[en] Thin films of nickel-carbon prepared by d.c. magnetron sputter deposition have previously been shown to exhibit passivity against corrosion as well as electrocatalytic activity towards the hydrogen oxidation reaction of the low-temperature acidic fuel cell. Pure nickel dissolves rapidly under such conditions. X-ray photoelectron spectroscopy (XPS) of Ni-C films containing between 13 and 64 at.% Ni, and polarized at +0.15 V(SHE) in 1.5 M H₂SO₄ at room temperature demonstrates that this passivity is not due to oxide formation, but rather to the presence of the carbon component. XPS identifies the Ni component as being in the metallic state, both before and after polarization in acid. The carbon component comprises a range of phases, with a graphitic or graphenic component being responsible for passivation

[en] Within the frame of the Huang–Rhys's lattice relaxation model, we theoretically studied the effects of lattice relaxation due to the electrons (holes)-surface optical (SO) phonons coupling on the magneto-optical (MO) transitions in monolayer molybdenum disulphide on three different types of polar substrates. The lattice relaxation resulted in the peak position shifting and the linewidths broadening in MO transitions. The dependences of MO transitions on the magnetic field, temperature and polarization strength of substrates have been discussed in detail. The obtained results may provide a possible method to measure the coupling strength between the electrons (holes) and SO phonons in MO experiments. - Highlights: • Magneto-optical transitions were studied in the Huang–Rhys's model. • Lattice relaxation was studied in monolayer MoS_2 on polar substrates. • Lattice relaxation results in the renormalization of the Landau levels.

[en] Supercritical CO₂-cooled reactor, as a promising reactor, is at the conceptual design stage. The physical and mathematical models of the main parts of the primary circuit of supercritical CO₂-cooled micro-modular reactor (MMR) designed by Korea Advanced Institute of Science and Technology (KAIST) were established, and the transient and safety analysis code TRA_-SCR for supercritical CO₂-cooled reactor was preliminarily developed with FORTRAN language. Steady state analysis shows the stability and dependability of TRA_-SCR code for KAIST MMR. The variations of main parameters for loss of flow and reactivity insertion accidents without protection were calculated, and the transient safety characteristics of this system were preliminarily studied. The results show that KAIST MMR has strong inherent negative feedback characteristics, and under these two accidents, the temperatures of the cladding, fuel and coolant do not exceed the safety limitation. However, the outlet temperature of the core coolant is close to the safety limitation in loss of flow accident without protection, which shows that the outlet core temperature is the key factor limiting the safety performance of the system. (authors)

[en] The flow structures of gas-liquid two-phase flow and the shape of bubbles in a double sub-channels tight lattice bundle were measured using a dual wire-mesh sensor (WMS). The experiments were carried out under room temperature and pressure, using water as the liquid phase and air as the gas phase. The superficial velocity range is from 0.921 m/s to 1.84 m/s for the liquid phase and 0.0770 m/s to 1.103 m/s for the gas phase. The flow regime included bubbly flow, cap-bubbly flow, and slug flow. Due to the small size of the tight lattice bundle, the cap bubbles were confined in a single sub-channel. The cap bubbles were arranged alternately in the two sub-channels. With the increasing of the bubble size, slug bubbles that can cross the gap and span the whole channel cross-section can be observed. (authors)

[en] Flow-induced acoustic resonance in closed side branch is a flow-acoustic-coupling phenomenon caused by the interaction of flow and acoustic fields in special structure. The flow-induced acoustic resonance characteristic experiments were carried out on cylindrical closed side branch to study the influences of the velocity in main pipe and the height of the side branch on acoustic resonance. The range of occurrence and characteristics of pressure pulsation were analyzed. Five heights of side branches (H/d = 6, 8, 10, 12, 14) are experimentally studied and the Reynolds number in the experiment is 3.24 × 10⁴-2.89 × 10⁵ while the Mach number is 0.029-0.26. It is found that the resonance frequency shows a lock-in phenomenon with the increase of velocity. As the height of the side branch increasing, the acoustic mode frequency decreases while the amplitude of the acoustic pressure show s no significant changes as the wall of the side branch approximately equals to rigid wall. In the considered structure, the acoustic resonance occurs when Strouhal number is in the range of 0.2-0.55. (authors)

[en] In this paper, primary attention is paid to the local mechanical response of NiTi shape memory alloy (SMA) under uniaxial tension. With the help of in situ digital image correlation, sets of experiments are conducted to measure the local strain field at various thermomechanical conditions. Two types of mechanical responses of NiTi SMA are identified. The residual strain localization phenomena are observed, which can be attributed to the localized phase transformation (PT) and we affirm that most of the irreversibility is accumulated simultaneously during PT. It is found that temperature and PT play important roles in inducing delocalization of the reverse transformation. We conclude that forward transformation has more influence on the transition of mechanical response in NiTi SMA than reverse transformation in terms of the critical transition temperature for inducing delocalized reverse transformation. (technical note)

[en] RT-PCR and Western Blot were performed to determine the mRNA and protein levels of AP1S1 gene, respectively, at 8, 24 h post-radiation; refraining the AP1S1 gene expression of AHH-1 cell with AP1S1 siRNA, cell proliferation used CCK-8, Bystander cell culture medium levels of NO used Nitric Oxide Assay Kit. Result: 1) the mRNA and protein level of AP1S1 in the directly irradiated cell and bystander cells upregulated at different time point compared with the control groups in dose-dependant manner. In addition, the bystander cells upregulated significantly. 2) the cell proliferation increased after AP1S1 gene expression refrained, it shows AP1S1 has a contribution to bystander effect damage at least. NO levels of each group changed little, P>0.05, no statistical significance, indicating AP1S1 gene in bystander effect of ionizing radiation signal membrane transport may play a role, but inhibition expression of AP1S1 can not reduce the bystander effect cell NO generation. (authors)

[en] The mechanical performance of superelastic NiTi with various grain sizes (GSs) in nanocrystalline regime (GS  <  30 nm) are investigated. With the help of digital image correlation, both global and local mechanical responses of NiTi during quasi-static test and fatigue cycling are recorded. If GS is below 14 nm, NiTi deforms homogenously; if GS is above 14 nm, NiTi deforms in a heterogeneous manner. The mechanical response, the fatigue life, the dissipation energy and the resistance to the dissipation energy degradation of nanostructured NiTi are addressed and analyzed. The results indicate that the mechanical performance of NiTi can be designed and optimized by controlling GS in a moderate regime. (paper)

[en] In order to investigate the convective heat transfer at supercritical pressures, experimental research was conducted on heated Freon R134a flowing upward through an I.D 25 mm vertical circular tube under supercritical pressure condition. The experimental data covers a wide range of conditions. The pressure is at 4.5 MPa and 4.7 MPa. The mass flow flux varies from 400 to 700 kg/(m²·s) and the heat flux ranges from 30 to 60 kW/m². Both enhanced and deteriorated heat transfer were analyzed and the parametric sensitivity was also carried out. The heat transfer performance was evidently enhanced near the pseudo-critical point. The deteriorated heat transfer appeared at lower mass flow velocity or at higher heat flux under a certain ratio of q/G = 0.06 kj/kg. At a mass flux of 500 kg/(m²·s) two types of deteriorated heat transfer were observed in the experiment: the first type appeared at the near entrance region of the tube and existed within different range of fluid inlet temperature; The second type appeared at any section inside the tube than entrance but only within a certain enthalpy range. Heat transfer can be enhanced by increasing mass flow velocity, decreasing heat flux or decreasing pressure, while the variance of the heat transfer deterioration is opposite. (authors)

[en] An indirect effect induced by ionizing radiation called bystander effect is being highly concentrated. The new achievement by application of advanced tools provides powerful evidence to explain how bystander effects happen and the regulation mechanism. (authors)