Reactive transport of gentisic acid in a hematite-coated sand column: Experimental study and modeling     

K. Hanna  B. Rusch  A. Hofmann 《Geochimica et cosmochimica acta》2010,74(12):3351-4418

The adsorption of gentisic acid (GA) by hematite nano-particles was examined under static and dynamic conditions by conducting batch and column tests. To simulate natural sediments, the iron oxide was deposited on 10 μm quartz particles. The GA adsorption was described by a surface complexation model fitted to pH-adsorption curves with GA concentrations of 0.1-1 mM in a pH range of 3-10. The surface was described with one type of site (FeOH°), while gentisic acid at the surface was described by two surface complexes (FeLH₂°, log K_int = 8.9 and FeLH⁻, log K_int = −8.2). Modeling was conducted with PHREEQC-2 using the MINTEQ database. From a kinetic point of view, the intrinsic chemical reactions were likely to be the rate-limiting step of sorption (∼10⁻³ s⁻¹) while external and internal mass transfer rates (∼10² s⁻¹) were much faster. Under flow through conditions (column), adsorption of GA to hematite-coated sand was about 7-times lower than under turbulent mixing (batch). This difference could not be explained by chemical adsorption kinetics as shown by test calculations run with HYDRUS-1D software. Surface complexation model simulations however successfully described the data when the surface area was adjusted, suggesting that under flow conditions the accessibility to the reactive surface sites was reduced. The exact mechanism responsible for the increased mobility of GA could not be determined but some parameters suggested that decreased external mass transfer between solution and surface may play a significant role under flow through conditions.  相似文献   

Permittivity in the microwave region of some natural minerals     

F. F. Hanna  I. K. Hakim  A. M. Bishai  A. L. Saad 《Pure and Applied Geophysics》1982,120(4):772-777

The permittivity measured at a frequency of 10 GHz normalized to constant density is the same within the experimental error for talc, baryte and dolomite. In the case of clay and kaolin, it is about 10% higher. This is attributed to the high content of Al₂O₃ (30–40%) in them, which interpretation is proved by experiment.  相似文献   

Air quality model performance evaluation   总被引：3，自引：0，他引：3  

J. C. Chang  S. R. Hanna 《Meteorology and Atmospheric Physics》2004,87(1-3):167-196

Summary This paper reviews methods to evaluate the performance of air quality models, which are tools that predict the fate of gases and aerosols upon their release into the atmosphere. Because of the large economic, public health, and environmental impacts often associated with the use of air quality model results, it is important that these models be properly evaluated.A comprehensive model evaluation methodology makes use of scientific assessments of the model technical algorithms, statistical evaluations using field or laboratory data, and operational assessments by users in real-world applications. The focus of the current paper is on the statistical evaluation component. It is important that a statistical model evaluation exercise should start with clear definitions of the evaluation objectives and specification of hypotheses to be tested. A review is given of a set of model evaluation methodologies, including the BOOT and the ASTM evaluation software, Taylors nomogram, the figure of merit in space, and the CDF approach. Because there is not a single best performance measure or best evaluation methodology, it is recommended that a suite of different performance measures be applied. Suggestions are given concerning the magnitudes of the performance measures expected of good models. For example, a good model should have a relative mean bias less than about 30% and a relative scatter less than about a factor of two.In order to demonstrate some of the air quality model evaluation methodologies, two simple baseline urban dispersion models are evaluated using the Salt Lake City Urban 2000 field data. The importance of assumptions concerning details such as minimum concentration and pairing of data are shown. Typical plots and tables are presented, including determinations of whether the difference in the relative mean bias between the two models is statistically significant at the 95% confidence level.  相似文献   

Abiotic typology of Polish lakes   总被引：3，自引：0，他引：3  

Agnieszka Kolada  Hanna Soszka  Dorota Cydzik  Ma&#x;gorzata Go&#x;ub 《Limnologica》2005,35(3):145-150

According to the requirements of the Water Framework Directive 2000/60/EC, all member states of the EU have to establish the typology of their surface waterbodies. The typology is aimed at defining the type-specific reference conditions against which the ecological state of waters can be assessed. The abiotic typology of Polish lakes of an area greater than 50 ha was established based on morphometric, hydrographic and physico-chemical data taken from the Polish national monitoring dataset. The current dataset comprises 749 out of a total of 1042 lakes with an area greater than 50 ha in Poland. Lake types were identified based on a combination of abiotic characteristics of lakes specified in Annex II of the Water Framework Directive such as ecoregions, size, altitude, mean depth, geology and an additional factor – Schindler's ratio. Altogether 13 abiotic lake types were established.  相似文献   

Circularization of Binary Orbits     

Magdy Hanna  Pavel Mayer  Yousry Hanna 《Astrophysics and Space Science》1998,262(2):171-176

In a previous paper Mayer and Hanna (1991) discussed the process of binary orbit circularization for detached eclipsing binaries. An agreement of observational data with Tassoul's circularization time formula for binaries with masses greater than 2.5 M was found. In the present paper we also examine orbital circularization in evolved spectroscopic binaries.  相似文献   

Geographic clustering of firms and urban form: a multivariate analysis   总被引：1，自引：0，他引：1  

Hanna Maoh  Pavlos Kanaroglou 《Journal of Geographical Systems》2007,9(1):29-52

This paper provides an empirical framework that applies spatial statistics methods to assess the relation between the change in the geographical clustering of firms and the emergence of urban form. We contend that where firms locate and eventually cluster give rise to the way commercial and industrial land uses are organized over space, which in turn defines the shape of urban form. Accordingly, the objectives of our work are twofold: (1) to identify the extent and shape of firm clustering and co-location at the intra-metropolitan level, and (2) examine how the change in the geographic clustering of different industries contributes to decentralization and the evolution of urban form. Spatial statistics methods and tools were vital and helped to fulfill these objectives.   相似文献   

Business establishment mobility behavior in urban areas: a microanalytical model for the City of Hamilton in Ontario,Canada   总被引：1，自引：0，他引：1  

Hanna Maoh  Pavlos Kanaroglou 《Journal of Geographical Systems》2007,9(3):229-252

We present a microanalytical firm mobility model for the City of Hamilton, Canada, developed with data from the Statistics Canada Business Register. Contributing to the scarce literature on firm migration behavior, we explore and model the determinants of mobility among small and medium size firms who retained less than 200 employees between 1996 and 1997. Our exploratory results suggest that short distance moves are more common and tend to occur among smaller firms. Econometric modeling results support these assertions and indicate that the willingness to move can be explained by a firm’s internal characteristics (e.g. age, size, growth and industry type) as well as location factors related to the urban environment where the firm is located. The modeling results will serve as input for the development of an agent-based firmographic decision support system that can be used to inform the planning process in the study area.   相似文献   

Luminescence Variations in Fast-Growing Stalagmites from Uppsala, Sweden     

Hanna Sofia Sundqvist  y Baker  Karin Holmgren 《Geografiska Annaler: Series A, Physical Geography》2005,87(4):539-548

Two fast‐growing stalagmites from a cellar vault in Uppsala, southeast Sweden, are analysed for their luminescent properties. The results indicate that variations in luminescence intensity in the stalagmites are annual. Due to problems in finding a suitable absolute dating method this assumption cannot yet be firmly tested; however, results from radiocarbon dating of one of the stalagmites do not contradict the proposal that the laminae are annual. If so, the speleothems have been growing for 10–15 years with a growth rate of 3–8 mm per year, which is a similar rate to other fast‐growing speleothems in Great Britain that have formed from the reaction of lime mortar and carbon dioxide. It is likely that the assumed annual laminae of the luminescence record represent a flush of organic material.  相似文献   

Using Astrophysical Data Archives In Astrophysical Research: RXTEAs A Case Study     

Hanna A. Sabat 《Astrophysics and Space Science》2000,273(1-4):141-153

In this paper, we highlight the significance of astrophysical dataarchives, and the great opprtunities they are offering for researchersin general, and those in the developing countries in particular. Wefocus on high energy astrophysical data archives, taking RXTE as a casestudy, where we give a brief introduction to this satellite and itsinstrumentation. Then we explain in certain detail the processes ofsearch and retrieval of RXTE's archival data, finally touching verybriefly upon its data analysis.  相似文献   

Passive earth pressure on embedded vertical plate anchors in sand   总被引：1，自引：1，他引：0  

Adel Hanna  Farhana Rahman  Tahar Ayadat 《Acta Geotechnica》2011,6(1):21-29

Passive earth pressure on embedded anchor plates constitutes a viable resisting force for the design of underground structures. In the current practice, these forces are empirically calculated, ignoring the effects of the depth of embedment and the level of consolidation of the surrounding soil, which takes place during plate installation on the in situ stress levels. Accordingly, wide discrepancies between predicted and measured pullout capacities of these plates were reported in the literature. Numerical model was developed using finite-element technique and the constitutive law of Mohr?CCoulomb to simulate the case of a retaining wall partially supported by an embedded anchor plate in sand. The results produced in this investigation showed that the passive earth pressure acting on anchor plates increases due to the increase of angle of shearing resistance and the overconsolidation ratio of sand, and it decreases due to an increase of the embedment depth of anchor. Design theories were developed for the case of embedded anchor plate in overconsolidated sand. The theories developed will satisfy the design needed in terms of allowable pullout load and/or displacement.  相似文献