On the Determination of the Polarized Sea Distributions of the Nucleon

The possibilities to determine the flavor structure of the polarized sea (antiquark) distributions of the nucleon via vector boson $(\gamma^*, W^{\pm}, Z^0)$ production at high energy polarized hadron--hadron colliders, such as the Relativistic Heavy--Ion Collider (RHIC), are studied in detail. In particular the perturbative stability of the expected asymmetries in two representative models for the (un)broken flavor structure are investigated by confronting perturbative QCD leading order predictions of the expected asymmetries with their next--to--leading order counterparts.Comment: 28 pages, LaTe

The jet quenching in high energy nuclear collisions and quark-gluon plasma

e investigate the energy loss of quark and gluon jets in quark-gluon plasma produced in central Au+Au collisions at RHIC energy. We use the physical characteristic of initial and mixed phases, which were found in effective quasiparticle model for SPS and RHIC energy. At investigation of energy loss we take into account also the production of hot glue at first stage. The energy loss in expanding plasma is calculated in dominant first order of radiation intensity with accounting of finite kinematic bounds. We calculate the suppression of $\pi^0$ - spectra with moderate high $p_{\perp}$, which is caused by energy loss of quark and gluon jets. The comparison with suppression of $\pi^0$ reported by PHENIX show, that correct quantitative description of suppression we have only in model of phase transition with decrease of thermal gluon mass and effective coupling $G(T)$ in region of phase transition plasma into hadrons (at $T \simeq T_c$). However quasiparticle model with increase of these values at $T \to T_c$ in accordance with perturbative QCD lead to too great energy loss of gluon and quark jets, which disagrees with data on suppression of $\pi^0$. Thus it is possible with help of hard processes to investigate the structure of phase transition. We show also, that energy losses at SPS energy are too small in order to be observable. This is caused in fact by sufficiently short plasma phase at this energy.Comment: 17 pages, 3 figures, 2 table

Monetary and exchange rate policy in Austria: an early example of policy coordination

This paper describes the evolution of Austrian exchange rate and monetary policy as an example of the benefits of policy coordination and credibility. This policy proved the performance of the Central Bank in achieving its twin objective of stabilizing the internal and external value of the currency. In this process, policymakers have sought to exploit the advantages of credibility by building a reputation for sticking to their policy. The evidence presented exhibits the increased coordination between Austrian and German nominal aggregates in the course of time. These accomplishments have apparently not tequired tying the real performance of the Austrian economy to any adverse permanent real consequences of German monetary policy, in particular, to its inflation-unemployment trade off.Austria ; Monetary policy - Austria

Concurrent processing simulation of the space station

The development of a new capability for the time-domain simulation of multibody dynamic systems and its application to the study of a large angle rotational maneuvers of the Space Station is described. The effort was divided into three sequential tasks, which required significant advancements of the state-of-the art to accomplish. These were: (1) the development of an explicit mathematical model via symbol manipulation of a flexible, multibody dynamic system; (2) the development of a methodology for balancing the computational load of an explicit mathematical model for concurrent processing; and (3) the implementation and successful simulation of the above on a prototype Custom Architectured Parallel Processing System (CAPPS) containing eight processors. The throughput rate achieved by the CAPPS operating at only 70 percent efficiency, was 3.9 times greater than that obtained sequentially by the IBM 3090 supercomputer simulating the same problem. More significantly, analysis of the results leads to the conclusion that the relative cost effectiveness of concurrent vs. sequential digital computation will grow substantially as the computational load is increased. This is a welcomed development in an era when very complex and cumbersome mathematical models of large space vehicles must be used as substitutes for full scale testing which has become impractical

The Kinetic Interpretation of the DGLAP Equation, its Kramers-Moyal Expansion and Positivity of Helicity Distributions

According to a rederivation - due to Collins and Qiu - the DGLAP equation can be reinterpreted (in leading order) in a probabilistic way. This form of the equation has been used indirectly to prove the bound $|\Delta f(x,Q)| < f(x,Q)$ between polarized and unpolarized distributions, or positivity of the helicity distributions, for any $Q$. We reanalize this issue by performing a detailed numerical study of the positivity bounds of the helicity distributions. To obtain the numerical solution we implement an x-space based algorithm for polarized and unpolarized distributions to next-to-leading order in $\alpha_s$, which we illustrate. We also elaborate on some of the formal properties of the Collins-Qiu form and comment on the underlying regularization, introduce a Kramers-Moyal expansion of the equation and briefly analize its Fokker-Planck approximation. These follow quite naturally once the master version is given. We illustrate this expansion both for the valence quark distribution $q_V$ and for the transverse spin distribution $h_1$.Comment: 38 pages, 27 figures, Dedicated to Prof. Pierre Ramond for his 60th birthda

Solving for Micro- and Macro- Scale Electrostatic Configurations Using the Robin Hood Algorithm

We present a novel technique by which highly-segmented electrostatic configurations can be solved. The Robin Hood method is a matrix-inversion algorithm optimized for solving high density boundary element method (BEM) problems. We illustrate the capabilities of this solver by studying two distinct geometry scales: (a) the electrostatic potential of a large volume beta-detector and (b) the field enhancement present at surface of electrode nano-structures. Geometries with elements numbering in the O(10^5) are easily modeled and solved without loss of accuracy. The technique has recently been expanded so as to include dielectrics and magnetic materials.Comment: 40 pages, 20 figure

Full Carbon Account for Russia.

The Forestry Project (FOR) at IIASA has produced a full carbon account (FCA) for Russia for 1990, together with scenarios for 2010. Currently, there are rather big question marks regarding the existing carbon accounts for Russia, and Russia is critical to the global carbon balance due to its size. IIASA is in a position to perform solid analysis of Russia because of the databases that the Institute has built over the years. FOR based this work on a comprehensive geographic information system comprising georeferenced descriptions of the environment and land of Russia, which in turn are based on a number of thematic, digitized maps and databases. For the Russian energy sector and other industrial sectors (except the forest industry), the project used emissions estimates from the recent IIASA study "Global Energy Perspectives" (1998). The project carried out a separate substudy for the Russian forest industry sector. According to FOR's estimate, the total fluxes (including energy and industry sectors) in Russia were a net source of 527 teragrams of carbon (Tg C) in 1990. To illustrate the possible development of the carbon pools and fluxes over the next 10 years, FOR developed three different scenarios for the period 1990-2010, reflecting different assumptions regarding Russia's GDP growth. According to these scenarios, Russia will continue to be a net source of carbon to the atmosphere with 156-385 Tg C in 2010, including the emissions from energy and other industrial sectors. However, analysis of the FCA also shows considerable uncertainties involved in the carbon accounting. These uncertainties exceed the calculated changes in the full flux balance for the period 1990-2010. At present, this raises grave questions regarding the reliability of any accounting system used to measure terrestrial ecosystems for compliance with the Kyoto Protocol.

Bloom-Gilman duality of the nucleon structure function and the elastic peak contribution

The occurrence of the Bloom-Gilman duality in the nucleon structure function is investigated by analyzing the Q**2-behavior of low-order moments, both including and excluding the contribution arising from the nucleon elastic peak. The Natchmann definition of the moments has been adopted in order to cancel out target-mass effects. It is shown that the onset of the Bloom-Gilman duality occurs around Q**2 ~ 2 (GeV/c)**2 if only the inelastic part of the nucleon structure function is considered, whereas the inclusion of the nucleon elastic peak contribution leads to remarkable violations of the Bloom-Gilman duality.Comment: in Proc. of the XVI European Conference on Few-body Problems in Physics, Autrans (France), July 199

Design of a real-time wind turbine simulator using a custom parallel architecture

The design of a new parallel-processing digital simulator is described. The new simulator has been developed specifically for analysis of wind energy systems in real time. The new processor has been named: the Wind Energy System Time-domain simulator, version 3 (WEST-3). Like previous WEST versions, WEST-3 performs many computations in parallel. The modules in WEST-3 are pure digital processors, however. These digital processors can be programmed individually and operated in concert to achieve real-time simulation of wind turbine systems. Because of this programmability, WEST-3 is very much more flexible and general than its two predecessors. The design features of WEST-3 are described to show how the system produces high-speed solutions of nonlinear time-domain equations. WEST-3 has two very fast Computational Units (CU's) that use minicomputer technology plus special architectural features that make them many times faster than a microcomputer. These CU's are needed to perform the complex computations associated with the wind turbine rotor system in real time. The parallel architecture of the CU causes several tasks to be done in each cycle, including an IO operation and the combination of a multiply, add, and store. The WEST-3 simulator can be expanded at any time for additional computational power. This is possible because the CU's interfaced to each other and to other portions of the simulation using special serial buses. These buses can be 'patched' together in essentially any configuration (in a manner very similar to the programming methods used in analog computation) to balance the input/ output requirements. CU's can be added in any number to share a given computational load. This flexible bus feature is very different from many other parallel processors which usually have a throughput limit because of rigid bus architecture