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RISS 인기검색어
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- 저자 : Shahzad, M.A. (검색결과 277 건)
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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.
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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
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Shahzad, A.,Wijewardhana, K. R.,Song, J. K. Royal Society of Chemistry 2017 Journal of Materials Chemistry A Vol.5 No.45
<P>Chen et al. suggested a skin- contact type triboelectric energy harvesting device [Chen et al., J. Mater. Chem. A, 2017, 5, 12361], which can give a rise to an electrostatic charge issue adversely affecting a person's physical experience. Here we show that adoption of a higher ranking triboelectric material than skin on the positive electrode and size optimisation of the two electrodes can ensure both high power generation and resolution of the electrostatic charge issue.</P>
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Shahzad, F.,Abdullah, M.,Chaudhry, A.S.,Bhatti, J.A.,Jabbar, M.A.,Ahmed, F.,Mehmood, T.,Asim, M.,Ahmed, S.,Kamran, Z.,Irshad, I.,Tahir, M.N. Asian Australasian Association of Animal Productio 2016 Animal Bioscience Vol.29 No.3
The study was carried out to explore the effects of replacing wheat straw with fungal treated wheat straw as an ingredient of total mixed ration (TMR) on the growth performance and nutrient digestibility in Nili Ravi buffalo male calves. Fungal treated wheat straw was prepared using Arachniotus sp. Four TMRs were formulated where wheat straw was replaced with 0 (TMR1), 33 (TMR2), 67 (TMR3), and 100% (TMR4) fungal treated wheat straw in TMR. All TMRs were iso-caloric and iso-nitrogenous. The experimental TMRs were randomly assigned to four groups of male calves (n = 6) according to completely randomized design and the experiment continued for four months. The calves fed TMR2 exhibited a significant improve in dry matter intake, average daily weight gain, feed conversion ratio and feed economics compared to other groups. The same group also showed higher digestibility of dry matter, crude protein, neutral-, and acid detergent fibers than those fed on other TMRs. It is concluded that TMR with 33% fungal-treated wheat straw replacement has a potential to give an enhanced growth performance and nutrient digestibility in male Nili Ravi buffalo calves.
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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>
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An improved indirect evaporative cooler experimental investigation
Shahzad, Muhammad Wakil,Burhan, Muhammad,Ybyraiymkul, Doskhan,Oh, Seung Jin,Ng, Kim Choon ELSEVIER 2019 Applied Energy Vol. No.
<P><B>Abstract</B></P> <P>Air conditioning has enhanced the work efficiency and improved life style by maintaining comfortable environment. The growing demand of air conditioning has negative impact on energy and environment. In 2015, air conditioning consumed 6% of total global electricity produced and it is expected to increase to 20% by 2050. The leveling-off conventional chiller’s efficiency at 0.85 ± 0.03 kW/Rton due to pairing of dehumidification and cooling processes in one machine is not only the major reason of high energy consumption but also the key limitation in efficiency improvement. The de-coupling of dehumidification and cooling processes can be one of the solution to achieve the quantum jump in the performance, 0.6 ± 0.03 kW/Rton, by improving individual processes. We proposed an improved indirect evaporative cooler system for sensible cooling that can be combined with dehumidification processes to achieve sustainable cooling goals. The experimentation on 800 mm long and 280 mm wide generic cell showed that it can produce temperature differential up to 10 °C with small area of heat transfer. It was showed that the proposed vertical heat exchanger configuration with multi point injection of working air is the best configuration of the indirect evaporative cooler, achieving coefficient of performance level of 78 for cooling alone. We expect that overall coefficient of performance level of 7–8 is achievable by incorporating efficient dehumidification processes. We also presented detailed design parameters that can be used as a reference for commercial system design.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Decoupling of latent and sensible load in cooling is the key for sustainability. </LI> <LI> The indirect evaporative cooler integrated with dehumidification is one of the solution. </LI> <LI> Improved IEC with three major modification can achieve COP up to 78 for cooling only. </LI> <LI> The dehumidification system COP around 4–5 can help to achieve overall COP of 7–8. </LI> <LI> The proposed multi injection vertical heat exchanger design has the best performance. </LI> </UL> </P>
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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>
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Shahzad, Amir,Song, Jang-Kun IOP 2016 Journal of Physics. D, Applied Physics Vol.49 No.38
<P>Electrowetting (EW) offers a facile manipulation of a liquid droplet on a surface, and several different systems have been suggested to utilize EW on various applications. In this letter, the manipulation of an electrolyte droplet with a floating movable substrate was investigated on a solid substrate. Two types of approaches were made; firstly, we controlled the vertical position of a floating substrate using EW property of droplets. The tilting angle of a floating substrate can be precisely controlled along two orthogonal directions independently, which can be used to devise a beam deflector. In the other case, mechanical wetting of droplets via external pressure was used to detect the position of a floating substrate; this position sensor has at least four orders of magnitude higher sensitivity than the conventional position sensor based on capacitance.</P>
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