Lernen im Team: Zusammenhänge zwischen Personen- und Teammerkmalen und der Leistung von Multiplikatoren [Learning in teams: Relationships between individual and team characteristics and the performance of multipliers]

The continuous mutual transfer of knowledge and skills within work teams is increasingly important for organizational practice. According to the situational and experience-based approaches of applied learning research, certain individual and social prerequisites have to be met for successful learning in teams. In a field study at an automobile production site, it was investigated which personal characteristics of multipliers and which characteristics of teams are related to the performance of multipliers in 31 teams with 291 coworkers. Using multi-level analyses (HLM), the amount of variance explained by the predictor variables in teaching success of multipliers and learning success of coworkers was examined. Results showed that multipliers' conscientiousness and team cohesion were related to teaching success of multipliers; extraversion and team cohesion were related to the learning success of coworkers. In closing, the scientific and practical implications for the investigation and promotion of work-based learning processes in teams are discussed.

Das juedische Buch im Dritten Reich 1933-1945

Draft of published version which examines the status of Jewish authors and publishers in Nazi Germany; continues with the process of removing Jewish works from Nazi-German society, with special attention to the difficulties with Heinrich Heine and the Schocken Press.

Staubkorn im Sandsturm.

Fate of the Jewish physician Karl Goldberg, novel written in 1944. Novel is only partially autobiographical.

Three-level inverter fed open-end winding IM drive with common mode voltage elimination and reduced power device count

A three-level space phasor generation scheme with common mode elimination and with reduced power device count is proposed for an open end winding induction motor in this paper. The open end winding induction motor is fed by the three-level inverters from both sides. Each two level inverter is formed by cascading two two-level inverters. By sharing the bottom inverter for the two three-level inverters on either side, the power device count is reduced. The switching states with zero common mode voltage variation are selected for PWM switching so that there is no alternating common mode voltage in the pole voltages as well as in phase voltages. Only two isolated DC-links, with half the voltage rating of a conventional three-level neutral point clamped inverter, are needed for the proposed scheme.

Improved switching frequency variation control of hysteresis controlled voltage source inverter-fed IM drives using current error space vector

A constant switching frequency current error space vector-based hysteresis controller for two-level voltage source inverter-fed induction motor (IM) drives is proposed in this study. The proposed controller is capable of driving the IM in the entire speed range extending to the six-step mode. The proposed controller uses the parabolic boundary, reported earlier, for vector selection in a sector, but uses simple, fast and self-adaptive sector identification logic for sector change detection in the entire modulation range. This new scheme detects the sector change using the change in direction of current error along the axes jA, jB and jC. Most of the previous schemes use an outer boundary for sector change detection. So the current error goes outside the boundary six times during sector change, in one cycle,, introducing additional fifth and seventh harmonic components in phase current. This may cause sixth harmonic torque pulsations in the motor and spread in the harmonic spectrum of phase voltage. The proposed new scheme detects the sector change fast and accurately eliminating the chance of introducing additional fifth and seventh harmonic components in phase current and provides harmonic spectrum of phase voltage, which exactly matches with that of constant switching frequency voltage-controlled space vector pulse width modulation (VC-SVPWM)-based two-level inverter-fed drives.

Switching frequency variation control in hysteresis PWM controller for IM drives using variable parabolic bands for current error space phasor

Variation of switching frequency over the entire operating speed range of an induction motor (M drive is the major problem associated with conventional two-level three-phase hysteresis controller as well as the space phasor based PWM hysteresis controller. This paper describes a simple hysteresis current controller for controlling the switching frequency variation in the two-level PWM inverter fed IM drives for various operating speeds. A novel concept of continuously variable hysteresis boundary of current error space phasor with the varying speed of the IM drive is proposed in the present work. The variable parabolic boundary for the current error space phasor is suggested for the first time in this paper for getting the switching frequency pattern with the hysteresis controller, similar to that of the constant switching frequency voltage-controlled space vector PWM (VC-SVPWM) based inverter fed IM drive. A generalized algorithm is also developed to determine parabolic boundary for controlling the switching frequency variation, for any IM load. Only the adjacent inverter voltage vectors forming a triangular sector, in which tip of the machine voltage vector ties, are switched to keep current error space vector within the parabolic boundary. The controller uses a self-adaptive sector identification logic, which provides smooth transition between the sectors and is capable of taldng the inverter up to six-step mode of operation, if demanded by drive system. The proposed scheme is simulated and experimentally verified on a 3.7 kW IM drive.

Elimination of common mode voltage and fifth and seventh harmonics in a multilevel inverter fed IM drive using 12-sided polygonal voltage spacephasor

A multilevel inverter with 12-sided polygonal voltage space vector structure is proposed in this paper. The present scheme provides elimination of common mode voltage variation and 5(th) and 7(th) order harmonics in the entire operating range of the drive. The proposed multi level structure is achieved by cascading only the conventional two-level inverters with asymmetrical DC link voltages. The bandwidths problems associated with conventional hexagonal voltage space vector structure current controllers, due to the presence of 5(th) and 7(th) harmonics, in the over modulation region, is absent in the present 12-sided structure. So a linear voltage control up to 12-step operation is possible, from the present twelve sided scheme, with less current control complexity. An open-end winding structure is used for the induction motor drive.

Generation of parabolic trajectories for current error space phasor similar to an SVPWM controller for control of switching frequency variation in current hysteresis PWM controlled IM drives

Switching frequency variation over a fundamental period is a major problem associated with hysteresis controller based VSI fed IM drives. This paper describes a novel concept of generating parabolic trajectories for current error space phasor for controlling the switching frequency variation in the hysteresis controller based two-level inverter fed IM drives. A generalized algorithm is developed to determine unique set of parabolic trajectories for different speeds of operation for any given IM load. Proposed hysteresis controller provides the switching frequency spectrum of inverter output voltage, similar to that of the constant switching frequency VC-SVPWM based IM drive. The scheme is extensively simulated and experimentally verified on a 3.7 kW IM drive for steady state and transient performance.

Die mündliche Sprachkompetenz finnischer Deutschlernender aus Sicht der grammatikalischen Korrektheit : Eine Fehleranalyse im Rahmen des HY-TALK-Projekts

Tutkielman päätavoitteena on analysoida suomalaisten, saksaa opiskelevien lukiolaisten suullisen testin suorituksia kielen oikeellisuuden näkökulmasta virheanalyysin avulla. Aineistona on osa Helsingin yliopiston HY-TALK-hankkeen saksan kielen tutkimusaineistosta: videoinnit suullisen kielitaidon testeistä sekä asiantuntijaraadin arvioinnit suorituksista. Koska aineisto on suullinen, tutkielmassa tarkastellaan aluksi suullisen kielen piirteitä. Virheanalyysin pohjana ovat muun muassa Corderin, Nickelin, Kleppinin ja Jamesin esittämät teoriat. Tutkielmassa analysoidaan kolmentoista, selkeästi joko A1.3- tai A2.2-taitotasolle arvioidun opiskelijan suoritukset. Virheanalyysin tavoitteena on saada selville kielioppivirheiden määrät, kullekin taitotasolle tyypilliset kielioppivirheet sekä selvittää tasojen välisiä eroja. Virheanalyysissä ei huomioida leksikaalisia eikä ääntämisvirheitä, vaan keskitytään morfologisiin ja syntaktisiin virheisiin. Virheet jaotellaan eri virheluokkiin (nominaalilausekkeiden deklinaatio, pronomini, taipumattomat sanaluokat, kysymyssanat, kieltoilmaukset, verbit ja lauserakenne) ja ne tilastoidaan taulukoihin. Lisäksi pohditaan virheiden syitä sekä virheiden vaikutusta kielen ymmärrettävyyteen. Jälkimmäistä selvitetään saksaa äidinkielenään puhuvan, kolmihenkisen raadin avulla. Raadin sekä numeeriset että verbaaliset arvioinnit ovat myös osa tutkielman aineistoa. Toinen tutkielman päätavoite on opetussuunnitelman taitotasoasteikon validointi. Tarkoituksena on selvittää oikeellisuuden taitotasokuvausten toimivuutta arvioinnissa A1.3- ja A2.2-tasojen osalta. Tätä tavoitetta varten selvitetään myös kielitaidon arvioinnin taustalla olevia teorioita. HY-TALK-asiantuntijaraadin arviointeja verrataan virheanalyysin tuloksiin korrelaatiokertoimen ja regressiosuoran avulla. Virheanalyysin perusteella voidaan todeta, että molemmilla tasoilla olevat opiskelijat tekevät eniten virheitä nominaalilausekkeiden deklinaatiossa (A2.2-tasolla 60,0 prosenttia kaikista virheistä ja A1.3-tasolla 42,2 prosenttia). A1.3-tasolle arvioidut opiskelijat tekevät paljon virheitä myös verbeissä ja lauserakenteissa, kun taas A2.2-tason opiskelijat hallitsevat nämä rakenteet paremmin. A1.3-tasolle arvioidut opiskelijat tekevät enemmän virheitä (22,10 virhettä sataa sanaa kohden) kuin A2.2-tasolle arvioidut (9,80 virhettä sataa sanaa kohden). Virheiden syitä ovat muun muassa testitilanne, puhekumppanin vaikutus ja interferenssi. Kielen ymmärrettävyyteen vaikuttavat saksalaisen raadin mukaan kielioppivirheiden lisäksi muun muassa puheen sujuvuus ja leksikaaliset ongelmat. Vakavimpina virheinä pidetään virheitä lauserakenteessa, sillä ne haittaavat usein ymmärrettävyyttä. Deklinaatiovirheitä puolestaan ei yleensä pidetä vakavina virheinä. Taitotasokuvaukset toimivat A1.3- ja A2.2-tasojen osalta hyvin, sillä virheanalyysin virhemäärät ja HY-TALK-raadin arvioinnit korreloivat keskenään, kun otetaan huomioon molemmat tasot A1.3 ja A2.2. Kielioppivirheiden määrä siis vaikuttaa kielen oikeellisuuden arviointiin. Taitotasokuvauksia olisi kuitenkin joiltain osin syytä tarkentaa ja yhtenäistää esimerkiksi konkreettisten esimerkkien avulla (esim. mikä on peruskielioppivirhe?) ja kuvaamalla myös kielen ymmärrettävyyttä joka tasolla.

A novel metal binding mode of a pyrimidine nucleotide. Crystal structure of [Cu(5′-UMP)(im)2(H2O)]·4H2O

X-ray analysis of the ternary complex [Cu(5′-UMP)(im)2(H2O)]·4H2O, where 5′-UMP uridine-5′-monophosphate and IM = imidazole, reveals a novel metal binding mode of pyrimidine nucleotide through the ribose group.

A Rotor Flux Estimation During Zero and Active Vector Periods Using Current Error Space Vector From a Hysteresis Controller for a Sensorless Vector Control of IM Drive

This paper proposes a sensorless vector control scheme for general-purpose induction motor drives using the current error space phasor-based hysteresis controller. In this paper, a new technique for sensorless operation is developed to estimate rotor voltage and hence rotor flux position using the stator current error during zero-voltage space vectors. It gives a comparable performance with the vector control drive using sensors especially at a very low speed of operation (less than 1 Hz). Since no voltage sensing is made, the dead-time effect and loss of accuracy in voltage sensing at low speed are avoided here, with the inherent advantages of the current error space phasor-based hysteresis controller. However, appropriate device on-state drops are compensated to achieve a steady-state operation up to less than 1 Hz. Moreover, using a parabolic boundary for current error, the switching frequency of the inverter can be maintained constant for the entire operating speed range. Simple sigma L-s estimation is proposed, and the parameter sensitivity of the control scheme to changes in stator resistance, R-s is also investigated in this paper. Extensive experimental results are shown at speeds less than 1 Hz to verify the proposed concept. The same control scheme is further extended from less than 1 Hz to rated 50 Hz six-step operation of the inverter. Here, the magnetic saturation is ignored in the control scheme.

A current error space vector based hysteresis controller with constant switching frequency and simple online boundary computation for VSI fed IM drive

This paper proposes a simple current error space vector based hysteresis controller for two-level inverter fed Induction Motor (IM) drives. This proposed hysteresis controller retains all advantages of conventional current error space vector based hysteresis controllers like fast dynamic response, simple to implement, adjacent voltage vector switching etc. The additional advantage of this proposed hysteresis controller is that it gives a phase voltage frequency spectrum exactly similar to that of a constant switching frequency space vector pulse width modulated (SVPWM) inverter. In this proposed hysteresis controller the boundary is computed online using estimated stator voltages along alpha and beta axes thus completely eliminating look up tables used for obtaining parabolic hysteresis boundary proposed in. The estimation of stator voltage is carried out using current errors along alpha and beta axes and steady state model of induction motor. The proposed scheme is simple and capable of taking inverter upto six step mode operation, if demanded by drive system. The proposed hysteresis controller based inverter fed drive scheme is simulated extensively using SIMULINK toolbox of MATLAB for steady state and transient performance. The experimental verification for steady state performance of the proposed scheme is carried out on a 3.7kW IM.