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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.
Shahzad Kashif,Amin Arslan Ahmed 대한전기학회 2021 Journal of Electrical Engineering & Technology Vol.16 No.5
In this paper, the optimal planning of Distributed Energy Storage Systems (DESSs) in Active Distribution Networks (ADNs) has been addressed. As the proposed problem is mixed-integer, non-convex, and non-linear, this paper has used heuristic optimization techniques. In particular, fi ve optimization techniques namely Genetic algorithm, Particle swarm optimization, Tabu search, Simulated annealing, and Pattern search optimization techniques have been applied to optimal planning of DESS. The problem has been formulated to consider distributed storage units’ optimal locations and sizes to be placed in an ADN while respecting the constraints of the system. The problem has been addressed on two levels. In the fi rst level, an optimization technique is applied for DESS planning to determine the optimal solution and in the second level, the fi tness value of this solution is evaluated by solving a daily AC Optimal Power Flow (OPF) problem. Simulations have been done for the IEEE 34 and IEEE 123 nodes network to demonstrate and compare the effi ciency of diff erent optimization techniques. The comparison of these optimization techniques has shown that Particle swarm optimization and Tabu search optimization (with a particular value of tabu tenure found by hit and trial) have performed better in fi nding the lowest DESS location corresponding to minimum fi tness value as compared to other optimization techniques both for IEEE 34 nodes and IEEE 123 nodes network
Sulfur-doped graphene laminates for EMI shielding applications
Shahzad, Faisal,Kumar, Pradip,Yu, Seunggun,Lee, Seunghwan,Kim, Yoon-Hyun,Hong, Soon Man,Koo, Chong Min The Royal Society of Chemistry 2015 Journal of Materials Chemistry C Vol.3 No.38
<▼1><P>Herein, for the first time, we demonstrate that a laminated structure of sulfur-doped reduced graphene oxide (SrGO) provides significant potential for electromagnetic interference shielding applications.</P></▼1><▼2><P>Herein, for the first time, we demonstrate that a laminated structure of sulfur-doped reduced graphene oxide (SrGO) provides significant potential for electromagnetic interference shielding applications. In this study, SrGO was prepared through the reaction between graphene oxide and hydrogen disulfide (H2S) gas at elevated temperatures. The doping degree of S was controlled through varying the time and temperature of the reaction and the maximum doping content of 5.6 wt% was achieved. Because of the n-type doping contribution of the S atom to the doped graphene, SrGO laminate not only revealed a 47% larger electrical conductivity (75 S cm<SUP>−1</SUP>) than undoped reduced graphene oxide laminate (51 S cm<SUP>−1</SUP>) but also revealed 119% larger EMI shielding effectiveness (33.2 dB) than the undoped one (15.5 dB) at the same sample thickness.</P></▼2>
Shahzad, Aamir,Udagepola, Kalum Priyanath,Lee, Young-keun,Park, Soojin,Lee, Malrey SAGE Publications 2015 INTERNATIONAL JOURNAL OF DISTRIBUTED SENSOR NETWOR Vol.2015 No.-
<P>This study examined the security of SCADA system and its protocols, more specifically, SCADA/DNP3 protocol security. To achieve the study goals, a SCADA simulation environment is designed for water pumping process through connectivity of intelligent sensors, the payload is constructed, and security is deployed inside DNP3 protocol stack and then bytes are multicast to subcontrollers.</P>
Dual targeting of EphA2 and FAK in ovarian carcinoma.
Shahzad, Mian M K,Lu, Chunhua,Lee, Jeong-Won,Stone, Rebecca L,Mitra, Rahul,Mangala, Lingegowda S,Lu, Yiling,Baggerly, Keith A,Danes, Christopher G,Nick, Alpa M,Halder, Jyotsnabaran,Kim, Hye-Sun,Vivas- Landes Bioscience 2009 Cancer Biology & Therapy Vol.8 No.11
<P>EphA2 gene silencing has been shown to result in antitumor efficacy. Here we considered whether silencing additional targets downstream of EphA2 would further enhance the therapeutic effect. EphA2 targeted siRNA was tested in combination with either FAK or Src targeted siRNA using DOPC nanoliposomes in orthotopic models of ovarian carcinoma. The effects of therapy were determined by changes in tumor weight, proliferation (Ki-67), and microvessel density (CD31). In our initial in vivo study, EphA2 plus FAK silencing resulted in the greatest reduction in tumor growth (by 73%, p < 0.005) as compared to control siRNA alone. In the SKOV3ip1 and HeyA8 ovarian cancer models, EphA2 siRNA-DOPC treatment resulted in a 50-67% decrease in tumor growth (p < 0.02, for both), and FAK siRNA-DOPC resulted in a 61-62% decrease in tumor growth (p < 0.009, p < 0.05, respectively). EphA2 plus FAK siRNA-DOPC treatment resulted in a significant reduction (SKOV3ip1: 76%, p < 0.007, HeyA8: 90%, p < 0.003) in tumor growth compared to control siRNA-DOPC. Combination treatment with EphA2 + FAK siRNA-DOPC resulted in significant decreases in tumor cell proliferation (p < 0.001) and microvessel density compared to control siRNA-DOPC (80%; p < 0.001), or the monotherapy groups (p values <0.001). These data suggest that the antitumor efficacy of in vivo EphA2 targeting is enhanced in combination with FAK silencing. Dual targeting of EphA2 and FAK may have therapeutic implications for ovarian cancer management.</P>
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.
Shahzad, Ahsan,Ko, Seunguk,Lee, Samgyu,Lee, Jeong-A,Kim, Kiseon IEEE 2017 IEEE SENSORS JOURNAL Vol.17 No.20
<P>Falls are a major cause of morbidity and long-term hospitalization among growing older population. An automated and accurate fall-risk assessment system is vital to identify high fall-risk population and to prevent falls by early intervention. Therefore, this paper provides an objective, cost-effective, and unsupervised method to obtain functional balance and mobility assessment-based fall-risk of community-dwelling older adults. More specifically, waist-mounted triaxial accelerometer signals acquired from directed routine (supervised control movements) are used to estimate the well-known clinical assessment score-Berg balance scale (BBS). The trunk acceleration signals are used to extract features and to find the optimal subset of features for each training data during repeated tenfold cross validation of the BBS estimation model. The average of two BBS estimates based on test and retest yielded a strong correlation rho = 0.86 with the standard BBS score. Also, high correlation (rho = 0.90) and low root-mean-square error (1.66) was observed between the two estimates of each subject. The proposed method is well suited for the assessment of balance impairment and pre-screening of quantitative fall-risk in an unsupervised setting. It has the potential to act as a surrogate of the standard clinical assessment-BBS.</P>
Shahzad, Faisal,Zaidi, Shabi Abbas,Koo, Chong Min American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.28
<P>Doping with heteroatoms is a well-established method to tune the electronic properties and surface chemistry of graphene. Herein, we demonstrate the synthesis of a fluorine-doped reduced graphene oxide (FrGO) at low temperatures that offers multiple opportunities in applied fields. The as-synthesized FrGO product shows a better electrical conductivity of 750 S m(-1) than that of undoped rGO with an electrical conductivity of 195 S m(-1). To demonstrate the multifunctional applications of the as-synthesized FrGO, it was examined for electromagnetic interference shielding and electrochemical sensing of histamine as an important food biomarker. A laminate of FrGO delivered an EMI shielding effectiveness value of 22 dB in Ku band as compared with 11.2 dB for an rGO laminate with similar thickness. On the other hand, an FrGO modified sensor offered an excellent sensitivity (similar to 7 nM), wide detection range, and good selectivity in the presence of similar biomarkers. This performance originates from the better catalytic ability of FrGO as compared with rGO, where fluorine atoms play the role of catalytic active sites owing to their high electronegativity. The fluorination reaction also helps to improve the reduction degree of the chemically synthesized graphene, consequently enhancing the electrical conductivity, which is a prime requirement for increasing the electromagnetic and electrochemical properties of graphene.</P>