Partial Relaxation Approach: An Eigenvalue-Based DOA Estimator Framework

In this paper, the partial relaxation approach is introduced and applied to DOA estimation using spectral search. Unlike existing methods like Capon or MUSIC which can be considered as single source approximations of multi-source estimation criteria, the proposed approach accounts for the existence of multiple sources. At each considered direction, the manifold structure of the remaining interfering signals impinging on the sensor array is relaxed, which results in closed form estimates for the interference parameters. The conventional multidimensional optimization problem reduces, thanks to this relaxation, to a simple spectral search. Following this principle, we propose estimators based on the Deterministic Maximum Likelihood, Weighted Subspace Fitting and covariance fitting methods. To calculate the pseudo-spectra efficiently, an iterative rooting scheme based on the rational function approximation is applied to the partial relaxation methods. Simulation results show that the performance of the proposed estimators is superior to the conventional methods especially in the case of low Signal-to-Noise-Ratio and low number of snapshots, irrespectively of any specific structure of the sensor array while maintaining a comparable computational cost as MUSIC.Comment: This work has been submitted to IEEE for possible publication. Copyright may be transferred without notice, after which this version may no longer be accessibl

Developing resilient safety culture for construction projects in Vietnam

Although traditional safety culture approach has significantly contributed to accident reduction, it may be inadequate in responding to all of the changing and unforeseen safety risks associated with the complex nature of construction projects. Resilient safety culture has been therefore proposed as a promising concept to address the limitation of traditional safety culture approach in order to achieve a sustained improvement of safety performance in the construction environment. The aim of this study is to investigate the development of resilient safety culture in the construction environment. To fulfil the research aim and objectives, a quantitative approach and a survey research design were adopted. Data were collected using questionnaires targeting the construction project managers involved in the delivery of 78 recently completed building projects in Vietnam. The structural equation modelling (SEM) technique with partial least-squares estimation (PLS) was used to analyse the data. The key findings pertaining to the research objectives are: (1) This study examined the dimensions of resilient safety culture of construction projects. The results confirm 24 measurable scale items comprising three dimensions (i.e. psychological resilience, contextual resilience and behavioural resilience) to define and assess resilient safety culture. (2) This study explored the drivers of resilient safety culture. It was found that hazard prevention practice has a positive impact on contextual and behavioural resilience, error management practice has a positive impact on psychological resilience, and mindful organising practice has a positive impact on contextual resilience. (3) This study examined the interactive effects of resilient safety culture and project complexity on safety performance of construction projects. It was found that resilient safety culture dimensions have positive impacts on safety performance. Psychological resilience has a weaker impact on accident prevention under higher contextual and behavioural resilience levels. Technical and environmental project complexities have negative impacts on safety performance. The negative impact of project complexity on safety performance becomes less significant when there is a higher level of psychological, contextual and behavioural resilience; while this impact might be not significant if psychological, contextual and behavioural resilience were high. The findings of this study contribute to the knowledge of construction safety management by providing the theoretical development and empirical evidence to clarify the concept of resilient safety culture in terms of definition, purpose, value, and assessment and improvement mechanisms in the context of construction projects. Practically, this study (1) provides a frame of safety practices to assess the organisations’ capabilities to manage safety risks and achieve a sustained improvement of safety performance regardless of the changing complexity levels of construction projects, and (2) recommends the appropriate strategies to build up such capabilities

Formation Control of Rigid Graphs with a Flex Node Addition

This paper examines stability properties of distance-based formation control when the underlying topology consists of a rigid graph and a flex node addition. It is shown that the desired equilibrium set is locally asymptotically stable but there exist undesired equilibria. Specifically, we further consider two cases where the rigid graph is a triangle in 2-D and a tetrahedral in 3-D, and prove that any undesired equilibrium point in these cases is unstable. Thus in these cases, the desired formations are almost globally asymptotically stable.Comment: The full version of this paper with general extensions has been submitted to a journal for publicatio

Wind, Water, Wall-Woman

Excerpts from I-Blue, a book in progres