Thickness Of Dome Research Articles

Numerical Method for Predicting Transient Aerodynamic Heating in Hemispherical Domes

In this research, a streamlined numerical approach designed for the quick estimation of temperature profiles across the finite thickness of a hemispherical dome subjected to aerodynamic heating is introduced. Hemispherical domes, with their advantageous aerodynamic, structural, and optical properties, are frequently utilized in the front sections of objects traveling at supersonic velocities, including missiles or vehicles. The proposed method relies on one-dimensional analyses of fluid dynamics and flow characteristics to approximate the local heat flux across the exterior surface of the dome. By calculating these local heat flux values, it is also possible to predict the temperature variations within the thickness of the dome by employing the finite difference technique, to solve the heat conduction equation in spherical coordinates. This process is iterated over successive time intervals, to simulate the entire flight duration. Unlike traditional Computational Fluid Dynamics (CFD) simulations, the proposed strategy offers the benefits of significantly lower computational time and resource demands. The primary objective of this work is to provide an efficient numerical tool for evaluating aerodynamic heating impact and temperature gradients on hemispherical domes under specific conditions. The effectiveness of the proposed method will be validated by comparing the temperature profiles derived for a standard flight scenario against those obtained from 2-D axisymmetric transient CFD simulations performed using ANSYS-Fluent 2022 R2.

Accessibility and Thickness of Medial and Lateral Talar Body Cartilage for Treatment of Ankle and Foot Osteochondral Lesions.

The purposes of this study were to determine (1) if cartilage thicknesses on the talar dome and medial/lateral surfaces of the talus were similar, (2) whether there was sufficient donor cartilage surface area on the medial and lateral talar surfaces to repair talar dome cartilage injuries of the talus, and (3) whether the cartilage surface could be increased following anterior talofibular ligament (ATFL) and sectioning of the tibionavicular and tibiospring portion of the anterior deltoid. Medial and lateral approaches were utilized in 8 cadaveric ankles to identify the accessible medial, lateral, and talar dome cartilage surfaces in 3 conditions: (1) intact, (2) ATFL release, and (3) superficial anterior deltoid ligament release. The talus was explanted, and the cartilage areas were digitized with a coordinate measuring machine. Cartilage thickness was quantified using a laser scanner. The mean cartilage thickness was 1.0 ± 0.1 mm in all areas tested. In intact ankles, the medial side of the talus showed a larger total area of available cartilage than the lateral side (152 mm2 vs 133 mm2). ATFL release increased the available cartilage area on the medial and lateral sides to 167 mm2 and 194 mm2, respectively. However, only the lateral talar surface had sufficient circular graft donor cartilage available for autologous osteochondral transplantation (AOT) procedures of the talus. After ATFL and deltoid sectioning, there was an increase in available graft donor cartilage available for AOT procedures. The thickness of the medial and lateral talar cartilage surfaces is very similar to that of the talar dome cartilage surface, which provides evidence that the medial and lateral surfaces may serve as acceptable AOT donor cartilage. The surface area available for AOT donor site grafting was sufficient in the intact state; however, sectioning the ATFL and superficial anterior deltoid ligament increased the overall lateral talar surface area available for circular grafting for an AOT procedure that requires a larger graft. These results support the idea that lateral surfaces of the talus may be used as donor cartilage for an AOT procedure since donor and recipient sites are similar in cartilage thickness, and there is sufficient cartilage surface area available for common lesion sizes in the foot and ankle. This anatomical study investigates the feasibility of talar osteochondral autografts from the medial or lateral talar surfaces exposed with standard approaches. It confirms the similar cartilage thickness of the talar dome and the ability to access up to an 8- to 10-mm donor graft from the lateral side of the talus after ligament release. This knowledge may allow better operative planning for use of these surfaces for osteochondral lesions within the foot and ankle, particularly in certain circumstances of a revision microfracture.

Minimum thrust and minimum thickness of spherical masonry domes: A semi-analytical approach

A semi-analytical approach is proposed for addressing the minimum thrust and minimum thickness analysis of spherical masonry domes under their self-weight. The classical differential equilibrium equations of axially symmetric shells are resorted to, calling for the exact computation of self-weight and center of mass of an infinitesimal dome voussoir. The minimum thrust analysis is accomplished by determining a statically admissible stress state in the dome, that is associated to a kinematically admissible settlement mechanism of minimum thrust. Such a stress state entails vanishing hoop stresses in the lower part of the dome, where the opening of meridional cracks occurs. An original numerical scheme is proposed for automatically computing a distribution of hoop stresses in the dome cap, producing a statically admissible stress state. A suitable modification of the semi-analytical procedure for the minimum thrust analysis is then adopted to perform the minimum thickness analysis. Numerical results are presented for spherical domes with parameterized oculus and embrace angles, complemented by the comparison with alternative equilibrium models, and with approximate treatments of the dome self-weight adopted in the literature. The merit of the proposed procedure is finally proved in application to a real case. As an iconic result, a refined estimate of the minimum thickness of a hemispherical dome is derived, resulting in 0.04284 times the radius of the mid-surface.

Evaluating imaging quality of optical dome affected by aero-optical transmission effect and aero-thermal radiation effect.

The imaging quality of the aerodynamically heated optical dome was evaluated under the comprehensive influence of aero-optical transmission effect and aero-thermal radiation effect. The ray propagating algorithm based on the fourth order Runge-Kutta method was used to trace the target ray and the thermal radiation ray of the optical dome. Three imaging quality evaluation parameters were proposed to evaluate aero-optical effect: Modulation transfer function (MTF), irradiance, peak signal-to-noise ratio (PSNR) of distorted images. The results show that: as the flight speed increased, the MTF decreased observably compared with the diffraction-limit MTF, the irradiance on the photosensitive surface of the detector increased gradually, and the distorted imaging quality under the influence of the comprehensive aero-optical effect gradually deteriorated. However, as the thickness of the optical dome increased, the MTF decreased sharply and the irradiance decreased gradually, that indicated the aero-optical transmission effect was reinforced and the aero-thermal radiation effect was weakened. The imaging quality improved with thickness increasing. The influence of aero-thermal radiation effect on the PSNR of the image was more serious than that of the aero-optical transmission effect.

The role of different sliding resistances in limit analysis of hemispherical masonry domes

A limit analysis method for masonry domes composed of interlocking blocks with non-isotropic sliding resistance is under development. This paper reports the first two steps of that work. It first introduces a revision to an existing limit analysis approach using the membrane theory to find the minimum thickness of a hemispherical dome under its own weight and composed of conventional blocks with finite isotropic friction. The coordinates of an initial axisymmetric membrane surface are the optimization variables. During the optimization, the membrane satisfies the equilibrium conditions and meets the sliding constraints where intersects the block interfaces. The results of the revised procedure are compared to those obtained by other approaches finding the thinnest dome. A heuristic method using convex contact model is then introduced to find the sliding resistance of the corrugated interlocking interfaces. Sliding of such interfaces is constrained by the Coulomb’s friction law and by the shear resistance of the locks keeping the blocks together along two orthogonal directions. The role of these two different sliding resistances is discussed and the heuristic method is applied to the revised limit analysis method.

半球形整流罩厚度对气动热辐射的影响

Aerodynamically heated high temperature dome will produce strong infrared radiation. In some serious cases when the probe reaches saturation, the detecting precision of the seeker for target can be severely affected. In order to reduce the aerodynamic thermal radiation of the dome, a mathematical model of aerodynamic thermal radiation was developed. The aerodynamic heat and the aerodynamic thermal radiation of the hemispherical dome with different thickness were simulated numerically by software of finite element analysis and the mathematical model of aerodynamic thermal radiation. The influence of the thickness of hemispherical dome on the aerodynamic thermal response and aerodynamic heat radiation was analyzed and obtained. Research indicates that in the same flight conditions and in 10 s, when the thickness of hemispherical dome increases from 3 mm to 8 mm, the stagnation point temperature of the dome reduces by 16.41%; the thermal deformation of the dome reduces by 54.2%; the maximum irradiance of receiving surface of the detector decreases by 84.43%. Therefore increasing the thickness of the dome can not only reduce the temperature of the dome, but also effectively reduce the thermal deformation of the dome and the interference radiation illumination received on the detector.

The North American Late Wisconsin ice sheet and mantle viscosity from glacial rebound analyses

Observations of sea level and crustal response to glacial loading cycles provide constraints on the mantle rheology function, E, and as well as on the ice load, I, with the latter being largely free from a-priori glaciological or climate assumptions and appropriate, therefore, for testing any such hypotheses. This paper presents new results for both continental-mantle E and I for the Late Wisconsin ice sheet, using geological evidence for relative sea-level change (rsl) and tilting of palaeo-lake shorelines, complemented with loose constraints from observations of present-day radial crustal displacement across North America. The focus is on evidence from near or within the former maximum ice margins and the resulting earth response is representative of sub-continental mantle conditions. The inversion of the sea-level information has limited resolution for earth rheology and simple three-layer models, characterized by depth-averaged effective lithospheric thickness (H) and upper- and lower-mantle viscosities (ηum and ηum respectively) adequately describe the response function, yielding parameters (earth model E-6) of H = 102 (85–120) km, ηum = 5.1 × 1020 (3.5–7.5)x1020, ηlm = 1.3 × 1022 (0.8–2.8)x1022 where the numbers in parenthesis are 95% confidence limits. The details of the ice sheet, with one exception, are not strongly dependent on the rheological assumptions within this range. The exception is the lower mantle viscosity that remains correlated with the magnitude scaling of the ice sheet: a link that is largely broken by introducing constraints from glacial loading effects on the Earth's rotation and dynamic flattening. The difference between the continental ηum and the comparable estimate of (1–2.5)x1020 for ocean mantle is statistically significant. Shoreline gradient information from Glacial Lakes McConnell, Agassiz, Algonquin and Ojibway provide strong constraints on the response within the interior of the ice sheet and the resulting ice sheet model (LW-6) is characterized by multiple ice domes from at least ∼17–18 ka onwards. The resolution for earlier periods is largely constrained by global ice volume considerations. The two principal domes are over southern Nunavut (the Keewatin Dome) and over Québec-Labrador, both of ≥3500 m thickness, separated by an ice ridge some 1500 m lower than the domes, the latter a requirement imposed by the gradient information. Over western Canada ice thickness gradients east of the Cordilleras are partly constrained by the shoreline data for former Lake McConnell (as is the lateglacial ice thickness of the Keewatin dome) and indicate that any ice-free corridor between the Laurentian and Cordilleran components is unlikely to have existed before ∼13ka. Reconstructions of the glacial lakes are consistent with the locations and timing of the observational evidence for the four major lake systems with the likely drainage routes identified. The evolution of the LW-6 ice-volume function, expressed as equivalent sea level, is characterized by a rapid decrease in ice volume from ∼15 to 14.5 ka, corresponding to the Bølling-Allerød period, in the main from rapid ice retreat along the southern margin, with further contributions from drainage through the St Lawrence River valley and from ice retreat from the major northern straits and gulfs, but not Hudson Strait where the rsl data point to late removal of ice (after 10 ka). The contribution of the drainage of the lakes to global sea level rise is small, < 1 m at the end of 9 ka, with final drainage of the Agassiz, Algonquin and Ojibway lakes occurring through Hudson Strait. The comparison of model predictions based on the above model parameters are, with one exception, consistent with observed GPS rates but do indicate a differential offset between the origins of the geodetic and geophysical reference frames, with the geodetic frame moving relative to the geophysical frame in direction approximately parallel to the earth's rotation axis.

Finite element thrust line analysis of axisymmetric masonry domes

A new method for analysis of axisymmetric masonry domes is proposed here combining the simplicity of the thrust line with the versatility of the finite element approach, where a modified axisymmetric element incorporates the hoop tension effects. This method is able to obtain the thrust line of an axisymmetric masonry dome more accurately than the existing graphical approaches. The case study on a hemispherical axisymmetric dome shows the effectiveness of the proposed method. The results reaffirm the notions of classical thrust line analysis and postulates on the minimum thickness of a stable dome.

Ultrasound assessment of bladder wall thickness as a screening test for detrusor instability

The aim of the current study was to evaluate the diagnostic accuracy of transvaginal ultrasound measurement of bladder wall thickness (BWT) in diagnosis of over active bladder (OAB). The current prospective study was conducted at Ain Shams University Maternity Hospital over 2 years. Patients presented to the urogynecology outpatient clinic with symptoms of urinary frequency, urgency, nocturia and/or urge incontinence were included in this study. The allocated patients were divided into two groups; Group 1(study group): fifty (50) patients with urodynamic diagnosis of detrusor instability (OAB) were included. Group 2 (control): fifty (50) patients with urodynamic diagnosis of stress incontinence were included. Using a transvaginal probe, BWT was measured in three sites at the thickest part of (a) the dome of the bladder (b) the trigone, and (c) the anterior wall of the bladder. An average of the three measurements was considered as the mean bladder thickness. A total of 100 patients with lower urinary symptoms were finally analyzed. There were no statistical significant differences between both groups regarding age, parity and body mass index, while there was statistically longer disease duration in group 2. Excluding urgency, there was statistical significant difference (P < 0.001) regarding lower urinary tract symptoms namely frequency, urgency incontinence, coital incontinence and nocturia. Patients in group 1 were more positive to symptoms of frequency, urgency incontinence, and nocturia, while patients in group 2 were more positive regarding coital incontinence. The thickness of trigon, dome, anterior wall and mean BWT was significantly higher in group 1 when compared to group 2. Receiver operator characteristics curve was constructed for estimating the association between mean BWT and prediction of OAB in patients with lower urinary tract symptoms. Mean BWT at 4.78 mm was considered as best cut-off value for prediction of OAB with sensitivity of 90 % and specificity of 78 %. Mean BWT was significantly associated with OAB > 4.78 mm as denoted by the significantly large area under the curve [AUC], AUC was 0.905. In women with lower urinary tract symptom, transvaginal ultrasounds measured mean BWT seems to be an effective non invasive diagnostic tool for prediction of OAB.

The Radiation Environment on the Moon from Galactic Cosmic Rays in a Lunar Habitat

We calculated how the radiation environment in a habitat on the surface of the Moon would have depended on the thickness of the habitat in the 1977 galactic cosmic-ray environment. The Geant4 Monte Carlo transport code was used, and a hemispherical dome made of lunar regolith was used to simulate the lunar habitat. We investigated the effective dose from primary and secondary particles including nuclei from protons up to nickel, neutrons, charged pions, photons, electrons and positrons. The total effective dose showed a strong decrease with the thickness of the habitat dome. However, the effective dose values from secondary neutrons, charged pions, photons, electrons and positrons all showed a strong increase followed by a gradual decrease with the habitat thickness. The fraction of the summed effective dose from these secondary particles in the total effective dose increased with the habitat thickness, from approximately 5% for the no-habitat case to about 47% for the habitat with an areal thickness of 100 g/cm(2).

Design of rotational dielectric dome with linear array feed for wide‐angle multibeam antenna applications

AbstractThis paper proposes a method for design of the shape and thickness of a dielectric dome by optimization, aiming at achieving multibeam emission with a uniform high gain for a wide range of angles. The dielectric dome has the features that it does not require a tremendous number of elements, as in the constrained lens, and that excellent multibeam characteristics can be realized over a wider range of angles than in the conventional dielectric lens. These features are demonstrated through an example of the design of a dielectric dome in which a decrease in gain is avoided over a wide range of angles up to 70°. The validity of the proposed method is verified by numerical analysis, and also by measurement and evaluation of the radiation pattern of the constructed dielectric dome antenna in the Ka band. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 90(5): 49– 57, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.20254

Vertical dimensions and age of the Wicklow Mountains ice dome, Eastern Ireland, and implications for the extent of the last Irish Ice Sheet

Patterns of erratic distribution show that the Wicklow Mountains formerly supported an independent ice cap or ice dome. Geomorphological mapping of the upper limits of evidence for glaciation (ice-scoured and moulded bedrock, perched boulders) and the distribution of features indicative of prolonged periglacial conditions (tors, frost-shattered rock, blockfields) indicates that along the main axis of high ground erosive warm-based ice buried all but the highest (>725 m) summits and over-ran adjacent lower peaks and cols. The presence of gibbsite in soil samples from above the inferred upper limit of glacial erosion and its absence in all samples from below this limit is consistent with the geomorphological evidence and implies removal of gibbsitic soils below ∼725 m by glacial erosion during the last glacial stage. Cosmogenic 10Be exposure ages for rock outcrops above the inferred upper limit of glacial erosion yield pre-last glacial maximum (LGM) ages of (>) 46.9±3.0 ka to (>) 95.9±6.1 ka, whereas rock outcrops on summits over-ridden by warm-based ice give post-LGM ages of 18.2±1.2 to 19.1±1.2 ka. All geomorphological and dating evidence thus indicates an LGM age for the ice dome. The thickness of the ice dome and limited lateral dispersal of erratics indicate that at the LGM the Wicklow ice was encircled by and confluent with thick, powerful ice streams moving SE from the Irish Midlands and southwards down the Irish Sea basin. This conclusion is irreconcilable with the traditional view that the last Irish ice sheet terminated at the ‘South Ireland end moraine’, but consistent with recent proposals that the last ice sheet was much more extensive than previously believed, and over-ran the south coast of Ireland.

Cartilage thickness of the talar dome

To perform a successful operation, accurate information on the articular cartilage thickness of the talus is essential. The purpose of this study was to determine the articular cartilage thickness of the talar dome in the area where osteochondritis dissecans is common. Convenient samples. Articular cartilage thickness of the mid talar dome was measured in 29 ankles of 17 cadavers. The average age of the specimens was 70 years (range, 53 to 91 years). Twenty-two were from men and 7 were from women. Coronal sections of the mid talar domes were obtained from the specimens measuring 2 mm in width and 5 mm in depth. Radiographs of the sectioned specimens were taken and were enlarged with a personal computer. The thickness of the articular cartilage was measured at 9 areas: medial gutter (area 1), medial corner (area 2), medial edge of the dome plateau (area 3), lateral edge of the dome plateau (area 7), lateral corner (area 8), lateral gutter (area 9), and quarter points between areas 3 and 7 (areas 4, 5, and 6). The average thickness of the total areas was 1.35 +/- 0.22 mm in the male specimens and 1.11 +/- 0.28 mm in the female specimens. The thickest was area 2, which represented the medial corner, and the thinnest was area 9, which represented the lateral gutter in both men and women. There was a relationship between the thickness of the cartilage and the width of the talar dome. The thickness was usually less than 2 mm. However, the cartilage thickness varies widely by gender, area, and individual. Our report will help surgeons predict the volume of cartilage that needs to be repaired and produce treatment at a reasonable cost without an excessive invasion of patients.

Decoding the dipstick: Thickness of Siple Dome, West Antarctica, at the Last Glacial Maximum

Ice thickness in West Antarctica at the Last Glacial Maximum (LGM) is poorly known, yet is key information for understanding ice streams and interpreting ice cores. Although trim lines, moraine limits, and exposure-age dating provide geologic constraints on ice thickness near the Transantarctic Mountains and in Marie Byrd Land, lack of exposed bedrock hampers traditional geologic methods in a central, ;2 3 10 6 km 2 region. Here we infer ice-sheet thickness changes in the central Ross Sea Embayment by using a tran- sient ice-flow model to find combinations of accumulation-rate and ice-sheet thickness histories that match the depth-age relationship and the measured layer-thickness pattern in the Siple Dome ice core. After we reject unreasonable accumulation-rate histories, the remaining history pairs indicate thinning of 200-400 m since the LGM. Our estimate is lower than previous reconstructions that were constrained by geologic evidence from the Transantarctic Mountains and by marine data from the Ross Sea floor, which indicate that a grounded ice sheet extended to the continental shelf margin during the last glacial period. Low surface elevations in the central Ross Sea Embayment during the LGM do not preclude thicker ice along its boundaries. However, if this grounded ice sheet came over 1000 km from interior West Antarctica, as is usually assumed, then it had very low surface slope, requiring a very slippery bed. Alternatively, the grounded Ross Sea ice might have flowed from the Transantarctic Mountains and western Marie Byrd Land.

Imaging Structural Elements Of A CathedralUsing Ground Penetrating Radar

The Basilica of the Assumption of the Blessed Virgin Mary in Baltimore, Maryland is the first Catholic cathedral to be established in the United States. The cathedral was designed by architect Benjamin Henry Latrobe and is an important religious building as well as a significant example of the Greek Revival style in the United States. As part of a condition assessment and historical research program, the configuration and condition of several critical structural elements of the cathedral were evaluated in the autumn of 2000. Ground penetrating radar (GPR) was used to nondestructively determine the thickness of the cathedral dome at numerous locations. The radar was also used to determine the configuration of a main supporting colu~nn for the dome and a column supporting one of the two bell towers at the cathedral. A comprehensive image of the columns could be reconstructed based on their accessibility from all sides. The results from the GPR investigations at the tower column agreed well with borescope observations and the results from a previously conducted investigation using acoustic tomography. Ground penetrating radar has been shown to provide valuable information about building components (structural and nonstructural) nondestructively. The radar data reveals voids, construction layers, the presence of other materials (e.g. metal inclusions), as well as the thickness of the element. In some instances, it is the only practical nondestmctive technique capable of providing the required information.