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排序方式: 共有194条查询结果,搜索用时 218 毫秒
101.
Mubasher Jamil Farook Rahaman Mehedi Kalam 《The European Physical Journal C - Particles and Fields》2009,60(1):149-156
The standard model of cosmology is investigated using a time-dependent cosmological constant Λ and Newton gravitational constant G. The total energy content is described by the modified Chaplygin gas equation of state. It is found that the time-dependent
constants coupled with the modified Chaplygin gas interpolate between the earlier matter to the later dark-energy dominated
phase of the universe. We also achieve a convergence of the parameter ω→−1, almost at the present time. Thus our model fairly alleviates the cosmic-coincidence problem, which demands ω=−1 at the present time. 相似文献
102.
Nurul Huda Gazi Safiur Rahaman Khan Charu Gopal Chakrabarti 《Nonlinear Analysis: Hybrid Systems》2009,3(1):74-86
The paper deals with the dynamical behavior of fish and mussel population in a fish farm where external food is supplied. The ecosystem of the fish farm is represented by a set of nonlinear differential equations involving the nutrient (food), fish and mussels. We have studied the boundedness, local stability and global stability of the model system. We have incorporated the discrete type gestational delay of fish and analyze effect of the delay on the dynamical behavior of the model system. The delay parameter complicates the dynamics depending on the external food from changing the stable state to unstable damped periodic trajectories leading to a limit cycle oscillation. We have studied the Hopf-bifurcation of the model system in the neighborhood of the coexisting equilibrium point considering delay as a variable bifurcation parameter. We have performed numerical simulation to verify the analytical results. The entire study reveals that the external food supply controls the dynamics of the system. 相似文献
103.
Eronen T Elomaa V Hager U Hakala J Jokinen A Kankainen A Moore I Penttilä H Rahaman S Rissanen J Saastamoinen A Sonoda T Aystö J Hardy JC Kolhinen VS 《Physical review letters》2006,97(23):232501
The beta-decay Q(EC) values of the superallowed beta emitters 26Alm, 42Sc, and 46V have been measured with a Penning trap to a relative precision of better than 8 x 10(-9). Our result for 46V, 7052.72(31) keV, confirms a recent measurement that differed from the previously accepted reaction-based Q(EC) value. However, our results for 26Alm and 42Sc, 4232.83(13) keV and 6426.13(21) keV, are consistent with previous reaction-based values. By eliminating the possibility of a systematic difference between the two techniques, this result demonstrates that no significant shift in the deduced value of Vud should be anticipated. 相似文献
104.
Kimet Jusufi Nayan Sarkar Farook Rahaman Ayan Banerjee Sudan Hansraj 《The European Physical Journal C - Particles and Fields》2018,78(4):349
Weak gravitational lensing by black holes and wormholes in the context of massive gravity (Bebronne and Tinyakov, JHEP 0904:100, 2009) theory is studied. The particular solution examined is characterized by two integration constants, the mass M and an extra parameter S namely ‘scalar charge’. These black hole reduce to the standard Schwarzschild black hole solutions when the scalar charge is zero and the mass is positive. In addition, a parameter \(\lambda \) in the metric characterizes so-called ‘hair’. The geodesic equations are used to examine the behavior of the deflection angle in four relevant cases of the parameter \(\lambda \). Then, by introducing a simple coordinate transformation \(r^\lambda =S+v^2\) into the black hole metric, we were able to find a massless wormhole solution of Einstein–Rosen (ER) (Einstein and Rosen, Phys Rev 43:73, 1935) type with scalar charge S. The programme is then repeated in terms of the Gauss–Bonnet theorem in the weak field limit after a method is established to deal with the angle of deflection using different domains of integration depending on the parameter \(\lambda \). In particular, we have found new analytical results corresponding to four special cases which generalize the well known deflection angles reported in the literature. Finally, we have established the time delay problem in the spacetime of black holes and wormholes, respectively. 相似文献
105.
106.
Rauth C Ackermann D Blaum K Block M Chaudhuri A Di Z Eliseev S Ferrer R Habs D Herfurth F Hessberger FP Hofmann S Kluge HJ Maero G Martín A Marx G Mukherjee M Neumayr JB Plass WR Rahaman S Rodríguez D Scheidenberger C Schweikhard L Thirolf PG Vorobjev G Weber C 《Physical review letters》2008,100(1):012501
The masses of six neutron-deficient rare holmium and thulium isotopes close to the proton drip line were determined with the SHIPTRAP Penning trap mass spectrometer. For the first time the masses of the proton-unbound isotopes 144,145Ho and 147,148Tm were directly measured. The proton separation energies were derived from the measured mass values and compared to predictions from mass formulas. The new values of the proton separation energies are used to determine the location of the proton drip line for holmium and thulium more accurately. 相似文献
107.
Kankainen A Elomaa VV Batist L Eliseev S Eronen T Hager U Hakala J Jokinen A Moore ID Novikov YN Penttilä H Popov A Rahaman S Rinta-Antila S Rissanen J Saastamoinen A Seliverstov DM Sonoda T Vorobjev G Weber C Aystö J 《Physical review letters》2008,101(14):142503
Nuclides in the vicinity of 94Ag have been studied with the Penning trap mass spectrometer JYFLTRAP at the Ion-Guide Isotope Separator On-Line. The masses of the two-proton-decay daughter 92Rh and the beta-decay daughter 94Pd of the high-spin isomer in 94Ag have been measured, and the masses of 93Pd and 94Ag have been deduced. When combined with the data from the one-proton- or two-proton-decay experiments, the results lead to contradictory mass excess values for the high-spin isomer in 94Ag, -46 370(170) or -44 970(100) keV, corresponding to excitation energies of 6960(400) or 8360(370) keV, respectively. 相似文献
108.
C. Rauth D. Ackermann G. Audi M. Block A. Chaudhuri S. Eliseev F. Herfurth F. P. Heßberger S. Hofmann H.-J. Kluge A. Martín G. Marx M. Mukherjee J. B. Neumayr W. R. Plaß S. Rahaman D. Rodríguez L. Schweikhard P. G. Thirolf G. Vorobjev C. Weber 《The European physical journal. Special topics》2007,150(1):329-335
109.
J. Rissanen V. -V. Elomaa T. Eronen J. Hakala A. Jokinen S. Rahaman S. Rinta-Antila J. Äystö 《The European Physical Journal A - Hadrons and Nuclei》2007,34(2):113-118
The feasibility of the JYFLTRAP for in-trap spectroscopy has been studied. Several internally converted transitions have been
measured for isomers of fission products with good accuracy. High-resolution spectroscopic data free of source effects have
been obtained proving that trapped radioactive ions can provide excellent conversion electron sources. The shortest-lived
isomer studied in this work was 117m
Pd with a half-life of 19.1ms, for which a superior peak-to-total ratio and an excellent line shape at the 9.9keV conversion
electron line have been observed. Detection efficiencies and related phenomena of the present setup are analyzed. 相似文献
110.
H. Penttilä J. Äystö V.-V. Elomaa T. Eronen D. Gorelov U. Hager J. Hakala A. Jokinen A. Kankainen P. Karvonen T. Kessler I. Moore S. Rahaman S. Rinta-Antila V. Rubchenya T. Sonoda 《The European physical journal. Special topics》2007,150(1):317-318
A novel method to determine independent yields in proton induced fission employing ion counting after a Penning trap has
been developed.
A satisfactory agreement with previous measurements was found for independent yields of Cs isotopes in 50 MeV proton
induced fission. 相似文献