[en] The Digital I and C systems are believed to improve a plants safety and reliability generally. The reliability analysis of digital I and C system has become one research hotspot. Traditional fault tree method is one of means to quantify the digital I and C system reliability. Review of advanced nuclear power plant AP1000 digital protection system evaluation makes clear both the fault tree application and analysis process to the digital system reliability. One typical digital protection system special for advanced reactor has been developed, which reliability evaluation is necessary for design demonstration. The typical digital protection system construction is introduced in the paper, and the process of FMEA and fault tree application to the digital protection system reliability evaluation are described. Reliability data and bypass logic modeling are two points giving special attention in the paper. Because the factors about time sequence and feedback not exist in reactor protection system obviously, the dynamic feature of digital system is not discussed

[en] Because of the high reliability of Digital instrumentation and control (I and C) systems, the analog I and C systems are upgraded by use of digital ones widely in the nuclear power plants (NPPs), especially in NPPs under construction and consideration currently. The operation of digital system the dynamic features distinctly which include time sequence, feedback of signal, etc. According to some studies which been supported by United States Nuclear Regulatory Commission (USNRC), the Dynamic Flowgraph Methodology (DFM) is one of the top two methods with the most positive features and least negative or uncertain features when evaluated against the requirements for the reliability modeling of digital I and C systems. In this paper, the reliability of typical dual-CPU structure of typical digital system will be evaluated by DFM model to demonstrate the availability of DFM and find the difficulties in the process of modeling and quantity

[en] Based on Schaaff's theory of ultrasonic speed in an organic liquid, new expressions of acoustic parameters, including those of the temperature coefficient of ultrasonic speed (∂C/∂T)_p, the pressure coefficient (∂C/∂P)_T, and the nonlinearity parameter B/A were derived and analyzed. It was found that the expressions could generally describe and compound acoustic properties of the liquid, and could even determine the parameters quantitatively. The expressions have two features: (i) they connect the acoustic parameters with the molecular radius of the medium; (ii) they indicate that under atmospheric pressure and at room temperature, the temperature coefficient (∂C/∂T)_p is negative while the pressure coefficient (∂C/∂P)_T is positive, and under the same conditions the B/A value in an organic liquid always exceeds 8. These results are confirmed by the experimental data from the literature. 23 refs., 2 tabs

[en] An NMR study on the home-made high T_c superconductor Y₁Ba₂Cu₃O_7-δ in high field (7.05 T) is reported. The NMR spectrum and NQR frequencies of the ⁶³Cu in superconductor Y₁Ba₂Cu₃O_7-δ in room temperature is measured and the quadrupole coupling constant C and the asymmetry parametre η of the ⁶³Cu is calculated. In addition, the peak split in Cu(I)-NMR spectrum has been observed

[en] Highlights: • Surfactant P123 is first used to prepare supercapacitor composite electrode PoPD/MnO₂. • P123 efficiently influences the morphology and improve the dispersity of PoPD/MnO₂. • Specific surface area and pore structure of P123 assisted samples are greatly improved. • Composites with P123 shows highly enhanced capacitance performances universally. • P123 dosage has an optimal impact value, in which C_sp is as high as 292.4 F g⁻¹. - Abstract: Composite material poly(o-phenylenediamine)/manganese dioxide (PoPD/MnO₂) used as supercapacitor electrode was one-step synthesized by liquid phase co-precipitation. To obtain good electrochemical performance, such as capacitance performance, rate capability and cycle stability, non-ionic surfactant P123 (poly(ethylene oxide)–poly(propylene oxide)–poly(ethyl oxide), PEO–PPO–PEO) is employed to regulate the morphology, structure and dispersity of PoPD/MnO₂. As evidenced by infrared spectroscopy and X-ray diffraction, PoPD/MnO₂ are all amorphous structure with weak crystallinity. It is worth noting that P123 imposes great influence on morphology, specific surface area and capacitance behavior of PoPD/MnO₂. As P123 increases, PoPD/MnO₂ initially presents as large irregular blocky aggregates, gradually evolves into near-spherical nanoparticles (50–80) nm, and eventually changes to the coexistence state of both. Sample PoPD/MnO₂-0.8 obtained under the optimum P123 dosage 0.8 g (0.0035 mol L⁻¹) has the largest Brunauer–Emmett–Teller specific surface area (123.2 m² g⁻¹) and specific capacitance (292.4 F g⁻¹) at 500 mA g⁻¹, much higher than that of PoPD/MnO₂-0 without P123 (47.2 m² g⁻¹ and 62.1 F g⁻¹). Meanwhile, the rate capability and the cycle stability of PoPD/MnO₂-0.8 improve significantly as well. The equivalent series resistance, electrons transfer resistance and diffusion impedance of samples prepared with suitable amount of P123 all reduced to some extent

[en] By adopting the differential age method, we select 17 832 luminous red galaxies from the Sloan Digital Sky Survey Data Release Seven covering redshift 0 < z < 0.4 to measure the Hubble parameter. Using the full spectrum fitting package UlySS, these spectra are reduced with single stellar population models and optimal age information from our selected sample is derived. With the decreasing age-redshift relation, four new observational H(z) data (OHD) points are obtained, which are H(z) = 69.0 ± 19.6 km s⁻¹ Mpc⁻¹ at z = 0.07, H(z) = 68.6 ± 26.2km s⁻¹ Mpc⁻¹ at z = 0.12, H(z) = 72.9 ± 29.6 km s⁻¹ Mpc⁻¹ at z = 0.2 and H(z)=88.8 ± 36.6 km s⁻¹ Mpc⁻¹ at z = 0.28, respectively. Combined with 21 other available OHD data points, the performance of the constraint on both flat and non-flat ΛCDM models is presented

[en] Our real universe is locally inhomogeneous. Dyer and Roeder introduced the smoothness parameter α to describe the influence of local inhomogeneity on angular diameter distance, and they obtained the angular diameter distance-redshift approximate relation (Dyer-Roeder equation) for locally inhomogeneous universe. Furthermore, the Distance-Duality (DD) relation, D_L(z)(1+z)⁻²/D_A(z) = 1, should be valid for all cosmological models that are described by Riemannian geometry, where D_L and D_A are, respectively, the luminosity and angular distance distances. Therefore, it is necessary to test whether if the Dyer-Roeder approximate equation can satisfy the Distance-Duality relation. In this paper, we use Union2.1 SNe Ia data to constrain the smoothness parameter α and test whether the Dyer-Roeder equation meet the DD relation. By using χ² minimization, we get α = 0.92_−0.32^+0.08 at 1σ and 0.92_−0.65^+0.08 at 2σ, and our results show that the Dyer-Roeder equation is in good consistency with the DD relation at 1σ

[en] The angular distribution of energy for synchrotron radiation in low frequency band (ω << ω_c) is obtained by rigorously solving the Nicolo Tartaglia equation. The result shows that the critical angle increases with decreasing frequency, but it cannot exceed 90°. The relation between critical angle θ_c and frequency is common covering all wavelengths. For the small angle case, it is consistent with the result obtained by Jackson. With the increase of emanative angle, the radiant intensity increases first, then decays

[en] One of the most widely used methods to estimate core damage during a nuclear power plant accident is containment radiation measurement. The evolution of severe accidents is extremely complex, leading to uncertainty in the containment dose rate (CDR). Therefore, it is difficult to accurately determine core damage. This study proposes to conduct uncertainty analysis of CDR for core damage assessment. First, based on source term estimation, the Monte Carlo (MC) and point-kernel integration methods were used to estimate the probability density function of the CDR under different extents of core damage in accident scenarios with late containment failure. Second, the results were verified by comparing the results of both methods. The point-kernel integration method results were more dispersed than the MC results, and the MC method was used for both quantitative and qualitative analyses. Quantitative analysis indicated a linear relationship, rather than the expected proportional relationship, between the CDR and core damage fraction. The CDR distribution obeyed a logarithmic normal distribution in accidents with a small break in containment, but not in accidents with a large break in containment. A possible application of our analysis is a real-time core damage estimation program based on the CDR

[en] We present a model-independent determination of the curvature parameter Ω _k using the Hubble parameter H(z) and the angular diameter distance D_A (z) from recent baryon acoustic oscillation (BAO) measurements. Each H(z) and D_A (z) pair from a BAO measurement can constrain a curvature parameter. The accuracy of the curvature measurement improves with increased redshift of H(z) and D_A (z) data. By using the H(z) and D_A (z) pair derived from a BAO Lyman α forest measurement at z = 2.36, the Ω _k is confined to be –0.05 ± 0.06, which is consistent with the curvature of −0.037_−0.042^+0.044 constrained by the nine year Wilkinson Microwave Anisotropy Probe data only. Considering future BAO measurements, at least one order of magnitude improvement of this curvature measurement can be expected