scholarly journals The Response of Vegetated Dunes to Wave Attack

2021 ◽  
Author(s):  
Duncan Bryant ◽  
Mary Bryant ◽  
Jeremy Sharp ◽  
Gary Bell ◽  
Christine Moore
Keyword(s):  
Belowground Biomass ◽  
Coastal Communities ◽  
Limited Data ◽  
Dune Vegetation ◽  
Wave Condition ◽  
Model Study ◽  
Coir Fibers ◽  
Dune Stability ◽  
Storm Impact ◽  
The Stability

Vegetation is believed to increase the stability of dunes during wave attack, but limited data is available. A physical model study was performed to evaluate changes in the dune stability with and without biomass, both above and belowground. The above and belowground biomass was modeled using wooden dowels and coir fibers, respectively. For both the collision and overwash storm impact regimes, the results of this study clearly demonstrate that the inclusion of biomass in the model dune reduces the erosion and overwash. The combination of both above and belowground biomass was the most effective at reducing erosion followed by belowground biomass, with aboveground biomass providing the smallest benefit regardless of the wave condition and water level. Additionally, the overwash of sediment and water was decreased with the inclusion of biomass, following the same trends as the erosion. As the dune eroded, the storm impact regime transitioned from collision to overwash. The inclusion of biomass delays this transition in storm impact regime, providing greater protection to coastal communities. This study highlights the need to consider dune vegetation for dune construction and coastal planning.

Stability of Pt near surface alloys under electrochemical conditions: a model study

2014 ◽  
Vol 16 (31) ◽  
pp. 16615-16622 ◽  
Author(s):  
Xiaoming Zhang ◽  
Shansheng Yu ◽  
Weitao Zheng ◽  
Ping Liu
Keyword(s):  
Fuel Cell ◽  
Automotive Applications ◽  
Surface Alloys ◽  
Near Surface ◽  
Model Study ◽  
The Stability

The stability is one of the key requirements for commercializing the fuel cell electrocatalysts in automotive applications.

scholarly journals Stability and Compatibility of Diphenhydramine Hydrochloride in Intravenous Admixtures: A New Look at an Old Drug

2018 ◽  
Vol 54 (5) ◽  
pp. 330-334
Author(s):  
Daniel Sabins ◽  
Tuong Diep ◽  
Pamela McCartan ◽  
Shashi Patel ◽  
Fang Zhao
Keyword(s):  
Sodium Chloride ◽  
High Performance ◽  
Hplc Method ◽  
Stability Study ◽  
Limited Data ◽  
Diphenhydramine Hydrochloride ◽  
Drug Concentrations ◽  
The Stability ◽  
Initial Drug ◽  
Predetermined Time

Purpose: Intravenous (IV) admixtures of diphenhydramine are widely used in hospitalized patients to prevent or treat hypersensitivity reactions. However, there is limited data to support the admixture preparation in this manner. This study was designed to investigate the stability and compatibility of diphenhydramine in IV admixtures with a goal to establish a 14-day beyond-use dating with storage under refrigeration. Methods: The commercially available 50 mg/mL diphenhydramine hydrochloride injection vials were used to prepare the 0.2 and 1.0 mg/mL IV admixtures in 0.9% sodium chloride injection and 5% dextrose injection in 50 mL polyvinyl chloride (PVC) bags. The IV bags were sealed and stored under refrigeration (2°C-8°C) for the stability study. At each predetermined time point, samples were taken for visual inspection, pH measurement, and analysis by a stability-indicating high-performance liquid chromatography (HPLC) method. Results: The freshly prepared IV admixtures appeared clear, colorless, and particulate-free with pH readings of 4.44 to 4.60. The initial drug concentrations of all samples were confirmed by HPLC to be within 101.8% to 103.6% of the label claims. Over the 14 days of the study period, there was no significant change in the appearance or pH values for all stability samples. The HPLC results also confirmed that there was no more than ±2% change of the initial drug concentration in any stability samples. Conclusion: Diphenhydramine hydrochloride IV admixtures of 0.2 and 1.0 mg/mL are compatible with 0.9% sodium chloride injection and 5% dextrose injection in PVC bags. These IV admixtures are stable chemically and physically for up to 14 days when stored under refrigeration (2°C-8°C).

scholarly journals Stability of SG1 nitroxide towards unprotected sugar and lithium salts: a preamble to cellulose modification by nitroxide-mediated graft polymerization

2013 ◽  
Vol 9 ◽  
pp. 1589-1600 ◽  
Author(s):  
Guillaume Moreira ◽  
Laurence Charles ◽  
Mohamed Major ◽  
Florence Vacandio ◽  
Yohann Guillaneuf ◽  
...  
Keyword(s):  
Graft Polymerization ◽  
Polymer Chains ◽  
Lithium Salts ◽  
Organic Media ◽  
Cellulose Derivatives ◽  
Cellulose Modification ◽  
Model Study ◽  
The Stability ◽  
Grafting From ◽  
Intramolecular Hydrogen

The range of applications of cellulose, a glucose-based polysaccharide, is limited by its inherently poor mechanical properties. The grafting of synthetic polymer chains by, for example, a “grafting from” process may provide the means to broaden the range of applications. The nitroxide-mediated polymerization (NMP) method is a technique of choice to control the length, the composition and the architecture of the grafted copolymers. Nevertheless, cellulose is difficult to solubilize in organic media because of inter- and intramolecular hydrogen bonds. One possibility to circumvent this limitation is to solubilize cellulose in N,N-dimethylformamide (DMF) or N,N-dimethylacetamide (DMA) with 5 to 10 wt % of lithium salts (LiCl or LiBr), and carry out grafted polymerization in this medium. The stability of nitroxides such as SG1 has not been studied under these conditions yet, even though these parameters are of crucial importance to perform the graft modification of polysaccharide by NMP. The aim of this work is to offer a model study of the stability of the SG1 nitroxide in organic media in the presence of unprotected glucose or cellobiose (used as a model of cellulose) and in the presence of lithium salts (LiBr or LiCl) in DMF or DMA. Contrary to TEMPO, SG1 proved to be stable in the presence of unprotected sugar, even with an excess of 100 molar equivalents of glucose. On the other hand, lithium salts in DMF or DMA clearly degrade SG1 nitroxide as proven by electron-spin resonance measurements. The instability of SG1 in these lithium-containing solvents may be explained by the acidification of the medium by the hydrolysis of DMA in the presence of LiCl. This, in turn, enables the disproportionation of the SG1 nitroxide into an unstable hydroxylamine and an oxoammonium ion. Once the conditions to perform an SG1-based nitroxide-mediated graft polymerization from cellobiose have been established, the next stage of this work will be the modification of cellulose and cellulose derivatives by NMP.

scholarly journals Classification of Atlantic Coastal Sand Dune Vegetation Using In Situ, UAV, and Airborne Hyperspectral Data

2020 ◽  
Vol 12 (14) ◽  
pp. 2222 ◽  
Author(s):  
Quentin Laporte-Fauret ◽  
Bertrand Lubac ◽  
Bruno Castelle ◽  
Richard Michalet ◽  
Vincent Marieu ◽  
...  
Keyword(s):  
Plant Species ◽  
Ground Cover ◽  
Coastal Dune ◽  
Landscape Patterns ◽  
Small Scale ◽  
Anthropogenic Pressure ◽  
Dune Vegetation ◽  
Dune System ◽  
Entire Study ◽  
Dune Stability

Mapping coastal dune vegetation is critical to understand dune mobility and resilience in the context of climate change, sea level rise, and increased anthropogenic pressure. However, the identification of plant species from remotely sensed data is tedious and limited to broad vegetation communities, while such environments are dominated by fragmented and small-scale landscape patterns. In June 2019, a comprehensive multi-scale survey including unmanned aerial vehicle (UAV), hyperspectral ground, and airborne data was conducted along approximately 20 km of a coastal dune system in southwest France. The objective was to generate an accurate mapping of the main sediment and plant species ground cover types in order to characterize the spatial distribution of coastal dune stability patterns. Field and UAV data were used to assess the quality of airborne data and generate a robust end-member spectral library. Next, a two-step classification approach, based on the normalized difference vegetation index and Random Forest classifier, was developed. Results show high performances with an overall accuracy of 100% and 92.5% for sand and vegetation ground cover types, respectively. Finally, a coastal dune stability index was computed across the entire study site. Different stability patterns were clearly identified along the coast, highlighting for the first time the high potential of this methodology to support coastal dune management.

A Model Study of Instabilities Present in the Mean-Field Description and in Linearized Correlation Schemes

1989 ◽  
Vol 44 (2) ◽  
pp. 117-124
Author(s):  
Michael C. Böhm ◽  
Gerd Bubeck ◽  
Andrzej M. Oles
Keyword(s):  
Theoretical Calculations ◽  
Mean Field ◽  
Numerical Data ◽  
Local Approach ◽  
Stability Range ◽  
Hartree Fock ◽  
Model Study ◽  
Correlation Models ◽  
The Stability ◽  
Hf Wave

Abstract In this work we discuss the cooperative occurrence of instabilities in the Hartree-Fock (HF) approximation and linearized correlation models. Both breakdown phenomena can be analyzed via eigenvalues of characteristic matrices. The well known HF instabilities follow from a quasidegeneracy between the symmetry-adapted mean-field state and singly excited configurations. Quasi-degeneracies between the HF wave function and doubly excited configurations restrict the applicability of linearized correlation models. In the theoretical calculations the method of the local approach (LA) has been employed to derive the correlated ground state. For a system of the general topology XH2 (X = C, Si, etc.) the bond orbital approximation (BOA) has been used to derive analytic formulae indicating the stability range of linearized correlation schemes. Numerical calculations on the basis of a simple model-Hamiltonian are given for the π systems C2H4 and C2H2, respectively, which have been studied as a function of the CC bondlength. The comparison of the respective numerical data indicates that both breakdown phenomena are enhanced via coupling terms between strongly correlated bonds.

Underground Barrier Protection against the Spread of Vibration - A Model Study

2014 ◽  
Vol 1020 ◽  
pp. 451-456
Author(s):  
Tomáš Petřík ◽  
Eva Hrubesova ◽  
Miroslav Pinka ◽  
Alice Hastíková
Keyword(s):  
Finite Element Method ◽  
Urban Areas ◽  
Seismic Waves ◽  
Static Load ◽  
Geological Environment ◽  
The Finite Element Method ◽  
Ground Vibrations ◽  
Industrial Activity ◽  
Model Study ◽  
The Stability

The designs of the buildings are in addition to the static load exposed to ground vibrations spreading from the surrounding geological environment. Ground vibrations, which are produced by anthropogenic phenomena, are not usually the crucial load for the stability of the building. But this load have an adversely affect the walls of buildings or sensitive equipment in these buildings. This article will be deal with model study of underground barriers utilized as a protection against the spread of ground vibrations in geological environment. These underground barriers maybe used in the vicinity of roads or railway lines or in urban areas around the halls with heavy industrial activity. Material of underground barriers will be designed from material with different parameters, so that it could be assessed the best variant in terms of absorption of seismic waves. The different variations of the thickness of underground barriers and different distances from the source of vibration will be designed in the analysis. The analysis will be performed in mathematical models that will be created in the software’s based on the finite element method.

Enterprises' Participation in Energy-Saving Activities' Motivation Mechanism Model Study

2013 ◽  
Vol 869-870 ◽  
pp. 404-407
Author(s):  
Rong Sheng Lv ◽  
Hui Ran Liu
Keyword(s):  
Energy Saving ◽  
Linear Time ◽  
Influential Factors ◽  
Research Review ◽  
Motivation Mechanism ◽  
Linear Time Invariant ◽  
Mechanism Model ◽  
Model Study ◽  
The Stability ◽  
Linear Time Invariant System

Based on the research review about enterprises' participation in energy-saving activities' influential factors, we defined the motivation mechanism of enterprises' participation in energy-saving activities. Decision Preference, goal, pressure, energy efficiency, dissemination and diffusion, government supports and other influential factors were analyzed. In this paper, through the establishment of assumptions, a variable interacted motivation mechanism linear time-invariant system was built and the stability of the system was analyzed. Finally, we proposed the motivations of enterprises' participation in energy-saving activities and the interactions among influencing factors.

scholarly journals SAND TRANSPORT AND COASTAL STABILITY, LANCASHIRE, U.K.

1974 ◽  
Vol 1 (14) ◽  
pp. 48
Author(s):  
William Reginald Parker
Keyword(s):  
Sediment Transport ◽  
Qualitative Description ◽  
Sand Transport ◽  
Residence Times ◽  
Coastal Evolution ◽  
Dune Erosion ◽  
Sediment Fluxes ◽  
Dune Stability ◽  
Transport Patterns ◽  
The Stability

The stability of an alluvial coast depends upon the local sediment budget. Along the shore, changes from erosion to accretion may reflect changing sediment fluxes, sediment residence times and patterns of sediment movement. Processes influencing these parameters, such as mud sedimentation or migration of intertidal channels will, through their influence on beach gradients and sediment transport patterns, affect the processes and rates of coastal dune erosion and the safety of the dune protected hinterland. A qualitative description of some of the various processes and phenomena linking foreshore and dune stability with sediment circulation and coastal evolution is presented.

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