Gaussian Effective Potential and the Coleman's normal-ordering Prescription : the Functional Integral Formalism

For a class of system, the potential of whose Bosonic Hamiltonian has a Fourier representation in the sense of tempered distributions, we calculate the Gaussian effective potential within the framework of functional integral formalism. We show that the Coleman's normal-ordering prescription can be formally generalized to the functional integral formalism.Comment: 6 pages, revtex; With derivation details and an example added. To appear in J. Phys.

On the rooted Tutte polynomial

The Tutte polynomial is a generalization of the chromatic polynomial of graph colorings. Here we present an extension called the rooted Tutte polynomial, which is defined on a graph where one or more vertices are colored with prescribed colors. We establish a number of results pertaining to the rooted Tutte polynomial, including a duality relation in the case that all roots reside around a single face of a planar graph. The connection with the Potts model is also reviewed.Comment: plain latex, 14 pages, 2 figs., to appear in Annales de l'Institut Fourier (1999

Soluble kagome Ising model in a magnetic field

An Ising model on the kagome lattice with super-exchange interactions is solved exactly under the presence of a nonzero external magnetic field. The model generalizes the super-exchange model introduced by Fisher in 1960 and is analyzed in light of a free-fermion model. We deduce the critical condition and present detailed analyses of its thermodynamic and magnetic properties. The system is found to exhibit a second-order transition with logarithmic singularities at criticality.Comment: 8 pages, 8 figures, references adde

GRB 060206: hints of precession of the central engine?

Aims. The high-redshift (z=4.048) gamma-ray burst GRB 060206 showed unusual behavior, with a significant rebrightening by a factor of ~4 at about 3000 s after the burst. We argue that this rebrightening implies that the central engine became active again after the main burst produced by the first ejecta, then drove another more collimated jet-like ejecta with a larger viewing angle. The two ejecta both interacted with the ambient medium, giving rise to forward shocks that propagated into the ambient medium and reverse shocks that penetrated into the ejecta. The total emission was a combination of the emissions from the reverse- and forward- shocked regions. We discuss how this combined emission accounts for the observed rebrightening. Methods. We apply numerical models to calculate the light curves from the shocked regions, which include a forward shock originating in the first ejecta and a forward-reverse shock for the second ejecta. Results. We find evidence that the central engine became active again 2000 s after the main burst. The combined emission produced by interactions of these two ejecta with the ambient medium can describe the properties of the afterglow of this burst. We argue that the rapid rise in brightness at ~3000 s in the afterglow is due to the off-axis emission from the second ejecta. The precession of the torus or accretion disk of the central engine is a natural explanation for the departure of the second ejecta from the line of sight

GRB 060206: Evidence of Precession of Central Engine

The high-redshift (z = 4.048) gamma-ray burst GRB 060206 showed unusual behavior, with a significant re-brightening about 3000 s after the burst. We assume that the central engine became active again 2000 s after the main burst and drove another more collimated off-axis jet. The two jets both interacted with the ambient medium and contributed to the whole emission. We numerically fit this optical afterglow from the two jets using the forward-shock model and the forward-reverse shock model. Combining with the zero time effect, we suggest that the fast rise at ~3000 s in the afterglow was due to the off-axis emission from the second jet. The precession of the torus or accretion disk of the gamma ray burst engine is the natural explanation for the symmetry axes of these two jets not to lie on the same line

Cyber-Physical Systems and Digital Twins for “Cognitive Building” in the Construction Industry

Purpose: Despite the growing attention on the relevance of improved building management systems with cognition in recent years in the architecture, engineering, construction and operation (AECO) community, no review has been conducted to understand the human-environment interaction features of cyber-physical systems (CPS) and digital twins (DTs) in developing the concept of a cognitive building (CB). Thus, this paper aims to review existing studies on CPS and DTs for CB to propose a comprehensive system architecture that considers human-environment interactions. Design/methodology/approach: Scientometric analysis and content analysis were adopted for this study. Findings: The scientometric analysis of 1,042 journal papers showed the major themes of CPS/DTs for CB, and these can be categorized into three key technologies to realize CB in the AECO community: CPS, DTs and cognitive computing (CC). Content analysis of 44 relevant publications in the built environment assisted in understanding and evidently confirming the claim of this study on the integration of CPS and DTs for CB in construction by also involving the CC. It is found and confirmed that CB can be realized with CPS and DTs along with the CC. A CB system architecture (CBSA) is proposed from the three key technologies considering the human-environment interactions in the loop. The study discovered the potential applications of the CBSA across the building lifecycle phases, including the design, construction and operations and maintenance, with the potential promise of endowing resilience, intelligence, greater efficiency and self-adaptiveness. Based on the findings of the review, four research directions are proposed: human-environment interactions, CB for sustainable building performance, CB concept for modular buildings and moving beyond CB. Originality/value: This study stands out for comprehensively surveying the intellectual core and the landscape of the general body of knowledge on CPS/DTs for CB in the built environment. It makes a distinctive contribution to knowledge as it does not only propose CBSA by integrating CPS and DTs along with CC but also suggests some potential practical applications. These may require expert judgments and real case examples to enhance reproducibility and validation

Responses to the COVID-19 pandemic in the Construction Industry: A literature review of academic research

Over the past 3 years, the global construction sector has been severely affected by the noxious coronavirus (COVID-19) pandemic. Visionary construction stakeholders, including governments, practitioners, and academia, all have been actively devising strategies to deal with the crisis caused by the pandemic. Despite the rich contributions by academia, an in-depth review of their research works to understand how the pandemic has been handled to position the construction industry for post-pandemic actions and future pandemics is hitherto lacking. Hence, an up-to-date literature review is conducted in this study to better understand this terra incognita. It does so by adopting a six-step thematic analysis of 159 empirical peer-reviewed research articles in relation to COVID-19 on construction. The review discovered a growing research interest from different countries from 2020 to 2022. The existing studies can be put under four major topics, namely the COVID-19 impacts, challenges and opportunities, responding strategies, and post-COVID-19 interventions. A framework consisting of four categories of responding strategies, namely vaccination, personal responsibility of workers, government-instructional practices, and organisation-based approaches, is proposed through the lens of the socio-technical system theory to handle the pandemic crisis in construction. Limitations of the existing studies were further identified. Four pertinent research directions were finally proposed: building upon and testing the proposed COVID-19 response framework, adoption of more advanced innovative strategies to increase productivity amid pandemics and survive the risk of future pandemics, beyond the technological response to COVID-19 in construction, and post-pandemic view of the construction industry. This study contributes to the knowledge body by providing a candid evaluation of the knowledge contributed by academia to deal with the risks of future pandemics in the global construction industry

Major opportunities of digital twins for smart buildings: a scientometric and content analysis

Purpose: Digital twins provide enormous opportunities for smart buildings. However, an up-to-date intellectual landscape to understand and identify the major opportunities of digital twins for smart buildings is still not enough. This study, therefore, performs an up-to-date comprehensive literature review to identify the major opportunities of digital twins for smart buildings. Design/methodology/approach: Scientometric and content analysis are utilised to comprehensively evaluate the intellectual landscape of the general knowledge of digital twins for smart buildings. Findings: The study uncovered 24 opportunities that were further categorised into four major opportunities: efficient building performance (smart “building” environment), efficient building process (smart construction site environment), information efficiency and effective user interactions. The study further identified the limitations of the existing studies and made recommendations for future research in the methodology adopted and the research domain. Five research domains were considered for future research, namely “real-time data acquisition, processing and storage”, “security and privacy issues”, “standardised and domain modelling”, “collaboration between the building industry and the digital twin developers” and “skilled workforce to enable a seamless transition from theory to practice”. Practical implications: All stakeholders, including practitioners, policymakers and researchers in the field of “architecture, engineering, construction and operations” (AECO), may benefit from the findings of this study by gaining an in-depth understanding of the opportunities of digital twins and their implementation in smart buildings in the AECO industry. The limitations and the possible research directions may serve as guidelines for streamlining the practical adoption and implementation of digital twins for smart buildings. Originality/value: This study adopted scientometric and content analysis to comprehensively assess the intellectual landscape of relevant literature and identify four major opportunities of digital twins for smart building, to which scholars have given limited attention. Finally, a research direction framework is presented to address the identified limitations of existing studies and help envision the ideal state of digital twins for smart buildings