The collusion among various generating units has been a problematic issue affecting the fairness and transparency of electricity markets.Therefore,it is of great significance to assess the potential of such collusion ...The collusion among various generating units has been a problematic issue affecting the fairness and transparency of electricity markets.Therefore,it is of great significance to assess the potential of such collusion in the electricity market.However,the previous assessment studies primarily focused on the bidding behaviors of collusive generating units,without considering the influences of generation flexibility,such as ramp rates.In this paper,a novel assessment method is proposed to evaluate the collusion potential in the electricity market considering generation flexibility.First,a bi-level optimization model is developed to simulate the collusive strategies of dif-ferent generating units,including the withholding of generation capacities and ramp rates,as well as the uplifting of minimum outputs and bidding prices.In the upper-level problem,collusive generating units optimize their offering strategies to optimize the generation profits without violating the regulatory laws.The lower-level problem is a day-ahead economic dispatch model which minimizes the dispatching costs.Based on the optimal collusive strategies determined by the bi-level model,a framework is then proposed to assess the collusion potential in electricity markets.Moreover,price-based and profit-based indices are proposed to quantitatively evaluate the collusion potential of different generating units.Finally,the proposed assessment method is validated on a modified IEEE 39-node system.The numerical results demonstrated that generation flexibility can be exploited collusively for making excessive profits,particularly during load peaks and valleys.Index Terms-Collusionpotential,economic cdispatch,generation flexibility,ramp rates,strategic withholding.展开更多
Since the introduction of Bitcoin,numerous studies on Bitcoin mining attacks have been conducted,and as a result,many countermeasures to these attacks have been proposed.The reputation-based mining paradigm is a compr...Since the introduction of Bitcoin,numerous studies on Bitcoin mining attacks have been conducted,and as a result,many countermeasures to these attacks have been proposed.The reputation-based mining paradigm is a comprehensive countermeasure solution to this problem with the goal of regulating the mining process and preventing mining attacks.This is accomplished by incentivizing miners to avoid dishonest mining strategies using reward and punishment mechanisms.This model was validated solely based on game theoretical analyses,and the real-world implications of this model are not known due to the lack of empirical data.To shed light on this issue,we designed a simulated mining platform to examine the effectiveness of the reputation-based mining paradigm through data analysis.We implemented block withholding attacks in our simulation and ran the following three scenarios:Reputation mode,non-reputation mode,and no attack mode.By comparing the results from these three scenarios,interestingly,we found that the reputation-based mining paradigm decreases the number of block withholding attacks,and as a result,the actual revenue of individual miners becomes closer to their theoretical expected revenue.In addition,we observed that the confidence interval test can effectively detect block withholding attacks;however,the test also results in a small number of false positive cases.Since the effectiveness of the reputation-based model relies on attack detection,further research is needed to investigate the effect of this model on other dishonest mining strategies.展开更多
Bitcoin is the most famous and the most used cryptocurrency in the world,such that it has received extreme popularity in recent years.However the Bitcoin system is accompanied by different attacks,including the block ...Bitcoin is the most famous and the most used cryptocurrency in the world,such that it has received extreme popularity in recent years.However the Bitcoin system is accompanied by different attacks,including the block withholding(BWH)attack.When a miner plays the BWH attack,it will withhold all the blocks newly discovered in the attack pool,damaging the honest miners’right to obtain the fair reward.In this paper,we consider a setting in which two miners may honestly mine or perform the BWH attack in a mining pool.Different strategy profiles will bring different payoffs,in addition influence the selection of the strategies.Therefore,we establish an evolutionary game model to study the behavior tendency of the miners and the evolutionary stable strategies under different conditions,by formulating the replicator dynamic equations.Through numerical simulations,we further verify the theoretical results on evolutionary stable solutions and discuss the impact of the factors on miners’strategic choice.Based on these simulation results,we also make some recommendations for the manager and the miners to mitigate the BWH attack and to promote the cooperation between miners in a mining pool.展开更多
目的评价重症监护室(intensive care unit,ICU)的医务人员对生命终末期患者的认识及态度,为ICU生命终末期的治疗和护理提供伦理学依据。方法使用自制调查问卷对国内综合ICU内医护人员进行调查。问卷内容包括人口统计数据和受访者对生命...目的评价重症监护室(intensive care unit,ICU)的医务人员对生命终末期患者的认识及态度,为ICU生命终末期的治疗和护理提供伦理学依据。方法使用自制调查问卷对国内综合ICU内医护人员进行调查。问卷内容包括人口统计数据和受访者对生命终末期的认识及态度。应用Likert5级计分法,非常赞同计1分,完全不赞同计5分。结果在ICU医护人员中发放330份问卷,回复率为95.4%。87.2%的受访者赞同对ICU生命终末期患者实施限制或撤除生命支持治疗,但超过一半的受访者不赞同对生命终末期患者停止机械通气治疗,不愿意主动提出限制或撤除生命支持的建议。结论 ICU医护人员对生命终末期患者实施撤除生命支持治疗持肯定态度,但不愿主动提出限制或撤除生命支持的建议。展开更多
This study focuses on the taxation of foreign investments in Poland in terms of withholding tax.Over the past three years,there have been significant changes in the way they are taxed,as a result of which the relief a...This study focuses on the taxation of foreign investments in Poland in terms of withholding tax.Over the past three years,there have been significant changes in the way they are taxed,as a result of which the relief at source mechanism has been replaced by the pay and refund mechanism.Despite the urgent need to implement this reform,the application of the new mechanism was repeatedly suspended due to its inconvenience for entrepreneurs.Enterprises that are able to obtain all the necessary information from their contractors will be able to benefit more easily from preferential taxation contained in the EU law or in tax treaties on double taxation avoidance(DTT).On the other hand,companies that have a weaker market position may face difficulties in obtaining information from the recipient of the payment,so they de facto will have to credit the recipients of their payments.展开更多
基金supported in part by the Science and Technology Project of SGCC Technical report on multi-objective global optimal allocation model and strategy research of power trading in the new era under Grant No.SGZJ0000KXJS1900181.
文摘The collusion among various generating units has been a problematic issue affecting the fairness and transparency of electricity markets.Therefore,it is of great significance to assess the potential of such collusion in the electricity market.However,the previous assessment studies primarily focused on the bidding behaviors of collusive generating units,without considering the influences of generation flexibility,such as ramp rates.In this paper,a novel assessment method is proposed to evaluate the collusion potential in the electricity market considering generation flexibility.First,a bi-level optimization model is developed to simulate the collusive strategies of dif-ferent generating units,including the withholding of generation capacities and ramp rates,as well as the uplifting of minimum outputs and bidding prices.In the upper-level problem,collusive generating units optimize their offering strategies to optimize the generation profits without violating the regulatory laws.The lower-level problem is a day-ahead economic dispatch model which minimizes the dispatching costs.Based on the optimal collusive strategies determined by the bi-level model,a framework is then proposed to assess the collusion potential in electricity markets.Moreover,price-based and profit-based indices are proposed to quantitatively evaluate the collusion potential of different generating units.Finally,the proposed assessment method is validated on a modified IEEE 39-node system.The numerical results demonstrated that generation flexibility can be exploited collusively for making excessive profits,particularly during load peaks and valleys.Index Terms-Collusionpotential,economic cdispatch,generation flexibility,ramp rates,strategic withholding.
基金The research was sponsored by the Army Research Office and was accomplished under Grant Number W911NF-18-1-0483The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the official policies,either expressed or implied,of the Army Research Office or the U.S.Government.The U.S.Government is authorized to reproduce and distribute reprints for Government purposes notwithstanding any copyright notation herein.
文摘Since the introduction of Bitcoin,numerous studies on Bitcoin mining attacks have been conducted,and as a result,many countermeasures to these attacks have been proposed.The reputation-based mining paradigm is a comprehensive countermeasure solution to this problem with the goal of regulating the mining process and preventing mining attacks.This is accomplished by incentivizing miners to avoid dishonest mining strategies using reward and punishment mechanisms.This model was validated solely based on game theoretical analyses,and the real-world implications of this model are not known due to the lack of empirical data.To shed light on this issue,we designed a simulated mining platform to examine the effectiveness of the reputation-based mining paradigm through data analysis.We implemented block withholding attacks in our simulation and ran the following three scenarios:Reputation mode,non-reputation mode,and no attack mode.By comparing the results from these three scenarios,interestingly,we found that the reputation-based mining paradigm decreases the number of block withholding attacks,and as a result,the actual revenue of individual miners becomes closer to their theoretical expected revenue.In addition,we observed that the confidence interval test can effectively detect block withholding attacks;however,the test also results in a small number of false positive cases.Since the effectiveness of the reputation-based model relies on attack detection,further research is needed to investigate the effect of this model on other dishonest mining strategies.
基金the National Nature Science Foundation of China(11871366)Qing Lan Project for Young Academic Leaders+1 种基金Qing Lan Project for Key Teachersthe Research Innovation Program for College Graduate Students of Jiangsu Province(KYCX20-2790)。
文摘Bitcoin is the most famous and the most used cryptocurrency in the world,such that it has received extreme popularity in recent years.However the Bitcoin system is accompanied by different attacks,including the block withholding(BWH)attack.When a miner plays the BWH attack,it will withhold all the blocks newly discovered in the attack pool,damaging the honest miners’right to obtain the fair reward.In this paper,we consider a setting in which two miners may honestly mine or perform the BWH attack in a mining pool.Different strategy profiles will bring different payoffs,in addition influence the selection of the strategies.Therefore,we establish an evolutionary game model to study the behavior tendency of the miners and the evolutionary stable strategies under different conditions,by formulating the replicator dynamic equations.Through numerical simulations,we further verify the theoretical results on evolutionary stable solutions and discuss the impact of the factors on miners’strategic choice.Based on these simulation results,we also make some recommendations for the manager and the miners to mitigate the BWH attack and to promote the cooperation between miners in a mining pool.
文摘目的评价重症监护室(intensive care unit,ICU)的医务人员对生命终末期患者的认识及态度,为ICU生命终末期的治疗和护理提供伦理学依据。方法使用自制调查问卷对国内综合ICU内医护人员进行调查。问卷内容包括人口统计数据和受访者对生命终末期的认识及态度。应用Likert5级计分法,非常赞同计1分,完全不赞同计5分。结果在ICU医护人员中发放330份问卷,回复率为95.4%。87.2%的受访者赞同对ICU生命终末期患者实施限制或撤除生命支持治疗,但超过一半的受访者不赞同对生命终末期患者停止机械通气治疗,不愿意主动提出限制或撤除生命支持的建议。结论 ICU医护人员对生命终末期患者实施撤除生命支持治疗持肯定态度,但不愿主动提出限制或撤除生命支持的建议。
文摘This study focuses on the taxation of foreign investments in Poland in terms of withholding tax.Over the past three years,there have been significant changes in the way they are taxed,as a result of which the relief at source mechanism has been replaced by the pay and refund mechanism.Despite the urgent need to implement this reform,the application of the new mechanism was repeatedly suspended due to its inconvenience for entrepreneurs.Enterprises that are able to obtain all the necessary information from their contractors will be able to benefit more easily from preferential taxation contained in the EU law or in tax treaties on double taxation avoidance(DTT).On the other hand,companies that have a weaker market position may face difficulties in obtaining information from the recipient of the payment,so they de facto will have to credit the recipients of their payments.
