Flat Maximum Research Articles

Experimental and numerical investigation on the potential of wake mixing by dynamic yaw for wind farm power optimization

This study investigates open-loop dynamic yaw control as a strategy for enhancing wind farm performance through wake mixing. The focus is on understanding the potential for enhanced wake mixing under different turbulence intensities, and the mechanisms triggering mixing. Experimental tests are conducted using scaled wind tunnel experiments with two model wind turbines. The wake flow is analysed by large eddy simulations (LES). Dynamic yawing is prescribed by sinusoidally varying the yaw angle at different excitation frequencies. The study reveals that dynamic yaw control, particularly at low inflow turbulence, leads to increased wake mixing. The resulting enhanced wind farm power capture has a rather flat maximum around an optimal Strouhal number. This is in contrast to high inflow turbulence, where the effectiveness of the control strategy is significantly reduced. The meandering motion of the wake induced by dynamic yaw excitation is identified as the key mechanism for improved wake recovery.

Evolution of Young’s modulus and damping of Czech kaolins during sintering monitored via impulse excitation

The evolution of Young’s modulus and damping is investigated for Czech kaolins in situ via the impulse excitation technique (IET) from room temperature to 1250 and 1400 °C. During heating the processes of drying, dehydroxylation, spinel formation, mullitization, silica release and glass melting are clearly discernible. During cooling Young’s modulus increases, exhibiting a flat maximum around 800 °C and a steep decrease below 200 °C when the cristobalite content is high. Differential IET curves are introduced as a new representation of IET results, and damping curves are shown to provide additional information. The phase composition is determined via XRD, including the glass phase. Based on the densities, Young’s moduli and volume fractions of the individual phases, the densities and Young’s moduli of the kaolin-based ceramics are calculated and compared to theoretical predictions, showing that Young’s modulus is nicely predicted by a benchmark relation for partially sintered ceramics with concave pores.

Comparison of keratometric values and anterior segment parameters measured using Scheimpflug Sirius topography and Lenstar biometry.

This study aimed to evaluate the consistency of preoperative keratometric values, anterior segment, and intraocular lens (IOL) power measurements in patients with cataract and no comorbidities using the Sirius topography device (CSO, Italy) and Lenstar LS 900 (Haag-Streit AG, Köeniz, Switzerland). Patients with grade 2 and 3 cataracts who applied to Ophthalmology Clinic of Dışkapı Yıldırım Beyazıt Education and Research Hospital, University of Health Sciences and planned for cataract surgery were included the study. Forty eyes with cataract from 40 patients were taken in the study. All patients underwent preoperative assessment using a combined Scheimpflug-Placido disc-based tomography device (Sirius) and Lenstar before cataract surgery. Keratometric measurements, such as flat keratometry (K1), steep keratometry (K2), and maximum keratometry (Kmax), and anterior segment parameters, white-to-white (WTW) distance, IOL power, astigmatism (AST), anterior chamber depth (ACD), aqueous depth (AD), and central cornea thickness (CCT), were recorded. There were significant differences between K1Lenstar and K1Sirius, K2Lenstar and K2Sirius, KmaxLenstar and KmaxSirius, WTWLenstar and WTWSirius, and IOL powerLenstar versus IOL powerSirius. However, there were insignificant differences between ASTLenstar and ASTSirius, ACDLenstar versus ACDSirius, ADLenstar and ADSirius, and CCTLenstar and CCTSirius variables. Furthermore, it was found that Sirius measured significantly higher than Lenstar, especially in terms of IOL power. Significant differences were observed between Lenstar and Sirius in terms of keratometric values, WTW distance, and IOL power. The IOL power value measured with Sirius was found to be higher than the IOL power value measured with Lenstar.

Halogen-assisted octet binding electrons construction of pnictogens towards wide-bandgap nonlinear optical pnictides

The design of pnictide nonlinear optical crystals is quite different from chalcogenide and oxide those, in which a new paradigm need be developed to regulate the band gap, one of key optical parameters. In this work, two non-centrosymmetric halidepnictides, [Cd2P]2[CdBr4] (CPB) and [Cd2As]2[CdBr4] (CAB) were reported. The complete octet binding electrons of pnictogens were constructed by four Cd-P polar covalent bonds under the anchoring effect of halogens, creating an extremely flat valence band maximum with band dispersion of only 0.17 eV. As expected, the balance of the covalency and ionicity in CPB and CAB was successfully realized, leading to a wide band gap of 2.58 eV and 1.88 eV. Remarkably, CPB not only has a widest band gap among Cd-containing pnictides, but also exhibits a SHG effect of 1.2 × AgGaS2, moderate birefringence (0.088@visible light and calcd. 0.043@2050 nm) and a wide IR transmission range. This is the first time that the octet binding electrons construction strategy was utilized to design non-diamond like NLO pnictides with excellent performances.

Cluster spin glass in off-stoichiometric Ni2.01Mn1.58Sn0.41 alloy

The Ni2.01Mn1.58Sn0.41 alloy is a member of the Heusler material family which undergoes diffusionless structural transition from cubic austenite to orthorhombic martensite during its cooling. The transition was observed at temperature 398 K from paramagnetic austenite to martensite with complex magnetic structure. The measurement of AC magnetic susceptibility of the alloy confirmed spin-glass state at temperatures below 155 K and from the frequency dependence of the cups in AC susceptibility, a presence of clusters (11 nm3 in size) with strong interaction is deduced. The alloy shows anomalous Hall effect (AHE) of the order of 0.051 μΩ cm at 2 K in the spin-glass state of the alloy and its sign changes at around 140 K. The ordinary Hall coefficient of the metallic alloy is strikingly positive in the whole studied temperature region, and it points to complex magnetic and electronic structure of the alloy. The electrical resistance of the sample shows a flat maximum of 220 μΩ cm at spin-glass transition temperature. The magnetoresistance is of the order of 1% and is negative in the whole temperature region which points to a standard scattering of charge carriers on magnetic fluctuations. Quantum-mechanical calculations of supercells with compositions Ni32Mn25Sn7, Ni32Mn26Sn6 and Ni32Mn24Sn8 simulated different arrangement of Mn and Sn atoms. Ni32Mn25Sn7 composition is thermodynamically the most stable, although its magnetic moment is 1.67 μB/f.u., twice higher than the measured value. The combination of the latter two states, with additional Mn–Sn swaps, provides the magnetic moments matching the experimental value at a very small energy cost. Theoretical results then indicate that a scenario of local chemical variations and clustering is likely in the studied alloy.

Unusual features of lattice dynamics in lawsonite near its phase transitions

Lattice dynamics of a single crystal of lawsonite were studied over a broad range of frequencies (1 Hz to 20 THz) using impedance, THz time-domain and infrared spectroscopies. Based on polarized spectra of complex permittivity hat{varepsilon } measured as a function of temperature between 10 K and 500 K, we analyzed the properties of the two known phase transitions—an antiferrodistortive one near T_{mathrm{c}1}=270,mathrm{K} and a ferroelectric one, occurring at T_{mathrm{c}2}=124,mathrm{K}. The former one is accompanied by a flat maximum in the THz-range permittivity hat{varepsilon }_{mathrm{c}} near T_{mathrm{c}1}, which is due to an overdamped polar excitation in the mathbf {E} parallel c spectra reflecting the dynamics of water and hydroxyl groups. The strength of this mode decreases on cooling below T_{mathrm{c}1}, and the mode vanishes below T_{mathrm{c}2} due to hydrogen ordering. At the pseudoproper ferroelectric phase transition, two independent anomalies in permittivity were observed. First, hat{varepsilon }_a exhibits a peak at T_{mathrm{c}2}=124,mathrm{K} due to critical slowing down of a relaxation in the GHz range. Second, infrared and THz spectra revealed an optical phonon softening towards T_{mathrm{c}2} which causes a smaller but pronounced maximum in hat{varepsilon }_b. Such anomaly, consisting in a soft mode polarized perpendicularly to the ferroelectric axis, is unusual in ferroelectrics.

Evaluation of corneal tomography in children and adolescents without ocular or systemic allergy.

To determine normal corneal tomographic parameters in children and adolescents without corneal disease or atopy diagnosis. This descriptive cross-sectional study evaluated patients aged 8-16 years who underwent a complete slit-lamp biomicroscopic examination and tomographic corneal evaluation by a dual Scheimpflug analyzer, excluding those with ocular disease (including allergic conjunctivitis) or a positive prick test for systemic atopies. A total of 170 patients were evaluated, and 34 patients (68 eyes) were analyzed once the exclusion criteria were applied. The sample's mean age was 10.76 ± 2.31 years; with 19 (55.9%) men and 15 (44.1%) women. The mean keratometry in the flat meridian (Kflat), steep meridian (Ksteep), and maximum (Kmax) were 42.37 ± 1.63D, 43.53 ± 1.65D, and 43.90 ± 1.73D, respectively. The mean values for corneal asphericity (ε2) and thinnest point were 0.28 ± 0.11 and 550.20 ± 37.90 μm, respectively. The inferior-superior asymmetry ratio (I-S) and coma were 0.74 ±0.59D and 0.28 ± 0.12D, respectively. The knowledge of normal corneal tomographic parameters and their variation in children and adolescents without corneal disease or atopy may be useful for diagnosing keratoconus and initiating early disease treatment.

Properties of 2 mol% Yttria Stabilized Zirconia–Alumina–Cerium Hexaaluminate Composites

Yttria stabilized zirconia (Y-TZP) has become a standard material in a variety of biomedical and mechanical engineering applications due to its high strength and toughness. In order to obtain improved properties in terms of strength, hardness and low temperature degradation resistance second phases, typically alumina are added. In this study an alumina toughened zirconia recipe with 20 vol% alumina in a 2Y-TZP matrix was modified by progressive substitution of alumina by up to 10 vol% cerium hexaaluminate (CA6). Samples were produced by hot pressing. The cerium hexaaluminate was synthesized in situ by reduction of tetravalent ceria and reaction sintering with alumina at 1450 °C. The materials reach attractive 4-point bending strength values of greater than 1170–1390 MPa at a fracture resistance of 6.4–7 MPa√m. Vickers hardness is slightly reduced from 1405 HV10 to 1380 HV10 with increasing CA6 fraction. Results show that substitution of alumina by low amounts CA6 does not lead to drastic changes in the mechanical properties. Hardness is slightly reduced while strength reaches a flat maximum at 4 vol% CA6 substitution. The toughness slightly declines with CA6 addition which is caused by reduced transformability of the tetragonal zirconia phase despite a slight coarsening of the matrix observed upon CA6 addition.

An experimental study of the effects of the parapet walls geometry on the discharge coefficient of trapezoidal piano key weirs

Parapet walls on the crown of piano key weirs (PKW) are employed in the channels to regulate or increase water levels of the upstream. They are also used in the reservoirs to increase water storage. Most recent surveys concerning discharge coefficient and parapet walls have been conducted on the rectangular piano key weirs (RPKW) while not many of them devoted to trapezoidal piano key weirs (TPKW). Also, the effects of its parapet wall and crest shape are rarely investigated in this regard. The aim of this research was to study the impacts of height (R), installation arrangements (S), and crest shape of parapet walls (flat, triangular, and semicircular) on changes of the upstream water level and discharge coefficient of TPKW. The weir height (P) was 15 cm. The parapet walls were installed on the crest of weir with three different arrangements: S1 (on the crest overall), S2 (on the sidewalls and inlet key), and S3 (on the sidewalls). The results indicated that the influence of installation arrangement on changes of water level increased with the growth of parapet walls height. In the case of a flat parapet walls, maximum and minimum increase rates of total head were recorded for S1 and S3 arrangements, respectively. There was also a direct relationship between discharge coefficient (C) and the heights of parapet walls in a constant water level at upstream. When installing flat parapet walls with R/P = 0.3, the value of C for S2 exceeded those for S1 and S3.

Optical conductivity of multifold fermions: The case of RhSi

We measured the reflectivity of the multifold semimetal RhSi in a frequency range from 80 to 20000 cm$^{-1}$ (10 meV - 2.5 eV) at temperatures down to 10 K. The optical conductivity, calculated from the reflectivity, is dominated by the free-carrier (Drude) contribution below 1000 cm$^{-1}$ (120 meV) and by interband transitions at higher frequencies. The temperature-induced changes in the spectra are generally weak: only the Drude bands narrow upon cooling, with an unscreened plasma frequency that is constant with temperature at approximately 1.4 eV, in agreement with a weak temperature dependence of the free-carrier concentration determined by Hall measurements. The interband portion of conductivity exhibits two linear-in-frequency regions below 5000 cm$^{-1}$ ($\sim$ 600 meV), a broad flat maximum at around 6000 cm$^{-1}$ (750 meV), and a further increase starting around 10000 cm$^{-1}$ ($\sim$ 1.2 eV). We assign the linear behavior of the interband conductivity to transitions between the linear bands near the band crossing points. Our findings are in accord with the predictions for the low-energy conductivity behavior in multifold semimetals and with earlier computations based on band structure calculations for RhSi.

Low potassium mobility in iron pyrophosphate glasses

Structural and electrical properties of glasses of the molar composition xK2O−(40−x/2)Fe2O3−(60−x/2)P2O5, x = 0–36 mol%, are investigated by Raman, Mössbauer and Impedance spectroscopy. All glasses show pyrophosphate structure with a growing tendency for depolymerization with increasing K2O content. The DC conductivity changes in a non-monotonic fashion, exhibiting a broad flat maximum as K2O gradually substitutes Fe2O3 and P2O5. The observed conductivity trend could be related to the changes in the number density of polarons which depends on Fe2O3 and fraction of ferrous ions, indicating dominant polaronic conduction mechanism in all glasses. Interestingly, a relatively small addition of K2O, up to 12 mol%, has a positive effect on the polaronic transport due to slight modifications of glass network. Potassium ions are weakly mobile in iron pyrophosphate glass network and have a negligible contribution to the electrical transport even when their molar fraction is as high as 36 mol%.

Dynamic Susceptibility of Thiochromite FeCr2S4

The magnetic susceptibility of the ferrimagnet FeCr2S4 was studied by a dynamic method in order to highlight the nature of a magnetic transition in the region of T = 60 K. The properties of the compound were measured in zeroth DC magnetic field НDC = 0 in the temperature range 4–230 K at the modulation amplitudes НАC = 1 and 17 Oe and the AC frequencies ν = 10, 100, 1000, and 10 000 Hz. At T > 60 K, the properties of FeCr2S4 correspond to the long-range ferrimagnetic order with local spin disorder. Spin lattice distortions (microareas or magnetic clusters) strongly increase in the region of 150 K, where a local spin glass appears with the spin freezing temperature Tf = 155 K. The flat maximum of the impurity spin glass in FeCr2S4 at T = 155 K can be considered as a mere assembly or conglomerate of especially large magnetic clusters with the effective Curie temperature T = 155 K.

Light Speed Expansion and Rotation of a Very Dark Machian Universe Having Internal Acceleration

We present a Machian model of Quantum Cosmology with full dark matter and light speed expansion and rotation. During galaxy formation and evolution, fraction of dark matter transforms to visible matter with a relation of the form, m_vis = constant * (m_dark)2/3. Using this relation and replacing MOND’s “critical acceleration” with “current cosmic maximum angular acceleration”, galactic flat rotation speed range of (50 to 500) km/sec can be fitted well. Estimated flat rotation speeds of DD168, Milky Way and UGC12591 are 49.96 km/sec, 199.66 km/sec and 521.75 km/sec respectively. Based on these striking coincidences, it is possible to say that, MOND’s approach is implicitly connected with cosmological estimation of 95% invisible matter. With reference to SPARC data for flat rotation speeds and current cosmic maximum angular acceleration, galactic total mass can be estimated. Considering galactic total mass, galactic visible mass and dark mass can be estimated. Proceeding further, galactic working radii, angular velocity and visible matter density can be estimated. Estimated Milky Way’s effective radius is 293 kpc. Even though, this model is free from “big bang”, “inflation”, “dark energy”, “flatness” and “red shift” issues, at 2.722 K, estimated present Hubble parameter is 66.24 km/sec/Mpc, cosmic radius is 146.3 times of the Hubble radius, angular velocity is 146.3 times lower than the Hubble parameter and cosmic age is 146.3 times of the Hubble age. With future observations and advanced telescopes, it may be possible to see far distant galaxies and very old stars far beyond the current observable cosmic radius.

Flattening of isothermal magnetic entropy change versus temperature curve in amorphous Fe–Mn–Mo–B ribbons

Microstructure, Curie temperature and isothermal magnetic entropy change of the amorphous Fe70Mn10Mo5B15 alloy in the as-quenched state and after annealing within the amorphous state at Ta1=723K and after the accumulative annealing at Ta1=723K and then at Ta2=753K for 0.5 h have been studied. The transmission Mössbauer spectra recorded at 300K are typical of a paramagnetic amorphous alloy and do not reveal distinct changes on annealing. The spectra in all cases are decomposed into a set of symmetric quadrupole doublets ascribed to the amorphous phase and a single line stemming from medium range ordered (MRO) regions which are paramagnetic at room temperature. The volume fraction of such MRO regions is small and increases only slightly on annealing. The Curie temperature of the amorphous phase decreases from 298 K in the as-quenched state to 268 K after the annealing at Ta1 and then increases to 282 K after the accumulative heat treatment at Ta1 and Ta2 due to invar effect. The isothermal magnetic entropy change of the alloy exhibits the “caret like” behavior with the peak values near the Curie points of the amorphous phase. The composites consisted of two adherent ribbons with different mass fraction (α) subjected to the annealing and made of two ribbons in the as-quenched state and after the heat treatment at Ta1 show the flat maxima of the magnetic entropy change in the temperature spans 14K and 34K for α=0.7 and α=0.5 in the former and latter composite, respectively. Parameter α denotes the mass fraction of the ribbon annealed at Ta1 in the composites. The flat maximum of the magnetic entropy change is obtained for the composite made of two ribbons with the same chemical composition but different thermal history. The refrigerant capacity (RC) of the amorphous Fe70Mn10Mo5B15 alloy is about 115 J/kg in the as-quenched state and decreases slightly on annealing. RC is enhanced for the composites in comparison with their components.

On the operational efficiency of different feature types for telco Churn prediction

Churn prediction in telco remains a very active research topic. Due to the uptake of social network analytics and the results of previous benchmarking studies showing a rather flat maximum performance effect of predictive modeling techniques, the focus has mainly shifted to expanding and exploring the relevant feature space. While previous studies generally agree that adding features typically increases predictive performance, they rarely discuss the accompanying issues such as data availability and computational cost. In this work, we bridge the gap between predictive performance and operational efficiency by devising a new feature type classification and a novel reusable method to determine optimal feature type combinations based on Pareto multi-criteria optimization. Our results provide several insights that can serve as a guideline for industry practitioners.

The Baryonic Collapse Efficiency of Galaxy Groups in the RESOLVE and ECO Surveys

Abstract We examine the z = 0 group-integrated stellar and cold baryonic (stars + cold atomic gas) mass functions (group SMF and CBMF) and the baryonic collapse efficiency (group cold baryonic to dark matter halo mass ratio) using the RESOLVE and ECO survey galaxy group catalogs and a galform semi-analytic model (SAM) mock catalog. The group SMF and CBMF fall off more steeply at high masses and rise with a shallower low-mass slope than the theoretical halo mass function (HMF). The transition occurs at the group-integrated cold baryonic mass 1011 . The SAM, however, has significantly fewer groups at the transition mass ∼1011 and a steeper low-mass slope than the data, suggesting that feedback is too weak in low-mass halos and conversely too strong near the transition mass. Using literature prescriptions to include hot halo gas and potential unobservable galaxy gas produces a group BMF with a slope similar to the HMF even below the transition mass. Its normalization is lower by a factor of ∼2, in agreement with estimates of warm-hot gas making up the remaining difference. We compute baryonic collapse efficiency with the halo mass calculated two ways, via halo abundance matching (HAM) and via dynamics (extended all the way to three-galaxy groups using stacking). Using HAM, we find that baryonic collapse efficiencies reach a flat maximum for groups across the halo mass range of , which we label “nascent groups.” Using dynamics, however, we find greater scatter in baryonic collapse efficiencies, likely indicating variation in group hot-to-cold baryon ratios. Similarly, we see higher scatter in baryonic collapse efficiencies in the SAM when using its true groups and their group halo masses as opposed to friends-of-friends groups and HAM masses.

134: THE EFFECTIVENESS OF CXL IN THE TREATMENT OF KERATOCONUS

Background and aims:Keratoconus is characterized by corneal ectasia and irregular astigmatism, which can lead to diminished vision and corneal scarring. Keratoconus is a condition that causes corneal ectasia and reduced...

Broadband beam‐steering reconfigurable antenna

ABSTRACTA broadband reconfigurable antenna (RA) capable of steering its main beam into three different directions is presented. The ∼15% bandwidth of the antenna covers the frequency range of ∼5.1 – 5.9 GHz compatible with IEEE 802.11ac standard. This RA consists of an aperture‐coupled stacked patch with a parasitic layer placed above it. The surface of the parasitic layer has a grid of 3 × 2 electrically small rectangular‐shaped metallic pixels. The pixels are connected/disconnected by means of switching resulting in reconfigurability in beam‐direction. Only two PIN diode switches are utilized to provide three beam‐steering directions yielding a simple RA. The simulations and measurements from fabricated prototypes show that the antenna maintains its beam‐steering capability with a flat maximum realized gain (∼6.5 dB) over the whole operational bandwidth. An RA Array (RAA) formed by the linear combination of four (4 × 1) identical RA elements is also designed, fabricated and measured. Despite being linear this RAA is capable of performing beam‐steering in the plane, which is perpendicular to the plane containing the central line of the array. The measured and simulated results agree well indicating a flat maximum realized array gain of ∼12.2 dB from 5.2 to 5.8 GHz. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:63–65, 2017

Minimax Play at Wimbledon Redux

Initial tests of the predictive power of the mixed-strategy Nash equilibrium in the laboratory pointed to significant deviations. In response to the flat maximum critique, that incentives in the lab were not high enough to induce Nash behavior, researchers turned to the field, particularly sporting environments, where the monetary incentives were high. Field experiments overall, found predictions closer to the marginal distribution of actions predicted by the mixed strategy Nash equilibrium; however, evidence of deviations from the prediction of independent behavior across rounds have been mixed. I use a new dataset of tennis match serves that is two orders of magnitude greater than those used in previous tennis studies. Similarly to previous findings, the marginal distributions of professionals’ serves are not significantly different from the prediction of the normative solution, but there exists significant serial dependence across serves. This behavior is found even among players who at some point in their careers were ranked Number 1 in the world. The deviations of these top players cannot be explained as a strategic best response to expectations of lower-ranked players’ deviations from the Nash equilibrium.

Thermodynamics of aromatic polar compound (alkanone, alkanal or alkanoate) + hydrocarbon mixtures

Liquid-liquid equilibrium (LLE) temperatures have been determined for the mixtures: phenyl acetone + CH3(CH2)uCH3 (u = 8,10,12,14), or + 2,2,4-trimethylpentane, benzyl acetone + decane and benzyl acetate + dodecane by means of the critical opalescence method using a laser scattering technique. All the systems are characterized by an upper critical solution temperature (UCST). The coexistence curves have a rather flat maximum, and become shifted to higher concentrations of phenyl acetone when the alkane size increases. Aromatic alkanone, or alkanal or alkanoate + alkane, or + benzene mixtures have been investigated using DISQUAC. The interaction parameters for the X/aliphatic and X/aromatic contacts (X = CO, CHO, COO) are reported. The model correctly describes experimental data on LLE, vapour-liquid equilibria (VLE) and excess molar enthalpies (HmE). UNIFAC (Dortmund version) results are poorer. This shows that new UNIFAC groups for the mentioned aromatic systems should be defined. Proximity effects depend on the number of CH2 groups (n) between the phenyl ring and the polar group of the aromatic compound considered. Proximity effects lead to enhanced dipolar interactions, which change in the order n = 1 > n = 2 > n = 0. Comparison of thermodynamic properties for systems with isomeric molecules (benzyl ethanoate and phenyl acetone) shows that dispersive interactions are more relevant in the benzyl ethanoate system.