Spectrum Technique Research Articles

The synthesis and characterization of α-Fe2O3 nanowires decorated with ZnO nanoparticles

In this study, the [Formula: see text]-Fe2O3 nanowires were synthesized and decorated by ZnO nanoparticles using the hydrothermal method. The structural and morphological study of samples was carried out using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectrum (EDS), High resolution transmission electron microscopy (HRTEM), and Fourier transform infrared spectroscopy (FTIR) techniques. FTIR was employed for [Formula: see text]-Fe2O3 and [Formula: see text]-Fe2O3 decorated with ZnO nanoparticles composites to verify the presence of ZnO in the composite after decorating. Furthermore, the optical properties was carried out using UV-vis spectrophotometer and photoluminescence spectra (PL) techniques. XRD analysis showed [Formula: see text]-Fe2O3 nanowires had a rhombohedral structure with a preferred crystal plane (104). In the [Formula: see text]-Fe2O3 nanowires decorated by ZnO nanoparticles, ZnO nanoparticles showed a hexagonal structure. Due to SEM images, the nanowires had an average diameter of 41 nm, and ZnO nanoparticles had a spherical shape with a maximum diameter of 70 nm. A uniform distribution was observed for both the [Formula: see text]-Fe2O3 nanowires and the [Formula: see text]-Fe2O3 nanowires decorated with ZnO nanoparticles. Furthermore, the result of bandgap energy calculation was 2.12 eV for [Formula: see text]-Fe2O3, while for [Formula: see text]-Fe2O3 nanowires decorated with ZnO nanoparticles was 3.17 eV which is near to the bandgap energy of ZnO nanoparticles. PL spectra revealed a few transitions in which the origin of these emissions would be associated to oxygen vacancies, iron vacancies, defects and band-to-band transition. The PL emission peaks of [Formula: see text]-Fe2O3 nanowires decorated with ZnO nanoparticles are similar to [Formula: see text]-Fe2O3 nanowires, but notably quenched with the ZnO nanoparticles. Based on the result of this study, it is possible to tune bandgap energy for various applications. In addition, this composite is promising candidates for solar cell photo electrodes and gas sensor applications.

One-Pot Synthesis of Biocompatible Glycine Protected Chromium Doped ZnS Nanoparticles and their Optical Properties

Here in, we report the synthesis and characterization of Chromium doped Zinc Sulfide nanoparticles (ZnS NPs). Initially, ZnS NPs are synthesized by bio-compatible glycine cap using simple one-pot co-precipitate method, and further it is doped by Chromium. The structure and morphology of these ZnS NPs was confirmed by X-Ray Diffractometry (XRD) and Scanning Electron Microscope with Elementary Dispersive Spectrum (SEM with EDS) techniques. The optical characterization techniques reveal that the Chromium doping affected the absorption and photoluminescence properties of the NPs. Photoluminescence of these NPs shifts from 384 nm to 428 nm upon Chromium doping. By using Tauc plot we obtained the energy band gap of 4.7 eV and it reduces to 3.9 eV for Chromium dope. The resultant ZnS NPs have size of 2.17nm and 1.86nm (with Chromium doping), also it gives Cubic Zinc blend phase as proved by XRD. The instrumentation techniques SEM with EDS, XRD, FTIR confirms that high purity Chromium doped ZnS NPs can be obtained by the proposed simple, low cost and highly effective method.

Exceptional photodecomposition activity of heterostructure NiTiO3–TiO2 catalyst

Mesoporous TiO 2 mixed with NiTiO 3 at various concentrations was synthesized by combining sol–gel and eco-friendly hydrothermal methods. The properties of the NiTiO 3 –TiO 2 (NTO–Ti) photocatalyst were characterized using Χ-ray diffraction, Raman spectroscopy, scanning electron microscopy, Fourier-transform infrared spectroscopy, Brunauer–Emmett–Teller adsorption, energy dispersive X-ray, and UV–vis absorption spectra techniques. The photocatalytic activity of NTO–Ti catalysts was assessed by way of the photodegradation of cinnamic acid (CA) under UV-A irradiation. The effects of the operating parameters, including catalyst dosage, airflow, and initial solution pH on the photodecomposition efficiency of CA were also investigated. Research results confirm that NTO–Ti heterostructure catalysts are synthesized in the crystalline phase with high crystallinity. Compared with pure TiO 2 , the NTO–Ti catalysts have a smaller particle size and average crystallite size (8.6–9.0 nm versus 34.8 nm) and lower band gap energy (3.02–3.08 eV versus 3.20 eV). The catalysts also enable a redshift in the absorption band from UV (λ = 385 nm) to UV-A light (λ = 404–412 nm). The study showed that the physicochemical and photochemical properties and the photocatalytic performance of the NTO–Ti catalysts are controlled by the NiTiO 3 loading. NTO–Ti with NiTiO 3 1.0 wt.% was found to maximize CA photodegradation. Under the most favorable conditions, CA removal of 82.8% was obtained after 120 min, which is higher than for pure TiO 2 (68.7%) and NiTiO 3 (3.8%) catalysts under the same conditions. • Mesoporous TiO 2 nanomaterials mixed with NiTiO 3 of various concentrations were synthesized. • The heterostructured NiTiO 3 -TiO 2 nanomaterials had advantages of properties and photocatalytic performance over the pure TiO 2 . • 1.0%NiTiO 3 -TiO 2 was found to be the most effective catalyst with the 120 min TOS removal efficiency of CA reached 82.8%.

Spectroscopic Analysis of CdO: Fe Plasma Generated by Nd: YAG Laser

In this work, the optical emission spectrum technique was used to analyze the optical emission spectrum of (CdO: Fe) plasma produced by laser Nd: YAG with a wavelength of (532) nm, a period of 10 ns, and a focal length of 10 cm in the energy range of (200-500) mJ. The electron temperature (Te) was determined using the method of line intensities ratio. Using the Saha-Boltzmann equation, the electron density (ne) was determined. Other plasma parameters such as plasma frequency (fp), Debye length (λD) and Debye number (ND) were also measured. The CdO: Fe (at a mixing ratio of X= 0.5.) plasma spectrum was observed for different energies. As a function of the laser energies, the changes in electron temperature and densities were studied. The value of the electron temperature, at X=0.5, was (0.420 - 1.160) eV for laser energy (200-500) mJ, respectively.

Development of spectrophotometric method for simultaneous determination of copper β-resorcylate, lead β-resorcylate and lead oxide in double base solid propellants using mean centering of ratio spectra technique

Development of spectrophotometric method for simultaneous determination of copper β-resorcylate, lead β-resorcylate and lead oxide in double base solid propellants using mean centering of ratio spectra technique

Constraining simulated black hole feedback in the Perseus Cluster

Active galactic nuclei in galaxy clusters can produce tightly collimated jets that inject energy into the surrounding intracluster medium (ICM). This feedback process can offset cooling losses from X-ray radiation that otherwise would result in cooling flow structures. Jet-inflated bubbles can heat the cluster via a turbulent cascade. The density fluctuation spectrum inferred from X-ray maps of the cluster shows different levels and scales of turbulence in different regions of the clusters, and can be used to determine the contribution of different driving mechanisms. By applying observational power spectrum techniques to synthetic X-ray data from feedback simulations of the Perseus cluster, we find that the density fluctuation spectra produced by a single episode of jet activity are broadly consistent with analysis of Chandra observations inside 60 kpc. The velocity dispersion effected by the AGN approaches Hitomi's measurement of turbulence in Perseus during the AGN episode, but is underpredicted later in the simulation. A fully established volume-filling turbulent cascade therefore requres multiple periods of jet activity, along with turbulence driven by other processes outside of the inner 60 kpc core. This also suggests the X-ray fluctuations directly associated with the jet bubble substantially contribute to the overall density fluctuation spectrum.

Guided Wave Phase Velocity Dispersion Reconstruction Based on Enhanced Phased Spectrum Method.

Fibre-reinforced composite laminates are frequently used in various engineering structures, due to their increased weight-to-stiffness ratio, which allows to fulfil certain regulations of CO2 emissions. Limited inter-laminar strength makes composites prone to formation of various defects, which leads to progressive degradation of residual strength and fatigue life of the structure. Using ultrasonic guided waves is a common technique for assessing the structural integrity of composite laminates. Phase velocity is one of the fundamental characteristics of guided waves and can be used for defect detection, material property estimation, and evaluation of dispersion. In this paper, a phase velocity reconstruction approach, based on the phase-shift method, was proposed, which uses frequency sweep excitation to estimate velocity at specific frequency harmonics. In contrast to the conventional phase spectrum technique, the proposed approach is applicable to the narrowband piezoelectric transducers and suitable for the reconstruction of dispersion curves for direct, converted, and multiple co-existing modes with high accuracy. The proposed technique was validated with finite element simulations and experiments, both on isotropic and anisotropic structures, analysing the direct, converted, and overlapped modes. The results demonstrated that, using the proposed technique, the phase velocity dispersion can be reconstructed at −20 dB level bandwidth of the transducer, with a relative error of ±4%, compared to the theoretical velocity predictions.

Double-quantum–zero-quantum 2D coherent spectroscopy reveals quantum coherence between collective states in an atomic vapor

We report a novel, to the best of our knowledge, double-quantum-zero-quantum two-dimensional coherent spectroscopy (2DCS) that allows direct detection of the quantum coherence between multiparticle collective states. Through correlating the double-quantum coherence and the zero-quantum coherence, signatures for coherence between collective states can be well isolated as side peaks and readily identified in the 2D spectrum. The experiment is implemented in a vapor of rubidium atoms in a collinear 2DCS setup. Good agreement with a theoretical simulation using density matrix confirms the essential role of the interatomic correlation effect in generating the side peak signals. This 2D spectrum technique paves a new avenue for studying the coherent coupling of highly excited states and many-body properties.

Bimagnetic hard/soft and soft/hard ferrite nanocomposites: Structural, magnetic and hyperthermia properties

Recent studies show that the chemical composition and shape of magnetic nanoparticles (NPs) play an important role in their properties. In particular, the bimagnetic NPs display useful and in many cases, more interesting properties than single-phase NPs. In this work, we prepared Fe 3 O 4 and CoFe 2 O 4 cube-like NPs and bimagnetic hard/soft (CoFe 2 O 4 /Fe 3 O 4 ) and soft/hard (Fe 3 O 4 /CoFe 2 O 4 ) nanocomposites (core/coating) using a facile and eco-friendly co-precipitation method that allows the synthesis of the cube-like NPs at temperatures near room temperature. The phase purity and the crystallinity of the NPs with a spinel structure were confirmed by the X-ray diffraction and infrared spectra techniques. Transmission electron microscopy (TEM) images revealed that the NPs have a cubic-like shape with an average dimension of 20 nm. Energy dispersive X-ray analysis, Mössbauer spectroscopy and SQUID magnetic measurements indicated the co-existence of Fe 3 O 4 and CoFe 2 O 4 phases in nanocomposites. In addition, the hysteresis loops exhibited a single-phase behavior in the nanocomposites that indicates there is a good exchange-coupling interaction between the hard and soft magnetic phases. The CoFe 2 O 4 /Fe 3 O 4 nanocomposites presented a larger saturation magnetization than the CoFe 2 O 4 NPs that is effective for their use in magnetic hyperthermia. Finally, we studied the hyperthermia properties of samples in an alternating magnetic field with a frequency of 276 kHz and field amplitude of 13.9 kA/m. Our results showed that magnetic hyperthermia efficiency simultaneously depends on the composition of samples along with magnetic anisotropy and saturation magnetization.

Processing ambient noise using wavelet analysis tools: the Iraqi Seismological broadband Network Data at Iraqi Meteorological Organization and seismology (IMOS)

The purpose of this study is to reduce the noise of passive seismic signals recorded across the Iraqi Seismological Network Data at Iraqi Meteorological Organization and seismology (IMOS). The seismic records from six broadband stations of IMOS are largely affected by human activities in the populated cities of Iraq. We utilized several well-developed amplitude power spectrum and wavelet analysis techniques to improve signal-to-noise ratio. The results obtained from this comparison show that continuous wavelet transform can largely improve signal with minimal changes in the waveform shape of interest, even in presence of high noise levels. In addition, has overwhelmingly strong vitality and gains substantial development in the field of signal processing. Several mother wavelets were tested and Morlet and Coiflet selected as the optimum waves based on the signal characteristics and the noise reduction objective (maximizing SNR or reducing errors). Hence, the quality of the final seismic signal is crucial for the moment tensor analysis. However, traditional filters including discrete wavelet packet transform and 1-D wavelet analysis methods can be affective to reduce distortion in the signal.

Synthesis and Toxicological Effect of Some New Pyrrole Derivatives as Prospective Insecticidal Agents against the Cotton Leafworm, Spodoptera littoralis (Boisduval).

Herein, a series of biologically active pyrrole derivatives, namely 2-[(3-cyano-5-aryl-1H-pyrrol-2-yl)thio]acetic acids 2a-c, 2-[(2-hydroxyethyl)-thio]-5-aryl-1H-pyrrole-3-carbonitriles 3a-c, and 2-[(2-amino-ethyl)thio]-5-aryl-1H-pyrrole-3-carbonitriles 4a-c, 2,2′-disulfanediylbis(5-aryl-1H-pyrrole-3-carbonitriles) 5a-c, 2-((3-cyano-5-aryl-1H-pyrrol-2-yl)thio)acetates 6a-c, 2-[(3-cyano-5-phenyl-1H-pyrrol-2-yl)thio]acetohydrazides 7a-c, and 2-{2-[(3-cyano-5-aryl-1H-pyrrol-2-yl)thio]acetyl}-N-phenyl-hydrazinecarbothioamides 8a-c, as insecticidal agents, were synthesized via adaptable, smoothly accessible 2-(2-oxo-2-arylylethyl)malononitriles 1a-c. The structures were proved using infrared (IR), nuclear magnetic resonance (NMR), and mass spectrum (MS) techniques. Under laboratory conditions, the toxicological characteristics were tested towards Spodoptera littoralis, cotton leafworm insect type. In respect to the LC50 values, compounds 6a, 7a, 8c, and 3c possess the highest insecticidal bioefficacy, with values of 0.5707, 0.1306, 0.9442, and 5.883 ppm, respectively. The study paves the way towards discovering new materials for potential use as insecticidal active agents.

Joint optimisation techniques for trade-off aware spectrum sensing in cognitive radio network

Cognitive radio (CR) network is considered a promising domain to enhance spectrum efficiency to access underutilised frequency bands. However, due to the influence of channel fading and shadowing, accuracy in primary user (PU) detection by CR gets hampered. This paper designs a joint optimisation technique for spectrum sensing in CR network to optimise energy, delay, and throughput with increased sensing accuracy. Initially, simple energy detection is exhibited for sensing the presence of PU in band. Further, the algorithm is developed to achieve an energy-throughput trade-off, and delay-throughput trade-off. Hence, the optimisation algorithm for detecting energy, reducing delay, and enhancing throughput are developed to optimise complete sensing performance. Furthermore, the joint optimisation model assists in acquiring trade-offs amongst energy, delay, and throughput. The assessment of the technique is performed using delay, energy, and throughput. Moreover, the software-defined radio (SDR) configuration is performed for validating the result.

A Neuro Fuzzy with Improved GA for Collaborative Spectrum Sensing in CRN

Cognitive Radio Networks (CRN) have recently emerged as an important solution for addressing spectrum constraint and meeting the stringent criteria of future wireless communication. Collaborative spectrum sensing is incorporated in CRNs for proper channel selection since spectrum sensing is a critical capability of CRNs. According to this viewpoint, this study introduces a new Adaptive Neuro Fuzzy logic with Improved Genetic Algorithm based Channel Selection (ANFIGA-CS) technique for collaborative spectrum sensing in CRN. The suggested method’s purpose is to find the best transmission channel. To reduce spectrum sensing error, the suggested ANFIGA-CS model employs a clustering technique. The Adaptive Neuro Fuzzy Logic (ANFL) technique is then used to calculate the channel weight value and the channel with the highest weight is selected for transmission. To compute the channel weight, the proposed ANFIGA-CS model uses three fuzzy input parameters: Primary User (PU) utilization, Cognitive Radio (CR) count and channel capacity. To improve the channel selection process in CRN, the rules in the ANFL scheme are optimized using an updated genetic algorithm to increase overall efficiency. The suggested ANFIGA-CS model is simulated using the NS2 simulator and the results are investigated in terms of average interference ratio, spectrum opportunity utilization, average throughput, Packet Delivery Ratio (PDR) and End to End (ETE) delay in a network with a variable number of CRs.

Joint optimisation techniques for trade-off aware spectrum sensing in cognitive radio network

Joint optimisation techniques for trade-off aware spectrum sensing in cognitive radio network

Development of activated carbon-doped TiO2 nanoparticle thin film for application in dye-sensitized solar cells

Carbon This research aims to study the preparation of activated carbon-doped TiO2 nanoparticle thin films with basellaceae, malvaceae and hylocereus dyes for application in dye-sensitized solar cells (DSSCs). The physical and chemical properties of as-prepared thin films were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-vis diffuse reflectance spectra (UV-vis DRS) techniques. Results revealed that the basellaceae dye (JSC is 13.5 mA/cm2, VOC is 0.450 V and η (%) is 1.59) on thin film showed the highest efficiency compared with the malvaceae (JSC is 10.2 mA/cm2, VOC is 0.425 V and η (%) is 1.08) and hylocereus (JSC is 12.1 mA/cm2, VOC is 0.325 V and η (%) is 1.17) dyes. Moreover, we observed that activated carbon/TiO2 nanoparticle thin film exhibited a higher efficiency than other thin film samples. This might be due to the activated carbon doped into the TiO2 leading to facilitate the separation of photogenerated charge carriers, resulting in its enhanced efficiency.

Prenos u proširenom spektru - frekvencijsko skakanje - istorija, principi i primena

Introduction/purpose: The frequency hopping spread spectrum (FH-SS) technique assumes the carrier generated by the syntesizer to hop from frequency to frequency over a wide bandwidth, according to a pseudonoise code sequence defined by the code sequence generator. The article presents the history, principles and applications of the FH-SS technique. Both military and commercial applications are discussed. Methods: This article presents an overview of data from the technical literature, with appropriate comments. Results: After presenting the history and principles of the FH-SS technique, the article summarizes its use with examples of military and commercial applications. The importance of using FH-SS in the described applications is highlighted. Conclusion: The FH-SS technique has been successfully implemented in many military and commercial technologies due to its high protection against interference, making communication difficult for reconnaissance and eavesdropping, and its ability to provide code division multiple access.

Synthesis and Biological Evaluation of Novel 1,3-Benzoxathiol-2-one Sulfonamides against Toxic Activities of the Venom of Bothrops jararaca and Bothrops jararacussu Snakes

This work describes the synthesis of new 1,3-benzoxathiol-2-one sulfonamides and evaluation of their ability to inhibit some in vitro (coagulant, proteolytic and hemolytic) and in vivo (hemorrhagic, edematogenic and lethality) toxic activities of Bothrops jararaca and Bothrops jararacussu venoms. Compounds have been synthesized from the coupling of intermediate 5-amino-6-methoxybenzo[d] [1,3]oxathiol-2-one 4 with benzenesulfonyl chlorides. Characterization of the products was achieved by nuclear magnetic resonance (NMR) and electrospray ionization mass spectra (ESI-MS) techniques. Biological assay results have shown that most of compounds inhibited the main toxic activities of the venom of the two snake species. Compound 5b (N-(6-methoxy-2-oxobenzo[d] [1,3]oxathiol-5-yl)-4-nitrobenzenesulfonamide) was the most efficient in inhibiting hemolysis of B. jararaca, and coagulation and proteolysis induced by both venoms. For in vivo activities, all compounds inhibited the edema, from 35 to 72%, and most of them exhibited antihemorrhagic and antilethality activities. Thus, the results pointed to the biological potential of these compounds, being promising molecules to treat envenomation by these snakes as well as to aid the current antivenom serum therapy.

Spectrum Sharing Between Radar and Communication Systems Based on Overlapped Virtual Subarrays

In this paper, we propose a new technique for spectrum sharing between radar and communication systems. The new technique enjoys the advantages of null-space projecting which can be used to mitigate the interference between radar and communication systems. In order to reduce the number of radar antennas and reduce the requirement of manufacture, deploy and implementation, we also introduce virtual subarray architecture to reap more effective transmit array aperture. The essence is to partition the multiple-input multiple-output (MIMO) antenna array into multiple overlapped subarrays to reap a compromise between coherent gain and diversity gain. We show that the configuration with overlapped subarrays can be used to form narrower beams with lower sidelobes, which is good for reaping higher performance in target detection. In order to evaluate the impact on the performance of radar systems with the implementation of spectrum sharing, the generalized likelihood ratio test for target detection is derived. It is shown that, although the implementation of the proposed spectrum sharing method would loss the radar system’s target detection performance, we can reap the benefits of spectrum sharing. That is to say, we achieve a good tradeoff between spectrum sharing and target detecting.

Real Time Monitoring of Muscle Fatigue with IoT and Wearable Devices

Wearable monitoring devices are in demand in recent times for monitoring daily activities including exercise. Moreover, it is widely utilizing for preventing injuries of athletes during a practice session and in few cases, it leads to muscle fatigue. At present, emerging technology like the internet of things (IoT) and sensors is empowering to monitor and visualize the physical data from any remote location through internet connectivity. In this study, an IoT-enabled wearable device is proposing for monitoring and identifying the muscle fatigue condition using a surface electromyogram (sEMG) sensor. Normally, the EMG signal is utilized to display muscle activity. Arduino controller, Wi-Fi module, and EMG sensor are utilized in developing the wearable device. The Time-frequency domain spectrum technique is employed for classifying the three muscle fatigue conditions including mean RMS, mean frequency, etc. A real-time experiment is realized on six different individuals with developed wearable devices and the average RMS value assists to determine the average threshold of recorded data. The threshold level is analyzed by calculating the mean RMS value and concluded three fatigue conditions as >2 V: Extensive); 1–2 V: Moderate, and

Aggregated CDMA Crossbar With Hybrid ARQ for NoCs

Network-on-chips (NoCs) are the dominant interconnection technique in modern system-on-chips (SoCs). The medium access technique used in the physical layer of NoC routers profoundly impacts the performance and footprint of the router. Code division multiple access (CDMA) is a medium access technique widely deployed in various wireless communication systems, and it has recently been proposed as a prominent switching method for NoC routers. In a CDMA crossbar, several processing elements (PEs) can communicate simultaneously over a single communication channel by applying the direct-sequence spread spectrum technique to digital interconnects. However, existing CDMA switches are bit-wise architectures in which a binary data bit is spread and serially communicated on an exclusive digital channel while replicating this configuration to communicate multiple data bits, which increases the crossbar area and wiring density. In this work, we propose aggregated CDMA (ACDMA) to improve the area, throughput, and power consumption of existing CDMA NoC routers. ACDMA exploits the static nature and relative noise immunity of on-chip interconnects to aggregate transmission of multiple data bits into M-ary symbols on a single digital communication channel, which significantly reduces the wiring density and area overhead of the crossbar. Serial and parallel variants of the ACDMA crossbar offering a wide range of area-speed trade-offs are implemented in the ASIC <inline-formula> <tex-math notation="LaTeX">$65~nm$ </tex-math></inline-formula> standard cell technology. The implementation results show that the throughput-per-area (TPA) of the serial and parallel ACDMA crossbars is improved by 96.3&#x0025;, 18.2&#x0025;, and 118.6&#x0025;; and 400&#x0025;, 255.3&#x0025;, and 184.2&#x0025; compared to the serial and parallel counterparts of the Walsh Basis (WB), Standard Basis (SB), and Overloaded CDMA Interconnect (OCI) crossbars, respectively. A 65-node ACDMA NoC router is fully realized and compared to the state-of-the-art CDMA and CONNECT NoC routers under multiple synthetic workloads. Communication reliability of the ACDMA NoC router subject to noise is investigated and a hybrid ARQ approach is proposed to improve the interconnect reliability.