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  • Springer  (515)
  • 1995-1999  (294)
  • 1985-1989  (207)
  • 1960-1964  (3)
  • 1935-1939  (8)
  • 1920-1924
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  • 11
    Digitale Medien
    Digitale Medien
    A generalSU(2) L ×SU(2) R ×U(1) B−L gauge model and experimental constraints (1985)
    Springer
    The European physical journal 28 (1985), S. 219-223 
    Details
    ISSN: 1434-6052
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Relevant low energy data are analyzed in the framework of a generalSU(2) L ×SU(2) R ×U(1) B−L electroweak gauge model. The model is general in that it allows for a left-right asymmetric gauge coupling and introduces a most general mass term for the weak gauge bosons. It is shown that the recent μ-decay measurement, combined with neutral-current data, leads to the boundM w 2〉~180 GeV on the mass of the second charged weak boson. It is also noted that the recentB-meson life-time measurement, combined with constraints from theK L 0 −K S 0 mass difference, gives a weaker bound, i.e.M w 2≳140 GeV, independently of the structure of the leptonic sector.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01575726
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  • 12
    Digitale Medien
    Digitale Medien
    High output power operation of 1.3-μm strained MQW lasers with low threshold currents at high temperature (1996)
    Springer
    Optical and quantum electronics 28 (1996), S. 503-511 
    Details
    ISSN: 1572-817X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik
    Notizen: Abstract We have investigated the temperature dependencies of the slope efficiency and the threshold current for strained multiquantum well (MQW) lasers as a parameter of the well number. Smaller well numbers mean larger temperature dependencies of the slope efficiency and the threshold current, while larger well numbers mean larger internal loss and broadening of the photoluminescence linewidth of the MQW structure. Furthermore, the change in the slope efficiency with temperature change is related to the change in internal loss. In this work, the 1.3-μm strained MQW laser with a compressive strain of 1.0% and 7 wells shows the highest output power of 6.8 mW for an injection current of 50 mA and the lowest threshold current of 5.5 mA at 85°C, and the lowest variation in output power of 2.0 dB from 25–85°C at injection current of 50 mA.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00943618
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  • 13
    Digitale Medien
    Digitale Medien
    Blue Luminescence from Silicon Nanoparticles Suspended in Organic Liquids (1999)
    Springer
    Journal of cluster science 10 (1999), S. 359-380 
    Details
    ISSN: 1572-8862
    Schlagwort(e): Silicon ; nanoparticles ; luminescence
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract We have prepared several nanometer-sized silicon colloids in organic liquids in the range from 3.7 to 9.8 nm with a constant weight density of 1 mg/ml by a gas evaporation technique. The blue–green luminescent energy was found to be independent of size, in contrast to its intensity and optical absorption, which showed a clear size effect. Special emphasis is placed on the advantage of using a colloidal system: controllability of mass density in a unit volume, isolation of each particle, selection of wide band-gap substances, capability of absolute quantum efficiency, and easy surface modification. As an example of the above advantages, we have determined the absolute quantum yield as a function of size. From the quantum yield thus derived and the proposed model that combines surface as well as volume effects, experimentally obtained parameters such as the diffusion velocity of an electron–hole pair and the initial flight distance of this pair are found to be consistent with those obtained from other data.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1021981714227
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  • 14
    Digitale Medien
    Digitale Medien
    Fe-Promoted selective methanol synthesis in CO hydrogenation catalyzed on SiO2-supported Ir4Fe and Pd6Fe6 bimetallic carbonyl cluster-derived catalysts (1989)
    Springer
    Catalysis letters 2 (1989), S. 227-233 
    Details
    ISSN: 1572-879X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The bimetallic catalysts prepared from Ir4Fe and Pd6Fe6 carbonyl clusters exhibited high activities and selectivities towards methanol from CO + H2. In contrast, hydrocarbons and CO2 were preferentially obtained on the catalyst prepared from Fe-rich PdFe4 cluster. The promotion towards methanol synthesis on the SiO2-supported Ir4Fe and Pd6Fe6 cluster catalysts was proposed to be associated with Pd-Fe3+ and Ir-Fe3+ sites located at the metal-support interface.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00766211
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  • 15
    Digitale Medien
    Digitale Medien
    Cu/Ni colloidal dispersions stabilised by calcium and barium stearates for the amination of oxo-alcohols (1996)
    Springer
    Catalysis letters 40 (1996), S. 123-130 
    Details
    ISSN: 1572-879X
    Schlagwort(e): Cu/Ni colloidal dispersion ; barium stearate ; calcium stearate ; protective colloid ; amination of oxo-alcohols ; tertiary amine
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Bimetallic Cu/Ni colloidal dispersions (the core catalyst) stabilised by a combination of calcium and barium stearates as protective colloids (catalyst C) showed a remarkable catalytic activity-several times higher than that of the core catalyst stabilised by barium stearate only (catalyst A) for the amination reaction of low reactive oxo-alcohols, having steric hindrance by branched alkyls, with dimethylamine to prepare N,N-dimethyl tertiary amines. Application of the catalyst C for the same amination reaction of dodecyl alcohol could be performed at a lower catalyst concentration of even 100 ppm based on copper at 220° C with a tertiary amine yield of 92% in a three hours' reaction. The reaction mixture containing catalyst C formed a gel at room temperature and formed a stable homogeneous solution with acetone as a polar solvent. It is postulated that water-repellency of calcium stearate and further incorporation of barium stearate as a second promoter yields a doubly stabilised structure for the core catalyst resulting in a remarkable increase in catalytic activity.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00807469
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  • 16
    Digitale Medien
    Digitale Medien
    Cellulose/poly(acryloyl morpholine) composites: synthesis by solution coagulation/bulk polymerization and analysis of phase structure (1998)
    Springer
    Cellulose 5 (1998), S. 123-134 
    Details
    ISSN: 1572-882X
    Schlagwort(e): cellulose ; poly(acryloyl morpholine) ; composite ; interpenetrating polymer network
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract Cellulose/poly(acryloyl morpholine) (CELL/PACMO) compo sites were synthesized by bulk polymerization in the gel state of cellulose impregnated with reactive ACMO monomer. The thermal transition behaviour and phase structure of the CELL/PACMO composites obtained in film form were investigated by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and solid-state 13C NMR spectroscopy. For compositions rich in PACMO (CELL ≤ 30 wt %), it was revealed by DSC and DMA that the synthesized samples gave a composition-dependent Tg value higher than that of PACMO homopolymer, and the magnitude of the lowering of their dynamic modulus E′ in the glass transition region became extremely small in comparison with the corresponding drop in E′ noted for plain PACMO samples. These observations were interpreted as being due to the development of an interpenetrating polymer network (IPN)-type organization, resulting from successful fixation of an original netw ork structure of cellulose gels into the polymerized bulks. From the measurements of proton spin-lattice relaxation times in the NMR study, the IPN-like composites were estimated to be substantially homogeneous on a scale of a few nanometers. 0969--0239 © 1998 Blackie Academic & Professional
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009224931504
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  • 17
    Digitale Medien
    Digitale Medien
    Lattice path counting andM/M/c queueing systems (1995)
    Springer
    Queueing systems 19 (1995), S. 193-214 
    Details
    ISSN: 1572-9443
    Schlagwort(e): M/M/c queue ; transient solution ; lattice path counting ; depth of path
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Notizen: Abstract We apply the lattice path counting method to the analysis of the transientM/M/c queueing system. A closed-form solution is obtained for the probability of exactlyi arrivals andj departures within a time interval of lengtht in anM/M/c queueing system that is empty at the initial time. The derivation of the probability is based on the counting of paths from the origin to(i,j) on thexy-plane, that have exactly rd x-steps whose depth from the liney=x isd (d=0,1,...,c−1). The closed-form solution has an expression useful for numerical calculation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01148946
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  • 18
    Digitale Medien
    Digitale Medien
    AnM/M/s-consistent diffusion model for theGI/G/s queue (1995)
    Springer
    Queueing systems 19 (1995), S. 377-397 
    Details
    ISSN: 1572-9443
    Schlagwort(e): GI/G/s queues ; diffusion model ; conditional departure process ; renewal-process approximations ; consistent discretization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Notizen: Abstract This paper develops a diffusion-approximation model for a stableGI/G/s queue: The queue-length process in theGI/G/s queue is approximated by a diffusion process on the nonnegative real line. Some heuristics on the state space and the infinitesimal parameters of the approximating diffusion process are introduced to obtain an approximation formula for the steady-state queue-length distribution. It is shown that the formula is consistent with the exact results for theM/M/s andM/G/∞ queues. The accuracy of the approximations for principal congestion measures are numerically examined for some particular cases.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01151930
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  • 19
    Digitale Medien
    Digitale Medien
    Formation of stars by implosion of a gas cloud (1987)
    Springer
    Astrophysics and space science 129 (1987), S. 261-269 
    Details
    ISSN: 1572-946X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The evolution of the molecular gas cloud embedded in anHii region is studied. We consider a spherical, uniform, and stable molecular gas cloud, which is exposed to strong ionizing radiation from nearby massive stars. The gas cloud is strongly compressed by the surrounding high-pressure ionized gas and a shock wave is formed. The shock compressed gas forms a shell which converges toward the center of the cloud sweeping up the inner material. As the shell accumulates the swept up gas, it becomes gravitationally unstable. The growth time of the instability is less than the time-scale of the whole collapse of the cloud. Thus, the shell will break into fragments before it reaches the center of the cloud, leading to formation of a stellar association or a cluster.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00642644
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  • 20
    Digitale Medien
    Digitale Medien
    Recirculating feed operation of bipolar packed-bed and trickle-bed electrode cells equipped with mesh spacers (1987)
    Springer
    Journal of applied electrochemistry 17 (1987), S. 724-730 
    Details
    ISSN: 1572-8838
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Abstract Unsteady state changes in ion concentration, liquid conductivity and electric current via different pathways in a bipolar packed-bed electrode cell were investigated by using the electrochemical reduction of Cu(II) ions. Ferrite pellets were used as particle electrodes and were packed in layers separated by plastic spacers. The electrode reaction rate was controlled by the diffusion of Cu(II) ions. The faradaic current passing through the pellets decreased with time, while the bypass current through the liquid bulk phase increased with time because of the production of hydrogen ions. The faradaic and bypass currents and the overall current efficiency were well simulated by a proposed reactor model. The overall current efficiency unavoidably decreased with time when the electrolyte was recirculated. However, the employment of trickle flow reduced the liquid hold-up in the bed and consequently reduced the bypass current. The overall current efficiency in the trickle-bed electrode cell was 20–30% higher than that in the flooded packed-bed electrode cell.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01007807
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