Single-parameter controlled-variable amplitude change function for digital filtering

A single-parameter controlled-variable amplitude change function has been constructed for digital filtering using multiple units of a prototype filter. The limits of variation are discussed. The technique is shown to be useful not only for the reduction of errors in either the pass band or the stop band of the overall filter, but also for varying the cutoff frequency of the overall filter over a wide range. Hardware implementation problems resulting from a wide variation are shown to be overcome by a modular approach.     

Fullerenes and Nanotubes from Coal

Abstract

Graphite has normally been used to synthesise fullerenes and nanotubes. However, coal is a cheaper and more suitable industrial material. Because coal is a molecular solid, unlike graphite, the mechanism by which fullerene and nanotubes are formed is different. Moreover, other products such as polyaromatic hydrocarbons (PAHs) and microfibres are also formed. In this review, the mechanism of formation of fullerene and nanotubes from coal is discussed. It is shown that the pathway involved is other than through the C₁ intermediate route. The influence of other elements in coal such as hydrogen, oxygen, sulfur and iron is also discussed. It appears that, hydrogen, oxygen, iron and sulfur affect the yield and type of fullerenes and nanotubes formed.     

Catheter for diagnosis and therapy with infrared evanescent waves

We have developed an optical delivery device (catheter) capable of transmitting broadband infrared light (IR wavelengths from 2 to 10 microm) for both diagnostic and therapeutic applications. The catheter is 1.68 mm in outer diameter and 1 m in length. It consists of two hollow glass waveguides coupled to a high-refractive-index optic tip. The IR light interacts with the tissue at the optic-tissue interface to measure the spectral signatures and perform therapy on the tissue at this interface. Fourier-transform IR spectrophotometer light is used to obtain the spectral signatures, and an IR free-electron laser (FEL) is used to study the therapeutic interaction of evanescent waves with the tissue. We present our catheter design; preliminary IR spectroscopy of aorta, blood, fatty tissue, and muscle; and IR FEL therapy on atheroslerotic aorta.     

Fullerenes and Nanotubes from Coal

Graphite has normally been used to synthesise fullerenes and nanotubes. However, coal is a cheaper and more suitable industrial material. Because coal is a molecular solid, unlike graphite, the mechanism by which fullerene and nanotubes are formed is different. Moreover, other products such as polyaromatic hydrocarbons (PAHs) and microfibres are also formed. In this review, the mechanism of formation of fullerene and nanotubes from coal is discussed. It is shown that the pathway involved is other than through the C₁ intermediate route. The influence of other elements in coal such as hydrogen, oxygen, sulfur and iron is also discussed. It appears that, hydrogen, oxygen, iron and sulfur affect the yield and type of fullerenes and nanotubes formed.     

On characterization of linear phase nonuniform filter banks

In this paper, a condition termed as linear phase condition (LPC), which ensures that the filters of a nonuniform filter bank are linear phase, is presented. It is observed that the proposed LPC is also applicable to the uniform filter bank case. Further, the utility of this LPC to find (i) necessary restrictions on the filters lengths, (ii) the number of symmetric and antisymmetric filters in the filter bank and (iii) filter bank decimation factors is also investigated. The results obtained for the different cases are also presented in the form of tables. These tables will facilitate the design of nonuniform filter bank by ruling out the non-solvable cases and by reducing the search space, thus saving the designers’ precious time.     

Efficient and good Delaunay meshes from random points

We present a Conforming Delaunay Triangulation (CDT) algorithm based on maximal Poisson disk sampling. Points are unbiased, meaning the probability of introducing a vertex in a disk-free subregion is proportional to its area, except in a neighborhood of the domain boundary. In contrast, Delaunay refinement CDT algorithms place points dependent on the geometry of empty circles in intermediate triangulations, usually near the circle centers. Unconstrained angles in our mesh are between 30° and 120°, matching some biased CDT methods. Points are placed on the boundary using a one-dimensional maximal Poisson disk sampling. Any triangulation method producing angles bounded away from 0° and 180° must have some bias near the domain boundary to avoid placing vertices infinitesimally close to the boundary.Random meshes are preferred for some simulations, such as fracture simulations where cracks must follow mesh edges, because deterministic meshes may introduce non-physical phenomena. An ensemble of random meshes aids simulation validation. Poisson-disk triangulations also avoid some graphics rendering artifacts, and have the blue-noise property.We mesh two-dimensional domains that may be non-convex with holes, required points, and multiple regions in contact. Our algorithm is also fast and uses little memory. We have recently developed a method for generating a maximal Poisson distribution of n output points, where n=Θ(Area/r²) and r is the sampling radius. It takes O(n) memory and O(nlogn) expected time; in practice the time is nearly linear. This, or a similar subroutine, generates our random points. Except for this subroutine, we provably use O(n) time and space. The subroutine gives the location of points in a square background mesh. Given this, the neighborhood of each point can be meshed independently in constant time. These features facilitate parallel and GPU implementations. Our implementation works well in practice as illustrated by several examples and comparison to Triangle.     

Finding nonfaulty subtrees in faulty binary tree architectures

In this paper we have studied fault tolerance of a full binary tree in terms of availability of non-faulty (full) subtrees. When an unaugmented full binary tree is faulty, then the computation can be carried out on the largest available non-faulty (full) binary subtree.It is shown that the minimum number of faulty nodes required to destroy all subtrees of height h in a full binary tree of height n is given as f_bt(n, h) = (2ⁿ−1)/(2^h−1). It follows that the availability of a non-faulty subtree of height h = n−w, in an n level full binary tree containing u faulty nodes, can be ensured, where w is the smallest integer such that u ≤ 2^w.An algorithm which evaluates whether a given set of faulty nodes will destroy all subtrees of some specified height, is given. This algorithm can also evaluate the largest available non-faulty subtree in a faulty full binary tree. We also study the availability of a non-faulty subtree in some augmented binary tree architectures.