Slot Heights Research Articles

3D-printed zirconia orthodontic brackets: Effect of printing method on dimensional accuracy.

This study investigated the effect of additive manufacturing (AM) methods on the slot height dimensions and accuracy of 3D-printed orthodontic brackets. A 3D model of a standard Mclaughlin Bennett Trevisi bracket was used as a reference to print the ceramic bracket in a 90° orientation using two representative AM methods: digital light processing (DLP) and material jetting (MJ). The dimensional accuracy and slot heights were determined using a scanning electron microscope and an optical scanner. Also, all specimens were analysed using the Geomagic Control X 3D inspection software. The root mean square (RMS) values were used for trueness and precision assessment. Statistical analyses were performed using an independent sample t-test. Slot height dimensions, trueness RMS, and precision RMS were statistically affected by different AM methods (p < .01). There was a significant difference between the different printing methods, with DLP meeting the tolerance requirements (mean slot height = 0.557 ± 0.018 mm) and MJ being slightly below them (mean slot height = 0.544 ± 0.021 mm). However, MJ significantly outperformed DLP in terms of accuracy. Among the two printing methods, MJ was associated with higher trueness (RMS = 0.025 ± 0.004 mm) and precision (RMS = 0.038 ± 0.005 mm). Both tested AM methods yielded clinically acceptable outcomes, with the RMS range set to ±100 μm and the slot height tolerance established at 0.549-0.569 mm. The MJ technology achieved the highest accuracy.

Numerical Analysis of the Influence of Side Slot and Fin Heights in a Hypervapotron Channel on Heat Transfer

Numerical Analysis of the Influence of Side Slot and Fin Heights in a Hypervapotron Channel on Heat Transfer

A scanning electron microscopy investigation of the precision of three orthodontic bracket slot systems

ObjectiveOne of the most imprortant factors in achieving ideal teeth positions is the precision of the slot dimensions of orthodontic brackets into the archwires are inserted.This study aimed to assess the accuracy of the dimensions of orthodontic bracket slots and molar buccal tube apertures and to compare them with the specifications provided by the manufacturers.MethodA total of sixty brackets and ten molar buccal tubes with varying slot heights were examined using a scanning electron microscope from the mesial side. The dimensions and morphology of these bracket slots and buccal tubes apertures were assessed using the AutoCAD Software. A one-sample t-test was conducted to compare the measurements with the values provided by the manufacturer.ResultsThe findings of the present study indicated that the height of the measured bracket slots and buccal tube apertures dimensions were significantly larger than the actual dimensions and exhibiting divergent walls. On the other hand, the depth of the brackets slots showed significantly smaller values than the actual one.ConclusionA need for careful consideration when selecting a commercially accessible brand for everyday use is essential as certain materials may not meet acceptable standards.

3D-printed patient specific surgical guides: Balancing accuracy with practicality

IntroductionThree-dimensional (3D) printing technology has been used in orthopaedic surgery in recent years to manufacture customized surgical cutting jigs. However, there is scarcity of literature and information regarding the optimal parameters of an ideal jig. Our study aims to determine the optimum parameters to design surgical jigs that can produce accurate cuts, and remain practical for use, to serve as a guide for jig creation in future. Methods and materialsA biomechanical lab study was designed to investigate whether the thickness of a jig and the height of its cutting slot can significantly affect cutting accuracy. Surgical jigs were 3D printed in medical grade, and an oscillating sawblade was used to mimic intraoperative surgical cuts through the cutting slots onto wooden blocks, which were then analysed to determine the accuracy of cuts. ResultsStatistical analysis was performed on a total of 72 cuts. The cutting accuracy increased when the thickness of the jig increased, at all slot heights. The cutting accuracy also increased as the slot height decreased, at all jig thicknesses. Overall, the parameters for jig construction that yielded the most accurate cuts were a jig thickness of 15 mm, in combination with a slot height of 100 % of the width of the sawblade. Additionally, at a jig thickness of 15 mm, there was no statistically significant difference in cutting accuracy when increasing the slot height to 120 %. ConclusionThis study is the first to propose tangible parameters that can be applied to surgical jig construction to obtain reproducible accurate cuts. Provided that a jig of 15 mm thickness can be accommodated by the size of the wound, the ideal surgical jig with a superior balance of accuracy and useability is 15 mm thick, with a cutting slot height of 120 % of the sawblade thickness.

In-House 3D-Printed vs. Conventional Bracket: An In Vitro Comparative Analysis of Real and Nominal Bracket Slot Heights

Aims: The purpose of this study was to evaluate the accuracy of the slot height of in-house 3D-printed resin brackets, comparing them with other types of brackets on the market today, both ceramic and metallic. Methods: Seven different types of bracket systems were selected. For each system, ten brackets for tooth 2.1 with 0.022 × 0.028-inch slots were selected (total n° 70). Considering the whole sample, five types were commercially available and two were in-house 3D-printed. The entire sample was divided into four different groups according to the bracket material and the method of holding the archwire. Precision pin gauges with 0.002-mm increments were inserted inside the slot of each bracket, and the slot heights were measured, microscopically ensuring that the gauge completely filled the slot, with full contact between both the bottom and the top of the slot. Results: With respect to the other five types of brackets on the market, the two types of in-house 3D-printed resin brackets showed great accuracy of slot height (0.558 ± 0.001 mm). There was a statistically significant difference between the real height measured and the nominal height declared by the manufacturers (p &lt; 0.05) of all the samples investigated, with the exception of in-house 3D-printed resin brackets. Furthermore, the difference in slot height accuracy between commercially manufactured and in-house 3D-printed resin brackets was statistically significant. Conclusions: In-house 3D-printed resin brackets have a remarkably precise slot height, unlike commercially available brackets, whose slot heights tend to be significantly oversized with respect to the nominal values declared by the manufacturers.

Experimental investigation of static pressure characteristics in a slotted short pin array

ABSTRACT A common heat exchange method used for most new designs is the use of heat sinks such as short pin fins. This experimental study investigated the static pressure characteristics developed in a short pin fin. Different fin array arrangements, fin longitudinal and transverse spacing ratios and individual slot heights in the fin were investigated. It was found that the row removed arrangement has superior flow efficiency, but to enhance heat transfer the staggered array is a better choice; the greater the fin spacing and slot height in each fin are, the less the pressure loss was experienced in the array.

Experimental Study on Cooling Efficiency of Hypersonic Optical Window

The cooling effectiveness of optical window influences the imaging quality of hypersonic vehicles. This study focuses on the supersonic film cooling efficiency on the optical window of a blunt cone in hypersonic flow. The experiments were conducted in a gun tunnel equipped with a Mach 8 nozzle providing a total pressure and temperature of 9 MPa and 900 K respectively. Three tangential 2D nozzles with different combinations of slot heights and Mach numbers were designed to detect the film cooling length under different injection pressures. The heat flux on window surface was measured by Thin Film Gauges and the flow field was monitored by schlieren technique. When the jet pressure matched the mainstream, the window was completely cooled, and the minimum mass flow rate was achieved when the slot height was 5mm and the jet Mach number was 2.5. If the pressure ratio of jet continues to increase, the heat flux density could be furtherly reduced, but the cooling efficiency of unit coolant mass flow decreased significantly. The data correlation results showed that the cooling efficiency presented a nonlinear relationship of second order polynomial with (x/Sh)λ-0.8 , and the effective cooling length of film was positively correlated with the cooling mass flow ratio (λ) and slot height of the nozzle. Besides, the increase of jet pressure resulted in thickening the mixing layer, which enhanced the heat insulation effect and reduced the heat flux as a result.

Permanent magnet generator with axial magnetic flow for wind plants

The results of numerical and experimental studies of an electric generator with permanent magnets and axial magnetic flux for low-power wind turbines are presented. In order for wind turbines to successfully compete with sources of autonomous power supply based on solar energy, it is necessary to reduce the specific cost of electric generators. One of the possible ways to reduce the cost of a wind turbine is to replace a quiet-running multi-pole generator with a high-speed one, which is paired with a magnetic step-up gear. In this case, the electric generator can be designed for rotation frequency n = 1000 ÷ 3000 rpm. It is for this range of rotational speed that the optimal configuration and dimensions of the magnetic system of the electric generator have been determined, at which the maximum power value is reached. Comparisons of the calculated and experimental characteristics of the generator are carried out, the good coincidence of which confirms the adequacy of the developed mathematical models. These computer models are then used to study the dependence of the specific power of the generator on the height of the stator slots and the section of the winding wire made of copper tape. It is shown that for optimal geometrical parameters the magnetomotive force of the stator winding must be matched with the magnetomotive force of permanent magnets. Only for a certain range of slot heights is the maximum power at the rated current ensured. The characteristics of the investigated generators were calculated using the Simcenter MagNet software package.

Optimization of slot permeance coefficient with average differential evolution algorithm for maximum torque values by minimizing reactances in induction machines

This study focused, the stator and rotor slot permeance coefficient values of an induction motor with a 3-phase squirrel cage are optimized using the Average Differential Evolution (ADE) algorithm and it is aimed to maximize the torque values (starting, maximum, and nominal) of the motor. In this context, the stator and rotor slot parameters of the motor (slot heights, widths, etc.) are optimized to give the minimum stator / rotor inductance and leakage reactance values. Thanks to obtained the new stator and rotor slot geometries, an improvement of 12.07% at the starting torque, an improvement of 5.40% at maximum torque and an increase of 1.13% at nominal torque value were achieved. In addition, total permeance, inductance and leakage reactance values and convergence curves for different slip conditions are given comparatively.

Study on flow and heat transfer of liquid metal in a new top-slotted microchannel heat sink

In order to overcome the disadvantage of large pump power required to maintain flow with the large flow resistance caused by high viscosity and high density of liquid metal in microchannel heat sink, a new top-slotted microchannel is designed in this paper. The flow and heat transfer performance of microchannel heat sink with different slot heights was studied by numerical simulation. The results show that the lowest pump power of 0.00157W is obtained when the slot height is 0.8mm without affecting the cooling performance of the microchannel heat sink, which is 16.5% lower than that of the traditional channel.

Layouts of Unit-Load Warehouses with Multiple Slot Heights

We describe a method to generate layouts for unit-load warehouses that use multiple slot heights as a way to maximize warehouse space utilization. The problem has two parts: slots must be arranged into rack-bays, and rack-bays must be arranged into a layout. We describe two methods for the first subproblem, depending on whether the warehouse has directed picking and put-away. For the second, we describe a simulation model and a greedy procedure based on the duration-of-stay storage policy. We observe significant benefits of using multiple slot heights in unit-load warehouses with respect to footprint, expected travel time, and cost of racking. For a typical warehouse, we expect space savings between 25% and 35%, depending on the number of slot types, and savings of between 15% and 25% in annual operating costs.

Effects of Lip Thickness on the Flowfield Structures of Supersonic Film Cooling

Schlieren visualizations of flowfield structures of supersonic film cooling in a backward-facing step were conducted in a Mach 2.95 suction wind tunnel with the film coolant tangentially ejected through half-Laval nozzles, all of which were designed in Mach 1.5 but with different lip thicknesses. The film coolants were fed with pressures matching the mainstream, and the flowfield changes of supersonic film cooling under different lip thicknesses between the slot and mainstream were clearly visualized under the conditions of the same step and slot heights. When the step height was kept the same, an increase in lip thickness decreased the angle of the shock wave emanating from the upper tip of the lip, and it decreased the strength of the reattachment shock wave when it was larger than a certain value. When the slot height was kept the same, the increase in lip thickness tended to decrease the angles of the shock waves emanating from the upper and lower tips of the lip and reattachment shock waves. This work provides an in-depth understanding of the flowfields of supersonic film cooling near the backward-facing step and may be used as a reference for the design of supersonic film cooling.

How to determine slot sizes in a unit-load warehouse

Storage racks in a unit-load warehouse typically have slots of equal height, whereas the unit-loads themselves have heights that vary significantly. The result of this mismatch is unused vertical space and storage areas larger than they otherwise could be. We propose the use of storage racks with multiple slot heights to better match the distribution of pallet heights. The slot profile design problem seeks the best set of slot heights and their corresponding quantities such that a desired service level is met, where service level is the probability that all pallets present in a period can be stored. Using data from several companies, we found that the potential space savings of using multiple slot heights are between 29% and 45%.

Experimental investigation on airflow pattern for active chilled beam system

Experimental results of the airflow pattern for Active Chilled Beams (ACB) system are investigated in this paper, where the air velocity and turbulence intensity for the air jet near the ceiling are tested and recorded under both isothermal and non-isothermal conditions. Based on the results, the velocity profile along streamwise direction is found to be significant in analyzing air detachment from the ceiling. It is revealed that the Coandă effect can be enhanced by a high pressure drop of ACB terminal unit and impeded by the temperature difference between supply air and room air. The self-similarity for the air jet is observed to be feasible for a certain downstream distance where the vertical maximum velocity is within 1.25 slot heights. A comparison study has been conducted for two mathematical models describing the self-similarity with the experimental data. It turns out that Verhoff's model has an overall better performance than Schwarz and Cosart's model. The turbulence intensity, which tends to be larger for points with lower velocity, is higher in areas where the entrainment effect is stronger.

Gaseous film cooling investigation in a multi-element splash platelet injector

Film cooling is an effective technique that protects chamber walls in rocket combustion against chemical attacks and heat fluxes. This study discusses cooling effect in a multi-element GO2/CH4 splash platelet injector. Influence parameters, such as slot height, slot number, percentage of coolant, and injection position on cooling effect, were investigated. GCH4 with 298.15 K was applied as film coolant. In the first step, slot heights of 0.2 and 0.4 mm were compared by applying a constant film mass flow rate. Temperature, CH4 mole fraction distribution, and flow field structure were obtained. The effects of slot number, percentage of coolant, and injection position on wall temperature distribution were then determined. Finally, the reasons for the low cooling efficiency were analyzed. Improvement in the method is proposed to achieve improved cooling effect for splash platelet injectors.

Standard Versus Real Versus Fake Braces: Design And Microstructure Comparison

Introduction: The growing demand for orthodontic braces among Malaysian community has led to the development of "fake" and "real" braces. "Fake" braces refer to braces that are worn as costume and are not bonded to teeth hence unable to produce movement of teeth. "Real" braces refer to braces that are bonded to tooth structure and are able to produce tooth movement. The braces are bonded by unqualified practitioners with no formal dental education and they provide braces treatment in unlicensed premises such as hotel rooms or patients' own homes. Materials and Methods: This study was conducted to investigate the design and microstructure of several types of "fake", "real" and standard braces. A total of 9 upper right central incisor brackets were scanned using high resolution scanning electron microscopy (SEM) with magnifications of 65x, 500x and 1000x. Brackets slot heights and depths were also measured to compare slot dimensions between "fake", "real" and standard braces. Results: The surface textures of "fake" and "real" braces were noticeably more granular and unpolished as compared to conventional brackets. Furthermore, all "fake" and some "real" braces upper right central incisor bracket designs were distinctly different from the standard braces. The slot dimensions of "fake" and "real" braces were also significantly larger that standard braces. Conclusion(s): In conclusion, the surface texture and morphology of "fake" and "real" braces were crude and different when compared to conventional brackets.

A DUAL GRATING WAVEGUIDE STRUCTURE FOR WAKEFIELD ACCELERATION AT THZ

A dual grating waveguide accelerator structure is investigated and compared with the dielectric wakefleld accelerator at THz frequencies. In a dielectric wakefleld accelerator, thinner liners for a given current and liners having lower dielectric constant are not preferable due to the fact that they generate much lower axial wakeflelds. This limits the operation of the device at THz. On the other hand, it is shown that a grating waveguide is tuned at THz with shallower slot heights with competitive wakefleld gradients than a dielectric wakefleld accelerator.

Large-eddy simulation of shock-cooling-film interaction at helium and hydrogen injection

Laminar helium and hydrogen films at a Mach number 1.3 are injected through a slot into a fully turbulent freestream air flow at a Mach number 2.44. To numerically study by large-eddy simulations the impact of an impinging shock on various cooling films, first, reference solutions without shock impingement are computed and then, the helium and hydrogen cooling films interacting with an oblique shock at a pressure ratio of p3/p1 = 2.5 are analyzed. The comparison of the helium and hydrogen injections without shock shows the hydrogen injection to have a 1.14-fold better cooling effectiveness at 60% of the blowing rate of the helium injection. The shock-cooling-film interaction causes a massive separation bubble that is 23% larger at the hydrogen than at the helium injection. Nevertheless, the shock influenced cooling effectiveness at the hydrogen injection is only 30% reduced compared to a 40% decrease at the helium injection 100 slot heights downstream of the injection. The intense mixing in the shock-cooling-film interaction region shows a more rapid reduction of the helium and hydrogen mass fractions than in the zero-pressure gradient reference configurations. Overall, the cooling effectiveness of the hydrogen film is superior to that of the helium film independent from the streamwise pressure gradient.

An Experimental Study of a Turbulent Wall Jet on Smooth and Transitionally Rough Surfaces

The effect of surface roughness on the mean velocity and skin friction characteristics of a plane turbulent wall jet was experimentally investigated using laser Doppler anemometry. The Reynolds number based on the slot height and exit velocity of the jet was approximately Re = 7500. A 36-grit sheet was used to create a transitionally rough flow (44 &lt; ks+ &lt; 70). Measurements were carried out at downstream distances from the jet exit ranging from 20 to 80 slot heights. Both conventional and momentum-viscosity scaling were used to analyze the streamwise evolution of the flow on smooth and rough walls. Three different methods were employed to estimate the friction velocity in the fully developed region of the wall jet, which was then used to calculate the skin friction coefficient. This paper provides new experimental data for the case of a plane wall jet on a transitionally rough surface and uses it to quantify the effects of roughness on the momentum field. The present results indicate that the skin friction coefficient for the rough-wall case compared to a smooth wall increases by as much as 140%. Overall, the study suggests that for the transitionally rough regime considered in the present study, roughness effects are significant but mostly confined to the inner region of the wall jet.

Exploring the aerodynamic characteristics of a blown annular wing for vertical/short take-off and landing applications

This article explores, theoretically and experimentally, a new wingform, based on an annular wing wrapped around a radial flow generator, potentially creating a vehicle with no external moving parts, reduced vehicle aerodynamic losses compared to previous vertical/short take-off and landing technologies, and substantially eliminating induced drag. Concentrating on hovering and slow flight, it is shown that such a wing works best with a thick aerofoil section and appears to offer greatest potential at a micro-aerial vehicle scale. Experimental methods are described along with results, and this work shows that wing efficiency can be substantially improved by the use of upper surface blowing technology and the Coanda effect. The main causes of efficiency loss are annular flow expansion and problems with achieving acceptable slot heights. Experimental efficiency remains below theoretical efficiency, partly due to flow asymmetry but possibly also other factors. This work is also very early in the development of this technology, and so recommendations are made for future work.