Study of electron bunching in vacuum devices: Electron gun, Linear accelerator

Department of Electrical EngineeringElectron bunching is an interesting issue with practical and scientific applications. In this thesis, I will present two topics of electron bunching in vacuum devices: electron gun, linear accelerator. For the electron gun, I will present a theoretical approach of bunching condition in dc-biased ac-driven vacuum devices. There are two different approaches. The one is electron bunching from a DC-biased single surface multipactor. Generation of electron bunch from a dc biased, single surface multipactor was studied theoretically and by PIC simulations. The condition for a spatially narrow bunch was obtained and verified by PIC simulations. This kind of multipactor is proposed to be used as a compact electron gun for various applications, such as linear accelerators. The other one is a theoretical correlation between the periodicity of an electron micro-bunch train and the transit phase of each electrons passing through a vacuum gap in a dc-biased ac-driven diode was derived. The upper frequency limitation by the transit time effect could be explained by abnormal exclusion of a certain range of transit phase analyzed for the first time by our theory. In a particle-in-cell simulation guided by our theory to evade the deficiency, a micro-bunch train with 1.41 picosecond periodicity (0.707 THz) could be obtained from a gap of 50 ??m regarded as excessively large owing to severe suffering from the transit time effect. For the linear accelerator, A 9.3 GHz 6 MeV linear accelerator (LINAC) was analyzed by using three-dimensional (3D) particle-in-cell (PIC) simulations with 3D time-domain electromagnetic simulations. In the 3D PIC simulations, field data of a p /2 standing wave mode extracted from the 3D time-domain field calculations were injected into a side-coupled LINAC composed of 25 acceleration and 24 coupling cavities. Acceleration of an electron beam of 20 kV, 300 mA in the 3D full LINAC structure was analyzed without spatial or time segmentations, which resulted in maximum energy of 6 MeV and average current of 68.5 mA when 9.3 GHz, 1.6 MW radio frequency (RF) power was assumed. By virtue of in-depth data from the 3D electromagnetic and PIC simulations aided by a one-dimensional (1D) particle code developed by ourselves, the analysis for a full LINAC structure being reported first in this paper, may be informative and useful because experimental reports about an X-band (9.3 GHz) 6 MeV side-coupled LINAC have been rare until now.ope

The Impact of Network Neutrality Violation on the Streaming Platform Ecosystem : Evidence from Twitch TV

The widespread use of media streaming services has resulted in a surge in network traffic, triggering debates on network usage fees between Internet service providers (ISPs) and content providers (CPs). As a response to network usage fees imposed by ISPs, CPs have opted to provide discriminatory service quality as a means of mitigating costs associated with high traffic volume. In 2022, a leading Korean ISP charged discriminatory network usage fees to Twitch TV, the media streaming platform, due to its excessive network traffic. In response, Twitch implemented a discriminatory service quality reduction policy. Our study examines the impact of this policy on the streaming platform ecosystem. Our results indicate that the implementation of the service quality reduction led to a remarkable decline in the number of viewers, which then resulted in adverse effects for streamers. This study contributes to the literature on network neutrality violation by offering empirical evidence

Stringent Nucleotide Recognition by the Ribosome at the Middle Codon Position.

Accurate translation of the genetic code depends on mRNA:tRNA codon:anticodon base pairing. Here we exploit an emissive, isosteric adenosine surrogate that allows direct measurement of the kinetics of codon:anticodon University of California base formation during protein synthesis. Our results suggest that codon:anticodon base pairing is subject to tighter constraints at the middle position than at the 5'- and 3'-positions, and further suggest a sequential mechanism of formation of the three base pairs in the codon:anticodon helix

Design and Application of a Collocated Capacitance Sensor for Magnetic Bearing Spindle

This paper presents a collocated capacitance sensor for magnetic bearings. The main feature of the sensor is that it is made of a specific compact printed circuit board (PCB). The signal processing unit has been also developed. The results of the experimental performance evaluation on the sensitivity, resolution and frequency response of the sensor are presented. Finally, an application example of the sensor to the active control of a magnetic bearing is described

How Did the Clinical Medicine Progress during the Unified Silla Era: Installment of the Medical Education Center ‘Uihak 醫學’, and Its Effects

In this research, I aimed to recognize the historical meaning of installing the medical education center, ‘Uihak 醫學’, during the Silla 新羅 dynasty. ‘Uihak’ was installed in 692, in the first year of King Hyoso 孝昭 ’s rule. ‘Uihak’ was founded by using various Chinese medical classics as its textbooks for medical education, such as the Classic of Plain Questions 素問經.The wooden prescriptions excavated from Anapji 雁鴨池, which is thought to have been created in the middle of the 8th century, and the Chinese medical book Prescriptions for Universal Benefit 廣利方, which the envoy of Silla tried to acquire in 803, reflect the idea on medicine during that period in Silla. By this time, the field of medicine began to develop the idea to discern the locations and mechanism of disease patterns by centering on the viscera and bowels 臟腑 while making use of the herbal prescriptions based on various drugs. This means that clinical medicine founded upon the medical education achieved in ‘Uihak’ was being realized in the medical fields as well. According to the Chronicles of the Three States 三國史記, for the illness of Queen Sunduk 善德 in 636, medicine, praying, and the method of esoteric Buddhism 密敎 was tried out as a means of her cure. Comparatively, for the treatment of the first rank Chunggong 忠公 in 822, the Kingdom’s representative doctor 國 醫 with professional medical knowledge was sought out to fine a cure. The analyses of the human disease, diagnosis, treatment method, etc., given by the kingdom’s representative doctor were identical to those recommended in the medical textbooks used in ‘Uihak’. As such, we can posit that his academic background was ‘Uihak’ and the education given there.The Classic of Materia Medica 本草經, which was also used in ‘Uihak’, was a book professionally centered on the drug branch of medicine. The Classic of Materia Medica is a terminology referring to various books on drugs, including the Shennong’s Classic of Materia Medica 神農本草經, the Variorum of the Classic of Materia Medica 本草經集注, the Newly Revised Materia Medica 新修本草, etc. Thus, we cannot specify what the classic of Materia Medica actually taught, based on only its terminology. However, based on the wooden prescriptions excavated from Anapji, and from the terminology of drugs recorded in the drug trading document Purchase List for Silla goods 買新羅物解 preserved in Shosoin 正倉院 of Japan, we can hypothesize that in the middle of the 8th century, the Newly Revised Materia Medica was indeed being circulated. Based on these evidences, we can also hypothesize that Silla was part of the network of drug trading that encompassed the entire region of Asia.After unifying the Korean peninsula, the Kingdom of Silla actively adopted the medical educational system of Tang 唐 China. By using the obtained medical knowledge, Silla cured illnesses and used the medical knowledge on various drugs recorded in the Newly Revised Materia Medica to pursue trade with China, Japan, and other countries. Through the installation of ‘Uihak’, the same medicine has now begun to be officially used in East Asia, including Silla

Phase stability of hafnium oxide and zirconium oxide on silicon substrate

Phase stabilities of Hf-Si-O and Zr-Si-O have been studied with first-principles and thermodynamic modeling. From the obtained thermodynamic descriptions, phase diagrams pertinent to thin film processing were calculated. We found that the relative stability of the metal silicates with respect to their binary oxides plays a critical role in silicide formation. It was observed that both the HfO$_2$/Si and ZrO$_2$/Si interfaces are stable in a wide temperature range and silicide may form at low temperatures, partially at the HfO$_2$/Si interface.Comment: 5 pages, 3 figure

Quality Based Software Project Staffing and Scheduling with Budget and Deadline

Abstract-Software project planning is becoming more complicated and important as the size of software project grows. Many approaches have been proposed to help project managers by providing optimal staffing and scheduling in terms of minimizing the salary cost or duration. Unfortunately, the software quality, another critical factor in software project planning, is largely overlooked in previous work. In this paper, we propose the quality based software project staffing and scheduling approach. We provide better software project plans considering quality with either cost bound (Budget) or duration bound (Deadline) for software project managers