385 research outputs found
Analysis of the Impact of Urbanization and Enhanced Incomes on Demand for Food Quality in Hanoi
This study relates the demand for quality foods in Hanoi in terms of its nutritional composition, diversity, price, processing stage, source, and extent eaten outside home with urbanization and enhanced incomes. The vast differences in these foods quality parameters across different socioeconomic groups and regions in and around Hanoi city suggest the changing nature of the food quality with increased income and urbanization. One lesson learned from this analysis is that urbanization and increased income may not necessarily bring all positive changes in food quality. While the diet becomes more balanced in terms of micronutrient, the increased demand for fat-based calories, processed and restaurant foods, and drift away from fresh sources of farm and home-garden foods raised alarm for food quality and safety. These trends provide a space for government policies to intervene for the purpose of maintaining hygiene standards of food and public health.Demand and Price Analysis, Food Consumption/Nutrition/Food Safety,
Dilaton in Two-Time Physics as trigger of electroweak phase transition and inflation
Within the SP(2, R) symmetry, the Two-time model (2T model) has six dimension
with two time dimensions. The model has a dilaton particle that makes the
symmetry breaking differently from the Standard Model. By reducing the 2T
metric to the Minkowski one (1T metric), we consider the electroweak phase
transition picture in the 2T model with the dilaton as the trigger. Our
analysis shows that Electro-weak Phase Transition (EWPT) is a first-order phase
transition at the GeV scale, its strength is about and the
mass of dilaton is in interval GeV. Furthermore, the metric of 2T
model can be reduced to the Randall-Sundrum model, so the dilaton acts as
inflaton with the slow-roll approximation. Therefore the 2T-model indirectly
suggests that extra-dimension can be also a source of EWPT and inflation. The
EWPT problem can be used to determine scale parameters that refer to
relationships between two metrics.Comment: 25 pages, 2 figure
On the Total Energy Efficiency of Cell-Free Massive MIMO
We consider the cell-free massive multiple-input multiple-output (MIMO)
downlink, where a very large number of distributed multiple-antenna access
points (APs) serve many single-antenna users in the same time-frequency
resource. A simple (distributed) conjugate beamforming scheme is applied at
each AP via the use of local channel state information (CSI). This CSI is
acquired through time-division duplex operation and the reception of uplink
training signals transmitted by the users. We derive a closed-form expression
for the spectral efficiency taking into account the effects of channel
estimation errors and power control. This closed-form result enables us to
analyze the effects of backhaul power consumption, the number of APs, and the
number of antennas per AP on the total energy efficiency, as well as, to design
an optimal power allocation algorithm. The optimal power allocation algorithm
aims at maximizing the total energy efficiency, subject to a per-user spectral
efficiency constraint and a per-AP power constraint. Compared with the equal
power control, our proposed power allocation scheme can double the total energy
efficiency. Furthermore, we propose AP selections schemes, in which each user
chooses a subset of APs, to reduce the power consumption caused by the backhaul
links. With our proposed AP selection schemes, the total energy efficiency
increases significantly, especially for large numbers of APs. Moreover, under a
requirement of good quality-of-service for all users, cell-free massive MIMO
outperforms the colocated counterpart in terms of energy efficiency
Mirror Prox Algorithm for Large-Scale Cell-Free Massive MIMO Uplink Power Control
We consider the problem of max-min fairness for uplink cell-free massive
multiple-input multiple-output (MIMO) subject to per-user power constraints.
The standard framework for solving the considered problem is to separately
solve two subproblems: the receiver filter coefficient design and the power
control problem. While the former has a closed-form solution, the latter has
been solved using either second-order methods of high computational complexity
or a first-order method that provides an approximate solution. To deal with
these drawbacks of the existing methods, we propose a mirror prox based method
for the power control problem by equivalently reformulating it as a
convex-concave problem and applying the mirror prox algorithm to find a saddle
point. The simulation results establish the optimality of the proposed solution
and demonstrate that it is more efficient than the known methods. We also
conclude that for large-scale cell-free massive MIMO, joint optimization of
linear receive combining and power control provides significantly better user
fairness than the power control only scheme in which receiver coefficients are
fixed to unity.Comment: in IEEE Communications Letters, 202
A general formula for the index of depth stability of edge ideals
By a classical result of Brodmann, the function
is asymptotically a constant, i.e. there is a number such that
for . One
calls the smallest number with this property the index of depth stability
of and denotes it by . This invariant remains
mysterious til now. The main result of this paper gives an explicit formula for
when is an arbitrary ideal generated by
squarefree monomials of degree 2. That is the first general case where one can
characterize explicitly. The formula expresses
in terms of the associated graph. The proof involves
new techniques which relate different topics such as simplicial complexes,
systems of linear inequalities, graph parallelizations, and ear decompositions.
It provides an effective method for the study of powers of edge ideals.Comment: 23 pages, 4 figure
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