Results 111 to 120 of about 10,065 (268)

A hydraulic specific energy performance indicator for coiled tube turbodrilling

, 2012
Efficient drilling of hard rocks in mineral exploration requires a comprehensive knowledge of the energy spent at the bit. The use of mechanical specific energy (MSE) proposed in the past for drilling performance studies does not consider the impact of ...
Rasouli, Vamegh, Mokaramian, A., Cavanough, G.   +2 more
core  

The Accuracy Smoothness Dilemma in Prediction: A Novel Multivariate M‐SSA Forecast Approach

Journal of Time Series Analysis, EarlyView.
ABSTRACT Forecasting presents a complex estimation challenge, as it involves balancing multiple, often conflicting, priorities and objectives. Conventional forecast optimization methods typically emphasize a single metric, such as minimizing the mean squared error (MSE), which may neglect other crucial aspects of predictive performance. To address this
Marc Wildi
wiley   +1 more source

Prediction of ionospheric TEC during the occurrence of earthquakes in Indonesia using ARMA and CoK models

Frontiers in Astronomy and Space Sciences
Predicting ionospheric Total Electron Content (TEC) variations associated with seismic activity is crucial for mitigating potential disruptions in communication networks, particularly during earthquakes.
S. Kiruthiga, S. Mythili
doaj   +1 more source

Marchenko–Pastur Laws for Daniell Smoothed Periodograms

Journal of Time Series Analysis, EarlyView.
ABSTRACT Given a sample X0,…,Xn−1$$ {X}_0,\dots, {X}_{n-1} $$ from a d$$ d $$‐dimensional stationary time series (Xt)t∈ℤ$$ {\left({X}_t\right)}_{t\in \mathbb{Z}} $$, the most commonly used estimator for the spectral density matrix F(θ)$$ F\left(\theta \right) $$ at a given frequency θ∈[0,2π)$$ \theta \in \left[0,2\pi \right) $$ is the Daniell smoothed ...
Ben Deitmar
wiley   +1 more source

Matrix representations of spectral coefficients of randomly sampled ARMA models

, 1994
The paper is devoted to the spectrum of univariate randomly sampled autoregressive moving-average (ARMA) models. We determine precisely matrix representations for the spectrum numerator coefficients of the randomly sampled ARMA models.
Mokkadem, Abdelkader, Kadi, Amina
core   +1 more source

On Testing for Independence Between Generalized Error Models of Several Time Series

Journal of Time Series Analysis, EarlyView.
ABSTRACT We define generalized innovations associated with generalized error models having arbitrary distributions, that is, distributions that can be mixtures of continuous and discrete distributions. These models include stochastic volatility models and regime‐switching models with possibly zero‐inflated regimes.
Kilani Ghoudi, Bouchra R. Nasri, Bruno N. Rémillard   +2 more
wiley   +1 more source

Penalized Convex Estimation in Dynamic Location Models

Journal of Time Series Analysis, EarlyView.
ABSTRACT This paper studies L1$$ {L}^1 $$‐penalized estimation for location models yt=mt+ϵt$$ {y}_t={m}_t+{\epsilon}_t $$, where mt$$ {m}_t $$ is defined by a possibly non‐Markovian recursion and ϵt$$ {\epsilon}_t $$ is a martingale difference sequence with possibly time‐varying conditional variance.
Reda Alami Chentoufi
wiley   +1 more source

Christian Nationalism and the Vote for Donald Trump in the 2024 Presidential Election: A State‐Level Analysis

Nations and Nationalism, EarlyView.
ABSTRACT Within the US electoral system, where states are conceived of and vote as discrete entities, state‐level characteristics are vital to consider because they reflect sociocultural context influencing voter behaviour. Though numerous studies have documented the connection between Christian nationalist ideology and voting for Donald Trump in 2016,
Andrew L. Whitehead, Samuel L. Perry
wiley   +1 more source

Ecological and genomic variation in ectomycorrhizal fungal exploration types

New Phytologist, EarlyView.
Summary Ectomycorrhizal fungi (EMF) produce mycelia with variable extension and complexity, which can be classified according to soil ‘exploration types’ (ETs). ETs have received attention as one of the few mycorrhizal trait frameworks, but without an empirical classification of ET functional diversity and environmental preferences, understanding and ...
Thomas M. Mansfield, Artin Zarsav, Filipa Cox, Laura M. Suz, Martin I. Bidartondo, Sietse van der Linde, Nadia Barsoum, Colin Averill, Alan Kuo, Leho Tedersoo, Pasi Rautio, Arthur Gessler, Bruno De Vos, Luc Croisé, Henning Meesenburg, Markus Wagner, Frank Jacob, Paweł Lech, Anna Kowalska, Martin Greve, Genoveva Popova, Beat Frey, Marcus Schaub, Marco Ferretti, Peter Waldner, Vicent Calatayud, Roberto Canullo, Giancarlo Papitto, Aleksander Marinšek, Lars Vesterdal, Morten Ingerslev, Helge Meissner, Volkmar Timmermann, Nadine Eickenscheidt, Andreas Schmitz, Francis M. Martin, Joseph Spatafora, Peter G. Kennedy, Annegret Kohler, Jonathan M. Plett, Ian C. Anderson, Sara Branco, Igor V. Grigoriev, Chris J. Pires, Sarah A. Unruh, Lawrence W. Zettler, Otto Miettinen, Ilya Viner, Tom W. May, Teresa Lebel, David E. A. Catcheside, Pamela S. Catcheside, Helen P. Vonow, Leigh A. Burgoyne, Julia Haska, Mark A. Anthony   +55 more
wiley   +1 more source

Application of Copula Models in Stock Market Analysis

Informatika
Objectives. The objective of the study is to use copula models to analyze shares of the Russian stock market and describe changes in the relationship between the shares before and during the coronavirus infection (COVID-19).Methods.
A. M. Kendys, M. M. Troush
doaj   +1 more source