Next-generation optical storage area networks: the light-trails approach

Multiple architectures, technologies, and standards have been proposed for storage area networks, typically in the WAN environment. The transport aspect of storage signifies that optical communications is the key underlying technology. The contemporary SAN over optical network concept uses the optical layer for pure transport with minimal intelligence. This leads to high cost and overprovisioning. Future optical networks, however, can be expected to play a role in optimizing SAN extension into the WAN. An essential characteristic of SAN systems is tight coupling between nodes in a SAN network. Nodes in a SAN system have two critical functions that are presently emulated by data layers and can be offloaded to the optical layer. First, nodes need to signal among each other to achieve tasks such as synchronous and asynchronous storage. Second, to benefit from an optimized network, nodes need to allocate bandwidth dynamically in real time. In this article we show how the optical layer can be furthered from just pure transport to creating opportunities in provisioning as well as providing the mirroring function of SAN systems (multicasting) and consequently lead to reduction in cost. We demonstrate that the light-trail model is one way of efficiently utilizing the optical layer for SAN.     

Steady-State Analysis of a Permanent Magnet Synchronous Motor Drive with Current Source Inverter

A steady-state analysis is presented of a permanent magnet (PM) synchronous motor drive with a current source inverter (CSI). The torque-speed profile required of the drive is a constant torque region from zero to base speed and a constant power region above base speed. The analysis assumes position feedback control. Optimum control strategies are obtained for the two regions of the torque-speed profile. Using these optimum strategies, performance curves of the drive are predicted and experimentally verified. The time harmonics in the motor are a function of the presence and configuration of the dampers in the motor. An expression is obtained for the equivalent inductance seen by the harmonics for different damper configurations. A Fourier series approach is used to predict the line-to-line voltage waveforms. Even though the presence of the dampers is not essential to the operation of the drive, their presence reduces the voltage spikes present in the line-to-line voltage.     

Barium hexaferrite magnet by topotactic reaction method

A new topotactic sintering method using Fe₂O₃ (obtained from FeO · OH) and BaCO₃ is developed for preparing cheaper grain oriented barium hexaferrite. Fe₂O₃ and BaCO₃ (precipitate grade) are wet mixed in a ball mill in stoichiometric proportion. The mixed slurry is then dried at 110° C for about 12h. The dried powder mixture containing moisture as a binder is uniaxially compacted at 5×10⁶–10×10⁶ kg m^–2 pressure. The green compacts are air sintered in the temperature range 1100–1300° C for 1 H. The best results of the sintered ferrite show maximum energy product (BH) _max in the range 7–10 kTAm^–1. The bulk of commercial requirements for toy magnets etc. may be met by this method of production which eliminates steps like calcination and cost intensive wet magnetic compaction.     

Value-added services in next-generation SONET/SDH networks

Advances in next-generation SONET/SDH have introduced novel features for generic protocol framing/encapsulation, virtual concatenation, inverse multiplexing, dynamic circuit adjustment, and so on. In turn, these provisions have enabled much improved multi-tiered service provisioning and are viewed very favorably by carriers, particularly incumbents. This article looks at this evolved framework with a particular focus on value-added services creation. Results from a sample performance evaluation study also are presented to quantify some of the achievable gains.     

A localized version of the method of Lagrange multipliers and its applications

This paper describes a novel version of the method of Lagrange multipliers for an improved modeling of multi-point constraints that emanate from contact-impact problems, partitioned structural analysis using parallel computers, and structural inverse problems. It is shown that the classical method of Lagrange multipliers can lead to a non-unique set of constraint conditions for the modeling of interfaces involving more than two or multi-point substructural interface nodes. The proposed version of the method of Lagrange multipliers leads not only to unique construction of constraints but also encounters no singularity in modeling an arbitrary number of multi-point constraints. An important utilization of the present method is in the regularized modeling of interfaces whose rigidities are radically different from one to another. The present approach is demonstrated via several examples for its simplicity in modeling constraints, ease of implementation and computational advantages. Received November 1998     

Error Performance of Double Space Time Transmit Diversity System

The theoretical error performance of double space time transmit diversity (DSTTD) system with optimum combining receiver is analyzed in this paper. By employing both spatial multiplexing and transmit diversity in one system, DSTTD provides practical tradeoff between system spectral efficiency and diversity gain. We derive exact analytical expressions to describe the symbol error rate for DSTTD systems. The effects of both diversity gain and antenna interference introduced by spatial multiplexing are quantified in the results. In addition, the performance of DSTTD system with successive interference cancellation is also investigated. Simulation results are in excellent agreement with the theoretical results obtained in this paper.     

Magnetic Properties of Topochemically Sintered Barium Hexaferrite

This communication describes the method of topochemical reaction sintering for the production of barium hexaferrite. Topochemical reaction sintering overcomes crucial process steps that are used in the conventional wet magnetic compaction method, such as calcination, wet grinding, and wet magnetic compaction. Chemical reaction sintering of the above-mentioned ferrite has been performed in air and under vacuum. Barium hexaferrite that has been topochemically sintered in air at a temperature of 1473 K for 60 min shows a maximum magnetic energy product (( BH )_max) of 6.56 kJ/m³, whereas barium hexaferrite that has been topochemically sintered at a temperature of 1423 K for 30 min under vacuum (10^-2 mm Hg (∼0.133 Pa)) shows ( BH )_max= 7.6 kJ/m³. The variation of the magnetic properties of the topochemically sintered ferrites is interrelated to process variables such as temperature and sintering duration (time).     

Delay Sensitive Smoothed Round Robin (DS2R2) Scheduler for High-Speed Optical Networks

Smoothed round robin (SRR) is an 0(1) scheduler that efficiently schedules flows based on flow granularity leading to short-term fairness. We propose DS2R2 - delay sensitive smoothed round robin scheduler that enhances SRR by adhering to delay constraints of flows. Scalability and performance issues of DS2R2 for high-speed optical networks are considered.