Article
Meteorology & Atmospheric Sciences
Sadik Alashan
Summary: In this study, the Mann-Kendall (MK) method is improved to detect non-monotonic trends and applied to the precipitation series of the Murat River basin. The results show that the classical MK method cannot detect any trend, but the improved non-monotonic MK (NMK) method can detect important decreasing and increasing trends at certain stations. Stationarity analysis reveals that the precipitation series at Bingol station is non-stationary, while Mus station retains its stationarity characteristic. These findings contribute to a better understanding of the effects of climate change on hydro-meteorological historical records and provide insights for predicting future events and designing more efficient hydraulic structures.
THEORETICAL AND APPLIED CLIMATOLOGY
(2023)
Article
Agriculture, Multidisciplinary
Agda L. G. Oliveira, Joaquim P. Lima, Thiago L. Brasco, Lucas R. Amaral
Summary: This study evaluates the influence of considering anisotropy and trend in semivariogram modeling on the improvement of maps used in precision agriculture. The results indicate that modeling directional effects can improve the accuracy of kriging-generated maps. REML method performs better in strong anisotropy, while MoM method is more efficient in fields with weaker anisotropy.
COMPUTERS AND ELECTRONICS IN AGRICULTURE
(2022)
Article
Management
Nathan Lassance
Summary: This paper reconciles mean-variance portfolio theory with non-Gaussian returns by identifying the optimal portfolio among all portfolios on the mean-variance efficient frontier that optimizes a chosen higher-moment criterion. Numerical simulations and empirical analysis show that the proposed portfolio strikes a favorable tradeoff between specification and estimation error, outperforming the global-optimal portfolio in terms of out-of-sample Sharpe ratio and higher moments.
EUROPEAN JOURNAL OF OPERATIONAL RESEARCH
(2022)
Editorial Material
Computer Science, Interdisciplinary Applications
Zhe Luo
Summary: In a finite element model, finer meshes are used in areas of higher interest, while coarser meshes are used in areas of lower interest to save computational resources and maintain accuracy. However, when incorporating random field modeling into FEM with unequal element sizes, consistent local averaging of soil properties and mesh-dependent variance reduction factors are necessary to ensure the generated random field is stationary.
COMPUTERS AND GEOTECHNICS
(2022)
Article
Environmental Sciences
Yao Jun-Qiang, Chen Jing, Zhang Tong-Wen, Tuoliewubieke Dilinuer, Mao Wei-Yi
Summary: The study investigated the stationarity of precipitation variability in arid Central Asia using observational records, tree-ring reconstructions, and CMIP5 simulations. The results suggest that precipitation totals and extremes in the region may exhibit stationary behavior, with the potential for increased extreme events in the future. Although mean precipitation changes can be predicted within certain limits, the detection and prediction of precipitation changes remain challenging.
ADVANCES IN CLIMATE CHANGE RESEARCH
(2021)
Article
Fisheries
Olav Nikolai Breivik, Anders Nielsen, Casper W. Berg
Summary: The state-space assessment model (SAM) was extended by allowing a functional relationship between observation variance and prediction, which led to significant improvements in the official assessments of North East Arctic cod and haddock.
ICES JOURNAL OF MARINE SCIENCE
(2021)
Article
Mathematics, Applied
Wei Liu, Na Li, Ahmadjan Muhammadhaji
Summary: This paper addresses the problem of portfolio selection and adjustment for target benefit plans (TBP) with longevity trends and partial information. The longevity trends are modeled using a time-varying force function. The financial market includes risk-free assets and stocks, with the return rate of stocks being a stochastic process that is not completely observable. An optimization criterion based on the mean-variance utility model is adopted to maximize the terminal value of the pension fund and the excess pension benefit after retirement. Game theory is utilized to develop the optimization equations and obtain explicit solutions for equilibrium strategies. Numerical analysis is conducted to explore the influence of longevity trends on the internal structure of the pension system and the sensitivity of equilibrium strategies to related parameters. The results of this study demonstrate that the model can provide stable and adequate retirement benefits for participants.
Article
Green & Sustainable Science & Technology
Tie Zhang, Guijie Ding, Jiangping Zhang, Yujiao Qi
Summary: This study evaluated the spatial heterogeneity of aboveground forest biomass in Guizhou province and analyzed the contribution rates of biotic and abiotic factors to the spatial variation. It was found that biotic and abiotic factors contributed 34.4% and 19.2% to the spatial variation of forest biomass, with stand average height and annual precipitation having the greatest influence. Spatial factors only explained 0.7% of the spatial variation, indicating that they could be explained by some measured abiotic factors.
Article
Soil Science
Johanna I. F. Slaets, Runa S. Boeddinghaus, Hans-Peter Piepho
Summary: This paper demonstrates the benefits of integrating geostatistical covariance structures and ANOVA procedures into a linear mixed modeling framework. The independence assumption in analysis of variance is justified based on randomization, while geostatistical models imply a correlation of errors and can improve efficiency. In cases lacking randomization, spatial correlation can be accounted for in a mixed model.
EUROPEAN JOURNAL OF SOIL SCIENCE
(2021)
Article
Geosciences, Multidisciplinary
Arnaud J. A. M. Temme, Ilona Van der Kroef, Cathelijne R. Stoof, Michael E. Ketterer
Summary: A study on soil-landscape relations in a natural grassland found that even without the influence of trees, there is considerable variation in soil properties, with short-range variation similar to long-range variation. This suggests that non-tree related natural processes could disrupt the formation of clear catenas in the landscape.
Article
Mathematics, Applied
Qian-Ying Feng, Xu Wu, Lin-Lin Zhang, Jia Li
Summary: This paper constructs an effective portfolio selection model that accurately measures the risk and return on assets based on the fractal theory. By incorporating fractal statistical measures into the return-risk criterion, the fractal portfolio selection model is established, and the closed-form solution is provided. Empirical analysis shows that the fractal portfolio outperforms the traditional portfolio in terms of investment performance and robustness, especially when the asset returns obey the asymmetric power-law distribution.
Article
Multidisciplinary Sciences
Gwowen Shieh
Summary: This paper aims to describe and compare confidence interval estimation methods for the standardized contrasts of treatment effects in ANCOVA designs. Sample size procedures are also presented to assure informative and precise estimation. The proposed approaches and developed computer programs provide accurate sample size determinations under the precision considerations.
Article
Engineering, Geological
N. M. Khan, L. Ma, K. Cao, A. J. S. Spearing, W. Liu, Y. Jie, M. Yousaf
Summary: In this study, the authors utilize infrared radiation indexes to evaluate variance and autocorrelation for the early prediction of violent rock failure. The results show that autocorrelation can be used as a reliable precursor for rock failure, with its stress level decreasing inversely with the loading rate.
ROCK MECHANICS AND ROCK ENGINEERING
(2022)
Article
Environmental Sciences
F. Wang, G. H. Huang, G. H. Cheng, Y. P. Li
Summary: This study examines the impact of climate variations on non-stationary changes of streamflow across 279 watersheds in Canada, identifying that most nonstationary changes occur in Prairie Provinces and the eastern coast. Climate variations, such as Atlantic Multidecadal Oscillation and El Niño, have significant impacts on Canadian streamflow, with varying effects depending on watersheds and seasons. Different climate variations have different time-varying effects on streamflow, and four spatial patterns are identified across all watersheds.
ENVIRONMENTAL RESEARCH
(2021)
Editorial Material
Environmental Sciences
Gabriele Villarini, Conrad Wasko
Summary: Changes in river discharge due to climate change are highly uncertain, and a recent study found that streamflow changes occurred more often in basins impacted by human disturbances than in pristine ones, with no clear signal from climate change alone.
NATURE CLIMATE CHANGE
(2021)
Article
Geosciences, Multidisciplinary
Julian M. Ortiz, Willy Kracht, Giovanni Pamparana, Jannik Haas
MATHEMATICAL GEOSCIENCES
(2020)
Article
Geosciences, Multidisciplinary
Hernan Calderon, Felipe Santibanez, Jorge F. Silva, Julian M. Ortiz, Alvaro Egana
MATHEMATICAL GEOSCIENCES
(2020)
Article
Geosciences, Multidisciplinary
Gonzalo F. Diaz, Julian M. Ortiz, Jorge F. Silva, Rodrigo A. Lobos, Alvaro F. Egana
MATHEMATICAL GEOSCIENCES
(2020)
Article
Energy & Fuels
Jannik Haas, Simon Moreno-Leiva, Tobias Junne, Po-Jung Chen, Giovanni Pamparana, Wolfgang Nowak, Willy Kracht, Julian M. Ortiz
Article
Geosciences, Multidisciplinary
Felipe A. Santibanez-Leal, Julian M. Ortiz, Jorge F. Silva
NATURAL RESOURCES RESEARCH
(2020)
Article
Geosciences, Multidisciplinary
Mauricio Garrido, Exequiel Sepulveda, Julian Ortiz, Brian Townley
NATURAL RESOURCES RESEARCH
(2020)
Article
Computer Science, Interdisciplinary Applications
Sebastian Avalos, Julian M. Ortiz
COMPUTERS & GEOSCIENCES
(2020)
Article
Metallurgy & Metallurgical Engineering
Sebastian Avalos, Willy Kracht, Julian M. Ortiz
MINING METALLURGY & EXPLORATION
(2020)
Article
Geochemistry & Geophysics
Sebastian Avalos, Willy Kracht, Julian M. Ortiz
Article
Geosciences, Multidisciplinary
Alvaro I. Riquelme, Julian M. Ortiz
Summary: Assessing spatial uncertainty over an arbitrary volume is usually done by generating multiple simulations and averaging the property over each to build its uncertainty distribution. Multi-Gaussian kriging offers a simpler alternative by directly computing conditional probability density functions of random variables. This approach demonstrates accuracy in synthetic data and can be applied to real mining cases to determine uncertainty in scheduled production volumes.
MATHEMATICAL GEOSCIENCES
(2021)
Article
Geochemistry & Geophysics
Ilkay S. Cevik, Gema R. Olivo, Julian M. Ortiz
Summary: The Vazante Group in Minas Gerais, Brazil, hosts world-class zinc silicate deposits and Pb-Zn sulfide deposits. A recent study revealed base metal sulfide mineralization in siliciclastic rocks prior to orogenic events. Multivariate analysis showed that the siliciclastic rocks exhibit preorogenic mineralization geochemical signature traits.
JOURNAL OF GEOCHEMICAL EXPLORATION
(2021)
Correction
Geosciences, Multidisciplinary
Alvaro I. Riquelme, Julian M. Ortiz
Summary: Publisher apologized for a mistake in the original article and it has been corrected.
MATHEMATICAL GEOSCIENCES
(2021)
Article
Metallurgy & Metallurgical Engineering
Fouad Faraj, Julian M. Ortiz
Summary: In natural resource industries, the increasing amount of data recorded during sampling sites has made geostatistical analysis more challenging. Traditional methods of establishing domains are time-consuming, but a newly proposed unsupervised classification workflow allows practitioners to input domain knowledge easily and can be applied for various purposes.
MINING METALLURGY & EXPLORATION
(2021)
Article
Metallurgy & Metallurgical Engineering
Ilkay S. Cevik, Oy Leuangthong, Antoine Cate, Julian M. Ortiz
Summary: The paper introduces a methodology to assist a qualified person in mineral resource classification by clustering blocks with similar parameters and then classifying them in a consistent and automatic manner. The results are comparable to classifications done by qualified persons using conventional methods, providing a quick and consistent classification approach.
MINING METALLURGY & EXPLORATION
(2021)
Article
Mathematics
Enrique Jelvez, Nelson Morales, Julian M. Ortiz
Summary: In the context of planning the exploitation of an open-pit mine, this study presents a stochastic programming model for the final pit limit problem. By modeling the uncertainty of ore grades using conditional simulations, the model maximizes the expected profit of mining business while minimizing the risk of losses. It generates a set of optimal solutions in the expected return vs. risk space for decision makers to choose from.