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
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have been significant changes in the way they are taxed,as a result of which the relief at source mechanism has been replaced by the pay and refund mechanism.Despite the urgent need to implement this reform,the application of the new mechanism was repeatedly suspended due to its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
目的调查重症患者限制或撤离医疗措施,在重症医学科(intensive care unit,ICU)的实施现状。方法前瞻性观察研究,纳入2009年6月至2011年5月,在首都医科大学附属复兴医院重症医学科住院过程中,由亲属或医生方提出"限制或撤离医疗措施...目的调查重症患者限制或撤离医疗措施,在重症医学科(intensive care unit,ICU)的实施现状。方法前瞻性观察研究,纳入2009年6月至2011年5月,在首都医科大学附属复兴医院重症医学科住院过程中,由亲属或医生方提出"限制或撤离医疗措施",并签署《医疗措施限制撤离确定书》(下称"签署")的重症患者。搜集该患者群人口学资料,签署原因,医疗费用种类,疾病严重度及预后。并根据签署内容进行分组,分为限制治疗组(A组),撤离治疗组(B组)和仅不实施临终心肺复苏组(C组)。比较上述参数的差别。结果研究期间共有86名患者的亲属进行"签署",占同期收治患者的7.2%,其中68.6%为患者亲属方提出。86例患者高龄且疾病严重度高,53.5%的医疗费用为公费医疗。"签署"至死亡/转出ICU中位数时间41 h,ICU病死率80.2%。"签署"后死亡的患者,占同期死亡患者的30.9%。"签署"主要原因为病情无法逆转和希望减轻痛苦。3组患者疾病严重度、住ICU平均费用差异无统计学意义。C组病死率(50.0%)显著低于A组(89.5%)和B组(91.1%)。"签署"后至死亡/转出ICU间的医疗费用中位数,B组显著低于A组和C组(105.0元/h vs 220.0元/h,160.7元/h,P=0.001)。签署后至转出/死亡中位数时间,B组显著少于C组(24.0 h vs 73.5 h,P=0.000)。结论 ICU住院期间"签署"的比例较低,主要为高龄和疾病严重度高的患者。患者亲属方为主要提出方。"签署"后死亡患者仅占同期死亡患者1/3。撤离治疗在一定程度上降低医疗费用。展开更多
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.
文摘目的调查重症患者限制或撤离医疗措施,在重症医学科(intensive care unit,ICU)的实施现状。方法前瞻性观察研究,纳入2009年6月至2011年5月,在首都医科大学附属复兴医院重症医学科住院过程中,由亲属或医生方提出"限制或撤离医疗措施",并签署《医疗措施限制撤离确定书》(下称"签署")的重症患者。搜集该患者群人口学资料,签署原因,医疗费用种类,疾病严重度及预后。并根据签署内容进行分组,分为限制治疗组(A组),撤离治疗组(B组)和仅不实施临终心肺复苏组(C组)。比较上述参数的差别。结果研究期间共有86名患者的亲属进行"签署",占同期收治患者的7.2%,其中68.6%为患者亲属方提出。86例患者高龄且疾病严重度高,53.5%的医疗费用为公费医疗。"签署"至死亡/转出ICU中位数时间41 h,ICU病死率80.2%。"签署"后死亡的患者,占同期死亡患者的30.9%。"签署"主要原因为病情无法逆转和希望减轻痛苦。3组患者疾病严重度、住ICU平均费用差异无统计学意义。C组病死率(50.0%)显著低于A组(89.5%)和B组(91.1%)。"签署"后至死亡/转出ICU间的医疗费用中位数,B组显著低于A组和C组(105.0元/h vs 220.0元/h,160.7元/h,P=0.001)。签署后至转出/死亡中位数时间,B组显著少于C组(24.0 h vs 73.5 h,P=0.000)。结论 ICU住院期间"签署"的比例较低,主要为高龄和疾病严重度高的患者。患者亲属方为主要提出方。"签署"后死亡患者仅占同期死亡患者1/3。撤离治疗在一定程度上降低医疗费用。
