Showing papers by "Tampere University of Technology published in 1983"

Decentralization of process nets with centralized control

Abstract: The behavior of a net of interconnected, communicating processes is described in terms of the joint actions in which the processes can participate. A distinction is made between centralized and decentralized action systems. In the former, a central agent with complete information about the state of the system controls the execution of the actions; in the latter no such agent is needed. Properties of joint action systems are expressed in temporal logic. Centralized action systems allow for simple description of system behavior. Decentralized (two-process) action systems again can be mechanically compiled into a collection of CSP processes. A method for transforming centralized action systems into decentralized ones is described. The correctness of this method is proved, and its use is illustrated by deriving a process net that distributedly sorts successive lists of integers.

Roundoff noise in error-feedback state-space filters

Abstract: Error-feedback is an effective technique for reducing multiplier wordlengths in fixed-point recursive digital filter implementations. In this paper, a new roundoff noise formula for error-feedback state-space filters is derived and used in optimizations.

Design of optimum recursive digital filters with zeros on the unit circle

Abstract: This paper presents an efficient algorithm for the design of low-pass recursive digital filters with Chebyshev passband and stopband, all zeros on the unit circle, and different order numerator and denominator. The procedure takes advantage of the possibility of generating analytically magnitude squared functions with Chebyshev passband and adjustable zeros or Chebyshev stopband and adjustable poles. The resulting algorithm requires only one approximation interval making it more efficient than other existing design procedures. The number of multiplications per sample required in realizing the resulting filters is discussed and the optimal denominator and numerator orders are considered in narrow-band, wide-band, and intermediate applications. It turns out that the classical elliptic filters are seldom the best representatives of the filter class discussed in the paper. Simple explanations of some properties of the filters with denominator order lower than numerator order are given, such as the existence of an extra ripple in the passband and the minimum attainable passband ripple.

Robust controller for boundary control systems

Abstract: Some basic results of robust controller theory are generalized to distributed parameter systems with unbounded control and perturbation operators. The theory presented is then applied to construct a flow adaptive robust controller for heat exchangers.

Transcutaneous, dual channel phrenic nerve stimulator for diaphragm pacing

Abstract: An electrical stimulation system for bilateral diaphragm pacing was constructed. The stimulator instrument comprises a transmitter and two implantable receivers and nerve electrodes. An optimised transcutaneous link system is described which utilises a radio frequency coupling to transmit both power and stimulus information to the receiver. The receiver unit was constructed in thick-film hybrid technology using bipolar and c.m.o.s. circuits and was packaged in a hermetically sealed metal case. The construction of the transmitter allows a high reliability, low power consumption and flexibility of the stimulus parameter control. A complete, bilateral phrenic nerve pacing system was implanted into a patient suffering from tetraplegia. It is concluded that electrical phrenic nerve stimulation to pace the diaphragm is capable of being used in clinical therapy.

On some variants of Post's Correspondence Problem

Abstract: A variant of Post's Correspondence Problem is considered where two different index words are allowed provided that one of them can be obtained from the other by permuting a fixed number of subwords. It is shown that this variant is undecidable. Post's Correspondence Problem is also extended to circular words, doubly infinite words and doubly infinite powers of words, and shown to be undecidable in all these extensions.

Surface and Bulk Electronic Structure of Disordered Metallic Alloys

Abstract: The understanding of electronic structure of disordered alloys has advanced rapidly during the last decade, and the basic elements of a band theory of the bulk electronic structure of random alloys have emerged clearly during this period. In providing an overview of this theory, we focus on the question of how the concept of a Bloch energy band generalizes to the disordered case; illustrative examples of Cu-based solid solutions are presented. On the experimental side, the application of angle-resolved photoemission spectroscopy (ARPES) to the alloy problem is discussed. The use of ARPES in this context is quite recent, although extensive studies of alloys, using a variety of solid state techniques, have been carried out. The existing ARPES work aimed at delineating the surface and bulk electronic structure in metallic alloys is reviewed. We also allude to some of the relevant theoretical and experimental issues that arise in connection with developing this application of the ARPES.

Design of a neutron flux control system by the inverse Nyquist array method

Abstract: The problem of stabilizing power distribution in a reactor core is discussed. First, transfer-function models are derived by modal technique from a distributed-parameter model employing the eight first modes. Four control rods are used in a symmetric and a non-symmetric configuration. Utilizing INA it is shown that it is possible to design static pro- and postcompensators to achieve good dynamic performance

Computationally efficient narrowband linear-phase FIR filters

Abstract: A new approach is presented for synthesising and implementing narrowband linear-phase nonrecursive digital filters requiring a small number of arithmetic operations. The approach is based on transformations implemented by replacing subnetworks with transfer function (1+ Z−2)/2 in a prototype network by a subnetwork whose transfer function is a polynomial in (1+ Z−2)/2 but can be expressed in a form containing no multipliers. By appropriately designing the prototype network and selecting the sub-network, the resulting filter implementations require significantly less multiplications and additions per sample than conventional nonrecursive designs, at the expense of an increased filter order. Examples show that even a reduction from 1017 to 17 multipliers is possible. The new filters present also considerable advantages over nonrecursive filters composed of cascaded decimators and interpolators.

An X-ray diffraction and electron spectroscopic study of metallic glass In20Te80

Abstract: Results of X-ray diffraction and X-ray photoelectron spectroscopy investigations on the crystallization behaviour of an amorphous In20Te80 system and the effects of crystallization on the electronic core levels of In and Te atoms are presented. During controlled heat treatments three crystalline phases, Te, α-In2Te3, and In2Te5-I, were observed in this system. In addition, a few splat-cooled samples were found to exhibit a new metastable crystalline phase. Photoelectron measurements revealed that the Te 3d and 4d core levels of amorphous In20Te80 were shifted downwards in energy from their characteristic values of pure Te metal. The In 3d and 4d levels experienced large energy shifts due to alloying, but remained unaffected by heating at temperatures below 520 K.

Atomic Composition of r.f.-Sputtered Alumina Coatings Determined by XPS Method

Abstract: The O/Al ratios of r.f.-sputtered alumina coatings were analyzed by the XPS (ESCA) method. The coatings were prepared from an Al2O3 target by two commercial deposition devices. The effects of the following deposition parameters on the chemical composition of the coatings were studied: sputtering voltage from 1.3 to 1.9 kV, bias voltage from 0 to - 100 V, excess oxygen partial pressure from 0 to 4%, and total pressure from 0.6 to 2.0 Pa. The sputtering gas was argon. The measured values of the O/Al ratio varied from 1.33 to 1.50 in the alumina coatings. The compositions were very close to stoichiometry when excess oxygen of 1% and bias voltage of - 100 V were applied. However, a deviation in the O/Al ratio was found when the deposition was carried out at a high excess oxygen concentration of 4% which yielded a very oxygen deficient coating with the O/Al ratio of only 1.01. The sputtering voltage and the total pressure had no observable effects on the chemical composition.

A porous glass fibre/resin composite: Structure, properties, and weather resistance

Abstract: The structure and properties of a porous composite manufactured from glasswool and phenol-formaldehyde resin with pressure and heat, were studied in a density range of 800 – 1500 kg/m3. Fibre structure of the composite is almost randomly orientated in two directions, and high open porosity is a typical property. Specific strength of the composite is high compared to other similar materials, but the composite is relatively brittle. The composite is very durable in a normal atmosphere in spite of the open porosity of the composite. Only freezing water and a large enough thermal shock are capable of breaking the composite structure. Struktur und Eigenschaften eines Verbundwerkstoffs aus Glaswolle und Phenolformaldehydharz mit Dichten von 800 bis 1500 kg/m3 wurden untersucht. Die Faserorientierung ist in zwei Richtungen nahezu zufallig, und eine sehr hohe Offenporigkeit ist fur diesen Verbundstoff typisch. Seine Festigkeiten sind irn Vergleich zu entsprechenden anderen Materialien sehr hoch, aber das Material ist relativ sprode. Die Bestandigkeit gegen atmospharische Einflusse ist trotz der offenen Poren ziemlich gut. Nur durch gefrierendes Wasser oder einen groljen thermischen Schock kann der Aufbau des Verbundwerkstoffs zerstort werden.

Optimizing vector magnetocardiographic lead fields by using a physical torso model

Abstract: The ideality and sensitivity of several vector magnetocardiographic leads were tested by using an inhomogeneous, physical torso model. The postero-anterior component of the heart’s magnetic vector was found easiest to detect. New, more ideal leads for the other two components are suggested. However, these have lower sensitivity. The differences from the results of former investigators can be explained by the differences of the models.

Interaction of microporous glassy carbon and living tissue

Abstract: Preliminary animal implantation tests with rats showed that microporous glassy carbon has good biocompatibility. Microporous glassy carbon is also stable and suitable for a hard biocompatible implant.

Microelectrode amplifier for intracellular stimulation and recording.

Abstract: The operation and construction of a microelectrode amplifier intended for routine use in studying the electrical behaviour of a cell membrane under various stimulation conditions are described in this paper. For the sake of versatility the microelectrode amplifier includes a stimulator, iontophoretic current generator, membrane resting potential and electrode resistance meters, filters and capacitance neutralisation circuits in addition to the amplifiers. Some measurements to verify the desired operation are included.

Zn, P and ATP in the sediments of two lakes in South Finland

Abstract: This investigation is concerned with the impact of industrial and municipal waste discharge on lakes near the city of Tampere, Finland. The record of P, Zn and ATP in the recent sediments of Vanajavesi I, a polluted lake, and Mallasvesi, a largely unpolluted lake, are compared.

Adaptive Prediction of Water Quality in the River Cam

Abstract: Modeling can be used for two main purposes — prediction or control. This must be kept in mind when methods for either, or both, of the purposes are chosen. In this paper the prediction of water quality in a river is investigated.