Momentum Transfer
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Noboru Watanabe ◽  
Masahiko Takahashi

Abstract We report a theoretical study of electronic excitation in CH3Cl and CF3Cl by electron impact. Momentum-transfer-dependent generalized oscillator strengths (GOSs) are calculated for transitions to low-lying excited singlet-states at the equation-of-motion coupled-cluster singles and doubles level. The influence of molecular vibration is taken into account in the calculation. The theoretical results show reasonable overall agreement with experimental data reported in the literature. The shapes of the GOS profiles reveal that the 1 1E state of CH3Cl has a valence-Rydberg mixed nature, while that of CF3Cl is of a predominant C-Cl antibonding character. A comparison with the experimental GOSs of CH3Cl provides unambiguous evidence that the 3pe state is lower in energy than the 3pa1 state. Optical oscillator strengths are also calculated and comparison is made with available experimental and other theoretical results.

Robotics ◽  
2022 ◽  
Vol 11 (1) ◽  
pp. 11
Daniele Costa ◽  
Cecilia Scoccia ◽  
Matteo Palpacelli ◽  
Massimo Callegari ◽  
David Scaradozzi

Bio-inspired solutions devised for Autonomous Underwater Robots are currently investigated by researchers as a source of propulsive improvement. To address this ambitious objective, the authors have designed a carangiform swimming robot, which represents a compromise in terms of efficiency and maximum velocity. The requirements of stabilizing a course and performing turns were not met in their previous works. Therefore, the aim of this paper is to improve the vehicle maneuvering capabilities by means of a novel transmission system capable of transforming the constant angular velocity of a single rotary actuator into the pitching–yawing rotation of fish pectoral fins. Here, the biomimetic thrusters exploit the drag-based momentum transfer mechanism of labriform swimmers to generate the necessary steering torque. Aside from inertia and encumbrance reduction, the main improvement of this solution is the inherent synchronization of the system granted by the mechanism’s kinematics. The system was sized by using the experimental results collected by biologists and then integrated in a multiphysics simulation environment to predict the resulting maneuvering performance.

2022 ◽  
Vol 2022 (01) ◽  
pp. 016
Cristian Gaidau ◽  
Jessie Shelton

Abstract We re-examine the gravitational capture of dark matter (DM) through long-range interactions. We demonstrate that neglecting the thermal motion of target particles, which is often a good approximation for short-range capture, results in parametrically inaccurate results for long-range capture. When the particle mediating the scattering process has a mass that is small in comparison to the momentum transfer in scattering events, correctly incorporating the thermal motion of target particles results in a quadratic, rather than logarithmic, sensitivity to the mediator mass, which substantially enhances the capture rate. We quantitatively assess the impact of this finite temperature effect on the captured DM population in the Sun as a function of mediator mass. We find that capture of DM through light dark photons, as in e.g. mirror DM, can be powerfully enhanced, with self-capture attaining a geometric limit over much of parameter space. For visibly-decaying dark photons, thermal corrections are not large in the Sun, but may be important in understanding long-range DM capture in more massive bodies such as Population III stars. We additionally provide the first calculation of the long-range DM self-evaporation rate.

2022 ◽  
Vol 2150 (1) ◽  
pp. 012028
V I Popov ◽  
A V Kuznetsov

Abstract The method of integral momentum transfer relations has been extended to polymer systems with a locally nonequilibrium relaxation microstructure. The influence of the locally non-equilibrium transfer of the impulse flux on the characteristics of the development of their boundary-layer motion is analyzed.

S.D. Raducan ◽  
M. Jutzi ◽  
T.M. Davison ◽  
M.E. DeCoster ◽  
D.M. Graninger ◽  

2021 ◽  
Xiaoli Zhao ◽  
Kedong Wang

Abstract We present elastic electron scattering cross sections with holmethane molecules CH2Br2 and CCl2Br2 in the low energy region ranging from 0.01 to 20 eV. The calculations are performed with R-matrix method in static-exchange plus polarization (SEP) and close-coupling (CC) approximations. The integral, differential, and momentum transfer cross sections are calculated. The convergence of the obtained cross sections is checked at four different levels of SEP approximation. The predicted positions of the resonances agree well with available results. The precise resonance parameters are found to be sensitive to the treatment of polarization effects employed. We found that the polarization has a substantial effect on the cross sections, and this effect becomes even more important for lower impact energies.

2021 ◽  
Vol 9 ◽  
Qi Wang ◽  
Fu-Hu Liu ◽  
Khusniddin K. Olimov

The squared momentum transfer spectra of light mesons, π0, π+, η, and ρ0, produced in high-energy virtual photon-proton (γ*p) → meson + nucleon process in electron-proton (ep) collisions measured by the CLAS Collaboration are analyzed by the Monte Carlo calculations, where the transfer undergoes from the incident γ* to emitted meson or equivalently from the target proton to emitted nucleon. In the calculations, the Erlang distribution from a multi-source thermal model is used to describe the transverse momentum spectra of emitted particles. Our results show that the average transverse momentum (⟨pT⟩) and the initial-state temperature (Ti) increase from lower squared photon virtuality (Q2) and Bjorken variable (xB) to higher one. This renders that the excitation degree of emission source, which is described by ⟨pT⟩ and Ti, increases with increasing of Q2 and xB.

Prashant Unnikrishnan Nair

In real-world water injection applications, an in-line injection facilitates a pressure differential that boosts the current flow. A pressure differential created by the injection of a pressurized flow into the mainline of flow is derived from the momentum transfer equation. Heat loss is disregarded, and such empirical equations provide a ballpark value to these pressure differentials during the injection. In industrial applications, injection of the fluid is done on the surface, due to weld and other constraints where losses due to friction and eddy current formation are imminent. On the other hand, penetration injection provides a far more augmented pressure differential that has a polynomial impact based on the mainline flow rate and the injection flow rate. This paper aims to derive an accurate representation of the pressure differential values obtained from a penetration injection through experimentation and compare it against a surface injection or empirical calculation. The paper concludes by indicating that the penetration injection augments the pressure differential with a new empirical formula for the derived pressure differential as a polynomial equation for this apparatus and can be extended across different sizes of the mainline and injection line diameters. This work provides a precise formula that can be used to derive pressure differential and estimate the flow and pressure rates. The formula also provides a platform for further utility in the fracturing operations where fracture flow from the well upstream presents multiple injection fractures to the mainline through fracture pores.

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