20,371 research outputs found
Transferable silicon nanowire arrays embedded in flexible polymer for color tuning with metal insulator metal structure
No full textYeong Jae Kim Young Jin Yoo Gil Ju Lee Dong Eun Yoo Dong Wook Lee, Vantari Siva, Hansung Song, Il Suk Kang, Young Min Song
Here, we present the transferable color-tuning structures. These structures are comprised of a polymer embedded silicon nanowire arrays (Si NWAs) stacked on a metal/insulator/metal (MIM) cavity. Upon stacking the Si NWAs on the MIM cavity, these cyan, magenta and yellow colors can be tuned to a color gamut by varying parameters of the Si NWAs such as diameter, height and periods. The fine tuning of these colors were explained on the basis of the measured reflectance spectra, which was further supported by the theoretical simulations
TIME-DEPENDENT DOUBLE DIFFUSION IN A STABLY STRATIFIED FLUID UNDER LATERAL HEATING
No full textA numerical study is made of double diffusive convection in a rectangle. The fluid is initially at rest with a pre-existing stably stratified solutal gradient. The motion is initiated by abruptly raising the temperature at one vertical sidewall. Comprehensive and systematically-organized numerical solutions to the full, Navier-Stokes equations under the Boussinesq fluid assumption have been acquired. Far-reaching analyses are made of the numerical results over a wide range of the solutal Rayleigh numbers R(s) using the thermal Rayleigh number, R(t) = 10(7). Elaborate plots displaying the details of the evolutions of the flow, temperature and solutal fields in the cavity are presented. The vertical profiles of the velocity, temperature, solute, and the local Nusselt number are constructed, delineating the influence of solutal buoyancy effect relative to the thermal effect. The behaviour of the details of the computed flow characteristics is in good qualitative agreement with the available experimental visualizations. The categorization of the basic character of the flow into the supercritical (Ra > Ra(c)) and subcritical regimes (Ra < Ra(c)), which is based on experimental observations, is satisfactorily verified by the numerical results. The present numerical simulations are also supportive of the prior observations, which illustrated the qualitative difference in the time-dependent patterns of the formation of the layered structure in the supercritical and subcritical regimes. By assessing the present numerical results, the previous estimate of the value of Ra(c) congruent-to 1.5 x 10(4) is found to be reasonably accurate
Temporal Convolutional Network-Based Time-Series Segmentation
No full textTime-series segmentation is useful to identify the underlying characteristics of time series and summarize time series as a sequence of states. Partitioning time series into the states makes the complex time series easily understandable and interpretable. However, as labels for time points are not normally available, it is challenging to Figure out the accurate segments and their states. Therefore, we propose an unsupervised time-series segmentation using the inherent properties in times series. The states can be characterized by diverse length patterns inherent in time series, and thus capturing diverse patterns is crucial in an unsupervised time-series segmentation. We adopt a temporal convolutional network (TCN) as our key component to learn diverse length patterns since the intermediate layers in TCN contain both short and long patterns hierarchically. In this paper, we propose a novel unsupervised time-series segmentation TCTS, which is featured with the joint optimization of two modules. The TCN-based pattern learning module aims to grasp diverse length patterns that are characterized differently by the states, while the clustering-based classification module improves the separability of the representations between the states. We conduct experiments by comparing several baselines with multiple datasets and demonstrate the superiority of TCTS
Role of the Lipid Membrane and Membrane Proteins in Tau Pathology
Get PDFAbnormal accumulation of misfolded tau aggregates is a pathological hallmark of various tauopathies including Alzheimer's disease (AD). Although tau is a cytosolic microtubule-associated protein enriched in neurons, it is also found in extracellular milieu, such as interstitial fluid, cerebrospinal fluid, and blood. Accumulating evidence showed that pathological tau spreads along anatomically connected areas in the brain through intercellular transmission and templated misfolding, thereby inducing neurodegeneration and cognitive dysfunction. In line with this, the spatiotemporal spreading of tau pathology is closely correlated with cognitive decline in AD patients. Although the secretion and uptake of tau involve multiple different pathways depending on tau species and cell types, a growing body of evidence suggested that tau is largely secreted in a vesicle-free forms. In this regard, the interaction of vesicle-free tau with membrane is gaining growing attention due to its importance for both of tau secretion and uptake as well as aggregation. Here, we review the recent literature on the mechanisms of the tau-membrane interaction and highlights the roles of lipids and proteins at the membrane in the tau-membrane interaction as well as tau aggregation. © 2021 Bok, Leem, Lee, Lee, Yoo, Lee and Kim.1
Spin-up of a double-diffusive fluid in a cylinder
No full textA numerical study is made of the linearized spin-up process of a double-diffusive fluid in a vertically mounted cylindrical vessel of aspect ratio 0(1). Both the temperature and concentration conditions render gravitationally stable contributions to the overall density profile. Numerical solutions are acquired to the time-dependent axisymmetric Navier-Stokes equations, using the standard Boussinesq fluid approximations. The major nondimensional parameters are identified. Results are compiled for small Ekman number, the Prandtl number similar to 0(1), and broad ranges of the stratification number St, buoyancy ratio R-p, and Lewis number Le, are dealt with. The evolution of the azimuthal velocities is described, and the attendant meridional flows are depicted. The global spin-up process is retarded for a double-diffusive fluid, and this trend is more pronounced as R-p increases. The spatial nonuniformity of the rate of spin-up is enhanced as St and R-p increase. The effects of double-diffusion on the fields of perturbation density, temperature, and concentration are plotted. The impact of Le on spin-up is illustrated, and the plots of the perturbation physical variables of interest are presented. (C) 1997 by Elsevier Science Inc
TRANSIENT NATURAL-CONVECTION IN A SQUARE CAVITY OF A FLUID WITH TEMPERATURE-DEPENDENT VISCOSITY
No full textn-Gram/2L: A Space and Time Efficient Two-Level n-Gram Inverted Index Structure
No full textThe n-gram inverted index has two major advantages: language-neutral and error-tolerant. Due to these advantages, it has been widely used in information retrieval or in similar sequence matching for DNA and protein databases. Nevertheless, the n-gram inverted index also has drawbacks: the size tends to be very large, and the performance of queries tends to be bad. In this paper, we propose the two-level n-gram inverted index (simply, the n-gram/2L index) that significantly reduces the size and improves the query performance while preserving the advantages of the n-gram inverted index. The proposed index eliminates the redundancy of the position information that exists in the n-gram inverted index. The proposed index is constructed in two steps: 1) extracting subsequences of length m from documents and 2) extracting n-grams from those subsequences. We formally prove that this two-step construction is identical to the relational normalization process that removes the redundancy caused by a non-trivial multivalued dependency. The n-gram/2L index has excellent properties: 1) it significantly reduces the size and improves the performance compared with the n-gram inverted index with these improvements becoming more marked as the database size gets larger; 2) the query processing time increases only very slightly as the query length gets longer. Experimental results using databases of 1 GBytes show that the size of the n-gram/2L index is reduced by up to 1.9 ~ 2.7 times and, at the same time, the query performance is improved by up to 13.1 times compared with those of the n-gram inverted index
Analytical Models of Exoplanetary Atmospheres. II. Radiative Transfer via the Two-Stream Approximation
Get PDFWe present a comprehensive analytical study of radiative transfer using the method of moments and include the effects of non-isotropic scattering in the coherent limit. Within this unified formalism, we derive the governing equations and solutions describing two-stream radiative transfer (which approximates the passage of radiation as a pair of outgoing and incoming fluxes), flux-limited diffusion (which describes radiative transfer in the deep interior) and solutions for the temperature-pressure profiles. Generally, the problem is mathematically under-determined unless a set of closures (Eddington coefficients) is specified. We demonstrate that the hemispheric (or hemi-isotropic) closure naturally derives from the radiative transfer equation if energy conservation is obeyed, while the Eddington closure produces spurious enhancements of both reflected light and thermal emission. We concoct recipes for implementing two-stream radiative transfer in stand-alone numerical calculations and general circulation models. We use our two-stream solutions to construct toy models of the runaway greenhouse effect. We present a new solution for temperature-pressure profiles with a non-constant optical opacity and elucidate the effects of non-isotropic scattering in the optical and infrared. We derive generalized expressions for the spherical and Bond albedos and the photon deposition depth. We demonstrate that the value of the optical depth corresponding to the photosphere is not always 2/3 (Milne's solution) and depends on a combination of stellar irradiation, internal heat and the properties of scattering both in optical and infrared. Finally, we derive generalized expressions for the total, net, outgoing and incoming fluxes in the convective regime
Knowledge-assisted Optimization Model Formulation UNIK-OPT
No full textIn this paper, we describe a knowledge-assistedoptimizationmodelformulation system UNIK-OPT (UNIfied Knowledge-OPTimization). To envision the desirable features of UNIK-OPT, we first establish the design criteria of knowledge-assisted modeling systems. The most distinctive criterion pursued in this research is the independent management of knowledge base from multiple optimizationmodels. To achieve these criteria, we articulate four levels of modeling views: semantic view, modeling language view, mathematical notational view and tabular view. In semantic view, the associations between attributes, blocks of terms and constraints are represented in a constraint network, and a block of terms is represented as a pair of coefficient and variable. Thus, the formulation reasoning is esteemed as a process of helping the construction of a specific semantic model by adding user's problem definition to the extracted relevant semantic level modeling knowledge. Then the specific semantic model can be transformed into other views of model automatically. The prototype UNIK-OPT is developed to realize this idea, and is illustrated with a refinery plant
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