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991.
以Lewis酸碱理论为基础发展起来的酸碱软硬度的理论广泛地应用于解释各类化学现象,包括类质同象置换,共生,应用于评价和预测化学反应极为简便和实用。然而,软硬酸碱度原理的理论基础尚在不断地充实之中。本文简要讨论了硫化物矿物的酸碱势标度,用酸碱软硬度理论解释了矿物的类质同象现象,是应用酸碱软硬度理论揭示和完善矿物成矿理论的一种偿试。 相似文献
992.
INTRODUCTIONCiliates,alwaysdominatingalltheprotozoans,arethecommonandimportantmembersoffreshwaterzooplanktoncommunities.Asmainconsumersofbacteria,picoplanktonandnannoplankton(Finlay,1978;Porteretal.,1985;Taylor,1984,1987;Simeketal.,1996)compriseanimportanttrophiclinka… 相似文献
993.
Effects of algal concentration and initial density on the population growth of Diaphanosoma celebensis Stingelin (Crustacea, Cladocera) 总被引:1,自引:0,他引:1
The effects of algal concentration and initial density on the population growth of the estuarine cladocera,Diaphanosoma celebensis Stingelin,were evaluated in an indoor experiment.A 2 × 4 layout that included two algal concentrations(Chlorella pyrenoidosa,1 × 106 and 3 × 106 cell/mL) and four inoculation densities(100,200,300 and 400 ind./L) were established.Diaphanosoma celebensis were reared in 150 mL flasks containing 50 mL of algal medium at 22°C,under salinity of 10 and a photoperiod of 12 h L:12 h D.T... 相似文献
994.
Morphodynamic modelling of open-sea tidal channels eroded into a sandy seabed, with reference to the channel systems on the China coast 总被引:3,自引:0,他引:3
In this contribution, the morphodynamics of open-sea tidal channels eroded into sandy seabed in regions of flow constriction
is simulated by a one-dimensional model using the Bagnold formula for bedload transport rate, and accounting for the effect
of bed slope. The results show that equilibrium conditions for such channels can be reached over a period of 102–103 years. Sediment eroded from the channel floor is transported in the direction of the dominant current, and deposited beyond
the regions of flow constriction where the current looses competence due to spreading. In this way, the material remobilized
from older strata in the channels is deposited in younger sand banks near the channel heads. Where several successive channels
are incised along the current axis, they interact in their morphological evolution. The morphodynamic equilibrium of a tidal
channel is reached once the combined interacting sedimentological and hydrodynamic factors, such as sediment particle diameter,
tidal current velocity and flood/ebb dominance, are balanced. The model output shows that the equilibrium shape of the tidal
channels appears to be related mainly to flow field characteristics and, to a lesser extent, to particle size. A positive
correlation exists between the depth of the channels and their response times. The equilibrium water depths of the channels
are more sensitive to current speed than to either particle size or the time–velocity asymmetry of the flow field. The response
times for overall morphological equilibrium are sensitive to all of the above-mentioned parameters. In particular, sediment
characteristics associated with critical current velocities have far-reaching effects on the morphodynamic behaviour of tidal
channels. 相似文献
995.
The governing equations for one‐dimensional consolidation of layered structured soils under time‐dependent loading are established. Using simplified k‐σ′ and mv‐σ′ models, n‐layered structured soils are transformed into (n + 1) or (n + 2)‐layered soils in which the thickness of upper and lower layers are gradually changing. The approximate solutions for the governing equations are then obtained under two types of boundary conditions, and the computer program is developed. Based on the solutions and computer program, the consolidation behavior of layered structured soils with soft interlayer is studied. It is shown that the permeability and compressibility of the soft interlayer have the greatest influences on the rate of settlement and rate of the dissipation of excess pore water pressure. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
996.
Fish sonars have long been used to survey and monitor migratory salmon in rivers and at sea. However, research has been lacking in the development of algorithms to extract fish tracks from data collected in a riverine or oceanic environment. Current fish trackers, based on a pulse-to-pulse tracking method, only work well under ideal conditions when targets are well separated and the signal-to-noise ratio is high. Fisheries biologists often have to identify fish traces visually from raw echograms. This approach is both labor-intensive and time-consuming, limiting the usefulness of hydroacoustic techniques for fisheries management. This paper presents a fish-tracking algorithm which sorts randomly distributed echoes into coherent fish traces. Fish counts obtained with the algorithm compare well with visual counts at two quite different sites in the Fraser River watershed. The key features of the algorithm are: (1) the linking mechanisms among sequential fish echoes are range-dependent; (2) the growth echo for a developing track depends not only on its space-time relation with the previous track echo (the pulse-to-pulse statistics) but also on its relation to the entire track being constructed; (3) there are a total of only five echo-association criteria in the algorithm; (4) the simplicity of the algorithm structure provides a convenient platform for implementing specific and sophisticated tracking criteria to meet specific needs; and (5) the user can fully control the performance of the algorithm by choosing values for the 11 well-defined tracking parameters 相似文献
997.
GRV 90027 is a Martian lherzolitic shergottites (L-S) containing poikilitic, non-poikilitic, and melted pocket components. GRV 99027 is mainly composed of olive (55 vol%) and pyroxene (37.5 vol%), with minor maskelynite (6 vol%) and chromite (1.5 vol%), and trace whitelockite and troilite, ect. In this paper, the mineralogy and petrology of GRV 99027 are reported; in addition, the geochemical characteristics of the REEs and H isotopes in the GRV 99027 are also further investigated. The ΣREE in GRV 99027 is relatively low; HREEs are enriched in olivine and pyroxene grains; LREEs are enriched in plagioclase with a high positive Eu anomaly. High ΣREE value is found in rare mineral whitlockite (less than 0.2 vol%), LREE≈HREE, and whitlockite has a negative Eu anomaly. The REE distribution patterns of the whole -rock of GRV 99027 is similar to but different from that of other L-S Martian meteorites, indicating that they came from different location of Mars. GRV 99027 has a high δD value. Different water-bearing minerals give different contribution for δD value. The δD of phosphates generally does not correlate with water content, and δD has a weak negative correlation with water content. GRV 99027 can be classified as an L-S Martian meteorite based on mineralogical assemblage patterns, REE distribution patterns, and hydrogen isotope. The isotope data of Sr, Nd, Pb, Os and REE from other L-S Martian meteorites were collected to discuss the formation history of the GRV 99027. Similar to other L-S Martian meteorites, GRV 99027 originated from part of Mar's mantle; during one strong impact event about 4M years ago, the meteorites were ejected from deep mantle into space, and traveled for a different duration in space (indicated by different cosmic exposure time), and captured by the Earth later in different time, ultimately falling on the Antarctica as L-S Martian meteorites. 相似文献
998.
Preparation by enzymolysis and bioactivity of iron complex of fish protein hydrolysate (Fe-FPH)from low value fish 总被引:6,自引:0,他引:6
Preparation of Fe^2+ chelate of fish protein hydrolysate (Fe-FPH) obtained from low value fish proteins was introduced and its bioactivity was studied by compound enzymolysis. The optimum conditions for hydrolysate chelating Fe^2+ are DH (degree of hydrolysis) at 5%, pH 7.0, 20℃ and 15 min chelating time for FM (material not being defatted). Four types of Fe-FPH including CA (deposit after chelating), CB (deposit in 50% of absolute ethanol solution), CC (suspended deposit in 80% of absolute ethanol solution), and CD (bottom deposit in 80% of absolute ethanol solution) were fractionated with absolute ethanol from FM. Structural analysis through infra-red spectrum revealed that Fe^2+ was combined strongly with amino-group and carboxyl-group in each chelate and each Fe^2+ could form two five-member ring structures. All of the four chelates were shown more significant antioxidative activity and can be used as natural hydrophobic and hydrophilic antioxidant. Among all the chelates, the CB possesses the most effective antioxidative activity at 92% as high as that of a-tocopherol. Among all Fe-FPHs, only CD showed the most effective antibacterial activity against Escherichia coli, Staphylococcus aureus, Salmonella typhi, and Bacillus subtilis and can be used as natural antibacterial. It provides a more effective way for utilization of low value fish proteins and key information of Fe-FPH as additive in food industry. 相似文献
999.
This article discusses how the Chinese seafood industry will affect the rest of the world's fishing industries. The analysis is based on theories of economic comparative advantage, the international division of labour and the internationalization process related to trade activities. Given the increasing domestic demand for fish in China, the limited availability of domestic fish stocks and less success for farmed marine fish in China are considered some of the most important factors in restricting the growth in Chinese seafood production. The necessity of raw fish imports into China may increase pressure on global fish stocks and international fish prices, resulting in tighter supplies worldwide and higher seafood prices for the Chinese. Sustainable fish harvests and trade require stronger fishery management, in particular in the relations between seafood companies and governments along the entire international value chain supplying China. Such structural changes may allow new value-added possibilities for fish farming and the upgrading of certain fish species for human consumption that were previously utilized purely for fish feed. 相似文献
1000.
应用GPS数据确定法和地震矩率法计算了川滇南部主要活动断裂分段特征地震复发间隔,在此基础上,运用实时概率模型计算了各条断裂未来10年、30年、50年、100年的发震概率.结果表明,川滇南部未来百年特征地震复发的可能性按概率值大小依次为:安宁河断裂带小相岭段,小江断裂东川段,安宁河断裂带冕宁西昌段,则木河断裂带,丽江-小金河断裂丽江宁蒗段,小江断裂带华宁段,小江断裂带嵩明宜良段和红河断裂带北西段. 相似文献