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721.
土壤水力侵蚀能量力学机理的理论分析 总被引:3,自引:0,他引:3
根据力学和物质与能量原理,对土壤水力侵蚀这一自然地理现象从哲学的高度进行分析,认为水动力作用是土壤水力侵蚀的根本原因;物质与能量守恒是土壤水力侵蚀的基本法则;侵蚀与沉积并存是土壤水力侵蚀的普遍规律。提出基于能量力学机理的3个土壤水力侵蚀的新理论,即侵蚀平衡理论、最大梯度理论和水流侵蚀力理论。指出按这种思想建立的数学模型能揭示土壤水力侵蚀的规律,因而具有重要的理论和应用价值。 相似文献
722.
Thomas Durt 《Foundations of Science》2011,16(4):315-318
As was mentioned by Nicolas Lori in his (Found Sci, 2010) commentary, the definition of Information in Physics is something about which not all authors agreed. According to physicists
like me Information decreases when Entropy increases (so entropy would be a negative measure of information), while many physicists,
seemingly the majority of them, are convinced of the contrary (even in the camp of Quantum Information Theoreticians). In
this reply I reproduce, and make more precise, some of my arguments, that appeared here and there in my (2010) paper, in order to clarify the presentation of my personal point of view on the subject. 相似文献
723.
This paper aims to contribute to the literature on the explanatory power of behavior models with heterogeneous agents. The
authors present a new nonlinear structural stock market model which is a nonlinear deterministic process buffeted by dynamic
noise. An exogenous noise is introduced to the model with the assumption of IID normal innovations of the fundamental value
in order to investigate how noisy dynamics interacts with deterministic process. The market is composed of two typical trader
types: the rational fundamentalists and the boundedly rational traders governed by greed and fear. The interaction between
noise and deterministic element determines the evolution process of the system as key parameters are changed. The authors
find the model is able to generate time series that exhibit dynamical and statistical properties closely resembling those
of the S&P500 index, such as volatility clustering, fat tails (leptokurtosis), autocorrelation in square and absolute return,
larger amplitude, crashes and bubbles. The authors also investigate the nonlinear dependence structure in our data. The results
indicate that the GARCH-type model cannot completely account for all nonlinearity in our simulated market, which is thus consistent
with the results from real markets. It seems that the nonlinear structural model is more powerful to give a satisfied explanation
to market behavior than the traditional stochastic approach. 相似文献
724.
This paper considers the optimal investment strategy for an insurer under the criterion of mean-variance. The risk process
is a compound Poisson process and the insurer can invest in a risk-free asset and multiple risky assets. This paper obtains
the optimal investment policy using the stochastic linear quadratic (LQ) control theory with no-shorting constraint. Then
the efficient strategy (optimal investment strategy) and efficient frontier are derived explicitly by a verification theorem
with the viscosity solution of Hamilton-Jacobi-Bellman (HJB) equation. 相似文献
725.
This paper considers a class of stochastic variational inequality problems. As proposed by Jiang and Xu (2008), by using the
so-called regularized gap function, the authors formulate the problems as constrained optimization problems and then propose
a sample average approximation method for solving the problems. Under some moderate conditions, the authors investigate the
limiting behavior of the optimal values and the optimal solutions of the approximation problems. Finally, some numerical results
are reported to show efficiency of the proposed method. 相似文献
726.
New acquisition decision algorithm for multiple access interference suppression in DSSS system
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For decreasing the multiple access interference of weaker signal acquisition in direct sequence spread spectrum(DSSS) systems,a new single decision algorithm is presented.The maximum value of correlation results is conventionally detected.However,there may be not only one strong peak among correlation results when the cross-correlation noise is strong enough to affect the correlation results.The proposed algorithm decreases the false alarm probability through the decision of the ratio of the maximum value and the second maximum value of the correlation results.Theoretical analysis and simulation results indicate that the proposed algorithm effectively suppresses the acquisition problem of multiple access interference in DSSS system. 相似文献
727.
In this paper, the dynamic behaviors of a discrete epidemic model with a nonlinear incidence rate obtained by Euler method
are discussed, which can exhibit the periodic motions and chaotic behaviors under the suitable system parameter conditions.
Codimension-two bifurcations of the discrete epidemic model, associated with 1:1 strong resonance, 1:2 strong resonance, 1:3
strong resonance and 1:4 strong resonance, are analyzed by using the bifurcation theorem and the normal form method of maps.
Moreover, in order to eliminate the chaotic behavior of the discrete epidemic model, a tracking controller is designed such
that the disease disappears gradually. Finally, numerical simulations are obtained by the phase portraits, the maximum Lyapunov
exponents diagrams for two different varying parameters in 3-dimension space, the bifurcation diagrams, the computations of
Lyapunov exponents and the dynamic response. They not only illustrate the validity of the proposed results, but also display
the interesting and complex dynamical behaviors. 相似文献
728.
J. D. R. de Raadt 《Systemic Practice and Action Research》2011,24(6):509-521
Starting from the crisis in our communities—research has indicated it to be widely spread—the author explores the scientific
tradition preceding the rise of modernism in order to draw out a more humane way of thinking that may help our contemporary
societies. He discerns between two types of Renaissance humanism, one characterised by its cleverness, the other by its compassion
and desire to restore dignity to the lives of people struggling to escape the clutches of medievalism. The father of the latter
is Erasmus of Rotterdam and we follow the development of his conception of a social humanism as it branches out, through the
work of his successors, into every scientific discipline, both natural and human. These disciplines are united by an embracing
systemic idea of philosophy that unites the mind with the heart and which Erasmus called “Philosophia Christi”. We examine
the two main pillars upon which this philosophy is built, love for our neighbour and education as the only legitimate instrument
to change society, and the extraordinary impact it had on science and on communities living in the seventeenth century. We
contrast this with the idea of power, the chosen instrument of modernity to transform society, and trace some of its tragic
outcomes. We conclude by discussing the incorporation of an Erasmian type of social humanism into systems education and the
future development of such programmes. 相似文献
729.
The effect of Mg substitution for La on microstructure, hydrogen storage and electrochemical properties of the annealed La_(1-x) Mg_x Ni_3.5(x=0.20, 0.23, 0.25 at%) alloys have been studied. All the samples were mainly composed of(LaMg)_2Ni_7,(LaMg)Ni_3, and LaNi_5 phases. Mg substitution for La changed the phase abundance, but did not change the constitution of all phases, which is con fi rmed by the results of backscattered SEM images and EDS analysis. The P–C isotherms indicated that the La_(1-x) Mg_x Ni_3.5alloys reversibly absorbed and desorbed hydrogen smoothly at 298 K. The hydrogen absorption cyclic stabilities of La_(1-x) Mg_x Ni_3.5alloy after 5 hydrogen absorption/desorption cycles reached the maximum values of91.9% and 96.0% at 298 K and 323 K, respectively. The hydrogen desorption capacity and plateau pressure for the La_(1-x) Mg_x Ni_3.5alloy reached the maximum values of 1.055 H/M and 0.074 MPa, respectively. The desorption capacities of La_(1-x) Mg_x Ni_3.5reached 0.193 H/M and 0.565 H/M in the fi rst minute at 298 K and 323 K, respectively. Electrochemical property measurement indicated that La_(1-x) Mg_x Ni_3.5(x=0.20,0.23, 0.25 at%) alloys possessed excellent activation capability and were completely activated within3 cycles. Discharge capacities of La_(1-x) Mg_x Ni_3.5alloys reached 378.2 m A h/g(x = 0.20 at%), 342.7 m A h/g(x = 0.23 at%), and 369.6 m A h/g(x = 0.25 at%), respectively. Moreover, energy density of La_(1-x) Mg_x Ni_3.5alloy was much larger than that of La_0.80Mg_0.20Ni_3.5 alloy and nearly approaches the maximum value of La0.75Mg0.25Ni3.5. Thus, the La_(1-x) Mg_x Ni_3.5alloy exhibits optimum comprehensive properties of hydrogen storage and electrochemistry. 相似文献
730.
In this paper, large scale hierarchically assembled Ni O nanosheets have been favorably fabricated through a facile hydrothermal route. The as-prepared Ni O nanosheet assembles were characterized in detail by various analytical techniques. The results showed these nanosheets present the thickness of about 30 nm and the surface area is 116.9 m~2 g~(-1). These NiO nanosheet assembles were used as the working electrode materials in electrochemical tests, which demonstrated a specific capacitance value of 81.67 Fg ~(-1)at the current density of 0.5 Ag~(-1)and excellent long cycle-life stability with 78.5% of its discharge specific capacitance retention after 3000 cycles at the current density of 0.5 Ag~(-1), revealing the as-synthesized NiO nanosheet assembles might be a promising electrode material for supercapacitor applications. 相似文献