scholarly journals Travel Time Modelling Using Time Series of Nitrate Concentration in Groundwater Improves Hydrological Process Understanding : A Case Study of a Small Agricultural Catchment in Brittany, France.

2021 ◽  
Author(s):  
Baibaswata Bhaduri ◽  
Muddu Sekhar ◽  
Ophélie Fovet ◽  
Laurent Ruiz
Keyword(s):  
Time Series ◽  
Travel Time ◽  
Nitrate Concentration ◽  
Hydrological Process ◽  
Process Understanding ◽  
Concentration Time Series ◽  
Time Determination ◽  
Well Posed

Rivers can act as mirrors to in-catchment processes, but integrated concentration-discharge dynamics might not be sufficient for constructing a well-posed solute travel time determination problem. One remedy is to look inside the catchment and see if the extra information provided by long-term time series of groundwater solutes constrains the problem or provides us with some additional insight on retrieving the processes which the stream is aggregating. To test this notion, we used data for Kerrien, a well-studied agriculture dominated small headwater catchment of the French Critical Zone Observatory in Brittany. It contains long-term nitrate concentration time-series from a network of piezometers as well as a stream outlet. In this study, a parsimonious, conceptual dual-permeability mixing model already developed for streams was adapted for piezometers along with detailed uncertainty and sensitivity analysis. We found out the nitrate flushing times of mid to upslope piezometers were consistently higher than the stream outlet. We further observed an asynchronicity in seasonal concentration-discharge dynamics between the piezometers and the stream. We hypothesize the reason behind this counterintuitive finding to be extensive riparian denitrification, vertical stratification of groundwater and disconnect between the stream and the deeper flowpaths that carry legacy contamination, evidenced by the non-closure of water budget at the stream outlet. As a consequence, we argue that in headwater catchments the stream signature might not fully reflect internal processes which can be revealed only by using piezometer data. This adapted conceptual framework could be of great interest for semi-arid catchments where groundwater monitoring could be used in combination or as an alternate to ephemeral streams in travel time determination.

Time Series Forecasting in Retail Sales Using LSTM and Prophet

2021 ◽  
pp. 241-262
Author(s):  
Clony Junior ◽  
Pedro Gusmão ◽  
José Moreira ◽  
Ana Maria M. Tome
Keyword(s):  
Time Series ◽  
Data Science ◽  
Short Term Memory ◽  
Special Kind ◽  
Time Series Forecasting ◽  
Short Term ◽  
Term Memory ◽  
Use Of Time

Data science highlights fields of study and research such as time series, which, although widely explored in the past, gain new perspectives in the context of this discipline. This chapter presents two approaches to time series forecasting, long short-term memory (LSTM), a special kind of recurrent neural network (RNN), and Prophet, an open-source library developed by Facebook for time series forecasting. With a focus on developing forecasting processes by data mining or machine learning experts, LSTM uses gating mechanisms to deal with long-term dependencies, reducing the short-term memory effect inherent to the traditional RNN. On the other hand, Prophet encapsulates statistical and computational complexity to allow broad use of time series forecasting, prioritizing the expert's business knowledge through exploration and experimentation. Both approaches were applied to a retail time series. This case study comprises daily and half-hourly forecasts, and the performance of both methods was measured using the standard metrics.

Evaluation of phytoplankton quality and toxicity risk based on a long-term time series previous to the implementation of a bivalve farm (Basque coast as a case study)

2017 ◽  
Vol 10 ◽  
pp. 10-19 ◽  
Author(s):  
Oihane Muñiz ◽  
Marta Revilla ◽  
José Germán Rodríguez ◽  
Aitor Laza-Martínez ◽  
Sergio Seoane ◽  
...  
Keyword(s):  
Time Series ◽  
Toxicity Risk ◽  
Basque Coast

Detecting and Correcting Biases in Long-Term Ocean Observatory Time Series: Case Study on Current Directions Estimated From Acoustic Doppler Current Profiler Data

2016 ◽  
Vol 50 (3) ◽  
pp. 109-113
Author(s):  
Michael G. Morley ◽  
Marlene A. Jeffries ◽  
Steven F. Mihály ◽  
Reyna Jenkyns ◽  
Ben R. Biffard
Keyword(s):  
Time Series ◽  
Acoustic Doppler Current Profiler ◽  
Lessons Learned ◽  
Ocean Current ◽  
Data Types ◽  
Current Profiler ◽  
Future Data ◽  
Multiple Deployments

AbstractOcean Networks Canada (ONC) operates the NEPTUNE and VENUS cabled ocean observatories to collect continuous data on physical, chemical, biological, and geological ocean conditions over multiyear time periods. Researchers can download real-time and historical data from a large variety of instruments to study complex earth and ocean processes from their home laboratories. Ensuring that the users are receiving the most accurate data is a high priority at ONC, requiring QAQC (quality assurance and quality control) procedures to be developed for a variety of data types (Abeysirigunawardena et al., 2015). Acquiring long-term time series of oceanographic data from remote locations on the seafloor presents significant challenges from a QAQC perspective. In order to identify and study important scientific events and trends, data consolidated from multiple deployments and instruments need to be self-consistent and free of biases due to changes to instrument configurations, calibrations, metadata, biofouling, or a degradation in instrument performance. As a case study, this paper describes efforts at ONC to identify and correct systematic biases in ocean current directions measured by ADCPs (acoustic Doppler current profilers), as well as the lessons learned to improve future data quality.

Effects of periodization in long-term training on the dynamics of changes in punch endurance of a boxer – case study

2017 ◽  
Vol 2 (8) ◽  
pp. 111-115
Author(s):  
Pavol Hlavačka ◽  
Ľuboslav Šiška ◽  
Jaroslav Broďáni
Keyword(s):  
Time Series ◽  
Statistical Significance ◽  
Cumulative Effect ◽  
Time Shift ◽  
Endurance Test ◽  
Special Training ◽  
Transformation Stage ◽  
Level Of Significance

Introduction. The aim of this work was to monitor the changes a boxer undergoes in the punch endurance test in relation to special training indicators and subsequently, by means of correlation of the time series, to determine the time shift of the delayed cumulative effect in long-term preparation of boxers. Material and methods. The work has an intraindividual basis. By means of the training logs, we recorded the special training indicators and periodization in the training cycles in accordance with the sporting calendar. The athlete under observation carried out a special punch endurance test on the punch bag in regular 4-week intervals, whose duration was identical with the competitive match. The test was issued by the International Boxing Association (AIBA) in the AIBA Coaches Manual (AIBA Coaches Commission, 2011). When correlating the time series, we used the Spearman’s correlation coefficient. The statistical significance of the relationships has been judged at a 20 % level of significance. Results. The average count in the punch endurance test was RTC1 830,17 ± 75,67 punches and RTC2 867 ± 40,36 punches. Statistically significant correlations with training means of speed endurance (SpdE) 1-2 time shifts (2-4 weeks) and sparring (TT S) 1-3 time shifts (2-6 weeks) have been demonstrated. Conclusions. In terms of the dynamics of changes in special punch endurance, the development copied the systematic periodization of training load, the level improved from accumulation, through the intensification up to the transformation stage, where the best test results were achieved before the top events.

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