Cavity Diameter Research Articles

Drag reduction by means of an array of staggered circular cavities at moderate Reynolds numbers

Further insight into the physics of boundary layers developing over an array of circular cavities at moderate Reynolds numbers (Reθ up to 3400) is gained from hot wire boundary layer surveys on a range of parameters. The findings are consistent with literature as to the possibility of reducing skin friction drag with circular perforations. The results evidence a modification of the mean velocity profile, an increase of the wake parameter and the shape factor associated to a decrease of the skin friction. The modifications of the boundary layer as well as the skin friction reduction are more pronounced when the open area ratio is increased, which is achieved by increasing the cavity diameter or equivalently by decreasing the inter-cavity spacing. The turbulent activity is shifted in the upward direction, the burst intensity decreases in the buffer layer (10<Y+<35) and increases in the upper part of the logarithmic region/beginning of outer layer (80<Y+<200) with the formation of an outer peak in the turbulence intensity profile. The premultiplied spectra and the streamwise shear stress profiles evidence an energy surplus in the same part of the boundary layer and for the highest open area ratios a “bi-hump” behaviour. The formation of outer quasi-streamwise rollers is believed to be the cause of this energy hump in the spectrum. The turbulence statistics show a striking similarity with the turbulent boundary layer in presence of wall-normal blowing. It is believed that the cavities promote a vertical velocity component that displaces the turbulent activity towards the outer region. Different hypotheses to explain the modification of the flow statistics are detailed in the paper.

Microscale Simultaneous Measurement of Carbon and Nitrogen Isotopes on Natural Diamond

Simultaneous analysis of carbon and nitrogen isotope ratios by SIMS was applied for the first‐time to a natural diamond from the Kelsey Lake kimberlite, State Line Distinct, Colorado (UWD‐1). This in situ procedure is faster, reduces sample size for analysis, and measures both isotope ratios from a single ~ 10 μm diameter pit, a critical advantage for zoned diamonds. The carbon isotope ratio (expressed as δ13CVPDB) of the bulk UWD‐1 crystal, determined by the conventional combustion method in the present study, is ‐5.9‰ ± 0.2‰ (VPDB, 2s). Nitrogen mass fraction ([N]) and isotope ratio (expressed as δ15NAir) were determined by stepwise combustion and gas‐source mass‐spectrometry, resulting in 553 ± 64 μg g‐1 and ‐6.7‰ ± 1.1‰ (Air, 2s), respectively. Secondary ions of 12C2‐, 12C13C‐, 12C14N‐, and 12C15N‐ were simultaneously measured by SIMS using three Faraday cups and one electron multiplier. The spot‐to‐spot reproducibility of δ13C and δ15N values for the UWD‐1 (178 spots on sixteen chips, 10 μm spots), were 0.3‰ and 1.6‰, respectively (2s). While 12C14N‐/12C2‐ ratios, which are an indicator for [N], varied up to 12% among these sixteen chips, such variation did not correlate with either δ13C or δ15N values. We propose that UWD‐1 is a suitable reference sample for microscale in situ analysis of δ13C and δ15N values in diamond samples.

Sex and Age Estimation using the Morphometric Assessment of the Femur

Anthropological assessment becomes the sole available medium for identification of the deceased in most forensic cases. We hope therefore to assess metrically if the femur bone could be used to estimate the age and sex of individuals by focusing on some rare morphological parameters. The skeletal samples of the right femur from 105 individuals (78 males and 27 females), who are within the age range of 21 and 60 years were harvested. The male samples had 53 profiled and 25 specimens non-profiled for age, while the females had 10 profiled and 17 specimens non- profiled for age. Direct measurements were taken for the marrow cavity diameter (MCD) and cortical thickness or radius (CT or Cr) using a centimeter rule and a sliding digital caliper to the nearest 0.1mm.The Marrow Cavity Diameter in our study is higher in the male population (1.70± 0.05) than the female population (1.43± 0.05). This variation was statistically significant (P&lt;0.05) using the student t-test. The radius or thickness of the cortex decreases with age in females but is higher in the female population (0.73±0.03) than the males (0.68±0.03). ANOVA shows that there is a significant variation across male age groups (P=0.00) for the MCD, MA and Area of cortex. The marrow cavity diameter increases with age in males while area of cortex reduces with age in females. It is imperative therefore that the marrow cavity diameter, the medullary area and area of cortex are good assessors of age and sex.

Do the Mechanical Properties of Calcium-Silicate-Based Cements Influence the Stress Distribution of Different Retrograde Cavity Preparations?

The aim of the present study was to investigate the influence of the mechanical properties of three different calcium-silicate-based cements on the stress distribution of three different retrograde cavity preparations. Biodentine™ "BD", MTA Biorep "BR", and Well-Root™ PT "WR" were used. The compression strengths of ten cylindrical samples of each material were tested. The porosity of each cement was investigated by using micro-computed X-ray tomography. Finite element analysis (FEA) was used to simulate three retrograde conical cavity preparations with an apical diameter of 1 mm (Tip I), 1.4 mm (Tip II), and 1.8 mm (Tip III) after an apical 3 mm resection. BR demonstrated the lowest compression strength values (17.6 ± 5.5 MPa) and porosity percentages (0.57 ± 0.14%) compared to BD (80 ± 17 MPa-1.22 ± 0.31%) and WR (90 ± 22 MPa-1.93 ± 0.12%) (p < 0.05). FEA demonstrated that the larger cavity preparation demonstrated higher stress distribution in the root whereas stiffer cement demonstrated lower stress in the root but higher stress in the material. We can conclude that a respected root end preparation associated with cement with good stiffness could offer optimal endodontic microsurgery. Further studies are needed to define the adapted cavity diameter and cement stiffness in order to have optimal mechanical resistance with less stress distribution in the root.

Single-Micelle-Templated Synthesis of Hollow Barium Carbonate Nanoparticle for Drug Delivery

A laboratory-synthesized triblock copolymer poly(ethylene oxide-b-acrylic acid-b-styrene) (PEG-PAA-PS) was used as a template to synthesize hollow BaCO3 nanoparticles (BC-NPs). The triblock copolymer was synthesized using reversible addition-fragmentation chain transfer radical polymerization. The triblock copolymer has a molecular weight of 1.88 × 104 g/mol. Transmission electron microscopy measurements confirm the formation of spherical micelles with a PEG corona, PAA shell, and PS core in an aqueous solution. Furthermore, the dynamic light scattering experiment revealed the electrostatic interaction of Ba2+ ions with an anionic poly(acrylic acid) block of the micelles. The controlled precipitation of BaCO3 around spherical polymeric micelles followed by calcination allows for the synthesis of hollow BC-NPs with cavity diameters of 15 nm and a shell thickness of 5 nm. The encapsulation and release of methotrexate from hollow BC-NPs at pH 7.4 was studied. The cell viability experiments indicate the possibility of BC-NPs maintaining biocompatibility for a prolonged time.

Preparation of densified glass-ceramics with less shrinkage cavities from molten copper slag by Petrurgic method

Petrurgic method is used to prepare glass-ceramics by directly controlling crystallization during the cooling process of the melts, which can realize the integrated utilization of both molten copper slag and its sensible heat. In this study, molten copper slag with no added agents was used to fabricate glass-ceramics using Petrurgic method. The temperature difference between the center and edges of molten copper slag with dimensions of 40 mm × 40 mm × 20 mm during the cooling process was measured, and its effects on crystallization and shrinkage cavities were studied. The results showed that the main phases of the glass-ceramics were magnetite and olivine, both of which crystallized significantly during the high-temperature cooling process. There were compact parts, transition parts and large cavity parts in the whole glass-ceramics and the cavities were caused by asynchronous crystallization of olivine owing to the temperature gradient distribution of the molten copper slag in the mold. Increasing the holding temperature during the heat treatment process reduced the temperature difference between the center and the edges and even inhibited the degree of crystallization, which further decreased the formation of shrinkage cavities. When the holding temperature was increased from 900 to 1150 °C, there were no longer large cavity parts in the non-compact parts but only transition parts. A higher holding temperature is thus beneficial for reducing the diameter of shrinkage cavities.

Lagrangian approach embed with discrete element method for extreme deformation study in frangible bullet designs fragmentation and penetration on viscoelastic ballistic gel

Development of a model for analyzing a bullet’s impact is important in the military field to design a bullet with desired properties. This study uses a finite element model with a Lagrangian framework and Lagrange-discrete element method (DEM) model by ANSYS Explicit Dynamic to investigate the effect of frangible bullet designs on bullet deformation and penetration in ballistic gel setting. A modeling approach with ballistic gel can analyzed the extreme deformation of bullets much faster compared to the more resource intensive real life ballistic gel test. The study starts with developing a 3D model, then importing it to an ANSYS workbench to solve the problems. Overall, the results of Lagrange-DEM shows deeper penetration and better accuracy to represent the real life ballistic gel test than other simulation method. The fluted bullet design has a shorter penetration depth but a bigger temporary cavity diameter than the flat-nosed one due to its notch and asymmetrical design, which becomes the part that is easily deformed and leads to directional deformation.

Study of the Jet Output Characteristics under Multi−Source Coupling

The challenges posed by elevated rock hardness, deficient drillability, excessive friction torque, and significant underpressure in extended−reach horizontal wells are the primary factors that contribute to low ROP (Rate of Penetration) and limited horizontal reach during the drilling operation. Reducing drag and friction is one of the primary methods of addressing the aforementioned challenges. To augment the pulse output characteristics of the oscillating jet and bolster the energy of the hydrodynamic impact load, we developed and designed a multi−source impact oscillation speed−increasing tool coupled with blade rotation disturbance and multi−order oscillation cavity self−excitation. We utilized fluid dynamics software to model and conduct numerical analysis on the multi−source pulsed jet generator. Furthermore, we constructed a prototype and subjected it to testing. This paper examines the impact of dimensionless structural parameters on the pressure output characteristics of the multi−source pulse−jet generator. Specifically, we used three dimensionless quantities (cavity length ratios, cavity diameter ratios, and inner wall collision angle ratios) to study this effect. The findings indicate that the multi−source impact oscillation speed−increasing tool is capable of augmenting the pulse oscillation amplitude, and the frequency of pulse oscillation can be adjusted within the range of 5 Hz to 15 Hz. During the study, we determined that the optimal oscillation output characteristics can be achieved when the cavity diameter ratio is 0.8, the cavity length ratio is 1.0, and the inner wall collision angle ratio is 1.5. These findings present a novel approach for the development of downhole hydraulic impact oscillation speed−increasing tools.

Fleas and lesions in armadillo osteoderms.

Armadillos are bitten by several species of flea. Females of the genus Tunga penetrate the epidermis and when in place are fertilised by males, after which the abdomen swells enormously to form a 'neosome'. Within the penetrans group, T. perforans, makes lesions that perforate the osteoderms within the integument to form ~3 mm diameter cavities occupied by a discoid neosome. We examined these lesions in carapace material from animals which had died in the wild to see whether we could recruit evidence as to how they may be generated, either by the insect or by the host. We studied one species without such lesions, the nine-banded armadillo Dasypus novemcinctus, and two species with, the greater hairy armadillo Chaetophractus villosus and the southern three-banded armadillo Tolypeutes matacus, both showing the characteristic 'flea bite' holes in the external surfaces of the osteoderms. Samples were studied by three-dimensional backscattered electron mode scanning electron microscopy and X-ray microtomography. Both methods showed resorption pit complexes in the external surfaces of the osteoderms characteristic of those made by osteoclasts in active bone resorption. Lesions involved both the syndesmoses (sutures) between adjacent bones and the central regions of the osteoderms. Many lesions showed extensive repair by infilling with new bone. We conclude that the T. perforans neosome creates a local host response which causes bone resorption, creating the space in which it can grow.

Mathematical simulation of rock mass destruction zones by explosion

Purpose. Improving the parameters of the rock mass destruction zones by a blasting, depending on the pressure of the explosion products in the charging cavity and the physical and mechanical properties of rocks by combining analytical and numerical mathematical simulation. The methodology of research. Using the theory of elasticity and the main provisions of the quasi-static wave hypothesis of the mechanism of destruction of a solid medium under the action of an explosion, an analytical simulation of the parameters of the formation of crush zones and grinding of a rock mass around the charging cavity under its explosive load was carried out. After the change in the stress-strain state of the massif under the action of the explosion, numerical simulation of the crushing zones, intensive grinding and cracking by the finite element method was carried out. To establish the suitability of the obtained analytical models for calculating the radii of the indicated zones, the results of analytical and numerical simulation were compared. Findings. Analytical models have been developed for the radii of the zones of crushing, intense grinding and cracking, which are formed around the charging cavity in the rock mass under its explosive load, taking into account the pressure of the explosion products, the tensile-compressive strength of the rocks, their structural structure, and fracturing. Numerical simulation of the destruction of rocks around the charging cavity established the power-law dependences of the change in the radii of the crushing zones and the grinding of the massif depending on the diameter of the charging cavity, the pressure of the explosion products, and the compressive strength of the rocks. By comparing the results of analytical and numerical simulation for rigid boundary conditions of a homogeneous non-fractured massif, the discrepancy between the radii of the indicated zones is found to be 4, 8 and 6%, respectively. The originality. The radii of the zones of crushing, intense grinding and cracking, established by mathematicalsimulation, formed during the explosive destruction of the rock mass, change according to a power law dependence on the diameter of the explosive charge, the pressure of the explosion products in the charging cavity, the strength of the rocks in tension-compression, the coefficients of the rock structure, structural weakening and compaction, determine the increase in the accuracy of estimating the parameters of the destruction of the rock mass up to 50%. Practical implications. Based on mathematical models of the radii of the zones of crushing, intense grinding and cracking, which are formed in the rock mass around the charging cavity under the action of an explosion, improved parameters of drilling and blasting operations are determined for mine workings, special-purpose cavities and breaking of the massif.

Numerical investigation on the characteristics of cavity-transpiration combined cooling for hypersonic vehicle leading edge

During the flight of hypersonic vehicles, the wedge-shaped leading edge is exposed to severe thermal loads, so a reliable cooling system is required to provide protection. Transpiration cooling has been shown to be an efficient thermal protection technique for hypersonic vehicles. In this paper, the cavity-transpiration combined cooling is applied to the wedge-shaped leading edge of vehicles and an optimization scheme of lip blunting for the combined cooling is proposed. The effects of flight angle of attack, aspect ratio of the cavity and coolant injection mode are studied using the full field coupled numerical method. And the cooling characteristics of cavity-transpiration combined cooling with lip blunting are analyzed. The results reveal the following novel and valuable phenomena: (1) The existence of the cavity reduces the lift-drag ratio of the leading edge, and the lift drag ratio increases with the increase of the angle of attack. (2) When no coolant is injected, the temperature and pressure of the stagnation point decrease with the increase of the length and diameter of the cavity. When the coolant is injected at a constant mass flow rate, the cooling efficiency at stagnation point decreases with the increase of cavity length and diameter, but the driving force decreases. When the coolant is injected at a constant pressure, the mass flow of the coolant increase, the cooling efficiency at the stagnation point is increased by 9%. (3) The temperature at the stagnation point of lip blunting structure is decreased by 94.78 K compared with no blunting, and the cooling efficiency is increased by 9.8%.

Biomechanical evaluation of interlocking nail and locking compression plating for stabilization of ovine critical-sized segmental tibia defects.

Segmental large volume bone loss resulting from fracture or osseous neoplasia is a major challenge to orthopedic surgeons and there is an ongoing quest to identify treatments that optimize healing. To advance treatment, large animal translational models-such as the ovine critical-sized tibia defect model-are instrumental for testing of novel scaffolds for bone regeneration. However, little standardization in the implants utilized for defect stabilization has been determined and current commercially available implants may be inadequate to replicate the strength of the native tibia. We hypothesize that a 10-mm interlocking nail (ILN) would be stiffer in axial, bending, and torsional loading than its 8-mm counterpart and would be stiffer in axial and torsional loading compared to a 4.5-mm broad locking compression plate (LCP). Tibias were harvested from 24 ovine hind limbs from skeletally mature ewes euthanized for reasons unrelated to this study and were randomized to treatment group. An ex vivo comparison of a novel 10-mm angle-stable non-tapered ILN was compared to a commercially available 8-mm angle-stable tapered ILN and a broad LCP in an ovine critical-sized (5-cm) tibia defect model. Axial stiffness, torsional stiffness, and bending stiffness were determined in control intact tibia and tibial constructs in the three treatment groups. Following implantation, radiography was performed in all limbs and tibia length and cortical and medullary cavity diameter were measured. Comparisons between groups were assessed with a one-way analysis of variance. Significance was set at P<0.05. The 10-mm ILN in tibia containing a 5-cm ostectomy gap most closely replicated the structural properties of intact tibia compared with other constructs. The 10-mm ILN had significantly stronger torsional (P<0.001) and bending (P=0.002) stiffness than the 8-mm ILN, and was significantly stronger than the LCP in axial (P=0.04) and torsional (P=0.01) stiffness. A 10-mm ILN used to stabilize an ovine critically-sized tibia defect most closely mimicked the structural properties of the intact tibia when compared to a 8-mm ILN or broad LCP. Further in vivo testing will aid in determining which stabilization method is best suited for testing of novel tissue engineering and bone healing studies.

Seismic Response and Damage Analysis of Shield Tunnel with Lateral Karst Cavity under Oblique SV Waves

The dynamic effects of the lateral karst cavity on the shield tunnels under different incident angles of seismic waves are investigated by numerical analysis in this paper, based on the Dalian Metro Line 5 project. The viscous-spring artificial boundary is applied and verified to guarantee the accuracy of seismic input. A simplified finite element model of shield tunnel is established based on the equivalent bending stiffness model. This paper compares the seismic response characteristics and damage states of the tunnel under different incident angles by analyzing the axial deformation, stress distribution, and damage severity, respectively. A new damage state classification criterion is proposed by introducing the relationship between cracks and tensile damage. The results show that the tunnel’s affected scope by the lateral karst cavity is twice the cavity diameter. As the incident angle increases, the tunnel’s displacement and stress increase and show the structural spatial difference, and the tunnel’s damage state is increasingly severe. The displacement and stress reach the max values when the incident angle is 30°. The cracks along the axial direction extend on the outer surface of the vault and bottom, and the crack width is greater than 0.2 mm, as that angle is 30°. The damage severity at the tunnel’s central zone is minimum along axial directions during seismic action, while the damage concentration occurs on the bottom at the end of seismic. The lateral karst cavity plays an energy dissipation and vibration reduction role to a certain extent, but it also aggravates the local damage. This paper can serve as a reference for the seismic design of tunnels in karst regions.

Two-State Lasing in Microdisk Laser Diodes with Quantum Dot Active Region

The two-state lasing phenomenon, which manifests itself in simultaneous laser emission through several optical transitions of quantum dots, is studied in microdisk diode lasers with different cavity diameters. The active region represents a multiply stacked array of self-organized InAs/InGaAs/GaAs quantum dots emitting in the wavelength range of 1.1–1.3 µm. Two-state lasing, which involves the ground-state and the first excited-state optical transitions, is observed in microdisks with cavity diameters of 20 to 28 µm, whereas two-state lasing via the first and the second excited-state optical transitions is observed in 9 µm microdisks. The threshold currents for one-state and two-state lasing are investigated as functions of the microdisk diameter. Optical loss in the microdisk lasers is evaluated by comparing the two-state lasing behavior of the microdisks with that of edge-emitting stripe lasers made of the same epitaxial wafer.

Laparoscopic Anatomic Segment III Procurement in Pediatric Living Donor Liver Transplantation Using Real-Time ICG Fluorescence In Situ Reduction by the Glissonean Approach

Nowadays, anatomic hepatectomy has been widely accepted and acknowledged as a feasible practice during laparoscopic procedure. We herein report the first case of laparoscopic anatomic segment III (S3) procurement in pediatric living donor liver transplantation using real-time indocyanine green (ICG) fluorescence in situ reduction by Glissonean approach. A 36-year-old father volunteered for living donation to his daughter who was diagnosed with liver cirrhosis and portal hypertension due to biliary atresia. Preoperative liver function was normal with mild fatty liver. Liver dynamic computed tomography showed a left lateral graft volume of 379.43 cm3 with a graft to recipient weight ratio (GRWR) of 4.77%. The ratio of the maximum thickness of the left lateral segment to the anteroposterior diameter of the recipient's abdominal cavity was 1.20. Hepatic veins of segment II (S2) and S3 separately flowed into the middle hepatic vein. The estimated S3 volume was 173.16 cm3 and GRWR was 2.18%. The estimated S2 volume was 118.54 cm3 and GRWR was 1.49%. Laparoscopic anatomic S3 procurement was scheduled. Liver parenchyma transection was divided into 2 steps. Step I: Anatomic in situ reduction of S2 by using real-time ICG fluorescence. Step II: Separating the S3 along the right side of sickle ligament. The left bile duct was identified and divided by ICG fluorescence cholangiography. The total operation time was 318 minutes without transfusion. The final graft weight was 208 g with GRWR of 2.62%. The donor was discharged uneventfully on postoperative day 4, and the graft function recovered to normal in the recipient without any graft related complication. Laparoscopic anatomic S3 procurement with in situ reduction is a feasible and safe procedure in selected donors in pediatric living donor liver transplantation.

Visual evaluation of warehousing humidity and time on bamboo performance

The inventories of Moso bamboo (Phyllostachys pubescens) resources are considered to be one of the most important strategic resources for economic construction and ecological building materials. Warehousing humidity is one of the objective factors that induce mold deterioration and quality deterioration of bamboo. To investigate the effect of environment humidity on the use value of bamboo, humidity levels of 45 %, 60 %, 75 % and 95 % and indoor environments were artificially simulated and regularly monitored for changes in quality during warehousing. During the 56-day storage period, with the increase of humidity in the warehousing environment, the dimensional expansion rate of the cortex side of bamboo was larger than that of the pith side and the cavity diameter ratio gradually decreased, Total color difference value, and mass density loss rate gradually decreased, and the peak compressive stress-strain displacement gradually increased, respectively. 95 % RH is beneficial to mold reproduction and only infect the surface, Fourier Transform Infrared Spectroscopy analysis showed that the quality changes during storage were more related to the decrease in the signal peak of the hemicellulose functional group of the material itself accompanied by the degradation of various monosaccharides, the lignin functional group corresponded to the decrease in L* and Total color difference, and the degree of pyrolysis tolerance was inversely proportional to the signal intensity of the cellulose functional group. Redundancy analysis showed that the positive contribution of humidity in the storage environment to the physical quality of bamboo was Bamboo pith linear > Width dimension > Bamboo cortex linear > Water content > Weight loss rate > Length Dimension > a*, and the storage time was closely related to the L* value and compression strength.

Geometric variation of the human tibia-fibula: a public dataset of tibia-fibula surface meshes and statistical shape model.

Variation in tibia geometry is a risk factor for tibial stress fractures. Geometric variability in bones is often quantified using statistical shape modelling. Statistical shape models (SSM) offer a method to assess three-dimensional variation of structures and identify the source of variation. Although SSM have been used widely to assess long bones, there is limited open-source datasets of this kind. Overall, the creation of SSM can be an expensive process, that requires advanced skills. A publicly available tibia shape model would be beneficial as it enables researchers to improve skills. Further, it could benefit health, sport and medicine with the potential to assess geometries suitable for medical equipment, and aid in clinical diagnosis. This study aimed to: (i) quantify tibial geometry using a SSM; and (ii) provide the SSM and associated code as an open-source dataset. Lower limb computed tomography (CT) scans from the right tibia-fibula of 30 cadavers (male n = 20, female n = 10) were obtained from the New Mexico Decedent Image Database. Tibias were segmented and reconstructed into both cortical and trabecular sections. Fibulas were segmented as a singular surface. The segmented bones were used to develop three SSM of the: (i) tibia; (ii) tibia-fibula; and (iii) cortical-trabecular. Principal component analysis was applied to obtain the three SSM, with the principal components that explained 95% of geometric variation retained. Overall size was the main source of variation in all three models accounting for 90.31%, 84.24% and 85.06%. Other sources of geometric variation in the tibia surface models included overall and midshaft thickness; prominence and size of the condyle plateau, tibial tuberosity, and anterior crest; and axial torsion of the tibial shaft. Further variations in the tibia-fibula model included midshaft thickness of the fibula; fibula head position relative to the tibia; tibia and fibula anterior-posterior curvature; fibula posterior curvature; tibia plateau rotation; and interosseous width. The main sources of variation in the cortical-trabecular model other than general size included variation in the medulla cavity diameter; cortical thickness; anterior-posterior shaft curvature; and the volume of trabecular bone in the proximal and distal ends of the bone. Variations that could increase the risk of tibial stress injury were observed, these included general tibial thickness, midshaft thickness, tibial length and medulla cavity diameter (indicative of cortical thickness). Further research is needed to better understand the effect of these tibial-fibula shape characteristics on tibial stress and injury risk. This SSM, the associated code, and three use examples for the SSM have been provided in an open-source dataset. The developed tibial surface models and statistical shape model will be made available for use at: https://simtk.org/projects/ssm_tibia.

On the Eccentrically Loaded Strip Footing Resting Over a Circular Cavity in the Rock Mass: Adaptive Finite-Element Analysis, Observations, and Recommendations

In this study, the effect of an eccentric load on the ultimate bearing capacity (UBC) of a strip footing of width B resting above a circular cavity in the rock mass is investigated using upper -and lower-bound finite-element limit analysis incorporating an adaptive meshing technique. The effect of governing independent variables, such as the diameter of the circular cavity, dc, load eccentricity, e, distance of the cavity from the footing (horizontal, P, and vertical, Q), and rock mass parameters based on the generalized Hoek–Brown (GHB) failure criterion on the reduction of the UBC, is studied using a reduction coefficient, Rc. This study reveals that the influence of the cavity on the UBC is minimal for a cavity beyond a depth of Q/B ≥ 2.5 when e/B ≥ 0.3; and that Q/B ≥ 3 when 0.1 ≤ e/B ≤ 0.2, irrespective of P/B. Similarly, a cavity situated at −2 ≤ P/B ≥ 2 and Q/B ≥ 2 when e/B = 0.3–0.4, and −3.5 ≤ P/B ≥ 3.5 and Q/B ≥ 2.5 when 0.1 ≤ e/B ≤ 0.2, does not show any significant impact on the reduction of the UBC. Dominant potential failure patterns that could cover at least all the representative cases are presented and discussed to strengthen the insight into the possible mechanism of such a footing failure.

Description of sound absorption by a flat resonator stacking metamaterial with double porosity model

Acoustic metamaterials can be designed by inserting along the path of a sound wave periodically spaced side resonators. An example of efficient design was recently proposed consisting of a perforated stacking of flat annular cavities (the pancake resonator), the perforation allowing the propagation of sound waves. The pancake resonator is used in absorber mode and the theoretical description of sound absorption can be achieved with the help of the theory of sound propagation in fluid saturated porous media in which two porosities are considered: the main porosity associated with the perforation and a porosity associated with the flat cavity volumes. Considering a perforation diameter and flat cavity thickness ranging from submillimetric values to a few millimeters allows a wide range of material permeabilities and permeability contrasts between main pore and stacking of cavities. The relatively small values of diameter and cavity thickness also results in the existence of viscous and thermal boundary layers in the main pore (the perforation) and in the flat cavities. This metamaterial makes simultaneous use of viscothermal losses and periodicity in order to achieve low frequency sound absorption for an overall small absorber thickness. Experimental results are also presented for the validation of the model.

Simulation of yolk-shell nanostructures optical properties

A yolk-shell structure is a double-layer hollow nanostructure, which is composed of a shell, a cavity, and a core. The yolk-shell structures have fascinating properties because of their attractive localized surface plasmon resonance (LSPR) feature, which arouses considerable interest in both optically active nanostructures and practical applications. Compared with the single metal nanostructure, a yolk shell has a more controlled degree of freedom, superior optical properties, and potential applications in photocatalysis and solar cell. However, the preparation of yolk shells often requires multiple steps, making it difficult to control the geometric parameters accurately, which leads to uncontrollability of the experimental results. Therefore, it is necessary to study how the size and composition of a yolk shell affect LSPR properties to further guide and optimize the experimental process. Based on the discrete dipole approximation (DDA) method, the absorption spectra, near-field enhancement, and sensing properties of yolk-shell nanoparticles were analyzed. By adjusting the diameters of cavities, cores, shells, and the materials of the shells, we study the influence of yolk-shell structures on the LSPR properties. In detail, the thicknesses of the shells are set from 5 to 20 nm, the diameters of the cavities being set from 50 to 70 nm and the diameters of the yolks are set from 20 to 40 nm. The materials of the shells are set to be dielectric TiO2 and metallic Au, and both of them have Au cores. It is found that Au@Au yolk shells with large cavities or thick shells have better absorption efficiency, but Au @ TiO2 yolk shells are just the opposite. For near-field intensity, Au@Au yolk shells are higher than Au @ TiO2. A yolk-shell structure with larger cavity has smaller full width at half maximum. These results can effectively guide the design of yolk-shell structures for sensing and optoelectronic applications based on LSPR.