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The swimming pool-type low-temperature heating reactor (SPLTHR) has low thermal parameters, large heat capacity, and high inherent safety, so it is a suitable reactor type for nuclear heating reactors. Because the SPLTHR has a long shutdown time and the temperature difference between the cold and heat sources is small, it has certain requirements on the heat transfer capability of the passive residual heat removal system (PRHRS). Basing on the characteristics of SPLTHR, a singlephase natural circulation experiment system of PRHRS of SPLTHR was designed by H2TS (hierarchical twotiered scaling) proportion analysis method, and the flow and heat transfer characteristics of the singlephase natural circulation of the PRHRS were studied experimentally. In order to get closer to the prototype system, the center height difference of the cold and heat source of the experimental system was the same as that of the prototype system, which was 9 m. The ranges of the pool water temperature, air temperature and air flow rate in the experiment were 50-90 ℃, 15-30 ℃ and 15 000-35 000 m3/h, respectively. The results show that the experimental system designed by H2TS proportion analysis method can achieve the designed heat transfer capacity when the temperature difference between the cold and heat source is 54 ℃, which means the method is suitable for the design of singlephase natural circulation system under low temperature difference. There is flow oscillation in the system startup process, and the system can be stabilized gradually with the operation. The hot and cold water in the primary loop alternately enters the heat exchanger and aircooler, causing the driving force of the system to change, which leads to fluctuations in circulation flow rate and heat transfer capacity. The change of boundary conditions mainly affects the heat transfer capacity of the system and the time to reach stability, but has little effect on the shape and number of fluctuations before the system reaches stability. For the PRHRS heat exchanger tube bundle, which is neither a constant heat flow nor a constant wall temperature boundary, it is more appropriate to use the natural convective heat transfer temperature difference as the parameter of the Grashof number. Due to the tube bundle effect, the traditional singletube natural convection heat transfer correlations have a low predictive value for the natural convection heat transfer outside the tube bundle. According to the experimental data, the correlation of natural convection heat transfer outside the tube bundle with the applicable range 351×103

Track-Before-Detect (TBD) approaches have important applications such as the detection of small, dim targets in a long-range Infrared Detection and Tracking (IRDT) system. The movement model of target limited by TBD is extended to that of target with constant acceleration in this work. An algorithm based on linear variant-coefficient difference equation for moving target indication is proposed. Moreover, based on parametric models of target and background, this paper presents an analysis of its optimal signal-to-noise ratio (SNR) gain versus target and background characteristics as well as the sensitivity of this gain to mismatch.

One-dimensional (1D) Ag/AgBr/TiO2 nanofibres (NFs) have been successfully fabricated by the one-pot electrospinning method. In comparison with bare TiO2 NFs and Ag/AgBr/PVP (polyvinylpyrrolidone) NFs, the 1D Ag/AgBr/TiO2 NFs photocatalyst exhibits much higher photocatalytic activity in the degradation of a commonly used dye, methylene blue (MB), under visible light. The photocatalytic removal efficiency of MB over Ag/AgBr/TiO2 NFs achieves almost 100 % in 20 min. The photocatalytic reaction follows the first-order kinetics and the rate constant (k) for the degradation of MB by Ag/AgBr/TiO2 NFs is 5.2 times and 6.6 times that of Ag/AgBr/PVP NFs and TiO2 NFs, respectively. The enhanced photocatalytic activity is ascribed to the stronger visible light absorption, more effective separation of photogenerated electron-hole pairs, and faster charge transfer in the long nanofibrous structure. The Ag/AgBr/TiO2 NFs maintain a highly stable photocatalytic activity due to its good structural stability and the self-stability system of Ag/AgBr. The mechanisms for photocatalysis associated with Ag/AgBr/TiO2 NFs are proposed. The degradation of MB in the presence of scavengers reveals that h+ and •O− 2 significantly contribute to the degradation of MB. [ABSTRACT FROM AUTHOR]

Fischer-Tropsch synthesis (FTS), an important process for the production of liquid fuels and chemicals from syngas derived from coal and biomass, is receiving renewed interest for both industrial and academic applications. Adjusting the product distribution of hydrocarbons is the focus of research in this field. Herein, a novel carbon-encapsulated Fe3O4 nanocatalyst was synthesized by a simple one-step solvothermal method without calcination. The catalyst exhibited excellent catalytic activity and higher selectivity for C5-12 hydrocarbons (gasoline range products) than the traditional Fe2O3 catalyst. A 45.25 % C5-12 selectivity was obtained for Fe3O4@C, which is close to the maximum value from the Anderson-Schulz-Flory distribution. [ABSTRACT FROM AUTHOR]

The Al 2 O 3 –CeO 2 composite supported Ni catalyst was developed for synthetic natural gas (SNG) from bio-syngas methanation. The physico-chemical properties of the Ni-based catalysts were characterized by BET, H 2 -TPR, XRD, SEM and TG. The methanation tests showed that Ni/Al 2 O 3 –CeO 2 presented the highest methanation performances at low temperature (91.6% CO conversion with 92% CH 4 selectivity at 350 °C) compared with Ni/Al 2 O 3 , Ni/ZrO 2 and Ni/Al 2 O 3 –SiO 2 , etc. The characterization results indicated that combination of CeO 2 with Al 2 O 3 restrained the entering of Ni species into the inside, increasing the Ni species amounts and promoting the dispersion of NiO on the surface of Al 2 O 3 –CeO 2 . In addition, adding CeO 2 into Ni/Al 2 O 3 weakened the interaction of NiO–Al 2 O 3 via the strengthening of NiO–CeO 2 interaction, promoting the reduction of NiO and formation of active metallic Ni. All of these factors improved the catalytic activity for bio-syngas methanation to SNG and the resistance to carbon deposition for Ni/Al 2 O 3 –CeO 2 . [ABSTRACT FROM AUTHOR]