Displaying publications 161 - 180 of 605 in total

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  1. Fulltext A new graph-based molecular descriptor using the canonical representation of the molecule
    Hentabli H, Saeed F, Abdo A, Salim N
    ScientificWorldJournal, 2014;2014:286974.
    PMID: 25140330 DOI: 10.1155/2014/286974
    Molecular similarity is a pervasive concept in drug design. The basic idea underlying molecular similarity is the similar property principle, which states that structurally similar molecules will exhibit similar physicochemical and biological properties. In this paper, a new graph-based molecular descriptor (GBMD) is introduced. The GBMD is a new method of obtaining a rough description of 2D molecular structure in textual form based on the canonical representations of the molecule outline shape and it allows rigorous structure specification using small and natural grammars. Simulated virtual screening experiments with the MDDR database show clearly the superiority of the graph-based descriptor compared to many standard descriptors (ALOGP, MACCS, EPFP4, CDKFP, PCFP, and SMILE) using the Tanimoto coefficient (TAN) and the basic local alignment search tool (BLAST) when searches were carried.
    Matched MeSH terms: Computer Simulation
  2. Fulltext A synchronous-asynchronous particle swarm optimisation algorithm
    Ab Aziz NA, Mubin M, Mohamad MS, Ab Aziz K
    ScientificWorldJournal, 2014;2014:123019.
    PMID: 25121109 DOI: 10.1155/2014/123019
    In the original particle swarm optimisation (PSO) algorithm, the particles' velocities and positions are updated after the whole swarm performance is evaluated. This algorithm is also known as synchronous PSO (S-PSO). The strength of this update method is in the exploitation of the information. Asynchronous update PSO (A-PSO) has been proposed as an alternative to S-PSO. A particle in A-PSO updates its velocity and position as soon as its own performance has been evaluated. Hence, particles are updated using partial information, leading to stronger exploration. In this paper, we attempt to improve PSO by merging both update methods to utilise the strengths of both methods. The proposed synchronous-asynchronous PSO (SA-PSO) algorithm divides the particles into smaller groups. The best member of a group and the swarm's best are chosen to lead the search. Members within a group are updated synchronously, while the groups themselves are asynchronously updated. Five well-known unimodal functions, four multimodal functions, and a real world optimisation problem are used to study the performance of SA-PSO, which is compared with the performances of S-PSO and A-PSO. The results are statistically analysed and show that the proposed SA-PSO has performed consistently well.
    Matched MeSH terms: Computer Simulation
  3. Fulltext A novel sample based quadrature phase shift keying demodulator
    Mohamed Moubark A, Ali SH
    ScientificWorldJournal, 2014;2014:107831.
    PMID: 25197687 DOI: 10.1155/2014/107831
    This paper presents a new practical QPSK receiver that uses digitized samples of incoming QPSK analog signal to determine the phase of the QPSK symbol. The proposed technique is more robust to phase noise and consumes up to 89.6% less power for signal detection in demodulation operation. On the contrary, the conventional QPSK demodulation process where it uses coherent detection technique requires the exact incoming signal frequency; thus, any variation in the frequency of the local oscillator or incoming signal will cause phase noise. A software simulation of the proposed design was successfully carried out using MATLAB Simulink software platform. In the conventional system, at least 10 dB signal to noise ratio (SNR) is required to achieve the bit error rate (BER) of 10(-6), whereas, in the proposed technique, the same BER value can be achieved with only 5 dB SNR. Since some of the power consuming elements such as voltage control oscillator (VCO), mixer, and low pass filter (LPF) are no longer needed, the proposed QPSK demodulator will consume almost 68.8% to 99.6% less operational power compared to conventional QPSK demodulator.
    Matched MeSH terms: Computer Simulation
  4. Fulltext Transmission and control of Plasmodium knowlesi: a mathematical modelling study
    Imai N, White MT, Ghani AC, Drakeley CJ
    PLoS Negl Trop Dis, 2014 Jul;8(7):e2978.
    PMID: 25058400 DOI: 10.1371/journal.pntd.0002978
    INTRODUCTION: Plasmodium knowlesi is now recognised as a leading cause of malaria in Malaysia. As humans come into increasing contact with the reservoir host (long-tailed macaques) as a consequence of deforestation, assessing the potential for a shift from zoonotic to sustained P. knowlesi transmission between humans is critical.

    METHODS: A multi-host, multi-site transmission model was developed, taking into account the three areas (forest, farm, and village) where transmission is thought to occur. Latin hypercube sampling of model parameters was used to identify parameter sets consistent with possible prevalence in macaques and humans inferred from observed data. We then explore the consequences of increasing human-macaque contact in the farm, the likely impact of rapid treatment, and the use of long-lasting insecticide-treated nets (LLINs) in preventing wider spread of this emerging infection.

    RESULTS: Identified model parameters were consistent with transmission being sustained by the macaques with spill over infections into the human population and with high overall basic reproduction numbers (up to 2267). The extent to which macaques forage in the farms had a non-linear relationship with human infection prevalence, the highest prevalence occurring when macaques forage in the farms but return frequently to the forest where they experience higher contact with vectors and hence sustain transmission. Only one of 1,046 parameter sets was consistent with sustained human-to-human transmission in the absence of macaques, although with a low human reproduction number (R(0H) = 1.04). Simulations showed LLINs and rapid treatment provide personal protection to humans with maximal estimated reductions in human prevalence of 42% and 95%, respectively.

    CONCLUSION: This model simulates conditions where P. knowlesi transmission may occur and the potential impact of control measures. Predictions suggest that conventional control measures are sufficient at reducing the risk of infection in humans, but they must be actively implemented if P. knowlesi is to be controlled.

    Matched MeSH terms: Computer Simulation
  5. Fulltext g-Jitter mixed convective slip flow of nanofluid past a permeable stretching sheet embedded in a Darcian porous media with variable viscosity
    Uddin MJ, Khan WA, Amin NS
    PLoS One, 2014;9(6):e99384.
    PMID: 24927277 DOI: 10.1371/journal.pone.0099384
    The unsteady two-dimensional laminar g-Jitter mixed convective boundary layer flow of Cu-water and Al2O3-water nanofluids past a permeable stretching sheet in a Darcian porous is studied by using an implicit finite difference numerical method with quasi-linearization technique. It is assumed that the plate is subjected to velocity and thermal slip boundary conditions. We have considered temperature dependent viscosity. The governing boundary layer equations are converted into non-similar equations using suitable transformations, before being solved numerically. The transport equations have been shown to be controlled by a number of parameters including viscosity parameter, Darcy number, nanoparticle volume fraction, Prandtl number, velocity slip, thermal slip, suction/injection and mixed convection parameters. The dimensionless velocity and temperature profiles as well as friction factor and heat transfer rates are presented graphically and discussed. It is found that the velocity reduces with velocity slip parameter for both nanofluids for fluid with both constant and variable properties. It is further found that the skin friction decreases with both Darcy number and momentum slip parameter while it increases with viscosity variation parameter. The surface temperature increases as the dimensionless time increases for both nanofluids. Nusselt numbers increase with mixed convection parameter and Darcy numbers and decreases with the momentum slip. Excellent agreement is found between the numerical results of the present paper with published results.
    Matched MeSH terms: Computer Simulation
  6. Fulltext Expanded DEMATEL for determining cause and effect group in bidirectional relations
    Falatoonitoosi E, Ahmed S, Sorooshian S
    ScientificWorldJournal, 2014;2014:103846.
    PMID: 24693224 DOI: 10.1155/2014/103846
    Decision-Making Trial and Evaluation Laboratory (DEMATEL) methodology has been proposed to solve complex and intertwined problem groups in many situations such as developing the capabilities, complex group decision making, security problems, marketing approaches, global managers, and control systems. DEMATEL is able to realize casual relationships by dividing important issues into cause and effect group as well as making it possible to visualize the casual relationships of subcriteria and systems in the course of casual diagram that it may demonstrate communication network or a little control relationships between individuals. Despite of its ability to visualize cause and effect inside a network, the original DEMATEL has not been able to find the cause and effect group between different networks. Therefore, the aim of this study is proposing the expanded DEMATEL to cover this deficiency by new formulations to determine cause and effect factors between separate networks that have bidirectional direct impact on each other. At the end, the feasibility of new extra formulations is validated by case study in three numerical examples of green supply chain networks for an automotive company.
    Matched MeSH terms: Computer Simulation
  7. Fulltext Linking Ayurveda and Western medicine by integrative analysis
    Fauzi FM, Koutsoukas A, Lowe R, Joshi K, Fan TP, Glen RC, et al.
    J Ayurveda Integr Med, 2013 Apr;4(2):117-9.
    PMID: 23930045 DOI: 10.4103/0975-9476.113882
    In this article, we discuss our recent work in elucidating the mode-of-action of compounds used in traditional medicine including Ayurvedic medicine. Using computational ('in silico') approach, we predict potential targets for Ayurvedic anti-cancer compounds, obtained from the Indian Plant Anticancer Database given its chemical structure. In our analysis, we observed that: (i) the targets predicted can be connected to cancer pathogenesis i.e. steroid-5-alpha reductase 1 and 2 and estrogen receptor-β, and (ii) predominantly hormone-dependent cancer targets were predicted for the anti-cancer compounds. Through the use of our in silico target prediction, we conclude that understanding how traditional medicine such as Ayurveda work through linking with the 'western' understanding of chemistry and protein targets can be a fruitful avenue in addition to bridging the gap between the two different schools of thinking. Given that compounds used in Ayurveda have been tested and used for thousands of years (although not in the same approach as Western medicine), they can potentially be developed into potential new drugs. Hence, to further advance the case of Ayurvedic medicine, we put forward some suggestions namely: (a) employing and integrating novel analytical methods given the advancements of 'omics' and (b) sharing experimental data and clinical results on studies done on Ayurvedic compounds in an easy and accessible way.
    Matched MeSH terms: Computer Simulation
  8. Fulltext Semisolid metal processing techniques for nondendritic feedstock production
    Mohammed MN, Omar MZ, Salleh MS, Alhawari KS, Kapranos P
    ScientificWorldJournal, 2013;2013:752175.
    PMID: 24194689 DOI: 10.1155/2013/752175
    Semisolid metal (SSM) processing or thixoforming is widely known as a technology that involves the formation of metal alloys between solidus and liquidus temperatures. For the procedure to operate successfully, the microstructure of the starting material must consist of solid near-globular grains surrounded by a liquid matrix and a wide solidus-to-liquidus transition area. Currently, this process is industrially successful, generating a variety of products with high quality parts in various industrial sectors. Throughout the years since its inception, a number of technologies to produce the appropriate globular microstructure have been developed and applied worldwide. The main aim of this paper is to classify the presently available SSM technologies and present a comprehensive review of the potential mechanisms that lead to microstructural alterations during the preparation of feedstock materials for SSM processing.
    Matched MeSH terms: Computer Simulation
  9. Reduced dynamics of two oscillators collectively coupled to a thermal bath
    Tay BA
    Phys Rev E Stat Nonlin Soft Matter Phys, 2013 May;87(5):052117.
    PMID: 23767497
    We study the reduced dynamics of a pair of nondegenerate oscillators coupled collectively to a thermal bath. The model is related to the trilinear boson model where the idler mode is promoted to a field. Due to nonlinear coupling, the Markovian master equation for the pair of oscillators admits non-Gaussian equilibrium states, where the modes distribute according to the Bose-Einstein statistics. These states are metastable before the nonlinear coupling is taken over by linear coupling between the individual oscillators and the field. The Gibbs state for the individual modes lies in the subspace with infinite occupation quantum number. We present the time evolution of a few states to illustrate the behaviors of the system.
    Matched MeSH terms: Computer Simulation
  10. Fulltext A discrete event simulation model for evaluating the performances of an m/g/c/c state dependent queuing system
    Khalid R, Nawawi MK, Kawsar LA, Ghani NA, Kamil AA, Mustafa A
    PLoS One, 2013;8(4):e58402.
    PMID: 23560037 DOI: 10.1371/journal.pone.0058402
    M/G/C/C state dependent queuing networks consider service rates as a function of the number of residing entities (e.g., pedestrians, vehicles, and products). However, modeling such dynamic rates is not supported in modern Discrete Simulation System (DES) software. We designed an approach to cater this limitation and used it to construct the M/G/C/C state-dependent queuing model in Arena software. Using the model, we have evaluated and analyzed the impacts of various arrival rates to the throughput, the blocking probability, the expected service time and the expected number of entities in a complex network topology. Results indicated that there is a range of arrival rates for each network where the simulation results fluctuate drastically across replications and this causes the simulation results and analytical results exhibit discrepancies. Detail results that show how tally the simulation results and the analytical results in both abstract and graphical forms and some scientific justifications for these have been documented and discussed.
    Matched MeSH terms: Computer Simulation
  11. Fulltext A Cobb Douglas stochastic frontier model on measuring domestic bank efficiency in Malaysia
    Hasan MZ, Kamil AA, Mustafa A, Baten MA
    PLoS One, 2012;7(8):e42215.
    PMID: 22900009 DOI: 10.1371/journal.pone.0042215
    Banking system plays an important role in the economic development of any country. Domestic banks, which are the main components of the banking system, have to be efficient; otherwise, they may create obstacle in the process of development in any economy. This study examines the technical efficiency of the Malaysian domestic banks listed in the Kuala Lumpur Stock Exchange (KLSE) market over the period 2005-2010. A parametric approach, Stochastic Frontier Approach (SFA), is used in this analysis. The findings show that Malaysian domestic banks have exhibited an average overall efficiency of 94 percent, implying that sample banks have wasted an average of 6 percent of their inputs. Among the banks, RHBCAP is found to be highly efficient with a score of 0.986 and PBBANK is noted to have the lowest efficiency with a score of 0.918. The results also show that the level of efficiency has increased during the period of study, and that the technical efficiency effect has fluctuated considerably over time.
    Matched MeSH terms: Computer Simulation
  12. Fuzzy time-optimal controller (FTOC) for second order nonlinear systems
    Nagi F, Ahmed SK, Zularnain AT, Nagi J
    ISA Trans, 2011 Jul;50(3):364-75.
    PMID: 21353218 DOI: 10.1016/j.isatra.2011.01.014
    The motivation behind this paper is to seek alternative techniques to achieve a near optimal controller for non-linear systems without solving the analytical problem. In classical optimal control systems, the system states and optimization co-state parameters generate a two-point boundary value problem (TPBVP) using Pontryagin's minimum principle (PMP). The paper contributes a new fuzzy time-optimal controller to the existing fuzzy controllers which has two regular inputs and one bang-bang output. The proposed controller closely approximates the output of the classical time-optimal controller. Further, input membership function are tuned on-line to improve the time-optimal output. The new controller exhibits optimal behaviour for second order non-linear systems. The rules are selected to satisfy the stability and optimality conditions of the new fuzzy time-optimal controller. The paper describes a systematic procedure to design the controller and how to achieve the desired result. To benchmark the new controller performance, a sliding mode controller is used for guidance and comparison purpose. Simulation of three non-linear examples shows promising results. The work described here is expected to incite researcher's interest in fuzzy time-optimal controller design.
    Matched MeSH terms: Computer Simulation
  13. Sewage sludge composting simulation as carbon/nitrogen concentration change
    Kabbashi N
    J Environ Sci (China), 2011;23(11):1925-8.
    PMID: 22432320
    Available composting models do not describe accurately the dynamics of composting processes. Difficulty in modeling composting processes is attributed mainly to the unpredicted change in process rate caused by change in activation energy value (E). This article presented the results of an attempt made to utilize patterns of change in carbon, nitrogen and temperature profiles to model sewage sludge composting process as a multi-stage process. Results of controlled sewage sludge composting experiments were used in the study. All the experiments were carried out as batch experiments in a 300-liter Horizontal Drum Bioreactor (HDB). Analysis of the profiles of carbon, nitrogen and temperature has indicated that there were clear patterns that could be used to develop simple models of the process, the initial C/N ratio was between 7-8 and the final C/N ratio of the compost in most experiments were found to be around 15.0, indicating the compost was fully matured and could be used safely for agricultural purpose. Electrical conductivity of composting material decreased from 1.83 to 1.67 dS/m, after a period, it increased gradually from 2.01 to 2.23 dS/m and remained at around 2.33 dS/m till the end of composting. It is found that change in the concentration of total carbon can reasonably be described by three constant process rate coefficients (k1, k2, k3). It is found that the process starts with a certain process rate coefficient (k1) and continues until peak temperature is reached, then it reaches lower process (k2) in the declining phase of the thermophilic stage, and finally it proceeds with a faster process rate (k3) when maturation is reached. Change in the concentration of total nitrogen has shown to have the same patterns of change as carbon.
    Matched MeSH terms: Computer Simulation
  14. Modeling of reaction kinetics for transesterification of palm-based methyl esters with trimethylolpropane
    Kamil RN, Yusup S
    Bioresour Technol, 2010 Aug;101(15):5877-84.
    PMID: 20304636 DOI: 10.1016/j.biortech.2010.02.084
    A mathematical model describing chemical kinetics of transesterification of palm-based methyl esters with trimethylolpropane has been developed. The model was developed by utilizing nonlinear regression method, which is an efficient and powerful way to determine rate constants for both forward and reverse reactions. A comparison with previous study which excludes the reverse reactions was made. The model was based on the reverse mechanism of transesterification reactions and describes concentration changes of trimethylolpropane, monoesters and diesters production. The developed model was validated against data from the literature. The reaction rate constants were determined using MATLAB version 7.2 and the ratios of rate constants obtained were well in agreement with those reported in the literature. A good correlation between model simulations and experimental data was observed. It was proven that both methods were able to predict the rate constants with plausible accuracy.
    Matched MeSH terms: Computer Simulation
  15. Effect-compartment equilibrium rate constant (keo) for propofol during induction of anesthesia with a target-controlled infusion device
    Lim TA, Wong WH, Lim KY
    J Anesth, 2006;20(2):153-5.
    PMID: 16633780
    The effect-compartment concentration (C(e)) of a drug at a specific pharmacodynamic endpoint should be independent of the rate of drug injection. We used this assumption to derive an effect-compartment equilibrium rate constant (k(eo)) for propofol during induction of anesthesia, using a target controlled infusion device (Diprifusor). Eighteen unpremedicated patients were induced with a target blood propofol concentration of 5 microg x ml(-1) (group 1), while another 18 were induced with a target concentration of 6 microg x ml(-1) (group 2). The time at loss of the eyelash reflex was recorded. Computer simulation was used to derive the rate constant (k(eo)) that resulted in the mean C(e) at loss of the eyelash reflex in group 1 being equal to that in group 2. Using this population technique, we found the k(eo) to be 0.57 min(-1). The mean (SD) effect compartment concentration at loss of the eyelash reflex was 2.39 (0.70) microg x ml(-1). This means that to achieve a desired C(e) within 3 min of induction, the initial target blood concentration should be set at 1.67 times that of the desired C(e) for 1 min, after which it should revert to the desired concentration.
    Matched MeSH terms: Computer Simulation
  16. Automatic generation of controllers for embodied legged organisms: a Pareto evolutionary multi-objective approach
    Teo J, Abbass HA
    Evol Comput, 2004;12(3):355-94.
    PMID: 15355605
    In this paper, we investigate the use of a self-adaptive Pareto evolutionary multi-objective optimization (EMO) approach for evolving the controllers of virtual embodied organisms. The objective of this paper is to demonstrate the trade-off between quality of solutions and computational cost. We show empirically that evolving controllers using the proposed algorithm incurs significantly less computational cost when compared to a self-adaptive weighted sum EMO algorithm, a self-adaptive single-objective evolutionary algorithm (EA) and a hand-tuned Pareto EMO algorithm. The main contribution of the self-adaptive Pareto EMO approach is its ability to produce sufficiently good controllers with different locomotion capabilities in a single run, thereby reducing the evolutionary computational cost and allowing the designer to explore the space of good solutions simultaneously. Our results also show that self-adaptation was found to be highly beneficial in reducing redundancy when compared against the other algorithms. Moreover, it was also shown that genetic diversity was being maintained naturally by virtue of the system's inherent multi-objectivity.
    Matched MeSH terms: Computer Simulation
  17. Fulltext Complex Network Theory Applied to the Growth of Kuala Lumpur's Public Urban Rail Transit Network
    Ding R, Ujang N, Hamid HB, Wu J
    PLoS One, 2015;10(10):e0139961.
    PMID: 26448645 DOI: 10.1371/journal.pone.0139961
    Recently, the number of studies involving complex network applications in transportation has increased steadily as scholars from various fields analyze traffic networks. Nonetheless, research on rail network growth is relatively rare. This research examines the evolution of the Public Urban Rail Transit Networks of Kuala Lumpur (PURTNoKL) based on complex network theory and covers both the topological structure of the rail system and future trends in network growth. In addition, network performance when facing different attack strategies is also assessed. Three topological network characteristics are considered: connections, clustering and centrality. In PURTNoKL, we found that the total number of nodes and edges exhibit a linear relationship and that the average degree stays within the interval [2.0488, 2.6774] with heavy-tailed distributions. The evolutionary process shows that the cumulative probability distribution (CPD) of degree and the average shortest path length show good fit with exponential distribution and normal distribution, respectively. Moreover, PURTNoKL exhibits clear cluster characteristics; most of the nodes have a 2-core value, and the CPDs of the centrality's closeness and betweenness follow a normal distribution function and an exponential distribution, respectively. Finally, we discuss four different types of network growth styles and the line extension process, which reveal that the rail network's growth is likely based on the nodes with the biggest lengths of the shortest path and that network protection should emphasize those nodes with the largest degrees and the highest betweenness values. This research may enhance the networkability of the rail system and better shape the future growth of public rail networks.
    Matched MeSH terms: Computer Simulation
  18. Fulltext Pliable Cognitive MAC for Heterogeneous Adaptive Cognitive Radio Sensor Networks
    Al-Medhwahi M, Hashim F, Ali BM, Sali A
    PLoS One, 2016;11(6):e0156880.
    PMID: 27257964 DOI: 10.1371/journal.pone.0156880
    The rapid expansion of wireless monitoring and surveillance applications in several domains reinforces the trend of exploiting emerging technologies such as the cognitive radio. However, these technologies have to adjust their working concepts to consider the common characteristics of conventional wireless sensor networks (WSNs). The cognitive radio sensor network (CRSN), still an immature technology, has to deal with new networks that might have different types of data, traffic patterns, or quality of service (QoS) requirements. In this paper, we design and model a new cognitive radio-based medium access control (MAC) algorithm dealing with the heterogeneous nature of the developed networks in terms of either the traffic pattern or the required QoS for the node applications. The proposed algorithm decreases the consumed power on several fronts, provides satisfactory levels of latency and spectrum utilization with efficient scheduling, and manages the radio resources for various traffic conditions. An intensive performance evaluation is conducted to study the impact of key parameters such as the channel idle time length, node density, and the number of available channels. The performance evaluation of the proposed algorithm shows a better performance than the comparable protocols. Moreover, the results manifest that the proposed algorithm is suitable for real time monitoring applications.
    Matched MeSH terms: Computer Simulation
  19. Fulltext Ringed Seal Search for Global Optimization via a Sensitive Search Model
    Saadi Y, Yanto IT, Herawan T, Balakrishnan V, Chiroma H, Risnumawan A
    PLoS One, 2016;11(1):e0144371.
    PMID: 26790131 DOI: 10.1371/journal.pone.0144371
    The efficiency of a metaheuristic algorithm for global optimization is based on its ability to search and find the global optimum. However, a good search often requires to be balanced between exploration and exploitation of the search space. In this paper, a new metaheuristic algorithm called Ringed Seal Search (RSS) is introduced. It is inspired by the natural behavior of the seal pup. This algorithm mimics the seal pup movement behavior and its ability to search and choose the best lair to escape predators. The scenario starts once the seal mother gives birth to a new pup in a birthing lair that is constructed for this purpose. The seal pup strategy consists of searching and selecting the best lair by performing a random walk to find a new lair. Affected by the sensitive nature of seals against external noise emitted by predators, the random walk of the seal pup takes two different search states, normal state and urgent state. In the normal state, the pup performs an intensive search between closely adjacent lairs; this movement is modeled via a Brownian walk. In an urgent state, the pup leaves the proximity area and performs an extensive search to find a new lair from sparse targets; this movement is modeled via a Levy walk. The switch between these two states is realized by the random noise emitted by predators. The algorithm keeps switching between normal and urgent states until the global optimum is reached. Tests and validations were performed using fifteen benchmark test functions to compare the performance of RSS with other baseline algorithms. The results show that RSS is more efficient than Genetic Algorithm, Particles Swarm Optimization and Cuckoo Search in terms of convergence rate to the global optimum. The RSS shows an improvement in terms of balance between exploration (extensive) and exploitation (intensive) of the search space. The RSS can efficiently mimic seal pups behavior to find best lair and provide a new algorithm to be used in global optimization problems.
    Matched MeSH terms: Computer Simulation
  20. Fulltext A Negative Index Metamaterial-Inspired UWB Antenna with an Integration of Complementary SRR and CLS Unit Cells for Microwave Imaging Sensor Applications
    Islam MT, Islam MM, Samsuzzaman M, Faruque MR, Misran N
    Sensors (Basel), 2015 May 20;15(5):11601-27.
    PMID: 26007721 DOI: 10.3390/s150511601
    This paper presents a negative index metamaterial incorporated UWB antenna with an integration of complementary SRR (split-ring resonator) and CLS (capacitive loaded strip) unit cells for microwave imaging sensor applications. This metamaterial UWB antenna sensor consists of four unit cells along one axis, where each unit cell incorporates a complementary SRR and CLS pair. This integration enables a design layout that allows both a negative value of permittivity and a negative value of permeability simultaneous, resulting in a durable negative index to enhance the antenna sensor performance for microwave imaging sensor applications. The proposed MTM antenna sensor was designed and fabricated on an FR4 substrate having a thickness of 1.6 mm and a dielectric constant of 4.6. The electrical dimensions of this antenna sensor are 0.20 λ × 0.29 λ at a lower frequency of 3.1 GHz. This antenna sensor achieves a 131.5% bandwidth (VSWR < 2) covering the frequency bands from 3.1 GHz to more than 15 GHz with a maximum gain of 6.57 dBi. High fidelity factor and gain, smooth surface-current distribution and nearly omni-directional radiation patterns with low cross-polarization confirm that the proposed negative index UWB antenna is a promising entrant in the field of microwave imaging sensors.
    Matched MeSH terms: Computer Simulation
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