Effect of feed salinity on the performance of humidification dehumidification desalination

Humidification dehumidification (HDH) is a thermal desalination technology that imitates the rain cycle in an engineered setting. It can be advantageous is small-scale, decentralized applications. In addition, the components used in HDH systems are fairly robust, and can treat highly saline water. The technology has recently been commercialized in order to treat highly saline produced water from hydraulically fractured oil and gas wells. That plant has proved HDH’s ability to treat water that most current seawater desalination technologies are unable to treat. The major disadvantage of HDH is its low energy efficiency compared to other desalination technologies when treating seawater. Previous studies have shown that the system’s energy efficiency can be improved greatly by varying the water-to-air mass flow rate ratio within the system. This translates into operating two or more adjacent stages at different mass flow rate ratios, which is done by extracting an air stream from an intermediate location in the humidifier and injecting it at an intermediate location in the dehumidifier. Previous models have used fixed effectiveness or fixed pinch approaches to evaluate the benefits of multi-staging, but these do not take account of the size of the system. In physical systems, what remains constant when going from a single-stage to a multi-stage system is the total size of the system and not the effectiveness or the pinch. Therefore, comparing systems with the same total heat exchanger area is the best way to understand the effect of extraction/injection and whether its implementation is beneficial or not. In this paper, a numerical heat and mass transfer model is used to simulate the operation of HDH at various feed salinities. For each case, the performance of the single-stage system is compared to that of a two-stage system of the same size at different values of feed salinity. The ability of HDH to treat feeds with varying salinity is also studied.Center for Clean Water and Clean Energy at MIT and KFUPM (Project R4-CW-08

Entropy generation analysis of electrodialysis

Electrodialysis (ED) is a desalination technology with many applications. In order to better understand how the energetic performance of this technology can be improved, the various losses in the system should be quantified and characterized. This can be done by looking at the entropy generation in ED systems. In this paper, we implement an ED model based on the Maxwell-Stefan transport model, which is the closest model to fundamental equations. We study the sources of entropy generation at different salinities, and locate areas where possible improvements need to be made under different operating conditions. In addition, we study the effect of the channel height, membrane thickness, and cell-pair voltage on the specific rate of entropy generation. We express the second-law efficiency of ED as the product of current and voltage utilization rates, and study its variation with current density. Further, we define the useful voltage that is used beneficially for separation. We derive the rate of entropy generation that is due to the passage of ions through a voltage drop, and we investigate whether voltage drops themselves can provide a good estimate of entropy generation.Kuwait Foundation for the Advancement of Sciences (KFAS) (Project No. P31475EC01

Contribution à l'étude clinique et biologique des réactions tissulaires de radiosensibilité observées après radiothérapie de cancers prostatiques : effet potentiellement radioprotecteur des statines

The tissue response of patients undergoing radiotherapy, despite identical treatment protocols, could have important variations. One of the questions asked to the radiobiology is to explain these variations (a posteriori approach) and if possible to predict it (a priori approach). The response of an organism and complex tissues to radiotherapy is the result of many determinants. Some belong to the tissue dynamics and homeostasis (inflammation, cytokines, etc.) and others to the sensitivity and cellular response (intrinsic sensitivity, DNA repair, regulation of cell death, etc.). About cellular determinants, our research team proposed to classify humans into three groups of different radiosensitivity levels, the first considered as normal is by far the largest (almost 75% of individuals), group II of intermediate radiosensitivity represents the majority of individuals having an abnormal response to radiotherapy. Group III gathers extremely rare conditions associated with marked or very marked hyper-radiosensitivity which are usually life threatening. Therefore patients in group II show either unexpected therapeutic response or severe radiation early or late side effects after doses for which normal tolerance is expected. Patients in group II can also be characterized by a strong predisposition to cancer and radiation-induced tumors. There is an inherent variability related to endogenous factors, such as the quality of DNA repair, or the spontaneous production of micronuclei; and exogenous factors. In this regard, certain medications may alter the cellular response to radiation therapy, such as statins, antiplatelet agents or anticoagulants. A posteriori approach: a single-center clinical study of 68 patients with prostate cancer treated by the same radiation oncologist in the same conditions, the frequency and severity of rectal side effects are compared to the use or not of statins : a radioprotective effect of statins toward radiation proctitis cannot be excluded. A priori approach: by studying the cellular and molecular radiation response in human fibroblasts (especially from healthy bowel tissue). Were studied: signaling and repair of DNA double-strand breaks by analysis of nuclear foci of MRE11; H2AX and pATM; radiation induced ATM protein transit from the cytoplasm to the nucleus was observed for the first time in rectal tissue fibroblasts. Statins appear to speed up this transit, making possible a radioprotective effect. These results open perspectives for further studies for the use of medications readily available that can modulate the severity of side effects of radiotherapy.La réponse tissulaire des patients soumis à une radiothérapie, malgré des protocoles de traitement identiques, est variable avec des extrêmes importants. Une des questions posées à la radiobiologie est d'expliquer ces variations (approche a posteriori) et si possible de les prévoir (approche a priori). La réponse d'un organisme et de tissus complexes à la radiothérapie est la résultante de nombreux déterminants. Certains appartiennent à la dynamique et à l'homéostasie tissulaire (inflammation, cytokines, etc.) d'autre à la sensibilité et à la réponse cellulaire (sensibilité intrinsèque, réparation de l'ADN, régulation de la mort cellulaire, etc.). Concernant les déterminants cellulaires, l'Equipe d'Accueil a proposé de classer les humains en 3 groupes de radiosensibilités différentes, le premier considéré comme normal est de loin le plus important (près de 75% des individus), le groupe II de radiosensibilité intermédiaire représente la majeure partie des individus pour lesquels une réponse anormale est constatée après radiothérapie. Le groupe III rassemble des pathologies particulièrement rares associées à une hyper-radiosensibilité marquée, voire très marquée. Les patients du groupe II présentent donc une réponse thérapeutique inattendue et / ou des effets secondaires précoces ou tardifs sévères à des doses d'irradiation dont on attend une tolérance normale. Les patients du groupe II peuvent aussi être caractérisés par une forte prédisposition au cancer et aux tumeurs radio induites. Il existe une variabilité intrinsèque liée à des facteurs endogènes tels que la qualité de réparation de l'ADN, ou la production spontanée de micronoyaux ; et des facteurs exogènes. A cet égard, certaines médications sont susceptibles de modifier la réponse cellulaire à la radiothérapie, telles que les statines, les anticoagulants ou les antiagrégants plaquettaires. Approche a posteriori : par une étude clinique unicentrique de 65 patients atteints de cancers de la prostate et traités par le même radiothérapeute dans les mêmes conditions, la fréquence et la gravité des effets secondaires rectaux par rapport à la prise ou non de statines ont été étudiées : un effet radioprotecteur des statines vis-à-vis de la rectite radique a été mis en évidence in vivo sur des arguments statistiques pertinents. Approche a priori : par l'étude de la réponse cellulaire et moléculaire aux radiations de fibroblastes humains (notamment issus de tissus intestinaux sains). Ont été étudiés : la réparation et la signalisation des cassures double-brin de l'ADN par l'analyse des foci nucléaires H2AX et pATM ; le transit radioinduit de la protéine ATM du cytoplasme vers le noyau a été observé pour la première fois sur des fibroblastes humains rectaux. Les statines semblent accélérer ce transit, produisant un effet modérateur de la sévérité des rectites. L’étude des différents produits antioxydants et stimulateurs de la réparation de l’ADN a permis de montrer que les statines ont effet non équivoqué sur la réparation cellulaire après irradiation. Ces résultats ouvrent des perspectives pour des études plus approfondies de l'usage de médications facilement accessibles capables de moduler la gravité des effets secondaires de la radiothérapie

Design thinking mindset to enhance education 4.0 competitiveness in Malaysia

Education 4.0 will be the next aspect of the curriculum since programming has been taught from the primary school level. Training 4.0 requires teachers to equip students with not only the knowledge and information but also encourage students to be able to process information, develop creative thinking, and acquire problem-solving skills. However, the competency of teachers to encourage creative thinking and problem-solving skills is still questionable. The purpose of this concept paper is to provide an understanding of the conceptual framework for enhancing the teachers’ competency to enhance creativity and innovation in fulfilling the desire of education 4.0. design thinking is an innovative method that places people right at the center of problem solving. It discusses the variables that may affect the quality of teachers in education 4.0 and presents a literature review of approaches that can contribute to the creation of effective teaching methods to develop successful students and satisfy the demands of the workforce for industrial revolution 4.0. It is found that teachers need to be competent to build students' skills in meeting a competitive and innovative workforce in the wake of the industrial revolution 4.0. There are seven dimensions in the design thinking mindset that teachers need to understand to meet the 4.0 education requirements

A Numerical Solution Algorithm for a Heat and Mass Transfer Model of a Desalination System Based on Packed-Bed Humidification and Bubble Column Dehumidification

The humidification-dehumidification (HDH) desalination system can be advantageous in small-scale, off-grid applications. The main drawback of this technology has been its low energy efficiency, which results in high water production costs. Previous studies have approached this issue through thermodynamic balancing of the system; however, most theoretical work on the balancing of HDH has followed a fixed-effectiveness approach that does not explicitly consider transport processes in the components. Fixing the effectiveness of the heat and mass exchangers allows them to be modeled without explicitly sizing the components and gives insight on how the cycle design can be improved. However, linking the findings of fixed-effectiveness models to actual systems can be challenging, as the performance of the components depends mainly on the available surface areas and the flow rates of the air and water streams. In this study, we present a robust numerical solution algorithm for a heat and mass tranfer model of a complete humidification-dehumidification system consisting of a packed-bed humidifier and a multi-tray bubble column dehumidifier. We look at the effect of varying the water-to-air mass flow rate ratio on the energy efficiency of the system, and we compare the results to those reached following a fixed-effectiveness approach. In addition, we study the effect of the top and bottom temperatures on the performance of the system. We recommended the implementation a control system that varies the mass flow rate ratio in order to keep the system balanced in off-design conditions, especially with varying top temperature.Center for Clean Water and Clean Energy at MIT and KFUPM (Project R4-CW-08

Use of multiple extractions and injections to thermodynamically balance the humidification dehumidification desalination system

Humidification dehumidification (HDH) desalination systems are well suited for small scale, off-grid desalination. These systems are very robust and can tolerate a wide range of feed salinities, making them a good candidate for treating produced water from hydraulically fractured natural gas wells. A primary engineering challenge for these systems is their high thermal energy consumption. In this study, we examine the use of multiple air extractions and injections to thermodynamically balance the HDH system, so as to make it more energy efficient. The effect of the number of extractions on several performance parameters is studied. In addition, we study the effect of the enthalpy pinch, which is a measure of performance for a heat and mass exchanger, on these performance parameters. Finally, we present results that can be used as guidelines in designing HDH systems. These results include the identification of appropriate temperatures for the extracted/injected air streams, the division of the heat duty between stages, and the value of the mass flow rate ratio in each stage at various values of enthalpy pinch.Center for Clean Water and Clean Energy at MIT and KFUPM (Project R4-CW-08

Thermodynamic balancing of a fixed-size two-stage humidification dehumidification desalination system

Humidification dehumidification (HDH) is a desalination technology that has shown promise in small scale, decentralized applications. Previous studies on the multi-staging of HDH have used fixed-effectiveness models which do not explicitly account for transport processes in the components. However, to fully understand the effect of the variation of the mass flow rate ratio, it is necessary to implement heat and mass transfer models of the HDH system. In this paper, we model an HDH system consisting of a packed-bed humidifier and a multi-tray bubble column dehumidifier. We study the effect of the mass flow rate ratio on the performance of a fixed-size system, and we consider its effect on the entropy generation and the driving forces for heat and mass transfer. In addition, we define a generalized energy effectiveness for heat and mass exchangers. We also implement an air extraction/injection and simulate a wide range of operating conditions. We define criteria for the best system performance, and we study the effect of the distribution of available area between separate stages. We also present a thorough explanation of why the direction of extraction should always be from the humidifier to the dehumidifier.Center for Clean Water and Clean Energy at MIT and KFUPM (Project R4-CW-08

Reflective practices to explore postgraduate students learning experience in mobile learning platform

Mobile Learning (M-learning) has great potential to be an effective learning tool in creating meaningful learning experiences. The purpose of this study is to explore postgraduate students M-learning experiences in Massive Open Online Courses (MOOCs) platform. Reflective practice is used to measure the students M-learning experience based on mobile-based task-centered activity. This study is qualitative in nature employed thematic analysis method. Therefore, 34 postgraduate students from a public university in Malaysia were selected for this purposive sampling. The postgraduate students were initially introduced to M-learning course content in FutureLearn platform followed by reflective practices. Pre-reflective practice happened before students are enlisted into the M-learning process, During-reflective process in FutureLearn platform and Post-reflective upon completion of task-centered activity. The findings revealed that majority of these students were unsure of M-learning platform during the pre-reflective stage. This is due to lack of prior knowledge and experience in M-learning platform using mobile devices as real time hindered the students from exploring. However, most of them progress to gained positive M-learning experiences as their able to monitoring and self-evaluate their own learning development throughout this learning process and completed the task-centered activity successfully. Therefore, the reflective approach practice has given students insight on their meaningful learning experience and their own learning capabilities

The impact of course evaluation on instructors' teaching performance

An investigation of the university course evaluation scores over four semesters was conducted to determine the impact of the University Teaching Evaluation practice on faculty teaching performance in general and (1) to measure how instructors perceive the effectiveness of the University Teaching Evaluation Programme, (2) to compare the course evaluation results based on gender, academic rank, and faculty, and (3) to determine additional measurement methods for evaluating teaching in particular.The results obtained lead us to conclude that most faculty members did not believe that course evaluation is valid and reliable. However, most of them indicated that the course evaluation practised in Universiti Utara Malaysia (UUM) has positive impact on them with regard to their awareness about their own teaching.Extraneous variables such as gender, academic rank, and faculty were significantly related to course evaluation mean scores.However, participation in the teaching certification programme was not a significant factor.Course evaluation, though believed to be lacking validity and reliability, was considered as good as some other more objective measures by the faculty members. There was also no evidence to suggest that improvement in course evaluation scores reflect better students’ learning. However, the questionnaire used may have captured not only some aspects of teaching effectiveness but also certain factors that are not related to teaching effectiveness.In conclusion, the course evaluation practice at UUM may not have produced better learning outcome as measured by students’ GPA, nevertheless, it has impacted positively on faculty members’ awareness about their own teaching performance