122,225 research outputs found
Geothermal reservoir potential of volcaniclastic settings: The Valley of Mexico, Central Mexico
No full textThe Anisian carbonate ramp system of Central Europe (Peri-Tethys Basin): Sequences and reservoir characteristics
No full textVolcanic settings and their reservoir potential : an outcrop analog study on the Miocene Tepoztlán Formation, Central Mexico
No full textThe reservoir potential of volcanic and associated sedimentary rocks is less documented in regard to groundwater resources, and oil and gas storage compared to siliciclastic and carbonate systems. Outcrop analog studies within a volcanic setting enable to identify spatio-temporal architectural elements and geometric features of different rock units and their petrophysical properties such as porosity and permeability, which are important information for reservoir characterization. Despite the wide distribution of volcanic rocks in Mexico, their reservoir potential has been little studied in the past. In the Valley of Mexico, situated 4000 m above the Neogene volcanic rocks, groundwater is a matter of major importance as more than 20 million people and 42% of the industrial capacity of the Mexican nation depend on it for most of their water supply. Here, we present porosity and permeability data of 108 rock samples representing five different lithofacies types of the Miocene Tepoztlán Formation. This 800 m thick formation mainly consists of pyroclastic rocks, mass flow and fluvial deposits and is part of the southern Transmexican Volcanic Belt, cropping out south of the Valley of Mexico and within the two states of Morelos and Mexico State. Porosities range from 1.4% to 56.7%; average porosity is 24.8%. Generally, permeabilities are low to median (0.2–933.3 mD) with an average permeability of 88.5 mD. The lavas are characterized by the highest porosity values followed by tuffs, conglomerates, sandstones and tuffaceous breccias. On the contrary, the highest permeabilities can be found in the conglomerates, followed by tuffs, tuffaceous breccias, sandstones and lavas. The knowledge of these petrophysical rock properties provides important information on the reservoir potential of volcanic settings to be integrated to 3D subsurface models.University of Pretoria and TU Darmstadt Energy Center.http://www.elsevier.com/locate/jvolgeoresnf201
Palynomorph preservation in volcaniclastic rocks of the Miocene Tepoztlan formation (Central Mexico) and implications for paleoenvironmental reconstruction
No full textPalynomorph preservation in sedimentary rocks is strongly affected by various taphonomic
factors related to transport, deposition, diagenesis and preservation potential. The
palynological record may contribute to distinguish different taphonomic factors and also
displays changes in paleoenvironment, especially in volcanic settings where a very complex
interaction of eruptive, gravitational and fluvial processes in time and space can be observed.
Herein, we report on new palynological data from the Miocene Tepoztlán Formation. The 800
m thick formation mainly consists of pyroclastic rocks, mass flow units (lahars) and fluvial
deposits. It is part of the southern Transmexican Volcanic Belt, cropping out south of the
Valley of Mexico and within the two states of Morelos and Mexico State. The volcaniclastic
succession records various stages of recovery of vegetation related to a wide variety of
disturbance factors and mechanisms. During the entire period of deposition, mixed
mesophytic forests appear to have been widespread in the lowlands along streams and midaltitude
uplands surrounding the valley. Pollen assemblages were repeatedly reset by volcanic
eruptions or their secondary effects (lahars) to more limited assemblages with gradual recoveries to the initial stages before the eruption. A clear distinction can be made between
samples taken from different transport regimes (fluvial, lahar and pyroclastic flow transport).
The highest percentages of well-preserved, amorphous, and crumpled palynomorphs can be
found in fluvial sediments while the highest percentage of fragmented palynomorphs is
characteristic of lahar deposits. In contrast, the highest percentage of corroded palynomorphs
can be found in deposits originating from pyroclastic flows.http://palaios.sepmonline.orghb201
A Brain-Computer Interface for robotic arm control
No full textLenhardt A. A Brain-Computer Interface for robotic arm control. Bielefeld: Universität Bielefeld; 2011.Brain-Computer Interfaces (BCI) are tools that open a new channel of communication between humans and machines.
The majority of human input devices for computers require proper functioning of our primary sensors and motor
functions like grasping, moving and visual perception. In the case of severe motor disabilities, like amyotrophic
lateral sclerosis (ALS) or spinal chord injury (SCI),
The most common method to measure brain activity suitable for BCI are electroencephalographic measurements (EEG)
due to their relative cost effectiveness and ease of use. Alternative ways to extract brain signals exist but
either require invasive procedures, i.e. opening the skull, or are very costly and bulky (MEG, fMRI)
which renders them unusable for home appliance.
One of the most popular brain controlled input methods is the P300-Speller paradigm
which gives the user control over a virtual keyboard to enter text. The term P300 refers to a specific EEG component
that can be measured whenever a rare task relevant stimulus is interspersed with many non-relevant stimuli. This method requires
the ability to control the visual presentation of stimuli and therefore also requires some sort of computer controlled display.
The recognition rates for this type of BCI, yet already quite high with roughly 80-90% accuracy,
are still prone to errors and may not be suitable for critical applications like issuing movement commands to a wheelchair
in a highly populated environment. Commands to stop the wheelchair might be recognized too late.
Further, it is impossible with the standard stimulus matrix to react to external influences like obstacles or select physical objects
in a scene which does not allow the user to interact with a dynamic environment.
This work aims to fuse state of the art BCI techniques into one single system to control an artificial actuator
like a robot arm and use it to manipulate the physical environment. To achieve this goal, multiple techniques originating
from different fields of research as augmented reality, computer vision, psychology, machine learning and data mining have
to be combined to form a robust, intuitively to use input device
Geothermal Energy from the Main Karoo Basin (South Africa): An Outcrop Analogue Study of Permian Sandstone Reservoir Formations
No full textAbstractThe geothermal potential of the Main Karoo Basin has not been addressed in the past. A first assessment of Permian sandstone formations in the Eastern Cape Province, including down-hole temperature data from deep boreholes, and evaluation of groundwater temperature and heat flow values from literature leads to 3130 TWh (11.3 EJ) of power generation potential within the central and southern parts of the basin. The low permeability lithotypes may be operated as enhanced geothermal systems (EGS), depending on the fracture porosity in the deeper subsurface. In some areas auto-convective thermal water circulation might be expected and direct heat use becomes reasonable
A Multi-Language Comparison of Influences on Author Verification using Character N-Grams
No full textWe create a new multi-language corpus for author verification based on Wikipedia talkpages, and evaluate the influence that differences in topic and time have on character n-gram author profiles. Topic alignment between two texts is found to increase author verification precision, and an authors writing style is found to change over time, but not more significantly after 3 years than after 1 year.Information ArchitectureWISElectrical Engineering, Mathematics and Computer Scienc
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Influence of crown height, root length and crown-to root ratio on the survival of healed teeth after surgical retreatment
No full textN/
The vanishing author in computer-generated works: a critical analysis of recent Australian case law
No full textAbstract
The use of software is ubiquitous in the creation of many copyright works, yet the requirement in copyright law that every work have a human author who engages in independent intellectual effort means that its use may prevent copyright subsistence. Several recent Australian cases have refocused attention on authorship as an essential criterion of copyright subsistence, and these cases suggest that much computer-produced output may be authorless and thus lack copyright protection. This article, the first in a two-part series, analyses how each case deals with the question of authorship of computer-produced works and why the use of software diminishes copyright protection for a significant number of computer-generated works. The article critiques the application of conventional notions of human authorship developed in the pre-computer age to modern productions and suggests alternative approaches to authorship that satisfy both the major objectives of copyright policy and the need to adapt to the computer age. The article argues that, without a broader judicial approach to authorship of computer-generated works, Parliament must remedy the lacuna in protection for these ‘authorless’ works. Possible solutions for reform are suggested. In a forthcoming article, the author comprehensively examines those reform proposals
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