Alice Munro,a famous Canadian Canadian short-story writer.She gained the Nobel Prize for Literature in 2013.Munro’s works focus on women and adolescents.She also writes about the illness and love of the elderly.“The...Alice Munro,a famous Canadian Canadian short-story writer.She gained the Nobel Prize for Literature in 2013.Munro’s works focus on women and adolescents.She also writes about the illness and love of the elderly.“The Bear Came over the Mountain”is one of them.In this story,Munro adopts unreliable narration to depict love between Grant and Fiona.This paper aims to study the love writing and its unreliable narration in this story.Based on the text of love writing,this paper analyzes the specific strategies of unreliable narration.The author believes that the unreliable narration of the love text in the story can be divided into the unreliable narration of character type and information type.Through analysis of these two types of narration in the story,special meaning of unreliable narration to describe love can be found.Besides,Munro’s description also contains her own insight of love:the course of true love does not always run smooth.展开更多
The work deals with the development of analytical model of multichannel technical queuing system with unreliable servers and input memory where server failure flows and incoming request flows comply with Poissonian la...The work deals with the development of analytical model of multichannel technical queuing system with unreliable servers and input memory where server failure flows and incoming request flows comply with Poissonian laws, while the flows of failed facilities repairs and flows of incoming requests comply with exponential laws of probability distribution. Random process of system change-over is a Markovian process with continuous time and discrete states. Relations binding basic parameters and output characteristics of the system indicated are obtained as probabilities of system staying in the given moment in one of the possible states. The proposed model is the most generalized compared to some models known in literature which could be considered as special cases of the considered model.展开更多
Based on rhetorical research methods of the unreliability,the paper intends to explore the unreliable narrative strategies of the narrator in Grace Paley's The Loudest Voice from the perspectives of the Wayne Boot...Based on rhetorical research methods of the unreliability,the paper intends to explore the unreliable narrative strategies of the narrator in Grace Paley's The Loudest Voice from the perspectives of the Wayne Booth's criterion of the distance between the narrator and the implied author and James Phelan's extension of unreliability on the basis of classical rhetorical narratology,point⁃ing out that the unreliability serves as the narrative trap which is set up to reveal the inner theme of the work:"The loudest voice"-what the protagonist thought she certainly possessed was only her illusion instead of the truth,and Eastern European Jewish com⁃munity was de facto marginalized by the mainstream culture at that time.展开更多
The Tell-Tale Heart is a short story by Edgar Allan Poe. The story is first-person narrative of a narrator who murdered an old man with a clouded eye. This paper aims at identifying the speaker"I"as an unrel...The Tell-Tale Heart is a short story by Edgar Allan Poe. The story is first-person narrative of a narrator who murdered an old man with a clouded eye. This paper aims at identifying the speaker"I"as an unreliable narrator through analyzing the motivation, process and confession of the crime. It is found out that the narrator symbolizes man of evil, while, the old man's vulture eye symbolizes virtue. It's a story about the conflict between evil and virtue.展开更多
As an encyclopedic novel and the summit of Chinese classical literary creation,Hongloumeng has not received due critical attention to its unusual narrative style,let alone abundant unreliable narrative.From unreliable...As an encyclopedic novel and the summit of Chinese classical literary creation,Hongloumeng has not received due critical attention to its unusual narrative style,let alone abundant unreliable narrative.From unreliable narration of narrator and character,this research probes into effective translation strategies to achieve a balance between source text and target text,in light of a comparative analysis of typical illustrations taken from A Dream of Red Mansions and The Story of the Stone.展开更多
Cyber-physical systems(CPSs)have emerged as an essential area of research in the last decade,providing a new paradigm for the integration of computational and physical units in modern control systems.Remote state esti...Cyber-physical systems(CPSs)have emerged as an essential area of research in the last decade,providing a new paradigm for the integration of computational and physical units in modern control systems.Remote state estimation(RSE)is an indispensable functional module of CPSs.Recently,it has been demonstrated that malicious agents can manipulate data packets transmitted through unreliable channels of RSE,leading to severe estimation performance degradation.This paper aims to present an overview of recent advances in cyber-attacks and defensive countermeasures,with a specific focus on integrity attacks against RSE.Firstly,two representative frameworks for the synthesis of optimal deception attacks with various performance metrics and stealthiness constraints are discussed,which provide a deeper insight into the vulnerabilities of RSE.Secondly,a detailed review of typical attack detection and resilient estimation algorithms is included,illustrating the latest defensive measures safeguarding RSE from adversaries.Thirdly,some prevalent attacks impairing the confidentiality and data availability of RSE are examined from both attackers'and defenders'perspectives.Finally,several challenges and open problems are presented to inspire further exploration and future research in this field.展开更多
This paper deals with a production-inventory system in which there are amachine consisting of multiple unreliable units and a storage facility of fixed capacity. Theproduct produced is stored in the storage facility. ...This paper deals with a production-inventory system in which there are amachine consisting of multiple unreliable units and a storage facility of fixed capacity. Theproduct produced is stored in the storage facility. The demand process for product is acompound Poisson process. We assume that the demand-size distributions are arbitrary,and the unsatisfied demand is backlogged rather than lost. Our main results are to provean existence theorem on stationary distribution of the slack capacity and to derive anexpression of its stationary distribution function.展开更多
In this paper, we consider the completion time of a job processed on an unreliable machine. Assume that the lifetime and the repair time of the machine and the service time of the job have general distributions. We ob...In this paper, we consider the completion time of a job processed on an unreliable machine. Assume that the lifetime and the repair time of the machine and the service time of the job have general distributions. We obtain the Laplace-Stieltjes transforms and the expectations of the distributions of the completion time, the interruption time and the actual service time. Under some special cases, we derive sufficient and necessary (or sufficient) conditions such that the completion time is larger and smaller than the service time in the sense of the Laplace transform order (or the expectation),展开更多
As a popular distributed machine learning framework,wireless federated edge learning(FEEL)can keep original data local,while uploading model training updates to protect privacy and prevent data silos.However,since wir...As a popular distributed machine learning framework,wireless federated edge learning(FEEL)can keep original data local,while uploading model training updates to protect privacy and prevent data silos.However,since wireless channels are usually unreliable,there is no guarantee that the model updates uploaded by local devices are correct,thus greatly degrading the performance of the wireless FEEL.Conventional retransmission schemes designed for wireless systems generally aim to maximize the system throughput or minimize the packet error rate,which is not suitable for the FEEL system.A novel retransmission scheme is proposed for the FEEL system to make a tradeoff between model training accuracy and retransmission latency.In the proposed scheme,a retransmission device selection criterion is first designed based on the channel condition,the number of local data,and the importance of model updates.In addition,we design the air interface signaling under this retransmission scheme to facilitate the implementation of the proposed scheme in practical scenarios.Finally,the effectiveness of the proposed retransmission scheme is validated through simulation experiments.展开更多
Multicollinearity in factor analysis has negative effects, including unreliable factor structure, inconsistent loadings, inflated standard errors, reduced discriminant validity, and difficulties in interpreting factor...Multicollinearity in factor analysis has negative effects, including unreliable factor structure, inconsistent loadings, inflated standard errors, reduced discriminant validity, and difficulties in interpreting factors. It also leads to reduced stability, hindered factor replication, misinterpretation of factor importance, increased parameter estimation instability, reduced power to detect the true factor structure, compromised model fit indices, and biased factor loadings. Multicollinearity introduces uncertainty, complexity, and limited generalizability, hampering factor analysis. To address multicollinearity, researchers can examine the correlation matrix to identify variables with high correlation coefficients. The Variance Inflation Factor (VIF) measures the inflation of regression coefficients due to multicollinearity. Tolerance, the reciprocal of VIF, indicates the proportion of variance in a predictor variable not shared with others. Eigenvalues help assess multicollinearity, with values greater than 1 suggesting the retention of factors. Principal Component Analysis (PCA) reduces dimensionality and identifies highly correlated variables. Other diagnostic measures include the condition number and Cook’s distance. Researchers can center or standardize data, perform variable filtering, use PCA instead of factor analysis, employ factor scores, merge correlated variables, or apply clustering techniques for the solution of the multicollinearity problem. Further research is needed to explore different types of multicollinearity, assess method effectiveness, and investigate the relationship with other factor analysis issues.展开更多
Based on the narrative theory of Shlomith Rimmon-Kenan,the present paper will analyze the close connection between the choice and order of the focalizers and the themes of the novel to show that they are chosen and ar...Based on the narrative theory of Shlomith Rimmon-Kenan,the present paper will analyze the close connection between the choice and order of the focalizers and the themes of the novel to show that they are chosen and arranged deliberately and accorded to its themes.展开更多
The work is dedicated to the development of analytical model of probability estimation of reliability, productivity, quality and efficiency of functioning of the complex technical queuing system consisting of the arbi...The work is dedicated to the development of analytical model of probability estimation of reliability, productivity, quality and efficiency of functioning of the complex technical queuing system consisting of the arbitrary number of marked groups of the service devises (channels, facilities, servers) differing with reliable characteristics (parameters of refusals and restorations) of forming their composition (also of arbitrary number) marked, identical, unreliable and restorable serving channels in which for serving come in requirements with intensities depending on marking of channels. In the considered system it is supposed that the currents of refusals of serving devices and currents of coming requirements are subdued to Poisson, and the currents of restorations of refused devices and the currents of services of coming requirements—exponential laws of distribution of probabilities. A stochastic process of transfers of a system by that is Markovian process with continuous time and discrete states. Correlations linking the basic parameters and exit characteristics of the systems of the pointed out type are obtained in a view of probabilities of the system location in the given moment of time in one of the possible states.展开更多
Since its publication, Wuthering Heights has won great popularity home and abroad for the complexity and delicacy of the narration. However, the story is not true as the unreliability of its narrator is obvious as far...Since its publication, Wuthering Heights has won great popularity home and abroad for the complexity and delicacy of the narration. However, the story is not true as the unreliability of its narrator is obvious as far as it is judged by Rimmon-Kenan's theory of narrative unreliability.展开更多
In order to improve performance and robustness of clustering,it is proposed to generate and aggregate a number of primary clusters via clustering ensemble technique.Fuzzy clustering ensemble approaches attempt to impr...In order to improve performance and robustness of clustering,it is proposed to generate and aggregate a number of primary clusters via clustering ensemble technique.Fuzzy clustering ensemble approaches attempt to improve the performance of fuzzy clustering tasks.However,in these approaches,cluster(or clustering)reliability has not paid much attention to.Ignoring cluster(or clustering)reliability makes these approaches weak in dealing with low-quality base clustering methods.In this paper,we have utilized cluster unreliability estimation and local weighting strategy to propose a new fuzzy clustering ensemble method which has introduced Reliability Based weighted co-association matrix Fuzzy C-Means(RBFCM),Reliability Based Graph Partitioning(RBGP)and Reliability Based Hyper Clustering(RBHC)as three new fuzzy clustering consensus functions.Our fuzzy clustering ensemble approach works based on fuzzy cluster unreliability estimation.Cluster unreliability is estimated according to an entropic criterion using the cluster labels in the entire ensemble.To do so,the new metric is dened to estimate the fuzzy cluster unreliability;then,the reliability value of any cluster is determined using a Reliability Driven Cluster Indicator(RDCI).The time complexities of RBHC and RBGP are linearly proportional with thnumber of data objects.Performance and robustness of the proposed method are experimentally evaluated for some benchmark datasets.The experimental results demonstrate efciency and suitability of the proposed method.展开更多
Blockchain has recently emerged as a research trend,with potential applications in a broad range of industries and context.One particular successful Blockchain technology is smart contract,which is widely used in comm...Blockchain has recently emerged as a research trend,with potential applications in a broad range of industries and context.One particular successful Blockchain technology is smart contract,which is widely used in commercial settings(e.g.,high value financial transactions).This,however,has security implications due to the potential to financially benefit from a security incident(e.g.,identification and exploitation of a vulnerability in the smart contract or its implementation).Among,Ethereum is the most active and arresting.Hence,in this paper,we systematically review existing research efforts on Ethereum smart contract security,published between 2015 and 2019.Specifically,we focus on how smart contracts can be maliciously exploited and targeted,such as security issues of contract program model,vulnerabilities in the program and safety consideration introduced by program execution environment.We also identify potential research opportunities and future research agenda.展开更多
The modern in-memory database(IMDB)can support highly concurrent on-line transaction processing(OLTP)workloads and generate massive transactional logs per second.Quorum-based replication protocols such as Paxos or Raf...The modern in-memory database(IMDB)can support highly concurrent on-line transaction processing(OLTP)workloads and generate massive transactional logs per second.Quorum-based replication protocols such as Paxos or Raft have been widely used in the distributed databases to offer higher availability and fault-tolerance.However,it is non-trivial to replicate IMDB because high transaction rate has brought new challenges.First,the leader node in quorum replication should have adaptivity by considering various transaction arrival rates and the processing capability of follower nodes.Second,followers are required to replay logs to catch up the state of the leader in the highly concurrent setting to reduce visibility gap.Third,modern databases are often built with a cluster of commodity machines connected by low configuration networks,in which the network anomalies often happen.In this case,the performance would be significantly affected because the follower node falls into the long-duration exception handling process(e.g.,fetch lost logs from the leader).To this end,we build QuorumX,an efficient and stable quorum-based replication framework for IMDB under heavy OLTP workloads.QuorumX combines critical path based batching and pipeline batching to provide an adaptive log propagation scheme to obtain a stable and high performance at various settings.Further,we propose a safe and coordination-free log replay scheme to minimize the visibility gap between the leader and follower IMDBs.We further carefully design the process for the follower node in order to alleviate the influence of the unreliable network on the replication performance.Our evaluation results with the YCSB,TPC-C and a realistic microbenchmark demonstrate that QuorumX achieves the performance close to asynchronous primary-backup replication and could always provide a stable service with data consistency and a low-level visibility gap.展开更多
In this paper I examine the contribution of feelings to the reader's literary understanding,focussing on aspects of response that have been studied through the use of empirical methods.I first provide a review of ...In this paper I examine the contribution of feelings to the reader's literary understanding,focussing on aspects of response that have been studied through the use of empirical methods.I first provide a review of several components of feeling that have been found of importance in literary reading.I then focus on the role of feelings at several different levels.At the level of the stylistics of the text I consider studies of response to foregrounding and phonetic iconicity.At an intermediate level I look at a study of how feelings help to characterize episodes in narrative.Lastly I present a study at the largest scale(comprising a whole short story) of the role of feeling in elaborating an unreliable narrator,working largely through the comments of one reader.As a whole,the paper offers evidence for the range and variety of literary phenomena that draw on the capacities of feeling.展开更多
In 1985, Bollinger firstly introduced a repairable system model——a strict consecutive-k-out-of-n: F systems(abbreviated to Bollinger model) in terms ofa nonrepairable system 'consecutive-k-out-of-n: F systems...In 1985, Bollinger firstly introduced a repairable system model——a strict consecutive-k-out-of-n: F systems(abbreviated to Bollinger model) in terms ofa nonrepairable system 'consecutive-k-out-of-n: F systems'. However, some conditions in Bollinger modal were assumed too ideally to be used in engineering. For instance, some states (e.g. FGFFFFFFF, n=9, k=2) have already made the system dislocated, but by the assumptions in展开更多
文摘Alice Munro,a famous Canadian Canadian short-story writer.She gained the Nobel Prize for Literature in 2013.Munro’s works focus on women and adolescents.She also writes about the illness and love of the elderly.“The Bear Came over the Mountain”is one of them.In this story,Munro adopts unreliable narration to depict love between Grant and Fiona.This paper aims to study the love writing and its unreliable narration in this story.Based on the text of love writing,this paper analyzes the specific strategies of unreliable narration.The author believes that the unreliable narration of the love text in the story can be divided into the unreliable narration of character type and information type.Through analysis of these two types of narration in the story,special meaning of unreliable narration to describe love can be found.Besides,Munro’s description also contains her own insight of love:the course of true love does not always run smooth.
文摘The work deals with the development of analytical model of multichannel technical queuing system with unreliable servers and input memory where server failure flows and incoming request flows comply with Poissonian laws, while the flows of failed facilities repairs and flows of incoming requests comply with exponential laws of probability distribution. Random process of system change-over is a Markovian process with continuous time and discrete states. Relations binding basic parameters and output characteristics of the system indicated are obtained as probabilities of system staying in the given moment in one of the possible states. The proposed model is the most generalized compared to some models known in literature which could be considered as special cases of the considered model.
文摘Based on rhetorical research methods of the unreliability,the paper intends to explore the unreliable narrative strategies of the narrator in Grace Paley's The Loudest Voice from the perspectives of the Wayne Booth's criterion of the distance between the narrator and the implied author and James Phelan's extension of unreliability on the basis of classical rhetorical narratology,point⁃ing out that the unreliability serves as the narrative trap which is set up to reveal the inner theme of the work:"The loudest voice"-what the protagonist thought she certainly possessed was only her illusion instead of the truth,and Eastern European Jewish com⁃munity was de facto marginalized by the mainstream culture at that time.
文摘The Tell-Tale Heart is a short story by Edgar Allan Poe. The story is first-person narrative of a narrator who murdered an old man with a clouded eye. This paper aims at identifying the speaker"I"as an unreliable narrator through analyzing the motivation, process and confession of the crime. It is found out that the narrator symbolizes man of evil, while, the old man's vulture eye symbolizes virtue. It's a story about the conflict between evil and virtue.
文摘As an encyclopedic novel and the summit of Chinese classical literary creation,Hongloumeng has not received due critical attention to its unusual narrative style,let alone abundant unreliable narrative.From unreliable narration of narrator and character,this research probes into effective translation strategies to achieve a balance between source text and target text,in light of a comparative analysis of typical illustrations taken from A Dream of Red Mansions and The Story of the Stone.
基金the Natural Sciences and Engineering Research Council(NSERC)of Canada。
文摘Cyber-physical systems(CPSs)have emerged as an essential area of research in the last decade,providing a new paradigm for the integration of computational and physical units in modern control systems.Remote state estimation(RSE)is an indispensable functional module of CPSs.Recently,it has been demonstrated that malicious agents can manipulate data packets transmitted through unreliable channels of RSE,leading to severe estimation performance degradation.This paper aims to present an overview of recent advances in cyber-attacks and defensive countermeasures,with a specific focus on integrity attacks against RSE.Firstly,two representative frameworks for the synthesis of optimal deception attacks with various performance metrics and stealthiness constraints are discussed,which provide a deeper insight into the vulnerabilities of RSE.Secondly,a detailed review of typical attack detection and resilient estimation algorithms is included,illustrating the latest defensive measures safeguarding RSE from adversaries.Thirdly,some prevalent attacks impairing the confidentiality and data availability of RSE are examined from both attackers'and defenders'perspectives.Finally,several challenges and open problems are presented to inspire further exploration and future research in this field.
文摘This paper deals with a production-inventory system in which there are amachine consisting of multiple unreliable units and a storage facility of fixed capacity. Theproduct produced is stored in the storage facility. The demand process for product is acompound Poisson process. We assume that the demand-size distributions are arbitrary,and the unsatisfied demand is backlogged rather than lost. Our main results are to provean existence theorem on stationary distribution of the slack capacity and to derive anexpression of its stationary distribution function.
基金the National Key Project of China (No.970211017) and the NationalNatural Sciences Foundation of China (No.69674013).
文摘In this paper, we consider the completion time of a job processed on an unreliable machine. Assume that the lifetime and the repair time of the machine and the service time of the job have general distributions. We obtain the Laplace-Stieltjes transforms and the expectations of the distributions of the completion time, the interruption time and the actual service time. Under some special cases, we derive sufficient and necessary (or sufficient) conditions such that the completion time is larger and smaller than the service time in the sense of the Laplace transform order (or the expectation),
文摘As a popular distributed machine learning framework,wireless federated edge learning(FEEL)can keep original data local,while uploading model training updates to protect privacy and prevent data silos.However,since wireless channels are usually unreliable,there is no guarantee that the model updates uploaded by local devices are correct,thus greatly degrading the performance of the wireless FEEL.Conventional retransmission schemes designed for wireless systems generally aim to maximize the system throughput or minimize the packet error rate,which is not suitable for the FEEL system.A novel retransmission scheme is proposed for the FEEL system to make a tradeoff between model training accuracy and retransmission latency.In the proposed scheme,a retransmission device selection criterion is first designed based on the channel condition,the number of local data,and the importance of model updates.In addition,we design the air interface signaling under this retransmission scheme to facilitate the implementation of the proposed scheme in practical scenarios.Finally,the effectiveness of the proposed retransmission scheme is validated through simulation experiments.
文摘Multicollinearity in factor analysis has negative effects, including unreliable factor structure, inconsistent loadings, inflated standard errors, reduced discriminant validity, and difficulties in interpreting factors. It also leads to reduced stability, hindered factor replication, misinterpretation of factor importance, increased parameter estimation instability, reduced power to detect the true factor structure, compromised model fit indices, and biased factor loadings. Multicollinearity introduces uncertainty, complexity, and limited generalizability, hampering factor analysis. To address multicollinearity, researchers can examine the correlation matrix to identify variables with high correlation coefficients. The Variance Inflation Factor (VIF) measures the inflation of regression coefficients due to multicollinearity. Tolerance, the reciprocal of VIF, indicates the proportion of variance in a predictor variable not shared with others. Eigenvalues help assess multicollinearity, with values greater than 1 suggesting the retention of factors. Principal Component Analysis (PCA) reduces dimensionality and identifies highly correlated variables. Other diagnostic measures include the condition number and Cook’s distance. Researchers can center or standardize data, perform variable filtering, use PCA instead of factor analysis, employ factor scores, merge correlated variables, or apply clustering techniques for the solution of the multicollinearity problem. Further research is needed to explore different types of multicollinearity, assess method effectiveness, and investigate the relationship with other factor analysis issues.
文摘Based on the narrative theory of Shlomith Rimmon-Kenan,the present paper will analyze the close connection between the choice and order of the focalizers and the themes of the novel to show that they are chosen and arranged deliberately and accorded to its themes.
文摘The work is dedicated to the development of analytical model of probability estimation of reliability, productivity, quality and efficiency of functioning of the complex technical queuing system consisting of the arbitrary number of marked groups of the service devises (channels, facilities, servers) differing with reliable characteristics (parameters of refusals and restorations) of forming their composition (also of arbitrary number) marked, identical, unreliable and restorable serving channels in which for serving come in requirements with intensities depending on marking of channels. In the considered system it is supposed that the currents of refusals of serving devices and currents of coming requirements are subdued to Poisson, and the currents of restorations of refused devices and the currents of services of coming requirements—exponential laws of distribution of probabilities. A stochastic process of transfers of a system by that is Markovian process with continuous time and discrete states. Correlations linking the basic parameters and exit characteristics of the systems of the pointed out type are obtained in a view of probabilities of the system location in the given moment of time in one of the possible states.
文摘Since its publication, Wuthering Heights has won great popularity home and abroad for the complexity and delicacy of the narration. However, the story is not true as the unreliability of its narrator is obvious as far as it is judged by Rimmon-Kenan's theory of narrative unreliability.
文摘In order to improve performance and robustness of clustering,it is proposed to generate and aggregate a number of primary clusters via clustering ensemble technique.Fuzzy clustering ensemble approaches attempt to improve the performance of fuzzy clustering tasks.However,in these approaches,cluster(or clustering)reliability has not paid much attention to.Ignoring cluster(or clustering)reliability makes these approaches weak in dealing with low-quality base clustering methods.In this paper,we have utilized cluster unreliability estimation and local weighting strategy to propose a new fuzzy clustering ensemble method which has introduced Reliability Based weighted co-association matrix Fuzzy C-Means(RBFCM),Reliability Based Graph Partitioning(RBGP)and Reliability Based Hyper Clustering(RBHC)as three new fuzzy clustering consensus functions.Our fuzzy clustering ensemble approach works based on fuzzy cluster unreliability estimation.Cluster unreliability is estimated according to an entropic criterion using the cluster labels in the entire ensemble.To do so,the new metric is dened to estimate the fuzzy cluster unreliability;then,the reliability value of any cluster is determined using a Reliability Driven Cluster Indicator(RDCI).The time complexities of RBHC and RBGP are linearly proportional with thnumber of data objects.Performance and robustness of the proposed method are experimentally evaluated for some benchmark datasets.The experimental results demonstrate efciency and suitability of the proposed method.
基金This work was supported by the National Key Research and Development(R&D)Plan of China(2019YFB2101700)the Science and Technology Program of Guangzhou(201902020016)+2 种基金the Shenzhen Fundamental Research Program(JCYJ20170413114215614)the Guangdong Provincial Science and Technology Plan Project(2017B010124001)the Guangdong Provincial Key R&D Plan Project(2019B010139001).
文摘Blockchain has recently emerged as a research trend,with potential applications in a broad range of industries and context.One particular successful Blockchain technology is smart contract,which is widely used in commercial settings(e.g.,high value financial transactions).This,however,has security implications due to the potential to financially benefit from a security incident(e.g.,identification and exploitation of a vulnerability in the smart contract or its implementation).Among,Ethereum is the most active and arresting.Hence,in this paper,we systematically review existing research efforts on Ethereum smart contract security,published between 2015 and 2019.Specifically,we focus on how smart contracts can be maliciously exploited and targeted,such as security issues of contract program model,vulnerabilities in the program and safety consideration introduced by program execution environment.We also identify potential research opportunities and future research agenda.
基金This work was partially supported by National Key R&D Program of China(2018YFB1003404)NSFC(Grant Nos.61972149,61977026)ECNU Academic Innovation Promotion Program for Excellent Doctoral Students.
文摘The modern in-memory database(IMDB)can support highly concurrent on-line transaction processing(OLTP)workloads and generate massive transactional logs per second.Quorum-based replication protocols such as Paxos or Raft have been widely used in the distributed databases to offer higher availability and fault-tolerance.However,it is non-trivial to replicate IMDB because high transaction rate has brought new challenges.First,the leader node in quorum replication should have adaptivity by considering various transaction arrival rates and the processing capability of follower nodes.Second,followers are required to replay logs to catch up the state of the leader in the highly concurrent setting to reduce visibility gap.Third,modern databases are often built with a cluster of commodity machines connected by low configuration networks,in which the network anomalies often happen.In this case,the performance would be significantly affected because the follower node falls into the long-duration exception handling process(e.g.,fetch lost logs from the leader).To this end,we build QuorumX,an efficient and stable quorum-based replication framework for IMDB under heavy OLTP workloads.QuorumX combines critical path based batching and pipeline batching to provide an adaptive log propagation scheme to obtain a stable and high performance at various settings.Further,we propose a safe and coordination-free log replay scheme to minimize the visibility gap between the leader and follower IMDBs.We further carefully design the process for the follower node in order to alleviate the influence of the unreliable network on the replication performance.Our evaluation results with the YCSB,TPC-C and a realistic microbenchmark demonstrate that QuorumX achieves the performance close to asynchronous primary-backup replication and could always provide a stable service with data consistency and a low-level visibility gap.
文摘In this paper I examine the contribution of feelings to the reader's literary understanding,focussing on aspects of response that have been studied through the use of empirical methods.I first provide a review of several components of feeling that have been found of importance in literary reading.I then focus on the role of feelings at several different levels.At the level of the stylistics of the text I consider studies of response to foregrounding and phonetic iconicity.At an intermediate level I look at a study of how feelings help to characterize episodes in narrative.Lastly I present a study at the largest scale(comprising a whole short story) of the role of feeling in elaborating an unreliable narrator,working largely through the comments of one reader.As a whole,the paper offers evidence for the range and variety of literary phenomena that draw on the capacities of feeling.
文摘In 1985, Bollinger firstly introduced a repairable system model——a strict consecutive-k-out-of-n: F systems(abbreviated to Bollinger model) in terms ofa nonrepairable system 'consecutive-k-out-of-n: F systems'. However, some conditions in Bollinger modal were assumed too ideally to be used in engineering. For instance, some states (e.g. FGFFFFFFF, n=9, k=2) have already made the system dislocated, but by the assumptions in
