scholarly journals The Structure of Oxide Film on the Porous Silicon Surface

2020 ◽  
Vol 65 (1) ◽  
pp. 75
Author(s):  
O. I. Zavalistyi ◽  
O. V. Makarenko ◽  
V. A. Odarych ◽  
A. L. Yampolskyi
Keyword(s):  
Refractive Index ◽  
Surface Layer ◽  
Porous Silicon ◽  
Structural Changes ◽  
Mean Squared Error ◽  
Single Layer ◽  
Prolonged Stay ◽  
Near Surface ◽  
Squared Error ◽  
The Matrix

A prolonged stay of porous silicon in the air environment gives rise to structural changes in its surface layer, and the standard single-layer model is not sufficiently accurate to describe them. In this work, the structure of the near-surface layer in porous silicon is studied using the polygonal ellipsometry method. A combined approach is proposed to analyze the angular ellipsometry data for the parameters ф and Δ. It consists in the application of the multilayer medium model and the matrix method, while simulating the propagation of optical radiation in this medium in order to obtain the theoretical angular dependences of tan ф and cosΔ. In this method, the dependence of the sought optical profile on the specimen depth is an additional condition imposed on the multilayer model. Evolutionary numerical methods are used for finding the global minimum of the mean squared error (MSE) between the corresponding theoretical and experimental dependences, and the parameters of an optical profile are determined. A model in which the inner non-oxidized layer of porous silicon is homogeneous, whereas the refractive index in the outer oxidized layer has a linear profile, is analyzed. It is shown that the linear and two-step models for the refractive index of an oxidized film provided the best agreement with the experimental ellipsometric functions. The adequacy of the theoretical model is also confirmed by determining the color coordinates of the specimen.

The Sensitivity of Springtime Arctic Mixed-Phase Stratocumulus Clouds to Surface-Layer and Cloud-Top Inversion-Layer Moisture Sources

2014 ◽  
Vol 71 (2) ◽  
pp. 574-595 ◽  
Author(s):  
Amy Solomon ◽  
Matthew D. Shupe ◽  
Ola Persson ◽  
Hugh Morrison ◽  
Takanobu Yamaguchi ◽  
...  
Keyword(s):  
Surface Layer ◽  
Mixed Layer ◽  
Inversion Layer ◽  
Single Layer ◽  
Mixed Phase ◽  
Specific Humidity ◽  
Cloud System ◽  
Energy Budgets ◽  
Quasi Equilibrium ◽  
Near Surface

Abstract In this study, a series of idealized large-eddy simulations is used to understand the relative impact of cloud-top and subcloud-layer sources of moisture on the microphysical–radiative–dynamical feedbacks in an Arctic mixed-phase stratocumulus (AMPS) cloud system. This study focuses on a case derived from observations of a persistent single-layer AMPS cloud deck on 8 April 2008 during the Indirect and Semi-Direct Aerosol Campaign near Barrow, Alaska. Moisture and moist static energy budgets are used to examine the potential impact of ice in mixed-phase clouds, specific humidity inversions coincident with temperature inversions as a source of moisture for the cloud system, and the presence of cloud liquid water above the mixed-layer top. This study demonstrates that AMPS have remarkable insensitivity to changes in moisture source. When the overlying air is dried initially, radiative cooling and turbulent entrainment increase moisture import from the surface layer. When the surface layer is dried initially, the system evolves to a state with reduced mixed-layer water vapor and increased surface-layer moisture, reducing the loss of water through precipitation and entrainment of near-surface air. Only when moisture is reduced both above and below the mixed layer does the AMPS decay without reaching a quasi-equilibrium state. A fundamental finding of this study is that, with or without cloud ice and with or without a specific humidity inversion, the cloud layer eventually extends into the temperature inversion producing a precipitation flux as a source of water into the mixed layer.

scholarly journals A new modified ridge-type estimator for the beta regression model: simulation and application

2021 ◽  
Vol 7 (1) ◽  
pp. 1035-1057
Author(s):  
Muhammad Nauman Akram ◽  
◽  
Muhammad Amin ◽  
Ahmed Elhassanein ◽  
Muhammad Aman Ullah ◽  
...  
Keyword(s):  
Regression Model ◽  
Mean Squared Error ◽  
Model Simulation ◽  
Beta Regression ◽  
Explanatory Variables ◽  
Squared Error ◽  
The Matrix ◽  
Biased Estimators ◽  
Highly Correlated ◽  
Beta Regression Model

<abstract> <p>The beta regression model has become a popular tool for assessing the relationships among chemical characteristics. In the BRM, when the explanatory variables are highly correlated, then the maximum likelihood estimator (MLE) does not provide reliable results. So, in this study, we propose a new modified beta ridge-type (MBRT) estimator for the BRM to reduce the effect of multicollinearity and improve the estimation. Initially, we show analytically that the new estimator outperforms the MLE as well as the other two well-known biased estimators i.e., beta ridge regression estimator (BRRE) and beta Liu estimator (BLE) using the matrix mean squared error (MMSE) and mean squared error (MSE) criteria. The performance of the MBRT estimator is assessed using a simulation study and an empirical application. Findings demonstrate that our proposed MBRT estimator outperforms the MLE, BRRE and BLE in fitting the BRM with correlated explanatory variables.</p> </abstract>

scholarly journals Features of changes in optical response within the surface oxide layer in Si and GaAs

2018 ◽  
pp. 99-104
Author(s):  
O. Makarenko ◽  
O. Zavalistyi ◽  
A. Yampolskiy ◽  
L. Poperenko
Keyword(s):  
Mean Squared Error ◽  
Optical Response ◽  
Homogeneous Layer ◽  
Surface Oxide Layer ◽  
Radiation Beam ◽  
Matrix Methods ◽  
Near Surface ◽  
Reflected Waves ◽  
Squared Error ◽  
Ultrathin Layers

In this paper, the angular ellipsometric studies of natural oxidized surface layer on silicon and gallium arsenide are carried out. The mean wavelength of probe radiation beam was λ = 625 nm, with FWHM = 10 nm. Angular dependencies of ellipsometric parameters ψ and Δ (azimuth of restored linear polarization and phase shift between p- and s- components of reflected radiation) were recorded. The combined approach for their analysis, which consists in sectioning the investigated medium near-surface area into 500 ultrathin layers interconnected by the dielectric permittivity function and determining the ellipsometric parameters of the medium by applying matrix methods for calculating the amplitudes and phases of the reflected waves from such a system in two polarizations, was used. The depth of the optical response profile was determined by the method of differential evolution by varying optical constants in accordance with the chosen theoretical model to achieve a minimum deviation (MSE, Mean Squared Error) between the calculated and measured ellipsometric parameters. Optical response profiles corresponding to the models of half-infinite medium, a homogeneous layer, as well as the linear and exponential profiles are analyzed.

Optical Interference Filters Made of Porous Silicon

1996 ◽  
Vol 431 ◽  
Author(s):  
M. Thönissen ◽  
M. G. Berger ◽  
M. Krüger ◽  
S. Billat ◽  
R. Arens-Fischer ◽  
...  
Keyword(s):  
Refractive Index ◽  
Porous Silicon ◽  
Current Density ◽  
Layer Structure ◽  
Single Layer ◽  
Bragg Reflectors ◽  
Optical Interference ◽  
Interference Filters ◽  
Thickness Measurements ◽  
Reflectance Measurements

AbstractPorous silicon (PS) layers can easily be formed by an electrochemical etch process using a mixture of hydrofluoric acid (HF) and ethanol. The microstructure and porosity of the layers depend on the HF concentration, the doping level of the substrate and the current density applied during the etch process. Changing the current density during the etch process will result in a well defined layer structure consisting of layers with different porosities. Each single layer can be treated as an effective medium exhibiting a refractive index depending mainly on the porosity of the layer. Using reflectance measurements we have investigated the dependence of the refractive index of PS layers on the formation current density for different substrates. In addition the etch rate was determined by thickness measurements with an electron microscope. Based on these results various kinds of optical interference filters were studied. We have formed samples consisting of discrete single layers with different porosities (e.g. Bragg reflectors) as well as samples with continuous variation of the refractive index (rugate filters). Combining these PS filters with standard photolithography steps, microoptical devices such as spectral sensitive photodiodes can be realized.

scholarly journals Preprocessing Images Algorithm without Gaussian Shaped Particles for PIV Analysis and Imaging Vortices on the Epicardial Surface

2021 ◽  
Author(s):  
Daria Mangileva ◽  
Alexander Kursanov ◽  
Alena Tsvetkova ◽  
Olesya Bernikova ◽  
Alexey Ovechkin ◽  
...  
Keyword(s):  
Vector Fields ◽  
Mean Squared Error ◽  
Motion Artifacts ◽  
Binary Images ◽  
Squared Error ◽  
Image Velocimetry ◽  
The Matrix ◽  
Canny Edge ◽  
The Mean ◽  
Piv Analysis

e intense movement of the heart and the presence of blood on surface, the application of the necessary small markers is rather difficult, and the use of luminous chemicals would harm physiological functioning. Moreover, these videos contain motion artifacts that complicate further analysis with Particle Image Velocimetry. In this paper, an image preprocessing algorithm was proposed. It is based on approximate tracking individual fragments using the Mean Squared Error for the matrix. The result is binary images where small points are built instead of each fragment. In this study, the proposed algorithm showed better results in comparison with the most suitable filtering methods for specific frames, namely, the Sobel filter and the Canny edge detector. This can be partially explained by the higher density of vector fields due to the absence of unreliable vectors. Thus, the proposed method, unlike others, allows to get vector fields with visible vortex-like mechanical movements.

Estimating network edge probabilities by neighbourhood smoothing

Biometrika ◽  
2017 ◽  
Vol 104 (4) ◽  
pp. 771-783 ◽  
Author(s):  
Yuan Zhang ◽  
Elizaveta Levina ◽  
Ji Zhu
Keyword(s):  
Network Structure ◽  
Efficient Method ◽  
Error Rate ◽  
Adjacency Matrix ◽  
Link Prediction ◽  
Mean Squared Error ◽  
Smoothing Method ◽  
Computationally Efficient ◽  
Squared Error ◽  
The Matrix

Summary The estimation of probabilities of network edges from the observed adjacency matrix has important applications to the prediction of missing links and to network denoising. It is usually addressed by estimating the graphon, a function that determines the matrix of edge probabilities, but this is ill-defined without strong assumptions on the network structure. Here we propose a novel computationally efficient method, based on neighbourhood smoothing, to estimate the expectation of the adjacency matrix directly, without making the structural assumptions that graphon estimation requires. The neighbourhood smoothing method requires little tuning, has a competitive mean squared error rate and outperforms many benchmark methods for link prediction in simulated and real networks.

scholarly journals Surface Processing of TlBr Crystals for X- and γ-ray Detectors

2008 ◽  
Vol 45 (3) ◽  
pp. 43-49
Author(s):  
M. Shorohov ◽  
F. Muktepavela ◽  
J. Maniks
Keyword(s):  
Surface Layer ◽  
Energy Resolution ◽  
Chemical Etching ◽  
Structural Changes ◽  
High Energy ◽  
High Energy Resolution ◽  
Indentation Hardness ◽  
Surface Processing ◽  
Near Surface ◽  
Γ Ray

Surface Processing of TlBr Crystals for X- and γ-ray DetectorsA procedure for surface processing of TlBr crystals to be applied as X-and ?-ray detectors has been developed, providing removal of a mechanically destroyed surface layer by deep chemical etching, allowing the surfaces of good topography and thus the detectors with high energy resolution and stability to be obtained in a repeatable way. The surface quality and structural changes in the near-surface layer are estimated by the optical microscopy and indentation hardness technique.

Recombination Characteristics of Single-Crystalline Silicon Wafers with a Damaged Near-Surface Layer

2013 ◽  
Vol 58 (2) ◽  
pp. 142-150 ◽  
Author(s):  
A.V. Sachenko ◽  
◽  
V.P. Kostylev ◽  
V.G. Litovchenko ◽  
V.G. Popov ◽  
...  
Keyword(s):  
Surface Layer ◽  
Crystalline Silicon ◽  
Silicon Wafers ◽  
Single Crystalline Silicon ◽  
Near Surface ◽  
Single Crystalline

Use of reflectance spectroscopy to estimate the organic carbon and CaCO3 contents of soils

2012 ◽  
Vol 61 (2) ◽  
pp. 277-290 ◽  
Author(s):  
Ádám Csorba ◽  
Vince Láng ◽  
László Fenyvesi ◽  
Erika Michéli
Keyword(s):  
Organic Carbon ◽  
Least Squares ◽  
Partial Least Squares ◽  
Partial Least Squares Regression ◽  
Mean Squared Error ◽  
Reflectance Spectroscopy ◽  
Least Squares Regression ◽  
Root Mean Squared Error ◽  
Squared Error

Napjainkban egyre nagyobb igény mutatkozik olyan technológiák és módszerek kidolgozására és alkalmazására, melyek lehetővé teszik a gyors, költséghatékony és környezetbarát talajadat-felvételezést és kiértékelést. Ezeknek az igényeknek felel meg a reflektancia spektroszkópia, mely az elektromágneses spektrum látható (VIS) és közeli infravörös (NIR) tartományában (350–2500 nm) végzett reflektancia-mérésekre épül. Figyelembe véve, hogy a talajokról felvett reflektancia spektrum információban nagyon gazdag, és a vizsgált tartományban számos talajalkotó rendelkezik karakterisztikus spektrális „ujjlenyomattal”, egyetlen görbéből lehetővé válik nagyszámú, kulcsfontosságú talajparaméter egyidejű meghatározása. Dolgozatunkban, a reflektancia spektroszkópia alapjaira helyezett, a talajok ösz-szetételének meghatározását célzó módszertani fejlesztés első lépéseit mutatjuk be. Munkánk során talajok szervesszén- és CaCO3-tartalmának megbecslését lehetővé tévő többváltozós matematikai-statisztikai módszerekre (részleges legkisebb négyzetek módszere, partial least squares regression – PLSR) épülő prediktív modellek létrehozását és tesztelését végeztük el. A létrehozott modellek tesztelése során megállapítottuk, hogy az eljárás mindkét talajparaméter esetében magas R2értéket [R2(szerves szén) = 0,815; R2(CaCO3) = 0,907] adott. A becslés pontosságát jelző közepes négyzetes eltérés (root mean squared error – RMSE) érték mindkét paraméter esetében közepesnek mondható [RMSE (szerves szén) = 0,467; RMSE (CaCO3) = 3,508], mely a reflektancia mérési előírások standardizálásával jelentősen javítható. Vizsgálataink alapján arra a következtetésre jutottunk, hogy a reflektancia spektroszkópia és a többváltozós kemometriai eljárások együttes alkalmazásával, gyors és költséghatékony adatfelvételezési és -értékelési módszerhez juthatunk.

Sign in / Sign up

Export Citation Format

Share Document