to improve workplace design to reduce workplace injuries and enhance worker productivity.

Understanding the Behavior of π–π Interactions in Crystal Structures in Light of Geometry Corrected Statistical Analysis: Similarities and Differences with the Theoretical Models

Statistical analyses on π–π interactions among benzenoid dimers and pyridinoid dimers have been performed. The population distributions in these analyses are not in accordance with the theoretical study on benzene dimers and pyridine dimers. A geometrical correction has been proposed and incorporated into the statistical analysis, and then the population distributions have been compared with the theoretical models. The preferred interplanar angles, interplanar distances, offset distances, offset directions, and relative orientation of the pyridyl ring in the T-shaped geometry and relative orientation of the dipoles of two pyridyl rings have been evaluated from the geometry-corrected population distribution. Interestingly, all these parameters are in good agreement with the geometries predicted in a theoretical study. In addition, this analysis also reveals the presence of a small offset in the T-shaped geometry of pyridinoid dimers, which was overlooked in the theoretical study.

Effect of lateral offset on microstructure and strength of friction stir welded 2A14-T6 aluminum alloy

In this paper, the effects of different lateral offset directions on the microstructure and mechanical properties of the welded joints of 2A14-T6 aluminum alloy during friction stir welding (FSW) were studied. The results indicate that the center of the weld nugget (WN) always coincides with the center of the welding tool. There is some influence on the shape of the WN when the offset condition is present. The movement of the location of the WN with the offset of the welding tool changes the location of the initial contact surface (ICS), resulting in the change of the severe level of stirring at the ICS and the pressure at the joint root. There are varying degrees of lack of penetration when the welding tool shifts to the retreating side (RS) and the advancing side (AS) respectively. The presence of the defects has an important influence on the mechanical property and fracture, especially when the welding tool shifts to the AS. The joint performance has obvious reduction. In summary, the quality of the joint is more sensitive to the condition of AS offset.

Computing Textural Feature Maps for N-Dimensional images

This document describes a new remote module implemented for the Insight Toolkit ITK, itkTextureFeatures. This module contains two texture analysis filters that are used to compute feature maps of N-Dimensional images using two well-known texture analysis methods. The two filters contained in this module are itkScalarImageToTextureFeaturesImageFilter (which computes textural features based on intensity-based co-occurrence matrices in the image) and itkScalarImageToRunLengthFeaturesImageFilter (which computes textural features based on equally valued intensity clusters of different sizes or run lengths in the image). The output of this module is a vector image of the same size than the input that contains a multidimensional vector in each pixel/voxel. Filters can be configured based in the locality of the textural features (neighborhood size), offset directions for co-ocurrence and run length computation, the number of bins for the intensity histograms, the intensity range or the range of run lengths. This paper is accompanied with the source code, input data, parameters and output data that we have used for validating the algorithm described in this paper. This adheres to the fundamental principle that scientific publications must facilitate reproducibility of the reported results.

Determination of wavefront attributes by differential evolution in the presence of conflicting dips

The common-reflection surface (CRS) method represents a multidimensional stacking approach; i.e., the stacking surface is determined in the midpoint and offset directions. In the 2D case, three attributes span the stacking surface, thus requiring a three-parameter search contrary to a one-parameter search in the classic common-midpoint stack. However, CRS wavefront attributes use data redundancy in the midpoint direction as well, which makes them very useful in several seismic applications, e.g., data preconditioning, velocity model building, and migration. Contrary to previous works, we simultaneously estimate CRS attributes using differential evolution in subcubes of the 3D search space. Differential evolution is a global optimization technique that performs particularly well when the objective function is unknown. Because we apply DE for each subcube, we could find local maxima, additionally to the global maximum. Therefore, conflicting dips are recognized and can be used for the stack and subsequent CRS attribute-based processing, which has been an issue in the past. Our land data results from the Donbas Foldbelt in southeast Ukraine demonstrate that our method reduces coherent steep dipping noise and reveal more subsurface structures. Application of the CRS attributes for prestack data enhancement shows that velocity analysis can be carried out more reliably.

The Effect of a Meter-Diffuser Offset on Shaped Film Cooling Hole Adiabatic Effectiveness

Shaped film cooling holes are used extensively in gas turbines to reduce component temperatures. These holes generally consist of a metering section through the material and a diffuser to spread coolant over the surface. These two hole features are created separately using electrical discharge machining (EDM), and occasionally, an offset can occur between the meter and diffuser due to misalignment. The current study examines the potential impact of this manufacturing defect to the film cooling effectiveness for a well-characterized shaped hole known as the 7-7-7 hole. Five meter-diffuser offset directions and two offset sizes were examined, both computationally and experimentally. Adiabatic effectiveness measurements were obtained at a density ratio of 1.2 and blowing ratios ranging from 0.5 to 3. The detriment in cooling relative to the baseline 7-7-7 hole was worst when the diffuser was shifted upstream (aft meter-diffuser offset), and least when the diffuser was shifted downstream (fore meter-diffuser offset). At some blowing ratios and offset sizes, the fore meter-diffuser offset resulted in slightly higher adiabatic effectiveness than the baseline hole, due to a reduction in the high-momentum region of the coolant jet caused by a separation region created inside the hole by the fore meter-diffuser offset. Steady Reynolds-averaging Navier–Stokes (RANS) predictions did not accurately capture the levels of adiabatic effectiveness or the trend in the offsets, but it did predict the fore offset's improved performance.

Prediction Method on Vehicle Acceleration in Frontal Offset Impact Sled Test

Vehicle impact acceleration has been widely used to reproduce the impact process in crash CAE analysis and the sled test. In the sled test for frontal rigid barrier impact, B-pillar lower accelerations were used as input pulses. But for the frontal offset impact, the magnitudes and directions of left and right B-pillar lower accelerations are significantly different, which makes the selection of vehicle acceleration complicated. By simplifying the vehicle impact kinetic model, a new prediction algorithm for calculation the acceleration of any point on vehicle body was deduced. The new method was verified with the full scale impact data and the test results show that both the trends of the acceleration curves and the peaks of the calculated values have a strong consistency with the measured values.

Enabling affordable omnidirectional subsurface extended image volumes via probing

ABSTRACTImage gathers as a function of subsurface offset are an important tool for the inference of rock properties and velocity analysis in areas of complex geology. Traditionally, these gathers are thought of as multidimensional correlations of the source and receiver wavefields. The bottleneck in computing these gathers lies in the fact that one needs to store, compute, and correlate these wavefields for all shots in order to obtain the desired image gathers. Therefore, the image gathers are typically only computed for a limited number of subsurface points and for a limited range of subsurface offsets, which may cause problems in complex geological areas with large geologic dips. We overcome increasing computational and storage costs of extended image volumes by introducing a formulation that avoids explicit storage and removes the customary and expensive loop over shots found in conventional extended imaging. As a result, we end up with a matrix–vector formulation from which different image gathers can be formed and with which amplitude‐versus‐angle and wave‐equation migration velocity analysis can be performed without requiring prior information on the geologic dips. Aside from demonstrating the formation of two‐way extended image gathers for different purposes and at greatly reduced costs, we also present a new approach to conduct automatic wave‐equation‐based migration‐velocity analysis. Instead of focusing in particular offset directions and preselected subsets of subsurface points, our method focuses every subsurface point for all subsurface offset directions using a randomized probing technique. As a consequence, we obtain good velocity models at low cost for complex models without the need to provide information on the geologic dips.

Numerical analysis of self-lubricating radial spherical plain bearings and investigations on fatigue damage mechanisms of the liner

With ABAQUS software, a 3D simplified model for finite element analysis (FEA) was established for a radial spherical plain bearing with Kevlar/PTFE fabric woven liner, which can simulate different motions of the inner ring. Motion directions, friction forces and wear depths can cause offset distributions of higher concentrated contact pressures on the liner. The amplitudes or offset directions of higher contact pressures change periodically during motions. Different fatigue damage mechanisms such as surface fatigue wear, impact effect, and sweep deformation of the liner were analyzed. Fatigue behaviors of the liner were validated by experimental results.

Prediction on Vehicle Crash Acceleration Based on Circle of Constant Acceleration Method

Vehicle crash acceleration was essential for automotive passive safety analysis. Especially in CAE analysis and sled test, B-pillar lower accelerations are considered as vehicle acceleration and often used as crash pulse to reproduce the real crash conditions. But for frontal offset impact, the magnitudes and directions of the B-pillars lower accelerations were significantly different,which made the selection of vehicle acceleration very complicate. In this paper,a prediction algorithm based on Circle of Constant Acceleration method that can calculate the acceleration of any point on vehicle was presented. And then it is verified with the full scale impact data. The results show that both the trend of the acceleration curves and the curve peak of the calculated value have a strong consistency with the measured value.

Long-lasting visual integration of form, motion, and color as revealed by visual masking

When two similar visual stimuli are presented in rapid succession at the same location, they fuse. For example, a red and a green disk are perceived as one single yellow disk. Likewise, verniers with opposite offset directions are perceived as one vernier with an almost aligned vernier offset. In fusion, observers have no conscious access to the individual stimuli. Using transcranial magnetic stimulation (TMS), it has been shown that feature fusion for verniers can be modulated for about 400 ms in that either the first or the second vernier dominates the percept, depending on TMS onset. Here, we use light masks to modulate feature fusion for verniers, motion, and color. Our results are similar to the TMS experiment and show that individual visual features are stored for a substantial amount of time before they are integrated.

Two primes priming: Does feature integration occur before response activation?

Responses to a target can be sped up or slowed down by a congruent or incongruent prime, respectively. Even though presentations are rapid, the prime and the target are thought to activate motor responses in strict sequence, with prime activation preceding target activation. In feature fusion, the opposite seems to be the case. For example, a vernier offset to the left is immediately followed by a vernier offset to the right at the same location. The two verniers are not perceived as two elements in sequence but as a single, aligned vernier. Here, we ask the question as to how features are integrated: before or after motor activation? We presented two vernier primes with opposite offset directions preceding a single vernier target. No priming effect occurred when the vernier primes were presented at the same location, indicating that verniers integrate before motor activation. There was also no priming effect when the primes were presented simultaneously at different locations, indicating that there is an integration stage different from the perceptual fusion stage. When the second prime is delayed, it determines priming, even for very long delays. To explain these long integration times, we argue that there is a buffer preceding motor activation.

The temporal dynamics of feature integration for color and form

When two visual stimuli are presented in rapid succession only one fused image is perceived. For example, a red disk followed by a green disk is perceived as a single yellow disk (e.g., Efron, Perc Psychophys, 1973). For two verniers that last 30ms each, it has been shown that the fusion process can be disrupted up to 420ms after stimulus onset by applying TMS over visual cortex (Scharnowski et al., J Vis, 2009). Here, we show that feature fusion can also be modulated with light masks. In Experiment 1, we used the same procedure as in the above TMS experiment: Two verniers were presented in rapid succession with opposite offset directions. Subjects had to indicate the offset direction of the fused vernier. In Experiment 2, a red and a green disk were presented in rapid succession and subjects had to indicate whether the fused disk appeared red or green. Verniers were presented for 30ms and disks for 10ms each. Light masks were presented from -100 to 240ms relative to the onset of the first stimulus. When masks were presented before the stimuli, the second stimulus dominated the percept and when masks were presented after the stimuli, the first stimulus dominated the percept. Feature fusion was modulated for a period of 240ms for both color and vernier stimuli. Our results indicate that for this duration individual memories exist for each vernier or color stimulus separately. Fusion is not completed beforehand. Taken together, our results show that light masks have similar effects on feature fusion as TMS and provide an adequate alternative to investigate feature integration. In addition, we showed that the process of unconscious feature fusion outlasts the physical duration of the stimuli by far.