566 research outputs found
Pareto-optimal pilot design for cellular massive MIMO systems
We introduce a non-orthogonal pilot design scheme that simultaneously minimizes two contradicting targets of channel estimation errors of all base stations (BSs) and the total pilot power consumptions of all users in a multi-cell massive MIMO system, subject to the transmit power constraints of the users in the network. We formulate a multi-objective optimization problem (MOP) with two objective functions capturing the contradicting targets and find the Pareto optimal solutions for the pilot signals. Using weighted-sum-scalarization technique, we first convert the MOP to an equivalent single-objective optimization problem (SOP), which is not convex. Assuming that each BS is provided with the most recent knowledge of the pilot signals of the other BSs, we then decompose the SOP into a set of distributed non-convex optimization problems to be solved at individual BSs. Finally, we introduce an alternating optimization approach to cast each one of the resulting distributed optimization problems into a convex linear matrix inequality (LMI) form. We provide a mathematical proof for the convergence of the proposed alternating approach and a complexity analysis for the LMI optimization problem. Simulation results confirm that the proposed approach significantly reduces pilot power, whilst maintaining the same level of channel estimation error as in [1]
Practical use of reactor anti-neutrinos for nuclear safeguard in Vietnam
One of the most abundant man-made sources of low energy (few~MeVs) neutrinos,
reactor neutrino, is not only useful for studying neutrino properties, but it
is also used in practical applications. In this study, we investigate the
practical use of reactor neutrino detectors for nuclear safeguard in Vietnam,
specifically at the Dalat Nuclear Reactor, a future research facility, and
presumably commercial reactors with 500~kW, 10~MW, and 1000~MW thermal powers,
respectively. We compute the rate of observed inverted beta decay events, as
well as the statistical significance of extracting isotope composition under
the practical assumptions of detector mass, detection efficiency, and
background level. We find that a 1-ton detector mass can allow us to detect the
reactor's on-off transition state from a few hours to a few days, depending on
the standoff distance and reactor thermal power. We investigate how background
and energy resolution affect the precision of the extracted weapon-usable
isotope. We conclude that in order to distinguish the 10\%
variation of the in the 10~MW thermal power reactor, a
1-ton detector placed 50~m away must achieve 1\% background level. Increasing
the statistics by using a 10x larger detector or placing it times
closer to the reactor alleviates the requirement of the background level to
10\%
Stringent constraint on CPT violation with the synergy of T2K-II, NOA extension, and JUNO
Neutrino oscillation experiments have measured precisely the mass-squared
differences of three neutrino mass eigenstates, and three leptonic mixing
angles by utilizing both neutrino and anti-neutrino oscillations. The possible
CPT violation may manifest itself in the difference of neutrino and
anti-neutrino oscillation parameters, making these experiments promising tools
for testing CPT invariance. We investigate empirically the sensitivity of the
CPT test via the difference in mass-squared splittings () and in leptonic mixing angles () with the synergy of T2K-II, NOA
extension, and JUNO experiments. If the CPT symmetry is found to be conserved,
the joint analysis of the three experiments will be able to establish limits of
< and <
at 3 C. L. on the possible CPT violation. We find that with (), the dependence of the statistical
significance on the relevant parameters to exclude the CPT conservation is
marginal, and that, if the difference in the best-fit values of and measured by MINOS(+) and NOA
persists as the true, the combined analysis will rule out the CPT conservation
at 4 C. L.. With the (), the statistical significance to exclude CPT
invariance depends strongly on the true value of
. In case of maximal mixing of
, the CPT conservation will be excluded at 3 C. L. or more
if the difference in the best-fit values of and
remains as the true.Comment: 10 pages, 10 figure
Mass transfer properties of Acacia mangium plantation wood
This study investigated the mass transfer properties (permeability and mass diffusivity) in the longitudinal, radial and tangential directions of plantation-grown Acacia mangium in VinhPhuc province,northeast, Vietnam. These properties will be used to complement a conventional drying model in the future. Measurements of gas and liquid permeability were performed using a Porometer (POROLUXTM1000). Mass diffusivity was determined in a constant humidity and temperature chamber using PVC-CHA vaporimeters. Results showed the gas permeability was significant higher than liquid with the descending order of longitudinal, radial, and tangential directions. The permeability anisotropy ratios from the longitudinal to transverse directions of Acacia mangium were much lower than other published species. However, the obvious anisotropy ratios from radial to tangential for both permeability and diffusivity, is one of concerns as they can exacerbate defects during drying. Besides, the high permeability and diffusivity of Acaciamangium compared to some other species reported compounds its relatively fast drying rate
Mass transfer properties of Acacia mangium plantation wood
This study investigated the mass transfer properties (permeability and mass diffusivity) in the longitudinal, radial and tangential directions of plantation-grown Acacia mangium in VinhPhuc province,northeast, Vietnam. These properties will be used to complement a conventional drying model in the future. Measurements of gas and liquid permeability were performed using a Porometer (POROLUXTM1000). Mass diffusivity was determined in a constant humidity and temperature chamber using PVC-CHA vaporimeters. Results showed the gas permeability was significant higher than liquid with the descending order of longitudinal, radial, and tangential directions. The permeability anisotropy ratios from the longitudinal to transverse directions of Acacia mangium were much lower than other published species. However, the obvious anisotropy ratios from radial to tangential for both permeability and diffusivity, is one of concerns as they can exacerbate defects during drying. Besides, the high permeability and diffusivity of Acaciamangium compared to some other species reported compounds its relatively fast drying rate
The CIPAZ study protocol: an open label randomised controlled trial of azithromycin versus ciprofloxacin for the treatment of children hospitalised with dysentery in Ho Chi Minh City, Vietnam
Background: Diarrhoeal disease remains a common cause of illness and death in children <5 years of age. Faecal-oral infection by Shigella spp. causing bacillary dysentery is a leading cause of moderate-to-severe diarrhoea, particularly in low and middle-income countries. In Southeast Asia, S. sonnei predominates and infections are frequently resistant to first-line treatment with the fluoroquinolone, ciprofloxacin. While resistance to all antimicrobials is increasing, there may be theoretical and clinical benefits to prioritizing treatment of bacillary dysentery with the azalide, azithromycin. In this study we aim to measure the efficacy of treatment with azithromycin compared with ciprofloxacin, the current standard of care, for the treatment of children with bacillary dysentery.
Methods and analysis: We will perform a multicentre, open-label, randomized controlled trial of two therapeutic options for the antimicrobial treatment of children hospitalised with dysentery. Children (6â60 months of age) presenting with symptoms and signs of dysentery at Childrenâs Hospital 2 in Ho Chi Minh City will be randomised (1:1) to treatment with either oral ciprofloxacin (15mg/kg/twice daily for 3 days, standard-of-care) or oral azithromycin (10mg/kg/daily for 3 days). The primary endpoint will be the proportion of treatment failure (defined by clinical and microbiological parameters) by day 28 (+3 days) and will be compared between study arms by logistic regression modelling using treatment allocation as the main variable.
Ethics and dissemination: The study protocol (version 1.2 dated 27th December 2018) has been approved by the Oxford Tropical Research Ethics Committee (47â18) and the ethical review boards of Children's Hospital 2 (1341/NÄ2-CÄT). The study has also been approved by the Vietnamese Ministry of Health (5044/QÄ-BYT).
Trial registration: Clinicaltrials.gov: NCT03854929 (February 26th 2019)
Universality in odd-even harmonic generation and application in terahertz waveform sampling
Odd-even harmonics emitted from a laser-target system imprint rich, subtle
information characterizing the system's dynamical asymmetry, which is desirable
to decipher. In this Letter, we discover a simple universal relation between
the odd-even harmonics and the asymmetry of the THz-assisted laser-atomic
system -- atoms in a fundamental mid-IR laser pulse combined with a THz laser.
First, we demonstrate numerically and then analytically formulize the harmonic
even-to-odd ratio as a function of the THz electric field, the source of the
system's asymmetry. Notably, we suggest a scaling that makes the obtained rule
universal, independent of the parameters of both the fundamental pulse and
atomic target. This universality facilitates us to propose a general pump-probe
scheme for THz waveform sampling from the even-to-odd ratio, measurable within
a conventional compact setup
Seasonal variation of phytoplankton in My Thanh River, Mekong delta, Vietnam
A study on the seasonal variation of phytoplankton composition was conducted at the upper, middle, and lower parts of the My Thanh River, which supplies an important source of water for aquaculture. Qualitative and quantitative samples of phytoplankton were collected monthly at both high and low tide. The results showed that a total of 171 phytoplankton (algae) species were recorded, belonging to 59 genera and 5 phyla. Diatoms were the most abundant group with the highest species number, followed by green algae. The other phyla possessed a lower number of species. The species composition was more diverse in the rainy season and at high tide at most of the sampling sites. The mean density of algae varied from 30,900-43,521 ind.L^-1^. The density of diatoms was higher in the middle and lower parts. At the same time, euglenoids displayed the highest density in the upper part, showing a difference in the dominant algae group under the influence of salinity. Salinity was found to be significantly positively correlated (p<0.01) with diatoms, whereas it was negatively correlated (p<0.05) with blue-green algae and euglenoids. The algae composition was quite diverse, with the H' index ranging from 2.0-3.3, showing the water quality was slightly to moderately polluted
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