Hardware architecture of the Protein Processing Associative Memory and the effects of dimensionality and quantisation on performance

The Protein Processor Associative Memory (PPAM) is a novel hardware architecture for a distributed, decentralised, robust and scalable, bidirectional, hetero-associative memory, that can adapt online to changes in the training data. The PPAM uses the location of data in memory to identify relationships and is therefore fundamentally different from traditional processing methods that tend to use arithmetic operations to perform computation. This paper presents the hardware architecture and details a sample digital logic implementation with an analysis of the implications of using existing techniques for such hardware architectures. It also presents the results of implementing the PPAM for a robotic application that involves learning the forward and inverse kinematics. The results show that, contrary to most other techniques, the PPAM benefits from higher dimensionality of data, and that quantisation intervals are crucial to the performance of the PPAM.     

Element distinctness on one-tape Turing machines: a complete solution

We give a complete characterization of the complexity of the element distinctness problem for n elements of bits each on deterministic and nondeterministic one-tape Turing machines. We present an algorithm running in time for deterministic machines and nondeterministic solutions that are of time complexity . For elements of logarithmic size , on nondeterministic machines, these results close the gap between the known lower bound and the previous upper bound . Additional lower bounds are given to show that the upper bounds are optimal for all other possible relations between m and n. The upper bounds employ hashing techniques, while the lower bounds make use of the communication complexity of set disjointness.Received: 23 April 2001, Published online: 2 September 2003Holger Petersen: Supported by Deutsche Akademie der Naturforscher Leopoldina, grant number BMBF-LPD 9901/8-1 of Bundesministerium für Bildung und Forschung.     

Performance evaluation of semantic registries: OWLJessKB and instanceStore

Service discovery is a critical task in distributed computing architectures for finding a particular service instance. Semantic annotations of services help to enrich the service discovery process. Semantic registries are an important component for the discovery of services and they allow for semantic interoperability through ontology-based query formulation and dynamic mapping of terminologies between system domains. This paper evaluates two semantic registries—OWLJessKB implementation and instanceStore—to determine the suitability of these with regards to the query response time and the overall scalability for use in mathematical services. Mathematical ontologies from the MONET project are used to undertake comparison. The results demonstrate that the performance of registries may be compared across two axes: (1) time to initialize (i.e. time to load an initial ontology into memory); (2) time to query (i.e. time to reason with an ontology loaded into memory).     

On Locally Decodable Codes, Self-Correctable Codes, and t-Private PIR

A k-query locally decodable code (LDC) allows to probabilistically decode any bit of an encoded message by probing only k bits of its corrupted encoding. A stronger and desirable property is that of self-correction, allowing to efficiently recover not only bits of the message but also arbitrary bits of its encoding. In contrast to the initial constructions of LDCs, the recent and most efficient constructions are not known to be self-correctable. The existence of self-correctable codes of comparable efficiency remains open.     

Listening to Natural and Synthesized Speech while Driving: Effects on User Performance

The effects of message type (navigation, E-mail, news story), voice type (text-to-speech, natural human speech), and earcon cueing (present, absent) on message comprehension and driving performance were examined. Twenty-four licensed drivers (12 under 30, 12 over 65, both equally divided by gender) participated in the experiment. They drove the UMTRI driving simulator on a road consisting of straight sections and constant radius curves, thus yielding two levels of low driving-workload. In addition, as a control condition, data were collected while participants were parked. In all conditions, participants were presented with three types of messages. Each message was immediately followed by a series of questions to assess comprehension. Navigation messages were about 4 seconds long (about 9 words). E-mail messages were about 40 seconds long (about 100 words) and news messages were about 80 seconds long (about 225 words). For all message types, comprehension of text-to-speech messages, as determined by accuracy of response to questions, and by subjective ratings, was significantly worse than comprehension of natural speech (79 versus 83 percent correct answers; 7.7/10 versus 8.6/10 subjective rating). Driving workload did not affect comprehension. Interestingly, neither the speech used (synthesized or natural) nor the message type (navigation, E-mail, news) had a significant effect on basic driving performance measured by the standard deviations of lateral lane position and steering wheel angle.     

Densification of alumina by SPS and HP: A comparative study

In this study, the densification of alumina by spark plasma sintering (SPS) was investigated and compared to conventional hot pressing. It was shown that SPS is very effective in the sintering of alumina leading to higher densities and allows to work at lower temperatures and with shorter sintering cycles. The effect of the heating rate is dependent on the heating mode (SPS or HP). The identification of active sintering mechanisms was attempted by an isothermal and an anisothermal methods, showing that other mechanisms probably related to electrical effects enhance the densification. We suggest the higher contribution of surface diffusion mainly during the initial stage of sintering and an influence of the presence of impurities segregated at the grain boundaries. They could create conductive layers and also introduce ions with a lower valence than Al³⁺; defects are created in the surface layers and the diffusion of the species is increased.