Partial Density Plots Research Articles

Shading and PAR under different density agrivoltaic systems, their simulation and effect on wheat productivity

The introduction of renewable energy to mitigate climate change and the need for sufficient land to increase food production are mutually exclusive. Agrivoltaic systems (AVS) integrate the production of agricultural crops and electric power on the same piece of land but the main issue is the reduced availability of light to crops below the AVS, which restricts optimum crop growth and yield. This study examines the radiation and shade distribution over the crop surface among three densities of photovoltaic (PV) panels {Partial density (PD), Half density (HD) and Full density (FD)} under the AVS. Wheat variety GW 496 was chosen to grow under the AVS with line sowing and drip irrigation. Among three densities of photovoltaic (PV) panels, the proportion of shaded area over the crop surface was found highest in full density plot and lowest in partial density plot. The shaded area under AVS varied from 24.1% to 75.4% of the total area. The shaded area under different density plots, adversely affects the availability of photosynthetically active radiation (PAR) over the crop surface. The reduction of PAR under the AVS was more affected by panel density. Maximum reduction in PAR under AVS was observed in FD plot and minimum in the PD plot. A sharp increase in the PAR level was observed from shading to open sun conditions. The lowest value of PAR level (56 μmol m−2 s1) was recorded in just below the panel’s array. The consistent overestimation of PAR was observed during the crop growing period in all the PVPs density plots. The result revealed that the grid points under shade conditions showed a better association between observed and simulated incident PAR than unshaded grid points. Furthermore, the simulation results revealed that the model modeled PAR better in PD plot. The study also found that wheat grown under no shade yielded 4.51 t/ha over reduced light either in PD (3.06 t/ha), HD (2.77 t/ha), and FD plots (2.62 t/ha). Shading treatments showed that the crop yield decreased with an increase in shading intensity.

Interpreting STM and AFM Images

AbstractThe necessity for a rational interpretation of scanning tunneling microscopy (STM) and atomic force microscopy (AFM) images is demonstrated by our recent STM/AFM studies of layered transition‐metal chalcogenides, layered transition‐metal halides, organic conducting salts, and alkanes adsorbed on graphite. To a first approximation, the STM image of a surface is described by the partial density plot ρ(r0, ef) of the surface, and the AFM image by the total density plot ρ(r0). The contribution of an atom to the ρ(r0, ef) plot increases with decreasing distance to the tip and with increasing electronic contribution to the energy levels around the Fermi level. Since the atoms that protrude more do not necessarily make greater contributions to the energy levels near the Fermi level, it is difficult to achieve a rational interpretation of STM images unless appropriate partial density plots are calculated. For a variety of layered compounds, the STM and AFM images are well simulated by the ρ(r0, ef) and ρ(r0) plots calculated by the extended Hückel tight‐binding electronic band structure method. Partial and total density plot calculations provide not only a basis for a rational interpretation of ideal STM and AFM images but also a step toward systematic studies of how tip–surface interactions and tunneling conditions affect the images.