Cavity Shape Research Articles

Numerical study on the influence of floating ice on the water-exit hydrodynamic characteristics of a trans-media vehicle

In low-temperature combat conditions, the strong interference of floating ice on the water-exit process of trans-media weapons must be considered. The evolution of the cavity shape, hydrodynamic and ballistic characteristics during the water-exit process of a high-speed vehicle penetrating water (without floating ice) and ice-water mixture were studied in comparison based on computational fluid dynamics (CFD) and the discrete element method (DEM). The results revealed that the floating ice accelerates the collapse of the attached cavity, delays the collapse time of the tail cavity, and changes the vehicle’s wet degree. The floating ice causes the vehicle to be subjected to a severe fluctuating alternating load and lasts for a longer time, which changes the trajectory characteristics of the vehicle, reducing its motion stability and intensifying trajectory deviation. The findings can provide a reference for the design and development of cross-media weapons in low-temperature environments in winter.

Beneath the Surface: Identifying Subsurface Caves in "Gua Pandan" Using Integrated Electrical Profiling Method

One of the geopark tourism areas in East Lampung Regency, "Gua Pandan," has run into rock subsidence on the surface. As part of the subsidence prevention, indirect electrical methods between resistivity and chargeability profiling were applied to identify the presence of a subsurface cave in the study area. Two measurement lines were carried out with Wenner Alpha and Wenner Schlumberger arrays. Because the depth target is shallow (approximately 10 m) and to obtain a better resolution, each line has a stretch length of 70 m and 2 m electrode spacing. A line was measured over a known underground cave to produce a desired outcome, and the other was in an area with no cavities. Based on the results from each profile of resistivity and chargeability, an air-filled target has a value of over 5,000 and under 6 ms, respectively. Then, integrated processing of both methods generated a metal factor (MF) profile to view the presence and estimated shape of the cave/ cavities. The result represents that an MF value under 1.5 ms/Ωm is a cavity, and solid rock is over 1.5 ms/Ωm. Also, the MF level from both configurations delineates a similar section. However, a modest difference occurs in estimating the cavity shape geometry, for Wenner Apha and for Wenner Schlumberger. Furthermore, this study can be an initial step in safety assessment in the area.

Precise Control of Single-Crystal Perovskite Nanolasers.

Efficient control of integrated light sources is crucial to advancing practical applications of nanophotonics. Despite the success of microlasers, their sophisticated nanostructures are not applicable in nanolasers. The situation for bottom-up-synthesized nanolasers becomes more challenging due to the constraints of fixed cavity shapes and fragile material stability. Here, the physics of exceptional points (EPs) is employed, and a strategy is demonstrated to precisely tune the lasing actions in lead halide perovskite nanorods. By placing a nanoparticle to the boundary of a square nanocavity, it is shown that EPs regularly and controllably emerge as a function of the nanoparticle position. Consequently, both the internal lasing actions and their far-field radiation can be completely reversed with a tiny displacement of <100nm. The new strategy for controlling lasing actions in nanocavities is confirmed with numerical simulations and lasing experiments. This research can also bring new avenues for ultrasensitive position sensing.

Morphological classification and measurement of the glenoid cavity using three-dimensional reconstruction in a Chinese population.

The purpose of this study was to examine the various shapes and record the morphometric data of the glenoid cavity in a Chinese population. A total of 501 scapulae, 247 left and 254 right, were analysed. We classified the shape of the glenoid cavity as type I (pear-shaped), type II (oval-shaped), type III (teardrop-shaped), type IV (calabash-shaped) or type V (inverted comma-shaped). Four defined parameters, the superior-inferior glenoid diameter (AB), upper anterior-posterior glenoid diameter (CD), lower anterior-posterior glenoid diameter (EF) and glenoid index (GI), were measured, and five shapes were classified via three-dimensional reconstruction. The mean AB, CD, EF and GI values of the glenoid were 3.51 ± 0.41 cm, 1.95 ± 0.28 cm, 2.60 ± 0.34 cm, and 1.35 ± 0.12 cm, respectively. The AB value of type II glenoid cavities was significantly smaller than that of type I and III glenoid cavities (p < 0.05), but the GI value of type II glenoid cavities was larger than that of type III cavities (p < 0.05). The CD value showed a difference between type I and type III glenoid cavities (p < 0.05). For the EF parameter, the values of type III glenoid cavities were significantly larger than those of type I and II glenoid cavities (p < 0.05). Measuring and observing the variety of shapes and sizes of the glenoid cavity in Chinese people is conducive to for better understand its morphological features. This information can also guide surgeons in the design and selection of suitable prostheses for total shoulder arthroplasty in the Chinese population in order to reduce postoperative complications.

A research on excavation compensation theory for large deformation disaster control and a review on the multiphysical–multiscale responses of salt rock for underground gas storage

A research on excavation compensation theory for large deformation disaster control and a review on the multiphysical–multiscale responses of salt rock for underground gas storage

A common ecogeographic trend in the internal nasal cavity variation across Mesolithic to Bronze Age Eastern European and Caucasian populations

AbstractThe ecogeographic trends in the shape of the internal nasal cavity and external facial skeleton were explored in a sample of Mesolithic, Neolithic, and Bronze Age skulls from Northeastern Europe and the Caucasus and tested against a background of the variation in recent populations from the same area. The volume, surface area, and several linear dimensions of the internal nasal cavity as well as a set of 3D landmarks of the external mid‐face were collected in a sample of computed tomography (CT) scans of 121 adult male skulls from six modern human populations of Eastern Europe, Anatolia, and Caucasus (74 individuals) and seven ancient burial sites (47 individuals). Various measures of the association between nasal cavity morphology and climate revealed moderate to high levels of correlation. The modern populations from colder climates and all but one ancient group display a substantial decrease in the nasal cavity heights and widths, volume and nasal protrusion, a relative narrowing of the nasal cavity, and a substantial increment in length of the maxillary part of the cavity. These groups also exhibit a less protruding external nose, smaller orbits, and a vertically taller zygomatic region. Our results show that the suite of morphological features associated with living in a cold climate is more strongly pronounced in ancient Europeans compared with the Medieval or modern groups of the same continent.

On the cavity flow of a cylinder exiting water obliquely

The water exit of a high-speed cavitation vehicle is a highly complex problem. Especially when the vehicle exits the water at different angles, the cavity shape and motion stability are affected by the air-water interface, resulting in significant changes in the mechanical environment and dynamics of the vehicle during the water exit. To solve this problem, a CFD method based on VOF multiphase flow interface-capturing technique and overset mesh technique is adopted to numerically calculate the interaction of vapor-liquid-air multiphase flow during the oblique water exit of a high-speed cylinder. Based on the verification of the computational model by mesh convergence and water-entry experiment, the cavitation evolution and flow distribution characteristics of the high-speed cylinder during oblique water exit is analyzed. Moreover, the effects of water-exit angles on the surface pressure distribution and drag characteristics of the cylinder are studied. The results show that the fluid at the end of the cavity impacts the shoulder of the cylinder during oblique water exit, resulting in the pressure difference between the upper and lower surfaces of the cylinder, which may finally leads to motion deviation. With the decreasing water-exit angle, the negative peak drag coefficient decreases while the peak lateral force coefficient increases, and there is a critical range of water-exit angel for lateral force and pitch angle variation.

Numerical Comparison in Aerodynamic Drag and Noise of High-Speed Pantographs with or without Platform Sinking

Flat roofs and platform sinking are two common installation configurations for high-speed pantographs. The cavity formed by the platform sinking is a potential source of aerodynamic drag and noise. In this paper, the shape of the rectangular cavity is optimized, and the aerodynamic performance of the high-speed pantograph with or without platform sinking is compared and discussed based on the optimized cavity results. The flow field and sound propagation are predicted by the improved delayed detached eddy simulation (IDDES) method and the FW-H equation. The results show that the rectangular cavity produces the largest aerodynamic drag and radiation noise. The upstream, downstream, and bottom surfaces of the cavity can be optimized by rounded and sloped edges to reduce aerodynamic drag and noise. The unstable shear flow and recirculation zone formed by flow separation and reattachment can be reduced by modifying the upstream and downstream surfaces of the cavity. In addition, the vortex in front of the downstream surface of the cavity can be reduced or even eliminated by modifying the bottom surface. When the upstream and downstream surfaces of the cavity are rounded and the bottom surface is sloped (R/H = 0.8), the aerodynamic performance of the cavity is better. Compared with the pantograph installed on the flat roof, the aerodynamic drag and noise of the pantograph with platform sinking are significantly reduced due to the shielding of the lower structure by the cavity, and the total drag and noise are reduced by 5.22% and 1.45 dBA, respectively.

Ge/Si interfaced label free nanowire BIOFET for biomolecules detection - analytical analysis

This paper comprehensively investigates a dielectric modulated Ge/Si interfaced label free nanowire BIOFET for biomolecules detection. The main highlight of this work is the structural novelty in nanowire BIOFET which is integrated with a germanium source and triple material gate and has been investigated for biosensing application by studying the work function and doping optimization for the enhancement of sensitivity for the very first time. Channel potential, threshold voltage and subthreshold swing have been analytically evaluated and the results have shown an excellent agreement with the simulated results. The biosensor has been comprehensively investigated to study its sensitivity dependence on different device parameters such as cavity shape, cavity dimensions and doping. Work function optimization for sensitivity enhancement has also been studied in detail. Practical limiting factors such as steric hindrance and its effect of on sensitivity has been included in the analysis by considering different fill-in factor and fill-in profile of biomolecules.

Hysteroscopic Fenestration with Precise Incision of the Cavity Septum: A Novel Minimally Invasive Surgery of Complete Septate Uterus with Double Cervix

This study aimed to develop and describe a novel surgical procedure that involves hysteroscopic fenestration with precise incision of the complete uterine septum and double cervix preservation after magnetic resonance imaging (MRI) evaluation in patients and to evaluate its efficacy. A prospective consecutive clinical study. A university teaching hospital. Twenty-four patients with complete septate uterus and double cervix. Three-dimensional reconstruction of uterus was performed with pelvic MRI and three-dimensional SPACE sequence scanning. Hysteroscopic fenestration with precise incision of the cavity septum and double cervix preservation was performed in patients. Three months after operation, follow-up pelvic MRI and second-look hysteroscopy were performed conventionally. Operating time, blood loss, operative complications, MRI and hysteroscopic changes of uterus, symptoms improvement, and reproductive outcomes were assessed. The surgery was successfully completed without any intraoperative complications in all patients. Operating time was 21.71 ± 8.28 minutes (range, 10-40 minutes) and blood loss was 9.92 ± 7.14 mL (range, 5-30 mL). Postoperative MRI showed the uterine anteroposterior diameter (3.66 cm vs 3.92 cm; p <.05) was increased. Postoperative MRI and the second-look hysteroscopy showed the cavity shape and uterine volume were expanded to the normal. Symptoms of dysmenorrhea, abnormal uterine bleeding, and dyspareunia were ameliorated after the surgery in 70% of patients (7 of 10), 60% of patients (3 of 5), and 1 patient, respectively. The preoperative spontaneous abortion rate was 80% (4 of 5) and the postoperative spontaneous abortion rate was 11.11% (1 of 9). After the surgery, there were 2 ongoing pregnancies and 6 pregnancies ended in term births. Two live births were delivered by cesarean section and 4 by vaginal delivery without cervical incompetence during pregnancy. Hysteroscopic fenestration with precise incision of the uterine septum and double cervix preservation is an effective surgical procedure.

Power enhancement of vertical axis wind turbine using optimum trapped vortex cavity

Vertical Axis Wind Turbine (VAWT) blades experience stall conditions at lower tip speed ratios during rotation, resulting in inefficient power performance. The power performance can be augmented by improving the blade's aerodynamic efficiency using active or/and passive flow control mechanisms. In this research, the power performance of 2-D H-type VAWT is enhanced by employing an optimum cavity on the suction side of the NACA 0018 blade airfoil. The optimum cavity shape was found using the Genetic Algorithm coupled with the Gaussian Process Regression (GPR) model at an airfoil static stall angle of attack in an isolated environment to reduce the computational cost of the optimization process. Two GPR models were employed to predict lift and drag coefficients, while the lift-to-drag ratio was used as an objective function in the optimization algorithm. 80 CFD runs were utilized for initial training and testing of the models, which reduced computational effort by 97% compared to a pure CFD-based optimization approach. The aerodynamic efficiency of the optimum cavity shape predicted by GPR models was also confirmed by CFD simulation, which showed only a 0.5% difference. For an airfoil with an optimum cavity, the aerodynamic efficiency was consistent at lower angles of attack. However, a significant rise of up to 31.8% was observed in the near stall region between 12° to 16° angle of attack in comparison to clean airfoil. The optimum cavity on baseline VAWT blades enhanced power performance by 63.8% at a TSR of 1.5. Moreover, at TSRs of 2, 2.5, 3, and 3.5, the enhancement in power performance was achieved by 34.4%, 22.2%, 16.1%, and 3.2%, respectively. This demonstrates the potential of employing an optimum cavity on the suction side for performance augmentation without applying the suction and a cost-effective solution by conducting optimization in an isolated environment.

Design and low-power measurement of 1.5 GHz TM020-type harmonic cavity for KEK future synchrotron light source

We designed a normal-conducting (NC) 1.5 GHz harmonic cavity that can be used in a future synchrotron light source at High Energy Accelerator Research Organization (KEK). By utilizing a higher TM020 mode for beam acceleration, this cavity has lower R/Q and higher unloaded Q as compared to those of conventional NC cavities. These features are advantageous in reducing the fluctuations in harmonic RF voltages when the bunch gaps are introduced. Harmful parasitic modes other than the TM020 mode can be heavily damped using coaxial slots located at the node of the TM020 mode. We made a concerted effort to lower the coupling impedances of parasitic modes while maintaining high Q value of the accelerating mode. We found that maintaining the axial symmetry of the cavity is essential for minimizing the leakage power of the accelerating mode into the coaxial slots. In this article, we present the optimization of the cavity shape, low-power measurement, and the basic design of a high-power model.

Cavity Characterization in Supramolecular Cages.

Confining molecular guests within artificial hosts has provided a major driving force in the rational design of supramolecular cages with tailored properties. Over the last 30 years, a set of design strategies have been developed that enabled the controlled synthesis of a myriad of cages. Recently, there has been a growing interest in involving in silico methods in this toolbox. Cavity shape and size are important parameters that can be easily accessed by inexpensive geometric algorithms. Although these algorithms are well developed for the detection of nonartificial cavities (e.g., enzymes), they are not routinely used for the rational design of supramolecular cages. In order to test the capabilities of this tool, we have evaluated the performance and characteristics of seven different cavity characterization software in the context of 22 analogues of well-known supramolecular cages. Among the tested software, KVFinder project and Fpocket proved to be the most software to characterize supramolecular cavities. With the results of this work, we aim to popularize this underused technique within the supramolecular community.

Cavitation dynamics of the semi-sealed cylindrical shell during high-speed water entry

This paper experimentally investigates the vertical high-speed water entry of a semi-sealed cylindrical shell, which has one end sealed and one end opened. The unsteady water-entry cavitating flow characteristics of the shell are analyzed, and the evolution of cavities and jet impacts with different structures is studied. The results show that a nested multi-cavity is generated due to the self-jet phenomenon during water entry. The jet causes the diameter of the secondary cavity to be much larger than that of the primary cavity, and the morphology of the secondary cavity is more atomized. Due to the irregular motion of the jet, the primary cavity undergoes neck-shrinking phenomenon and is compressed, and the neck-shrinking position moves up as the secondary cavity grows. After secondary impact, a small jet appears at the bottom of the shell, which ejects out from the shell and increases the size of the bottom cavity, leading to the formation of quaternary cavity. Moreover, as the inner wall length increases, the time of the primary jet is advanced, while the depth of secondary cavity shortens. With the increase in the thickness, cavity shape becomes more similar to traditional supercavity, and the maximum diameter of the primary cavity increases.

Decidual cast severe pelvic pain mimics acute appendicitis in an adolescent girl

Background: Decidual Cast is a reaction to hormonal medications resulting in the formation of a cast taking the shape of the uterine cavity. Its incidence is unknown; however, it is usually associated with heavy menstrual bleeding, dysmenorrhoea and pelvic pain.

Effects of Lateral Flows on the Supercavitation and Hydrodynamic Characteristics of Underwater Series and Parallel High-Speed Projectiles

In this paper, the supercavitation of the parallel and tandem projectiles moving underwater with high-speed under the condition with/without lateral flows is numerically simulated by the volume of fraction (VOF) model. The motion of the projectiles was handled by the overlapping grid and six degrees of freedom (DOF) techniques. The supercavitation evolution and the hydrodynamic characteristics of the projectiles were analyzed for the parallel and tandem projectiles under different conditions. The results show that the cavity shape is symmetrical under the condition without lateral flows, but is no longer symmetrical under the conditions with lateral flows. The asymmetry of the cavity contour increases with the velocity of the lateral flow. For the parallel projectiles, the change trends of the axial velocity of projectile 1 and projectile 2 are nearly the same. The offset velocity of projectile 1 and projectile 2 increases with the increase in the velocity of the lateral flow. The deflection angle of projectile 1 decreases with the increase in the lateral flow velocity but that of projectile 2 increases with the increase in the lateral flow velocity. At t = 3.0 ms, the deflection angle of projectile 2 is up to 20° under the condition of the lateral flow velocity of 11.25%, while the deflection angle of projectile 1 and 2 under other conditions is in the range of 5°. For the tandem projectiles, the axial velocity of projectile 1 gradually decreases. The change trend of the axial velocity of projectile 2 at first is the same as that of projectile 1, and then the change is dependent on the velocity of the lateral flow. Under the condition of the lateral flow velocity with 11.25%Vp, projectile 2 cannot enter the cavity of the front projectile. The change trend of the axial velocity of projectile 2 is similar as but somewhat slower than that of projectile 1. For the parallel projectiles, the ballistic stability of the projectile on the oncoming side is better than that of the projectile on the backflow side. Whether parallel or tandem projectiles, the ballistic stability of projectile 2 becomes worse with the increase in the lateral flow velocity.

Morphological study of glenoid cavity of scapula

Scapula is a flat triangular bone lies on chest wall from second to sixth ribs. Its lateral angle is truncated and shows variable morphology in shape. The objectives of the present study were to obtain morphometric data of scapulae and the glenoid cavity specifically the diameters and various shape of glenoid.: The present study was conducted on 90 right scapulae and 90 left scapulae. Metrical and nonmetrical measurements were noted. Length of scapulae, breadth of scapulae, height of Glenoid cavity, antero-posterior diameter 1 and antero-posterior diameter 2 were observed. Shape of Glenoid cavity was noted.Length of scapula on right side was 135.40±13.2mm and on left side it was 136.5±12.9mm. Breadth of scapula on right side was 98.7 ±7.2mm on left side it was 98.2±6.8mm but the difference was not statistically significant. The height of Glenoid cavity on right side was 35.2±2.9mm and on left side it was 35.8±3.1. Antero-posterior diameter 1 of Glenoid cavity on right side was 24.2±2.3 mm and on left side it was 23.9±2.1 mm. Antero-posterior diameter 2 of Glenoid cavity on right side was16.8±2.5 mm and on left side it was 16.7±2.4mm. The most common shape of glenoid cavity was pear shaped followed by oval and least common was inverted comma shape.Knowledge of various measurements of Glenoid cavity is important for prosthesis of shoulder orthoplasty. It is useful in evaluation of various pathological conditions of shoulder joint. Since this study was conducted on limited number of scapulae further clinical, cadaveric and radiological studies are required.

Underwater sound absorption characteristic of the rubber core sandwich structure with funnel-shaped cavities reinforced by carbon fiber columns

This paper introduces a multi-functional rubber core sandwich structure with funnel-shaped cavities (RCSSFC) reinforced by carbon fiber columns (CFC), which has the potential to meet requirements of the pressure resistance and acoustic stealth for the underwater equipment in deep sea. A test sample of the RCSSFC with CFC is firstly manufactured and the acoustic propagation experiment is conducted by the pulse tube method to gain the sound absorption coefficient. Then the approximate theoretical model of the RCSSFC is built to predict the sound absorption performance via the layered gradient discretization of cavities, the equivalent theory of the cylindrical tube and the transfer matrix method. Both the obtained experimental and theoretical results are compared with the ones from finite element (FE) analyses conducted in the software COMSOL and the good agreements are achieved. Characteristic analyses are further done to investigate the effects of the diameter of CFC, the shape of cavities, the backing of the structure and the underwater pressure. The design of localized resonances is introduced to improve the low-frequency sound absorption performance. It is found that there are three sound absorption peaks (SAPs) on the curves at lower, middle and higher frequencies, which are respectively dominated by the longitudinal vibration of the structure, the resonances of cavities and the local vibration of the face sheet. Characteristic parameters mainly affect the sound absorption coefficients by changing the above three vibration behaviors. Besides, the CFC greatly improves the pressure resistance property, and the sound absorption performance of the RCSSFC with CFC is insensitive to the change of the pressure. Localized resonances show the excellent effect on increasing the low-frequency sound absorption of the RCSSFC with CFC.

The Effect of the Isolator Design on the Efficiency of Rotary Piston Compressors

The current work investigates the relationship between the shape of an isolator of a concentric rotary piston compressor and the secondary peak pressure developed during each operating cycle. This peak pressure is developed when the piston passes through the isolator cavity, and it is negative for compressor efficiency. The aim of this paper is to identify the isolator cavity shape that minimizes this secondary peak to improve compressor efficiency. This study covers five different cavities that may be used in such compressors. Contrary to our expectations, the conclusion is that the best geometry is the one that can be manufactured with CNC machining. The geometry that can be manufactured with 3D printing also produces a significantly lower secondary peak pressure, but it is not cost-efficient. Another limitation of the 3D printing design is the thin walls that this cavity creates. Very thin walls may cause significant deformation during the compression cycle. The conclusion is that there is a CNC machining design that is cost-efficient and allows for higher compressor performance.

Hemolysis of red blood cells in blood vessels modeled via computational fluid dynamics.

The research aims to verify the universal relationship between vessel shape and the risk of hemolysis using a rheological model of blood reflecting the physiological processes related to blood for any blood vessel. Blood is a multi-component fluid, the rheology of which depends on many factors, such as the concentration of red blood cells and local shear stress, which significantly affect the process of hemolysis. Blood rheology models used so far cannot be used for all flows and geometries. Therefore, a new rheology model has been introduced suitable for modeling hemolytic flows observed in arteries with atherosclerotic lesions in the in vivo environment. The previously presented model also has advantages in modeling local viscosity in stenosis. Geometries of the blood vessels from computed tomography scans and simplified models of the actual arteries observed during medical procedures were used in the calculations. Population Balance Based Rheology model predicts the concentration of single, deagglomerated red blood cells and the concentration and size of red blood cell agglomerates, which affect blood rheology and hemolysis. Based on the simulations carried out, a correlation was found between the shape of the vessel cavity and the risk of hemolysis. Presented results can be used in the future to create a correlation between the shape of the atherosclerotic lesions and the risk of hemolysis in the blood to make an initial risk assessment for a given patient.