910 resultados para Andersen and Newman model


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A scanning tunneling microscope can probe the inelastic spin excitations of a single magnetic atom in a surface via spin-flip assisted tunneling in which transport electrons exchange spin and energy with the atomic spin. If the inelastic transport time, defined as the average time elapsed between two inelastic spin flip events, is shorter than the atom spin-relaxation time, the scanning tunnel microscope (STM) current can drive the spin out of equilibrium. Here we model this process using rate equations and a model Hamiltonian that describes successfully spin-flip-assisted tunneling experiments, including a single Mn atom, a Mn dimer, and Fe Phthalocyanine molecules. When the STM current is not spin polarized, the nonequilibrium spin dynamics of the magnetic atom results in nonmonotonic dI/dV curves. In the case of spin-polarized STM current, the spin orientation of the magnetic atom can be controlled parallel or antiparallel to the magnetic moment of the tip. Thus, spin-polarized STM tips can be used both to probe and to control the magnetic moment of a single atom.

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In this paper we propose a two-component polarimetric model for soil moisture estimation on vineyards suited for C-band radar data. According to a polarimetric analysis carried out here, this scenario is made up of one dominant direct return from the soil and a multiple scattering component accounting for disturbing and nonmodeled signal fluctuations from soil and short vegetation. We propose a combined X-Bragg/Fresnel approach to characterize the polarized direct response from soil. A validation of this polarimetric model has been performed in terms of its consistency with respect to the available data both from RADARSAT-2 and from indoor measurements. High inversion rates are reported for different phenological stages of vines, and the model gives a consistent interpretation of the data as long as the volume component power remains about or below 50% of the surface contribution power. However, the scarcity of soil moisture measurements in this study prevents the validation of the algorithm in terms of the accuracy of soil moisture retrieval and an extensive campaign is required to fully demonstrate the validity of the model. Different sources of mismatches between the model and the data have been also discussed and analyzed.

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In the tropics, bats are an essential component of many native ecosystems, through providing various ecological services including pollination and insect pest control, in addition to seed dispersal. Many Philippine bat species roost in caves and underground habitats. However, many caves are disturbed by people, to exploit resources for food, recreation, and mineral and guano extraction. The misunderstanding of the importance of bats to the ecosystem is also considered a threat to many cave roosting species. Understanding the conflicts between humans and ecosystems which provide essential services is important to maintain ecosystem service provision. A total of 100 local respondents from the village of Pisan, Kabacan North Cotabato in south central Mindanao were interviewed through semi-structured interviews and focus group discussions. Respondents were asked about their views, levels of knowledge, use, interaction, and awareness towards both the caves and bats in their locality. Our survey found that most of the respondents are aware of the presence of bats from the caves in their locality. Unfortunately, a large proportion of the respondents noted that bats are hunted in caves for bush meat and trade, and most people perceived bats as pest to fruit crops such as durian. These factors are among the main factors of the execution of many bat colonies in caves of south central Mindanao. In general, cave bats are under appreciated species in caves. The unregulated tourism, hunting for bush meat and trade, and guano extraction are among the alarming threats occurring for both caves and bats in the locality and possibly to other localities in the country. Furthermore, the establishment of strong and effective model conservation education programs and the strengthening the participation of local government, academic, and community are essential steps to preserve the current state of cave bats in the area.

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Implant failures and postoperative complications are often associated to the bone drilling. Estimation and control of drilling parameters are critical to prevent mechanical damage to the bone tissues. For better performance of the drilling procedures, it is essential to understand the mechanical behaviour of bones that leads to their failures and consequently to improve the cutting conditions. This paper investigates the effect of drill speed and feed-rate on mechanical damage during drilling of solid rigid foam materials, with similar mechanical properties to the human bone. Experimental tests were conducted on biomechanical blocks instrumented with strain gauges to assess the drill speed and feed-rate influence. A three-dimensional dynamic finite element model to predict the bone stresses, as a function of drilling conditions, drill geometry and bone model, was developed. These simulations incorporate the dynamic characteristics involved in the drilling process. The element removal scheme is taken into account and allows advanced simulations of tool penetration and material removal. Experimental and numerical results show that generated stresses in the material tend to increase with tool penetration. Higher drill speed leads to an increase of von-Mises stresses and strains in the solid rigid foams. However, when the feed-rate is higher, the stresses and strains are lower. The numerical normal stresses and strains are found to be in good agreement with experimental results. The models could be an accurate analysis tool to simulate the stresses distribution in the bone during the drilling process.

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A lively debate emerged on the proposed “Connected Continent” legislative package presented by the European Commission in September 2013. The package contains a proposed rule on the ‘open Internet’, which was heavily discussed in European Parliament hearings in early December. This commentary argues that while the proposed rule is in principle balanced and appealing, it is utterly impractical due to the enormous uncertainty that its application would entail. At the same time, the rule is very far from what neutrality proponents have argued for almost a decade: rather than the place for internet freedom, it would transform the Web into a place requiring constant micro-management and tutoring of user behaviour. Both arguments lead to the conclusion that the current proposal should be at once reformed and analysed under a more holistic lens. On the one hand, Europe should launch an ambitious project for the future, converged infrastructure by mobilising resources and reforming rules to encourage investment into ubiquitous, converged, ‘always on’ connectivity. On the other hand, enhanced legal certainty for broadband investment could justify a more neutrality-oriented approach to traffic management practices on the Internet. The author proposes a new approach to Internet regulation which, altogether, will lead to a more balanced and sustainable model for the future, without jeopardising user freedom.

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The economy of breakaway Transnistria is a peculiar combination of the command-and-distribution model inherited from the USSR with elements of a free-market economy which is heavily dependent on Russian energy and financial subsidies. The main pillars of the region’s economy are several large industrial plants, built in the Soviet era, which generate more than half of its GDP (in 2012, Transnistria’s GDP reached around US$1 billion). As a consequence, the condition of each of these companies, whose production is almost exclusively export- -oriented, has a huge impact on the economic situation in Transnistria. This makes the region extremely sensitive to any changes in the economic situation of its key trade partners. This problem is additionally aggravated by the extremely low diversification of Transnistrian exports. The only major economic entity in Transnistria which regularly yields profits and is not so heavily dependent on the external situation is Sheriff. This corporation controls the greater part of the local wholesale and retail trade, as well as a major part of the services sector on the domestic market.

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This course, then, investigates the effects of integration on European citizens as well as the duality of the EU as a competitive and social model. It is sensitive to the involvement of social groups, protest, and domestic politics in the study of market integration. Some of the questions we explore are: What are the effects of regulatory policy-making on social actors, how do such actors’ strategies and behaviors change as a consequence, and how to they overcome their collective action problems? Why is it that the logic of integration has at times followed a logic of “permissive consensus” while at other times it has been described as a “constraining dissensus”? What is the importance of discourse in domestic politics in order to articulate and legitimate Europeanization? How do European identities change as a consequence of policymaking as well as of protest? To what extent do ordinary Europeans matter in terms of accepting and opposing the project of European integration, how do European citizens in core and peripheral EU states experience Europeanization, and how is their involvement in the integration project to be conceptualized?

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The representation of the thermal behaviour of the building is achieved through a relatively simple dynamic model that takes into account the effects due to the thermal mass of the building components. The model of a intra-floor apartment has been built in the Matlab-Simulink environment and considers the heat transmission through the external envelope, wall and windows, the internal thermal masses, (i.e. furniture, internal wall and floor slabs) and the sun gain due to opaque and see-through surfaces of the external envelope. The simulations results for the entire year have been compared and the model validated, with the one obtained with the dynamic building simulation software Energyplus.

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Major elements, S, F, Cl concentrations and relative proportions of S6+ to total S were analyzed with electron microprobe in sideromelane glass shards from Pleistocene volcaniclastic sediments drilled during ODP Leg 157. Glasses are moderately to strongly evolved and represent a spectrum from alkali basalt, basanite and nephelinite through hawaiite, mugearite and tephrite to phonolitic tephrite. Measured S6+/SumS (0.03±0.98) and calculated Fe2+/Fe3+ (2.5±5.8) ratios in the melt yield preeruptive redox conditions ranging from NNO-1.4 to NNO+2.1. The morphology of the glass shards, variations of S and Cl concentrations (0.010±0.127 wt% S, 0.018±0.129 wt% Cl), calculated preeruptive temperatures (1030±1200 °C) and oxygen fugacities suggest that glasses deposited even within the same ash layers have diverse origin and may have resulted from both submarine and subaerial eruptions. Most vesicle-free glasses are characterized by high concentrations of S and represent undegassed or slightly degassed submarine lavas, whereas vesiculated glasses with low concentrations of S and Cl are strongly degassed and can be ascribed to the eruptions in shallow water or on land. Sideromelane glass shards at Sites 953 are thought to have resulted from submarine eruptions northeast of Gran Canaria, glasses at Site 954 represent mostly volcaniclastic material of shallow water submarine and subaerial eruptions on Gran Canaria and Tenerife, and glasses deposited at Site 956 resulted from submarine or explosive eruptions on Tenerife.

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In this study, the Mean Transit Time and Mixing Model Analysis methods are combined to unravel the runoff generation process of the San Francisco River basin (73.5 km**2) situated on the Amazonian side of the Cordillera Real in the southernmost Andes of Ecuador. The montane basin is covered with cloud forest, sub-páramo, pasture and ferns. Nested sampling was applied for the collection of streamwater samples and discharge measurements in the main tributaries and outlet of the basin, and for the collection of soil and rock water samples. Weekly to biweekly water grab samples were taken at all stations in the period April 2007-November 2008. Hydrometric data, Mean Transit Time and Mixing Model Analysis allowed preliminary evaluation of the processes controlling the runoff in the San Francisco River basin. Results suggest that flow during dry conditions mainly consists of lateral flow through the C-horizon and cracks in the top weathered bedrock layer, and that all subcatchments have an important contribution of this deep water to runoff, no matter whether pristine or deforested. During normal to low precipitation intensities, when antecedent soil moisture conditions favour water infiltration, vertical flow paths to deeper soil horizons with subsequent lateral subsurface flow contribute most to streamflow. Under wet conditions in forested catchments, streamflow is controlled by near surface lateral flow through the organic horizon. Exceptionally, saturation excess overland flow occurs. By absence of the litter layer in pasture, streamflow under wet conditions originates from the A horizon, and overland flow.

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Bolt, Beranek and Newman, Inc., Van Nuys, Calif.

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Mode of access: Internet.

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The report is preceded by the Bureau of Ships' Analysis of Arthur Andersen and Company shipbuilding cost study (22 L.)

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Mode of access: Internet.