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GMM Estimation of Continuous-Time Bilinear Processes 连续双线性过程的GMM估计
Pub Date : 2020-10-08 DOI: 10.19139/soic-2310-5070-902
A. Bibi, F. Merahi
This paper examines the moments properties in frequency domain of the class of …first order continuous-timebilinear processes (COBL(1,1) for short) with time-varying (resp. time-invariant) coefficients. So, we used theassociated evolutionary (or time-varying) transfer functions to study the structure of second-order of the process and its powers. In particular, for time-invariant case, an expression of the moments of any order are showed and the continuous-time AR (CAR) representation of COBL(1,1) is given as well as some moments properties of special cases. Based on these results we are able to estimate the unknown parameters involved in model via the so-called generalized method of moments (GMM) illustrated by a Monte Carlo study and applied to modelling two foreign exchange rates of Algerian Dinar against U.S-Dollar (USD/DZD) and against the single European currency Euro (EUR/DZD).
本文研究了具有时变(resp)的…一类一阶连续双线性过程(简称COBL(1,1))在频域上的矩量性质。定常系数。因此,我们使用相关的进化(或时变)传递函数来研究过程的二阶结构及其幂。特别地,对于定常情况,给出了任意阶矩的表达式,给出了COBL(1,1)的连续时间AR (CAR)表示以及特殊情况下的一些矩的性质。基于这些结果,我们能够通过所谓的广义矩量方法(GMM)估计模型中涉及的未知参数,该方法由蒙特卡洛研究说明,并应用于阿尔及利亚第纳尔对美元(USD/DZD)和对单一欧洲货币欧元(EUR/DZD)的两种外汇汇率建模。
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引用次数: 0
A New Family of Hybrid Conjugate Gradient Methods for Unconstrained Optimization 一类新的无约束优化混合共轭梯度方法
Pub Date : 2020-10-08 DOI: 10.19139/SOIC-2310-5070-480
O. J. Adeleke, A. Ezugwu, I. Osinuga
The conjugate gradient method is a very efficient iterative technique for solving large-scale unconstrained optimization problems. Motivated by recent modifications of some variants of the method and construction of hybrid methods, this study proposed four hybrid methods that are globally convergent as well as computationally efficient. The approach adopted for constructing the hybrid methods entails projecting ten recently modified conjugate gradient methods. Each of the hybrid methods is shown to satisfy the descent property independent of any line search technique and globally convergent under the influence of strong Wolfe line search. Results obtained from numerical implementation of these methods and performance profiling show that the methods are very competitive with well-known traditional methods.
共轭梯度法是求解大规模无约束优化问题的一种非常有效的迭代技术。受最近对该方法的一些变体和混合方法构造的修改的启发,本研究提出了四种全局收敛且计算高效的混合方法。构造混合方法所采用的方法需要投影十个最近修改的共轭梯度方法。每种混合方法都满足独立于任何线性搜索技术的下降特性,并且在强Wolfe线性搜索的影响下全局收敛。从这些方法的数值实现和性能评测中获得的结果表明,这些方法与众所周知的传统方法具有很强的竞争力。
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引用次数: 1
A Geometrical Approach for the Optimal Control of Sequencing Batch Bio-Reactors 序批式生物反应器优化控制的几何方法
Pub Date : 2020-09-26 DOI: 10.19139/SOIC-2310-5070-868
Nahla Abdellatif, Walid Bouhafs, J. Harmand, F. Jean
In this work, we consider an optimal control problem of a biological sequencing batch reactor (SBR) for the treatment of pollutants in wastewater. This model includes two biological reactions, one being aerobic while the other is anoxic. The objective is to find an optimal oxygen-injecting strategy to reach, in minimal time and in a minimal time/energy compromise, a target where the pollutants concentrations must fulfill normative constraints. Using a geometrical approach, we solve a more general optimal control problem and thanks to Pontryagin’s Maximum Principle, we explicitly give the complete optimal strategy.
在这项工作中,我们考虑了生物序批式反应器(SBR)处理废水中污染物的最优控制问题。该模型包括两种生物反应,一种是好氧反应,另一种是缺氧反应。目标是找到一个最佳的氧气注入策略,在最短的时间和最短的时间/能量折衷下,达到污染物浓度必须满足规范约束的目标。使用几何方法,我们解决了一个更一般的最优控制问题,并感谢庞特里亚金的极大值原理,我们明确地给出了完整的最优策略。
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引用次数: 0
The Topp-Leone odd log-logistic Gumbel Distribution: Properties and Applications Topp-Leone奇对数-logistic甘贝尔分布:性质及应用
Pub Date : 2020-09-26 DOI: 10.19139/SOIC-2310-5070-903
Fazlollah Lak, M. Alizadeh, H. Karamikabir
In this article, the Topp-Leone odd log-logistic Gumbel (TLOLL-Gumbel) family of distribution have beenstudied. This family, contains the very flexible skewed density function. We study many aspects of the new model like hazard rate function, asymptotics, useful expansions, moments, generating Function, R´enyi entropy and order statistics. We discuss maximum likelihood estimation of the model parameters. Further, we study flexibility of the proposed family are illustrated of two real data sets.
本文研究了Topp-Leone奇对数-logistic甘贝尔分布族。这个族包含了非常灵活的偏态密度函数。我们研究了新模型的许多方面,如危险率函数、渐近性、有用展开式、矩、生成函数、R´enyi熵和序统计量。我们讨论了模型参数的极大似然估计。进一步,我们研究了两个真实数据集的灵活性。
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引用次数: 1
Nonsmooth Vector Optimization Problem Involving Second-Order Semipseudo, Semiquasi Cone-Convex Functions 二阶半拟、半拟锥凸函数的非光滑向量优化问题
Pub Date : 2020-09-26 DOI: 10.19139/SOIC-2310-5070-839
S. Sharma, Priyanka Yadav
Recently, Suneja et al. [26] introduced new classes of second-order cone-(η, ξ)-convex functions along with their generalizations and used them to prove second-order Karush–Kuhn–Tucker (KKT) type optimality conditions and duality results for the vector optimization problem involving first-order differentiable and second-order directionally differentiable functions. In this paper, we move one step ahead and study a nonsmooth vector optimization problem wherein the functions involved are first and second-order directionally differentiable. We introduce new classes of nonsmooth second-order cone-semipseudoconvex and nonsmooth second-order cone-semiquasiconvex functions in terms of second-order directional derivatives. Second-order KKT type sufficient optimality conditions and duality results for the same problem are proved using these functions.
最近,Suneja et al.[26]引入了一类新的二阶锥-(η, ξ)-凸函数及其推广,并利用它们证明了二阶Karush-Kuhn-Tucker (KKT)型最优性条件和对偶性结果,该问题涉及一阶可微函数和二阶方向可微函数。在本文中,我们进一步研究了一个非光滑向量优化问题,其中所涉及的函数是一阶和二阶方向可微的。从二阶方向导数的角度引入了一类新的非光滑二阶锥-半拟凸函数和非光滑二阶锥-半拟凸函数。利用这些函数证明了同一问题的二阶KKT型充分最优性条件和对偶性结果。
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引用次数: 1
A Simulation Study of Semiparametric Estimation in Copula Models Based on Minimum Alpha-Divergence 基于最小散度的Copula模型半参数估计仿真研究
Pub Date : 2020-09-11 DOI: 10.19139/soic-2310-5070-974
M. Mohammadi, M. Amini, M. Emadi
The purpose of this paper is to introduce two semiparametric methods for the estimation of copula parameter. These methods are based on minimum Alpha-Divergence between a non-parametric estimation of copula density using local likelihood probit transformation method and a true copula density function. A Monte Carlo study is performed to measure the performance of these methods based on Hellinger distance and Neyman divergence as special cases of Alpha-Divergence. Simulation results are compared to the Maximum Pseudo-Likelihood (MPL) estimation as a conventional estimation method in well-known bivariate copula models. These results show that the proposed method based on Minimum Pseudo Hellinger Distance estimation has a good performance in small sample size and weak dependency situations. The parameter estimation methods are applied to a real data set in Hydrology.
本文的目的是介绍两种估计耦合参数的半参数方法。这些方法是基于用局部似然概率变换方法得到的非参数的联结密度估计与真联结密度函数之间的最小α散度。基于Hellinger距离和Neyman散度作为alpha -散度的特殊情况,进行蒙特卡罗研究来衡量这些方法的性能。仿真结果与最大伪似然(MPL)估计作为一种传统的估计方法在众所周知的二元联结模型中进行了比较。结果表明,基于最小伪海灵格距离估计的方法在小样本量和弱依赖性情况下具有良好的性能。将参数估计方法应用于实际水文数据集。
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引用次数: 1
Convergence Analysis of a Stochastic Progressive Hedging Algorithm for Stochastic Programming 随机规划中一种随机递进套期保值算法的收敛性分析
Pub Date : 2020-08-06 DOI: 10.19139/soic-2310-5070-964
Zhenguo Mu, Junfeng Yang
Stochastic programming is an approach for solving optimization problems with uncertain data whose probability distribution is assumed to be known, and progressive hedging algorithm (PHA) is a well-known decomposition method for solving the underlying model. However, the per iteration computation of PHA could be very costly since it solves a large number of subproblems corresponding to all the scenarios. In this paper, a stochastic variant of PHA is studied. At each iteration, only a small fraction of the scenarios are selected uniformly at random and the corresponding variable components are updated accordingly, while the variable components corresponding to those not selected scenarios are kept untouch. Therefore, the per iteration cost can be controlled freely to achieve very fast iterations. We show that, though the per iteration cost is reduced significantly, the proposed stochastic PHA converges in an ergodic sense at the same sublinear rate as the original PHA.
随机规划是一种求解概率分布已知的不确定数据优化问题的方法,渐进对冲算法(progressive hedging algorithm, PHA)是求解底层模型的一种著名的分解方法。然而,PHA的每次迭代计算可能非常昂贵,因为它解决了与所有场景对应的大量子问题。本文研究了PHA的一个随机变量。在每次迭代中,只有一小部分场景被均匀随机选择,相应的变量成分被更新,而未被选择的场景对应的变量成分保持不变。因此,每次迭代成本可以自由控制,以实现非常快速的迭代。我们表明,尽管每次迭代成本显著降低,但所提出的随机PHA在遍历意义上以与原始PHA相同的次线性速度收敛。
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引用次数: 2
Volatility Modelling of the BRICS Stock Markets 金砖国家股票市场的波动性模型
Pub Date : 2020-07-25 DOI: 10.19139/soic-2310-5070-977
Rosinah M Mukhodobwane, C. Sigauke, Wilbert Chagwiza, W. Garira
Volatility modelling is a key factor in equity markets for risk and portfolio management. This paper focuses on the use of a univariate generalized autoregressive conditional heteroscedasticity (GARCH) models for modelling volatility of the BRICS (Brazil, Russia, India, China and South Africa) stock markets. The study extends the literature by conducting the volatility modelling under the assumptions of seven error distributions that include the normal, skewed-normal, Student’s t, skewed-Student’s t, generalized error distribution (GED), skewed-GED and the generalized hyperbolic (GHYP) distribution. It was observed that using an ARMA(1, 1)-GARCH(1, 1) model, volatilities of the Brazilian Bovespa and the Russian IMOEX markets can both be well characterized (or described) by a heavy-tailed Student’s t distribution, while the Indian NIFTY market’s volatility is best characterized by the generalized hyperbolic (GHYP) distribution. Also, the Chinese SHCOMP and South African JALSH markets’ volatilities are best described by the skew-GED and skew-Student’s t distribution, respectively. The study further observed that the persistence of volatility in the BRICS markets does not follow the same hierarchical pattern under the error distributions, except under the skew-Student’s t and GHYP distributions where the pattern is the same. Under these two assumptions, i.e. the skew-Student’s t and GHYP, in a descending hierarchical order of magnitudes, volatility with persistence is highest in the Chinese market, followed by the South African market, then the Russian, Indian and Brazilian markets, respectively. However, under each of the five non-Gaussian error distributions, the Chinese market is the most volatile, while the least volatile is the Brazilian market.
波动性建模是股票市场风险和投资组合管理的一个关键因素。本文重点研究了单变量广义自回归条件异方差(GARCH)模型对金砖国家(巴西、俄罗斯、印度、中国和南非)股市波动性的建模。该研究通过在七个误差分布的假设下进行波动率建模来扩展文献,这些误差分布包括正态、偏态、学生t、偏态学生t、广义误差分布(GED)、偏态GED和广义双曲(GHYP)分布。研究发现,使用ARMA(1,1)-GARCH(1,2)模型,巴西Bovespa和俄罗斯IMOEX市场的波动率都可以用重尾Student’s t分布来很好地表征(或描述),而印度NIFTY市场的波动性最好用广义双曲(GHYP)分布来表征。此外,中国上证综合指数和南非日线市场的波动性最好分别用偏斜的GED和偏斜的Student t分布来描述。该研究进一步观察到,在误差分布下,金砖国家市场波动的持续性并不遵循相同的层次模式,但在偏斜的Student’s t和GHYP分布下,模式是相同的。在这两个假设下,即偏斜的Student’s t和GHYP,按降序排列,中国市场的持续波动性最高,其次是南非市场,然后分别是俄罗斯、印度和巴西市场。然而,在五种非高斯误差分布下,中国市场波动性最大,而巴西市场波动性最小。
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引用次数: 3
Sample Paths Properties of Stochastic Processes from Orlicz Spaces, with Applications to Partial Differential Equations Orlicz空间随机过程的样本路径性质及其在偏微分方程中的应用
Pub Date : 2020-07-25 DOI: 10.19139/soic-2310-5070-880
L. Sakhno, Y. Kozachenko, E. Orsingher, O. Hopkalo
In this paper we obtain conditions for stochastic processes from Orlicz spaces defined on unbounded domains to have almost sure bounded and continuous sample paths. Estimates for distributions of suprema of the processes are presented. Conditions are given in terms of entropy integrals and majorant characteristics of Orlicz spaces. Possible applications to solutions of partial differential equations are discussed. Examples of processes are given for which the conditions of the main results are satisfied.
本文从定义在无界域上的Orlicz空间得到随机过程具有几乎确定的有界连续样本路径的条件。给出了过程上确界分布的估计。利用熵积分和Orlicz空间的多数特征给出了条件。讨论了偏微分方程解的可能应用。给出了满足主要结果条件的过程实例。
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引用次数: 0
Minimax-robust forecasting of sequences with periodically stationary long memory multiple seasonal increments 具有周期性平稳长记忆多季节增量序列的极小鲁棒预测
Pub Date : 2020-07-22 DOI: 10.19139/soic-2310-5070-998
M. Luz, M. Moklyachuk
We introduce stochastic sequences $zeta(k)$ with periodically stationary generalized multiple increments of fractional order which combines cyclostationary, multi-seasonal, integrated and fractionally integrated patterns. We solve the problem of optimal estimation of linear functionals constructed from unobserved values of stochastic sequences $zeta(k)$ based on their observations at points $ k<0$. For sequences with known spectral densities, we obtain formulas for calculating values of the mean square errors and the spectral characteristics of the optimal estimates of functionals. Formulas that determine the least favorable spectral densities and minimax (robust) spectral characteristics of the optimal linear estimates of functionals are proposed in the case where spectral densities of sequences are not exactly known while some sets of admissible spectral densities are given.
我们引入了具有周期平稳的分数阶广义多增量的随机序列$zeta(k)$,它结合了循环平稳、多季节、积分和分数积分模式。我们基于随机序列$zeta(k)$在点$k<0$处的观测,解决了由其未观测值构造的线性泛函的最优估计问题。对于具有已知谱密度的序列,我们得到了泛函最优估计的均方误差值和谱特性的计算公式。在序列谱密度不完全已知的情况下,给出了一些可容许谱密度集,提出了确定泛函最优线性估计的最不利谱密度和最小最大(鲁棒)谱特性的公式。
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引用次数: 5
期刊
Statistics, optimization & information computing
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