Universal asynchronous iterative arrays of Mealy automata

Summary Asynchronous two-dimensional iterative arrays of automata will be introduced where the underlying automata are not of Moore-type but of Mealy-type. We will prove that there exists a Mealy automaton, , with only two states and one input and output for each of its four distinguished directions, such that any given Mealy-automaton can be realized by an iterative array with only for its component-machines. It is known that loop-free nets cannot be as powerful as Mealy automata; however, we will show that any Mealy automaton can be realized by a network, N, with very restrictive component machines, where no signal may pass a loop in N. Using this fact asynchronous iterative arrays can be built up with one component machine, such that any given Mealy automaton can be realized under the restriction that no signal passes a loop more than once. contains only four states and one input and output for each direction.     

无线现场总线RFieldbus的性能分析及评价

RFieldbus是在现场总线PROFIBUS基础上研制的一种具有传送IP数据包能力的无线实时通讯系统，又称无线现场总线。本文在介绍了其基本结构后，对该系统的实时性能和差错特性做了理论的分析，随后在实验中对数据交换周期、TCP／IP的吞吐量及丢包率等参数做了详细的测试。评测结果表明，RFieldbus可以在并发TCP／IP流量的情况下满足大多数工业控制环境的实时性能要求。     

CoCasl at Work — Modelling Process Algebra

CoCasl[11], a recently developed coalgebraic extension of the algebraic specification language Casl[2], allows for modelling systems in terms of inductive datatypes as well as of co-inductive process types. Here, we demonstrate how to specify process algebras, namely CCS[10] and CSP[8,17], within such an algebraic-coalgebraic framework. It turns out that CoCasl can deal with the fundamental concepts of process algebra in a natural way: The type system of communications, the syntax of processes and their structural operational semantics fit well in the algebraic world of Casl, while the additional coalgebraic constructs of CoCasl cover the various process equivalences (bisimulation, weak bisimulation, observational congruence, and trace equivalence) and provide fully abstract semantic domains. CoCasl hence becomes a meta-framework for studying the semantics and proof theory of reactive systems.     

Model-based software configuration: patterns and languages

The common presupposition of enterprise systems (ES) is that they lead to significant efficiency gains. However, this is only the case for well-implemented ES that are well-aligned with the organisation. The list of ES implementation failures is significant which is partly attributable to the insufficiently addressed fundamental problem of adapting an ES efficiently. As long as it is not intuitively possible to configure an ES, this problem will prevail because organisations have a non-generic character. A solution to this problem consists in re-thinking current practices of ES provision. This paper proposes a new approach based on configurable process models, which reflect ES functionalities. We provide in this paper a taxonomy of situations that can occur from a business perspective during process model configuration. This taxonomy is represented via so-called semantic configuration patterns. In the next step, we discuss so-called syntactic configuration patterns. This second type of configuration patterns implements the semantic configuration patterns for specific modelling techniques. We chose two popular process modelling languages in order to illustrate our approach.     

Modeling Time-Bounded Prefix Kolmogorov Complexity

In the literature, prefix Kolmogorov complexity is defined either in terms of self-delimiting Turing machines or in terms of partial recursive prefix functions. These notions of prefix Kolmogorov complexity are equivalent because, as Chaitin showed, every partial recursive prefix function can be simulated by a self-delimiting Turing machine. However, the simulation given by Chaitin's construction is not efficient, and so questions regarding the time-bounded equivalence of these notions remained unresolved. Here we closely examine these questions. As our main result, we show that every partial recursive prefix function can be simulated with polynomial efficiency by a self-delimiting Turing machine if and only if P = NP. Thus, it is unlikely that Chaitin's construction can be used to show the polynomial-time equivalence of these notions of prefix Kolmogorov complexity. Here we further examine the relationships between these notions of time-bounded prefix Kolmogorov complexity. Received March 25, 1997, and in final form October 8, 1999.     

Why Computational Complexity Requires Stricter Martingales

The word "martingale" has related, but different, meanings in probability theory and theoretical computer science. In computational complexity and algorithmic information theory, a martingale is typically a function d on strings such that E(d(wb)| w) = d(w) for all strings w, where the conditional expectation is computed over all possible values of the next symbol b. In modern probability theory a martingale is typically a sequence $\xi_0,\xi_1,\xi_2,\ldots$ of random variables such that $E(\xi_{n+1}| \xi_0,\ldots,\xi_n) = \xi_n$ for all n. This paper elucidates the relationship between these notions and proves that the latter notion is too weak for many purposes in computational complexity, because under this definition every computable martingale can be simulated by a polynomial-time computable martingale.     

Efficient pulsed 946-nm laser emission from Nd:YAG pumped by a titanium-doped sapphire laser

Efficient pulsed room-temperature laser emission at 946 nm is obtained from a Nd:YAG rod pumped by a Ti-doped sapphire laser in the free-running mode. Three bonded YAG rods of 3-mm diameter with different Nd concentrations and active lengths were tested. A maximum output energy of 83.5 mJ at 3 Hz was obtained with a slope efficiency of 32.3% in an end-pumping configuration.     

Isolation of a bacterial strain with the ability to utilize the sulfonated azo compound 4-carboxy-4'-sulfoazobenzene as the sole source of carbon and energy

A bacterial strain (strain S5) which grows aerobically with the sulfonated azo compound 4-carboxy-4'-sulfoazobenzene as the sole source of carbon and energy was isolated. This strain was obtained by continuous adaptation of "Hydrogenophaga palleronii" S1, which has the ability to grow aerobically with 4-aminobenzenesulfonate. Strain S5 probably cleaves 4-carboxy-4'-sulfoazobenzene reductively under aerobic conditions to 4-aminobenzoate and 4-aminobenzene-sulfonate, which are mineralized by previously established degradation pathways.     

On Inconsistency and Unsatisfiability

We study inconsistency and unsatis ability and their relation to soundness, completeness, paraconsistency and conservative extension in generic logical systems (formalized as institutions equipped with an entailment system).     

Differential effects of head-mounted displays on visual performance

Head-mounted displays (HMDs) virtually augment the visual world to aid visual task completion. Three types of HMDs were compared [look around (LA); optical see-through with organic light emitting diodes and virtual retinal display] to determine whether LA, leaving the observer functionally monocular, is inferior. Response times and error rates were determined for a combined visual search and Go-NoGo task. The costs of switching between displays were assessed separately. Finally, HMD effects on basic visual functions were quantified. Effects of HMDs on visual search and Go-NoGo task were small, but for LA display-switching costs for the Go-NoGo-task the effects were pronounced. Basic visual functions were most affected for LA (reduced visual acuity and visual field sensitivity, inaccurate vergence movements and absent stereo-vision). LA involved comparatively high switching costs for the Go-NoGo task, which might indicate reduced processing of external control cues. Reduced basic visual functions are a likely cause of this effect.