Apparent Edge Research Articles

Reducing edge chipping defect in rotary ultrasonic machining of optical glass by compound step-taper tool

The machining induced edge chipping of hole manufacturing restricts the productivity and design capability of products made from brittle materials. Rotary ultrasonic machining (RUM) has been sufficiently proved as a suitable approach for hole drilling in brittle materials with reduced cutting force and improved hole edge quality. However, apparent edge chipping is still an important restriction of RUM application. In this study, a compound step-taper tool for RUM was designed to further reduce the edge chipping defects via tool design. RUM tests on quartz glass were conducted to evaluate the effectiveness of the compound step-taper tool. The experimental results demonstrated that the compound tool could reduce the edge chipping size at the hole exit and entrance by 60%–80% and 35%–50%, respectively. The mechanism of edge chipping reduction at the hole exit is that cutting force decreased as the undrilled thickness decreased. This is due to the wedge-type contact structure between the tool’s taper face and the workpiece material. Furthermore, the edge chipping reduction at the hole entrance occurs because of the shielding effect of residual cracks. Residual cracks produced by the second outermost abrasives of the tool’s taper face suppressed the initiation and propagation of lateral cracks that were produced by the outermost abrasives of the tool’s taper face. Theoretical analysis indicated that the compound tool step is beneficial for guaranteeing the effectiveness of tool’s taper face.

Improved interpretation of asphalt binder parallel plate dynamic shear rheometer fatigue tests

The time sweep test, consisting of cyclic, torsional loading in the dynamic shear rheometer (DSR), has been employed for the fatigue characterisation of asphalt binders. The parallel plate geometry imposes radially inhomogeneous strain field, which results in a radial inhomogeneous stress field. Past efforts have inferred fatigue damage in DSR tests based on monitoring the apparent edge stress, which is calculated using linear radial mapping to the total torque. The assumption of linear variation in the shear stress response with radial distance from the specimen centre is erroneous of material or geometric nonlinearities such as cracking. To improve the interpretation of parallel plate fatigue tests, a means to account for the non-linear radial gradient in stress response is derived using simplified viscoelastic continuum damage (S-VECD) modelling. The developed methodology is validated through comparison to cone and plate results where the stress state is uniform. The results demonstrate that the developed methodology allows for accurate determination of S-VECD model coefficients using parallel plate testing alone.

Improvement of magnesium alloy edge cracks by multi-cross rolling

In order for the edge cracks during the AZ31 Mg alloy rolling to be reduced, the hot-rolling microstructure and texture were modified through multi-cross rolling (MCR) during the deformation. The AZ31B magnesium alloy sheets were hot rolled at a temperature ranging from 250 °C to 400 °C and at a rolling speed of 0.5 m/s. Four different multi-cross rolling (MCR) routes were selected in the test. The macroscopic morphology, microstructure and texture of the as-rolled AZ31B sheets were characterized to investigate the edge-crack behavior during the rolling with various rolling routes and temperatures. Through the various rolling routes comparison, the grain size, the texture and the twins were the main factors that affected the cracks. It was demonstrated that the grain refinement and weak basal textures obtained by RII where the rolling direction was changed by 90° between two adjacent passes, could significantly reduce the edge cracks during the rolling at an elevated temperature. When rolling with RII at 400 °C, no apparent edge cracks appear on the sheet rolled with four passes. The propagation mechanism of the crack tips was studied in details at the temperature of 350 °C, whereas the results demonstrated that a high-sized area of grain boundaries in-between the finer grains could increase the crack propagation resistance.

A new method for measuring the contact angles from digital images of liquid drops

The drop hitting a solid surface may be symmetric or asymmetric, which depends on the surface texture and external force orientations. The accurate measurement of the contact angle is of fundamental importance for the purpose of scientific research, while having a substantial role in a wide range of practical applications.This paper presents a new image processing based method, as a computational scheme to measure the inclination angle of apparent edge curves in digital images. The main concept of the scheme is the emulation of a moving goniometer mask coupled with a Gaussian weighted function, which does not require edge fitting with analytic curves for the angle calculation. The algorithm produces as follow: allocating the exact position of the contact points by Harris corner detector function, selecting a series of points on the drop boundary near the contact points, setting goniometric mask on each given point and calculating the angles, applying the Gaussian weighted average function on the calculated angles and measure the objective contact angle. The scheme is tested on several images from recent studies in the available literature. The comparison between analytical and calculated angles shows less than 1° difference.

Establishment phase productivity of loblolly pine and switchgrass when grown across a gradient of cultural treatment and site productivity

A three-year field study was established to evaluate the production potential of an intercropping system of loblolly pine (Pinus taeda L.) and switchgrass (Panicum virgatum L.) in the southeastern United States. Tree-grass competitive interactions are expected to negatively affect overall productivity within this system, but a better understanding of these relationships will aid in developing cultural practices to mitigate competitive effects. We hypothesized that interspecific competitive interactions would decrease the productivity of both species within this system. We also hypothesized that productivity declines, due to interspecific competition, could be mitigated through management. We established loblolly pine and switchgrass intercropping systems at varying rates of competitive intensity initiated by cultural practices (pine only, switchgrass only, pine planted directly into switchgrass, pine planted into a 1.2m vegetation removal zone, and pine planted into a 2.4m vegetation removal zone) at two sites in northeastern Mississippi. Over the study duration, we observed decreased production in loblolly pine due to switchgrass competition. However, the establishment of 1.2 or 2.4m vegetation removal zones surrounding pine seedlings allowed for tree growth equal to or greater than the pine only control at both sites. Likewise, intercropped switchgrass production was equal to or greater than the switchgrass only treatment by year 3 due to an apparent edge effect occurring at the tree-grass interface. Our results demonstrate that cultural practices intended to reduce interspecific competition were effective in mitigating productivity declines of intercropped loblolly pine while preserving or increasing switchgrass productivity. The dual-species productivity gains observed in this study advocate the loblolly pine-switchgrass intercropping system as a possible alternative to switchgrass monoculture. This study only examined production dynamics during the initial three growing years of this system and further research is needed to elucidate productivity patterns throughout the rotation.

CdTe films grown using a rotating sublimate vapor effusion source in glancing angle deposition mode

Thin films of CdTe were deposited on glass substrates using a rotating sublimate vapor effusion source combined with glancing angle deposition substrate mode. The samples were prepared with different incident deposition flux angles of α=0°, 40°, 50° and 60° using substrate rotation of 55rpm in the opposite direction to the source which was in turn rotated at 40rpm. The Scanning electron and atomic force microscopy images showed that the sample with α=0° and without substrate rotation presented dense columnar structures with variable shapes and dimensions. However, the sample with substrate rotation presented dense coalesced columnar structures with uniform shapes. When the substrate is simultaneously tilted and rotated the columnar forms is more individuality defined. The X-ray diffraction measurements demonstrated that all samples crystallized in the CdTe-cubic phase structure, which exhibits a diffraction peak with full width at half-maximum of the (111) Bragg reflection of 390.4arcsec corresponding to a crystallite size of ∼75nm for the sample with α=50°. The crystallite size decreased as α increased. The apparent absorption edge shifting towards lower wavelength regions for samples grown at α=50° and 60° was attributed to light scattering by the columnar structures. The optical band gap for all samples presented an average value of ∼1.5eV.

Apparent velocity of shadow edges caused by moving clouds

Even the largest photovoltaic (PV) power plants are widely affected by overpassing cloud shadows which have several harmful effects on the operation of PV systems. Irradiance transitions caused by edges of cloud shadows can be very steep and large and might lead to situations where the grid inverter is not able to follow the global maximum power point. Further, partial shading of PV systems causes mismatch losses and fast fluctuations of the power fed to the electric grid can cause power balance and quality problems.In this paper, a method to determine apparent shadow edge velocity from measured data of three irradiance sensors is presented. A total of around 43,000 irradiance transitions were first identified in 15months of data measured with one of the sensors around midsummer in 2011–2014. Out of those about 27,000 transitions were identified by all the three irradiance sensors and their apparent shadow edge velocity, length, etc. were analysed. The apparent shadow edge speed varies greatly with an average value of around 9m/s. The lengths of irradiance transitions caused by edges of moving clouds are typically around 100m, which is large enough to affect the operation of PV power plants of all sizes.

SU‐E‐T‐675: Remote Dosimetry with a Novel PRESAGE Formulation

Purpose:3D‐gel dosimetry provides high‐resolution treatment validation; however, scanners aren't widely available. In remote dosimetry, dosimeters are shipped out from a central base institution to a remote site for irradiation, then shipped back for scanning and analysis, affording a convenient service for treatment validation to institutions lacking the necessary equipment and resources. Previous works demonstrated the high‐resolution performance and temporal stability of PRESAGE. Here the newest formulation is investigated for remote dosimetry use.Methods:A new formulation of PRESAGE was created with the aim of improved color stability post irradiation. Dose sensitivity was determined by irradiating cuvettes on a Varian Linac (6MV) from 0–15Gy and measuring change in optical density at 633nm. Sensitivity readings were tracked over time in a temperature control study to determine long‐term stability. A large volume study was performed to evaluate the accuracy for remote dosimetry. A 1kg dosimeter was pre‐scanned, irradiated on‐site with an 8Gy 4field box treatment, post‐scanned and shipped to Princess Margaret Hospital for remote reading on an identical scanner.Results:Dose sensitivities ranged from 0.0194–0.0295 ΔOD/(Gy*cm)—similar to previous formulations. Post‐irradiated cuvettes stored at 10°C retained 100% initial sensitivity over 5 days and 98.6% over 10 weeks while cuvettes stored at room temperature fell to 95.8% after 5 days and 37.4% after 10 weeks. The immediate and 5‐day scans of the 4field box dosimeter data was reconstructed, registered to the corresponding eclipse dose‐distribution, and compared with analytical tools in CERR. Immediate and 5‐day scans looked visually similar. Line profiles revealed close agreement aside from a slight elevation in dose at the edge in the 5‐day readout.Conclusion:The remote dosimetry formulation exhibits excellent temporal stability in small volumes. While immediate and 5‐day readout scans of large volume dosimeters show promising agreement, further development is required to reduce an apparent time dependent edge elevation.

Structural and optical properties of nanocrystalline Sb2S3 films deposited by chemical solution deposition

Films of Sb2S3 nanocrystals were deposited using chemical solution deposition. The structural and optical properties of the deposited films were investigated as a function of reaction time and temperature of the solution bath. The X-ray diffractometric studies confirmed the orthorhombic phase of Sb2S3 in the deposited films with steady variation in crystallinity. The effect of the bath conditions apparently was found to be playing a significant role in controlling the reaction rate resulting in the morphological evolution of the Sb2S3 nanocrystals. The band gaps of the deposited Sb2S3 films obtained from the optical absorption studies were found to be in the range 1.9–2.0eV and suggest the possibility of band gap tunability of Sb2S3 in the visible region. The photoluminescence studies revealed that the Sb2S3 nanocrystals showed apparent band edge luminescence at around 610nm and Stokes shifted defect induced emission at around 717nm.

Interactions of higher order tip effects in critical dimension-AFM linewidth metrology

A major challenge in critical dimension atomic force microscope width metrology is accounting for the effects of the tip on the apparent features in an image. The overall effect of the tip is to broaden the apparent width of lines and narrow the apparent width of trenches as a result of the geometrical interaction of the tip with the surface. To a first approximation, this effect can be well-modeled as a constant bias in width measurements, independent of the specific feature characteristics, by the width of the tip. Beyond this approximation, there are a number of smaller tip effects related to the measurement details. Some of these result from the details and interactions of the tip shape and feature shape, resulting in small variations of the tip bias from feature to feature and measurement to measurement. These effects are sometimes called shape effects, secondary effects, or higher order tip effects. One source of higher order effects is due to the lateral dithering of the tip, which increases the effective tip width. However, in addition to this known effect, the tip dither may also affect the apparent edge heights of the tip flare. Although the apparent tip width is expected to depend on lateral dither, the apparent edge height, at least in principle, would not be expected to depend on lateral dither. Our analysis suggests that this apparent dependence results from the interaction of the fine details of the tip flare shape and the dither envelope with the specific algorithm used to estimate the edge height. Consequently, both the sign and the magnitude of the dependence are specific to every tip. This is one example of the inter-dependencies that can be present when evaluating higher-order tip effects. Although these are often small, accurate metrology in some applications may require consideration of possible interactions between such smaller, secondary tip effects. The authors illustrate this with examples from photomask metrology, where measurement of chrome features on binary masks requires some attention to secondary tip effects.

Tracking Nonpalpable Breast Cancer for Breast-conserving Surgery With Carbon Nanoparticles

To examine the feasibility of using carbon nanoparticles to track nonpalpable breast cancer for breast-conserving surgery.During breast-conserving surgery, it is often very challenging to determine the boundary of tumor and identify involved lymph nodes. Currently used methods are useful in identifying tumor location, but do not provide direct visual guidance for resection margin during surgery.The study was approved by the Institutional Review Board of the Fuzhou General Hospital (Fuzhou, China). The current retrospective analysis included 16 patients with nonpalpable breast cancer receiving breast-conserving surgery under the guidance of preoperative marking using a carbon nanoparticle, as well as 3 patients receiving carbon nanoparticle marking followed by neoadjuvant treatment and then breast-conserving surgery. The Tumor Node Metastasis stage in the 16 cases included: T1N0M0 in 7, T1N1M0 in 2, T2N0M0 in 4, and T2N1M0 in the remaining 3 cases. The nanoparticle was injected at 12 sites at 0.5 cm away from the apparent edge under colored ultrasonography along 6 tracks separated by 60 degrees (2 sites every track). Lymph node status was also examined.The resection edge was free from cancer cells in all 16 cases (and the 3 cases with neoadjuvant treatment). Cancer cells were identified in majority of stained lymph nodes, but not in any of the unstained lymph nodes. No recurrence or metastasis was noticed after the surgery (2 to 22-month follow-up; median: 6 months).Tracking nonpalpable breast cancer with carbon nanoparticle could guide breast-conserving surgery.

A goniometric mask to measure contact angles from digital images of liquid drops

Abstract A computational scheme to measure the inclination angle of apparent edge curves in binary images is proposed. The main concept of the scheme is the emulation of a goniometer tool, which does not require edge fitting with analytic curves for the angle calculation. The algorithm produces an output matrix with same size of the input binary image, where the computed angle values are placed in the same locations of edge pixels. The scheme is tested both on a synthetic binary image displaying an object with irregular contour, and on a stack of images displaying a water droplet impacting on a hydrophobic substrate. The comparison between analytical and calculated angles shows that results depend both on the mask size and, in particular, on the image resolution.

Management of Riparian Buffers: Upslope Thinning with Downslope Impacts

We examined the potential of using upslope density management to influence growth and drought tolerance of trees in untreated downslope riparian forests. Increment cores from Douglas-fir trees in three mature stands in western Oregon, USA, were collected and measured. Trees responded to an apparent edge effect up t o1 5 m downslope of thinned areas but not downslope of gaps. Growth responses in riparian trees were not affected by slope or potential solar radiation (as a function of location and topography). In addition, in a retrospective analysis of tree growth and allocation patterns (represented by the ratio of earlywood to latewood) and climate after treatment over a 12-year period, trees in our study area did not appear to be water limited and did not show a strong correlation with regional drought metrics. We hypothesize that vegetation layers in these riparian forest stands responded differentially to additional resources becoming available as a result of thinning, with overstory trees in riparian areas responding downslope of thinned uplands and subdominant canopy layers responding downslope of gaps. Our study demonstrates that managers can affect riparian forests with upland treatments to a limited spatial extent, which may be the only option in areas where direct riparian management is restricted due to concerns for other ecosystem services.

An update on distribution models for Rhipicephalus microplus in West Africa

The cattle tick, Rhipicephalus microplus, which reached the West African region approximately 8 years ago, has established viable populations in Côte d'Ivoire and Benin and spread rapidly from the assumed points of introduction. However, existing maps of its distribution range do not agree on the areas at risk, most probably due to suboptimal modelling approaches. Therefore, we undertook a re-investigation of the potential distribution range based on a high-quality dataset from West Africa that includes information on 104 farms located all over Benin. Focussing on climate suitability and applying advanced modelling, a subset of representative and uncorrelated climate variables was selected and fed into Maxent software to obtain an estimate of climate suitability for West Africa. The resulting map was validated using an independent dataset of 13 farms along the apparent distribution edge. The entire southern part of West Africa (covering southern Nigeria, Benin, Togo and Ghana) features high climate suitability for R. microplus. All of Côte d'Ivoire is inside the distribution range of this tick and the southern rim of Burkina Faso is expected to be suitable for the establishment of R. microplus populations. The validation of the distribution, dated one year after the initial field visit, confirmed the predicted distribution range, although a small number of individuals of R. microplus were found north of the predicted limit. These low numbers might indicate that the climate is not suitable for the establishment of a viable tick population. An alternative explanation is the recent introduction by nomadic cattle herds passing through this location. In this region of the world, it is quite common for cattle owners to lead their livestock over distances of more than 500 km in search of food and water.

Structure and tectonics of the northwestern United States from EarthScope USArray magnetotelluric data

The magnetotelluric component of the EarthScope USArray program has covered over 35% of the continental United States. Resistivity tomography models derived from these data image lithospheric structure and provide constraints on the distribution of fluids and melt within the lithosphere. We present a three-dimensional resistivity model of the northwestern United States which provides new insight into the tectonic assembly of western North America from the Archean to present. Comparison with seismic tomography models reveals regions of correlated and anti-correlated resistivity and velocity that help identify thermal and compositional variations within the lithosphere. Recent (Neogene) tectonic features reflected in the model include the subducting Juan de Fuca–Gorda plate which can be traced beneath the forearc to more than 100 km depth, high lithospheric conductivity along the Snake River Plain, and pronounced lower-crustal and upper-mantle conductivity beneath the Basin and Range. The latter is abruptly terminated to the northwest by the Klamath–Blue Mountains Lineament, which we interpret as an important structure during and since the Mesozoic assembly of the region. This boundary is interpreted to separate hot extended lithosphere from colder, less extended lithosphere. The western edge of Proterozoic North America, as indicated by the Cretaceous initial 87Sr/86Sr = 0.706 contour, is clearly reflected in the resistivity model. We further image an Archean crustal block (“Pend Oreille block”) straddling the Washington/Idaho border, which we speculate separated from the Archean Medicine Hat block in the Proterozoic. Finally, in the modern Cascades forearc, the geometry and internal structure of the Eocene Siletz terrane is reflected in the resistivity model. The apparent eastern edge of the Siletz terrane under the Cascades arc suggests that pre-Tertiary rocks fill the Washington and Oregon back-arc.

The effects of solvents on the highly oriented ZnO films prepared using sol–gel method

The effects of solvents in ZnO precursor solutions on highly oriented ZnO films is studied in this work. Three different solvents, including ethanol, isopropanol and 2-methoxyethanol, are used for the preparation of ZnO film on fused quartz wafer substrates in this study. The structural properties of ZnO films are investigated by X-ray diffraction and scanning electron microscopy analysis. It is found that ZnO film formed using 2-methoxyethanol precursor solution shows a strong preferred orientation and has the smoothest surface among the films. The properties of ZnO sol solutions are also studied using the thermal gravimetric-differential thermal analysis and ultraviolet–visible spectroscopy. The absorbance spectrum of the sol using 2-methoxyethanol as solvent shows an apparent ZnO absorbance edge while the others do not, which means ZnO nano-particles are formed in the sol. The mechanism of the formation of highly oriented ZnO films using different solvents is also discussed in this paper.

Daily and seasonal movements of a shrubland-obligate breeder in relation to mature forest edge habitat

The effects of edge habitat on wildlife populations have been studied extensively in recent decades, but most studies have focused on describing patterns of edge effects rather than identifying the mechanisms driving these effects. Based on evidence of lower densities of shrubland birds in edge versus interior habitat, we tested four hypotheses that could produce a pattern of apparent edge avoidance: (1) active avoidance of edges due to high risk of predation in edge habitat, (2) conspecific interactions that promote greater use of interior habitat due to territorial defense, (3) passive displacement of avian home ranges, such that sampling in the interior is more likely to intersect multiple home ranges compared to sampling at edges, and (4) home range expansion along edges. To test these hypotheses, we radio-marked 39 male Yellow-breasted Chats (Icteria virens) during the breeding seasons of 2005 and 2006 and relocated each bird 4–5days/week. Our results did not support the hypothesis that Yellow-breasted Chats avoided habitat edges in either home range placement or habitat usage within their home ranges though there was some support for greater usage of interior habitat during the peak of the breeding season. Size of home ranges did not vary with distance from edge. These results support the passive displacement hypothesis and, to a lesser extent, the conspecific interactions hypothesis. The passive displacement hypothesis predicts lower abundances in the edges compared to the center of a habitat patch because areas in the patch center receive individuals from all directions whereas areas near the edges do not. Thus, edge habitat may still provide quality habitat for shrubland birds in our system.

Solvent dipole modulation of conduction band edge shift and charge recombination in robust dye-sensitized solar cells

Molecular modification is certified as a powerful strategy to adjust the energy alignment and electron transfer dynamics of dye-sensitized solar cells (DSCs). Herein, devices are assembled with three robust solvent (3-methoxypropionitrile, N,N-dimethylformamide and γ-butyrolactone) based electrolytes to elucidate the solvent dipole effects at the semiconductor-dye-electrolyte interface. Photovoltaic results demonstrate that open-circuit photovoltages of the devices vary linearly with the dipole moment of the solvents, along with an adverse dependence of the short-circuit photocurrent density under simulated irradiation. Impedance analysis reveals an apparent dipole moment-modulated conduction band edge shift of the nanocrystalline TiO(2) electrodes with respect to the redox potential of the electrolyte. Furthermore, the adverse shifts of the short-circuit photocurrent are explained by a dipole dependence of the driving force for electron injection and the interfacial charge recombination, together with a notably changed charge collection efficiency. Therefore, this study draws attention to the feasibility of tuning the electron transfer dynamics and energy alignment in photoelectrochemical devices by judiciously selecting the electrolyte solvents for further efficiency improvement, especially for those alternative organic sensitizers or quantum dots with inadequate electron injection driven forces.

Crepuscular rays: laboratory experiments and simulations

Model simulations of laboratory-generated and natural crepuscular rays are presented. Rays are created in the laboratory with parallel light beams that pass through artificial fogs and milk-water solutions. Light scattered by 90° in a dilute mixture of whole milk first increases in intensity with distance from the source to a maximum as a result of multiple scattering by mainly small angles before decreasing exponentially due to extinction as distance continues to increase. Crepuscular rays are simulated for three cloud configurations. In case 1, the Sun at the zenith is blocked by a cloud with an overhanging anvil. The rays appear white against blue sky and are brightest when atmospheric turbidity, β≈11. Shading by the anvil separates maximum brightness from apparent cloud edge. In case 2, a ray passes through a rectangular gap in a cloud layer. The ray is faint blue in a molecular atmosphere but turns pale yellow as β and solar zenith angle, φ(sun), increase. At φ(sun)=60° it appears most striking when the cloud is optically thick, β≈5, and the beam width Δx≈1000 m. In these cases, increasing aerosol radius, r(aer), to about 1000 nm brightens, narrows, and shortens rays. In case 3, the twilight Sun is shaded by a towering cloud or mountain. The shaded rays are deeper blue than the sunlit sky because the light originates higher in the atmosphere, where short waves have suffered less depletion from scattering. The long optical path taken by sunlight at twilight makes color and lighting contrasts of the rays greatest when the air is quite clean, i.e., for β-1≪1. In all cases, the brightest rays occur when sunlight passes through an optical thickness of atmosphere, τ≈O(1).

On the Observable Transition to Living Matter

In recent developments in chemistry and genetic engineering, the humble researcher dealing with the origin of life finds her(him)self in a grey area of tackling something that even does not yet have a clear definition agreed upon. A series of chemical steps is described to be considered as the life–nonlife transition, if one adheres to the minimalistic definition: life is self-reproduction with variations. The fully artificial RNA system chosen for the exploration corresponds sequence-wise to the reconstructed initial triplet repeats, presumably corresponding to the earliest protein-coding molecules. The demonstrated occurrence of the mismatches (variations) in otherwise complementary syntheses (“self-reproduction”), in this RNA system, opens an experimental and conceptual perspective to explore the origin of life (and its definition), on the apparent edge of the origin.