Single Angle Research Articles

Failure Analysis of a Cruciform-Leg Transmission Line Tower

Design of latticed steel power transmission towers is a challenging task, which involves lengthy modeling and detailing of significant amount of steel members and connections. The tower is analyzed and designed as a space truss and various members of tower are checked for Tension, Compression and Slenderness Ratio. Sometimes, due to unavailability of required sections or economical point of view, single angle sections are replaced by Cruciform Sections (made of two angles connected toe to toe). The cruciform section, when connected with single angle sections, generate bending moments due to eccentric loading at connection on application of loads on tower, which subsequently results failure of the tower. In the present work, a full-scale testing of a 400 kV tower with built-up leg (Cruciform Leg connected with Single-Angle Leg) has been conducted and the behavior of joint on application of loads has been studied. While testing, one of the legs buckled at the connection. The failure pattern of the leg has been validated using FEM analysis, and the reason of failure has been discussed. In order to confirm the quality of steel, mechanical testing of steel used in leg has been carried out using UTM and results have been explained in the papers. The paper also gives some suggestions for the connection of this type of built-up sections used in tower in order to avoid such failures.

Accelerating convergence to the thermodynamic limit with twist angle selection applied to methods beyond many-body perturbation theory.

We recently developed a scheme to use low-cost calculations to find a single twist angle where the coupled cluster doubles energy of a single calculation matches the twist-averaged coupled cluster doubles energy in a finite unit cell. We used initiator full configuration interaction quantum Monte Carlo as an example of an exact method beyond coupled cluster doubles theory to show that this selected twist angle approach had comparable accuracy in methods beyond coupled cluster. Furthermore, at least for small system sizes, we show that the same twist angle can also be found by comparing the energy directly (at the level of second-order Moller-Plesset theory), suggesting a route toward twist angle selection, which requires minimal modification to existing codes that can perform twist averaging.

Analysis of Structural Response of Subway Shield Tunnel Lining under the Influence of Cavities

The existence of cavities behind the shield tunnel lining can cause cracking, broken pieces, water leakage, and other problems, which reduces the durability and safety of the shield tunnel segment structure. In order to clarify the mechanism of cavity damage, a more systematic study of the effects of cavities on the shield tunnel lining structure from the angle, depth, and the number of cavities is carried out using model tests and numerical simulations without considering the effects of the stiffness reduction effect at the tunnel segment joints and groundwater seepage in this paper. The findings show that the bending moment value and the cavity angle value are approximately linear with the increase of single cavity angle, and the bending moment at the vault arch is reversed when the angle of the cavity behind the arch is greater than 30°. With the increase of single cavity depth, the axial force and bending moment at the cavity increase, and the distribution of bending moment remains unchanged, and the bending moment tends to be stable and unchanged beyond a certain depth. With the increase of single cavity angle and depth, the structural safety coefficient of the segment decreases, and the degree of influence is angle value > depth value. The existence of multiple cavities intensifies the influence of each cavity on the segment, especially when there are cavities behind the top and bottom of the vault; the bending moment value of the top of the vault increases by 22.53% compared with that of the single cavity condition.

On-site focus alignment of a fresnel mirror field

Linear concentrating Fresnel collectors are available in various scales for providing solar thermal heat in the temperature range beyond 100 °C. For raising the flexibility in applying such collector systems on mounting sites with restricted space availability, the presented research project investigated the possibilities for adapting an existing Fresnel collector with a mirror surface of 22 m2towards more compactness by using only one half of the mirror field. Therefore, the receiver was relocated and the focus alignment of the mirrors had to be adapted. The theoretical approach by geometrical calculation of the single mirror angles using MATLAB™ was successful, although the required effort for developing such an optical model was high. Furthermore, the resulting angle information obtained by the calculation is difficult to realise on the mirror field, because a high-precision goniometer would be necessary in order to adjust the mirror stripes accordingly. On the other hand, an experimental approach was analysed for realising on-site focus alignment of the single mirror field. The focussed beam of a conventional laser pointer was directed to each of the mirror stripes, while adjusting the corresponding mirror angle until the reflected beam impinged on the center of the receiver. In the end, the experimental procedure turned out to be favourable, because it is simple and reliable, and it requires much less effort. In this way, the adaption of the Fresnel mirror field was successful, as the concentration and the tracking is working as expected.

Synthesis of Micro-Doppler Signatures of Human Activities From Different Aspect Angles Using Generative Adversarial Networks

In this paper, we propose to produce synthesized micro-Doppler signatures from different aspect angles through conditional generative adversarial networks (cGANs). Micro-Doppler signatures of non-rigid human body motions vary considerably as a function of the radar's aspect angle. Because the direction of the human motion can be arbitrary, a large volume of training data across diverse aspects is needed for practical target activity classification through machine learning. As measurements can require significant monetary and labor costs, the synthesis of micro-Doppler signatures can be an alternate solution. Therefore, we investigate the feasibility of data augmentation through synthesizing micro-Doppler signatures of human activities from diverse radar aspect angles with input data from a single aspect angle. For the training data, the micro-Doppler radar signatures of 12 human activities are generated from different angles ranging from 0 to 315 degrees, at 45-degree increments, through simulations. For each angle, cGANs are trained to synthesize the micro-Doppler signatures for that specific angle given micro-Doppler signatures from another angle. The output of each model is evaluated by calculating mean-square errors and structural similarity indexes between the synthesized micro-Doppler signatures and the ground-truth ones obtained from simulations. We test three different scenarios, and report the respective results.

Correlation between clinical tests for gait and stability using biomechanical variables in the gait of institutionalized elderly subjects

Abstract Study aim: This study aims to identify biomechanical gait variables explaining clinical test results in institutionalized elderly people. Material and methods: Twenty-nine elderly (82.0 ± 6.3 years) residents in a nursing home were assessed. They were able to walk 10 meters without walking aids. First, the spontaneous gait was assessed using inertial measurement units in a 10-meter long corridor. Fifteen biomechanical gait variables were analyzed. Then, three clinical tests usually used in elderly subjects were applied: the Timed Up and Go (TUG) test, the Tinetti Scale and the Sit to Stand (STS) test. A correlation matrix using Pearson’s correlation coefficient between clinical and biomechanical variables was performed, obtaining a total of 45 potential correlations. A stepwise multiple linear regression analysis was then performed to determine the influence of each variable. Results: TUG, Tinetti and STS were significantly correlated with similar biomechanical variables, including temporal, temporo-spatial and kinematic variables. Adults over 80 years old and women showed stronger correlations. Single support and ankle angle at takeoff were the two most important variables in stepwise regression analysis. Conclusions: In institutionalized elderly subjects, clinical variables for gait and postural stability are correlated with the biomechanical gait variables, especially in women and adults aged over 80 years.

AoA-Based Localization System Using a Single IoT Gateway: An Application for Smart Pedestrian Crossing

During the last decade, the concept of smart cities is gaining popularity, and many cities all around the globe are adopting it. Lately, the Smart Pedestrian Crossing (SPC) idea has become an important part of the smart city concept. The main objective of the SPC is to achieve a safe and smooth traffic flow of pedestrians and vehicles in the smart city. In this paper, we present a simple yet efficient localization system which is suitable for locating people over a pedestrian crossing. By adopting the proposed localization system, the people flow over the pedestrian crossing can be observed. Consequently, a safe and efficient traffic flow in the smart city can be achieved. The proposed system utilizes Internet of Things (IoT) transceivers that are carried by the pedestrians or embedded in the pedestrians’ smart devices. These transceivers can be activated to transmit a signal every few seconds when the pedestrian passes over a pedestrian crossing. These periodic signals will be received by a single Angle of Arrival (AoA) estimation system to estimate the direction of the pedestrian. Furthermore, the pedestrian direction and the environmental features of the pedestrian crossings are utilized in a 1D particle filter to estimate accurately the pedestrian’s location. The proposed system has been validated experimentally in the smart zone of Antwerp city. The experimental results reveal that the proposed localization system can provide an accurate, cost effective and reliable localization solution to this specific problem without violating the pedestrian privacy.

Doublet achromatic metalens for broadband optical retroreflector

A retroreflector that reflects light along its incident direction has found numerous applications in photonics, but the available metasurface schemes suffer from the issue of narrow bandwidth and/or a single angle of incidence. Here, a retroreflector using double layers of achromatic gradient metasurfaces is reported, which can realize retroreflection over a continuous range of incidence angles within a wide spectral band. The first metasurface serves as a transmissive achromatic lens that performs a broadband spatial Fourier transform and its inverse, while the second metasurface works as a reflective achromatic lens that undergoes wavelength- and position-dependent phase dispersions. Using this design strategy, a near-infrared retroreflector comprised of silicon nanopillars with the cross sections of square pillars and square holes is numerically demonstrated, providing a high-performance retroreflection for polarization-independent incident light waves over a continuous range of incidence angles from 0° to 16° within an extremely broad wavelength range between 1.35 and 1.95 µm. The scheme herein can offer a design strategy of broadband retroreflectors and impact numerous photonics applications.

Unsteady overflow behavior of polydisperse granular flows against closed type barrier

The overflow behavior of polydisperse granular flows against closed type barrier is a crucial yet poorly understood aspect of multiple-barrier design. We use a robust numerical model based on the three-dimensional discrete element method (DEM) to simulate polydisperse granular flows and identify fundamental mechanisms. The morphology of the dead zone behind the upstream barrier significantly influences the overflow behavior of granular flows. This implies that aside from the case of a gentler barrier (<70°), the launch direction is controlled by the inclination surface of the dead zone. We identified a three-stage evolution process of the overflow velocity. The velocity component in the z-direction controls the first stage, whereas the latter two stages are controlled by the velocity component in the x-direction. The launch angle is usually larger than 45° during the initial overflow stage. Such a high launch angle is maintained for about 0.2–0.3 s. Boulders are transported downstream by the overflow process owing to particle-size segregation and a more concentrated load is received by the downstream barrier, which can lead to localized barrier damage. A different overflow mechanism would result in a different launch distance. Steeper (135°) and gentler (70°) barrier configurations are dangerous because the normalized launch distance is up to 20% larger than that of a barrier with a medium inclination. And a point-mass based assumption is used to estimate the maximum launch distance with the use of maximum overflow velocity and a single launch angle. In addition, we discuss some limitations of numerical modelling, including the effect of fluid phase on overflow, as well as the direct application of our results in engineering design.

Toward Cloud Tomography from Space Using MISR and MODIS: Locating the “Veiled Core” in Opaque Convective Clouds

Abstract For passive satellite imagers, current retrievals of cloud optical thickness and effective particle size fail for convective clouds with 3D morphology. Indeed, being based on 1D radiative transfer (RT) theory, they work well only for horizontally homogeneous clouds. A promising approach for treating clouds as fully 3D objects is cloud tomography, which has been demonstrated for airborne observations. However, more efficient forward 3D RT solvers are required for cloud tomography from space. Here, we present a path forward by acknowledging that optically thick clouds have “veiled cores” (VCs). Sunlight scattered into and out of this deep region does not contribute significant information about the inner structure of the cloud to the spatially detailed imagery. We investigate the VC location for the MISR and MODIS imagers. While MISR provides multiangle imagery in the visible and near-infrared (IR), MODIS includes channels in the shortwave IR, albeit at a single view angle. This combination will enable future 3D retrievals to disentangle the cloud’s effective particle size and extinction fields. We find that, in practice, the VC is located at an optical distance of ~5, starting from the cloud boundary along the line of sight. For MODIS’s absorbing wavelengths the VC covers a larger volume, starting at smaller optical distances. This concept will not only lead to a reduction in the number of unknowns for the tomographic reconstruction but also significantly increase the speed and efficiency of the 3D RT solver at the heart of the algorithm by applying, say, the photon diffusion approximation inside the VC.

Inertial Sensor Algorithms to Characterize Turning in Neurological Patients With Turn Hesitations.

One difficulty in turning algorithm design for inertial sensors is detecting two discrete turns in the same direction, close in time. A second difficulty is under-estimation of turn angle due to short-duration hesitations by people with neurological disorders. We aimed to validate and determine the generalizability of a: I. Discrete Turn Algorithm for variable and sequential turns close in time and II: Merged Turn Algorithm for a single turn angle in the presence of hesitations. We validated the Discrete Turn Algorithm with motion capture in healthy controls (HC, n = 10) performing a spectrum of turn angles. Subsequently, the generalizability of the Discrete Turn Algorithm and associated, Merged Turn Algorithm were tested in people with Parkinson's disease (PD, n = 124), spinocerebellar ataxia (SCA, n = 51), and HC (n = 125). The Discrete Turn Algorithm shows improved agreement with optical motion capture and with known turn angles, compared to our previous algorithm by El-Gohary et al. The Merged Turn algorithm that merges consecutive turns in the same direction with short hesitations resulted in turn angle estimates closer to a fixed 180-degree turn angle in the PD, SCA, and HC subjects compared to our previous turn algorithm. Additional metrics were proposed to capture turn hesitations in PD and SCA. The Discrete Turn Algorithm may be particularly useful to characterize turns when the turn angle is unknown, i.e., during free-living conditions. The Merged Turn algorithm is recommended for clinical tasks in which the single-turn angle is known, especially for patients who hesitate while turning.

Zymogen and activated protein C have similar structural architecture

Activated protein C is a trypsin-like protease with anticoagulant and cytoprotective properties that is generated by thrombin from the zymogen precursor protein C in a reaction greatly accelerated by the cofactor thrombomodulin. The molecular details of this activation remain elusive due to the lack of structural information. We now fill this gap by providing information on the overall structural organization of these proteins using single molecule FRET and small angle X-ray scattering. Under physiological conditions, both zymogen and protease adopt a conformation with all domains vertically aligned along an axis 76 Å long and maximal particle size of 120 Å. This conformation is stabilized by binding of Ca2+ to the Gla domain and is affected minimally by interaction with thrombin. Hence, the zymogen protein C likely interacts with the thrombin-thrombomodulin complex through a rigid body association that produces a protease with essentially the same structural architecture. This scenario stands in contrast to an analogous reaction in the coagulation cascade where conversion of the zymogen prothrombin to the protease meizothrombin by the prothrombinase complex is linked to a large conformational transition of the entire protein. The presence of rigid epidermal growth factor domains in protein C as opposed to kringles in prothrombin likely accounts for the different conformational plasticity of the two zymogens. The new structural features reported here for protein C have general relevance to vitamin K-dependent clotting factors containing epidermal growth factor domains, such as factors VII, IX, and X.

Influence of motion characteristics of dual stealth aircraft on monopulse radar performance

In view of the difficulties to effectively evaluate the influence of penetration of dual stealth aircraft formation on monopulse radar angle tracking error under different flight speeds, the dynamic track model of the dual stealth aircraft under different navigation speeds is established for the first time, and the acquisition method of the dynamic Radar cross section of the dual stealth aircraft formation under different navigation speeds is proposed; the dynamic signal-to-noise ratio of the dual stealth aircraft under different navigation speeds is used as a reference and the model of single pulse radar angle tracking error is established. This paper analyzes the influence of the formation motion characteristics of dual stealth aircraft on the angle tracking error performance of monopulse radar. It is the first time to conclude that the acceleration of the navigation speed of dual stealth aircraft will increase the angle tracking error of monopulse radar when there is no interference.

Deformation characteristics in 3D free-bending forming of complex spiral tubes

Free-bending is a novel bending technology suitable for tube and profile bending. It can achieve accurate bending of tubes or profiles with different bending radii without die. In current study, a new theoretical analysis of a spiral tube formed by 3D free-bending is proposed to reveal the relationship between the spiral tube and the parameters of free-bending forming technology. The results obtained from the proposed theoretical analysis were compared with those achieved from FE modelling and experimentation. The maximum error of forming was less than 7%, which verified the accuracy and the reliability of the proposed theoretical model. The forming limits of the spiral tubes based on 3D free-bending were explored. It was noticed that the spiral diameter was mainly influenced by the eccentricity and the distance between the center of the bending die and the front end of the guide mechanism in the Z–direction (distance A). Furthermore, the spiral diameter is inversely proportional to the eccentricity, and directly proportional to the distance A. In addition, the screw pitch is mainly influenced, and directly proportional to the spiral diameter and the single spiral circle swing angle of the spherical bearing.

Experimental Demonstration of Microwave Two-Dimensional Airy Beam Generation Based on Single-Layer Metasurface

In this article, a 2-D Airy beam is experimentally generated at microwave frequency by using a simple and thin metasurface composed of a single-layer of square C-shaped complementary split-ring resonators (C-SRRs). It is shown that the cross-polarization transmission coefficient, including the magnitude and phase, of a single C-SRR unit can be controlled by modifying the single C-SRR unit rotation angle, and this property is herein used to reshape the impinging field in accordance with the desired 2-D Airy beam profile. The designed metasurface is then fabricated to measure the most significant features of the generated microwave Airy beam, including quasi-nondiffraction, self-bending, and self-healing properties, thus achieving good results in agreement with those predicted by theory. The generated microwave 2-D Airy beam with its properties can be widely applied for high-efficiency wireless power transfer, wireless covert communication, and directional communication.

Ignition criteria and the effect of boundary layers on wedge-stabilized oblique detonation waves

Abstract Simulations of a supersonic, premixed, reacting flow over a wedge were performed to investigate the effect of a boundary layer on the wedge surface on ignition and stability of oblique detonation waves (ODWs). Two computational domains were used: one containing a wedge of a single angle with a straight after-body, and the other containing a double-angle wedge geometry. Both domains were channels with a supersonic inflow of stoichiometric hydrogen-air and a nonreflecting outflow, and the wedge was modeled using an immersed boundary method. The compressible reactive Navier–Stokes equations were solved using a high-order numerical algorithm on an adapting grid. Inviscid and viscous wedge surfaces were modeled using slip and no-slip adiabatic boundary conditions, respectively. Inviscid wedge surface cases are presented for a range of inflow conditions and compared to previous work outlining several different ODW structures. An ignition criterion is established as an accurate method of predicting the formation of an ODW for a given inflow temperature, Mach number, wedge angle, and length of the inviscid wedge surface. A viscous wedge surface is then considered for a Mach 5 inflow at temperatures of 600 K, 700 K, and 800 K. The 600 K flow ignites in the boundary layer, but does not detonate, while the 700 K and 800 K flows ignite and form ODWs. It was determined that ODW formation depends on the degree of augmentation of the leading oblique shock wave by the burning boundary layer and that ODW formation is therefore predictable based on the ignition criterion. The 700 K flow produces a unique oscillatory mode of a receding ODW followed by a redetonation event occurring near the leading edge. A mechanism for this cycle, which repeats indefinitely, is proposed.

Snow wetness retrieved from close-range L-band radiometry in the western Greenland ablation zone

AbstractClose-range (CR) L-band radiometry and quasi-simultaneous in situ snow characterizations were conducted in May 2019 at the Swiss Camp research site in the ablation zone of the western Greenland ice sheet. Snow liquid-water and its melt/refreeze are retrieved from microwave antenna temperatures measured with the ground-based L-band radiometer ELBARA-III. The emission model (EM) used in the retrieval is a two-layer configuration of the ‘L-Band Specific Microwave Emission Model of Layered Snowpack’. Consistent snow wetness retrievals were achieved from both single- and multi-angle CR observations of L-band antenna temperatures. This suggests that multi-angle observation is not a pre-requisite for snow wetness retrieval. Therefore, in addition to soil moisture and ocean salinity (SMOS) multi-angle measurements, snow wetness can be estimated from spaceborne L-band brightness temperatures measured at a single observation angle, such as from NASA's SMAP satellite. Our results provide partial validation of a recently presented snow wetness retrieval approach based on the same EM and applied over Greenland using multi-angle SMOS brightness temperatures. Agreement between measured CR antenna temperatures and SMOS brightness temperatures is found to be within the 95% confidence intervals of ELBARA-III and SMOS measurement uncertainties. Our measurements confirm the modeled response of antenna temperatures to diurnal variations of snow wetness.

An Experimental Study of the Influence of Eccentricity on Shear Lag Effects in Welded Connections

In the 2010 AISC Specification, the shear lag factor for longitudinally welded tension members was applicable only to plate-type members having equal length welds on each side with a minimum length equal to the distance between the welds (AISC, 2010). Fortney and Thornton (2012) used experimental data from three previous research programs consisting of 175 various tension members to develop a generalized shear lag model that addresses the aforementioned limitations. The members comprising this dataset consisted of 158 flat plates with equal weld lengths, 4 single angles with unequal but balanced weld lengths, and 13 other members having equal weld lengths. The shear lag factor presented in the 2016 AISC Specification Table D3.1, Case 4 (AISC, 2016b) is a product of Fortney and Thornton’s work and applies to longitudinally welded plates, angles, channels, tees, and W-shapes having equal or unequal lengths and no length-to-width limitation. This paper presents an experimental study on the shear lag effects in longitudinally welded tension members under both in-plane and out-of-plane eccentricity through the testing of eight 3×1/2 plate sections and twelve 3×3×1/2 single-angle sections having both equal and unequal longitudinal weld lengths. Experimental shear lag factors were determined for each of the 20 tested specimens and compared to three theoretical values: (1) the shear lag factor in the 2010 AISC Specification (AISC, 2010), (2) the shear lag factor based on a bi-planar model (Fortney and Thornton, 2012), and (3) the shear lag factor from Case 4 in the 2016 AISC Specification. The findings of this experimental study confirm that shear lag factor given by Case 4 in the 2016 AISC Specification provides the best prediction of shear lag factors in welded connections subject to both in-plane and out-of-plane eccentricity.

Morphology and mechanical properties of poly (acrylonitrile‐butadiene‐styrene)/multi‐walled carbon nanotubes nanocomposite specimens prepared by fused deposition modeling

AbstractIn this work, poly(acrylonitrile‐butadiene‐styrene) (ABS) filaments containing 0, 1, 3, and 5 wt% multi‐walled carbon nanotubes (MWCNT) were prepared by extrusion. The filaments were then used to make the required specimens with a fused deposition modeling machine. The results obtained from the tensile measurements revealed that with the increase in the layer thickness, the tensile strength of the printed specimens decreased; however, the raster angle did not have any significant effect on the properties. The transmission electron microscope images showed that for the sample containing 3 wt% MWCNT, nanoparticles were reasonably dispersed throughout the matrix. The scanning electron microscope images illustrated that the size of the voids formed within the specimens was increased with increasing of the layer thickness from 0.05 to 0.2 mm. It was also found that the maximum properties could be obtained by using the layer thickness, raster angle and MWCNT concentration of 0.05 mm, 45/−45°, and 3 wt%, respectively. The results showed that both the tensile strength and elastic modulus of the filaments progressively increased with the increase of the nanofiller content in the range studied. It was found that for the constant layer thickness of 0.05 mm, all the specimens printed with single raster angles of 0, 45, and 90° showed higher tensile strength in comparison with their counterparts printed with two raster angles of 0/90° and 45/−45°.

New approach to neutrino masses and leptogenesis with Occam’s razor

The minimal type-I seesaw framework with texture-zero Yukawa and mass matrices inspired by Occam's razor is incompatible with normally-ordered neutrino masses (currently preferred by data) when lepton mixing originates solely from the neutrino sector. Moreover, the lightest right-handed neutrino mass required to generate the observed baryon asymmetry of the Universe via leptogenesis ($M_1 \sim 10^{14}$ GeV) is in conflict with vanilla scenarios for Peccei-Quinn) axion dark matter where the reheating temperature of the Universe is typically below $10^{12}$ GeV. In this work, we present a new Occam's razor setup which overcomes these problems by including charged-lepton mixing parametrized by a single angle, which is predicted to be very close to the quark Cabibbo angle. Furthermore, the atmospheric mixing angle lies in the second octant and the leptogenesis scale is lowered to $\sim 5.5\times 10^{10}$ GeV, lifting the tension with the axion dark-matter hypothesis.