Variation Of Cd Research Articles

Drag coefficient and upstream influence in three-dimensional stratified flow of finite depth

A numerical study of the three-dimensional stratified flow past a vertical square flat plate in a channel of finite depth is described. Particular attention is paid to the anomalous dependence of the drag coefficient CD on parameter K( = ND/-πU), where N is the Brunt-Väisälä frequency, D is the half depth of the channel and U is the upstream velocity. It is shown that CD generally increases with K, while it decreases locally at integral values of K. Time development of the upstream columnar disturbance and the corresponding variation of CD reveals that the periodic variation of CD with time for K > 1 comes from the successive upstream radiation of the columnar disturbances of the first internal wave mode. Although the propagation speed of the columnar disturbance is consistent with the prediction of linear theory, its time-dependent structure is different from the weakly nonlinear theory as has been shown by laboratory experiments.

Zinc Cu, Ni and Cd in the forest floor in the Northeastern United States

A regional study was conducted to assess current levels of trace metals in the forest floor, and to establish a baseline for future studies of metal accumulation. Quantitative forest floor samples collected from 78 sites in 9 states in the northeastern United States in 1978 and 1980 were analyzed for Zn, Cu, Ni, and Cd. Mean amounts present in the forest floor were 9.8 ± 1.9 (standard error of the mean), 1.7 ± 0.2, 0.86 ± 0.08, and 0.13 ± 0.01 kg ha−1, for Zn, Cu, Ni, and Cd, respectively. Mean concentrations were 133 ± 25, 19.5 ± 1.6, 11 ± 0.8, and 1.7 ± 0.1 mg kg−1, respectively. Differences in metal and organic matter concentrations and amounts among forest types were attributed to geographic location of specific forest types rather than to direct biotic influence. No element was strongly correlated with elevation for the entire sample area. Regional patterns of elemental amounts showed that trace metal levels are slightly higher in the southern part than in the northern part of the study region. Regional variation of Zn, Cu, Ni, and Cd in the forest floor was not indicative of atmospheric deposition except near point sources of pollution.

Hypersonic Low-Density Cone Drag

T objective of this experimental study has been to obtain precise cone drag data in the transition regime of lowdensity hypersonic flow. Data of sufficient quality to 1) establish the variation of CD over this regime, 2) allow meaningful comparison with theory, and 3) allow single parameter studies to be conducted has been sought. In conjunction with a capability of high resolution, the first and perhaps foremost requirement of such data is reproducibility since common systematic uncertainties are usually more tolerable when variations (especially normalized) are of primary interest or when relative comparisons (to determine a single parameter's influence) are to be made.

Effects of Beta Ratio and Reynold’s Number on Coefficient of Discharge of Orifice Meter

Orifice meter is a very common flow measuring device installed in a pipe line with minimum troubles and expenses. A coefficient of discharge (Cd) is to be used to get actual discharge from theoretical discharge as different head losses occur in the orifice. An experiment was carried out in the Hydraulic Laboratory of Bangladesh Agricultural University (BAU), Mymensingh to see the variation of Cd with beta ratio, β and Reynold's number, Re. The test was conducted with five orifice plates having beta ratios of 0.30, 0.35, 0.47, 0.59 and 0.71 installed concentrically in a pipe of 8.5 cm diameter, flowing water through it. Differential pressure head was recorded by a differential mercury U-tube manometer to calculate the theoretical discharges from Bernoulli's energy equation. It was found that Cd had a positive linear relationship with beta ratio where its dependency was stronger on β than Re in case of low flow rate with highest value of coefficient of determination (R2 = 0.8931) for four-fifth valve opening condition. On the other hand, Cd followed a curvilinear (concave) relationship with Re for all beta ratios except 0.47 which showed convex relationship. However, strong relationships with the value of R2 0.944 and 0.9563 were found for greater beta ratios 0.59 and 0.71, respectively. A combined interpretations of experimental data from a bar diagram revealed that orifice meter with beta ratio 0.60 can be used for efficient pipe flow measurement. Key words: Beta ratio; Reynold's Number; coefficient of orifice meter. DOI: 10.3329/jard.v7i1.4436 J Agric Rural Dev 7(1&2), 151-156, June 2009

The ac impedance at Cu electrodes and the electrodeposition of Cu

The ac impedance at spherical Cu microelectrodes in 1 N H 2SO 4 (double-layer impedance) and in CuSO 4H 2SO 4 solutions (faradaic impedance in parallel with the double-layer impedance) was studied at 50–5000 Hz. Reagents and solutions were purified carefully. Potentiostatic control was maintained where appropriate. A limiting double-layer capacitance of approximately 30 μF per apparent cm 2 was found at high frequency. Faradaic parameters were evaluated for each CuSO 4 solution. The variation of exchange cd with Cu 2+ concentration (10 −3−10 −2M), and a rate constant for the process Cu 2+ + 2 e − → Cu, are deduced. Results are compared with previous studies.