A speed sensorless control based on a MRAS applied to a double fed induction machine drive

This paper proposes a new MRAS method to estimate the mechanical quantities in a double fed induction machine. In the traditional formulation the integral term, introduced by the PI MRAS regulator, is canceled in the transfer function between the estimated and the real speed. As a novelty, an additional term depending on the reference rotor flux through a constant gain g is introduced in the adjustable model of the MRAS. This innovation restores the integral term in the transfer function. As a consequence, during the closed loop operation, the estimated speed does not exhibit anymore a steady state error. The influence of the inverter non-linearities and of the non-linear rotor brush resistance on the speed estimation is also discussed. Some experimental tests validate the proposed method.     

Linking care felt to engagement in innovative behaviors in the workplace: The mediating role of psychological conditions.

This study examines the relationships between care felt and engagement in innovative behaviors at work. We posit that when an individual perceives that coworkers care for him or her (i.e., care felt), this cultivates psychological conditions such as safety, meaningfulness, and availability, which result in a higher level of motivation and by implication engagement in innovative behaviors at work. A sample of 218 employees took part in the assessment of the relationship between the psychological conditions linked to care felt (measured at Time 1) and motivation and engagement in innovative behaviors (measured at Time 2). The results of structural equation modeling (SEM) indicate that care felt is positively linked to psychological conditions. The latter is positively related directly and indirectly (through motivation) to engagement in innovative behaviors. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Linking perceived external prestige and collective identification to collaborative behaviors in R&D teams

Research efforts have long been directed at understanding variations in collaborative behaviors among work teams with burgeoning interest in teams operating in knowledge-intensive settings. One of the largely unexplained issues is how does team image and collective identification facilitate collaborative behaviors. Here, survey data were collected from nineteen highly technical work teams engaging in software development in an R&D division of a multinational NASDAQ firm involved in multimedia communications and information processing technology. The relationships between perceived external prestige, collective team identification and team collaborative behaviors were examined. The results of the team-level analyses suggest that perceived external prestige augments collective team identification (measured at Time 1), which in turn engenders a high degree of collaboration and interaction within the team (measured at Time 2). When past team performance was controlled for, the results consistently supported the hypothesized model.     

Direct torque control as variable structure control: Existence conditions verification and analysis

The aim of this paper is to propose a formal approach to derive direct torque control (DTC). Using the theory of variable structure control (VSC) and in particular the sliding mode approach, a detailed analysis of the possible operating regions for both induction and brushless machines are described. This analysis allows to clarify the consequences of a specific switching table in terms of control stability. In particular, DTC is presented and analysed as a special case of sliding mode strategy. Sliding mode existence conditions are verified and the most critical operating regions are obtained. The proposed formal analysis allows to define more sophisticated switching tables which assure stable operation.     

Sensitive substrates for neprilysin (neutral endopeptidase) and thermolysin that are highly resistant to serine proteases

Tripeptide derivatives like 3-carboxypropanoylalanyl-alanyl-leucine 4-nitroanilide or 3-carboxypropanoyl-alanyl-alanyl-phenylalanine 4-nitroanilide are very sensitive substrates for neprilysin (k cat > 10(2)s(-1); k cat/Km > or = 10(6) s(-1) x M(-1)) and are widely employed in investigations of the enzyme. However, these compounds are also good substrates for the serine proteases chymotrypsin and subtilisin (k cat approximately 1s(-1)-34s(-1)). By substituting the N-terminal alanine of the substrates with proline, the catalytic efficiency of the enzymic reaction, by the serine proteases, is diminished by 2-3 orders of magnitude, whereas that by neprilysin and theromlysin decreases only slightly. These effects demonstrate that structural alterations in peptide substrates that impair secondary sub-site interactions with one class of peptidases may enhance the selectivity of the substrates towards another class of peptidases.     

How leaders cultivate social capital and nurture employee vigor: Implications for job performance.

This study examined how leader relational behaviors (i.e., relational leadership) cultivate bonding social capital among organizational members and the way bonding social capital augments feelings of vigor at work. In addition, the authors examined how vigor enhances employee job performance. Using a sample of 209 participants in Israeli community centers, the results of structural equation modeling indicate a 2-stage mediation model in which leader relational behaviors are positively related to bonding social capital; this, in turn, results in feelings of vigor, which are positively associated with manager ratings of employee job performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cluster analysis using multi-algorithm voting in cross-cultural studies

The goal of this study was to overcome three main shortcomings in using a single algorithm to determine a particular clustering of a phenomenon. We addressed this issue by considering cross-cultural research as a case in point and applied Multi-Algorithm Voting (MAV) methodology to cluster analysis. Specifically, this study was designed to provide more systematic supportive decision tools for researchers and managers alike when attempting to cluster analyzing phenomena. To assess the merits of the methodology of MAV for cluster analysis, we analytically examined cross-cultural data from Merritt [Merritt, A. (2000). Culture in the cockpit Do Hofstede’s dimensions replicate? Journal of Cross-Cultural Psychology, 31, 283–301] study as well as data scored and ranked by Hofstede [Hofstede, G. (1980). Culture’s consequences: International differences in work-related values. Beverly Hills, CA: Sage; Hofstede, G. (1982). Values survey module (Tech. Paper). Maastricht, The Netherlands: Institute for Research on Intercultural Cooperation].Our study contributes to the literature in several ways. From a methodological point of view, we show how researchers can avoid arbitrary decisions in determining the number of clusters. We provide the researcher with more compelling and robust methodologies not only for analyzing the results of cluster analysis, but also for more better-grounded decision-making through which theoretical insights and implications can be drawn.