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Copper sulfide deposition on cellulosic insulating materials in oil-immersed transformers is evaluated by heating tests stipulated by IEC 62535. Although this method is suitable for evaluation of the corrosivity of unused insulating oil, the subject remains in diagnosis of the insulating oil used. It is because dibenzyl disulfide (DBDS), which is the prime compounds that cause copper sulfide deposition, is consumed by the reaction with copper during operating of transformer. Therefore, it is necessary to detect the existence of DBDS in insulating oil diagnosed as non-corrosivity by IEC 62535. The proceeding paper [6] reports that Bibenzyl (BiBz) and Dibenzyl sulfide (DBS) will be formed in the insulating oil as by-products of copper sulfide formation between copper and DBDS in oxygen-poor atmosphere which imitated the closed-type transformers. These by-products are considered to be the indication of copper sulfide formation. However, the influence of oxygen and addition agent (e.g. 2,6-di-tert-butylp- cresol) on the mechanism of the by-product formation is unclear. The purpose of this study is to elucidate the influence of oxygen and DBPC in by-products formation for development of diagnosis. It became apparent that benzyl alcohol, benzaldehyde and benzoic acid generate as by-products of copper sulfide formation in the air atmosphere which imitated the open-breathing transformers. Furthermore, it became apparent that the reaction product of benzyl radical and the radical of DBPC generates as by-product of copper sulfide formation in the insulating oil containing DBPC. These by-products are detectable even if DBDS disappears. Therefore, it is thought that diagnosis of the open-breathing transformer is possible by detecting these by-products. [ABSTRACT FROM AUTHOR]

Copper sulfide deposition on cellulosic insulating materials in oil-immersed transformers was investigated by heating tests stipulated by IEC 62535 with controlled atmospheres to which mineral insulating oils were exposed. Both oxygen in the atmosphere and 2,6-di-tert-butyl-p-cresol (DBPC) in the oil were found to accelerate the copper sulfide deposition on the insulating paper when the oil contains dibenzyl disulfide (DBDS). The weight of copper sulfide deposition on the insulating paper was found to increase when the oxygen concentration was increased up to 20 volume %. X-ray absorption near edge structure (XANES) analysis was applied to study the chemical bonding state of copper atoms in copper deposits on the insulating paper for the first time. It can be clarified the copper deposits on the insulating paper are mainly Cu2S and small amounts of CuO are contained. [ABSTRACT FROM PUBLISHER]

A low-cost and simple-arranged paper-based microplasma array device made by tape and Xerox paper was presented. Uniform array of discharge can be sustained in Ar, He, and ambient air atmosphere. Stable discharge can be sustained for at least 55 min when plasma is ignited in Ar ambient, based on the examination of time-resolved optical emission spectra. Throughout the conditions investigated, the power consumed by the device was well below 0.3 W. We also demonstrated that stable and uniform discharge can be generated when the device was bent to a radius of curvature of 2.5 mm. [ABSTRACT FROM PUBLISHER]

This paper reports the first use of a 3-D radar imaging for observing E-region field-aligned plasma irregularities (FAIs) in the midlatitude ionosphere. Five carrier frequencies equally spaced between 46.25 and 46.75 MHz were transmitted alternately with consecutive radar pulses, and 20 receivers were employed for receiving the radar echoes. The experiments were carried out using the middle and upper atmosphere radar (34.85°N, 136.10°E), with the radar beams steered to the geographic north and 6.6° north by east, at the zenith angles of 51.0° and 51.5°, respectively. The 2-D imaging with the echoes collected by the 19 of the 20 receivers revealed that in zonal dimension, the off-beam direction of arrival (DOA) of the echo region changed alternately between positive and negative values, which can be attributed to the highly localized FAIs drifting zonally through the radar beam. On the other hand, the off-beam DOA in meridional dimension was negative and positive, respectively, at higher and lower range locations, which were supposed to be due to the meridional drift component of FAIs. A combination of 5 frequencies and 19 receivers achieved a 3-D imaging of the FAI structures, illustrating small-scale FAI striations and bubblelike plasma structures in the radar volume. Moreover, declination of geomagnetic field line was examined from the imaged 3-D brightness distribution in the radar volume; the estimated declination of geomagnetic field line was in agreement with that computed from the International Geomagnetic Reference Field model in 2011. This paper has demonstrated some capabilities of radar imaging for ionospheric investigation. [ABSTRACT FROM AUTHOR]

In this paper, we report the vertical profiles of CO2 and CH4 measured with a cavity ring-down spectrometer (CRDS) on a research aircraft from near-ground level to 8 km above mean sea level. The airborne platform employed in this paper is an Alpha Jet aircraft operated from NASA's Ames Research Center. Flights were undertaken to Railroad Valley, NV, USA, to coincide with overpasses of the Greenhouse Gases Observing Satellite (GOSAT). Ground-based CO2 and CH4 were simultaneously measured using CRDS, at the time and location of the airborne and satellite measurements. Results of three GOSAT coordinated aircraft profiles and ground-based measurements in June 2011 are presented and discussed in this paper. The accuracy of the CO2 and CH4 measurements has been determined based upon laboratory calibrations (World Meteorological Organisation traceable standard) and pressure/temperature flight simulations in a test chamber. The overall uncertainty for the airborne measurements ranged from 0.31 to 0.39 ppm for CO2 and from 3.5 to 5.6 ppb for CH4. Our column-averaged CO2 and CH4 measurements, which include about 61% of the total atmospheric mass, are extrapolated, using different techniques, to include the remainder of the tropospheric and stratospheric CO2 and CH4. The CO2 data are then analyzed using the Atmospheric CO2 Observations from Space 2.9 and 3.3 algorithms. For methane data, the RemoTeC v2.1 algorithm was used in its full physics setup. Column-averaged CO2 and XCO2, measured by GOSAT and analyzed from our data, ranged from 388.1 to 396.4 ppm, and XCH4 ranged from 1.743 to 1.822 ppm. The agreement of the satellite and aircraft CO2 mixing ratios, as well as ground measurements, falls within the uncertainties of the methods employed to acquire these numbers. [ABSTRACT FROM PUBLISHER]

The ozone mapping and profiler suite (OMPS) is carried onboard the Suomi National Polar-orbiting Partnership satellite that was launched on October 28, 2011. The OMPS mission objectives concern atmospheric ozone concentrations and their variations in the earth atmosphere. A successful thorough on-orbit sensor calibration enabled current validated operational sensor data record (SDR) stage, providing quality sensor data that meet the requirements and users’ expectations. The calibration coefficients derived from this paper have been successfully used in a life-cycle SDR reprocessing to improve sensor data quality. In this paper, we present our qualitative analyses and the results of OMPS nadir mapper SDR on-orbit calibration, and address current SDR data quality in relation to instrument detector performance, stray light correction, and wavelength registration. Our OMPS SDR calibration experience sets a reference for the successor instruments for accurate long-term monitoring of ozone total column concentrations. [ABSTRACT FROM AUTHOR]

The objective of this paper is to review various methods of determining the extent of hazardous areas in industrial facilities where explosive gas or vapor atmospheres may be present. Three different approaches are analyzed and compared. The first one is recommended in North American Standards, such as API 500, API 505, and NFPA 497. The second is one of the proposals for the second edition of the International Standard IEC 60079-10-1 (adopted as European standard EN 60079-10-1). The third approach had been previously worked out with the authors' contribution and had been adopted by the Italian Guide CEI 31-35 since 2001. The last two approaches are analytical, meanwhile the first one is prescriptive. In the second part of this paper, both analytical approaches are applied to the releases which are analyzed in NFPA 497 as practical examples. Resulting hazardous area extents are compared, and the differences among the three methods are discussed. [ABSTRACT FROM PUBLISHER]

In this paper, we discuss the measurements of spectral surface reflectance (ρlambda;8) in the wavelength range 350-2500 nm measured using a spectroradiometer onboard a low-flying aircraft over Bangalore (12.95° N, 77.65° E), an urban site in southern India. The large discrepancies in the retrieval of aerosol properties over land by the Moderate-Resolution Imaging Spectroradiometer (MODIS), which could be attributed to the inaccurate estimation of surface reflectance at many sites in India and elsewhere, provided motivation for this paper. The aim of this paper was to verify the surface reflectance relationships assumed by the MODIS aerosol algorithm for the estimation of surface reflectance in the visible channels (470 and 660 nm) from the surface reflectance at 2100 nm for aerosol retrieval over land. The variety of surfaces observed in this paper includes green and dry vegetations, bare land, and urban surfaces. The measuredreflectance data were first corrected for the radiative effects of atmosphere lying between the ground and aircraft using the Second Simulation of Satellite Signal in the Solar Spectrum (6S) radiative transfer code. The corrected surface reflectance in the MODIS's blue (ρ4708), red (ρ6608), and shortwave-infrared (SWIR) channel (ρ21008)) was linearly correlated. We found that the slope of reflectance relationship between 660 and 2100 nm derived from the forward scattering data was 0.53 with an intercept of 0.07, whereas the slope for the relationship between the reflectance at 470 and 660 nm was 0.85. These values are much higher than the slope (~0.49) for either wavelengths assumed by the MODIS aerosol algorithm over this region. The reflectance relationship for the backward scattering data has a slope of 0.39, with an intercept of 0.08 for 660 nm, and 0.65, with an intercept of 0.08 for 470 nm. The large values of the intercept (which is very small in the MODIS reflectance relationships) result in larger values of absolute surface reflectance in the visible channels. The discrepancy between the measured and assumed surface reflectances could lead to error in the aerosol retrieval. The reflectance ratio (ρ6608)/(ρ21008) showed a clear dependence on the NDVIswia where the ratio increased from 0.5 to 1 with an increase in NDVISWIR from 0 to 0.5. The high correlation between the reflectance at SWIR wavelengths (2100, 1640, and 1240 nm) indicated an opportunity to derive the surface reflectance and, possibly, aerosol properties at these wavelengths. We need more experiments to characterize the surface reflectance and associated inhomogeneity of land surfaces, which play a critical role in the remote sensing of aerosols over land. [ABSTRACT FROM AUTHOR]

To extend the lifetime of commercial and scientific satellites in low Earth orbit (LEO) and below (100–250 km of altitude) recent years showed an increased activity in the field of air-breathing electric propulsion as well as beamed-energy propulsion systems. However, preliminary studies showed that the propellant flow necessary for electrostatic propulsion at these altitudes exceeds the mass intake possible within reasonable limits, and that electrode erosion due to oxygen flow might limit the lifetime of eventual thruster systems. The pulsed plasma thruster (PPT), however, can be successfully operated with smaller mass intake and at relatively low power. This makes it an interesting candidate for air-breathing application in LEO and its feasibility is investigated within this paper. An analysis of such an air-breathing PPT system shows that for altitudes between 150 and 250 km, drag compensation is at least partially feasible assuming a thrust-to-power ratio of 30 mN/kW and a specific impulse of 5000 s. Further, to avoid electrode erosion, inductively heated electrothermal plasma generator technology is discussed to derive a possible propulsion system that can handle gaseous propellant without unfavorable side effects. Current technology can be used to create an estimated 4.4 mN of thrust per 1 mg/s of mass flow rate, which is sufficient to compensate the drag for small satellites in altitudes between 150 and 250 km. [ABSTRACT FROM PUBLISHER]

Satellite remote sensing has accumulated decades of normalized difference vegetation index (NDVI) data. For long-term environmental studies, multisensor NDVI discrepancies should be initially corrected via intersensor NDVI calibration. This paper proposes a generalized model and its simplified form for the calibration by incorporating sensor-, atmosphere-, and observational geometry-related parameters into an analytical function. The models are first validated using the tandem Landsat-5 Thematic Mapper and Earth Observing One (EO-1) Advanced Land Imager (ALI) NDVIs and then used to evaluate current intercalibration methods. The results show that surface reflectance is the most critical factor for linear intercalibrations followed by water vapor. While other atmospheric parameters as well as solar zenith angle have minor effects on linear intercalibrations. The strong nonlinear relationships between the spectral band adjustment factors and NDVI may explain why quadratic functions are used for NDVI intercalibration. Although quadratic intercalibrations are generally more accurate than linear intercalibrations, they may still perform poorly when water vapor exhibits significant spatial variations. In addition, the uncertainties associated with current NDVI intercalibrations are discussed based on the proposed models. This paper furthers the understanding of multisensor NDVI intercalibration and provides insight into intercalibration of other remote sensing indices. [ABSTRACT FROM AUTHOR]

Geosocial networks like Yelp and Foursquare have been rapidly growing and accumulating plenty of data such as social links between users, user check-ins to venues, venue geographical locations, venue categories, and user textual comments on venues. These data contain rich knowledge on the user's social interactions in communities, geographical mobility patterns between regions, categorical preferences on activities, aspect interests in topics, and opinion expressions for sentiments. Such knowledge is essential for two key applications, namely, text sentiment classification and venue recommendations, which will be developed in this paper. To extract the knowledge from the data, the key task is to discover the latent communities, regions, activities, topics, and sentiments of users. However, these latent variables are interdependent, e.g., users in the same community usually travel on nearby regions and share common activities and topics, which renders a big challenge for modeling these latent variables. To tackle this challenge, in this study, we propose an LDA-based model called CRATS that jointly mines the latent Communities, Regions, Activities, Topics, and Sentiments based on the important dependencies among these latent variables. To the best of our knowledge, this is the first study to jointly model these five latent variables. Finally, we conduct a comprehensive performance evaluation for CRATS in different applications, including text sentiment classification and venue recommendations, using three large-scale real-world geosocial network data sets collected from Yelp and Foursquare. Experimental results show that CRATS achieves significantly superior performance against other state-of-the-art techniques. [ABSTRACT FROM PUBLISHER]

Cu (II) ion has potential roles in a lot of living metabolisms that its detection and removal are extremely important for flagship branches of science. In this paper, fluorescent and easy-make silica gel immobilized BODIPY were successfully prepared via a simple synthesis procedure for the rapid recognition of Cu (II) ions. The optimal emission and excitation wavelength of the synthesized hybrid material, Si-APTMS-BODIPY, was 543 nm and 460 nm, respectively. The new solid support surface fully characterized by several techniques has notable results and visual data for the detection of Cu (II) ion. The maximum fluorescent intensity of Si-APTMS-BODIPY was clearly quenched following the adding of Cu (II) ion owing to static and dynamic quenching mechanisms. Maybe, more importantly, there was a notable linear correlation between several concentrations of Cu (II) solution and the fluorescence quenching processes with a limit of detection (LOD) of $1.7 ~\mu \text{M}$. Based on these, a fluorescent hybrid material having high selectivity and sensitivity was made up, and it provides a precious proposal for the recognition of Cu (II) ions. [ABSTRACT FROM AUTHOR]

In the autumn and winter, aerosol is the important atmospheric pollutant over the Beijing–Tianjin–Hebei region. For monitoring aerosol in the autumn and winter, the lack of vegetation and the aging of MODIS sensor are two problems that needed to be solved. In this paper, after analyzing the characteristics of aerosol radiance in the red and shortwave infrared ($2.12~\mu \text{m}$) bands of MODIS, we develop a new algorithm for terrestrial aerosol with the assumption that the reflectance ratio between the red and $2.12~\mu \text{m}$ bands is invariant. With MODIS data over the Beijing–Tianjin–Hebei region from September 2016 to February 2017, the algorithm is applied to aerosol retrieval. The retrieved aerosol optical depth images show that our algorithm can retrieve aerosol over sparse vegetation, and the validation with the AERONET/PHOTONS Beijing site shows that the correlation is greater than 0.9% and 77% of the retrievals fall within the expected error. An error analysis shows that a 2% error in the proportion of the soot component can lead to 15% retrieval error, and over more than 60% of the surface area, the error from the changes in the ratio between the red and $2.12~\mu \text{m}$ bands can lead to retrieved errors less than 0.1. [ABSTRACT FROM AUTHOR]

The recent advancements in power conversion efficiency for organic solar cells is still complained by their reliability and stability remaining the main bottlenecks for organic photovoltaics large scale production and commercialization. In this paper, we aim to provide further insights understanding in degradation processes affecting stability in small molecule flat heterojunction (Glass/ITO/MoO3/ZnPc/C60/BCP/Ag) solar cells through a systematic aging study coupled with optoelectrical characterizations. In particular, the burn-in phenomenon affecting short-circuit current in thermal-stressed samples has been clearly correlated with the C60 domain coarsening process and eventually to the decreased exciton lifetime. [ABSTRACT FROM AUTHOR]

This paper debates the requirements mentioned in some of the current editions of the International Electrotechnical Commission standards related to equipment and installations in hazardous locations. The main requirements recently introduced are shown, and some points of concern from installers are highlighted. [ABSTRACT FROM AUTHOR]

Anomalous GPS radio occultation (RO) events are characterised as those with L1 bending angle greater than their corresponding L2 bending angle. An investigation by EUMETSAT and the United Kingdom Meteorological Office revealed there are regions in the earth’s atmosphere where at times up to 60% of Global Navigation Satellite System Receiver for Atmospheric Sounding RO events, at the Tangent Point height of 50 km, exhibited anomalous bending angle results. The exact source of these anomalous RO events has been unclear to the RO data user community, i.e., data processing artifact or atmospheric phenomenon. In this paper, the regions of increased occurrence of anomalous RO have been identified to be the mid-latitude ionospheric trough, ionospheric polar hole, and poleward edges of the equatorial anomaly. They are more frequent at nighttime and in the southern hemisphere winter months. This is when the plasma density in these regions is depleted. However, within these regions, there are ionospheric features of increased electron density gradients such as at the walls of the mid-latitude ionospheric trough. 3-D numerical ray tracing simulations of GPS RO are presented, showing that these increased electron density features in a weakly ionized ionosphere can produce the anomalous bending angle results. [ABSTRACT FROM AUTHOR]

This paper presents results from the continued application of a new technique for the remote online partial discharge (OLPD) testing and monitoring of in-service high-voltage (HV) explosive atmosphere (Ex)/atmosphere-explosive (ATEX) motors operating in hazardous gas zones. The technique employs high-current wideband high-frequency current transformer sensors located remotely from the motor under test, at the switchboard end of the HV feeder cable. Significant cost and operational benefits can be gained from this remote monitoring technique as the stator winding condition of these motors can be monitored without having to enter the hazardous gas (Ex/ATEX) zone. The work described in this paper is a continuation of that carried out by the same authors, as reported at the 2012 IEEE Petroleum and Chemical Industry Technical Conference, and includes the development of proposed condition guidelines for assessing the condition of the stator winding insulation systems of large populations of aged HV motors, based on an OLPD “league-table” database. Two case studies are presented wherein the HV stator insulation condition and reliability of in-service motors, operating in hazardous gas zones, and HV generators were assessed using both online and offline partial discharge (PD) testing and monitoring techniques. The case studies emphasize the importance of carrying out extended continuous OLPD monitoring of in-service rotating HV machines to detect underlying trends in PD activity over time. This paper concludes with how condition monitoring data can support reliability-centered maintenance and condition-based management regimes. [ABSTRACT FROM PUBLISHER]

High spatial resolution (HSR) imagery scene classification, which involves labeling an HSR image with a specific semantic class according to the geographical properties, has received increased attention, and many algorithms have been proposed for this task. The employment of the probabilistic topic model to acquire latent topics and the convolutional neural networks (CNNs) to capture deep features for representing HSR images has been an effective ways to bridge the semantic gap. However, the midlevel topic features are usually local and significant, whereas the high-level deep features convey more global and detailed information. In this paper, to discover more discriminative semantics for HSR images, the adaptive deep sparse semantic modeling (ADSSM) framework combining sparse topics and deep features is proposed for HSR image scene classification. In ADSSM, the fully sparse topic model and a CNN are integrated. To exploit the multilevel semantics for HSR scenes, the sparse topic features and deep features are effectively fused at the semantic level. Based on the difference between the sparse topic features and the deep features, an adaptive feature normalization strategy is proposed to improve the fusion of the different features. The experimental results obtained with four HSR image classification data sets confirm that the proposed method significantly improves the performance when compared with the other state-of-the-art methods. [ABSTRACT FROM AUTHOR]

Monitoring the flow of radiative energy at top of atmosphere (TOA) is essential for understanding Earth’s climate and how it is changing with time. The determination of TOA global net radiation budget using broadband nonscanner instruments has received renewed interest recently due to advances in both instrument technology and the availability of small satellite platforms. The use of such instruments for monitoring Earth’s radiation budget was attempted in the past from satellite missions such as the Nimbus-7 and the Earth Radiation Budget Experiment (ERBE). This paper discusses the important lessons learned from the operation of the ERBE nonscanner instrument and the production of the ERBE nonscanner TOA radiation budget data set that have direct relevance to current nonscanner instrument efforts. [ABSTRACT FROM AUTHOR]

This paper successfully achieved the recognition and quantitative prediction of different amine vapors in high humid atmosphere through the combination of PPy-metal oxide semiconductor (MOS)-based sensor array and multiple linear regression (MLR)-based signal processing technique. PPy-MOS hybrid nanocomposite films with various metal oxide semiconductor materials, including WO3, NiO, ZnO-NiO, and SnO2-NiO were successfully prepared and deposited on interdigitated electrodes by electrospinning technique. The synthesized metal oxide particles and PPy-MOS hybrid nanocomposites were characterized in terms of their crystalline structures, morphologies, and compositional features by XRD, FE-SEM, and EDAX methods. The sensing performance of the designed array exposed to various alkyl amines, including methyl-, dimethyl-, ethyl- and propylamine, ethanol, acetone, and water vapors have been studied. The principal component analysis was utilized to test the ability of the proposed sensor array to recognize different gas classes. MLR technique was used for simultaneous determination of amine vapors in humid atmosphere. The results showed the capability of developed fabricated sensor array for identification and quantification of different amine vapors in humid atmosphere at low temperature. [ABSTRACT FROM PUBLISHER]

Results of theoretical research on ionization of dry air at different low and moderate values of constant electric field are described. Ionization processes at subthreshold, near-threshold, and suprathreshold values of electric field have been considered. Special attention to the processes of electron attachment to oxygen molecules and electron detachment from negative ions has been paid. New data on the detachment of electrons from oxygen molecular negative ions are taken into account. Plasma ionization during thermal instability has been considered. [ABSTRACT FROM AUTHOR]

In the satellite hyperspectral measures, the contributions of light, surface, and atmosphere are mixed. Applications need separate access to the sources. Conventional inversion techniques usually take a pixelwise spectral-only approach. However, recent improvements in retrieving surface and atmosphere characteristics use heuristic spatial smoothness constraints. In this paper, we theoretically justify such heuristics by analyzing the impact of spatial information on the uncertainty of the solution. The proposed analysis allows to assess in advance the uniqueness (or robustness) of the solution depending on the curvature of a likelihood surface. In situations where pixel-based approaches become unreliable, it turns out that the consideration of spatial information always makes the problem to be better conditioned. With the proposed analysis, this is easily understood since the curvature is consistent with the complexity of the sources measured in terms of the number of significant eigenvalues (or free parameters in the problem). In agreement with recent results in hyperspectral image coding, spatial correlations in the sources imply that the intrinsic complexity of the spatio-spectral representation of the signal is always lower than its spectral-only counterpart. According to this, the number of free parameters in the spatio-spectral inverse problem is smaller, so the spatio-spectral approaches are always better than spectral-only approaches. Experiments using ensembles of actual reflectance values and realistic MODTRAN irradiance and atmosphere radiance and transmittance values show that the proposed analysis successfully predicts the practical difficulty of the problem and the improved quality of spatio-spectral retrieval. [ABSTRACT FROM PUBLISHER]

Nanosilver paste is a promising material for power device interconnects. Interconnects are fabricated from nanosilver paste through a sintering process that drives off solvents and dispersants and fuses the silver particles. The integrity of the resulting interconnect is affected by the silver microstructure. This paper explored how sintering temperature, atmosphere, and time influenced microstructure as revealed by transmission electron microscopy and 3-D imaging via dual-beam serial sectioning. Nanosilver paste was sintered in combinations of the following parameters: a sintering atmosphere of air or nitrogen; temperatures of 120 °C or 255 °C; and sintering times of 5, 10, or 30 min. For the 255 °C temperature, oxygen in air facilitated removal of organic solvent and dispersant molecules and led to a microstructure with a coarser ligament network than samples sintered at the same temperature and times in nitrogen. The coarser ligament network was characterized by thick connected ligaments, large connected pores, and few isolated pores; this microstructure has been correlatedwith improved mechanical strength. Details of both 2-D and 3-D ligament network morphology, grain morphology, grain size, and the associated grain boundaries are discussed. [ABSTRACT FROM PUBLISHER]

A cold bias of \sim\!-2 K was found for Channel 6 (13.3 \mu\m) of the Imager instrument on the 13th of Geostationary Operational Environmental Satellite (GOES-13) during its postlaunch tests. Similar bias was found previously for GOES-12 and for other instruments (the High Resolution Infrared Radiation Sounder, the Moderate Resolution Imaging Spectroradiometer, and the Spinning Enhanced Visible and Infrared Imager) in the similar spectral region. It was often suspected that the spectral response function (SRF) of these instruments may be in error; in some cases, it had been demonstrated that an altered SRF can eliminate most of the differences between the measured and the expected values. Using products recently developed for the Global Space-based Inter-Calibration System, this paper concluded that an SRF error is the root cause for the GOES Imager Channel 6 bias. Based on this theory, an algorithm was developed to correct for the bias. Application of this correction to GOES-13 Imager Channel 6 resulted in an SRF shift of -2.1\ \cm^-1. The remaining biases have mean of nearly zero and much reduced standard deviation and are independent of the thermal structure of the interlaying atmosphere. This correction has also been successfully applied of other channels and of other GOES, which was described in a companion paper. [ABSTRACT FROM PUBLISHER]

This paper presents an investigation into cloud-to-ground lightning activity over the continental territory of Portugal with data collected by the national Lightning Location System. The Lightning Location System in Portugal is first presented. Analyses about geographical, seasonal, and polarity distribution of cloud-to-ground lightning activity and cumulative probability of peak current are carried out. An overall ground flash density map is constructed from the database, which contains the information of more than five years and almost four million records. This map is compared with the thunderstorm days map, produced by the Portuguese Institute of Meteorology, and with the orographic map of Portugal. Finally, conclusions are duly drawn. [ABSTRACT FROM AUTHOR]

Foreground segmentation of moving objects in adverse atmospheric conditions such as fog, rain, low light, and dust is a challenging task in computer vision. The advantages of thermal infrared imaging at night time under adverse atmospheric conditions have been demonstrated, which are due to the long wavelength. However, the existing state-of-the-art object detection techniques have not been useful in such scenarios. In this paper, we propose an improved background model that utilizes both thermal pixel intensity features and spatial video salient features. The proposed spatial video salient features are represented as an Akin-based per-pixel Boolean string over a local region block, and depend on the effect of neighboring pixels on a center pixel. The result of this Boolean procedure is referred to as the- Akin-Based Local Whitening Boolean Pattern (ALWBP), which differentiates foreground and background region accurately, even against a cluttered background. The background model is controlled via 1) the automatic adaptation of parameters such as the decision threshold $\text{R}_{\mathrm {T}}$ and, learning parameter L, and 2) the updating of background samples $\text{B}_{\mathrm {sample\_{}int}}$ and,- $\text{B}_{\mathrm {sample\_{}ALWBP}}$ to minimize 1) the effect of the background dynamics of outdoor scenes and 2) the temperature polarity changes during the maiden appearance of a moving object in thermal frame sequences. The performance of this model is evaluated using nine existing standard segmentation performance metrics on our newly created-Tripura University Video Dataset at Night Time (TU-VDN) and on the publicly available CDnet-2014 dataset. Our newly created weather-degraded video dataset, namely, TU-VDN, consists of sixty video sequences that represent four atmospheric conditions, namely, low light, dust, rain, and fog. The results of a performance comparison with 14 state-of-the-art detection techniques also demonstrate the high accuracy of the proposed technique. [ABSTRACT FROM AUTHOR]

In this paper, we introduce a method to retrieve the optical thickness of tropical cirrus clouds using the isolated visible cirrus reflectance (without atmospheric and surface effects). The isolated cirrus reflectance is inferred from level 1b calibrated 0.66- and 1.375-μm Moderate Resolution Imaging Spectroradiometer (MODIS) data. We created an optical properties database and optical thickness lookup library using previously calculated single- scattering data in conjunction with the discrete ordinates radiative transfer (DISORT) code. An algorithm was constructed based on this lookup library to infer the optical thickness of tropical cirrus clouds for each pixel in a MODIS image. We demonstrate the applicability of this algorithm using several independent MODIS images from the Terra satellite. The present method is complimentary to the MODIS operational cloud retrieval algorithm for the case of cirrus clouds. [ABSTRACT FROM AUTHOR]

This paper focuses on revealing flame image characteristics in a pilot-scale air combustion and oxygen-enriched combustion furnace. Changes in flame image parameters were examined according to flame behavior patterns, and 3-D temperature field distribution had been investigated under different air to oxy-fuel combustion conditions. These differences were controlled by regulating operation parameters (the amount of coal, circulating rate of flue gas, and oxygen concentration in primary air and secondary air). The analysis results show that combustion features such as flame length and igniting position can be increased as the increment of coal feeder frequency and flue gas circulation ratio at a certain oxygen concentration scope, but the flame brightness should be weakened. The variation trend of furnace temperature has revealed in quantity that the average temperature in oxy-fuel combustion is less 120 °C than that in air condition. In addition, flame brightness is enhanced as oxygen concentration increases, possibly decreasing the igniting distance, flame length, and combustion intensity in the higher CO2 concentration atmospheres; switch operation from air to oxy-fuel combustion should be stable with the circulation ratio of flue gas at a scope of 0.6–0.8 and about 28% oxygen concentration under oxy-fuel combustion. The flame behavior analysis method proposed here may represent an effective online monitoring and diagnostics tool for application in oxy-fuel combustion systems. [ABSTRACT FROM PUBLISHER]

Phase shifters based on double dielectric slab-loaded air-filled substrate-integrated waveguide (SIW) are proposed for high-performance applications at millimeter-wave frequencies. The three-layered air-filled SIW, made of a low-cost multilayer printed circuit board process, allows for substantial loss reduction and power handling capability enhancement compared with the conventional dielectric-filled counterpart. It is of particular interest for millimeter-wave applications that generally require low-loss transmission and high-density power handling. Its top and bottom layers may make use of a low-cost standard substrate, such as FR-4, on which baseband analog or digital circuits can be implemented so to obtain very compact, low cost, and self-packaged millimeter-wave integrated systems compared with the systems based on rectangular waveguide while achieving higher performance than the systems based on the conventional SIW. In this paper, it is demonstrated that transmission loss can be further improved at millimeter-wave frequencies with an additional polishing of the top and bottom conductor surfaces. Over Ka-band, an improvement of average 1.56 dB/m is experimentally demonstrated. Using the air-filled SIW fabrication process, dielectric slabs can be implemented along conductive via rows without any additional process. Based on the propagation properties of the obtained double dielectric slab-loaded air-filled SIW, phase shifters are proposed. To obtain a broadband response, an equal-length compensated phase shifter made of two air-filled SIW structures, offering a reverse varying propagation constant difference against frequency, is proposed and demonstrated at Ka-band. Finally, a single dielectric slab phase shifter is investigated for comparison and its bandwidth limitation is highlighted. [ABSTRACT FROM AUTHOR]

Based on the construction of the Chinese Meridian Project, two mesosphere, stratosphere, and troposphere (MST) radars were designed and located in Beijing and Chongyang, Hubei province, China, to investigate the atmospheric dynamics in the troposphere, stratosphere, and mesosphere. The official names of the two radio systems are Beijing MST radar and Wuhan MST radar. They are the monostatic radars with an active phased antenna array consisting of 576 Yagi antennas and operated by a 53.8-MHz frequency. The three-element Yagi antennas are arranged in a square grid of 96-m side length to form the aperture of 9216 m2. This antenna array arrangement forms the five symmetric radar beams of vertex, east, west, south, and north. The beamwidth is 3.2°, the maximum directive gain is 34.8 dB, and the total transmitting peak power is ∼172 kW. The zenith angle of the oblique beams is adjustable between 0 and 20° with a 1° step. The average power aperture product of the radars is 3.2\times 10^8\ \textWm^2. There are three operating modes of the MST radars, including the low, middle, and high modes, applied to observe the troposphere, stratosphere, and mesosphere, respectively. Thus, these two coherent pulse Doppler MST radars have the ability to study the features of the midlatitude atmospheric turbulence and wind field vector from the troposphere to the lower thermosphere with high spatiotemporal resolution. In this paper, the antenna array, system hardware, and signal processing methods, as well as the typical observation results of the troposphere, stratosphere, and mesosphere, are introduced. [ABSTRACT FROM PUBLISHER]

Global Positioning System (GPS) radio-occultation (RO) is an atmospheric sounding technique utilizing the received GPS signal through the stratified atmosphere to measure refractivity, which provides information on temperature and humidity. The GPS-RO technique is now operational on several Low Earth Orbiting (LEO) satellites, which cannot provide high temporal and spatial resolution soundings necessary to observe localized transient events, such as tropical storms. An airborne RO (ARO) system has thus been developed for localized GPS-RO campaigns. RO signals in the lower troposphere are adversely affected by rapid phase accelerations and severe signal power fading. These signal dynamics often cause the phase-locked loop in conventional GPS survey receivers to lose lock in the lower troposphere, and the open-loop (OL) tracking in postprocessing is used to overcome this problem. OL tracking also allows robust processing of rising GPS signals, approximately doubling the number of observed occultations. An approach for “backward” OL tracking was developed, in which the correlations are computed sequentially in reverse time so that the signal can be acquired and tracked at high elevations for rising occultations. Ultimately, the signal-to-noise ratio (SNR) limits the depth of tracking in the atmosphere. We have developed a model relating the SNR to the variance in the residual phase of the observed signal produced from OL tracking. In this paper, we demonstrate the applicability of the phase variance model to airborne data. We then apply this model to set a threshold on refractivity retrieval based upon the cumulative unwrapping error bias to determine the altitude limit for reliable signal tracking. We also show consistency between the ARO SNR and collocated COSMIC satellite observations and use these results to evaluate the antenna requirements for an improved ARO system. [ABSTRACT FROM AUTHOR]

This paper reports on the preparation and growth of Eu-doped strontium iodide (SrI2) single crystals by modified micro-pulling-down method. Influence of the Eu^2 + and Eu^3 + (introduced in form of EuI2 and EuCl3) on the luminescence and scintillation properties is analyzed. Sufficient optical quality of prepared single crystals was obtained allowing further characterization of their absorption, radio- and photoluminescence spectra. Photoluminescence and scintillation decay time of grown SrI2 crystals irradiated under \gamma -ray source were evaluated as well. [ABSTRACT FROM AUTHOR]

In this paper, the thermal decomposition characteristics of epoxy resin in SF 6 was studied using simultaneous thermal analysis (TG/DSC) and gas chromatograph-mass spectrometry (GC-MS). The concentrations of the decomposed gas components were tested, and the method of determining whether the failure of SF 6 gas insulation equipment is caused by thermal decomposition of the insulating epoxy resin material is proposed. TG-DSC shows that the epoxy resin starts to lose weight sharply at 350 °C, and heating from 350 to 450 °C shows that the main gas products are CO 2 , SO 2 , H 2 S and SOF 2. The concentrations of the four gases are significantly higher than where no epoxy resin is present and only pure SF 6 is injected. The concentrations of SO 2 F 2 , CF 4 and CS 2 were all kept below 0.5 ppm in the given temperature range. H 2 S is generated at about 325 °C while it can hardly be detected in the decomposition products of pure SF 6 without epoxy resin at the same temperature. Based on our observations, it is concluded that when the concentration of CO 2 reaches 5 times the sum of the concentrations of SO 2 and H 2 S, and when the concentration of H 2 S is higher than 0.5 ppm, failure of electrical equipment occurs by thermal decomposition of epoxy resin will occur. [ABSTRACT FROM AUTHOR]

The Gaussian beam for atmospheric refraction (GBAR) method is used to model the effects of the refractive atmosphere between a global navigation satellite system (GNSS) satellite and a low earth orbit (LEO) satellite in a radio occultation (RO) configuration. The wave transmitted by the GNSS satellite is expanded into Gaussian beams using a multibeam expansion procedure (MEP). The wave is modeled in the troposphere by Gaussian beams, and additional MEPs are processed if needed. The refractive atmosphere is modeled by a grid of rectangular cells within each of which is defined a constant and vertical refractivity gradient. The propagation factor at the LEO satellite is used to retrieve the refractivity profile at the perigees. The inverse method is recalled, and the global spherical symmetry assumption is emphasized. The inversion of the simulated propagation factor amplitude data is tested in two simulations. The first one considers a spherically symmetrical refractive atmosphere characterized by a standard exponential refractivity distribution. The second one uses data from weather research and forecast (WRF) simulations in the Caribbean region. The error brought by the spherical symmetry assumption is investigated. The GBAR method provides a new tool for the remote sensing of planetary atmospheres. [ABSTRACT FROM AUTHOR]

Accurate correction of atmospheric effects on data captured by an infrared (IR) camera is crucial for several applications such as vegetation monitoring, temperature monitoring, satellite images, hyperspectral imaging, numerical model simulations, surface properties characterization, and IR measurement interpretation. Atmospheric effects depend on the temporal changes, i.e., year, season, day, hour, etc., and on the geometry between the camera and the measured scene, i.e., line of sight. The orientation and the optical depth of the camera significantly affect the variation of the geometry across the pixels. In this paper, we propose a method to estimate the range and zenith angle of each pixel using only the Global Positioning System (GPS) coordinates of the camera and a point of interest in the scene. The estimated geometry and measured meteorological data are used to obtain the spectral atmospheric transmittance and path radiance. Furthermore, we propose an atmospheric effects removal, i.e., atmospheric correction, method that considers the spectral characteristics of the detector, lens, and filter. The proposed atmospheric correction process is analyzed in detail with the simultaneous measurements of two IR cameras. In this process, an enhanced temperature calibration method is developed and it is shown that the temperature accuracy for the dynamic range of the IR camera is very close to the noise equivalent temperature difference (NETD) value of the camera. [ABSTRACT FROM PUBLISHER]

This paper describes a methodology that uses Hyperion imagery as reference data to calibrate the Chinese Hyperspectral Imager (HSI) onboard the HJ-1A satellite. Two test sites near Dunhuang in Gansu and in Inner Mongolia were used for the cross-calibration. To account for the uncertainties in the top of atmosphere (TOA) reflectance due to the bidirectional reflectance distribution function (BRDF) and relative spectral response (RSR) differences between the two sensors, a model is adopted to transfer the Hyperion TOA reflectance to the effective HSI TOA reflectance. The influence of BRDF is analyzed, and two BRDF correction approaches are applied to the two test sites, respectively. For the Dunhuang test site, the ground synchronously measured reflectance in different solar zenith angles is used for BRDF correction. For the Inner Mongolia test site, a kernel-driven model is applied. The influence of RSR mismatch is computed using a spectral profile adjustment factor (SPAF), which takes into account the spectral profile of the target and the RSR of each sensor. The SPAF is calculated according to the TOA reflectance simulated using moderate resolution atmospheric transmission. One-point calibration and multipoint calibration coefficients are computed, respectively. Ground reflectance data measured in June 2010 at the Inner Mongolia test site were used to validate the cross-calibration coefficients based on the Hyperion image. The results support the proposal that the cross-calibration method between two hyperspectral sensors is effective, and the use of multipoint calibration coefficient with nonzero offset has great potential for hyperspectral sensor calibration. [ABSTRACT FROM PUBLISHER]

Geosynchronous synthetic aperture radar (GEO SAR) has been studied for several decades but has not yet been implemented. This paper provides an overview of mission design, describing significant constraints (atmosphere, orbit, temporal stability of the surface and atmosphere, measurement physics, and radar performance) and then uses these to propose an approach to initial system design. The methodology encompasses all GEO SAR mission concepts proposed to date. Important classifications of missions are: 1) those that require atmospheric phase compensation to achieve their design spatial resolution; and 2) those that achieve full spatial resolution without phase compensation. Means of estimating the atmospheric phase screen are noted, including a novel measurement of the mean rate of change of the atmospheric phase delay, which GEO SAR enables. Candidate mission concepts are described. It seems likely that GEO SAR will be feasible in a wide range of situations, although extreme weather and unstable surfaces (e.g., water, tall vegetation) prevent 100% coverage. GEO SAR offers an exciting imaging capability that powerfully complements existing systems. [ABSTRACT FROM PUBLISHER]

Sparse grid collocation methods are used for uncertainty quantification in electromagnetic propagation problems. The first application here involves waves propagating in lossy media with uncertain permittivities and permeabilities, for which several cases with increasing random-space dimensionality are exemplified. The objective in the second application is to compute expected signal strength above flat Earth surface at ranges far from transmitter location, where randomness is present due to uncertain refractivity of the atmosphere. Two different sparse grid algorithms are demonstrated throughout the paper, and the deterministic evaluators are accessed as a black box by the sparse grid algorithms. The difficult task of a priori method adaption is overcome by a first order check that enforces the black box solver only a few times. Through the results considered, strengths of the two algorithms are differentiated depending on the characteristics of the randomness. The advantage of a new routine used in this work is emphasized by showing its numerical contribution to the field estimation problem in a specific example. By means of the sparse grid methods used, we quantitatively provide the relative importance of each RV in contributing to the changes in the field distribution received at the observation range. [ABSTRACT FROM PUBLISHER]

Pressureless sintering of nanosilver paste has been widely demonstrated for bonding power semiconductor devices on silver- or gold-coated substrates. In this paper, we extended the application of nanosilver bonding to bare copper surface by controlling sintering atmosphere in an effort to prevent surface oxidation of copper during sintering. Three different atmospheres were evaluated: 1) pure nitrogen (N2); 2) nitrogen with 1 vol% oxygen (1% O2/N2); and 3) a forming gas consisting of 4 vol% hydrogen and 96 vol% nitrogen (4% H2/N2). The bonding strengths of sintered joints were evaluated by die-shear test. The joints sintered in 1% O2/N2 had the lowest average bonding strength of approximately 15 MPa due to the formation of copper oxide clearly visible on the failure surface of the substrate. The joints sintered in 4% H2/N2 had the highest average bonding strength of over 40 MPa. Microstructure characterization of the sintered joints showed that the bond-line density was strongly affected by the sintering atmosphere. The joints sintered in the forming gas had a denser microstructure than those sintered in pure nitrogen. It is believed that the higher sintered density is a result of catalytic hydrogenation and hydrogenolysis of organic binder in the paste, which occurred at the sintering temperature with nanoparticles of silver as catalyst. This increase in microstructure density and prevention of copper surface oxidation led to the high bonding strength of the sintered joints formed on copper in the forming gas. [ABSTRACT FROM PUBLISHER]

This paper proposed a new approach to attach power devices on nonmetallized direct bonding copper (DBC) substrates by pressureless sintering of nanosilver paste in poor-oxygen sintering atmosphere and formic acid reduction atmosphere. The average shear strength of die-attach joints could reach 25 MPa, and the copper oxidation issue of the nonmetallized DBC substrates was avoided. Based on the pressureless sintering approach of nanosilver paste, insulated-gate bipolar transistor (IGBT) modules were prototyped to verify the feasibility of this approach for mass production of power modules. The electrical and thermal characteristics of the IGBT modules bonded with sintered nanosilver were then compared with those of the commercialized ones using Pb92.5Sn5Ag2.5 solder alloy. This approach could extend the applications to bonding power devices on nonmetallized DBC substrates by nanosilver paste, and guide fabricating power modules in a mass productive, low facility costs, and high-yield way. [ABSTRACT FROM AUTHOR]

Single image dehazing, which aims to recover the clear image solely from an input hazy or foggy image, is a challenging ill-posed problem. Analyzing existing approaches, the common key step is to estimate the haze density of each pixel. To this end, various approaches often heuristically designed haze-relevant features. Several recent works also automatically learn the features via directly exploiting convolutional neural networks (CNN). However, it may be insufficient to fully capture the intrinsic attributes of hazy images. To obtain effective features for single image dehazing, this paper presents a novel ranking convolutional neural network (Ranking-CNN). In Ranking-CNN, a novel ranking layer is proposed to extend the structure of CNN so that the statistical and structural attributes of hazy images can be simultaneously captured. By training Ranking-CNN in a well-designed manner, powerful haze-relevant features can be automatically learned from massive hazy image patches. Based on these features, haze can be effectively removed by using a haze density prediction model trained through the random forest regression. Experimental results show that our approach outperforms several previous dehazing approaches on synthetic and real-world benchmark images. Comprehensive analyses are also conducted to interpret the proposed Ranking-CNN from both the theoretical and experimental aspects. [ABSTRACT FROM PUBLISHER]

In this paper, the possibility to accurately reconstruct the energy and direction of high-energy cosmic rays using a network of 192 radio detectors, assembled on an area of about 20 km2, is investigated. Measurements are influenced by the properties of the detecting equipment; therefore, its behavior and limiting effects are discussed. The responses of the detection chain to radio pulses generated by cosmic particles with different characteristics are analyzed, and it is concluded that individual stations can serve as first estimators for the types of cosmic particles. The proposed radio network can resolve events (with energies higher than \10^18\,eV) coming from N–NW direction, with zenith angles higher than 44°. Simulations have also shown that lighter particles that interact closer to the Earth are more likely to be detected. [ABSTRACT FROM PUBLISHER]

The ScaRaB payload onboard the low-inclination Megha-Tropiques (MT) satellite has been making observations of radiative fluxes at the top of the atmosphere (TOA) for different local times (LTs) of the day over the tropics since October 2011. This provides a unique opportunity to investigate the diurnal variation of the regional instantaneous aerosol direct radiative effect efficiency (IADREE) at TOA, which is otherwise not possible using the available long-term satellite observations carried out using similar sensors onboard polar sun-synchronous satellites. In this paper, the diurnal variations of the IADREE over the Arabian Sea and the Atlantic Ocean during June–September, when both these regions are engulfed by large-scale mineral dust plumes transported from the adjoining deserts, are investigated using collocated multiyear (2012–2014) observations of the MT-ScaRaB measured shortwave fluxes and MODIS-derived aerosol optical depth. The estimates of the IADREE made using the MT-ScaRaB data at 13:30 LT are found to be in agreement with those derived from the Cloud and the Earth’s Radiant Energy System data at this LT, at which the latter observations are carried out. The IADREE derived from the MT-ScaRaB shows diurnal peak value of −53 ± 10 Wm $^{{{-2}}}\tau _{{{550}}}^{{{-1}}}$ and −40 ± 3 Wm $^{{{-2}}}\tau _{{{550}}}^{{{-1}}}$ at solar zenith angle of ~40° over the Arabian Sea and the Atlantic Ocean, respectively. Diurnal mean aerosol direct radiative effect efficiency at TOA during June–September is −22 ± 4.5 Wm $^{{{-2}}}\tau _{{{550}}}^{{{-1}}}$ over the Arabian Sea and −18 ± 3.6 Wm $^{{{-2}}}\tau _{{{550}}}^{{{-1}}}$ over the Atlantic Ocean. [ABSTRACT FROM PUBLISHER]

The Kerr self-focusing and group-velocity dispersion (GVD) effects play important roles when a high-power pulsed laser beam propagates from the ground through the nonlinear and dispersive atmosphere to space orbits. For an annular pulsed laser beam, the Kerr self-focusing and GVD effects on the beam quality on the target is studied in this paper. Due to self-focusing, the maximum intensity Imax on the target arrives when the beam power P = Popt (Popt is called the optimal beam power), and the intensity on the target will decrease as the beam power P increases further when P > Popt. The Popt of nanosecond and picosecond pulsed beams is lower than that of femtosecond pulsed beams, while the maximum intensity Imax on the target of nanosecond and picosecond pulsed beams is higher than that of femtosecond pulsed beams. The Popt and Imax of annular pulsed beams are higher than those of Gaussian pulsed beams. In addition, the B integral and the Strehl ratio are also adopted to describe the beam quality on the target. On the other hand, because of the interplay of Kerr self-focusing and GVD effects, the temporal pulse splitting and self-healing may take place on propagation, and the temporal pulse splitting may take place more than once. The results obtained in this paper are useful for laser ablation propulsion's applications in space.

The frequency range that extends from 70 to 115 GHz presents low gaseous attenuation and offers the possibility of implementing radio links with capabilities of transporting more than 1 Gb/s over distances up to a few kilometers. A better knowledge of the propagation characteristics of the atmosphere at these frequencies can benefit future technological advances, providing better performance in terms of the use of radio resources. Unfortunately, the number of propagation results communicated for this band is very small. In this paper, propagation in this frequency range is analyzed on the basis of two-year experimental measurements carried out in Madrid, Spain, on a commercial link working at 75 and 85 GHz. Rain attenuation is the most relevant propagation effect in the W-band. Attenuation measurements are processed to remove wet antenna effects, leaving only the path attenuation time series. Statistics obtained from these time series are compared with a number of model predictions that use rain information of various types as input data, assessing in this way their precision and usefulness. [ABSTRACT FROM AUTHOR]