The AzTEC mm-wavelength camera

AzTEC is a mm-wavelength bolometric camera utilizing 144 silicon nitride micromesh detectors. Here, we describe the AzTEC instrument architecture and its use as an astronomical instrument. We report on several performance metrics measured during a three-month observing campaign at the James Clerk Maxwell Telescope and conclude with our plans for AzTEC as a facility instrument on the Large Millimetre Telescope.     

Spitzer IRAC infrared colours of submillimetre-bright galaxies

High-redshift submillimetre-bright galaxies identified by blank field surveys at millimetre and submillimetre wavelengths appear in the region of the Infra Red Array Camera (IRAC) colour–colour diagrams previously identified as the domain of luminous active galactic nuclei (AGNs). Our analysis using a set of empirical and theoretical dusty starburst spectral energy distribution (SED) models shows that power-law continuum sources associated with hot dust heated by young (≲100 Myr old), extreme starbursts at z > 2 also occupy the same general area as AGNs in the IRAC colour–colour plots. A detailed comparison of the IRAC colours and SEDs demonstrates that the two populations are distinct from each other, with submillimetre-bright galaxies having a systematically flatter IRAC spectrum (≳1 mag bluer in the observed [4.5]–[8.0] colour). Only about 20 per cent of the objects overlap in the colour–colour plots, and this low fraction suggests that submillimetre galaxies powered by a dust-obscured AGN are not common. The red infrared colours of the submillimetre galaxies are distinct from those of the ubiquitous foreground IRAC sources, and we propose a set of infrared colour selection criteria for identifying SMG counterparts that can be used even in the absence of radio or Multiband Imaging Photometer for Spitzer (MIPS) 24 μm data.     

Identification of absorption lines of short half-life actinides in the spectrum of Przybylski’s star (HD 101065)

Absorption lines of some actinides, namely, actinium (Z = 89), protactinium (91), neptunium (93), plutonium (94), americium (95), curium (96), berkelium (97), californium (98), and einsteinium (99), were identified in the spectrum of one of the most peculiar main-sequence stars HD 101065 (Przybylski’s star). In the identification we used a high-resolution spectrum (R = 80 000) acquired at the 8.2-m ESO telescope.     

Measurement of the prominences magnetic field

A new type of magnetograph has been built capable to measure weak magnetic fields in the chromosphere and corona. Measurements of magnetic field in two prominences are demonstrated as examples.     

Contribution of ionospheric irregularities to the error of dual-frequency GNSS positioning

This paper investigates the third-order residual range error in the dual-frequency correction of ionospheric effects on satellite navigation. We solve the two-point trajectory problem using the perturbation method to derive second-approximation formulas for the phase path of the wave propagating through an inhomogeneous ionosphere. It is shown that these formulas are consistent with the results derived from applying perturbation theory directly to the eikonal equation. The resulting expression for the phase path is used in calculating the residual range error of dual-frequency global positioning system (GPS) observations, in view of second- and third-order terms. The third-order correction includes not only the quadratic correction of the refractive index but also the correction for ray bending in an inhomogeneous ionosphere. Our calculations took into consideration that the ionosphere has regular large-scale irregularities, as well as smaller-scale random irregularities. Numerical examples show that geomagnetic field effects, which constitute a second-order correction, typically exceed the effects of the quadratic correction and the regular ionospheric inhomogeneity. The contribution from random irregularities can compare with or exceed that made by the second-order correction. Therefore, random ionospheric irregularities can make a significant (sometimes dominant) contribution to the residual range error.     

Paleoenvironmental changes of the Yellow Sea during the Late Quaternary

 Based on stable isotope data and carbon and sulfur elemental analyses, the sedimentary environment of the Yellow Sea was significantly influenced by the sea level changes during the Late Quaternary. At the low sea level stand when the sea level was lower by 56 m, the salinity of seawater was reduced to about 7.6‰, and the sedimentation rate in the central part of the Yellow Sea was three times higher than the present rate. The high C/S ratio during the low sea level stand is strong evidence that sedimentation took place in a lower salinity environment than exists at present. Received: 25 September 1997 / Revision reveived: 15 June 1998     

Numerical models and ductile ultimate deformation response of post‐tensioned self‐centering moment connections

New steel moment‐resisting connections that incorporate post‐tensioning elements to provide a self‐centering capacity and devices to dissipate seismic input energy have recently been proposed and experimentally validated. Experimental studies have confirmed that these connections are capable of undergoing large lateral deformations with negligible residual drifts. To facilitate their implementation, accurate modeling of the behavior of systems incorporating post‐tensioned connections must be readily available to designers and researchers. A number of simplified models have been suggested in the literature by researchers trying to capture experimental results at the beam–column connections and thereby to predict the global response of structures incorporating such connections. To provide a clear set of guidelines for the modeling of post‐tensioned steel frames, for practicing engineers as well as researchers, in this paper three types of numerical models of increasing complexity are presented: (i) a sectional analysis procedure, (ii) a lumped plasticity spring frame leveled approach and (iii) a non‐linear solid finite element analysis to predict the response at ultimate deformation levels. The analytical results obtained from the numerical models predict well the structural behavior of these connections when compared with available experimental data. Even at the ultimate deformation level, analytical results are in good agreement with test results. Furthermore, detailing requirements are proposed to assure that flexural hinges form in the beams in order to improve the cyclic response of steel self‐centering connections when drifts exceeding the design drifts are imposed to the system. Experimental and analytical studies demonstrate that steel post‐tensioned self‐centering connections incorporating the proposed detailing in the beams develop an increased deformation capacity and thereby exhibit a ductile response while avoiding a sudden loss of their strength and stiffness. Copyright © 2008 John Wiley & Sons, Ltd.     

Seismic performance of a 1 : 15‐scale 25‐story RC flat‐plate core‐wall building model

Earthquake simulation tests were conducted on a 1 : 15‐scale 25‐story building model to verify the seismic performance of high‐rise reinforced‐concrete flat‐plate core‐wall building structures designed per the recent seismic code KBC 2009 or IBC 2006. The following conclusions can be drawn from the test results: (1) The vertical distribution of acceleration during the table excitations revealed the effect of the higher modes, whereas free vibration after the termination of the table excitations was governed by the first mode. The maximum values of base shear and roof drift during the free vibration are either similar to or larger than the values of the maximum responses during the table excitation. (2) With a maximum roof drift ratio of 0.7% under the maximum considered earthquake in Korea, the lateral stiffness degraded to approximately 50% of the initial stiffness. (3) The crack modes appear to be a combination of flexure and shear in the slab around the peripheral columns and in the coupling beam. Energy dissipation via inelastic deformation was predominant during free vibration after the termination of table excitation rather than during table excitation. Finally, (4) the walls with special boundary elements in the first story did not exhibit any significant inelastic behavior, with a maximum curvature of only 21% of the ultimate curvature, corresponding to an ultimate concrete compressive strain of 0.00638 m/m intended in the displacement‐based design approach. Copyright © 2014 John Wiley & Sons, Ltd.     

An integrated urban systems model with GIS

The main purpose of this paper is to explore a possible integration for the entire transportation modeling procedure – from data inventory to future demand forecasting – by implementing integrated land use and transportation models with a geographic information system (GIS). In order to make an integrated, procedural modeling system possible, Land Use and Transportation modeling system with GIS (LUTGIS) has been developed and presented in this paper.  There are four sub-systems in LUTGIS: (1) a data inventory system, (2) a traffic analysis zone generation system, (3) an integrated land use and transportation modeling system, and (4) a graphic user interface (GUI) system. Since the main target of this paper is to explore a possible way to create a viable system, LUTGIS integrates currently available and user-friendly computing technologies. For both transportation planners and administrative decision-makers, such an operable system is very desirable for sharing information so they may arrive at a consensus through the use of LUTGIS, an integrated land use and transportation modeling system. Received: 22 October 1998/Accepted 11 July 1999     

The Korean Integrated Model (KIM) System for Global Weather Forecasting

The Korea Institute of Atmospheric Prediction Systems (KIAPS) began a national project to develop a new global atmospheric model system in 2011. The ultimate goal of this 9-year project is to replace the current operational model at the Korea Meteorological Administration (KMA), which was adopted from the United Kingdom’s Meteorological Office’s unified model (UM) in 2010. The 12-km Korean Integrated Model (KIM) system, consisting of a spectral-element non-hydrostatic dynamical core on a cubed sphere grid and a state-of-the-art physics parameterization package, has been launched in a real-time forecast framework, with initial conditions obtained via the advanced hybrid four-dimensional ensemble variational data assimilation (4DEnVar) over its native grid. A development strategy for KIM and the evolution of its performance in medium-range forecasts toward a world-class global forecast system are described. Outstanding issues in KIM 3.1 as of February 2018 are discussed, along with a future plan for operational deployment in 2020.