[en] The mathematical model of the neutron dynamic system of the nuclear reactor is transformed into a sort of controlled auto-regressive integrated moving average (CARIMA) model. A generalized predictive control method for the neutron flux density is developed. This new control strategy can efficiently eliminate the influence of uncertain perturbations and non-linearity and can enhance control precision and dynamic qualities of the system. The advantages over the classical control methods are demonstrated by computer simulation

[en] Objective: To investigate the protective effects of quercetin (Que) on endothelial cells from hypoxia. Methods: Human umbilical vein cells (HUVEC) were cultured in vitro and hypoxia was applied to induce damage of HUVEC. Radioimmunoassay (RIA) and colorimetry were used to assess the amounts of ET-1 and NO in the supernatant of normal HUVEC, or HUVEC damaged by hypoxia. Results: Following the treatment of the cultured HUVEC with hypoxia for 48 h, the level of NO in the supernatant was decreased while that of ET-1 was increased. Pretreatment of HUVEC with Que (10, 20, 40, 80 μmol/L), could significantly attenuate these changes. Conclusion: Que can increase the concentration of NO and decrease that of ET-1 released by HUVEC during hypoxia, which could be the possible mechanism of its protection on HUVEC

[en] This paper is to present measuring method, together with primary analytical result, for the specific activity of ¹³⁷CS in environmental water of Shanghai during 2001∼2003. The results indicate that specific activity of ¹³⁷Cs in seawater varies from 2.72 < 10^-4 to 7.47 < 10^-4 Bq/L and that of freshwater is below l.00 × 10^-4 Bq/L. (authors)

[en] The simulation result of thermal distortion of DCM crystal indirectly cooled by liquid nitrogen (LN₂) at Shanghai synchrotron radiation facility (SSRF) has been reported. The source is U27 undulator. The maximum of power density at 24 m is 60 W/mm². The authors give the correlation of the slope error of crystal surface vs. Bragg angle, the convection film coefficient, the bulk temperature of LN₂ and total power absorbed by the first crystal, respectively. The slope error is less than 3 arcsec when the Bragg angle is less than 30 degree, the thickness of crystal is larger than 30 mm, the current of storage ring is up to 400 mA and cooled by 78 K LN₂. (authors)

[en] In this article we discuss the design of double-crystal monochromator control system of 3B3 middle-energy beam line in Beijing Synchrotron Radiation Factory. The multimedia timer and multithread technique were used to solve the high speed data transmission in serial port system and data communication in multi-serial port system. The real time graph drawing and dynamic zooming in double-crystal monochromator debugging system accomplished by VC++6.0 were also described. (authors)

[en] Using mathematical statistical mechanics methods, this paper shows that decisions to heavily promote entrepreneurship beyond a certain threshold in a society would lead to an increase in the society’s Gini coefficient, and thus to more economic inequalities. More specifically, we show that, in a heterogeneous society made up of both entrepreneurs (Es) and ordinary agents (OAs), economic inequalities reach a minimum at an optimal ratio of ‘Es to OAs’. When dealing with a purely homogeneous society made up of entrepreneurs only or ordinary agents only, economic inequalities would decrease as trading activities intensify among the society’s agents. In particular, ideologies that consist in flattening the wealth/income of citizens (as it was recommended, for example, by communist regimes in the last century) to reduce economic inequalities through strict government interventions, may not lead to positive outcomes. We also show that introducing a little heterogeneity into a purely homogeneous society will help reduce economic inequalities in this society. Thus, a society that is composed of ordinary agents only will see its economic inequalities decrease if a number of entrepreneurs join this society. Vice-versa, a society of entrepreneurs only will have its inequalities reduced if some ordinary agents join this society and engage the pre-existing entrepreneurs in trading activities; one could think of southern San Francisco Bay Area, Silicon Valley, as a concrete example of such a situation. To encourage ordinary agents become entrepreneurs, governments could design and implement tax-incentive policies for their respective societies. While such tax-incentive policies would help increase the number of entrepreneurs in the targeted society, they would also have unintended consequences: the society’s middle class gets depleted at equilibrium, and the inequalities that result from implementing the aforementioned policies will be uniformly bigger than the ones that result from an equal tax redistribution policy. The paper concludes with a discussion section that raises a number of questions about socio-economic phenomena and explains how these phenomena can be accounted for using physics laws and principles.

[en] The studies of thermal fission rates are relevant to novel reactors, astrophysical environments, and survival probabilities of compound superheavy nuclei. This has been conventionally studied by the Bohr-Wheeler statistical model that depends on phenomenological level densities and fission barriers. In this context, we propose to study the thermal fission rates based on microscopic temperature dependent nuclear energy density functional theory. The microscopic temperature dependent fission barrier heights and curvatures, and collective mass parameters can be self-consistently obtained. The fission lifetimes from low to high temperatures can be given by the imaginary free energy method in a consistent framework. Microscopic temperature dependent fission barriers play an essential role in fission studies. (authors)

[en] Wave propagation in two-dimensional generalized honeycomb lattices is studied. By employing the tight-binding (TB) approximation, the linear dispersion relation and associated discrete envelope equations are derived for the lowest band. In the TB limit, the Bloch modes are localized at the minima of the potential wells and can analytically be constructed in terms of local orbitals. Bloch-mode relations are converted into integrals over orbitals. With this methodology, the linear dispersion relation is derived analytically in the TB limit. The nonlinear envelope dynamics are found to be governed by a unified nonlinear discrete wave system. The lowest Bloch band has two branches that touch at the Dirac points. In the neighborhood of these points, the unified system leads to a coupled nonlinear discrete Dirac system. In the continuous limit, the leading-order evolution is governed by a continuous nonlinear Dirac system. This system exhibits conical diffraction, a phenomenon observed in experiments. Coupled nonlinear Dirac systems are also obtained. Away from the Dirac points, the continuous limit of the discrete equation leads to coupled nonlinear Schroedinger equations when the underlying group velocities are nearly zero. With semiclassical approximations, all the parameters are estimated analytically.

[en] High-quality BiOCl with {001} facets were successfully synthesized via a facile solvothermal method by controlling the volume ratio of ethanol (ET) and ethylene glycol (EG). The diameters of BiOCl nanosheets with {001} facets varied from 600 to 50 nm with the increase of EG content while the thickness nearly remained the same (∼20 nm). In the meantime, the morphologies of BiOCl turned into 3D hierarchical microspheres from 2D nanosheets. The 91.84 % {001} facets-exposed BiOCl nanosheets with diameter of 300–600 nm exhibited the best photocatalytic activity for the degradation of rhodamine B (RhB) under visible-light irradiation on account of the strong adsorption property of the effective electron injection as well as the sequent reactive radical formation. More importantly, the RhB-sensitized BiOCl nanosheets showed effective photocatalytic property for breaking down methylene blue (MB) and methyl orange (MO) while RhB keeping almost intact until MB and MO had been photodegraded. It was found that the sensitizer radical cation (·RhB"+) could react with MB and MO and their suitable redox potential confirms that as well. These findings may provide a promising approach method for synthesizing other metal oxyhalide materials with controllable diameters of nanosheets and deepen our comprehending for the role of the semiconductor in the sensitization process.

[en] Scroll waves exist ubiquitously in three-dimensional excitable media. The rotation centre can be regarded as a topological object called the vortex filament. In three-dimensional space, the vortex filaments usually form closed loops, and can be even linked and knotted. We give a rigorous topological description of knotted vortex filaments. By using the φ-mapping topological current theory, we rewrite the topological current form of the charge density of vortex filaments, and using this topological current we reveal that the Hopf invariant of vortex filaments is just the sum of the linking and self-linking numbers of the knotted vortex filaments. We think that the precise expression of the Hopf invariant may imply a new topological constraint on knotted vortex filaments