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Study on the transient characteristics of the sensor tube of a thermal mass flow meter
Full text linkIn the present work, a simple numerical model for transient heat transfer phenomena involving the sensor tube of a thermal mass flow meter (TMFM) is presented. In order to validate the proposed model, extensive experimental investigations are performed. Based on the results of the proposed model, the transient heat transfer mechanism in the sensor tube is explained. Finally, a correlation for predicting the response time of the sensor tube is presented. This correlation can estimate the response time of the sensor tube quantitatively with errors of less than 30%. By using the proposed correlation, physical meanings and characteristics of the response time of the sensor tube are presented. (c) 2005 Elsevier Ltd. All rights reserved.The present work was funded by Korea Institute of
Science & Technology Evaluation and Planning under
grant number 2-578 through the National Research
Lab Program. This assistance is greatly appreciated
Very small oxide-confined vertical microcavity lasers with high-contrast AlGaAs-AlxOy mirrors
No full textWe report the photo-pumped lasing action from a very small oxide-confined 870-nm vertical microcavity lasers with high-contrast AlGaAs-AlxOy mirrors. The effective cavity length is as small as 0.37 mu m, and the oxide aperture size is 0.74 mu m, estimated from the blue-shift of lasing mode due to the lateral confinement. The observed blue-shift of the lasing mode is 13.4 nm, the largest one ever reported for vertical cavity lasers. The optical losses seem to be size-independent for these small microcavity lasers. Our results indicate the possibility of the ultimate microcavity of order of lambda(3).The authors thank M. J. Noble in AFIT/ENG for the helpful
discussions
Study on the steady-state characteristics of the sensor tube of a thermal mass flow meter
Full text linkIn the present work, a simple numerical model for steady-state heat transfer phenomena occurring in the sensor tube of a thermal mass flow meter (TMFM) is presented. In order to validate the proposed model, extensive experimental investigations are performed. Based on the results from the validated model, a correlation for predicting the linear range of the TMFM is presented. Finally, the effects of engineering parameters on the linear range are investigated. (c) 2006 Elsevier Ltd. All rights reserved.This work was supported by KOSEF (Korea Science and
Engineering Foundation) through the National Research
Lab Program (Grant No. M1060000022406J000022410)
Oxide-apertured photodetector integrated on vertical cavity surface emitting laser
No full textThe authors have designed and fabricated oxide-apertured photodetectors Integrated with vertical cavity surface emitting lasers (VCSELs). The photocurrent originating from spontaneous emission is suppressed by more than a factor of 10 in this integrated photodetector owing to the use of nonradiative recombination at the GaAs/oxide interface. In addition, the unavoidable internal loss from the detector is minimised by locating the GaAs detection layer as far as possible from the VCSEL cavity.The authors are grateful to K.H. Ha for helpful discussion, to H.W. Choi for deutron implantation, and to Samsung for the VCSEL wafer
1.5 mu m vertical-cavity surface-emitting lasers utilising low loss AlxOy/GaAs mirrors
No full textLow threshold power vertical-cavity surface-emitting lasers are fabricated by using low loss AlxOy/GaAs mirrors as output couplers. A 5 mu m-aperture laser with a low threshold CW pump power of 1.4 mW at room temperature and a 16 mu m-aperture laser operating in CW mode up to 64 degrees C are produced
Continuous room-temperature operation of optically-pumped two dimensional photonic crystal lasers at 1.6 ㎛
No full textEffect of nonradiative recombination on light emitting properties of two-dimensional photonic crystal slab structures
No full textInGaAsP-based two-dimensional photonic crystal light emitting structures are fabricated by employing wafer fusion and characterized optically. The structure does not contain defect regions and the whole area of the photonic crystal is used for light generation and extraction. The effect of nonradiative recombination is studied as a function of pump power. The relative contribution of surface recombination can be as low as 10% as pump power increases since carrier recombination is dominated by Auger recombination. In spite of the large surface-to-volume ratio of the photonic crystal pattern, over four-fold enhancement of photoluminescence extraction efficiency is observed. (C) 2001 American Institute of Physics.This work was supported by the National Laboratory
Project of Korea
GaAs/AlGaAs quantum well intermixing using buried Al-oxide layer
No full textUsing burial wet-oxidised AlxOy layers to enhance impurity free vacancy diffusion. the intermixing of GaAs/AlGaAs quantum wells has been achieved A 70 Angstrom thick GaAs quantum well shows a blueshift of 59meV when the sample is annealed at 950 degrees C for 120s. By cathodeluminescence measurements. it is confirmed that the bandgap transition region is localised laterally within 1 mu m of the oxide/nonoxide interface
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