Browsing by Author "Chang, Cheng-Ping"

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Double thermoelectric power factor of a 2D electron system
(2018-06-20)
Zhang, Yuqiao
;
Feng, Bin
;
Hayashi, Hiroyuki
;
Chang, Cheng-Ping
;
Sheu, Yu-Miin
Two-dimensional electron systems have attracted attention as thermoelectric materials, which can directly convert waste heat into electricity. It has been theoretically predicted that thermoelectric power factor can be largely enhanced when the two-dimensional electron layer is far narrower than the de Broglie wavelength. Although many studies have been made, the effectiveness has not been experimentally clarified thus far. Here we experimentally clarify that an enhanced two-dimensionality is efficient to enhance thermoelectric power factor. We fabricated superlattices of [N unit cell SrTi1-xNbxO3 vertical bar 11 unit cell SrTiO3](10)-there are two different de Broglie wavelength in the SrTi1-xNbxO3 system. The maximum power factor of the superlattice composed of the longer de Broglie wavelength SrTi1-xNbxO3 exceeded similar to 5 mWm(-1) K-2, which doubles the value of optimized bulk SrTi1- xNbxO3. The present approach-use of longer de Broglie wavelength-is epoch-making and is fruitful to design good thermoelectric materials showing high power factor.
Exposure assessment of nano-sized and respirable particles at different workplaces
(2011-09-01)
Tsai, Chuen-Jinn
;
Huang, Cheng-Yu
;
Chen, Sheng-Chieh
;
Ho, Chi-En
;
Huang, Cheng-Hsiung
In this study, nanoparticle (NP, diameter < 100 nm) and respirable particles measurements were conducted at three different nanopowder workplaces, including the mixing area of a nano-SiO(2)-epoxy molding compound plant (primary diameter: 15 nm), bagging areas of a nano-carbon black (nano-CB) (primary diameter: 32 nm) and a nano-CaCO(3) (primary diameter: 94 nm) manufacturing plant. Chemical analysis of respirable particle mass (RPM) and NPs was performed to quantify the content of manufactured nanoparticles in the collected samples. Nanopowder products obtained from the plants were used in the laboratory dustiness testing using a rotating drum tester to obtain particle mass and number distributions. The obtained laboratory data were then used to elucidate the field data. Both field and laboratory data showed that NP number and mass concentrations of manufactured materials were close to the background level. Number concentration was elevated only for particles with the electrical mobility diameter > 100 nm during bagging or feeding processes, unless there were combustion-related incidental sources existed. Large fraction of nanomaterials was found in the RPM due to agglomeration of nanomaterials or attachment of nanomaterials to the larger particles. From this study, it is concluded that RPM concentration measurements are necessary for the exposure assessment of nanoparticles in workplaces.
Measurements of respirable dust and nanoparticle concentrations in a titanium dioxide pigment production factory
(2010)
Huang, Cheng-Hsiung
;
Tai, Chih-Yuan
;
Huang, Cheng-Yu
;
Tsai, Chuen-Jinn
;
Chen, Chun-Wan
This study compared respirable dust and nanoparticle concentrations measured by different sampling devices at a titanium dioxide pigment factory. Respirable particle mass concentrations, nanoparticle concentrations, particle size distribution and particle metallic content were measured at different sampling locations. The sampling results of the Multi-orifice Uniform Deposit Impactor (MOUDI) showed that the particle size distribution at this titanium dioxide production factory fell in the range of 1-10 mu m. Generally, the higher levels of the respirable particle mass concentrations and nanoparticle number concentrations were near the packing site of the pigment titanium dioxide production factory. Metal analysis results revealed that the titanium dioxide concentrations in respirable dust and nanoparticles were within the limits specified by National Institute for Occupational Safety and Health (NIOSH). During sampling, particle metallic content analysis is essential for identifying the source of particles and for measuring respirable dust and nanoparticle concentrations.