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Spatiotemporal analysis of some extreme rainfall indices over Iraq (1981–2017)

Al-Lami Alaa M., Al-Timimi Yaseen K., Al-Shamarti Hasanain K. A.

Przegląd Naukowy Inżynieria i Kształtowanie Środowiska

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2021

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Vol. 30, No. 2

221--235

EN

Extreme rainfall is one of the environmental hazards with disastrous effects on the human environment. Water resources management is very vulnerable to any changes in rainfall intensities. A spatiotemporal analysis is essential for study the impact of climate change and variability on extreme rainfall. In this study, daily rainfall data for 36 meteorological stations in Iraq during 1981–2017 were used to investigate the spatiotemporal pattern of 10 extreme rainfall indices using RClimDex package. These indices were classified into two categories: rainfall total (PRCPTOT, SDII, R95p, R99p, RX1day, and RX5day) and rainfall days (CDD, CWD, R10, and R20). Depending on the mean annual precipitation data, the study area was divided into three climatic zones to examine the time series features of those 10 indices. Results showed a tendency to increase in precipitation toward the northwestern part of Iraq, and more than 70% of stations achieved a positive trend for most indices. The most frequent negative trend appeared in eight stations distributed in the western and southern parts of Iraq, namely (Heet, Haditha, Anah, Rutba, Qaim, Nukheb, Najaf, and Fao). A significant positive trend appeared obviously in PRCPTOT and R95p with a rate of 0.1–4.6 and 0.5–2.7 mm per year, respectively. Additionally, the least trend increasing appeared in all precipitation days indices specifically in R10 and R20. Time series analyses revealed a positive trend in all regions under study, except SDII in the southern region. The most significant rate of change was noticed in regions one and two (northern and middle parts of Iraq), particularly for PRCPTOT and R95p 3.26 and 2.45 mm per day, respectively. Only the northern and eastern regions of Iraq experienced a high probability of significant extreme rainfall.

2

The portfolio management: investigation of the Fama-French five- and six-factor asset pricing models

Ben Mrad Douagi Fatma Wyeme, Chaouachi Olfa, Sow Mory

Polish Journal of Management Studies

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2021

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Vol. 23, No. 1

106--118

EN

The novel contribution of this paper is to test if the Fama-French five- and six-factor models can explain the portfolio returns in the Regional Stock Exchange of Ivory Coast Securities (BRVM) between January 2007 and December 2018. For the Fama-French five-factor model, the results show that the only useful factors for describing the portfolio excess return are the market, value and profitability when the OLS and the GARCH techniques are used. For the augmented Fama French six-factor model, the results report that only the market, value, profitability and illiquidity factors played an eminent role in explaining the portfolio excess return. Moreover, using the OLS technique, it is found that the Fama-French five-factor model and the augmented Fama-French six-factor model can capture the portfolio returns. However, when the GARCH technique is used, the findings show that these models can fully explain the portfolio returns. The results found can help portfolio managers to identify extensive factors that have an impact on the equity returns and to estimate the required return on the stock. Moreover, traders can employ these factor models to control investment risk.

PL

Nowatorskim wkładem tego artykułu jest sprawdzenie, czy pięcioi sześcioczynnikowe modele Famy-French mogą wyjaśnić zwroty portfelowe na Regionalnej Giełdzie Papierów Wartościowych Wybrzeża Kości Słoniowej (BRVM) w okresie od stycznia 2007 r. do grudnia 2018 r. Dla Famy -Francuski model pięcioczynnikowy, wyniki pokazują, że jedynymi użytecznymi czynnikami do opisania nadwyżki zwrotu portfela są rynek, wartość i rentowność, gdy stosuje się techniki OLS i GARCH. W przypadku rozszerzonego sześcioczynnikowego modelu Famy French, wyniki wskazują, że tylko czynniki rynkowe, wartości, rentowności i braku płynności odegrały znaczącą rolę w wyjaśnieniu nadwyżki zwrotu z portfela. Ponadto, stosując technikę OLS, stwierdzono, że pięcioczynnikowy model Famy-Frencha i rozszerzony sześcioczynnikowy model Famy-Frencha mogą uchwycić zwroty portfela. Jednak w przypadku zastosowania techniki GARCH wyniki pokazują, że modele te mogą w pełni wyjaśnić zwroty z portfela. Osiągnięte wyniki mogą pomóc zarządzającym portfelami zidentyfikować rozległe czynniki, które mają wpływ na zwroty z akcji i oszacować wymagany zwrot z akcji. Co więcej, handlowcy mogą stosować te modele czynnikowe do kontrolowania ryzyka inwestycyjnego.

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3D crosswell electromagnetic inversion based on radial basis function neural network

Fang Sinan, Zhang Zhansong, Chen Wei, Pan Heping, Peng Jun

Acta Geophysica

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2020

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Vol. 68, no. 3

711--721

EN

Crosswell electromagnetic (EM) method has fundamentally improved the horizontal detection ability of well logging and will become an increasingly promising approach for the secondary exploration of hydrocarbon reservoir. We applied orthogonal least squares (OLS) radial basis function neural network (RBFNN) based on improved Gram–Schmidt (G–S) procedure to three-dimensional (3D) crosswell EM inversion problems. In the inversion process of the simplifed crosswell model with single-grid conductivity anomalies and normal oil reservoir, compared the inversion results of other fve neural networks, OLS-RBFNN was proved to have the best global optimization ability and the fastest sample learning speed and the average inversion error of low conductivity anomalies model (4%) and oil reservoir model (9%) can meet the inversion requirements of crosswell EM method. Only the OLS-RBFNN could achieve ideal inversion results in the most concerned central area of crosswell model, and the inversion accuracy of this algorithm will be more outstanding when the model becomes more complex. Merely using the three-component time-domain crosswell EM data of two wells, the inversion of 3D medium conductivity in the crosswell dominant exploration area can be efectively realized through the nonlinear approximation of the OLS-RBFNN.

4

Managing nation building through human capital accumulation : ASEAN perspective

Zandi Gholamreza, Kong-Yueq Renathii, Rasiah Ratneswary, Turner Jason James

Polish Journal of Management Studies

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2019

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Vol. 19, No. 2

442--453

EN

This paper aims to analyse how the ASEAN-5 countries manage nation-building through human capital accumulation. This quantitative study analysed the macroeconomic and human capital data of 5 ASEAN countries from 1970 to 2016. The independent variables incorporated in this study are physical capital, population growth, human capital and trade openness. The theoretical framework of this study is based on Mankiw, Romer and Weil’s endogenous Human Capital Augmented Solow model of economic growth. Ordinary Least Squares estimation technique was employed and the empirical results of this study deduce that human capital has a significant positive impact on economic growth in Malaysia and Singapore. Physical capital was found to have a significant positive impact on economic growth in Indonesia and Thailand. In Philippines, Indonesia and Thailand, it is demonstrated that population growth has a significant negative impact on economic growth, while trade openness is inferred to have a significant positive impact on economic growth only in Malaysia.

PL

Niniejszy artykuł ma na celu przeanalizowanie, w jaki sposób kraje ASEAN-5 zarządzają budowaniem narodu poprzez akumulację kapitału ludzkiego. W tym badaniu ilościowym przeanalizowano dane makroekonomiczne i dotyczące kapitału ludzkiego z 5 krajów ASEAN w latach 1970-2016. Zmiennymi niezależnymi uwzględnionymi w tym badaniu są kapitał fizyczny, wzrost liczby ludności, kapitał ludzki i otwartość handlowa. Teoretyczne ramy tego badania opierają się na endogenicznym modelu wzrostu gospodarczego w kapitale ludzkim Mankiw, Romer i Weil. Zastosowano technikę szacowania najmniejszych kwadratów, a wyniki empiryczne tego badania wskazują, że kapitał ludzki ma znaczący pozytywny wpływ na wzrost gospodarczy w Malezji i Singapurze. Stwierdzono, że kapitał fizyczny ma znaczący pozytywny wpływ na wzrost gospodarczy w Indonezji i Tajlandii. Na Filipinach, w Indonezji i Tajlandii wykazano, że wzrost liczby ludności ma znaczący negatywny wpływ na wzrost gospodarczy, podczas gdy otwartość handlowa wywodzi się z istotnego pozytywnego wpływu na wzrost gospodarczy tylko w Malezji.

5

Entropy Coder for Audio Signals

Ulacha G., Stasinski R.

International Journal of Electronics and Telecommunications

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2015

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Vol. 61, No. 2

219-224

EN

In the paper an effective entropy coder designed for coding of prediction errors of audio signals is presented. The coder is implemented inside a greater structure, which signal modeling part is a lossless coding backward adaptation algorithm consisting of cascaded Ordinary Least Squares (OLS), three Normalized Least Mean Square (NLMS), and prediction error bias correction sections. The technique performance is compared to that of four other lossless codecs, including MPEG-4 Audio Lossless (ALS) one, and it is shown that indeed, on the average the new method is the best. The entropy coder is an advanced context adaptive Golomb one followed by two context adaptive arithmetic coders.