Preliminary Spectral Analysis Research Articles

AstroSat Investigation of X-ray Flares on Two Active K-M Systems: CC Eri and AB Dor

We present an X-ray and UV investigation of five X-ray flares detected on two active systems, CC Eri and AB Dor, using the AstroSat observatory. The peak X-ray luminosities of the flares in the 0.3–7.0 keV band are found to be within 1031−33 erg s−1. Preliminary spectral analysis indicates the presence of three and four-temperature corona for CC Eri and AB Dor, respectively, where the highest temperature is found to vary with flare. The flare temperatures peaked at 51–59 MK for CC Eri and 29–44 MK for AB Dor. The peak emission measures of the flaring loops are estimated to be ∼1054 for CC Eri and ∼1055 cm−3 for AB Dor. Global metallic abundances were also found to increase during flares.

Experimental assessment of wing lower surface buffet effects induced by the installation of a UHBR nacelle

The installation of large bypass ratio engines on classical under wing configurations may lead to shock/boundary layer interaction on the wing lower surface, limiting the flight envelope in a similar way to classical buffet occurring on the wing suction side at high incidences in transonic flight. In this study, buffet effects on the lower surface of the wing induced by the installation of a Ultra-High-Bypass-Ratio through flow nacelle are assessed by means of wind tunnel testing. Unsteady pressure sensitive paint measurements were used to assess the pressure field on the wing with high temporal and spatial resolution. Strong unsteady shock motion associated with shock induced separation was found on the wing lower surface for various combinations of Mach number, Reynolds number and angle of attack. The wing lower surface buffet effects are found to increase with reducing angle of attack and are present over a wide range of Reynolds numbers. Preliminary spectral analysis suggests an upper limit for the buffet frequency at a Strouhal number of about 0.4.

Preliminary spectral matching analysis of RDE site at Serpong Indonesia

In concurrent with the plan to build small experimental power reactor at Serpong site, site specific response spectra evaluation is required to ensure the reactor safety. Site response spectra involved the spectral matching analysis which incorporates the seismic characteristics of the site and the design spectra. This paper presented the preliminary spectral matching analysis of selected natural earthquake records by comparing Al Atik & Abrahamson (2006) algorithm and Hancock et. al (2010) algorithm. The natural earthquake records were selected based on their similarity of their characteristics such as magnitude, distance resulting from deagregation analysis and site-specific conditions. Two subset periods were employed in the spectral matching analysis. Fourier spectrum and wave envelope analysis showed that both algorithms have maintained the original non-stationary characteristics. PGA, PGV and PGD values resulting from spectral matching have significant changes from the original as an implication of accelerogram amplitude scaling. From the spectral matching analysis, KAU083 record resulting from Hancock et. al (2006) algorithm has yielded the best matched to the target spectra compared to other selected records.

The First Dynamical Mass Determination of a Nitrogen-rich Wolf–Rayet Star Using a Combined Visual and Spectroscopic Orbit

Abstract We present the first visual orbit for the nitrogen-rich Wolf–Rayet binary, WR 133 (WN5o + O9I), based on observations made with the CHARA Array and the MIRC-X combiner. This orbit represents the first visual orbit for a WN star and only the third Wolf–Rayet star with a visual orbit. The orbit has a period of 112.8 days, a moderate eccentricity of 0.36, and a separation of a = 0.79 mas on the sky. We combine the visual orbit with an SB2 orbit and Gaia parallax to find that the derived masses of the component stars are and , with the large errors owing to the nearly face-on geometry of the system combined with errors in the spectroscopic parameters. We also derive an orbital parallax that is identical to the Gaia-determined distance. We present a preliminary spectral analysis and atmosphere models of the component stars, and find the mass-loss rate in agreement with polarization variability and our orbit. However, the derived masses are low compared to the spectral types and spectral model. Given the close binary nature, we suspect that WR 133 should have formed through binary interactions, and represents an ideal target for testing evolutionary models given its membership in the cluster NGC 6871.

High-frequency imaging for flaw detection of microelectronics elements with high resolution

This paper presents various diagnostic methods for microelectronic devices, in particular integrated circuits (IC). Features with the use of electron microscopes, scanning infrared microscopes, as well as X-ray flaw detection are considered. In particular, it is proposed to use a method based on electromagnetic radiation from the terahertz frequency range as an alternative to X-ray computed tomography (PXCT). For flaw detection of integrated circuits, it is planned to create a database of materials by preliminary spectral analysis of the materials used to create them. The possibility of analysis by creating two-dimensional patterns of the distribution of the intensity of electromagnetic radiation transmitted through the sample is also considered.

Diagnostic method by using vibration analysis for pump fault detection

Pump cavitation is a common problem affecting pumping systems. It occurs when the pressure of the liquid in the pump drops below a threshold and causes the liquid to vaporize creating tiny bubbles that, when they implode or collapse, trigger intense shockwaves inside the pump determining destructive damage. Excessive vibration on the pump casing could indicate cavitation. Consequently, vibration monitoring can help the detection and prevention of this harmful and undesired phenomenon.The purpose of this research is to analyze the capability of vibration-based techniques to detect, monitor and prevent pump cavitation. Experimental tests were performed on a gear pump used in the lubrication circuit of internal combustion engines. The pump, installed on a dedicated test bench, was forced to cavitate by placing a calibrated orifice on the suction side. Main working parameters, like oil flow rate, suction and delivery pressure, shaft speed, were accurately measured. Different pump operating conditions with and without cavitation occurrence were investigated through the use of a non-intrusive accelerometer, installed in proximity of the suction port so as to monitor the phenomenon in terms of vibration amplitude. A preliminary spectral analysis, based on the Fast Fourier Transform (FFT) of the vibrational signal, was performed in order to easily identify cavitation fundamental frequencies. A time-domain analysis technique was then implemented, aiming to realize an on line pump cavitation detection. Specifically, a NonLinear AutoRegressive (NLAR) approach based on the use of Artificial Neural Networks (ANN) was applied for modeling system behavior.In the paper, the results of the vibration-based method are discussed in depth, highlighting the pros and cons of the methodology. The presented outcomes demonstrate the ability of the proposed algorithm in accurately detect the presence of cavitation phenomena and to determine its intensity in pump real time operation. Hence, it may turn out to be a powerful tool for early detection of pumps incipient faults.

Diversity and bioprospecting of fungal communities associated with endemic and cold-adapted macroalgae in Antarctica

We surveyed the distribution and diversity of fungi associated with eight macroalgae from Antarctica and their capability to produce bioactive compounds. The collections yielded 148 fungal isolates, which were identified using molecular methods as belonging to 21 genera and 50 taxa. The most frequent taxa were Geomyces species (sp.), Penicillium sp. and Metschnikowia australis. Seven fungal isolates associated with the endemic Antarctic macroalgae Monostroma hariotii (Chlorophyte) displayed high internal transcribed spacer sequences similarities with the psychrophilic pathogenic fungus Geomyces destructans. Thirty-three fungal singletons (66%) were identified, representing rare components of the fungal communities. The fungal communities displayed high diversity, richness and dominance indices; however, rarefaction curves indicated that not all of the fungal diversity present was recovered. Penicillium sp. UFMGCB 6034 and Penicillium sp. UFMGCB 6120, recovered from the endemic species Palmaria decipiens (Rhodophyte) and M. hariotii, respectively, yielded extracts with high and selective antifungal and/or trypanocidal activities, in which a preliminary spectral analysis using proton nuclear magnetic resonance spectroscopy indicated the presence of highly functionalised aromatic compounds. These results suggest that the endemic and cold-adapted macroalgae of Antarctica shelter a rich, diversity and complex fungal communities consisting of a few dominant indigenous or mesophilic cold-adapted species, and a large number of rare and/or endemic taxa, which may provide an interesting model of algal-fungal interactions under extreme conditions as well as a potential source of bioactive compounds.

200–300 Hz movement modulated oscillations in the internal globus pallidus of patients with Parkinson's Disease

Symptoms in Parkinson's Disease (PD) have been linked to oscillatory activity within the basal ganglia. In humans, such activity has been detected mainly in the local field potentials (LFPs) recorded from electrode contacts used for deep brain stimulation.Although most studies have focused on activity within the subthalamic nucleus (STN), the internal part of the globus pallidus (GPi) is considered an equally efficacious site for therapeutic neuromodulation. Moreover, while most investigations have evaluated changes in oscillatory activity in the beta (12–35Hz) and gamma (35–100Hz) bands, our preliminary spectral analysis of LFP signals in the GPi suggested distinct activity at higher frequencies as well. We hypothesized there is a unique LFP signature in the GPi that consists of movement modulated spectral power increases above 100Hz. Using invasive recordings from the GPi of patients undergoing DBS, in addition to confirming increased beta band activity within the GPi of patients with PD, we have identified and characterized a previously undescribed peak between 200 and 300Hz centered at approximately 235Hz, whose height and width but not center frequency are movement modulated. An increase in peak height is not transient, but rather persists for the duration of movement. The 200–300Hz rhythms in the GPi could have a functional role in the basal ganglia reentrant circuits by encoding output information entering the thalamo-cortical network or by organizing downstream activity for the successful execution of tasks.

Exploring the long-term and interannual variability of biogeochemical variables in coastal areas by means of a data assimilation approach

Dynamic Harmonic Regression (DHR) models are applied here to the investigation of the interannual changes in the trend and seasonality of biogeochemical variables monitored in coastal areas. A DHR model can be regarded as a time-series component model, where the phases and amplitudes of the seasonal component, as well as the trend, are parameters that vary with time, reflecting relevant changes in the evolution of the biogeochemical variables. The model parameters and their confidence bounds are estimated by data assimilation algorithms, i.e. the Kalman filter and the Fixed Interval smoother. The DHR model structure is here identified by a preliminary spectral analysis and a subsequent minimization of the Bayesian Information Criterion, thus avoiding subjective choices of the frequencies in the seasonal component. The methodology was applied to the investigation of the long-term and interannual variability of ammonia, nitrate, orthophosphate and chlorophyll-a monitored monthly in the lagoon of Venice (Italy) during the years 1986–2008. It was found that the long-term evolutions of the biogeochemical variables were characterized by non-linear patterns and by statistically significant changes in the trend. The seasonal cycles of all the variables were characterized by a marked interannual variability. In particular, the changes in the seasonality of chlorophyll and nitrate were significantly related to the changes in the seasonality of water temperature at the study site and of nutrient concentrations in river discharges, respectively. These results indicate that the methodology could be a sound alternative to more traditional approaches for investigating the impacts of changes in environmental and anthropogenic forcings on the evolution of biogeochemical variables in coastal areas.

Nondestructive Identification of Freezing-Induced Cracks in Concrete Sleepers of High-Speed Railways in South Korea

The construction of a high-speed railway in South Korea was recently impeded by the unexpected problem of cracks in sleepers. These were presumably induced by the volume expansion of freezing water entrapped in the fastening assemblies during the winter. A total of 306,000 sleepers had to be investigated on an urgent basis for hairline cracks and possible latent cracks. These findings suggested that an appropriate nondestructive testing (NDT) technique for the inspection of concrete sleepers should be designed to meet two requirements: speed and reliability in testing. Research was performed to identify an optimal NDT technique by using sleepers with three different crack conditions: without any cracks, with a surface-opening crack, and with a hairline crack and possible latent cracks. Flexural rigidity rather than material stiffness or depth to multiple reflections was chosen as a key parameter for assessment of the structural integrity of a sleeper. The results allowed the design of a two-stage testing procedure: the flexural rigidity assessment of concrete tracks by antisymmetric Lamb (FRACTAL) waves technique for preliminary scanning and spectral analysis of surface waves (SASW) tests for in-depth investigation. A total of 18,177 sleepers that required testing were examined using FRACTAL tests, and 387 of these sleepers were double-checked using SASW tests. Before the overall examination of sleepers, a series of statistical analyses were performed to establish the criteria for defining the quality of a sleeper. The results of the FRACTAL test agreed with those of the SASW test in identifying sleepers with hairline cracks or possible latent cracks.

Induced Seismicity Monitoring of an Underground Salt Cavern Prone to Collapse

Within the framework of a large research project launched to assess the feasibility of microseismic monitoring of growing underground caverns, this specific work focuses on the analysis of the induced seismicity recorded in a salt mine environment. A local seismic network has been installed over an underground salt cavern located in the Lorraine basin (Northeast of France). The microseismic network includes four 3-components and three single component geophones deployed at depths between 30 and 125 m in cemented boreholes drilled in the vicinity of the study area. The underground cavern under monitoring is located within a salt layer at 180 m depth and it presents a rather irregular shape that can be approximated by a cylindrical volume of 50 m height and 180 m diameter. Presently, the cavern is full of saturated brine inducing a significant pressure on its walls (~2.0 MPa) to keep the overburden mechanically stable. Nevertheless some small microseismic events were recorded by the network and analyzed (approximately 2,000 events in 2 years of recording). In October 2005 and April 2007, two controlled pressure transient experiments were carried out in the cavern, in order to analyze the mechanical response of the overburden by tracking the induced microseismicity. The recorded events were mainly grouped in clusters of 3–30 s of signal duration with emergent first arrivals and rather low frequency content (between 20 and 120 Hz). Some of these events have been spatially located by travel-time picking close to the actual cavern and its immediate roof. Preliminary spectral analysis of isolated microearthquakes suggests sources with non-negligible tensile components possibly related to fluid-filled cracks. Rock-debris falling into the cavern from delamination of clay marls in the immediate roof is probably another source of seismic excitation. This was later confirmed when the most important seismic swarms occurred at the site during May 2007, accompanied by the detachment of more than 8 × 104 m3 of marly material on top of the cavern roof. In any case, no clear evidence of classical brittle ruptures in the most competent layers of the overburden has been observed during the analyzed period. Current work is focused on the discrimination of all these possible mechanisms to better understand the damage processes in the cavern overburden and to assess its final collapse hazard.

WASP-1b and WASP-2b: two new transiting exoplanets detected with SuperWASP and SOPHIE

We have detected low-amplitude radial-velocity variations in two stars, USNO-B1.0 1219–0005465 (GSC 02265–00107 = WASP–1) and USNO-B1.0 0964–0543604 (GSC 00522–01199 = WASP–2). Both stars were identified as being likely host stars of transiting exoplanets in the 2004 SuperWASP wide-field transit survey. Using the newly commissioned radial-velocity spectrograph SOPHIE at the Observatoire de Haute-Provence, we found that both objects exhibit reflex orbital radial-velocity variations with amplitudes characteristic of planetary-mass companions and in-phase with the photometric orbits. Line-bisector studies rule out faint blended binaries as the cause of either the radial-velocity variations or the transits. We perform preliminary spectral analyses of the host stars, which together with their radial-velocity variations and fits to the transit light curves yield estimates of the planetary masses and radii. WASP-1b and WASP-2b have orbital periods of 2.52 and 2.15 d, respectively. Given mass estimates for their F7V and K1V primaries, we derive planet masses 0.80–0.98 and 0.81–0.95 times that of Jupiter, respectively. WASP-1b appears to have an inflated radius of at least 1.33 RJup, whereas WASP-2b has a radius in the range 0.65–1.26 RJup.

Real-Time Seismic Monitoring of the New Cape Girardeau Bridge and Preliminary Analyses of Recorded Data: An Overview

This paper introduces the state-of-the-art seismic monitoring system implemented for the 1,206-m-long (3,956 ft) cable-stayed Bill Emerson Memorial Bridge in Cape Girardeau (Missouri), a new Mississippi River crossing, approximately 80 km from the epicentral region of the 1811 and 1812 New Madrid earthquakes. The real-time seismic monitoring system for the bridge includes a broadband network consisting of superstructure and free-field arrays and comprises a total of 84 channels of accelerometers deployed on the superstructure (towers and deck), pier foundations (caisson tops and bents), and in the vicinity of the bridge (e.g., free-field, both surface and downhole). The paper also introduces the high-quality response data obtained from the broadband network that otherwise would not have been possible with older instruments. Such data is aimed to be used by the owner, researchers, and engineers to (1) assess the performance of the bridge, (2) check design parameters, including the comparison of dynamic characteristics with actual response, and (3) better design future similar bridges. Preliminary spectral analyses of low-amplitude ambient vibration data and that from a small earthquake reveal specific response characteristics of this new bridge and the free-field in its proximity. There is coherent tower-cable-deck interaction that sometimes results in amplified ambient motions. Also, while the motions at the lowest (triaxial) downhole accelerometers on both Missouri and Illinois sides are practically free from any feedback of motions of the bridge, the motions at the middle downhole and surface accelerometers are influenced significantly even by amplified ambient motions of the bridge.

The hard X-ray emission from the Vela pulsar wind nebula

We present the results of a preliminary spectral analysis performed on the BeppoSAX and XMM observations of the Vela plerion. The broad energy range covered by the instruments on board the two observatories allows an evaluation of the spectral parameters of the high energy emission model and provides an indication on the morphology of the source emission above 10 keV. We confirm the softening of the PWN spectrum (3–10 keV band) at distances greater than 4′ from the pulsar and estimate the diameter of the high energy (>10 keV) emission region to be on the order of 25′–30′.

X-ray spectroscopy and variability of AGN detected in the 2 Ms Chandra Deep Field-North Survey

We investigate the nature of the faint X-ray source population through X-ray spectroscopy and variability analyses of 136 active galactic nuclei (AGN) detected in the 2 Ms Chandra Deep Field-North Survey with >200 background-subtracted 0.5–8.0 keV counts [ F 0.5–8.0 keV = (1.4−200) × 10 −15 erg cm −2 s −1]. Our preliminary spectral analyses yield median spectral parameters of Γ = 1.61 and intrinsic N H = 6.2 × 10 21 cm −2 ( z = 1 assumed when no redshift available) when the AGN spectra are fitted with a simple absorbed power-law model. However, considerable spectral complexity is apparent (e.g., reflection, partial covering) and must be taken into account to model the data accurately. Moreover, the choice of spectral model (i.e., free vs. fixed photon index) has a pronounced effect on the derived JVH distribution and, to a lesser extent, the X-ray luminosity distribution. We also find that among the 136 AGN, 10 (≈7%) show significant Fe Kα emission-line features with equivalent widths in the range 0.1–1.3 keV. Two of these emission-line AGN could potentially be Compton thick (i.e., Γ < 1.0 and large Fe Kα equivalent width). Finally, we find that 81 (≈60%) of the 136 AGN show signs of variability, and that this fraction increases significantly (≈80–90%) when better photon statistics are available.

First results from TOO observations of the Aql X-1 field with INTEGRAL

We present results of observations of the Aql X-1 field performed in March-April 2003 with the INTEGRAL observatory. This TOO (Target Of Opportunity) INTEGRAL observations was initiated upon receiving an indication from the ASM/RXTE that the source started an outburst. Thirteen X-ray sources were detected by the INTEGRAL imagers, JEM-X and IBIS, during these observations. We present a preliminary spectral and timing analysis for several bright sources in the field, Aql X-1, X1901+03, 4U1907+097, XTE J1908+094 and X1908+075. We also detected two X-ray bursts from Aql X-1 near the end of the general outburst episode.

Seismic monitoring of the Olkaria Geothermal area, Kenya Rift valley

Seismic monitoring of the Olkaria Geothermal area in the southern Rift Valley region of Kenya has been carried out since 1985. The initial purpose of this effort was to determine the background level of seismicity before full exploitation of the geothermal resource was started. This monitoring began with one seismic station. However, since May 1996, a seismic network comprising six stations was operated and focused mainly on the East Production Field. During the 5 months of network recording up to mid-September 1996, more than 460 local events originating within the Olkaria Geothermal area ( T s− T p<5 s) were recorded, out of which 123 were well-located. Also, 62 events were recorded at regional distances (5 s< T s− T p<40 s), and 44 events at teleseismic distance ( T s− T p>40 s). During this period, the local microseismicity was found to be continuous with swarms occurring every 4–5 days. Duration magnitudes based on the coda length did not exceed 3.0. Preliminary spectral analysis shows three kinds of seismic signals, with only the first type displaying well-defined P- and S-phases. The seismicity is mainly concentrated in the central area of the recording network, and the linear alignments in the epicenters are striking. A prominent alignment occurs along the Ololbutot fault zone extending from the northern end of the greater Olkaria volcanic complex to the south near the southern terminus of Hell's gorge. Two other prominent alignments occur along NW–SE trends that coincide with fault zones which have been detected by geological and gravity studies. Consequently, they are interpreted to be associated with fluid movement in the geothermal field. These preliminary results suggest that seismic monitoring will be useful to both monitor the field during production and to help site additional wells.

Design of a Randomized Tining Rake for Portland Cement Concrete Pavements Using Spectral Analysis

Uniformly spaced, transverse-tined portland cement concrete (PCC) pavements have been in extensive use in the United States since the early 1970s. However, driving on tined pavements generates an uncomfortable acoustic “whine”that has a discrete frequency. Recent research by the Wisconsin Department of Transportation (WisDOT) and FHWA led to an interim guideline for randomization of the tining pattern. The guideline called for tine spacing varying from 10 to 40 mm, with 50 percent of the spacing below 25 mm. At least five states have experimented with this random pattern, with limited success in eliminating the whine. A study was completed recently as part of a WisDOT contract with Marquette University and the HNTB Corporation, and funded by FHWA, to analyze all of the pavements. The tonal properties of acoustical noise were related to the serial arrangement of the tining, showing that the frequencies can be predicted from the power spectrum of the series of tines. A method of designing the series of tines that minimizes and possibly eliminates the presence of these whines is proposed and explained. By predicting the tonal properties of acoustical noise at the rake-design stage, the construction effort in building and researching noise and texture characteristics is substantially reduced. A random rake, designed using the proposed methodology, has been used in tining a road section, and preliminary spectral analysis of the acoustic noise revealed no tining-related discrete tones.

Preliminary spectral analysis of SN 19941

We present optical spectra of the Type Ic supernova 1994I in M51 and preliminary non-LTE analysis of the spectra. Our models are not inconsistent with the explosions of C+O cores of massive stars. While we find no direct evidence for helium in the optical spectra, our models cannot rule out small amounts of helium. More than 0.1~\msol\ of helium seems unlikely.

Strong gamma-ray bursts observed by COMPTEL during its second year of operation

The imaging Compton telescope COMPTEL onboard the Compton Gamma Ray Observatory can localize gamma-ray bursts occurring inside its ∼1 sr field-of-view in the energy range from 0.75 to 30 MeV with location accuracy of ∼1°. Additional time-resolved spectral measurements in the energy range 0.1 to 10 MeV are made by individual COMPTEL ‘burst’ detectors. During its second year of operation. COMPTEL observed several gamma-ray bursts. Locations of five strong bursts (including the rapidly imaged events GRB 930131 and GRB 930309) are presented here along with the findings from preliminary spectral analysis.