Perpendicular Angle Research Articles

Exceptional anisotropic superhydrophobicity of sword-lily striated leaf surface and soft lithographic biomimicking using polystyrene replica

Herein, we report unusually high anisotropic superhydrophobicity, unidirectional self-cleaning, and biomimicking of adaxial sword-lily (Gladiolus hortulanus) leaf comprising three distinct levels of surface textures. Observably, the static anisotropic wetting and rolling of water droplets are more favourable in the parallel (or, striation) direction than in the perpendicular direction. Inspired from such water repellency of the sword lily leaf surface, here bio-mimicked polystyrene (PS) leaf construct is developed through a soft lithographic technique. Considering different water droplet sizes (4–10 μl) on natural lily leaf and bio-mimicked PS construct surfaces, the respective parallel (θ ||) and perpendicular (θ ⊥) water contact angles (WCAs) stand at, θ || ∼143°–147°, θ ⊥ ∼156°–169°; and θ || ∼130°–139°, θ ⊥ ∼142°–145°. Moreover, the specimens under study exhibit roll-off angles ranging, α || ∼8°–23° (α ⊥ ∼16°–41°) and α || ∼21°–49° (α ⊥ ∼40°–55°) along parallel (and perpendicular) directions; respectively. A noticeable difference in α ⊥ and α || values can be ascribed to the profound three-phase contact line (TCL) pinning along the perpendicular direction taking advantage of striation as means of barrier. The roll-off angles can also alter due to a variation in the droplet volume. The unusual anisotropic superhydrophobicity and unidirectional droplet roll-off can be attributed to the entrapped air within the micro-nano texture beneath the water droplet along with the pinning effect in the perpendicular direction caused by the striated heights.

Evidence for bipolar explosions in Type IIP supernovae

Aims. Recent observations of core-collapse supernovae (SNe) suggest aspherical explosions. Globally, aspherical structures in SN explosions are thought to encode information regarding the underlying explosion mechanism. However, the exact explosion geometries from the inner cores to the outer envelopes are poorly understood. Methods. Here, we present photometric, spectroscopic, and polarimetric observations of the Type IIP SN 2021yja and discuss its explosion geometry in comparison to those of other Type IIP SNe that show large-scale aspherical structures in their hydrogen envelopes (SNe 2012aw, 2013ej and 2017gmr). Results. During the plateau phase, SNe 2012aw and 2021yja exhibit high continuum polarization characterized by two components with perpendicular polarization angles. This behavior can be interpreted as being due to a bipolar explosion, where the SN ejecta is composed of a polar (energetic) component and an equatorial (bulk) component. In such a bipolar explosion, an aspherical axis created by the polar ejecta would dominate at early phases, while the perpendicular axis along the equatorial ejecta would emerge at late phases after the photosphere in the polar ejecta has receded. Our interpretation of the explosions in SNe 2012aw and 2021yja as bipolar is also supported by other observational properties, including the time evolution of the line velocities and the line shapes in the nebular spectra. The polarization of other Type IIP SNe that show large-scale aspherical structures in the hydrogen envelope (SNe 2013ej and 2017gmr) is also consistent with the bipolar-explosion scenario, although this is not conclusive.

Ultra-broadband absorber based on algorithmic optimization of MgF2–Fe stacked structure

Broadband absorbers possess a wide array of potential applications, including electromagnetic cloaking, solar energy harvesting, and solar power generation. However, achieving excellent ultra-broadband absorption with plasma-metal materials remains challenging due to their inherently narrow bandwidth. To tackle this issue, we propose an ultra-broadband absorber, free from lithography, composed of a multilayer stack of magnesium-iron fluoride (MgF2–Fe). In this study, we optimized the structural parameters of the absorber using a particle swarm optimization algorithm to achieve theoretically optimal absorptivity. Numerical simulations revealed that the absorber achieved an impressive theoretical average absorption of 98.4% across a broad wavelength range from ultraviolet to near-infrared (321–1800 nm). Importantly, it exhibited stable absorption performance at large incidence angles (0–70°), while maintaining high absorption efficiency. Furthermore, it demonstrated polarization independence at perpendicular incidence angles. Subsequently, experimental preparations and tests were conducted on absorber samples to evaluate their solar energy absorption capacity. Both experimental and theoretical comparisons underscored the promising potential of this structure for applications in solar energy collection, conversion, and solar power generation.

Comparison of the Ionospheric Dynamo Current of Mars Above InSight and Zhurong Landing Sites: A Modeling Study

AbstractPrevious observational studies suggest that the surface time‐varying magnetic field of Mars originates in large part from the dynamo currents in the Martian ionosphere. However, whether there are significant differences in the strength, configuration, diurnal, and seasonal variations of the dynamo currents above different regions need to be further studied. In this study, using the ionospheric parameters from Mars Climate Database version 5.3 (MCD v5.3) and 7 years of MAVEN magnetic field measurements, we compare the ionospheric dynamo currents above the landing sites of InSight (4.50°N, 135.62°E) and Zhurong (25.07°N, 109.90°E) and the resulting surface magnetic variations at the two landing sites by conducting a modeling study. We find that the average dynamo current as well as its diurnal magnetic field amplitude on the Martian surface is significantly stronger at InSight than that at Zhurong due to the stronger background magnetic field strength and more perpendicular angle between magnetic field and neutral wind vectors in the dynamo region, though the conductivities is always weaker over InSight landing site. The seasonal variation of the current intensity (represented by differences between northern winter and summer solstices) is prominent over InSight than that over Zhurong because the heliospheric distance effect‐resulted conductivity difference is the dominate factor for the seasonal variations over InSight while both the heliospheric distance and solar zenith angle (SZA) contribute to the current intensity at different Ls over Zhurong. The two factors partially offset each other and lead to a smaller seasonal variation. The role of crustal field, as well as the latitude effects on dynamo currents is also discussed. This study provides an attempt to promote the understanding of the solar wind‐induced magnetosphere‐ionosphere‐surface coupling process.

Effects of mid-passage gap with a variable surface angle on a turbine vane endwall’s aerothermal and film cooling performances

The mid-passage gap is an inevitable structure in a vane passage due to turbine vanes being manufactured individually. The coolant from this gap is able to prevent hot mainstream ingression and provide cooling protection for the endwall. A novel idea of enlarging the endwall’s coverage area and reducing the endwall’s thermal load by applying the mid-passage gap with variable surface angles is carried out in this paper. The endwall’s aerothermal and film cooling performances under four mid-passage gap modes at three typical mass flow ratio conditions are numerically investigated. Results indicate that under the traditional mid-passage mode, the coolant flows into the mainstream with a perpendicular incidence angle and can’t stick to the endwall. Thus, cooling failure occurs, and the endwall’s thermal load is badly increased. The film cooling level at the suction-side endwall is improved when applying the mid-passage gap of a 45° surface angle due to the secondary vortex being suppressed. In addition, when applying the mid-passage gap of a 135° surface angle, the horseshoe vortex is pushed away, and the coverage area at the pressure-side endwall is enlarged significantly. The best film cooling performance is achieved when the upstream surface angle is 135° and the downstream surface angle is 45° due to the adiabatic film cooling effectiveness being increased at both the pressure- and suction-side endwall. When the mass flow ratio is 1.5%, the coverage area is enlarged by 43%, and the area-averaged adiabatic film cooling effectiveness is increased by 37%, when compared with those under the traditional mid-passage mode.

Anisotropy of the R1/T2* value dependent on white matter fiber orientation with respect to the B0 field

The R1 (1/T1) map divided by the T2* map (R1/T2* map) draws attention as a high-resolution myelin-related map. However, both R1 and R2* (1/T2*) values demonstrate anisotropy dependent on the white matter (WM) fiber orientation with respect to the static magnetic (B0) field. Therefore, this study primarily aimed to investigate the comprehensive impact of these angular-dependent anisotropies on the R1/T2* value.This study enrolled 10 healthy human volunteers (age = 25 ± 1.3) on the 3.0 T MRI system. For R1/T2* map calculation, whole brain R1 and T2* maps were repeatedly obtained in three head tilt positions by magnetization-prepared two rapid gradient echoes and multiple spoiled gradient echo sequences, respectively. Afterward, all maps were spatially normalized and registered to the Johns Hopkins University WM atlas. R1/T2*, R1, and R2* values were binned for fiber orientation related to the B0 field, which was estimated from diffusion-weighted echo-planar imaging data with 3° intervals, to investigate angular-dependent anisotropies in vivo.A larger change in the R1/T2* value in the global WM region as a function of fiber orientation with respect to the B0 field was observed compared to the R1 and R2* values alone. The minimum R1/T2* value at the near magic-angle range was 18.86% lower than the maximum value at the perpendicular angle range. Furthermore, R1/T2* values in the corpus callosum tract and the right and left cingulum cingulate gyrus tracts changed among the three head tilt positions due to fiber orientation changes. In conclusion, the R1/T2* value demonstrates distinctive and complicated angular-dependent anisotropy indicating the trends of both R1 and R2* values and may provide supplemental information for detecting slight changes in the microstructure of myelin and axons.

Small-amplitude Compressible Magnetohydrodynamic Turbulence Modulated by Collisionless Damping in Earth’s Magnetosheath: Observation Matches Theory

Plasma turbulence is a ubiquitous dynamical process that transfers energy across many spatial and temporal scales and affects energetic particle transport. Recent advances in the understanding of compressible magnetohydrodynamic (MHD) turbulence demonstrate the important role of damping in shaping energy distributions on small scales, yet its observational evidence is still lacking. This study provides the first observational evidence of substantial collisionless damping (CD) modulation on the small-amplitude compressible MHD turbulence cascade in Earth’s magnetosheath using four Cluster spacecraft. Based on an improved compressible MHD decomposition algorithm, turbulence is decomposed into three eigenmodes: incompressible Alfvén modes and compressible slow and fast (magnetosonic) modes. Our observations demonstrate that CD enhances the anisotropy of compressible MHD modes because CD has a strong dependence on wave propagation angle. The wavenumber distributions of slow modes are mainly stretched perpendicular to the background magnetic field ( B 0) and weakly modulated by CD. In contrast, fast modes are subjected to a more significant CD modulation. Fast modes exhibit a weak, scale-independent anisotropy above the CD truncation scale. Below the CD truncation scale, the anisotropy of fast modes enhances as wavenumbers increase. As a result, fast-mode fractions in the total energy of compressible modes decrease with the increase of perpendicular wavenumber (to B 0) or wave propagation angle. Our findings reveal how the turbulence cascade is shaped by CD and its consequences for anisotropies in the space environment.

Novel benzoxazole-based liquid crystals with negative dielectric anisotropy and moderate optical anisotropy

ABSTRACT A series of new liquid crystal compounds with negative dielectric anisotropy was synthesised by regulating the orientation of the substituents on the benzoxazole ring, namely, 5–4-(2-(4-(alkoxy)phenyl)-2,3-difluorophenyl)benzo[d]oxazole derivatives (nPP(2,3)FO). These compounds mainly display enantiotropic nematic mesophases in the ranges of 8.62–16.09°C (heating process) and 23.98–30.32°C (cooling process), moderate birefringence (Δn) ranging from 0.25–0.32 (DFT theoretical calculation) and 0.22–0.28 (experimental measurement), as well as negative dielectric anisotropy (Δɛ) ranging from −2.77 to −2.94. These characterises are ascribed to the larger perpendicular dipole moments and orientation angles of benzoxazole. This work provides new ideas for the rational design of negative dielectric anisotropy liquid crystals.

Biomechanics of brain tissue damage caused by fiber endoscope penetration in third ventriculostomy surgery

Third ventriculostomy is the preferred treatment for obstructive hydrocephalus, but the biomechanics of brain tissue damage caused by fiber endoscopes remains unclear. In this study, brain tissue material parameters were tested based on the Ogden model to simulate needle puncture mechanics, and replicated the entire fiber endoscope advancement process during third ventriculostomy. It was found that a smaller diameter fiber endoscope, a perpendicular puncture angle, and a faster puncture speed would decrease the damage of brain tissue caused by the fiber endoscope. This study provides valuable insights for optimizing the instrumentation and surgical process of third ventriculostomy.

The influence of penetration angle on anti-penetration performance and reverse penetration ricochet phenomenon of UHMWPE laminates

Penetration angle refers to the angle between the normal of laminates and the projectile trajectory. In actual battlefield conditions, projectiles may hit Ultra-High Molecular Weight Polyethylene fiber (referred to as UHMWPE) laminates from various angles, resulting in ricochet phenomena and secondary injuries. Currently, research on bullets hitting penetrating laminates at a perpendicular angle is relatively well-developed, while research on the penetration of laminates by bullets at other angles is limited. Therefore, this study combined experiments and numerical calculations to investigate the penetration of 7.62 mm steel core projectiles at different angles on UHMWPE laminates. The study found that UHMWPE laminates enhanced bullet resistance through yawing and bending the penetrating projectiles at different angles. The influence of penetration angle on the impact area of the projectile-facing surface, the height of the bulge on the backside, and the penetration depth, as well as the trajectory and morphology of the projectile, were mastered in this study. Notably, a penetration angle of 50° was the limit condition for projectile to produce reverse penetration ricochet phenomenon of projectiles in UHMWPE laminates with a thickness of 30 mm. These research findings provide a theoretical basis and technical support for the bulletproof design of UHMWPE laminates.

Benzoxazole-terminated liquid crystals with large birefringence and negative dielectric anisotropy

We synthesized heterocyclic liquid crystals with large birefringence and negative dielectric anisotropy, namely, 5–4-(2-(4-(alkoxy)phenyl)-2,3-difluorophenyl)benzo(d)oxazole derivatives (nPFO). These compounds display enantiotropic nematic mesophases with wide mesophase range of 45.9–84.0 °C (heating process) and 61.3–119.6 °C (cooling process). Compared with reference analogues of traditional benzoxazole compound 6PFB with different orientation of benzoxazole-terminated structure, the compounds nPFO roughly give lower melting points and clearing points because of their increased dihedral angle. Meanwhile, compounds nPFO show obviously large birefringence (Δn, 0.28–0.39 and 0.39–0.48 for experimental measurement and DFT theoretical calculation, respectively) due to the enhanced π-conjugation caused by the ethynyl bridge group in molecules. Benefitting from the larger perpendicular dipole moments and orientation angles, nPFO displays negative dielectric anisotropy (Δɛ) ranging from −3.60 to −4.10. These compounds can endow a commercial negative LC mixture the larger Δn and higher values of figure of merit, suggesting they are suitable dopant to further improve the performance of some commercial LC mixtures.

Development of a radiographic technique for porcine head ballistic research

IntroductionThe porcine model shows structural features comparable to that of humans and are routinely used within research, due to the ethical, legal, and practical use of post-mortem human samples. Methods for obtaining high quality and comparable reference data using standardised acquisition protocols are essential. MethodsThe decapitated heads of three adult white sows were subjected to radiographic imaging before and after cranial trauma (9 mm, Heckler and Koch MP5). Digital radiographs were generated using a Siemens MULTIX TOP system with an Agfa digital detector, with foam blocks and sandbags as ancillary equipment. An iterative approach was adopted by the authors to generate reproducible radiographic views from two perpendicular angles. Specimens were kept at 5 °C and wrapped in polythene bags to reduce the impact of putrefaction. ResultsStandardised head radiography technique was developed for superior-inferior and lateral views demonstrating porcine anatomy. Key parameters included: automatic exposure control for tube current (∼4 mAs), tube voltage of 73 kVp, 100 cm source to image receptor distance, and an anti-scatter grid. Slight variances in specimen morphology, developmental status, and soft tissue changes did not affect imaging outcomes. ConclusionThe technique and positioning proposed in this study allows for the acquisition of high quality and reproducible radiographic images for comparable ballistic research datasets. Specimen positioning and centring of the primary beam may be applied across porcine breeds, although individual radiographic parameters may differ according to equipment specifications and specimen size. Implications for practiceDevelopment of a reproducible radiographic technique of porcine heads in forensic and veterinary research.

A Three-Dimensional Finite Element Analysis of the Stress Distribution Around the Bone Mini-Implant Interface Based on the Mini-Implant Angle of Insertion, Diameter, and Length.

Temporary anchorage devices or mini implants have gained great attraction due to their capability to provide absolute anchorage, low cost, versatility, and can be loaded immediately after placement. Finite element analysis was used to evaluate the distribution of stress at the bone mini implant interface based on different angles of insertion (30°, 45°, 60°, and 90°) mini implant diameter (1.3 mm, 1.6 mm, and 2 mm) and mini implant length (6 mm, 8 mm, and 10 mm). A retraction force of 2 N was applied. Areas of maximum stress concentration were the head and neck of the mini implant and cortical bone around the mini implant. A very minimal amount of stress was found in the cancellous bone. The maximum stress found in the cortical bone was 5.1301 MPa and in the mini implant was 26.355 MPa with an angle of insertion of 30°, a 1.3 mm diameter, and a 6 mm length. The minimum stress found in the cortical bone was 1.4702 MPa and that in the mini implant was 5.3895 MPa with an angle of insertion of 90°, a 2 mm diameter, and a 10 mm length. For maximum stability, mini implants should be placed at a perpendicular angle of insertion with sufficient diameter and length.

Arthroscopic Posterior HAGL Repair Using a Direct Transaxillary Portal

Humeral avulsion of the glenohumeral ligament (HAGL lesion) is a challenging problem in surgery for shoulder instability. Open and arthroscopic approaches and techniques have been described to address this issue. Especially posterior HAGL lesions increase the surgical complexity, as open anterior approaches provide limited visibility and access for successful repair. This article describes an alternative technique using an arthroscopic transaxillary approach to deploy the suture anchor with a perpendicular angle to the humeral bone, thus, improving the ability to perfectly position the anchor at the anatomic insertion of the inferior humeral ligament.

Characterisation of acoustic louvres panel for Heating Ventilating and Air Conditioning (HVAC) noise control

This paper presents the results of research about louvre panels with 4 blades, 5 blades, and 6 blades for mechanical and acoustical performance which installed at the outlet of the ducting system. The mechanical performance will show up the airflow velocity and pressure drop, for the acoustical performance will analysed for its ability to reduce noise in the HVAC System. The measurement method used a rectangular linear duct with the inlet of a fan as an airflow source and loudspeaker as a noise source. The ability tested from the acoustic parameters of TL and the directivity of the noise from the outlet section, as well as mechanical analysis performance based on airflow and pressure drop. For the pressure drop parameter value is up to 20 Pa for 4 blades louvre, and about 24 Pa for 5 blades and 6 blades louvre. By using third octave band filter from 20 to 8000 Hz, the highest TL value is at 27 dB at a frequency of 63 Hz. For the directivity used to determine the distribution of sound energy around the outlet, it shows that the highest SPL value is at a frequency of 1 kHz with the difference from the perpendicular angle of the outlet after being given a louvre acoustic panel of 12 dB. So, the installation of louvre panels has small of pressure drop effect, but it can be effective for noise reduction.

Evaluating the Cyclic Behavior of the Sloped Extended End-plate Beam-to-column Connections

In the Northridge and Kobe earthquakes, brittle failure of the welded beam-to-column connections was observed in steel structures. So, bolted connections were considered as an alternative to these kinds of connections. Extended end-plate beam-to-column con-nection is one of the most commonly used connections in steel structure. In this article, the behavior of the sloped extended end-plate beam-to-column connections is studied. Finite element method was used to investigate the behavior of the connection by ABAQUS software. The main aim of the study was to investigate the cyclic behavior of the four beam-to-column connections with beam angles of 0, 10, 15, and 20 degrees with respect to horizon. Also, the behavior of the mentioned connections was compared with extended end-plate connections with perpendicular angle. Results showed that the ductility and moment-resisting capacity of the sloped extended end-plate beam-to-column connections decrease by increasing beam angle, but rotational and moment-resisting capacities of the models satisfy the limitation of the design codes such as 0.04 drift limit for bearing capacity before failure.

Experimental and numerical analysis of a helically-coiled solar water collector at various angular placements

Solar water collectors are widely utilized for providing hot water to be used in different applications. In this work, a solar water collector with a helically coiled absorber has been designed, fabricated, and examined at different test conditions to specify its overall performance. One of the major goals of using a tube-type absorber is to upgrade the thermal efficiency of the collector by providing a perpendicular angle between the absorber and incident solar rays. Also, using a helically-coiled structure make it possible to increase the absorber surface in a relatively small volume in comparison to conventional solar water collectors. In the first step of this research, the designed helically-coiled solar collector has been simulated using a solar radiation model. In the next step, the manufactured helically-coiled solar collector has been experimentally tested at three different inclination angles and various water flow rates. According to the experimental results, mean thermal efficiencies of horizontal, vertical, and angular helically-coiled collectors were obtained in the ranges of 29.48–48.23%, 27.17–47.03%, and 32.50–52.71%, respectively. In addition, sustainability index values for horizontal, vertical and angular helically-coiled collectors were achieved between the ranges of 1.0041–1.0091, 1.0039–1.0087, and 1.0043–1.0102, respectively. Moreover, the maximum deviation between numerical and experimental findings was calculated as 14%.

Fixation Methods for Replacement Screws in Scaphoid Fractures: A Biomechanical Study

To investigate the changes in biomechanical fixation of an initial and replacement headless compression screw by quantifying interfragmentary compression and shear displacement. A bone model was created with 2 blocks of rigid polyurethane foam to simulate a fracture site. A 24-mm headless compression screw was inserted into the model at a perpendicular or oblique angle, removed, and replaced with the 22-mm screw. The 22-mm screw replaced the 24-mm screw in either the same or reverse direction of initial insertion. All 4 methods of initial and replacement screw fixation were trialed 15 times for a total of 60 trials. Two button load cells measured compression. A digital microscope recorded shear displacement. Statistical analysis was performed to determine the differences in compression and sheer between the initial and replacement screw for each angle and screw insertion group with a 2-sided paired Student t test. In comparison with the average compression force achieved by placement of the primary screw, there was a significant loss of average compression force when the secondary screw was placed in the same direction and perpendicular to the fracture plane (50 N, P < .001), in the reverse direction and perpendicular to the fracture plane (9 N, P= .049), and in the same direction and 60º to the fracture plane (11 N, P < .001). A significantly greater average shear displacement was noted for initial screw insertion at oblique compared with perpendicular orientations (0.03 mm, P < .001). This study demonstrates loss of compression when replacing screws despite varying orientations. Additionally, shear displacement in obliquely placed screws increased compared with perpendicularly placed screws. This study provided quantitative evidence to support the importance of establishing the correct screw length initially to avoid compression loss caused by replacing a primary screw.

Bioinspired On-Demand Directional Droplet Manipulation Surfaces

In this study, we exploited the properties of nature-inspired hierarchical structures to propose surfaces capable of on-demand directional droplet manipulation. A microline polydimethylsiloxane structure that simulated a bamboo leaf was fabricated, and silica particles were embedded onto its surface to create hierarchical structures. The as-fabricated multiscale line structures exhibited anisotropic wetting properties along the advancing direction. As the embedded particle size increased, the perpendicular roll-off angle (ROA) decreased and the anisotropic roll-off characteristic disappeared, adopting lotus-leaf characteristics. Consequently, the fabricated surface exhibited characteristics of both bamboo and lotus leaves. The roll off could be controlled through different ROAs by changing the particles size of silica on the same surface.

Orthogonal dual-channel single-camera spectral imaging for online measurement of three-dimensional space–time evolution of temperature field in laser melt pool

Current temperature measurement technology in laser manufacturing cannot obtain the internal three-dimensional (3D) temperature distribution of the melt pool. Necessary information for laser-manufacturing process optimization is lacking, including the melt pool depth and depth-to-width ratio. We propose a method for 3D temperature measurement based on orthogonal dual-channel single-camera spectral imaging. The 3D temperature field distribution of the melt pool can be obtained by collecting projected radiation data from two perpendicular angles. Use of a single monochrome camera for spectral imaging at three wavelengths ensures excellent spatial and temporal consistency during measurements. To verify the feasibility of the method, we measured the 3D temperature field in a melt pool of 304 stainless steel irradiated by a Gaussian laser beam (continuous laser, 500 W) with different irradiation times. The results indicate that the temperature field exhibits an approximately axisymmetric distribution on each cross-section at different depths. The temperature is highest in the center and gradually decreases around it. As the depth increases, the high-temperature area (>1730 K) gradually becomes smaller, and the temperature of each cross-section decreases. The maximum temperature, depth, width, and depth-to-width ratio of the melt pool at different times were obtained from the measured 3D temperature distributions. With an irradiation time of 0–80 s, the maximum temperature of the melt pool exhibited three stages: rapid increase (20–2230 K), slow increase (2230–2280 K), and stabilization. The growth of the width and depth of the melt pool indicated a similar process, increasing rapidly at first and gradually slowing. The depth-to-width ratio decreased rapidly at first and gradually stabilized. The proposed method for 3D temperature measurement has potential use in laser manufacturing for process control and quality improvement.