Delay Dependent Robust Stability of Singular Systems with Time-Varying Delay

Noreddine Chaibi,El Houssaine Tissir 제어·로봇·시스템학회 2012 International Journal of Control, Automation, and Vol.10 No.3

This paper deals with the problem of robust stability of uncertain singular continuous systems with time-varying delays. The parametric uncertainties are assumed to be norm bounded. Delay dependent conditions are given to ensure that the uncertain singular system is regular, impulse free, and stable for all admissible uncertainties. The results are given in terms of linear matrix inequalities (LMIs). Finally, numerical examples are provided to illustrate the effectiveness of the proposed method, and to compare with previous works.

Evaluation of Biofouling in a Forward Osmosis - Reverse Osmosis Integrated Seawater Desalination System

Youngjin Kim,Lanhee Kim,Noreddine Ghaffour 한국막학회 2020 한국막학회 총회 및 학술발표회 Vol.2020 No.11

New Delay Dependent Robust Stability Criteria for T–S Fuzzy Systems with Constant Delay

Said Idrissi,El Houssaine Tissir,Ismail Boumhidi,Noreddine Chaibi 제어·로봇·시스템학회 2013 International Journal of Control, Automation, and Vol.11 No.5

This paper deals with the problem of delay dependent robust stability for T–S fuzzy time delay systems. The approach based on constructing a new Lyapunov-Krasovskii functional by dividing uniformly the delay interval into N segment with N is positive integer, and using Finsler’s lemma. This new Lyapunov-Krasovskii functional is chosen with different weighted matrices corresponding to dif-ferent segments. The perturbations considered are norm bounded, and the results are expressed in terms of linear matrix inequality (LMIs). Numerical examples are provided to show the effectiveness of the present method, compared with some recent previous ones.

Environmental and economic impacts of fertilizer drawn forward osmosis and nanofiltration hybrid system

Kim, Jung Eun,Phuntsho, Sherub,Chekli, Laura,Hong, Seungkwan,Ghaffour, Noreddine,Leiknes, TorOve,Choi, Joon Yong,Shon, Ho Kyong Elsevier 2017 Desalination Vol.416 No.-

<P><B>Abstract</B></P> <P>Environmental and economic impacts of the fertilizer drawn forward osmosis (FDFO) and nanofiltration (NF) hybrid system were conducted and compared with conventional reverse osmosis (RO) hybrid scenarios using microfiltration (MF) or ultrafiltration (UF) as a pre-treatment process. The results showed that the FDFO-NF hybrid system using thin film composite forward osmosis (TFC) FO membrane has less environmental impact than conventional RO hybrid systems due to lower consumption of energy and cleaning chemicals. The energy requirement for the treatment of mine impaired water by the FDFO-NF hybrid system was 1.08kWh/m<SUP>3</SUP>, which is 13.6% less energy than an MF-RO and 21% less than UF-RO under similar initial feed solution. In a closed-loop system, the FDFO-NF hybrid system using a TFC FO membrane with an optimum NF recovery rate of 84% had the lowest unit operating expenditure of AUD $0.41/m<SUP>3</SUP>. Besides, given the current relatively high price and low flux performance of the cellulose triacetate and TFC FO membranes, the FDFO-NF hybrid system still holds opportunities to reduce operating expenditure further. Optimizing NF recovery rates and improving the water flux of the membrane would decrease the unit OPEX costs, although the TFC FO membrane would be less sensitive to this effect.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Environmental impacts of the FDFO-NF(TFC) hybrid system can be lower than RO hybrid systems. </LI> <LI> The FDFO-NF hybrid system consumes 21% less energy than the UF-RO hybrid system. </LI> <LI> The unit OPEX cost of FDFO-NF (TFC) system is 14% lower than UF-RO hybrid system. </LI> <LI> Improving flux and lowering the cost of the CTA FO membrane can make the FDFO-NF cost effective. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Effect of non-woven net spacer on a direct contact membrane distillation performance: Experimental and theoretical studies

Kim, Young-Deuk,Francis, Lijo,Lee, Jung-Gil,Ham, Min-Gyu,Ghaffour, Noreddine Elsevier 2018 Journal of membrane science Vol.564 No.-

<P><B>Abstract</B></P> <P>This study provides a comprehensive and systematic overview of the fundamental characteristics of heat and mass transfer in the direct contact membrane distillation (DCMD) process that employs different types of spacers on one or both surfaces of the membrane. Detailed theoretical investigations were carried out to demonstrate the effects of spacers adjacent to the membrane surface on heat and mass transfer enhancement in the DCMD with a PTFE/PP composite membrane, complemented with experimental data for model validation. Thus, this work aimed to propose and demonstrate the heat transfer correlation for spacer-filled channels to reliably predict the heat and mass transfer improvement by non-woven net spacers in the DCMD process. The results showed that the permeate flux enhancement by the spacers ranged between 7% and 19% only for the spacer-filled permeate channels and between 21% and 33% only for the spacer-filled feed channels even at higher flow rates, thus indicating lower flux enhancements in the spacer-filled permeate channels. This was because the influence of spacers on flux improvement became more evident at higher temperatures owing to higher temperature polarization. In this study, the maximum flux enhancement of approximately 43% over the empty channels was achieved using the thinnest and densest spacer with a hydrodynamic angle of 90°, adjacent to both membrane surfaces.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The effect of spacers on heat and mass transfer enhancement in DCMD is demonstrated. </LI> <LI> The heat transfer correlation for spacer-filled channels is proposed and demonstrated. </LI> <LI> The predicted and measured data on the mean permeate flux are shown to be in good agreement. </LI> <LI> The effect of spacers on permeate flux improvement is more prominent at higher temperatures. </LI> <LI> The effect of bulk temperature on temperature polarization is more pronounced than that of mass flow rate. </LI> </UL> </P>

Human urine as a forward osmosis draw solution for the application of microalgae dewatering

Volpin, Federico,Yu, Hyeonjung,Cho, Jaeweon,Lee, Changsoo,Phuntsho, Sherub,Ghaffour, Noreddine,Vrouwenvelder, Johannes S.,Shon, Ho Kyong Elsevier 2019 Journal of hazardous materials Vol.378 No.-

<P><B>Abstract</B></P> <P>Human urine is a unique solution that has the right composition to constitute both a severe environmental threat and a rich source of nitrogen and phosphorous. In fact, between 4–9% of urine mass consists of ions, such as K<SUP>+</SUP>, Cl<SUP>−</SUP>, Na<SUP>+</SUP> or NH<SUB>4</SUB> <SUP>+</SUP>. Because of its high ionic strength, urine osmotic pressure can reach values of up to 2000 kPa. With this in mind, this work aimed to study the effectiveness of real urine as a novel draw solution for forward osmosis. Water flux, reverse nitrogen flux and membrane fouling were investigated using fresh or hydrolysed urine. Water flux as high as 16.7 ± 1.1 L m<SUP>−2</SUP> h<SUP>−1</SUP> was recorded using real hydrolysed urine.</P> <P>Additionally, no support layer membrane fouling was noticed in over 20 h of experimentation. Urine was also employed to dewater a <I>Chlorella vulgaris</I> culture. A fourfold increase in algal concentration was achieved while having an average flux of 14.1 L m<SUP>−2</SUP> h<SUP>−1</SUP>. During the algae dewatering, a flux decrease of about 19% was noticed; this was mainly due to a thin layer of algal deposition on the active side of the membrane. Overall, human urine was found to be an effective draw solution for forward osmosis.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Hydrolysed urine can reach more than 2000 kPa in osmotic pressure. </LI> <LI> Real urine exhibited flux up to 16.7 ± 1.1 L m<SUP>−2</SUP> h<SUP>−1</SUP>. </LI> <LI> Support layer fouling caused by unfiltered urine was found negligible. </LI> <LI> Four times algal concentration was achieved using real urine as draw solution. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

A novel multi-stage direct contact membrane distillation module: Design, experimental and theoretical approaches

Lee, Jung-Gil,Kim, Woo-Seung,Choi, June-Seok,Ghaffour, Noreddine,Kim, Young-Deuk Elsevier 2016 Water research Vol.107 No.-

<P><B>Abstract</B></P> <P>An economic desalination system with a small scale and footprint for remote areas, which have a limited and inadequate water supply, insufficient water treatment and low infrastructure, is strongly demanded in the desalination markets. Here, a direct contact membrane distillation (DCMD) process has the simplest configuration and potentially the highest permeate flux among all of the possible MD processes. This process can also be easily instituted in a multi-stage manner for enhanced compactness, productivity, versatility and cost-effectiveness. In this study, an innovative, multi-stage, DCMD module under countercurrent-flow configuration is first designed and then investigate both theoretically and experimentally to identify its feasibility and operability for desalination application. Model predictions and measured data for mean permeate flux are compared and shown to be in good agreement. The effect of the number of module stages on the mean permeate flux, performance ratio and daily water production of the MDCMD system has been theoretically identified at inlet feed and permeate flow rates of 1.5 l/min and inlet feed and permeate temperatures of 70 °C and 25 °C, respectively. The daily water production of a three-stage DCMD module with a membrane area of 0.01 m<SUP>2</SUP> at each stage is found to be 21.5 kg.</P> <P><B>Highlights</B></P> <P> <UL> <LI> An innovative MDCMD module with a countercurrent-flow configuration is proposed. </LI> <LI> Feasibility and operability of module design are demonstrated experimentally and theoretically. </LI> <LI> Model predictions and measured data for mean permeate flux are shown to be in good agreement. </LI> <LI> Effect of the number of module stages on the performance of the MDCMD system is identified. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

A closed-loop forward osmosis-nanofiltration hybrid system: Understanding process implications through full-scale simulation

Phuntsho, Sherub,Kim, Jung Eun,Hong, Seungkwan,Ghaffour, Noreddine,Leiknes, TorOve,Choi, Joon Yong,Shon, Ho Kyong Elsevier Scientific Pub. Co 2017 Desalination Vol. No.

<P><B>Abstract</B></P> <P>This study presents simulation of a closed-loop forward osmosis (FO)-nanofiltration (NF) hybrid system using fertiliser draw solution (DS) based on thermodynamic mass balance in a full-scale system neglecting the non-idealities such as finite membrane area that may exist in a real process. The simulation shows that the DS input parameters such as initial concentrations and its flow rates cannot be arbitrarily selected for a plant with defined volume output. For a fixed FO-NF plant capacity and feed concentration, the required initial DS flow rate varies inversely with the initial DS concentration or vice-versa. The net DS mass flow rate, a parameter constant for a fixed plant capacity but that increases linearly with the plant capacity and feed concentration, is the most important operational parameter of a closed-loop system. Increasing either of them or both increases the mass flow rate to the system directly affecting the final concentration of the diluted DS with direct energy implications to the NF process. Besides, the initial DS concentration and flow rates are also limited by the optimum recovery rates at which NF process can be operated which otherwise also have direct implications to the NF energy. This simulation also presents quantitative analysis of the reverse diffusion of fertiliser nutrients towards feed brine and the gradual accumulation of feed solutes within the closed system.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Initial DS flow rate and concentration cannot be set at any arbitrary values. </LI> <LI> Initial DS flow rate and concentration vary inversely for a fixed plant capacity. </LI> <LI> Net DS mass flow rate <I>m</I> <SUB>D</SUB> is the most important parameter for a closed system. </LI> <LI> <I>m</I> <SUB>D</SUB> is constant for a fixed plant capacity but increases with capacity and feed TDS. </LI> <LI> FO and NF rejection rates influence feed solute accumulation in the closed system. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Effect of seawater-coolant feed arrangement in a waste heat driven multi-stage vacuum membrane distillation system

Lee, Jung-Gil,Bak, Chul-u,Thu, Kyaw,Ghaffour, Noreddine,Kim, Young-Deuk Elsevier 2019 Separation and purification technology Vol.212 No.-

<P><B>Abstract</B></P> <P>This paper proposes two types of seawater-coolant feed arrangements of a heat recovery unit (HRU) for improving the performance of a multi-stage vacuum membrane distillation (VMD) system: backward feed (BF) and parallel feed (PF). Theoretical studies were performed to assess the effect of the BF and PF feed arrangements on the system performance. In addition, to comprehensively understand the thermochemical phenomena in both the BF and PF arrangements, spatial variations in the temperature, permeate pressure, permeate flux, and salinity were investigated using a rigorous simulation model that considered the heat and mass transfer across the hollow fibers coupled with the transport behavior on the feed side. To determine the superior HRU configuration between BF and PF, the water production, recovery ratio, and specific energy consumption of the multi-stage VMD system were investigated. It was found that the total water production in the PF arrangement was approximately 2.94 m<SUP>3</SUP>/d, which was approximately 6% higher than in the BF arrangement; however, the BF arrangement was more efficient for the production of freshwater than the PF arrangement when a smaller number of module stages was employed. Furthermore, the optimum number of HRUs in the BF arrangement was determined based on this theoretical study.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Effect of BF and PF arrangements on MVMD system performance was theoretically evaluated. </LI> <LI> BF arrangement with a smaller number of module stages was more efficient for water production. </LI> <LI> Inappropriate number of module stages had a negative effect on MVMD system performance. </LI> <LI> Four HRU stages with BF arrangement showed an improved efficiency of the MVMD system. </LI> </UL> </P>

An advanced online monitoring approach to study the scaling behavior in direct contact membrane distillation

Lee, Jung-Gil,Jang, Yongsun,Fortunato, Luca,Jeong, Sanghyun,Lee, Sangho,Leiknes, TorOve,Ghaffour, Noreddine Elsevier 2018 Journal of membrane science Vol.546 No.-

<P><B>Abstract</B></P> <P>One of the major challenges in membrane distillation (MD) desalination is scaling, mainly CaSO<SUB>4</SUB> and CaCO<SUB>3</SUB>. In this study, in order to achieve a better understanding and establish a strategy for controlling scaling, a detailed investigation on the MD scaling was performed by using various analytical methods, especially an in-situ monitoring technique using an optical coherence tomography (OCT) to observe the cross-sectional view on the membrane surface during operation. Different concentrations of CaSO<SUB>4</SUB>, CaCO<SUB>3</SUB>, as well as NaCl were tested separately and in different mixed feed solutions. Results showed that when CaSO<SUB>4</SUB> alone was employed in the feed solution, the mean permeate flux (MPF) has significantly dropped at lower volume concentration factor (VCF) compared to other feed solutions and this critical point was observed to be influenced by the solubility changes of CaSO<SUB>4</SUB> resulting from the various inlet feed temperatures. Although the inlet feed and permeate flow rates could contribute to the initial MPF value, the VCF, which showed a sharp MPF decline, was not affected. It was clearly observed that the scaling on the membrane surface due to crystal growth in the bulk and the deposition of aggregated crystals on the membrane surface abruptly appeared close to the critical point of VCF by using OCT observation in a real time. On the other hand, NaCl + CaSO<SUB>4</SUB> mixed feed solution resulted in a linear MPF decline as VCF increases and delayed the critical point to higher VCF values. In addition, CaCO<SUB>3</SUB> alone in feed solution did not affect the scaling, however, when CaSO<SUB>4</SUB> was added to CaCO<SUB>3</SUB>, the initial MPF decline and VCF met the critical point earlier. In summary, calcium scaling crystal formed at different conditions influenced the filtration dynamics and MD performances.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A comprehensive analysis of calcium-based scaling behavior in DCMD was investigated. </LI> <LI> OCT was employed to monitor the scaling behavior in real-time during MD operation. </LI> <LI> CaSO<SUB>4</SUB>, CaCO<SUB>3</SUB>, and NaCl were tested separately and in mixed feed solutions. </LI> <LI> CaSO4 scaling occurred by deposition of bulk crystal on the membrane surface. </LI> <LI> A critical point of VCF at which MPF decreased significantly has been observed. </LI> </UL> </P>