7,241 research outputs found
Space charge and charge trapping characteristics of cross-linked polyethylene subjected to ac electric stresses
This paper reports on the result of space charge evolution in cross-linked polyethylene (XLPE) planar samples of approximately 220 ?m thick. The space charge measurement technique used in this study is the PEA method. There are two phases to this experiment. In the first phase, the samples were subjected to dc 30 kVdc/mm and ac (sinusoidal) electric stress level of 30 kVpk/mm at frequencies of 1 Hz, 10 Hz and 50 Hz ac. In addition, ac space charge under 30 kVrms/mm and 60 kVpk/mm electric stress at 50 Hz was also investigated. The volts off results showed that the amount of charge trapped in XLPE sample under dc electric stress is significantly bigger than samples under ac stress even when the applied ac stresses are substantially higher. The second phase of the experiment involves studying the dc space charge evolution in samples that were tested under ac stress during the first phase of the experiment. Ac ageing causes positive charge to become more dominant over negative charge. It was also discovered that ac ageing creates deeper traps, particularly for negative charge. This paper also gave a brief overview of the data processing methods used to analyse space charge under ac electric stress
Si/Ge hole-tunneling double-barrier resonant tunneling diodes formed on sputtered flat Ge layers
We have demonstrated Si/Ge hole-tunneling double-barrier resonant tunneling diodes (RTDs) formed on flat Ge layers with a relaxation rate of 89% by our proposed method; in this method, the flat Ge layers can be directly formed on highly B-doped Si(001) substrates using our proposed sputter epitaxy method. The RTDs exhibit clear negative differential resistance effects in the static current–voltage (I–V) curves at room temperature. The quantized energy level estimation suggests that resonance peaks that appeared in the I–V curves are attributed to hole tunneling through the first heavy- and light-hole energy levels
A Bibliometric Review on Risk Management and Building Information Modeling for International Construction
International construction is complicated and involves high risks. However, with the development of technological innovation, Building Information Modeling (BIM) emerged and seems to be able to address certain risks. To understand BIM applications in risk management for international construction, a state-of-the-art review is required. Therefore, this paper aims to identify the research trends and opportunities for risk management in BIM-enabled international construction by reviewing 526 peer-reviewed journal articles for the years 2007-2017. Thus five steps of bibliometric analysis were conducted based on the proposed frameworks of BIM risk management in international construction (BIM-RM-INTL). The results show that the popularization of BIM not only attracts all stakeholders' interests but also brings some risks. For example, financial factors are hard to detect and control through BIM, information loss during transmission stands out, and BIM has no unified standards and regulations for international construction. The research has mapped existing research results and their relationships for future risk management in BIM-enabled international construction
DEVELOPMENT OF A UNIFIED OPEN E-LOGISTICS STANDARDS DIFFUSION MODEL FOR MANUFACTURING SUPPLY CHAIN INTEGRATIONS
Open E-Logistics Standards (OELS) is important to facilitate the integration of the supply chain. In OELS, the transmission and the manipulation of data are governed by open data and process standards that define their format, structure, and the semantics of data flow between trading partners. Despite the significant investments made by governments and leading firms, there remain concerns about OELS’ slow development progress and low adoption rates. The potential failure of OELS represents a significant stumbling block for governments and supply chain practitioners who have envisioned a globalized supply chain network electronically enabled by OELS. Researchers are also concerned about the inadequate models that are used to explain and understand the adoption of OELS. Although analysing adopter configurations in what is known as configuration analysis has been examined in disciplines related to science and economics, its application in the study of OELS remains sparse. This research aims to integrate multiple theoretical views, and apply configuration analysis with an improved methodological approach in order to examine OELS diffusion decisions and processes. The project will result in a new algorithm integrating structural equation modelling and neural network, and a decision support system which helps firms improve their OELS adoption decision
Improvement of dielectric loss of doped Ba0.5Sr0.5TiO3 thin films for tunable microwave devices
Al2O3-Ba0.5Sr0.5TiO3 (Al2O3-BST) thin films, with different Al2O3 contents,
were deposited on (100) LaAlO3 substrate by pulsed laser deposition (PLD)
technique. The Al2O3-BST films was demosnstrated to be a suitable systems to
fabricate ferroelectric thin films with low dielectric loss and higher figure
of merit for tunable microwave devices. Pure BST thin films were also
fabricated for comparison purpose. The films' structure and morphology were
analyzed by X-ray diffractiopn and scanning electron microscopy, respectively;
nad showed that the surface roughness for the Al2O3-BST films increased with
the Al2O3 content. Apart from that, the broadening in the intensity peak in XRD
result indicating the grain size of the Al2O3-BST films reduced with the
increasing of Al2O3 dopant. We measured the dielctric properties of Al2O3-BST
films with a home-made non-destructive dual resonator method at frequency ~ 7.7
GHZ. The effect of doped Al2O3 into BST thin films significantly reduced the
dielectric constant, dielectric loss and tunability compare to pure BST thin
film. Our result shows the figure of merit (K), used to compare the films with
varied dielectric properties, increased with the Al2O3 content. Therefore
Al2O3-BST films show the potential to be exploited in tunable microwave
devices.Comment: 8 pages, 4 figures, 1 table. Accepted & tentatively for Feb 15 2004
issue, Journal of Applied Physic
Life Cycle Aware Computing: Reusing Silicon Technology
Despite the high costs associated with processor manufacturing, the typical chip is used for only a fraction of its expected lifetime. Reusing processors would create a food chain of electronic devices that amortizes the energy required to build chips over several computing generations
Lepton flavor violating semileptonic decays in a topcolor scenario
The contributions of the neutral top-pion and the non-universal
gauge boson predicted by topcolor scenario to the lepton flavor violating
semileptonic decays
and are discussed. We find that the contributions of
to these decay processes are generally larger than those from .
can only make the value of the branching ratio
in the range of 1 1, which is far below
the sensitivity of foreseeable experiments. With reasonable values of the free
parameters, the non-universal gauge boson can make the value of the
branching ratio reach 1, which
might approach the observable threshold of near-future experiments.Comment: 15 pages. Discussions added, some typos correcte
A scalar field instability of rotating and charged black holes in (4+1)-dimensional Anti-de Sitter space-time
We study the stability of static as well as of rotating and charged black
holes in (4+1)-dimensional Anti-de Sitter space-time which possess spherical
horizon topology. We observe a non-linear instability related to the
condensation of a charged, tachyonic scalar field and construct "hairy" black
hole solutions of the full system of coupled Einstein, Maxwell and scalar field
equations. We observe that the limiting solution for small horizon radius is
either a hairy soliton solution or a singular solution that is not a regular
extremal solution. Within the context of the gauge/gravity duality the
condensation of the scalar field describes a holographic
conductor/superconductor phase transition on the surface of a sphere.Comment: 16 pages including 8 figures, v2: discussion on soliton solutions
extended; v3: matches version accepted for publication in JHE
PT-Symmetric Electronics
We show both theoretically and experimentally that a pair of inductively
coupled active LRC circuits (dimer), one with amplification and another with an
equivalent amount of attenuation, display all the features which characterize a
wide class of non-Hermitian systems which commute with the joint parity-time PT
operator: typical normal modes, temporal evolution, and scattering processes.
Utilizing a Liouvilian formulation, we can define an underlying PT-symmetric
Hamiltonian, which provides important insight for understanding the behavior of
the system. When the PT-dimer is coupled to transmission lines, the resulting
scattering signal reveals novel features which reflect the PT-symmetry of the
scattering target. Specifically we show that the device can show two different
behaviors simultaneously, an amplifier or an absorber, depending on the
direction and phase relation of the interrogating waves. Having an exact
theory, and due to its relative experimental simplicity, PT-symmetric
electronics offers new insights into the properties of PT-symmetric systems
which are at the forefront of the research in mathematical physics and related
fields.Comment: 17 pages, 7 figure
- …