Numerical Simulations of Hydromagnetic Mixed Convection Flow of Nanofluids inside a Triangular Cavity on the Basis of a Two-Component Nonhomogeneous Mathematical Model

Nanofluids have enjoyed a widespread use in many technological applications due to their peculiar properties.Numerical simulations are presented about the unsteady behavior of mixed convection of Fe_(3)O_(4)-water,Fe_(3)O_(4)-kerosene,Fe_(3)O_(4)-ethylene glycol,and Fe_(3)O_(4)-engine oil nanofluids inside a lid-driven triangular cavity.In particular,a two-component non-homogeneous nanofluid model is used.The bottom wall of the enclosure is insulated,whereas the inclined wall is kept a constant(cold)temperature and various temperature laws are assumed for the vertical wall,namely:
θ=1(Case 1),θ=Yð1YÞ(Case 2),andθ=sinð2-YÞ(Case 3).A tilted magnetic field of uniform strength is also present in the fluid domain.From a numerical point of view,the problem is addressed using the Galerkin weighted residual finite element method.The role played by different parameters is assessed,discussed critically and interpreted from a physical standpoint.We find that a higher aspect ratio can produce an increase in the average Nusselt number.Moreover,the Fe_(3)O_(4)-EO and Fe_(3)O_(4)-H2O nanofluids provide the highest and smallest rate of heat transfer,respectively,for all the considered(three variants of)thermal boundary conditions.

Diversity and structural composition of species in dipterocarp forests:a study from Fasiakhali Wildlife Sanctuary, Bangladesh

Fasiakhali Wildlife Sanctuary is a protected area composed of tropical remnant rainforest that harbor substantial number of large,old Garjan（Dipterocarpus spp.）trees.The present study assessed composition,structure and diversity of the species in this protected area.A total of 32 trees species were recorded with DBH ≥ 11 cm belonging to 24 genera and 19 families.The forest is low in plant diversity as represented by Shannon–Wiener diversity and Simpson Dominance indices.Dipterocarpus turbinatus was the most dominant species with maximum relative density,frequency,dominance,and importance value index.Syzygium firmum and Tectona grandis followed in terms of dominance.The structural composition indicated higher number of individuals in the medium growth classes（41 to 〈 511 cm DBH and 16–20 m height ranges）,whereas D.turbinatus was the only species that dominated most of the growth classes.Poor stem density in lower growth classes indicated meager recruitment of regeneration which may be due to lower annual precipitation,increased grazing and encroachments.This study will help to understand the patterns of tree species composition and diversity in the remnant dipterocarp forests of Bangladesh.It will also contribute to identifying threatened plants to undertake D.turbinatus based conservation and sustainable management of the Fasiakhali Wildlife Sanctuary.

Effects of bi-kappa distributed electrons on dust-ion-acoustic shock waves in dusty superthermal plasmas

The basic properties of dust-ion-acoustic （DIA） shock waves in an unmagnetized dusty plasma （containing inertial ions, kappa distributed electrons with two distinct temperatures, and negatively charged immobile dust grains） are investi- gated both numerically and analytically. The hydrodynamic equation for inertial ions has been used to derive the Burgers equation. The effects of superthermal bi-kappa electrons and ion kinematic viscosity, which are found to modify the basic features of DIA shock waves significantly, are briefly discussed.

Pre-sowing treatments for improved germination and growth of two rare native species of Bangladesh

Pre-sowing treatments are expected to increase seed germination.This evaluates response to pre-sowing treatments and the growth performance of two native and rare tree species,Garuga pinnata Roxb.and Vitex glabrata R.Br.The hard seed coats were treated by rubbing with sand paper,nail clipping,and immersion in water and acid（H_2SO_4）.Results indicate that G.pinnata showed a 90% germination rate and 30% germination energy when seed coats were nicked with a nail clipper.Rubbing with sand paper was the best pre-sowing treatment for V.glabrata,resulting a 80% germination rate and 30% germination energy.G.pinnata and V.glabrata seedlings from seeds soaked 24h in water resulted in maximum heights and collar diameters.These were significantly higher（at p〈0.05） than those of other treatments.The results indicate that scarification or nicking of seeds may have some negative impacts on seedling growth.Therefore,it is difficult to recommend a pre-sowing treatment of seeds for achieving both maximum germination and good early seedling growth.

Economic profitability of cane based furniture enterprises of Chittagong City Corporation Area, Bangladesh

An exploratory survey was conducted to assess economic profitability of cane based furniture enterprises in Chittagong City Corporation area of Bangladesh. A multistage random sampling was adopted to carry out the study. Based on the total investment the enterprises were divided into large, medium and small.. Most of the entrepreneurs （55%） are in the age class 40-50 years and only （18.33%）are ＞50 years. In small and medium category lowest entrepreneurs （8.33% each） are found graduate and 18.33% in large farm. Most of the enterprises are in the small category （45%） and 66.67% labors are skilled whereas only 33.33% are unskilled. Seven articles of sixteen different sizes were identified made from cane, which are Sofa （45 cm × 45 cm, 50 cm × 50 cm and 55 cm × 55 cm）, Dinning （4ch. 1tab,and 6ch. 1tab.）, Bed （1 m × 2m, 1.3 m × 2.3 m and 1.5 m × 2.3 m）, Chair （45 cm × 45 cm and 50 cm ×50 cm）, Rocking chair （large size,medium and small size）, Dolna （Hanging and Running） and Partition. In all the three category enterprises chair （45 cm × 45 cm） was produced in highest number and the lowest production was Bed （1.5 m × 2.3 m）. The total net benefit （2089 US$） and benefit cost ratio （1：16）was the highest for large cane enterprises. So among three categories of the cane enterprises the large enterprises are more profitable than others.

Electrostatic Nonplanar Positron-Acoustic Shock Waves in Superthermal Electron-Positron-Ion Plasmas

The basic properties of the nonlinear propagation of the nonplanar （cylindrical and spherical） positronacoustic （PA） shock waves （SHWs） in an unmagnetized electron-positron-ion （e-p-i） plasma containing immobile positive ions, mobile cold positrons, and superthermal （kappa distributed） hot positrons and electrons are investigated both analytically and numerically. The modified Burgers equation （roBE） is derived by using the reductive perturbation method. The basic features of PA SHWs are significantly modified by the cold positron kinematic viscosity （U）, superthermal parameter of electrons （ke）, superthermal parameter of hot positrons （kp）, the ratio of the electron temperature to hot positron temperature （or）, the ratio of the electron number density to cold positron number density （μe）, and the ratio of the hot positron number density to cold positron number density （μph）. This study could be useful to identify the basic properties of nonlinear electrostatic disturbances in dissipative space and laboratory plasmas.

Cylindrical and Spherical Electron-Acoustic Shock Waves in Electron-Positron-Ion Plasmas with Nonextensive Electrons and Positrons

Electron-acoustic shock waves （EASWs） in an unmagnetized four-component plasma （containing hot elec- trons and positrons following the q-nonextensiv.e distribution, cold mobile viscous electron fluid, and immobile positive ions） are studied in nonplanar （cylindrical and spherical） geometry. With the help of the reductive perturbation method, the modified Burgers equation is derived. Analytically, the effects of nonplanar geometry, nonextensivity, relative number density and temperature ratios, and cold electron kinematic viscosity on the basic properties （viz. amplitude, width, speed, etc.） of EASWs are discussed. It is exarmined that the EASWs in nonplanar geometry significantly differ from those in planar geometry. The results of this investigation can be helpful in understanding the nonlinear features of EASWs in various astrophysical plasmas.