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

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.

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.

Annular CPW Branch-line Bandpass Filter for Planar Integrated Millimeter-wave Circuits

Hoang Nguyen Van 동국대학교 2011 국내석사

Millimeter-wave frequency band is widely applied for high resolution communication such as passive imaging systems, inter-satellite communications, and radar systems, which are being developed using the specific properties of free space propagation. Especially, 94 GHz used in this study has been noticed for the military applications such as a FMCW (Frequency Modulation Continuous Wave) radar system due to the least atmospheric attenuation in millimeter-wave frequency. The millimeter?wave bandpass filters are the key circuit block in the planar integrated millimeter-wave circuits. The planar structure in millimeter-wave circuits reduces the fabrication costs due to the simple process. The typical transmission lines having the planar structure are a microstrip line, a micromachined line and a CPW (CoPlanar Wave guide). In comparison with microstrip line and micromachined line, a CPW has many advantages. A CPW is planar, permits both series and shunt connections of the circuit elements, and has low radiation losses in the odd mode. The CPW parameters are not sensitive functions of the substrate thickness, and a wide range of impedance is achievable on the thick substrates reasonably. Over the last few years, one of the most followed choices in researches on microwave filter topologies is based on the use of circuits with more than one input-to-output signal propagation path. Microwave transversal filters are a good exponent of this trend, appearing from the extrapolation to the analog domain of the theoretical concepts involved in classic design techniques of digital filters. This thesis presents a design of a 94 GHz low-loss annular CPW branch-line bandpass filter for planar integrated millimeter-wave circuits. In this design, we use annular branch-line coupler as a transversal filtering section by loading the coupled ports of the coupler with suitable open load stubs and taking the isolated port as an output node. The 94 GHz annular CPW branch-line bandpass filter has a low insertion loss of 0.71 dB with a 14.9 % 3 dB relative bandwidth at center frequency of 94 GHz and return loss is better than -27 dB at the center frequency. The designed bandpass filter achieves a good performance for planar integrated millimeter-wave circuits.

Towards A Fault-Tolerant Routing Protocol for Mobile Ad hoc Network

Hoang Nguyen,  Minh Duc 명지대학교 대학원 2023 국내석사

MANET(Mobile Ad Hoc Network)은 기존 네트워크 리소스 없이 통신 시스템을 신속하게 배포해야 하는 시나리오에 특히 적합합니다. 예를 들어 MANET은 기본 라우팅 프로토콜이 중요한 데이터 패킷의 보급 기능을 유지하는 데 중요한 자연 재해에서 구조 대원 간의 상호 통신 프로세스를 용이하게 할 수 있습니다. 그러나 모든 MANET의 백본, 즉 라우팅 프로토콜은 노드의 통신 범위, 고속 이동성 및 에너지 용량 제약에 의해 제한됩니다. 본 연구에서는 이러한 MANET 노드의 특성에 의존하여 데이터 전송을 위한 신뢰할 수 있는 경로를 결정하는 내결함성 임시 주문형 라우팅 프로토콜(FT-AORP)을 제안했습니다. 그 후, 발견된 경로 중 2개는 내결함성을 최대화하기 위해 원본 데이터 패킷의 복제본을 전송하는 데 사용되었습니다. 또한 OMNeT++ 네트워크 시뮬레이터를 사용하여 네트워크 노드 수, 노드 속도, 데이터 패킷 전송률의 세 가지 시뮬레이션 매개 변수에 대한 광범위한 시뮬레이션 실험을 통해 제안 시스템의 성능을 평가했습니다. 시뮬레이션 결과는 FT-AORP가 다른 기준 라우팅 프로토콜과 비교하여 패킷 전달 비율을 크게 개선하고 종단 간 지연을 줄였으며 전송 경로의 더 높은 잔류 에너지 수준을 유지했음을 보여주었습니다. Mobile ad hoc networks (MANETs) are particularly suited for scenarios that demand rapid deployment of a communication system without any existing network resources. For instance, a MANET can facilitate the intercommunication process between members of a rescue party in a natural disaster, where the underlying routing protocol is crucial to maintaining the dissemination capability of data-critical packets. However, the backbone of every MANET, i.e., their routing protocol, is limited by the communication range of nodes, their high-speed mobility, and the capacity constraints of energy. This study proposed a fault-tolerant ad hoc on-demand routing protocol (FT-AORP) that relies on these characteristics of MANET nodes to determine reliable paths for data transmission. Subsequently, two of the discovered paths were used to transmit the duplicates of an original data packet to maximize fault tolerance. Further, using the OMNeT++ network simulator, the performance of the proposed system was evaluated through extensive simulation experiments against three simulation parameters: the number of network nodes, node speed, and data packet sending rate. The simulation results demonstrated that FT-AORP greatly improved the packet delivery ratio, reduced end-to-end delay, and maintained a higher residual energy level of the transmission path, compared to other baseline routing protocols.

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.

Event-driven descriptive models by internet of knowledge

Nguyen, Hoang Long 중앙대학교 대학원 2019 국내박사

사물 인터넷의 대두와 함께, 우리는 소셜 미디어 사용자들을 대규모 소셜 데이터를 생성하는 소셜 센서로 볼 수 있게 되었다. 이 소셜 데이터로부터 지식을 추출함으로써, 우리는 우리 사회에 어떤 일이 일어나는지에 대한 보다 깊은 이해를 얻을 수 있다. 하지만, 소셜 데이터와 데이터 원들의 막대한 규모는 그 자체로 그들을 처리하기 위한 현행 기술들에 큰 도전 과제가 되고 있다. 더욱이, 이로부터 추출된 지식들은 우리 사회의 변화에 따라 동적으로 변화하기 까지 한다. 위에서 언급된 문제들을 해결하기 위하여, 본 논문에서는 지식 인터넷(IoK; Internet of Knowledge)를 정의하는데 초점을 맞춘다. 이 새로운 개념은 다양한 데이터 원들로부터 추출된 소셜 지식들을 그들의 주요한 특성인 유동성, 상황 정보, 연관 관계를 바탕으로 설명할 수 있도록 한다. 이에 따라, 나는 소셜 이벤트들을 이해하고 연결하여 지식 인터넷을 생성하기 위한 이벤트 기반 기술 모델(Event-driven Descriptive Model)을 제안한다. 또한, 소셜 이벤트들의 이야기화(Storification)이라는 본 연구의 활용 사례를 사례 연구들과 함께 보임으로써, 본 연구의 활용 가능성을 논의한다. 마지막으로, 본 연구에서는 지식 인터넷을 기술하기 위한 자동화된 프레임워크를 구현하였다. 이 시스템을 통하여, 사용자들은 추가적인 학습이나 비용 소모 없이, 소셜 데이터를 수집하고 분석하는데 필요한 주요한 기능들을 제공받을 수 있다. 이 프레임워크의 성능은 소셜 빅 데이터를 다루는 역량에 초점을 두고 평가되었다. With the support of the Internet of Things, people are considered as social sensors to generate a massive amount of social data. By extracting knowledge from social data, we obtain deeper insights into what is happening in our society. However, the sheer volume of social data sources is actually a big challenge for current techniques for effectively analyzing them. Besides this, social knowledge is not static but dynamically changes with the evolution of our society. In order to solve aforementioned problems, my dissertation focuses on defining the Internet of Knowledge (IoK), which is a new concept with three essential characteristics (i.e., dynamic, contextual, and linked properties) for connecting knowledge from various data sources to understand our society. In this regard, I propose event-driven descriptive models for comprehending and linking social events to generate IoK. An application called Storification accompanied by some case studies are discussed in detail for proving the utilization of my research. Finally, an automated framework is implemented for describing IoK. With this integrated system, users are provided with necessary features, which support collecting and analyzing social data, to obtain all essential knowledge without spending their own effort and time. The performance of this framework is carefully evaluated to demonstrate its ability to handle social big data.

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.

(The) application of immobilized chlorella sorokiniana in poly(vinyl alcohol) cryogels for nutrient removal

Nguyen, Hoang Tam Sungkyunkwan university 2020 국내석사

미세조류는 바이오매스 내에 있는 영양소를 흡수하는 능력 때문에 폐수처리를 하는데 있어서 좋은 주체다. 미세조류를 기반으로 한 시스템은 부가가치가 높은 부산물로 자급자족적 치료를 달성하기 위한 영양소 제거에 대해 집중적으로 연구되어왔다. 그러나 처리수에서 미세조류를 분리시키는 것은 최상의 처리효율을 얻기 위한 주요 난제 중 하나이다. 미세조류의 고정화는 이러한 문제를 해결하고 미세조류를 기반으로 한 폐수처리의 가능성을 높이는 효과적인 접근법이 될 수 있다. 폴리비닐알코올(PVA)은 저비용, 높은 내구성, 화학적 안정성, 그리고 살아있는 세포에 대해 독성을 나타내지 않기 때문에 잠재적인 고정화 물질로 꼽히고 있다. 본 연구는 반복적 동결-해동법에 의한 미세조류인 Chlorella sorokiniana를 캡슐화하기 위한 PVA 크라이오겔의(cryogel) 사용을 처음으로 평가하고 폐수처리에서의 적용을 평가한다. 제작 후 고정된 미세조류를 함유한 PVA 크라이오겔을 이용하여 다양한 조건에서의 연속반응식 광생물반응기(continuous stirred-tank photobioreactor)에서 영양소 제거효율을 평가했다. PVA 크라이오겔에 고정된 Chlorella sorokiniana의 사용 시 혼합영양배양조건하에서 총 질소를 완전히 제거하였으며 총 인을 최대 97.2%까지 제거했다. 영양소 제거 시 PVA 크라이오겔의 최대 용량은 총 질소와 총 인 제거 시 각각 0.033mg N/cube/d 와 0.0047mg P/cube/d로 나타났다. 또한 미세조류의 영양소 제거에 영양을 미치는 유기탄소와 질소공급원의 형태를 조사하여 적절한 배양 조건을 찾아냈다. PVA 크라이오겔의 크기에 따른 성능을 비교한 결과, 6mm 크기를 가진 크라이오겔이 영양소 제거와 반응기 내에서의 겔의 물리적 안정성을 위한 최적의 크기로 결정되었다. Microalgae are an attractive phycoremediation agent for wastewater treatment due to its ability to assimilate nutrient into biomass. The application of microalgae-based systems has been studied intensively for nutrient removal to achieve self-sufficient treatment with value-added byproducts. However, the separation of microalgae from treated water is the major challenge to achieve the ultimate treatment efficiency. Immobilization of microalgae can be an effective approach to overcome this issue and enhance the feasibility of microalgae-based wastewater treatment. Poly(vinyl alcohol) (PVA) is a potential immobilization material due to its low cost, high durability, chemical stability, and non-toxicity to viable cells. This study for the first time evaluates the use of PVA cryogels to encapsulate microalgae Chlorella sorokiniana by the iterative freezing-thawing method and its application in wastewater treatment. After being successfully fabricated, the PVA cryogels with immobilized microalgae were tested for nutrient removal efficiency in a continuous stirred-tank photobioreactor under different conditions. The results showed that the use of microalgae Chlorella sorokiniana immobilized in PVA cryogels achieved complete TN removal and up to 97.2% TP removal under mixotrophic cultivation in wastewater. The maximum capacities of PVA cryogel in removing nutrient were calculated to be 0.033 mg N/cube/d and 0.0047 mg P/cube/d, respectively for TN and TP removal. The effects of influent organic carbon and the form of nitrogen source on the nutrient removal efficiency of microalgae were also investigated to find the appropriate culturing condition. Comparing the performance of different PVA cryogel sizes, 6-mm cryogel was determined to be the optimal size for nutrient removal and mechanical stability of the gel inside the reactor.