Recursos de colección

Repositorio Institucional UN (153.203 recursos)

Repositorio de acceso abierto de la Universidad Nacional de Colombia, en el cual se administran, preservan y difunden todas las obras monográficas que la Universidad ha producido a través de su historia, incluyendo libros, tesis y trabajos de grado, trabajos docentes, entre otros

Tipo = Artículo - Article

Mostrando recursos 1 - 20 de 27.434

  1. Letter from editor

    Vargas, Carlos A.
    During the outgoing year, successful events took place, as Latin American and Caribbean Seismological Commission Assembly, on July 23, 24, 25, in Bogotá, Colombia. In that academic event, the relevant results associated with the seismotectonic behavior of the Latin America and Caribbean region were addressed, as well as the implications of active exploration of the tectonic conditions, the socio-economic impacts of exploration and extraction of economic resources, and the implementation of non-conventional techniques for exploring and mining that can contribute to sustainable development. Another event was the Shale Colombia 2014, unconventional oil and gas development congress, aimed to determine the...

  2. Study of the mineralization potential of the intrusives around Valis (Tarom-Iran)

    Bahajroy, Mojtaba; Taki, Saeed
    The study area is located in northwestern Iran in the central Iran zone, specifically the western Alborz sub-zone south of the Tarom-Hashtjin metallogenic zone. The exposed rock units in this area generally include Eocene volcanic rocks (lava flows and pyroclasts belonging to the Karaj formation) and Oligocene granitoid intrusive bodies. The intrusive bodies in the area have a petrographic composition of granite, syenite and monzonite and are mostly metaluminous. The dual characteristics of these intrusives (for example, the behavior of elements such as Rb, P, Ga/Al, Y/Nb, K/Na, and FeO/Fe2O3, the Rb/Nb ratios, the A/CNK molar ratios and the ACF...

  3. Land ecological security assessment for Yancheng city based on catastrophe theory

    Liang, Wang; Zhengfu, Bian; Hongquan, Chen
    Based on actual land use in Yancheng city, this paper establishes the ecological security of the land index system from the perspectives of economy, society and ecological environment. Using the catastrophe theory and pressure-state-response (PSR) model, the purpose of the research was to judge the degree of land ecological security in Yancheng city from 2002 to 2011 and determine the requirements to ensure the sustainable development of this region. The results showed that over the ten years, the pressure, state, response and synthetic values of the land ecological security were evaluated as safe in 2003 and 2007 and at middle...

  4. Spatial distribution of sediment pollution in the Khajeh Kory River using Kriging and GIS

    Zare, Maryam
    The aim of this research was to study of sediment pollution conditions in the river bed of Khajeh Kory, which passes from the southern border of the Caspian Sea in Astara City. To determine the pollution of river bed sediment along the route, from the river source in the heights to estuary in the Caspian sea, sampling was conducted at 10 stations. Afterward, each sample was divided into two groups based on size (>63 µm and <63 µm). The concentration of heavy metals Cu, Cd, Co, Zn, Pb, Ni, Fe, and Mn in each group was measured using ICP-OES. In...

  5. Critical undrained shear strength of sand-silt mixtures under monotonic loading

    Bensoula, Mohamed; Missoum, Hanifi; Bendani, Karim
    This study uses experimental triaxial tests with monotonic loading to develop empirical relationships to estimate undrained critical shear strength. The effect of the fines content on undrained shear strength is analyzed for different density states. The parametric analysis indicates that, based on the soil void ratio and fine content properties, the undrained critical shear strength first increases and then decreases as the proportion of fines increases, which demonstrates the influence of fine content on a soil’s vulnerability to liquefaction. A series of monotonic undrained triaxial tests were performed on reconstituted saturated sand-silt mixtures. Beyond 30% fines content, a fraction of...

  6. Compression ratio of municipal solid waste simulation using artificial neural network and adaptive neurofuzzy system

    Mokhtari, Maryam; Heshmati R., Ali Akbar; Shariatmadari, Nader
    The compression ratio of Municipal Solid Waste (MSW) is an essential parameter for evaluation of waste settlement. Since it is relatively time-consuming to determine compression ratio from oedometer tests and there exist difficulties associated with working on waste materials, it will be useful to develop models based on waste physical properties. Therefore, present research attempts to develop proper prediction models using ANFIS and ANN models. The compression ratio was modeled as a function of the physical properties of waste including dry unit weight, water content, and biodegradable organic content. A reliable experimental database of oedometer tests, taken from the literature,...

  7. Estimating shear wave velocity using acceleration data in Antakya (Turkey)

    Buyuksarac, Aydın; Over, Semir; Genes, Mehmet Cemal; Bikce, Murat; Kacin, Selcuk; Bektas, Ozcan
    This manuscript presents a site response analysis and an estimation of S-wave velocity that are dependent on acceleration data. First, existing data, such as density, seismic wave velocity, and soil cross-sections, are obtained from previous seismic microzonation studies and used to prepare input data for a suite of MATLAB routines, which are referred to as SUA software. Acceleration data are obtained from four free-field strong-motion stations of the SERAMAR project, which was conducted between 2006 and 2009 in conjunction with a Turkish-German joint research project, and inputted into the software as basic data. The results include a 1D velocity cross-section...

  8. Geostatistical Analysis for delineating sterile inclusions in Sidi Chennane' phosphatic series, Morrocco

    Baba, Khadija; Bahi, Lahcen; Ouadif, Latifa
    The anomalies detected in phosphatic series of Sidi Chennane, one of phosphatic basins in Morocco, hinder the proper exploitation of phosphate levels and the assessing phosphate reserves seems incorrect. The purpose of this study was the evaluation of geostatistical methods for delimitation of these disturbances. To cover all the zones being able to be disturbed, we carried out, during the geophysical prospection in a parcel of 50 ha, 5151 resistivity measurements as horizontal profiling using the well-known Schlumberger array, in order to map the spatial distribution of  the sterile hardpan inclusions.Geostatistical tools were used to quantify the spatial correlation between...

  9. Severity Classification of a Seismic Event based on the Magnitude-Distance Ratio Using Only One Seismological Station

    Ochoa Gutiérrez, Luis Hernán; Niño, Luis F; Vargas, Carlos A.
    Seismic event characterization is often accomplished using algorithms based only on information received at seismological stations located closest to the particular event, while ignoring historical data received at those stations. These historical data are stored and unseen at this stage. This characterization process can delay the emergency response, costing valuable time in the mitigation of the adverse effects on the affected population. Seismological stations have recorded data during many events that have been characterized by classical methods, and these data can be used as previous "knowledge" to train such stations to recognize patterns. This knowledge can be used to make...

  10. Shear-wave velocity structure of Australia from Rayleigh-wave analysis

    Corchete, Víctor
    The elastic structure beneath Australia is shown by means of S-velocity maps for depths ranging from zero to 400 km, determined by the regionalization and inversion of Rayleigh-wave dispersion. The traces of 233 earthquakes, occurred from 1990 to 2010, have been used to obtain Rayleigh-wave dispersion data. These earthquakes were registered by 65 seismic station located in Australia and the surrounding area. The dispersion curves were obtained for periods between 5 and 250 s, by digital filtering with a combination of MFT (Multiple Filter Technique) and TVF (Time Variable Filtering), filtering techniques. Later, all seismic events (and some stations) were...

  11. Caving Depth Classification by Feature Extraction in Cuttings Images

    Galvis, Laura Viviana; Corzo Rueda, Reinel; Arguello, Henry
    The estimation of caving depth is of particular interest in the oil industry. During the drilling process, the rock classification problem is studied to analyze the concentration of cuttings at the vibrating shale shakers through the classification of caving images. To date, depth estimation based on caving rock images has not been treated in the literature. This paper presents a new depth caving estimation system based on the classification of caving images through feature extraction. To extract the texture descriptors, the cutting images are first mapped on a common space where they can be easily compared. Then, textural features are...

  12. Sand dunes of the Gaza Strip (southwestern Palestine): morphology, textural characteristics and associated environmental impacts

    Ubeid, Khalid Fathi; Albatta, Alhasan S.
    Sand dunes are wide spread in the Gaza Strip and are present in its northern, central and southern regions. Thirty sand samples were collected at seven locations along the middle region of the Strip. The coordinates for each sampling site were positioned using GPS and processed with ArcGIS software.Mechanical and chemical properties were examined to determine the textural characteristics and carbonate contents of the dune sands. The mean grain size is fine to medium, and the sands range from moderate- to well-sorting. The skewness is fine to very fine, and the kurtosis ranges from mesokurtic to very leptokurtic. Additionally, the...

  13. A semi-automatic approach to identify first arrival time: the Cross-Correlation Technique

    Senkaya, Mustafa; Karslı, Hakan
    The high-quality interpretation of seismic refraction data depends on the accurate and reliable identification of the first arrival times. First arrivals can be identified on a graphic or image by conventional picking, but this process depends on external factors, such as the scale and quality of the imaging data, amplitude ratio, sensitivity of the picking cursor and user experience. Under these considerations, identifying first arrivals in noisy data becomes more complex and unstable. In this study, the Cross-Correlation Technique (CCT), which is widely used in the process of analyzing reflection data, has been used to pick the first arrival times...

  14. Letter from editor

    Vargas Jiménez, Carlos A.
    More than two decades ago we have been working steadily to providereaders and scientific community with articles on a broad range of geosciences field around the world. This achievement would not be possible without the support of the Universidad Nacional de Colombia, mainly, and partners who help bring these high-quality papers to light. One of those partners is Colciencias, a Colombian Government-owned agency that support research in our country. Currently, Colciencias is carrying out a national strategic plan for Science, Technology and Innovation in Geosciences aimed to promote and develop megaprojects in the area, provide a management tool, and create a...

  15. Using GIS And Geophysics In Selecting Suitable Basins With Freshwater Aquifers For An Efficient Exploration Strategy - A Case Study From Petra-Region, Jordan

    Al Farajat, Mohammmad; Schaefers, Bernhard; Al Hassanat, Hussein; Al Atteyat, Nedal; Al Jahed, Nidal; Khataibeh, Jamal
    In this study, an effective and time-saving strategy for groundwater exploration in alluvium basins in arid-semiarid lands was applied by integrating GIS and geophysics. Three steps were followed to locate productive local groundwater aquifers prone to annual recharge in the Region of Petra, which covers an area of 800 km². In the first step, geological, structural and geomorphological knowledge was applied to determine the parts of the sedimentary basin having potentials of being local groundwater aquifers. Some locality of the selected area with suitable hydrological conditions for recharge was chosen for an optimization process using GIS. In the second step,...

  16. Petrology and mineralogy of the Fenghuanshan granodiorite, Anhui Province, China: implications for petrogenesis and metallogenesis implication

    Aiping, Zhang; Du, Yangsong; Cao, Yi; Pang, Zhenshan; Luo, Gan; Xu, Kangkang
    The Fenghuangshan copper deposit, in the Tongling area of Anhui Province, China, is genetically associated with the Fenghuangshan granodiorite, which contains amphiboles that can be used to determine the pressure and temperature history of the magmas that formed this intrusion. Here, we investigate the petrography and mineralogy of the Fenghuangshan granodiorite, focusing on variations in amphibole composition and determining the conditions of amphibole crystallization. The data are used to determine the petrogenetic history and metallogenic significance of the hosting granodiorite. The amphiboles within the intrusion can be divided by texture into phenocryst, matrix, and poikilocrystal amphiboles. Electro model, combined with...

  17. Altimetric and hypsometric analysis for soil and water conservation: A case study of Anjani and Jhiri river basin, Northern Maharashtra, India

    Golekar, Rushikesh Baburao; Baride, Mukund Vasantrao; Patil, Sanjaykumar Narayan; Adil, S H
    The present paper contains longitudinal profile, hypsometric analysis of river basin and geomorphological studies for future planning of soil and water conservation in Anjani and Jhiri river basin, Jalgaon district, Maharashtra, India (20°45’ to 21°08’N Latitude and 75°09’ to 75°27’E Longitude). The main aim of the present study is to recommend a suitable site for soil and water conservation in Anjani and Jhiri river basin, Northern Maharashtra, India. The study area is geologically covered by Deccan trap basalts of the Cretaceous to the lower Eocene age, and some part is covered by thick alluvium of the Quaternary age. Drainage map...

  18. Gis Based SCS - CN Method For Estimating Runoff In Kundahpalam Watershed, Nilgries District, Tamilnadu

    Raja, Viji
    Divination and determination of catchment surface runoff are the most important contestable process of hydrology. Soil Conservation Service - Curve Number (SCS – CN) method is employed to estimate the runoff. It is one of the physical based and spatially distributed hydrological models. In this model, the curve number is a primary factor used for runoff calculation. The selection of curve number is based on the land use pattern and HSG (Hydrological Soil Group) present in the study area. Since the spatial distribution of CN estimation by the conventional way is very difficult and time consuming, the GIS (Geographic Information...

  19. A Review Of Road‒Related Soil Erosion: An Assessment Of Causes, Evaluation Techniques And Available Control Measures

    Seutloali, Khoboso Elizabeth; Reinhard Beckedahl, Heinrich
    Road construction has increased significantly worldwide in the last decades to meet the demands of the increasing human population and this has led to serious soil erosion problems, the bulk of which is unaccounted for, especially in the developing world. For comprehensive land management decisions and monitoring strategies, a review of work that has been done to assess soil erosion due to roads is critical. This article, therefore, reviews the causes of road‒related soil erosion, assessment methods and available control measures. Specifically, work provides an overview of (i) the linkages between roads and soil erosion; (ii) measurement and prediction of...

  20. Ti-clinohumite in the Ciénaga skarn-type mineralogy, Sierra Nevada de Santa Marta Massif (Colombia): Occurrence and petrologic significance

    Ríos, Carlos Alberto; Castellanos, Óscar Mauricio; Chacón, Carlos Alberto
    This study reports the occurrence and petrologic significance of Ti-clinohumite for the first time in the Ciénaga skarn, Sierra Nevada de Santa Marta Massif. Ti-Clinohumite occurs as thin bands hosted in the Ciénaga Marbles of lower Cretaceous age, which consist of quartz-wollastonite-diopside-garnet-clinohumite marbles. We focus the attention on the occurrence of Ti-clinohumite-bearing domains, highlighting some interesting textures as well as the mineralogy and chemistry of the Ti-clinohumite. On the basis of its geologic situation, petrography, mineral composition and metamorphic history, we discuss the origin of Ti-clinohumite. ResumenEl estudio reporta la presencia y el significado petrológico de Ti-clinohumita por primera vez en...

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