Social problems encountered during prenatal care in a Paris maternity ward]

Post-renal-transplantation bone disease is a well known entity. Immunosuppressive agents and persistence of hyperparathyroidism have primarily been implicated in its etiology. Renal transplantation patients are unique in that the bone changes occur on a background of pre-existing renal osteodystrophy. This review focuses on post-renal-transplantation bone disease. Unfortunately, the existing data in the review period, besides being scanty, provide conflicting information. This is due to the diversity of immunosuppressive regimens employed, the patient populations studied, diagnostic tools and criteria used by different centers, and the lack of formal trials.     

Engineering properties of the magmatic rocks at the Pamukluk Dam site, Turkey

 The paper discusses the magmatic rocks that form the foundation material for the Pamukluk Dam, Tarsus, Turkey. The area has suffered extensive dyke intrusion and significant tectonic disturbance. The paper reports the results of both in situ tests and laboratory tests on block and borehole core samples. In general, the diorites and microdiorites have suffered little alteration and remained strong. The granophyres and less weathered acidic rocks are moderately strong while the gabbros are the weakest materials. The elastic moduli vary between 830 and more than 3500 MPa. Pressuremeter tests indicated that for a 120 m high dam, the settlement would vary between some 33 and 69 mm. Received: 3 August 1999 · Accepted: 18 May 2000     

Constructing convex directions for stable polynomials

New constructions of convex directions for Hurwitz stable polynomials are obtained. The technique is based on interpretations of the phase-derivative conditions in terms of the sensitivity of the root-locus associated with the even and odd parts of a polynomial     

PID Stabilization of MIMO Plants

Closed-loop stabilization using proportional-integral-derivative (PID) controllers is investigated for linear multiple-input-multiple-output (MIMO) plants. General necessary conditions for existence of PID-controllers are derived. Several plant classes that admit PID-con- trollers are explicitly described. Plants with only one or two unstable zeros at or "close" to the origin (alternatively, at or close to infinity) as well as plants with only one or two unstable poles which are at or close to origin are among these classes. Systematic PID-controller synthesis procedures are developed for these classes of plants.     

Disturbance decoupling problems via dynamic output feedback

This paper considers the disturbance decoupling problems, with or without internal stability and pole placement, via dynamic output feedback using polynomial and rational matrix techniques. We show that in all three problems considered, the central solvability condition can be expressed as a two-sided matching problemA = BXC, whereA, B, andCare the polynomial system matrices of certain natural subsystems of the system model andXis to be determined over various subrings of the rational functions. This matching problem can in turn be reduced to certain appropriate zero-cancellation conditions on the polynomial system matricesA, B, andC.     

Decentralized control: a stable proper fractional approach

Three decentralized control problems are considered in a fractional setup for two-channel multivariable systems. All three problems are instances of decentralized control or local output feedback problems. The problems are: (i) making the system stabilizable and detectable through the first channel via dynamic output feedback around the second channel, (ii) the first problem with the constraint of internal stability, and (iii) the decentralized stabilization problem. All three problems are equivalent as far as the solvability conditions are concerned. A characterization of all solutions in each case is given. The results apply to a class of systems having fractional representations over an arbitrary principal ideal domain     

Decentralized blocking zeros and the decentralized strongstabilization problem

This paper is concerned with a new system theoretic concept, decentralized blocking zeros, and its applications in the design of decentralized controllers for linear time-invariant finite-dimensional systems. The concept of decentralized blocking zeros is a generalization of its centralized counterpart to multichannel systems under decentralized control. Decentralized blocking zeros are defined as the common blocking zeros of the main diagonal transfer matrices and various complementary transfer matrices of a given plant. As an application of this concept, we consider the decentralized strong stabilization problem (DSSP) where the objective is to stabilize a plant using a stable decentralized controller. It is shown that a parity interlacing property should be satisfied among the real unstable poles and real unstable decentralized blocking zeros of the plant for the DSSP to be solvable. That parity interlacing property is also sufficient for the solution of the DSSP for a large class of plants satisfying a certain connectivity condition. The DSSP is exploited in the solution of a special decentralized simultaneous stabilization problem, called the decentralized concurrent stabilization problem (DCSP). Various applications of the DCSP in the design of controllers for large-scale systems are also discussed     

Ultrasonic monitoring of the seal quality in flexible food packages

Ultrasonic Backscattered Amplitude Integral (BAI) values are used to detect critical and major defects such as nonbonding, wrinkles and bubbles distributed within the seal area of flexible food packages. The BAI‐mode imaging by itself is not capable of detecting such nonbonding, wrinkles and bubbles distributed within the seal area. For this study, model delects in the seal region of all‐plastic and foil‐containing films were created by varying the sealing‐bar temperature. Seal regions were scanned by a 17.3‐MHz ultrasonic transducer, and the waveform for each scan point was processed by the BAI‐mode method. The mean and the coefficient of variation of the BAI values (BAICV) were calculated. It is shown that a combination of mean BAI vaiae and BAICV value can detect defects distributed in seals in flexible food packages. This technique has the potential of providing a real‐time, on‐line control by sensing whether a proper seal has been achieved.     

Channel defect detection in food packages using integrated backscatter ultrasound imaging

Hermetically-sealed flexible food packages require very effective seal integrity testing to extend the shelf stability of thermally processed food. The initial goal of this study was to estimate the detection limits of laboratory-generated channels which simulate defects in food packages using pulse-echo ultrasonic imaging techniques. Packages with well characterized (via transmission optical microscopy) laboratory-generated channels that simulate defects with diameters between 9 and 325 mum in the seal plane traversing the major axis of the heat seal were generated in heat-sealed microwavable retort-pouch plastic film (trilaminate). Pulse-echo techniques in the 13-17 MHz center frequency range were investigated. The samples were examined with a conventional B-mode imaging technique, which was found to be inadequate for subwavelength imaging of the types of typical channel defects found in shelf-stable food packages. Based on conventional B-mode image features, a new goal of this study was established to develop and evaluate an imaging technique which would exhibit subwavelength imaging capabilities. The new imaging technique called backscattered amplitude integral (BAI) is introduced here. It was observed that BAI-mode imaging has the ability for subwavelength detection of channel defects, e.g., detection of a 10-mum diameter channel defect at a center frequency of 13.1 MHz (lambda=182 mum).     

Regulator problem with internal stability: A frequency domain solution

This paper considers the general regulator problem with internal stability where the measured outputs are not necessarily the same as the regulated outputs. Using polynomial matrix techniques, necessary and sufficient conditions are obtained in terms of skew-primeness of two polynomial matrices; one of these polynomial matrices represents the disturbance modes, whereas the other is the polynomial system matrix representing the system zeros. Various special cases considered in the literature are also analyzed in terms of these necessary and sufficient conditions.