| 1. |
- Häggström, Cecilia
(författare)
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The Absent Meaning of Concrete Form in Theory of Architecture
- 1996
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The aim of this dissertation is to discuss architecture as forming practical conditions for our way-of-being, and to clarify that which prevents traditional theory of architecture from dealing with these practical conditions as such. The dissertation investigates a theoretical problem concerning the nature of the relation between human being and the built environment. The main question is: In what way can we treat architecture as concrete material form, involved in such a way in our practical being, that it contributes to the maintenance and development of our way-of-being? A related question is: Why is this practical meaning usually so hard to treat in theory? By comparing and discussing a selection of theoretical works marked by their turning away, in different ways, from the actual concrete material form (towards something else), the traditional embrace of a Cartesian concept of human being is found to be what prevents theory of architecture from treating a practical meaning of architecture. The persistence of this concept is also found to be strengthened by the influences of closely related practices in which the use of architectural images, as a means to certain knowledges, play a vital role.
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| 2. |
- Jonsson, Magnus, 1969-
(författare)
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High performance fiber-optic interconnection networks for real-time computing systems
- 1999
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Parallel and distributed computing systems become more and more powerful and hence place increasingly higher demands on the networks that interconnect their processors or processing nodes. Many of the applications running on such systems, especially embedded systems applications, have real-time requirements and, with increasing application demands, high-performance networks are the hearts of these systems. Fiber-optic networks are good candidates for use in such systems in the future. This thesis contributes to the relatively unexplored area of fiber-optic networks for parallel and distributed real-time computer systems and suggests and evaluates several fiber-optic networks and protocols. Two different technologies are used in the networks, WDM (Wavelength Division Multiplexing) and fiber-ribbon point-to-point links. WDM offers multiple channels, each with a capacity of several Gbit/s. A WDM star network in which protocols and services are efficiently integrated to support different kinds of real-time demands, especially hard ones, has been developed. The star-of-stars topology can be chosen to offer better network scalability. The WDM star architecture is attractive but its future success depends on components becoming more commercially mature. Fiber-ribbon links, offering instead an aggregated bandwidth of several Gbit/s, have already reached the market with a promising price/performance ratio. This has motivated the development and investigation of two new ring networks based on fiber-ribbon links. The networks take advantage of spatial bandwidth reuse, which can greatly enhance performance in applications with a significant amount of nearest downstream neighbor communication. One of the ring networks is control channel based and not only has support for real-time services like the WDM star network but also low level support for, e.g., group communication. The approach has been to develop network protocols with support for dynamic real-time services, out of time-deterministic static TDMA systems. The focus has been on functionality more than pure performance figures, mostly on real-time features but also on other types of functionality for parallel and distributed systems. Worst-case analyses, some simulations, and case studies are reported for the networks. The focus has been on embedded supercomputer applications, where each node itself can be a parallel computer, and it is shown that the networks are well suited for use in the radar signal processing systems studied. Other application examples in which these kinds of networks are valuable are distributed multimedia systems, satellite imaging and other image processing applications.
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| 3. |
- Nordlander, Johan, 1962
(författare)
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Reactive Objects and Functional Programming
- 1999
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The construction of robust distributed and interactive software is still a challenging task, despite the recent popularity-increase for languages that take advanced programming concepts into the mainstream. Several problematic areas can be identified: most languages require the reactivity of a system to be manually upheld by careful avoidance of blocking operations; mathematical values often need to be encoded in terms of stateful objects or vice versa; concurrency is particularly tricky in conjunction with encapsulated software components; and static type safety is often compromised because of the lack of simultaneous support for both subtyping and polymorphism. This thesis presents a programming language, O'Haskell, that has been consciously designed with these considerations in mind. O'Haskell is defined by conservatively extending the purely functional language Haskell with the following features: A central structuring mechanism based on reactive objects, which unify the notions of objects and concurrent processes. Reactive objects are asynchronous, state-encapsulating servers whose purpose is to react to input messages; they cannot actively block execution or selectively filter their sources of input. A monadic layer of object-based computational effects, which clearly separates stateful objects from stateless values. Apart from higher-order functions and recursive data structures, the latter notion also includes first-class commands, object templates, and methods. A safe, polymorphic type system with declared record and datatype subtyping, supported by a powerful partial type inference algorithm. It is claimed that these features make O'Haskell especially well-adapted for the task of modern software construction. The thesis presents O'Haskell from both a practical and a theoretical perspective. The practical contributions are a full implementation of the language, a number of non-trivial programming examples that illustrate the merits of reactive objects in a realistic context, and several reusable programming methods for such applications as graphical user interfaces, embedded controllers, and network protocols. The theoretical results serve to substantiate the informal claim made regarding usability, and include a provably sound polymorphic subtyping system, soundness and partial completeness for the inference algorithm, a formal dynamic semantics, and a result that characterizes the conservative extension of a purely functional language with state and concurrency.
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| 4. |
- Carlsson, Jan, 1962
(författare)
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Computation of EMC Properties of Slots and Printed Circuit Boards
- 1998
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis deals with the numerical solution of electromagnetic compatibility (EMC) problems for electronic systems, such as radiated emission, susceptibility and crosstalk on printed circuit boards and transmission through slots. The analysis of printed circuit boards is done by using an electric field integral equation (EFIE) expressed in the frequency domain, which is solved by using the method of moments. In order to incorporate the dielectric substrate of the circuit board a spectral domain formulation is used which makes use of a physical asymptotic solution to speed up convergence. The theory has been implemented in a user-friendly computer code which has been extensively tested against previously published results and against results obtained by other methods and programs. The crosstalk on printed circuit boards is also studied in a different way by using multi-conductor transmission line (MTL) theory. In order to use this formulation the per unit length parameters of the MTL have to be known. These parameters are computed by a developed finite difference program. The parameters are then used for modelling the MTL as lumped circuit element sections by means of the circuit program SPICE. They are also used directly in a separately developed computer program based on the finite difference time domain technique (FDTD). This FDTD program solves the transmission line equations in the time domain and the crosstalk can be obtained either in the time domain or in the frequency domain through a FFT (fast fourier transform) routine. The induced currents due to incident electromagnetic fields and transmission line networks can also be calculated by the program. The transmission of electromagnetic fields through slots is also considered. It is shown that by using the concept of soft and hard surfaces methods for reducing the transmission can be understood. The analysis of slots with corrugations or chokes is done by using an integral equation approach which is solved by the method of moments. Results for different corrugated slots are presented and compared with results from measurements.
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