Adaptive cell division for ray tracing

In ray tracing the two most commonly used data structures are the octree and uniform cell division. The octree structure allows efficient adaptive subdivision of space, while taking care of the spatial coherence of the objects in it; however, the tree structure locating the next node in the path of a ray is complex and time consuming. The cell structure, on the other hand, can be stored in a three-dimensional array, and each cell can be efficiently accessed by specifying three indices. However, such a uniform cell division does not take care of object coherence. The proposed data structure combines the positive features of the above data structures while minimising their disadvantages. The entire object space is implicitly assumed to be a three-dimensional grid of cells. Initially, the entire object space is a single voxel which later undergoes “adaptive cell division.” But, unlike in the octree structure, where each voxel is divided exactly at the middle of each dimension, in adaptive cell division, each voxel is divided at the nearest cell boundary. The result is that each voxel contains an integral number of cells along each axis. Corresponding to the implicit cell division we maintain a three-dimensional array, with each array element containing the voxel number which is used to index into the voxel array. The voxel array is used to store information about the structure of each voxel, in particular, the objects in each voxel. While a ray moves from one voxel to another we always keep track of the cell through which the ray is currently passing. Since only arrays are involved in accessing the next voxel in the path of the ray, the operation is very efficient.     

适合消费电子产品的电流转换逻辑技术

消费电子和通信产业正见证着I／O解决方案从并行到高速串行的转变：能够降低成本、简化设计，并具备可延展性，满足全新带宽的要求。这类接口I／O技术的市场潜力巨大，包括移动电话、DVD-RW和高清晰度LCD电视机，而低功耗、低电磁干扰(EMI)和高数据吞吐量在这些应用中极为重要。因此，业界一直致力于设计和开发这些串行I／O，以低功耗提供高速的数据速     

Nano-octopus: a new form of branching carbon nanofiber

A new multibranched octopus-type structure of carbon nanofibers is synthesized from a natural precursor, camphor, by a thermal chemical vapor deposition technique. An alloy of Cu:Ni catalyst is prepared by electrochemically coating nickel on a copper sheet, with nickel sulfate as an electrolyte, and heating that nickel-coated copper sheet to a higher temperature. Deposition of carbon on these substrates leads to the formation of a branched nanostructure in the temperature range of 923 K to 1023 K. The fiber diameter increases from 30 nm to 250 nm with increasing pyrolysis temperature. Detailed morphology and the internal structure of these fibers are studied by scanning and transmission electron microscopy.     

Handover scheme for mobile cellular communication systems

A new scheme for minimising handover failure probability in mobile cellular communication systems, by exchanging channels between two mobiles moving in opposite directions across the endeavour area of adjacent cells is presented. The performance evaluation of the new scheme is carried out by computer simulation of a two cell model     

Effect of gravity on visco-elastic surface waves in solids involving time rate of strain and stress of first order

The aim of the present paper is to study the effect of gravity on visco-elastic surface waves in solids. The wave velocity equations are deduced from Biot’s theory of initial stress on the assumption that gravity creates a type of initial stress — hydrostatic in nature. Resulting equations are used to investigate surface waves of the Rayleigh, Love and Stoneley types. Results are in good agreement with corresponding classical results when gravity and viscosity are neglected.     

Telecommunications: at least a phone in every village

India is home to more than 850 million people, but to very few telephones. For every thousand inhabitants, it has only about eight phones, versus an average of 100 in the developing world, and 600 in developed countries. Here, the author describes how liberalization, in short, while forcing Indian manufacturers to compete against multinationals with state-of-the-art technologies, is opening up opportunities in improving this situation. Indian companies will continue working with the multinationals on joint development, not only as a way of leap-frogging into the state of the art, but to bring the country up to world standards in the availability and quality of its telecommunications