The aim of the thesis is to identify an appropriate model in forecasting Value-at-Risk on a morevolatile period than that one from which the model is estimated. We estimate 1-day-ahead and10-days-ahead Value-at-Risk on a number of exchange rates. The Value-at-Risk estimates arebased on three models combined with three distributional assumptions of the innovations, andthe evaluations are made with Kupiec's (1995) test for unconditional coverage. The data rangesfrom January 1st 2006 through June 30th 2011. The results suggest that the GARCH(1,1) andGJR-GARCH(1,1) with normally distributed innovations are models adequately capturing theconditional variance in the series.

Organic shales have become one of the greatest sources of hydrocarbon thanks to novel production techniques such as hydraulic fracturing. A successful hydraulic fracturing job, however, is dependent on several rock properties such as mineralogy and elasticity. A reliable estimation of such properties is therefore necessary to determine ideal rocks for horizontal well placement. In this study, rock types within the Eagle Ford shale that would be suitable for hydraulic fracturing are identified through interpretations of available well logs and core data. A comparative study of petrophysical properties such as mineral content, kerogen type and maturity, porosity, and saturation in six wells is performed to characterize the Eagle Ford shale. Two of the wells studied are within the wet gas window of the shale while the remaining four are in the oil window. Based on the calculated petrophysical properties, rock typing was performed using k-means clustering. Two rock types (RT1 and RT2) were identified and their compositions compared in each well. Elastic properties for the various rock types identified were then estimated using the differential effective medium (DEM) theory and were validated through simulation of slowness logs. The final rock type assessment was then performed to identify ideal rocks for hydrofracturing. Results indicate that the Eagle Ford mineralogy varies greatly with depth and with geographic location relative to the San Marcos Arch, a geological arching prominence across the shale. Northeast of the arch, the Eagle Ford shale is clay-rich. Preferred rocks for hydrocarbon production, RT1, are characterized by volumetric concentrations of ~0.44 carbonate, ~0.09 kerogen, ~0.07 porosity, and ~0.42 clay; RT1 also exhibits high sonic velocities (> 3400 m/s and > 1500 m/s compressional and shear, respectively) and high apparent electrical resistivity (> 2 ohm-m). In the Southwest region, on the other hand, the Eagle Ford shale is mostly calcareous. Ideal rocks in the region, RT1, are rich in kerogen (~0.1) with carbonate content of ~0.56, ~0.1 porosity, ~0.19 clay content, and resistivity > 20 ohm-m. In both regions, porosity and pore aspect ratio displayed substantial effects on elastic properties. For example, over 80% decrease in Young’s modulus was quantified when pore aspect ratio approached zero; high pore aspect ratio is preferred for stiff rocks. Poisson’s ratio estimates were not always reliable therefore fracturability was assessed based on Young’s modulus estimates. The study shows that depth intervals exhibiting Young’s moduli above 18GPa and 21GPa in the Northeast and Southwest region, respectively, are suitable for hydrofracturing. / text

Due to their structural efficiency and architectural elegance, concrete arches have long been used in bridge applications. However, the construction of concrete arches requires significant temporary supporting structures, which prevent their widespread use in modern bridges. A relatively new form of arch bridges is the network arch, in which a dense arrangement of inclined hangers is used. Network arches are subjected to considerably smaller bending moments and deflections than traditional arches and are therefore suitable for modern, accelerated construction methods in which the arches are fabricated off-site and then transported to the bridge location. However, service-level stresses, which play a critical role in the performance of the structure, are relatively unknown for concrete network arches and have not been sufficiently investigated in the previous research on concrete arches. The primary objective of this dissertation is to improve the understanding of short-term and time-dependent stresses in concrete arches, and more specifically, concrete network arches. The research presented herein includes extensive field monitoring of the West 7th Street Bridge in Fort Worth, Texas, which is the first precast network arch bridge and probably the first concrete network arch bridge in the world. The bridge consists of twelve identically designed concrete network arches that were precast and post-tensioned before they were transported to the bridge site and erected. A series of vibrating wire gages were embedded in the arches and were monitored throughout the construction and for a few months after the bridge was opened to traffic. The obtained data were processed, and structural response parameters were evaluated to support the safe construction of the innovative arches, identify their short-term and time-dependent structural behavior, and verify the modeling assumptions. The variability of stresses among the arches was also used to assess the reliability of stress calculations. The results of this study provide valuable insight into the elastic, thermal, and time-dependent behavior of concrete arches in general and concrete network arches in particular. The knowledge gained in this investigation also has broader applications towards understanding the behavior of indeterminate prestressed concrete structures that are subjected to variable boundary conditions and thermal and time-dependent effects.

The foot keeps body balance and stability during walking, running and performing various physical activities. It has been determined that mechanical properties of musculoskeletal system influence motion control, body balance maintenance (Richardson et al., 2005; Biewener, Daley, 2007; Nishikawa, 2007). However, it is yet unclear whether there is a relation between body stability and foot arch stability. The relation is yet unknown between the mechanical and physiological properties of the foot and foot arch stability. The aim of the research is to determine the relation between foot arch stability and the mechanical and physiological properties of the foot. The objectives of the research were: 1. To determine whether feet distribution according to arch type depends on different foot arch assessment methods applied. 2. To determine the mechanical properties of foot, Achilles tendon and plantar fascia. 3. To investigate whether there is a relation between foot arch stability and body stability. 4. To investigate whether there is a relation between mechanical and physiological properties of the foot. METHODS The research was carried out according to the principles of Convention on Human Rights and Biomedicine adopted on 19 November 1996 (Convention on Human Rights and Biomedicine) (Rogers and Bousingen, 2001). The license for the research was issued by Kaunas Regional Biomedical Research Ethics Committee (protocol No BE-2-53). 5 studies were conducted: 1 study: the analysis of... [to full text] / Žmogui einant, bėgant, atliekant įvairias fizines veiklas, pėda išlaiko kūno pusiausvyrą, stabilumą. Net mažas struktūros ar funkcijos pokytis gali turėti įtakos pėdos hiper-, hipomobilumui, kurie siejami su traumų atsiradimu. Šio darbo tikslas buvo nustatyti pėdos skliauto stabilumo ir mechaninių bei fiziologinių savybių sąveiką. Atlikti penki tyrimai. Pirmojo tyrimo tikslas – nustatyti, ar pėdų pasiskirstymas pagal skliauto tipus priklauso nuo skirtingų skliauto nustatymo metodų. Tyrime dalyvavo 91 tiriamasis ir buvo ištirtos 182 pėdos. Tyrime taikyti F. Forriol, L. T. Staheli, H. H. Clarke ir D. S. Williams pėdos skliauto nustatymo metodai. Gauti tyrimo rezultatai rodo, kad pagal skirtingas metodikas pėdos pagal normalų, žemą ir aukštą pėdos skliauto tipą pasiskirstė nevienodai. Antrojo tyrimo tikslas – nustatyti normalaus, žemo ir aukšto pėdos skliauto deformaciją, santykinę deformaciją ir standumą. Buvo tirtos 42 pėdos. Biomechaniniai pėdos parametrai apskaičiuoti naudojant pėdos gniuždymo metodiką. Nustatyta, kad pėdos deformacija ir standumas priklauso nuo pėdos skliauto tipo. Žemo skliauto standumas yra mažesnis ir jis daugiau deformuojasi negu normalaus ir aukšto pėdos skliautas. Trečiojo tyrimo tikslas – nustatyti in vitro pėdos deformaciją, santykinę deformaciją ir standumą esant skirtingam gniuždymo greičiui. Tirtos viena su minkštaisiais audiniais ir šešios be minkštųjų audinių pėdos. Tyrime pėdos buvo gniuždomos Tinius Olsen H25K-T bandymų mašina. Pėdos... [toliau žr. visą tekstą]

Baigiamajame magistro darbe atliekama plieninių neskėtrių arkinių tiltų pastovumo plokštumoje analizė. Pirmajame skyriuje apžvelgiami pavienių gniuždomųjų strypų, arkų ir arkinių tiltų pastovumo tikrinimo metodai, pateikiamos projektavimo normos ir jų taikymo sritys. Antrajame skyriuje pateikiamas analiziniais ir skaitiniais metodais apskaičiuotų pavienių strypų ir arkų pastovumo parametrų palyginimas. Konstrukcijų pastovumo analizei atlikti naudojamas programinis paketas „Sofistik“. Skaičiuojant pastovumo parametrus vertinama arkos geometrinė apybrėža, apkrovimo pobūdis, lenkiamasis standis, aukščio ir tarpatramio santykis. Nustatomi racionalūs arkos geometriniai parametrai. Trečiajame skyriuje nagrinėjami dvimačiai neskėtrių arkinių tiltų modeliai. Vertinama tinklelio pakabų skaičiaus ir išdėstymo įtaka pastovumui. Palyginami neskėtrių arkinių tiltų stabilumo analizės rezultatai. Pateikiamos išvados ir rekomendacijos. Darbą sudaro: įvadas, trys skyriai, bendrosios išvados ir rekomendacijos, literatūros sąrašas, priedai. Darbo apimtis – 96 puslapiai, 66 paveikslai, 26 lentelės, 32 bibliografiniai šaltiniai. / The master thesis is carried out for in plane stability analysis of tied steel arch bridges. In first chapter overview of the individual compression bars, arches and arch bridges stability testing methods is presented. The first chapter also provides design standards and their application areas. The whole structural stability analysis was performed using “Sofistik” finite element software. Using software two dimensional models of arches and arch bridges were made. Second chapter concludes comparison of analytical and numerical stability analysis of single arches. Stability parameter and effective length factor was calculated according to arch geometric outlines, load type, bending stiffness, height and span ratio. The third chapter consists of stability analysis of two dimensional arch bridge models. Different suspension cable grids were used in order to compare and evaluate stability analysis results. Comparison of stability factors of various versions of arch bridges was made. Conclusions and recommendations are presented in the final chapter. The work contains: introduction, three chapters, conclusions and recommendations, references and appendices. The whole work consists of – 96 pages, 66 figures, 26 tables, 32 references.

In this dissertation we proposed two generalizations of the Second-Order Least Squares (SLS) approach in two popular dynamic econometrics models. The first one is the regression model with time varying nonlinear mean function and autoregressive conditionally heteroskedastic (ARCH) disturbances. The second one is a linear dynamic panel data model. We used a semiparametric framework in both models where the SLS approach is based only on the first two conditional moments of response variable given the explanatory variables. There is no need to specify the distribution of the error components in both models. For the ARCH model under the assumption of strong-mixing process with finite moments of some order, we established the strong consistency and asymptotic normality of the SLS estimator. It is shown that the optimal SLS estimator, which makes use of the additional information inherent in the conditional skewness and kurtosis of the process, is superior to the commonly used quasi-MLE, and the efficiency gain is significant when the underlying distribution is asymmetric. Moreover, our large scale simulation studies showed that the optimal SLSE behaves better than the corresponding estimating function estimator in finite sample situation. The practical usefulness of the optimal SLSE was tested by an empirical example on the U.K. Inflation. For the linear dynamic panel data model, we showed that the SLS estimator is consistent and asymptotically normal for large N and finite T under fairly general regularity conditions. Moreover, we showed that the optimal SLS estimator reaches a semiparametric efficiency bound. A specification test was developed for the first time to be used whenever the SLS is applied to real data. Our Monte Carlo simulations showed that the optimal SLS estimator performs satisfactorily in finite sample situations compared to the first-differenced GMM and the random effects pseudo ML estimators. The results apply under stationary/nonstationary process and wih/out exogenous regressors. The performance of the optimal SLS is robust under near-unit root case. Finally, the practical usefulness of the optimal SLSE was examined by an empirical study on the U.S. airfares.

The purpose of this thesis is to identify the best volatility model for Value-at-Risk(VaR) estimations. We estimate 1 % and 5 % VaR figures for Nordic indices andstocks by using two symmetrical and two asymmetrical GARCH models underdifferent error distributions. Out-of-sample volatility forecasts are produced usinga 500 day rolling window estimation on data covering January 2007 to December2014. The VaR estimates are thereafter evaluated through Kupiec’s test andChristoffersen’s test in order to find the best model. The results suggest thatasymmetrical models perform better than symmetrical models albeit the simpleARCH is often good enough for 1 % VaR estimates.

In the original Vasicek model interest rates are calculated assuming that volatility remains constant over the period of analysis. In this study, we constructed a stochastic volatility model for interest rates. In our model we assumed not only that interest rate process but also the volatility process for interest rates follows the mean-reverting Vasicek model. We derived the density function for the stochastic element of the interest rate process and reduced this density function to a series form. The parameters of our model were estimated by using the method of moments. Finally, we tested the performance of our model using the data of interest rates in Turkey.

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The wide variation in infant maxillary morphology and cleft size of children with unilateral cleft lip and palate (UCLP) and isolated cleft palate (CP) raise concerns about their possible influences on treatment outcome. The studies in this thesis aimed to investigate the relation between cleft size in infancy and crossbite at 5 years of age (Paper I); the impact of primary surgery on cleft size and maxillary arch dimensions from infancy to 5 years of age (Paper II); associations between cleft size, maxillary arch dimensions and facial growth in both UCLP and CP children (Paper III); and, to evaluate the relation between infant cleft size and nasal airway size and function in adults treated for UCLP (Paper IV). In homogenously treated groups of children with UCLP and CP, dental casts were used to measure cleft size and maxillary arch dimensions from infancy up to 5 years of age, and for crossbite recording at 5 years. Serial lateral cephalometric radiographs taken between 5 and 19 years of age in the same groups were used to study facial growth. Nasal airway size and function were evaluated by acoustic rhinometry, rhinomanometry, peak nasal inspiratory flow and odour test in a group of adults treated for UCLP. The main findings were: crossbite was a frequent malocclusion at 5 years of age in children with UCLP and large cleft widths at the level of the cuspid points in infancy were associated with less anterior and posterior crossbite in this group (Paper I). Cleft widths decreased after lip closure and/or soft palate closure in both UCLP and CP children. Initially, UCLP children had wider maxillary arch dimensions, but after hard palate closure, the transverse growth was reduced, and at 5 years, they had smaller maxillary arch widths than CP children had (Paper II). Maxillary arch depths and cleft widths in infancy were correlated with maxillary protrusion and sagittal jaw relationships in both UCLP and CP children (Paper III), but cleft width in infancy was not correlated with nasal airway size and function in adults treated for UCLP (Paper IV).