1,911 research outputs found
Treatment of sanitary sewer overflow with fixed media bioreactors
Fixed media bioreactors (biofilters) are a promising and proven technology used for wastewater treatment in unsewered rural areas. As an on-site treatment system, it cart potentially provide high treatment efficiency with a relatively low cost and maintenance. This research expanded the application of fixed media bioreactors and tested their feasibility in the treatment of sanitary sewer overflows (SSO) at high hydraulic loading of 0.2 m/h. Sand, peat, and textile (felt) were used as media to treat simulated 6-h peak flows for a 25-year SSO event in the city of Columbus, Ohio. The influent SSO was a mixture of primary sludge from a wastewater treatment plant diluted with tap water. The efficiency of treatment was measured as changes in the concentrations of biochemical oxygen demand (BOD5), chemical oxygen demand (COD), and total suspended solids (TSS). Sand as a filter medium had the best removal of organic matter with average 84% reduction of BOD5 and 90% of COD. The TSS removal was more than 90% in all media. Peat and felt were,somewhat more efficient than the sand in the TSS removal. The media type and influent BOD5 concentration were two major factors that impacted the treatment of BOD5 (p<0.007). For the treatment of COD, significant factors were media type, influent concentration, and time course of loading in each SSO event (ps <= 0.001)
Carbon dioxide fluxes and carbon balance of an agricultural grassland in southern Finland
A significant proportion of the global carbon emissions to the atmosphere originate from agriculture. Therefore, continuous long-term monitoring of CO2 fluxes is essential to understand the carbon dynamics and balances of different agricultural sites. Here we present results from a new eddy covariance flux measurement site located in southern Finland. We measured CO2 and H2O fluxes at this agricultural grassland site for 2 years, from May 2018 to May 2020. In particular the first summer experienced prolonged dry periods, which affected the CO2 fluxes, and substantially larger fluxes were observed in the second summer. During the dry summer, leaf area index (LAI) was notably lower than in the second summer. Water use efficiency increased with LAI in a similar manner in both years, but photosynthetic capacity per leaf area was lower during the dry summer. The annual carbon balance was calculated based on the CO2 fluxes and management measures, which included input of carbon as organic fertilizers and output as yield. The carbon balance of the field was -57 +/- 10 and -86 +/- 12 g C m(-2) yr(-1) in the first and second study years, respectively.Peer reviewe
Planck-LFI radiometers' spectral response
The Low Frequency Instrument (LFI) is an array of pseudo-correlation
radiometers on board the Planck satellite, the ESA mission dedicated to
precision measurements of the Cosmic Microwave Background. The LFI covers three
bands centred at 30, 44 and 70 GHz, with a goal bandwidth of 20% of the central
frequency.
The characterization of the broadband frequency response of each radiometer
is necessary to understand and correct for systematic effects, particularly
those related to foreground residuals and polarization measurements. In this
paper we present the measured band shape of all the LFI channels and discuss
the methods adopted for their estimation. The spectral characterization of each
radiometer was obtained by combining the measured spectral response of
individual units through a dedicated RF model of the LFI receiver scheme.
As a consistency check, we also attempted end-to-end spectral measurements of
the integrated radiometer chain in a cryogenic chamber. However, due to
systematic effects in the measurement setup, only qualitative results were
obtained from these tests. The measured LFI bandpasses exhibit a moderate level
of ripple, compatible with the instrument scientific requirements.Comment: 16 pages, 9 figures, this paper is part of the Prelaunch status LFI
papers published on JINST:
http://www.iop.org/EJ/journal/-page=extra.proc5/jins
The linearity response of the Planck-LFI flight model receivers
In this paper we discuss the linearity response of the Planck-LFI receivers,
with particular reference to signal compression measured on the 30 and 44 GHz
channels. In the article we discuss the various sources of compression and
present a model that accurately describes data measured during tests performed
with individual radiomeric chains. After discussing test results we present the
best parameter set representing the receiver response and discuss the impact of
non linearity on in-flight calibration, which is shown to be negligible.Comment: this paper is part of the Prelaunch status LFI papers published on
JINST: http://www.iop.org/EJ/journal/-page=extra.proc5/jinst; This is an
author-created, un-copyedited version of an article accepted for publication
in JINST. IOP Publishing Ltd is not responsible for any errors or omissions
in this version of the manuscript or any version derived from it. The
definitive publisher authenticated version is available online at
10.1088/1748-0221/4/12/T12011
Student Engagement in Adolescence : A Scoping Review of Longitudinal Studies 2010-2020
We systematically mapped and analyzed the longitudinal research on adolescent student engagement published during 2010-2020. A total of 104 studies of 104,304 adolescents met inclusion criteria. Studies were mainly conducted in North America (43%) or Europe (34%). Over half studied engagement across one or more years. Most studies (93%) focused on antecedents of engagement rather than outcomes of engagement (38%). Data were commonly collected using self-report questionnaires (87%) and analyzed using path, growth, and cross-lagged models. Studies mainly examined engagement in classroom activities, school, or schoolwork; and focused on behavioral engagement (70%), followed by emotional (61%), then cognitive engagement (35%). No studies used a specific theory of engagement development, but instead referred to self-determination, ecological systems, and stage-environment fit theories.Peer reviewe
Planck pre-launch status: calibration of the Low Frequency Instrument flight model radiometers
The Low Frequency Instrument (LFI) on-board the ESA Planck satellite carries
eleven radiometer subsystems, called Radiometer Chain Assemblies (RCAs), each
composed of a pair of pseudo-correlation receivers. We describe the on-ground
calibration campaign performed to qualify the flight model RCAs and to measure
their pre-launch performances. Each RCA was calibrated in a dedicated
flight-like cryogenic environment with the radiometer front-end cooled to 20K
and the back-end at 300K, and with an external input load cooled to 4K. A
matched load simulating a blackbody at different temperatures was placed in
front of the sky horn to derive basic radiometer properties such as noise
temperature, gain, and noise performance, e.g. 1/f noise. The spectral response
of each detector was measured as was their susceptibility to thermal variation.
All eleven LFI RCAs were calibrated. Instrumental parameters measured in these
tests, such as noise temperature, bandwidth, radiometer isolation, and
linearity, provide essential inputs to the Planck-LFI data analysis.Comment: 15 pages, 18 figures. Accepted for publication in Astronomy and
Astrophysic
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