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Modeling Bid and Ask Price Dynamics with an Extended Hawkes Process and Its Empirical Applications for High-Frequency Stock Market Data
No full text<jats:title>Abstract</jats:title>
<jats:p>This study proposes a versatile model for the dynamics of the best bid and ask prices using an extended Hawkes process. The model incorporates the zero intensities of the spread-narrowing processes at the minimum bid???ask spread, spread-dependent intensities, possible negative excitement, and nonnegative intensities. We apply the model to high-frequency best bid and ask price data from U.S. stock markets. The empirical findings demonstrate a spread-narrowing tendency, excitations of the intensities caused by previous events, the impact of flash crashes, characteristic trends in fast trading over time, and the different features of market participants in the various exchanges.</jats:p>
Rate-Splitting Multiple Access for Downlink MIMO: A Generalized Power Iteration Approach
No full textRate-splitting multiple access (RSMA) is a general multiple access scheme for downlink multi-antenna systems embracing both classical spatial division multiple access and more recent non-orthogonal multiple access. Finding a linear precoding strategy that maximizes the sum spectral efficiency of RSMA is a challenging yet significant problem. In this paper, we put forth a novel precoder design framework that jointly finds the linear precoders for the common and private messages for RSMA. Our approach is first to approximate the non-smooth minimum function part in the sum spectral efficiency of RSMA using a LogSumExp technique. Then, we reformulate the sum spectral efficiency maximization problem as a form of the log-sum of Rayleigh quotients to convert it into a tractable form. By interpreting the first-order optimality condition of the reformulated problem as an eigenvector-dependent nonlinear eigenvalue problem, we reveal that the leading eigenvector of the derived optimality condition is a local optimal solution. To find the leading eigenvector, we propose an algorithm inspired by a power iteration. Simulation results show that the proposed RSMA transmission strategy provides significant improvement in the sum spectral efficiency compared to the state-of-the-art RSMA transmission methods
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No full textDepartment of Mechanical EngineeringAdvancements in electronics, software, and sensors have led to various developments in unmanned aerial vehicles (UAVs), ranging from sophisticated models to simpler ones with lightweight avionics. Researchers have explored the use of multiple UAVs in a distributed multi-agent system (MAS) to overcome the limitations of a single UAV, thereby extending their capabilities. Utilizing multiple UAVs in a distributed MAS provides advantages such as improved efficiency, robustness, flexibility, and reliability. To fully benefit from a distributed MAS, cooperation and coordination among agents through local interactions are crucial. Flocking, a coordination strategy where agents exchange information with neighboring agents, enables a small team of operators to control multiple UAVs as a unified and stable unit, ensuring safe flights without collisions and continuous communication.
However, in order to safely and effectively achieve a flocking state in practical situations, the flocking controller needs to take into account uncertainties in the environment, limitations of the agents involved, and intricate mission requirements. Therefore, the main goal of this thesis is to develop distributed flocking control algorithms that are both safe and efficient, and can be successfully implemented in real-world scenarios. The algorithm incorporates dynamic characteristics, such as applying the concept of inactivity inspired by the natural world, to achieve effective swarming in difficult scenarios with constraints, particularly for fixed-wing aircraft. Furthermore, optimization of flocking control parameters performs a safe and efficient execution of complex missions, including target tracking through flocking flight. In addition, the proposed method introduces an optimal flocking control approach that explicitly guarantees collision avoidance and optimizes flocking control performance. Unlike model predictive control, which calculates futures for collision avoidance, the proposed method employs a control barrier function to ensure collision avoidance based on the current state, efficiently generating optimal control inputs. Additionally, a distributed estimator is proposed to estimate the position and speed information of non-neighboring agents by observing only the position and velocity information of its neighbors in stochastic environments. This estimator contributes to the development of a flocking control algorithm that can achieve desired final flocking state. The effectiveness and performance of the proposed algorithms in achieving safe and efficient flocking control in various scenarios are demonstrated through numerical simulations.clos
Comprehensive and Experimental Analysis of the Composite Fiber-Reinforced Polymer (CFRP) for Drilling Process
No full textDepartment of Mechanical EngineeringThis destination focuses on the modeling of carbon fiber-reinforced plastic (CFRP) drilling. The dexel model is utilized to understand the mechanics of drilling, considering the fiber orientation angle of the workpiece and tool. The accuracy of the model depends on the mathematical model employed in the simulation. The cutting angle is continuously changing because of tool rotation, with uncut fibers and delamination being common occurrences. A feed-force model based on analytical techniques has been developed to calculate the feed force throughout the drilling process. The maximum lengths of uncut fibers were derived using the Euler-Bernoulli beam theory. Critical cutting angles were calculated to validate experimental data obtained under various machining conditions. Predictions were derived using an analytical Dexel model that employs self-generating 3D software, with drilling tools moved using NC-code kinematics or manually in the X, Y, and Z directions. An analytical model, based on the Euler-Bernoulli beam theory, is employed to analyze the cutting thrust forces and calculate the uncut fiber length in the critical cutting angle region by extending the single fiber cutting forces with integration boundary limits. A new methodology is introduced to compute the feed force more accurately, which considers the material's deformation and fracture behavior. This innovative approach is expected to contribute substantially to the development of more accurate predictive models for CFRP drilling at the industrial level. Overall, this research has implications for the optimization of the machining processes for fiber-reinforced composites. In this discusses two different studies on CFRP drilling. The first study focuses on offline monitoring of CFRP hole drilling. The researchers employed image processing to monitor drilling and generated a contour of the drill hole to facilitate the identification of the affected area of the uncut fiber and the length of delamination. The study also revealed that low spindle speed and low feed rate parameters are recommended to minimize errors and achieve optimal results in CFRP drilling. The second study aims to minimize uncut fiber length (UFL) in bidirectional CFRP drilling. The researchers varied cutting parameters, such as spindle speed and feed rate, to determine their effect on UFL. The study employed a liquified nitrogen (LN) system, and the drilling process involved dry machining, drilling with liquid nitrogen (LN) as a cooling agent, and drilling with ice as a bottom support. The results showed that the use of liquid nitrogen as a coolant in the drilling process of CFRP materials is a promising approach that can improve hole quality, reduce tool wear, and increase drilling efficiency. The study also revealed that the cutting speed, feed rate, drill geometry, and cutting tool material had a significant influence on the hole quality and maximum UFL. In conclusion, both studies highlight the challenges of CFRP drilling due to the anisotropic nature of the material and the potential for damage to the material during drilling. The studies emphasize the importance of optimizing the drilling process to minimize damage to the material and maintain the integrity of the CFRP structure.clos
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Get PDFDepartment of Biomedical EngineeringGene therapy has benefited from the use of retroviruses, particularly lentiviruses, as effective gene transfer system to host cells. Lentiviruses have been utilized for treating various genetic diseases and developing cancer immunotherapy strategies. However, the integration of viral genomes into host cells can pose safety concerns because of the unpredictable integration sites. Thus, the detailed profiling of viral genome integration sites is crucial for ensuring safety and quality control in viral applications. Therefore, I developed the unbiased genome-wide detection method, UniQuE-seq. This method is simple and easy to produce the library for sequencing and improves detection sensitivity by using custom transposon loaded Tn5 and lambda exonuclease. I conducted the UniQuE-seq to validate that this method can detect the lentivirus integration sites. A comparison between whole genome sequencing and UniQuE-Seq revealed specific locations where simultaneous outcomes occurred. Interestingly, only 7 integration sites were consistent with whole genome sequencing in the experimental results using a monoclonal stable cell line. Moreover, the number of sites with a significantly low P-value (P-value < 0.0001) was about two times less when lambda exonuclease was treated. Sensitivity analysis demonstrated that UniQuE-Seq is feasible to detect even a single integrated site as well. Furthermore, UniQuE-seq enables to identify the genome-wide integration sites at complex populations.
In conclusion, UniQuE-Seq is an unbiased method for detecting viral genome integration sites and improves selective amplification of targeted sequences by using lambda exonuclease and custom-designed transposon-loaded Tn5.clos
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No full textGraduate School of Semiconductor Materials and Engineeringclos
PCNA Cycling and Ubiquitination: Insights into R-loop Dynamics and Alternative Lengthening of Telomeres
No full textDepartment of Biological Sciencesclos
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No full textDepartment of Materials Science and Engineeringclos
The highly reliable dielectric ceramic materials
No full textDepartment of Materials Science and Engineeringclos
Development of a Monitoring System for Electro-Chemo-Mechanics in All-Solid-State Batteries
No full textSchool of Energy and Chemical Engineering (Energy Engineering (Battery Science and Technology))All-solid-state batteries have gained attentions because of their higher theoretical energy density and improved safety than the conventional lithium-ion batteries. However, the ionic transport at the interface between solid materials poses a limitation. Research has exhibited that the applying external stack pressure can effectively reduce the electrochemical resistance at the interface between the solid electrolyte pellet and the anode/cathode, ensuring the long-term cycle life of the battery. This highlights the significant influence of stack pressure on the solid-state battery performance. Additionally, the stack pressure is influenced by the volume changes of the solid active materials during electrochemical tests. The evolution of mechanical stress presents a challenge, as there is a lack of materials capable of absorbing the stress generated within the electrode. To understand the relationship between the electrochemical reaction and stack pressure evolution, it is necessary to develop a technique that sensitively measures the electro-chemo-mechanical responses occurred in solid-state batteries. In this work, we have developed two different cellsthe volume-fixed cell is used to differentiate the stack pressure signals coming from two different degradation mechanisms at the interface between the electrolyte and lithium metal, and the variable volume cell integrated with compression springs is effective to mitigate the mechanical stress responses during the electrochemical tests.
In part 1, we have used the volume-fixed cell, and monitored the stack pressure to offer the new insight into the effect of the stress on the interfacial contact within two different electrolytes: Li10SnP2S12 and Li6PS5Cl. Those materials show the different mechanisms for degradations including the interphase formation for Li10SnP2S12 or lithium filamentary growth for Li6PS5Cl. We found that the measurement of stack pressure can sensitively identify the different degradation mechanismsthe stack pressure decreases faster for the interphase formation, and the signature of stack pressure decrease can be seen in the lithium plating process. Our findings advance the non-destructive technique that can evaluate the electro-chemo-mechanical degradation in the solid-state batteries.
In part 2, we have developed a variable volume cell by integrating compression springs into the conventional volume-fixed cell. This integration enables the cell to mitigate mechanical stress, and maintain the desired initial stack pressure, promoting sufficient contact at the interface. We found that the compression springs effectively store and release the force, facilitating expansion and contraction of the cell volume. To measure the deformation of the springs, we have used two laser displacement sensors to track the cell thickness on both the right and left sides. These results offer valuable insights into the mechanical deformation occurring in the solid-state batteries, and contribute to the advancement of solid-state battery technology by addressing the issue of stress reduction in these batteries. This research opens new avenues for improving the overall design and operation of solid-state battery system.clos