Techno-Economic Evaluation of the Centralized Hybrid Renewable Energy Systems for Off-Grid Rural Electrification

Atif Naveed Khan,Pervaiz Akhter,Gussan Maaz Mufti 보안공학연구지원센터 2016 International Journal of Smart Home Vol.10 No.5

Pakistan is an energy deficient country and the current power crisis of Pakistan is hampering its economic development. Pakistan is naturally benefitted with different renewable energy resources; out of which solar and wind energy are the main highlights. This research work will provide an assessment of the renewable energy potential of the Baluchistan region. A comparison of the economic and financial analysis for a centralized hybrid renewable energy system has been simulated by using Homer software. Three cases have been proposed in which centralized standalone solar PV system, centralized standalone wind energy system and a hybrid combination of both centralized standalone solar and wind energy system have been studied. Homer software has been used to devise the most optimal solution. The simulations confirm that the best optimal solution is the hybrid renewable energy system for the rural electrification of the proposed region.

Improved Physical Layer Implementation of VANETs

Khan, Latif Ullah,Khattak, M. Irfan,Khan, Naeem,Khan, Atif Sardar,Shafi, M. The Institute of Electronics and Information Engin 2014 IEIE Transactions on Smart Processing & Computing Vol.3 No.3

Vehicular Ad-hoc Networks (VANETs) are comprised of wireless mobile nodes characterized by a randomly changing topology, high mobility, availability of geographic position, and fewer power constraints. Orthogonal Frequency Division Multiplexing (OFDM) is a promising candidate for the physical layer of VANET because of the inherent characteristics of the spectral efficiency and robustness to channel impairments. The susceptibility of OFDM to Inter-Carrier Interference (ICI) is a challenging issue. The high mobility of nodes in VANET causes higher Doppler shifts, which results in ICI in the OFDM system. In this paper, a frequency domain com-btype channel estimation was used to cancel out ICI. The channel frequency response at the pilot tones was estimated using a Least Square (LS) estimator. An efficient interpolation technique is required to estimate the channel at the data tones with low interpolation error. This paper proposes a robust interpolation technique to estimate the channel frequency response at the data subcarriers. The channel induced noise tended to degrade the Bit Error Rate (BER) performance of the system. Parallel concatenated Convolutional codes were used for error correction. At the decoding end, different decoding algorithms were considered for the component decoders of the iterative Turbo decoder. A performance and complexity comparison among the various decoding algorithms was also carried out.

A new anti-Helicobacter pylori juglone from Reynoutria japonica

Atif Ali Khan Khalil,박우성,Jeehoon Lee,김혜진,Kazi Marjahan Akter,Young-Min Goo,Ji-Yeong Bae,Man-Seog Chun,Junghwan Kim,Mi-Jeong Ahn 대한약학회 2019 Archives of Pharmacal Research Vol.42 No.6

A 70% ethanol extract from the root portion of Reynoutria japonica afforded one new and three known juglone derivatives, namely, 2-methoxy-6-acetyl-7-methyljuglone (1), 2-ethoxy-6-acetyl-7-methyljuglone (2), 2-methoxy-7-acetonyljuglone (3), and 3-acetyl-7-methoxy-2-methyljuglone (4) together with two phenolics (5 and 6), an anthraquinone (7), a stilbene (8) and a phthalide (9). Their structures were elucidated on the basis of comprehensive spectroscopic studies including IR, MS, and 1H, 13C, 2D NMR spectra. Compound 3 is a new compound in nature, and compounds 4–6 have been isolated for the first time from R. japonica. The isolates were evaluated for their antibacterial activity against three strains (43504, 51, and 26695) of Helicobacter pylori. The four isolated juglone derivatives (1–4) showed potent growth inhibitory activity. Among them, compounds 1–3 exhibited stronger inhibitory activity than those of the positive controls, juglone and metronidazole, for the three strains and that of another reference, clarithromycin, for the 43504 and 51 strains. Specifically, the new juglone compound 3 displayed the most potent antibacterial activity against all three strains, 43504, 51, and 26695, with MIC values of 0.06, 0.06 and 0.13 μM, respectively, and MIC50 values of 0.14, 0.11 and 0.15 μM, respectively.

Junctionless Diode Enabled by Self-Bias Effect of Ion Gel in Single-Layer MoS₂ Device

Khan, Muhammad Atif,Rathi, Servin,Park, Jinwoo,Lim, Dongsuk,Lee, Yoontae,Yun, Sun Jin,Youn, Doo-Hyeb,Kim, Gil-Ho American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.32

<P>The self-biasing effects of ion gel from source and drain electrodes on electrical characteristics of single layer and few layer molybdenum disulfide (MoS2) field-effect transistor (FET) have been studied. The self-biasing effect of ion gel is tested for two different configurations, covered and open, where ion gel is in contact with either one or both, source and drain electrodes, respectively. In open configuration, the linear output characteristics of the pristine device becomes nonlinear and on off ratio drops by 3 orders of magnitude due to the increase in 'off' current for both single and few layer MoS2 FETs. However, the covered configuration results in a highly asymmetric output characteristics with a rectification ofaround 10(3) and an ideality factor of 1.9. This diode like behavior has been attributed to the reduction of Schottky barrier width by the electric field of self-biased ion gel, which enables an efficient injection of electrons by tunneling at metal-MoS2 interface. Finally, finite element method based simulations are carried out and the simulated results matches well in principle with the experimental analysis. These self-biased diodes can perform a crucial role in the development of high-frequency optoelectronic and valleytronic devices.</P>

P-doping and efficient carrier injection induced by graphene oxide for high performing WSe₂ rectification devices

Khan, Muhammad Atif,Rathi, Servin,Lee, Inyeal,Li, Lijun,Lim, Dongsuk,Kang, Moonshik,Kim, Gil-Ho American Institute of Physics 2016 APPLIED PHYSICS LETTERS Vol.108 No.9

Lupeol supplementation improves the developmental competence of bovine embryos <i>in vitro</i>

Khan, Imran,Chowdhury, M.M.R.,Song, Seok-Hwan,Mesalam, Ayman,Zhang, Shimin,Khan Khalil, Atif Ali,Jung, Eun-Hee,Kim, Ju-Boong,Jafri, Laila,Mirza, Bushra,Kong, Il-Keun Elsevier 2018 Theriogenology Vol.107 No.-

<P><B>Abstract</B></P> <P>Lupeol is a triterpene with various pharmacological properties. This study investigated the effect of lupeol on the <I>in vitro</I> development of bovine embryos. Oocytes <B>(</B>270 per group, 1620 in total<B>)</B> obtained from slaughterhouse-derived ovaries were matured and fertilized <I>in vitro</I> and then cultured for 8 days in a humidified atmosphere of 5% CO<SUB>2</SUB> in air at 38.5 °C. The <I>in vitro</I> maturation medium was supplemented with 0.5, 1.0, 2.0, 3.0, and 4.0 μM lupeol. Treatment with 2.0 μM lupeol significantly (<I>P</I> < 0.05) improved blastocyst development. Hoechst 33342 staining and terminal deoxynucleotidyl transferase dUTP nick-end labeling showed that treatment with 2.0 μM lupeol improved blastocyst quality by increasing the total cell number and reducing the apoptotic cell number. Confocal microscopy confirmed that treatment with 2.0 μM lupeol significantly (<I>P</I> < 0.05) reduced the level of 8-oxoguanine, an indicator of reactive oxygen species. Lupeol treatment also significantly attenuated protein expression of nuclear factor-kappa B subunit 1 (NFKB1), cyclooxygenase (COX) 2, and CASP3. Real-time PCR analysis of <I>nitric oxide synthase 2</I>, <I>NFKB1</I>, <I>COX2</I>, <I>CASP3</I>, and <I>BCL2-associated X protein</I> supported the immunofluorescence data. In conclusion, lupeol is a potent antioxidant that improves bovine embryo development <I>in vitro</I>.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Lupeol is a potent antioxidant and it significantly improves the cleavage and blastocyst developmental potentials <I>in vitro</I>. </LI> <LI> Lupeol protects oocytes against oxidative stress in in <I>vitro</I>-culture system. </LI> <LI> Lupeol improves the embryo quality by increasing the total cell numbers and decreasing the apoptotic nuclei of embryo. </LI> <LI> Lupeol down regulates the NF-kB pathway and improves the bovine embryo quality <I>in vitro</I>. </LI> </UL> </P>

Tunable Electron and Hole Injection Enabled by Atomically Thin Tunneling Layer for Improved Contact Resistance and Dual Channel Transport in MoS₂/WSe₂ van der Waals Heterostructure

Khan, Muhammad Atif,Rathi, Servin,Lee, Changhee,Lim, Dongsuk,Kim, Yunseob,Yun, Sun Jin,Youn, Doo-Hyeb,Kim, Gil-Ho American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.28

<P>Two-dimensional (2D) material-based heterostructures provide a unique platform where interactions between stacked 2D layers can enhance the electrical and opto-electrical properties as well as give rise to interesting new phenomena. Here, the operation of a van der Waals heterostructure device comprising of vertically stacked bilayer MoS<SUB>2</SUB> and few layered WSe<SUB>2</SUB> has been demonstrated in which an atomically thin MoS<SUB>2</SUB> layer has been employed as a tunneling layer to the underlying WSe<SUB>2</SUB> layer. In this way, simultaneous contacts to both MoS<SUB>2</SUB> and WSe<SUB>2</SUB> 2D layers have been established by forming a direct metal-semiconductor to MoS<SUB>2</SUB> and a tunneling-based metal-insulator-semiconductor contacts to WSe<SUB>2</SUB>, respectively. The use of MoS<SUB>2</SUB> as a dielectric tunneling layer results in an improved contact resistance (80 kΩ μm) for WSe<SUB>2</SUB> contact, which is attributed to reduction in the effective Schottky barrier height and is also confirmed from the temperature-dependent measurement. Furthermore, this unique contact engineering and type-II band alignment between MoS<SUB>2</SUB> and WSe<SUB>2</SUB> enables a selective and independent carrier transport across the respective layers. This contact engineered dual channel heterostructure exhibits an excellent gate control and both channel current and carrier types can be modulated by the vertical electric field of the gate electrode, which is also reflected in the on/off ratio of 10<SUP>4</SUP> for both electron (MoS<SUB>2</SUB>) and hole (WSe<SUB>2</SUB>) channels. Moreover, the charge transfer at the heterointerface is studied quantitatively from the shift in the threshold voltage of the pristine MoS<SUB>2</SUB> and the heterostructure device, which agrees with the carrier recombination-induced optical quenching as observed in the Raman spectra of the pristine and heterostructure layers. This observation of dual channel ambipolar transport enabled by the hybrid tunneling contacts and strong interlayer coupling can be utilized for high-performance opto-electrical devices and applications.</P> [FIG OMISSION]</BR>

High performance self-gating graphene/MoS₂ diode enabled by asymmetric contacts

Khan, Muhammad Atif,Rathi, Servin,Lee, Changhee,Kim, Yunseob,Kim, Hanul,Whang, Dongmok,Yun, Sun Jin,Youn, Doo-Hyeb,Watanabe, Kenji,Taniguchi, Takashi,Kim, Gil-Ho IOP 2018 Nanotechnology Vol.29 No.39

<P>A graphene-MoS<SUB>2</SUB> (GM) heterostructure based diode is fabricated using asymmetric contacts to MoS<SUB>2</SUB>, as well as an asymmetric top gate (ATG). The GM diode exhibits a rectification ratio of 5 from asymmetric contacts, which is improved to 10<SUP>5</SUP> after the incorporation of an ATG. This improvement is attributed to the asymmetric modulation of carrier concentration and effective Schottky barrier height (SBH) by the ATG during forward and reverse bias. This is further confirmed from the temperature dependent measurement, where a difference of 0.22 eV is observed between the effective SBH for forward and reverse bias. Moreover, the rectification ratio also depends on carrier concentration in MoS<SUB>2</SUB> and can be varied with the change in temperature as well as back gate voltage. Under laser light illumination, the device demonstrates strong opto-electric response with 100 times improvement in the relative photo current, as well as a responsivity of 1.9 A W<SUP>−1</SUP> and a specific detectivity of 2.4?×?10<SUP>10</SUP> Jones. These devices can also be implemented using other two dimensional (2D) materials and suggest a promising approach to incorporate diverse 2D materials for future nano-electronics and optoelectronics applications.</P>

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.

Spatial investigation of electronic properties in composite electrolytes for solid oxide fuel cells using embedded probes

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>