Corner Structures Research Articles

Influence of main cutting edge structure on hole defects in CFRP/titanium alloy stacks drilling

Tool structure plays an important role in CFRP/titanium alloy (Ti) stacks drilling. The purpose of this paper is to study the performance of drills with different main cutting edge structures in CFRP/Ti stacks drilling. The effects of the main cutting edge structure on thrust force, chip morphology, interface damage and burr are analyzed. The results show that the interface damage is the least after candle stick drill drilling, because the outer corner tip structure can remove part of heat that left on the machined surface in the cutting stage of the main cutting edge. Compared with the other two kinds of drill bits, the height of burr produced by candle stick drill at titanium alloy layer is the smallest. The reason is that outer corner tip structure of the candle stick drill can counteract part of the radial cutting force which produced by the main cutting edge, and push the material inside to facilitate material removal. The outer corner structure of the drill bit has an important influence on the thrust force, the interface damage and the exit burr, so the special drill design for CFRP/Ti stacks must focus on the outer corner structure.

Effect of mold corner structures on the fluid flow, heat transfer and inclusion motion in slab continuous casting molds

Mold corner structures will influence the multiphase flow, heat transfer and inclusion motion behaviors in the mold, which have significant impacts on the quality of strands. Herein, a three-dimensional fluid flow and heat transfer mold model was employed to investigate the effect of four different corner structures (right-angle, big-chamfered, multi-chamfered and fillet) on the multiphase flow, heat transfer and inclusion motion behaviors in the mold. The Volume of Fluid model was used to describe the molten steel and slag, while the Discrete Phase Model was employed to track the motion of non-metallic inclusions. The dynamic mesh was applied to simulate the mold oscillation. Results show that the chamfered structures can obviously increase the flow velocity around the strand corner, especially for the big-chamfered mold. The chamfered molds can remarkably improve the corner temperature of strands at the mold exit, and the fillet mold is the most effective. The temperature on the narrow and chamfered faces of the copper plate in the chamfered molds is lower than that in the right-angle mold. The maximum amplitude of temperature fluctuation of the meniscus reaches 4.6 K. The shell thickness around the strand corner in the chamfered molds is obviously thinner than that in the right-angle mold. In addition, the chamfered structures will increase the number of inclusion particles around the strand corner.

Study on the Propagation Characteristics of Partial Discharge Electromagnetic Waves in Gas Insulated Line

Defects in the gas insulated line can cause partial discharge, and the electromagnetic wave is generated. The finite difference time domain method is used to research the propagation of electromagnetic wave in gas insulated line structures. The electric field strength of time-domain waveform is selected as characteristic factor for analysis. By changing the gas insulated line model, the attenuation of electromagnetic wave through double insulator, L-type corner, T-type corner, straight tube and different GIL sizes is studied. In the straight tube structure, the amplitude attenuation of electromagnetic wave is linear and the attenuation band is between 1 GHz and 1.7 GHz. In the insulator, basin insulator has more serious influence on signal isolation than disc insulator. After passing through the insulator, the signal attenuation is obvious in the frequency band above 1 GHz. The amplitude of electromagnetic wave decreases more seriously through the corner structure, and the attenuation is at the whole frequency band. In different sizes of gas insulated line, the larger diameters of shell and conductor, the larger electromagnetic wave will be, and the faster attenuation will be; the length of gas insulated line cavity has little effect on electromagnetic wave. The theoretical research is expected to help to arrange the position of ultra-high frequency sensor reasonably.

Application of graphene/two-dimensional amorphous ZrO2 supported Pd single atom catalysts in CO oxidation: First principles

• The development and design of transition metal single atomic catalysts with high stability and high reaction activity is an urgent but challenging task at the same time. In this paper, the crystal (amorphous) ZrO2/graphene sandwich structure supported transition noble metal Pd single atom catalysts was designed creatively, and the interlayer oxidation of CO was studied. In the theoretical calculation, we find that the SACs with this structure has a high carrier mobility. At the same time, the formation energy, the adsorption energy of Pd and the surface energy of IS and FS fully confirm that the sandwich structure can exist stably, and the single atom has effective chemical adsorption on this structure. Graphene rotation will also better protect the surface of ZrO 2 adsorbed by Pd single atom. It further affects the environment of electron distribution, activates the dissociation of CO molecules, and speeds up the progress of the reaction. Therefore, the sandwich structure combines the advantages of the two materials and plays an important role in the stability, adsorption configuration, electron transfer mechanism, adsorption energy and potential barrier of single atom catalysts. Based on the first-principles method of density functional theory (DFT), a two-dimensional graphene/amorphous ZrO 2 composite carrier supported precious metal Pd single atom catalyst was designed, and the catalytic efficiency and catalytic stability of CO to CO 2 in limited domain were discussed. And the effect of the rotation angle between graphene and catalyst carrier on its performance was studied. The electronic properties, transition energy barrier and partial density of states of the relaxed catalysts were calculated and analyzed by first-principles method. The results show that the sandwich structure has good stability and high electron migration, while the corner structure protects the precious metal from escaping from the surface. The reaction energy barrier shows that the catalyst can complete the reaction within the energy barrier of 0.1~0.6 eV in the process of CO catalysis, and the rotation angle can move the reactant orbit faster near the Fermi level, speeding up the reaction. We propose a structural design method for a new type of single atom catalyst, and provide a reliable design basis and new design ideas for CO catalytic oxidation and green energy.

Investigation of heat transfer and flow properties in separated flow and reattachment regions for liquid sodium flow at fast reactors

In many engineering applications, such as heating and cooling systems, flow around an automobile or building, separation and reattachment regions are formed. These regions are very important for controlling the amount of heat and mass transfer. Liquid sodium is used as heat transfer fluid in many areas having a high temperature, especially nuclear reactors. In this work, the effects of flow separation and reattachment on the heat transfer and flow properties of step corner structures with different chamfer lengths as h/4, h/2, 3 h/4 and h comparing with and without chamfer (normal) geometry have been numerically investigated in the vertically positioned backward facing step flow geometry for fast reactors that need to be cooled efficiently. One of the walls behind the backward facing step has a constant temperature while the others are adiabatic. The results of the work have been determined by solving steady conservation equations with three dimensional and k-ε turbulence model with Boussinesq approach using ANSYS-FLUENT computer program. Water and liquid sodium have been employed as working fluids. The expansion rate of the backward-facing step is 1.5. The study has been carried out at two different Reynolds numbers: 5000 and 10000. The presented work has been compared with the numerical results of the study found in the literature and it has been seen that they are compatible and acceptable with each other. The results have been exhibited as the variations of Nu number, fluid temperature, turbulence kinetic energy and pressure. Besides, temperature, velocity and streamline distributions have been visualized in backward facing step flow geometry. For Re = 10000, it has been determined that average fluid temperature increment value of the backward facing step geometry with h chamfer length in the liquid sodium flow has been 6.54 K higher than in water.

Enhancement of passive mixing via arc microchannel with sharp corner structure

A novel microfluidic device for efficient passive mixing is reported. A series of sharp corner structures designed on side wall of an arc microchannel was utilized to induce three-dimensional vortices, which strongly stretched and folded the interface and significantly increased the interfacial contact area between different fluids. Additionally, the sharp corner structure induced high radial velocity and reduced the diffusion length because of the restricted effect of the geometrical structure. Eventually, the fluid mixing was significantly enhanced, and a mixing efficiency from ∼87% to 92% was achieved at moderate Reynolds number (Re) from 3.0 to 24.2 (10 to 80 μl min−1). The influence of the sharp corner position on the mixing was also investigated by the experiment and the numerical simulation. With single-layer structure and high mixing efficiency, the present device has great potential in the mixing process in variety of lab-chip applications, such as clinic diagnosis and analytic chemistry.

Microstructural and mechanical investigation of brazing 304L Stainless Steel with corner joint using a Ni-based shim and wire

This study investigated a suitable filler metal, diffusion depth of the elements of this filler metal in the base metal, and its effect on the mechanical properties of brazing bonding of sheets with different thicknesses of 304L stainless steel. For this purpose, brazing was performed with thermal induction under a vacuum of 10−5 mbar and filler metal BNi-2 at the corner structures. First, the microstructure of different joint regions including base metals, Ni affected areas, and interfaces were examined by scanning electron microscopy and then the relationships between microstructure and microhardness were compared. In sheets with different thicknesses, the differences in diffusion depth were observed. Moreover, the microhardness of different areas of the braze was revealed to be completely affected by the diffusion of nickel. Finally, it was found that, for the bonding between 304L sheets with different thicknesses, BNi-2 filler metal had reasonable strength, diffusion, and filling for vacuum applications.

Detection of the corner structures in 3D arrays using scalable masks

Detection of the corner structures in 3D arrays using scalable masks

Benefits of endoscope-assisted microsurgery in the management of pediatric brain tumors.

Microsurgical and endoscopic techniques are vastly utilized in brain tumor surgery. Combining both techniques in the same procedure has different forms and applications. The aim of this work was to discuss the usefulness and describe the technical benefits of endoscope-assisted microsurgery (EAMS) in treating pediatric brain tumors in various anatomical locations. The medical records of 106 children who had undergone EAMS for brain tumors at Children's Cancer Hospital Egypt (CCHE-57357) between January 2009 and January 2017 were reviewed. The patients' ages ranged from 1 to 16 years (mean age 7.5 years). Technical variations, difficulties, complications, strategies, and extent of resection were addressed according to anatomical location. In general, EAMS enabled closer inspection of tumor extension and surrounding vital structures, especially in the hidden corners not appreciable by the microscope alone, such as tumors in the internal auditory canal and cerebellopontine angle contents in 14 cases, all of which were totally excised, and the undersurface of the optic apparatus in 65 craniopharyngiomas. Total excision was achievable in 51 of the 65 craniopharyngiomas; residual tumor was intentionally left behind under endoscopic guidance in the remaining 14 patients to ensure better hypothalamic function. Vision improved in 15 of 16 patients who initially presented with visual defects. Only 4 patients had new-onset postoperative endocrinopathies. For intraventricular tumors, EAMS allowed earlier recognition of tumor pedicle and, hence, earlier control of the blood supply of the tumor and safer total excision of 12 lateral ventricle, 6 pineal and third ventricle, and 9 fourth ventricle tumors. The tandem use of the endoscope and microscope enabled safer tumor dissections that were performed with more confidence in situations in which pure microscopic excision was either not achievable or less safe. Technical strategies, pitfalls, difficulties, and precautions were categorized and described per tumor location. EAMS of pediatric brain tumors is a promising, user-friendly tool that complements microsurgery in the management of these complex lesions. The benefits of 2D endoscopy are added to the benefits of stereoscopic perception. EAMS is especially helpful during the removal of different complex pediatric brain tumors. Simultaneous or tandem endoscopic and microscopic approaches may have the potential for better functional outcomes through better visualization and preservation of vital structures in corners that are hidden from the microscope.

Building wall corner structures, its microclimate and seismic resistance

Widespread low-rise residential buildings with a seismically resistant concrete frame and brick infill walls have lower microclimate levels in cold seasons due to low temperatures on the inner wall corner surfaces.These temperatures are lower if there is a corner column. For Bishkek, this temperature is 4.6 °C lower than that for permissible microclimate, even when the external wall has the required 70 mm of mineral wool slab insulation. It is caused by the negative effect of the wall corner thermal bridge. This effect is determined by ArchiCAD 20 software packages by visualizing the temperature distribution in the cross-section of the corner, which needs an additional thermal insulation layer of 40 mm. Using the LiraSAPR 2013 software package, the authors reduced the square cross-section dimensions of the column by 40 mm to allow for that additional thermal insulation layer. The optimal width of this layer is determined for different options for the meeting angle of two external walls from 70° to 180°. For a typical 90° angle, an acceptable width is 860 mm. With this insulation, it is possible to achieve the required temperature at the corner. The authors eliminated the negative thermal effect of the corner by rounding it with cement-sand plaster. Using the isotherms, it was determined that the rounding radius of 300 mm allowed for equal temperatures on the corner and inner surface of the external walls. The achieved results show that the microclimate formed as in a room without external wall corners.

Theoretical prediction and analysis of hybrid material hat-shaped tubes with strengthened corner structures under quasi-static axial loading

This paper proposes an innovative hybrid material hat-shaped tube with strengthened corner structures (HMHT-SCS) to overcome the disadvantages of the limited energy absorption capacity and lightweight potential of conventional hat-shaped tubes. First, an improved theoretical prediction model of a corner element is established by modifying the simplified super folding element theory, and analytical formulas for energy absorption are derived under quasi-static axial loading. Second, a prediction model of the HMHT-SCS is developed based on the improved prediction model of corner element. Analytical formulas for the mean crushing force (MCF) of single-hat HMHT-SCS and double-hat HMHT-SCS are derived. Then, the accuracy of the analytical formulas is validated through axial crushing tests and simulation analysis. Finally, a discussion is performed. The total effect generation method is proposed to visually characterise the effects of input parameters on output responses. The parametric study showed that the thickness of the hat element of HMHT-SCS has the strongest effect on the MCF, and the thickness and material type of the hat element have similar effects on mass. The thickness of the corner element has a noticeable effect on MCF, while its section width has the weakest effect on the MCF and mass. Furthermore, the comparative analysis showed that the specific energy absorption (SEA) of the HMHT-SCS is larger than that of conventional hat-shaped tubes with one single material. Additionally, the SEA of the ‘aluminium & steel’ HMHT-SCS is larger than that of the ‘steel & aluminium’ HMHT-SCS under the same flow stress.

Research on the variation of mesh stiffness and transmission error for spur gear with tooth profile modification and wear fault

Tooth profile modification and wear are unavoidable, even intentional tooth profile deviations. Both of them have a significant influence on gear mesh stiffness and quasi-static transmission error (QSTE). In this paper, to efficiently and accurately obtain the two internal excitations of spur gear pairs with the above two kinds of deviations together, improved analytical mesh stiffness and QSTE models are proposed. And the effects of corner contact and structure coupling are considered together to overcome the defect of previous works. By comparing with the results of the finite element method, the established models are verified. Through the models, the mesh stiffness and QSTE of the gear pairs with the tooth profile modification and wear simultaneously can be obtained. The results show that both of the two kinds of deviations have significant effects on the limit value and distribution of the mesh stiffness and QSTE. Besides, it can be found that there is a competition between tooth profile modification and wear, and the influence extent of wear is gradually increasing that eventually can override the modification effect. Moreover, wear can affect the selection of tooth profile modification.

A Study on Cross-Shaped Structure of Invar Material Using Cold Wire Laser Fillet Welding (PART I: Feasibility Study for Weldability)

With the need for eco-friendly energy increasing rapidly due to global environmental issues, there is a rapidly increasing demand for liquefied natural gas (LNG). LNG is liquefied at minus 163 degrees Celsius, and its volume decreases to 1/600, giving it a relatively higher storage and transport efficiency than gaseous natural gas (NG). The material for the tanks that store cryogenic LNG must be a material with high impact toughness at cryogenic temperatures. Invar, which contains 36% nickel and has a very low coefficient of thermal expansion, is used for the membranes and corner structures of LNG cargo holds. The cross-shaped Invar structure used in an LNG cargo hold is manufactured through manual tungsten inert gas (TIG) fillet welding, which causes welding distortion and weldability problems. This study is a feasibility study that aims to reduce welding distortion, increase weldability with welding speed, and reduce the steps in an existing process by half by replacing the existing manufacturing method with automatic fiber laser fillet welding. Laser welding using fiber laser parameters are controlled for 1.5 and 3.0 mm thick Invar materials and weldability is secured through cross-section observation. Then, the optimal welding conditions with top and back beads secured are derived through a trial and error method.

WOODWORKING IN THE NORTHERN BUKOVYNA DURING 12th — EARLY 13th CENTURIES

The article deals with the development of woodworking industry in the medieval settlements of Northern Bukovyna which for a long time remained poor studied. During the Middle Ages this territory was covered with significant forest areas, in which there were 22 local breeds of both industrial and rare trees. Accordingly, the woodworking industry here, as well as throughout the territory of Old Rus, had many branches. Being well acquainted with the technical properties of wood the local masters widely used this knowledge depending on the physical and mechanical properties of the breed. Constructing fortifications they used mainly oak and beech, for residential and commercial buildings they used pine and fir. Hardwood (maple, ash) was spread in manufacturing of dishes, while spoons were made from the yarrow, juniper. The remains of precise or carved wooden dishes were discovered in the settlements of Northern Bukovyna. Beech and oak were used in the craft. Containers were made from lime to store loose materials. Local carpenters were aware of various ways of connecting individual wooden elements to each other in a particular product or construction. When erecting dwellings or household structures in corners, the main method was to connect the locks, and when connected horizontally, direct, overhead, spit joints were widely used. At the archaeological sites of Northern Bukovyna, as the open settlements were almost not explored, considerable woodworking toolkit was discovered. It is represented as forms and fragments of blades, ax, bits, drill bits, knives, nail, etc. Their typology has wide analogies among archeological materials from other territories of the Old Rus state and is fully integrated into the generally accepted typology. Thus, materials that characterize the woodworking industry of Northern Bukovyna completely allow trace the evolution of the woodworking business, which developed in terms of economic development of Old Rus.

Meniscofibular ligament: how much do we know about this structure of the posterolateral corner of the knee: anatomical study and review of literature.

The present study is a systematic review of a relatively unknown structure of the posterolateral corner of the knee, the meniscofibular ligament (MFL), aiming at summarizing and broadening current scientific knowledge regarding this ligament anatomy, function, imaging and injury. A systematic review was performed according to the PRISMA guidelines. Medline (PubMed) and Cochrane Library databases were reviewed for every kind of study reporting on the MFL through December 2019. Due to between-study differences in (anatomy, function, imaging, injury) examining the ligament, the findings were summarized from each study, but the results were not pooled. The MFL is a ligament extending between the inferolateral portion of lateral meniscus, just anterior to the popliteus tendon, and the fibular head. It provides stability to the posterolateral corner of the knee joint, it can be demonstrated in magnetic resonance imaging and magnetic resonance arthrography and has a potential role in lateral meniscus injuries. Further research is required to clearly understand the prognosis and management of MFL injury. The current systematic review, focusing only on the MFL of the knee, summarizes the existing knowledge on anatomy, gross morphology, histology, function, biomechanics and imaging and contributes to the further understanding of the MFL.

Detection of the corner structures in images by scalable masks

Under consideration are the scalable masks for detection of corner structures in digital images which are used when processing by a window sliding through an image. The proposed matrices of masks of arbitrary size are constructed by adding rows and columns along the perimeter to the matrix of smaller masks. The submatrices remain unchanged, whereas some new elements are added by repeating the submatrix entries that preserve the structure of the corner. The algorithm can be used in processing visual data of robotics, aerial photography, and crystallography.

Medial-Sided Injuries in the Multiple Ligament Knee Injury.

Multiligament knee injuries (MLKI) are complex and challenging to treat. The posteromedial corner (PMC) structures are commonly torn in MLKI. A thorough and systematic evaluation is imperative to avoid a missed diagnosis and for planning treatment. With several structures injured, the treatment method (operative vs. nonoperative, repair vs. reconstruction), availability of allografts, timing of surgery, and rehabilitation are some of the factors that have to be considered in the decision-making. Persistent valgus instability because of untreated or not healed medial collateral ligament (MCL) tears will increase graft forces on the cruciate ligament grafts, thus increasing the risk of reconstruction graft failure. In recent years, there has been a growing body of literature on the anatomy and biomechanics of the medial structures that has aided in the development of biomechanically and clinically validated anatomic PMC reconstructions. Despite good healing potential of the MCL, in MLKI, surgical treatment is recommended for grade III PMC injuries to aid early rehabilitation and reduce the risk of surgical failure. Several studies have reported satisfactory outcomes after surgical treatment of MLKI involving the medial side. Early functional rehabilitation is imperative to reduce the risk of arthrofibrosis.

Single-longitudinal-mode injection-seeded Q-switched Ho:YLF laser injection-seeded by a double corner cubes unidirectional ring laser

A single-longitudinal-mode pulsed Ho:YLF laser was demonstrated and studied experimentally at 2065.68 nm via injecting a unidirectional seed laser with double corner cubes to a Q-switched Ho:YLF power-oscillator. Up to 733-mW single-longitudinal-mode Ho:YLF laser with a structure of double corner cubes cavity is employed as seed laser with the advantages of narrow linewidth and high antimisalignment sensitivity. For single-longitudinal-mode injection-seeded Q-switched Ho:YLF laser, the output energy of 4.41 mJ is obtained with the repetitive frequency of 100 Hz, pulse width of 136 ns, and slope efficiency of 19.3%. The experimental results show that this method is a potential way to realize single-longitudinal-mode injection-seeded Q-switched Ho:YLF laser with narrow linewidth and high antimaladjustment sensitivity.

Analysis and Optimization Design of Cantilever Structure of Shear Wall Corner

In the frame-shear wall high-rise building, it is necessary to design a special cantilever structure to connect shear wall with two mutually perpendicular frame beams when they do not intersect. In the paper an innovative simplified approach to design special cantilever structure with steel reinforced concrete is presented, which includes two steps as design of feasible steel structure and design of reinforced concrete based on structural analysis and optimization. The demonstrated design idea and design method provide valuable reference for innovative design of complex cantilever structure of shear wall corner with frame beams.

Collateral Ligament Knee Injuries in Pediatric and Adolescent Athletes.

The majority of research on medial (MCL) and lateral (LCL) collateral ligament injuries has focused on adults and combined collateral/cruciate injuries. The purpose of this study was to determine characteristics associated with isolated collateral ligament injuries in adolescents, and assess timing for return to sports. Electronic medical records were queried to identify patients aged below 17 years who sustained a magnetic resonance imaging-confirmed isolated MCL or LCL injury over an 8-year period. Retrospective review then documented patient and injury characteristics and clinical course. General linear modeling was used to analyze risk factors for prolonged return to sports, continued pain or reinjury. Fifty-one knees (33 in males, 65%), mean age 13.8 years (range, 5 to 17), were identified, of which 40 (78%) had MCL injuries. Over half (29, 57%) of knees had an open distal femoral physis including all 5 bony avulsion injuries. Eleven (22%) had LCL injuries of which 3 (6%) had concurrent posterolateral corner injuries. Forty-two (82%) knees had injuries that occurred during sports. Eleven knees (28%) with MCL tears had a simultaneous patellar instability episode. Knee injuries that occurred during sports had 37% shorter recovery time (P=0.02). Eight knees (16%) experienced a reinjury and 12 (24%) were followed over an extended period of time for various knee issues. Football injuries were more likely to be grade 3 (P=0.03), and football and soccer accounted for all grade III injuries. The mean return to sports was 2.2 months, with grade III cases returning at 2.4 months, and 95% of cases within 4 months. Isolated collateral ligament injuries are rare in adolescent athletes. MCL injuries, one-quarter of which occurred in conjunction with patellar instability events, were 4 times more common than LCL injuries, one quarter of which have other posterolateral corner structures involved. Grade III injuries represent 20% to 25% of collateral ligament injuries and occurred most commonly in football and soccer. Level IV-retrospective case series.