12,270 research outputs found
A very important process of nucleosynthesis in stars
When some nuclei are free from strong gravitational field, they are unstable and will become stable nuclei by competitions of following processes: (1) neutron-evaporation; (2) spontaneous fission; and (3) beta prime 3-decay. At the initial stage, (1) and (2) are important and (3) can be ignored. The qualitative results are as follows: (1) it seems that nuclei with A 100 come from the spontaneous fission and beta prime decay of neutron-evaporated nuclei with A similiar to 140-440, which can replace the r-process; (2) the super-heavy elements with Z=114--126 (A similiar to 330--360) can be formed. They can be observed in cosmic rage if they have the halftime T 10 to the 7th poweer years; (3) the peak in the rare-earth elements comes from the symmetric fission of super-heavy elements; (4) there are more neutron-rich nuclei in the fragments; and (5) the abundances of a 83 elements in cosmic rays are one order of magnitude higher than that in the solar system
Compressed Air Energy Storage-Part I: An Accurate Bi-linear Cavern Model
Compressed air energy storage (CAES) is suitable for large-scale energy
storage and can help to increase the penetration of wind power in power
systems. A CAES plant consists of compressors, expanders, caverns, and a
motor/generator set. Currently used cavern models for CAES are either accurate
but highly non-linear or linear but inaccurate. Highly non-linear cavern models
cannot be directly utilized in power system optimization problems. In this
regard, an accurate bi-linear cavern model for CAES is proposed in this first
paper of a two-part series. The charging and discharging processes in a cavern
are divided into several virtual states and then the first law of
thermodynamics and ideal gas law are used to derive a cavern model, i.e., model
for the variation of temperature and pressure in these processes. Thereafter,
the heat transfer between the air in the cavern and the cavern wall is
considered and integrated into the cavern model. By subsequently eliminating
several negligible terms, the cavern model reduces to a bi-linear (linear)
model for CAES with multiple (single) time steps. The accuracy of the proposed
cavern model is verified via comparison with an accurate non-linear model.Comment: 8 page
Nucleosynthesis in the terrestrial and solar atmospheres
Variations of Delta D, delta C-13, Delta C-14 and Delta O-18 with time were measured by a lot of experiments. Many abnormalities of isotope abundances in cosmic rays were found by balloons and satellites. It is suggested that these abnormalities are related to nuclearsynthesis in the terrestrial and solar atmospheres and are closely related to solar activities
Distributed Stochastic Optimization over Time-Varying Noisy Network
This paper is concerned with distributed stochastic multi-agent optimization
problem over a class of time-varying network with slowly decreasing
communication noise effects. This paper considers the problem in composite
optimization setting which is more general in noisy network optimization. It is
noteworthy that existing methods for noisy network optimization are Euclidean
projection based. We present two related different classes of non-Euclidean
methods and investigate their convergence behavior. One is distributed
stochastic composite mirror descent type method (DSCMD-N) which provides a more
general algorithm framework than former works in this literature. As a
counterpart, we also consider a composite dual averaging type method (DSCDA-N)
for noisy network optimization. Some main error bounds for DSCMD-N and DSCDA-N
are obtained. The trade-off among stepsizes, noise decreasing rates,
convergence rates of algorithm is analyzed in detail. To the best of our
knowledge, this is the first work to analyze and derive convergence rates of
optimization algorithm in noisy network optimization. We show that an optimal
rate of in nonsmooth convex optimization can be obtained for
proposed methods under appropriate communication noise condition. Moveover,
convergence rates in different orders are comprehensively derived in both
expectation convergence and high probability convergence sense.Comment: 27 page
Error Function Attack of chaos synchronization based encryption schemes
Different chaos synchronization based encryption schemes are reviewed and
compared from the practical point of view. As an efficient cryptanalysis tool
for chaos encryption, a proposal based on the Error Function Attack is
presented systematically and used to evaluate system security. We define a
quantitative measure (Quality Factor) of the effective applicability of a chaos
encryption scheme, which takes into account the security, the encryption speed,
and the robustness against channel noise. A comparison is made of several
encryption schemes and it is found that a scheme based on one-way coupled
chaotic map lattices performs outstandingly well, as judged from Quality
Factor
Compressed Air Energy Storage-Part II: Application to Power System Unit Commitment
Unit commitment (UC) is one of the most important power system operation
problems. To integrate higher penetration of wind power into power systems,
more compressed air energy storage (CAES) plants are being built. Existing
cavern models for the CAES used in power system optimization problems are not
accurate, which may lead to infeasible solutions, e.g., the air pressure in the
cavern is outside its operating range. In this regard, an accurate CAES model
is proposed for the UC problem based on the accurate bi-linear cavern model
proposed in the first paper of this two-part series. The minimum switch time
between the charging and discharging processes of CAES is considered. The whole
model, i.e., the UC model with an accurate CAES model, is a large-scale mixed
integer bi-linear programming problem. To reduce the complexity of the whole
model, three strategies are proposed to reduce the number of bi-linear terms
without sacrificing accuracy. McCormick relaxation and piecewise linearization
are then used to linearize the whole model. To decrease the solution time, a
method to obtain an initial solution of the linearized model is proposed. A
modified RTS-79 system is used to verify the effectiveness of the whole model
and the solution methodology.Comment: 8 page
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