Meander Type Research Articles

GENERATOR OF POWERFUL HIGH-FREQUENCY PACKAGE CURRENT PULSES FOR POWER SUPPLY OF ULTRASONIC ELECTROMAGNETIC-ACOUSTIC TRANSDUCERS

It is possible to increase the sensitivity of electromagnetic-acoustic transducers by three main methods: increasing the induction of a polarizing magnetic field; increase in strength of high-frequency current in the inductor of the converter; using modern methods of processing information packet pulses excited and received from the product. The increase in magnetic field induction of the converter is limited by the capabilities of modern powerful permanent magnets. In addition, there are significant difficulties in monitoring ferromagnetic control samples, due to the large pressing force between the sample and the transducer and sticking of scale to the transducer. Usage of modern processing methods significantly complicates and increases the cost of electromagnetic-acoustic testing devices. Of the selected sensitivityincreasingmethods, the most acceptable way is to increase the power of high-frequency current generators under the condition of excitation of packet pulses. Power supply process of the converter is carried out in two stages. Meander type powerful high-frequency current pulses are excited, which ensures operation of the output transistors in key mode. Isolation of a powerful sinusoidal high-frequency packet current pulse is carried out directly on the electromagnetic - acoustic transducer, the elements of which are included in the resonant circuit with low quality factor. Based on the transistors switched in the push-pull circuit in the key mode, a small-sized generator design has been created that excites a peak current of up to 800 A in the electromagnetic-acoustic transducer and a voltage of up to 3 kV in the transducer in the frequency range 0.3 ... 8 MHz. It was experimentally determined that the new design of the probe pulse generator made it possible to increase the amplitude of pulses reflected from a flat-bottom reflector with a diameter of 2 mm with respect to the interference amplitude by more than 2 times.

Mass Production of Highly Active NK Cells for Cancer Immunotherapy in a GMP Conform Perfusion Bioreactor.

NK cells have emerged as promising candidates for cancer immunotherapy, especially due to their ability to fight circulating tumor cells thereby preventing metastases formation. Hence several studies have been performed to generate and expand highly cytotoxic NK cells ex vivo, e.g., by using specific cytokines to upregulate both their proliferation and surface expression of distinct activating receptors. Apart from an enhanced activity, application of NK cells as immunotherapeutic agent further requires sufficient cell numbers and a high purity. All these parameters depend on a variety of different factors including the starting material, additives like cytokines as well as the culture system. Here we analyzed PBMC-derived NK cells of five anonymized healthy donors expanded under specific conditions in an innovative perfusion bioreactor system with respect to their phenotype, IFNγ production, and cytotoxicity in vitro. Important features of the meander type bioreactors used here are a directed laminar flow of medium and control of relevant process parameters. Cells are cultivated under “steady state” conditions in perfusion mode. Our data demonstrate that expansion of CD3+ T cell depleted PBMCs in our standardized system generates massive amounts of highly pure (>85%) and potent anti-cancer active NK cells. These cells express a variety of important receptors driving NK cell recruitment, adhesion as well as activation. More specifically, they express the chemokine receptors CXCR3, CXCR4, and CCR7, the adhesion molecules L-selectin, LFA-1, and VLA-4, the activating receptors NKp30, NKp44, NKp46, NKG2D, DNAM1, and CD16 as well as the death ligands TRAIL and Fas-L. Moreover, the generated NK cells show a strong IFNγ expression upon cultivation with K562 tumor cells and demonstrate a high cytotoxicity toward leukemic as well as solid tumor cell lines in vitro. Altogether, these characteristics promise a high clinical potency of thus produced NK cells awaiting further evaluation.

Detailed assessment of spatial and temporal variations in river channel changes and meander evolution as a preliminary work for effective floodplain management. The example of Sajó River, Hungary

The quasi-natural meandering type of alluvial rivers is quite unusual in Central European watersheds. The lack of extensive regulation allows such rivers to shift along their floodplain and cause erosion of natural and agricultural lands. Description of channel morphometric parameters over decadal timescales allows a better understanding of such river systems like Sajó River (Slovakia-Hungary) where no preliminary work is available regarding channel dynamics. In addition, to just describing the geomorphic processes, the environmental management implications of these meandering rivers need to be investigated as well. Thus, this study represents a bend-scale morphological analysis on the 124 km long section of the Sajó River in the Hungarian territory in eight different periods between 1952 and 2011. Archive aerial imagery, orthophotographs and topographical maps were organized into a database, then GIS-based analyses were performed to quantify the rate and extent of channel shifts, bend development and the area of erosion/accretion. On the bend scale, we have calculated several morphometric parameters (bend length, chord, amplitude, the radius of curvature) to quantify the evolutionary trajectory of reaches. Hydrological time series data were evaluated to reveal its possible role in the processes. Based on the available GIS-data of natural elements and anthropogenic intervention, we delineated 12 different reaches showing similar characteristics, from which six reaches were defined as natural. According to the morphometric parameters of the natural reaches, channel widths became narrower and the planform became more concentrated spatially in most of the reaches while the overall sinuosity of almost all natural reaches increased. Although artificial cutoffs mainly reduced the reach complexity, in some cases, they have accelerated the bend development downstream in the following few years. Erosion and accretion activity were higher in the periods when the discharge was higher than the effective discharge but its effect became less apparent in the second half of the investigated time period. By 1980, major artificial cutoffs and bank protection works were carried out that could have an impact in reducing the potential channel shifting. Based on our results, we propose a possible preservation and some modifications along the Hungarian part of the Sajó River reaches to be carried out by the local river management authorities. We conclude that this study provides a detailed demonstration of the Sajó River morphodymanics which can be used for further land planning to avoid harmful consequences of recent bank erosion processes not only along the Sajó River, but other similar rivers in Europe.

Universal knot diagrams

We study collections of planar curves that yield diagrams for all knots. In particular, we show that a very special class called potholder curves carries all knots. This has implications for realizing all knots and links as special types of meanders and braids. We also introduce and apply a method to compare the efficiency of various classes of curves that represent all knots.

Understanding blood oxygenation in a microfluidic meander double side membrane contactor

Lung disease is one of the most important causes of high morbidity in preterm infants. In this work, we study a simple and easy to fabricate microfluidic device that demonstrates a great potential for blood oxygenation. A meander type architecture with double side vertical membrane arrangement has been selected as reference model to investigate the oxygenation process. The design criteria for the fabricated devices has been to maximize the oxygen saturation level while ensuring the physiological blood flow in order to avoid thrombus formation and channel blockage during operation. A mathematical model for the oxygen transfer has been developed and validated by the experimental study. The obtained results demonstrate that blood was successfully oxygenated up to approximately 98% of O2 saturation and that the oxygen transfer rate at 1 mL/min blood flow rate was approximately 92 mL/min m2. Finally, a sensitivity analysis of the key parameters, i.e. size of the channel, oxygen concentration in the gas phase and oxygen permeation properties of the membrane, is carried out to discuss the performance limits and to settle the guidelines for future developments.

Design and Performance Analysis of Low Pull-In Voltage of Dimple Type Capacitive RF MEMS Shunt Switch for Ka-Band

This paper deals with the study of dimple type RF MEMS capacitive shunt switch using different meandering techniques for high isolation and low actuation voltage. The novelty of the proposed RF MEMS switch is it incorporates the meanders and dimples, which help to reduce the actuation voltage. The proposed switch structure is optimized, designed, and simulated with FEM analysis such as electromechanical and electromagnetic by using COMSOL and HFSS tools respectively. The best performance of the switch is observed by varying different parameters such as beam material, beam thickness, dielectric thickness, and airgap. The proposed switch with different meandering techniques attains the pull-in voltage in the range of 10.3-46 V, particularly the three uniform meander technique has low actuation voltage of 10.3 V. The RF performance of the device is particularly tuned in the range of 26.5-40 GHz frequency range and it is analyzed for all types of meanders. Among them, the non-uniform single meander has attained the best isolation of -54.13 dB at 40 GHz in the off state. The insertion and return losses of the device are -0.514 dB and -17.35 dB over 1-40 GHz frequency in on state.

Issues of Meander Development: Land Degradation or Ecological Value? The Example of the Sajó River, Hungary

The extensive destruction of arable lands by the process of lateral bank erosion is a major issue for the alluvial meandering type of rivers all around the world. Nowadays, land managers, stakeholders, and scientists are discussing how this process affects the surrounding landscapes. Usually, due to a land mismanagement of agroforestry activities or urbanization plans, river regulations are designed to reduce anthropogenic impacts such as bank erosion, but many of these regulations resulted in a degradation of habitat diversity. Regardless, there is a lack of information about the possible positive effects of meandering from the ecological point of view. Therefore, the main aim of this study was to investigate a 2.12 km long meandering sub-reach of Sajó River, Hungary, in order to evaluate whether the process of meander development can be evaluated as a land degradation processes or whether it can enhance ecological conservation and sustainability. To achieve this goal, an archive of aerial imagery and UAV (Unmanned Aerial Vehicle)-surveys was used to provide a consistent database for a landscape metrics-based analysis to reveal changes in landscape ecological dynamics. Moreover, an ornithological survey was also carried out to assess the composition and diversity of the avifauna. The forest cover was developed in a remarkable pattern, finding a linear relationship between its rate and channel sinuosity. An increase in forest areas did not enhance the rate of landscape diversity since only its distribution became more compact. Eroding riverbanks provided important nesting sites for colonies of protected and regionally declining migratory bird species such as the sand martin. We revealed that almost 70 years were enough to gain a new habitat system along the river as the linear channel formed to a meandering and more natural state.

Enhanced Magnetic Nanoparticle Detection Sensitivity in Non-Linear Magnetoimpedance-Based Sensor

The capacity to detect magnetic nanoparticles (MNPs) of a sensor based on non-linear giant magnetoimpedance effect has been addressed. A meander type sensor was designed with four nearly zero magnetostrictive ribbons connected in series. Different amounts of MNPs, in aqueous solutions, were cumulatively added to the sensor surface. The associated evolution of magnetoinductive voltage of first ( $V_{Z}$ ) and second harmonic ( $V_{2f}$ ) was analyzed as a function of external magnetic field $H $ (maximum value, $H_{\text {MAX}} = 4.4$ kA/m) and as a function of exciting frequency, $f $ (100 kHz–3 MHz). Both harmonics exhibited optimal detection ratios at $H_{\text {MAX}}$ due to the effect of MNPs stray fields on the transverse permeability of the sensing ribbons. Further analysis with frequency was performed to quantify the amount of MNPs. Different parameters were respectively defined, $m_{\text {LF}} $ and ${m}_{\text {HF}}^{2}$ (proportional to permeability) and $R_{0}$ revealing the highest sensitivity of second harmonic for the detection of MNPs. In order to further confirm the role of stray fields in MNPs detection, a comparative study was performed employing diamagnetic gold nanoparticles.

Spin wave steering in three-dimensional magnonic networks

We report the concept of three-dimensional (3D) magnonic structures which are especially promising for controlling and manipulating magnon currents. The approach for fabrication of 3D magnonic crystals (MCs) and 3D magnonic networks is presented. A meander type ferromagnetic film grown at the top of the initially structured substrate can be a candidate for such 3D crystals. Using the finite element method, transfer matrix method, and micromagnetic simulations, we study spin-wave propagation in both isolated and coupled 3D MCs and reconstruct spin-wave dispersion and transmission response to elucidate the mechanism of magnonic bandgap formation. Our results show the possibility of the utilization of proposed structures for fabrication of a 3D magnonic network.

The Lower Siwalik foreland basin sedimentation in the Kumaun Himalaya (India): A transition from megafan setting to incised valley fills

About 300–900 m thick the Lower Siwalik Subgroup exposed in the Kumaun Himalaya has been studied along three far spaced sections, which show variable stratigraphic changes in sedimentation pattern. Available magnetostratigraphic dates in the Kathgodam–Ranibagh section indicate Late Miocene age (12–10Ma) of the Lower Siwalik Subgroup. Detailed lithofacies analysis reveals four depositional settings namely, the Sandstone Lithofacies Association (Channel deposits), the Mudstone Lithofacies Association (Floodplain deposits), the Mottled Mudstone Lithofacies Association (Distal floodplain palaeosols), and the Mottled Siltstone Lithofacies Association (Interfluve deposits). Based on available data on channel pattern, lithofacies association, palaeocurrent pattern, and petrography, stratigraphic cyclicity is analyzed. The complete group is interpreted to be deposited in two Megacycles A and B. About 500 m thick, coarsening upward Megacycle A is internally made up of two Lithofacies sucessions I and II. The cycle is made up of meandering and anastomosing rivers towards the base (Lithofacies Succession I) that gradually evolves into braided rivers towards top (Lithofacies Succession II). This megacycle is inferred as prograding megafan deposit.In contrast, about 400 m thick Megacycle B, made up of two Lithofacies successions III and IV, is fining upward. This cycle is made up of thickly developed meandering – braided river systems at base interbedded with thick interfluve and distal flood plain deposits (Lithofacies Succession III) that gradually becomes thinner towards top, and river system changes to predominantly meandering type (Lithofacies Succession IV). The Megacycle B is inferred to be deposited in tectonically active basin, characterized by incision of rivers.

Design and miniaturization of dual band implantable antennas

Two types of miniaturized dual band implantable antennas are designed and presented, one of a meander type and the other is the so called comb antenna. In medical applications the electromagnetic characteristic changes of tissue in different situations and the corresponding resonant frequency shifts, should not disturb the data transmission. The objective is to design dual band antennas in 400 MHz and 2.4 GHz with suitable bandwidths and small sizes. The meander type antenna was fabricated and its S parameters were measured using an equivalent liquid phantom of skin, fat and muscle which included propanol, butanol, purified water and salt. The experimental results are shown and compared.

Transformation of different reaches of the Niida River (Japan) after extreme flood

Extreme floods can have different effects on the river bottom relief depending on several factors. The geomorphological impact of the extreme flood occurring in the Niida River basin (Fukushima prefecture, Honshu inland, Japan) on the channels and river bottom of different reaches of the river is analyzed. High-resolution satellite images and field assessments were used for quantitative evaluation of river bottom transformation which mainly occurred in the lower reach of the Niida river. The lower reach of the Niida River was divided on three subzones according the channel gradient changes. Each sub-zones is correspond with the dominance of a certain type of channel (straight, meandering and wandering). It was found that bank erosion exceeded in- channel deposition in 1,7-2,7 times for all types of river channel in the low reach located within the coastal floodplain. However, floodplain sedimentation is the most active processes for the river sections with meandering and wandering types of the river channel. Floodplain sedimentation exceed bank-erosion in 2.2 times for river sections with the meandering type of channel and in 2.9 time for the river sections with wandering type of channel. It was found that bank erosion exceeded in- channel deposition in 1,7-2,7 times for all types of river channel in the low reach located within the coastal floodplain. However, floodplain sedimentation is the most active processes for the river sections with meandering and wandering types of the river channel. Floodplain sedimentation exceed bankerosion in 2.2 times for river sections with the meandering type of channel and in 2.9 time for the river sections with wandering type of channel. The bank erosion exceeds floodplain deposition in 1,2 times only within the river sections with straight type of channel. Total sedimentation (in-channel + floodplain) in 2.6 times higher than bank erosion in the lower reach of the Niida River after extreme flood event with probability 4-5%.

Characterization and modeling of a new magnetorheological damper with meandering type valve using neuro-fuzzy

This paper presents the characterization and hysteresis modeling of magnetorheological (MR) damper with meandering type valve. The meandering type MR valve, which employs the combination of multiple annular and radial flow passages, has been introduced as the new type of high performance MR valve with higher achievable pressure drop and controllable performance range than similar counterparts in its class. Since the performance of a damper is highly determined by the valve performance, the utilization of the meandering type MR valve in an MR damper could potentially improve the damper performance. The damping force characterization of the MR damper is conducted by measuring the damping force as a response to the variety of harmonic excitations. The hysteresis behavior of the damper is identified by plotting the damping force relationship to the excitation displacement and velocity. For the hysteresis modeling purpose, some parts of the data are taken as the training data source for the optimization parameters in the neuro-fuzzy model. The performance of the trained neuro-fuzzy model is assessed by validating the model output with the remaining measurement data and benchmarking the results with the output of the parametric hysteresis model. The validation results show that the neuro-fuzzy model is demonstrating good agreement with the measurement results indicated by the average relative error of only around 7%. The model also shows robustness with no tendency of growing error when the input values are changed.

Моделирование характеристик низковольтного МЭМС-переключателя латерального типа с пружиной типа "Меандр"

Моделирование характеристик низковольтного МЭМС-переключателя латерального типа с пружиной типа "Меандр"

Fabrication process induced changes in scattering parameters of meander type RFMEMS shunt switch

This paper reports about the effect of fabrication process induced changes on scattering parameters of RF MEMS switch structure with meander geometry for 18–40 GHz (Ka-band) application. The designed structure showed a return loss better than 15 dB with a maximum isolation of 43 dB at 35 GHz. From the parametric analysis, both the return loss and isolation parameters are found to be more dependent on the meander width and dielectric thickness compared to the other dimensions. The switch structure is fabricated by surface micromachining technique. The effect of variation of fabricated device dimensions, due to the various processing steps, on the isolation characteristic is also studied. The fabricated structure exhibited an on–off capacitance ratio of ~200:1. The pull-down voltage is found to be 12.5 V. The return loss of the fabricated switch structure is found to be better than 13.5 dB; whereas, the maximum isolation (32 dB) is observed at 33 GHz. The shift in the resonance is due to the reduction of silicon nitride layer thickness during sacrificial layer removal (to release the switch structure) in diluted HF solution. The measured scattering parameters are found to be matching well with the corresponding simulation data of the fabricated switch dimensions.

Caracterización del patrón hidromorfológico del Arroyo de la Ventana en su tramo medio alto (Buenos Aires, Argentina)

En este trabajo se determina el patrón fluvial del Arroyo de la Ventana a través de las características hidrogeomorfológicas del tramo medio alto del curso fluvial. Se generó un Modelo Digital del Terreno (MDT) de la cuenca media-alta del curso en base a los datos de las curvas de nivel de la carta topográfica de Tornquist, a escala 1:50.000. La cartografía geomorfológica del curso fue realizada a partir de la información del vuelo fotogramétrico del año 1981 a escala 1:20.000. Asimismo se realizó un relevamiento in situ de tres secciones transversales del cauce. Se identificaron dos patrones fluviales diferenciados: tipo trenzado, en el tramo alto del curso y otro de tipo meandriforme en el tramo medio. La dinámica fluvial actual del curso muestra una tendencia general a la incisión en el tramo analizado.

Development of a modular MR valve using meandering flow path structure

The extensive development of the magnetorheological (MR) valve has successfully introduced a new high-performance compact-class MR valve using a meandering flow path structure. Aside from the performance improvement, in real applications, the ease of performance adjustment also needs to be improved. This study focused on the development of a new design of a modular MR valve using a meandering flow path to improve the adjustability of the valve performance. The approach is proposed based on the high-performance advantages of a meandering flow path structure, while at the same time utilizing the benefit of the modular structure in terms of performance flexibility. In order to evaluate the performance of the modular structure, the analytical assessment was conducted for three different module stages: the single-stage module, the double-stage module, and triple-stage module. To predict the strength of the magnetic field in the effective area, the magnetic simulation was conducted through an open-source software called the FEMM (Finite Element Method Magnetics). The quasi-steady mathematical model of the proposed valve was also derived to conduct the analytical assessment as well as to predict the valve performance. In order to validate the simulation results, the prototypes of the proposed valve are experimentally tested with the aid of the hydraulic cylinder on a dynamic test machine. The results of the MR valve assessment from both the simulation and experimental test demonstrated that the pressure drop rating of the meandering type MR valve can be easily modified using modular structure by changing the number of module stages.

Modeling k-noncrossing closed RNA secondary structures via meandric compression.

In this chapter we present the transformation of a meander to its compression and we apply this new formulation for the modeling of k-noncrossing closed RNA secondary structures. We obtain this by using curves which consist parts of their meandric curve. We prove basic properties and produce generating procedures. Two new types of meanders arise: the simple and the perpendicular, in order to be used as representatives of k-noncrossing closed RNA secondary structures.

논산천의 서식처 유형별 어류군집의 분포특성

The spatial distribution characteristic of fish community were investigated at the 10 habitat types in the Nonsan stream from August, 2008 to June, 2009. The collected species during the surveyed period were 26 species belong to 6 families. Korean endemic species were Sarcocheilichthys nigripinnis morii, Squalidus japonicus coreanus, Hemiculter eigenmanni, Pseudobagrus koreanus, and Odontobutis interrupta which showed 19.2% ratio of total species. Dominant species was Zacco platypus, and subdominant species was Tridentiger brevispinis. Dominant species according to habitat types were Micropterus salmoides(substrate type pool and rock type pool), Lepomis macrochirus(channel connected pool and channel unconnected pool/abandoned type pool), T. brevispinis(channel unconnected pool/overflow type and run) and Z. platypus(riffle, meander type pool, side channel, and dam type pool). As a results of community analysis in side channel, diversity index showed relatively high values, indicating that habitat types in the Nonsan stream have relatively stable community structure. Bray-curtis cluster analysis indicated that the meander type pool and riffle showed the most similar values(80.8%). Moreover, cluster and principal component analysis were classified as 2 groups(lotic and lentic habitats).

탐색 및 구조 시스템용 구명조끼 내장형 안테나

선박이 운항 중 해난 사고가 발생하여 선원이나 승객이 물에 빠지는 경우 신속히 이들을 구조하는 것은 매우 중요한 일이다. 대부분의 해난 사고의 경우 물에 빠진 사람이 구명조끼를 입고 있으므로, 구명조끼에 GPS 및 Cospas-Sarsat 통신을 위한 모듈이 내장된다면 구조가 용이할 것이다. 본 논문에서는 구명조끼에 내장이 가능하며 GPS 및 Cospas-Sarsat 통신을 위한 이중대역 안테나를 개발하고자 한다. 안테나는 두께 0.2mm 인 FR4 기판을 사용하여 유연성을 확보하였고, 1.575 GHz와 406MHz에서 동작하며, 구명조끼의 어깨 부근에 장착이 될 수 있는 안테나를 설계하였다. GPS 통신용 안테나는 원형편파 특성을 갖는 링 슬롯 안테나로 구현하였고, 미앤드 형태의 선형 편파 안테나를 Cospas-Sarsat 통신용으로 사용하였다. 단일 마이크로스트립 선로를 통해 급전이 이루어지며, 두 공진 안테나간의 상호 간섭을 최소화하기 위해 개방형 스터브를 사용하였다. 제작한 안테나를 구명조끼에 장착하여 반사손실 측정을 통해 GPS 및 Cospas-Sarsat 주파수에서 안테나의 성능을 확인하였다. When the crew or passengers fall into the water due to marine accident of vessel, it is very important to rescue them quickly. In the case of marine accidents, most people in distress have been wearing a lifejacket, so if the GPS and Cospas-Sarsat communication module will be integrated within the lifejacket, it is easy to rescue them. In this paper, development of the dual band lifejacket-integrated antenna for GPS and Cospas-Sarsat communication is discussed. The antenna with the FR-4 substrate of 0.2mm thickness for flexibility was designed that it can be fitted close to the shoulder of the life jacket and operate at 1.575GHz and 406MHz. The GPS communication antenna was implemented with a ring-slot antenna having a circular polarized characteristic and a meander type linear polarized antenna is used as Cospas-Sarsat communication. The two antennas are fed by a single microstrip line and an open stub is used to minimize the mutual interference between the two antennas. The performance of the fabricated antenna attached to the life vest is confirmed by the measurement of the return loss at GPS and Cospas-Sarsat frequency bands.