5,699 research outputs found
Remote sensing and GIS-based analysis of cave development in the Suoimuoi Catchment (Son La - NW Vietnam)
Integration of remotely sensed imagery with ground surveys is a promising method in cave
development studies. In this research a methodology was set up in which a variety of remote
sensing and GIS techniques support cave analysis in the tropical karst area of the Suoimuoi
catchment, NW Vietnam. In order to extract the maximum information from different remotely
sensed data, the hue invariant IHS transformation was applied to integrate Landsat multispectral
channels with the high resolution Landsat 7 ETM panchromatic channel. The resulting
fused image was used, after enhancement, to visually and digitally extract lineaments.
Aerial photos evaluated the extracted lineaments. Based on lineament density indices a fracture
zone favorable for cave development is defined. The distance between caves and faults
was investigated as well as the correspondence between the cave occurrence and the fracture
zone
Some estimates of Wang-Yau quasilocal energy
Given a spacelike 2-surface in a spacetime and a constant future
timelike unit vector in , we derive upper and lower estimates
of Wang-Yau quasilocal energy for a given isometric
embedding of into a flat 3-slice in . The quantity itself depends on the choice of , however the infimum of
over does not. In particular, when lies
in a time symmetric 3-slice in and has nonnegative Brown-York quasilocal
mass \mby(\Sigma), our estimates show that equals \mby (\Sigma). We also study the spatial limit of , where is a large coordinate sphere in a
fixed end of an asymptotically flat initial data set and is
an isometric embeddings of into .
We show that if has future timelike ADM energy-momentum, then
equals the ADM mass
of .Comment: 17 page
Preparation and Foliar Application of Oligochitosan - Nanosilica on the Enhancement of Soybean Seed Yield
Oligochitosan with weight average molecu-lar weight (Mw) of 5000 g/mol was prepared by gamma Co-60 radiation degradation of 4% chitosan solution containing 0.5% H2O2 at 21 kGy. Nanosilica with size of 10 – 30 nm was synthesized by calcination of acid treated rice husk at 700o C for 2 h. The mixture of 2% oligo-chitosan-2% nanosilica was prepared by dispersion of nanosilica in oligochitosan solution. Oligochitosan, nanosilica and their mixture were characterized by gel permeation chromatography (GPC), transmission electr-on microscopy (TEM), X-ray diffraction (XRD), energy dispersive x-ray spectroscopy (EDX), Ultraviolet-visible spectroscopy (UV-Vis), and Furrier transform infrared spectroscopy (FT-IR). Effect of foliar application of oli-gochitosan and oligochitosan-nanosilica on soybean seed yield was conducted in experimental field. Results indi-cated that soybean seed yield increased 10.5 and 17.0% for oligochitosan and oligochitosan-nanosilica, respect-tively for the control. Radiation degraded oligo-chitosan and its mixture with nanosilica can be potentially used for cultivation of soybean with enhanced seed yield
Transverse coronal loop oscillations excited by homologous circular-ribbon flares
We report our multiwavelength observations of two homologous circular-ribbon
flares (CRFs) in active region 11991 on 2014 March 5, focusing on the
transverse oscillations of an extreme-ultraviolet (EUV) loop excited by the
flares. The transverse oscillations are of fast standing kink-mode. The
first-stage oscillation triggered by the C2.8 flare is decayless with lower
amplitudes (310510 km). The periods (115118 s) in different wavelengths
are nearly the same, indicating coherent oscillations. The magnetic field of
the loop is estimated to be 6578 G. The second-stage oscillation triggered
by the M1.0 flare is decaying with larger amplitudes (12501280 km). The
periods decreases from 117 s in 211 {\AA} to 70 s in 171 {\AA}, implying a
decrease of loop length or an implosion after a gradual expansion. The damping
time, being 147315 s, increases with the period, so that the values of
are close to each other in different wavelengths. The thickness of the
inhomogeneous layer is estimated to be 0\farcs45 under the assumption of
resonant absorption. This is the first observation of the excitation of two
kink-mode loop oscillations by two sympathetic flares. The results are
important for understanding of the excitation of kink oscillations of coronal
loops and hence the energy balance in the solar corona. Our findings also
validate the prevalence of significantly amplified amplitudes of oscillations
by successive drivers.Comment: 5 pages, 5 figures, accepted for publication in A&
The prescribed mean curvature equation in weakly regular domains
We show that the characterization of existence and uniqueness up to vertical
translations of solutions to the prescribed mean curvature equation, originally
proved by Giusti in the smooth case, holds true for domains satisfying very
mild regularity assumptions. Our results apply in particular to the
non-parametric solutions of the capillary problem for perfectly wetting fluids
in zero gravity. Among the essential tools used in the proofs, we mention a
\textit{generalized Gauss-Green theorem} based on the construction of the weak
normal trace of a vector field with bounded divergence, in the spirit of
classical results due to Anzellotti, and a \textit{weak Young's law} for
-minimizers of the perimeter.Comment: 23 pages, 1 figure --- The results on the weak normal trace of vector
fields have been now extended and moved in a self-contained paper available
at: arXiv:1708.0139
On geometric problems related to Brown-York and Liu-Yau quasilocal mass
We discuss some geometric problems related to the definitions of quasilocal
mass proposed by Brown-York \cite{BYmass1} \cite{BYmass2} and Liu-Yau
\cite{LY1} \cite{LY2}. Our discussion consists of three parts. In the first
part, we propose a new variational problem on compact manifolds with boundary,
which is motivated by the study of Brown-York mass. We prove that critical
points of this variation problem are exactly static metrics. In the second
part, we derive a derivative formula for the Brown-York mass of a smooth family
of closed 2 dimensional surfaces evolving in an ambient three dimensional
manifold. As an interesting by-product, we are able to write the ADM mass
\cite{ADM61} of an asymptotically flat 3-manifold as the sum of the Brown-York
mass of a coordinate sphere and an integral of the scalar curvature plus
a geometrically constructed function in the asymptotic region outside
. In the third part, we prove that for any closed, spacelike, 2-surface
in the Minkowski space for which the Liu-Yau mass is
defined, if bounds a compact spacelike hypersurface in ,
then the Liu-Yau mass of is strictly positive unless lies on
a hyperplane. We also show that the examples given by \'{O} Murchadha, Szabados
and Tod \cite{MST} are special cases of this result.Comment: 28 page
Multivariate morphometric analysis of Apis cerana of southern mainland Asia
Multivariate morphometric analyses were performed on a series of worker honeybees, Apis cerana, representing 557 colonies from all of southern mainland Asia extending from Afghanistan to Vietnam south of the Himalayas. Scores from the principal components analysis revealed five statistically separable but not entirely distinct morphoclusters of bees: (1) the Hindu Kush, Kashmir, N. Myanmar, N. Vietnam and S. China; (2) Himachal Pradesh region of N. India; (3) N. India, Nepal; (4) central and S. Myanmar and Vietnam, Cambodia, Thailand, S. China and peninsular Malaysia; (5) central and S. India. The major morphoclusters are distributed coherently with the different climatic zones of the region. While populations are definable, nomenclatural adjustments remain for the future
Assessing decentralised policy implementation in Vietnam : The case of land recovery and resettlement in the Vung Ang Economic Zone
From 2006 plans were implemented to create a deep-sea water port linked to an Economic Zone in the coastal Province of Ha Tinh, located in north central Vietnam. The multi-purpose Zone entitled ‘Vung Ang’, was to attract foreign investors, while the port would provide a link to nearby Laos and Thailand. The project obviously had large implications for the administrations at various levels of governance from Hanoi to the coastal communes and villages, but even more serious impacts on the people living in the affected areas. A large area of about 23,000 hectares was to be cleared, affecting the people of 9 communes, in some of which all inhabitants had to leave their houses and homesteads, to be relocated to completely new settlements about 10 miles inland. These tightly knit communities were not too happy with the prospect to leave their homes and land, the burial places of their ancestors, and the long term comforts of community support networks. While initial decision making process started at the highest levels of Vietnam Governance, the implementation of port and industrial park construction and the related relocation policy was delegated to Ha Tinh province, which is consistent with current decentralisation policies in Vietnam. Actual implementation was carried out by the affected District and Commune level officials – with support from the Communist Party led Mass Organisations – who were in charge of the planning and implementation of the relocation process. This entailed a complex and sensitive series of steps to inform affected households, prepare relocation areas and allocate compensation and alternative housing. This paper describes the implementation dynamics of relocation by depicting and assessing the roles of all stakeholders involved, including the impacts - for better or for worse – of the relocated households. It brings out the way local authorities dealt with affected people, including efforts linked to the ideal of grass-roots democracy. Key areas of contestation are uncovered, such as inadequate infrastructure and low compensation rates. The paper has a second objective to assess the degree to which decentralisation in Vietnam has been actually implemented, and how this affects policy making processes such as the Vung Ang port/industrial zone project. The paper concludes that the relocation policy was implemented in a fairly efficient and harmonious way – with a very intensive engagement of the entire provincial administrative machinery, but that it is too early to assess the livelihood opportunities of the relocated households
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