A New Class of Parallel Cross Mechanisms

International audienceThis paper addresses the new parallel-cross mechanisms, their classification and analysis. Several crossing kinematic chains of these mechanisms are located between the parallel kinematic chains. The contribution concerning to these mechanisms is their more large workspace than this of parallel mechanisms

Design a cryptosystem using elliptic curves cryptography and Vigenère symmetry key

In this paper describes the basic idea of elliptic curve cryptography (ECC) as well as Vigenère symmetry key. Elliptic curve arithmetic can be used to develop elliptic curve coding schemes, including key exchange, encryption, and digital signature. The main attraction of elliptic curve cryptography compared to Rivest, Shamir, Adleman (RSA) is that it provides equivalent security for a smaller key size, which reduces processing costs. From the theorical basic, we proposed a cryptosystem using elliptic curves and Vigenère cryptography. We proposed and implemented our encryption algorithm in an integrated development environment named visual studio 2019 to design a safe, secure, and effective cryptosystem

Activity data on crop management define uncertainty of CH4_4 and N2_2O emission estimates from rice: A case study of Vietnam

Background: Globally, rice systems are a major source of atmospheric CH$_4$ and for major rice-producing countries, such as Vietnam, CH$_4$ as well as N$_2$O emissions from agricultural land used for rice production may represent about one-fourth of total national anthropogenic greenhouse gas (GHG) emissions. However, national-scale estimates of GHG emissions from rice systems are uncertain with regard to its magnitude, spatial distribution, and seasonality. Aims: Here, we used the biogeochemical model LandscapeDNDC to calculate emissions of CH$_4$ and N$_2$O from rice systems in Vietnam (Tier 3 IPCC approach). Our objectives were to identify hotspot regions of emissions and to assess the contribution of N$_2$O to the total non-CO$_2$ (CH$_4$+N$_2$O) GHG balance of rice systems as well as the seasonal and interannual variability of fluxes in dependence of uncertain input data on field management . Methods: The biogeochemical model LandscapeDNDC model was linked to publicly available information on climate, soils, and land management (fertilization, irrigation, crop rotation) for calculating a national inventory in daily time steps of CH$_4$ and N$_2$O emissions from rice systems at a spatial resolution of 0.083° × 0.083°. Uncertainty in management practices related to fertilization, use of harvest residues or irrigation water, and its effects on simulated CH$_4$ and N$_2$O fluxes was accounted for by Latin Hypercube Sampling of probability distribution functions. Results: Our study shows that CH$_4$ and N$_2$O fluxes from rice systems in Vietnam are highly seasonal, with national CH$_4$ and N$_2$O emissions totaling to about 2600 Gg CH$_4$ y$^{–1}$ and 42 Gg N$_2$O y$^{–1}$, respectively. Highest emissions were simulated for double and triple rice cropping systems in the Mekong Delta region. Yield-scaled emissions varied largely in a range of 300–3000 kg CO$_2$-eq Mg$^{–1}$ y$^{–1}$, with CH$_4$ emissions during the rice season(s) dominating (>82%) the total annual non-CO$_2$ GHG balance of rice systems. In our study, uncertainty in field management information (nitrogen fertilization, ratio synthetic to organic fertilization, residue management, availability of irrigation water) were major drivers of uncertainty of the national CH$_4$ and N$_2$O emission inventory. Conclusions: Our study shows that Tier 3 approaches, that is, process-oriented model approaches combined with GIS databases, for estimating national-scale GHG emissions from rice systems are ready to be applied at national scale. Generally, this approach is powerful as it allows to identify regions with elevated emissions, thereby accounting not only for CH$_4$, but as well for N$_2$O emissions. However, our study also shows that specifically better information on land management is required to narrowing uncertainties

Thermophysical behavior of three algal biodiesels over wide ranges of pressure and temperature

ACLInternational audienc

Identifying Flow Eddy Currents in the River System as the Riverbank Scouring Cause: A Case Study of the Mekong River

River morphological change is the complex evolution of riverbed states, which can lead to serious riverbank failures, and is a worldwide concern. However, revealing the cause of the evolution, in particular, the potential morphological scouring by eddy currents, is difficult. Accordingly, we propose a comprehensive combination of 2D and 3D simulations to reveal the eddy currents. We selected the Vam Nao, part of the Mekong River, with semi-tidal effects and confluence flows as the case study. We created two unstructured 40 m × 40 m triangular meshes using inverse distance interpolation. This study used the Saint–Venant equations (TELEMAC2D) and Navier–Stokes equations (TELEMAC3D) to reveal the eddy currents for 2009, 2017, and 2018. TELEMAC2D (the simplified form of TELEMAC3D) was assessed for 15 days, 3 months, and 1 year, which met a satisfactory level. The eddy currents’ appearance was verified by local knowledge. We found recirculating currents near the riverbank to the East (right at the riverbank failures), whose velocity was approximately half and 1/3–1/4 of the mainstream flow velocity in the dry and flood seasons, respectively. Our study approach performed well in revealing the eddy currents, which can aid in assessing potential riverbank failures and can be applicable to similar contexts

Studies in the flow of granular materials

A number of problems related to the flow of cohesionless granular materials in hoppers are investigated. An approximate solution to the flow of granular materials in a conical hopper is presented. The material is modeled as a rigid-perfectly plastic continuum which satisfies the Mohr-Coulomb yield condition. Unknown geometries of the upper and lower free surfaces are determined from the stress-free conditions. The results are compared to those based on different constitutive postulates as well as to experimental observations. The computed mass flow rate and wall stress compare well with the experimental measurements made with small and full size hoppers. The flow field in a hopper with a vertical bin is observed to gain a better understanding of the details of the flow field. The observations seem to correspond to the recent results obtained by other investigators using X-ray radiography. The funnel flow regime in hoppers is studied in detail. The different types of flow which exist are identified and classified. The possibility of having a transition from one type of flow into another one is recorded as a function of the material properties and hopper geometry. Finally, the boundary between the moving and stagnant material is studied as a function of the hopper geometry. Other parameters such as the effect of the hopper thickness and wall roughness on the flow field are also studied

Étude par RMN de composés organo-phosphorés

La plupart des composés de formule générale(C6H5)n P(X)(YCH3)3—n(où X, Y = O, S et dans certains cas Se ; n = 1 ou 2) ont fait l’objet d’une étude détaillée en résonance magnétique nucléaire du phosphore et du proton. La première apporte des renseignements sur l’importance de l’ensemble des liaisons π du phosphore ; la seconde, grâce à l’analyse sub-spectrale d’une partie des motifs aromatiques, renseigne sur les modifications que les substitutions amènent dans chaque groupe de la molécule

A New Class of Parallel Cross Mechanisms

International audienceThis paper addresses the new parallel-cross mechanisms, their classification and analysis. Several crossing kinematic chains of these mechanisms are located between the parallel kinematic chains. The contribution concerning to these mechanisms is their more large workspace than this of parallel mechanisms