scholarly journals A STUDY FOR THE GENERATION MECHANISM OF THE RIP CURRENT AT THE ENCLOSED BEACH BY THE GROIN

2017 ◽  
pp. 14
Author(s):  
Naoyuki Inukai ◽  
Yoshifumi Ejiri ◽  
Takeshi Ootake ◽  
Hiroshi Yamamoto ◽  
Tokuzo Hosoyamada
Keyword(s):  
Large Scale ◽  
Aerial Photograph ◽  
Field Survey ◽  
Sea Water ◽  
Generation Mechanism ◽  
Rip Current

This study tried to comprehend the generation mechanism of the rip current at the enclosed beach by the groins. Firstly, this study did field survey and comprehended the large scale and velocity of the rip current. In this method, the rip current was pigmented by the sea water colorant, and the pigmented current was recorded as the aerial photograph by the multi-copter. Secondly, this study simulated the rip current in accordance with the results of field survey, and the results of simulation and filed survey ware compared.

scholarly journals LABORATORY MODEL TEST OF TRANSIENT RIP CURRENTS DUE TO PSEUDO HONEYCOMB PATTERN WAVES

2018 ◽  
pp. 19
Author(s):  
Junwoo Choi ◽  
Min Roh ◽  
Hyung-sik Hwang
Keyword(s):  
Large Scale ◽  
Wave Pattern ◽  
Nodal Line ◽  
Generation Mechanism ◽  
Wave Crest ◽  
Laboratory Model ◽  
Rip Current ◽  
Rip Currents ◽  
Wave Trains ◽  
Honeycomb Pattern

The Haeundae coast of South Korea is famous for its beautiful beach, but the rip current, from which the beach-guards rescue more than 100 people every summer at the beach, is now a notorious phenomenon. The large-scale Haeundae rip current is known to be a transient rip current caused by multi-directional wave trains rather than the topography-induced rip current, for example, due to a gap of sandbar. In other words, the rip current seems develop along the cross-shore nodal line area in the honeycomb wave-crest pattern (Dalrymple et al., 2011) which are generated in a shallow water when two wave trains propagate with slightly different wave directions (i.e., interference pattern). The wave pattern is formed by the refraction of incident swells over submerged shoals and ridges of the Haeundae coast. The Haeundae rip current is an example explained by the vortex generation due to the ends of wave crests in Peregrine(1998), which is known of the basic generation mechanism of rip currents(Johnson and Pattiaratchi, 2006; Clark et al., 2012; Feddersen, 2014). To understand the generation mechanism and verify the numerical model results of the Haeundae rip current, the laboratory experiment was planned. This study showed the preliminary laboratory observations which include the pseudo honeycomb pattern of incident waves and its resultant rip current.

Concrete Strength and Deformation Property under Sea Water Erosion Environment

2012 ◽  
Vol 446-449 ◽  
pp. 2554-2559 ◽  
Author(s):  
Jian Jun Cai ◽  
Feng Zhang ◽  
Wei Cui ◽  
Shou Shan Chen ◽  
Pu Lun Liu
Keyword(s):  
Large Scale ◽  
Failure Modes ◽  
Deformation Property ◽  
Sea Water ◽  
Dynamic Stiffness ◽  
Concrete Strength ◽  
Strain Curve ◽  
Water Erosion ◽  
Strength And Deformation ◽  
Erosion Environment

In order to effectively assess the concrete strength and deformation property under sea water erosion environment, concrete stress and strain curve was researched with the number of wet and dry cycle of 0 times, 10 times , 20 times, 30 times, 40 times, 50 times and 60 times based on the large-scale static and dynamic stiffness servo test set. The stress - strain curves of concrete was tested for the lateral pressure 10.8MPa, 14.4MPa, and 18.8MPa at different dry-wet cycles, The failure modes and superficial cracking characteristics of specimens are reported at different dry-wet cycles. Concrete elastic modulus and compressive strength were researched. Based on concrete mechanical theory , the classic Kufer-Gerstle strength criteria of concrete was used, a large number of test samples of multivariate data were nonlinear regressed, a biaxial concrete strength criterion was established taking into account the stress ratio and the number of dry-wet cycles.

scholarly journals Pengembangan Bahan Ajar Untuk Meningkatkan Pemahaman Materi Mata Kuliah Demografi Teknik

2012 ◽  
Vol 4 (2) ◽  
Author(s):  
Trisnawati
Keyword(s):  
College Student ◽  
Field Study ◽  
Large Scale ◽  
Field Survey ◽  
Student Understanding ◽  
Average Score ◽  
Study Material ◽  
Study Evaluation ◽  
Post Test ◽  
Or Task

Problems of this research are the difficulty of collage students to understand technique demography study material and the unavailability of appropriate teaching material. This research is aimed to increase college student understanding toward technique demography study material and study achievement. Developing material of teaching was done by: (1) Product analyzed by reducing and increasing study material; (2) Wrote material of teaching; (3) Expert validation and revised, by material of teaching expert, instructional developing, study evaluation, demography and environmental expert; (4) Small group test and revised, toward 10 collage student of geography field study; and (5) Large scale of field survey test and final product, on odd semester 2006/2007, toward 30 collage student of geography field study, FKIP, Lampung University.Pre test and post test was done in every study. The using of teaching study and doing exercise question or task in the last meeting are used in this research. The result are: (1) The increasing of college student understanding toward technique demography study material, average score in post  test higher (57,76) than average score in pre test (30,42); (2) There is a significant relationship between understanding level with collage student study achievement, r-count (0,396) higher than r-table (0,361) in significant level 5% and N = 30.

scholarly journals High-Resolution Vegetation Mapping Using eXtreme Gradient Boosting Based on Extensive Features

2019 ◽  
Vol 11 (12) ◽  
pp. 1505 ◽  
Author(s):  
Heng Zhang ◽  
Anwar Eziz ◽  
Jian Xiao ◽  
Shengli Tao ◽  
Shaopeng Wang ◽  
...  
Keyword(s):  
New Zealand ◽  
High Resolution ◽  
Large Scale ◽  
Field Survey ◽  
Terrestrial Ecosystems ◽  
Google Earth ◽  
Gradient Boosting ◽  
Global Changes ◽  
Vegetation Map ◽  
Extreme Gradient Boosting

Accurate mapping of vegetation is a premise for conserving, managing, and sustainably using vegetation resources, especially in conditions of intensive human activities and accelerating global changes. However, it is still challenging to produce high-resolution multiclass vegetation map in high accuracy, due to the incapacity of traditional mapping techniques in distinguishing mosaic vegetation classes with subtle differences and the paucity of fieldwork data. This study created a workflow by adopting a promising classifier, extreme gradient boosting (XGBoost), to produce accurate vegetation maps of two strikingly different cases (the Dzungarian Basin in China and New Zealand) based on extensive features and abundant vegetation data. For the Dzungarian Basin, a vegetation map with seven vegetation types, 17 subtypes, and 43 associations was produced with an overall accuracy of 0.907, 0.801, and 0.748, respectively. For New Zealand, a map of 10 habitats and a map of 41 vegetation classes were produced with 0.946, and 0.703 overall accuracy, respectively. The workflow incorporating simplified field survey procedures outperformed conventional field survey and remote sensing based methods in terms of accuracy and efficiency. In addition, it opens a possibility of building large-scale, high-resolution, and timely vegetation monitoring platforms for most terrestrial ecosystems worldwide with the aid of Google Earth Engine and citizen science programs.

scholarly journals Geological factors affecting the chemical characteristics of the thermal waters of the carbonate karstified aquifers of Northern Vietnam

2000 ◽  
Vol 4 (2) ◽  
pp. 332-340 ◽  
Author(s):  
C. Drogue ◽  
N. N. Cat ◽  
J. Dazy
Keyword(s):  
Carbonate Rock ◽  
Large Scale ◽  
Sea Water ◽  
Major Ions ◽  
Thermal Waters ◽  
Chemical Characteristics ◽  
Factors Affecting ◽  
Northern Vietnam ◽  
Air Temperatures ◽  
Rock Formations

Abstract. In northern Vietnam, exposed carbonate rock formations cover an area of more than 50,000 km2 .Their accumulated thickness from the Cambrian to the Triassic is in some places as much as 3000 m. Numerous thermal waters (springs and wells) occur in these strongly karstified carbonate massifs. This is the result of significant ancient and present orogenic activity, as the region demonstrates by its strong seismic activity. These karstic formations are water-bearing and strongly recharged by rainfall of between 1600 mm and 2000 mm per year in 90% of the area concerned. In view of the average annual air temperatures (17°C-25°C according to the region), 23 sample springs or wells were chosen with water temperatures of between 29°C and 68°C. Hydrochemical characteristics of these thermal waters emerging in different carbonate-rock units were examined by chemical analyses of major ions. In this large region, thermal waters are divided into four hydrochemical types: the Na-Cl type resulting from the intrusion of sea water for distances of up to several kilometres inland and depths of 1000 m, the Ca-SO4 type, probably resulting from the leaching of deposits of metallic sulphides that are widely distributed in these carbonate-rock units, and finally the Ca-HCO3 and Mg-HCO3 types which are chemically similar to fresh karstic waters in limestones and dolostones. The occurrence of these thermal groundwaters as well as their chemical characteristics seem to indicate the existence of large-scale deepseated groundwater flow systems in the karstic aquifers. Keywords: Vietnam; thermal waters; karst; hydrochemistry

scholarly journals Stratigraphy, stable isotopes and salinity in multi-year sea ice from the rift area, south George VI Ice Shelf, Antarctic Peninsula

1991 ◽  
Vol 37 (127) ◽  
pp. 357-367
Author(s):  
J.-L. Tison ◽  
E. M. Morris ◽  
R. Souchez ◽  
J. Jouzel
Keyword(s):  
Stable Isotopes ◽  
Sea Ice ◽  
Fresh Water ◽  
Large Scale ◽  
Sea Water ◽  
Ice Core ◽  
Ice Shelf ◽  
The Core ◽  
Brackish Ice ◽  
Ice Production

AbstractResults from a detailed profile in a 5.54 m multi-year sea-ice core from the rift area in the southern part of George VI Ice Shelf are presented. Stratigraphy, stable isotopes and Na content are used to investigate the growth processes of the ice cover and to relate them to melting processes at the bottom of the ice shelf.The thickest multi-year sea ice in the sampling area appears to be second-year sea ice that has survived one melt season. Combined salinity/stable-isotope analyses show large-scale sympathetic fluctuations that can be related to the origin of the parent water. Winter accretion represents half of the core length and mainly consists of frazil ice of normal sea-water origin. However, five major dilution events of sea water, with fresh-water input from the melting base of the ice shelf reaching 20% on two occasions, punctuate this winter accretion. Two of them correspond to platelet-ice production, which is often related to the freezing of ascending supercooled water from the bottom of the ice shelf.Brackish ice occurs between 450 and 530 cm in the core. It is demonstrated that this results from the freezing of brackish water (Jeffries and others, 1989) formed by mixing of normal sea water with melted basal shelf ice, with dilution percentages of maximum 80% fresh water.

scholarly journals Small-strain behaviour and crushability of Ballyconnelly carbonate sand under monotonic and cyclic loading

2018 ◽  
Vol 55 (7) ◽  
pp. 979-987 ◽  
Author(s):  
S. Nanda ◽  
V. Sivakumar ◽  
S. Donohue ◽  
S. Graham
Keyword(s):  
Cyclic Loading ◽  
Large Scale ◽  
Sea Water ◽  
High Stress ◽  
Small Strain ◽  
Offshore Structures ◽  
Particle Breakage ◽  
Triaxial Tests ◽  
Bender Element ◽  
Carbonate Sand

In various parts of the globe, carbonate sands are found at shallow sea water depth. These types of sands are very susceptible to large-scale particle breakage. Offshore structures like wind turbines and sea defences are constructed on these types of soils. From a design perspective, it is essential to assess the extent of particle breakage and the subsequent change in soil properties that occur under working load conditions. This paper presents the data obtained from a number of drained monotonic and cyclic triaxial tests on crushable carbonate sand (“Ballyconnelly sand”) in conjunction with small-strain shear stiffness (Gmax) measurements using the bender element technique. The soils were allowed to shear under three different loading patterns to understand the factors influencing the breakage of particles. The degree of crushing was quantified and analysed based on the total energy input. It was observed that, apart from applied stress, the total strain accumulation governs the amount of particle breakage. It was observed that Gmax increased significantly under high stress ratio. Gmax also increased noticeably during resting periods without any change in loading conditions as a result of creep, and subsequently during cyclic loading although at a reduced rate.

Generation mechanism of a hierarchy of vortices in a turbulent boundary layer

2019 ◽  
Vol 865 ◽  
pp. 1085-1109 ◽  
Author(s):  
Yutaro Motoori ◽  
Susumu Goto
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Energy Spectrum ◽  
Turbulent Boundary Layer ◽  
Large Scale ◽  
Generation Mechanism ◽  
Small Scale ◽  
Generation Process ◽  
Mean Flow ◽  
The Mean

To understand the generation mechanism of a hierarchy of multiscale vortices in a high-Reynolds-number turbulent boundary layer, we conduct direct numerical simulations and educe the hierarchy of vortices by applying a coarse-graining method to the simulated turbulent velocity field. When the Reynolds number is high enough for the premultiplied energy spectrum of the streamwise velocity component to show the second peak and for the energy spectrum to obey the$-5/3$power law, small-scale vortices, that is, vortices sufficiently smaller than the height from the wall, in the log layer are generated predominantly by the stretching in strain-rate fields at larger scales rather than by the mean-flow stretching. In such a case, the twice-larger scale contributes most to the stretching of smaller-scale vortices. This generation mechanism of small-scale vortices is similar to the one observed in fully developed turbulence in a periodic cube and consistent with the picture of the energy cascade. On the other hand, large-scale vortices, that is, vortices as large as the height, are stretched and amplified directly by the mean flow. We show quantitative evidence of these scale-dependent generation mechanisms of vortices on the basis of numerical analyses of the scale-dependent enstrophy production rate. We also demonstrate concrete examples of the generation process of the hierarchy of multiscale vortices.

New Non-Grid Wind Power Desalination Systems Research

2014 ◽  
Vol 488-489 ◽  
pp. 970-974
Author(s):  
Gang Wang ◽  
Jian Zhong Shi
Keyword(s):  
Water Resources ◽  
Wind Power ◽  
Fresh Water ◽  
Large Scale ◽  
Sea Water ◽  
Rapid Development ◽  
Clean Energy ◽  
High Energy ◽  
Water Desalination ◽  
Systems Research

the large-scale application of non-grid-connected wind power in sea water desalination industry has not only solved the difficulty in grid connection of wind power, but also can be an inexhaustible clean energy supply for the sea water desalination. Such application, breaking through the traditional sea water desalination technology and wind power development ideas and realizing the 100% local use of renewable energies, is a perfect combination of the new energy industry and the power consumption industry. The large-scale industrialization application of non-grid-connected wind power sea water desalination can not only maximize the efficiency of wind power and realize the unification of social benefit, environmental benefit and economic benefit, but also is of great strategic significance in accelerating the transformation of the economic development mode of China, and meanwhile, plays a leading role in the diversified development of the world wind power industry. 1. High-energy consumption factors restrict the development of sea water desalination Sea water desalination is a source-opening incremental technology for realizing the utilization of water resources, which can increase the total amount of fresh water and is not limited by time, space and climate with good water quality, and can guarantee the stable water supply of drinking water for coastal residents and industrial water supplementation. Since sea water desalination is the substitutional and incremental technology of fresh water resources, many countries are attaching more and more importance on it. With the rapid development of the economy and society of China, especially with the acceleration of urbanization, some coastal developed areas and large cities near the sea are having a greater and greater demand on water resources. In this condition, the development of sea water desalination has a great strategic significance in the supplementation of water resources in the sustainable development process of these areas[1,2].

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