Cavity Height Research Articles

Prediction of shallow salt cavity geometry from surface subsidence configurations

Physical model tests are used to simulate surface subsidence induced by shallow salt cavity occurred at the interface between salt bed and overlying soil formation. Uniform fine sand with properties similar to the overburden soil is used in the models. The width and depth of sinkhole or subsidence trough induced under various cavity widths, heights, and depths are measured using 3-D laser scanner. The results indicate that for relatively shallow cavity, the increase of sinkhole depth closely relates to the increase of cavity height. The extent of subsidence area is sensitive to depth and width of the cavity. The maximum subsidence is not sensitive to cavity depth. The physical model results are fitted to empirical equations. They can be used to estimate the cavity height and width from the subsidence configurations under similar geologic conditions.

Red-headed Woodpecker (Melanerpes erythrocephalus) winter roost-site selection in a burned forest stand

In temperate regions, winter is characterized by high thermoregulatory demands and low food availability. For woodpeckers, winter survival depends on selecting habitat that provides both suitable roost trees and adequate food. The Red-headed Woodpecker (Melanerpes erythrocephalus) has experienced precipitous declines across much of its range in the past 50 yr, yet causes of declines remain elusive. Although previous studies have focused primarily on the breeding season, understanding winter roost-site requirements is crucial for the maintenance of Red-headed Woodpecker populations across the full annual cycle. Our study investigated winter roost-site characteristics at 3 spatial scales (roost patch, tree, and cavity) in a 41 ha fire-affected forest stand located in northern Virginia. From February to April of 2016 we tracked Red-headed Woodpeckers to 42 roost-sites during evening surveys. To determine the features driving roost-site selection, we compared vegetation surrounding the roost to random sites within the same forest stand, and occupied roost snags (standing dead trees) were compared to the closest available snag. Cavity height and orientation were also examined. We modelled roost-site selection at both the patch and tree scales using logistic regression and identified important variables and their influence by estimating regression coefficients and their model-averaged parameter weights. Habitat within the patch surrounding roost trees had higher basal area of snags and mast-producing trees compared to random sites. Red-headed Woodpeckers selected roost snags with signs of decay and showed preferences based on snag taxon. Our findings indicate that managing land that produces and retains both snags and mature mast-producing trees will benefit overwintering populations of Red-headed Woodpeckers. This study provides the first detailed analysis of winter roost-site selection in this declining species.

Low cost joining of SS304-SS304 through microwave hybrid heating without filler-powder

In this paper, a novel microwave joining technique for SS304-SS304 has been proposed, implemented and optimized, which does not require any filler-material at the joint interface. Absence of filler-powder drastically reduces the material cost of the joining process. The vertical cavity-type charcoal feeder has been used to concentrate heating effect around the joint region. Results of physical and mechanical characterization tests confirm the achievement of good homogeneity, hardness, tensile strength, and ductility in the joint region. Additionally, the process time has been optimized under geometric constraints on diameter and height of cavity. Optimization results show that the fastest joining process is achieved when cavity diameter and height are set to be 15 mm and 31.1 mm respectively.

Formation and growth of cavities in tensile deformation of Poly(ε-caprolactone) and its miscible blends

Microstructural development of poly(ε-caprolactone) (PCL) and its miscible blends with poly(vinyl methyl ether) (PVME) and poly(styrene-co-acrylonitrile) (SAN) were investigated as a function of strain in the process of uniaxial stretching using in situ synchrotron ultrasmall- and small-angle X-ray scattering (USAXS and SAXS) techniques. The addition of amorphous polymer SAN gives rise to a distinct reduction in the entanglement density of the amorphous phase of PCL, whereas an introduction of PVME does not affect the entanglement density in the blend. At small strains, the initial cavities in pure PCL are oriented perpendicular to the drawing direction, while the cavities at the onset of their formation are oriented along the extensional direction for the PCL/PVME blend. Nevertheless, no cavity scattering is observed in PCL/SAN blend during the process of tensile deformation. These results confirm that the cavitation is directly linked to the lamellar crystallites with their orientation parallel to the drawing direction at small extension ratios. For the two cavitated samples, the volume fraction of cavities was assessed from the integrated scattering intensity based on a three phase model. A critical stress value, above which the lamellar mosaic blocks begin to be pulled apart and the cavitation just sets in, was found to be nearly constant at around 15 MPa. Furthermore, the dimensions of cavities were evaluated at different deformations via direct cylinder model fitting to the USAXS patterns. The height of cavities is much larger than the long spacing of lamellar stacks even at the early stages of cavity formation, which indicates the cavities emanating from the lamellae into several amorphous phases at small elongations. Analysis of the SAXS patterns shows an independence of lamellar long spacing on the sample composition at large strains, which strongly supports the deformation scheme of stress-induced fragmentation and recrystallization.

Quintuple-mode wideband bandpass filters with improved out-of-band rejection

AbstractThis paper presents design of quintuple-mode wideband bandpass filters, implemented with off-centered perturbed metallic cylinders in a rectangular waveguide cavity. Three perturbation cylinders are placed at the bottom of the rectangular waveguide cavity, along with a pair of perpendicularly fed coaxial lines; excite five quasi-transverse magnetic modes to realize the desired passband. The height of the waveguide cavity and the shape of the perturbation cylinders are exploited to shift the resonant modes far away from the passband and achieve a good out-of-band rejection and sharp skirt selectivity. The filter operates at the center frequency of 2.68 GHz with a wide fractional bandwidth of 43%. The proposed filter is fabricated with aluminum. The measured and simulated results are in good agreement with each other.

An application for Olze’s method and tooth coronal index for age estimation of a Turkish adult population

ABSTRACT The aim of this study is to evaluate the applicability of the tooth coronal index (TCI) and Olze’s method for age estimation in Turkish individuals. The digital panoramic radiographs of 860 individuals ranging from 18 to 60 years of age were evaluated. The TCI was calculated using the ratio between coronal pulp cavity height and crown height in mandibular premolar teeth. We also analysed, four dental parameters (secondary dentin formation, attrition, periodontal recession, cementum apposition) of Olze’s method. Linear and multiple regression models were established for each tooth groups. The correlations between age and TCIs were r= -0.45 and r= -0.53 for the mandibular first and second premolars, respectively (p<0.01). The regression equations that were derived for age estimation using TCI showed a coefficient of determination (R2) ranging between 0.20 to 0.32; the standard errors of estimates (SEE) ranged from 10.01 to 10.96 years. For Olze’s method, R2 values ranged between 0.76 and 0.80; SEE ranged from 5.64 to 6.08 years. We concluded that Olze’s method was useful for age estimation among Turkish adults. The TCI method found to be of more limited the use in age estimation due to a higher standard error of estimations, compared with Olze’s method.

Theoretical Modeling, Numerical Simulations and Experimental Study of Micro Thermal Convective Accelerometers

We present a one-dimensional (1D) theoretical model for the design analysis of a micro thermal convective accelerometer (MTCA). Systematical design analysis was conducted on the sensor performance covering the sensor output, sensitivity, and power consumption. The sensor output was further normalized as a function of normalized input acceleration in terms of Rayleigh number R $_{\mathrm {a}}$ (the product of Grashof number G $_{\mathrm {r}}$ and Prandtl number P $_{\mathrm {r}}$ ) for different fluids. A critical Rayleigh number ( R ac = 3,000) is founded, for the first time, to determine the boundary between the linear and nonlinear response regime of MTCA. Based on the proposed 1D model, key parameters, including the location of the detectors, sensor length, thin film thickness, cavity height, heater temperature, and fluid types, were optimized to improve sensor performance. Accordingly, a CMOS compatible MTCA was designed and fabricated based on the theoretical analysis, which showed a high sensitivity of 1,289 mV/g. Therefore, this efficient 1D model, one million times faster than CFD simulation, can be a promising tool for the system-level CMOS MEMS design.

Computed tomography measurement of the bone matrix of vertebral pedicle and its clinical significance

To provide the anatomic basis for the clinical application of the transpedicular screw fixation. Thirty spine (C2-L5) specimens were used. The width of the pedicle cortex and width of the pedicle medullary cavity (WPC and WPMC), and the height of the pedicle cortex and height of the pedicle medullary cavity (HPC and HPMC) were measured at the isthmus of the pedicle using computed tomography (CT) scanning. Width of the pedicle medullary cavity changed in a three-dovetailed-saddle shape with four peaks and three valleys, namely C2 (high), C4`5 (low), T2 (high), T4 (the lowest), T12 (high), L1 (low) and L5 (the highest). HPMC of the cervical pedicle changed in a saddle shape, gradually increasing from C5-L5. WPC, WPMC, HPC and HPMC showed a regular change, respectively. In each segment, the superior border of the pedicle cortex had a nearly consistent thickness to the interior border within an identical pedicle, while the pedicle cortex thickness radio of the medial and lateral border was nearly 3:1 among the cervical pedicles, 2:1 among thoracic pedicles, and 1:1 among lumbar pedicles. Both HPMC and WPMC are the dominant factors for the choice of screw diameter, but HPMC should also be considered in C2-T1 pedicles, especially C6 and C7. Additionally, the screw for C3-6 or T4-6 pedicles should be about 3.0 mm in diameter.

Cooling of an isothermal surface having a cavity component by using CuO-water nano-jet

PurposeThe purpose of this study is to numerically analyze the convective heat transfer features for cooling of an isothermal surface with a cavity-like portion by using CuO-water nano jet. Jet impingement cooling of curved surfaces plays an important role in practical applications. As compared to flat surfaces, fluid flow and convective heat transfer features with jet impingement cooling of a curved surface becomes more complex with additional formation of the vortices and their interaction in the jet wall region. As flow separation and reattachment may appear in a wide range of thermal engineering applications such as electronic cooling, combustors and solar power, jet impingement cooling of a surface which has a geometry with potential separation regions is important from the practical point of view.Design/methodology/approachNumerical simulations were performed with a finite volume-based solver. The study was performed for various values of the Reynolds number (between 100 and 400), length of the cavity (between 5 w and 40 w), height of the cavity (between w and 5w) and solid nano-particle volume fraction (between 0 and 4 per cent). Artificial neural network modeling was used to obtain a correlation for the average Nusselt number, which can be used to obtain fast and accurate predictions.FindingsIt was observed that cavity geometrical parameters of the cooling surface can be adjusted to change the flow field and convective heat transfer features. When the cavity length is low, significant contribution of the inclined wall of the cavity on the average Nusselt number is achieved. As the cavity length and height increase, the average Nusselt number, respectively, reduce and slightly enhance. At the highest value of cavity height, significant changes in the convective flow features are obtained. By using nanofluids instead of water, enhancement of average heat transfer in the range of 35-46 per cent is obtained at the highest particle volume fraction.Originality/valueIn this study, jet impingement cooling of an isothermal surface which has a cavity-like portion was considered with nanofluids. Addition of this portion to the impingement surface has the potential to produce additional vortices which affects the fluid flow and convective features in the jet impingement heat transfer. This geometry has the forward-facing step for the wall jet region with flow separation reattachment in the region. Based on the above literature survey and to the best of the authors’ knowledge, jet impingement cooling for such a geometry has never been reported in the literature despite its importance in practical thermal engineering applications. The results of this study may be useful for design and optimization of such systems and to obtain best performance in terms of fluid flow and heat transfer characteristics.

Numerical study of effect of front cavity on hydrogen/air premixed combustion in a micro-combustion chamber

The micro-combustion chamber is the key component for micro-TPV systems. To improve the combustor wall temperature level and its uniformity and efficiency an improved flat micro-combustor with a front cavity is built, and the combustion performance of the original and improved combustors of premixed H2/air flames under various inlet velocities and equivalence ratios is numerically investigated. The effects of the front cavity height and length on the outer wall temperature and efficiency are also discussed. The front cavity significantly improves the average outer wall temperature, outer wall temperature uniformity, and combustion efficiency of the micro-combustor, increases the area of the high temperature zone, and enhances the heat transfer between the burned blends and inner walls. The micro-combustor with the front cavity length of 2.0 mm and height of 0.5 mm is suitable for micro-TPV system application due to the relatively high outer wall temperature, combustion efficiency, and the most uniform outer wall temperature.

Early bleb parameters as long-term prognostic factors for surgical success: a retrospective observational study using three-dimensional anterior-segment optical coherence tomography

BackgroundThe object of this study is to investigate the effect of early bleb parameters measured by three-dimensional anterior-segment optical coherence tomography on the surgical success of trabeculectomy.MethodsThis retrospective study included 45 patients with 19 of exfoliation glaucoma, 17 of primary open angle glaucoma, 4 of neovascular glaucoma, 4 of uveitic glaucoma and 1 of glaucoma caused from familial amyloid polyneuropathy who underwent trabeculectomy. Bleb parameters, such as total bleb height, the position and the width of filtration openings on the scleral flap, bleb wall thickness, fluid-filled cavity height, and bleb wall intensity were assessed by three-dimensional anterior-segment optical coherence tomography 0.5 months after trabeculectomy, and were subjected to a Cox proportional hazard model as potential prognostic factors. Surgical success was defined as: IOP < 21 mmHg (A), < 18 mmHg (B), < 15 mmHg (C) with (qualified success) or without medication (complete success). Complete failure was defined as hypotony and additional glaucoma surgeries required.ResultsThe width of filtration openings was identified as a prognostic factor for all criteria. By multivariable analysis, the width of the filtration openings was a prognostic factor in all criteria tested, and the preoperative IOP were significant prognostic factors for surgical success in qualified success in criteria B and C. Separate from the median widths of filtration openings, wide filtration opening showed significant survival ratio for qualified success in criteria A and B and for complete success in all criteria, respectively.ConclusionsThe width of filtration opening at an early stage is a prognostic factor for surgical success of trabeculectomy.

Orthogonal numerical simulation on stability of urban underground cavities

The effects of cavity shape factors and mechanical parameters on the stability of underground cavity are studied by orthogona l numerical simulation test. According to the characteristics of underground cavities in the city, the orthogonal numerical values of six factors and five levels are carried out by selecting the factors such as cavity span, cavity height, overlying soil thickness, pavement load, cohesive force and interna l friction angle. The comprehensive evaluation model of multi-index orthogonal simulation test based on index satisfaction is set up, and four indexes of roof settlement, minimum principal stress, maximum principal stress and plastic zone volume are selected to study the multi-index comprehensive evaluation and sensitivity analysis. The results show that the pavement load and void span is the most sensitive to the stability of underground cavity. The cohesion and thic kness of overlying soil are the second sensitive cause, and the influence of cavitation height and internal friction angle are the least.

Analysis of Anti-jet Penetration Characteristics of Axial Single-cell / Multi-cell Closed Structure

To analyze the mechanical properties of jet penetration on a single-cell / multi-cell liquid composite closed structure, the motion equation of jet penetrating a metal target is established, and the energy equation of the penetration system is derived. The simulation results show the radial convergence effect of the liquid in the single-cell increases with the increase of the height of the inner cavity of the closed structure. The radial convergence effect of liquid in multi-cell also has the same phenomenon, but the phenomenon of liquid disjunction appears, which leads to the convergence of liquid into segments. The pressure in the single-cell liquid appears at the bottom of the cell, but the multi-cell liquid appears in the last cell. The pressure distribution of the single-cell is concentrated on the bottom of the cell, and the pressure distribution is circular. The pressure distribution of multi-cell is more uniform, and there is no obvious concentrated distribution phenomenon. The energy of the closed cell structure increases with the increase of the height and the number of the cell.

Loss mechanism of the SISL and the experimental verifications

In this study, the loss mechanism of substrate integrated suspended line (SISL) is investigated and the experimental verification is given. The strategy to reduce the total circuit losses, including the radiation loss, the conductor loss, and the dielectric loss based on SISL platform, is investigated. For the three cases in the form of uniform transmission lines, their characteristic impedance, phase constant, and attenuation constant are simulated and compared. The influences caused by the height of the air cavity, the distance between the centre trace to the side wall, dielectric loss tangent, and metal conductivity are also investigated. Finally, the experimental verifications using uniform transmission lines are given.

1.1 THz tenth harmonic mixer based on planar GaAs Schottky diode

Here, the tenth harmonic mixing technology based on planar GaAs Schottky diode is first proposed for the 1.1 terahertz (THz) frequency conversion module. The first higher order mode cut-off frequency of the suspended microstrip line has been investigated to determine the appropriate cross-sectional dimension of transmission line shield cavity in the radio frequency (RF) circuit portion. The height of shield cavity of transmission line is designed to be discontinuous in order to facilitate the assembly of the diode. A modelling approach combining field and circuit is used to achieve joint simulation of linear passive structure and diode non-linear characteristics. The simulation results show that the frequency conversion loss of this mixer is <55 dB in the RF frequency range of 1.03–1.154 THz, and the best frequency conversion loss is 50 dB at RF of 1.098 THz.

An Analytical Model for Bandwidth Enhancement of Air-Coupled Unsealed Helmholtz Structural CMUTs

Capacitive micromachined ultrasonic transducers (CMUTs) were reported to own high potential in air-coupled ultrasonic applications such as noncontact nondestructive examination and gas flow measurement. The unsealed CMUTs which utilized the squeeze film effect were reported to overcome the narrow output pressure bandwidth of the conventional sealed CMUTs in air operation. This kind of unsealed CMUTs can also be regarded as Helmholtz resonators. In this work, we present the air-coupled unsealed Helmholtz structural CMUTs which utilize both the squeeze film effect and the Helmholtz resonant effect to enhance the output pressure bandwidth. Based on the mechanism of vibration coupling between membrane and air pistons in membrane holes, we propose an analytical model to aid the design process of this kind of CMUTs. We also use finite element method (FEM) to investigate this kind of CMUTs for our analytical model validation. The FEM results show that the significant bandwidth enhancement can be achieved when the Helmholtz resonant frequency is designed close to the fundamental resonant frequency of the CMUT membrane. Compared with the conventional sealed CMUT cell, the 4-hole unsealed Helmholtz structural CMUT cell improves both the 3-dB fractional bandwidth and SPL-bandwidth product around 35 times. Furthermore, it is found that, with more holes under the same hole area ratio or with a smaller ratio of the cavity height to the viscous boundary layer thickness, the Helmholtz resonant effect becomes weaker and thus the output pressure bandwidth decreases.

Effects of material properties and geometric parameters on electromagnetic-assisted transfer printing

Flexible and stretchable electronics are rapidly evolving to be used in a wide range of applications, including wearable medical devices, implantable health monitoring devices, and bio-integrated systems. As an important method to integrate heterogeneous materials and functional components toward flexible and stretchable electronic systems, transfer printing technology has attracted increasing attention. Among the different approaches in transfer printing, electromagnetic-assisted transfer printing provides a versatile method that allows remote control. In order to investigate the effects of various materials and geometric parameters on the electromagnetic-assisted transfer printing process, a theoretical analysis is combined with the finite element method to investigate the underlying physics. The desirable ranges of parameters (e.g. thickness, radius, and elastic modulus of the upper and lower films in the design) are obtained for the optimized operation. The results indicate that the radii of the upper and lower films should be selected with large values and their upper limits are bound by the size of the functional components to be transferred. Moreover, the radii ratio between the upper to lower film should be within the range of 0.6–0.9. Though small thickness and elastic modulus are preferred in the upper and lower films, the values should be sufficiently large to ensure the strength. Meanwhile, the thickness ratio of upper to lower film should be within the range of 0.5–2. At the same time, the elastic modulus ratio and the height of the lower pickup cavity are shown to have little influence on the maximum displacement of the lower film. With the theoretical predictions validated by the finite element analysis, the results presented in this study are expected to provide useful guidelines for the experimental design.

MHD mixed convection of nanofluid in a cubic cavity with a conductive partition for various nanoparticle shapes

PurposeThis paper aims to numerically examine the mixed convection of SiO2-water nanofluid flow in a three-dimensional (3D) cubic cavity with a conductive partition considering various shapes of the particles (spherical, cylindrical, blade, brick). The purpose is to analyze the effects of various pertinent parameters such as Richardson number (between 0.1 and 10), Hartmann number (between 0 and 10), solid nanoparticle volume fraction (between 0 and 0.04), particle shape (spherical, cylindrical, blade, brick) and different heights and lengths of the conductive partition on the fluid flow and heat transfer characteristics.Design/methodology/approachThe numerical simulation was performed by using Galerkin-weighted residual finite element method for various values of Richardson number, Hartmann number, solid nanoparticle volume fraction, particle shape (spherical, cylindrical, blade, brick) and different heights and lengths of the conductive partition. Two models for the average Nusselt number were proposed for nanofluids with spherical and cylindrical particle by using multi-layer feed-forward neural networks.FindingsIt was observed that the average Nusselt number reduces for higher values of Richardson number and Hartmann number, while enhances for higher values of nanoparticle volume fraction. Among various types of particle shapes, blade ones perform the worst and cylindrical ones perform the best in terms of heat transfer enhancement, but this is not significant which is less than 3 per cent. The average Nusselt number deteriorates by about 6.53per cent for nanofluid at the highest volume fraction of spherical particle shapes, but it is 11.75per cent for the base fluid when Hartmann number is increased from 0 to 10. Conductive partition geometrical parameters (length and height) do not contribute to much to heat transfer process for the 3D cavity, except for the case when height of the partition reaches 0.8 times the height of the cubic cavity, the average Nusselt number value reduces by about 25per cent both for base fluid and for nanofluid when compared to case with cavity height which is 0.2 times the height of the cubic cavity.Originality/valueBased on the literature survey, a 3D configuration for MHD mixed convection of nanofluid flow in a cavity with a conductive partition considering the effects of various particle shapes has never been studied in the literature. This study is a first attempt to use a conductive partition with nanofluid of various particle shapes to affect the fluid flow and heat transfer characteristics in a 3D cubic cavity under the influence of magnetic field. Partial or all findings of this study could be used for the design and optimization of realistic 3D thermal configurations that are encountered in practice and some of the applications were already mentioned above. In this study, thermal performance of the system was obtained in terms of average heat transfer coefficient along the hot surface, and it is modeled with multi-layer feed-forward neural networks.

Quadruple-Mode Wideband Bandpass Filter with Improved Out-of-Band Rejection

This paper proposes a method for designing a quadruple-mode wideband bandpass filter using off-centered perturbed metallic cylinders in a rectangular waveguide cavity with compact size and improved out-of-band rejection. Two off-centered perturbation cylinders were placed at the bottom of the rectangular waveguide cavity along with a pair of perpendicularly-fed coaxial lines, which excited four quasi-transverse magnetic (TM) modes to realize the desired passband. The height of the waveguide cavity and the shape of the perturbation cylinders were exploited to achieve an all quasi-TM modes filter with good out-of-band rejection and sharp skirt selectivity. The proposed filter operates at 2.93 GHz center frequency with 38% wide fractional bandwidth (FBW). The proposed filter is fabricated using aluminum. The measured and simulated results are in good agreement with each other.

Thermal environments within aspen (Populus tremuloides) tree cavities during summer: Implications for breeding and roosting cavity users

Summer temperature patterns within tree cavities might influence occupancy of cavities by different animals such as birds and bats, and furthermore, cavity temperatures can influence processes such as embryonic development or the development of young. Our study aimed to identify the environmental variables influencing cavity temperatures during summer (June–July) in quaking aspen (Populus tremuloides) in southeastern Idaho. We collected temperature data between June 22 and July 27, 2015 using iButtons distributed across 30 tree cavities in 30 aspen stands in the Craters of the Moon National Monument, Idaho. We used every third day of data to ensure temporal independence amongst readings from the same cavity. We used a multi-model selection framework to examine how environmental characteristics might influence cavity thermal environments, and we modeled how environmental variables, tree, and cavity characteristics might influence daily maximum cavity temperatures. Cavity temperatures ranged as low as 1 °C to as high as 46 °C. Approximately 13% of the cavities experienced temperatures above 40 °C for at least an hour, and these temperatures are noted to be lethal to developing avian embryos. The two top competing models explaining the daily maximum cavity temperatures included tree diameter at cavity height, canopy cover, cavity orientation, and daily maximum ambient temperature. Daily maximum cavity temperatures were significantly associated with daily maximum ambient temperatures and canopy cover; warmer cavities were positively associated with warmer ambient temperatures and negatively associated with canopy cover. Because cavities in aspen are an important resource for multiple species, understanding the factors that influence the microclimate of tree cavities can have broad implications for cavity using species in the context of changing climates.