Recent Previous Work Research Articles

Energy and reserve scheduling under correlated nodal demand uncertainty: An adjustable robust optimization approach

This paper presents a nonparametric approach based on adjustable robust optimization to consider correlated nodal demand uncertainty in a joint energy and reserve scheduling model with security constraints. In this model, up- and down-spinning reserves provided by generators are endogenously defined as a result of the optimization problem. Adjustable robust optimization is used to characterize the worst-case load variation under a given user-defined uncertainty set. This paper differs from recent previous work in two respects: (i) nonparametric correlations between nodal demands are accounted for in the uncertainty set and (ii) based on the binary expansion linearization approach, a mixed-integer linear model is provided for the optimization related to the worst-case demand. The resulting problem is formulated as a trilevel program and solved by means of Benders decomposition. Empirical results suggest that the effect of nodal correlations can be effectively captured by the robust scheduling model.

A demand based route generation algorithm for public transit network design

This paper presents a public transit network route generation algorithm. The main contribution of this work is the introduction of new route generation algorithms. The proposed route generation algorithm is tested on Mandl׳s Swiss Road network and the four large networks presented in recent previous work. Three parameters are used to evaluate the route sets generated by the proposed algorithm. These are the zero transfer percentage, the average travel time, and the total route cost. The route sets generated for the large networks have better parameter values compared to recent previous work.

The Prediction of Contaminant Transport through Soil: A Novel Two-Dimensional Model Approach

The transport of contaminants has been a problematic issue for many years, mainly due to the adverse impact of the contaminants on the quality of groundwater. In order to analyse this, this study has developed a prediction model that allows the early detection of possible contamination. Firstly, the paper introduces the concept of the modelling of contamination transport through a soil matrix. Then it presents a two-dimensional Convection-Dispersion Equation (CDE) for contaminant transport in a soil matrix. This includes the investigation of different reaction coefficients and time-dependent inlet boundary conditions, from which a numerical solution is derived. The study also verifies recent previous work in this area through the use of numerical programming. The results for soil contamination in two dimensions are presented in this research.

Thin Film Characterization Using Rotating Polarizer Analyzer Ellipsometer with a Speed Ratio 1:3

In a recent previous work, we proposed a rotating polarizer-analyzer ellipsometer (RPAE) in which the two elements are rotating synchronously in the same direction with a speed ratio 1:3. We applied this technique to bulk samples. In this work, we present theoretically the characterization of 100 nm SiO2 thin film using this spectroscopic RPAE. We assume a structure consisting of air (ambient)/SiO2 (thin film)/c-Si (substrate). The ellipsometric parameters ψ and Δ are calculated when a clean signal is received by the detector and when a hypothetical noise is imposed on this signal. The film thickness and the optical constants of the film are calculated for the noisy signal in the spectrum range 200 - 800 nm. The results are compared with the proposed thickness and with the accepted values for SiO2 optical constants.

Topological phases and the quantum spin Hall effect in three dimensions

The $Z_2$ invariant for filled bands in the ground states of systems with time reversal invariance characterizes the number of stable pairs of edge states. Here we study the $Z_2 $ invariant using band touching methods discussed in a recent previous work \cite{roy2006zcq} and extend the study to three dimensions. Band collisions preserve the $Z_2 $ invariant both in two and three dimensions, but there are crucial differences in the two cases. In three dimensions,we find a novel fourth $Z_2 $ invariant which is characterized by a "trapped monopole" in momentum space. If the monopole charge in half the Brillouin zone is odd, then atleast one of the monopoles cannot recombine with another monopole and vanish unlike the case when the monopole charge is even. We also point out the possibility of a three dimensional quantum spin Hall effect and discuss the connection of various topological invariants to such an effect.

The Human Touch and Mass Catastrophe

The valuable review by Hobfoll and his colleagues is an important distillation of recent science and previous work that can inform early response to those affected by mass violence. The five themes endorsed through this consensus process fit well with those identified through a range of other sources, including concepts such as psychological first aid and extending into the subsequent early intervention phase as the emergency settles. In many ways this review provides a challenge, or indeed to many challenges, for those who wish to take this field forward. Firstly, there must be recognition, not only of the cognitions, but of the affects that are the basic instinctive components of human response to catastrophe, to horror, to death, and to destruction. Fear, terror, anger, helplessness, rage, shock, grief, and many other feelings will dominate responses for both those directly affected and those who would help. This is central to one’s humanity. Intense attachment ideation also dominates response if there is separation from loved ones or if survival is threatened (Henderson & Bostock, 1977). Affects may impact on cognition. Experiencing the chaos of mass violence—the blood, dirt, gore, and devastation—means, as suggested, that safety is indeed a relative concept, often for a long time afterwards, one that is perhaps never experienced again, in the same way as it was before. As Slovic (1987), Slovic & Peters (2006), and others working in the area of risk perception have so clearly delineated, “risk as feelings” powerfully drives response with an automatic, rapid, “gut instinct,” “experiential” appraisal of threat. Perhaps immediate, intense affect is difficult for us, both scientifically and personally, so that how we stay with it and with those experiencing it, through uncertainty, danger, and the difficulties of the aftermath, requires knowledge and emotional skill repertoires we have to further define. I searched the article for the words compassion and empathy, but I could not find them, although I know all the contributors to be people with great compassion and great empathy. We will not have mass catastrophe without chaos, without affects, without compassion, and we should encompass these challenges in what we do and what we would advise others to do, through guidelines like these. The second challenge lies in the fluidity of human interactions through such experiences and the shifting interfaces of the victim/affected person-helper engagements. Psychiatry 70(4) Winter 2007 329

A statistically selected Chandra sample of 20 galaxy clusters - I. Temperature and cooling time profiles

We present an analysis of 20 galaxy clusters observed with the Chandra X-ray satellite, focusing on the temperature structure of the intracluster medium and the cooling time of the gas. Our sample is drawn from a flux-limited catalogue but excludes the Fornax, Coma and Centaurus clusters, owing to their large angular size compared to the Chandra field of view. We describe a quantitative measure of the impact of central cooling, and find that the sample comprises nine clusters possessing cool cores (CCs) and 11 without. The properties of these two types differ markedly, but there is a high degree of uniformity amongst the CC clusters, which obey a nearly universal radial scaling in temperature of the form T ∝ r ∼0.4 , within the core. This uniformity persists in the gas cooling time, which varies more strongly with radius in CC clusters (tcool ∝ r ∼1.3 ), reaching tcool < 1 Gyr in all cases, although surprisingly low central cooling times (<5 Gyr) are found in many of the non-CC systems. The scatter between the cooling time profiles of all the clusters is found to be remarkably small, implying a universal form for the cooling time of gas at a given physical radius in virialized systems, in agreement with recent previous work. Our results favour cluster merging as the primary factor in preventing the formation of

Prediction of High-Pressure Adsorption Equilibrium of Supercritical Gases Using Density Functional Theory

In this paper, we present the results of the prediction of the high-pressure adsorption equilibrium of supercritical gases (Ar, N2, CH4, and CO2) on various activated carbons (BPL, PCB, and Norit R1 extra) at various temperatures using a density-functional-theory-based finite wall thickness (FWT) model. Pore size distribution results of the carbons are taken from our recent previous work,(1,2) using this approach for characterization. To validate the model, isotherms calculated from the density functional theory (DFT) approach are comprehensively verified against those determined by grand canonical Monte Carlo (GCMC) simulation, before the theoretical adsorption isotherms of these investigated carbons calculated by the model are compared with the experimental adsorption measurements of the carbons. We illustrate the accuracy and consistency of the FWT model for the prediction of adsorption isotherms of the all investigated gases. The pore network connectivity problem occurring in the examined carbons is also discussed, and on the basis of the success of the predictions assuming a similar pore size distribution for accessible and inaccessible regions, it is suggested that this is largely related to the disordered nature of the carbon.

Crystal growth, microhardness and oxidation behavior of RMn2Si2 compounds (R = La, Ce, Pr, Nd, Sm, Gd)

RMn2Si2 (R=La, Ce, Pr, Nd, Sm, Gd) single crystals were grown from high temperature lead metal flux by slowly cooling under an argon atmosphere. The RMn2Si2 (R=Ce, Pr, Nd, Sm, Gd) crystals were obtained as thin plates with well-developed {001} faces. The largest crystals have maximum dimensions of about 2.3mm×2.3mm×0.02mm. LaMn2Si2 was generally obtained as powder of irregular shape. The as-grown RMn2Si2 (R=Ce, Pr, Nd, Sm, Gd) crystals were used for measurements of Vickers micro-hardness at room temperature, oxidation resistance heated in air, and magnetic susceptibility using a SQUID magnetometer at low temperatures. The values of the Vickers micro-hardness for the {001} faces of RMn2Si2 are in the range of 5.8±0.4 to 6.5±0.5GPa. The oxidation process of crystals was studied at temperatures below 1473K by TG–DTA analyses. The TG curves show that the oxidation of CeMn2Si2, PrMn2Si2, NdMn2Si2, SmMn2Si2, and GdMn2Si2 crystals starts at about 738, 979, 999, 784, and 763K, respectively. Weight gains of the compounds after TG determination were measured to be in the range of 16.4–29.2mass%. The results of the magnetic susceptibility measurements agree with recent previous work which has been done on these compounds.

Synthesis and characterisation of uranyl substituted malonato complexes: Part II: 13C CPMAS NMR spectroscopy related to structural diversity

The reaction of aliphatic diamine with malonic or substituted malonic acid and uranyl nitrate in the ratio 2:2:1 in aqueous media leads in most cases to one predominant product, usually with a metal–ligand ratio of 1:2, but in a few cases it leads to oligomers with metal–ligand ratios of 2:3, 3:4 and 3:5. The crystalline products are salts with diprotonated diamines as cations, but crystals can also be formed with salts of hexaaminecobalt(III). Representative structures have been determined by single crystal X-ray diffraction for: (C 4H 12N 2)[UO 2(C 4H 4O 4) 2(H 2O)]·1.5H 2O ( 5); (C 4H 14N 2)[UO 2(C 4H 4O 4) 2(H 2O)]·2H 2O ( 7); (C 4H 12N 2)[UO 2(C 7H 10O 4) 2(H 2O)]·H 2O ( 9); (C 10H 26N 2)[UO 2(C 7H 10O 4) 2(H 2O)]·2H 2O ( 10); (C 10H 26N 2)[(UO 2) 3(C 7H 10O 4) 5]·2H 2O ( 11) and {[Co(NH 3) 6][UO 2(C 4H 4O 4)(C 5H 6O 4)]} 2Cl 2·6H 2O ( 20). Compounds 5, 7, 9 and 10 possess similar, monomeric anion structures. The anion in 11 has an infinite zigzag chain structure containing three distinct types of U centres, linked by three kinds of bridging ligands. Compound 20 has a dimeric anion structure. Three new types of bonding mode have been identified in this study, tridentate (μ 2-1,3-bidentate and 1,5-bidentate), tetradentate (1,3-bidentate through both carboxylate groups) and tridentate (1,3-bidentate through one carboxylate group and 1-monodentate through the other). Several types of carbonyl environments have been identified by X-ray crystallography in the present and recent previous work [Zhang et al., Polyhedron 21 (2002) 69; Zhang et al., J. Alloys Compounds 271 (1998) 139; Tilley et al., unpublished data] and a general correlation between isotropic chemical shift values in the 13C CPMAS NMR spectra and the carbonyl type has been identified.

Solar cycle forecasting: A nonlinear dynamics approach

The problem of prediction of a given time series is examined on the basis of recent nonlinear dynamics theories. Particular attention is devoted to forecast the amplitude and phase of one of the most common solar indicator activities, the international monthly smoothed sunspot number. It is well known that the solar cycle is very dicult to predict due to the intrinsic complexity of the related time behaviour and to the lack of a successful quantitative theoretical model of the Sun's magnetic cycle. Starting from a recent previous work, we checked the reliability and accuracy of a forecasting model based on concepts of nonlinear dynamical systems applied to experimental time series, such as embedding phase space, Lyapunov spectrum, chaotic behaviour. The model is based on a local hypothesis of the behaviour on embedding space, utilising an optimal number of neighbour vectors to predict the future evolution. The performances of this method for the current 23rd solar cycle suggest its valuable insertion in the set of the so-called non-precursor statistical- numerical prediction techniques. The main task is to set up and to compare a promising numerical nonlinear prediction technique, essentially based on an inverse problem, with the most accurate prediction methods, like the so-called \precursor which appear now reasonably accurate in predicting \long-term Sun activity, with particular reference to \solar and \geomagnetic precursor methods based on a solar dynamo theory.

High‐Precision Radial Velocity Measurements of Some Southern Stars

ABSTRACTPrecise absolute radial velocities have been obtained at Mount John University Observatory for a number of southern stars, using the 1 m telescope and fiber‐fed echelle spectrograph. Only the stars that have been observed three or more times are presented, including 14 IAU standards and 11 program stars. Six echelle orders in the green (5000–5600 Å) are used. Many delicate steps have been undertaken in order to maintain the same conditions in both recording and reducing the spectra over a period of 27 months. The Th‐Ar lamp has been used for the wavelength calibration. The absolute radial velocities have been determined by cross‐correlation with synthetic spectra computed by R. L. Kurucz. The zero point has been adjusted using blue‐sky spectra. An additional strong correlation, between the measured velocities and photon counts in stellar and Th‐Ar spectra, has been detected for the PM3000 CCD camera and has been eliminated. A resulting precision of about 20–30 m s−1 has been obtained. The overall uncertainty of the absolute radial velocities was estimated to be about 100–200 m s−1. The present paper is a continuation of our recent previous work, including more details on the reduction process and the presentation of the radial velocities for more stars.

Pseudo-quaternary boro-carbides: a two sub-lattice model

We consider recently studied boro-carbides RE(Ni 1− x M x ) 2B 2C, with emphasis in RE=Y and Ho. Ho compounds exhibit in some cases spiral magnetic order. We extended a recent previous work on Heusler compounds to study the specific heat of Y boro-carbides doped with Co and to calculate the coupling between Ho moments in neighbouring planes. The effect of impurity disorder is included in the electronic structure via the Coherent Potential Approximation (CPA) and in the absence of experimental data for the pseudoquaternary specific heat, we restricted ourselves to the dilute limit and determine the impurity potential via Friedel's sum rule. The electron–phonon coupling ( λ( x)) is extracted from the measured superconducting transition temperature, using the Allen–Dines formula. The existent specific heat data for Y compounds is used to fix the parameters of the two sub-lattice model. Finally we study the change, with transition metal concentration, of the angle between moments of the spiral magnetic order.

The application of the vacuum degassing technique in steel plant in order to obtain new quality grades in non-oriented magnetic steel sheet

In the light of the author's more recent publications and previous research work, this paper seeks to review the progress made in the iron and steel manufacturing processes, and the new quality grades obtained in the field of non-oriented magnetic steel sheet as a consequence of eliminating impurities by applying the modern technique of vacuum degassing in steel plant.

Combined effects of sodium nitroprusside and propranolol on hypoxic pulmonary vasoconstriction.

Recent clinical experience and previous experimental work indicate that propranolol may reverse sodium-nitroprusside-induced inhibition of hypoxic pulmonary vasoconstriction (HPV). Accordingly, the authors decided to test this possibility in an experimental model that allows direct examination of pharmacologic influence on HPV. Six mongrel dogs were anesthetized with pentobarbital and intubated. Following a left thoracotomy, the left lower lobe (LLL) was ventilated independently but synchronously with the rest of the lung. Selective hypoxia of the LLL (95% nitrogen and 5% CO2) caused a 59 +/- 6% (mean +/- SE) decrease in the electromagnetically measured fraction of the cardiac output perfusing the LLL and a 287 +/- 65% increase in the pulmonary vascular resistance of the LLL from their respective prehypoxic values. Propranolol, 1 mg/kg intravenously, caused a 76 +/- 5% beta-blockade, as determined by an isoproterenol infusion test, but did not cause a significant change in the LLL HPV response. Sodium nitroprusside (SNP) infusion, caused a 38 +/- 4% decrease in systemic arterial pressure, and nearly abolished LLL HPV. Most important, the addition of propranolol to sodium nitroprusside did not significantly change the SNP induced inhibition of LLL HPV. The authors conclude that in acute lung disease, propranolol does not alter lobar HPV and does not reverse sodium nitroprusside inhibition of lobar HPV.

Branching ratios for transitions in Ne II and Ar II

Branching ratios have been measured for Ne II and Ar II transitions by observing the emission of photons produced by a beam of electrons incident on Ne and Ar at pressurs between 10 -3 and 10 -2 torr. In this way many difficulties encountered previously by using more conventional light sources to obtain absolute transition probabilities, are avoided. Our results are compared with branching ratios from recent theoretical calculations and previous experimental work. The theoretical results for Ne II appear to be quite reliable, while those for Ar II are not yet satisfactory.