OPTIMAL DESIGN OF HIGHWAY CRASH CUSHIONS

Crash cushions are deployed at gores and in front of other fixed objects along the roadway when their proximity to the travelled way poses an unacceptable risk to the travelling public. A crash cushion is intended to act as a deformable shield that causes an errant vehicle to decelerate more slowly, dramatically reducing the potential severity of injuries suffered by vehicle occupants. This paper formulates the design of such a system as a constrained optimization problem which is solved using contemporary search techniques implemented in commercial software. The methodology is demonstrated on high-molecular-weight, high-density polyethylene (HMW/HDPE) cylinders arrayed in a single line to form a crash cushion which carries the trade name REACT® 350 system. The wall thickness of each cylinder in the array is treated as a design variable. The diameter of the cylinders and the total number in the array are treated as parameters and not directly addressed by the optimization process. A simple one dimensional array of masses and nonlinear springs are used to simulate the dynamic interaction of a vehicle and the cushion system and yield a value for the Occupant Impact Velocity (OVI) and Ride Down Acceleration (RDA) for a given set of cylinder parameters. Prescribed upper limits on OVI and RDA under impact of two standard mass vehicles form the four implicit, nonlinear constraints in the problem. The objective function to be minimized is the total weight of the barrels used over all cylinders in the system. Optimization results are presented for one REACT® system reported in the literature

K-quantum Nonlinear Jaynes-Cummings Model in Two Trapped Ions

A k-quantum nonlinear Jaynes-Cummings model for two trapped ions interacting with laser beams resonant to k-th red side-band of center-of-mass mode, far from Lamb-Dicke regime, has been obtained. The exact analytic solution showed the existence of quantum collapses and revivals of the occupation of two atoms.Comment: 8 pages, 3 figure

Minimal Dark Matter in the Local B−LB-L Extension

The minimal gauge group extension to the standard model (SM) by the local $U(1)_{B-L}$ (MBLSM) is well known as the minimal model to understand neutrino mass origins via the seesaw mechanism, following the gauge principle. This "small" symmetry also has deep implication to another big thing, dark matter (DM) stability. We demonstrate it in the framework of minimal dark matter (MDM), which aims at addressing two basic questions on DM, stability and the nature of interactions. However, stability and perturbativity may only allow the fermionic quintuplet. The situation is very different in the MBLSM, which leaves the subgroup of $U(1)_{B-L}$, the matter parity $(-1)^{3(B-L)}$, unbroken; it is able to stabilize all of the weakly-interacting {MDM candidates } after assigning a proper $U(1)_{B-L}$ charge. For the candidates with nonzero hypercharge, the phenomenological challenge comes from realizing the inelastic DM scenario thus evading the very strict DM direct detention bounds. We present two approaches that can slightly split the CP-even and -odd parts of the neutral components: 1) using the dimension 5 operators, which works for the $U(1)_{B-L}$ spontaneously breaking at very high scale; 2) mixing with {other fields} having zero hypercharge, which instead works for a low $U(1)_{B-L}$ breaking scale.Comment: 13 pages without figure

The Evidence for a Binary origin of the Young Planetary Nebula HB 12

The young planetary nebulae play an important role in stellar evolution when intermediate- to low-mass stars (0.8 $\sim$ 8 M$_\odot$) evolve from the proto-planetary nebulae phase to the planetary nebulae phase. Many young planetary nebulae display distinct bipolar structures as they evolve away from the proto-planetary nebulae phase. One possible cause of their bipolarity could be due to a binary origin of its energy source. Here we report our detailed investigation of the young planetary nebula, Hubble 12, which is well-known for its extended hourglass-like envelope. We present evidence with time-series photometric observations the existence of an eclipsing binary at the center of Hubble 12. Low-resolution spectra of the central source show, on the other hand, absorption features such as CN, G-band & Mg b{\arcsec}, which can be suggestive of a low-mass nature of the secondary component.Comment: 9 pages, 11 figures, Accepted for publication in A