Felled Trees as a Rockfall Protection System, Experimental Study for Numerical Models Calibration

2014 ◽  
Vol 566 ◽  
pp. 449-454
Author(s):  
I. Olmedo ◽  
Franck Bourrier ◽  
D. Bertrand ◽  
Frédéric Berger ◽  
Ali Limam
Keyword(s):  
Numerical Model ◽  
Numerical Models ◽  
Contact Point ◽  
Protective Capacity ◽  
Mountain Areas ◽  
Optimal Position ◽  
Energy Forest ◽  
Device Interaction ◽  
The Impact

In mountain areas, natural hazards, such as snow avalanches, landslides and rockfall threat towns, communication routes and people. It is known that forests have a major capacity to dissipate rockfall energy. Forest maintenance or storms can reduce forest’s protective capacity; after such a reduction, felled trees can be strategically left on the slopes in order to replace live trees. The efficacy of these devices and their optimal position can be analyzed by developing a numerical model describing the rock-wooden device interaction. To develop a relevant model of these wooden devices when impacted, the research was focused, in one hand, on a rigorous characterization of the fresh wood mechanical properties to recreate the real dynamic response of stems after the impact. In the other hand, the local impactor-wood stem interaction at the contact point was analyzed. Laboratory experiments using Charpy pendulum, presented in this text, have been carried out to assess the calibration of the numerical model. Experimental results of the impact force and their relation with stems mass and the impact energy level were treated and commented. A second serie of experiments has enabled to characterize the law describing the contact between the stem and the impactor.

scholarly journals FINAL DESIGN OF THE NAGS HEAD BEACH NOURISHMENT PROJECT USING A LONGSHORE NUMERICAL MODEL

2012 ◽  
Vol 1 (33) ◽  
pp. 64 ◽  
Author(s):  
Haiqing Liu Kaczkowski ◽  
Timothy W Kana
Keyword(s):  
Numerical Model ◽  
Large Scale ◽  
Numerical Models ◽  
Normal Wave ◽  
Beach Nourishment ◽  
Shoreline Evolution ◽  
Longshore Transport ◽  
Final Design ◽  
Model Setup ◽  
The Impact

Nags Head, located at the northeastern part of North Carolina in the U.S., has sustained chronic erosion over the past 50 years. In 2005, Coastal Science & Engineering (CSE) was retained by the town of Nags Head to develop an interim beach restoration plan. Profile volume change was used in the planning and preliminary design of the project, and longshore and cross-shore numerical models were used in the final design to refine the preliminary nourishment plan and increase potential longevity of the project. This paper focuses on the key factors of the longshore numerical model setup for the project. These include model selection, input data and parameters, model calibration, and applications under different design alternatives. The Generalized Model for Simulating Shoreline Changes (GENESIS) was used in this study to evaluate shoreline evolution under normal wave conditions during various stages of the design life following the beach nourishment project. The model was used to identify the potential occurrence of erosional hotspots and to optimize the nourishment design so that the effects of such hotspots could be avoided or minimized where possible. Model results were also used to evaluate the impact of borrow area dredging on longshore transport in the project area and the impact of nourishment on shoaling in the adjacent inlet. The project encompasses 10.11 miles (mi) (16.28 kilometers-km) of ocean shoreline, and the design nourishment volume is based on the total permitted volume of 4 million cubic yards (cy) (3 million cubic meters-m³). [Note: As-built length was 10.0 mi and volume was 4.615 million cubic yards.] The final design has fill densities varying from north to south in relation to historical erosion rates and model projections. The average fill density is 75 cubic yards per foot (cy/ft) (188 m³/m) and ranges from 38 cy/ft to 150 cy/ft (95 m³/m to 375 m³/m). In conclusion, it is shown that the numerical model selected in this study was capable of predicting the overall performance of the large scale beach nourishment project in Nags Head as well as the performance at a particular location within or adjacent to the project, and its design methods can offer guidance to future projects.

scholarly journals Static Characterization of the Birefringence Effect in the Semiconductor Optical Amplifier Using the Finite Difference Method

2015 ◽  
Vol 5 (1) ◽  
pp. 38
Author(s):  
A. Elyamani ◽  
A. Zatni ◽  
H. Bousseta ◽  
A. Moumen
Keyword(s):  
Numerical Model ◽  
Semiconductor Optical Amplifier ◽  
Optical Power ◽  
Optical Amplifier ◽  
Input Power ◽  
Geometrical Parameters ◽  
Saturated Gain ◽  
Birefringence Effect ◽  
The Impact

Knowing the various physical mechanisms of the semiconductor optical amplifier (SOA) helps us to develop a more complete numerical model. It also enables us to simulate more realistically the static behavior of the SOA<sub>s</sub>’ birefringence effect. This way, it allows us to study more precisely the behavior of SOA<sub>s</sub>, and particularly the impact of the amplified spontaneous emission (ASE) or the pump and probe signals as well as the optical functions based on the non-linearity of the component. In static regime, the SOA<sub>s</sub> possess a very low amplification threshold and a saturation power of the gain which mainly depends on the optical power injected into the active region. Beyond the optical input power, the SOA is in the saturated gain regime which gives it a nonlinear transmission behavior. Our detailed numerical model offers a set of equations and an algorithm that predict their behavior. The equations form a theoretical base from which we have coded our model in several files.cpp that the <strong>Language C++</strong> executes. It has enabled us, from the physical and geometrical parameters of the component, to recover all the relevant values ​​for a comprehensive study of SOA<sub>s</sub> in static and dynamic regimes. In this paper, we propose to make a static characterization of the effect of the nonlinear polarization rotation by realizing a pump-probe assemblage to control the power and state of polarization at the entering of the SOA.

scholarly journals Dynamic Response of a Single-Layer Reticulated Dome during Aircraft Impact Based on S-J Modeling Method

2019 ◽  
Vol 2019 ◽  
pp. 1-12
Author(s):  
Li Lin ◽  
Bo Huang ◽  
Yunhui Sun ◽  
Yu Zhu ◽  
Duozhi Wang
Keyword(s):  
Numerical Model ◽  
Temperature Effect ◽  
Failure Modes ◽  
Numerical Models ◽  
Material Model ◽  
Modeling Method ◽  
Dynamic Responses ◽  
Shell Structures ◽  
Large Strains ◽  
The Impact

In previous numerical models developed for the impact dynamic responses of reticulated domes, mostly BEAM 161 elements and piecewise linear plastic material model have been employed and spherical joints have been simplified as intersection points of beams, which is called the B-P method. The B-P method can be employed in studying the dynamic responses of reticulated shells under low- to moderate-speed impacts with no obvious temperature effect. However, the analysis of the dynamic responses of reticulated shells under moderate- and high-speed impacts of missiles and other aircraft using this method had errors because it could not take into account the temperature effect. To accurately describe the mechanical responses of reticulated shells under aircraft impacts, the Johnson–Cook material model considering temperature effect with corresponding SHELL 163 element was selected for determining the members of the numerical model and the shell element was used to establish the spherical joints of reticulated shells; the whole process was called the S-J modeling method. This modeling method was capable of considering the effects of high strain rates, high temperatures, large strains, stress state change, and loading history. S-J and B-P methods were used to model the reticulated shell structures. Comparing the numerical analysis results of the drop hammer impact of the two developed methods with experimental results verified the accuracy of the S-J modeling method. In addition, based on the results obtained from the S-J modeling method and LS-DYNA finite element analysis software, a numerical model was established for small aircraft impact reticulated shells and the failure modes and dynamic responses of reticulated shell structures under aircraft impacts were studied. In terms of energy analysis, it was found that the effects of roof plates, spherical joints, and temperature softening could not be ignored in such studies.

scholarly journals Fixed Grid Numerical Models for Solidification and Melting of Phase Change Materials (PCMs)

2019 ◽  
Vol 9 (20) ◽  
pp. 4334 ◽  
Author(s):  
José Henrique Nazzi Ehms ◽  
Rejane De Césaro Oliveski ◽  
Luiz Alberto Oliveira Rocha ◽  
Cesare Biserni ◽  
Massimo Garai
Keyword(s):  
Numerical Model ◽  
Boundary Conditions ◽  
Phase Change ◽  
Latent Heat ◽  
Phase Change Materials ◽  
Source Term ◽  
Numerical Models ◽  
Fixed Grid ◽  
Numerical Studies ◽  
The Impact

Phase change materials (PCMs) are classified according to their phase change process, temperature, and composition. The utilization of PCMs lies mainly in the field of solar energy and building applications as well as in industrial processes. The main advantage of such materials is the use of latent heat, which allows the storage of a large amount of thermal energy with small temperature variation, improving the energy efficiency of the system. The study of PCMs using computational fluid dynamics (CFD) is widespread and has been documented in several papers, following the tendency that CFD nowadays tends to become increasingly widespread. Numerical studies of solidification and melting processes use a combination of formulations to describe the physical phenomena related to such processes, these being mainly the latent heat and the velocity transition between the liquid and the solid phases. The methods used to describe the latent heat are divided into three main groups: source term methods (E-STM), enthalpy methods (E-EM), and temperature-transforming models (E-TTM). The description of the velocity transition is, in turn, divided into three main groups: switch-off methods (SOM), source term methods (STM), and variable viscosity methods (VVM). Since a full numerical model uses a combination of at least one of the methods for each phenomenon, several combinations are possible. The main objective of the present paper was to review the numerical approaches used to describe solidification and melting processes in fixed grid models. In the first part of the present review, we focus on the PCM classification and applications, as well as analyze the main features of solidification and melting processes in different container shapes and boundary conditions. Regarding numerical models adopted in phase-change processes, the review is focused on the fixed grid methods used to describe both latent heat and velocity transition between the phases. Additionally, we discuss the most common simplifications and boundary conditions used when studying solidification and melting processes, as well as the impact of such simplifications on computational cost. Afterwards, we compare the combinations of formulations used in numerical studies of solidification and melting processes, concluding that “enthalpy–porosity” is the most widespread numerical model used in PCM studies. Moreover, several combinations of formulations are barely explored. Regarding the simulation performance, we also show a new basic method that can be employed to evaluate the computing performance in transient numerical simulations.

Solving a harbor accretion problem: the case of Miller and, Îles-de-la-Madeleine, Quebec

1989 ◽  
Vol 16 (6) ◽  
pp. 924-935 ◽  
Author(s):  
Yvon Ouellet ◽  
François Anctil ◽  
Louis Desjardins
Keyword(s):  
Numerical Model ◽  
Numerical Models ◽  
Wave Climate ◽  
Physical Models ◽  
Diffraction Reflection ◽  
East Side ◽  
Littoral Drift ◽  
Reflection Model ◽  
The Impact ◽  
La Madeleine

This paper summarizes a group of studies regarding Millerand harbor, located on the Îles-de-la-Madeleine coast, which blocks most of the local littoral drift. The understanding and quantification of this sedimentological problem was first carried out using numerical models. Various schemes were then tested in two mobile-bed physical models. Finally, the impact of these solutions on the wave climate in the harbor and in the entrance channel was compared using a diffraction–reflection numerical model. The results show that accretion in Millerand harbor will only be controlled by the construction of a breakwater. This breakwater must close the east side of the harbor and must reach at least 2 m depth at its toe. It is also strongly recommended that two groins be built on the east-side beach to control the erosion of the cliff. The results of the diffraction–reflection model finally give some latitude to the harbor planners, as several schemes present satisfactory wave agitation maps. Key words: erosion, accretion, breakwater, diffraction–reflection, harbor, littoral drift, numerical model, physical model, wave hindcasting.

scholarly journals Analysis of a Tubular Torsionally Resonating Viscosity–Density Sensor

Sensors ◽  
2020 ◽  
Vol 20 (11) ◽  
pp. 3036
Author(s):  
Daniel Brunner ◽  
Joe Goodbread ◽  
Klaus Häusler ◽  
Sunil Kumar ◽  
Gernot Boiger ◽  
...  
Keyword(s):  
Numerical Model ◽  
Numerical Models ◽  
Experimental Results ◽  
Static Case ◽  
Flow Loop ◽  
Actual Measurement ◽  
Wide Range ◽  
Laminar And Turbulent Flow ◽  
The Impact ◽  
Good Agreement

This paper discusses a state-of-the-art inline tubular sensor that can measure the viscosity–density ( ρ η ) of a passing fluid. In this study, experiments and numerical modelling were performed to develop a deeper understanding of the tubular sensor. Experimental results were compared with an analytical model of the torsional resonator. Good agreement was found at low viscosities, although the numerical model deviated slightly at higher viscosities. The sensor was used to measure viscosities in the range of 0.3–1000 mPa·s at a density of 1000 kg/m3. Above 50 mPa·s, numerical models predicted viscosity within ±5% of actual measurement. However, for lower viscosities, there was a higher deviation between model and experimental results up to a maximum of ±21% deviation at 0.3 mPa·s. The sensor was tested in a flow loop to determine the impact of both laminar and turbulent flow conditions. No significant deviations from the static case were found in either of the flow regimes. The numerical model developed for the tubular torsional sensor was shown to predict the sensor behavior over a wide range, enabling model-based design scaling.

The Analyses of Learning Strategies in English as a Second Language: Theoretical Classification and Measurement Test

2020 ◽  
Vol 4 (2) ◽  
pp. 118-129
Author(s):  
Asti Gumartifa ◽  
◽  
Indah Windra Dwie Agustiani
Keyword(s):  
Language Learning ◽  
Learning Outcomes ◽  
Learning Strategies ◽  
Learning Process ◽  
English Learners ◽  
English Language ◽  
Point Of View ◽  
Effective Learning ◽  
The Impact

Gaining English language learning effectively has been discussed all years long. Similarly, Learners have various troubles outcomes in the learning process. Creating a joyful and comfortable situation must be considered by learners. Thus, the implementation of effective learning strategies is certainly necessary for English learners. This descriptive study has two purposes: first, to introduce the classification and characterization of learning strategies such as; memory, cognitive, metacognitive, compensation, social, and affective strategies that are used by learners in the classroom and second, it provides some questionnaires item based on Strategy of Inventory for Language Learning (SILL) version 5.0 that can be used to examine the frequency of students’ learning strategies in the learning process. The summary of this study explains and discusses the researchers’ point of view on the impact of learning outcomes by learning strategies used. Finally, utilizing appropriate learning strategies are certainly beneficial for both teachers and learners to achieve the learning target effectively.

scholarly journals Modulation of Gut Microbiota and Oxidative Status by β-Carotene in Late Pregnant Sows

2020 ◽  
Vol 7 ◽  
Author(s):  
Xupeng Yuan ◽  
Jiahao Yan ◽  
Ruizhi Hu ◽  
Yanli Li ◽  
Ying Wang ◽  
...  
Keyword(s):  
Gut Microbiota ◽  
Dietary Supplementation ◽  
Basal Diet ◽  
Fecal Microbiota ◽  
Control Group ◽  
Metabolic Activities ◽  
The Impact ◽  
Positive Effect ◽  
Β Carotene

Recent evidences suggest that gut microbiota plays an important role in regulating physiological and metabolic activities of pregnant sows, and β-carotene has a potentially positive effect on reproduction, but the impact of β-carotene on gut microbiota in pregnant sows remains unknown. This study aimed to explore the effect and mechanisms of β-carotene on the reproductive performance of sows from the aspect of gut microbiota. A total of 48 hybrid pregnant sows (Landrace × Yorkshire) with similar parity were randomly allocated into three groups (n = 16) and fed with a basal diet or a diet containing 30 or 90 mg/kg of β-carotene from day 90 of gestation until parturition. Dietary supplementation of 30 or 90 mg/kg β-carotene increased the number of live birth to 11.82 ± 1.54 and 12.29 ± 2.09, respectively, while the control group was 11.00 ± 1.41 (P = 0.201). Moreover, β-carotene increased significantly the serum nitric oxide (NO) level and glutathione peroxidase (GSH-Px) activity (P &lt; 0.05). Characterization of fecal microbiota revealed that 90 mg/kg β-carotene increased the diversity of the gut flora (P &lt; 0.05). In particular, β-carotene decreased the relative abundance of Firmicutes including Lachnospiraceae AC2044 group, Lachnospiraceae NK4B4 group and Ruminococcaceae UCG-008, but enriched Proteobacteria including Bilophila and Sutterella, and Actinobacteria including Corynebacterium and Corynebacterium 1 which are related to NO synthesis. These data demonstrated that dietary supplementation of β-carotene may increase antioxidant enzyme activity and NO, an important vasodilator to promote the neonatal blood circulation, through regulating gut microbiota in sows.

scholarly journals Clonal approaches to understanding the impact of mutations on hematologic disease development

Blood ◽  
2019 ◽  
Vol 133 (13) ◽  
pp. 1436-1445 ◽  
Author(s):  
Jyoti Nangalia ◽  
Emily Mitchell ◽  
Anthony R. Green
Keyword(s):  
Somatic Mutations ◽  
Clonal Selection ◽  
Single Cells ◽  
Driver Mutations ◽  
Great Promise ◽  
Tumor Evolution ◽  
Disease Development ◽  
Hematopoietic Tissue ◽  
The Impact

Abstract Interrogation of hematopoietic tissue at the clonal level has a rich history spanning over 50 years, and has provided critical insights into both normal and malignant hematopoiesis. Characterization of chromosomes identified some of the first genetic links to cancer with the discovery of chromosomal translocations in association with many hematological neoplasms. The unique accessibility of hematopoietic tissue and the ability to clonally expand hematopoietic progenitors in vitro has provided fundamental insights into the cellular hierarchy of normal hematopoiesis, as well as the functional impact of driver mutations in disease. Transplantation assays in murine models have enabled cellular assessment of the functional consequences of somatic mutations in vivo. Most recently, next-generation sequencing–based assays have shown great promise in allowing multi-“omic” characterization of single cells. Here, we review how clonal approaches have advanced our understanding of disease development, focusing on the acquisition of somatic mutations, clonal selection, driver mutation cooperation, and tumor evolution.

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