Change of groundwater chemistry from 1896 to present in the Mid-Levels area, Hong Kong   总被引：1，自引：0，他引：1  

Chi-man Leung  Jiu Jimmy Jiao 《Environmental Geology》2006,49(7):946-959

In this study, groundwater quality information collected in 1896 (well waters), 1980/1981 (piezometric and seepage samples) and 2002/2003 (seepage samples) in the regions centered by the Mid-Levels area, Hong Kong Island, was compared to illustrate how groundwater quality has changed over a century and the processes controlling it. As shown by saline ammonia and nitrate levels in the late nineteenth century, groundwater was severely polluted by widespread and obvious leakage from poorly designed wastewater collection systems, although groundwater was still a drinking water source for local residents. The extremely high residual chlorines in groundwater demonstrated that large doses of disinfection agents were added to wells at that time. In view of the decline in saline ammonia and nitrate levels, groundwater became less organically polluted in the 1980s probably due to significant improvement of the design of underground sewers. However, more leakage from sources such as salty flushing water and fresh water pipes emerged in the past few decades which added complexity to groundwater chemical systems. Some chemicals were used to identify possible locations of leakages. The temporal variations of the distribution of these chemicals over the area may shed light on the rate of leakage. Leakage from service pipes seems to have improved from the early 1980s to 2002/2003. However, the area is still suffering from widespread and small-scale leakage from service pipes. More efforts should be paid to control small leakages in the future. The findings will be instructive to various government organizations such as the Water Supplies Department and Drainage Services Department to identify possible locations of unobvious leakages in the area.  相似文献   

Simple model for transient soil loading in earthquake analysis. II. Non-associative models for sands     

M. Pastor  O. C. Zienkiewicz  K. H. Leung 《国际地质力学数值与分析法杂志》1985,9(5):477-498

This paper extends the bounding surface, generalized plasticity, model of Part I to reproduce the behaviour of sands under both static and transient loading. The essential features of the first model are preserved but the following changes are introduced:

• (i) The shape of the yield surface is modified.
• (ii) A non-associative flow rule is introduced.
• (iii) The hardening parameter of the bounding surface includes not only volumetric but also deviatoric plastic strain.
• (iv) Plastic volumetric and deviatoric strains are introduced during unloading.

Each of these modifications can be introduced separately in a hierarchical manner to model in an improved way the behaviour of sands. Good comparison with experimental observations is recorded. The simplicity of the original model is preserved with modifications being introduced progressively to model rising complexity of the phenomena.  相似文献   

Spreadsheets for the Analysis of Aquifer-Test and Slug-Test Data     

Jiu Jimmy Jiao  Chi-man Leung 《Ground water》2003,41(1):9-10

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Structural vibration control by shape memory alloy damper     

Yu‐Lin Han  Q. S. Li  Ai‐Qun Li  A. Y. T. Leung  Ping‐Hua Lin 《地震工程与结构动力学》2003,32(3):483-494

A damper device based on shape memory alloy (SMA) wires is developed for structural control implementation. The design procedures of the SMA damper are presented. As a case study, eight such SMA dampers are installed in a frame structure to verify the effectiveness of the damper devices. Experimental results show that vibration decay of the SMA damper controlled frame is much faster than that of the uncontrolled frame. The finite‐element method is adopted to conduct the free and forced vibration analysis of the controlled and uncontrolled frame. The experimental and numerical results illustrate that the developed SMA dampers are very effective in reducing structural response and have great potential for use as efficient energy dissipation devices with the advantages of good control of force and no lifetime limits, etc. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

Effects of heavy metals on the survival and feeding behaviour of the sandy shore scavenging gastropod Nassarius festivus (Powys)     

S. G. Cheung  K. K. Tai  C. K. Leung  Y. M. Siu 《Marine pollution bulletin》2002,45(1-12)

The effects of Cu, Cd, Zn and Cr on the survival and feeding behaviour of the sandy shore scavenging gastropod Nassarius festivus were compared. The 96-h LC₅₀ for Cu, Cd, Zn and Cr were 0.36, 1.52, 1.76 and 36.9 mg l⁻¹, respectively. Four sublethal concentrations of each metal plus a control were prepared and the snails were exposed to experimental solutions for 96 h. Feeding behaviour was studied after the snails were starved for five days. As compared with the control, the number of individuals feeding was significantly reduced by exposure to 0.05 mg l⁻¹ Cu, 0.2 mg l⁻¹ Zn, 0.5 mg l⁻¹ Cd and 5 mg l⁻¹ Cr. The time spent feeding was greater for individuals exposed to greater concentrations of Zn and Cd but no effect was found for Cu and Cr. Chemoreception of food was studied by placing the snails at a fixed distance of 15 cm from the bait. The success rate of reaching the bait was less for individuals exposed to Cr but no effect was found for Zn, Cu or Cd. The time required for an individual to reach the bait decreased as the concentration of Zn increased. In contrast, a longer time was required for individuals exposed to Cr whereas the effect of Cd and Cu was insignificant. The potential of using feeding behaviour and chemoreception in contaminant evaluations is discussed.  相似文献   

Elevation Dependence of Winter Wheat Production in Eastern Washington State with Climate Change: A Methodological Study     

Allison M. Thomson  Robert A. Brown  Steven J. Ghan  R. Cesar Izaurralde  Norman J. Rosenberg  L. Ruby Leung 《Climatic change》2002,54(1-2):141-164

Crop growth models, used in climate change impact assessments to project production on a local scale, can obtain the daily weather information to drive them from models of the Earth's climate. General Circulation Models (GCMs), often used for this purpose, provide weather information for the entire globe but often cannot depict details of regional climates especially where complex topography plays an important role in weather patterns. The U.S. Pacific Northwest is an important wheat growing region where climate patterns are difficult to resolve with a coarse scale GCM. Here, we use the PNNL Regional Climate Model (RCM) which uses a sub-grid parameterization to resolve the complex topography and simulate meteorology to drive the Erosion Productivity Impact Calculator (EPIC) crop model. The climate scenarios were extracted from the PNNL-RCM baseline and 2 × CO₂ simulationsfor each of sixteen 90 km² grid cells of the RCM, with differentiation byelevation and without correction for climate biases. The dominant agricultural soil type and farm management practices were established for each grid cell. Using these climate and management data in EPIC, we simulated winter wheat production in eastern Washington for current climate conditions (baseline) and a 2 × CO₂ `greenhouse' scenario of climate change.Dryland wheat yields for the baseline climate averaged 4.52 Mg ha^–1 across the study region. Yields were zero at high elevations where temperatures were too low to allow the crops to mature. The highest yields (7.32 Mgha^–1) occurred at intermediate elevations with sufficientprecipitation and mild temperatures. Mean yield of dryland winter wheat increased to 5.45 Mg ha^–1 for the 2 × CO₂ climate, which wasmarkedly warmer and wetter. Simulated yields of irrigated wheat were generally higher than dryland yields and followed the same pattern but were, of course, less sensitive to increases in precipitation. Increases in dryland and irrigated wheat yields were due, principally, to decreases in the frequency of temperature and water stress. This study shows that the elevation of a farm is a more important determinant of yield than farm location in eastern Washington and that climate changes would affect wheat yields at all farms in the study.  相似文献   

LOCATIONAL CHARACTERISTICS OF FOREIGN EQUITY JOINT VENTURE INVESTMENT IN CHINA, 1979–1985     

Chi Kin Leung 《The Professional geographer》1990,42(4):403-421

An examination of the locational characteristics of intended foreign equity joint venture (EJV) investment in China during the period 1979 to 1985 indicates that foreign EJV investment was highly concentrated in the coastal region, in the more developed areas of the provinces, and in large cities. The locational characteristics, however, differed between economic sectors and between countries of origin of investment. Although foreign EJV investment became spatially more dispersed through time, the impacts on the development of inland regions and backward areas in China remained limited.  相似文献   

A Photometry Campaign for IR Geminorum in Quiescence     

Kam-Ching Leung  C.Martin Gaskell 《中国天文和天体物理学报》2004,4(1):88-96

We report a V band photometry of the SU UMa star IR Gem at quiescence in January 2002. The observations were made with two telescopes spaced - 160° apart in longitude. Several photometric modulations have been found. One gives a period of 98.50(13) min, exactly equal to the orbital period determined spectroscopically. Two others occasionally strengthen and seem to be positive and negative superhumps with periods of 103.6(4) and 95.4(4) min, 5.2% longer and 3.1% shorter than the orbital period, respectively. A signal at - 0.6 c/d in the power spectrum is roughly consistent with the expected period of nodal precession of the disk. There is a puzzling peak at 0.21(3) c/d corresponding to the - 4.3 d sine wave seen in the raw light curve. We suspect it to be a beat frequency between the frequencies of apsidal and nodal precessions of the disk. Quasi-periodic cycles with amplitudes 0.15-0.6 mag can be seen in the light curve. The mechanism underlying this modulation is not clear.  相似文献   

The de-correlation of westerly winds and westerly-wind stress over the Southern Ocean during the Last Glacial Maximum     

Wei Liu  Jian Lu  L. Ruby Leung  Shang-Ping Xie  Zhengyu Liu  Jiang Zhu 《Climate Dynamics》2015,45(11-12):3157-3168

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Eddy fluxes and sensitivity of the water cycle to spatial resolution in idealized regional aquaplanet model simulations     

Samson Hagos  L. Ruby Leung  William I. Gustafson Jr.  Balwinder Singh 《Climate Dynamics》2014,42(3-4):931-940

A multi-scale moisture budget analysis is used to identify the mechanisms responsible for the sensitivity of the water cycle to spatial resolution using idealized regional aquaplanet simulations. In the higher resolution simulations, moisture transport by eddy fluxes dry the boundary layer enhancing evaporation and precipitation. This effect of eddies, which is underestimated by the physics parameterizations in the low-resolution simulations, is found to be responsible for the sensitivity of the water cycle both directly, and through its upscale effects on the transport of mean moisture by the mean circulation. Correlations among moisture transport by eddies at adjacent ranges of scales provides a potential for reducing this sensitivity by representing the unresolved eddies by their marginally resolved counterparts.  相似文献