1,410 research outputs found
The cost of ending groundwater overdraft on the North China Plain
Overexploitation of groundwater reserves is a major environmental problem
around the world. In many river basins, groundwater and surface water are
used conjunctively and joint optimization strategies are required. A
hydroeconomic modeling approach is used to find cost-optimal sustainable
surface water and groundwater allocation strategies for a river basin, given
an arbitrary initial groundwater level in the aquifer. A simplified
management problem with conjunctive use of scarce surface water and
groundwater under inflow and recharge uncertainty is presented. Because of
head-dependent groundwater pumping costs the optimization problem is
nonlinear and non-convex, and a genetic algorithm is used to solve the
one-step-ahead subproblems with the objective of minimizing the sum of
immediate and expected future costs. A real-world application in the
water-scarce Ziya River basin in northern China is used to demonstrate the
model capabilities. Persistent overdraft from the groundwater aquifers on
the North China Plain has caused declining groundwater levels. The model
maps the marginal cost of water in different scenarios, and the minimum cost
of ending groundwater overdraft in the basin is estimated to be CNY 5.58 billion yr−1. The study shows that it is cost-effective to slowly recover the
groundwater aquifer to a level close to the surface, while gradually lowering
the groundwater value to the equilibrium at CNY 2.15 m−3. The model can
be used to guide decision-makers to economic efficient long-term sustainable management
of groundwater and surface water resources
The upper limit of the e+e- partial width of X(3872)
The e+e- decay partial width of the recently observed state, X(3872), is
estimated using the ISR data collected at the center of mass energy 4.03 GeV in
e+e- annihilation experiment by BES at BEPC. It is found that the product of
the e+e- partial width and X(3872) --> pi+ pi- J/psi decay branching fraction
is less than 10 eV at 90 % confidence level if the J(PC) of X(3872) is 1(--).
Together with the potential models and other information, we conclude that
X(3872) is very unlikely to be a vector state.Comment: 5 pages, 1 figur
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