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Javaid, Saqib,Myung, Chang Woo,Pourasad, S.,Rakshit, Bipul,Kim, Kwang S.,Lee, Geunsik The Royal Society of Chemistry 2018 Journal of Materials Chemistry A Vol.6 No.38
<P>Degradation of perovskite halide materials under humid conditions is one of the major hurdles in the commercialization of organic-inorganic perovskite solar cells. Herein, we studied the interface between highly hydrophobic fluorographene (FGr) and cubic methylammonium lead iodide (MAPbI3, MA: CH3-NH3) by employing density functional theory (DFT)-based simulations. We demonstrate that the adsorption of FGr on MAPbI3 results in the formation of a stable interface with appreciable binding energy (∼0.4 eV per Pb atom). Thorough assessment of energy-level alignment indicates that the FGr/MAPbI3 interface has desirable properties with regard to the electron transfer (hole blockage) process. These results underscore the potential of using FGr as an interlayer for electron transport between a perovskite layer and an electron transfer medium (such as TiO2) as well as a moisture blocker for achieving high perovskite stability by perfect waterproofing. The future research study towards the integration of hydrophobic FGr or electronically optimized partially fluorinated graphene-based systems within perovskite halide photovoltaic devices may pave the way for stable and efficient solar cell technologies.</P>
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Organic cation steered interfacial electron transfer within organic-inorganic perovskite solar cells
Javaid, Saqib,Myung, Chang Woo,Yun, Jeonghun,Lee, Geunsik,Kim, Kwang S. The Royal Society of Chemistry 2018 Journal of materials chemistry. A, Materials for e Vol.6 No.10
<P>Methylammonium lead-iodide (MAPbI3, MA: CH3-NH3) interfaced with rutile TiO2is widely used in photovoltaic devices. These devices utilize the electron transfer from MAPbI3to TiO2, which may not be explained solely by the band structures of the two bulk materials. To elucidate the interface dynamics and its impact on the electron transfer process, we have studied the interfacial features of a TiO2/MAPbI3system. First principles calculations and<I>ab initio</I>molecular dynamics simulations show that the rotational freedom of MA present within the bulk is considerably suppressed due to interaction of MA with the TiO2substrate, highlighting orientationally ordered MA at the interface. The optimized interface structure shows the C-N axis of MA titled towards the TiO2surface so as to maximize the interaction between N-attached H and underlying O. The very short O⋯H⋯N distance with very large hydrogen bonding energy identifies short strong hydrogen bonding (SSHB) as the origin of structural re-organization at the interface. As for the electronic structure, this proton sharing between MA and TiO2has a critical impact on the energy level alignment at the interface, thus driving the electron transfer process from MA to TiO2. Indeed, significant reduction in the electron transfer barrier is observed for the energetically optimal interface configuration which promotes the electron transfer across the interface and photovoltaic properties.</P>
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Javaid, A.,Nisa, Mahr-un,Sarwar, M.,Aasif Shahzad, M. Asian Australasian Association of Animal Productio 2008 Animal Bioscience Vol.21 No.1
Four ruminally cannulated Nili-ravi buffalo bulls were used in a $4{\times}4$ Latin Square design to determine the influence of varying levels of ruminally degradable protein (RDP) on ruminal characteristics, digestibility, blood pH, blood urea nitrogen (BUN) and nitrogen (N) balance. Four isonitrogenous and isocaloric diets were formulated (NRC, 2001). The control diet contained 50% RDP. The medium (MRDP), high (HRDP) and very high (VHRDP) ruminally degradable protein diets had 66, 82 and 100% RDP, respectively. Increasing the level of dietary RDP resulted in a linear decrease in ruminal pH. A quadratic effect of RDP on ruminal pH was also observed with quadratic maxima at the 66% RDP diet. Dietary RDP had a quadratic effect on total bacterial and protozoal count with maximum microbial count at the 82% RDP diet. Increased microbial count was due to increasing level of ruminal ammonia nitrogen ($NH_3-N$). Increasing dietary RDP resulted in a linear increase in dry matter digestibility. Provision of an adequate amount of RDP caused optimum microbial activity, which resulted in improvement in DM digestibility. Increasing the level of dietary RDP resulted in a linear decrease in crude protein (CP) and neutral detergent fiber digestibility. Blood pH remained unaltered across all diets. A linear increase in ruminal $NH_3-N$ and BUN was noted with increasing level of dietary RDP. The increase in BUN was due to increased ruminal $NH_3-N$ concentrations. A positive N balance was noted across all diets. The results are interpreted to suggest that buffalo bulls can utilize up to 82% RDP of total CP (16%) with optimum results.
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Javaid, Muhammad Yasar,Ovinis, Mark,Hashim, Fakhruldin B.M.,Maimun, Adi,Ahmed, Yasser M.,Ullah, Barkat The Society of Naval Architects of Korea 2017 International Journal of Naval Architecture and Oc Vol.9 No.4
We are developing a prototype underwater glider for subsea payload delivery. The idea is to use a glider to deliver payloads for subsea installations. In this type of application, the hydrodynamic forces and dynamic stability of the glider is of particular importance, as it has implications on the glider's endurance and operation. In this work, the effect of two different wing forms, rectangular and tapered, on the hydrodynamic characteristics and dynamic stability of the glider were investigated, to determine the optimal wing form. To determine the hydrodynamic characteristics, tow tank resistance tests were carried out using a model fitted alternately with a rectangular wing and tapered wing. Steady-state CFD analysis was conducted using the hydrodynamic coefficients obtained from the tests, to obtain the lift, drag and hydrodynamic derivatives at different angular velocities. The results show that the rectangular wing provides larger lift forces but with a reduced stability envelope. Conversely, the tapered wing exhibits lower lift force but improved dynamic stability.
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Integration of context awareness in Internet of Agricultural Things
Nadeem Javaid 한국통신학회 2023 ICT Express Vol.9 No.2
This work explores an efficient integration of IoT devices based on context awareness in the agricultural sector. A four-layered framework is proposed in which automation techniques are embedded to get real-time context aware insights from the ecosystem of IoT. The framework is evaluated using a strategic tool called threats, opportunities, weaknesses and strengths (TOWS) matrix to measure the performance of automation techniques. This analysis points out various opportunities to innovate the livelihood of agrarian society around the globe.
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Effect of the Uncorrelated Profile of Rails on Train-Track-Ground Induced Vibrations
Omer Javaid,최동호 한국강구조학회 2021 International Journal of Steel Structures Vol.21 No.2
In predicting the track-ground vibrations induced by moving trains, it is generally assumed that the irregularities of two rails of a track are identical and fully correlated. This assumption leads to identical contact forces at the contact point of wheels and rails. In the present paper, the uncorrelated profi le of the two rails is considered to investigate their infl uence on the train-track-ground vibrations. For this purpose, a three-dimensional (3D) fi nite element model capable of simulating interactions between a 3D train and track by using a nonlinear Hertz contact method is developed. Nonlinear Hertz contact is represented by the tensionless stiff ness between the wheels and rails. The rails are modeled as 3D Euler–Bernoulli beam elements. Solid brick elements represent the model components, such as the track (other than rail) and ground. A detailed description of an iterative numerical algorithm is presented to establish the integrations of the train and track system. This iterative numerical algorithm can calculate the responses and forces at the interaction point between each wheel and rail to incorporate the uncorrelated profi le of two rails, instead of only considering the interaction at the centroid of the wheelset axle and the center of the track. A comparative study is conducted by considering various train speeds and three diff erent track cases. The results show that an increase in train speed causes an increase in ground vibration in the case of uncorrelated profi les of two rails of a track. Moreover, the eff ects of correlated and uncorrelated profi les of two rails of a track are investigated in terms of the train-track-ground responses.
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Composite Back Stepping Anti-unwinding Control of Spacecraft with Finite Time Convergence
Umair Javaid,Qing Lei Hu 제어로봇시스템학회 2018 제어로봇시스템학회 국제학술대회 논문집 Vol.2018 No.10
Quaternion representation of spacecraft results in dual equilibrium points. Unwinding phenomenon occurs if both the points are not considered stable while designing control law. This research note proposes anti-unwinding attitude stabilization control of rigid body spacecraft in presence of external disturbance and inertial uncertainties. In pursuit of our goal, we formulated sliding surface using scalar component of quaternion and developed composite anti-unwinding control law using back-stepping technique (BT), in accomplice with sliding mode control (SMC). Furthermore, state transformation is performed to facilitate application of observer for estimation of lumped uncertainties. We employed extended state observer (ESO) to compensate for external disturbance and inertial uncertainties. The control law gives precise and smooth steady state performance along with faster transient response. Additionally, it has better uncertainty rejection capabilities and alleviates chattering phenomenon. Close loop stability of the system is proved using Lyapunov’s theory and Barbalat’s lemma in finite time (FT). Simulation results demonstrate effectiveness of the presented control law.
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Shiekh Javaid A.,Sofi Ishfaq Bashir,Bhat Zahid A.,Parah Shabir A. 한국통신학회 2023 ICT Express Vol.9 No.5
Energy and spectral efficiency are attracting attention as “emerging technology” that exploits the opportunities of sensing, communications and artificial intelligence. This paper proposes the features of these state of art techniques a new energy and spectrum efficient technique for 5G and beyond networks. By using Interference aware (IA) beam selection in beam-space MIMO, the large number of users are supported with a smaller number of radio-frequency (RF) chains at the same time and frequency resource. It has been observed from the proposed scheme that the achievable sum-rate of mm-wave channel model is also improved. From the simulation results it is found that Interference aware (IA) beam selection is used in beam-space to minimize the total obligatory RF-chains in mm-wave massive MIMO communication systems without noticeable loss in performance.
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