In the first essay, Persistence in Swedish Unemployment Rates, we study if there is no or weak tendency in unemployment rates to revert back to previous levels. Persistence is caused by: natural rate shocks, long unemployment cycles, and spill-over from cyclical to permanent unemployment. We find evidence of high persistence. The results suggest that the quick rise of unemployment rates during 1992-1994 was caused by large permanent and cyclical shocks in combination with spill-over effects. In the second essay, The Equilibrium Rate of Unemployment in a Small Open Economy, we challenge the common and simplifying assumption that the economy is closed. We set up and estimate a structural unobserved components open economy model for the unemployment rate and the real exchange rate. Our estimates indicate that the foreign sector is of substantial importance when explaining movements in the NAIRU. In the third essay, A Simultaneous Model of the Swedish Krona, the US Dollar and the Euro, we simultaneously estimate the real exchange rates between the Swedish Krona, the US Dollar and the Euro. The exchange rate movements are well explained by potential output, the output gap, terms of trade, the fraction of prime-aged people in the population, and structural government budget deficits. The models work well in an out of sample exercise. In the last essay, Wages, Employment, and Unemployment: The Effect of Benefits, Taxes and Labor Mobility, we study how wages and employment are affected by unemployment insurance and labor mobility. We show that the wage effect of higher unemployment benefits can be either positive or negative, depending on the specification of union utility function and the taxation scheme for financing the benefits. The common claim that wages are lower when a sector bears a higher fraction of unemployment costs does not hold in general. We also show that labor mobility across sectors and increased competition reduces wages and unemployment.

A new procedure was studied to obtain concentrated methane hydrates in bulk, at medium-low pressure, avoiding the use of the spray process. Methane hydrate was formed at about 5 MPa and 2 °C in a reaction calorimeter with the volume of two liters. The clathrate concentration was about 30% and the final reactor pressure was 2.7 MPa. Any further repressurization at 2 °C had no noticeable effect on the hydrate formation. However, by repressurizing the vessel again to 4 MPa and increasing the temperature near the decomposition value (about 6° C) more clathrate was formed. Repressurizing again the reactor at 4 MPa and controlling the temperature at the same level, a concentration of 88% hydrate in the bulk was reached. Respect to the hydrate produced by the spray process, this procedure takes more time, but it can be sped up and made continuous by using teo reaction vessels, one for hydrate formation and the other for hydrate concentration. The advantage is the production of concentrated hydrates, by a simple equipment, working at relatively low pressures.

El objetivo de esta tesis ha sido estudiar y desarrollar metodologias analíticasusando un sistema de inyección secuencial (SIA) con un espectrofotómetro de diodos enfila para obtener datos de segundo orden. Para tratar estos datos, las herramientasquimiométricas usadas han sido; resolución de curvas multivariante mediante mínimoscuadrados alternados (MCR-ALS) y otras técnicas relacionadas a ésta como el análisisde componentes principales (PCA) y SIMPLISMA. Además se han aplicado estrategiasde diseño de experimentos para obtener las condiciones experimentales óptimas. Estametodología se aplicó a la determinación de amoxicilina y ácido clavulánico enmedicamentos.El primer capítulo de la tesis contiene una descripción de la amoxicilina y del ácidoclavulánico, una explicación de los fundamentos teóricos tanto del sistema instrumentalcomo de las herramientas quimiométricas usadas y por último, se describen los diseñosde experimentos usados y la función de deseabilidad.En los dos siguientes capítulos, se muestran en forma de artículos científicos lostrabajos experimentales realizados. En un primer artículo, se realizó una clasificación delos medicamentos dependiendo si se tenían interferentes o no, para posteriormenteproponer el tipo de calibrado. Un paso previo a la diferenciación de los medicamentos,fue buscar una secuencia analítica que permitiera obtener un sistema en evolución. Estaetapa se llevó a cabo mediante un diseño de experimentos.En el segundo artículo, se determinó la cantidad de amoxicilina en losmedicamentos que tenían interferentes y además no tenían zonas selectivas. Para llevara cabo de forma correcta la etapa de calibración se realizó un estudio de una serie deparámetros asociados a MCR-ALS. En un tercer artículo se realizó la determinaciónsimultánea del ácido clavulánico y de la amoxicilina que poseían unas característicasácido-base y una sensibilidad espectral similar. Por tal de determinar simultáneamenteambos analitos se rediseñó todo el experimental. En el cuarto artículo se hizo unarevisión bibliográfica de ambas técnicas a partir del año 2004 y se discutió el potencial deusar un sistema de inyección secuencial para generar datos de segundo orden.Con la experimentación realizada se comprobó que el paso clave en estasmetodologias era obtener una buen sistema en evolución, es decir diseñar una buenasecuencia analítica. Por lo que se profundizó en estrategias basadas en diseños deexperimentos. En el quinto artículo, se estudiaron qué factores podían afectar a lasecuencia analítica. También se propusieron respuestas que representaran de una formacuantitativa una buena resolución. Se realizó un diseño Plackett-Burman con el objetivode eliminar los factores no relevantes, para posteriormente modelar una superficie derespuesta a partir de los factores relevantes que permite visualizar las condicionesóptimas de la secuencia analítica.El inconveniente de utilizar la metodología de superficie de respuesta es que enlos casos donde el número de factores relevantes sea superior a 3 o 4, el número deexperiencias aumenta considerablemente. En estos casos, una técnica alternativa essimplex que dio lugar a un sexto artículo.El último capítulo de la tesis contiene las conclusiones. Como una conclusióngeneral, se puede decir que la combinación de un sistema de inyección secuencial (SIA)y una herramienta quimiométrica como la resolución de curvas multivariante mediantemínimos cuadrados alternados (MCR-ALS) puede ser usado tanto para realizar unanálisis cualitativo y cuantitativo ya que proporciona información de los perfiles deconcentración y perfiles espectrales de las diferentes especies a estudio. / The objective of this thesis is to study and develop analytical methods to determineamoxicillin and clavulanic acid in pharmaceuticals using sequential injection analysis (SIA)with a diode-array spectrophotometric detector to obtain second-order data. To treat thesedata, the chemometric tool used was; multivariate curve resolution with alternating leastsquares (MCR-ALS) and the techniques involved in the resolution process are: principalanalysis components (PCA) and simple-to-use interactive self-modelling mixture analysis(SIMPLISMA).The first chapter contains a brief description of the theoretical backgrounds thathave been used during this thesis. We explain the characteristics and properties ofamoxicillin and clavulanic acid, we describes the instrumental and the chemometric toolsused and at the end, we introduce the experimental designs used and the desirabilityfunction.In the next two chapters contain the bulk of the work carried out for this thesis andincorporate papers published in journals. In the first paper, the pharmaceuticals wereclassified according to their selective zones in order to propose the type of calibration. In aprevious step, the experimental work was conducted to find an analytical sequence thatallows us to obtain an evolving system. This step was carried out using experimentaldesign. In the second paper, the quantity of amoxicillin in the pharmaceuticals withinterferents or without selective zones was determined. To carry out correctly thecalibration step, we studied different conditions related to the MCR-ALS process.In the third paper, we propose the simultaneous determination of amoxicillin andclavulanic acid which they have the acid-base characteristics and spectral profile similar.To determine both analytes, a new analytical sequence was redesigned. In the fourthpaper, we describe the state of the art of sequential injection analysis (SIA) andmultivariate curve resolution with alternating least squares (MCR-ALS) by reviewing thebibliography since 2004. We discuss the potential of SIA for generating second-orderdata.In previous papers, we found that the most critical step in the development ofanalytical methods based on SIA and MCR-ALS was to obtain an analytical sequence thatprovides an evolving system. To resolve so, we developed the method of experimentaldesign to obtain the optimal analytical sequence.In the forth paper, we studied all the factors and analysed how they affect to theanalytical sequence. We also proposed responses to quantitatively represent a goodresolution. Once these factors and responses were proposed, we used a Plackett-Burmandesign to remove the non-relevant factors and then modelled a response surface. In themaximum of response surface, the optimum conditions for the analytical sequence couldbe visualised. To transform several responses into a single response, we used the overalldesirability function. In the sixth paper, we applied an alternative optimisation methodknows as the simplex approach. We aimed to determine amoxicillin and clavulanic acidsimultaneously when the number of factors and responses was higher than in theprevious paper.The last chapter contains the conclusions of the thesis. In general, we concludethat a combined sequential injection analysis (SIA) with a multivariate detector (i.e. diodearray spectrophotometer) and multivariate curve resolution with alternating least squares(MCR-ALS) can be used for both qualitative and quantitative analyses since, it providesconcentration and spectra profiles for the different species of the sample.

Longitudinal joints are one of the critical factors that cause premature pavement failure. Poor-quality joints are characterized by a low density and high permeability; which generates surface distresses such as ravelling or longitudinal cracking. Density has been traditionally considered as the primary performance indicator of joint construction. Density measurements consist of taking cores in the field and determining their density in the laboratory. Although this technique provides the most accurate measure of joint density, it is destructive and time consuming. Nuclear and non-nuclear gauges have been used to evaluate the condition of longitudinal joint non-destructively, but did not show good correlation with core density tests. Consequently, agencies are searching for other non-destructive testing (NDT) options for longitudinal joints evaluation. NDT methods have significantly advanced for the evaluation of pavement structural capacity during the past decade. These methods are based either on deflection or wave velocity measurements. The light weight deflectometer (LWD) is increasingly being used in quality control/quality assurance to provide a rapid determination of the surface modulus. Corresponding backcalculation programs are able to determine the moduli of the different pavement layers; these moduli are input parameters for mechanistic-empirical pavement design. In addition, ultrasonic wave-based methods have been studied for pavement condition evaluation but not developed to the point of practical implementation. The multi-channel analysis of surface waves (MASW) consists of using ultrasonic transducers to measure surface wave velocities in pavements and invert for the moduli of the different layers. In this study, both LWD and MASW were used in the laboratory and in the field to assess the condition of longitudinal joints. LWD tests were performed in the field at different distances from the centreline in order to identify variations of the surface modulus. MASW measurements were conducted across the joint to evaluate its effect on wave velocities, frequency content and attenuation parameters. Improved signal processing techniques were used to analyze the data, such as Fourier Transform, windowing, or discrete wavelet transform. Dispersion curves were computed to determine surface wave velocities and identify the nature of the wave modes propagating through the asphalt pavement. Parameters such as peak-to-peak amplitude or the area of the frequency spectrum were used to compute attenuation curves. A self calibrating technique, called Fourier transmission coefficient (FTC), was used to assess the condition of longitudinal joints while eliminating the variability introduced by the source, receivers and coupling system. A critical component of this project consisted of preparing an asphalt slab with a joint in the middle that would be used for testing in the laboratory. The compaction method was calibrated by preparing fourteen asphalt samples. An exponential correlation was determined between the air void content and the compaction effort applied to the mixture. Using this relationship, an asphalt slab was prepared in two stages to create a joint of medium quality. Nuclear density measurements were performed at different locations on the slab and showed a good agreement with the predicted density gradient across the joint. MASW tests were performed on the asphalt slabs using different coupling systems and receivers. The FTC coefficients showed good consistency from one configuration to another. This result indicates that the undesired variability due to the receivers and the coupling system was reduced by the FTC technique. Therefore, the coefficients were representative of the hot mix asphalt (HMA) condition. A comparison of theoretical and experimental dispersion curves indicated that mainly Lamb waves were generated in the asphalt layer. This new result is in contradiction with the common assumption that the response is governed by surface waves. This result is of critical importance for the analysis of the data since MASW tests have been focusing on the analysis of Rayleigh waves. Deflection measurements in the field with the LWD showed that the surface modulus was mostly affected by the base and subgrade moduli, and could not be used to evaluate the condition of the surface course that contains the longitudinal joints. The LWDmod software should be used to differentiate the pavement layers and backcalculate the modulus of the asphalt layer. Testing should be performed using different plate sizes and dropping heights in order to generate different stress levels at the pavement surface and optimize the accuracy of the backcalculation. Finally, master curves were computed using a predictive equation based on mix design specifications. Moduli measured at different frequencies of excitation with the two NDT techniques were shifted to a design frequency of 25 Hz. Design moduli measured in the field and in the laboratory with the seismic method were in good agreement (less than 0.2% difference). Moreover, a relatively good agreement was found between the moduli measured with the LWD and the MASW method after shifting to the design frequency. In conclusion, LWD and MASW measurements were representative of HMA condition. However, the condition assessment of medium to good quality joints requires better control of the critical parameters, such as the measurement depth for the LWD, or the frequency content generated by the ultrasonic source and the coupling between the receivers and the asphalt surface for the MASW method.

Compare the accuracy of two continuous-scale tests is increasing important when a new test is developed. The traditional approach that compares the entire areas under two Receiver Operating Characteristic (ROC) curves is not sensitive when two ROC curves cross each other. A better approach to compare the accuracy of two diagnostic tests is to compare the areas under two ROC curves (AUCs) in the interested specificity interval. In this thesis, we have proposed bootstrap and empirical likelihood (EL) approach for inference of the difference between two partial AUCs. The empirical likelihood ratio for the difference between two partial AUCs is defined and its limiting distribution is shown to be a scaled chi-square distribution. The EL based confidence intervals for the difference between two partial AUCs are obtained. Additionally we have conducted simulation studies to compare four proposed EL and bootstrap based intervals.

It is an important step in clinical practice to discriminate real diseased patients from healthy persons. It would be great to get such discrimination from some common information like personal information, life style, and the contact with diseased patient. In this study, a score is calculated for each patient based on a survey through generalized linear model, and then the diseased status is decided according to previous sexually transmitted diseases (STDs) records. This study will facilitate clinics in grouping patients into real diseased or healthy, which in turn will affect the method clinics take to screen patients: complete screening for possible diseased patient and some common screening for potentially healthy persons.

Credit Line Analysis plays a very important role in the housing market, especially with the situation of large number of frozen loans during the current financial crisis. In this thesis, we apply the methods of kernel estimate and the Receiver Operating Characteristic (ROC) curve in the credit loan application process in order to help banks select the optimal threshold to differentiate good customers from bad customers. Better choice of the threshold is essential for banks to prevent loss and maximize profit from loans. One of the main advantages of our study is that the method does not require us to specify the distribution of the latent risk score. We apply bootstrap method to construct the confidence interval for the estimate.

Stulpinaitė A. Parameters of low cycle fatigue curves according to elastic and plastic strain: Master thesis of mechanical engineer / research advisor associate professor dr. R. Šniuolis; Šiauliai University, Technological Faculty, Mechanical Engineering Department. – Šiauliai, 2004. -60p. Parameters of fracture (parameters of low cycle fatigue curves m, C) are determined at homogeneous stress state and symmetric or asymmetric low cycle straining. Low cycle loading in structures appear near stress concentrators, cracks in little volumes of material which is limited of elastic strained zones. The elastic plastic loading may be in the welded joints, too. In the condition of variable loading the elastic strained metal impedes the accumulation of strain in these areas. Therefore the conditions of straining in these areas are similar to low cycle straining. At low cycle loading lifetime depends on reduction of areay. Coffin’s equation for calculation of constant C is not suitable for most materials and more complex equations must be used. Parameter C markedly differs from the experimental, therefore high errors occur in evaluating lifetime of the material. It is noticed in many works that parameter proposed by Coffin is close to experimental. Parameter m = 0,5, proposed by Coffin, is determined according the low cycle fatigue curves in coordinates . In some works the total strain e is used instead of plastic strain d . The difference of values of parameter m in this case is... [to full text]

For a power series which converges in some neighborhood of the origin in the complex plane, the zeros of its partial sums often behave in a controlled manner. We give an overview of some of the major results in the study of this phenomenon in the past century, focusing on recent developments which build on the theme of asymptotic analysis. Inspired by this work, we study the asymptotic behavior of the zeros of partial sums of power series for entire functions defined by exponential integrals of a certain type. Most of the zeros of the n'th partial sum travel outwards from the origin at a rate comparable to n, so we rescale the variable by n and explicitly calculate the limit curves of these normalized zeros. We discover that the zeros' asymptotic behavior depends on the order of the critical points of the integrand in the aforementioned exponential integral. / 62+x pages, 24 figures

Darbe analizuojamas natūralus nedarbo lygis, Filipso kreivė. Darbo tikslas - įvertinti natūralų nedarbo lygį Lietuvoje. Pirmoje dalyje teoriškai nagrinėjama Filipso kreivė ir jos modifikacijos, kuri yra natūralaus nedarbo lygio teorinis pamatas, bei natūralų nedarbo lygį veikiantys faktoriai, analizuojamos vertinimo metodikos. Antroje dalyje analizuojami Filipso kreivę veikiančių faktorių dinamika Lietuvoje: valstybės išlaidos, komercinių bankų suteiktos paskolos, importo infliacija, naftos, dujų, elektros ir maisto žaliavų kainos. Analizuojami galimi Filipso kreivės struktūriniai lūžiai. Analizuojami natūralų nedarbo lygį veikinatys faktoriai: jaunimo nedarbo lygis ir santykinis dydis darbo jėgoje, emigracija, socialinės apsaugos lygis bei darbo produktyvumas, pateikiama natūralaus nedarbo lygio vertinimo metodologija. Trečioje dalyje vertinamos įvairių Filipso kreivių modifikacijų galiojimo Lietuvoje hipotezės bei vertinamas natūralus nedarbo lygis, apžvelgiami rezultatai ir jų patikimumas. Tyrime statistiškai patikimas Filipso kreivės modelis nebuvo rastas. Apskaičiuotas 12,04% Lietuvos natūralus nedarbo lygio įvertinimas yra tik iš dalies patikimas. Visi regresiniai modeliai parodė statistiškai reikšmingą neigiamą nedarbo lygio ir infliacijos priklausomybę. / Thesis is focused on natural rate of unemployment and variations of Phillips curve. Estimation of natural rate of unemployment in Lithuania is the main objective. In the first part Phillips curve and its variations, which is foundation for natural rate of unemployment as well as other infuencing factors are analysed on theoretical basis. Various estimation techniques are compared. In the second part various factors are analysed in the context of Phillips curve in Lithuania together with possible structural breaks in Phillips curve relationship. Conclusions are drawn from analysis of factors influencing natural rate of unemployment, particularly emigration and social security. Estimation methodology is specified in the second part. In the last part hipothesis of Phillips curve and natural rate of unemployment are tested. In conclusion, no statistically reliable model of Phillips curve based on empirical data is found, though all models proved negative inflation and unemployment relationship in Lithuania. Results show natural rate of unemployment to be 12,04%, though it is important to note, that results are drawn from statistically unreliable model.