Significant Height Variation Research Articles

Multimodal optical imaging of the oculofacial region using a solid tissue-simulating facial phantom.

Spatial frequency domain imaging (SFDI) applies patterned near-infrared illumination to quantify the optical properties of subsurface tissue. The periocular region is unique due to its complex ocular adnexal anatomy. Although SFDI has been successfully applied to relatively flat in vivo tissues, regions that have significant height variations and curvature may result in optical property inaccuracies. We characterize the geometric impact of the periocular region on SFDI imaging reliability. SFDI was employed to measure the reduced scattering coefficient ( ) and absorption coefficient ( ) of the periocular region in a cast facial tissue-simulating phantom by capturing images along regions of interest (ROIs): inferior temporal quadrant (ITQ), inferior nasal quadrant (INQ), superior temporal quadrant (STQ), central eyelid margin (CEM), rostral lateral nasal bridge (RLNB), and forehead (FH). The phantom was placed on a chin rest and imaged nine times from an "en face" or "side profile" position, and the flat back of the phantom was measured 15 times. The measured and of a cast facial phantom are accurate when comparing the ITQ, INQ, STQ, and FH to its flat posterior surface. Paired tests of ITQ, INQ, STQ, and FH and concluded that there is not enough evidence to suggest that imaging orientation impacted the measurement accuracy. Regions of extreme topographical variation, i.e., CEM and RLNB, did exhibit differences in measured optical properties. We are the first to evaluate the geometric implications of wide-field imaging along the periocular region using a solid tissue-simulating facial phantom. Results suggest that the ITQ, INQ, STQ, and FH of a generalized face have minimal impact on the SFDI measurement accuracy. Areas with heightened topographic variation exhibit measurement variability. Device and facial positioning do not appear to bias measurements. These findings confirm the need to carefully select ROIs when measuring optical properties along the periocular region.

Evaluating uncertainty in particle roughness of coated sand and its implication to coating abrasion

Coated soils have recently been spotlighted for their prospective applications in geotechnical engineering. Prior studies have shown that Polydimethylsiloxane (PDMS) coatings can substantially mitigate surface roughness and have suggested that such coatings may experience abrasion under stress conditions. However, comprehensive studies exploring the impacts of these coatings on particle surface attributes have been scarce. In this work, we scrutinize the surface properties of coated sands with varying mass ratios (MRs), applying probabilistic analysis to account for inherent uncertainty. According to the uncertainty quantification investigation via experimental data, the Gamma distribution is optimal to examine increasing MRs, highlighting a steady decline in surface roughness and corresponding dispersion. Furthermore, a probabilistic assessment of a specific coated sand sample (3% MR) exposed to different stress levels are conducted. The findings suggest that polymer coatings may endure abrasion as stress levels rise, with the average roughness values incrementally converging towards those of natural sands. The detailed examination of particle surface characteristics also unveils the existence of more pronounced peaks and valleys at elevated stress levels, implying significant height variations and evident heterogeneity in surface profiles. Overall, the use of probabilistic analysis techniques provides a more precise understanding of how particle surface properties depend on increasing MRs and their notable dispersion under escalating stress levels. This methodology could be instrumental in probing the mechanical behavior of coated sands, known for their considerable uncertainty.

Full-period fringe order correction method based on dual-threshold cellular automaton

In traditional temporal phase unwrapping (TPU) methods, the fringe order is obtained pixel-to-pixel by multi-frequencies or multi-wavelengths. The direct calculation and error non-accumulation features accelerate the prosperity of TPU. Nevertheless, the noise, defocusing, and non-uniform reflectivity may inevitably lead to some fringe order errors. These errors are powerless against the evolving TPUs such as Gray code and phase coding. In this paper, a full-period fringe order correction method based on dual-threshold cellular automaton is proposed for machine 3D vision. Initially, an advanced dual-threshold cellular automaton algorithm is employed to extract both the strong and weak edges of the wrapped phase individually. Superior to conventional single-threshold edge detection methods, this approach effectively mitigates the edge breakage problem caused by significant height variations. Subsequently, the N-filled map, N-residue mask, and N-start points concepts are introduced to sequentially segment independent connected domains based on the tightly graphical coupling. In addition, by performing edge compensation in the same period, accurate fringe order correction can be achieved even if excessive edge points are identified, as long as the broken edges are effectively connected. The experimental results exhibit exceptional correction performance of the proposed method for intricate isolated objects, objects with non-uniform reflectivity, and dynamic scenes.

A Full-Wave Reference Simulator for Computing Surface Reflectance

Computing light reflection from rough surfaces is an important topic in computer graphics. Reflection models developed based on geometric optics fail to capture wave effects such as diffraction and interference, while existing models based on physical optics approximations give erroneous predictions under many circumstances (e.g. when multiple scattering from the surface cannot be ignored). We present a scalable 3D full-wave simulator for computing reference solutions to surface scattering problems, which can be used to evaluate and guide the development of approximate models for rendering. We investigate the range of validity for some existing wave optics based reflection models; our results confirm these models for low-roughness surfaces but also show that prior rendering methods do not accurately predict the scattering behavior of some types of surfaces. Our simulator is based on the boundary element method (BEM) and accelerated using the adaptive integral method (AIM), and is implemented to execute on modern GPUs. We demonstrate the simulator on domains up to 60 × 60 × 10 wavelengths, involving surface samples with significant height variations. Furthermore, we propose a new system for efficiently computing BRDF values for large numbers of incident and outgoing directions at once, by combining small simulations to characterize larger areas. Our simulator will be released as an open-source toolkit for computing surface scattering.

Distribution, Growth and Yield of <i>Santalum album</i> L. in Karnataka, India

Santalum album L. is distributed from Indonesia in the West to Juan Fernandez Islands in the East and from Hawaiian Archipelago in the North to New Zealand in the South. Sandalwood is one of the most important economic tree species harvested mainly for its heartwood and oil and is used in India from the earliest historic times. The sandalwood stands are under immense pressure and their management is becoming increasingly complex. Unfortunately, efforts aimed at conserving the genetic resources of sandalwood suffer from want of precise information on the area coverage, present status, growth characteristics and diameter size class distribution. In Karnataka, S. album is mainly found in Shimoga, Chickamagalur, Coorg, Hassan, Mysore, Dharwad, Bangalore, Kolar, Belguam, Uttar Kannada, Dakshin Kannada, Bellary and Tumkur districts. Keeping this in view, 41 sample plots were layed-out in sandal wood estates under Karnataka Forest Department. Out of 41 plots, 19 plots were laid out in sandalwood plantations (plantation plots), 4 plots were laid in regeneration plot and 18 plots are natural plots. The younger age plantations (3 - 6 years) are seen in Kadur, Bidar, Bangarpete, Srinivaspur, Malur, Mysore, Dharwad, Yelawala, and Kaggalipura ranges. Older plantation (15 - 20 years) are seen in Ambligola, Shkaripura, Shiralkoppa, Bangalore, Dundsi, Dharwad and JB kaval range. Significant variation in height and diameter growth was observed in all the sampled plots. Growth in Bangalore forest range was superior with 10.39 m of height and 11.52 cm of dbh compared to other ranges having natural distribution. Among the older trees grown under natural conditions, trees in Kadur range showed better height of 7.8 m and diameter of 8.31 cm.

A vision guided robotic system for flexible gluing process in the footwear industry

Abstract This paper presents a novel gluing machine comprising a Cartesian robot and a vision system. The vision system enables the location and reconstruction of the shape of objects to be glued; the detected information is then used to plan the trajectory of the robot whose end-effector is a glue gun and to move the robot with an error suitable to industrial gluing operations. A calibration procedure that enables transforming coordinates between the robot frame and the vision system frame is described. The calibration considers several mechanical inaccuracies and its effectiveness was evaluated using error maps. In particular, the paper examines objects to be glued along their edges, as frequently occurs for fabrics, leathers, and shoe soles. For this, two procedures to plan the trajectories of the robot are proposed: the first is for objects that can be treated as flat 2D objects, that is, their height variation is negligible; the second procedure is for 3D objects, that is, those with significant height variation. Several applicative examples are reported to highlight the flexibility of the gluing process.

X-ray standing wave study of Si clusters on a decagonal Al-Co-Ni quasicrystal surface

Quantitative adsorption structure determinations on quasicrystals are scarce because most techniques for measuring surface structures are not well suited to the complex and infinite unit cells of quasicrystals. The normal incidence standing x-ray wave field technique presents a solution to these problems because it can be made inherently surface sensitive and does not involve extensive computational effort. We describe a method for applying this technique to adsorbates on quasicrystals, with specific application to a submonolayer of Si atoms on a decagonal Al-Co-Ni surface. We demonstrate the sensitivity of the technique to both adsorption site and geometry, leading to the conclusion that the Si atoms, which form six-atom pentagonal clusters, have an average height of $1.77\ifmmode\pm\else\textpm\fi{}0.05\phantom{\rule{0.16em}{0ex}}\AA{}$ above pentagonal hollow sites, with a significant height variation among the Si atoms in the cluster. In particular, the central Si atom sits more deeply than the five surrounding Si atoms, which are, on average, $2.7\phantom{\rule{0.16em}{0ex}}\AA{}$ away from the central Si atom. Although this study was performed on a decagonal quasicrystal that is periodic perpendicular to the surface, we describe how the technique can be applied to cases with no periodicity.

Nanoimprinted backside reflectors for a-Si:H thin-film solar cells: critical role of absorber front textures.

The development of optimal backside reflectors (BSRs) is crucial for future low cost and high efficiency silicon (Si) thin-film solar cells. In this work, nanostructured polymer substrates with aluminum coatings intended as BSRs were produced by positive and negative nanoimprint lithography (NIL) techniques, and hydrogenated amorphous silicon (a-Si:H) was deposited hereon as absorbing layers. The relationship between optical properties and geometry of front textures was studied by combining experimental reflectance spectra and theoretical simulations. It was found that a significant height variation on front textures plays a critical role for light-trapping enhancement in solar cell applications. As a part of sample preparation, a transfer NIL process was developed to overcome the problem of low heat deflection temperature of polymer substrates during solar cell fabrication.

Morphological and physiological responses of Triglochin buchenaui Köcke, Mering & Kadereit to various combinations of water and salinity: implications for resilience to climate change

Impacts of abiotic factors on low lying salt marsh species have been closely evaluated as unique stressors, but few studies have determined the physiological and morphological responses to predicted climate change conditions. This study investigated the effects of water state (tidal, flooded and drought) and salinity on Triglochin buchenaui Kocke, Mering and Kadereit, newly separated from the Triglochin bulbosa L. complex. Growth, proline concentration, relative water content, electrolyte leakage, chlorophyll concentration and morphological analyses were done following 3 months of treatments. Results showed significant variation in height (7.57 ± 0.5–29 ± 1.55 cm, p < 0.005, df = 55), leaf area increments and relative growth rates which decreased with increasing salinity under all water states. There was almost a cessation of growth under submergence which reduces the plant’s regeneration potential under these conditions. Proline accumulation (1.84 ± 0.23–3.36 ± 0.38 mg g−1 DW), response of photosynthetic pigments and electrolyte leakage (8.17 ± 0.80–38.36 ± 7.42 % μS g−1 FW) were fundamental to osmotic and membrane response regulation. Plants survived in all water states at salinity up to 45 ppt, but the optimum range was 0–18 ppt, and best water state was the tidal condition. Viable rhizomes were produced under drought conditions but in the absence of seed banks, regeneration of the species following prolonged submergence may not be possible due to absence of both rhizomes and seeds. In their natural habitat, highly succulent T. buchenaui plants (29 ± 1.55 cm tall and above) are indicative of freshwater conditions.

MeV Si ion beam implantation as an effective patterning tool for the localized formation of porous silicon

Porous silicon (PS), in the form of single layer and multilayer structures, is a low-cost nanomaterial with applications in a wide range of fields. Hence, there is an increasing interest on the fabrication of laterally patterned PS structures. In biophysics for example, PS is a promising material for the development of low cost optical biochips, due to its remarkable biocompatibility and adjustable surface chemistry and optical properties. However, conventional lithography processes have shown to be not suitable for the proper patterning of PS. In this work, implantation of MeV Si ions is proposed as an effective tool for the localized formation of PS in the micrometer range. As previously reported by other groups, irradiation of silicon with H and He keV ions can inhibit the formation of PS. In the case of heavier ions, its higher damage efficiency allows for lower implantation doses to achieve PS growth inhibition, which allows shorter process times, and at the same time provides good lateral resolution below the micrometric range. Besides, the usage of ions of the same elementary nature as the target material avoids inconvenient side effects that may be ascribed to the implanted species. Two dimensional PS patterns with feature size of few micrometers have been successfully fabricated. Fluorescence and scanning electron microscopy reveal the proper transfer of different mask motifs into a PS/silicon patterned structure. Patterns present well defined lateral contrast and flat surface with no significant height variations, mandatory features for the development of PS based biochips. A resistivity increase has been observed on irradiated samples which could explain the inhibition of PS formation. This effect is attributed to dopant deactivation by the ion beam, since backscattering channeling measurements show no significant lattice damage.

Phenotypic Selection of Calycophyllum spruceanum on Farms in the Peruvian Amazon: Evaluating a Low-Intensity Selection Strategy

Abstract A low-intensity selection strategy was recommended for timber trees in the Peruvian Amazon to maintain genetic variation on farms and produce modest gains in tree growth. The effectiveness of this strategy was evaluated using Calycophyllum spruceanum. Farmers selected 66 mother trees of different ages on farms in seven locations (~20% of all trees in the locations) in one watershed, based on a visual assessment of growth, form and external disease symptoms. Another 66 mother trees were chosen at random. Tree height, stem diameter, stem bifurcations and mortality of progeny of the selected and random groups of mother trees were evaluated at 15, 26 and 38 months in a provenance/progeny test located on farms in the same watershed. Height was significantly greater (10%) in the selected group at 15 months, but it did not differ significantly between the selected and random groups at 26 and 38 months. There were no significant differences in diameter, bifurcations and mortality between the groups. There was significant variation in height and diameter at all measurement ages due to families, and results suggested that variation in bifurcations and mortality due to families was also significant. Based on approximate 95% confidence intervals, family variances in height and diameter did not differ significantly between the selected and random groups at any measurement age, but evaluations should continue to confirm these tentative conclusions. Some practical implications for tree improvement programs are discussed.

Genetic variation in growth of Guazuma crinita (Mart.) trees at an early age in the Peruvian Amazon

Guazuma crinita (Mart.) is an important timber-tree species for agroforestry plantations in the Peruvian Amazon Basin. Trees are typically harvested at 6–10 years of age, but demand for wood is forcing farmers and loggers to harvest trees at increasingly younger ages. Previous research in farming communities led to the recommendation that local seed sources should be used for agroforestry plantations. Therefore, a provenance/progeny test of G. crinita was established in farming communities to determine if there was significant genetic variation within a representative watershed. The test includes 7 provenances and 200 families from the Aguaytía watershed, and is replicated in three planting zones (upper, middle and lower elevations) in the same watershed. Tree height and stem diameter were analyzed at 12 months across and within planting zones. In the analysis across planting zones, there was significant variation in height and diameter due to provenances, but in height only due to families within provenances. Means for provenances and families were relatively stable across zones, suggesting that the best provenance and families within that provenance could be used for agroforestry projects throughout the watershed. Variation due to provenances and families within provenances was most significant in the upper planting zone where trees grew most rapidly. Heritability of height and diameter was relatively low across zones, but again was notably higher in the planting zone where trees grew most rapidly. Results suggest that there is potential to improve yield of G. crinita by selecting faster-growing provenances and families within watersheds. However, selection would not be very efficient at 12 months since heritability was quite low at this stage of development (0–0.14 depending on planting zone). Heritability of growth traits, genetic correlations between growth and wood traits, and variation in mortality should be evaluated for at least 3 more years before deciding on the tree improvement strategy. To our knowledge, this is the first study to demonstrate significant variation due to provenances and families within a single small watershed in the Amazon. Results suggest that watershed-scale genetic studies should be conducted for other tropical hardwood species that are of interest to local communities.

Zn 2+ and Sr 2+ adsorption at the TiO 2 (110)–electrolyte interface: Influence of ionic strength, coverage, and anions

The X-ray standing wave technique was used to probe the sensitivity of Zn 2+ and Sr 2+ ion adsorption to changes in both the adsorbed ion coverage and the background electrolyte species and concentrations at the rutile ( α-TiO 2) (110)–aqueous interface. Measurements were made with various background electrolytes (NaCl, NaTr, RbCl, NaBr) at concentrations as high as 1 m. The results demonstrate that Zn 2+ and Sr 2+ reside primarily in the condensed layer and that the ion heights above the Ti–O surface plane are insensitive to ionic strength and the choice of background electrolyte (with <0.1 Å changes over the full compositional range). The lack of any specific anion coadsorption upon probing with Br −, coupled with the insensitivity of Zn 2+ and Sr 2+ cation heights to changes in the background electrolyte, implies that anions do not play a significant role in the adsorption of these divalent metal ions to the rutile (110) surface. Absolute ion coverage measurements for Zn 2+ and Sr 2+ show a maximum Stern-layer coverage of ∼0.5 monolayer, with no significant variation in height as a function of Stern-layer coverage. These observations are discussed in the context of Gouy–Chapman–Stern models of the electrical double layer developed from macroscopic sorption and pH-titration studies of rutile powder suspensions. Direct comparison between these experimental observations and the MUltiSIte Complexation (MUSIC) model predictions of cation surface coverage as a function of ionic strength revealed good agreement between measured and predicted surface coverages with no adjustable parameters.

Vertical structure of mesospheric echoes from the Indian MST radar

An experiment has been carried out using the Indian MST Radar located at Gadanki (13.5° E, 79.2° N) to investigate the radio wave (53 MHz) scattering characteristics from mesospheric region and associated dynamical phenomena. The main objective is to study the temporal variation of the vertical structure of the radar return echo power and the dynamics of the scattering regions within the mesosphere based on the observations conducted during the period March 1998–July 1999 with radar time provided for 2 days per month. The results presented here show general agreement with those obtained earlier using the Jicamarca radar. However, some of the new features brought out by the analysis of data include (a) significant height variation of the main scattering field/layer occurring between 68 and 76 km with lowest in winter and highest in summer months, (b) the intensity of radar return echo shows periodic variations indicating generation and decay of major scattering centres caused by neutral turbulence and (c) the absolute magnitudes of the line-of-sight velocities are found to be anti-correlated with the strength of the return echo power. The mechanisms leading to the fluctuations in the refractive indices responsible for mesospheric echoes are discussed and a synthesised view is presented for possible explanations to these results.

Tapping Mode Atomic Force Microscopy for Nanoparticle Sizing: Tip−Sample Interaction Effects

The use of tapping mode atomic force microscopy as a sizing tool for nanoparticles is investigated. Height of CdSe nanocrystals measured on different substrates is found to be significantly lower than the particle diameters as determined by transmission electron microscopy. Only minor height variations were found upon particle surface ligand exchange, but significant height variations were found for particles imaged on surfaces with different chemical natures. The distorted height data is attributed to shifts of the tip resonance frequency during imaging, induced by the attractive capillary forces near the substrate. Particle height variations observed when using different drive frequencies of the cantilever corroborate this assignment.

Assessment of height variations by GPS at Mediterranean and Black Sea coast tide gauges from the SELF projects

In the framework of the European Union SEa Level Fluctuations (SELF) I and the SELF II Projects designed to study sea level variations around the Mediterranean and Black Seas, the Global Positioning System (GPS) technique was adopted to measure the ongoing crustal movements at tide gauge stations. Tide gauges measure sea-level variations with respect to a ground benchmark. In order to determine true sea-level variations of a few millimeters per year, it is necessary to estimate the ground vertical movement to a high degree of accuracy. Countries involved in the projects were Spain, France, Italy, Greece, Bulgaria and Russia. In the period from 1993 to 1998 repeated observations at more than 28 tide gauges and at a number of reference and intermediate stations were conducted. GPS measurements were complemented by Water Vapor Radiometers (WVR) at selected sites. Individual campaigns were evaluated and analyzed and showed height variations in the millimeter–centimeter range. All data were processed following common standards using the Bernese Software in a unified analysis to generate a combined solution. Based on the normal equations of all of the campaigns, a combined solution for the SELF Projects sites was generated. In the analysis of multi-technique anchor sites to the International Terrestrial Reference Frame ITRF97, it is shown that vertical rates of different techniques may be of different sign with respect to each other and also with respect to the ITRF97 combination. Vertical rates are not reliable in general and even the restriction to the use of long the long-time series sites KOSG, ONSA, WTZR, MADR, GRAZ and MATE did not ensure significant and unique vertical rates. Nevertheless, they had to be used for the reference frame definition. The results of repeated gravity observations and the continuous GPS observations at Porto Corsini and Medicina were compared to the epoch-wise GPS campaigns and revealed that the vertical rates are in conformance with each other if taken over the same period in time. The impact of the WVR observations on tide gauge position variation estimation is shown to improve the vertical component in the case of baseline-wise observations with two WVRs by up to 50%. It is shown, that the time span is too short for epoch-type observations to resolve significant height variations. The estimated rates of about 0–20 mm/year are most likely explained by systematic and random errors in the GPS observations. The absolute gravity observations at selected tide gauges are accurate to ±3 μGal and are in general agreement with the zero result from GPS. The main outcome of the SELF campaign observations therefore was the determination of a homogeneous zero-epoch data set and the creation of a database that includes the complete link from the GPS sites to the sea level in the five Mediterranean countries involved.

Variation in attack by the mahogany shoot borer, Hypsipyla grandella (Lepidoptera: Pyralidae), in relation to host growth and phenology

AbstractIn order to evaluate the relationships between attacks by the mahogany shoot borer Hypsipyla grandella (Zeller) and host growth and phenology, field trials of Spanish cedar Cedrela odorata and American mahogany Swietenia macrophylla established in Costa Rica were assessed intensively over an 84 week period. Height growth of C. odorata was approximately twice that of S. macrophylla, with mean growth rates of 2.0 and 1.3 cm week−1 respectively. Cedrela odorata displayed pronounced temporal variation in leaf phenology, with a minimum of 51% of trees in leaf during a relatively dry period. In contrast, the minimum proportion of foliated S. macrophylla trees was 87%. No shoot borer attacks were recorded on S. macrophylla until week 50 after the onset of assessments, whereas initial attacks of C. odorata were recorded during week 6. By week 84, the proportion of trees attacked was 74% and 77%, respectively. In both species, attacks were concentrated in seasonal peaks, coinciding with the production of new shoots. Pronounced spatial variation in attack was observed in both species. At week 12, the number of attacks per block in C. odorata was negatively correlated with available calcium concentration (r=0.85, P&lt;0.001), whereas mean height growth of C. odorata was positively correlated with available phosphate concentration (r=0.84; P&lt;0.0001). Significant variation in height to first damaging attack was observed in both species. By the end of the observational period, only 6% of C. odorata and 0.4% S. macrophylla remained undamaged to a height of 3 m. It is suggested that control methods for the mahogany shoot borer should take account of temporal dynamics in attack, and relationship to host phenology. Manipulation of the soil nutrient status may also form part of an integrated approach to pest management.

Measurement of the Coronal Electron Temperature at the Total Solar Eclipse on 1994 November 3

A spectroscopic observation was carried out at the total solar eclipse on 1994 November 3 in Putre, Chile, in order to investigate the electron temperature and the expanding motion of the corona. The shape of weak depressions at 3900 Å and 4300 Å in the continuous coronal spectra was compared with the theoretical electron-scattered coronal spectra; thus, the magnitude of the electron thermal motion was determined directly. It was found that a coronal streamer on the eastern limb and a coronal hole on the south-pole have overall temperatures of about 1.5–1.7 MK and 0.9–1.1 MK, respectively. No significant height variation in the temperature was found in the streamer, while the coronal hole shows evidence of increasing temperature with height. An acceleration of the expanding motion between 1.1 R⊙ and 2.0 R⊙ by ∼ 80 km s−1 was found in the streamer.

The height variation of vertical heat flux near the ground

AbstractProfiles of vertical heat flux were obtained by subtracting the component of temperature change due to long‐wave radiation flux divergence from some observed temperature changes and integrating the resultant temperature change. the method of computing the radiative component was essentially one suggested by Funk (1961). the resultant fluxes of sensible heat showed significant height variations near the ground at night but almost no variation near the ground in the day. At night the coefficient of eddy conductivity increased with height up to about 50 metres and subsequently decreased. In the daytime the concept of thermal diffusion does not appear to adequately describe the sensible heat flux.