High-Energy emissions from the Pulsar/Be binary system PSR J2032+4127/MT91 213

PSR J2032+4127 is a radio-loud gamma-ray-emitting pulsar; it is orbiting around a high-mass Be type star with a very long orbital period of 25-50years, and is approaching periastron, which will occur in late 2017/early 2018. This system comprises with a young pulsar and a Be type star, which is similar to the so-called gamma-ray binary PSR~B1259-63/LS2883. It is expected therefore that PSR J2032+4127 shows an enhancement of high-energy emission caused by the interaction between the pulsar wind and Be wind/disk around periastron. Ho et al. recently reported a rapid increase in the X-ray flux from this system. In this paper, we also confirm a rapid increase in the X-ray flux along the orbit, while the GeV flux shows no significant change. We discuss the high-energy emissions from the shock caused by the pulsar wind and stellar wind interaction and examine the properties of the pulsar wind in this binary system. We argue that the rate of increase of the X-ray flux observed by Swift indicates (1) a variation of the momentum ratio of the two-wind interaction region along the orbit, or (2) an evolution of the magnetization parameter of the pulsar wind with the radial distance from the pulsar. We also discuss the pulsar wind/Be disk interaction at the periastron passage, and propose the possibility of formation of an accretion disk around the pulsar. We model high-energy emissions through the inverse-Compton scattering process of the cold-relativistic pulsar wind off soft photons from the accretion disk.Comment: 18 pages, 23 figures, 1 Table, accepted for publication in Ap

A critical review and comparative analysis of cost management on prefabricated construction research (2000–2022)

Prefabrication construction has gained attention in the construction industry. The cost of prefabrication has got mixed reviews. Cost management in prefabricated construction (CMPC) includes many cost considerations such as initial design costs, supply chain cost considerations, maintenance costs and assembly costs. These costs are inter-linked and thorough understanding on cost management is essential. It is important to develop a holistic cost management system to capture all the economic, social and environmental aspects of prefabricated construction. The aim of this research is to conduct as a critical review and analysis of cost management in prefabricated construction holistically. The literature review selected 63 articles for this research study from 2000 to 2022. The research showed that there is an uptake in research on this research area since 2005. The study identified four main research categories in CMPC namely 1) cost estimating, 2) cost optimization, 3) economic performance and 4) cost management models. Previous studies mostly focused on estimating costs and comparison studies with conventional construction. Recently studies focused more on developing cost model to integrate supply chains and other considerations into cost evaluation. Based on the literature review, there are several future directions in CMPC. Cost estimating should now focus on identifying the effect of each cost determinant in project scenarios to provide more accurate results. Future studies are also expected to focus on BIM and big-data based optimization models. © 2023 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group

The X-ray modulation of PSR J2032+4127/MT91 213 during the Periastron Passage in 2017

We present the Neil Gehrels Swift Observatory (Swift), Fermi Large Area Telescope (Fermi-LAT), and Karl G. Jansky Very Large Array (VLA) observations of the gamma-ray binary PSR J2032+4127/MT91 213, of which the periastron passage has just occurred in November 2017. In the Swift X-ray light curve, the flux was steadily increasing before mid-October 2017, however, a sharp X-ray dip on a weekly time-scale is seen during the periastron passage, followed by a post-periastron X-ray flare lasting for ~20 days. We suggest that the X-ray dip is caused by (i) an increase of the magnetization parameter at the shock, and (ii) the suppression due to the Doppler boosting effect. The 20-day post-periastron flare could be a consequence of the Be stellar disk passage by the pulsar. An orbital GeV modulation is also expected in our model, however, no significant variability is seen in the Fermi-LAT light curve. We suspect that the GeV emission resulted from the interaction between the binary's members is hidden behind the bright magnetospheric emission of the pulsar. Pulsar gating technique would be useful to remove the magnetospheric emission and recover the predicted GeV modulation, if an accurate radio timing solution over the periastron passage is provided in the future.Comment: 6 pages, including 2 figures. Accepted for publication in Ap

Unusual Dynamical Scaling in the Spatial Distribution of Persistent Sites in 1D Potts Models

The distribution, n(k,t), of the interval sizes, k, between clusters of persistent sites in the dynamical evolution of the one-dimensional q-state Potts model is studied using a combination of numerical simulations, scaling arguments, and exact analysis. It is shown to have the scaling form n(k,t) = t^{-2z} f(k/t^z), with z= max(1/2,theta), where theta(q) is the persistence exponent which characterizes the fraction of sites which have not changed their state up to time t. When theta > 1/2, the scaling length, t^theta, for the interval-size distribution is larger than the coarsening length scale, t^{1/2}, that characterizes spatial correlations of the Potts variables.Comment: RevTex, 11 page

Quasinormal Modes of Dirty Black Holes

Quasinormal mode (QNM) gravitational radiation from black holes is expected to be observed in a few years. A perturbative formula is derived for the shifts in both the real and the imaginary part of the QNM frequencies away from those of an idealized isolated black hole. The formulation provides a tool for understanding how the astrophysical environment surrounding a black hole, e.g., a massive accretion disk, affects the QNM spectrum of gravitational waves. We show, in a simple model, that the perturbed QNM spectrum can have interesting features.Comment: 4 pages. Published in PR

Insulated Wall Systems to Tackle Global Warming

Brief introduction to the problem: the growing awareness of climate change and its link to carbon dioxide emissions have caused concerns in the community. A substantial amount of carbon dioxide emitted is due to the energy consumed by residential households. Heating/cooling of a residential house consumes a large proportion of the total household energy. Purpose: This paper explores the concept by comparing thermal efficiency of the four most common external wall structures, with varying amounts of insulation added in the context of Sydney, Australia. Design/methodology/approach: Cost and thermal analysis for each wall type are calculated. Life cycle cost saving and payback period are then evaluated. Findings: It is found that up to 95.7% cost saving can be achieved in heating/cooling in comparing the use of insulated wall systems and air film. Cement sheet wall system is found to be the most cost effective wall system for insulation with minimum 50% of cost saving can be achieved. The results also identify substantial energy cost required for heating/cooling a house without insulation when the climate gets extreme. The payback period for the installation of the insulated wall systems can be achieved in 4.98 years for normal climate condition or 2.58 years for extreme climate condition. Practical implications: The community is currently at great risk of being unable to deal with climate change issue as not clear the effective use of insulated wall systems. This paper can help provide insight and suggestions for residential households in tackling global warming issue

Series Expansion Calculation of Persistence Exponents

We consider an arbitrary Gaussian Stationary Process X(T) with known correlator C(T), sampled at discrete times T_n = n \Delta T. The probability that (n+1) consecutive values of X have the same sign decays as P_n \sim \exp(-\theta_D T_n). We calculate the discrete persistence exponent \theta_D as a series expansion in the correlator C(\Delta T) up to 14th order, and extrapolate to \Delta T = 0 using constrained Pad\'e approximants to obtain the continuum persistence exponent \theta. For the diffusion equation our results are in exceptionally good agreement with recent numerical estimates.Comment: 5 pages; 5 page appendix containing series coefficient

Prospective Study on Retinal Nerve Fibre Layer Thickness Changes in Isolated Unilateral Retrobulbar Optic Neuritis

Purpose. To investigate the retinal nerve fibre layer (RNFL) thickness after unilateral acute optic neuritis using optical coherence tomography (OCT). Patients and Methods. This prospective cohort study recruited consecutive patients with a first episode of isolated, unilateral acute optic neuritis. RNFL thickness and visual acuity (VA) of the attack and normal fellow eye were measured at presentation and 3 months in both the treatment and nontreatment groups. Results. 11 subjects received systemic steroids and 9 were treated conservatively. The baseline RNFL thickness was similar in the attack and fellow eye (P≥0.4). At 3 months, the attack eye had a thinner temporal (P=0.02) and average (P=0.05) RNFL compared to the fellow eye. At 3 months, the attack eye had significant RNFL thinning in the 4 quadrants and average thickness (P≤0.0002) compared to baseline. The RNFL thickness between the treatment and nontreatment groups was similar at baseline and 3 months (P≥0.1). Treatment offered better VA at 3 months (0.1 ± 0.2 versus 0.3 ± 0.2 LogMAR, P=0.04). Conclusion. Generalized RNFL thinning occurred at 3 months after a first episode of acute optic neuritis most significantly in the temporal quadrant and average thickness. Visual improvement with treatment was independent of RNFL thickness

Fiber Bragg grating sensor for simultaneous measurement of displacement and temperature

Author name used in this publication: Hwayaw TamAuthor name used in this publication: Muhtesem Suleyman Demokan2000-2001 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe