16,772 research outputs found
Nonvolatile memories using deep traps formed in HfOā by Nb ion implantation
We report nonvolatile memories (NVMs) based on deep-energy trap levels formed in HfOā by metal ion implantation. A comparison of Nb- and Ta-implanted samples shows that suitable charge-trapping centers are formed in Nb-implanted samples, but not in Ta-implanted samples. This is consistent with density-functional theory calculations which predict that only Nb will form deep-energy levels in the bandgap of HfOā. Photocurrent spectroscopy exhibits characteristics consistent with one of the trap levels predicted in these calculations. Nb-implanted samples showing memory windows in capacitanceāvoltage (V) curves always exhibit current (I) peaks in IāV curves, indicating that NVM effects result from deep traps in HfOā. In contrast, Ta-implanted samples show dielectric breakdowns during the IāV sweeps between 5 and 11 V, consistent with the fact that no trap levels are present. For a sample implanted with a fluence of 10Ā¹Ā³Nb cmā»Ā², the charge losses after 10ā“ s are ā¼9.8 and ā¼25.5% at room temperature (RT) and 85Ā°C, respectively, and the expected charge loss after 10 years is ā¼34% at RT, very promising for commercial NVMs
Dipole-Allowed Direct Band Gap Silicon Superlattices
Silicon is the most popular material used in electronic devices. However, its
poor optical properties owing to its indirect band gap nature limit its usage
in optoelectronic devices. Here we present the discovery of super-stable
pure-silicon superlattice structures that can serve as promising materials for
solar cell applications and can lead to the realization of pure Si-based
optoelectronic devices. The structures are almost identical to that of bulk Si
except that defective layers are intercalated in the diamond lattice. The
superlattices exhibit dipole-allowed direct band gaps as well as indirect band
gaps, providing ideal conditions for the investigation of a direct-to-indirect
band gap transition. The transition can be understood in terms of a novel
conduction band originating from defective layers, an overlap between the
valence- and conduction-band edge states at the interface layers, and zone
folding with quantum confinement effects on the conduction band of
non-defective bulk-like Si. The fact that almost all structural portions of the
superlattices originate from bulk Si warrants their stability and good lattice
matching with bulk Si. Through first-principles molecular dynamics simulations,
we confirmed their thermal stability and propose a possible method to
synthesize the defective layer through wafer bonding
What is Needed the Most in MT-Supported Paper Writing
PACLIC / The University of the Philippines Visayas Cebu College Cebu City, Philippines / November 20-22, 200
Application of Artificial Neural Network to Search for Gravitational-Wave Signals Associated with Short Gamma-Ray Bursts
We apply a machine learning algorithm, the artificial neural network, to the
search for gravitational-wave signals associated with short gamma-ray bursts.
The multi-dimensional samples consisting of data corresponding to the
statistical and physical quantities from the coherent search pipeline are fed
into the artificial neural network to distinguish simulated gravitational-wave
signals from background noise artifacts. Our result shows that the data
classification efficiency at a fixed false alarm probability is improved by the
artificial neural network in comparison to the conventional detection
statistic. Therefore, this algorithm increases the distance at which a
gravitational-wave signal could be observed in coincidence with a gamma-ray
burst. In order to demonstrate the performance, we also evaluate a few seconds
of gravitational-wave data segment using the trained networks and obtain the
false alarm probability. We suggest that the artificial neural network can be a
complementary method to the conventional detection statistic for identifying
gravitational-wave signals related to the short gamma-ray bursts.Comment: 30 pages, 10 figure
Ultraviolet photodepletion spectroscopy of dibenzo-18-crown-6-ether complexes with alkali metal cations
Ultraviolet photodepletion spectra of dibenzo-18-crown-6-ether complexes with alkali metal cations (M+-DB18C6, M = Cs, Rb, K, Na, and Li) were obtained in the gas phase using electrospray ionization quadrupole ion-trap reflectron time-of-flight mass spectrometry. The spectra exhibited a few distinct absorption bands in the wavenumber region of 35450ā37800 cm^(ā1). The lowest-energy band was tentatively assigned to be the origin of the S_0-S_1 transition, and the second band to a vibronic transition arising from the ābenzene breathingā mode in conjunction with symmetric or asymmetric stretching vibration of the bonds between the metal cation and the oxygen atoms in DB18C6. The red shifts of the origin bands were observed in the spectra as the size of the metal cation in M^+-DB18C6 increased from Li^+ to Cs^+. We suggested that these red shifts arose mainly from the decrease in the binding energies of larger-sized metal cations to DB18C6 at the electronic ground state. These size effects of the metal cations on the geometric and electronic structures, and the binding properties of the complexes at the S_0 and S_1 states were further elucidated by theoretical calculations using density functional and time-dependent density functional theories
An Efficient Building Evacuation Algorithm in Congested Networks
This paper proposes a new network model for the building evacuation problem considering congestion levels and provides a mixed integer linear programming (MILP) model and an efficient heuristic algorithm solving the problem. Constructing an optimization model with several congestion levels, we introduce a new network called the multi-class time-expanded (MCTE) network having several exclusive arcs connecting the same tail and head nodes. The MCTE networks make both the MILP model and the heuristic algorithm reflect a realistic situation in congested networks. Considering MCTE networks makes the problem difficult to solve, which motivates us to develop an efficient heuristic algorithm. We test our heuristic algorithm using several real-world networks such as a multiplex cinema, a subway station, and a large-size complex shopping mall in addition to an artificial network for clear comparison between the proposed algorithm and the MILP approaches. The results indicate that the proposed algorithm runs fast and produces a near-optimal solution compared with those from MILP models with a commercial solver.11Ysciescopu
Implicit Inverse Force Identification Method of Acoustic Liquid-structure Interaction Finite Element Model
The two-field vibroacoustic finite-element (FE) model requires a relatively
large number of degrees of freedom compared to the monophysics model, and the
conventional force identification method for structural vibration can be
adjusted for multiphysics problems. In this study, an effective inverse force
identification method for an FE vibroacoustic interaction model of an interior
fluid-structure system was proposed. The method consists of: (1) implicit
inverse force identification based on the Newmark- time integration
algorithm for stability and efficiency, (2) second-order ordinary differential
formulation by avoiding the state-space form causing large degrees of freedom,
(3) projection-based multiphysics reduced-order modeling for further reduction
of degrees of freedom, and (4) Tikhonov regularization to alleviate the
measurement noise. The proposed method can accurately identify the unmeasured
applied forces on the in situ application and concurrently reconstruct the
response fields. The accuracy, stability, and computational efficiency of the
proposed method were evaluated using numerical models and an experimental
testbed. A comparative study with the augmented Kalman filter method was
performed to evaluate its relative performance.Comment: 31 Pages, 20 Figures, 5 Table
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