353 research outputs found
Ion exchange system design for removal of heavy metals from acid mine drainage wastewater
This paper discusses the methodology used to determine the optimal ion-exchange column size to process all separate batchesof feeds from acid mine drainage wastewater.The optimal design ensures the best utilization of resin material and therefore results in a minimum amount of spent resins.Ion exchanger materials have been studied for removing heavy metals from a metal bearing wastes. For the current treatment,a facility has been designed for the removal of heavy metals from the acid mine drainage (AMD) waste by the ion-exchange technology
Modeling and gPROMS based simulation of adsorption process for the removal of Cu (II) from aqueous wastewater
40-46The present work studies the performance of Indion 730 (Strong acid) ion exchange resin for the removal of Cu (II). The modeling and gPROMS based simulation is used to study the sorption capacity, equilibrium, and performances of Indion 730 ion exchange resin. The extraction effectiveness of the resin is studied by using breakthrough curves. The experimental and simulation results were compared. A numerical model is proposed for the investigation of the ion exchange phenomenon using gPROMS using various optimized parameters like flow rate, bed height, and initial concentration of wastewater containing Cu (II) heavy metal ion in the column. For instance, the effects of flow rate, bed height, and inlet concentration of heavy metal on a breakthrough curve are investigated in depth. The results illustrate that the predicted theoretical breakthrough curves show analogous patterns with the corresponding investigational output with a discrepancy of the equilibrium time. The predictions of the model will help to discover the optimal conditions of operation
Variable Scintillation Arcs of Millisecond Pulsars observed with the Large European Array for Pulsars
We present the first large sample of scintillation arcs in millisecond
pulsars, analysing 12 sources observed with the Large European Array for
Pulsars (LEAP), and the Effelsberg 100\,m telescope. We estimate the delays
from multipath propagation, measuring significant correlated changes in
scattering timescales over a 10-year timespan. Many sources show compact
concentrations of power in the secondary spectrum, which in PSRs J06130200
and J16003053 can be tracked between observations, and are consistent with
compact scattering at fixed angular positions. Other sources such as PSRs
J16431224 and J0621+1002 show diffuse, asymmetric arcs which are likely
related to phase-gradients across the scattering screen. PSR B1937+21 shows at
least three distinct screens which dominate at different times and evidence of
varying screen axes or multi-screen interactions. We model annual and orbital
arc curvature variations in PSR J06130200, providing a measurement of the
longitude of ascending node, resolving the sense of the orbital inclination,
where our best fit model is of a screen with variable axis of anisotropy over
time, corresponding to changes in the scattering of the source. Unmodeled
variations of the screen's axis of anisotropy are likely to be a limiting
factor in determining orbital parameters with scintillation, requiring careful
consideration of variable screen properties, or independent VLBI measurements.
Long-term scintillation studies such as this serve as a complementary tool to
pulsar timing, to measure a source of correlated noise for pulsar timing
arrays, solve pulsar orbits, and to understand the astrophysical origin of
scattering screens.Comment: Submitted to MNRAS, first revision. 18 pages, 16 figure
Prototype tasks: Improving crowdsourcing results through rapid, iterative task design
Low-quality results have been a long-standing problem on
microtask crowdsourcing platforms, driving away requesters and justifying low wages for workers. To date, workers have been blamed for low-quality results: they are said to make as little effort as possible, do not pay attention to detail, and lack expertise. In this paper, we hypothesize that requesters may also be responsible for low-quality work: they launch unclear task designs that confuse even earnest workers, under-specify edge cases, and neglect to include examples. We introduce prototype tasks, a crowdsourcing strategy requiring all new task designs to launch a small number of sample tasks. Workers attempt these tasks and leave feedback, enabling the requester to iterate on the design before publishing it. We report a field experiment in which tasks that underwent prototype task iteration produced higher-quality work results than the original task designs. With this research, we suggest that a simple and rapid iteration cycle can improve crowd work, and we provide empirical evidence that requester “quality” directly impacts result quality
Usefulness of Crossword Puzzles in Helping First-Year BVSc Students Learn Veterinary Terminology
Boomerang: Rebounding the consequences of reputation feedback on crowdsourcing platforms
Paid crowdsourcing platforms suffer from low-quality workand unfair rejections, but paradoxically, most workers and requesters have high reputation scores. These inflated scores, which make high-quality work and workers difficult to find,stem from social pressure to avoid giving negative feedback. We introduce Boomerang, a reputation system for crowdsourcing that elicits more accurate feedback by rebounding the consequences of feedback directly back onto the person who gave it. With Boomerang, requesters find that their highly rated workers gain earliest access to their future tasks, and workers find tasks from their highly-rated requesters at the top of their task feed. Field experiments verify that Boomerang causes both workers and requesters to provide feedback that is more closely aligned with their private opinions. Inspired by a game-theoretic notion of incentive-compatibility, Boomerang opens opportunities for interaction design to incentivize honest reporting over strategic dishonesty
Assessing the Competitive Ability of Rhynchosia capitata; an Emerging Summer Weed in Asia
Biomarker Changes Associated with Tuberculin Skin Test (TST) Conversion: A Two-Year Longitudinal Follow-Up Study in Exposed Household Contacts
Background:A high prevalence (50-80%) of Tuberculin Skin Test Positivity (TST+ \u3eor=10 mm indurations) has been reported in TB endemic countries. This pool forms a huge reservoir for new incident TB cases. However, immune biomarkers associated with TST conversion are largely unknown. The objective of this study was to identify immune biomarkers associated with TST conversion after acute Mycobacterium tuberculosis (MTB) Methodology/Principal Findings:A 24 month longitudinal study was carried out in a recently MTB exposed cohort of household contacts (HC = 93, 75% TST+). Control group consisted of unexposed community controls (EC = 59, 46%TST+). Cytokine secretion was assessed in whole blood cultures in response to either mycobacterial culture filtrate (CF) antigens or mitogens (PHA or LPS) using Elisa methodology. Compared to the EC group, the HC group at recruitment (Kruskal-Wallis Test) showed significantly suppressed IFN gamma (p = 0.0001), raised IL-10 (p = 0.0005) and raised TNF alpha (p = 0.001) in response to CF irrespective of their TST status. Seventeen TST-HC, showed TST conversion when retested at 6 months. Post TST conversion (paired t tests) significant increases were observed for CF induced IFN gamma (p = 0.038), IL-10 (p = 0.001) and IL-6 (p = 0.006). Cytokine responses were also compared in the exposed HC group with either recent infection [(TST converters (N = 17)] or previous infection [TST+ HC (N = 54)] at 0, 6, 12 and 24 months using ANOVA on repeated measures. Significant differences between the exposed HC groups were noted only at 6 months. CF induced IFN gamma was higher in previously infected HC group (p = 0.038) while IL-10 was higher in recently infected HC group (p = 0.041). Mitogen induced cytokine secretion showed similar differences for different group.Conclusions/Significance:Our results suggest that TST conversion is associated with early increases in IFN gamma and IL-10 responses and precedes latency by several months post exposure
Low Frequency (100-600 MHz) Searches with Axion Cavity Haloscopes
We investigate reentrant and dielectric loaded cavities for the purpose of
extending the range of axion cavity haloscopes to lower masses, below the range
where the Axion Dark Matter eXperiment (ADMX) has already searched. Reentrant
and dielectric loaded cavities were simulated numerically to calculate and
optimize their form factors and quality factors. A prototype reentrant cavity
was built and its measured properties were compared with the simulations. We
estimate the sensitivity of axion dark matter searches using reentrant and
dielectric loaded cavities inserted in the existing ADMX magnet at the
University of Washington and a large magnet being installed at Fermilab.Comment: 33 pages, 24 figure
Search for the Cosmic Axion Background with ADMX
We report the first result of a direct search for a Cosmic
Background CB - a relativistic background of axions that is not dark matter
- performed with the axion haloscope, the Axion Dark Matter eXperiment (ADMX).
Conventional haloscope analyses search for a signal with a narrow bandwidth, as
predicted for dark matter, whereas the CB will be broad. We introduce a
novel analysis strategy, which searches for a CB induced daily modulation in
the power measured by the haloscope. Using this, we repurpose data collected to
search for dark matter to set a limit on the axion photon coupling of the CB
originating from dark matter decay in the 800-995 MHz frequency range. We find
that the present sensitivity is limited by fluctuations in the cavity readout
as the instrument scans across dark matter masses. Nevertheless, we demonstrate
that these challenges can be surmounted with the use of superconducting qubits
as single photon counters, and allow ADMX to operate as a telescope searching
for axions emerging from the decay of dark matter. The daily modulation
analysis technique we introduce can be deployed for various broadband RF
signals, such as other forms of a CB or even high-frequency gravitational
waves.Comment: 9 pages, 4 figure
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