974 resultados para LC-ESI-LTQ-Orbitrap
Resumo:
Liquid chromatography is often used for the determination of pesticide multiresidues in foods. In Brazil, the strawberry crop is an example of a food with high levels of irregularities because of the application of pesticides. This is a major concern from the perspective of food safety, environmental protection, and certification for food export. The purpose of this study is to evaluate and compare chromatographic separation and detection methods in relation to a newly developed and validated method using ultra high performance liquid chromatography (LC) coupled with tandem mass spectrometry (MS/MS) for the analytical determination of pesticides in strawberries. The comparisons were based on evaluations of the analysis time, consumption of the solvent in the mobile phase, injection volume, detectability, matrix effect, and recovery. The results showed that the LC–MS/MS and UHPLC–MS/MS techniques were both extremely efficient at analyzing pesticide residues with different physico-chemical parameters that were present at low concentrations in a complex matrix. The UHPLC separation method provided better chromatographic performance and productivity, which contributed favorably to routine analytical determinations. Detection by MS/MS had better detectability and selectivity compared with the diode array detector.
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Drug trafficking and the introduction of new drugs onto the illicit market are one of the main challenges of the forensic community. In this study, the chemical profile of a new designer drug, 2-(4-iodine-2,5-dimethoxyphenyl)-n-[(2-methoxyphenyl)methyl]etamine or 25I-NBOMe was explored using thin layer chromatography (TLC), ultraviolet-visible spectrophotometry (UV-Vis), attenuated total reflection with Fourier transform infrared spectroscopy(ATR-FTIR), gas chromatography mass spectrometry (GC-MS) and electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FT-ICR MS). First, the TLC technique was effective for identifying spots related to 25C-, 25B- and 25I-NBOMe compounds, all with the same retention factor, Rf ≈ 0.50. No spot was detected for 2,5-dimethoxy-4-bromoamphetamine, 2,5-Dimethoxy-4-chloroamphetamine or lysergic acid diethylamide compounds. ATR-FTIR preserved the physical-chemical properties of the material, whereas GC-MS and ESI-MS showed better analytical selectivity. ESI(+)FT-ICR MS was used to identify the exact mass (m/z428.1706 for the [M + H]+ ion), molecular formula (M = C18H22INO3), degree of unsaturation (DBE = 8) and the chemical structure (from collision induced dissociation, CID, experiments) of the 25I-NBOMe compound. Furthermore, the ATR-FTIR and CID results suggested the presence of isomers, where a second structure is proposed as an isomer of the 25I-NBOMe molecule.
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Tämän kandidaatintyön tarkoituksena on tarkastella toimintolaskennan käyttöä ulkomaalaisten yli-opistojen hallinnossa. Työ painottuu Iso-Britannian yliopistojen toimintolaskentaan, mutta esimerk-kejä toimintolaskennan käytöstä yliopistoissa on otettu myös Espanjasta, Yhdysvalloista, Australi-asta ja Malesiasta. Eri maiden toimintolaskennan käytössä on maakohtaisia ominaispiirteitä, ja esi-merkiksi Iso-Britanniassa on kehitetty yliopistoille soveltuva toimintolaskennan sovellus TRAC. Toimintolaskentaa on käytetty ulkomaalaisissa yliopistoissa jo kauan, ja sen avulla on saavutettu useita etuja. Toimintolaskennan käyttöönoton myötä esimerkiksi yliopistojen kustannustietoisuus on lisääntynyt ja päätöksenteko helpottunut. Yliopistojen lisäksi toimintolaskentaa käytetään kus-tannuslaskentamenetelmänä muissa julkisissa organisaatioissa. Esimerkiksi Suomessa toimintolas-kentaa käytetään muun muassa Ilmatieteen laitoksella, Kansaneläkelaitoksella ja Kehitysvammalii-tossa. Uudistuneen yliopistolain aiheuttamien rahoituspaineiden seurauksena myös suomalaisten yliopis-tojen on kiinnitettävä yhä enemmän huomiota kustannustensa johtamiseen. Tämän kandidaatintyön tuloksena tarkastellaan toimintolaskennan soveltuvuutta Lappeenrannan teknillisen yliopiston kus-tannusten laskentamenetelmäksi. Tarkastelun perustana voidaan pitää sekä ulkomaalaisia yliopistoja että suomalaisia julkisia organisaatioita, jotka ovat käyttäneet toimintolaskentaa onnistuneesti.
Resumo:
Suomessa sähkönjakeluverkko koostuu pääasiassa 20 kV ja 400 V jännitetasoista. Tällöin sähkö viedään lähelle kuluttajia suuremmalla jännitetasolla ja muunnetaan alhaisemmaksi lähellä asiakkaita. Haittapuolena on se, että haja-asutusalueilla jakelumuuntajien määrä kasvaa suureksi, koska ne täytyy sijoittaa lähelle kuluttajaa. Vaihtoehtona on toteuttaa osa sähkönjakelusta tasajännitteellä, jolloin tehollinen jännite olisi suurempi. Tällöin sähköä voitaisiin siirtää pidempiä matkoja ilman, että asiakaskohtaisia tai muutaman asiakkaan kattavia 20 kV siirtolinjoja tarvitsisi käyttää. Tämä taasen edellyttää asiakaskohtaisien vaihtosuuntaajien käyttöä. Tässä työssä esiteltävällä 1 kVA vaihtosuuntaajalla muodostetaan tasasähköjakeluverkosta saatavasta 750 V tasasähköstä yksivaiheista (230 VRMS, 50 Hz) verkkojännitettä. Laite on suunniteltu toteuttamaan galvaaninen erotus mahdollisimman hyvän hyötysuhteen puitteissa. Vaihtosuuntaaja on toteutettu käyttämällä resonanssikonvertteria, joka vaihtosuuntaa jakelujännitteen korkeataajuiseksi vaihtojännitteeksi. Tämän jälkeen toteutetaan galvaaninen erotus käyttäen suurtaajuusmuuntajaa. Tätä seuraa syklokonvertteri, joka pulssintiheysmodulaatiota soveltaen muodostaa lähtöjännitteen. Tämä suodatetaan lopuksi LC- alipäästösuotimella säröltään standardin mukaiseksi. Laite on jaettu työssä kolmeen osaan, joista jokaisen toiminta on selitetty ja simuloitu itsenäisesti. Lopussa koko järjestelmä on simuloitu yhtenä kokonaisuutena. Hyötysuhteeksi arvioitiin karkeasti 94 % ja lopullisista tuloksista voidaan päätellä, että laitteen toteuttaminen prototyypiksi voisi olla kannattavaa.
Resumo:
The aim of the thesis is to investigate the hybrid LC filter behavior in modern power drives; to analyze the influence of such a du/dt filter on the control system stability. With the implementation of the inverter output RLC filter the motor control becomes more complicated. And during the design process the influence of the filter on the motor should be considered and the filter RLC parameters should be constrained.
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In recent years, the network vulnerability to natural hazards has been noticed. Moreover, operating on the limits of the network transmission capabilities have resulted in major outages during the past decade. One of the reasons for operating on these limits is that the network has become outdated. Therefore, new technical solutions are studied that could provide more reliable and more energy efficient power distributionand also a better profitability for the network owner. It is the development and price of power electronics that have made the DC distribution an attractive alternative again. In this doctoral thesis, one type of a low-voltage DC distribution system is investigated. Morespecifically, it is studied which current technological solutions, used at the customer-end, could provide better power quality for the customer when compared with the current system. To study the effect of a DC network on the customer-end power quality, a bipolar DC network model is derived. The model can also be used to identify the supply parameters when the V/kW ratio is approximately known. Although the model provides knowledge of the average behavior, it is shown that the instantaneous DC voltage ripple should be limited. The guidelines to choose an appropriate capacitance value for the capacitor located at the input DC terminals of the customer-end are given. Also the structure of the customer-end is considered. A comparison between the most common solutions is made based on their cost, energy efficiency, and reliability. In the comparison, special attention is paid to the passive filtering solutions since the filter is considered a crucial element when the lifetime expenses are determined. It is found out that the filter topology most commonly used today, namely the LC filter, does not provide economical advantage over the hybrid filter structure. Finally, some of the typical control system solutions are introduced and their shortcomings are presented. As a solution to the customer-end voltage regulation problem, an observer-based control scheme is proposed. It is shown how different control system structures affect the performance. The performance meeting the requirements is achieved by using only one output measurement, when operating in a rigid network. Similar performance can be achieved in a weak grid by DC voltage measurement. An additional improvement can be achieved when an adaptive gain scheduling-based control is introduced. As a conclusion, the final power quality is determined by a sum of various factors, and the thesis provides the guidelines for designing the system that improves the power quality experienced by the customer.
Resumo:
Utgångspunkten för avhandlingen är finländska konstnärsresor till Spanien under 1800-talet, och kontakterna med spansk konst och kultur. Endast ett fåtal finländare reste till Spanien, och inledningsvis utrycktes intresset för spansk konst i form av kopior efter gamla mästare, utförda både efter original utanför Spanien, och reproduktioner. Denna föga imponerande start efterföljdes av ett litet antal målare som verkligen reste till Spanien under 1800-talets senare hälft: Adolf von Becker (1831–1909), Albert Edelfelt (1854–1905) och Venny Soldan (1863–1945). Jag undersöker hur deras syn på landet manifesterades i deras resebilder i förhållande till den växande turistindustrin. Syftet med avhandlingen är att visa hur den resande målaren, likt en turist, föreställde sig, upplevde och tolkade den främmande kulturen, och hur detta avbildades och uttrycktes i deras resebilder. Vid sidan av ikonografisk analys och stilkritik utnyttjas forskningsmetoder från turismteorin. Resultatet av undersökningen visar att de flesta konstnärerna dyrkade konsten på Prado-museet, beundrade flamenco, Andalusiens vackra kvinnor, tjurfäktningar och zigenarna. De längtade efter en förgången och exotisk tid, samtidigt som de följde de vältrampade turiststigarna och hänfördes av de sedvanliga sevärdheterna; de reste i ett delvis mytiskt och delvis verkligt land. Likt turister (i allmänhet), såg de det de ville se, och sökte sig till på förhand inpräntade mentala (före)bilder. Resebilderna kan med fog tolkas som medvetet konstruerade minnen från resan, souvenirs d’Espagne. Samtidigt förstärkte och upprätthöll valen av motiv uppfattningen att Spaniens äldre konst och samtida kultur var mer ”äkta” (autentiska) än den kultur man själv tillhörde. Spanien uppfattades som en kvarleva från en förgången tid som hölls levande i nuet
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O fungo Cylindrocladium spathiphylli causa podridão no colo e nas raízes de espatifilo, induzindo amarelecimento e murcha nas folhas da parte aérea. Há poucos estudos com o fungo quanto às enzimas extracelulares. Assim, delineou-se ensaio inteiramente casualizado in vitro, com três tratamentos (dois isolados normais: LFEEI016 - EPAGRI/SC e MMBF 01/01 - IB/SP; mais testemunha) e seis repetições, visando a detecção de enzimas. A amilase (AM), lipase (LP), carboximetilcelulase (CMC) e lacase (LC) foram mensuradas pelo cálculo da área da coroa circular, local de atividade das enzimas. A catalase (CT) e gelatinase (GL) foram mensuradas por símbolos, depois transformados em notas (1 a 4, de ausência à intensa produção). O isolado MMBF 01/01 produziu as maiores áreas e com mais intensidade as enzimas. Das enzimas, a maior área foi a da LC e depois a LP. LFEEI016 e MMBF 01/01 não apresentaram área para AM e CMC e exibiram intensidade fraca e igual para CT. A intensidade de GT foi moderada no MMBF 01/01 (nota média 3,0) e ausente para o LFEEI016 (nota média 1,0). Após a produção das enzimas extracelulares, os isolados foram alterados vegetativamente por temperatura. Instalou-se ensaio inteiramente ao acaso, em fatorial contendo disco de micélio dos isolados do fungo versus três temperaturas [23ºC (T1); 33ºC (T2) e de 33ºC para 23ºC (T3)] versus quatro períodos (3; 6; 9 e 12 dias), com oito repetições, em placa de Petri com BDA mantida em BOD. O diâmetro das colônias foi medido diariamente (mm) em dois sentidos. As alterações de temperatura vistas foram: inócuo, fungistático (FS) e fungicida (FC). Aplicou-se estatística nas temperaturas T1 e T3 dos isolados para checar efeito FS e escolher aqueles com maior e menor efeito. O isolado LFEEIO16 mostrou efeito FS com três dias às temperaturas 33ºC e de 33ºC para 23ºC. Nos demais períodos, o isolado sofreu efeito FC. O MMBF 01/01 mostrou efeito FS em todos os períodos. Ambos isolados sofreram, estatisticamente, efeito FS. O MMBF 01/01 mostrou maior efeito FS aos nove dias, nas temperaturas referidas e menor com três dias. Após a constatação de alteração na taxa de crescimento micelial dos isolados, procurou-se verificar, novamente, a produção de enzimas extracelulares. Os isolados alterados e utilizados foram o MMBF 01/01 com três e nove dias e o LFEEIO16 com três dias. A produção e a avaliação das enzimas foram realizadas da mesma maneira para os isolados normais. O isolado MMBF 01/01 - três dias produziu as maiores áreas e com mais intensidade as enzimas. Das enzimas, a maior área foi a da LC. Após LC, a área da LP foi maior que a da CMC nos isolados. Não se detectou área de AM nos isolados. A intensidade de GL foi maior que a da CT nos isolados MMBF 01/01 com três e nove dias. Para LFEEI016 - três dias, a intensidade média de CT foi nota 2,0 e ausência de GL (nota média 1,3). Sugere-se investigar a severidade da doença na planta entre os isolados e em condições naturais investigar a evolução da LC em comparação as demais enzimas na patogênese do fungo na cultura.
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Paineilmaa on kutsuttu neljänneksi perushyödykkeeksi veden, sähkön ja kaasun lisäksi. Paineilman kuluttaja on usein myös sen tuottaja. EU:n alueen teollisuudessa keskimää-rin 16 % kulutetusta kokonaissähkötehosta kuluu ilmakompressoreiden käyttöön. Taa-juusmuuttajan käyttö on viime vuosikymmeninä lisääntynyt merkittävästi, kun on pyrit-ty energiatehokkaisiin ratkaisuihin esimerkiksi pumppaus- ja puhallinjärjestelmissä. Kompressorijärjestelmissä taajuusmuuttajien käyttö ei ole vielä yhtä yleistä kuin esi-merkiksi pumppukäytöissä, vaikka taajuusmuuttajan käytöllä saavutetaan useimmissa tapauksissa huomattavia etuja. Tässä työssä tutkitaan taajuusmuuttajan hyödyntämismahdollisuuksia kompressorijär-jestelmien käytönaikaisten elinkaarikustannusten optimoimisessa. Työssä selvitetään säästöpotentiaalia, ja pohditaan pyörimisnopeussäädöllä saavutettavia etuja eri komp-ressorityypeillä. Lopuksi muodostetaan elinkaarikustannusanalyysit kahdelle todelliselle teollisuuden kompressorikohteelle. Tutkimusmenetelminä ovat kirjallisuustyö sekä asi-antuntijahaastattelut teollisuudesta. Työn tavoitteena on kartoittaa taajuusmuuttajan hyödyntämispotentiaalia kompressorijärjestelmissä ja luoda pohjaa mahdolliselle jatko-tutkimukselle.
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This study aimed at quantifying total organic carbon stocks and its pools in Acrisol under agroforestry systems with six (AFS6) and thirteen years old (AFS13), slash-and-burn agriculture (SBA) and savanna native forest (SNF) in northeastern Brazil. Soil samples were collected at 0-0.05 m, 0.05-0.10 m, 0.10-0.20 m and 0.20-0.40 m depths in the dry and rainy seasons to evaluate total organic carbon (TOC) stocks and labile carbon (LC), fulvic acid fraction (C-FAF), humic acid fraction (C-HAF), humin (C-HF) and microbial biomass carbon (Cmic) contents. Additionally, carbon management index (CMI) was determined. Higher TOC stocks (97.7 and 81.8 Mg ha-1 for the 0-0.40 m depth in the dry and rainy seasons, respectively) and LC, humic substances and Cmic contents were observed in the AFS13 in all the depths. CMI also was higher in the AFS13 (0-0. 05 m: 158 and 86; 0.05-0.10 m: 171 and 67, respectively for the dry and rainy seasons) especially when compared to the SBA (0-0.05 m: 5.6 and 5.4; 0.05-0.10 m: 5.3 and 5.8, respectively for dry and rainy seasons). The agroforestry systems increased soil quality through the conservation of organic matter and can be considered an excellent strategy to assurance sustainability in tropical soil of Northeastern Brazil
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The aim of this study was to identify, by multivariate statistical technique, the physic, chemical and biological variables that best characterize the quality of surface waters in two small rural catchments with different land uses (eucalyptus silviculture (SC) vs. pasture and extensive livestock (LC)) located in Rosário do Sul, RS - Brazil. Monitoring was conducted during the months of August 2011 to August 2012 and the following parameters were analyzed: Ca2+, Mg2+, K+, SO42-, Cl-, pH, electrical conductivity, turbidity, alkalinity, suspended and dissolved solids, biochemical oxygen demand , total coliforms, Escherichia coli and temperature, flow and rainfall. Through the use of FA/PCA, it was found that the model best fit to express water quality of in LC that was composed of five factors which account for 83.5% of the total variance, while for SC, four factors accounted for 85.12% of the variance. In LC, the five main factors were, respectively, soluble salts, diffuse pollution, solid, and both anthropogenic and organic factors. In SC, the four factors were namely: soluble salts, mineral, nutritional and diffuse pollution factors. The results of this study showed that by replacing the traditional soil usage (pasture and livestock) with planted forest, diffuse pollution was attenuated but, however, it did not result in major changes in the physical-chemical and biological characteristics of the water. Another point to note is that factorial analysis did not result in a large reduction in the number of variables, once the best model fit occurred with the addition of 15 of 18 analyzed variables (LC) and 17 of 18 analyzed variables (SC).
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Os solos submetidos a sistemas de produção que não incluem o preparo do solo, estão condicionados, em sua sustentabilidade, a um manejo que priorize o acompanhamento da compactação que o tráfego de máquinas provoca. Foram realizados ensaios de campo com o objetivo de avaliar a reologia de um solo Typic Hapludert, submetido ao tráfego de veículos em dois sistemas de preparo do solo (preparo convencional - LC, e semeadura direta - SD). Os subtratamentos foram quatro intensidades de tráfego (0; 80; 160 e 240 Mg km ha-1). As variáveis experimentais dependentes foram: índice de cone (IC) e densidade aparente a seco (DA). Para 160 e 240 Mg km ha-1, encontraram-se diferenças estatísticas significativas no IC em relação à testemunha. Para o LC, com as maiores intensidades de tráfego, encontraram-se valores de DA superiores a 1,83 Mg m-3. O comportamento mecânico do solo sob tráfego é mais diferente em SD que em LC. Existe uma relação direta entre o número de passadas e a profundidade onde se localiza a camada de maior resistência à penetração nos solos sob tratamento com LC.
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Hawthorn (Crataegus sp.) is widely distributed in the northern hemisphere (Asia, Europe and North America). It has been used as a medicinal material and food for hundreds of years both in Europe and in China. Clinical investigations and other research suggest that extracts of hawthorn fruits and leaves have multiple health effects including hypolipidaemic, anti-atherosclerotic, hypotensive, cardioprotective and blood vessel relaxing activities. Hawthorn fruit extracts have also displayed antioxidant and radical scavenging activities. Emblic leafflower fruit (Phyllanthus emblica) is widely used in Chinese and Indian traditional medicine. It has been found to have anti-cancer, hypoglycaemic and hypolipidaemic activities as well as cardioprotective effects and antioxidant activity. The fruit is currently used as a functional food targeted at obese people in China. Phenolic compounds, procyanidins (PCs), flavonols and C-glycosyl flavones in hawthorn and hydrolysable tannins in emblic leafflower fruits are considered among the major bioactive compounds in these berries. Moreover, hawthorn and emblic leafflower fruits are rich in vitamin C, triterpenoids, fruit acids, sugar alcohols and some other components with beneficial effects on the health of human beings. The aim of the thesis work was to characterise the major phenolic compounds in hawthorn fruits and leaves and emblic leafflower fruits as well as other components contributing to the nutritional profile and sensory properties of hawthorn fruits. Differences in the content and compositional profile of the major phenolic compounds, sugars, acids and sugar alcohols within various origins and species of hawthorn were also investigated. Acids, sugars and sugar alcohols in the fruits of different origins/cultivars belonging to three species (C. pinnatifida, C. brettschneideri and C. scabrifolia) of hawthorn were analysed by gas chromatography (GC-FID) and mass spectrometry (Publication I). Citric acid, quinic acid, malic acid, fructose, glucose, sorbitol and myo-inositol were found in all the subspecies. Sucrose was present only in C. scabrifolia and three cultivars of C. pinnatifida var. major. Forty-two phenolic compounds were identified/tentatively identified in fruits of C. pinnatifida var. major by polyamide column chromatography combined with high-performance liquid chromatograph-electrospray ionisation mass spectrometry (HPLC-ESI-MS) (Publication II). Ideain, chlorogenic acid, procyanidin (PC) B2, (-)-epicatechin, hyperoside and isoquercitrin were the major phenolic components identified. In addition, 35 phenolic compounds were tentatively identified based on UV and mass spectra. Eleven major phenolic compounds (hyperoside, isoquercitrin, chlorogenic acid, ideain, (-)-epicatechin, two PC dimers, three PC trimers and a PC dimer-hexoside) were quantified in the fruits of 22 cultivars/origins of three species of Chinese hawthorn by HPLC-ESI-MS with single ion recording function (SIR) (Publication III). The fruits of the hawthorn cultivars/origins investigated fell into two groups, one rich in sugars and flavonols, the other rich in acids and procyanidins. Based on the compositional features, different biological activities and sensory properties may be expected between cultivars/origins of the two groups. The results suggest that the contents of phenolic compounds, acids, sugars and sugar alcohols may be used as chemotaxonomic information distinguishing the hawthorn species from each other. Phenolic compounds in fruits and leaves of C. grayana and their changes during fruit ripening/harvesting were investigated using HPLC-UV-ESI-MS (Publication IV). (-)-Epicatechin, PC B2 and C1, hyperoside and a quercetin-pentoside were the major phenolic compounds in both fruits and leaves. Three C-glycosyl flavones (a luteolin-C-hexoside, a methyl luteolin-C-hexoside and an apigenin-C-hexoside) were present in leaves in abundance, but only at trace levels in fruits. Ideain and 5-O-caffeoylquinic acid were found in fruits only. Additionally, eleven phenolic compounds were identified/tentatively identified in both leaves and fruits (three B-type PC trimers, two B-type PC tetramers, a quercetin-rhamnosylhexoside, a quercetin-pentoside, a methoxykaempferol-methylpentosylhexoside, a quercetin-hexoside acetate, a methoxykaempferol-pentoside, chlorogenic acid and an unknown hydroxycinnamic acid derivative). The total content of phenolic compounds reached the highest level by the end of August in fruits and by the end of September in leaves. The compositional profiles of phenolic compounds in fruits and leaves of C. grayana were different from those of C. pinnatifida, C. brettschneideri, C. scabrifolia, C. pinnatifida. var. major, C. monogyna, C. laevigata and C. pentagyna. Phenolic compounds in emblic leafflower fruits were characterised by Sephadex LH-20 column chromatography combined with HPLC-ESI-MS (Publication V). A mucic acid gallate, three isomers of mucic acid lactone gallate, a galloylglucose, gallic acid, a digalloylglucose, putranjivain A, a galloyl-HHDP-glucose, elaeocarpusin and chebulagic acid represented the major phenolic compounds in fruits of emblic leafflower. In conclusion, results of this study significantly increase the current knowledge on the key bioactive and nutritional components of hawthorn and emblic leafflower fruits. These results provide important information for research on the mechanism responsible for the health benefits of these fruits.
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Upseerien virkaura on pidentynyt viidestä seitsemään vuodella valtion eläkelakiin vuoden 1995 alusta voimaantulleiden muutosten johdosta. Muutosten vaikutuksia on edelleen voimistanut eläkkeitä leikkaavan elinaikakertoimen käyttöönotto. Tutkimuksen tavoitteeksi asetettiin kuvata ajalli-sesti upseerien virkauran muuttumista vuosina 1981–2010. Tutkimus sai alkunsa Upseeriliiton esi-tyksestä, ja se tehtiin ensisijaisesti puolustusvoimien sekä sidosryhmien käyttöön. Opinnäyte on empiirinen tutkimus, jossa vertailtiin tilastollisin menetelmin eri vuosina valmistu-neiden kadettikurssien palvelusuria. Tutkimuksen viitekehyksen teoreettisen perustan muodostavat ympäröivissä järjestelmissä tapahtuneet muutokset tarkasteltavalla ajanjaksolla. Virkauran tiedettiin muuttuneen 1990- ja 2000-luvuilla tapahtuneiden eläkeiän nousun, koulutusjärjestelmäuudistusten ja puolustusvoimien rakennemuutosten myötä. Tutkimuksen perusjoukkona ovat puolustusvoimissa vuosina 1981–2010 palvelleet upseerit. Perusjoukosta vertailtiin viittä tänä aikana valmistunutta kadettikurssia. Tutkimusasetelmalla pyrittiin löytämään selkeästi mitattavia ja vertailtavia eroja. Tutkimuksella selvitettiin, miten kurssien palvelusurat eroavat toisistaan ja miten tulokset suhteutu-vat teoriana käsiteltyihin muutoksiin. Tutkimuksen empiirisen aineiston muodosti Puolustusvoimi-en palkattua henkilöstöä koskeva rekisteritieto. Viitekehyksessä esitetyt muutokset ovat selvästi havaittavissa tutkimuksen tuloksissa. Esiupseeri-kurssi ja samalla yleisesikuntaupseerikurssi ovat siirtyneet suhteellisesti jo myöhemmäksi vir-kauralla kuin ne olivat ennen eläkeuudistusta. Vaikka ylennykset eivät ole enää samalla tavoin si-doksissa käytettävissä oleviin virkoihin, ne ovat silti osin sidottuja suoritettuun jatkokoulutukseen. Jatkokoulutuksen siirtäminen myöhemmäksi virkauralla on siis samalla myöhentänyt esiupseerien ja yleisesikuntaupseerien ylennyksiä. Virkauran pidentyminen ja koulutusjärjestelmän muutokset ovat nähtävissä selvinä eroina kurssien välillä. Organisaatiossa tapahtuneiden muutosten arviointi on tehtävärakenteen valossa haasteelli-sempaa, mutta myös niistä on havaittavissa viitteitä. Tulosten perusteella tullaan siihen johtopää-tökseen, että upseerin ura on pidentynyt ajallisesti ja suhteellisesti eniten uran alkuvaiheessa, ennen esiupseeri- ja yleisesikuntaupseerikurssia. Samalla voidaan todeta, että upseerien siirtyminen esiup-seeritason suunnittelu- ja komentajatehtäviin on myöhentynyt.
Resumo:
Frequency converters are widely used in the industry to enable better controllability and efficiency of variable speed AC motor drives. Despite these advantages, certain challenges concerning the inverter and motor interfacing have been present for decades. As insulated gate bipolar transistors entered the market, the inverter output voltage transition rate significantly increased compared with their predecessors. Inverters operate based on pulse width modulation of the output voltage, and the steep voltage edge fed by the inverter produces a motor terminal overvoltage. The overvoltage causes extra stress to the motor insulation, which may lead to a prematuremotor failure. The overvoltage is not generated by the inverter alone, but also by the sum effect of the motor cable length and the impedance mismatch between the cable and the motor. Many solutions have been shown to limit the overvoltage, and the mainstream products focus on passive filters. This doctoral thesis studies an alternative methodology for motor overvoltage reduction. The focus is on minimization of the passive filter dimensions, physical and electrical, or better yet, on operation without any filter. This is achieved by additional inverter control and modulation. The studied methods are implemented on different inverter topologies, varying in nominal voltage and current.For two-level inverters, the studied method is termed active du/dt. It consists of a small output LC filter, which is controlled by an independent modulator. The overvoltage is limited by a reduced voltage transition rate. For multilevel inverters, an overvoltage mitigation method operating without a passive filter, called edge modulation, is implemented. The method uses the capability of the inverter to produce two switching operations in the same direction to cancel the oscillating voltages of opposite phases. For parallel inverters, two methods are studied. They are both intended for two-level inverters, but the first uses individual motor cables from each inverter while the other topology applies output inductors. The overvoltage is reduced by interleaving the switching operations to produce a similar oscillation accumulation as with the edge modulation. The implementation of these methods is discussed in detail, and the necessary modifications to the control system of the inverter are presented. Each method is experimentally verified by operating industrial frequency converters with the modified control. All the methods are found feasible, and they provide sufficient overvoltage protection. The limitations and challenges brought about by the methods are discussed.