PFVIBAT—a computer program for plane frame vibration analysis by an exact method

The described program PFVIBAT uses the exact displacement method to perform free and forced vibration analysis entirely within the differential equation theory of beams thus avoiding assumed modes and lumped masses. The frame may contain rigid bodies. Clamped, hinged, guided and rolling connections are allowed for. Consideration of rotatory inertia, shear deformation and second-order bending moments and shear forces as caused by static axial load is optional. Eigenfrequencies and modal masses are calculated with an accuracy that may be specified. Displacement and moment modes are plotted. Transient vibrations are studied.     

The order of any stabilizing regulator is sufficient a priori information for adaptive stabilization

Let the unknown linear system , be given, together with the a priori information that for a known, nonnegative integer l, there is a (nonadaptive) regulator of order l which stabilizes the system. It is shown that this suffices as a priori information for an adaptive stabilizing controller. An example of such an algorithm is given. This yields a continuous regulator, which does not utilize probing signals. It is based on a dense search through parameter space, and does not utilize high-gain properties, as opposed to the ‘universal regulators’ proposed before [3–6]. In the absence of information of such an l, it is shown how to modify the algorithm to search over the regulator structures, i.e. the controller's dimension.     

Accuracy in multiangle light scattering measurements for molar mass and radius estimations. Model calculations and experiments

Multiangle light scattering (MALS) is a well-established technique used to determine the size of macromolecules and particles. In this study, different extrapolation procedures used in MALS were investigated with regard to accuracy and robustness in the obtained molar mass and rms radius. Three different mathematical transformations of the light scattering function referred to as the Debye, Zimm, and Berry methods for constructing the Debye plot were investigated for two idealized polymer shapes, homogeneous spheres and random coils, with radii from 25 to 250 nm. The effect of the angular interval used for the extrapolation was investigated, as was the robustness of the different transformations toward errors in the measured light scattering intensity at low angles. For an rms radius less than 50 nm, the relative error in molar mass due to extrapolation was less than 1% independent of the method used. For larger radii, the error increased and the extrapolation procedure became more critical. For random coil polymers, the Berry method was superior in terms of accuracy and robustness. For spheres, the Debye method was superior. The Zimm method was inferior to the others. The different extrapolation methods were evaluated and compared on experimental data from a size exclusion chromatography-MALS analysis of an ultrahigh molar mass poly(ethylene oxide) (PEO). The PEO data qualitatively verified the calculations and stressed the importance of optimizing the extrapolation procedure after careful evaluation of the experimental data. A discussion of how to detect erroneous data in an experimental Debye plot is given.     

Control of fuel cell power output

A simplified dynamic model for fuel cells is developed, based on the concept of instantaneous characteristic, which is the set of values of current and voltage that a fuel cell can reach instantaneously. This is used to derive a theorem that indicates the conditions under which the power output of fuel cells can, in theory, be perfectly controlled. A fuel cell connected to a DC/DC converter is simulated numerically, with a control system based on switching rules in order to control the converter’s output voltage. The resulting transients settle in about 5–10 ms. The converter is then used as an actuator in a cascade control loop to control the torque output of a DC electric motor with a PI controller in the external loop. In this loop, the resulting in transients settle in less than 0.2 s.     

Molar volumes of Al,Li, Mg and Si

The molar volumes of the fcc, bcc, hcp and liquid phases of Al, Li, Mg and Si as well as diamond Si have been evaluated as functions of temperature based on experimental data from the literature. The molar volume of each element in each structure is described by a single polynomial expression as a function of temperature. These polynomials can be used above around 150 K. The molar volumes of the liquids were described by a linear temperature dependence. The molar volumes of nonstable structures were evaluated with the help of lattice parameter measurements of the corresponding solid solutions. A large majority of the solid solutions studied showed negative excess volumes. The molar volumes of the relatively closely packed fcc, bcc and hcp structures were always found to be very close to each other, and a reasonably good approximation would be to set them as equal.     

Quantitative methods for regulatory control layer selection

In this paper, we apply the self-optimizing control ideas to find optimal controlled variables in the regulatory layer. The regulatory layer is designed to facilitate stable operation, to regulate and to keep the operation in the linear operating range. Its performance is here quantified using the state drift criterion and the method is evaluated on two distillation column case studies with one, two or more closed loops.     

Developing control logic using aspect-oriented programming and sequence planning

A fundamental functionality of a Programmable Logic Controller (PLC) is to control and execute a set of operations. But a large part of the program code is more involved in supporting the user with concerns like alarm, HMI, communication, safety and manual control. Code related to these supporting concerns is often tangled with operation execution code, the core concerns, which makes it hard to reuse.This paper describes a method to reuse code and functionality when developing PLC programs and code libraries. The method proposes that core concerns are planned with a software tool called Sequence Planner, and the supporting concerns are integrated into the core concerns with a tool based on aspect-oriented programming.     

Materials Emission of Chemicals – PVC Flooring Materials

Abstract Data of chemical emissions from flooring materials have been collected and investigated in a database known as METS. The emission tests are performed using the Field and Laboratory Emission Cell (FLEC). The emission rates of total volatile organic compounds (TVOC) in the boiling point range of hexane to octa-decane varies from around 4,000 μg/(m²· h) to less than 10 μg/ (m²· h). Results obtained 1994/95 are presented and compared with the results obtained in 1992 for similar materials. The tests are performed 4 weeks and 26 weeks after the manufacturing of the material. The emission rates of TVOC decrease on the average approximately 60% from 4 to 26 weeks. The differences and trends in emission rates of individual chemicals and their use are discussed. For many VOCs emission rates decrease rapidly and become near to or below 2 μg/(m²· h) (the detection limit) after 26 weeks. For a small number of individual compounds the emission rate decrease little over 26 weeks. A small number of chemicals are singled out for particular interest in a health and comfort evaluation based on the emission results.     

An industrial and academic perspective on plantwide control

The purpose of this paper is to stress the importance of selecting the right plantwide control structure and the need for a formalized approach that can encompass the many issues that arise in plantwide control design. Since the concept of process control design based on a holistic view of the process came about, the variety of procedures and approaches to the design problem has illustrated the difficulty of a unified approach. Using examples, the need and advantages of using a systematic approach based on considering the plant economics are highlighted. The examples deal with disturbance rejection, throughput maximization and economic optimization of plants consisting of parallel units.