214 research outputs found
Influence of the "second gap" on the transparency-conductivity compromise in transparent conducting oxides: an ab initio study
Transparent conducting oxides (TCOs) are essential to many technologies.
These materials are doped (\emph{n}- or \emph{p}-type) oxides with a large
enough band gap (ideally 3~eV) to ensure transparency. However, the high
carrier concentration present in TCOs lead additionally to the possibility for
optical transitions from the occupied conduction bands to higher states for
\emph{n}-type materials and from lower states to the unoccupied valence bands
for \emph{p}-type TCOs. The "second gap" formed by these transitions might
limit transparency and a large second gap has been sometimes proposed as a
design criteria for high performance TCOs. Here, we study the influence of this
second gap on optical absorption using \emph{ab initio} computations for
several well-known \emph{n}- and \emph{p}-type TCOs. Our work demonstrates that
most known \emph{n}-type TCOs do not suffer from second gap absorption in the
visible even at very high carrier concentrations. On the contrary,
\emph{p}-type oxides show lowering of their optical transmission for high
carrier concentrations due to second gap effects. We link this dissimilarity to
the different chemistries involved in \emph{n}- versus typical \emph{p}-type
TCOs. Quantitatively, we show that second gap effects lead to only moderate
loss of transmission (even in p-type TCOs) and suggest that a wide second gap,
while beneficial, should not be considered as a needed criteria for a working
TCO.Comment: 6 pages, 4 figures, APS March Meetin
Physico-chemical properties of fourteen popular cocoa bean varieties in Dongnai-highland Vietnam
Cocoa (Theobroma cacao L.) is a major, crucial economic, global crop and has been maintained several nutritional benefits. The exporting volume of Vietnamese cocoa bean is increasing in the world cocoa trade. The beans of fourteen popular cocoa varieties that are commonly cultivated in Trang Bom (Dong Nai, Vietnam) were characterized for their physico-chemical qualifications on the background of post-fermented cocoa beans and dehydration in the region of Trang Bom-Dong Nai. The physical properties were determined based on mass ratio and bean’s dimension (lengh, width and thickness) as well as chemical (proximate) composition (total crude protein, ash, moisture, and lipid). These values were analysed using AOAC methods. The largest-size beans were found for the TD8 variety (1.5 g of mass, 25.02 mm of length, 14.28 mm of width and 7.96 mm of thickness). The moisture content of the cocoa beans was in the range between 5.64 and 6.99 (% wb) and the ash content in the range between 3.67% and 2.47% (wb). Noticeably, the fat content ratio (the most important value of cocoa bean) found in 8 varieties (TD1, TD2, TD5, TD9, TD11, TD12, TD13, TD14) was over 50%, thus these varieties are worthy chemical component especially for exported cocoa bean and industrized cultivation (extending the cultivation producing area)
An Extended Occlusion Detection Approach for Video Processing
Occlusions become conspicuous as failure regions in video processing when unified over time because the contraventions of the restriction of brightness have accumulated and evolved in occluded regions. The accuracy at the boundaries of the moving objects is one of the challenging areas that required further exploration and research. This paper presents the work in process approach that can detect occlusion regions by using pixel-wise coherence, segment-wise confidence and interpolation technique. Our method can get the same result as usual methods by solving only one Partial Differential Equations (PDE) problem; it is superior to existing methods because it is faster and provides better coverage rates for occlusion regions than variation techniques when tested against a varied number of benchmark datasets. With these improved results, we can apply and extend our approach to a wider range of applications in computer vision, such as background subtraction, tracking, 3D reconstruction, video surveillance, video compression
Computationally-driven, high throughput identification of CaTe and LiSb as promising candidates for high mobility -type transparent conducting materials
High-performance -type transparent conducting materials (TCMs) must
exhibit a rare combination of properties including high mobility, transparency
and -type dopability. The development of high-mobility/conductivity -type
TCMs is necessary for many applications such as solar cells, or transparent
electronic devices. Oxides have been traditionally considered as the most
promising chemical space to dig out novel -type TCMs. However, non-oxides
might perform better than traditional -type TCMs (oxides) in terms of
mobility. We report on a high-throughput (HT) computational search for
non-oxide -type TCMs from a large dataset of more than 30,000 compounds
which identified CaTe and LiSb as very good candidates for
high-mobility -type TCMs. From our calculations, both compounds are expected
to be -type dopable: intrinsically for LiSb while CaTe would
require extrinsic doping. Using electron-phonon computations, we estimate hole
mobilities at room-temperature to be about 20 and 70 cm/Vs for CaTe and
LiSb, respectively. The computed hole mobility for
LiSb is quite exceptional and comparable with the electron
mobility in the best -type TCMs.Comment: 10 pages, 5 figure
Photo-to-heat conversion of broadband metamaterial absorbers based on TiN nanoparticles under laser and solar illumination
We theoretically investigate photothermal heating of ultra-flexible
metamaterials, which are obtained by randomly mixing TiN nanoparticles in
polydimethylsiloxane (PDMS). Due to the plasmonic properties of TiN
nanoparticles, incident light is perfectly absorbed in a broadband range
(300-3000 nm) to generate heat within these metamaterials. Under irradiation of
an 808 nm near-infrared laser with different intensities, our predicted
temperature rises as a function of time agree well with recent experimental
data. For a given laser intensity, the temperature rise varies
non-monotonically with concentration of TiN nanoparticles because the
enhancement of thermal conductivity and absorbed energy as adding plasmonic
nanostructures leads to opposite effects on the heating process. When the model
is extended to solar heating, photothermal behaviors are qualitatively similar
but the temperature increase is less than 13 . Our studies would provide
good guidance for future experimental studies on the photo-to-heat conversion
of broadband perfect absorbers.Comment: 8 pages, 7 figures, accepted for publications in Materials Today
Communication
Economic, social and environmental disclosure, a theoretical framework and its application in Vietnam
This study focuses on the appraisal of firms performance and on its representation and reporting. Using interviews and inquiries in firms operating in the cement industry in Vietnam, two points are investigated. First, whether firms top executives consider that firms sustainable performance may include economic, social or environmental performance that is not integrated in financial statements. The theoretical framework is the stakeholder theory complemented with the institutional theory. Second, whether economic, social and environmental performance should be disclosed to answer the expectations of the various stakeholders. Therefore, our research contributes to corporate governance studies by focusing on reporting dedicated to all the stakeholders
Determination of Fluoroquinolone antibiotics in sludge matrix using pressurized liquid extraction technique combined with high performance liquid chromatography/fluorescence detection
Joint Research on Environmental Science and Technology for the Eart
FIRST RESULTS ON NITROGEN AMMONIA REMOVAL FROM GROUND WATER BY NITRIFICATION AT CEETIA LAB
Joint Research on Environmental Science and Technology for the Eart
BASTAF : NEW TECHNOLOGY IN DECENTRALIZED WASTEWATER MANAGEMENT FOR VIETNAMESE CONDITIONS
Joint Research on Environmental Science and Technology for the Eart
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