Operations standards for global ATM networks: network element view

The International Telecommunication Union (ITU) has completed work on a series of standards on asynchronous transfer mode (ATM) equipment functional operations and network element management. The objective of these standards is to enable flexible design and interoperability of network elements for use in a global ATM network, independent of any specific implementation. This article discusses these standards with respect to their development and application in planning ATM networks. Specifically, it addresses the following: the modeling approach taken in the development of the ITU standards, key operational features specified in the ATM network element functional model, and the capabilities of the ATM network element management interface. Examples of ATM equipment are provided to illustrate how the functional models specified in the ITU standards may be used by network planners and equipment manufacturers to specify and develop ATM equipment tailored to specific needs, while ensuring network interoperability. The article concludes with some points on the future enhancement of these and related ATM equipment operations standards     

Theory of soliton stability in asynchronous modelocking

A new type of fiber laser modelocking is examined where a phase modulator is driven asynchronously with respect to a harmonic of the roundtrip cavity frequency. An asynchronous drive is able to produce high repetition rate (>1 GHz) soliton pulses that are shorter than the classic, active modelocking pulse width limit. It is shown that with a proper choice of fiber parameters, noise cleanup and soliton pulse shaping can be obtained using filtering and asynchronous phase modulation. Limits of asynchronous detuning are derived and a comparison with the parameters ranges for synchronous phase modulation is also presented     

Modeling and classification of natural sounds by product codehidden Markov models

Linear predictive coding (LPC), vector quantization (VQ), and hidden Markov models (HMMs) are three popular techniques from speech recognition which are applied in modeling and classifying nonspeech natural sounds. A new structure called the product code HMM uses two independent HMM per class, one for spectral shape and one for gain. Classification decisions are made by scoring shape and gain index sequences from a product code VQ. In a series of classification experiments, the product code structure outperformed the conventional structure, with an accuracy of over 96% for three classes     

Advanced generating technologies: motivation and selection processin electric utilities

The constant search by electric utilities for advanced methods for generating electricity to meet future demand is discussed. The primary goal is to generate electricity with minimum damage to the environment and to use resources that are abundant. The evaluation of the role of these technologies in the future utility system, considering both quantifiable and nonquantifiable benefits and risks, is discussed from the perspective of the utility planning process     

Semiconductor yield improvement: results and best practices

The results of a world-wide study on yield improvement are presented. Die yields collected from 21 fabs are transformed via a logit formula and compared. The die yields and die yield improvement rates of the fabs are compared, and manufacturing yield improvement practices are evaluated. Preliminary results of this continuing study indicate that die yield improvement is a function of computer-aided manufacturing practices and statistical process control practices in addition to commonly cited practices such as particle control and advanced manufacturing technology     

Doubling the engineer's utility

The big challenge for military forces and their industrial supporters since the end of the cold war is how to convert technologies once viewed as exclusively military to serve civilian ends as well. The authors discuss a case of dual use in which a rigorous military method for designing complex computer systems appears suited to complicated civilian projects. The method is supported by a new language, CaRT-Spec, which is application independent and therefore suitable for both military and civilian applications     

Single motor unit myoelectric signal analysis with nonstationarydata

The information content of the myoelectric signal (MES) is commonly revealed by statistical measures in the time or frequency domain. Empirical analyses of the MES from a single motor unit have generally assumed that features are invariant with time. Theoretical and experimental work has been done to demonstrate how nonstationary behavior in the discharge statistics of a motor neuron may affect estimates of features extracted from the motor unit's contribution to the MES. Specifically, it has been shown that nonstationary behavior can markedly influence estimates of features describing motor neuron firing behavior and consequently, the low-frequency portion of the MES power spectral density. These results may help to explain the discrepancies in the literature which report empirical models of motor neuron firing statistics     

Operation of a nonlinear optical loop mirror with orthogonally polarized waves in nonpolarization-preserving, single-mode fiber

We demonstrate stable operation of a NOLM using orthogonally polarized control and signal beams in nonpolarization-preserving, single-mode fiber. The NOLM can transcribe data from an optically incoherent input at one wavelength to a coherent output over a range of wavelengths. Operation of the NOLM without tuning for the input bit rate is possible over a range of bit rates from less than 1 Gb/s to more than 50 Gb/s.     

Compact optical millimetre-wave source using a dual-modesemiconductor laser

The authors demonstrate the optical generation of extremely narrow linewidth millimetre-wave signals between 40 and 60 GHz using a single-chip semiconductor laser. A dual-mode long-cavity multisection DFB semiconductor laser is driven at a subharmonic of the free-running-mode beat signal frequency to produce phase-locked millimetre waves with a 3 dB linewidth of less than 10 Hz and a 3 dB locking range of ~500 MHz     

Trade-offs in cycle time management: hot lots

In manufacturing, higher priority is given to hot lots to reduce their cycle time. The impact of hot lots on the cycle time of other lots in the system is studied here. Object-oriented simulation experiments of a wafer fabrication model were run to investigate the above impact. The simulation results showed that as the proportion of hot lots in the work-in progress increases, both the average cycle time and the corresponding standard deviation for all other lots increase dramatically. Thus, it is argued that hot lots induce either a deterioration in service level for regular lots or an increase in inventory costs. Sound management accounting would require that these costs be estimated, possibly using an approach outlined here