Rounded Profile Research Articles

Texture-Based Photogrammetry Accuracy on Curved Surfaces

Photogrammetry is a preferred technique for noncontact measurement of flexible structures, such as large membranes and flapping-wing vehicles. Traditionally, discrete features are triangulated between photos. New techniques use the local texture of a surface to match random speckle among images. Texture-based photogrammetry allows for higher resolution surfaces, and this paper tests if the precision is similar to traditional photogrammetry. Test surfaces provide known, rounded profiles used to compare surface reconstructions. Many images are taken of an object with a projected texture, and the depth error is used to quantify the accuracy of the results. Results on surfacemeshes from800 to 2500 points show accuracy on the order of 1:2000, or nearly that of one pixel. Camera locations had a surprisingly minor effect on surface quality. There is a slight correlation of more parallel views tomore points on the surface. To show that the technique extends to practical use, results are shown for aflapping cycle of amembranewing.Dense surfacemeshes are important for higherfidelitymodels in computational fluid dynamics and finite element analysis.

Pressure dependence of confined liquid behavior subjected to boundary-driven shear

Non-equilibrium molecular dynamics simulations of boundary-driven sheared Lennard-Jones liquids at variable pressure up to 5 GPa (for argon) reveal a rich out-of-equilibrium phase behavior with a strong degree of shear localization. At the lowest apparent shear rate considered (wall speed ~1 m s(-1)) the confined region is an homogeneously sheared solid (S) with no slip at the walls. This transforms at higher shear rates to a non-flowing plug with slip at the walls, referred to as the plug slip (PS) state. At higher shear rate a central localized (CL) state formed in which the shear gradient was localized in the center of the film, with the rest of the confined sample in a crystalline state commensurate with the wall lattice. The central zone liquidlike region increased in width with shear rate. A continuous rounded temperature profile across the whole system reflects strong dynamical coupling between the wall and confined region. The temperature rise in the confined film is consistent with the Brinkman number. The transition from the PS to CL states typically occurred at a wall speed near where the shear stress approached a critical value of ~3% of the shear modulus, and also near the peak in the traction coefficient, μ. The peak traction coefficient values computed, ~0.12-0.14 at 1000 MPa agree with those found for traction fluids and occur when the confined liquid is in the PS and CL states. At low wall speeds slip can occur at one wall and stick at the other. Poorly wetting liquids manifest long-lived asymmetries in the confined liquid properties across the system, and a shift in solid-liquid phase co-existence to higher shear rates. A non-equilibrium phase diagram based on these results is proposed. The good agreement of the tribological response of the Lennard-Jones fluid with that of more complicated molecular systems suggests that a corresponding states scaling of the tribological behavior could apply.

Influence of variations in the pressure distribution on the friction of the finger pad

We investigated the influence of the contact pressure distribution on the friction of the index finger pad. The skin contact pressure distributions were characterised by round profiles for low forces. At higher loads, the pressure distributions of the finger pad became asymmetric and conical. Additional experiments with the knuckle revealed pressure distributions with sharp peaks. The friction coefficients of the finger pad and the knuckle indicated a common behaviour in accordance with the adhesion friction model. Varying pressure distributions were found to influence the friction coefficients of skin, contributing to the variation of measurement results at comparable normal loads.

Effect of shock vibrations due to speed control humps to the health of city bus drivers

Speed Control Humps (SCH) are used to slow down the vehicles and improve traffic safety. While passing over the humps, the drivers of public transport buses are exposed to shock vibrations. An analysis of the effects of shock vibrations to the health of a city bus driver, while passing over three types of SCHs, is made by simulation, using an original oscillatory model with five degrees of freedom (DOF). The evaluation is carried out using the method and criteria accepted by ISO 2631-5 standard. The assessment of the effects of shock vibrations to the health of the bus driver on public transport line 26 in Belgrade is also made. While passing over a rounded profile, the driver's health is more affected at lower bus speeds (15 km/h), even as over flat platform, harmful effects are more significant at higher speeds (over 40 km/h). If the bus on the line 26 is driven over humps at 40 km/h, harmful effects to the driver's health occur at the age of 50. By driving at or under 30 km/h, the driver can almost avoid harmful effects at all. Key words: ISO 2631-5 standard, shock vibrations, city bus, driver's health, simulation.

Effect of shock vibrations due to speed control humps to the health of city bus drivers

Speed Control Humps (SCH) are used to slow down the vehicles and improve traffic safety. While passing over the humps, the drivers of public transport buses are exposed to shock vibrations. An analysis of the effects of shock vibrations to the health of a city bus driver, while passing over three types of SCHs, is made by simulation, using an original oscillatory model with five degrees of freedom (DOF). The evaluation is carried out using the method and criteria accepted by ISO 2631-5 standard. The assessment of the effects of shock vibrations to the health of the bus driver on public transport line 26 in Belgrade is also made. While passing over a rounded profile, the driver's health is more affected at lower bus speeds (15 km/h), even as over flat platform, harmful effects are more significant at higher speeds (over 40 km/h). If the bus on the line 26 is driven over humps at 40 km/h, harmful effects to the driver's health occur at the age of 50. By driving at or under 30 km/h, the driver can almost avoid harmful effects at all. Key words: ISO 2631-5 standard, shock vibrations, city bus, driver's health, simulation.

A Technique for Fabrication of an Extracoronal Attachment‐Retained Removable Partial Denture to Fit an Existing Fixed Partial Denture

Precision attachments have been used for many years to retain removable partial dentures (RPDs). Common reasons for a failed attachment-retained RPD are fracture of the framework, fracture of the roots or teeth, and irretrievable decrease of retention. When an RPD framework major connector has been fractured, it should be remade. This article describes a technique to remake a fractured mandibular RPD using cast round profile attachment analogs without the need for replacement of the fixed partial denture.

Study on Axial Contact Deformation of Planetary Roller Screw

Based on the current study of planetary roller screw(PRS), a summary of how to match the main parameters of the PRS is obtained. A mathematic model for contact analysis is developed, where series of equivalent balls are used to replace the rounded profile of the roller. At the same time, the formula of axial contact deformation of the PRS is derived. Then a simplified finite element model of the PRS is established and the contact analysis is conducted by FEA. The FEA results and the theoretical ones agree well with each other, so the accuracy of the calculation method and the validity of the equivalent method are verified.

Systematic characterization of feature dimensions and closing pressures for microfluidic valves produced via photoresist reflow

Multilayer soft lithography (MSL) provides a convenient and low-cost method for fabricating poly(dimethyl siloxane) (PDMS) microfluidic devices with on-chip valves for automated and precise control of fluid flow. MSL casting molds for flow channels typically incorporate small patches of rounded positive photoresist at valve locations to achieve the rounded cross-sectional profile required for these valves to function properly. Despite the importance of these rounded features for device performance, a comprehensive characterization of how the rounding process affects feature dimensions and closing pressures has been lacking. Here, we measure valve dimensions both before and after rounding and closing pressures for 120 different valve widths and lengths at post-rounding heights between 15 and 84 μm, for a total of 1200 different geometries spanning a wide range of useful sizes. We find that valve height and width after rounding depend strongly on valve aspect ratios, with these effects becoming more pronounced for taller and narrower features. Based on the measured data, we provide a simple fitted model and an online tool for estimating the pre-rounding dimensions needed to achieve desired post-rounding dimensions. We also find that valve closing pressures are well explained by modelling valve membranes in a manner analogous to a suspension bridge, shedding new light on device physics and providing a practical model for estimating closing pressures during device design.

Toxicity of endogenous peroxynitrite and effects of puerarin on transplanted retinal pigment epithelial sheets in the subretinal space in mice.

To evaluate the toxicity of endogeneous peroxynitrite on transplanted retinal pigment epithelial (RPE) sheets and the effect of puerarin on their survival in the C57BL/6 mice after RPE sheets have been transplanted into SD rats' subretinal space . C57BL/6 mice eyes were used to culture RPE cells. Ninety-six SD rats were involved in the experiment. They were divided into control (block control), streptozotocin (STZ, negative control), untransplanted RPE (positive control) and transplanted RPE groups respectively. Diabetes was induced in SD rats by intra-peritoneal STZ injection in the latter three groups. Saline was injected into the subretinal space of 24 SD rats in the untransplanted RPE group and primary RPE sheets were injected into the subretinal space of 24 SD rats in the transplanted RPE group. Puerarin (45mg/kg) was administrated into both untransplanted RPE and transplanted RPE groups of diabetic rats through intra-peritoneal injection route after RPE sheets transplantation. At 20, 40, 60 days after surgery, Western blotting analysis, DNA ladder and RT-PCR were used for determining the differences in expression of nitrotyrosine (NT, the foot print of peroxynitrite ), apoptosis and iNOS mRNA in the control, STZ, untransplanted RPE and transplanted RPE groups respectively. HE staining was used for determining the RPE survival in the subretinal space of the transplanted RPE group. Apoptosis and expression of NT and iNOS mRNA were observed in STZ, untransplanted RPE and transplanted RPE groups, but were delayed in untransplanted RPE and transplanted RPE groups in a time-dependent manner compared with control and STZ groups (P<0.01). There were no differences between the two groups (P>0.01). NT, DNA ladder, iNOS mRNA were down-regulated, which were associated with the decrease of expression of peroxynitrite. Numerous pigmented cells emerged and increased in number in the subretinal space during the 60-day observation period after transplantation. On day 20, heavily pigmented cells were visible at the transplant site; On day 40, monolayer and multilayered transplant was visible in the subretinal space; On day 60, heavily pigmented monolayer and multilayered transplants with round apical profile were present along Bruch's membrane. Puerarin increased the 60-day survival of C57BL/6 mice RPE xenografts in the SD rats' subretinal space, which may be related to its direct inhibition of apoptosis of RPE cells and antagnism of damage of peroxynitrite to RPE cells.

Fabrication of PDMS Microchannels with Round Profiles Using Glycerol Molds

Poly(dimethylsiloxane) (PDMS) based soft lithography has been widely used to make microfluidic devices, while the cross-sections of the microchannels using the solid molds are mostly rectangle. We present a method for fabricating PDMS channels with a round profile, which utilizes hydrophilic/hydrophobic modification of substrates and glycerol molds. The glycerol mold was formed by letting glycerol stay on the patterned hydrophilic area surrounded by hydrophobic area. The different aspect ratios of the profiles were realized using different hydrophilic/hydrophobic modifications with small channel widths. The round profile channels with 10%-30% aspect ratios were obtained.

Trailing Edge Film Cooling of Gas Turbine Airfoils—External Cooling Performance of Various Internal Pin Fin Configurations

Abstract The present paper describes an experimental study on trailing edge film cooling of modern high pressure turbine blades using coolant ejection through planar slots on a pressure side cutback. The experimental test section consists of a generic scaled-up trailing edge model in an atmospheric open loop wind tunnel, which has been used in several earlier studies. An infrared thermographic measurement technique is employed, which allows for the application of engine-realistic density ratios around 1.6 by increasing the main flow temperature. The effects of different geometric configurations on the structure and performance of the cooling film are investigated in terms of film cooling effectiveness, heat transfer, and discharge behavior. Among other issues, the interaction of internal turbulators, namely, an array of pin fins, with the ejection slot lip is of major interest. Therefore, different designs of the coolant ejection lip are studied. Four different ratios of lip thickness to ejection slot height (t/H=0.2,0.5,1.0,1.5), as well as three different lip profiles representing typical manufacturing imperfections and wear, are investigated. Other geometric variations comprise elliptic pin fins with spanwise and streamwise orientations and the application of land extensions from the internal coolant cavity onto the cutback surface. The blowing ratio is varied at 0.2&amp;lt;M&amp;lt;1.25. In terms of film cooling effectiveness, the results show a strong dependency on ejection lip thickness, and minor improvements are obtained with a rounded ejection lip profile. Significant improvements are achieved using land extensions. The elliptic pin fins have a strong effect on discharge behavior as well as on film cooling effectiveness and heat transfer. Except for the elliptic pin fins, the geometric variations have only a minor influence on heat transfer.

A comparative study of fracture in Al: Quantum mechanical vs. empirical atomistic description

A comparative study of fracture in Al is carried out by using quantum mechanical and empirical atomistic description of atomic interaction at crack tip. The former is accomplished with the density functional theory (DFT) based quasicontinuum method (QCDFT) and the latter with the original quasicontinuum method (EAM-QC). Aside from quantitative differences, the two descriptions also yield qualitatively distinctive fracture behavior. While EAM-QC predicts a straight crack front and a micro-twinning at the crack tip, QCDFT finds a more rounded crack profile and the absence of twinning. Although many dislocations are emitted from the crack tip in EAM-QC, they all glide on a single slip plane. In contrast, only two dislocations are nucleated under the maximum load applied in QCDFT, and they glide on two adjacent slip planes. The electron charge density develops “sharp corners” at the crack tip in EAM-QC, while it is smoother in QCDFT. The physics underlying these differences is discussed.

Effects of histamine H1R—H4R—agonist on the airway epithelium of rabbits

Objective To explore the exact role of histamine receptors in respiratory system. Methods The cohort comprised of six groups (group I control and group II-VI treated) containing five rabbits in each group. Control-group received vehicle (sterile distilled water) and treated groups received subcutaneous histamine (100 μg/kg, b.i.d.), and H1R-agonist (HTMT), H2R-agonist (amthamine), H3R-agonist (R-(−)-α-methylhistamine) and H4R-agonist (clobenpropit) each in a dose of 10 μg/kg, b.i.d. for 30 subsequent days. After completion of treatment, animals were euthanized and perfused with 10% buffered formalin. Small tissue blocks of trachea and lungs were processed for paraffin embedding. Observations were recorded in sample photomicrographs taken from 10 μm thick. Haematoxylin and eosin stained sections. Results It was observed that trachea and bronchi from histamine, H1R and H4R groups had only patches of hyperplastic and hypertrophied epithelium and in general, cells in the affected region were taller heaped up. The bronchiolar epithelia from all treated groups showed hypertrophy and hyperplasia throughout with most of the cells having rounded profile and appeared to bud out from the basal cells. Conclusions It is concluded that histamine receptors on induction via its specific agonist can induce hypertrophy, hyperplasia of respiratory tract epithelia suggesting its role akin to growth stimulating factor and warranting further long-term study.

Buckled Bridges Using Film Stress for Three‐Dimensional Structures: Effects of Lateral Designs on Vertical Profiles and Dynamic Characteristics

AbstractBridges buckled by film stress can generate a vertical displacement resulting in three‐dimensional structures. We have demonstrated a micromirror lifted by buckled bridges and a vertical comb drive actuator. The structures show rounded profiles in a stable manner. The detailed profiles of the bridges and the lifted micromirrors are examined. The relations between the lateral design and its effect on the vertical profile and the dynamic characteristics are studied. Copyright © 2010 Institute of Electrical Engineers of Japan. Published by John Wiley &amp; Sons, Inc.

In vitro evaluation of a nitinol based vein cuff for external valvuloplasty

This study shows first in vitro tests of a nitinol based vein cuff developed for external valvuloplasty. In contrary to currently existing vein cuffs the tested model enables minimal invasive implantation and also maintains its round pre-shaped profile at body temperature (37 degrees C). The examination of the cuff surface structure by scanning electron microscopy, profilometry and X-ray photoelectron spectroscopy after sterilization with ethylene oxide and before cyto-compatibility testing revealed a nearly smooth surface (mean square roughness Rq 66 +/- 33 nm) which was primarily composed of nickel, oxygen, titanium, carbon and silicon where nickel was the least fraction (Ni: 0.7%, Ti: 1.7%, Si: 15.8%, O: 29.5%, C: 52.3%) of the surface elements. Si and C are supposed to be contaminations caused by a final cuff polishing with silicon carbide at the end of the manufacturing process. To evaluate cyto-compatibility initial cell adherence and cell activity were assessed. The results showed good initial cell adherence of L929 fibroblast-like cells on the cuff surface already after 24 h. The results also revealed no inhibitory effects on the activity of these cells (MTS test) later on. The test setup developed to analyse functionality in a dynamic mode was shown to be suited at blood pressures up to 300 mmHg. The cuff successfully limited dilation of varicose veins (Vena saphena magna) at physiological blood pressures (< 120 mmHg) and also in cases of hypertonia (300 mmHg) to the diameter determined by the cuff (4.0 mm) over thecomplete testing period. This indicates that the clasp based cuff closure mechanism is suited to close the cuff under variable physiological and pathological blood pressure conditions. The cuff structure only allowed minimal adaptation on the inhomogenously dilating vein profile in the both peripheral cuff modules. Both peripheral modules followed the vessel dilation in correlation to the applied pressure. At pressures within the physiological range </= 120 mmHg) the variation of the lateral arch module diameter was only marginal, whereas at 300 mmHg pressure the peripheral modules followed vein dilation up to a diameter of 5.0 to 5.5 mm. The cuff also maintained the pre-shaped round profile in the central and peripheral modules during the pressure increase and the consecutive cuff expansion. The study showed that the first nitinol based vein cuff for external valvuloplasty was processed well enough by electropolishing and sterilization to allow culturing of L929 fibroblast-like cells on the cuff surface as a test of general biocompatibility. The cuff also proved to limit dilation of varicose veins at physiological and pathological blood pressures in vitro. Further tests with primary cells from the venous wall will follow to test the specific biocompatibility before tests in vivo can be envisaged.

The initial process of enamel prism arrangement and its relation to the Hunter-Schreger bands in dog teeth

The three-dimensional architecture of enamel prisms at early stages of enamel formation and its spatial relationship to the Hunter-Schreger bands were examined in canine tooth germs by light and electron microscopy. In serial semithin sections of demineralized tooth germs tangential to the enamel-dentin junction, a straight row of enamel prisms was depicted along the longitudinal tooth axis at the level of the enamel-dentin junction and then their three-dimensional arrangement was reconstructed using computer software. The spatial arrangement of the groups of enamel rods oriented in specific sideward directions was also reconstructed in deep layers of the enamel. Initially, all enamel prisms were parallel to perpendicular toward the enamel-dentin junction, but at 10µm from the enamel-dentin junction, some small specks, or groups of enamel prisms--tilting to the right or the left--emerged as small islands. In each speck of enamel prism, the inclined prisms were uniformly oriented in a sideward direction and gradually expanded their boundary until merging with the neighboring specks inclined in the same direction. Consequently, at 50µm from the enamel-dentin junction, the group of enamel prisms oriented either to the right or the left formed alternately arranged horizontal belt-like zones, corresponding to the parazone or the diazone of the Hunter-Schreger bands. Reversed images of scanning electron-micrographs of the exposed surfaces of the developing enamel revealed round and bulb-like profiles of Tomes' processes at early amelogenesis and its changes into a characteristic structure combined with flat secretory and enclosing nonsecretory faces that dictated the orientation of corresponding enamel prisms. The results suggest that the groups of enamel prisms oriented in sideward directions first appear as small island-like specks near the enamel-dentin junction, which later merge and form alternating horizontal belt-like zones as a consequence of morphological changes of the Tomes' processes. However, the mechanisms whereby the functional grouping of secretory ameloblasts with similarly oriented Tomes' processes is induced are yet to be determined.

Dual Roles for Perivascular Macrophages in Immune-to-Brain Signaling

Cytokines produced during infection/inflammation activate adaptive central nervous system (CNS) responses, including acute stress responses mediated by the hypothalamo-pituitary-adrenal (HPA) axis. The mechanisms by which cytokines engage HPA control circuitry remain unclear, though stimulated release of prostanoids from neighboring vascular cells has been implicated in this regard. How specific vascular cell types, endothelial cells (ECs) versus perivascular cells (PVCs; a subset of brain-resident macrophages), participate in this response remains unsettled. We exploited the phagocytic activity of PVCs to deplete them in rats by central injection of a liposome-encapsulated proapoptotic drug. This manipulation abrogated CNS and hormonal indices of HPA activation under immune challenge conditions (interleukin-1) that activated prostanoid synthesis only in PVCs, while enhancing these responses to stimuli (lipopolysaccharide) that engaged prostanoid production by ECs as well. Thus, PVCs provide both prostanoid-mediated drive to the HPA axis and an anti-inflammatory action that constrains endothelial and overall CNS responses to inflammatory insults.

A New Species of Corydoradinae Catfish (Ostariophysi: Siluriformes: Callichthyidae) from Rio Solimões Basin, Brazil

Abstract A new species of Corydoras from the Rio Urucu basin, a right-bank tributary of the Rio Solimoes is described. The new species shares a distinctive pigmentation pattern with Corydoras arcuatus, C. gracilis, and C. narcissus, composed of a uniform light ground color on the body, and a dark, arched stripe from tip of snout to caudal-fin base along the upper portion of the dorsolateral body plates. The new species is readily distinguished from these congeners by the absence of a continuation of the arc-like stripe onto the snout. It also differs from Corydoras gracilis and C. narcissus by the posterior part of the arc-stripe reaching the base of the lower caudal-fin rays, and from C. arcuatus and C. narcissus by the distinctly rounded profile of the snout in lateral view, a greater preadipose distance, and the position of the posterior limit of the cleithrum. Despite the general resemblance, investigation about the position of the new species in light of previous phylogenetic hypotheses concerning th...

An Extension of the Two-Dimensional JKR Theory to the Case with a Large Contact Width

In the Hertz and JKR theories, parabolic assumptions for the rounded profiles of the sphere or cylinder are adopted under the condition that the contact radius (width) should be very small compared to the radius of the sphere or cylinder. However, a large contact radius (width) is often found in experiments even under a zero external loading. We aim at extending the plane strain JKR theory to the case with a large contact width. The relation between the external loading and the contact width is given. Solutions for the Hertz, JKR and rounded-profile cases are compared and analyzed. It is found that when the ratio of a/R is approximately larger than about 0.4, the parabolic assumptions in the Hertz and JKR theories are no longer valid and the exact rounded profile function should be used.

Localization of the Shear Zone in Extrusion Processes by Means of Finite Element Analysis

A characteristic feature of extrusion processes is the formation of a shear zone, which separates the deformation zone and the dead metal zone [1, 2]. The deformations occurring in the shear zone cause inner separation and welding effects, which are of great importance for the material flow and the microstructure development of the extruded profiles. The material in the dead metal zone is not participating directly in the forming process but the shape of this zone influences eminently the forming zone and thus the forming of the extruded profile. Furthermore the extreme shear deformation causes according to the Hall-Petch relationship a significant grain refinement in these regions of extruded profiles [3, 4]. So the knowledge on the effects in the shear zone during extrusion processes is fundamental for subsequent numerical investigations on the microstructure development for example regarding quenching techniques. The aim of this study is to localize the formation of the shear zone during extrusion processes by means of the finite element analysis. On the basis of the assumption that separation and welding effects take place in the shear zone, numerical investigations were carried out to indicate these microscopic effects on the macroscopic scale. The considered process was the extrusion of a solid round profile of the alloy EN AW 6082 at 450°C with a punch velocity of 10.5 mm/s. For the localization of the shear zone mechanical parameters were chosen for a shear criterion, which are taken from numerical simulations. A user subroutine was implemented into the FE-models in order to evaluate the shear criterion for the localization of the shear zone. According to [5, 6] the friction model used for the numerical simulations has a strong influence on the formation of the shear zone. In this study a combined friction model according to [7] was used.