Leaning Angles Research Articles

Physical and numerical modeling of the mechanisms of bath entrainment from the aluminum tapping tube intake

The present study aims to investigate the entrainment of the electrolytic bath with aluminum tapping flows from the reduction cell. The physical water modeling technique was used together with numerical simulations.The physical model experiments were carried out in a one-tenth-scale model of an aluminum reduction cell and tapping system. The model comprises a transparent acrylic rectangular container, measuring 800 mm wide, 200 mm, long 300 mm deep and a 26 mm-diameter PVC pipe. Water and canola –oil were used at room temperature to simulate molten aluminum and electrolytic bath, respectively. The modified Froude number-based similarity was used to ensure dynamic similarity between the model and the prototype. Numerical simulations were conducted on a three-dimensional model of an aluminum cell using Ansys Fluent Multiphase and the realizable turbulent k−ε models. Reynolds Averaged Navier -Stokes equations and k−ε realizable turbulence equations were solved using Coupled solver for pressure and velocity coupling by Fluent. The withdrawal pipe positions and leaning angles were considered.From experimental and numerical results, it was observed that the entrainment of oil (simulated bath) increased with the pipe diameter and decreased with the pipe leaning angle. Entrainment was associated with a free surface vortex when the flow was dynamic and wavy with significant circulation. Entrainment occurs without a vortex when the interface between the two fluids drops in a quiescent flow regime.

Influence of the blade leaning angle on the performance of a radial impulse turbine for OWC converters

Abstract Oscillating Water Column systems (OWC) have been in the spotlight in the last 20 years since these devices are considered one of the most promising devices among wave energy technology. These systems produce electricity by means a generator driven by a turbine, which takes advantage of the bidirectional flow created by the OWC itself. Among these turbines suitable for bidirectional flows, it is possible to find radial impulse turbines, which are the focus of this work. Traditionally, the radial impulse turbines have shown lower efficiencies than their competitors. However, the radial turbines present interesting mechanical features and, recently, some research show that the difference has been reduced. Following this thread, this work deals with another modification in the radial impulse turbine looking for a further improvement. By using a validated CFD model, it has been analysed the influence of the lean angle of the blade. Until now, all the turbines present in the literature are leaned zero degrees, leading to a strong interaction between the guide vanes and the blades. This work shows results of the same turbine, equipped with blades leaning from -5deg to 25deg, in order to determine the influence such a modification on the maximum total-to-static efficiency. Results have revealed a slight improvement in the maximum efficiency for positive leaning angles, whereas negative angles drive the turbine to worse performance.

The "Chiang Mai Lean Forward" Radiographic View for Acromioclavicular Joint Injuries: A Cadaveric Study.

Background:Operative treatment is suggested for unstable type 3 acromioclavicular (AC) joint injuries; however, there is no clear consensus regarding the definition of an unstable type 3 injury. We propose a new radiographic method, the “Chiang Mai lean forward” view, to verify horizontal displacement in an unstable AC joint injury.Hypothesis:A radiograph taken with the torso leaning forward would allow the detection of a higher proportion of AC joint injuries.Study Design:Descriptive laboratory study.Methods:A total of 20 shoulders from 10 fresh whole-body cadaveric specimens (mean age, 68.8 years) were tested at 3 different torso leaning angles (30°, 45°, and 60°) to determine the best position for projecting the x-ray beam. The shoulders were dissected sequentially starting with the AC ligament (stage 1), then additional sectioning of the partial coracoclavicular (CC) ligament with either the trapezoid ligament cut first (stage 2A) or the conoid ligament cut first (stage 2B), and finally complete sectioning of the CC ligament (stage 3). Radiography was performed after each stage to evaluate the degree of displacement of the anterior border of the acromion relative to the anterior border of the clavicle. Paired t tests were used to compare the degree of displacement at each stage to that of the shoulder before cutting.Results:Leaning at an angle of 30° provided better visualization of the AC joint in the “Chiang Mai lean forward” view. Compared with the intact condition, complete isolated cutting of the AC ligament produced 5.21 mm of horizontal displacement of the AC joint (P < .0001), complete tearing of the AC ligament and partial cutting of the CC ligament resulted in a displacement of <12 mm (7.91 mm at stage 2A [P = .0003] and 8.10 mm at stage 2B [P = .0013]), and complete tearing of both the AC and the CC ligaments resulted in a displacement of 26.37 mm (P < .0001).Conclusion:The “Chiang Mai lean forward” radiographic view is a potentially useful tool for determining the degree of the injury and the stability of the AC joint.

Probabilistic framework for assessing the vulnerability of power distribution infrastructures under extreme wind conditions

Utility poles would collapse by their structural instability as well as time-dependent material deterioration. Particularly, the moment carrying capacity of leaning poles would be dramatically reduced during extreme wind events. In this paper, we regard leaning poles as warning signs of potential failures that can affect the power distribution network performance and estimate the failure probability of leaning poles. To analyze the moment behavior of leaning poles, we propose a new probabilistic framework for computing three types of loads by wind pressure, overturning force, and conductor tension. A set of fragility curves of utility poles with given ages and leaning angles are presented to assess the impact of leaning on the probability of failure. The proposed analytics are tested through a case study on the parts of the power distribution network in Houston, TX. By examining the progress of failure in the network, this method enables to analyze potentially vulnerable utility poles that are likely to threaten the power distribution system reliability under varying wind speed. Thus, this research has the potential to support risk-informed decision-making for power distribution infrastructure systems and ultimately enhance the urban community resilience to blackouts caused by the power distribution system disruption in extreme weather.

Optical and morphological studies of aluminium oxide films fabricated at different leaning angles using ion assisted E-Beam deposition technique

Present work describes the evaporation of aluminium oxide (Al2O3) in the form of thin films on glass and silicon substrates at different leaning angles (10−80°) using Ion-Assisted E-beam deposition (IAD). The optical, morphological and wettability studies of the films reveal a variation in film properties. Refractive index of the film material was found to be varied from 1.67 to 1.64 for 10 to 80° leaning angles. Films thickness was calculated using transmission data with envelope method. The obtained film thickness value was further compared with the thickness data of cross-sectional scanning electron microscopy (SEM) micrographs and coherence co-relation interferometer (CCI) results. Fabricated Al2O3 films show decreased values of refractive index and contact angle with higher leaning angles.

Parametric Analysis and Optimization of Leaning Angle in Torque Converters

Abstract Torque converters are durable fluid couplings that can provide output torque multiplication. Blade leaning angle represents the angular position of a blade chord with respect to its radial reference line, and it is an important blade variable regarding both hydrodynamic performance and manufacturability of a torque converter. In traditional design processes, blade leaning angles are often determined based on experiences of engineers; hence, this study proposed a design approach using the combination of computational fluid dynamics (CFD) and optimization. Two CFD models were developed to design blade leaning angles. A steady-state periodic CFD model was employed for the parameter study and the optimization, and a transient full three-dimensional (3D) model was performed to study the flow mechanism and evaluate the performance with higher accuracy. Design of experiment (DOE) technique was employed to investigate the relationship between blade leaning angles and hydrodynamic performance, and a reduced cubic model was derived from the results. It was found that blade leaning angles had profound effects on torque converter performance; a large blade leaning angle intensified the flow blockage effect, thus resulting in a lower mass flowrate and torque capacity. Seven torque converters with different blade leaning angles were tested to validate the obtained numerical results, and the test data were found to be in good agreement with the CFD predictions. Finally, the hydrodynamic performance of the base model torque converter was optimized by a multi-objective genetic algorithm.

Digital anatomic study on sacral lateral mass screw for sacral fracture

Objective To investigate the anatomical features of the safe zone for sacral lateral mass screw placement and find the safe trajectory, so as to provide reference for clinical application. Methods The three-dimensional computed tomography scan materials of sacrococcygeal vertebrae in 60 patients admitted to the Liaocheng People's Hospital of Shandong Province were analyzed by Mimics software to establish three-dimensional models. There were 33 males and 27 females, aged 25-78 years, with an average age of 45.7 years. After the safe zone was separated from sacral lateral mass model, a maximum cylinder was placed into the safe zone according to its anatomical feature. The cylinder was established as safe trajectory. Anatomical data were measured, including the length and diameter of screw trajectory, the distance between the entry point and the middle jaw, and adjacent upper and lower foramen, as well as the intersection angle between the screw direction and sagittal plane, between the screw direction and the adjacent upper end plate. Results The restriction factor of screw size on S1, S2 lateral mass was transverse diameter, while the restriction factor on S3, S4 was the distance between adjacent intervertebral foramen. The maximal length of screw from S1 to S4 was 30 mm, 35 mm, 30 mm, 14 mm respectively, while the maximal diameter was 12 mm, 9 mm, 5 mm, 5 mm respectively. The best entry point of S1 mass screw was lateral to the zygopophysis. The best entry point of S2-S4 mass screw was located at the midpoint of a line connecting the lateral edge of adjacent posterior sacral foramen approximately about 2 cm from median sacral crest. The leaning angles of screw was increased successively, and the sagittal plane was slightly inclined. There were significant differences between male and female groups in the leaning angle in S2 [male: (35.8±1.2)°, female: (37.9±3.7)°] and the distance between entry point and median sacral crest [male: (20.5±1.0)mm, female: (19.1±1.4)mm](P 0.05). Conclusions Cylindrical bony channel which is feasible for screw placement can be found in the lateral mass of sacrum. Individualized measurement can provide reference for application of lateral mass screw. Key words: Sacrum; Computer-aided design; Models, anatomic; Bone screws

Static and dynamic failure behavior of transparent polycrystalline spinel (MgAl2O4) under compression/shear loading experiments

Compression tests were conducted on transparent polycrystalline spinel (MgAl2O4) at strain rates from 10−4 s−1 to 103 s−1. Besides normal cubic samples that only bear compression along the loading direction, leaning cubic samples with different leaning angles (10° and 20°) were also employed in order to induce higher shear stress during compression. Results show that cracks were initiated from the loading end and inside of the cubic sample, but they preferred to initiate in stress-concentrated regions in leaning cubic samples. After initiation, cracks mainly propagated along the loading direction in the cubic sample, whereas they propagated parallel with the leaning side in the leaning cubic sample. The failure strength of leaning cubic MgAl2O4 is lower than cubic ones due to the introduced shear stress, but it is in direct proportional to the strain rate in samples of both geometrical shapes. For leaning cubic samples, this strain-rate strengthening behavior is not affected by the leaning angles. Sizes of MgAl2O4 fragments increase when larger shear stress is introduced, but they decrease with the increase of strain rate.

Influence of Stator Blade Geometry on Torque Converter Cavitation

Cavitation in torque converters may cause degradation in hydrodynamic performance, severe noise, or even blade damage. Researches have highlighted that the stator is most susceptible to the occurrence of cavitation due to the combination of high flow velocities and high incidence angles. The objective of this study is to therefore investigate the effects of cavitation on hydrodynamic performance as well as the influence of stator blade geometry on cavitation. A steady-state homogeneous computational fluid dynamics (CFD) model was developed and validated against test data. It was found that cavitation brought severe capacity constant degradation under low-speed ratio (SR) operating conditions and vanished in high-speed ratio operating conditions. A design of experiments (DOE) study was performed to investigate the influence of stator design variables on cavitation over various operating conditions, and it was found that stator blade geometry had a significant effect on cavitation behavior. The results show that stator blade count and leaning angle are important variables in terms of capacity constant loss, torque ratio (TR) variance, and duration of cavitation. Large leaning angles are recommended due to their ability to increase the cavitation number in torque converters over a wide range of SRs, leading to less stall capacity loss as well as a shorter duration of cavitation. A reduced stator blade count is also suggested due to a reduced TR loss and capacity loss at stall.

Postural Control in Young People with Visual Impairments and Various Risks of Falls

Introduction Early diagnosis of postural control deficiencies facilitates implementation of an individual rehabilitation plan to prevent falls. The aim of the study was to assess the risk of falling in individuals with visual impairments, and to compare performance-based and theoretical limits of stability in subjects with various risks of falling. Methods The study was comprised of 23 participants with severe visual impairments. The risk of fall was assessed with the Step Test. Performance-based limits of stability were measured with the Advanced Mechanical Technology, Inc. (AMTI) platform, and theoretical limits of stability were calculated based on the height of the center of mass (COM) and maximum body sway leaning angles. Results COM displacement values, corresponding to performance-based limits of stability, in individuals with visual impairments whose risk of falling was classified as high were significantly lower than the theoretical values (p ≤ .05). Similar differences were not observed in participants with visual impairments whose risk of falling was assessed as low. Individuals from the low-risk group showed significantly higher values of performance-based limits of stability than the participants from the high-risk group (p ≤ .01 for medio-lateral direction and p ≤ .05 for forward-backward direction). Discussion Nearly half of young people with visual impairments are at increased risk of falling. Such persons showed lower performance-based limits of stability than participants with visual impairments with a low risk of falling. Performance-based limits of stability in individuals with visual impairments with a high risk of falling are lower than their theoretical limits of stability. Implications for practitioners The fact that nearly half of young people with visual impairments are at an increased risk of falling necessitates implementation of preventive measures in this group, as well as among individuals who are blind.

Study on design parameters of leaning-type arch bridges

Leaning-type arch bridge is a new spatial structural system composed of two vertical arches and two leaning arches. So far there has been no contrast analysis of leaning type arch bridge with different systems. This paper focus on a parametric study of leaning type arch bridge with different systems to find the influential rules on structural forces and stability and to provide some reference for practical designs. The parametric analysis is conducted with different rise-to-span ratios and bending rigidities of arch ribs by comparing internal forces. The internal forces decline obviously with the increase of the rise-to-span ratio. The bending moments at the centers of the main arches and the leaning arches are sensitive to the bending rigidities of arch ribs. Parametric studies are also carried out with different structural systems and leaning angles of the leaning arch by comparing the static stability. The lateral stiffness of leaning-type arch bridge is less than the in-plan stiffness. Compared with the leaning-type arch bridge without thrust, the leaning-type arch bridge with thrust has a lower stability safety coefficient. The stability safety coefficient rises gradually with the increase of inclining angle of the leaning arch. This study shows that the rise-to-span ratio, bending rigidities of arch ribs, structural system and leaning angles of the leaning arch are all critical design parameters. Therefore, these parameters in unreasonable range should be avoided.

Effect of suction pipe leaning angle and water level on the internal flow of pump sump

The pump sump, which connects forebay and intake of pump station, supplies good flow condition for the intake of the pump. If suction sumps are improperly shaped or sized, air entraining vortices or submerged vortices may develop. This may greatly affect pump operation if vortices grow to an appreciable extent. Moreover, the noise and vibration of the pump can be increased by the remaining of vortices in the pump flow passage. Therefore, the vortices in the pump flow passage have to be reduced for a good performance of pump sump station. In this study, the effect of suction pipe leaning angle on the pump sump internal flow with different water level has been investigated by CFD analysis. Moreover, an elbow type pipe was also investigated. There are 3 leaning angles with 0°, 45° and 90° for the suction pipe. The suction pipe inlet centre is kept same for all the cases. In addition, the three different water levels of H/D=1.85, 1.54, and 1.31, is applied to different suction pipe types. The result shows that the amount of air sucked into the suction pipe increases with increasing the suction pipe leaning angle. Especially for the horizontal suction pipe, there is maximum air sucked into the suction pipe. However, there is certain effect of the elbow type bell mouth installation in the horizontal suction pipe on suppressing the amount of air sucked into the pipe. Moreover, vertical suction pipe plays an effective role on reducing the free surface vortex intake area.

Scapula behavior associates with fast sprinting in first accelerated running.

The arm-swing motion is important for coordinated lower limb movement during a fast sprint and is composed of three-dimensional scapulothoracic and glenohumeral joint motion. Here, we aimed to clarify the role of the scapula during the initiation of a sprint running when sprinter run with high horizontal acceleration. Ten sports-active students participated in four 5-m dashes, with scapular constraint using non-elastic therapy tape (constraint condition) and without scapular constraint (free condition). The sprinting kinematics was assessed by a 16-camera motion capture system. In the constraint condition, the 2-m sprint time was significantly longer than that in the free condition. At the instants of foot-contact and take-off during the first step, no significant difference in the humerothoracic flexion angle was seen between these two conditions. In contrast, at the instants of foot-contact and take-off during the first step, the humerothoracic extension angle in the constraint condition was significantly smaller than that in the free condition. The forward leaning vector angle of center of mass during the first step was significantly greater than that in the constraint condition. Although no significant difference in hip extension and foot forward leaning angles was seen at the instant of foot contact during the first step between the two conditions, at the instant of take-off, the hip extension and foot forward leaning angles in the constraint condition were significantly smaller than those in the free condition. Therefore, scapular behavior in first accelerated running contributes to larger upper- and lower-limb motions and facilitates coordinating whole-body balance for a fast sprint.

Does knee motion contribute to feet-in-place balance recovery?

Although knee motions have been observed at loss of balance, the ankle and hip strategies have remained the focus of past research. The present study aimed to investigate whether knee motions contribute to feet-in-place balance recovery. This was achieved by experimentally monitoring knee motions during recovery from forward falling, and by simulating balance recovery movements with and without knee joint as the main focus of the study. Twelve participants initially held a straight body configuration and were released from different forward leaning positions. Considerable knee motions were observed especially at greater leaning angles. Simulations were performed using 3-segment (feet, shanks+thighs, and head+arms+trunk) and 4-segment (with separate shanks and thighs segments) planar models. Movements were driven by joint torque generators depending on joint angle, angular velocity, and activation level. Optimal joint motions moved the mass center projection to be within the base of support without excessive joint motion. The 3-segment model (without knee motions) generated greater backward linear momentum and had better balance performance, which confirmed the advantage of having only ankle/hip strategies. Knee motions were accompanied with less body angular momentum and a lower body posture, which could be beneficial for posture control and reducing falling impact, respectively.

Shape and Confinement Effects of Various Terminal Siloxane Groups on Supramolecular Interactions of Hydrogen-Bonded Bent-Core Liquid Crystals

To investigate the shape and confinement effects of the terminal siloxane groups on the self-assembled behavior of molecular arrangements in hydrogen-bonded (H-bonded) bent-core complexes, four H-bonded bent-core complexes S1, P1, C4, and P8 with string-, ring-, and cage-like siloxane termini (i.e., linear siloxane unit −Si–O–Si–O–Si–, cyclic siloxane unit (Si–O)4, and silsesquioxane unit POSS, respectively) were synthesized and investigated. By X-ray diffraction measurements, different types of SmCG (B8) phases and leaning angles were controlled by the shape effect of the string- and cage-like siloxane termini for S1 and P1 (with only one arm of H-bonded bent-core), respectively. In addition, the confinement effect of P1, C4, and P8 (accompanied by increasing the numbers of attached H-bonded bent-core arms) resulted in higher transition temperatures and the diminishing of mesophasic ranges (even the disappearance of mesophase in P8). Moreover, AFM images showed the bilayer smectic CG phases of S1 and P1 ...

Double-level ball-riding robot balancing: From system design, modeling, controller synthesis, to performance evaluation

In this research, a new robot, double-level ball-riding robot, is introduced. The robot consists of an upper ball-riding subsystem and a lower ball-riding subsystem. The robot’s dynamics model can be considered separately in two identical planes. Euler–Lagrange equation of motion is applied in order to obtain the dynamics model. Motors are included in the robot’s model. The model is then linearized. The robot’s parameters are identified. The robot’s prototype is manufactured and assembled. Linear Quadratic Regulator with Integral (LQR+I) controller is proposed and applied in order to balance both levels of the robot. The complementary and orientation transformation are used to fuse sensors in order to obtain robot leaning angles. Balancing performance of the developed double-level ball-riding robot is evaluated by simulations and experiments. The results show efficient control performance of LQR+I controller.

Nonlinear dynamics of adhesive micro-spherical particles on vibrating substrates

The coupled (rocking and out-of-plane) vibrational dynamics of micro-spherical particles on vibrating flat substrates is studied experimentally, analytically, and computationally. In the experimental spectral responses of some of vibrating particles, in addition to their predicted rocking resonance frequencies, extra resonance peaks at the doubles of these predicted frequencies have been previously observed and reported. To understand and explain the rocking resonance frequency doubling effect, a two-dimensional mathematical model describing the coupled dynamics of a micro-spherical particle in the out-of-plane and rocking coordinates is developed and reported. Previously, the doubling effect was leading to ambiguity in adhesion characterization. It is determined that the frequency doubling observed in the spectral domain responses of particles is caused by nonlinear coupling between the out-of-plane and in-plane modes of motion while the particle is experiencing a whirling-like motion taking place around a nearly stationary axis tilted with respect to the substrate normal (as opposed to the substrate normal itself). In current study, the leaning angles of the rocking motion with whirling of a set of polystyrene latex particles are approximated by utilizing the coupled dynamic model. Also, the work-of-adhesion values extracted from the experimental resonance frequencies of a set of particles using the developed model are compared to those reported in the literature and a good agreement is found. The detection and analysis of the reported motion is relevant to adhesion bond characterization and particle manipulation.

Effect of leaning angle of gecko-inspired slanted polymer nanohairs on dry adhesion

We present analysis of adhesion properties of angled polymer nanohairs with a wide range of leaning angles from 0° to 45° and ultraviolet (UV)-curable polyurethane acrylate (PUA) materials of two different elastic moduli (19.8 and 320 MPa). It is demonstrated that shear adhesion and adhesion hysteresis can be greatly enhanced by increasing the leaning angle of nanohairs both for soft and hard materials due to increased contact area and reduced structural stiffness.

A nontransferring dry adhesive with hierarchical polymer nanohairs

We present a simple yet robust method for fabricating angled, hierarchically patterned high-aspect-ratio polymer nanohairs to generate directionally sensitive dry adhesives. The slanted polymeric nanostructures were molded from an etched polySi substrate containing slanted nanoholes. An angled etching technique was developed to fabricate slanted nanoholes with flat tips by inserting an etch-stop layer of silicon dioxide. This unique etching method was equipped with a Faraday cage system to control the ion-incident angles in the conventional plasma etching system. The polymeric nanohairs were fabricated with tailored leaning angles, sizes, tip shapes, and hierarchical structures. As a result of controlled leaning angle and bulged flat top of the nanohairs, the replicated, slanted nanohairs showed excellent directional adhesion, exhibiting strong shear attachment (approximately 26 N/cm(2) in maximum) in the angled direction and easy detachment (approximately 2.2 N/cm(2)) in the opposite direction, with a hysteresis value of approximately 10. In addition to single scale nanohairs, monolithic, micro-nanoscale combined hierarchical hairs were also fabricated by using a 2-step UV-assisted molding technique. These hierarchical nanoscale patterns maintained their adhesive force even on a rough surface (roughness <20 microm) because of an increase in the contact area by the enhanced height of hierarchy, whereas simple nanohairs lost their adhesion strength. To demonstrate the potential applications of the adhesive patch, the dry adhesive was used to transport a large-area glass (47.5 x 37.5 cm(2), second-generation TFT-LCD glass), which could replace the current electrostatic transport/holding system with further optimization.

Weight measurement using image-based pose analysis

Image-based gait analysis as a means of biometric identification has attracted much research attention. Most of the existing methods focus on human identification, posture analysis and movement tracking. There have been few investigations on measuring the carried load based on the carrier’s gait characteristics by automatic image processing. Nevertheless, this measurement is very useful in a number of applications, such as the study of the carried load on the postural development of children and adolescence. In this paper, we investigate how to automatically estimate the carried weight from a sequence of images. We present a method to extract human gait silhouette based on an observation that humans tend to minimize the energy during motion. We compute several angles of body leaning and determine the relationship of the carried weight, the leaning angles and the centroid location according to a human kinetic study. Our weight determination method has been verified successfully by experiments.