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“Less Give More”: Evaluate and zoning Android applications
No full textThe Android security mechanism is the first approach to protect data, system resource as well as reduce the impact of malware. Past malware studies tend to investigate the novel approaches of preventing, detecting and responding to malware threats but little attention has been given to the area of risk assessment. This paper aims to fill that gap by presenting a risk assessment approach that evaluate the risk zone for an application. The permission-based approach is presented for evaluating and zoning the Android applications (EZADroid), based on risk assessment. The EZADroid applies the Analytic Hierarchy Process (AHP) as a decision factor to calculate the risk value. A total of 5000 benign and 5000 malware applications were drawn from the AndroZoo and Drebin datasets for evaluation. Results showed that the EZADroid had achieved 89.82% accuracy rate in classifying the application into a different level of risk zones (i.e. very low, low, medium, and high)
Passively Q-switched fiber laser tunable by Sagnac interferometer operation
No full textIn this paper, a stable passively Q-switched Erbium-doped fiber laser (EDFL) tunable by Sagnac interferometer operation was described by using a graphene oxide saturable absorber (SA) as a Q-switcher. The wavelength operation of the Q-switched EDFL was tunable from 1566.3 nm to 1559.3 nm by increasing the temperature of sagnac loop mirror (SLM) from 30 °C to 70 °C in the figure-of-eight laser configuration. At 1566.3 nm operation, by increasing the pump from the threshold power of 77.3 mW to 126.5 mW, the repetition rate can be increased from 30.7 kHz to 41.5 kHz while the pulse width was narrowed from 10.2 to 7.3 μs. The Q-switching threshold pump power increased with the increase of the temperature, which then shifted the operation to a shorter wavelength. However, the laser efficiency increased at a shorter wavelength operation. At 1561.4 nm operation, the maximum pulse energy of 20.5 nJ was obtained at 161.0 mW pump power
An automatic zone detection system for safe landing of UAVs
No full textAs the demand increases for the use Unmanned Aerial Vehicles (UAVs) to monitor natural disasters, protecting territories, spraying, vigilance in urban areas, etc., detecting safe landing zones becomes a new area that has gained interest. This paper presents an intelligent system for detecting regions to navigate a UAV when it requires an emergency landing due to technical causes. The proposed system explores the fact that safe regions in images have flat surfaces, which are extracted using the Gabor Transform. This results in images of different orientations. The proposed system then performs histogram operations on different Gabor-oriented images to select pixels that contribute to the highest peak, as Candidate Pixels (CP), for the respective Gabor-oriented images. Next, to group candidate pixels as one region, we explore Markov Chain Codes (MCCs), which estimate the probability of pixels being classified as candidates with neighboring pixels. This process results in Candidate Regions (CRs) detection. For each image of the respective Gabor orientation, including CRs, the proposed system finds a candidate region that has the highest area and considers it as a reference. We then estimate the degree of similarity between the reference CR with corresponding CRs in the respective Gabor-oriented images using a Chi square distance measure. Furthermore, the proposed system chooses the CR which gives the highest similarity to the reference CR to fuse with that reference, which results in the establishment of safe landing zones for the UAV. Experimental results on images from different situations for safe landing detection show that the proposed system outperforms the existing systems. Furthermore, experimental results on relative success rates for different emergency conditions of UAVs show that the proposed intelligent system is effective and useful compared to the existing UAV safe landing systems
Transport and retention behavior of carbonaceous colloids in natural aqueous medium: Impact of water chemistry
No full textCarbon based materials are emerging as a sustainable alternative to their metal-oxide counterparts. However, their transport behavior under natural aqueous environment is poorly understood. This study investigated the transport and retention profiles of carbon nanoparticles (CNPs) and graphene oxide quantum dots (GOQDs) through column experiments in saturated porous media. CNPs and GOQDs (30 mg/L) were dispersed in natural river water (RW) and passed through the column at a flow rate of 1 mL/min, which mimicking the natural water flow rate. After every 10 min, the column effluents were collected and the mass recovery and retention profiles were monitored. Results indicated that the transport of both carbonaceous colloids was predominantly controlled by surface potential and ionic composition of natural water. The CNPs with its high surface potential (−40 mV) exhibited more column transport and was less susceptible to solution pH (5.6–6.8) variation as compared to GOQDs (−24 mV). The results showed that, monovalent salt (NaCl) was one of the dominating factors for the retention and transport of carbonaceous colloids compared to divalent salt (CaCl2). Furthermore, the presence of natural organic matter (NOM) increased the transport of both carbonaceous colloids and thereby decreases the tendency for column retention
4-Imidazol-1-yl-butane-1-sulfonic acid or a novel liquid salt? The NMR analysis and dual solvent-catalytic efficiency for one-pot synthesis of xanthenes
No full textThe reaction of the equimolar mixture of imidazole and 1,4-butane sultone was performed at 90 °C in ethylbenzene for 12 h, and the structure of the product was investigated by the NMR analysis in CD3OD and DMSO‑d6. This work demonstrated that 4-imidazol-1-yl-butane-1-sulfonic acid could not be obtained through the above reaction and the mixture of zwitterionic (I) and ionic (II) structure is produced. The structure of the liquid salt (I + II) was characterized and analyzed by 2D NMR. Then, the dual solvent-catalytic efficiency of the liquid salt (I + II) was studied for the synthesis of a variety of xanthenes under mild conditions which afforded the desired products in good to excellent yields within short reaction times. The recyclability of the liquid salt (I + II) was studied with an average recovered yield of 89% for three subsequent runs. The recycled liquid salt showed no significant loss of the catalytic activity even after three runs and its structure remain same as fresh liquid salt (I + II)
Bioethanol production from agarophyte red seaweed, Gelidium elegans, using a novel sample preparation method for analysing bioethanol content by gas chromatography
No full textIn this study, Gelidium elegans is investigated for ethanol production. A combination of factors including different temperatures, acid concentration and incubation time was evaluated to determine the suitable saccharification conditions. The combination of 2.5% (w/v) H2SO4 at 120 °C for 40 min was selected for hydrolysis of the seaweed biomass, followed by purification, and fermentation to yield ethanol. The galactose and glucose were dominant reducing sugars in the G. elegans hydrolysate and under optimum condition of dilute acid hydrolysis, 39.42% of reducing sugars was produced and fermentation resulted in ethanol concentration of 13.27 ± 0.47 g/L. A modified method was evaluated for sample preparation for gas chromatography (GC) analysis of the ethanol content. A solvent mixture of acetonitrile and iso-butanol precipitated dissolved organic residues and reduced water content in GC samples at least by 90%. Results showed that this method could be successfully used for bioethanol production from seaweed
Improved efficiency of Cu(In,Ga)Se2 thinfilm solar cells using a buffer layer alternative to CdS
No full textThe chalcopyrite semiconductor CuInSe2 and its constitutes Ga and/or S [Cu (InGa)Se2 or Cu (InGa)(Se,S)2], commonly referred as CIGS have been leading thinfilms for incorporation in high-efficiency photovoltaics. In conventional ZnO-N/i-ZnO/CdS/CIGS solar cells, the traditional CdS buffer is nearly optimum for the commonly used 1.15 eV (CIGS) but less optimal for higher Ga. To overcome this limitation, Cd1-yZnyS is proposed as an alternative buffer layer to replace the standard CdS in CIGS thinfilm solar cells containing an ordered vacancy compound (OVC) layer. Next, the dependence of solar cells performance on the change of Ga and Zn concentrations in absorber and buffer layers, respectively, was investigated using the AMPS-1D software. The results are potential improvement in CIGS efficiency that was obtained with replacement of CdS buffer material by its alternative in one hand, another hand by formation of OVC layer. Lastly, the optimum values of Ga and Zn concentrations were found at 0.7 and 0.6, respectively, leading to a high conversion efficiency of around 23.71%
Photoelectrocatalytic oxidation of methanol over RuO2MnO2Co3O4 supported porous anatase under visible light irradiation
No full textAnatase supported heterogeneous photocatalyst consisting of RuO2, MnO2 and Co3O4 (1:13:13 ratio) was synthesized by a precipitation method and tested for photoelectrocatalytic (PEC) oxidation of methanol in 0.1 M KOH under visible light irradiation. The as-prepared photocatalyst was characterized by FTIR, UV–vis, XRD, Raman spectroscopy, FESEM/EDX, TEM, BET, XPS and TPR. The PEC studies by cyclic voltammetry indicated that the oxidation of methanol to CO2 and H2O upon exposure to visible light occurs between 400 and 800 nm. The smaller value of the charge transfer resistance (Rct) of the RuO2–MnO2–Co3O4 supported anatase TiO2 electrode indicates a faster rate of charge transfer at the electrode-electrolyte interface compared to the Pt/C catalyst, which could be promising for direct methanol fuel cell application
Non suitability of silver ion conducting polymer electrolytes based on chitosan mediated by barium titanate (BaTiO3) for electrochemical device applications
No full textIn this study, we report the non-suitability of silver ion conducting polymer electrolytes mediated by barium titanate (BaTiO3) for electrochemical device applications. Various amounts of BaTiO3 fillers have been added to chitosan: silver triflate (CS:AgTf) solution to prepare polymer composites. Electrical impedance spectroscopy (EIS) has been used to characterize electrical properties of the samples. Charge transfer resistance has been correctly estimated for the samples using electrical equivalent circuit (EEC) model. At 3 and 5 wt % of BaTiO3 filler, the charge transfer resistance was found to increase and diameter of the impedance plots are shown to be widened due to the increase of grain boundaries. The dielectric constant is also observed to decrease with the increase of BaTiO3 concentration. DC conductivities for the composite samples are estimated from AC conductivity spectra. The DC conductivity was found to decrease from 4.7 × 10−7 S/cm to 5.4 × 10−9 S/cm for CS:AgTf system incorporated with BaTiO3 filler. Such decrease has revealed that the electrolytes are not suitable for electrochemical device applications. Shifting of relaxation peaks of imaginary part of electric modulus towards low frequency side has indicated the increase of relaxation time and hence the decrease in DC conductivity. The relaxation processes are also studied using Argand plots. The existence of metallic silver nanoparticles has been examined via ultraviolet–visible (UV–Vis) spectroscopy. The UV–Vis spectra showed that surface plasmon resonance (SPR) peaks are broadened and increased in their intensity as the BaTiO3 concentration increased from 1 to 3 wt %. This implied that the reduction rate of silver ions to silver nanoparticles is increased. Moreover, disappearance of SPR peak was found for the BaTiO3 concentration of 5 wt %, revealing the bulk formation of silver metals. Transmission electron microscopy (TEM) images were obtained for the samples, in which the formation of bulk metallic sizes of silvers was found to be obvious. This growth of bulk silver metals at high BaTiO3 concentration was further supported by optical and scanning electron microscopy (SEM) techniques. The distribution of white specs due to silver nanoparticles on the surface of chitosan-silver triflate solid film was investigated. Large white sheets were appeared on the surface of CS:AgTf incorporated with 5 wt% BaTiO3 and related to the huge amount of aggregated metallic silver particles. Sharp intense peaks due to metallic silver particles and weak peaks due to BaTiO3 fillers have been observed in the analyses of energy dispersive X-ray (EDX) spectra
Dental age estimation in Malaysian adults based on volumetric analysis of pulp/tooth ratio using CBCT data
No full textForensic odontology plays an important role in human identification and dental age estimation is an integral part of this process. The aim of the study was to investigate the association between chronological age and pulp/tooth volume ratio in a Malaysian population (Malays and Chinese) from cone-beam computed tomography (CBCT) scans, enhanced with Mimics software. Three hundred CBCT scans of 153 males and 147 females, aged between 16 and 65 years were divided into 5 age groups. Volumetric analysis of the pulp/tooth ratio was performed in maxillary left canines, maxillary right canines and maxillary right central incisors. Simple linear regression and Pearson correlation analysis indicated the strongest coefficient of correlation (R) values for maxillary right central incisors (0.83) followed by maxillary right canines (0.74) and maxillary left canines (0.73). Fisher's Z test indicated that dental age estimation is gender independent. The derived regression equations were further validated on an independent group of 126 teeth. The results indicated mean absolute error (MAE) values of 6.48 and 8.58 years for maxillary right central incisors and maxillary canines respectively. It was also noticed that MAE values were higher among the age groups ranging from 46 to 65 years. This study showed that a volumetric change in the pulp cavity with age is a valuable assessment method for dental age estimation among Malaysian population