Browsing by Author "Wu, Chia-Hao"

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Digital Control Strategy for Efficiency Optimization of a BLDC Motor Driver with VOPFC
(2009)
Wu, Chia-Hao
;
Tzou, Ying-Yu
;
電機工程學系
;
Department of Electrical and Computer Engineering
This paper proposes a dual-mode control strategy for BLDC motor drivers with power factor correction used in high-efficiency compressor applications. The motor driver consists of a front-stage variable output voltage PFC (VOPFC) converter and a rear-stage 3-phase PWM inverter. The VOPFC converter is a cascaded buck-boost converter with two power switches to regulate the input line current with low total harmonic distortion (THD) and at the same time to maintain an adjustable dc-link voltage which can be either higher or lower than the peak of the rectified line voltage. The output inverter stage can be operated in pulse amplitude modulation (PAM) mode or PWM mode with reduced switching frequency for efficiency optimization of the compressor motor driver to maintain a constant V/Hz ratio with specified current ripples. The proposed control scheme has been verified with a DSP-controlled VOPFC PWM/PAM motor driver and an efficiency improvement of 3% has been achieved.
Gray-level patterning of gold nanoparticles with scanning probe lithography of self-assembly monolayer
(2007)
Sheu, Jeng-Tzong
;
Wu, Chia-Hao
;
Liu, Hao-Heng
;
Chao, Tieng-Sheng
;
材料科學與工程學系奈米科技碩博班
Novel Field-Induced Gray-Level Selective Patterning of Self-Assembled Aminosilane Monolayer on SiO(2) Surfaces by Scanning Probe Bond-Breaking Lithography
(2009-04-01)
Wu, Chia-Hao
;
Lee, Ten-Min
;
Sheu, Jeng-Tzong
;
Chao, Tieng-Sheng
;
材料科學與工程學系奈米科技碩博班
We demonstrated a successful strategy for combining the straightforward scanning probe chemical bond-breaking lithography and self-assembly monolayer (SAM) techniques for constructing nanoscale architectural structures of gold nanoparticles (AuNPs) onto modified SiO(2) surfaces. The hydroxyl-terminated surface of the sample substrate was modified by silanization with N-(2-aminoethyl)-3-aminopropyl-trimethoxysilane (AEAPTMS) molecules. Local-field-induced scanning probe bond-breaking lithography is adopted to selectively decompose the chemical bonds of AEAPTMS SAMs on aminosilane-modified SiO(2) surfaces. From the experiments, a tip bias of less than 4.5 V cannot effectively decompose chemical bonds of AEAPTMS SAMs. Gray-level selectively patterned pictures were successfully observed on a modified 2.5-nm-thick SiO(2) surface by applying dc voltage (2.5-5.5V) between the atomic force microscopy (AFM) conductive tip and the SiO(2) surface under ambient conditions. After the scanning probe selective decomposition of AEAPTMS SAMs, AuNPs with negative-charged citrate surfaces were selectively anchored in the selective patterning region via Coulomb electrostatic force. With proper control, it is considered that this novel technique can be applicable to the generation of various nanofabricated devices. (C) 2009 The Japan Society of Applied Physics
Novel Field-Induced Gray-Level Selective Patterning of Self-Assembled Aminosilane Monolayer on SiO2 Surfaces by Scanning Probe Bond-Breaking Lithography
(2009-04-01)
Wu, Chia-Hao
;
Lee, Ten-Min
;
Sheu, Jeng-Tzong
;
Chao, Tieng-Sheng
;
電子物理學系
We demonstrated a successful strategy for combining the straightforward scanning probe chemical bond-breaking lithography and self-assembly monolayer (SAM) techniques for constructing nanoscale architectural structures of gold nanoparticles (AuNPs) onto modified SiO2 surfaces. The hydroxyl-terminated surface of the sample substrate was modified by silanization with N-(2-aminoethyl)-3-aminopropyl-trimethoxysilane (AEAPTMS) molecules. Local-field-induced scanning probe bond-breaking lithography is adopted to selectively decompose the chemical bonds of AEAPTMS SAMs on aminosilane-modified SiO2 surfaces. From the experiments, a tip bias of less than 4.5 V cannot effectively decompose chemical bonds of AEAPTMS SAMs. Gray-level selectively patterned pictures were successfully observed on a modified 2.5-nm-thick SiO2 surface by applying dc voltage (2.5-5.5V) between the atomic force microscopy (AFM) conductive tip and the SiO2 surface under ambient conditions. After the scanning probe selective decomposition of AEAPTMS SAMs, AuNPs with negative-charged citrate surfaces were selectively anchored in the selective patterning region via Coulomb electrostatic force. With proper control, it is considered that this novel technique can be applicable to the generation of various nanofabricated devices. (C) 2009 The Japan Society of Applied Physics
Scanning probe lithography of self-assembled N-(2-aminoethyl)-3-aminopropyltrimethoxysilane monolayers on SiO2 surface
(2007-09-01)
Wu, Chia-Hao
;
Sheu, Jeng-Tzong
;
Chen, Chia Hao
;
Chao, Tieng-Sheng
;
材料科學與工程學系奈米科技碩博班
A new approach is introduced for the selective deposition of colloidal gold nanoparticles (AuNPs) onto the surface of unpatterned self-assembled monolayers (SAMs). The patterning of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (AEAPTMS) SAMs is realized by local field-induced bond breaking using scanning probe lithography (SPL) on a thin SiO2 surface. Different tip/sample biases were investigated to determine the bond breaking efficiency of AEAPTMS SAMs. It was found that bond breaking efficiency was limited by tunneling current through the thin SiO2 film so that both the tip bias and the tip scanning speed play important roles. AuNPs with negatively charged citrate surfaces were selectively anchored onto the unpatterned area via electrostatic force between AEAPTMS SAMs and AuNPs. Single-digit numbers of AuNPs anchored onto unpatterned AEAPTMS SAMs were demonstrated.
The effect of nanoscale confinement on the collective electron transport behavior in an nanoparticles self-assembled in a nanostructured polystyrene-block-poly(4-vinylpyridine) diblock copolymer ultra-thin film
(2007-09-24)
Li, Chung-Ping
;
Wu, Chia-Hao
;
Wei, Kung-Hwa
;
Sheu, Jeng-Tzong
;
Huang, Jung Y.
This study involves the collective electron transport behavior of sequestered Au nanoparticles in a nanostructured polystyrene-block-poly(4-vinylpyridine). The monolayer thin films (ca. 30 nm) consisting of Au nanoparticles self-assembled in the 30-nm spherical poly (4-vinylpyridine) domains of an polystyrene-block-poly (4-vinylpyridine) diblock copolymer were prepared. From the current-voltage characteristics of these thin films, the collective electron transport behavior of Au nanoparticles sequestered in the spherical poly (4-vinylpyridine) nanodomains was found to be dictated by Coulomb blockade and was quasi one-dimensional, as opposed to the three-dimensional behavior displayed by An nanoparticles that had been dispersed randomly in homo-poly(4-vinylpyridine). The threshold voltage of these composite increased linearly upon increasing the inter-nanoparticle distance. The electron tunneling rate constant in the case of Au nanoparticles confined in poly(4-vinylpyridine) nanodomains is eight times larger than that in the randomly distributed case and it increases upon increasing the amount of Au nanoparticles. This phenomenon indicates that manipulating the spatial arrangement of metal nanoparticles by diblock copolymer can potentially create electronic devices with higher performance.