排序方式： 共有30条查询结果，搜索用时 15 毫秒
11.
The Red River drains 242000 km2 with 90% of this area being downstream of discharges from naturally occurring brine seeps and springs. The upstream area
has been designated as a major chloride emission area in Texas and Oklahoma. Ten major brine source emission areas along the
tributaries to the Red River were identified by U.S. Public Health Service and U.S. Army Corps of Engineers. Eight of these
areas were deemed suitable for the control of brine emissions by structural methods including a ring dike to enclose brine
springs; low flow dams to capture and divert stream flows with high chloride content to evaporation lakes; and shallow aquifer
brine collection wells with a deep-well disposal system. Two adjacent emission areas, designated as Areas XIII and XIV, contribute
500 metric tons of salt per day to the Red River. These areas, along Jonah Creek and Salt Creek, tributaries to the Prairie
Dog Town Fork of the Red River were selected for investigation to control brine emission by utilization of shallow collection
wells and disposal by deep injection wells. Drilling programs and pumping tests were performed to determine the number and
location of shallow collection wells. Eighteen wells with 12 operating full time, will be located in the primary emission
areas. The collected brine will be conveyed through corrosion-resistant pipelines to a treatment facility for filtration at
a rate of 300 l/s. Additional pipelines will convey the filtered brine to deep injection wells for disposal. Nine deep wells
will be installed with seven operating full time. Design criteria for the project are 100-year life expectancy and automated
operation with minimum supervision and maintenance. The required minimum operating, maintenance and supervision coupled with
100-year life expectancy of the project added significantly to the estimated US $58 million capital cost of the project. However,
the reduction in annual cost for labor, repairs and replacement of the component of the system should result in a lower life
cycle cost. The estimated annual operating and maintenance cost is US $4.7 million.
Received: 5 May 1998 · Accepted: 30 June 1998 相似文献
12.
An investigation of urban heat island intensity (UHII) as an indicator of urban heating 总被引：2，自引：0，他引：2
The objective of this paper is to evaluate the reliability of urban heat island intensity (UHII) as an indicator of urban heating. The diurnal patterns of air and surface-temperature based UHII and variations in urban and rural area heating were analyzed and discussed. The detailed air-temperature based UHII patterns were determined in one urban and four suburban areas of Hong Kong. UHII was determined as spatially-averaged air-temperature difference between an urban/suburban area and its surrounding rural area. Additionally, reported air and surface-temperature based UHII patterns were integrated in the discussion to carry out a comprehensive analysis. The urban and rural area heating variations (i.e., the diurnal variations in net radiation, sensible heat flux, latent heat flux, and heat stored by an area) were examined in the light of UHII patterns to validate UHII as an indicator for urban heating. It is noted that the air-temperature based UHIIs were higher and positive in the night-time but lower and negative during the daytime. On the other hand, most of the surface-temperature based UHIIs, investigated through satellite data were positive during both the daytime and night-time. It is revealed that UHII can well reflect urban heating during night-time and early morning. However, the lower and negative UHII during solar peak time (daytime when solar radiation is the dominant source of heating) has seemingly not been representing urban heating. 相似文献
13.
Japanese threadfin bream Nemipterus japonicus(Bloch, 1791) is among the most abundant and commercially important species in Pakistan. From the coast of Pakistan, four demersal trawl surveys in October–November 2009 and May–June, August, October and November in 2010 were carried out. The purpose of this study is to estimate the population dynamics and status of the stock of the N. japonicus from Pakistani waters based on the research trawl surveys from the research area. The data consist of n=784 length-weight pairs and n=7 530 length frequency with the maximum length and weight of 29 cm and 358 g respectively. The length frequency data were analyzed using ELEFAN method in FiSAT computer package. The parameters of length and weight relationship were b=2.778, a=0.032 and R2=0.973. The estimated von Bertalanffy growth function parameters were L∞=30.45 cm, K=0.270 year-1. Based on length-converted catch curve analysis the total mortality(Z) during this study was estimated at 0.960 year-1. The natural mortality coefficient(M) was 0.74 year-1 using Pauly's equation(the annual average sea surface temperature was 27°C), therefore, the fishing mortality coefficients(F) were 0.22 year-1. The yield per recruit analysis indicated that when tc was 2, Fmax was estimated at 1.2 and F0.1 at 1.1. When tc was 1, Fmax was estimated at 0.95 and F0.1 at 0.8. Because current age at first capture is about 1 year and Fcurrent was 0.22, Fcurrent is smaller than F0.1 and Fmax, which indicated that the fishery is about in a safe condition. When using Gulland(1971) biological reference point, Fopt was equals to M(0.74). The current fishing mortality rate of 0.22 was smaller than the target biological reference point. 相似文献
14.
Sorting and concentration of a variety of heavy minerals along the coast between Gadani and Phornala, Baluchistan, are facilitated by the coincidence of the periods of maximum turbulence and wave activity, maximum percipitation, and sediments discharge. Sediment samples from different intertidal zones between Gadani and Phornala were collected for grain size analysis and petrographic/petrological study. Variations in grain size and mineral assemblage in the intertidal zones have been noted. Concentration of dark color heavy minerals has been noted in fine grain sediments, light color minerals are ubiquitous. The sediments exhibit wide ranges of sorting. 相似文献
15.
Bashir A. Memon Asadullah Kazi William J. Powell A. S. Bazuhair 《Environmental Geology》1986,8(3):153-160
Groundwater recharge by natural replenishment for the unconsolidated alluvial aquifer in Wadi Al-Yammaniyah is estimated on
a daily basis instead of the conventional monthly basis The study reveals that during the two-year period (1978 and 1979),
the estimated recharge in the area is about 40% of the total average annual rainfall of 155 mm Subsurface underflow estimated
at 36×10−6 m3/yr from the Wadi Al-Yammaniyah aquifer occurs in the vicinity of Wadi Ash-Shamiyah A comparison of the recharge and extracted
volumes of water from the aquifer indicates that there is a net increase of 10 million m3 and 38 million m3 of water in the storage for 1978 and 1979, respectively 相似文献
16.
Dynamic flow systems and transport of contaminants in karstic aquifers result from the actions of physical and chemical processes involving aqueous systems containing certain contaminants. These processes are elaborated, and pertinent mathematical and chemical equations are discussed, herein. Contaminant transport in karstic aquifers can be mathematically expressed by the basic equations evaluated primarily for the flow in porous, highly permeable aquifers. The effects of advection, hydrodynamic dispersion, and dilution are elaborated as physical processes that effect the movement of contaminants through groundwater in permeable rocks. Physical and chemical mechanisms that govem contaminant movement and groundwater flow through fractured media are proposed as the basis of an approximate scenario of contaminant transport through karstified carbonate rocks. 相似文献
17.
A continuous time delay-diff erence model (CTDDM) has been established that considers continuous time delays of biological processes. The southern Atlantic albacore (Thunnus alalunga) stock is the one of the commercially important tuna population in the marine world. The age structured production model (ASPM) and the surplus production model (SPM) have already been used to assess the albacore stock. However, the ASPM requires detailed biological information and the SPM lacks the biological realism. In this study, we focus on applying a CTDDM to the southern Atlantic albacore (T. alalunga) species, which provides an alternative method to assess this fishery. It is the first time that CTDDM has been provided for assessing the Atlantic albacore (T. alalunga) fishery. CTDDM obtained the 80% confidence interval of MSY (maximum sustainable yield) of (21 510 t, 23 118t). The catch in 2011 (24 100 t) is higher than the MSY values and the relative fishing mortality ratio (F 2011/F MSY) is higher than 1.0. The results of CTDDM were analyzed to verify the proposed methodology and provide reference information for the sustainable management of the southern Atlantic albacore stock. The CTDDM treats the recruitment, the growth, and the mortality rates as all varying continuously over time and fills gaps between ASPM and SPM in this stock assessment. 相似文献
18.
19.
20.
Predicting flow liquefaction,a constitutive model approach 总被引：1，自引：1，他引：0
In this paper, flow liquefaction criterion for contractive loose sands is analytically extracted based on the fundamental definition of flow liquefaction. In order to obtain the closed form of this criterion, Dafalias–Manzari constitutive model is employed; so the stress ratio at the onset of flow liquefaction is presented as a function of model parameters, state parameter and void ratio. Flow liquefaction line, as a graphical form of suggested criterion in stress space, shows that the peak points of undrained stress paths with same void ratios are not necessarily in a straight line. In order to validate the reliability of proposed flow liquefaction line to predict the onset of instability, it has been compared with the results of experimental tests performed on Toyoura, Ottawa and Leighton Buzzard sands. The verification results show that the present criterion can satisfactorily predict the onset of flow liquefaction in monotonic and cyclic undrained tests of saturated sands as well as the structural collapse in constant deviatoric stress tests of loose dry sands. 相似文献