• Progress in Superconductivity and Cryogenics
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• v.9 no.1
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• pp.67-71
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• 2007

HTS transformers which have been developed until now had only fundamental structures. Among the auxiliary functions of conventional transformers, voltage regulating is the most important one. For the voltage regulation, conventional transformers are equipped with on load tap changers (OLTCS). In this paper, we describe the possibility of the HTS transformer with OLTC. For the case study, we designed a single phase 33 MVA HTS transformer with OLTC. It is one of three individual HTS transformers which composes a 3 phase, 100 MVA transformer. It is expected to substitute for a 3 phase, 60 MVA conventional transformer in Korea. The parameters of an HTS transformer are varied due to the gap length between primary and secondary windings. The length was decided for the transformer to have the impedance of 12 %. Its size was limited to the one of the conventional transformer. The characteristics of the HTS transformer were analyzed in both case of having OLTC and not.

• International Journal of Korean Welding Society
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• v.1 no.1
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• pp.17-22
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• 2001

Because the quantitative relationships between welding parameters and welding result are not yet blown, optimal values of welding parameters for $CO_2$ robotic arc welding is a difficult task. Using the various artificial data processing methods may solve this difficulty. This research aims to develop an expert system for $CO_2$ robotic arc welding to recommend the optimal values of welding parameters. This system has three main functions. First is the recommendation of reasonable values of welding parameters. For such work, the relationships in between the welding parameters are investigated by the use of regression analysis and fuzzy system. The second is the estimation of bead shape by a neural network system. In this study the welding current voltage, speed, weaving width, and root gap are considered as the main parameters influencing a bead shape. The neural network system uses the 3-layer back-propagation model and a generalized delta rule as teaming algorithm. The last is the optimization of the parameters for the correction of undesirable weld bead. The causalities of undesirable weld bead are represented in the form of rules. The inference engine derives conclusions from these rules. The conclusions give the corrected values of the welding parameters. This expert system was developed as a PC-based system of which can be used for the automatic or semi-automatic $CO_2$ fillet welding with 1.2, 1.4, and 1.6mm diameter the solid wires or flux-cored wires.

• Korea Trade Review
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• v.47 no.2
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• pp.89-101
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• 2022

International remittances play a crucial role in the economic management of each country, especially in developing countries. Its functions are diverse, including procurement of foreign currency, serving as a cushion for the balance of payments and foreign exchange reserves by reducing the adverse external shocks, driving economic growth, easing the gap between the rich and the poor, and maintaining macroeconomic stability. However, previous studies on remittances have mainly focused on macro-and micro-economic aspects to analyze the determinants. Therefore, this study attempts to identify the determinants of remittances in 122 countries over the past 25 years from macroeconomic and educational aspects as well as institutional qualities. In addition, given the fact that almost all of the world's top 10 recipient countries in terms of GDP and total remittance size are developing countries, developed and developing countries are separated and analyzed for comparison, assuming that there may be a difference between the two groups. Results show that the coefficients of developed and developing countries are different in four areas: Control of Corruption (CC), Rule of Law (RL), Voice and Accountability (VA), and Regulatory Quality (RQ) among the six institutional variables of interest in this study. These results implicate that even the same institutions and policies should be applied and implemented differently depending on the circumstances of each country. In addition, as suggested by the World Bank, policymakers in all countries should double their policy efforts to lower the costs of remittance and improve access to the financial system for immigrants or dispatched workers to ensure a steady inflow of remittances.

• Structural Engineering and Mechanics
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• v.90 no.1
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• pp.1-18
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• 2024

The present study conducts a thorough analysis of thermal vibrations in functionally graded porous nanocomposite beams within a thermal setting. Investigating the temperature-dependent material properties of these beams, which continuously vary across their thickness in accordance with a power-law function, a finite element approach is developed. This approach utilizes a nonlocal strain gradient theory and accounts for a linear temperature rise. The analysis employs four different patterns of porosity distribution to characterize the functionally graded porous materials. A novel two-variable shear deformation beam nonlocal strain gradient theory, based on trigonometric functions, is introduced to examine the combined effects of nonlocal stress and strain gradient on these beams. The derived governing equations are solved through a 3-nodes beam element. A comprehensive parametric study delves into the influence of structural parameters, such as thicknessratio, beam length, nonlocal scale parameter, and strain gradient parameter. Furthermore, the study explores the impact of thermal effects, porosity distribution forms, and material distribution profiles on the free vibration of temperature-dependent FG nanobeams. The results reveal the substantial influence of these effects on the vibration behavior of functionally graded nanobeams under thermal conditions. This research presents a finite element approach to examine the thermo-mechanical behavior of nonlocal temperature-dependent FG nanobeams, filling the gap where analytical results are unavailable.

• IMMUNE NETWORK
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• v.23 no.5
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• pp.36.1-36.16
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• 2023

Thymic epithelial cells (TECs) play a critical role in thymic development and thymopoiesis. As individuals age, TECs undergo various changes that impact their functions, leading to a reduction in cell numbers and impaired thymic selection. These age-related alterations have been observed in both mice and humans. However, the precise mechanisms underlying age-related TEC dysfunction remain unclear. Furthermore, there is a lack of a comprehensive study that connects mouse and human biological processes in this area. To address this gap, we conducted an extensive transcriptome analysis of young and old TECs in mice, complemented by further analysis of publicly available human TEC single-cell RNA sequencing data. Our analysis revealed alterations in both known and unknown pathways that potentially contribute to age-related TEC dysfunction. Specifically, we observed downregulation of pathways related to cell proliferation, T cell development, metabolism, and cytokine signaling in old age TECs. Conversely, TGF-β, BMP, and Wnt signaling pathways were upregulated, which have been known to be associated with age-related TEC dysfunctions or newly discovered in this study. Importantly, we found that these age-related changes in mouse TECs were consistently present in human TECs as well. This cross-species validation further strengthens the significance of our findings. In conclusion, our comprehensive analysis provides valuable insight into the biological and immunological characteristics of aged TECs in both mice and humans. These findings contribute to a better understanding of thymic involution and age-induced immune dysfunction.

• Environmental and Resource Economics Review
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• v.25 no.1
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• pp.27-60
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• 2016

An integrated assessment model of climate and the economy (IAM) has been a standard tool for the economic analysis of climate change and policy recommendations. Since policy measures to address climate change take places at a national level, a regional integrated assessment model of climate and the economy (RIAM) is gaining more importance. A RIAM is a useful tool for the assessment of regional (or national) impacts of climate change. This paper investigates the main features of the currently available RIAMs. The focus is social welfare functions and the regional aspects of climate change. The comparative analysis shows that there is a huge gap between the economics of climate change and its applications to RIAMs. As an application, this paper examines the effect of social welfare functions on optimal solutions of the RICE (Regional Integrated model of Climate and the Economy) model. It is found that optimal climate policy such as carbon tax or emissions control rate is very sensitive to the assumptions on social welfare functions of RIAMs. It is better for each country to have their own RIAM as a basic tool for national climate policy-making and for international bargaining in greenhouse-gas mitigation. This is because a country's own preferences such as efficiency, equity, and sustainable development as well as national circumstances can be reflected in RIAM. The Republic of Korea has not developed its own RIAM yet. The comparative analysis and the numerical model in this paper can be a stepping stone for the development of such a national model.

• Development and Reproduction
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• v.12 no.1
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• pp.41-49
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• 2008

Ultrastructural changes occurring during the course of development and degeneration of oocytes in female Ruditapes philippinarum (Adams & Reeve, 1850) are described for clams collected from Gomso Bay, Korea. During the early stages of oogenesis, desomosome-like gap junctions localized between the early vitellogenic oocyte and the follicle cells. Vitellogenesis occurs through a process of autosynthesis, involving the combined activity of the Golgi complex, mitochondria and rough endoplasmic reticulum, and heterosynthesis in which extraovarian precursors are incorporated into oocytes by endocytotic activity, involving the basal region of the early vitellogenic oocytes prior to the formation of the vitelline envelope. The follicle cells appear to play an integral role in vitellogenesis and oocyte degeneration: phagocytosis and intracellular digestion of products originating from oocyte degeneration. These functions can permit a transfer of yolk precursors necessary to vitellogenesis, and they can accumulate nutrients in the cytoplasm, as glycogen and lipids, which can be employed by the vitellogenic oocyte. During the period of oocyte degeneration, follicle cells may have lysosomal system for breakdown, and resorb various phagosomes in the cytoplasm for nutrient storage. But follicle cells probably are not the major source of yolk precursors in vitellogenesis.

• Applied Science and Convergence Technology
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• v.26 no.5
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• pp.118-128
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• 2017

The scope of this work is to determine and compare the effect of electron temperature ($T_e$) and number density ($N_e$) on the yield rate and concentration of reactive chemical species ($^{\bullet}OH$, $H_2O_2$ and $O_3$) in an argon, air and oxygen injected negative DC (0-4 kV) capillary discharge with water flow(0.1 L/min). The discharge was created between tungsten pin-to pin electrodes (${\Phi}=0.5mm$) separated by a variable distance (1-2 mm) in a quartz capillary tube (2 mm inner diameter, 4 mm outer diameter), with various gas injection rates (100-800 sccm). Optical emission spectroscopy (OES) of the hydrogen Balmer lines was carried out to investigate the line shapes and intensities as functions of the discharge parameters such as the type of gas, gas injection rate and inter electrode gap distances. The intensity ratio method was used to calculate $T_e$ and Stark broadening of Balmer ${\beta}$ lines was adopted to determine $N_e$. The effects of $T_e$ and $N_e$ on the reactive chemical species formation were evaluated and presented. The enhancement in yield rate of reactive chemical species was revealed at the higher electron temperature, higher gas injection rates, higher discharge power and larger inter-electrode gap. The discharge with oxygen injection was the most effective one for increasing the reactive chemical species concentration. The formation of reactive chemical species was shown more directly related to $T_e$ than $N_e$ in a flowing water gas injected negative DC capillary discharge.

• Journal of Service Research and Studies
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• v.10 no.3
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• pp.67-80
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• 2020

The information system audit service has been recognized for its effectiveness in improving the management efficiency of informatization projects in the public sector and improving the quality of information systems. However, according to several recent studies, it is not very helpful in securing quality by indicating formal audit performance and incorrect functions or errors in a short audit period. So, if the effectiveness of audit is proved to ensure the quality of the information system from the perspective of the software life cycle and to successfully operate and maintain it, the use of audit for the successful construction of the information system will be an essential factor. Therefore, this study investigated whether the current audit service users are satisfied with the current information system audit and what they expect. If it is different from what was expected, the difference between expectations and performance was analyzed to improve user satisfaction, and a survey was conducted through interviews with experts in the information system field. Based on the empirical results through the questionnaire, in order to reduce the difference in expectations from the user's point of view in the information system audit service, a plan to improve the audit system suitable for the new audit environment was proposed.

• Cross-Cultural Studies
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• v.53
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• pp.73-102
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• 2018

The purpose of this study was to explain, using Jacques Lacan's theory of desire, how Ellen Olenska functions as the object petit a in her relationship with Newland Archer and to connect the impossibility of Newland and Ellen's love with the impossibility of desire, in Edith Wharton's The Age of Innocence. In New York society in the 1870s, the unpleasant truth was avoided, personal opinions were excluded, no room for imagination existed, and other-ness was expelled. In that society, Newland realized that true love and true emotions were lacking in his life. For Newland, Ellen was the gap in New York society and the object that could fill that gap. Ellen functioned as the object petit a. But the romance between Newland and Ellen was forbidden in New York society, where everything was dominated by strict social codes, and especially because Newland was engaged to Ellen's cousin, May Welland. Ellen became inaccessible to Newland and this set Newland's desire for Ellen in motion. He idealized Ellen as the objet petit a, based on the fantasy that she would fill the void in his life. However, at every critical moment, Newland delayed unification with Ellen by resorting to social codes. His actions betrayed that the goal of his desire was not the fulfillment, but the reproduction of desire, with its circular movement. His decision not to see Ellen in Paris again at the end of the novel can be interpreted as Newland's effort to maintain Ellen as the inaccessible object, objet petit a, forever. It is this impossibility of desire that the romance of Newland and Ellen is predicated upon. Another purpose of this study was to expand this impossibility of desire to the relationship between man and woman and to interpret The Age of Innocence as a story showing the characteristics of the relationship between the sexes. The relationship between Newland and Ellen shows that there is no harmonious relationship between the sexes and that woman exists only as a fantasy object, objet petit a for man.