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Quasi-elastic scattering angular distribution for the 94.5 MeV ~(17)F radioactive ion beam on the ~(208)Pb target has been measured. To describe the experimental quasielastic scattering angular distribution and explore the reactio...
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Quasi-elastic scattering angular distribution for the 94.5 MeV ~(17)F radioactive ion beam on the ~(208)Pb target has been measured. To describe the experimental quasielastic scattering angular distribution and explore the reaction dynamic, firstly, the optical potentials with the doublefolding S?o Paulo and AkyüzWinther potentials for both real and imaginary parts were used to analyze the experimental data. It is observed that both theoretical angular distributions are very similar. The optical model results describe reasonably the experimental data until 100° but underpredict the data for larger angles. Secondly, the continuum discretized coupled channel method (CDCC) was used to study the effect of the breakup channel on the elastic scattering. The double-folding S?o Paulo and Akyüz Winther potentials were used as nuclear interactions giving again similar results. The agreement with the data is slightly improved at intermediate angles. The sensibility of the CDCC effects upon the nuclear interaction potential was checked. Finally, the influence of inelastic states of both projectile and target, the one-proton, one-neutron, two-neutron and α transfer channels on the quasi-elastic scattering angular distribution is analyzed in the frame of the coupled channel and coupled reaction channel methods, respectively. It is observed that the coupling to the first excited state of ~(17)F is the one that affects more the elastic scattering, although the inelastic channels of the target also influence it when compared with the optical model results. The effect of the transfer channels on the quasi-elastic angular distribution is negligible.
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Stresses in a two-dissimilar-materials joint under an axisymmetric deformation are analysed. The similarity and the difference between the stresses in an axisymmetric deformation joint and in a plane strain deformation joint are p...
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Stresses in a two-dissimilar-materials joint under an axisymmetric deformation are analysed. The similarity and the difference between the stresses in an axisymmetric deformation joint and in a plane strain deformation joint are pointed out. The similarity is that the stresses near the bond edges of the joints have the same singularity. The difference is that the stresses in an axisymmetric deformation joint cannot be determined by only two composite material parameters, which is a correct conclusion in a plane strain deformation joint under prescribed traction. Therefore, asymptotic descriptions for the stress fields near the bond edges of the joints must be different under axisymmetric deformation and under plane strain deformation, even though the stress singularities are same.
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Unambiguous knowledge of magnetic field structure and the electric current distribution is critical for understanding the origin, evolution, and related dynamic properties of magnetic flux ropes (MFRs). In this paper, a survey of ...
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Unambiguous knowledge of magnetic field structure and the electric current distribution is critical for understanding the origin, evolution, and related dynamic properties of magnetic flux ropes (MFRs). In this paper, a survey of 13 MFRs in the Earth’s magnetotail are conducted by Cluster multipoint analysis, so that their force-free feature, i.e., the kind of magnetic field structure satisfying J × B = 0, can be probed directly. It is showed that the selected flux ropes with the bipolar signature of the south-north magnetic field component generally lie near the equatorial plane, as expected, and that the magnetic field gradient is rather weak near the axis center, where the curvature radius is large. The current density (up to several tens of nA/m~2) reaches their maximum values as the center is approached. It is found that the stronger the current density, the smaller the angles between the magnetic field and current in MFRs. The direct observations show that only quasi force-free structure is observed, and it tends to appear in the low plasma beta regime (in agreement with the theoretic results). The quasi force-free region is generally found to be embedded in the central portion of the MFRs, where the current is approximately field aligned and proportional to the strength of core field. It is shown that ~60% of surveyed MFRs can be globally approximated as force free. The force-free factor α is found to be nonconstantly varied through the quasi force-free MFR, suggesting that the force-free structure is nonlinear.
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Numerical simulation of sheet metal forming process using the meshless method called reproducing kernel particle method (RKPM) is studied in this paper. Owing to limitations of meshless approximation under parametric coordinate sy...
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Numerical simulation of sheet metal forming process using the meshless method called reproducing kernel particle method (RKPM) is studied in this paper. Owing to limitations of meshless approximation under parametric coordinate system, a constrained reproducing kernel (RK) approximation under Cartesian coordinate system is employed to describe the sheet metal deformation. Several technologies are used to solve the crucial problems involved in the numerical procedure. RKPM shape function is modified to impose essential boundary conditions; stabilized conforming nodal integration method is adopted to implement numerical integration of weak formulation; and an algorithm based on moment method is used to treat contact detection during sheet metal forming process. A program based on constrained RK approximation is developed to simulate two sheet metal forming examples: square-cup deep drawing and hemispherical part drawing. Numerical results are presented to demonstrate the effectiveness of the RKPM in numerical simulation of sheet metal forming.
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This work developed an apparatus by which the coke powder can be injected into a cupola through tuyeres for raising the carbon level in the tap iron. The primary objective is to achieve the flexibility of varying the make-up in th...
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This work developed an apparatus by which the coke powder can be injected into a cupola through tuyeres for raising the carbon level in the tap iron. The primary objective is to achieve the flexibility of varying the make-up in the metallic charge (steel scrap vs. pig iron + foundry returns), while still maintaining the desired chemistry of the tap iron. The effects of selected processing variables, including the injection rate of the coke powder, percentage of oxygen enrichment, and the make-up of the metallic charge, on the chemistry (the C content in particular) of the liquid iron were studied. In addition, rates of carbon pickup from the injected coke powder as a function of percent steel scrap in the charge were analyzed. Based upon the results obtained herein, optimal operation conditions regarding the injection rate of coke powder and the amount of oxygen enrichment for attaining the desired chemistry of the tap iron under various charge make-ups were summarized.
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The problem of a joint of dissimilar materials with arbitrary edge angles exposed to thermal loading is treated. Emphasis is placed on the investigation of the stress distribution around the singular point for complex singular eig...
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The problem of a joint of dissimilar materials with arbitrary edge angles exposed to thermal loading is treated. Emphasis is placed on the investigation of the stress distribution around the singular point for complex singular eigenvalues. For this case, an analytical form of the stress is obtained. Some examples are given to show the stress distribution around the singular point and the oscillation of the stress. The range of the stress oscillations is extremely small.
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The development of physical vapor deposition systems that employ inert gas jets to entrain and deposit atomic and molecular fluxes have created an interest in the atomic assembly of thin films under high pressure (10-500 Pa) depos...
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The development of physical vapor deposition systems that employ inert gas jets to entrain and deposit atomic and molecular fluxes have created an interest in the atomic assembly of thin films under high pressure (10-500 Pa) deposition conditions. Thin films grown under elevated pressure and low surface mobility conditions can contain a higher volume fraction of porosity and a different pore morphology to coatings created by conventional, low pressure (<10~(-4) Pa) deposition processes. A recent direct simulation Monte Carlo simulation analysis of binary vapor-gas jet atom interactions has shown that the incident angle distribution (IAD) for vapor atom impacts with a substrate is strongly effected by the background pressure. Here, these results are combined with a kinetic Monte Carlo technique to simulate the high pressure growth of vapor deposited nickel films and identify the mechanisms of pore formation. We find that when the surface atom mobility is low, shadowing of oblique angle arrivals by features on the substrate result in the incorporation of porosity with a hierarchical size distribution that includes elongated, inter-columnar pores and finer scale intra-columnar pores. The nucleation of the inter-columnar pores is related not only to the IAD, but also to the height and spacing of the initial asperities on the substrate and to those that subsequently evolve during deposition. The volume fraction of the inter-columnar pores is found to increase as both the fraction of oblique atom arrivals and the height of the asperities increase. For each prescribed IAD and asperity height, an asperity spacing is found that maximizes
the inter-columnar pore fraction. By varying the IAD for a given substrate surface topology, in conjunction with intermittent observations of the coating structure during the growth process, the flux shadowing mechanisms that govern the inter-columnar pore nucleation have been determined.
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Short rigid large-diameter monopiles have been widely used for offshore wind turbines. The rotation of the piles is strictly controlled to render safe operation of the wind turbines. Consequently, the determination of the bearing ...
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Short rigid large-diameter monopiles have been widely used for offshore wind turbines. The rotation of the piles is strictly controlled to render safe operation of the wind turbines. Consequently, the determination of the bearing capacity within an allowable angular rotation of the monopiles is an important issue. In this study, six lateral loading tests (at 1 g) were conducted on a rigid model pile in low liquid limit silt (ML) soil (with two relative densities). The tests reveal a rotational center at a depth of (0.75-0.85)L (L = embedded length of the pile) and work-hardening load-displacement curves (a continual increase in soil pressures even at a very large rotational angle). The test results were used to establish new p-y curves using a coefficient of subgrade reaction n_h, that is correlated to the local pile displacement. In particular, an analytical expression is developed to estimate the net lateral soil resistance p on a circular pile using peak-on-pile radial stress. The new p-y curves and analytical solutions capture the measured p-y curves and the load-displacement relationship of the monopiles in cohesionless soils.
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This study established the cupola technology of tuyere injection of coke powder and oxygen enrichment for raising the carbon level in the tap iron melt. The primary objective was to achieve the flexibility of varying the ratio bet...
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This study established the cupola technology of tuyere injection of coke powder and oxygen enrichment for raising the carbon level in the tap iron melt. The primary objective was to achieve the flexibility of varying the ratio between the steel scrap and pig iron in the charge materials, while still can obtain the desired chemistries of the iron melt. The effects of selected processing and metallurgical parameters, including the injection rate of the coke powder, air blow rate, % oxygen enrichment and ratio of steel scrap to pig iron, on the chemistries of the tap iron (especially the C content) were studied. Based upon the results obtained in this study, a database regarding the optimal operational conditions (e.g., injection rate of the coke powder and % oxygen enrichment) for achieving the desired chemistries of the tap iron was established.
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In this study, betamethasone disodium phosphate-loaded microparticles were fabricated for sustained release using poly(lactide-co-glycolide) (PLGA) by spray drying and emulsion solvent evaporation/extraction techniques. Encap-sula...
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In this study, betamethasone disodium phosphate-loaded microparticles were fabricated for sustained release using poly(lactide-co-glycolide) (PLGA) by spray drying and emulsion solvent evaporation/extraction techniques. Encap-sulation efficiencies ranged from 59-80% using a water-in-oil-in-oil (W/O/O) double emulsion technique and more than 90% for a spray-drying method were obtained. This was a significant improvement compared to fabrication by a water-in-oil-in-water (W/O/W) double emulsion process, which had an encapsulation efficiency of less than 15%. Multiple-phase and biphasic release profiles were observed for microparticles of PLGA 50/50 and PLGA of higher lactide contents, respectively. The PLGA 50/50 hollow microparticles fabricated using the W/O/O double emulsion technique provided a sustained release of betamethasone disodium phosphate over 3 weeks.
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