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An Anti-Eavesdrop Transmission Scheduling Scheme Based on Maximizing Secrecy Outage Probability in Ad Hoc Networks

China Communications 2016年第1期13卷 176-184页

作者： wang yajun LIAO Tongqing wang Chuanan School of Mathematical and Information Engineering Anhui Science and Technology University Ministry of Educational Key Laboratory of Intelligent Computing and Signal Processing Anhui University

In this paper,we consider a wireless ad hoc network consisting of multiple source nodes transmitting to their respective destinations,where an eavesdropper attempts to intercept their *** propose an optimal transmission scheduling scheme to defend against the eavesdropper,where a source node having the highest secrecy rate is scheduled to access the wireless medium for transmitting to its destination in an opportunistic *** be specific,the secrecy rate between a pair of the source and destination in the presence of an eavesdropper varies temporally due to the wireless fading *** proposed optimal transmission scheduling scheme opportunistically selects a source node with the highest secrecy rate to transmit its data for the sake of maximizing the security of the ad hoc network against eavesdropping *** comparison purposes,we also consider the conventional round-robin scheduling as a benchmark,where multiple source nodes take turns in accessing their shared wireless medium for transmitting to their respective *** derive closed-form secrecy outage probability expressions of both the round-robin scheduling and the proposed optimal scheduling schemes over Rayleigh fading *** results show that the proposed transmission scheduling scheme outperforms the conventional round-robin method in terms of its secrecy outage ***,upon increasing the number of source-destination pairs,the secrecy outage probability of the round-robin scheme keeps unchanged,whereas the secrecy outage performance of the proposed transmission scheduling significantly improves,showing the security benefits of exploiting transmission scheduling for protecting wireless ad hoc networks against eavesdropping.

关键词： transmission scheduling eavesdropping secrecy outage probability secrecy rate rayleigh fading

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Rating Prediction Model Based on Causal Inference Debiasing Method in Recommendation

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Chinese Journal of Electronics 2023年第4期32卷 932-940页

作者： NAN Jiangang wang yajun wang Chengcheng School of Electronic Information Engineering Liaoning University of Technology

The rating prediction task plays an important role in the recommendation model. Most existing methods predict ratings by extracting user and items characteristics from historical review data. However, the recommended strategies in historical review data are often based on partial observational data, which having the problems of unbalanced distribution, lack of robustness,and inability to obtain unbiased prediction results. Therefore, a novel rating prediction model based on causal inference debiasing(CID) method is proposed. The model can mitigate the negative effects of context bias and improve the robustness by studying the causal relationship between review information and user ratings. The proposed CID rating prediction model is plug-and-play and is not limited to one baseline prediction method. The proposed method is tested on four open datasets. The results show that the proposed method is feasible. Compared with the most advanced models, the prediction accuracy of the CID rating prediction model has been further improved. The experimental results show the debiasing effectiveness of the CID rating prediction model.

关键词： Training Analytical models Predictive models Robustness Behavioral sciences Data mining Task analysis

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Microstructures and fatigue properties of electron beam welds with beam oscillation for heavy section TC4-DT alloy

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Chinese Journal of Aeronautics 2014年第4期27卷 1015-1021页

作者： Fu Pengfei Mao Zhiyong Zuo Congjin wang yajun wang Chunming College of Materials Science and Engineering Huazhong University of Science and Technology Science and Technology on Power Beam Processes Laboratory Beijing Aeronautical Manufacturing Technology Research Institute Institute of Mechanical Engineering and Automation Beihang University

With the development of the manufacturing technology, electron beam welding（EBW） is capable of producing titanium alloy large parts in aero fields. To increase the applications and improve the properties, EBW with beam oscillation was investigated on TC4-DT alloy with50 mm thickness. We detected the welding samples by X-ray NDT, observed the microstructures of the welds, and tested the fatigue properties of the joints. The results showed that EBW with beam oscillation improved the weld morphology as well as welding quality, and the microstructure homogeneity of the welds and HAZ along the weld penetration were also improved. The fatigue properties of the joints with beam oscillation were more excellent than those of conventional EBW, even equal to those of the base metal under high stresses. The influences of the processing and the microstructure on the properties with beam oscillation were discussed.

关键词： Beam oscillation Electron beam welding(EBW) Fatigue Microstructure Titanium alloy

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Experimental studies of explosion energy output with different igniter mass

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Defence Technology（防务技术） 2019年第5期15卷 808-814页

作者： Heyang Xu Weibing Li Wenbin Li yajun wang Nanjing University of Science and Technology

For study the energy output law of cylindrical charge with shell induced by different input energies,four different black powder masses were selected to ignite the main *** degree of the shell was qualitatively analyzed by the area of holes on the witness plate and the recovered fragments *** theoretical analysis,established the functional relationship between the average mass of fragments and the relative energy output of warhead,obtained how the relative energy output of charge changed with different initial energy *** results showed that the change of input energy could lead to obvious variation in fragment characteristics,and could also control the output of *** the igniter mass increases from 1.55 g to 5.00 g,the relative energy output of the charge increases by 26.28%.Excessive initial input energy will destroy the shell confine in advance,resulting in a decrease in the relative energy output of charge.

关键词： analysis, energy mass

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Groundwater hydrochemistry and isotope geochemistry in the Turpan Basin, northwestern China

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Journal of Arid Land 2014年第4期6卷 378-388页

作者： Lu CHEN GuangCai wang FuSheng HU yajun wang Liang LIU School of Water Resources and Environment China University of Geosciences The First Brigade of Hydrogeology Xinjiang Bureau of Geology and Minerals

The Turpan Basin is located in the arid zone of northwestern China and is a typical closed inland basin surrounded by high mountains. It is one of the most arid regions in the world and, as a result, the groundwater in this area is very important for both domestic and agricultural uses. In the present study, the relationships of major elements（K＋, Na＋, Ca2＋, Mg2＋, HCO3-, SO42- and Cl-） and environmental isotopes（δ18O, δ2H and T） in groundwater were analyzed to investigate the evolution of the regional hydrochemistry within the Turpan Basin. The hydrochemistry results demonstrate that groundwater with high total dissolved solids（TDS） concentration is dominated by sodium chloride（Na-Cl） and sodium sulfate（Na-SO4） type water, whereas that with low TDS concentration（typically from near mountain areas） is dominated by calcium bicarbonate（Ca-HCO3） type water. The evolution of groundwater hydrochemistry within the Turpan Basin is a result of calcium carbonate precipitation, evaporation concentration, cation exchange and dissolution of evaporites（i.e. halite, mirabilite and gypsum）. Furthermore, evaporite dissolution associated with irrigation practice plays a key role in the groundwater salinization, especially in the central part of the basin. Environmental isotopes reveal that the groundwater is recharged by precipitation in the mountain areas and fast vertical infiltration of irrigation return flow. In the southern sub-basin the shallow groundwater and the deep groundwater is separated at a depth of about 40 m, with substantial differences in terms of hydrochemical and isotopic characteristics. The results are useful for decision making related to sustainable water resource utilization in the Turpan Basin and other regions in northwestern China.

关键词： hydrochemistry environmental isotopes groundwater salinization evaporite dissolution Turpan Basin

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Research on modeling of heat source for electron beam welding fusion-solidification zone

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Chinese Journal of Aeronautics 2013年第1期26卷 217-223页

作者： wang yajun Fu Pengfei Guan Yongjun Lu Zhijun Wei Yintao School of Mechanical Engineering and Automation Beihang University Science and Technology on Power Beam Processes Laboratory Beijing Aeronautical Manufacturing Technology Research Institute State Key Laboratory of Nonlinear Mechanics Institute of Mechanics Chinese Academy of Sciences State Key Laboratory of Automotive Safety and Energy Department of Automotive Engineering Tsinghua University

In this paper, the common heat source model of point and linear heat source in the numerical simulation of electron beam welding （EBW） were summarized and introduced. The combined point-linear heat source model was brought forward and to simulate the welding temperature fields of EBW and predicting the weld shape. The model parameters were put forward and regulated in the combined model, which included the ratio of point heat source to linear heat source Qpr and the distribution of linear heat source Lr. Based on the combined model, the welding temperature fields of EBW were investigated. The results show that the predicted weld shapes are conformable to those of the actual, the temperature fields are reasonable and correct by simulating with combined point-linear heat source model and the typical weld shapes are gained.

关键词： Electron beam welding (EBW) Fusion-solidification zone Heat source model Temperature fields Weld shape

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The effects of humus moisture content on underground fires in a Larix gmelinii plantation

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Journal of Forestry Research 2022年第3期33卷 865-873页

作者： Xiyue Han Hening Xu Tiantian wang Sainan Yin Bo Gao yajun wang Yanlong Shan Beihua University Science and Technology Innovation Center of Wildland Fire Prevention and Control Forestry College of Beihua University3999 Binjiang East RoadJilin City132013Jilin ProvincePeople’s Republic of China

Underground fires are a smoldering combustion with a slow spread rate, low temperatures and no flame. They can last from days to several months, and can even become overwintering fires. They are difficult to find, leading to considerable damage to the forests. The moisture content of combustible fuels is an important factor in the occurrence and persistence of underground forest fires. The Daxing’an Mountains are a hot spot for underground fires in China. This paper looks at the influence of different moisture contents on underground fire characteristics using simulation combustion experiments in the laboratory. The study showed that peak temperature and spread rate fluctuation of humus at different moisture levels increased with humus depth. Peak temperature and spread rate fluctuation of humus at different depths decreased with increased moisture;moisture content and depth of humus had a significant effect on peak temperature and spread rate fluctuation;peak temperature at different depths decreased with increased moisture;the spread rate in upper layers increased with moisture content, while the spread rate in the lower layers decreased with increased moisture content.

关键词： Daxing’an Mountains Underground fire Moisture content Peak temperature Spread rate

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The impact of land use change on soil organic carbon and labile organic carbon stocks in the Longzhong region of Loess Plateau

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Journal of Arid Land 2012年第3期4卷 241-250页

作者： LiHua ZHANG ZhongKui XIE RuiFeng ZHAO yajun wang Gaolan Experiment Station for Ecology and Agriculture Research Cold and Arid Regions Environmental and EngineeringResearch Institute Chinese Academy of Sciences Lanzhou 730000 China College of Geography and Environment Science Northwest Normal University Lanzhou 730070 China

Land use change （LUC） is widely recognized as one of the most important driving forces of global carbon cycles. The soil organic carbon （SOC） and labile organic carbon （LOC） stores were investigated at arable land （AL）, artificial grassland （AG）, artificial woodland （AW）, abandoned arable land （AAL） and desert steppe （DS） in the Longzhong region of the Loess Plateau in Northwest China. The results showed that conversions from DS to AL, AL to AG and AL to AAL led to an increase in SOC content, while the conversion from DS to AW led to a decline. The differences in SOC content were significant between DS and AW at the 20-40 cm depth and between AL and AG at the 0-10 cm depth. The SOC stock in DS at the 0-100 cm depth was 39.4 t/hm2, increased by 28.48% after cultivation and decreased by 19.12% after conversion to AW. The SOC stocks increased by 2.11% from AL to AG and 5.10% from AL to AAL. The LOC stocks changed by a larger magnitude than the SOC stocks, which suggests that it is a more sensitive index of carbon dynamics under a short-term LUC. The LOC stocks increased at 0-20 cm and 0-100 cm depths from DS to AW, which is opposite to that observed for SOC. The proportion of LOC to SOC ranged from 0.14 to 0.20 at the 0-20 cm depth for all the five land use types, indicating low SOC dynamics. The allocation proportion of LOC increased for four types of LUC conversion, and the change in magnitude was largest for DS to AW （40.91%）. The afforestation, abandonment and forage planting on arable land led to sequestration of SOC; the carbon was lost initially after afforestation. However, the carbon sink effect after abandonment may not be sustainable in the study area.

关键词： carbon sequestration labile organic carbon land use cultivation abandonment Loess Plateau

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Porous hollow carbon tube derived from kapok fibres as efficient metal-free oxygen reduction catalysts

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Science China(Technological Sciences) 2019年第10期62卷 1710-1718页

作者： TANG JiaHuan wang yajun ZHAO WenQi YE Wen Yuan ZHOU ShunGui Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation College of Resources and EnvironmentFujian Agriculture and Forestry University

Pyrogenic biomass carbon has been deemed a promising alternative to Pt/C for the oxygen reduction reaction(ORR) owing to its low cost, excellent activity, and eco-friendly properties. Herein, a porous carbon tube material derived from kapok fibres was prepared by combining activation with pyrolysis. Electrochemical measurements demonstrated that the kapok fibre-derived material prepared at 900°C had excellent ORR performance with a half-wave potential –0.14 V(vs. Ag/Ag Cl) close to that of commercial Pt/C(–0.13 V vs. Ag/Ag Cl) in 0.1 mol L–1 KOH. The prepared material also displayed remarkable methanol tolerance and durability. Furthermore, the maximum power density output of the microbial fuel cell using the prepared material was(801±40) mW m–2, comparable to that of the Pt/C cathode((778±31) mW m–2). The present work provides a facile way of using economical and renewable biomass to develop a porous structure and high-activity cathode ORR catalyst for fuel cell applications.

关键词： kapok fibre porous carbon tube oxygen reduction reaction microbial fuel cell

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Progress in systematics and biogeography of Orchidaceae

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Plant Diversity 2024年第4期46卷 425-434页

作者： yajun wang Hanchen wang Chao Ye Zhiping wang Chongbo Ma Dongliang Lin Xiaohua Jin State Key Laboratory of Plant Diversity and Specialty Crops Institute of Botanythe Chinese Academy of SciencesBeijing 100093China University of Chinese Academy of Sciences Beijing 100093China China National Botanical Garden Beijing 100093China

Orchidaceae are one of the largest families of angiosperms in terms of species *** the last decade,numerous studies have delved into reconstructing the phylogenetic framework of Orchidaceae,leveraging data from plastid,mitochondrial and nuclear *** studies have provided new insights into the systematics,diversification and biogeography of Orchidaceae,establishing a robust foundation for future ***,pronounced controversies persist regarding the precise placement of certain lineages within these phylogenetic *** address these discrepancies and deepen our understanding of the phylogenetic structure of Orchidaceae,we provide a comprehensive overview and analysis of phylogenetic studies focusing on contentious groups within Orchidaceae since 2015,delving into discussions on the underlying reasons for observed topological *** also provide a novel phylogenetic framework at the subtribal ***,we examine the tempo and mode underlying orchid species diversity from the perspective of historical biogeography,highlighting factors contributing to extensive ***,we delineate avenues for future research aimed at enhancing our understanding of Orchidaceae phylogeny and diversity.

关键词： Diversification Orchid phylogenetics Phylogenetic conflicts Biogeography Taxonomy

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