Shape Of Bracket Research Articles

The effect of orthodontic bracket base shape on shear bond strength to human enamel, an in vitro study.

The purpose of this study was to evaluate the in vitro effect of orthodontic bracket base shape on shear bond strength (SBS) to human enamel and assess the nature of debonding fractures using the Adhesive Remnant Index (ARI). Orthodontic brackets with different-shaped bases (flower, heart, rectangle) were bonded to 120 extracted human third molars. Shear bond strength was measured using a Servohydraulic Test System at 24 h and 2 months after bonding. Adhesive Remnant Index scores were evaluated under 10x magnification to assess the amount of resin left on the tooth. The control bracket (rectangular base shape) had the highest mean SBS (26.8 ± 8.2 megapascals [MPa]), and significantly differed from the flower (17.2 ± 4.4 MPa) and heart (18.9 ± 3.5 MPa) base shapes (p < 0.001). The mean SBS between debonding times at 24 h (21.5 ± 7.4 MPa) and 2 months (20.4 ± 6.7 MPa) were not statistically significant (p > 0.05). Analysis of ARI scores showed a significant difference between flower-24 h versus heart-2 months (p = 0.039), flower-24 h versus heart-24 h (p = 0.004), and control-2 months versus heart-24 h (p = 0.015). Bracket base shape influenced SBS, with the rectangular base shape having a higher mean SBS compared to flower and heart base shapes. Variations in ARI scores occurred based on bracket shape and were of a mixed adhesive-cohesive nature. All bracket shapes had bond strengths above the clinically acceptable range of 6-8 MPa, and may thus provide adequate SBS in a clinical situation.

Coracoid Process of Scapula: Morphometric Analysis in South Indian Population

Introduction: Shoulder pain in subcoracoid impingement syndrome was due to intrusion of rotator cuff tendons in the coracohumeral space. One of the predisposing factors for subcoracoid impingement syndrome was limited subcoracoid space which causes impingement of lesser tubercle of humerus against the coracoid process to produce pain in the anterior region of shoulder. Coracoid process was also used as graft in Latarjet operation done to treat glenohumeral instability. So, understanding the morphometry of coracoid process is very important for orthopaedic surgeons for various surgical procedures. Aim: To analyse the morphometry of coracoid process, coracoglenoid distance and shape of coracoglenoid space among South Indian population. Materials and Methods: This was a cross-sectional study done between March 2018 to September 2018 on 100 dried human scapulae obtained from the bone bank of Department of Anatomy of Private Medical Colleges in South India. Maximum length, breadth, thickness, height of coracoid process, coracoglenoid distance and maximum width of glenoid cavity were measured in millimetres (mm) using digital vernier callipers with the precision of 0.01 mm. Results: Total of 100 dried human scapulae (51 of right side, 49 of left side) were studied and analysed. The average length of coracoid process was 39.47±3.29 mm. The average breadth of coracoid process was 13.91±1.36 mm. The mean thickness of coracoid process was 8.24±1.003 mm. The mean coracoglenoid distance was 27.19±2.42 mm. Breadth of coracoid represents 57.92% of Glenoid width and thickness of coracoid represents 34.27% of Glenoid width. Most common variety of coracoglenoid space found in our study was round bracket shape which was in 51% of scapulae, followed by square bracket shaped in 30% and fish hooked shaped in 19% of scapulae. Conclusion: Morphometry of coracoid process will be taken into account while treating patients with subcoracoid impingement syndrome. Thickness of coracoid process was always smaller than the breadth of coracoid. Hence, the breadth was taken into account when coracoid process was used as a graft to reconstruct glenoid bone loss in recurrent shoulder dislocation.

Lightweight design method and application of MEWP bracket based on multi-level optimization

&lt;abstract&gt; &lt;p&gt;Mobile elevating work platform (MEWP) is a large-scale engineering machinery equipment that transports workers and tools to the designated height for operation. As the key supporting component of MEWP, the bracket simultaneously needs to meet the performances of high stiffness and strength. Furthermore, the mechanical performance of the bracket can be significantly influenced by its cross-sectional shape. However, the optimal cross-sectional shape of bracket is not easily to obtain owing to the lacking of lightweight design method. Thus, a lightweight design method of MEWP bracket based on multi-level optimization is proposed in this paper. Firstly, the multi-case topology optimization model of MEWP bracket is constructed by using the compromise programming method, and the optimal section configuration of MEWP bracket is obtained based on Solid Isotropic Material with Penalization (SIMP). Secondly, the parameterization of the cross-sectional shape of bracket is realized using the mesh deformation technology, and the multi-case optimization mathematical model of the MEWP bracket is established. Then, the cross-sectional shape and gauge of the bracket are optimized using multi-level optimization method. The optimized results show that weight reduction mass is 11.66 kg and the ratio is 52.4% under the premise that the stiffness of the bracket does not decrease. Furthermore, the weight of MEWP bracket optimized by the multi-level optimization method reduced by 1.27 kg compared with single gauge optimization method. Finally, a physical prototype is developed according to the optimization results.&lt;/p&gt; &lt;/abstract&gt;

The Staple-Shape Plate Springs Engineering Calculation Method

The new types of elastic devices – staple-shape plate spring and leaf spring - have been developed at the Kyiv National University of Construction and Architecture. The staple-shape plate spring is an elastic plate where the ends are deflected from its middle part in the same direction and are made in the form of consoles equipped with hinge attachments. The middle part of the plate as a parallel to the line of the load action is designed with variable length section. In each section, the axis, relative to which the moment of the section inertia is a maximum, is perpendicular to the spring bending plane, designed as the equal resistance beam. This article substantiates the feasibility of using a staple-shape plate spring to improve the elastic suspension of truck cabs. The recommendations for choosing the most promising mass production directions, as well as the engineering calculation methods of such springs, have been developed. Objects of the study are devices intended for machines and their components dynamic loads shock absorption, differing in having a bracket shape and being a subject to bending in the plane of the highest rigidity of their cross sections, as well as shock absorbers using these springs, in particular KamAZ cabs suspension. This research implementation allows significantly reducing the metal consumption and elastic devices manufacture complexity, as well as can be useful in the design and operation of elastic car suspensions.Keywords: elastic device, staple-shaped plate spring, leaf spring, elastic suspension

Experimental and Numerical Evaluation of Reinforced Concrete Bracket Design for Supporting Middle Slab in Double-Deck Tunnel

This research was conducted to evaluate the design of reinforced concrete brackets that support middle slabs in a double-deck tunnel by performing experimental and numerical analyses. The most distinctive feature of double-deck tunnel is the existence of middle slabs. Since the brackets attached to the tunnel liner sustain all the loads applied on middle slabs, it is crucial to design brackets appropriately to ensure safety against falling of middle slab, failure of tunnel liner, and associated human and material damages. The structural design of bracket was performed based on currently available design methods. Test specimens of the bracket attached tunnel liner structure were fabricated and loading tests were conducted to verify appropriateness of the design, to evaluate safety factors to damages and failures, and to find the failure mode. The numerical analysis models of the bracket attached tunnel liner structure were also developed and analyses were performed to confirm the bracket design and to evaluate the effect of bracket shape on the structural capacity of bracket. Based on the experimental and numerical analysis results, the safety factors to damage and failure of bracket were obtained to be large enough. However, since the shape of bracket may reduce the safety factors, suggestions were finally provided to improve the design of bracket for the use in double-deck tunnels.

Debinding Rate Enhancement of 17-4 Precipitation Hardening Stainless Steel Solvent Debinding on Metal Injection Molding Process as the Material for Orthodontic Bracket

Brackets fabrication should be done by a suitable process to produce great result. Processes commonly used are investment casting, machining, and metal injection molding. Investment Casting has a drawback in which the surface roughness is quite high for the standard of brackets and require further processing. Machining is done by removing unwanted part to get desire shape, whereas bracket shape requires a high accuracy and is quite complicated. In Metal Injection Molding, feedstock is injected into a mold where complicated shapes can be achieved with a better surface roughness. The weakness is the stages within the process are quite long. One of the problem is the efficiency of debinding stage. We conducted an experiment to enhance binder removal rate through solvent debinding with stirring and under vacuum condition. Sample use for this experiment is a cubic shape of 0.5 x 0.5 x 0.5 cm3. Experiment is done on magnetic stirrer and in vacuum furnace. The temperature is hold at 50°C. Drying process afterward is done in the vacuum furnace for 1 hour with temperature around 50°C. Amount of binder left is confirmed by STA and the particle morphology is seen by SEM. Results showed that stirring treatment enhances binder removal rate due to stirring mechanism that causes possibility of collisions between particles increases. Binder removal rate on the vacuum treatment has a mechanism similar to stirring, but with the addition of the solvent to be done on a regular basis due to decrease of solvent boiling point under vacuum. There were no cracks found on the surface with an increased rate of debinding. Stirring is use for experiment with sample of actual bracketorthodontic form. Debinding rate of the bracket sample is faster than the cubic sample. This result is affected by the dissimilarity on the volume to surface area.

후판을 이용한 힌지 브래킷 성형 공정 설계

In the transportation between countries using container, too many empty containers must be transported due to the transportation unbalance. For transportation efficiency, therefore, foldable containers are being developed. Hinge brackets are important parts of foldable containers because great force is applied on the hinges during loading onto and unloading from ships. In this study, the hinge bracket for a foldable container is designed to be made using thick plate or bulk materials to endure the heavy loads. The forming process for the hinge bracket using a thick plate is designed via numerical analysis. First of all, the shape of bracket is designed for the better formability. Bending and successive side wall thickening processes are employed for the forming of the hinge bracket. Maximum thickening that can be achieved in a single stage of forming without a folding defect is determined and three stage of thickening processes are designed.

Influence of Preadjusted Bracket Shape and Positioning Reference on Angulation of Upper Central Incisor

To verify the influence of different bracket shapes and placement references according to Andrews and MBT systems on the expression of angulation in upper central incisors (UCI). Bracket positioning and mesiodistal dental movement simulations were performed and the angulations produced in the dental crown were evaluated, based on computed tomography scan images of 30 UCI and AutoCAD software analysis. Rectangular (Andrews) and rhomboid (MBT) brackets were placed according to the references recommended by Andrews and MBT systems - long axis of the clinical crown (LACC) and incisal edge (IE) respectively. Data showed that the use of LACC as reference for bracket positioning produced 5° and 4° UCI angulations in Andrews and MBT brackets respectively. The use of IE produced a 1.2° mean angulation in UCI for both brackets. When the LACC was used as reference for bracket positioning, the UCI crown angulation corresponded to the angulation built into the brackets, regardless of shape, while the use of IE resulted in natural crown angulation, regardless of bracket shape. This research contributes to guide the orthodontist in relation to the different treatment techniques based on the use of preadjusted brackets.

Computer aided design of manufacturing of automotive part made of magnesium alloy

Evaluation of the possibility of substitution of steel part in the car body by the one made of AZ31 alloy was the objective of the paper. Bracket in the support of the steering wheel was selected for the analysis. Two criteria were selected to evaluate the possibility of using the Mg alloy part: i) stiffness of this part cannot be lower than that of the steel part, ii) Manufacturing of the part has to be possible. The objective of the research was a design of the shape of the bracket, that meets assumed criteria including manufacturing and assembly possibilities. The optimization task was formulated to reach this objective. Maximum stiffness of the part was the objective function and technological limitations were the constraints. Dimensions of the bracket were the optimization variables. Optimal shape was designed and numerical simulations were performed to evaluate possibility of stamping of this part. Simulations have shown that the decrease of the thickness is within of acceptable limits and that the strains are below the limiting strains. Thus, proposition of the shape of the magnesium alloy bracket, which can be safely manufactured by stamping, is the main output of the paper.

Prenatal MRI diagnosis of fetal bowel obstruction

Objective To investigate the clinical value of prenatal MRI in the diagnosis of fetal bowel obstruction. Methods Pregnant women suspected to have fetal abdominal abnormalities by ultrasonography were suggested to undergo MRI examinations within two days. Scanning sequence included FIESTA, SSFSE and T1WI SPGR sequence, with field of view focused on the fetal abdomen. After the final diagnoses of the cases were obtained by induced labor pathological examination or postpartum imaging or operation, the imaging data and the clinical data were reviewed and analyzed retrospectively. Results A total of 23 cases with bowel obstruction were included in the study. Four fetuses with duodenal atresia showed low T1 signal, high T2 signal characterized by double-bubble sign on MRI. There were 10 fetuses with jejunoileal atresia, showing bowel dilatation and hyperintense micro-colon on T1WI. Five cases of them depicted expansion of the terminal ileum with high T1 meconium signal.One each fetus had colonic atresia, intestinal malrotation with double-bubble and whirl sign. Annular pancreas with double-bubble sign and pressure trace of the bracket shape was detected in 3 fetuses. Meconium peritonitis was present in 4 fetuses, with 2 of them showing dilatation of intestine, ascites and pseudocysts. Conclusions According to the signal characteristics of amniotic fluid and meconium in the gastrointestinal tract on MRI, the obstructive level and development status of the distal bowel can be determined with MRI. It can provide additional information to ultrasonography, which brings clinical significance to prenatal diagnosis and intrapartum surgical operation. Key words: Magnetic resonance imaging; Fetus; Intestinal obstruction

캘리퍼 브레이크 스퀼 소음의 불안정성 해석에 관한 연구

This paper deals with analytical methods for low frequency and high frequency brake squeal noise on brake-rear caliper. In order to improve low frequency and high frequency squeal noise, we take survey caliper bracket shape parameters and housing shape parameters. Besides, using the combination of bracket and housing parameter were surveyed. Thus, using the combination of bracket Alt_05 and housing Alt_45 specifications, instability analysis and brake dynamo test were carried out. Based upon the two models, low and high frequency squeal noise of base model were improved. But, for 6.0 kHz frequency noise, which is not improved, it needs to additionally study on instability analysis and combination of the other brake components.

Topology optimization of compressor bracket

Topology optimization is very useful engineering technique especially at the concept design stage. It is common habit to design depending on the designer’s experience at the early stage of product development. Structural analysis methodology of compressor bracket was verified on the static and dynamic loading condition with 2 bracket samples for the topology optimization base model. Topology optimization is able to produce reliable and satisfactory results with the verified structural model. Base bracket model for the topology optimization was modeled considering the interference with the adjacent vehicle parts. Objective function was to minimize combined compliance and the constraint was the first natural frequency over 250 Hz. Multiple load cases such as normal mode calculation and gravity load conditions with 3-axis direction were also applied for the optimization, expecting an even stress distribution and vibration durability performance. Commercial structural optimization code such as optistruct of Altair Engineering was used for the structural topology optimization. Optimization was converged after 14 iterations with the satisfaction of natural frequency constraint. New bracket shape was produced with the CATIA based on the topology optimization result. The new bracket from topology optimization result was compared with the traditional concept model and topology optimization base model under 4 load cases. 14 % 1’st natural frequency of new bracket with only 4 % mass increment increased compared to the concept model. 31 % mass decreased compared to the base model without the increment of stress under gravity load cases. It was analyzed thata new bracket would not fail during a vibration durability test, and these results were verified with a fabricated real sample under the durability condition.

A Study on Characteristic and Internal Flow Condition in a Winnowing Fan.

This paper describes the performance in the winnowing fan, which are used for head feeding type combines mainly used in Asia. The effects of blade angle and the bracket configurations at the inlet on the efficiency and internal flow conditions are experimentally investigated. The fan efficiency and the uniformity of flow along an axis are improved by reforming blade angle and bracket shape with holes. In addition, in this experiment we found that both of these two methods uniform the velocity distributions at fan exit and combination of these two methods make it possible to improve the fan efficiency in the limited design condition.

Studies on lateral vibration characteristics of transverse member of large sized ships

One of the principal causes of the fractures around the slot of transverse web is considered to be the effect of lateral vibration of transverse member.In this report, at first, exciting tests were carried out with the bottom trans. model of 1/4 scale actual ship in order to investigate the natural frequencies and modes in detail.Secondly, during the sea trial of 224, 841 DWT and 284, 495 DWT oil tanker, comprehensive vibration measurements of ship hull and bottom trans. were carried out and those data were used to find response characteristics and excitation sources.Finally, the theoretical analysis of natural frequency and hydrodynamic pressure for the lateral vibration of trans. member were carried out and the former results were compared with the measured values.The results obtained are as follows : (1) Calculated natural frequencies and modes except for modes in water showed considerably good agreement with those of the measurement. Natural frequency of 2 nd order in water is less than or nearly equal to one of the O-node axial vibration of shaft system.(2) Hydrodynamic pressure distribution depends on natural mode of member itself, correlation between adjacent ones and the shape of bracket and face plate. Therefore, further investigation is necessary to estimate virtual added mass.(3) Engine and propeller induced axial forces of shaft system are mainly transferred to the bottom trans. and amplified through axial vibration of shaft system and ship hull vibration.