16,940 research outputs found
Adoption of e-commerce by the agri-food sector in China: the case of Minyu e-commerce company
In recent years, increasing numbers of smallholders in developing countries such as China have begun to sell agricultural products directly to consumers via online shops using a third-party trade platform. It is increasingly clear that e-commerce has become a new and effective way to help smallholders gain access to the market. The investigation of agricultural e-commerce practices has a significant role in helping to understand the development of the agri-food sector in China. This teaching case provides an example of adopting e-commerce in the interaction and trading activities between participants in the food sector through a typical agricultural products e-commerce company in China, Minyu E-commerce. Particularly, the case analyzes the business model evolution through the ecosystem life cycle at the company. This case can be used to teach graduate/postgraduate students in agricultural business, MBA and executive programmes about the agri-food e-commerce business model
Fast Monte Carlo Simulation for Patient-specific CT/CBCT Imaging Dose Calculation
Recently, X-ray imaging dose from computed tomography (CT) or cone beam CT
(CBCT) scans has become a serious concern. Patient-specific imaging dose
calculation has been proposed for the purpose of dose management. While Monte
Carlo (MC) dose calculation can be quite accurate for this purpose, it suffers
from low computational efficiency. In response to this problem, we have
successfully developed a MC dose calculation package, gCTD, on GPU architecture
under the NVIDIA CUDA platform for fast and accurate estimation of the x-ray
imaging dose received by a patient during a CT or CBCT scan. Techniques have
been developed particularly for the GPU architecture to achieve high
computational efficiency. Dose calculations using CBCT scanning geometry in a
homogeneous water phantom and a heterogeneous Zubal head phantom have shown
good agreement between gCTD and EGSnrc, indicating the accuracy of our code. In
terms of improved efficiency, it is found that gCTD attains a speed-up of ~400
times in the homogeneous water phantom and ~76.6 times in the Zubal phantom
compared to EGSnrc. As for absolute computation time, imaging dose calculation
for the Zubal phantom can be accomplished in ~17 sec with the average relative
standard deviation of 0.4%. Though our gCTD code has been developed and tested
in the context of CBCT scans, with simple modification of geometry it can be
used for assessing imaging dose in CT scans as well.Comment: 18 pages, 7 figures, and 1 tabl
Non-Abelian Medium Effects in Quark-Gluon Plasma
Based on the kinetic theory, the non-Abelian medium property of hot
Quark-Gluon Plasma is investigated. The nonlinearity of the plasma comes from
two aspects: The nonlinear wave-wave interaction and self-interaction of color
field. The non-Abelian color permittivity is obtained by expanding the kinetic
equations to third order. As an application, the nonlinear Landau damping rate
and the nonlinear eigenfrequency shift are calculated in the longwave length
limit.Comment: 12 pages(Revtex), no figure
Anisotropic nonlinear elasticity in a spherical bead pack: influence of the fabric anisotropy
Stress-strain measurements and ultrasound propagation experiments in glass
bead packs have been simultaneously conducted to characterize the
stress-induced anisotropy under uniaxial loading. These measurements, realized
respectively with finite and incremental deformations of the granular assembly,
are analyzed within the framework of the effective medium theory based on the
Hertz-Mindlin contact theory. Our work shows that both compressional and shear
wave velocities and consequently the incremental elastic moduli agree fairly
well with the effective medium model by Johnson et al. [J. Appl. Mech. 65, 380
(1998)], but the anisotropic stress ratio resulting from finite deformation
does not at all. As indicated by numerical simulations, the discrepancy may
arise from the fact that the model doesn't properly allow the grains to relax
from the affine motion approximation. Here we find that the interaction nature
at the grain contact could also play a crucial role for the relevant prediction
by the model; indeed, such discrepancy can be significantly reduced if the
frictional resistance between grains is removed. Another main experimental
finding is the influence of the inherent anisotropy of granular packs, realized
by different protocols of the sample preparation. Our results reveal that
compressional waves are more sensitive to the stress-induced anisotropy,
whereas the shear waves are more sensitive to the fabric anisotropy, not being
accounted in analytical effective medium models.Comment: 9 pages, 8 figure
Two-dimensional Superconductivity from Dimerization of Atomically Ordered AuTe2Se4/3 Cubes
The emergent phenomena such as superconductivity and topological phase
transitions can be observed in strict two-dimensional crystalline matters.
Artificial interfaces and one atomic thickness layers are typical 2D materials
of this kind. Although having 2D characters, most bulky layered compounds,
however, do not possess these striking properties. Here, we report the 2D
superconductivity in bulky AuTe2Se4/3,where the reduction in dimensionality is
achieved through inducing the elongated covalent Te-Te bonds. The
atomic-resolution images reveal that the Au, Te and Se are atomically ordered
in a cube, among which are Te-Te bonds of 3.18 A and 3.28 A. The
superconductivity at 2.85 K is discovered, which is unraveled to be the
quasi-2D nature owing to the BKT topological transition. The nesting of nearly
parallel Fermi sheets could give rise to strong electron-phonon coupling. It is
proposed to further depleting the thickness could result in more
topologically-related phenomena.Comment: 16 pages, 5 figures,To be published in Nature Communication
Vortices, circumfluence, symmetry groups and Darboux transformations of the (2+1)-dimensional Euler equation
The Euler equation (EE) is one of the basic equations in many physical fields
such as fluids, plasmas, condensed matter, astrophysics, oceanic and
atmospheric dynamics. A symmetry group theorem of the (2+1)-dimensional EE is
obtained via a simple direct method which is thus utilized to find \em exact
analytical \rm vortex and circumfluence solutions. A weak Darboux
transformation theorem of the (2+1)-dimensional EE can be obtained for \em
arbitrary spectral parameter \rm from the general symmetry group theorem. \rm
Possible applications of the vortex and circumfluence solutions to tropical
cyclones, especially Hurricane Katrina 2005, are demonstrated.Comment: 25 pages, 9 figure
Sustainable supply chain management in developing countries: An analysis of the literature
This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record.The purpose of this paper is to present an analysis of the academic literature addressing Sustainable Supply Chain Management (SSCM) practices in developing countries. A systematic literature review method was adopted; selected papers were reviewed from 2000 to 2016 that matched our inclusion criteria. Common themes across the literature were identified covering four factors regarding the adoption of SSCM: drivers, barriers, mechanisms and outcomes. A conceptual model integrating these factors and based on institutional theory was advanced to explain the adoption of sustainability practices along supply chains in developing countries. The paper concludes by identifying gaps in the literature that require further research on this topic, particularly for the context of developing countries. To the best of our knowledge this is the first paper reviewing the existing research on SSCM in developing countries that includes both social and environmental dimensions.We sincerely appreciate the financial support of Newton Caldas Institutional Link grant funded by British Council (grant no. 172727857). The paper is a result of the collaboration between University of Exeter, UK and University of Los Andes in Colombia
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