Showing papers by "Eindhoven University of Technology published in 1989"

Distance-Regular Graphs

Abstract: Consider a connected simple graph with vertex set X of diameter d. Define Ri X2 by (x, y) Ri whenever x and y have graph distance

Simulated Annealing and Boltzmann Machines: A Stochastic Approach to Combinatorial Optimization and Neural Computing

Abstract: SIMULATED ANNEALING. Combinatorial Optimization. Simulated Annealing. Asymptotic Convergence. Finite-Time Approximation. Simulated Annealing in Practice. Parallel Simulated Annealing Algorithms. BOLTZMANN MACHINES. Neural Computing. Boltzmann Machines. Combinatorial Optimization and Boltzmann Machines. Classification and Boltzmann Machines. Learning and Boltzmann Machines. Appendix. Bibliography. Indices.

Security-control methods for statistical databases: a comparative study

Abstract: This paper considers the problem of providing security to statistical databases against disclosure of confidential information. Security-control methods suggested in the literature are classified into four general approaches: conceptual, query restriction, data perturbation, and output perturbation.Criteria for evaluating the performance of the various security-control methods are identified. Security-control methods that are based on each of the four approaches are discussed, together with their performance with respect to the identified evaluation criteria. A detailed comparative analysis of the most promising methods for protecting dynamic-online statistical databases is also presented.To date no single security-control method prevents both exact and partial disclosures. There are, however, a few perturbation-based methods that prevent exact disclosure and enable the database administrator to exercise "statistical disclosure control." Some of these methods, however introduce bias into query responses or suffer from the 0/1 query-set-size problem (i.e., partial disclosure is possible in case of null query set or a query set of size 1).We recommend directing future research efforts toward developing new methods that prevent exact disclosure and provide statistical-disclosure control, while at the same time do not suffer from the bias problem and the 0/1 query-set-size problem. Furthermore, efforts directed toward developing a bias-correction mechanism and solving the general problem of small query-set-size would help salvage a few of the current perturbation-based methods.

Structure and Function of the Catalyst and the Promoter in Co—Mo Hydrodesulfurization Catalysts

Abstract: Etude de la structure d'un catalyseur utilise pour une hydrodesulfuration et plus particulierement etude de la localisation et de la structure des ions molybdene et cobalt a la surface de l'alumine. Discussion sur le role d'un promoteur modifiant un catalyseur, notamment determination du nombre de sites actifs

The annealing algorithm

Abstract: 1 The Annealing Algorithm: A Preview.- 1.1 Combinatorial optimization.- 1.2 Moves and local minima.- 1.3 Hill climbing.- 1.4 Simulated annealing.- 1.5 Applications.- 1.6 Mathematical model.- 1.7 Discussion.- 2 Preliminaries from Matrix Theory.- 2.1 Matrices. Notation and basic properties.- 2.2 Pseudo-diagonal normal forms.- 2.3 Norms and limits of matrices.- 2.4 Quadratic forms.- 2.5 Discussion.- 3 Chains.- 3.1 Terminology.- 3.2 Linear arrangement, an example.- 3.3 The chain limit theorem.- 3.4 Reversible chains.- 3.5 Discussion.- 4 Chain Statistics.- 4.1 Density Functions.- 4.2 Expected values.- 4.3 Sampling.- 4.4 Maximum likelyhood densities.- 4.5 Aggregate functions.- 4.6 Discussion.- 5 Annealing Chains.- 5.1 Towards low scores.- 5.2 Maximal accessibility.- 5.3 The acceptance function.- 5.4 Properties of annealing chains.- 5.5 Discussion.- 6 Samples from Normal Distributions.- 6.1 Characteristic functions.- 6.2 Quadratic forms and characteristic functions.- 6.3 Sampling distributions.- 6.4 Asymptotic properties of sampling distributions.- 6.5 Discussion.- 7 Score Densities.- 7.1 The density of states.- 7.2 Weak control.- 7.3 Strong control.- 7.4 Three parameter aggregates.- 7.5 Discussion.- 8 The Control Parameter.- 8.1 Initialization.- 8.2 Decrements in the control parameter.- 8.3 A stop criterion.- 8.4 Proper convergence.- 8.5 Discussion.- 9 Finite-Time Behavior of the Annealing Algorithm.- 9.1 Rate of convergence of chains.- 9.2 Minimum number of iterations.- 9.3 Finite-time optimal schedules.- 9.4 Discussion.- 10 The Structure of the State Space.- 10.1 Chain convergence.- 10.2 The topography of the state space.- 10.3 The set of moves.- 10.4 Global convergence.- 10.5 Discussion.- 11 Implementation Aspects.- 11.1 An implementation.- 11.2 The selection function.- 11.3 Other speed-up methods.- References.

An alternative to metric rescaling in Viterbi decoders

Abstract: In the Viterbi algorithm, the negative log-likelihood estimates, accumulated distances, or path metrics are unboundedly increasing functions of time. For implementation, all variables must be confined to a finite range. The following properties of the Viterbi algorithm can be exploited for this purpose: (1) path selection depends only on differences of metrics; an (2) the difference between metrics is bounded. In the rescaling scheme, at each iteration the minimum metric is subtracted from all metrics. The use of two's complement arithmetic is proposed as an alternative to the rescaling method. This scheme avoids any kind of rescaling subtractions. Obvious advantages in implementation are hardware savings and a speedup inside the metric update loop, which is critical to the decoder's computational throughput. >

Thermodynamic generalization of the Saha equation for a two-temperature plasma.

Abstract: A thermodynamic generalization of the Saha equation for the case of a two-temperature plasma is given on basis of a modification of the free energy. The resulting equation depends in the first approximation on the electron temperature only. This result has been obtained earlier on basis of kinetic arguments.

Dependence balance bounds for single-output two-way channels

Abstract: If in a transmission the inputs of a single-output two-way channel exhibit some interdependence, this dependence must have been created during earlier transmissions. The idea that no more dependence can be consumed than is produced is used to obtain new upper bounds to the capacity region of the discrete memoryless single-output two-way channel. With these upper bounds it is shown that C.E. Shannon' (1961) inner bound region is the capacity region for channels in a certain class, and the Zhang-Berger-Schalkwijk upper bound (1986) for Blackwell's multiplying channel is improved upon. >

Simulated annealing : an introduction

Abstract: Simulated annealing is a general approach for approximately solving large combinatorial optimization problems. The algorithm is based on an intriguing combination of ideas from at first sight completely unrelated fields of science, viz. combinatorial optimization and statistical physics. On the one hand the algorithm can be viewed as an analogue of an algorithm used in statistical physics for computer simulation of the annealing of a solid to its minimum–energy state, on the other hand it can be considered as a generalization of the well–known iterative improvement approach to combinatorial optimization problems. In this introductory paper we give a mathematical description of the simulated annealing algorithm and discuss its behaviour from both a theoretical and a practical point of view. The latter is illustrated by applying the algorithm to the travelling salesman problem. This paper was written to familiarize the readers of Statistica Neerlandica with simulated annealing. It is a summary of papers written earlier by the authors and does not contain any new material.

Silica gel dissolution in aqueous alkali metal hydroxides studied by 29SiNMR

Abstract: The rate of silica gel dissolution in aqueous alkaline media was investigated using 29Si nuclear magnetic resonance spectroscopy. A profound difference of alkali metal hydroxides on the dissolution rate of amorphous silica gel was observed. The dissolution rate increases in order LiOH ≈ CsaOH) < (RbOH ≈ NaOH) < KOH, as was confirmed by the β = silicomolybdate complexation method. Silica gel dissolution involved formation of monomeric silicic acid, Q0. The monomeric anions oligomerise into dimer species, which in turn form cyclic and lineartrimer species. The structure of highly polymerised silicate species depends on the alkali metal cation, i.e. low pH silicate solutions have structurally different silicate species as a function of alkali metal hydroxide, as is shown by 29Si-NMR spectroscopy. Potassium cations gave rise to more polymerised silica species compared with other alkali metal cations studied. On the contrary, when lithium hydroxide and silica gel are mixed in a molar SiO2/Li2O = 1:1, a microcrystalline phase is formed which consists of lithium silicate crystals. Crystallisation of the lithium silicate proceeds via monomeric silica being in solution.

Spin-exchange and dipole relaxation rates in atomic hydrogen: Rigorous and simplified calculations

Abstract: We calculate the magnetic field and temperature dependence of the rates for all two-body spin-exchange and dipolar transitions among hyperfine levels in cryogenic H gas by means of the coupled-channels method. A description of this method and its practical application is presented. A simple interpretation of the rates is given, in some cases with associated simple closed-form formulas, based on the degenerate-internal-states approximation.

Polymerization of MMA at the surface of inorganic submicron particles

Abstract: Inorganic submicron particles, such as TiO2, were modified with titanate coupling agents. The structure and stability of some titanates, both in solution and at the particle surface, were investigated by various methods. The modified titanium dioxide was dispersed in a solution of sodium dodecylsulphate (SDS) in water. The surfactant adsorbs at the now hydrophobic particle surface, thus creating a micellelike structure with an inorganic particle in the centre. In this system an emulsion polymerization of methyl methacrylate was carried out. Product formed at the particle surface is either physically bound by entanglement or chemically bound by covalent bonding to the titanates. In this way a core-shell morphology is obtained with an inorganic core and a polymer shell. The effects of several reaction parameters on the kinetics of the polymerization were studied. The encapsulated TiO2 particles may offer interesting prospects in those applications where good coupling between polymer matrix and inorganic particles is necessary, such as latex paints and polymer composite materials.

Flow Induced Pulsations in Gas Transport Systems: Analysis of the Influence of Closed Side Branches

Abstract: A theoretical analysis is presented of the low frequency aero-acoustic behavior of closed side branches along a gas transport pipe. The theory predicts the hydrodynamic conditions for moderate and strong pulsations. A model is proposed which predicts the order of magnitude of the power generated by the aero-acoustic source. The theoretical analysis leads to the design of spoilers which reduce the pulsation level by 30 to 40 dB. The results obtained by theoretical analysis and model experiments (Reynolds number 10-6) have been confirmed in full scale tests (Reynolds number 10-8).

Trapping of neutral atoms with resonant microwave radiation.

Abstract: We duscuss a resonant microwave trap for neutral atoms. Because of the long spontaneous radiation time this trap is remarkably different from the optical trap. It also has advantages over static magnetic traps that trap the excited spin state of the lowest electronic level, in that atoms predominantly in the spin ground state can be trapped. We analyze the relaxation-ejection lifetime of atoms in such a trap using the formalism of dressed atomic states. Results are appliedi to atomic hydrogen and the possibility of Bose-Einstein condensation is considered.

Simple bounds and monotonicity results for finite multi-server exponential tandem queues

Abstract: Simple and computationally attractive lower and upper bounds are presented for the call congestion such as those representing multi-server loss or delay stations. Numerical computations indicate a potential usefulness of the bounds for quick engineering purposes. The bounds correspond to product-form modifications and are intuitively appealing. A formal proof of the bounds and related monotonicity results will be presented. The technique of this proof, which is based on Markov reward theory, is of interest in itself and seems promising for further application. The extension to the non-exponential case is discussed. For multiserver loss stations the bounds are argued to be insensitive.

On the diffusion of carbon in titanium carbide

Abstract: The chemical diffusion coefficient of carbon in TiC1-y was determined as a function of stoichiometry and temperature in the range between 1000 and 1600°C using the diffusion couple technique. In marker experiments carbon was found to be virtually the only diffusing component. Accurate carbon analyses were performed using EPMA, both in diffusion couples and in the carbides present in equilibrated alloys. The homogeneity region of TiC1-y in this temperature range and the concentration profiles were accurately determined. From these profiles it is immediately clear that the diffusivity of carbon is a function of the carbon concentration. The interdifussion coefficient { % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfKttLearuatLrhDLjhih9gDOL2yG0evae% XatLxBI9gBamXvP5wqSXMqHnxAJn0BKvguHDwzZbqegm0B1jxALjhi% ov2DaeHbuLwBLnhiov2DGi1BTfMBaebbnrfifHhDYfgasaacH8srps% 0lbbf9q8WrFfeuY-Hhbbf9v8qqaqFr0xc9pk0xbba9q8WqFfea0-yr% 0RYxir-Jbba9q8aq0-yq-He9q8qqQ8frFve9Fve9Ff0dmeaabaqaci% GacaGaaeqabaWaaqaafaaakeaaiqGaceWFebGbaGaaaaa!3F06! $$\tilde D$$ } increases with decreasing carbon concentration and can be expressed by; { % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGabmirayaaia% GaaiikaGqaaiaa-rfacaWFPbGaa83qamaaBaaaleaacaWF0bGaeyOe% I0IaamyEaaqabaGccaGGPaGaeyypa0Jaai4waiaaicdacaGGUaGaaG% inaiaaiIdacaqGGaGaaeyzaiaabIhacaqGWbGaaeikaiaabMdacaqG% UaGaaeOmaGqaciaa+LhacaWFPaGaa8xxaiaa-bcacaWFLbGaa8hEai% aa-bhacaWFGaacdiGaa03eGmaabmaabaWaaSaaaeaacaWFZaGaa8xo% aiaa-vdacaWFWaGaa8hmaaqaaiaa+rfaaaaacaGLOaGaayzkaaGaae% iiaiaabogacaqGTbWaaWbaaSqabeaacaqGYaaaaOGaai4laiaa-nha% aaa!5B33! $$\tilde D(TiC_{t - y} ) = [0.48{\text{ exp(9}}{\text{.2}}y)] exp --\left( {\frac{{39500}}{T}} \right){\text{ cm}}^{\text{2}} /s$$ } A number of often conflicting results have been published on diffusion in titanium carbide. It is shown that nearly all reported values can be fitted within the range found in the present work, in which the marked variation of { % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfKttLearuatLrhDLjhih9gDOL2yG0evae% XatLxBI9gBamXvP5wqSXMqHnxAJn0BKvguHDwzZbqegm0B1jxALjhi% ov2DaeHbuLwBLnhiov2DGi1BTfMBaebbnrfifHhDYfgasaacH8srps% 0lbbf9q8WrFfeuY-Hhbbf9v8qqaqFr0xc9pk0xbba9q8WqFfea0-yr% 0RYxir-Jbba9q8aq0-yq-He9q8qqQ8frFve9Fve9Ff0dmeaabaqaci% GacaGaaeqabaWaaqaafaaakeaaiqGaceWFebGbaGaaaaa!3F06! $$\tilde D$$ } with carbon content is taken into account. Comparison between the interdiffusion coefficient { % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfKttLearuatLrhDLjhih9gDOL2yG0evae% XatLxBI9gBamXvP5wqSXMqHnxAJn0BKvguHDwzZbqegm0B1jxALjhi% ov2DaeHbuLwBLnhiov2DGi1BTfMBaebbnrfifHhDYfgasaacH8srps% 0lbbf9q8WrFfeuY-Hhbbf9v8qqaqFr0xc9pk0xbba9q8WqFfea0-yr% 0RYxir-Jbba9q8aq0-yq-He9q8qqQ8frFve9Fve9Ff0dmeaabaqaci% GacaGaaeqabaWaaqaafaaakeaaiqGaceWFebGbaGaaaaa!3F06! $$\tilde D$$ } and the tracer diffusion coefficientD c * is difficult because of uncertainties in the thermodynamic factor.

Bulk and surface 1/f noise

Abstract: The 1/f noise of an n-type silicon MOSFET has been studied under conditions ranging from accumulation to depletion at 300 K. The experimental results are interpreted in terms of a bulk phenomenon and are characterized by Hooge's empirical 1/f noise parameter alpha with values between 10/sup -7/ and 10/sup -5/. The alpha value for surface conduction at strong accumulation can be at least one order of magnitude larger than the value for bulk conduction. >

Black-box identification of mimo transfer functions: Asymptotic properties of prediction error models

Abstract: Identification of multi-input/multi-output (MIMO) transfer functions is considered. The transfer function matrix is parametrized as black-box models which have certain shift properties; no structure or order is chosen a priori. In order to obtain a good transfer function estimate, we allow the order of the model to increase to infinity as the number of data tends to infinity. The expression of asymptotic covariance of the transfer function estimates is derived, which is asymptotic both in the number of data and in the model order. The result indicates that the joint covariance matrix of the transfer function estimates of the process and of the noise filter is proportional to the (generalized) ratio of output noise to imput signal; the factor of proportionality is the ratio of model order to number of data. The result is independent of the particular model structure used. This result is the MIMO extension of the theory of Ljung. The application of this theory for defining the upper bounds of identification errors is highlighted.

A test reaction for titanium silicalite catalysts

Abstract: The catalytic hydroxylation of phenol to hydroquinone and catechol can be used for checking the quality of titanium silicate catalysts since the selectivity of these catalysts is strongly affected by the presence of small amounts of non-framework titania. Titanium silicates prepared by modification of [Al]ZSM-5 exhibits the same catalytic properties as hydrothermally synthesized TS-1 of high purity.

Perspectives on parallel computing

Abstract: Most scheduling research has treated individual job processing times as fixed parameters. In many practical situations, however, a manager may exert processing time control through the allocation of a limited resource. We consider the problem of joint sequencing and resource allocation when the scheduling criterion of interest is the number of tardy jobs. Theoretical results are derived that aid in developing the tradeoff curve between the number of tardy jobs and the total amount of allocated resource.

Regiospecific inhibition of DNA duplication by antisense phosphate-methylated oligodeoxynucleotides

Abstract: A new synthesis route for long phosphate-methylated oligodeoxynucleotides is described, which were used as antisense inhibitors of the DNA replication. Phosphate-methylated oligomers hybridize more strongly with natural DNA than their natural analogues, due to the absence of electrostatic interstrand repulsions. Compared with phosphate-ethylated and methyl phosphonate systems, phosphate-methylated systems are preferable as antisense DNA, which was concluded from the high Tm values and sharp melting transitions of duplexes of phosphate-methylated and natural DNA. By using the Sanger dideoxy technique, it was shown that a complementary phosphate-methylated 18-mer can effectively and site-specifically block the DNA replication process at room temperature.

A condition for the overflow stability of second-order digital filters that is satisfied by all scaled state-space structures using saturation

Abstract: A set of conditions is derived that ensures overflow stability of second-order digital filters for different classes of overflow arithmetics, involving only the elements of the state-transition matrix. The well-known arithmetic saturation, zeroing, and two's-complement lead to different stability conditions, the condition for saturation being the least restrictive. As a result, all properly scaled second-order state-space structures are zero-input overflow stable if saturation is used for overflow correction. Conditions are derived for stable second-order digital filters in a nonzero input situation by introducing a weaker form of stability of the forced response. The analysis is based on determining the set of Lyapunov functions for a general second-order state-transition matrix, given a certain overflow arithmetic. >

A finite element analysis of the steady laminar entrance flow in a 90° curved tube

Abstract: SUMMARY A standard Galerkin finite element penalty function method is used to approximate the solution of the threedimensional Navier-Stokes equations for steady incompressible Newtonian entrance flow in a 90" curved tube (curvature ratio 6 = 1/6) for a triple of Dean numbers (K = 41,122 and 204) The computational results for the intermediate Dean number (K = 122) are compared with the results of laser-Doppler velocity measurements in an equivalent experimental model For both the axial and secondary velocity components, fair agreement between the computational and experimental results is found