Browsing by Author "Chen, DR"

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A universal calibration curve for the TSI aerodynamic particle sizer
(2004-05-01)
Tsai, CJ
;
Chen, SC
;
Huang, CH
;
Chen, DR
;
環境工程研究所
A universal calibration curve for the accurate determination of particle aerodynamic diameter by the TSI APS (TSI, Inc., St. Paul, MN, USA) operating at various temperature, pressure, particle, and gas properties is proposed. The previous dimensionless APS response function proposed by Chen et al. (1985) uses the Stokes number as the governing parameter and is valid in the Stokesian regime only. In the non-Stokesian regime, an additional non-Stokesian correction factor is needed to correct for the indicated aerodynamic diameters of the APS. The universal curve in the present study is based on the relationship between V-p* and Stm, where V-p* = V-p /V-g and V-p is particle velocity, V-g is gas velocity at the nozzle exit, and Stm is modified Stokes number. Stm incorporates the non-Stokesian effect and is defined as 24St/(Re* C-D), where Re is the flow Reynolds number and C-D is the particle drag coefficient. We find that the new calibration curve can predict the particle aerodynamic diameter accurately within 6% of error under different operating conditions and particle/gas properties from the referenced condition without the need to introduce additional correction factors.
Interfacial reactions of Pd/Si0.76Ge0.24 by pulsed KrF laser annealing
(1998-09-07)
Chen, DR
;
Luo, JS
;
Lin, WT
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Chang, CY
;
Shih, PS
The interfacial reactions of Pd/Si0.76Ge0.24 were studied by pulsed KrF laser annealing as a function of energy density and pulse number. At an energy density of 0.1-0.4 J/cm(2), a continuous germanosilicide layer composed of a low-temperature phase, Pd-2(Si1-xGex), and a high-temperature phase, Pd(Si1-xGex), was formed. Incontrast to vacuum annealing, Ge segregation out of the germanosilicide layer and the strain relaxation of the residual Si0.76Ge0.24 film could be effectively suppressed by pulsed KrF laser annealing at 0.1 J/cm(2). Multiple pulse annealing at 0.1 J/cm(2) could further homogenize the Pd concentration of the germanosilicide layer and promote the growth of Pd(Si1-xGex). Concurrently, the smoothness of the germanosilicide layer was substantially improved in comparison with those grown by vacuum annealing at temperatures above 200 degrees C. The studies also revealed that for multiple pulse annealing at 0.1 J/cm(2) with a low repetition rate, 1 Hz, the evolution of phase formation and Pd diffusion could be proceeded by each individual laser pulse. (C) 1998 American Institute of Physics. [S0003-6951(98)04136-9].
Theoretical and experimental study of an axial flow cyclone for fine particle removal in vacuum conditions
(2004-09-01)
Tsai, CJ
;
Chen, DR
;
Chein, HM
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Chen, SC
;
Roth, JL
An axial flow cyclone to remove fine particles at low pressure conditions (6-23 torr) was designed and tested. The inner diameter of the cyclone is 3.0 cm and tested flow rates are 0.455 and 1.0 slpm. A theoretical evaluation was first carried out to calculate the particle collection efficiency and cutoff diameter for the axial flow cyclone. Experiments were then conducted to test the theory at different flow rates, pressures and cyclone designs. It was demonstrated that at sufficiently low pressure of 6 torr (flow rate = 0.455 slpm), the axial flow cyclone is able to remove particles below 100 nm efficiently, and the flow Reynolds number was found to have a great effect on the particle collection efficiency. (C) 2004 Elsevier Ltd. All rights reserved.
Thermophoretic deposition of particles in laminar and turbulent tube flows
(2004-02-01)
Tsai, CJ
;
Lin, JS
;
Aggarwal, SG
;
Chen, DR
;
環境工程研究所
Thermophoretic deposition of aerosol particles (particle diameter ranges from 0.038 to 0.498 mum) was measured in a tube (1.18 m long, 0.43 cm inner diameter, stainless steel tube) using monodisperse NaCl test particles under laminar and turbulent flow conditions. In the previous study by Romay et al., theoretical thermophoretic deposition efficiencies in turbulent flow regime do not agree well with the experimental data. In this study, particle deposition efficiencies due to other deposition mechanisms such as electrostatic deposition for particles in Boltzmann charge equilibrium and laminar and turbulent diffusions were carefully assessed so that the deposition due to thermophoresis alone could be measured accurately. As a result, the semiempirical equation developed by Lin and Tsai in laminar flow regime and the theoretical equation of Romay et al. in turbulent flow regime are found to fit the experimental data of thermophoretic deposition efficiency very well with the differences of less than 1.0% in both flow regimes. It is also found that Talbot's formula for the thermophoretic coefficient is accurate while Waldmann's free molecular formula is only applicable when Kn is greater than about 3.0.