Some aspects of rolling friction resistance in a complex tribological pair – the bicycle wheel bearing

Bicycles are an important means of transport — over 20 million are manufactured worldwide each year, and, because their source of motive energy is human, their energy conversion, as measured by their resistance to motion, is critical. The bearings used in bicycles are rolling bearings, but are normally of different materials and construction quality to the roller bearings used in other applications. The present paper is intended to provide an indication of the phenomena influencing the resistance to motion and loss of energy of these bearings, and is based on a rolling bearing test stand designed by the author. A mathematical model derived from experimental observation is presented, and the theoretical results compared with experimental results.     

Finding all the DC solutions of a certain class of piecewise-linear circuits

The problem of finding all the DC solutions of a certain class of piecewise-linear electronic circuits containing locally passive and locally active one-ports is considered in this paper. An effective method enabling us to locate the solutions is developed. The method constitutes the crucial point of an algorithm based on the idea of successive contraction, division, and elimination that is capable of determining all the solutions. Several numerical examples are given, and some comparison analyses are performed confirming the usefulness of the proposed approach.This work was supported by the State Committee for Scientific Research (KBN) under grant 8T11B0911.     

Polymer Microtips Fabricated at the Extremity of Photonic Crystal Fibers

In this paper, a simple method of manufacturing micrometer-sized polymer elements （microtips） at the extremities of the photonic crystal fibers （PCFs）, which are replacing standard optical fibers in many applications due to their unique properties, is presented. The method of microtips fabrication is based on the phenomena of photopolymerization, which is successfully used by the first time, to be best of our knowledge, to manufacture microtip at PCF. The three component photopolymerizable formulation consists of photo-initiating system and multifunctional triacrylate. The photopolymerization is carried out by green laser with the microtip growth controlled by the light exposure parameters （i.e. power and time）. Results of mic：rotip fabrication on standard fiber （SMF-28e＋） and large mode area PCF （LMA-10） are provided. Theinfluence of the initial process parameters on the final microtip characteristics （i.e., length, diameter and profile） is discussed. The potential applications of such polymer microtips are near-field scanning optical microscopy, coupling light sources with fibers and sensing.