Various Angles Of Inclination Research Articles

On the Effects of Self-obscuration in the (Sub)Millimeter Spectral Indices and the Appearance of Protostellar Disks

Abstract In this paper we explore the effects of self-obscuration in protostellar disks with a radially decreasing temperature gradient and a colder midplane. We are motivated by recent reports of resolved dark lanes (“hamburgers”) and (sub)millimeter spectral indices systematically below the ISM value for optically thin dust, α ISM = 3.7. We explore several model grids, scaling disk mass and varying inclination angle i and observing frequency ν from the VLA Ka band (∼37 GHz) to ALMA Band 8 (∼405 GHz). We also consider the effects of decreasing the index of the (sub-)millimeter dust opacity power-law β from 1.7 to 1. We find that a distribution of disk masses in the range M disk = 0.01–2 M ⊙ is needed to reproduce the observed distribution of spectral indices, and that assuming a fixed β = 1.7 gives better results than β = 1. A wide distribution of disk masses is also needed to produce some cases with α < 2, as reported for some sources in the literature. Such extremely low spectral indices arise naturally when the selected observing frequencies sample the appropriate change in the temperature structure of the optically thick model disk. Our results show that protostellar disk masses could often be underestimated by > ×10, and are consistent with recent hydrodynamical simulations. Although we do not rule out the possibility of some grain growth occurring within the short protostellar timescales, we conclude that self-obscuration needs to be taken into account.

Experimental Characterization of a Direct Metal Deposited Cobalt-Based Alloy on Tool Steel for Component Repair

Casting dies made of tool steel are subject to impact, abrasion, and cyclic thermo-mechanical loading that can result in damage such as wear, corrosion, and cracking. To repair these defects, materials enveloping the defects need to be machined off and then refilled. In this study, V-shaped defects with varied sidewall inclination angles were prepared on H13 tool steel substrates and refilled with a cobalt-based alloy using direct metal deposition process (DMD) for superior hardness and wear resistance. The microstructure of rebuilt samples was characterized using an optical microscope (OM) and scanning electron microscope (SEM). Elemental distribution from the substrate to deposits was analyzed using energy-dispersive spectrometry (EDS). The mechanical properties of repaired samples were evaluated by tensile testing and microhardness measurement. A fracture mechanism in tensile testing was analyzed by observing the fracture surface. The experimental result reveals that V-shaped defects with sidewall beyond certain angles can be successfully remanufactured. The deposits were fully dense and free of defects. The microstructure and tensile testing confirm the solid bonding along the interface. The tensile testing shows the average ultimate tensile strength (UTS) of the repaired samples is approximately 620 MPa, where samples fractured at the deposits region. The hardness measurement reveals the hardness of deposits is around 800 HV, which is much higher than the hardness of the substrate.

Projecting by conical screw lines with constant step

The relevance of the study: The formation of surfaces by analytical methods and their visualization using computer graphics is one of the topical problems of applied geometry. Purpose of the study is to investigate non-traditional projection systems, to select congruence parameters of conical helical lines that cover the entire complex of surface requirements, obtained by projecting with conic rays an arbitrary flat or spatial line and using computer graphics in visualization of the surface. Methods of research: The general analytical theory of applied surface molding, developed by prof. Skidan I A and a single unit, which is based on the mathematical support of computer technologies for designing and creating objects of complex shape. Results of the research: An example of an analytical interpretation of the image of curvilinear projection by conical screw lines of a constant step and an example of congruence of conical screw lines, located on coaxial cones with a common vertex and a variable angle of inclination of the generator to the axis. The properties are investigated, the parameters of the helical line of the congruence, passing through an arbitrary point of space that does not belong to the axis, are determined. A method is proposed for constructing spiral surfaces, the framework of which consists of rays projecting an arbitrary line.

Study of particle migration and deposition in mixed convective pipe flow of nanofluids at different inclination angles

Mixed convection flow of aluminium-oxide nanoparticles in water through a circular tube was modelled using the discrete phase model and implemented on ANSYS-Fluent 17.0 through customised user-defined functions. The inclination angle was varied to study its effect on the migration and deposition of the nanoparticles. Experimentally determined thermo-physical properties were used in the analysis instead of theoretical or empirical models from the literature. Varying inclination angles were found to significantly affect the migration and deposition of nanoparticles. A critical angle of maximum deposition of approximately 30° was found for volume concentrations 1%, 3% and 5%. The effect of varying inclination angle on the heat transfer coefficient was minimal for low angles of inclination between 0 and 35% and decreased significantly after 40%. The effect of Saffman’s lift, thermophoretic, Magnus and Brownian effects were also investigated, and results show that thermophoretic and Brownian effects were most dominant effects.

Combined mixed convection and radiation simulation of inclined lid driven cavity

This paper presents a numerical investigation of the laminar mixed convection flow of a radiating gas in an inclined lid-driven cavity. The fluid is treated as a gray, absorbing, emitting, and scattering medium. The governing differential equations including continuity, momentum and energy are solved numerically by the computational fluid dynamics techniques (CFD) to obtain the velocity and temperature fields. The discretized forms of these equations are obtained by the finite volume method and solved by using the SIMPLE algorithm. Since the gas is considered as a radiating medium, besides convection and conduction heat transfer, radiation also takes place in the gas flow. For computing the radiative term in the gas energy equation, the radiative transfer equation (RTE) is solved numerically by the discrete ordinate method (DOM). The streamline and isotherm plots and the distributions of convective, radiative and total Nusselt numbers along the bottom wall of the cavity are presented. In this work, an attempt is made to investigate the hydrodynamic and thermal behavior of the mixed convection flow of a radiating gas at different values of the cavity inclination angle. The numerical results reveal that the variation of inclination angle causes a sweep behavior in the flow pattern inside the cavity. Besides, it is found that the value of radiative Nusselt number along the heated wall has a decreasing trend when the medium optical thickness is increases. Comparisons between the present numerical results with those obtained by other investigators in the cases of conduction-radiation and pure convection systems show good consistencies.

Effects of strain rate on the mechanical and fracturing behaviors of rock-like specimens containing two unparallel fissures under uniaxial compression

Rocks containing unparallel fissures are likely to be subjected to dynamic loading resulting from earthquakes in various civil engineering structures. Since dynamic loading rate significantly affects the mechanical behaviors of fissured rocks, understanding the mechanical properties and fracture mechanism of fissured rocks under different loading rates is thus crucial in rock engineering applications. This study investigates the effects of strain rate on the mechanical and fracturing behaviors of rock-like specimens containing two unparallel fissures with varying inclination angles (α2). Our experimental results demonstrate that α2 and strain rate significantly affect the strength and deformation characteristics and the failure modes of fissured specimens. Both the strength and elastic modulus of the rock-like specimens highly depend on the strain rates, and the strain rate dependence is more sensitive for fissured specimen than that for the intact specimen. Under the same strain rate, the strength of fissured specimens decreases as α2 increases up to 60°, and then increases. The fissured specimens with greater α2 are characterized by higher elastic modulus. Furthermore, the fracture mechanism of the fissured specimen is numerically revealed, and the energy characteristics of fissured models are also analyzed on a micro-level.

Wa-Chair: A concept for development of economical stair-climbing wheelchair

In this paper, a concept for development of cost effective and reliable stair climbing wheelchair is being proposed. Slider-crank mechanism is being used to compensate for any variation in inclination angle of the wheelchair during ascent or descent on stairs. Controlling wheelchair’s inclination angle can reduce risk for the rider as it prevents the wheelchair from toppling. A prototype is being developed to validate proposed mechanism. Proposed mechanism allows rider to view in the direction of progress which adds additional safety to the rider.

Effect of Post Weld Heat Treatment on Al 5052-SS 316 Explosive Cladding with Copper Interlayer

This study focuses on effect of post weld heat treatment (PWHT) on interfacial and mechanical properties of Al 5052-SS 316 explosive clad with copper interlayer at varied loading ratios and inclination angles. The use of interlayer is proposed for the control of additional kinetic energy dissipation and to alleviate the formation of intermetallic compounds at the interface. The Al-Steel clads are subjected to PWHT at varied temperatures (300°C-450°C) for 30 minutes and the results are presented. The microstructural characterization of as-clad and PWHT samples is observed by an optical microscope and Scanning Electron Microscope (SEM). Maximum hardness is obtained at the interface of the as-clad and PWHT samples. Increase in PWHT temperature enhances the tensile strength of the composite, whereas, the tensile strength decreases at 300°C due to the diffusion of Al and Cu elements and the formation of detrimental intermetallic compounds.

Cooling slope casting of cast iron

AbstractThe aim of the present work is to study the effect of semi‐solid processing using cooling slope method on the microstructure and mechanical properties of grey cast iron. A water cooled castable cement coated steel plate with a variable inclination angle is used to make a mechanical treatment on the semi‐solid flow of grey cast iron. The experiment is repeated for three different pouring temperatures and three inclination angles. The tensile test, hardness test and microstructure examination is used to compare the new properties of the new resulting grey cast irons. The results show that the sharp edged carbon flakes can be refined and the mechanical properties is enhanced. The carbon particles average circularity is increased followed with a decrease in carbon particle size due to the effect of the cooling plate.

Effects of nozzle positioning on single-phase spray cooling

The effects of nozzle positioning on spray cooling is experimentally studied using water sprays generated by a full-cone nozzle to cool a sputter-coated thin-film heater on a silicon wafer. Infrared camera is used to measure surface temperature with high spatial resolution. The nozzle positioning can be adjusted by moving the nozzle toward or away from the cooling surface to change spray height and/or by tilting the nozzle to change inclination angle. The study is composed of three components: (1). Flow in the spray cone is specified by polar and azimuthal angles (β,φ), and it impacts and cools the surface at (x,y). The relation between the two coordinates, and the flow flux as a function of (β,φ) are derived, and both are dependent on the spray height and inclination angle. (2). The effect of spray height is experimentally investigated for normal spray impact. It is discovered that the optimal spray height providing the most effective cooling is smaller than the height required for covering the entire heater area. It is found that the optimal height decreases with increasing the spray flow rate. (3). The effect of inclination is experimentally studied by changing the inclination angle while maintaining the major-axis length of the elliptical spray-covered area constant. Using the derived relation, from the measured local cooling at (x,y) we track the cooling performance of the flow at (β,φ). The flux of the flow is calculated and compared using the derived flux equation for varied inclination angles. The enhancement and diminishment of the cooling performance are found to be in general agreement with the increase and decrease of the flow flux.

Performance analyses of a steam condensation tube immersed in a saturated water pool: Effects of tube inclination

Two-phase heat exchanger immersed in a passive containment cooling water storage tank (PCCWST) is a key component of the passive containment cooling system (PCCS) in light water reactors. Condensation and boiling heat transfer phenomena taking place on the inside and outside walls are crucial to the performance of the heat exchanger tube. The performances of such phenomena can be readily affected by the inclination angle of the heat exchanger tube under buoyancy-driven convection conditions in a PCCWST. However, to date no systematic examination of the effects of inclination angle on pool heat exchanger performance has been reported. This paper presents the results of numerical and experimental analyses of how inclination angle affects the performance of a single steam condensation tube immersed in a saturated water pool. To concurrently predict the two-phase heat transfer processes inside and outside the heat exchanger tube, an explicit heat structure coupling of two thermal-hydraulic codes was implemented using open media models. An experimental facility was also constructed to test a single-tube heat exchanger under the same conditions as the simulation. A comparison of simulation data and experimental results obtained for the reference case (tube inclination of 30°) confirmed that the coupled code could predict the heat transfer rate in the pool heat exchanger within the error limits of the experimental measurements. In light of this, additional simulations and experiments were conducted at varying inclination angles, from 3° to 90°. The results of simulations and experimental studies revealed that the heat transfer rate of a heat exchanger tube in a saturated pool is hardly influenced by tube inclination. Although an increase in inclination angle caused the vapor slug to spread around the heat exchanger tube surface, preventing liquid from getting to the surface of the tube, thereby decreasing boiling heat transfer coefficients, this was compensated for by an increase in condensation heat transfer coefficients as the inclination angle increased as a result of accelerated condensate liquid film in the tube. Thus, the overall effect of inclination angle on the thermal performance of a single-tube pool heat exchanger is inconsequential.

Simulation on Natural Convection of a Nanofluid along an Isothermal Inclined Plate

A numerical algorithm is presented for studying laminar natural convection flow of a nanofluid along an isothermal inclined plate. By means of similarity transformation, the original nonlinear partial differential equations of flow are transformed to a set of nonlinear ordinary differential equations. Subsequently they are reduced to a first order system and integrated using Newton Raphson and adaptive Runge-Kutta methods. The computer codes are developed for this numerical analysis in Matlab environment. Dimensionless velocity, temperature profiles and nanoparticle concentration for various angles of inclination are illustrated graphically. The effects of Prandtl number, Brownian motion parameter and thermophoresis parameter on Nusselt number are also discussed. The results of the present simulation are then compared with previous one available in literature with good agreement.

Experimental investigation of phase change in a cavity for varying heat flux and inclination angles

In this study, the effect of heat flux and inclination angle variation in a rectangular PCM containing cavity is investigated. In order to investigate of effect of heat flux variation on melting process, the cavity is heated through the bottom plate by 3 levels of heat flux. Also to investigate the effect of inclination angle variation, 3 levels of inclination angle (0°, 45°, 90°) are considered. The changes of the liquid–solid boundaries are recorded using Canon G9 camera. 32 thermocouples at 9 heights of the container and 3 thermocouples on heater’s plate are implemented by which average temperature of the PCM, liquid fraction, average temperature of the heating surface, the amount of absorbed energy, temperature contour, the phases boundaries deformation, the average temperature at a specific distance of the heater and Nusselt number are analyzed. The results show that, as the heat flux input strengthens, melting time reduces and the rate of heat transfer and heater’s temperature increases. The driven Nusselt number implies that as the heat flux increases, the dominant heat transfer mechanism turns to natural convection sooner.

Flat Plate Solar Collector Characteristic with Shutter Glass Distance Variation and Collector Inclination Angle

It has been done a research to determine the solar thermal collector efficiency of the flat plate collector. The testing of the collector was conducted on 30th November 2005, 1st, 3rd, 5th, 6th, 7th December 2005 with the variation of distance between one glass covers were varied from 3 cm, 6 cm, and 9 cm; and with inclination angle variation of collector from 10°, 20°, 30°, and 40°. Solar thermal collectors absorb the radiant energy from the sun and convert it to heat between the bottom glass cover and absorbing plates in the collector. Parameters which influence on the collector performance include distance between plate collector with glass covers and the inclination angle. It was found that the difference between output-input temperatures is the highest on a distance of 3 cm and inclination angle of 10°. This is influenced that inclination angle 10° more close to zenith angle. The solar thermal collector efficiency is not a constant; The solar collector efficiency depends on solar radiation intensity, input-output temperature difference and air flow. The smaller the inclination angle of solar collector, the higher the absorption radiation. If inclination angle of collector same with zenith angle, so the absorption radiation will maximum.

Thermal Environment and Inclination Angle Dependencies on the Surface Quality of Selective Laser Melted 316L Steel

Additive manufacturing processes offer the ability to manufacture highly complex geometries, but are limited in terms of the achievable surface quality. These limitations are based on physical restrictions, especially the need of support and the powder-bed environment, and economic decisions. In this study, the development of the morphology of surfaces with varying inclination angles was investigated on the example of 316L stainless steel. Surfaces with low inclination angles to the manufacturing plane suffered extensively from the process related staircase effect, whereas perpendicular side faces revealed high dependencies on the interaction with the powder-bed.

Investigation on the edge forces in ball end milling of inclined surfaces

This work focuses on the analysis of the edge forces generated in ball end milling of hardened alloy 55NiCrMoV6 steel. The investigated forces consider the effects of friction, rubbing and ploughing mechanisms between the work piece and tool flank face during machining process. The primary objective of the paper concentrates on the determination of edge forces in the range of variable surface inclination angles and increasing tool wear. The proposed approach involves the measurements of instant cutting forces in machine coordinates (Fz, Fy, Fz). Subsequently, the measured forces are converted to the forces in the tool coordinates (Ft_av, Fr_av, Fa_av). In the next step, the Ft_av, Fr_av, Fa_av forces are expressed in function of average uncut chip thickness. In order to obtain the edge forces values, the extrapolation of forces in the tool coordinates to the zero uncut chip thickness is made. The investigations reveal that edge forces are strongly affected by surface inclination angle and progressing tool wear. The growth of the tool wear induced the monotonic increase in edge forces values. Nevertheless, in case of surface inclination angles α≥15° the influence of this factor on edge forces was low. It was also shown that cutting force estimation with the consideration of the variable edge forces is characterized by a higher accuracy than one based on constant edge forces. Therefore, the proposed method can be employed in the reliable calibration of specific force coefficients contained in mechanistic cutting force models dedicated to the finish ball end milling of sculptured surfaces.

Effect of inclination angle on the performance of a shell and tube heat storage unit – An experimental study

This study includes experimental investigation on the performance of a shell and tube heat exchanger subjected to inclination angle variation. Paraffin RT35 is used as phase change material (PCM). The investigation was performed for modified Stefan numbers of 0.47, 0.53 and 0.59 and inclination angle rang from 0° to 90°. The Reynolds number is about 770 and the Grashof number is in the range of 4.6×104–5.8×104 which indicated that the flow is laminar. Results show that as the inlet temperature increases melting process accelerates and complete melting time reduces. Results also indicated that the rate of melting process in the first half of the process is more in the horizontal system with respect to the other inclinations. It is also revealed that the angle’s variation doesn’t affect the rate of heat transfer and the temperature during solidification which is due to the domination of conduction in this process. Results also clarified that during melting, the rate of heat transfer of the horizontal system is more than that of vertical, however the reverse is true for the solidification. It is also concluded that the average temperature of the horizontal heat exchanger sections closer to the inlet is more than the section nearer to outlet. However, when the 30°, 60° and 90° cases are considered, the PCM average temperatures of the sections nearer to the outlet are more.

Analysis of thermal management on processing of fluids within rhombic cavities: Heatlines vs. entropy generation

The present work involves the detailed heat flow visualization with the distribution of the entropy generation in order to estimate the energy efficiency of rhombic cavities with various angles of inclination (φ=45∘,60∘ and 75°) for different areas (A=0.5,1 and 1.5) with Ra=103−105 for Pr=0.015 and 1000. The cavities involve isothermally hot bottom wall in the presence of cold side and top walls. Results have been presented in the form of isotherms (θ), streamlines (ψ), heatlines (Π), entropy generation due to heat transfer (Sθ) and fluid friction (Sψ). Results have also been compared with the square cavity (φ=90∘) in terms of the total entropy generation (Stotal), average Bejan number (Beav) and average heat transfer rate (Nub¯ and Nul¯). The numerical studies clearly demonstrate that, the square enclosure may not be the optimal choice based on the lesser heat transfer rate and higher entropy generation. Overall, the rhombic cavities with φ=45∘ at A=0.5 may be concluded as the optimal design for the efficient thermal processing based on the higher heat transfer rate and lower entropy generation.

Scalable fabrication of microneedle arrays via spatially controlled UV exposure.

This paper describes a theoretical estimation of the geometry of negative epoxy-resist microneedles prepared via inclined/rotated ultraviolet (UV) lithography based on spatially controlled UV exposure doses. In comparison with other methods based on UV lithography, the present method can create microneedle structures with high scalability. When negative photoresist is exposed to inclined/rotated UV through circular mask patterns, a three-dimensional, needle-shaped distribution of the exposure dose forms in the irradiated region. Controlling the inclination angles and the exposure dose modifies the photo-polymerized portion of the photoresist, thus allowing the variation of the heights and contours of microneedles formed by using the same mask patterns. In an experimental study, the dimensions of the fabricated needles agreed well with the theoretical predictions for varying inclination angles and exposure doses. These results demonstrate that our theoretical approach can provide a simple route for fabricating microneedles with on-demand geometry. The fabricated microneedles can be used as solid microneedles or as a mold master for dissolving microneedles, thus simplifying the microneedle fabrication process. We envision that this method can improve fabrication accuracy and reduce fabrication cost and time, thereby facilitating the practical applications of microneedle-based drug delivery technology.

Braking index of isolated pulsars. II. A novel two-dipole model of pulsar magnetism

The magnetic dipole radiation (MDR) model is currently the best approach we have to explain pulsar radiation. However a most characteristic parameter of the observed radiation, the braking index n$_{\rm obs}$ shows deviations for all the eight best studied isolated pulsars, from the simple model prediction n$_{\rm dip}$ = 3. The index depends upon the rotational frequency and its first and second time derivatives, but also on the assumption of that the magnetic dipole moment and inclination angle, and the moment of inertia of the pulsar are constant in time. In a recent paper [Phys. Rev. D 91, 063007 (2015)] we showed conclusively that changes in the moment of inertia with frequency alone, cannot explain the observed braking indices. Possible observational evidence for the magnetic dipole moment migrating away from the rotational axis at a rate $\dot\alpha$ $\sim$ 0.6$^{\circ}$ per 100 years over the life time of the Crab pulsar has been recently suggested by Lyne et al. In this paper, we explore the MDR model with constant moment of inertia and magnetic dipole moment but variable inclination angle $\alpha$. We first discuss the effect of the variation of $\alpha$ on the observed braking indices and show they all can be understood. However, no explanation for the origin of the change in $\alpha$ is provided. After discussion of the possible source(s) of magnetism in pulsars we propose a simple mechanism for the change in $\alpha$ based on a toy model in which the magnetic structure in pulsars consists of two interacting dipoles. We show that such a system can explain the Crab observation and the measured braking indices.