Spatial Based Pilot Allocation (SBPA) in Crowded Massive MIMO Systems

Nowadays, the internet of things (IoT) has gained significant research attention. It is becoming critically imperative to protect IoT devices against cyberattacks with the phenomenal intensification. The malicious users or attackers might take control of the devices and serious things will be at stake apart from privacy violation. Therefore, it is important to identify and prevent novel attacks in the IoT context. This paper proposes a novel attack detection system by interlinking the development and operations framework. This proposed detection model includes two stages such as proposed feature extraction and classification. The preliminary phase is feature extraction, the data from every application are processed by integrating the statistical and higher-order statistical features together with the extant features. Based on these extracted features the classification process is evolved for this, an optimized deep convolutional neural network (DCNN) model is utilized. Besides, the count of filters and filter size in the convolution layer, as well as the activation function, are optimized using a new modified algorithm of the innovative gunner (MAIG), which is the enhanced version of the AIG algorithm. Finally, the proposed work is compared and proved over other traditional works concerning positive and negative measures as well. The experimental outcomes show that the proposed MAIG algorithm for application 1 under the GAF-GYT attack achieves higher accuracy of 64.52, 2.38 and 3.76% when compared over the methods like DCNN, AIG and FAE-GWO-DBN, respectively.

     

Dependence of coupling coefficient and lasing wavelength on injection current in pure gain-coupled distributed feedback semiconductor lasers

A theoretical analysis of purely gain-coupled distributed feedback lasers (PGC-DFB) with antireflection facets is given. The effects of longitudinal non-uniformity of photon and carrier density above a threshold circumstance are considered. In addition, the influence of carrier-induced refractive index change on the coupling coefficient of the PGC-DFB structure is assumed. It is shown that the coupling coefficient in this structure varies with injected current and it gets a real part or an index coupled term. As a result the normalized coupling coefficient, κL, becomes a complex number. So, above the threshold condition, the PGC-DFB laser operates like a complex coupled one. Variation of the oscillation wavelength and the threshold gain of the PGC-DFB laser in terms of current is analyzed too. Numerical analysis shows that this structure has wavelength tunability with respect to current. The theoretical model is based on the self-consistent solution of coupled wave equations and the carrier rate equation by the transfer matrix method.     

A novel cost-optimizing demand response control for a heat pump heated residential building

The present article describes the integration of a data-driven predictive demand response control for residential buildings with heat pump and on-site energy generation. The data driven control approach schedules the heating system of the building. In each day, the next 24 hours heating demand of buildings, including space heating and domestic hot water consumption, are predicted by means of a hybrid wavelet transformation and a dynamic neural network. Linear programming is implemented to define a cost-optimal schedule for the heat pump operation. Moreover, the study discusses the impact of heat demand prediction error on performance of demand response control. In addition, the option of energy trading with the electrical grid is considered in order to evaluate the possibility of increasing the profit for private householders through on-site energy generation. The results highlight that the application of the proposed predictive control could reduce the heating energy cost up to 12% in the cold Finnish climate. Furthermore, on-site energy generation declines the total energy cost and consumption about 43% and 24% respectively. The application of a data-driven control for the demand prediction brings efficiency to demand response control.     

In‐plane functionalizing graphene nanolayers with polystyrene by atom transfer radical polymerization: Grafting from hydroxyl groups

Graphene oxide (GO) was prepared from the oxidation of graphite and then it was functionalized with (3‐aminopropyl)triethoxysilane (APTES) from hydroxyl groups by a coupling reaction. Subsequently, alpha‐bromoisobutyryl bromide (BiBB) was attached to the APTES groups to yield initiator anchored graphene nanolayers (GOHBr). Then, GOHBr was used in different amounts as the precursor for atom transfer radical polymerization of styrene to evaluate the effect of graphene loading along with the graft density on the properties of final product. Successful in‐plain attachment of APTES, BiBB, and polystyrene to GO was evaluated by Fourier transform infrared spectroscopy. Graphene interlayers expansion by oxidation and functionalization processes was evaluated using X‐ray diffraction. The ordered and disordered crystal structures of carbon were evaluated by Raman spectroscopy. Morphology of graphene nanolayers was studied by scanning electron microscopy and also transmission electron microscopy. POLYM. COMPOS., 35:386–395, 2014. © 2013 Society of Plastics Engineers     

Conductive chitosan/multi walled carbon nanotubes electrospun nanofiber feasibility

The current study focuses on the electrospinning of chitosan (CHT)/multi walled carbon nanotubes (MWNTs) composite nanofiber using a highly stable dispersion. The acetic acid (1–100%) and trifluoroacetic acid/dichloromethane (TFA/DCM 70: 30) was tested as solvent, and the TFA/DCM (70 : 30) is most preferred for fiber formation process with acceptable electrospinnability. Moreover, a new protocol was used to establish proper technique for preparation of electrospinning solution. FT-IR spectroscopy utilized to infer the extent of interaction between CHT polymer chain and MWNT filaments. A quite simple technique was employed to show the stability of electrospinning solution before nanofiber formation process. Scanning electronic microscope (SEM) was employed to show the influence of spinning parameters on surface morphology of electrospun fiber. Under optimized condition, homogeneous and beadfree CHT/MWNTs nanofibers and known physical characteristics were prepared. The formation of conducting nanofibers based on CHT nanocomposites can be considered as a significant improvement in electrospinning of CHT/CNT dispersion. The direct outcome of the current study includes the homogeneous CHT/MWNTs nanofibers with an average diameter of 275 nm and a conductivity of 9×10⁻⁵ S/cm. These results are extremely important for further investigation regarding biomedical applications.     

Properties of PMMA/Carbon nanotubes nanocomposites prepared by “grafting through” method

A number of batch polymerizations were performed to study the effect of multi‐walled carbon nanotubes (MWCNTs) on the properties of PMMA/MWCNTs nanocomposites. To improve the dispersion of nanotubes in PMMA matrix, MWCNTs were functionalized with methacrylate groups via a four‐step modification process and the modified nanoparticles were used to synthesize the nanocomposites. The prepared samples were characterized by Raman spectroscopy, thermogravimetric analysis, dynamic mechanical thermal analysis, differential scanning calorimetry, gel permeation chromatography, UV–visible, and TEM techniques. According to the results, modified nanotubes improved thermal and mechanical properties better than the pristine MWCNTs. The main improvement in the mechanical and thermophysical properties was achieved for the nanocomposite containing 0.5 wt% of MWCNTs. POLYM. COMPOS., 2012. © 2011 Society of Plastics Engineers     

Encapsulation of organomodified montmorillonite with PMMA via in situ SR&;NI ATRP in miniemulsion

Encapsulation of organomodified montmorillonite within poly (methyl methacrylate) via in situ atom transfer radical polymerization with simultaneous reverse and normal initiation system (SR&NI ATRP) was successfully performed. Miniemulsion polymerization technique has been employed for its abundant advantages to encapsulate inorganic materials. Successful SR&NI ATRP was carried out using 4,4′-dinonyl-2,2′-bipyridine (dNbPy) as a hydrophobic ligand and cetyltrimethylammonium bromide (CTAB) as an effective cationic surfactant at high temperatures. Homogeneous distribution of droplets and particles with sizes in the range of around 170 nm was evaluated by dynamic light scattering (DLS) analysis. Final monomer conversion and molecular weight were determined by gravimetry and size exclusion chromatography (SEC) respectively. By increasing nanoclay content, conversion and molecular weight of nanocomposites decreased. Meanwhile, an increase in PDI values was also observed. X-ray diffraction (XRD) analysis results display organoclay layers disordered and delaminated in the polymer matrix. Thermal stability improvement of all the nanocomposites in comparison with the neat polymer was revealed by thermogravimetric analysis (TGA). Homogeneous distribution of spherical particles with sizes in the range of 170 nm was demonstrated by scanning electron microscopy (SEM) images. These results are complied with the DLS results. Transmission electron microscopy (TEM) image display a dispersion of partially exfoliated clay stacks in the matrix of PMNM 2.     

High‐performance doubly fed induction machine drive system using predictive direct torque control drive system fed by indirect matrix converters

This paper presents a novel predictive direct torque control for doubly fed induction machine based on indirect matrix converter (IMC), which is characterized by its simple structure, minimal‐torque ripple, and constant switching frequency. Nowadays, the control strategies based on predictive methods have proved their efficiency to improve drive systems capabilities. So, in this paper, one of the best predictive methods that have recently been suggested for doubly fed induction machine drive systems is applied to IMC. The purpose of this combination is to modify the control parameters and size/volume reduction of drive system structure, which is difficult to achieve in conventional systems based on voltage source inverters. The good tracking behavior with reduced torque and flux ripple for both motoring and generating modes as well as removing bulky electrolytic capacitor from the DC link of a converter resulted by using three vectors, two active vectors together with one zero vector per switching period, and applying these vectors to the inverter stage of IMC. To improve the motor drive system performance and reduce losses caused by snubber circuits, the rectifier four‐step commutation method in rectifier bridge is used. In the inverter stage, the predictive direct torque control method is employed. The simulation results of the proposed model confirm its effectiveness and accuracy. Copyright © 2013 John Wiley & Sons, Ltd.     

Fault‐driven stress testing of distributed real‐time software based on UML models

In a previous article, a stress testing methodology was reported to detect network traffic‐related Real‐Time (RT) faults in distributed RT systems based on the design UML model of a System Under Test (SUT). The stress methodology, referred to as Test LOcation‐driven Stress Testing (TLOST), aimed at increasing the chances of RT failures (violations in RT constraints) associated with a given stress test location (an network or a node under test). As demonstrated and experimented in this article, although TLOST is useful in stress testing different test locations (nodes and network, it does not guarantee to target (test) all RT constraints in an SUT. This is because the durations of message sequences bounded by some RT constraints might never be exercised (covered) by TLOST. A complementary stress test methodology is proposed in this article, which guarantees to target (cover) all RT constraints in an SUT and detect their potential RT faults (if any). Using a case study, this article shows that the new complementary methodology is capable of targeting the RT faults not detected by the previous test methodology. Copyright © 2009 John Wiley & Sons, Ltd.