Showing papers by "University of Paderborn published in 1990"

Combinatorial Algorithms for Integrated Circuit Layout

Abstract: Feel lonely? What about reading books? Book is one of the greatest friends to accompany while in your lonely time. When you have no friends and activities somewhere and sometimes, reading book can be a great choice. This is not only for spending the time, it will increase the knowledge. Of course the b=benefits to take will relate to what kind of book that you are reading. And now, we will concern you to try reading combinatorial algorithms for integrated circuit layout as one of the reading material to finish quickly.

Embedding one interconnection network in another

Abstract: Embedding one Interconnection Network in Another. We review results on embedding network and program structures into popular parallel computer architectures. Such embeddings can be viewed as high level descriptions of efficient methods to simulate an algorithm designed for one type of parallel machine on a different network structure and/or techniques to distribute data/program variables to achieve optimum use of all available processors.

Elastic-plastic fracture behavior of an aluminum alloy under mixed mode loading

Abstract: M ixed mode elastic-plastic fracture tests were carried out by using A5083-O aluminum alloy compacttension-shear specimens, in which the angle between the loading axis and the crack surface was varied from 90° (mode I) to 0° (mode II) by employing a special loading device. A fractographic investigation was made at various stages of crack tip blunting and stable crack growth. Under mixed mode loadings, opposite deformations appeared at the crack tip: sharpening and blunting. With increasing mode II component, cracks due to shear type fracture initiated at the sharpened corner of the crack tip near the surfaces of the specimen, and then another crack due to dimple type fracture occurred at the blunted corner of the crack tip near the midthickness of the specimen. These experimental results were explained qualitatively by taking account of the stress and strain singularities and triaxial stress distributions near the surface and midthickness of the specimen. Fracture mechanics parameters appropriate for mixed mode elastic-plastic fractures were also studied based on the experimental data.

Hypercomplex numbers in digital signal processing

Abstract: A new number system, reduced biquaternions (RBs), is introduced. They are related to the quaternions and biquaternions proposed by W.R. Hamilton (1969). It is shown that a further reduction of systems degree will occur if RBs are used. An example shows the realization of a fourth-order real filter by means of a first-order RB filter. With the introduction of the RBs a new method is obtained for the design of wave digital Hilbert transformers. >

Soliton eigenfunction equations: the ist integrability and some properties

Abstract: Eigenfunctions of the linear eigenvalue problems for the soliton equations obey nonlinear differential equations. It is shown that these eigenfunction equations are integrable by the inverse spectral transform (IST) method. They have triad operator representations. Eigenfunction equations are the generating equations and possess other interesting properties. Eigenfunction equations form a new wide class of nonlinear integrable equations. Eigenfunction equations for several typical, well-known (1+1)-, (2+1)- and multi-dimensional soliton equations are considered. A general method for constructing the auxiliary linear systems for the eigenfunction equations is proposed. It is shown that the vertical hierarchies of the eigenfunction equations contain only finite numbers of different members in the cases considered. The properties of such hierarchies for soliton equations are closely connected with their Painleve properties. Some “linear” properties of the eigenfunction equations are also discussed.

General models and algorithms for over-the-cell routing in standard cell design

Abstract: When an over-the-cell routing layer is available for standard cell layout, efficient utilization of routing space over the cells can significantly reduce layout area. In this paper, we present three physical models to utilize the area over the cells for routing in standard cell designs. We also present efficient algorithms to choose and to route a planar subset of nets over the cells so that the resulting channel density is reduced as much as possible. For each of the physical models, we show how to arrange inter-cell routing, over-the-cell routing and power/ground busses to achieve valid routing solutions. Each algorithm exploits the particular arrangement in the corresponding physical model and produces provably good results in polynomial time. We tested our algorithms on several industrial standard cell designs. In our tests, this method reduces total channel density as much as 21%.

Automatic high level synthesis of partitioned busses

Abstract: A high level synthesis system maps operations of the behavior specification to functional units, minimizing the number of registers, multiplexers and wires. Arranging the results by a floorplanner often leads to a rather large amount of space for interconnections. This situation can be drastically improved if partitioned busses are generated instead of individual connections. For this purpose, a parameterized and powerful target architecture is defined. A method is presented which partitions a data flow graph towards a bus oriented design. A novel allocation method is introduced for this purpose. First experiments with this approach were successful and led to very small designs. >

Fault-tolerant programs and their reliability

Abstract: The authors review and extend available techniques for achieving fault-tolerant programs. The representation of the techniques is uniform and is illustrated by simple examples. For each technique a fault tree has been developed to derive failure probability from the probabilities of the basic fault events. This allows the subsequent analysis of program-failure causes and the reliability modeling of computer programs. Numerical examples are given to support the comparison of the reviewed techniques. The models can be used to evaluate numerical values of program reliability in a relatively simple way. The models deal with program reliability for a single run, which seems more practical and straightforward than dealing with distributions as for hardware systems. Evaluations obtained by using models correspond to those used in the literature; however, the authors' procedures are computationally simpler. >

Distributed game tree search

Abstract: We present a distributed algorithm for searching game trees. A general strategy for distributed computing is used that can be applied also to other search algorithms. Two new concepts are introduced in order to reduce search overhead and communication overhead: the “Young Brothers Wait Concept” and the “Helpful Master Concept”. We describe some properties of our distributed algorithm including optimal speedup on best ordered game trees.

A robust framework for hierarchical floorplanning with integrated global wiring

Abstract: A floorplanning system was implemented that is based on circuit partitioning and incorporates hierarchical global wiring. Besides unifying several existing ideas in floorplanning, the system introduces the following components: (1) a novel and more accurate estimate of wiring area during the floorplan sizing process and (2) a systematic optimization procedure during the selection of suitable floorplan patterns in the top-down phase that integrates floorplanning and hierarchical wiring. Experiments with the system prove the feasibility of the approach. >

Biological treatment of effluents from a coal tar refinery using immobilized biomass

Abstract: An airlift-loop reactor with a fluidized bed was used for the microbiological removal of a complex mixture of aromatic substances originating from coal tar process waters. A specially adapted mixed microbial culture derived from several soil and sludge samples was immobilized on fluidized sand particles and retained in a reactor at high biomas concentrations of 3 to 16 g dry matter per liter, depending on the COD-load. In a two-stage pilot plant, those aromatic substances which passed through the first stage either unaltered or only partially oxidized were effectively eliminated by the immobilized biomass in the second stage. Whereas most of the waste water components such as phenols and quinoline were already degraded by a conventional activated sludge system in the first stage, the majority of nitrogen-containing aromatic bases could be sufficiently eliminated with specially adapted micro-organisms in the second stage. Although the COD-feed load was increased to 12 and 15 kg m−3 d−1 in the first and second stages, respectively, it was removed to the extent of 87% on the average with an overall residence time varying between 11.5 and 29 h.

Mn2+ defects in LiNbO3: an electron nuclear double resonance (ENDOR) investigation of the Mn2+ site and the local disorder

Abstract: With ENDOR, Mn2+ centres in both stoichiometric and congruent LiNbO3 have been investigated. An analysis of four identified Li shells with 24 Li neighbours gives sufficient proof for the Mn2+ occupying a Li site. In stoichiometric LiNbO3 both neighbouring on-axis Nb nuclei were also identified and found to experience changed electric field gradients compared with remote Nb nuclei and NMR data in the literature. Signs of the parameters of the Mn2+ spin Hamiltonian (A/sub //, perpendicular to / O, P>0) have been determined. Most centres probably contain a defect such as charge-compensating Li vacancy in the first Li shell. As inferred from line-broadening effects, additional defects, especially in congruent crystals, have a measurable influence on the relaxation of nuclei near to the Mn2+.

Recursion Operators and Hamiltonian Structures in Sato's Theory

Abstract: Following Sato's famous construction of the KP hierarchy as a hierarchy of commuting Lax equations on the algebra of microdifferential operators, it is shown that n-reduction leads to a recursive scheme for these equations. Explicit expressions for the recursion operators and the Hamiltonian operators are obtained.

Optimum algorithms for dissemination of information in some interconnection networks

Abstract: The problems of gossiping and broadcasting in one-way communication mode are considered for some prominent families of graphs. The complexity is measured as the number of communication rounds in the gossip and broadcast algorithms. The main result of the paper is the precise estimation of the gossip problem complexity in cycles. To obtain this result a new combinatorial analysis of gossiping in cycles is developed. This analysis leads to an optimal lower bound on the number of rounds, and also to the design of an optimal algorithm for gossiping in cycles. The optimal algorithm for gossiping is later used to design new, eeective algorithms for gossiping in important families of interconnection networks (cube connected cycles; butterf ly networks). Further, a new, eeective algorithm for broadcasting in Shuue-Exchange networks is developed.

The action-angle transformation for soliton equations

Abstract: For third order completely integrable equations in 1 + 1 dimensions canonical transformations which map (in the multi-soliton case) gradients of action variables to gradients of angle variables are constructed. Furthermore, this action-angle map is shown always to be an infinitesimal symmetry group generator of the interacting soliton equation.

Comparison of two anthryl-modified silica stationary phases for the HPLC separation of PAHs and nitro-PAHs

Abstract: Two different anthryl-modified silica packings were investigated for the separation of PAHs and nitro-PAHs. Plots of k′ versus mobile phase composition show distinct selectivity both with acetonitrile/water and with methanol/water. PAHs are separated by π-π-interactions, whereas the corresponding nitrosubstituted compounds are longer retained on both stationary phases due to charge-transfer interactions being possible.

Effects of suboptimal environmental conditions on immobilized bacteria growing in continuous culture

Abstract: Two immobilized bacterial cultures with the ability to metabolize 6-amino-2-naphthalenesulfonic acid (6A2NS) and 2-naphthalene-sulfonic acid (2NS) were investigated under suboptimal environmental growth conditions. The cultures were employed in continuously operated airlift loop-reactors. The physico-chemical growth parameters such as pH, temperature and dissolved oxygen concentration were varied. It was found that a decreasing growth rate in suboptimal conditions was compensated by increasing biomass concentration over a wide range. Operated continuously for more than 20 months, the 6A2NS-degrading system appeared to be reliable. After pH-shockloadings and long-term oxygen default, the immobilized microorganisms recovered almost immediately and stable operating conditions were achieved again within less than 48 h. These remarkable results were sustained with the 2NS degrading system.

CACE tool for multi-input, multi-output systems using a new vector optimization method

Abstract: A design environment specially tailored to problems in control engineering is presented. It contains, apart from plant models and operating environments, the formulation of the experimental environment. Linear controllers of any desired structure are designed with the aid of the characteristic variables of the experiments, using a vector optimization procedure in an interactive design process. The hierarchical description of the model, based on an interpreter solution, was realized in the ADA programming language. A complex problem in controller design, taken from the field of vehicle suspension, proves the efficiency and performance of the design tool.

Neural network based multi sensor heart sound analysis

Abstract: It is demonstrated how neural nets, used for nonlinear modeling and signal classification, can estimate from a continuous recording of an acoustical stethoscope signal the beginning of a cardiac cycle, the systolic and diastolic time intervals and suggest suitable diagnoses in case of heart failures and arrhythmia. While during the training phase multisensor signals and catheterized verifications of heart failures have been utilized, the PC-based diagnostic system analyzes heart sound signals quasi-on-line in a way similar to how physicians perform their subjective learning and interpretation of stethoscopic signals. The systolic and diastolic time intervals of healthy probands as well as patients with heart failures estimated by the neural network were found to be in excellent correspondence with measurements. Also, the sound pattern recognition results demonstrate the high accuracy, though training and test sets were based on different sources. Using this method a valuable documentation of heart failure development or treatment with the auscultation technique is possible. >

Phenomenological thermodynamics of irreversible processes within Lagrange formalism

Abstract: Lagrange formalism allows for phenomenological thermodynamics of irreversible processes. This statement is exemplified for heat transport, diffusion and chemical reactions. Traditional formulations of thermodynamics can be included into Lagrange formalism. However, Lagrange formalism goes beyond the scope of traditional thermodynamics. By means of this most general field theoretical approach a unified phenomenological theory of material behaviour including thermodynamics, mechanics and electromagnetism might be obtained. In this paper the skeleton of the theory concerning thermodynamics is briefly reported.

Placement, Assignment, and Floorplanning

Abstract: In real-life applications, the provably good layout algorithm presented in Chapter 5 does not perform well enough to be of service. Thus, in practice, the layout problem is solved in a sequence of phases that attack subproblems with exact algorithms or heuristically. These phases are combined with a suitable usage of the circuit hierarchy. The first layout phase usually solves some variant of the placement problem.

Operations Research and Statistics

Abstract: In this chapter, we will look at optimization problems from a different point of view—from one that is, in some sense, more fundamental. We will interpret finding the optimum solution of an optimization problem as a search process on the space of legal configurations. (From now on, we will mostly be concerned with legal configurations. Thus, we will omit the word legal unless it is not clear from the context what kind of a configuration we mean.) The configuration space can be represented as a set of geometric points or, alternatively, as a directed graph, and we will choose whatever representation is better suited to our purpose. There exists a large number of search heuristics and strategies for optimization problems; we will survey the ones that are most important for layout design.

Action-Angle Representation of Multisolitons by Potentials of Mastersymmetries

Abstract: Using the algebra of symmetries/mastersymmetries a purely alge- braic construction for the action/angle representation of multisolitons is given. By the same method an explicit construction of the potentials of the eigen- states of the recursion operator is performed in terms of partial derivatives of a fundamental scalar field.

Service integration in FDDI

Abstract: Performance issues of the FDDI-II protocol, an upward-compatible enhancement of the basic fiber distributed data interface (FDDI), are discussed. The main characteristics of the FDDI protocol are examined. The performance of FDDI-II is studied for scenarios including asynchronous traffic, synchronous traffic and isochronous traffic. The results make clear that basic FDDI meets the requirements imposed by traditional local area network (LAN) application and that from a performance point of view FDDI-II is an excellent candidate for complex communications environments. When compared to the distributed-queue-dual bus (DQDB) protocol, FDDI-II yields much better efficiency in traditional LAN applications. >