Terms Of Simulation Research Articles

Analysis of P-Glycoprotein Transport Cycle Reveals a New Way to Identify Efflux Inhibitors.

P-glycoprotein (P-gp) is found to be of considerable interest for the design of drugs capable of treating chemoresistant tumors. This transporter is an interesting target for which an efficient approach has not yet been developed in terms of computer simulation. In this work, we use a combination of docking, molecular dynamics, and metadynamics to fully explore the states that occur during the capture of a ligand and subsequent efflux by P-gp. The proposed approach allowed us to substantiate a number of experimentally established facts, as well as to develop a new criterion for identifying potential P-gp inhibitors.

Simple Iterative Channel Coding and Modulation for Harbor Wireless Communications

Monitoring systems at the harbor require a simple communication technique to save battery energy, strong in error correction, and suitable to the harbor channel model, of which the channel is predicted to have more number of path. This paper proposes (i) a harbor channel model and (ii) a simple iterative repetition coding for harbor wireless communication of monitoring systems. The harbor channel model is derived using a series of computer simulations based on real-field harbor environmental parameters, while the proposed iterative channel coding is based on the repetition codes assisted by a doped accumulator (ACC) with a doping technique. Channel coding and doping rates are designed using an Extrinsic Information Transfer (EXIT) chart and are evaluated using a series of computer simulations in terms of Bit Error Rate (BER) and Frame Error Rate (FER) performances with an outage performance as the theoretical baseline for comparison. Since the EXIT curve of the repetition codes has steep curve, we use a non-Gray Quadrature Phase Shift Keying (QPSK) to achieve a better matching between the decoder and the demapper of harbor channels. We found that the proposed simple repetition codes and non-Gray demapper provide excellent performances for harbor communications with a cliff of BER curve. The results of this paper are expected to contribute to the development of a reliable wireless communications for the harbor monitoring applications.

Hybrid beam selection scheme in millimeter-wave beamspace MIMO-NOMA with lens antenna array

Beam selection is a notable issue for recent wireless communications. A conventional single beam selection (SBS) concept is utilized to minimize the number of necessary radio frequency chains in millimeter-wave (mmWave) multiple-input multiple-output non-orthogonal multiple access (MIMO-NOMA) systems. In general, the traditional SBS concept cannot implement a multiple beam group selection opportunity for every supported user. In this circumstance, the user side spends too much computational burden to measure the decoded message and suffer a beam optimization problem. Therefore, we propose a hybrid beam selection (HBS) scheme to utilize a multiple SBS scheme in beamspace MIMO-NOMA systems. Consequently, each supported user can easily achieve a low beam optimization problem by selecting a reliable SBS group from the proposed HBS scheme and significantly increase the spectral performance. Furthermore, we demonstrate an iterative beam power maximization algorithm utilizing the HBS scheme to solve the power allocation problem in this paper. The numerical results are verified by computer simulations in terms of a downlink beamspace MIMO-NOMA channel with a lens antenna array environment.

On the Design of Thermal-Aware Duty-Cycle MAC Protocol for IoT Healthcare.

Wireless Body Area Networks (WBANs) are designed to provide connectivity among diverse miniature body sensors that support different Internet of Things (IoT) healthcare applications. Among diverse body sensors, WBANs exploit in-vivo sensor nodes that detect and collect the required biometric data of certain physiological change inside the human body, and transmits the sensed data utilizing wireless communication. However, sensing and wireless communication activities of in-vivo sensors produce heat and could result thermal damage to the human tissue if the sensing and communication continues for a long period. Furthermore, Quality of Service (QoS) provisioning for diverse traffic types is another striking requirement for WBANs. These pressing yet conflicting concerns trigger the design of ThMAC—a Thermal aware duty cycle MAC protocol for IoT healthcare. The protocol regulates the communication operation of a body sensor based on estimated temperature surrounding a tissue to maintain moderate temperature level in a body, also avoiding hotspot. Exploiting both contention-based and contention free channel access mechanisms, ThMAC introduces a superframe structure, where disjoint periods are allocated for diverse traffic types to achieve QoS provisioning. Moreover, ThMAC ensures a reliable and timely delivery of sporadically generated emergency data through an emergency data management mechanism. ThMAC performance is evaluated through computer simulations in terms of thermal rise, energy consumption as well as QoS metrics such as delay and reliability. The results show superior performance of ThMAC compared to that of IEEE 802.15.6.

Evaluation Method of ARAS Combining Simulator Experiment and Computer Simulation in Terms of Cost-Benefit Analysis

In this study, we propose an evaluation method for an Advanced Rider Assistance System (ARAS) for two-wheeled vehicles, combining riding simulator experiments and computer simulations in terms of cost-benefit analysis. This evaluation method focuses on the collision warning system at intersections using an ARAS for two-wheeled vehicles. The study was carried out experiments with 30 test subjects who have two-wheeled vehicle licenses and are not novice riders. To quantify the accident-reduction effect, a Monte-Carlo simulation based on a time-series reliability model was used. Based on the collision probability results derived from the Monte-Carlo Simulation, the overall error probability as a human-machine system was calculated based on an integrated error model. In addition, cost-benefit analysis was conducted to quantify the social benefits and costs of introducing the ARAS to the market. As a result, we confirmed that the system can be beneficial after 4 years when introduced into the market.

Multisatellite Cooperative Random Access Scheme in Low Earth Orbit Satellite Networks

Multisatellite cooperative random access (MSC-RA) scheme is proposed in low earth orbit (LEO) satellite networks. In the scheme, a packet structure based on single carrier interleaved frequency division multiple access (SC-IFDMA) is designed to overcome the effect of users’ propagation delays on the received signals at satellite nodes, which ensures the synchronization of received signals. The transmission model from multiple terminals to multiple satellite nodes in a slot can be equivalent to a virtual multi-input multioutput model, and MSC detection is employed to decode multiple collided packets. The MSC detection can be applied to slotted ALOHA (SA), contention resolution diversity slotted ALOHA (CRDSA), CRDSA-3, and irregular repetition slotted ALOHA (IRSA) protocols, which are dubbed MSC-SA, MSC-CRDSA, MSC-CRDSA-3, and MSC-IRSA, respectively. At the gateway station, the MSC detection and iterative interference cancellation processing are alternately conducted for multiple collided packets at satellite nodes. The performance of these MSC-RA schemes is evaluated via mathematical analysis and computer simulation in terms of throughput, stability and energy efficiency. Simulation results show that MSC-SA, MSC-CRDSA, MSC-CRDSA-3, and MSC-IRSA schemes significantly outperform conventional ones, and the MSC-CRDSA scheme is superior to MSC-SA, MSC-CRDSA-3 and MSC-IRSA schemes.

LOCATING THE BURIED OBJECT IN THE NON-DESTRUCTIVE STRUCTURES USING TH-BPSK UWB SYSTEM

The ultra-wideband (UWB) communication system utilizing impulse signals is an attractive technique which can achieve low power consumption, high data rate, and high accuracy in location estimation. One of the applications of UWB is ground penetrating radar (GPR) which has been using to investigate non-destructive structures. In this paper, we proposed a method of locating a buried object in non-destructive structures (concrete, dry soil) using time hopping BPSK UWB (TH-BPSK UWB) modulation system with a certain pulse shape combined with Gauss-Newton nonlinear estimation algorithm. The results of the proposed method were evaluated using computer simulation in terms of the errors of estimated position and spatial resolution.

Mutation Spectrum in TPO Gene of Bangladeshi Patients with Thyroid Dyshormonogenesis and Analysis of the Effects of Different Mutations on the Structural Features and Functions of TPO Protein through In Silico Approach.

Although thyroid dyshormonogenesis (TDH) accounts for 10-20% of congenital hypothyroidism (CH), the molecular etiology of TDH is unknown in Bangladesh. Thyroid peroxidase (TPO) is most frequently associated with TDH and the present study investigated the spectrum of TPO mutations in Bangladeshi patients and analyzed the effects of mutations on TPO protein structure through in silico approach. Sequencing-based analysis of TPO gene revealed four mutations in 36 diagnosed patients with TDH including three nonsynonymous mutations, namely, p.Ala373Ser, p.Ser398Thr, and p.Thr725Pro, and one synonymous mutation p.Pro715Pro. Homology modelling-based analysis of predicted structures of MPO-like domain (TPO142-738) and the full-length TPO protein (TPO1-933) revealed differences between mutant and wild type structures. Molecular docking studies were performed between predicted structures and heme. TPO1-933 predicted structure showed more reliable results in terms of interactions with the heme prosthetic group as the binding energies were -11.5 kcal/mol, -3.2 kcal/mol, -11.5 kcal/mol, and -7.9 kcal/mol for WT, p.Ala373Ser, p.Ser398Thr, and p.Thr725Pro, respectively, implying that p.Ala373Ser and p.Thr725Pro mutations were more damaging than p.Ser398Thr. However, for the TPO142-738 predicted structures, the binding energies were -11.9 kcal/mol, -10.8 kcal/mol, -2.5 kcal/mol, and -5.3 kcal/mol for the wild type protein, mutant proteins with p.Ala373Ser, p.Ser398Thr, and p.Thr725Pro substitutions, respectively. However, when the interactions between the crucial residues including residues His239, Arg396, Glu399, and His494 of TPO protein and heme were taken into consideration using both TPO1-933 and TPO142-738 predicted structures, it appeared that p.Ala373Ser and p.Thr725Pro could affect the interactions more severely than the p.Ser398Thr. Validation of the molecular docking results was performed by computer simulation in terms of quantum mechanics/molecular mechanics (QM/MM) and molecular dynamics (MD) simulation. In conclusion, the substitutions mutations, namely, p.Ala373Ser, p.Ser398Thr, and p.Thr725Pro, had been involved in Bangladeshi patients with TDH and molecular docking-based study revealed that these mutations had damaging effect on the TPO protein activity.

A Matching Theory Framework for Tasks Offloading in Fog Computing for IoT Systems

Fog Computing (FC) is an emerging paradigm that extends cloud computing toward the edge of the network. In particular, FC refers to a distributed computing infrastructure confined on a limited geographical area within which some Internet of Things applications/services run directly at the network edge on smart devices having computing, storage, and network connectivity, named fog nodes (FNs), with the goal of improving efficiency and reducing the amount of data that needs to be sent to the Cloud for massive data processing, analysis, and storage. This paper proposes an efficient strategy to offload computationally intensive tasks from end-user devices to FNs. The computation offload problem is formulated here as a matching game with <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">externalities</i> , with the aim of minimizing the worst case service time by taking into account both computational and communications costs. In particular, this paper proposes a strategy based on the deferred acceptance algorithm to achieve the efficient allocation in a distributed mode and ensuring stability over the matching outcome. The performance of the proposed method is evaluated by resorting to computer simulations in terms of worst total completion time, mean waiting, and mean total completion time per task. Moreover, with the aim of highlighting the advantages of the proposed method, performance comparisons with different alternatives are also presented and critically discussed. Finally, a fairness analysis of the proposed allocation strategy is also provided on the basis of the evaluation of the Jain’s index.

Linear Algebraic Beamforming Design for Multiuser MISO Interference Channels: A Reduction in Search Space Dimension.

Near-optimal transmit beamformers are designed for multiuser multiple-input single-output interference channels with slowly time-varying block fading. The main contribution of this article is to provide a method for deriving closed-form solutions to effective beamforming in both low and high signal-to-noise ratio regimes. The proposed method basically leverages side information obtained from the channel correlation between adjacent coding blocks. More specifically, our methodology is based on a linear algebraic approach, which is more efficient than the optimal scheme based on the Gaussian input in the sense of reducing the average number of search space dimensions for designing the near-optimal transmit beamformers. The proposed method is shown to exhibit near-optimal performance via computer simulations in terms of the average sum-rate.

An agent-based model for emotion contagion and competition in online social media

Recent studies suggest that human emotions diffuse in not only real-world communities but also online social media. However, a comprehensive model that considers up-to-date findings and multiple online social media mechanisms is still missing. To bridge this vital gap, an agent-based model, which concurrently considers emotion influence and tie strength preferences, is presented to simulate the emotion contagion and competition. Our model well reproduces patterns observed in the empirical data, like anger’s preference on weak ties, anger-dominated users’ high vitalities and angry tweets’ short retweet intervals, and anger’s competitiveness in negative events. The comparison with a previously presented baseline model further demonstrates its effectiveness in modeling online emotion contagion. It is also surprisingly revealed by our model that as the ratio of anger approaches joy with a gap less than 12%, anger will eventually dominate the online social media and arrives the collective outrage in the cyber space. The critical gap disclosed here can be indeed warning signals at early stages for outrage control. Our model would shed lights on the study of multiple issues regarding emotion contagion and competition in terms of computer simulations.

Planar powered Swing-By maneuvers to brake a spacecraft

The Swing-By maneuver is a technique used in many space mission to modify the trajectory of a spacecraft. The most usual goal is to increase the energy of the spacecraft, but it is also possible to reduce this energy. An important application is to break a spacecraft coming to the Earth using a Swing-By with the moon, which is the example used in the present paper. Other possibilities also exist, such as reducing the velocity of a spacecraft going to the planets Mercury or Venus. The goal is to help a possible capture by the planet, or at least to provide a passage with smaller velocities to allow better observations during the passage. Therefore, the goal of the present paper is to study the energy loss that a spacecraft may have during a powered Swing-By maneuver, which is a maneuver that combines a close approach by a celestial body with the application of an impulsive maneuver. The behavior of the energy variation is analyzed as a function of the parameters related to the pure gravity maneuver: periapsis radius, angle of approach and approach velocity; and the parameters related to the impulsive maneuver: the location of application of the impulse and its direction and magnitude. The maneuver is performed in a system composed by two bodies, such as the Earth–moon system, around the secondary body, and the energy is measured with respect to the primary body of the system. This problem is solved by developing a mathematical algorithm that guides larger efforts in terms of computer simulations. The results show maps of conditions made from the numerical simulations for different points of application and direction of the impulse, where the maneuver is advantageous and how much more energy can be removed from the spacecraft.

Practical Implementation of Index Modulation-Based Waveforms

Orthogonal frequency division multiplexing (OFDM) with index modulation (OFDM-IM) technique has been recently proposed to provide performance improvements over conventional OFDM. OFDM-IM includes a different data transmission mechanism, where additional data bits are transmitted over subcarrier patterns by specifically activating selected subcarriers and nulling the others. However, such a mechanism inherently causes some inefficiency due to the inactive subcarriers. To improve the spectral efficiency of the OFDM-IM technique, dual-mode OFDM with index modulation (DM-OFDM) is proposed, where nulled subcarriers are activated by using a second signal constellation. With DM-OFDM, a significant data rate improvement can be obtained. As an important missing issue in the literature, OFDM-IM and its effective variations, such as DM-OFDM, have only been studied in terms of computer simulations and theoretical analysis. Therefore, their real-time performance is not yet investigated to assess their potential for next-generation networks. Addressing this gap, in this paper, OFDM-IM and DM-OFDM techniques are implemented in real-time by using software defined radio technology. National Instruments USRP-2921 nodes are used in a single-input single-output configuration. With this implementation, detailed real-time results and performance observations are provided. Moreover, a hybrid OFDM-IM (H-OFDM-IM) scheme, which can be seen as the combination of OFDM-IM and DM-OFDM, is proposed by targeting the limitations of both OFDM-IM and DM-OFDM in terms of spectral containment and error performance. With H-OFDM-IM, noticeable improvements in spectral containment and error performance can be obtained, and these observations show its suitability for real-time use and next-generation networks. With comprehensive computer simulation and test results, these claims are verified.

Conformational analysis of 5-bromo-5-nitro-1,3-dioxane

Conformational analysis of 5-bromo-5-nitro-1,3-dioxane has been performed by computer simulation in terms of HF/pVDZ, hybrid DFT PBE/3ξ, and RI-MP2/λ2 quantum chemical methods. The global minimum on the potential energy surface corresponds to the chair conformer with axial nitro group, and the other two minima have been identified as chair conformer with equatorial nitro group and 2,5-twist. All transition states on the route of conformational transformations of the title molecule have been revealed.

생체모방 기법을 활용한 OFDMA기반 무선 메쉬 네트워크의 분산 시간 및 주파수 동기화 알고리듬의 수렴성 분석

This paper deals with distributed time and frequency synchronization algorithms using the flocking technique for OFDMA-based wireless mesh networks. We propose a time and frequency synchronization model taking into account channel propagation delays existing in wireless mesh networks, and analyze the convergence condition of the proposed synchronization algorithm. Convergence performance of the proposed synchronization algorithm is analyzed via computer simulation in terms of synchronization parameters in the time and frequency synchronization model.

CINR Performance of Downlink Mobile WiMAX IEEE 802.16e Deployed Using Coexistence Cellular Terrestrial and HAPS

Deploying WiMAX through High Altitude Platform Station (HAPS) system is a new means of wireless delivery method and thus attracting much the attention in a telecommunication society. However delivering WiMAX through the terrestrial network has already been started a few years ago. Therefore, we need to look at the scenario of coexistence system both of HAPS and terrestrial in delivering WiMAX services. This paper evaluates the performance of coexistence system between cellular HAPS and terrestrial for the downlink scenario when they are transmitting WiMAX mobile 802.16e services. Our evaluation is based on the performance simulation of coexistence model using two methods. First method is a footprint exchange between the two systems.The second method is a combination of footprint exchange and HAPS footprint enhancement. The proposed methodsare then evaluated by computer simulation in terms of carrier to interference plus noise ratio (CINR) performance. In general, both methods resulting performance enhancement in CINR quality compared with coexistence deployment with normal scenario of the cell configuration used by HAPS and terrestrial. The method of combining footprint exchange and HAPS footprint enhancement is able to improve CINR more than 10 dB compared with the normal footprint configuration for all users location inside the coverage.

Adaptive Equalizer for DS-CDMA Multi-User Communication System Using Sign-Algorithm Based on Laguerre Filter Structure

This paper proposes a sign-algorithm based on adaptive Laguerre filter structure for improving the performance of the direct sequence-code division multiple access (DS-CDMA) communication system. The proposed adaptive equalizer employs a combination of sign and least mean square (LMS) algorithms to minimizing the effect of inter-symbol interference (ISI) that arises due to multipath propagation, and the computational complexity of equalizer. The performance of proposed equalizer was compared with traditional equalizers such as LMS and RLS algorithms in terms of varying path. The function detail and performance results of the proposed equalizer are described by computer simulations in terms of the bit error rate (BER).

Vertical Beamforming Inuence on Cellular Networks

&#x0D; This paper proposes a vertical beamforming concept to a cellular network employing fractional frequency reuse technique. The reference antenna utilized in this paper is the one currently employed at base station. The idea of using two different vertical beams is proposed for cell-center and cell-edge regions, separately. The proposed concept is validated through computer simulation in terms of SINR and channel capacity. The obtained results indicate that the proposed concept can improve the performance of the cellular networks comparing with the ones employing horizontal beamforming and one spot beam covering cell sector.&#x0D;

Comparative Performance Study of Localization Schemes in Wireless Sensor Networks

Localization is one of the most important tasks for location-aware applications in wireless sensor networks (WSNs). The accuracy of positioning information gives the applications a great number of advantages and, thus, it is very important to choose a localization scheme with the highest accuracy. In this paper, we review three typical localization schemes for WSNs and, then, compare their performance via computer simulation in terms of localization accuracy. The simulation study shows that the probability grid localization scheme achieves the best performance with the minimum location error rate.

An Energy-Efficient Clustering Scheme in Underwater Acoustic Sensor Networks

In this paper, an energy efficient clustering scheme using self organization method is proposed. The proposed scheme selects a cluster head considering not only the number of neighbor nodes but also the residual battery amount. In addition, the network life time is extended by re-selecting the cluster heads only in case the current cluster head`s residual energy falls down below a certain threshold level. Accordingly, the energy consumption is evenly distributed over the entire network nodes. The cluster head delivers the collected data from member nodes to a Sink node in a way of multi-hop relaying. In order to evaluate the proposed scheme, we run computer simulation in terms of the total residual amount of battery, the number of alive nodes after a certain amount of time, the accumulated energy cost for network configuration, and the deviation of energy consumption of all nodes, comparing with LEACH which is one of the most popular network clustering schemes. Numerical results show that the proposed scheme has twice network life-time of LEACH scheme and has much more evenly distributed energy consumption over the entire network.