Number Of Meanders Research Articles

Exploring Geomorphic Features in Lower Sabarmati River Basin as Signatures of Palaeoenvironmental Change, Gujarat: A Remote Sensing Approach

Abstract The aim of this work is to unravel the role of geomorphic indicators and/or signatures to be used as evidence for palaeo-environmental changes and other forcing mechanisms from the lower reaches of the Sabarmati river basin, Gujarat, India region. In the present study, geomorphic features have been used as archives to debate the past land-sea interactions using satellite imagery. In the lower reaches of the Sabarmati river, a number of meanders, sinuosity changes, palaeochannels, and scroll plains have been identified. As a result of the rise and fall of the sea during the Holocene period, the changes in hydrodynamic and steady-state conditions of the river can be visualized in terms of changes in landforms. Thus, the intriguing geomorphic landforms in the lower portions of the Sabarmati basin delineate the likely archives and signs of previous environmental change, in particularly ~ the relative sea level change. This approach provides first-hand documentation of the fluvial evolution under the direct impact of the varying forcing mechanisms. This attempt shows the effectiveness of satellite images in unravelling the clues to past changes from the landscape in a fast and insightful manner.

Assessment of the Geomorphological Effects of Human Activity in Russeifa District, Jordan

The results of the study showed that the population growth rate in Ruseifa ranged between 13.5% to 8.35% for the period from 1952-1994, due to the displacement of refugees from Palestine and the Gulf due to wars, in addition to the industrial expansion of the area and the decline in land prices. That urban expansion and multiplicity of human activities in the Russeifa district resulted in a change in the features of the region, both topographically and geomorphologically, as the altitudes ranging from 690 to 720 widened from what they were previously, and reached 25%, while altitudes ranging from 600-630 decreased to 3% from the study area, and it witnessed a change in all elevation categories, and the nature of the slopes changed from flat and medium gradients to medium and light gradients, but the northeastern direction of the slope is still the predominant, and it reaches 15.36% in the study area, as the study showed a change in the characteristics of the stream. Over a period of 51 years from 1967 to 2017, when the length of the stream each decreased by approximately, 110 meters, and its area decreased by 10,000 square meters. The river meander rate decreased by 0.02%, and there was a clear decrease in the number of meanders from 19 to 16 meanders. This indicates the progression of the erosion phase, the narrowing of the stream, and the speed of water reaching the downstream.

Design of the artificial magnetic conductors with meander line elements: reduction in the first and second resonant frequencies

A novel design for a planar artificial magnetic conductor (AMC) with meander line element is used to achieve miniaturization, reduction in the second/first resonant frequency ratio, and multi-band operation. It is known that various parameters—such as geometry, dielectric substrate thickness, the gap between patches, the length and width of a patch, the size of unit cell, permittivity, and permeability—strongly affect the resonant frequency. To obtain a miniaturized AMC, in this paper, we investigate the role of the metallic patch effective length on resonant frequency. Meander-shape is used to change the effective length in the direction of the incident wave polarization. A discussion of the design parameters and the electric field distribution is presented. Six different configurations are proposed. Miniaturization and reduction in the first/second resonant frequency ratio is achieved. In addition, the meander-shape allows the appearance of different operating bands that depend on the number of meanders. For instance, four bands are observed for one meander (U-shape). Therefore, a simple way to obtain AMC miniaturization and multi-band devices is proposed. The results are obtained by the finite element method. To validate our design some results have been compared against experimental testing presented in literature.

Temporal and Spatial Variations of Zarrineh-Rood River Morphology Using RS and GIS

Identification of changes and their effects on the morphology of river bed and riverside lands is a necessity for river management. This study focuses to identify the trend of river morphological evolution and changes in the riverbed territory at the final 25-kilometer downstream section of the Zarrineh-rood River leading to Urmia Lake in West Azerbaijan during the last 50 years using aerial photos taken in 1955 and 1967, topography maps produced in 1996, and SPOT satellite images taken in 2011 with field survey. They were interpretated to 3 land types of sandy beaches, permanent riverbed and sandy barriers. Distinguished land type maps overlayd and compared using GIS ILWIS software. Surface area of land types, river meandering and sinusoidal coefficients were calculated and the trend of the river interpretated. Results showed that the area of the riverbed territory has reduced form 561.1 to 221.3 ha, and the riverbed morphology and the shape of river bends have evolved. From 1967 to 2011, natural features such as sand dunes inside the riverbed have reduced from 13.68 to 2.86 ha, which indicates high fluctuations of discharge and changes in hydrological and hydraulic conditions of the river. The number of meanders has decreased from 4 to 3 and the riverbed has become straighter and more arterial. Land types surface area of sandy beaches decreased from 503.66 to 140.78, permanent riverbed increased from 54.83 to 77.68 and Sand dune is almost stable. The sine coefficient of the river is about 1.5 that indicates river classified as meandering. Deposition plays a mail role in morphological changes. 60% reduction in the riverbed territory is alarming, and current riverbed with its sedimentation prone conditions will not be able to discharge floods with average and above average return period. The most effective factors in morphological changes are the changes in hydrological regime because of dam construction, reduction of runoff, and accumulation of sediment loads on the riverbed.

Low Voltage Rf Mems Capacitive Shunt Switches

Micro-electro-mechanical-systems(MEMS) switches have low resistive loss, negligible power consumption, good isolation and high power handling capability compared with semiconductor switches. Lifetime of capacitive shunt switches strongly depends on the actuation voltage so low voltage switches is necessary to enhance its performance as well as to broaden its application area. This paper presents the design and simulation of low voltage capacitive shunt MEMS switches together with its RF performance for high frequency applications. The low voltage switches are realized by lowering the spring constant of the beam using serpentine spring designs together with large capacitive area so as to achieve the good RF performance as well. The pull-in voltage is analyzed with commercial CAD finite element analysis software CoventorWare. The electromagnetic performance in terms of scattering parameters, insertion loss, and isolation are analyzed with software Ansoft HFSS10. The switches achieved insertion loss $$<$$ < 0.47 dB in on state from 2 to 40 GHz; it provided better than 25 dB isolation in off state with a capacitance ratio of 94---96. The actuation voltage as low as 1.5 V with actuation area $$110\,\times \,100\,\upmu \mathrm{m^2}$$ 110 × 100 μ m 2 along with good RF performance is reported. The design parameter optimization including selection of appropriate number of meanders and its width found to be one of the most sensitive factors affecting the spring stiffness and actuation voltage.

Use of multitemporal remote sensing data for mapping the Alfios River network changes from 1977 to 2000

Alfios is the biggest river of the Peloponnese and the ninth longest river in Greece. It drains an area of almost 2575 km2 in Western Peloponnese and discharges at Kiparissiakos Gulf. Due to its extent, the Alfios basin presents complex physiography and geomorphology. During the last 50 years, major direct human activities have had an important impact on the river network shape and on the valley floor morphology. The most important human activities were the channel straightening caused by meander cut-offs in 1950, the construction of two dams: the Ladonas dam in 1955 and the Flokas dam in 1968 and the illegal in-stream gravel extraction that started in the 1960s and continues until today. As a result, the Alfios riverbed has presented very rapid vertical and horizontal (lateral) erosion and significant changes to its network shape. The drainage network follows a straighter course, the number of meanders has been reduced and the seventh order branch is deeply incised. Besides the morphological impacts to the river network shape there are also serious economic damages caused by human activity. During the winter of 1999, the Flokas dam bridge was closed for a long period due to damages at its foundation caused by the heavy rain and illegal gravel extraction. Transportation between the villages in the area became extremely difficult and time consuming and the cost of the repairs was estimated at 500 000 euros. In this study, there is an effort to map the network shape transformation for the period 1977–2000 using multitemporal and multisensor satellite images. One Landsat MSS image, three Landsat TM images, two Landsat ETM images, and one Terra ASTER image have been orthorectified and processed in order to cover the specific period. Principal Component Analysis (PCA) method and Geographical Information System (GIS) techniques have been applied to map the changes in the Alfios River channel. The drainage network straightening and the cut-off of five big meanders were detected and mapped. These changes occurred between 1986 and 2000.

Stochastic Wave Radiation by the Gulf Stream

Abstract A linear, small amplitude model of Rossby waves forced by idealized meanders is presented in order to ascertain whether or not the observed low frequency motions near the Gulf Stream are capable of being so generated. Two crucial ingredients are shown to be necessary; the meandering activity must vary in the downstream direction and the meanders must have a transient behavior. Cast as a stochastic average over a large number of meanders the predicted amplitudes of the kinetic energy and Reynolds stresses are similar to those observed. Implications for the forcing of a mean flow are discussed.