Many properties of natural fractures are uncertain,such as their spatial distribution,petrophysical properties,and fluid flow performance.Bayesian theorem provides a framework to quantify the uncertainty in geological...Many properties of natural fractures are uncertain,such as their spatial distribution,petrophysical properties,and fluid flow performance.Bayesian theorem provides a framework to quantify the uncertainty in geological modeling and flow simulation,and hence to support reservoir performance predictions.The application of Bayesian methods to fractured reservoirs has mostly been limited to synthetic cases.In field applications,however,one of the main problems is that the Bayesian prior is falsified,because it fails to predict past reservoir production data.In this paper,we show how a global sensitivity analysis(GSA)can be used to identify why the prior is falsified.We then employ an approximate Bayesian computation(ABC)method combined with a tree-based surrogate model to match the production history.We apply these two approaches to a complex fractured oil and gas reservoir where all uncertainties are jointly considered,including the petrophysical properties,rock physics properties,fluid properties,discrete fracture parameters,and dynamics of pressure and transmissibility.We successfully identify several reasons for the falsification.The results show that the methods we propose are effective in quantifying uncertainty in the modeling and flow simulation of a fractured reservoir.The uncertainties of key parameters,such as fracture aperture and fault conductivity,are reduced.展开更多
Falsified antibacterial agents continue to pose serious public health problems around the world. They are notably responsible for resistance emergence in the treatment of infectious diseases that can lead to death. Th...Falsified antibacterial agents continue to pose serious public health problems around the world. They are notably responsible for resistance emergence in the treatment of infectious diseases that can lead to death. The aim of this study was to summarize the literature on the methods developed and validated to detect poor quality antibacterial agents in order to assess the impact of these available methods in the fighting against Counterfeit/substandard medicines. Thus, studies published in the time from January 2000 to July 2017, were accessible via Google Scholar and Pubmed and allowed to analyze 41 papers. The majority (30) of developed and validated methods concerned LC methods, 9 regarded UV/V is spectrophotometry and two studies simultaneously developed both methods. Antibacterial agents belonging to beta-lactams group were the most concerned by the methods developed and validated (39%), followed by quinolones (18%) and macrolides (12%). Regarding active ingredients, amoxicillin (12%) was the most concerned by the development and validation methods. In spite of several available methods to detect substandard drugs, antibacterial agents for which methods were developed and validated were the most concerned by worldwide detected non-conformities. The fight against this scourge should not be only limited by their detection, but it also requires an effective involvement of different actors notably: health authorities, international organizations, pharmaceutical industries etc.展开更多
A recent literature on qualitative analysis has shown that its successful application in testing the consistency of the sign patterns of a proposed structure and an estimated reduced form was far less restricted than ...A recent literature on qualitative analysis has shown that its successful application in testing the consistency of the sign patterns of a proposed structure and an estimated reduced form was far less restricted than a previous literature had proposed. A frequent example used in this demonstration was the qualitative analysis of Klein’s Model I. For this, the proposed structural sign pattern was falsified by the sign pattern of the estimated reduced form. As a result, the subsequent application two-stage least squares would always find quantifications of the structure that could not possibly have resulted in the sign pattern of the estimated reduced form. We view this result as a diagnostic calling for further analysis. We show that the Klein model fails standard over identification tests. We make modest amendments to the model that resolves this problem but find that the resulting estimated reduced form still falsifies the structure, calling for further developmental effort. Our point is that qualitative falsification should be viewed as a diagnostic in developing a model, rather than a criterion for entirely dismissing the model.展开更多
In cognitive radio networks, spectrum sensing is one of the most important functions to identify available spectrum for improving the spectrum utilization. Due to the open characteristic of the wireless electromagneti...In cognitive radio networks, spectrum sensing is one of the most important functions to identify available spectrum for improving the spectrum utilization. Due to the open characteristic of the wireless electromagnetic environment, the wireless network is vulnerable to be attacked by malicious users(MUs), and spectrum sensing data falsification(SSDF) attack is one of the most harmful attacks on spectrum sensing performance. In this article,an algorithm based on the evidence theory and fuzzy entropy is proposed to resist SSDF attacks. In this algorithm, secondary users(SUs) obtain the corresponding degree of membership function and basic probability assignment function based on the local energy detection result. The new conflicting coefficient is calculated based on the evidence distance and classical conflicting coefficient, and the conflicting weight of the evidence is obtained.The fuzzy weight is calculated by the fuzzy entropy. The credibility weight is obtained by updating the credibility. On this basis, the probability assignment function of the evidence is corrected, and the final result is obtained by using the fusion formula. Simulation results show that the proposed algorithm has a higher detection probability and lower false alarm probability than other algorithms.It can effectively defend against SSDF attacks and improve the performance of spectrum sensing.展开更多
文摘Many properties of natural fractures are uncertain,such as their spatial distribution,petrophysical properties,and fluid flow performance.Bayesian theorem provides a framework to quantify the uncertainty in geological modeling and flow simulation,and hence to support reservoir performance predictions.The application of Bayesian methods to fractured reservoirs has mostly been limited to synthetic cases.In field applications,however,one of the main problems is that the Bayesian prior is falsified,because it fails to predict past reservoir production data.In this paper,we show how a global sensitivity analysis(GSA)can be used to identify why the prior is falsified.We then employ an approximate Bayesian computation(ABC)method combined with a tree-based surrogate model to match the production history.We apply these two approaches to a complex fractured oil and gas reservoir where all uncertainties are jointly considered,including the petrophysical properties,rock physics properties,fluid properties,discrete fracture parameters,and dynamics of pressure and transmissibility.We successfully identify several reasons for the falsification.The results show that the methods we propose are effective in quantifying uncertainty in the modeling and flow simulation of a fractured reservoir.The uncertainties of key parameters,such as fracture aperture and fault conductivity,are reduced.
文摘Falsified antibacterial agents continue to pose serious public health problems around the world. They are notably responsible for resistance emergence in the treatment of infectious diseases that can lead to death. The aim of this study was to summarize the literature on the methods developed and validated to detect poor quality antibacterial agents in order to assess the impact of these available methods in the fighting against Counterfeit/substandard medicines. Thus, studies published in the time from January 2000 to July 2017, were accessible via Google Scholar and Pubmed and allowed to analyze 41 papers. The majority (30) of developed and validated methods concerned LC methods, 9 regarded UV/V is spectrophotometry and two studies simultaneously developed both methods. Antibacterial agents belonging to beta-lactams group were the most concerned by the methods developed and validated (39%), followed by quinolones (18%) and macrolides (12%). Regarding active ingredients, amoxicillin (12%) was the most concerned by the development and validation methods. In spite of several available methods to detect substandard drugs, antibacterial agents for which methods were developed and validated were the most concerned by worldwide detected non-conformities. The fight against this scourge should not be only limited by their detection, but it also requires an effective involvement of different actors notably: health authorities, international organizations, pharmaceutical industries etc.
文摘A recent literature on qualitative analysis has shown that its successful application in testing the consistency of the sign patterns of a proposed structure and an estimated reduced form was far less restricted than a previous literature had proposed. A frequent example used in this demonstration was the qualitative analysis of Klein’s Model I. For this, the proposed structural sign pattern was falsified by the sign pattern of the estimated reduced form. As a result, the subsequent application two-stage least squares would always find quantifications of the structure that could not possibly have resulted in the sign pattern of the estimated reduced form. We view this result as a diagnostic calling for further analysis. We show that the Klein model fails standard over identification tests. We make modest amendments to the model that resolves this problem but find that the resulting estimated reduced form still falsifies the structure, calling for further developmental effort. Our point is that qualitative falsification should be viewed as a diagnostic in developing a model, rather than a criterion for entirely dismissing the model.
基金supported by the National Natural Science Foundation of China(61701134,51809056)the Fundamental Research Funds for the Central Universities of China(HEUCFM180802)+1 种基金the National Key Research and Development Program of China(2016YFF0102806)the Natural Science Foundation of Heilongjiang Province,China(F2017004)。
文摘In cognitive radio networks, spectrum sensing is one of the most important functions to identify available spectrum for improving the spectrum utilization. Due to the open characteristic of the wireless electromagnetic environment, the wireless network is vulnerable to be attacked by malicious users(MUs), and spectrum sensing data falsification(SSDF) attack is one of the most harmful attacks on spectrum sensing performance. In this article,an algorithm based on the evidence theory and fuzzy entropy is proposed to resist SSDF attacks. In this algorithm, secondary users(SUs) obtain the corresponding degree of membership function and basic probability assignment function based on the local energy detection result. The new conflicting coefficient is calculated based on the evidence distance and classical conflicting coefficient, and the conflicting weight of the evidence is obtained.The fuzzy weight is calculated by the fuzzy entropy. The credibility weight is obtained by updating the credibility. On this basis, the probability assignment function of the evidence is corrected, and the final result is obtained by using the fusion formula. Simulation results show that the proposed algorithm has a higher detection probability and lower false alarm probability than other algorithms.It can effectively defend against SSDF attacks and improve the performance of spectrum sensing.
