34 research outputs found
The Effects of Trade, Aid, and Investment on China's Image in Developing Countries
One goal of China’s Go Out policy is to create goodwill in countries around the world. At the same time, China’s growing economic engagement has provoked much criticism. This paper is the first to study whether these activities change the attitudes of individuals in developing countries towards China at both the national and subnational level. Using repeated cross-sectional survey data from the Latinobarómetro, we analyze whether and how growing amounts of exports, foreign aid, and foreign direct investment from China to Latin America affect opinions on China within 18 Latin American countries over the 2002-2013 period. We run instrumental-variables regressions by exploiting exogenous variation in the supply of Chinese exports, aid, and investment proxied by China’s market penetration of developing countries outside Latin America. In contrast to the widespread criticism, we do not find evidence that China’s growing economic activities in the respective countries deteriorate average attitudes towards China — neither at the national nor the provincial level. However, our results show that the young, educated, and economically privileged population develops more positive views of China. We interpret this as evidence that China’s economic engagement creates winners and losers
Experimentelle Methoden in der Informatik
Dieser Report enthaelt die Ausarbeitungen von Vortraegen aus einem
Seminar gleichen Namens, das am 3./4. Juli 1995 am Institut f"ur
Programmstrukturen und Datenorganisation unter Leitung von Walter
Tichy, Ernst Heinz, Paul Lukowicz und Lutz Prechelt stattfand.
Die Artikel geben einen Ueberblick ueber die moegliche Funktion
und den Stellenwert experimentellen Vorgehens in verschiedenen Teilen
der Informatik, sowie einerseits deren wissenschaftstheoretische
Grundlage und andererseits ihre bisherige praktische Umsetzung
On kaonic hydrogen. Quantum field theoretic and relativistic covariant approach
We study kaonic hydrogen, the bound K^-p state A_(Kp). Within a quantum field
theoretic and relativistic covariant approach we derive the energy level
displacement of the ground state of kaonic hydrogen in terms of the amplitude
of K^-p scattering for arbitrary relative momenta. The amplitude of low-energy
K^-p scattering near threshold is defined by the contributions of three
resonances Lambda(1405), Lambda(1800) and Sigma^0(1750) and a smooth elastic
background. The amplitudes of inelastic channels of low-energy K^-p scattering
fit experimental data on near threshold behaviour of the cross sections and the
experimental data by the DEAR Collaboration. We use the soft-pion technique
(leading order in Chiral Perturbation Theory) for the calculation of the
partial width of the radiative decay of pionic hydrogen A_(pi p) -> n + gamma
and the Panofsky ratio. The theoretical prediction for the Panofsky ratio
agrees well with experimental data. We apply the soft-kaon technique (leading
order in Chiral Perturbation Theory) to the calculation of the partial widths
of radiative decays of kaonic hydrogen A_(Kp) -> Lambda^0 + gamma and A_(Kp) ->
Sigma^0 + gamma. We show that the contribution of these decays to the width of
the energy level of the ground state of kaonic hydrogen is less than 1%.Comment: 33 pages, 1 figure, latex, References are adde
Modelization of the EOS
This article summarizes theoretical predictions for the density and isospin
dependence of the nuclear mean field and the corresponding nuclear equation of
state. We compare predictions from microscopic and phenomenological approaches.
An application to heavy ion reactions requires to incorporate these forces into
the framework of dynamical transport models. Constraints on the nuclear
equation of state derived from finite nuclei and from heavy ion reactions are
discussed.Comment: 17 pages, 13 figures, contributed paper to the World Consensus
Initiative (WCI) book "Dynamics and Thermodynamics with Nucleonic Degrees of
Freedom
Effective Field Theory of Nuclear Forces
The application of the effective field theory (EFT) method to nuclear systems
is reviewed. The roles of degrees of freedom, QCD symmetries, power counting,
renormalization, and potentials are discussed. EFTs are constructed for various
energy regimes of relevance in nuclear physics, and are used in systematic
expansions to derive nuclear forces in terms of a number of parameters that
embody information about QCD dynamics. Two-, three-, and many-nucleon systems,
including external probes, are considered.Comment: 83 pages, 20 figures, commissioned for Prog. Part. Nucl. Phy
Nucleon and hadron structure changes in the nuclear medium and impact on observables
We review the effect of hadron structure changes in a nuclear medium using
the quark-meson coupling (QMC) model, which is based on a mean field
description of non-overlapping nucleon (or baryon) bags bound by the
self-consistent exchange of scalar and vector mesons. This approach leads to
simple scaling relations for the changes of hadron masses in a nuclear medium.
It can also be extended to describe finite nuclei, as well as the properties of
hypernuclei and meson-nucleus deeply bound states. It is of great interest that
the model predicts a variation of the nucleon form factors in nuclear matter.
We also study the empirically observed, Bloom-Gilman (quark-hadron) duality.
Other applications of the model include subthreshold kaon production in heavy
ion collisions, D and D-bar meson production in antiproton-nucleus collisions,
and J/Psi suppression. In particular, the modification of the D and D-bar meson
properties in nuclear medium can lead to a large J/Psi absorption cross
section, which explains the observed J/Psi suppression in relativistic heavy
ion collisions.Comment: 143 pages, 77 figures, references added, a review article accepted in
Prog. Part. Nucl. Phy
Roy-Steiner-equation analysis of pion-nucleon scattering
We review the structure of Roy-Steiner equations for pion-nucleon scattering,
the solution for the partial waves of the t-channel process , as well as the high-accuracy extraction of the pion-nucleon S-wave
scattering lengths from data on pionic hydrogen and deuterium. We then proceed
to construct solutions for the lowest partial waves of the s-channel process
and demonstrate that accurate solutions can be found if the
scattering lengths are imposed as constraints. Detailed error estimates of all
input quantities in the solution procedure are performed and explicit
parameterizations for the resulting low-energy phase shifts as well as results
for subthreshold parameters and higher threshold parameters are presented.
Furthermore, we discuss the extraction of the pion-nucleon -term via
the Cheng-Dashen low-energy theorem, including the role of isospin-breaking
corrections, to obtain a precision determination consistent with all
constraints from analyticity, unitarity, crossing symmetry, and pionic-atom
data. We perform the matching to chiral perturbation theory in the subthreshold
region and detail the consequences for the chiral convergence of the threshold
parameters and the nucleon mass.Comment: 101 pages, 28 figures; journal versio
AlN/GaN HEMTs grown by MBE and MOCVD: Impact of Al distribution
Binary AlN/GaN high electron mobility transistors (HEMTs) were grown by plasma-assisted molecular beam epitaxy (PA-MBE) as well as metal-organic chemical vapor deposition (MOCVD) and compared with regard to their structural and electrical properties. The investigated structures differ in Al distribution and composition of the AlN barrier due to characteristic differences of the two growth methods such as growth temperature and interface sharpness. While we observe a nearly pure AlN layer and an abrupt interface for MBE growth, a graded "AlN" barrier with a significant amount of Ga is found for the MOCVD grown structures which is reflected by the electrical properties of the HEMT structures. Si-implanted ohmic contacts were formed on MBE as well as MOCVD grown structures. The activation anneal step subsequent to implantation at temperatures ~1100°C changes the observed Al profiles of MBE structures and damages the active region, whereas MOCVD samples react insensitively and thus were able to be further processed. A maximum drain current of ~1.46 mm(-1) at a gate source voltage of +3 V is observed for the processed devices. A current-gain cut-off frequency of 89 GHz and maximum oscillation frequency of 208 GHz were measured, which demonstrate an excellent small-signal performance of AlN/GaN devices with 100nm gate length