Longitudinal Angle Research Articles

Hydrodynamic force coefficients for spherical triangle shell fragments: Dependence on the aspect ratio and flatness

Euler–Lagrange simulations of particle-laden flow require hydrodynamic models of drag and lift forces for individual particles. Our goal is to develop models that can prescribe these forces for arbitrarily orientated shell objects. Here, we use computational fluid dynamics simulations of steady bottom-boundary layer flow over a series of spherical triangle shell fragments to calculate the hydrodynamic forces. The simulations explicitly resolve the wall boundary layers using grid resolution on the order of y+=1 at the shell fragment surface and use the SST k-omega turbulence closure model. These fragments cover a range of aspect ratio and flatness characteristics. The shell fragments are generated as triangular selections of a spherical shell with azimuthal and longitudinal angles proscribed based on elongation and flatness parameters (varying between 1 to 5, and 0.02 to 0.2 respectively), while characteristic length of the fragment is held constant to define the overall fragment size. Fragment orientations are considered with independently varying pitch, roll, and yaw each ranging from 0 to 180 degrees. The numerical estimates for the forces from all simulations were used to develop robust parameterizations of the drag and lift as a function of aspect ratio and flatness characteristics, as well as orientation of the shell fragments.

Modelling the maximum ceiling temperature with bifurcated plume in tunnel fires

Evaluation of the temperature profile induced by tunnel fire is of great significance for fire detection and structural damage assessment. In this work, a special plume model, namely, the “plume bifurcation” is introduced, and its impact on the temperature distribution is analysed theoretically. Full-scale tunnel fire experiments and numerical simulations are conducted to investigate the plume evolution under various heat release rates and ventilation conditions. Results show that the plume will sperate into two sub-streams under strong ventilation condition, resulting in the multi-dimensional plume movement pattern when rising. The sub-plume impingement point location, quantified by the longitudinal vertical deflection angle θv and horizontal bifurcation angle θh, is correlated with the fire heat release rate and ventilation condition. The plume bifurcation angle is 0 when the dimensionless ventilation velocity V′≤0.33, marking a single-stream plume; and rapidly increase and then slowly decrease with V′ when V′>0.33, representing the sudden occurrence and decay trend of plume bifurcation with the ventilation velocity. Finally, a novel bifurcated plume-based model to estimate the maximum ceiling temperature is proposed. This study reveals the role of multi-dimensional smoke movement in reshaping the temperature field, providing new perspectives for a deeper understanding of the smoke transport behaviour in longitudinally ventilated tunnel fires.

High-efficiency thermo-optic control of a longitudinal radiation angle in a silicon-based optical phased array by leveraging the backside air trench structure.

We proposed a 2D 1 × 64 silicon optical phased array with a backside silicon-etched structure to achieve high tuning efficiency and a wide longitudinal steering range. At the radiator array, the n-i-n heater was implemented to steer the light in a longitudinal direction through the thermo-optic effect. The deep reactive ion etching process was utilized to generate the 600 µm depth air trench with a 1.8 cm2 area from the backside of the radiator array. We achieved almost 100% increment in terms of tuning efficiency, which is 1.56°/W for the proposed structure and 0.78°/W for the conventional structure.

Lumbar Pedicle Dimensions Using CT Scan in Adults of South-Eastern Nigeria as Related to Transpedicular Fixation.

Transpedicular fixation depends on accuracy of the entry points, angle of insertion and pedicular isthmus width for adequate screw insertion. Preoperative measurements of pedicle dimensions reduce the chances of failure during insertion. These pedicle dimensions (transverse diameter, longitudinal diameter, and maximum length of purchase [MLP]) vary with sex and race. Such data, from a large-scale study, are not available for our population. The study aims to evaluate the dimensions of pedicle that are relevant for pedicle screw fixation in Southeast Nigerian population. A prospective multi-slice CT based clinical anatomy study done at Memfys Hospital for Neurosurgery, Enugu. This study is on the lumbar pedicle dimensions that are related to transpedicular fixation (transverse and longitudinal diameters of the pedicle, MLP, pedicle transverse and longitudinal angles of inclination). Sample size (273) was calculated with the confidence interval formula based on the number of patients that present for images. Consent and ethical approval were obtained. The mean values are as follow: LD1 8.22 mm, LD2 7.73 mm, LD3 7.40 mm, LD4 7.16 mm, LD5 6.87 mm TD1 5.05 mm, TD2 5.31 mm, TD3 6.72 mm, TD4 8.27 mm, TD5 11.31 mm, MLP1 46.60 mm, MLP2 47.97 mm, MLP3 47.14 mm, MLP4 45.54 mm, MLP5 43.47 mm TA1 17.8°, TA2 19.34°, TA3 20.80°, TA4 22.00°, TA5 25.70° LA1 19.42°, LA2 18.61°, LA3 18.00°, LA4 17.09°, LA5 16.40°. Unlike transverse diameter, transverse angle, longitudinal dimension, longitudinal angle (LA), MLP there was significant correlation between age and mean LA. The mean values also correlated significantly with the gender. The mean values varied with the different vertebral levels and was good correlations between some of the parameters with age and gender.

Experimental study of bond behavior of geopolymer concrete under different curing condition using a pull-out test

Researchers recently have focused on geopolymer concrete as it has several advantages compared to traditional Portland cement, such as lower carbon footprint, high early strength, chemical resistance and long-lasting structural performance. This paper designed 192 pull-out specimens to investigate the influence of factors on the bond-slip behavior between geopolymer and steel bar such as curing condition (ambient and 80 °C for 7 hours), longitudinal rib angle, the position of longitudinal bar, bar diameter (12 mm and 24 mm), stirrup usage (with and without stirrup) and bond length (2d and 4d). The maximum bond strength, bond failure modes, and bond stress-slip relations were discussed. The test results showed that the longitudinal rib angle, and the position of rebar play a vital role in determining the bond strength as well as the bar diameter. In comparison with the specimens without the stirrup, the bond performance of specimens with stirrup increased more significantly, and this phenomenon became even more pronounced as the bar diameter increased. The stirrup usage in samples under ambient and heat cure increased the bond strength by an average of 45 % and %40, respectively. Moreover, it has been determined that the curing conditions have a significant effect on the bond performance, as especially the compressive and tensile strengths of the samples under heat cure improve. In samples exposed to both ambient and heat cure, doubling the bond length increased the bond strength by 70 %. Furthermore, increasing the bar diameter increased the bond strength of the samples exposed to ambient and heat curing by a maximum of 84 % and 79 %, respectively. The findings lay the groundwork for understanding the bond behavior of geopolymer, which is critical for the successful application of geopolymer-bonded rebar.

Erosion, deposition and breach evolution of landslide dams composed of various dam material types based on flume tests

The accurate and rapid prediction of breach outflow rates of landslide dams is crucial for effective risk assessment and mitigation strategies. However, challenges arise due to the complexities associated with breaching mechanisms. In this study, 12 flume tests were conducted on landslide dams composed of various material types, including fine-grained, coarse-grained, well-graded, and gap-graded materials, each with two dry densities. This study comprehensively investigated erosion, deposition, and breach evolution, providing the foundation for the development of breach evolution models. A comprehensive logic diagram, focusing on shear stress and grain size distribution, was proposed to forecast the failure modes of landslide dams. The study also suggested a method to assess the longitudinal breach evolution based on the prediction of the Erosion Point (EP) and Deposition Point (DP), and to assess the lateral breach evolution by considering both steep and gentle breach side slopes. Our findings indicate that fine-grained materials undergo layer erosion, coarse-grained materials remain stable, well-graded materials develop erosion pits, and gap-graded materials are prone to piping. The existence of an interface can result in piping channels, even when the overall hydraulic gradient is insufficient to initiate piping. Incorporating the longitudinal slope angle and its influence on both driving and resisting forces into the traditional erosion rate equation can significantly enhance its accuracy, especially when coarse particles are present. Coarse particles play a pivotal role in erosion and deposition behavior and reshaping the breach evolution as the initiation of coarse particles is dominated by rolling instead of slipping in fine particles. Deposition on the downstream slope of a dam can significantly influence the longitudinal breach process, leading to changes in the downstream topography and grain size distribution. The proposed method for assessing longitudinal breach evolution unifies the previous methodologies by predicting the positions of EP and DP based on erosion and deposition.

Analysis of output characteristics of positive feedback piezoelectric energy harvester based on nonlinear magnetic coupling.

In light of the limitations of the current piezoelectric energy harvesters and the demand for self-power supply in wireless sensor nodes, a novel positive feedback piezoelectric energy harvester based on nonlinear magnetic coupling is proposed. The operational characteristics of this energy harvester are investigated from three perspectives: theory, simulation, and experiment. First, a nonlinear electromechanical coupling mathematical model that describes the dynamic response of the energy harvester system is established by combining the Hamilton variational principle with the piezoelectric theory. This provides a theoretical foundation for subsequent research. Second, finite element method simulations are employed to optimize the structural parameters of the energy harvester and study the impact of nonlinear magnetic force on its output performance. Finally, an experimental prototype is fabricated and an experimental test system is constructed to validate the designed positive feedback piezoelectric energy harvester. The results demonstrate that changes in the longitudinal beam angle have minimal effect on energy capture efficiency. By appropriately increasing the bending surface length, reducing initial magnetic moment, and augmenting mass block weight, wider working frequency bands and higher power generation capacity can be achieved when vibrating in low-energy orbits. The experimental findings align closely with theoretical design values and contribute to advancing broadband multi-directional piezoelectric energy harvesting technology in order to provide high-performance vibration-based power solutions for wireless applications.

Modeling of Acoustic Coupling of Ultrasonic Probes for High-Speed Rail Track Inspection

The paper presents the modeling of transmission of the ultrasonic plane wave through an uniform liquid layer. The considered sources of the ultrasonic wave were normal (straight) beam longitudinal wave probes and angle beam sheer waves probes commonly used in non-destructive testing. Coupling losses (CL) introduced by the presence of the coupling layer are discussed and determined applying the numerical procedure. The modeling applies to both monochromatic waves and short ultrasonic pulses with a specified frequency bandwidth. Model implementation and validation was performed using a specialized software. The predictions of the model were confirmed by coupling losses measurements for a normal beam longitudinal wave probe with a delay line made of polymethyl methacrylate (PMMA). The developed model can be useful in designing ultrasonic probes for high-speed rail track inspections, especially for establishing the optimal thickness of the water coupling layer and estimation of coupling losses, due to inevitable changes of the water gap during mobile rail inspection.

Sensitivity analysis of truck tire tread material properties for on-road applications

This research delves into the sensitivity analysis of a truck tire rubber compound concerning its impact on tire–road interaction characteristics. Initially, the study employs finite element analysis to model a 315/80R22.5 truck tire, which is subsequently validated through static and dynamic response assessments via various simulation tests. Following validation, the established tire model is utilized to conduct a sensitivity analysis of the tire rubber compound specifically applied on the tread. This analysis encompasses several material definitions, including Mooney–Rivlin, visco-Mooney–Rivlin, linear viscoelastic, and nonlinear viscoelastic materials. By exploring the effects of these material models, the research scrutinizes their influence on tire–road interaction characteristics across diverse operating conditions. The tire–road interaction characteristics include the rolling resistance coefficient, and the cornering force at operating conditions including the longitudinal speed, vertical load, and slip angle. This comprehensive investigation offers insights into the intricate relationship between tire composition and performance, thereby enhancing our understanding of tire behavior and informing potential advancements in tire technology.

Improving the quality of mustard seeds during pre-sowing preparation

Improving the quality of mustard seeds during pre-sowing preparation

Experimental Investigation of the Influence of Longitudinal Tilt Angles on the Thermal Performance of a Small-Scale Linear Fresnel Reflector

This paper analyses the influence of the longitudinal tilt angle of the secondary system of a low-concentration photovoltaic system based on a small-scale linear Fresnel reflector. Several evaluation indicators, such as useful heat gain, thermal efficiency, incident solar irradiance gain on the photovoltaic cells, and total useful energy gain, were evaluated for five wind speed conditions and six locations in the Northern Hemisphere. The tests were performed with two small-scale linear Fresnel reflector configurations: the classical large-scale linear Fresnel reflector configuration (base configuration) and the optimal longitudinal tilt angle configuration (longitudinal tilt configuration). An experimental platform based on an open-loop wind tunnel was designed and built for this purpose. As far as useful heat production, the longitudinal tilt configuration performs worse as the longitudinal tilt angle and wind speed increase. A useful heat gain 33.91% lower than the base configuration is obtained with a wind speed of 10.03 (m/s) at the 36.86 (°) latitude location. Thermal efficiency decreases with increasing wind speed and longitudinal tilt angle. The thermal efficiency is between 0.3 and 0.2 with wind speeds of 4.99 (m/s) and 10.03 (m/s). The longitudinal tilt configuration shows the best increase in total useful energy gain in the absence of wind (up to 53% at a latitude of 36.86 (°)). This increase is 25% at this same location with a wind speed of 10.03 (m/s). It can be concluded that the effect of the longitudinal tilt of the secondary system has a positive effect. To highlight the importance of this work, the results obtained in the configuration comparison were used to compare a nonconcentrating photovoltaic system and a low-concentration photovoltaic system. The incident solar irradiance on the photovoltaic cells is much higher with nonconcentrating photovoltaic technology. This solar irradiance gain is over 60% for the base configuration and 45% for the longitudinal tilt configuration. The total useful energy gain is 70% in the absence of wind and at the 36.86 (°) latitude location in favour of the low-concentration photovoltaic system. The nonconcentrating photovoltaic system performs better with a wind speed of 10.03 (m/s).

Morphological and Position Factors of Vertical Surface Light Source Affecting Discomfort Glare Perception

Distinguished from conventional lighting, the LED vertical surface light source (VSLS) is directly exposed to human view, and the effects of which form it takes on visual perception are non-negligible. In the current discomfort glare evaluation system, the solid angle and the position index, which represent the relative relation between the glaring light source and human visual field, are not completely applicable for large-area VSLS, and hence are awaiting supplementation and modification. In this study, a physical experimental setup was established to conduct an evaluation experiment on discomfort glare, employing an LED display and white translucent frosted film to simulate vertical surface light sources (VSLS). The experiments were arranged with 21 VSLS shapes (comprising 3 areas and 7 length-to-width ratios) and 11 mounting positions. Subjective ratings and four eye-movement data parameters—namely, the change rate of pupil diameter (CRPD), mean saccadic amplitude (SA), blinking frequency (BF), and saccadic speed (SS)—were collected from 24 participants under each working condition using the Boyce Evaluation Scale and eye tracking techniques. The main results of this study are the following: (a) CRPD is the most appropriate eye-movement index for characterizing VSLS glare perception; (b) The area of the VSLS is the primary shape element influencing discomfort glare. Furthermore, with the same surface area, the lateral view angle (LaVA) and the longitudinal view angle (LoVA) perceived by the human eye also impact glare perception; (c) A functional equation between the VSLS area, LaVA, and LoVA to the borderline luminance between comfort and discomfort (BCD luminance) is fitted; (d) Based on the eccentric angle and the azimuthal angle, a modified position index P’ is proposed to represent the relative position of the VSLS in the visual field, and the ratio function of BCD luminance of the VSLS at non-central positions and the central position is fitted.

Analysis of Off-Road Tire Cornering Characteristics by Using Advanced Analytical Techniques

ABSTRACT This paper focuses on analysis of the cornering characteristics of an off-road truck tire running under several operating conditions over different soils. The finite element analysis (FEA) method is used to model the Goodyear RHD 315/80R22.5 truck tire, and the smoothed-particle hydrodynamics (SPH) method is used to model the soil. The goal of this research is to provide a virtual testing environment in Pam-Crash software as an alternative to actual tests for FEA and SPH analyses of rolling tire interactions on deformable terrains. The study on the effects of different operating parameters on the cornering performance combined with the sensitivity study can be of interest to tire engineers or vehicle engineers because they provide insight into the design and real-time behavior of a vehicle. Tire and soil models are validated using experimental data and published measurements, showing good agreement. The tire–soil interaction is investigated under different tire conditions, such as longitudinal speed, inflation pressure, vertical load, and slip angle, and under various soil characteristics, such as cohesion, internal friction angle, and rut depth. Cornering force, self-aligning moment, and overturning moment are studied as the fundamental cornering characteristics that affect truck lateral stability and control. Owing to the excessive computational demands posed by the FEA-SPH tire–soil models, we propose unique mathematical relationships for estimating the cornering characteristics of free-rolling as well as driven truck tires in an efficient manner. The genetic algorithm (GA) technique is used to develop relationships between the cornering parameters and operating conditions. We conclude that the identified mathematical relationships could provide very good estimations of the cornering characteristics under a broad range of operating conditions and soils. The GA equations will ultimately be implemented into a full vehicle model to evaluate the full vehicle performance.

A novel three-dimensional orthogonal star honeycomb structure with negative Poisson’s ratio

A novel three-dimensional(3D) orthogonal star honeycomb structure with increased strength and negative Poisson’s ratio(NPR) performance that is not subject to angle constraints was proposed, and the calculation model of Young’s modulus and Poisson’s ratio of the cell structure under axial load was derived in this study. Through the investigation of the deformation mode and the finite element (FE) research results of the structure, it is found that the longitudinal length parameter l2 and angle parameter θ2 are important concave axes that affect the mechanical properties of materials. The quasi-static compression experimental results shows that the constraints of adjacent elements can enhance the strength of the structure to a certain extent, and the theoretical analysis results and the FE simulation results were in good agreement with the experimental results. In addition, the results are also concluded that the prediction of Young’s modulus and Poisson’s ratio and the designability of mechanical properties of 3D orthogonal star honeycomb structures could be achieved by the theoretical calculation formula derived in this study.

Discrete element simulation of vibration compaction of slag subgrade

In this study, to improve the compaction quality and parameters of slag, discrete element models of irregular rock particles (10–60 mm) and circular soil particles (5 mm) were established based on on-site slag screening results. The motion of the vibratory roller was captured by coupling the roadbed model with the roller model in a simulation in which the roller vibrated and compacted the slag subgrade. The results indicated that (1) the best compaction was achieved when the small particle content was 40%, the medium particle content was 20%, and the large particle content was 40%. (2) When the slag was dominated by small rock particles, the optimum compaction frequency was 28 Hz, and when large rock particles dominated, the optimum compaction frequency was 33 Hz. (3) Rock particles were the primary particles that experienced stress in the vibration compaction, and the compressive force and displacement depended on the particle size. (4) The longitudinal and vertical displacements and rotation angles of the soil and rock particles were examined. The results of this study are conducive for advancing the understanding of slag compaction and improving the working efficiency and compaction quality of rollers.

Study and Analysis of the Relationship between Longitudinal Moment Coefficient and Angle of Attack or Lift Coefficient based on the Stability and Controllability of the ekranoplan

The ekranoplan, as a special type of vessel, combines the performance of an aircraft and a ship. It boasts high speed, low radar visibility, good maneuverability, excellent amphibious capabilities, and a unique feature that sets it apart from other vessels: it is immune to torpedo and mine attacks. This article aims to introduce the main component design of the ekranoplan, the composition of its power system, and analyze its stability and controllability. Through graphical analysis, the relationship between the longitudinal moment coefficient, attack angle, and lift coefficient of an aircraft was studied. The results indicate that ensuring stability for the ekranoplan is more challenging compared to an aircraft. The paper provides a good basis for subsequent seakeeping experiments on ground-effect winged vehicles, which is of great significance.

Measurement of Kerr rotation and ellipticity in magnetic thin films by MOKE magnetometry

When polarized light is incident on a magnetic material, the magneto-optical Kerr effect (MOKE) rotates the polarization and induces ellipticity in the reflected light, which allows the magnetization direction to be probed optically. The Kerr rotation and ellipticity determine the magnitude of the effect and are usually measured using dedicated ellipsometers. Here, we demonstrate a simple method for extracting Kerr rotation and ellipticity in magnetic thin films using a conventional MOKE magnetometer consisting of two polarizers and a quarter waveplate. Using this technique, we report the longitudinal Kerr angle of BiYIG, GdCo, and TbCo. We additionally observe a linear decrease in polar complex Kerr angle magnitude in 3 nm GdCo films as the atomic fraction of Gd is increased.

Design and Optical Performance Evaluation of the Three-Dimensional Solar Concentrators with Multiple Compound Parabolic Profiles and Elliptical and Rectangular Receiver Shapes

The compound parabolic concentrator (CPC) is a core technology in the field of solar concentration. Nevertheless, it only has one degree of freedom in the choice of its half-acceptance angle. In this study, extending the idea of the three-dimensional CPC, a design method for new kinds of concentrators having a CPC shape at each profile with various acceptance angles in all directions is proposed. The feature of this method is that the receiver can take any shape. Here, elliptical and rectangular receivers are assumed, and the shape and concentration performance of the concentrators with multiple CPC profiles and an elliptical receiver (MultiPro-ECPCs) and the concentrators with multiple CPC profiles and a rectangular receiver (MultiPro-RCPCs) are derived. The new designs are compared to the conventional CPC and a mirrorless flat receiver through ray-tracing simulations in terms of energy distribution on the receiver, optical efficiency, and optical concentration ratio based on axial and solar angles. The results show that in terms of optical efficiency, the MultiPro-RCPCs cover a wider range of incident angles after the 3DCPC. In terms of the optical concentration ratio, the MultiPro-ECPC with a longitudinal half-acceptance angle of 15° has the highest peak value of 19.5, followed by the MultiPro-RCPC. This study enlightens that with the concentration system settings adapted to the acceptance range of the proposed concentrators, a higher concentration can be achieved with the MultiPro-ECPC and MultiPro-RCPC compared to the conventional CPC.

Enhancing high-speed steering stability of wheel-legged vehicles by active roll control

Wheel-legged vehicles (WLVs) combine the speed of wheels with the active control of legs to traverse challenging terrain, which presents a new development possibility for enhancing the system’s mobility and stability. Most of the existing studies mainly focus on the stability of low-speed trajectory optimization or obstacle-surmounting by hybrid walking-driving. Without considering the stability of high-speed driving. To enhance the vehicle stability at high-speed steering, with the additional roll moment generated by the active roll motion taken into account, a 15-degree-of-freedom nonlinear yaw-roll coupled vehicle model is developed. Specifically, a fusion dynamic stability factor for skid steering is presented as the rollover threshold to determine the three-dimensional stability region of longitudinal speed, yaw rate and roll angle, based on which the vehicle’s ideal roll angle is obtained. Subsequently, a hierarchical parallel control scheme is proposed to decouple the yaw and roll motions of the wheel-legged vehicle. The fusion dynamic stability factor is regarded as the switching threshold of the upper-level controller, while the lower-level controller adopts the linear quadratic regulator and the sliding mode control to actively control additional roll moment and direct yaw moment, respectively. Furthermore, the studies for the dynamic model and the proposed controller are conducted through vehicle tests. Corresponding test results validate the advantages of the proposed control scheme over conventional schemes without active roll control, in which vehicle stability is effectively improved, thereby preventing vehicle rollover in the case of high-speed steering.

Parametric comparison of a CPVT performance evaluation under standard testing procedures - ISO 9806:2017 and IEC 62108:2016 - for an automated and manual 2-axis tracking solar system stand

Currently, a noticeable lack of literature with respect to a wide-ranging comparison of the precision exhibited by automated and manual two-axis tracking solar systems, particularly within the context of adhering to the standard testing protocols delineated by ISO and IEC. To address this research gap, a symmetrical concentrating Photovoltaic-Thermal solar collector underwent a detailed evaluation encompassing two standard testing procedures such as ISO 9806:2017 and IEC 62108:2016. This comprehensive assessment covered thermal and electrical performance parameters, unfolding across two distinct geographical locations: Athens (Greece) and Gävle (Sweden). Within this experimental framework, an automated two-axis tracking solar system stand was employed at the Greek testing site, while in Sweden it was characterized by the employment of a manual two-axis tracking solar system. The collective peak power performance presented marginal divergence within a narrow range of ± 1% across both testing sites. This culminated in an overall peak power output of 1550 Wpeak, which included an electrical peak capacity of 218 Wpeak and a thermal peak power of approximately 1332 Wpeak. Notably, the most pronounced deviation has been materialized in the transversal and longitudinal Incidence Angle Modifier coefficients, with disparities remaining limited to a threshold of < 5%. These findings underscore the commendable precision hallmarking. In summary, the outcomes presented in this study not only contribute to the extant body of knowledge by bridging the existing gap in literature, but also emphasize the precision inherent to manual two-axis tracking solar systems when compared with automated equivalents.