scholarly journals Medium term high frequency observation of discharges and suspended sediment in a Mediterranean mountainous catchment

2019 ◽  
Vol 568 ◽  
pp. 562-574 ◽  
Author(s):  
M. Esteves ◽  
C. Legout ◽  
O. Navratil ◽  
O. Evrard
Keyword(s):  
Suspended Sediment ◽  
High Frequency ◽  
Medium Term ◽  
Mountainous Catchment ◽  
Frequency Observation

Effect of high frequency cathodic pulses on steel embedded in mortar: short and medium term tests

2011 ◽  
Vol 46 (4) ◽  
pp. 493-498
Author(s):  
A Bautista ◽  
F Velasco ◽  
S Guzmán ◽  
F J Martínez ◽  
R Calabrés
Keyword(s):  
High Frequency ◽  
Medium Term

Inferring suspended sediment carbon content and particle size at high frequency from the optical response of a submerged spectrometer 

2021 ◽  
Author(s):  
Dhruv Sehgal ◽  
Núria Martínez-Carreras ◽  
Christophe Hissler ◽  
Victor Bense ◽  
AJF (Ton) Hoitink
Keyword(s):  
Particle Size ◽  
Absorption Spectrum ◽  
Carbon Content ◽  
Suspended Sediment ◽  
High Frequency ◽  
Suspended Sediments ◽  
Ex Situ ◽  
Frequency Measurements ◽  
Component Form

<p>Manual and unattended sampling in the field and laboratory analysis are common practices to measure suspended sediment (SS) carbon content and particle size. However, one of the major drawbacks of these ex-situ methods is that they make high frequency measurements challenging. This includes restricted data collection due to limited access to the sampling locations during turbulent conditions or high flows, when the largest amount of sediments is transported downstream, introducing uncertainty in quantification of SS properties (particle size and carbon content) and sediment loads. Knowledge on SS carbon content and particle size is also important to better understand the multi-component form of suspended sediments (i.e. flocs) that directly affect sediment transport and other sediment properties (e.g. settling velocity and density). Moreover, SS carbon content and particle size exert an impact on the optical sensor readings that are traditionally used to measure turbidity. In that respect, high frequency measurements of SS carbon content and particle size could eventually help us to move from ‘local’ calibrations towards ‘global’ dependencies based on in-situ SS characterization.</p><p>In this study, we propose to use a submerged UV-VIS spectrometer to infer SS carbon content and particle size. The sensor measures the entire light absorption spectrum of water between 200 nm and 750 nm at sampling intervals as short as 2-minutes. To this end, we first test our approach under controlled conditions with an experimental laboratory setup consisting of a cylindrical tank (40-L) with an open top. An UV-VIS spectrometer and a LISST-200X sensor (to measure particle size distribution) are installed horizontally. A stirrer facilitates the homogeneous mixing of SS and prevents the settling of heavy particles at the bottom. We use the sediments sampled from 6 sites in Luxembourg with contrasting composition and representing different land use types and geological settings. The sampled sediments were wet sieved into 3 size classes to clearly recognize the effect of particle size on absorption. In our investigation, we use specific wavelengths, chemometric techniques and carbon content specific absorbance indices to infer SS composition and particle size from the absorption spectrum. Results are then validated using in-situ field data from two instrumented field sites in Luxembourg. Amid the challenge of associating laboratory and field results, the preliminary results indicate that the absorption spectrum measured with a submerged UV-VIS spectrometer can be used to estimate SS particle size and carbon content.</p>

scholarly journals COVID-19 and Inequality in Asia

2020 ◽  
Vol 20 (217) ◽  
Author(s):  
Emilia Jurzyk ◽  
Medha Madhu Nair ◽  
Nathalie Pouokam ◽  
Tahsin Saadi Sedik ◽  
Anthony Tan ◽  
...  
Keyword(s):  
High Frequency ◽  
Medium Term ◽  
Safety Nets ◽  
Younger Workers ◽  
Distributional Consequences ◽  
Policy Measures ◽  
Fiscal Space ◽  
The Impact ◽  
Initial Coverage ◽  
Model Based Analysis

The COVID-19 pandemic risks exacerbating inequality in Asia. High frequency labor surveys show that the pandemic is having particularly adverse effects on younger workers, women and people that are more vulnerable. Pandemics have been shown to increase inequalities. As a result, income inequality, which was already high and rising in Asia before the pandemic, is likely to rise further over the medium term, unless policies succeed in breaking this historical pattern. Many Asian governments have implemented significant fiscal policy measures to mitigate the pandemic’s effect on the most vulnerable, with the impact depending on the initial coverage of safety nets, fiscal space, and degree of informality and digitalization. The paper includes model-based analysis which shows that policies targeted to where needs are greatest are effective in mitigating adverse distributional consequences and underpinning overall economic activity and virus containment.

scholarly journals High frequency observation during the sand and dust storms in the Qingtu Lake Observatory

2021 ◽  
Author(s):  
Xuebo Li ◽  
Yongxiang Huang ◽  
Guohua Wang ◽  
Xiaojing Zheng
Keyword(s):  
High Frequency ◽  
Power Analysis ◽  
Isotropic Turbulence ◽  
Sonic Anemometer ◽  
Sampling Frequency ◽  
Dust Storms ◽  
Scaling Exponent ◽  
Detailed Measurement ◽  
Frequency Observation ◽  
Dust Monitor

Abstract. Partially due to the global climate change, the sand and dust storms (SDS) occurred more and more frequently, yet a detailed measurement of the SDS event at different heights is still lacking. Here we provide a high frequency observation in the Qingtu Lake Observation Array (QLOA), China. The wind and dust information were measured simultaneously at different wall-normal heights during the SDS process. The datasets span the period from 17 March to 9 June 2016. The wind speed and direction are recorded by a sonic anemometer with a sampling frequency 50 Hz, while the particulate matter 10 (PM10) is sampled simultaneously by a dust monitor with a sampling frequency 1 Hz. The wall-normal array had 11 sonics and monitors spaced logarithmically from z = 0.9 to 30 m, where the spacing is about 2-meter between the sonic anemometer and dust monitor at the same height. Based on its non-stationary feature, the SDS event can be divided into three stages, i.e., ascending, stabilizing and descending stages, in which the dynamic mechanism of the wind and dust fields might be different. This is preliminarily characterized via the classical Fourier power analysis. Temporal evolution of the scaling exponent from Fourier power analysis suggests slightly below the classical Kolmogorov value of −5/3 for the three-dimensional homogeneous and isotropic turbulence. During the stabilizing stage, the collected PM10 shows a very intermittent pattern, which can be further linked with the burst events in the turbulent atmospheric boundary layer. This dataset is valuable for a better understanding the SDS dynamics, which has being publicly available at Zenodo through the DOI 10.5281/zenodo.5034196 (Li et al., 2021a).

scholarly journals What do deviation cycles measure? An analysis of the informational content of filter-based business cycles

2018 ◽  
Vol 21 (1) ◽  
Author(s):  
Willem H. Boshoff ◽  
Lewis McLean
Keyword(s):  
Business Cycles ◽  
Business Cycle ◽  
High Frequency ◽  
Informational Content ◽  
Alternative Theory ◽  
Frequency Range ◽  
Medium Term ◽  
Medium Frequency ◽  
Smoothing Filter ◽  
The Business Cycle

Background: Empirical business cycle research typically commences with the extraction of a so-called deviation cycle using a time-series smoothing filter. This methodology is appealing for its pragmatism; it is easy to implement, and the output it produces is conveniently interpreted as percentage deviations from the natural level of output. However, recent literature offers staunch criticism of deviation cycle analysis, especially with regards to the assumption implicitly underlying it – that business cycle fluctuations are restricted to distinct intervals on the frequency domain.Aim: Despite its lack of a basis in theory, the analysis of deviation cycles over particular frequency ranges may still yield useful stylised business cycle facts. This, however, hinges on whether the information that a frequency filter captures consistently aligns with relevant theory-based business cycle concepts. Whether this is the case is an empirical matter, and herein lies the rationale for our research.Setting: We investigate the informational content of South Africa’s output deviation cycles.Methods: We extract deviation cycles at standard high- and medium-frequency ranges (denoted as short- and medium-term deviation cycles respectively) and analyse their informational overlap with the components of an alternative theory-based estimate of the business cycle, decomposed into demand, supply, domestic and foreign sources of business cycle dynamics.Results: Our findings suggest that the contents of deviation cycles extracted over a high-frequency range do not neatly correspond to the transitory ‘demand-driven’ business cycle, while cycles extracted over a medium-frequency range correspond closely to the combined path of permanent output shocks.Conclusion: One should thus be cautious of drawing strong conclusions about the nature of business cycles from filter-based deviation cycle estimates, particularly if the objective of the study relies on assuming that high-frequency deviation cycles correspond to transitory demand shocks.

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