Techno-economical optimization of the production of hydrogen from PV-Wind systems connected to the electrical grid

This paper shows a complete techno-economical analysis on facilities that make use of wind turbines and photovoltaic (PV) generators for the production of hydrogen by means of electrolysis. Besides, the surplus of electrical energy produced can be sold and injected to the electrical grid.In the case studies, several scenarios have been considered with changing values for the prize of the electricity sold to the electrical grid as this is one of the parameters that most influences economical calculations.We have also made a sensitivity analysis depending on the prize of components and on the economical and meteorological changes.In each scenario – for each hour and for a period of one year – a great number of possible combinations of the system components have been simulated.These components are: photovoltaic generator, wind turbines, rectifier, inverter, electrolyser and other auxiliary elements.Each system, each combination of elements, once simulated, has been economically evaluated thus making it possible to select the best one.In the assessment of each system, there were two objectives to minimize: one of them is hydrogen selling price so the Net Present Value (NPV) equals nil and the other one is hydrogen selling price in order to recover the invested capital in a given number of years.The results achieved show that with the present cost of the components needed, and with the solar irradiation and wind conditions considered in this study, the selling price of hydrogen produced by means of electrolysis should be high in order to recover the initial investment of a PV-Wind system in a reasonable lapse of time (ten years).Nevertheless, the rising price of the spare energy sold and injected to the electrical grid by this type of equipment could help decrease hydrogen selling price.     

Non-dissipative decoherence in Rabi oscillation experiments

Abstract

Decoherence may be due to the fluctuations of some classical variable or parameter of a system, and not only to the entanglement with the environment. Here we derive a model-independent formalism for this non-dissipative decoherence, which is then applied to describe the decoherence observed in some recent Rabi oscillation experiments.     

Sensitivity to status-based rejection: Implications for African American students' college experience.

The authors proposed a process model whereby experiences of rejection based on membership in a devalued group can lead people to anxiously expect, readily perceive, and intensely react to status-based rejection. To test the model, the authors focused on race-based rejection sensitivity (RS-race) among African Americans. Following the development and validation of the RS-Race Questionnaire (Studies 1 and 2), the authors tested the utility of the model for understanding African American students' experiences at a predominantly White university (Study 3). Students high in RS-race experienced greater discomfort during the college transition, less trust in the university, and relative declines in grades over a 2- to 3-year period. Positive race-related experiences, however, increased feelings of belonging at the institution among students high in RS-race. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Thermodynamic analysis of steel deoxidization processes during tapping and refining operations

A thermodynamic model based on the interaction parameter approach for molten metal solutions and a quasi‐chemical model for molten slags and non‐metallic inclusions was employed to analyze steel deoxidization during tapping and refining operations in a ladle furnace. This model is able to predict the mineralogical nature of non‐metallic inclusions and their amount through thermodynamics and mass balances. It was found that the addition sequence of deoxidizers during a tapping procedure influences the nature and amount of the different inclusions. Besides, the metal‐slag equilibrium is readily reached after tapping and at the end of steel treatment in the ladle furnace. The model proved to be useful for steel cleanliness assessments and the design of steel deoxidization practices.     

Neural projection techniques for the visual inspection of network traffic

A crucial aspect in network monitoring for security purposes is the visual inspection of the traffic pattern, mainly aimed to provide the network manager with a synthetic and intuitive representation of the current situation. Towards that end, neural projection techniques can map high-dimensional data into a low-dimensional space adaptively, for the user-friendly visualization of monitored network traffic. This work proposes two projection methods, namely, cooperative maximum likelihood Hebbian learning and auto-associative back-propagation networks, for the visual inspection of network traffic. This set of methods may be seen as a complementary tool in network security as it allows the visual inspection and comprehension of the traffic data internal structure. The proposed methods have been evaluated in two complementary and practical network-security scenarios: the on-line processing of network traffic at packet level, and the off-line processing of connection records, e.g. for post-mortem analysis or batch investigation. The empirical verification of the projection methods involved two experimental domains derived from the standard corpora for evaluation of computer network intrusion detection: the MIT Lincoln Laboratory DARPA dataset.     

A randomized experiment comparing random and cutoff-based assignment.

In this article, we review past studies comparing randomized experiments to regression discontinuity designs, mostly finding similar results, but with significant exceptions. The latter might be due to potential confounds of study characteristics with assignment method or with failure to estimate the same parameter over methods. In this study, we correct the problems by randomly assigning 588 participants to be in a randomized experiment or a regression discontinuity design in which they are otherwise treated identically, comparing results estimating both the same and different parameters. Analysis includes parametric, semiparametric, and nonparametric methods of modeling nonlinearities. Results suggest that estimates from regression discontinuity designs approximate the results of randomized experiments reasonably well but also raise the issue of what constitutes agreement between the 2 estimates. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Factors affecting smoking of elementary and high school children from Chile

The outcome of orthodontic treatment involving early extraction of 4 second molars was evaluated in 52 patients (29 girls, 23 boys). Computer-assisted analysis of cephalograms, casts and panoramic X-rays was performed at the start (T1, mean age 11.5 years) and at the end (T2, mean age 14.4 years) of treatment. Following treatment, mesial migration of upper and lower first molars was counteracted; however, treatment only moderately influenced normal development of the position of the incisors and the profile. At the end of treatment, the third molars had erupted in only 3 patients. Nevertheless, on average a significant mesial movement of these teeth was observed. In addition, there was a significant improvement in the axial inclination of the third molars, especially in the upper arch. This improvement was correlated with the original position of the teeth. All patients needed a longer follow-up period and it seems reasonable that some of them might require a second treatment phase to adjust the position of the third molars.     

Robust design of a shape memory actuator with slider and slot layout and passive cooling control

Microsystem Technologies - This work proposes a new shape memory actuator based on a slider and slot mechanism. The device is composed by two couples of opposed SMA coil elements. The SMA elements...     

M-CASH: A real-time resource reclaiming algorithm for multiprocessor platforms

Resource reclaiming schemes are typically applied in reservation-based real-time uniprocessor systems to support efficient reclaiming and sharing of computational resources left unused by early completing tasks, improving the response times of aperiodic and soft tasks in the presence of overruns. In this paper, we introduce a novel and efficient reclaiming algorithm, named M-CASH, for multiprocessor platforms. M-CASH leverages the resource reservation approach offered by the Multiprocessor CBS server offering significant improvements. The correctness of the algorithm is formally proven and its performance is evaluated through extensive synthetic simulations.