Depth Angle Research Articles

Research on the distribution structure of 2D piston electro-hydraulic pump based on fluid-structure interaction

To address the drawbacks of traditional hydraulic power units, we embedded a 2D piston pump inside the motor rotor, proposing a 2D piston electro-hydraulic pump. The space cam mechanism serves as the primary force-bearing structure during its operation. Excessive wear occurs at the highest point of the space cam when subjected to significant axial forces, which leads to deviations between the motion law of the 2D piston and the theoretical design. Aiming this problem, we conduct research from two perspectives: theoretical analysis and fluid-structure interaction. Firstly, the operational principle of the electro-hydraulic pump is introduced. Then, the contact normal stress of the space cam mechanism is studied, and backflow and chamber pressure overshooting are discussed. Finally, the fluid-structure interaction model of the electro-hydraulic pump is established. Based on the fluid-structure interaction model, the effects of the width and depth angles of the triangular damping groove on the backflow and chamber pressure overshooting are analyzed. The simulation results demonstrate that adding triangular damping grooves can improve the flow field characteristics. With the increase in the width and depth angles, the peak flow of the backflow and chamber pressure overshooting increase, with the depth angle exerting a more pronounced effect.

Research on Multi-Objective Optimization of Low Pulsation Unloading Damping Groove of Axial Piston Pump

The high- and low-pressure switching of the axial piston pump is realized by the structure of the valve plate, and the buffer-groove structure on the valve plate is very important to reduce the pressure shock and flow fluctuation. In order to optimize the structural parameters of the buffer tank of the piston pump, the influence of the triangular-groove structure on the outlet pressure–flow characteristics was analyzed, and the low-pulsation buffer-groove structure was designed. First, the relationship between the structure of the triangular buffer tank and the output pressure and flow characteristics of the pump was analyzed theoretically. The Computational Fluid Dynamics (CFD) method was used to calculate the pressure and flow characteristics of the whole pump flow field of the triangular-groove structure, and the influence of the buffer-groove structure parameters on the outlet flow pulsation characteristics was studied. The multi-objective optimization algorithm was used to optimize the structure parameters of the buffer tank, and the optimized structure significantly reduced the outlet pressure–flow pulsation of the piston pump. The results show that, after optimization, the width angle of the front and rear triangular groove is 82.3°, the depth angle is 12.7°, the optimized pressure pulsation rate is 0.3%, and the optimized flow pulsation rate is 13.7%.

Fluoroscopically calibrated 3D-printed patient-specific instruments improve the accuracy of osteotomy during bone tumor resection adjacent to joints

BackgroundInadequate surface matching, variation in the guide design, and soft tissue on the skeletal surface may make it difficult to accurately place the 3D-printed patient-specific instrument (PSI) exactly to the designated site, leading to decreased accuracy, or even errors. Consequently, we developed a novel 3D-printed PSI with fluoroscopy-guided positioning markers to enhance the accuracy of osteotomies in joint-preserving surgery. The current study was to compare whether the fluoroscopically calibrated PSI (FCPSI) can achieve better accuracy compared with freehand resection and conventional PSI (CPSI) resection.MethodsSimulated joint-preserving surgery was conducted using nine synthetic left knee bone models. Osteotomies adjacent to the knee joint were designed to evaluate the accuracy at the epiphysis side. The experiment was divided into three groups: free-hand, conventional PSI (CPSI), and fluoroscopically Calibrated PSI (FCPSI). Post-resection CT scans were quantitatively analyzed. Analysis of variance (ANOVA) was used.ResultFCPSI improved the resection accuracy significantly. The mean location accuracy is 2.66 mm for FCPSI compared to 6.36 mm (P < 0.001) for freehand resection and 4.58 mm (P = 0.012) for CPSI. The mean average distance is 1.27 mm compared to 2.99 mm (p < 0.001) and 2.11 mm (p = 0.049). The mean absolute angle is 2.16° compared to 8.50° (p < 0.001) and 5.54° (p = 0.021). The mean depth angle is 1.41° compared to 8.10° (p < 0.001) and 5.32° (p = 0.012). However, there were no significant differences in the front angle compared to the freehand resection group (P = 0.055) and CPSI (P = 0.599) group. The location accuracy observed with FCPSI was maintained at 4 mm, while CPSI and freehand resection exhibited a maximum deviation of 8 mm.ConclusionThe fluoroscopically calibrated 3D-printed patient-specific instruments improve the accuracy of osteotomy during bone tumor resection adjacent to joint joints compared to conventional PSI and freehand resection. In conclusion, this novel 3D-printed PSI offers significant accuracy improvement in joint preserving surgery with a minimal increase in time and design costs.

Insertion Results and Hearing Outcomes of a Slim Lateral Wall Electrode.

The clinical outcomes of cochlear implantation vary for several reasons. It is necessary to study the different electrodes and variables for further development. The aim of this study is to report the clinical outcomes of a new slim lateral wall electrode (SlimJ). Data of 25 cochlear implantations in 23 patients with the SlimJ electrode were retrospectively collected. The insertion results were assessed by image fusion of the preoperative computed tomography (CT), magnetic resonance imaging (MRI), and postoperative cone-beam CT. The hearing outcomes were evaluated by the improvement of speech recognition in noise, measured preoperatively and at follow-up. Postoperative pure-tone thresholds were obtained in cases with preoperative functional low frequency hearing [PTA (0.125-0.5 kHz) ≤ 80 dB HL]. The preoperative mean speech reception threshold (SRT) was +0.6 dB signal-to-noise ratio (SNR) (SD ± 4.2 dB) and the postoperative -3.5 dB SNR (SD ± 2.3 dB). The improvements between the preoperative and postoperative SRT levels ranged from 0.0 to 15.1 dB, with a mean improvement of 4.2 dB (SD ± 3.6 dB). Residual hearing in low frequencies (mean PTA(125-500 Hz)) was preserved within 30 dB HL in 70% and within 15 dB HL in 40% of patients who had preoperatively functional low frequency hearing. Mean insertion depth angle (IDA) was 401° (SD ± 41°). We observed scalar translocations from scala tympani to scala vestibuli in 2 ears (9%). The relatively atraumatic insertion characteristics make the SlimJ array feasible for hearing preservation cochlear implantation. The hearing outcomes are comparable to those reported for other electrodes and devices.

The Sound Field Intensity Distribution in the Deep Sea in the “Depth—Angle–Time” Phase Space

The Sound Field Intensity Distribution in the Deep Sea in the “Depth—Angle–Time” Phase Space

The Sound Field Intensity Distribution in the Deep Sea in the “Depth—Angle–Time” Phase Space

The transition from the traditional representation of the wave field in the vertical section of an underwater sound channel as a function of depth and time to the distribution of this field in the 3D phase space “depth–angle–time” is considered. For this purpose, the method of coherent states developed in quantum theory is used. The meaning of the proposed transition is that the field intensity distribution in the specified phase space is less sensitive to sound velocity fluctuations than in the original 2D depth–time space. This fact can be used in solving inverse problems. As an example, we consider the reconstruction of the coordinates of a source in a waveguide from measurements of the field intensity distribution of this source in phase space.

MRI in rectal cancer patients on 'watch and wait': patterns of response and their evolution.

Evaluate MR patterns of response and their evolution in rectal cancer patients on watch and wait (WW). We retrospectively reviewed 337 MRIs of 60 patients (median follow-up: 12 months; range: 6-49 months). Baseline MRIs (available in 34/60 patients) were evaluated for tumor morphology, location, thickness, circumferential involvement, nodal status and EMVI. First post-treatment MRIs (in all patients) were additionally evaluated for pattern of response on T2 and DWI. Change in post-treatment scar thickness and scar depth angle between the first and second post-treatment scans was also evaluated. Evolution of the response pattern/recurrence were evaluated till the last available scan. On the baseline scans, 20/34 (59%) patients had polypoidal tumor with 12/20 having ≤ 25% circumferential wall involvement. We saw five patterns of response-normalized rectal wall (2/60-3%), minimal fibrosis (23/60-38%), full thickness fibrosis (16/60-27%), irregular fibrosis (11/60-18%) and split scar (6/60-10%), with 2/60 (3%) showing possible residual disease. On the first post-treatment scans, 12/60 (20%) had restricted diffusion, with 3/12 having persistent restriction till last follow-up. Post-treatment fibrosis/split scar remained stable in 44/60 (73%) cases and improved further in the rest. 9/60 (15%) patients developed regrowth/recurrence. Patients with recurrence had < 10 mm scar thickness and < 21° change in scar angle between the first and second post-treatment MRIs. Most patients on WW protocol developed minimal or full thickness fibrosis, majority of which remained stable on follow-up.

Facial and Intraoral Photographic Traits Related to Sleep Apnea in a Clinical Sample with Genetic Ancestry Analysis.

Rationale: Craniofacial and pharyngeal morphology influences risk for obstructive sleep apnea (OSA). Quantitative photography provides phenotypic information about these anatomical factors and is feasible in large samples. However, whether associations between morphology and OSA severity differ among populations is unknown. Objectives: The aim of this study was to examine this question in a large sample encompassing people from different ancestral backgrounds. Methods: Participants in SAGIC (Sleep Apnea Global Interdisciplinary Consortium) with genotyping data were included (N = 2,393). Associations between photography-based measures and OSA severity were assessed using linear regression, controlling for age, sex, body mass index, and genetic ancestry. Subgroups (on the basis of 1000 Genomes reference populations) were identified: European (EUR), East Asian, American, South Asian, and African (AFR). Interaction tests were used to assess if genetically determined ancestry group modified these relationships. Results: Cluster analysis of genetic ancestry proportions identified four ancestrally defined groups: East Asia (48.3%), EUR (33.6%), admixed (11.7%; 46% EUR, 27% Americas, and 22% AFR), and AFR (6.4%). Multiple anatomical traits were associated with more severe OSA independent of ancestry, including larger cervicomental angle (standardized β [95% confidence interval (CI)] = 0.11 [0.06-0.16]; P < 0.001), mandibular width (standardized β [95% CI] = 0.15 [0.10-0.20]; P < 0.001), and tongue thickness (standardized β [95% CI] = 0.06 [0.02-0.10]; P = 0.001) and smaller airway width (standardized β [95% CI] = -0.08 [-0.15 to -0.002]; P = 0.043). Other traits, including maxillary and mandibular depth angles and lower face height, demonstrated different associations with OSA severity on the basis of ancestrally defined subgroups. Conclusions: We confirm that multiple facial and intraoral photographic measurements are associated with OSA severity independent of ancestral background, whereas others differ in their associations among the ancestrally defined subgroups.

Theoretical Model of Self-Magnetic Flux Leakage and Its Application in Estimating the Depth Direction of a Fatigue Crack

In this study, theoretical models were proposed to explain the changes in self-magnetic flux density (SMFD) due to fatigue cracks in the presence and absence of external magnetic fields. Three theoretical models were proposed: rotation domain model (RDM), concentration domain model (CDM), and vertical domain model (VDM), considering the deformation and non-deformation possibilities. To prove the theoretical model, fatigue cracks with different depth angles were fabricated through fatigue testing and EDM processing on the CT specimens. In addition, tunnel magnetoresistance (TMR) sensors were used to evaluate the 3-axis distribution of SMFD. Comparing the simulation and experimental results, similar tendencies of the occurrence and depth angle of fatigue cracks and their effect on the distribution of SMFD were observed. According to the RDM, the distribution of SMFD occurs in the direction of the crack length (y-direction), while the CDM explains that the SMFD does not occur if the fatigue crack is in a direction perpendicular to the surface. In addition, the VDM shows that SMFDs occur in a direction perpendicular to the crack length (x-direction) and the specimen surface (z-direction). Interestingly, these trends agree with the experimental results, which confirms the validity of the theoretical model and thus can be used to estimate the depth direction of a fatigue crack.

Attack behavior leading cannibalism in tropical gar (Atractosteus tropicus) larvae under different tank colors and shelter type

Aggressivity expressed as cannibalism in fish larvae is a problem that limits the development of many species in aquaculture, therefore, understanding it and generating strategies to reduce its impact is important. This study described cannibalistic attacks behavior in Tropical gar (Atractosteus tropicus) larvae. The larvae were exposed to different tank colors and shelters (rocks and plastic vegetation), in pairs (2 larvae) and in groups (10 larvae). In addition, attacks behavior, types of attacks, and morphometric aspects related to cannibalism were described. In pairs, attacks occurred in greater numbers with white background color (8.50 ± 0.70) and fewer for yellow and purple (0.66 ± 0.57, p < 0.05). The largest number of group attacks was observed with the background colors pink, blue and yellow, and purple to a lesser extent. The presence of shelters (artificial vegetation) decreased the attacks in pairs and in groups compared to the use of rocks as refuge. A. tropicus larvae show a clear preference for artificial vegetation. It was found that morphologically, both juveniles and larvae (10 Days after hatching (DAH)) can consume prey greater than their own body depth (1.59 ± 0.22, 1.00 ± 0.12) and body width (1.74 ± 0.29, 0.94 ± 0.12). The mouth depth angle was significantly higher in larvae (10 DAH) (85.63 ± 6.41°), which decreases as age increases. A total of 452 events were recorded, four behaviors were described: interaction (214 events, 47 attacks, effectiveness of the attack (EA) 21.96%), chasing (127 events, 44 attacks, EA 34.64%), escape (62 events), and fast swimming (47 events). Three types of attacks were recorded: frontal (41.24%), lateral (29.94%), and posterior (28.81%), with three attack regions: head (31.64%), body (10.72%), and tail (57.63%). The most frequent attack was posterior tail with 70 events (39.55%). Attacker presented a S-like curvature prior to the attack (30.50%). Differences were determined in the percentage of weight (g) and total length (cm) between the attacker larvae and the attacked larvae 16.39 ± 10.86% and 15.23 ± 5.68%, respectively. In conclusion, A. tropicus larvae show cannibalism Type I, II, and two variants of Type III. It is suggested that this species is a more efficient cannibal than an interspecific predator. The relation of the greater number of attacks in the white color tanks could be related to the contrast with the bottom, thus, there is a less preference for this color. This information is essential to carry out a more efficient sorting of the larvae during their culture and reduce cannibalism in the larval stage in A. tropicus. The results of this study could be useful to understand this behavior in other species.

A new perspective on the relationship between anchorage and palatal morphology: Three-dimensional digital model analysis.

The tooth movements were generally analyzed in two dimensions on cephalometric radiographs. Nowaday, 3D digital model analysis, which does not have any harmful effects on patients, can be used to evaluate the palatal morphology and coronal tooth movements in a very comfortable and easy way. To investigate the effect of palatal morphology on anchorage reinforcement during intraoral molar distalization with pendulum appliance using 3D model analysis. The material consisted of before (T0) and after (T1) dental plaster models of Class II malocclusion patients (17 females, 3 males) treated with pendulum appliance for molar distalization and Nance appliance for anchorage. T0 and T1 digital models were superimposed using the palatal area as a reference via three points and surface-matching software, and the changes in teeth movement were calculated for left and right central incisors, first premolars, and first and second molars. Palatal morphology was evaluated at T0 on digital models as palatal inclination, palatal depth angles, and anterior hard palate area. Wilcoxon test was used to evaluate the treatment results and Spearman's correlation analysis was performed to evaluate the relationship between palatal morphology and dental movement. The upper limit for the level of significance was taken as 0.05. Mesial movement of first premolars and distal movement of first and second molars were found to be statistically significant (P < 0.001). A weak negative correlation was found between the palatal inclination and the movement of first premolars (P < 0.045 and P < 0.003). Palatal depth angles and anterior hard palate area had no correlation with dental movements. Presented results supported that the mesial movement of premolar teeth decreased as the inclination of the palate increased.

Influence Rule of Annular Notch Geometric Parameter on the Tubing Surface: A Case Study

In regards to the problem of tubing precision separation, the high-efficiency precision separation method for tubing under eccentric wheel high-speed rotational bending fatigue loading is proposed, which aims to promote the initiation of fatigue cracks at the root of the annular V-notch on the tubing surface. Research on the stress concentration effect of the annular notch on the tubing surface is carried out. The design of the notch takes into account the characteristics of tubing precision separation. The numerical simulation calculation includes four kinds of notches, namely, annular V-notch, annular U-notch, asymmetric V-notch towards the blanking end direction 45°, and asymmetric V-notch away from the blanking end direction 45°. The crack propagation lengths produced by each notch under the same experimental conditions are investigated experimentally. According to the findings, the annular V-notch is suitable for this separation method. By analyzing the theoretical stress concentration factor of the annular V-notch on the tubing surface, three main parameters affecting the annular V-notch root stress field are determined, namely, notch angle, notch depth, and notch root base angle radius. Through calculation and analysis, the influence law of tubing annular V-notch angle, notch depth, and notch root base angle radius on the stress concentration effect is obtained. Based on the process characteristics of tubing precision separation, the ideal tubing annular V-notch geometric parameter is presented within a reasonable value range. For the validation experiment of tubing precision separation, 45# steel, 304 stainless steel, and T2Y copper tube are selected, respectively. Finally, a great tubing precision separation effect is achieved, which verifies the reasonable selection of the tubing surface annular V-notch geometric parameter.

Spiral Groove Parametric Study of Solid Particles Deposition Characteristics in Sealing Lubrication Film

In order to study the effect of groove parameters on solid particles’ deposition in mechanical face seal lubrication film, a multi-phase flow calculation model for the sealing micro-gap lubricating film was established based on the Laminar model, mixture multi-phase flow model, Zwart–Gerber–Belamri cavitation model, and DPM model in Fluent, and a numerical simulation of the effect of groove parameters is presented. The results show that, with the increase of groove depth, the circumferential sedimentary zone in the dam area decreases or even disappears, and the groove area becomes the main sedimentary part; the particle deposition rate decreases first and then increases with the increase of groove depth and spiral angle. The influence of groove depth on the deposition rate at low speed is more significant than that at high speed. The increase of deposition rate caused by a spiral angle that is too large is greater than that caused by a spiral angle that is too small. The optimal groove depth and spiral angle are around 6 µm and 18°, respectively; when the rotating speed is 1000 rpm, the deposition rate increases obviously with the increase of the groove diameter ratio; meanwhile, when the rotating speed increases to more than 2000 rpm, the deposition rate increases first and then decreases with the increase of the groove diameter ratio. When the groove diameter ratio is about 0.5, the deposition rate is the largest. For example, when the rotating speed is 2000 rpm, the deposition rate of the groove diameter ratio, 0.5, is about 200% higher than that of groove diameter ratio, 0.2. The lower the speed, the more sensitive the deposition rate is to the groove diameter ratio. The sensitivity at 1000 rpm is 14 times that at 5000 rpm. The deposition rate increases with the increase of the groove width ratio. The higher the rotating speed, the smaller the rate of deposition rate increase. However, when the rotating speed is 5000 rpm and the groove width ratio is higher than 0.7, the deposition rate increases sharply.

A novel method of light projection and modular jigs to improve accuracy in bone sarcoma resection.

We developed a novel method using a combined light-registration/light-projection system along with an off-the-shelf, instant-assembly modular jig construct that could help surgeons improve bone resection accuracy during sarcoma surgery without many of the associated drawbacks of 3D printed custom jigs or computer navigation. In the novel method, the surgeon uses a light projection system to precisely align the assembled modular jig construct on the bone. In a distal femur resection model, 36 sawbones were evenly divided into 3 groups: manual-resection (MR), conventional 3D-printed custom jig resection (3DCJ), and the novel projector/modular jig (PMJ) resection. In addition to sawbones, a single cadaver experiment was also conducted to confirm feasibility of the PMJ method in a realistic operative setting. The PMJ method improved resection accuracy when compared to MR and 3DCJ, respectively: 0.98 mm versus 7.48 mm (p < 0.001) and 3.72 mm (p < 0.001) in mean corner position error; 1.66 mm versus 9.70 mm (p < 0.001) and 4.32 mm (p = 0.060) in mean maximum deviation error; 0.79°-4.78° (p < 0.001) and 1.26° (p > 0.999) in mean depth angle error. The PMJ method reduced the mean front angle error from 1.72° to 1.07° (p = 0.507) when compared to MR but was slightly worse compared to 0.61° (p = 0.013) in 3DCJ. The PMJ method never showed an error greater than 3 mm, while the maximum error of other two control groups were almost 14 mm. Similar accuracy was found with the PMJ method on the cadaver. A novel method using a light projector with modular jigs can achieve high levels of bone resection accuracy, but without many of the associated drawbacks of 3D printed jigs or computer navigation technology.

Numerical simulation of thermal stress and life assessment of a thin double-layer metal hydride bed under combined thermal and mechanical loads

In this work, the finite element model of the hydrogen absorption process in the thin double-layered metal hydride bed (MHB) has been established. The Johnson–Cook constitutive model, considering the temperature softening and strain rate hardening effect, was used to simulate the mechanical behavior of 316L stainless steel during the hydrogen absorption and desorption processes. The simulation results agree well with the experimental results, which verifies the effectiveness of the numerical model. The equivalent stress distribution of the stainless steel bed in the process of hydrogen absorption and desorption has been calculated by the aforementioned model. The influence of the defect depth and opening angle on tank safety has been calculated and analyzed considering the possible defects in the welding process and service life. Finally, according to the American Society of Mechanical Engineers boiler and pressure vessel code criterion, the fatigue–creep interaction condition of the MHB was predicted and analyzed. This work can provide an effective reference for the design of a hydrogen storage bed.

Vibration Analysis of Deep Groove Ball Bearing Using Finite Element Analysis and Dimension Analysis

Abstract Condition monitoring of rotor dynamic is recognized as an advanced preventative maintenance technique for fault-free operation. Faulty bearings in rotating machines may cause severe problems and even untimely breakdowns. This work demonstrates the power of the finite element analysis (FEA) model and dimension analysis technique (DAT) to analyze the effect of the depth and slope angle of surface faults on the bearing contact characteristic. Experimentation is performed to investigate the vibration characteristics of ball bearings. The FEA, DAT, and experimentation show that vibration amplitude is a vital function of surface fault size. The current approach of FEA with DAT reflects their reliability and accuracy for the diagnosis of rotor systems. The present method was found effective in predicting vibration amplitude and defect frequency within acceptable error.

Effective Prediction of Monthly Heat Transfer Characteristics in a Thin-Layer Cascade Reactor Subjected to Outdoor Conditions

Algal biofuels are intriguingly a renewable energy source that could partially substitute fossil fuels, but further research is required to optimise the growth parameters and establish competitive large-scale cultivation systems. Algal growth is directly dependent on momentum, heat, and mass transfer within the photobioreactor and environmental conditions. Therefore, in this computational study, the heat transfer between the thin-layer cascade (TLC) reactor and its surrounding was reported based on static (location and reactor geometry) and dynamic (air temperature, solar irradiance, and wind velocity) parameters. The resulting model was validated using experimental data. The Nusselt number and the monthly average water temperature were computed to investigate the heat transfer phenomena between the TLC reactor and atmosphere. In addition, a novel corelation was used to estimate the evaporative losses from the TLC reactor. The effect of geometric properties (inclination angle of the reactor, water depth, and channel width) was evaluated on heat transfer. Results showed that heat transfer rate and the optimum water temperature for algal growth were significantly affected by hydrodynamics, environmental conditions, and reactor design. Water temperature decreased with the increase in channel width, water depth, and slope angle of the reactor. Furthermore, algal productivity declined with the increase in the amount of evaporated water.

Thermal non-destructive characterization of rail networks by using Infrared Thermography and FEM simulation

Because of the repeated passage of trains, anomalies are created inside the rails in the form of cracks of different shapes and position. These are due essentially to the wheel – rail contact. They present a hazard causing at the final stage rail failure, train derailment and accidents. Detecting track anomalies has become a major issue for the entire rail industry around the world. This paper focuses on the degradation of rails in urban railways in terms of cracks. The purpose is to develop an approach to detect and predict rail breaks, which will optimize maintenance task. Infrared thermography was used in order to characterise the effect of a defect on the acquired thermogram. Different defects were considered by varying their size, depth and inclination angle with respect to the rail surface.

Clinical and anatomical characteristics associated with obstructive sleep apnea severity in children

PurposeTo determine the clinical and anatomical characteristics associated with obstructive sleep apnea severity in children with adenotonsillar hypertrophy. MethodsThe authors conducted a cross-sectional multidisciplinary survey and selected 58 Brazilian children (4‒9 years old) with adenotonsillar hypertrophy, parental complaints of snoring, mouth-breathing, and witnessed apnea episodes. The authors excluded children with known genetic, craniofacial, neurological, or psychiatric conditions. Children with a parafunctional habit or early dental loss and those receiving orthodontic treatment were not selected. All children underwent polysomnography, and three were excluded because they showed an apnea-hypopnea index lower than one or minimal oxygen saturation higher than 92%. The sample consisted of 55 children classified into mild (33 children) and moderate/severe (22 children) obstructive sleep apnea groups. Detailed clinical and anatomical evaluations were performed, and anthropometric, otorhinolaryngological, and orthodontic variables were analyzed. Sleep disorder symptoms were assessed using the Sleep Disturbance Scale for Children questionnaire. All children also underwent teleradiography exams and Rickett's and Jarabak's cephalometric analyses. ResultsThe mild and moderate/severe obstructive sleep apnea groups showed no significant differences in clinical criteria. Facial depth angle, based on Ricketts cephalometric analysis, was significantly different between the groups (p = 0.010), but this measurement by itself does not express the child's growth pattern, as it is established by the arithmetic mean of the differences between the obtained angles and the normal values of five cephalometric measurements. ConclusionsThe clinical criteria and craniofacial characteristics evaluated did not influence the disease severity.

Brush grinding aluminum alloy mechanism of single steel wire based on finite element approach

In the process of surface treatment, steel wire brush can not only efficiently remove surface contaminants, such as deteriorated paint film and rust, but also increase the adhesive strength. However, the associated brush mechanics of material removal is still not clear. In order to reveal the brush mechanics of material removal, this paper assumed the tip of steel wire were ball–cone shaped, constructed contact force model, and calculated the brush grinding force under different process conditions based on finite element approach. The simulated results show that the brush grinding can be changed from plastic plowing to chip formation when the penetration depth is increased to 10 μm, then changed from chip formation to plastic plowing when the inclination angle is increased to 30°, respectively. The simulated value of brush force rises with the increasing penetration depth and inclination angle, which was consistent with the experimentally obtained values, and the relative errors are within 9%. The quantity of material removal increases with the ascending of penetration depth, and decreases with the ascending of inclination angle. This paper provides guidance to understand the mechanics of material removal, predict the brush grinding force, and contribute well to an automatic grinding control application.