bluuebunny/crossref_metadata_2025_split huggingface dataset:
Parallel feedforward and simplified adaptive control
Authors: Bar‐Kana Izhak 
Published: July 2007

AbstractSimple adaptive control systems were recently shown to be globally stable and to maintain robustness in the presence of disturbances if the controlled plant is ‘almost strictly positive real’, namely, if there exists a positive definite static output feedback (unknown and not needed for implementation) such that the resulting closed‐loop transfer function is strictly positive real.This paper is an attempt to show in an intuitive way how to use parallel feedforward and the stabilizability properties of systems in order to satisfy the ‘almost positivity’ condition. The feedforward configuration may be stationary, if some prior knowledge is given, or adaptive, in general.This way, simple adaptive controllers can be implemented in a large number of complex control systems, without requiring the order of the plant or the pole excess as prior knowledge
Rheological behavior of a polymer melt under the impact of a vibration force field
Authors: Zeng Guang‐sheng , Qu Jin‐ping 
Published: July 2007

AbstractA model for the molecular motion of a polymer melt under the impact of a vibration force field was developed. From complicated theory deduction, an expression of the relaxation time and dynamic apparent viscosity were obtained. The effect of a vibration frequency and amplitude on the melt's dynamic apparent viscosity is explained in terms of shear‐thinning and untie‐tangle criteria. The model is supplemented by a calculation sample and experiment, which show that dynamic apparent viscosity of a melt will tend to decrease as the vibration frequency or amplitude increases. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007
Steady flow simulation of a polymer‐diluent solution through an abrupt axisymmetric contraction using internally consistent rheological scaling
Authors: Shukla Shunahshep , Koelling Kurt W. 
Published: July 2007

AbstractIn this work, a new methodology is developed that describes the viscoelastic scaling of a polymer‐physical foaming agent (PFA) solution in a detailed and internally consistent manner. The approach is new in that while previous researchers have largely focused on scaling down experimentally obtained high pressure polymer‐PFA solution viscosity data onto a master curve for the viscosity of the undiluted polymer melt at a reference temperature and atmospheric pressure, we have generated the shear viscosity data required for our simulations by systematically scaling up the viscosity values obtained from measurements on a pure polymer melt to the desired temperature, pressure, and concentration values characterizing the flow. Simulations have been run for the flow of a polymer‐PFA solution through an extrusion foaming die with an abrupt axisymmetric contraction and good qualitative agreement is obtained with experimental pressure drop measurements obtained previously in our laboratory. The pressure drop rates and temperature rise rates have been estimated at the surface of incipient nucleation. Because of the short residence times in the die for the microcellular foaming process, approximating the flow through the die as a single phase flow in our simulations still gives useful insights into the dynamics of the flow. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Zur Zwillingsbildung in MgZn2
Authors: Paufler P. , Schulze G. E. R. 
Published: July 2007

AbstractAn der Laves‐Phase MgZn2 wurde nach Basisgleitung Zwillingsbildung der Form {1121} {0001} und seltener {1011} {0001} beobachtet. Das erste Gesetz kann man sich durch gekoppelte Versetzungsbewegung in der {0001}‐Ebene entstanden denken. Dabei werden, abgesehen von einer kleinen Grenzschicht, wie beim gewöhnlichen Gleitvorgang nur Bindungen in der Gleitebene gestört. Bei komplizierten Atomanordnungen könnte dies zu einer Bevorzugung gegenüber Mechanismen kleinerer Schiebung führen.Für Orientierungsbestimmungen werden die zugehörigen Transformationsmatrizen angegeben.Bei Kristallzüchtungsversuchen traten Wachstumszwillinge vom Typ {1126} [1121] {11124} [2243] auf.
Züchtung und Eigenschaften von Mangan‐, Kobalt‐und Zinkmanganatkristallen
Authors: Petzold D. R. 
Published: July 2007

AbstractCrystals of the manganates of manganese, cobalt, zinc have been grown from a flux solution of PbO‐PbF2 by slow cooling. Their lattice constants are compared with dates of sintered products (from literature). It resulted by comparison of the densities obtained by X‐ray and by pycnometer that the deficit of oxygen is caused by anionic vacancies in the lattice.
Band gap of triglycine selenate, triglycine fluorine beryllate, triglycine sulfate and its variation under γ‐irradiation
Authors: Sirota N. N. , Korina R. V. 
Published: July 2007

AbstractThe band gap for three ferroelectrics (triglycine selenate, triglycine fluorine berryllate and triglycine sulfate) is determined using an optic method. A shift of self‐absorption edge towards longer wave lengths is observed when exposed to irradiation by γ rays with a dosage of ∽ (2 ÷ 7) · 107 r as well as corresponding decrease of band gap. The observed changes are connected with the chemical nature of the studied substances.
Conditions of Formation of Calcite Crystals of Tabular and Acute Rhombohedral Habits
Authors: Kirov G. K. , Vesselinov I. , Cherneva Z. 
Published: July 2007

AbstractCalcite crystals are grown under pure conditions by the method of counterdiffusion of calcium and carbonate ions in water. An extension of the diffusion method is used making possible the crystallization of calcite in a medium containing calcium or carbonate ions in excess of their stoichiometric amounts in calcite. Calcite crystals grown in the presence of an excess of Ca2+ ions exhibit an elongated habit determined by the prevailing development of some of the acute negative rhombohedra φ. {0221}, θ. {0441} or π. {0881}, whereas with an excess of CO ions the habit varies from thick ‐to fine‐tabular due to the considerable development of the pinacoid (c {0001}). The habit of crystals grown in a medium in which both ions are approximately in stoichiometric amounts or in which the excess of one of them frequently alternates with an excess of the other, is determined by the supersaturation and varies from basic rhombohedron to acute rhombohedron m. {4041}.The results are discussed in the light of some of the existing theoretical ideas on the influence of admixtures on habit. It is shown that the order of morphological importance which can be derived on the basis of various extensions of Bravais' law agrees neither with the experimental results nor with the observations in nature. The particular habits observed in experiments, tabular and acute rhombohedral, are exactly those which Kalb had included in his morphogenetic order of calcite crystals as first and fifth habit types. Since they are the result of specific conditions in the medium they ought to deviate from the general order. The remaining three habit types, therefore, will determine the habit variations of calcite due to the decrease of supersaturation.
Elektronenstrahl‐Mikroanalyse einiger Minerale aus dem System Cu12As4S13‐Cu12Sb4S13
Authors: Morawiec H. , Kubica L. 
Published: July 2007

AbstractFolgendes wurde festgestellt: Bei den durch Zonarbau gekennzeichneten Mineralien treten Kupfer, Arsen, Antimon, Zink, Eisen und Schwefel als Komponenten auf. Es besteht eine gegenseitige Substituierung von Arsen und Antimon sowie auch von Kupfer, Zink und Eisen.Die einzelnen Zonen sind hinsichtlich der Mengenzusammensetzung Bestandteile der isomorphen Tetraedrit‐Tennantit‐Reihe und können mit der Formel (Cu, Zn, Fe)12 (Sb, As)4S13 beschrieben werden. Die quantitative Zusammensetzung ändert sich an der Zonengrenze sprunghaft.
On the Mechanism of Crystal Growth from Undercooled Melts
Authors: Gutzow I. , Razpopov A. , Pancheva E. , Kaischew R. 
Published: July 2007

AbstractThe mechanism of crystal growth from undercooled melts is studied experimentally by means of a simple capillary technique. Thymol and Na2S2O3 · 5 H2O are used as model substances. Dislocation‐free crystal faces of these compounds are obtained by continuous growth in the capillary or by prolonged annealing under appropriate conditions. Two‐dimensional mechanism of growth was experimentally verified on such perfect crystal planes. The conditions under which the surface nuclation mechanism operates are described accounting for the supersaturation, the influence of impurities etc. Transition from two‐dimensional into spiral growth of purposedly defected crystal faces is demonstrated and investigated. The mechanism of formation of perfect crystals is discussed and further experimental evidence on the possibility of two‐dimensional growth from melts is given.
The cation distributions in the spinel phases of the mixed vanadium oxides LiZnx V2‐xO4 and LiMgx V2‐xO4
Authors: Pollert Emil 
Published: July 2007

AbstractCation distributions and values of the oxygen parameter in the spinel phases of mixed vanadium oxides with the general formula LixMeV2–xO4, where Me is Zn or Mg, respectively, were studied by X‐ray diffraction measurements. The distribution of cations on the sublattices in the zinc series can be expressed by the formula Li1–x–δ Znx Vδ [Lix+δ V2–x‐δ] and for the magnesium series by the formula Li1–δ Vδ [Liδ Mgx V2–x‐δ]. For the zinc series a general uniform increase of the oxygen parameter was determined. The substitution of magnesium ions leads to an anomal course of this parameter, which is possible to explain by substitution of magnesium ions on intersticial sites. The results are discussed using the values of the Madelung energy. The recently observed tetragonal deformation of the spinel lattice for the bulk composition Li Mg0.375 V1.625 O4 is explained by a cooperative Jahn Teller effect of V4+ ions.
Non‐stoichiometry of apatites at high temperatures
Authors: Arends J. , Schuthof J. , Flim G. J. 
Published: July 2007

AbstractSchottky defects in apatites are formed by a decomposition reaction at temperatures in excess of 1000°K. In this investigation thermogravimetrie experiments on fluorapatite single crystals and powders have been carried out in the temperature range 1000–1600°K. Relative weightlosses of 1.2 × 10−3 per hour corresponding to Ca/P decreases of 0.0002 per hour have been observed at 1675°K. In the temperature range studied the number of vacancy triplets formed per second is in the order of 1018. The activation energy (1.15 eV) involved indicates that dislocations might play an important role in the decomposition process.
Crystal size distribution in precipitates
Authors: Dunning W. J. 
Published: July 2007

AbstractAfter a short introduction on the principles of nucleation and growth – here especially considering defect crystals – particle size distribution in precipitates is discussed. At first batch crystallization is referred to briefly. The situation in stirred continuous tank crystallizers is investigated in detail. Size distribution is considered in dependence on steady state flow rates of the reacting solutions, residence time of crystals in the tank, resulting in an exponential equation for the number of crystals per unit volume: \documentclass{article}\pagestyle{empty}\begin{document}$ n\left(r \right) = \frac{{\dot n_0 }}{{f\left(s \right)}}e^ - \frac{{vr}}{{V \cdot f\left(s \right)}} $\end{document}. With two and more tanks in series size distribution additionally becomes dependent on the difference of the supersaturations, of the occurrence of nucleation, and of the residence time of crystals in the various tanks. Equations for the size distribution are given for special conditions with two and more tanks in series.
Phasenbildung in Ni/Si‐Schichten
Authors: Beck U. , Neumann H.‐G. , Becherer G. 
Published: July 2007

AbstractNi‐bedampfte amorphe Si‐Schichten werden während des Temperns im Elektronenmikroskop untersucht. Es wird gezeigt, daß im Verlauf des Diffusionsprozesses in Abhängigkeit vom Ni‐Anteil and der Schicht acht Phasen gebildet werden. Generell entstehen zunächst metallarme Verbindungen. Aus den Ergebnissen wurde geschlossen, daß die Phasenumwandlungen kinetisch und nicht thermodynamisch bedingt sind.
Ein Beitrag zur quantitativen Auswertung von Reflexionselektronenbeugungsdiagrammen dünner, texturierter Schichten mit Hilfe photographischer Äquidensiten
Authors: Schützler H.‐P. , Pätz W. 
Published: July 2007

AbstractEs wird die Kristallitverkippung von texturierten dünnen Schichten quantitativ aus Reflexionselektronenbeugungsdiagrammen bestimmt. Dazu wird die Methode der photographischen Äquidensitometrie verwendet.
Kinetics of Polymorphous Transformations of Anodic Alumina
Authors: Sirota N. N. , Shokhina G. N. 
Published: July 2007

AbstractExperimental kinetic curves of anodic alumina isothermal transformations in the temperature 800–1200°C are given. The mechanism of transformation and the structure of transformation intermediate and end products are discussed. One‐half period curves of monotropic isothermal transformation of amorphous anodic alumina in metastable γ‐, δ‐, and stable α‐phases are given.
The Precipitation of Alkaline‐Earth Metal Carbonate Powders from Aqueous Solution. Crystal Numbers and Final Sizes
Authors: Packter A. , Uppaladini S. C. 
Published: July 2007

AbstractThe precipitations of magnesium carbonate trihydrate, basic magnesium carbonate and calcium, strontium and barium carbonates was studied from equivalent solutions of concentrations from 0.0005 M to 1M, at pHs from 10 to 7, by optical microscopy and other methods. Crystal growth started after induction periods: the precipitations of the more sparingly‐soluble metal carbonates — mainly studied at medium to high supersaturation — were homogeneously nucleated while the magnesium carbonate trihydrate precipitations — studied at low supersaturations at pH ≦ 7.6 — were heterogeneously nucleated. The crystal forms and numbers of the final precipitates depended on the type and numbers of nuclei (and crystallites) formed during the induction periods. Crystal numbers generally increased with increasing initial mean metal carbonate concentration according to the relation N = N1CMCO3β; β was 3 for the metal carbonate precipitations and β was 4 for the basic magnesium carbonate precipitations. N1 values increased in the order basic MgCO3 (at pH ≧ 9), or MgCO3 · 3H2O (at pH ≦ 7.6) < CaCO3 < SrCO3 < BaCO3. The final crystal lengths then generally decreased, from maximum values, with increasing initial concentration according to the relation lfin = l1/Cγ, where γ was 0.7 and 1.0. For precipitation at any concentration and pH, smaller crystal sizes were generally obtained in precipitates from solutions of the metal carbonate of lower solubility.
The Molecular and Crystal Structure of Bis‐Dimethyl Pentamethine Cyanine Perchlorate, C9H17N2Cl04
Authors: Sieber K. , Kutschabsky L. , Kulpe S. 
Published: July 2007

AbstractBis‐dimethyl pentamethine cyanine perchlorate crystallizes in the space groupP(21/c) with the lattice constantsa= 6.230 Å;b= 14.970 Å;c= 14.005 Å; β = 83.54°. The carboncarbon bonds show the bond length compensation, typical of polymethines, towards a partial double bond (1.39 Å) between formally sp2‐hybridized C atoms. The two CN bond lengths (mean value 1.32 Å) similarly correspond to partial NC double bonds. The CN bond lengths to the methyl carbon atoms (mean value 1.45 Å) correspond to normal CN single bonds. The size of the bond lengths confirms the assumption as to the characteristic features of the π electron system of such polymethines. The valence angles at the carbon atoms of the pentamethine chain clearly alternate and deviate systemically from 120°. This is also observed in other structures of a similar type. The bond lengths determined by experiment are compared with different π bond orders calculated on the basis of quantum chemistry. Here approximate agreement becomes apparent between all MO calculations and the results of the X‐ray crystallographic analysis. The perchlorate tetrahedra show disorder‐like behaviour in their crystal structure. The pentamethine chains approach each other as far as the contact spacing of 3.5 to 3.7 Å between unsaturated compounds and form two‐dimensional extended aggregates (“masonry” aggregation) within the crystal lattice.
Messung Realstrukturinduzierter Doppelbrechung in kubischen kristallen
Authors: Dietrich B. 
Published: July 2007

AbstractVon SQUIRE und ZAMECKI wurde eine polarisationsoptische Apparatur zu vergleichenden Untersuchungen realstrukturinduzierter Spannungsdoppelbrechung benutzt. Für Proben, die aus verschieden doppelbrechenden Bereichen bestehen, wird der quantitative Zusammenhang des Meßsignals mit Mittelwerten der Spannungsdoppelbrechung hergeleitet.
The crystallization of cadmium germanates in aqueous solutions of sodium hydroxide and sodium chloride under hydrothermal conditions
Authors: Duderov N. G. , Demianets L. N. , Lobachev A. N. 
Published: July 2007

AbstractThe crystallization in GeO2‐NaCl‐H2O, CdO‐NaOH(NaCl)–H2O. CdO–GeO2–H2O, CdO–GeO2–NaOH (NaCl)–H2O systems investigated under hydrothermal conditions depending on the initial ratio of CdO and GeO2 oxides in starting material and solvent concentration. Single crystals of six Cd‐germanates and five accessory compounds are obtained. The influence of the mineralizer on Cd‐germanates crystallization and the chemism of the interaction of the charge components and the solvent are discussed.
Liquid phase epitaxy of AlxGa1–xAs‐GaAs heterostructures
Authors: Alferov Zh. I. , Andreyev V. M. , Konnikov S. G. , Larionov V. R. , Shelovanova G. N. 
Published: July 2007

AbstractThis paper is concerned with the investigation of the peculiarities of the application of liquid phase epitaxy for obtaining multilayer structures with heterojunctions in the AlAs–GaAs system. Segregational depletion of Al in liquid and in solid phases is characteristic of this system. It is proved that supercooling of the substrate and numerous inclusions of Al allow to decrease this segregational depletion of Al and to obtain layers of nearly constant composition up to 600 μm in thickness.A new technique of crystallization of structures from a limited volume of melt with the change of solutions by way of compulsory squeezing out of the foregoing solution by the following one is put forward with the view to perfect the planarity of multilayer structures with abrupt heterojunctions and to improve the complete change of solutions on a substrate.The results of the study of various methods of controlling the value and direction of the Al concentration gradient are listed.It has been proved that structures with fluent increase of Al concentration during the crystallization process and also structures with alteration in the gradient direction of Al concentration may be obtained by way of artificial slowing down or acceleration of the process of mixing up solutions of various compositions.
O− centre formation in YAG crystals doped with rare earth ions
Authors: Kvapil Jiří , Kvapil Josef , Perner Bohumil 
Published: July 2007

AbstractColour changes of YAG crystals doped with rare earth ions and annealed in hydrogen, oxygen, vacuum or argon are described. The influence of UV irradiation is also given. Some crystals were further doped with Ca, Sr, Ba, or Cr, respectively. Yellow or brown colouring of the crystals is attributed to the O− centre formation which causes an increase of the absorption peak at 395–410 nm. Most intensive colouring showed the crystals containing a combination of Yb or Eu with Nd or Cr after oxygen annealing followed by UV irradiation.
Einfluß der Oberflächenbearbeitung auf die Röntgenstrahl‐Totalreflexionsprofile
Authors: Brümmer O. , Höche H. R. 
Published: July 2007

AbstractBei der Totalreflexion von Röntgenstrahlen an realen Oberflächen tritt eine Verbreiterung des einfallenden Röntgenstrahlbündels auf. Diese Verbreiterung ist eine sehr empfindliche und experimentell leicht erfaßbare Größe, mit der die Qualität lichtoptisch spiegelnder Oberflächen charakterisiert werden kann.
Recrystallization rates at periodic temperature changes
Authors: Vacek V. , Žáček S. , Horsák I. 
Published: July 2007

AbstractThis paper gives account of earlier published data on total rates of recrystallization. In the theoretical part, a simple model of recrystallization at oscillating temperature is presented. This model is evaluated for selected special cases. The resulting rate of recrystallization is compared with experimental data obtained in a laboratory double crystallizer.
Abscheidung dünner Siliziumschichten durch Zersetzung eines Siliziumtetrahlorid‐Wasserstoff‐Gemisches in einer Hochfrequenz‐Glimmentladung
Authors: Klaus M. , Hecht G. , Burgemeister D. , Andexel H.‐J. 
Published: July 2007

AbstractDas in der vorliegenden Arbeit beschriebene Verfahren gestattet es, dünne Siliziumschichten durch Zersetzung eines SiCl4/H2‐Gemisches in einer HF‐Glimmentladung auf verschiedenen Substratmaterialien abzuscheiden. In Abhängigkeit von den Wachstumsparametern und den verwendeten Substraten entstehen amorphe, polykristalline oder auch gute einkristalline Si‐Schichten. Durch Gasphasenätzung in der Versuchsapparatur lassen sich einkristalline Si‐Substrate unterschiedlicher Orientierung so vorbehandeln, daß sie für nachfolgende Epitaxie als Unterlage dienen können.
Zur Versetzungsbildung an Ritzen auf einkristallinen Silizium‐Oberflächen
Authors: Kirscht F.‐G. , Richter H. , Baehr R. , Hansch C. , Brocke H.‐D. 
Published: July 2007

AbstractDefiniert geritzte (111)‐Scheiben wurden bei 850 °C und 1000 °C getempert und mittels Strukturätzen, Röntgentopographie und Elektronenmikroskopie untersucht. Es wird der Zusammenhang zwischen Versetzungsanordnung und dem erzeugenden Verspannungszustand diskutiert. Die elektronenmikroskopischen Beobachtungen lassen sich interpretieren, wenn man eine Reaktion unter Bildung von Lomer‐Versetzungen annimmt.
Strukturuntersuchung an aufgedampften mit Aluminium modifizierten Nickel/Chrom‐schichten
Authors: Schippel E. 
Published: July 2007

AbstractDer TK des elektrischen Widerstands von aufgedampften niederohmigen Ni/Cr‐Schichten wird durch Modifizierung der Schicht mit Aluminium auf Werte um Null gesenkt. Nach den Ergebnissen der röntgenographischen und der Elektronenbeugungsuntersuchungen treten in der ternären Legierungsschicht vier Phasen auf, die α‐Phasen (Cr), die β‐Phase (NiAl), die γ‐Physe (Ni) und die γ′‐Phase (Ni3Al), die in der ungetemperten Widerstandsschicht einen sehr unvollkommenen Ordnungs‐ und Ausbildungszustand haben. Die kleinsten Werte für den TK zeigen diejenigen Schichten, in denen entsprechend der Zusammensetzung die β‐Phase entstehen kann.
Zum Einsatz der quantitativen Lichtmikroskopie bei der Versetzungsdichtebestimmung von GaAs‐〈100〉‐Kristallen
Authors: Richter H. , Fröhlich H. 
Published: July 2007

AbstractDas Prinzip der Linearanalyse mit dem EPIQUANT ist für die metallographische Messung der Versetzungsdichte von GaAs‐〈100〉‐Kristallen anwendbar. Die linearanalytischen Meßdaten werden unter Verwendung von mathematisch‐statistischen Beziehungen in Flächendaten umgerechnet. Für große Versetzungsdichten ergibt die Registrierung des Schnittlängenanteils NLE der Versetzungsätzgruben genauere Meßwerte gegenüber der Anzahl NE der von der Meßlinie geschnittenen Versetzungsätzgruben.
Positronenannihilationsuntersuchungen zur Elektronenstruktur des Systems Pd1–xAgxHnunter besonderer Berücksichtigung von Kristallbaufehlern
Authors: Brümmer Otto , Dlubek Günter 
Published: July 2007

AbstractAus Winkelkorrelationsmessungen am System Pd1–xAgxHnund an Pd1–xAgx‐Legierungen sowohl nach der H‐Desorption als auch in den Zuständen rekristallisiert und deformiert werden die folgenden Schlußfolgerungen gezogen: Die beobachtete Änderung der Winkelkorrelationskurve von PdH0,65im Vergleich zu Pd wird durch Kristallbaufehler verursacht, die bei der H‐Absorption entstehen. Für Pd0,80Ag0,20H0,43und Pd0,60Ag0,40H0,20wird solch ein Verformungseffekt nicht beobachtet. Die Ergebnisse für die Legierungen können mit Hilfe der Bandstrukturberechnungen von SWITENDICKerklärt werden.