An Experimental Study on Granulated Blast Furnace Slag Geopolymer Concrete

NGUYEN HONG CHAN Sejong University graduate school 2015 국내석사

The demand of concrete is increasing day by day for the need of development of infrastructure facilities. However, it is well known that the production of ordinary Portland cements not only consumes significant amount of natural resources and energy but also releases substantial quantity of carbon dioxide to the atmosphere. Therefore, it is essential to find alternatives to make the concrete environment friendly. And also, there are needs for finding the renewable materials to satisfy the increasing demand for building structures. Geopolymers have received considerable attention because they may result environmental benefits such as the reduction in consumption of natural resources and the decrease in the net production of carbon dioxide. In the recent years, interest in geopolymer is increasing manifold due to their reported advantages over ordinary Portland cements. Geopolymer materials are reported to possess high early strength, better durability and have almost no alkali-aggregate reaction. These materials are therefore projected to be cement for the future. Granulated blast furnace slag (GBFS) is kind of raw material in Geopolymer, and also it is industrial wastes. Granulated blast furnace slag is formed in processes such as pig iron manufacture from iron ore, combustion residue of coke, and fluxes such as limestone, serpentine, and other materials. Granulated blast furnace slag is a non-toxic material, and can be a good raw material for making high-value geopolymers which can be utilized in fire resistant applications. Generally, Geopolymer based on granulated blast furnace slag not only reduce the environmental effect by the emission of carbon dioxide but also resolving industrial wastes. In this thesis, the granulated blast furnace slag Geopolymer was a kind of concrete without using Portland cement. All main properties of concrete have been tested such as: workability, compressive strength and rest period. The properties of geopolymer concrete depend on the geopolymerization which needs energy to occur. Thus, higher curing temperature resulted in larger compressive strength and longer curing time resulted in higher compressive strength. This characteristic of granulated blast furnace slag geopolymer concrete is similar to the others kinds of geopolymer concrete. In the other hand, because of special chemical properties of granulated blast furnace slag, the optimization temperate is 130oC which can provide the highest compressive strength of slag based on geopolymer concrete after 4 hours in curing conditions. Additionally, final compressive strengths were almost same whenever the curing conditions appeared, even though the delays were 1, 2, 3, 4, or 5 days. Beside, granulated blast furnace slag geopolymer concrete is the good material for sulfate resistance and corrosion environment also. It not only uninfluenced by sulfate factors but also improved the compressive strength in those environments.

A study on cultural challenges influencing on immigration of Uzbek diaspora and ethnic Koreans in South Korea

Kamalov Khamid Sejong University graduate school 2019 국내석사

Globalization is making closer parts of the world closer than ever before, initiating more international migration and transnational companies, and establishing global cities with multiethnic, multicultural, multilingual populations. Globalization has strengthened the economic and practical roles of adaptive diasporas. In the era of globalization, multicultural societies are being formed over the world, where different kind of nationalities are living. South Korean is not an exception since globalization affects developed and developing countries also. Different kind of diasporas has been forming in this country. All of them may face cultural challenges, which can show us the importance of understanding to study cultural challenges. Despite the growing influx of migrants from Uzbekistan including ethnic Koreans, no research has been conducted to understand cross-cultural challenges in this area. Thus, this research tries to identify and observes cultural challenges both Uzbek diaspora and ethnic Koreans in Korea, compares and predicts migration trends. In addition, this study aims to explain and offer suggestions on how to deal with cross-cultural challenges for people came from Uzbekistan, including ethnic Koreans. A relevant literature review has been made on Diasporas, Uzbek ethnicity, migration Koreans to Central Asia, factors influencing on immigration to Korea. Research includes mixed methods of qualitative and quantitative research, as some hypothesis may come after reviewing literature resources or after collecting and analyzing data. The survey was provided among different types of groups such as students, workers and ethnic Koreans. Results show us what kind of cultural challenges and difficulties Uzbek diaspora faces in Korea, their preference in solving these challenges and faster adaptation. I hope that this study would contribute to study cultural challenges on migration. Moreover, it may help to understand these challenges and prevent negative consequences. Keywords: Diaspora, migration, adaptation, cultural challenges.

china`s one belt one road innitiative and its effect on relations with neighbor countries

Siddique Muhammad Amjad Sejong University, Graduate school of Public Polic 2018 국내석사

One belt one road, an initiative by china is accountable for strengthening Chinese economic leadership via enormous platform of substructure building all over the neighboring states pertaining to china. It was done after confrontation of the 2008 s global crises financially. The approach was set as a symbol of more practicality display by Xi Jinping the new Chinese leader trying to meet leadership and global obligation concerning expectations on china. Intended to associate Asian regions, United Kingdom, African domain and Oceania, the edge offers incredible openings of global monetary collaboration. China’s involvement to global community belongings, as in the mark of financial moderation, as China's brilliant approach, it is very self-protective than unpleasant in nature. Notwithstanding perils and doubts happen, the implementation will enhance China's impact and situation in local and global institute. Keywords: China, OBOR, policy, international

The Transformation of Spatial Morphology of Hanoi : 하노이 공간구조의 변화

NGUYEN QUOC THANH Graduate School, Sejong University 2015 국내석사

Along with the development periods, Hanoi has undergone vigorous changes in urban morphology in which the most significant transformation happened from the Nguyen dynasty to the French colonization. During development process, numerous prominent conversions in politics, society and economy have been implemented. Previous urban literatures have dealt with these historical changes extensively while the transformation of spatial morphology of the city, which reflects the historical context, seems being ignored. To fill this gap, this research aims to provide a transparent appearance of urban transformation of Hanoi in two main points: the transformation of spatial configuration and the relation of spatial change with the historical evolution of the political socio-economic background of the city. In order to do that, we first analyze in terms of space syntax methodology the spatial configuration of Hanoi’s street network, with a view to grasping the transformation of its spatial morphology. The comparison of the city’s spatial morphology in different periods will be then made with historical clarification to figure out the association between spatial structure and historical context. By tracing out the spatial change of historical vibrant areas and their relative functions against the process of growing the hot spots pattern of socio-economic aspect of the city, we expect that the functional transitions of urban centers can be highlighted most effectively. This research contributes a significant part in the study of historical evolution of Hanoi by showing ways how this city’s morphology changed throughout history. It pointed out that the relation between spatial evolution and historical background in terms of political socio-economic aspect of the city could be established in the development process. In that, it showed the leading effects of the French to the urban planning of Hanoi since decisions by the French changed dramatically the whole urban context of the city and gave distinctive patterns that still affect to the current condition of the city both in spatial structure and socio-economy. This study is believed to offer a clear understanding about the development of current scenario of the city morphology in the context of historical evolution of center and new extended areas.

Experimental Study of Extrinsic and Intrinsic Motivation : with Reference to the ESL Classroom

Robert Riski GRADUATE SCHOOL SEJONG UNIVERSITY 2000 국내석사

본 연구는 동기유발의 내적 요인(extrinsic motivational variables)과 외적 요인(intrinsic motivational variables)의 변별력을 설정하고자 하는 의도에서 수행되었다. 각기 유형에 따른 변별력이란 어휘적 정의에서뿐만 아니라 두 가지 유형의 결과론적으로도 나타날 수 있음을 알게 될 것이다. 외적인 동기유발요인이란 외부적 보상이나 칭찬 등에서 얻어질 수 있다. 그와 동시에 벌에 대한 두려움의 결과에서 얻어질 수 있는 것 도 외부적 동기유발에 속한다 할 수 있다. 다시 말해 외적 동기유발(extrinsic motivation)의 요인이란 외부적 환경에서 온다는 것이 여러 변인들 중에 공통점이라 할 수 있다. 이러한 외적 동기유발은 말 그대로 내적 동기유발요인에 반대되는 개념인 것이다. 내적으로 동기유발이 된 학습자라 함은 자신이 처해 있는 세계 에 대한 끈임 없는 호기심과 지가 실행력을 소유한 사람을 들 수 있다. 본 논문의 목적은 외국어를 학습하는 환경에서 외적 동기유발의 효과성보다 학습자 자신의 내적 동기 유발성이 학습시 훨씬 더 효과가 있다는 것을 검증하기 위해서였다. 지금까지 동기유발에 대한 많은 연구가 선행되었고 외국어 학습의 효과와 내적 동기유발성과의 밀접한 상호관계가 있음이 발견되기도 했다. 본 연구에서는 세종대학 재학생으로 교양영어과정을 필수적으로 수강하고 있는 학생들을 실험대상으로 하여 외적 동기유발과 내적동기유발(intrinsic motivation)의 상호관계를 연구하였다. 그 결과 외적 동기 유발보다는 내적 동기유발 변인들이 외국어 학습효과에 더 밀접한 영향을 미치고 있음이 실험결과로 검증되었다. 동기유발의 외적에 대비된 내적 동기유발성에 대해서는 앞으로도 더 연구되어야 할 부분으로 판단되며 이러한 내적동기유발에 대한 연구가 더 수행될 때 우리 모두는 보다 효율적인 외국어 교사나 학습자가 될 것으로 기대된다.

Wide field-of-view optical receiver using a ball lens for resonant beam charging

NAQVI SYED FARHAN ALI Graduate School Sejong University 2023 국내석사

Resonant Beam Charging (RBC) has emerged as a promising wireless power transfer technology, offering the advantage of self-alignment. However, the effectiveness of power transfer in RBC relies on the line-of-sight principle, requiring the receiver and transmitter to be within each other's field of view. This constraint imposes limitations on the achievable field of view (FOV) for efficient power transfer. To address this limitation, this study explores the utilization of a ball lens retroreflector to enhance the FOV. Although the use of a ball lens retroreflector improves the FOV, the presence of surface reflections on the spherical ball lens still restricts the achievable FOV. To mitigate this issue, we investigate the implementation of anti-reflection coatings on the ball lens to minimize surface reflections and further improve the FOV. Furthermore, with the shrinking size of portable devices, there is a growing need for compact receivers that can be integrated into any rechargeable device. Previous studies have implemented RBC receivers using cat eye, corner cube and ball lens retroreflectors, which exhibit limited FOV, high reflection losses and are comparatively bulky in sizes. In this study, we presented an experimental demonstration to showcase the potential of a high reflection coated ball lens retroreflector with anti-reflection coatings in expanding the FOV in RBC. By overcoming the limitations posed by surface reflections on the spherical ball lens, this research contributes to enhancing the field of view for efficient power transfer in RBC. The proposed receiver model achieves a FOV of ±80 degrees. The current system utilizes a bidirectional gain scheme with a Semiconductor Optical Amplifier (SOA) as the gain medium operating at the center wavelength of 1060 nm. A 3 mm ball lens retroreflector acts as a resonator at the receiver, significantly increasing the effective field of view. To optimize the output power, a highly reflective material is coated on the rear side of the ball lens, while the front side is coated with an anti-reflection coating to minimize surface reflections. By adjusting these coating parameters, 3mm ball lens provides a resonating power of 50 mW and when the line of sight is blocked by any obstacle the system goes back to safety mode featuring 2.3 mW output power. The proposed receiver model holds the potential to improve the efficiency of photovoltaic receivers by increasing the illumination area. To validate its performance, an RBC scheme with an 11.2 mm beam diameter and a 10×10 mm² GaSb photovoltaic cell is employed. The results demonstrate a peak optical-to-electrical conversion efficiency of 25% from the photovoltaic cell at an input power of 78 mW from the SOA gain medium. The findings of this study contribute to the development of practical implementations for wireless power transfer technologies, particularly for small and portable devices.

Production-to-Fracturing Approach to Optimize Productivity of Transversely Muti-Fractured Horizontal Wells in Shale Gas Reservoir : 셰일 가스전에서 횡 방향 다단 파쇄 수평정의 생산성을 최적화하기 위한 Production-to-Fractured 접근에 대한 연구

DANG THANH SON Sejong University Graduate school 2015 국내석사

The content of this Thesis is the study related to the design and optimization of hydraulic fracturing treatment for transversely multi-fractured horizontal wells in shale gas formation. Unconventional reservoirs such as shale gas, tight gas… pose a uniquely different problem to those engineering exercises. Unfortunately, not many researches have been conducted so as to clarify the feasibility of applying those, which have been developed for conventional cases, to the newly discovered types of reservoirs. Not to mention that, a uniquely-appropriate approach should be developed to be solely applied to those unconventional reservoirs, to provide engineers with a systematic method to solve the problems at hand. Those aforementioned are the objectives of this Thesis. By using a production-to-fracturing approach, the economics of transversely multi-fractured horizontal wells can be optimized. This unique approach composes of two steps. The first one is to select the optimum number of stages and number of clusters by using a simple-and-accurate analytical production model, economic analysis and response surface methodology (RSM). After that, an optimum proppant and fluid schedule (slurry design) will be proposed to create hydraulic fractures (or fracture network) of which the geometries have been previously determined. The results from this study are then compared with the works of previous authors, where its major similarities and discrepancies are analyzed.

Optimum design of laminated composite thin-walled beams considering flexural-torsional buckling : Flexural-torsional buckling을 고려한 laminated composite thin-walled beams의 최적설계

NguyenXuanHoang Sejong University Graduate School, Department of 2015 국내석사

The main objective of this study is to present formulation and solution methodology for optimum design of thin-walled composite beams. The geometric parameters and fiber orientations of beams are treated as design variables simultaneously. The objective function of the optimization problem is to maximize the critical flexural-torsional buckling loads of axially loaded beams. The constraints of the optimization problem are imposed by the presence of upper bound of cross-sectional area of beams, limitation ranges of ratios of length to web’s height and web’s height to flanges’ width of beams. The analysis of thin-walled composite beams for flexural-torsional buckling problem in which warping function is introduced in displacement field is conducted by displacement-based one-dimensional finite element model. The displacement fields are assumed to follow the classical laminated beam theory and applied for arbitrary laminate stacking sequence configuration. Varational formulation in which the principal of total potential energy is employed is used to derive the governing equations and finite element model of flexural-torsional buckling problem. Results from the parametric studies show that the effects of fiber angles and cross section geometry on the critical buckling load are varied for different boundary conditions and length of beams. In some cases, the increase of ratio of web’s height to flanges’ width is followed by the decrease of critical buckling load through the range of fiber angles. On the other hand, the variation of ratio of web’s height to flanges’ width produces diverse trends of critical buckling load with respect to fiber angle changes. A micro genetic algorithm (micro-GA) is employed as a tool for obtaining optimal solutions. It offers faster convergence to the optimal results with smaller number of populations than the conventional GA. Several types of lay-up scheme as well as different beam lengths and boundaries conditions are investigated in the optimization problems of I-section composite beams. The optimal results are compared to regular design whose cross-sectional area of thin-walled beams are same in order to illustrate the feasibility and validity of the proposed methodology for optimization of flexural-torsional buckling problems. In addition, obtained numerical results show a little more sensitivity of geometric parameters on the critical flexural-torsional buckling loads than that of fiber angles.

A study on automated demand response in resource-constrained IOT platforms for smart grid : 스마트 그리드를 위한 자원 제약 사물인터넷 플랫폼에서의 자동 수요 반응에 관한 연구

Hasan Wajahat Sejong University, Graduated School 2015 국내석사

The traditional electric grid has always suffered from the lack of steady demand for electricity and unlike other markets, electricity is one product that cannot be stored so its production has to be increased or decreased in real-time. However, smart grid with its two-way flow of information and electricity can resolve this issue through the use of demand response (DR). DR is the shifting or shedding of load by the user in response to a demand from power utilities. The two end points in a load reduction event are the utility and the device which reduces its power consumption; currently to achieve this load reduction would require a combination of DR standards or of DR standards with other protocols like BACnet. But with the spread of internet of things (IOT), electric devices are becoming capable of communication by themselves and this should govern the future direction of DR protocols. In our thesis first common automated DR (ADR) standards known as open automated demand response 2.0 (openADR 2.0) was explored. To understand DR messages and events and to show the inadequacies of the current DR systems we developed a fully functional DR client. For openADR 2.0 to fully function, it needs a DR client which means, having to install an extra device or software in every house and for that software to have the capability to communicate with electronic devices which sometimes use proprietary protocols. But with IOT the same functions can be done by the devices themselves, with the support from the right ADR protocol. OpenADR 2.0 is heavily dependent on XML but for a utility to communicate with millions of devices, XML is too verbose. In our thesis we have proposed the use of efficient XML interchange (EXI) as serialization technique for DR standards as it can provide the advantages of XML but requires far less battery, memory and processing capabilities. A network model of smart grid on OPNET was created and a DR event simulated using both XML and EXI. The results show that EXI significantly generate far less data than XML. Using these results a new DR protocol was proposed which targets constrained devices and is an end-to-end DR protocol. The proposed protocol is designed specifically for small devices and divides devices in to categories which can help the utility to generate DR events more efficiently. The proposed protocol is based on web of things and uses constrained application protocol (CoAP) and EXI. The protocol was implemented using contiki and the analysis done using traffic generated showed that our protocol generated far less traffic than openADR 2.0 without constant updating and with constant update it generated nearly the same. This shows that an end-to-end DR protocol for constrained devices is feasible and advantageous.

The Establishment of Electrochemical Series in Ionic Liquids from the Electrodeposition Behavior of Metals

PriyandiKusumah Sejong University graduate school 2015 국내석사

이온성 액체는 1000C 이하의 낮은 녹는점을 갖는, 양이온과 음이온만으로 구성된 새로운 종류의 용매이다. 낮은 증발성, 낮은 휘발성, 넓은 전기화학적 창, 높은 전도도 그리고 높은 열적 안정성이 이온성 액체를 특히 금속 전착과 같은 응용처에서 각광받게 하고 있다. 특히 물과 공기 분위기에서 안정한 이온성 액체는 수분과의 반응성이 없고 물과 잘 섞이지 않아서 관련 연구가 활발하다. 비록 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([BMP]TFSI)처럼 물과 공기에 안정한 이온성 액체는 물과 잘 섞이지 않음에도 불구하고 우리가 시약회사로부터 상용 이온성 액체를 구입할 경우 이 이온성 액체가 소량의 수분을 함유하게 된다. 따라서 이온성 액체를 진공 건조할 경우 처음 상태의 전도도와 전기화학적 창 값의 차이가 생기게 된다. 보통 이온성 액체에서 수분의 존재는 물분해로 인하여 이온성 액체의 산화안정영역을 더 낮추게 된다. 반면에, 이온성 액체에서 수분의 양이 줄어듦에 따라 전도도는 같이 감소하게 된다. 다음 연구로, [BMP]TFSI에서의 전기화학적 반응성의 확립을 위해 16종 금속(Li, Mg, Au, Ag, Pt, Pd, Si, In, Nd, Ta, Ti, Al, Cu, Fe, Ni and Zn)의 전기화학적 거동을 조사하였다. 전기화학적 거동은 potentiodynamic polarization 방법을 사용하여 조사되었으며 이로써 open circuit potential (OCP), exchange current density 추정, cyclic voltammetry (CV) 등의 방법을 사용하였다. 전기화학적 시리즈의 결정은 각 금속들의 이온성 액체에서 나타내는 OCP값을 기반으로 추정하였는데, Nd이 가장 낮은 값을, In이 가장 높은 값을 나타내었다. 따라서 Nd이 [BMP]TFSI에서 가장 잘 녹고, In이 가장 녹기 힘들 것으로 사료된다. Exchange current density는 전기화학적 시리즈와는 다른 경향성을 나타내었는데, Mg이 가장 낮은 값을, Zn가 가장 높은 값을 나타내었다. 이로부터 Mg이 산화/환원 시 가장 높은 과전압을, Zn는 가장 낮은 과전압을 필요로 할 것으로 예상된다. 각 금속의 전착 거동을 조사하기 위해 0.1 M 금속염을 [BMP]TFSI에 용해하여 CV를 상온에서 질소-충진된 글로브 박스를 이용하여 2 mV/s의 주사속도로 시행하였다. 먼저 2 mV/s의 낮은 주사속도를 선정하여 [BMP]TFSI만 있는 경우와 이 이온성 액체에 금속염이 들어가 있는 경우의 CV 비교를 하였다. 그리고 나서 좀 더 빠른 10 mV/s의 주사속도의 경우와 비교하여 주사속도의 금속 전착에 대한 영향을 살펴보았다. 주사속도는 산화, 환원 전류 피크의 위치에 대하여 영향을 미치는데, 주사속도를 빨리 할수록 산화, 환원 과전압이 줄어드는 경향을 보였다. 이 연구를 통해 [BMP]TFSI의 넓은 전기화학적 창 (~6 V)과 소수성이 금속 전착 응용에 도움이 되는 것을 알았고, 따라서 [BMP]TFSI가 금속 전착을 위한 용매로 유망한 이온성 액체라는 것을 확인할 수 있었다. Ionic liquids are a new class of solvents solely composed of anions and cations with low melting points below 1000C. Properties such as low volatility, low viscosity, large electrochemical window, high conductivity and a high thermal stability make ionic liquids very attractive for applications especially in metal electrodeposition.The development of ionic liquids, especially water- and air-stable types, has attracted extensive attention since they are known to be stable to moisture and immiscible with water. Although a water- and air-stable ionic liquid such as 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([BMP]TFSI) should be immiscible with water, it is inevitable that it contains a small amount of water when we receive a commercial ionic liquid product from a chemical company. Therefore, the conductivity and electrochemical window of [BMP]TFSI become different when it undergoes vacuum drying. It is usually shown that the presence of water lowers the anodic limit of ionic liquid due to water electrolysis. On the other hand, conductivity decreases with lower content of water in ionic liquid. In the next part of the study, the electrochemical behavior of 16 metals (Li, Mg, Au, Ag, Pt, Pd, Si, In, Nd, Ta, Ti, Al, Cu, Fe, Ni and Zn) was investigated for the purpose of determining the order of their reactivity in [BMP]TFSI. The study was carried out using potentiodynamic polarization for the open circuit potential (OCP) and exchange current density measurements, and cyclic voltammetry (CV) to study the electrodeposition of metals. The electrochemical series of metals in [BMP]TFSI based on their OCP values then sorted with Nd and In has the lowest and highest value, respectively. Therefore, Nd becomes the easiest metal to be dissolved in [BMP]TFSI while In is the hardest metal to be dissolved. Exchange current density shows a different tendency from the electrochemical series with Mg and Zn respectively having the lowest and highest value. It means that Mg needs more overpotential to be oxidized/reduced. On the other hand, Zn requires lower overpotential to be oxidized/reduced. CV study of the electrodeposition behavior of 0.1 M metal salts in [BMP]TFSI was conducted in nitrogen-filled glove box at room temperature with a scan rate of 2 mV/s. A slow scan rate was chosen in order to obtain the most accurate comparison between neat [BMP]TFSI and a 0.1 M metals salts dissolved in [BMP]TFSI solution. CVs of most of the metals investigated show the presence of anodic-cathodic peaks representing dissolution and deposition of metals. CVs with a higher scan rate, 10 mV/s, were performed to observed the effect of scan rate on electrodeposition behavior. It is shown that the scan rate affected the position of anodic and cathodic peaks due to redox overpotential decreasing at the higher scan rate. This study shows that [BMP]TFSI is a promising ionic liquid for the electrodeposition of metals because of its wide electrochemical window (up to 6 V) and hydrophobicity, which considered to be beneficial in practical use.