RLECN—A learning based dynamic threshold control of ECN

Shahzad,정은성,김형석 한국통신학회 2023 ICT Express Vol.9 No.6

Explicit congestion notification (ECN) enables the network routers to mark packets instead of dropping them. When the queue size reaches a certain threshold, the queued packets are marked to indicate predicted congestion. However, an optimal value of the ECN threshold is not defined. A pre-decided value is chosen either by estimation or by hit and trial and therefore, it does not generalize well under a wide range of network scenarios. We propose a reinforcement learning (RL)-based ECN mechanism that utilizes software-defined networks (SDN) to address this problem. Our solution enables the routers to keep a dynamic ECN threshold according to the current network conditions. SDN provides the network visibility and reach to train the RL model and to dynamically adjust the ECN threshold. We show through experimental results that our proposed model outperforms the current state of the art.

Foliar application of methyl jasmonate induced physio-hormonal changes in Pisum sativum under diverse temperature regimes

Shahzad, R.,Waqas, M.,Khan, A.L.,Hamayun, M.,Kang, S.M.,Lee, I.J. Gauthier-Villars ; Elsevier Science Ltd 2015 Vol. No.

Global climate change brings with it unwarranted shifts in both abiotic (heat stress, cold stress, wind, precipitation) and biotic (pathogens, pests) environmental factors, thus posing a threat to agricultural productivity across the world. In plants, lodging due to storms or herbivory causes wounding stress and consequently enhances endogenous jasmonates. In response, the plant growth is arrested as plant defense is prioritized. We pre-treated pea plants with elevated methyl jasmonate (MeJA) levels i.e. 50 μM, 100 μM and 200 μM under controlled growth chamber conditions. The pre-treated plants were then kept at 40 <SUP>o</SUP>C (heat stress-HS), 4 <SUP>o</SUP>C (cold stress-CS) and 20 <SUP>o</SUP>C (optimum/control temperature-OT) for 72 h. The effect of such treatments on plant growth attributes, photosynthesis, stomatal conductance, cell death rate, and regulation of endogenous hormones were observed. Elevated MeJA application hindered plant growth attributes under HS, CS and OT conditions. Moreover, elevated MeJA levels lowered the rate of photosynthesis and stomatal conductance, induced stomatal closure, caused higher cells mortality in leaves under HS, CS, and OT conditions. Endogenous ABA contents significantly declined in all MeJA treatments under HS and OT, but increased under CS conditions. Exogenous MeJA enhanced endogenous jasmonic acid contents of pea plants, but altered endogenous salicylic acid contents under varying temperatures. Current study shows that higher concentrations of exogenous MeJA strengthen plant defense mechanism by hindering plant growth under stress conditions.

Biomass-Derived Thermally Annealed Interconnected Sulfur-Doped Graphene as a Shield against Electromagnetic Interference

Shahzad, Faisal,Kumar, Pradip,Kim, Yoon-Hyun,Hong, Soon Man,Koo, Chong Min American Chemical Society 2016 ACS APPLIED MATERIALS & INTERFACES Vol.8 No.14

<P>Electrically conductive thin carbon materials have attracted remarkable interest as a shielding material to mitigate the electromagnetic interference (EMI) produced by many telecommunication devices. Herein, we developed a sulfur-doped reduced graphene oxide (SrGO) with high electrical conductivity through using a novel biomass, mushroom-based sulfur compound (lenthionine) via a twostep thermal treatment. The resultant SrGO product exhibited excellent electrical conductivity of 311 S cm(-1), which is 52% larger than 205 S cm(-1) for undoped rGO. SrGO also exhibited an excellent EMI shielding effectiveness of 38.6 dB, which is 61% larger than 24.4 dB measured for undoped rGO. Analytical examinations indicate that a sulfur content of 1.95 atom % acts as n-type dopant, increasing electrical conductivity and, therefore, EMI shielding of doped graphene.</P>

Seed-borne endophytic Bacillus amyloliquefaciens RWL-1 produces gibberellins and regulates endogenous phytohormones of Oryza sativa

Shahzad, R.,Waqas, M.,Khan, A.L.,Asaf, S.,Khan, M.A.,Kang, S.M.,Yun, B.W.,Lee, I.J. Gauthier-Villars ; Elsevier Science Ltd 2016 Vol. No.

<P>Some microorganisms are adapted to an endophytic mode, living symbiotically with plants through vertical transmission in seeds. The role of plant growth-promoting endophytes has been well studied, but those of seed-associated endophytic bacteria are less understood. The current study aimed to isolate and identify bacterial endophytes associated with rice (Oryza sativa L. 'Jin so mi') seeds, their potential to produce gibberellins (GAs), and role in improving host-plant physiology. The isolated bacterial endophyte RWL-1 was identified as Bacillus amyloliquefaciens by using 16S rRNA sequencing and phylogenetic analysis. The pure culture of B. amyloliquefaciens RWL-1, supplied with deuterated internal standards, was subjected to gas chromatography and mass spectrometric selected ion monitoring (GC-MS/SIM) for quantification of GAs. Results showed the presence of GAs in various quantities (ng/mL) viz., GA(20) (17.88 +/- 4.04), GA(36) (5.75 +/- 2.36), GA(24) (5.64 +/- 2.46), GA(4) (1.02 +/- 0.16), GA(53) (0.772 +/- 0.20), GA(9) (0.12 +/- 0.09), GA(19) (0.093 +/- 0.13), GA(5) (0.08 +/- 0.04), GA(12) (0.014 +/- 0.34), and GA(8) (0.013 +/- 0.01). Since endogenous seed GAs are essential for prolonged seed growth and subsequent plant development, we used exogenous GA(3) as a positive control and water as a negative control for comparative analysis of the application of B. amyloliquefaciens RWL-1 to rice plants. The growth parameters of rice plants treated with endophytic bacterial cell application was significantly increased compared to the plants treated with exogenous GA3 and water. This was also revealed by the significant up-regulation of endogenous GA(1) (17.54 +/- 2.40 ng), GA(4) (310 +/- 5.41 ng), GA(7) (192.60 +/- 3.32 ng), and GA(9) (19.04 +/- 2.49 ng) as compared to results of the positive and negative control treatments. Rice plants inoculated with B. amyloliquefaciens RWL-1 exhibited significantly higher endogenous salicylic acid (1615.06 +/- 10.81 mu g), whereas endogenous abscisic acid (23.31 +/- 2.76 ng) and jasmonic acid (25.51 +/- 4.20 ng) were observed to be significantly lower in these inoculated plants than in those treated with exogenous GA3 and water. Results of the present study suggest that B. amyloliquefaciens RWL-1 has the ability to produce GAs and that its inoculation in seedlings can be beneficial to rice plants. Broader field trials should be conducted to determine its use as an alternative biofertilizer. (C) 2016 Elsevier Masson SAS. All rights reserved.</P>

Identification of dominant structures and their flow dynamics in the turbulent two-phase flow using POD technique

Shahzad Munir,Muhammad Israr Siddiqui,Morgan Heikal,Abdul Rashid Abdul Aziz,Guillaume de Sercey 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.11

The Proper orthogonal decomposition (POD) method has seen increasingly used in the last two decades and has a lot of applicationsfor the comparison of experimental and numerically simulated data. The POD technique is often used to extract information about coherentstructures dominating the flow. The two-dimensional and two-component instantaneous velocity fields of both liquid and gas phasesof a slug flow were obtained by Particle image velocimetry (PIV) combined with Laser induced fluorescence (LIF). POD was applied tothe velocity fields of both phases separately to identify the coherent flow structures. We focused on POD eigenmodes and their correspondingenergy contents of both liquid and gas phases. The sum of first few eigenmodes that contain maximum turbulent kinetic energyof the flow represents the coherent structures. In the case of liquid phase the first eigenmode contained 42% of the total energy, while inthe gas phase the decaying energy distribution was flat. The POD results showed that the coefficient of mode 1 for the liquid phase oscillatedbetween positive and negative values and had the highest amplitude. For the visualization of coherent motion different linear combinationsof eigenmodes for liquid and gas phases were used. The phenomena of turbulent bursting events associated with Q2 events(low momentum fluid moving away from the wall) and Q4 events (high momentum flow moving towards the wall) were also discussedto assess its contribution in turbulence production.

Sulfur doped graphene/polystyrene nanocomposites for electromagnetic interference shielding

Shahzad, Faisal,Yu, Seunggun,Kumar, Pradip,Lee, Jang-Woo,Kim, Yoon-Hyun,Hong, Soon Man,Koo, Chong Min Elsevier 2015 COMPOSITE STRUCTURES -BARKING THEN OXFORD- Vol.133 No.-

<P><B>Abstract</B></P> <P>In this paper, for the first time, we present a simple and straightforward method to improve not only electrical conductivity and complex permittivity but also electromagnetic interference (EMI) shielding effectiveness of reduced graphene oxide (rGO)/polystyrene (PS) nanocomposites through sulfur doping. Sulfur-doped reduced graphene oxide with thiophene-like structure (2.6at.% S), synthesized through a simple heating process of a mixture of graphene oxide and sulfur powder, revealed almost three times larger electrical conductivity (1095Sm<SUP>−1</SUP>) than undoped rGO (395Sm<SUP>−1</SUP>). The SrGO/PS nanocomposite showed not only 150% larger electrical conductivity and 50% larger complex permittivity, but also improved EMI shielding effectiveness (24.5dB) at a frequency of 18GHz than rGO/PS nanocomposite (21.4dB) at the same loading level of 7.5vol.%. Considering the simplicity and effectiveness of process, sulfur doping of graphene is expected to be used as a versatile method to improve EMI shielding efficiency of graphene/polymer nanocomposites.</P>

Nafion-stabilized two-dimensional transition metal carbide (Ti₃C₂T_x MXene) as a high-performance electrochemical sensor for neurotransmitter

Shahzad, Faisal,Iqbal, Aamir,Zaidi, Shabi Abbas,Hwang, Suk-Won,Koo, Chong Min Elsevier 2019 Journal of industrial and engineering chemistry Vol.79 No.-

<P><B>Abstract</B></P> <P>Herein, we demonstrate the selective sensing of Dopamine (DA), an important neurotransmitter, by using Nafion-stabilized two-dimensional transition metal carbides (Ti<SUB>3</SUB>C<SUB>2</SUB>T<SUB>x</SUB> MXenes). Ti<SUB>3</SUB>C<SUB>2</SUB>T<SUB>x</SUB> was deposited on a glassy carbon electrode followed by Nafion coating to achieve a robust sensitivity (∼3nM), good selectivity, wide detection window (0.015–10μM), high stability, reproducibility, and outstanding recoveries for DA detection in real samples. MXene-based biosensor exhibited much better electrochemical performance when compared with reduced graphene oxide-based biosensor under similar experimental conditions due to the MXenes good electrical conductivity and negatively charged surface which assisted in the selective and sensitive detection of DA.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Ti₃C₂T_x MXene core-shell spheres for ultrahigh removal of mercuric ions

Shahzad, Asif,Nawaz, Mohsin,Moztahida, Mokrema,Jang, Jiseon,Tahir, Khurram,Kim, Jiho,Lim, Youngsu,Vassiliadis, Vassilios S.,Woo, Seung Han,Lee, Dae Sung Elsevier 2019 CHEMICAL ENGINEERING JOURNAL -LAUSANNE- Vol.368 No.-

<P><B>Abstract</B></P> <P>Two-dimensional (2-D) titanium carbide MXene core (Ti<SUB>3</SUB>C<SUB>2</SUB>T<SUB>x</SUB>) shell aerogel spheres (MX-SA) for mercuric ion removal were designed and fabricated with varying concentrations of Ti<SUB>3</SUB>C<SUB>2</SUB>T<SUB>x</SUB> MXene and sodium alginate (SA) using a facile method. Owing to their unique inside structures, high porosities, large specific surface areas, oxygenated functional groups of MXene nanosheets, and available active binding sites, the synthesized microspheres constitute a unique adsorbent for heavy metals removal in water. The MX-SA<SUB>4:20</SUB> spheres exhibit an exceptional adsorption capacity of 932.84 mg/g for Hg<SUP>2+</SUP>, which is among the highest value reported for adsorbents. The adsorbent exhibits high single- and multi-component removal efficiencies, with 100% efficiency for Hg<SUP>2+</SUP> and >90% efficiency for five heavy metal ions. The synthesized materials are highly efficient for Hg<SUP>2+</SUP> removal under extreme pH conditions (0.5–1.0 M HNO<SUB>3</SUB>) and have additional excellent reproducible properties. The micro-size and spherical shape of MX-SA<SUB>4:20</SUB> also allow it to be used in column-packed devices.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ti<SUB>3</SUB>C<SUB>2</SUB>T<SUB>x</SUB> nanosheets were synthesized using a low-toxicity etching agent (NH<SUB>4</SUB>F). </LI> <LI> Core-shell of MX-SA<SUB>4:20</SUB> spheres was capable of very effectively removing heavy metals. </LI> <LI> MX-SA<SUB>4:20</SUB> spheres exhibited exceptional Hg<SUP>2+</SUP> adsorption capacity of 932.84 mg g<SUP>−1</SUP>. </LI> <LI> MX-SA<SUB>4:20</SUB> performed excellently in extreme acidic conditions. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Fabrication of MX-SA<SUB>4:20</SUB> spheres through MXene-Alginate networking and their application in Hg<SUP>2+</SUP> uptake.</P> <P>[DISPLAY OMISSION]</P>

A Simple and Fast Aqueous-Phase Synthesis of Ultra-Highly Concentrated Silver Nanoparticles and Their Catalytic Properties

Shahzad, Aasim,Chung, Minsub,Yu, Taekyung,Kim, Woo-Sik Wiley (John WileySons) 2015 Chemistry - An Asian Journal Vol.10 No.11

<P>A simple and fast synthetic route to ultra-highly concentrated silver nanoparticles with long-term stability by reducing AgNO3 with ascorbic acid in the presence of polyethyleneimine (PEI) as a stabilizer in an aqueous phase is reported. The concentration of silver precursor was as high as 2000???mm (200???g of Ag nanoparticle per liter of water) and the reaction time was less than 10???min. The resulting silver nanoparticles show long-term stability after two months of storage at room temperature without any signs of particle aggregation or precipitation in an aqueous phase. The successful ligand exchange of PEI-stabilized silver nanoparticles to polyethylene glycol (PEG) and polyvinylpyrrolidone (PVP) without particle aggregation is also demonstrated. In addition, the catalytic activities of silver nanoparticles stabilized by various stabilizers prepared by the ligand exchange method was investigated. The PEI-stabilized silver nanoparticles exhibited a higher stability than those of PEG- and PVP-stabilized silver nanoparticles in the diffusion-controlled catalytic reduction of 4-nitrophenol to 4-aminophenol by NaBH4 .</P>

Reliable and Advanced Predictors for Corporate Financial Choices in Pakistan

SHAHZAD, Umeair,FUKAI, Luo,MAHMOOD, Faisal,JING, Liu,AHMED, Zahoor Korea Distribution Science Association 2020 The Journal of Asian Finance, Economics and Busine Vol.7 No.7

Existing studies disagree over the core predictors of firm-level financial choices in developing countries. The general practice only validates the traditional capital structure model, which leads to inconsistency and a lack of novelty. This study removed overfitting issues among existing factors and presented the most reliable and advanced capital structure model in Pakistani firms. The panel data include 368 Pakistani companies from 19 non-financial sectors over the period 2004 to 2017. We apply Akaike and Bayesian Information Criteria to remove overfitting issues among inconsistent proxies in the capital structure model. The fixed effects regression is used for basic results and the Generalized Method of Moments is applied to control the endogeneity. Besides the conventional proxies, we report that credit rating, distance from bankruptcy, managerial concentration, and institutional quality are the most advanced capital structure determinants in Pakistan. These predictors remain significant across firm size and growth levels. Also, the findings confirm that new predictors are reliable to define capital structure dynamics and improve the speed of adjustment in overall and sub-sample analysis. The major findings suggest that managers and policymakers should consider these advanced predictors to design their financial settings in firms.