Assessment of noise attenuating powertrain components

Forschung im Ingenieurwesen - Wind turbine noise used to be dominated by aerodynamic blade noise, effectively masking mechanical noise, originating from the drivetrain. Successful blade noise...     

Heat Treatment and Chemical Composition of Fatty Acids and Rosin Acids Mixtures: Effects on Their Thermal Properties and Morphology

Mixtures of fatty acids and rosin acids are industrially important products utilized as a raw material for several purposes. Their thermal properties, especially cold stability and crystallization behavior is also important. Several fatty acid and rosin acid mixtures both from industrial products and from commercially available fatty and rosin acids were prepared and treated for 30 min at 80 °C under an inert atmosphere. Thereafter, the mixture was cooled to the desired temperature. Determination of the cloud point, chemical analysis of liquid and solid phase, thermal analysis by differential scanning calorimetry as well as morphology analysis by scanning electron microscopy were performed. The results revealed that crystallization was more rapid when it occurred at 10 °C compared to 25 °C. The crystal sizes increased with decreasing the crystallization temperature. Furthermore, crystals were of irregular shape and agglomerated when rapid cooling of the mixture occurred. Chemical analysis revealed that liquid phase was enriched with stearic acid, whereas crystals contained large amounts of abietic, dehydroabietic and linoleic acids. The cloud point of the mixtures increased with increasing amount of stearic and rosin acids. Dehydroabietic acid addition improved the cold stability of the synthetic fatty acid–rosin acids mixture.     

Two-step purification strategy for enhanced recovery of recombinant hepatitis B surface antigen from Pichia pastoris

Univariate screening on factors affecting the purification performance of recombinant hepatitis B surface antigen (HBsAg) on ion exchange chromatography (IEC) and size exclusion chromatography (SEC) and the establishment of a two-step purification strategy were performed. Amongst four IEC adsorbents examined, the use of Q Sepharose XL IEC adsorbent under optimized conditions together with optimized SEC purification was able to efficiently purify HBsAg. An established purification strategy comprising the two techniques further demonstrated adaptability for scale-up operations with a final total purification factor (PF) of 94.82 ± 16.20, HBsAg purity of 95.48% and recovery yield of 78.07%.     

A model for a long-term diffusion of multispecies in concrete based on ion–cement-hydrate interaction

A model for simulating a long-term diffusion in concrete under submerged conditions has been developed. The model focuses on the interaction between cement hydrates and electrolyte solution adopting the physical properties of concrete as alternative parameters for estimating long-term diffusion. The model was verified by the large variety of long-term experimental data involving verification of cement hydrates, porosity properties, pH value, element distribution, and chloride penetration for sulphate-resistant Portland cement (SRPC) concretes. Evaluating impacts of hundreds of years’ exposure on concrete durability, a simulation was also performed for an exposure time of 500 years. The results confirmed the importance of ion–cement-hydrate interaction in the evaluation of a long-term diffusion of harmful substances such as chlorides into concrete. The simulation results show also that the solid phases of the SRPC concrete mix that was used are stable in the long-term. The threshold concentration of chlorides which may initiate reinforcement corrosion defined as Cl^?/OH^? ratio could be exceeded in concrete after moderate exposure period under the conditions investigated with typical protective concrete layers. Using of case-specific values for a threshold chloride content and evaluating the method used for estimating the initiation time of reinforcement corrosion are recommended in the structures with a long-design service life.     

Isospecific polymerization of vinyl ethers with titanium catalysts containing modified tridentate anionic donor ligands

BACKGROUND: Stereo‐regulated polymerization of vinyl ethers (VEs) assumes significance because of its elegance and the resultant unique polymer properties. Although several Lewis acid catalysts polymerize VEs with good control of molecular weight, achieving stereo‐regularity is quite challenging. There are literature reports of a few catalyst systems capable of producing highly isotactic poly(vinyl ether) (PVE) only at lower temperatures with the polymer becoming atactic with an increase in reaction temperature. Hence innovating new catalyst systems which can produce highly stereo‐regular PVEs with high molecular weight at ambient temperature is quite challenging. RESULTS: We used two different titanium pre‐catalysts (1‐TiCl₂ and 2‐TiCl₂) for the polymerization of VEs. These pre‐catalysts in combination with methylaluminoxane (MAO)/borate polymerized VEs in higher conversions. Highly isotactic poly(n‐butylvinyl ether) (PBVE; 75% dyad isotactic ratio) was obtained with 1‐TiCl₂/MAO at ambient temperature. CONCLUSION: We synthesized unimodal and highly isotactic PBVE with molecular weights of the order of 10⁵ g mol^?1 using the non‐metallocene‐type single‐site catalyst system 1‐TiCl₂/MAO even at ambient temperature. The symmetry around the metal centre in the pre‐catalyst and the polymerization temperature played a major role in controlling the stereo‐regularization of the olefin inserted. Copyright © 2009 Society of Chemical Industry     

Higher-order modelling of the diffusion dynamics in a bipolar transistor

A higher-order diffusion model for a bipolar transistor has been developed. This model is based on the Padé approximation of the quasi-static expansions of the base and collector currents and gives improved accuracy for the simulation of fast transients and periodic operation at high frequencies. the effect of higher-order circuit elements on accuracy is demonstrated by calculating the transient response to a step excitation and by determining the scattering parameters of a transistor model with higher-order elements linearized about an operating point. the higher-order model is replaced by an equivalent circuit including only conventional elements, and the transient behaviour of these two models is compared.     

Numerical study of near-field writing on a phase-change optical disk

Absorption in the phase-change layer of an optical disk located in the near field of a Fabry-Perot laser diode is studied with a combination of finite-difference time domain (FDTD) analysis and a phenomenological laser model that predicts the operational characteristics of a laser diode. Some numerical simulations are performed and results are presented. In addition, the combined FDTD/laser-simulation model is described briefly.     

A Broadband Quadrature-Modulator in Standard 0.13 μm CMOS

A polyphase filtering topology is proposed which uses parallel switchable RC-networks for accurate broadband 90^∘ phasing. A 0.13μm CMOS prototype using the quadrature-generation network in a direct-conversion quadrature-modulator achieves a measured image-rejection ratio of −39 dBc or better in 0.6–2.5 GHz while consuming only 66 mW from a 2.2 V single supply. Esa Tiiliharjuwas born in Rovaniemi, Finland, in 1966. He received the M.Sc. degree in Information Technology in 1995, and the Lic.Tech degree in electrical engineering in 1998, both from Helsinki University of Technology, Finland. From 1996 to July 1997 he was employed as an assistant at Helsinki University of Technology. He has held a position as a research assistant since 1997, and he is currently working towards his Ph.D. degree in the Electronic Circuit Design Laboratory at Helsinki University of Technology. His research interests include the design of integrated low-power circuits for portable telecommunication applications. He has designed and measured several integrated circuits for this application area. He is the author or co-author of several internationally-refereed conference and journal publications on analog integrated circuits. Kari A.I. Halonenwas born in Helsinki, Finland, on May 23, 1958. He received the M.Sc. degree in electrical engineering from the Helsinki University of Technology (HUT) in 1982 and the Ph.D. degree in electrical engineering from the Katholieke Universiteit Leuven, Heverlee, Belgium, in 1987. From 1982 to 1984, he was with HUT as an Assistant and with the Technical Research Center of Finland as a Research Assistant. From 1984 to 1987, he was a Research Assistant with the E.S.A.T. Laboratory, Katholieke Universiteit Leuven, with a temporary grant from the Academy of Finland. Since 1988, he has been with the Electronic Circuit Design Laboratory, HUT, as a Senior Assistant from 1988 to 1990, and as the Director of the Integrated Circuit Design Unit of the Microelectronics Center from 1990 to 1993. He was on leave of absence during the academic year 1992–1993, acting as Research and Development Manager with Fincitec Inc., Finland. From 1993 to 1996, he was an Associate Professor, and since 1997, he has been a full Professor with the Faculty of Electrical Engineering and Telecommunications, HUT. He became the Head of Electronic Circuit Design Laboratory year 1998. He was the Technical Program Committee Chairman for the European Solid-State Circuits Conference in 2000. He is the author or coauthor of over 150 international and national conference and journal publications on analog integrated circuits, and holds several patents on analog integrated circuits. His research interests are in CMOS and BiCMOS analog integrated circuits, particularly for telecommunication applications. Dr. Halonen was an Associate Editor of the IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS–PART I: FUNDAMENTAL THEORY AND APPLICATIONS from 1997 to 1999. He has been a Guest Editor for the IEEE JOURNAL OF SOLID-STATE CIRCUITS. He received the BeatriceWinner Award from the IEEE International Solid-State Circuits Conference in 2002.[c-halonen.eps]