Analytical and finite element models of the thermal behavior for lead-free soldering processes in electronic assembly

The development of a simplified analytical model to describe the thermal history of a printed circuit board assembly (PCA) during convective reflow soldering is discussed in this paper. Verification of the assumptions was done by Finite Element Modeling, as well as comparison with experimental measured temperature profiles. The important parameter determining how fast a component heats up is the so called time constant which describes the time needed for the component to reach the set temperature. Comparison between finite element model-based estimations and measured values for three different components, CCGA, PBGA and μBGA, has been made and a reasonable agreement has been obtained.     

FAMOUS: A Network Architecture for Delivering Multimedia Services to FAst MOving USers

When today’s commuters in the train or in a car want to access the Internet, they see themselves restricted to simple web surfing or e-mail. Interactive multimedia services, like online gaming or video conferencing are still unavailable to them, even with promising new technologies like UMTS or WiMAX. The impact of high bit rate multimedia traffic on the access network and aggregation network is an important topic, that has not been addressed in enough detail before. We designed a network architecture for offering these multimedia services to fast moving users. We refer to the overall network architecture as the FAMOUS network architecture, which consists of two parts: (i) an access network part which has to deal with large number of users, asking for a high bandwidth, while experiencing a high handoff frequency and (ii) an aggregation network part which has to deal with dynamic tunnels of very high bandwidth, while experiencing a low handoff frequency. In this paper, we detail the FAMOUS architecture, together with optimized handoff strategies, an optical switching architecture, a design methodology for dimensioning aggregations networks and automatic tunnel pre-configuration and activation. Moreover, performance results of these mentioned aspects will be presented.Filip De Greve was born in Gent, Belgium, in 1978. He received his Master of Science degree in Electrotechnical Engineering from Ghent University, Gent, Belgium in 2001. In 2002, he joined the Department of Information Technology of the Faculty of Applied Sciences, University of Ghent as a doctoral researcher. Besides specific Ethernet-related research topics, his current research interests are related to broadband communication networks and include design, routing and reliability of access and aggregation networks.Bart Lannoo was born in Torhout, Belgium, in 1979. He received his Master of Science degree in Electrotechnical Engineering from Ghent University, Ghent, Belgium in 2002. Since August 2002, he has been working with Department of Information Technology (INTEC) of the Faculty of Applied Sciences, Ghent University as a doctoral researcher. His current research interests are in optical access networks, including both fixed access networks (FTTx) and optical access for wireless communication.Liesbeth Peters received the degree in Electrotechnical Engineering from Ghent University, Belgium in 2001. Since August 2001, she has been working as a doctoral researcher with the Department of Information Technology of Ghent University, where she joined the Broadband Communications Networks Group. Since October 2002, she works there as a research assistant of the Fund for Scientific Research – Flanders (F.W.O.-V., Belgium). Her current research interests are in broadband wireless communication and the support of IP mobility in wired cum wireless networks.Tom Van Leeuwen was born in Gent, Belgium, in 1979. He received his masters degree in Computer Engineering from the Ghent University, Gent, Belgium in 2002. Since 2002, he has been working with Department of Information Technology of Ghent University (INTEC) as a doctoral researcher. In 2004 he received a PhD grant from the Institute for the Promotion of Innovation through Science and Technology in Flanders (IWT-Vlaanderen). His current research interests are in broadband wireless communication.Frederic Van Quickenborne (M. Sc. Degree in Electrotechnical Engineering, University of Ghent, Belgium, 2002) published different papers on the growing importance of ethernet in aggregation and core networks. Besides his interest in ethernet related topics (QoS, VLANs, xSTP), he is also involved in projects concerning video-streaming and is working on a Click-based ethernet testbed. This research is funded by a PhD grant from the Institute for the Promotion of Innovation through Science and Technology in Flanders (IWT-Vlaanderen), that he obtained in 2004.Didier Colle received a M.Sc. degree in electrotechnical engineering (option: communications) from the Ghent University in 1997. Since then, he has been working at the same university as researcher in the department of Information Technology (INTEC). He is part of the research group INTEC Broadband Communication Networks (IBCN) headed by Prof.: Piet Demeester. His research lead to a Ph.D. degree in February 2002. From January 2003 on, he was granted a postdoctoral scholarship from the “Instituut voor de aanmoediging van Innovatie door Wetenschap en Technologie in Vlaanderen (IWT-Vlaanderen)”. His research deals with design and planning of communication networks. His work is focussing on optical transport networks, to support the next-generation Internet. Up till now, he has actively been involved in three IST projects (LION, OPTIMIST and DAVID) and in the COST266 action. His work has been published in more than 40 scientific publications in international conferences and journals.Filip de Turck received his M.Sc. degree in Electronic Engineering from the Ghent University, Belgium, in June 1997. In May 2002, he obtained the Ph.D. degree in Electronic Engineering from the same university. From October 1997 to September 2001, Filip De Turck was research assistant with the Fund for Scientific Research-Flanders, Belgium (F.W.O.-V.). At the moment, he is a part-time professor and a post-doctoral fellow of the F.W.O.-V., affiliated with the Department of Information Technology of the Ghent University. Filip De Turck is author or co-author of approximately 80 papers published in international journals or in the proceedings of international conferences. His main research interests include scalable software architectures for telecommunication network and service management, performance evaluation and optimization of routing, admission control and traffic management in telecommunication systems.Ingrid Moerman was born in Gent, Belgium, in 1965. She received the degree in Electro-technical Engineering and the Ph.D degree from the Ghent University, Gent, Belgium in 1987 and 1992, respectively. Since 1987, she has been with the Interuniversity Micro-Electronics Centre (IMEC) at the Department of Information Technology (INTEC) of the Ghent University, where she conducted research in the field of optoelectronics. In 1997, she became a permanent member of the Research Staff at IMEC. Since 2000 she is part-time professor at the Ghent University. Since 2001 she has switched her research domain to broadband communication networks. She is currently involved in the research and education on broadband mobile & wireless communication networks and on multimedia over IP. She is author or co-author of more than 300 publications in the field of optoelectronics and communication networks.Mario Pickavet received an M.Sc. and Ph.D. degree in electrical engineering, specialized in telecommunications, from Ghent University in 1996 and 1999, respectively. Since 2000, he is professor at Ghent University where he is teaching telecommunication networks and algorithm design. His current research interests are related to broadband communication networks (WDM, IP, (G-)MPLS, OPS, OBS) and include design, long-term planning and routing of core and access networks. In this context, he is currently involved a.o. in the European IST projects “All-Optical Label Swapping Employing Optical Logic Gates in Network Nodes” (LASAGNE) and “Optical Networks: Towards Bandwidth Manageability and Cost Efficiency” (e-Photon/ONe) and in several national research projects. He has published about a hundred international publications, both in journals (e.g. IEEE JSAC, IEEE Comm. Mag., JLT) and in proceedings of conferences. He is one of the authors of the book ‘Network Recovery: Protection and Restoration of Optical, SONET-SDH, IP, and MPLS’.Bart Dhoedt received a degree in Engineering from the Ghent University in 1990. In September 1990, he joined the Department of Information Technology of the Faculty of Applied Sciences, University of Ghent. His research, addressing the use of micro-optics to realize parallel free space optical interconnects, resulted in a PhD degree in 1995. After a 2 year post-doc in opto-electronics, he became professor at the Faculty of Applied Sciences, Department of Information Technology. Since then, he is responsible for several courses on algorithms, programming and software development. His research interests are software engineering and mobile & wireless communications. Bart Dhoedt is author or co-author of approximately 70 papers published in international journals or in the proceedings of international conferences. His current research addresses software technologies for communication networks, peer-to-peer networks, mobile networks and active networks.Piet Demeester finished his PhD thesis at the Department of Information Technology (INTEC) at the Ghent University in 1988. At the same department he became group leader of the activities on Metal Organic Vapour Phase Epitaxial growth for optoelectronic components. In 1992 he started a new research group on Broadband Communication Networks. The research in this field resulted in already more than 300 publications. In this research domain he was and is a member of several programme committees of international conferences, such as: ICCCN, the International Conference on Telecommunication Systems, OFC, ICC, and ECOC. He was Chairman of DRCN’98. In 2001 he was chairman of the Technical Programme Committee ECOC’01. He was Guest Editor of three special issues of the IEEE Communications Magazine. He is also a member of the Editorial Board of the Journals “Optical Networks Magazine” and ldquo;Photonic Network Communications”. He was a member of several national and international PhD thesis commissions. Piet Demeester is a member of IEEE (Senior Member), ACM and KVIV. His current research interests include: multilayer networks, Quality of Service (QoS) in IP-networks, mobile networks, access networks, grid computing, distributed software, network and service management and applications (supported by FWO-Vlaanderen, the BOF of the Ghent University, the IWT and the European Commission). Piet Demeester is currently full-time professor at the Ghent University, where he is teaching courses in Communication Networks. He has also been teaching in different international courses.     

Diffusion in Liquid Associating Systems

A recently developed model for the prediction of pseudo‐binary Maxwell‐Stefan diffusion coefficients on the basis of a multicomponent approach applicable to binary associating and/or solvating systems is further examined. For this purpose two example calculations are added to illustrate and to answer the following questions: What are the capabilities and limits of the new model? How does the model actually compute binary diffusivities from a multicomponent approach? What information must be supplied by the user? How does the model perform on example calculations?     

A subspace algorithm for the identification of discrete time frequency domain power spectra

In this paper we present a new subspace algorithm for the identification of multi-input multi-output linear discrete time systems from measured power spectrum data. We show how the state space system matrices can be determined by taking the inverse discrete Fourier transform of the given data and applying the result to a new realization algorithm. Special attention is paid to ensure the positive realness of the identified power spectrum. The computational speed is improved by applying a Lanczos algorithm. The algorithm is illustrated with two practical examples.     

An interdisciplinary framework to predict premature roller element bearing failures in wind turbine gearboxes

Forschung im Ingenieurwesen - Roller element bearings present in the intermediate and high-speed stages of wind turbine gearboxes operate in dynamic working conditions and in some cases may fail...     

The use of integrated countercurrent nanofiltration cascades for advanced separations

BACKGROUND: The concept of integrated countercurrent nanofiltration cascades is derived from fractional distillation and results in an enriched and a depleted stream, the volume and purity of which can be controlled by changing the operating parameters. The aim of this study was to assess the potential of integrated countercurrent nanofiltration cascades for advanced separation of individual organic components in aqueous solution by means of single‐stage filtration experiments using xylose and maltose and cascade simulations. The influence of module recovery, membrane characteristics, recycled fraction and the number of modules was evaluated. RESULTS: It was found that, in order to obtain a high product purity with a limited number of modules, there has to be a sufficiently high rejection difference between the components. Membranes with high rejections for the studied components (e.g. NF70 and UTC20) allow one to obtain a good separation factor but a low product recovery in a cascade configuration. A higher product recovery but lower separation factors are obtained for a cascade consisting of membranes with low rejections (e.g. NFPES10). Independently of the difference in rejection between the components, the number of modules, the recycled fraction and the module recovery determine the separation to a large extent. CONCLUSION: The optimal number of modules depends on the trade‐off between a high selectivity and a high xylose recovery; the module recovery should be as high as (practically) possible. Higher selectivities and higher product recoveries are also obtained when the retentate is recycled to the previous module. This is different from the traditional cascade approach where retentates are recycled to the next module. Copyright © 2008 Society of Chemical Industry     

Role of Dams in Irrigation,Drainage and Flood Control

The International Commission on Irrigation and Drainage (ICID) is a scientific and technical, non-governmental international organization. The objectives of ICID are to stimulate and promote the development and application of irrigation, drainage, flood control, river training and environmental management in all their technical, economic, social and environmental aspects, as well as the needed research leading to the use of modern techniques. During the past years intensive discussions have been going on at a global scale regarding the future of dams. These discussions have mainly been initiated due to environmental concerns and resettlement problems related to the development of new reservoirs. In the light of these discussions ICID was asked to clarify its position. Since then a position paper on the 'Role of dams for irrigation, drainage and flood control' has been prepared which was almost unanimously approved by ICID's national committees. In this paper the main issues and findings as described in the position paper are presented. The future steps ICID is planning to take in order to contribute to the finding of sustainable solutions and improvements in decision-making processes on dams are also illustrated.     

Mitogenic effects of urokinase on melanoma cells are independent of high affinity binding to the urokinase receptor

The structural and functional properties of the urokinase-type plasminogen activator (u-PA) that are involved in the mitogenic effect of this proteolytic enzyme on human melanoma cells M14 and IF6 and the role of the u-PA receptor (u-PAR) in transducing this signal were analyzed. Native u-PA purified from urine induced a mitogenic response in quiescent IF6 and M14 cells that ranged from 25 to 40% of the mitogenic response obtained by fetal calf serum. The half-maximum response in M14 and IF6 cells was reached at u-PA concentrations of approximately 35 and 60 nM, respectively. Blocking the proteolytic activity of u-PA resulted in a 30% decrease of the mitogenic effect, whereas inhibition of plasmin activity did not alter the mitogenic effect. No mitogenic response was elicited by low molecular weight u-PA, lacking the growth factor domain and the kringle domain. The ATF domain of u-PA induced a mitogenic response that was similar to complete u-PA. Defucosylated ATF and recombinant u-PA purified from Escherichia coli lacking all post-translational modifications did not induce a mitogenic response. Blocking the interaction of u-PA with u-PAR, using a specific monoclonal antibody, did not alter the mitogenic effect induced by u-PA. The binding of radiolabeled u-PA to M14 and IF6 cells was characterized by high affinity binding mediated by u-PAR and low affinity binding to an unknown binding site. These results demonstrate that proteolytically inactive u-PA is able to induce a mitogenic response in quiescent melanoma cells in vitro by a mechanism that involves the ATF domain but is independent of high affinity binding to u-PAR. Furthermore, it suggests that u-PA is able to bind with low affinity to a hitherto unidentified membrane associated protein that could be involved in u-PA-induced signal transduction.     

A New State-space-based Algorithm to Assess the Stability of the Finite-difference Time-domain Method for 3D Finite Inhomogeneous Problems

The finite-difference time-domain (FDTD) method is an explicit time discretization scheme for Maxwell's equations. In this context it is well-known that explicit time discretization schemes have a stability induced time step restriction. In this paper, we recast the spatial discretization of Maxwell's equations, initially without time discretization, into a more convenient format, called the FDTD state-space system. This in turn allows us to derive a new algorithm in order to determine the stability limit of FDTD for lossy, inhomogeneous finite problems. It is shown that a crucial parameter is the spectral norm of the matrix resulting from the spatial discretization of the curl operator. In a rectangular simulation domain the time step upper bound can be calculated in closed form and results in a time step limit less stringent than the Courant condition. Finally, the validity of the technique is illustrated by means of some pertinent numerical examples.