Fundamental Reflections Research Articles

Formation and relaxation of coherency strain in the nickel-base superalloy SC16.

An in situ study of the kinetics of relaxation of the gamma-gamma' lattice mismatch in the single-crystal Ni-base superalloy SC16 was carried out by means of high-energy synchrotron radiation diffraction. The high resolution achievable was exploited to measure the time variation of the gamma and gamma' lattice parameters during isothermal ageing at several temperatures, starting from the gamma' solvus point. On cooling from the solvus temperature (1523 K) the gamma' precipitate phase nucleates and grows following concurrent mechanisms. The variations of the gamma and gamma' peak position and integrated intensity could be followed by means of fundamental and superstructure reflections. At each temperature T < 1473 K the integrated intensity follows an Avrami time law. The gamma' Volume fraction increases as a function of time at each temperature. It increases with cooling, until saturation occurs at temperatures as low as 1075 K. The lattice mismatch follows an exponential time decay, while having larger values at high temperatures. The pArticles are born fully coherent, and the coherency strains the set-up. Over time, long-term ageing shows a stabilization of the misfit value, while the precipitates are supposed to lose their coherency to the matrix (within 3-4 h) and the strains relax.

On the logic of event causation. Part I. Fundamental reflections

The paper outlines an analysis of token causation. It contains reasons for the choice of event tokens and a list of properties of causal relations. After defining the notion event it is shown, in which form classical philosophical problems arise and how they can be solved: Causality is interpreted as an second order property of first order relations. Temporal order can be induced from causal order. Token causation does not involve neither any kind of necessity, nor probability. Causal laws are generalizations on sentences about token causation by quantifying over event types. Two explications of Causal law are suggested, differing in the ability of allowing for exceptions.

Une question interdite

Is legal history a left-over or is it waiting for a takeover bid (just like a company in serious trouble) which would allow the expression of new analyses and outlines for a better understanding of the contemporary western world? Its propositions of erudition, are they just interesting for small academic circles, or could they open a new pathway for fundamental reflections on the phenomenon of norms in general and the structure of its evolution in the special case of norm-production coming from Roman Christianity? And what is the significance of the idea of »legal tradition«, an idea forged in Western Europe, within the framework of a presumed global westernization without any counter-balance? The essay discusses the illegibility of legal history in today’s culture. Under the well reflected motto »The Forbidden Question« it concludes firmly: To renovate itself, this discipline has to perform its work in a new way, guided by a very precise and distinct vision on theory. The author examines the conditions for this. Recommended citation: Legendre, Pierre, Une question interdite, in: Rechtsgeschichte - Legal History Rg 03 (2003) 33-37, online: http://dx.doi.org/10.12946/rg03/033-037

Phase separation in Ni-rich Ni–Ti: the metastable states

The microstructure of Ni-11.3 at.% Ti single crystals was investigated after quenching from the solid solution at 1440 K and after ageing at 873 K for various periods of time by using transmission electron microscopy and X-ray scattering near fundamental reflections and superstructure reflections of the ordered precipitates. The two-stage decomposition sequence with the initial formation of metastable γ″ precipitates followed by metastable γ′ precipitates as found by small-angle neutron scattering is confirmed. The long-range order parameter of these precipitates is always close to the maximum value achievable at a given composition. The presence of the first metastable state (γ″) is related to a rearrangement of the precipitates on a macro-lattice in order to minimize the elastic energy due to coherency strains.

The EU Chemicals Policy Review from a Legal Perspective: For a Progressive, Coherent and Integrated Approach that Preserves the Internal Market

This paper analyses the Commission White Paper on a Strategy for New Chemicals Policy from a legal perspective. In concentrating its efforts towards resolving the “burden of the past”, the White Paper does not provide the fundamental justification of the choice of a single system applicable to both new and existing chemicals and many uncertainties remain as to the scope and functioning of this system. Ensuring the coherency of the future legislation will require clarifying the fundamental legal nature and consequences of each phase of the proposed “REACH” system, and streamlining the REACH processes on the basis of centralised, efficient, and transparent decision-making processes. The White Paper does not specify how the Commission intends to ensure that the new legislation preserves the internal market for chemicals, another fundamental objective of the reform. This will require that the new legislation be based on Article 95 of the EU Treaty, that it clarifies some of the grey zones of the existing chemical legislation, and that the Commission effectively enforces the internal market discipline with respect to those cases where national competencies remain. Finally, efficacy will require the prioritisation of the scope of the REACH system to avoid duplication of efforts and a fundamental reflection on the interactions between the different EU policies and legislation affecting chemicals to ensure that the future chemical legislation is integrated and coherent.

Analysis of deep waveguide gratings: an efficient cascading and doubling algorithm in the method of lines framework

In this work, a computationally fast, numerically stable, and memory-efficient cascading and doubling algorithm is proposed within the method of lines framework to model long planar waveguide gratings having thousands of periods in the propagation direction. This algorithm can model 2/sup n/ grating periods in n calculational steps and needs N/sup 2/ matrices for N sample points in the problem space. It can model periodic, quasi-periodic, symmetric, and asymmetric gratings efficiently. Different deep waveguide gratings are modeled using this scheme and results for the fundamental TE mode spectral reflectivity are compared with published results showing excellent agreement.

Determination of the order parameter of CuPt-B ordered GaInP2 films by x-ray diffraction

We present quantitative characterization of atomic ordering in semiconductor alloy films by x-ray diffractometry. In particular, we show that the order parameter of CuPt-B ordered GaInP2 films can be determined without measuring the fundamental reflections or examining structural details of the ordered domains. Our method is based on the fact that the ordering peak is modulated by statistical displacements of atom planes, which is a function of the degree of ordering. Therefore, by comparing two or more ordering peaks in an x-ray spectrum, the order parameter of an ordered film can be extracted solely for those regions that are, in fact, ordered. The method can straightforwardly be extended to other ordered alloys.

Energy-filtered electron diffraction and high-resolution electron microscopy on short-range ordered structure in GaAs(0.5)Sb(0.5).

Characteristic intensity distribution of diffuse scattering in III-V alloy semiconductor GaAs(0.5)Sb(0.5) epitaxially grown was observed by the energy-filtered electron diffraction method with [110] incidence. The diffuse scattering situates at the one-third positions between the fundamental reflections extending parallel to the q002 direction in the reciprocal space. A high-resolution electron microscope image shows weak contrast modulation corresponding to the diffuse scattering. The image processed with the Fourier transform by selecting the diffuse scattering and a fundamental reflection shows small regions consisting of bright dots being elongated along the (111) planes and aligning on the (002) planes, which are considered to result from the ordering of As and Sb during the growth process. The effect of including the fundamental reflection for imaging the ordered regions in the image processing method is also discussed. Finally, based on the results obtained by energy-filtered electron diffraction and high-resolution electron microscopy, a simple structure model for the short-range ordered structure in GaAs(0.5)Sb0.5 is proposed.

Study of the effect of thermal annealing on the optical and electrical properties of vacuum evaporated amorphous thin films in the system Ge20Te80-xBix

We systematically studied the effect of thermal annealing on the optical and electrical properties of amorphous semiconducting thin films in the system Ge20Te80−xBix (x = 0, 0.19, 2.93, 7.35) prepared by flash evaporation in a vacuum of 1 × 10−6 Torr. The films are characterized by x-ray diffraction (XRD) and electron probe micro analysis. The annealing temperature is kept at 150 °C, 180 °C and 220 °C. No crystallization of the thin films is achieved on annealing up to the temperature of 150 °C. At a higher temperature of annealing, microcrystals of Te, Bi2Te3, Ge–Te, etc, are observed along with an amorphous phase as indicated by XRD analysis. The fundamental optical absorption edge and reflection spectra of as-prepared and annealed films are determined. Optical interband transitions are observed for various films (as-prepared and annealed). The presence of crystalline Bi2Te3 in films annealed at 220 °C is also supported by the reflection spectrum. The optical energy gap (Eg), the slope parameter (Δ) of the absorption edge and the tailing parameter (B−1) of the energy band tails are computed from the optical data. The dc electrical conductivity (σdc) of various films is studied in the temperature range of 150–450 K. We observe that two types of conduction take place: conduction through extended states in the higher temperature region, and conduction through localized states in the band tails and at the Fermi level by the hopping process assisted by phonons at lower temperatures. The data at higher temperatures have been fitted with the expression σdc = σ0exp(−ΔE/kT) and the electrical parameters, ΔE and σ0, are also determined. It is observed that the bismuth concentration and annealing temperature dependences of the optical and electrical parameters are different in the two regions of compositions, x ≤ 2.93 and x > 2.93, indicating structural differences in the two sets of compositions. It is pointed out that the bulk form of these amorphous semiconductors exhibits a carrier sign reversal at a bismuth concentration of about 3.5 at%. However, the thin-film form of these amorphous semiconductors does not show such a carrier sign reversal in the electrical transport.

Electron microscopy studies of microstructures in β-Ga 2O 3 single crystals

Microstructures of as-grown and annealed β-Ga 2O 3 single crystals were studied by electron microscopy. Energy filtered electron diffraction patterns exhibited weak diffuse scattering at 1/2 and 1/4 positions between the fundamental reflections along the q 20 4 ̄ vector. Dark-field images observed with the 1/2 diffuse scattering showed a characteristic domain-like structure, where the size of each domain was less than 5 nm. The diffused scattering was somewhat weakened by annealing the specimen. The observations indicate a non-homogeneous structural modulation, which is considered to be related to the distribution of oxygen vacancies.

Nanostructured cation distribution in FeNbO4: A synchrotron powder diffraction and transmission electron microscopy investigation

The real structure of FeNbO4 was determined by a combination of electron microscopy investigations and high resolution synchrotron powder diffraction. It is shown that the order-disorder phase transition from the orthorhombic high-temperature modification (α-PbO2-type structure) to the monoclinic low-temperature modification (wolframite-type structure) of FeNbO4 is translationengleich and leads to a domain structure that consists of a coherent mixture of the orthorhombic and the monoclinic modification. Domains of the monoclinic phase are separated by antiphase boundaries with an antiphase vector \((\tfrac{1}{2},\tfrac{1}{2} \cdot 0)\). The real structures of eight different samples have been investigated in terms of domain size and degree of cation ordering by peak-shape analysis and the ratio between integrated intensities of split-structure and fundamental reflections. The obtained real structure is correlated with the conditions of synthesis.

«Immigrant business» en Allemagne : Une réflexion critique sur les modèles d'explication dominants

„Immigrant Business" in Germany : A critical review of the dominating explanatory concepts The most recent debate about a new 'Turkish entrepreneurship" in Germany triggered off the fundamental reflections on the necessarily critical conceptualization of the relation between "culture" and entrepreneurial action. The dominating concepts in the field of "ethnic business"/ in which questions of cultural orientation in entrepreneurial action have been a central issue for some time, can serve as a starting point for this analysis. For understanding the term culture and the conceptualization of culture in conjunction with entrepreneurial action, a few critical remarks and a shift in perspective are necessary. Contributions of economic geography inspired by the "cultural turn", which shows alternative ways of thinking about the connection between culture and economy by using a new understanding of culture may be utilized here. Focusing on the group of "German-Turkish entrepreneurs" this paper concludes with an outline of a number of conceptual considerations for action-oriented research on the relation between culture and entrepreneurial action.

Modeling the diffraction profiles of CVD-grown perovskite oxide superlattices

(BaTiO 3 /SrTiO 3 ) 15 superlattices are grown by chemical vapor deposition of organic metals (MOCVD) on oriented Nb-doped SrTiO, substrates. The source uses a pulsed liquid-injection system, with a unique precursor solution for each compound. Using a monochromatic, parallel X-ray synchrotron beam in the θ/2θ reflection diffraction geometry, the (OOL) diffraction profiles are recorded from L=1 to L=8. The observed satellite peaks around the fundamental (OOL) Bragg reflections indicate a highly coherent superlattice arrangement, well epitaxied on the substrate. The diffraction profiles are fitted, taking into account the structural and chemical disorder which depart from the ideal defect-free perovskite superlattice. The statistical fluctuations of the thickness of each sub-layer and the coherence length of the stacking are introduced. With this modelisation, we have quantified the macro-strain and the large interdiffusion which take place at the BaTiO 3 /SrTiO 3 interface.

Phase Separation in InGaN Epitaxial Layers

Epitaxial layers of InGaN were deposited by metalorganic chemical vapor deposition on a GaN layer/sapphire substrate in order to ascertain compositional variation in the GaN-InN system. Samples were examined with In contents from x = 0.09 to 0.31. Plan-view images obtained by transmission electron microscopy reveal a domain structure within which the composition is modulated. Satellites appear around the fundamental reflections in the diffraction pattern. The spacing between the satellite and the reflection can be related to the wavelength of the modulations. Equations are derived for modulations in the [101] and [112] directions. Modulations were measured in the [101] direction and found to be about λ = 3.2 nm for all samples. Strain energy considerations explain the observation of modulations along different directions.

Phase Separation in InGaN Epitaxial Layers

Epitaxial layers of InGaN were deposited by metalorganic chemical vapor deposition on a GaN layer/sapphire substrate in order to ascertain compositional variation in the GaN–InN system. Samples were examined with In contents from x = 0.09 to 0.31. Plan-view images obtained by transmission electron microscopy reveal a domain structure within which the composition is modulated. Satellites appear around the fundamental reflections in the diffraction pattern. The spacing between the satellite and the reflection can be related to the wavelength of the modulations. Equations are derived for modulations in the [100] and [110] directions. Modulations were measured in the [100] direction and found to be about λ = 3.2 nm for all samples. Strain energy considerations explain the observation of modulations along different directions.

Radiometric characterization of field radiometers in support of the 1997 Lunar Lake, Nevada, experiment to determine surface reflectance and top-of-atmosphere radiance

A continuing series of field campaigns to Lunar Lake, Nevada, has been established to develop measurement protocols and assess the uncertainties of ground-based calibrations of on-orbit satellite sensors. In June 1997, an ensemble of field radiometers was deployed to validate the fundamental reflectance and radiance measurements of the Land Satellite (Landsat-5) Thematic Mapper (TM) and Satellite Pour l'Observation de la Terre (SPOT-2) Haute Resolution Visible (HRV) satellite instruments. Prior their deployment to Lunar Lake, many of the field instruments measured a common sphere source at the University of Arizona (UA). The results, presented in this work, showed variations in the relative stabilities of the field instruments, and demonstrate the need for in-depth characterization of field instruments for an accurate assessment of instrument performance and measurement uncertainty.

STeam

Learning is a socially embedded design process. But most of todays hypermedia systems fail to properly support the design-related and the social aspects of learning. Authoring and Web-publishing systems aim to support the authors design processes. Consequently, the activities of learners are confined to selecting and reading. Based on some fundamental reflections on the role of technology in learning processes, we conclude that top priority must be given to the construction of infrastructures that support cooperative learning processes if we are to properly harness the technologys potential. We present a learner-centered, wholly Web-based approach for structuring information in teams (sTeam). In sTeam the key concept is virtual space. It draws cooperation and communication together, while at the same time embodying the common external memory of a (virtual) learning group. Hence, the focus is not on interactive systems for individual access of knowledge bases, but on the cooperative management and structuring of distributed knowledge bases.

Precursor effects of martensitic transformations in Ti-based alloys studied by electron microscopy with energy filtering.

Precursor effects of martensitic transformations in two well-known shape memory alloys, Ti50Ni48Fe2 and Ti50Pd34Fe16, were studied extensively by energy-filtered electron microscopy, including in-situ observations, and high-resolution electron microscopy. Energy-filtered dark-field images, where weak diffuse scattering was utilized, clearly showed the microstructure in the premartensitic state of Ti50Ni48Fe2. Tiny domains observable in this state were close to spherical rather than thin and slender, and the temperature dependence of the domain-like structure was clarified by the in-situ observations. It was found that Ti50Pd34Fe16 exhibited a domain-like structure similar to that of Ti50Ni48Fe2, which was attributed to a transverse lattice displacement. High-resolution images of Ti50Pd34Fe16 showed that a domain was coupled with other ones with different orientations of distortion, so as to reduce the total strain due to their formations. Furthermore, effects of including a fundamental reflection, in addition to the diffuse scattering, on dark-field images were discussed based on the observations and the image processing.

On the stability of 𝛃-SiC with respect to chemical disorder induced by irradiation with energetic particles

X-ray diffraction measurements of changes in the long-range structural orderof 𝛃-SiC thin films have been performed during irradiation with energetic ions atlow temperature. The decrease in both the chemical and the topological order wasanalysed in situ using the superstructure (002) and the fundamental (004)reflections of the zincblende-type structure, in a dose range up to completeamorphization. The data indicate that the crystalline-to-amorphous transitionis a continuous process rather than a sudden collapse of a defective crystalstructure and that, in contrast with previous assumptions, 𝛃-SiC remains stablewith respect to amorphization up to a high degree of chemical disorder.

Vprašanje slogovne opredelitve skladb – poskus njegove obravnave na primeru cerkvenih del Jakoba F. Zupana (I)

Članek obsega prvi del avtorjevega razmisleka o vprašanjih, ki zadevajo slogovno klasificiranje skladb in – kot izhodišče obravnave teh vprašanj – povzema nekatere važnejše pomisleke glede primernosti opredelitve dveh cerkvenih del Jakoba Frančiška Zupana (1734–1810), Lavretanskih litanij in G in skladbe Te Deum laudamus, s slogovnima konceptoma barok in klasicizem. Dileme, ki se ob tem pojavljajo namreč ne tematizirajo le sprejemljivosti dosedanjih označitev skladateljevega Te Deuma za baročno in Litanij za klasicistično skladbo, glede na nekatere uveljavljene razvrstitve slogovnih značilnosti glasbenega baroka in klasicizma (npr. Blumejeve, v Epochen der Musikgeschichte iz leta 1974), temveč tudi nagovarjajo načelni premislek o konceptualnih izhodiščih epohnoslogovnega pristopa k zgodovini glasbe in zlasti posledicah nekritične aplikacije te vrste zgodovinopisne perspektive pri pisanju zgodovine glasbe »robnih območij« (M. Bergamo) Evrope, kot je vsaj do nedavnega bilo tudi slovensko.