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Passivity arguments have long been used in the analysis of systems with friction. This paper proves a new set of integral quadratic constraints, which reduces the conservatism of such methods. The result is used to derive a quantitative bound on the amount of integrator leakage that is needed to remove stiction-induced oscillations in a servo system. Finally, an incremental version of the circle c

We consider a two-echelon distribution inventory system with a central warehouse and a number of retailers. The retailers face stochastic demand. The system is controlled by continuous review installation stock (R,Q) policies with given batch quantities. One way to decentralize the system control is to provide a backorder cost to the warehouse, and let the warehouse choose its reorder point so tha

The modelling of large systems is greatly simplified if their hierarchical decomposition and interconnection structure can be described graphically. The paper describes a system allowing input of block diagrams and continuous zooming to view internal details. Model equations are automatically transformed to assignment statements when possible, allowing efficient explicit integration routines to be

Stability of systems with hysteresis nonlinearities, parametric uncertainty and finite dimensional unmodelled dynamics is considered. Conditions for exponential decay of the signals in the system to an equilibrium position are given. The equilibrium is generally not unique. The stability condition is given in terms of a frequency domain inequality, which involves the transfer function of the nomin

Computers are used in the outdoors and in connection with cold store work. Cold hand and fingers limit data input, as studied here. Six input devices; trackballs, pens, and a mouse were tested by 19 participants in a Fitts' target acquisition task with 2 target sizes under 2 experimental conditions; warm and cold right hand. Measures were acquisition times, number of errors, participant's preferen

In this pilot study, the authors introduce a new system to assess hypnosis style. The Feature-Based Coding System (FBCS) comprises 24 standard individual hypnosis sessions, which were videotaped and coded according to both a previous and the new coding system. In addition, both subjects and hypnotists filled the Archaic Involvement Measure (AIM), the Phenomenology of Consciousness Inventory (PCI),

Changes in oxytocin and cortisol levels were tested in healthy volunteers during hypnotic interactions in standardized laboratory sessions. Preto posthypnosis changes of oxytocin and cortisol were related to the hypnotic susceptibility of subjects and the relational experiences reposted by subjects and hypnotists on several paper-and-pencil tests. Results show that the changes in oxytocin are not

A general method is discussed, the δ-test, which establishes functional dependencies given a table of measurements. The approach is based on calculating conditional probabilities from data densities. Imposing the requirement of continuity of the underlying function the obtained values of the conditional probabilities carry information on the variable dependencies. The power of the method is illust

Standard lot-sizing models are often not directly applicable in practice. Different assumptions in lot-sizing models and the extent to which these assumptions are valid in various practical situations are discussed. Practitioners also tend to prefer simple standard methods even for complex problems, which means that adjustment of the lot sizes may be desirable. The ways in which such adjustments c

The directional stability of an originally straight crack under symmetric remote loading is studied after introduction of an infinitesimal disturbance at one or both tips of the crack. The crack is assumed to grow slowly under vanishing mode II stress intensity factor. Directional stability is defined to prevail if the angle formed by the straight line between the crack tips and the original crack

The experimentally known phenomenon that originally collinear mode I cracks seem to avoid each other before coalescence is studied by investigating the stability of straight crack paths. To this end a periodic array of approximately collinear but slightly curved cracks is considered. Stress intensity factors for modes I and II are derived and the growth of originally straight cracks under mode I c

Even cracks which seem to be favourably oriented for mode II growth might extend in mode I by kinking. The conditions that favour mode I or mode II growth are examined. It is shown that a high confining pressure promotes mode II growth and so does a low ratio between the critical stress intensity factors of modes II and I. Quantitative results are given for different coefficients of friction and c

The most unfavourable orientation of a straight crack of given length is investigated, assuming mode I growth. It is shown that this orientation is not always the one perpendicular to the largest principal stress. If the smallest in-plane principal stress is compressive and its magnitude more than about one third of the largest (tensile) in-plane stress, then some other orientations are more unfav

Chebyshev polynomial techniques for solution of singular integral equations leading to square root singularities at the ends of the interval of integration are studied. It is shown that the results are less accurate when a singularity, albeit a weak one, appears between the interval ends. Typical examples are problems involving kinked cracks. Some attempts to improve the accuracy are discussed.

The directional stability of the crack path during wedging of a strip is investigated, using finite element methods. Linearly elastic material and plane conditions are considered. No dynamic effects are included. Stable crack growth in the direction of maximum mode I stress intensity factor at the tip of the crack is assumed. It is found that directional stability seems to prevail if the thickness

Fracture from a straight crack under mixed mode loading conditions and small scale of yielding is studied. It is assumed that crack growth occurs in either mode I or mode II. Comparison of theoretically obtained values of the mode I stress intensity factor at incipient kinking with experimental results indicates that mode I is preferred to mode II when the loading is such that the crack surfaces a