The response of the upper atmospheric temperature to changes in solar EUV radiation and geomagnetic activity

Solar radiation and magnetic effects on upper atmospheric neutral temperatures derived from satellite dra

Reversal of particle-hole scattering-rate asymmetry in Anderson impurity model

We study the particle-hole asymmetry of the scattering rate in strongly correlated electron systems by examining the cubic $\omega^3$ and $\omega T^2$ terms in the imaginary part of the self-energy of the Anderson impurity model. We show that the sign is opposite in the weak-coupling and strong-coupling limits, explaining the differences found in theoretical approaches taking the respective limits as the starting points. The sign change in fact precisely delineates the cross-over between the weak and strong correlation regimes of the model. For weak interaction $U$ the sign reversal occurs for small values of the doping $\delta=1-n$, while for interaction of order $U \approx 2 \Gamma$, $\Gamma$ being the hybridization strength, the cross-over curve rapidly shifts to the large-doping range. This curve based on the impurity dynamics is genuinely different from other cross-over curves defined through impurity thermodynamic and static properties.Comment: 4 pages, 5 figure

Synchronous and Asynchronous Mott Transitions in Topological Insulator Ribbons

We address how the nature of linearly dispersing edge states of two dimensional (2D) topological insulators evolves with increasing electron-electron correlation engendered by a Hubbard like on-site repulsion $U$ in finite ribbons of two models of topological band insulators. Using an inhomogeneous cluster slave rotor mean-field method developed here, we show that electronic correlations drive the topologically nontrivial phase into a Mott insulating phase via two different routes. In a synchronous transition, the entire ribbon attains a Mott insulating state at one critical $U$ that depends weakly on the width of the ribbon. In the second, asynchronous route, Mott localization first occurs on the edge layers at a smaller critical value of electronic interaction which then propagates into the bulk as $U$ is further increased until all layers of the ribbon become Mott localized. We show that the kind of Mott transition that takes place is determined by certain properties of the linearly dispersing edge states which characterize the topological resilience to Mott localization.Comment: 4+ pages, 5 figure

Methodology for testing and validating knowledge bases

A test and validation toolset developed for artificial intelligence programs is described. The basic premises of this method are: (1) knowledge bases have a strongly declarative character and represent mostly structural information about different domains, (2) the conditions for integrity, consistency, and correctness can be transformed into structural properties of knowledge bases, and (3) structural information and structural properties can be uniformly represented by graphs and checked by graph algorithms. The interactive test and validation environment have been implemented on a SUN workstation

Video data compression using artificial neural network differential vector quantization

An artificial neural network vector quantizer is developed for use in data compression applications such as Digital Video. Differential Vector Quantization is used to preserve edge features, and a new adaptive algorithm, known as Frequency-Sensitive Competitive Learning, is used to develop the vector quantizer codebook. To develop real time performance, a custom Very Large Scale Integration Application Specific Integrated Circuit (VLSI ASIC) is being developed to realize the associative memory functions needed in the vector quantization algorithm. By using vector quantization, the need for Huffman coding can be eliminated, resulting in superior performance against channel bit errors than methods that use variable length codes

Rebirth of self and identity: an analysis of Meena Alexander’s Manhattan music

This paper illustrates how Meena Alexander explores the prospect of outgrowing the sense of rootlessness of Asian immigrants in America in Manhattan Music. According to her it is managed by vocational and social engagements, and bonding with fellow expatriates. Alienation, search for identity and emotional insecurity of immigrants have hitherto been the dominant themes of diasporic literature. However, in the context of globalisation the concept of ‘home’ as a giver of emotional security cries for a redefinition. Meena Alexander’s Manhattan Music analyses the impact of transplantation from natal to post-marital space in the lives of women characters. Sandhya Rosenblum, Draupadi Dinkins, Sakhi and a few others despite the differences in their upbringing, experience the trauma of dislocation at first, but outgrow the same. Sandhya wrestles between her conflicting roles, a mother in New York and a daughter revisiting India, and in neither does she feel at home. But after her recovery from the shock of suicide, she escapes from racial thinking. It constitutes a rebirth of self for her. Similarly, Draupadi, the alter-ego of Sandhya, comes to realise being an American is only a part of her Self. Meena Alexander’s central vision in all her writings is the need of the immigrants for adapting themselves to the changed environment to find meaning in their lives. In Manhattan Music, the writer emphasises this idea by portraying Sandhya’s inner conflict in her adopted country at first and later her awakening to the truth that we all have several “homes” or as Homi Bhabha suggests we have to “desire for social solidarity: I am looking for the join…I want to join…I want to join.” (Bhabha 1994, p.18

Behavior of topside and bottomside spread F at equatorial latitudes

Diurnal variation of topside and bottomside spread-F and geomagnetic effects from Alouette I ionogram