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  • American Institute of Physics (AIP)
  • Molecular Diversity Preservation International (MDPI)
  • 1
    Electronic Resource
    Electronic Resource
    Focused ion-beam fabrication of fiber probes with well-defined apertures for use in near-field scanning optical microscopy (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 3133-3135 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a focused ion-beam (FIB) fabrication method for very clean and well-defined subwavelength fiber probes with metallic apertures of a desired diameter for use in near-field scanning optical microscopy. Such probes exhibit improved features compared to probes coated with metal by the conventional angled evaporation technique. Examples of FIB fabricated fiber probes are shown and images of a test sample are presented using one of the probes in a near-field microscope. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.121570
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    An electronic mechanism for electron pairing in antiferromagnetic bridged mixed-valence systems (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 3255-3261 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: One- and two-dimensional bridged mixed-valence systems consisting of metal atoms M and polarizable ligands L are discussed. It is argued that when the valence state of the metal atom is changed, the energy gap and the effective resonance integral between M and L orbitals are also changed. The former is due to electron–electron repulsion and the latter to ligand polarization. A Hubbard model Hamiltonian with an occupation-dependent resonance integral is adopted to describe these systems. Approximate solutions are obtained by the Hartree–Fock method. One-dimensional chains and two-dimensional nets are studied, in which metal ions are joined together by bridging ligands. The fully oxidized system is taken to have one electron per metal orbital, with the ligand orbitals vacant. The electron spin vectors are aligned in an antiferromagnetic fashion. Upon the addition of extra electrons, low-lying vacancies can be formed under certain conditions, which can lead to interesting p-type conductive properties in one or two dimensions. In the one-dimensional system, the formation of such a low-lying vacancy requires that the regional orbitals which contain the added electron are delocalized over seven units or more. (If the bridging ligands are monatomic and the metal–ligand bond distance is about 2 A(ring), then the delocalization length is about 12 A(ring).)This phenomenon is unlikely to be realizable in one dimension for the present type of system since it only occurs in parts of parameter space with an unrealistically small value for the electron–electron repulsion U. However, in two dimensions, low-lying vacancies are sometimes predicted by the present model for reasonable values for U. Furthermore, the minimum delocalization radius required for the generation of low-lying vacancies is somewhat smaller in two dimensions than in one. The relative stability of one isolated versus two paired excess electrons is also explored, although some crude assumptions about the delocalization lengths of two vs one excess electrons had to be made. When a single excess electron is delocalized over three units or more, the total energy for two paired excess electrons may be lower than that for two isolated excess electrons. Possible superconductivity by such an electronic mechanism is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461970
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  • 3
    Electronic Resource
    Electronic Resource
    On the projective representations of finite Abelian groups. II (1985)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 26 (1985), S. 3033-3035 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: Complete sets of inequivalent irreducible projective representations of Cnm ={w1,⋅⋅⋅,wn; wmi =1, i=1,...,n; wiwj =wjwi, i, j=1,...,n} with respect to a class of factor sets α are determined, where α(wi,wj) =θα(wj,wi), 1≤i〈j≤n and θ is a fixed mth root of unity. A single irreducible projective representation of Cnm for each factor set α is constructed and called the basic projective representation. The rest of the representations are obtained by tensoring the basic projective representations with some ordinary representations of Cnm. Projective representations of Cnm are thus parametrized in terms of its ordinary representations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.526679
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  • 4
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    The energy crisis in Pakistan: A possible solution via biomass-based waste (2016)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2016-08-05
    Description: Developing countries like Pakistan need a continuous supply of clean and cheap energy. It is a very common fear in today's world that the fossil fuels will be depleted soon and the cost of energy is increasing day-by-day. Renewable energy sources and technologies have the potential to provide solutions to long-standing energy problems faced by developing countries. Currently, Pakistan is experiencing a critical energy crisis and renewable energy resources can be the best alternatives for quickly terminating the need for fossil fuels. The renewable energy sources such as solar energy, wind energy, and biomass energy combined with fuel cell technology can be used to overcome the energy shortage in Pakistan. Biomass is a promising renewable energy source and is gaining more interest because it produces a similar type of fuel like crude oil and natural gas. Energy from biomass only depends upon the availability of raw materials; therefore, biomass can play an important role to fulfill the energy requirements of the modern age. The use of energy has increased greatly since the last century and almost all human activities have become more dependent on energy. Biomass, being a potential and indigenous candidate, could be a good solution to meet the energy needs of Pakistan. In this review paper, the detailed current energy requirements and solutions from available energy resources and the scope, potential, and implementation of biomass conversion to energy in Pakistan are explored with a special focus on the major province of Punjab and the advantages of biomass for energy purposes.
    Electronic ISSN: 1941-7012
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by American Institute of Physics (AIP)
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  • 5
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    Physical properties and electronic structure of a new barium titanate suboxide Ba1+δTi13−δO12 (δ = 0.11) (2015)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2015-04-14
    Description: The structure, transport, thermodynamic properties, x-ray absorption spectra (XAS), and electronic structure of a new barium titanate suboxide, Ba 1+δ Ti 13−δ O 12 ( δ = 0.11), are reported. It is a paramagnetic poor metal with hole carriers dominating the transport. Fermi liquid behavior appears at low temperature. The oxidization state of Ti obtained by the XAS is consistent with the metallic Ti 2+ state. Local density approximation band structure calculations reveal the material is near the Van Hove singularity. The pseudogap behavior in the Ti- d band and the strong hybridization between the Ti- d and O- p orbitals reflect the characteristics of the building blocks of the Ti 13 semi-cluster and the TiO 4 quasi-squares, respectively.
    Electronic ISSN: 2166-532X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by American Institute of Physics (AIP)
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  • 6
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    Accuracy limit of rigid 3-point water models (2016)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2016-08-16
    Description: Classical 3-point rigid water models are most widely used due to their computational efficiency. Recently, we introduced a new approach to constructing classical rigid water models [S. Izadi et al. , J. Phys. Chem. Lett. 5 , 3863 (2014)], which permits a virtually exhaustive search for globally optimal model parameters in the sub-space that is most relevant to the electrostatic properties of the water molecule in liquid phase. Here we apply the approach to develop a 3-point Optimal Point Charge (OPC3) water model. OPC3 is significantly more accurate than the commonly used water models of same class (TIP3P and SPCE) in reproducing a comprehensive set of liquid bulk properties, over a wide range of temperatures. Beyond bulk properties, we show that OPC3 predicts the intrinsic charge hydration asymmetry (CHA) of water — a characteristic dependence of hydration free energy on the sign of the solute charge — in very close agreement with experiment. Two other recent 3-point rigid water models, TIP3PFB and H2ODC, each developed by its own, completely different optimization method, approach the global accuracy optimum represented by OPC3 in both the parameter space and accuracy of bulk properties. Thus, we argue that an accuracy limit of practical 3-point rigid non-polarizable models has effectively been reached; remaining accuracy issues are discussed.
    Print ISSN: 0021-9606
    Electronic ISSN: 1089-7690
    Topics: Chemistry and Pharmacology , Physics
    Published by American Institute of Physics (AIP)
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  • 7
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    A new distribution power system planning approach for distributed generations with respect to reliability assessment (2016)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2016-07-02
    Description: Conventional methods for solving distribution systems planning (DSP) problem are related to the expansion of distribution systems such as substation reinforcement and feeder replacement. Nowadays, distributed generations (DGs) in various types are a new option for DSP. This paper presents a new approach to solve the DSP problem including DGs with respect to the reliability of the system. The impact of different types of DGs in order to improve the system reliability are modeled and studied by the adequacy transition rate using the Markov model. The objective functions of this optimization problem are power losses, DGs installation and operation cost, reliability indices such as energy not supplied, average interruption frequency, and average interruption duration. Since this optimization problem has a nonlinear complex nature, classical mathematical methods cannot guarantee to achieve the global optimum solution. To solve this problem, a fuzzy interactive multi-objective particle swarm optimization is developed based on Pareto solutions. The model resolves decision variables as follows: location, size, and type of the DG units. The results on IEEE 34-bus distribution system show the effectiveness of the proposed method rather than previous works for reliability assessment.
    Electronic ISSN: 1941-7012
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by American Institute of Physics (AIP)
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  • 8
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    Influences of different gases on the terahertz radiation based on the application of two-color laser pulses (2015)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2015-10-23
    Description: In this work, using a two-dimensional Particle In Cell-Monte Carlo Collision simulation method, a comparative study is performed on the influences of different types of atomic and molecular gases at various background gas pressures on the generation of broadband and intense Terahertz (THz) radiation via the application of two-color laser pulses. These two modes are focused into Argon (Ar), Xenon (Xe), Nitrogen (N 2 ), Oxygen (O 2 ), and air as the background gaseous media and the plasma channel is created. It is observed that the THz radiation emission dramatically changes due to the propagation effects. A wider THz pulse is emitted from the formed plasma channel at the higher gas pressures. The significant effects of the propagation features of the emitted THz pulse on its energy at the longer lengths of the plasma channel are observed.
    Print ISSN: 1070-664X
    Electronic ISSN: 1089-7674
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 9
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    Interference in multilayer relativistic mirrors (2015)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2015-10-15
    Description: In this paper, reflection coefficient of a relativistic ultra-thin electron multilayer is calculated using electromagnetic interference procedures. The relativistic electron layers are assumed to be formed by nonlinear plasma wake waves that constitute the electron density cusps. It is shown that the interference between successive relativistic mirrors is restricted by the condition, τ p ≫ ( 2 γ 0 ) 5 / 2 / ω p 0 , where τ p is the laser pulse duration. The results showed that tailoring the pulse amplitude, incident wave frequency value, incidence angle, and plasma density leads to increasing reflection coefficient a few orders of magnitudes. This constructive interference condition can be used for increasing conversion efficiency in the reflected energy from relativistic mirrors for the purpose of generating ultra-short coherence pulses in the extreme ultraviolet and x-ray regions. We also performed reflection from relativistic thin electron layers using relativistic 1D3V electromagnetic particle-in-cell (PIC) simulation. It was found that the results of PIC simulation are in agreement with analytical considerations.
    Print ISSN: 1070-664X
    Electronic ISSN: 1089-7674
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 10
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    Kinetic study of terahertz generation based on the interaction of two-color ultra-short laser pulses with molecular hydrogen gas (2016)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2016-06-02
    Description: In this work, using a two dimensional particle in cell-Monte Carlo collision simulation scheme, interaction of two-color ultra-short laser pulses with the molecular hydrogen gas (H 2 ) is examined. The operational laser parameters, i.e., its pulse shape, duration, and waist, are changed and, their effects on the density and kinetic energy of generated electrons, THz electric field, intensity, and spectrum are studied. It is seen that the best pulse shape generating the THz signal radiation with the highest intensity is a trapezoidal pulse, and the intensity of generated THz radiation is increased at the higher pulse durations and waists. For all the operational laser parameters, the maximum value of emitted THz signal frequency always remains lower than 5 THz. The intensity of applied laser pulses is taken about 10 14 w/cm 2 , and it is observed that while a small portion of the gaseous media gets ionized, the radiated THz signal is significant.
    Print ISSN: 1070-664X
    Electronic ISSN: 1089-7674
    Topics: Physics
    Published by American Institute of Physics (AIP)
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