Helsinki University of Technology

About: Helsinki University of Technology is a based out in . It is known for research contribution in the topics: Thin film & Vortex. The organization has 8962 authors who have published 20136 publications receiving 723787 citations. The organization is also known as: TKK & Teknillinen korkeakoulu.

Long-Chain Branching in Metallocene-Catalyzed Polyethylenes Investigated by Low Oscillatory Shear and Uniaxial Extensional Rheometry

Abstract: This paper explores shear and extensional rheological behavior of unimodal, metallocene-catalyzed polyethylenes with low contents of long-chain branching (LCB). The polymers were produced in semiba...

1-V 9-bit pipelined switched-opamp ADC

Abstract: A 9-bit 1.0-V pipelined analog-to-digital converter has been designed using the switched-opamp technique. The developed low-voltage circuit blocks are a multiplying analog-to-digital converter (MADC), an improved common-mode feedback circuit for a switched opamp, and a fully differential comparator. The input signal for the converter is brought in using a novel passive interface circuit. The prototype chip, implemented in a 0.5-/spl mu/m CMOS technology, has differential nonlinearity and integral nonlinearity of 0.6 and 0.9 LSB, respectively, and achieves 50.0-dB SNDR at 5-MHz clock rate. As the supply voltage is raised to 1.5 V, the clock frequency can be increased to 14 MHz. The power consumption from a 1.0-V supply is 1.6 mW.

Inverter Harmonic Elimination Through a Colony of Continuously Exploring Ants

Abstract: In this paper, the authors have developed a novel algorithm for selective harmonic elimination in a pulsewidth-modulated inverter based on the foraging behavior of a colony of ants. The problem of selective harmonic elimination, together with output voltage regulation, is redrafted as an optimization problem, and the solution is sought through the novel concept. The proposed scheme has several advantages, such as computational simplicity, derivative-free operation, and guaranteed near-optimal convergence with random initial guess. It is shown that a newly introduced parameter in the algorithm- quantum of the step movement of ants- largely influences the speed of convergence of the algorithm. Theoretical and practical results are included. Furthermore, the proposed algorithm is compared with the conventional Newton-Raphson method and genetic algorithm, and conclusions are presented.

An expert system for analyzing firewall rules

Abstract: When deploying firewalls in an organization, it is essential to verify that the firewalls are configured properly. The problem of finding out what a given firewall configuration does occurs, for instance, when a new network administrator takes over, or a third party performs a technical security audit for the organization. While the problem can be approached via testing, non-intrusive techniques are often preferred. Existing tools for analyzing firewall configurations usually rely on hard-coded algorithms for analyzing access lists. In this paper we present a tool based on constraint logic programming (CLP) which allows the user to write higher level operations for, e.g., detecting common configuration mistakes. Our tool understands Cisco router access lists, and it is implemented using Eclipse, a constraint logic programming language. The problem of analyzing firewall configurations lends itself quite naturally to be solved by an expert system. We found it surprisingly easy to use logic statements to express knowledge on networking, firewalls, and common configuration mistakes, for instance. Using an existing generic inference engine allowed us to focus on defining the core concepts and relationships in the knowledge base.