Surface Tilt Angle Research Articles

Correction to: A Novel Approach for the Determination of Surface Tilt Angles in Two-Dimensional Digital Image Correlation Experiments

The original article has been corrected on the line “These two parameters are the average…” and on Eqs. 19, 20, 21 and 23.

Анализ параметров шероховатости поверхностей заготовок, полученных методом аддитивных технологий

The investigation results of surface roughness parameters in billets obtained by the method of additive technology (laser sintering) are presented. There are obtained dependences of roughness parameter Ra upon a surface tilt angle regarding a plane of billet formation and an angle of a surface turn with regard to a cutter motion.

A Novel Approach for the Determination of Surface Tilt Angles in Two-Dimensional Digital Image Correlation Experiments

Two-dimensional digital image correlation (2D-DIC) is increasingly being used in a wide variety of applications. This technique is capable of measuring the in-plane deformations and strains of planner surfaces. A basic condition for using this technique is having the camera to observe the target surface perpendicularly. If the camera is not perpendicular to the surface, errors will be introduced in the measured displacements and strains. Small amounts of camera misalignment can easily go undetected during the initial setting of the experimental setup. In this paper, a novel approach for verifying the perpendicularity of the camera with respect to the target surface in 2D-DIC experiments is introduced. If the camera is not perpendicular to the surface, the tilt angles about both of the two in-plane axes can be calculated using this novel approach. A simple in-plane rigid-body-translation of the specimen in any of the two in-plane directions (horizontal or vertical direction relative to the camera image), is used for detecting camera non-perpendicularity and calculating the tilt angle(s). This approach uses the normal and shear strain errors, induced in DIC results due to camera non-perpendicularity, to determine the surface tilt angle(s), if any is present. The tilt angle(s) are calculated using simple analytical equations that are developed based on the pinhole camera model. The proposed approach is validated using experiments performed while the target surface is tilted at angles ranging from 0.5° to 4°. The experimental results show that this approach is able to confidently detect camera misalignment for tilt angles of 1° or larger and the tilt angles can be calculated with less than 0.3° error.

Compact picometer-scale interferometer using twisted light.

We propose a simple compact interferometer using twisted light to detect picometer displacement on a solid or liquid surface. The heart of the interferometer lies in producing a daisy petal pattern formed by interference between two oppositely charged twisted beams. The sample being probed is an active component of the interferometer. By analyzing the rotation of the petal pattern, caused by the relative displacement between the cylindrical lens (CL) and solid/liquid surface, we exhibit picometer resolution in displacement measurements. Remarkably, we explore the significance of a radial quantum number in the measurement of surface displacement and surface tilt angle. We also investigate the arbitrary surface deformation profile with similar precision by modifying the set-up. We perform simulations in realistic experimental settings and show that they are in excellent agreement with the predictions of analytic expressions. The proposed set-up can be further miniaturized by a small focal length CL and will open routes for tremendous applications in picometer-scale displacement measurement of a solid or liquid interface by various excitations.

2500-Channel single-shot areal profilometer using hyperspectral interferometry with a pinhole array

Surface profilometry techniques such as coherent scanning interferometry or focus variation require long scan times and are thus vulnerable to environmental disturbance. Hyperspectral interferometry (HSI) overcomes the problem by recording all the spatial and spectral information necessary to reconstruct a 2D surface height map in a single shot. In this paper, we present a new HSI system that uses a pinhole array to provide the necessary gaps for the spectral information. It is capable of measuring 2500 independent points, twice the previous maximum number, with a maximum unambiguous depth range of ∼825 µm and a larger maximum surface tilt angle of 33.3 mrad. The use of phase information allows height to be measured to a precision of ∼6 nm, an order of magnitude improvement on previous HSI systems.

Calibrating the Young’s modulus of soft materials with surface tilt angle measured by atomic force microscopy

We investigated the apparent Young’s modulus, Em, of soft materials with the surface tilt angle, as measured by colloidal probe atomic force microscopy (AFM). The AFM measurements of soft polymer hydrogels and natural unfertilized eggs showed a clear universal behavior of Em as a function of the tilt angle, θ, of the sample surface at the local contact area. We found that the observed θ dependence of Em was well fitted with a simple modified Hertz contact model, in which the pressure distribution in the contact area follows the conventional Hertz contact model, the vertical component of the net force balances the loading force, and the remaining lateral component of the net force is approximately ignored. We demonstrated how a simple analytical formula derived from the modified Hertz contact model can calibrate the Em values for single cells in a spherical embryo and for single isolated cells and a confluent cell monolayer adhered on flat substrates.

Sticky hydrophobic behavior of cellulose substrates impregnated with alkyl ketene dimer (AKD) via sub- and supercritical carbon dioxide

Cellulose fibers were impregnated with alkyl ketene dimer (AKD) dissolved in n-heptane and carbon dioxide via sub- and supercritical impregnation techniques. The mechanistic pathways and hydrophobic performance at short and long times were investigated by contact angle (CA) analysis, scanning electron microscopy (SEM) with micrographs analyzed using Image-Pro Premier, and Fourier Transform Infrared (FTIR) analysis. The sizing development was significant after two days of treatment, and hydrophobic performance became uniform after two weeks regardless of the impregnation conditions investigated. Samples prepared at 100 and 200 bar produced more rapid development than those at higher and lower impregnation pressures, with the average CA at 200 bar and 21 °C being 140 ± 5°. ‘Sticky’ hydrophobicity was observed on surfaces treated at 200 and 250 bar at long times (> 140 days), and adhesive forces between the droplet (>20 μL) and surface were observed at surface tilt angles between 0 – 180°. SEM micrographs of the impregnated samples showed a reduction in substrate pore-size area (PSA) as hydrophobicity developed with time. There was little evidence of reaction-based sizing as the characteristic ketone and ester peaks were not observed in FTIR studies. The lactone ring remained intact. The 200 bar sample showed highest peak intensity for various hydrocarbon bonds observed – suggesting the optimal solubility of AKD in supercritical carbon dioxide (scCO2). Spreading of AKD across the fiber surfaces appeared to be the main sizing pathway, and identification of hydrogen bonding between AKD and cellulose fibers suggested a possible attachment method.

Referent control of the orientation of posture and movement in the gravitational field.

This study addresses the question of how posture and movement are oriented with respect to the direction of gravity. It is suggested that neural control levels coordinate spatial thresholds at which multiple muscles begin to be activated to specify a referent body orientation (RO) at which muscle activity is minimized. Under the influence of gravity, the body is deflected from the RO to an actual orientation (AO) until the emerging muscle activity and forces begin to balance gravitational forces and maintain body stability. We assumed that (1) during quiet standing on differently tilted surfaces, the same RO and thus AO can be maintained by adjusting activation thresholds of ankle muscles according to the surface tilt angle; (2) intentional forward body leaning results from monotonic ramp-and-hold shifts in the RO; (3) rhythmic oscillation of the RO about the ankle joints during standing results in body swaying. At certain sway phases, the AO and RO may transiently overlap, resulting in minima in the activity of multiple muscles across the body. EMG kinematic patterns of the 3 tasks were recorded and explained based on the RO concept that implies that these patterns emerge due to referent control without being pre-programmed. We also confirmed the predicted occurrence of minima in the activity of multiple muscles at specific body configurations during swaying. Results re-affirm previous rejections of model-based computational theories of motor control. The role of different descending systems in the referent control of posture and movement in the gravitational field is considered.

Weak antilocalization effect due to topological surface states in Bi2Se2.1Te0.9

We have investigated the weak antilocalization (WAL) effect in the p-type Bi2Se2.1Te0.9 topological system. The magnetoconductance shows a cusp-like feature at low magnetic fields, indicating the presence of the WAL effect. The WAL curves measured at different tilt angles merge together when they are plotted as a function of the normal field components, showing that surface states dominate the magnetoconductance in the Bi2Se2.1Te0.9 crystal. We have calculated magnetoconductance per conduction channel and applied the Hikami-Larkin-Nagaoka formula to determine the physical parameters that characterize the WAL effect. The number of conduction channels and the phase coherence length do not change with temperature up to T = 5 K. In addition, the sample shows a large positive magnetoresistance that reaches 1900% under a magnetic field of 35 T at T = 0.33 K with no sign of saturation. The magnetoresistance value decreases with both increasing temperature and tilt angle of the sample surface with respect to the magnetic field. The large magnetoresistance of topological insulators can be utilized in future technology such as sensors and memory devices.

Investigation of solar energy potential on inclined surfaces

Solar energy is considered environmentally friendly because the sun is a natural energy source that does not require the fossil fuels and the associated air emissions. The solar energy data in the sloped surfaces are essential for the design of solar energy applications. The values of the daily average total solar radiation on a horizontal plane are nearly available. However, the radiation values on inclined surfaces are generally not available. This paper deals with the analysis to f‐chart method of solar energy utilization for horizontal surface and various tilt angles of solar panel such as optimum tilt angle, seasonal, summer‐winter applications. The values of the highest HT and f are the surface with optimum tilt angle, seasonal, summer‐winter, s = φ ± 15°, s = φ, s = φ–15°, s = φ + 15° and horizontal, respectively. In comparison of the surfaces of the optimum tilt angles and horizontal, it is seen that the increment in the annual fractions of the surface with the optimum tilt angle is 21%. The yearly total values of the HT on the surface of the optimum tilt angle and horizontal are found as 6719.3 and 5602.2 MJ/m2, respectively. © 2017 American Institute of Chemical Engineers Environ Prog, 37: 524–532, 2018

Relationship Between Anterior Lamina Cribrosa Surface Tilt and Glaucoma Development in Myopic Eyes.

To evaluate the anterior lamina cribrosa (LC) surface tilt angle in myopic eyes and associate it with glaucoma development. In this retrospective study, medical records of myopic patients referred for glaucoma examination from July 1, 2012 to March 30, 2016 were reviewed. Comprehensive ophthalmic examination including spectral-domain optical coherence tomography were performed. We measured the angle of anterior LC surface tilt against Bruch's membrane opening from optical coherence tomography images at the center of the clinical optic disc margin. In horizontal and vertical sections, the angles were defined as α and β, respectively. Patients were grouped according to the presence of glaucomatous damage and factors including optic nerve head morphologic parameters and LC tilt angles were compared between the 2 groups. Among 138 patients originally enrolled, 102 patients were finally analyzed. One eye from 1 patient was randomly chosen. Fifty-five eyes had glaucoma and 47 were normal. The degree of myopia and all optic nerve head morphologic parameters were not significantly different between the 2 groups. However, |α| and |β| were significantly larger in the glaucoma group (all P<0.001), and significances were maintained in multivariate analysis (P<0.001). Larger anterior LC surface tilt angles were related to the presence of glaucoma in normal-pressure myopic eyes. Angulation of the LC against Bruch's membrane opening plane might be associated with increased glaucoma susceptibility in myopic eyes. Further investigations are warranted before clinical utilization of LC tilt as glaucoma susceptibility biomarker.

Effects of hysteresis of static contact angle (HSCA) and boundary slip on the hydrodynamics of water striders

It is known that contact lines keep relatively still on solids until static contact angles exceed an interval of hysteresis of static contact angle (HSCA), and contact angles keep changing as contact lines relatively slide on the solid. Here, the effects of HSCA and boundary slip were first distinguished on the micro-curvature force (MCF) on the seta. Hence, the total MCF is partitioned into static and dynamic MCFs correspondingly. The static MCF was found proportional to the HSCA and related with the asymmetry of the micro-meniscus near the seta. The dynamic MCF, exerting on the relatively sliding contact line, is aroused by the boundary slip. Based on the Blake–Haynes mechanism, the dynamic MCF was proved important for water walking insects with legs slower than the minimum wave speed \(23\,\hbox {cm}\cdot \hbox {s}^{-1}\). As insects brush the water by laterally swinging legs backwards, setae on the front side of the leg are pulled and the ones on the back side are pushed to cooperatively propel bodies forward. If they pierce the water surface by vertically swinging legs downwards, setae on the upside of the legs are pulled, and the ones on the downside are pushed to cooperatively obtain a jumping force. Based on the dependency between the slip length and shear rate, the dynamic MCF was found correlated with the leg speed U, as \(F\sim C_{1}U+C_{2} U^{2+\varepsilon }\), where \(C_{1}\) and \(C_{2}\) are determined by the dimple depth. Discrete points on this curve could give fitted relations as \(F\sim U^{b}\) (Suter et al., J. Exp. Biol. 200, 2523–2538, 1997). Finally, the axial torque on the inclined and partially submerged seta was found determined by the surface tension, contact angle, HSCA, seta width, and tilt angle. The torque direction coincides with the orientation of the spiral grooves of the seta, which encourages us to surmise it is a mechanical incentive for the formation of the spiral morphology of the setae of water striders.

Cramer-Rao lower bound on ranging precision of pulsed laser circular-viewing detection

To analyze ranging precision of laser circular-viewing detection system, received Laser signal model is established, echo signal equation is derived as target is flat surface. Based on the Cramer-Rao lower bound (CRLB) in the estimation theory, the CRLB calculation formula for estimating the variance of the range estimation with Gauss noise is derived. The effects of various parameters on the CRLB of ranging precision are analyzed by computer simulation. The results demonstrate that with the increase of tilt angle of flat surface or decrease of diffuse reflection, ranging precision descends. With the increase of pulse width, distance accuracy shows a trend from decline to rises.

Design and Fabrication of a Hybrid Superhydrophobic-Hydrophilic Surface That Exhibits Stable Dropwise Condensation.

Condensation of water vapor is an essential process in power generation, water collection, and thermal management. Dropwise condensation, where condensed droplets are removed from the surface before coalescing into a film, has been shown to increase the heat transfer efficiency and water collection ability of many surfaces. Numerous efforts have been made to create surfaces which can promote dropwise condensation, including superhydrophobic surfaces on which water droplets are highly mobile. However, the challenge with using such surfaces in condensing environments is that hydrophobic coatings can degrade and/or water droplets on superhydrophobic surfaces transition from the mobile Cassie to the wetted Wenzel state over time and condensation shifts to a less-effective filmwise mechanism. To meet the need for a heat-transfer surface that can maintain stable dropwise condensation, we designed and fabricated a hybrid superhydrophobic-hydrophilic surface. An array of hydrophilic needles, thermally connected to a heat sink, was forced through a robust superhydrophobic polymer film. Condensation occurs preferentially on the needle surface due to differences in wettability and temperature. As the droplet grows, the liquid drop on the needle remains in the Cassie state and does not wet the underlying superhydrophobic surface. The water collection rate on this surface was studied using different surface tilt angles, needle array pitch values, and needle heights. Water condensation rates on the hybrid surface were shown to be 4 times greater than for a planar copper surface and twice as large for silanized silicon or superhydrophobic surfaces without hydrophilic features. A convection-conduction heat transfer model was developed; predicted water condensation rates were in good agreement with experimental observations. This type of hybrid superhydrophobic-hydrophilic surface with a larger array of needles is low-cost, robust, and scalable and so could be used for heat transfer and water collection applications.

Synthesis of Triptycene-Based Molecular Rotors for Langmuir-Blodgett Monolayers.

We describe syntheses of six triptycene-containing molecular rotors with several single-crystal X-ray diffraction analyses. These rod-shaped molecules carrying an axial rotator are designed to interleave on an aqueous surface into Langmuir-Blodgett (LB) monolayers containing a two-dimensional trigonal array of dipoles rotatable about an axis normal to the surface. Monolayer formation was verified with the simplest of the rotor structures. On an aqueous subphase containing divalent cations (Mg(2+), Ca(2+), Zn(2+), Sr(2+), or Cd(2+)), the LB isotherm yielded an area of 53 ± 3 Å(2)/molecule (monolayer of type A), compatible with the anticipated triangular packing of axes normal to the surface. On pure water, the area is 30 ± 3 Å(2)/molecule, and it is proposed that in this monolayer (type B), the molecular axes are tilted by 40-45° to a structure similar to those observed in single crystals of related triptycenes. After transfer to a gold surface, ellipsometry and PM IRRAS yield tilt angles of 29 ± 4° (monolayers of type A) and 38 ± 4° (type B). A full-scale examination of monolayers from all the rotors on a subphase and after transfer is underway and will be reported separately.

High-precision surface measurement with an automated multiangle low coherence interferometer.

We propose a novel measurement system based on a low coherence Michelson interferometer and six-axis hexapod platform to accurately measure structures with high aspect ratio using different tilt angles of the measured surface. In order to realize automatic measurement, the system is designed to automatically perform autofocusing, adjust the tilt angle of the test surface, make surface measurements, and merge the measurement data sets. Due to certain topography, e.g., structures with high aspect ratio, the interferometer cannot obtain enough reflected light to evaluate the height information in some areas of the test surface. For this reason, we developed a measurement system that uses measurements from different tilt angles of the test surface and stitching algorithms to realize a complete surface measurement data set. The performance of the proposed measurement system is evaluated experimentally and compared to the results of measurements using a perthometer.

Analysis of the Annual Performance of Bifacial Modules and Optimization Methods

Bifacial modules have the advantage of capturing sunlight from front as well as from rear surfaces, and therefore, they are able to produce larger amounts of energy, compared with standard (monofacial) modules. However, their performance depends on the spatial distribution of the irradiance incident on the rear module surface, which is strongly affected by several site-specific conditions, such as albedo, reflective surface size, module elevation, and tilt angle. In this study, we elaborate upon the individual and combined effects of these factors on the annual energy yield of stand-alone south-facing bifacial modules through simulations at two site locations with contrary climatic conditions. Following the optimization of the tilt angle of bifacial modules dependent on the site, albedo, and module elevation, we demonstrate that the annual energy yield of a bifacial module increases linearly with albedo, which shows a monotonically increasing but, in addition, saturating behavior versus reflective surface size, and increases up to a certain module elevation. Through the simultaneous consideration of these dependences, we suggest an optimal positioning of bifacial modules. Finally, we show that under these optimal conditions, bifacial modules can supply up to 25% more energy compared with standard modules.

Investigating different diffuse solar radiation models to analyse solar radiation on inclined surfaces in Oman

In this paper, a detailed analysis of the solar radiation on horizontal and tilted surfaces for six locations in Oman is presented. The locations are (from North to South): Majis/Sohar, Sur, Fahud, Masira, Marmul, and Salalah. These locations spread over Oman and cover different types of landscape. The method is validated through the use of measured data. The effect of tilt angle and orientation on the incident solar radiation is presented along with optimum surface tilt angles and directions for maximum solar radiation collection in these six locations. The solar radiation models used in this paper show good agreement with measured data. The results presented in this paper are extremely useful for quick estimation of solar radiation for calculations of buildings’ cooling load and solar collector system performance. This can be easily extended for other locations with similar landscapes and geographical conditions.

A novel approach for site-specific atom probe specimen preparation by focused ion beam and transmission electron backscatter diffraction.

Atom probe tomography (APT) is a suitable technique for chemical analyses with almost atomic resolution. However, the time-consuming site-specific specimen preparation can be improved. Recently, transmission electron backscatter diffraction (t-EBSD) has been established for high resolution crystallographic analyses of thin foils. In this paper we present the first successful application of a combined focused ion beam (FIB)/t-EBSD preparation of site-specific APT specimens using the example of grain boundary segregation in technically pure molybdenum. It will be shown that the preparation of a grain boundary can be substantially accelerated by t-EBSD analyses in-between the annular milling FIB procedure in the same microscope. With this combined method, a grain boundary can easily be recognized and positioned in the first 220nm of an APT sample much faster than e.g. with complementary investigations in a transmission electron microscope. Even more, the high resolution technique of t-EBSD gives the opportunity to get crystallographic information of the mapped area and, therefore, an analysis of the grain boundary character to support the interpretation of the APT data files. To optimize this newly developed technique for the application on needle-shaped APT specimens, a parameter study on enhanced background correction, acceleration voltage, and tilt angle was carried out. An acceleration voltage of 30kV at specimen surface tilt angles between -45° and -35° from horizontal plane leads to the best results. Even for molybdenum the observation of crystal orientation data up to about 200nm specimen thickness is possible.

Design of Landslide Monitoring and Early Warning System Based on Internet of Things

This paper designed a kind of efficient IOT transmission platform based on wireless sensor network and GPRS network. Using the multi-mode sensor nodes composed of temperature-humidity senor and acceleration sensor, realize the effective detection of geological disaster, such as landslide and debris flow. After experimental verification, the IOT platform based on the two levels of network structures, can effectively transmit the monitoring point's information, such as the surface humidity, tilt angle and displacement. The system has long transmission distance and low power consumption.The system will have certain engineering value in the field of geological monitoring.