936 resultados para Allen’s Time Interval Calculus


Relevância:

100.00% 100.00%

Publicador:

Resumo:

Long-term environmental time series of continuously collected data are fundamental to identify and classify pulses and determine their role in aquatic systems. This paper presents a web based archive for limnological and meteorological data collected by integrated system for environmental monitoring (SIMA). The environmental parameters that are measured by SIMA are: chlorophyll-a (µg/L), water surface temperature (ºC), water column temperature by a thermistor string (ºC), turbidity (NTU), pH, dissolved oxygen concentration (mg/L), electric conductivity (µS/cm), wind speed (m/s) and direction (º), relative humidity (%), short wave radiation (W/m**2), barometric pressure (hPa). The data are collected in preprogrammed time interval (1 hour) and are transmitted by satellite in quasi-real time for any user in a range of 2500 km from the acquisition point. So far 11 hydroelectric reservoirs being monitored using the SIMA buoy. A basic statistics (mean and standard deviation) for some parameters and an example of time series were displayed. The main observed problem are divided into sensors and satellite. The sensors problems is due to the environmental characteristics of each water body. In acid waters the sensors of water quality rapidly degrade, and the collected data are invalid. Another problem is the infestation of periphyton in the sensor. SIMA buoy makes the parameters readings every hour, or 24 readings per day. However, not always received all readings because the system requires satellites passing over the buoy antenna to complete the transfer and due to the satellite constellation position, some locations inland are not met as often as necessary to complete all transmissions. This is the more often causes for lack in the time series.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

The eruption of Eyjafjallajökull volcano in 2010 lasted for 39 days, 14 April-23 May. The eruption had two explosive phases separated by a phase with lava formation and reduced explosive activity. The height of the plume was monitored every 5 min with a C-band weather radar located in Keflavík International Airport, 155 km distance from the volcano. Furthermore, several web cameras were mounted with a view of the volcano, and their images saved every five seconds. Time series of the plume-top altitude were constructed from the radar observations and images from a web camera located in the village Hvolsvöllur at 34 km distance from the volcano. This paper presents the independent radar and web camera time series and performs cross validation.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Deep-water benthic ostracodes from the Pliocene-Pleistocene interval of ODP Leg 107, Hole 654A (Tyrrhenian Sea) were studied. From a total of 106 samples, 40 species considered autochthonous were identified. Detailed investigations have established the biostratigraphic distribution of the most frequent ostracode taxa. The extinction levels of Agrenocythere pliocenica (a psychrospheric ostracode) in Hole 654A and in some Italian land sections lead to the conclusion that the removal of psychrospheric conditions took place in the Mediterranean Sea during or after the time interval corresponding to the Small Gephyrocapsa Zone (upper part of early Pleistocene), and not at the beginning of the Quaternary, as previously stated. Based on a reduced matrix of quantitative data of 63 samples and 20 variables of ostracodes, four varimax assemblages were extracted by a Q-mode factor analysis. Six factors and eight varimax assemblages were recognized from the Q-mode factor analysis of the quantitative data of 162 samples and 47 variables of the benthic foraminifers. The stratigraphic distributions of the varimax assemblages of the two faunistic groups were plotted against the calcareous plankton biostratigraphic scheme and compared in order to trace the relationship between the benthic foraminifers and ostracodes varimax assemblages. General results show that the two populations, belonging to quite different taxa, display almost coeval changes along the Pliocene-Pleistocene sequence of Hole 654A, essentially induced by paleoenvironmental modifications. Mainly on the base of the benthic foraminifer assemblages (which are quantitatively better represented than the ostracode assemblages), it is possible to identify such modifications as variations in sedimentation depth and in bottom oxygen content.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

We consider a problem of robust performance analysis of linear discrete time varying systems on a bounded time interval. The system is represented in the state-space form. It is driven by a random input disturbance with imprecisely known probability distribution; this distributional uncertainty is described in terms of entropy. The worst-case performance of the system is quantified by its a-anisotropic norm. Computing the anisotropic norm is reduced to solving a set of difference Riccati and Lyapunov equations and a special form equation.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

The purpose of this study was to determine the extent to which oceanic anoxic events (OAE's) are recorded in deep-water deposits of the former western Tethyan Sea, by investigating the Cenomanian-Turonian time interval characterized by the worldwide OAE 2 event. The study improved our knowledge of the possible controlling mechanisms that triggered this event at these sites, and furthered our understanding of this global phenomenon. This was examined by high-resolution, multi-proxy analyses of sediments at DSDP Sites 386 and 144, including sedimentology, scanning electron microscopy, stable isotopes, bulk and clay mineralogy, major and trace element geochemistry, biomarkers, and paleontological data. ^ The results provide a better stratigraphic resolution for the Cenomanian-Turonian, which allowed for more precise determination of chronologic boundaries, sedimentation rates at DSDP Site 386, and a more accurate calculation of the frequency of the cycles recorded in the sequence, which fall predominantly within the precession (∼23 kyr) and short eccentricity (∼100 kyr) ranges. The combined proxies allow assessment of the correlation of δ13Corg, and major and trace elements with the predominance of cyanobacteria. These organisms were the main producers of the organic matter during the dysoxic and euxinic conditions of OAE 2 at DSDP Site 386. A huge amount of microcrystalline quartz of eolian origin is also associated with OAE 2. The geochemical proxies further provide evidence that OAE 2 was linked to increased volcanism outside the deep water of the proto-Atlantic Ocean. The clays in the Turonian sediments are terrigenous and derived predominantly from eolian transport. Comparing DSDP Site 386 and 144 with stratotype sections, the δ13C org and TOC data indicate that OAE 2 seems diachronous throughout the proto-Atlantic Ocean. ^ This study concludes that the development of anoxic conditions in the deep water of the Atlantic during the latest Cenomanian-Turonian resulted from a combination of factors related to local oceanic setting and mitigated by global tectonism and climate. The data provide a more comprehensive view of the interacting factors that led to sustained high productivity of the cyanobacteria and photosynthetic protists that produced organic-carbon-rich deposits in the world's oceans. ^

Relevância:

100.00% 100.00%

Publicador:

Resumo:

One commonality across the leadership and knowledge related literature is the apparent neglect of the leaders own knowledge. This thesis sought to address this issue through conducting exploratory research into the content of leader’s personal knowledge and the process of knowing it. The empirical inquiry adopted a longitudinal approach, with interviews conducted at two separate time periods with an extended time-interval between each. The findings from this research contrast with images of leadership which suggest leaders are in control of what they know, that they own their own knowledge. The picture that emerges is one of individuals struggling to keep abreast of the knowledge required to deal with the dynamics and uncertainties of organisational life. Much knowledge is tacit, provisional and perishable and the related process of knowing more organic, evolutionary and informal than any structured or orchestrated approach. The collective nature of knowing is a central feature, with these leaders embedded in networks of uncontrollable relationships. In view of the indeterminate nature of knowing, the boundary between what is known and what one needs to know is both amorphous and ephemeral, and the likelihood of knowledge-absences is escalated. A significant finding in this regard is the identification of two critical points where not-knowing is most likely (entry and exit from role) and the differing implications of each. Overtime the knowledge that is legitimised or prioritised is significantly altered as these leaders replace the dogmas that were previously held in high esteem with the lessons from their own experience. This experience brings increased self-knowledge and a deeper appreciation of the values and morals instilled in their early lives. In view of the above findings, this study makes theoretical contribution to a number of core literatures: authentic leadership, role transition and knowledge-absences. In terms of leadership development, the findings point to the necessity to prepare leaders for the challenges they will encounter at the pivotal stages of the leadership role.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

The data set consists of maps of total velocity of the surface current in the North-Western Tyrrhenian Sea and Ligurian Sea averaged over a time interval of 1 hour around the cardinal hour. Surface ocean velocities estimated by HF Radar are representative of the upper 0.3-2.5 meters of the ocean. Total velocities are derived using least square fit that maps radial velocities measured from individual sites onto a cartesian grid. The final product is a map of the horizontal components of the ocean currents on a regular grid in the area of overlap of two or more radar stations.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

The data set consists of maps of total velocity of the surface current in the Southeastern Bay of Biscay averaged over a time interval of 1 hour around the cardinal hour. Surface ocean velocities estimated by this HF Radar(4.65 MHz) are representative of the upper 2-3 meters of the ocean. The main objective of near real time processing is to produce the best product from available data at the time of processing. Total velocities are derived using least square fit that maps radial velocities measured from individual sites onto a cartesian grid. The final product is a map of the horizontal components of the ocean currents on a regular grid in the area of overlap of two or more radar stations.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

In the Salgesch forest in the Canton of Valais in Switzerland, the understory has been removed to test whether effects on pine tree vitality. The data set published here compromises 120 time series of 60 soil temperature and 60 volumetric water content (VWC) sensors (EC-TM and 5-TM) (Decagon Devices, WA, USA) at three soil depth levels (5, 30, 60 cm) employed in the direct vicinity of six control trees and six trees with the undergrowth removed. At the levels 5 and 60 cm, three replications were made whereas 4 replications were made at level 30 cm. Six loggers recorded hourly data since 2010 with 18% gaps or 11% when not considering winter months December, January and February. The figure attached to this repository shows the average VWC and temperature of all measurements within the same depth and treatment specific setting aggregated in a defined time interval and period. In addition to that, the standard deviations are plotted as transparent polygons. In case of insufficient values for calculating standard deviations, the setting specific mean standard deviation of the considered time period are inserted.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Neste trabalho, generalizamos o Princípio da Mínima Ação proposto por Riewe para sistemas não conservativos, contendo forças dissipativas lineares dependentes de derivadas temporais de qualquer ordem. A Ação generalizada é construída a partir de funções Lagrangianas dependentes de derivadas de ordem inteira e fracionária. Diferente de outras formulações, o uso de derivadas fracionárias permite a construção de Lagrangianas físicas para sistemas não conservativos. Uma Lagrangiana é dita física se fornece relações fisicamente consistentes para o momentum e o Hamiltoniano do sistema. Neste Princípio da Mínima Ação generalizado, as equações de movimento são obtidas a partir da equação de Euler-Lagrange e, tomando-se o limite indo à zero para o intervalo de tempo definindo a Ação. Finalmente, como exemplo de aplicação, formulamos pela primeira vez uma Lagrangiana física para o problema da carga pontual acelerada.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

To investigate the degree of T2 relaxometry changes over time in groups of patients with familial mesial temporal lobe epilepsy (FMTLE) and asymptomatic relatives. We conducted both cross-sectional and longitudinal analyses of T2 relaxometry with Aftervoxel, an in-house software for medical image visualization. The cross-sectional study included 35 subjects (26 with FMTLE and 9 asymptomatic relatives) and 40 controls; the longitudinal study was composed of 30 subjects (21 with FMTLE and 9 asymptomatic relatives; the mean time interval of MRIs was 4.4 ± 1.5 years) and 16 controls. To increase the size of our groups of patients and relatives, we combined data acquired in 2 scanners (2T and 3T) and obtained z-scores using their respective controls. General linear model on SPSS21® was used for statistical analysis. In the cross-sectional analysis, elevated T2 relaxometry was identified for subjects with seizures and intermediate values for asymptomatic relatives compared to controls. Subjects with MRI signs of hippocampal sclerosis presented elevated T2 relaxometry in the ipsilateral hippocampus, while patients and asymptomatic relatives with normal MRI presented elevated T2 values in the right hippocampus. The longitudinal analysis revealed a significant increase in T2 relaxometry for the ipsilateral hippocampus exclusively in patients with seizures. The longitudinal increase of T2 signal in patients with seizures suggests the existence of an interaction between ongoing seizures and the underlying pathology, causing progressive damage to the hippocampus. The identification of elevated T2 relaxometry in asymptomatic relatives and in patients with normal MRI suggests that genetic factors may be involved in the development of some mild hippocampal abnormalities in FMTLE.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

We tested the hypothesis that chronic pain development (pain chronification) and ongoing chronic pain (chronic pain) reduce the activity and induce plastic changes in an endogenous analgesia circuit, the ascending nociceptive control. An important mechanism mediating this form of endogenous analgesia, referred to as capsaicin-induced analgesia, is its dependence on nucleus accumbens μ-opioid receptor mechanisms. Therefore, we also investigated whether pain chronification and chronic pain alter the requirement for nucleus accumbens μ-opioid receptor mechanisms in capsaicin-induced analgesia. We used an animal model of pain chronification in which daily subcutaneous prostaglandin E2 (PGE2) injections into the rat's hind paw for 14 days, referred to as the induction period of persistent hyperalgesia, induce a long-lasting state of nociceptor sensitization referred to as the maintenance period of persistent hyperalgesia, that lasts for at least 30 days following the cessation of the PGE2 treatment. The nociceptor hypersensitivity was measured by the shortening of the time interval for the animal to respond to a mechanical stimulation of the hind paw. We found a significant reduction in the duration of capsaicin-induced analgesia during the induction and maintenance period of persistent mechanical hyperalgesia. Intra-accumbens injection of the μ-opioid receptor selective antagonist Cys(2),Tyr(3),Orn(5),Pen(7)amide (CTOP) 10 min before the subcutaneous injection of capsaicin into the rat's fore paw blocked capsaicin-induced analgesia. Taken together, these findings indicate that pain chronification and chronic pain reduce the duration of capsaicin-induced analgesia, without affecting its dependence on nucleus accumbens μ-opioid receptor mechanisms. The attenuation of endogenous analgesia during pain chronification and chronic pain suggests that endogenous pain circuits play an important role in the development and maintenance of chronic pain.