Impulse Radio Systems with Multiple Types of Ultra-Wideband Pulses

Spectral properties and performance of multi-pulse impulse radio ultra-wideband systems with pulse-based polarity randomization are analyzed. Instead of a single type of pulse transmitted in each frame, multiple types of pulses are considered, which is shown to reduce the effects of multiple-access interference. First, the spectral properties of a multi-pulse impulse radio system is investigated. It is shown that the power spectral density is the average of spectral contents of different pulse shapes. Then, approximate closed-form expressions for bit error probability of a multi-pulse impulse radio system are derived for RAKE receivers in asynchronous multiuser environments. The theoretical and simulation results indicate that impulse radio systems that are more robust against multiple-access interference than a "classical" impulse radio system can be designed with multiple types of ultra-wideband pulses.Comment: To be presented at the 2005 Conference on Information Sciences and System

Structural efficiency study of composite wing rib structures

A series of short stiffened panel designs which may be applied to a preliminary design assessment of an aircraft wing rib is presented. The computer program PASCO is used as the primary design and analysis tool to assess the structural efficiency and geometry of a tailored corrugated panel, a corrugated panel with a continuous laminate, a hat stiffened panel, a blade stiffened panel, and an unstiffened flat plate. To correct some of the shortcomings in the PASCO analysis when shear is present, a two step iterative process using the computer program VICON is used. The loadings considered include combinations of axial compression, shear, and lateral pressure. The loading ranges considered are broad enough such that the designs presented may be applied to other stiffened panel applications. An assessment is made of laminate variations, increased spacing, and nonoptimum geometric variations, including a beaded panel, on the design of the panels

A penalty approach for nonlinear optimization with discrete design variables

Introduced here is a simple approach to minimization problems with discrete design variables by modifying the penaly function approach of converting the constrained problems into sequential unconstrained minimization technique (SUMT) problems. It was discovered, during the course of the present work, that a similar idea was suggested by Marcal and Gellatly. However, no further work has been encountered. A brief description of the SUMT is presented. The form of the penalty function for the discrete-valued design variables and strategy used for the implementation of the procedure is discussed next. Finally, several design examples are used to demonstrate the procedure, and results are compared with the ones available in the literature

Two-sided eigenvalue bounds for the spherically symmetric states of the Schrödinger equation

AbstractThe eigenvalues of the radial Schrödinger equation are calculated very accurately by obtaining exact upper and lower bounds. By truncating the usual unbounded domain [0, ∞) of the system to a finite interval of the form [0,l], two auxiliary eigenvalue problems are defined. It is then proved that the eigenvalues of the resulting confined systems provide upper and lower bounds converging monotonically to the true eigenvalues required. Moreover, each auxiliary eigenvalue problem gives rise to an orthonormal set involving Bessel functions. The matrix representation of the Hamiltonian is, therefore, derived by expanding the wave function into a Fourier-Bessel series. Numerical results for single- and double-well polynomial oscillators as well as Gaussian type non-polynomial potentials illustrate that the eigenvalues can be calculated to an arbitrary accuracy, whenever the boundary parameter l is in the neighborhood of some critical value, denoted by lcr

Ultra Wideband Impulse Radio Systems with Multiple Pulse Types

In an ultra wideband (UWB) impulse radio (IR) system, a number of pulses, each transmitted in an interval called a "frame", is employed to represent one information symbol. Conventionally, a single type of UWB pulse is used in all frames of all users. In this paper, IR systems with multiple types of UWB pulses are considered, where different types of pulses can be used in different frames by different users. Both stored-reference (SR) and transmitted-reference (TR) systems are considered. First, the spectral properties of a multi-pulse IR system with polarity randomization is investigated. It is shown that the average power spectral density is the average of the spectral contents of different pulse shapes. Then, approximate closed-form expressions for the bit error probability of a multi-pulse SR-IR system are derived for RAKE receivers in asynchronous multiuser environments. The effects of both inter-frame interference (IFI) and multiple-access interference (MAI) are analyzed. The theoretical and simulation results indicate that SR-IR systems that are more robust against IFI and MAI than a "conventional" SR-IR system can be designed with multiple types of ultra-wideband pulses. Finally, extensions to multi-pulse TR-IR systems are briefly described.Comment: To appear in the IEEE Journal on Selected Areas in Communications - Special Issue on Ultrawideband Wireless Communications: Theory and Application

Management of Cervical Root Fracture Using Orthodontic Extrusion and Crown Reattachment: A Case Report

Root fractures involve damage to pulp, cementum, dentin, and periodontal ligaments. These injuries affect 0.5% to 7% of permanent teeth. Cervical root fractures are less frequently seen and have a worse prognosis compared with the fractures in the apical or middle third of the root. This case report describes the treatment of a cervical root fracture in a maxillary central incisor. After removal of the coronal fragment, the root was filled temporarily with calcium hydroxide and orthodontic extrusion was initiated. The remaining root portion was elevated above the epithelial attachment and a successful coronal restoration was made using the natural crown of the traumatized tooth

Buccal and Palatal Talon Cusps with Pulp Extensions on a Supernumerary Primary Tooth

This paper reports an unusual occurrence of talon cusp on a supernumerary primary incisor, presenting on both labial and palatal sides. The tooth was scheduled for extraction due to its interference with the occlusion. Morphometric analysis of the taloned cusps was performed on digitized replicas of the tooth crown using open-source image analysis toolkit (ImageJ). Further non-destructive investigation of the taloned crown under cone-beam X-ray computed tomography revealed pulpal extensions in both talon cusps

Abyssal upwelling in the Indian Ocean: Radiocarbon diagnostics

The GEOSECS Indian Ocean radiocarbon and carbonate chemistry data set are used to estimate the mean upwelling transport of bottom water in the Indian Ocean north of 30S. The study uses an adjusted radiocarbon concentration which is corrected for the effects of addition of particulate radiocarbon to the deep ocean. The cross-basin uniformity in the vertical gradients of adjusted radiocarbon allows quantification of vertical transfer processes using horizontally averaged concentration and fluxes. The estimated total upwelling flux, north of 30S, is 8.2 ± 1.5 × 106 m3 s-1. The mean upwelling velocity and the vertical diffusivity, in the 3000-4500 m depth range, are estimated as 3 × 106 m s-1 and 2.5 × 10-4 m2 s-1, respectively. The results also suggest faster upwelling in the western Indian Ocean

Unusual Ectopic Eruption of a Permanent Central Incisor Following an Intrusion Injury to the Primary Tooth

Intrusive luxation of primary teeth carries a high risk of damage to underlying permanent tooth germs. Ectopic eruption of permanent incisors is an unusual outcome of traumatic injury to their predecessors. In this case report, we describe the multidisciplinary management of the consequences of a primary tooth intrusion that led to severe ectopic eruption of the permanent left central incisor in a horizontal position at the level of the labial sulcus

Acute torsion of the gallbladder: a case report

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