β-decay studies of the neutron-rich 18,21N isotopes

The β-decay studies of neutron-rich ^18,21N isotopes have been performed using β-n, β-γ, and β-n-γ coincidence methods. The ^18,21N ions were produced by the fragmentation of the ²²Ne and ²⁶Mg beams, respectively, on a thick beryllium target. The time of flight of the emitted neutrons following the β-decay of ^18,21N was measured by a neutron detector system with wide energy detection range and low-energy detection threshold. In addition, several clover germanium detectors were used to detect the β-delayed γ-rays. The half-lives of the β-decays of ¹⁸N and ²¹N were determined to be (619±2) ms and (82.9±7.5) ms, respectively. Several new β-delayed neutron groups were observed with a total branching ratio of (6.98±1.46)% and (90.5±4.2)% for ¹⁸N and ²¹N, respectively. The level schemes of ¹⁸O and ²¹O were deduced. The experimental Gamow-Teller β-decay strengths of ¹⁸N and ²¹N to these levels were compared with the shell model calculations.     

β-decay studies of the neutron-rich ~(18,21)N isotopes

The β-decay studies of neutron-rich 18,21N isotopes have been performed using β-n, β-γ, and β-n-γ coincidence methods. The 18,21N ions were produced by the fragmentation of the 22Ne and 26Mg beams, respectively, on a thick beryllium target. The time of flight of the emitted neutrons following the β-decay of 18,21N was measured by a neutron detector system with wide energy detection range and low-energy detection threshold. In addition, several clover germanium detectors were used to detect the β-delayed γ-r...     

A numerical investigation of the evolution of 2-D disturbances in hypersonic boundary layers and the effect on the flow structure due to the existence of shocklets

~~A numerical investigation of the evolution of 2-D disturbances in hypersonic boundary layers and the effect on the flow structure due to the existence of shocklets~~     

Immersed boundary method for the simulation of 2D viscous flow based on vorticity–velocity formulations

A new immersed boundary method based on vorticity–velocity formulations for the simulation of 2D incompressible viscous flow is proposed in present paper. The velocity and vorticity are respectively divided into two parts: one is the velocity and vorticity without the influence of the immersed boundary, and the other is the corrected velocity and the corrected vorticity derived from the influence of the immersed boundary. The corrected velocity is obtained from the multi-direct forcing to ensure the well satisfaction of the no-slip boundary condition at the immersed boundary. The corrected vorticity is derived from the vorticity transport equation. The third-order Runge–Kutta for time stepping, the fourth-order finite difference scheme for spatial derivatives and the fourth-order discretized Poisson for solving velocity are applied in present flow solver. Three cases including decaying vortices, flow past a stationary circular cylinder and an in-line oscillating cylinder in a fluid at rest are conducted to validate the method proposed in this paper. And the results of the simulations show good agreements with previous numerical and experimental results. This indicates the validity and the accuracy of present immersed boundary method based on vorticity–velocity formulations.     

Effect of the shape of an organic water–coal fuel particle on the condition and characteristics of its ignition in a hot air flow

The results of experimental studies of the effect of the shape of an organic water–coal fuel (OCWF) particle on its ignition delay time and the time of its complete burnout in a hot air flow are reported. Three most common shapes of real particles, such as spherical, ellipsoidal, and irregular-polyhedron-like, are considered. It is shown that the shortest ignition delay time and the time of complete burnout correspond to polyhedron- shaped OCWF particles. Conditions are identified under which this factor significantly influences the ignition characteristics. The experiments were carried out at initial particle sizes (averaged maximum values) of 0.5–5 mm and temperatures and velocities of the oxidant flow of 600–900 K and 0.5–5 m/s, respectively. The main components of the studied fuels were coal processing wastes and waste motor, turbine, and transformer oils.     

New limit on the half-life of 78Kr with respect to the 2K(2ν)-capture decay mode

The features of data accumulated for 1817 h in an experimental search for the 2K(2ν)-capture mode of ⁷⁸Kr decay are discussed. A new limit on the half-life for this decay is found: T _1/2≥2.3×10²⁰ yr (at a 90% C.L.).     

Letter to the Editor: On the evolution of dissipation rate and resolved kinetic energy in ALDM simulations of the Taylor–Green flow

We correct a data processing error in the article “Construction of explicit and implicit dynamic finite difference schemes and application to the large-eddy simulation of the Taylor–Green vortex” by Dieter Fauconnier, Chris De Langhe and Erik Dick published in the Journal of Computational Physics 228 (2009), pp. 8053–8084.