Breakdown points,breakdown probabilities,midpoint sensitivity curves,and optimization of stack filters

Three new concepts — breakdown points, breakdown probabilities, and midpoint sensitivity curves — for stack filter analysis are introduced and analyzed in this paper. Breakdown points and probabilities can be used as measures of the robustness of stack filters. Midpoint sensitivity curves in turn give information on how sensitive the output of a stack filter is to the changes of a single value in the input window. The second major contribution of this paper is the extension of the current optimality theory of stack filters. This theory combines noise attenuation and different constraints on the filter's behavior. New constraints are introduced in this paper. A new optimization approach based on breakdown probability as a noise attenuation measure is also derived. In certain special cases it is shown that the optimal stack filter that achieves the best noise attenuation subject to given constraints can be obtained in closed form. An algorithm for finding this form is given in this paper, and its modification for finding a stack filter having (approximately) a required rank selection vector is presented.     

Distributed objects and object databases

Due to the on-going shift from centralised to decentralised computing and a general trend towards the globalisation of commercial, economic and social activities, the information systems community has been faced with strong demands to develop distributed information systems (DISs) that span wide geographical areas. Three technologies have had significant impact on the new generation of DISs — distributed object technology, object database technology and Web technology. The paper examines two of these — DOT and ODBT. Each has advantages over the other, but more importantly they complement each other, and ways of using them together are explored.     

Loss and Noise Characteristics of Microwave Direct Modulated Optical Links

Loss and noise figure of optical links transmitting microwave signals —e.g. for remote antennas in wireless communications — are dealt with.Conditions are rather general and include arbitrary matching conditions, shotnoise, and laser relative intensity noise. Specific and somewhat surprisingcharacteristics are derived. Among others, it is shown, that — likepassive, purely microwave systems — noise figure is not proportional toelectrical loss and it can be even lower than loss itself. Optical powershould be as low as possible — this limit is mainly determined by therequired dynamic range of the system. Loss and noise figure were measured inan experimental setup. Results of the measurements proved the theoreticalfindings rather well. Preliminary results on the transmission of 32TCM signalsover the link are briefly presented.     

Electronic Commerce Back-office Integration

This paper discusses some of the lessons learned from integrating two customers' back-office systems with a pilot BT-managed business-to-business electronic catalogue service. An overview of the two pilot implementations describes the experience and offers some important lessons learned.Three types of lesson learned are presented in this paper — firstly based on the design and implementation of both pilot catalogue systems, secondly about the importance of proper site security for Internet applications, and lastly about relationship building and information gathering — in the hope that others will be able to use this information in helping to avoid some of the mistakes and pitfalls encountered in this work. As George Santayana once said: 'Those who cannot remember the past are condemned to repeat it.'     

A New Network Architecture for Wireless Communications

Current cellular systems are based on theconcept of the cell. Although the cell allows channelreuse, it has also become a metaphor for channelconfinement and leads to the thorny problem of handoffand call dropping. The problem will get much worseas wireless networks move toward smaller cells andmultirate. A new network architecture for wirelesscommunications is presented in this paper. Thearchitecture — called MAWCC for its main characteristic,MAcrodiversity Without Channel Confinement — hasno ping-pong effect in handoff. Furthermore, itscapacity gain from macrodiversity can be freelyconverted into handoff reduction. The new architecture offers manyoptions to handle mobility which are not possible in aconventional cellular architecture.     

Interactive collaborative media environments

Virtual reality (VR) provides a revolutionary interface between man and machine. However, present display and interface peripherals limit the potential of virtual environments within many activities or scenarios. Mainstream immersive VR is centred on head mounted display (HMD) based solutions in which the user is isolated from their surrounding environment. The occlusion of real world interaction within such systems imposes unnatural social and physical constraints on the user. Media environments can be classified as one form of enhanced reality based around immersive physical spaces intensified for effective collaborative activities. Current research is directed at three forms of enhanced spaces — immersive projected displays, interactive video environments, and immersive desktop environments. While HMD and desktop VR facilitates many collaborative tasks, the synthesis of real and virtual realities within a life-size environment offers distinct advantages within other applications. This paper introduces the concepts behind media environments, reviews current research and presents applications being explored at BT Laboratories.     

Microelectronics'' and reliability''s new tool: UNIX today

Today's quality paradigms deal with a very broad array of concepts and approaches. This paper describes these in detail. No longer is quality the “policeman”, but now a needed “team player”. It is important that all concerned understand and apply these new tools.     

Architecture Concepts for Multimedia Signal Processing

Architectural concepts are presented aimed at future multimedia processing schemes. Starting from an analysis of current and future multimedia applications, specific computational requirements are derived. It will be shown that multimedia applications benefit from an exhaustive and flexible exploitation of parallelism. Three architectural concepts—reconfigurable computing, simultaneous multithreading, and associative controlling—are presented, and their potential to increase further the performance on future multimedia applications is investigated.     

AntiGroupWare and Second Messenger

Decision-making in groups has great potential due to the possibilities for pooling ideas and sharing knowledge, but also great drawbacks due to the social pressures inherent in these situations that can limit free exchange of these ideas and knowledge. This paper presents two technology-based approaches to improving group decision-making, Second Messenger and AntiGroupWare. Second Messenger — a system that encourages groups to change their interaction styles during meetings — is designed to improve meetings, while AntiGroupWare — an on-line polling system that allows companies to gather information through flexible, iterative polling of its employees — is designed to avoid them altogether.     

Special issue on rational approximations for systems

Conclusions To conclude our discussion we can only confess to our shortcomings as organizers and editors. We have been incomplete, we have been biased, and, worst of all, we have not been able to produce the most essential connections in any firm way. Perhaps our major achievement — if we may say so — has been to point the way to many possible new results and to new research. The field discussed here seemed at first very conventional. May we have convinced the reader that it is not. That the major problems have not been solved. That here lies an open field for system engineers, numerical analysts, and mathematicians.The workshop on rational approximations for systems and the present editorial work were partially supported by the NFWO (Brussels), the Belgian Ministry of Education and Culture, and the Third Cycle Research Fund of the Katholische Universiteit Leuven.     

NEFCLASS-X — a Soft Computing Tool to Build Readable Fuzzy Classifiers

Neuro-fuzzy classification systems offer a means of obtaining fuzzy classification rules by a learning algorithm. Although it is usually no problem to find a suitable fuzzy classifier by learning from data, it can, however, be hard to obtain a classifier that can be interpreted conveniently. There is usually a trade-off between accuracy and readability. This paper discusses NEFCLASS — a neuro-fuzzy approach for classification problems — and its implementation NEFCLASS-X. It is shown how a readable fuzzy classifier can be obtained by a learning process and how interactive strategies for pruning rules and variables from a trained classifier can enhance its interpretability.     

Interconnect Geometry Optimization Using Modular Artificial Neural Networks

This paper describes a methodology for crosstalk prediction and minimization in interconnect wiring using artificial neural networks. Neural networks are used as parameterized models to achieve two important mappings. The first—forward map—maps the geometric and material parameters of interconnects (for example width, length, separation, conductivity, dielectric constant k) to equivalent electrical parameters (for example, R,L,C,G). Such a relationship would normally require quasi-TEM solutions of EM problems. The second—reverse map—is the reverse of the first mapping equivalent electrical parameters to interconnect geometric and material parameters. The crosstalk minimization approach proposed involves topological decomposition of interconnect into standard cells—portions of interconnect referred to as wirecells—and the derivation of the above two mappings for each wirecell. Crosstalk is iteratively minimized in the domain of SPICE circuit parameters and the resulting optimized SPICE equivalent circuit mapped back into the wirecell geometric domain using the reverse neural net mapping. For computational efficiency and high accuracy, the technique initially establishes a library of re-usable neural wirecell models using a field solver coupled with a circuit simulator and a neural network multi-paradigm prototyping system. The approach offers two important advantages. First, the simultaneous effect of multiple non-correlated geometric and material wirecell characteristics on crosstalk can be accurately computed and crosstalk minimized by iterative modification of interconnect geometry and material characteristics. Second, the approach produces—as a by-product—system level contours of equicoupling called isocouples to guide design activities such as placement and route. Crosstalk prediction and minimization results are presented for a high performance operational transconductance amplifier in which reduction in crosstalk by variation of interconnect layout geometry resulted in a 41% increase in gain.     

Is 'Empowerment' Just a Fad? Control, Decision-Making, and Information Technology

The logic in this paper shows why greater decentralization in business (including 'empowerment') is a response to fundamental changes in the economics of decision-making that are enabled by new information technologies. Our research suggests that a simple pattern of three successive stages underlies many of the changes that are taking place: As communication costs fall, independent decentralized decision-makers are replaced, first by centralized decision-makers, and then by connected decentralized decision-makers. This pattern explains important aspects of economic history in this century, and suggests that empowerment is not just a fad, but likely to become even more important in the next century.The paper also suggests that our very notions of centralization and decentralization are incomplete. When most people talk about empowerment, they are only thinking about going 'halfway' toward what is possible. To fully exploit the possibilities of new information technologies, we may need to expand our thinking to include 'radically decentralized organizations' — like the Internet and market economies.     

One-multiplier adaptive lattice algorithm for recursive filters

The formulation of one-multiplier lattice structures of the Gray-Markel type forinfinite impulse response filters is reviewed. Several special cases of this formulation — including the well-known Gray-Markel normalized lattice—are presented as scaled polynomial versions of the two-multiplier lattice. A new adaptive algorithm is presented for updating the parameters of one-multiplier lattice structured recursive filters. The LMS-based algorithm requires fewer computations than earlier reported algorithms [1]–[4].The research reported here was conducted with funds administered by the Naval Postgraduate School research council.     

Terminal Developments and Their Media Capabilities

Building a 3G network is like building a PC — just because you buy the fastest elements, it does not mean that you get the most efficient PC. It is important to integrate and optimise all the elements correctly in order to achieve the best performance. The 3G network is the same — each element of the solution is important. This paper focuses on one aspect of the complete 3G solution, i.e. the handsets/mobile devices that give the customer a gateway into the network services. Key elements of the mobile device that provide the best user experience are identified and briefly discussed and an insight is provided into the direction of the future technology.     

Trading Environments

Many organisations are now adopting the Internet as a new channel to market — and in particular are publishing their product catalogues on-line with the capability of accepting orders. However, as more catalogues emerge the reliance upon discrete catalogues will become less tenable for suppliers and buyers alike — buyers would be unlikely to find the best merchant without some sort of sophisticated help, and similarly suppliers would find it hard to reach their potential customer base. This approach, driven by the supplier, will almost certainly be complemented by other kinds of market-place, driven more from the buyer' perspective. Three main kinds of market-place are envisaged, namely seller-driven, buyer-driven and open markets.In order to support these trading models, different approaches to system architectures are emerging, and these are also discussed.     

New Styles of Thinking for the Era of Organic Networks

When people see patterns in the world, they often assume that there is some type of centralised control, even when it does not exist. This 'centralised mindset' could act as a braking function on the spread of organic networks — if people are not able to think about and understand the decentralised interactions that underlie organic networks, they will not be able to conceive, design, implement, and sustain such networks. In this paper, I discuss how we can help people move beyond the centralised mindset, helping them develop more 'ecological' styles of thinking that are more suited to the era of organic networks.     

CCGA packages for space applications

Commercial-off-the-shelf (COTS) area array packaging technologies in high reliability versions are now being considered for applications, including use in a number of NASA electronic systems being utilized for both the Space Shuttle and Mars Rover missions. Indeed, recently a ceramic package version specifically tailored for high reliability applications was used to provide the processing power required for the Spirit and Opportunity Mars Rovers built by NASA-JPL. Both Rovers successfully completed their 3-months mission requirements and continued exploring the Martian surface for many more moths, providing amazing new information on previous environmental conditions of Mars and strong evidence that water exists on Mars.Understanding process, reliability, and quality assurance (QA) indicators for reliability are important for low risk insertion of these newly available packages in high reliability applications. In a previous investigation, thermal cycle test results for a non-functional daisy-chained peripheral ceramic column grid array (CCGA) and its plastic ball grid array (PBGA) version, both having 560 I/Os, were gathered and are presented here. Test results included environmental data for three different thermal cycle regimes (−55/125 °C, −55/100 °C, and −50/75 °C). Detailed information on these—especially failure type for assemblies with high and low solder volumes—are presented. The thermal cycle test procedure followed those recommended by IPC-9701 for tin–lead solder joint assemblies. Its revision A covers guideline thermal cycle requirements for Pb-free solder joints. Key points on this specification are also discussed.In a recent investigation a fully populated CCGA with 717 I/Os was considered for assembly reliability evaluation. The functional package is a field-programmable gate array that has much higher processing power than its previous version. This new package is smaller in dimension, has no interposer, and has a thinner column wrapped with copper for reliability improvement. This paper will also present thermal cycle test results for assemblies of this and its plastic package version with 728 I/Os, both of which were exposed to four different cycle regimes. Two of these cycle profiles are specified by IPC-9701A for tin–lead, namely, −55 to 100 °C and −55 to 125 °C. One is a cycle profile specified by Mil-Std-883, namely, −65/150 °C, generally used for ceramic hybrid packages screening and qualification. The last cycle is in the range of −120 to 85 °C, a representative of electronic systems directly exposed to the Martian environment without use in a thermal control enclosure. Per IPC-9701A, test vehicles were built using daisy chain packages and were continuously monitored and/or manually checked for opens at intervals. The effects of many process and assembly variables—including corner staking commonly used for improving resistance to mechanical loading such as drop and vibration loads—were also considered as part of the test matrix. Optical photomicrographs were taken at various thermal cycle intervals to document damage progress and behavior. Representative samples of these are presented along with cross-sectional photomicrographs at higher magnification taken by scanning electron microscopy (SEM) to determine crack propagation and failure analyses for packages.