A method to regenerate the damaged Chironomidae slides in entellan mounting solution     

Armin Namayandeh  Joseph Culp 《Journal of Paleolimnology》2015,53(2):251-253

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Cantilever beam analogy for modal analysis of rocking core-moment frames     

Nima Rahgozar  Abdolreza S. Moghadam  Armin Aziminejad 《Bulletin of Earthquake Engineering》2018,16(9):4081-4106

Unlike conventional seismic resisting systems, rocking core-moment frame (RCMF) combinations as low-damage assemblies are being developed to mitigate, or even eliminate structural damage and residual deformations following a severe earthquake. Despite extensive studies on the performance of specific rocking cores, dynamic characteristics and strength demands of a generic RCMF have not been addressed. By utilizing cantilever beam analogy, the current article proposes a modal analysis method to formulate RCMF demands. The proposed model and obtained analytical charts provide a manual method for rapid study and preliminary design of low- to mid-rise RCMFs with relatively uniform properties over the height. An extensive parametric study investigates the effects of rocking core base-fixity and frame-to-core stiffness on demand values. An independent computer analysis verifies the validity and accuracy of the proposed formulas. Findings show significant higher-mode effects in several RCMF combinations.  相似文献   

Implementation of online model updating in hybrid simulation          下载免费PDF全文

M. Javad Hashemi  Armin Masroor  Gilberto Mosqueda 《地震工程与结构动力学》2014,43(3):395-412

Hybrid simulation combines numerical and experimental methods for cost‐effective, large‐scale testing of structures under simulated earthquake loading. Structural system level response can be obtained by expressing the equation of motion for the combined experimental and numerical substructures, and solved using time‐stepping integration similar to pure numerical simulations. It is often assumed that a reliable model exists for the numerical substructures while the experimental substructures correspond to parts of the structure that are difficult to model. A wealth of data becomes available during the simulation from the measured experiment response that can be used to improve upon the numerical models, particularly if a component with similar structural configuration and material properties is being tested and subjected to a comparable load pattern. To take advantage of experimental measurements, a new hybrid test framework is proposed with an updating scheme to update the initial modeling parameters of the numerical model based on the instantaneously‐measured response of the experimental substructures as the test progresses. Numerical simulations are first conducted to evaluate key algorithms for the selection and calibration of modeling parameters that can be updated. The framework is then expanded to conduct actual hybrid simulations of a structural frame model including a physical substructure in the laboratory and a numerical substructure that is updated during the tests. The effectiveness of the proposed framework is demonstrated for a simple frame structure but is extendable to more complex structural behavior and models. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

How do granitoid magmas mix with each other? Insights from textures,trace element and Sr–Nd isotopic composition of apatite and titanite from the Matok pluton (South Africa)     

Oscar?LaurentEmail author  Armin?Zeh  Axel?Gerdes  Arnaud?Villaros  Katarzyna?Gros  Ewa?S?aby 《Contributions to Mineralogy and Petrology》2017,172(9):80

In plutonic systems, magma mixing is often modelled by mass balance based on whole-rock geochemistry. However, magma mixing is a chaotic process and chemical equilibration is controlled by non-linear diffusive–advective processes unresolved by the study of bulk samples. Here we present textural observations, LA-(MC-)ICP-MS trace element and Sr–Nd isotopic data of accessory apatites and titanites from a hybrid granodiorite of the Neoarchean Matok pluton (South Africa), collected in a zone of conspicuous mixing between mafic and felsic magmas. Apatite grains mostly show a pronounced zoning in CL images, corresponding to abrupt changes in REE and HFSE concentrations recording their transfer through compositionally different melt domains during mixing. These grains crystallized early, at temperatures of 950–1000 °C. Titanite grains crystallized at temperatures of 820–900 °C (Zr-in-sphene thermometry). They show limited intra-grain chemical variations but huge inter-grain compositional scatter in REE and HFSE, pinpointing crystallization within a crystal mush, from isolated melt pockets having different composition from one another owing to incomplete chemical homogenization and variable Rayleigh fractionation. These chemical–textural characteristics, in combination with partitioning models and Polytopic Vector Analysis, point to “self-mixing” between co-genetic dioritic and granodioritic/granitic magmas. Both resulted from differentiation of mantle-derived mafic melts, showing that mixing does not necessarily involve magmas from contrasted (crust vs. mantle) sources. Systematic variations in εNd _t (?4.5 to ?2.5) and ⁸⁷Sr/⁸⁶Sr_(i) (0.703–0.707) of titanite and apatite grains/domains crystallized from the two magmas point to an isotopically inhomogeneous mantle source, which is not resolved by bulk-rock isotopic data. Interaction between the two magmas must have occurred at relatively high temperatures (ca. 900°C) so that their viscosity contrast remained low, allowing efficient mechanical mixing. Despite this, chemical homogenization was incomplete, as recorded by diffusive fractionation between REE–HFSE and Sr. Modelling thereof reveals that chemical exchange between the liquid phases of the two mixed magmas did not last more than a few tens to hundreds of years. The chemical equilibration between mixed magmas thus strongly depends on the considered elements and observational length scales.  相似文献   

Platiniferous gold–tourmaline aggregates in the gold–palladium belt of Minas Gerais,Brazil: implications for regional boron metasomatism     

Cabral  Alexandre Raphael  Tupinambá  Miguel  Zeh  Armin  Lehmann  Bernd  Wiedenbeck  Michael  Brauns  Michael  Kwitko-Ribeiro  Rogerio 《Mineralogy and Petrology》2017,111(6):807-819

Mineralogy and Petrology - The platiniferous gold–palladium belt of Minas Gerais, Brazil, forms an approximately 240-km-long, roughly north–south-trending domain that includes numerous...  相似文献   

Abundance, diversity and succession of aquatic Coleoptera and Heteroptera in a cluster of artificial ponds in the North German Lowlands     

Armin Bloechl  Barbara Philippi  Albert Melber 《Limnologica》2010,40(3):215-188

Our study describes and evaluates environmental influences on assemblages of aquatic Coleoptera and Heteroptera in artificial ponds situated near Lake Steinhude in Lower Saxony (Germany). We determined temporal dynamics and colonization patterns for 14 ponds of different age. In total, we recorded 4941 individuals that represented 87 species of aquatic beetles and bugs. Between 30 and 40 species were found in most of the ponds. Heteropteran species of the families Corixidae and Notonectidae acted as pioneer species in new ponds, while aquatic coleopterans predominated in older ponds. The results of Canonical Correspondence Analyses (CCA) showed that among the key factors affecting community structure were land use, vegetation cover, water chemistry and the age of the ponds. We found that the distribution of adjacent ponds on areas with different land use has a positive influence on the diversity and abundance of the aquatic insect fauna.  相似文献   

Automated Determination of Sulfadiazine in Water,Fish Plasma and Muscle by HPLC with On‐Line Column‐Switching          下载免费PDF全文

Muhammet Altunok  Armin König  Waleed M.M. Mahmoud Ahmed  Tarek Haddad  Tibiriçá G. Vasconcelos  Klaus Kümmerer 《洁净——土壤、空气、水》2016,44(8):967-974

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Investigation of NDVI in relation to the growth phases of beech leaves in forest     

Seyed Armin Hashemi  Mir Mozaffar Fallah Chai 《Arabian Journal of Geosciences》2013,6(9):3341-3347

The main objective of the science of phenology is to identify the time of the occurrence of conspicuous periodic phenomena in plants under the impact of climatic factors. The study of phonologic phenomena through visual observations and terrestrial studies and temperature registration using a thermo hydrometer in different altitudinal levels and using the satellite data of IRS1C/1D LISSIII in twelve 1-ha plots in pure beech stands in the altitudinal range of 500 to 1,200 m above the sea level from April to December was carried out in such a way that for each month, one image of sensor was allocated. The produced vegetation indices were matched with terrestrial observations of the phenology periods in each month in the beech plots. The results show that the increase of the altitude above the sea level functions like latitude and its most remarkable impact is the decreasing of the temperature and the shortening of growing season. The terrestrial observations carried out in the plots show that a sudden increase in the temperature leads to the faster growth and emergence of the leaves. The produced correlation coefficient between the temperature and the emergence of the leaves was (p?=?0.01) r?=?0.87. Moreover, the end of fall in the studied region has a direct and significant relation with temperature. The amount of correlation coefficient between the temperature and end of fall in the studied region is equal to (p?=?0.01) r?=?0.91. Normalized difference vegetation index (NDVI) is more related to the growth and nurturing of the leaves. The amount of NDVI during the growth of the leaves, completion of the leaves, and fall of the leaves is equal to 0.35, 0.6, and 0.25, respectively.  相似文献   

An analysis of vegetation indices in relation to tree species diversity using by satellite data in the northern forests of Iran     

Seyed Armin Hashemi  Mir Mozaffar Fallah Chai  Shohreh Bayat 《Arabian Journal of Geosciences》2013,6(9):3363-3369

Vegetation indices have been introduced for analyzing and assessing the status of quantitative and qualitative characteristics of vegetation using satellite images. However, choosing the best indices to be used in forest biodiversity and vegetation is one of the important problems faced by the users. The purpose of this research is to evaluate six vegetation indices in the analysis of tree species diversity in the northern forests of Iran. The present research uses LISS III sensor data from IRS-P6 satellite. Geometric rectification of images was performed using ground control points, and Chavez model was used for atmospheric correction of the data. The six spectral vegetation indices included NDVI, IPVI, Ashburn Vegetation Index (AVI), TVI, TTVI, and RVI. Shannon–Wiener species diversity index was used to analyze diversity, and the value of the index was calculated in each sample plot. Then, the spectral values of each sample plot were extracted from different bands. The best subset regression was used to analyze the relationship between species diversity and the related bands. The results obtained from the regression showed that polynomial equations under scrutiny as independent variables can assess tree and shrub species diversity better than other bands and compounds used (R ²?=?0.47). The obtained results also indicated a higher capacity in the case of the AVI index for estimating tree species diversity in the under study area.  相似文献   

On the Occurence of Extreme Events in Long-term Correlated and Multifractal Data Sets     

Mikhail I. Bogachev  Jan F. Eichner  Armin Bunde 《Pure and Applied Geophysics》2008,165(6):1195-1207

We review recent studies of the statistics of return intervals (i) in long-term correlated monofractal records and (ii) in multifractal records in the absence (or presence) of linear long-term correlations. We show that for the monofractal records which are long-term power-law correlated with exponent γ, the distribution density of the return intervals follows a stretched exponential with the same exponent γ and the return intervals are long-term correlated, again with the same exponent γ. For the multifractal record, significant differences in scaling behavior both in the distribuiton and correlation behavior of return intervals between large events of different magnitudes are demonstrated. In the absence of linear long-term correlations, the nonlinear correlations contribute strongly to the statistics of the return intervals such that the return intervals become long-term correlated even though the original data are linearly uncorrelated (i.e., the autocorrelation function vanishes). The distribution density of the return intervals is mainly described by a power law.  相似文献