Oval Holes Research Articles

Краніологічні особливості ондатри (Ondatra) та її відмінності від роду Arvicola

An overview of the craniological differences between muskrats and sympatric Arvicola based on materials from Ukraine is presented. One of the most notable differences is the absence of cement on the molars of muskrats, which is typical for all Arvicolini. The shape of the occlusal surface of muskrat molars is also characterised by a smaller number of enamel loops and a more rounded shape. The shape of the connection between the pterygoid processes of the sphenoid bones and the auditory bulla is different in these two genera. A number of other differences have been described, including the shape of the sphenoid bone openings, which are wider in muskrats with deeper paired oval holes.

Mechanical assessment of two hybrid plate designs for pancarpal canine arthrodesis under cyclic loading.

Pancarpal canine arthrodesis (PCA) sets immobilization of all three carpal joints via dorsal plating to result in bony fusion. Whereas the first version of the plate uses a round hole (RH) for the radiocarpal (RC) screw region, its modification into an oval hole (OH) in a later version improves versatility in surgical application. The aim of this study was to mechanically investigate the fatigue life of the PCA plate types implementing these two features-PCA-RH and PCA-OH. Ten PCA-RH and 20 PCA-OH stainless steel (316LVM) plates were assigned to three study groups (n = 10). All plates were pre-bent at 20° and fixed to a canine forelimb model with simulated radius, RC bone and third metacarpal bone. The OH plates were fixed with an RC screw inserted either most proximal (OH-P) or most distal (OH-D). All specimens were cyclically tested at 8Hz under 320N loading until failure. Fatigue life outcome measures were cycles to failure and failure mode. Cycles to failure were higher for RH plate fixation (695,264 ± 344,023) versus both OH-P (447,900 ± 176,208) and OH-D (391,822 ± 165,116) plate configurations, being significantly different between RH and OH-D, p = 0.03. No significant difference was detected between OH-P and OH-D configurations, p = 0.09. Despite potential surgical advantages, the shorter fatigue life of the PCA-OH plate design may mitigate its benefits compared to the plate design with a round radiocarpal screw hole. Moreover, the failure risk of plates with an oval hole is increased regardless from the screw position in this hole. Based on these findings, the PCA plate with the current oval radiocarpal screw hole configuration cannot be recommended for clinical use.

Effects of the inclination angle of oval film holes on the aero-thermal performance of a squealer blade tip

The investigation and study on the characteristics of the flow and wall heat transfer on the squealer tip is of vital importance to the safe and durable operation of a turbine rotor. The numerical model of the blade squealer tip with discrete film cooling holes (round and oval holes) was constructed and validated in this paper. The effects of the radial and axial inclination of oval-holes on aero-thermal performance were systematically investigated, which received little attentions in previous studies. The result shows that the streamline deflection produced by negative inclination structures significantly improves the coverage of film, but the development of the jet vortex leads to an enhancement in leakage flow. The lift-off of film is effectively restrained by positive inclination structures, however, the jet outflow contraction limits the expansion of film coverage. Besides, the scraping between tip cavity flow and leakage flow is also an important factor to the leakage flow control, which can reduce the momentum of leakage flow. Overall, the negative radial inclination structure achieves the optimal performance of film cooling, whose tip average cooling effectiveness at 0.5 blowing ratio is even 132% higher than that in the round hole reference at 1.5 blowing ratio. The highest relative reduction of leakage flow is obtained by the positive axial inclination structure with 62.79% at the blowing ratio of 1.5.

Influence of the oval hole on rock mechanical mechanism under uniaxial and biaxial compression: insights from the combined finite-discrete element method

To investigate the effects of the oval hole on the strength and the failure mechanisms of rock materials, a series of uniaxial and biaxial compression numerical simulations were carried out using the combined finite-discrete element method (FDEM). Based on the numerical simulation results, the effects of dip angle (β), major–minor ratio (ω) and position of the oval hole on rock strength characteristics crack initiation and development process and final failure modes were analysed in detail. The numerical simulation results indicate that: (1) Under uniaxial compression, the ultimate failure modes of rock containing oval holes can be mainly classified into single inclined plane shear failure, X-shaped tensile-shear composite failure and Y-shaped tensile-shear composite failure. Under biaxial compression, the ultimate failure mode is single-inclined plane shear failure dominated by shear cracks. Whether it is uniaxial compression or biaxial compression, the crack initiation position of the main fracture surface is near the end of the major axis of the oval hole. (2) Under uniaxial compression, the axial stress–strain curve of rock containing the oval hole is smooth before and after the peak, but under biaxial compression, there is obvious fluctuation in the post-peak stage due to crack initiation and propagation. In both uniaxial and biaxial compression, the pre-peak elastic stage of the axial stress–strain curve of the rock containing the oval hole is significantly shortened and the peak stress is significantly reduced compared with the intact rock, which indicates that the bearing capacity of the rock is seriously reduced by the existence of oval hole. (3) When the position and major–minor axis ratio of the oval hole remain unchanged, the uniaxial compressive strength and biaxial compressive strength increase with the increase of the dip angle of the oval hole. When the position and dip angle of the oval hole remain unchanged, the uniaxial compressive strength and biaxial compressive strength decrease with the increase of the major–minor axis ratio of the oval hole. (4) At different dip angles, the brittleness index Bi of rock containing oval holes decreases with the increase of confining pressure, and the brittleness degree shows a gradual weakening trend. At the same time, when the dip angle increases, the decreasing amplitude of brittleness index Bi decreases with the increase of confining pressure.

Crashworthiness of a hybrid tube with an auxetic layer

Hybrid tubes of different forms have been designed and used in various sectors such as automotive, medical, pipeline, and aerospace industries for protective equipment, oesophageal stents, oil and gas pipes, and superior vibration dampers. Auxetic materials and structures have received increasing attention due to their unique properties such as negative Poisson’s ratio. They laterally expand under uniaxial tension or laterally contract under uniaxial compression. In this work, an innovative hybrid tube with an auxetic tube as the outer tube and a conventional tube as the inner tube has been investigated. All the inner tubes were made of extruded aluminum alloy 6063 with T5 heat treatment, and the outer tubes were made of stainless steel 304 and 316L with oval holes, respectively. Quasi-static compressive tests have been conducted to study the crashworthiness of such hybrid tubes. The effects of outer tube material and geometry on the deformation mode, force–displacement curve and energy absorption of hybrid tubes have been discussed. The results show that the outer auxetic tube changes the deformation of the inner tube. The load carry capacity and energy absorption of a hybrid tube increase with the strength of the outer auxetic tube.

The role of smoking in the development of strokes at a young age

Stroke in young patients is a disease based on a number of known specific non-modifiable factors (extracranial artery dissection, thrombophilia, open oval hole, etc.) and modifiable factors (alcohol abuse, drug use, smoking, etc.), in combination leading to the development of pathology. Smoking is a generally recognized modifiable risk factor for stroke, which is directly proportional to the number of tobacco-containing products smoked. Quitting smoking is the basis of prevention, an integral part of the treatment and rehabilitation of stroke patients. If it is impossible to completely give up smoking combustible cigarettes, it is advisable to switch to alternative smokeless products. This article presents the results of current studies on the comparative assessment of the risk of stroke in young people when using combustible cigarettes and smokeless analogues.

Stress intensity factor calculation of the cracks interacted by the oval-holes in anisotropic elastic solids under remote and non-uniform surface stresses

In underground rock engineering, natural defects (such as cracks, joints, cavities of arbitrary shape) and anisotropy of rock mass are main factors influencing the engineering strength. Calculating stress intensity factors (SIFs) of anisotropic elastic solids with multiple oval-holes and cracks is of great significance not only for designing the stop-holes to improve the stability of mining exploitation, but also for optimizing the hydraulic fracturing parameters to improve the productivity of geothermal/shale-gas utilization. Current studies are mainly focused on the loading case of remote stresses, regardless of the surface stresses applied onto the holes and cracks. In this paper, both remote uniform stresses and non-uniform surface stresses are taken into account to calculate the multi-crack SIFs interacted by the multiple oval-holes in anisotropic elastic solids. Two elementary solutions for traction components of single oval-hole and single crack subjected to the surface point-forces in the anisotropic solids are analytically deduced based on Cauchy integral approach in complex variable theory. A new integral equation approach is established to solve the interacting SIFs of multiple oval holes and cracks in the two-dimensional anisotropic elastic solids, without any limitation of the number, sizes, orientations and locations for oval-holes and cracks. Its accuracy and feasibility are validated by comparing our SIF solutions against the available exact solutions, approximated solutions and finite element solutions. The new method has high accuracy (with almost the same SIF solutions as the exact ones), simple formulation (without any singularity) and wide applicability (under both remote uniform stresses and non-uniform surface stresses). It can be further developed for three-dimensional anisotropic hole-crack problem under the same complex stress states.

Topology Optimization Design With Addictive Manufacturing Constraints for Centrifugal Impeller

Abstract Weight reduction of centrifugal impeller is of great significance for improving thrust-weight ratio of aero-engine. In this paper, the weight reduction design for a centrifugal impeller considering additive manufacturing constraints was carry out. First of all, reducing the structure weight by using the topology optimization method based on variable density method. Secondly, reconstructing the results of topology optimization based on the overhang angle, minimum length, connectivity and other additive manufacturing constraints, whose structure contains the self-supporting cavity, oval powder discharge holes and annular convex plate. Finally, adjusting the reconstructed model by using size optimization, which obtained an innovative hollow centrifugal impeller with both lightweight and high mechanical performance. The results indicate that the mass of the optimized centrifugal impeller reduces by 18.5% compared with the original model at the same stress level. The method and scheme can provide reference for the structural optimization design of aero-engine centrifugal impeller.

Uneven deposition on the Al electrode under tension strain

Structural deformation and dendrite formation, which would impact the electrochemical processes of rechargeable metal batteries, are usually observed in the high-energy density metal electrodes. Herein, we design an in-situ optical mechano-electrochemical system to study Al deposition on the Al electrode in non-aqueous Al batteries under non-uniform strain. Inhomogeneous distribution of applied strain is realized by creating an oval hole in the Al electrode. The results of the in-situ experiments suggest that the dense Al deposition, which is related to the evolution of surface morphology and increasing reactive sites, is achieved in the regions of stress concentration. The evolution of surface morphology is monitored by the in-situ tension experiments using scanning electron microscope and atomic force microscope. Besides, a qualitative mathematical model is employed to analyze the changes of the local reaction rate owing to the changed surface morphology and the cracks of oxide film under tensile stress. The results are useful to understand the Al deposition when the mechanical force is applied to the metal electrode.

Abrasive water jet piercing of straight and inclined holes on Yttria-Stabilized Zirconia coated Ni-based superalloy

ABSTRACT The present work investigates the Abrasive Water Jet (AWJ) drilled holes with different hole angles such as 0°, 15°, 30°, and 45° on Yttria-Stabilized Zirconia (YSZ)-coated nickel-based superalloy using a piercing mode of operation. These types of holes were used as film cooling holes for the aero engine modules. The water jet pressure, hole piercing angle, and garnet flow rate were taken as variable operational parameters. The effect of these factors on hole features, such as entry and exit hole diameters, taper angle and coating removal rate, was analyzed. The machining time and surface roughness were also investigated. The results indicated the water jet pressure and hole piercing angle having significant effects on the hole geometrical features. Lower water jet pressure produced the exit hole cap, hairline burrs on the exit hole, and surface chipping. However, these defects were not found with an increment in the water jet pressure. Besides, circular and oval shape hole profiles were observed at different hole angles for film cooling applications. The AWJ pierced hole was seen having free of cracks, delamination, and other material defects. However, removal of excess YSZ coating was noticed near the hole by lateral erosion. This could be significantly reduced by optimizing the operational parameters for making quality holes on the ceramic-coated nickel-based superalloys.

Модернизация и испытание устройства для восстановления автомобильных пружин

Abstract. The relevance of study is determined by development of technologies that allow restoring operational parameters of springs used in automobile transport, achieving an increase in durability of components and assemblies in which they are included. A general block diagram model of research methods for improving technology of restoring automobile springs is presented. For technological operation of stretching springs, it is necessary to use a device for stretching springs. The known devices have not found wide application in the conditions of car repair enterprises. The disadvantage of the considered device for stretching springs is complexity of design and limitations of its use for stretching springs with different geometries. The purpose of this work is to improve the device for stretching springs. The device design based on the use of settling surface and a schematic diagram of known device is proposed. In the proposed design of the device, labor-intensive T-shaped grooves used to make contact of support rollers with threaded mandrel by moving lunette and roller contact with spring coil by moving the head are replaced, respectively by non-labor-intensive oval holes in base of lunette and by fork moved in hole of head. The design of device is suitable for stretching springs with a different pitch of turns and internal diameter, for which it is necessary to make appropriate nut with threaded mandrel and ring and roller for clamping the spring, without making the device again, which gives an economic effect. The spring stretching device has been manufactured and tested. According to test results, height of springs during tension was increased by an average of 4.9 mm. Thus, in order to perform subsequent technological operations restoring the power and geometric parameters after stretching of internal valve springs of VAZ cars, an allowance of 6.5 mm is provided. The proposed device design is recommended in design and manufacture of devices for restoring parameters of large springs used in automobile transport, for example, suspension springs.

Профилактика осложнений тонко-толстокишечных анастомозов в условиях перитонита

Th e aim of the research. To improve treatment outcomes for patients requiring formation of entero-colonic anastomoses using a new method for prevention of their leakage. Material and methods. A total of 60 patients operated on for peritonitis who potentially required entero-colonic anastomosis were divided into 2 groups. Th e retrospective comparison group included 33 subjects and 27 subjects were enrolled into the prospective main group. Anastomoses for patients in the main group were formed according to the proprietary method that improves blood fl ow along the suture line. Th e method consisted in the following: the leading segment of the small intestine was crossed at an angle of 50-60° to its mesenteric edge. Th e colon stump was also formed by crossing at an angle of 50-60° to its mesenteric edge; a “window” was cut in the antimesenteric part of the colon wall: an oval-shaped area with an area corresponding to the cross-sectional area of the small intestine, the end of the small intestine was connected to the oval hole in the colon “end to side” using a single-row continuous intestinal suture. Primary endpoint: development of leakage in the formed entero-colonic anastomosis. Secondary endpoint: mortality of patients in the postoperative period until discharge from the hospital. Results. Th e proportion of leakage amounted to 3.7% in the main group, and 33.3 % in the comparison group (p=0.007). Th e mortality was 7.4 % and 36.3 %, respectively (p=0.012). Conclusion. The proposed technique for entero-colonic anastomosis formation has advantages due to a signifi cant reduction in the frequency of fistula leakage and mortality

Аulacoseira granulata (Bacillariophyta): двугубые выросты

Characters of rimoportulae are important in the taxonomy of the genus Aulacoseira, but data on the variability of these structures are scarce. We study the rimoportulae number, position and morphology in the centric diatom Aulacoseira granulata from a population оf the Nizhny Tagil Reservoir (Sverdlovsk Region, Russia). A significant variation in the number of rimoportulae on the half of the valve mantle (1–3) and their location (along the entire surface of the valve mantle) is found. Two different types of the rimoportulae on the inner surface of valves within the same species of Aulacoseira are shown. Most often each rimoportula looks like a long spiral tube, less often such tube is short and straight. Externally, each rimoportula opening resembles a funnel-shaped hole which is often accompanied by an oval hole of an unclear function.

Disordered auxetic metamaterials architected by random peanut-shaped perturbations

Previous discussions about perforated auxetic metamaterials primarily focused on the ordered systems with high degree of geometric symmetry. However, it is difficult to manufacture or retain the perfect auxetic systems in practical applications. In this paper, three types of disordered perforated auxetic systems including orientated disordered system, dimensional disordered system and complete-disordered system are explored thoroughly. The perforations of interest are oval holes which are advantageous in ensuring auxeticity, reducing stress level and improving material distribution. The designed disordered systems are fabricated by 3D printing technology and then are tested by the uniaxial tension to reveal their mechanical properties and verify the related finite element models. Thereafter, the evolution of mechanical properties of these disordered systems is investigated numerically for the varied perturbed geometric parameters such as the orientation and dimension of oval hole. The results reveal that the disordered systems still show great robustness in auxetic behavior, although the disorder in orientation and dimension exists. A high degree of symmetry in microstructure is not necessary for designing perforated auxetic systems. This provides a great convenience for the flexible and practicable design and application of perforated auxetic metamaterials.

Translation of N.B.K. Sänger’s (1871) “Peripatus capensis Gr. and Peripatus leuckartii n. sp.” (Onychophora), along with remarks about the author and significance of his work

ABSTRACT The basic biology of onychophorans was revealed slowly and controversially during much of the 19th century. Communications were in Latin, French, Spanish, German and English. This information was synthesised in the monumental monographs of Bouvier in 1905 and 1907. However, amongst this multicultural endeavour is a significant Russian contribution by Nikolai Sänger, a student of Professor Leuckart of the Zoological Institute in Leipzig, Germany. Sänger requested a specimen of Onychophora from the Institute’s collection for serial sectioning. This resulted in a detailed account of the anatomy of Peripatopsis capensis. Sänger’s description of the extensive slime glands was the first to recognise them as the hallmark of onychophorans for defence and prey capture, and not the male reproductive system as previously claimed. Based on these morphological observations, he correctly concluded that onychophorans are not hermaphrodites and, furthermore, are “predominantly predaceous” animals. He further appropriately assigned the slime glands and salivary glands to the slime papilla segment, despite the lack of embryological data at that time. Sänger also identified the excretory organs (nephridia) and their openings, although he erroneously assigned them to a dual role of excretion and respiration. Moreover, he highlighted the importance of the position of the genital opening as a diagnostic character, described the ventral/preventral organs as “subcutaneous glandules”, identified the neurilemma enclosing the central nervous system, and recognised “oval holes of different sizes” in each nerve cord that were subsequently demonstrated to represent giant fibres. Of interest to parasitologists, he discovered a larval acanthocephalan encysted within the cutaneous muscles of his specimen of P. capensis, suggesting that onychophorans act as a secondary host for this parasite. Sänger’s memoir concludes with a brief but important description of the first species of Onychophora recorded from Australia, “northwest of Sydney, New Holland”. This species is now known as Euperipatoides leuckartii with a neotype designated from a specific location northwest of Sydney.

An Atypical Path of the Lingual Nerve in the Retromolar Region: Incidence in Oral Surgery.

The Lingual nerve is frequently anesthetized during oral, maxillofacial, or otorhinolaryngology surgery. It originates below the oval hole in the infratemporal region, follows its path down and forward, and moves away from the medial surface of the ramus. From there, it goes just above the mylohyoid line. It approaches the lateral margin of the tongue and crosses the Wharton's canal, and divides into numerous branches. Some cases of temporomandibular joint syndrome or myofascial pain syndrome could be a result of its anatomical variations. Also, the jurisprudence has always condemned the practitioner if for not demonstrating that the path of the injured nerve presents an anomaly which makes his involvement inevitable. The purpose is to present one of the multiple atypical paths of the lingual nerve not described in the retromandibular trigone, demonstrating that its damage constitutes a risk that cannot be controlled.

Drilling high aspect ratio holes by femtosecond laser filament with aberrations.

A near-infrared femtosecond laser is focused by a 100 mm-focal-length plano-convex lens to form a laser filament, which is employed to drill holes on copper targets. By shifting or rotating the focusing lens, additional aberration is imposed on the focused laser beam, and significant influence is produced on the aspect ratio and cross-sectional shape of the micro-holes. Experimental results show that when proper aberration is introduced, the copper plate with a thickness of 3 mm can be drilled through with an aspect ratio of 30, while no through-holes can be drilled on 3-mm-thickness copper plates by femtosecond laser with minimized aberration. In addition, when femtosecond laser filament with large astigmatism is used, micro-holes that had a length to width ratio up to 3.3 on the cross-section are obtained. Therefore, the method proposed here can be used to fabricate long oval holes with high aspect ratios.

Multi-functional gallium arsenide photonic crystal polarization splitter with a gold core

A multi-functional dual-core photonic crystal fiber (PCF) polarization beam splitter with a central oval hole filled with gold is designed and described. The first layer on the circular holes around the core is filled with the nematic liquid crystal (NLC) to enhance birefringence. The full-vector finite element method is employed to study the characteristics of the polarization beam splitter and derive the optimal parameters. When the fiber length is 14.55 [Formula: see text]m, the polarized light in the [Formula: see text]- and [Formula: see text]-directions can be separated at a wavelength of 1.31 [Formula: see text]m and the bandwidths are 257 and 238 nm, respectively, for extinction ratios bigger than 10 dB. When the fiber length is 10.86 [Formula: see text]m, the polarized light in the [Formula: see text]- and [Formula: see text]-directions can be separated at a wavelength of 1.55 [Formula: see text]m and the bandwidths are 239 and 174 nm, respectively for extinction ratios larger than 10 dB. The multifunctional polarization beam splitter with an ultra-short fiber length and broad bandwidth improves the sensing performance in comparison with single-function devices and our results provide insights into the design of beam splitters with multiple functions.

Feeding traces on postcranial sauropod remains from Bajo de la Carpa Formation (Upper Cretaceous, Santonian), northern Neuquén Basin, Patagonia, Argentina

Bite marks in non-avian dinosaur fossil records can constitute the best evidence of predator-prey interactions even if they are uncommon, ambiguous, or of uncertain origin. In this contribution, we present new evidence of feeding traces on an isolated sauropod element from Bajo de la Carpa Formation outcrops (Upper Cretaceous, Santonian), northern Neuquén province, Patagonia, Argentina. The specimen is composed of a partial dorsal vertebral centrum (MAU-Pv–CO–651; deposited at the Museo Municipal Argentino Urquiza, Rincón de los Sauces, Neuquén, Argentina). We tentatively refer it to an indeterminate titanosaur sauropod due to the presence of an opisthocoelic articulation and an internal pneumatic camellate condition. Three kinds of marks are preserved on the lateroventral face of the centrum: large and deep parallel marks, small and shallow longitudinal marks, and deep oval holes that we tentatively consider as punctures. These fossil marks can be considered to be feeding traces produced by a large-bodied carnivore to deflesh the bone and/or to obtain bone nutrients, probably during a single scavenging event. The marks and the punctures on the vertebral centrum can be referred to a theropod dinosaur due to their pattern and distribution. Viavenator exxoni (Filippi et al., 2016) represents the most likely trace-maker candidate among the several theropod and crocodile taxa present in the Bajo de la Carpa Formation fossil record. The fossil feeding traces reported here improve our knowledge about the feeding behaviour of large scavengers in the north of the Neuquén Basin, at least during the Santonian.

Ultra-short and dual-core photonic crystal fiber polarization splitter composed of metal and gallium arsenide

Two ultra-short polarization beam splitters (PBSs) based on surface plasma resonance (SPR) are designed for wavelengths of 1.31 and 1.55 μm. The center of the PCF has an oval hole filled with gold and the first layer of the air holes around the core is filled with the nematic liquid crystal (NLC) to enhance birefringence. In this work, the full vector finite element method is used to optimize the structural parameters. Two sets of parameters with extinction ratios of 114.02 and 111.86dB and lengths of 14.52328 and 11.02418μm are designed at wavelengths of 1.31 and 1.55 μm respectively. The results reveal that the beam splitters with broadband and short fiber length have important prospects in communication applications.