船厂滑道工程水下段施工技术

滑道工程分为陆地段和水下段,陆地段按常规法施工;而如何确保滑道工程水下段在水中施工的质量和安全,是本工程的重点和难点,也是我们研究探讨课题和所面临的风险挑战。

Analysis of Characteristics of Grazed Artificial Pastures in the South of Guizhou

＂Ryegrass, orchard grass, Festuca arundinacea and Trifolium repens＂ were researched in Dushan County, Guizhou Province, in order explore grass characteristics by different grazing methods in seasons. The results show that grass community height in different groups was of little differences（P0.05）; the group of moderate grazing in spring, summer and autumn dominated in grass cover; grass density showed insignificant variations among different treatment groups（P0.05） and in the groups of heavy grazing in spring and autumn and moderate grazing in summer and of moderate grazing in spring, summer and autumn, grass community density was higher compared with the other groups（P0.05）; as for above-ground biomass, the group of moderate grazing in spring and autumn and heavy grazing in summer and of moderate grazing in spring, summer and autumn dominated.

Long-term changes in wintertime persistent heavy rainfall over southern China contributed by the Madden-Julian Oscillation

During the boreal winter,abundant persistent heavy rainfall(PHR)amount and significant rainfall variability at subseasonal timescale are generally observed over the southern sector of East China,where the large-scale circulation and moisture transport are tightly connected with the equatorial Madden-Julian Oscillation(MJO).As the MJO convections occur over the equatorial Indian Ocean(MJO phases 1-4),the low-level moisture convergence is enhanced over southern China(SC,108°-120°E,21°-26°N)with the divergence to the north.Thus,a positive anomaly of PHR amount appears in SC but a negative anomaly of PHR amount is seen in the Yangtze River valley(YR,113°-122°E,28°-30°N).In contrast,the divergence(convergence)of moisture flux anomalies in the SC(YR)associated with the western equatorial Pacific MJO convections(phases 5-8)limits(benefits)the occurrence of PHR in the SC(YR).The wintertime PHR over southern China is found to undergo a long-term change over the past three decades(1979-2011)with a decreasing(an increasing)trend of PHR amount in the SC(YR).The change in PHR amount occurs consistently with the decadal change in MJO activity.In the earlier decade(1979-1994,E1),the active Indian Ocean(western Pacific)MJO events appeared more frequently while they became less frequent in the recent decade(1995-2011,E2).Accordingly,the Indian Ocean(western Pacific)MJO-related moisture convergence(divergence)anomalies in the SC tend to be weakened(enhanced),contributing to the decrease in PHR amount over the SC in the recent decade.

Super Typhoon Activity over the Western North Pacific and Its Relationship with ENSO

This paper analyzes the characteristics of super typhoons （STYs） over the western North Pacific （WNP） from 1965 to 2005 and describes the seasonal variability of STY activity. The relation between STY activity and the E1 Nifio-Southern Oscillation （ENSO） as well as the possible reason for the influence of the ENSO on STY activity are also investigated. The results showed that about one fifth of the tropical cyclones （TCs） over the WNP could reach the rank of STY. Most STYs appeared from July to November while there was a highest ratio between number of STYs and total number of TCs in November. Most STYs appeared east of the Philippine Sea. In E1 Nino years, affected by sea surface temperature （SST）, monsoon trough and weak vertical wind shear, TC formation locations shifted eastward and there were more STYs than in La Nifia years when the affecting factors changed.

Seasonal timing of stratospheric final warming associated with the intensity of stratospheric sudden warming in preceding winter

The association of seasonal timing of stratospheric final warming events(SFWs) in spring and the occurrence of major and minor stratospheric sudden warming events(SSWs) in midwinter were investigated through statistical analysis, parallel comparison, and composite analysis, based on the NCEP-NCAR reanalysis dataset covering 1958–2012. It was found that the intensity and occurrence of winter SSW events can largely affect the timing of spring SFWs. Specifically, the SFW onset dates tend to be later(earlier) after the occurrence(absence) of winter major SSWs. However, the occurrence or absence of minor SSWs does not change the frequency of early and late SFWs. A parallel comparison of the temporal evolution of the anomalous circulation and planetary-waves between major SSW and minor SSW winters indicates that the stratospheric polar vortex(polar jet) will keep being anomalously stronger 30 days after major SSW onset. And the associated significant negative Eliassen-Palm(EP) flux anomalies can persist for as long as 45 days after major SSW events. In contrast, the circulation anomalies around the occurrence of minor SSW events can last only a few days. To further verify the possible influence of the occurrence of major SSWs on the seasonal timing of SFWs, composite analysis was performed respectively for the 21 major-SSW years, 15 minor-SSW years, and the 15 non-SSW years. Generally, planetary-wave activity in the extratropical stratosphere tends to be stronger(weaker) and the westerly polar jet is anomalously weaker(stronger) in major-SSW(non-SSW) winters. But in the following spring, the planetary-wave activity is weaker(stronger) accompanied with an anomalously stronger(weaker) stratospheric polar vortex. In spring after minor-SSW years, however, the stratospheric polar vortex and the westerly polar jet exhibit a state close to climatology with relatively gentle variations.

Seasonal dynamic variation of pollination network is associated with the number of species in flower in an oceanic island community

Aims Plant-pollinator interaction networks are dynamic entities,and seasonal variation in plant phenology can reshape their structure on both short and long timescales.However,such seasonal dynamics are rarely considered,especially for oceanic island pollination networks.Here,we assess changes in the temporal dynamics of plant-pollinator interactions in response to seasonal variation in floral resource richness in oceanic island communities.Methods We evaluated seasonal variations of pollination networks in the Yongxing Island community.Four temporal qualitative pollination networks were analyzed using plant-pollinator interaction data of the four seasons.We collected data on plant-pollinator interactions during two consecutive months in each of the four seasons.Four network-level indices were calculated to characterize the overall structure of the networks.Statistical analyses of community dissimilarity were used to compare this community across four seasons to explore the underlying factors driving these patterns.We also evaluated the temporal variation in two species-level indices of plant and pollinator functional groups.Important Findings Both network-level specialization and modularity showed a significantly opposite trend compared with plant species richness across four seasons.Increased numbers of plant species might promote greater competition among pollinators,leading to increased niche overlap and causing decreased specialization and modularity and vice versa.Further analyses suggested that the season-to-season turnover of interactions was dominated by interaction rewiring.Thus,the seasonal changes in niche overlap among pollinators lead to interaction rewiring,which drives interaction turnover in this community.Hawkmoths had higher values of specialization and Apidae had higher values of species strength compared with other pollinator functional groups.These findings should be considered when exploring plant-pollinator interactions in ecosystems of isolated oceanic islands and in other ecosystems.