An analysis has been carried out to study the combined effects of radiation absorption and chemical reaction on an incompressible, electrically conducting and radiating flow of a Rivlin-Ericksen fluid along a semi-infinite vertical permeable moving plate in the presence of a transverse applied magnetic field. It is assumed that the suction velocity, the temperature and the concentration at the wall are exponentially varying with time. The dimensionless governing equations for this investigation are solved analytically using two-term harmonic and non-harmonic functions. A comparison is made with the available results in the literature for a special case and our results are in very good agreement with the known results. A parametric study of the physical parameters is made and results are presented through graphs and tables. The results indicate that the fluid velocity and temperature could be controlled by varying the radiation absorption.
surface in the presence of chemical reaction . – Forsch. Ingenieurwes, vol.67, 129.
. Kandasamy R., Periasamy K. and Prabhu K.K.S. (2005): Chemical reaction, heat and mass transfer on MHD flow over a vertical stretching surface with heat source and thermal stratification effects . – Int. J. Heat Mass Transfer, vol.48, No.21-22, pp.4557-4561.
. Ibrahim F.S., Elaiw A.M. and Bakr A.A. (2008): Effect of the chemical reaction and radiationabsorption on the unsteady MHD free convection flow past a semi-infinite vertical permeable moving plate with heat
The research we have undertaken seeks to clarify some aspects concerning the specific characteristics of aforest microclimate. Spot measurements were carried out for 12 hours/day, on certain days that are typical for the period of vegetation and, respectively, for the period of vegetative rest. Measurements regarding the intensity of light were conducted across surfaces where progressive felling had been applied. The research findings about the light regime are presented below: 1. Surfaces subjected to the progressive felling treatment I - seeding fellings that create cut block sites in the mature stand canopy u. a. 74 B, UP III, Nirajul Mic, the Sovata Forestry. In these regeneration areas appear noticeable changes of the light regime, caused by the intensity of the fellings, the size of the cut block sites and the position of each cut block site sector. Thus, in clear cut block sites, having an elliptical shape of 0.5 H3 X 0.75 H*, in which seedlings have not yet been planted, the amount of light that reaches the soil surface, in relation to the open field solar radiation, is approx. ¼ - 1/3 in the eastern and southern sectors, 2/3 in the central sector and, respectively, 2/5 - ½ in the western and northern sectors. In the case of elliptical cut block sites, with diagonals of 1.0 H X 1.5 H, we have found some variations, in the sense that the eastern and the southern sectors receive, at ground surface, approx. 1/5 - 2/5 of the light from an unforested area, the central sector receives a little over 2/3, while the western and the northern sectors receive 4/5 -1/1 of the light from an unforested area, which is also the area with relatively maximum light availability. 2. Surfaces subjected to the progressive felling treatment II - fellings for expandingcut block sites UP VI, Valea Soveții, u.a 127,the Sovata Forestry. Thus, in an elliptical cut block site (1.0 H X 1.5 H) from UP VI, u.a. 127, at1 p.m.,when the sky was overcast, 50% of full light reached the eastern sector, 40% reached the southern sector, approx. 80-90% reached the center of the cut block site, and 75-85% of the amount of light from an unforested area reached the western and the northern sectors at soil surface level. Forest ecosystems are characterized by a great capacity of solar radiation absorption. As a result of selective processes of absorption, reflection and transmission, carried out at the level of the “active surface”, the light regime inside the forest presents a series of distinct features. Light intensity decreases from the top of the canopy to the ground. The decrease is accentuated in the canopy and much slower in the space underneath the canopy, all the way to the ground. Thus, while an average of 66-67% is recorded at the level of the canopy (2/3 of full light), underneath the canopy it reaches 9% (under 1/10 of full light) and only 6-7% of the light from an unforested area is recorded at ground level. Differences are found from one measurement point to another, within the same level, as a result of the foliage structure and the different thickness of the foliage mass located above the measurement point.
The present study investigates the onset of penetrative convection in- duced by selective absorption of radiation in a magnetic nanofluid saturated porous medium. The influence of Brownian motion, thermophoresis, and magnetophoresis on magnetic nanofluid treatment is taken into consideration. The Darcy’s model is selected for the porous medium. We conduct a linear stability analysis to examine the onset of instability and evaluate the results for two different configurations, namely, when the layer is heated from below and when the layer is heated from above. The numerical investigations are carried out by applying the Chebyshev pseudospectral method. The effect of the porosity parameter E, parameter Y (represents the ratio of internal heating to boundary heating), Lewis number Le, concentration Rayleigh number Rn, Langevin parameter αL, width of nanofluid layer d, diffusivity ratio η, and modified diffusivity ratio NA is examined at the onset of convection. The results indicate that the convection commences easily with an increase in the value of Y, Le, and NA but opposite in the case with a decrease in the value of E, αL, η and d for both the two configurations. The parameter Rn advances the onset of convection when the layer is heated from below, while delays the onset of convection when the layer is heated from above.
Aliaksandr Abukhovich, Stefan Pietkiewicz, Romualda Karwowska, Jolanta Kobryń and Hazem Kalaji
Canopy Architecture and Yielding of Different Tomato Morphotypes Under Glasshouse Conditions
Two tomato morphotypes (cvs. Favorita, Organza and Azarro) of different fruit size were grown during 2005-2006 on a rockwool substrate under greenhouse conditions. Leaf area index (LAI), solar radiation absorption coefficient (TAO) and leaf area duration (LAD) were determined. Tested tomato cultivars proved different yielding strategies expressed by dissimilar values of the measured and calculated physiological indices (LAI, LAD, TAO and the canopy yielding efficiency). Cv. Organza showed the highest canopy yielding efficiency, cv. Azarro showed a negative dependence between LAD and yield, while cv. Favorita canopy architecture allowed to achieve better penetration of light energy to lower canopy layers and showed better tolerance of this cultivar to thermal stress.
Rakesh Kumar (2009): Combined effects of Hall current and rotation on free convection MHD flow in a porous channel. – Ind. J. of Pure and Appl. Phys., vol.47, pp.617-623.
 Ahmed N. and Sarma H.K. (2011): MHD transient flow past an impulsively started infinite horizontal porous plate in a rotating system with Hall current. − Int. J. of Appl. Math. and Mech., vol.7, No.2, pp.1-15.
 Satyanarayana P.V., Venkateswarlu B. and Venkataramana S. (2013): Effects of Hall current and radiationabsorption on MHD micropolar fluid in a rotating system. − Ain
vertical surfaces in porous media considering Soret and Dufour effects. – Heat and Mass Transfer, vol.43.
 Hossain A.M., Alim M.A. and Rees D.A.S. (1999): Effect of radiation on free convection from a porous a vertical plate. – International Journal of Heat and Mass Transfer, vol.42, pp.181-191.
 Ibrahim F.S., Elaiw A.M. and Bakr A.A. (2008): Effect of the chemical reaction and radiationabsorption on the unsteady MHD free convection flow past a semi infinite vertical permeable moving plate with heat source and suction. – Comm. Nonlinear Sci. Numer
.K. (2005): Effects of chemical reaction, heat and mass transfer along a wedge with heat source and concentration in the presence of suction or injection. − Int. J. Heat and Mass Transfer, vol.48, No.7, pp.1388-1394.
 Ibrahim F.S, Elaiw A.M. and Bakr A.A. (2008): Effects of chemical reaction and radiationabsorption on the unsteady MHD free convection flow past a semi-infinite vertical permeable moving plate with heat source and suction . − Commun. in Non-Linear Sci. Numerical Simulation, vol.13, No.6, pp.1056-1066.
 Muthucumaraswamy R. and
M.H. Shahrajabian, W. Sun, Q. Cheng and M. Khoshkharam
, L. (2013). Effect of planting dates and different levels of nitrogen on seed yield and yield components of nuts sunflower ( Helianthus annuus L.). African J.Agric.Res., 8(46): 5802-5805.
Soleymani, A., Shahrajabian, M.H. & Khoshkharam, M. (2016). The impact of barley residue management and tillage on forage maize. Rom.Agric.Res., 33: 161-167.
Soleymani, A. & Shahrajabian, M.H. (2017). Effects of planting dates and row distance on sugar content, root yield and solar radiationabsorption in sugar beet at different plant densities. Rom. Agric
.S. (2004). Natural convection flow along a vertical wary surface temperature in the presence of heat generations /absorption . – Int. J. Thermal Science, vol.43, pp.157-163.
Natural convection flow along a vertical wary surface temperature in the presence of heat generations /absorption
Int. J. Thermal Science
Kesavaiah D.Ch., Satyanarayana P.V. and Venkataramana S. (2011): Effects of the chemical reaction and radiationabsorption on unsteady MHD convective heat and mass transfer flow