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Electronic transport properties, namely the electrical resistivity and the thermoelectric power, of liquid less-simple metals, Zn, Cd, Hg, In, Tl, Sn, Pb, Sb, and Bi, are calculated using Ziman's theory. The effective electron-ion and ion-ion interactions are described by the Bretonnet-Silbert model. The static structure factors are evaluated by the self-consistent Variational Modified Hyper-netted Chain (VMHNC) integral equation of liquids. The results for the electrical resistivity are fairly good when compared with experimental data, but the agreement improves significantly when the blurring of the Fermi surface due to the finite electron mean free path is accounted for. The values of the thermoelectric power, for most systems, have the same sign and order of magnitude as the experimental ones. The results for the thermopower also show that the contribution of the energy dependent term of the electron-ion potential is significant for the concerned systems.

The partial static structure factors, using the Faber-Ziman (FZ) theory, have been calculated for Ag-In alloy. For 20% Ag at 623 K and 70% Ag at 973 K, the interionic pair potential based on the Bretonnet-Silbert (BS) formalism are calculated and the hard sphere diameters for the component elements are estimated from the potential profile using the linearised Weeks-Chandler-Andersen (LWCA) method. The average number densities are calculated on the assumption that the atomic volumes are simply additive. The calculated structure factors are compared with the experimental values. The partial structure factors for Ag-Ag at 20% Ag and In-In at 70% Ag appear to be slightly out of phase with the calculated values particularly in large q-region. From the calculations it appears that this discrepancy is related to the process of derivation of the experimental structure factors from the total one, and the Ag-In alloy can be described by a mixture of hard spheres.

We have investigated a number of structural, thermodynamic and atomic transport properties of various liquid noble and transition metals. The underlying theory combines a simple form of the N-body potential and the thermodynamically self-consistent variational modified hypernetted chain (VMHNC) theory of liquid. The static structure factors calculated by using the VMHNC resemble, as expected, the hard sphere (HS) values. Consequently the HS model is used to calculate thermodynamic properties, viz. the specific heat, entropy, isothermal compressibility and the shear viscosity of liquid Ni, Cu, Ag, and Au. The results are in reasonable accord with the experimental values.

Static structure factors, S(q), thermodynamic properties and shear viscosities for liquid Zn, Cd, Hg. In. Tl, Sn, Pb, Sb, and Bi are investigated systematically. A model pseudotential which combines the sp- and d-band contributions is employed to derive interionic interactions. The liquid state is described by using the thermodynamically self-consistent variational modified hypernetted chain (VMHNC) integral equation theory, and also by using the linearised version of the Weeks-Chandler-Andersen (LWCA) thermodynamic perturbation theory of liquids. Results of calculations for all of the above properties are found to be in good agreement with available experimental data. The calculated results also reveal qualitatively that there is a relationship between the rate of change of viscosity with temperature and the depth of the potential well concerned.

The results of calculations for static structure factors, S ( q ), and shear viscosities for less simple liquid metals, Zn, Cd, In, Hg and Pb, are presented. These have been studied by using effective interionic pair potentials which are derived from a local approach that successfully combines the sp-band contribution with the contribution of sd mixing. Specifically the sp-band contribution is described by an empty core model and the d-band contribution is deduced from the scattering phase shift by applying an inverse scattering method. The liquid structure is investigated by using two liquid state theories. These are the thermodynamically self consistent variational modified hypernetted chain integral equation theory and the linearised version of the Weeks–Chandler–Andersen thermodynamic perturbation theory of liquids. The viscosity is calculated on the assumption that this property of a liquid metal resembles that of an appropriate hard sphere liquid. Theoretical results for both properties are found to be in good agreement with available experimental data.

Effective pair potentials for liquid rare earth metals have been derived from the embedded atom method approach. Liquid structure and thermodynamic properties namely the Helmholtz free energy, internal energy, and entropy are calculated using the above potentials. A good agreement with the experimental data for structure, free and internal energies has been found. Results of entropies across the lanthanide series show a systematic difference between the calculated and experimental values. The difference reveals that the electronic plus magnetic contribution to the entropy is important in the case of liquid rare earth metals. This discrepancy also indicates that the present EAM scheme is unable to account properly for the above two contributions.

The pair distribution function, g(r), for Ni and Cu at various temperatures above melting are investigated by using the Finnis-Sinclair (FS) many-body potentials and the thermodynamically self-consistent Variational Modified Hypernetted Chain (VMHNC) theory. The overall agreement with experiment is reasonably good. The calculations indicate that the many-body interactions, precisely taken care of by the FS potentials, are important for the study of g(r) for the liquid transition and noble metals. The results also permit us to examine the applicability of the temperature independent approximation of the FS potentials.

We have investigated the roles of the coordination numbers and interatomic interactions on Einstien temperatures 0e for a number of bee 3d transition metals. We have employed a few of the popular transition metal pseudopotentials in the Calculations aiming at a comparative survey of the roles of these pseudopotentials on the Einstein temperature; the role of the neighboring atoms on the latter emerges as a by-product of the calculations.

Liquid structure for the 3d transition metals near melting is investigated using the linearized Weeks-Chandler-Andersen (LWCA) theory. Here the effective interionic pair potential is described by the Wills-Harrison model. Results show that LWCA predicts the structure factor much better than that of WCA. Results also show that in the middle of the 3d series LWCA predicts reasonable liquid structure where the WCA-ORPA has been unsuccessful.

An economic anylysis was made to determine the cost of fish production in the floodplains at Daudkandi Upazilla in Comilla district during the period form January to April, 2007. Survey method was followed to collect data from 20 floodplain aquaculture projects. The projects record books and personal interviews of the NGOs and Fisheries officers were the main instruments of data collection. Statistical tools such as: range, mean, standard deviation and percentage were employed for analysis of data. The Cobb-Douglas production function model was used to estimate the values of co-efficients and related statistics of production function of fish culture in floodplains. Out of eleven explanatory variables, seven co-efficients had positive sign while only four co-efficients showed negative sign. The co-efficients bearing positive sign i.e., embankment construction, nursery and land lease, fertilizer and lime, fingerlings, feed, labor and staff wages and miscellaneous cost made positive impact on the farm income, while the co-efficients having negative sign i.e., area of floodplain, Office management, compensation and harvesting and marketing cost decreased the farm income. Summation of the production co-efficients i.e., return to scale (Σbi) was found 1.023 which implies that per one taka investment in floodplain fish culture will give rise to a profit of Tk. 1.02. The value of R2 was found 0.892, which means that the variations in farm income could be explained to the extent of 89.2% by the included variables. The remaining 10.8% variations could not be accounted for by the multiple regression analysis. Average fish production in the selected floodplains was 2920.43 kg/ha of which production of cultured fish and indigenous fish was 2697.35 and 223.08 kg/ha respectively. The cost of fish production, total return and net income were estimated Tk. 1,153,08.55, 1,76,385.49 and 61,076.94 /ha. respectively. Benefit cost ratio was found 1.53. Keywords: Floodplain; Aquaculture; Economic analysis; Resource productivity; Community DOI: 10.3329/jbau.v8i2.7945 J. Bangladesh Agril. Univ. 8(2): 323-332, 2010

The static structure factors, S(q), for a number of liquid noble and transition metals are calculated. The underlying theory combines together a simple form of the N-body potential and the thermodynamically self-consistent variational modified hypernetted chain (VMHNC) theory of liquid. The static structure factors calculated by using the VMHNC resemble the hard sphere (HS) and these are consistent with experiments.