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71.
72.
An alternative approach is suggested to determine the spot-size of a multi-mode laser beam. It has been shown by simulations
that the suggested approach can give the beam quality factor and characteristic radius with less than 5% error. Unlike the
power content method, the proposed method is applicable to the beams even with diameter one tenth of the CCD size. The new
approach has been applied to a multi-mode diode laser output and it is shown that the ABCD matrix analysis can be used for beam propagation, with the measured parameters of the laser. 相似文献
73.
Shashwati Sen DK Aswal Ajay Singh TV Chandrasekhar Rao KP Muthe JC Vyas LC Gupta SK Gupta VC Sahni 《Pramana》2002,58(5-6):867-870
The MgB2 superconductor, synthesized using solid-state and liquid-phase sintering methods, have been characterized for various properties.
The upper critical field, irreversibility line and critical current density have been determined using magnetization data.
The current-voltage characteristics recorded under an applied magnetic field revealed the existence of vortex glass transition.
The surface analysis using X-ray photoelectron spectroscopy shows that MgB2 is sensitive to atmospheric degradation. 相似文献
74.
Abstract The problem of crystalline to amorphous (c → a) phase transformation, in the context of shock loading, is analyzed. The studies under static pressures show that beyond the stability field of the ambient phase, an amorphous phase may be realized if the kinetic conditions are not favorable to the accessibility of equilibrium phase of higher coordination. The examination of shock results of some of these substances reveals that the so-called “mixed phase” region begins at the pressureswhich are same as that oc c → a transformation in the static experiments. Further the Hugoniot temperatures at these pressures are far lower than required for the realization of the high pressure crystalline phase. From these observations as well as from an understanding gained through static experiments, we infer that these materials amorphize under shock loading. The analysis indicates that the existence of hot-spots is not essential to the formation of diaplectic glass. Instead, it seems to emerge directly from the solid-solid phase transformation, adequately aided by favourable kinetic conditions. 相似文献
75.
A De A Mitra A Ray SR Banerjee M Sengupta A Chatterjee S Kailas HS Patel MG Betigiri SK Dutta 《Pramana》1999,53(3):549-552
In this paper, we report our measurements of back-angle oxygen and carbon particle yields from 16O+89Y, 12C+93Nb reactions forming the same compound nucleus 105Ag at the same excitation energy and spin distribution. We find anomalously large oxygen yield and entrance channel dependence
at high excitation energies from 16O+89Y reaction implying formation of a dinuclear orbiting complex. Possible connection between nuclear orbiting and fast fission
is also discussed. 相似文献
76.
High pressure behaviour of FePO4 in berlinite form has been investigated up to 10 GPa using vibrational Raman spectroscopy and energy dispersive x-ray diffraction.
Combination of these techniques along with studies on pressure quenched samples reveal structural transitions in this material
from its room pressure trigonal phase to a disordered and a crystalline phase near 3±0.5 GPa. The latter is the Cmcm phase
which is the equilibrium structure at high pressures. These high pressure phases do not revert back to its initial structure
after release of pressure. Irreversibility of these transformations indicates that FeO4 tetrahedra do not regain their initial coordination. These high pressure transitions can be rationalized in terms of the
three level free energy diagram for such systems. 相似文献
77.
The slope of the linear curve relating shock velocity and particle velocity in shock wave experiments has been examined by the pseudopotential energy band method for sp metals. The limiting density ration resulting from this linear relation is interpreted by defining a shock “hard core” for single shocks and its relation to Ashcroft's core radius is examined. 相似文献
78.
79.
Vandana Tripathi Lagy T Baby PV Madhusudhana Rao SK Hui R Singh JJ Das P Sugathan N Madhavan AK Sinha 《Pramana》1999,53(3):535-539
The ground state and excited state transfer yields for the 2-neutron pickup channel in the 28Si+68Zn system have been measured explicitly. The recoil mass separator at the nuclear Science Centre, New Delhi was used for the
measurement. A NaI(T1) detector was used for detecting the deexcitation γ’s from the transfer products. The kinematic coincidence technique was employed for the transfer measurement. Simplified coupled
channels calculations show that out of all transfer channels the major contribution to the sub-barrier enhancement comes from
the ground state 2 neutron pickup channel with a ground state Q-value of+1.83 MeV. 相似文献
80.
Bivash R Behera Subinit Roy P Basu M K Sharan S Jena M Satpathy SK Datta L Satpathy ML Chatterjee 《Pramana》1999,53(3):563-566
Time of flight and energy of fission fragments were measured using pulsed beam. Fission fragment mass and energy integrated
angular distributions were extracted. Fission fragment anisotropy was explained in the framework of saddle point model. 相似文献