Cavity Width Research Articles

Dimensional changes of upper airway after slow vs rapid miniscrew-supported maxillary expansion in adolescents: a cone-beam computed tomography study

BackgroundTo date, the effects of different activation rates of miniscrew-supported expanders on the airway have not been compared. Hence, the purpose of this retrospective study was to evaluate and compare the effects of slow and rapid miniscrew-supported maxillary expansion on the upper airway dimensions using cone-beam computed tomography (CBCT).MethodsData of 20 patients (Age 12 to 16 years old) treated using miniscrew-supported expanders at the Faculty of Dentistry, Alexandria University was collected. The patients were equally divided into two groups according to the activation protocol; slow maxillary expansion (SME): activation once every other day, and rapid maxillary expansion (RME): activation twice daily. CBCT scans obtained pre-expansion and 5 months post-expansion were used to evaluate the changes in the upper airway dimensions. Comparisons between the two time points within each group were done using paired samples t-test. SME and RME groups were compared using independent samples t-test. Significance level was set at p < 0.05.ResultsBoth groups showed a significant increase in anterior, middle, and posterior nasal cavity width. SME resulted in significantly greater increase of the anterior nasal cavity width than RME (Mean difference between the groups, 2.64 mm; 95% CI, 0.83, 4.45; p = 0.007). The dimensions of the retropalatal and retroglossal airways did not change significantly in either group. Both groups resulted in a significant increase of maxillary width, palatal width, and inter-molar width. RME showed a significantly larger increase of inter-molar width than SME (Mean difference between the groups, − 2.44 mm; 95% CI, − 3.88, − 1.00; p = 0.002).ConclusionsThe use of either a slow or rapid activation protocol is effective in expanding the nasomaxillary complex, with greater expansion achieved in the anterior section of the nasal cavity using the slow rate. However, the expander design employed in the current study does not affect the dimensions of the retropalatal or retroglossal airways.

Truncated Double Layer Microchannel Heat Sink and Its Performance Improvement by Implicating Secondary Channel Combined along with Appropriate Cavities and Ribs in Channel Flow

The reliability of double layer microchannel heat sink can be upgraded if the top liquid channel is made shorter or truncated. Because heating effect on the bottom channel coolant caused by top the channel’s hot coolant is relieved for truncated double layer microchannel heat sink. In the present study, the performance parameters of truncated double layer microsinks have been improved by utilizing secondary sub-channel, appropriate cavities, and ribs in their flow channels. In the primary analysis, before utilizing appropriate secondary sub-channel, cavities, and ribs, truncation effect of the upper channel is evaluated by varying design variable, i.e., truncated length ratio from 0.5 to 1, where truncated length ratio = 0.8 has been found as optimum value. In the second analysis, the design variable, i.e., cavity width–depth ratio of 2.4, 3.2, 3.6 for the optimally truncated double layer microsinks possessing secondary channel, cavities, and ribs, are compared. In this study of total eight cases, 43% and 29% enhancement in Nusselt number ratio and thermal performance factor respectively are optimally predicted in the heat sink designs by implicating the appropriate secondary channel, cavities, and ribs into the flow channel.

Surrogate-based parameter exploration for the design of MEMS calorimetric wall shear stress sensors by means of CFD

A family of MEMS calorimetric wall shear stress sensors is experimentally and numerically investigated to determine their most significant design parameters. Fifteen sensor prototypes are first calibrated in a range of ± 2 Pa to generate an experimental database for validation of the subsequent numerical investigation. Then, a fully parameterized numerical setup is used to investigate the effect of three geometric design parameters, namely the cavity height, the cavity width, and the inter-beam distance, on amplitude and sensitivity of the sensor. This is done by building a surrogate model based on Gaussian Process interpolation (Kriging) in the four-dimensional space consisting of the three design parameters and the shear velocity in the flow. Thanks to this methodology, the calibration curves of all possible sensor designs in the investigated range can be estimated with an error of less than 2 %. A detailed study of this model reveals that the most significant design parameters are the inter-beam distance and the cavity width, while the cavity height is found to be of minor importance. • CFD Simulation of MEMS calorimetric wall shear stress sensor. • Static calibration of a family of 15 sensors in the range ±2 Pa. • Surrogate-based parameter space exploration of three design parameter. • Interpolation of sensor’s signal and sensitivity for all sensors in defined limits.

Optimizing the Geometric Parameters of a Stepped Labyrinth Seal to Minimize the Discharge Coefficient

A series of numerical simulations were performed to study the discharge coefficient based on the geometric parameters of a stepped labyrinth seal that sealed the secondary flow path of a gas turbine. In contrast with straight-through seals, stepped labyrinth seals introduce additional geometrical parameters related to the steps. In this study, three shape variables were observed: step height (SH), position, and cavity width (CW). The sensitivity to the leakage flow of the shape variable in the stepped labyrinth seal was analyzed. The mechanism for improving the sealing performance of stepped labyrinth seals was investigated. The results indicated that the stepped labyrinth seal exhibited up to 17.9% higher leakage-suppression performance than the straight labyrinth seal. Seals with large discharge coefficients had a large vena contracta upstream of each tooth structure and a rapidly accelerated axial velocity in the radial direction. We could observe that the discharge coefficient changed according to the flow field in the cavity. The wall shear stress was sensitive to the SH but not to the CW or step position.

Numerical Analysis for Supercavitation Characteristics around Underwater Vehicle according to Ventilated Gas Temperature

Supercavitation is a phenomenon in which the cavity covers the entire underwater vehicle. The purpose of this paper is to compare and analyze the thermal effect on the cavity characteristics by changing the ventilated gas temperature through computational analysis. For this study, a homogeneous mixture model based on the 3D Navier-Stokes equation was used. As a phase change model, it is its own code considering both pressure change and temperature change. A dimensionless number &lt;i&gt;T&lt;sub&gt;m&lt;/sub&gt;&lt;/i&gt; was presented to analyze the numerical results, and as the &lt;i&gt;T&lt;sub&gt;m&lt;/sub&gt;&lt;/i&gt; increased, the cavity length increased by about 3.6 times and the cavity width by about 3.3 times at 393.15 K compared to room temperature. Analyzing these thermal effects, it was confirmed that rapid heat exchange and heat transfer between the gas phase and the liquid phase occurred at the location where the ventilated gas was sprayed, affecting the cavity characteristics. In addition, it can be confirmed that the initial cavity surface becomes unstable as the ventilated gas temperature increases, and it can be confirmed based on the numerical analysis results that the critical temperature at which the cavity surface becomes unstable is 373.15 K.

Theoretical modelling of a deformation based concave square ring-square disc (SR-SD) silver structure for pressure sensing

A compact nanosensor that explores the tie-in between stress-induced deformation and optical resonance characteristics is theoretically proposed for pressure sensing. The structure modeling, electromagnetic (EM) wave simulation, and performance evaluations were carried out using the 2D finite element method (FEM). The proposed surface plasmon resonance (SPR) based metal-insulator-metal (MIM) model responds to the pressure induced on the top-facing side of an Ag concave square ring-square disc arrangement (Concave SR-SD) in terms of a structural curve-in into the insulator cavity. These deformations alter the electromagnetic field distributions and plasmonic resonance conditions, shifting the absorption cross-section profiles towards higher wavelengths. The shift in the resonant wavelength (Δλ) for specific measured deformations (d) exhibited by the normal SR-SD hinds at the application level perspective of the designed system in pressure sensing via its optomechanical correlation. Further, multiple parameters like insulator cavity width (W I ) and structure wise modifications in the outer ring structure are investigated for performance optimization, and subline sensitivity values (maximum) of 24.496 nm/MPa and 40.46 nm/MPa are observed from normal and concave SR-SD systems respectively. The suggested nano pressure sensor of suitable sensitivity and broad sensing range promises strong applicability in biomedicine, health monitoring, nanomechanics, chip-based devices, and nanoelectronics.

Design and Studying the Effect of Inner Bore Diameter of Unipolar Lens

This work investigated the development of magnetic and optical properties and the invention of a previously unused lens. Many new designs have been suggested for a unipolar magnetic lens based on changing the width of the inner bore and fixing the other geometrical parameters of the lens to improve the performance of unipolar magnetic lenses. The investigation of a study of each design included the calculation of its axial magnetic field the magnetization of the lens in addition to the magnetic flux density using Finite Element Method (FEM). it was found that the best magnetizing properties, the highest value of magnetic flux and the lowest value of band width of the axial magnetic field strength have been obtained when the width of the inner cavity was (55 mm). The effect of current density on the optical properties has been also studied, and it was found that the optical properties have been improved also, and the chromatic and spherical aberration values have decreased significantly. Thus, the lens (55 mm) was chosen as the best design among the proposed designs.

A novel plasmonic device: Filtering and switching functions with quasi-rectangular spectrum based on dual Fano resonances

Compact filters and switches are essential building blocks for performing interference-mitigation and signal-selection in photonic integrated loop. A plasmonic device that exhibits multifunctions including filter and switch is proposed in this paper. The device consists of a hexagonal resonator with rotatable oval core, a stub and two tooth cavities coupled with bus waveguide, respectively. The temporal coupled-mode theory reveals that dual Fano resonances occur in the structure. Finite-difference time-domain method indicates that the bandwidth and transmission of the spectrum can be manipulated by adjusting the parameters of elliptical rotor and stub cavity. Passband ripple is calculated under different structural parameters, and spectrum with low passband ripple of 0.023 dB is realized. Moreover, rotation of the elliptical rotor in the hexagonal resonator will alter transmission spectrum of the output port. Ultimately, filtering and switching functions with quasi-rectangular spectrum are implemented in the designed structure, which will enhance device performance and reduce signal distortion. The fabrication tolerance is analyzed considering widths of stub and tooth cavities. Furthermore, the selectivity of working wavelength at different channels is researched and presented. This novel plasmonic device with low passband ripple has a great impact on improving the quality of signals on chips.

The Inheritance Pattern of Key Desirable Agronomic and Fruit Quality Traits in Elite Red Papaya Genotypes

Knowledge of the heritability, genetic advance, and stability of key traits, such as the height to the first fruit, trunk circumference, number of marketable fruit, wasted fruit, fruit weight, fruit width, fruit length, flesh thickness, cavity width, cavity length, and soluble solid contents, is required. These were determined in ten advanced generation red papaya recombinant inbred lines (RIL; F5 generation). The F5 RIL were grown in four field sites, two each within two distinct agroecological climates: the Tablelands and Coastal regions. At each site, biological replicates (trees) of each RIL and the industry-standard red papaya cultivar, RB1, were grown. Agronomic traits and fruit-specific traits were assessed at five and 10 months, respectively, after seedling transplantation to the field. Height to first fruit, trunk circumference, fruit weight, and soluble solid contents were highly heritable and stable at all field sites (h2b.s, 0.7–0.9) with genetic gains of almost 18% observed for height to first fruit and fruit weight. Across all sites, the trunks of the F5 lines were 37% wider, the trees set fruit 47% closer to the ground and had 20% more marketable fruit with 33% smaller fruit cavity widths, and their fruit was 11% heavier and 12% sweeter than RB1.

Molecular Character of Mylonchulus hawaiiensis and Morphometric Differentiation of Six Mylonchulus (Nematoda; Order: Mononchida; Family: Mylonchulidae) Species Using Multivariate Analysis

Mononchida members are predatory nematodes with the potential to reduce the number of plant-parasitic nematodes in the soil. During a survey on Mononchida in Iran, several populations of Mylonchulus were recovered from various localities. A population of M. hawaiiensis was studied using 18S rDNA. The phylogenetic analysis using Bayesian inference placed the sequenced M. hawiinesis (OP210758) together with other M. hawaiiensis from Japan (AB361438-AB361442) with a 1.00 posterior probability support. In addition, morphological differences between six Mylonchulus (Nematoda; order: Mononchida; Family: Mylonchulidae) populations were investigated in Iran using discriminant analyses (DA), PERMANOVA, and principal coordinate analysis (PCoA). The purpose was to evaluate the efficacy of PCoA and DA in separating the Mylonchulus species, namely M. sigmaturus, M. paitensis, M. lacustris, M. brachyuris, M. kermaninesis, and M. hawaiiensis. To achieve this, 16 morphometric measurements (body length, a, b, c, c′, V, G1, G2, buccal cavity length, buccal cavity width, dorsal tooth apex, dorsal tooth length, neck length, amphid from anterior end, rectum, and tail length) were made on 160 specimens. The analysis of variance showed that all features were significantly different among the species, except a, b, and the amphid position from the anterior end and tail length. The stepwise discriminant analysis revealed that body length, tail length, neck length, and c′ value were the four most discriminating variables useful to distinguish clearly the six species of Mylonchulus. The variables with strong discriminatory power correctly classified 98.87% of individuals from Iran’s sample of known Mylonchulus species. The results provide a morphometric basis for effectively distinguishing Mylonchulus species.

Terahertz groove gap waveguide leaky wave antenna

AbstractA groove gap waveguide (GGW) leaky wave antenna with a wide scan angle in the terahertz (THz) band (430–560 GHz) is presented in this study. The unnecessary tight contact between the top plate and pins of the GGW makes it easy for the fine fabrication and assembly of this THz antenna. Scanning of pointing directions with frequency, together with the low side‐lobe level (SLL), is designed for the pins' heights and intervals as well as the groove cavity width. Measurement results of S11 parameters remain about −20 dB, besides, the antenna scan angle range is 15o within 430–560 GHz, and the gains are also above 15 dB within that working frequency bands.

Investigation of the relationship between maxillary dimensions and labial and palatal maxillary impacted canines using cone beam computed tomography

ObjectivesTo compare the maxillary dimensions of individuals with labial and palatal bilateral maxillary canine impaction and a control group of individuals with no impaction using CBCT. Methods45 patients were included in the study with age range of 13 to 18 and consisted of 22 females and 23 males. The sample included three groups of 15 patients as the control, labial and palatal group. The measurements made on the axial and coronal planes were made on the levels of the 1st premolar and the 1st molar. Also nasal cavity and anteroposterior depth were measured. ResultsThe maxillary anteroposterior depth, basal first molar width, alveolar first molar and premolar width and first molar palatal vault depth of the control group were significantly higher than labial and palatal groups (p<0.05).The basal first premolar width of the control group was significantly higher than palatal group (p<0.05). The first premolar palatal vault depth and nasal cavity width of the palatal group were significantly lower than other groups (p<0.05). ConclusionsThe basal and alveolar widths associated with the molars and the palatal depths were lower in the impacted group than control group. The anatomical structures in the female patients were affected by the position of impaction to a higher extent in comparison to the anatomical structures in the male patients.

Computational fluid dynamics using finite volume method: A numerical model for Double Skin Façades with renewable energy source in cold climates

Double-skin façades often rely on proper cavity design, which unleashes a significant potential for inhabitation and renewable energy integration in cold climates. A co-model between Matlab and Ansys Fluent was developed to investigate the performance of a new typology for such façades. The steady-state energy balance equations for heat transfer were introduced with governing non-isothermal turbulent flow such that energy was conserved at each element of the assembly. Internal and mixed-mode ventilation schemes were utilized with multiple cavity widths and boundary conditions. The numerical model was validated against experimental measurements where the average temperature deviation was 1.9 °C. For the renewable energy source, the system utilized photovoltaics and microalgae modules which were brought in contact with the occupied space in order to counter the heat loss to the cold ambient. Results showed that double-skin façades were more energy efficient than an insulated double-glazed assembly regardless of the cavity ventilation scheme. The flow of heat transfer was reversed from 82.1 W/m2 loss to the surrounding to 35.7 W/m2 gain into the occupied space. Microalgae photobioreactors were found to have higher heating potential by generating 8.1% more than that of photovoltaics. Introducing ventilation into the cavity led to enhanced photovoltaics efficiency by 7.5% associated with a minimum drop in the cavity's temperature from 16.3 °C to −6.8 °C. Photobioreactors' functionability was enhanced by feeding water at a mean flow of 0.26 kg/s. The study recommended utilizing adjustable external air vents that can be regulated depending on the ambient temperature and the personal occupancy level in the cavity whenever its size fits.

Effect of cavity parameters on the fire dynamics of ventilated façades

Narrow gaps and cavities present in modern construction systems have been identified as one of the key elements that may enable fire spread after an initial fire ignition. Although there are existing models to predict the exposure of the inner linings of a cavity when exposed to a fire, these models have a significant amount of error or are limited to small ranges of application. A parametric experimental study was performed to characterise the fire dynamics in a cavity using a medium-scale non-combustible parallel wall testing rig. Three different cavity widths, three different heat release rates and two air entrainment conditions at the base of the setup (i.e. closed, with no air entrainment at the base; open, with unrestricted air entrainment at the bottom) were varied. Measurements of the flame height and the total external heat flux on the cavity walls were performed. It has been shown that both the heat fluxes and the flame heights increased as the cavity width was reduced. It was found that the radiative component dominates the heat transfer at the bottom of the setup and is less relevant as the height increases, the cavity width increases and the burner output is reduced. Correlations were developed to quantify the heat exposure of a cavity as a function of the geometry of the system, the size of the fire and the ventilation condition. The results obtained can be further used as a baseline in the modelling of upward flame spread in confined spaces featuring combustible linings, and for assessing the potential risks of ignition of combustible elements in ventilated façade systems.

Drainage of infiltrated rainwater in wall assemblies: Test method, experimental quantification, and recommendations

Drainage reduces the amount of water able to infiltrate toward the interior of wall assemblies. However, a portion of the infiltrated water remains in the assembly after drainage has occurred. The degree to which this retained portion of water affects the durability of the wall assembly can be evaluated by means of hygrothermal simulations. However, the number of studies reporting information on the retention percentage that can be applied as input for hygrothermal simulations and on the drainage performance of wall assemblies is, in general, quite limited. Therefore, an experimental study was developed, to assess governing test methods to evaluate drainage characteristics and to quantify retention of water in wall test specimens having various cavity widths and incorporating different drainage materials. It was concluded that apart from the absolute amount of retained water, the lateral spreading of water in the cavity and the overall wetted area, should also be considered, thereby resulting in reporting the retained amount relative to the wetted area. The latter values provide more detailed information on the behavior of water in the cavity. Additionally, it was concluded that a clear cavity of 1 mm can drain water more efficiently than a cavity of 10 mm. As well, the surface texture of drainage materials affected the spreading and retention of water within the cavity and the use of a drainage mat in the cavity resulted in an increased relative retention but a reduced lateral spreading of the water.

LNG 펌프의 누설 유량 최소화를 위한 래버린스 실 형상의 수치적 연구

In the submersible pump used in an LNG cargo, the leakage flow (gap flow) occurs between the pump rotor and the casing, and the pump efficiency decreases. The labyrinth-shaped pattern is applied between these gaps to decrease the leakage flow, which is called Labyrinth Seal. This research studied the difference in flow characteristics when liquefied methane which accounts for most LNG composition passes through labyrinth seals of different shapes using computational fluid dynamics (CFD). Four shape variables were considered: clearance size(s), cavity width(b), cavity height(g), and number of cavity(z). Parametric study was performed by changing only the input value of one variable without changing other variables within a limited range. As the gap of the labyrinth seal increased, the leakage flow rate increased. But the effect of the cavity-related variables was different. As a result of analyzing the effects of three cavity variables using full factorial design, they were found to be almost independent of each other. As the cavity width and number increase, the leakage flow rate decreases linearly. And the cavity height has a maximum leakage flow rate at one point, but has the smallest influence among all variables.

Shear behavior of stainless-steel plate connectors for insulated precast concrete sandwich panels

In this study, 24 double-shear tests were performed on precast concrete insulated sandwich panels using stainless-steel plate connectors. Parameters in the test program included connector shear directions (in-plane/out-of-plane), presence of insulation (with/without), cavity widths (30 mm/80 mm/120 mm) and connector heights (120 mm/160 mm). In order to test the pure shear capacity of connectors, the insulation was removed in the in-plane shear tests. The test results indicated that the connectors with 80 mm and 120 mm cavity width failed by shear buckling and the connectors with a cavity width of 30 mm were pulled out after buckling when subjected to in-plane shear. For the out-of-plane shear tests, bending of connectors occurred in the specimens without insulation, and connectors were pulled out in the specimens with insulation. For in-plane shear connectors with cavity widths of 30 mm, 80 mm and 120 mm, the shear capacities of 120 mm high connectors were 31.8 kN, 25.8 kN and 11.5 kN respectively, while the shear capacities of connectors with a height of 160 mm were 49.3 kN, 30.2 kN and 17.6 kN. The shear capacities of the out-of-plane connectors was only 3.7% of the in-plane connectors. It was also indicated that the presence of insulation significantly contributed to shear transfer in out-of-plane shear tests, leading to 28.6 times higher shear capacity than the specimens without insulation. Based on Basler's tension field theory, an analytical model was developed to predict the shear capacity of plate connectors. Compared with test results in this paper and other studies, the predictions were in good agreement.

Obstructive sleep apnea and anatomical structures of the nasomaxillary complex in adolescents.

The aim of the present study was to reveal the associations between skeletal and soft tissue features of the nasomaxillary complex and development and severity of obstructive sleep apnea (OSA) in adolescents. A total of 100 adolescents (mean age, 14.9 ± 1.4 years; age range, 13–17 years) were enrolled. All participants underwent full-night polysomnography and had an assessment of size and position of the tongue, tonsillar size, body mass index (BMI), and circumference of the waist, neck, and hip. The skeletal features of the nasomaxillary complex, including the zygomatic arch width, nasal cavity width, nasal base width, intercanine width, intermolar width, maxillary dental arch length, palatal vault angle, palatal depth, and SNA were measured on the three-dimensional images constructed with computed tomography data. Participants with an apnea and hypopnea index (AHI) of lower than 5 (AHI ≤ 5) were classified as control and participants while those with an AHI of greater than 5 were classified as OSA group. Each variable with a significant outcome in the independent T-test and age and sex factors were integrated into the multivariate linear regression and the dependent variable was AHI. There were significant differences in the BMI and hip circumference between two groups. The width of nasal base, palatal vault angle and SNA also showed significant differences between groups. The results from multivariate linear regression demonstrated that the BMI, width of the nasal base, and SNA showed significant contributions to the severity of OSA in adolescents. The features of the nasomaxillary complex seemed to have significant influences on development and severity of OSA.

Comparative study of simultaneous use of a double or a triple skin facade with phase change materials, green roof, and photovoltaics in residential buildings of Iran

AbstractResearchers have proposed and studied many methods to reduce energy consumption in the construction sector. However, simultaneous use of phase‐change material (PCM) and green roofs in a building with double‐ or triple‐skin facades (DSF or TSF) has not been analyzed to date. Accordingly, this is the first study to evaluate and compare the design of two scenarios combining passive and active methods, including (1) simultaneous use of a DSF, PCM, green roof, and photovoltaics (PV), and (2) simultaneous use of a TSF, PCM, green roof, and PV in hot arid steppe‐dry mid‐latitude (Tehran) desert biome‐dry tropical (Yazd), and mild‐humid climate (Amol) in Iran. It was found that the first scenario works better in reducing the heating load and the second scenario is more effective in reducing the cooling load. The results indicate that the reduction of the annual heating load in the first scenario was 49, 45.1, and 40.7 MWh/year in Tehran, Yazd, and Amol, respectively, and that the reduction of cooling load in the second scenario was 48.4, 31.9, and 16 MWh/year in Yazd, Tehran, and Amol, respectively. The 14 different modes of combining these passive methods and PV system were then compared. The results indicate that the second proposed scenario caused the lowest annual energy consumption compared to that of other modes and saved 70% of annual energy consumption. Consequently, the effect of leaf area index, cavity width, and orientation that are selected as primary parameters affecting the thermal performance of the mentioned methods on this scenario were investigated.

Research on coupled cavity mechanical tuning extended interaction oscillator with broad tuning range.

This paper proposes a new way to improve the tuning range of the extended interaction oscillator (EIO). Compared with the conventional EIO structure, the fundamental wave changes from the forward wave to the backward wave when the circuit structure changes from the strong-coupling characteristic of the grating to the weak-coupling characteristic. Simultaneously, the tuning range of the EIO can be greatly enhanced by mechanically tuning the coupling cavity. The results show that, compared with the strong-coupling structure of the grating, the extended interaction oscillation circuit has stronger dispersion sensitivity and greater frequency tuning characteristics under the weak-coupling characteristics of the grating. By mechanically tuning the width of the coupling cavity by 0.8mm, its center frequency can be varied by 9.5GHz. This paper also studies and compares the electronic displacement jump phenomenon that occurs in the mechanical tuning process. Similar to the electronic voltage tuning, the output dips suddenly at the operating point of the coupling mismatch. The effective output can be obtained by changing the operating mode in conjunction with electronic tuning. This article provides a new reference method for expanding the tuning range of the extended interaction oscillator.