EXPERIMENTAL AND MODELLING STUDIES OF FENTON REACTION SYSTEMS

남궁규철 University of Manchester Institute of Science and 2002 해외박사

Anthropogenic pollutants, particularly non-biodegradable or refractory organic pollutants have been one of the main causes leading to environmental degradation since the late 20th century. Advanced oxidation processes (AOPs) have been developed as a promising technology for destruction of those pollutants at a low level in water for the last two decades. However, since they are relatively costly for practical applications and are affected by many factors some of which may be unknown, research to support design of cheaper processes is required. Recently, Fenton and modified Fenton (particularly photo-Fenton) oxidation processes have emerged as one of the cost-effective AOPs. The work in this thesis focused on Fenton oxidation, which is the basis of all modified Fenton oxidation processes. Controlling parameters in the Fenton oxidation of organic pollutants are pH, dosage and ratio of hydrogen peroxide and ferrous iron, temperature, mixing, oxygen, scavenging materials, materials forming complexes with iron species, properties of organic pollutants, and initial concentration of organic pollutants. The objective of this study was to investigate the in fluence of ionic strength, anions, oxygen, and the type of organic substrate on the Fenton reaction. A mechanistic model was developed to simulate the Fenton reaction system and results from the model were compared with experimental results. The increase of ionic strength from 0.01 to 0.3 M led to a decrease of degradation of hydrogen peroxide during the Fenton reaction. Comparison of the effects of nitrate ions and sulphate ions on Fenton reactions showed that sulphate ions caused a significant decrease of H₂O₂ decomposition. The experimental data and modelling results supported the hypothesis that direct reactions of sulphate ions and intermediates from the Fenton reaction led to reduction of H₂O₂ decomposition. The modelling results also supported the view that Fe(III)-sulphate complexes may have low reactivity. A lumped factor (α) for the reduction of Fe(III) complex reactivity, which seems to arise from sulphate complexation, was introduced into the model. Modelling results with α=0.80∼0.90 were in good agreement with experimental data. In the early stages of oxidation of 4-chlorophenol by Fenton's reagent, experimental results showed that TOC removal is affected significantly by oxygen concentration in the solution. It was suggested that there were fast reactions between oxygen and organic intermediate species. The decomposition of hydrogen peroxide was enormously faster in the presence of 4-chlorophenol than in the absence of 4-chlorophenol. Modelling results supported that the occurrence of a Hamilton-like system (catechol-like organics/Fe(III)/ H₂O₂) during Fenton oxidation of 4-chlorophenol could lead to the fast decomposition of hydrogen peroxide by reducing Fe(III) to Fe(II). Further modelling work and experiments were carried out to investigate the influence of organic substrate on the Fenton reaction. Fenton oxidation of 1,4-dioxane did not show such fast degradation of hydrogen peroxide as 4-chlorophenol. A simple model assuming stepwise oxidation of organic substrate and its intermediates by hydroxyl radicals, often used by other researchers, was tested with comparison of 4-chlorophenol and 1,4-dioxane. While modelling results for 1,4-dioxane were in relatively good agreement with experimental data, the simple model totally failed to simulate the 4-chlorophenol / Fenton reagent system. These results supported the view that the 4-chlorophenol / Fenton reagent system could lead to the occurrence of a Hamilton-like system. It is suggested that the approach to development of a more generalised model, which contains parameters investigated in this work, for Fenton oxidation systems could be used for other AOPs.

Productivity analysis in construction using an expert system approach

조문영 University of Manchester Institute of Science and 1994 해외박사

본 논문에서 기술된 연구의 목적은 건설사업의 생산성에 크게 영향을 미치는 주요 관리요인 (managerial factor)들을 정하고 이들 각 요인간의 因果關係 (causal relationship)를 구축한 연구모델 (causal research model)의 정립과, 이 연구모델을 기초로 첨단 컴퓨터기술 응용분야인 지식을 기반으로 하는 전문가 시스템 (Knowledge Based Expert System)기법을 이용하여 건설사업의 생산성분석을 위한 프로토타입 (prototype)시스템의 개발이다. 본 시스템은 건설사업에 직접 참여한 건설관리자 (construction manager)나 기술인력 (engineer)이 건설현장에서 생산성과 연관된 문제가 발생하였을 경우 이에 대한 분석, 발생원인의 규명을 위한 진단 (diagnose) 및 이의 해결방안을 전문가를 대신하여 제시한다. 즉 그 문제와 연관된 정보를 현장참여자와의 질의 및 응답을 통해 수집하여 현황을 파악하고, 이를 시스템안에 구축되어 있는 추론엔진 (inference engine)과 지식베이스 (knowledge base)에 적용, 분석하여 확율적으로 가장 가능성이 높은 원인을 찾아 해결방안을 제시한다. 시스템의 지식구조 (knowledge structure)는 78개의 생산성에 영향을 주는 管理要因들과 이들간의 상호 因果關偈의 형태로 이루어진 10개의 의사결정트리 (decision tree)로 구성되었다. 본 시스템의 개발환경은 퍼스널컴퓨터를 기반으로 전문가시스템툴 (expert system tool)을 활용하여 개발하였으며 총 11개의 프로그램으로 구성되었다. 본 연구의 결과는 건설사업의 생산성 분석을 위한 정립된 이론적 모델을 전산화하여 현장에서 실제 활용할 수 있는 가능성을 보여주었고, 또한 개발된 전문가시스템은 경험이 부족한 기술인력이나 대학교의 건설관련학과 학생들의 교육에 이용할 수 있음을 보여주었다.

Analysis of an Inkjet Print Head

신동윤 University of Manchester Institute of Science and 2003 해외박사

The full analysis of oscillatory fluid flow in a piezoelectric drop-on-demand (DOD) cylindrical inkjet print head is performed in this thesis. It starts from the development of an analytic solution for an immersed piezoelectric cylinder, which is used to measure the speed of sound in a liquid with measured impedance and phase angle data, because acoustic characteristics plays a key role in a DOD inkjet print head. The actuation of a piezoelectric (PZT) transducer and the oscillatory fluid behaviour inside a chamber are modelled with analytic solutions. In addition, the analytic solution for a tapered nozzle is developed and proper pressure boundary conditions upstream and downstream are derived. The mean axial velocity history, computed with analytic solutions, is fed into a further drop formation simulation using a simplified one-dimensional (1D) finite difference method (FDM) model. The strengths and weaknesses of the 1D approach are identified. The uncertainty in these solutions is discussed and a numerical factor is introduced into the developed analytic solutions. With this factor determined empirically, numerical predictions concerning drop mass delivered per second are compared with experimental data and the influence of print head design is discussed.

Cooling water system design

김진국 University of Manchester, Institute of Science and 2001 해외박사

Research on cooling systems to date has focussed on the individual components of cooling systems, not the system as a whole. Cooling water systems should be designed and operated with consideration of all the cooling system components because of the interactions between cooling water networks and the cooling tower performance. In re-circulating cooling water systems, cooling water from the cooling tower is supplied to a network of coolers that usually has a parallel configuration. However, re-use of cooling water between different cooling duties enables cooling water networks to be designed with series arrangements. This allows better cooling tower performance and increased cooling tower capacity, both in the context of new design and retrofit. A novel methodology has been developed for the design of cooling networks to satisfy any supply conditions for the cooling tower. A model of cooling tower performance allows interactions between the performance of the cooling tower and the design of cooling water networks to be explored systematically. An approach to the automated design of cooling water systems has been developed from the systematic investigation of interactions between cooling tower performance and the cooling water network design. As the series arrangement of heat exchangers results in a pressure drop increase owing to the cooling water re-use, an optimization model for cooling water networks has been developed to achieve multiple objectives such as pressure drop constraints, complexity of networks and efficient use of the cooling tower. A new node-superstructure model is suggested to consider the intensive property of pressure and the sequence of connections simultaneously. Physical insights are used to provide a good initialization for the resulting optimization problem. In debottlenecking situations, better design of the cooling network using the new method, including increasing cooling tower blowdown, taking hot blowdown and strategic use of air coolers, can all be used to avoid investment in new cooling tower capacity and to improve the performance of the cooling tower in a systematic way. A case study is presented to illustrate the new design method for cooling water systems and to suggest retrofit solutions for overloading of cooling systems. Reduction of cooling water make-up is considered by recovering wastewater into the cooling systems from the observation that wastewater before or after treatment can be used as a cooling water makeup replacement. Temperature restrictions on aqueous effluents dictate that streams with a temperature higher than the permitted level needed to pass through cooling systems to reduce the effluent temperature before discharge. This thesis introduces methods for the design of effluent cooling systems. Inappropriate mixing of effluents with different temperatures reduces opportunities to recover heat from effluents and degrades driving forces for cooling systems. A new systematic method is introduced for the segregation strategy for effluents to deal with effluent temperature problems most effectively by a combination of heat recovery and effluent cooling. This can lead to distributed effluent cooling systems. The design procedure sets targets before design. A design procedure then allows the targets to be achieved by following design rules for distributed cooling. An optimization model has been developed to search for the most economic design of cooling systems. A case study involving retrofit is presented to illustrate the design methodology and the optimization model of cooling systems.

Internationalisation of Korea industry : a study of the performance of the plant and construction industry

유규열 University of Manchester Institute of Science and 1989 해외박사

Since the mid-1970s, Korea has adopted an export-led economic policy based upon the development of her heavy chemical industry to make her export industry more competitive. The essence of this policy was to continue with steady export growth and to maintain its status as a Newly Industrialised Country (NIC). In this respect, it was thought that the pursuit of plant and construction exports could significantly contribute to a sustained export performance and the growth of the national product. The internationalisation of the plant and construction industry was assumed to have certain implications for Korea's export performance. This study attempts to investigate differences between Korean and non-Korean firms and between plant and construction firms in terms of: a) firm characteristics; b) success and failure among tenders; c) risk management; d) contract strategy; and e) international competitiveness. The study has been undertaken by means of sociological and organisational analysis from an overall national level down to the firm level. A more deductive macro level approach has been pursued to diagnose the Korean export environment in terms of its international competitiveness and technological competence. While the investigation has involved general sociological, economic and technological considerations, more emphasis has been given a) to the failure of the industry to achieve a higher level orders for plant and construction exports and b) to an estimation of the international competitiveness of the industry and its ability to achieve a sustained export performance. The empirical work of the study was carried out at the country and industry level and involved the choice of a sample of 62 firms (29 plant and 33 construction firms) in 12 countries. Resorting to data obtained through questionnaires, interviews and documentary sources, an inductive approach has been employed to examine the export performance of these firms and the implications far Korean firms. The findings of the study indicate that, in general, Korean firms have been inferior to non-Korean firms in terms of technology, tender and contract strategy, risk management and competitive strategy. These disadvantages would have been lessened had government export and industrial policy and corporate strategy been accompanied by adequate policies in the field of: a) improving the technological level; b) enhancing productivity; c) adjusting industrial structure; d) cultivating small and medium-sized enterprises; e) making advances into overseas markets; and f) improving governmental support systems. The research has shown that successful tendering for plant and construction exports can best be explained by: i) cooperation with importing countries (i.e. joint-ventures and consortia membership); 11) the quality of bids (i.e, meeting delivery date, after-sales services, product quality and experience of the tender process); iii) relationships with importing countries (close political and cultural ties); iv) willingness to meet incidental conditions imposed by importing countries (e.g. demands for favourable and competitive credit terms and a commitment to high local procurement ratios); and v) price competitiveness.

Synthesis of Continuous Heterogeneous Catalytic Reactors

황성원 University of Manchester Institute of Science and 2003 해외박사

A new methodology has been developed to design non-isothermal, non-adiabatic heterogeneous catalytic fixed-bed and tubular reactors. This thesis initially focuses on the use of side-stream and inert catalyst to control the temperature profiles, in addition to external cooling. These two aspects of reactor design have so far been developed separately and mainly applied to laboratory-scale reaction systems. In this work, a practical and optimal reactor design procedure is illustrated considering the combination of these two systems simultaneously. Nitrobenzene hydrogenation and ethylene oxidation in non-isothermal and non-adiabatic reactors are used as case studies. Catalyst characteristics such as pellet diameter, shape and activity distributions inside a pellet are considered simultaneously for reactor design. Various types of non-uniform activity distributions inside a pellet are modelled and optimised for the maximisation of a certain objective such as yield or selectivity. For example, Dirac-δ, layered and general non-uniform distribution profiles such as egg-shell, egg-yolk and middle peak distributions are applied for the reactor design. The research demonstrates that different catalyst distribution profiles can approach the optimum performance. Whilst it is known that the Dirac-δ profile (an its step-function equivalent) always gives the best performance for undegraded catalyst, other profiles can offer advantages under degraded conditions. A profile-based synthesis approach is applied to generate various shapes of activity profiles for multiple sections along the reactor during the optimisation of nonuniform catalyst pellets. A case study with the ethylene oxidation process illustrates that the catalyst characteristics such as activity distribution profiles inside a pellet, sizes and shapes can be manipulated to control the temperature through the reactor very effectively, leading to significant improvements in selectivity or yield. The non-uniform catalyst pellet is further applied to various reactor configurations such as inert mixing and side stream distributions. This work is the first to consider all of these effects simultaneously. The methodology for the design of an optimum heterogeneous catalytic reactor is extended further by considering non-uniform catalyst pellet design under catalyst deactivation such as non-selective or selective catalyst deactivation. The activity distributions inside catalyst pellets for a certain number of reactor beds have been optimised simultaneously over the catalyst lifetime for the maximisation of the overall reactor performance. The consideration of catalyst deactivation for a certain catalyst lifetime produces different reactor design results, which are more reliable and practical than the results obtained in the absence of deactivation. Furthermore, the temperature control strategy during the reactor operating time is accounted for. A profile-based synthesis method has been used for the generation of the temperature profile through time. These novel methods produce optimum reactor and catalyst design with a temperature control strategy for the catalyst life. The approach is illustrated using a methanation processes. For optimisation, the combination of deterministic optimisation and stochastic optimisation such as SQP (Successive Quadratic Programming) and SA (Simulated Annealing) are used together with the profile generation method. This approach enhances the computational capability to solve a highly non-linear problem in an efficient way.

Limit and shakedown analyses of axisymmetric structures by numerical methods

염대준 University of Manchester Institute of Science and 1996 해외박사

본 연구에서는, 축 대칭 하중을 받는 축 대칭 구조물의 리미트와 쉐이크다 운 하중 (Limit and Shakedown Load)을 예측하기 위한 여러가지 수치 해석 기법들을 제시하고, 그들을 컴퓨터 프로그램으로 개발하여 아래와 같이 명명하 였다. 즉, ·UPLAP (Upper Bound Limit Analysis Program) ·LOLAP (Lower Bound Limit Analysis Program) ·EFESA (Equilibrium Finite Element Stress Analysis Program) UPLAP과 LOLAP은 쉘 이론 (Shell Theory)에 근거하고, 각각 상한 및 하한 리 미트 해석 정리 (Upper and Lower Bound Limit Theorem)을 이용하여 작성되었다. 따라서 이들을 이용하면 상대적으로 얇은 벽 두께를 갖은 축 대칭 구조 물에 대한 상한 (Upper Bound)과 하한 (Lower Bound)의 리미트 하중을 동시에예측할 수 있으므로, 실제 리미트 하중 (True Limit Load)의 확신있는 예측이가능하다. EFESA는 쉘 이론 대신 3 차원 해석법에 기초함으로써 일반화된 형상에 대한 해석을 가능케 한다. 이를 위하여, 솔리드 (Solid)요소를 기본으로 하는 평 형 유한 요소법 (Equilibrium Finite Method)을 도입하고 리미트와 쉐이크다 운 해석을 위해 하한 해석법을 채용하는 새로운 방법을 제시·정립하였다. 결과적으로 EFESA를 이용하면 축 대칭인 임의 형상의 구조물에 대한 탄성한 도 해석은 물론 리미트 및 쉐이크다운 해석이 가능하다. 개발된 프로그램들의 실효성 및 정확성을 확인하기 위하여 다양한 형상에 대 하여 적용하였고, 그 결과를 발표된 해석 결과들뿐만 아니라, 본 연구중에 수행된 상용 유한 요소 해석 프로그램인 ABAQUS 를 이용한 비선형 해석 결과와 도 비교하였다. 비교 결과 LOLAP, UPLAP 그리고 EFESA 는 만족한 결과를 주 는 것으로 판명되었다.

Plasma sputtering deposition on high performance fibres

서호영 University of Manchester Institute of Science and 2002 해외박사

The work presented in this thesis is concerned mainly with plasma coating on high performance fibres using various magnetrons. The analysis of thin metal coating on textile fibres, particularly high performance fibres, has been performed with a scanning electron microscope (SEM) to describe the surface morphology of the thin metal coating on the fibres. High performance fibres are mainly used because they usually have a high melting temperature as well as high tenacity. First of all, the thesis presents research concerning the properties of plasma, which is generated in the magnetron. A thermocouple probe is built in this experiment to estimate the temperature of the substrate during the plasma sputtering deposition. A Langmuir probe is also used to measure various plasma parameters that affect the plasma sputtering processes such as heat flux, electron and ion density of the plasma. After analysing properties of plasma, a planar magnetron is used to deposit a metal coating on these high performance fibres with different coating conditions. Along with the planar magnetron, a continuous yarn feeding system is also developed to coat the fibres with a thin metal coating. The yarn feeding system can change the speed of the yarn winding so that the metal deposition rate can be tailored. Yarn travels between the two rods in a ribbon pattern to be exposed to the target ion and atom flow from the magnetron. The coating state and uniformity of the fibres are examined mainly by a scanning electron microscope (SEM). Besides using the SEM, different analysis techniques like energy dispersive x-ray spectroscopy (EDX) are reviewed to monitor the presence and distribution of metal deposition on the substrates. Other complementary techniques, which can be used to determine the coating thickness, are described. A few shortcomings of the planar magnetron, such as the shielding-effect of each fibre from the metal atom flow, and melting of polyolefin fibres were observed during the deposition. A torus magnetron configuration was designed and manufactured during the project to overcome these disadvantages of the planar magnetron. This new torus magnetron in this project increases the efficiency of the sputtering process because the yarn travels through the cylindrical target of the torus magnetron with the continuous winding system. Different power sources, such as direct current (DC) and pulsed DC, are also used to coat the metal deposit with the same torus magnetron. Different configurations of the torus magnetron are also reviewed in this thesis. Metal coating deposited by the torus magnetron on the fibres is mainly analysed using the scanning electron microscope (SEM) to assess the coating thickness. The method of increasing the coating deposition is also reviewed in terms of voltage and mean free path. The voltage needs to be increased to gain a better sputtering rate while the feed of the working gas needs to be decreased in the vacuum chamber to increase the mean free path of the sputtered metal atoms. Both planar and torus magnetrons can deposit a thin-metal coating on the substrates with adequate setting and condition of the magnetrons. The electrical resistance of the metal-coated fibres has also been observed to assess the conductivity of the metal deposited fibres.

The roles of high affinity cAMP dependent phosphodiesterase in Candida albicans

정원희 University of Manchester Institute of Science and 2003 해외박사

The cAMP dependent pathway, which regulates the yeast hyphal transition in Candida albicans, is controlled by changes in cAMP levels determined by the processes of synthesis and hydrolysis. Both low- and high-affinity cAMP phosphodiesterases are encoded in the C. albicans genome. I have cloned PDE2, encoding the high-affinity cAMP phosphodiesterase, and shown it to be toxic in S. cerevisiae upon over expression under pGAL1 but functional under the moderate pMET3. Heterozygous and homozygous pde2 mutants, and reconstituted control strains were generated, and characterised. The results show that in C. albicans deletion of PDE2 causes elevated cAMP levels and responsiveness to exogenous cAMP, higher sensitivity to heat shock, severe growth defects at 42°C, and highly reduced levels of EFG1 transcription. Under in vitro hyphal inducing liquid media, PDE2 deletion prohibits normal hyphal development, but not pseudohyphal growth. On solid media pde2 mutants form aberrant hyphae, with fewer branches and almost no lateral buds, which are deficient in hypha to yeast reversion. The phenotypic defects of pde2 mutants show that the cAMP-dependent pathway plays specific roles in hyphal and pseudohyphal development, its regulatory role however, being greater in liquid than on solid in vitro conditions. The increased expression of PDE2 after serum addition correlates well with a drop in cAMP levels following the initial rise in response to the hyphal inducer. The results suggest that Pde2p mediates a desensitisation mechanism by lowering basal cAMP levels in response to environmental stimuli in C. albicans. The roles of PDE2 in cell wall/membrane integrity in C. albicans had also been investigated, and, deletion of PDE2 caused increased sensitivity to the cell wall/membrane disrupting agents (SDS, CFW), increased ergosterol content, and reduced levels of b-glucans and decreased cell wall thickness, suggesting the cell wall related function of Pde2. Deletion of PDE2 also resulted in increased susceptibility to amphotericin B, and caused reduced tolerance to fluconazole suggesting the possibility of a novel antifungal therapy upon combination with phosphodiesterase inhibitors.

The application of deuterium exchange and FTIR to the problem of irreversible pore closure during the recycling of paper

김형진 University of Manchester. Institute of Science and 1997 해외박사

셀룰로오스 섬유를 건조처리하면 섬유의 세포벽은 불가역적인 기공의 폐쇄현상이 일어나게 되며 이러한 현상은 섬유의 연속적인 회수처리 과정에 있어서 문제점을 야기하는 한 요소이다. 이러한 섬유의 회수처리 영향을 중수소치환 기법을 이용하여 조사하였으며 중수소 치환반응은 퓨리어전환 적외선흡수 스펙트럼 (FTIR)으로 측정하였다. 중수소치환반응의 평가는 적외선흡수 스펙트럼으로부터 얻은 2500/2900cm( )band의 intensity의 비를 사용하였으며 중수소화의 정도를 측정하는 수단으로 사용되었다. 중수소화의 정도는 광투과 (transmission) 방법에 의해 얻어진 FTIR 스펙트럼으로부터 평가되었으며 이때 시료의 중수소화에는 특수한 IR cell이 사용되었다. 종이의 반복적인 건조 및 습윤처리에 의한 영향은 중수소화의 정도를 측정함으로서 연구되었으며, 이의 해석은 건조처리에 의해 야기되는 셀룰로오스 섬유의 본래의 accessible hydroxyls 상태가 less accessible 또는 inaccessible 상태로 변화되었다는 것을 의미한다. 이러한 변화는 셀룰로오스 섬유의 구조가 변경되었기 때문이며 세포벽내의 기공의 양이 불가역적으로 감소함으로서 야기된다. 고해된 섬유와 미고해된 섬유의 중수소화의 정도 역시 조사되었으며, 이들의 차이는 셀룰로오스 microfibril의 표면에 accessible hydroxyl 들이 새롭게 배열되었기 때문인 것으로 사료된다. 셀룰로오스의 미세구조의 변화를 조사하기 위하여 IR accessibility와 deconvolution 방법에 의해 얻어진 스펙트럼 band의 연구가 이용되었다. 또한 회수처리동안 셀룰로오스 섬유의 불가역적인 hornification. 현상은 Water Retention Value (WRV)에 의하여 평가되었다. WRV는 반복적인 섬유의 건조 및 습윤 처리에 의해 감소되었으며, 특히 1회 건조된 섬유에서 급격한 감소를 보였다. 또한 섬유간의 hydrogen bonding이나 섬유의 표면 특성과 깊은 관련이 있는 인장강도, 결합강도지수, 광산란계수 등과 같은 물리적, 광학적 특성도 연구되었다. 섬유의 회수처리 중 발생하는 불가역적인 hornification에 관한 문제점을 평가하는 수단으로 중수소 치환 방법에 의한 응용은 매우 유익한 기법으로 사용될 수 있다.