Search

Given a set of dot pattern point set P with the size n in the plane, we propose a Delaunay triangulation-based shape reconstruction algorithm, entitled prudent carving, that can reconstruct the inner boundaries (holes) and outer boundaries of P with the same approach. Our prudent carving algorithm is a parameter-free algorithm that has the ability to detect multiple components, sharp corners, and nested holes independent from the number of them in the total O (n log n) time. The qualitative and quantitative comparison of the results with the state-of-the-art algorithms shows that the prudent carving algorithm provides an enhancement over the previously best-known algorithms for reconstructing the boundaries of points. [ABSTRACT FROM AUTHOR]

A graph is ℓ-holed if all its induced cycles of length at least four have length exactly ℓ. We give a complete description of the ℓ -holed graphs for each ℓ ≥ 7. [ABSTRACT FROM AUTHOR]

The efficiency of widespread technological processes of sieve sifting of loose materials depends on timely cleaning of holes from the blocked particles. The blocking of holes occurs under specific conditions related to mechanical-and-physical properties of loose material particles, constructive and technological parameters of perforated sifting surfaces and clean-up systems. We established the conditions that contribute to blocking of holes of sifting surfaces and identified all significant factors, namely size, mass, constant of friction and Young's modulus for loose material particles; form and size of hole, thickness of perforated surface; loose material layer thickness and velocity. Using analytical and experimental methods, we identified variation range of these factors for loose material particles of biological origin, such as buckwheat, wheat, peas, corn. As a result of this study, we received analytical equations for determination of force of adhesion of loose materials particles with the edge of holes of perforated surfaces. The numeric calculations allowed establishing the dependence of the force of adhesion on moisture and thickness of loose material layer, as well as thickness and shape of the holes of the perforated surfaces. We have also established the dependence of constant of friction, mass, Young's modulus from the moisture of particles of loose material. The obtained results make it possible to determine the force of adhesion and prediction the power necessary for unblocking this hole, created by the cleaning system elements, such as brushes and elastic impact cleaners. The use of this method will make it possible to justify the parameters of the system for cleaning holes of perforated sifting surfaces with different types of holes and when separating different types of loose materials. [ABSTRACT FROM AUTHOR]

In this study, underwater explosion tests with 2.5 g trinitrotoluene explosive under different fixed plates with prefabricated holes were conducted. The experimental results showed that the air inflow from the prefabricated hole caused the bubble to collapse earlier with an increase in the hole diameter. In addition, the deformation mode of the thin plate transitioned from "convex" to "concave" (up to down). Next, the coupled Eulerian-Lagrangian method was used to perform the corresponding numerical simulation. The accuracy of the numerical simulation method was verified through a comparison with the experimental data. In addition, a series of numerical simulations were conducted with different prefabricated-hole diameters, blast distances, and prefabricated-hole shapes. The results showed that the bubble-pulsating water jet substantially influenced the deformation of the thin plate when the diameter of the prefabricated hole was within the theoretical maximum bubble radius. When the blast distance was within the theoretical maximum bubble radius, the thin plate was subjected to only a single bubble pulsation owing to the air inflow from the prefabricated hole. [ABSTRACT FROM AUTHOR]

The efficiency of widespread technological processes of sieve sifting of loose materials depends on timely cleaning of holes from the blocked particles. The blocking of holes occurs under specific conditions related to mechanical-and-physical properties of loose material particles, constructive and technological parameters of perforated sifting surfaces and clean-up systems. We established the conditions that contribute to blocking of holes of sifting surfaces and identified all significant factors, namely size, mass, constant of friction and Young's modulus for loose material particles; form and size of hole, thickness of perforated surface; loose material layer thickness and velocity. Using analytical and experimental methods, we identified variation range of these factors for loose material particles of biological origin, such as buckwheat, wheat, peas, corn. As a result of this study, we received analytical equations for determination of force of adhesion of loose materials particles with the edge of holes of perforated surfaces. The numeric calculations allowed establishing the dependence of the force of adhesion on moisture and thickness of loose material layer, as well as thickness and shape of the holes of the perforated surfaces. We have also established the dependence of constant of friction, mass, Young's modulus from the moisture of particles of loose material. The obtained results make it possible to determine the force of adhesion and prediction the power necessary for unblocking this hole, created by the cleaning system elements, such as brushes and elastic impact cleaners. The use of this method will make it possible to justify the parameters of the system for cleaning holes of perforated sifting surfaces with different types of holes and when separating different types of loose materials.

Abstract Caverns and tunnels are constantly exposed to dynamic loads, posing a potentially significant threat to the safety of rock structures. To facilitate the understanding of dynamic fracture around openings, a series of discrete element models were established to numerically examine the effect of hole shape on dynamic mechanical properties and crack evolution. The results indicate that the existence of a hole greatly reduces dynamic strength, and the reduction is closely related to hole shape. The strain variation of pre-holed specimens is more complicated and even larger than the value of intact specimens. Although crack initiation differs for varying hole shapes, the entire structural collapse of specimens is controlled by macro shear cracks along the diagonal direction of the specimen, which are effectively identified by velocity trend arrows and contact force distribution. Finally, comparative analysis between failure pattern of pre-holed specimens under static and dynamic loads were conducted.

This paper is a summary of many of the key findings on the application of geosynthetics in tailings storage facilities. Topics include the compressibility and permeability of tailings, the equations predicting leakage through circular and non-circular geomembrane holes, the effect of the subgrade permeability, and the effect of a lateral drainage system within tailings on leakage predictions. Two commonly encountered engineering problems relating to the piping through circular geomembrane holes and the opening width of non-circular defective geomembrane seams are given to demonstrate the potential application of leakage prediction equations. Meanwhile, issues related to the subgrade imperfection and the long-term performance of both high-density polyethylene (HDPE) and bituminous geomembranes in tailings storage applications are addressed. The research highlights that an appropriate HDPE geomembrane liner can be expected to perform very well for an extremely long time, limiting leakage and contaminant migration from the facility into the surrounding environment if the liner is well constructed on a suitable subgrade.

The mechanisms of creation of intrinsic and impurity trapping centers, the interaction of which forms combined or induced electronic states under the conduction band, have been studied using optical and thermal activation spectroscopy. It is shown that electron-hole trapping centers are created when free electrons are trapped by impurities and ions of the SO2-4 matrix, as well as a result of charge transfer from the excited SO2-4 anion to impurities and to neighboring ions by the reaction (Ο2--Eu3+) and (Ο2-SO2-4). The hole component of the trapping center is formed when holes are localized above the valence band. During relaxation, the combined emission state decays with the transfer of energy from its own matrix to the emitters. [ABSTRACT FROM AUTHOR]

Nitinol alloy is widely utilized across various industries due to its special properties. In this paper, the compound effects of two kinds of energy fields on material removal rate (MRR), hole wall quality, machining accuracy, and recast layer in ultrasonic combined magnetic field assisted EDM (UV-MFEDM were studied and analyzed. In addition, the influence of magnetic field intensity on the efficiency and accuracy of micro-hole machining is analyzed systematically. The results show that the surface quality of the micropore is significantly improved, the MRR is increased by 31.6%, the taper of the micropore is reduced by nearly 30%, the overcut diameter is reduced by nearly 23%, the recast layer is more uniform and the thickness of the recast layer is reduced by nearly half. Appropriate magnetic field intensity proves beneficial for improving micro-hole machining efficiency while reducing both taper angle and diameter overcut of micro-holes. [ABSTRACT FROM AUTHOR]

The oxalic acid complexation method and sulfuric acid heat treatment method were used to synthesize the YMnO3 (YMO) and YMO-SO42- (YMO-SO) photocatalysts. The YMO-SO photocatalyst maintained the crystal structure of YMO, but the particle size increased slightly and the optical band gap decreased significantly. The YMO-SO photocatalyst demonstrates a wide range of light absorption capabilities, covering ultraviolet, visible and near-infrared light. The photocatalytic activity of YMO-SO was investigated with ibuprofen as the target pollutant. The YMO-SO photocatalyst exhibits high ultraviolet (UV), visible and near-infrared photocatalytic activity. Experiments with different environmental parameters confirmed that the best catalyst content was 1g/L, the best drug concentration was 75 mg/L and the best pH value was 7. The capture experiment, free radical detection experiment and photocatalytic mechanism analysis confirmed that the main active species of YMO-SO photocatalyst were hole and superoxide free radical. [ABSTRACT FROM AUTHOR]

This paper is a summary of many of the key findings on the application of geosynthetics in tailings storage facilities. Topics include the compressibility and permeability of tailings, the equations predicting leakage through circular and non-circular geomembrane holes, the effect of the subgrade permeability, and the effect of a lateral drainage system within tailings on leakage predictions. Two commonly encountered engineering problems relating to the piping through circular geomembrane holes and the opening width of non-circular defective geomembrane seams are given to demonstrate the potential application of leakage prediction equations. Meanwhile, issues related to the subgrade imperfection and the long-term performance of both high-density polyethylene (HDPE) and bituminous geomembranes in tailings storage applications are addressed. The research highlights that an appropriate HDPE geomembrane liner can be expected to perform very well for an extremely long time, limiting leakage and contaminant migration from the facility into the surrounding environment if the liner is well constructed on a suitable subgrade. [ABSTRACT FROM AUTHOR]

The nature of the impurity emission and the process of creating intrinsic and impurity electron-hole trapping centers were studied by spectroscopic and thermal activation methods in Na2SO4 - Pb and K2SO4 - Pb phosphors. The combined radiative electronic state is formed from intrinsic SO3−4- SO−4 and impurity Pb+ - SO−4 electron-hole trapping centers in UV-irradiated phosphors with a photon energy of 6.2 eV at 80 K. Emissions of 3.2 eV and 3.6 eV resulting from irradiation with photons with an energy of 6.2 eV are associated with intracenter transitions of 3p1- 1s0 in Pb2+ located in nonequivalent positions of the Na2SO4 lattice.

Orifice reduction strategies for da Vinci robotic surgery have been a hot topic of research in recent years. We retrospectively analyzed the perioperative outcomes of robotic-assisted thoracoscopic surgery (RATS) with two, three, and four-hole approaches in radical lung cancer surgery. Our results revealed that the two-hole group has advantages in terms of operative time, postoperative 3-day drainage, postoperative drainage time, postoperative hospital stay and postoperative day 3 visual analogue scale (VAS) pain scores. There were no significant differences between the three groups in terms of intraoperative bleeding, number of lymph nodes dissected, VAS pain scores on postoperative days 1 and 2, and postoperative complications. In addition, the two-hole group was superior to the three-hole and four-hole groups in terms of C-reactive protein (CRP), procalcitonin (PCT) and interleukin 10 (IL-10). In summary, the RATS two-hole approach has advantages in operation time, rapid recovery after operation and some postoperative inflammatory indicators, and is worth promoting in hospitals that are skilled in three-hole and four-hole da Vinci robot surgery and have conditions. [ABSTRACT FROM AUTHOR]

This article investigates the microscopic mechanism of crack initiation and propagation in three-dimensional embedded cracks in brittle materials containing circular holes. First, a method for the development of transparent, brittle materials is proposed. Second, UCS tests were conducted on transparent, brittle materials containing circular holes and internally embedded three-dimensional cracks. Finally, a numerical model was established in PFC3D to analyze the crack initiation and propagation mechanism. The results show that when α = 0° (α refers to the pre-existing crack inclination), the upper tip of the pre-existing crack appears as a tensile wing crack, and the lower tip of the pre-existing crack appears as a tensile–shear mixed crack. When α = 30°, no wing crack appears, and the tensile crack on the fracture surface only appears after the hole cracks. When α = 60 and 90°, a tensile wing crack and an anti-wing tensile–shear mixed crack appear at the upper tip of the pre-existing crack. A tensile wing crack appears at the lower tip of the pre-existing crack and appears "self-limiting". During the propagation of wing cracks to the surface of the specimen, the transition sequence of the crack propagation mechanism is tensile through failure—tension-shear mixed failure—tensile failure. It can be seen that the interaction between the crack and hole has an important influence on the evolution mechanism of the crack and the failure mode of the specimen. [ABSTRACT FROM AUTHOR]

The oxalic acid complexation method and sulfuric acid heat treatment method were used to synthesize the YMnO3 (YMO) and YMO-SO42- (YMO-SO) photocatalysts. The YMO-SO photocatalyst maintained the crystal structure of YMO, but the particle size increased slightly and the optical band gap decreased significantly. The YMO-SO photocatalyst demonstrates a wide range of light absorption capabilities, covering ultraviolet, visible and near-infrared light. The photocatalytic activity of YMO-SO was investigated with ibuprofen as the target pollutant. The YMO-SO photocatalyst exhibits high ultraviolet (UV), visible and near-infrared photocatalytic activity. Experiments with different environmental parameters confirmed that the best catalyst content was 1 g/L, the best drug concentration was 75 mg/L and the best pH value was 7. The capture experiment, free radical detection experiment and photocatalytic mechanism analysis confirmed that the main active species of YMO-SO photocatalyst were hole and superoxide free radical.

We prove that there exists a function f(k) = O (k² log k) such that for every C4-free graph G and every kEin N, G contains either k vertex-disjoint holes of length at least 6 or a set X of at most f(k) vertices such that G X has no hole of length at least 6. This answers a question of Kim and Kwon. [ABSTRACT FROM AUTHOR]

A new metal-cutting tool is developed—reamer-broacher, which improves the cutting process by minimizing adverse factors. By theoretical and experimental studies the regularities of the influence of cutting modes on the quality of processing with the subject tool are established. [ABSTRACT FROM AUTHOR]

The influence of surface texture in the form of pits on the wear resistance of tribo-compounds under conditions of limit friction was investigated. At the first stage of research, the mechanism of lubricant behavior between the contacting surfaces and inside the holes was modeled. The limiting condition of the rotation frequency of the sample (n>27) was established, under which a drop of lubricant “leaves” the hole in the upper position of the sample and remains in the space between the sample and the surface of the counter body, ensuring the regeneration of the boundary lubricating film on the surface of the tribo-contact when it is destroyed. When the rotation frequency of the sample is reduced (n<27), the lubricant droplet remains in the hole and does not affect the processes of the boundary lubricant film. At the second stage, experimental studies of tribo-combinations with a textured hole surface under conditions of extreme friction were carried out. It was established that the high wear resistance of the textured hole surfaces is provided by the high protective effect of the texture, as well as the high efficiency of the marginal lubricating film. It has been proven that the strengthening of the surface texture by the method of ion-plasma thermocyclic nitriding additionally increases the wear resistance by 1.7 times due to the high protective effect of surface nitrided layers and their high hardness (up to 9500 MPa). This strengthens the effect of inhibiting the occurrence of defects in the surface layers of tribo-contact, ensures a high rate of wetting of the places of actual contact of tribo-connections, and speeds up the process of regeneration of the boundary lubricating film. Research results can be used to modify the surface layer of heavily loaded parts operating under extreme operating conditions with limited supply of lubricant under various types of friction and wear. [ABSTRACT FROM AUTHOR]

The creation of a combined radiative state at 2.95–3.1 eV in the phosphor C a S O 4 − D y   3 + has been investigated using vacuum ultraviolet and thermoactivation spectroscopy methods. It is shown that the combined radiative electronic state is formed from the radiative electronic states of the impurity electronic trapping centers D y   2 + −   S O 4 − and the intrinsic electronic radiative states S O 4 3 − − S O 4 − during the excitation of the anion complex S O 4 2 − , as a result of charge transfer from the excited anion complex O   2 − − D y   3 + to the impurities and the neighboring anion complex O 2 − −   S O 4 2 − . In the C a S O 4 − D y phosphor, the combined radiative electronic state and impurity emission of D y   3 + , 2.16 eV and 2.56 eV are excited by photons with energies of 3.95–4.0 eV and 4.5–4.6 eV. Energy transfer from the matrix to the D y   3 + impurities is revealed upon thermal exposure as a result of the ionization of the electronic capture centers of D y 2 + and S O 4 3 − . [ABSTRACT FROM AUTHOR]

The article presents a numerical simulation of nonstationary heat conduction problems under complex heat transfer, which includes such heat transfer mechanisms as heat conduction, convection, and radiation. The Stefan-Boltzmann law describes the resulting heat transfer by radiation between two bodies, where the heat transfer coefficient is a function of the body surface temperature. An algorithm and software for solving the heat conduction problem using the finite element method were developed, and the influence of external impacts on the temperature field distribution in the vicinity of an insulated circular hole in the center of the body was studied. The temperature fields were investigated for various boundary conditions in the hole of the plate and the corresponding isotherms were given.

Holes and joints are widespread and coexisting flaws in natural rock. The spatial distribution of combined flaw significantly affects the instability process of fractured rock. To study the influence of ligament length and joint angle on failure characteristics, uniaxial compression experiments are carried out on specimens containing hole-joint combined flaw assisted by acoustic emission (AE) and digital image correlation (DIC) technologies. As the ligament length increases, the mechanical parameter curves decrease first and then rise, showing a U-shape or V-shape. DIC results show that the hole performs a strong inhibition on the crack propagation from the inner joint tips, which will be weakened with the increase of ligament length. The driving displacement field of wing cracks and the type of cracks outside the joint are affected by joint angle variation. The cracks in rock bridge area are generally tensile-shear or shear type. According to AE analysis, the proportion of tensile signals decreased from the pre-peak failure stage to the post-peak stage, and the tensile signal is lower than 50% in the late loading stage, indicating that the shear crack dominates the final failure of specimens.

Graphene derivatives have been attracting extensive interest as effective antimicrobial agents. In the present study, ternary nanocomposites are prepared based on graphene oxide quantum dots (GOQD), polyaniline (PANI), and manganese oxides. Because of the hydrophilic GOQD and PANI, the resulting GPM nanocomposites are readily dispersible in water and upon photoirradiation at 365 nm exhibit antimicrobial activity toward both Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus epidermidis (S. epidermidis). Notably, the nanocomposite with a high Mn2+ and Mn4+ content is found to be far more active than that with a predominant Mn3+ component, although both samples feature a similar elemental composition and average Mn valence state. The bactericidal activity is largely ascribed to the photocatalytic production of hydroxy radicals and photogenerated holes; both are known to exert oxidative stress on bacterial cells. Further antimicrobial contributions may arise from the strong affinity of the nanocomposites to the cell surfaces. These results suggest that the metal valence state may be a critical parameter in the design and engineering of high-performance antimicrobial agents based on metal oxide nanocomposites.

The Na2SO4 − Dy samples were obtained by slow evaporation method. The spectroscopic methods were used to study the mechanisms of formation of electron and hole trapping centers. Intrinsic recombination emission of 2.9–3.1 eV and impurity emission of 2.55 eV and 2.15 eV are excited at 4.0–4.5 eV. Intrinsic SO3−4 − SO−4 and impurity Dy2+ − SO−4 trapping centers were revealed. The local levels corresponding between the electron and hole trapping center are 4.0–4.5 eV.

The current study employs the finite element method to compare stress concentration pertaining to a graphite / epoxy rectangular laminated composite plate that possess holes in different shapes. The hole enables redistributing in-plane stresses, impacts the stress concentration factor (SCF), and focuses maximum stress near the hole. The ANSYS program has been designed to be employed for parametric studies pertaining to plates that have a hole under uniaxial in-plane load. Analysis was done for angle-ply, four-layered symmetrically laminated rectangular plates that include different stacking sequences ± θ.

This article focuses on the technologies used by a manufacturing company to produce threads in chrome–nickel steel 1.4301 at specific sheet thicknesses. To enhance production quality, two specific technologies were chosen for hole formation, considering the requirements of the company. Both conventional drilling and nonconventional laser cutting methods were evaluated as potential techniques for hole production. Conventional thread-cutting technology and progressive forming technology were employed to create metric internal threads. The aim of integrating these diverse technologies is to identify the optimal solution for a specific sheet thickness in order to prevent the occurrence of defective threads that could not fulfil the intended purpose. The evaluation of the threads and holes relies on the examination of surface characteristics, such as the quality of the surface, as well as the lack of any signs of damage, cracks, or burrs. Furthermore, residual stresses in the surface layer were monitored because these stresses have the potential to cause cracking. Additionally, extensive monitoring was performed to guarantee that the form and size of the manufactured threads were correct to ensure smooth assembly and optimal functionality. [ABSTRACT FROM AUTHOR]

Graphyne is a material that has unique mechanical properties, but little is known about how these properties change when the material has holes. In this work, the effect of hole geometry, considering circular, triangle, and rhombus hole configurations, on the mechanical nonlinear response of γ-graphyne structures is studied. Graphyne, graphdiyne, graphyne-3, and graphyne-4 structures are under investigation. An efficient nonlinear finite element analysis (FEA) method is adequately implemented under large deformations for this purpose. The study varied the size and shape of the holes to understand how these changes affect the nanostructure's mechanical response. The results indicate that the hole geometry significantly impacts the mechanical nonlinear response of γ-graphyne structures. The holes' size and shape affect the structures' elastic behavior, deformation, and strength. The findings can be used to optimize the design of γ-graphyne structures for specific mechanical applications. The study highlights the importance of considering the hole geometries in the design and fabrication of these materials. [ABSTRACT FROM AUTHOR]

The symmetrical fissures located within the surrounding rock of the roadway (borehole) in tunnel engineering activities can easily induce damage and instability of the surrounding rock. Therefore, studying the impact of perforated symmetrical fissures on the mechanical properties of rock with a hole has significant practical significance. Based on indoor experimental results, conventional triaxial compression simulations were performed on symmetrical fissure-hole sandstone using PFC2D. The impact of the dip angle and length of symmetric fissures on the mechanical properties of the hole-containing sandstone was analyzed. Furthermore, the relationship between crack propagation and the macroscopic mechanical properties of the specimen was discussed. The results show that: (1) The deterioration effect of symmetric fissures on hole-containing sandstone can be controlled by increasing the fissure dip angle, suppressing the stress drop phenomenon. However, increasing the fissure length exacerbates the deterioration effect. (2) The effect of symmetrical fissure dip angle on the displacement field near the hole decreases with increasing dip angle while increasing fissure length exacerbates the effect of fissures on the displacement field. (3) As the angle between the fissure and the vertical principal stress increases, the degree of tensile failure weakens while the degree of shear failure increases. (4) During the crack development phase, the extension of the stress concentration zone drives rapid crack growth. It exhibits a stress drop in the macroscopic mechanical properties, followed by the evolution of the stress field with loading, allowing rapid expansion of the microcracks and eventually leading to rock destabilization damage. [ABSTRACT FROM AUTHOR]

Perforeli çimentolu levhalar özellikle iç mekân gürültü kontrolünde bir ses emici malzeme olarak kullanılmaktadır. Bu çalışmada, plakaların bir yüzeyinden ortalama 4 mm genişliğinde ve 6 mm derinliğinde oluklar (yarıklar) açılarak bir yüzü oluklu ve derzli form kazandırılmıştır. Çalışma kapsamında akustik performans irdelemesi için üç ayrı perforasyon oranı tasarlanmış olup sırasıyla %5.5, %8.0 ve %12.6 oranları elde edilecek şekilde levha örneklerinin diğer yüzeyinde ortalama 10 mm derinliğinde delikler açılarak perforeli test örnekleri hazırlanmıştır. Bu forma dönüştürülen levhaların ses yutma özellikleri irdelenmiştir. Delikli perforeli test örnekleri için uygulanabilirlik kesitine bağlı olarak 3 ayrı grup numune hazırlanmıştır. Bunlar; tek bileşenli yalın formda derzli perforeli çimento bağlayıcılı akustik levha (Yalın-I levhası), geotekstil katmanlı iki bileşenli derzli perforeli çimento bağlayıcılı kompozit akustik levha (Geo-II levhası) ve polietilen esaslı kauçuk katmanlı iki bileşenli derzli perforeli çimento bağlayıcılı kompozit akustik levha (PE-II levhası). Her üç grubun ses yutma özelliği referans örneği olarak test edilen düz-dolu yüzey formunda herhangi bir derz ve perfore işlemi yapılmamış elyaf takviyeli çimentolu yalın levha örneği (kontrol levhası) ile karşılaştırılmıştır. Çalışma sonuçlarına göre, derzli perforeli form kazandırılmış levha örneklerinin perforesiz düz levha formu performansları ile karşılaştırıldığında görüldüğü üzere düz levhanın absorpsiyon özelliği yüksek frekans band değişiminde artış gösterirken, derzli perforeli levhaların absorpsiyon özelliğinin ise düşük frekans bölgelerinde daha etkin absorpsiyon özelliği göstermektedir. Ayrıca, polietilen esaslı kauçuk malzemenin yalıtım katmanı olarak kullanımı, derzli ve perforeli kompozit formda çimento bağlayıcılı akustik levhaların ses azaltma karakteristiğine perforasyon oranına bağlı olarak yüksek emici ve/veya mükemmel emici birer nitelik kazandırmaktadır.

The Na2SO4 samples were obtained by slow evaporation method. The mechanisms of the formation of electron and hole trapping centers are investigated by spectroscopic methods. Intrinsic recombination emission of 2.9–3.1 eV and impurity emission of 1.85 eV are excited at 4.0–4.5 eV. Intrinsic SO3−4 − SO−4 and impurity Mn+ − SO−4 trapping centers were revealed. The local levels corresponding between the electron and hole trapping center are 4.0–4.5 eV. The decay of intrinsic and impurity trapping centers was recorded at temperatures of 130–150 K and 280–350 K.

Drilling is an extremely important process widely used in the manufacture of fuel control equipment. The sustainable drilling process of aluminum alloy is promising for today's industry, which reduces energy and coolant consumption without compromising the quality of workmanship. This article examines the effect of feed and spindle speed on maximum power input, the height of the burrs generated during drilling, and the resulting deviation in the diameter of the drilled hole.

This article investigates the microscopic mechanism of crack initiation and propagation in three-dimensional embedded cracks in brittle materials containing circular holes. First, a method for the development of transparent, brittle materials is proposed. Second, UCS tests were conducted on transparent, brittle materials containing circular holes and internally embedded three-dimensional cracks. Finally, a numerical model was established in PFC3D to analyze the crack initiation and propagation mechanism. The results show that when α = 0° (α refers to the pre-existing crack inclination), the upper tip of the pre-existing crack appears as a tensile wing crack, and the lower tip of the pre-existing crack appears as a tensile–shear mixed crack. When α = 30°, no wing crack appears, and the tensile crack on the fracture surface only appears after the hole cracks. When α = 60 and 90°, a tensile wing crack and an anti-wing tensile–shear mixed crack appear at the upper tip of the pre-existing crack. A tensile wing crack appears at the lower tip of the pre-existing crack and appears “self-limiting”. During the propagation of wing cracks to the surface of the specimen, the transition sequence of the crack propagation mechanism is tensile through failure—tension-shear mixed failure—tensile failure. It can be seen that the interaction between the crack and hole has an important influence on the evolution mechanism of the crack and the failure mode of the specimen.

There is a real and distinct connection between anxiety and nightmare, as it had been pointed out by both Freud and Lacan. To which Joyce seems to add: "History is a nightmare from which I am trying to awake". Moreover, the dream can be considered as having a kind of nightmarish kernel, in the same way in which fantasy has a kind of comical twist, and science has its truth revealed as sciencefiction. The subject is first of all the subject of the unconscious, filled with guilt when faced with his destiny as crushing demand of the Other. It is only within the psychoanalytic discourse that this feeling of guilt is deconstructed and reveals the hole out of which one can say "that no" to both castration and to this totalitarian demand of the Other, source of anxiety, and thus of nightmare, be it as history in general or for the individual. Mircea Daneliuc brilliantly decodes this intricate link between history and nightmare in his film The Cruise (1981), which takes place in Ceaușescu's Romania in the 1980s. [ABSTRACT FROM AUTHOR]

Surface tension has a significant influence on the mechanical response of solids at small scales to external loadings. Conventional small deformation theories remain effective in capturing such an influence provided the corresponding boundary condition incorporates some measure of the deformed configuration of the solid's surface in evaluating the surface tension–induced traction acting on the solid. Since the governing equations arising from conventional small deformation theories for the bulk of the solid are defined strictly in the undeformed configuration, they may be sometimes incompatible with the surface tension–related boundary condition incorporating certain measure of the deformed configuration, leading to an inconsistent boundary value problem. To clarify how to pose a self-consistent boundary value problem involving surface tension, we consider the plane deformation of a perforated medium with its internal boundary endowed with surface tension and surface elasticity and its external boundary subjected to a mechanical loading. We first review three kinds of related boundary conditions on the internal boundary of the medium: the Gurtin–Murdoch-type boundary condition and two modified boundary conditions based on the change-in-curvature formula. We then derive the resultant force and moment of the traction caused by surface tension and surface elasticity for each of the boundary conditions. We show that for the Gurtin–Murdoch-type boundary condition, the resultant force vanishes unconditionally but the resultant moment depends on the rigid-body rotation of the medium, while for the two modified boundary conditions, both the resultant force and resultant moment (about a certain point) rely on local deformation gradients and the curvature of the internal boundary of the medium. Consequently, for the Gurtin–Murdoch-type boundary condition, one may easily establish a self-consistent boundary value problem by specifying an appropriate mechanical loading, while for the two modified boundary conditions, the boundary value problem is only occasionally self-consistent for some special and compatible combinations of the geometry of the internal boundary and the mechanical loading. Nevertheless, if the medium becomes infinitely large with its external boundary extremely distant from the internal boundary, then the boundary value problem corresponding to either of the three boundary conditions is always self-consistent for an arbitrary configuration of the internal boundary and an arbitrary far-field loading. [ABSTRACT FROM AUTHOR]

A numerical code has been designed and implemented to find the stress at any material point in a holed wedge material due to any number of crystal or real screw dislocations in the wedge. The code implements the image dislocation method together with the collocation-point method to find stresses at any material point. We demonstrate that the combined analytical–numerical method (analytical with the image dislocations and numerical with the collocation-point method) is valid in that it produces stress fields giving rise to zero traction on free surfaces as well at an arbitrary number of collocation points on void surfaces. In addition, the method makes it possible to find the Peach–Koehler force (PKF) acting on a real screw dislocation at any point in the wedge, as well as to determine points of equilibrium, where the PKF is zero. Numerous and easy to interpret contour plots reveal the utility of this method which was carried out using the mathematical software MATLAB. [ABSTRACT FROM AUTHOR]

The dynamic performance of high-speed railway systems' stability, comfort, and safety is an essential topic worldwide. The multiorder elastic modes of components are the key factors. It is the core technology to ensure the quality of the backfill layer of flexible cement-emulsified asphalt mortar (CA mortar) in reducing the elastic vibration structure of the car body. This research results from the manufacturability verification of the Beijing–Shanghai high-speed railway. Four theoretical model methods are used in the research: experimental observation data analysis, simplified orthogonal test, phase contrast and computational analysis, and grey relational analysis to improve the performance indicators of CA mortar. The research conclusion confirms that the best mix ratio, high gas content, and poor fluidity are the core factors affecting the technical indicators of mortar and the focus on quality control. Through this research work, a wealth of theoretical methods and practical experience data to ensure the quality and qualified indicators of mortar have been summarized, and the prevention of acute diseases (bubble and through-holes) has played a guiding role. The research result ensured the optimal quality characteristics and indexes of viscoelastic materials, and the operation of high-speed railways was safe. [ABSTRACT FROM AUTHOR]

Copyright of Polymer Materials Science & Engineering is the property of Sichuan University, Polymer Research Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Aerospace and aircraft companies follow a pyramidal structure of testing, ranging from specimen tests to full‐scale structure tests, for aircraft structural design. At the base level, open hole strength evaluation is one of the qualification procedures for composite components. The holes are made in the structural components to accommodate bolts and rivets in order to assemble the parts into a single unit. Holes in the component are also used to fulfill functional requirements, such as the passage of wire bundles. FRP components are sensitive to these holes/cutouts as substantial decrement in the strength is observed in several experiments. The degradation in the strength of the component is due to stress concentration around the hole. This review aims to comprehend the effect of the hole on the mechanical properties of FRP laminates; the emphasis is mainly on CFRP laminates and experimental results. An overview of tensile, compressive, flexural and post buckling properties of laminates with the hole is presented to aid in the optimal design of the component. Finally, the failure mechanism during loading is discussed and described through a graphical presentation. [ABSTRACT FROM AUTHOR]

In recent years, cotton fabrics, especially summer clothing, have been increasingly favored by young people in domestic market for their mercerization, moisture absorption, breathability and soft touch and the market potential demanding for cotton cloth has been huge. Under the requirement of energy saving and emission reduction for high energy-consumption printing and dyeing enterprises by the Chinese government, most of the dyeing plants have adopted the more efficient short process of one-bath one-step cold pad-batch for cotton cloth bleaching. The hydrogen peroxide added in this process is over three times more than that of the traditional process. After oxygen bleaching mercerization of the cotton cloth, local excessive oxidation occurs and oxygen bleaching holes are more likely to occur. In the production process of cotton cloth, the selection process of different cotton cloth specifications is different, resulting in complex reasons for holes.Therefore, it is necessary to find out the causes of holes in the production process and formulate corresponding preventive measures and technological processes. In this experiment, aldehyde cellulose produced by bleaching cotton cloth with hydrogen peroxide was oxidized by self-made weak oxidation reagent, so that metal silver atoms could be directly precipitated on the cloth surface. According to the number of silver atoms precipitated from the cloth surface and the hole opening, the color depth was formed, the intensity of hydrogen peroxide decomposition was judged, and whether the hole on cotton cloth was caused by excessive oxidation was proved from the side. Then, 1 mL of 8% silver nitrate solution, and 2 mL of mixed solution of 20% sodium bicarbonate and 20% caustic soda were added into 17 mL of deionized water. and shaken up quickly. Subsequently, 5g of cloth with holes was boiled in the solution for 2 min under100 ˚C, and then it was washed with deionized water. The color difference around the hole of that fabric was observed. The cotton cloth with holes were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscope (SEM) and X-ray photoelectron spectroscopy.The self-made test results show that the holes caused by mechanical and other external forces have the same color as the holes on the cloth surface, indicating that the silver content precipitated is basically the same As for holes caused by local overoxidation, the color of the opening is darker than the cloth surface, and the silver content of the hole area is obviously higher than that of other parts. During the test, it is found that the decomposition rate of hydrogen peroxide is affected by temperature, pH value and metal ions, and the symbionts and textile auxiliaries in gray cloth can inhibit the decomposition of hydrogen peroxide. Fourier transform infrared spectroscopy shows that the structure of most cotton fiber polysaccharides changes into dialdehyde cellulose after oxygen bleaching. After treatment with self-made hole breaking detection reagent, the aldehyde group and silver ions have oxidation-reduction reaction, and the aldehyde group disappears. Through characterizing the cotton cloth tested by self-made hole detection reagent, it is concluded that the black particulate matters on the cotton cloth surface are silver atoms. The hole areas are the same shade as the other cloth surface, such as burnt holes, hook holes, weak yarn strength holes and damp mildew holes. Nevertheless, compared with the main elements of the cloth surface, there are more black silver atoms in the hole than in other places, which makes the color darker than in other places. As the demand for oxygen bleached mercerized cotton cloth is gradually increasing in domestic market, it is significant to determine the causes of holes for production prevention, which will be beneficial to cost saving and energy conservation and emission reduction. For the cotton cloth with holes during the production process, the semi-finished cotton cloth can be treated through lower tension process on the machines, increase the friction between yarns by adding adhesives, or even be changed to the overflow or air cylinder with low tension for dyeing, so to reduce the probability of holes as much as possible and minimize the loss. In the future, the weaving mill will equip the magnetic metal cloth inspection machine in the gray cloth inspection. As long as the fabric has more than a certain amount of metal ions, the metal alarm device on the cloth inspection machine will raise the alarm to prevent the problematic gray cloth flowing into the next process, which guarantees the good quality. [ABSTRACT FROM AUTHOR]

Aluminum alloy Ak5m is widely used in the aerospace and automotive industries to replace heavier alloys. This is due to its excellent properties of high specific strength, high corrosion resistance, good formability and low manufacturing cost. Ductility and heat generation during drilling AK5MCH often leads to the formation of burrs at the inlet and outlet from the surface of the workpiece. This study shows the effect of cutting speed and drilling conditions on the formation of burrs in the AK5MCH alloy. Drilling is carried out using coolant and without coolant using drills made of high-speed steel with a diameter of 6,0 mm with cutting speeds of 20, 42 and 60 m/min at a constant feed of 0,15 mm/rev. This study showes that drilling AK5MCH with a cutting speed of 42 m/min using a coolant is advantageous, as it leads to the least tool wear and minimal burr formation.

In wireless sensor networks, sensor nodes are deployed to collect data, perform calculations, and forward information to either other nodes or sink nodes. Recently, geographic routing has become extremely popular because it only requires the locations of sensor nodes and is very efficient. However, the local minimum phenomenon, which hinders greedy forwarding, is a major problem in geographic routing. This phenomenon is attributed to an area called a hole that lacks active sensors, which either prevents the packet from being forwarded to a destination node or produces a long detour path. In order to solve the hole problem, mechanisms to detect holes and determine landmark nodes have been proposed. Based on the proposed mechanisms, landmark-based routing was developed in which the source node first sends a packet to the landmark node, and the landmark node then sends the packet to the destination. However, this approach often creates a constant node sequence, causing nodes that perform routing tasks to quickly run out of energy, thus producing larger holes. In this paper, a new approach is proposed in which two virtual ellipses are created with the source, landmark, and destination nodes. Then guide the forwarding along the virtual ellipses. Furthermore, a recursive algorithm is designed to ensure a shortcut even if there are multiple holes or a hole has multiple landmarks. Thus, the proposed approach improves both geographic routing and energy efficiency routing. Simulation experiments show that the proposed approach increases the battery life of sensor nodes, lowers the end-to-end delay, and generates a short path.

An offset of roller cone rotation centerlines is used to increase the mechanical penetration rate while drilling in soft rocks. This enables increasing the area of a cutting structure teeth contact with a bottom hole. The analysis of offset cone drill bit (cutting structure) teeth wear showed that particularly significant wear is characteristic of the transition zone from the heel cone to the nose cone; which leads to significant reduction in the mechanical rate of penetration and a rapid decrease in the hole diameter. The purpose of this paper is to conduct a theoretical research on the nature and conditions of interaction between heel and peripheral nose cones of offset roller cone bits with a bottom hole; which is aimed at improving the efficiency of rock cutting by offset roller cone bits. To achieve the purpose; the authors analyzed data on the nature and causes of wear of existing offset roller cone bit cutting structure (teeth); developed a mathematical model in a cylindrical coordinate system allowing to determine the location and geometric parameters of the gage cone contact area with the hole wall for different roller cone bits sizes; developed a computer solid model for checking the adequacy of the mathematical model by comparing these two models; prepared recommendations for further improvement of the design of existing offset roller cone bit cutting structure (teeth). The research was carried out by the method of mathematical simulation of geometric figures and bodies corresponding to roller cones and a hole. The research has revealed that significant adjustments need to be made to the geometry of the roller cone teeth (currently being patented). This would allow decreasing the areas of cone heel blunting by 15–20 % as well as providing more prolonged contact of base and gage cones with bottom hole and wall surfaces. This allows to reduce wear of teeth in the transition zone of the generatrix from the peripheral nose cone to the gage (heel) cone of the roller cone and to maintain the required specific pressure on the cut rock for a longer period of time and; as a result; to increase both the mechanical penetration rate and the service life of the drilling tools.