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  • Springer  (56)
  • American Institute of Physics  (6)
  • 1985-1989  (59)
  • 1960-1964  (3)
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  • 1
    ISSN: 1435-1536
    Keywords: Orientation of polymer chains ; mechanical properties ; birefringence ; deformation scheme
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The computation of the orientational averages is a great problem in the case of semicrystalline polymers. In a previous communication [1] it has been shown that sinθ=f(λ) sinθ′ describes the orientational changes satisfactorily for a certain class of polymers. In this paper some alternative deformation schemes are also discussed. It has been concluded that birefringence provides a useful guideline in the choice of a deformation scheme.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Queueing systems 4 (1989), S. 249-261 
    ISSN: 1572-9443
    Keywords: Processor-sharing ; discrimination function ; gating mechanism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In this paper we consider a single server queue in which arrivals occur according to a Poisson process and each customer's service time is exponentially distributed. The server works according to the gated process-sharing discipline. In this discipline, the server provides service to a batch of at mostm customers at a time. Once a batch of customers begins service, no other waiting customer can receive service until all members of the batch have completed their service. For this queue, we derive performance characteristics, such as waiting time distribution, queue length distribution etc. For this queue, it is possible to obtain the mean conditional response time for a customer whose service time is known. This conditional response time is a nonlinear function (as opposed to the linear case for the ordinary processor-sharing queue). A special case of the queue (wherem=∞) has an interesting and unusual solution. For this special case, the size of the batch for service is a Markov chain whose steady state distribution can be explicitly written down. Apart from the contribution to the theory of Markov chains and queues, the model may be applicable to scheduling of computer and communication systems.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Queueing systems 1 (1986), S. 67-83 
    ISSN: 1572-9443
    Keywords: Assembly queue ; manufacturing ; approximations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In this paper we study a queueing model of assembly-like manufacturing operations. This study was motivated by an examination of a circuit pack testing procedure in an AT & T factory. However, the model may be representative of many manufacturing assembly operations. We assume that customers fromn classes arrive according to independent Poisson processes with the same arrival rate into a single-server queueing station where the service times are exponentially distributed. The service discipline requires that service be rendered simultaneously to a group of customers consisting of exactly one member from each class. The server is idle if there are not enough customers to form a group. There is a separate waiting area for customers belonging to the same class and the size of the waiting area is the same for all classes. Customers who arrive to find the waiting area for their class full, are lost. Performance measures of interest include blocking probability, throughput, mean queue length and mean sojourn time. Since the state space for this queueing system could be large, exact answers for even reasonable values of the parameters may not be easy to obtain. We have therefore focused on two approaches. First, we find upper and lower bounds for the mean sojourn time. From these bounds we obtain the asymptotic solutions as the arrival rate (waiting room, service rate) approaches zero (infinity). Second, for moderate values of these parameters we suggest an approximate solution method. We compare the results of our approximation against simulation results and report good correspondence.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Chemie 116 (1985), S. 431-436 
    ISSN: 1434-4475
    Keywords: Cyclopentadienyl ; Titanium(IV) complexes ; Conductometric ; IR ; 1H-NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Es wurden Titan(IV)-dithiocarbamat-Komplexe vom TypCpTi(S2CNHR)Cl2 undCpTi(S2CNHR)2Cl mitR=C8H5N2S, C9H5N2SCl2 und C9H7N2S mittels der Reaktion von Monocyclopentadienyltitan(IV)trichlorid mit dem Kaliumsalz der entsprechenden Dithiocarbaminsäure in wasserfreiem Dichlormethan dargestellt. Leitfähigkeitsmessungen und IR-Untersuchungen zeigen, daß diese Komplexe Nichtelektrolyte sind, bei denen alle Dithiocarbamat-Liganden zweizähnig sind. Demnach können 5-, bzw. 6-koordinierte Strukturen für die Komplexe des TypsCpTi(S2CNHR)Cl2, bzw.CpTi(S2CNHR)2Cl angenommen werden. Die1H-NMR Spektren zeigen eine rasche Rotation des Cyclopentadienylrings um die Metall-Ring Achse an.
    Notes: Abstract Titanium(IV) dithiocarbamato complexes of the typesCpTi(S2CNHR)Cl2 andCpTi(S2CNHR)2Cl, whereR=C8H5N2S, C9H5N2SCl2 and C9H7N2S, have been prepared by the reaction of monocyclopentadienyl titanium(IV) trichloride with the potassium salt of the appropriate dithiocarbamic acid in anhydrous dichloromethane. Conductance and infrared studies indicate that these complexes are non-electrolytes in which all dithiocarbamate ligands are bidentate. Therefore, 5 and 6 coordinate structures can be assigned toCpTi(S2CNHR)Cl2 andCpTi(S2CNHR)2Cl complexes, respectively.1H-NMR spectra indicate that there is rapid rotation of the cyclopentadienyl ring about the metal ring axis.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Distributed computing 2 (1987), S. 45-59 
    ISSN: 1432-0452
    Keywords: Database systems ; Concurrency ; Optimistic protocols ; Distributed algorithms ; Rollbacks ; Transactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Concurrency control algorithms have traditionally been based on locking and timestamp ordering mechanisms. Recently optimistic schemes have been proposed. In this paper a distributed, multi-version, optimistic concurrency control scheme is described which is particularly advantageous in a query-dominant environment. The drawbacks of the original optimistic concurrency control scheme, namely that inconsistent views may be seen by transactions (potentially causing unpredictable behavior) and that read-only transactions must be validated and may be rolled back, have been eliminated in the proposed algorithm. Read-only transactions execute in a completely asynchronous fashion and are therefore processed with very little overhead. Furthermore, the probability that read-write transactions are rolled back has been reduced by generalizing the validation algorithm. The effects of global transactions on local transaction processing are minimized. The algorithm is also free from dedlock and cascading rollback problems.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Heat and mass transfer 24 (1989), S. 169-175 
    ISSN: 1432-1181
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Description / Table of Contents: Zusammenfassung Es wurde eine theoretische Untersuchung der Wärme-, Massen- und Impulsübertragung eines verdampfenden kugelförmigen Fluidtropfens, welcher plötzlich in eine gleichgerichtete Fluidströmung höherer Temperatur eingeleitet wird, untersucht. Das Geschwindigkeitsprofil um den Fluidtropfen herum wurde als konstant und als ein Hadamard-Rybczynski-Profil angenommen. Unter Benutzung eines ADI-Schemas der Finiten-Differenzen-Methode wurden numerische Lösungen der Erhaltungsgleichungen für Energie und Dampfmasse gewonnen. Zeitliche Gesetzmäßigkeiten der durchschnittlichen Nusselt und Sherwood-Zahlen (Nu, Sh) und des Widerstandsbeiwertes (C D ) bis zur vollständigen Verdampfung des Tropfens wurden in Abhängigkeit von den zugehörigen Eingabeparametern nämlich der Anfangs-und momentanen Peclet-Zahl (Pe i ,Pe) der Lewis-Zahl und dem Verhältnis von freier Strömungstemperatur zur Eintrittstemperatur des Tropfens (T a ′ /T i ) berechnet. Ebenso werden die lokalen Nusselt und Sherwood-Zahlen in Abhängigkeit von der Peclet-Zahl im Bereich der stationären Verdampfung dargestellt. Es wurde festgestellt, daß Werte der Nusselt-Zahl im Bereich der stationären Verdampfung von Tropfen in guter Übereinstimmung mit den entsprechenden berechneten Größen aus der empirischen Gleichung von Eisenklam liegen.
    Notes: Abstract A theoretical analysis is made of the heat, mass and momentum transfer from an evaporative liquid sphere which is suddenly introduced into a parallel stream of fluid at a higher temperature. The velocity field around the liquid sphere is assumed to be steady and of the Hadamard-Rybczynski type. Numerical solutions of energy and the vapour mass continuity equations have been carried out using the alternate direction implicit scheme of finite difference method. Temporal histories of the average Nusselt and Sherwood numbers (Nu, Sh) alongwith the drag coefficient (C D ) during the life time of an evaporating drop have been predicted in terms of the pertinent input parameters, namely, initial and instantaneous Peclet number (Pe i ,Pe), Lewis number (Le), and the ratio of free stream to initial droplet temperature (T a ′ /T i ). Variations of local Nusselt and Sherwood numbers withPe, in the region of steady state evaporation, have also been presented. Values ofNu for steady state droplet evaporation are found to be in fair agreement with the corresponding values evaluated from the empirical equation of Eisenklam [5].
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  • 7
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Applications of the different formulations of garnet-clinopyroxene geothermometers to crustal granulites and particularly to metamorphosed manganese formations show a wide scatter of estimates. This is primarily related to the uncertainty associated with the formulation of the activity-composition relationship in garnet solid solution besides that in the clinopyroxene solid solution. The largest uncertainty appears to have resulted from the adopted Mg-Mn interaction parameter in garnet which is yet to be experimentally determined. A fresh statistical regression of eleven pairs of garnet and clinopyroxene equilibrated at identical P-T conditions from a manganese formation in India yields W Mg-Mn Gt (=WMn-Mg) value of 1600±500 cal/mols. An extension of the Ellis and Green (1979) geothermometer, known to work well in normal granulites, incorporating terms associated with the activity coefficients of the exchangeable cations, now yields consistent temperature estimation from normal granulites as well as from metamorphosed manganese formations. The geothermometer, however, will not work well for garnet having XFe≥0.65 and clinopyroxenes containing appreciable Na, Al and/or Fe3+.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Journal of thermal analysis and calorimetry 31 (1986), S. 387-393 
    ISSN: 1572-8943
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Die Thiocarbamato-Komplexe von Titanyl(IV), Zirkonyl(IV) und Hafnyl(IV) der allgemeinen Formel MO(S2CNRR′)2·n H2O (M=Ti, Zr oder Hf;R=H, R′=C5H9;R=H, R′=C7H11;n=1 für Ti undn=2 für Zr und Hf) wurden in wässrigem Medium hergestellt und durch Elementaranalyse, Messung der magnetischen Suszeptibilität und IR-Spektraluntersuchungen charakterisiert. Das thermische Verhalten dieser Verbindungen unter nicht-isothermen Bedingungen wurde durch TG, DTG und DSC in Stickstoff- und Sauerstoffatmosphäre untersucht. Die nach verschiedenen thermischen Zersetzungsschritten erhaltenen Zwischenprodukte wurden durch chemische Analyse und IR-Spektroskopie identifiziert. Kinetische Parameter, wie die scheinbare Aktivierungsenergie und die Reaktionsordnung, wurden nach der graphischen Methode von Coats und Redfern bestimmt. Für die einzelnen Zersetzungsschritte wurden die Reaktionswärmen aus den DSC-Kurven berechnet.
    Abstract: Резюме Дитиокарбаматные ко мплексы титанила, цирконила и гафнила. о бозначенные как MO(S2CNRR′)2·nH2O (M=ТI, Zr, Hf,R=H,R 1=C5H9, C7H11,n=1 для ТI ип =2 для циркония и гафния) был и получены в водной ср еде и охарактеризованы эл ементным анализом, ИК спектрами и измере ниями магнитной восприимчивости. Тер мическое поведение с оединений было исследовано в не изотермических усло виях методом ТГ, ДТГ и ДСК в атмосфер е кислорода и азота. Про межуточные продукты, полученные в конце каждой стадии разложения, были идентифицирова ны элементным анализ ом и ИК спектрами. Кажущаяся энергия активации и порядок реакции был и определены графиче ски по методу Коутса-Рэдфер на. На основе кривых ДСК были вычислены те плоты реакций различ ных стадий разложения.
    Notes: Abstract The dithiocarbamato complexes of titanyl(IV), zirconyl(IV) and hafnyl(IV), abbreviated as MO(S2CNRR)2·nH2O(M=Ti, Zr or Hf,R=H,R′=C5H9;R=H,R′=C7H11,n=1 for Ti andn=2 for Zr and Hf), were prepared in aqueous medium and characterized by elemental analyses, magnetic susceptibility measurements and IR spectral studies. The thermal behaviour of these compounds under non-isothermal conditions was investigated by thermogravimetric, derivative thermogravimetric and differential scanning calorimctric techniques in nitrogen and oxygen atmospheres. The intermediates obtained at the end of various thermal decomposition steps were identified on the basis of analyses and IR spectral studies. Kinetic parameters, such as apparent activation energy and order of reaction, were determined by the graphical method of Coats and Redfern. The heats of reaction for the different decomposition steps were calculated from the DSC curves.
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  • 9
    ISSN: 1572-901X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Ruthenium(III) complexes of types [Ru(L)3], [Ru(L′)Cl(H2O)2], [Ru(L″)Cl2]n, [Ru(L‴)Cl(H2O)]n(LH =Schiff bases derived from anthranilic acid and benzaldehyde, acetophenone, vanillin, cinnamaldehyde orm-hydroxyacetophenone; L′H2=Schiff bases derived from anthranilic acid and salicylaldehyde oro-hydroxyacetophenone; L″H=Schiff bases derived fromp-aminobenzoic acid and benzaldehyde, acetophenone, vanillin, cinnamaldehyde orm-hydroxyacetophenone; L‴H2=Schiff bases derived fromp-aminobenzoic acid and salicylaldehyde oro-hydroxyacetophenone) have been synthesized and characterized on the basis of elemental analyses, conductance, magnetic moment and spectral (electronic, i.r. and1H n.m.r.) data. The wavelengths of the principal electronic absorption peaks have been accounted for quantitatively in terms of crystal field theory and various parameters have been evaluated. On the basis of the electronic spectra, an octahedral geometry has been established for all these complexes except [Ru(L″)Cl2]n. The complexes [Ru(L″)Cl2]n are pentacoordinate and a trigonal-bipyramidal environment, D3h, is suggested for the ruthenium(III) ion. The thermal behaviour of these complexes has also been studied by t.g., d.t.g and d.s.c techniques. Heats of reaction for the decomposition steps were calculated from the d.s.c. curves. The antifungal and antiviral activities of the complexes with Schiff bases derived from anthranilic acid were also investigated.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 4 (1985), S. 1085-1088 
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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