Toward best-effort services over WDM networks with fair access andminimum bandwidth guarantee

Most existing wavelength-division multiplexed (WDM) networks employ circuit switching, typically with one session having exclusive use of one entire wavelength. Consequently, they are not suitable for data applications involving bursty traffic patterns. The All-Optical Network (AON) Consortium has developed an all-optical LAN/MAN test bed which provides time-slotted WDM service. We explore extensions of this service to achieve fine-grained statistical multiplexing with different virtual circuits time sharing the wavelengths in a fair manner. We develop a very fast, best effort time-slotted WDM network protocol with very good fairness and throughput characteristics. As an additional design feature, our protocol supports the assignment of guaranteed bandwidths (GBW) to selected sessions. This feature acts as a first step toward supporting integrated services at the optical layer in WDM networks     

Hollow Silica Spheres of Controlled Size and Porosity by Sol—Gel Processing

A new technique particularly suitable for fabricating uniform, hollow silica spheres of controlled size and porosity is described. The technique, which combines sol—gel processing with a hollow-drop generation technique, consists of producing a continuous stream of uniform, hollow drops of a tetraethyl orthosilicate solution and then converting the drops into a rigid form by exposing them to an ammoniated vapor gelation medium. The parameters controlling the properties of the resulting silica spheres are the detailed chemical makeup of the reactant solution and the gelation medium, and the dimensions and relative positions of the nozzles used for drop generation.     

A monolithic InP/SOI platform for integrated photonics

The deployment of photonic integrated circuits (PICs) necessitates an integration platform that is scalable, high-throughput, cost-effective, and power-efficien...     

The efficient maintenance of offshore structural integrity using reliability analysis

Efficient maintenance of offshore structures is one of the priority development areas of the offshore industry world-wide. The maintenance of the installations in a hostile environment such as the North Sea poses a particular problem. Owing to the large number of wave-induced stress cycles experienced by the structures, the integrity is subject to progressive degradation under fatigue crack growth. If cracks are discovered in service, the operators of the structures will need to decide on the appropriate course of action. The priorities for actions will also need to be determined for cracks of various sizes found in different locations of the structures. In the past, the above decisions have depended very much on engineering judgement. However, the latest developments in reliability fracture mechanics (RFM) analysis have for the first time provided an objective criterion for this type of decision making. Moreover, this criterion is consistent with the established structural design criteria based on reliability analysis of strength—load interaction. Therefore, it has become a real possibility to incorporate structural integrity considerations by design. The reliability-fracture-mechanics-based fatigue analysis includes studies on the uncertainties of load history, materials crack growth behaviour, fracture mechanics modelling, non-destructive inspection and other environmental factors. This paper will review the development in this methodology. In order to integrate the above analysis into the overall design process, it is useful to carry out reliability analysis for the complete structural system. The current state of the art of structural system reliability analysis is therefore briefly reviewed. The necessary development in order to accommodate fatigue reliability degradation is then discussed.     

A 2-bit MONOS nonvolatile memory cell based on asymmetric double gate MOSFET structure

A novel 2-bit/cell nonvolatile memory (NVM) with metal-oxide-nitride-oxide-semiconductor (MONOS) asymmetric double gate (ADG) MOSFET structure is proposed. With the double gate structure, the two conducting channels provide the ability to store 2 bits in a cell. Program and erase can be performed by channel hot electron (CHE) injection and Fowler-Nordheim (FN) tunneling respectively. The read operation and the array structure of the proposed novel NVM are also studied and described in this paper.     

The bathtub does not hold water any more

This is the first part of a three part article under the general heading of ‘Off the bathtub onto the roller-coaster curve’, a short version¹ of which was presented at the 1988 Annual Reliability and Maintainability Symposium in U.S.A. The other two parts, to be published in later issues of this journal, are entitled ‘The roller-coaster curve is in’ and ‘Physical basis for the roller-coaster hazard rate curve’. This three-part article provides detailed discussions of the findings leading to the conclusions on the roller-coaster characteristics for the hazard rate curve for electronics. Part 1 being presented here covers the discussions on problems with the bathtub curve. The problems include making erroneous decisions resulting in reliability demonstration risks against the manufacturers, windfall profits for satellite manufacturers, false claims in reliability growth and reliability prediction accuracy and stress screening shortfalls. More important than the erroneous short-term decisions is the long-term reliability engineering methodology development. It is critical that we must reshape the course of reliability methodology development away from the bathtub misconception.     

Enhancement of two-dimensional projections from electron microscope images using spatial correlations

The analysis of particle images displaying the same orientation in the electron micrographs is carried out by enhancement of auto-correlations of image densities as a function of the spatial coordinates of single particle images. The averaging of the spatial correlations, which is “incoherent” since it does not require alignment of the individual images, is compared to existing coherent averaging methods of enhancement using lattices and single particle images aligned by cross correlations.