Performance restoration of direct methanol fuel cells in long-term operation using a hydrogen evolution method

Mehmood, Asad,Ha, Heung Yong Elsevier 2014 APPLIED ENERGY Vol.114 No.-

<P><B>Abstract</B></P> <P>A detailed study has been carried out to investigate the changes taking place in the electrodes of a direct methanol fuel cell (DMFC) upon their exposure to the hydrogen gas that is electrochemically evolved <I>in situ</I> in the electrodes. It is found that the individual, as well as the combined, H<SUB>2</SUB> evolution treatment of both the anode and the cathode for a short amount of time causes a substantial improvement in the cell performance, which is attributed to their improved catalytic activities. The exposure of Pt and PtRu catalysts to evolved H<SUB>2</SUB> is beneficial in reducing the surface oxides that are formed during DMFC operation. The performance losses originating from the catalyst oxidation in a continuous operation are successfully recovered by the H<SUB>2</SUB> evolution method, and the DMFC has experienced a voltage loss of only 15mV during a 1383h durability test. These results show the effectiveness of using the H<SUB>2</SUB> evolution method to reduce catalyst oxides and recover the performance losses of a DMFC. Various physical and electrochemical analyses are carried out to fully understand the mechanism and the consequences of the H<SUB>2</SUB> evolution treatment in DMFCs.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Hydrogen gas is electrochemically evolved <I>in situ</I> in DMFC electrodes. </LI> <LI> DMFC performance is considerably improved after H<SUB>2</SUB> evolution treatment. </LI> <LI> Exposure of Pt and PtRu catalysts to H<SUB>2</SUB> gas can reduce their surface oxides. </LI> <LI> H<SUB>2</SUB> evolution is used as a new approach to recover performance losses in DMFC. </LI> </UL> </P>

Physical degradation of cathode catalyst layer: A major contributor to accelerated water flooding in long-term operation of DMFCs

Mehmood, A.,An, M.G.,Ha, H.Y. Applied Science Publishers 2014 APPLIED ENERGY Vol.129 No.-

This study presents a comprehensive investigation on the water flooding of direct methanol fuel cells (DMFCs) during long-term testing with regard to the structural changes of the catalyst layer and gas diffusion layer (GDL) of the cathode. Two separate durability operations of DMFCs are conducted for 1000 and 1261h in order to determine the relative contributions of the cathode catalyst layer and the GDL to time-dependent water flooding during the aging process. The voltage decay rates caused by flooding and non-flooding degradation phenomena are calculated and compared. DMFCs undergo serious voltage decay due to water accumulation in the cathode, and the rate of flooding degradation multiplies approximately every 500h during the duration of testing. The cathode catalyst layer is found to be severely deformed due to surface wrinkling and cracking during the aging of the membrane electrode assembly (MEA). The morphological alteration of the cathode catalyst layer, particularly the formation of wide and deep cracks is identified as the main reason for the acceleration of water flooding, while degradation of the cathode GDL is minor. This demonstrates that during the long-term operation of DMFCs, the physical disintegration of the cathode catalyst layer is a crucial issue affecting water management, which should be carefully addressed.

Tailoring cathode structure of catalyst coated membranes for performance enhancement in direct methanol fuel cells

Mehmood, A.,An, M.,Ha, H.Y. Pergamon Press 2016 International journal of hydrogen energy Vol.41 No.46

<P>In this study, we demonstrate how the formulation of colloidal catalyst ink and fabrication conditions affect the cathode microstructure of catalyst coated membranes (CCMs) prepared via decal technique. The CCMs based on conventional and high concentration cathode inks are compared in a direct methanol fuel cell (DMFC). It is found that the cathode catalyst layer made with a high concentration ink possesses superior porosity, leading to an improved DMFC performance. The temperature of roll-press used for preparing CCM is varied ranging from 170 to 210 degrees C in order to determine the optimal fabrication conditions for high concentration ink-based cathode. The CCM hot-pressed at 200 degrees C (advanced CCM) retains a significantly higher pore volume and outperforms' the conventional CCM by delivering an excellent DMFC performance with a maximum power density of 155 mW cm(-2), which is 20% higher than that of the conventional CCM. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.</P>

Variable selection of spectroscopic data through monitoring both location and dispersion of PLS loading weights

Mehmood Tahir,Turk Arslan Munir 한국통계학회 2021 Journal of the Korean Statistical Society Vol.50 No.4

High dimensional data sets against the small sample size is essential for most of the sciences. The variable selection contributes to a better prediction of real-life phenomena. A multivariate approach called partial least squares (PLS) has the potential to model the high dimensional data, where the sample size is usually smaller than the number of variables. Truncation for variables selection in PLS T−PLS is considered a reference method. T−PLS and many others only monitors the location of PLS loading weights for variable selection. In the current article, we propose to monitor both location and dispersion of PLS loading weights for variable selection over the high dimensional spectral data. The proposed PLS variants are based on location, dispersion, both location and dispersion and at least location or dispersion monitoring of PLS loading weights, and are denoted by X−PLS, S−PLS, X&S−PLS and X|S−PLS respectively. Proposed PLS variants are compared with standard PLS and T−PLS through the Monte Carlo simulation of 100 runs on simulated and real data sets which includes corn, milk, and oil contents prediction based on spectroscopic data. X&S−PLS shows the best capability in selecting the real variables over the simulated data. The validated RMSE comparison indicates X|S−PLS and X&S−PLS outperforms compared to other methods in predicting corn, milk, and oil contents. X&S−PLS selects the smallest number of variables. Interestingly, selected variables by X&S−PLS are more consistent compared to all other methods. Hence X&S−PLS appears a potential candidate for variable selection in high dimensional data.

A novel feature extraction method based on late positive potential for emotion recognition in human brain signal patterns

Mehmood, R.M.,Lee, H.J. Pergamon Press ; Elsevier Science Ltd 2016 Computers & electrical engineering Vol.53 No.-

<P>Several methods for collecting psychophysiological data from humans have been developed, including galvanic skin response (GSR), electromyography (EMG), electroencephalography (EEG), and the electrocardiogram (ECG). This paper proposes a feature extraction method for emotion recognition in EEG-based human brain signals. In this research, emotions were elicited from subjects using emotion-related stimuli from the International Affective Picture System (IAPS) database. We selected four kinds of emotional stimuli in the arousal-valence domain. Raw brain signals were preprocessed using independent component analysis (ICA) to remove artifacts. We introduced a feature extraction method using LPP, and implemented a benchmark based on statistical and frequency domain features. The LPP-based results show the highest accuracy when using SVM in the all-selected feature set. The results also provide evidence and suggest a way for further developing a more specialized emotion recognition system using brain signals. (C) 2016 Elsevier Ltd. All rights reserved.</P>

A novel high performance configuration of electrochemical cell to produce alkali for sequestration of carbon dioxide

Mehmood, A.,Iqbal, M.I.,Lee, J.Y.,Hwang, J.,Jung, K.D.,Ha, H.Y. Pergamon Press 2016 ELECTROCHIMICA ACTA Vol.219 No.-

We propose a new configuration of a 3-compartment electrochemical cell for producing alkali that is subsequently utilized for mineralization of carbon dioxide. In this new membrane configuration, a second cation exchange membrane (CEM) replaces the anion exchange membrane (AEM) employed in a standard cell configuration. The electrochemical cell comprising of two cation exchange membranes (a CEM-CEM system) eliminates the issues associated with the AEM such as low ionic conductivity and inferior mechanical strength. All of tested CEM-CEM combinations exhibit superior electrochemical performance with considerable reduction of energy requirement for NaOH production in comparison to the standard AEM-CEM configuration. The optimized two-CEMs-based system presents a remarkable enhancement of output current density by 2.5-fold and a substantial input energy savings up to 740kWhton<SUP>-1</SUP> for mineralization of carbon dioxide to produce sodium carbonate.

Integrated Power Optimization with Battery Friendly Algorithm in Wireless Capsule Endoscopy

Mehmood, Tariq,Naeem, Nadeem,Parveen, Sajida International Journal of Computer ScienceNetwork S 2021 International journal of computer science and netw Vol.21 No.11

The recently continuous enhancement and development in the biomedical side for the betterment of human life. The Wireless Body Area Networks is a significant tool for the current researcher to design and transfer data with greater data rates among the sensors and sensor nodes for biomedical applications. The core area for research in WBANs is power efficiency, battery-driven devices for health and medical, the Charging limitation is a major and serious problem for the WBANs.this research work is proposed to find out the optimal solution for battery-friendly technology. In this research we have addressed the solution to increasing the battery lifetime with variable data transmission rates from medical equipment as Wireless Endoscopy Capsules, this device will analyze a patient's inner body gastrointestinal tract by capturing images and visualization at the workstation. The second major issue is that the Wireless Endoscopy Capsule based systems are currently not used for clinical applications due to their low data rate as well as low resolution and limited battery lifetime, in case of these devices are more enhanced in these cases it will be the best solution for the medical applications. The main objective of this research is to power optimization by reducing the power consumption of the battery in the Wireless Endoscopy Capsule to make it battery-friendly. To overcome the problem we have proposed the algorithm for "Battery Friendly Algorithm" and we have compared the different frame rates of buffer sizes for Transmissions. The proposed Battery Friendly Algorithm is to send the images on average frame rate instead of transmitting the images on maximum or minimum frame rates. The proposed algorithm extends the battery lifetime in comparison with the previous baseline proposed algorithm as well as increased the battery lifetime of the capsule.

Effect of Human Related Factors on Requirements Change Management in Offshore Software Development Outsourcing: A theoretical framework

Mehmood, Faisal,Zulfqar, Sukana Institute of Information Science and Technology 2021 Soft computing and machine intelligence Vol.1 No.1

Software development organizations are globalizing their development activities increasingly due to strategic and economic gains. Global software development (GSD) is an intricate concept, and various challenges are associated with it, specifically related to the software requirement change management Process (RCM). This research aims to identify humans' related success factors (HSFs) and human-related challenges (HCHs) that could influence the RCM process in GSD organizations and propose a theoretical framework of the identified factors concerning RCM process implementation. The Systematic Literature Review (SLR) method was adopted to investigate the HSFs and HCHs. Using the SLR approach, a total of 10 SFs and 10 CHs were identified. The study also reported the critical success factors (HCSFs) and critical challenges (HCCHs) for RCM process implementation following the factors having a frequency 50% as critical. Our results reveal that five out of ten HSFs and 4 out of ten HCHs are critical for RCM process implementation in GSD. Finally, we have developed a theoretical framework based on the identified factors that indicated a relationship among the identified factors and the implementation of the RCM process in the context of GSD. We believe that the results of this research can help tackle the complications associated with the RCM in GSD environment, which is vigorous to the success and progression of GSD organizations.

The Reaction of the Malaysian Stock Market to the COVID-19 Pandemic

Mehmood, Waqas,Mohd-Rashid, Rasidah,Aman-Ullah, Attia,Shafique, Owais,Tajuddin, Ahmad Hakimi World Association for Triple Helix and Future Stra 2021 Journal of Contemporary Eastern Asia Vol.20 No.2

The present study was conducted to understand the turmoil effects of COVID-19 pandemic on the Malaysian stock market during the different periods of the Movement Control Order (MCO). The present study was based on the secondary data extracted from the DataStream and Bloomberg from 2nd January 2020 to 29th May 2020 to evaluate the effects of COVID-19 pandemic on the Malaysian stock market. The findings suggested that during the different periods of the Movement Control Order (MCO) from the 1st January to 29th May 2020, the COVID-19 pandemic adversely affected the performance of KLCI index and all sectoral indices. The weakest performance indices were energy, property, and finance while the least affected indices were healthcare, technology, telecommunications, and media. This paper provides a review of the impacts of COVID-19 pandemic on the Malaysian stock market throughout the different periods of MCO.

Dynamic Fractional Frequency Reuse Diversity Design for Intercell Interference Mitigation in Nonorthogonal Multiple Access Multicellular Networks

Mehmood, Kashif,Niaz, Muhammad Tabish,Kim, Hyung Seok Hindawi Limited 2018 WIRELESS COMMUNICATIONS AND MOBILE COMPUTING Vol.2018 No.-

<P>Nonorthogonal multiple access (NOMA) is one of the few promising techniques that can ensure the achievement of benefits foreseen in next-generation 5G wireless networks and beyond. By using superposition coding, NOMA allows multiple users to share the same time and frequency resources, thereby enhancing user connectivity, spectral efficiency, and a considerable increase in user throughput. Interference mitigation is an important consideration in NOMA and is considerably more influencing in multicellular environments. First, a brief description of the impairments that can arise in a NOMA cellular network along with responsible factors is provided. Second, different approaches adopted to minimize these impairments are discussed. Finally, a possible solution is proposed that consists of a coordinated approach between the individual cells in the NOMA domain to minimize interferences and improve user throughput. Adaptive fractional frequency reuse (FFR) is used to allocate distinct frequency resources to edge users of different cells to minimize intercell interference in NOMA. Simulation results prove that the proposed NOMA scheme plays an important role in minimizing impairment effects and enhancing the SINR and the throughput performance of edge users while ensuring fairness in its design.</P>