Frontal Surfaces Research Articles

АЭРОДИНАМИКА МОДЕЛИ ЖЕЛЕЗНОДОРОЖНОГО ГРУЗОВОГО ВАГОНА ПРИ РАЗНЫХ УГЛАХ АТАКИ ВОЗДУШНОГО ПОТОКА

The problem solution is considered for an airstream flow around a rectangular parallelepiped railway car model. The results of computer modeling in ANSYS CFX software system of air flow aerodynamics at its deviation from the longitudinal axis of the car are given. The k-ε turbulence model is used to close the Navier–Stokes equations averaged by Reynolds. The distribution diagrams of the flow velocities and pressures on the frontal and side surfaces of the vehicle are obtained. The values of aerodynamic drag coefficients of the car depending on the attack angle are determined. It is shown that when the attack angle increases from 0 to 10°, the aerodynamic coefficient changes nonlinearly, and this increase corresponds to the experimental values. The developed numerical modeling technique makes it possible to analyze the airflow around both railways rolling stock and automobiles.

Singularities of Frontal Surfaces

Singularities of Frontal Surfaces

Average surface wind pressure surrounding tall buildings with cruciform shapes

Abstract Building shape affects wind pressure on building surfaces, while limited studies have examined how building shape affects the wind pressure on cruciform-shaped tall buildings. This article investigated the variation of the average wind pressure coefficient (AWPC) on cruciform-shaped tall buildings with the height–width ratio (HWR) and height–thickness ratio (HTR). The results demonstrated the occurrence of building blockage, wind separation, wind re-circulation, and wind re-attachment on building surfaces. The frontal surface of the main building was always the windward surface with positive wind pressure. At 2/3 of the building height (H), the peak AWPCs in all scenarios were ~0.70. However, in the case with an HWR of 3.66, the side surfaces of the main building and the frontal surfaces of the branch building, wind pressure was all negative. With the HWR reduction by building width increase, wind pressure on these surfaces became positive, where the AWPCs in the HWR = 1.41 case were 0.60–0.63 and 0.64–0.69 on side and frontal surface, respectively. With the HWR decrease, both positive and negative wind pressure intensified. Along the central axis (M1) in the vertical direction, wider buildings had stronger positive wind pressure on the frontal surfaces below 0.10H, while narrower buildings had stronger positive wind pressure above 0.82H. In comparison, HTR made limited differences to the wind pressure on the frontal surface. Overall, vertical results showed that scenarios with smaller HWR underwent stronger positive and negative wind pressures. On the HTR cases, wind pressure on top surfaces showed complicated results, while thicker buildings had weaker negative wind pressure on the back surface. Overall, this study is important to understand the characteristics of wind load on cruciform-shaped tall buildings and generate implications for wind resistance, natural ventilation design, and wind electricity generation over tall buildings.

Singularities of Gauss maps of frontal surfaces with non-front singular points

Singularities of Gauss maps of frontal surfaces with non-front singular points

Properties of Black Silicon Layers Fabricated by Different Techniques for Solar Cell Applications

Black silicon (BS) layers coated with passivation films are widely used as antireflective frontal surfaces for solar cells. The most common BS fabrication techniques are reactive ion etching (RIE), metal‐assisted chemical etching, and laser‐induced processing. Herein, the structural and optical properties, as well as the minority carrier lifetime, of BS are compared with and without atomic layer deposited HfO2 passivation films produced by the above formation methods. The antireflection behavior of the samples is discussed based on the light trapping effect and the change in the BS refractive index from air to the bulk of crystalline Si. Finally, test solar cells are manufactured, and their photovoltaic parameters are studied. The comparison results show that RIE is the most preferred in all technical respects. The features of using different BS fabrication techniques from the solar cell manufacturing point of view are analyzed.

Development and sexual dimorphism of branchiae in Streblospio benedicti

AbstractThe Spionidae is one of the largest and most studied annelid families, but to date, the development and differentiation of post‐metamorphic anatomy have not been documented. This study used scanning electron microscopy to examine the development of the branchiae, presumed respiratory organs, in Streblospio benedicti. Branchiae in this species are prominent, paired head structures and first appear around the time of metamorphosis, but do not complete their development until the worm reaches the older juvenile or adult stages. We observed that as the branchiae grew, their overall morphology changed through four different shapes: small bud, tubular, tapered, and, finally, bilimbate. In addition, the abfrontal and frontal surfaces each possessed a unique set of cilia patterns, which we named, and these arose in a particular sequence between the 8‐ and 35‐chaetiger stages. This detailed examination of every stage of branchial development led us to discover that branchia in Streblospio benedicti was a sexually dimorphic organ. Streblospio benedicti is one of approximately eight Spionidae in which there is any type of structural sexual dimorphism, and it is the only species in which sexually dimorphic branchiae are found. The male's frontal surface had four unique cilia patterns, and we hypothesize that those located around the medial protrusion capture and control the release of the spermatophores. This first documentation of a spionid's branchial developmental sequence revealed that not only is this respiratory organ involved in reproduction, but it significantly differentiates after metamorphosis through adulthood.

Fine Back Surfaces Oriented Human Reconstruction for Single RGB‐D Images

AbstractCurrent single RGB‐D image based human surface reconstruction methods generally take both the RGB images and the captured frontal depth maps together so that the 3D cues from the frontal surfaces can help infer the full surface geometries. However, we observe that the back surfaces can often be quite different from the frontal surfaces and, therefore, current methods can mess the recovery process by adopting such 3D cues, especially for the unseen back surfaces. We need to do the back surface inference without the frontal depth map. Consequently, a novel human reconstruction framework is proposed, so that human models with fine geometric details, especially for the back surfaces, can be obtained. In this approach, a progressive estimation method is introduced to effectively recover the unseen back depth maps. The coarse back depth maps are recovered by the parametric models of the subjects, with the fine ones further obtained by the normal‐maps conditioned GAN. This framework also includes a cross‐attention based denoising method for the frontal depth maps. This method adopts the cross attention between the features of the last two layers encoded from the frontal depth maps and thus suppresses the noise for fine depth maps by the attentions of features from the low‐noise and globally‐structured highest layer. Experimental results show the efficacies of the proposed ideas.

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A Six-Surface System to Describe Anatomy of Anterior Clinoid Process and Its Application in Anterior Clinoidectomy and Resection of Paraclinoid Meningioma

The anterior clinoid process (ACP) is surrounded by nerves and vessels that, together, constitute an intricate anatomical structure with variations that challenges the performance of individualized anterior clinoidectomy in treating lesions with different extents of invasion. In the present study, we established a 6-surface system for the ACP based on anatomical landmarks and analyzed its value in guiding ACP drilling and resection of paraclinoid meningiomas. Using the anatomical characteristics of 10 dry skull specimens, we set 9 anatomical landmarks to delineate the ACP into 6 surfaces. Guided by our 6-surface system and eggshell technique, 5 colored silicone-injected anatomical specimens were dissected via a frontotemporal craniotomy to perform anterior clinoidectomy. Next, 3 typical cases of paraclinoid meningioma were selected to determine the value of using our 6-surface system in tumor resection. Nine points (A-H and T) were proposed to delineate the ACP surface into frontal, temporal, optic nerve, internal carotid artery, cranial nerve III, and optic strut surfaces according to the adjacent tissues. Either intradurally or extradurally, the frontal and temporal surfaces could be identified and drilled into depth, followed by skeletonization of the optic nerve, cranial nerve III, internal carotid artery, and optic strut surfaces. After the residual bone was removed, the ACP was drilled off. In surgery of paraclinoid meningiomas, our 6-surface system provided great benefit in locating the dura, nerves, and vessels, thus, increasing the safety of opening the optic canal and relaxing the oculomotor or optic nerves and allowing for individualized ACP drilling for meningioma removal. Our 6-surface system adds much anatomical information to the classic Dolenc triangle and can help neurosurgeons, especially junior ones, to increase their understanding of the paraclinoid spatial structure and accomplish individualized surgical procedures with high safety and minimal invasiveness.

An experimental study of rime ice accretion on bundled conductors

The dynamic ice accretion process on bundled electrical power conductors and icing-induced effects on the aerodynamic forces acting on the conductors were examined experimentally. An Icing Research Tunnel was used to generate a typical atmospheric rime icing condition experienced by power transmission cables. Two pieces of Aluminum-Conductor-Steel-Reinforced (ACSR) cables were mounted in the icing wind tunnel with different spacing and angular displacements with respect to the incoming airflow. While ice accretion was found to take place primarily on the frontal surfaces of the bundled conductors, the accreted ice layers resembled well the twisted outer strands of the ACSR conductors. Averaged outer profiles of the iced conductors were elliptical with the semi-minor axis being the radius of the conductors and the semi-major axis passing through the foremost frontal points of the accreted ice layers. The icing process on the windward conductor was almost unaffected by the existence of the leeward conductor. The ice accretion and resultant aerodynamic force acting on the leeward conductor were found to vary significantly, depending on the spacing and angular displacements between the bundled conductors. The windward conductor was found to induce a “shadowing effect” by intercepting airborne supercooled water droplets to prevent them from impinging onto the leeward conductor, resulting in much less ice accretion and smaller aerodynamic drag acting on the leeward conductor. The aerodynamic force measurements were correlated with the acquired ice accretion images and wake flow field around the bundled conductors to elucidate the underlying physics.

ВЛИЯНИЕ ОСНОВНОЙ И ПУЛЬСАЦИОННОЙ СОСТАВЛЯЮЩИХ ВЕТРА НА ЗДАНИЯ ПРИЗМАТИЧЕСКОЙ ФОРМЫ

The existing methods for determining the wind load coefficients are analyzed in order to identify the features of the influence of the type of distribution on the forces from the impact of the wind on the structures of buildings and structures of a prismatic type with different proportions of the frontal surface. Reinforced concrete buildings with the first frequency of natural vibrations greater than the limit value were considered. The study was carried out on the basis of the study and analysis of the main provisions of regulatory documents regulating design and development activities in the Russian Federation, as well as relevant works of domestic and foreign scientists relevant to research in this area. The research method is structural-analytical analysis using the correlation dependences of the studied factors. Analytical dependences are given to determine the forces from the wind with various methods of assigning the coefficient of the pulsating wind load along the height of the building, taking into account the shape and proportions of the wind surface, as well as their graphical interpretation. The work is based on the provisions of domestic building codes and regulations and relevant information contained in other domestic and foreign sources and standards. It has been established that in buildings of a prismatic shape there are separate sections where the forces from the components of the wind load significantly depend not only on the proportions of the frontal surfaces, but also on the methods used to establish the distribution law of the coefficients. The conducted research indicates the ambiguity of the results obtained, allowing the possibility of exceeding or underloading structures or individual elements. The results of the work make it possible to correct calculations for establishing the values of wind loads for the considered types of buildings and height ranges and to predict for other objects with different parameters.

Evaluating the Meteorological Conditions Associated With Dusty Atmospheric Rivers

AbstractTrans‐Pacific dust has been shown to influence the micro‐physical characteristics of atmospheric rivers that make landfall along the U.S. west coast. Atmospheric Rivers (AR) reaching North America provide valuable water resources, but also can produce damaging floods. While substantial research has been devoted to understanding the structure and meteorological drivers of atmospheric rivers, far less is known about the conditions that lead to the presence of dust within and around these storms. Here, we utilize an 18‐year record of the dust content of AR surroundings combined with satellite, reanalysis, and observational meteorological data to understand the drivers of ARs embedded within dusty environments, or “dusty ARs,” as compared to ARs in more pristine environments. We find that dusty ARs are associated with transport of dust from the east Asian coast to North America. Dusty ARs are characterized by conditions that are especially conducive to transport of dust across the Pacific; namely, enhanced mid‐ to upper‐tropospheric westerly winds over Asian dust source regions and over the Pacific. In contrast, ARs in more pristine environments are associated with a persistent ridge over the central Pacific, which blocks zonal westerly flow, as well as continental dust. We also show that while trans‐Pacific dust is largely confined to the 600–200 hPa levels, this dust flows downward along post‐cold frontal isentropic surfaces into the AR environment in the lower troposphere.

Разработка пористых титановых имплантатов для межтелового спондилодеза

Relevance Application of 3D printing using the method of selective laser fusion for production of intervertebral cages is a topical trend of the spinal surgery. Purpose Assessment of the efficiency and safety of original interbody fusion implant application made of titanium alloy according to 3D printing technology with selective laser fusion. Materials and methods The original flattened bean-shaped cages, with an integral side part and an internal configuration in the shape of three-dimensional 1.5 × 1.8 mm porous lattice were tested . The products were made of Ti6Al4V powder using 3D printing technology with selective laser fusion. Post-processing of the products surface included abrasive blast cleaning using the SLA method and sterilization with ethylene oxide. Experiments on modeling interbody fusion with replacement of intervertebral discs with cages at levels L4 – L5 and L5 – L6 were performed in 8 mongrels. Additional primary stabilization of the lumbar spine was produced with an external fixator within 30 days after implantation. The total follow-up period lasted 180 days. Radiography, scanning electron microscopy, roentgenospectral and biochemical analysis methods were applied. Results X-ray examination demonstrated the contact between the frontal surfaces of the cages and the bone tissue of the vertebral bodies and the development of fusion in all experimental animals. Biochemical analysis did not reveal the signs of intoxication, indicating the danger of the products application. The microrelief of the implants was characterized by microroughness ranged from 1to 50 μm. In the surface layer of products, in addition to the elements of titanium, aluminum and vanadium, the carbon, oxygen, silicon, trace amounts of other organic and inorganic elements were found. Newly formed bone trabeculae were macroscopically and submicroscopically visualized in the sawcuts of bone blocks in the porous lattice of the internal part of the implants. Conclusions Experimental testing of porous implants made of titanium alloy using selective laser fusion has shown their effectiveness in obtaining interbody fusion and acceptable safety.

The entropy generation analysis of forward and backward laminar water flow in a plate-pin-fin heatsink considering three different splitters

The application of splitters has been proven to be useful to control the separated wake downstream of the pin-fins. This paper aims to evaluate the thermal (Ṡth) and frictional (Ṡf) irreversibility rates in the fluid flow inside the plate-pin-fin heatsinks (PPFHSs). To this end, the numerical analysis of forward and backward water flow inside the PPFHS with three different attached splitters was performed considering Re of between 50 and 250. The main objective was to determine the locations with intense thermal and frictional entropy generation rates inside the fluid flow geometry. Based on the results, the frictional entropy generation rate is significantly lower than that the thermal term. Also, the pin-fin with arched splitter has the minimum thermal irreversibilities as compared to straight and wavy splitters. Furthermore, the major irreversibilities are associated with the locations near the pin-fin lateral and frontal surfaces as well as the plate fin walls and heatsink upper case and lower base. Moreover, it was shown that for all considered cases and two flow directions, the increasing of the Re results in decreasing and increasing the thermal and frictional entropy generation rates, respectively.

Analysing the potential of hydrophilic adhesive systems to optimise orthodontic bracket rebonding

IntroductionBond failure during fixed orthodontic treatment is a frequently occurring problem. As bracket rebonding is associated with reduced shear bond strength, the aim of the present investigation is to analyse the effect of different innovative rebonding systems to identify optimised rebonding protocols for orthodontic patient care.MethodsMetallic brackets were bonded to the frontal enamel surfaces of 240 bovine lower incisors embedded in resin bases. Teeth were randomly divided into two major experimental groups: in group 1 a hydrophilic primer (Assure™ PLUS) was compared to commonly used orthodontic adhesives (Transbond XT™, BrackFix®, Grengloo™) and a zero control. In group 2 different rebonding systems were analysed using a hydrophilic primer (Assure™ PLUS), a methyl methacrylate-consisting primer (Plastic Conditioner) and a conventional adhesive (Transbond XT™). All teeth were tested for shear bond strength according to the DIN-13990 standard, the Adhesive Remnant Index and enamel fracture rate.ResultsThe hydrophilic primer enhanced shear bond strength at first bonding (Assure™ PLUS 20.29 ± 4.95 MPa vs. Transbond XT™ 18.45 ± 2.57 MPa; BrackFix® 17 ± 5.2 MPa; Grengloo™ 19.08 ± 3.19 MPa; Meron 8.7 ± 3.9 MPa) and second bonding (Assure™ PLUS 16.76 ± 3.71 MPa vs. Transbond XT™ 13.06 ± 3.19 MPa). Using Plastic Conditioner did not seem to improve shear bond strength at rebonding (13.57 ± 2.94). When enamel etching was left out, required shear bond strength could not be achieved (Plastic Conditioner + Assure™ PLUS 8.12 ± 3.34 MPa; Plastic Conditioner: 3.7 ± 1.95 MPa). Hydrophilic priming systems showed decreased ARI-scores (second bonding: 2.63) and increased enamel fracture rates (first bonding: 55%; second bonding 21,05%).ConclusionsBased on the present study we found that rebonding strength could be compensated by the use of hydrophilic priming systems. The additional use of a methyl methacrylate-consisting primer does not seem to enhance shear bond strength. No etching approaches resulted in non-sufficient bond strength.

Zygomaticus major muscle bony attachment site: a Thiel-embalmed cadaver study

Thezygomaticus major is a principal muscle of facial expression which is engaged when smiling. The zygomaticus major origin of the zygomatic bone is often discussed relevant to its importance in the field of plastic surgery. In addition, the zygomaticus major attachment site is also significant for forensic craniofacial reconstruction, separating the cheek into frontal and lateral surfaces. However, there are discrepancies amongst published articles regarding the precise origin of the zygomaticus major muscle. The aim of this study is to investigate more distinctive and palpable landmarks as the bony attachment of the zygomaticus major. This project is the first zygomaticus major dissection study utilising Thiel embalmed cadavers. Fifty-two facial dissections were investigated in 26 Thiel embalmed bodies, bequeathed to the Centre for Anatomy and Human Identification at The University of Dundee between 2013 and 2015. This study found that the origin of zygomaticus major muscle was located at the superior margin of the temporal process on the lateral surface of zygomatic bone. Moreover, the zygomaticus major muscle overlapped the anterosuperior border of the masseter muscle. One out of 52 zygomaticus major muscles presented bifurcation. The origin site of zygomaticus major is considered important to increase resemblance in forensic craniofacial reconstruction. Furthermore, since zygomaticus major is a salient muscle involved in facial expression, the potential effects for cosmetic/surgical procedures are also relevant to the medical field and successful surgical outcomes. The current study provided easily palpable landmarks of zygomaticus major origin site which is beneficial for both surgeons and forensic craniofacial reconstruction practitioners.

Numerical prediction of dynamic failure in concrete targets subjected to projectile impact by a modified Kong-Fang material model

Typical failures such as cratering, cracking and spalling are frequently observed on the frontal and distal surfaces of concrete slabs when subjected to impact loadings. A high-fidelity physical-based numerical simulation should not only predict the ballistic parameters, but these failures, where an accurate material model and an appropriate algorithm are crucial. To this end, the Kong-Fang concrete material model recently proposed (Kong et al., 2018) is firstly modified. Modifications are made to the strength surfaces (including residual strength surface and yield strength surface) and definition of compression damage. The modified model is then implemented in the AUTODYN hydrocode through the user subroutine in which a new crack softening model is introduced to account for the triaxial tensile failure. Comprehensive single element tests are conducted to validate the improved performances due to these modifications focused on the tensile behavior and compressive behavior under high confinement. Then the modified Kong-Fang concrete material model is combined with the Smooth Particle Hydrodynamics (SPH) method to numerically predict ballistic parameters and dynamic failures in several sets of concrete penetration/perforation tests by steel projectiles. Compared with the RHT model and the original Kong-Fang model, the modified model can well capture the cratering, tunneling, cracking and the scabbing failure phenomena and numerical predicted ballistic parameters are found to be in excellent agreement with corresponding experimental data.

Proliferating activity in a bryozoan lophophore.

Bryozoans are small benthic colonial animals; their colonies consist of zooids which are composed of a cystid and polypide. According to morphological and molecular data, three classes of bryozoans are recognized: Phylactolaemata, Gymnolaemata and Stenolaemata. Bryozoans are active suspension feeders and their feeding apparatus, the lophophore, is fringed with a single row of ciliated tentacles. In gymnolaemates, the lophophore is bell-shaped and its tentacles may be equal in length (equitentacled lophophores) or some tentacles may be longer than others (obliquely truncated lophophores). In encrusting colonies, polypides with obliquely truncated lophophores usually border specific sites of excurrent water outlets (colony periphery and chimneys) where depleted water has to be removed. It is known that during colony astogeny, colony-wide water currents rearrange: new chimneys are formed and/or location of the chimneys within a given colony changes with time. Such rearrangement requires remodeling of the lophophore shape and lengthening of some tentacles in polypides surrounding water outlets. However, proliferating activity has not been described for bryozoans. Here, we compared the distribution of S-phase and mitotic cells in young and adult polypides in three species of Gymnolaemata. We tested the hypothesis that tentacle growth/elongation is intercalary and cell proliferation takes place somewhere at the lophophore base because such pattern does not interfere with the feeding process. We also present a detailed description of ultrastructure of two parts of the lophophore base: the oral region and ciliated pits, and uncover the possible function of the latter. The presence of stem cells within the ciliated pits and the oral region of polypides provide evidence that both sites participate in tentacle elongation. This confirms the suggested hypothesis about intercalary tentacle growth which provides a potential to alter a lophophore shape in adult polypides according to rearrangement of colony wide water currents during colony astogeny. For the first time deuterosome-like structures were revealed during kinetosome biogenesis in the prospective multiciliated epithelial cells in invertebrates. Tentacle regeneration experiments in Electra pilosa demonstrated that among all epidermal cell types, only non-ciliated cells at the abfrontal tentacle surface are responsible for wound healing. Ciliated cells on the frontal and lateral tentacle surfaces are specialized and unable to proliferate, not even under wound healing. Tentacle regeneration in E. pilosa is very slow and similar to the morphallaxis type. We suggest that damaged tentacles recover their length by a mechanism similar to normal growth, powered by proliferation of cells both within ciliated pits and the oral region.

Effects of 445-nm Diode Laser-Assisted Debonding of Metallic Brackets on Shear Bond Strength and Enamel Surface Morphology.

Objective: To evaluate the effect of a 445-nm diode laser on the shear bond strength (SBS) of metallic brackets before debonding. Background: Due to the new blue laser technology, very few studies are available in this context. Methods: Seventy metallic brackets (Discovery; Dentaurum, Ispringen, Germany) were bonded to the frontal enamel surfaces of 70 caries-free bovine incisors in a standardized way. Each sample was randomly assigned to the control or laser group, with 35 samples per group. The brackets in the laser group were irradiated with the diode laser (SIROLaser Blue®; Sirona, Bensheim, Germany) on three sides of the bracket bases for 5 s each (lateral-coronal-lateral, a total of 15 s) immediately before debonding. SBS values were evaluated for the control group and laser group. Micrographs of the enamel surface were taken with 10 × magnification to assess the adhesive remnant index (ARI) and the degree of enamel fractures after debonding. Results: There were no statistically significant differences in SBS in the laser group in comparison with the control group (p > 0.05). The distribution of ARI scores was also not statistically significantly different in the laser group in comparison with the control group (p > 0.05). Three enamel fractures occurred in the control group and one in the laser group after debonding. Conclusions: Irradiation of metallic brackets with the 445-nm diode laser before debonding does not significantly reduce the SBS values and does not influence the remaining amount of adhesive on the enamel surface. The risk of enamel fractures during debonding is therefore not clinically affected.

Numerical predictions of failures in concrete structures subjected to intense dynamic loadings using the Smooth Particle Hydrodynamics method

Typical failures such as cratering and spalling are frequently observed on the frontal and distal surfaces of concrete structures when subjected to blast and impact loadings. Numerical predictions of these failures call for an accurate material model and an appropriate algorithm, which is a topic of current research. In this paper, the inherent limitations of the frequently-used finite element method to predict dynamic failures in concrete with the aid of element erosion technique are firstly discussed. Motivated by the natural advantages of the meshfree method to describe the high deformation and large strain situations, the Smooth Particle Hydrodynamics (SPH) method is then combined with our recent KFCW material model to numerically predict dynamic failures in concrete structures. By comparing the numerical predicted failures with the post-test observations of two field tests, it is demonstrated that the SPH method combined with the new material model provides a promising way to predict the dynamic failures without introducing empirical and artificial parameters.