[en] Highlights: • Oxygen distribution in unreduced and reduced powder section were systematically analyzed and compared, and the oxygen depth distribution curves fit well with exponential decay function shown as Y = f(x) = A₁exp(− x/t₁) + A₂exp(− x/t₂) + y₀. • A model of particle oxygen distribution was set up for quantitative analysis of oxygen, which will be useful for further research of reduction kinetics. • The micro process of the reduction of oxides and the thickness decrease of the oxygen-rich layer were systematically analyzed. - Abstract: The characterization of surface oxides composition and the depth distribution of oxides in water-atomized steel powder is vital to adjust the reduction condition for sufficient removal of the oxides. To systematically analyze the composition, depth distribution and morphology of surface oxides in water-atomized low alloy steel powder containing manganese (0.3 wt.%), X-ray photoelectron spectroscopy (XPS) combined with Ar-cluster-ion sputtering, X-ray diffraction (XRD), scanning electron microscope (SEM) and energy disperse spectroscopy (EDS) were utilized. The results show that surface oxygen exists in the form of “Oxides Island”, and the surface oxygen content is much higher than the bulk. In the unreduced powder, the oxygen-rich surface layer contains 67% of total oxygen within a depth of 1800 nm (0.072R, R denotes the radius of the powder); while for the reduced powder, the oxygen-rich surface layer contains 28% of the total oxygen in the powder within a depth of 80 nm (0.0032R). The oxygen depth distribution curves fit well with exponential decay function as Y = f(x) = A₁exp(− x/t₁) + A₂exp(− x/t₂) + y₀. The oxides mainly exist in the forms of γ-Fe₂O₃, FeO, Mn₂O₃ and MnO in the unreduced powder and γ-Fe₂O₃, FeO, Mn₂O₃ in the reduced powder

[en] Based on the analysis of the physical properties and the calculation result of an assembly, this paper points out that it may cause errors in calculating the assembly parameters containing gadolinium, which is of the simplified formula without considering the energy from capture reaction and the short of the capture cross section and the energy parameter in some nuclear data library. At the same time the correct formula is showed with the improved algorithm and the mature program. (authors)

[en] Based on the conformal mapping, Green function method was applied in hexagonal geometry. Conformal mapping was used to map a hexagonal node to a rectangular node before transverse integration. Then, the transverse integration equations were resolved using Green function method with the second boundary condition. A three dimensional multi-energy-groups static program NACK was programmed based on those theories. The code was verified by VVER-1000-type core without the reflector, VVER 440-type three-dimensional two-energy-groups core and two-dimensional core with discontinuity factors. The eigenvalue error is less than 50 pcm, and the maximum relative error of the node average power is less than 2%. The accuracy of NACK is as good as that of other advanced node method codes. (authors)

[en] The MCATHAS system of coupled neutronics/thermal-hydraulics in the supercritical water reactor is described, which considers the interaction between the obvious axial evolution of material temperature and density and the power distribution. This code is coupled externally. The MCNP code with the library of continuous cross section is used for neutronics analysis. The sub-channel code ATHAS is for thermal-hydraulics analysis and the ORIGEN code for burn-up analysis. The calculation results for the assembly of HPLWR show that the results from this code is reliable. (authors)

[en] In PWR three-dimensional transient coupling calculation software CORCA-K, the nodal Green's function method and diagonal implicit Runge Kutta method are used to solve the spatiotemporal neutron dynamic diffusion equation, and the single-phase closed channel model and one-dimensional cylindrical heat conduction transient model are used to calculate the coolant temperature and fuel temperature. The LMW, NEACRP and PWR MOX/UO₂ benchmarks and FangJiaShan (FJS) nuclear power plant (NPP) transient control rod move cases are used to verify the CORCA-K. The effects of burnup, fuel effective temperature and ejection rate on the control rod ejection process of PWR are analyzed. The conclusions are as follows: (1) core relative power and fuel Doppler temperature are in good agreement with the results of benchmark and ADPRES, and the deviation between with the reference results is within 3.0% in LMW and NEACRP benchmarks; 2) the variation trend of FJS NPP core transient parameters is consistent with the results of SMART and ADPRES. And the core relative power is in better agreement with the SMART when weighting coefficient is 0.7. Compared with SMART, the maximum deviation is -5.08% in the rod ejection condition and while -5.09% in the control rod complex movement condition

[en] Highlights: • Ni–Mn_3O_4 nanocomposites have been synthesized simply. • Mn_3O_4 particles were deposited on surface of Ni particles with OH functional groups. • Ni–Mn_3O_4 composites could be quickly conditioned to birnessite-type MnO_2. • A specific capacitance of 230 F g"−"1 was obtained for Ni (17.3%)–Mn_3O_4 nanocomposite. - Abstract: Ni–Mn_3O_4 nanocomposite has been prepared successfully by chemical oxidation in an alkaline solution of Mn"2"+ on the surface of Ni nanoparticles with OH functional groups using one-pot method. The obtained Ni–Mn_3O_4 nanocomposite was characterized using a scanning electron microscope (SEM), a transmission electron microscope (TEM), X-ray diffraction (XRD) analysis and various electrochemical techniques, such as cyclic voltammetry (CV), galvanostatic charge/discharge (GC/D) and electrochemical impedance spectroscopy (EIS). The average crystal sizes of Mn_3O_4 were found to decrease linearly with increasing Ni content in the Ni–Mn_3O_4 composite. The Ni–Mn_3O_4 nanocomposite could be easily conditioned and inverted to birnessite-type MnO_2. A specific capacitance of 230 F g"−"1 (based on pure Mn_3O_4) was obtained for the Ni (17.3%)–Mn_3O_4 nanocomposite at a current rate of 0.25 A g"−"1, and 94% of the initial capacitance was retained after 1000 GC/D cycles at a current rate of 1 A g"−"1. It is concluded that the Ni–Mn_3O_4 nanocomposite is a promising electrode materials for supercapacitors

[en] Utilizing the linear-stability analysis, this paper analytically investigates and calculates the condition and gain spectra of cross-phase modulation instability in optical fibres in the case of exponential saturable nonlinearity and high-order dispersion. The results show that, the modulation instability characteristics here are similar to those of conventional saturable nonlinearity and Kerr nonlinearity. That is to say, when the fourth-order dispersion has the same sign as that of the second-order one, a new gain spectral region called the second one which is far away from the zero point may appear. The existence of the exponential saturable nonlinearity will make the spectral width as well as the peak gain of every spectral region increase with the input powers before decrease. Namely, for every spectral regime, this may lead to a unique value of peak gain and spectral width for two different input powers. In comparison with the case of conventional saturable nonlinearity, however, when the other parameters are the same, the variations of the spectral width and the peak gain with the input powers will be faster in case of exponential saturable nonlinearity. (classical areas of phenomenology)

[en] Starting from the extended nonlinear Schrödinger equation in which the self-steepening effect is included, the evolution and the splitting processes of continuous optical wave whose amplitude is perturbed into time related ultra-short optical pulse trains in an optical fibre are numerically simulated by adopting the split-step Fourier algorithm. The results show that the self-steepening effect can cause the characteristic of the pulse trains to vary with time, which is different from the self-steepening-free case where the generated pulse trains consist of single pulses which are identical in width, intensity, and interval, namely when pulses move a certain distance, they turn into the pulse trains within a certain time range. Moreover, each single pulse may split into several sub-pulses. And as time goes on, the number of the sub-pulses will decrease gradually and the pulse width and the pulse intensity will change too. With the increase of the self-steepening parameter, the distance needed to generate time-dependent pulse trains will shorten. In addition, for a large self-steepening parameter and at the distance where more sub-pulses appear, the corresponding frequency spectra of pulse trains are also wider. (classical areas of phenomenology)

[en] A new means of generating all-optically high-repetition-rate pulse trains is proposed and numerically demonstrated in an optical fiber. Our numerical simulations show that, due to the modulation instability effect, the initial continuous-wave with a weak optical pulse instead of conventional weak sinusoidal modulation imposed on it can gradually evolve into high-repetition-rate pulse trains. However, the generated pulse trains take on different features from the conventional case in terms of their widths, intensities, intervals, numbers, and pedestals. (fundamental areas of phenomenology(including applications))

[en] On the basis of the standard linear stability analysis and Drude electromagnetic model, the impacts of higher-order dispersions and three kinds of typical saturable nonlinearities on modulation instability (MI) have been analyzed and calculated for negative-refractive metamaterials (MMs). Our results show that the MI gain spectra consist of only one spectral region instead of one or two regions in ordinary materials, which may be close to or far from the zero point. Particularly, the spectrum far from the zero point has a high cut-off frequency but a narrow spectral width, which is obviously beneficial to the generation of high-repetition-rate pulse trains. Moreover, MI characteristics here will vary with the normalized angular frequency which can be modified by adjusting the structures of negative-refractive MMs, signifying the controllability of bistable solitons and MI based applications. The effects of saturable nonlinearities are similar to those in ordinary materials