Single Square Research Articles

Mode Matching Analysis of an E-Plane $90^{\circ }$ Bend With a Square Step in Parallel-Plate Waveguide

We present a numerical model for the analysis of an E-plane right-angle bend in parallel-plate waveguide (PPW), with a single square step for matching purposes. This design can achieve wideband matching and can be implemented using hollow waveguides as well as multilayer printed circuit boards. An even-and odd-mode analysis is performed exploiting the symmetry of the structure. Two auxiliary problems are defined considering the bisecting plane of the bend as a perfect electric conductor or a perfect magnetic conductor, respectively. They are solved using a mode matching method. The mathematical derivations are discussed in detail. The proposed procedure can be embedded in efficient tools for the analysis of complex PPW systems, such as feed networks for antenna arrays.

Joint attention enhances visual working memory.

Joint attention-the mutual focus of 2 individuals on an item-speeds detection and discrimination of target information. However, what happens to that information beyond the initial perceptual episode? To fully comprehend and engage with our immediate environment also requires working memory (WM), which integrates information from second to second to create a coherent and fluid picture of our world. Yet, no research exists at present that examines how joint attention directly impacts WM. To investigate this, we created a unique paradigm that combines gaze cues with a traditional visual WM task. A central, direct gaze 'cue' face looked left or right, followed 500 ms later by 4, 6, or 8 colored squares presented on one side of the face for encoding. Crucially, the cue face either looked at the squares (valid cue) or looked away from them (invalid cue). A no shift (direct gaze) condition served as a baseline. After a blank 1,000 ms maintenance interval, participants stated whether a single test square color was present or not in the preceding display. WM accuracy was significantly greater for colors encoded in the valid versus invalid and direct conditions. Further experiments showed that an arrow cue and a low-level motion cue-both shown to reliably orient attention-did not reliably modulate WM, indicating that social cues are more powerful. This study provides the first direct evidence that sharing the focus of another individual establishes a point of reference from which information is advantageously encoded into WM. (PsycINFO Database Record

Recursive Frequency Domain Decomposition for Multidimensional Ambient Modal Estimation

This paper proposes a multidimensional recursive ambient modal analysis algorithm called recursive frequency domain decomposition (recursive FDD or RFDD). The method enables simultaneous processing of a large number of synchrophasor measurements for real-time ambient modal estimation. The method combines a previously proposed multidimensional block processing algorithm FDD with a single input recursive least square (RLS) algorithm into developing a new frequency domain multidimensional recursive algorithm. First, an auto-regressive model is fitted onto the sampled data of each signal using the time-domain RLS approach. Subsequent modal analysis is carried out in frequency domain in the spirit of FDD. The conventional FDD method uses non-parametric methods for power spectrum density (PSD) estimation. The proposed method in this paper by estimating PSD with a parametric method provides smoother PSD estimation which results in less standard deviation in RFDD estimates compared to FDD. The algorithm is tested on archived synchrophasor data from a real power system.

Modeling the Response of Anopheles gambiae (Diptera: Culicidae) Populations in the Kenya Highlands to a Rise in Mean Annual Temperature.

A dynamical model of Anopheles gambiae larval and adult populations is constructed that matches temperature-dependent maturation times and mortality measured experimentally as well as larval instar and adult mosquito emergence data from field studies in the Kenya Highlands. Spectral classification of high-resolution satellite imagery is used to estimate household density. Indoor resting densities collected over a period of one year combined with predictions of the dynamical model give estimates of both aquatic habitat and total adult mosquito densities. Temperature and precipitation patterns are derived from monthly records. Precipitation patterns are compared with average and extreme habitat estimates to estimate available aquatic habitat in an annual cycle. These estimates are coupled with the original model to produce estimates of adult and larval populations dependent on changing aquatic carrying capacity for larvae and changing maturation and mortality dependent on temperature. This paper offers a general method for estimating the total area of aquatic habitat in a given region, based on larval counts, emergence rates, indoor resting density data, and number of households.Altering the average daily temperature and the average daily rainfall simulates the effect of climate change on annual cycles of prevalence of An. gambiae adults. We show that small increases in average annual temperature have a large impact on adult mosquito density, whether measured at model equilibrium values for a single square meter of habitat or tracked over the course of a year of varying habitat availability and temperature.

Pricing Bounds for VIX Derivatives via Least Squares Monte Carlo

Derivatives on the Chicago Board Options Exchange volatility index (VIX) have gained significant popularity over the last decade. The pricing of VIX derivatives involves evaluating the square root of the expected realised variance which cannot be computed by direct Monte Carlo methods. Least squares Monte Carlo methods can be used but the sign of the error is difficult to determine. In this paper, we propose new model independent upper and lower pricing bounds for VIX derivatives. In particular, we first present a general stochastic duality result on payoffs involving concave functions. This is then applied to VIX derivatives along with minor adjustments to handle issues caused by the square root function. The upper bound involves the evaluation of a variance swap, while the lower bound involves estimating a martingale increment corresponding to its hedging portfolio. Both can be achieved simultaneously using a single linear least square regression. Numerical results show that the method works very well for VIX futures, calls and puts under a wide range of parameter choices.

Seed predation has the potential to drive a rare plant to extinction

Summary Pre‐dispersal seed predation is sometimes considered unlikely to dramatically affect plant population growth because plants are generally expected to produce more seeds than there are safe sites for germination. Lupinus constancei is a rare herb of limited distribution, with fewer than 400 reproductive individuals restricted to a single square kilometre of north‐western California, USA. In addition to the vulnerability resulting from its extremely small population size, L. constancei faces heavy seed predation by small mammals. As a stop‐gap measure to prevent population decline, managers began covering a large number of the reproductive plants with herbivory exclosures in 2003, but the population‐level effects of seed predation and the effectiveness of this caging treatment were unknown. We used 10 years of demographic data to compare the population dynamics of plants inside herbivory exclosures with those sustaining ambient rodent seed predation. We found that the stochastic population growth rate would be robust without seed predation (λs = 1·17), but without continued human intervention (i.e. use of exclosures), the current rate of predation would result in a decline towards extinction (λs = 0·92). After our study concluded, high mortality due to two extreme winter droughts followed by a wildland fire reduced the number of reproductive plants to ∼103, making extinction of L. constancei more likely. Synthesis and applications. The prevalence of consumer‐driven population decline is largely unknown, but this study demonstrates that pre‐dispersal seed predation by rodents can have powerful population‐level effects, and represents one set of conditions under which consumer pressure has the potential to drive plant extinction. However, with continued management to limit the effects of seed predation in the short‐term and investigation into the ultimate drivers of this high seed predation rate in the long term, the Lassics lupine population could be restored to a robust rate of growth.

The effects and mechanism of electrical stimulation on esophageal muscle in rat: an experimental study

Objective To explore the correlation between smooth muscle contraction and stimulation parameters, and mechanism of electrical stimulation on the esophageal body muscle strips in normal rats. Methods A segment of lower part esophagus of 20 healthy male WISTAR rats was obtained. Single phase square wave(width 25 ms)was used and the electrical stimulation lasted for 3 s with varied electrical parameter(current: 1.5 V, 3.0 V, 5.0 V, 8.0 V; frequency: 5 Hz, 10 Hz, 20 Hz). The correlation between tension and stimulation parameters was studied.Fifty healthy male rats were divided randomly into control group(n=10), ATR group(n=10), PHT group(n=10), L-NNA group(n=10), TTX group(n=10). Respective drugs were given 10 minutes before lower part of esophagus was stimulated with single phase square wave(5.0 V; 20 Hz; width 25 ms), the tension was recorded and compared among groups. Results At frequency 20 Hz and width 25 ms, the peak value of contraction in 1.5 V group was 0 g. The peak value of contraction in 5.0 V group was more than 3.0 V group and less than 8.0 V group(P 0.1, P 0.1, P 0.05). Conclusion The electrical stimulation of esophageal muscle in normal rats could cause effective contraction immediately. The peak value of contraction is correlated positively with volgage and frequency of electrical stimulation. The effect of electrical stimulation on esophageal muscle is not influenced by nurontransmeters. Key words: Achalasia; Mechanism; Neurotransmitter; Electrical stimulus; Esophageal muscle

A single mode porous-core square lattice photonic crystal fiber for THz wave propagation

Interests on low-loss terahertz (THz) waveguides are increasing due to their remarkable applications in various fields. Since most the materials are highly absorbent to THz waves therefore it is an ongoing challenge to obtain a low-loss waveguide. This paper presents a novel porous-core square lattice photonic crystal fiber (PCF) for efficient transmission of THz waves. The guiding properties of the proposed fiber are characterized by using finite element method (FEM) with circular perfectly matched layer (PML) boundary conditions. It is demonstrated that the designed PCF shows very low effective material loss (EML) of 0.076 cm-1 at 1.0 THz that indicates about 62 % reduction of bulk absorption loss of the background material. In addition to this, the proposed fiber exhibits low confinement loss of 8.96 × 10-3 dB/cm and low flattened dispersion of 0.96 ± 0.086 ps/THz/cm for the optimal design parameters. Other important propagation characteristics such as single mode propagation, power fraction, and bending loss are also investigated thoroughly. A porous-core PCF is an efficient mechanism for the transmission of THz waves. The proposed low-loss and low-dispersion PCF can find numerous applications in THz regime.

Critical analysis of frequency selective surfaces embedded composite microwave absorber for frequency range 2–8 GHz

Radar wave absorbers are important for the reduction of radar cross section of the target for stealth applications. Earlier the radars were available in the frequency range 8–12 GHz (X-band) and 12–18 GHz (Ku-Band). Due to recent advancement in radar technology, radars are now available from 2 to 18 GHz frequency range. So there is an urgent need to develop such a material that can work as radar wave absorber in the lower frequency band of the microwave spectrum i.e., 2–8 GHz. For this purpose the selection of material is an important criterion as the radar wave absorption depends primarily upon the material characteristics i.e., complex permittivity and complex permeability. For lower frequency radar wave absorption, the material must also possess the conducting property along with dielectric and magnetic properties. Therefore, an attempt has been made to develop a radar wave absorbing nano-composite material by selecting constituent materials with such inherent properties that can work for the absorption of radar wave in the lower frequency range. It is observed that the developed composite give good absorption in the lower frequency range but with narrow radar wave absorption bandwidth (4–7 GHz). So we have explored the possibility of the efficient use of an advanced electromagnetic technique like frequency selective surface to enhance the radar wave absorption bandwidth in the lower frequency region of the microwave frequency spectrum and precaution has been taken such that complexity due to FSS can be avoided. It has been observed that the synthesised single layer absorber with single square loop, cross dipole and Jerusalem cross FSSs provides radar wave absorption bandwidth in the frequency range 2–8 GHz.

Effect of Reynolds Numbers on Flow Past a Square Cylinder in Presence of Multiple Control Cylinders at Various Gap Spacings

In this paper, the numerical investigations for drag reduction and vortex shedding suppression behind a square cylinder are carried out in presence of small control cylinders placed both at upstream and downstream locations of main cylinder. The numerical computations are performed in the ranges of \(80 \le Re \le 200\) and \(0.5 \le g \le 6\), (where Re is the Reynolds number and g is the gap spacing between the control cylinders and main square cylinder, respectively) using a single relaxation time lattice Boltzmann method (SRT-LBM). Firstly, the present code is validated for flow past a single square cylinder at different Reynolds numbers. The effects of Re and g are investigated in terms of vortex shedding frequency, time-history analysis of drag and lift coefficients, energy spectra analysis of lift coefficient, vorticity contours visualization and forces exerted on the cylinder. Three different types of flow patterns are observed at different combinations of Reynolds numbers and gap spacings. The maximum reduction in the mean drag force and root-mean-square value of lift coefficient is found. Furthermore, the applications of SRT-LBM for suppression of vortex shedding and reduction in the drag force are also discussed.

Modulated magnetism and anomalous electronic transport inCe3Cu4As4O2

The complex magnetism and transport properties of tetragonal Ce$_3$Cu$_4$As$_4$O$_2$ were examined through neutron scattering and physical properties measurements on polycrystalline samples. The lamellar structure consists of alternating layers of $\rm CeCu_4As_4$ with a single square Ce lattice and oxygen-linked Ce bi-layer $\rm Ce_2O_2$. Extending along $\bf c$, a tube-like Fermi surface from DFT calculations points to a quasi-two-dimensional electronic system. Peaks in the specific heat at the Ne\'{e}l temperature $T_{N}=24$ $\rm K$, $T_{2}~=~16 $ $\rm K$ and $T_{3}~=~1.9$ $ \rm K$ indicate three magnetic phase transitions or distinct cross-over phenomena. For $T<T_{N}$ neutron diffraction indicates the development of ferromagnetic ab sheets for both Ce sites, with alternating polarization along $\bf{c}$, a wave vector ${\bf k}_{1}={\bf c}^*$. For $T<T_{2}$, quasi-two-dimensional low-energy spin fluctuations with ${\bf k}_{2}=\frac{1}{2}{\bf a}^*$ and polarized perpendicular to ${\bf k}_{2}$ are suppressed. The data are consistent with quasi-two-dimensional antiferromagnetic order in the $\rm CeCu_4As_4$ planes polarized along the ${\bf k}_{2}$ wave vector. $T_{3}$ marks a spin-flop transition where the ${\bf k}_{1}$ staggered magnetization switches to in-plane polarization. While the narrow 4f bands lie deep below the Fermi surface, there are significant transport anomalies associated with the transitions; in particular a substantial reduction in resistivity for $T<T_{N}$. At $T=100$ $ \rm mK$ the ${\bf k}_1$ modulated staggered moment is $0.85~\mu_B$, which matches the $0.8~\mu_B$ saturation magnetization achieved for H $~=~7$ $ \rm T$ at $T~=~2$ $ \rm K$. From low T Lorentzian fits the correlation length is in excess of 75 \AA. We argue the unusual sequence of magnetic transitions results from competing interactions and anisotropies for the two Ce sites.

Effect of the grid geometry on the convective heat transfer of impinging jets

Passive methods are recognized as one of the most efficient means to achieve high heat and mass transfer in impinging jets. In a recent study, Cafiero et al. (2014) demonstrated the effectiveness of square fractal grids (SFGs, obtained repeating the same square pattern at increasingly smaller scales) in terms of heat transfer enhancement when locating the grid in correspondence of the nozzle exit section. Indeed, the capability of producing turbulence at multiple scales and the possibility of tuning the peak in the turbulence intensity profile as a function of the grid geometric parameters are both extremely appealing for heat transfer enhancement purposes. In this study, the effect of the grid geometry on the convective heat transfer rate of impinging jets is assessed and discussed. Three main effects are taken into account: the grid thickness ratio (obtained by varying the thickness of the first iteration of the SFG), the effect of the secondary grid iterations and the choice of the initial pattern. It is demonstrated how a larger thickness ratio, which in the present case corresponds to an anticipated location of the peak in the turbulence intensity profile, is beneficial to get a spotted high convective heat transfer rate at short nozzle to plate distances. Either the use of a single square grid, or the choice of a different initial pattern (for example a circular fractal grid) is instead indicated when it is desirable a uniform distribution of the convective heat transfer rate.

Effects of short splitter plates on vortex shedding and sound generation in flow past two side-by-side square cylinders

Effects of short splitter plates on vortex shedding and sound generation in a low subsonic flow past two side-by-side square cylinders were examined experimentally at Reynolds numbers $${{{Re}}} = 1.0 - 3.3 \times 10^4$$ . The experiment was mainly conducted with the center-to-center distance between the two cylinders of 3.6d (d is the side length of a square cylinder) where vortex shedding from the two cylinders was synchronized with anti-phase relation, generating a quadrupole-like sound source that radiated in-phase sound in the far field. The results showed that the attachment of short splitter plates whose length (c) was ≤0.5d could reduce the sound pressure level of Aeolian tone significantly. Even with the shortest splitter plates of $$c{/}d=0.1$$ , SPL was reduced by 6 dB at Mach number $$M_{\infty }=0.15$$ . This was in contrast to the case of a single square cylinder, for which the attachment of a short splitter plate <0.2d led to no noticeable noise reduction. It was also shown that even when short splitter plates with a spanwise length as long as or less than the correlation length of shed vortices were attached on the two cylinders in a staggered array, the anti-phase vortex shedding and the corresponding in-phase sound radiation were still dominant.

Experimental study on transient cooling characteristics of a realistic thermoelectric module under a current pulse operation

This paper presents an experimental investigation on cooling characteristics of a realistic thermoelectric module (TEM) that operates under single and continuous square current pulse. The experimental system is built and the related study is performed. A cooling temperature enhancement of 3.0°C relative to steady current operation on a realistic TEM is demonstrated. Further experimental data reveal that there exists an optimum initial steady current which provides the maximum cooling temperature enhancement in the current pulse operation. In addition, the value of the supercooling and the temperature overshoot always stay close. Moreover, continuous temperature enhancement in each current pulse is achieved on a realistic TEM operated with continuous current pulses. Cooling temperature in each current pulse shows an increasing trend similar to that of a first order step response. The cooling characteristics under different cooling loads are quite similar, except for the different initial temperatures.

Spatiotemporal proximity effects in visual short-term memory examined by target-nontarget analysis.

Visual short-term memory (VSTM) is a limited-capacity system that holds a small number of objects online simultaneously, implying that competition for limited storage resources occurs (Phillips, 1974). How the spatial and temporal proximity of stimuli affects this competition is unclear. In this 2-experiment study, we examined the effect of the spatial and temporal separation of real-world memory targets and erroneously selected nontarget items examined during location-recognition and object-recall tasks. In Experiment 1 (the location-recognition task), our test display comprised either the picture or name of 1 previously examined memory stimulus (rendered above as the stimulus-display area), together with numbered square boxes at each of the memory-stimulus locations used in that trial. Participants were asked to report the number inside the square box corresponding to the location at which the cued object was originally presented. In Experiment 2 (the object-recall task), the test display comprised a single empty square box presented at 1 memory-stimulus location. Participants were asked to report the name of the object presented at that location. In both experiments, nontarget objects that were spatially and temporally proximal to the memory target were confused more often than nontarget objects that were spatially and temporally distant (i.e., a spatiotemporal proximity effect); this effect generalized across memory tasks, and the object feature (picture or name) that cued the test-display memory target. Our findings are discussed in terms of spatial and temporal confusion "fields" in VSTM, wherein objects occupy diffuse loci in a spatiotemporal coordinate system, wherein neighboring locations are more susceptible to confusion. (PsycINFO Database Record

Study on the impact of the system of rice intensification in less water endowed areas of Tamil Nadu

System of rice intensification (SRI) is a novel method of rice cultivation based on a set of simple synergistic practices. They aim to change the management of rice plants and soil, water and nutrients that supports them in simple but specific ways. Success of SRI depends on strict adoption of its five major components viz., young seedlings with mat nursery, single seedling planting, square planting, alternate wetting and drying of irrigation management and mechanical weeder usage. Among the five components, raising young seedling in the mat nursery, planting single seedling and square planting are the most important components that paves the way for increasing the yield of rice crop in irrigated rice systems. Proponents of SRI have reported that the average rice yield with SRI can be doubled from the current average yield level and there exists potential to the tune of increasing the yield level by three to four times. An attempt was made to evaluate the impact of adoption of SRI practices on rice yields, its economics in rice cultivation and labour inputs based on field research conducted in Varahanadhi Sub Basin, Villupuram and Tiruvannamalai districts, Tamil Nadu State, India. Rice yields with SRI were higher than those under conventional paddy cultivation by 34.35 per cent and net returns were higher by 33.24 per cent. SRI adoption enabled farmers consistently to enhance rice yields, increase returns and save labour cost and enhance productivity with respect to the key inputs in terms of rice output per unit of seed, water and fertilizer. SRI promises to be a significant alternative not only for raising rice yields, but also for managing rice based farming in wet lands ecosystem.

SU-G-BRB-06: Commissioning and Evaluation of EPID-Based in Vivo Dosimetry Software Using a Tissue-Maximum Ratio Approach

Purpose: To commission and evaluate an in vivo EPID-based transit dosimetry software (EPIgray, DOSIsoft, Cachan, France) using simple fields and TG119-based IMRT treatment plans. Methods: EPIgray was commissioned on a Truebeam based on finite tissue-maximum ratio (fTMR) measurements with solid water blocks of thicknesses between 0 and 37 cm. Field sizes varied from 2×2 to 20×20 cm2. Subsequently, treatment plans of single and opposed beams with field sizes between 4×4 and 15×15 cm2 as well as IMRT plans were measured to evaluate the dose reconstruction accuracy. Single field dose predictions were made for anterior-posterior and lateral beams. IMRT plans were created based on TG119 recommendations. The reconstructed dose was compared to the planned dose for selected points at isocenter and away from isocenter. Results: For single square fields, the dose in EPIgray was reconstructed within 3% accuracy at isocenter relative to the planned dose. Similarly, the relative deviation of the total dose was accurately reconstructed within 3% for all IMRT plans with points placed inside a high dose region near the isocenter. Predictions became less accurate than 5% when the evaluation point was outside the majority of IMRT beam segments. Additionally, points 5 cm or more away from the isocenter or within an avoidance structure were predicted less reliably. Conclusion: EPIgray formalism accuracy is adequate for an efficient error detection system. It provides immediate intra-fractional feedback on the delivery of treatment plans without affecting the treatment beam. Besides the EPID, no additional hardware is required, which makes it accessible to all clinics. The software evaluates point dose measurements to verify treatment plan delivery and patient positioning within 5% accuracy, depending on the placement of evaluation points. EPIgray is not intended to replace patient-specific quality assurance but should be utilized as an additional layer of safety for continuous patient treatment verification. This research is supported by DOSIsoft.

An Implementation of a Compact Smart Resistive Sensor Based on a Microcontroller with an Internal ADC

Abstract In the paper a new implementation of a compact smart resistive sensor based on a microcontroller with internal ADCs is proposed and analysed. The solution is based only on a (already existing in the system) microcontroller and a simple sensor interface circuit working as a voltage divider consisting of a reference resistor and a resistive sensor connected in parallel with an interference suppression capacitor. The measurement method is based on stimulation of the sensor interface circuit by a single square voltage pulse and on sampling the resulting voltage on the resistive sensor. The proposed solution is illustrated by a complete application of the compact smart resistive sensor used for temperature measurements, based on an 8-bit ATxmega32A4 microcontroller with a 12-bit ADC and a Pt100 resistive sensor. The results of experimental research confirm that the compact smart resistive sensor has 1°C resolution of temperature measurement for the whole range of changes of measured temperatures.

Analysis of Turbulence Characteristics in the Laminar Sub-Layer Region of a Perturbed Turbulent Boundary Layer

Turbulent boundary layer plays an important role for generation of aerodynamic drag. Shear force and pressure force due to the presence of boundary layer separation from the body surface contribute to the total drag. Studies of drag reduction due the the boundary layer effect are continuously performed by many researchers. Present study is intended to evaluate the behaviour of the laminar sub-layer in a turbulent boundary layer using a hot-wire anemometer system. The study was conducted in a low-speed wind tunnel at a Reynolds number based on the momentum thickness of approximately Reθ = 1000. A smooth-flat plate and a plate with a single transverse square groove was used in the study of the boundary layer characteristics. The groove size of 10 mm x 10 mm was cut transversally across the test plate. The results show that no significant differences in the streamwise mean velocity, steamwise turbulence intensity, and velocity signals for the smooth-and grooved-wall cases. For the the energy spectra for the two cases, however, show significant differences.

Dynamics of paramagnetic squares in uniform magnetic fields

The magnetic forces between paramagnetic squares cannot be calculated using a classic dipolar model because the magnetic field distribution is not uniform within square particles. Here, we present the calculation of magnetic forces and torques on paramagnetic squares in a uniform 2-D magnetic field using a Laplace's equation solver. With these calculations, we simulate the variations in equilibrium configurations as a function of number of interacting squares. For example, a single square orients with its diagonal directed to the external field while a system of multiple squares will assemble into chain-like structures with their edges directed to the external field. Unlike chains of spherical magnetic particles, that easily stagger themselves to aggregate, chains consisting of magnetic squares are unable to aggregate due to interchain repulsion.