Rounded Edges Research Articles

Evaluation on explosion characteristics and parameters of pulverized coal for low-quality coal: experimental study and analysis

Fully utilizing the energy generated by the explosion of pulverized coal will contribute to realize the clean and efficient exploitation of coal resources. The pulverized coal explosion characteristics will be a far-reaching and important task to explore. In this paper, ten kinds of low-quality coals such as high sulfur, high ash, and low metamorphic degree coals were investigated and the minimum ignition energy (MIE), lower explosion limit (LEL), and explosion intensity (EI) parameters under different particle sizes and coal powder concentration conditions were also analyzed combined with a 1.2-L Hartmann tube and a 20-L explosion sphere experimental system. Finally, the morphological characteristics of the exploded coal powder surface were evaluated by scanning electron microscopy (SEM). The results show that the particle size is positively correlated with MIE. LEL shows an inverted "U"-shaped trend with the increasing degree of coal deterioration. The low-rank coal is more flammable and explosive. The maximum pressure PMax at the LEL concentration and maximum pressure rise rate (dP/dt)Max overall value is small. Here, optimum pulverized coal particle size (75μm) for explosive utilization of low-quality coal was determined. Within 50-225 g/m3 of pulverized coal concentration range, the explosion intensity increases with increasing concentration. The smaller the particle size of pulverized coal, the greater the possibility of agglomeration of pulverized coal particles. The surface of the exploded coal particles produces more developed pores. They are irregularly shaped and have more rounded edges than the original coal.

Formulation and optimization of terbinafine HCl loaded chitosan/xanthan gum nanoparticles containing gel: Ex-vivo permeation and in-vivo antifungal studies

Superficial fungal infections require a therapeutic concentration of terbinafine HCl (TB) in the targeted skin tissue, hard to achieve after oral administration due to high protein binding. Therefore, the present study aimed to develop a polymeric nanoparticle-loaded gel system for topical terbinafine delivery with maximum drug retention in skin layers. Terbinafine loaded CH/XG nanoparticles produced by polyelectrolyte complexation method followed by incorporation in carbopol gel. All prepared formulations fell in a size range of 194.28–406.67 nm showing a significantly increasing trend by increasing the concentration of the polymer. Entrapment efficiency was amplified (up to 98.44%) by increasing the polymer concentration due to the increase in solution viscosity. Morphological characteristics of formulation revealed particles of round edges. FTIR analysis confirmed the compatibility of ingredients by showing no interaction between the drug and other components. Ex-vivo permeation studies revealed the drug's biphasic release (initial burst release for 2 h and then slow release) with maximum permeation of 13.95%. Percentage retention of the drug was up to 80.5%, which was significantly higher than marketed formulation. In vivo studies revealed that developed formulation provided a rapid and complete removal of the fungal burden compared to control and marketed formulation.

Experimental analysis on partial replacement of cement with brick powder in concrete

The aim of this research is to interrogate the feasibility of using Waste brick powder (WBP) successfully in concrete as a substitute of cement. The replacement levels were kept at 5% and 10%, compared to the reference concrete. The tests consisted of slump, density, compressive, flexural and splitting tensile strengths, Schmidt Hammer, Ultrasonic Pulse Velocity and microscopic analysis. The results revealed an increase in workability, which is attributed to the particle size and shape of WBP. WBP particles have round edges and smooth surfaces, which lubricate the mix and give a ball bearing effect. The decrease in density is attributed to the lower density of WBP. The increase in compressive, split tensile, and flexural strengths highlighted an indication of the improvement of concrete quality by WBP inclusion: This is attributed to compact structure of the specimens owing to the location of pozzolanic products in concrete voids. Rebound Hammer and Ultrasonic pulse velocity also validated enhancement of the quality of concrete. Scanning Electron Microscopy (SEM) confirmed the formation of primary ettringite and enhanced CSH content in WBP-replaced samples. Energy Dispersive Spectra (EDS) showed highest peaks of Ca and Si (enhanced quantity of CSH) and low peak of Al (Ettringite) in WBP-containing concrete specimens.

Optical properties of water-coated sea salt model particles

We investigate the optical properties of marine aerosol in dependence of the water content. To this end we develop a model geometry that realistically mimics the morphological changes as the salt particles take up more water. The results are compared to morphologically simpler models, namely, homogeneous and inhomogeneous superellipsoids, as well as cube-sphere hybrids. The reference model yields depolarization ratios, depending on size and water uptake, in the range from 0 to 0.36 ± 0.12. Overall, the simple models can reproduce optical properties of the reference model. The overall nonsphericity, as well as inhomogeneity are identified as key morphological parameter, while rounding of edges only has a minor impact on optical properties.

A Comparison between a Classical and a Modified Root Fillet

Abstract The main purpose of this paper consists in improving the rigidity of the gear tooth by applying various root fillet forms that differ from the classical 0.38m radius circle arc. During the research the necessity of the re-formulation of the undercut appeared. It appears much later in case of applying rounded addendum edge planing comb as in case of using a classic generating profile tool. Therefore, the limits of the profile shifting can be significantly extended without weakening the tooth dedendum. The paper presents the stress repartitions under equal load, which occur on classic teeth, and on teeth having a modified root fillet. In this last case, the modified root fillet is the envelope of the curve family constituted by the rounded edge curves, in the relative motion of the comb related to the cut gear.

Repair of Fire Damaged Axially Loaded Short RC Columns Using GFRP Wrap

Fire damaged columns can be repaired with glass fibre reinforced polymer (GFRP) wrap to regain its full strength or even more. In the present work, short reinforced concrete (RC) rectangular columns which are exposed to elevated temperature at 4000℃ for 2 hours duration are repaired using GFRP wrap glued with epoxy resin. Strengthening of existing columns using GFRP wrap is a simple, easy and economical solution. GFRP wrap enhances the stiffness of the column in lateral direction, which improves the load carrying capacity of the column. The behaviour of GFRP wrapped column is different from the behaviour of column without GFRP wrap in response to the applied load. The behavior of GFRP strengthened column depends on various factors such as column cross sectional area aspect ratio, radius of rounded edges of the column, number of GFRP layers wrapped, width of GFRP strip, wrap pattern, epoxy properties etc. Various wrap patterns are tried to obtain effective one which greatly enhances the load taking capacity of short axially loaded columns. GFRP wrapping using strips showed good results than using continuous layer. The load carrying capacity of fire damaged GFRP repaired columns is increased by 42.3% compared with undamaged column without GFRP wrap and increased by 112.6% compared with fire damaged column without GFRP. Designer should fairly estimate the capacity of the strengthened column. Mathematical models are developed to predict the strength of repaired columns.

Experimental Study of a NACA0015 Circulation Control Airfoil Using Synthetic Jet Actuation

Wind tunnel testing is conducted on a NACA0015 airfoil with a rounded trailing edge, known as a circulation control airfoil, at the chord Reynolds number of and at the angles of attack of 0–15°. An array of synthetic jet actuators is installed next to the rounded trailing edge to produce synthetic jet at the excitation frequency range of 150–600 Hz and the momentum coefficient range of 0.00021–0.0134 across the airfoil span length. For the circulation control airfoil at prestall angles of attack, the current study suggested that the reduced excitation frequency of a synthetic jet should approximately be on an order of the Strouhal number based on the diameter of the Coanda surface to achieve optimal lift augmentation.

A Numerical Analysis of the Effect of Impeller Rounding on Centrifugal Pump as Turbine

Pump as turbine (PAT) is one of the micro-hydro system components. It can be used alone as a generator in remote areas without power supply, and in hydraulic networks instead of pressure-reducing valves. However, its hydraulic optimization still remains an open research problem. One of the optimization techniques is the rounding of the sharp edges at the blade periphery. Existing studies are mostly based on prototype experiments to obtain the optimization effect. In order to more intuitively analyze the influence of this structural optimization on the internal flow of PAT, this paper uses the CFD method to study the influence of the leading edge of the centrifugal pump blade and the fillet of the impeller on the turbine performance. By simulating the PAT performance at different flow rates and speeds, the internal hydraulic performance changes caused by the inverted circular blade are analyzed. Simulation results show that, under various operating conditions, the impeller inverted circle improves the efficiency of PAT to different degrees. At the speed of 1500 rpm, the efficiency is most obviously improved, which can reach 8.09%. Internal flow results show that the efficiency increases along with the decrease in impeller inlet resistance and the flow separation region in the impeller. This paper provides an effective method for studying the PAT hydraulic optimization problem.

Consistent Rounding of Edge Weights in Graphs

Often, the edge weights of graphs are given in implicitly infinite or overly high precision (think of Euclidean lengths) which leads to both theoretical as well as practical challenges. In this paper we investigate how to round edge weights of a given graph G(V,E,w) such that the rounded weights of paths satisfy certain consistency criteria. Natural consistency criteria are, for example, preserving optimality of paths, and bounding relative change in weight after the rounding procedure. Low precision edge weights allow for more space efficient implementations, faster arithmetic operations, and in general more stable and efficient algorithms. We present an ILP based rounding approach as well as a greedy rounding heuristic. We show experimentally for large road networks and grid graphs that our new rounding approaches are significantly better than common deterministic or randomized rounding schemes.

Hydrothermal Synthesis and Characterization of Zeolite A from Corn (Zea Mays) Stover Ash.

This study deals with the impact of calcination, alkalinity, and curing time parameters on the hydrothermal synthesis of zeolite A. The zeolite A sample, produced from corncob-stalk-and-leaves (corn stover) ash was characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermo-gravimetric analysis (TGA), and scanning electron microscopy (SEM). The results showed that calcination, alkalinity, and curing time have significant effects on the crystallization and the morphology of zeolite A. In addition, these parameters also impacted the cation exchange capacity. Furthermore, the synthesized zeolite A was obtained using a calcination temperature of 500 °C within two hours of airflow, which is much lower than the temperatures previously reported in the literature for an agricultural waste and other waste materials. A fusion ratio of corn stover ash:NaOH of 1.0:1.5 and a curing time of nine hours were achieved. This is a major result as this curing time is much lower than those featured in other studies, which can reach up to twenty-four hours. In this paper, cubic crystal with rounded edge of zeolite A, having a cation exchange capacity of 2.439 meq Na+/g of synthesized anhydrous zeolite A, was obtained, which can be a good candidate for ion-exchange separation.

Surface Machining of Stainless Steel Cardiovascular Stents by Fluid Abrasive Machining and Electropolishing

The typical manufacturing process of tubular metallic cardiovascular stents includes laser cutting, sand blasting, acid pickling, electropolishing, surface passivation, and cleaning. The most commonly used material for cardiovascular stents is stainless steel, such as SUS 304 and SUS 316. After the laser cutting process, substantial improvement of the stent surface morphology is required to obtain acceptable surface roughness, edge roundness, and reduction of surface defects. This study focuses on a novel post-treatment method of fluid abrasive machining to replace the conventional sand blasting and acid pickling processes, resulting in the surface smoothness and edge roundness that are suitable for cardiovascular stent fabrication. The dross deposition and striations retained after laser cutting can be significantly removed with fluid abrasive machining. Both DC current and pulse current electropolishing techniques were performed to attain the final surface and structural quality after the fluid abrasive machining process. The experimental results show that an extremely fine surface roughness and a satisfactory edge roundness can be achieved for stents through both DC current and pulse current electropolishing. The pulse electropolishing process is more effective than the DC current electropolishing process to achieve edge roundness with less weight removal.

Terahertz high-Q quasi-bound states in the continuum in laser-fabricated metallic double-slit arrays.

A laser-fabricated metallic resonator based on a double-slit array (DSA) is numerically and experimentally demonstrated at terahertz frequencies. Such free-standing resonators achieve a sharp resonance with high quality (Q) factor, arising from a distortion of symmetry-protected bound states in the continuum (BIC). By breaking the structural symmetry of DSAs, the BIC with infinite Q-factor can be transformed into quasi-BICs, and the Q-factors decrease gradually as the asymmetry parameter increases. We analyzed the influence of the imperfection in experimental samples such as the round edge and the trapezoid shape on the transmission properties of DSAs. Different from the DSAs composed of ideal perfect electrical conductors, copper DSAs show lower Q-factor because of the Ohmic loss. The effect of metal thickness on the quasi-BICs for DSAs is also investigated. Results exhibit that thinner resonators can achieve sharper quasi-BICs. These findings suggest that such metallic resonators with high Q-factors have great potential for practical applications in electromagnetic wave filtering and biomolecular sensing.

AYURVEDIC MANAGEMENT OF STANAGRANTHI W.S.R TO FIBROADENOMA OF BREAST- A SINGLE CASE STUDY

The most common benign tumour of the female breast is fibroadenoma which is most common in young women under the age of 30. It accounts for approximately 25% of all lesions in asymptomatic women. It is a new growth formed of both fibrous and glandular tissues. This tumour is said to develop as the result of increased sensitivity of a focal area of the breast to estrogen. This tumour most commonly presented as a painless, slowly growing, solitary lump in the breast. In modern medicine after a systemic review of available conservative management like hormonal therapy, keeping in mind the side effect of hormonal treatment, surgeries like lumpectomy and mastectomy becomes the ideal option which also has its own physical and psychological impact on women’s life. A balanced and rational approach to the management of fibroadenoma of the breast needs to address the crucial questions about its associ- ation with breast cancer, which is ideally done by imaging techniques like mammography where fibroadenoma appears as a distinct area from other breast tissue, with smooth round edges and breast ultrasound where it is typi- cally seen as well-circumscribed, round to ovoid or macro lobulated mass or if necessary, a minimally invasive biopsy may be performed via a core needle biopsy i.e., FNAC. According to Ayurveda, this can be correlated toGranthi explained by many Acharya’s which develop due to abnormal vitiation of Dosha and Dushya. According to Acharya Charaka, Granthi can be equated with all types of small-sized glandular or nodular swelling in any part of the body due to benign tumours or cysts. There is no direct reference for Stana Granthi but Mamsaja Granthi occurs in Stana is having a close resemblance with fibroadenoma of the breast. So, in the present study, a patient with fibroadenoma was successfully treated by Ayurvedic management of tab Kanchanara guggulu and abyanga with Chandana bala lakshadi taila which got the significant result. Keywords: Abyanga, Estrogen, Fibroadenoma, Granthi, Mammography, Ultrasound.

Modeling of Contact Forces for Brushing Tools

Brushing with bonded abrasives is a flexible finishing process used for the deburring and the rounding of workpiece edges as well as for the reduction of the surface roughness. Although industrially widespread, insufficient knowledge about the contact behavior of the abrasive filaments mainly causes applications to be based on experiential values. Therefore, this article aims to increase the applicability of physical process models by introducing a new prediction method, correlating the contact forces of single abrasive filaments, obtained by means of a multi-body simulation, with the experimentally determined process forces of full brushing tools during the surface finishing of ZrO2. It was concluded that aggressive process parameters may not necessarily lead to maximum productivity due to increased tool wear, whereas less aggressive process parameters might yield equally high contact forces and thus higher productivity.

Spatiotemporal correlation and control of wall pressure fluctuations induced by subsonic cavity flows

Strong wall pressure fluctuations are generated mostly by a high-speed flow passing over a cavity and should be accurately predicted and controlled for the structural design of aircraft. In this work, a spatiotemporal analysis was performed to estimate wall pressure fluctuations and reveal the mechanism of flow control by a sawtooth-like vortex generator installed on the leading edge or by the use of a rounded trailing edge in suppressing wall pressure fluctuations. Both the cavity tones and overall sound pressure level were analyzed under different flow speeds and flow control approaches. To investigate the power transfer in the temporal and spatial domains, power spectral density contours were drawn and discussed. For the mode separation, the phased array technique with an improved beamforming algorithm was adopted to calculate the wavenumber map and then to separate the acoustic modes from the convective modes by utilizing the spatial correlation of the wall pressure fluctuations. The mode separation results show that the convective modes contribute mainly to the low-frequency pressure fluctuations, while the acoustic modes contribute to both the low-frequency and high-frequency pressure fluctuations. Flow control by the rounded trailing edge approach is more effective than that by the serrated structure approach in reducing the cavity acoustic environment, which enables wall pressure fluctuations to transfer from the high-frequency range to the low-frequency range compared with the “no control” case.

Theory of Formation of Edge’s Surface Roughness Finished by Radial Polymer-Abrasive Brushes

Formation of roughness during treatment by polymer-abrasive brushes occurred as a result of interaction of cutting micro-relief with processed surface. The cutting micro-relief of abrasive instrument is described in the form of random process with normal distributional law. When calculation of roughness, the depths of penetration of cutting lugs in processed material as well as regularity of changing of radial radius of rounding of peaks of cutting lugs from modes of treatment are taken into consideration. Set are relations of roughness of processed edge from modes of treatment (deformations of instrument, cutting velocities, feeding) as well as from constituent cutting force. It is proved that usage of polymer-abrasive brushes for rounding of edges faces all requirements of aviation industry on roughness of processed edges.

ДОСЛІДЖЕННЯ ДИНАМІЧНОГО МОМЕНТУ ОПОРУ ВЕДУЧОГО ВАЛУ ГАЛТУВАЛЬНОЇ МАШИНИ, УТВОРЕНОГО ПЕРЕМІЩЕННЯМ СИПКОГО МАСИВУ У РОБОЧІЙ ЄМКОСТІ

Galvanizing technological operations include the processes of cleaning the surfaces of parts from burrs, burrs, bumps and scale, corrosion products, rounding of sharp edges, separation of parts from castings, as well as processes to improve the quality of product surfaces: grinding or polishing. These technological operations are implemented using different types of equipment: vibrating, rotary and spindle machines, rotating drums, etc. The most promising are considered to be machines with complex spatial movement of working tanks. Analytical researches of definition of dynamic moment of resistance of a driving shaft of the shredding machine on the basis of laws of movement of loose mass in the middle of working capacity are carried out. The positions of the moving parts of the machine and the bulk array in the middle of the tank, which correspond to the maximum dynamic component of the moment of resistance on the drive shaft created by the bulk array loaded to the working tank. An expression is obtained to calculate the value of the dynamic component of the moment of resistance on the drive shaft of the machine, created by the bulk array loaded to the working tank. The obtained research results can be used by the relevant machine-building enterprises at the stage of designing galvanizing types of equipment with tanks performing complex spatial motion.

Effects of gradual flexibility and trailing edge shape on propulsive performance of pitching fins

This paper addresses hydrodynamic performance of fins regarding their trailing edge convexity–concavity and flexibility distribution. The effects of trailing edge convexity–concavity on propulsive performance and vortex dynamics were investigated experimentally utilizing time-resolved particle image velocimetry and force sensors. It was found that the convex trailing edge shape always outperforms the concave shape. Wake contracting by the bent shape of the trailing edge vortex of a convex trapezoidal form resulted in higher thrust and efficiency. The results also showed that the rounded edges of fish fins did not provide additional hydrodynamic advantages. Furthermore, we found that a gradually flexible fin delivered better propulsive performance over a uniformly flexible fin. The hydrodynamic performance of the flexible fins depended on the strength and relative positions of the trailing edge vortexes shed by each fin, which were affected by the flexible deformations of the fins. In the lower Reynolds number operation (approaching, but below the first resonant mode), the fins with larger camber produced a stronger momentum footprint especially considering the far wake elements, while in the higher Reynolds number range due to resonant deformation the extent of trailing edge excursion became dominant in affecting the propulsive performance. The results showed that gradually flexible fins can improve the performance of future watercraft.

Positioning of Cubic Shaped Particles with Different Edge Structures in Nematic Medium

Liquid crystals (LC) are phases of matter that possess long range orientational order while maintaining fluidic properties. LCs have been shown to provide a medium that result in self-assembly of the colloidal particles through elastic interactions. One parameter that affects the positioning of the particles in LC medium is the edge sharpness of the particles. Simulation studies in the literature suggests that the edge sharpness of the particles directly affect the LC director profile at the vicinity of the particles, and playing a critical role in the formation and the shapes of the topological defects. This study provides a systematic study to show the effects of the edge sharpness on the orientation and the defect structure around the cubic shaped particles. The particles were shown to orient with their diagonal preferably parallel to the direction of the far field nematic director when the particles mediate planar anchoring. Whereas the particles with homeotropic anchoring did not exhibit strong preference in their orientation. We also showed defect structures to form around the particles with homeotropic surface anchoring. The defect structure around the particles with round edges were ring shaped, whereas the defects with S-shapes were formed around sharp-edged or truncated particles. The findings herein were found to be consistent with the simulations present in literature. The findings would find use in next generation materials for optics, photonics and responsive systems.

Structure of V-shape twinned VO2 nanocrystals epitaxially grown on sapphire

We report on the synthesis and structure of ‘V’ shape twinned vanadium dioxide (VO2) nanocrystals epitaxially grown on c-plane sapphire substrates using a vapor transport method. The (100)M twin plane played a key role in determining the morphology of VO2 nanocrystals. The growth of VO2 nanocrystals begins at the twin plane and proceeds toward two possible monoclinic [100] (aM−axis) direction resulting in ‘V’ shape twinned crystals with the angle between the sides of approximately 115.4°. At a relatively low growth temperature of 900 °C, the growth of the sides of ‘V’ was limited producing ‘coffee-bean’ shape crystals in which flat crystal facet regions are connected with rounded edges. The twinned VO2 nanocrystals were epitaxial to the c-plane sapphire substrate with the monoclinic [010] (bM−axis) normal to the substrate. In the in-plane direction, the (001)M planes of the VO2 twin crystals were aligned to the direction ±2.3° away from the sapphire (112‾0) plane. The sides of ‘V’ exhibit a rectangular cross-section truncated by the substrate. In-situ synchrotron x-ray diffraction measurement across the metal-insulator transition of the twinned nanocrystals implies that the phase transition of the coffee-bean shape nanocrystals occurs at a lower temperature with a smaller hysteresis gap than the fully grown V-shape nanocrystals.