5,598 research outputs found
Compact Brillouin devices through hybrid integration on Silicon
A range of unique capabilities in optical and microwave signal processing
have been demonstrated using stimulated Brillouin scattering. The desire to
harness Brillouin scattering in mass manufacturable integrated circuits has led
to a focus on silicon-based material platforms. Remarkable progress in
silicon-based Brillouin waveguides has been made, but results have been
hindered by nonlinear losses present at telecommunications wavelengths. Here,
we report a new approach to surpass this issue through the integration of a
high Brillouin gain material, As2S3, onto a silicon chip. We fabricated a
compact spiral device, within a silicon circuit, achieving an order of
magnitude improvement in Brillouin amplification. To establish the flexibility
of this approach, we fabricated a ring resonator with free spectral range
precisely matched to the Brillouin shift, enabling the first demonstration of
Brillouin lasing in a silicon integrated circuit. Combining active photonic
components with the SBS devices shown here will enable the creation of compact,
mass manufacturable optical circuits with enhanced functionality
SWAT use of gridded observations for simulating runoff – a Vietnam river basin study
Many research studies that focus on basin hydrology have applied the SWAT model using station data to simulate runoff. But over regions lacking robust station data, there is a problem of applying the model to study the hydrological responses. For some countries and remote areas, the rainfall data availability might be a constraint due to many different reasons such as lacking of technology, war time and financial limitation that lead to difficulty in constructing the runoff data. To overcome such a limitation, this research study uses some of the available globally gridded high resolution precipitation datasets to simulate runoff. Five popular gridded observation precipitation datasets: (1) Asian Precipitation Highly Resolved Observational Data Integration Towards the Evaluation of Water Resources (APHRODITE), (2) Tropical Rainfall Measuring Mission (TRMM), (3) Precipitation Estimation from Remote Sensing Information using Artificial Neural Network (PERSIANN), (4) Global Precipitation Climatology Project (GPCP), (5) a modified version of Global Historical Climatology Network (GHCN2) and one reanalysis dataset, National Centers for Environment Prediction/National Center for Atmospheric Research (NCEP/NCAR) are used to simulate runoff over the Dak Bla river (a small tributary of the Mekong River) in Vietnam. Wherever possible, available station data are also used for comparison. Bilinear interpolation of these gridded datasets is used to input the precipitation data at the closest grid points to the station locations. Sensitivity Analysis and Auto-calibration are performed for the SWAT model. The Nash-Sutcliffe Efficiency (NSE) and Coefficient of Determination (<i>R</i><sup>2</sup>) indices are used to benchmark the model performance. Results indicate that the APHRODITE dataset performed very well on a daily scale simulation of discharge having a good NSE of 0.54 and <i>R</i><sup>2</sup> of 0.55, when compared to the discharge simulation using station data (0.68 and 0.71). The GPCP proved to be the next best dataset that was applied to the runoff modelling, with NSE and <i>R</i><sup>2</sup> of 0.46 and 0.51, respectively. The PERSIANN and TRMM rainfall data driven runoff did not show good agreement compared to the station data as both the NSE and <i>R</i><sup>2</sup> indices showed a low value of 0.3. GHCN2 and NCEP also did not show good correlations. The varied results by using these datasets indicate that although the gauge based and satellite-gauge merged products use some ground truth data, the different interpolation techniques and merging algorithms could also be a source of uncertainties. This entails a good understanding of the response of the hydrological model to different datasets and a quantification of the uncertainties in these datasets. Such a methodology is also useful for planning on Rainfall-runoff and even reservoir/river management both at rural and urban scales
Photoassisted tunneling from free-standing GaAs thin films into metallic surfaces
The tunnel photocurrent between a gold surface and a free-standing
semiconducting thin film excited from the rear by above bandgap light has been
measured as a function of applied bias, tunnel distance and excitation light
power. The results are compared with the predictions of a model which includes
the bias dependence of the tunnel barrier height and the bias-induced decrease
of surface recombination velocity. It is found that i) the tunnel photocurrent
from the conduction band dominates that from surface states. ii) At large
tunnel distance the exponential bias dependence of the current is explained by
that of the tunnel barrier height, while at small distance the change of
surface recombination velocity is dominant
Codes for Correcting Asymmetric Adjacent Transpositions and Deletions
Codes in the Damerau--Levenshtein metric have been extensively studied
recently owing to their applications in DNA-based data storage. In particular,
Gabrys, Yaakobi, and Milenkovic (2017) designed a length- code correcting a
single deletion and adjacent transpositions with at most
bits of redundancy. In this work, we consider a new setting where both
asymmetric adjacent transpositions (also known as right-shifts or left-shifts)
and deletions may occur. We present several constructions of the codes
correcting these errors in various cases. In particular, we design a code
correcting a single deletion, right-shift, and left-shift errors
with at most bits of redundancy where . In
addition, we investigate codes correcting -deletions, right-shift,
and left-shift errors with both uniquely-decoding and list-decoding
algorithms. Our main contribution here is the construction of a list-decodable
code with list size and with at most bits of redundancy, where . Finally, we construct
both non-systematic and systematic codes for correcting blocks of -deletions
with -limited-magnitude and adjacent transpositions
Exploring Tourist Dining Preferences Based on Restaurant Reviews
Dining is an essential tourism component that attracts significant expenditure from tourists. Tourism practitioners need insights into the dining behaviors of tourists to support their strategic planning and decision making. Traditional surveys and questionnaires are time consuming and inefficient in capturing the complex dining behaviors of tourists at a large scale. Thus far, the understanding about the dining preferences and opinions of different tourist groups is limited. This article aims to fill the void by presenting a method that utilizes online restaurant reviews and text processing techniques in analyzing the dining behaviors of tourists. The effectiveness of the proposed method is demonstrated in a case study on international tourists visiting Australia using a large-scale data set of more than 40,000 restaurant reviews made by tourists on 2,265 restaurants. The proposed method can help researchers gain comprehensive insights into the dining preferences of tourists. </jats:p
ADDMC: Weighted Model Counting with Algebraic Decision Diagrams
We present an algorithm to compute exact literal-weighted model counts of
Boolean formulas in Conjunctive Normal Form. Our algorithm employs dynamic
programming and uses Algebraic Decision Diagrams as the primary data structure.
We implement this technique in ADDMC, a new model counter. We empirically
evaluate various heuristics that can be used with ADDMC. We then compare ADDMC
to state-of-the-art exact weighted model counters (Cachet, c2d, d4, and
miniC2D) on 1914 standard model counting benchmarks and show that ADDMC
significantly improves the virtual best solver.Comment: Presented at AAAI 202
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