Weak Orlicz-Hardy Martingale Spaces

In this paper, several weak Orlicz-Hardy martingale spaces associated with concave functions are introduced, and some weak atomic decomposition theorems for them are established. With the help of weak atomic decompositions, a sufficient condition for a sublinear operator defined on the weak Orlicz-Hardy martingale spaces to be bounded is given. Further, we investigate the duality of weak Orlicz-Hardy martingale spaces and obtain a new John-Nirenberg type inequality when the stochastic basis is regular. These results can be regarded as weak versions of the Orlicz-Hardy martingale spaces due to Miyamoto, Nakai and Sadasue.Comment: 26 page

Two-phase flow dynamics in the gas diffusion layer of proton exchange membrane fuel cells: Volume of fluid modeling and comparison with experiment

This paper proposes a three-dimensional (3D) volume of fluid (VOF) study to investigate two-phase flow in the gas diffusion layer (GDL) of proton exchange membrane (PEM) fuel cells and liquid water distribution. A stochastic model was adopted to reconstruct the 3D microstructures of Toray carbon papers and incorporate the experimentally-determined varying porosity. The VOF predictions were compared with the water profiles obtained by the X-ray tomographic microscopy (XTM) and the Leverett correlation. It was found local water profiles are similar in the sample’s sub-regions under the pressure difference p = 1000 Pa between the two GDL surfaces, but may vary significantly under p = 6000 Pa. The water-air interfaces inside the GDL structure were presented to show water distribution and breakthrough

Investigating the in-/through-plane effective diffusivities of dry and partially-saturated gas diffusion layers

In this study, the effective oxygen diffusivity in the dry or partially-saturated gas diffusion layer (GDL) is numerically investigated by an oxygen diffusion model in GDLs reconstructed by a stochastic method. The predicted effective diffusivity in dry GDLs is compared with various diffusivity models from literatures. Reasonable agreements with other models were obtained. The effect of the PTFE loading in the dry Toray carbon paper is also investigated and compared with recent experimental data. It is found that the effective diffusivity becomes lower under higher PTFE loading due to the decreased pore volume, as expected. The relative effective oxygen diffusivity in partially-saturated GDLs is calculated using the two-phase volume of fluid (VOF) model and an oxygen diffusion model. The effects of different local water profiles and porosity distribution on the effective oxygen diffusivity in both the through-plane (TP) and in-plane (IP) directions are investigated and compared with a lattice Boltzmann model and experimental data. The present results are in good agreement with other studies. It is found that local water profile has significant impacts on the effective diffusivity in partially-saturated GDLs and the diffusivity in the TP direction is more sensitive to the water distribution than the IP direction

Preparation and electrochemical performance of hollow activated carbon fiber self-supported electrode for supercapacitor

Hollow activated carbon fiber (HACF) with high specific surface area and high charge storage capability was prepared by pre-oxidation, carbonization and KOH-activation from polyacrylonitrile (PAN). HACF was used as self-supported working electrode directly without any binder and conductive agent. The effect of the activation time on specific surface area of HACF was studied intensively. The results show that the specific surface area of HACF increased with the increase of activation time from 0.5 h to 1.5 h, and then decreased with further increase of activation time. Highest specific surface area of 1873 m(2)g(-1) and micropore volume of 0.61 cm(3)g(-1) were obtained in HACF activated for 1.5 h. Electrochemical properties of HACF can be improved with increase of activation time, but excessive activation results in the decrease of specific surface area and increase of internal resistance of HACF. The self-supported electrode of HACF possesses a large specific capacitance of 323 F g(-1) at 0.05 A g(-1) and 216 F g(-1) at 1 A g(-1). Therefore, HACF can be a promising self-supported electrode for high performance supercapacitors

Three Research Essays on Human Behaviors in Social Media

Social Media (SM) has grown to be one of the most popular Internet technologies for individual users and has fostered a global community. For instance, recent statistics reveal that monthly active users of Facebook are almost 1.5 billion by Mar 2015. At the same time, 20% of internet users in the US are expected to have Twitter accounts. This figure has grown from 15.2% in 2012, and is expected to rise to 24.2% by 2018 (Twitter 2015). People like spending their time on SM to track the latest news, seek knowledge, update personal status, and connect with friends. It is possible that being exposed to others’ positive information on SM could generate darker emotions, such as envy. Extant literature suggests that envy significantly influences human behaviors and life satisfaction (Krasnova et al. 2013). This dissertation, consisting of three essays, studies the effects of SM on human behaviors. Chapter 2 investigates how others’ positive information arouses envy and influences user behaviors from different angles. Chapter 3 focuses on how espoused national cultures reshape online benign envy and impact SM usage. Chapter 4 discusses the relationship between social media and envy with textual analysis techniques. Chapter 5 provides a summary and overall conclusion to this work. Chapter 2- Envy and How it can Influence SM Use Users tend to disclose the positive side of their lives on SM. Such information can be perceived in an extremely positive light in the eyes of their connections, which could leads to envy. In the current study, we develop a theoretical framework that elaborates the mechanism through which online envy is generated and consequently influences SM usage. We specify that online users experience two types of envy: malicious and benign envy, which have distinct impacts on IS use. Specifically, malicious envy plays a mitigating role and benign envy serves as an enhancer of SM use. Our findings provide valuable implications for both academic researchers and IS practitioners. Chapter 3 – Benign Envy, Social Media, and Culture Although envy universally exits in human society, its influence on human behaviors varies by cultural contexts. As shown in chapter 2, benign envy is a more salient factor in the social media context. In the current essay, we focus on investigating how different espoused national cultural values affect this relationship between online benign envy and consequent behaviors. We also developed a benign envy and IT usage model, which integrates four espoused national cultural values. We conceptualized several main constructs and then theoretically justified the relationships between them. As expected, if people experience benign envy when using SM, they are more likely to continue their use. Moreover, different espoused national culture values work as independent and moderating variables along with the envy procedures. People who hold different levels of culture behave distinctly. The study found that people who espouse a greater level of collectivism were be more likely to compare with other peers in order to evaluate their self-social status; people who espouse higher levels of uncertainty avoidance were more likely to experience benign envy; and the relationship between perceived enhancement and use intention was stronger for individuals with higher levels of espoused masculinity. However, espoused power distance values were not significantly moderating the relationship between perceived enjoyment and intended behavior in the current context (general SM). This study provided some theoretical and practical implications. Chapter 4 – Tweet, Favorite, Status, and Envy Many social media studies have demonstrated that aggregating social information could provide valuable insight into sociological, economical, healthcare, and other critical fields. Among these studies, Twitter has been one of the most popular social platforms that researchers value. It has a greater potential for academics to observe and explore critical social behaviors, such as envy, which could lead to avoidance of using certain IT platforms, emotional depression, and even worse, suicide. With text mining techniques, massive numbers of tweets can be collected, classified, and analyzed. The envy literature has largely theorized on the motivations of envy. However, in the IS context, envy related research is very limited, and the empirical tests are confounded by limited data. In order to address these gaps, we collected envy related tweets from Twitter and classified them into the two types (benign and malicious) of envy relying on text mining techniques with sentiment analysis (positive to negative). Based on the data set, we further analyzed the patterns of online envy. Additionally, by using logistic regression, the impacts of certain social media usage behaviors were tested on differentiating online envy. Our work included both qualitative observation and quantitative analysis, along with the evaluation of regression output