Managing the Provenance of Crowdsourced Disruption Reports

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The time and frequency comparisons via Loran-C and National TV Network in Yugoslavia

Time comparisons were made between cesium clocks in Yugoslavia and other cesium clocks in the country by the Laboratory of Federal Bureau of Measures and Precious Metals. Regional standard frequency and time signals dissemination is over National TV network by so called active TV system. International comparisons are performed via Loran-C system and by clock transportation. The method of calculation and approximation of the time signal propagation delays is given. Settled comparison results of the cesium clocks via TV network, Loran-C, and by clock transportation are also discussed in this paper

Fast Frequency Control Scheme through Adaptive Virtual Inertia Emulation

This paper presents a novel virtual inertia controller for converters in power systems with high share of renewable resources. By combining the analytical study of system dynamics and a Linear-Quadratic Regulator (LQR)-based optimization technique, the optimal state feedback gain is determined, adapting the emulated inertia constant according to the frequency disturbance in the system. The optimality is achieved through trade-off between the critical frequency limits and the required control effort, i.e. utilization of the internal energy storage. The proposed controller is integrated into a state-of-the-art converter control scheme and verified through EMT simulations. The results show a significant improvement in the frequency response compared to an open-loop system, while also preserving drastically more DC-side energy than a non-adaptive controller

Applications of Trajectory Data From the Perspective of a Road Transportation Agency: Literature Review and Maryland Case Study

Transportation agencies have an opportunity to leverage increasingly-available trajectory datasets to improve their analyses and decision-making processes. However, this data is typically purchased from vendors, which means agencies must understand its potential benefits beforehand in order to properly assess its value relative to the cost of acquisition. While the literature concerned with trajectory data is rich, it is naturally fragmented and focused on technical contributions in niche areas, which makes it difficult for government agencies to assess its value across different transportation domains. To overcome this issue, the current paper explores trajectory data from the perspective of a road transportation agency interested in acquiring trajectories to enhance its analyses. The paper provides a literature review illustrating applications of trajectory data in six areas of road transportation systems analysis: demand estimation, modeling human behavior, designing public transit, traffic performance measurement and prediction, environment and safety. In addition, it visually explores 20 million GPS traces in Maryland, illustrating existing and suggesting new applications of trajectory data

Size distribution of alkyl amines in continental particulate matter and their online detection in the gas and particle phase

An ion chromatographic method is described for the quantification of the simple alkyl amines: methylamine (MA), dimethylamine (DMA), trimethylamine (TMA), ethylamine (EA), diethylamine (DEA) and triethylamine (TEA), in the ambient atmosphere. Limits of detection (3σ) are in the tens of pmol range for all of these amines, and good resolution is achieved for all compounds except for TMA and DEA. The technique was applied to the analysis of time-integrated samples collected using a micro-orifice uniform deposition impactor (MOUDI) with ten stages for size resolution of particles with aerodynamic diameters between 56 nm and 18 μm. In eight samples from urban and rural continental airmasses, the mass loading of amines consistently maximized on the stage corresponding to particles with aerodynamic diameters between 320 and 560 nm. The molar ratio of amines to ammonium (R<sub>3</sub>NH<sup>+</sup>/NH<sub>4</sub><sup>+</sup>) in fine aerosol ranged between 0.005 and 0.2, and maximized for the smallest particle sizes. The size-dependence of the R<sub>3</sub>NH<sup>+</sup>/NH<sub>4</sub><sup>+</sup> ratio indicates differences in the relative importance of the processes leading to the incorporation of amines and ammonia into secondary particles. The technique was also used to make simultaneous hourly online measurements of amines in the gas phase and in fine particulate matter using an Ambient Ion Monitor Ion Chromatograph (AIM-IC). During a ten day campaign in downtown Toronto, DMA, TMA + DEA, and TEA were observed to range from below detection limit to 2.7 ppt in the gas phase. In the particle phase, MAH<sup>+</sup> and TMAH<sup>+</sup> + DEAH<sup>+</sup> were observed to range from below detection limit up to 15 ng m<sup>−3</sup>. The presence of detectable levels of amines in the particle phase corresponded to periods with higher relative humidity and higher mass loadings of nitrate. While the hourly measurements made using the AIM-IC provide data that can be used to evaluate the application of gas-particle partitioning models to amines, the strong size-dependence of the R<sub>3</sub>NH<sup>+</sup>/NH<sub>4</sub><sup>+</sup> ratio indicates that using bulk measurements may not be appropriate

Determining the Cosmic Equation of State Using Future Gravitational Wave Detectors

The expected chirp mass distribution of observed events for future gravitational wave detectors is extensively investigated in the presence of an exotic fluid component with an arbitrary equation of state, $-1 \leq \omega_x \equiv p_x/\rho_x < 0$, i.e., the so-called dark energy component. The results for a flat model dominated by a dark energy are compared to those for the standard flat model dominated by cold dark matter. It is found that for a flat universe the chirp mass distribution shows a sensitive dependence on $\omega_x$, which may provide an independent and robust constraint on the cosmic equation of state.Comment: 5 pages, four figures, aa.sty LaTex fil

The effect of meteorological and chemical factors on the agreement between observations and predictions of fine aerosol composition in southwestern Ontario during BAQS-Met

The Border Air Quality and Meteorology Study (BAQS-Met) was an intensive, collaborative field campaign during the summer of 2007 that investigated the effects of transboundary pollution, local pollution, and local meteorology on air quality in southwestern Ontario. This analysis focuses on the measurements of the inorganic constituents of particulate matter with diameter of less than 1 μm (PM&lt;sub&gt;1&lt;/sub&gt;), with a specific emphasis on nitrate. We evaluate the ability of AURAMS, Environment Canada's chemical transport model, to represent regional air pollution in SW Ontario by comparing modelled aerosol inorganic chemical composition with measurements from Aerosol Mass Spectrometers (AMS) onboard the National Research Council (NRC) of Canada Twin Otter aircraft and at a ground site in Harrow, ON. The agreement between modelled and measured &lt;i&gt;p&lt;/i&gt;NO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;&amp;minus;&lt;/sup&gt; at the ground site (observed mean (M&lt;sub&gt;obs&lt;/sub&gt;) = 0.50 μg m&lt;sup&gt;−3&lt;/sup&gt;; modelled mean (M&lt;sub&gt;mod&lt;/sub&gt;) = 0.58 μg m&lt;sup&gt;−3&lt;/sup&gt;; root mean square error (RSME) = 1.27 μg m&lt;sup&gt;−3&lt;/sup&gt;) was better than aloft (M&lt;sub&gt;obs&lt;/sub&gt; = 0.32 μg m&lt;sup&gt;−3&lt;/sup&gt;; M&lt;sub&gt;mod&lt;/sub&gt; = 0.09 μg m&lt;sup&gt;−3&lt;/sup&gt;; RSME = 0.48 μg m&lt;sup&gt;−3&lt;/sup&gt;). Possible reasons for discrepancies include errors in (i) emission inventories, (ii) atmospheric chemistry, (iii) predicted meteorological parameters, or (iv) gas/particle thermodynamics in the model framework. Using the inorganic thermodynamics model, ISORROPIA, in an offline mode, we find that the assumption of thermodynamic equilibrium is consistent with observations of gas and particle composition at Harrow. We develop a framework to assess the sensitivity of PM&lt;sub&gt;1&lt;/sub&gt; nitrate to meteorological and chemical parameters and find that errors in both the predictions of relative humidity and free ammonia (FA ≡ NH&lt;sub&gt;3&lt;/sub&gt;&lt;sub&gt;(g)&lt;/sub&gt; + &lt;i&gt;p&lt;/i&gt;NH&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;+&lt;/sup&gt; − 2 · &lt;i&gt;p&lt;/i&gt;SO&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;2-&lt;/sup&gt;) are responsible for the poor agreement between modelled and measured values

Brown carbon aerosol in the North American continental troposphere: sources, abundance, and radiative forcing

Chemical components of organic aerosol (OA) selectively absorb light at short wavelengths. In this study, the prevalence, sources, and optical importance of this so called brown carbon (BrC) aerosol component are investigated throughout the North American continental tropospheric column during a summer of extensive biomass burning. Spectrophotometric absorption measurements on extracts of bulk aerosol samples collected from an aircraft over the central USA were analyzed to directly quantify BrC abundance. BrC was found to be prevalent throughout the 1 to 12 km altitude measurement range, with dramatic enhancements in biomass-burning plumes. BrC to black carbon (BC) ratios, under background tropospheric conditions, increased with altitude, consistent with a corresponding increase in the absorption Ångström exponent (AAE) determined from a three-wavelength particle soot absorption photometer (PSAP). The sum of inferred BC absorption and measured BrC absorption at 365 nm was within 3 % of the measured PSAP absorption for background conditions and 22 % for biomass burning. A radiative transfer model showed that BrC absorption reduced top-of atmosphere (TOA) aerosol forcing by ∼ 20 % in the background troposphere. Extensive radiative model simulations applying this study background tropospheric conditions provided a look-up chart for determining radiative forcing efficiencies of BrC as a function of a surface-measured BrC : BC ratio and single scattering albedo (SSA). The chart is a first attempt to provide a tool for better assessment of brown carbon’s forcing effect when one is limited to only surface data. These results indicate that BrC is an important contributor to direct aerosol radiative forcing

Aircraft study of the impact of lake-breeze circulations on trace gases and particles during BAQS-Met 2007

High time-resolved aircraft data, concurrent surface measurements and air quality model simulations were explored to diagnose the processes influencing aerosol chemistry under the influence of lake-breeze circulations in a polluted region of southwestern Ontario, Canada. The analysis was based upon horizontal aircraft transects conducted at multiple altitudes across an entire lake-breeze circulation. Air mass boundaries due to lake-breeze fronts were identified in the aircraft meteorological and chemical data, which were consistent with the frontal locations determined from surface analyses. Observations and modelling support the interpretation of a lake-breeze circulation where pollutants were lofted at a lake-breeze front, transported in the synoptic flow, caught in a downdraft over the lake, and then confined by onshore flow. The detailed analysis led to the development of conceptual models that summarize the complex 3-D circulation patterns and their interaction with the synoptic flow. The identified air mass boundaries, the interpretation of the lake-breeze circulation, and the air parcel circulation time in the lake-breeze circulation (3.0 to 5.0 h) enabled formation rates of organic aerosol (OA/&amp;Delta;CO) and SO&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;2&amp;minus;&lt;/sup&gt; to be determined. The formation rate for OA (relative to excess CO in ppmv) was found to be 11.6–19.4 &amp;mu;g m&lt;sup&gt;−3&lt;/sup&gt; ppmv&lt;sup&gt;−1&lt;/sup&gt; h&lt;sup&gt;−1&lt;/sup&gt; and the SO&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;2&amp;minus;&lt;/sup&gt; formation rate was 5.0–8.8% h&lt;sup&gt;−1&lt;/sup&gt;. The formation rates are enhanced relative to regional background rates implying that lake-breeze circulations are an important dynamic in the formation of SO&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;2&amp;minus;&lt;/sup&gt; and secondary organic aerosol. The presence of cumulus clouds associated with the lake-breeze fronts suggests that these enhancements could be due to cloud processes. Additionally, the effective confinement of pollutants along the shoreline may have limited pollutant dilution leading to elevated oxidant concentrations