bluuebunny/crossref_metadata_2025 huggingface dataset:
Zur quantentheoretischen Berechnung von Aktivierungsenergien für den Stoffübergang an Phasengrenzflächen von Ionenkristallen (IV). Zur radiochemischen Bestimmung und quantentheoretischen Berechnung von Aktivierungsenergien für den Stoffübergang an den Kristallflächen des NaCl
Authors: Winzer A.
Published: July 2007

ES wird gezeigt, daß zwischen der Aktivierungsenergie für den Stoffübergang an der jeweiligen Kristallfläche von Ionenkristallen und der Frequenz der Phonenen (longitudinal optische) eine direkte Proportionalität besteht, wobei wiederum als Proportionalitätskonstante das Plancksche Wirkungsquantum gefunden wurde. Damit konnte nachgewiesen werden, daß die in verschiedenen Zeitintervallen gemessenen unterschiedlichen Aktivierungsenergien für die Stoffübergangsprozesse an Phasengrenzflächen von Ionenkristallen auf das flächenspezifische Wachstum der Kristalle zurückgeführt werden können. So wurde mit NaCl‐Kristallfraktionen, die mechanisch beansprucht wurden (gemahlen und gesiebt) und somit relativ viele {111}‐ bzw. {110}‐Flächen enthielten, experimentell eine Aktivierungsenerhalten, die mit dem quantentheoretisch berechneten Wert übereinstimmt, wenn die Frequenz der Phononen für diese Ausbreitungsrichtung in die abgeleitete Gleichung eingesetzt wurde. Auch bei NaCl‐Kristallfraktionen, die nahezu ausschließlich Würfelflächen enthielten, konnte diese Beziehung bestätigt werden. Dies ist ein weiterer Hinweis dafür, daß bei Stoffübergangsprozessen an Phasengrenzflächen von Ionenkristallen quantenmechanische Gesetzmäßigkeiten von Bedeutung sind.
Herstellung und ausgewählte physikalische Eigenschaften von ZnSiP2
Authors: Becherer H. , Buhrig E. , Hein K. , John M. , Kirsten P. , Schneider H. A. , Siegel W. , Winkler K.
Published: July 2007

Undotierte ZnSiP2‐Kristalle, die nach verschiedenen Methoden gezüchtet wurden (Gasphasentransport, Lösungszüchtung), zeigen teilweise beträchtliche Differenzen in ihren physikalischen Eigenschaften. Ziel der Arbeit ist, es, Zusammenhänge zwischen der Herstellung von ZnSiP2, der Qualität der eingesetzten Ausgangsstoffe und den physikalischen Eigenschaften der halbleitenden Verbindung aufzuzeigen. Messungen des Hall‐Effektes, der Leitfähigkeit, der Lumineszenz und der Protonenrückstreuung ergaben Informationen über die Perfektion und die Homogenität der Kristalle sowie über Störstellen und Rekombinationszentren, die für die verschiedenen Züchtungsmethoden charakteristisch sind. Der Einfluß der Dotierung durch verschiedene Elemente auf die Eigenschaften von lösungsgezüchteten ZnSiP2‐Kristallen wurde untersucht.
A simple scheme for describing the motion of dislocations in silicon
Authors: Fischer A.
Published: July 2007

The velocity of dislocations in silicon single crystals was investigated in dependence on temperature and stress. A simple scheme for the description of dislocation motion valid in the temperature range of 650 to 850 °C and the stress range of 0.2 to 5.0 kp/mm2 was derived.
Metallurgy of bronze‐process A‐15 superconducting composites
Authors: Livingston J. D.
Published: July 2007

Several aspects of the metallurgy of multifilamentary composites of Nb3Sn, V3Ga, and other A‐15 superconductors produced by the bronze process are reviewed. Among the factors discussed are phase diagrams, reaction kinetics, alloying effects, and microstructure‐properties relations.
Investigations on nitride layer formation at the iron surface during gas nitriding
Authors: Jentzsch W.‐D. , Böhmer S.
Published: July 2007

The morphology of the nitride layer forming at gas nitriding can decisively be influenced by the pretreatment of the surface. At a temperature of about 550 °C an activated surface very swiftly covers with iron nitrides. After passivating of the surface the nitride formation and the geometrical order of the nitride layer are determined by the heating rate. At high heating rates the formation of iron nitrides is localized to a few spots and the extension of the nitride layer proceeds by the growth of these spots. At low heating rates the surface is reactivated by the reducing gas before reaching the nitriding temperature. By further investigations is shown that nitriding of the surface starts with the formation of γ′‐nitrides. ϵ‐Nitrides occur in the further process of nitriding as a second layer on the γ′‐phase.
Growth of sapphire by the kyropoulus method
Authors: Perner B. , Kvapil Josef , Stránský V. , Kvapil Jiři
Published: July 2007

Single crystals of leuko‐sapphire (α‐Al2O3) are grown from the melt by an improved Kyropoulos technique using Mo or W crucibles. The influence of the temperature field on the structural and optical quality has been studied. Best results were obtained when heat losses from crystal and melt are minimized.
Switching Behaviour of Pb5Ge3O11 Single Crystals
Authors: Blumberg H. , Kürsten H. D.
Published: July 2007

Single crystals of lead germanate have been grown by Czochralski method. Hysteresis and switching pulses could only be measured after treating the crystal samples at elevated temperature and electrical a.c. field. Hysteresis is strongly frequency dependent. We observed the motion of the domain walls in polarized light simultaneously. The hysteresis loop is distorted at elevated temperature because of electric conductivity of the crystals. Temperature dependence of electric conductivity has been measured.
EPR and Optical Absorption Spectra of Cr3+ Ions in Lithium Sulphate Single Crystals
Authors: Alybakov A. A. , Bujko V. M. , Sharsheev K.
Published: July 2007

Optical absorption and EPR spectra of Li2SO4 · H2O crystals doped with Cr3+ are studied at liquid nitrogen temperature. The bands are found in absorption spectra with maxima about 17000, 23 800 and 37 200 cm−1, assigned to the 4A2 → 4T2, 4A2 → 4T1 and 4A2 → 4T1 (4P) transitions, respectively. The crystal field theory parameters were determined and appeared to be as follows: Dq = 1700 cm−1, B = 667 cm−1, C = 3002 cm−1.

The lines resulting from Cr3+ ions are found in EPR spectra. All lines are doublets, which is indicative of presence of two magnetically unequivalent centre positions, and have the hyperfine structure resulting from interaction of the unpaired electron spin with Cr53 isotope nucleus. Centres are oriented in such a way, that z‐axes, corresponding to two centre positions, are situated at both sides of a‐axis at an angle of about 3°. Spin Hamiltonian parameters were found as follows: gx = 1.985, gy = 1.984, gz = 1.988, D = 0.130 cm−1, E = 0.016 cm−1, |A| = 17.8 · 10−4 cm−1.
In‐situ Deformation of Polymers in the HVEM
Authors: Michler G. H.
Published: July 2007

The advantages of the High Voltage Electron Microscopy for investigations of the deformation mechanisms in polymers are mentioned. Amorphous one‐ and tow‐phase polymers, showing microprocesses of deformation and fracture in close connection with crazing, are investigated in detail. In the glassy polymers the structure of the crazes can be very different in dependence on the polymer morphology, the testing parameters, and others. Semi‐quantitative relationships between the microprocesses, the fracture toughness, and the polymer morphology could be obtained for high‐impact polymers.
Temperature dependence of secondary electron emission from SiO2‐layers
Authors: Fitting H.‐J.
Published: July 2007

By means of a “random walk model” the escape depths of secondary electrons (SE) can be obtained as a consequence of interaction with LO‐phonons. The measured temperature dependence of the SE‐yield leads to a high energetic LO‐mode with ħω ⋍ 140 meV in amorphous SiO2 influencing dominantly the electronic slowing down process.
Investigation of PbTiO3 crystal lattice defects by transmission electron microscopy
Authors: Dobrikov A. A. , Presnyakova O. V. , Zaitsev V. I. , Prisedskii V. V. , Pan'ko G. F.
Published: July 2007

The investigation of PbTiO3 single crystal structure was carried out by the method of transmission electron microscopy (TEM). It is shown that the following types of defects are observed: ferroelectric 90°‐and 180°‐domain boundaries, dislocations and their complexes, and planar defects.
Kinetics of dissolution of BaF2 crystals
Authors: Smirnov A. E. , Urusovskaya A. A.
Published: July 2007

Kinetics of dissolution of BaF2 crystals in aqueous solutions of HNO3 and HCl acids have been studied for the different acid concentrations in the temperature interval 20–100°C. It is established that this process is diffusion controlled. Activation energy is constant, but pre‐exponential factor is dependent on the concentration of the acid.
Etching of CaF2 single crystals in silica gels
Authors: Patel A. R. , Kotak M. D.
Published: July 2007

Etching of {111} cleavage faces of CaF2 crystals in aqueous solution of 50% HCl is carried out in citric acid set silica gel, and the kinetics of growth of etch pits at the sites of dislocations is investigated as a function of temperature, time of etching and height of gel column above the crystal surface. It is observed that the transient period required to initiate etch pit at the sites of a dislocation decreases (1) at particular temperature, with a decrease in gel height, and (2) for a particular gel height, with an increase in the temperature of etching. It is also observed that the morphology of dislocation etch pits remains triangular irrespective of the gel height and the temperature of etching. The results are compared with those of solution etching and discussed.
Dielectric relaxation in nematic, smectic A and C phases in the MHz region
Authors: Kresse H. , Wiegeleben A. , Demus D.
Published: July 2007

The dielectric properties of four 4‐n‐alkyloxyphenyl 4‐n‐alkyloxybenzoates with nematic, smectic C and partly additional SA phases were investigated. In 2 substances for ϵ′ reproducible values also in the smectic phases resulted allowing to conclude on a good orientation in the samples. In all 4 substances the dielectric relaxation in the MHz region was measured and the respective activation energies were determined. The molecular mobility in the SC phases is higher than in the SA phases, however comparable with that of the nematic phases. In all 3 phase types a single relaxation mechanism exists, which is explained as rotation of the molecules around a short axis.
Investigation of the interaction of quartz with H2 under supply of mechanical energy (I)
Authors: Hennig H.‐P. , Ebert I. , Steinike U. , Geissler H. , Kretzschmar U.
Published: July 2007

The gas molecules absorbed during mechanical activation of quartz in a H2 atmosphere are situated as well as the formed E′ centres in the amorphous ranges. The concentrations of the E′ centres are about one order of magnitude less after activation in H2 than after an activation in Ar. Hence and because of the existence of a proton doublet (splitting of about 73 G) in the EPR spectra a chemical interaction of a part of the absorbed H2 molecules with quartz is concluded.
On the characterization of electrically active inhomogeneities in semiconductor silicon by charge collection at schottky barriers using the SEM‐EBIC (II). Contrast due to defects
Authors: Kittler M.
Published: July 2007

The influence of the control variables (E0, Ib, Ur) as well as the semiconductor parameters (ϱ, L) on the defect contrast of direct irradiated Schottky barriers is investigated. The resolution of the subsurface regions is enhanced by increasing the primary beam energy E0. The sharply imaged region can be extended into the depth of the crystal by applying a reverse bias Ur. Contrast width broadenings are observed in high‐ohmic material, if increasing the beam current Ib, which may be annuled by switching on Ur. Against the generally held view the diffusion‐induced contrast width broadening of defects (or parts of them) located outside the depletion layer was found as an extremely small fraction of the diffusion length L. Thus in rough approximation the contrasts can be interpreted as a superposition of the in general club‐shaped generation volume and the defect shape.
A model of the effect of R.T. preageing on the nucleation of η′‐precipitation in Al‐Zn‐Mg alloys
Authors: Radomsky M. , Löffler H. , Lendvai J. , Ungár T. , Kovács I.
Published: July 2007

The effect of R.T. preageing on the precipitation of the η′ particles was investigated in two Al‐Zn‐Mg alloys. The results are explained by a model according to which during or immediately after the quench to RT vacancy, or vacancy‐zinc clusters (nuclei) are formed. The heterogeneous formation of η′ particles during the artificial ageing takes place at the nuclei or at over‐critical size GPZ in the more concentrated alloy or at solute‐rich regions left behind after the complete reversion of GPZ in the alloy with lower Zn concentration.
The interaction of oxygen with the iron (111) surface, mainly studied by AES
Authors: Müsig H.‐J. , Arabczyk W.
Published: July 2007

The cleaned surface was oxidized by means of pure oxygen at a pressure of 3 × 10−6 – 3 × 10−3 pa and at temperatures of 300 K, 370 K, and 620 K. The Auger peaks of high energy (for oxygen at 510 eV and for iron at 703 eV) were used for the quantitative determination of the oxygen coverage on the iron surface. The experimental results on the change of oxygen coverage as a function as a function of the dose are interpreted by means of a theoretical model and provided definite informations about the bonding state of the adsorbate. In the lower energy part of the Auger spectrum there appear peak shape modifications during oxidation. These observations allow us to suppose that in the process of oxidation there are in action two kinds of chemical bonding of oxygen with iron differing by density of states in the valence band.
The structure and electrical resistance of thin scandium films (II). F.C.C.–lattice phase observed in films obtained in a vacuum of 10−8 Torr
Authors: Loboda V. B. , Protsenko I. E.
Published: July 2007

Phase composition of the Sc‐films up to 200 Å thick obtained in a vacuum of 3 · 10−8 Torr, condensation rate being ω ⋍ 1 to 6 Å/s and ω ⋍ 40 å/s up to 10−7 Torr, have been studied by an electron‐diffraction examination. A phase with an f.c.c.‐lattice and a lattice parameter a = 4.76 to 4.80 ± 0.01 Å 0.01 Å is observed in films d ≲ 60 Å thick, whilst with films having a thickness d ≳ 90 Å a h.c.p.‐phase is characteristic for solid specimens. Two‐phase composition is observed in an interjacent interval of thicknesses.

An analysis performed permitted to conclude that the f.c.c.‐phase observed is a ScHx‐hydride forming during the post‐condensation delay time on a basis of a poly‐morphic modification.
Information on the early decomposition behaviour in Al‐Zn(6)‐Mg(X) alloys by an analytical description of isothermal resistivity curves
Authors: Fabian H.‐G.
Published: July 2007

Based on a theoretically derived expression for the extra‐resistivity resulting from the formation of GP‐Zones

equation image

isothermal resistivity measurements with Al‐Zn(6 at.%)–Mg(0.81; 1.73 at.%) alloys were analysed. A comparison of both expressions d(ln ϱex)/dt and d(ln f)/dt yields statements on the early stage of decomposition behaviour, especially, whether up to a considered time point size growth happened. The evaluated examples lead to the conclusion that size growth is most probably to exclude up to the time point of 4T.

The Ta‐dependence of the maximum value of extra‐resistivity is explained by an equilibrium distribution of bigger particles of a smaller number at higher aging temperatures, of smaller particles of a greater number at lower aging temperatures and by the assumption, that the amount of solute atoms inside the GP‐zones is decreasing with rise of Ta.
Comparative structural investigations of mechanically‐treated MgO powder (I) type of stress: Pressure and shear
Authors: Kretzschmar U. , Ebert I. , Steinike U. , Hennig H.‐P.
Published: July 2007

MgO is treated up to 95 hours in a vibration mill by means of pressure and shear. The. type and distribution of the mechanically‐induced disorder in the grains of the powder is investigated by X‐ray diffraction and electronparamagnetic resonance (EPR). The disorder investigated by the two methods is characterized by an almost equal temperature behaviour which is determined by strongly disturbed surface‐near ranges of the individual grains. By means of mechanical treatment a high dislocation density is achieved in these ranges. The EPR‐spectra are assigned to V‐centres and O−‐ions in strongly distorted ranges.
On the reproducibility of the orientation distribution function of texture samples from pole figures (VII) reliability of reproduced ODF's; standard functions
Authors: Matthies S.
Published: July 2007

The reliability of ODF's reproduced from pole figures, which were derived in diffraction experiments, is discussed from a general point of view. Standard functions simplifying investigations in texture analysis are presented.
On the influence of the pre‐ageing temperature on the reversion behaviour of an Al‐4.5 at.% Zn‐2.0 at.% Mg alloy
Authors: Gueffroy B. , Löffler H.
Published: July 2007

The reversion behaviour of an Al‐Zn(4.5)‐Mg(2.0) alloy was investigated by SAXS in dependence of the pre‐ageing temperature, Tpre, (ranging between 60°C and 100°C) and the reversion temperature, Trev, (120°C till 200°C) starting with precipitates having a radius of (1.2 ± 0.1) nm and (1.5 ± 0.1) nm, respectively. During the reversion treatment applied up to Trev = 160°C three stages could be distinctly distinguished, namely the dissolution of unstable zones, the growth of the stable zones on the expense of the dissolved one, and at last the coarsening of the precipitates by the OSTWALD‐ripening process, where the structure changes become independent of the pre‐history (start radius). The change of Tpre from 60°C to 100°C does not influence the structure changes going on at Trev, that means between 60°C and 100°C the same type of G.P. zones grows.
Contribution to the habit of hydrothermally grown corundum
Authors: Franke W. , Ghobarkar H.
Published: July 2007

The growth of corundum crystals without the influence of extraneous ions was achieved by the treatment of single crystals of topaz with supercritical water. The result is in agreement with previous calculations and considerations of other authors. A review of the different indexation of the corundum lattice is given.
Simple calculation of the axial temperature characteristics of a unidirectionally solidified sample
Authors: Vetter J. , Fruehauf J. , Schneider H. G.
Published: July 2007

The model described in this paper treats the numerical solution of a heat transfer problem in a one‐dimensional way determining the axial temperature characteristics. The physical quantities are considered as values depending on temperature and the real wall temperature profile of the heating‐cooling system is included. The sample shape corresponds to the numerous cases of long and thin cylinders. The calculation were carried out by a medium desk computer. The results of the calculation are in good line with the experimental data.
Forecasting future canadian residential heating demand: An illustration of forecasting with aggregated and disaggregated data
Authors: Berkowitz M. K. , Haines G. H.
Published: July 2007

This paper examines the sensitivity of forecasts to the level of aggregation of the data. A relative shares regression model and a multinominal logit model are tested with both aggregate and disaggregate survey data from 2109 respondents. The results indicate the appropriate model to use depends on whether the data are disaggregate or aggregate in form. Forecasts of solar heating of dwelling unit demand and market shares are also reported for Canada in terms of the solar price relative to the natural gas price and solar reliability relative to natural gas reliability.
Forecasting quality and information
Authors: Brockhoff Klaus
Published: July 2007

It is assumed that demand for information that subjectively appears to be relevant for forecasting improves forecasting quality. To study this hypothesis a number of forecasting experiments were conducted. Fifty managers from the housing business, from banking, and from a research institution were asked to forecast interest rates, using a Delphi process. They communicated via a computer system, and, to support their judgements, they had access to a data bank that was stored in the same system. Their communication with the system was automatically recorded. Part of the data collected in these experiments is used to study the existence of a relationship between information activities and forecasting results. A weak positive relationship is found if non‐linear functions are tested, where information demand is corrected by those data retrievals that seem to have resulted from an inability to handle the information system. For further research a more general, albeit less informative, Boolean model is suggested.
The use of growth curves in forecasting market development—a review and appraisal
Authors: Meade Nigel
Published: July 2007

The growth curves suitable for forecasting market development are identified and described. The underlying theoretical basis, if any, for their use is examined, and published examples of their applications are given. Doubt is cast on the value of long‐term forecasts derived from growth curves applied to markets for consumables. The problems of choice between competing curves are demonstrated by means of some examples. The requirements that a growth curve should meet in order to be an appropriate forecasting tool are identified and illustrated. Many of the published examples of growth curve use are shown to be vulnerable to criticism under one or more of these criteria.
Forecasting the price evolution of new electronic products
Authors: Dino Richard N.
Published: July 2007

This study tests the hypothesis that prices in new markets change in a pattern similar to and related to the product life cycle. Three stages of price decline have been identified in electronic product markets and can be associated with the introduction, take‐off and growth, and maturity stages of the product life cycle. The study integrates the methodologies of the product life cycle concept and experience curve theory and analyses price and product behaviour for radios, monochrome (black and white) televisions, colour televisions and video cassette recorders. The empirical evidence supports the hypothesis and suggests, as a general rule, that a better understanding of a product's life cycle and the factors that affect it can aid in the development of price forecasts. In fact, the marriage of experience curve theory and the product life cycle concept provides a methodology for quantifying the impact of influential factors and gives the analyst the ability to bound the uncertainty around price forecasts, ultimately leading to better strategic decisions, today, for tomorrow's markets.
Computing the variance of the forecast error for the holt‐winters seasonal models
Authors: Sweet Arnold L.
Published: July 2007

This paper presents expressions for the variance of the forecast error for arbitrary lead times for both the additive and multiplicative Holt‐Winters seasonal forecasting models. It is shown that even when the smoothing constants are chosen to have values between zero and one, when the period is greater than four, the variance may not be finite for some values of the smoothing constants. In addition, the regions where the variance becomes infinite are almost the same for both models. These results are of importance for practitioners, who may choose values for the smoothing constants arbitrarily, or by searching on the unit cube for values which minimize the sum of the squared errors when fitting the model to a data set. It is also shown that the variance of the forecast error for the multiplicative model is nonstationary and periodic.
Using the bootstrap to evaluate forecasting equations
Authors: Peters Stephen C. , Freedman David A.
Published: July 2007

The bootstrap, like the jack‐knife, is a technique for estimating standard errors. The idea is to use Monte Carlo simulation, based on a non‐parametric estimate of the underlying error distribution. The bootstrap will be applied to an econometric equation describing the demand for energy by industry, to determine multi‐period forecasting error and choose among competing specifications. The delta method for estimating forecast errors turns out to be too optimistic by a factor of 2.
Extraneous expert information
Authors: Clemen Robert T.
Published: July 2007

When a Bayesian decision maker has to choose among information sources, he should consider the anticipated impact that the information will have on his posterior distribution. In some cases he may determine at the outset that an information source will have no effect on his posterior beliefs, no matter what that source says. Such an information source is called extraneous. In this paper we discuss Bayesian conditions for extraneous information sources, and show a hypothetical example involving experts with overlapping information. Analysis of U.S. weather forecasts demonstrates how this concept can be operationalized to test hypotheses concerning the use of information by forecasters.
A model of calibration for subjective probability distributions and its application to aggregation of judgements
Authors: Curtis Paula E. , Ferrell William R. , Solomon Ira
Published: July 2007

A simple model is proposed of the statistical structure underlying the calibration of auditors' subjective probability distributions for account balances, and potentially for other unknown quantities. The model relates calibration curve shape to two parameters which represent over‐ or underconfidence and over‐ or underestimation. It is fitted to data from expert auditors. Different types of account appear to have different calibration characteristics. The model helps predict approximately the effects on calibration of aggregating individual subject distributions. Aggregation improves accuracy, but produces a strong tendency towards underconfidence. One aggregation method, predicting the best judgement in the group and using it as the group judgement, is found to be quite effective, much better than averaging the fractiles of individual distributions.
Beyond heuristics and biases: A contingency model of judgemental forecasting
Authors: Beach Lee Roy , Barnes Valerie E. , Christensen‐Szalanski Jay J. J.
Published: July 2007

The conflicting viewpoints about the quality of judgemental forecasts are examined and a model is proposed that attempts to resolve the conflict. The model sees forecasts as contingent upon the repertory of forecasting strategies that the forecaster brings to the forecasting task, the strategy that he or she selects as a function of the characteristics of the task, and the rigour with which he or she applies the strategy as a function of the motivating characteristics of the environment in which the task is encountered. The implications of differences in subjects' and experimenters' assumptions about which strategies are appropriate in experimental studies are examined, as are the implications of the differences between the motivating aspects of experimental and applied settings on both performance and on the generatizability of the results of experiments to applied judgemental forecasting.
A super‐resolution algorithm for spectral estimation and time series extrapolation
Authors: Moutter S. P. , Bodger P. S. , Gough P. T.
Published: July 2007

Recent developments in the signal processing field of electrical engineering have resulted in several frequency domain methods of extrapolating a time series. Insight gained in testing one such method, the Papoulis algorithm, has been used to suggest modifications which greatly improve its performance under most operating conditions where real data are concerned.

The modified Papoulis method thus developed has been applied to electricity load forecasting over the short and medium term, as well as to world economic and energy data, to assess the cyclic structure present in each series about a trend.
Expert judgments of political riskiness
Authors: Mumpower Jeryl L. , Livingston Steven , Lee Thomas J.
Published: July 2007

Professional analysts' judgments of the political riskiness of 49 focal countries for the period 1983‐1985 were studied. Data were collected on nine predictor variables; each was significantly correlated at the 0.01 level with ratings of political riskiness. The highest correlation was withinfant mortalityandlife expectancy; either accounted for roughly 50% of the variance in ratings. Different variables were better predictors of political risk within different geographic regions. A factor analysis suggested the presence of three underlying factors. The predictor variable with the highest loading was chosen to represent each of the three factors. These were:exchange rate differential; estimated inflation rate; andinfant mortality rate. Approximately 75% of the variance in ratings could be accounted for on the basis of a linear combination of the three predictor variables. These three variables were capable of good prediction even for various subsets of countries based on geographic region or other criteria. Using all nine variables as predictors resulted in only marginal improvement. A cluster analysis revealed little difference among clusters of judges. Ratings by undergraduate students closely paralled those of professional analysts. As in previous studies of expert predictions and forecasts, claims of expertise in political risk analysis were better supported by command of factual knowledge than by differentially superior predictive ability.
Comparing ex‐ante forecasts from a sem and var model: An application to the italian economy
Authors: Boero Gianna
Published: July 2007

The predictive performance of a large‐scale structural econometric model (SEM) of the Italian economy the Prometeia model is compared in this paper with a vector autoregressive (VAR) model estimated for a selection of six main variables of interest. The paper concentrates on the quarterly ex‐ante forecasts of GDP growth rate and the annual forecasts of GDP growth and inflation rate, over the period 1980‐85. It concludes that no forecaster is systematically better than the other. In particular, the VAR model outperforms the SEM in short‐run forecasts, suggesting that, for the latter, more careful attention should be addressed to questions of dynamic specification. On the other hand, for longer intervals, the SEM forecasts are more accurate than the VAR forecasts, in that they can benefit from the judgemental interventions of the model users and the model can pick up the non‐linearities of the economy which cannot be captured by the VAR. Given the different kinds of information that can be extracted from the two approaches, it seems more reasonable to consider them as complementary rather than alternative tools for modelling and forecasting. Therefore, rather than attempting to establish the superiority of one type of model over the other, this kind of comparisons should be seen as a useful diagnostic tool for detecting types of model misspecification.
Improved business planning through an awareness of political cycles
Authors: Young Peg , Marcus Lfred A. , Koot Ronald S. , Mevorach Baruch
Published: July 2007

Can business planning be improved if more attention is paid to underlying political cycles? This paper compares practitioner and researcher perspectives on this issue. While practioners stand to gain useful insights from a careful examination of past political cycles, these insights may be disconfirmed by rigorous tests carried out by researchers. In this paper we isolate and examine five hypotheses from the literature on the political‐economic cycle.
Optimal selection of forecasts
Authors: Chen Lian , Anandalingam G.
Published: July 2007

Many studies have shown that, in general, a combination of forecasts often outperforms the forecasts of a single model or expert. In this paper we postulate that obtaining forecasts is costly, and provide models for optimally selecting them. Based on normality assumptions, we derive a dynamic programming procedure for maximizing precision net of cost. We examine the solution for cases where the forecasters are independent, correlated and biased. We provide illustrative examples for each case.
Hydrological effects of changes in levels of atmospheric carbon dioxide
Authors: Wolock D. M. , Hornberger G. M.
Published: July 2007

The potential influence of increasing levels of atmospheric carbon dioxide (CO2 ) on water resources includes changes in evapotranspiration that result from control of stomatal resistance by CO2 and changes in precipitation and temperature caused by ‘greenhouse’ warming. In this study we investigate the potential effects of CO2 change on the hydrological response of a forested catchment in Shenandoah National Park, Virginia. Steady temporal trends are superimposed on stochastically derived time series of precipitation and temperature. These input data, which account for the natural variability of the system and the hypothetical effects of climate change, are then used to drive TOPMODEL, a variable‐source‐area hydrological model. A variety of climate‐change scenarios is simulated and temporal trends in annual average flow, peak flow, and basin yield are detected using Kendall's tau statistic. The direction and magnitude of the runoff trends are dependent on the relative magnitudes of the induced trends in precipitation, temperature, and stomatal resistance. Stochastic variability in temperature and precipitation obscure the runoff trends even when real trends in precipitation, temperature, and stomatal resistance are significant.
Is it possible to find an econometric law that works well in explanation and prediction? The case of Australian money demand
Authors: Swamy P. A. V. B. , Tavlas George S.
Published: July 2007

Pratt and Schlaifer's (1984, 1988) research employed in efforts to produce laws in economics are considered and their use in predicting future data is described. Data for Australia are used to illustrate the approaches.
Seasonality in large‐scale macroeconometric models
Authors: Fisher Paul G. , Wallis Kenneth F.
Published: July 2007

Macroeconomic indicators are typically appraised in seasonally adjusted form, and forecasts are often presented in a similar way (as annual changes, for example). Moreover, the quarterly macroeconomic models used in forecasting are commonly estimated from seasonally adjusted data. Nevertheless, these models can generate forecasts with seasonal patterns, and this paper assesses the cause and cure of this phenomenon. It is found that forecast seasonality is induced by seasonality in the various inputs: exogenous variables, residual adjustments, the dynamic specification of certain equations, and annual changes in policy variables. Series changing annually but observed quarterly are termed ‘intercalated series’, and are simple examples of periodic processes. Forecast seasonality can be removed by appropriate adjustment of all these inputs. Models containing explicit future expectations variables solved in a model‐consistent manner are also considered: numerical sensitivity to the terminal quarter may result from terminal conditions that require adjustment when seasonality is present.
The real exchange rate, fiscal policy and the role of wealth an analysis of equilibrium in a monetary union
Authors: Barrell R. , In't Veld J. W. , Gurney A.
Published: July 2007

This paper is concerned with the adjustment processes within a potential European monetary union and looks in particular at permanent asymmetric shocks that require an adjustment in a country's (or region's) real exchange rate. We first consider some of the implications of EMU and the question of asymmetries within the European economy. The presence of asymmetries and, in particular, different institutional structures in labour markets is a potential source of tension within a union and it could make a union difficult to sustain. However, automatic adjustment processes will be at work within a monetary union as a result of changes in relative price levels, which change real exchange rates, and also as a result of changes in wealth stocks. We use our econometric world model, NIGEM, to investigate the effects of asymmetric fiscal expansions and real exchange rate misalignments within a monetary union. In order to quantify the effects of such permanent asymmetric shocks we have introduced wealth into our model. Our simulations suggest that the principal impact of the fiscal expansion on both output and the price level will occur within the country in which the expansion occurs. Short‐term gains are crowded out in the medium term, and while monetary union reduces crowding out in the short term, it increases the rate at which crowding out occurs thereafter. We also analyse the effects of real exchange rate misalignments and find that the processes of adjustment may be very protracted. This could cause strain on the union as adjustment costs are shared unequally.
Simulating the European economies under alternative monetary policy assumptions
Authors: Richardson Pete
Published: July 2007

This paper examines the implications of alternative monetary policy rules for economic stabilization within Europe, using the OECD world model, INTERLINK. The results suggest that policy linkage through the Exchange Rate Mechanism will have differing effects on the effectiveness of stabilization policies depending on the nature of economic shocks. For demand shocks, the choice of monetary rule in the country of the ‘anchor’ currency is of more consequence than the flexibility of exchange rates. For supply shocks, exchange rate rigidity is likely to have more problematic effects on economic adjustment. Spillover effects are also important when the shock is felt primarily by the ‘anchor’ economy.
Comparative simulation analysis of the European multi‐country models
Authors: Whitley John D.
Published: July 2007

This paper is a product of the SPES programme on multi‐country models and describes a set of diagnostic simulations on five European‐based multi‐country models. These are the EEC's model QUEST as operated by the Deutsches Institut fur Wirtschaftsforschung (DIW); the GEM model jointly operated by the National Institute of Economic and Social Research and the London Business School; the Oxford Economic Forecasting model; the MIMOSA model used by the Observatoire Francais des Conjonctures Economiques (OFCE) and Centre D'Etudes Prospectives et D'Informations Internationales (CEPII), and OECD's Interlink model. The simulation experiments are designed to clarify the interdependencies and relative structures of the major European economies using both (internal) single‐country and external common shocks.

All the models tend to adopt similar specifications across the different countries but differences in simulation responses still occur and cross‐model differences often dominate those between countries. Several general qualitative conclusions can be drawn, however. For example, independent fiscal policy under a monetary policy of fixed real interest rates has only limited power to raise output, although full crowding out does not occur. Spillover effects to the other European economies are weak with respect to independent fiscal expansions but stronger for an external shock.

The model comparisons reveal differences in modelling strategies, notably with respect to the treatment of inflation on consumption, the role of activity on import behaviour and the influence of excess demand on wages. These; are all key factors in explaining simulation differences between the models. Not all the models currently have endogenous exchange rate determination and this becomes an essential requirement for analysis of non‐EMS and EMS‐style regimes.
Monitoring for outliers and level shifts in kalman filter implementations of exponential smoothing
Authors: Kirkendall Nancy J.
Published: July 2007

This paper presents a new application of a Kalman filter implementation of exponential smoothing with monitoring for outliers and level shifts. The assumption is that each observation comes from one of three models: steady, outlier, or level shift. This concept was introduced as a multiprocess model by Harrison and Stevens (1976). However, their handling of the models is different. In this paper four different model‐selection criteria are introduced and compared by applying them to data. The new features of the application include the four model‐selection criteria and the estimation of the required parameters by maximum likelihood.
Analysis of many short time sequences: Forecast improvements achieved by shrinkage
Authors: Ledolter Johannes , Lee Chang‐Soo
Published: July 2007

Credibility models in actuarial science deal with multiple short time series where each series represents claim amounts of different insurance groups. Commonly used credibility models imply shrinkage of group‐specific estimates towards their average. In this paper we model the claim size yu in group i and at time t as the sum of three independent components: yit = μr + δi + ϵit. The first component, μt = μt−1 + mt, represents time‐varying levels that are common to all groups. The second component, δi, represents random group offsets that are the same in all periods, and the third component represents independent measurement errors. In this paper we show how to obtain forecasts from this model and we discuss the nature of the forecasts, with particular emphasis on shrinkage. We also assess the forecast improvements that can be expected from such a model. Finally, we discuss an extension of the above model which also allows the group offsets to change over time. We assume that the offsets for different groups follow independent random walks.
Estimation and testing of time‐varying coefficient regression models in the presence of linear restrictions
Authors: Leybourne S. J.
Published: July 2007

A linear regression model with random walk coefficients is extended to allow for linear restrictions between the coefficients to be satisfied at each point in time. Estimation in this model is shown to be no more involved than estimation in the standard model. It is also demonstrated how, after a slight modification to the testing problem, classical test procedures may be applied to the problem of testing for such restrictions. The performance of the Lagrange Multiplier test for a variety of different restrictions is then investigated via simulation. An empirical application involving testing for homogeneity in a random walk coefficient version of the AIDS model is given.
Interactions of real GNP business cycles in a three‐country time‐series model
Authors: Aoki Masanao
Published: July 2007

The paper describes a procedure for examining short‐run dynamic interactions among macroeconomic models by constructing aggregate state‐space submodels for dynamic modes corresponding with short‐run response patterns. Using the quarterly real GNP from the US, Germany, and Japan for 1974. III to 1991. I we examine dynamic interactions in the frequency ranges roughly comparable with a range of business cycle frequencies. We find that there is no (worldwide) shock common to the three countries even though the German and Japanese real GNP are affected by a common shock.
New methods for the analysis of long‐memory time‐series: Application to Spanish inflation
Authors: Delgado Miguel A. , Robinson Peter M.
Published: July 2007

Models for long‐memorya time series are considered in which the autocovariance sequence is parameterized only at very long lags or the spectral density is parameterized only at very low frequencies. reently proposed methods for estimating the differencing parameters are reviewed and are applied to an economic time series of sprices of Spain.
Vector auto regression modeling and forecasting
Authors: Holden Ken
Published: July 2007

This paper provides an introduction to vector auto regression models, explaining their origins and their use for modeling and forecasting. The recent developments of structural modeling and the treatment of non‐stationary variables are also considered.
Implementation and design of biosignal optical telemetry system based on enforced synchronization
Authors: Karita Nobuo , Kawahito Shoji , Ishida Makoto , Usui Shiro , Nakamura Tetsuro , Nishikado Masafumi , Nagaoka Shunji
Published: July 2007

This paper discusses the optical telemetry system for a life science experiment conducted in a space station, the feature of which is the telemetry of multichannel biosignals from a number of objects in the same booth.

First, the enforced synchronization telemetry system is proposed. This system is based on two‐way communication which forms the key to the simultaneous biosignal telemetry from a number of objects. Based on the proposal, an experimental system is constructed. The external system sends a command signal to the object side and then receives and demodulates the telemetry signal from the object side. This system was implemented on a breadboard.

The control unit for the multiplex telemetry system attached to the biological object is designed and constructed using dedicated BiCMOS. In this unit, approximately 400 elements are integrated into a 3.6 × 4.6 mm2 chip, realizing the function to telemeter four channel signals from up to four objects with the sampling frequency of 1 kHz.

A series of operations was verified as satisfactory. Then include the reception of the optical command signal, selection of the object, multiplexing of a number of biosignals, and the transmission of telemetry signals. Using the experimental telemetry system based on the enforced synchronization, the operation of the parallel telemetry is verified as a principle for the two‐channel biosignals from two objects. The result is evaluated.
Defect‐ and fault‐tolerant static ram module designs based on parity checking and automatic testing
Authors: Tsuda Nobuo
Published: July 2007

Advanced redundancy configurations are presented for static RAM modules. These extend the word duplication and selection by horizontal parity checking (WDSH) and error correction by horizontal and vertical parity checking (ECHV) configurations to enhance yields of wafer‐scale integrated circuits. They use automatic spare block replacements for bit‐lines and word‐lines, word selection by access error checking, pair unit replacement, and two‐level hierarchical redundancy.

A simulation using a 1.5‐μm, 128 k‐bit CMOS static RAM module suggests that defect‐ and fault‐tolerance capability is improved nine or 17 times over the basic redundancy configurations. These values are four or six times that achieved by conventional triple‐modular redundancy (TMR).
Enumeration of multiple‐valued kleenean functions and some related properties
Authors: Hata Yutaka , Yuhara Masaharu , Miyawaki Fujio , Yamato Kazuharu
Published: July 2007

The set of multiple‐valued Kleenean functions define a model of a Kleene algebra (a fuzzy algebra) suitable for treating ambiguity. This paper enumerates the Kleenean functions exactly, using the relation that the mapping from p‐valued Kleenean functions to monotonic ternary input p‐valued output functions is a bijection. Thus, the number pn of input vectors that should be searched is 3n for p‐valued n‐variable Kleenean functions. In this paper, we show how to obtain this number for 4‐ to 8‐valued Kleenean functions with 3 or fewer variables. We show that the number increases stepwise as the radix becomes larger and that the number of even (2m)‐valued Kleenean functions is uniquely determined by the number of odd (2m ‐ 1)‐valued Kleenean functions. These results show that the essence of Kleenean algebra is principally revealed by its odd‐valued functions. Moreover, the number of input variables increases exponentially as the variable becomes larger, and increases logarithmically as the radix becomes larger. Thus, increasing the number of variables has more of an effect on increasing this number than does incrementing the radix.