Essays on Textual Information in Corporate Disclosure

Textual information in various corporate disclosures, despite its unstructured feature, provides useful information beyond numeric information contained in financial statements such as earnings and cash flows. Using textual analysis methods, I examine how firms convey their textual information to users and how their communication impacts capital market and business decisions. This dissertation consists of two self-contained studies. Chapter 2 examines the real effects of a UK disclosure mandate that, with the aim of enhancing performance reporting, requires a subset of London Stock Exchange firms to describe their strategic aspects of value creation, such as business models and strategies, in their annual reports. Using an instrumented difference-in-differences design, I find that compliance with this initiative, evidenced by more disclosures of performance measures and commentaries relating to business operations and strategies, promotes intangible investments. My analysis of external and internal control systems suggests that enhanced performance reporting promotes investments because it attracts long-term investors and reduces CEO pay sensitivity to earnings performance. Chapter 3 examines management discussion of accruals and cash flows in earnings call. Using earnings call transcripts of S&P 500 firms, I extract cash flows and earnings measures within management presentation and calculate the weighted average of accruals attention. I find that relative emphasis on accruals varies with the ability of accruals addressing the mismatching problem of cash flows and the limitation of accruals. However, I also find that relative emphasis on accruals also reflects managerial incentives to downplay unfavorable information and that such abnormal emphasis on accruals predicts one year ahead poor performance. The return analysis shows that the negative signal of abnormal emphasis on accruals is not incorporated into stock prices immediately. The evidence suggests that abnormal emphasis on accruals may obscure true picture of periodic performance and influence investors’ decision-making. Combined together, the two studies contribute to the accounting literature by deepening our understanding of business communication reflected in financial texts and the incentives and behaviours of managers and investors

On Correcting Errors in Existing Mathematical Approaches for UAV Trajectory Design Considering No-Fly-Zones

Motivated by the fact that current mathematical methods for the trajectory design of an unmanned aerial vehicle (UAV) considering no-fly-zones (NFZs) cannot perfectly avoid NFZs throughout the entire continuous trajectory, this study introduces a new constraint that ensures the complete avoidance of NFZs. Moreover, we provide mathematical proof demonstrating that a UAV operating within the proposed constraints will never violate NFZs. Under the proposed constraint on NFZs, we aim to optimize the scheduling, transmit power, length of the time slot, and the trajectory of the UAV to maximize the minimum throughput among ground nodes without violating NFZs. To find the optimal UAV strategy from the non-convex optimization problem formulated here, we use various optimization techniques, in this case quadratic transform, successive convex approximation, and the block coordinate descent algorithm. Simulation results confirm that the proposed constraint prevents NFZs from being violated over the entire trajectory in any scenario. Furthermore, the proposed scheme shows significantly higher throughput than the baseline scheme using the traditional NFZ constraint by achieving a zero outage probability due to NFZ violations.Comment: 6 pages, 6 figure

Opportunistic behaviors of credit rating agencies and bond issuers

Using credit rating data from the three credit rating agencies (CRAs) in Korea, we examine whether bond issuers and CRAs engage in rating shopping and catering. First, we find that Korean bond issuers, who are required by law to receive two or more ratings, tend to fire or switch from CRAs that assign lower ratings than other CRAs. Second, when a bond issuer hires an additional CRA, the new CRA assigns a higher rating than incumbent CRAs. Lastly, we see that increased competition, which is measured by the number of CRAs hired by a given bond issuer, affects the likelihood of an upgrade occurring. Although CRAs often upgrade ratings when their rivals assign higher ratings, our findings show that higher competition further increases the likelihood that CRAs will upgrade ratings when there are rating disagreements. These results imply that bond issuers and CRAs engage in opportunistic behaviors that undermine the quality of credit ratings

Holographic entanglement entropy probe on spontaneous symmetry breaking with vector order

We study holographic entanglement entropy in 5-dimensional charged black brane geometry obtained from Einstein-SU(2)Yang-Mills theory defined in asymptotically AdS space. This gravity system undergoes second order phase transition near its critical point affected by a spatial component of the Yang-Mills fields, which is normalizable mode of the solution. This is known as phase transition between isotropic and anisotropic phases. We get analytic solutions of holographic entanglement entropies by utilizing the solution of bulk spacetime geometry given in arXiv:1109.4592, where we consider subsystems defined on AdS boundary of which shapes are wide and thin slabs and a cylinder. It turns out that the entanglement entropies near the critical point shows scaling behavior such that for both of the slabs and cylinder, $\Delta_\varepsilon S\sim\left(1-\frac{T}{T_c}\right)^\beta$ and the critical exponent $\beta=1$, where $\Delta_\varepsilon S\equiv S^{iso}-S^{aniso}$, and $S^{iso}$ denotes the entanglement entropy in isotropic phase whereas $S^{aniso}$ denotes that in anisotropic phase. We suggest a quantity $O_{12}\equiv S_1-S_2$ as a new order parameter near the critical point, where $S_1$ is entanglement entropy when the slab is perpendicular to the direction of the vector order whereas $S_2$ is that when the slab is parallel to the vector order. $O_{12}=0$ in isotropic phase but in anisotropic phase, the order parameter becomes non-zero showing the same scaling behavior. Finally, we show that even near the critical point, the first law of entanglement entropy is hold. Especially, we find that the entanglement temperature for the cylinder is $\mathcal T_{cy}=\frac{c_{ent}}{a}$, where $c_{ent}=0.163004\pm0.000001$ and $a$ is the radius of the cylinder.Comment: 1+29 pages, 4 figure

Optimization of the Trajectory, Transmit Power, and Power Splitting Ratio for Maximizing the Available Energy of a UAV-Aided SWIPT System

In this study, we investigate the maximization of the available energy for an unmanned aerial vehicle (UAV)-aided simultaneous wireless information and power transfer (SWIPT) system, in which the ground terminals (GTs) decode information and collect energy simultaneously from the downlink signal sent by the UAV based on a power splitting (PS) policy. To guarantee that each GT has a fair amount of available energy, our aim is to optimize the trajectory and transmit power of the UAV and the PS ratio of the GTs to maximize the minimum average available energy among all GTs while ensuring the average spectral efficiency requirement. To address the nonconvexity of the formulated optimization problem, we apply a successive convex optimization technique and propose an iterative algorithm to derive the optimal strategies of the UAV and GTs. Through performance evaluations, we show that the proposed scheme outperforms the existing baseline schemes in terms of the max–min available energy by adaptively controlling the optimization variables according to the situation

On the Effect of Traffic Self-Similarity on Network Performance

Recent measurements of network traffic have shown that self-similarity is an ubiquitous phenomenon present in both local area and wide area traffic traces. In previous work, we have shown a simple, robust application layer causal mechanism of traffic self-similarity, namely, the transfer of files in a network system where the file size distributions are heavy-tailed. In this paper, we study the effect of scale-invariant burstiness on network performance when the functionality of the transport layer and the nteraction of traffic sources sharing bounded network resources is incorporated. First, we show that transport layer mechanisms are important factors in translating the application layer causality into link traffic self-similarity. Network performance as captured by throughput, packet loss rate, and packet retransmission rate degrades gradually with increased heavy-tailedness while queueing delay, response time, and fairness deteriorate more drastically. The degree to which heavy-tailedness affects self-similarity is determined by how well congestion control is able to shape a source traffic into an on-average constant output stream while conserving information. Second, we show that increasing network resources such as link bandwidth and buffer capacity results in a superlinear improvement in performance. When large file transfers occur with nonnegligible probability, the incrementa

Optimization of the Trajectory, Transmit Power, and Power Splitting Ratio for Maximizing the Available Energy of a UAV-Aided SWIPT System

In this study, we investigate the maximization of the available energy for an unmanned aerial vehicle (UAV)-aided simultaneous wireless information and power transfer (SWIPT) system, in which the ground terminals (GTs) decode information and collect energy simultaneously from the downlink signal sent by the UAV based on a power splitting (PS) policy. To guarantee that each GT has a fair amount of available energy, our aim is to optimize the trajectory and transmit power of the UAV and the PS ratio of the GTs to maximize the minimum average available energy among all GTs while ensuring the average spectral efficiency requirement. To address the nonconvexity of the formulated optimization problem, we apply a successive convex optimization technique and propose an iterative algorithm to derive the optimal strategies of the UAV and GTs. Through performance evaluations, we show that the proposed scheme outperforms the existing baseline schemes in terms of the max–min available energy by adaptively controlling the optimization variables according to the situation

Hand Biometric Recognition Based on Fused Hand Geometry and Vascular Patterns

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On the Relationship Between File Sizes, Transport Protocols, and Self-Similar Network Traffic

Recent measurements of local-area and wide-area traffic have shown that network traffic exhibits variability at a wide range of scales. In this paper, we examine a mechanism that gives rise to self-similar network traffic and present some of its performance implications. The mechanism we study is the transfer of files or messages whose size is drawn from a heavy-tailed distribution. First, we show that in a "realistic" client/server network environment---i.e., one with bounded resources and coupling among traffic sources competing for resources---the degree to which file sizes are heavy-tailed can directly determine the degree of traffic self-similarity at the link level. We show that this causal relationship is robust with respect to changes in network resources (bottleneck bandwidth and buffer capacity), network topology, the influence of crosstraffic, and the distribution of interarrival times. Second, we show that properties of the transport layer play an important role in preser..

The Effects of Traffic Self-Similarity on TCP Performance

Recent measurements of network traffic have shown that self-similarity is a ubiquitous phenomenon present in both local area and wide area traffic traces. In this paper, we investigate the impact of scale-invariant burstiness on network performance including its effect on throughput, packet loss rate, response time, and buffer occupancy. This is done in the context of a client/server network model using transport and network layer simulations. First, we study the effect of self-similarity on performance when a UDP-based unreliable transport protocol is employed and network resources including bottleneck buffer capacity and bandwidth are varied. We find that as the degree of self-similarity is increased, all performance variables deteriorate superlinearly. The severity of the performance degradation is related to the greediness of the application agent, decreasing with the increased throttling of the average output rate. The degree of self-similarity is controlled by a novel mechanism b..