Convex Profile Research Articles

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.

Divergence of High-Order Harmonic Generation by a Convex Plasma Surface

The electron density profile on a plasma surface has a decisive influence on the mechanism and characteristics of the plasma high-order harmonic generation. When the pre-pulse has a similar spatial and temporal distribution as the main laser pulse, the plasma surface on the target will expand to form a convex profile of the similar size as the focal spot of the main pulse. We experimentally observed that the divergence of the harmonics generated by the relativistic laser light incident on a silica target has a saddle-shaped structure. The two-dimensional particle-in-cell simulation with convex plasma surfaces explains the experimental results very well and infers a 0.12λL plasma scale length around the center of the convex profile. Further, we qualitatively explained that the asymmetry of the saddle-shaped harmonic divergence is caused by oblique incidence.

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.

Investigation on Billets and Tools Geometry in Cold Forging of the Straight Bevel Gear

Straight bevel gears are an essential component of mechanical transmissions; they are widely used in the automotive, aerospace, shipbuilding industries and are made by shaping methods such as metal forming, casting, or machining. To market products, with proper function and properties, at a low cost, this gear component is usually fabricated by precise cold forging (the billet is forged in a closed-die at room temperature). In cold forging, the geometry of the billet and the forming tool plays an important role. It determines the ability to fill the die cavity, creating a finished product profile that meets the required geometric parameters. In this study, by 3D numerical simulation, some geometric shapes of workpieces and tools were investigated to find the optimal parameters. The results obtained from the simulation method were determined that a cylindrical workpiece with a tapered end and a die bottom with a convex profile will increase material flow velocity, improving cavity filling, uniform distribution stress in the forming specimen, and forging products without defects. Experimentally also verified the simulation results, which were cold forging with optimized workpiece and tool geometry, the straight bevel gear part was fully shaped, ensuring geometrical accuracy. The result of this study is a suggestion to apply to the design of a cold forging die for similar features.

An Eocene conger eel (Teleostei, Anguilliformes) from the Lillebælt Clay Formation, Denmark

A conger eel (Anguilliformes, Congridae) is described from the lower Lutetian concretionary nodules of the Lillebælt Clay Formation exposed at Trelde Næs, eastern Jutland, based on two partially complete articulated cranial skeletons. One of the cranial specimens exhibits an otolith void from which a cast was taken, used by Schwarzhans (2007) to describe the extinct Pseudoxenomystax treldeensis, which is placed herein within the new genus Smithconger gen. nov. Smithconger treldeensis (Schwarzhans, 2007) is characterized by well-developed lateral processes on the frontals, supraoccipital crest absent, sphenotic spine rather large, anteriorly pointed and exposed on the flattened surface of the skull roof, otic bullae considerably reduced, maxilla almost straight and distally pointed, maxillary and dentary teeth numerous and arranged in multiple rows, dentary with slightly convex ventral profile, opercle with smooth posterior margin and subopercle short. The otoliths of Smithconger treldeensis show high dorsal rim, broad and deep dorsal depression, no ventral furrow, sulcus straight, shallow, centrally positioned with anteriorly reduced colliculum, and ostial channel at anterior tip of colliculum short, not reaching the predorsal rim. The otolith-based species Bathycongrus waihaoensis Schwarzhans, 2019 from the Kaiatan (Bartonian/Priabonian) of New Zealand is also assigned to the genus Smithconger. Smithconger is tentatively referred to the congrid subfamily Congrinae due to the lack of hypohyals in the hyoid bar. This new Eocene genus of conger eel shows a certain degree of similarity with the extant Bassanago. The diversity and relationships of other Eocene congrids is also briefly discussed.

Orthodontic Treatment of Severe Bimaxillary Dentoalveolar Protrusion with Skeletal Class II Malocclusion Without Using Miniscrews

Bimaxillary dentoalveolar protrusion is characterized by the proclined anterior teeth, protrusive lips, and a convex profile. A proper orthodontic treatment modality for efficient anchorage control is necessary to retract the anterior teeth and improve the facial esthetics significantly. The commonly used miniscrew could provide absolute anchorage, however, it is accompanied by some risks and complications, especially in adolescent females. This case report described a 16-year-old female with diagnosis of skeletal Class II, normal mandibular plane angle, and Angle Class I malocclusion associated with proclined upper and lower anterior teeth, excessive overjet, and a convex profile with lip incompetence. We extracted her four first premolars first. Then, the Tip-Edge Plus bracket system and differential force method were applied to replace the temporary anchorage device. The total treatment duration was 27 months. Her dentoalveolar protrusion was decreased, both lips were significantly retracted, the mentalis strain was reduced, and her chin projection was improved. This case demonstrated that differential tooth movement with controlled light orthodontic forces could be an effective strategy to treat severe bimaxillary protrusion.

An Eocene conger eel (Teleostei, Anguilliformes) from the Lillebælt Clay Formation, Denmark

A conger eel (Anguilliformes, Congridae) is described from the lower Lutetian concretionary nodules of the Lillebælt Clay Formation exposed at Trelde Næs, eastern Jutland, based on two partially complete articulated cranial skeletons. One of the cranial specimens exhibits an otolith void from which a cast was taken, used by Schwarzhans (2007) to describe the extinct Pseudoxenomystax treldeensis, which is placed herein within the new genus Smithconger gen. nov. Smithconger treldeensis (Schwarzhans, 2007) is characterized by well-developed lateral processes on the frontals, supraoccipital crest absent, sphenotic spine rather large, anteriorly pointed and exposed on the flattened surface of the skull roof, otic bullae considerably reduced, maxilla almost straight and distally pointed, maxillary and dentary teeth numerous and arranged in multiple rows, dentary with slightly convex ventral profile, opercle with smooth posterior margin and subopercle short. The otoliths of Smithconger treldeensis show high dorsal rim, broad and deep dorsal depression, no ventral furrow, sulcus straight, shallow, centrally positioned with anteriorly reduced colliculum, and ostial channel at anterior tip of colliculum short, not reaching the predorsal rim. The otolith-based species Bathycongrus waihaoensis Schwarzhans, 2019 from the Kaiatan (Bartonian/Priabonian) of New Zealand is also assigned to the genus Smithconger. Smithconger is tentatively referred to the congrid subfamily Congrinae due to the lack of hypohyals in the hyoid bar. This new Eocene genus of conger eel shows a certain degree of similarity with the extant Bassanago. The diversity and relationships of other Eocene congrids is also briefly discussed.

EARLY TREATMENT OF CLASS II DIVISION 1 MALOCCLUSION USING TWIN BLOCK APPLIANCES: A CASE REPORT

Background: Malocclusion is dentofacial growth deviation from its normal size and shape, thus causing abnormal occlusion. One of its etiology is heredity. Removable twin block, a functional appliance that can be used in interceptive orthodontic treatment, can be used to treat Class II malocclusion with large overjet in children during skeletal growth and development. Case: An 11-year-old boy came to pediatric dental specialist clinic with Class II division 1 Angle malocclusion (SNA 82°; SNB 74°; ANB 8°, CVM CS 4, overjet 14 mm, overbite 7 mm, and convex profile). Removable twin block for Class II malocclusion was chosen as the therapy. Case management: Removable twin block appliance with acrylic occlusal bite block was used on maxilla and mandible separately. An angle of 70° was made in the occlusal bite block, which was made based on the bite registration wax during centric occlusion. This device is used 24-hours a day. Monthly dental visit was done to reduce the maxillary and mandibular occlusal bite blocks. After 9 months, an overjet of 5 mm was obtained. Cephalometry calculations became SNA 82°; SNB 7 9 °; ANB 3 °. The patient was given further phase 2 treatment with fixed orthodontic appliance. Conclusion: With proper case selection and good patient cooperation, removable twin block appliance can correct skeletal malocclusion, improve facial profile, reduce overjet and overbite, and correct molar relations.

Orthodontic management in an adult patient with a class II division 1 malocclusion using T-loop: A case report

The most common type of malocclusion encountered in India is a Class II div I malocclusion. They are distinguished by a mild to severe Class II skeletal base with an Angle’s Class II molar relation and Class II canine and incisor relations, proclined maxillary incisors, and an increased overjet, as well as a convex profile with incompetent lips. For the treatment of Class II div 1 malocclusion, various treatment modalities have been presented. This case study features a 15-year-old female with a Class II division 1 malocclusion, an orthognathic maxilla, and an 8mm overjet. Treatment goals included achieving functionally optimal and aesthetically acceptable occlusion, eliminating dental arch crowding, reducing overjet, and achieving competency of lips and a balanced soft tissue profile. The treatment plan called for extraction of the upper first and lower second premolars, followed by space closure with a T-loop. Following treatment, a satisfactory result was obtained with an ideal, static, and functional occlusion, facial profile, smile and lip competence, and treatment result stability.

A Study to Evaluate Cephalometric Hard Tissue Profile of Maharashtrian Population for Orthognathic Surgery

Aim: Variability exists in the ethnic groups that are separated by culture and geographic boundaries. The aim of this study was to evaluate hard tissue profile of well-balanced and clinically acceptable Maharashtrian population. Furthermore, compare the cephalometric values of Maharashtrian population with the established norms of Caucasians. Materials and Methods: Lateral cephalogram of 100 patients (50 males and 50 females) in the age group of 20–30 years, were taken in the natural head position. Cephalometric analysis was performed on them and compared to the values of the Caucasians. Results: Statically significant differences were obtained in the between the Maharashtrian population and the Caucasians. Maharashtrian males have a straighter profile, reduced vertical height, and reduced mandibular divergence compared to Caucasian males. Maharashtrian females have a convex profile, reduced vertical height and reduced mandibular divergence. Conclusion: Since significant differences were found in the Maharashtrian population compared to the Caucasians. These values should be taken into consideration when assessing the Maharashtrian patient with facial deformity to obtain optimal results.

Skeleto-dental features among a sample of Saudi female children compared to British standards: A cephalometric study.

This cross-sectional observational retrospective study aimed at assessing the cephalometric skeleto-dental features of class I, II, and III skeletal relationship of Saudi female school children sample and comparing the results to the established British Caucasian cephalometric standards. The sample consisted of 205 retrospective lateral cephalometric radiographs of female school children. The age range of the subjects were between 10 and 13 years old with a mean age of 11 ± 1 years. Several cephalometric and constructed points were identified. Angular, linear, and proportional measurements were obtained and analyzed. The skeleto-dental features of class II and class III were compared to class I of this sample and then compared with the established British Caucasian population. Different angular, linear, and proportional variables were investigated. Descriptive statistics and Student's t-test were used for data analysis. The distribution of the skeletal relationship revealed that 68.3% of the sample showed class I relationship, 16.1% class II, and 15.6% class III. The result indicates significant differences among the different classes. A greater tendency towards class II facial pattern and more convex profile among Saudis were detected in the present study compared to Caucasians. Furthermore, The dento-alveolar relationship results showed more bi-maxillary protrusion among Saudi females compared to the British Caucasians. The results of the study can serve as a base-line for future investigations in Saudi Arabia. Furthermore, the results obtained can also be of great value in distinguishing the various skeleto-dental features in the different skeletal classes among the Saudi females, and in the clinical diagnosis and treatment planning.

Number of Teeth Is Related to Craniofacial Morphology in Humans.

Simple SummaryIn modern humans, congenital absence of one or more permanent teeth has a prevalence of 22.6% when considering the third molars and of 6.4% when not. Its high prevalence, in conjunction with evolutionary findings pinpointing to a steady reduction in teeth number, raises the question whether the congenital absence of teeth in modern humans is an evolutionary trend rather than an anomaly. Previous studies have shown that modern humans with less teeth also have smaller faces; however, the association between teeth number and craniofacial morphology remains unclear. Here, we show that less teeth are associated with a flatter profile and a decreased facial height. These findings support the claim of a broader relationship between number of teeth and overall craniofacial development and have evolutionary implications, since face reduction comprises also an evolutionary trend in humans.One of the most common dental anomalies in humans is the congenital absence of teeth, referred to as tooth agenesis. The association of tooth agenesis to craniofacial morphology has been previously investigated but remains unclear. We investigated this association by applying geometric morphometric methods in a large sample of modern humans. In line with previous studies, we report here that a reduced teeth number is linked to a less convex profile, as well as to a shorter face. The effects were similar for males and females; they increased as the severity of the tooth agenesis increased and remained unaltered by the inclusion of third molars and of allometry in the analysis. Furthermore, in cases with tooth agenesis only in the maxilla, there was no detectable effect in mandibular shape, whereas maxillary shape was affected independently of the location of missing teeth. The robustness of the present sample along with the shape analysis and the statistical approach applied, allowed for thorough testing of various contributing factors regarding the presence but also the magnitude of effects. The present findings suggest a relationship between number of teeth and overall craniofacial development and have evolutionary implications.

Solution of transient heat transfer in graded‐material fins of varying thickness under step changes in boundary conditions using the Lattice Boltzmann Method

AbstractGraded materials (GM) possess superior thermo‐mechanical properties, which are not feasible to obtain with homogeneous materials (HM), and hence in this paper, the transient response of a longitudinal fin of varying geometry made up of GM is reported. The temperature‐dependent convection coefficient and heat generation parameters are considered to account for real‐world high‐temperature applications of fins. Fin material properties such as density and specific heat remain constant while thermal conductivity is assumed to vary axially based on four different physically possible variations namely, linear, quadratic, power, and exponential variations. The typical nonlinear differential equation obtained for fins was solved by using a mesoscopic scale‐based particle tracking method called the Lattice Boltzmann method. The Lattice Boltzmann solver has been implemented in form of an in‐house MATLAB code and validated with existing results, thereafter it is developed for solving the foregoing problems. The results obtained are reported for rectangular, triangular, convex, and concave profiles under step change in base temperature and base heat flux. The performance of graded fins is investigated in terms of time required to attain steady‐state and fin tip temperature which are inherent design parameters in the case of the transient fin. Inhomogeneity index and profile function have a significant effect on the performance of fin in terms of resistance to heat flow. Hereby, in comparison with HM fins, GM fins have lower resistance to heat flow irrespective of fin profiles. Concurrently, comparative analysis for fins of different profiles made of HM and GM is also done to facilitate the designer in selecting the most appropriate fins.

Deformed Butler–Volmer Models for Convex Semilogarithmic Current-Overpotential Profiles of Li-ion Batteries

The Butler-Volmer (BV) equation links the current flux crossing an electrochemical interface to the electric potential drop across it with the assumption of Arrhenius kinetics and the Boltzmann factor. Applying the semilogarithmic Tafel analysis in which the logarithm of current is plotted vs. the overpotential one expects straight lines from which the fundamental reaction rate of the kinetic process can be computed. However, some Li-ion battery data, which is the focus here, show nonlinear convex profiles that cannot be adequately fitted with the standard BV model. We propose instead two deformed BV models for the analysis of such types of behaviors constructed from the superposition of cells exhibiting only local equilibrium and thus giving rise to the power-law $q$-exponential and $\kappa$-exponential functions. Non-Boltzmann distributions have been successfully employed for the modeling of a wide spectrum of physical systems in nonequilibrium situations, but not yet for batteries. We verify the validity of the deformed BV models on experimental data obtained from \ce{LiFePO4} and \ce{Li}-\ce{O2} batteries.

自己整列微粒子の形状転写によるマイクロレンズアレイの製作とモールド変形を利用した非球面化の検討

Aspheric micro-lens arrays have been attracting great attention to improve light distribution control. This study proposes a simple and efficient method for fabricating close-packed aspheric micro-lens array. First, silica particles of ϕ10 μm were self-assembled over ϕ10 mm area using sedimentation method. Then the convex profile of the self-assembled particles was replicated to a spherical micro-lens array mold. The mold material was silicone elastomer or polydimethylsiloxane (PDMS). Then, the mold profile was replicated into ultraviolet (UV) curing resin. By applying uniaxial stretching to the mold during the secondary replication, aspheric micro-lens array was fabricated. Deformation of the PDMS mold under uniaxial stretching was analyzed by using finite element analysis (FEA) for rough estimation. Experimental results showed that intended lens profile was obtained though some defects were observed due to the nonuniformity of the particle diameters. Optical characteristic of elliptic micro-lens array was made clear.

An analytical model integrated with toolpath design for wrinkling prediction in conventional spinning

Blank wrinkling is the most frequently encountered material processing failure in spinning. Design of toolpath profiles and selection of process parameters are important in preventing wrinkling. Existing studies employ simplified toolpath profiles and rely on the calculation of maximum and critical stresses of the blank to determine the onset of wrinkling, often requiring time-consuming Finite Element simulations. To overcome these limitations, this paper develops an analytical wrinkling prediction model integrated with toolpath design in developing multi-pass conventional spinning. The toolpath design is parameterised for concave, convex and linear profiles and a wrinkling-wave function using a concave profile is developed to capture geometrical characteristics of a wrinkled blank. The forming depth is introduced as a critical variable in designing a toolpath profile to control wrinkling. Material plastic deformation is analysed by employing the Donnell-Mushtari-Vlasov theory and wrinkling initiation is predicted by the occurrence of the instability of the blank as a doubly-curved thin shell. Experimental tests of first-pass conventional spinning using concave, convex and linear toolpath profiles are performed to validate the developed wrinkling prediction model. The experimental validation confirms that the proposed critical forming depth of toolpath profile is an accurate and effective measure in predicting the onset of wrinkling. The results show the significant effect of the design of toolpath profile, blank thickness, spin ratio and feed ratio on the onset of the wrinkling. The wrinkling prediction model is capable of producing processing maps of these key parameters to prevent wrinkling for the spinning process development in practical applications.

Evaluating the Effects of the Rill Longitudinal Profile on Flow Resistance Law

In this paper, for the first time, the effect of the longitudinal profile shape of the rill (uniform, concave, and convex) on flow resistance law was studied. The first part of the paper is based on a theoretical equation to estimate the Darcy–Weisbach friction factor f, deduced from the power velocity distribution and rill measurements performed on a plot. At first, the equation to estimate the Γ parameter of the velocity profile was calibrated using all available measurements. Then an analysis of the hydraulic characteristics at reach scale, for comparable values of discharge, was carried out, comparing the different profile shapes. To assess the influence of the rill profile shape on flow resistance law, this calibration was also carried out using the data categorized by profile. In the second part of the paper, an analysis of the scour depth and eroded rill volume was developed for four rills of each configuration. The results showed that an accurate estimate of f can be obtained by calibrating the flow resistance equation for each profile shape. The component of the Darcy–Weisbach friction factor that is due to the profile shape varied from 0.68 to 14.6% of the overall friction factor for the concave profile, and from 3.4 to 26.9% for the convex profile. The analysis also showed that, for the convex profile, the scour was concentrated downstream of the slope change, while for the uniform and concave profiles, it was uniformly distributed. Furthermore, the scour depth measured in correspondence of the rill thalweg had a generally increasing trend, with discharge for all the investigated profile shapes. Total eroded rill volume of the concave profile was lower than those detected for the uniform and convex profiles and was characterized by a reduction of 57.9%, as compared to the uniform profile.

A non-cephalometric two-dimensional appraisal of soft tissue changes by functional therapy in Class II patients: a systematic review and meta-analysis.

Facial attractiveness has social, psychological, and economic repercussions. Class II malocclusions are associated with a retroposition of the mandible, facial convexity, protruded upper lip, retruded lower lip, and pronounced mentolabial fold. Functional appliances (FA) try to increase mandibular length and normalize lip position, thereby decreasing the facial profile convexity and aesthetics. The aim of this review and meta-analysis is to investigate the effects of FA on the soft tissues in a non-cephalometric two-dimensional manner. Medline (via PubMed), Embase (via Ovid), Web of Science, and Cochrane Central were used to identify studies describing the soft tissue results of FA in a non-cephalometric way. The search was conducted up to July 2021. Prospective and retrospective studies investigating the effects of FA appliances on the soft tissues, with non-ionizing, two-dimensional imaging, including an attractiveness assessment based on Visual Analogue Scale or Likert scale, were considered eligible. Data extraction was performed separately by two authors. Risk of bias was assessed using the ROBINS-I tool. From the eight eligible studies, four were included in the meta-analysis to investigate the influence of assessors on facial attractiveness scores. Age range of the included studies varied from 8 to 21 years old including 313 Caucasian patients whereof 64% females. Six out of eight studies used growing patients as treatment group and only two studies reported follow-up after the end of treatment. Overall facial attractiveness increased after treatment with FA, resulting from a decrease in facial convexity and a normalization of the lip relationship. Orthodontists score higher aesthetic improvements after FA treatment as compared to laypeople. Current evidence suggests the positive effects of FA on the facial attractiveness in growing and non-growing patients. FA normalize the lip relationship. Furthermore, they tend to decrease facial convexity and advance the chin point. More pleasing results can be expected in growing patients. Orthodontists are more generous when assessing treatment changes as compared to laypeople. PROSPERO registration (CRD42021254835).

Correction of Class II malocclusion in a patient using the forsus fatigue resistant appliance – A case report

Functional appliances, fixed or removable, are primarily orthopaedic tools used to influence the facial skeleton in a growing child. Class II malocclusion with a retrognathic mandible in a non -compliant post pubertal patient can be treated using the fixed functional appliances. One such appliance which is in common use in clinical practice today is the Forsus Fatigue Resistant Device. To treat a 13 year old female patient having a class II base, a retrognathic mandible, horizontal growth pattern, convex profile, an overjet of 7mm, mild proclination of maxillary and mandibular incisors, Class II molar and canine relationship bilaterally and a positive VTO.

Orthodontic management of skeletal Class II malocclusion using three mini-implants- A case report

Vertical dimension issues are frequently regarded as the most difficult dentofacial problems to treat in clinical practice. The difficulty level increases when vertical dysplasia is paired with sagittal discrepancy. The use of mini-implants in Orthodontics has broadened the scope of orthodontic treatment options. The treatment of a 14-year-old female patient with skeletal Class II malocclusion, slight hyperdivergent profile, and enhanced incisor visibility with four premolar extraction followed by comprehensive orthodontic treatment to correct the convex profile and increased incisor visibility, with two posterior implants for retraction and a midline mini implant for intrusion of the anterior maxillary dentoalveolar segment is described in this case report. The active therapy period was 25 months long.