| 1. |
- Wallerstedt, Cecilia, 1976, et al.
(författare)
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Socioculturally-informed Interaction Analysis (SIA): Methodology and theoretical and empirical contributions of an emerging research program in early childhood education
- 2022
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Ingår i: International Research in Early Childhood Education. - 1838-0689. ; 12:1, s. 1-23
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Tidskriftsartikel (refereegranskat)abstract
- Over the last decade, a Swedish research group has conducted several empirical studiesin the field of Early Childhood Education (ECE). These studies are examples of what is sometimes referred to as practice-based studies, and they are often conducted in collaboration with ECE personnel. In this meta-study, we review 37 publications from the research group to highlight key contributions in terms of methodological issues or challenges identified,as well as empirical findings and theoretical developments. We argue that these studies constitute an emerging research program, termed Socioculturally-informed Interaction Analysis(SIA). Key aspects of SIA are:examining learning as a process, using recordings to avoid bias, considering pragmatic validity when working with transcriptions, making claims closely aligned with what is studied (ecological validity), and viewing context as an analytical rather than as a descriptive concept,and generalising at a conceptual level, which affords empirical generalisation.
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| 2. |
- Andersson, Ola, 1976-, et al.
(författare)
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Spectral shaping of DAC nonlinearity errors through modulation of expected errors
- 2001
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Ingår i: Circuits and Systems, 2001. ISCAS 2001. The 2001 IEEE International Symposium on. - : IEEE. - 0780366859 ; , s. 417-420
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Konferensbidrag (refereegranskat)abstract
- Traditionally, delta-sigma modulation has been used for shaping of quantization noise. We present a modified version of delta-sigma modulation which also takes into account unwanted nonlinearities by feeding back not only the quantization error, but also the expected physical error. Behavioral-level simulations of a 5th-order structure showing an improvement of up to 4 effective bits are included
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| 3. |
- Eriksson, Lars-Erik, 1950, et al.
(författare)
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Development of a Cooled Radial Flameholder for the F404/RM12 Afterburner: Part III Afterburner Rumble Prediction and Suppression
- 2003
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Ingår i: ISABE-2003-1060, proc. of 16th ISABE Conf, Cleveland Ohio, September 2003.
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Konferensbidrag (refereegranskat)abstract
- One-dimensional methods used for solving acoustic instabilities are of doubtful value in the design of afterburner systems. In this paper a three-dimensional method developed and used at Volvo Aero Corporation is described. The method deals with the mean flow and the perturbation flow separately. The perturbation part is based on the linearized Euler equations (time domain) for compressible multi-species flow together with a spectrum trans-formation and Arnoldis method for eigenmode extraction.
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| 4. |
- Lai, Szhau, 1985, et al.
(författare)
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Accurate Phase-Noise Prediction for a Balanced Colpitts GaN HEMT MMIC Oscillator
- 2013
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Ingår i: IEEE Transactions on Microwave Theory and Techniques. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9480 .- 1557-9670. ; 61:11, s. 3916-3926
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents an X-band balanced Colpitts oscillator in GaN HEMT technology and a method to calculate its phase noise accurately. The method employs a low-frequency (LF) noise measurement and the oscillator waveforms from a harmonic-balance simulator. These data are post-calculated by Hajimiri's phase-noise model, in which the LF noise can be activated with a cyclo-stationary effect in the calculation of phase noise. Compared to commercial phase-noise simulation using predefined stationary noise, the calculation gives significantly improved phase-noise prediction in the 30-dB/decade region near carrier. The prediction is within 3-dB accuracy at 10-kHz, 100-kHz, and 1-MHz offset frequencies. In addition to the method used for phase-noise prediction, the potential for wideband tuning of this oscillator topology is analytically investigated. The measured phase noise of the oscillator is -102 dBc/Hz at 100-kHz offset from a 8.6-GHz carrier frequency for drain voltage and current of Vd = 15 V amd Id = 40 mA.
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| 5. |
- Sudow, Mattias, 1980, et al.
(författare)
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An AlGaN/GaN HEMT-Based Microstrip MMIC Process for Advanced Transceiver Design
- 2008
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Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 56:8, s. 1827-1833
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Tidskriftsartikel (refereegranskat)abstract
- A MMIC process in AlGaN/GaN technology for advanced transceiver design has been developed. The process is based on microstrip technology with a complete model library of passive elements and AlGaN/GaN HEMTs. The transistor technology in this process is suitable for both power and low noise design, demonstrated with a power density of 5 W/mm, and an ${rm NF}_{min}$ of 1.4 dB at $X$ -band. Process stability of subcircuits, complementary to power amplifiers and LNAs, in a transceiver system have been investigated. The results indicate that an all AlGaN/GaN MMIC transceiver is realizable using this technology.
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| 6. |
- Sudow, Mattias, 1980, et al.
(författare)
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An SiC MESFET-based MMIC process
- 2006
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Ingår i: IEEE Transactions on Microwave Theory and Techniques. ; 54:12, Part 1, s. 4072-4078
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Tidskriftsartikel (refereegranskat)abstract
- A monolithic microwave integrated circuit (MMIC)process based on an in-house SiC MESFET technology has been developed. The process uses microstrip technology, and a complete set of passive components, including MIMcapacitors, spiral inductors,thin-film resistors, and via-holes, has been developed. The potential of the process is demonstrated by an 8-W power amplifierat 3 GHz, a high-linearity -band mixer showing a third-order intercept point of 38 dBm, and a high-power limiter.
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| 7. |
- Sudow, Mattias, 1980, et al.
(författare)
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The Chalmers microstrip SiC MMIC Process
- 2005
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Ingår i: Conference Proceedings Gighahertz 2005.
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Konferensbidrag (refereegranskat)abstract
- A generic microstrip MMIC process targeted for SiC and GaN technology has beendeveloped. Passive components for high power operation were developed and verified. Circuit modelsfor both passive and active components have been formulated. Using the developed MMIC process anamplifier and a limiter have been manufactured.
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| 8. |
- Thorsell, Mattias, 1982, et al.
(författare)
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An X-Band AlGaN/GaN MMIC Receiver Front-End
- 2010
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Ingår i: IEEE Microwave and Wireless Components Letters. - 1558-1764 .- 1531-1309. ; 20:1, s. 55-57
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Tidskriftsartikel (refereegranskat)abstract
- This letter presents an integrated AlGaN/GaN X-band receiver front-end. This is to the authors knowledge the first published results of an integrated AlGaN/GaN MMIC receiver front-end. The receiver uses an integrated SPDT switch to reduce size, weight and cost compared to circulator based transceiver front-ends. The integrated front-end has more than 13 dB of gain and a noise figure of 3.5 dB at 11 GHz.
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| 9. |
- ÖZEN, MUSTAFA, 1984, et al.
(författare)
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High efficiency RF pulse width modulation with tunable load network class-E PA
- 2011
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Ingår i: 2011 IEEE 12th Annual Wireless and Microwave Technology Conference, WAMICON 2011. - 9781612840819
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Konferensbidrag (refereegranskat)abstract
- In this paper, a 10 W peak power 2 GHz highly efficient RF pulse width modulation (RF-PWM) based transmitter is presented. RF-PWM signals are generated with a dedicated 65 nm CMOS modulator and subsequently amplified with a GaN Class-E power amplifier (PA). The modulator use extended drain MOS (EDMOS) high voltage transistors to provide the required voltage swing to drive the GaN used as a switch. The imaginary load impedance of the Class-E is electronically tunable and is implemented with in-house high breakdown voltage SiC varactors. The tunable imaginary load impedance enables optimization of the Class-E versus the duty cycle (pulse width). The peak efficiency is therefore preserved over a wide range of output power levels. The measured drain efficiency of the Class-E output stage is above 70% over a 6.5 dB output power dynamic range. The overall transmitter efficiency is above 60% for the same dynamic range.
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| 10. |
- Abou-Taouk, Abdallah, 1982, et al.
(författare)
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CFD analysis of a SGT-800 burner in a combustion RIG
- 2016
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Ingår i: ASME Turbo Expo, June 13 – 17, 2016, Seoul, South Korea. ; 4B-2016
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Konferensbidrag (refereegranskat)abstract
- This work focuses on 3D turbulent reacting flow modeling of a SGT-800 3rd generation dry low emission (DLE) burner at both atmospheric and engine-like conditions. At atmospheric pressure the burner is fitted in a test rig with high pre-heating of the incoming air. To reduce the computational cost, the M4 mechanism previously developed by Abou-Taouk et al. (2013) is used for operating pressure of 1 bar. A new novel optimized 4-step reaction mechanism for methane-air mixture is developed in the present work at an operating pressure of 20 bar. The mechanism is based on a large sample of detailed chemistry solutions that are processed by an iterative optimization procedure. This leads to a reduced 4-step mechanism, reproducing the targeted detailed chemistry solutions in terms of laminar flame speeds, species profiles and temperatures. The CFD simulations are performed using the combined eddy dissipation model / finite rate chemistry (EDM/FRC) turbulence chemistry interaction model. The turbulence is modeled using both the k-ω SST and the scale adaptive simulation (SAS) turbulence models. A comprehensive testing and measurement campaign carried out at atmospheric pressure for this burner was previously performed in a combustion test rig. The CFD results are compared to measurement data which includes for example flame position and pressure drop.
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