Concave Profile Research Articles

Experimental assessment on the contact characteristics of 3D printed flexible poly lactic acid (PLA) soft fingertips

Abstract This purpose of this research work primarily focuses on assessing the contact characteristics of a novel 3D printed flexible poly lactic acid (PLA) fingertip exposed to a normal load ranging from 1–750 N. The 3D printed fingertip is pressed against three different target surfaces having concave, convex and flat profiles to facilitate a rational comparison. The growth of contact area is recorded for a wide range of applied normal force against the fingertip on logging sheets and the same is converted in vector format for facilitating digital measurements. From close examination of the results, it may be noted that the rate of growth of contact area follows the parametric relationship a = cN γ . A weighted least squares fit algorithm is used to formulate the parametric relationship based on experimental data. Further, the contact characteristics of the 3D printed fingertip follows the same pattern of soft neoprene fingertip, and it is well in line with the expected results. Hence, it is evident that 3D printed fingertips could be utilized for handling fragile to hard objects and capable of handling multi-profiled objects in dexterous robotic manipulation. Moreover, complex profiled fingertips can easily be manufactured by 3D printing, and it can be considered as a better alternative for conventionally manufactured anthropomorphic robotic grippers. Practical implications of this research will be highly useful for development of soft-fingered robotic grippers for dexterous robotic manipulations.

Numerical Investigation on the Effect of Profile and Blade Numbers in a Savonius Vertical Axis Wind Turbine

Small-scale wind turbines are considered recently as an attractive source of renewable energy, especially at remote area with respect to city centre. The design and characterization of a small vertical wind turbine are introduced through this work. A CFD analysis has been used as a first step in design to simulate the flow around the vertical blades of the small wind turbine. Different parameters have been taken into account in this work such as blades number, shape, and existence of stator blades deflector. Three different versions depend on blade profile have been examined. The turbulence model with sliding mesh in CFD have been performed. In this paper, a performance of small-scale of vertical wind turbine represented by CFD results of power coefficient, and optimal freestream velocity of this model are presented. The results showed that using 8 blades of VAWT instead of 4 blades with the same profile of blade has enhanced VAWT performance up to 64%. Also, increasing the concave profile of the blade can rise the torque produced by approximately 8%, however more increase in concave shape cause drop down by 5.6 %. Moreover, including stator deflector to the VAWT design has ability to increase the torque produced by 70 %. The output of these results will help to choose the optimum configuration of the small vertical wind turbine to implement this design experimentally as a next step.

Feedbacks between sea-floor spreading, trade winds and precipitation in the Southern Red Sea

Feedbacks between climatic and geological processes are highly controversial and testing them is a key challenge in Earth sciences. The Great Escarpment of the Arabian Red Sea margin has several features that make it a useful natural laboratory for studying the effect of surface processes on deep Earth. These include strong orographic rainfall, convex channel profiles versus concave swath profiles on the west side of the divide, morphological disequilibrium in fluvial channels, and systematic morphological changes from north to south that relate to depth changes of the central Red Sea. Here we show that these features are well interpreted with a cycle that initiated with the onset of spreading in the Red Sea and involves feedbacks between orographic precipitation, tectonic deformation, mid-ocean spreading and coastal magmatism. It appears that the feedback is enhanced by the moist easterly trade winds that initiated largely contemporaneously with sea floor spreading in the Red Sea.

A polynomial framework for design of drag reducing periodic two-dimensional textured surfaces

Periodic and symmetric two-dimensional textures with various cross-sectional profiles have been employed to improve and optimize the physical response of the surfaces such as drag force, superhydrophobicity, and adhesion. While the effect of the height and spacing of the textures have been extensively studied, the effect of the shape of the textures has only been considered qualitatively. Here, a polynomial framework is proposed to mathematically define the cross-sectional profiles of the textures and offer a quantitative measure for comparing the physical response of the textured surfaces with various shapes. As a case study, textured surfaces designed with this framework are tested for their hydrodynamic frictional response in the cylindrical Couette flow regime in Taylor–Couette flows. With the reduction in torque as the objective, experimental and numerical results confirm that textures with height-to-half-spacing ratios of lower and equal to unity with concave profiles offer a lower torque compared to both smooth surfaces and triangular textures. In addition, across multiple polynomial orders, textures defined by second-order polynomials offer a wide range of responses, eliminating the need for considering polynomials of higher orders and complexity. While the case study here is focused on the laminar flow regime and the frictional torque, the same type of analysis can be applied to other surface properties and physical responses as well.

Technology of Manufacturing of ZC Cylindrical Worm.

Cylindrical worms are generally machined by the hobbing method using rotary tools, and they are formed in the finishing pass at the full profile height. In this case, the profile of the tool-action surface determines the profile of the machined surface, and for technological reasons, a rectilinear (less frequently circular) axial profile of the tool-action surface is generally assumed. In the currently known technology, machining takes place on special machine tools, and on tools that are specially prepared for a specific outline. The research objective of the article is to present the possibility of creating a helical surface with a circular concave profile on a CNC lathe with a universal tool: a ball-end mill cutter. In the case of the proposed processing method, the surface of the worm is shaped with a spherical-end mill cutter in many passes, and its shape depends on the setting of the tool. This machining method must be performed on CNC machines, and the tool is not geometrically related to the shape of the machined profile. The paper presents the mathematical apparatus for generating a concave helical surface. Based on the calculations, the worm was processed with a spherical-end mill on a CLX350 V4 DMG MORI turning machining center. The surface-quality analysis was carried out on a contact profilographometer, while the dimensional accuracy was verified on a coordinate-measuring machine, and the maximum tolerance field of the measurement was 13 μm. On the basis of the measurements made, the accuracy of the worm outline is consistent with the theoretical assumptions. Using the presented method of machining, we can shape helical surfaces with an assumed profile in the axial section on a CNC machine tool with the use of universal tools.

A Shock Loss Reduction Method Using a Concave Suction Side Profile for a Zero Inlet Swirl Turbine Rotor

Abstract A zero inlet swirl turbine rotor (ZISTR) works with axial inlet gas flow directly exhausted from a combustion chamber without any upstream vanes. The suction side trailing edge shock of the ZISTR generates a significant amount of aerodynamic loss. A shock loss reduction method is presented for the ZISTR. The principle of the method is to replace the single shock by double shocks. For minimizing the shock loss, the strength of the double shocks is set to be equal. This is based on a design criterion that multiple shocks should be with equal strength to achieve the minimum shock loss. This design criterion has been widely used for supersonic inlet design, but it is first extended to the transonic turbine design in the present article. A shock model, using aerodynamic relations of oblique shock, is put forward to quantitatively determine the shape of the concave suction-side profile. Numerical simulations indicate that the concave suction-side profile induces a new shock upstream of the suction-side trailing edge shock, and these two shocks are with nearly equal strength in the improved ZISTR. The shock loss of the improved ZISTR is obviously reduced. The concave tip profile would redistribute the blade load on the tip and increase the tip leakage flow loss. Hence, it is suggested that the concave profiles should be designed between 0% and 80% blade span, and the tip profile should keep unchanged. The improved ZISTR with an unchanged tip profile achieves an improvement of turbine efficiency by 0.8% at the design condition.

Active mechanical metamaterial with embedded piezoelectric actuation

Metamaterials are artificially structured materials and exhibit properties that are uncommon or non-existent in nature. Mechanical metamaterials show exotic mechanical properties, such as negative stiffness, vanishing shear modulus, or negative Poisson’s ratio. These properties stem from the geometry and arrangement of the metamaterial unit elements and, therefore, cannot be altered after fabrication. Active mechanical metamaterials aim to overcome this limitation by embedding actuation into the metamaterial unit elements to alter the material properties or mechanical state. This could pave the way for a variety of applications in industries, such as aerospace, robotics, and high-tech engineering. This work proposes and studies an active mechanical metamaterial concept that can actively control the force and deformation distribution within its lattice. Individually controllable actuation units are designed based on piezostack actuators and compliant mechanisms and interconnected into an active metamaterial lattice. Both the actuation units and the metamaterial lattice are modeled, built, and experimentally studied. In experiments, the actuation units attained 240 and 1510 µm extensions, respectively, in quasi-static and resonant operation at 81 Hz, and 0.3 N blocked force at frequencies up to 100 Hz. Quasi-static experiments on the active metamaterial lattice prototype demonstrated morphing into four different configurations: Tilt left, tilt right, convex, and concave profiles. This demonstrated the feasibility of altering the force and deformation distribution within the mechanical metamaterial lattice. Much more research is expected to follow in this field since the actively tuneable mechanical state and properties can enable qualitatively new engineering solutions.

Anterior implant restorations with a convex emergence profile increase the frequency of recession: 12-month results of a randomized controlled clinical trial.

To test whether the emergence profile (CONVEX or CONCAVE) of implant-supported crowns influences the mucosal margin stability up to 12 months after insertion of the final restoration. Forty-seven patients with a single implant in the anterior region were randomly allocated to one of three groups: (1) CONVEX (n= 15), implant provisional and an implant-supported crown both with a convex profile; (2) CONCAVE (n= 16), implant provisional and an implant-supported crown both with a concave profile; (3) CONTROL (n= 16), no provisional (healing abutment only) and an implant-supported crown. All patients were recalled at baseline, 6, and 12 months. The stability of mucosal margin along with clinical, aesthetic, and profilometric outcomes as well as time and costs were evaluated. To predict the presence of recession, multivariable logistic regressions were performed and linear models using generalized estimation equations were conducted for the different outcomes. Forty-four patients were available at 12 months post-loading. The frequency of mucosal recession amounted to 64.3% in group CONVEX, 14.3% in group CONCAVE, and 31.4% in group CONTROL. Regression models revealed that a CONVEX profile was significantly associated with the presence of recessions (odds ratio: 12.6, 95% confidence interval: 1.82-88.48, p= .01) compared with the CONCAVE profile. Pink aesthetic scores amounted to 5.9 in group CONVEX, 6.2 in group CONCAVE, and 5.4 in group CONTROL, with no significant differences between the groups (p= .735). Groups CONVEX and CONCAVE increased the appointments and costs compared with the CONTROL group. The use of implant-supported provisionals with a CONCAVE emergence profile results in a greater stability of the mucosal margin compared with a CONVEX profile up to 12 months of loading. This is accompanied, however, by increased time and costs compared with the absence of a provisional and may not necessarily enhance the aesthetic outcomes. German Clinical Trials Register; DRKS00009420.

Assessment of thermal distribution through an inclined radiative-convective porous fin of concave profile using generalized residual power series method (GRPSM)

The thermal distribution in a convective-radiative concave porous fin appended to an inclined surface has been examined in this research. The equation governing the temperature and heat variation in fin with internal heat generation is transformed using non-dimensional variables, and the resulting partial differential equation (PDE) is tackled using an analytical scheme, generalized residual power series method (GRPSM). Moreover, a graphical discussion is provided to examine the consequence of diverse non-dimensional variables including the parameters of convection-conduction, ambient temperature, radiation, heat generation, and porosity effect on the thermal field of the fin. Also, a graph is plotted to analyze the variations in unsteady temperature gradient using the finite difference method (FDM) and generalized residual power series method (GRPSM). The major result of this investigation unveils that as the convection-conduction parameter scale upsurges, the distribution of temperature in the fin diminishes. For the heat-generating parameter, the thermal distribution inside the fin increases.

Paranasal Augmentation: A Viable and Simplified Modality With Diced Expanded Polytetrafluoroethylene.

A flat or concave lower midface profile is generally considered less attractive. Paranasal augmentation is usually performed to move paranasal deficiency to relative convexity. Herein, we present a viable and simplified modality with diced expanded polytetrafluoroethylene to correct paranasal deficiency. Between February of 2020 and April of 2021, 19 patients underwent procedures to correct paranasal deficiency. Paranasal augmentation was performed with diced expanded polytetrafluoroethylene. All procedures were performed via intranasal approach. Preoperative and postoperative photographs were taken. Of these 19 patients (18 women and 1 man), deficiency of 18 patients were caused by congenital factors and 1 by cleft deformities. All but 1 procedures were carried out bilaterally. Procedures were performed in conjunction with additional operations mainly including rhinoplasty and minimally invasive midface lift. Age of patients ranged from 19 to 57 years, with a mean of 37 years. Follow-up time ranged from 8 to 22 months, with a mean of 12.6 months. All patients were satisfied with esthetic improvement and facial holistic profile. No severe complications and reoperation arisen in any of the patients. Temporary discomfort involved foreign body sensation in 1 case and numbness in 2 cases. The present technique provides a viable and simplified method to give the face a more balanced appearance and achieves esthetically superior results.

The Correction of Multiple Diastemas in Adult Patients with Bad Tongue Habit (A Case Report)

There are various options in multiple diastemas correction due to the multifactorial malocclusion aetiology. The treatment of this malocclusion is a challenging task for clinicians not only for aesthetic achievement but also for the stability of orthodontic treatment. The multidisciplinary approaches depend on the aetiology of malocclusion and patient compliance. This reported case aims to describe the correction of multiple diastemas in adult patients with bad tongue habits. A 27-year-old male patient came to dental hospital Universitas Sumatera seekingrthodontics treatment with multiple spacing as the chief complaint. The comprehensive lateral cephalometry analysis showed class III skeletal malocclusion, concave profile skeletal trend, and abnormal dental inclination. There was also tongue thrusting in speech and swallowing based on functional examination. The initial orthodontic treatment was started by controlling the patient’s bad tongue habit along with orthodontic treatment. After seven-month of orthodontic treatment, this malocclusion was corrected and good interdigitation was achieved. Albeit there were no skeletal significant changes in this orthodontic treatment, the dental inclination showed a significant change based on cephalometry evaluation analysis. The success of the orthodontic treatment in the adult patient is not only dependent on proper mechanotherapy but also relied on the patient’s compliance with tongue habit control. Therefore, early bad oral habit detection as one of the etiologic factors in treating this malocclusion can support the success of orthodontic achievement.

Improving profile accuracy and surface quality of blisk by electrochemical machining with a micro inter-electrode gap

Electrochemical machining (ECM) has emerged as an important option for manufacturing the blisk. The inter-electrode gap (IEG) distribution is an essential parameter for the blisk precise shaping process in ECM, as it affects the process stability, profile accuracy and surface quality. Larger IEG leads to a poor localization effect and has an adverse influence on the machining accuracy and surface quality of blisk. To achieve micro-IEG (<50 μm) blisk finishing machining, this work puts forward a novel variable-parameters blisk ECM strategy based on the synchronous coupling mode of micro-vibration amplitude and small pulse duration. The modelling and simulation of the blisk micro-IEG machining have been carried out. Exploratory experiments of variable-parameters blisk ECM were carried out. The results illustrated that the IEG width reduced with the progress of variable parameter process. The IEG width of the blade’s concave part and convex part could be successfully controlled to within 30 μm and 21 μm, respectively. The profile deviation for the blade’s concave surface and convex surface are 49 μm and 35 μm, while the surface roughness reaches Ra = 0.149 μm and Ra = 0.196 μm, respectively. The profile accuracy of the blisk leading/trailing edges was limited to within 91 μm. Compared with the currently-established process, the profile accuracy of the blade’s concave and convex profiles was improved by 50.5 % and 53.3 %, respectively. The surface quality was improved by 53.2 % and 50.9 %, respectively. Additionally, the machined surface was covered with small corrosion pits and weak attacks of the grain boundary due to selective dissolution. Some electrolytic products were dispersed on the machined surface, and their components were mainly composed of the carbide and oxide products of Ti and Nb elements. The results indicate that the variable-parameters strategy is effective for achieving a tiny IEG in blisk ECM, which can be used in engineering practice.

Orthodontic Correction of a Completely Transposed Impacted Maxillary Canine

In complete dental transposition, aligning the transposed teeth to its normal anatomic position is always a complicated and difficult challenge, which needs multiple clinical considerations. This case report illustrates an orthodontic treatment of a 20-year-old female patient who had a concave profile, skeletal and dental Class III malocclusion with anterior crossbite and complete transposed maxillary left lateral incisor and impacted canine. The correction of transposition was performed by moving the canine by maintaining its high position in the vestibular fold and use lever arm and temporary anchorage device (TAD) to facilitate traction of the maxillary canine. Vestibular incision subperiosteal tunnel access (VISTA) technique also provided as a minimally invasive approach for the tooth exposure. After 48-month of treatment duration, improvement of facial profile and favorable occlusion were achieved with the involved teeth that were moved to their clinically normal sequence without extraction.

On the performance of cyclone separators with different shapes of the conical section using CFD

The present work evaluates the effect of various geometrical shapes of the conical segment on cyclone performance. For this, five different shapes of the cone walls viz. a straight profile, concave profile, convex profile, followed by hybrid concave-convex as well as convex-concave profiles, are analysed. The performance of all the models is predicted using the Reynolds stress model considering two pressure-strain options viz. the linear pressure-strain and the stress-omega models – the latter very well captures the mean velocity field, coherent fluctuations, and the precessing frequency of the vortex core. The different profiles of the conical segment were found to affect pressure drop more than the collection efficiency. Conclusive results indicate that the performance of the convex variant – particularly at high flow rates – outperforms the baseline model and other variants and could be preferred over the conventional design. The concave variant experiences the highest pressure drop with enhanced collection efficiency.

Cavity-dumped burst-mode Nd:YAG laser master-oscillator power-amplifier system with a flat-top beam output realized by gain profile-controlled side pumping.

We report a compact cavity-dumped burst-mode Nd:YAG laser master-oscillator power-amplifier system with a flat-top intensity distribution across the output-beam section. Custom-designed gain profile-controlled diode side pumping modules providing flat-top and concave gain profiles were utilized to generate a uniform beam profile and suppress thermal lensing during amplification, respectively. Bursts with an energy of 2.0 J and duration of 1.6 ms were operated at 10 Hz. Within the bursts, single pulses with an energy of 12.7 mJ and pulse width of 3.3 ns were achieved at 100 kHz.

CFD Investigations of Cyclone Separators with Different Cone Heights and Shapes

Due to the great achievements in the field of optimization of the design of cyclone separators, non-standard solutions are sought to increase their performance. Therefore, in this study, we consider the impact of different cone and cylinder height variants on the performance of cyclone separators. Additionally, we propose non-standard shapes for these sections. Three different heights: H/D = 0.5, 1.0, and 1.5, with D (the main cyclone body diameter), are analyzed. Since the cone is one of the most important geometrical entities, three different shapes viz. a straight (conventional) profile, a concave profile as well as a convex profile are also taken into account. Cyclone performance is rated at three different inlet velocities viz. Uin = 10 m/s, 15 m/s, and 20 m/s. Hence, a total of 27 simulations have been performed using the Reynolds stress model. It becomes apparent from the present study that the pressure loss is lowest in the convex variant, whereas the separation efficiency is better in the conventional design. Furthermore, an increase in the length of the cylindrical section reduces pressure drop with a mild decrease in the collection efficiency in all variants.

Forming of Multiple Straight Convex Shapes on Aluminum Sheet Using Impulsive Water Pressure

Several types of multiple straight convex shapes were formed on a thin aluminum sheet with a grooved die using impulsive water pressure. The maximum pressure was 160 MPa in the high-speed forming, wherein a drop hammer testing machine was used, whereas it was 100 MPa in the low-speed forming because of the limitations of the press machine. The effects of the forming speed, cross-sectional shape, and pitch of the grooves on the deformation behavior were investigated. The increase in the impulsive water pressure was found to be affected significantly by the compressibility of water. The symmetricity of the convex shape in the cross-section decreased at both ends for a smaller pitch because of the imbalance of the material flow at both peripheries of the groove. The concave surface profile of the pressure side was more rounded in the high-speed forming than that in the low-speed forming when semicircular and rectangular grooved dies were used. This may be attributed to the fact that the plastic deformation becomes more uniform owing to the positive strain rate sensitivity of the test material. In the forming with rectangular grooves, fracture occurred under the low- and high-speed conditions, wherein the maximum pressure was set to 100 MPa. However, the material did not fracture during high-speed forming with a pressure of 160 MPa, where the convex shape was higher and the material contacted the bottom of the groove. This behavior may be because the dislocation density of the material did not increase rapidly owing to the strain rate being maintained high until the material suddenly stopped deforming in the latter condition. In forming with a trapezoidal grooved die, the formed profiles were considerably similar under all conditions because the strain was considerably smaller than that with the other grooves.

Probable ice-rich deposits on north-facing slopes in Alba Patera, Mars

We examine unconformable lobate deposits along the north-facing slopes of Alba Patera (40°N, 250°E with an elevation of ~6 km), Mars, using data from the Mars Reconnaissance Orbiter Context Camera, High-Resolution Imaging Science Experiment, and the Mars Orbiter Laser Altimeter. We interpret the lobate north-facing slope deposits (NSFDs) to be small (<3 km from source to toe) lobate debris aprons (LDAs), making them the highest-elevation LDAs yet identified on Mars. The total volume of the deposits along the caldera walls is ~5–11 km3. Deposits filling impact craters around the Alba Mons summit appear to be similar to the NFSDs. These NFSDs bear two distinct textures either singly or together: a hummocky surface of decameter-scale hills and a smooth surface. Smooth-textured NFSDs have lobate margins and convex-up topographic profiles, and show evidence of having flowed; hummocky NSFDs have concave or linear topographic profiles and are generally found on steep slopes. These deposits likely formed due to reduced insolation on north-facing slopes, which allowed for the preferential accumulation or preservation of water ice. The presence of small LDAs restricted to north-facing slopes could indicate that Alba Patera was only a marginal environment for glaciation, possibly because little water vapor was available at such a high elevation. The hummocky material is interpreted to be the eroded remnants of a mantle of ice-cemented dust that was superposed on the NFSDs. This mantle has been almost completely removed in smooth-textured areas. This difference in rates of ice removal was the result of either lower insolation on steep north-facing slopes than on shallow slopes or the greater mobility of the thicker, lobate portions of NFSDs producing a more densely fractured mantle.

Hydrodynamic performance of concave front pile-supported breakwaters integrated with a louver wave screen

Pile supported breakwaters for water depths greater than 20 m are environmentally friendly and are more economical than the rubble mound breakwaters. An experimental investigation is carried out to explore the hydrodynamic performance of two different concave front pile-supported breakwaters integrated with a louver wave screen (LWS) on their seaside. The LWS consists of an array of plates inclined at 60° to the horizontal and mounted one above the other with spacing such that the porosity is 25%. The breakwater models are subjected to the action of regular waves in a wave flume covering intermediate to deep-water conditions. It is found while, the wave transmission past the breakwaters in presence of LWS is not significantly altered, the reflection from the structure significantly reduces, the rate of reduction being higher for the model with a steeper slope. The study also shows a reduction in the wave run-up and induced pressures over the concave profiles in the presence of LWS. The usefulness of wave screens in improving the performance of a breakwater depends on the breakwater profile in addition to the type of the wave screen which is the main finding of the study.

Prevalence of Malocclusion in Mewat District of Haryana: A Cross-sectional Study.

Aim and objectiveTo determine the prevalence of malocclusion in the Mewat district of Haryana.Materials and methodsA cross-sectional study was conducted in government/private schools of Mewat district. A total of 3,042 subjects were selected, age ranging from 11-18 years. Parameters studied were molar relationship, facial profile, overjet, overbite, reverse overjet, open bite, and supernumerary teeth. The Chi-square test was used for calculating the p -value.ResultsThe prevalence of normal occlusion was seen in 77.4%, Angle's class I malocclusion was present in 13.5%, class II in 7.7%, and class III was seen in 2.8% of the study population which is statistically significant. Straight facial profile was observed in 91%, 7.9% had convex and 1.08% had a concave profile. Increased overjet was present in 33.5% of cases and reverse overjet was seen in 1.08%. The normal overbite was recorded in 70%, increased bite was seen in 29% and the open bite was present in 0.95% of the examined population, supernumerary teeth were seen in 18 children.ConclusionThere is a high prevalence of normal occlusion in the Mewati population. The results may provide baseline data for research and planning orthodontic services.How to cite this articleSharma A, Bihani T. Prevalence of Malocclusion in Mewat District of Haryana: A Cross-sectional Study. Int J Clin Pediatr Dent 2022;15(1):90-93.