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RISS 인기검색어
- 검색키워드
- 저자 : H. Cifuentes (검색결과 6 건)
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Peñuela Mauricio,Viáfara-Vega Ronald,Arias Leidy Laura,Cifuentes-Silva Héctor,López José,Cárdenas Heiber 한국작물학회 2022 Journal of crop science and biotechnology Vol.25 No.2
Usually is common to see great diferences among plants in our crops, this can allow us to think about selection of some plants with the best traits in order to show that character in the next generation and thus improve our crops. Nevertheless, we forget that the observed phenotypic variance of our crop is due to several factors as genetic and environmental components. Knowing how these factors afect traits is an important question because it can tell us whether a selection program is viable or not, which can save efort, time, and money. Here, we present a case of study in a Tabasco chili pepper crop from southwestern Colombia where farmers generally practice selection ignoring the genetic and environmental components of the selected traits. To reveal these components, we proposed to use the estimation of heritability in a narrow sense, for which we developed measurements in two generations of plants and we applied a simple regression model in concordance with the expected inbreeding value for an autogamous species. Subsequently, we amplifed microsatellite molecular markers to support heritability values based on genetic diversity and confrmed whether the assumed inbreeding value for their estimation based on the life history of the species, was correct.
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Numerical simulation of fish nets in currents using a Morison force model
Cifuentes, Cristian,Kim, M.H. Techno-Press 2017 Ocean systems engineering Vol.7 No.2
For complex flexible structures such as nets, the determination of drag forces and its deformation is a challenging task. The accurate prediction of loads on cages is one of the key steps in designing fish farm facilities. The basic physics with a simple cage, can be addressed by the use of experimental studies. However, to design more complex cage system for various environmental conditions, a reliable numerical simulation tool is essential. In this work, the current load on a cage is calculated using a Morison-force model applied at instantaneous positions of equivalent-net modeling. Variations of solidity ratio ($S_n$) of the net and current speed are considered. An equivalent array of cylinders is built to represent the physical netting. Based on the systematic comparisons between the published experimental data for Raschel nets and the current numerical simulations, carried out using the commercial software OrcaFlex, a new formulation for $C_d$ values, used in the equivalent-net model, is presented. The similar approach can also be applied to other netting materials following the same procedure. In case of high solidity ratio and current speed, the hybrid model defines $C_d$ as a function of Re (Reynolds number) and $S_n$ to better represent the corresponding weak diffraction effects. Otherwise, the conventional $C_d$ values depending only on Re can be used with including shielding effects for downstream elements. This new methodology significantly improves the agreement between numerical and experimental data.
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Cifuentes, Cristian,Kim, Seungjun,Kim, M.H.,Park, W.S. Techno-Press 2015 Ocean systems engineering Vol.5 No.2
In the present study, the coupled dynamic response of a Submerged Floating Tunnel (SFT) and mooring lines under regular waves is solved by using two independent numerical simulation methods, OrcaFlex and CHARM3D, in time domain. Variations of Buoyancy to Weight Ratio (BWR), wave steepness/period, and water/submergence depth are considered as design and environmental parameters in the study. Two different mooring-line configurations, vertical and inclined, are studied to find an optimum design in terms of limiting tunnel motions and minimizing mooring-line tension. The numerical results are successfully validated by direct comparison against published experimental data. The results show that tunnel motions and tether tensions grow with wave height and period and decrease with submergence depth. The inclined mooring system is more effective in restricting tunnel motions compared to the vertical mooring system. Overall, the present study demonstrates the feasibility of this type of structure as an alternative to traditional bridges or under-seabed tunnels.
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H. Cifuentes,F. Montero-Chacón,J. Galán,J. Cabezas,A. Martínez-De la Concha 한국콘크리트학회 2019 International Journal of Concrete Structures and M Vol.13 No.6
This paper presents a general procedure based on fracture mechanics models in order to analyze the level of crack-ing and structural safety in reinforced concrete elements at early ages, depending on the stripping time. Our proce-dure involves the development of a thermo-mechanical numerical model based on the finite element method that accounts for the change in the mechanical properties of concrete with time. Moreover, fracture mechanisms are analyzed by means of a material damage model, which is characterized via specific experimental results obtained for standard specimens and notched beams under three-point bending testing. The loading conditions are both thermal and mechanical, and are obtained from the hydration process for a given concrete dosage. The presented methodol-ogy allows for the determination of the optimal stripping time, whereas it helps assessing the analysis of the cracking and the stress states of the elements under consideration. A practical application, namely the analysis of a retaining wall, is used to validate our methodology, showing its suitability in engineering practice.
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Local dynamic buckling of FPSO steel catenary riser by coupled time-domain simulations
Eom, T.S.,Kim, M.H.,Bae, Y.H.,Cifuentes, C. Techno-Press 2014 Ocean systems engineering Vol.4 No.3
Steel catenary riser (SCR) is a popular/economical solution for the oil/gas production in deep and ultra-deep water. The behavioral characteristics of SCR have a high correlation with the motion of floating production facility at its survival and operational environments. When large motions of surface floaters occur, such as FPSO in 100-yr storm case, they can cause unacceptable negative tension on SCR near TDZ (touch down zone) and the corresponding elastic deflection can be large due to local dynamic buckling. The generation, propagation, and decay of the elastic wave are also affected by SCR and seabed soil interaction effects. The temporary local dynamic buckling vanishes with the recovery of tension on SCR with the upheaval motion of surface floater. Unlike larger-scale, an-order-of-magnitude longer period global buckling driven by heat and pressure variations in subsea pipelines, the sub-critical local dynamic buckling of SCR is motion-driven and short cycled, which, however, can lead to permanent structural damage when the resulting stress is greatly amplified beyond the elastic limit. The phenomenon is extensively investigated in this paper by using the vessel-mooring-riser coupled dynamic analysis program. It is found that the moment of large downward heave motion at the farthest-horizontal-offset position is the most dangerous for the local dynamic buckling.
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