Inverse dynamics of spatial open-chain flexible manipulators with lumped and distributed actuators

This article addresses the problem of inverse dynamics for three-dimensional flexible manipulators with both lumped and distributed actuators. A recursive procedure is presented for computing the lumped inverse dynamic torques and the distributed piezoelectric actuator inputs for simultaneously tracking a prescribed end-point trajectory and reducing induced vibrations in the manipulator. The procedure sequentially solves for the non-causal inverse dynamic torques and piezoelectric voltages applied to each link in the manipulator, starting from the last element in the chain and proceeding to the base element. The method allows trajectory tracking wherein controllability of the structural vibrations is assured in all possible configurations through the use of only one motor at each intermediate joint and three motors at the ground. Numerical simulation shows that the elastic vibrations can be reduced significantly through the use of distributed actuators while at the same time satisfying the trajectory tracking requirement through the use of inverse dynamics. © 1994 John Wiley & Sons, Inc.     

Modeling of the solidification process in a continuous casting installation for steel slabs

The development of a computational simulation system for modeling the solidification process in a continuous casting facility for steel slabs is discussed. The system couples a module for solving the direct problem (the calculation of temperatures in the steel strand) with an inverse analysis module that was developed for evaluating the steel/mold heat fluxes from the information provided by thermocouples installed in the continuous casting mold copper plates. In order to cope with the non-uniqueness of the inverse analysis, a priori information on the solution, based on the consideration of the problem physics, is incorporated. The stability of the system predictions are analyzed and the influence of the first trial used to start the evaluation procedure is discussed. An industrial case is analyzed.     

Severe acute liver failure as the initial manifestation of haematological malignancy

Acute liver failure is rarely secondary to lymphoma or leukaemia and it is extremely uncommon as the initial presentation of malignancy. We report a case of a young adult patient with severe acute liver failure referred for liver transplant, in which a Burkitt acute lymphoblastic leukaemia was diagnosed by bone marrow examination. A complete recovery and long remission were obtained with chemotherapy.     

Effects of Storage Humidity on the Mechanical, Microstructural, and Drug Release Properties of Hydroxypropylmethylcellulose-Based Hydrophilic Matrix Tablets

The effects of storage humidity on the properties of hydroxypropylmethylcellulose (HPMc)-based hydrophilic matrix tablets were investigated. Hydrochlorothiazide tablets prepared with HPMCs of different thickening capacities were stored for 6 months (a) at a relative humidity corresponding to the prestorage equilibrium moisture content of the HPMCs, or (b) at a higher relative humidity. Only tablets stored at the higher humidity showed significant changes in properties, indicating that the observed changes (reduced crushing strength, increased total porosity, and increased mean pore diameter) were due to water uptake. All changes were completed within 1 month of storage. Drug release properties were unaffected, even after 6 months. Effectively identical results were obtained regardless of whether the HPMC variety used had a nominal viscosity of 4,000 cP or 100,000 cP.     

A PDP constructive algorithm for system modelling

A new constructive algorithm is presented for building neural networks that learn to reproduce output temporal sequences based on one or several input sequences. This algorithm builds a network for the task of system modelling, dealing with continuous variables in the discrete time domain. The constructive scheme makes it user independent. The network's structure consists of an ordinary set and a classification set, so it is a hybrid network like that of Stokbro et al. [6], but with a binary classification. The networks can easily be interpreted, so the learned representation can be transferred to a human engineer, unlike many other network models. This allows for a better understanding of the system structure than just its simulation. This constructive algorithm limits the network complexity automatically, hence preserving extrapolation capabilities. Examples with real data from three totally different sources show good performance and allow for a promising line of research.     

Effects of Switching Angle Phase Shift on PWM Techniques

The behavior of some well-known pulsewidth modulation (PWM) techniques is investigated under perturbation conditions of power semiconductor gating signals. An evaluation of different PWM techniques is performed considering the effect of PWM timing errors on the output spectra of switch-mode converters.     

Tracer diffusion of crown ethers in chlorobenzene from 301 to 373 K

Tracer diffusivities are reported for s-trioxane, 12-crown-4, 15-crown-5, and 18-crown-6 in chlorobenzene from 301 to 373 K. The results are discussed in terms of Arrhenius equation for diffusion, Stokes' law, and Hildebrand's free-volume model. An extension of Dymond's hard sphere self-diffusion equation to tracer diffusion has been found to successfully correlate the data reported here.     

Spontaneous Infiltration of Alumina by Copper-Oxygen Alloys

Infiltration of alumina powder compacts by molten copper-oxygen alloys under controlled oxygen partial pressures has been studied. Spontaneous infiltration occurred for copper alloys containing more than approximately 5 at.% oxygen. Despite supersaturation of the copper with oxygen, no Cu₂O or interfacial reaction layers of CuAlO₂ were resolved by TEM, suggesting the critical wettability for infiltration is not determined by interfacial chemical reaction. CuAlO₂ did form, but as discrete inclusions up to 0.5 mm in diameter. Infiltration and microstructure development are discussed in terms of the observed wetting behavior and available data on interfacial oxygen adsorption.     

Metal ion binding capability of the water‐soluble poly(vinyl phosphonic acid) for mono‐, di‐, and trivalent cations

A water‐soluble polymer containing phosphonic acid groups was investigated as a polychelatogen by using the liquid‐phase polymer‐based retention technique (LPR) under different experimental conditions. The maximum retention capacity of this polymer was determined at different pHs and polymer–metal ion ratios. The metal ions investigated were Ag(I), Cu(II), Co(II), Ni(II), and Cr(III). The maximum retention capacity values of the divalent metal ions were very similar and higher than those for the trivalent cations, indicating that the polymer–metal ion interaction was basically through electrostatic type. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2917–2922, 2004