Some guidelines for economic evaluation of geochemical engineering projects     

F. Hahn 《Journal of Geochemical Exploration》1998,62(1-3)

Most geochemical engineering projects aim at commercial application. The proper economical analysis during the initial stages of the engineering process are of the utmost importance for the successful realisation of such projects. Many of the costs are committed at this stage. Important issues are: the scale of the project, the product quality and the choice of raw materials. For chemical plants, the Zevnik/Buchanan method is often used to make a rough estimation of the economic viability in an early stage. After the preliminary design of a geochemical process or other application has been completed, a more accurate estimation can be made by means of an economic balance. Guidelines for various costs are given in this article. Generally two criteria are used by companies to make a decision about further commercial realisation. One is the return on investment (R.O.I.), the annual profit divided by the total investment. The other is the pay-out time, the inverse of the R.O.I., the time needed to earn back the invested sum. This article provides geochemical engineers with some basic tools, that can be used to make an estimation of the economic potential of new geochemical engineering methods.  相似文献   

Properties of dark matter haloes in clusters, filaments, sheets and voids     

Oliver Hahn  Cristiano Porciani  C. Marcella Carollo  Avishai Dekel 《Monthly notices of the Royal Astronomical Society》2007,375(2):489-499

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The slow rotation of 253 Mathilde     

Stefano Mottola  William D. Sears  Anders Erikson  Alan W. Harris  Jim W. Young  Gerhard Hahn  Mats Dahlgren  Beatrice E. A. Mueller  Bill Owen  Ricardo Gil-Hutton  Javier Licandro  M. Antonietta Barucci  Claudia Angeli  Gerhard Neukum  Claes-Ingvar Lagerkvist  J. Felix Lahulla 《Planetary and Space Science》1995,43(12)

CCD photometry of the NEAR mission fly-by target 253 Mathilde is presented. Measurements taken during 52 nights of observations, from February to June 1995, allow a rotation period of 17.406±0.010 days and a lightcurve amplitude of 0.45±0.02 mag to be determined. A B-V color index of 0.67±0.02 and a V-R of 0.35±0.02 are measured, which are compatible with C-type membership. The determination of the phase relation results in H = 10.28±0.03 and G = 0.12±0.06. Indications that the lightcurve is not strictly singly-periodic are found. A power-spectrum analysis detects a secondary frequency f₂ = 0.0322±0.0010 d⁻¹, which is interpreted as evidence for a complex rotation state.  相似文献   

Oxygen variance and meridional oxygen supply in the Tropical North East Atlantic oxygen minimum zone     

J. Hahn  P. Brandt  R. J. Greatbatch  G. Krahmann  A. Körtzinger 《Climate Dynamics》2014,43(11):2999-3024

The distribution of the mean oceanic oxygen concentration results from a balance between ventilation and consumption. In the eastern tropical Pacific and Atlantic, this balance creates extended oxygen minimum zones (OMZ) at intermediate depth. Here, we analyze hydrographic and velocity data from shipboard and moored observations, which were taken along the 23°W meridian cutting through the Tropical North East Atlantic (TNEA) OMZ, to study the distribution and generation of oxygen variability. By applying the extended Osborn–Cox model, the respective role of mesoscale stirring and diapycnal mixing in producing enhanced oxygen variability, found at the southern and upper boundary of the OMZ, is quantified. From the well-ventilated equatorial region toward the OMZ core a northward eddy-driven oxygen flux is observed whose divergence corresponds to an oxygen supply of about 2.4 μmol kg^?1 year^?1 at the OMZ core depth. Above the OMZ core, mesoscale eddies act to redistribute low- and high-oxygen waters associated with westward and eastward currents, respectively. Here, absolute values of the local oxygen supply >10 μmol kg^?1 year^?1 are found, likely balanced by mean zonal advection. Combining our results with recent studies, a refined oxygen budget for the TNEA OMZ is derived. Eddy-driven meridional oxygen supply contributes more than 50 % of the supply required to balance the estimated oxygen consumption. The oxygen tendency in the OMZ, as given by the multidecadal oxygen decline, is maximum slightly above the OMZ core and represents a substantial imbalance of the oxygen budget reaching about 20 % of the magnitude of the eddy-driven oxygen supply.  相似文献   

Mg-rich harzburgites from Vesta: Mantle residua or cumulates from planetary differentiation?          下载免费PDF全文

Timothy M. Hahn Jr.  Nicole G. Lunning  Harry Y. McSween Jr.  Robert J. Bodnar  Lawrence A. Taylor 《Meteoritics & planetary science》2018,53(3):514-546

We describe petrographic, electron microprobe, and laser ablation ICP-MS analyses of Mg-rich harzburgite clasts in the Dominion Range 2010 howardites, and conclude that they are xenolithic samples of the vestan mantle. Key chemical and petrologic characteristics of these rocks provide tests for differentiation models. Our results indicate the mantle of Vesta formed through variable degrees of partial melting, which left behind a harzburgite and possibly dunite residuum. The Mg-rich clasts are composed of orthopyroxene and olivine, with minor clinopyroxene, FeNi metal, and distinctive pyroxene–chromite symplectites. We use mineral chemistry to demonstrate the absence of a genetic link between diogenites and the Mg-rich harzburgites. We propose a secondary origin for the formation of symplectites: interaction of silicate and metallic melts during primordial differentiation and core formation. The occurrence of FeNi metal containing ~1.5 wt% Cr within the assemblage indicates a very reducing environment during mantle differentiation (≪IW). Our study suggests that Vesta did not experience complete melting early in its history, and instead supports the formation of a shallow magma ocean.  相似文献   

Potential climate change effects on warm-season livestock production in the Great Plains   总被引：1，自引：0，他引：1  

Terry L. Mader  Katrina L. Frank  John A. Harrington Jr.  G. Leroy Hahn  John A. Nienaber 《Climatic change》2009,97(3-4):529-541

Projected production responses were derived for confined swine and beef and for milk-producing dairy cattle based on climate change projections in daily ambient temperature. Milk production from dairy cattle and the number of days to grow swine and beef cattle were simulated. Values were obtained for three central United States transects and three climate scenarios which were based on projected mean daily ambient temperatures associated with a baseline, doubling, and tripling of atmospheric greenhouse gas (CO₂) levels for the period June 1 to October 31. For swine, a slight northwest to southeast gradient is evident. Transect 1 (west side) shows no losses under the doubling scenario and losses up to 22.4% under the tripling scenario. Transect 3 (east side) displays losses of over 70% under the tripling scenario. For beef, positive benefits were simulated in Transect 1 with increasing temperatures, although a northwest to southeast gradient was also evident. For dairy, no positive benefits in milk production were found due to climate effects. Projected production declines ranged from 1% to 7.2%, depending on location. However, ranges in predicted differences were less than those simulated for beef and swine. These simulations suggest regional differences in animal production due to climate change will be apparent. For small changes in climate conditions, animals will likely be able to adapt, while larger changes in climate conditions will likely dictate that management strategies be implemented. Exploration of the effects of climate changes on livestock should allow producers to adjust management strategies to reduce potential impact and economic losses due to environmental changes.  相似文献   

Different Behavior of Iron(III) and Aluminum(III) Salts To Coagulate Silica Particle Suspension     

Panyue Zhang  Hermann H. Hahn  Erhard Hoffmann 《洁净——土壤、空气、水》2003,31(2):145-151

The different coagulation‐flocculation behavior of iron(III) and aluminum(III) to coagulate silica particle suspension with four coagulants — FeCl₃, Fe₂(SO₄)₃, AlCl₃, and in our laboratory produced polyaluminum chloride PACl‐2.0 — was investigated through studying particle property changes and coagulation efficiency, for example, variations in zeta potential of particles, particle number, average particle diameter, particle size distribution, and residual turbidity of the supernatant water. Influences of flocculation intensity and pH value on the coagulation‐flocculation process were also studied. The results suggest that, under the test conditions, among these four coagulants FeCl₃ possesses an obviously stronger ability to form larger flocs and to remove turbidity, on the other hand, PACl‐2.0 obviously showed a better charge neutralization ability.  相似文献   

The groundwater resources and sustainable yield of Cheju volcanic island, Korea   总被引：2，自引：0，他引：2  

J. Hahn  Y. Lee  N. Kim  C. Hahn  S. Lee 《Environmental Geology》1997,33(1):43-53

 Hydrogeologic data of 455 water wells comprising geologic logs, water qualities, and aquifer test results are analyzed to determine hydrogeological characteristics, water quality, and sustainable yield of the groundwater resources of Cheju volcanic island. The groundwater of the island occurs in unconsolidated pyroclastic deposits and clinkers interbedded in highly jointed basaltic and andesitic rocks as high-level, basal, and parabasal groundwater under unconfined conditions. The total storage of groundwater is estimated at about 44 billion m³. The average transmissivity and specific yield of the aquifer are at about 0.34 m² s^–1(29300 m² day^–1) and 0.12, respectively. The average annual precipitation is about 3.39 billion m³, of which 1.49 billion m³– equivalent to 44.0% of the total annual precipitation – is recharged into aquifers, with 0.638 billion m³ year^–1 of runoff and 1.26 billion m³ year^–1 of evapotranspiration. Based on a groundwater budget analysis, the sustainable yield is estimated at about 0.62 billion m³ year^–1, equivalent to 41.6% of annual recharge. A low-permeability marine sedimentary formation (Sehwari formation), composed of loosely cemented sandy silt, was recently found to be situated at 120±68 m below mean sea level. If the said marine sediment is distributed as a basal formation of the freshwater zone of the island, most of its groundwater will be of parabasal type. So the marine sediment is one of the most important hydrogeological boundaries and groundwater occurrences in the area. Received: 16 January 1997 / Accepted: 16 June 1997  相似文献   

Urban Waste Waters. Treatment for Use in Steam and Power Generation Von K. M. Abdullaev,I. A. Malakhov,L. N. Polestaev und A. S. Sobol Ellis Horwood Limited,Chichester, 1992, ISBN 0-13-929977-7, 245 Seiten, $ 89.95     

H. H. Hahn 《洁净——土壤、空气、水》1993,21(2):121-122

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Erosion of bentonite particles at the interface of a compacted bentonite and a fractured granite     

Min-Hoon Baik  Won-Jin Cho  Pil-Soo Hahn 《Engineering Geology》2007,91(2-4):229-239

Compacted bentonite has been considered as a candidate buffer material in the underground repository for the disposal of high-level radioactive waste. An erosion of bentonite particles caused by a groundwater flow at the interface of a compacted bentonite and a fractured granite was studied experimentally under various geochemical conditions. The experimental results showed that bentonite particles could be eroded from a compacted bentonite buffer by a flowing groundwater depending upon the contact time, the flow rate of the groundwater, and the geochemical parameters of the groundwater such as the pH and ionic strength.

A gel formation of the bentonite was observed to be a dominant process in the erosion of bentonite particles although an intrusion of bentonite into a rock fracture also contributed to the erosion. The concentration of the eroded bentonite particles eroded by a flowing groundwater was increased with an increasing flow rate of the groundwater. It was observed from the experiments that the erosion of the bentonite particles was considerably affected by the ionic strength of a groundwater although the effect of the pH was not great within the studied pH range from 7 to 10. An erosion of the bentonite particles in a natural groundwater was also observed to be considerable and the eroded bentonite particles are expected to be stable at the given groundwater condition.

The erosion of the bentonite particles by a flowing groundwater did not significantly reduce the physical stability and thus the performance of a compacted bentonite buffer. However, it is expected that an erosion of the bentonite particles due to a groundwater flow will generate bentonite particles in a given groundwater condition, which can serve as a source of the colloids facilitating radionuclide migration through rock fractures.  相似文献