Az árfolyamsávok empirikus modelljei és a devizaárfolyam sávon belüli előrejelezhetetlensége = Empirical models of exchange rate target zones

A sávosan rögzített devizaárfolyamok elméleti és gyakorlati vizsgálatai a nemzetközi közgazdaságtan egyik legnépszerűbb témaköre volt a kilencvenes évek elején. A gyakorlati módszerek közül az alkalmazások és hivatkozások száma tekintetében az úgynevezett eltolódással igazítás módszere emelkedett ki. A módszert alkalmazó szerzők szerint amíg a lebegő árfolyamú devizák előrejelzése céltalan feladatnak tűnik, addig sávos árfolyam esetén az árfolyam sávon belüli helyzetének előrejelzése sikeresen végezhető. E tanulmány bemutatja, hogy az Európai Monetáris Rendszer és az északeurópai államok sávos árfolyamrendszereinél e módszer alkalmazásával adódott eredmények például a lebegő árfolyamú amerikai dollárra és az egységgyökfolyamatok többségére is érvényesek. A tanulmány feltárja e látszólagos ellentmondás okait, és bemutat egy olyan, a sávos árfolyamrendszerek főbb megfigyelt jellemzőire épülő modellt, amelynek keretei között a sávon belüli árfolyam előrejelzése nem feltétlenül lehetséges, mert a leértékelés előtti időszakban a sávon belüli árfolyam alakulása kaotikus lehet. / === / Following the development of the first exchange rate target zone model at the end of the eighties dozens of papers analyzed theoretical and empirical topics of currency bands. This paper reviews different empirical methods to analyze the credibility of the band and lays special emphasis on the most widely used method, the so-called drift-adjustment method. Papers applying that method claim that while forecasting a freely floating currency is hopeless, predicting an exchange rate within the future band is successful. This paper shows that the results achieved by applications to EMS and Nordic currencies are not specific to data of target zone currencies. For example, application to US dollar and even to most unit root processes leads qualitatively to the same. This paper explores the solutions of this puzzle and shows a model of target zones in which the exchange rate within the band is not necessarily predictable since the process might follow chaotic dynamics before devaluation.

Development of operational performance models for truck-lane restrictions on freeway corridors

Highways are generally designed to serve a mixed traffic flow that consists of passenger cars, trucks, buses, recreational vehicles, etc. The fact that the impacts of these different vehicle types are not uniform creates problems in highway operations and safety. A common approach to reducing the impacts of truck traffic on freeways has been to restrict trucks to certain lane(s) to minimize the interaction between trucks and other vehicles and to compensate for their differences in operational characteristics. ^ The performance of different truck lane restriction alternatives differs under different traffic and geometric conditions. Thus, a good estimate of the operational performance of different truck lane restriction alternatives under prevailing conditions is needed to help make informed decisions on truck lane restriction alternatives. This study develops operational performance models that can be applied to help identify the most operationally efficient truck lane restriction alternative on a freeway under prevailing conditions. The operational performance measures examined in this study include average speed, throughput, speed difference, and lane changes. Prevailing conditions include number of lanes, interchange density, free-flow speeds, volumes, truck percentages, and ramp volumes. ^ Recognizing the difficulty of collecting sufficient data for an empirical modeling procedure that involves a high number of variables, the simulation approach was used to estimate the performance values for various truck lane restriction alternatives under various scenarios. Both the CORSIM and VISSIM simulation models were examined for their ability to model truck lane restrictions. Due to a major problem found in the CORSIM model for truck lane modeling, the VISSIM model was adopted as the simulator for this study. ^ The VISSIM model was calibrated mainly to replicate the capacity given in the 2000 Highway Capacity Manual (HCM) for various free-flow speeds under the ideal basic freeway section conditions. Non-linear regression models for average speed, throughput, average number of lane changes, and speed difference between the lane groups were developed. Based on the performance models developed, a simple decision procedure was recommended to select the desired truck lane restriction alternative for prevailing conditions. ^

Effect of blood flow patterns on localized platelet adhesion under physiologic flow conditions using two-dimensional and three-dimensional stent models: An experimental and computational approach

This dissertation presents dynamic flow experiments with fluorescently labeled platelets to allow for spatial observation of wall attachment in inter-strut spacings, to investigate their relationship to flow patterns. Human blood with fluorescently labeled platelets was circulated through an in vitro system that produced physiologic pulsatile flow in (1) a parallel plate blow chamber that contained two-dimensional (2D) stents that feature completely recirculating flow, partially recirculating flow, and completely reattached flow, and (2) a three-dimensional (3D) cylindrical tube that contained stents of various geometric designs. ^ Flow detachment and reattachment points exhibited very low platelet deposition. Platelet deposition was very low in the recirculation regions in the 3D stents unlike the 2D stents. Deposition distal to a strut was always high in 2D and 3D stents. Spirally recirculating regions were found in 3D unlike in 2D stents, where the deposition was higher than at well-separated regions of recirculation. ^

Models and empirical data for the production of referring expressions

Article Accepted Date: 29 May 2014 Acknowledgements The authors gratefully acknowledge the support of the Cognitive Science Society for the organisation of the Workshop on Production of Referring Expressions: Bridging the Gap between Cognitive and Computational Approaches to Reference, from which this special issue originated. Funding Emiel Krahmer and Albert Gatt thank The Netherlands Organisation for Scientific Research (NWO) for VICI grant Bridging the Gap between Computational Linguistics and Psycholinguistics: The Case of Referring Expressions (grant number 277-70-007).

Experimental and Theoretical Models to Probe Mechanisms of Biological Charge Flow

Nature is challenged to move charge efficiently over many length scales. From sub-nm to μm distances, electron-transfer proteins orchestrate energy conversion, storage, and release both inside and outside the cell. Uncovering the detailed mechanisms of biological electron-transfer reactions, which are often coupled to bond-breaking and bond-making events, is essential to designing durable, artificial energy conversion systems that mimic the specificity and efficiency of their natural counterparts. Here, we use theoretical modeling of long-distance charge hopping (Chapter 3), synthetic donor-bridge-acceptor molecules (Chapters 4, 5, and 6), and de novo protein design (Chapters 5 and 6) to investigate general principles that govern light-driven and electrochemically driven electron-transfer reactions in biology. We show that fast, μm-distance charge hopping along bacterial nanowires requires closely packed charge carriers with low reorganization energies (Chapter 3); singlet excited-state electronic polarization of supermolecular electron donors can attenuate intersystem crossing yields to lower-energy, oppositely polarized, donor triplet states (Chapter 4); the effective static dielectric constant of a small (~100 residue) de novo designed 4-helical protein bundle can change upon phototriggering an electron transfer event in the protein interior, providing a means to slow the charge-recombination reaction (Chapter 5); and a tightly-packed de novo designed 4-helix protein bundle can drastically alter charge-transfer driving forces of photo-induced amino acid radical formation in the bundle interior, effectively turning off a light-driven oxidation reaction that occurs in organic solvent (Chapter 6). This work leverages unique insights gleaned from proteins designed from scratch that bind synthetic donor-bridge-acceptor molecules that can also be studied in organic solvents, opening new avenues of exploration into the factors critical for protein control of charge flow in biology.

A reconciliation of empirical and mechanistic models of the air-sea gas transfer velocity

Models of the air-sea transfer velocity of gases may be either empirical or mechanistic. Extrapolations of empirical models to an unmeasured gas or to another water temperature can be erroneous if the basis of that extrapolation is flawed. This issue is readily demonstrated for the most well-known empirical gas transfer velocity models where the influence of bubble-mediated transfer, which can vary between gases, is not explicitly accounted for. Mechanistic models are hindered by an incomplete knowledge of the mechanisms of air-sea gas transfer. We describe a hybrid model that incorporates a simple mechanistic view—strictly enforcing a distinction between direct and bubble-mediated transfer—but also uses parameterizations based on data from eddy flux measurements of dimethyl sulphide (DMS) to calibrate the model together with dual tracer results to evaluate the model. This model underpins simple algorithms that can be easily applied within schemes to calculate local, regional, or global air-sea fluxes of gases.

A reconciliation of empirical and mechanistic models of the air-sea gas transfer velocity

Models of the air-sea transfer velocity of gases may be either empirical or mechanistic. Extrapolations of empirical models to an unmeasured gas or to another water temperature can be erroneous if the basis of that extrapolation is flawed. This issue is readily demonstrated for the most well-known empirical gas transfer velocity models where the influence of bubble-mediated transfer, which can vary between gases, is not explicitly accounted for. Mechanistic models are hindered by an incomplete knowledge of the mechanisms of air-sea gas transfer. We describe a hybrid model that incorporates a simple mechanistic view—strictly enforcing a distinction between direct and bubble-mediated transfer—but also uses parameterizations based on data from eddy flux measurements of dimethyl sulphide (DMS) to calibrate the model together with dual tracer results to evaluate the model. This model underpins simple algorithms that can be easily applied within schemes to calculate local, regional, or global air-sea fluxes of gases.

Chloride ingress into marine exposed concrete: A comparison of empirical- and physically- based models

In establishing the reliability of performance-related design methods for concrete – which are relevant for resistance against chloride-induced corrosion - long-term experience of local materials and practices and detailed knowledge of the ambient and local micro-climate are critical. Furthermore, in the development of analytical models for performance-based design, calibration against test data representative of actual conditions in practice is required. To this end, the current study presents results from full-scale, concrete pier-stems under long-term exposure to a marine environment with work focussing on XS2 (below mid-tide level) in which the concrete is regarded as fully saturated and XS3 (tidal, splash and spray) in which the concrete is in an unsaturated condition. These exposures represent zones where concrete structures are most susceptible to ionic ingress and deterioration. Chloride profiles and chloride transport behaviour are studied using both an empirical model (erfc function) and a physical model (ClinConc). The time dependency of surface chloride concentration (Cs) and apparent diffusivity (Da) were established for the empirical model whereas, in the ClinConc model (originally based on saturated concrete), two new environmental factors were introduced for the XS3 environmental exposure zone. Although the XS3 is considered as one environmental exposure zone according to BS EN 206-1:2013, the work has highlighted that even within this zone, significant changes in chloride ingress are evident. This study aims to update the parameters of both models for predicting the long term transport behaviour of concrete subjected to environmental exposure classes XS2 and XS3.

Model reduction for nonlinear aerodynamics and aeroelasticity using a Discrete Empirical Interpolation Method

A novel surrogate model is proposed in lieu of Computational Fluid Dynamics (CFD) solvers, for fast nonlinear aerodynamic and aeroelastic modeling. A nonlinear function is identified on selected interpolation points by
a discrete empirical interpolation method (DEIM). The flow field is then reconstructed using a least square approximation of the flow modes extracted
by proper orthogonal decomposition (POD). The aeroelastic reduce order
model (ROM) is completed by introducing a nonlinear mapping function
between displacements and the DEIM points. The proposed model is investigated to predict the aerodynamic forces due to forced motions using
a N ACA 0012 airfoil undergoing a prescribed pitching oscillation. To investigate aeroelastic problems at transonic conditions, a pitch/plunge airfoil
and a cropped delta wing aeroelastic models are built using linear structural models. The presence of shock-waves triggers the appearance of limit
cycle oscillations (LCO), which the model is able to predict. For all cases
tested, the new ROM shows the ability to replicate the nonlinear aerodynamic forces, structural displacements and reconstruct the complete flow
field with sufficient accuracy at a fraction of the cost of full order CFD
model.

Three dimensional models of water flow in the Persian Gulf

Persian Gulf region is globally of great importance due to its economical and political reasons. The importance lies in oil sources and sea exports. Geophysical phenomena dominated in the water circulation affected this region is called Monsoon it stretches from African coasts to the half way of Red Seal affected all coasts of Persian Gulf and goes toward east to the Indian ocean. Other essential factors in the water circulation in this region are net evaporation (several meters in per year), high density and high salinity. In this article the effects of wind stress and evaporation in the water circulation in the region will be considered and model equations for wind forces, density, pressure, gradient, and bottom friction for Persian Gulf will be discussed.

A STUDY OF HEAT TRANSFER AND FLOW CHARACTERISTICS OF RISING TAYLOR BUBBLES

Practical application of flow boiling to ground- and space-based thermal management systems hinges on the ability to predict the system’s heat removal capabilities under expected operating conditions. Research in this field has shown that the heat transfer coefficient within two-phase heat exchangers can be largely dependent on the experienced flow regime. This finding has inspired an effort to develop mechanistic heat transfer models for each flow pattern which are likely to outperform traditional empirical correlations. As a contribution to the effort, this work aimed to identify the heat transfer mechanisms for the slug flow regime through analysis of individual Taylor bubbles. An experimental apparatus was developed to inject single vapor Taylor bubbles into co-currently flowing liquid HFE 7100. The heat transfer was measured as the bubble rose through a 6 mm inner diameter heated tube using an infrared thermography technique. High-speed flow visualization was obtained and the bubble film thickness measured in an adiabatic section. Experiments were conducted at various liquid mass fluxes (43-200 kg/m2s) and gravity levels (0.01g-1.8g) to characterize the effect of bubble drift velocity on the heat transfer mechanisms. Variable gravity testing was conducted during a NASA parabolic flight campaign. Results from the experiments showed that the drift velocity strongly affects the hydrodynamics and heat transfer of single elongated bubbles. At low gravity levels, bubbles exhibited shapes characteristic of capillary flows and the heat transfer enhancement due to the bubble was dominated by conduction through the thin film. At moderate to high gravity, traditional Taylor bubbles provided small values of enhancement within the film, but large peaks in the wake heat transfer occurred due to turbulent vortices induced by the film plunging into the trailing liquid slug. Characteristics of the wake heat transfer profiles were analyzed and related to the predicted velocity field. Results were compared and shown to agree with numerical simulations of colleagues from EPFL, Switzerland. In addition, a preliminary study was completed on the effect of a Taylor bubble passing through nucleate flow boiling, showing that the thinning thermal boundary layer within the film suppressed nucleation, thereby decreasing the heat transfer coefficient.

Econometric models in foreign exchange market

According to the significance of the econometric models in foreign exchange market, the purpose of this research is to give a closer examination on some important issues in this area. The research covers exchange rate pass-through into import prices, liquidity risk and expected returns in the currency market, and the common risk factors in currency markets. Firstly, with the significant of the exchange rate pass-through in financial economics, the first empirical chapter studies on the degree of exchange rate pass-through into import in emerging economies and developed countries in panel evidences for comparison covering the time period of 1970-2009. The pooled mean group estimation (PMGE) is used for the estimation to investigate the short run coefficients and error variance. In general, the results present that the import prices are affected positively, though incompletely, by the exchange rate. Secondly, the following study addresses the question whether there is a relationship between cross-sectional differences in foreign exchange returns and the sensitivities of the returns to fluctuations in liquidity, known as liquidity beta, by using a unique dataset of weekly order flow. Finally, the last study is in keeping with the study of Lustig, Roussanov and Verdelhan (2011), which shows that the large co-movement among exchange rates of different currencies can explain a risk-based view of exchange rate determination. The exploration on identifying a slope factor in exchange rate changes is brought up. The study initially constructs monthly portfolios of currencies, which are sorted on the basis of their forward discounts. The lowest interest rate currencies are contained in the first portfolio and the highest interest rate currencies are in the last. The results performs that portfolios with higher forward discounts incline to contain higher real interest rates in overall by considering the first portfolio and the last portfolio though the fluctuation occurs.

FLOW REGIME DRIVEN THERMAL ENHANCEMENT IN INTERNALLY-GROOVED TUBES

Internally-grooved refrigeration tubes maximize tube-side evaporative heat transfer rates and have been identified as a most promising technology for integration into compact cold plates. Unfortunately, the absence of phenomenological insights and physical models hinders the extrapolation of grooved-tube performance to new applications. The success of regime-based heat transfer correlations for smooth tubes has motivated the current effort to explore the relationship between flow regimes and enhanced heat transfer in internally-grooved tubes. In this thesis, a detailed analysis of smooth and internally-grooved tube data reveals that performance improvement in internally-grooved tubes at low-to-intermediate mass flux is a result of early flow regime transition. Based on this analysis, a new flow regime map and corresponding heat transfer coefficient correlation, which account for the increased wetted angle, turbulence, and Gregorig effects unique to internally-grooved tubes, were developed. A two-phase test facility was designed and fabricated to validate the newly-developed flow regime map and regime-based heat transfer coefficient correlation. As part of this setup, a non-intrusive optical technique was developed to study the dynamic nature of two-phase flows. It was found that different flow regimes result in unique temporally varying film thickness profiles. Using these profiles, quantitative flow regime identification measures were developed, including the ability to explain and quantify the more subtle transitions that exist between dominant flow regimes. Flow regime data, based on the newly-developed method, and heat transfer coefficient data, using infrared thermography, were collected for two-phase HFE-7100 flow in horizontal 2.62mm - 8.84mm diameter smooth and internally-grooved tubes with mass fluxes from 25-300 kg/m²s, heat fluxes from 4-56 kW/m², and vapor qualities approaching 1. In total, over 6500 combined data points for the adiabatic and diabatic smooth and internally-grooved tubes were acquired. Based on results from the experiments and a reinterpretation of data from independent researchers, it was established that heat transfer enhancement in internally-grooved tubes at low-to-intermediate mass flux is primarily due to early flow regime transition to Annular flow. The regime-based heat transfer coefficient outperformed empirical correlations from the literature, with mean and absolute deviations of 4.0% and 32% for the full range of data collected.

Managing and utilizing information flow for new products’ periodic account sales process

The goal was to understand, document and module how information is currently flown internally in the largest dairy organization in Finland. The organization has undergone radical changes in the past years due to economic sanctions between European Union and Russia. Therefore, organization’s ultimate goal would be to continue its growth through managing its sales process more efficiently. The thesis consists of a literature review and an empirical part. The literature review consists of knowledge management and process modeling theories. First, the knowledge management discusses how data, information and knowledge are exchanged in the process. Knowledge management models and processes are describing how knowledge is created, exchanged and can be managed in an organization. Secondly, the process modeling is responsible for visualizing information flow through discussion of modeling approaches and presenting different methods and techniques. Finally, process’ documentation procedure was presented. In the end, a constructive research approach was used in order to identify process’ related problems and bottlenecks. Therefore, possible solutions were presented based on this approach. The empirical part of the study is based on 37 interviews, organization’s internal data sources and theoretical framework. The acquired data and information were used to document and to module the sales process in question with a flowchart diagram. Results are conducted through construction of the flowchart diagram and analysis of the documentation. In fact, answers to research questions are derived from empirical and theoretical parts. In the end, 14 problems and two bottlenecks were identified in the process. The most important problems are related to approach and/or standardization for information sharing, insufficient information technology tool utilization and lack of systematization of documentation. The bottlenecks are caused by the alarming amount of changes to files after their deadlines.

Thermal models, lithosphere thickness and heat flow in South Portugal. Some comments about the subject

Reinterpretation of old heat flow data or use of new data and new techniques of detection of the temperature under the surface have conducted to new heat flow density values in some regions of the globe. The problem of ice melting in Greenland and Antarctica caught the public's attention to the importance of knowledge on heat flow values and thermal structure of the globe. In the last years, several models were presented trying to obtain lithosphere and Moho thickness of the Iberia Peninsula. The work we intend to present is related with the SW part of the Iberia Peninsula ( south of the Ossa Morena zone, South Portuguese Zone and Algarve). The results obtained show a decrease in the thickness of the crust and the lithosphere in this region. Density anomalies in the crust are also referred. I intend to make the connection between the results of these models and the heat flow thermal conductivity, heat production and geological data available for the region, trying to explain the results of heat flow density data obtained.