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This paper uses numerical and experimental methods to look at how well Xar450 and Perform 700 high-strength steels protect against a 7.62 × 39 mm API BZ projectile. The numerical study of the target thicknesses varies from 3 mm to 4 mm and 6 mm. And they are struck at 0°, 15°, 30°, 45°, and 60° oblique angles. Numerical simulation results show that at a normal impact angle, the bullet can break through the Perform700 targets in all thicknesses; however, the resistance performance of the target plate increases with the rise of oblique angles. The Xar450 target plates of 4 mm and 6 mm can resist the bullet at any oblique angle, but the bullet can easily penetrate 3 mm thickness from 0° to 30° oblique angles. The experiment is based on the VPAM-APR 2006 standard. The experiment results showed that the bullet perforated through the Perform700 target plate with a thickness of 3 mm at 0° and 30° oblique angles. In contrast, the bullet cannot penetrate the Xar450 target thickness of 4 mm at a normal angle. The findings of this research are used in the formulation of the design methodology for a light armoured vehicle. Besides, they have considerable importance in the realm of calculating and developing anti-fracture structures for practical applications. [ABSTRACT FROM AUTHOR]

The flow mixing through secondary flow is critical for improving the heat transfer of microchannel heat sinks. This study investigates oblique fin heat sinks (OFHSs) under forced convection conditions with Al2O3-water nanofluid under the Re 100–500. The study is referenced with a straight channel heat sink for benchmarking purposes. Five oblique angle configurations (15°, 25°, 35°, 45°, and 55°) were investigated at the constant fin pitch and constant width ratio (primary width-to-secondary width ratio) of 2:1. The RNG k-ε model has been employed with enhanced thermofluidic effect and wall treatment. The findings revealed that secondary flow generation leads the thermal boundary layer to redevelop at each fin, resulting in continuous fluid flow development. Pressure drop increment has been noticed with oblique angles 15° to 25°, and the variation is almost insignificant among the 35°, 45°, and 55° OFHS. The secondary flow rates were found to have a profound effect in all the cases. The 25° degree shows a higher average convection coefficient among all the OFHSs. Also, the convection coefficient varied in the following order for both water and nanofluid: 15° < 25° > 35° > 45° > 55°. The 25° OFHS enables a more uniform water/nanofluids temperature to build up in the streamwise direction than the 35°, 45°, and 55° OFHS. The thermofluidic analysis suggests that the proposed designs have superior heat convection performance than their flow resistance penalty. Therefore, the 25° OFHS offers a promising option for further parametric research in the future. [ABSTRACT FROM AUTHOR]

In order to explore the flow characteristics and working principles of oblique stilling basins, model tests were carried out on six schemes with three inlet angles in two types of stilling basin (perpendicular and oblique). The outcomes demonstrated the feasibility of oblique stilling basin. However, the oblique angle of stilling basin has an impact on the flow, and the smaller the angle, the greater the impact. The specific manifestations are: Firstly, the hydraulic jump is oblique, and when the upstream energy exceeds a certain value, a hydraulic jump occurs on the obtuse angle side formed by the starting section, while no hydraulic jump occurs on the other side. And there is a large difference in the water level between the longitudinal and cross sections in the stilling basin, and the smaller the angle, the greater the difference caused. Secondly, the water level on the obtuse angle side is higher than that on the acute angle side, and the smaller the angle, the greater the change, with the lowest water level occurring on the acute angle side; the oblique angle of the stilling basin causes uneven energy at the starting section, with greater energy on the acute angle side than that on obtuse angle side, and smaller angles have greater energy. This research showed the working principle of oblique stilling basin and can serve as a basis for subsequent research. [ABSTRACT FROM AUTHOR]

The existing filtering methods for airborne LiDAR point cloud have low accuracy. An adaptive filtering algorithm is proposed which is improved based on multilevel resolution algorithm. First double index structure of Octree and KDtree is established. Then the initial reference surface is constructed by ground seed points. According to the slope fluctuation situation, the grid resolution of the ground referential surface is adjusted in an adaptive way. Finally, the refined surface is formed gradually by multilevel renewing resolution to provide filtered point cloud with high accuracy. Experimental results show that the error of Type II can be effectively reduced, the average Kappa coefficient increases by 0.53% and the average total error decreases by 0.44% compared with multiresolution hierarchical classification algorithm. The result tested by practically measured data shows that Kappa coefficient can reach 90%. Especially, it maintains advantages of high accuracy under complex topographic environment. [ABSTRACT FROM AUTHOR]

Ultrasonic mist vapor deposition (UMVD) is a widely used facile technique to prepare ZnO thin films. The surface properties of prepared thin films can be tuned via easily controllable UMVD deposition parameters. Herein, we utilized an oblique angle (OA) geometry in UMVD system named as OA-UMVD. The angle between incident flow and substrate (θs) was changed from 0° to 45°. Alteration of θs as well as substrate temperature (Ts) resulted in the deposition of ZnO thin films with different morphologies. For mild nozzle–substrate distance (D = 3 cm), fine vertical ZnO nanosheets with length of 123 nm and thickness of 23 nm were obtained for low Ts (330 °C) and small θs (≈ 0°). By increasing both Ts and θs, ZnO nanorods gradually appeared on the surface. Both nozzle–substrate distance (D) and Ts showed similar effect on deposition rate (Rd), and Rd decreased by increase of D and Ts, while deposition rate increased for larger θs. Confocal microscopy results revealed that using low Ts (330 °C), short distance (D = 1.5 cm) and large θs (45°) resulted in high macroscopic surface roughness (MRs) of 98 nm, while high Ts (500 °C), long D (5 cm) and small θs (≈ 0○) created compact and smooth surface with low MRs of 5 nm, in accordance with transmittance results. The ZnO wurtzite crystal structure was approved via X-ray diffraction patterns. The crystallite size in the layers was affected only by Ts, and θs had no significant effect on the layers' crystallinity. Obtaining different ZnO nanostructures with different MRs via easily and accurately controllable growth parameters is a great advantage for our employed OA-UMVD system, which could be used to prepare ZnO thin films with desired morphologies for widespread application fields. [ABSTRACT FROM AUTHOR]

This paper presents the elastoplastic behavior of beam-to-column connections with horizontally oblique angles under cyclic loading. We conducted a full-scale experiment and an element test to predict the critical sections of flanges subjected to tensile loading. Four element specimens were tested at different oblique angles. In the element test, strain concentration caused earlier failure of the specimens with oblique angles. Notably, the ductility of specimens with a 45° oblique angle decreased by 50% compared to those without an oblique angle. In the full-scale experiment, four specimens were tested. The hysteretic responses, skeleton curves, failure modes, and ductile performances of the specimens were analyzed. The experimental results from the full-scale experiment showed that all specimens, regardless of the oblique angles, exhibited stable hysteresis behavior and similar skeleton curves. Regarding failure modes, fractures occurred where local buckling developed, albeit with varying locations based on the oblique angle. However, strength deterioration behaviors following local buckling remained the same. A strain concentration phenomenon was observed at the beam end with analyzing strain range. Owing to local buckling, no apparent decrease in ductility with a change in the oblique angle was observed. • Oblique angles had little effect on the behavior of beam-to-column connections. • Larger oblique angles caused strain concentration in obtuse angle zones. • With increasing oblique angles, strength deterioration behavior was not affected. • Fatigue life with oblique angles was similar to that without oblique angles. • Premature fracture might appear at the obtuse angle zone of the beam end. [ABSTRACT FROM AUTHOR]

• In this manuscript, a new unidirectional SH wave EMAT with oblique permanent magnet for the inspection of the aluminum plate is presented for the first time.The oblique angle of the permanent magnet enhances the guided signal on one side and weakens the ultrasonic signal on the other side. • Therefore, the angled bias magnetic field can improve the focusing ability of the SH guided wave transducers effectively. • It is concluded that the oblique PPM can improve the focusing ability of the unidirectional point-focusing SH guided wave EMAT and suppress the influence of the reflected signal, and then improve the resolution of the ultrasonic signal at the focusing point. • In the study of the influence of the oblique angle of the permanent magnet on the focusing SH guided wave EMAT, the displacement amplitude at the focal point increases as the angle increases while the growth rate decreases. • For the other side of the focal position, the displacement amplitude at that point decreases linearly as the angle increases. We propose a new unidirectional point focusing shear horizontal (SH) guided wave electromagnetic ultrasonic transducer (EMAT) with an angled periodic permanent magnet (PPM) in this work. The angled PPM developed here provides an angled bias magnetic field to achieve the EMAT's unidirectional focusing capability. The characteristics of the magnetic field distribution are analyzed by numerical and theoretical calculations. The simulation and experimental results are proven to be in good agreement when studying the bidirectional normalized amplitudes of the displacement of the single-coil SH-guided EMAT with oblique permanent magnets. Both the proposed angled transducer structure and the traditional paralleled transducer structure are performed and simulated using the three-dimensional Finite Element Method (FEM) to compare their unidirectional focusing capabilities. The results show that the SH guided wave EMAT of the focusing coils with an oblique permanent magnet enhances the signal on the focusing side and weakens the signal on the other side effectively. This performance can suppress the influence of the reflected signal from the unfocused side and further improve the ultrasonic signal's resolution. Moreover, it is shown in the study that increasing the oblique angle of the PPM makes it difficult to increase the signal strength at the focal point when the angle reaches a certain value, but it is still effective at weakening the signal on the unfocused side. [ABSTRACT FROM AUTHOR]

The dynamic 'overstress', i.e., the apparent increase of strength of concrete at very high strain rates (10– 10 6 /s) experienced in projectile impact and penetration, has recently been explained by a new theory with partial analogy to turbulence. The increase is attributed to comminution of concrete driven by the release of local kinetic energy of the shear strain rate field of forming fragments which, in projectile impact problems, exceeds the strain energy of the fragments by orders of magnitude. This theory gives the particle size distribution and the additional local kinetic energy density, Δ K , proportional to the deviatoric strain rate square. To match test results, Δ K must be dissipated during finite element simulations of impact. In previous simulations, Δ K was, at first, dissipated by an artificial equivalent viscosity (not empirical but predicted by the theory). Later it was found that dissipation by upscaling material tensile strength is equally effective. This theoretically justified upscaling is adopted here since it is more realistic when microplane constitutive model M7 for fracturing damage in concrete is used. All artificial damping is eliminated from the computer program. While previous simulations with the comminution theory were limited to orthogonal impacts, and only the cases of penetration of slabs of various thickness by projectile of one velocity and penetration depths for different velocities, the present study also analyzes further test data on oblique impacts at various impact angles up to 35 ∘ , and on the exit velocities and penetration depths of projectiles of different velocities. For each test series on one and the same concrete, the material parameters are calibrated on one test and then, using the same parameters, all the other tests are predicted. All the predictions of exit velocities and penetration depths of projectiles, as well as entry and exit craters, are quite accurate. [ABSTRACT FROM AUTHOR]

Abstract Slope surface is unavoidable and has an important effect on the quality of final fabricated product in the selective laser melting (SLM) process. In this paper, finite element simulation and experimental research on the effect of slope surface with different oblique angles are performed. In the finite element model, the difference in thermal physical properties between the fabricated part and powder material are taken into account. The temperature distribution, melt pool shape, slope surface morphology, roughness and dimensional accuracy are investigated. It shows that the melt pool depth and length are significantly influenced by the oblique angle and the tail of melt pool trends to one side as the oblique angle becomes small. The quality of slope surface increases and the dimensional deviation decreases with the increasing oblique angle. Based on the results, large oblique angle is recommended when designing part, and rotation in the vertical direction is prompted for obtaining large oblique angle when fabricating product. In addition, large dimension compensation and intensified post processing are suggested for slope surface with small oblique angle. [ABSTRACT FROM AUTHOR]

In order to investigate the impact resistance of the Nomex honeycomb sandwich structures skinned with thin fibre reinforced woven fabric composites, both drop-weight experimental work and meso-mechanical finite element modelling were conducted and the corresponding output was compared. Drop-weight impact tests with different impact parameters, including impact energy, impactor mass and facesheets, were carried out on Nomex honeycomb-cored sandwich structures. It was found that the impact resistance and the penetration depth of the Nomex honeycomb sandwich structures were significantly influenced by the impact energy. However, for impact energies that cause full perforation, the impact resistance is characterized with almost the same initial stiffness and peak force. The impactor mass has little influence on the impact response and the perforation force is primarily dependent on the thickness of the facesheet, which generally varies linearly with it. In the numerical simulation, a comprehensive finite element model was developed which considers all the constituent materials of the Nomex honeycomb, i.e. aramid paper, phenolic resin, and the micro-structure of the honeycomb wall. The model was validated against the corresponding experimental results and then further applied to study the effects of various impact angles on the response of the honeycomb. It was found that both the impact resistance and the perforation depth are significantly influenced by the impact angle. The former increases with the obliquity, while the latter decreases with it. The orientation of the Nomex core has little effect on the impact response, while the angle between the impact direction and the fibre direction of the facesheets has a great influence on the impact response. [ABSTRACT FROM AUTHOR]

In the present work, the effect of channel cross section on the heat transfer performance of an oblique finned micro-channel heat sink was investigated. Water and Al 2 O 3 /water nanofluid of volume fraction 0.25% were used as a coolant. The oblique finned microchannels are designed with three channel cross-sections namely square, semicircle and trapezoidal. The primary work of this paper is to study the heat transfer and hydrodynamic characteristics in the oblique finned microchannel. The experimental setup and procedure are validated using water as coolant in a micro-channel heat sink. Heat transfer and flow characteristics are examined for three cross-sections of varying mass flux. The trapezoidal channel cross-section increases the considerable heat transfer rate improvement for both water and nanofluid by 3.133% and 5.878% compared to square and semicircle cross section. Also, the pressure drop is higher in the trapezoidal cross-section over the square and semicircle cross section. This is due to increase in friction loss of trapezoidal cross section. The results indicate that trapezoidal cross-section oblique finned micro-channel is more suitable for heat transfer in the electronic cooling application. [ABSTRACT FROM AUTHOR]

Laboratory experiments were conducted to investigate the dynamics of oblique particle cloud in stagnant water. Previous laboratory studies on vertically downward particle clouds indicated the importance of nozzle diameter d o and mass of sand particles in form of an aspect ratio of L o / d o where L o is the length of occupied sand particle in a pipe. In addition, particle size plays an important role in mixing capability of particle clouds. 30 laboratory experiments were carried out to consider the effects of L o / d o , particle size D 50 , angle of release θ , and release height H . In order to generalize the outcome of the present study, both particle size and release height were normalized to form Stokes number S t and release number η . Three classes of particle size were identified for 0 < S t < 1 and a relatively wide range of aspect ratio 0.8 ≤ L o / d o ≤ 40.1 was formed by changing the mass of sand particles. To consider the effects of release angle and release height, four release angles of θ = 15°, 30°, 45°, and 60° were chosen and three release numbers of η = 8.5, 13.2, and 17 were selected. Trajectories of particle clouds were identified based on the position of cloud front. Empirical formulations were developed to model the path of the frontal head of oblique particle clouds. Using a theoretical approach, the location of particle fall out was estimated within ± 10% accuracy. Variations of the frontal velocity of particle clouds in vertical direction were investigated and an empirical equation was proposed based on dimensional analysis to predict the frontal velocity at different initial conditions. Mixing efficiency of particle clouds was characterized by entrainment coefficient α e . The entrainment coefficients of particle clouds were computed using the theoretical entrainment hypothesis. It was found that the Stokes number can significantly alter the mixing capability of particle clouds. The influence of controlling parameters on particle−particle interactions can be studied by estimating the drag reduction due to particle grouping effects. The averaged drag coefficients C d of particle clouds were calculated from momentum equation and a semi-empirical model was proposed to estimate the drag reduction of particle clouds. Significant drag reduction occurred in particle clouds in comparison with individual particles. [ABSTRACT FROM AUTHOR]

Transverse vortex-induced vibrations (VIVs) of a near-wall cylinder under oblique flows are studied experimentally in a water flume for both increasing and decreasing velocities. The VIV responses and the wake flow patterns around the cylinder are measured with a synchronous measurement system and a PIV. The validity of the Independence Principle (IP) for a cylinder in proximity to a wall is examined in terms of the vibration amplitude, frequency and critical normal reduced velocity. The results show that the combinations of the gap ratio and oblique angle have significant effect on the VIV response of a circular cylinder. The IP is found to be valid in predicting the VIV response for small oblique angles ( θ ≤30°) and large gap ratios ( e / D ≥0.8) whereas for large oblique angles ( θ >30°) or small gap ratios ( e / D <0.8), the deviations from the IP are pronounced. The upper and lower critical normal reduced velocities for the onset of VIV are obtained for both increasing and decreasing velocities. Empirical relationships between the correction factor of the critical normal reduced velocity and gap ratio and the oblique angles ( θ ≤45°) are established. Based on the analyses of the wake flow patterns obtained by PIV, it is found that the difference in the onset of VIV for increasing and decreasing velocities corresponds to different vortex shedding modes at the initial branch: the 2S vortex shedding mode for increasing velocity and the C(2S) mode for decreasing velocity. [ABSTRACT FROM AUTHOR]

The initial oblique and attacking angles as well as the asymmetrical nose abrasion may lead to bending or even fracture of a projectile, and the penetration efficiency decreases distinctly. The structural stability of a high-speed projectile non-normally penetrating into concrete and the parametric influences involved are analyzed with the mass abrasion taken into account. By considering the symmetrical or asymmetrical nose abrasion as well as the initial oblique and attacking angles, both the axial and the transverse drag forces acting on the projectile are derived. Based on the ideal elastic-plastic yield criterion, an approach is proposed for predicting the limit striking velocity (LSV) that is the highest velocity at which no yielding failure has occurred and the projectile can still maintain its integral structural stability. Furthermore, some particular penetration scenarios are separately discussed in detail. Based on the engineering model for the mass loss and nose-blunting of ogive-nose projectiles established in Part I of this study, the above approach is validated by several high-speed penetration tests. The analysis on parametric influences indicates that the LSV is reduced with an increase in the asymmetrical nose abrasion, the length-diameter-ratio, and the concrete strength, as well as the oblique and attacking angles. Also, the LSV raises with an increase in the initial caliber-radius-head (CRH) and the dimensionless cartridge thickness of a projectile. [ABSTRACT FROM AUTHOR]

Abstract: A novel cylindrical oblique fin minichannel heat sink was proposed and studied for cooling heat source with cylindrical surfaces. To optimize and analyze the heat transfer performance of the heat sink, a similarity analysis and parametric study on the geometric dimensions of the heat sink were performed. Three dimensional conjugated heat transfer simulation using CFD (Computational Fluid Dynamics) approach was used to analyze the laminar convective heat transfer and apparent friction characteristics for 43 different cylindrical heat sinks with varied geometric dimensions. The studies were performed by varying the oblique angle from 20° to 45°, secondary channel gap from 1mm to 5mm and Reynolds number from 200 to 900. In this paper, the flow distribution was also investigated and reported, as the secondary channel gap, oblique angle and Reynolds number were varied. Based on the 259 numerical data points, multiple correlations for the average Nusselt number and the apparent friction constant were formulated, verified and presented. The average deviation for the approximation of average Nusselt number is from −5.8% to 7.0% while it is from −5.1% to 7.1% for the apparent friction constant. These correlations can be used for further studies such as performance prediction or geometrical optimization. [Copyright &y& Elsevier]

Abstract: Oblique angle ion etching at incidences of 30° and 75° from surface normal were used to produce sharp tipped topographical features on Ti6Al4V alloy. The 30° etching resulted in a random distribution of needles raising ~4μm from the base surface, while needles from the 75° etching laid closer to the surface. The cellular response of these surfaces was evaluated by a weeklong culture of hFOB 1.19 cells. It was shown that the features of the 30° etch prevented cells from spreading while cells on the 75° etched surface displayed preferential elongation in the direction of the needles. [Copyright &y& Elsevier]

The effect of oblique angle on the localized surface plasmon resonance of cone-shaped nanoparticles is explored. The finite difference time domain method is applied to analyze the extinction spectra and the electric field intensity. The simulation results show that cone nanoparticles with a small oblique angle exhibit a larger resonant wavelength than those with a large oblique angle. The full width at half maximum initially decreases and then increases as the oblique angle increases, with a turning point of 17.5°. The refractive index sensitivity and the sensing sensitivity both decrease when the oblique angle of the cone nanoparticles increases, achieving a maximum figure of merit (FOM) of 14.6 RIU−1. For cone-shaped nanoparticles, the shape can be described by the power exponent m of the curve in the cross-section. The larger the power exponent m, the larger the oblique angle. Cone-shaped nanoparticles with power exponent m < 1 (concave conical surface) exhibit larger FOM than those with m > 1 (convex conical surface). The largest FOM is achieved when m = 1/3. [ABSTRACT FROM AUTHOR]

Objective: The target in the thoracic sympathetic ganglion block (TSGB) is the anterior edge of the costovertebral articulation along the lateral surface of vertebral bodies T2-4. The present study attempts to determine an optimal safe angle for fluoroscopy in fluoroscope-assisted TSGB through the use of chest CT scan images. Additionally, we seek to determine if differences in these measurements exist in patients with chronic obstructive pulmonary disease (COPD). Methods: Chest CT scans from 320 patients were included. The range of angle and entry point distance to midline was measured in all subjects. The range of angle was from the minimum angle to thoracic sympathetic ganglion passing over the lateral aspect of body to the maximum angle to the thoracic sympathetic ganglion not puncturing the pleural space. Additionally, these measurements from 50 COPD patients were subsequently compared age-matched individuals without COPD. Results: No significant difference in optimal angle was found for any of the levels between T2 and T4. The optimal angle was significantly different between right and left sides, although no such difference was identified between genders. The older patients had a significantly smaller optimal angle than the younger. Similarly, individuals with COPD had a significantly smaller optimal angle and entry distance. Interpretation: The measurements derived from this study can be used as a reference for TSGB and radiofrequency lesioning to prevent the complications. Specifically, our data indicate that the optimal oblique angle of fluoroscopy is 18°-19° for non-COPD patients and 16°-17° for COPD patients. [ABSTRACT FROM AUTHOR]

Abstract: Piezoelectric composite materials, an important part of smart structure, have the ability to perform both sensing and actuating functions. The 1–3 piezoelectric composite consists of piezoelectric rods embedded across the polymer. Such materials have been applied effectively in the pulse-echo transducers used in medical ultrasonic imaging. The composite can also be used for underwater vibration or noise controlling with its high coupling factor and low acoustic impedance, for both the shear and the compression damping characteristics can be controlled by inclining the piezoelectric rods. In this paper, a simple physical model of 1–3 piezoelectric composite was developed to illustrate the material''s properties that are relevant to the hydrostatic response. It evaluated the influences of the oblique angles, volume fraction and the parameters of PZT rods and polymer to its hydrostatic properties and came up with a solution to maximize the electromechanical coupling factor and the acoustic impedance. [Copyright &y& Elsevier]

Abstract: An experimental study is performed to determine the combined effects of oblique angle (θ) and heating height (H) on the flame structure, temperature field and thermal efficiency of a laminar premixed methane–air flame impinging on a plane surface. A double-flame burning of a Bunsen flame under a fuel-rich condition is used. It is found that the flame structure, temperature distribution and thermal efficiency depend strongly on the oblique angle and heating height. The influence of the oblique angle on flame structure is stronger for lower heating heights but is relatively weak for higher heating heights. For normal impingement, axisymmetric temperature distributions are found, which is attributed to the axisymmetric flame structure. However, a jet flame impinging at an angle onto the horizontal plate creates an asymmetric flame structure and, thus, results in asymmetric temperature distributions. The results show that as the oblique angle is reduced from 90° to 60°, the high-temperature zone shifts toward the major flow region. An optimum operating condition of the burner, identified by the widest high-temperature zone and the highest thermal efficiency, is achieved under the condition of θ=60° and H=12 mm. In general, a decrease of the oblique angle leads to a decrease in thermal efficiency. However, for the cases of lower heating heights (i.e. H⩽12 mm), the trend may be reversed. Furthermore, for a fixed oblique angle, as the heating height is increased, the thermal efficiency first increases to a maximum value and then decreases. [Copyright &y& Elsevier]