Essays on Disclosure and Individual Investors

Essay 1: Using data from StockTwits.com, the most popular investment-dedicated social media network in the US, I develop new and direct measures of investors\u27 aggregate attention to the stock market, and to individual stocks. I then examine the behavior of investors\u27 aggregate attention and firm-specific attention. First, I show that investors\u27 aggregate attention to the stock market is higher during earnings season than non-earnings season, but is not lower on Fridays compared to other weekdays. Second, I show that investors\u27 firm-specific attention is positively related to Earnings Response Coefficients (ERCs) and negatively related to Post Earnings Announcement Drift (PEAD), indicating that investor attention, as directly measured using social media data, enhances the processing of information and price discovery around earnings announcements. Finally, I find that when multiple firms announce their earnings on the same day, each earning announcement is not equally distracting: larger firms and firms with better information environment distract more attention from smaller firms. Essay 2: Using data from StockTwits.com, the most popular social media network dedicated to the discussion of stock investment, I textually analyze the content of 11 million tweets written by both sophisticated and unsophisticated investors. From this analysis, I develop measures of the information content of sophisticated and unsophisticated investors\u27 tweets and a daily measure of the degree of information asymmetry between these two classes of investors. Using sporadic management forecasts as a research setting, I examine the impact of public disclosures on the information asymmetry between sophisticated and unsophisticated investors. I find that: 1) information asymmetry between these two classes of investors increases in the short term (about a week) after public disclosures-specifically, sporadic management forecasts; 2) information asymmetry decreases in the longer term (roughly a week) after public disclosures; and 3) more precise public disclosures result in a smaller short-term increase (and a larger long-term decrease) in information asymmetry

Correlation between flood frequency and geomorphologic complexity of river network -A case study of Hangzhou China

yesUrban flooding is a combined product of the climate and watershed geomorphology. River system is one of the vital components of watershed geomorphology. The geomorphic characteristics of rivers have important effect on the formation of flooding. However, there have been few attempts so far to investigate the relationship between flooding frequency, the probability of flooding, and the geomorphological complexity of river system. Such relationship is essential in order to predict likely responses of flooding frequency to the large-scale changes in the complexity of the river networks induced by accelerating urbanization around river. In this study we investigate the correlation between geomorphological characteristics of river system and the probability of flooding. Hangzhou city in China, which has suffered severe flooding, is chosen as a case study to evaluate this correlation and to investigate the impact of changes of drainage networks morphology on the local flooding. The fractal dimension, which is used to quantitatively assess geomorphological complexity of river network, is calculated by using box-counting method based on fractal geometry for eight sub river networks in Hangzhou. A model based on the correlation of flooding frequency and fractal dimension is established. The model is applied to investigate the effect of the rapid urbanization induced changes of river geomorphology on the local flood frequency in two typical regions in Hangzhou. The results show that the flood frequency/events increases with the decrease of fractal dimension of the river network, indicating that the geomorphologic complexity of river network has an important effect on flooding. This research has great referential value for future flood quantitative investigation and provides new method for urban flood control and river system protection.Key Scientific and Technical Project of Water Conservancy of Zhejiang Province (Grant No: RB1401

Auditor-Client Disagreements, Auditor Resignations, And Audit Fees Charged By Successor Auditors

This paper investigates the effects of auditor-client disagreement disclosure on auditor resignations and audit fee charged by successor auditors. Using a matched sample of auditor changes over the period 2003-2016, we find that auditor resignations are more often accompanied by auditor-client disagreements. We also find that Big 4 auditors are more likely to resign from their engagements when they disagree with their clients. Further, we document that successor auditors charge higher audit fees for firms that have disagreements with their predecessor auditors. Relative to non-Big 4 auditors, Big 4 successor auditors charge even higher audit fee for disagreement firms

Does the Dirac Cone Exist in Silicene on Metal Substrates?

Absence of the Dirac cone due to a strong band hybridization is revealed to be a common feature for epitaxial silicene on metal substrates according to our first-principles calculations for silicene on Ir, Cu, Mg, Au, Pt, Al, and Ag substrates. The destroyed Dirac cone of silicene, however, can be effectively restored with linear or parabolic dispersion by intercalating alkali metal atoms between silicene and the metal substrates, offering an opportunity to study the intriguing properties of silicene without further transfer of silicene from the metal substrates

Analytical solution of shallow water equations for ideal dam-break flood along a wet bed slope

YesThe existing analytical solutions of dam-break flow do not consider simultaneously the effects of wet downstream bottom and bed slope on the dam-break wave propagation. In this study, a new analytical solution for the shallow-water equations (SWE) is developed to remove this limitation to simulate the wave caused by an instantaneous dam-break. The approach adopts the method of characteristics and has been applied to simulate the dam-break flows with different downstream water depths and slopes. The analytical solutions have been compared with predictions by the lattice Boltzmann method and the agreement is good. Although the proposed analytical solution treats an idealized case, it is nonetheless suitable for assessing the robustness and accuracy of numerical models based on the SWE without the frictional slope.The National Key Research and Development Program of China (Grant No: 2018YFC1505000), National Natural Science Foundation of China (Grant Nos: 51879179; 51579166) and Sichuan Science and Technology Program (No. 2019JDTD0007); Open Fund from the State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University (SKHL1809).

Study of flow resistance in open channels

River hydrodynamicsBed roughness and flow resistanc