ALBERT

Description: ABSTRACT Spatiotemporal patterns of precipitation regimes in terms of precipitation amount and number of precipitation days at different time scales are investigated using the entropy-based methodologies in the Huai River basin, China. Trends of precipitation variability are quantitatively evaluated using the modified Mann–Kendall trend test method. Correlations between the largest 7-day precipitation amount (R × 7day) and precipitation variability within 1 year are also analysed. Results indicate the following: (1) there is increasing nonuniformity of annual precipitation amount and annual precipitation days from south to north in the Huai River basin, indicating larger precipitation variability in the northern parts. Transition of precipitation changes is evident in the basin which is reflected by decreasing precipitation variability in the north and increasing precipitation variability in the south. (2) The disorder indices (DIs) exhibit variations at different time scales. In general, precipitation variability is larger at shorter time scales, such as daily, and is smaller at longer time scales, such as annual. (3) Significant relations are identified between the DI and extreme precipitation events, i.e. significant relations between apportionment DI and the largest 7-day precipitation amount and it is particularly the case in the central and southwestern parts. Thus, it can be said that higher precipitation variability is due to higher frequency of extreme precipitation regimes. Results of this study are of practical significance for planning and management of water resources and agricultural irrigation and agricultural activities during climate change and particularly for enhancement of measures for mitigation of consequences of climate change.

Description: Dense (97.3%) zirconium diboride (ZrB 2 ) ceramics were obtained via gelcasting and pressureless sintering. Four wt% B 4 C was used as sintering aid. ZrB 2 , SiC, and B 4 C can codisperse well in the alkaline region, using a polyacrylate dispersant. Compared with monolithic ZrB 2 (Z), the mechanical properties of ZrB 2 -SiC (ZS) were enhanced. The Vickers hardness and fracture toughness of ZS were (13.1 ± 0.6) GPa and (2.5 ± 0.4) MPa m 1/2 , respectively.

Description: The dispersion of highly concentrated Zirconium diboride ( ZrB 2 ) suspension in aqueous media was investigated in terms of zeta potential and rheological measurements, with a salt of polyacrylate polymer (SD-07) as dispersant. The adsorption behavior of SD-07 on ZrB 2 particle surface was also studied. Results showed that acid cleaning improved the fluidity of aqueous ZrB 2 slurry. Concentrated (up to 50 vol%) and well-stabilized suspension was obtained in the alkaline pH region, with 0.60 mg/m 2 SD-07. On this basis, 50 vol% ZrB 2 gelcasting slurry was prepared. The linear shrinkage and flexural strength of as-casted green body were (3.42 ± 0.13)% and (9.4 ± 0.3) MPa, respectively.

Description: [1]  The 10-30 day extended range potential predictability of the BCC_AGCM2.1 model with high horizontal resolution has been evaluated and the associated influencing factors and possible physical mechanisms have been discussed through a case study of the long lasting extreme snow storms over southern China in early 2008. Comparison with meteorological observations suggests that the BCC_AGCM2.1 model forced by the real daily SST well reproduced the extraordinarily frequent and long lasting heavy snow storm process over southern China in early 2008 including the spatial distribution and temporal evolution of the 2 m air temperature and snow rainfall but produced relatively larger errors in precipitation. Overall, the BCC-AGCM2.1 model forced by the real daily SST shows good potential predictability on 10-30 day extended range time scale to some extent, at least from this extreme snow storm case study. Further analysis of the associated influencing factors and possible physical mechanisms indicates that the SST forcing is not as important as the initial conditions for the weather forecast within around 2 weeks in advance which is the upper limit of the daily weather forecast. However, the SST forcing with relatively larger day to day variability plays an important role in the potential predictability of the BCC_AGCM2.1 model on 10-30 day extended forecasting time scale through affecting the atmospheric variability. Results from this study provide us some necessary and valuable information for further development of an operational 10-30 day extended range forecasting system.

Description: Previous studies have demonstrated that denitrification rates are low in subtropical forest soils. However, the mechanisms governing this process are not well known. This study seeks to identify the mechanisms responsible for the low denitrification capacity and high nitrogen oxide gas ratio in subtropical forest soils in China. The denitrification capacity and nitric oxide (NO), nitrous oxide (N 2 O), and dinitrogen (N 2 ) emission rates were measured using the acetylene-inhibition method under conditions of added nitrate and anoxia. The abundance of nitrate reductase ( narG ), nitrite reductase ( nirK ), nitric oxide reductase ( cnorB ) and nitrous oxide reductase ( nosZ ) were measured using real-time, quantitative PCR, and sequencing of the nirK and norB products was performed to analyze the population structure of denitrifying bacteria. These results showed that the denitrification capacity in subtropical forest soils was lower than in temperate forest soils (p 〈 0.05). Multiple regression analysis showed that redox potential at the start of incubation (Eh i ), rather than soil pH or soil organic C, was the key soil variable influencing denitrification, and Eh i alone could explain 68% of the variations in denitrification capacity. The high Eh i in subtropical soils led to a low abundance of nir K and significant differences in the population structure of denitrifying bacteria between subtropical and temperate soils. Therefore, Eh i was responsible for the low denitrification capacity in subtropical forest soils. The ratio of NO to total denitrification gas products (p 〈 0.01) and the ratio of NO and N 2 O to total denitrification gas products (p 〈 0.05) were significantly higher in subtropical forest soils than in temperate forest soils, while the reverse trend was observed for the ratio of N 2 to total denitrification gas products (p 〈 0.05). A high Eh i reduced the specific reduction activity of each nosZ copy, and, in turn, resulted in a large ratio of NO and N 2 O to total denitrification gas products in subtropical soils. Thus, NO and N 2 O, but not N 2 , were the dominant denitrification gas products, accounting for 80%, even under the highly anaerobic conditions in subtropical forest soils and despite low denitrification capacity. These results were significant for understanding the “Hole in the Pipe” model and NO and N 2 O gases emission in subtropical forest soils. Despite the fact that the nitrogen flowing through the pipe (denitrification capacity) was low, the large holes in the pipe resulted in a large quantity of NO and N 2 O gases leaking out. This leakage may be a potential mechanism for the high levels of NO and N 2 O gase emission in subtropical forest soils and could partly explain why NO and N 2 O emissions are generally high in subtropical and tropical soils.

Description: With the highest population density in China, eastern China has an unshakable position in Chinese socioeconomic development. To understand the precipitation changes and the related mechanisms are of great significance for regional management of water resources and agricultural irrigation. In this study, the impacts of western north Pacific subtropical high (WNPSH) on precipitation changes in eastern China and the underlying processes are investigated. The results indicate that the strength and location of WNPSH are in close relations with the changes of summer precipitation in eastern China, and their influences vary across both space and time. In particular, WNPSH exerts remarkable impacts on precipitation in June and July in Jiang-Huai region and precipitation in June in South China such as the Pearl River basin. The inter-annual variations of WNPSH exhibit significant correlations with water vapor flux in East Asia, and the variations of the location and direction of west flank of WNPSH are well corroborated that influences of East Asian Summer Monsoon (EASM) on precipitation in eastern China. The westward extension of WNPSH tends to favor the strong moisture transport to East Asia, intensify the EASM and thus increasing water vapor flux in East Asia, which greatly benefits the occurrence of Meiyu regimes in Jiang-Huai region. Besides, analysis results also show that the westward extension of WNPSH drives tropical cyclones sourthwards so as to increase the occurrence of extreme precipitation in South China. This study helps to bridge the knowledge gap in the relationship between WNPSH, tropical cyclones, summer precipitation events in eastern China.

Description: Aurivillius single-phase Bi 4 Ti 2.5 Fe 0.25 Ta 0.25 O 12 ceramics was prepared via high-temperature solid-state reaction method. The detailed structural analysis of the doped Bi 4 Ti 3 O 12 compound was carried out by Rietveld refinement of the full XRD Pattern. Dielectric and electrical properties were studied in a wide range of temperature and frequency by dielectric/impedance spectroscopies. The comprehensive analysis of frequency spectrum reveals the occurrence of two relaxation behaviors in the ceramics at low frequency and high frequency, respectively. A phase transition was observed at ~650°C in Bi 4 Ti 2.5 Fe 0.25 Ta 0.25 O 12 somewhat lower than the ferroelectric transition temperature of Bi 4 Ti 3 O 12 . The possible reason for the decrease of ferroelectric transition temperature was discussed based on the structural analysis. The present results could be useful for designing and/or modifying properties of Bi 4 Ti 3 O 12 -related ceramics.