Edward E. E. Frietman

A method for detection of Alzheimer's disease using ICA-enhanced EEG measurements

OBJECTIVE Many researchers have studied automatic EEG classification and recently a lot of work has been done on artefact-removal from EEG data using independent component analyses (ICA). However, demonstrating that a ICA-processed multichannel EEG measurement becomes more interpretable compared to the raw data (as is usually done in work on ICA-processing of EEG data) does not yet prove that detection of (incipient) anomalies is also better possible after ICA-processing. The objective of this study is to show that ICA-preprocessing is useful when constructing a detection system for Alzheimers disease. METHODS AND MATERIAL The paper describes a method for detection of EEG patterns indicative of Alzheimers disease using automatic pattern recognition techniques. Our method incorporates an artefact removal stage based on ICA prior to automatic classification. The method is evaluated on measurements of a length of 8s from two groups of patients, where one group is in an initial stage of the disease (28 patients), whereas the other group is in a more progressed stage (15 patients). Both setups include a control group that should be classified as normal (10 and 21, respectively). RESULTS Our final classification results for the group with severe Alzheimers disease are comparable to the best results from literature. We show that ICA-based reduction of artefacts improves classification results for patients in an initial stage. CONCLUSION We conclude that a more robust detection of Alzheimers disease related EEG patterns may be obtained by employing ICA as ICA based pre-processing of EEG data can improve classification results for patients in an initial stage of Alzheimers disease.

Parallel optical interconnects: implementation of optoelectronics in multiprocessor architectures

Performance and efficiency of multiple processor computers depend strongly on the network that interconnects the distinct collaborating processors. Constrained connectivity forces much of the potential computing speed to be used to compensate for the limitation in connections. The availability of a multiple parallel I/O connections allows full unrestricted connectivity and is an essential prerequisite for an interprocessor network that is able to meet the ever growing communication demands. This paper emphasizes the design, building and application of an electrooptic communication system [EOCS]. The EOCS uses dedicated free space multiple data distributors and integrated optically writable inputbuffer arrays with fully parallel access.

Speeding up backpropagation training on a hypercube computer

Abstract Training algorithms for artificial neural networks (such as backpropagation) tend to be very time-consuming. It is therefore obvious to capitalize on the intrinsic parallelism of these systems in order to speed up the computations. This paper describes our simulation of backpropagation neural networks on an NCube/4+ parallel computer and the speed-up performances achieved.

Novel type of red-sensitive photopolymer system for optical storage

In this paper, a novel type of red sensitive photo-polymer system for optical storage, here called RSPP, is presented. First of all, the components in RSPP, for example, photo- sensitizer, photo-initiator, monomer, copolymer, combiner, stabilizer, hardener, and fabrication and processing technique of RSPP are given. Then, the absorption spectrum of RSPP material is measured. And the result shows the material is only sensitive to read light, whose absorption peak is at 662 nm and half-width of the absorption is about 100 nm. After that, the property of exposure in RSPP is studied. It is found that RSPP holographic plate has several advantages over the optical storage (holographic optical storage) material previously reported. First, this RSPP is fit to record both transmission holograms and reflection holograms. Second, the holograms recorded in RSPP plate can be processed both in dry and in wet processes due to its strong real-time effect. The performance parameters of the ESPP are following: (1) The photosensitivity is about 2 mJ/cm2 at 630 nm; (2) The resolution of the material is more than 4000 pp/mm; (3) The saturation refractive index modulation is 0.0034 and 0.0141 for real time and wet processing respectively. In the study of the exposure in RSPP holographic plate, some other phenomena concerning real time effect in RSPP, such as, light- amplification and modulation of single light beam effect, are found. The mechanism of these phenomena is discussed.

Wavelength division multiplexers/demultiplexers for optical interconnects in massively parallel processing

Communication between computing systems is recognized as the main limitation to increase the speed of all-electronic systems beyond levels currently achieved in existing supercomputers. Optical in- terconnects hold great promise in eliminating current communication bottlenecks because of properties that stem from optics inherent paral- lelism. Wavelength-division multiplexing (WDM) technology, by which multiple optical channels can be simultaneously transmitted at different wavelengths through a single optical transmission medium, is a useful means of making full use of optics parallelism in an application of inter- connects for massive parallel processing. We first briefly review the bottlenecks of electrical interconnects in massively parallel processing. Then we discuss the advantages of optical interconnects and present our approach of optoelectronic interconnects in massively parallel pro- cessing by WDM technology. We then review the working principles of wavelength division (de) multiplexers (WD(D)M) for optical interconnects in massively parallel processing and address the optical design issues of WD(D)Ms. Finally, we report experimental data of WD(D)Ms for this ap- plication. The devices exhibit low insertion loss, high reliability, and low cost.

The Detection of Eyeball Movements with the Eye-Sistant

The Eye-Sistant1 a portable instrument developed for the detection of eyeball movements detects horizontal and vertical eyeball movements separately on a non-contact basis. The final result, expressed in analogue form, is proportional to the amount of reflected I nfra R ed (IR) energy coming from the iris, pupil and sclera. The IR sources and light-sensitive elements are mounted on oculist spectacles, making the device also suitable for persons wearing spectacles. The EYE-SISTANT has already been applied in fundamental research and in the domain of communication aids for the disabled.

Optical link in the Delft parallel processor—an example of MOMI-connection in MIMD-supercomputers

Abstract Much attention is given to the problem how to avoid transfer-bound processing in MIMD supercomputers. The interactivity between processing tasks is compared with the interconnectability that exists between processors in the case of a multi-bus communication system. For this purpose quantitative measures are introduced for both the task interactivity and the processor interconnectability. For a MIMD computer with p processors and p busses the asymptotic speed-up is proportional to p both for tightly and loosely coupled tasks. For tightly coupled tasks a still larger speed-up can be achieved by taking more than p busses. For a MIMD computer with p processors in the case of 2-level parallelization considerably more speed-up can be obtained, but that requires at the 2nd level of parallelization p powerful interconnects (one per processor). Full processor interconnectability is ideal in the sense that no queueing problems can arise. In case of 1-level parallelization with p processors full interconnectability requires p 2 (one-word wide) interconnections. In the Delft Parallel Processor (DPP), instead of using a p 2 -tuple bus communication system, for this purpose a multibroadcast system with p data channels has been applied, where each data channel has p taps (one per processor) and each processor has a p-tuple accessible input memory (one input per channel). In the DPP84 (with maximally 16 processors) electric data channels have been applied. But for technical reasons for large p full interconnectability is only feasible by the way of optical data channels. This optical interconnect must be provided with electro-to-optic (E/O) and opto-to-electric (O/E) transducers as long as optical computing is not yet practically possible. The resulting Electro-Optic Communication System (EOCS) will be implemented in the DPP8X. The EOCS will consist of a combination of guided-wave and a p-tuple way starcoupler technique. Special E/O and O/E transducers have to be developed as well. An intelligent Opto-Electric logic element, the POWERRAM, is realized as a prototype p-tuple accessible input memory IC, capable to accept the multidata stream at the input of a processor in one clock cycle.

Optical interconnects in a multicomputer environment

The Deift Parallel Process, based on a multi-computer architecture and constructed with a Multi-Broadcast Interconnection topology, is a 16 processing no&s Multiple Instruction stream, Multiple Data stream computer developed at the Deift University of Technology in 1977 to evaluate software algorithms, architectures and interconnection topologies experimentally. The Processing Elements in the nodes, containing Weitek Floating Point Multiplier/ALU combinations, are going to be interconnected in a full parallel Electro-Optic Communication System. The Routing Elements, containing Transputers, are linked by an optical reconfigurable network, which enables a simultaneous communication between all the REs.

Current status and future research of the Delft 'supercomputer' project

In despite of the extensive class of computers a break-through of the implementation of Optical Interconnects in the Massive Parallel versions has still not taken place. Only a top-bottom approach will give a thorough insight where those techniques will satisfy forcing researchers in this area to cover almost all the knowledge of topics related to Computer Archi- Lectures Transport media Electro-Optic and Opto-Electronic technologies. Interconnecting Printed Circuit Boards through an Optical Backbone could be the first step© (1991) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Prospects for Optical Interconnects in Distributed, Shared-Memory Organized MIMD Architectures

The antipodes of the class of sequential computers, executing tasks with a single CPU, are the parallel computers containing large numbers of computing nodes. In the shared-memory category, each node has direct access through a switching network to a memory bank, that can be composed of a single but large or multiple but medium sized memory configurations. Opposite to the first category are the distributed memory systems, where each node is given direct access to its own local memory section. Running a program in especially the latter category requires a mechanism that gives access to multiple address spaces, that is, one for each local memory. Transfer of data can only be done from one address space to another. Along with the two categories are the physically distributed, shared-memory systems, that allow the nodes to explore a single globally shared address space. All categories, the performances of which are subject to the way the computing nodes are linked, need either a direct or a switched interconnection network for inter-node communication purposes. Linking nodes and not taking into account the prerequisite of scalability in case of exploiting large numbers of them is not realistic, especially when the applied connection scheme must provide for fast and flexible communications at a reasonable cost. Different network topologies, varying from a single shared bus to a more complex elaboration of a fully connected scheme, and with them the corresponding intricate switching protocols have been extensively explored. A different vision is introduced concerning future prospects of an optically coupled distributed, shared-memory organized multiple-instruction, multiple-data system. In each cluster, an electrical crossbar looks after the interconnections between the nodes, the various memory modules and external I/O channels. The clusters itself are optically coupled through a free space oriented data distributing system. Analogies found in the design of the Convex SPP1000 substantiate the closeness to reality of such an architecture. Subsequently to the preceding introduction also an idealized picture of the fundamental properties of an optically based, fully connected, distributed, (virtual) shared-memory architecture is outlined.