Investigation of Copper-containing photocathode for enhanced solar hydrogen production via photoelectrochemical water splitting

Nguyen Hoang Lam 영남대학교 대학원 2023 국내박사

최근 몇 년간, 환경 친화적이고 오염물질이 없는 수소 생산 방법으로써 광촉매 물분해에 대한 관심이 증가하고 있습니다. 이 분야에서의 주요 과제 중 하나는 태양광을 이용하여 효율적으로 물을 분해할 수 있는 시스템을 저렴하고 비독성인 재료를 사용하여 개발하는 것입니다. PEC(광전기화학) 수분해 시스템에 사용되는 광전극에서는 상업 생산에 사용될 수 있는 특정 속성을 갖는 반도체가 이상적입니다. 그러나 이러한 물질들의 보고된 효율은 때때로 이론적 최대값보다 낮습니다. 따라서 광촉매 활성을 향상시키기 위해서는 광전극의 효율을 제한하는 요인들에 대한 명확한 이해가 필요합니다. 본 논문의 4, 5, 6 장에는 실험에 대한 구체적인 내용이 수록되어 있습니다. 4장에는 XRD, SEM 및 TEM 기술을 사용하여 분석된 구리 기반 분말 NPs (Cu/Cu2O 나노복합상)의 결정 구조에 초점을 맞추었으며, W-H, N-R, Rietveld 정제 등의 몇 가지 방법을 사용하여 PNCs의 결정 구조를 심도있게 분석하기 위해 노력했습니다. 용액 합성 방법 중 다양한 합성 조건에서 PNC의 결정 구조 변화를 관찰하기 위해 두 가지 실험을 진행하였습니다. 해당 실험을 통해 결정 구조의 철저한 분석과 비교를 하였습니다. 5장에서는 CuO 박막의 구조적 및 광학적 특성 및 PEC 성능에 초점을 맞추었습니다. 브로콜리 모양을 가진 이 박막은 물분해 응용을 위한 광전극으로 사용하기 위해 수열법을 사용하여 제조하였습니다. XRD, SEM, XPS, PL 및 UV-Vis와 같은 다양한 기술을 사용하여 박막의 형태학적, 구조적 및 광학적 특성을 측정하였습니다. 또한 이러한 박막의 PEC 성능은 삼전극 시스템에서 평가되었습니다. 6장에서는 CuO 박막의 성능 향상 방법에 대해 설명합니다. PEC 물분해 응용에서 CuO의 단점을 해결하기 위해 수열법, 스핀 코팅 및 열처리를 통해 FTO 기판 상에 CuO와 CuBi2O4를 합성하여 이종접합 광전극을 제작했습니다 (FTO/CuO/CuBi2O4). 각 샘플의 특성(합성 방법, 구조, 구성, 형태 등)은 다양한 합성 조건에서 철저히 논의하였습니다. CuBi2O4를 CuO와 접합함으로써 두 개의 반도체가 밀접하게 결합되어 광전극의 PEC 효율이 향상되었습니다. 또한 CuO 층은 전자 생성 층으로 작용하고, CuBi2O4 층은 광부식을 방지하고 전자를 전극/전해질 접합부로 운반하여 HER을 용이하게 합니다 In recent years, there has been a growing interest in using photocatalytic water splitting as a way to produce hydrogen that is both environmentally friendly and free of pollutants. One of the primary challenges in this field is developing systems that can efficiently dissociate water using sunlight, while also relying on inexpensive and non-toxic materials. For photocathodes used in PEC water splitting systems, it is ideal to have semiconductors with specific properties that can be used in commercial production. However, the reported efficiencies for these materials are often below their theoretical maximum values. Therefore, it is important to have a clear understanding of the factors limiting the efficiency of these photocathodes if the photocatalytic activity is to be improved. The experiments in this dissertation are structured into three sections. The fourth chapter of this dissertation focused on the crystalline structure of copper-based powder NPs (Cu/Cu2O nanocomposite phase), which was analyzed using XRD, SEM, and TEM techniques. There are some methods such as W-H, N-R, and Rietveld refinement were used to deeply analyze the crystalline structure of PNCs. Two experiments were conducted to observe the changes in the crystalline structure of PNC under different synthesis conditions in the colloidal solution method. A thorough analysis and comparison of the crystalline structure were performed. In the fifth chapter, the focus is on the structural, and optical properties of CuO thin films, as well as their PEC performance. These thin films, which exhibit a broccoli-like structure, were prepared using a hydrothermal method to serve as a photocathode for water splitting applications. Various techniques, including XRD, SEM, XPS, PL, and UV-Vis, were used to measure and characterize the morphological, structural, and optical properties of the thin films. Additionally, the PEC performance of these thin films was evaluated in a three-electrode system. In the sixth chapter, a method for enhancing the performance of CuO thin films is described. To address the drawbacks of CuO in PEC water splitting applications, a heterojunction photocathode was produced by synthesizing CuO and CuBi2O4 on an FTO substrate (FTO/CuO/CuBi2O4) through hydrothermal methods, spin coating, and annealing. The characteristics of each sample under various synthesis conditions, including synthesis method, structure, composition, and morphology are thoroughly discussed. The integration of CuBi2O4 with CuO resulted in the two semiconductors being closely bonded, enhancing the PEC efficiency of the photocathode. Additionally, the layer of CuO acted as the electron-generating layer, while the CuBi2O4 layer prevented photo-corrosion and aided in the transportation of carriers to the electrode/electrolyte interface to facilitate HER

Asymmetric synthesis of N,O-Acetals and heterobiaryl compounds

Nguyen Hoang Nguyen 한양대학교 대학원 2023 국내박사

Catalytic asymmetric synthesis is a powerful tool for the preparation of optical pure compounds which are essential building blocks in a range of bioactive molecules, pharmaceutical drugs, natural products, and functional materials. Over the years, significant progress has been made in the development of novel catalytic asymmetric methodologies, enabling the synthesis of diverse chiral scaffolds. Given the background, this thesis aims to describe the development of the enantioselective synthesis of chiral N,O-acetals catalyzed by chiral Brønsted acid, and the atroposelective synthesis of axially chiral heterobiaryls catalyzed by transition metal. Part I: Transacetalization for the preparation of enantio-enriched N,O-acetals In part one, a new transacetalization protocol catalyzed by chiral Brønsted acid is described. Oxidation of ynamides by mCPBA led to β-oxygenation and resulted in α-N,O-acetals with a benzoyloxy functionality. These N,O-acetals are formed in high yields and can be stored at room temperature. Yet, they can be activated by a chiral Brønsted acid and underwent enantioselective transacetalization with a secondary alcohol into optically enriched N,O-acetals with an alkoxy function. This is postulated to proceed by way of an N-acyliminium ion that is ion-paired with the chiral phosphate anions. Subsequent diastereoselective transformations occurred to provide useful products, such as β-hydroxy-N,O-acetals and α-hydroxyaldehyde, with exceptional selectivity according to Felkin-Anh model. Part II: Asymmetric Synthesis of Heterobiaryl Compounds A strategy to invert the normal polarity of indoles in the heterobiaryl coupling was developed for chemo-, regio- and enantioselective heterobiaryl synthesis via C–H oxidation. N-Carboxyindoles may be employed as electrophilic coupling partners. A Brønsted acid or Cu(I) catalyst was able to activate N-carboxyindole, leveraging cross-coupling with phenols. Firstly, with N-carboxyindoles as umpoled indoles, an exclusively ortho-selective coupling with phenols has been realized in a racemic fashion. A range of phenols and N-carboxyindoles coupled with exceptional efficiency and selectivity at ambient temperature. Remarkably, the substrates bearing redox-active aryl halides smoothly coupled in an orthogonal manner under Cu(I) catalysis. The reaction was proposed to occur through SN2′ substitution with Brønsted acid or via radical mechanism with Cu(I) catalysts. Secondly, the atropselective heterobiaryl coupling have been demonstrated, employing the Cu(I)/chiral bisphosphine catalytic system. Through the optimization, we successfully found catalytic systems employing (R)-difluorphos, (R)-P-Phos, or (R)-DMM-Garphos ligands that can deliver the desired heterocoupling product in excellent yield with good enantiocontrol. The current Cu(I)/chiral bisphosphine catalytic system turned out to be exceptionally general in terms of both umpoled indoles and phenolic coupling partners. Mechanistic experiments suggested that a radical mechanism is involved in the oxidative addition of N-carboxyindoles, which accounted for the requirement of phenols and ortho-selectivity.

항원제시세포로서 CD40-활성 B 세포와 수지상세포의 기능 비교

NGUYEN HOANG TUYET MINH 전남대학교 대학원 2008 국내석사

종양항원에 특이적인 세포독성 T 림프구를 이용한 종양의 세포면역 치료는 종양에 대해서 특이 반응을 보이면서 부작용이 매우 적은 치료법으로 주목을 받고 있다. 이와 같이 종양-특이 T 세포 면역 반응을 유발시키기 위해서는 T 세포에 효과적으로 항원을 제시할 수 있는 항원제시세포의 매개가 필수적이다. 가장 강력한 항원제시세포로 알려진 수지상세포를 임상에 적용하기 위해서는 수회에 걸쳐서 다량의 수지상세포를 투여하여야 하는데, 시험관 내에서 수지상세포를 증폭할 수 없을 뿐만 아니라 대량 생산하는데 고비용이 소요되어서 임상적용을 하는데 어려운 문제점이 있다. 본 연구자는 이러한 수지상세포의 단점을 보완하여 종양에 대한 세포면역치료의 효과를 증대시킬 수 있는 대체 항원제시세포로서 CD40-활성 B 세포의 이용 가능성을 알아보기 위해서 CD40-활성 B 세포와 수지상세포의 항원제시기능을 비교 분석하였다. 정상인의 말초혈액에서 단핵구를 분리한 후 다시 림프구와 단구를 분리하였다. 분리된 단구는 GM-CSF와 IL-4를 첨가한 배양액에서 미성숙 수지상세포로 분화시켰으며, 배양 6일째에 IL-1β, TNFα, IL-6 및 PGE2를 첨가하여 표준 성숙 수지상세포로 분화시켰다. 림프구는 IL-4를 첨가한 배양액에서 CD40 리간드를 핵산전달감염시킨 J558 세포주와 공조배양하여 14일동안 B 세포를 활성화시켰다. 유세포분석기를 이용한 면역표현형 분석에서 CD40-활성 B세포와 수지상세포에서 항원제시세포의 기능과 연관된 costimulatory factor (CD80, CD86), 부착분자(CD54) 및 MHC-II 분자의 발현 정도가 두 세포에서 유사하게 높게 발현되었다. CCR7은 CD40-활성 B 세포에 비해 수지상세포에서 현저히 높게 발현되었지만, CD40-활성 B 세포의 표면에서도 이 분자의 발현이 증가되었다. CD40-활성화 B세포의 자가 T 림프구와 동종 T 림프구에 대한 자극 능력은 수지상세포에 비해서 다소 낮았다. 종양 특이 세포독성 T 림프구는 자가 CD3+ T 세포를 ARH77 세포주 융해질이 부가된 CD40-활성 B 세포나 수지상세포로 1주일 간격으로 3차례 반복 자극하여 제조되었으며, 자가 종양에 대한 세포독성 T 림프구에서 분비된 IFF-γ 분비 세포의 수는 ELSPOT 분석을 통해 측정하였다. 수지상세포로 자극되어 제조된 종양 특이 세포독성 T 림프구는 CD40-활성 B세포로 자극되어 제조된 것 보다 IFN- 분비능이 더 높게 나타났다. 그러나 CD40-활성 B 세포는 시험관내에서 대량 증폭이 가능함으로 종양항원-특이 세포독성 T 세포를 유도할 때 종양항원을 부가시킨 CD40-활성 B세포의 수를 두배 증가시켜 배양할 경우 발현된 IFN-γ 분비 세포의 수가 현저히 증가되어 수지상세포와 유사한 효과를 나타내었으며, 세포종양에 대한 살상효과는 오히려 약간 더 높게 나타났다. 결론적으로 본 연구는 종양 특이적인 세포면역치료에 있어서 CD40-활성 B세포가 향후 수지상세포를 대체할 수 있는 차세대 항원제시세포로써 매우 유용한 역할을 할 수 있음을 제시하였다. The use of cellular vaccines reliably generates tumor antigen-specific T cells both in animal models and in human. Highly efficient antigen presentation by professional antigen presenting cells (APCs) is a requisite for the development of T cell mediated immunity in vitro and in vivo. The potential need for continuous application of large number of dendritic cells (DCs) which are though as the most powerful APC might be a principle obstacle for clinical use of DC vaccines. In this study, we evaluated and compared the functions of antigen presentation of CD40-activated B (CD40-B) cells with those of DCs to confirm whether CD40-B cells could be an efficient alternative source of APCs which can compensate the limitation of DCs for cancer immunotherapy. Lymphocytes and monocytes were isolated from peripheral blood mononuclear cells (PBMCs) of normal donors using Percoll gradient centrifugation. To generate CD40-B cells, lymphocytes were co-cultured with CD40L-transfected J558 cell line in the presence of IL-4. Monocyte-derived DCs were differentiated from the same donor with conventional cytokine cocktail of IL-1, TNFα, IL-6 and PGE2. Both of CD40-B cells and DCs consistently expressed a high level of cell surface molecules related to APC function, such as CD80, CD86, CD54 and HLA-DR. Although the level of expression of CCR7 on mature DCs was much higher than that on CD40-B cells, this molecule was clearly up-regulated on CD40-B cells. Although DCs had superior capacity of allogeneic T cell stimulation compare to CD40-B cells, the level of cytotoxicity of cytotoxic T lymphocytes (CTLs) induced by CD40-activated B cells pulsed with ARH77 lysates against ARH77 was higher than that of CTLs induced by DCs pulsed with ARH77 lysates. CTLs stimulated by mature DCs pulsed with ARH77 lysates showed a larger number of IFN- secreting cells than those stimulated by CD40-B cells pulsed with ARH77 lysates in a culture ratio of 5:1. However, CTLs stimulated by CD40-B cells pulsed with ARH77 lysates at the 1:2.5 culture ratio demonstrated the increased number of IFN γ-secreting cells against ARH77 as much as CTLs stimulated by tumor antigen pulsed DCs at 5:1 culture ratio displayed. Because CD40-B cells can be easily expanded in vitro, these results suggest that CD40-B cells are an excellent alternative source of professional APCs for antigen-specific immunotherapy for cancer.

VOCs abatement using a DBD non-thermal plasma device

NGUYEN HOANG PHUONG Graduate School of Kyung Hee University, 2018 국내석사

Decomposition of VOCs such as toluene and MEK was performed to evaluate the operating efficiency of a novel surface dielectric barrier discharge non-thermal plasma device. Two reactors with different scale and configuration were assembled to carry out the experiments. The device was tested with various operating parameters including relative humidity (0 – 90% RH), discharge power (4.3 – 6.5 kV and 60 – 200 Hz) and discharge area (215 – 645 cm2) using a big reactor chamber. Then, the removal efficiency of single and mixture gases was comparatively evaluated using small serial reactors. The results showed a good decomposition efficiency for dilute phase flow (90 – 95% for inlet concentration of 20 ppmv). Removal rate decreased with the increment of inlet VOCs (50 – 60% for initial concentration of 100 ppmv). Relative humidity posed a limiting effect on VOCs destruction, and an optimum RH was found at 20% RH for toluene. Increase of both input power and plasma area positively influenced pollutant control, but caused reduction in energy efficiency of the system. Low energy efficiency was more significant for high concentration of inlet pollutants. On the other hand, the decomposition of single species of toluene and MEK or of mixed VOCs revealed that single MEK was easier to be completely eliminated than toluene. MEK acted as a limiting factor for mixture removal. Besides, higher molecular weight toluene aided high decomposition efficiency. In addition, ozone concentration was measured at a quite high level in this study (up to 2000 ppmv). Ozone generation rate was in proportional to the inlet power. Even though ozone played a little role in oxidizing the target pollutants, it can be utilized for further VOCs destruction as a source of oxygen atom with the assistance of suitable catalysts.

Fault diagnosis of rolling element bearings for rotating machinery using advanced signal processing methods

Nguyen, Hoang Phuong University of Ulsan, School of Electrical, Electro 2015 국내석사

Recent years, the demand for developing the reliable condition monitoring and fault diagnosis systems of the rotating machinery has been significantly increasing for the purpose of improving the availability and reliability of the industrial systems. These condition monitoring and fault diagnosis systems aim to detect abnormal symptoms at the early stages of the machinery failures, and precisely identify their root causes to prevent potentially fatal breakdown of machines, increase safety and product quality of the industrial systems, and reduce the maintenance costs. In that sense, this thesis presents comprehensive condition monitoring and fault diagnosis schemes of low-speed rolling element bearings for rotating machinery by using acoustic emission (AE) signal processing methods. To determine the operational health of bearings for detecting incipient failures at the early stages, this thesis proposes a robust condition monitoring methodology for bearing failures that employs empirical mode decomposition (EMD)-based denoising and discrete wavelet packet transform (DWPT)-based envelope analysis techniques. Firstly, the signal-to-noise ratio of an unknown incoming AE signal is enhanced by using an EMD-based denoising technique, which can effectively remove noise components inherent in the AE signal. Since intrinsic information about bearing failures can exist in either low- or high-frequency ranges, this method then explores the impact of sub-band signals decomposed by the DWPT technique, which is one of the most effective decomposition tools that can split the noiseless AE signal into uniformly spaced frequency sub-bands, and discriminates the most useful sub-band signal. Finally, envelope analysis is applied to the most informative sub-band signal in order to obtain an envelope power spectrum showing information about defective bearings. For reliably diagnosing the root causes of bearing defects, this thesis presents a comprehensive fault diagnosis methodology for rolling element bearing combining wavelet packet transform (WPT)-based kurtogram and vector median discriminant criterion (VMDC)-based feature analysis technique. The proposed approach first characterizes and extracts useful characteristic features related to bearing health conditions in time-domain, frequency-domain, and envelope power spectrum of an unknown incoming AE signal by using a wavelet kurtogram technique. Based on the linear discriminant analysis (LDA) technique, an enhanced VMDC-based feature analysis algorithm is then proposed to select the most discriminative bearing fault-related signatures from the heterogeneous pool of extracted features. Finally, the classification for fault diagnosis is performed by employing the Naïve Bayes (NB) classifier.

Supplementing Hongjam recovered behavioral and biochemical defects in APOE-/- mice

Hoang, Nguyen Minh Anh 한림대학교 대학원 2024 국내석사

홍잠 섭취에 의한APOE -/- 마우스의 행동 및 생화학적 결함 회복 2023. 석사학위논문 호앙 유엔 민 안 노화생명과학과 지도교수 고 영 호 일반적으로 경도인지장애(MCI)는 노화과정 중에 나타나는 정상적 기억력 감퇴와 기억력이 과도하게 손상되면서 나타나는 질병인 치매(dementia) 사이의 과도기 단계이다. 현재 치매 치료에 허가된 의약품들은 원치 않는 심각한 부작용이 보고 돼서, 아직도 치매를 대처하는 최선의 방법은 노화에 따른 기억력 저하로 인한 MCI로 진행을 억제하거나, 다시 정상으로 회복 시킬 수 있는 방법의 개발이 필요하다. 누에의 숙잠을 쪄서 제조하는 홍잠(HJ)은 최근의 연구결과에 따르면 기억력 개선 효과와 간 기능개선 효과와 건강수명 증대 효과가 있음이 밝혀졌다. HJ의 영양성분은 70% 이상의 단백질과 15%의 지질과 다양한 종류의 식물 유래 화합물들과 미네랄 등이 다량으로 함유되어 있다. 하지만, HJ이 유전적인 문제에 의하여 발병하는 고 지혈증과 혈관성 치매의 발병에 영향을 줄 수 있는지 여부는 연구되지 않았다. 본 연구에서는 APOE Knock Out (APOE-/-)마우스 모델을 이용하여 다양한 기억력 및 운동 능력 비교 연구와 생화학적인 연구를 진행하여 HJ가 어떠한 영향을 미치는 지에 대한 연구를 진행했다. 이전의 연구에 따르면, APOE-/- 암컷 쥐는 정상 대조군에 비해 유의하게 높은 치매 발병 위험과 고지혈증을 가지고 있다. 하지만, 본 연구에서 HJ를 섭취한 암컷 APOE-/- 쥐는 운동 능력과 공간 기억력과 사교성 및 새로운 자극에 대한 호기심이 일반 사료 섭취 암컷 APOE-/- 쥐와 비교하면 통계적으로 유의하게 향상됐다. 또한 HJ 섭취는 콜레스테롤, 젖산, 중성지방 수치에도 긍정적인 영향을 주었다. 그리고, HJ를 섭취한 실험동물 뇌 조직은 미토콘드리아 활성이 증가되어 있었다. 이 결과는 HJ의 섭취가 뇌를 포함한 다양한 조직과 기관의 마이토콘드리아의 활성을 증진시켜서 기능을 활성화 시킴으로 달성되는 것으로 추측된다. 본 논문의 연구 결과를 보면, HJ 섭취에 따른 효과는 단일 성분에 의해 발생하는 것이 아니라 단백질, 지방산, 미네랄, 식물 유래 화합물들의 상호작용에 의한 것으로 사료된다. 본 논문은 APOE의 유전적 결함에 의하여 발병하는 고지혈증과 혈관성 치매는 HJ을 섭취함으로써 질환의 발병을 억제하고 진전을 늦출 수 있음을 보여주므로 이에 대한 추가 연구가 필요하다. 키워드 : 알츠하이머병, APOE-/- 마우스 모델, HongJam, 행동검사, 효소분석, 미토콘드리아 복합체, ATP Mild cognitive impairment (MCI), in general, increases the risk of developing dementia and is often considered a transitional phase from healthy cognitive aging to unhealthy dementia. Due to unwanted side effects of commercial medicines, developing new treatments that can suppress memory deterioration during MCI is not only of high interest but a crucial necessity for a healthy aging. HongJam (HJ) contains a remarkable amount of nutrients and phytochemicals which are not only necessary for the nervous system function but also control blood cholesterol and glucose levels. However, it is not still clear whether HJ can influence the late-onset of AD as well as high triglycerides level. In order to determine the effectiveness of HJ food on cognition in the APOE-/- mice, several behavioral tasks and enzyme assays are used, which differ in sensitivity to detect cognitive impairments for this strain. Such rigorous assessments give insights into the most sensitive influence on the subject’s cognitive deficits based on the effect of HJ food concentration. Although female mice exhibited significantly greater risk of developing AD and greater dementia compared to normal controls, this study observed an improvement in female APOE-/-mice fed with HJ on better spatial memory, sociability and curiosity for new stimulations along with improved motor function. Moreover, HJ food also showed the positive effects on cholesterol, lactate and triglycerides level. In addition, it is possible that HJ proteins might increase mitochondrial activity to improve lifespan of the test subjects. Although the precise underlying mechanism and the details of the active substances in HJ food remained elusive, this herbal medicine might offer a novel approach for the prevention of dementia disease. The enhancing effects of HJ food are not caused by a single component, but by the combination of proteins, fatty acids, minerals, and phytochemicals interaction together which activate various signaling mechanisms including the mitochondrial activity increase in brain tissues. As a whole, in the future, it is necessary to study whether HJ may have precise mechanism in therapeutic effect of APOE-/- mice with clear AD symptoms and high triglycerides levels.

Experimental investigations and simulation on oxy-circulating fluidized bed combustion for high CO2 capture

Nguyen, Hoang Khoi Kunsan National University 2021 국내박사

Oxy-circulating fluidized bed combustion (Oxy-CFBC) has been developed in the power generation sectors to reduce amount of the greenhouse gas. Because this technology can produce a high content of CO2 in the flue gas for capture, and reducing pollutant emissions to the atmosphere. This study investigates oxy-combustion characteristics and dynamic behaviors to build the oxy-fuel database for the design, optimization, and operating strategy, using 0.1 MWth oxy-CFBC test-rig and a dynamic modeling. Three experiments were carried out to explore the combustion characteristics, pollutant emission behaviors, combustion efficiency, ash characterization, the possibility of carbon dioxide negative emission, and performance analysis of potassium capture with bed material additive. Three used fuels were sub-bituminous, lignite and the wood pellet with low heating value (less than 5000 kcal/kg). Investigation 1 explored oxy-coal fired characteristics, using a blend of sub-bituminous coal and lignite and solely lignite. The results showed that the CO2 purity can be obtained 96 vol.% (as dry basis) without air-ingress, and through a smooth transition from air mode to oxy mode. In investigation 2, effects of various input oxygen levels (from 21 to 29 vol.%), and different ratios of the domestic wood pellet co-firing with coal were explored. The high CO2 concentration can be obtained with 90 vol.% in all testing cases, indicating a good performance at an oxygen input level of 24 vol.% for high combustion efficiency, and low emission (Reduction to 29.4 % NO, 31.9 % SO2, and 18.5 % CO, compared to air-fired condition). The pollutant contents of SO2, CO, NO were found to be reduced with increasing biomass ratios. The CO2 negative emission was estimated to be – 647g/kWth with biomass firing 100%. In investigation 3, the characteristic of wood pellet with and without kaolin has been explored under pre-mixed of kaolin and wood pellet (kaolin/fuel ratio: 0.25) and separately feeding kaolin and wood pellet (kaolin/fuel ratio: 0.21). Results obtained from the XRF and XRD analysis revealed that the kaolin addition could reduce fouling index from 0.43 without kaolin to 0.15 (kaolin/wood pellet ratio: 0.25) and 0.07 (kaolin/wood pellet ratio: 0.21), and the presence of kalsilite (KAlSiO4) within the ash, which has a high melting temperature. In addition, the performance of potassium capture improved by up to 24 %. In terms of oxy-fuel operation, SO2 emission was observed to be decreased with kaolin employed, performing a high CO2 concentration of over 93 vol.% and combustion efficiency of over 99%. The obtained results indicate that kaolin can be an effective additive in oxy-biomass combustion system. The experiments also revealed in detailed advantages and operating techniques for the oxy-CFBC. The experimental database and operating techniques are a good reference to operation the oxy-circulating fluidized bed systems in a large-scale. For dynamic simulation, a dynamic model was developed by using the conservation principles of mass and energy, and reactions of coal to predict the dynamic behaviors of the gas concentration in the air-fired mode and oxy-fired mode under a configuration of 0.1 MWth oxy-circulating fluidized bed combustor. The CO2 concentration is predicted by about 13.8 vol.% in the air-fired and about 88.3 vol.% (wet basis) in oxy-fired condition. The dynamic behaviors during the transition process from air-fired mode to oxy-fired mode, and vice versa process were investigated. The results presented a smooth switching by using similar signal inputs of main flow rates: air-flow, purified oxygen flow, and recycled flue gas flow. The shifting duration was found to be about 13 min from the air-fired case to the oxy-fired case, and about 7.5 min for the vice versa process. By dynamic analysis under load changes and air ingress, the results revealed that the high purity of produced CO2 is highly dependent on the air ingress. With 5% of air in-leakage, the CO2 concentration was reduced by 25 % (from 88.2 vol.% to 66 vol.%). By validation against experimental data, the simulated results from the model may help engineers an understanding of, as well as gain skills in operation of the commercial plants. 발전 분야에서 온실 가스를 줄이기 위해 산소 순환 유동층 연소 (Oxy-CFBC)가 개발되었습니다. 이 기술은 점점 더 엄격 해지는 환경 규제 하에서 다양한 연료를 연소 할 수 있는 능력이 있으며, 높은 CO2 농도의 분리를 촉진하고 바이오매스를 동시에 연소함으로써 대기로 배출되는 온실 가스의 양을 크게 줄일 수 있다. 발전 분야에서 온실 가스를 줄이기 위해 산소 순환 유동층 연소 (Oxy-CFBC)가 개발되었습니다. 이 기술은 점점 더 엄격 해지는 환경 규제 하에서 다양한 연료를 연소 할 수 있는 능력이 있으며, 높은 CO2 농도의 분리를 촉진하고 바이오매스를 동시에 연소함으로써 대기로 배출되는 온실 가스의 양을 크게 줄일 수 있다. 본 연구에서는 0.1MWth oxy-CFBC 테스트 장비와 동적 모델링을 사용하여 연소로의 산소 연소 특성과 동적 행동을 조사하여 산소 연료 데이터베이스 또는 설계, 최적화 및 운영 전략을 구축한다. 연소 특성, 오염 물질 배출 거동, 연소 효율, 회분 특성화, 이산화탄소 마이너스 방출 가능성 및 층물질 첨가제를 사용한 칼륨 포집 성능 분석을 조사하기 위해 세 가지 실험이 수행되었다. 사용 된 세 가지 연료는 아역청탄, 갈탄 및 낮은 발열량 (5000 kcal / kg 미만)의 목재 펠릿이다. 조사 1에서는 아역청탄과 갈탄을 혼합하거나 갈탄만을 사용하여 산소 석탄 연소 특성을 조사하였다. 결과는 별도의 공기 유입 없이 그리고 공기 모드에서 산소 모드로의 원활한 전환을 통해 CO2 순도를 96 부피 % (건조 기준)로 얻을 수 있음을 보여주었다. 조사 2에서는 다양한 투입 산소 농도 (21 ~ 29 vol. %)의 영향과 목재 펠릿과 석탄의 혼소 비율에 대한 영향을 조사하였다. 산소 농도 24 vol. %를 적용했을 때 배출부에서 높은 90 vol. % CO2 농도를 얻을 수 있으며, 높은 연소 효율과 낮은 오염 배출 성능을 나타내었다 (29.4 % NO, 31.9 % SO2, 및 18.5 % CO, 공기 연소 조건과 비교). SO2, CO, NO의 오염 물질 함량은 바이오매스 비율이 증가함에 따라 감소하는 것으로 나타났다. CO2 마이너스 배출량은 바이오매스로 100 % 연소 될 때 – 647g / kWth로 추정되었습니다. 조사 3에서는 카올린과 목재 펠릿을 미리 혼합하거나 (카올린 /연료 비율: 0.25) 카올린과 목재 펠릿을 별도로 공급 (카올린 / 연료 비율 : 0.21)하여 카올린 유무에 따른 목재 펠릿의 연소 특성을 조사했습니다. XRF 및 XRD 분석에서 얻은 결과에 따르면 카올린을 첨가하면 fouling index 가 카올린이 없을 경우 0.43에서 카올린 첨가시 0.15 (카올린 / 나무 펠릿 비율 : 0.25) 및 0.07 (카올린 / 나무 펠릿 비율 : 0.21)으로 감소되었다. 회분내에는 그 융점이 매우 높은 칼실라이트 (KAlSiO4)가 존재하였다. 또한 칼륨 포집 성능이 최대 24 % 향상되었습니다. 산소 모드 운전의 경우, 카올린을 사용하면 SO2 배출량이 감소하는 것으로 관찰되었으며, 93 vol. % 이상의 높은 CO2 농도와 99 % 이상의 연소 효율을 나타냈다. 얻어진 결과는 카올린이 산소-바이오매스 연소 시스템에서 효과적인 첨가제가 될 수 있음을 나타낸다. 실험은 또한 oxy-CFBC에 대한 자세한 장점과 운전 기술을 보여준다. 이는 대규모 산소 순환 유동층 시스템 운전에 좋은 참고 자료가 될 것이다. 질량 및 에너지 보존 법칙과 석탄의 반응속도식을 사용하여 연소로의 동적 모델을 개발하였으며, 이를 통하여 0.1 MWth 산소 순환 유동층에서 공기 연소 모드 및 산소 연소 모드에서 가스 농도의 동적 거동을 예측했습니다. CO2 농도는 공기 연소 상태에서 약 13.8 부피 %, 산소 연소 상태에서 약 88.3 부피 % (습식기준) 로 예측되었다. 공기 연소 모드에서 산소 연소 모드로 전환하는 과정에서 동적 거동을 살펴보았다. 결과는 주요 유량의 유사한 신호 입력 (공기 흐름, 정화 된 산소 흐름 및 재활용 된 연도 가스 흐름)을 사용하여 원활한 전환을 나타낸다. 모드 간 이동 시간은 공기 연소 케이스에서 산소 연소 케이스까지 약 13 분, 그 반대의 경우 약 7.5 분인 것으로 밝혀졌다. 부하 변화 및 공기 누출시 동적 분석 결과는 생산된 CO2의 고순도는 공기 유입에 크게 의존한다는 것을 보여준다. 5 %의 공기 누출로 인하여 CO2 농도는 25 % 감소한다 (88.2 vol. %에서 66 vol. %로). 실험 데이터에 대한 검증을 통해 모델의 시뮬레이션 결과는 엔지니어가 상업 플랜트의 운영 기술을 이해하고 습득하는 데 도움을 줄 수 있다.

Cosmic-ray neutron probe soil moisture over different vegetation covers

Nguyen, Hoang Hai 성균관대학교 수자원전문대학원 2020 국내박사

Accurate field-scale soil moisture characterization is essential for hydro-meteorological, agricultural management and natural disasters mitigation. Cosmic-ray neutron probe (CRNP) is an innovative technique to provide both field-scale surface soil moisture (SSM) and root-zone soil moisture (RZSM) monitoring, which is expected to bridge the scale gap of point-based in-situ and pixel-based satellite measurements. However, there are several limitations related to CRNP utilization, icluding (1) the uncertainties in traditional CRNP calibration, (2) the shallow CRNP penetration depth due to various hydrogen sources presence that restricts RZSM measurement and (3) the unevaluable application of CRNP-based soil moisture for field-scale satellite soil moisture retrievals. To overcome these limitations, this study focuses on three objectives: (1) improving CRNP calibration with preferred soil wetness conditions selection, (2) improving RZSM measurement by combining CRNP and representative in-situ soil moisture through a merging framework (3) retrieving SAR Sentinel-1 (S-1) soil moisture using CRNP soil moisture For CRNP calibration improvement, better cosmic-ray soil moisture (CRSM) product can be obtained with calibration considering wettest soil conditions. Nonlinear weighting approach slightly improved the calibration performance. Over different vegetation covers, the temporal variations of measured fast neutrons and SSM are strongly depends on the canopy density and vegetation types. For CRNP penetration depth extension, the results indicated that local conditions, including differences in vegetation coverages and percolation rates majorly control the merged RZSM. Superior performance achieved by the merging framework demonstrated its robustness in improving field-scale RZSM measurement compared to other products. For SAR Sentinel-1 (S-1) soil moisture retrieval, interdependence of radar backscatter, vegetation, and CRSM is the main factor that control the accuracy of estimated soil moisture. Based on this interdependence, vine copula models has been developed for S-1 soil moisture inversion at different canopy types with uncertainty quantification. Accurate product with lowest uncertainties was obtained at herbaceous areas where low vegetation are present, whereas high uncertainties were at forested areas, where the double bounce effects induced by tree trunks and stems significantly affects S-1 radar backscatter signal.

Environmental pollution and bioconcentration by perfluoroalkyl substances in Korea and Vietnam

Nguyen, Hoang Lam Chonnam National University 2016 국내박사

Environmental contamination monitoring is the preliminary work to investigate ecotoxicology and potential risk on human health of a pollutant. Data on the occurrence and spatial distribution characteristics of a target pollutant is necessary for further understanding of the exposure level of the chemical in an ecosystem, which can be an important factor that directly or indirectly induces adverse effects on biotic and abiotic media in ecosystems, ecological food chains or human health. Perfluoroalkyl substances (PFASs) are a group of fully fluorinated chemicals which has the unique properties including resistance to hydrolysis, photolysis, bio-degradation and thermal stability and have been used in diverse commercial application since the 1950s. Although the production and use of the major concerns PFASs in environmental contamination, perfluorooctane sulfonic acid (PFOS) and its related chemicals had been widely banned, their homologues, neutral precursor and other new PFASs continue to be produced. Due to their persistence and bioaccumulation, some PFASs can elicit harmful effects in terrestrial and aquatic organisms. The toxicity and persistence of PFASs in human have raised considerable concerns and several biomonitoring studies in environment throughout the world. Despite this, available studies on PFASs in Korean and Vietnamese freshwater ecosystems are limited. The overall aim and objective of this study are to determine and support the baseline contamination extent and bioconcentration of PFASs in both abiotic and biotic matrices involved in freshwater aquatic environment of Korea and Vietnam. The ecological and human health potential risk due to expose of PFASs in the environmental matrices were evaluated. The target chemicals analyzed in this study are 13 non-polymer and ionic PFASs including nine perfluorocarboxylic acid (PFCAs; C4 and C6-C14) and four perfluoroalkyl sulfonic acid (PFSAs; C4, C6, C8 and C10). Water (n = 55), sediment (n = 55) and tissues (n = 466) of blood, liver and whole body of various freshwater fishes including crucian carp (Carassius auratus), catfish (Silurus asotus), common carp (Cyprinus carpio), northern snake head (Channa argus), skygager (Erythroculter erythropterus), Korean piscivourous chub (Opsariichthys uncirostris), barbell steed (Hemibarbus labeo), blue gill (Lepomis macrochirus), bass (Micropterus salmoides), mandarin fish (Siniperca scherzeri), and medaka fish (Oryzias latipes) were collected from thirty sampling sites located in six major rivers and lakes (Namhan River, Bukhan River, Nakdong River, Nam River, Yeongsan River and Sangsa Lake) and canals in nine rice field regions (Yeosu, Gwangyang, Hadong, Sacheon, Naju, Gimhae, Andong, Kunsan, Dangjin) in Korea from 2012 to 2014 were analyzed for the occurrence of PFASs. Furthermore, the spatial distribution of PFAS concentration in coastal water from forty two sampling sites in the southeastern coastal areas of Korea including Ulsan, Busan and Gwangyang Bays was investigated. PFOS and perfluorooctanoic acid (PFOA) were consistently found as predominant PFASs in waters and sediments. The greatest PFASs concentration of these compounds were 15.1 ng PFOS/L and 42.2 ng PFOA/L for waters and 1.09 ng PFOS/ g wet weight (ww) and 1.82 ng PFOA/g ww for sediments. The greatest concentrations of PFOS and PFOA in water samples were found in sites located downstream of sewage water treatment plants (WWTPs). PFOS (up to 365 ng/ml) and long chain PFCAs (LC-PFCAs) including perfluorodecanoic acid (PFDA; up to 261 ng/g wet weight), perfluoroundecanoic acid (PFUnDA; up to 141 ng/ml) and perfluorododecanoic acid (PFDoDA; up to 158 ng/ml) were predominant PFASs which accounted for 81.2% ± 16.4% of the total PFASs concentration in fish tissues analyzed. The mean ratios of PFAS concentration between crucian carp blood and liver were above 2 suggesting higher levels in blood than in liver of this fish. Significant positive correlations (p < 0.001) were observed between PFOS, PFDA, PFUnDA concentrations in blood and liver tissues of crucian carp. This result suggests that blood can be used for nonlethal monitoring of these compounds in this fish. A general ascending order of mean total PFASs concentration of water (0.013 ng/ml) < sediment (0.44 ng/g ww) < bass liver (0.64 ng/g ww) < northern snake head liver (9.71 ng/g ww) < common carp liver (10.1 ng/g ww) < blue gill liver (14.7 ng/g ww) < catfish liver (16.4 ng/g ww) < medaka fish whole body (22.7 ng/g ww) < crucian carp liver (24.5 ng/g ww) < barbel steed liver (50.9 ng/g ww) < mandarin fish liver (51.5 ng/ g ww) < crucian carp blood (83.7 ng/ml) < skygager liver (169 ng/g ww) < Korean piscivourous chub liver (351 ng/g ww). Except for the Nakdong River and Yeongsan River, the total PFAS concentrations in water samples collected in rivers and lakes from Korea were below 10 ng/L. No potential chronic and/or acute effects on aquatic organisms due to PFOS and PFOA levels measured in waters were expected. Potential risk of PFOS and PFOA exposure in sediment to benthic organisms and the immediate risk of PFOS exposure to fish were not likely. The interim Korea water quality criteria for PFOA (23.3 ng/L) and PFOS (34.0 ng/L) were calculated. Among individual PFASs, only PFOS was found to bioaccumulate to all of twelve fish tissues analyzed in this study. The mean bioconcentration factor (BCFs) of PFOS (concentration in biota/concentration in water) was as follows: bass liver (63 L/kg) < common carp liver (7,664 L/kg) < northern snake head liver (7,952 L/kg) < catfish liver (8,511 L/kg) < medada whole body (8,874 L/kg) < blue gill liver (9,245 L/kg) < crucian carp liver (11,577 L/kg) < Korean piscivorous chub liver (16,948 L/kg) < crucian carp blood (31,938 L/kg) < skygager liver (31,949 L/kg) < mandarin fish liver (34,788 L/kg) < barbel steed (58,086 L/kg). Although PFOS concentrations in water samples were comparable with those of PFOA, the BCFs of PFOA in fish tissues were hundred-fold less than those of PFOS. Similar to PFOS, LC-PFCAs including PFDA, PFUnDA, PFDoDA and PFTrDA were very bioaccumulative in most of fish tissues. Different PFAS composition patterns in fish tissues suggest species-specific and tissue-specific bioaccumulation. Only PFDA and PFOS were consistently found to be very bioaccumulative in medaka fish whole body tissues in 2012 – 2014. The overall trend of PFOS contamination in water is comparable to the trend of that found in whole body of medaka fish and significant positive correlation between PFOS concentration in water and medaka fish whole body (p = 0.014) was found. Medaka fish was suggested as a good bioindicator for monitoring PFOS in water. Despite the relatively consistent of PFASs concentration in environmental matrices, there is a continuous accumulating trend of PFASs in tissues of aquatic organisms in Korea whether they exposure to point sources (crucian carp) or non point sources (medaka fish) of PFASs discharging into their habitat. The profiles of occurrence and spatial distribution of PFASs in various environmental media suggest the existence of several sources of PFASs and the continuing input PFASs in Korean aquatic environment. Water (n = 36), sediment (n = 10) and biota tissues (n = 162) of liver, whole body, muscle and soft tissues from five fish species including stripped snake head (Chana striata), dusky sleeper (Eleotris fusca), shark catfish (Pangasius elongatus), flying barb (Esomus danricus), tilapia (Oreochrommic niloticus), two crustacean species including giant prawn (Macrobranchium rosengbergii) and freshwater paddle crab (Varuna litterata), one gastropod species of golden applesnail (Pomacea canaliculata) and one bivalve species of golden freshwater clam (Corbicula fluminea) were collected from 36 sampling sites in major river basins of Vietnam including the Sai Gon, Red, Ma, Da Rang, Da Nong, Cai, Quan Truong, Dong Nai and Mekong Rivers from 2013 to 2015 and analyzed for the presence of PFASs. Occurrence of PFASs in canal water in rice field areas (n = 3) coastal water (n = 2), tap water (n = 12) and well water (n = 8) collected in eight different regions in Vietnam was investigated. Water (n = 8) and sediment (n = 6) samples collected in the discharge canal of wastewater treatment plants (WWTPs) and landfills were analyzed to identify sources of pollution. In Vietnam, the PFASs concentration determined in waters, sediment and biota collected in major rivers were relatively low in a comparison with those previously reported in other countries including Korea. Overall, the results indicate a general ascending order of mean PFASs concentration in river ecosystem consisting water (1.79 ng/L), sediment (0.21 ng/g ww), gastropod tissues (0.33 ng/g ww), crustacean tissues (0.44 ng/g ww), bivalve tissues (0.73 ng/g ww) and fish tissues (2.81 ng/g ww). PFOS and PFOA were predominant PFASs in surface water with the greatest concentrations of 53.5 ng/L and 40.2 ng/L found in a surface water sample collected from a channel that receives wastewater treatment plant discharge, respectively. Except for the Sai Gon River, the total PFAS concentrations in water samples collected from the Red, Ma, Da Rang, Da Nong, Cai, Quan Truong, Dong Nai and Mekong Rivers from were less than 5 ng/L. PFOS and perfluorohexane sulfonic acid (PFHxS) were found as predominant PFASs in sediment. The greatest PFAS level in biota tissues was found as 16.9 ng PFUnDA/ g ww for a fish liver. Some long-chain PFCAs including perfluorononanoic acid (PFNA), PFUnDA and perfluorotridecanoic acid (PFTrDA) as well as PFHxS were more abundant than other compounds in biota tissues. Similar to profile of PFASs distribution in Korea aquatic ecosystems, different PFAS composition patterns in biota tissues suggest compound-, species-, and tissues-specific bioaccumulation. No potential chronic and/or acute effects on aquatic organisms due to exposure to PFOS and PFOA levels measured in surface water, and human health risk due to consuming tap and well water as drinking water were expected. The interim Vietnam water quality criteria for PFOA (9.32 ng/L) and PFOS (2.96 ng/L) were calculated. The rank order of mean BCF of PFOS in biological groups was; crustacean (115 L/kg), gastropod (1,117 L/kg), fish (1,120 L/kg) and bivalve (2,110 L/kg). WWTP discharge is probably the “point source” of aqueous discharges of PFASs into the aquatic environment. The profiles of occurrence and spatial distribution of PFASs in various environmental media in this study provide baseline information for a better understanding of the PFAS contamination characteristic in Vietnam. Although the relatively greater contamination levels of PFASs in Korea than those in Vietnam were found in the present study, it is difficult to explain this. Industrialization degree and economic growth gap may be attributed to this difference but the relationship between these factors and environmental pollution is complex and multi-dimensional. The relatively greater concentration of PFASs in environmental matrices from Korea than those from Vietnam in the present studies is consistent with previous studies and represents the historical and ongoing deposition of PFASs in Korean and Vietnamese aquatic environment. Further studies should focus on identifying the existence and status of PFASs sources in Korean freshwater ecosystems and more studies with greater numbers of water and aquatic organism samples are needed for accurate the sources and pathways of exposures, and bioaccumulation of PFASs in aquatic environment in Vietnam. It’s necessary to evaluate the combined potential adverse effect of multiple PFASs on aquatic organisms, especially long chain PFASs.

Mobile PCB design for 20Gbps PAM4 signaling

Hoang, Nguyen Van Sungkyunkwan university 2020 국내석사

These days, the explosion of the Internet of Things (IoT) and Artificial Intelligent (AI) demands the development of compatible hardware. Which includes a high-speed processor (CPU, GPU), high-capacity, and fast-access memory (RAM, DRAM), as well as the interconnect between the above devices in the motherboard, backplane, etc... One of the significant factors that degrade the efficiency of the whole system is the limitation due to data transmission between components, which is usually called the “bottleneck”. The bottleneck phenomenon can come from two factors. First is the data coding (RZ, NRZ, PAM4), which determines the limited bandwidth of all components in the system. Second is the bandwidth of connectors, interconnect (transmission line), which causes data loss and noise. Recently, PAM4 modulation is preferred in high-speed systems, because it can provide twice a data rate compared to the NRZ at the same bandwidth budget. However, PAM4 is more sensitive to noise than NRZ, so that it requires a sophisticated circuit such as CDR and equalizer at both transceiver and receiver. To lighten the burden on receiver designing, we should increase the performance of the interconnect. In this thesis, the author focusses on PCB optimization, especially at the vias, solder pads geometry, and transition segments, to improve the quality of the PAM4 signal at the receiver. The design was applied to 100mm of interconnect, which transfers the 20Gbps data rate for mobile application.