A device prototype, based on the superelastic properties of Shape Memory Alloys (SMAs), is proposed to enhance the thermal and seismic behavior of steel tie-rods. First, the thermal behavior of steel ...tie-rods with and without SMAs is presented based on the results of extensive experimental tests in thermal room. Next, the seismic performances of the proposed SMA system are discussed based on the results of a series of shaking table tests on a 1:4-scale timber roof truss model. In this article, the functioning principles of the proposed SMA-based device prototype are illustrated and the main aspects related to its implementation in practice are discussed in detail. Finally, a recent example of application of the proposed technology to a historic single-aisle church, realized in the 13th century in Brindisi (southern Italy), and equipped with inadequate and deteriorated steel tied rods, is shown.
In this paper, we first point out a missing active device while providing its theoretical definition and impact on electronics. This type of active devices has an inverse functionality of transistors ...and is suggested to be called trancitor rather than transistor, because it directly transfers an input signal into a voltage output. It is expected that a trancitor coupled with a transistor can provide a minimal circuit configuration, i.e., low circuit complexity, helping virtually to meet Moore's law. In addition, this may also lead to a lower power consumption and higher speed of circuits compared with a transistor-only circuit. These are supported with a circuit simulation and simple Tetris-like block analysis. In this regard, in the future, it should be required to find a trancitor to be another foundation of electronics along with transistors.
On-Device Tag Generation for Unstructured Text Chugani, Manish; Vatsal, Shubham; Ramena, Gopi ...
2021 IEEE 15th International Conference on Semantic Computing (ICSC),
2021-Jan.
Conference Proceeding
Open access
With the overwhelming transition to smart phones, storing important information in the form of unstructured text has become habitual to users of mobile devices. From grocery lists to drafts of emails ...and important speeches, users store a lot of data in the form of unstructured text (for eg: in the Notes application) on their devices, leading to cluttering of data. This not only prevents users from efficient navigation in the applications but also precludes them from perceiving the relations that could be present across data in those applications. This paper proposes a novel pipeline to generate a set of tags using world knowledge based on the keywords and concepts present in unstructured textual data. These tags can then be used to summarize, categorize or search for the desired information thus enhancing user experience by allowing them to have a holistic outlook of the kind of information stored in the form of unstructured text. In the proposed system, we use an on-device (mobile phone) efficient CNN model with pruned ConceptNet resource to achieve our goal. The architecture also presents a novel ranking algorithm to extract the top n tags from any given text.
•InGaAsN/AlGaAs QWIPs for e-SWIR.•CBO values reaching up to ∼1 eV with GaAs technology.•Room temperature photocurrent response that spans between 1.1 and 2.2 μm.•Room temperature responsivity of 15 ...and 1 A/W for 1.65 μm and 2 μm, respectively.•Corresponding detectivity values of ∼1010 and ∼5 × 108 cm·Hz1/2/W at 1.65 μm and 2.0 μm, respectively. Potential detectivity values as high as ∼2 × 1012 and ∼1 × 1011 cm·Hz1/2/W for ∼1.65 μm and 2.0 μm, respectively can be achieved.
We propose and demonstrate a novel concept to address high-performance, extended short wavelength (e-SWIR) photodetectors. Our approach is based on shifting the well-developed GaAs quantum-well infrared photodetector (QWIP) technology to e-SWIR wavelengths. In order to increase the available conduction band offsets (CBOs), we suggest incorporating nitrogen (N) atoms into the quantum well material. The incorporation of N atoms into III-Vs results in dilute-nitride highly mismatched alloys with lower bandgaps and higher CBOs. In our work, we demonstrate CBO values reaching up to ∼1 eV in InGaAsN/AlGaAs QWIPs. This large CBO makes these structures suitable for e-SWIR detection. The large CBO reduces the dark current dramatically and allows efficient detection at room temperature.
In our study, we devised two similar InGaAsN/AlGaAs QWIP devices with twofold, 1% and 2% N composition. Based on the measured dark current data, we extracted activation energy barriers of 780 meV and 580 meV for the 1% and 2% N devices, respectively. The dark current and photocurrent spectral response behave in correlation to the change in the barriers’ height. The photocurrent response of the 1% N device peaks at ∼2.25 μm and spans at a spectral range between 1.3 and 2.95 μm. The photocurrent response of the 2% N device is blue shifted to ∼1.42 μm and spans at a spectral range between 1.1 and 2.2 μm. The 2% N device exhibits lower dark currents and a strong photoresponse at room temperature, whereas the 1% N device exhibits a clear response only at temperatures below 150 K.
The detection mechanism in the InGaAsN/AlGaAs QWIP devices is based on optical excitation of carriers from the quantum wells into highly-localized nitrogen-related E+ defect-like states located energetically above the conduction band edge. For this reason, the photoresponse is insensitive to the radiation polarization and exhibits low absorption efficiency on the order of 0.15% per quantum well. However, at the same time, the responsivity and photocurrent gain are very high due to the long lifetime of the highly localized excited states.
The peak responsivity of the 2% N device is ∼70 A/W at room temperature. Significant responsivity is also available at the response tail at longer wavelengths, i.e., ∼15 and 1 A/W for 1.65 μm—the peak wavelength of the night glow emission and 2 μm—at the e-SWIR wavelengths, respectively. Corresponding detectivity values are ∼1010 and ∼5 × 108 cm·Hz1/2/W at 1.65 μm and 2.0 μm, respectively. These values are similar to those of other developing technologies. In-reach potential detectivity is estimated based on the measured data and can arrive easily to values as high as ∼2 × 1012 and ∼1 × 1011 cm·Hz1/2/W for ∼1.65 μm and 2.0 μm, respectively.
The presented characteristics and potential performance indicate that InGaAsN/AlGaAs quantum wells are most suitable for efficient e-SWIR photodetection.
Zinc-blende GaN: ab initio calculations Alves, J.L.A; Leite Alves, H.W; de Oliveira, C ...
Materials science & engineering. B, Solid-state materials for advanced technology,
12/1997, Volume:
50, Issue:
1
Journal Article, Conference Proceeding
Peer reviewed
The purpose of this paper is to contribute, on a theoretical basis, an understanding of future wide-gap device concepts and applications based on III–V nitride semiconductors. The electronic ...properties of zinc-blende structure GaN and their (110), (100) and (111) surfaces are investigated using ab initio calculations based on the full potential linear augmented plane-wave (FPLAPW) method within the large unit cell approach, and on the molecular Gaussian-92 code. Lattice constant, cohesive energy, bulk modulus are obtained from total energy calculations. Light-hole and heavy-hole effective masses along (100), (111) and (110) directions and electron masses at Γ point are extracted from band structure calculations and compared with previous ones based on pseudopotential methods. The hydrostatic pressure dependence of the ΓΓ, ΓX and ΓL energy gaps are also obtained. Comparing our band structure and `molecular cluster' calculations, the relaxations of the surfaces are found to be mostly determined by local rehybridization or valence effects and are basically independent of energy band features.
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