Electron transport properties of single crystal and polycrystalline natural mineral galena (PbS) samples from the Trep?a mine, Yugoslavia, were determined using the photoacoustic frequency transmission technique. Their thermal diffusivity (DT≈0.16 × 10?5 m2 s?1), the coefficient of diffusion (D between 0.15×10?2 0.16×10?2 m2 s?1) and lifetime of the excess carrier (τ≈35 μs and the front and rear recombination velocity (sg≈65.5 m s?1 and sb≈66.4 m s?1, respectively), were calculated by comparing the experimental results and the theoretical photoacoustic amplitude and phase signals. The lattice parameter obtained by X-ray work was a?=5.936?Å. The free carrier concentration of these single-crystal samples was measured using the Hall method (N?=?3×1018 cm?3). Measurements of the optical reflectivity of the same samples, as a function of wavelength, in the infrared and far infrared ranges, were performed. In the far infrared range a free electron plasma frequency was observed and numerically analyzed, using the least-squares fitting procedure. The values of optical parameters were calculated and the value of the free carrier concentration obtained by the Hall method was confirmed. 相似文献
This study Investigates a tracing method using dissolved noble gases to survey the groundwater flow in a large groundwater basin. The tracing method is based on measuring the concentrations of noble gases and the ratio of helium isotopes in groundwater samples. Since it is very difficult to detect trace amounts of noble gases and helium with high accuracy in a 15-ml groundwater sample, dissolved gases were extracted and purified, then a high-resolution mass spectrometer was used for measurement and comparison with standard samples. We used this method with samples from a confined aquifer formed by the deposition of pyroclastic flow in the Kumamoto Plain on the west side of Mt. Aso in central Kyushu, Japan. The groundwater basin under the plain is divided into four small basins, based on the helium concentrations and isotope ratios, with two major groundwater flows. One flow is buried by the Aso pyroclastic flow along the old Kase River; the other is along the Tsuboi River Valley. These two groundwater flows were identified from the different helium isotope-ratios. The helium component from the deep mantle is mixed into the groundwater under the Kumamoto Plain. Finally, data on the concentrations and ratios of3He to4He in groundwater samples were used to determine the location of faults in the volcanic aquifer. 相似文献
Growing demand for groundwater resources and stringent environmental concerns has led to large groundwater investigations, including characterization of aquifer systems that are hydraulically connected to springs. A pumping test is one of the most reliable means of quantifying hydraulic characteristics and the response of natural springs to pumping because it yields results that, in general, are representative of a larger area than are results from a single point observation. Recharge to the aquifer sustaining discharge from springs must be evaluated prior to the utilization of springs. The spring hydrograph is analyzed, as the shape of a hydrograph is a reflection of the response of the aquifer to recharge. The form and rate of recession provide significant information on the storage, lithological composition, and structural characteristics of the aquifer system sustaining the spring. Water tracing techniques have been developed and used over a period of centuries to delineate catchment boundaries, estimate groundwater flow velocities, determine areas of recharge, and identify sources of pollution of spring water. 相似文献
Although British Columbia experiences many natural hazards, there is as yet no unified policy to promote natural hazard management
in the province. The problem is not in the quantity and quality of geoscience assessment of natural hazards, but instead,
it is suggested, in the isolation of that work from broader risk perspectives and in the lack of clarity of division of responsibilities
between various levels of government. The example of recent changes in perception of the terrain stability problem illustrates
how natural hazard problems are driven by social and political priorities rather than by geoscience priorities.
Received: 22 November 1998 / Accepted: 22 November 1998 相似文献
This study investigated the adsorption and precipitation of phosphate by blast furnace slag (BFS) separately.
In order to evaluate the adsorption capacity of BFS, BFS was treated before its use by acid. The authors aim to develop a new porous carrier to adsorb simultaneously ammonium and phosphate from seawater under eutrophic conditions. The current paper deals with a promising new approach to improve the utilization of some industrial solid wastes such as BFS and zeolite synthesized from fly ash [ZFA(Fe)] by their solidification to cylindrical porous carriers using a hydrothermal hot-pressing (HHP) method.
Attempts to produce porous carriers using an arranged HHP method with different porosities (24%, 40% and 52% (v/v)) were carried out. Physical properties of carriers such as porosity, compressive strength and height have been investigated. Laboratory studies showed strong evidence that the porous carrier was very selective towards phosphate and ammonium. The results demonstrated the role of porosity in enhancing phosphate and ammonium adsorption by the increase of the surface area per weight. The estimates of the parameters and the correlation coefficients according to the Freundlich equations revealed that adsorption was related to the porosity of carriers and phosphate and ammonium were adsorbed well on the carriers having large porosity.
The results suggested that developing carrier with high porosity was a promising way to enhance nutrients adsorption. 相似文献