Tooth Height Research Articles

Machinability and Chip Morphology Study of Inconel 740H and Haynes 282 for Advanced-Ultra Supercritical Applications

Abstract: High speed machining of Nickel based alloys has gained a lot of research interest since the last decade owing to their applications in areas like power generation, aerospace, marine propulsion, and nuclear reactors. For the realization of an advanced ultra-supercritical (A-USC) thermal plant, operating at service temperatures of about 700 to 760oC and pressures of around 24 MPa, the use of Nickel-based super alloys is indispensable. Some these parts used for the application may be required to be machined before use, although the machinability of these materials is relatively poor. Chip morphological studies are performed for better understanding of cutting force and surface finish of the alloys. In this work, authors have tried to study the effect of machining parameters like cutting speed, feed rate, rake angle, and nose radius on chip morphology like peak height, valley height, tooth height, tooth pitch, and segmentation frequency. The results of chip morphology studies indicate the need for saw tooth chips for better machining. Accordingly, Inconel 740H is found to have better machinability than Haynes 282 for the used range of machining parameters. Moreover, higher cutting speeds, lower feed rates, and positive rake angles are found to yield optimum conditions for an improved machinability

Effects of Flow Path Geometrical Parameters on the Hydraulic Performance of Variable Flow Emitters at the Conventional Water Supply Stage

We created a subsurface drip irrigation (SDI)-specific variable flow emitter (VFE) that switches working stages automatically based on the inlet pressure (H) to achieve a step change in the flow rate. At working stage I (H = 0.1 MPa), namely the conventional water supply stage, the VFE provided a normal flow rate (qI) of 1–2 L/h for crop irrigation. At working stage II (H > 0.1 MPa; exceeding the design pressure), VFE delivered a larger flow rate (qII). The larger qII facilitated water movement upward from the underground to the surface seedbed during the crop planting, thus ameliorating crop germination issues under SDI. We focused on the impacts of four structural parameters of the flow channel: tooth height (E), tooth spacing (B), tooth angle (A), and flow channel depth (D) on the qI and VFE-flow index (x) at working stage I. Computational fluid dynamic (CFD) simulations were conducted along with a physical laboratory test to develop VFE using computerized numerical control (CNC) technology (accuracy = 0.05 mm). Nine VFEs were designed using an L9(34) orthogonal test. The combination of tetrahedral meshing with a six-layer boundary layer and the realizable k–ε turbulence model was found suitable for CFD simulations. The standard root-mean-square error (nRMSE) of the measured and simulated qIs was a minimum of 7.4%. The four parameters influenced qIs as D > B > E > A, and the four factors influenced the xs as B > E > D > A. Based on the numerical simulation data, multiple linear regression models were constructed for the qIs and xs with four parameters when H = 0.1 MPa. Aiming for the minimum x, the optimal combination of the flow channel structural parameters corresponding to different qIs was determined by the ergodic optimization algorithm. When qI was 1.5 L/h, the optimal structural combinations were E = 1.2 mm, B = 1.8 mm, A = 42°, and D = 1 mm. The VFE with a qI of 1.5 L/h was created by CNC technology. The relative errors of the measured and predicted qIs using the regression model were −0.19–6.31%, and their nRMSE was 6.76%. Thus, optimizing the flow channel structural parameters based on a multiple linear regression model and the ergodic optimization algorithm is a highly precise theoretical base for VFE development.

The position and morphology characteristics of multiple impacted anterior teeth in the unilateral maxillary area: A retrospective study based on cone-beam computed tomography

This study investigated the position and morphologic characteristics of multiple impacted anterior teeth in the unilateral maxillary area. Cone-beam computed tomography images of 21 patients (11 males and 10 females; median age 9.42 years [9.08-11.29]) with multiple teeth impacted were collected and imported into Dolphin Imaging software (Dolphin Imaging and Management Solutions, Chatsworth, Calif). The vertical height, crown orientation, twist direction, and root curvature of each impacted tooth were described. The crown length, root length, and root canal width of impacted and homonym teeth were measured. The positions of the impacted lateral incisors are lower than that of the other 2 anterior teeth. Most crowns of impacted central incisors are positioned distally, labial surfaces in mesial torsion, with most roots, bent toward the distal and labial. Crowns of impacted lateral incisors are positioned mesiolabially, with labial surfaces mostly in distal torsion, and most roots bent toward the mesial and labial. Crowns of impacted canines are mostly positioned mesiolabially, with labial surfaces in mesial torsion. The crowns and roots of the impacted central and lateral incisors were shorter than those of the homonym (P<0.05); however, the difference in crown length is clinically negligible, and there was no difference in root canal widths. There was no difference in the comparison of parameters for the canine group. There are certain rules in the vertical height, crown orientation, twist direction, and root curvature of multiple impacted anterior teeth in the unilateral maxillary area. Root development of impacted central and lateral incisors was restricted.

Effects of stator and rotor geometry on inline high shear mixers: Residence time distribution, flow, and energy consumption

Using high shear mixers (HSMs) as the vessel to intensify chemical processes requires knowledge of the residence time distribution (RTD) characteristic. Considering the numerous structural characteristics of HSMs, a series of pilot-scale HSMs was developed to investigate the RTD characteristics through pulse tracing and deconvolution. A number of structural parameters were included here, including tooth height, tooth thickness, and the number of rotor-stator tooth rows, slots, and stages. Meanwhile, by using CFD simulations with the large-eddy simulation model coupled with the sliding mesh method, the flow rate, power consumption, and energy dissipation rate distribution, as well as RTD of HSM were examined. It is illustrated that adding a distributor or increasing rotor speed improves the local energy dissipation, reducing short-circuits and dead zone. The RTD curves become smoother and closer to plug flow with increasing stator-rotor stages. Typical first/second-order reactions are favored by higher or thicker rotor-stator teeth, and HSM is better suited when kR1 > 1 s−1 or kR2cA0 > 5 s−1. Furthermore, the correlations of E(t), tR, σθ2, Potot, and qave, 1+ were obtained, which would provide useful guidance on the scale-up design and optimization of HSMs.

Visualising trends in dentition to lip mouth morphology using geometric morphometrics.

Linear measurements taken from bony landmarks are often utilised in facial approximation (FA) to estimate and plan the placement of overlying soft tissue features. This process similarly guides craniofacial superimposition (CFS) practices. Knowledge of how hard and soft tissue features spatially relate around the mouth region is, however, limited. Geometric morphometric techniques have thus been used to investigate size and shape variation in dentition-to-lip mouth morphology in a South African population. Twenty landmarks (twelve dentition, eight lips) were digitised, using cone-beam CT images of the anterior craniofacial complex in a Frankfurt/Frankfort position, for 147 individuals aged between 20 and 75 years. Principal Component Analysis and Canonical Variate Analysis established that much shape variation exists. A two-way ANOVA identified significant (p < 0.0001) population and sex variation with mouth shape. Black individuals presented with thicker lips, with the oral fissure aligning closely to the dental occlusion. Oral fissure position for white individuals corresponded to the inferior one-quarter (females) or one-sixth (males) of the maxillary central incisor crowns. Males presented larger dimensions than females, but females had a greater lip-to-teeth height ratio than their male counterparts. A pooled within-group regression analysis assessed the effect of age on the dentition and lips and found that it had a significant (p < 0.0001) impact on mouth shape. Ageing was associated with a reduced lip and teeth height, increased mouth width, and a lowered oral fissure and cheilion placement. The generated mean shape data, with metric guides, offer a visual and numerical guide that builds on existing FA and CFS standards, enhancing our understanding of hard and soft tissue relationships.

Precision of &lt;em&gt;In Vivo&lt;/em&gt; Quantitative Tooth Wear Measurement Using Intra-Oral Scans

Quantitative wear measurement is of increasing interest for measuring tooth wear progression. However, most research on quantitative wear measurement has focused on simulated wear or scanned gypsum casts. A 3D Wear Analysis (3DWA) protocol has been developed that analyzes tooth wear in vivo through intra-oral scanners available to dental clinicians. This study investigated the precision of the 3DWA protocol for measuring wear through maximum height loss (mm) and volume change (mm3). Observational prospective wear data from 55 patients were analyzed after 0-1-, 0-3-, and 0-5-year intervals to determine rates of wear, and convenience samples were chosen to test the protocol's precision on dentitions scanned twice in one sitting and its intra- and inter-rater precision on scans with 0-3- and 0-5-year intervals. Scans were made using intra-oral scanners (IOS) and superimposed using 3D measurement software. T-tests were performed to determine the structural and random error, and trimmed ranges were calculated to interpret the error. For protocol precision, the mean difference was 0.015 mm (-0.002; 0.032, p = 0.076) for height and -0.111 mm3 (-0.250; 0.023, p = 0.101) for volume. The duplicate measurement error was 0.062 mm for height and 0.268 mm3 for volume. The height measurements were precise enough to measure wear after intervals of 0-3 or 0-5 years; however, volume measurements were susceptible to procedural error and operator sensitivity. The 3DWA protocol is precise enough to adequately measure tooth height loss after intervals of a minimum of 3 years or in patients with severe wear progression, but it is not suited to measuring volumetric changes.

Precision of In Vivo Quantitative Tooth Wear Measurement using Intra-Oral Scans.

Quantitative wear measurement is of increasing interest for measuring tooth wear progression. However, most research on quantitative wear measurement has focused on simulated wear or scanned gypsum casts. A 3D Wear Analysis (3DWA) protocol has been developed that analyzes tooth wear in vivo through intra-oral scanners available to dental clinicians. This study investigated the precision of the 3DWA protocol for measuring wear through maximum height loss (mm) and volume change (mm3). Observational prospective wear data from 55 patients were analyzed after 0-1-, 0-3-, and 0-5-year intervals to determine rates of wear, and convenience samples were chosen to test the protocol's precision on dentitions scanned twice in one sitting and its intra- and inter-rater precision on scans with 0-3- and 0-5-year intervals. Scans were made using intra-oral scanners (IOS) and superimposed using 3D measurement software. T-tests were performed to determine the structural and random error, and trimmed ranges were calculated to interpret the error. For protocol precision, the mean difference was 0.015 mm (-0.002; 0.032, p = 0.076) for height and -0.111 mm3 (-0.250; 0.023, p = 0.101) for volume. The duplicate measurement error was 0.062 mm for height and 0.268 mm3 for volume. The height measurements were precise enough to measure wear after intervals of 0-3 or 0-5 years; however, volume measurements were susceptible to procedural error and operator sensitivity. The 3DWA protocol is precise enough to adequately measure tooth height loss after intervals of a minimum of 3 years or in patients with severe wear progression, but it is not suited to measuring volumetric changes.

Experimental investigation on mechanical characteristics of low-voltage driving traveling-wave ultrasonic motor with the flexible rotor

Classical traveling-wave ultrasonic motors (TWUMs) usually generate the elliptical clusters on the stator surface through the bending vibration of the annular stator on the basis of piezoelectric excitation, and the torque output and power transmission are realized by friction coupling under the rational preload. Stable and reliable working characteristics attracted the focus of various applications. High energy consumption and low efficiency are restricted factors for the service performance of motors. Displacement amplification and stress regulation based on flexible design become a possible approach to improve motor performances. In this study, a TWUM30 prototype was proposed with consideration of (sub) structure optimization, i.e., tooth height and backlash of the stator elastomer. The flexible design of the rotor structure was carried out for consideration of the contact area and stress regulation. After integrated bonding of the stator and PZT4, the electrical and vibration characteristics of the stator prototype are measured by an impedance analyzer and high-precision laser micro-displacement sensor. Results showed that the proposed TWUM30 is capable of operation under low-voltage driving (41.9 kHz @ 80 Vp), and the extreme mechanical performances presented the stall toque of 64mN∙m and the no-load speed of 153.8 rpm. With the combination of the flexible design and systematic integrated manufacturing of the stator/rotor, low-voltage driving of the TWUM30 motor under ultra-low preload was realized at low cost and the adverse effects of excessive preload were suppressed. This study is expected to provide support for high reliability design and long-life service of the TWUMs. It also provides a realistic possibility for the flexible design and application of energy-saving and high-efficient traveling-wave piezoelectric drivers.

Electromagnetic-thermal coupling analysis of a permanent-magnet in-wheel motor with cooling channels in the deepened stator slots

Heat generated inside a permanent-magnet (PM) in-wheel motor is usually not well dissipated due to the narrow space inside wheel hub, causing degrading performance and even safety risk. To improve the cooling performance of PM in-wheel motor, we propose a cooling structure in which cooling channels are moved into deepened stator slots. The cooling performance and electromagnetic influence are evaluated through electromagnetic-thermal coupling analysis. The results show that when the output power is kept unchanged, cooling channels at the bottom of deepened stator slots shortens the heat flow path from windings to coolant, lowering the maximum motor temperature from 153.7 to 144.4 °C compared with the scenario of cooling channels in housing. Meanwhile, the motor efficiency is slightly reduced by 0.02% due to the increase of stator teeth height. Moving cooling channels from the bottom to the middle of deepened stator slots increases the contact area between windings and cooling channels, which further lowers the maximum temperature to 129.5 °C. The motor efficiency is further reduced by 0.15% because of the change of winding position. The analysis shows that moving cooling channels into deepened stator slots can significantly lower the motor temperature and yet exerts little influence on the motor efficiency.

A review of the research status of scroll expander

In order to solve the problem of energy crisis and take the road of sustainable development, the development of renewable energy and recycling of low-grade waste heat have attracted more and more attention. As a new type of volumetric energy conversion device, scroll expander is wi dely used in Organic Rankine Cycle (ORC) waste heat recovery, because of its advantages such as small size and so on. Scroll profile is one of the main factors affecting scroll expander performance. Compared with the traditional constant section scroll profile with same suction volume, volume ratio and shell size, the new type of variable section scroll profile could reduce scroll tooth height, better mechanical properties and improve efficiency, therefore making it more suitable for working under complex operating conditions. In order to reduce the head invasion rate, airflow friction factor, the power loss at the air inlet, and improve the pneumatic power conversion efficiency, a new head correction method is proposed. Although R123, R134 and R245 are the most commonly used working medium in scroll fluid machinery, the selection of working medium in scroll expander is still a key problem. The overall performance of the scroll expander can be improved by designing different inlet shapes and positions or double-symmetrical exhaust ports. The radial leakage caused by axial clearance of scroll expander can be improved by developing new scroll profile to reduce the length of radial leakage line and optimizing the design of scroll top sealing mechanism. The tangential leakage caused by radial clearance can be improved by enhancing the manufacturing precision and installation accuracy of scroll plate and designing the radial variable mechanism. At present, fewer research has been carried out on the leakage of scroll expander. Therefore reducing the leakage loss to improve the performance of scroll expander is of great significance in the future research.

Sex-specific reference values for the crown heights of permanent anterior teeth and canines for assessing tooth wear

Objective We propose sex-specific reference values for the clinical crown height of anterior teeth and canines. Material and methods In this cross-sectional study, 1426 teeth were analysed from 169 undergraduate and postgraduate dental students (83 women and 86 men, median age 22 years). Teeth with worn or totally restored incisal edges, or gingival inflammation were excluded. Age, gender and body height were recorded and the degree of tooth wear was scored according to the quantification module of the Tooth Wear Evaluation System. The clinical crown heights of all anterior teeth and canines were measured from the gingival margin to the incisal edge with a digital calliper. Reference values for tooth groups were obtained at the percentiles 10, and expressed by sex if there was a significant difference between men and women. Results Mean crown heights were bigger in men than in women for each tooth group (p = .028). Clinical crown heights showed sexual dimorphism at the 10th percentiles for all tooth groups except for mandibular anterior teeth. Conclusions For assessing tooth wear, the sex-specific reference values for the clinical crown height of young adults Caucasoids range from 7.5 mm to 9.0 mm in women and from 7.5 mm to 9.5 in men.

CFD Analysis of Sine Baffles on Flow Mixing and Power Consumption in Stirred Tank

In order to enhance the fluid mixing in the stirred tank and reduce the power consumption under the condition of full baffle, a sinusoidal sawtooth baffle was established in the present study. Based on the Eulerian–Eulerian method, a numerical simulation of the mixed flow in the stirred tank was conducted, and the reliability of the simulation method was verified by means of PIV experiments. The different structural characteristics of a standard baffle and the sine baffle were compared, to explore the effect of the modified baffle on flow mixing and power consumption in the tank. The outcomes indicate that the sinusoidal sawtooth structure had the effect of reducing drag and shunting, which could lessen the backflow on the backside of the baffle, strengthen the intensity of fluid turbulence and strain rate, improve the uniformity of particle distribution, and significantly lower the power consumption. When the relative tooth height was 0.333 and the relative tooth width was 0.028, the power consumption was reduced by 11.7%.

Influence of the axial tooth structure on the pressure resistance of the magnetic fluid sealing device

Magnetic fluid sealing is one of the most advanced applications of magnetic fluids. Presently, the research field mainly focuses on the polar teeth, leaving a gap in the structure of the shaft. To effectively achieve the improvement of the compression resistance of the magnetic fluid sealing device, an improvement of the axial structure is required. From this perspective, this study presents a novel shaft axis gear structure for the establishment of a magnetic fluid static seal compression capacity for this model. The shaft is studied through the simulation analysis of the tooth height, the width and eccentric distance was investigated for the influence of the compression capacity. An experimental device was then used to validate the results and confirm the validity of the findings.

Study on the Influence of Shear Indenter Parameters on the In Situ Shear Strength Test

Cohesion and friction angle are important indicators of shear strength in mining engineering. Indoor testing methods are detached from the actual state of the rock mass and affected by disturbances and significant dimensional effects that do not fully reflect the shear strength of the rock mass itself. In situ borehole shear testing is of great practical importance because of its low disturbance and high speed. In this paper, a new testing device based on the principle of a rock borehole shear tester was designed to simulate the shear test in the laboratory. Seven shear indenters were designed to test the effect of different tooth heights, spacing, and angles on the shear strength of rock-like specimens, and the damage surface was scanned in three dimensions and compared with conventional triaxial tests and compression shear tests. The results show that as the tooth height increases, the flatness of the press-in damage surface increases, and the results will be closer to the press-shear test. As the spacing increases, the maximum damage angle and the damage surface between the grooves gradually decrease. The tooth angle has little effect on the friction angle, but cohesion decreases significantly when exceeds 60°.

Research and Optimization of Process Parameters for Internal Thread Forming Based on Numerical Simulation and Experimental Analysis.

In order to improve the forming quality of extruded thread, finite element analysis and experimental research are combined to reduce the two keys that affect thread quality in the machining process—extrusion torque and extrusion temperature. The effects of different processing parameters on the extrusion torque and temperature are obtained by numerical simulation, including the bottom hole diameter of the workpiece, the machine tool speed, and the lubrication medium. For the purpose of reducing extrusion torque and temperature, the process parameters for internal thread forming are further optimized by orthogonal design. It is determined that when machining the M22 × 2 internal thread on the connecting rod of the marine diesel engine made of 42CrMo4 steel, the bottom hole diameter of the workpiece should be ∅21.20 mm, the speed of the machine tool should be 40 RPM, and the lubricating medium should be PDMS polydimethylsiloxane coolant. Compared to before optimization, the maximum extrusion torque and the maximum extrusion temperature are reduced by 19.27% and 15.07%, respectively. On the premise of ensuring the thread connection strength, the height of the thread tooth is reduced by 0.052 mm, and the surface condition of the thread is improved. The surface microhardness at the root, top, and side of the thread increases by about 5 HV0.2, and the depth of the hardened layer increases by 0.05 mm. The results show that the quality of the optimized thread is higher.

Verification of the Effectiveness of Occlusal Treatment Using Postural Information: A Case Report

Occlusal treatments can cause irreversible dental changes without guaranteeing clinical success. To avoid this, an initial, non-mutilating, phase of treatment using splint, for example, followed by an objective evaluation of the effectiveness is required before moving to next phase that permanently freezes the new mandibular position. As an example, a 74 years-old European female who consulted for tinnitus was referred, prior to any procedure, to a posturologist who established an initial postural assessment. A splint was made to increase the height between posterior teeth. 6 months after the tinnitus had disappeared, the patient was sent for postural assessment (made by the same posturologist and using the same tests). After an additional increase in posterior teeth height validated by an additional postural analysis, new fixed prostheses were placed taking into account the respective increases in height validated during this initial phase of treatment. Monitoring the effectiveness of initial and reversible stage is important as in occlusodontology, the disappearance of clinical symptoms is not always synonymous with healing. Moreover this is an interesting way to improve the rigor of patient management.

Digitalized analysis of the gingival and bone morphology in the maxillary anterior teeth in patient with posterior dental implant

Objective: To explore and analyze the correlation between labial gingival morphology and alveolar bone morphology of maxillary anterior teeth in patients with posterior dental implant, so as to provide reference basis for restoration design and esthetic reconstruction of anterior teeth. Methods: Sixty-four patients [24 males, 40 females (25.6±3.3) years old] who planned to receive posterior dental implant restoration were recruited randomly with the inclusion and exclusion criteria in Department of Prosthodontics, School of Stomatology, The Fourth Military Medical University from May 2020 to May 2021. According to the visibility of periodontal probe through gingival margin, the subjects were divided into thin and thick gingival biotypes, including 29 cases of thin biotype and 35 cases of thick biotype. The 3Shape software was used to perform oral scanning, and cone beam CT (CBCT) was taken for each patient. Geomagic and Mimics software were used to measure and record the labial crown width and length, gingival papilla height, gingival angle, bone papilla height and bone margin angle of maxillary anterior teeth. Results: The crown width length ratios of maxillary central incisors, lateral incisors and canines were 0.85±0.08, 0.80±0.08 and 0.86±0.09 (F=10.71, P<0.01). The height of gingival papilla between maxillary central incisors, between central incisors and lateral incisors, between lateral incisors and canines were (3.93±0.86), (3.47±0.84) and (3.38±0.91) mm respectively (F=7.44, P<0.01), and the height of corresponding bone papilla were (3.44±0.88), (3.12±0.75) and (2.72±0.63) mm respectively (F=14.26, P<0.01). The gingival margin angles of maxillary central incisors, lateral incisors and canines were 88.3°±7.7°, 84.7°±8.9° and 81.2°±6.6° (F=13.15, P<0.01), and the bone margin angles were 103.2°±13.1°, 99.5°±11.2° and 110.6°±13.0° (F=13.25, P<0.01). The crown width length ratio (0.81±0.08), gingival margin angle (82.2°±7.4°) and bone margin angle (99.4°±12.9°) of thin gingival subjects were significantly lower than those of thick gingival subjects (0.85±0.09, 86.5°±8.6°, 108.5°±11.4°) (t=-2.79, 3.63, 5.20, P<0.01). The height of gingival papilla [(3.93±0.81) mm] and bone papilla [(3.43±0.80) mm] in thin gingival subjects were significantly lower than those in thick gingival subjects [(3.34±0.84) and (2.85±0.71) mm, respectively] (t=-4.89, -5.36, P<0.01). The height of labial gingival papilla of upper anterior teeth was positively correlated with that of bone papilla in all patients (r=0.66, P<0.01); the ratio of crown width to length of upper anterior teeth was positively correlated with the angle of bone margin (r=0.42, P<0.01); the height of anterior gingival papilla was negatively correlated with the angle of bone margin (r=-0.58, P<0.01), and the height of bone papilla was negatively correlated with the angle of bone margin (r=-0.82, P<0.01). Conclusions: The crown shape, gingival shape and alveolar bone shape of maxillary anterior teeth were different in different tooth positions. Patients with different periodontal phenotypes had different crown width length ratio, gingival papilla height, bone papilla height, gingival margin angle, and bone margin angle.

Influence of Process Parameters on the Height and Performance of Magnesium Alloy AZ91D Internal Thread by Assisted Heating Extrusion.

The quality of threaded connection is an important factor affecting the service life of equipment. Extruded thread has stronger mechanical properties than traditional cutting thread. The forming of magnesium alloy AZ91D internal thread by electromagnetic induction heating assisted extrusion is a new processing method. In this work, on the basis of this process, the height and performance of internal thread are selected as the evaluation index, and the response surface method is used to analyze the influence of the process parameters on the internal thread performance. The range of process parameters (auxiliary heating temperature, hole diameter, machine tool speed) is determined by slip line and empirical method, the test data are simulated, modeled and compared with the response surface analysis method, and the best mathematical model is selected to establish the regression model, the three-dimensional response surface curve of tooth height rate and maximum tensile force is obtained. Through simulation and prediction, it is found that the hole diameter and auxiliary heating temperature have significant influence on the tooth height rate and maximum tensile force of internal thread, and the order is that the hole diameter is larger than the auxiliary heating temperature than the machine tool speed. The research results show that the measured value of tooth height rate and maximum tensile force are close to the predicted value, and the errors are 1.8% and 2.7% respectively, and the model fits well. The better forming process parameters are as follows: auxiliary heating temperature to be 220 °C, hole diameter to be 11.35 mm, machine tool speed to be200 r/min. under this parameter, the tooth height rate and maximum tensile force to be 89.056% and 38.824 KN. At the same time, it is found that with the increase of thread height, the maximum tensile force of thread is also increasing, and the thread height affects the performance of thread. Finally, the optimal process parameters are obtained by response surface method, which improves the tensile properties of extruded internal threads.

An Estimation of the Discharge Exponent of a Drip Irrigation Emitter by Response Surface Methodology and Machine Learning

The discharge exponent is a general index used to evaluate the hydraulic performance of emitters, which is affected by emitters’ structural parameters. Accurately estimating the effect of change in structural parameters on the discharge exponent is critical for the design and optimization of emitters. In this research, the response surface methodology (RSM) and two machine learning models, the artificial neural network (ANN) and support vector regression (SVR), are used to predict the discharge exponent of tooth-shaped labyrinth channel emitters. The input parameters consist of the number of channel units (N), channel depth (D), tooth angle (α), tooth height (H) and channel width (W). The applied models are assessed through the coefficient of determination (R2), root-mean-square error (RMSE) and mean absolute error (MAE). The analysis of variance shows that tooth height had the greatest effect on the discharge exponent. Statistical criteria indicate that among the three models, the SVR model has the highest prediction accuracy and the best robustness with an average R2 of 0.9696, an average RMSE of 0.0037 and an average MAE of 0.0031. The SVR model can quickly and accurately simulate the discharge exponent of emitters, which is conducive to the rapid design of the emitter.

Will “selfies” solve the identification crisis in lower socio-economic South Africans? A dental feature analysis of “selfies”

Identification in forensic odontology requires that a known characteristic of an individual’s dentition be compared with the same characteristic of the unknown decedent. In South Africa a number of factors render forensic identification of unknown individuals challenging. Many South Africans do not have access to modern dentistry, and consequently do not have ante-mortem dental records. In South Africa, 22 million people are said to own a smart phone, which accounts for close to 40% of the country's population. The aim of the study was to investigate selfies as a source of dental feature information in a government clinic catering to previously disadvantaged patients. Identifiable dental features were observed in 61 (5.6%) of the collected images (N=1098). The low number of useable selfies collected in this study could be attributed to: a lack of smiles seen in the received images. Individuals with poor dental aesthetics would commonly choose to takea selfie with a closed mouth where their teeth would not be visible. The most commonly identified dental features included: diastemas (49.2%), dental jewellery (37.7%), crowding (16.4%), difference in tooth height (16.3%), discoloured (8.2%) and missing teeth (8.2%). This studyfound that selfies cannot solve the identification crisis in lower socio-economic South Africans. Awareness of the importance of selfies in forensic identification should be increased.