Classifying quadratic number fields up to Arf equivalence

Two number fields K and L are said to be Arf equivalent if there exists a bijection T : ­ΩK → Ω­L of places of K and of L such that KP and LTP are locally Arf equivalent for every place P ε ΩK. That is, |K*p/K*2p| = |L*TP/L*2TP|, type[( , )P] = type[( , )TP], and Arf(rP ) = Arf(rTP ) for every place P ε ΩK, where rP is the local Artin root number function and ( , )P is the Hilbert symbol on K*p. In this dissertation, an infinite set of quadratic number fields are classified up to Arf equivalence

Three essays on racial discrimination

The first chapter shows that small business owners in credit markets, in particular minority owners, have difficulty in securing sources of capital for their business operation in spite of their economic importance. The literature on credit market discrimination shows consistent results that can be interpreted as evidence that minority owners are discriminated against compared to their counterparts (i.e., white owners) in obtaining loans, which may be caused by lenders' discrimination, although such behavior is prohibited under current fair-lending laws. The first chapter uses pooled cross sectional data from the Survey of Small Business Finances (1993, 1998, and 2003) and a bivariate probit model based on Heckman's approach to deal with sample selection bias for those choosing to apply for loans that has been ignored in analyses of credit markets for small businesses owners. Our analyses confirm previous results suggesting that minority owners are discriminated against in credit markets. The second chapter examines the determinants of discriminatory preferences. The economic literature mainly presumes that racial preferences are exogenous in explaining racial disparities. The research in this area, however, has shown that economic and noneconomic considerations can influence racially prejudiced sentiments. The second chapter adds to the literature by 1) combining repeated cross-sectional survey data - from multiple waves (1976-2018) of the General Social Survey (GSS) - to get more precise estimates and test statistics with more power; 2) conducting regression analyses with different model specifications to show the robustness of the empirical results; 3) showing how empirical results are affected when careful controls for age, period, and cohort are included in the model; and 4) using a quantile regression approach to examine whether there exist differential effects of the variables of interest across the entire distribution of discriminatory preferences. Our findings show that unemployment rates are closely associated with discriminatory preferences, which is consistent with what classical labor market competition theories predict. Also, education seems to be particularly important in predicting discriminatory preferences, especially at the upper end of the preference distribution. The third chapter argues that it is important to investigate how age, period, and cohort impact the shift in racial preference, since any temporal change can be attributed to the effects of these three variables. However, it is noteworthy that there are few attempts in this area that examine the effects of these three time-dimensional variables in explaining the shifts in racial preference, reflecting the difficulties of obtaining estimates due to the linear dependence among them. To separate the contributions of age, period, and cohort on racial preference, the third chapter uses the General Social Survey from multiple waves (1972-2018) and estimates the bounds of the effects instead of obtaining point estimates. Our bounding analyses, combined with theoretical assumptions, is consistent with the theory in allowing for positive effects of age on discriminatory preferences, which interact with negative effects of period and cohort in explaining changing discriminatory preferences over time. These findings suggest that discriminatory preferences in the United States will continue to show a general downward trend, although there may be variations over time.Includes bibliographical references

Generating Realistic Images from In-the-wild Sounds

Representing wild sounds as images is an important but challenging task due to the lack of paired datasets between sound and images and the significant differences in the characteristics of these two modalities. Previous studies have focused on generating images from sound in limited categories or music. In this paper, we propose a novel approach to generate images from in-the-wild sounds. First, we convert sound into text using audio captioning. Second, we propose audio attention and sentence attention to represent the rich characteristics of sound and visualize the sound. Lastly, we propose a direct sound optimization with CLIPscore and AudioCLIP and generate images with a diffusion-based model. In experiments, it shows that our model is able to generate high quality images from wild sounds and outperforms baselines in both quantitative and qualitative evaluations on wild audio datasets.Comment: Accepted to ICCV 202

Coverage Analysis of Dynamic Coordinated Beamforming for LEO Satellite Downlink Networks

In this paper, we investigate the coverage performance of downlink satellite networks employing dynamic coordinated beamforming. Our approach involves modeling the spatial arrangement of satellites and users using Poisson point processes situated on concentric spheres. We derive analytical expressions for the coverage probability, which take into account the in-cluster geometry of the coordinated satellite set. These expressions are formulated in terms of various parameters, including the number of antennas per satellite, satellite density, fading characteristics, and path-loss exponent. To offer a more intuitive understanding, we also develop an approximation for the coverage probability. Furthermore, by considering the distribution of normalized distances, we derive the spatially averaged coverage probability, thereby validating the advantages of coordinated beamforming from a spatial average perspective. Our primary finding is that dynamic coordinated beamforming significantly improves coverage compared to the absence of satellite coordination, in direct proportion to the number of antennas on each satellite. Moreover, we observe that the optimal cluster size, which maximizes the ergodic spectral efficiency, increases with higher satellite density, provided that the number of antennas on the satellites is sufficiently large. Our findings are corroborated by simulation results, confirming the accuracy of the derived expressions

Spirits\u27 Dance: Sunrise Overture

The subtitle of Spirits’ Dance is Sunrise Overture. This overture is composed with five different themes of spirits’ dances: Light, Air, Water, Earth and Fire. The piece starts with the wind breeze in the darkness, mimicked by woodwinds and brass blowing their instruments without producing a tone. When the Sun rises the piece quietly begins. The beginning and ending express the sunrise and the sunset with the Light spirits’ dance. Air spirits softly introduce Water spirits. Mischievous Earth spirits pop up and carry a practical joke after the beautiful water sprits’ dance. Marching of Fire spirits brings dryness to the land and it builds suspense until the fire burns down. The spirits sing a faint gleam of hope and praise and the light at last shines magnificently. The Sun sets with the light of the glory and the piece is ended. This piece can be interpreted as the Creation, the prosperity of a nation, or one’s path of life; it questions what the alpha and omega are

Electron Transport in Graphene Nanoribbon Field-Effect Transistor under Bias and Gate Voltages: Isochemical Potential Approach

Zigzag graphene nanoribbon (zGNR) of narrow width has a moderate energy gap in its antiferromagnetic ground state. So far, first-principles electron transport calculations have been performed using nonequilibrium Green function (NEGF) method combined with density functional theory (DFT). However, the commonly practiced bottom-gate control has not been studied computationally due to the need to simulate an electron reservoir that fixes the chemical potential of electrons in the zGNR and electrodes. Here, we present the isochemical potential scheme to describe the top/back-gate effect using external potential. Then, we examine the change in electronic state under the modulation of chemical potential and the subsequent electron transport phenomena in zGNR transistor under substantial top-/back-gate and bias voltages. The gate potential can activate the device states resulting in a boosted current. This gate-controlled current-boosting could be utilized for designing novel zGNR field effect transistors (FETs).ope

The smallest quaternary ammonium salts with ether groups for high-performance electrochemical double layer capacitors

Electrochemical double layer capacitors (EDLCs) are energy storage devices that have been used for a wide range of electronic applications. In particular, the electrolyte is one of the important components, directly related to the capacitance and stability. Herein, we first report a series of the smallest quaternary ammonium salts (QASs), with ether groups on tails and tetrafluoroborate (BF4) as an anion, for use in EDLCs. To find the optimal structure, various QASs with different sized head groups and ether-containing tail groups were systematically compared. Comparing two nearly identical structures with and without ether groups, QASs with oxygen atoms showed improved capacitance, proving that ions with oxygen atoms move more easily than their counterparts at lower electric fields. Moreover, the ether containing QASs showed low activation energy values of conductivities, leading to smaller IR drops during the charge and discharge processes, resulting in an overall higher capacitance

Analysis of interface management tasks in a digital main control room

Development of digital main control rooms (MCRs) has greatly changed operating environments by altering operator tasks, and thus the unique characteristics of digital MCRs should be considered in terms of human reliability analysis. Digital MCR tasks can be divided into primary tasks that directly supply control input to the plant equipment, and secondary tasks that include interface management conducted via soft controls (SCs). Operator performance regarding these secondary tasks must be evaluated since such tasks did not exist in previous analog systems. In this paper, we analyzed SC-related tasks based on simulation data, and classified the error modes of the SCs following analysis of all operational tasks. Then, we defined the factors to be considered in human reliability analysis methods regarding the SCs; such factors are mainly related to interface management and computerized operator support systems. As these support systems function to reduce the number of secondary tasks required for SC, we conducted an assessment to evaluate the efficiency of one such support system. The results of this study may facilitate the development of training programs as well as help to optimize interface design to better reflect the interface management task characteristics of digitalized MCRs

A study of TiO2/carbon black composition as counter electrode materials for dye-sensitized solar cells

This study describes a systematic approach of TiO2/carbon black nanoparticles with respect to the loading amount in order to optimize the catalytic ability of triiodide reduction for dye-sensitized solar cells. In particular, the cell using an optimized TiO2and carbon black electrode presents an energy conversion efficiency of 7.4% with a 5:1 ratio of a 40-nm TiO2to carbon black. Based on the electrochemical analysis, the charge-transfer resistance of the carbon counter electrode changed based on the carbon black powder content. Electrochemical impedance spectroscopy and cyclic voltammetry study show lower resistance compared to the Pt counter electrode. The obtained nanostructures and photo electrochemical study were characterized.open6