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.

Numerical simulation of the coupled dynamic response of a submerged floating tunnel with mooring lines in regular waves

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.

Modified Disk-Shaped Compact Tension Test for Measuring Concrete Fracture Properties

Cifuentes, Hector,Lozano, Miguel,Holusova, Tana,Medina, Fernando,Seitl, Stanislav,Fernandez-Canteli, Alfonso Korea Concrete Institute 2017 International Journal of Concrete Structures and M Vol.11 No.2

A new approach for measuring the specific fracture energy of concrete denoted modified disk-shaped compact tension (MDCT) test is presented. The procedure is based on previous ideas regarding the use of compact tension specimens for studying the fracture behavior of concrete but implies significant modifications of the specimen morphology in order to avoid premature failures (such as the breakage of concrete around the pulling load holes). The manufacturing and test performance is improved and simplified, enhancing the reliability of the material characterization. MDCT specimens are particularly suitable when fracture properties of already casted concrete structures are required. To evaluate the applicability of the MDCT test to estimate the size-independent specific fracture energy of concrete ($G_F$),the interaction between the fracture process zone of concrete andthe boundary of theMDCTspecimens at the end of the test is properly analyzed. Further, the experimental results of $G_F$ obtained by MDCT tests for normal- and high-strength self-compacting concrete mixes are compared with those obtained using the well-established three-point bending test. The procedure proposed furnishes promising results, and the $G_F$ values obtained are reliable enough for the specimen size range studied in this work.

Augmented reality and dynamic infrared thermography for perforator mapping in the anterolateral thigh

Cifuentes, Ignacio Javier,Dagnino, Bruno Leonardo,Salisbury, Maria Carolina,Perez, Maria Eliana,Ortega, Claudia,Maldonado, Daniela Korean Society of Plastic and Reconstructive Surge 2018 Archives of Plastic Surgery Vol.45 No.3

Dynamic infrared thermography (DIRT) has been used for the preoperative mapping of cutaneous perforators. This technique has shown a positive correlation with intraoperative findings. Our aim was to evaluate the accuracy of perforator mapping with DIRT and augmented reality using a portable projector. For this purpose, three volunteers had both of their anterolateral thighs assessed for the presence and location of cutaneous perforators using DIRT. The obtained image of these "hotspots" was projected back onto the thigh and the presence of Doppler signals within a 10-cm diameter from the midpoint between the lateral patella and the anterior superior iliac spine was assessed using a handheld Doppler device. Hotspots were identified in all six anterolateral thighs and were successfully projected onto the skin. The median number of perforators identified within the area of interest was 5 (range, 3-8) and the median time needed to identify them was 3.5 minutes (range, 3.3-4.0 minutes). Every hotspot was correlated to a Doppler sound signal. In conclusion, augmented reality can be a reliable method for transferring the location of perforators identified by DIRT onto the thigh, facilitating its assessment and yielding a reliable map of potential perforators for flap raising.

A Finite Element-Based Methodology for the Thermo-mechanical Analysis of Early Age Behavior in Concrete Structures

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.

DYNAMIC RESPONSE OF A SPM CAGE UNDER WAVES AND CURRENTS

Cristian Cifuentes,M.H.Kim 한국수산과학회 양식분과 2015 한국수산과학회 양식분과 학술대회 Vol.2015 No.5

Modified Disk-Shaped Compact Tension Test for Measuring Concrete Fracture Properties

Hector Cifuentes,Miguel Lozano,Ta?a Holu?ova,Fernando Medina,Stanislav Seitl,Alfonso Ferna´ndez-Canteli 한국콘크리트학회 2017 International Journal of Concrete Structures and M Vol.11 No.2

A new approach for measuring the specific fracture energy of concrete denoted modified disk-shaped compact tension (MDCT) test is presented. The procedure is based on previous ideas regarding the use of compact tension specimens for studying the fracture behavior of concrete but implies significantmodifications of the specimen morphology in order to avoid premature failures (such as the breakage of concrete around the pulling load holes). The manufacturing and test performance is improved and simplified, enhancing the reliability of the material characterization. MDCTspecimens are particularly suitable when fracture properties of already casted concrete structures are required. To evaluate the applicability of theMDCT test to estimate the size-independent specific fracture energy of concrete (GF), the interaction between the fracture process zone of concrete and the boundary of theMDCTspecimens at the end of the test is properly analyzed. Further, the experimental results of GF obtained by MDCT tests for normal- and high-strength selfcompacting concrete mixes are compared with those obtained using the well-established three-point bending test. The procedure proposed furnishes promising results, and the GF values obtained are reliable enough for the specimen size range studied in this work.

Robot Formation Control Based on a Multi-potential Approach

Santiago Cifuentes,Jose M. Giron-Sierra,Juan F. Jimenez 제어로봇시스템학회 2010 제어로봇시스템학회 국제학술대회 논문집 Vol.2010 No.10

This paper proposes a new mobile robot formation control based on a multi-potential approach. The proposed method provides a pure reactive local mechanism that allows multiple robots to fit into formation pattern. Robots can deal with partially unknown scenarios and different formation patterns. The work is aimed to non-holonomic vehicles, constrains in speed and turn radius are considered.

Augmented reality and dynamic infrared thermography for perforator mapping in the anterolateral thigh

Ignacio Javier Cifuentes,Bruno Leonardo Dagnino,María Carolina Salisbury,María Eliana Perez,Claudia Ortega,Daniela Maldonado 대한성형외과학회 2018 Archives of Plastic Surgery Vol.45 No.3

Dynamic infrared thermography (DIRT) has been used for the preoperative mapping of cutaneous perforators. This technique has shown a positive correlation with intraoperative findings. Our aim was to evaluate the accuracy of perforator mapping with DIRT and augmented reality using a portable projector. For this purpose, three volunteers had both of their anterolateral thighs assessed for the presence and location of cutaneous perforators using DIRT. The obtained image of these “hotspots” was projected back onto the thigh and the presence of Doppler signals within a 10-cm diameter from the midpoint between the lateral patella and the anterior superior iliac spine was assessed using a handheld Doppler device. Hotspots were identified in all six anterolateral thighs and were successfully projected onto the skin. The median number of perforators identified within the area of interest was 5 (range, 3–8) and the median time needed to identify them was 3.5 minutes (range, 3.3–4.0 minutes). Every hotspot was correlated to a Doppler sound signal. In conclusion, augmented reality can be a reliable method for transferring the location of perforators identified by DIRT onto the thigh, facilitating its assessment and yielding a reliable map of potential perforators for flap raising.

Remembering How: Language, Memory, and the Salience of Manner

( Michele I Feist ),( Paula Cifuentes Ferez ) 서울대학교 인지과학연구소 2013 Journal of Cognitive Science Vol.14 No.4

Inspired by Talmy`s (1985, 2000) seminal work on the lexicalization of motion events, the linguistic encoding of elements of motion events has been an active area of research. Recently, Slobin (2003, 2004, 2006) refined Talmy`s typology, pointing out the differential salience of manner of motion across languages. Among the potential cognitive consequences of this differential salience of manner, Slobin (2003) postulates that manner might be more memorable for speakers of high-manner-salient languages than for speakers of low-manner-salient languages. In this paper, we take up this suggestion, asking whether English speakers and Spanish speakers will show different patterns of errors in a test of recognition for short video clips of motion events, consistent with the Linguistic Relativity Hypothesis. We observed that English speakers produced fewer errors overall, and fewer errors in responses to previously unseen items. Responses to previously viewed items revealed a more subtle effect, with the number of videos viewed at study playing a role in the language effect: English speakers made fewer errors on previously viewed items when they had seen fewer items at study, while Spanish speakers made fewer errors when they had seen more items at study. We discuss the implications of these findings for the Linguistic Relativity Hypothesis and for the role of manner salience in memory for motion events.