High-velocity gas associated ultracompact HII regions

We present the results of a survey for high-velocity¹²CO (1-0) emission associated H₂O masers and ultracompact (UC) HII regions. The aim is to investigate the relationship between H₂O masers, CO high-velocity gas (HVG) and their associated infrared sources. Our sample satisfies Wood & Churchwell criterion. Almost 70 % of the sources have full widths (FWs) greater than 15 km · s^-1 atT* _a = 100 mK and 15 % have FWs greater than 30 km · s^-1 In most of our objects there is excess high velocity emission in the beam. There is a clear correlation between CO line FWs and far-infrared luminosities: the FW increases with the FIR luminosity. The relation suggests that more luminous sources are likely to be more energetic and able to inject more energy into their surroundings. As a result, larger FW of the CO line could be produced. In most of our sources, the velocities of peak of the H₂O emission are in agreement with those of the CO cloud, but a number of them have a large blueshift with respect to the CO peak. These masers might stem from the amplifications of a background source, which may amplify some unobservable weak masers to an observable level.     

13CO mapping study for massive molecular cloud cores

Using the newly installed SIS receiving system on the 13.7 m telescope at Qinghai Station of PMO, United Radio Astronomy of CAS, CO isotope¹³CO J= 1-0 and C¹⁸O J= 1-0 lines were observed for three sources S241, S39 and ON3. Results show that the three sources have massive cores, of which the size is ～ 2-5 pc, masses are ～ 10³- 10⁴M⊙. The widths of lines are also larger than those in low mass cores. And high velocity characteristics were observed for all the sources. The V_LSR distribution presents rotation of the core in ON3. And all the three cores contain deeply embedded forming massive stars. The young stellar objects in S241 and ON3 seem to be moving away from their birth sites.     

Force constants,generalised meansquare amplitudes of vibration,shrinkage constants and coriolis coupling coefficients of GeH3CCH and GeD3CCH

General Valence force constants have been evaluated for GeH₃CCH and GeD₃CCH. Generalised mean-square amplitudes of vibration have been obtained and the shrinkage constants have been calculated using the perpendicular mean-square amplitudes of vibration. Coriolis coupling constants have also been determined.     

CO‐irredundant Ramsey numbers for graphs

The study of the CO‐irredundant Ramsey numbers t(n₁, ···, n_k) is initiated. It is shown that several values and bounds for these numbers may be obtained from the well‐studied generalized graph Ramsey numbers and the values of t(4, 5), t(4, 6) and t(3, 3, m) are calculated. © 2000 John Wiley & Sons, Inc. J Graph Theory 34: 258–268, 2000     

Modeling of cutting force prediction in machining high-volume SiCp/Al composites

Variations in cutting forces significantly influence the tool wear and part quality in machining high-volume SiC-particle-reinforced aluminum matrix (SiCp/Al) composites. Properties of the reinforcement SiC particles, such as size and volume fraction, contribute to the change in the cutting forces. This paper presents a cutting force model based on the geometrical and mechanical nature of the tool and workpiece, considering the effect of the SiC reinforcement particles. The cutting force is predicted as three components (F_z, F_x, and F_y) and the resultant cutting force F_τs. The cutting force was considered to generate three deformed zones: (a) shear deformed zone, (b) friction deformed zone on the chip–tool interface, (c) plow deformed zone. The effect of SiC reinforcement particles on friction deformed zone is analyzed emphatically. The friction force from friction deformed zone was obtained by calculating the sliding friction force and rolling friction force. To verify the feasibility and validity of the predicted model of cutting force, cutting experiments were performed with different combinations of cutting speed, feed rate, depth of cut, and tool nose radius. The predicted cutting force values demonstrate good agreement with the measured experimental cutting force values in most cutting conditions. The average percentages of the prediction error were 1.93%, 6.20%, and 10.48% for the F_z, F_x, and F_y components, respectively, thus proving the validity and accuracy of the predicted model of cutting forces.     

Mathematical modeling on the effect of equivalence ratio in emission characteristics of compression ignition engine with hydrogen substitution

The investigation presented in this paper concerns on the computational simulation of emissions characteristics in compression ignition engine with hydrogen substitution. Combustion process has been modeled based on Equilibrium Constants Method (ECM) with MATLAB program to calculate the mole fractions of 18 combustion products when hydrogen is burnt along with diesel fuel at variable equivalence ratios. It can be observed that hydrogen substitution causes significant increase in NH₃, H₂, atom H emissions during rich combustion and OH, NO₂, HNO₃ emissions during lean combustion. As the equivalence ratio increases during rich combustion, mole fractions of HCN, CH₄, CO and atom C decreases with increment of hydrogen substitution. N₂, atom N and CO₂ emissions decrease whereas no significant changes in O₂, NO, O₃ and atom O emissions throughout all equivalence ratios as hydrogen is added to the combustion.     

13CO mapping study for massive molecular cloud cores

Using the newly installed SIS receiving system on the 13.7 m telescope at Qinghai Station of PMO, United Radio Astronomy of CAS, CO isotope¹³CO J= 1-0 and C¹⁸O J= 1-0 lines were observed for three sources S241, S39 and ON3. Results show that the three sources have massive cores, of which the size is ∼ 2-5 pc, masses are ∼ 10³- 10⁴M⊙. The widths of lines are also larger than those in low mass cores. And high velocity characteristics were observed for all the sources. The V_LSR distribution presents rotation of the core in ON3. And all the three cores contain deeply embedded forming massive stars. The young stellar objects in S241 and ON3 seem to be moving away from their birth sites.     

High quality YBCO superconductive thin films fabricated by laser molecular beam epitaxy

High quality YBa₂.Cu₃O_{6 +x}(YBCO) superconductive thin films have been fabricated on the SrTiO₃(100) substrate using laser molecular beam epitaxy (laser-MBE). The active oxygen source was used, which made the necessary ambient oxygen pressure be 2–3 orders lower than that in pulsed laser deposition (PLD). T_c0 is 85–87 K, and J_c, 1.0 × 10⁶ A/cm². Atomic force microscopy (AFM) measurements show that no obvious particulates can be observed and the root mean square roughness is 7.8 nm. High stability DC superconducting quantum interference devices (DC-SQUID) was fabricated using this YBCO thin film.     

Leading term at infinity of steady Navier‐Stokes flow around a rotating obstacle

Consider a viscous incompressible flow around a body in $\mathbb R^3$ rotating with constant angular velocity ω. Using a coordinate system attached to the body, the problem is reduced to a modified Navier‐Stokes system in a fixed exterior domain. This paper addresses the question of the asymptotic behavior of stationary solutions to the new system as |x| → ∞. Under a suitable smallness assumption on the velocity field, u, and the net force on the boundary, N, we prove that the leading term of u is the so‐called Landau solution U, a singular solution of the stationary Navier‐Stokes system in $\mathbb R^3$ with external force kωδ₀ and decaying as 1/|x|; here $k\in \mathbb R$ is a suitable constant determined by N and δ₀ is the Dirac measure supported in the origin.     

Numerical simulation of methane partial oxidation in the burner and combustion chamber of autothermal reformer

This study aims to model the methane partial oxidation process in the burner and combustion chamber of autothermal reactor. The numerical simulation based on this model offers a powerful tool that can assist in reactor design and optimization and scale up of the process saving expensive pilot work. The steady-state governing equations were solved using the SIMPLE algorithm and the effect of turbulence on the mean flow field was accounted for using the RNG k–ε model. A two-step reaction mechanism was used for the gas combustion with CO as the intermediate species. The reaction rates were modeled using an Eddy-Dissipation Model. In terms of the geometrical model, a 3D model for burner was developed while an axis-symmetric model for the combustion chamber was implemented to reduce the computational costs. The model formulated was validated against a currently operating autothermal reactor and then has been used to investigate different aspects of these reactors. Results show that effect of oxygen to methane ratio is more than that of feed temperature. It is demonstrated that a 60% increase in O₂/CH₄ ratio causes a 15.4% decrease and 42.7% increase in H₂/CO ratio and methane conversion, respectively. In contrast, a 60% increase in feed temperature does not have a significant effect on the process.     

Conservative loads on shells

Generalized load vectorsp and edge load vectorsF are denned in terms of the body force and surface on a shell. Necessary and sufficient conditions are derived forp andF, and therefore the body force and the surface force, to be conservative. It is shown for example thatp must satisfyp _i=P _ijk q _j,1 q _k,2+Q _ij ¹ q _j,2–Q _ij ² q _j,1+R _i whereq is the generalized position vector andP _ijk, Q_i,j ¹ and Q_ij ² are skew tensors.The case of hydrostatic pressure is examined in detail.This work was supported in part by NSF grant MSM 8618657.     

Double‐mode modeling of nonlinear flexural vibration analysis for a symmetric rectangular honeycomb sandwich thin panel by the homotopy analysis method

Nonlinear flexural vibration of a symmetric rectangular honeycomb sandwich thin panel with simply supported along all four edges is studied in this paper. The nonlinear governing equations of the symmetric rectangular honeycomb sandwich panel subjected to transverse excitations are simplified to a set of two ordinary differential equations by the Galerkin method. Based on the homotopy analysis method, the average equations of the primary resonance and harmonic resonance are obtained. The influence of structural parameters, the transverse exciting force amplitude, and transverse damping to the symmetric rectangular honeycomb sandwich panel are discussed by using the analytic approximation method. Compared with the results obtained by single‐mode modeling technique, the results obtained by double‐mode modeling technique change the softening and hardening nonlinear characteristics when Ω ≈ ω₁, ω₁/3, and ω₂/3.     

Influence of inclusion on the stress intensity factors under thermomechanical loads in a PM superalloy

The interaction between a round inclusion and a crack under thermomechanical loading is analyzed based on a modified body force method. The traction-free condition on the crack line is mended by adding the resultant force induced by thermal stress to the force equilibrium equations, so that the coupling of mechanical and thermal loads could be taken into account. The series of integral equations can be discretized to a set of linear equations. Stress intensity factors (SIFs) are obtained through solving the linear equations. The calculated results in this paper are compared to those in open references to validate the method and code. The method is applied to a case of FGH95 PM superalloy containing Al₂O₃ inclusions under mechanical and thermal loads. The results show that the thermal load has little effect on SIF, while the mechanical load is the dominant factor.     

Anharmonicity factors and potential energy constants of B2H6 and B2D6

The anharmonicity factors of B₂H₆ and B₂D₆ have been calculated using Dennison’s method. Using the calculated harmonic wave numbers, the valence force constants have been obtained by the Wilson’s F-G matrix method.     

Investigation of the friction of rubber under constant compressive strain conditions at low pressure

A vacuum tribometer was developed which was used to investigate the maximum friction force occurring at the initial instant of slipping in rubber-metal friction pairs under conditions of a given (from 5 to 40%) compressive strain at a low pressure in the temperature range from +100 to –100°C. Filled rubbers on a base of nitrile-butadiene rubbers were studied. Up to the glass transition temperature T_g the vacuum had practically no effect on the maximum friction frocef _m; at temperatures T_g and lower the values off _m obtained in a vacuum were 10–15% higher than those obtained in the atmosphere. It is shown that with a decrease of temperature from 20°C to the glass transition temperature T_g the slope of the dependence of the maximum friction force on the degree of deformation increases, and below T_g decreases. The effect of the slipping speed v on the maximum friction forcef _m was also studied.Laboratory of Polymer Physics, V. I. Lenin Moscow State Pedagogical Institute. Leningrad Branch, Scientific Research Institute of the Rubber Industry. Translated from Mekhanika Polimerov, No. 3, pp. 486–492, May–June, 1970.     

Preparation and third-order nonlinear optical properties of self-organized complex oxide Ce: BaTiO3 quantum dots

Pulsed laser ablation epitaxial Strancky-Krastanow growth of self-organized complex oxide Ce:BaTiO₃ quantum dots on MgO(lOO) substrates is demonstrated. Atomic force microscopy and X-ray diffraction are used to observe the structure and the growth process of the self-organized complex oxide quantum dots. The average dimension, height, and the density of self-organized complex oxide Ce:BaTiO₃ quantum dots are given. The nonlinear refractive indexes of the wetting layer and the selforganized ordered quantum dots are determined by the single beam Z-scan method. The mechanisms of the nonlinear effect enhancement for these low-dimensional structure are discussed.     

Casimir force between metal plate and dielectric plate

The Casimir effect between metal plate and dielectric plate is discussed with 1 + 1-dimensional potential model without using cut-off method. Calculation shows that the Casimir force between metal plate and dielectric plate is determined not only by the potentialV ₀, the dielectric thickness and the distancea between the metal plate and dielectric plate, but also by the dimension of the vessel. Whena is far less than the dimension of the vessel, the Casimir forceF _c ∝a ^-1; converselyF _c ∝a ^-2 This result is significant for Casimir force experiment.     

Preparation and third-order nonlinear optical properties of self-organized complex oxide Ce: BaTiO3 quantum dots

Pulsed laser ablation epitaxial Strancky-Krastanow growth of self-organized complex oxide Ce:BaTiO₃ quantum dots on MgO(lOO) substrates is demonstrated. Atomic force microscopy and X-ray diffraction are used to observe the structure and the growth process of the self-organized complex oxide quantum dots. The average dimension, height, and the density of self-organized complex oxide Ce:BaTiO₃ quantum dots are given. The nonlinear refractive indexes of the wetting layer and the selforganized ordered quantum dots are determined by the single beam Z-scan method. The mechanisms of the nonlinear effect enhancement for these low-dimensional structure are discussed.     

Non-isothermal flow through a rotating straight duct with wide range of rotational and pressure driven parameters

Numerical study is performed to investigate the Non-isothermal flow in a rotating straight duct under various flow conditions. Spectral method is applied as a main tool for the numerical technique, where the Chebyshev polynomial, the Collocation methods, the Arc-length method and the Newton-Raphson method are also used as secondary tools. The characteristics of the flow mentioned above are described here. The incompressible viscous steady Non-isothermal flow through a straight duct of rectangular cross-section rotating at a constant angular velocity about the center of the duct cross-section is investigated numerically to examine the combined effects of Rotation parameter (Coriolis force), Grashof number (parameter which is used in heat, transfer studies involving free, forced or natural convection and is equql to \(\frac{{L^3 g\beta \Delta {\rm T}}}{{v^2 }}\), where L is the characteristic length, ρ the density, g the acceleration due to gravity, β the thermal expansion coefficient, ΔT the temperature difference, μ the viscosity and ν the kinematic viscosity of the fluid. The expansion coefficient β is a measure of the rate at which the volume V of the fluid changes with temperature at a given pressure P), Prandtl number, aspect ratio and Pressure-driven parameter (centrifugal force) on the flow. We examine the structures in case of rotation of the duct axis and the Pressure-driven parameter with large aspect ratio where other parameters are fixed. The calculations are carried out for 0 ≤ T _r ≤ 300, 2 ≤ γ ≤ 6, G _r = 100, P _r = 7.0 and 0 ≤ P _r ≤ 800 by applying the Spectral method. When Ω > 0 and the rotation is in the same direction as the Coriolis force enforces the centrifugal force, multiple solutions of Non-symmetric the secondary flow patterns with 10-vortex (maximum) are obtained in case of T _r = 100 and 150 with large aspect ratio. The intense of the temperature field is very strong near the heated wall in all cases. Finally, the overall solutions of the problems considered in conclusion.     

Influence of temperature dependent viscosity on peristaltic transport of a Newtonian fluid: Application of an endoscope

The effects of variable temperature dependent viscosity on peristaltic flow of Newtonian fluid in an annulus has been investigated with long wave length approximations. A regular perturbation method has been used to obtain explicit form for the velocity, temperature and relation between flow rate and pressure gradient. The expression for the pressure rise, friction force, velocity and temperature were plotted for different values of variable viscosity parameter β, radius ratio, amplitude ratio ?, heat absorption parameter β₁, and force convection parameter G_r. It is found that the pressure rise decrease as the viscosity parameter β increases and increases as the radius ratio as ? increases and β decreases.