A Popov criterion for networked systems

We consider robustness analysis of heterogeneous and homogeneous networked systems based on integral quadratic constraints (IQCs). First, we show how the analysis decomposes into lower dimensional problems if the interconnection structure is exploited. This generally leads to a significant reduction of the computational complexity. Secondly, by considering a set of IQCs that characterizes the eigenvalues of the interconnection matrices of symmetrically networked systems, we derive a Popov-like criterion for such systems. In particular, when the nodes of the networked system are single-input–single-output linear time-invariant operators, the criterion can be illustrated using a generalized Popov plot. In such cases, the Popov criterion is also a necessary condition in the sense that if the criterion is violated then a destabilizing network with the specified eigenvalue distribution can be constructed.     

Persistent nepotism in peer-review

In a replication of the high-profile contribution by Wennerås and Wold on grant peer-review, we investigate new applications processed by the medical research council in Sweden. Introducing a normalisation method for ranking applications that takes into account the differences between committees, we also use a normalisation of bibliometric measures by field. Finally, we perform a regression analysis with interaction effects. Our results indicate that female principal investigators (PIs) receive a bonus of 10% on scores, in relation to their male colleagues. However, male and female PIs having a reviewer affiliation collect an even higher bonus, approximately 15%. Nepotism seems to be a persistent problem in the Swedish grant peer review system.     

Katalysatoruntersuchungen an einer Technikumsanlage für Biomasse‐Kleinfeuerungen

In addition to the reduction of particulate matter, a catalytic supported emission reduction in small scale biomass combustion systems can also enable a conversion of toxic organic components into carbon dioxide and water. For catalyst investigations under practical conditions a special test facility was designed. The results show that products of incomplete combustion like carbon monoxide from stoves can be reduced by catalytic processes. Further developments and studies are necessary to achieve the targeted emission limits.     

Composite beam–columns with interlayer slip—Approximate analysis

An approximate second order analysis procedure for composite beam–columns with interlayer slip subjected to transverse loading and axial compressive loads is developed. The magnification factors to be applied to the first order solutions in order to estimate the deflections and internal forces obtained by the second order analysis approach are presented. The method of applying magnification factors to internal axial forces is discussed. The approximate second order analysis procedure is developed for the four Euler cases with various transverse load conditions. The procedure is applied to and the accuracy is illustrated for simply supported partially beam–columns of steel and concrete, and timber and concrete with different bending stiffness and interlayer slip properties. The deflections and internal forces obtained by the approximate method compared extremely well, except for slip forces in case of very flexible shear connectors, with those obtained by the more rigorous second order analysis approach for different composite action (partial interaction) parameters (shear connector stiffness values). The study also shows that the magnification factor associated with the deflections can be utilized to estimate also the internal actions, except shear forces in case of very flexible shear connectors, in the second order case with minimal error for simply supported beam–columns. Thus, for members with shear connector stiffness of structural significance the proposed approximate method can be used in general for simply supported beam–columns. For other boundary and loading conditions, the approximate method needs to be re-evaluated. The approach of using one magnification factor greatly simplifies the analysis task for those components.     

Effect of Ta on structure and mechanical properties of (Ti,Ta,W)(C,N)–Co cermets

The effect of Ta on the structure and mechanical properties of (Ti,Ta,W)(C,N)–Co cermets was investigated. A series of alloys of varying nominal composition were manufactured following normal powder metallurgical procedures. The alloys were characterized and their performance in metal cutting was evaluated. It was found that Ta enhances the resistance to plastic deformation (PD) of this system. By combining sets of alloys, several explanations for this enhancement could be eliminated. Plastic deformation was found to be caused by grain boundary sliding. Ta is believed to influence the interfacial energies of the system, yielding a stronger hard phase skeleton, which restricts grain boundary sliding.     

A model for micro-slip between flat surfaces based on deformation of ellipsoidal elastic asperities—parametric study and experimental investigation

Micro-slip is a phenomenon that occurs between contacting surfaces when a frictional load, less than that necessary to produce macro-slip, is applied to the contacting surfaces. A model is evaluated for micro-slip between a flat smooth surface and a flat rough surface. The rough surface is covered with uniformly distributed ellipsoidal elastic asperities. The results from simulations of the model show that anisotropy, material combination and number of contacts of the contacting surfaces influence the tangential stiffness at zero displacement, the length of the micro-slip zone and the energy dissipated in the contact. An experimental investigation verifies the results computed by the model.     

Roll forming of partially heated cold rolled stainless steel

Today you will find roll formed details in many different products, for example buildings, household appliances and vehicles. The industry, in order to save weight, tends to use more and more high strength steel. The disadvantage with these materials is that they can be difficult to form due to reduced ductility. A way to increase the ductility in the forming areas is by partially heat the steel.It is shown that partial heating substantially increases the ductility of high strength steel and make it possible to roll form large bend angles. When roll forming, the material will work hardening almost to the as-received condition in the outer and inner radius of the roll formed profile. Furthermore, the heating power decides the bend angle obtained. Finally, the mechanical properties after heating and roll forming are discussed.     

On the relations between color,gloss, and surface texture in injection‐molded plastics

The relation between color and gloss of injection‐molded plastic specimens was evaluated by means of a 45°/0° geometry spectrophotometer and a glossmeter. The specimens were plaques having one smooth, glossy field and one rougher, textured region made of two different polymeric materials (acrylonitrile‐butadiene‐styrene and polypropylene) in a range of colors. A significant influence of the lightness L* of the specimens on the measured gloss of the textured field, with a low gloss appearance, was found. This can probably be attributed to a contribution from bulk scattering, which is linked to the reflectance from within the specimen. The influence of texture on the measured color of the plaques was assessed by evaluating the color difference between the smooth field and the more textured area on the specimens. When the surface was textured, the color changed; in general it became lighter and less saturated. The magnitude of the change depended on the color of the material. The darker the material was, the larger was the increase in lightness L* as the surface became rougher. The shift in chroma C* was determined not only by the saturation but also by the lightness of the specimens. Darker specimens exhibited a larger decrease in chroma when the surface was textured. The change in the measured color caused by increasing the surface roughness could be predicted in a satisfactory manner using a model developed for xerographic printing paper. © 2009 Wiley Periodicals, Inc. Col Res Appl, 34, 291–298, 2009