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.

DYNAMICS OF PAKISTAN’S POST 9/11 CRISIS FOREIGN POLICY DECISION-MAKING PROCESS

Mehmood Hussain 한국정치사회연구소 2018 한국과 국제사회 Vol.2 No.2

이 연구는 파키스탄에서 9/11 테러 이후 외교정책 결정 과정을 추적하기 위해 4단계 위기에서의 국가 행동 모델 을 적용했다. 그것은 알카에다의 미국에 대한 불길한 공격과 테러에 맞서 싸우기 위한 부시대통령의 후속 선언이 t1 단계의 세계와 지역의 정치 안보 차원을 변화시켰다고 주장한다. 이웃 국가인 파키스탄의 지원은 테러와의 전쟁에서 불가피했고, 미국은 이슬람 바드의 협력을 얻기 위해 강압적인 외교를 취했다. 결과적으로, 미국의 요구를 수용하지 않을 경우 파키스탄은 국가의 기본 가치/목표에 대한 위협을 인식하고 동시에 시간 압박은 t2 단계에서 의사결정자들의 심리적 스트레스를 증폭시켰다. 따라서 의사결정 포럼은 t3 단계에서 시작되었고 파키스탄은 외교 정책 위기를 완화시킨 t4 단계로 미국에 합류하기로 결정했다. The study has applied the four stage Model of State Behavior in Crisis to trace the post 9/11 crisis foreign policy decision making process in Pakistan. It argues that ominous attacks on the United States by al-Qaeda and subsequent declaration of President Bush to fight against terrorism transformed the global and regional politico-security dimensions at t1 stage. Being a neighboring country, Pakistan’s support was inevitable in the war on terror and Washington applied coercive diplomacy to win the cooperation from Islamabad. Consequently, in case of decline to accept American demands, Pakistan perceived threat to basic values/objectives of the country and simultaneous time pressure amplified the psychological stress in decision makers at t2 stage. Therefore, the decisional forum was setup at t3 stage and Pakistan decided to join the United States at t4 stage, which defused the foreign policy crisis.

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>

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.

An efficient decal transfer method using a roll-press to fabricate membrane electrode assemblies for direct methanol fuel cells

Mehmood, A.,Ha, H.Y. Pergamon Press ; Elsevier Science Ltd 2012 International journal of hydrogen energy Vol.37 No.23

This study has focused on the development of a roll-press based decal transfer method to fabricate membrane electrode assemblies (MEAs) for direct methanol fuel cells (DMFCs). This method exhibits an outstanding transfer rate of catalyst layers from substrates to the membrane, despite hot-pressing at a considerably lower pressure and for a much shorter duration than the flat-press based conventional decal method. The MEA produced by a roll-press (R-MEA) delivers an excellent single-cell performance with power densities more than 30% higher than that fabricated using a flat-press (F-MEA). The new method considerably improves catalyst active sites in both electrodes and renders a high cathode porosity. The superior pore structure of the cathode makes the R-MEA more efficient in terms of performance and operation stability under lower air stoichiometries. Moreover, MEAs can be prepared in a continuous mode using this new method due to the unique design of the roll-press. All these advantages demonstrate the superiority of this method over the conventional flat-press decal method and make it suitable for use in the commercial manufacturing of MEAs for direct methanol fuel cells.

혼합형 태양조명 시스템의 효율적 적용을 통한 에너지절약 및 온실 가스 배출 감소 연구

Mehmood Uzair Muhammad,임상훈(Lim Sang Hoon),한현주(Han Hyun Joo),문성호(Moon Sung Ho),천원기(Chun Wongee) 한국에너지기후변화학회 2019 한국에너지기후변화학회 학술대회 Vol.2019 No.05

Corroborating social media echelon in cancer research

Mehmood, A.,On, B. W.,Lee, I.,Park, H. W.,Choi, G. S. Springer Science + Business Media 2018 Quality & quantity Vol.52 No.2

<P>Worldwide medical facilities differ, and for this reason, the causes of death can vary. Cancer is considered the second leading cause of death after heart disease worldwide, and the same causes of death are observed in the United States (US). Therefore, the purposes of this study are to explore worldwide research levels in the field of cancer and the social collaboration of researchers and institutions in this field. This article examines the structural patterns of international co-authors and co-institutions in science citation index papers in cancer research. The study uses measures from the social network analysis method, including degree centrality, betweenness centrality, eigenvector centrality, and effectiveness, to investigate the effects of social networks in the area of cancer research. Empirical analysis results identify the US is the most central country, followed by Germany, Italy, France, and China, in terms of co-authored networks in this research field. Institutional analysis results indicate that the University of Milan is at the top in terms of degree centrality. The Gustave Roussy Cancer Campus in France and German University of Dusseldorf occupy the second and fourth positions, respectively. The University of California in Los Angeles and Harvard University, both in the US, are at third and fifth positions, respectively.</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>