Ridge Shape Research Articles

Mapping and spatial statistical analysis of Mars Yardangs

Mars yardang fields were mapped using the newly available high-resolution Context Camera (CTX) mosaics (30°N to 30°S) through visual interpretation and manual digitization. We classified the Martian yardangs into three types according to their shapes: long ridge, inverted hull and curvilinear shapes, and found that the number of long ridge yardang fields account for 77.97% of all 394 yardang fields. The mapping results show that the total area of yardang fields is about 734,115 km2, within which the area of the Medusae Fossae Formation (MFF) yardangs is about 562,640 km2. We also identified and digitized individual yardang bodies wider than 500 m in the CTX mosaics. The resultant 466 yardang bodies are subsequently used as samples for statistical analysis of the morphometric parameters. Among all of the orientations, N–S is the dominant orientation of the yardang samples, and the average length and width are 5626 m and 993 m respectively. The length to width ratios vary from 1.2:1 to 46.9:1 within (30°N to 30°S) and vary from 1.5:1 to 46.9:1 in the most studied MFF. The mapping and statistical results provide important information about the spatial distribution of Mars yardangs and their morphological characteristics, which will be valuable to further study of the formation and evolution of Mars yardangs, and the aeolian environment.

Experimental study on pumping-induced land subsidence and earth fissures: a case study in the Su-Xi-Chang region, China

Land subsidence and earth fissures caused by excessive groundwater exploitation severely damage the surrounding property and environment. To examine changes caused by land subsidence and earth fissures, a large-scale physical-geological model was designed to simulate groundwater exploitation and the conditions of bedrock ridges. This model enables real-time monitoring of the groundwater level, soil strain, and changes to subsidence and fissures. It is based on a case study conducted on the ground surface of Guangming Village in the Su-Xi-Chang region, China. The results revealed the following: (1) the land subsidence lagged behind the decline in water level during the pumping process; (2) a strong agreement between the shape and location of the bedrock ridge and settlement was reached, and the region with the most severe subsidence corresponded to the distribution of the fissures; (3) the tensile-stress concentration of the soil mass was essentially the same as that during the stage when the fissures developed, (which is an important means of determining the fissure development); and (4) the rose diagram illustrating the fissures indicated the fissures in the area of the bedrock ridge propagated parallel to the contour lines of the bedrock ridge. These results are consistent with the changes in the earth fissures examined in the case study and, therefore, provide support for the use of the physical-geological model in future research on ground fissures.

Is a Ridge Classification Helpful when Assessing Edentulous Patients?

The edentulous ridge classifications most commonly used have their limitations in treatment planning. They do not provide an indication of the complexities that may occur when constructing a new set of complete dentures. The new classification system suggested in this article helps with improved record-keeping, information exchange between colleagues, and communication between patient and clinician. CPD/Clinical Relevance: The new edentulous ridge classification system links the various edentulous ridge shapes to possible complications that could arise during denture construction.

Mental structures

AbstractAn ongoing philosophical discussion concerns how various types of mental states fall within broad representational genera—for example, whether perceptual states are “iconic” or “sentential,” “analog” or “digital,” and so on. Here, I examine the grounds for making much more specific claims about how mental states are structured from constituent parts. For example, the state I am in when I perceive the shape of a mountain ridge may have as constituent parts my representations of the shapes of each peak and saddle of the ridge. More specific structural claims of this sort are a guide to how mental states fall within broader representational kinds. Moreover, these claims have significant implications of their own about semantic, functional, and epistemic features of our mental lives. But what are the conditions on a mental state's having one type of constituent structure rather than another? Drawing on explanatory strategies in vision science, I argue that, other things being equal, the constituent structure of a mental state determines what I call its distributional properties—namely, how mental states of that type can, cannot, or must co‐occur with other mental states in a given system. Distributional properties depend critically on and are informative about the underlying structures of mental states, they abstract in important ways from aspects of how mental states are processed, and they can yield significant insights into the variegation of psychological capacities.

Effects of heterogeneous surface geometry on secondary flows in turbulent boundary layers

The effect of spanwise heterogeneous surface geometry on turbulent boundary layer secondary flows and on skin friction is investigated experimentally. The surfaces consist of smooth streamwise-aligned ridges of different shapes and widths with spanwise wavelengths comparable to the boundary layer thickness ( ). Cross-stream stereoscopic particle image velocimetry combined with oil-film interferometry is used to investigate the flow field and assess the drag. Results show that the spanwise distribution of the skin friction varies as a consequence of the mean flow heterogeneity and is highly dependent on surface geometry. The swirling strength maps revealed remarkable changes in the secondary flow structures for different ridge shapes. For wide ridges, topological changes occur showing the appearance of tertiary vortices coexisting with the large-scale secondary structures. An imbalance in favour of these tertiary structures occurs over a certain width which take over the secondary structures, causing a swap in the locations of the low- and high-momentum pathways. Furthermore, the results indicate that the spanwise spacing alone is insufficient to characterise the surface heterogeneity. A new parameter ( ), which is based on the ratio of the perimeter over and below the mean surface height, is shown to adequately capture the changes in skin friction and streamwise circulation of the secondary motions. Triple decomposition allowed the quantification of the dispersive stresses for all these cases, which can contribute up to of the total shear stress when strong secondary motions occur.

Radiomorphometric analysis of edentulous posterior mandibular ridges in the first molar region: a cone-beam computed tomography study.

PurposeThe aim of our study was to determine the prevalence and degree of lingual concavities in the first molar region of the mandible to reduce the risk of perforating the lingual cortical bone during dental implant insertion.MethodsA total of 163 suitable cross-sectional cone-beam computed tomography images of edentulous mandibular first molar regions were evaluated. The mandibular morphology was classified as a U-configuration (undercut), a P-configuration (parallel), or a C-configuration (convex), depending on the shape of the alveolar ridge. The characteristics of lingual concavities, including their depth, angle, vertical location, and additional parameters, were measured.ResultsLingual undercuts had a prevalence of 32.5% in the first molar region. The mean concavity angle was 63.34°±8.26°, and the mean linear concavity depth (LCD) was 3.03±0.99 mm. The mean vertical distances of point P from the alveolar crest (Vc) and from the inferior mandibular border were 9.39±3.39 and 16.25±2.44, respectively. Men displayed a larger vertical height from the alveolar crest to 2 mm coronal to the inferior alveolar nerve (Vcb) and a wider LCD than women (P<0.05). Negative correlations were found between age and buccolingual width at 2 mm apical to the alveolar crest, between age and Vcb, between age and Vc, and between age and LCD (P<0.05).ConclusionsThe prevalence of lingual concavities was 32.5% in this study. Age and gender had statistically significant effects on the lingual morphology. The risk of lingual perforation was higher in young men than in the other groups analyzed.

Developing a Scene-Based Triangulated Irregular Network (TIN) Technique for Individual Tree Crown Reconstruction with LiDAR Data

LiDAR (Light Detection and Ranging)-based individual tree crown reconstruction is a challenge task due to the variable canopy morphologies and the penetrating properties of LiDAR to tree crown surfaces. Traditional methods, including LiDAR-derived rasterization, low-pass filtering smooth algorithm, and original triangular irregular network (TIN) model, have difficulties in balancing morphological accuracy and model smoothness. To address this issue, a scene-based TIN was generated with three steps based on the local scene principle. First, local Delaunay triangles were formed through connecting neighboring point sets. Second, key control points within each local Delaunay triangle, including steeple, inverted tip, ridge, saddle, and horseshoe shape control points, were extracted by analyzing multiple local scenes. These key points were derived to determine the fluctuations of forest canopies. Third, the scene-based TIN model was generated using the control points as nodes. Visual analysis indicates the new model can accurately reconstruct different canopy shapes with a relatively smooth surface, and statistical analysis of individual trees confirms that the overall error of the new model is smaller than others. Especially, the scene-based TIN derived raster reduced the average error to 0.18 m, with a standard deviation of 0.41, while the average errors of LiDAR-derived raster, low-pass filtered smooth raster, and original TIN derived raster have average errors of 0.96, 2.05, and 1.00 m, respectively. The local scene-based control point extraction also reduces data storage due to the elimination of redundant points, and furthermore the different point densities on different objects are beneficial for canopy segmentation.

Self-images contrast enhancement for displacement Talbot lithography by means of composite mesoscale amplitude-phase masks

We propose a new design of composite wavelength-scale amplitude-phase diffraction grating as applied to the displacement Talbot lithography. The grating is composed of a conventional metal amplitude binary mask with superposed dielectric phase steps and provides for manyfold optical contrast enhancement of the integrated ‘Talbot carpet’ as opposed to the amplitude and phase masks purely. By means of the finite element calculations, we analyze the spatial field structure in the proposed gratings with different geometric ridge shapes and show that due to Mie-type resonances excitation the semielliptical dielectric steps in the combination with metal amplitude mask demonstrate excellent spatial resolution (∼) and highest optical contrast (∼22 dB) of integrated Talbot self-images.

Processes that cause natural unforested areas in Canadian Rockies below temperature treeline

Naturally treeless areas surrounded by closed canopied forests are common below the temperature treeline in mountains. These areas are a result of several possible conditions, e.g. exposed un-weathered bedrock, blockfields, talus slopes, landslides, lithology and others. Here we show a Foothills ridge that is treeless because of its structural geology, lithology, regolith depth, regolith temperature gradient, wind and precipitation, all of which facilitate frost heave that in turn uproots seedlings. The ridge has a SE-NW striking fault that is perpendicular to the direction of the winter wind that blows snow off the ridge. There are nearby seed sources (within 15m) and enough growing season regolith moisture for tree seed germination. However, in the fall and winter the seedlings are uprooted due to regolith movement. The mechanism for this regolith movement is frost heave caused by the ridge's deeply weathered regolith, wind-blown snowless surface that results in a steep temperature gradient near the regolith surface with a close subsurface of near freezing (frozen fringe) followed by an unfrozen zone all in the top 30cm. The snow free ridge is caused by snow transport processes modeled in Liston's SNOWMODEL as a result of the ridge shape and orientation. The Rempel's frost heave process model explains that the cause is the regolith texture with no insulating snow cover resulting in the formation of near surface pump of water from a frozen fringe into a freezing zone at the surface.

Planar-type MEMS tactile sensor integrating micro-macro detection function of fingertip to evaluate surface touch sensation

In this study, a tactile sensor integrating micro- and macro-scale tactile detection components was developed to reproduce the micro/macro touch sensations of the human fingertip. The micro-scale tactile detection component comprises a 500 μm diameter contactor that mimics the shape and size of the fingerprint ridge, and detects the micro shape of surfaces and local friction with high spatial resolution. The macro-scale tactile detection component detects the overall contact force and slipperiness via a wide-area sensor that mimics the skin of the fingertip. Three fabric samples with different weave structures were analyzed using the fabricated device. The fine surface pattern of the fabrics and slip friction were detected, and the differences according to the weave structure clearly extracted. Additionally, the contact force dependency of the tactile information, which is an important factor with regard to the touch sensation of a fabric, was successfully obtained using the two detection components.

Tracing sea-level changes during the mid-Holocene in the southern Mediterranean coast: An example from the Gulf of Gabes

Mid-Holocene sea-level emergence was recorded along a mid-latitude coastal site in the Gulf of Gabes, Tunisia, in beach rock deposits. However, the post-emergence sea-level curve and associated hydro-sedimentary processes have rarely been documented. This study presents new records of sea-level changes along the Tunisian coast since the mid-Holocene. Each phase of the sea-level curve was evidenced and supported by lithostratigraphic, morphological and archaeologic markers. Post-emergence sea-level fall due to postglacial isostatic rebound was recognized in regressive sequences which vary depending on available accommodation space, from a small pocket beach to a well developed dune system. Sea-level stabilization following isostatic rebound has promoted the end phase deposits of the regressive sequences. However, this stability was interrupted during the late Holocene by a high-energy storm event that accumulated a transgressive boulder unit at 2 m above present. Shape and disposition of the boulder ridge behind a prograding modern shoreline suggests that sea level has not changed during the late Holocene. The existence of a Roman fish pond on the upper foreshore confirms stability of sea level during the last two millennia. The combination of lithostratigraphic, morphological and archaeologic markers represents a tool for improving the accuracy of dating of erosional and depositional periods in mid-coastal sections.

Design and evaluation of a one-operation shallow up-cut tillage sowing method for soybean production

ABSTRACTSowing using a rotary tiller rotating in reverse (up-cut) is a labor-saving technology for soybean production because it can perform tillage and sowing, make ridges, and bury winter crop residues in one operation. However, the power requirement of up-cut rotation is higher than of normal rotation (down-cut), resulting in lower working speeds. Shallow tillage sowing methods may be a solution to this problem. Here, we develop a shallow tillage sowing method using an up-cut rotary and a side-disk which could perform the aforementioned works in one operation and conducted field experiments in 2015 and 2016 to study the effect of our sowing method (up-cut shallow tillage; UST) on ridge shape, soil volumetric water content (VWC) and soybean growth and yield, compared to conventional sowing methods (up-cut conventional tillage; UCT, and down-cut conventional tillage; DCT). Ridge shape did not differ among sowing methods. The VWC at 10 and 20 cm depths in DCT was always higher than in UST and UCT, indicating poorer drainage. The VWC at 10 cm depth decreased quickly after rain in UST and UCT, indicating good surface-layer drainage, but at 20 cm depth in UCT, VWC was lower than in UST, especially during dry spells, indicating higher water-holding capacity in UST than in UCT. Shoot and root growth and seed yield did not differ among sowing methods, indicating that UST did not negatively affect soybean growth and yield. These results suggest that UST can be used for soybean production.

Stratified Flows over and around Long Dynamically Tall Mountain Ridges

AbstractUniformly stratified flows approaching long and dynamically tall ridges develop two distinct flow components over disparate time scales. The fluid upstream and below a “blocking level” is stagnant in the limit of an infinite ridge and flows around the sides when the ridge extent is finite. The streamwise half-width of the obstacle at the blocking level arises as a natural inner length scale for the flow, while the excursion time over this half-width is an associated short time scale for the streamwise flow evolution. Over a longer time scale, low-level horizontal flow splitting leads to the establishment of an upstream layerwise potential flow beneath the blocking level. We demonstrate through numerical experiments that for sufficiently long ridges, crest control and streamwise asymmetry are seen on both the short and long time scales. On the short time scale, upstream blocking is established quickly and the flow is well described as a purely infinite-ridge overflow. Over the long time scale associated with flow splitting, low-level flow escapes around the sides, but the overflow continues to be hydraulically controlled and streamwise asymmetric in the neighborhood of the crest. We quantify this late-time overflow by estimating its volumetric transport and then briefly demonstrate how this approach can be extended to predict the overflow across nonuniform ridge shapes.

3D modeling of growth ridge and edge facet formation in [formula omitted] floating zone silicon crystal growth process

A 3D quasi-stationary model for crystal ridge formation in FZ crystal growth systems for silicon is presented. Heat transfer equations for the melt and crystal are solved, and an anisotropic crystal growth model together with a free surface shape solver is used to model the facet growth and ridge formation. The simulation results for 4″ and 5″ crystals are presented and compared to experimental ridge shape data.

Analysis of the geometry of the growth ridges and correlation to the thermal gradient during growth of silicon crystals by the Czochralski-method

A contactless, non-destructive approach to measure the geometrical parameters of the growth ridge, based on surface topography, is presented and established. It allows a systematic, large scale analysis of growth ridges of single crystals of almost any type. Here, it is applied to Czochralski-grown silicon crystals. Based on the measurement results, Voronkov’s theory of the shape of the growth ridge is verified. This theory is used to calculate the temperature gradient at the growth ridge from the geometrical parameters. The presented method gives an easy, direct experimental access to the thermal conditions, both qualitative and quantitative, at the solid-liquid interface during the growth process.

A Variational Method for Sea Ice Ridging in Earth System Models

AbstractWe have derived an analytic form of the thickness redistribution function, Ψ, and compressive strength of sea ice using variational principles. By using the technique of coarse‐graining vertical sea ice deformation, or ridging, in the momentum equation of the pack, we isolate frictional energy loss from potential energy gain in the collision of floes. The method accounts for macroporosity of ridge rubble, ϕR, and by including this in the state space of the pack, we expand the sea ice thickness distribution, g(h), to a bivariate distribution, g(h,ϕR). The effect of macroporosity is for the first time included in the large‐scale mass conservation and momentum equations of frozen oceans. We make assumptions that have simplified the problem, such as treating sea ice as a granular material in ridges, and assuming that bending moments associated with ridging are perturbations around an isostatic state. Regardless of these simplifications, the coarse‐grained ridge model is highly predictive of macroporosity and ridge shape. By ensuring that vertical sea ice deformation observes a variational principle both at the scale of individual ridges and over the pack as a whole, we can predict distributions of ridge shapes using equations that can be solved in Earth system models. Our method also offers the possibility of more accurate derivations of sea ice thickness from ice freeboard measured by space‐borne altimeters over polar oceans.

Analysis of Reverse Currents Parameters and Gas Content in Liquid behind the Roughness Ridge

Based on experimental studies, the effect of gas content in the liquid behind the ridges of artificial helical roughness on film thickness and the value of the heat transfer coefficient is shown. The numerical results for the reverse currents velocity distribution and pressure difference along the ridge height and the cavity length, as well as experimental values of gas content in the liquid separation zone, arising from the flow over a regular roughness, are presented. The scale of reverse currents, their location behind the roughness ridge, and gas content depend on the height and shape of the ridge, the irrigation density, and the physical properties of the liquid. It was concluded that the gas bubbles in the liquid form in reverse current zones in the cavities of the artificial roughness due to reduced pressure compared to gas pressure at the interface and, therefore, gas suction from the interface zone. The dependence for calculating gas content via the thickness of the liquid layer in the roughness cavity is proposed.

Buccal fat pad-derived stem cells with anorganic bovine bone mineral scaffold for augmentation of atrophic posterior mandible: An exploratory prospective clinical study.

Application of adipose-derived stem cells originated from buccal fat pad (BFP) can simplify surgical procedures and diminish clinical risks compared to large autograft harvesting. This study sought to evaluate and compare the efficacy of buccal fat pad-derived stem cells (BFPSCs) in combination with anorganic bovine bone mineral (ABBM) for vertical and horizontal augmentation of atrophic posterior mandibles. Fourteen patients with atrophic posterior mandible were elected for this prospective exploratory study. BFP (3-5 mL) was harvested and BFPSCs were isolated and combined with ABBM at 50% ratio. The vertical and horizontal alveolar deficiencies were augmented by 50% mixture of ABBM with either BFPSCs (group 1) or particulated autologous bone (group 2). Titanium mesh was contoured to the desired 3D shape of the alveolar ridge and fixated to the host sites over the graft material of the two groups. At first, the amount of new bone areas was calculated by quantitative analysis of cone beam computed tomography (CBCT) images that were taken 6 months postoperatively according to regenerative techniques (group 1 vs group 2 without considering the type of bone defects). Second, these amounts were calculated in each group based on the type of defects. Quantitative analysis of CBCT images revealed the areas of new bone formation were 169.5 ± 5.90 mm2 and 166.75 ± 10.05 mm2 in groups 1 and 2, respectively. The area of new bone formation for vertical defects were 164.91 ± 3.74 mm2 and 169.36 ± 12.09 mm2 in groups 1 and 2, respectively. The area of new bone formation for horizontal deficiencies were 170.51 ± 4.54 mm2 and 166.98 ± 9.36 mm2 in groups 1 and 2, respectively. There were no statistically significant differences between the two groups in any of the pair-wise comparisons (P > 0.05). The findings of the present study demonstrated lack of difference in bone volume formation between BFPSCs and autologous particulate bone in combination with ABBM. If confirmed by future large-scale clinical trial, BFPSCs may provide an alternative to autogenous bone for reconstruction of alveolar ridge defects.

RELATIONSHIP BETWEEN SATISFACTION WITH COMPLETE DENTURES AND BASAL SEAT CHARACTERISTICS

Aim: To investigate the relationship between patients self perceived satisfaction and basal seat characteristics in edentulous patients attending a teaching hospital in Lagos.Materials and Methods: Consecutive edentulous patient seen for 6 months in Lagos University Teaching Hospital, Lagos were recruited for this longitudinal study. The data collected were basal seat characteristics and self perceived satisfaction.Results: A total of 30 patients were seen but only 24 complied with the study protocol. The use of objective assessment in classifying maxillary residual ridge showed that there was a significant association (P=0.045) between the ridge and self perceived satisfaction. There was no significant association between self perceived satisfaction and shape of mandibular ridge, palatal vault and vestibular depth.Conclusion: There was a significant association between shape of maxillary residual ridge and self perceived satisfaction. Objective preclinical assessment of residual ridge may help to project satisfaction and determine treatment option.

Comparative ultrastructural observations of the Egyptian schistosomes: Schistosoma mansoni and Schistosoma haematobium.

An ultrastructural topography has been made to the tegumental architectures of two Egyptian schistosomes namely S. mansoni and S. haematobium hosted in a model animal namely Cricentus auratus. The distribution of sensory papillae on the oral sucker were arranged in one circle around the rim in addition to some papillae in upper part of inner zone in male, female S. mansoni and in male S. haematobium. The differences in the types of papillae, their distribution and shape of ridges on various parts of the body surface which are quite specific for each species was studied. Also, the ventral tegument of female's displays larger and more numerous sensory papillae. Both ciliated and non-ciliated papillae were observed in this work which makes a link with another species of schistosome S. japonicum. Another characteristic feature in this study is unique of male of S. haematobium, the extensive formation of ridges and transformation to microvilli in the posterior region in males. These finding may provoke further study of schistosomes hosted in animal model for more detailed investigation at the molecular level.