Transformational leadership as a moderator of the relationship between psychological safety and learning behaviour in work teams in Ghana

Orientation: Transformational team leadership is an important variable that influences team members’ perception of the team as psychologically safe enough to engage in learning behaviours. Research purpose: The study was aimed at investigating the relationship between psychological safety and learning behaviour in teams, as well as the moderating role of transformational team leadership in this relationship. Motivation for the study: For a team to be effective, adaptive and innovative and engage in learning behaviours, the transformational team leader must set the right climate in the team, where he or she welcomes the team members’ opinions, questions and feedback at no risk to their image. An understanding of this will be important in team leader selection and training. Research design, approach and method: Using a cross-sectional survey design, 57 work teams comprising 456 respondents in teams of 7–9 members were purposively sampled from five financial institutions in Accra, Ghana. Hierarchical regression and moderation analyses were run on the data at the team level. Main findings: Results indicated a positive relationship between team psychological safety and team learning behaviour, with transformational team leadership moderating this relationship. Practical/managerial implication: Transformational team leadership is important in creating a climate of psychological safety that will enable team members to engage in learning behaviours. Contribution/value-add: The study provided theoretical and empirical evidence that, in organisational contexts, transformational team leadership is an important variable that can facilitate psychological safety and learning behaviour in teams

Accretion Disks Around Black Holes: Twenty Five Years Later

We study the progress of the theory of accretion disks around black holes in last twenty five years and explain why advective disks are the best bet in explaining varied stationary and non-stationary observations from black hole candidates. We show also that the recently proposed advection dominated flows are incorrect.Comment: 30 Latex pages including figures. Kluwer Style files included. Appearing in `Observational Evidence for Black Holes in the Universe', ed. Sandip K. Chakrabarti, Kluwer Academic Publishers (DORDRECHT: Holland

Proactivity Toward Workplace Safety Improvement: An Investigation of Its Motivational Drivers and Organizational Outcomes

Initiating a safety oriented change - or safety initiative - is conceptually distinct from other forms of safety participation and safety citizenship behaviour, yet little attention has been given to its performance outcomes or its motivational antecedents. An initial study with a sample composed of middle managers (N = 86) showed that safety initiative predicted objective improvement actions six months later, whereas, showing differential validity, safety compliance predicted the implementation of monitoring actions. Two subsequent studies focused on motivational antecedents. First, using a sample of team leaders (N = 295), we tested a higher-order structure of proactive motivation that incorporates three domains: “can do”, “reason to” and future orientation. Second, in a longitudinal study of chemical work operators (N = 188), after checking for the influence of potential confounds (past behaviours; accidents experience; perceived risk), we showed that safety initiative was predicted only by proactive motivation. Instead, safety compliance was found to be associated with affective commitment and scrupulousness, whereas safety helping was found to be associated with affective commitment. Self-reported behaviours were validated against rater assessments. This study supports the importance of distinguishing safety initiative from other safety behaviours, indicating how to create an organizational context supporting a proactive management of workplace safety

A Novel Blended State Estimated Adaptive Controller for Voltage and Current Control of Microgrid against Unknown Noise

© 2013 IEEE. In this study, a novel blended state estimated adaptive controller is designed for voltage and current control of microgrid against unknown noise. The core feature of the microgrid (MG) is its ability to integrate more than one distributed energy resource into the main grid. The state of a microgrid may deteriorate due to many reasons, for example malicious cyber-attacks, disturbances, packet losses, etc. Therefore, it is necessary to achieve the true state of the system to enhance the control requirement and automation of the microgrid. To achieve the true state of a microgrid, this study proposes the use of an algorithm based on the unscented kalman filter (UKF). The proposed state estimator technique is developed using an unscented-transformation and sigma-points measurement technique capable of minimizing the mean and covariance of a nonlinear cost function to estimate the true state of a single-phase, three-phase single-source and three-phase multi-source microgrid system. The advantage of the proposed estimator over using extended kalman filter (EKF) is investigated in simulations. The results demonstrate that the use of the UKF estimator produces a superior estimation of the system compared with the use of the EKF. An adaptive PID controller is also developed and used in system conjunction with the estimator to regulate its voltage and current against the number of loads. Deviation in load parameters hamper the function of the MG system. The performance of the developed controller is also evaluated against number of loads. Results indicate the controller provides a more stable and high-tracking performance with the inclusion of the UKF in the system

Disturbance observer based sliding mode control for a continuous stirred tank reactor (CSTR)

A continuous stirred tank reactor (CSTR) is typical of equipment found in the process control industry. The dynamics represent a wide class of second order nonlinear systems and thus as well as having specific industrial application, control of the CSTR is frequently used as a benchmark problem for application and testing of new control algorithms. Due to the high complexity of the CSTR system, the robust control design problem is challenging. This paper first establishes a mathematical model of the system. A disturbance observer is then designed to estimate the disturbance and a corresponding asymptotically stable sliding mode control is developed. Stability analysis is presented in terms of the Lyapunov method. Finally, based on experimental data, the proposed method is validated using simulation experiments

Undoped gallium antimonide studied by positron annihilation spectroscopy

Positron lifetime spectroscopy has been used to study the vacancy type defects in undoped gallium antimonide. Temperature dependent positron trapping into the VGarelated defect having a characteristic lifetime of 310ps was observed in the as-grown sample. The lifetime data were well described by a model involving the thermal ionization (0/-) of the VGa-related defect and its ionization energy was found to be E(0/)=83meV. For the electron irradiated sample, the VGa-related defect with lifetime of 310ps that was found in the non-irradiated samples was also identified. Moreover, another lifetime component (280ps) was only observed in the electron irradiated sample but not in the non-irradiated sample. It was also attributed to the V Ga-related defect. The two identified VGa-related defects should have different microstructures because of their difference in characteristic lifetimes. The 280ps component remains thermally stable after the 500°C annealing while the 310ps component anneals at 300°C.published_or_final_versio

Effects of Irrigation Frequency and Manure on Growth Parameters, Crop Coefficient and Yield of Okro (Abelmoscus Esculeutus)

It is essential to maintain readily available water in the soil if crops are to make satisfactory growth and give optimum yield. This work studied the response of Okro to the application of different regimes of irrigation water (W1, W2 and W3) in order to determine its growth performance and yield. Twenty seven (27) bucket of the volumetric capacity of 10litres each, Okro was planted in each bucket equal treatment of animal and organic fertilizer was applied in the ratio 6:1 while response to plant height observed were 13 cm, 10.8 cm and 15 cm, also, stem diameter observed were 0.06 mm, 0.12 mm, and 0.17 mm.The effects of irrigation frequency, average plant height (cm), average number of leaves; average Stem (diameter, mm) and yield (g) were studied.  W1 gave 13, 4, 0.06, 11.4; W2:  10.8, 6, 0.12, 18.1; W3: 15, 7, 0.17, 23.3. Plants under W3 recorded the highest plant height and it also produced the highest number of leaves at 7 stem diameter (0.17mm) and consequently the highest mean yield. The study showed that with readily available nutrients present in soil, the most desirable frequency of irrigation gives an optimum crop yield as nutrients is easily taken up by plants. It is recommended that a standard model green house be constructed to study various crop coefficients and consumptive use for this zone. Keywords: irrigation frequency, growth parameters, crop coefficient, yield, Okr

A design method for flexible retaining walls in clay

Design of retaining walls in clay is typically based on ultimate limit state calculations to prevent collapse, with arbitrary factors of safety used to limit deformations. These factors of safety do not take into account the different rates of strength mobilisation in the wide variety of clays found worldwide. As there is substantial uncertainty in this approach, conventional design tends to lead to excessive conservatism with associated high cost. The novel analysis procedure based on the fraction of the strength of soil mobilised for a given wall displacement developed here allows rapid assessment of wall deformations and stresses by way of a simple two-parameter constitutive model which can be easily calibrated using conventional triaxial data. The model is validated based on field and model case histories with a variety of different clays and propping conditions and is shown to exhibit good performance in predicting the behaviour of published case histories based on soil parameters extracted from previously published soil test data. This novel analysis provides for the first time a route for practising engineers to carry out fast, efficient design at early stages of the design process by considering many potential wall geometries without the computational overhead of complex finite-element or finite-difference numerical models. </jats:p