Spectral Transitions Research Articles

Revised and extended analysis of doubly ionized gold: Au III

The spectrum of doubly ionized gold (Au III) photographed in the region 450–2106 Å has been investigated. The gold spectra have been recorded at two places viz. at the National Institute of Standards and Technology (USA) on a 10.7-m normal incidence vacuum spectrograph (NIVS) using a sliding spark source as well as on a 3-m NIVS at the Antigonish laboratory in Canada with a triggered spark source. Au III has a ground configuration [4f14]5p65d9 with 2D5/2 as its lowest level. Excited configurations are quite complicated as the first excited odd parity configuration 5d86p alone contains 45 energy levels. Excitation of a single electron from the valence 5d shell produces configurations of the type 5d8nl. Various configurations arise due to multiple excitation of the 5d9 subshell, e.g., 5d76s6p, 5d76s2, 5d66s26p, 5d76p2, etc. Theoretical predictions were made using Cowan's quasi-relativistic Hartree-Fock code with the superposition of configurations involving 5p6 [5d9 + 5d8ns (n = 6–8) + 5d8nd (n = 6–8) + 5d76l2(l = 0–2)+5d7(6s6d+ 6s7s+ 6d7s)] in the even parity system and 5p5 [5d10 + 5d96s] + 5p6 [5d8np (n = 6–8) + 5d8nf (n = 5–7) + 5d7 (6s6p+ 6s7p+ 6p7s+ 6p6d+ 6s5f+ 6s6f) + 5d66s26p] in the odd parity matrix. A total of 262 energy levels belonging to the 5d9 + 5d8[6s+7s+6d+6p] + 5d7[6s2 + 6s6p] configurations have been established, 69 being new including three revised levels, one from each of the 5d86d, 5d87s and 5d76s6p configurations. In the process, 1504 spectral transitions have been classified in the wavelength region 570–3310 Å. The accuracy of the wavelength measurements for sharp and unblended lines is ±0.005 Å. The final interpretation of the results was made on the basis of least squares fitted parametric calculations. The level optimization was achieved with a computer program LOPT.

Sol-gel synthesis for stable green emission in samarium doped borosilicate glasses

In this work, novel green luminescent samarium doped-borosilicate glasses synthesized by the sol-gel route are reported. Although synthesis of crack-free monoliths was carried out in acid catalyzed reaction at room temperature with subsequent gelation at 50 °C, heating in N2/H2 atmosphere activated the luminescence. The results reveal the amorphous nature of glasses with embedded Sm2O3 nanoparticles in the reticular structure. From TEM analysis, the average particle size is estimated to be around 2.7 and 4.1 nm for the glasses without and with Na2O, respectively. The addition of Sm2O3 and Na2O promotes an increase in the glass transition and crystallization temperatures due to the boric anomaly. However, the optical band gap of undoped borosilicate glasses (3.65–3.86 eV) decreases with the addition of Sm2O3 and Na2O (3.39–3.57 eV). Furthermore, the observed green luminescence (545 nm), associated to 4F3/2 → 6H5/2 transition of Sm3+ ions in borosilicate glasses, is found to remain stable during the test period of 6 months. Therefore, glasses with high spectral purity and low-phonon losses have been obtained by easy sol-gel route, which is useful to promote the emergence of spectral transitions of higher energy with respect to the usually reported transitions at 600 nm (4G5/2 → 6H7/2).

Intense red and green luminescence from holmium activated zinc-sulfo-boro-phosphate glass: Judd-Ofelt evaluation

Rare-earth ions doped oxide glasses became prospective for high quality and inexpensive solid state laser development. To fulfill this need, zinc-sulfo-boro-phosphate glasses doped with holmium ions (Ho3+) were synthesized via melt-quenching method. Prepared glasses were characterized using diverse techniques to determine the influence of varied Ho3+ contents on their optical absorption and photoluminescence (PL) emission properties. The main purpose of this paper was to determine the structural and optical correlation in Ho3+ activated phosphate-based glass host involving the red and green lasing potency of holmium. Raman, XPS and FTIR spectra were recorded to analyze the structural properties of the synthesized glasses. Furthermore, Judd-Ofelt (J-O) intensity (Ωλ with λ = 2, 4 and 6) and radiative parameters were calculated. Absorption spectra of the studied glasses disclosed thirteen characteristic peaks associated to the transitions from the lowest electronic energy level (5I8) to various excited levels in Ho3+. The PL spectra of the proposed glasses revealed 3 significant peaks allocated to the 5F4 → 5I8, 5F5 → 5I8 and 5F4 → 5I7 transitions in Ho3+. Revelation of negative bonding parameter values implied the existence of ionic bond between the ligand and Ho3+ in the prepared glass host. Values of Ω2, Ω4 and Ω6 were observed in the range of (5.11–22.62)×10−20 cm2, (9.54–13.79)×10−20 cm2 and (3.71–6.78)×10−20 cm2, respectively. Lower Ω2 value signified the higher symmetry around Ho3+, whereas higher Ω4 and Ω6 values indicated the stronger rigidity of the glass network. The achieved large stimulated emission cross-section for the red and green spectral transitions from Ho3+ ((29.47–46.01)×10−21 cm2 for 5F4 → 5I8, (31.47–39.74)×10−21 cm2 for 5F5 → 5I8 and (13.34–31.63)×10−21 cm2 for 5F4 → 5I7) clearly displayed the lasing effectiveness of the proposed glasses.

Fine structure of the pygmy quadrupole resonance in 112,114Sn

The electric quadrupole response in 112,114Sn isotopes is investigated by energy-density functional (EDF) and three-phonon quasiparticle-phonon model (QPM) theory with special emphasis on electric quadrupole excitations located above the first collective 2+ state and below 5 MeV. Additional quadrupole strength clustering as a sequence of states similar to the recently observed pygmy quadrupole resonance in 124Sn is found. The spectral distributions and transition densities of these 2+ states show special features being compatible with oscillations of a neutron skin against the isospin-symmetric nuclear core. Furthermore, two (p, p′γ) Doppler-shift attenuation (DSA) coincidence experiments were performed at the SONIC@HORUS setup. 2+ states with excitation energies up to 4.2 MeV were populated in 112,114Sn. Lifetimes and branching ratios were measured allowing for the determination of E2 transition strengths to the ground state. A stringent comparison of the new data to EDF+QPM theory in 112Sn and 114Sn isotopes hints at the occurrence of a low-energy quadrupole mode of unique character which could be interpreted as pygmy quadrupole resonance.

An H i absorption distance to the black hole candidate X-ray binary MAXI J1535–571

ABSTRACT With the Australian Square Kilometre Array Pathfinder (ASKAP) we monitored the black hole candidate X-ray binary MAXI J1535–571 over seven epochs from 2017 September 21 to October 2. Using ASKAP observations, we studied the H i absorption spectrum from gas clouds along the line of sight and thereby constrained the distance to the source. The maximum negative radial velocities measured from the H i absorption spectra for MAXI J1535–571 and an extragalactic source in the same field of view are −69 ± 4 and −89 ± 4 km s−1, respectively. This rules out the far kinematic distance ($9.3^{+0.5}_{-0.6}$ kpc), giving a most likely distance of $4.1^{+0.6}_{-0.5}$ kpc, with a strong upper limit of the tangent point at $6.7^{+0.1}_{-0.2}$ kpc. At our preferred distance, the peak unabsorbed luminosity of MAXI J1535–571 was >78 per cent of the Eddington luminosity, and shows that the soft-to-hard spectral state transition occurred at the very low luminosity of (1.2–3.4) × 10−5 times the Eddington luminosity. Finally, this study highlights the capabilities of new wide-field radio telescopes to probe Galactic transient outbursts, by allowing us to observe both a target source and a background comparison source in a single telescope pointing.

Inter-Comparing SNPP and NOAA-20 CrIS Toward Measurement Consistency and Climate Data Records

The cross-track infrared sounder (CrIS) is a Fourier transform spectrometer that provides hyperspectral soundings of the atmosphere over three wavelength ranges onboard on both Suomi National Polar-orbiting Partnership (SNPP) and NOAA-20 satellites. Quantifying the radiometric difference and creating a calibration link between SNPP and NOAA-20 CrIS are crucial for creating CrIS long-term climate data records and establishing the space-based calibration standard. This study explores the inter-comparison strategy to identify the radiometric differences between SNPP and NOAA-20 CrIS along the finest spectral scale, including 1) direct comparison; and 2) the two double difference methods using infrared atmospheric sounding interferometer and radiative transfer calculations as transfer targets. Each method has its own advantages and disadvantages. The preliminary results based on the above methods suggest good agreement generally between SNPP and NOAA-20 CrIS. Some consistent findings are disclosed by the above three methods, including 1) around the CO2 absorption band at 650–750 cm−1 range, a consistent warm bias is found on the level of 0.1 K; 2) at the water vapor absorption band, the two CrIS instruments are well consistent to each other and their BT differences are close to zero lines albeit with spectral variation; 3) the largest BT difference of more than –0.6 K is found at the spectral line transition region (around 2380 cm−1). The root causes still need further investigation.

Hybrid-kinetic Simulations of Ion Heating in Alfvénic Turbulence

Abstract We present three-dimensional, hybrid-kinetic numerical simulations of driven Alfvén-wave turbulence of relevance to the collisionless near-Earth solar wind. Special attention is paid to the spectral transition that occurs near the ion-Larmor scale and to the origins of preferential perpendicular ion heating and of nonthermal wings in the parallel distribution function. Several novel diagnostics are used to show that the ion heating rate increases as the kinetic-Alfvén-wave fluctuations, which comprise the majority of the sub-ion-Larmor turbulent cascade, attain near-ion-cyclotron frequencies. We find that ≈75%–80% of the cascade energy goes into heating the ions, broadly consistent with the near-Earth solar wind. This heating is accompanied by clear velocity-space signatures in the particle energization rates and the distribution functions, including a flattened core in the perpendicular-velocity distribution and non-Maxwellian wings in the parallel-velocity distribution. The latter are attributed to transit-time damping and the pitch-angle scattering of perpendicularly heated particles into the parallel direction. Accompanying these features is a steepening of the spectral index of sub-ion-Larmor magnetic-field fluctuations beyond the canonical −2.8, as field energy is transferred to thermal energy. These predictions may be tested by measurements in the near-Earth solar wind.

Rotationless radiative lifetimes and transition probabilities of the seven lowest-lying doublet states of the AlO radical

In this work, we report the potential energy curves for the X2Π, A2Σ+, B2Σ+, G2Δ, G′2Σ-, C2Π, and D2Σ+ states of the AlO radical and the transition dipole moments between these states. The calculations are performed with the complete active space self–consistent field method, followed by the valence internally contracted multireference configuration interaction approach under the framework of the Born–Oppenheimer approximation. We find that the rotationless radiative lifetimes are in the order of several hundred ns for the B2Σ+ state, several tens of ns for the C2Π state, and several to more than ten ns for the first well of the D2Σ+ state. These lifetimes indicate that the transitions originated from these states easily occur. The rotationless radiative lifetimes are several to several hundred µs for the G2Δ and G′2Σ- states, and in the order of 10 to 100 µs for the A2Σ+ state. The Einstein coefficients of emissions from the B2Σ+–X2Σ+, C2Π–X2Σ+, and C2Π–A2Π systems, as well as from the first well of the D2Σ+ state to the X2Σ+ and A2Π states are very large, suggesting that the transitions from these systems should be able to be measured readily via spectroscopy. The rovibrational constants are first obtained from the analytic potential by numerically solving the rovibrational Schrödinger equation, and then the spectroscopic parameters are evaluated by fitting the vibrational levels. The distributions of the intensity and wavelength of the spectral transitions are new. The radiative lifetimes reported in this work are also new for all vibrational levels of the C2Π, G2Δ and G′2Σ- states, as well as for υ ≥ 1 levels of the C2Π state. The results reported in this study can be used to detect the 26Al16O radical in outer space.

Highly selective photonic glass filter for saturated blue structural color

Angle independent non-absorbing spectral filters are required for many applications such as sunscreens, structural colors, photovoltaics, and radiative cooling. One of the promising and simple to manufacture structures is based on the disordered arrangement of monodisperse spherical particles by self-assembly, also called photonic glasses. So far, reported photonic glasses inherently show poor spectral selectivity with a smooth transition in reflection. No significant improvement is usually expected from particles optimization as the Mie resonances are broad for small dielectric particles with a moderate refractive index. Via Fourier space engineering, we show here that it is, nonetheless, possible to obtain sharp spectral transitions from the synergetic effect of a core-shell geometry of the particles with the short range order of the photonic glass. We apply the developed approach to demonstrate a high color saturation of a non-iridescent blue structural color employing a photonic glass with hollow sphere particles, which features a sharp spectral transition in reflection. The experimental results support the theoretical predictions from the first-order approximation.

Spectral properties and quantum phase transitions in superconducting junctions with a ferromagnetic link

We study theoretically the spectral and transport properties of a superconducting wire with a magnetic defect. We start by modelling the system as a one dimensional magnetic Josephson junction and derive the equation determining the full subgap spectrum in terms of the normal-state transfer matrix for arbitrary length and exchange field of the magnetic region. We demonstrate that the quantum phase transition predicted for a short-range magnetic impurity, and associated with a change of the total spin of the system, also occurs in junctions of finite length. Specifically, we find that the total spin changes discontinuously by integer jumps when bounds states cross the Fermi level. The spin can be calculated by using a generalization of Friedel sum rule for the superconducting state, which we also derive. With these tools, we analyze the subgap spectrum of a junction with the length of the magnetic region smaller than the superconducting coherence length and demonstrate how phase transitions also manifest as change of the sign of the supercurrent.

Anomalous outbursts of H 1743-322

Abstract Using soft (1.5–3 keV) and hard (3–12 keV) photon counts of All Sky Monitor (ASM) in Rossi X-ray Timing Explorer (RXTE) satellite, we have proposed recently that there is a significant time lag between the infall time-scales of two components in the Two-Component Advective Flow paradigm, where a standard slow moving Keplerian disc is surrounded by a fast moving halo. The time lag is clearly due to the difference in viscosity in the flow components and the size of the Keplerian disc may be considered to be proportional to this arrival time lag. In this paper, using RXTE/ASM (1.5–12 keV) data, we examine eight successive outbursts of the low-mass X-ray binary H 1743-322 since 2003 from a new perspective. The day-to-day temporal evolution of a dynamic photon index, Θ, as well as its cross-correlation with the soft and hard energy fluxes show that the aforesaid time lag was the longest during the brightest outburst of 2003 – thereby indicating its largest Keplerian disc. The disc size diminished thereafter during subsequent weaker outbursts. Moreover, Θ decides spectral transitions of any outburst. We show from the behaviour of Θ alone that the outburst of October 2008 was anomalous while the outburst of 2003 was twin (anomalous + normal). In fact, each normal outburst was either preceded or followed by an otherwise premature outburst showing different degrees of anomaly. This makes H 1743-322 an enigmatic source and a subject of further study.

Synthesis, characterization and catalytic properties of dinuclear complexes of copper(II) and nickel(II): Oxidation of cyclohexane, toluene and cyclopentane

Oxidation of saturated hydrocarbon by transition metal complexes is of great importance because this would give industrially valuable organic fine chemicals. Here, dinuclear copper(II) and dinuclear nickel(II) complexes with same N,O donor ligand have been used as catalyst for the oxidation of cyclohexane, toluene and cyclopentane using hydrogen peroxide as the oxidant to examine their catalytic activity and effect of nature of metal center on catalysis. [Cu2(L1)2(μ2-Cl)Cl]·2.5H2O (1) and [Ni2(L1)2(μ2-N3)2 (CH3OH)2]·CH3OH (2) have been synthesized under mild conditions where HL1 is 1-((2-hydroxyethylimino)methyl)naphthalen-2-ol. These complexes have been characterized by elemental analysis, FT-IR, UV-Vis, mass spectroscopy, TGA-DTA and cyclic voltametric studies. Their structures have been confirmed by single crystal X-ray diffraction analysis. Some theoretical calculations have been performed to investigate spectral transitions. Copper(II) complex shows effective catalytic ability towards oxidation of the saturated hydrocarbons such as cyclohexane, toluene and cyclopentane in the presence of hydrogen peroxide when corresponding alcohols and ketones have been obtained as major products. However, complex 2 has been found to be inactive as catalyst for the oxidation. It is possible that Cu-hydroperoxo or Cu-peroxo species is formed during catalysis (as revealed from UV-vis spectral analysis) which could be the active species for the oxidation reaction.

The transition of gravity wave or mesoscale flow to boundary layer turbulence and implications for infrasound propagation conditions

Knowledge of the atmospheric boundary layer (ABL) is important for weather and climate forecasting as well as infrasound detection. In spite of many advances, the ABL is still not represented realistically in weather models, which leads to uncertainties in weather predictions. At the same time, the influence of the ABL on infrasound detectability is not well understood, which potentially limits the capability of the technique. In this work, a network of anemometers, microbarometers, and ceilometers is used to characterize gravity wave activity and turbulence in the ABL. The sensors are co-located at the Cabauw Experimental Site for Atmospheric Research (CESAR). The sensor network allows for the estimation of velocity and pressure spectra, as well as boundary-layer structure and mixing height. The goal of this work is to study the transition from gravity wave or mesoscale flow to boundary layer turbulence and to consider implications for infrasound propagation conditions. Here, an analysis of spectra under convective and stable conditions is presented with respect to both gravity wave and boundary-layer turbulence theory. Observed distinctions in the velocity and pressure spectral transitions will be discussed, including large-scale turbulence and the mesoscale spectral gap.Knowledge of the atmospheric boundary layer (ABL) is important for weather and climate forecasting as well as infrasound detection. In spite of many advances, the ABL is still not represented realistically in weather models, which leads to uncertainties in weather predictions. At the same time, the influence of the ABL on infrasound detectability is not well understood, which potentially limits the capability of the technique. In this work, a network of anemometers, microbarometers, and ceilometers is used to characterize gravity wave activity and turbulence in the ABL. The sensors are co-located at the Cabauw Experimental Site for Atmospheric Research (CESAR). The sensor network allows for the estimation of velocity and pressure spectra, as well as boundary-layer structure and mixing height. The goal of this work is to study the transition from gravity wave or mesoscale flow to boundary layer turbulence and to consider implications for infrasound propagation conditions. Here, an analysis of spectra under...

Modulation of fluorescence sensing properties of quinoline-based chemosensor for Zn2+: Application in cell imaging studies

Abstract An electron pushing group has been introduced to a Schiff-base compound, 2-((2-(quinolin-2-yl)hydrazono)methyl)phenol (HQP) to get another Schiff-base molecule, namely, 4-methyl-2-((2-(quinolin-2-yl)hydrazono)methyl)phenol (HMQP), to modulate the Zn2+ sensing properties of the probe. HQP and HMQP have been synthesized by Schiff-base condensation between 2-hydrazinylquinoline and the respective aldehyde in 1:1 ratio and characterized by standard methods. Both the compounds show their Zn2+ sensing ability but to different extents. The fluorescence intensity of HQP at ~490 nm (λex = 410 nm) increases by about 4.5 folds in the presence of one equivalent of Zn2+ ion. However, the fluorescence intensity is enhanced by around 30 folds in the presence of one equivalent of Zn2+ in case of HMQP. The fluorescence peak of HMQP at 502 nm (λex = 420 nm) is shifted to 515 nm in the presence of Zn2+ whereas same type of shifting for HQP is found to be negligible. Some theoretical calculations have been performed to look into the spectral transitions of HMQP. Fluorescence intensity enhancement is explained by PET mechanism. Limit of detection (LOD) value for HMQP has been determined to be 220.6 nM, showing its good sensitivity towards zinc. The color change of HMQP under visible light is not conclusive in the presence of different metal ions, but only Zn2+ can induce green coloration to HMQP solution under UV light, thus indicating the possibility of naked eye detection by the analyte. HMQP with one equivalent of Zn2+ displays high fluorescence intensity in the pH range of 7.0–9.0 indicating its suitability towards biological applications. The probe has been utilized to live cell imaging studies using C6 cells.

Thick-disc model to explain the spectral state transition in NGC 247

We propose the thick-disc model of Gu et al. 2016 to interpret the transition between soft ultraluminous state (SUL) and supersoft ultraluminous (SSUL) state in NGC 247. As accretion rate increases, the inner disc will puff up and act as shield to block the innermost X-ray emission regions and absorb both soft and hard X-ray photons. The absorbed X-ray emission will be re-radiated as a much softer blackbody X-ray spectrum. Hence NGC 247 shows flux dips in the hard X-ray band and transits from the SUL state to the SSUL state. The $\sim 200$s transition timescale can be explained by the viscous timescale. According to our model, the inner disc in the super-soft state is thicker and has smaller viscous timescale than in the soft state. X-ray flux variability, which is assumed to be driven by accretion rate fluctuations, might be viscous time-scale invariant. Therefore, in the SSUL state, NGC 247 is more variable. The bolometric luminosity is saturated in the thick disc; the observed radius-temperature relation can therefore be naturally explained.

Spectral transitions for Aharonov-Bohm Laplacians on conical layers

AbstractWe consider the Laplace operator in a tubular neighbourhood of a conical surface of revolution, subject to an Aharonov-Bohm magnetic field supported on the axis of symmetry and Dirichlet boundary conditions on the boundary of the domain. We show that there exists a critical total magnetic flux depending on the aperture of the conical surface for which the system undergoes an abrupt spectral transition from infinitely many eigenvalues below the essential spectrum to an empty discrete spectrum. For the critical flux, we establish a Hardy-type inequality. In the regime with an infinite discrete spectrum, we obtain sharp spectral asymptotics with a refined estimate of the remainder and investigate the dependence of the eigenvalues on the aperture of the surface and the flux of the magnetic field.

Dramatic spectral transition of X-ray pulsar GX 304−1 in low luminous state

Abstract We report on the discovery of a dramatic change in the energy spectrum of the X-ray pulsar GX 304−1 appearing at low luminosity. Particularly, we found that the cut-off power-law spectrum typical for accreting pulsars, including GX 304−1 at higher luminosities of LX ∼ 1036–1037 erg s−1, transformed at lower luminosity of LX ∼ 1034 erg s−1 to a two-component spectrum peaking around 5 and 40 keV. We suggest that the observed transition corresponds to a change of the dominant mechanism responsible for the deceleration of the accretion flow. We argue that the accretion flow energy at low accretion rates is released in the atmosphere of the neutron star, and the low-energy component in the source spectrum corresponds to the thermal emission of the optically thick, heated atmospheric layers. The most plausible explanations for the high-energy component are either the cyclotron emission reprocessed by the magnetic Compton scattering or the thermal radiation of deep atmospheric layers partly Comptonized in the overheated upper layers. Alternative scenarios are also discussed.

White light-emitting Dy3+-doped transparent chloroborosilicate glass: synthesis and optical properties

ABSTRACTDy3+-doped chloroborosilicate glasses with the composition 35.7SiO2–25.5B2O3–17BaO–3.4K2O–3.4Al2O3–15BaCl2 (mol%) were prepared using melt quenching technique. The glass transition temperature (Tg) was ~610°C. In UV–vis–NIR absorption spectra, characteristic absorption bands of Dy3+ appeared at 322, 347, 364, 388, 795 and 880 nm due to spectral transitions from the 6H15/2 level to various higher levels of Dy3+ ion. The excitation spectrum was recorded at within 200–550 nm by monitoring emissions at 576 nm. The excitation bands at 392, 428, 453 and 472 nm were attributed to the 6H15/2 → 4I13/2, 4G11/2, 4I15/2 and 4F9/2 transitions, respectively. Prominent emission bands were observed at wavelengths of 484, 576, 664 and 754 nm when excited at 447 nm. The bands correspond to the transitions 4F9/2 → 6H15/2, 4F9/2 → 6H13/2, 4F9/2 → 6H11/2 and 4F9/2 → 6H9/2 6F11/2, respectively. The emitted light from all the samples was found to be white. Their color coordinates lie within the white range. The sample containing 0.5 wt% Dy2O3 emitted white light with the color coordinates x = 0.351, y = 0.335, which are the very closest to pure white light and whose color temperature of 4716 K is similar to daylight. Such white light-emitting transparent glasses promise to be enormously useful for various photonic applications.

Ship roll damping via direct inverse neural network control system

Undesired roll motions of surface vessels under sea way have negative influence on passengers, crew members, equipment and cargo. Damping roll motions is a complex problem due to unpredictable and irregular nature of marine environmental disturbances that induce roll motions. There are several stabilizing systems regarding roll motions such as gyrostabilizers, anti-roll tanks, active fins and rudder roll stabilizers. Among all types of roll stabilizers or roll damping systems active fins practically represents the most effective roll damping technique and yet the most commonly used roll stabilizer. Assuming that the longitudinal location of fins corresponds to the vessel center of gravity a one degree of freedom nonlinear model can be used to identify ship dynamics. In this paper the performance and robustness of a proposed control system based on neural network approach applied to active fins that takes into account roll response spectral characteristics transitions due to not only varying sea state but also changing sailing conditions is assessed. The suggested control system achieves robust performance with adequate roll damping effect that ranges from 50 to 65% roll reduction according to severity of weather conditions and sailing status.

Scaling of X-ray spectral properties of a black hole in the Seyfert 1 galaxy NGC7469

We present our analysis of X-ray spectral properties observed from the Seyfert 1 galactic nucleus NGC 7469 using theRossiX-ray Timing Explorer (RXTE) and Advanced Satellite for Cosmology and Astrophysics mission (ASCA) observations. We demonstrate strong observational evidence that NGC 7469 undergoes spectral transitions from the low hard state (LHS) to the intermediate state (IS) during these observations. The RXTE observations (1996–2009) show that the source was in the IS ∼75% of the time only ∼25% of the time in the LHS. The spectra of NGC 7469 are well fitted by the so-called bulk motion Comptonization (BMC) model for all spectral states. We have established the photon index (Γ) saturation level, Γsat= 2.1 ± 0.1, in the Γ versus mass accretion rate,Ṁcorrelation. This Γ –Ṁcorrelation allows us to estimate the black hole (BH) mass in NGC 7469 to beMBH≥ 3 × 106M⊙assuming the distance to NGC 7469 of 70 Mpc. For this BH mass estimate, we use the scaling method taking Galactic BHs, GRO J1655–40, Cyg X–1, and an extragalactic BH source, NGC 4051 as reference sources. The Γ versusṀcorrelation revealed in NGC 7469 is similar to those in a number of Galactic and extragalactic BHs and it clearly shows the correlation along with the strong Γ saturation at ≈2.1. This is robust observational evidence for the presence of a BH in NGC 7469. We also find that the seed (disk) photon temperatures are quite low, of the order of 140–200 eV, which are consistent with a high BH mass in NGC 7469 that is more than 3 × 106solar masses.