Decentralized finance(DeFi)is a general term for a series of financial products and services.It is based on blockchain technology and has attracted people’s attention because of its open,transparent,and intermediary ...Decentralized finance(DeFi)is a general term for a series of financial products and services.It is based on blockchain technology and has attracted people’s attention because of its open,transparent,and intermediary free.Among them,the DeFi ecosystem based on Ethereum-based blockchains attracts the most attention.However,the current decentralized financial system built on the Ethereum architecture has been exposed to many smart contract vulnerabilities during the last few years.Herein,we believe it is time to improve the understanding of the prevailing Ethereum-based DeFi ecosystem security issues.To that end,we investigate the Ethereum-based DeFi security issues:1)inherited from the real-world financial system,which can be solved by macro-control;2)induced by the problems of blockchain architecture,which require a better blockchain platform;3)caused by DeFi invented applications,which should be focused on during the project development.Based on that,we further discuss the current solutions and potential directions ofDeFi security.According to our research,we could provide a comprehensive vision to the research community for the improvement of Ethereum-basedDeFi ecosystem security.展开更多
BACKGROUND:Automated external defibrillators(AEDs)enable laypeople to provide early defi brillations to patients undergoing cardiac arrest,but scant information is available on the general public’s ability to use AED...BACKGROUND:Automated external defibrillators(AEDs)enable laypeople to provide early defi brillations to patients undergoing cardiac arrest,but scant information is available on the general public’s ability to use AEDs.This study assessed the ability of laypeople to operate AEDs,the effect of a 15-minute training,and whether skills differed by age.METHODS:From May 1 to December 31,2018,a prospective simulation study was conducted with 94 laypeople aged 18–65 years(32 aged 18–24 years,34 aged 25–54 years,and 28 aged 55–65 years)with no prior AED training.The participants’AED skills were assessed individually pretraining,post-training,and at a three-month follow-up using a simulated cardiac arrest scenario.The critical actions and time intervals were evaluated during the AED operating process.RESULTS:Only 14(14.9%)participants(eight aged 18–24 years,four aged 25–54 years,and two aged 55–65 years)successfully delivered defi brillations before training.AED operation errors were more likely to occur among the participants aged 55–65 years than among other age groups.After training,the proportion of successful defi brillations increased signifi cantly(18–24 years old:25.0%vs.71.9%,P<0.01;25–54 years old:11.8%vs.70.6%,P<0.01;55–65 years old:7.1%vs.67.9%,P<0.01).After three months,26.1%of the participants aged 55–65 years successfully delivered defi brillations,which was signifi cantly lower than that of participants aged 18–24 years(54.8%)and 25–54 years(64.3%)(P=0.02).There were no differences in time measures among three age groups in each test.CONCLUSIONS:The majority of untrained laypeople cannot effectively operate AEDs.More frequent training and refresher courses are crucial to improve AED skills.展开更多
Recent advancements in decentralized finance(DeFi)have resulted in a rapid increase in the use of Automated Market Makers(AMMs)for creating decentralized exchanges(DEXs).In this paper,we organize these developments by...Recent advancements in decentralized finance(DeFi)have resulted in a rapid increase in the use of Automated Market Makers(AMMs)for creating decentralized exchanges(DEXs).In this paper,we organize these developments by treating an AMM as a neoclassical black-box characterized by the conversion of inputs(tokens)to outputs(prices).The conversion is governed by the technology of the AMM summarized by an‘exchange function’.Various types of AMMs are examined,including:Constant Product Market Makers;Constant Mean Market Makers;Constant Sum Market Makers;Hybrid Function Market Makers;and,Dynamic Automated Market Makers.The paper also looks at the impact of introducing concentrated liquidity in an AMM.Overall,the framework presented here provides an intuitive geometric representation of how an AMM operates,and a clear delineation of the similarities and differences across the various types of AMMs.展开更多
Ports play a fundamental role in a sustainable integration of Africa in International trade. Both importers and exporters, shipping companies and government, however face high cost for sea transport and substantial in...Ports play a fundamental role in a sustainable integration of Africa in International trade. Both importers and exporters, shipping companies and government, however face high cost for sea transport and substantial inefficiency in port operations. This has resulted in congestion, higher dwell time, higher costs which affect the competitive ability in sub regional and global economy. This study investigates the main factors explaining poor container handling operations and limited competitive ability in Cameroonian Ports and aggregating this to the competitive position of Cameroonian ports in the West and Central African sub-regions (WCA). Using Analytic Hierarchy Process (A.H.P), the paper seeks to provide a basic understanding of container transportation and port’s terminal operations problems (constraints & ineffectiveness) in Cameroon.展开更多
Nowadays,tungsten oxides,as a typical transition metal oxide,are widely and intensively investigated owing to their excellent material properties and device properties.Controlling oxygen defi ciency in tungsten oxides...Nowadays,tungsten oxides,as a typical transition metal oxide,are widely and intensively investigated owing to their excellent material properties and device properties.Controlling oxygen defi ciency in tungsten oxides is typically the key to enhance their performances for a variety of critical technological applications.With a gradual increase of oxygen defi ciency,various non-stoichiometric tungsten oxides can be formed by re-adjustment of the atomic arrangement,which exhibits superior performances than their traditional stoichiometric counterparts.This review mainly focuses on the recent advances in oxygen-defi cient tungsten oxides from the point of atomic structures,including the forming mechanism of non-stoichiometric tungsten oxides and the superiority of these oxygen-defi cient tungsten oxides in energy-related devices.Finally,the challenge and perspective of oxygen-defi cient tungsten oxides are also discussed.展开更多
基金supported by the Key-Area Research and Development Program of Guangdong Province 2020B0101090003CCF-NSFOCUS Kunpeng Scientific Research Fund (CCFNSFOCUS 2021010)+4 种基金Innovation Fund Program of the Engineering Research Center for Integration and Application of Digital Learning Technology of Ministry of Education under Grant No.1221027National Natural Science Foundation of China (Grant Nos.61902083,62172115,61976064)Guangdong Higher Education Innovation Group 2020KCXTD007 and Guangzhou Higher Education Innovation Group (No.202032854)Guangzhou Fundamental Research Plan of“Municipal-School”Jointly Funded Projects (No.202102010445)Guangdong Province Science and Technology Planning Project (No.2020A1414010370).
文摘Decentralized finance(DeFi)is a general term for a series of financial products and services.It is based on blockchain technology and has attracted people’s attention because of its open,transparent,and intermediary free.Among them,the DeFi ecosystem based on Ethereum-based blockchains attracts the most attention.However,the current decentralized financial system built on the Ethereum architecture has been exposed to many smart contract vulnerabilities during the last few years.Herein,we believe it is time to improve the understanding of the prevailing Ethereum-based DeFi ecosystem security issues.To that end,we investigate the Ethereum-based DeFi security issues:1)inherited from the real-world financial system,which can be solved by macro-control;2)induced by the problems of blockchain architecture,which require a better blockchain platform;3)caused by DeFi invented applications,which should be focused on during the project development.Based on that,we further discuss the current solutions and potential directions ofDeFi security.According to our research,we could provide a comprehensive vision to the research community for the improvement of Ethereum-basedDeFi ecosystem security.
基金the National Natural Science Foundation of China(81703303)Shanghai Municipal Government Pujiang Research Development Program(17PJC070)+1 种基金HeartRescue Project China Programand Innovative Research Team of High-level Local Universities in Shanghai.
文摘BACKGROUND:Automated external defibrillators(AEDs)enable laypeople to provide early defi brillations to patients undergoing cardiac arrest,but scant information is available on the general public’s ability to use AEDs.This study assessed the ability of laypeople to operate AEDs,the effect of a 15-minute training,and whether skills differed by age.METHODS:From May 1 to December 31,2018,a prospective simulation study was conducted with 94 laypeople aged 18–65 years(32 aged 18–24 years,34 aged 25–54 years,and 28 aged 55–65 years)with no prior AED training.The participants’AED skills were assessed individually pretraining,post-training,and at a three-month follow-up using a simulated cardiac arrest scenario.The critical actions and time intervals were evaluated during the AED operating process.RESULTS:Only 14(14.9%)participants(eight aged 18–24 years,four aged 25–54 years,and two aged 55–65 years)successfully delivered defi brillations before training.AED operation errors were more likely to occur among the participants aged 55–65 years than among other age groups.After training,the proportion of successful defi brillations increased signifi cantly(18–24 years old:25.0%vs.71.9%,P<0.01;25–54 years old:11.8%vs.70.6%,P<0.01;55–65 years old:7.1%vs.67.9%,P<0.01).After three months,26.1%of the participants aged 55–65 years successfully delivered defi brillations,which was signifi cantly lower than that of participants aged 18–24 years(54.8%)and 25–54 years(64.3%)(P=0.02).There were no differences in time measures among three age groups in each test.CONCLUSIONS:The majority of untrained laypeople cannot effectively operate AEDs.More frequent training and refresher courses are crucial to improve AED skills.
文摘Recent advancements in decentralized finance(DeFi)have resulted in a rapid increase in the use of Automated Market Makers(AMMs)for creating decentralized exchanges(DEXs).In this paper,we organize these developments by treating an AMM as a neoclassical black-box characterized by the conversion of inputs(tokens)to outputs(prices).The conversion is governed by the technology of the AMM summarized by an‘exchange function’.Various types of AMMs are examined,including:Constant Product Market Makers;Constant Mean Market Makers;Constant Sum Market Makers;Hybrid Function Market Makers;and,Dynamic Automated Market Makers.The paper also looks at the impact of introducing concentrated liquidity in an AMM.Overall,the framework presented here provides an intuitive geometric representation of how an AMM operates,and a clear delineation of the similarities and differences across the various types of AMMs.
文摘Ports play a fundamental role in a sustainable integration of Africa in International trade. Both importers and exporters, shipping companies and government, however face high cost for sea transport and substantial inefficiency in port operations. This has resulted in congestion, higher dwell time, higher costs which affect the competitive ability in sub regional and global economy. This study investigates the main factors explaining poor container handling operations and limited competitive ability in Cameroonian Ports and aggregating this to the competitive position of Cameroonian ports in the West and Central African sub-regions (WCA). Using Analytic Hierarchy Process (A.H.P), the paper seeks to provide a basic understanding of container transportation and port’s terminal operations problems (constraints & ineffectiveness) in Cameroon.
基金supported by the National Natural Science Foundation of China(No.61904080)the Macao Young Scholars Program of China(No.AM2020005)Guangdong Basic and Applied Basic Research Foundation(No.2022A1515110994).
文摘Nowadays,tungsten oxides,as a typical transition metal oxide,are widely and intensively investigated owing to their excellent material properties and device properties.Controlling oxygen defi ciency in tungsten oxides is typically the key to enhance their performances for a variety of critical technological applications.With a gradual increase of oxygen defi ciency,various non-stoichiometric tungsten oxides can be formed by re-adjustment of the atomic arrangement,which exhibits superior performances than their traditional stoichiometric counterparts.This review mainly focuses on the recent advances in oxygen-defi cient tungsten oxides from the point of atomic structures,including the forming mechanism of non-stoichiometric tungsten oxides and the superiority of these oxygen-defi cient tungsten oxides in energy-related devices.Finally,the challenge and perspective of oxygen-defi cient tungsten oxides are also discussed.
