Is Aging the Important Factor for Sustainable Agricultural Development in Korea? Evidence From the Relationship Between Aging and Farm Technical Efficiency

This paper examines the effects of aging and income subsidies on farm efficiency in Korea by utilizing the Korean Farm Household Economic Survey from 2008 to 2015. A stochastic frontier model with a non-monotonic assumption on the effect of efficiency factors is implemented to reflect a super aging and less developed production structure in Korean agriculture. This study finds continuously decreasing farm efficiency with age, which contradicts the commonly assumed inverted-U relationship between age and productivity. Especially, we find that labor is the most important factor to explain recent farm efficiency losses in Korea. Furthermore, this paper finds that the Korean income subsidy has a negative effect on farm efficiency. Our results provide two policy implications for the government of Korea. First, even though the “Returns to the Farm and Rural program” is appropriate, Korea should modify the program to encourage more young people to participate this program rather than old people, in order to attain the sustainable development of the agricultural sector. Second, a policy maker in Korea should consider a coupled subsidy that is directly related to farm production rather than a decoupled subsidy, regardless of the lower efficiency of the coupled subsidy in achieving agricultural development

Indium as an efficient ohmic contact to N-face n-GaN of GaN-based vertical light-emitting diodes

We propose indium (In), a low work function and nitride-forming element, as an efficient ohmic contact layer to N-face n-GaN. While conventional Al-based ohmic contacts show severe degradation after annealing at 300 C, In-based ohmic contacts display considerable improvement in contact resistivity. The annealing-induced enhancement of ohmic behavior in In-based contacts is attributed to the formation of an InN interfacial layer, which is supported by x-ray photoemission spectroscopy measurements. These results suggest that In is of particular importance for application as reliable ohmic contacts to n-GaN of GaN-based vertical light-emitting diodes.open3

Inaccuracy of Density Functional Theory Calculations for Dihydrogen Binding Energetics onto Ca Cation Centers

We investigate the mechanism of dihydrogen adsorption onto Ca cation centers, which has been the significant focus of recent research for hydrogen storage. We particularly concentrate on reliability of commonly used density-functional theories, in comparison with correlated wave function theories. It is shown that, irrespective of the chosen exchange-correlation potentials, density-functional theories result in unphysical binding of H2 molecules onto Ca1+ system. This suggests that several previous publications could contain a serious overestimation of storage capacity at least in part of their results.open262