The layered dependency structure matrix for managing collaborative design processes

Cataloged from PDF version of article.Effective collaboration and knowledge management are the major contributors of success in the construction industry. Although a huge amount of interdisciplinary knowledge is exchanged in building design processes, there is a lack of tools for representing information flows. Therefore, this paper focuses on the collaboration between architects and structural engineers and introduces an innovative matrix-based tool named “The Layered Dependency Structure Matrix” for modeling and managing the discipline-specific and collaborative design activities. The proposed method is compared with the conventional techniques used in the industry and its application is demonstrated in a beam design example

The Virtual Design Studio on the Cloud: a Blended and Distributed Approach for Technology-mediated Design Education

Cataloged from PDF version of article.The studio is widely accepted as the core in design education because it aims to integrate many curricular topics within its scope. However, learning environments in studio teaching have not been explored and exploited as a response to developing technology and changing socio-cultural context, yet. In order to alleviate the problem, this paper presents an innovative model for a virtual design studio which utilizes social networking media and cloud computing. The virtual design studio is conceptualized as a socio-technical system where intelligence is distributed across people and tools. The study proposes several means of augmenting intelligence in such a studio. The application of the theoretical framework is demonstrated in a real-life case study. The results of an empirical survey show that the proposed model was well accepted by the students. In the paper, the opportunities and challenges of this approach are discussed and suggestions are made for further studies

Experiences with Moodle as a communication tool for design teamwork: a users' perspective

Cataloged from PDF version of article

Blended learning in design education: an analysis of students' experiences within the disciplinary differences framework

Cataloged from PDF version of article.Blended learning has already become an indispensable part of education in many fields. However, the majority of existing research on blended learning has assumed homogeneity of disciplines. This study suggests that research highlighting disciplinary effects and differences is much needed to effectively develop courses and tools consonant with the characteristics of each discipline. To help close this research gap, this paper focuses on design education and analyses student experiences in a "blended design studio" that combined the Moodle learning management system, live videoconferencing, and social networking media (Facebook) with traditional face-to-face learning (design studio). Students' perceptions of the methods and tools were elicited through structured and open-ended questions and qualitative variations in responses were categorised. Subsequent quantitative analysis revealed that the characteristics of soft-applied fields require customisation in blended courses and educational system designs in several ways

Investigation of AlInN HEMT structures with different AlGaN buffer layers grown on sapphire substrates by MOCVD

Cataloged from PDF version of article.We investigate the structural and electrical properties of AlxIn1-xN/AlN/GaN heterostructures with AlGaN buffers grown by MOCVD, which can be used as an alternative to AlInN HEMT structures with GaN buffer. The effects of the GaN channel thickness and the addition of a content graded AlGaN layer to the structural and electrical characteristics were studied through variable temperature Hall effect measurements, high resolution XRD, and AFM measurements. Enhancement in electron mobility was observed in two of the suggested AlxIn1-xN/AlN/GaN/Al0.04Ga0.96N heterostructures when compared to the standard AlxIn1-xN/AlN/GaN heterostructure. This improvement was attributed to better electron confinement in the channel due to electric field arising from piezoelectric polarization charge at the Al0.04Ga0.96N/GaN heterointerface and by the conduction band discontinuity formed at the same interface. If the growth conditions and design parameters of the AlxIn1-xN HEMT structures with AlGaN buffers can be modified further, the electron spillover from the GaN channel can be significantly limited and even higher electron mobilities, which result in lower two-dimensional sheet resistances, would be possible. (C) 2012 Elsevier B.V. All rights reserved

Double subband occupation of the two-dimensional electron gas in InxAl1− xN/AlN/ GaN/AlN heterostructures with a low indium content (0.064≤x≤0.140) barrier

Cataloged from PDF version of article.We present a carrier transport study on low indium content (0.064≤x≤0.140) InxAl1−xN/AlN/GaN/AlN heterostructures. Experimental Hall data were carried out as a function of temperature (33–300 K) and a magnetic field (0–1.4 T). A two-dimensional electron gas (2DEG) with single or double subbands and a twodimensional hole gas were extracted after implementing quantitative mobility spectrum analysis on the magnetic field dependent Hall data. The mobility of the lowest subband of 2DEG was found to be lower than the mobility of the second subband. This behavior is explained by way of interface related scattering mechanisms, and the results are supported with a one-dimensional self-consistent solution of non-linear Schrödinger–Poisson equations

Electron transport properties in Al0.25Ga0.75N/AIN/GaN hetrostructures with different InGaN back barrier layers and GaN channel thickness grown by MOCVD

Cataloged from PDF version of article.The electron transport properties in Al0.25Ga0.75N/AlN/GaN/InxGa1-xN/GaN double heterostructures with various indium compositions and GaN channel thicknesses were investigated. Samples were grown on c-plane sapphire substrates by MOCVD and evaluated using variable temperature Hall effect measurements. In order to understand the observed transport properties, various scattering mechanisms, such as acoustic phonon, optical phonon, interface roughness, background impurity, and alloy disorder, were included in the theoretical model that was applied to the temperature-dependent mobility data. It was found that low temperature (T 160 K), optical phonon scattering is the dominant scattering mechanism for AlGaN/AlN/GaN/InGaN/GaN heterostructures. The higher mobility of the structures with InGaN back barriers was attributed to the large conduction band discontinuity obtained at the channel/buffer interface, which leads to better electron confinement. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinhei

Contributions of impurity band and electron-electron interactions to magnetoconductance in AlGaN

Low temperature electrical measurements of conductivity, the Hall effect and magnetoconductance were performed on a degenerate AlGaN sample. The sample exhibited negative magnetoconductance at low magnetic fields and low temperatures, with the magnitude being systematically dependent on temperature. The measured magnetoconductance was compared with models proposed previously by Sondheimer and Wilson [Proc. R. Soc. Lond. Ser. A 190 (1947) p. 435] and Lee and Ramakrishan [Rev. Mod. Phys. 57 (1985) p. 287]. Data were analyzed as the sum of the contribution of a two-band and electron-electron interactions to the magnetoconductance, applying these models to describe the observed behavior. Least-squares fits to the data are presented. In the sample, magnetoconductance can be explained reasonably well by assuming these contributions to the measured magnetoconductance. It was found that theoretical and experimental data were in excellent agreement. © 2010 Taylor & Francis

Investigation of AlInN HEMT structures with different AlGaN buffer layers grown on sapphire substrates by MOCVD

We investigate the structural and electrical properties of Al xIn 1-xN/AlN/GaN heterostructures with AlGaN buffers grown by MOCVD, which can be used as an alternative to AlInN HEMT structures with GaN buffer. The effects of the GaN channel thickness and the addition of a content graded AlGaN layer to the structural and electrical characteristics were studied through variable temperature Hall effect measurements, high resolution XRD, and AFM measurements. Enhancement in electron mobility was observed in two of the suggested Al xIn 1 -xN/AlN/GaN/Al 0.04Ga 0.96N heterostructures when compared to the standard Al xIn 1 -xN/AlN/GaN heterostructure. This improvement was attributed to better electron confinement in the channel due to electric field arising from piezoelectric polarization charge at the Al 0.04Ga 0.96N/GaN heterointerface and by the conduction band discontinuity formed at the same interface. If the growth conditions and design parameters of the Al xIn 1-xN HEMT structures with AlGaN buffers can be modified further, the electron spillover from the GaN channel can be significantly limited and even higher electron mobilities, which result in lower two-dimensional sheet resistances, would be possible. © 2012 Elsevier B.V. All rights reserved

Well parameters of two-dimensional electron gas in Al0.88In 0.12N/AlN/GaN/AlN heterostructures grown by MOCVD

Resistivity and Hall effect measurements were carried out as a function of magnetic field (0-1.5 T) and temperature (30-300 K) for Al0.88In 0.12N/AlN/GaN/AlN heterostructures grown by Metal Organic Chemical Vapor Deposition (MOCVD). Magnetic field dependent Hall data were analyzed by using the quantitative mobility spectrum analysis (QMSA). A two-dimensional electron gas (2DEG) channel located at the Al0.88In 0.12N/GaN interface with an AlN interlayer and a two-dimensional hole gas (2DHG) channel located at the GaN/AlN interface were determined for Al 0.88In0.12N/AlN/GaN/AlN heterostructures. The interface parameters, such as quantum well width, the deformation potential constant and correlation length as well as the dominant scattering mechanisms for the Al 0.88In0.12N/GaN interface with an AlN interlayer were determined from scattering analyses based on the exact 2DEG carrier density and mobility obtained with QMSA. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA