We examine the development of potential and actual trade in the Czech Republic, Hungary, and Poland, using the gravity model for trade as an analytical device. However, recent literature indicates ...that the point estimates of the gravity equation for estimating trade potential are highly uncertain. Hence we base our conclusions on the concept of speed of convergence to potential trade. Examining only the dynamics of actual and potential trade is less dependent on the estimation methodology. Using panel error-correction models we find significant convergence to the estimated potential trade. We also give an explanation for the differences in the speed of convergence among the three countries based on the product-structure of exports and the effects of foreign direct investment. The conclusions drawn from our measure of the speed of convergence are robust across diverse estimation methodologies. J. Comp. Econ., June 2001 29(2), pp. 276–292. Economics and Research Department, National Bank of Hungary, H-1850, Budapest, Szabadság tér 8/9, Hungary. Copyright 2001 Academic Press.
Journal of Economic Literature Classification Numbers: C21, C23, C50, F10, F11, F12, F15.
The alignment of the CMB Cold Spot and the Eridanus supervoid suggests a physical connection between these two relatively rare objects. We use galaxy cata\-logues with photometric (2MPZ) and ...spectroscopic (6dF) redshift measurements, supplemented by low-redshift compilations of cosmic voids, in order to improve the 3D mapping of the matter density in the Eridanus constellation. We find evidence for a supervoid with a significant elongation in the line-of-sight, effectively spanning the total redshift range \(z<0.3\). Our tomographic imaging reveals important substructure in the Eridanus supervoid, with a potential interpretation of a long, fully connected system of voids. We improve the analysis by extending the line-of-sight measurements into the antipodal direction that interestingly crosses the Northern Local Supervoid at the lowest redshifts. Then it intersects very rich superclusters like Hercules and Corona Borealis, in the region of the Coma and Sloan Great Walls, as a possible compensation for the large-scale matter deficit of Eridanus. We find that large-scale structure measurements are consistent with a central matter underdensity \(\delta_0 \approx -0.25\), projected transverse radius \(r_{0}^{\perp}\approx 195\) Mpc/h with an extra deepening in the centre, and line-of-sight radius \(r_{0}^{\parallel}\approx500\) Mpc/h, i.e. an ellipsoidal supervoid. The expected integrated Sachs-Wolfe imprint of such an elongated supervoid is at the \(\Delta T_{\rm ISW} \approx -40 \mu K\) level, thus inappropriate to accounting for the Cold Spot pattern in the CMB.
Self-assembled quantum dots based on III-V semiconductors have excellent properties for applications in quantum optics. However, the presence of a 2D wetting layer which forms during the ...Stranski-Krastanov growth of quantum dots can limit their performance. Here, we investigate wetting layer formation during quantum dot growth by the alternative droplet epitaxy technique. We use a combination of photoluminescence excitation spectroscopy, lifetime measurements, and transmission electron microscopy to identify the presence of an InGaAs wetting layer in these droplet epitaxy quantum dots, even in the absence of distinguishable wetting layer photoluminescence. We observe that increasing the amount of Ga deposited on a GaAs (100) surface prior to the growth of InGaAs quantum dots leads to a significant reduction in the emission wavelength of the wetting layer to the point where it can no longer be distinguished from the GaAs acceptor peak emission in photoluminescence measurements.
Closing the development gap between rural and urban areas is one of the most important issues and social challenges both in Europe and in Hungary. However, because the main rural disadvantages and ...the connected scientific conceptions and professional approaches may differ from country to country or even region to region, it is very difficult to give integrated answers to the specific local problems. Our research results indicate that the unified principles and the relatively rigid regulatory framework of the connected support system have not been successful enough in the past decades in Hungary. We do not argue that positive results have been generated in many areas and rurality has been revalued from many aspects, but some of the rural localities have not yet regained their vitality. Using statistical analysis and empirical experience we highlighted the differences in the situation of the rural areas in Hungary, and also identified lag-ging groups of settlements both in terms of living conditions and in economic development. Additionally we gave a critical approach of the contro-versial practice of rural development, which proved ineffective in solving real problems many times, and we formulated new conceptual principles for policy discourses.
There are multiple ways to formalise the metatheory of type theory. For some purposes, it is enough to consider specific models of a type theory, but sometimes it is necessary to refer to the syntax, ...for example in proofs of canonicity and normalisation. One option is to embed the syntax deeply, by using inductive definitions in a proof assistant. However, in this case the handling of definitional equalities becomes technically challenging. Alternatively, we can reuse conversion checking in the metatheory by shallowly embedding the object theory. In this paper, we consider the standard model of a type theoretic object theory in Agda. This model has the property that all of its equalities hold definitionally, and we can use it as a shallow embedding by building expressions from the components of this model. However, if we are to reason soundly about the syntax with this setup, we must ensure that distinguishable syntactic constructs do not become provably equal when shallowly embedded. First, we prove that shallow embedding is injective up to definitional equality, by modelling the embedding as a syntactic translation targeting the metatheory. Second, we use an implementation hiding trick to disallow illegal propositional equality proofs and constructions which do not come from the syntax. We showcase our technique with very short formalisations of canonicity and parametricity for Martin-L\"of type theory. Our technique only requires features which are available in all major proof assistants based on dependent type theory.
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