Cooperative spectrum sensing in cog- nitive radio is investigated to improve the det- ection performance of Primary User （PU）. Meanwhile, cluster-based hierarchical coop- eration is introduced for reducing the overh...Cooperative spectrum sensing in cog- nitive radio is investigated to improve the det- ection performance of Primary User （PU）. Meanwhile, cluster-based hierarchical coop- eration is introduced for reducing the overhead as well as maintaining a certain level of sens- ing performance. However, in existing hierar- chically cooperative spectrum sensing algo- rithms, the robustness problem of the system is seldom considered. In this paper, we pro- pose a reputation-based hierarchically coop- erative spectrum sensing scheme in Cognitive Radio Networks （CRNs）. Before spectrum sensing, clusters are grouped based on the location correlation coefficients of Secondary Users （SUs）. In the proposed scheme, there are two levels of cooperation, the first one is performed within a cluster and the second one is carried out among clusters. With the reputa- tion mechanism and modified MAJORITY rule in the second level cooperation, the pro- posed scheme can not only relieve the influ- ence of the shadowing, but also eliminate the impact of the PU emulation attack on a rela- tively large scale. Simulation results show that, in the scenarios with deep-shadowing or mul- tiple attacked SUs, our proposed scheme ach- ieves a better tradeoff between the system robustness and the energy saving compared with those conventionally cooperative sensing schemes.展开更多
The influence of the material stress state induced by internal and external forces on the erosion rate of pipelines has rarely been investigated in the literature.In order to fill this gap,using a tensile tester machi...The influence of the material stress state induced by internal and external forces on the erosion rate of pipelines has rarely been investigated in the literature.In order to fill this gap,using a tensile tester machine,a two–phase gas–solid particles jet erosion test was carried out considering a 316L stainless steel under different tensile stresses and different erosion angles.The results show that:1)In the elastic range,with the increase of stress,the erosion rate manifests a rising trend;2)In the metal plastic range,the increase of stress leads to a decrease of the erosion rate;3)The erosion rate at a small erosion angle is more sensitive to the increment of stress.The present research demonstrates that the combined effect of erosion and material internal stress can contribute to determine the effective resistance of the vulnerable parts of piping systems(such as elbows or similar components).展开更多
Cooperatively bimetallic organic catalysis,coupling actions of two metal centers in a catalytic organic transformation via co-activation of a single molecule or synergistic activation of two molecules,has witnessed ra...Cooperatively bimetallic organic catalysis,coupling actions of two metal centers in a catalytic organic transformation via co-activation of a single molecule or synergistic activation of two molecules,has witnessed rapid development in the last decades.展开更多
Background Great advances have been made in the diagnosis, molecular pathogenesis and treatment of acute lymphoblastic leukemia （ALL） in the past decade. Due to the lack of large population-based studies, the recent...Background Great advances have been made in the diagnosis, molecular pathogenesis and treatment of acute lymphoblastic leukemia （ALL） in the past decade. Due to the lack of large population-based studies, the recent trends in the incidence and geographic variations of ALL in Shanghai, China have not been well documented. To better understand the incidence and epidemiological features of ALL in Shanghai, we conducted a retrospective survey based on the database from the Shanghai Center for Disease Control and Prevention （CDC） and the medical records in all large-scale hospitals in Shanghai, especially those 30 major hospitals with hematology department. Methods According to the data from Shanghai CDC, 544 patients, with a median age of 32 years （ranging 1.2-89 years）, were diagnosed as de novo ALL from January 1, 2002 to December 31, 2006, and they were followed up until December 31,2007. Results The average annual incidence of ALL in Shanghai was 0.81/100 000. The incidence in men （0.86/100 000） was slightly higher than that in women （0.75/100 000）. The age-stratified incidence showed that the incidence was 2.31/100 000 in patients 〈17 years old, 0.54/100 000 in those 18-34 years old, 0.46/100 000 in those 35-59 years old, and 0.94/100 000 in those 〉60 years old. Moreover, there were substantial geographic variations in the incidence of ALL, with the incidence in Chongming county, an island in the east of Shanghai city being 0.60/100 000, much lower than those of other districts. Both French-American-British （FAB） and World Health Organization （WHO） classification systems were applied in the present study. Eighty-eight patients were diagnosed as L1 （26.2%）, 193 L2 （57.4%）, and 55 L3 （16.4%）. For 302 patients with immunophenotypic results, 242 were identified as B cell origin （80.1%）, 59 as T cell origin （19.5%）, and 1 as biphenotype （0.4%）. The leukemia cells in 61 patients co-expressed one or two myeloid antigen （20.2%）. For 269 patients with cytogenetic results, the incidences of t（9;22） in patients aged 〈10, 11-17, 18-44, 45-59 and 〉60 years old were 4.2%, 11.4%, 19.2%, 23.1% and 5.3%, respectively. Conclusion Compared with the previous data, the incidence of ALL is increased in Shanghai, and has a geographic distribution characteristic.展开更多
基金ACKNOWLEDGEMENT This work was partially supported by the Na- tional Natural Science Foundation of China under Grant No. 61071127 and the Science and Technology Department of Zhejiang Pro- vince under Grants No. 2012C01036-1, No. 2011R10035.
文摘Cooperative spectrum sensing in cog- nitive radio is investigated to improve the det- ection performance of Primary User （PU）. Meanwhile, cluster-based hierarchical coop- eration is introduced for reducing the overhead as well as maintaining a certain level of sens- ing performance. However, in existing hierar- chically cooperative spectrum sensing algo- rithms, the robustness problem of the system is seldom considered. In this paper, we pro- pose a reputation-based hierarchically coop- erative spectrum sensing scheme in Cognitive Radio Networks （CRNs）. Before spectrum sensing, clusters are grouped based on the location correlation coefficients of Secondary Users （SUs）. In the proposed scheme, there are two levels of cooperation, the first one is performed within a cluster and the second one is carried out among clusters. With the reputa- tion mechanism and modified MAJORITY rule in the second level cooperation, the pro- posed scheme can not only relieve the influ- ence of the shadowing, but also eliminate the impact of the PU emulation attack on a rela- tively large scale. Simulation results show that, in the scenarios with deep-shadowing or mul- tiple attacked SUs, our proposed scheme ach- ieves a better tradeoff between the system robustness and the energy saving compared with those conventionally cooperative sensing schemes.
基金This paper is financially supported from the National Natural Science Foundation of China(Grant No.51874340)the Natural Science Foundation of Shandong Province(Grant No.ZR2018MEE004)Project of China Petroleum Engineering Construction Co.,Ltd.,China(Grant No.CPECC2020KJ07).
文摘The influence of the material stress state induced by internal and external forces on the erosion rate of pipelines has rarely been investigated in the literature.In order to fill this gap,using a tensile tester machine,a two–phase gas–solid particles jet erosion test was carried out considering a 316L stainless steel under different tensile stresses and different erosion angles.The results show that:1)In the elastic range,with the increase of stress,the erosion rate manifests a rising trend;2)In the metal plastic range,the increase of stress leads to a decrease of the erosion rate;3)The erosion rate at a small erosion angle is more sensitive to the increment of stress.The present research demonstrates that the combined effect of erosion and material internal stress can contribute to determine the effective resistance of the vulnerable parts of piping systems(such as elbows or similar components).
基金the financial supports from the National Natural Science Foundation of China(Grant Nos.21901197,21907080)he Natural Science Basic Research Plan in Shaanxi Province of China(No.2019JM093)the start-up funds from Xi'an Jiaotong University.
文摘Cooperatively bimetallic organic catalysis,coupling actions of two metal centers in a catalytic organic transformation via co-activation of a single molecule or synergistic activation of two molecules,has witnessed rapid development in the last decades.
文摘Background Great advances have been made in the diagnosis, molecular pathogenesis and treatment of acute lymphoblastic leukemia （ALL） in the past decade. Due to the lack of large population-based studies, the recent trends in the incidence and geographic variations of ALL in Shanghai, China have not been well documented. To better understand the incidence and epidemiological features of ALL in Shanghai, we conducted a retrospective survey based on the database from the Shanghai Center for Disease Control and Prevention （CDC） and the medical records in all large-scale hospitals in Shanghai, especially those 30 major hospitals with hematology department. Methods According to the data from Shanghai CDC, 544 patients, with a median age of 32 years （ranging 1.2-89 years）, were diagnosed as de novo ALL from January 1, 2002 to December 31, 2006, and they were followed up until December 31,2007. Results The average annual incidence of ALL in Shanghai was 0.81/100 000. The incidence in men （0.86/100 000） was slightly higher than that in women （0.75/100 000）. The age-stratified incidence showed that the incidence was 2.31/100 000 in patients 〈17 years old, 0.54/100 000 in those 18-34 years old, 0.46/100 000 in those 35-59 years old, and 0.94/100 000 in those 〉60 years old. Moreover, there were substantial geographic variations in the incidence of ALL, with the incidence in Chongming county, an island in the east of Shanghai city being 0.60/100 000, much lower than those of other districts. Both French-American-British （FAB） and World Health Organization （WHO） classification systems were applied in the present study. Eighty-eight patients were diagnosed as L1 （26.2%）, 193 L2 （57.4%）, and 55 L3 （16.4%）. For 302 patients with immunophenotypic results, 242 were identified as B cell origin （80.1%）, 59 as T cell origin （19.5%）, and 1 as biphenotype （0.4%）. The leukemia cells in 61 patients co-expressed one or two myeloid antigen （20.2%）. For 269 patients with cytogenetic results, the incidences of t（9;22） in patients aged 〈10, 11-17, 18-44, 45-59 and 〉60 years old were 4.2%, 11.4%, 19.2%, 23.1% and 5.3%, respectively. Conclusion Compared with the previous data, the incidence of ALL is increased in Shanghai, and has a geographic distribution characteristic.
