Static Angle Research Articles

A hybrid particle-geometric scaling approach for elasto-plastic adhesive DEM contact models

The computation time of Discrete Element Method (DEM) simulations increases exponentially when particle size is reduced or the number of particles increased. This critical challenge limits the use of DEM simulation for industrial applications, such as powder flow in silos. Scaling techniques can offer a solution to reduce computation time. In this paper, we have developed a hybrid particle-geometric scaling approach with a focus on Elasto-Plastic Adhesive contact models. It established relationships between particle scaling factors and DEM contact input parameters. The isolated effects of varying particle size and geometric dimensions on bulk properties were also evaluated using uniaxial consolidation, static angle of repose, and ring shear tests. This paper shows how the particle scaling can be applied together with geometric scaling to incorporate two important aspects of bulk materials, their Elasto-Plastic behaviour and their cohesive forces.

Research on the multi-longitudinal mode laser self-mixing static angle-measurement system using a right-angle prism

Abstract A static absolute angle measurement method using a right-angle prism as the angle-sensing device is developed for measuring the deflection angle by means of the multi-longitudinal mode laser self-mixing sensor. In the experiment, a laser diode operating at multiple excitation longitudinal modes is exploited as the optical source for deflection angle measurement. The measured self-mixing waveforms are in accordance with the simulated waveforms, of which demonstrate that the multi-longitudinal mode laser self-mixing sensor is available for measuring the deflection angle. Meanwhile, the angle-measurement range of the self-mixing sensing system is as many as ±6.00° corresponding to 0.20° angular resolution. Furthermore, both of the absolute angle measurement error and the linear correlation of the measured angle and the actual angle are further analyzed and investigated.

On-Road Dynamic Pattern Projection Using an Active Mirror for Vehicle Warning Systems

Recently, the demand for vehicle warning systems to avoid collisions between vehicles and pedestrians has been increasingly growing. For the implementation of such systems, three types of vehicle-to-pedestrian (V2P) technologies are widely adopted. In the first, vehicles communicate with pedestrians via smart devices using dedicated short-range communications (DSRC), but it is neither simply intuitive nor fast responsive. In the second, vehicles generate a noise in order to help pedestrians avoid collisions, at the expense of disturbing others with unwelcome noise. In the last, an on-road short-range projection technique visually informs pedestrians that a vehicle is approaching, which can be more intuitive and responsive. However, the two main drawbacks of conventional on-road projections are that they involve a static pattern and narrow emission angle. This paper proposes an on-road dynamic pattern projection technique for grabbing more attention from pedestrians with various dynamic patterns and covering a wide emission angle using an active mirror. Theoretical analysis shows that the on-road projection pattern and its angle can easily be controlled by adjusting the switching frequency, duty-cycle, and amount of current flow in the control circuitry. The simulation and experimental results validate that various patterns can be projected within a projection angle of ±70° at a power consumption less than 0.98W.

Effect of guided growth intervention on static leg alignment and dynamic knee contact forces during gait

BackgroundLower limb malalignment in the frontal plane is one of the major causes of developing knee osteoarthritis. Growing children can be treated by temporary hemiepiphysiodesis when diagnosed with lower limb malalignment. Research questionIs there a difference between medial or lateral knee contact force (KCF) before (PRE) and after (POST) hemiepiphysiodesis in patients with valgus malalignment and compared to a typically developed control group (TD)? Does a linear relationship exist between the static radiographic mechanical axis angle and dynamic medial/lateral KCF? MethodsIn this prospective study, an OpenSim full body model with an adapted knee joint was used to calculate KCFs in the stance phase of 16 children with diagnosed genu valgum and 16 age- and sex-matched TDs. SPM was applied to compare KCFs before and after guided growth and to test a linear relationship between the mechanical axis angle and KCFs. ResultsAfter the intervention, POST revealed a significantly increased medial KCF (p < 0.001, 4–97 % of stance) and decreased lateral KCF (p < 0.001, 6–98 %) compared to PRE. Comparing POST with TD, short phases with a significant difference were found (medial: p = 0.039, 84–88 %; lateral: p = 0.019, 3–11 %). The static mechanical axis angle showed a longer phase of a significant relation to KCFs for POST compared to PRE. SignificanceThis study showed that temporary hemiepiphysiodesis in patients with valgus malalignment reduces the loading in the lateral compartment of the knee and thus the risk of developing osteoarthritis in this compartment. The determination of dynamic KCFs can be clinically relevant for the treatment of lower limb malalignment, especially for decision making before surgery, when compensatory mechanisms may play an important role. Additionally, the static radiographic mechanical axis angle does not necessarily represent the dynamic loading of the lateral knee compartment.

Study on calculation model of wind deflection response of transmission line

The wind deflection angle is directly related to the electric gap and the construction cost of the transmission line, so the accuracy of the wind deflection calculation method and the reasonable value of the relevant parameters are very important for the safe operation and economic rationality of the transmission line. In this paper, based on the nonlinear transient analysis method, the characteristics of aerodynamic damping on the transient response of transmission line wind deflection are revealed. At the same time, according to the code of transmission line design in China, the static wind deflection calculation method is used to solve the static wind deflection angle of transmission line, and the dynamic and static calculation models of wind deflection angle are compared.

EAC-1A: A novel large-volume lunar regolith simulant

The European Astronaut Centre (EAC) is currently constructing the European Lunar Exploration Laboratory (LUNA), a large training and operations facility to be located adjacent to EAC at the DLR (German Aerospace Centre) campus in Cologne, Germany. With an estimated representative lunar testbed area of approximately 660 m2, a large volume of lunar regolith simulant material is needed for this purpose. In this study, a basanitic sandy silt from a quarry located in the Siebengebirge Volcanic Field is evaluated as a large-volume source of material. The focus of this project has been to conduct a physical and chemical characterisation of the fine-grained material to be used in LUNA; the European Astronaut Centre lunar regolith simulant 1 (EAC-1 A). The physical characterisation tests undertaken include sphericity, density measurements, cohesion and static angle of repose, with mineralogical investigations via petrographical analysis with optical microscope and SEM, XRF, XRD and DSC measurements. The results of the EAC-1A tests are compared to published data on existing widely used lunar regolith simulants, namely JSC-1A, JSC-2A, NU-LHT-3M, DNA and FJS-1.

Experimental realization of incipient active failure in sand heap by seismic loading

Sand heaps avalanche when a static angle of repose is exceeded, and freeze at a dynamic angle of repose. The stress distribution in a planar sand heap stabilized at the angle of repose with an incipient active failure condition, by which the material is on the verge of failure everywhere, was examined. At the time of construction, the vertical pressure was initially not in the incipient failure. A slight amount of seismic loading using the sinusoidal motions of a shaking table was set up with just enough energy to rearrange the sand particles, to erase the formation history, and to fluctuate local density inside a sand heap without an excessive loss of mass. During the experiments, laser displacement sensors and pressure gauges were employed to monitor the vertical displacements above and the vertical pressures below the sand heap respectively. The non-linear differential equations, characterizing the stress distribution in an active sand heap, were formulated under the Mohr–Coulomb failure criterion and numerically solved by the Newton method. Bulk solids started flowing after the state of incipient failure; therefore, the experimental vertical pressure profiles were found to gradually conform to the theoretical vertical pressure profiles if the sand heap was subjected to sufficient excitation.

Novel helical carbon nanotubes-embedded reduced graphene oxide in three-dimensional architecture for high-performance flexible supercapacitors

The rapid development of flexible and portable electronics has brought great opportunities to develop flexible and lightweight energy-storage systems. Herein, a free-standing, mechanically flexible and binder-free three-dimensional (3D) sandwich-type network film electrode with reduced graphene oxide (RGO)-wrapped helical carbon nanotubes (HCNT) is designed and synthesized by a synergistic and applicable self-assembly strategy. HCNT in the composites serve as the inner skeleton, impede the stacking of RGO and enlarge the space between RGO effectively, which facilitate the creation of conductive 3D architectures and reinforce the structural stability. Moreover, the RGO coating and the voids are beneficial in improving electrochemical conductivity. As a result, the as-prepared RGO/HCNT electrodes show excellent electrochemical characteristics, yielding the specific capacitances of 336 F g−1 at a current density of 0.25 A g−1, and it offers the energy density of 7.5 Wh kg−1 with the corresponding power density of 100 W kg−1 as well as excellent cycling stability at approximately 89.5% capacitance retention exceeding 3000 cycles. The bending tests indicate that the flexible supercapacitors (SCs) can operate under different static bending angles, and the capacitance is hardly affected. The HCNT and corresponding flexible SCs are novel materials with potential applications in the next generation of wearable energy devices.

WITHDRAWN: Synchrotron-based Radiography of Conical- vs. Butt-joint Implant Abutment Connections.

Ahead of Print article withdrawn by publisher.

Size-based physical properties of hard-shell clam (Mercenaria mercenaria) shell relevant to the design of mechanical processing equipment

The knowledge of physical properties of food products is of fundamental importance for efficient design, dimensioning, manufacturing and operation of different mechanical equipment used in the processing of these products. Clams of different sizes are utilized during processing, thus, all the sizes must be given adequate consideration for efficient processing. This study was conducted to investigate the size-based physical properties of hard-shell clam (Mercenaria mercenaria) shell relevant to the design of mechanical processing equipment. The sizes of the clam shells were identified and categorized as small, medium and large; and its effect on the physical properties were studied. The parameters investigated were length, width, thickness, arithmetic and geometric diameters, surface area, sphericity, aspect ratio, moisture content, bulk and true densities, porosity, clam shell weight, coefficient of static friction and angle of repose. Increase in the length and width of clam shells increased the arithmetic and geometric diameters, and the surface area, but decreased the sphericity and aspect ratio. Moisture content, bulk and true densities, porosity and clam shell weight increased with increase clam shell size. Coefficient of static friction of clam shell was highest on rubber surface and lowest on glass surface, and was positively correlated with size; while angle of repose decreased with size. There was an excellent agreement between the prediction of the normal distribution and the actual distribution of the clam shell sizes. All the parameters were significantly different with respect to clam shell size at p < 0.05, which makes a strong case for the consideration of clam shell size during processing.

A Novel Piezoelectric Stack for Rotary Motion by d 15 Working Mode: Principle, Modeling, Simulation, and Experiments

A novel piezoelectric stack for rotary motion using d 15 working mode is proposed, fabricated, and tested in this article to achieve the high stiffness and high precision of rotation. This piezoelectric stack is fabricated by bonding process from only two components—lead zirconate titanate ceramics and electrodes, which is beneficial to realize the simple structure. A theoretical model based on the shear deformation theory is established to predict the static output performances. And the simulation with the finite-element method is adopted to evaluate the dynamic characteristics. An experimental system is built to verify the design and study the performances of the piezoelectric stack. The experimental results indicate that the static output angle changes from −13.25 to +13.33 μ rad, whereas the exciting voltage changes from −300 to +300 V, with good linear relationship and high repeatability accuracy. Under the condition of changing the exciting voltage by the step of 0.5 V, the stable resolution is measured to be higher than 0.022 μ rad. The large load capacity and width frequency response are verified, which reflect the high stiffness of the proposed piezoelectric stack. The proposed piezoelectric stack achieves accurate and stable rotary output motion with high resolution, rapid response, and large load capacity. Besides, the stack has regular shape and simple structure, and therefore, it is suitable to be integrated in the equipment in the fields of micro–nano manipulations, piezoelectric ultrasonic motors, etc.

Point-ahead analysis and pre-pointing link stability study of intersatellite laser communication

The static bias error angle obviously affects pre-pointing links’ stability in the presence of vibration in intersatellite laser communication. The 2nd order point-ahead angle is a source of misalignment which was ignored in most solutions, and this is the concern of our paper. In this study, we present a further analytical investigation into the point-ahead angle in complex satellite maneuvering environment. Static bias error angle induced by the 2nd order point-ahead angle has been studied under different intersatellite links. The probability density function of the pre-pointing links’ outage has been derived in the presence of pointing jitter taking consideration of the static bias angle, and the link budget has also been analyzed. Simulation model of link stability has been established to verify the numerical results by the Monte Carlo method in Matlab-Simulink environment. The results have shown that the 2nd order point-ahead angle has a significant detrimental impact on link stability in long distance links. It is a neglectable factor. This work is dedicated to intersatellite laser communication system design.

Sliding and accumulation characteristics of loose materials and its influencing factors based on discrete element method

Loose materials has loose structure and is the main source of geological disasters such as collapses and landslides. Its hazard range is greatly affected by factors such as stone content and slope. Traditional studies on the sliding and accumulation characteristics of loose materials were mostly macro or qualitative analysis. There is little research on the micro internal motion mechanism. In the present study, discrete element method was used to quantitatively analyze the influence of stone content and slope variation on the characteristic values of loose particles such as stroke, accumulation width, maximum thickness, accumulation area, accumulation contour shape, accumulation volume, static accumulation angle and the cumulative mass. In the meanwhile, the movement and accumulation characteristics of the loose materials during the catastrophe process were explored from the aspect of energy and contact force of the particles, so as to reveal the interaction mechanism between the particles. The results showed that: When the stone content increased in the range of 0 to 70%, the stroke, accumulation width and accumulation area increased firstly and then decreased, and in the end the cumulative mass decreased. As the slope increased from 30° to 65°, the stroke, accumulation width, accumulation area and accumulation mass increased; the maximum thickness decreased approximately linearly, while the static accumulation angle had a decrease similar to quadratic function. In addition, there was a critical distance &lt;i&gt;L&lt;/i&gt;&lt;sub&gt;c&lt;/sub&gt; for the volume share of coarse and fine particles in the accumulation area. When the distance from the toe line was &lt;i&gt;L&lt;/i&gt; &lt; &lt;i&gt;L&lt;/i&gt;&lt;sub&gt;c&lt;/sub&gt;, the fine particles were larger than the volume of the coarse particles; when &lt;i&gt;L&lt;/i&gt; &gt; &lt;i&gt;L&lt;/i&gt;&lt;sub&gt;c&lt;/sub&gt;, the fine particles were smaller than the volume occupied by coarse particles.

Measurement of Static Lateral Stability Angle and Roll Moment of Inertia for Agricultural Tractors with Attached Implements.

Each year, many fatalities result from rollovers of agricultural tractors in Japan. In addition to rollover protective structures (ROPS) and seat belts, a warning device that alerts the operator of impending rollover based on the tractor stability index is a measure used to prevent rollovers. The stability index requires inertial parameters, which have been measured only for the single body of the tractor, to calculate the warning threshold. In this study, the center of gravity (CoG) and lateral stability angles of three agricultural tractors were measured, and lateral stability angles were also calculated and compared with measured values for three tractor-tiller combinations to analyze the effect of the attached implement on the tractor stability as well as to verify the accuracy of the calculation methods. The roll moment of inertia (RMI) was also measured for two tractors and two rotary tillers, and RMI values for tractor-tiller combinations were calculated. The measurement and calculation results show that the attached implement increased the lateral stability angle of tractors in phase I rollover and decreased the lateral stability angle in phase II rollover, and for a certain tractor-tiller combination, there was no transition from phase I to phase II rollover. The difference between the measured and calculated lateral stability angles in phase I ranged from -3.5° to 2.5°, while that in phase II ranged from 0.2° to 5.2°. The RMI about the longitudinal axis through the CoG was 203 and 433 kg m-2 for tractors A and B, respectively, and 52 and 94 kg m-2 for rotary tillers D and F, respectively. The calculated RMI values were 265 and 540 kg m-2 for tractor-tiller combinations A-D and B-E, respectively.

Ensemble Learning Model-Based Test Workbench for the Optimization of Building Energy Performance and Occupant Comfort

Buildings consume tremendous energy for the improvement of living and working conditions. Control of daylight-artificial light has the potential to improve energy performance and occupant comfort in buildings. This research proposes an intelligent generalized ensemble learning technique to develop a novel control strategy for Venetian-blind positioning (up-down movement with static slat angle of 45°) of different window orientations. The proposed model helps to maintain occupant comfort and energy saving in a commercial building. The performance of the ensemble learning approach compared against Gaussian process regression, support vector regression and artificial neural network using conventional statistical indicators. Finally, the proposed data-driven model implemented in a real-time Labview-myRIO platform for the experimental validation. The data-driven model is compared with the baseline model and with the uncontrolled blind condition in terms of daylight glare, and energy consumption of lighting and air-conditioning system in the building. The data-driven model is derived using two years of data collected from a fuzzy-based daylight-artificial light integrated scheme. The blind position providing reduced energy consumption and daylight glare along with setpoint illuminance and temperature are validated. A high dynamic range image with EVALGLARE software used to verify the visual comfort based on daylight glare probability. While evaluating the overall energy savings, the ensemble learning model consumes 17% less power than the uncontrolled system and 15% less power than the baseline system. Here, though we are not controlling the air-conditioning system, the experimental validation confirmed that the air-conditioning system significantly reduces its energy consumption.

1H NMR linewidths of small organic guest molecules physisorbed on different mesoporous silicas

The excessive linewidths of 1H NMR spectra of solids is a longstanding difficulty. Organic molecules (crystalline at room temperatures) of different chemical characters (camphor, menthol, HMB, HMTA, biphenyl, terphenyl, anthracene, perylene, etc.) have been confined or physisorbed in regular (MCM-41, SBA-15) and irregular (aerogel) silica mesopores. Unexpectedly, steadily decreasing proton NMR linewidths have been observed upon increasing pore sizes. Comparison of the static 1H NMR spectra of the confined and “free” bulk molecules showed an impressive resolution improvement (a factor of 5–10). Static 1H NMR and 2H magic angle spinning (MAS) spectra pointed out the increased molecular mobility as origin. In a qualitative approach the possible reasons of mobility have been thoroughly discussed. The increased mobility seems to be easiest achievable in aerogel and so, in the future, this extreme light mesoporous silica nanomaterial (MSN) may be considered as “active” filling material in solid state NMR spectroscopy. Since sensitivity is not an issue in 1H MAS measurements the proposal - simultaneous dilution of the dense 1H–1H spin network and increasing the molecular mobility of the molecules of interest by confinement or physisorption in/on silica mesopores - may find applications, especially in laboratories where high magnetic fields and state of art ultra-fast MAS rotation are not available.

In vivo static and dynamic lengthening measurements of the posterior cruciate ligament at high knee flexion angles.

Rehabilitation is an important aspect of both non-operative and operative treatments of knee ligament tear. Posterior cruciate ligament (PCL) non-operative treatment consists of a step-by-step rehabilitation protocol and is well described. It goes from rest (phase I) to strengthening exercises (phase IV). More specific and high-intensity exercises such as cutting, sidestepping or jumps are, however, not described in detail, as no in vivo data exist to tell how these exercises constrain the ligaments and whether they have the same effect on all of them, in particular regarding lengthening. The goal of this study was to measure the ligament lengthening in static knee flexion based on 3D reconstructions from magnetic resonance imaging (MRI) and from motion capture and ligament simulation during dynamic exercises. The knee of nine volunteers was first imaged in a closed-bore MRI scanner at various static knee flexion angles (up to 110°), and the corresponding lengthening of the PCL and the other major knee ligaments was measured. Then, the volunteers underwent motion capture of the knee where dynamic exercises (sitting, jumping, sidestepping, etc.) were recorded. For each exercise, knee ligament elongation was simulated and evaluated. According to the MRI scans, maximal lengthening occurred at 110° of flexion in the anterior cruciate ligament and 90° of flexion in the PCL. Daily living movements such as sitting were predicted to elongate the cruciate ligaments, whereas they shortened the collateral ligaments. More active movements such as jumping put the most constrain to cruciate ligaments. This study provides interesting insights into a tailored postoperative regimen. In particular, knowing the knee ligament lengthening during dynamic exercises can help better define the last stages of the rehabilitation protocol, and hence provide a safe return to play.

Correlation between static limb alignment and peak knee adduction angle during gait is affected by subject pain in medial knee osteoarthritis

BackgroundAlthough increases in knee adduction moment (KAM) and angle (KAA) during gait are considered key pathologies that produce mechanical overload in the medial compartment of knee osteoarthritis (OA), it is unclear how these pathologies are related to subjective pain. The purpose of this study was to examine how subjective pain is related to such pathologies. MethodsGait analysis was performed in 31 participants with medial knee OA. The knees were classified into three groups based on Kellgren–Lawrence (KL) grade: early (0 and 1), moderate (2), and severe (3 and 4). Subjective pain was evaluated by the Western Ontario and McMaster Universities (WOMAC) osteoarthritis index pain score. The knees were classified into low- and high-pain groups based on the pain score. ResultsThe WOMAC pain score did not correlate with either peak KAM or peak KAA. Although a positive correlation between static limb alignment and peak KAA was observed in the low-pain group, it was not observed in the high-pain group. Knee flexion angle at heel strike correlated negatively with the gap between static femorotibial angle and peak KAA in the high-pain group. ConclusionsAlthough a direct correlation between subjective pain and peak KAM or KAA was not observed, our results suggest a compensatory movement in the high-pain group of participants to reduce KAA increases in the early stance phase. Such movements would be one of the reasons why it is difficult to obtain a consistent relationship between subjective pain and load-related parameters.

Slope, elevation, and thermal inertia trends of martian recurring slope lineae initiation and termination points: Multiple possible processes occurring on coarse, sandy slopes

Recurring slope lineae (RSL) are dark linear features on the surface of Mars that advance incrementally downslope, fading and re-growing annually. Numerous hypotheses have been proposed to explain RSL formation, including “wet” models that involve liquid water or brines and “dry” mechanisms involving liquid-free mass-wasting or solid-vapor phase changes that trigger granular flow. In part, hypotheses to explain RSL formation rely on observations of the physical characteristics of the slopes on which RSL are present. To determine if RSL exhibit physical characteristics typical of one particular formation mechanism, we examined the initiation and termination points of over 10,000 RSL across 16 confirmed RSL sites to determine their slope, elevation, orientation, and thermal inertia. RSL typically form within an envelope of high elevations at each mapping site, are oriented equatorward and west, and have hillslope thermal inertia values consistent with sand and gravel. Notably, the RSL begin and end at slopes above, within, and below the angle of repose required to trigger and sustain dry granular flows. Sensitivity testing indicates that these slope values are not a result of pixel-scale noise. Discontinuous RSL are observed at several study sites. The slope and thermal inertia values of the RSL, as well as these additional geomorphic observations of discontinuous dark features, are not consistent with the characteristics of dry flows in which continuous dust avalanches begin within the dynamic angle of repose and terminate within the static angle of repose. Although RSL are found to be common on coarse sandy and rocky slopes, not all sandy slopes in RSL regions that are close to the angle of repose contain RSL. We conclude that mechanisms other than dry mass wasting are needed to explain all of the observed geomorphic characteristics of RSL source and termination points.

An Error Evaluation Method for the Ship Angular Flexure Measurement Based on the Principle of Relevance

Due to the lack of true ship angular flexure data, it is difficult to evaluate its measurement error of the angular velocity matching method in practice. In this paper, the cause of the measurement error of the ship flexure angle is analyzed in theory, and an evaluation method for the ship angular flexure measurement error based on the principle of relevance is proposed. The proposed method provides a prediction formula to describe the estimation error of the static flexure angle based on the off-diagonal elements of the error covariance matrix P in Kalman filtering. In addition, the optimized coefficient F is introduced to make the prediction error range better describe the real error variation. The optimized coefficient F ensures that the proposed formula has good prediction effects in all three directions. Simulations based on the actual measured ship flexure data are carried out, and the simulation results verify the capability of the prediction formula. The proposed method can be used in the evaluation of the ship flexure measurement error.