Fast voltage contingency screening using radial basis function neural network

Power system security is one of the vital concerns in competitive electricity markets due to the delineation of the system controller and the generation owner. This paper presents an approach based on radial basis function neural network (RBFN) to rank the contingencies expected to cause steady state bus voltage violations. Euclidean distance-based clustering technique has been employed to select the number of hidden (RBF) units and unit centers for the RBF neural network. A feature selection technique based on the class separability index and correlation coefficient has been employed to identify the inputs for the RBF network. The effectiveness of the proposed approach has been demonstrated on IEEE 30-bus system and a practical 75-bus Indian system for voltage contingency screening/ranking at different loading conditions.     

Cooking at low temperatures: energy and time requirements

A flat plate solar collector can easily supply hot water at temperatures upto 90–95°C. At these temperatures, rice, potatoes and vegetables can be cooked without much difficulty. However, to design an efficient solar system for cooking, one must know the exact energy and time required for cooking at these temperatures. Our experiments show that the actual energy consumed in cooking rice, potatoes or green vegetables is only 0.06 to 0.10 kWh/kg at cooking temperatures of 82–88°C and the cooking time at these temperatures is 30–45 min.     

Fatty acids and fatty aldehydes of buffalo seminal plasma and sperm lipid

Analysis of the fatty acids of total and neutral lipids, glycolipids, phospholipids and gangliosides of buffalo spermatozoa and seminal plasma showed that there were high levels of polyunsaturated acids. Neutral lipids were the richest in polyunsaturated acids (55% in spermatozoa and 61% in seminal plasma). The major saturated acid of all the principal classes was stearic acid and the major unsaturated acid was docosahexaenoic acid (22:6omega3) except in the neutral lipids in which it was arachidonic acid (20:4omega6). The major aldehyde was palmitaldehyde (16:0) in buffalo sperm lipids and docosanal (22:0) in seminal plasma. More than 50% of the total aldehydes was contributed by aldehydes with a chain length greater than 18 carbon atoms.     

Hypersonic radiating merged shock layer near the blunt-body stagnation region

In the low Reynolds number flow, shock wave and viscous layer near the stagnation point of a blunt-body are merged together. This merged shock layer is investigated in this paper for a radiating gas. The radiating transfer is simplified to the emission-dominated case. The basic model of the flow is described by the full Navier-Stokes equations. Using the concept of local similarity, the equations are reduced to an eighth-order set of nonlinear, coupled ordinary differential equations. This set of equations is integrated numerically from the surface to the freestream under different prescribed conditions. Earlier, this problem was investigated by Liu and Sogame [3] within the framework of two thin-layer model. A number of inaccuracies of this analytical development are pointed out. It is shown that the present analysis gives more reliable and accurate information about the detailed behaviour of the radiating viscous flow at low Reynolds number.     

Designing surveys for tests of gravity

Modified gravity theories may provide an alternative to dark energy to explain cosmic acceleration. We argue that the observational programme developed to test dark energy needs to be augmented to capture new tests of gravity on astrophysical scales. Several distinct signatures of gravity theories exist outside the 'linear' regime, especially owing to the screening mechanism that operates inside halos such as the Milky Way to ensure that gravity tests in the solar system are satisfied. This opens up several decades in length scale and classes of galaxies at low redshift that can be exploited by surveys. While theoretical work on models of gravity is in the early stages, we can already identify new regimes that cosmological surveys could target to test gravity. These include: (i) a small-scale component that focuses on the interior and vicinity of galaxy and cluster halos, (ii) spectroscopy of low-redshift galaxies, especially galaxies smaller than the Milky Way, in environments that range from voids to clusters, and (iii) a programme of combining lensing and dynamical information, from imaging and spectroscopic surveys, respectively, on the same (or statistically identical) sample of galaxies.