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In this study, the amount of flood risk reduction due to applying one of natural flood management measures, in alluvial fans, was investigated. Usually, flood management is done by common structural and nonstructural methods, which are expensive and short-lived. Flood damage reduction and using more stable and flexible solutions for flood management, have been received more attention from researchers in recent years. Using natural flood management (NFM) is considered stable methods of flood management, and in this study by presenting a natural solution in the form of increasing the length of the river by creating a meander, to investigate its effect on the expected flood damage compared to the base mode is paid. The method of conducting this study is based on modeling, which uses three models: HEC-HMS, HEC-RAS 2D and ArcMap. The study area is Abbakhsha River catchment located in Bardsir city, Kerman province, with an area of 1136 square kilometers, has the state of an alluvial fan that numerous floods have occurred. Topography, precipitation and discharge are the most important data required for this study. According to the results of this research, creating a meander in the river reduces the expected annual damage (EAD) by 15.5%. The results of this research can be effective in the planning and policy making of optimal flood management solutions in the region. [ABSTRACT FROM AUTHOR]

Modeling dispersion of aircraft emissions is challenging because aircraft are mobile sources with varying emissions rates at different elevations depending on the operating mode. Aircraft emissions during landing and take-off cycle (LTO) influence air quality in and around the airport, and depending on the number of aircraft operations and location of the airport, this influence may be significant. AERMOD (v22112) incorporates a variety of conventional source types to characterize the intended emissions source, leaving the question of which conventional source type(s) best characterizes aircraft activities across the four modes of LTO cycle, unanswered. Currently, the publicly released version of FAA's Aviation Environmental Design Tool (version 3e) models aircraft emissions as a set of AREA sources for all flight segments. A research version of AEDT allows users to model aircraft sources—both fixed wing and rotorcraft—as a series of VOLUME sources in AERMOD. However, both source treatments do not account for plume rise of aircraft jet exhaust. This paper compares AERMOD's performance in describing SO2 concentrations associated with airport sources by comparing model results from the two source options during the summer campaign of the Air Quality Source Apportionment study conducted at the Los Angeles International Airport. We conclude that both VOLUME source and AREA treatments overestimate the highest observed SO2 concentrations despite not accounting for background sources. The VOLUME source option reduces this overestimation by using a higher initial plume spread than the AREA option does, and through the inclusion of meander. Our results suggest the need to include the plume rise of jet exhaust when using AERMOD for airport air quality studies. [ABSTRACT FROM AUTHOR]

The symbolism of the spiral and the meander is well known from the ornaments on Minoan and Mycenaean artifacts, while the roots of this symbolism can be traced chronologically much deeper than these cultures and have been fixed since the Paleolithic era. This symbolism has always been of interest to researchers, as it is evidence of the archetypal use of these symbols in the process of formation of religious views of Homo sapiens from the Paleolithic era to the present. In the proposed work, possible ways of formation of this symbolism are considered on the basis of the trajectory of the Sun's movement above the horizon line observed by the priests of various cultures and the represented path of the Sun's movement below the horizon line.

In this article, we investigate meandric systems having one shallow side: the arch configuration on that side has depth at most two. This class of meandric systems was introduced and extensively examined by I. P. Goulden, A. Nica, and D. Puder [Int. Math. Res. Not. IMRN 2020 (2020), 983-1034]. Shallow arch configurations are in bijection with the set of interval partitions. We study meandric systems by using moment-cumulant transforms for noncrossing and interval partitions, corresponding to the notions of free and Boolean independence, respectively, in non-commutative probability. We obtain formulas for the generating series of different classes of meandric systems with one shallow side by explicitly enumerating the simpler, irreducible objects. In addition, we propose random matrix models for the corresponding meandric polynomials, which can be described in the language of quantum information theory, in particular that of quantum channels. [ABSTRACT FROM AUTHOR]

We study global attractors A = A f of semiflows generated by semilinear partial parabolic differential equations of the form u t = u xx + f (x , u , u x) , 0 < x < 1 , satisfying Neumann boundary conditions. The equilibria v ∈ E ⊂ A of the semiflow are the stationary solutions of the PDE, hence they are solutions of the corresponding second order ODE boundary value problem. Assuming hyperbolicity of all equilibria, the dynamic decomposition of A into unstable manifolds of equilibria provides a geometric and topological characterization of Sturm global attractors A as finite regular signed CW-complexes, the Sturm complexes, with cells given by the unstable manifolds of equilibria. Concurrently, the permutation σ = σ f derived from the ODE boundary value problem by ordering the equilibria according to their values at the boundaries x = 0 , 1 , respectively, completely determines the Sturm global attractor A . Equivalently, we use a planar curve, the meander M = M f , associated to the the ODE boundary value problem by shooting. In the previous paper (Fiedler and Rocha in J Dyn Differ Equ, 2020. https://doi.org/10.1007/s10884-020-09836-5), we set up to determine the boundary neighbors of any specific unstable equilibrium O , based exclusively on the information on the corresponding signed hemisphere complex. In addition, a certain minimax property of the boundary neighbors was established. In the signed hemisphere decomposition of the cell boundary of O , this property identifies the equilibria which are closest to, or most distant from, O at the boundaries x = 0 , 1 , in each hemisphere. The main objective of the present paper is to derive this minimax property directly from the Sturm permutation σ , or equivalently from the Sturm meander M , based on the Sturm nodal properties of the solutions of the ODE boundary value problem. This minimax result simplifies the task of identifying the equilibria on the cell boundary of each unstable equilibrium, directly from the Sturm meander M . We emphasize the local aspect of this result by an example for which the identification of the equilibria is obtained from the knowledge of only a segment of the Sturm meander M . [ABSTRACT FROM AUTHOR]

The effect of saccharin concentration on magnetoimpedance ratio in multilayer permalloy structure i.e., [NiFe/Cu/NiFe]3/Cu/[NiFe/Cu/NiFe]3 on Cu printed circuit board (PCB) meander substrates have been discussed. The multilayer [NiFe/Cu/NiFe]3/Cu/[NiFe/Cu/NiFe]3 structure was prepared by using the electrodeposition method. The results of XRF characterization show that the composition of Ni:Fe is close to the calculation mol ratio permalloy of 80:20. The magnetoimpedance effect is evaluated by total impedance measurement at the various magnetic fields. The typical increase of the magneto-impedance ratio with frequency confirms in this experiment. Here, the magnetoimpedance ratio modifies from 0.07 to 1.63 % for frequency measurements of 20 and 100 kHz, respectively. Finally, the MI ratio monotonically decreases with an increase in additive saccharin concentration. The MI ratio slightly decreases by 17.17 % (=(1.63-1.35)/1.63) for additive saccharin concentration increase of 1 to 2 g/L. Then MI ratio drastically decreases by 40.0 % (=(1.35-0.81)/1.35) in the change of additive saccharin concentration from 2 to 4 g/L. Here, the change in the morphological surface should attribute to the decrease in the MI ratio. [ABSTRACT FROM AUTHOR]

A distinct Meander Curve Based Star Shaped novel Wearable Hybrid Fractal Antenna is explored in this paper. The Meander curve is utilized to build the geometry of the antenna. A Star Shaped structure is additionally built in the middle of the patch also. It is planned over the jean substrate having dielectric constant 1.7 and having dimensions 52.3 × 58.7 × 1 mm3. The antenna is energized by microstrip line feed, placed at the base corner. The PSO technique is specially used to optimize the width of the ground plane using the fitness function. A numerical model is determined utilizing the IFS to produce the fractal geometry in MATLAB programming. The planned design is compact, mathematical engaging, and offers adequate bandwidth. It operates over 2.33–2.56 GHz and 6.20–6.44 GHz with resonant frequencies 2.44 and 6.31 GHz respectively. It provides 230 and 240 MHz bandwidth at the corresponding resonant frequencies. This antenna provides 8.84 dB and 5.77 dB gain and stable radiation patterns at resonant frequencies. HFSS software is utilized for simulating and planning the antenna. The proposed antenna is fabricated and tested, and the simulated and experimental results are compared to examine the reliability of it. The performance of this antenna is further described by analyzing the behavior using different wearable substrate materials like wash cotton, felt, polyester, etc. [ABSTRACT FROM AUTHOR]

In the case of flooding in rivers, river regulation structures are important since scours occur on the outer meander due to high flow velocities. In this study, 2-array submerged vane structures were investigated which is a new method in the meandering part of open channels, both laboratory and numerically with an open channel flow discharge of 20 L/s. Open channel flow experiments were carried out by using a submerged vane and without a vane. The flow velocity results of the computational fluid dynamics (CFD) models were compared to the experimental results and the results were found compatible. The flow velocities were investigated along with depth using the CFD and found that the maximum velocity was reduced by 22–27% along the depth. In the outer meander, the 2-array submerged vane with a 6-vane structure was found to affect the flow velocity by 26–29% in the region behind the vane.

This paper proposes a hexagonal meander-shaped wideband electronically reconfigurable transmitarray (HMRTA) at Ku band for satellite communications and radar applications. The proposed transmitarray offers high gain, low profile, and wideband characteristics with beam-scanning and beam-forming features. The cascaded structure is a low-profile and compact transmitarray. The transmitter (Tx) layer has an angular hexagonal patch with a meandered shape and resonating parasitic patches to enhance the bandwidth. The receiver (Rx) layer comprises a two-part hexagonal receiver patch and a dual ring impedance-matching receiver layer. The current reversal phenomena have executed the 180° phase shift by integrating two diodes in opposite directions. The measured results of a unit cell achieve a minimum insertion loss of 0.86 dB and 0.92 dB for state I and state II. The maximum insertion loss is 2.58 dB from 14.12 GHz to 18.02 GHz and is about 24.83% at 16.5 GHz. The full-wave simulations of a 20 × 20 space-fed reconfigurable transmitarray were performed. Good radiation patterns at all scanning angles of two principal planes are achieved, and the cross-polarization level remains less than −20 dB. The simulated 3 dB gain fluctuation bandwidth of the array is 15.85~18.35 GHz, and the wideband characteristics are verified. The simulation results show that the array can perform beam scanning ±60° in the elevation (y-z) plane and obtain the beam-scanning characteristics for ±60° in the Azimuth (x-z) plane. [ABSTRACT FROM AUTHOR]

Regulation structures such as submerged vane are needed to reduce and eliminate environmental damage due to increased flooding in rivers. In particular, scours on the outer bank due to increased flow velocities cause the river bed to change and deteriorate. In this study, the effect on flow velocities was investigated experimentally by using 3-array submerged vane structures in areas close to the outer bank. The experimental vane results were performed in the open channel setup. The Computational Fluid Dynamics (CFD) results obtained with the numerical model were also verified and compared with experimental results. It has been observed that the CFD model gives results close to the real experimental results. The standard-based k-ε model was used as the turbulence model. In the outer meander, the 3-array submerged vane with a 3-vane structure was found to affect the flow velocity by 16–27% in the region behind the vane. The flow velocities were investigated along with depth using the CFD and found that the mean velocity was reduced by 14–21% along the depth. It is also recommended that submerged vane structures can be applied as an effective method in reducing flow velocities and directing flows. [ABSTRACT FROM AUTHOR]

Subject and Purpose. The paper presents results of numerical modeling and experimental studies of a disk-shaped microstrip antenna involving ‘meander’ type slotted inhomogeneities. The work has been aimed at optimizing the operating range of the antenna and matching it to external circuits through the use of additional structural elements and appropriate feeding techniques. Methods and Methodology. The design features a circular disk-shaped microstrip resonator containing within its plane groups of slotted inhomogeneities which form a segmented meander line, with the segments oriented relative one another at an angle of 120°. The antenna could be fed through a segment of a screened coplanar line. The location of the screening plane of the coplanar line, as well as its dimensions, were variable. Numerical simulation was carried out within the ‘semi-open resonator’ technique using the finite element method. The degree of optimization of the operating range was estimated, based on analyzing spectral characteristics of the antenna, for a variety of its geometric parameters, and the magnitude of the return loss over a given frequency range. Measurements of the VSWR were carried out with reflectometers. Results. Frequency and power characteristics of a monopole, disk-shaped microstrip antenna have been analyzed and optimized over a wide frequency range. Mechanical dimensions of the additional shielding plane and location thereof have been identified as factors having significant influence upon the frequency-dependent, polarizational and power characteristics of the antenna. Conclusions. The operating frequency range, spectral and power characteristics of a monopole, disk-shaped microstrip antenna have been studied both theoretically and experimentally. Numerical simulations were carried out with the use of the fi nite element method. Experimental studies of the frequency characteristics were performed using reflectometry techniques. The antenna considered can find practical application over a wide frequency range, either as a single radiating element in a device or system, or a constituent part of an antenna array.

Meandering rivers are among the most dynamic Earth-surface systems, which generally appear in fertile valleys, the most valuable lands for agriculture and human settlement. Landsat time series and morphological parameters are complementary tools for exploring river dynamics. Karun River is the most effluent and largest meandering river in Iran, which keeps the Karun's basin economy, agriculture, and industrial sections alive; hence, investigating morphological changes in this river is essential. The morphological characteristics of Karun have undergone considerable changes over time due to several tectonic, hydrological, hydraulic, and anthropogenic factors. This study has identified and analyzed morphological changes in Karun River using a time series of Landsat imagery from 1985–2015. On that basis, morphological dynamics, including the river's active channel width, meander's neck length, water flow length, sinuosity index, and Cornice central angle, were quantitatively investigated. Additionally, the correlation between the stream power and morphological factors was explored using the data adopted from the hydrometric stations. The results show that the dominant pattern of the Karun River, due to the sinuosity coefficient, is meandering, and the majority of the river falls in the category of developed meander rivers. Moreover, the number of arteries reduced in an anabranch pattern, and the river has been migrating towards the downstream and eastern sides since 1985. This phenomenon disposes a change in the future that can be hazardous to the croplands and demands specific considerations for catchment management. [ABSTRACT FROM AUTHOR]

Aim. In this work, the main aim was a retrospective analysis of the geo‐ecological state and problems of natural territorial complexes (NTC) of the valley of the plains area of the Kuma River in the context of hydrological and morphological dynamics for the period from the 18th century to the present.Material and Methods. The paper analyses the state of the landscape’s natural components in the region, for which topographic, sectoral and cadastral maps, digital relief model, satellite images were used. Openly available data of ministries, departments, archival and stock materials were used. The degree of anthropogenic transformation of the natural‐territorial complexes was calculated based on the coefficient of ecological stability of landscapes.Result. Using the example of the plains area of the Kuma River for the period of the 18th‐21st centuries, the geo‐ecological features of valley NTC were analysed. Studies have shown that at the present stage meandering remains an important condition for land use in the Kuma River valley in terms of both agricultural land and residential areas. Cartographic schemes of land use of a modelled plot in the valley of the Kuma River were constructed, allowing the assessment of the efficiency of the economic use of the fields of oxbow lakes.Conclusion. For the last two hundred years, valley NTC have remained significant for settlement purposes and related economic activities. The modern meandering belt together with the fields of the older such features create special environment forming conditions for the functioning of the stabilising components of the landscape, floodplain forest being a basic integral factor in the preservation of regional biodiversity. It is recommended that when organising the sustainable use of the land resources of river valleys for the purposes of territorial planning, the regional features of placement of meanders and oxbow lakes be taken into account.

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A unique dual hexagonal-shaped radiating patch design with hybrid fractal curves (Meander and Koch) is presented for quad-band wireless applications. Initially, the antenna from 0th to 2nd iteration of hybrid fractal curves with PGP (Partial Ground Plane) is designed and investigated. Further, to get better results of the designed antenna in respect of Bandwidth (BW) and coefficient of reflection these hybrid curves are superimposed on the limited ground plane of 1st and 2nd iteration of the antenna and the generated antennas are designated as Antenna–1 and Antenna–2. A comparison between both the antennas has been made and it is observed that Antenna–2 shows better results in respect of improved BW and coefficient of reflection. The proposed antenna exhibits four resonant frequency bands 1.6, 4.8, 6.9, and 8.8 GHz with improved corresponding impedance BW of 2.09, 1.36, 0.86, and 1.51 GHz. The designed antenna is simulated and made on FR4 glass epoxy substrate with an overall size of 20 × 40 × 1.6 mm3. The fabricated proposed antenna is tested experimentally for the authentication of simulated results with experimental results and these are compatible with each other. The other performance indicators like radiation pattern, peak realized gain, and radiation efficiency are also determined for the proposed Hybrid Fractal Antenna (HFA) and all are found satisfactory. Due to the improved operational parameters, the designed HFA can be considered as a suitable applicant for distinct wireless applications in anticipated operational frequency ranges. [ABSTRACT FROM AUTHOR]

The aim of this paper is to present the development of the Roman flooring types and decorations in the area of the colonia maritima of Crotone, in Calabria, built on the promontory of Capo Colonna (formerly Lacinio), where the Greek sanctuary of Hera Lacinia stood. The floorings, examined in relation to their building contexts, take on greater importance where they are integrated with mosaic tesserae inserts or enriched by more demanding mosaic bands or squares, among which the most important is that of the bath (balneum) with the names of the quinquennial duoviri [-] Lucilius Macer and T. Annaeus Thraso. [ABSTRACT FROM AUTHOR]

Natural wrinkling of metal films on silicone substrates can appear by means of the metal sputtering process and can be described by the continuous elastic theory and non-linear wrinkling model. Here, we report the fabrication technology and behavior of thin freestanding Polydimethylsiloxane (PDMS) membranes equipped with thermo-electric meander-shaped elements. The Cr/Au wires were obtained on the silicone substrate by magnetron sputtering. We observe wrinkle formation and suppose furrows appear once PDMS returns to its initial state after the thermo-mechanical expansion during sputtering. Although the substrate thickness is usually a negligible parameter in the theory of wrinkle formation, we found that the self-assembled wrinkling architecture of the PDMS/Cr/Au varies due to the membrane thickness of 20 µm and 40 µm PDMS. We also demonstrate that the wrinkling of the meander wire affects its length, and it causes a 2.7 times higher resistance compared to a calculated value. Therefore, we investigate the influence of the PDMS mixing ratio on the thermo-electric meander-shaped elements. For the stiffer PDMS with a mixing ratio of 10:4, the resistance due to wrinkle amplitude alterations is 25% higher compared to the PDMS of ratio 10:1. Additionally, we observe and describe a thermo-mechanically induced motion behavior of the meander wires on completely freestanding PDMS membrane under applied current. These results can improve the understanding of wrinkle formation, which influences thermo-electric characteristics and may promote the integration of this technology in applications.

In this paper, a meander monopole antenna array based electromagnetic band gap (EBG) structure is proposed for MIMO applications. For this, two monopoles of a meander structure are printed on an FR4 substrate of 1.6 mm thickness and fed with 50Ω microstrip lines. The ground plane is defected with EBG Hilbert shaped inclusions of the 3rd order on the substrate back profile within a limited array size. This is achieved by having a negative refractive index (NRI) to reflect the surface waves totally away from the space filling between the antenna elements. Such property occurs only when the EBG defect operation is combined with the EBG slots. To realize the proposed design performance, a Finite Integral Technique (FIT) of CST Microwave Studio (CSTMWS) numerical analysis is invoked. Nevertheless, another numerical simulation based on Finite Element Method (FEM) based HFSS simulations is conducted to validate the regarded results. The proposed antenna design is fabricated to achieve excellent matching bandwidths, S11<−10 dB, around 2.45 GHz. The proposed antenna radiation pattern is found in the side direction of the array with a gain of 2.1dBi at 2.45 GHz. The proposed antenna axial ratio (AR) is tested and found to be below 3 dB at 2.45 GHz; that makes the antenna subject for circularly polarized radiator. Such achievement is attributed to the effect the fractal structure additions. Finally, the maximum mutual coupling between the antenna elements within a distance of 0.16λo at 2.45 GHz is bellow −30 dB at the two frequency bands of interest. [ABSTRACT FROM AUTHOR]

A spur dike is mainly constructed as a river-training structure and is primarily used to prevent bank erosion. The restriction to flow caused by the construction of a spur dike promotes local scour around the structure. In the case of a dike placed in a channel bend, the scour becomes more aggressive. The literature review found that the research work related to local scour around a spur dike located in a meandering channel is very limited or minimal. Therefore, an experimental investigation was conducted to study the local scour process around a T-shaped spur dike placed at different locations along the outer bank (or concave) of a reverse-meandering channel. Non-dimensionalized empirical equations for temporal and maximum local scour depth were developed as the function of the Froude number of approach flow and spur dike location. It is observed that local scour around the dike increases with the increase in Froude number and location in the meander (measured from the entry to meander). The formulation for the maximum scour depth was further evaluated with the experimental data related to the 180° bend, from literature, and it was found that the proposed equation's application is very much limited. HIGHLIGHTS Scour process is studied around T-shaped spur dike located in reverse meandering channel.; Various factors affecting scour such as Froude number of approach flow, time of scouring, and spur dike have been evaluated and studied in detail.; Empirical relations have been developed to estimate temporal and maximum scour depth.; Some experimental observations regarding flow pattern and bed topography has been discussed.;

Abstract Aim Our objective was to describe the structure and spatial patterns of the zooplankton community in a small Brazilian river system (Paranaíba River sub-basin) and evaluate the role of an oxbow lake in the dynamics of this community. Methods Zooplankton samples were collected from sites located in an oxbow lake and the Aporé River bed during the rainy and dry seasons. We collected these samples from the surface and bottom levels of two different zones (littoral and channel). For each hydrological season, analysis of variance was conducted to determine the differences in species richness and abundance of zooplankton among different sites (longitudinal), zones (lateral), and depths (vertical). Cluster analysis was performed to assess the similarity in species composition. In addition, a canonical correspondence analysis was used to select the environmental variables that best explained the variation in zooplankton abundance data. Results We recorded 152 species: 70 rotifers, 53 testate amoebae, 20 cladocerans, and 9 copepods. We observed changes in the species richness and abundance of zooplankton along the longitudinal axis of the river in both the rainy and dry seasons. However, we did not detect any lateral or vertical changes in these attributes. Cluster analysis also indicated that the greatest differences in species composition were in the longitudinal axis of the river. The longitudinal variability of zooplankton was mainly associated with the influence of an upstream oxbow lake, as well as the changes in water flow velocity, turbidity, and concentrations of suspended solids downstream. Conclusions Our results demonstrate the importance of a heterogeneity of hydrological characteristics as a structuring factor of the zooplankton community in the Aporé River. Thus, we highlight the relevance of actions to protect and maintain the natural characteristics of these environments.

الملخص: إن زخرفة المتاهة والتي تعني المياندر، أو كما يطلق عليها البعض الزخارف المتعرجة: هى نوع من الزخارف الهندسية التي ظهرت في الفن المصري القديم، كما أنها ظهرت في الفن الإغريقي والروماني (الفترة الكلاسيكية) بأنواع وأشكال متعددة. أما زخرفة المتاهة (المياندر) في العمارة الإسلامية فلم ترصده دراسة متخصصة على الرغم من ظهور هذه الزخرفة على العمائر الإسلامية منذ العصر الأموي في بلاد الشام، وفي مصر وجدت الزخرفة على التحف الفنية والعمائر التي تُنسب إلى الحقبة القبطية، واستمر استخدامها في العصر (الفاطمي، الأيوبي والمملوكي) كإطارات تحدد الزخارف الرئيسة بالتحف أو داخل أشكال هندسية تفصل بينها بنفس الأسلوب الذي وجد على العمائر والتحف السلجوقية، وقد وجدت هذه الزخرفة على واجهات المنازل بمدينة رشيد وذلك منذ القرن 12ه/ 18م، وانتشر استخدامها منذ عصر محمد علي وأسرته مع الابتكار والتفنن في بعض الأحيان، والتنوع في المواد التي نفذت بها الزخرفة؛ لذا فقد تم تتبع هذه الزخرفة على العمائر الإسلامية والاستعانة ببعض التحف الفنية كنماذج لتوضيح طرق تنفيذ هذه الزخرفة وتتبع تطورها في الفنون الإسلامية. Abstract: Meander (meandros) is a kind of geometric decorations that appeared in the Ancient Egyptian art. It was also used in the Greek and Roman arts in various types and forms. Meander has not been investigated in the Islamic architecture, although it was utilized in the Islamic buildings in the Levant during the Umayyad era. It was also used in the artifacts and buildings of the Coptic era and was assumed in the (Fatimid, Ayyubid, and Mamluk) eras as a border or interior of the geometric forms following the same style of the Seljuk buildings and artifacts. It was implemented on the façades of houses in Rosetta in the 12th A.H. / 18th A.D. century. Furthermore, it spread and evolved in the reign of Muhammad Ali and his dynasty, when various materials were used for decoration. The present study explores this motif on the Islamic buildings and artifacts, which acted as models for illustrating its implementation and development in the Islamic arts.

The section of the Kura River from the downstream of the Mingechevir dam to the Caspian Sea is called the Lower Kura. The Kura River flows on an alluvial layer, created by him over the millennia. The water course has turbulent character, with transverse circulation. The dynamic axis of water flow wanders. Water has character of a disperse liquid. In turbulent flow the disperse liquid behaves as an emery paper. It considerably accelerates process of erosion of coastal dams. According to our field investigations and theoretical estimations, in some years of a high water annual displacement of meanders reaches 9 ÷10m. Case studies have shown that the displacement of the meander on the Kura River passing through the villages of Ashagy Surra, Yukhary Garaimanly and Kurgarabujag in the Neftchala region was 450 m over 50 years (1967-2017). The region is densely populated and has a dense infrastructure. The horizontal displacement of the meander leads to the destruction of coastal structures and creates the risk of flooding. The economic damage caused by the flooding in 2010 was over US $ 500 million. [ABSTRACT FROM AUTHOR]

The comprehensive review of hybrid fractal antenna (HFA) has been presented in this article. Distinguished researchers have designed, analyzed, and investigated numerous types of HFA's as per the requirement of the market. Firstly, it gives introduction about the fractal antennas (FAs) along with the need of integration of the fractal geometries then research motivation. The extensive literature survey has been divided into three different parts as, fusion of same type of fractal geometries, amalgamation of two distinct fractal geometries and concoction of three different fractal geometries, further, the comparative analysis among these HFA's has been made on the basis of their size, geometries used for designing, number of resonant frequency bands, gain, bandwidth, radiation efficiency, circular polarization, and their applications. The juxtaposition among different HFA's has also been delineated in tabular form for more limpidity along with the findings of individual research article. The challenges faced by researchers while designing the antennas are also being portrayed in this article. This review may be supportive for the novices to carry out their research on HFA as such type of comparative analysis on HFA's is not existing in the open state of art literature as per best of authors knowledge. [ABSTRACT FROM AUTHOR]

The morphological evolution of the fluvial relief in the lowland areas is determined by the dynamic of the lateral channel migration process. River meandering and lateral channel migration represent continuous, dynamic and complex processes, which intensity modifies alluvial plains. Accordingly, it is a current topic observed from the domain of various scientific disciplines and practices, including the geographical aspect of the study. Directly or indirectly, variations of natural and anthropogenic processes affect changes in the lateral migration intensity, which is later manifested through permanent consequences for the environment. The aim of this paper is to investigate the process of lateral channel migration, through the review and interpretation of theoretical and methodological concepts and results of contemporary scientific literature. In this paper, on specific sections of the South Morava River (Serbia), the values of maximum lateral migration over different time periods are determined. Three representative river sectors were singled out, spatial and temporal dynamic was determined, while the process of lateral channel migration was presented quantitatively and graphically. Based on the obtained data, a comparative analysis showed significant riverbank changes for the observed meanders, within the period 1924-2020. Special emphasis is on the analysis of the lateral channel migration in the last decade of the mentioned period. The obtained results can be further used in order to develop and implement plans of water and land management, environmental protection and socio-economic development strategies. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 176017]

The lagoons in the Amazon are being impacted by agricultural activities and the information about their sediments is scarce; therefore, the objective of the study was to determine the physicochemical characteristics of the sediments of the Laguna Bella, wetland which will contribute to the knowledge of its environmental quality. Thus, using standardized techniques, sediments collected at six sampling points were analyzed. The results show the values of density, organic matter, conductivity, pH, organic matter, N, P, Pb, Cu, Fe, Mn, Zn and K, which were compared with five international standards. Considering the Ontario standard, organic matter is below the severe effect level; N is between the lowest and most severe effect level, while P is below the lowest effect level concentration; Pb is at a moderately contaminated level, according to the USEPA standard, but exceeds the NOAA standard. Cu exceeded the maximum permissible level of the NOAA standard; Fe exceeds the maximum permissible level of USEPA, Ontario, and NOAA standards; Mn exceeds the maximum allowable level of NOAA standards, and Zn exceeds the NOAA standard. It is concluded that the density of the sediments is uniform, the pH is slightly alkaline, the salinity is negligible, and the concentration of metals, such as Fe > Mn > Zn > Pb > Cu, exceeds international standards and indicates the deterioration of the environmental quality of the wetland. [ABSTRACT FROM AUTHOR]

River meanders have always been an intriguing subject in fluvial geomorphology because of their ubiquity, dynamism, remarkable forms and practical consequences of their movement. Sometimes a relatively straight channel flowing over bedrock may develop a lone meander bend cut-off which is very out of the place from the surrounding area. The occurrence of a sudden bend along a river may not be a meandering bend but may be manifestation of sudden change in the river dynamism due to many reasons, such as, lithology, change in rainfall regime, tectonics etc. The formation of such features highlights the behavior of river in the past. One such striking feature has been observed along the River Pravara in the Deccan Trap Region, Maharashtra, India. Rivers in Deccan Trap Region do not meander and form cut-offs by rule. It is rocky country where rivers flow in deeply incised bedrock. Hence, the observed feature displays a striking anomaly in this region. Hence, an attempt has been made in the present paper to evaluate the mode of formation of this single cut-off along this channel. Morphological and sedimentological data were generated and analyzed for the channel loop and the link channel to understand the competence of the river in the past and present which were directly or indirectly responsible for the development of this channel anomaly in this reach. Based on the results of the analysis and intensive field observations, it has been inferred that this is a classic example of natural morphological adjustment of a river when a set of events occurred, first retardation of vertical erosion encountering bedrock followed by series of floods to induce the channel to divert from the original path to resume the present course. Presence of a tributary further aided to the process of the loop development. The study can provide additional knowledge to the studies involving anomalous channel cut-offs at any part of the world. [ABSTRACT FROM AUTHOR]

Morphological changes in rivers lead to serious damages, including changes in the width of the waterways, changes in the drainage plan, erosion and sedimentation of the bed and banks, structural failure and loss of valuable land. A two-dimensional numerical model called CCHE2D was used to simulate the effect of the flow pattern on the river bed changes in the reach of the natural floodplain of the Kor River between the Abbas Abad Bridge and the Dorudzan Bridge, the Province of Fars. The topographical maps of the study area, the geometry of the model, and the computational grid with different dimensions were prepared. Based on the measured flow parameters, a two-dimensional hydrodynamic model of the mean depth, performance and results such as the changes in depth, flow velocity, secondary flow and shear stress were extracted. Finally, two data sets of the RMSE and MAPE were compared using the numerical model simulation versus the collected data. The results showed that this model had a good accuracy in predicting the flow parameter values, ​​and the simulated data were similar to those obtained from field measurements. The results of changes in the flow pattern as an effective indicator in predicting the hydraulic behavior and hydrodynamics showed that by correcting the path and removing the bends in the clay meadows of the Kor River by straightening the meanders, the heavy erosion of meander most agricultural land will be prevented. It must be emphasized that straightening the waterway entails its lining with erosion-resisting materials. It can be seen that using the computational fluid dynamics for modeling the stream bed variations brings researchers closer to a more general predictions for governing the processes in riverine plains. Also, the CCHE2D model has a good ability to predict changes in meandering rivers.

The Shirley Basin is a small asymmetric synclinal structure located in northern Carbon County, Wyoming approximately 65 km (40 miles) south of Casper, Wyoming, USA. The basin formed during the Laramide orogeny of the Late Cretaceous to Early Tertiary (78–49 Ma) and contains economically significant uranium deposits. The underlying Cretaceous units form an angular unconformity with the overlying Tertiary units that represents a paleotopographic erosional surface characterized by stream channels and overbank deposits of interbedded sand and clay with some organic detritus. Furthermore, the Cretaceous shales function as the lower confining unit/aquitard for in-situ recovery (ISR) uranium mining, and the overlying Tertiary sandstones host the uranium mineralization. This study maps the K/T boundary in greater detail than previous studies and identifies paleotopographic features that influence sedimentary environments and structures that favor uranium mineralization. Using a larger study region and thousands of historical wells and associated electric logs not available to previous studies, this research identifies unit boundaries and enters them into Golden Software’s Surfer and Esri’s ArcGIS to construct a detailed structure contour map on the K/T surface. The map delineates paleotopography such as hills and river channels, with the latter showing a strong spatial association with uranium mineralization. Geologists can use these maps to identify thicker host sands and fluvial features which enhance uranium mineralization. Mining companies can reduce operational and exploration costs by drilling in these more favorable areas to efficiently delineate the ore body geometry and develop more accurate mine unit designs that will maximize uranium recovery.

The streams of rivers are extremely complex in nature. Rivers are beneficial for natural vegetation, animals, living organisms and human communities. The river provides the possibility of drinking water and irrigation of agricultural fields. Rivers are considered as active land cultivators with erosion and sedimentation. Some of the negative effects of rivers such as floods are considered as a natural disaster. Such natural disasters have been shown when the river by anthropogenic activities by changing the shape of the river and arched their plans change. Meandering parts of the rivers are vulnerable to floods. Therefore, river studies are very important in terms of hydraulic characteristics, sediment, width to depth ratio, morphology and arched plan. Kaleibar Chai basin has located on the North West of the country. This research pays attention to the arcuate plan of Kaleibar River from the city of Kaleibar to Jananloo village (one of the branches of Aras River). The study region is part of Kaleibar Chai River with 72 km of length. The channel consists of right, waving, meandering, and braided patterns. The study of horizontal plan of the river in relation to different active processes shows the mutual relationship between hydrological parameters and the materials in the river. The continual changes in sinuosity index in the channel are indicators of variations in the river behavior. For doing this research we used Google Earth and DEM 10m images. The river was divided into 4 openings in which topographic conditions were considered. The river sinuosity index was calculated for all 4 openings in GIS software under the formula: TSI= . In this equation TCI is topographic sinuosity index, CL is the length of the river channel, Al is the aerial length of the beginning and ending part of the channel. The maximum sinuosity index for different lengths of the Kaleibar Chai River was estimated at 1.05 to 1.83. The heterogeneity of bed materials causes erosion and deposition on the river bed of Kaleibar Chai. Erosion and depositional processes occur in the area during the spring and fall floods. The variety of materials and their sizes cause erosion and the collapse of the brinks and the loop in sinuosity index, which finally lead to channel changes. The study of sinuosity index and the identification of rivers patterns help ease the planning procedure

River morphology is the science of knowing the river system in terms of general shape, dimensions and characteristics of hydraulic geometry, the direction and longitudinal profile of the bed, as well as the mechanism of its changes. Morphological study is needed to understand the current conditions and the potential for future river changes in the future, and perhaps it is only that it is possible to predict the natural behavior of the river in relation to natural changes or actions arising from the implementation of various river engineering projects. Most of the water structures such as dams, bridges and pumping stations are located in the margins of rivers that can be affected by changes in river morphology. Application of remote sensing images and Geographical Information Systems (GIS) can be effective to achieve a more accurate analysis. Today, land use change, vegetation cover and morphological changes of rivers in River Engineering Sciences are of great importance using remote sensing and GIS techniques. Yamani and Sharafi (2012) showed that morphological changes and erosion of the Herrud River from the upstream downstream has decreased. Also, the geological and lithological structures of the bed and river bank are the most important factors in the stability of the bed. Yousefi et al. (2013). In order to investigate the changes of some Meander parameters in the Karun River using Landsat satellite images, morphological parameters of 20 Meanders were determined in an interval of 128 km length of Karun River after the preparation of a land use map for each period. Rashidi et al. (2016) studied geomorphologic changes of the Karoon River bed and its causes from 1334 to 1391. The results indicate significant changes in river morphology including latitudes, meanders, and sedimentary islands due to the decrease in the discharge, the construction of multiple bridges along the path, geological factors and vegetation. The study of past research shows that the study of river morphology in other countries has also been of great importance. Clerici et al. (2015) examined the morphological changes of the Taro River in Italy over the last two centuries and showed that human beings have made the most of the changes for agricultural and industrial purposes, the construction of multiple bridges and casualization. According to the research, the main issue of this research is to investigate the changes in the Gamasiab River, which in recent years has threatened the communication paths, landscapes and, in summary, human structures along the river banks. Therefore, the objective is to study the variation of the morphology of the Gamasiab river from the point of view of the central radius and angle, and the number of archs during the 1990-2013 period, and the extent of the development of the piers.

Analogous to the types A, B, and C cases, we address the computation of the index of seaweed subalgebras in the type-D case. Formulas for the algebra's index can be computed by counting the connected components of its associated meander. We focus on a set of distinguished vertices of the meander, called the tail of the meander, and using the tail, we provide comprehensive combinatorial formulas for the index of a seaweed in all the classical types. Using these formulas, we provide all general closed-form index formulas where the index is given by a polynomial greatest common divisor formula in the sizes of the parts that define the seaweed. [ABSTRACT FROM AUTHOR]

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The province of Tucumán, Argentina has a dense fluvial network, with rivers that have shown, over the last 45 years, complex and dynamic behaviors, as a result of high streamflows. In the upper basins, located in the mountainous zone and piedmont, diverse anthropic activities developed in contrasted reliefs and erosive slopes. The increase in rainfall recorded in the region since 1970 has increased both the erosive and depositional processes in the alluvial plain by modifying the design of the channels, with important consequences on the farmlands. In this paper, the Seco river bed is analyzed thoroughly. The Seco river is born on the eastern slope of the Aconquija mountains, runs through the piedmont and the alluvial plain in a west-east direction, and finally discharges into the Salí river, the main river bed of the fluvial network of the province. The main objective of this work is an analysis of meander morphology along 6.28 km of the Seco river for the period 1972 to 2017. The main parameters analyzed were the sinuosity of the channel, and meander cuts by overflow (chute cutoff) and by tangency (neck cutoff). These processes have accelerated the loss of agricultural land by lateral erosion on the river ravines, which are composed of fluvial-alluvial sediments, the parental materials of the productive soils of alluvial plains. To begin our study, the general characteristics of the Seco river basin have been considered, including geology, geomorphology, climate, soils, and anthropic activities. In addition, specific features of the sub-basin that contributes its waters to the meander section were also taken into account: the increase of the flows due to the change toward the use of surrounding soils, the slopes of the field, the geomorphological region and morphometry. Landsat and Sentinel satellite images, as well as the SRTM Digital Elevation Model (DEM), were used for mapping the channel and crops. The resulting maps are basin and sub-basin watershed contribution to the meanders, slopes, elevation curves, and drainage network. The results show that the sinuosity of the channel increased in the period 1972-2002, had a notable decrease in the period 2002-2011 due to the processes of meander cuts, and increased again in the period 2011-2017, together with the migration of the channel towards the southern quadrant. These changes resulted in the loss of 370.68 ha of productive soils, which represents 7.41 hm3 of sediments removed and transported by the current. The meanders of the Seco river reflect the degradation of its area of contribution, representing the situation of the basins of the Argentine Northwest, in which the increase in the intensity and frequency of the precipitations since 1970 have generated critical conditions, whose effects are more evident in low areas. [ABSTRACT FROM AUTHOR]

We introduce the meandric colliers as planar self-avoiding closed continuous curves crossing the 2n arcs of a meander 2r times. We describe their construction from meandering curves obtained by replacing the horizontal line of an open meander with a concave or convex line and we study their properties and deal with their enumeration. We also consider the problem of refolding a meander of great order into a vector of components of a meandric collier. [ABSTRACT FROM AUTHOR]