Generating extreme ship responses using non-uniform phase distributions     

Laura K. Alford  Armin W. Troesch 《Ocean Engineering》2009,36(9-10):641-649

Modified Gaussian phase distributions are used to generate short time series containing a specific extreme value of a ship response. The corresponding incident wave train is calculated via linear systems theory. Sample response and wave time series are compared to the expected time series as calculated by probabilistic analysis. The average of the sample response time series compares favorably to the expected time series, but the average of the sample wave trains does not, in general, match the expected wave train. These comparisons show the danger in estimating extreme ship responses considering only extreme waves. A sample analysis for a Great Lakes bulk carrier is included for illustration.  相似文献   

Comparative geometric and radiometric evaluation of mobile phone and still video cameras     

Devrim  Akca  Armin  Gruen 《The Photogrammetric Record》2009,24(127):217-245

This paper examines the potential of mobile phones to be used as front-end sensors for photogrammetric procedures and applications. For this purpose, two mobile phone cameras (Sony Ericsson K750i and Nokia N93) were calibrated over an indoor 3D testfield, using a self-calibrating bundle adjustment. Geometric accuracy tests were carried out in order to evaluate their metric performances and to compare the results with respect to two off-the-shelf digital still video cameras (Sony DSC W100 and Sony DSC F828). The geometric accuracy evaluation comprised an absolute accuracy test, JPEG test and temporal stability test. The radiometric capabilities of all cameras (except that the DSC W100 was replaced with a DSC T100 camera) were also evaluated and compared by carrying out modulation transfer function (MTF) analysis, image noise analysis and an operating range test. Substantial systematic errors were diagnosed in some systems. However, with proper calibration it is believed that these devices can be used for many photogrammetric tasks.  相似文献   

Interpretation of Pumping Tests in Heterogeneous Aquifers with Constant Head Boundary     

Armin Pechstein  Nadim K. Copty 《Ground water》2021,59(4):517-523

This paper investigates the impact of heterogeneity of the transmissivity field on the interpretation of steady-state pumping test data from aquifer systems delimited by constant head boundaries such as aquifers adjacent to lakes or rivers. Spatially variable transmissivity fields are randomly generated and used to simulate the drawdown due to a pumping well located at different distances from a constant head boundary. The steady-state drawdown simulated at different observation wells are then interpreted using the Hantush method (Hantush 1959). The numerical simulations show that, in contrast to the case of infinite aquifer domains, the interpreted transmissivity varies depending on well locations and the separation distance between pumping well and boundary relative to the correlation length. The ensemble-averaged estimated transmissivity varies between the geometric mean and the arithmetic mean, and can even exceed the arithmetic mean in a narrow domain adjacent to the boundary. It approaches the geometric mean of the underlying transmissivity field only if the distance between the pumping well is more than 20 times the characteristic length of the transmissivity field.  相似文献   

Spatial assessment of salinity and nitrate pollution in Amman Zarqa Basin: a case study   总被引：1，自引：0，他引：1  

Mustafa Al Kuisi  Mohammed Al-Qinna  Armin Margane  Taiseer Aljazzar 《Environmental Earth Sciences》2009,59(1):117-129

Intensive use of land resources in arid and semi-arid regions exert serious pressures on groundwater resources and jeopardize further socio-economical developments. The Amman-Zarqa Basin (AZB), the most vital basin in Jordan, is facing recent groundwater deterioration due to a very large increase in water demands for domestic, agricultural, and industrial uses. The objectives of this paper were to quantify the degree of contamination in the basin by evaluating the characteristics, distribution and seasonal variations of two pollution indicators (nitrate concentration and salinity) and to determine the impacts of human activities (land use) on groundwater quality. Based upon long-term data (1970–2005) of groundwater samples collected from 538 wells across the AZB, spatial analyses indicated that both indicators have a strong spatial dependence and are anisotropically distributed. Prediction maps of Ordinary Kriging and Indicator Kriging provided detailed indications of the major and minor sources of pollution in the basin. Inefficient wastewater treatment plants, industrial activities and agricultural practices were responsible for 91, 85, and 25% salinization of nearby wells, respectively. Nitrate pollution had reached 73% above threshold (50 mg/L) in some cases. The temporal analyses estimated the salinity buildup rate to be around 8 × 10⁻² μS/cm per day, while nitrate buildup rate was estimated to be around 6 × 10⁻² mg/L per day. Remote sensing and spatial analyses helped greatly in groundwater quality assessment not only in providing the environmental status of the AZB but also in delineating the potential of contamination risk zones and their correlation to human activities. Furthermore, the paper suggests some environmental protection strategies that should be adopted to protect the vital groundwater resources of the basin from further deterioration.  相似文献   

Protracted,coeval crust and mantle melting during Variscan late-orogenic evolution: U–Pb dating in the eastern French Massif Central     

Laurent  Oscar  Couzinié  Simon  Zeh  Armin  Vanderhaeghe  Olivier  Moyen  Jean-François  Villaros  Arnaud  Gardien  Véronique  Chelle-Michou  Cyril 《International Journal of Earth Sciences》2017,106(2):421-451

International Journal of Earth Sciences - The late stages of the Variscan orogeny are characterized by middle to lower crustal melting and intrusion of voluminous granitoids throughout the belt,...  相似文献   

Investigation of microrubbers,microplastics and heavy metals in street dust: a study in Bushehr city,Iran     

Sajjad Abbasi  Behnam Keshavarzi  Farid Moore  Hossein Delshab  Naghmeh Soltani  Armin Sorooshian 《Environmental Earth Sciences》2017,76(23):798

This study aimed to (1) investigate microrubbers (MRs) for the first time and identify microplastics (MPs) in street dust, (2) determine the physicochemical and mineralogical characteristics and morphology of dust particles, (3) understand the concentration and the possible source(s) of heavy metals/metalloids, (4) identify the chemical speciation and mobility potential of trace metals in urban street dusts, and (5) determine adverse health effects of street dust on children and adults living in the city of Bushehr in southwestern Iran. Generally, twenty four street dust samples were collected and analyzed. Calculated enrichment factors indicate high levels of contamination. Statistical analysis reveals that the two main sources of trace elements include road traffic emissions (Cu, Zn, Sb, Hg, Pb, Mo) and re-suspended soil particles (Al, Mn, Ni, Ti, Cd, Co). BCR sequential extraction results indicated that As, Zn, Cu, and Pb mainly occur in the exchangeable fraction and hence are highly bioavailable. X-ray powder diffraction analysis revealed the presence of calcite, dolomite, quartz, and magnetite. The size distribution of dust particles was also investigated using a scanning electron microscope (SEM), while elemental distribution was analyzed using an attached energy dispersive X-ray spectrometer (SEM–EDS) unit. Dust particles from heavy traffic areas are much finer compared with other investigated areas. MPs and MRs, mostly fibers and fragments, were detected in all samples [ranging from 210 to 1658 (MPs) and 44 to 782 (MRs) items/10 g dust] using fluorescence microscopy. The hazard index for As is higher than 10^?4 for children and adults indicative of high risk. According to the calculated potential ecological risk index, Hg indicated moderate ecological risk in the street dust of the study area.  相似文献   

Hafnium isotope homogenization during metamorphic zircon growth in amphibolite-facies rocks: Examples from the Shackleton Range (Antarctica)   总被引：2，自引：0，他引：2  

Armin Zeh  Axel Gerdes  Hartwig E. Frimmel 《Geochimica et cosmochimica acta》2010,74(16):4740-4758

Hafnium isotope analyses of a large number of metamorphic zircon grains of two garnet-kyanite-staurolite schist samples from the Shackleton Range yielded ¹⁷⁶Hf/¹⁷⁷Hf of 0.28160 ± 0.00003 and 0.28142 ± 0.00003, respectively. The variations of these analyses are less than ±1.2 epsilon units and indicate that all metamorphic zircon grains in the two rocks formed in environments with nearly homogenous Hf isotopic composition. The metamorphic origin of the zircon grains is constrained by textures as well as by their low Th/U (<0.2), ¹⁷⁶Lu/¹⁷⁷Hf (<0.0003), and ¹⁷⁶Yb/¹⁷⁷Hf ratios (<0.009), indicating that they grew in the presence of garnet. Furthermore, the grains yield Pb-Pb ages of c. 1.7 Ga, which is the time of amphibolite-facies metamorphism. In combination with petrological results, it is suggested that the observed ¹⁷⁶Hf/¹⁷⁷Hf homogeneity was caused by a fluid- and deformation-assisted dissolution of detrital zircon grains, followed by new zircon re-precipitation that was accompanied by Hf transport on at least a hand-specimen scale. This interpretation is supported by results obtained from an additional paragneiss sample that contains zoned zircon grains with xenocrystic cores formed at 2.6-1.8 Ga and metamorphic rims with a U-Pb age of 1.7 Ga. The ¹⁷⁶Hf/¹⁷⁷Hf variation of the zircon rims is mostly at ±0.0003, which is much less than that of the magmatic cores (±0.0019). The metamorphic fluid for the dissolution-homogenization-re-precipitation process most likely resulted from prograde reactions among the minerals chlorite-muscovite-biotite-garnet-staurolite-apatite, in agreement with thin section observations and P-T pseudosection calculations.  相似文献   

Green Hydropower: The contribution of aquatic science research to the promotion of sustainable electricity     

Bernhard Truffer  Christine Bratrich  Jochen Markard  Armin Peter  Alfred Wüest  Bernhard Wehrli 《Aquatic Sciences - Research Across Boundaries》2003,65(2):99-110

  相似文献   

Decline of fish catch in Switzerland     

Patricia Burkhardt-Holm  Armin Peter  Helmut Segner 《Aquatic Sciences - Research Across Boundaries》2002,64(1):36-54

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Mixing of rhyolite,trachyte and basalt magma erupted from a vertically and laterally zoned reservoir,composite flow P1, Gran Canaria   总被引：1，自引：0，他引：1  

Armin Freundt  Hans-Ulrich Schmincke 《Contributions to Mineralogy and Petrology》1992,112(1):1-19

The 14.1 Ma composite welded ignimbrite P1 (45 km³ DRE) on Gran Canaria is compositionally zoned from a felsic lower part to a basaltic top. It is composed of four component magmas mixed in vertically varying proportions: (1) Na-rhyolite (10 km³) zoned from crystal-poor to highly phyric; (2) a continuously zoned, evolved trachyte to sodic trachyandesite magma group (6 km³); (3) a minor fraction of Na-poor trachyandesite (<1 km³); and (4) nearly aphyric basalt (26 km³) zoned from 4.3 to 5.2 wt% MgO. We distinguish three sites and phases of mixing: (a) Mutual mineral inclusions show that mixing between trachytic and rhyolitic magmas occurred during early stages of their intratelluric crystallization, providing evidence for long-term residence in a common reservoir prior to eruption. This first phase of mixing was retarded by increasing viscosity of the rhyolite magma upon massive anorthoclase precipitation and accumulation. (b) All component magmas probably erupted through a ring-fissure from a common upper-crustal reservoir into which the basalt intruded during eruption. The second phase of mixing occurred during simultaneous withdrawal of magmas from the chamber and ascent through the conduit. The overall withdrawal and mixing pattern evolved in response to pre-eruptive chamber zonation and density and viscosity relationships among the magmas. Minor sectorial variations around the caldera reflect both varying configurations at the conduit entrance and unsteady discharge. (c) During each eruptive pulse, fragmentation and particulate transport in the vent and as pyroclastic flows caused additional mixing by reducing the length scale of heterogeneities. Based on considerations of magma density changes during crystallization, magma temperature constraints, and the pattern of withdrawal during eruption, we propose that eruption tapped the P1 magma chamber during a transient state of concentric zonation, which had resulted from destruction of a formerly layered zonation in order to maintain gravitational equilibrium. Our model of magma chamber zonation at the time of eruption envisages a basal high-density Na-poor trachyandesite layer that was overlain by a central mass of highly phyric rhyolite magma mantled by a sheath of vertically zoned trachyte-trachyandesite magma along the chamber walls. A conventional model of vertically stacked horizontal layers cannot account for the deduced density relationships nor for the withdrawal pattern.  相似文献