Constant Angle Research Articles

One Class of Resonance Precession Motions of a Rigid Body under the Action of Three Homogeneous Force Fields

The article is devoted to the problem on motion of a rigid body with a fixed point under the action of a force field, which is the superposition of three homogeneous force fields. Existence conditions are investigated for precession motions, which are characterized by the following property: the angular velocity of the precession of the body is two times more than the angular velocity of its proper rotation. It is established that the body has the dynamic symmetry with respect to an axis making a constant angle with a vector fixed in the immovable space. In the case of the body with the spherical mass distribution this angle equals to \({\text{arccos}}\frac{1}{4}\). Solution of the equations of motion of the body is expressed through the elliptic functions of time.

Влияние остаточных напряжений в стали У8 с грубопластинчатым перлитом на магнитную проницаемость

The physical reasons for the formation of peaks of that part of the magnetic permeability, which is caused by transitions of only 90-degree domain boundaries µ90(H0) in deformed steel U8 with coarse-plate perlite when the field changes along the back of the hysteresis loop, are considered. It is shown that the orientation relations of the Patch-Pitch between single-crystal ferrite and cementite plates in U8 steel lead to the appearance of a constant angle between the magnetic moments of these plates and, consequently, to the appearance of corresponding local scattering fields. The latter can significantly affect the values of the peak fields of the curve µ90(H0). Theoretical expressions for these fields containing contributions of scattering fields that should be taken into account when determining residual compressive stresses are obtained. It is also shown that to determine the residual stresses, two expressions for peak fields are not enough, and additional experiments are needed, as which it is proposed to use the dependences of the coercive force on elastic tensile stresses. This leads to a complication of the algorithm for determining residual compressive stresses in comparison with the case of low-carbon steels. A method for estimating the values of local scattering fields in the ferrite parts of U8 steel grains with residual compressive stresses is proposed.

Estimation of residual compressive stresses in deformed U8 steels with coarse-plate perlite by field dependences of magnetic permeability

The physical reasons for the formation of peaks of that part of the magnetic permeability, which is caused by transitions of only 90-degree domain boundaries μ90(H0) in deformed steel U8 with coarse-plate perlite when the field changes along the back of the hysteresis loop, are considered. It is shown that the orientation relations of the Patch-Pitch between single-crystal ferrite and cementite plates in U8 steel lead to the appearance of a constant angle between the magnetic moments of these plates and, consequently, to the appearance of corresponding local scattering fields. The latter can significantly affect the values of the peak fields of the curve μ90(H0). Theoretical expressions for these fields containing contributions of scattering fields that should be taken into account when determining residual compressive stresses are obtained. It is also shown that to determine the residual stresses, two expressions for peak fields are not enough, and additional experiments are needed, as which it is proposed to use the dependences of the coercive force on elastic tensile stresses. This leads to a complication of the algorithm for determining residual compressive stresses in comparison with the case of low-carbon steels. A method for estimating the values of local scattering fields in the ferrite parts of U8 steel grains with residual compressive stresses is proposed. Keywords: residual compressive stresses, deformed steel U8 with coarse-plate perlite, magnetic field, magnetization, magnetic permeability, 90-degree domain boundaries (DB), large-angle vicinity(LAV) and small-angle (SAV) grain boundaries of steel, orientation relations of the Patch-Pitch.

Вдосконалення конструкції бітерів дозатора кормів порційної дії

Вдосконалення конструкції бітерів дозатора кормів порційної дії

Cutaneous information processing differs with load type during isometric finger abduction.

During submaximal isometric contraction, there are two different load types: maintenance of a constant limb angle while supporting an inertial load (position task) and maintenance of a constant force by pushing against a rigid restraint (force task). Previous studies demonstrated that performing the position task requires more proprioceptive information. The purpose of this study was to investigate whether there would be a difference in cutaneous information processing between the position and force tasks by assessing the gating effect, which is reduction of amplitude of somatosensory evoked potentials (SEPs), and cutaneomuscular reflex (CMR). Eighteen healthy adults participated in this study. They contracted their right first dorsal interosseous muscle by abducting their index finger to produce a constant force against a rigid restraint that was 20% maximum voluntary contraction (force task), or to maintain a target position corresponding to 10° abduction of the metacarpophalangeal joint while supporting a load equivalent to 20% maximum voluntary contraction (position task). During each task, electrical stimulation was applied to the digital nerves of the right index finger, and SEPs and CMR were recorded from C3' of the International 10-20 system and the right first dorsal interosseous muscle, respectively. Reduction of the amplitude of N33 component of SEPs was significantly larger during the force than position task. In addition, the E2 amplitude of CMR was significantly greater for the force than position task. These findings suggest that cutaneous information processing differs with load type during static muscle contraction.

Optimization of 4D combined angiography and perfusion using radial imaging and arterial spin labeling.

To extend and optimize a non-contrast MRI technique to obtain whole head 4D (time-resolved 3D) qualitative angiographic and perfusion images from a single scan. 4D combined angiography and perfusion using radial imaging and arterial spin labeling (CAPRIA) uses pseudocontinuous labeling with a 3D golden ratio ("koosh ball") readout to continuously image the blood water as it travels through the arterial system and exchanges into the tissue. High spatial/temporal resolution angiograms and low spatial/temporal resolution perfusion images can be flexibly reconstructed from the same raw k-space data. Constant and variable flip angle (CFA and VFA, respectively) excitation schedules were optimized through simulations and tested in healthy volunteers. A conventional sensitivity encoding (SENSE) reconstruction was compared against a locally low rank (LLR) reconstruction, which leverages spatiotemporal correlations. Comparison was also made with time-matched time-of-flight angiography and multi-delay EPI perfusion images. Differences in image quality were assessed through split-scan repeatability. The optimized VFA schedule (2-9°) resulted in a significant (p < 0.001) improvement in image quality (up to 84% vs. CFA), particularly for the lower SNR perfusion images. The LLR reconstruction provided effective denoising without biasing the signal timecourses, significantly improving angiographic and perfusion image quality and repeatability (up to 143%, p < 0.001). 4D CAPRIA performed well compared with time-of-flight angiography and had better perfusion signal repeatability than the EPI-based approach (p < 0.001). 4D CAPRIA optimized using a VFA schedule and LLR reconstruction can yield high quality whole head 4D angiograms and perfusion images from a single scan.

A Comparative Study of Two Soil Models of Tower Settlement under Eccentric Loading Nearby Slope

Evaluation of settlement of structures constructed on flat ground is an important criteria, that importance increased when these structures available near slope which increase the settlement at certain distance over than its value on flat ground. This study evaluated maximum settlement of Communication Tower foundation using finite element method, this foundation presented near sand slope with constant height and angle, and subjected to eccentric load with constant ratio of eccentricity to foundation width (e/B) equal (0.15), the eccentricity of loading caused by moment, two constitutive models adopted in the study for (Loose, Medium and Dense) sand, the study examined effect of embedment depth, relative density of sand and constitutive model on the relation between maximum settlement and ratio of distance from crest of slope to foundation width (b/B). The results showed which of the two models is more appropriate to represent the problem of study, and showed that at the distance equal and more than half of width of foundation (b/B≥0.5), the effect of the slope on the values of the maximum settlement of foundation begin to disappear, loose sand has the greatest values of maximum settlement, medium and dense sand have a convergence results from each to other. In addition, the results showed the effect of embedment depth in reducing the maximum settlement rate by an approximate range of (32.6 – 42.6) %.

Familiar size affects perception differently in virtual reality and the real world.

The promise of virtual reality (VR) as a tool for perceptual and cognitive research rests on the assumption that perception in virtual environments generalizes to the real world. Here, we conducted two experiments to compare size and distance perception between VR and physical reality (Maltz et al. 2021 J. Vis. 21, 1-18). In experiment 1, we used VR to present dice and Rubik's cubes at their typical sizes or reversed sizes at distances that maintained a constant visual angle. After viewing the stimuli binocularly (to provide vergence and disparity information) or monocularly, participants manually estimated perceived size and distance. Unlike physical reality, where participants relied less on familiar size and more on presented size during binocular versus monocular viewing, in VR participants relied heavily on familiar size regardless of the availability of binocular cues. In experiment 2, we demonstrated that the effects in VR generalized to other stimuli and to a higher quality VR headset. These results suggest that the use of binocular cues and familiar size differs substantially between virtual and physical reality. A deeper understanding of perceptual differences is necessary before assuming that research outcomes from VR will generalize to the real world. This article is part of a discussion meeting issue 'New approaches to 3D vision'.

On the steady-state motion in the vertical plane of an airship of the classical scheme

We consider the construction of the mathematical model of motion in the vertical plane of an airship of the classical scheme and algorithms for calculating the parameters of its steady-state motion in various cases. The motion of an airship of rather small volume, for example, a remotely piloted airship, is investigated. Some types of possible motions in the vertical plane satisfying the proposed system of equations of steady-state motions are described. Such motions include horizontal flight with constant velocity, rectilinear flight in climbing mode, and descent at a constant trajectory slope angle. The cases of rectilinear flight of an airship along inclined trajectories, the inclination angle of which is not small, taking into account the nonlinear components of the aerodynamic characteristics, are also considered. We have developed algorithms for calculating the steady-state motions of an airship for various cases of flight along inclined trajectories corresponding to various methods of takeoff and landing of an airship without a special cable landing system. This allows us to construct trajectories that provide short takeoff distances and low landing speeds of the airship, which corresponds to the solution of the problem of safe operation of the airship as a technical system. The results of numerical calculations of steady-state motion parameters obtained in accordance with the constructed algorithms are presented. The calculation results are presented graphically.

Posteroinferior relevant scapular neck offset in reverse shoulder arthroplasty: key player for motion and friction-type impingement in a computer model.

Range of motion (ROM) and prevention of notching remain a challenge for reverse shoulder arthroplasty (RSA). Both may be affected by the morphology of the scapula. The purpose of this study was to define anteroinferior (a) and posteroinferior (p) relevant scapular neck offset (RSNO) and to examine the hypothesis that pRSNO is significantly smaller than aRSNO, and influences rigid body motion (RBM). Adapting glenosphere implantation strategies may therefore be of value. In this computer model study, we used deidentified computed tomographic scans of 22 patients (11 male and 11 female; mean age: 72.9 years) with massive cuff tears without joint space narrowing. Eight RSA glenoid configurations were tested with a constant neck-shaft angle (145°). Two baseplate types (25 mm; 25 + 3 mm lateralized) and 4 glenospheres (GS) (36 mm; 36 +2 mm of eccentricity; 39 mm; 39 + 3 mm) were used. RSNO was defined as the standardized measurement of the horizontal distance from the inferior extent of the GS to the bony margin of the scapula after baseplate positioning (flush to inferior glenoid extent; neutral position: 0° inclination and 0° version-both software computed). There was a highly significant difference between pRSNO and aRSNO for both genders (P<.001). pRSNO was always smaller than aRSNO. pRSNO was strongly correlated with external rotation (ERO: 0.84) and extension (EXT: 0.74) and moderately correlated with global ROM (GROM: 0.68). There was a moderately strong correlation between aRSNO and internal rotation (IRO: 0.69). pRSNO was strongly correlated with aRSNO, EXT, ERO, IRO, adduction (ADD) and GROM (0.82, 0.72, 0,8, 0.71, 0.82, 0.76) in female patients and with EXT and ERO (0.82, 0.89) in male patients. The median pRSNO allowing for at least 45° ERO and 40° EXT was 14.2 mm for men and 13.8 mm for women. For all patients and models, pRSNO ≥14 mm increased EXT, ERO, and GROM significantly compared with pRSNO <14 mm (P<.001). The combination of lateralization and inferior overhang (eccentricity) led to the most significant increase of pRSNO for each GS size (P<.001). This is one of the first RSA modeling studies evaluating nonarthritic glenoids of both genders. The lateral scapular extent to glenoid relationship is asymmetric. pRSNO is always smaller than aRSNO for both genders and was a critical variable for EXT and ERO, demonstrating additional strong correlation with aRSNO, IRO, ADD, and GROM in female patients. pRSNO ≥14 mm was a safe value to prevent friction-type impingement. Combining increased glenosphere size, lateralization, and inferior overhang gives the best results in this computer-simulated setting.

Error detection using EPID-based 3D in vivo dose verification for lung stereotactic body radiotherapy

PurposeTo investigate the error detectability limitations of an EPID-based 3D in vivo dosimetry verification system for lung stereotactic body radiation therapy (SBRT). MethodsThirty errors were intentionally introduced, consisting of dynamic and constant machine errors, to simulate the possible errors that may occur during delivery. The dynamic errors included errors in the output, gantry angle and MLC positions related to gantry inertial and gravitational effects, while the constant errors included errors in the collimator angle, jaw positions, central leaf positions, setup shift and thickness to simulate patient weight loss. These error plans were delivered to a CIRS phantom using the SBRT technique for lung cancer. Following irradiation of these error plans, the dose distribution was reconstructed using iViewDose™ and compared with the no error plan. ResultsAll errors caused by the central leaf positions, dynamic MLC errors, Jaw inwards movements, setup shifts and patient anatomical changes were successfully detected. However, dynamic gantry angle and collimator angle errors were not detected in the lung case due to the rotation-symmetric target shape. The results showed that the γmean and γpassrate indicators can detect 13 (81.3%) and 14 (87.5%) of the 16 errors respectively without including the gantry angle error, collimator angle error and output error. ConclusionsIn summary, iViewDose™ is an appropriate approach for detecting most types of clinical errors for lung SBRT. However, the phantom results also showed some detectability limitations of the system in terms of dynamic gantry angle and constant collimator angle errors.

Optimized flip angle schemes for the split acquisition offast spin-echo signals (SPLICE) sequence and application to diffusion-weighted imaging.

The diffusion-weighted SPLICE (split acquisition of fast spin-echo signals) sequence employs split-echo rapid acquisition with relaxation enhancement (RARE) readout to provide images almost free of geometric distortions. However, due to the varying T -weighting during k-space traversal, SPLICE suffers from blurring. This work extends a method for controlling the spatial point spread function (PSF) while optimizing the signal-to-noise ratio (SNR) achieved by adjusting the flip angles in the refocusing pulse train of SPLICE. An algorithm based on extended phase graph (EPG) simulations optimizes the flip angles by maximizing SNR for a flexibly chosen predefined target PSF that describes the desired k-space density weighting and spatial resolution. An optimized flip angle scheme and a corresponding post-processing correction filter which together achieve the target PSF was tested by healthy subject brain imaging using a clinical 1.5 T scanner. Brain images showed a clear and consistent improvement over those obtained with a standard constant flip angle scheme. SNR was increased and apparent diffusion coefficient estimates were more accurate. For a modified Hann k-space weighting example, considerable benefits resulted from acquisition weighting by flip angle control. The presented flexible method for optimizing SPLICE flip angle schemes offers improved MR image quality of geometrically accurate diffusion-weighted images that makes the sequence a strong candidate for radiotherapy planning or stereotactic surgery.

Online Monitoring and Control of Butt-Welded Joint Penetration during GMAW

Butt welding is an important link to ensure welding quality, and the penetration state of the weld is the main criterion to achieve this. Online monitoring and control of the penetration state of welded joints is an important measure to ensure welding quality. The molten pool image is monitored by a visual sensor in the gas metal arc welding (GMAW) process, and the bottom molten pool width is predicted by the regression network model. Combined with the real-time control method, the welding current is changed to monitor and control the bottom weld width in real time. Butt-welding experiments with different groove angles verified that the proposed method could achieve satisfactory control accuracy and generalization ability. For butt-welding experiments with constant groove angles of 30° and 45°, the MAE of the controlled backside melt width to the target values was 0.2603 mm and 0.2620 mm. Therefore, it provides a feasible method for the online control of weld penetration.

Celestial Liouville theory for Yang-Mills amplitudes

We consider Yang-Mills theory with the coupling constant and theta angle determined by the vacuum expectation values of a dynamical (complex, zero mass) dilaton field. We discuss the tree-level N-gluon MHV scattering amplitudes in the presence of a nontrivial background dilaton field and construct the corresponding celestial amplitudes by taking Mellin transforms with respect to the light cone frame energies. In this way, we obtain two-dimensional CFT correlators of primary fields on the celestial sphere. We show that the celestial Yang-Mills amplitudes evaluated in the presence of a spherical dilaton shockwave are given by the correlation functions of primary field operators factorized into the holomorphic current operators times the “light” Liouville operators. They are evaluated in the semiclassical limit of Liouville theory (the limit of infinite central charge) and are determined by the classical Liouville field describing metrics on the celestial sphere.

Prediction of Ply Angles of Air Springs According to Airbag Positions and Their Effects on Lateral and Torsional Stiffness

The stiffness in various directions of air springs have a great influence on the stability of high-speed trains. Due to the change in the bogie structure, the required functions of the air springs have also diversified, and the damping of various loading modes such as vertical, lateral, and torsional movements is emerging as important. The stiffnesses are affected by the shape of the air bag, the material, and the ply angles. In this paper, the relationship between the ply angle and the radial position is proposed by equations from deformation modes. The variable angles in the plies were compared and demonstrated in air-spring analysis using the rebar elements. The vertical, lateral, and torsional stiffness of air springs without auxiliary springs were compared between constant ply angles and variable ply angles with respect to the positions. When mainly dealing with the vertical stiffness, the effect of the angle variation was small; however, it was found that it had a large effect of more than 24% and 30% on the stiffness in the lateral direction and torsional direction, respectively.

Comparison of an optimized 3D-real IR and a 3D-FLAIR with a constant flip angle in the evaluation of endolymphatic hydrops

PurposeTo evaluate an optimized 3D-real IR sequence with a longer TR (16,000 ms) based on the modulated flip angle technique in refocused imaging with extended echo train (MATRIX) for the endolymphatic hydrops (EH) after intravenous (IV) single-dose gadolinium (Gd) administration, and compare it with a heavily T2-weighted 3D-FLAIR sequence with a constant flip angle. MethodThe 3D-FLAIR and 3D-real IR sequences were performed in forty patients with definite Meniere’s disease (MD) four hours after IV Gd administration. Image qualities of the two sequences were rated and compared. Contrast-to-noise ratios (CNRs) and signal-to-noise ratios (SNRs) of the two sequences were measured for quantitative comparison. EH was graded on the images of the two sequences by two radiologists. ResultsScores and CNRs of the 3D-real IR were significantly higher than those of the 3D-FLAIR (P < 0.05). SNRs of the two sequences were comparable between the two groups. 3D-real IR had a higher inter- and intra-observer reliability for the grading of cochlear and vestibular EH than 3D-FLAIR. Using 3D-real IR sequence, the detection rate of EH of the whole labyrinth was higher than using 3D-FLAIR (86.6 % vs 73.3 %, p = 0.031). In the patients with unilateral MD, SNRs in the affected sides were significantly higher than the unaffected sides (P < 0.05). ConclusionsThe optimized 3D-real IR with a longer TR is a robust sequence with an improved depiction of EH after IV administration of single-dose Gd. Compared with 3D-FLAIR, it may allow a more precise evaluation and grading of EH.

Theoretical and Numerical Studies of Liquid Lens Evaporation with Coupled Fields

The evaporation of the liquid lens on an immiscible liquid is widely adopted in many industrial and scientific applications, so it is crucial to predict the evaporation rate and lifetime of the liquid lens. During the evaporation, the internal thermocapillary flow, external natural convection, and interfacial evaporative cooling are coupled together and affect the evaporation characteristics greatly. In this paper, the slow and fast evaporation with coupled fields are studied by theoretical analysis and numerical simulation, respectively. It is found that the evaporative cooling can always inhibit the liquid lens evaporation, while the thermocapillary flow and natural convection can enhance the liquid lens evaporation. The total evaporation rate is determined by the competence between the interfacial evaporative flux and upper surface of the liquid lens. With the increasing liquid lens volume, the total evaporation rate will generally increase for fast evaporation, while for slow evaporation that only considers the evaporative cooling effect, the total evaporation rate may decrease at a low tangential angle ratio. The evaporation of the liquid lens follows the constant contact angle mode, the transient variation of volume satisfies the “2/3 law”, independent of evaporative cooling, thermocapillary flow, and natural convection, and it is analogous to the sessile droplet evaporation in constant contact angle mode. These findings can provide guidance for the wide application of liquid lens evaporation.

Surface characterization and paint bonding quality on chemically and thermally modified short rotation teak wood

ABSTRACT Chemical and thermal modification can change the hydrophilic properties of wood, and thus affect their coating performance. This study determined the surface characteristics of chemically and thermally modified short rotation teak wood. The characteristics studied were surface roughness, surface free energy (SFE), contact angle, wettability, and coating bonding quality. Results show that the surface of short rotation teak became smoother after chemical and thermal modifications; however, surface roughness increased after furfurylation. The total SFE of chemically and thermally modified teak wood decreased after treatment. The decrease in the total SFE caused the decrease in the constant contact angle change rate (K-value). The K-values for water-dispersed polyurethane and acrylic paints were nearly 0, which indicated their lower wettability. The paint bonding quality decreased after accelerated weathering. Short rotation teak with Glycerol-Maleic Anhydride (GMA)-thermal treatment can be considered for exterior applications with a proper selection of paint.

Three-dimensional simulation of droplet dynamics in a fractionally-wet constricted channel

This study presents droplet dynamics due to capillarity-wettability interaction through a constricted capillary channel. Previous research has investigated the droplet motion in a constricted capillary channel with a two-dimensional geometry and uniform wettability to determine the critical pressure necessary for the droplet to pass through the constriction, but did not consider the change of pressure as the droplet crosses through a constricted geometry. To explore the dynamic behavior of droplet motion across a constriction, a direct numerical simulation of a droplet in a three-dimensional fractionally-wet constricted channel is performed where we have two different contact angles on opposing faces of the constriction. The results show that the fractional wettability condition significantly affects the evolution of fluid-fluid and fluid-solid interfaces, pressure drop, and displacement patterns. We show that droplet dynamics in a fractionally-wet channel do not necessarily follow the same behavior as in a uniform capillary channel and cannot be predicted using uniform wettability surfaces depicted by an average contact angle. In particular, the pressure difference needed to push the droplet through the restriction with fractional wettability is lower than that for a uniform channel with a constant contact angle representing the less favorable wettability state. The fluid-fluid meniscus often forms saddle-shaped interfaces with curvature of opposite sign in orthogonal directions. Moreover, the effects of droplet size, capillary number, viscosity ratio, and constriction shape are elucidated. The pressure difference increases with droplet size and capillary number. Triangular cross-sections can be accessed at a lower pressure because of wetting layer flow.

Sustainable energy development technique of vertical axis wind turbine with variable swept area – An experimental investigation

The vertical axis wind turbine is one of the most attractive propulsion systems for sustainable energy generation around the globe. The performance of a vertical axis wind turbine is greatly dependent on wind speed, blade set angle and more importantly the rotational speed. The effective utilization of wind speed and rotational speed on power generation would be enhanced by the improvement of energy capturing capability. Therefore, an attempt has been made to develop the vertical axis wind turbine with a variable swept area of blades to enhance the torque and power output over a wide range of rotational speeds and set angles. In the first phase, the wind turbine is designed with flexibility in blade set angles through modification on the swept area and the developed wind turbine has been subjected to various wind speeds and rotational speeds in a wind tunnel. The experimental results revealed that the torque and power are increased with an increase in wind speed and rotational speeds under blade set angle of 30° to 120°. The peak torque and power have been attained at the average speed of the turbine and it has been eventually increased for a higher blade set angle. For constant set angle, the performance characteristics are also improved due to the enhancement in energy capturing ability of wind turbine at the variable swept area. Furthermore, torque and power coefficient are evident in a similar pattern at all wind speeds and rotational speeds under different tip speed ratios. The maximum torque coefficient would be around 0.3 for the tip speed ratio of 0.2–0.3 and the attainment of the peak value of power and torque coefficient has been shifted towards higher speed due to the improvement in blade dimensions. Thus, it is revealed that the vertical axis wind turbine with enhanced swept blade area would be an attractive propulsion system for sustainable energy generation.