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411.
412.
Taha A. Elwi Daniya Amer Jassim Hayder Hassan Mohammed 《International Journal of Communication Systems》2020,33(6)
This paper presents a design of an ultra‐wideband (UWB) cylindrical metamaterial (MTM) antenna for radio frequency (RF) energy harvesting to suit the fields of Internet of Things (IoT) applications. The patch circuitry is based on 3×5 Hilbert‐shaped MTM unit cells array to enhance the antenna bandwidth. While, the antenna ground plane is defected with an electromagnetic band gap structure to enhance the gain. The antenna is mounted on a polytetrafluoroethylene cylindrical substrate of an outer diameter of 15 mm and length of 32 mm with 1 mm in thickness. The substrate relative permittivity is 2.04, and the loss tangent is 0.0002. The antenna patch and the ground plane structures are printed with silver nanoparticles ink using a 2.5D CNC plotter machine. The fabricated prototype provides an UWB over the frequency range from 3.77 up to 13.89 GHz with a first separate resonant mode at 3 GHz. The antenna performance is tested numerically using two different software packages of CST MWS and HFSS. Then, an experimental validation is conducted to realize the performance of the proposed antenna in harvesting the RF energy. Excellent conversion efficiency, about 90%, is achieved at 5.8 GHz. Finally, the antenna radiation patterns and S11 spectrum are measured and compared against their simulated results to achieve good agreements. 相似文献
413.
Julia Beckert Veerle Vandeginste Tilden J. McKean Amer Alroichdi Cédric M. John 《International journal of remote sensing》2018,39(12):4088-4114
Recent research has shown hyperspectral imaging to be a powerful tool to distinguish carbonate phases with slight compositional differences on quarry cliff faces. The traditional remote sensing set-up uses an optimal short distance between the hyperspectral camera mounted on a tripod and a quarry wall characterized by a planar, mostly unweathered surface. Here we present results of a modified workflow geared to the application of ground-based hyperspectral imaging of rough and weathered cliff faces in order to map large scale dolomite bodies from a distance of up to several kilometres. The goal of the study was to determine unique spectral properties of fracture-controlled dolomite bodies in order to be able to distinguish them from a dolomitic host rock. In addition, the impact of weathering on carbonate phases and thus, the modification of the spectral signature between altered and unaltered carbonates is assessed. The spectral analysis is complemented by ICP-AES (inductively coupled plasma atomic emission spectroscopy) measurements of the spectrally measured powders. Furthermore, we examined the detection limits and characterisation potential of dolomite bodies from hyperspectral images captured at varying distances from cliff faces in the study area. Hyperspectral images of 10 natural cliffs distributed across the Central Oman Mountains were obtained with a Push broom scanner system. The high resolution of 5.45 nm (288 bands in total) enabled the visualization of small-scale changes in the near infrared continuous spectrum of all present lithofacies types. The determination of dolomite bodies of varying sizes (metre to hundreds of metres) on natural cliffs was achieved with the hyperspectral mapping approach and mapping results have been tested with the position of visually defined dolomite bodies on field panoramas. Spectra of natural cliffs contain a strong absorption peak indicative for iron which is absent in spectra of unweathered sample powders. However, ICP-AES analysis of powders revealed relatively low contents of iron of 12,392 ppm. The strong peaks in field images are interpreted as linked to intensive weathering associated with the precepitation of goethite, hematite, specularite and manganese as well as intensive dedolomitization. Dedolomitization is indicated by calcitic spectra derived from the dolomite bodies. The spectral difference of laboratory and field spectra interferes significantly the application of laboratory spectra of powdered samples for the identification of dolomite bodies in the field. Furthermore, the process of late dedolomitization puts an additional challenge on the determination of dolomite bodies. Due to these strong spectral variations between laboratory and field spectra, we recommend that the mapping approaches should not solely rely on spectral algorithms but also consider normal light field panoramas and representative outcrop analysis. We also note that the quality of resolution is too low for the determination of small-scale variations of diagenetic phases at distances larger than 4 km. However, when the limitations mentioned are taken into account, hyperspectral imaging proves to be a powerful tool that helps in the determination of the distribution of diagenetic phases, even in challenging conditions. 相似文献
414.
This paper represents the experimental trials to activate blast-furnace slag to produce cementless binding materials. The aims of the work is to study the properties of activated slag mixed with sodium hydroxide and sodium silicate liquid 6 wt% of granulated slag. Also, studying the effect of mixing water (tap and sea water) on the kinetic of activation. The rate of activation of the alkali activated slag (AAS) has been studied by FTIR, TGA, DTG and SEM techniques. The results revealed that the increase of NaOH content and mixing with sea water increase the combined water up to 90 days. On the other hand, the bulk density and compressive strength was increased by increasing Na2SiO3 content in presence of NaOH. The activated granulated slag showed good durability in sea water, i.e., the compressive strength increased gradually with immersing time up to 12 months. Whereas, the strength of sulfate resisting cement (SRC) pastes immersed in sea water increases up to 6 months then decreases up to one year. Therefore, it can be concluded that alkali activated slag are more durable in sea water than SRC pastes. 相似文献
415.
Weijun Ke Chuanxiao Xiao Changlei Wang Bayrammurad Saparov Hsin‐Sheng Duan Dewei Zhao Zewen Xiao Philip Schulz Steven P. Harvey Weiqiang Liao Weiwei Meng Yue Yu Alexander J. Cimaroli Chun‐Sheng Jiang Kai Zhu Mowafak Al‐Jassim Guojia Fang David B. Mitzi Yanfa Yan 《Advanced materials (Deerfield Beach, Fla.)》2016,28(26):5214-5221
416.
Jeffery A. Aguiar Adam Stokes Chun‐Sheng Jiang Toshihiro Aoki Paul G. Kotula Maulik K. Patel Brian Gorman Mowafak Al‐Jassim 《Advanced Materials Interfaces》2016,3(17)
The effects of alkali post‐deposition treatments and device properties for polycrystalline thin film Cu(In,Ga)Se2 have been investigated. It is reported that these surface treatments lead to differences in interface chemistry and device properties. The behavior of defects in the space charge region as a function of different growth parameters is investigated by correlative analytical microscopy. The latter combines electron microscopy based imaging, Kelvin probe force microscopy, and atom probe tomography. Alkali treatments lead to copper depletion and consequent sharpening of the compositional profiles, and the measured electric potential differences of exposed Cu(In1–x,Gax)Se2 surfaces. Measurable differences in resistivity and potential have also been observed, which are expected to relate to the improved open‐circuit voltage, fill‐factor, and device efficiency. This study frames one perspective as to why post‐deposition alkaline treatments lead to copper depletion, a mildly n‐type semiconductor interface, and higher efficiency for a Cu(In,Ga)Se2 thin‐film photovoltaic device. 相似文献
417.
A. M. Amer 《JOM Journal of the Minerals, Metals and Materials Society》2002,54(11):72-75
Aluminum dross tailings, an industrial waste, from the Egyptian Aluminium Company (Egyptalum) was used to produce two types
of alums: aluminum-sulfate alum [itAl2(SO4)3.12H2O]and ammonium-aluminum alum [(NH
4)2SO4AL2(SO4)3.24H2O]. This was carried out in two processes. The first process is leaching the impurities using diluted H2SO4 with different solid/liquid ratios at different temperatures to dissolve the impurities present in the starting material
in the form of solute sulfates. The second process is the extraction of aluminum (as aluminum sulfate) from the purifi ed
aluminum dross tailings thus produced. The effects of temperature, time of reaction, and acid concentration on leaching and
extraction processes were studied. The product alums were analyzed using x-ray diffraction and thermal analysis techniques. 相似文献
418.
Dawood Shah Tariq Shah Sajjad Shaukat Jamal Mohammad Mazyad Hazzazi Amer Aljaedi Adel R. Alharbi 《计算机、材料和连续体（英文）》2023,75(3):5073-5086
Data Encryption Standard (DES) is a symmetric key cryptosystem that is applied in different cryptosystems of recent times. However, researchers found defects in the main assembling of the DES and declared it insecure against linear and differential cryptanalysis. In this paper, we have studied the faults and made improvements in their internal structure and get the new algorithm for Improved DES. The improvement is being made in the substitution step, which is the only nonlinear component of the algorithm. This alteration provided us with great outcomes and increase the strength of DES. Accordingly, a novel good quality S-box construction scheme has been hired in the substitution phase of the DES. The construction involves the Galois field method and generates robust S-boxes that are used to secure the scheme against linear and differential attacks. Then again, the key space of the improved DES has been enhanced against the brute force attack. The outcomes of different performance analyses depict the strength of our proposed substitution boxes which also guarantees the strength of the overall DES. 相似文献
419.
Shital Joshi S. Manimurugan Ahamed Aljuhani Umar Albalawi Amer Aljaedi 《计算机系统科学与工程》2022,43(3):1111-1130
The Internet of Things (IoT) represents a radical shifting paradigm for technological innovations as it can play critical roles in cyberspace applications in various sectors, such as security, monitoring, medical, and environmental sectors, and also in control and industrial applications. The IoT in E-medicine unleashed the design space for new technologies to give instant treatment to patients while also monitoring and tracking health conditions. This research presents a system-level architecture approach for IoT energy efficiency and security. The proposed architecture includes functional components that provide privacy management and system security. Components in the security function group provide secure communications through Multi-Authority Ciphertext-Policy Attributes-Based Encryption (MA-CPABE). Because MA-CPABE is assigned to unlimited devices, presuming that the devices are reliable, the user encodes data with Advanced Encryption Standard (AES) and protects the ABE approach using the solutions of symmetric key. The Johnson’s algorithm with a new computation measure is used to increase network lifetime since an individual sensor node with limited energy represents the inevitable constraints for the broad usage of wireless sensor networks. The optimal route from a source to destination turns out as the cornerstone for longevity of network and its sustainability. To reduce the energy consumption of networks, the evaluation measures consider the node’s residual energy, the number of neighbors, their distance, and the link dependability. The experiment results demonstrate that the proposed model increases network life by about 12.25% (27.73%) compared to Floyd–Warshall’s, Bellman–Ford’s, and Dijkstra’s algorithms, lowering consumption of energy by eliminating the necessity for re-routing the message as a result of connection failure. 相似文献
420.
In this paper, we suggested and studied the inverse length biased Maxell distribution (ILBMD) as a new continuous distribution of one parameter. The ILBMD is obtained by considering the inverse transformation technique of the Maxwell length biased distribution. Statistical characteristics of the ILBMD such as the moments, moment generating function, mode, quantile function, the coefficient of variation, coefficient of skewness, Moors and Bowley measures of kurtosis and skewness , stochastic ordering, stress-strength reliability, and mean deviations are obtained. In addition, the Bonferroni and Lorenz curves, Gini index, the reliability function, the hazard rate function, the reverse hazard rate function, the odds function, and the distributions of order statistics for the ILBMD, are presented. The ILBMD parameter is estimated using the maximum likelihood method, the method of moments, the maximum product of spacing technique, the ordinary and weight least square procedures, and the Cramer-Von-Mises methods. The Fishers information, as well as the Rényi and q-entropies, are derived. To investigate the usefulness of the proposed lifetime distribution and to illustrate the purpose of the study, a real dataset of the relief times of 20 patients receiving an analgesic is used. 相似文献