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Infrastructure and sectoral output along the road to development
Rioja, Felix 한국국제경제학회 2004 International Economic Journal Vol.18 No.1
Public infrastructure is one of the foundations for economic growth. Empirical research has found that public infrastructure can have different effects in different sectors of the economy. The theoretical literature, however, has concentrated in one-sector growth models. This paper develops a three-sector model (agriculture, manufacturing and services) to study the effects of infrastructure. The model is calibrated and solved numerically using parameters from seven Latin American countries. Results show that the largest gains would have been obtained at an early stage of development in the 1960s decade. The seven Latin American countries would have also benefited from additional public investment in the 1990s, especially the service sector. This result also has implications for the early 2000s as infrastructure expenditures have not increased from the 1990s levels. [E62, O40]
Rioja, Marí,a J.,Dodson, Richard,Jung, TaeHyun,Sohn, Bong Won,Byun, Do-Young,Agudo, Ivá,n,Cho, Se-Hyung,Lee, Sang-Sung,Kim, Jongsoo,Kim, Kee-Tae,Oh, Chung Sik,Han, Seog-Tae,Je, Do-Heung,Ch American Institute of Physics 2014 The Astronomical journal Vol.148 No.5
<P>The Korean VLBI Network (KVN) is a new millimeter VLBI dedicated array with the capability to simultaneously observe at multiple frequencies, up to 129 GHz. The innovative multi-channel receivers present significant benefits for astrometric measurements in the frequency domain. The aim of this work is to verify the astrometric performance of the KVN using a comparative study with the VLBA, a well-established instrument. For that purpose, we carried out nearly contemporaneous observations with the KVN and the VLBA, at 14/7 mm, in 2013 April. The KVN observations consisted of simultaneous dual frequency observations, while the VLBA used fast frequency switching observations. We used the Source Frequency Phase Referencing technique for the observational and analysis strategy. We find that having simultaneous observations results in superior compensation for all atmospheric terms in the observables, in addition to offering other significant benefits for astrometric analysis. We have compared the KVN astrometry measurements to those from the VLBA. We find that the structure blending effects introduce dominant systematic astrometric shifts, and these need to be taken into account. We have tested multiple analytical routes to characterize the impact of the low-resolution effects for extended sources in the astrometric measurements. The results from the analysis of the KVN and full VLBA data sets agree within 2σ of the thermal error estimate. We interpret the discrepancy as arising from the different resolutions. We find that the KVN provides astrometric results with excellent agreement, within 1σ, when compared to a VLBA configuration that has a similar resolution. Therefore, this comparative study verifies the astrometric performance of the KVN using SFPR at 14/7 mm, and validates the KVN as an astrometric instrument.</P>
THE APPLICATION OF MULTIVIEW METHODS FOR HIGH-PRECISION ASTROMETRIC SPACE VLBI AT LOW FREQUENCIES
Dodson, R.,Rioja, M.,Asaki, Y.,Imai, H.,Hong, X.-Y.,Shen, Z. American Institute of Physics 2013 The Astronomical journal Vol.145 No.6
<P>High-precision astrometric space very long baseline interferometry (S-VLBI) at the low end of the conventional frequency range, i.e., 20 cm, is a requirement for a number of high-priority science goals. These are headlined by obtaining trigonometric parallax distances to pulsars in pulsar-black hole pairs and OH masers anywhere in the Milky Way and the Magellanic Clouds. We propose a solution for the most difficult technical problems in S-VLBI by the MultiView approach where multiple sources, separated by several degrees on the sky, are observed simultaneously. We simulated a number of challenging S-VLBI configurations, with orbit errors up to 8 m in size and with ionospheric atmospheres consistent with poor conditions. In these simulations we performed MultiView analysis to achieve the required science goals. This approach removes the need for beam switching requiring a Control Moment Gyro, and the space and ground infrastructure required for high-quality orbit reconstruction of a space-based radio telescope. This will dramatically reduce the complexity of S-VLBI missions which implement the phase-referencing technique.</P>
Dodson, Richard,Rioja, Marí,a J.,Jung, Tae-Hyun,Sohn, Bong-Won,Byun, Do-Young,Cho, Se-Hyung,Lee, Sang-Sung,Kim, Jongsoo,Kim, Kee-Tae,Oh, Chung-Sik,Han, Seog-Tae,Je, Do-Heung,Chung, Moon-Hee,Wi, American Institute of Physics 2014 The Astronomical journal Vol.148 No.5
<P>Oxygen-rich asymptotic giant branch (AGB) stars can be intense emitters of SiO (v = 1 and 2, J = 1 -> 0) and H2O maser lines at 43 and 22 GHz, respectively. Very long baseline interferometry (VLBI) observations of the maser emission provide a unique tool to probe the innermost layers of the circumstellar envelopes in AGB stars. Nevertheless, the difficulties in achieving astrometrically aligned H2O and v = 1 and v = 2 SiO maser maps have traditionally limited the physical constraints that can be placed on the SiO maser pumping mechanism. We present phase-referenced simultaneous spectral-line VLBI images for the SiO v = 1 and v = 2, J = 1 -> 0, and H2O maser emission around the AGB star R LMi, obtained from the Korean VLBI Network (KVN). The simultaneous multichannel receivers of the KVN offer great possibilities for astrometry in the frequency domain. With this facility, we have produced images with bona fide absolute astrometric registration between high-frequency maser transitions of different species to provide the positions of the H2O maser emission and the center of the SiO maser emission, hence reducing the uncertainty in the proper motions for R LMi by an order of magnitude over that from Hipparcos. This is the first successful demonstration of source frequency phase referencing for millimeter VLBI spectral-line observations and also where the ratio between the frequencies is not an integer.</P>
MEASURING THE CORE SHIFT EFFECT IN AGN JETS WITH THE EXTENDED KOREAN VLBI NETWORK
정태현,Richard Dodson,Maria J. Rioja,변도영,Mareki Honma,Jamie Stevens,Pablo de Vicente,손봉원 한국천문학회 2015 Journal of The Korean Astronomical Society Vol.48 No.5
We present our efforts for extending the simultaneous multi-frequency receiver system of the Korean Very Long Baseline Interferometry (VLBI) Network (KVN) to global baselines in order to measure the frequency-dependent position shifts in Active Galactic Nuclei (AGN) jets, the so called core shift effect, with an unprecedented accuracy (a few micro-arcseconds). Millimeter VLBI observations with simultaneous multi-frequency receiver systems, like those of the KVN, enable us to explore the innermost regions of AGN and high precision astrometry. Such a system is capable of locating the frequency dependent opacity changes accurately. We have conducted the feasibility test-observations with the interested partners by implementing the KVN-compatible systems. Here we describe the science case for measuring the core shift effect in the AGN jet and report progress and future plans on extending the simultaneous multi-frequency system to global baselines.}
KVN SOURCE-FREQUENCY PHASE-REFERENCING OBSERVATION OF 3C 66A AND 3C 66B
ZHAO, GUANG-YAO,JUNG, TAEHYUN,DODSON, RICHARD,RIOJA, MARIA,SOHN, BONG WON The Korean Astronomical Society 2015 天文學論叢 Vol.30 No.2
In this proceedings, preliminary results of the KVN Source-Frequency Phase-Referencing (SFPR) observation of 3C 66A and 3C 66B are presented. The motivation of this work is to measure the core-shift of these 2 sources and study the temporal evolution of the jet opacity. Two more sources were observed as secondary reference calibrators and each source was observed at 22, 43, and 86 GHz simultaneously. Our preliminary results show that after using the observations at the lower frequency to calibrate those at the higher frequency of the same source, the residual visibility phases for each source at the higher frequencies became more aligned, and the coherence time became much longer; also, the residual phases for different sources, within 10 degrees angular separations, follow similar trends. After reference to the nearby calibrator, the SFPRed maps were obtained as well as the astrometric measurements, i.e. the combined coreshift. The measurements were found to be affected by structural blending effects because of the large beamsize of KVN, but this can be corrected with higher resolution maps (e.g. KAVA maps).