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.

하폐수처리를 위한미생물 연료전지공정의 성능에 대한 영향인자

Nguyen Hoang Phuong Khanh 한국해양대학교 대학원 2007 국내석사

미생물 연료전지(Microbial Fuel Cell)는 유기물에 저장된 생화학적 에너지를 전기화학적으로 활성을 가진 미생물을 이용하여 전기 에너지로 변환시키는 장치이다. 본 MFC연구에서는 미생물의 종류(부유미생물, 생물막에 흡착된 미생물), 기질결핍의 영향,전자전달 효율을 높이기 위한 산화환원 매개체의 사용 그리고 미생물의 활성도를 알아보기 위해 여러 가지 종류의 미생물을 식종해 보았고, MFC시스템의 내부저항 및 전위손실에 관한 연구를 수행하였다. 본 연구의 모든 회분식 실험에서는 두개의 반응조로 구성된 ‘H’형 모양의 반응조를 사용하였다. MFC 시스템의 전기 생산 능력을 향상시키기 위해서 본 연구에서는 부유미생물과 생물막에 흡착된 미생물의 영향을 연구했고, 전기적으로 전위차가 다른 혐기성 및 호기성 미생물과 열처리된 미생물을 식종함으로써 미생물 식종에 따른 영향을 연구하였다. 음극에 식종된 다양한 식종 미생물에 대하여 수소생산의 가능성을 알아보았고 그리고 음극 반응조에 Fe3+/Mn4+ 이온과 같은 산화환원 매개체를 이용하여 전자전달에 영향을 주는 요소들에 대해 연구하였다. 부유미생물과 생물막에 흡착된 미생물의 영향을 알아보기 위해 기질결핍 상태와 기질이 충분한 상태의 조건아래서 실험하였다. 실험결과에서 보면 부유미생물을 이용한 실험에서 MFC 시스템의 내부저항이 감소하였다. 그리고 생물막에 흡착된 미생물을 이용한 실험이 전극에 미생물이 흡착되어 있지 않은 것보다 전기생산량이 더 높게 나타났다. 장시간의 기질결핍 조건에서는 정상상태가 유지되는 기간이 더 짧았다. 그러나 본연구에서 기질결핍 조건은 MFC 시스템의 전기 생산에는 효율적이지 않았다. 생물막에 흡착된 미생물을 이용한 기질결핍의 조건에서 전기생산량은 기질이 충분한 상태보다 높지 않았다. 철 이온과 망간이온을 이용한 실험에서 음극 반응조 미생물의 전자전달은 크게 향상되었다. Fe-MFC 와 Mn-MFC의 최대 전류값은 각각 2.06 ~1.92mA, 전력밀도는 69.02 ~ 61.84 mW/m2 를 나타내었다. Fe-MFC 와 Mn-MFC의 쿨롱 효율은 Control MFC보다 2-3배 높았다. 수소 생산 반응조의 최대 전압과 최대 수소 생산량은 Modified Gompertz방정식을 이용하여 만든 곡선식으로 분석하였다. Modified Gompertz방정식에 의하면 혐기성 슬러지를 식종한 MFC의 수소생산량이 46.91%로 가장 놓았고, 쿨롱효율이 66.36%로 제일 높은 효율을 나타냈다. 두 번째는 열처리 슬러지를 식종한 MFC로서 수소생산량 17.80%, 쿨롱 효율 47.20%를 나타냈다. 마지막 호기성 슬러지를 식종한 MFC는 수소 생산량 12.65%,쿨롱 효율 46.80%로서 수소 생산량과 쿨롱 효율이 가장 낮았다. 본 연구의 결과를 통해서 미생물 연료전지의 효율을 향상 시킬 두 가지 요인을 알수 있었다. 첫 번째로 철 이온, 망간 이온 같은 산화환원 매개체를 이용하여 음극에서 양극으로의 전자 이동속도를 향상시킬 수 있다. 두 번째는 미생물연료전지의 음극 반응조에서 수소를 생산 할 수 있다. 본 연구를 토대로 연속식 미생물 연료전지 반응조를 위한 중요한 실험 인자들을 찾을 수 있었다. The Microbial fuel cell (MFC) is a device that converts chemical energy to electrical energy by the catalytic reaction of microorganisms. The present study was to identify the basic characteristics of a MFC, for example, kinds of microorganism (e.g suspended microorganism, attached microorganism), environmetal condition (e.g. starvation), redox mediator (electron shutle) and microorganism sources (types of inoculum), which relate to microbial activity, internal resistance of MFC system and overpotential loss during electricity generation in MFC. Batch mode likely H-shape (dual chambered batch) was used for all experiments in this study. For improvement of electricity generation, this study examined some major factors influencing MFC performance such as the role of suspended (VSS) and/or attached microorganisms (biofilm) in the electron production, influence of redox mediators (e.g. Fe3+/Mn4+ ions) on electron transfer in anode compartment and electric potential of different inoculums (e.g. activated sludge, anaerobic sludge and heat-treated sludge). In addition to, potential of hydrogen production in anode compartment using various bacterial sources were also observed. To determine the effect of VSS and biofilm, power output under various environmental conditions (e.g. starvation, substrate concentration) was analized. The perusal of the results showed that internal resistance of the MFC system was reduced by the control of VSS concentration. Further, power output could be increased to higher value in the presence of biofilm on the surface of anode electrode than the electrode without attached to microorganism. Under starved condition, the longer operation the shorter steady stage was maintained. In this study, however, starvation gave a negligible effect on electricity generation of MFC. Starvation effect on power output by biofilm doesn’t get higher yield than no starvation. Electron transfer from bacteria to anode electrode was significantly enhanced by the presence of ferric and manganese ions. Maximum current of 2.06-1.92 mA and power density of 69.02-61.84 mW/m2 were obtained from Fe-MFC and Mn-MFC, respectively. The coulbomb efficiency of Fe-MFC and Mn-MFC were enhanced up to 2-3 folds comparing to control MFC. Maximum potential of hydrogen production and maximum rate were estimated by simulating a curve of cumulative hydrogen production using Modified Gompertz equation. According to Modified Gompertz equation, 1) MFC inoculated with anaerobic sludge gave highest yield of hydrogen production (46.91%) and the best performance coulomb efficiency of 66.36%, 2) MFC inoculated with heat treated sludge showed 17.80 % yield of hydrogen production and the coulomb efficiency of 47.20%, 3) MFC inoculated by activated sludge achieved only yield of 12.65% hydrogen production and 46.80% of coulomb efficiency. The observed results are significant in two major respects: 1) improvement of electron transfer by medox mediator (using ferric and manganese ions) and 2) capability of MFC system produces hydrogen gas in anode compartment. Based on this work, the findings have important implications for developing a continuous MFC reactor in further study.

Development of an efficient xylose utilizing strain of Saccharomyces cerevisiae by using CRISPR- Cas9

TRAN NGUYEN HOANG PHUONG UNIVERSITY OF SCIENCE AND TECHNOLOGY 2018 국내석사

Engineering Saccharomyces cerevisiae for efficient pentose fermentation and co- fermentation is required to achieve industrial biofuels/biochemical production from lignocellulosic biomass. Yet, pentose utilizing strains require further engineering to improve co-fermentation efficiency and diversify products. In this study, an easily engineerable strain of efficient glucose- xylose co- utilizing S. cerevisiae was developed through combinatorial engineering. Specifically, we integrated xylose metabolic pathway genes into GRE3 and PHO13 loci via marker- free genome editing tool of CRISPR- Cas9. The rationally engineered strain was then further improved through evolutionary engineering generating XUSE strain with comparable xylose fermentation performance with SXA- R2PE, one of the best xylose- fermenting S. cerevisiae. Interestingly, XUSE showed efficient glucose- xylose co- fermentation performance with negligible inhibition of glucose. The whole genome sequencing of XUSE revealed several potential candidates which can be beneficial mutations obtained by evolutionary engineering. In conclusion, our study provides a promising platform strain of S. cerevisiae for biofuels/biochemical production from lignocellulosic biomass. 대표적인 바이오연료 생산균주인 Saccharomyces cerevisiae 를 이용하여 목질계바이오매스로부터 바이오연료/화학소재를 생산하기 위해서는 목질계 바이오매스 내 육탄당 뿐 아니라 오탄당을 효과적으로 전환하는 재조합 균주의 개발이 필수적이다. 현재까지 개발 된 오탄당 전환 재조합 균주는 통합당 전환효율이 낮고, 생산물질이 바이오에탄올에 국한되어 있었다. 본 연구에서는, 바이오에탄올 이외에 다른 바이오연료/화학소재를 생산하기 위하여 추가적인 엔지니어링이 용이한 고효율 육탄당/오탄당 전환 S. cerevisiae 균주를 개발하였다. 이를 위하여, 새로운 유전자 편집기술인 CRISPR- Cas9를 이용하여 자일로스 대사 관련 유전자를 GRE3와 PHO13 loci 에 삽입하였다. 이후 진화공법을 이용하여 재조합균주의 성능을 향상시켜 기존에 보고 된 최고 성능의 자일로스 전환균주(SXA-R2P-E)와 동등한 성능을 가진 재조합균주(XUSE)를 개발하였다. 특히, XUSE는 통합당 발효 시 문제가 되는 글루코스 저해효과가 나타나지 않는 효과적인 통합당 전환균주임을 확인하였으며, 유전체 분석을 통하여 진화공법 과정에서 나타난 돌연변이를 확인할 수 있었다. 본 연구를 통하여 개발 된 재조합 균주는 목질계 바이오매스로부터 바이오연료/화학소재를 생산하기 위한 재조합 균주 개발에 있어서 유망한 플랫폼 균주로서 활용 될 수 있을 것으로 기대된다.

Development of an efficient glucose-xylose co-utilizing strain of Saccharomyces cerevisiae for lignocellulosic biorefinery

Phuong Nguyen Hoang Tran KIST school- UST 2022 국내박사

Lignocellulosic biorefinery enables economical and sustainable production of biofuels and biochemical from biomass. Saccharomyces cerevisiae, regarded as a promising host for lignocellulosic biorefinery, has been recently investigated to extend its product profiles. Nevertheless, the sequential and suboptimal conversion of xylose into target products, together with limited studies on production of biochemical by glucose/xylose co-utilizing strain of S. cerevisiae remains the main challenges for realizing efficient lignocellulosic biorefinery. Here, we aimed to address two essential missions involving (i) developing a powerful glucose/ xylose co-fermenting strain of S. cerevisiae through combinatorial engineering strategy, and (ii) expanding product profiles of engineered S. cerevisiae for achieving efficient lignocellulosic biorefinery. Initially, we improved the xylose assimilation pathway in xylose utilizing strain of S. cerevisiae through optimizing non-oxidative pentose phosphate (PP) pathway. By harnessing the power of DNA assembly and growth-based selection strategies, we were able effectively re-construct the PP pathway within one-step fashion and identified the critical overexpression target in PP pathway, RPE1. The xylose isomerase- harboring strain which expressed the key PP gene indicated an increase of xylose utilization rate and ethanol productivity, by 70.6% and 290.6%, respectively, compared to those obtained with non-expressing strain. This combinatorial approach not only save engineering efforts for strain development dealing with numerous overexpression targets but also more efficiently guarantee the intended effects without the interference of unnecessary genes. Furthermore, we demonstrated highly efficient co-fermentation of lignocellulosic hydrolysates by a newly engineered S. cerevisiae, XUSEA. By reinforcing xylose catabolism and elevating fermentation temperature, significantly improved glucose/xylose co- fermentation was achieved resulting in among the highest ethanol yield (0.48 g/g) and productivity (0.31 g/g.h) during lignocellulosic bioethanol production. Finally, we demonstrated the efficient production of PHB (polyhydroxybutyrate) by the powerful mixed sugar co-fermenting XUSEA strain. Through reconfiguration of PHB pathway sourced from Culpriavidus necator as a polycistronic expression system and enhancing the carbon flux towards PHB pathway using a pull-push-block approach, our strain showed 116.9% higher PHB accumulation over the chassis strain while maintaining high-yield ethanol production during co-fermentation of glucose and xylose. This suggests the feasibility of co-production of biofuels and biochemicals from lignocellulosic biomass. To the best of our knowledge, this study is the first study to report the successful co-production of PHB and ethanol during lignocellulosic fermentation of various biomass. In conclusion, the study provides a powerful glucose-xylose co-fermenting strain of S. cerevisiae which can be served as a promising platform host for lignocellulosic biorefinery.

SERS-Based ssDNA Composition Analysis Using Chemical Enhancement and Machine Learning Methods

Nguyen Hoang, Lan Phuong ProQuest Dissertations & Theses University of Cali 2022 해외박사(DDOD)

Surface-enhanced Raman spectroscopy (SERS) is an attractive method for bio-chemical sensing due to its potential for single molecule sensitivity and the prospect of DNA composition analysis. When employed in conjunction with post-processing machine learning (ML) methods, it becomes a promising technique for effective data analysis, allowing enhanced molecular and chemical composition analysis of information rich DNA molecules. In this work, we leverage metal specific chemical enhancement effect to detect differences in SERS spectra of 200-base length single-stranded DNA (ssDNA) molecules adsorbed on gold or silver nanorod substrates, and then develop and train multiple ML models to predict the composition of ssDNA. Our results indicate that employing substrates of different metals that host a given adsorbed molecule leads to distinct SERS spectra, allowing to probe metal-molecule interactions under distinct chemical enhancement regimes. Leveraging this difference and combining spectra from different metals as an input for our ML models, allows to significantly lower the detection errors compared to manual feature-choosing analysis as well as compared to the case where data from single metal is used. Additionally, we also were able to report on a room temperature inhomogeneous broadening as a function of increased adenine concentration, and employ this feature to develop one- and two-dimensional chemical composition classification models. Last but not least, we report on experimental results indicating that SERS spectra of adsorbed single-stranded DNA (ssDNA) isomers depend on the order on which individual bases appear in the 3-base long ssDNA due to intra-molecular interaction between DNA bases. Furthermore, we experimentally demonstrate that the effect holds under more general conditions when the molecules don't experience chemical enhancement due to resonant charge transfer effect and also under standard Raman scattering without electromagnetic or chemical enhancements. Our numerical simulations qualitatively support the experimental findings and indicate that base permutation results in modification of both Raman and chemically enhanced Raman spectra.