Showing papers by "Tallinn University of Technology published in 2004"
TL;DR: This paper explored the equilibrium levels of China's real and nominal exchange rates using a Johansen cointegration framework and found that the renminbi is somewhat undervalued against the dollar, but the misalignment is not nearly as exaggerated as many popular claims.
Abstract: Given that the value of China's currency has been hot topic recently, this paper explores the equilibrium levels of China's real and nominal exchange rates. Employing a Johansen cointegration framework, we focus on the behavioral equilibrium exchange rate (BEER) and permanent equilibrium exchange rate (PEER) models. Our results suggest that, while the renminbi is somewhat undervalued against the dollar, the misalignment is not nearly as exaggerated as many popular claims.
161 citations
TL;DR: A quantitative annual mean temperature reconstruction from an annually laminated lake-sediment sequence in Estonia, eastern Europe, shows a distinct cold period at 8400-8080 yr B.P. as mentioned in this paper.
Abstract: A quantitative annual mean temperature reconstruction from an annually laminated lake-sediment sequence in Estonia, eastern Europe, shows a distinct cold period at 8400– 8080 yr B.P. (= before A.D. 2000); the timing is consistent with that seen in the Greenland ice-core data and various high-resolution records from western Europe. During maximal cooling at 8250–8150 yr B.P., the annual mean temperature in Estonia was ∼2.0 °C colder than prior to and ∼3.0 °C colder than after the cooling. The pollen-stratigraphic and sedimentological data suggest especially cold and snowy winter conditions. The duration and amplitude of the cold event agree with the modeled impact of a sudden freshening of the North Atlantic surface water and subsequent perturbation of the thermohaline circulation. Provided that the cold event was caused by a pulse of freshwater—from the melting Laurentide Ice Sheet—to the North Atlantic, the results indicate a strong teleconnection between the North Atlantic oceanic forcing and the east European climate at least up to long 26°E, mediated probably by the changing intensity of the zonal atmospheric circulation.
148 citations
TL;DR: This work proposes a novel approach, which is based on an analysis of key, data and attribute correlations, as well as their combination, which can be applied to migrating data-intensive Web pages, which are usually based on relational databases, into the ontology-based Semantic Web.
Abstract: A majority of the work on reverse engineering has been done on extracting entity-relationship and object models from relational databases. There exist only a few approaches that consider ontologies, as the target for reverse engineering. Moreover, the existing approaches can extract only a small subset of semantics embedded within a relational database, or they can require much user interaction for semantic annotation. In our opinion, the potential source of these problems lies in that the primary focus has been on analyzing key correlation. Data and attribute correlations are considered rarely and thus, have received little or no analysis. As an attempt to resolve the problems, we propose a novel approach, which is based on an analysis of key, data and attribute correlations, as well as their combination. Our approach can be applied to migrating data-intensive Web pages, which are usually based on relational databases, into the ontology-based Semantic Web.
127 citations
TL;DR: As a low-soluble phosphate mineral capable of binding various metal ions, apatite can be used to immobilize toxic metals in soils and waters and the factors affecting sorption and desorption of Cd2+ and Zn2+ ions on/from apatites are investigated.
Abstract: As a low-soluble phosphate mineral capable of binding various metal ions, apatite can be used to immobilize toxic metals in soils and waters. In the present research the factors affecting sorption and desorption of Cd2+ and Zn2+ ions on/from apatites are investigated. Batch experiments were carried out using synthetic hydroxy-, fluoride-, and carbonate-substituted apatites having various specific surface area (SSA). Apatite sorption capacity was found to depend mainly on its SSA, ranging from 16 to 78 and from 11 to 79 mmol per 100 g of apatite for Cd2+ and Zn2+, respectively. The solution composition (pH, and presence of Cl- and NO3- ions) had no essential impact on sorption. Desorption of bound cations depended both on the sorption level and solution composition. The amount of desorbed Cd2+ and Zn2+ increased proportionally to the amount of sorbed cations. However, apatites having higher sorption capacity release relatively less sorbed cations. Desorption increases with increasing Ca2+ concentration in the solution, reaching 8-20% of sorbed Cd2+ in 0.002 M, 10-35% in 0.01 M, and 33-45% in 0.05 M Ca(NO3)2 solution. Compared to nitrate solutions, the presence of Cl- ions in the solution promotes the release of bound cations. Desorption of Zn2+ is slightly higher than that of Cd2+. The desorption mechanism was assumed to include both ion-exchange and adsorption of Ca2+ ions on apatite surface.
96 citations
TL;DR: The properties of eventlog data are discussed, the suitability of popular mining algorithms for processing event log data is analyzed, and an efficient algorithm for mining frequent patterns from event logs is proposed.
Abstract: Today, event logs contain vast amounts of data that can easily overwhelm a human. Therefore, the mining of frequent patterns from event logs is an important system and network management task. This paper discusses the properties of event log data, analyses the suitability of popular mining algorithms for processing event log data, and proposes an efficient algorithm for mining frequent patterns from event logs.
90 citations
TL;DR: The Middle Caradoc Facies and Faunal Turnover can be described as a succession of related environmental changes in the Baltoscandian area as discussed by the authors, which is comparable to a similar succession of changes in North America.
89 citations
TL;DR: In this paper, the authors describe nitrogen losses from, and the characteristics of, 35 selected catchments (12 to 2000 ha) in the Nordic and Baltic countries in the 1990s.
Abstract: . This paper describes nitrogen losses from, and the characteristics of, 35 selected catchments (12 to 2000 ha) in the Nordic and Baltic countries. Average annual losses of N in 1994–1997 ranged from 5 to 75 kg ha-1, generally highest and characterised by significant within-country and interannual variations, in Norway and the lowest losses were observed in the Baltic countries. An important finding of the study is that the average nutrient losses varied greatly among the studied catchments. The main explanations for this variability were water runoff, fertiliser use (especially the amount of manure), soil type and erosion (including stream bank erosion). However, there were several exceptions, and it was difficult to find general relationships between the individual factors. For example, there was poor correlation between nitrogen losses and surpluses. Therefore, the results suggest that the observed variability in N losses cannot have been due solely to differences in farm management practices, although the studied catchments do include a wide range of nutrient application levels, animal densities and other relevant elements. There is considerable spatial variation in the physical properties (soil, climate, hydrology, and topography) and the agricultural management of the basins, and the interaction between and relative effects of these factors has an important impact on erosion and nutrient losses. In particular, hydrological processes may have a marked effect on N losses measured in the catchment stream water. The results indicate that significant differences in hydrological pathways (e.g. the relationship between fast- and slow-flow processes) lead to major regional differences in N inputs to surface waters and therefore also in the response to changes in field management practices. Agricultural practices such as crop rotation systems, nutrient inputs and soil conservation measures obviously play a significant role in the site-specific effects, although they cannot explain the large regional differences observed in this study. The interactions between agricultural practices and basic catchment characteristics, including hydrological processes, determine the final losses of nitrogen to surface waters, hence it is necessary to understand these interactions to manage diffuse losses of agricultural nutrients efficiently. Keywords: agriculture, catchments, diffuse sources, nitrogen, losses, Baltic, Nordic
88 citations
01 Jan 2004
TL;DR: It is shown that with the correct personal calibration it is possible to estimate the beat to beat systolic arterial blood pressure during the exercise with comparable accuracy to conventional noninvasive methods.
Abstract: This paper gives an overview of a research, which is focused on the development of the convenient device for continuous non-invasive monitoring of arterial blood pressure The blood pressure estimation method is based on a presumption that there is a singular relationship between the pulse wave propagation time in arterial system and blood pressure The parameter used in this study is pulse wave transit time (PWTT) The measurement of PWTT involves the registration of two time markers, one of which is based on ECG R peak detection and another on the detection of pulse wave in peripheral arteries The reliability of beat to beat systolic blood pressure calculation during physical exercise was the main focus for the current paper Sixty-one subjects (healthy and hypertensive) were studied with the bicycle exercise test As a result of current study it is shown that with the correct personal calibration it is possible to estimate the beat to beat systolic arterial blood pressure during the exercise with comparable accuracy to conventional noninvasive methods
73 citations
TL;DR: Treatment performances of ozonation applied for the degradation of nitrophenols (NPs) were assessed in terms of biodegradability improvement, and toxicity reduction in this article.
67 citations
05 Dec 2004
TL;DR: In this article, a new security condition for hash-based time-stamping schemes, called chain-resistance, was proposed and proved to be provably secure, assuming that the underlying hash function is collision-resistant.
Abstract: It is almost a folklore-knowledge that hash-based time-stamping schemes are secure if the underlying hash function is collision-resistant but still no rigorous proofs have been published. We try to establish such proof and conclude that the existing security conditions are improper because they ignore precomputations by adversaries.After analyzing a simplistic patent filing scenario, we suggest a new security condition for time-stamping schemes that leads to a new security property of hash functions – chain-resistance. We observe that if the variety of possible shapes of hash-chains is polynomial (and the verification procedure is suitably improved), then the time-stamping scheme becomes provably secure, assuming that the underlying hash function is collision-resistant. Finally, we show that in some sense, the restrictions in the security definition are necessary – conventional black-box techniques are unable to prove that chain-resistance follows from collision-resistance.
52 citations
23 May 2004
TL;DR: This article describes a novel approach to fault diagnosis suitable for at-speed testing of board-level interconnect faults based on a new parallel test pattern generator and a specifically fault detecting sequence.
Abstract: This article describes a novel approach to fault diagnosis suitable for at-speed testing of board-level interconnect faults.This approach is based on a new parallel test pattern generator and a specifically fault detecting sequence. The test sequence has tree major advantages.At first, it detects both static and dynamic faults upon interconnects. Secondly, it allows precise on-chp at-speed fault diagnosis of interconnect faults.Third, the hardware implementation of both the test generator and the response analyzer is very efficient in terms of silicon area.
TL;DR: In this article, the friction and wear properties of TiC-NiMo/steel rubbing pairs were investigated under dry condition, and the sliding wear tests were carried out on the testing device at a velocity of 2.2 m/s and a load of 40 N. The study has shown that the coefficient of friction was approximately the same for all the samples.
TL;DR: The structure of algebras of wellfounded and non-wellfounded terms is studied for a very general notion of signature permitting both simple variable binding operators as well as operators of explicit substitution.
TL;DR: In this paper, the authors used density functional theory to calculate hydration enthalpy for nine of the 10 fourth-period transition metal cation complexes with 6 and 18 water molecules.
TL;DR: In this paper, a coupled beam method is proposed to estimate elastic response in the longitudinal bending of a passenger ship with a large multi-deck superstructure, which can be applied during an early project stage, when detailed three-dimensional finite element modelling is not yet possible.
TL;DR: In this article, the first gaseous products of 1, between 200 and 240°C, are carbon disulfide (CS2) and ammonia (NH3), and an exothermic oxidation of CS2 vapors occurs resulting in a sudden release of sulphur dioxide (SO2), carbonyl sulphide (COS), and isothiocyanic acid (HNCS).
Abstract: Identification and monitoring of gaseous species released during thermal decomposition of the title compound 1, Zn(tu)2Cl2, (tu=thiourea, (NH2)2C=S) have been carried out in flowing air atmosphere up to 800°C by both online coupled TG-EGA-FTIR and simultaneous TG/DTA-EGA-MS. The first gaseous products of 1, between 200 and 240°C, are carbon disulfide (CS2) and ammonia (NH3). At 240°C, an exothermic oxidation of CS2 vapors occurs resulting in a sudden release of sulphur dioxide (SO2) and carbonyl sulphide (COS). An intense evolution of hydrogen cyanide (HCN) and beginning of the evolution of cyanamide (H2NCN) and isothiocyanic acid (HNCS) are also observed just above 240°C. Probably because of condensation and/or polymerization of cyanamide vapors on the windows and mirrors of the FTIR gas cell optics, some strange baseline shape changes are also occurring above 330°C. Above 500°C the oxidation process of organic residues appears to accelerate which is indicated by the increasing concentration of CO2, while above 600°C zinc sulfide starts to oxidize resulting in the evolution of SO2. All species identified by FTIR gas cell were also confirmed by mass spectrometry, except for HNCS.
TL;DR: In this article, the location and the height of the global maximum of the solution as well as its symmetry properties are established for the case when the maximum amplitude of the interaction pattern exceeds the sum of amplitudes of the interacting solitons.
04 Nov 2004
TL;DR: A semantics for inductive types based on limits of algebra structure forgetting functors and it is shown that it is equivalent to the usual initial algebra semantics.
Abstract: We give a semantic footing to the fold/build syntax of programming with inductive types, covering shortcut deforestation, based on a universal property. Specifically, we give a semantics for inductive types based on limits of algebra structure forgetting functors and show that it is equivalent to the usual initial algebra semantics. We also give a similar semantic account of the augment generalization of build and of the unfold/destroy syntax of coinductive types.
TL;DR: The cloning and characterization of a closely related COX protein (97% amino acid sequence identity) from the S-variety of P. homomalla demonstrates that very minor sequence divergence accounts for the content of epimeric PGs in the two variants of P., and that the differences do not arise by isomerization of the products.
Abstract: It has been known for 30 years that the gorgonian coral Plexaura homomalla contains either 15S- or 15R-configuration prostaglandins (PGs), depending on its location in the Caribbean. Recently we showed that the 15R-PGs in the R-variety of P. homomalla are formed by a unique cyclooxygenase (COX) with 15R oxygenation specificity [Valmsen, K., Jarving, I., Boeglin, W.E., Varvas, K., Koljak, R., Pehk, T., Brash, A.R. & Samel, N. (2001) Proc. Natl. Acad. Sci. USA98, 7700]. Here we describe the cloning and characterization of a closely related COX protein (97% amino acid sequence identity) from the S-variety of P. homomalla. Functional expression of the S-variant COX cDNA in Sf9 insect cells followed by incubation with exogenous arachidonic acid resulted in formation of PG products with > 98% 15S-configuration. Mutational analysis was performed on a suggested active site determinant of C-15 oxygenation specificity, position 349 (Val in all S-specific COX, Ile in 15R-COX). The 15S-COX Val349 to Ile mutant formed 35% 15R-PGs, while the reverse mutation in the 15R-COX (Ile349Val) led to formation of 70% 15S-products. This establishes position 349 as an important determinant of the product stereochemistry at C-15. Our characterization of the enzyme variants demonstrates that very minor sequence divergence accounts for the content of epimeric PGs in the two variants of P. homomalla and that the differences do not arise by isomerization of the products.
TL;DR: In this article, the applicability of high-performance size exclusion chromatography (HPSEC) to characterize lake-sediment pore-water dissolved organic matter (DOM) was demonstrated.
Abstract: This paper demonstrates the applicability of high-performance size exclusion chromatography (HPSEC) to characterize lake-sediment pore-water dissolved organic matter (DOM). Two shallow nonstratified Estonian lakes – Harku and Karujarv – were investigated. The HPSEC results for pore waters were compared with those obtained by spectroscopic methods such as fluorescence spectroscopy and UV-absorption, and with other analyses carried out on sediments (sediment composition, C/N and H/C ratios). The average molecular weight values for UV absorbing DOM were close to pore waters of the studied lakes, not exceeding 5000 for weight- and 3000 for average-number, respectively. Low MW size fractions (<1000) dominated in Lake Harku pore waters, while the opposite was recorded in Lake Karujarv pore waters. Besides the traditional paleolimnological methods, the method used (HPSEC) seems to be promising in detailed sediment pore water characterization.
TL;DR: A setup of turbulence mechanics for averaged description of turbulence, founded on laws of momentum, moment of momentum and energy, complemented by common rheological principles for formulating constitutive relations between generalized forces and generalized velocities of the description is presented.
Abstract: This paper presents a setup of turbulence mechanics for averaged description of turbulence, founded on laws of momentum, moment of momentum, and energy, complemented by common rheological principles for formulating constitutive relations between generalized forces and generalized velocities of the description. A kinematical-geometrical principle is adopted to determine internal rotating degrees of freedom of turbulent media generated by the eddy structure of turbulent flow fields. The connection between the formulated mechanics and some models (as $K\text{\ensuremath{-}}\ensuremath{\epsilon}$ model), widely used in practical engineering flow calculations, is established. As an example, the formulated mechanics is applied to describe some classical flow patterns.
TL;DR: In this article, the concept of a recursive coalgebra of a functor from the perspective of programming semantics is discussed and sufficient conditions for the recursiveness of such a coalgebra are given.
TL;DR: In this paper, the synthesis of dodecylbenzenesulfonate and doped polypyrrole (PPy/DBS) onto polystyrenesulphonate (PSS−) modified gold EQCM electrode was studied.
TL;DR: In this article, the combined thermogravimetric (TG) Fourier transform infrared (FTIR) techniques were used for studying the gaseous compounds evolved at thermooxidation of oil shale samples from different deposits (Estonia, Jordan, Israel).
Abstract: The combined thermogravimetric (TG) Fourier transform infrared (FTIR) techniques were used for studying the gaseous compounds evolved at thermooxidation of oil shale samples from different deposits (Estonia, Jordan, Israel). In addition to H2O and CO2as the major species, the formation and emission of CO, SO2, HCl and a number of organic species as methane, ethane, ethylene, methanol, formic acid, formaldehyde, chlorobenzene, etc. was determined. Differences in the absorbance of respective bands in FTIR spectra depending on the origin of oil shale and on the heating rate used were established.
TL;DR: In this paper, a simple method for the synthesis of enantiopure homocitric acid γ-lactone and its 4-hydroxy analogues starting from spiro-γ-dilactone, in up to 74% isolated yield is described.
TL;DR: In this paper, the authors used electron spin resonance (ESR) and optically-stimulated luminescence (OSL) methods to date the Varzuga section of the Kola Peninsula.
Abstract: The occurrence of sandy clay deposited in a warm marine environment just below the till of the last glaciation has created controversy about its age and stratigraphic position in the sedimentary basin of the Kola Peninsula. Data on marine microfauna, diatoms, malacofauna and pollen composition indicate that during the period when the sandy clay was deposited the climate was similar or even warmer than at present. According to 14C dates, sedimentation of the sandy clay occurred around 40 ka BP. Based on these data, some researchers have attributed these marine deposits to the third Late Pleistocene Belomorian (sensu Lavrova 1960) interglacial transgression. At the same time there are geological indications suggesting re-deposition of these subtill sediments. To solve this problem we have reinvestigated the subtill interglacial marine deposits from the Varzuga section (˜66.4° N and 36.6° E). Four different marine shell species and enclosing sandy clay sediments taken from the subtill marine unit of the section were dated by the electron spin resonance (ESR) and optically-stimulated luminescence (OSL) methods at about 103 and 104 ka, respectively. The results indicate that the subtill marine deposits belong to the first Late Pleistocene Boreal transgression that, according to our previous studies of the marginal areas of the Eurasian North, has occurred in the time interval from approximately 145 to 70 ka BP.
TL;DR: In this article, the authors investigated the basal sediment section from the main crater lake, Kaali jrv, consisting of crushed and in-washed dolomite diamiction.
Abstract: The Kaali meteorite impact crater field, which consists of a 110 m diameter main crater and eight satellite craters on the island of Saaremaa, Estonia is a unique object as its meteoritic origin is well proven, it lies in a densely populated area and fell in the relatively recent past. The precise age of the impact that generated the craters is still disputed. We investigated the basal sediment section from the main crater lake, Kaali jrv, consisting of crushed and in-washed dolomite diamiction. AMS dating of terrestrial macrofossils from these sediment layers places the age of the impact at 1690�1510 B.C. The age is about 1000 years older than revealed from the impact marker-horizon in a contemporaneous peat sequence 6 km northwest of the Kaali crater. The pollen, diatom and chemical data suggest the instant formation of a shallow hard-water lake environment in the main crater depression after the impact, and a rapid post-impact sedimentation of crushed dolomite dust. Archaeological evidence on the crater slopes points to human activity around 700- 200 B.C., indicating that the crater ring wall was inhabited by Bronze Age people soon after the impact event, and the structure of the main crater is mimicked in nearby ar- chaeological sites.
TL;DR: Combining PGs with α-tocopherol or quercetin with low concentrations of iloprost allows the use of prostaglandins at lower concentrations to inhibit platelet aggregation.
Abstract: Prostaglandin (PG) I2 (prostacyclin), PGE1 and their analogues are effective inhibitors of platelet aggregation. However, a clinical use of these compounds for the treatment of cardiovascular diseases is restricted due to unwanted side effects. Alpha-tocopherol and quercetin are weak antiplatelet agents. At the same time, they have mild if any side effects when consumed medicinally. The aim of this work was to study the possibility to decrease the effective antiplatelet concentrations of PGs combining them with alpha-tocopherol or quercetin. Platelet-rich plasma (PRP) was prepared from human blood. The inhibition of adenosine diphosphate-induced platelet aggregation was caused by PGs in the presence and absence of alpha-tocopherol or quercetin and corresponding concentration-effect curves were obtained. At a subthreshold concentration 200 and 2 microM, respectively, both alpha-tocopherol and quercetin essentially increased the antiplatelet effects of PGI2, PGE1 and iloprost. Especially effective was the combination of alpha-tocopherol with low concentrations of iloprost. Thus, combination of PGs with alpha-tocopherol or quercetin allows the use of prostaglandins at lower concentrations to inhibit platelet aggregation.
TL;DR: In this article, it is shown, that different mathematical hysteretic models can describe the dynamic behavior of the hammer felt and that the equivalence of these models is proved for all realistic values of hammer velocity.
Abstract: Experimental testing of piano hammers, which consist of a wood core covered with several layers of compressed wool felt demonstrates, that all hammers have the hysteretic type of the force-compression characteristics. It is shown, that different mathematical hysteretic models can describe the dynamic behavior of the hammer felt. In addition to the four-parameter nonlinear hysteretic felt model, another new three-parameter hysteretic model is presented. Both models are based on the assumption that the hammer felt made of wool is a microstructured material possessing history-dependent properties. The equivalence of these models is proved for all realistic values of hammer velocity.
TL;DR: In this paper, the authors focused on the investigation of the heat transfer augmentation by various turbulator inserts in gas-heated channels and conducted experiments directly in a convective part of a two fire-tube boiler.