Algebraic Bethe ansatz for integrable Kondo impurities in the one-dimensional supersymmetric t-J model

An integrable Kondo problem in the one-dimensional supersymmetric t-J model is studied by means of the boundary supersymmetric quantum inverse scattering method. The boundary K matrices depending on the local moments of the impurities are presented as a nontrivial realization of the graded reflection equation algebras in a two-dimensional impurity Hilbert space. Further, the model is solved by using the algebraic Bethe ansatz method and the Bethe ansatz equations are obtained. (C) 1999 Elsevier Science B.V.

Integrable Kondo impurities in the one-dimensional supersymmetric U model of strongly correlated electrons

Integrable Kondo impurities in the one-dimensional supersymmetric U model of strongly correlated electrons are studied by means of the boundary graded quantum inverse scattering method. The boundary K-matrices depending on the local magnetic moments of the impurities are presented as non-trivial realizations of the reflection equation algebras in an impurity Hilbert space. Furthermore, the model Hamiltonian is diagonalized and the Bethe ansatz equations are derived. It is interesting to note that our model exhibits a free parameter in the bulk Hamiltonian but no free parameter exists on the boundaries. This is in sharp contrast to the impurity models arising from the supersymmetric t-J and extended Hubbard models where there is no free parameter in the bulk but there is a free parameter on each boundary.

Integrable Kondo impurities in the one-dimensional supersymmetric extended Hubbard model

An integrable Kondo problem in the one-dimensional supersymmetric extended Hubbard model is studied by means of the boundary graded quantum inverse scattering method. The boundary K-matrices depending on the local moments of the impurities are presented as a non-trivial realization of the graded reflection equation algebras in a two-dimensional impurity Hilbert space. Further, the model is solved by using the algebraic Bethe ansatz method and the Bethe ansatz equations are obtained.

ERP 'old/new' effects: memory strength and decisional factor(s)

Event-related potentials (ERPs) were recorded while subjects made old/new recognition judgments on new unstudied words and old words which had been presented at study either once ('weak') or three times ('strong'). The probability of an 'old' response was significantly higher for strong than weak words and significantly higher for weak than new words. Comparisons were made initially between ERPs to new, weak and strong words, and subsequently between ERPs associated with six strength-by-response conditions. The N400 component was found to be modulated by memory trace strength in a graded manner. Its amplitude was most negative in new word ERPs and most positive in strong word ERPs. This 'N400 strength effect' was largest at the left parietal electrode (in ear-referenced ERPs). The amplitude of the late positive complex (LPC) effect was sensitive to decision accuracy (and perhaps confidence). Its amplitude was larger in ERPs evoked by words attracting correct versus incorrect recognition decisions. The LPC effect had a left > right, centro-parietal scalp topography (in ear-referenced ERPs). Hence, whereas, the majority of previous ERP studies of episodic recognition have interpreted results from the perspective of dual-process models, we provide alternative interpretations of N400 and LPC old/new effects in terms of memory strength and decisional factor(s). (C) 2002 Elsevier Science Ltd. All rights reserved.

Model specification tests in nonparametric stochastic regression models

In this paper, we consider testing for additivity in a class of nonparametric stochastic regression models. Two test statistics are constructed and their asymptotic distributions are established. We also conduct a small sample study for one of the test statistics through a simulated example. (C) 2002 Elsevier Science (USA).

Spatial data infrastructures model for developing countries: A case study of Nigeria

Dissertation submitted in partial fulfilment of the requirements for the Degree of Master of Science in Geospatial Technologies

Model spaces and Toeplitz kernels in reflexive Hardy spaces

This paper considers model spaces in an Hp setting. The existence of unbounded functions and the characterisation of maximal functions in a model space are studied, and decomposition results for Toeplitz kernels, in terms of model spaces, are established

Bayesian Inference in the Time Varying Cointegration Model

There are both theoretical and empirical reasons for believing that the parameters of macroeconomic models may vary over time. However, work with time-varying parameter models has largely involved Vector autoregressions (VARs), ignoring cointegration. This is despite the fact that cointegration plays an important role in informing macroeconomists on a range of issues. In this paper we develop time varying parameter models which permit cointegration. Time-varying parameter VARs (TVP-VARs) typically use state space representations to model the evolution of parameters. In this paper, we show that it is not sensible to use straightforward extensions of TVP-VARs when allowing for cointegration. Instead we develop a specification which allows for the cointegrating space to evolve over time in a manner comparable to the random walk variation used with TVP-VARs. The properties of our approach are investigated before developing a method of posterior simulation. We use our methods in an empirical investigation involving a permanent/transitory variance decomposition for inflation.

Extended truncated Tweedie-Poisson model

It has been argued that by truncating the sample space of the negative binomial and of the inverse Gaussian-Poisson mixture models at zero, one is allowed to extend the parameter space of the model. Here that is proved to be the case for the more general three parameter Tweedie-Poisson mixture model. It is also proved that the distributions in the extended part of the parameter space are not the zero truncation of mixed poisson distributions and that, other than for the negative binomial, they are not mixtures of zero truncated Poisson distributions either. By extending the parameter space one can improve the fit when the frequency of one is larger and the right tail is heavier than is allowed by the unextended model. Considering the extended model also allows one to use the basic maximum likelihood based inference tools when parameter estimates fall in the extended part of the parameter space, and hence when the m.l.e. does not exist under the unextended model. This extended truncated Tweedie-Poisson model is proved to be useful in the analysis of words and species frequency count data.

El reto del paisaje urbano en China, del Mall Comercial al espacio público

Las categorías del espacio introvertido y extrovertido definen por excelencia la estructura espacial, que ordena el ámbito de lo privado y lo público en la ciudad. La dualidad del espacio abierto y cerrado, vinculado a la estructura espacial de la ciudad clásica China, quedaba ordenado, justificado y vinculado mediante una estructura espacial muy definida. Sin embargo en el modelo de ciudad contemporánea, aflora la cuestión de la integración de estas categorías espaciales y su articulación dentro de una estructura urbana heterogénea y fuertemente alterada. ¿Cuáles serán los factores de cambio de la transición de un espacio comunitario introvertido a un espacio cívico abierto? Este proceso es un proceso que debe discurrir a un doble nivel espacial y político. Debe discurrir en paralelo a la transición de las categorías espaciales que ordenan identitariamente el ámbito urbano y la progresiva transición socio-cultural y política de una sociedad que debe gradualmente identificar y adoptar como propias las instituciones de gobierno local y su escenario, la ciudad.

Modelling the Knowledge Interface between Sales and Production Functions of a Company. Case: New Service Development Process.

Yrityksen sisäisten rajapintojen tunteminen mahdollistaa tiedonvaihdon hallinnan läpi organisaation. Idean muokkaaminen kannattavaksi innovaatioksi edellyttää organisaation eri osien läpi kulkevaa saumatonta prosessiketjua sekä tietovirtaa. Tutkielman tavoitteena oli mallintaa organisaation kahden toiminnallisesti erilaisen osan välinen tiedon vaihto. Tiedon vaihto kuvattiin rajapintana, tietoliittymänä. Kolmiulotteinen organisaatiomalli muodosti tutkimuksen pääteorian. Se kytkettiin yrityksen tuotanto- ja myyntiosiin, kuten myös BestServ-projektin kehittämään uuteen palvelujen kehittämisen prosessiin. Uutta palvelujen kehittämisen prosessia laajennettiin ISO/IEC 15288 standardin kuvaamalla prosessimallilla. Yritysarkkitehtuurikehikoita käytettiin mallintamisen perustana. Tietoliittymä nimenä kuvastaa näkemystä siitä, että tieto [tietämys] on olemukseltaan yksilöiden tai ryhmien välistä. Mallinnusmenetelmät eivät kuitenkaan vielä mahdollista tietoon [tietämykseen] liittyvien kaikkien ominaisuuksien mallintamista. Tietoliittymän malli koostuu kolmesta osasta, joista kaksi esitetään graafisessa muodossa ja yksi taulukkona. Mallia voidaan käyttää itsenäisesti tai osana yritysarkkitehtuuria. Teollisessa palveluliiketoiminnassa sekä tietoliittymän mallinnusmenetelmä että sillä luotu malli voivat auttaa konepajateollisuuden yritystä ymmärtämään yrityksen kehittämistarpeet ja -kohteet, kun se haluaa palvelujen tuottamisella suuremman roolin asiakasyrityksen liiketoiminnassa. Tietoliittymän mallia voidaan käyttää apuna organisaation tietovarannon ja tietämyksen mallintamisessa sekä hallinnassa ja näin pyrkiä yhdistämään ne yrityksen strategiaa palvelevaksi kokonaisuudeksi. Tietoliittymän mallinnus tarjoaa tietojohtamisen kauppatieteelliselle tutkimukselle menetelmällisyyden tutkia innovaatioiden hallintaa sekä organisaation uudistumiskykyä. Kumpikin tutkimusalue tarvitsevat tarkempaa tietoa ja mahdollisuuksia hallita tietovirtoja, tiedon vaihtoa sekä organisaation tietovarannon käyttöä.

Dynamic Model of a Small Once-Through Boiler

In this study, a model for the unsteady dynamic behaviour of a once-through counter flow boiler that uses an organic working fluid is presented. The boiler is a compact waste-heat boiler without a furnace and it has a preheater, a vaporiser and a superheater. The relative lengths of the boiler parts vary with the operating conditions since they are all parts of a single tube. The present research is a part of a study on the unsteady dynamics of an organic Rankine cycle power plant and it will be a part of a dynamic process model. The boiler model is presented using a selected example case that uses toluene as the process fluid and flue gas from natural gas combustion as the heat source. The dynamic behaviour of the boiler means transition from the steady initial state towards another steady state that corresponds to the changed process conditions. The solution method chosen was to find such a pressure of the process fluid that the mass of the process fluid in the boiler equals the mass calculated using the mass flows into and out of the boiler during a time step, using the finite difference method. A special method of fast calculation of the thermal properties has been used, because most of the calculation time is spent in calculating the fluid properties. The boiler was divided into elements. The values of the thermodynamic properties and mass flows were calculated in the nodes that connect the elements. Dynamic behaviour was limited to the process fluid and tube wall, and the heat source was regarded as to be steady. The elements that connect the preheater to thevaporiser and the vaporiser to the superheater were treated in a special way that takes into account a flexible change from one part to the other. The model consists of the calculation of the steady state initial distribution of the variables in the nodes, and the calculation of these nodal values in a dynamic state. The initial state of the boiler was received from a steady process model that isnot a part of the boiler model. The known boundary values that may vary during the dynamic calculation were the inlet temperature and mass flow rates of both the heat source and the process fluid. A brief examination of the oscillation around a steady state, the so-called Ledinegg instability, was done. This examination showed that the pressure drop in the boiler is a third degree polynomial of the mass flow rate, and the stability criterion is a second degree polynomial of the enthalpy change in the preheater. The numerical examination showed that oscillations did not exist in the example case. The dynamic boiler model was analysed for linear and step changes of the entering fluid temperatures and flow rates.The problem for verifying the correctness of the achieved results was that there was no possibility o compare them with measurements. This is why the only way was to determine whether the obtained results were intuitively reasonable and the results changed logically when the boundary conditions were changed. The numerical stability was checked in a test run in which there was no change in input values. The differences compared with the initial values were so small that the effects of numerical oscillations were negligible. The heat source side tests showed that the model gives results that are logical in the directions of the changes, and the order of magnitude of the timescale of changes is also as expected. The results of the tests on the process fluid side showed that the model gives reasonable results both on the temperature changes that cause small alterations in the process state and on mass flow rate changes causing very great alterations. The test runs showed that the dynamic model has no problems in calculating cases in which temperature of the entering heat source suddenly goes below that of the tube wall or the process fluid.

Applying the principles of life cycle assessment and costing in process modeling to examine profit-making capability

Static process simulation has traditionally been used to model complex processes for various purposes. However, the use of static processsimulators for the preparation of holistic examinations aiming at improving profit-making capability requires a lot of work because the production of results requires the assessment of the applicability of detailed data which may be irrelevant to the objective. The relevant data for the total assessment gets buried byirrelevant data. Furthermore, the models do not include an examination of the maintenance or risk management, and economic examination is often an extra property added to them which can be performed with a spreadsheet program. A process model applicable to holistic economic examinations has been developed in this work. The model is based on the life cycle profit philosophy developed by Hagberg and Henriksson in 1996. The construction of the model has utilized life cycle assessment and life cycle costing methodologies with a view to developing, above all, a model which would be applicable to the economic examinations of complete wholes and which would require the need for information focusing on aspects essential to the objectives. Life cycle assessment and costing differ from each other in terms of the modeling principles, but the features of bothmethodologies can be used in the development of economic process modeling. Methods applicable to the modeling of complex processes can be examined from the viewpoint of life cycle methodologies, because they involve the collection and management of large corpuses of information and the production of information for the needs of decision-makers as well. The results of the study shows that on the basis of the principles of life cycle modeling, a process model can be created which may be used to produce holistic efficiency examinations on the profit-making capability of the production line, with fewer resources thanwith traditional methods. The calculations of the model are based to the maximum extent on the information system of the factory, which means that the accuracyof the results can be improved by developing information systems so that they can provide the best information for this kind of examinations.

From Full stopping to transparency in a holographic model of heavy ion collisions

We numerically simulate planar shock wave collisions in anti-de Sitter space as a model for heavy ion collisions of large nuclei. We uncover a crossover between two different dynamical regimes as a function of the collision energy. At low energies the shocks first stop and then explode in a manner approximately described by hydrodynamics, in close similarity with the Landau model. At high energies the receding fragments move outwards at the speed of light, with a region of negative energy density and negative longitudinal pressure trailing behind them. The rapidity distribution of the energy density at late times around midrapidity is not approximately boost invariant but Gaussian, albeit with a width that increases with the collision energy.

Influence of software development process quality on product quality

Ohjelmistojen tärkeys nykypäivän yhteiskunnalle kasvaa jatkuvasti. Monia ohjelmistoprojekteja vaivaavat ongelmat aikataulussa pysymisestä, korkean tuottavuuden ylläpitämisestä ja riittävän korkeasta laadusta. Ohjelmistokehitysprosessien parantamisessa on naiden ongelmien minimoimiseksi tehty suuria investointeja. Investointien syynä on ollut olettamus ohjelmistokehityksen kapasiteetin suora riippuvuus tuotteen laadusta. Tämän tutkimuksen tarkoituksena oli tutkia Ohjelmistokehitysprosessien parantamisen mahdollisuuksia. Olemassaolevat ohjelmistokehityksen ja Ohjelmistokehitysprosessin parantamisen mallit, tekniikat ja metodologiat esiteltiin. Esiteltyjen mallien, tekniikoiden ja metodologioiden soveltuvuus analysoitiin ja suositus mallien käytöstä annettiin.