On Regularity of Abnormal Subriemannian Geodesics

We prove the smoothness of abnormal minimizers of subriemannian manifolds of step 3 with a nilpotent basis. We prove that rank 2 Carnot groups of step 4 admit no strictly abnormal minimizers. For any subriemannian manifolds of step less than 7, we show all abnormal minimizers have no corner type singularities, which partly generalize the main result of Leonardi-Monti.Comment: This paper has been withdrawn by the author due to a crucial computation error in (F_t^1)_sta

Analysis of RSA based on Quantitating Key Security Strength

AbstractRSA is an asymmetric crypto algorithm which is applied widely in the information security of E-Commerce and Internet-Bank. Its security has been withstanding tests since several decades ago. But the key security isn’t equal to that of algorithm, which is often neglected by most of users and scholars. As to most constructions, they lack definite recognition to the safety of the RSA key. As a result, even some strong crypto-algorithms used it still meets the security predicament. In this paper, start with the known plaintext attack to RSA public key crypto scheme, we pioneer the mechanism of quantitation of the RSA key security strength, the concept of key security coefficient, the evaluation model of security coefficient and the algorithm to extract security strength. Further more, an innovative method of generating secure keys is proposed. After some experimentations, the security performance of key and distribution of secure key-amount, and their key security coefficient are surveyed and analyzed in detail. The theoretic analysis and statistics demonstrate that our mechanism could elevate security of RSA in effect

Achieving SDG related sexual and reproductive health targets in China: what are appropriate indicators and how we interpret them?

Background: Sexual and Reproductive Health (SRH) targets have been included as part of the United Nations Sustainable Development Goals and thus indictors are important to monitor the progress towards these targets. SRH indicators are recommended for setting norms and measuring progress at global level. However, given the diverse political, socioeconomic and cultural contexts in different countries, and lack of global agreement on broad indicators, it is important to select appropriate indicators for specific countries. Based on internationally recommended indicators and data availability in China, this paper selected four indictors to reflect SRH in China and interpreted these indictors by analyzing the underlying factors. Methods: we employed secondary data analysis and key informant interview. The major secondary data were obtained from the China Health Statistical Year Book (2005-2017), China Statistical Year Book (2005-2017), and the sub-national estimates of the Global Burden Diseases Study 2016. We also interviewed 36 key informants at national and sub-national levels. Results: the four selected SRH indicators are contraceptive prevalence rate (CPR), adolescent birth rate, abortion rate, and availability of school sex education. CPR of married women has remained above 75% over the last three decades, indicating a high level of access to family planning (FP) services; however, unmarried but sexually active women have significant unmet needs for FP services. Although adolescent birth rates in China remain low, the abortion rate, abortion numbers, and the ratio of abortions to births increased from 2014-2016 while FP policy was relaxed in China. This suggests that abortion among unmarried women is a significant contributor to the overall figures. Qualitative analysis of the availability of school sex education reveals a situation of policy absence and the conservative attitude of key stakeholders. Conclusion: Since SRH challenges vary significantly between socio-economic, political and cultural contexts, indicators for measuring progress towards SRH targets of SDGs should be selected based on country context. The CPR and abortion rate are currently available and important indicators to monitor the most basic part of SRH in China, but require modification to ensure they can reflect universal access to quality reproductive healthcare by all reproductive age women, regardless their marriage status. Indicators on sex education need to be carefully developed to fit the context in China

Water invasion performance of complex fracture-vuggy gas reservoirs based on classification modeling

   The complexity of the pore structure, spatial development, fractures, and pore distribution of fractured-vuggy carbonate reservoirs influences the water invasion dynamics of gas reservoirs, which is crucial in the dynamic research of strongly heterogeneous reservoirs. In this study, the collocation relationship of pore-vuggy fractures is described by the quantitative characterization of their attribute parameters. The discrete fracture network model is used to match and construct the fractures in different modes. The distribution classification method is used to model three-dimensional geological reservoirs in terms of their geometric and attribute characteristics. Bottom-water and edge-water gas reservoirs are constructed separately using numerical simulation, and the dynamic characteristics of water invasion are described. The results show that the proposed method is suitable for the geological modeling of fractured-vuggy gas reservoirs with strong heterogeneity and complexity. The modeling accuracy is improved because the gas reservoir heterogeneity and water invasion’s dynamic characteristics can be described accurately. Six stages of water invasion are identified from the numerical simulation of water invasion. This method provides theoretical guidance for the study of heterogeneous gas reservoirs with water.Cited as: Han, X., Tan, X., Li, X., Pang, Y., Zhang, L. Water invasion performance of complex fracture-vuggy gas reservoirs based on classification modeling. Advances in Geo-Energy Research, 2021, 5(2): 222-232, doi: 10.46690/ager.2021.02.1

Passively testing routing protocols in wireless sensor networks

International audienceSmart systems are today increasingly developed with the number of wireless sensor devices that drastically increases. They are implemented within several contexts through our environment. Thus, sensed data transported in ubiquitous systems are important and the way to carry them must be efficient and reliable. For that purpose, several routing protocols have been proposed to wireless sensor networks (WSN). However, one stage that is often neglected before their deployment, is the conformance testing process, a crucial and challenging step. Active testing techniques commonly used in wired networks are not suitable to WSN and passive approaches are needed. While some works propose to specify the protocol with state models or to analyze them with simulators and emulators, we here propose a logic based approach for formally specifying some functional requirements of a novel WSN routing protocol. We provide an algorithm to evaluate these properties on collected protocol execution traces. Further, we demonstrate the efficiency and suitability of our approach by its application into common WSN functional properties as well as specific ones designed from our own routing protocol. We provide relevant testing verdicts through a real indoor testbed and the implementation of our protocol. We show that our approach may model and passively test common and particular test objectives illustrating its flexibility, genericity and practicability. As far as we know, this is the first work on formal passive testing of routing protocols in wireless sensor network

Investigation of material removal distributions and surface morphology evolution in non-contact ultrasonic abrasive machining (NUAM) of BK7 optical glasses

A non-contact ultrasonic abrasive machining approach provides a potential solution to overcome the challenges of machining efficiency in the high-precision polishing of optical components. Accurately modeling the material removal distribution (removal function (RF)) and surface morphology is very important in establishing this new computer-controlled deterministic polishing technique. However, it is a challenging task due to the absence of an in-depth understanding of the evolution mechanism of the material removal distribution and the knowledge of the evolution law of the microscopic surface morphology under the complex action of ultrasonic polishing while submerged in liquid. In this study, the formation of the RF and the surface morphology were modeled by investigating the cavitation density distribution and conducting experiments. The research results showed that the material removal caused by cavitation bubble explosions was uniformly distributed across the entire working surface and had a 0.25 mm edge influence range. The flow scour removal was mainly concentrated in the high-velocity flow zone around the machining area. The roughness of the machined surface increased linearly with an increase in the amplitude and gap. Increasing the particle concentration significantly improved the material removal rate, and the generated surface exhibited better removal uniformity and lower surface roughness