When Does Relay Transmission Give a More Secure Connection in Wireless Ad Hoc Networks?

Relay transmission can enhance coverage and throughput, while it can be vulnerable to eavesdropping attacks due to the additional transmission of the source message at the relay. Thus, whether or not one should use relay transmission for secure communication is an interesting and important problem. In this paper, we consider the transmission of a confidential message from a source to a destination in a decentralized wireless network in the presence of randomly distributed eavesdroppers. The source-destination pair can be potentially assisted by randomly distributed relays. For an arbitrary relay, we derive exact expressions of secure connection probability for both colluding and non-colluding eavesdroppers. We further obtain lower bound expressions on the secure connection probability, which are accurate when the eavesdropper density is small. By utilizing these lower bound expressions, we propose a relay selection strategy to improve the secure connection probability. By analytically comparing the secure connection probability for direct transmission and relay transmission, we address the important problem of whether or not to relay and discuss the condition for relay transmission in terms of the relay density and source-destination distance. These analytical results are accurate in the small eavesdropper density regime.Comment: Accepted for publication in IEEE Transactions On Information Forensics and Securit

Los factores que influyen en la satisfacción en el trabajo y su relación con la intención de baja laboral: tomando a los empleados que inician su carrera como ejemplo.

Job satisfaction of early-career employees has a significant effect on employee work behavior and work attitude. This study investigated the influence factors of job satisfaction and its relationship with turnover intention. Early-career employees were selected as the research subject. Questionnaires were distributed and the stratified random sampling method was used to analyze the 418 samples collected. The dimensions of job satisfaction were analyzed by exploratory factor analysis and confirmatory factor analysis, and a structural equation model was constructed to discuss the relationship between job satisfaction and turnover intention. First, for early-career employees, job satisfaction as a higher order factor consists of 6 first-order factors; personal growth’s influence on job satisfaction is the greatest, with a path coefficient reaching .918. Next come salary and welfare, work itself, interpersonal relationships and leader behavior. Additionally, job competency has a minimal effect on job satisfaction; its path coefficient is only .214. Second, job satisfaction has a significantly negative effect on turnover intention, indicating that the job satisfaction structure of early-career employees has its unique characteristics because they focus more on personal growth and development space. Through improving job satisfaction, turnover behavior of early-career employees can be effectively controlled.La satisfacción en el trabajo en empleados que inician su carrera tiene un efecto significativo en la conducta laboral y en la actitud ante el trabajo en los empleados. Este estudio investiga los factores que influyen en la satisfacción en el trabajo y su relación con el bajas laborales. Se seleccionaron empleados en su fase inicial como sujetos de investigación. Se distribuyeron cuestionarios según un método de muestreo aleatorizado estratificado para analizar 418 muestras recogidas. Las dimensiones de la satisfacción en el trabajo fueron analizadas mediantes análisis factorial exploratorio y análisis factorial confirmatorio, y con ello se construyó un modelo de ecuaciones estructurales para discutir la relación entre satisfacción en el trabajo y los motivos de bajas laborales. Primero, para empleados iniciales, la satisfacción en el trabajo como factor de orden superior consistía en seis factores de primer orden; la influencia del desarrollo personal en la satisfacción en el trabajo fue la mayor, con un coeficiente path de .918. El siguiente fue el salario y el bienestar, el trabajo por sí mismo, las relaciones interpersonales y la conducta de liderazgo. Adicionalmente, la competencia laboral tuvo un efecto mínimo sobre la satisfacción en el trabajo; su coeficiente path es sólo .214. En segundo lugar, la satisfacción en el trabajo tuvo un efecto significativamente negativo sobre los motivos de baja laboral, indicando que la estructura de satisfacción en el trabajo de los empleados iniciales tiene características propias, puesto que ellos se centran más en el desarrollo personales y el espacio de desarrollo. Mejorando la satisfacción laboral, la conducta de baja laboral de los empleados iniciales puede ser controlada efectivamente

Preparation and characterization of organic silver based conductive inks for flexible electronics

Flexible electronics is of considerable interest for many applications due to the distinctive features of low-cost, flexibility and light weight capabilities. However, in translating the technology from research to practical applications there are several challenges. One of them is to formulate suitable ink materials. Organic silver ink, also known as particle free ink, has attracted great interest due to their flexibility in preparation, excellent stability and a relatively low sintering temperature (150~200°C) in comparison with nano silver ink. Although various kinds of organic silver inks have been created, they are still not ideal due to the low throughput, the complex synthetic process, and high temperatures for conductivity near bulk silver (generally>150°C). Therefore, it has been necessary to develop new types of low-temperature sintering organic silver conductive inks using simple procedures for practical applications on flexible substrates such as polymer films. The aim of this thesis was to develop novel, low-temperature sintering (≤150°C) and highly conductive (near bulk silver) organic silver based inks using simple procedures for flexible electronics and study their properties and application. Three strategies were adopted to develop such inks. The first was to synthesize an organic silver/rGO hybrid ink. The second was to develop novel organic silver precursors with desirable electronic and thermal properties to formulate such inks. The third was to optimize the properties of the formulated inks. Three types of highly conductive organic silver-based inks, silver/rGO ink, silver citrate ink and silver oxalate ink, were developed by using a facile, high yielding and environmentally friendly procedure respectively. The chemical reaction mechanisms in the ink formation and the film formation process were studied in each case. The effects of sintering parameters such as temperature and time on the microstructure and electrical properties of the films have been investigated in detail. In the case of Ag/rGO ink, a remarkable improvement in conductivity was observed, which was attributed to the role of rGO platelets. In the case of silver citrate ink, defects such as the coffee ring effect were eliminated by using solvents containing active components. An optimal silver oxalate ink was formulated finally for a simple circuit application, producing silver films with good quality and favorable conductivity at a sintering temperature of 150°CEngineering and Physical Sciences Research Council (EPSRC

H19 potentiates let-7 family expression through reducing PTBP1 binding to their precursors in cholestasis

Cholestasis induces the hepatic long non-coding RNA H19, which promotes the progression of cholestatic liver fibrosis. However, microRNAs that are dysregulated by H19 during cholestasis remain elusive. Using miRNA-sequencing analysis followed by qPCR validation, we identified marked upregulation of eight members of the let-7 family in cholestatic livers by bile duct ligation (BDL) and H19 overexpression. In particular, the expression of let-7a-1/7d/7f-1 was highly induced in H19-BDL livers but decreased in H19KO-BDL livers. Interestingly, H19 decreased the nuclear let-7 precursors as well as the primary transcripts of let-7a-1/7d/7f-1 levels in BDL mouse livers. Bioinformatics, RNA pull-down, and RNA immunoprecipitation (RIP) assays revealed that the crucial RNA-binding protein polypyrimidine tract-binding protein 1 (PTBP1), an H19 interaction partner, interacted with the precursors of let-7a-1 and let-7d and suppressed their maturation. Both PTBP1 and let-7 expression was differentially regulated by different bile acid species in hepatocyte and cholangiocyte cells. Further, H19 negatively regulated PTBP1's mRNA and protein levels but did not affect its subcellular distribution in BDL mouse livers. Moreover, we found that H19 restrained but PTBP1 facilitated the bioavailability of let-7 miRNAs to their targets. Taken together, this study revealed for the first time that H19 promoted let-7 expression by decreasing PTBP1's expression level and its binding to the let-7 precursors in cholestasis

Coupled analytical solutions for circular tunnels considering rock creep effects and time-dependent anchoring forces in prestressed bolts

Acknowledgement This work is supported by the National Science Foundation of China (51979281; 52034010), and the Natural Science Foundation of Shandong Province China (ZR2018MEE050).Peer reviewedPostprintPostprin

Analysing airport efficiency in East China using a three-stage data envelopment analysis

This paper evaluates the Technical Efficiencies (TEs) of a group of airports in East China by applying a three-stage Data Envelopment Analysis (DEA) method. The merit of this method allows us to consider the impact of the environmental factors on measuring airport efficiencies. Three variables, i.e. per capita Gross Domestic Product (GDP), the proportion of the tertiary industry, and the number of tourists, are used to represent the environmental factors. The results show that the environmental factors have airport-specific impacts on the value of the efficiencies. Additionally, airport TE are dominated by both Pure Technical Efficiency (PTE) and Scale Efficiency (SE). Based on empirical results, airport specific strategies can be provided to enhance airport efficiency, such as taking the effects of environmental variables and the statistical noise into consideration when analysing the airport efficiency, improving airport efficiencies according to their own conditions and improving the PTE or SE according to their categorizations