A New Time Series Similarity Measure and Its Smart Grid Applications

Many smart grid applications involve data mining, clustering, classification, identification, and anomaly detection, among others. These applications primarily depend on the measurement of similarity, which is the distance between different time series or subsequences of a time series. The commonly used time series distance measures, namely Euclidean Distance (ED) and Dynamic Time Warping (DTW), do not quantify the flexible nature of electricity usage data in terms of temporal dynamics. As a result, there is a need for a new distance measure that can quantify both the amplitude and temporal changes of electricity time series for smart grid applications, e.g., demand response and load profiling. This paper introduces a novel distance measure to compare electricity usage patterns. The method consists of two phases that quantify the effort required to reshape one time series into another, considering both amplitude and temporal changes. The proposed method is evaluated against ED and DTW using real-world data in three smart grid applications. Overall, the proposed measure outperforms ED and DTW in accurately identifying the best load scheduling strategy, anomalous days with irregular electricity usage, and determining electricity users' behind-the-meter (BTM) equipment.Comment: 7 pages, 6 figures conferenc

N2_{2}O isotopocule measurements using laser spectroscopy: analyzer characterization and intercomparison

For the past two decades, the measurement of nitrous oxide (N2O) isotopocules – isotopically substituted molecules $^{14}$N$^{15}$N$^{16}$O, $^{15}$N$^{14}$N$^{16}$O and $^{14}$N$^{14}$N$^{18}$O of the main isotopic species $^{14}$N$^{14}$N$^{16}$O – has been a promising technique for understanding N2O production and consumption pathways. The coupling of non-cryogenic and tuneable light sources with different detection schemes, such as direct absorption quantum cascade laser absorption spectroscopy (QCLAS), cavity ring-down spectroscopy (CRDS) and off-axis integrated cavity output spectroscopy (OA-ICOS), has enabled the production of commercially available and field-deployable N$_{2}$O isotopic analyzers. In contrast to traditional isotope-ratio mass spectrometry (IRMS), these instruments are inherently selective for position-specific $^{15}$N substitution and provide real-time data, with minimal or no sample pretreatment, which is highly attractive for process studies. Here, we compared the performance of N$_{2}$O isotope laser spectrometers with the three most common detection schemes: OA-ICOS (N$_{2}$OIA-30e-EP, ABB – Los Gatos Research Inc.), CRDS (G5131-i, Picarro Inc.) and QCLAS (dual QCLAS and preconcentration, trace gas extractor (TREX)-mini QCLAS, Aerodyne Research Inc.). For each instrument, the precision, drift and repeatability of N$_{2}$O mole fraction [N$_{2}$O] and isotope data were tested. The analyzers were then characterized for their dependence on [N$_{2}$O], gas matrix composition (O$_{2}$, Ar) and spectral interferences caused by H$_{2}$O, CO$_{2}$, CH$_{4}$ and CO to develop analyzer-specific correction functions. Subsequently, a simulated two-end-member mixing experiment was used to compare the accuracy and repeatability of corrected and calibrated isotope measurements that could be acquired using the different laser spectrometers. Our results show that N$_{2}$O isotope laser spectrometer performance is governed by an interplay between instrumental precision, drift, matrix effects and spectral interferences. To retrieve compatible and accurate results, it is necessary to include appropriate reference materials following the identical treatment (IT) principle during every measurement. Remaining differences between sample and reference gas compositions have to be corrected by applying analyzer-specific correction algorithms. These matrix and trace gas correction equations vary considerably according to N$_{2}$O mole fraction, complicating the procedure further. Thus, researchers should strive to minimize differences in composition between sample and reference gases. In closing, we provide a calibration workflow to guide researchers in the operation of N$_{2}$O isotope laser spectrometers in order to acquire accurate N$_{2}$O isotope analyses. We anticipate that this workflow will assist in applications where matrix and trace gas compositions vary considerably (e.g., laboratory incubations, N$_{2}$O liberated from wastewater or groundwater), as well as extend to future analyzer models and instruments focusing on isotopic species of other molecules

N2O isotopocule measurements using laser spectroscopy:analyzer characterization and intercomparison

For the past two decades, the measurement of nitrous oxide (N2O) isotopocules – isotopically substituted molecules 14N15N16O, 15N14N16O and 14N14N18O of the main isotopic species 14N14N16O – has been a promising technique for understanding N2O production and consumption pathways. The coupling of non-cryogenic and tuneable light sources with different detection schemes, such as direct absorption quantum cascade laser absorption spectroscopy (QCLAS), cavity ring-down spectroscopy (CRDS) and off-axis integrated cavity output spectroscopy (OA-ICOS), has enabled the production of commercially available and field-deployable N2O isotopic analyzers. In contrast to traditional isotope-ratio mass spectrometry (IRMS), these instruments are inherently selective for position-specific 15N substitution and provide real-time data, with minimal or no sample pretreatment, which is highly attractive for process studies. Here, we compared the performance of N2O isotope laser spectrometers with the three most common detection schemes: OA-ICOS (N2OIA-30e-EP, ABB – Los Gatos Research Inc.), CRDS (G5131-i, Picarro Inc.) and QCLAS (dual QCLAS and preconcentration, trace gas extractor (TREX)-mini QCLAS, Aerodyne Research Inc.). For each instrument, the precision, drift and repeatability of N2O mole fraction [N2O] and isotope data were tested. The analyzers were then characterized for their dependence on [N2O], gas matrix composition (O2, Ar) and spectral interferences caused by H2O, CO2, CH4 and CO to develop analyzer-specific correction functions. Subsequently, a simulated two-end-member mixing experiment was used to compare the accuracy and repeatability of corrected and calibrated isotope measurements that could be acquired using the different laser spectrometers. Our results show that N2O isotope laser spectrometer performance is governed by an interplay between instrumental precision, drift, matrix effects and spectral interferences. To retrieve compatible and accurate results, it is necessary to include appropriate reference materials following the identical treatment (IT) principle during every measurement. Remaining differences between sample and reference gas compositions have to be corrected by applying analyzer-specific correction algorithms. These matrix and trace gas correction equations vary considerably according to N2O mole fraction, complicating the procedure further. Thus, researchers should strive to minimize differences in composition between sample and reference gases. In closing, we provide a calibration workflow to guide researchers in the operation of N2O isotope laser spectrometers in order to acquire accurate N2O isotope analyses. We anticipate that this workflow will assist in applications where matrix and trace gas compositions vary considerably (e.g., laboratory incubations, N2O liberated from wastewater or groundwater), as well as extend to future analyzer models and instruments focusing on isotopic species of other molecules.ISSN:1867-1381ISSN:1867-854

Semaglutide and NYHA functional class in obesity-related heart failure with preserved ejection fraction the STEP-HFpEF program

Background In the Semaglutide Treatment Effect in People with obesity and HFpEF (STEP-HFpEF) program, semaglutide improved heart failure (HF)-related symptoms, physical limitations, and exercise function, and reduced bodyweight in patients with obesity-related heart failure with preserved ejection fraction (HFpEF). Whether semaglutide improves functional status, as assessed by NYHA functional class, is unknown. Objectives The goal of this study was to examine the effects of semaglutide on change in NYHA functional class over time. We also investigated the effects of semaglutide on HF-related symptoms, physical limitations, and bodyweight and other trial endpoints across baseline NYHA functional class categories. Methods This was a prespecified analysis of pooled data from 2 international, double-blind, randomized trials (STEP-HFpEF and STEP-HFpEF type 2 diabetes [STEP-HFpEF DM], comprising the STEP-HFpEF program), which collectively randomized 1,145 participants with obesity-related HFpEF to once-weekly semaglutide 2.4 mg or placebo for 52 weeks. The outcome of interest for this analysis was the change in NYHA functional class (baseline to 52 weeks). We also investigated the effects of semaglutide on the dual primary, confirmatory secondary, and selected exploratory endpoints according to baseline NYHA functional class. Results More semaglutide-treated than placebo-treated patients had an improvement in NYHA functional class (32.6% vs 21.5%, respectively; OR: 2.20 [95% CI: 1.62-2.99; P < 0.001]) and fewer semaglutide-treated patients experienced deterioration in NYHA functional class (2.09% vs 5.24%, respectively; OR: 0.36 [95% CI: 0.19-0.70; P = 0.003]) at 52 weeks. Semaglutide (vs placebo) improved the Kansas City Cardiomyopathy Questionnaire-Clinical Summary Score (KCCQ-CCS) across NYHA functional class categories; this was especially pronounced in those in NYHA functional classes III/IV (10.5 points [95% CI: 6.6-14.4 points]) vs NYHA functional class II (6.0 points [95% CI: 3.4-8.6 points]) (P interaction = 0.06). By contrast, the degree of reduction in bodyweight was similar with semaglutide vs placebo regardless of baseline NYHA functional class category (NYHA functional class II, −8.4% [95% CI: −9.4% to −7.3%]; NYHA functional classes III/IV, −8.3% [95% CI: −9.9% to −6.8%]; P interaction = 0.96). Semaglutide consistently improved 6-minute walking distance (6MWD), the hierarchical composite endpoint (death, HF events, differences in KCCQ-CSS, and 6MWD changes), and reduced C-reactive protein and N-terminal prohormone of brain natriuretic peptide across NYHA functional class categories (all P interactions = NS). Conclusions In patients with obesity-related HFpEF, fewer semaglutide-treated than placebo-treated patients had a deterioration, and more had an improvement, in NYHA functional class at 52 weeks. Semaglutide consistently improved HF-related symptoms, physical limitations, and exercise function, and reduced bodyweight and biomarkers of inflammation and congestion in all NYHA functional class categories. Semaglutide-mediated improvements in health status were especially large in patients with NYHA functional classes III/IV

Hidden Markov Models for indirect classification of occupant behaviour

Even for similar residential buildings, a huge variability in the energy consumption can be observed. This variability is mainly due to the different behaviours of the occupants and this impacts the thermal (temperature setting, window opening, etc.) as well as the electrical (appliances, TV, computer, etc.) consumption. It is very seldom to find direct observations of occupant presence and behaviour in residential buildings. However, given the increasing use of smart metering, the opportunity and potential for indirect observation and classification of occupants’ behaviour is possible. This paper focuses on the use of Hidden Markov Models (HMMs) to create methods for indirect observations and characterisation of occupant behaviour. By applying homogeneous HMMs on the electricity consumption of fourteen apartments, three states describing the data were found suitable. The most likely sequence of states was determined (global decoding). From reconstruction of the states, dependencies like ambient air temperature were investigated. Combined with an occupant survey, this was used to classify/interpret the states as (1) absent or asleep, (2) home, medium consumption and (3) home, high consumption. From the global decoding, the average probability profiles with respect to time of day were investigated, and four distinct patterns of occupant behaviour were observed. Based on the initial results of the homogeneous HMMs and with the observed dependencies, time dependent HMMs (inhomogeneous HMMs) were developed, which improved forecasting. For both the homogeneous and inhomogeneous HMMs, indications of common parameters were observed, which suggests further development of the HMMs as population models

Can colonoscopy diagnose transmural ischaemic colitis after abdominal aortic surgery? An evidence-based approach

AbstractObjectives: to assess the diagnostic value of colonoscopy in ischaemic colitis following abdominal aortic surgery, based on a literature review, and to introduce the concept of evidence-based medicine. Method: a review of the literature according to evidence-based principles was made by all doctors of our department. Results: seven prospective non-randomised reports on routine colonoscopy after abdominal aortic surgery were found. None of the participants found all the reports, and the last was identified by the reviewer. Conclusions: Endoscopy may disclose ischaemic colitis, but cannot separate transmural from the clinically less important mucosal ischaemia. Endoscopy had no impact on mortality in any of the prospective series. The evidence-based conference was an inspiring teaching modality, and illustrated for the participants the difficulty in performing a targeted literature search

Comparison of N2O isotope spectrometers for high-precision measurements in ambient air and incubation experiments

Over the last two decades, research involving N2O site specific isotopic analysis has been stimulated by continuing analytical progress in isotope-ratio mass-spectrometry (IRMS) and more recently mid-infrared laser spectroscopy. This development has been triggered by the invention and availability of quantum cascade lasers (QCL), which offer high optical power in continuous wave operation at room temperature. QCL light sources have been combined with different detection schemes such as direct absorption (QCLAS), cavity ring down (CRDS) and off-axis integrated cavity output (OA-ICOS) to realize compact, field-deployable analyzers.The availability of temporal resolved N2O isotopic information in real-time will deepen our process-level understanding of the nitrogen cycle. It will also open up entirely new research areas that will attract an increasing number of application-oriented scientists. Provided that the novel laser spectrometers produce compatible and thus accurate results (i.e. traceable to the international isotope ratio scales, AIR-N2 for 15N/14N and VSMOW for 18O/16O), the implementation of these instruments will lead to a further dissemination of N2O isotopic research.We will present results of an inter-comparison study on the three most common commercial N2O isotope analyzers, including Aerodyne Research (dual QCLAS, with/without TREX), Picarro (G5131-i) and Los Gatos Research (Model 914-0027). Most importantly, gas matrix effects were investigated by determining the dependence of N2O isotope deltas on the analysis in an “ambient” N2/O2/Ar/CO2/CH4/CO versus a simplified N2/O2/Ar or N2/O2 matrix. In addition, spectral interferences of enhanced trace gas concentrations (CO2, CH4, CO, H2O) were characterized and strategies for removal tested. Short-term and long-term repeatability, drift and dependence of isotope deltas on N2O concentrations were also quantified and compared among instruments. Based on these results a calibration strategy was established and the accuracy of individual analyzers assessed combining the studied uncertainty contributions.Our study will guide the selection of instruments for specific applications (e.g. ambient air versus incubation studies), and foster the development of N2O isotope reference gases optimized for laser spectrometers currently ongoing within the EMPIR project “Metrology for Stable Isotope Reference Standards (SIRS)”

Photocatalytic chloride to chlorine conversion by ionic iron in aqueous aerosols: A combined experimental, quantum chemical and chemical equilibrium model study

Aerosol chamber experiments show that the ligand-to-metal charge transfer absorption in iron(III) chlorides can lead to the production of chlorine. Based on this mechanism, the photocatalytic oxidation of chloride in mineral dust-sea spray aerosols was recently shown to be the largest source of chlorine over the North Atlantic. However, there has not been a detailed analysis of the mechanism including the aqueous formation equilibria and the absorption spectra of the iron chlorides; neither has there been an analysis of which iron chloride is the main chromophore. Here we present the results of experiments of photolysis FeCl_3 · 6H_2O in specific wavelength bands, an analysis of the absorption spectra of the title compounds from n=1..4 made using density functional theory, and the results of an aqueous phase model that predicts the abundance of the iron chlorides with changes in pH and ion concentrations. Transition state analysis is used to determine the energy thresholds of the dissociations of the species. Based on a speciation model with conditions extending from dilute water droplet to acidic seawater droplet to brine to salty crust, and the absorption rates and dissociation thresholds, we find that FeCl_2^+ is the most important species for chlorine production for a wide range of conditions. The mechanism was found to be active in the range of 400 to 530 nm with a maximum around 440 nm. We conclude that iron chlorides will form in atmospheric aerosols from the combination of iron(III) cations with chloride and that they will be activated by sunlight, generating chlorine (Cl_2/Cl) from chloride (Cl-), in a process that is catalytic in both chlorine and iron

A comparison of commercially-available quantum cascade laser spectrometers to measure N2O isotopocules (δ15Nα, δ15Nβ & δ18O) at ambient concentrations

Over the last two decades, research involving N2O isotopic analysis has been stimulated by continuing analytical progress in isotope-ratio mass-spectrometry (IRMS) and more recently by the development of mid-infrared laser spectroscopy. The advancement of laser spectroscopic techniques was enabled by the invention and availability of quantum cascade lasers (QCL), which have been coupled with different detection schemes such as direct absorption quantum cascade laser absorption (QCLAS), cavity ring down (CRDS) and off-axis integrated cavity output spectroscopy (OA-ICOS) to realize compact field-deployable analyzers. To improve the accuracy and reliability of these instrumental techniques, analyzer-specific calibration procedures and correction algorithms are required to account for matrix effects, spectral interferences and drift during measurements. We performed an inter-comparison study of three commercially-available N2O isotope laser spectrometers (δ15Nα, δ15Nβ & δ18O); Aerodyne Research (dual QCLAS, with/without pre-concentration, Picarro (G5131-i) and Los Gatos Research (Model 914-0027). Gas matrix effects were investigated by determining the dependence of N2O isotope deltas on the analysis in an “ambient” N2/O2/Ar/CO2/CH4/CO versus a simplified N2/O2/Ar or N2/O2 matrix. In addition, spectral interferences of enhanced trace gas concentrations (CO2, CH4, CO, H2O) were characterized and strategies for removal tested. Short-term and long-term repeatability, drift and dependence of isotope deltas on N2O concentrations were also quantified and compared among instruments. Using these results, we evaluated the accuracy of individual analyzers and developed calibration strategies tailored to each machine. Our study will guide the selection of instruments for specific applications (e.g. ambient air versus chamber measurements), and foster the development of N2O isotope reference gases optimized for laser spectrometers currently ongoing within the EMPIR project “Metrology for Stable Isotope Reference Standards (SIRS)”