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Full-Text Articles in Social and Behavioral Sciences

Encapsulation Of Validation Tests In The Esp-R Simulation Program, Paul Strachan, Georgios Kokogiannakis, I Macdonald Jan 2005

Encapsulation Of Validation Tests In The Esp-R Simulation Program, Paul Strachan, Georgios Kokogiannakis, I Macdonald

Faculty of Engineering and Information Sciences - Papers: Part A

It is well recognised that validation of dynamic building simulation programs is a long-term complex task. There have been many large national and international efforts that have led to a well-established validation methodology comprising analytical, inter-program comparison and empirical validation components, and a significant number of tests have been developed. As simulation usage increases, driven by such initiatives as the European Energy Performance of Buildings Directive, such tests are starting to be incorporated into national and international standards. Although many program developers have run many of the developed tests, there does not appear to have been a systematic attempt to ...


A Post-Compilation Register Re-Assignment Technique For Improving Hamming Distance Based Code Compression, Montserrat Ros, Peter Sutton Jan 2005

A Post-Compilation Register Re-Assignment Technique For Improving Hamming Distance Based Code Compression, Montserrat Ros, Peter Sutton

Faculty of Engineering and Information Sciences - Papers: Part A

Code compression is a field where compression ratios between compiler-generated code and subsequent compressed code are highly dependent on decisions made at compile time. Most optimizations employed by compilers tend to focus on parameters such as program performance, minimizing resource dependencies and sometimes the option of reducing code size. This paper describes a post-compilation technique for the greedy reassignment of general purpose scratch registers to improve Hamming distance based code compression. The code translation renumbers registers based on the frequency of registers used by isomorphic instructions and employs a Gray coding scheme to reduce Hamming distances between similar instructions. Register ...


Reinforcement Of Macroscopic Carbon Nanotube Structures By Polymer Intercalation: The Role Of Polymer Molecular Weight And Chain Conformation, C J. Frizzell, Marc In Het Panhuis, D H. Coutinho, K J. Balkus, A Minett, W J. Blau, J N. Coleman Jan 2005

Reinforcement Of Macroscopic Carbon Nanotube Structures By Polymer Intercalation: The Role Of Polymer Molecular Weight And Chain Conformation, C J. Frizzell, Marc In Het Panhuis, D H. Coutinho, K J. Balkus, A Minett, W J. Blau, J N. Coleman

Faculty of Engineering and Information Sciences - Papers: Part A

Novel polymer nanotube composites were fabricated by intercalating poly(vinylpyrrolidone) into Buckypaper from solution. This was carried out for both low (10kg∕mol) and very high (1.3Mg∕mol) molecular weight polymers. Measurements of the polymer mass uptake as a function of time allowed the calculation of diffusion coefficients as 1.66×10−9cm2∕s and 3.08×10−12cm2∕s for the low and high molecular weight strands, respectively. Taking into account the molecular weights, comparison of these coefficients suggests that each polymer type undergoes a different mode of diffusion: normal diffusion for the 10kg∕mol polymer, but reptation ...


Drag Reduction In A Flat-Plate Turbulent Boundary Layer Flow By Polymer Additives, Shu-Qing Yang, G Dou Jan 2005

Drag Reduction In A Flat-Plate Turbulent Boundary Layer Flow By Polymer Additives, Shu-Qing Yang, G Dou

Faculty of Engineering and Information Sciences - Papers: Part A

This paper presents a theoretical study on the velocity distribution and the friction factor of boundary layer flows with polymer additives starting from the concept of “stress deficit.” A novel method of order of magnitude analysis is developed, which converts the governing equations of boundary layer flow into a solvable ordinary differential equation, thus the total shear stress distribution is obtained, then the formulas for the mean velocity profiles and the friction factor for a boundary layer flow are derived after introducing appropriate expressions for the “effective viscosity” and the thickness of viscous sublayer. The derived velocity equation is able ...


Design Of Monolimb Using Finite Element Modelling And Statistics-Based Taguchi Method, Winson Lee, Ming Zhang Jan 2005

Design Of Monolimb Using Finite Element Modelling And Statistics-Based Taguchi Method, Winson Lee, Ming Zhang

Faculty of Engineering and Information Sciences - Papers: Part A

Background. Monolimb is a transtibial prosthesis having the socket and shank molded into one piece of thermoplastic material. If properly designed, the shank of a monolimb can have a controlled deflection during walking which simulates the ankle joint motions to some extent. However, there is no clear guidance for the design of monolimb considering the dilemma between shank flexibility and structural integrity. Methods. Finite element analysis was used to simulate structural tests based on ISO10328 on monolimbs of different configurations. Statistics-based Taguchi method was employed to identify the significance of each design factor in controlling the deformation and stress within ...


Infrared-Active Phonons Of Homn/Sub 1-X/Co/Sub X/O/Sub 3/ (X = 0-0.8), Feng Gao, Xiaolin Wang, M Farhoudi, R A. Lewis, Shi Xue Dou Jan 2005

Infrared-Active Phonons Of Homn/Sub 1-X/Co/Sub X/O/Sub 3/ (X = 0-0.8), Feng Gao, Xiaolin Wang, M Farhoudi, R A. Lewis, Shi Xue Dou

Faculty of Engineering and Information Sciences - Papers: Part A

Polycrystalline HoMn/sub 1-x/Co/sub x/O/sub 3/ was synthesized by solid-state reaction. The infrared active phonons of the samples were investigated. The infrared transmission spectra of the sample at x = 0-0.8 doping level was also measured at room temperature. Also, X-ray diffraction (XRD) was used to analyze the crystal structure of the samples.


Turbo Equalization Based On Factor Graphs, Qinghua Guo, Li Ping, Hans-Andrea Loeliger Jan 2005

Turbo Equalization Based On Factor Graphs, Qinghua Guo, Li Ping, Hans-Andrea Loeliger

Faculty of Engineering and Information Sciences - Papers: Part A

This paper presents a factor graph approach to turbo equalization. Unlike the existing linear MMSE turbo equalization methods, which operate with truncated windows (sliding or extending window), the proposed is a full-window approach with low complexity. This approach supports a high-speed parallel implementation technique, which makes it an attractive option in practice.


Mimo-Ofdm Channel Estimation In The Presence Of Carrier Frequency Offset, Jun Y. Li, Guisheng Liao, Qinghua Guo Jan 2005

Mimo-Ofdm Channel Estimation In The Presence Of Carrier Frequency Offset, Jun Y. Li, Guisheng Liao, Qinghua Guo

Faculty of Engineering and Information Sciences - Papers: Part A

A multiple-input multiple-output (MIMO) wireless communication system with orthogonal frequency division multiplexing (OFDM) is expected to be a promising scheme. However, the estimation of the carrier frequency offset (CFO) and the channel parameters is a great challenging task. In this paper, a maximum-likelihood- (ML-) based algorithm is proposed to jointly estimate the frequency-selective channels and the CFO in MIMO-OFDM by using a block-type pilot. The proposed algorithm is capable of dealing with the CFO range nearly ±1/2 useful OFDM signal bandwidth. Furthermore, the cases with timing error and unknown channel order are discussed. The Cramér-Rao bound (CRB) for the ...


Optimized Collimator Designs For Small Animal Spect Imaging With A Compact Gamma Camera, Yujin Qi Jan 2005

Optimized Collimator Designs For Small Animal Spect Imaging With A Compact Gamma Camera, Yujin Qi

Faculty of Engineering and Information Sciences - Papers: Part A

The aim of this study to design optimized pinhole and parallel-hole collimators for the development of a high-resolution microSPECT system using a compact pixelleted scintillation detector. The detector has a field-of-view of 11 cm with pixellated crystal elements of 1.0 mm pixel size and 1.12 mm pixel pitch. The relative resolution and sensitivity advantages of pinhole and parallel-hole collimators for mice and rats imaging were investigated using analytic formulations and Monte Carlo simulations. The optimized collimator designs were obtained by maximizing the system detection efficiency for a given object resolution. The collimator designs were optimized for 140 keV ...


Development And Characterization Of A High-Resolution Microspect System For Small-Animal Imaging, Yujin Qi, Benjamin Tsui, Yuchuan Wang, Brian Yoder, R Wojcik, S Majewski, A G Weisenberger Jan 2005

Development And Characterization Of A High-Resolution Microspect System For Small-Animal Imaging, Yujin Qi, Benjamin Tsui, Yuchuan Wang, Brian Yoder, R Wojcik, S Majewski, A G Weisenberger

Faculty of Engineering and Information Sciences - Papers: Part A

We developed a high-resolution microSPECT system and investigated its performance characteristics for small animal imaging. The microSPECT system consists of a stationary compact gamma camera with interchangeable pinhole and parallel-hole collimators and vertical object rotation mechanism. The modular camera is based on a pixellated NaI(Tl) crystal array with 1.2 mm pixel size and 1.4 mm pixel pitch coupled to a 5” diameter Hamamatsu R3292 PSPMT. The pinhole collimator has a 10cm focal length fitted with keel-edge pinhole apertures with diameters of 1.0, 1.5 and 2.0 mm. The system performance was characterized by the measurements ...


Eliciting And Specifying Requirements For Highly Interactive Systems Using Activity Theory, Robert B. K. Brown, Peter Hyland, Ian C. Piper Jan 2005

Eliciting And Specifying Requirements For Highly Interactive Systems Using Activity Theory, Robert B. K. Brown, Peter Hyland, Ian C. Piper

Faculty of Engineering and Information Sciences - Papers: Part A

The processes of eliciting user requirements and formalising these into specifications are critical for the success of highly interactive systems. These processes are still poorly understood, partly because current methods are usually ad hoc and lack any theoretical basis. A number of researchers have used Activity Theory (AT) to refine these processes and have met with some success. To date, this approach has been more useful explaining the processes post hoc. This positional paper proposes an AT method for requirement elicitation and specification definition. The method is sufficiently prescriptive and well formed that it does not require any detailed understanding ...


A Comprehensive Numerical Simulation Of Heavily Irradiated P-Type And N-Type Silicon Detectors, Marco Petasecca, Francesco Moscatelli, Daniele Passeri, Giorgio Umberto Pignatel, Carlo Scarpello, Giovanni Caprai Jan 2005

A Comprehensive Numerical Simulation Of Heavily Irradiated P-Type And N-Type Silicon Detectors, Marco Petasecca, Francesco Moscatelli, Daniele Passeri, Giorgio Umberto Pignatel, Carlo Scarpello, Giovanni Caprai

Faculty of Engineering and Information Sciences - Papers: Part A

In the framework of the CERN-RD50 Collaboration, the adoption of p-type substrates has been proposed as a suitable mean to Improve the radiation hardness of silicon detectors up to fluences of 1016n/cm2. In this work the simulated electrical characteristics of Irradiated p-type and n-type detectors are reported, for comparison with experimental measurements collected from the literature. The behaviour of the silicon devices at a fluence of 1016n/cm2 shows better results In term of charge collection efficiency using a p-type silicon detector.


Advanced Active Pixel Architectures In Standard Cmos Technology, Alessandro Marras, Daniele Passeri, Guido Matrella, Pisana Placidi, Marco Petasecca, Leonello Servoli, Gian Mario Bilei, Paolo Ciampolini Jan 2005

Advanced Active Pixel Architectures In Standard Cmos Technology, Alessandro Marras, Daniele Passeri, Guido Matrella, Pisana Placidi, Marco Petasecca, Leonello Servoli, Gian Mario Bilei, Paolo Ciampolini

Faculty of Engineering and Information Sciences - Papers: Part A

This paper aims at exploring and validating the adoption of standard fabrication processes for the realization of CMOS active pixel sensors, for particle detection purposes. The goal is to implement a single-chip, complete radiation sensor system, including on a CMOS integrated circuit the sensitive devices, read-out and signal processing circuits. A prototype chip (RAPS01) based on these principles has been already fabricated, and a chip characterization has been carried out; in particular, the evaluation of the sensitivity of the sensor response on the actual operating conditions was estimated, as well as the response uniformity. Optimization and tailoring of the sensor ...


Cmos-Aps For Hep Applications: Design And Test Of Innovative Architectures, Alessandro Marras, Daniele Passeri, Pisana Placidi, Guido Matrella, Marco Petasecca, Leonello Servoli, Gian Mario Bilei, Paollo Ciampolini Jan 2005

Cmos-Aps For Hep Applications: Design And Test Of Innovative Architectures, Alessandro Marras, Daniele Passeri, Pisana Placidi, Guido Matrella, Marco Petasecca, Leonello Servoli, Gian Mario Bilei, Paollo Ciampolini

Faculty of Engineering and Information Sciences - Papers: Part A

A set of innovative active pixel architectures has been conceived and implemented in standard CMOS technology. Active circuits are introduced into the pixel, to increase S/N ratio and to perform basic signal processing. Testing of such devices, however, becomes critical, due to the circuit relative complexity and to the need of accurately evaluating timing and position of the impinging radiation. A test strategy has thus been devised, exploiting a NIR laser source, which has been carefully characterized and tuned. The NIR laser allows for emulating, in a much more controllable fashion, a MIP event. This allow for validation of ...


Learning Texture Similarity With Perceptual Pairwise Distance, Yan Gao, Lei Wang, Kap Luk Chan, Wei-Yan Yau Jan 2005

Learning Texture Similarity With Perceptual Pairwise Distance, Yan Gao, Lei Wang, Kap Luk Chan, Wei-Yan Yau

Faculty of Engineering and Information Sciences - Papers: Part A

In this paper, we demonstrate how texture classification and retrieval could benefit from learning perceptual pairwise distance of different texture classes. Textures as represented by certain image features may not be correctly compared in a way that is consistent with human perception. Learning similarity helps to alleviate this perceptual inconsistency. For textures, psychological experiments were shown to be able to construct perceptual pairwise distance matrix. We are going to show how this distance information could be utilized in learning similarity by Support Vector Machines for efficient texture classification and retrieval.


Dynamic Channel Allocation For Mobile Cellular Systems Using A Control Theoretical Approach, Yaya Wei, Chuang Lin, Raad Raad, Fengyuan Ren Jan 2005

Dynamic Channel Allocation For Mobile Cellular Systems Using A Control Theoretical Approach, Yaya Wei, Chuang Lin, Raad Raad, Fengyuan Ren

Faculty of Engineering and Information Sciences - Papers: Part A

The guard channel scheme in wireless mobile networks has attracted and is still drawing research interest owing to easy implementation and flexible control. Dynamic guard channel schemes have already been proposed in the literature to adapt to varying traffic load. This paper presents a novel control-theoretic approach to dynamically reserve guard channels called PI-Guard Channel (PI-GC) controller that maintains the handoff blocking probability (HBP) to a predefined value; while it still improves the channel resource utilization.


A Multimedia Guidebook Implementation Using A Bluetooth Wireless Information Point Network, Matthew D'Souza, Adam Postula, Neil Bergmann, Montserrat Ros Jan 2005

A Multimedia Guidebook Implementation Using A Bluetooth Wireless Information Point Network, Matthew D'Souza, Adam Postula, Neil Bergmann, Montserrat Ros

Faculty of Engineering and Information Sciences - Papers: Part A

This paper describes the implementation of a Bluetooth Village Guide Book (VGB) scenario for use in the Kelvin Grove Urban Village located in Brisbane, Australia. An Information Point Station Network (IPSN) was developed, along with software for two types of mobile computing devices. The implementation consists of several Information Point Stations (IPSs) placed at locations of significance, with access to information items on a centralized server. Once a user is registered on the network, he/she is given the opportunity to experience context and eventually user aware information on demand and in various multimedia formats. These information items are selected ...


Using Wireless Sensors As Selection Devices For A Multimedia Guidebook Scenario, Montserrat Ros, Matthew D'Souza, Michael Chan, Konstanty Bialkowski, Adam Postula, Neil Bergmann, Andras Toth Jan 2005

Using Wireless Sensors As Selection Devices For A Multimedia Guidebook Scenario, Montserrat Ros, Matthew D'Souza, Michael Chan, Konstanty Bialkowski, Adam Postula, Neil Bergmann, Andras Toth

Faculty of Engineering and Information Sciences - Papers: Part A

This paper describes the implementation of a wireless sensor network for a multimedia guidebook scenario incorporating a pointer-sensor system for the selection of locality-aware information. An Information Point Station Network (IPSN) was developed and consists of several Information Point Stations (IPSs) placed at locations of significance, with access to information items on a centralized server. In the multimedia guidebook scenario, a user selects a particular information item to view, either by way of a menu system appearing on their mobile computing device (MCD) or a more intuitive pointer-sensor system as described in this paper. Laser sensors are placed next to ...


A Bluetooth Based Protocol For Multimedia Guidebooks On Mobile Computing Devices, Matthew D'Souza, Adam Postula, Neil Bergmann, Montserrat Ros Jan 2005

A Bluetooth Based Protocol For Multimedia Guidebooks On Mobile Computing Devices, Matthew D'Souza, Adam Postula, Neil Bergmann, Montserrat Ros

Faculty of Engineering and Information Sciences - Papers: Part A

This paper presents a Bluetooth based communications protocol used for multimedia guidebooks on mobile computing devices. Multimedia guidebooks are used in museums to allow users to access information about museum exhibits. The multimedia guidebook protocol was successfully implemented on a personal digital assistant and mobile (cell) phone platforms. The protocol overcomes some of the wireless file transfer protocol limitation issues with mobile computing devices. The protocol uses Bluetooth wireless connections as a communications medium. The protocol can be used to transfer various file formats such as image or audio files. The protocol also identifies the language content of the information ...


Mobile Locality-Aware Multimedia On Mobile Computing Devices, Matthew D'Souza, Adam Postula, Neil Bergmann, Montserrat Ros Jan 2005

Mobile Locality-Aware Multimedia On Mobile Computing Devices, Matthew D'Souza, Adam Postula, Neil Bergmann, Montserrat Ros

Faculty of Engineering and Information Sciences - Papers: Part A

This paper describes the implementation of a Bluetooth Village Guide Book (VGB) scenario for use in the Kelvin Grove Urban Village located in Brisbane, Australia. An Information Point Station Network (IPSN) was developed, along with software for two types of mobile computing devices. The implementation consists of several Information Point Stations (IPSs) placed at locations of significance, with access to information items on a centralized server. Once a user is registered on the network, he/she is given the opportunity to experience context- (and eventually user-) aware information on demand and in various multimedia formats. These information items are selected ...


A Bluetooth Wireless Network Infrastructure For Multimedia Guidebooks On Mobile Computing Devices, Matthew D'Souza, Montserrat Ros, Adam Postula, Neil Bergmann Jan 2005

A Bluetooth Wireless Network Infrastructure For Multimedia Guidebooks On Mobile Computing Devices, Matthew D'Souza, Montserrat Ros, Adam Postula, Neil Bergmann

Faculty of Engineering and Information Sciences - Papers: Part A

This paper describes the implementation of a Bluetooth Village Guide Book (VGB) scenario for use in the Kelvin Grove Urban Village located in Brisbane, Australia. An Information Point Station Network (IPSN) was developed, along with software for two types of mobile computing devices. The implementation consists of several Information Point Stations (IPSs) placed at locations of significance, with access to information items on a centralized server. Once registered, the user is given the opportunity to experience context-aware information on demand and in various multimedia formats. These information items are selected by the user, either by way of a menu system ...


Dynamic Modeling And Simulation Of A Multi Effect Humidification-Dehumidification Desalination Unit, Mohammed I. Sohel, B Dawoud Jan 2005

Dynamic Modeling And Simulation Of A Multi Effect Humidification-Dehumidification Desalination Unit, Mohammed I. Sohel, B Dawoud

Faculty of Engineering and Information Sciences - Papers: Part A

Recently solar distillation using Multi Effect Humidification-dehumidification (MEH) cycle is receiving special attention. In this communication detailed models of MEH are presented that take into account most of the dynamic behavior with reasonable accuracy. Using these models simulation was carried out and the results of simulation were discussed in this paper. To find out the competence of the newly developed models, some of the simulation results were compared with the available experimental data in the literature. It turned out that the result of simulation give a very good agreement with the experimental data. The maximum deviation between simulation and experimental ...


A Simple Convergence Comparison Of Gallager Codes Under Two Message-Passing Schedules, Sheng Tong, Xinmei Wang Jan 2005

A Simple Convergence Comparison Of Gallager Codes Under Two Message-Passing Schedules, Sheng Tong, Xinmei Wang

Faculty of Engineering and Information Sciences - Papers: Part A

The convergence rate of iterative decoding of Gallager codes on the additive white Gaussian noise (AWGN) channel using the sum-product algorithm (SPA) under the flooding schedule (FS) is compared with that under the turbo-decoding schedule (TDS). Analyses using extrinsic information transfer (EXIT) charts show that TDS exhibits a much faster convergence behavior than FS.


Convergence Rates Comparison Of Sum-Product Decoding Of Ra Codes Under Different Message-Passing Schedules, Sheng Tong, Baoming Bai, Xinmei Wang Jan 2005

Convergence Rates Comparison Of Sum-Product Decoding Of Ra Codes Under Different Message-Passing Schedules, Sheng Tong, Baoming Bai, Xinmei Wang

Faculty of Engineering and Information Sciences - Papers: Part A

In iterative decoding of turbo-like codes, serial schedule generally provides a much faster convergence rate compared with parallel schedule. With the aid of extrinsic information transfer (EXIT) charts, sum-product decoding of repeat accumulate (RA) codes under both message passing schedules is investigated as an example for verifying the above statement.


Box-Minus Operation And Application In Sum-Product Algorithm, S Tong, P Wang, D Wang, X Wang Jan 2005

Box-Minus Operation And Application In Sum-Product Algorithm, S Tong, P Wang, D Wang, X Wang

Faculty of Engineering and Information Sciences - Papers: Part A

A new formula for box-minus operation, which separates the box-minus operation into sign and reliability operations, was derived. Its application in the sum-product algorithm (SPA) was also investigated. Both box-plus operation and box-minus operation were divided into sign operation and reliability operation. The results show that on using the box-minus operation, SPA can be implemented with less decoding latency and complexity.


Ozchi 2005 Doctoral Consortium Application, Robert B. K. Brown Jan 2005

Ozchi 2005 Doctoral Consortium Application, Robert B. K. Brown

Faculty of Engineering and Information Sciences - Papers: Part A

Formal methods of generating and specifying requirements have a chequered past when it comes to dealing with interface design. The Human Computer Interface (HCI) community have not adopted formal methods with open arms [Paterno 96]. If the accurate determination of stakeholder requirements is a significant factor in determining software project success, this thesis turns to a theory based in psychology and sociology to understand these capricious actors, the misunderstanding of whose whims can bring down 70% of software projects. This thesis will deploy Activity Theory as a basis for a proposed system design method and present initial conceptions and some ...


Measuring Preparedness To Teach With Ict, Patricia A. Forster, Vaille M. Dawson, Doug Reid Jan 2005

Measuring Preparedness To Teach With Ict, Patricia A. Forster, Vaille M. Dawson, Doug Reid

Faculty of Engineering and Information Sciences - Papers: Part A

In this paper we discuss the development and implementation of a questionnaire that measures preparedness to teach secondary school science with information and communication technologies (leT). The questionnaire was designed for the purpose of evaluating the effectiveness of instruction in a science education unit in a Graduate Diploma teacher education course. Rasch analysis of the pre- and post-unit responses indicated domains of expertise for which students perceived they had improved their knowledge during the unit, and domains for which they perceived they were less knowledgeable after the unit than before it. We discuss students' responses in relation to the unit ...


Some Analytical Solutions For Problems Involving Highly Frictional Granular Materials, Ngamta Thamwattana Jan 2005

Some Analytical Solutions For Problems Involving Highly Frictional Granular Materials, Ngamta Thamwattana

Faculty of Engineering and Information Sciences - Papers: Part A

Published abstract of thesis submitted to The University of Wollongong, August 2004. Full thesis can be found at http://ro.uow.edu.au/theses/239.


An Alexsandrov Type Theorem For K-Convex Functions, Nirmalendu Chaudhuri, Neil Trudinger Jan 2005

An Alexsandrov Type Theorem For K-Convex Functions, Nirmalendu Chaudhuri, Neil Trudinger

Faculty of Engineering and Information Sciences - Papers: Part A

In this note we show that k-convex functions on Rn are twice differentiable almost everywhere for every positive integer k > n/2. This generalises Alexsandrov's classical theorem for convex functions.


Subquotients Of Hecke C*-Algebras, Nathan Brownlowe, Nadia Larsen, Ian Putnam, Iain Raeburn Jan 2005

Subquotients Of Hecke C*-Algebras, Nathan Brownlowe, Nadia Larsen, Ian Putnam, Iain Raeburn

Faculty of Engineering and Information Sciences - Papers: Part A

We realize the Hecke C*-algebra CQ of Bost and Connes as a direct limit of Hecke C*-algebras which are semigroup crossed products by NF, for F a finite set of primes. For each approximating Hecke C*-algebra we describe a composition series of ideals. In all cases there is a large type I ideal and a commutative quotient, and the intermediate subquotients are direct sums of simple C*-algebras. We can describe the simple summands as ordinary crossed products by actions of ZS for S a finite set of primes. When |S|=1, these actions ...