29 research outputs found
A Jamming Attacks Detection Approach Based on CNN based Quantum Leap Method for Wireless Sensor Network
The wireless sensor network is the most significant largest communication device. WSN has been interfacing with various wireless applications. Because the wireless application needs faster communication and less interruption, the main problem of jamming attacks on wireless networks is that jamming attack detection using various machine learning methods has been used. The reasons for jamming detection may be user behaviour-based and network traffic and energy consumption. The previous machine learning system could not present the jamming attack detection accuracy because the feature selection model of Chi-Squared didn’t perform well for jamming attack detections which determined takes a large dataset to be classified to find the high accuracy for jamming attack detection. To resolve this problem, propose a CNN-based quantum leap method that detects high accuracy for jamming attack detections the WSN-DS dataset collected by the Kaggle repository. Pre-processing using the Z-score Normalization technique will be applied, performing data deviations and assessments from the dataset, and collecting data and checking or evaluating data. Fisher’s Score is used to select the optimal feature of a jamming attack. Finally, the proposed CNN-based quantum leap is used to classify the jamming attacks. The CNN-based quantum leap simulation shows the output for jamming attacks with high precision, high detection, and low false alarm detection
Ideal Bandgap in a 2D Ruddlesden-Popper Perovskite Chalcogenide for Single-junction Solar Cells
Transition metal perovskite chalcogenides (TMPCs) are explored as stable,
environmentally friendly semiconductors for solar energy conversion. They can
be viewed as the inorganic alternatives to hybrid halide perovskites, and
chalcogenide counterparts of perovskite oxides with desirable optoelectronic
properties in the visible and infrared part of the electromagnetic spectrum.
Past theoretical studies have predicted large absorption coefficient, desirable
defect characteristics, and bulk photovoltaic effect in TMPCs. Despite recent
progresses in polycrystalline synthesis and measurements of their optical
properties, it is necessary to grow these materials in high crystalline quality
to develop a fundamental understanding of their optical properties and evaluate
their suitability for photovoltaic application. Here, we report the growth of
single crystals of a two-dimensional (2D) perovskite chalcogenide, Ba3Zr2S7,
with a natural superlattice-like structure of alternating double-layer
perovskite blocks and single-layer rock salt structure. The material
demonstrated a bright photoluminescence peak at 1.28 eV with a large external
luminescence efficiency of up to 0.15%. We performed time-resolved
photoluminescence spectroscopy on these crystals and obtained an effective
recombination time of ~65 ns. These results clearly show that 2D
Ruddlesden-Popper phases of perovskite chalcogenides are promising materials to
achieve single-junction solar cells.Comment: 4 Figure
Built-in and induced polarization across LaAlO/SrTiO heterojunctions
Ionic crystals terminated at oppositely charged polar surfaces are inherently
unstable and expected to undergo surface reconstructions to maintain
electrostatic stability. Essentially, an electric field that arises between
oppositely charged atomic planes gives rise to a built-in potential that
diverges with thickness. In ultra thin film form however the polar crystals are
expected to remain stable without necessitating surface reconstructions, yet
the built-in potential has eluded observation. Here we present evidence of a
built-in potential across polar \lao ~thin films grown on \sto ~substrates, a
system well known for the electron gas that forms at the interface. By
performing electron tunneling measurements between the electron gas and a
metallic gate on \lao ~we measure a built-in electric field across \lao ~of 93
meV/\AA. Additionally, capacitance measurements reveal the presence of an
induced dipole moment near the interface in \sto, illuminating a unique
property of \sto ~substrates. We forsee use of the ionic built-in potential as
an additional tuning parameter in both existing and novel device architectures,
especially as atomic control of oxide interfaces gains widespread momentum.Comment: 6 pages, 4 figures. Submitted to Nature physics on May 1st, 201
Colossal optical anisotropy from atomic-scale modulations
In modern optics, materials with large birefringence ({\Delta}n, where n is
the refractive index) are sought after for polarization control (e.g. in wave
plates, polarizing beam splitters, etc.), nonlinear optics and quantum optics
(e.g. for phase matching and production of entangled photons),
micromanipulation, and as a platform for unconventional light-matter coupling,
such as Dyakonov-like surface polaritons and hyperbolic phonon polaritons.
Layered "van der Waals" materials, with strong intra-layer bonding and weak
inter-layer bonding, can feature some of the largest optical anisotropy;
however, their use in most optical systems is limited because their optic axis
is out of the plane of the layers and the layers are weakly attached, making
the anisotropy hard to access. Here, we demonstrate that a bulk crystal with
subtle periodic modulations in its structure -- Sr9/8TiS3 -- is transparent and
positive-uniaxial, with extraordinary index n_e = 4.5 and ordinary index n_o =
2.4 in the mid- to far-infrared. The excess Sr, compared to stoichiometric
SrTiS3, results in the formation of TiS6 trigonal-prismatic units that break
the infinite chains of face-shared TiS6 octahedra in SrTiS3 into periodic
blocks of five TiS6 octahedral units. The additional electrons introduced by
the excess Sr subsequently occupy the TiS6 octahedral blocks to form highly
oriented and polarizable electron clouds, which selectively boost the
extraordinary index n_e and result in record birefringence ({\Delta}n > 2.1
with low loss). The connection between subtle structural modulations and large
changes in refractive index suggests new categories of anisotropic materials
and also tunable optical materials with large refractive-index modulation and
low optical losses.Comment: Main text + supplementar
High frequency atomic tunneling yields ultralow and glass-like thermal conductivity in chalcogenide single crystals
Crystalline solids exhibiting glass-like thermal conductivity have attracted substantial attention both for fundamental interest and applications such as thermoelectrics. In most crystals, the competition of phonon scattering by anharmonic interactions and crystalline imperfections leads to a non-monotonic trend of thermal conductivity with temperature. Defect-free crystals that exhibit the glassy trend of low thermal conductivity with a monotonic increase with temperature are desirable because they are intrinsically thermally insulating while retaining useful properties of perfect crystals. However, this behavior is rare, and its microscopic origin remains unclear. Here, we report the observation of ultralow and glass-like thermal conductivity in a hexagonal perovskite chalcogenide single crystal, BaTiS₃, despite its highly symmetric and simple primitive cell. Elastic and inelastic scattering measurements reveal the quantum mechanical origin of this unusual trend. A two-level atomic tunneling system exists in a shallow double-well potential of the Ti atom and is of sufficiently high frequency to scatter heat-carrying phonons up to room temperature. While atomic tunneling has been invoked to explain the low-temperature thermal conductivity of solids for decades, our study establishes the presence of sub-THz frequency tunneling systems even in high-quality, electrically insulating single crystals, leading to anomalous transport properties well above cryogenic temperatures
Unconventional Charge-density-wave Order in a Dilute d-band Semiconductor
Electron-lattice coupling effects in low dimensional materials give rise to
charge density wave (CDW) order and phase transitions. These phenomena are
critical ingredients for superconductivity and predominantly occur in metallic
model systems such as doped cuprates, transition metal dichalcogenides, and
more recently, in Kagome lattice materials. However, CDW in semiconducting
systems, specifically at the limit of low carrier concentration region, is
uncommon. Here, we combine electrical transport, synchrotron X-ray diffraction
and optical spectroscopy to discover CDW order in a quasi-one-dimensional (1D),
dilute d-band semiconductor, BaTiS3, which suggests the existence of strong
electron-phonon coupling. The CDW state further undergoes an unusual transition
featuring a sharp increase in carrier mobility. Our work establishes BaTiS3 as
a unique platform to study the CDW physics in the dilute filling limit to
explore novel electronic phases
In silico design and biological evaluation of a dual specificity kinase inhibitor targeting cell cycle progression and angiogenesis
Methodology: We have utilized a rational in silico-based approach to demonstrate the design and study of a novel compound that acts as a dual inhibitor of vascular endothelial growth factor receptor 2 (VEGFR2) and cyclin-dependent kinase 1 (CDK1). This compound acts by simultaneously inhibiting pro-Angiogenic signal transduction and cell cycle progression in primary endothelial cells. JK-31 displays potent in vitro activity against recombinant VEGFR2 and CDK1/cyclin B proteins comparable to previously characterized inhibitors. Dual inhibition of the vascular endothelial growth factor A (VEGF-A)-mediated signaling response and CDK1-mediated mitotic entry elicits anti-Angiogenic activity both in an endothelial-fibroblast co-culture model and a murine ex vivo model of angiogenesis