How does country risk matter for foreign direct investment?

In this paper, we aim to identify the political and financial risk components that matter most for the activities of multinational corporations. Our paper is the first paper to comprehensively examine the impact of various components of not only political risk but also financial risk on inward FDI, from both long-run and short-run perspectives. Using a sample of 93 countries (including 60 developing countries) for the period 1985-2007, we find that among the political risk components, government stability, socioeconomic conditions, investment profile, internal conflict, external conflict, corruption, religious tensions, democratic accountability, and ethnic tensions have a close association with FDI flows. In particular, socioeconomic conditions, investment profile, and external conflict appear to be the most influential components of political risk in attracting foreign investment. Among the financial risk components, only exchange rate stability yields statistically significant positive coefficients when estimated only for developing countries. In contrast, current account as a percentage of exports of goods and services, foreign debt as a percentage of GDP, net international liquidity as the number of months of import cover, and current account as a percentage of GDP yield negative coefficients in some specifications. Thus, multinationals do not seem to consider seriously the financial risk of the host country.

Efficient Model-based 3D Tracking by Using Direct Image Registration

This thesis deals with the problem of efficiently tracking 3D objects in sequences of images. We tackle the efficient 3D tracking problem by using direct image registration. This problem is posed as an iterative optimization procedure that minimizes a brightness error norm. We review the most popular iterative methods for image registration in the literature, turning our attention to those algorithms that use efficient optimization techniques. Two forms of efficient registration algorithms are investigated. The first type comprises the additive registration algorithms: these algorithms incrementally compute the motion parameters by linearly approximating the brightness error function. We centre our attention on Hager and Belhumeur’s factorization-based algorithm for image registration. We propose a fundamental requirement that factorization-based algorithms must satisfy to guarantee good convergence, and introduce a systematic procedure that automatically computes the factorization. Finally, we also bring out two warp functions to register rigid and nonrigid 3D targets that satisfy the requirement. The second type comprises the compositional registration algorithms, where the brightness function error is written by using function composition. We study the current approaches to compositional image alignment, and we emphasize the importance of the Inverse Compositional method, which is known to be the most efficient image registration algorithm. We introduce a new algorithm, the Efficient Forward Compositional image registration: this algorithm avoids the necessity of inverting the warping function, and provides a new interpretation of the working mechanisms of the inverse compositional alignment. By using this information, we propose two fundamental requirements that guarantee the convergence of compositional image registration methods. Finally, we support our claims by using extensive experimental testing with synthetic and real-world data. We propose a distinction between image registration and tracking when using efficient algorithms. We show that, depending whether the fundamental requirements are hold, some efficient algorithms are eligible for image registration but not for tracking.

Influence of Current Pulse Shape on Directly Modulated Systems Performance in Metro Area Optical Networks

Due to the fact that a metro network market is very cost sensitive, direct modulated schemes appear attractive. In this paper a CWDM (Coarse Wavelength Division Multiplexing) system is studied in detail by means of an Optical Communication System Design Software; a detailed study of the modulated current shape (exponential, sine and gaussian) for 2.5 Gb/s CWDM Metropolitan Area Networks is performed to evaluate its tolerance to linear impairments such as signal-to-noise-ratio degradation and dispersion. Point-to-point links are investigated and optimum design parameters are obtained. Through extensive sets of simulation results, it is shown that some of these shape pulses are more tolerant to dispersion when compared with conventional gaussian shape pulses. In order to achieve a low Bit Error Rate (BER), different types of optical transmitters are considered including strongly adiabatic and transient chirp dominated Directly Modulated Lasers (DMLs). We have used fibers with different dispersion characteristics, showing that the system performance depends, strongly, on the chosen DML?fiber couple.

Selective ablation with UV lasers of a-Si:H thin film solar cells in direct scribing configuration

Monolithical series connection of silicon thin-film solar cells modules performed by laser scribing plays a very important role in the entire production of these devices. In the current laser process interconnection the two last steps are developed for a configuration of modules where the glass is essential as transparent substrate. In addition, the change of wavelength in the employed laser sources is sometimes enforced due to the nature of the different materials of the multilayer structure which make up the device. The aim of this work is to characterize the laser patterning involved in the monolithic interconnection process in a different configurations of processing than the usually performed with visible laser sources. To carry out this study, we use nanosecond and picosecond laser sources working at 355nm of wavelength in order to achieve the selective ablation of the material from the film side. To assess this selective removal of material has been used EDX (energy dispersive using X-ray) analysis

A silviculture-oriented spatio-temporal model for germination in Pinus pinea L. in the Spanish Northern Plateau based on a direct seeding experiment

Natural regeneration in Pinus pinea stands commonly fails throughout the Spanish Northern Plateau under current intensive regeneration treatments. As a result, extensive direct seeding is commonly conducted to guarantee regeneration occurrence. In a period of rationalization of the resources devoted to forest management, this kind of techniques may become unaffordable. Given that the climatic and stand factors driving germination remain unknown, tools are required to understand the process and temper the use of direct seeding. In this study, the spatio-temporal pattern of germination of P. pinea was modelled with those purposes. The resulting findings will allow us to (1) determine the main ecological variables involved in germination in the species and (2) infer adequate silvicultural alternatives. The modelling approach focuses on covariates which are readily available to forest managers. A two-step nonlinear mixed model was fitted to predict germination occurrence and abundance in P. pinea under varying climatic, environmental and stand conditions, based on a germination data set covering a 5-year period. The results obtained reveal that the process is primarily driven by climate variables. Favourable conditions for germination commonly occur in fall although the optimum window is often narrow and may not occur at all in some years. At spatial level, it would appear that germination is facilitated by high stand densities, suggesting that current felling intensity should be reduced. In accordance with other studies on P. pinea dispersal, it seems that denser stands during the regeneration period will reduce the present dependence on direct seeding.

Current collection by an active spherical electrode in an unmagnetized plasma

A theoretical model for the steady-state response of anodic contactors that emit a plasma current Ii and collect electrons from a collisionless, unmagnetized plasma is presented. The use of a (kinetic) monoenergetic population for the attracted species, well known in passive probe theory, gives both accuracy and tractability to the theory. The monoenergetic population is proved to behave like an isentropic fluid with radial plus centripetal motion, allowing direct comparisons with ad hoc fluid models. Also, a modification of the original monoenergetic equations permits analysis of contactors operating in orbit-limited conditions. Besides that, the theory predicts that, only for plasma emissions above certain threshold current a presheath/double layer/core structure for the potential is formed (the core mode), while for emissions below that threshold, a plasma contactor behaves exactly as a positive-ion emitter with a presheath/sheath structure (the no-core mode). Ion emitters are studied as a particular case. Emphasis is placed on obtaining dimensionless charts and approximate asymptotic laws of the current-voltage characteristic.

The Lagrangian description of aperiodic flows: a case study of the Kuroshio Current

This article reviews several recently developed Lagrangian tools and shows how their com- bined use succeeds in obtaining a detailed description of purely advective transport events in general aperiodic flows. In particular, because of the climate impact of ocean transport processes, we illustrate a 2D application on altimeter data sets over the area of the Kuroshio Current, although the proposed techniques are general and applicable to arbitrary time depen- dent aperiodic flows. The first challenge for describing transport in aperiodical time dependent flows is obtaining a representation of the phase portrait where the most relevant dynamical features may be identified. This representation is accomplished by using global Lagrangian descriptors that when applied for instance to the altimeter data sets retrieve over the ocean surface a phase portrait where the geometry of interconnected dynamical systems is visible. The phase portrait picture is essential because it evinces which transport routes are acting on the whole flow. Once these routes are roughly recognised it is possible to complete a detailed description by the direct computation of the finite time stable and unstable manifolds of special hyperbolic trajectories that act as organising centres of the flow.

Direct and indirect economic impacts of drought in the agri-food sector in the Ebro River basin (Spain).

The economic evaluation of drought impacts is essential in order to define efficient and sustainable management and mitigation strategies. The aim of this study is to evaluate the economic impacts of a drought event on the agricultural sector and measure how they are transmitted from primary production to industrial output and related employment. We fit econometric models to determine the magnitude of the economic loss attributable to water storage. The direct impacts of drought on agricultural productivity are measured through a direct attribution model. Indirect impacts on agricultural employment and the agri-food industry are evaluated through a nested indirect attribution model. The transmission of water scarcity effects from agricultural production to macroeconomic variables is measured through chained elasticities. The models allow for differentiating the impacts deriving from water scarcity from other sources of economic losses. Results show that the importance of drought impacts are less relevant at the macroeconomic level, but are more significant for those activities directly dependent on water abstractions and precipitation. From a management perspective, implications of these findings are important to develop effective mitigation strategies to reduce drought risk exposure.

Low Voltage Ride-through in DFIG Wind Generators by Controlling the Rotor Current without Crowbars

Among all the different types of electric wind generators, those that are based on doubly fed induction generators, or DFIG technology, are the most vulnerable to grid faults such as voltage sags. This paper proposes a new control strategy for this type of wind generator, that allows these devices to withstand the effects of a voltage sag while following the new requirements imposed by grid operators. This new control strategy makes the use of complementary devices such as crowbars unnecessary, as it greatly reduces the value of currents originated by the fault. This ensures less costly designs for the rotor systems as well as a more economic sizing of the necessary power electronics. The strategy described here uses an electric generator model based on space-phasor theory that provides a direct control over the position of the rotor magnetic flux. Controlling the rotor magnetic flux has a direct influence on the rest of the electrical variables enabling the machine to evolve to a desired work point during the transient imposed by the grid disturbance. Simulation studies have been carried out, as well as test bench trials, in order to prove the viability and functionality of the proposed control strategy.

Direct Vlasov simulations of electron-attracting cylindrical Langmuir probes in flowing plasmas

Current collection by positively polarized cylindrical Langmuir probes immersed in flowing plasmas is analyzed using a non-stationary direct Vlasov-Poisson code. A detailed description of plasma density spatial structure as a function of the probe-to-plasma relative velocity U is presented. Within the considered parametric domain, the well-known electron density maximum close to the probe is weakly affected by U. However, in the probe wake side, the electron density minimum becomes deeper as U increases and a rarified plasma region appears. Sheath radius is larger at the wake than at the front side. Electron and ion distribution functions show specific features that are the signature of probe motion. In particular, the ion distribution function at the probe front side exhibits a filament with positive radial velocity. It corresponds to a population of rammed ions that were reflected by the electric field close to the positively biased probe. Numerical simulations reveal that two populations of trapped electrons exist: one orbiting around the probe and the other with trajectories confined at the probe front side. The latter helps to neutralize the reflected ions, thus explaining a paradox in past probe theory.

Análisis experimental de las transmisiones indirectas en particiones de doble hoja de fábrica de ladrillo, propuesta de métodos de cuantificación para la mejora del aislamiento acústico

Esta investigación aborda el estudio de la influencia de las uniones en el aislamiento acústico a ruido aéreo en los edificios y el análisis de las transmisiones indirectas producidas en particiones de dos hojas de ladrillo cerámico sobre bandas elásticas. La transmisión de ruido entre dos recintos separados por una partición se produce por dos vías: La vía directa a través del elemento que separa los dos recintos y la vía indirecta, a través de los elementos de flanco, como forjados, particiones, fachadas, etc. que conectados a dicho elemento de separación, vibran en presencia del campo acústico transmitiendo sus vibraciones al recinto receptor. Si las transmisiones indirectas son dominantes, el aislamiento acústico “in situ” puede ser menor que el esperado. El parámetro que expresa la atenuación acústica en las uniones es el índice de reducción vibracional en la unión o Kij. Éste parámetro se utiliza en los métodos de cálculo del aislamiento acústico a ruido aéreo, que permiten la justificación del cumplimiento de la normativa actual, el Documento Básico DB HR Protección frente al ruido del CTE. La determinación de los índices Kij de las uniones es una cuestión que debe abordarse de forma experimental. Existen diferentes expresiones empíricas obtenidas en varios laboratorios europeos que permiten el cálculo del índice Kij, pero no se han validado con ensayos realizados en soluciones habituales en la construcción española, como las estudiadas en este trabajo. El objetivo de este trabajo es la medida, análisis y cuantificación de las transmisiones indirectas producidas en las uniones de elementos de dos hojas de fábrica de ladrillo cerámico. Se ha recurrido a una campaña de ensayos en la que se reproducían las condiciones de un edificio real y se ha medido el aislamiento acústico a ruido aéreo y los índices Kij de diferentes configuraciones de uniones. Del análisis de los resultados, se demuestra que el aislamiento acústico a ruido aéreo depende de las uniones, pudiéndose obtener mejoras significativas al variar la forma de unión entre los elementos constructivos. Las mejoras de aislamiento acústico están relacionadas con un buen diseño de las uniones y con valores elevados del índice Kij. Este trabajo aporta valores experimentales de Kij para soluciones de fábrica de ladrillo y pone en discusión los valores teóricos que actualmente aparecen en la normativa vigente. ABSTRACT This research work deals with the effects of junction construction details on airborne sound insulation in buildings and the analysis of flanking transmissions across double ceramic brick walls with elastic interlayers. The sound transmission between two adjacent rooms comprises two paths: the direct path, caused by the incident sound on a separating wall, and the indirect path, through flanking elements connected to the separating wall, such as floors, internal walls, ceilings, etc. Flanking elements vibrate when excited in the sound field, thus transferring sound via structure borne to the receiving room. Dominant flanking transmissions can decrease the field sound insulation performance of the building. The vibration reduction index, Kij. expresses the acoustic attenuation of construction joints. This is an input parameter in the calculation models designed to estimate the airborne sound insulation between adjoining rooms in buildings. These models are used to comply with the acoustic requirements set by Basic Document DB HR Protection against noise included in the Spanish Building Code. The characterization of Kij. must be addressed experimentally by means of measurements. The available empirical Kij. formulae were developed in different European laboratories, but they have not been validated with standard tests performed on common Spanish walls, such as those studied in this work. The aim of this work is the measurement, analysis and quantification of indirect transmissions though joints of double ceramic brick walls. Airborne sound insulation tests and Kij measurements were performed in a laboratory which emulated the conditions of a real building. These tests were performed in different partitions whose joints were modified. It follows from the analysis of the results that airborne sound insulation depends strongly on the design of joints. Sound insulation improves when the joints between construction elements are modified to eliminate acoustic bridges. The increase in sound insulation corresponds to best practice design of joints and to high Kij values. This research work provides experimental Kij data of double ceramic brick walls and the results put in discussion the theoretical values set in the current Standards.

A Survey on Underwater Acoustic Sensor Network Routing Protocols

Underwater acoustic sensor networks (UASNs) have become more and more important in ocean exploration applications, such as ocean monitoring, pollution detection, ocean resource management, underwater device maintenance, etc. In underwater acoustic sensor networks, since the routing protocol guarantees reliable and effective data transmission from the source node to the destination node, routing protocol design is an attractive topic for researchers. There are many routing algorithms have been proposed in recent years. To present the current state of development of UASN routing protocols, we review herein the UASN routing protocol designs reported in recent years. In this paper, all the routing protocols have been classified into different groups according to their characteristics and routing algorithms, such as the non-cross-layer design routing protocol, the traditional cross-layer design routing protocol, and the intelligent algorithm based routing protocol. This is also the first paper that introduces intelligent algorithm-based UASN routing protocols. In addition, in this paper, we investigate the development trends of UASN routing protocols, which can provide researchers with clear and direct insights for further research.

Direct radiocarbon dates for Vindija G1 and Velika Pećina Late Pleistocene hominid remains

New accelerator mass spectrometry radiocarbon dates taken directly on human remains from the Late Pleistocene sites of Vindija and Velika Pećina in the Hrvatsko Zagorje of Croatia are presented. Hominid specimens from both sites have played critical roles in the development of current perspectives on modern human evolutionary emergence in Europe. Dates of ≈28 thousand years (ka) before the present (B.P.) and ≈29 ka B.P. for two specimens from Vindija G1 establish them as the most recent dated Neandertals in the Eurasian range of these archaic humans. The human frontal bone from Velika Pećina, generally considered one of the earliest representatives of modern humans in Europe, dated to ≈5 ka B.P., rendering it no longer pertinent to discussions of modern human origins. Apart from invalidating the only radiometrically based example of temporal overlap between late Neandertal and early modern human fossil remains from within any region of Europe, these dates raise the question of when early modern humans first dispersed into Europe and have implications for the nature and geographic patterning of biological and cultural interactions between these populations and the Neandertals.

Mechanisms underlying kainate receptor-mediated disinhibition in the hippocampus

Kainate (KA) receptor activation depresses stimulus-evoked γ-aminobutyric acid (GABA-mediated) synaptic transmission onto CA1 pyramidal cells of the hippocampus and simultaneously increases the frequency of spontaneous GABA release through an increase in interneuronal spiking. To determine whether these two effects are independent, we examined the mechanism by which KA receptor activation depresses the stimulus-evoked, inhibitory postsynaptic current (IPSC). Bath application of the α-amino-3-hydroxy-5-methyl-4-isoxazole proprionic acid (AMPA)/KA receptor agonist KA in the presence of the AMPA receptor antagonist GYKI 53655 caused a large increase in spontaneous GABA release and a coincident depression of the evoked IPSC. The depressant action on the evoked IPSC was reduced, but not abolished, by the GABAB receptor antagonist SCH 50911, suggesting that the KA-induced increase in spontaneous GABA release depresses the evoked IPSC through activation of presynaptic GABAB receptors. KA had no resolvable effect on the potassium-induced increase in miniature IPSC frequency, suggesting that KA does not act through a direct effect on the release machinery or presynaptic calcium influx. KA caused a decrease in pyramidal cell input resistance, which was reduced by GABAA receptor antagonists. KA also caused a reduction in the size of responses to iontophoretically applied GABA, which was indistinguishable from the SCH 50911-resistant, residual depression of the evoked IPSC. These results suggest that KA receptor activation depresses the evoked IPSC indirectly by increasing interneuronal spiking and GABA release, leading to activation of presynaptic GABAB receptors, which depress GABA release, and postsynaptic GABAA receptors, which increase passive shunting.

Nerve growth factor acutely reduces chemical transmission by means of postsynaptic TrkA-like receptors in squid giant synapse

Tyrosine phosphorylation has been shown to be an important modulator of synaptic transmission in both vertebrates and invertebrates. Such findings hint toward the existence of extracellular ligands capable of activating this widely represented signaling mechanism at or close to the synapse. Examples of such ligands are the peptide growth factors which, on binding, activate receptor tyrosine kinases. To gain insight into the physiological consequences of receptor tyrosine kinase activation in squid giant synapse, a series of growth factors was tested in this preparation. Electrophysiological, pharmacological, and biochemical analysis demonstrated that nerve growth factor (NGF) triggers an acute and specific reduction of the postsynaptic potential amplitude, without affecting the presynaptic spike generation or presynaptic calcium current. The NGF target is localized at a postsynaptic site and involves a new TrkA-like receptor. The squid receptor crossreacts with antibodies generated against mammalian TrkA, is tyrosine phosphorylated in response to NGF stimulation, and is blocked by specific pharmacological inhibitors. The modulation described emphasizes the important role of growth factors on invertebrate synaptic transmission.