850,782 research outputs found
A More Precise Extraction of |V_{cb}| in HQEFT of QCD
The more precise extraction for the CKM matrix element |V_{cb}| in the heavy
quark effective field theory (HQEFT) of QCD is studied from both exclusive and
inclusive semileptonic B decays. The values of relevant nonperturbative
parameters up to order 1/m^2_Q are estimated consistently in HQEFT of QCD.
Using the most recent experimental data for B decay rates, |V_{cb}| is updated
to be |V_{cb}| = 0.0395 \pm 0.0011_{exp} \pm 0.0019_{th} from B\to D^{\ast} l
\nu decay and |V_{cb}| = 0.0434 \pm 0.0041_{exp} \pm 0.0020_{th} from B\to D l
\nu decay as well as |V_{cb}| = 0.0394 \pm 0.0010_{exp} \pm 0.0014_{th} from
inclusive B\to X_c l \nu decay.Comment: 7 pages, revtex, 4 figure
Momentum distribution and correlation of two-nucleon relative motion in He and Li
The momentum distribution of relative motion between two nucleons gives
information on the correlation in nuclei. The momentum distribution is
calculated for both He and Li which are described in a three-body
model of ++. The ground state solution for the three-body
Hamiltonian is obtained accurately using correlated basis functions. The
momentum distribution depends on the potential model for the -
interaction. With use of a realistic potential, the He momentum
distribution exhibits a dip around 2 fm characteristic of -wave
motion. In contrast to this, the Li momentum distribution is very similar
to that of the deuteron; no dip appears because it is filled with the -wave
component arising from the tensor force.Comment: 14 pages, 9 figure
Pilot decision making in a computer-aided flight management situation
An experimental representation of a computer-aided multi-task flight management situation has been developed. A computer aiding program was implemented to serve as a back-up decision maker. An experiment was conducted with a balanced design of several subject runs for different workload levels. This was achieved using three levels of subsystem event arrival rates, three levels of control task involvement, and three levels of availability of computer aiding. Experimental results compared quite favorably with those from a computer simulation which employed a queueing model. It was shown that the aiding had enhanced system performance as well as subjective ratings, and that the adaptive aiding policy further reduced subsystem delay
Three New Species of Hyperaspis from Eastern North America (Coleoptera: Coccinellidae)
Excerpt: A number of apparently related species, including the three which are newly described in this paper, belong to the large binotata group of Dobzhansky (1941). It has been found necessary to re-examine this group and to divide it into smaller, more homogeneous species clusters. These new species clusters may indicate more clearly the relationships of the species involved
Voltage-Mode Highpass, Bandpass, Lowpass and Notch Biquadratic Filters Using Single DDCC
A new voltage-mode multifunction biquadratic filter using one differential difference current conveyor (DDCC), two grounded capacitors and three resistors is presented. The proposed circuit offers the following attractive advantages: realizing highpass, bandpass, lowpass and notch filter functions, simultaneously, from the same circuit configuration; employing grounded capacitors, which is ideal for integration and simpler circuit configuration
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