Browsing by Author "Chung, C. C."

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Development of TDR penetrometer through theoretical and laboratory investigations: 1. Measurement of soil dielectric permittivity
(2006-07-01)
Lin, C. P.
;
Tang, S. H.
;
Chung, C. C.
;
交大名義發表
;
National Chiao Tung University
To better characterize a bulk soil electrically, both the electrical conductivity and dielectric permittivity should be measured. This study developed a time domain reflectometry (TDR) penetrometer to allow simultaneous measurements of dielectric permittivity and electrical conductivity during cone penetration. A TDR penetrometer is formed by placing a multiple-conductor waveguide around a nonconducting shaft. Probe design considerations and calibration methods for measuring dielectric constant were first theoretically discussed and then evaluated through laboratory investigations. A prototype TDR penetrometer was fabricated and used to perform simulated penetration tests in a calibration chamber. The effect of penetration disturbance on dielectric constant is quantitatively reported and explained. The implications of the data that can be measured by the TDR penetrometer are also discussed.
Development of TDR penetrometer through theoretical and laboratory investigations: 2. Measurement of soil electrical conductivity
(2006-07-01)
Lin, C. P.
;
Chung, C. C.
;
Tang, S. H.
;
交大名義發表
;
National Chiao Tung University
A TDR penetrometer was introduced to allow simultaneous measurements of dielectric permittivity and electrical conductivity during cone penetration. This study focused on the theoretical development and experimental evaluation of electrical conductivity measurement using the TDR penetrometer. Theoretical development takes into account the cable resistance and nonconducting cone shaft, leading to a new data reduction equation and calibration procedure. Measurement sensitivity and spatial sampling bias were experimentally evaluated for various probe configurations. The results show that the measurement sensitivity of interest may be controlled by the geometric factor of the probe. The complication and implications of the spatial weighting bias are discussed. A prototype TDR penetrometer was calibrated and used to perform simulated penetration tests in a soil. Experimental results do not show significant errors in electrical conductivity due to the penetration disturbance, verifying the effectiveness of the TDR penetrometer for electrical conductivity measurement.
Effect of substrate misorientation on the material properties of GaAs/Al(0.3)Ga(0.7)As tunnel diodes
(2010-12-06)
Yu, H. W.
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Chang, E. Y.
;
Nguyen, H. Q.
;
Chang, J. T.
;
Chung, C. C.
The effect of substrate misorientation on the material quality of the N(++)-GaAs/P(++)-AlGaAs tunnel diodes (TDs) grown on these substrates is investigated. It is found that the misorientation influences both surface roughness and interface properties of the N(++)-GaAs/P(++)-AlGaAs TDs. Smooth surface (rms roughness: 1.54 angstrom) and sharp interface for the GaAs/Al(0.3)Ga(0.7)As TDs were obtained when the (100) tilted 10 degrees off toward [111] GaAs substrate was used. Besides, the oxygen content in N(++)-GaAs and P(++)-AlGaAs layers grown on the 10 degrees off GaAs substrates was reduced due to the reduction of sticking coefficient and number of anisotropic sites. (C) 2010 American Institute of Physics. [doi:10.1063/1.3525158]
Effect of substrate misorientation on the material properties of GaAs/Al0.3Ga0.7As tunnel diodes
(2010-12-06)
Yu, H. W.
;
Chang, E. Y.
;
Nguyen, H. Q.
;
Chang, J. T.
;
Chung, C. C.
The effect of substrate misorientation on the material quality of the N++-GaAs/P++-AlGaAs tunnel diodes (TDs) grown on these substrates is investigated. It is found that the misorientation influences both surface roughness and interface properties of the N++-GaAs/P++-AlGaAs TDs. Smooth surface (rms roughness: 1.54 angstrom) and sharp interface for the GaAs/Al0.3Ga0.7As TDs were obtained when the (100) tilted 10 degrees off toward [111] GaAs substrate was used. Besides, the oxygen content in N++-GaAs and P++-AlGaAs layers grown on the 10 degrees off GaAs substrates was reduced due to the reduction of sticking coefficient and number of anisotropic sites. (C) 2010 American Institute of Physics. [doi:10.1063/1.3525158]