Introduction: Bracket debonding is a frequent issue that clinicians encounter, leading to increased chair time, lost revenue, and material usage. In addition to patient compliance with their diet recommendations, the ...Introduction: Bracket debonding is a frequent issue that clinicians encounter, leading to increased chair time, lost revenue, and material usage. In addition to patient compliance with their diet recommendations, the preparation and conditioning of teeth for bonding significantly influence bond strength and consequently impact orthodontic treatment success and efficiency. Because of OBA-MCP’s (orthodontic bonding adhesive with modified calcium phosphate) decreased shear bond strength (SBS), the purpose of this study was to evaluate the effects of conditioning with 5.25% sodium hypochlorite (NaOCl) before etching in the bonding protocol. Materials and Methods: 90 extracted teeth were divided into 3 groups to be bonded with orthodontic brackets with different bonding protocols: 1) Transbond XT with regular bonding protocol (etch + prime + adhesive);2) OBA-MCP with regular bonding protocol;and 3) OBA-MCP with NaOCl prior to acid etching in the regular bonding protocol. SBS (in Newtons) were measured using an MTS universal testing machine with a custom jig to apply a vertical force onto the bracket and ARI (adhesive remnant index) scores were recorded for each sample after de-bond to rate the amount of adhesive remaining. Results: The addition of NaOCl to the bonding protocol statistically significantly increased the SBS of OBA-MCP to comparable levels to Transbond XT. The ARI scores showed that when NaOCl was added, more adhesive remained. Conclusion: The addition of NaOCl to the bonding protocol can increase the SBS of adhesives with historically weaker bond strengths. However, the increased amount of adhesive remaining and the increased time spent during bonding must be considered. Further testing can be done in vivo to demonstrate the practicality of this new procedure.展开更多
With the increasing global demand for renewable energy,solar photovoltaic power generation technology has been widely applied in China and even globally.Especially in mountainous areas,complex terrain resources are cl...With the increasing global demand for renewable energy,solar photovoltaic power generation technology has been widely applied in China and even globally.Especially in mountainous areas,complex terrain resources are cleverly utilized in the construction of photovoltaic power stations,but this also brings severe challenges to the anti-corrosion of photovoltaic brackets.This paper focuses on the anti-corrosion technology of mountain photovoltaic brackets,and deeply explores the influence of natural factors such as mountain climate,sandstorms,and precipitation on the corrosion of photovoltaic brackets.The research results show that the key to improving anti-corrosion performance lies in the selection of bracket materials and optimization of coating processes.After comparing various anti-corrosion treatment methods such as hot-dip galvanizing,spray aluminum coating,and new anti-corrosion materials,it is found that nano coating technology exhibits excellent protective effects in corrosive environments.This study is of great significance for promoting the sustainable development of photovoltaic power generation,providing solid theoretical support and practical guidance for the anti-corrosion design of mountain photovoltaic power stations.展开更多
With the increasing global demand for renewable energy,the application of photovoltaic power generation in mountainous areas is gradually increasing.However,the complex wind environment in mountainous areas poses seve...With the increasing global demand for renewable energy,the application of photovoltaic power generation in mountainous areas is gradually increasing.However,the complex wind environment in mountainous areas poses severe challenges to the design and optimization of solar photovoltaic brackets.Traditional design methods are difficult to cope with the changeable wind speed and direction in mountainous areas,resulting in structural instability or material waste.Researchers have identified the key factors affecting wind response through parametric research and dynamic wind response analysis,so as to optimize the brackets design and improve its adaptability and stability in complex wind environments.In this paper,the complexity of wind speed,wind direction and turbulence characteristics in mountainous areas and their influence on brackets design are explored.Through static and dynamic wind load analysis,the geometrical shape and material selection of the bracket are optimized to enhance its wind resistance.The application of multi-objective optimization model and intelligent optimization algorithm provides an effective solution for the design of solar photovoltaic brackets,ensuring their safety and reliability in complex wind environments.展开更多
Introduction: The stability of orthodontic brackets throughout orthodontic treatment plays a critical role in the treatment’s effectiveness. The present in vitro study was designed to assess the impact of various die...Introduction: The stability of orthodontic brackets throughout orthodontic treatment plays a critical role in the treatment’s effectiveness. The present in vitro study was designed to assess the impact of various dietary components on the performance of orthodontic brackets. Methods: Metal orthodontic brackets were bonded to 66 extracted anterior teeth divided into groups based on the solution type: Milk, Gatorade, Cold Coffee, and a control group using water. Each group consisted of 20 teeth except for the control group, which included six teeth. The bracketed teeth were submerged in their respective solutions for 15 minutes three times daily at different intervals to mimic an in vivo environment and were stored in artificial saliva at room temperature (23?C). The specimens underwent artificial aging through 10,000 cycles of thermocycling (representing one clinical year) between 5?C and 55?C. Shade measurements were taken using a VITA Easy Shade device, capturing the classic shade and L*, a*, and b* values. Delta E values were calculated immediately post-bonding and after 7 days, 1 month, 1, and 2 clinical years. The shear bond strength of each bracket was measured using an ultra-tester machine. Results: After two clinical years, significant differences in ΔE color values were observed across all groups, with the most substantial change noted in teeth immersed in cold coffee. Brackets submerged in milk demonstrated lower shear bond strength than other solutions, whereas the control group exhibited the highest shear bond strength (P = 0.01). Conclusion: The study indicates that dietary components significantly influence tooth color stability and the shear bond strength of orthodontic brackets, underscoring the importance of considering these factors in orthodontic treatment planning.展开更多
The Bracket Set(dougong)is an important aspect of traditional Chinese architecture known for its exquisite structure,complexity,and rich variations.This design element has been used since the Qin and Han Dynasties and...The Bracket Set(dougong)is an important aspect of traditional Chinese architecture known for its exquisite structure,complexity,and rich variations.This design element has been used since the Qin and Han Dynasties and is still prevalent today.It highlights hierarchy and spiritual connotations in the design of a building.This article explores the application of Bracket Set elements in modern architectural design.It analyzes the specific application strategies of this design element,highlighting its value in modern architecture.The goal is to provide modern architectural designers with multiple perspectives and strategies to fully utilize the advantages of Bracket Set elements in architectural design and enhance the artistic value of their work.展开更多
Combination of topology optimization and additive manufacturing technologies provides an effective approach for the development of light-weight and high-performance structures.A heavy-loaded aerospace bracket is desig...Combination of topology optimization and additive manufacturing technologies provides an effective approach for the development of light-weight and high-performance structures.A heavy-loaded aerospace bracket is designed by topology optimization and manufactured by additive manufacturing technology in this work.Considering both mechanical forces and temperature loads,a formulation of thermo-elastic topology optimization is firstly proposed and the sensitivity analysis is derived in detail.Then the procedure of numerical optimization design is presented and the final design is additively manufactured using Selective Laser Melting(SLM).The mass of the aerospace bracket is reduced by over 18%,benefiting from topology and size optimization,and the three constraints are satisfied as well in the final design.This work indicates that the integration of thermo-elastic topology optimization and additive manufacturing technologies can be a rather powerful tool kit for the design of structures under thermal-mechanical loading.展开更多
The investment on semi-solid die casting processes of AZ91D magnesium alloy brackets for generators in JH70-type motorbikes is introduced. The processes of low super-heat and cooling slope for the preparation of bille...The investment on semi-solid die casting processes of AZ91D magnesium alloy brackets for generators in JH70-type motorbikes is introduced. The processes of low super-heat and cooling slope for the preparation of billets with non-dendritic microstructure, the remelting of billets for thixoforming and the parameters in the process of semi-sohd thixoforming have been researched. The results show that primary billets with non-dendritical structures can be prepared by forming great amount of nuclei in melt via the process of low super heat. By optimizing the remelting process through adjusting the current of the induced equipment, semi-solid billets with a structure of spherical grains were obtained from the primary billets with non-dendritical structure. The range of 580℃ to 583℃ is the proper remelting temperatures by which the billets have an expected thixotropy and can be transferred to a die-casting machine. The optimized parameters of semi-solid forming in a die-casting machine are as follows： the area of the ingate in the die is 383.5 mm^2, the speed of the pierce of the machine 5 m/s, the shot pressure of the pierce 75 MPa, and the maintenance pressure of the pierce 350 MPa. The castings of brackets for supporting generators in JH70 type motorbikes were formed by adopting the optimized processes and parameters mentioned above.展开更多
In the aviation industry,cable bracket is one of the most common parts.The traditional assembly state inspection method of cable bracket is to manually compare by viewing 3 D models.The purpose of this paper is to add...In the aviation industry,cable bracket is one of the most common parts.The traditional assembly state inspection method of cable bracket is to manually compare by viewing 3 D models.The purpose of this paper is to address the problem of inefficiency of traditional inspection method.In order to solve the problem that machine learning algorithm requires large dataset and manually labeling of dataset is a laborious and time-consuming task,a simulation platform is developed to automatically generate synthetic realistic brackets images with pixel-level annotations based on 3 D digital mock-up.In order to obtain accurate shapes of brackets from 2 D image,a brackets recognizer based on Mask R-CNN is trained.In addition,a semi-automatic cable bracket inspection method is proposed.With this method,the inspector can easily obtain the inspection result only by taking a picture with a portable device,such as augmented reality(AR)glasses.The inspection task will be automatically executed via bracket recognition and matching.The experimental result shows that the proposed method for automatically labeling dataset is valid and the proposed cable bracket inspection method can effectively inspect cable bracket in the aircraft.Finally,a prototype system based on client-server framework has been developed for validation purpose.展开更多
Although the shell mould casting process has a wide range of application in many fields,the prediction of casting defects is still a problem.In the present work,a typical leaf spring bracket casting of ZG310-570 was f...Although the shell mould casting process has a wide range of application in many fields,the prediction of casting defects is still a problem.In the present work,a typical leaf spring bracket casting of ZG310-570 was fabricated by shell mold casting.The finite element model and ProCAST software were utilized for simulating the filling and solidification processes of the casting;and the formation mechanism of the gas pore,and shrinkage porosity defects were analyzed.The results indicate that the gas pore and shrinkage porosity defects are formed due to air entrapment,insufficient feeding and non-sequential solidification.Subsequently,through changing the position of risers,adding a connecting channel between the risers,and setting blind risers at the U-shaped brackets,an optimized gating and feeding system was established to improve the quality of the casting.After optimization,the gas pore and shrinkage porosity defects of the leaf spring bracket casting are effectively eliminated.The experiment results with the optimized casting process are in good agreement with the numerical simulation,which verifies the validity of the finite element model in the shell mould casting.展开更多
The hoist bracket links the rescue hoist with the helicopter cabin, and its structure design greatly affects the operation convenience and safety of the hoistman and lifeguard in the rescue process with a helicopter.T...The hoist bracket links the rescue hoist with the helicopter cabin, and its structure design greatly affects the operation convenience and safety of the hoistman and lifeguard in the rescue process with a helicopter.This paper firstly builds the force model of the hoist and bracket, and gives five kinds of typical working conditions as the design ones of the bracket. Then this paper puts forward a design process of the hoist bracket based on the topology optimization and strength analysis with the 3D modeling and finite element analysis. This design process can make the bracket's structure lightweight by achieving the optimal material layout under the conditions of maximizing the static stiffness or minimizing the compliance of the bracket. And this improves the dynamic performance of the helicopter, and reduces the fuel consumption and cost under the strength constraints. Finally,taking the design of the hoist bracket used in a rescue helicopter as an example, this paper illustrates the proposed model and method. The analysis results show that the mass of the hoist bracket decreases by 12.5% while the static stiffness of the hoist bracket is achieved. The optimization design results meet the strength requirements of the hoist.展开更多
For a semi-submersible platform in repair, the eight old main brackets which connect columns with pontoons need to be replaced by new ones. In order to ensure the safety of the cutting operation of the old main bracke...For a semi-submersible platform in repair, the eight old main brackets which connect columns with pontoons need to be replaced by new ones. In order to ensure the safety of the cutting operation of the old main bracket and calculate the initial stress condition of new main bracket, the structural stress monitoring of eight key spots is carried out, and then the calibrated finite element model is established according to the field monitoring results. Before cutting the main bracket and all associated structures, eight rectangular rosettes were installed, and a tailored cutting scheme was proposed to release the initial stress, in which the main bracket and associated column and pontoon plates were partly cut. During the cutting procedure, the strains of the monitoring spots were measured, and then the structural stress of the monitored spots were obtained. The stress variation characteristics at different spots during the initial cutting operation were shown and the initial stress condition of the monitored spots was figured out. The loading and support conditions of the semi-submersible platform were calibrated based on the measured initial stress condition, which made the finite element model more credible. The stress condition with the main bracket and associated structures being entirely cut out is analyzed by the Finite Element Method (FEM), which demonstrates the cutting operation to be safe and feasible. In addition, the calibrated finite element model can be used to calculate the initial stress condition of the new main bracket, which will be very helpful for the long-term stress monitoring on the main bracket.展开更多
Objective: To determine quantitatively the amount of demineralization and the ability of commercially available products and an experimental cream to inhibit or reverse orthodontic related demineralization.Methods: A ...Objective: To determine quantitatively the amount of demineralization and the ability of commercially available products and an experimental cream to inhibit or reverse orthodontic related demineralization.Methods: A total of 20 patients who were 25–35 years old and having orthodontic treatment for 6–8 months were chosen.Caries risk assessments were done for each patient and ones with "moderate risk" were included.Patients with fixed orthodontic appliances were divided into 4 groups(5 patients each) including one control and 3 study groups.All patients used same toothpaste 2 times a day during the 3 weeks study period.Additional to the toothpaste first study group used MI Paste Plus(GC, Tokyo, Japan), second study group used Remin Pro(Voco, Cuxhaven, Germany) and third group used an experimental remineralizing cream per day for 3 weeks.Maxillary central and lateral incisors of each patient were examined by FluoreCam(Daraza Therametric Technologies, USA) device.The examinations were performed at baseline and at the end of 1st, 2nd and 3rd weeks.Results: According to the FluoreCam measurements the control group showed significant amount of demineralization at the end of 3 weeks, moreover the amount of demineralization has gradually increased in time.At the end of the study all 3 study groups showed significant amount of remineralization and the amount of remineralization for all the 3 study groups has gradually increased in time.However the amount of remineralization for 3rd study group was lesser than the 1st and 2nd study groups.The remineralization amounts for the 1st and 2 nd study groups were determined to be identical.Conclusions: This study demonstrated that demineralization is measurable around orthodontic brackets and the demineralization can be completely inhibited and/or reversed by the use of commercially available remineralization products.展开更多
To evaluate the shear bond strength（SBS） and bond failure interface after the debonding of orthodontic brackets with a resin-modified glass ionomer cement（RMGIC） under six bonding conditions, 140 premolar teeth we...To evaluate the shear bond strength（SBS） and bond failure interface after the debonding of orthodontic brackets with a resin-modified glass ionomer cement（RMGIC） under six bonding conditions, 140 premolar teeth were randomly divided into seven groups. The brackets of all groups, except for control group, were bonded using a RMGIC. The teeth were debonded using a universal testing machine. The shear bond strength, adhesive remnant index （ARI） and enamel fracture were examined for each debonding. A significant difference existed in SBS under wet and dry conditions in two groups of Fuji Ortho LC. Different degree of enamel fracture was seen in groups of Fuji Ortho LC（dry/37% phosphoric acid treated） after debonding. Bond failed predominantly at the enamel-adhesive interface, except for phosphoric acid treated groups. The RMGIC achieve a clinically effective adhesion in orthodontics under different bonding conditions.展开更多
Helicopter rescue has become an important way of life and property relief in modern society.The structure and parameters of the helicopter hoist bracket influence the convenience,safety and reliability of the rescue o...Helicopter rescue has become an important way of life and property relief in modern society.The structure and parameters of the helicopter hoist bracket influence the convenience,safety and reliability of the rescue operation for the lifeguard and hoistman.Based on fatigue analysis theory and ANSYS workbench software,the fatigue life analysis of the hoist bracket is carried out.First,the structure of the hoist bracket is modeled according to the body standard of the hoistman and lifeguard.Then an approach is presented to obtain the S-N curve of the hoist bracket by modifying the S-N curve of the bracket material based on Goodman curve while considering the influences of the shape,size,surface state,loading conditions and the average stress.Further,based on the ANSYS workbench analysis,the life and safety nephogram of the bracket under the fluctuating cyclic load can be obtained.Finally,the designed bracket is analyzed with the proposed method.The cycles number of the bracket is greater than 107 under the extreme conditions of the pulsating cyclic load,which may be considered as the unlimited life and meets the requirement of the fatigue strength.展开更多
We introduce a simple recursive relation and give an explicit formula of the Kauffman bracket of two-strand braid link . Then, we give general formulas of the bracket of the sequence of links of three-strand braids . ...We introduce a simple recursive relation and give an explicit formula of the Kauffman bracket of two-strand braid link . Then, we give general formulas of the bracket of the sequence of links of three-strand braids . Finally, we give an interesting result that the Kauffman bracket of the three-strand braid link is actually the product of the brackets of the two-strand braid links and . Moreover, a recursive relation for is also given.展开更多
The shape and size optimization of brackets in hull structures was conducted to achieve the simultaneous reduction of mass and high stress,where the parametric finite element model was built based on Patran Command La...The shape and size optimization of brackets in hull structures was conducted to achieve the simultaneous reduction of mass and high stress,where the parametric finite element model was built based on Patran Command Language codes.The optimization procedure was executed on Isight platform,on which the linear dimensionless method was introduced to establish the weighted multi-objective function.The extreme processing method was applied and proved effective to normalize the objectives.The bracket was optimized under the typical single loads and design waves,accompanied by the different proportions of weights in the objective function,in which the safety factor function was further established,including yielding,buckling,and fatigue strength,and the weight minimization and safety maximization of the bracket were obtained.The findings of this study illustrate that the dimensionless objectives share equal contributions to the multi-objective function,which enhances the role of weights in the optimization.展开更多
A foot bracket is a metal panel bracket used to mount and support the footrest in two-wheeler systems.It holds the footrest in place while rigidly supporting it.In working conditions,this element has often been observ...A foot bracket is a metal panel bracket used to mount and support the footrest in two-wheeler systems.It holds the footrest in place while rigidly supporting it.In working conditions,this element has often been observed to fail when specific load-fluctuation conditions are established at its rear end.Appropriate materials therefore need to be identified to overcome such a recurring failure.To address these issues,the present study has been implemented with the specific objective to determine the response of selected Al6061-T6 and Al7075-T6 Hybrid Metal Matrix Composites(HMMC).The results,obtained using the ANSYS Software,show that the selected composites can withstand 636,962 N/m^(2)of maximum stress and 8.88×10^(−6)m of minimum displacement.These results are also compared with relevant mathematical models and it is concluded that the identified material combination provides the required improvement of structural stability that can withstand the load fluctuation on the foot bracket.展开更多
Arc-soft-toe bracket(ASTB), as a joint structure in the marine structure, is the hot spot with significant stress concentration, therefore, fatigue behavior of ASTBs is an important point of concern in their design. S...Arc-soft-toe bracket(ASTB), as a joint structure in the marine structure, is the hot spot with significant stress concentration, therefore, fatigue behavior of ASTBs is an important point of concern in their design. Since macroscopic geometric factors obviously influence the stress flaws in joints, the shapes and sizes of ASTBs should represent the stress distribution around cracks in the hot spots. In this paper, we introduce a geometric magnification factor for reflecting the macroscopic geometric effects of ASTB crack features and construct a 3D finite element model to simulate the distribution of stress intensity factor(SIF) at the crack endings. Sensitivity analyses with respect to the geometric ratio Ht/Lb, R/Lb, Lt/Lb are performed, and the relations between the geometric factor and these parameters are presented. A set of parametric equations with respect to the geometric magnification factor is obtained using a curve fitting technique. A nonlinear relationship exists between the SIF and the ratio of ASTB arm to toe length. When the ratio of ASTB arm to toe length reaches a marginal value, the SIF of crack at the ASTB toe is not influenced by ASTB geometric parameters. In addition, the arc shape of the ASTB slope edge can transform the stress flowing path, which significantly affects the SIF at the ASTB toe. A proper method to reduce stress concentration is setting a slope edge arc size equal to the ASTB arm length.展开更多
The Moyal bracket is an exemplification of Weyl＇s correspondence to formulate quantum mechancis in terms of Wigner function. Here we present a formalism of Weyl-ordered operator Moyal bracket by virtue of the method...The Moyal bracket is an exemplification of Weyl＇s correspondence to formulate quantum mechancis in terms of Wigner function. Here we present a formalism of Weyl-ordered operator Moyal bracket by virtue of the method of integral within a Weyl ordered product of operators and the Weyl ordering operator formula.展开更多
文摘Introduction: Bracket debonding is a frequent issue that clinicians encounter, leading to increased chair time, lost revenue, and material usage. In addition to patient compliance with their diet recommendations, the preparation and conditioning of teeth for bonding significantly influence bond strength and consequently impact orthodontic treatment success and efficiency. Because of OBA-MCP’s (orthodontic bonding adhesive with modified calcium phosphate) decreased shear bond strength (SBS), the purpose of this study was to evaluate the effects of conditioning with 5.25% sodium hypochlorite (NaOCl) before etching in the bonding protocol. Materials and Methods: 90 extracted teeth were divided into 3 groups to be bonded with orthodontic brackets with different bonding protocols: 1) Transbond XT with regular bonding protocol (etch + prime + adhesive);2) OBA-MCP with regular bonding protocol;and 3) OBA-MCP with NaOCl prior to acid etching in the regular bonding protocol. SBS (in Newtons) were measured using an MTS universal testing machine with a custom jig to apply a vertical force onto the bracket and ARI (adhesive remnant index) scores were recorded for each sample after de-bond to rate the amount of adhesive remaining. Results: The addition of NaOCl to the bonding protocol statistically significantly increased the SBS of OBA-MCP to comparable levels to Transbond XT. The ARI scores showed that when NaOCl was added, more adhesive remained. Conclusion: The addition of NaOCl to the bonding protocol can increase the SBS of adhesives with historically weaker bond strengths. However, the increased amount of adhesive remaining and the increased time spent during bonding must be considered. Further testing can be done in vivo to demonstrate the practicality of this new procedure.
文摘With the increasing global demand for renewable energy,solar photovoltaic power generation technology has been widely applied in China and even globally.Especially in mountainous areas,complex terrain resources are cleverly utilized in the construction of photovoltaic power stations,but this also brings severe challenges to the anti-corrosion of photovoltaic brackets.This paper focuses on the anti-corrosion technology of mountain photovoltaic brackets,and deeply explores the influence of natural factors such as mountain climate,sandstorms,and precipitation on the corrosion of photovoltaic brackets.The research results show that the key to improving anti-corrosion performance lies in the selection of bracket materials and optimization of coating processes.After comparing various anti-corrosion treatment methods such as hot-dip galvanizing,spray aluminum coating,and new anti-corrosion materials,it is found that nano coating technology exhibits excellent protective effects in corrosive environments.This study is of great significance for promoting the sustainable development of photovoltaic power generation,providing solid theoretical support and practical guidance for the anti-corrosion design of mountain photovoltaic power stations.
文摘With the increasing global demand for renewable energy,the application of photovoltaic power generation in mountainous areas is gradually increasing.However,the complex wind environment in mountainous areas poses severe challenges to the design and optimization of solar photovoltaic brackets.Traditional design methods are difficult to cope with the changeable wind speed and direction in mountainous areas,resulting in structural instability or material waste.Researchers have identified the key factors affecting wind response through parametric research and dynamic wind response analysis,so as to optimize the brackets design and improve its adaptability and stability in complex wind environments.In this paper,the complexity of wind speed,wind direction and turbulence characteristics in mountainous areas and their influence on brackets design are explored.Through static and dynamic wind load analysis,the geometrical shape and material selection of the bracket are optimized to enhance its wind resistance.The application of multi-objective optimization model and intelligent optimization algorithm provides an effective solution for the design of solar photovoltaic brackets,ensuring their safety and reliability in complex wind environments.
文摘Introduction: The stability of orthodontic brackets throughout orthodontic treatment plays a critical role in the treatment’s effectiveness. The present in vitro study was designed to assess the impact of various dietary components on the performance of orthodontic brackets. Methods: Metal orthodontic brackets were bonded to 66 extracted anterior teeth divided into groups based on the solution type: Milk, Gatorade, Cold Coffee, and a control group using water. Each group consisted of 20 teeth except for the control group, which included six teeth. The bracketed teeth were submerged in their respective solutions for 15 minutes three times daily at different intervals to mimic an in vivo environment and were stored in artificial saliva at room temperature (23?C). The specimens underwent artificial aging through 10,000 cycles of thermocycling (representing one clinical year) between 5?C and 55?C. Shade measurements were taken using a VITA Easy Shade device, capturing the classic shade and L*, a*, and b* values. Delta E values were calculated immediately post-bonding and after 7 days, 1 month, 1, and 2 clinical years. The shear bond strength of each bracket was measured using an ultra-tester machine. Results: After two clinical years, significant differences in ΔE color values were observed across all groups, with the most substantial change noted in teeth immersed in cold coffee. Brackets submerged in milk demonstrated lower shear bond strength than other solutions, whereas the control group exhibited the highest shear bond strength (P = 0.01). Conclusion: The study indicates that dietary components significantly influence tooth color stability and the shear bond strength of orthodontic brackets, underscoring the importance of considering these factors in orthodontic treatment planning.
文摘The Bracket Set(dougong)is an important aspect of traditional Chinese architecture known for its exquisite structure,complexity,and rich variations.This design element has been used since the Qin and Han Dynasties and is still prevalent today.It highlights hierarchy and spiritual connotations in the design of a building.This article explores the application of Bracket Set elements in modern architectural design.It analyzes the specific application strategies of this design element,highlighting its value in modern architecture.The goal is to provide modern architectural designers with multiple perspectives and strategies to fully utilize the advantages of Bracket Set elements in architectural design and enhance the artistic value of their work.
基金supported by the National Key Research and Development Program of China(Nos.2017YFB1102800,2016YFB0201600)the National Natural Science Foundation of China(Nos.11672239,51735005)。
文摘Combination of topology optimization and additive manufacturing technologies provides an effective approach for the development of light-weight and high-performance structures.A heavy-loaded aerospace bracket is designed by topology optimization and manufactured by additive manufacturing technology in this work.Considering both mechanical forces and temperature loads,a formulation of thermo-elastic topology optimization is firstly proposed and the sensitivity analysis is derived in detail.Then the procedure of numerical optimization design is presented and the final design is additively manufactured using Selective Laser Melting(SLM).The mass of the aerospace bracket is reduced by over 18%,benefiting from topology and size optimization,and the three constraints are satisfied as well in the final design.This work indicates that the integration of thermo-elastic topology optimization and additive manufacturing technologies can be a rather powerful tool kit for the design of structures under thermal-mechanical loading.
文摘The investment on semi-solid die casting processes of AZ91D magnesium alloy brackets for generators in JH70-type motorbikes is introduced. The processes of low super-heat and cooling slope for the preparation of billets with non-dendritic microstructure, the remelting of billets for thixoforming and the parameters in the process of semi-sohd thixoforming have been researched. The results show that primary billets with non-dendritical structures can be prepared by forming great amount of nuclei in melt via the process of low super heat. By optimizing the remelting process through adjusting the current of the induced equipment, semi-solid billets with a structure of spherical grains were obtained from the primary billets with non-dendritical structure. The range of 580℃ to 583℃ is the proper remelting temperatures by which the billets have an expected thixotropy and can be transferred to a die-casting machine. The optimized parameters of semi-solid forming in a die-casting machine are as follows： the area of the ingate in the die is 383.5 mm^2, the speed of the pierce of the machine 5 m/s, the shot pressure of the pierce 75 MPa, and the maintenance pressure of the pierce 350 MPa. The castings of brackets for supporting generators in JH70 type motorbikes were formed by adopting the optimized processes and parameters mentioned above.
基金supported by the Civil Airplane Technology Development Program。
文摘In the aviation industry,cable bracket is one of the most common parts.The traditional assembly state inspection method of cable bracket is to manually compare by viewing 3 D models.The purpose of this paper is to address the problem of inefficiency of traditional inspection method.In order to solve the problem that machine learning algorithm requires large dataset and manually labeling of dataset is a laborious and time-consuming task,a simulation platform is developed to automatically generate synthetic realistic brackets images with pixel-level annotations based on 3 D digital mock-up.In order to obtain accurate shapes of brackets from 2 D image,a brackets recognizer based on Mask R-CNN is trained.In addition,a semi-automatic cable bracket inspection method is proposed.With this method,the inspector can easily obtain the inspection result only by taking a picture with a portable device,such as augmented reality(AR)glasses.The inspection task will be automatically executed via bracket recognition and matching.The experimental result shows that the proposed method for automatically labeling dataset is valid and the proposed cable bracket inspection method can effectively inspect cable bracket in the aircraft.Finally,a prototype system based on client-server framework has been developed for validation purpose.
基金financially supported by the Major Science and Technology Projects in Anhui Province (No. 18030901097)the Natural Science Foundation of Anhui Province (No.1908085QE197)the Fundamental Research Funds for the Central Universities (JZ2018HGBZ0133, JZ2019HGTA0043)
文摘Although the shell mould casting process has a wide range of application in many fields,the prediction of casting defects is still a problem.In the present work,a typical leaf spring bracket casting of ZG310-570 was fabricated by shell mold casting.The finite element model and ProCAST software were utilized for simulating the filling and solidification processes of the casting;and the formation mechanism of the gas pore,and shrinkage porosity defects were analyzed.The results indicate that the gas pore and shrinkage porosity defects are formed due to air entrapment,insufficient feeding and non-sequential solidification.Subsequently,through changing the position of risers,adding a connecting channel between the risers,and setting blind risers at the U-shaped brackets,an optimized gating and feeding system was established to improve the quality of the casting.After optimization,the gas pore and shrinkage porosity defects of the leaf spring bracket casting are effectively eliminated.The experiment results with the optimized casting process are in good agreement with the numerical simulation,which verifies the validity of the finite element model in the shell mould casting.
基金the Science and Technology Project of Ministry of Transport of China(No.2013328225080)the Natural Science Foundation of Liaoning Province of China(No.2015020121)+1 种基金the Research Fund for the Doctoral Program of Higher Education of China(No.20122125120013)the Fundamental Research Funds for the Central Universities of China(Nos.3132016069 and 3132016354)
文摘The hoist bracket links the rescue hoist with the helicopter cabin, and its structure design greatly affects the operation convenience and safety of the hoistman and lifeguard in the rescue process with a helicopter.This paper firstly builds the force model of the hoist and bracket, and gives five kinds of typical working conditions as the design ones of the bracket. Then this paper puts forward a design process of the hoist bracket based on the topology optimization and strength analysis with the 3D modeling and finite element analysis. This design process can make the bracket's structure lightweight by achieving the optimal material layout under the conditions of maximizing the static stiffness or minimizing the compliance of the bracket. And this improves the dynamic performance of the helicopter, and reduces the fuel consumption and cost under the strength constraints. Finally,taking the design of the hoist bracket used in a rescue helicopter as an example, this paper illustrates the proposed model and method. The analysis results show that the mass of the hoist bracket decreases by 12.5% while the static stiffness of the hoist bracket is achieved. The optimization design results meet the strength requirements of the hoist.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.51709170 and 51979167)the Ministry of Industry and Information Technology of China(Project No.[2016] 546)+1 种基金the Shanghai Sailing Program(Grant No.17YF1409700)the Open Foundation of State Key Laboratory of Ocean Engineering(Grant No.1716)
文摘For a semi-submersible platform in repair, the eight old main brackets which connect columns with pontoons need to be replaced by new ones. In order to ensure the safety of the cutting operation of the old main bracket and calculate the initial stress condition of new main bracket, the structural stress monitoring of eight key spots is carried out, and then the calibrated finite element model is established according to the field monitoring results. Before cutting the main bracket and all associated structures, eight rectangular rosettes were installed, and a tailored cutting scheme was proposed to release the initial stress, in which the main bracket and associated column and pontoon plates were partly cut. During the cutting procedure, the strains of the monitoring spots were measured, and then the structural stress of the monitored spots were obtained. The stress variation characteristics at different spots during the initial cutting operation were shown and the initial stress condition of the monitored spots was figured out. The loading and support conditions of the semi-submersible platform were calibrated based on the measured initial stress condition, which made the finite element model more credible. The stress condition with the main bracket and associated structures being entirely cut out is analyzed by the Finite Element Method (FEM), which demonstrates the cutting operation to be safe and feasible. In addition, the calibrated finite element model can be used to calculate the initial stress condition of the new main bracket, which will be very helpful for the long-term stress monitoring on the main bracket.
文摘Objective: To determine quantitatively the amount of demineralization and the ability of commercially available products and an experimental cream to inhibit or reverse orthodontic related demineralization.Methods: A total of 20 patients who were 25–35 years old and having orthodontic treatment for 6–8 months were chosen.Caries risk assessments were done for each patient and ones with "moderate risk" were included.Patients with fixed orthodontic appliances were divided into 4 groups(5 patients each) including one control and 3 study groups.All patients used same toothpaste 2 times a day during the 3 weeks study period.Additional to the toothpaste first study group used MI Paste Plus(GC, Tokyo, Japan), second study group used Remin Pro(Voco, Cuxhaven, Germany) and third group used an experimental remineralizing cream per day for 3 weeks.Maxillary central and lateral incisors of each patient were examined by FluoreCam(Daraza Therametric Technologies, USA) device.The examinations were performed at baseline and at the end of 1st, 2nd and 3rd weeks.Results: According to the FluoreCam measurements the control group showed significant amount of demineralization at the end of 3 weeks, moreover the amount of demineralization has gradually increased in time.At the end of the study all 3 study groups showed significant amount of remineralization and the amount of remineralization for all the 3 study groups has gradually increased in time.However the amount of remineralization for 3rd study group was lesser than the 1st and 2nd study groups.The remineralization amounts for the 1st and 2 nd study groups were determined to be identical.Conclusions: This study demonstrated that demineralization is measurable around orthodontic brackets and the demineralization can be completely inhibited and/or reversed by the use of commercially available remineralization products.
文摘To evaluate the shear bond strength（SBS） and bond failure interface after the debonding of orthodontic brackets with a resin-modified glass ionomer cement（RMGIC） under six bonding conditions, 140 premolar teeth were randomly divided into seven groups. The brackets of all groups, except for control group, were bonded using a RMGIC. The teeth were debonded using a universal testing machine. The shear bond strength, adhesive remnant index （ARI） and enamel fracture were examined for each debonding. A significant difference existed in SBS under wet and dry conditions in two groups of Fuji Ortho LC. Different degree of enamel fracture was seen in groups of Fuji Ortho LC（dry/37% phosphoric acid treated） after debonding. Bond failed predominantly at the enamel-adhesive interface, except for phosphoric acid treated groups. The RMGIC achieve a clinically effective adhesion in orthodontics under different bonding conditions.
基金Research Fund for the Doctoral Program of Higher Education of China(No.20122125120013)Department of Transportation Technology of Construction Project,China(No.2013328225080)+1 种基金Scientific Research Fund of Liaoning Provincial Education Department,China(No.L2013206)the Fundamental Research Funds for the Central Universities,China(Nos.3132015087,3132014303)
文摘Helicopter rescue has become an important way of life and property relief in modern society.The structure and parameters of the helicopter hoist bracket influence the convenience,safety and reliability of the rescue operation for the lifeguard and hoistman.Based on fatigue analysis theory and ANSYS workbench software,the fatigue life analysis of the hoist bracket is carried out.First,the structure of the hoist bracket is modeled according to the body standard of the hoistman and lifeguard.Then an approach is presented to obtain the S-N curve of the hoist bracket by modifying the S-N curve of the bracket material based on Goodman curve while considering the influences of the shape,size,surface state,loading conditions and the average stress.Further,based on the ANSYS workbench analysis,the life and safety nephogram of the bracket under the fluctuating cyclic load can be obtained.Finally,the designed bracket is analyzed with the proposed method.The cycles number of the bracket is greater than 107 under the extreme conditions of the pulsating cyclic load,which may be considered as the unlimited life and meets the requirement of the fatigue strength.
文摘We introduce a simple recursive relation and give an explicit formula of the Kauffman bracket of two-strand braid link . Then, we give general formulas of the bracket of the sequence of links of three-strand braids . Finally, we give an interesting result that the Kauffman bracket of the three-strand braid link is actually the product of the brackets of the two-strand braid links and . Moreover, a recursive relation for is also given.
基金This work was financially supported by the Key Research and Development Project of Shandong Province(Grant No.2020CXGC010702).
文摘The shape and size optimization of brackets in hull structures was conducted to achieve the simultaneous reduction of mass and high stress,where the parametric finite element model was built based on Patran Command Language codes.The optimization procedure was executed on Isight platform,on which the linear dimensionless method was introduced to establish the weighted multi-objective function.The extreme processing method was applied and proved effective to normalize the objectives.The bracket was optimized under the typical single loads and design waves,accompanied by the different proportions of weights in the objective function,in which the safety factor function was further established,including yielding,buckling,and fatigue strength,and the weight minimization and safety maximization of the bracket were obtained.The findings of this study illustrate that the dimensionless objectives share equal contributions to the multi-objective function,which enhances the role of weights in the optimization.
文摘A foot bracket is a metal panel bracket used to mount and support the footrest in two-wheeler systems.It holds the footrest in place while rigidly supporting it.In working conditions,this element has often been observed to fail when specific load-fluctuation conditions are established at its rear end.Appropriate materials therefore need to be identified to overcome such a recurring failure.To address these issues,the present study has been implemented with the specific objective to determine the response of selected Al6061-T6 and Al7075-T6 Hybrid Metal Matrix Composites(HMMC).The results,obtained using the ANSYS Software,show that the selected composites can withstand 636,962 N/m^(2)of maximum stress and 8.88×10^(−6)m of minimum displacement.These results are also compared with relevant mathematical models and it is concluded that the identified material combination provides the required improvement of structural stability that can withstand the load fluctuation on the foot bracket.
基金supported by the National Natural Science Foundation of China (NSFC) (Nos. 51490675 and 11572300)the Natural Science Foundation of Shandong Province (NSFSD) (No. ZR2015EM025)the Fundamental Research Fund for Central Universities (Ocean University of China)
文摘Arc-soft-toe bracket(ASTB), as a joint structure in the marine structure, is the hot spot with significant stress concentration, therefore, fatigue behavior of ASTBs is an important point of concern in their design. Since macroscopic geometric factors obviously influence the stress flaws in joints, the shapes and sizes of ASTBs should represent the stress distribution around cracks in the hot spots. In this paper, we introduce a geometric magnification factor for reflecting the macroscopic geometric effects of ASTB crack features and construct a 3D finite element model to simulate the distribution of stress intensity factor(SIF) at the crack endings. Sensitivity analyses with respect to the geometric ratio Ht/Lb, R/Lb, Lt/Lb are performed, and the relations between the geometric factor and these parameters are presented. A set of parametric equations with respect to the geometric magnification factor is obtained using a curve fitting technique. A nonlinear relationship exists between the SIF and the ratio of ASTB arm to toe length. When the ratio of ASTB arm to toe length reaches a marginal value, the SIF of crack at the ASTB toe is not influenced by ASTB geometric parameters. In addition, the arc shape of the ASTB slope edge can transform the stress flowing path, which significantly affects the SIF at the ASTB toe. A proper method to reduce stress concentration is setting a slope edge arc size equal to the ASTB arm length.
基金The project supported by National Natural Science Foundation of China under Grant No. 10475056
文摘The Moyal bracket is an exemplification of Weyl＇s correspondence to formulate quantum mechancis in terms of Wigner function. Here we present a formalism of Weyl-ordered operator Moyal bracket by virtue of the method of integral within a Weyl ordered product of operators and the Weyl ordering operator formula.
