A study on designing liquid/solid ionic conductive electrode materials for high-performance and stretchable single-electrode triboelectric nanogenerators

Harishkumarreddy Patnam Kyung Hee University, Graduate School 2023 국내박사

Abstract A study on designing liquid/solid ionic conductive electrode materials for high-performance and stretchable single-electrode triboelectric nanogenerators Harishkumarreddy Patnam Student ID: 2017315489 Department of Electronics and Convergence Engineering The Graduate school of Kyung Hee University Advised by Professor Jae Su Yu With the emerging science and technologies every day, the usage of the internet of things (IoT), electronic gadgets and wearable sensors are routine in a human's life and they consume a lot of power indicating trouble in fulfilling the energy demands for continuous operation. Still, the inconvenience of periodically charging these gadgets for long hours or carrying additional backup power sources all the time restricted their large-scale applications. Presently, most of the energy is generated from non-renewable sources such as fossil fuels and radioactive materials, which have affected nature by polluting the environment by dumping nuclear and fossil fuel waste causing increased carbon emission, global warming, and climate change. Thus, harvesting electrical energy from mechanical energy is a better approach for present and future needs. With the development of the electronic industry, the transition of these devices to flexible, less-weight, and durable designs depends on the use of green energy and self-powered system by storing energy to power these devices. Mechanical energy is abundantly and widely accessible in our daily environment. Thus, the transform of mechanical energy into electricity in ambient conditions is extensively advised to be a better alternative energy conversion approach. Triboelectric nanogenerators (TENG) have attracted significant interest in the present days due to the harvesting of mechanical energy from ambient sources based on the triboelectric effect. Moreover, TENGs has been the ability to harvest mechanical energy from distinct sources such as movements, rotations, flowing water, and deformations. The TENG was extensively utilized to harvest mechanical energies owing to its facile and cost-effective fabrication method, long lifetime, better power density, and fast charge-discharge ability. The TENG output performance is mainly based on the electrode materials, active dielectric layer, morphology, chemical composition, and fabrication methods. Flexible and deformable triboelectric materials such as dielectric layers and conductive electrodes attained great interest because of the demand for wearable electronic devices. Especially, highly flexible and deformable conductive electrodes are a hot research topic. Up to now, several researchers developed novel conductive materials and demonstrated their performance in practical applications. However, the electrical output of the TENG under severe circumstances such as rough weather and extreme stretching conditions without sacrificing the flexibility of the device is a challenging task. Therefore, research is still ongoing to develop better materials for wearable electronics under extreme conditions. In the process of researching the new novel conductive materials, in chapter 3, we demonstrated an easy preparation process to fabricate a highly conductive hydrogel and organogel to be utilized as an electrode for high-performance TENGs. Particularly, the hydrogel modified with additional dopants showed excellent electrical and mechanical properties. The enhanced output performance of the devices is explained by additional characterizations. The biocompatible organogel was prepared by facile method and studied their electrical properties. The organogel-based TENG exhibited outstanding results and the preparations are facile, scalable, and cost-effective for wearable TENG operated in single-electrode mode. In chapter 4, we also presented the liquid conductive electrodes based on the polyaniline polymer (PANI) and carboxymethyl cellulose sodium salt (CMC) for flexible, stretchable, and wearable TENGs. The fabricated TENG with CMC ionic conductive liquid showed desirable performance under extreme environmental conditions. Additionally, the CMC ionic conductive liquid-based TENG was used as a wearable sensor and it showed significant results. The demonstration of the TENG under extreme environmental conditions indicated that the TENG is desirable for practical applications. Besides, the PANI liquid electrode showed enhanced output performance under extremely deformable conditions. The obtained results show that the ionic conducive liquid electrodes can serve as an excellent choice for wearable electronics. Keywords: single electrode; Conductivity; Triboelectric nanogenerator; wearable sensors; Energy harvesting

A study on hybrid supercapacitors based on binder-free hierarchical nanostructured electrodes with multi-metal oxides/hydroxides

ANKIREDDYMULE Kyung Hee University Graduate School 2023 국내박사

Abstract A study on hybrid supercapacitors based on binder-free hierarchical nanostructured electrodes with multi-metal oxides/hydroxides Mule Anki Reddy Student ID: 2017315488 Department of Electronics and Information Convergence Engineering The Graduate School, Kyung Hee University Advised by Professor Jae Su Yu Emerging new trends in modern consumer electronics have stimulated the researchers to develop alternative, sustainable, economically-viable, and preeminent energy storage techniques to mitigate the reliance on conventional energy resources. Particularly, rechargeable batteries and supercapacitors (SCs) have been garnered a substantial attraction among the developed energy storage technologies. The rechargeable batteries demonstrate high capacity and energy density properties on the point of the Faradaic charge storage technique. Whereas, the SCs exhibit high power density, prolonged lifetime, and prompt energy storage ability due to the surface-controlled reaction mechanism. Though the charge storage mechanism is different in these two energy technologies, some common factors such as electrode material and its contact with the current collector, chemical composition, morphology, and preparation methods perform an active function in their energy storage performance. Especially electrode materials are the main and common factors in attaining the high energy storage performance. Accordingly, the investigation unity has been focusing on the development of versatile electrode materials, including deepened redox performance, high electrochemical conductive nature, great valence states, and good structural stability. Besides the electrode materials, their preparation methods affect the large-scale production and cost of the device fabrication. Therefore, simple and cost-effective preparation methods -need to be developed to ease the abovementioned issues. Employing such simple and economically-viable methods, designing the nanoarchitectures with benefit-enriched characteristics of high surface area, porosity, hierarchical connection, and multi-component configuration would be a promising approach. Considering all the above factors, chapter 3 describes we developed the hierarchical high surface and redox-active amorphous NiMn NSs on crystalline and conductive 1D NiMo NRs using a simple hydrothermal technique. The fabrication and charge storage properties of hybrid supercapacitors are deliberated in brief. To demonstrate the practical applicability, the hybrid HC was built with NiMoNRs@NiMnNSs as positive and activated carbon layered NF (AC@NF) as negative electrodes, respectively. The fabricated hybrid HC device also exhibited more enormous energy storage performance along with well-meaning cycling permanence. Besides, the stable performance of HSC was investigated even under different flexed conditions. Chapter 4 introduces a novel the multi-component like CoFe hydroxides (CFH) nanowire array@ CoNiMn hydroxides (CNMH) nanosheet (NSTs) array on redox-active and conductive Ag-coated NF and CC substrates were developed and employed in SCs. The formation mechanism and effect of each component on electrochemical performance are systematically discussed. Moreover, both fabricated HCs demonstrated excellent electrochemical performance, and their real-time applications were verified by powering different electronic devices with stored solar energy in HCs. Furthermore, practical applications are also demonstrated by harvesting solar energy, thereby switching the electronic components In the process of developing novel materials, Chapter 5 of this thesis introduces the multilayered active materials films coated Nickel foam as a low-cost and highly performance electrode. The hierarchical multilayered (ZNHC@NHC@PEDOT) architectures with versatile morphological structures are developed on NF as binder electrodes. The prepared high electrochemical active (ZNHC@NHC@PEDOT) architectured electrode showed superior energy storage performance and was employed in the fabrication of hybrid HC. The assembled device demonstrated excellent charge storage with high rate capability performance, and practical applicability was verified through its energy storage capabilities. Key words Binder-free, multi-metals, Transition metal oxides/hydroxides, Hybrid supercapacitors

Anti-tumorigenic microorganisms : Anticancer effect on human non-small cell lung cancer A549 cells

Hee-Ju Lee Kyung Hee University Graduate School 2022 국내석사

Abstract Anti-tumorigenic microorganism Kyung Hee University Department of Oriental Medicine Biotechnology Hee-Ju Lee Cancer is a serious disease that is a major threat to human health worldwide. Lung cancer is one of the main causes of cancer-related death, accounting for approximately 25% of cancer mortalities. Lung cancer is divided into small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC) according to histopathological criteria. NSCLC accounts for approximately 85% of all lung cancers. Chemotherapy for NSCLC varies from patient to patient and generally causes serious side effects including organ damage. Therefore, effective therapy for patients with advanced NSCLC remains lacking. The issues with the current anticancer drugs include high toxicity to normal cells, incapacity to treat deep tumor tissues, and drug resistance of tumor cells. Therefore, the development of new therapeutic agents is required. Microorganisms can produce structurally diverse secondary metabolites, which can be applied to many compounds with high therapeutic potential. We identified Enterococcus faecium LCM001, a microorganism that showed the highest cytotoxicity to A549 cells and low toxicity to human lung fibroblast WI-38 cells among 37 microorganisms, and its active ingredient, Cyclo(L-Pro-L-Tyr) was isolated. Cyclo(L-Pro-L-Tyr) induced cell proliferation inhibition, apoptosis and G2/M cell cycle arrest in A549 cells. Cyclo(L-Pro-L-Tyr) induced apoptosis, as demonstrated by cleavage of PARP and increase of phosphorylated p53. Cyclo(L-Pro-L-Tyr) blocks the PI3K/Akt pathway by inhibiting phosphorylation of epidermal growth factor receptor (EGFR), which is overexpressed and highly mutated in human non-small cell lung cancer. Additionally, inhibition of phosphorylation of human fibroblast growth factor receptor 4 (FGFR4), which is overexpressed in tumors, blocks the PI3K/Akt pathway, suggesting a correlation between the anti-tumor activity. These findings suggest the potential of Cyclo(L-Pro-L-Tyr) as an anti-tumor therapeutic agent for NSCLC by targeting EGFR and FGFR4 and inhibiting PI3K/Akt. Keywords: Anti-tumor, NSCLC, microorganisms, Enterococcus faecium, Cyclo(L-Pro-L-Tyr), EGFR, FGFR4, PI3K, apoptosis, G2/M arrest

The Influence of SNS Characteristics on Travel Decision among Chinese SNS Users

Feng Han Kyung Hee University Graduate School 2016 국내석사

There has been rapid growth in the world of social networking service (as known as “SNS”). SNS is a popular and important channel for people to communicate in an easier and more convenient way with each other. Because it’s used widely and popular, SNSs, especially Weibo and WeChat in China, have become one of the most important and efficient ways for marketers to attract individuals’ attention and have an effective marketing, particularly in tourism industry. This study involves Chinese tourists’ travel decision making influenced by SNS characteristics; its purpose to make contributions to tourism marketing and travel decision research. Information quality, system quality, timing, reciprocal communication and value are five variables for analyzing SNS characteristics. Three factors, consisting of tourists’ perceived ease of use (PEOU), perceived usefulness (PU) and satisfaction toward SNS using, are used as mediators between SNS characteristics and travel decision making. This study makes an integrated research model from TAM model, D & M IS success model and extended D & M Model to analyze the influence from SNS characteristics, PEOU, PU and satisfaction to travel decision. For the purpose of the research, 302 valid survey responses were collected online by targeting Chinese tourists using Weibo and WeChat. Frequency analysis was conducted to examine the answers’ demographic and the general characteristics. Reliability and an exploratory factor analysis (EFA) was carried out to confirm the reliability of measurement items by SPSS 22.0 and a Confirmatory Factor Analysis (CFA) was utilized to assess the construct validity by AMOS 21.0. Regression analysis was carried out to test the structure relationships among the latent constructs in order to test the hypothesis. The study results show that the new combined research model has a good model fit for analyzing SNS characteristics, PEOU, PU, satisfaction and travel decision. All eight hypotheses proposed in this study were revealed to be supported by the empirical results. SNS characteristics have positive significant influence on travel decision making. What’s more, PEOU, PU and satisfaction have positive mediating effects between SNS characteristics and travel decision, except that PEOU does not have mediated effect between reciprocal communication, value and travel decision. The most important influential factor to travel decision is satisfaction, following by PU. SNS characteristics influence satisfaction strongly, and influence more on PU than PEOU; in addition, PU has stronger influence on satisfaction than PEOU. Regression results also show that tourists consider PU more influential than PEOU. Overall, this research validated the influences of SNS characteristics to travel decision with the mediating effect of PEOU, PU and satisfaction. The findings of this research could be helpful for future researchers, educators and marketers involved in the field of tourism and SNS.

A study on The Stability of Finite Element Glerkin Method for Some Special Case Rosenau Equation

박정준 Graduate School Kyung Hee University 1993 국내석사

Riemannian Structures on Differentiable Manifold : 미분가능 다양체의 리만구조

최황용 Graduate School Kyung Hee University 1994 국내박사

FREDHOLM INTEGRAL EQUATIONS ON A NORMED SPACE

이명현 Graduate School Kyung Hee University 1994 국내박사

Wintering Ecology of Red-crowned Crane Grus japonensis and White-naped Crane Grus vipio in Cholwon Basin, Korea : 철원분지에 도래하는 두루미와 재두루미의 추동생태

배성환 Graduate School Kyung Hee University 1994 국내박사

Effects of Aging on Concentrations of Very-Low-Density-Lipoprotein Cholesterol and Lipoprotein lipase Activities in Rats : 가령이 흰쥐의 최저-밀도 지질 단백질-콜레스테롤 농도와 지단백질 리파제 활성에 미치는 영향

조마야 Graduate School Kyung Hee University 1994 국내박사

Experimental Numerical Studies on Vibrating Equations

박철홍 Graduate School Kyung Hee University 1994 국내박사