Development of PM2.5 management strategy in the industrial city of Ulsan : A comprehensive approach to understanding the risk and sources of PM2.5

Sang-Jin Lee Ulsan National Institute of Science and Technology 2024 국내박사

Particulate matter (PM) with an aerodynamic diameter of less than 2.5 μm (PM2.5) is major air pollutants in northeast Asia, with their primary sources being fuel combustion from industrial activity, heating, transportation, and power generation facilities. In addition, gaseous precursors such as sulfur oxides (SOX), nitrogen oxides (NOX), and volatile organic compounds (VOCs) generate secondary aerosols through chemical reactions. The major sources for high PM2.5 events in metropolitan cities are generally local vehicle emissions and secondary formation. Long-range atmospheric transport (LRAT) is also a major reason for high PM events in East Asian megacities such as the Seoul Metropolitan Area, which are frequently influenced by Asian continental outflow. On the other hand, industrial cities are often more strongly influenced by emissions from local industrial activity. The metropolitan city of Ulsan, with a population of 1.13 million, is located in the southeast of the Korean Peninsula. The east coast of Ulsan has a number of petrochemical, nonferrous, automobile, and shipbuilding facilities. Thus, the air quality in Ulsan is greatly influenced by the emissions of various air pollutants from these industrial complexes. However, studies on investigations of PM2.5 pollution in Ulsan have been limited, and there is a need to address the health of residents in an industrial city facing air pollution issues. In this study, we aim to develop comprehensive PM2.5 management strategies by considering source identification, human health assessment, and emission reduction. Currently, episodes of high levels of PM2.5 frequently occur in South Korea as a result of both local emissions and the LRAT of yellow dust and haze events from the Asian continent. Therefore, we investigated the characteristics of PM2.5 pollution episodes semi-continuous measurements obtained from the Yeongnam intensive air quality monitoring station (YN station) in Ulsan. The major source of PM2.5 for the pollution period during winter was LRAT from eastern China and North Korea. The industrial facilities in Ulsan were also responsible for the elevated PM2.5 concentration in winter. The major source of PM2.5 for the pollution period during summer was the local industrial facilities and ship emissions. In addition, secondary formation was enhanced by the air stagnation, high relative humidity, and low PBL height. The influence of thermal power stations and national industrial areas in southern coastal cities was also identified. Moreover, to comprehensively understand the pollution of primary and secondary PM2.5, we developed a technique by combining monitoring and modeling methods to map the spatial distribution of PM2.5. The monitoring data for PM2.5 components and precursors, as well as the air dispersion and receptor modeling data for Ulsan, South Korea were used. It was revealed that the petrochemical and non-ferrous industrial complexes are primary sources of PM2.5 in Ulsan. Similar levels between primary and secondary sulfate were observed, while nitrate concentrations were more influenced by secondary formation rather than primary emissions. Ammonium sulfate concentrations were significantly influenced by industrial activities, while ammonium nitrate concentrations were influenced by both industrial and urban emissions. Significant contributions to SOA formation were observed from the automobile, shipbuilding, and petrochemical industrial complexes, with aromatic compounds such as BTEX playing a significant role. Based on these findings, optimized strategies for managing PM2.5 were proposed for urban areas in individual districts and industrial complexes in Ulsan. However, it should be noted that the estimated concentration of SOA may be underestimated due to the limited number of analyzed VOC species. Particulate matter (PM) contains hazardous air pollutants (HAPs) that may adversely affect human health. In particular, residents living in an industrial city are seriously concerned about the health risks associated with major drivers of cancer risk, such as polycyclic aromatic hydrocarbons (PAHs) and heavy metals. Therefore, in this study, a novel index called the comprehensive air-risk index (CARI) was developed, which represents the human health risks associated with HAPs. Furthermore, to enhance the spatiotemporal resolution of CARI, a machine-learning approach was implemented using measurement data for PAHs and heavy metals. Over the course of eight years, the risk of PAHs decreased, whereas the risk of heavy metals exhibited a different trend in Ulsan. In addition, the trends of PM2.5 concentration and risk can differ in Ulsan. Earlier studies have also documented elevated concentrations of highly toxic heavy metals in PM2.5 in Ulsan. CARI, CAI and AQHI displayed different seasonal patterns. Hence, in large industrial cities, the proportion of HAPs within PM2.5 and meteorological conditions bears greater significance in health risk assessment than the mass concentration of PM2.5. The effectiveness of CARI in reflecting the health risks associated with HAPs in an industrial city can be conclusively affirmed. Utilizing machine learning and the novel risk index, CARI allows for the identification of priority risk areas in an industrial city at high spatio-temporal resolution. While the average CARI was higher in petrochemical and nonferrous industrial areas, it did not surpass the ‘Unhealthy’ threshold of 150, and there were areas that only exceeded the ‘Unhealthy for sensitive groups’ level of 100. In addition, the Onsan and Yaeum districts were identified as high-risk areas, despite having low population density, as they are primarily industrial areas. Finally, to propose the most effective PM2.5 emission reduction policies in Ulsan, machine learning approach was considered based on reduction scenarios. Emission reduction scenarios were simulated for the major components of PM2.5, including SO4 2-, NO3 -, NH4 +, OC, and EC, which contribute significantly to the PM2.5 mass concentration. When the concentrations of five components were uniformly reduced, PM2.5 mass concentration exhibited the most significant decrease in the scenario where OC concentration was reduced. Moreover, 'Bad' days determined by PM2.5 concentration (exceed 35 µg/m3) also showed the greatest decreased in the scenario with decreased OC concentration. SO2 and meteorological conditions were found to be the main factors for CARI related to human health risks caused by HAPs. In addition to SO2, NH4 +, OC, and EC showed high importance. When simulating the concentration reduction scenarios for these four components, the CARI decreased the most when the SO2 concentration was reduced. Moreover, 'Unhealthy' days determined by CARI (exceed 150) also showed the greatest decreased in the scenario with decreased SO2 concentration. This means that SO2 emission should be prioritized for control to reduce the risk of PM2.5. In conclusion, OC-related (i.e. VOCs) emissions should be controlled to efficiently reduce PM2.5 mass concentration, and SO2-related emissions (i.e. industrial activity) should be controlled to reduce human health risk. These studies provide basic information for improving air quality and will benefit the residents of Ulsan. It can also be applied to other major cities around the world to help improve global air quality.

Analyzing the Fire Safety and Thermal Performances of the Liquid-Immersion Battery (LImB) Energy Storage System (ESS)

Junho Bae Ulsan National Institute of Science and Technology 2025 국내박사

Lithium-ion batteries (LIBs) are a leading energy storage technology, recognized for their high energy density and outstanding electrochemical performance. They are widely used in electric vehicles (EVs), energy storage systems (ESS), and consumer electronics. However, a significant challenge for LIBs is their susceptibility to thermal runaway, which can lead to fire and explosion. This issue is particularly important in ESS applications where a large number of high-energy cells are concentrated. In these systems, the risk of thermal runaway is affected by heat generation, the presence of combustible materials, and oxygen exposure, so safety is a top priority in all applications. A variety of safety measures have been developed to reduce the risk of fire, such as battery thermal management systems (BTMS), fire extinguishers, and other suppression methods. Existing extinguishment technologies typically rely on oxygen separation or cooling mechanisms to control combustion. Chemicals such as Novec 1230, ABC powders, and phosphoric acid-based compounds are typically used to suppress flames, while cooling systems use liquid nitrogen or refrigerants to reduce battery temperature. However, these solutions only work after a fire has started and are reactive rather than preventive. These systems also struggle to manage the challenges of high-energy systems such as ESS, where slow heat release, excessive suppression, and anaerobic propagation limit their effectiveness. Among the various LIB applications, ESS poses the greatest safety risk due to its high concentration of high-density cells. ESS plays a critical role in grid stabilization and renewable energy integration, but safety concerns have hindered its widespread adoption. For example, South Korea, a leader in ESS deployment, has reported more than 50 fire-related ESS failures, destroying approximately 1 GWh of storage capacity, equivalent to 10% of its total installed capacity. These incidents are concerning because the root cause of the fires remains uncertain, complicating the development of effective countermeasures. Given the limitations of existing fire suppression systems, recent research has explored immersion- based cooling methods that continuously submerge batteries in a coolant. This approach provides immediate heat release and continuous thermal management in the event of thermal runaway. However, practical implementation is hampered by the lack of an appropriate immersion agent that meets safety and performance criteria. Ideally, the immersion agent should be non-corrosive, electrically non-conductive, and have high thermal conductivity and capacity. Unfortunately, most existing solutions are ineffective and incomplete in suppressing fires due to poor heat dissipation. Therefore, immersion-based solutions are primarily used for fire prevention rather than active suppression. Despite these challenges, fire suppression systems play a critical role in large-scale ESS with capacities exceeding 1,000 kWh, while smaller ESS (~10 kWh) commonly used in residential environments often lack adequate fire prevention measures. This gap in safety protocols exacerbates the risks in the rapidly expanding ESS market. To ensure the safe deployment of ESS, next-generation fire prevention and suppression technologies need to go beyond conventional response strategies. Future developments should focus on integrated thermal management solutions that provide both continuous fire prevention and effective suppression to enhance safety in large-scale ESS applications. 1. Battery-in-Fire-Proof Material (BIF) Module To expand the applicability of fire extinguishers, we have developed a system that immerses batteries in a fire-resistant material (BIF) with a hermetic seal to prevent direct exposure to fire extinguishers. In this system, all battery cells are fully immersed in a liquid fire-retardant material (FPM) with high thermal conductivity and heat capacity. This setup allows for immediate fire suppression under extreme conditions while improving electrochemical performance through effective thermal management during normal operation. This study investigates the key components and practical applications of BIF technology. First, the key materials, including fire-retardant and sealing materials, are described in detail and how they are integrated into the BIF cell and module. Second, a method to prevent fire propagation by intentionally overheating a single cell within the BIF module is evaluated and the results are compared to a conventional LIB module. Third, the electrochemical performance of the BIF system is analyzed, including cycle, capacity, EIS, maximum charge rate, and operating temperature under severe conditions. The BIF system overcomes the limitations of conventional post-ignition fire suppression methods and achieves breakthroughs in fire safety and thermal management. By providing both fire prevention and thermal control, BIF technology shows significant potential in the fields of electric mobility (e.g., electric scooters, kickboards), energy storage systems (ESS), and electric vehicles (EVs). 2. LImB (Liquid Immersion Battery) ESS This study evaluates the fire prevention and suppression performance of a liquid-immersed 10kWh ESS battery system compared to a conventional LIB-ESS equipped with a standard fire extinguisher such as ABC powder. In the fire stability test, the conventional LIB-ESS system experienced thermal runaway, which resulted in rapid fire spread and system destruction, with a maximum temperature exceeding 1300°C. In contrast, the liquid-immersed system effectively mitigated the fire risk. The maximum temperature of the abused battery was only 498°C, and the adjacent cells were kept below 50°C, preventing fire spread. The initial fire was extinguished within 2 seconds, significantly reducing the size and speed of the spread. In addition to the fire suppression function, the liquid-immersed system provides improved thermal management during normal operation. Compared with conventional LIBs, it reduces the temperature rise by 6.3 times and reduces the temperature fluctuation between cells from 3.4°C to 1.5°C, ensuring stable and uniform operation. To further evaluate the practical applicability, the liquid-immersed ESS was deployed in an independent power plant and underwent actual operation tests. Despite the increasing demand for small-scale ESS, empirical studies on fire suppression and thermal management are lacking. There are few studies that systematically compare empirical data according to various fire suppression methods in ESS, leaving a gap in the development of standardized operating requirements for ESS safety. This study aims to fill this gap, establish key performance indicators for ESS safety, and contribute to the development of science-based safety guidelines for the popularization of safe and reliable ESS technology.

Secondary Organic Aerosol and Ozone Formation Potential from Anthropogenic and Biogenic Volatile Organic Compounds in Ulsan, South Korea, in Summer

Geunwoo Lee Ulsan National Institute of Science and Technology 2021 국내석사

A large quantity of anthropogenic and biogenic volatile organic compounds (VOCs) is emitted in Ulsan because Ulsan has huge multi-industrial complexes in its eastern coastal area and high mountainous regions in the western hinterland. Some of the VOCs are oxidized and form tropospheric ozone and secondary organic aerosol (SOA) in the atmosphere. Not only high temperature and radiation but also the transport of VOCs from their sources could aggravate the photochemical oxidation reactions in the atmosphere in Ulsan in summer. Despite the environmental importance of photochemical reactions of VOCs, few studies on photochemical VOCs in Ulsan have been carried out. The objectives of this study are to investigate the spatial concentration levels of photochemical VOCs, estimate the formation potentials of ozone and SOA, and propose further research to figure out how much VOCs have contributed to high tropospheric ozone and particulate matter episodes in Ulsan, South Korea, in summer. Hybrid VOC monitoring was conducted with diffusive passive samplers (Radiello, Instituti Clinici Scientifici Maugeri, Itay) and active pumped adsorbent tube samplers (Sequential tube sampler-25, PerkinElmer, UK) at 17 sites (5 industrial, 6 rural, 6 urban sites) and three sites (1 control, 1 industrial, 1 rural site), respectively, in Ulsan from May to August 2020. Through the hybrid VOC sampling, the temporal and spatial resolution of Ulsan VOC monitoring was highly improved. The target VOCs were selected as photochemical assessment monitoring stations (PAMS) ozone precursor 53 VOCs (36 aliphatics and 17 aromatics). Both anthropogenic VOCs like benzene, toluene, ethylbenzene, and o,m,p-xylene (BTEX) and a biogenic VOC, isoprene, were included. All 240 VOC adsorbent samples were analyzed with a thermal desorber-coupled gas chromatography/mass spectrometer (TD-GC/MS, UNITY series 2, Markes, UK-7890B/5977A, Agilent, USA). Every sampling trip had field blank samples to track any contaminations from the whole analytical process. A 3:1 signal to noise ratio was applied to the quantification of VOCs. The concentration spatiotemporal distribution of the VOCs was comprehensively interpreted with the data of 16 meteorological observation stations in Ulsan, considering the physicochemical properties of the 53 VOCs. From May to August, the atmospheric temperature in Ulsan increased except for in July because July is the rainy period. Heavy rain was observed in July, causing relatively low temperatures and radiation. Due to the land-sea breeze in Ulsan, the transport of VOCs from industrial areas to highly urbanized areas occurred in the daytime while transport of VOCs from mountainous areas to the urban region occurred in the nighttime. Criteria air pollutants (CAPs) in rural and industrial sites were compared. Although the concentration of fine particulate matter (PM2.5) did not show statistically significant differences between the sites, NO2 was higher, and O3 was lower in the industrial site than in the rural sites. Also, O3 and the fine particulate matter to coarse particulate matter (PM10) ratio, whose change could indicate the secondary aerosol formation, showed strong diurnal variations in the rural sites but not in the industrial site. These differences in the concentration levels of NO2 and O3 and the diurnal variation between industrial and rural sites need to be contemplated in a further SOA and O3 formation study in Ulsan. Total VOCs (TVOCs), BTEX, and aliphatics exhibited significantly higher concentrations in industrial sites than in rural and urban sites. However, isoprene, a well known biogenic VOC (BVOC), showed a higher concentration in rural sites than in industrial and urban sites. This was obvious due to the BVOCs being emitted from the vegetation. In addition, isoprene concentrations had strong diurnal cycles depending on temperature and solar radiation. In order to identify the source and aging status of BTEX in each site, diagnostic ratios were applied to the BTEX concentration in each sampling site. Toluene to benzene ratio and m,p-xylene to ethylbenzene ratio were used as indicators for traffic emission and aging, respectively. BTEX in automobile and shipbuilding industrial areas were highly affected by fresh and non-traffic sources while BTEX in the harborside petrochemical industrial area were mostly influenced by fresh and traffic sources. Most rural and urban sites were affected by aged both traffic and non-traffic BTEX sources. The top 5 VOC contributors of ozone and SOA formation potentials (OFP and SOAFP) in different sites were compared in this study. In urban and rural sites, toluene, ethylbenzene, and xylenes (TEX) were dominant in the top 5 OFP contributors. In addition to TEX, n-octane and 3-methylpentane significantly contributed to OFP in industrial sites. Regardless of the sites, TEX made the biggest contribution to SOAFP. OFP and SOAFP from VOCs were highest in petrochemical and automobile industrial areas, respectively, in this study. However, the estimated formation potential of O3 and SOA could not explain the spatiotemporal variations of O3 and SOA based on the observed data. To improve the accuracy of the estimations, more VOCs, especially BVOCs, should be included in VOC monitoring and a better methodology to calculate formation potential with meteorological conditions needs to be developed. In conclusion, TEX largely influenced OFP and SOAFP in Ulsan in the summer. While controls for TEX over the Ulsan need to be enhanced to reduce photochemical oxidation reactions forming O3 and SOA, the study on BVOCs such as isoprenes and terpenes, is also needed due to the lack of understanding BVOCs in Ulsan. In order to improve the estimation of O3 and SOA formation, the key factors, such as meteorological conditions and atmospheric composition, should be investigated and considered in a non-linear way like through a machine learning approach.

How Did It Evolve? Developing a Policy Design Experiment for Sustainability Transitions of a National Museum of Modern and Contemporary Art

Hyori Lee Ulsan National Institute of Science and Technology 2023 국내석사

As museums and cultural institutions have responded to the environmental challenges posed by the climate crisis, they have become critical arenas in driving sustainable design practices. Designers can contribute to those communities for sustainability transitions on multiple scales of society and various timelines by using their creative and decisive agency. However, there needs to be more practical knowl- edge of the design approaches for operationalizing sustainability transitions of such institutions. This thesis presents a multi-layered account of the development process of a policy design experiment for sustainability transitions at the National Museum of Modern and Contemporary Art in South Korea. The author retrospectively traced the entire process, conducted interviews with the project team members, including the director and student designers, and performed a thematic analysis to identify how the pro- cess could evolve. The findings suggest that the process of a policy design experiment for sustainability transitions of a public art museum follows a non-linear and complex process intertwined with multiple design activities. This research’s insights can inspire design researchers, practitioners, museums, and cultural institutions seeking systemic and long-term innovation for sustainability.

Factors Influencing the Public Acceptance of the Floating Offshore Wind Farm Development in Ulsan

Seonghee Yang Ulsan National Institute of Science and Technology 2022 국내석사

This thesis investigates the determinants of the public acceptance of the floating offshore wind farm development in Ulsan, highlighting the role of the community profit-sharing schemes. The Ulsan project is currently the largest floating offshore wind farm plan in the world and aims to install a total capacity of 9GW by 2030. As many cases at home and abroad demonstrated, public acceptance is a key success factor of large-scale renewable projects. Although there are many factors influencing public acceptance, profit-sharing schemes for local communities have recently drawn a significant attention from local residents and policy-makers alike. This thesis examines the individual effects of profit-sharing schemes and further their joint effects with other factors such as prior knowledge, trust, distributive and procedural justice, perceived risks and perceived costs, and perceived benefits. We collected data from a survey of 500 individuals who live in Ulsan and analyzed the data using OLS. The theoretical and policy implications of our empirical findings are discussed.

Arrangement Free Wireless Power Transfer for Mid-range Applications via Electrically Strong Resonance

Bonyoung Lee Ulsan National Institute of Science and Technology 2024 국내박사

Wireless Power Transfer (WPT) is a cutting-edge technology that enables energy transfer without the need for physical connectors, offering significant potential for various applications. This thesis provides an in-depth examination of the challenges, benefits, and trade-offs associated with different WPT technologies, with a particular focus on enhancing the degree of freedom between power transmitters and receivers. Achieving greater freedom in positioning and mounting of these components is critical for mitigating issues related to wear, damage, and maintenance costs, thereby improving the overall reliability and usability of WPT systems. The realm of WPT can be divided into near-field and far-field methodologies, each characterized by distinct degrees of freedom and efficiency considerations. Near-field WPT includes technologies such as Inductive Power Transfer (IPT) and Magnetic Resonant Wireless Power Transfer (MRWPT). IPT is limited by its requirement for close proximity between the transmitter and receiver, typically in the millimeter to centimeter range, resulting in minimal spatial freedom. MRWPT, developed by MIT researchers in 2007, offers greater flexibility but its efficiency is highly dependent on the relative orientations of the transmitter and receiver. Despite advancements in these technologies, the quest for an optimal balance between system complexity and freedom remains ongoing. Far-field WPT, particularly microwave WPT, provides another approach, achieving high efficiency through focused energy transmission. However, this method restricts freedom to a quasi-one- dimensional domain, and while three-dimensional freedom can be attained through omni-directional energy dispersion, it comes at the cost of significant efficiency loss. This thesis underscores the necessity of balancing efficiency with the degree of freedom to drive broader adoption of WPT technologies. Central to this research is the introduction of a novel two-dimensional WPT paradigm utilizing Spoof Surface Plasmon Polaritons (SSPP) and surface waves. This approach offers a middle ground, providing greater flexibility than one-dimensional systems while maintaining reasonable efficiency. The use of plasmonic metamaterial structures, such as lattice-type SSPP unit-cells, allows for fine-tuning of propagation characteristics, optimizing the system for microwave applications. Additionally, the implementation of surface wave receivers and the incorporation of non-reciprocal ferrite components enhance the specificity and effectiveness of power transfer. Beyond two-dimensional WPT, this thesis proposes Electrical Resonant Wireless Power Transfer (ERWPT) as a significant advancement over traditional MRWPT. ERWPT leverages the monopole capabilities of electric fields to overcome the spatial limitations imposed by magnetic dipole configurations. This new approach facilitates consistent PTE despite variations in receiver arrangement, demonstrating non-radiative power transfer of up to 50 watts with a PTE of 46% over a distance of 2 meters. The theoretical foundation of ERWPT is rooted in Maxwell's equations and the fundamental equivalence of electric and magnetic forces, providing a robust framework for exploring electric field- based WPT. The findings of this research highlight the potential of ERWPT to address longstanding challenges in WPT, offering a more versatile and efficient solution compared to magnetic field-based approaches. By revisiting the principles of electromagnetism and examining the intrinsic properties of electric and magnetic fields, this thesis lays the groundwork for future advancements in WPT technologies. The practical implementation of ERWPT at midrange distances represents a significant step forward, with implications for a wide range of applications, from consumer electronics to industrial automation. In conclusion, this thesis contributes to the WPT field by presenting innovative solutions that enhance the flexibility and efficiency of power transmission systems. The introduction of the development of ERWPT demonstrate the potential for overcoming current limitations and driving the next generation of wireless power technologies. This research not only advances our understanding of WPT mechanisms but also paves the way for practical and versatile wireless power solutions capable of meeting the diverse needs of modern technology.

Highly Sensitive Plasmonic Terahertz Detector Based on Asymmetric FET Integrated with Sub-Wavelength Aperture

Min Jae Kim Ulsan National Institute of Science and Technology 2024 국내석사

Because of the peculiar characteristics of THz waves, which include penetrability and distinctiveness in feature recognition, Terahertz (THz) technology has great potential. THz imaging technology is unique among THz-frequency range technologies because of its extremely low energy levels, which make it safe for human health. In particular, field-effect transistor (FET)-based THz imaging detectors for real-time THz imaging are presently undergoing extensive research in a multi-pixel array configuration. This is due to the technology's ability to leverage silicon (Si) benefits, which include low cost and high integration density. The plasmonic wave detection technique based on FETs, which is not constrained by the cut-off frequency as in transit mode, has two attractive features: robustness against high THz input power and enhanced responsivity (RV) with rising frequency in the THz range. An analytical device model based on device physics has been built in order to fully comprehend the principles underlying the operation of THz plasmonic detectors. Not constrained by the cut-off frequency as in transit mode, the FET-based plasmonic wave detection mechanism has two attractive features: robustness against high THz input power and enhanced responsivity RV with rising frequency in the THz range. However, because of the diffraction limit, achieving sub-wavelength (λSub) resolution in the THz frequency range—which is characterized by long wavelengths (λ) is intrinsically difficult. A lot of emphasis has recently been paid to near-field approaches, which include both aperture-type and aperture-less (probe-tip) types. These methods remain independent of the THz wavelength; instead, the spatial resolution is dictated by the aperture or tip apex size. In order to improve resolution, a great deal of research has been done on various materials and architectures in aperture-based approaches as well as increasing the field that is transmitted in tip-based techniques. While the overdamped plasma wave drives the FET-based plasmonic detector to function as a power detection mechanism in NR mode, a significant amount of the signal is reflected at the aperture plane as it passes via the aperture. Specifically, for real-time imaging, the transmitted field (E) amplitude diminishes further with increasing pixel count. Addressing the low transmission issue at the aperture-based device level is therefore imperative. In this dissertation, we used 65-nm CMOS technology to examine the effects of aperture location and structural asymmetry on a FET-based plasmonic THz detector with aperture integration. Adding structural asymmetry between the FET's source and drain resulted in a photoresponse (Δu) of 9.3 mV (7-fold) when the aperture was placed close to the gate, compared to a symmetric FET. Furthermore, by creating an asymmetry in feeding the incoming THz wave with the aperture located at the drain, we were able to experimentally demonstrate significantly better detection performance—achieving an 18.5 mV (2-fold) Δu in contrast to the aperture located at the gate.

Research on the Induction Heating Technology using Load Temperature Estimation and High-Voltage Output

GeunWook Kim Ulsan National Institute of Science and Technology 2022 국내석사

The induction heater directly applies electrical energy to the target and heats it by thermal energy conversion, unlike the conventional heating method. There are advantages of heating performance, high efficiency, and cleanliness through this. Unlike the existing fossil fuel combustion type, a current of AC frequency is generated through a coil to generate a magnetic field. This magnetic field forms an eddy current at the target, and heat is generated in the part where the current inside the target is generated. This operation procedure is different from making carbon gas such as coal and petroleum LPG as by-products. It has the advantage of not making flames and by-products accordingly, and safe heating is possible through electrical control. Application is roughly divided into domestic and industrial applications, and the research directions of the two fields are different. First of all, home applications focus on user convenience technology. For example, various studies have been conducted, such as a technology that enables operation in all-metal containers, a technology that reduces EMC emission caused by high frequency during operation, and estimating the temperature of the load. Among them, measuring the impedance of the load and estimating the temperature based on the impedance has expectations for automatic cooking in the future. Automatic cooking is a technique that informs the user of the recipe for the desired food and helps put the right ingredients at the right time. Estimating load impedance in the domestic cooker IH field to predict the state or temperature of cooking will serve as the basis for automatic cooking technology. In addition, it can be applied to secure safety by creating an alarm that informs water boiling alarm or overheating of the contents. In this thesis, user convenience technology has been studied for home applications by applying the above research direction. In industrial applications, research is being conducted to increase output power and speed up the heating of loads. The industry is demanding a method of increasing the temperature of the load by increasing output power rather than user convenience technology. To achieve a high output IH, an output voltage should be increased, and a device capable of operating at a constant frequency should be used. When a full-bridge inverter is implemented using a MOSFET device, there is a limitation in manufacturing high-power IH due to manufacturing a withstand voltage protection circuit and an increase in the unit price of a switching device. Using more switching elements, it is difficult to reconstruct a system suitable for the output power to expand the output capacity. This thesis proposes a method of stabilizing the system and easily extending the output by manufacturing an induction heating inverter in a modular manner and connecting input-parallel output-series. In this thesis, this study would like to present a design method for analyzing and producing induction heaters used as home cooking containers in the industry. In addition, for home cooking containers, user convenience technology was studied by adding impedance estimation technology. Industrial induction heaters constructed a modular inverter and increased the output voltage to study how to quickly heat and increase the range of operations that can be output. The above study was verified by simulation and experiment through a 2kW class induction heater.

A Gene-Centric Perspective of Scientific and Technological Innovations

Woochul Jung Ulsan National Institute of Science and Technology 2023 국내석사

유전자와 유전자 산물에 대한 연구는 현대 생명공학의 기초가 되며, 의학, 농업, 식량산업, 에너지 공급, 환경 정화 등 여러 분야로 응용이 가능한 것으로 알려져 있다. 이러한 과학적 발견들과 기술 혁신을 유전자 중심의 관점에서 거시적으로 조사하고자, 본 논문에서는 연구 논문과 특허에 대한 대규모 선별이 진행되었다. 각 유전자가 갖는 과학적 파급력을 보기 위해서 PubMed에서 접근 가능한 연구 논문 중 제목과 초록에 유전자 또는 유전자 산물이 언급된 자료들을 수집하였다. 기술 혁신 부분에 대응하는 자료로는 미국특허청(USPTO)에서 공개된 특허 출판물이 수집되었다. 문헌 자료 선별과 함께, 유럽 생물정보학 연구소에서 관리하는 UniProt 협의체 데이터베이스 중 선별·제공되는 일부 항목들의 유전자-단백질 명칭을 수집하였고, 이는 이후 유전자 간에 지나치게 중복된 명칭이나 두문자어로 인한 혼동을 방지하기 위해 원소가 공유되지 않는 집합들로 일관되게 군집되었다. 결과적으로 제목/초록에 이러한 유전자 항목을 언급한 논문과 특허들의 연도별 수치를 바탕으로 인간 유전체 프로젝트가 시작된 이후의 추세를 보고하였다. 각 유전자 인용 추세는 연구 논문에서와 비교할 때 발명 문헌에서 변동이 더 큰 것으로 보였고, 두 부문 모두 의료 분야에서 유전자 인용에 대한 기여가 두드러졌다. 지금까지 유전자를 인용한 문헌들은 증가 추세였으나 제목이나 초록에 새롭게 언급되는 유전자의 수는 최근들어 감소하였다. 반면, 이미 연구된 유전자들의 새로운 조합들이 활발히 탐구되는 것으로 보이며, 이러한 조합에 자주 포함된 유전자일수록 단순 인용 횟수의 상위권 유전자보다 생명공학의 발전을 잘 설명히는 것으로 보인다. Research on genes and gene products is a foundation of modern biotechnology, and recognized for its applicability in medicine, agriculture, food industry, energy supply, environmental remediation, and many others. To investigate a macroscopic and gene-centric perspective of scientific discoveries and technological innovations, we employed a large-scale curation of research papers and patents. As a raw data to represent the scientific impact of each gene, we collected the entire set of research articles available on PubMed, that have the names of genes or gene products in their title or abstract. The more dedicated literature source, the United States Patent and Trademark Office (USPTO) patent publication, was retrieved as a source data to represent the counterpart in technological innovations. In parallel with this literature curation, the gene symbols were collected from curated subset of UniProt consortium database maintained by European Bioinformatics Institute, and then clustered into the non-overlapping standardized sets to eliminate the overwhelming duplicates and possible contamination by common acronyms. Based on the annual counts of papers or patents whose titles/abstracts include a given gene, we show the overall trends of genetic research since the launch of the Human Genome Project. The gene citation fluctuated more in inventive activity compared to those in the research, while both sides were largely contributed by medicinal discipline. The volume of publications mentioning genes has been increased while the debut of new genes on titles and abstracts has been deflated. In contrast, new combinations of previously-studied genes kept actively explored, and their frequently adopted genes informed biotechnology innovations rather than sheerly top-studied genes.

Differences in Public Perception of Geothermal Energy in Korea : National vs. Local

Hae-In Baek Ulsan National Institute of Science and Technology 2021 국내석사

This study investigates the public perception differences in geothermal power generation at the national and local levels through media content analysis and survey analysis. Media content analysis results indicated that the previously positive media framing for environment and technology drastically changed to a negative framing of risk after the Pohang earthquake, and there were no significant differences between national and local coverage. However, survey data showed that the local perception of geothermal energy was significantly more negative than that at the national level. The proximity to the earthquake epicenter was negatively correlated with the perception of geothermal energy. Regarding energy source preferences among local residents, geothermal power plants and nuclear power plants were placed in the same category. Pohang residents seemed to associate geothermal power plants with nuclear power plants in terms of risk discourse. They viewed several similarities, i.e., high risks, between the two technologies. As a result of the Pohang earthquakes being byproducts of geothermal power generation, geothermal energy is recognized as a threat or potential danger rather than a risk-free and environment-friendly renewable energy source. To reduce the renewable energy perception gap between the national public opinion and the locals’ view, sufficient and carefully planned communications with local residents are required. Before introducing renewable energy to a region, a strategically planned science/technology education outreach venture accompanied by an honest risk assessment for the locals is essential.