A novel radiation imaging sensor based on self-activated pixels

A new position sensitive detector for charged particles and X-rays is proposed based on pixels containing MOS transistors as preamplifiers. The output of the preamplifiers is shorted to strip buses to obtain two-dimensional information with readout requirements similar to a strip detector. The total pixel capacitance is low enough (20-40 fF) to allow a large potential increase at the pixel that collected the charge. The nonlinearity introduced by the large voltage rise effectively switches on the transistors of this pixel and leaves all the other pixels of the same line at a low transconductance state, resulting in an excellent noise performance     

The inverse medium problem in heterogeneous PML-truncated domains using scalar probing waves

We discuss the inverse medium problem associated with semi-infinite domains. In particular, we attempt to image the spatial variability of shear moduli or shear wave velocities from scant surficial measurements of an arbitrarily heterogeneous semi-infinite domain’s response to prescribed dynamic excitations.We use a full waveform approach to drive the inversion process, within a PDE-constrained optimization framework. Due to the semi-infinite extent of the targeted domains, we introduce perfectly-matched-layers (PMLs) to arrive at finite computational domains. The numerical implementation is based on a mixed finite-element method that is used to resolve the ensuing state and adjoint boundary-value problems, both of which are PML-endowed. To alleviate the inherent solution multiplicity, we use Tikhonov and total variation (TV) regularization schemes, in conjunction with a regularization factor continuation scheme. To further improve the optimizer’s chances to converge, we also discuss a source-frequency continuation scheme.We report on two-dimensional numerical experiments using synthetic data. Included are layered profiles, and profiles involving inclined layers and inclusions. We also report on our methodology’s reconstruction of the highly-heterogeneous Marmousi benchmark velocity model.     

Developmental trajectories of disruptive behavior problems among sons of alcoholics: Effects of parent psychopathology, family conflict, and child undercontrol.

This study examined trajectories of disruptive behavior problems from preschool to early adolescence in 302 boys from a community-recruited sample of high-risk families. Growth modeling showed that paternal alcoholism was associated with elevated levels of sons' disruptive behavior problems. Family conflict predicted more disruptive behaviors at school entry and a slower rate of decline in such problems. Parent antisocial personality disorder (ASPD) exacerbated the effects of high preschool levels of sons' undercontrol on level of disruptive behaviors at school entry; this effect became progressively stronger across time. Low levels of undercontrol protected sons of ASPD parents from experiencing heightened levels of disruptive behaviors both at school entry and increasingly as sons grew older. Implications for subsequent maladjustment are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A Modeling System for the Evaluation of Water Resources Management Strategies in Thessaly,Greece

A modeling system was developed to evaluate the sustainability of water resources management strategies in the two major basins of Thessaly Region in Greece, namely the Pinios River and the Lake Karla basins. The intense and extensive agriculture of water demanding crops, such as cotton, and the absence of reasonable water resources management have lead to a remarkable water demand increase, which is usually fulfilled by the over-exploitation of groundwater resources. This unsustainable practice has deteriorated the already disturbed water balance and accelerated water resources degradation. The modeling system consists of a hydrological model, a reservoir operation model and methods for the estimation of water demands. The study area was sub-divided into sub-basins and water balance analyses were performed for each sub-basin and each control node of the system for a number of water resources management strategies. Four strategies of hydro-technical project development were coupled with two strategies of groundwater withdrawal and three water demand strategies. In total, more than 24 water management strategies were evaluated. The results showed that, under the existing water resources management, the water deficit of the Pinios River and Lake Karla basins is very large. However, the development of proposed hydro-technical projects in the Pinios River basin coupled with water demand management measures, like improvement of existing water distribution systems, change of irrigation methods, and changes of crop cultivation could alleviate the problem and lead to sustainable and ecological use of water resources in the study area.     

A sparse and spatially constrained generative regression model for fMRI data analysis

In this study, we present an advanced Bayesian framework for the analysis of functional magnetic resonance imaging (fMRI) data that simultaneously employs both spatial and sparse properties. The basic building block of our method is the general linear regression model that constitutes a well-known probabilistic approach. By treating regression coefficients as random variables, we can apply an enhanced Gibbs distribution function that captures spatial constrains and at the same time allows sparse representation of fMRI time series. The proposed scheme is described as a maximum a posteriori approach, where the known expectation maximization algorithm is applied offering closed-form update equations for the model parameters. We have demonstrated that our method produces improved performance and functional activation detection capabilities in both simulated data and real applications.     

Predicting fluid phase equilibrium via histogram reweighting with Gibbs ensemble Monte Carlo simulations

One of the most challenging areas to which molecular simulation has contributed significantly over the last decades is without a doubt the accurate and efficient prediction of fluid phase equilibria. In this work we combine two of the most powerful methods that have greatly enhanced our ability to simulate accurately fluid phase equilibria: (a) the “Gibbs ensemble” method (A.Z. Panagiotopoulos, Molecular Physics 61 (1987) 813-826) and (b) the multiple histogram method (A.M. Ferrenberg, R.H. Swendsen, Physical Review Letters 61 (1988) 2635-2638). The result of such combination is a simple and very accurate method of predicting fluid phase equilibrium close to and away from the critical point.     

Pipe jacking a sewer under Athens

A deep level sewer installation, employing a trenchless technology method required as a result of excavations for a new freeway in Athens, is described. For the first time, pipes had to be jacked to drive sections over 200 m in length under the city. In addition to its technical merits, the method provided advantages in terms of social and environmental issues. Very little traffic disturbance was caused, together with no disruption of other services or creation of dust pollution during construction. It also did not damage the pavements of the city. This contrasts to the scars left on the roads, due to trenching. Pipe jacking, however, needs the construction of shafts along the alignment, arranged at distances determined by the cost effectiveness of the system to jack the pipes. It was decided to monitor the jacking force requirements as the pipes advanced. This response during driving was then analyzed and compared to the predictions presented by other researchers. Such measurements and analyses may allow for the formation of a database to permit the right choice of an appropriate excavation unit and the successful planning of any future similar projects.     

Comparing Two Hydro-Economic Approaches for Multi-Objective Agricultural Water Resources Planning

Hydro-economic models are valuable tools that can be used in irrigated agriculture in order to improve the understanding of the status quo of water resources, the role of water in agriculture, and the system behavior under changing conditions. The present paper attempts to give insights on how different water management objectives and data availability may influence the specification/application of hydro-economic modeling, as well as the reliability and interpretation of their results. A Greek rural watershed located in Central Greece (Region of Thessaly) is used as a case study application. A common hydro-economic framework for sustainable water resources management in irrigated agriculture is examined, aiming to provide a simple and understandable tool for policymakers. In this framework two hydro-economic models (HEMs) were developed to address challenges regarding data limitations, spatial analysis, and scenario-based problems (e.g. agri-economic scenarios, water policy scenarios, environmental scenarios, etc.). A set of selection criteria was then used to qualitatively compare these two models, based on their advantages and disadvantages. The results of this analysis indicate that HEMs’ development must be quite flexible about their settings and must take into consideration the desired accuracy level that is likely to satisfy their main purpose/goal. The optimal approach is the one that can achieve a balance between simplicity, flexibility, accuracy and robustness.