Showing papers by "Wrocław University of Technology published in 2004"
TL;DR: The observation of strong coupling of a single two-level solid-state system with a photon, as realized by a single quantum dot in a semiconductor microcavity, may provide a basis for future applications in quantum information processing or schemes for coherent control.
Abstract: Cavity quantum electrodynamics, a central research field in optics and solid-state physics, addresses properties of atom-like emitters in cavities and can be divided into a weak and a strong coupling regime. For weak coupling, the spontaneous emission can be enhanced or reduced compared with its vacuum level by tuning discrete cavity modes in and out of resonance with the emitter. However, the most striking change of emission properties occurs when the conditions for strong coupling are fulfilled. In this case there is a change from the usual irreversible spontaneous emission to a reversible exchange of energy between the emitter and the cavity mode. This coherent coupling may provide a basis for future applications in quantum information processing or schemes for coherent control. Until now, strong coupling of individual two-level systems has been observed only for atoms in large cavities. Here we report the observation of strong coupling of a single two-level solid-state system with a photon, as realized by a single quantum dot in a semiconductor microcavity. The strong coupling is manifest in photoluminescence data that display anti-crossings between the quantum dot exciton and cavity-mode dispersion relations, characterized by a vacuum Rabi splitting of about 140 microeV.
1,809 citations
TL;DR: In this paper, coal and pitch-derived carbonaceous materials were activated for 5h at 800°C using potassium hydroxide and 1:4 component ratio, and the porosity development of the resultant activated carbons was assessed by N2 sorption at 77 K and their capability of the charge accumulation in electric double layer was determined using galvanostatic, voltammetric and impedance spectroscopy techniques.
403 citations
TL;DR: Unstructured kinetic models to describe microalgal culture system including photoautotrophic, heterotrophic and mixotrophic specific growth rate as a function of light intensity and glucose concentration were proposed and demonstrated that the light intensity for autotrophic culture was 30–50 W m−2, glucose concentration forheterotrophic growth was >0.5 g l−1 and for mixotroph growth of Spirulina sp.
318 citations
TL;DR: This paper deals with a classic flow-shop scheduling problem with makespan criterion and proposes a new very fast local search procedure based on a tabu search approach.
295 citations
TL;DR: In this article, the authors address the issue of modeling spot electricity prices and present a number of models proposed in the literature to fit a jump diffusion and a regime switching model to spot prices from the Nordic power exchange.
Abstract: In this paper we address the issue of modeling spot electricity prices. After summarizing the stylized facts about spot electricity prices, we review a number of models proposed in the literature. Afterwards we fit a jump diffusion and a regime switching model to spot prices from the Nordic power exchange and discuss the pros and cons of each one.
245 citations
TL;DR: In this article, the binding energy of dihydrogen-bonded complexes of methane and its fluoro and chloro derivatives with lithium hydride was analyzed using ab initio methods as well as the Bader theory.
Abstract: The dihydrogen-bonded complexes of methane and its fluoro and chloro derivatives with lithium hydride are analyzed using ab initio methods as well as the Bader theory. All calculations were performed using Pople's basis sets (6-311++G(d,p), 6-311++G(2df,2pd), and 6-311++G(3df,3pd)) and the Dunning bases (aug-cc-pVDZ and aug-cc-pVTZ) within the MP2 method. The results of the calculations show that the binding energy for the analyzed complexes increases with the increase of the number of fluoro or chloro substituents, up to ∼7 kcal/mol. In the same order there is an increase of the electrostatic energy term, showing that for the CF3H···HLi complex the dihydrogen bond interaction is similar in nature as for the water dimer where a conventional O−H···O hydrogen bond exists, while for the CCl3H···HLi dimer the exchange energy term outweighs the electrostatic energy. Hence, the other attractive energy terms are important. A topological analysis based on the Bader theory supports the results of the ab initio cal...
242 citations
TL;DR: Strong NP-hardness of the makespan minimization problem for two different models of job processing time is proved for makespan, total completion time and total weighted completion time.
Abstract: The paper is devoted to some single machine scheduling problems, where job processing times are defined by functions dependent on their positions in the sequence. It is assumed that each job is available for processing at its ready time. We prove some properties of the special cases of the problems for the following optimization criteria: makespan, total completion time and total weighted completion time. We prove strong NP-hardness of the makespan minimization problem for two different models of job processing time. The reductions are done from the well-known 3-Partition Problem. In order to solve the makespan minimization problems, we suggest the Earliest Ready Date algorithms, for which the worst-case ratios are calculated. We also prove that the makespan minimization problem with job ready times is equivalent to the maximum lateness minimization problem.
242 citations
TL;DR: An analysis of the energetic parameters of the local minima suggests that rare AT base pair conformation is not populated due to the shallowness of this minimum, which completely disappears from the Gibbs free energy surface.
Abstract: The results of a comprehensive study on the double-proton transfer in Adenine−Thymine (AT) and Guanine−Cytosine (GC) base pairs at room temperature in gas phase and with the inclusion of environmental effects are obtained. The double-proton-transfer process has been investigated in the AT and GC base pairs at the B3LYP/6-31G(d) and MP2/6-31G(d) levels of theory. It has been predicted that the hydrogen-bonded bases possess nonplanar geometries due to sp3 hybridization of nitrogen atoms and because of the soft intermolecular vibrations in the molecular complexes. An analysis of the energetic parameters of the local minima suggests that rare AT base pair conformation is not populated due to the shallowness of this minimum, which completely disappears from the Gibbs free energy surface. The stabilization of canonic or rare forms of the DNA bases by water molecules and metal cations has been predicted by calculating the optimal configuration of charges (using differential product/transition state stabilization...
203 citations
TL;DR: In this paper, a new idea of increasing operational bandwidth of a compact planar inverted F antenna (PIFA) by introducing open-end slots in the ground plane under the radiating patch is described.
Abstract: This letter describes a new idea of increasing operational bandwidth of a compact planar inverted F antenna (PIFA) by introducing open-end slots in the ground plane under the radiating patch. The slots are not in the way of active modules of a wireless transceiver and thus the proposed antenna size reduction method is attractive from the point of view of practical implementation.
196 citations
TL;DR: This work investigates the behavior of the Schwarz Bayesian information criterion (BIC) by explaining the phenomenon of the overestimation and proposing a novel modification of BIC that allows the detection of main effects and pairwise interactions in a backcross population.
Abstract: The problem of locating multiple interacting quantitative trait loci (QTL) can be addressed as a multiple regression problem, with marker genotypes being the regressor variables. An important and difficult part in fitting such a regression model is the estimation of the QTL number and respective interactions. Among the many model selection criteria that can be used to estimate the number of regressor variables, none are used to estimate the number of interactions. Our simulations demonstrate that epistatic terms appearing in a model without the related main effects cause the standard model selection criteria to have a strong tendency to overestimate the number of interactions, and so the QTL number. With this as our motivation we investigate the behavior of the Schwarz Bayesian information criterion (BIC) by explaining the phenomenon of the overestimation and proposing a novel modification of BIC that allows the detection of main effects and pairwise interactions in a backcross population. Results of an extensive simulation study demonstrate that our modified version of BIC performs very well in practice. Our methodology can be extended to general populations and higher-order interactions.
186 citations
02 Mar 2004
TL;DR: In this article, the fault location in parallel transmission lines with availability of complete measurements from one end of the lines is considered, and a very simple first-order formula is derived, which does not require knowledge of impedances of the equivalent systems behind the line terminals.
Abstract: Fault location in parallel transmission lines with availability of complete measurements from one end of the lines is considered. Generalised models of fault loops and faults are used for formulation of the fault location algorithm. The derived algorithm has a very simple first-order formula and does not require knowledge of impedances of the equivalent systems behind the line terminals as well as use of pre-fault measurements. Application of the fault location algorithm to impedance measurement of the adaptive distance protection is considered. An issue of improving the fault location accuracy by compensating for shunt capacitances of the lines is addressed. Results of the evaluation with use of ATP-EMTP simulations are reported and discussed.
TL;DR: In this article, the application of natural zeolites from clinoptilolite group for mercury removal from industrial effluents from copper smelter and refinery was discussed.
TL;DR: In this paper, the authors present recent advances in the hydride-generation (HG) technique hyphenated with different discharges of the atomic emission spectrometry (AES) serving as excitation sources of hydrides-forming elements.
Abstract: This article presents recent advances in the hydride-generation (HG) technique hyphenated with different discharges of the atomic emission spectrometry (AES) [i.e. inductively-coupled plasma (ICP), microwave-induced plasma (MIP), direct-current plasma (DCP) and glow discharge (GD)], serving as excitation sources of hydride-forming elements. It surveys and discusses various aspects of vapour-phase introduction, comprising the instrumentation for performing the reaction, the influence of the chemical reaction conditions, the existence of chemical and non-chemical interference effects and the approaches to eliminating or lessening the interferences, as well as the analytical applications to real samples. In addition, it presents the latest trends in the technique, such as expansion of the scope to some transition and noble metals and the usage of organised surfactant-based media for the enhancement of the reaction properties.
TL;DR: In this paper, a connection between the semigroup of the Cauchy process and a mixed boundary value problem for the Laplacian in one dimension higher, known as the Mixed Steklov Problem, was established.
TL;DR: In this paper, a mean reverting jump diffusion model was proposed to model spot electricity prices and fit the model to data from the Nord Pool power exchange and find that it nearly duplicates the spot price's main characteristics.
Abstract: In this paper we address the issue of modeling spot electricity prices. After analyzing factors leading to the unobservable in other financial or commodity markets price dynamics we propose a mean reverting jump diffusion model. We fit the model to data from the Nord Pool power exchange and find that it nearly duplicates the spot price’s main characteristics. The model can thus be used for risk management and pricing derivatives written on the spot electricity price.
TL;DR: In this article, the applicability of microalga Spirulina sp. for trace element removal from the conditioned industrial effluent, from copper smelter and refinery, containing a variety of trace elements, particularly mercury, cadmium, ammonia-nitrogen in concentrations exceeding Polish permissible limits for effluents discharged into water and soil.
TL;DR: The activation of γ δ T cells by a broad range of bisphosphonates is reported and a pharmacophore model for γδ T cell activation is developed and a comparative molecular similarity index analysis (CoMSIA) approach is used to make quantitative relationships between γ ΔT cell activation by bisph phosphonates and their three-dimensional structures.
Abstract: γδ T cells are the first line of defense against many infectious organisms and are also involved in tumor cell surveillance and killing. They are stimulated by a broad range of small, phosphorus-containing antigens (phosphoantigens) as well as by the bisphosphonates commonly used in bone resorption therapy, such as pamidronate and risedronate. Here, we report the activation of γδ T cells by a broad range of bisphosphonates and develop a pharmacophore model for γδ T cell activation, in addition to using a comparative molecular similarity index analysis (CoMSIA) approach to make quantitative relationships between γδ T cell activation by bisphosphonates and their three-dimensional structures. The CoMSIA analyses yielded R2 values of ∼0.8−0.9 and q2 values of ∼0.5−0.6 for a training set of 45 compounds. Using an external test set, the activities (IC50 values) of 16 compounds were predicted within a factor of 4.5, on average. The CoMSIA fields consisted of ∼40% hydrophobic, ∼40% electrostatic, and ∼20% steric ...
TL;DR: In this article, the effects of adding isopropyl alcohol (IPA) to KOH etch depth measurements were investigated. And it was shown that adding IPA to Koh etch results in bulky hillocks formation on the whole etched area.
Abstract: Silicon wafers with (1 1 0), (3 3 1), (3 1 1) and (2 1 1) crystallographic orientations etched in KOH and KOH saturated with isopropyl alcohol solutions have been studied. Etch rates of selected (h k l) planes were estimated by direct etch depth measurements. The effects of IPA additive on etch rates, hillocks formation and surface roughness of considered planes were analysed. It was shown that IPA affects the planes of (h h l)-type, causing both their etch rate reduction and surface quality improvement. IPA addition to KOH solution does not reduce etch rates of (h l l)-type planes but results in bulky hillocks formation on the whole etched area. The type of IPA interaction with different crystallographic planes probably depends on bond configuration on a particular plane.
TL;DR: In this article, a detailed mechanism of oxidation of Re particles with different sizes is proposed based on a quantitative analysis of the XPS, O 2 uptake, TEM, and previous Raman results.
TL;DR: It is shown that, without precedence constraints and under the assumption that all processing times are bounded above, the makespan minimization problem is solvable in polynomial time, whereas the introduction of precedence constraints makes even the simplest version of this problem NP-hard.
TL;DR: Transition state stabilization (by electrostatic interactions, including hydrogen bonds) is found to be central to catalysis by the enzyme, with contributions from residues Arg90, Arg7, and Arg63.
Abstract: To investigate fundamental features of enzyme catalysis, there is a need for high-level calculations capable of modelling crucial, unstable species such as transition states as they are formed within enzymes. We have modelled an important model enzyme reaction, the Claisen rearrangement of chorismate to prephenate in chorismate mutase, by combined ab initio quantum mechanics/molecular mechanics (QM/MM) methods. The best estimates of the potential energy barrier in the enzyme are 7.4–11.0 kcal mol−1
(MP2/6-31+G(d)//6-31G(d)/CHARMM22) and 12.7–16.1 kcal mol−1
(B3LYP/6-311+G(2d,p)//6-31G(d)/CHARMM22), comparable to the experimental estimate of ΔH‡
= 12.7 ± 0.4 kcal mol−1. The results provide unequivocal evidence of transition state (TS) stabilization by the enzyme, with contributions from residues Arg90, Arg7, and Arg63. Glu78 stabilizes the prephenate product (relative to substrate), and can also stabilize the TS. Examination of the same pathway in solution (with a variety of continuum models), at the same ab initio levels, allows comparison of the catalyzed and uncatalyzed reactions. Calculated barriers in solution are 28.0 kcal mol−1
(MP2/6-31+G(d)/PCM) and 24.6 kcal mol−1
(B3LYP/6-311+G(2d,p)/PCM), comparable to the experimental finding of ΔG‡
= 25.4 kcal mol−1 and consistent with the experimentally-deduced 106-fold rate acceleration by the enzyme. The substrate is found to be significantly distorted in the enzyme, adopting a structure closer to the transition state, although the degree of compression is less than predicted by lower-level calculations. This apparent substrate strain, or compression, is potentially also catalytically relevant. Solution calculations, however, suggest that the catalytic contribution of this compression may be relatively small. Consideration of the same reaction pathway in solution and in the enzyme, involving reaction from a ‘near-attack conformer’ of the substrate, indicates that adoption of this conformation is not in itself a major contribution to catalysis. Transition state stabilization (by electrostatic interactions, including hydrogen bonds) is found to be central to catalysis by the enzyme. Several hydrogen bonds are observed to shorten at the TS. The active site is clearly complementary to the transition state for the reaction, stabilizing it more than the substrate, so reducing the barrier to reaction.
TL;DR: An extended version of Kaczmarz's algorithm is considered, previously analyzed by one of the authors, for overcoming the difficulty of inconsistent problems and it is proved that the approximations obtained are at a certain distance from the set of exact least-squares solutions.
TL;DR: Comparison with the active site of the enzyme from those of several species shows that the positions of charged active site residues correspond closely to the optimal catalytic field, showing that the enzyme has evolved specifically to stabilize the TS relative to the substrate.
Abstract: Chorismate mutase is a key model system in the development of theories of enzyme catalysis. To analyze the physical nature of catalytic interactions within the enzyme active site and to estimate the stabilization of the transition state (TS) relative to the substrate (differential transition state stabilization, DTSS), we have carried out nonempirical variation−perturbation analysis of the electrostatic, exchange, delocalization, and correlation interactions of the enzyme-bound substrate and transition-state structures derived from ab initio QM/MM modeling of Bacillus subtilis chorismate mutase. Significant TS stabilization by approximately −23 kcal/mol [MP2/6-31G(d)] relative to the bound substrate is in agreement with that of previous QM/MM modeling and contrasts with suggestions that catalysis by this enzyme arises purely from conformational selection effects. The most important contributions to DTSS come from the residues, Arg90, Arg7, Glu78, a crystallographic water molecule, Arg116, and Arg63, and a...
TL;DR: In this paper, the dynamics of the lattice response in the strongly nonlinear regime is governed by a semiclassical resonance between the phonon modes and the optically driven dynamics.
Abstract: Optically controlled coherent dynamics of charge (excitonic) degrees of freedom in a semiconductor quantum dot under the influence of lattice dynamics (phonons) is discussed theoretically. We show that the dynamics of the lattice response in the strongly nonlinear regime is governed by a semiclassical resonance between the phonon modes and the optically driven dynamics. We stress on the importance of the stability of intermediate states for the truly coherent control.
TL;DR: In this article, a heat and mass transfer model for grain drying in a spouted bed dryer with a draft tube was used. But the model was only applied to predict gas−solid flow behavior.
Abstract: For a description of the heat and mass transfer occurring during the drying of grain in a spouted bed dryer with a draft tube, a CFD modeling technique was used. The Eulerian−Eulerian multifluid modeling approach was applied to predict gas−solid flow behavior. A heat- and mass-transfer model was added as compiled executable code by means of UDF programming to FLUENT 6.1, expanding its abilities. Moisture was treated as UDS, and its transport in each phase and exchange between phases were predicted. The kinetics of drying was described by classical and diffusional models for periods I and II of drying, respectively. Results of the simulations were compared with experimental data and with values obtained from various correlations. CFD simulations predict very well the mass-transfer rate but underpredict the heat-transfer rate. Predicted values of the Nusselt and Sherwood numbers are above 2, in agreement with theory. The heat- and mass-transfer rates obtained from the correlations and CFD simulations were u...
TL;DR: In this article, an anthracite was chemically activated with sodium hydroxide under nitrogen flow at temperatures ranging from 600 to 830 °C, with a constant mass ratio: hydroxides/anthracite = 3.5 MPa.
TL;DR: In this paper, an analysis of the geometrical and energetic parameters was performed, indicating that the more strongly bonded complexes could be classified as X−H+δ−δ-δH−Y dihydrogen bonds, whereas the weaker ones may belong to the X −H···σ category.
Abstract: Ab initio studies of complexes HCCH···H2, FCCH···H2, HCCH···HLi, FCCH···HLi, HCCH···HBeH, FCCH···HBeH, HCCH···HBeF, and FCCH···HBeF with H···H intermolecular binding contacts were carried out up to the MP2/6-311++G(3df,3pd)/MP2/aug-cc-pVQZ level of theory. Binding energies extrapolated to the complete basis set (CBS) limit indicate that the results obtained at the MP2/6-311++G(3df,3pd) level of theory are almost saturated. An analysis of the geometrical and energetic parameters was performed, indicating that the more strongly bonded complexes could be classified as X−H+δ···-δH−Y dihydrogen bonds, whereas the weaker ones may belong to the X−H···σ category. In the first case, the electrostatic and exchange contributions are the most important energetic terms, whereas in the second case, the correlation term also makes a sizable contribution to the overall dimer stability. The atoms in molecules (AIM) theory was also applied to explain the nature of all of the complexes. A complete analysis of the different ...
Journal Article•
TL;DR: This paper focuses on providing a procedure that enables building analytical models of Cyclic Concurrent Processes Systems belonging to a system class considered in the paper, and the max-plus algebra formalism is employed.
Abstract: This paper is addressing an issue of distributed systems designing aimed at automated prototyping of Cyclic Concurrent Processes Systems. In such systems concurrent processes compete for access to shared system resources. In order to ensure that a system is deadlock and starvation-free, certain conditions must be satisfied. In this paper, these conditions guarantee that for a given pair (an initial state, a set of dispatching rules) the system - belonging to a specific class - has a steady cyclic state. However, system designers are interested in values of performance indices, such as a rate of resources or processes utilization or the period of the system cycle. Nowadays, the values of performance indices are provided mainly as a result of a simulation process, which requires much more processor power than in case of an analytical method. Thus, in this paper the authors focus on providing a procedure that enables building analytical models of Cyclic Concurrent Processes Systems belonging to a system class considered in the paper. To reach this aim the max-plus algebra formalism is employed. Both the conditions ensuring a cyclic process flow and steps of the procedure are the basis of a software tool, which can be used by designers to prototype systems of desired values of the performance indices. Thanks to the computer program the designers receive a useful tool that helps to validate and allocate distributed control procedures, even in a complex system, which is a composition of simpler systems. The procedure together with the software tool is the main outcome of this paper.
TL;DR: The results show that the stress-related and geometrical effects decrease the phase modal birefringence in both structures, which results in negative signs of dB/dp and dG/dp.
Abstract: We calculated the sensitivity of phase (dB/dp) and group (dG/dp) modal birefringence to hydrostatic pressure versus wavelength in two birefringent holey fibers of different construction, where B is the phase modal birefringence, G is the group modal birefringence, and p is the pressure applied to the fiber. The contributions of the geometrical effects that were related only to deformation of the holey structure and the stress-related contribution to the overall pressure sensitivities were analyzed separately. Our results show that these two factors decrease the phase modal birefringence in both structures, which results in negative signs of dB/dp and dG/dp. Furthermore, we demonstrate that the geometrical effects are much weaker than the stress-related effects and contribute only a few percent to the overall pressure sensitivity.
TL;DR: In this article, the spectral dependence of the phase modal birefringence for E 11 and E 21 spatial modes was measured for both spatial modes using scanning wavelength method.