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Niaz, Atif Khan,Lim, Hyung-Tae The Korean Electrochemical Society 2022 Journal of electrochemical science and technology Vol.13 No.3
In this study, the stability of an anion exchange membrane water electrolyzer (AEMWE) cell was evaluated in an on-off cycling operation with respect to an applied electric bias, i.e., a current density of 500 mA cm<sup>-2</sup>, and an open circuit. The ohmic and polarization resistances of the system were monitored during operation (~800 h) using electrochemical impedance spectra. Specific consideration was given to the ohmic resistance of the cell, especially that of the membrane under on-off cycling conditions, by consistently feeding the cell with KOH solution. Owing to an excess feed solution, a momentary increase in the polarization resistance was observed immediately after the open-circuit. The excess feed solution was mostly recovered by subjecting the cell to the applied electric bias. Stability tests on the AEMWE cell under on-off cycling with continuous feeding even under an open circuit can guarantee long-term stability by avoiding an irreversible increase in ohmic and polarization resistances.
Tracing Resistances of Anion Exchange Membrane Water Electrolyzer during Long-term Stability Tests
Niaz, Atif Khan,Lee, Woong,Yang, SeungCheol,Lim, Hyung-Tae The Korean Electrochemical Society 2021 Journal of electrochemical science and technology Vol.12 No.3
In this study, an anion exchange membrane water electrolysis (AEMWE) cell was operated for ~1000 h at a voltage bias of 1.95 V. Impedance spectra were regularly measured every ~ 100 h, and changes in the ohmic and non-ohmic resistance were traced as a function of time. While there was relatively little change in the I-V curves and the total cell resistance during the long-term test, we observed various electrochemical phenomena in the cell: 1) initial activation with a decrease in both ohmic and non-ohmic resistance; 2) momentary and non-permanent bubble resistance (non-ohmic resistance) depending on the voltage bias, and 3) membrane degradation with a slight increase in the ohmic resistance. Thus, the regular test protocol used in this study provided clear insights into the performance degradation (or improvement) mechanism of AEMWE cells.
Niaz, Muhammad Tabish,Imdad, Fatima,Soomi Kim,Hyung Seok Kim IET 2017 IET optoelectronics Vol.11 No.4
<P>This study proposes a receiver for an asymmetrically clipped optical orthogonal frequency-division multiplexing system that utilises the total least-squares (TLS) technique. Commonly used estimation techniques such as least squares, diversity combining, minimum-mean-square-error, and pairwise maximum likelihood ignore the perturbation present while estimating the received signal, which causes the estimated signal to be inaccurate. In this study, a TLS-based receiver is proposed, which takes into consideration the errors present in both the data matrix (channel) and the observation matrix (received signal). While this technique is suboptimal, it is shown that with reasonable computational complexity it has an acceptable performance in a scenario with low processing capability and low battery power. Simulations are carried out for both line-of-sight and non-line-of-sight optical channels and the performance is analysed on the basis of bit error rate versus E-b/N-0 where E-b is the energy received per information bit and N-0 is the noise power spectral density.</P>
Niaz Morshedul Haque,구인수 한국인터넷방송통신학회 2022 International Journal of Internet, Broadcasting an Vol.14 No.1
In the paper, we propose a TSCH-based scheduling scheme for IEEE 802.15.4e, which is able to perform the scheduling of its own network by avoiding collision from interference network cluster (INC). Firstly, we model a bipartite graph structure for presenting the slot-frame (channel-slot assignment) of TSCH. Then, based on the bipartite graph edge weight, we utilize the Hungarian assignment algorithm to implement a scheduling scheme. We have employed two features (maximization and minimization) of the Hungarian-based assignment algorithm, which can perform the assignment in terms of minimizing the throughput of INC and maximizing the throughput of own network. Further, in this work, we called the scheme “dual-stage Hungarian-based assignment algorithm”. Furthermore, we also propose deep learning (DL) based deep neural network (DNN) scheme, where the data were generated by the dual-stage Hungarian-based assignment algorithm. The performance of the DNN scheme is evaluated by simulations. The simulation results prove that the proposed DNN scheme provides similar performance to the dual-stage Hungarian-based assignment algorithm while providing a low execution time.
Niaz, Atif Khan,Jung, Myung Geun,Park, Jun-Young,Virkar, Anil V.,Lim, Hyung-Tae Elsevier 2019 Journal of Power Sources Vol.438 No.-
<P><B>Abstract</B></P> <P>Local electronic conduction is spatially investigated through two types of co-ionic conducting composite electrolytes, BCY15 (BaCe<SUB>0.85</SUB>Y<SUB>0.15</SUB>O<SUB>3-d</SUB>) - GDC20 (Gd<SUB>0.2</SUB>Ce<SUB>0.8</SUB>O<SUB>2-d</SUB>) and BZY15 (BaZr<SUB>0.85</SUB>Y<SUB>0.15</SUB>O<SUB>3-d</SUB>) - NDC10 (Nd<SUB>0.1</SUB>Ce<SUB>0.9</SUB>O<SUB>2-d</SUB>), to understand their durability under abnormal operating conditions. Electrical potential variation is measured through the electrolytes using embedded Pt probes under open circuit conditions, from which we find that an effective electrolyte region (with high electronic resistance) is expanded in both composite electrolytes, in comparison with doped ceria (single phase) electrolyte. In BCY15-GDC20, most of the electrolyte region shows high electronic resistance, except for the region close to the anode. A contrast tendency is observed in BZY15-NDC10 showing mixed conduction in the region close to the cathode. Both types of composite electrolytes degrade under negative voltage conditions, but they are stable under positive voltage conditions. Post-analysis reveals that electrode/electrolyte delamination occurs at the cathode side in BCY15-GDC20 while it occurs at the anode side in BZY15-NDC10. Thus, we can say that the local electronic properties of composite electrolytes determine their stability, and the high electronic resistance region is vulnerable when the cell is subjected to abnormal conditions such as negative cell voltages.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Anode supported BCY15-GDC20 and BZY15-NDC10 cells were fabricated. </LI> <LI> Local electronic conduction was spatially investigated using embedded probes. </LI> <LI> Local electronic properties determined the composite electrolytes' stability. </LI> <LI> High electronic resistance region was vulnerable under negative voltage conditions. </LI> </UL> </P>
( Haider Niaz ),유준,홍성수 한국공업화학회 2020 한국공업화학회 연구논문 초록집 Vol.2020 No.-
Renewable energies have an increasing demand throughout the region due to the fact of increase in greenhouse emissions and depleting natural resources. In this perspective, renewable hydrogen has been recognized as a promising future energy carrier. Although several methods have been and are being developed for the production of hydrogen from renewable energy sources, the only state-of-the-art technique is alkaline water electrolysis. In this study, a comparative techno-economic study for solar photovoltaic (PV) powered AWE, with and without BESS, is conducted to evaluate the levelized cost of hydrogen (LCOH). One-point sensitivity analysis was performed to observe the effect of parameters towards cost. Estimated variation in the raw material price and economic parameter variables highlighted the efficacy of the BESS and AWE hybrid design to ensure a continuous hydrogen production operation at a relatively lower cost.
Smokeless tobacco (paan and gutkha) consumption, prevalence, and contribution to oral cancer
Kamal Niaz,Faheem Maqbool,Fazlullah Khan,Haji Bahadar,Fatima Ismail Hassan,Mohammad Abdollahi 한국역학회 2017 Epidemiology and Health Vol.39 No.-
Smokeless tobacco consumption, which is widespread throughout the world, leads to oral submucous fibrosis (OSMF), which is a long-lasting and devastating condition of the oral cavity with the potential for malignancy. In this review, we mainly focus on the consumption of smokeless tobacco, such as paan and gutkha, and the role of these substances in the induction of OSMF and ultimately oral cancer. The list of articles to be examined was established using citation discovery tools provided by PubMed, Scopus, and Google Scholar. The continuous chewing of paan and swallowing of gutkha trigger progressive fibrosis in submucosal tissue. Generally, OSMF occurs due to multiple risk factors, especially smokeless tobacco and its components, such as betel quid, areca nuts, and slaked lime, which are used in paan and gutkha. The incidence of oral cancer is higher in women than in men in South Asian countries. Human oral epithelium cells experience carcinogenic and genotoxic effects from the slaked lime present in the betel quid, with or without areca nut. Products such as 3-(methylnitrosamino)-proprionitrile, nitrosamines, and nicotine initiate the production of reactive oxygen species in smokeless tobacco, eventually leading to fibroblast, DNA, and RNA damage with carcinogenic effects in the mouth of tobacco consumers. The metabolic activation of nitrosamine in tobacco by cytochrome P450 enzymes may lead to the formation of N-nitrosonornicotine, a major carcinogen, and micronuclei, which are an indicator of genotoxicity. These effects lead to further DNA damage and, eventually, oral cancer.