One-layer Model Research Articles

Circularly Polarized Helical Antenna for ISM-Band Ingestible Capsule Endoscope Systems

A multilayer miniaturized circularly polarized (CP) helical antenna is designed and experimentally demonstrated for industrial, scientific, and medical (ISM) (2.4-2.48 GHz) ingestible capsule endoscope systems. The proposed antenna is composed of three open loops at various layers connected by via holes to form an axial-mode helical structure to generate traveling wave radiation. A one-layer muscle phantom model is used for initial design and optimization. The footprint of the proposed antenna is π×(5.5) <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ×3.81 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> . The simulated and measured impedance bandwidth is over 40% and 26% in the one-layer muscle phantom, respectively. The simulated axial ratio (AR) bandwidth is around 33.3%. The CP purity of the proposed antenna is calculated by comparing the communication link levels for two orthogonal polarizations. Additionally, electrical components are modeled inside the capsule to evaluate the effects on the antenna performance. CST voxel Gustav human body is utilized to study the design in a realistic environment. Finally, an omnidirectional CP exterior antenna is designed and the communication link is evaluated.

Precisiones sobre el intercambio agua superficial/agua subterránea en el acuífero superior de Florida, centro norte de Florida (EEUU), a partir de datos de caudales de la corriente y modelado numérico

Surface-water/groundwater exchange impacts water quality and budgets. In karst aquifers, these exchanges also play an important role in dissolution. Five years of river discharge data were analyzed and a transient groundwater flow model was developed to evaluate large-scale temporal and spatial variations of exchange between an 80-km stretch of the Suwannee River in north-central Florida (USA) and the karstic upper Floridan aquifer. The one-layer transient groundwater flow model was calibrated using groundwater levels from 59 monitoring wells, and fluxes were compared to the exchange calculated from discharge data. Both the numerical modeling and the discharge analysis suggest that the Suwannee River loses water under both low- and high-stage conditions. River losses appear greatest at the inside of a large meander, and the former river water may continue across the meander within the aquifer rather than return to the river. In addition, the numerical model calibration reveals that aquifer transmissivity is elevated within this large meander, which is consistent with enhanced dissolution due to river losses. The results show the importance of temporal and spatial variations in head gradients to exchange between streams and karst aquifers and dissolution of the aquifers.

Numerical modeling of geomagnetically induced currents in a Brazilian transmission line

Rapid changes in the external geomagnetic field induce electric currents in conducting materials at the Earth’s surface. These geomagnetically induced currents (GIC) are mostly studied in transmission lines at high-latitude due to their frequent hazards. However, recent studies have shown that low- and middle-latitude regions may also be subject to problems due to GIC occurrences. In this work we apply a numerical model, using plane wave theory and a one-dimensional electrical resistivity model of the region, to calculate the geoelectric field and the GIC measured directly at the Itumbiara–São Simão (IS) transmission line (Southeast Brazil) during a magnetic storm occurred between 7–10th November 2004. We use two electrical resistivity models: (a) one-layer model, in which our results do not reproduce the measured GIC directly in the IS transmission line, and (b) four-layer model, which presents similar patterns of temporal variation and intensities of the measured electric fields and GIC. After validating the four-layer numerical model, we calculate the electric fields and GIC during the “Halloween storm” (29th October–1st November 2003). Our results of the Halloween storm show maximum GIC amplitudes of 25A, which are higher than registered in other middle latitude countries, such as South Africa and Uruguay. These results indicate that the Brazilian power network might be subjected to the GIC hazards in the future due to strong magnetic storms. In addition, our numerical model might be used as a potential tool for different geological sets, electrical resistivity models, transmission lines with distinct characteristics and for a range of magnetic storms intensities.

Burnett hypersonic thin shock layer near the windward side of a flat plate

A one-layer model of a Burnett thin shock layer is simplified to fit the problem of a rarefied gas hypersonic flow along the windward side of a flat plate placed at a large angle of attack with an incident flow; here, the mathematical apparatus of the theory of a two-layer hypersonic thin viscous shock layer near nonthin bodies is used. This theory suggests that in the structure of a flow, between the followed body’s surface and the incident undisturbed flow, we have two typical regions-sublayers (a smeared pressure shock plus the shock layer proper). It is shown that the considered Burnett thin shock layer problem in the two-layer approximation completely reduces to the corresponding Navier-Stokes problem.

Development of GWNU (Gangneung-Wonju National University) one-layer transfer model for calculation of solar radiation distribution of the Korean peninsula

Gangneung-Wonju National University (GWNU) one-layer solar radiation model is developed in order to resolve the lack of the vertical structure of atmospheric components and fast calculation with high horizontal spatial resolution. GWNU model is based on IQBAL and NREL methods and corrected by precise multi-layer Line-By-Line (LBL) model. Further, the amount of solar radiation reaching the surface by using 42 types of vertical atmospheric data as input data was compared with detailed models and one-layer models. One-layer solar radiation models were corrected depending on sensitivity of each input data (i.e., total precipitable water, ozone, mixed gas, and solar zenith angle). Global solar radiation was calculated by corrected GWNU solar model with satellites (MODIS, OMI and MTSAT-2), KLAPS model prediction data in Korea peninsula in 2010, and the results were compared to surface solar radiation observed by 22 KMA solar radiation sites. Calculated solar radiation annually accumulated showed highest solar radiation distribution in Andong, Daegu, and Jinju regions, meanwhile the observation data showed lower solar radiation in Daegu region compared to model result values.

A Heuristic Model of Dansgaard–Oeschger Cycles. Part I: Description, Results, and Sensitivity Studies

Abstract A simple model for studying the Dansgaard–Oeschger (D-O) cycles of the last glacial period is presented, based on the T. Dokken et al. hypothesis for D-O cycles. The model is a column model representing the Nordic seas and is composed of ocean boxes stacked below a one-layer sea ice model with an energy-balance atmosphere; no changes in the large-scale ocean overturning circulation are invoked. Parameterizations are included for latent heat polynyas and sea ice export from the column. The resulting heuristic model was found to cycle between stadial and interstadial states at times scales similar to those seen in the proxy observational data, with the presence or absence of perennial sea ice in the Nordic seas being the defining characteristic for each of these states. The major discrepancy between the modeled oscillations and the proxy record is in the length of the interstadial phase, which is shorter than that observed. The modeled oscillations were found to be robust to parameter changes, including those related to the ocean heat flux convergence (OHFC) into the column. Production of polynya ice was found to be an essential ingredient for such sustained oscillatory behavior. A simple parameterization of natural variability in the OHFC enhances the robustness of the modeled oscillations. The authors conclude by discussing the implications of such a hypothesis for the state of the Nordic seas today and its state during the Last Glacial Maximum and contrasting the model to other hypotheses that invoke large-scale changes in the Atlantic meridional overturning circulation for explaining millennial-scale variability in the climate system. An extensive time-scale analysis will be presented in the future.

Impact of Megacity Shanghai on the Urban Heat-Island Effects over the Downstream City Kunshan

The impact of upstream urbanization on the enhanced urban heat-island (UHI) effects between Shanghai and Kunshan is investigated by analyzing seven years of surface observations and results from mesoscale model simulations. The observational analysis indicates that, under easterly and westerly winds, the temperature difference between Shanghai and Kunshan increases with wind speed when the wind speed $$<$$ 5 m s $$^{-1}$$ . The Weather Research and Forecasting (WRF) numerical model, coupled with a one-layer urban canopy model (UCM), is used to examine the UHI structure and upstream effects by replacing the urban surface of Shanghai and/or Kunshan with cropland. The WRF/UCM modelling system is capable of reproducing the surface temperature and wind field reasonably well. The simulated urban canopy wind speed is a better representation of the near-surface wind speed than is the 10-m wind speed at the centre of Shanghai. Without the urban landscape of Shanghai, the surface air temperature over downstream Kunshan would decrease by 0.2–0.4 $$^{\circ }$$ C in the afternoon and 0.4–0.6 $$^{\circ }$$ C in the evening. In the simulation with the urban landscape of Shanghai, a shallow cold layer is found above the UHI, with a minimum temperature of about $$-0.2$$ to $$-$$ 0.5 $$^{\circ }$$ C during the afternoon hours. Strong horizontal divergence is found in this cold layer. The easterly breeze over Shanghai is strengthened at the surface by strong UHI effects, but weakened at upper levels. With the appearance of the urban landscape specific humidity decreases by 0.5–1 g kg $$^{-1}$$ within the urban area because of the waterproof property of an urban surface. On the other hand, the upper-level specific humidity is increased because of water vapour transferred by the strong upward vertical motions.

Influence of Embedded Fibers and an Epithelium Layer on the Glottal Closure Pattern in a Physical Vocal Fold Model

PURPOSE The purpose of this study was to explore the possible structural and material property features that may facilitate complete glottal closure in an otherwise isotropic physical vocal fold model. METHOD Seven vocal fold models with different structural features were used in this study. An isotropic model was used as the baseline model, and other models were modified from the baseline model by either embedding fibers aligned along the anterior-posterior direction in the body or cover layer, adding a stiffer outer layer simulating the epithelium layer, or a combination of the 2 features. Phonation tests were performed with both aerodynamic and acoustic measurements and high-speed imaging of vocal fold vibration. RESULTS Compared with the isotropic one-layer model, the presence of a stiffer epithelium layer led to complete glottal closure along the anterior-posterior direction and strong excitation of high-order harmonics in the resulting acoustic spectra. Similar improvements were observed with fibers embedded in the cover layer, but to a lesser degree. The presence of fibers in the body layer did not yield noticeable improvements in glottal closure or harmonic excitation. CONCLUSION This study shows that the presence of collagen and elastin fibers and the epithelium layer may play a critical role in achieving complete glottal closure.

Experimental and numerical studies on wave breaking characteristics over a fringing reef under monochromatic wave conditions.

Fringing reefs play an important role in protecting the coastal area by inducing wave breaking and wave energy dissipation. However, modeling of wave transformation and energy dissipation on this topography is still difficult due to the unique structure. In the present study, two-dimensional laboratory experiments were conducted to investigate the cross-shore variations of wave transformation, setup, and breaking phenomena over an idealized fringing reef with the 1/40 reef slope and to verify the Boussinesq model under monochromatic wave conditions. One-layer and two-layer model configurations of the Boussinesq model were used to figure out the model capability. Both models predicted well (r 2 > 0.8) the cross-shore variation of the wave heights, crests, troughs, and setups when the nonlinearity is not too high (A 0/h 0 < 0.07 in this study). However, as the wave nonlinearity and steepness increase, the one-layer model showed problems in prediction and stability due to the error on the vertical profile of fluid velocity. The results in this study revealed that one-layer model is not suitable in the highly nonlinear wave condition over a fringing reef bathymetry. This data set can contribute to the numerical model verification.

PERFORMANCE OF AN IMPLANTED ELECTRICALLY COUPLED LOOP ANTENNA INSIDE HUMAN BODY

Implanted antennas are widely used in hyperthermia and biomedical applications. The antenna needs to be extremely small while maintaining a permissible Speciflc Absorption Rate (SAR) and being able to cope with the detuning efiects due to the dielectric properties of human body tissues. Most of the proposed antennas for implanted applications are electric fleld antennas such as Planner Inverted-F Antennas (PIFA) and micro-strip patch antennas. By minimizing the size of an electric fleld antenna, the near zone electric fleld will increase, resulting in higher SAR. This work is devoted to design a miniaturized magnetic fleld antenna to overcome the above limitations. The proposed electrically coupled loop antenna (ECLA) has high magnetic fleld and low electric fleld in the near zone and therefore, has a small SAR and is less sensitive to detuning efiects. ECLA is designed at the Medical Implanted Communication Service (MICS) band with dimensions of (5£5£3mm 3 ). ECLA has been simulated inside one-layer human body model, three-layer spherical human head model, human head and human body. From the simulation results, ECLA inside the human body has a 5MHz{3dB bandwidth, i14dB gain, and radiation e-ciency of 0.525%. The 1g average SAR inside the human body for 10mW input power is about 1W/kg which is 7times lower than the SAR for a patch antenna of the same size with the same accepted power.

Ni-CeO2 Cermets Synthesis by Solid State Sintering of Ni/CeO2 Multilayer

Nickel and gadolinium doped cerium oxide (GDC) cermet is intensively investigated for an application as an anode material for solid oxide fuel cells based on various electrolytes. The purpose of the present investigation is to analyze morphology, microstructure, and optical properties of deposited and annealed for one hour in the temperatures from 500 ºC to 900 ºC Ni/CeO2 multilayer thin films deposited by sputtering. The crystallographic structure of thin films was investigated by X-ray diffraction. The morphology of the film cross-section was investigated with scanning electron microscope. The elemental analysis of samples was investigated by energy-dispersive X-ray spectroscopy. The fitting of the optical reflectance data was made using Abeles matrix method that is used for the design of interference coatings. The film cross-section of the post-annealed samples consisted of four layers. The first CeO2 layer (on Si) had the same fine columnar structure with no features of Ni intermixing. The part of Ni (middle-layer) after annealing was converted to NiO with grain size exceeding 100 nm. The CeO2 layer deposited on Ni was divided into two layers. Lower layer had small grains not exceeding 25 nm and consisting of NiO and CeO2 mixture. Upper layer consisted of CeO2 columns with approximate thickness of 50 nm. Ni sample annealed at 600 ºC was fully oxidized. The NiO thickness and refraction index were almost steady after annealing in various temperatures. The approximation of experimental reflectance data was successful only for the samples with one transparent homogeneous layer. The reflectance of the Ni/CeO2 samples annealed at intermediate temperatures could not be fitted using one-layer or three-layer model. That may show that a simplified model could not be implemented. The real system has complicated distribution of refraction index. DOI: http://dx.doi.org/10.5755/j01.ms.19.4.3073

Resonant excitation of coastal Kelvin waves in the two-layer rotating shallow water model

Abstract. Resonant excitation of coastal Kelvin waves by free inertia–gravity waves impinging on the coast is studied in the framework of the simplest baroclinic model: two-layer rotating shallow water with an idealized straight coast. It is shown that, with respect to the previous results obtained with the one-layer model, new resonances leading to a possible excitation of Kelvin waves appear. The most interesting ones, described in the paper, are resonances of a baroclinic inertia–gravity wave with either another wave of this kind, or with a coastal current, leading to generation of a barotropic Kelvin wave. A forced Hopf equation results in any case for the evolution of the Kelvin wave amplitude.

Comparison between SAR Soil Moisture Estimates and Hydrological Model Simulations over the Scrivia Test Site

In this paper, the results of a comparison between the soil moisture content (SMC) estimated from C-band SAR, the SMC simulated by a hydrological model, and the SMC measured on ground are presented. The study was carried out in an agricultural test site located in North-west Italy, in the Scrivia river basin. The hydrological model used for the simulations consists of a one-layer soil water balance model, which was found to be able to partially reproduce the soil moisture variability, retaining at the same time simplicity and effectiveness in describing the topsoil. SMC estimates were derived from the application of a retrieval algorithm, based on an Artificial Neural Network approach, to a time series of ENVISAT/ASAR images acquired over the Scrivia test site. The core of the algorithm was represented by a set of ANNs able to deal with the different SAR configurations in terms of polarizations and available ancillary data. In case of crop covered soils, the effect of vegetation was accounted for using NDVI information, or, if available, for the cross-polarized channel. The algorithm results showed some ability in retrieving SMC with RMSE generally &lt;0.04 m3/m3 and very low bias (i.e., &lt;0.01 m3/m3), except for the case of VV polarized SAR images: in this case, the obtained RMSE was somewhat higher than 0.04 m3/m3 (≤0.058 m3/m3). The algorithm was implemented within the framework of an ESA project concerning the development of an operative algorithm for the SMC retrieval from Sentinel-1 data. The algorithm should take into account the GMES requirements of SMC accuracy (≤5% in volume), spatial resolution (≤1 km) and timeliness (3 h from observation). The SMC estimated by the SAR algorithm, the SMC estimated by the hydrological model, and the SMC measured on ground were found to be in good agreement. The hydrological model simulations were performed at two soil depths: 30 and 5 cm and showed that the 30 cm simulations indicated, as expected, SMC values higher than the satellites estimates, with RMSE higher than 0.08 m3/m3. In contrast, in the 5-cm simulations, the agreement between hydrological simulations, satellite estimates and ground measurements could be considered satisfactory, at least in this preliminary comparison, showing a RMSE ranging from 0.054 m3/m3 to 0.051 m3/m3 for comparison with ground measurements and SAR estimates, respectively.

Two-layer shallow-water dam-break solutions for gravity currents in non-rectangular cross-area channels

AbstractWe consider the propagation of a high-Reynolds-number gravity current in a horizontal channel along the horizontal coordinate $x$. The bottom and top of the channel are at $z= 0, H$, and the cross-section is given by the quite general $- {f}_{1} (z)\leq y\leq {f}_{2} (z)$ for $0\leq z\leq H$. We develop a two-layer shallow-water (SW) formulation, and we implement it for the solution of the dam-break problem. The dependent variables are the position of the interface, $h(x, t)$, and the velocity (averaged over the area of the current), $u(x, t)$. The non-rectangular cross-section geometry enters the formulation via $f(h)$ and integrals of $f(z)$ and $zf(z)$, where $f(z)= {f}_{1} (z)+ {f}_{2} (z)$ is the width of the channel. For a given geometry $f(z)$, the free input parameters of the lock-release problem are: (i) the height ratio $H/ {h}_{0} $ of ambient to lock; and (ii) the density ratio of ‘light’ to ‘heavy’ fluids, $R$. We show that the dam-break problem is amenable to solution by the method of characteristics, but various complications (internal jumps, critical restrictions) appear when the return flow in the ambient is significant; these features are not captured by a one-layer shallow-water model. The role of the non-standard geometry in the detection and calculation of the internal and reflected jumps, and on the dam-break flow field, is elucidated. The methodology is illustrated for Boussinesq flow in typical geometries: power-law ($f(z)= b{z}^{\alpha } $, where $b, \alpha $ are positive constants), trapezoidal and circle (full or sector); we solved for full-depth ($H= 1$) and part-depth ($H\gt 1$) lock-release configurations. The approach seems to work well: in all the tested cases, the solution was obtained with simple mathematical and numerical tools (a Runge–Kutta integrator and a secant-method solver); the insights are compatible with our previous understanding of the problem; and the standard (rectangular) case is recovered in the appropriate limit (i.e. when the side-boundaries of the trapezium cross-section are vertical or far apart). A comparison of the speed of propagation with available experiments is also presented, and the agreement is satisfactory. The present solution is a significant generalization of the classical two-layer gravity–current dam-break problem. The classical formulation for a rectangular (or laterally unbounded) channel is now just a particular case, $f(z)= $ const., in the wide domain of cross-sections covered by the new model.

An Enhanced Cross-Layer MAC Design for Energy Efficiency in Wireless Sensor Networks

In wireless sensor networks, the main research objective is the development of algorithms and protocols ensuring minimal energy consumption. Most proposed solutions are based on one-layer stack model approach. In this paper, we propose an energy efficient MAC protocol that applies routing and MAC layers jointly. In this new approach, the interactions between MAC and Routing layers are fully exploited to achieve energy efficiency for wireless sensor networks. In the proposed MAC protocol, we solve the forced wake-up problem in the adaptive S-MAC to reduce energy consumption of the nodes, by exploiting routing information to wake-up only nodes belonging to a routing path. Simulation results show that the proposed CL-MAC protocol significantly improves energy efficient compared to the adaptive S-MAC.

Miniaturised slot antenna for biomedical applications

An implantable slot antenna with a miniaturised size of 139.7 mm3 (10 × 11 × 1.27 mm) for biomedical applications is proposed. Operating at the Medical Implant Communications Service (MICS) band, miniaturisation of the antenna is realised by etching a meandered slot on the top metal with one end open. A microstrip line is utilised as excitation with a shorting connected to the radiator. In addition, two U-shaped stubs are adopted to match the feeding impedance to 50 Ω. The antenna is simulated in a one-layer skin model as well as in the arm of a human model and measured in skin-mimicking tissue. Good agreements can be obtained and the measurement results show that a broad bandwidth of 28.3% (from 354 to 469 MHz) for |S11| less than − 10 dB can be achieved.

Snow specific surface area simulation using the one-layer snow model in the Canadian LAnd Surface Scheme (CLASS)

Abstract. Snow grain size is a key parameter for modeling microwave snow emission properties and the surface energy balance because of its influence on the snow albedo, thermal conductivity and diffusivity. A model of the specific surface area (SSA) of snow was implemented in the one-layer snow model in the Canadian LAnd Surface Scheme (CLASS) version 3.4. This offline multilayer model (CLASS-SSA) simulates the decrease of SSA based on snow age, snow temperature and the temperature gradient under dry snow conditions, while it considers the liquid water content of the snowpack for wet snow metamorphism. We compare the model with ground-based measurements from several sites (alpine, arctic and subarctic) with different types of snow. The model provides simulated SSA in good agreement with measurements with an overall point-to-point comparison RMSE of 8.0 m2 kg–1, and a root mean square error (RMSE) of 5.1 m2 kg–1 for the snowpack average SSA. The model, however, is limited under wet conditions due to the single-layer nature of the CLASS model, leading to a single liquid water content value for the whole snowpack. The SSA simulations are of great interest for satellite passive microwave brightness temperature assimilations, snow mass balance retrievals and surface energy balance calculations with associated climate feedbacks.

Gravity currents with double stratification: a numerical and analytical investigation

We consider high-Reynolds-number Boussinesq gravity current and intrusion systems in which both the ambient and the propagating “current” are linearly stratified. The main focus is on a current of fixed volume released from a rectangular lock; the height ratio of the fluids \(H\), the stratification parameter of the ambient \(S\), and the internal stratification parameter of the current, \(\sigma \), are quite general. We perform two-dimensional Navier–Stokes simulation and compare the results with those of a previously-published one-layer shallow-water model. The results provide insights into the behavior of the system and enhance the confidence in the approximate model while also revealing its limitations. The qualitative predictions of the model are confirmed, in particular: (1) there is an initial “slumping” stage of propagation with constant speed \(u_N\), after which \(u_N\) decays with time; (2) for fixed \(H\) and \(S\), the increase of \(\sigma \) causes a slower propagation of the current; (3) for some combinations of the parameters \(H,S, \sigma \) the fluid released from the lock lacks initially (or runs out quickly of) buoyancy “driving power” in the horizontal direction, and does not propagate like a gravity current. There is also a fair quantitative agreement between the predictions of the model and the simulations concerning the spread of the current.

Synchronism of variations in the main geomagnetic field and earth rotation velocity fluctuations

Variations in the value of the source magnetic moment, responsible for the dipole component of the main geomagnetic field, and Earth rotation velocity fluctuations have been studied comparatively. Three quasi-harmonic components with close periods, for which their own phase shifts were obtained, have been detected in time series of the analyzed processes. The mantle conductivity effect on these shifts has been studied in the scope of a one-layer model; for this purpose, the amplitude-phase characteristic of the mantle as a filter has been constructed. The mantle conductivity has been estimated (σ = 270 ± 20 S m−1) on the assumption that the phase shift mainly depends on the mantle effect. It has been assumed that the variations in the time series of the analyzed processes are almost cophased and can be caused by one external factor, e.g., tides.

Publisher's Note: “Gravity currents in non-rectangular cross-section channels: Analytical and numerical solutions of the one-layer shallow-water model for high-Reynolds-number propagation” [Phys. Fluids 25, 026601 (2013)

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