First-principles study of the effect of charge on the stability of a diamond nanocluster surface

Effects of net charge on the stability of the diamond nanocluster are investigated using the first-principles pseudopotential method with the local density approximation. We find that the charged nanocluster favors the diamond phase over the reconstruction into a fullerene-like structure. Occupying the dangling bond orbitals in the outermost surface, the excess charge can stabilize the bare diamond surface and destabilize the C-H bond on the hydrogenated surface. In combination with recent experimental results, our calculations suggest that negative charging could promote the nucleation and further growth of low-pressure diamond.open8

EVALUASI PENERAPAN AKUNTANSI ATAS PENGAKUAN PENDAPATAN JASA PADA PT. INFIMEDIA SOLUSI PRATAMA

EVALUASI PENERAPAN AKUNTANSI ATAS PENGAKUAN PENDAPATAN JASA PADA PT. INFIMEDIA SOLUSI PRATAMA

REFLECTIONS ON THE FUTURE ELECTRIC POWER GRID MONITORING SYSTEM

A shortcoming of the contemporary power grid monitoring is that the system does not know its own state. Instead of taking automatic note of energy-flow disruptions, one deals with haphazard telephone reports of "no light in our house". We propose a novel monitoring system that requires no restructuring of the power distribution network and can be applied both to the existing grids and the future "smart grids". The proposed system is based on a network of inexpensive sensors, installed on every connecting line and communicating measured data to a central processing unit. Our approach is topological in nature, based on the connectivity aspects of the power grid embodied in Kirchhoff's current law that must be valid at every node of the network. We argue that the state of the network can be adequately characterized by specifying the RMS currents and the direction of energy flow in all connecting lines. It is essential that in this description one does not have to know the magnitude of the energy flow, only its direction. This eliminates the need to measure voltage, which would be prohibitively costly on the massive scale. In contrast, the relative phase between the current and voltage can be measured easily. Another essential point is that the instantaneous RMS currents are impractical to record and communicate, hence local averaging is required. Since Kirchhoff's law should remain valid upon averaging, the latter must be carried out at each sensor synchronously over the entire network with global synchronization provided by the GPS

Influence of POSS Type on the Space Environment Durability of Epoxy-POSS Nanocomposites

In order to use polymers at low Earth orbit (LEO) environment, they must be protected against atomic oxygen (AO) erosion. A promising protection strategy is to incorporate polyhedral oligomeric silsesquioxane (POSS) molecules into the polymer backbone. In this study, the space durability of epoxy-POSS (EPOSS) nanocomposites was investigated. Two types of POSS molecules were incorporated separately—amine-based and epoxy-based. The outgassing properties of the EPOSS, in terms of total mass loss, collected volatile condensable material, and water vapor regain were measured as a function of POSS type and content. The AO durability was studied using a ground-based AO simulation system. Surface compositions of EPOSS were studied using high-resolution scanning electron microscopy and X-ray photoelectron spectroscopy. It was found that with respect to the outgassing properties, only some of the EPOSS compositions were suitable for the ultrahigh vacuum space environment, and that the POSS type and content had a strong effect on their outgassing properties. Regardless of the POSS type being used, the AO durability improved significantly. This improvement is attributed to the formation of a self-passivated AO durable SiO2 layer, and demonstrates the potential use of EPOSS as a qualified nanocomposite for space applications