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  • 1
    Publication Date: 2015-08-14
    Description: In this paper, we propose a new parameter for glass-forming ability (GFA) based on the combination of thermodynamic (stability of stable and metastable liquids by ΔT m  =  T m mix − T l and ΔT x  =  T x − T g , respectively) and kinetic (resistance to crystallization by T x ) aspects for glass formation. The parameter is defined as ε  = ( ΔT m  +  ΔT x  +  T x )/ T m mix without directly adding T g while considering the whole temperature range for glass formation up to T m mix , which reflects the relative position of crystallization curve in continuous cooling transformation diagram. The relationship between the ε parameter and critical cooling rate ( R c ) or maximum section thickness for glass formation ( Z max ) clearly confirms that the ε parameter exhibits a better correlation with GFA than other commonly used GFA parameters, such as Δ T x (= T x − T g ), K (=[ T x − T g ]/[ T l − T x ]), Δ T *(=( T m mix − T l ) /T m mix ), T rg (= T g / T l ), and γ (=[ T x ]/[ T l  +  T g ]). The relationship between the ε parameter and R c or Z max is also formulated and evaluated in the study. The results suggest that the ε parameter can effectively predict R c and Z max for various glass-forming alloys, which would permit more widespread uses of these paradigm-shifting materials in a variety of industries.
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
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  • 2
    Publication Date: 2015-06-12
    Description: A sensitive radioactive aerosols sensor has been designed and developed. Its design guidance is based on the need for a low operational cost and reliable measurements to provide daily aerosol monitoring. The exposure of diethylene-glycol bis (allylcarbonate) to radiation causes modification of its physico-chemical properties like surface roughness and reflectance. In the present study, optical sensor based on the reflectance measurement has been developed with an aim to monitor real time presence of alpha radioactive aerosols emitted from thorium nitrate hydrate. The results shows that the fabricated sensor can detect 0.0157 kBq to 0.1572 kBq of radio activity by radioactive aerosols generated from (Th(NO 3 ) 4 ⋅ 5H 2 O) at 0.1 ml/min flow rate. The proposed instrument will be helpful to monitor radioactive aerosols in/around a nuclear facility, building construction sites, mines, and granite polishing factories.
    Print ISSN: 0034-6748
    Electronic ISSN: 1089-7623
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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  • 3
    Publication Date: 2014-12-02
    Description: The Pohang Light Source upgrade (PLS-II) project has successfully upgraded the Pohang Light Source (PLS). The main goals of the PLS-II project are to increase the beam energy to 3 GeV, increase the number of insertion devices by a factor of two (20 IDs), increase the beam current to 400 mA, and at the same time reduce the beam emittance to below 10 nm by using the existing PLS tunnel and injection system. Among 20 insertion devices, 10 narrow gap in-vacuum undulators are in operation now and two more in-vacuum undulators are to be installed later. Since these narrow gap in-vacuum undulators are most likely to produce coupled bunch instability by the resistive wall impedance and limit the stored beam current, a bunch by bunch feedback system is implemented to suppress coupled bunch instability in the PLS-II. This paper describes the scheme and performance of the PLS-II bunch by bunch feedback system.
    Print ISSN: 0034-6748
    Electronic ISSN: 1089-7623
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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  • 4
    Publication Date: 2014-11-12
    Description: This Note presents a nonlinear device model for organic light emitting diodes (OLEDs), which can describe dynamic and static characteristics of OLEDs consistently. The parameters of the proposed model are estimated by using a particle swarm optimization algorithm. Some of the resulting parameters relate with physical characteristics of OLEDs. With only one set of experiments leading to a time response of an OLED device, this nonlinear model, together with all the parameters, is obtained, which can be a big advantage for the fast quality control of the OLEDs.
    Print ISSN: 0034-6748
    Electronic ISSN: 1089-7623
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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  • 5
    Publication Date: 2016-11-01
    Description: Modulation of electrical properties in MoS 2 flakes is an attractive issue from the point of view of device applications. In this work, we demonstrate that an ambipolar behavior in MoS 2 field effect transistors (FETs) can be easily obtained by heating MoS 2 flakes under air atmosphere in the presence of cobalt oxide catalyst (MoS 2  + O 2  → MoO x  + SO x ). The catalytic oxidation of MoS 2 flakes between source-drain electrodes resulted in lots of MoO x nanoparticles (NPs) on MoS 2 flakes with thickness reduction from 64 nm to 17 nm. Consequently, N-type behavior of MoS 2 FETs was converted into ambipolar transport characteristics by MoO x NPs which inject hole carriers to MoS 2 flakes.
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
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  • 6
    Publication Date: 2015-07-21
    Description: A transistor structure composed of an individual single-walled carbon nanotube (SWNT) channel with a graphene electrode was demonstrated. The integrated arrays of transistor devices were prepared by transferring patterned graphene electrode patterns on top of the aligned SWNT along one direction. Both single and multi layer graphene were used for the electrode materials; typical p-type transistor and Schottky diode behavior were observed, respectively. Based on our fabrication method and device performances, several issues are suggested and discussed to improve the device reliability and finally to realize all carbon based future electronic systems.
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
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  • 7
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 7222-7227 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The magnetoconductivity of two kinds of iodine doped helical polyacetylene, R- and S-polyacetylene, were investigated to understand the effect of the intrafibril and the interfibrillar interaction in the polyacetylene system. The zero-field resistivity ratio, ρr=ρ(1.2 K)/ρ(300 K), is comparable to that of stretch-oriented high-density polyacetylene film, which indicates the partial alignment of chains inside a polymer fiber. At low magnetic fields, the small negative component of magnetoconductivity (positive magnetoresistance) was observed and its magnitude increases as the ρr value increases. In the high field region, the magnetoconductivity is positive and it clearly shows the linear dependence on the magnetic field up to H=30 T. The linear field dependence of magnetoconductivity is different from what is expected in the three-dimensional localization-interaction picture. For the same ρr value samples, the magnitude of negative magnetoconductivity of S-polyacetylene is much bigger than that of R-polyacetylene, which could be attributed to the difference in the degree of helicity determining the strength of interfibrillar interaction. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 175-180 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: SnO2 thin films were grown on p-InSb (111) substrates by radio-frequency magnetron sputtering at low temperature. Atomic force microscopy images showed that the root mean square of the average surface roughness of the SnO2 films grown on the InSb (111) substrates with an Ar/O2 flow rate of 0.667 and at a temperature of 200 °C had a minimum value of 2.71 nm, and x-ray diffraction and transmission electron microscopy (TEM) measurements showed that these SnO2 thin films were polycrystalline. Auger electron spectroscopy and bright-field TEM measurements showed that the SnO2/p-InSb(111) heterointerface was relatively abrupt. High-resolution TEM measurements revealed that the SnO2 films were nanocrystalline and that the grain sizes of the nanocystalline films were below 6.8 nm. The capacitance–voltage measurements at room temperature showed that the type and the carrier concentration of the nominally undoped SnO2 film were n type and approximately 1.67×1016 cm−3, respectively, and the current–voltage curve indicated that the Au/n-SnO2/p-InSb diode showed tunneling breakdown. Photoluminescence spectra showed that peaks corresponding to the donor acceptor pair transitions were dominant and that the peak positions did not change significantly as a function of the measured temperature. These results indicate that the SnO2 nanocrystalline thin films grown on p-InSb (111) substrates at low temperature hold promise for new kinds of potential optoelectronic devices based on InSb substrates, such as superior gas sensors and high-efficiency solar cells. © 2001 American Institute of Physics.
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 2503-2505 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Selected area electron diffraction pattern (SADP) and transmission electron microscopy (TEM) measurements were carried out to investigate the ordered structures in lattice-mismatched InxGa1−xAs/InyAl1−yAs multiple quantum wells (MQWs). The SADP showed two sets of extra spots with asymmetrical intensity, and the high-resolution TEM image showed doublet periodicity in the contrast of the (001) lattice planes. The results of the SADP and the TEM measurements showed that a CuAu–I-type ordered structure was observed near the lattice-mismatched InxGa1−xAs/InyAl1−yAs heterointerfaces. This CuAu–I-type ordered structure had an antiphase boundary in the periodically regular InxGa1−xAs/InyAl1−yAs lattice-mismatched region. The existence of a CuAu–I-type ordered structure in InxGa1−xAs/InyAl1−yAs MQWs might originate from the lattice mismatch between the InxGa1−xAs and the InyAl1−yAs layers. These results provide important information on the microstructural properties for improving operating efficiencies in long-wavelength optoelectronic devices, such as strain compensated electroabsorption modulators utilizing lattice-mismatched InxGa1−xAs/InyAl1−yAs MQWs. © 2001 American Institute of Physics.
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 5253-5255 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The phase equilibria in the system Co–Mn–Sn have been studied with compositions along the join Co–CoMnSn. This is part of an effort to form a macroscopic ferrimagnet with two metallic ferromagnetic phases, Co and Co2MnSn. As-cast arc melted alloys have been made with Co compositions from 33 to 78 at. %. Three different phase and magnetization regions are observed with increasing Co composition. Cobalt becomes the primary phase at more than 71 at. % Co and crystallizes out of a Co2MnSn rich matrix. It is shown from x-ray diffraction analysis and the Tc change with Co compositions that the Co phase in Co2MnSn matrix is probably a Co–Mn solid solution. From the break in the magnetization vs temperature curves of two phase magnets with two different compositions, Curie temperatures are determined as approximately 160 °C and 175 °C for the Co–Mn solid solution phase. The exchange coupling at phase boundary is proposed by the analysis of coercivity vs temperature data. © 1996 American Institute of Physics.
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