湿地功能快速评价中的若干理论问题

针对目前湿地功能快速评价中存在的不足之处,分析了产生这些不足的原因及湿地功能快速评价过程中存在的一些基本理论问题。分析表明:湿地功能快速评价方法是为了达到“湿地功能无净损失”目的,是在需要评价的湿地如此之多而从事湿地功能评价的专业人员又极其缺乏的情况下发展起来的。它对于湿地恢复与重建以及湿地受人类活动干扰程度的评价是非常有效的;在湿地功能快速评价过程中,把相对未受人类干扰的参照湿地的功能指数规定为1,这就使得快速评价方法不能对参照湿地的功能进行评价,而目前最需要评价其功能的湿地往往就是这些相对未受人类活动干扰的湿地;在相同水文地貌的湿地类型内评价湿地功能之间的差异,这使得快速评价方法不能评价湿地的水文地貌功能;由于快速评价的结果都是相对的功能指数,并不能说明湿地所提供的功能量是否满足人们的需求,因而在决策中不能单独使用;快速评价都是“一次调查就获得结果”,同时由于快速评价过程中指标选择的主观性、指标赋值的主观性、采样点空间设置的主观性以及采样时间的主观性,对于具有时空变化特征的湿地功能的评价结果的可重复性和科学性是很低的。为了使湿地功能评价的结果对管理和决策具有指导意义,基于湿地功能量计算的、定量的评价湿地功能的方法必须开发出来。针对不同的评价目的,湿地功能评价可采用双重参照标准:一是以自然为参照来评价湿地功能受人类活动影响的程度以及湿地恢复与重建成功与否;二是以人类需要为标准来评价湿地提供的功能量是否满足了我们的期望,以便采取措施改进湿地功能来满足人类的需求。     

Nitrification in Kochi backwaters

Nitrification rates, as oxidation of ¹⁵N-labelled ammonium and loss of nitrite from N-Serve treated samples, were measured in Kochi backwaters during three seasons. Nitrification rates ranged from undetectable to 166 nmol N L⁻¹ h⁻¹ in the water column and up to 17 nmol N (g wet wt)⁻¹ h⁻¹ in sediments. Nitrification rates were higher in intermediate salinities than in either freshwater or seawater end. Within this salinity range, nitrification rates could be related to ammonium concentrations. As shown by the relation between ammonification and nitrification rates, it is also likely that nitrification is more regulated by renewal rates, rather than by in situ concentrations, of substrate. Among other environmental parameters, temperature and pH may have an influence on nitrification. Potential nitrification rates calculated from loss of nitrite from N-Serve treated, nitrite-enriched samples were about 800 nmol N L⁻¹ h⁻¹ in the water column and 40 nmol N (g wet wt)⁻¹ h⁻¹ in sediments. While these rates are in balance with those of biological ammonium production they may be inadequate to mitigate ammonium pollution in this estuary.     

1996年上半年世界地震灾害综述

１９９６年上半年全世界共发生６级以上地震５８次，其中７级以上地震１０次，成灾的地震１０次，死亡人数总５１０人，伤约１．５万人，经济损失为８３亿－１００亿元人民币。其中我国境内灾害地震３次，死亡人数共计３４９人，伤约１．４５万人，经济损失约７８亿元人民币。我国因地震死亡的总人数约占全世界地震     

On the acceleration of solar-flare charged particles in a collapsing magnetic trap with an electric potential

We consider the kinetic problem of charged-particle acceleration in a magnetic trap with converging magnetic mirrors. We show that for a positive electrostatic potential of the trap plasma relative to the mirrors, the efficiency of confinement and acceleration increases for electrons and decreases for ions.     

A quantitative analysis of the prototype [WCL] star CPD-56° 8032

We present a detailed, quantitative study of the standard [WC10] Wolf-Rayet central star CPD-56^o 8032 based on new high resolution AAT UCLES observations and the Hillier (1990) WR standard model. Our analysis of CPD-56^o 8032 gives the wind properties (T _*=34500K, lg (L/L )=3.8, lg (M/M a^–1)=–5.4,v =225 km s^–1) and chemistry (C/He=0.5, O/He=0.1, by number), the latter suggesting an intimate relationship with the Ovi PN central stars and the PG 1159-035 objects. A comparison between the wind properties of CPD-56^o 8032 and Sk-66^o 40 (WN 10) indicates that low excitation, low wind velocity WR winds are common to both low mass PN central stars (WC sequence) and high mass post-LBV's (WN sequence).     

ROSAT HRI observations of P Cyg and surrounding area

We present a detailed analysis of deep ROSAT HRI observations of the luminous blue variable P Cyg and its surrounding radio nebula. The HRI image provides a point source at the position of P Cyg. However, we show that this emission can be attributed to the ultraviolet leak of the ROSAT HRI. The X‐ray flux upper limit derived from the HRI data of this star is discussed in the context of X‐ray emission from hot stars. Furthermore, we present a search for diffuse X‐ray emission possibly associated with the radio nebula surrounding P Cyg. We compare our results to model predictions and X‐ray fluxes observed for shells around other hot stars. Additionally, we detect 10 X‐ray sources in the field of view. All but one of these X‐ray emitters have stellar counter parts in the Palomar Sky Survey. We suggest that they are active late‐type stars possibly belonging to Cyg OB1.     

Infrared photometry of AGB stars

The goal of this article is to show that, if one avoids star forming regions, mass-losing AGB stars can generally be selected from the data that will be provided by the near-infrared surveys which are presently considered. Also, if IRAS data are available, the separation between carbon-rich and oxygen-rich stars can be operated by their positions in infrared colour diagrams. In extragalactic systems, red supergiants can be discriminated from AGB stars by their luminosities.based on observations obtained with the ESO 1-m telescope     

Some integrable cases of the two-body problem with mass depending both on time and distance

an extension of the Gylden-Meshcherskii problem when the mass depends both on time and distance between two bodies is considered. certain mass loss laws as well as the Meshcherskii position vector and time transformation are used to convert the problem into the cases with equations of motion arising from integrable potentials.     

Energy losses in compound open channels

This paper investigates energy losses in compound channel under non-uniform flow conditions. Using the first law of thermodynamics, the concepts of energy loss and head loss are first distinguished. They are found to be different within one sub-section (main channel or floodplain). Experimental measurements of the head within the main channel and the floodplain are then analyzed for geometries with constant or variable channel width. Results show that head loss differs from one sub-section to another: the classical 1D hypothesis of unique head loss gradient appears to be erroneous. Using a model that couple 1D momentum equations, called “Independent Sub-sections Method (ISM)”, head losses are resolved. The relative weights of head losses related to bed friction, turbulent exchanges and mass transfers between sub-sections are estimated. It is shown that water level and the discharge distribution across the channel are influenced by turbulent exchanges for (a) developing flows in straight channels, but only when the flow tends to uniformity; (b) flows in skewed floodplains and symmetrical converging floodplains for small relative flow depth; (c) flows in symmetrical diverging floodplains for small and medium relative depth. Flow parameters are influenced by the momentum flux due to mass exchanges in all non-prismatic geometries for small and medium relative depth, while this flux is negligible for developing flows in straight geometry. The role of an explicit modeling of mass conservation between sub-sections is eventually investigated.