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A NECESSARY AND A SUFFICIENT CONDITION FOR THE EXISTENCE OF THE POSITIVE RADIAL SOLUTIONS TO HESSIAN EQUATIONS AND SYSTEMS WITH WEIGHTS

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Acta Mathematica Scientia 2017年第1期37卷 47-57页

作者： Dragos-Patru COVEI Department of Applied Mathematics The Bucharest University of Economic StudiesBucharest 010374Romania

In this article, we consider the existence of positive radial solutions for Hessian equations and systems with weights and we give a necessary condition as well as a sufficient condition for a positive radial solution to be large. The method of proving theorems is essentially based on a successive approximation technique. Our results complete and improve a work published recently by Zhang and Zhou（existence of entire positive k-convex radial solutions to Hessian equations and systems with weights. Applied Mathematics Letters,Volume 50, December 2015, Pages 48–55）.

关键词： existence Keller-Osserman condition k-Hessian equation and system

CVaR-based stochastic wind-thermal generation coordination for Turkish electricity market

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Journal of Modern Power Systems and Clean Energy 2019年第5期7卷 1307-1318页

作者： Aycan AYDOGDU Osman Bulent TOR Ali Nezih GUVEN Department of Electrical and Electronics Engineering Middle East Technical UniversityAnkara 06800Turkey The bucharest university of economic studies BucharestRomania

Uncertainties in wind power forecasting,dayahead and imbalance prices for the next day possess a great deal of risks for the profit of generation companies participating in a day-ahead electricity *** companies are exposed to imbalance penalties in the balancing market for unordered mismatches between associated day-ahead power schedule and real-time *** of wind and thermal power plants alleviates the risks raised from wind *** paper proposes a novel optimal coordination strategy by balancing wind power forecasting deviations with thermal units in the Turkish day-ahead electricity *** main focus of this study is to provide an optimal trade-off between the expected profit and the risk under wind uncertainty through conditional value at risk(CVa R)*** problem is formulated as a two-stage mixed-integer stochastic programming problem,where scenario-based wind power approach is used to handle the stochasticity of the wind *** programming approach is utilized to attain the commitment status of thermal *** of the coordination with different day-ahead bidding strategies and trade-off between expected profit and CVa R are examined with comparative scenario studies.

关键词： Conditional value at risk(CVaR) Windthermal coordination Electricity market Wind power Thermal power

A three-stage approach for resilience-constrained scheduling of networked microgrids

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Journal of Modern Power Systems and Clean Energy 2019年第4期7卷 705-715页

作者： Saeed TEIMOURZADEH Osman Bulent TOR Mahmut Erkut CEBECI Adela BARA Simona Vasilica OPREA Engineering ProcurementResearch and Analysis(EPRA)Electric Energy Co.AnkaraTurkey Department of economic Informatics and Cybernetics Faculty of CyberneticsStatistics and Economic InformaticsBucharest University of Economic Studies(BUES)BucharestRomania

This paper deals with optimal scheduling of networked microgrids(NMGs)considering resilience *** proposed scheme attempts to mitigate the damaging impacts of electricity interruptions by effectively exploiting NMG capabilities.A three-stage framework is *** Stage 1,the optimal scheduling of NMGs is studied through determining the power transaction between the NMGs and upstream network,the output power of distributed energy resources(DERs),commitment status of conventional DERs as well as demand-side *** Stage 2,the decisions made at Stage 1 are realized considering uncertainties pertaining to renewable generation,market price,power consumption of loads,and unintentional islanding of NMGs from the upstream network and *** 3 deals with uncertainties of unintentional islanding of each MG from the rest of islanded NMGs and *** problem is formulated as a mixed-integer linear programming problem and its effectiveness is assured by simulation studies.

关键词： Networked microgrid(NMG) Distributed energy resource(DER) Power system resilience Point estimate method

Deepening Collaboration China and Africa need to further align development strategies to realise the immense potential of economic cooperation

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ChinAfrica 2025年第1期17卷 24-26页

作者： EHIZUELEN MICHAEL MITCHELL OMORUYI Centre for Nigerian studies Institute of African StudiesZhejiang Normal University

Humming factories,bustling ports,and shuttling merchants highlight the vibrancy of China-Africa economic and trade *** the years,this partnership has grown significantly,optimising trade structures and fostering mutual *** deepening collaboration is evident in China’s role as Africa’s largest bilateral trading partner for 15 consecutive *** the first seven months of 2024,trade between China and African countries reached$167 billion,reflecting a 5.5-percent increase compared to the same period in *** to the International Monetary Fund,approximately 20 percent of Africa’s exports now go to China,while 16 percent of its imports originate there.

关键词： trading deepening Africa

Vulnerability to Earthquake Hazard:bucharest Case Study,Romania

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International Journal of Disaster Risk Science 2017年第2期8卷 182-195页

作者： Iuliana Armas Dragos Toma-Danila Radu Ionescu Alexandru Gavris Department of Geomorphology-Pedology-Geomatics Faculty of GeographyUniversity of Bucharest National Institute for Earth Physics Department of Tourism and Geography Bucharest University of Economic Studies

Recent seismic events show that urban areas are increasingly vulnerable to seismic damage,which leads to unprecedented levels of *** are complex systems and as such their analysis requires a good understanding of the interactions between space and the socioeconomic variables characteristic of the inhabitants of urban *** is a clear need to develop and test detailed models that describe the behavior of these interactions under seismic *** article develops an overall vulnerability index to seismic hazard based on a spatial approach applied to bucharest,Romania,the most earthquake-prone capital in the European *** methodology relies on:(1) spatial post-processed socioeconomic data from the2011 Romanian census through multicriteria analysis;and(2) analytical methods(the Improved Displacement Coefficient Method and custom-defined vulnerability functions)for estimating damage patterns,incorporated in a GIS *** computed vulnerability indices for the128 census tracts of the *** sensitivity assessment tested the robustness of spatially identified patterns of building vulnerability in the face of uncertainty in model *** results show that useful seismic vulnerability indices can be obtained through interdisciplinaryapproaches that enhance less detailed datasets,which leads lead to better targeted mitigation efforts.

关键词： bucharest Romania Seismic loss estimation Seismic risk Spatial multicriteria analysis Vulnerability index

Probability of informed trading during the COVID‑19 pandemic:the case of the Romanian stock market

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Financial Innovation 2023年第1期9卷 889-915页

作者： Cosmin Octavian Cepoi Victor Dragotă Ruxandra Trifan Andreea Iordache Department of Money and Banking and CEFIMO Faculty of Finance and BankingBucharest University of Economic StudiesBucharestRomania Department of Finance and CEFIMO Faculty of Finance and BankingBucharest University of Economic StudiesBucharestRomania Doctoral School of Finance Faculty of Finance and BankingBucharest University of Economic StudiesBucharestRomania

Using data from the bucharest Stock Exchange,we examine the factors influencing the probability of informed trading(PIN)during February—October 2020,a COVID-19 pandemic *** on an unconditional quantile regression approach,we show that PIN exhibit asymmetric dependency with liquidity and trading ***,building a customized database that contains all insider transactions on the bucharest Stock Exchange,we reveal that these types of orders monotonically increase the infor-mation asymmetry from the 50th to the 90th quantile throughout the PIN ***,we bring strong empirical evidence associating the level of information asym-metry to the level of fake news related to the COVID-19 *** novel result suggests that during episodes when the level of PIN is medium to high(between 15 and 50%),any COVID-19 related news classified as misinformation released during the lockdown period,is discouraging informed traders to place buy or sell orders condi-tioned by their private information.

关键词： PIN COVID-19 Market microstructure Insider trading

Crowdfunding model for financing movies and web series

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International Journal of Innovation studies 2021年第2期5卷 99-105页

作者： Mina Fanea-Ivanovici Hasnan Baber Department of economics and economic Policies Bucharest University of Economic StudiesBucharest010374Romania Endicott College of International studies Woosong UniversityDaejeon34606South Korea

Movies and web series are the most popular destinations of crowdfunding,and various approaches have been followed by project *** may use specialized or general crowdfunding platforms to raise money,propose fixed or flexible budgets,and use reward-based or equity-based *** may entirely or just partially finance *** date,no standard model has been used for the production of movies and web series through ***,content-based web series on over-the-top(OTT)platforms,such as Netflix and Amazon Prime,have gained *** aim of this study is to fill this conceptual gap and propose a crowdfunding model for movies and web series that can be applied and used to benefit all stakeholders:filmmakers,backers,distributors,platform owners,and the entire future *** model consists of nine chronologically interlinked phases and six types of flows:information/content,funds,audition,decision-making,content,promotion,and *** conceptual model proposed herein is based on a critical analysis of the extant literature in the field,mainly qualitative analyses performed on successfully and unsuccessfully crowdfunded and professional films in connection with the current technical platform functionalities.

关键词： Crowdfunding Movies Web series Model Creative Reward-based

Exploring the asymmetric effect of COVID‑19 pandemic news on the cryptocurrency market:evidence from nonlinear autoregressive distributed lag approach and frequency domain causality

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Financial Innovation 2023年第1期9卷 692-749页

作者： Ştefan Cristian Gherghina Liliana Nicoleta Simionescu Department of Finance Bucharest University of Economic Studies6 Romana Square010374 BucharestRomania

This paper explores the asymmetric effect of COVID-19 pandemic news,as measured by the coronavirus indices(Panic,Hype,Fake News,Sentiment,Infodemic,and Media Coverage),on the cryptocurrency *** daily data from January 2020 to September 2021 and the exponential generalized autoregressive conditional heter-oskedasticity model,the results revealed that both adverse and optimistic news had the same effect on Bitcoin returns,indicating fear of missing out behavior does not ***,when the nonlinear autoregressive distributed lag model is esti-mated,both positive and negative shocks in pandemic indices promote Bitcoin’s daily changes;thus,Bitcoin is resistant to the SARS-CoV-2 pandemic crisis and may serve as a hedge during market *** analysis of frequency domain causality supports a unidirectional causality running from the Coronavirus Fake News Index and Sentiment Index to Bitcoin returns,whereas daily fluctuations in the Bitcoin price Granger affect the Coronavirus Panic Index and the Hype *** findings may have significant policy implications for investors and governments because they highlight the impor-tance of news during turbulent *** empirical results indicate that pandemic news could significantly influence Bitcoin’s price.

关键词： COVID-19 Bitcoin NARDL EGARCH Frequency domain causality

Does board gender diversity affect firm performance?Empirical evidence from Standard & Poor’s 500 Information Technology Sector

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Financial Innovation 2021年第1期7卷 1124-1168页

作者： Liliana Nicoleta Simionescu Ştefan Cristian Gherghina Hiba Tawil Ziad Sheikha Department of Finance Bucharest University of Economic Studies6 Romana Square010374 BucharestRomania

The essence of this study is to investigate the influence of the board gender diversity on firms’accounting and market-based performance using a sample of Standard&Poor’s 500 companies belonging to the information technology sector over 12 *** the pooled ordinary least squares(OLS)method,the outcomes provide evidence for a positive influence of women on corporate boards on both measures of company performance,except for the percentage of female executives in the case of return on assets(ROA).After estimating the fixed effects and random-effects through panel data,the econometric outcomes show no statistically significant association among board gender diversity and ROA but a positive influence of the number and percentage of women on board on price-to-earnings ratio.

关键词： Gender diversity Firm performance Pooled OLS Fixed-effects Randomeffects