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1.
Begum Moni Jewel Md. Abu Sayed Haque Md. Ayenuddin Khatun Mst. Samsad 《中国海洋湖沼学报》2019,37(3):1030-1036
The seasonal abundance of flagellates has been monitored over a period of 1 year from December2013 to November 2014(divided into 4 conjugative seasons namely winter, spring, summer, and autumn) in an experimental pond located in Rajshahi City Corporation area, Bangladesh. To our knowledge, this study is the first to shed light on the occurrence and possible interrelationships among heterotrophic flagellates(HF),bacteria and zooplankton in Bangladesh and the result obtained by this study will be beneficial for similar water ecosystem all over the world. Standard methods were used to determine the prescribed hydrological parameters and zooplankton cell density. Maximum HF abundance(14 346.00 cells/mL) was found in the spring and the minimum(5 215.00 cells/mL) occurred in the summer. Inverse to HF, significantly(P0.05)higher zooplankton abundance was found during the winter(782.00±47.62 cells/mL) and the lowest value was found in the autumn(448.00±39.15 cells/mL). Whereas similar to the HF, total bacterial abundance was significantly higher during the spring((2.25±1.05)×10~5 cells/mL) and lower in the summer((0.79±0.06)×105 cells/mL). Multivariate analyses(ANOSIM and MDS) have shown significant seasonal differences for cell numbers where MDS ordination plot and cluster analysis based on similarity in the genera abundance of HF revealed overlapping condition between winter and spring. Canonical correspondence analysis(CCA) also showed a distinct separation among the genera based on the prevailing hydrological situation and indicated that temperature, pH, BOD_5, and NO_3~- were the most important environmental variables in determining the observed variation in HF community structure. Among the biological factors, zooplankton showed negative but total bacteria were positively correlated with HF abundance. 相似文献
2.
The impact of two boundary-layer parameterisation schemes on the prediction of Indian monsoon systems by a global spectral model has been investigated. The turbulent kinetic energy closure scheme shows a positive impact on the prediction of some important synoptic features, including the genesis of monsoon lows, the tracking of monsoon depressions, and precipitation. 相似文献
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4.
Biraja Kumar Sahu Mehmuna Begum M.K. Khadanga Dilip Kr Jha N.V. Vinithkumar R. Kirubagaran 《Marine pollution bulletin》2013,66(1-2):246-251
Port Blair is the capital city of Andaman & Nicobar Islands, the union territory of India. More than 50% of the population of these islands lives around Port Blair Bay. Therefore the anthropogenic effects in the bay water were studied for monitoring purpose from seven stations. Physico-chemical parameters of seawater were analyzed in samples collected once in every 3 months for 2 years from seven sampling stations located in Port Blair Bay, South Andaman Island to evaluate the spatial and tidal variation. Cluster analysis and factor analysis were applied to the experimental data in an attempt to understand the sources of variation of physico-chemical parameters. In cluster analysis, the stations Junglighat Bay and Phoenix Bay having high anthropogenic influence formed a separate group. The factors obtained from factor analysis indicated that the parameters responsible for physico-chemical variations are mainly related to land run-off, sewage outfall and tidal flow. 相似文献
5.
Mohammad Rezwanul Islam Syeda Fahliza Begum Yasushi Yamaguchi Katsuro Ogawa 《水文研究》1999,13(17):2907-2923
Every year the Ganges and Brahmaputra rivers in Bangladesh transport 316 and 721 million tonnes of sediment, respectively. These high loads of suspended sediment reflect the very high rate of denudation in their drainage basins. The average mechanical denudation rate for the Ganges and Brahmaputra basins together is 365 mm 103 yr−1. However, the rate is higher in the Brahmaputra Basin than that in the Ganges Basin. Several factors, including mean trunk channel gradient, relief ratio, runoff, basin lithology and recurring earthquakes are responsible for these high denudation rates. Of the total suspended sediment load (i.e. 1037 million tonnes) transported by these rivers, only 525 million tonnes (c. 51% of the total load) are delivered to the coastal area of Bangladesh and the remaining 512 million tonnes are deposited within the lower basin, offsetting the subsidence. Of the deposited load, about 289 million tonnes (about 28% of the total load) are deposited on the floodplains of these rivers. The remaining 223 million tonnes (about 21% of the total load) are deposited within the river channels, resulting in aggradation of the channel bed at an average rate of about 3·9 cm yr−1. Although the Brahmaputra transports a higher sediment load than the Ganges, the channel bed aggradation rate is much higher for the Ganges. This study also documents a wide range of interannual, seasonal and daily variation in suspended sediment transport and water discharge. Interannual variation in sediment deposition within the basin is also suggested. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
6.
An exact analysis of the effects of mass transfer on the flow of a viscous incompressible fluid past an uniformly accelerated vertical porous and non-porous plate has been presented on taking into account the free convection currents. The results are discussed with the effects of the Grashof number Gr, the modified Grashof number Sc, the Schmidt number Sc, and the suction parametera for Pr (the Prandtl number)=0.71 representating air at 20°C.Nomenclature
a
suction parameter
-
C
species concentration
-
C
species concentration at the free stream
-
g
acceleration due gravity
- Gc
modified Grashof number (vg*(C
–C
)/U
0
3
)
- Pr
Prandtl number (C
p/K)
-
T
temperature of the fluid near the plate
-
T
dimensionless temperature near the plate ((T-T
)/(T
-T
))
-
U(t)
dimensionless velocity of the plate (U/U
0)
-
v
normal velocity component
-
v
0
suction/injection velocity
-
x, y
coordinate along and normal to the plate
-
v
kinematic viscosity (/gr)
-
C
p
specific heat at constant pressure
-
C
w
species concentration at the plate
-
C
non-dimensional species concentration ((C-C
)/(C
w
-C
))
- Gr
Grashof number (g(T
w
-T
)/U
0
3
)
-
D
chemical molecular diffusivity
- K
thermal conductivity
- Sc
Schmidt number (/D)
-
T
w
temperature of the plate
-
T
free stream temperature
-
t
time variable
-
t
dimensionless time (tU
0
2
/)
-
U
0
reference velocity
-
u
velocity of the fluid near the plate
-
u
non-dimensional velocity (u/U
0)
-
v
dimensionless velocity (v/U
0)
-
v
0
non-dimensionalv
0
(v
0
/U0)=–at–1/2
-
y
dimensionless ordinate (yU
0/)
-
density of the fluid
-
coefficient of viscosity 相似文献
7.
Sanzidur Rahman Ismat Ara Begum Mohammad Jahangir Alam 《Singapore journal of tropical geography》2012,33(2):241-254
This paper re‐examines the effect of green revolution (GR) diffusion on factor/inputs demand in Bangladesh using an empirical model that allows for simultaneous determination of factors influencing adoption of GR technology at the current mature stage, as well as access to irrigation. Results reveal some alignments with conventional wisdom as well as few surprises. For example, while an increased demand for major inputs is expected, an increased demand for organic manure is an unexpected positive outcome. The GR adoption rate is significantly higher in villages with access to irrigation and fertile soils and, surprisingly, in infrastructurally underdeveloped villages. Together with other expected findings of GR technology uptake with higher cereal prices and irrigation use encouraged by access to credit, tenurial status and fertile soils, our findings suggest that investment in irrigation and soil conservation, as well as implementing measures to improve cereal prices and provide agricultural credit, could boost GR technology adoption. 相似文献
8.
Prasun Dutta Ayesha Begum Somnath Bharadwaj Jayaram N. Chengalur 《Monthly notices of the Royal Astronomical Society》2009,398(2):887-897
We estimate the power spectrum of H i intensity fluctuations for a sample of eight galaxies (seven dwarf and one spiral). The power spectrum can be fitted to a power-law for six of these galaxies, indicating turbulence is operational. The estimated best-fitting value for the slope ranges from ∼−1.5 (AND IV, NGC 628, UGC 4459 and GR 8) to ∼−2.6 (DDO 210 and NGC 3741). We interpret this bi-modality as being due to having effectively 2D turbulence on length-scales much larger than the scale-height of the galaxy disc and 3D otherwise. This allows us to use the estimated slope to set bounds on the scale-heights of the face-on galaxies in our sample. We also find that the power-law slope remains constant as we increase the channel thickness for all these galaxies, suggesting that the fluctuations in H i intensity are due to density fluctuations and not velocity fluctuations, or that the slope of the velocity structure function is ∼0. Finally, for the four galaxies with '2D turbulence' we find that the slope α correlates with the star formation rate (SFR) per unit area, with larger SFRs leading to steeper power laws. Given our small sample size, this result needs to be confirmed with a larger sample. 相似文献
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