Ground-state order and spin-lattice coupling in tetrahedral spin systems Cu2Te2O5X2 (X = Br or Cl)

High-resolution ac susceptibility and thermal conductivity measurement on Cu2Te2O5X2 (X=Br,Cl) single crystals are reported. For Br-sample, sample dependence prevents one from distinguishing between possibilities of magnetically ordered and spin-singlet ground states. In Cl-sample a three-dimensional transition at 18.5 K is accompanied by almost isotropic behavior of susceptibility and almost switching behavior of thermal conductivity. Thermal conductivity studies suggest the presence of a tremendous spin-lattice coupling characterizing Cl- but not Br-sample. Below the transition Cl-sample is in a complex magnetic state involving AF order but also the elements consistent with the presence of a gap in the excitation spectrum.

Metabolism of oral glucose in children born small for gestational age : evidence for an impaired whole body glucose oxidation

Résumé Les études épidémiologiques indiquent que la restriction intra-utérine confère un risque accru de développement de diabète de type 2 au cours de la vie. Certaines études ont documenté la présence d'une résistance à l'insuline chez les jeunes adultes ou les adolescents nés petits pour l'âge gestationnel. Comme la plupart des études ont impliqués des individus post-pubères et comme la puberté influence de manière marquée le métabolisme énergétique, nous avons évalué le devenir du glucose administré oralement dans un groupe incluant essentiellement des enfants pré-pubères ou en début de puberté avec restriction intra-utérine, et chez des enfants matchés pour l'âge et pour le poids. Tous les enfants ont eu une évaluation de leur composition corporelle par mesure des plis cutanés. Ils ont ensuite été étudiés dans des conditions standardisées et ont reçu 4 charges consécutives orales de glucose à raison de 180 mg/kg de poids corporel jusqu'à atteindre un état d'équilibre relatif. La dépense énergétique et l'oxydation des substrats ont été évaluées durant la quatrième heure par calorimétrie indirecte. Comparativement avec les enfants matchés pour l'âge et le poids, les enfants nés petits pour l'âge gestationnel avaient une plus petite stature. Leur dépense énergétique n'était pas significativement abaissée, mais leur oxydation du glucose était plus basse. Ces résultats indiquent que des altérations métaboliques sont présentes précocement chez les enfants nés petits pour l'âge gestationnel, et qu'elles sont possiblement reliées à des altérations de la composition corporelle. Abstract: Epidemiological studies indicate that intrauterine growth restriction confers an increased risk of developing type 2 diabetes mellitus in subsequent life. Several studies have further documented the presence of insulin resistance in young adults or adolescent children born small for gestational age. Since most studies addressed postpubertal individuals, and since puberty markedly affects energy metabolism, we evaluated the disposal of oral glucose in a group including mainly prepubertal and early pubertal children with intrauterine growth restriction and in healthy age- and weight-matched control children. All children had an evaluation of their body composition by skinfold thickness measurements. They were then studied in standardized conditions and received 4 consecutive hourly loads of 180 mg glucose/kg body weight to reach a near steady state. Energy expenditure and substrate oxidation were evaluated during the fourth hour by indirect calorimetry. Compared to both age- and weight-matched children, children born small for gestational age had lower stature. Their energy expenditure was not significantly decreased, but they had lower glucose oxidation rates. These results indicate that metabolic alterations are present early in children born small for gestational age, and are possibly related to alterations of body composition.

The diet of the Alpine mouse Apodemus alpicola in the Swiss Alps

In this study, we used faecal analysis to determine the diet of the alpine mouse Apodemus alpicola in the field for the first time. This species consumes mainly insects in spring and fruits and seeds of small herbaceous dicotyledons in summer and autumn. Compared to the two congeneric species A. flavicollis and A. sylvaticus, which also occur in the Alps, the diet of A. alpicola is rich in contrasts, with a very pronounced difference between spring and summer. The absence of tree seeds also suggests a mostly terrestrial behaviour. We explain these facts by the specificity of the habitat of A. alpicola: the extreme weather conditions produce great seasonal changes in the vegetation, and the rocky ground favours the adaptation to rock climbing rather than to arboreal Living. (c) 2005 Elsevier GmbH. All rights reserved.

Metadifferentiation of iris nevi after iridectomy: a clinicopathological small case series

Abstract Purpose Iridectomy of suspicious pigmented tumors provides the presumed advantage of both a histopathological diagnosis and treatment of the lesion. We present 2 patients that developed an iris melanoma with extrascleral extension at the site of their iridectomy of a histopathologically proven nevus, 46 and 2.5 years later. Methods Retrospective, clinicopathological small case series of 2 patients. Results Two patients underwent iridectomy for a suspicious tumor, the first in 1963 and the second in 2006. Pathological diagnosis was a benign and a borderline nevus respectively. In 2009, both patients presented with a recurrent melanocytic iridociliary tumor with an extrascleral extension adjacent to the surgical scar. Pathological examination confirmed melanoma. Consequently, the two patients underwent proton beam therapy of the whole anterior segment, with limbus deposition and reposition. Conclusion Iridectomy of a histopathologically proven nevus doesn't exclude the possibility of a metadifferentiation of remaining nevus cells into melanoma, even after 46 years. Additionally, treatment in case of a recurrence is more complicated than a primary radiotherapy of the unbiopsied iris tumor, with clinical proof of growth, would have been.

Small proline-rich protein 1A is a gp130 pathway- and stress-inducible cardioprotective protein.

The interleukin-6 cytokines, acting via gp130 receptor pathways, play a pivotal role in the reduction of cardiac injury induced by mechanical stress or ischemia and in promoting subsequent adaptive remodeling of the heart. We have now identified the small proline-rich repeat proteins (SPRR) 1A and 2A as downstream targets of gp130 signaling that are strongly induced in cardiomyocytes responding to biomechanical/ischemic stress. Upregulation of SPRR1A and 2A was markedly reduced in the gp130 cardiomyocyte-restricted knockout mice. In cardiomyocytes, MEK1/2 inhibitors prevented SPRR1A upregulation by gp130 cytokines. Furthermore, binding of NF-IL6 (C/EBPbeta) and c-Jun to the SPRR1A promoter was observed after CT-1 stimulation. Histological analysis revealed that SPRR1A induction after mechanical stress of pressure overload was restricted to myocytes surrounding piecemeal necrotic lesions. A similar expression pattern was found in postinfarcted rat hearts. Both in vitro and in vivo ectopic overexpression of SPRR1A protected cardiomyocytes against ischemic injury. Thus, this study identifies SPRR1A as a novel stress-inducible downstream mediator of gp130 cytokines in cardiomyocytes and documents its cardioprotective effect against ischemic stress.

Domestic architecture and social differences in North-Eastern Iberia during the iron age (c.525-200 BC)

This paper is concerned with the organization of societies in north-eastern Iberia (present-day Catalonia) during the Iron Age, using data provided by domestic architecture and settlement organization. I offer an analysis of the social differences detected in the dwellings based on a sample of houses excavated at different types of settlement. Although many Iberian houses had simple layouts and small surface areas, some larger dwellings at the main sites are distinguished by the shape of their ground plans, their surface areas, architectural features, and central locations; these houses are believed to be the residences of the Iberian elite. Such dwellings are not found at all sites and the data suggest that there was a relationship between the category of the settlement (or its function) and the types of dwelling in it.

Long-term effects of neonatal hypoglycemia on brain growth and psychomotor development in small-for-gestational-age preterm infants.

OBJECTIVE: To investigate the effects of neonatal hypoglycemia on physical growth and neurocognitive function.Study design: A systematic detection of hypoglycemia (<2.6 mmol/L or 47 mg/dL) was carried out in 85 small-for-gestational-age preterm neonates. Prospective serial evaluations of physical growth and psychomotor development were performed. Retrospectively, infants were grouped according to their glycemic status. RESULTS: The incidence of hypoglycemia was 72.9%. Infants with repeated episodes of hypoglycemia had significantly reduced head circumferences and lower scores in specific psychometric tests at 3.5 years of age. Hypoglycemia also caused reduced head circumferences at 18 months and lower psychometric scores at 5 years of age. Infants with moderate recurrent hypoglycemia had lower scores at 3.5 and 5 years of age compared with the group of infants who had 1 single severe hypoglycemic episode. CONCLUSION: Recurrent episodes of hypoglycemia were strongly correlated with persistent neurodevelopmental and physical growth deficits until 5 years of age. Recurrent hypoglycemia also was a more predictable factor for long-term effects than the severity of a single hypoglycemic episode. Therefore repetitive blood glucose monitoring and rapid treatment even for mild hypoglycemia are recommended for small-for-gestational-age infants in the neonatal period.

Etude systématique, cladistique et biogéographique des Baetidae (Ephemeroptera) de Madagascar

Les Ephéméroptères constituent un ordre très archaïque d?insectes ailés, comprenant un nombre réduit d?espèces (actuellement environ 2500 espèces). Les larves sont aquatiques; la durée de ce stade est en général d?une année. Le stade adulte est par contre extrêmement bref: de quelques heures à quelques jours. La fonction quasi unique de ce stade est la reproduction. Par sa superficie, Madagascar est la quatrième île du monde. Elle est située dans la partie occidentale de l?Océan Indien à plus de 300 km de la côte africaine. Madagascar faisait partie du super-continent Gondwana. Elle s?est séparée de l?Afrique (-165 M.a.), puis a migré vers le Sud (-125 M.a.) avant de se détacher du sous-continent indien (-65 M.a.). La connaissance des Ephéméroptères malgaches était, jusqu?à très récemment, extrêmement limitée. Grâce au programme Biodiversité et biotypologie des eaux continentales malgaches, lancé conjointement par l?ORSTOM (actuel IRD, France) et le CNRE (Madagascar), un inventaire à large échelle de la macrofaune benthique malgache a été entrepris. La systématique de plusieurs familles d?Ephéméroptères (Tricorythidae, Polymitarcyidae, Palingeniidae,?), ainsi que d?autres groupes d?invertébrés (Trichoptères, Simuliidae, macrocrustacés) a fait l?objet d?études approfondies. La présente étude consistue un des volets de ce programme. Jusqu?au milieu des années 1990, seules quatre espèces valides appartenant à trois genres différents étaient décrites de Madagascar. En 6 ans, ce ne sont pas moins de 25 articles qui sont consacrés à la systématique des Baetidae, permettant de décrire 50 espèces et 8 genres nouveaux. La faune malgache des Baetidae compte actuellement 22 genres et 54 espèces. Malgré sa taille, Madagascar possède une richesse, tant générique que spécifique équivalente à celle d?un continent. Notre connaissance des Baetidae est suffisamment avancée pour mener une étude cladistique et biogéographique. La reconstruction phylogénétique a permis de mettre en évidence cinq lignées principales à Madagascar et de préciser, pour chacune d?elles, les genres inclus et les caractères propres. La faune des Baetidae malgaches présente un taux d?endémicité très élevé: 53 des 54 espèces et un tiers des genres sont endémiques. Elle montre des affinités extrêmement fortes avec la faune africaine, puisque 90% des genres présents à Madagascar ou en Afrique ont une répartition strictement restreinte à cette région. Les autres composantes, notamment orientales et océaniennes, sont négligeables; ces régions n?ont en commun avec Madagascar qu?un nombre restreint de genres cosmopolites. Ces affinités sont en contradiction avec les données géologiques de la dislocation du Gondwana. Plusieurs explications peuvent être données pour résoudre cette contradiction. La plus vraisemblable est que le pouvoir de dispersion des Ephéméroptères, et des Baetidae en particulier, est nettement sous-estimé. L?étude des faunes des îles volcaniques récentes, telles que les Comores, démontre clairement que les Baetidae sont capables de dispersion sur une distance de plus de 300 km. Il est donc possible d?envisager une colonisation de Madagascar à partir de l?Afrique continentale postérieure à la séparation des deux plaques. Nous avons établi des scénarios retraçant l?histoire biogéographique de chacune des cinq lignées. Pour quatre d?entre elles, l?Afrique continentale est le centre d?origine. La cinquième lignée aurait une origine paléarctique; l?Afrique représenterait un centre secondaire de spéciation. Ces lignées auraient secondairement colonisé Madagascar à partir de l?Afrique continentale. Ce travail ouvre donc d?importantes perspectives. Il rend possible l?utilisation à un niveau générique, voire spécifique, des Baetidae pour des travaux de faunistique ou d?écologie, en particulier pour des études liées à la dégradation de la qualité de l?eau. Il devrait également pouvoir servir de base pour l?étude et la compréhension des phénomènes de dispersion et colonisation dans les îles et archipels de l?Ouest de l?Océan Indien.<br/><br/>Mayflies (Ephemeroptera) are among the oldest known flying insects and encompass a very small number of species (ca 2500 species). Larvae are strictly freshwater inhabitants; this stage lasts generally one year. The imaginal stage is extremely short, from few hours to few days, and is devoted almost entirely to reproduction. Madagascar is the fourth largest island in the world by area. It is situated in the western part of the Indian Ocean, at a distance of more than 300 km from the African coast. Madagascar belonged to Gondwana. It was first separated from the African plate (-165 M.y.), then moved to the South (-65 M.y.), before the break-off with the Indian plate (-65 M.y.). Knowledge of the Malagasy mayflies was until recently extremely poor. The program Biodiversity and Biotypology of Malagasy Freshwaters, jointly run by the French ORSTOM and the Malagasy CNRE, began a global survey of the freshwater macroinvertebrates. The systematics of several mayfly families (Tricorythidae, Polymitarcyidae, Palingeniidae,?), and other invertebrate groups (Caddisflies, Blackflies,?) was the subject of ground studies. Our present study is one part of this global program. Until the middle of the nineties, only four baetid species belonging to three different genera had been described from Madagascar. During the last six years, 25 papers were dedicated to the systematics of the Baetidae, allowing the description of 50 new species and 8 new genera. The Malagasy fauna encompasses now 22 genera and 54 species. Despite its size, Madagascar has the same diversity, at specific and generic level, as a continent. Our knowledge of the Baetidae is sufficient to perform a cladistic and biogeographical study. Our phylogenetic reconstruction allows us to propose five main lineages and to indicate, for each of them, the genera included and their features. The Malagasy fauna of Baetidae possesses a high level of endemicity: 53 of the 54 species and one third of the genera are endemic. It shows extremely strong affinities with the African fauna, as more than 90% of the genera present in Madagascar or in Africa have a distribution restricted to this area. Other components, especially Oriental and Oceanian, are negligible. These areas share with Madagascar only a few widespread genera. These African affinities are in contradiction with the geological events, especially the break-off history of Gondwana. Some explanations can be given to solve this contradiction. The most likely is that the dispersal power of the mayflies, especially of the Baetidae, is greatly underestimated. The study of recent volcanic islands, particularly of the Comoros, clearly demonstrates that the Baetidae are able to disperse over more than 300 km. Consequently, a colonisation by the Baetidae, of Madagascar from the continental Africa, after the break-off must be considered as possible. We have established scenarios explaining the biogeographical history of each of the five lineages. For four of them, Africa has to be regarded as the centre of origin. The fifth lineage probably has a Palearctic origin; Africa should be considered as a secondary centre of speciation. These lineages should have secondarily colonised Madagascar from continental Africa. This work opens up new perspectives. It allows the use of the Baetidae for faunistic and ecological studies, especially for problems related to water quality. It must be also considered as a first step for understanding the dispersion and colonisation of the islands of the western part of the Indian Ocean.

Computational Analysis and Optimization of Real Gas Flow In Small Centrifugal Compressors

Small centrifugal compressors are more and more widely used in many industrialsystems because of their higher efficiency and better off-design performance comparing to piston and scroll compressors as while as higher work coefficient perstage than in axial compressors. Higher efficiency is always the aim of the designer of compressors. In the present work, the influence of four partsof a small centrifugal compressor that compresses heavy molecular weight real gas has been investigated in order to achieve higher efficiency. Two parts concern the impeller: tip clearance and the circumferential position of the splitter blade. The other two parts concern the diffuser: the pinch shape and vane shape. Computational fluid dynamics is applied in this study. The Reynolds averaged Navier-Stokes flow solver Finflo is used. The quasi-steady approach is utilized. Chien's k-e turbulence model is used to model the turbulence. A new practical real gas model is presented in this study. The real gas model is easily generated, accuracy controllable and fairly fast. The numerical results and measurements show good agreement. The influence of tip clearance on the performance of a small compressor is obvious. The pressure ratio and efficiency are decreased as the size of tip clearance is increased, while the total enthalpy rise keeps almost constant. The decrement of the pressure ratio and efficiency is larger at higher mass flow rates and smaller at lower mass flow rates. The flow angles at the inlet and outlet of the impeller are increased as the size of tip clearance is increased. The results of the detailed flow field show that leakingflow is the main reason for the performance drop. The secondary flow region becomes larger as the size of tip clearance is increased and the area of the main flow is compressed. The flow uniformity is then decreased. A detailed study shows that the leaking flow rate is higher near the exit of the impeller than that near the inlet of the impeller. Based on this phenomenon, a new partiallyshrouded impeller is used. The impeller is shrouded near the exit of the impeller. The results show that the flow field near the exit of the impeller is greatly changed by the partially shrouded impeller, and better performance is achievedthan with the unshrouded impeller. The loading distribution on the impeller blade and the flow fields in the impeller is changed by moving the splitter of the impeller in circumferential direction. Moving the splitter slightly to the suction side of the long blade can improve the performance of the compressor. The total enthalpy rise is reduced if only the leading edge of the splitter ismoved to the suction side of the long blade. The performance of the compressor is decreased if the blade is bended from the radius direction at the leading edge of the splitter. The total pressure rise and the enthalpy rise of thecompressor are increased if pinch is used at the diffuser inlet. Among the fivedifferent pinch shape configurations, at design and lower mass flow rates the efficiency of a straight line pinch is the highest, while at higher mass flow rate, the efficiency of a concave pinch is the highest. The sharp corner of the pinch is the main reason for the decrease of efficiency and should be avoided. The variation of the flow angles entering the diffuser in spanwise direction is decreased if pinch is applied. A three-dimensional low solidity twisted vaned diffuser is designed to match the flow angles entering the diffuser. The numerical results show that the pressure recovery in the twisted diffuser is higher than in a conventional low solidity vaned diffuser, which also leads to higher efficiency of the twisted diffuser. Investigation of the detailed flow fields shows that the separation at lower mass flow rate in the twisted diffuser is later than in the conventional low solidity vaned diffuser, which leads to a possible wider flow range of the twisted diffuser.

Introducing Basic Systematic Requirements Engineering Practices in Small Organizations with an Easy to Adopt Method

Requirements-relatedissues have been found the third most important risk factor in software projects and as the biggest reason for software project failures. This is not a surprise since; requirements engineering (RE) practices have been reported deficient inmore than 75% of all; enterprises. A problem analysis on small and low maturitysoftware organizations revealed two; central reasons for not starting process improvement efforts: lack of resources and uncertainty; about process improvementeffort paybacks.; In the constructive part of the study a basic RE method, BaRE, was developed to provide an; easy to adopt way to introduce basic systematic RE practices in small and low maturity; organizations. Based on diffusion of innovations literature, thirteen desirable characteristics; were identified for the solution and the method was implemented in five key components:; requirements document template, requirements development practices, requirements; management practices, tool support for requirements management, and training.; The empirical evaluation of the BaRE method was conducted in three industrial case studies. In; this evaluation, two companies established a completely new RE infrastructure following the; suggested practices while the third company conducted continued requirements document; template development based on the provided template and used it extensively in practice. The; real benefits of the adoption of the method were visible in the companies in four to six months; from the start of the evaluation project, and the two small companies in the project completed; their improvement efforts with an input equal to about one person month. The collected dataon; the case studies indicates that the companies implemented new practices with little adaptations; and little effort. Thus it can be concluded that the constructed BaRE method is indeed easy to; adopt and it can help introduce basic systematic RE practices in small organizations.

Essays on Innovativeness and its Evaluation in Small and Medium-sized Enterprises

Tutkimus koostuu neljästä artikkelista, jotka käsittelevät suomalaisten pienten ja keskisuurten teollisuusyritysten (PKT-yritysten) innovatiivisuutta, sen attribuutteja (ominaispiirteitä) sekä indikaattoreita. Tutkimuksessa tarkastellaan sekä kirjallisuudessa esitettyjä että PKT-johtajien ja PKT-yritystenkehityshankkeiden rahoituspäätöksiin osallistuvien yritystutkijoiden haastatteluissa esittämiä innovatiivisuuden määritelmiä. Innovatiivisuusindikaattoreista tarkastellaan PKT-yritysten kehittämishankkeille sovellettavia rahoitus- ja arviointikriteerejä sekä yritysten ulkopuolisten rahoittajien että PKT-johtajien näkökulmasta. Erityistä huomiota kohdistetaan sovellettuihin laadullisiin ja ei-numeerisiin innovatiivisuuden arviointikriteereihin. Sekä kirjallisuudessa että kymmenen yritystutkijan ja kuuden esimerkkiyrityksen johtajan haastatteluissa innovaation uutuus yhdistetään innovatiivisuuteen. Muita tärkeitä innovatiivisuuteen liitettyjä ominaisuuksia olivat markkinat, muista yrityksistä erottuminen ja yksilöiden luovuus. Ihmisläheiset ja yksilöihin liittyvät näkökulmat korostuvat yritystutkijoiden ja PKT-johtajien innovatiivisuuden määritelmissä, kun taas kirjallisuudessa annetaan enemmän painoa ympäristölle, tuotteille ja markkinoille. Yritystutkijat pitivät yritykseen ja sen johtajaan liittyviä tekijöitä tärkeinä rahoitettavien kehittämishankkeiden panosten arviointikriteereinä. Tuotteiden kaupallinen menestys oli rahoittajan kannalta tärkein tulostekijä. Tarkastelluissa esimerkkiyrityksissä kehityshankkeista päättäminen ja hankkeiden arviointi on toisaalta intuitiivista ja saattaa olla tiedostamatontakin, koska yritysten kehittämistoiminta on vähäistä. Pienyritysten johtajat korostavat arvioinnissa rahallisiamittareita, vaikka sekä numeerisia että laadullisia kriteereitä sovelletaan. Todennäköisin syy tälle on pienyritysten rajalliset taloudelliset voimavarat. Toinen mahdollinen syy rahoituksellisten tekijöiden painottamiseen on, että tämän päivän ihannejohtaja ymmärretään analyyttiseksi ja mm.rahavirtoja valvovaksi. Kuitenkin innovatiiviset yritysjohtajat pitävät innovaatioiden luomista yhtenä elämän hauskoista puolista. Innovatiiviset esimerkkiyritykset ovat tulevaisuuteen ja kasvuun suuntautuneita strategisella tasolla. Operationaalisella tasolla ne tuottavat keksintöjä ja innovaatioita. Patentteja tarkastelluilla yrityksillä on kuitenkin vähän. Sekä innovatiiviset että vähemmän innovatiiviset esimerkkiyritykset ovat voimakkaasti asiakassuuntautuneita ja erikoistuneita tiettyihin tuotteisiin ja asiakkaisiin. Asiakkaiden tarpeita tyydytetään kehittämällä niitä vastaavia tuotteita. Tästä johtuu, että valtaosa yritysten kehittämistoiminnasta kohdistuu tuotteisiin tai tuotantoon.

Dynamic Model of a Small Once-Through Boiler

In this study, a model for the unsteady dynamic behaviour of a once-through counter flow boiler that uses an organic working fluid is presented. The boiler is a compact waste-heat boiler without a furnace and it has a preheater, a vaporiser and a superheater. The relative lengths of the boiler parts vary with the operating conditions since they are all parts of a single tube. The present research is a part of a study on the unsteady dynamics of an organic Rankine cycle power plant and it will be a part of a dynamic process model. The boiler model is presented using a selected example case that uses toluene as the process fluid and flue gas from natural gas combustion as the heat source. The dynamic behaviour of the boiler means transition from the steady initial state towards another steady state that corresponds to the changed process conditions. The solution method chosen was to find such a pressure of the process fluid that the mass of the process fluid in the boiler equals the mass calculated using the mass flows into and out of the boiler during a time step, using the finite difference method. A special method of fast calculation of the thermal properties has been used, because most of the calculation time is spent in calculating the fluid properties. The boiler was divided into elements. The values of the thermodynamic properties and mass flows were calculated in the nodes that connect the elements. Dynamic behaviour was limited to the process fluid and tube wall, and the heat source was regarded as to be steady. The elements that connect the preheater to thevaporiser and the vaporiser to the superheater were treated in a special way that takes into account a flexible change from one part to the other. The model consists of the calculation of the steady state initial distribution of the variables in the nodes, and the calculation of these nodal values in a dynamic state. The initial state of the boiler was received from a steady process model that isnot a part of the boiler model. The known boundary values that may vary during the dynamic calculation were the inlet temperature and mass flow rates of both the heat source and the process fluid. A brief examination of the oscillation around a steady state, the so-called Ledinegg instability, was done. This examination showed that the pressure drop in the boiler is a third degree polynomial of the mass flow rate, and the stability criterion is a second degree polynomial of the enthalpy change in the preheater. The numerical examination showed that oscillations did not exist in the example case. The dynamic boiler model was analysed for linear and step changes of the entering fluid temperatures and flow rates.The problem for verifying the correctness of the achieved results was that there was no possibility o compare them with measurements. This is why the only way was to determine whether the obtained results were intuitively reasonable and the results changed logically when the boundary conditions were changed. The numerical stability was checked in a test run in which there was no change in input values. The differences compared with the initial values were so small that the effects of numerical oscillations were negligible. The heat source side tests showed that the model gives results that are logical in the directions of the changes, and the order of magnitude of the timescale of changes is also as expected. The results of the tests on the process fluid side showed that the model gives reasonable results both on the temperature changes that cause small alterations in the process state and on mass flow rate changes causing very great alterations. The test runs showed that the dynamic model has no problems in calculating cases in which temperature of the entering heat source suddenly goes below that of the tube wall or the process fluid.

Analysis of the voltage source inverter with small DC-link capacitor

IIn electric drives, frequency converters are used to generatefor the electric motor the AC voltage with variable frequency and amplitude. When considering the annual sale of drives in values of money and units sold, the use of low-performance drives appears to be in predominant. These drives have tobe very cost effective to manufacture and use, while they are also expected to fulfill the harmonic distortion standards. One of the objectives has also been to extend the lifetime of the frequency converter. In a traditional frequency converter, a relatively large electrolytic DC-link capacitor is used. Electrolytic capacitors are large, heavy and rather expensive components. In many cases, the lifetime of the electrolytic capacitor is the main factor limiting the lifetime of the frequency converter. To overcome the problem, the electrolytic capacitor is replaced with a metallized polypropylene film capacitor (MPPF). The MPPF has improved properties when compared to the electrolytic capacitor. By replacing the electrolytic capacitor with a film capacitor the energy storage of the DC-linkwill be decreased. Thus, the instantaneous power supplied to the motor correlates with the instantaneous power taken from the network. This yields a continuousDC-link current fed by the diode rectifier bridge. As a consequence, the line current harmonics clearly decrease. Because of the decreased energy storage, the DC-link voltage fluctuates. This sets additional conditions to the controllers of the frequency converter to compensate the fluctuation from the supplied motor phase voltages. In this work three-phase and single-phase frequency converters with small DC-link capacitor are analyzed. The evaluation is obtained with simulations and laboratory measurements.