The spectrum allocation in any auctioned wireless service primarily depends upon the necessity and the usage of licensed primary users (PUs) of a certain band of frequencies. These frequencies are ...utilized by the PUs as per their needs and requirements. When the allocated spectrum is not being utilized in the full efficient manner, the unused spectrum is treated by the PUs as white space without believing much in the concept of spectrum scarcity. There are techniques invented and incorporated by many researchers, such as cognitive radio technology, which involves software-defined radio with reconfigurable antennas tuned to particular frequencies at different times. Cognitive radio (CR) technology realizes the logic of the utility factor of the PUs and the requirements of the secondary users (SU) who are in queue to utilize the unused spectrum, which is the white space. The CR technology is enriched with different frequency allocation engines and with different strategies in different parts of the world, complying with the regulatory standards of the FCC and ITU. Based on the frequency allocation made globally, the existing CR technology understands the nuances of static and dynamic spectrum allocation and also embraces the intelligence in time allocation by scheduling the SUs whenever the PUs are not using the spectrum, and when the PUs pitch in the SUs have to leave the band without time. This paper identifies a few of the research gaps existing in the earlier literature. The behavioral aspects of the PUs and SUs have been analyzed for a period of 90 days with some specific spectrum ranges of usage in India. The communal habits of utilizing the spectrum, not utilizing the spectrum as white space, different time zones, the requisites of the SUs, the necessity of the applications, and the improvement of the utility factor of the entire spectrum have been considered along with static and dynamic spectrum usage, the development of the spectrum policy engine aligned with cooperative and opportunistic spectrum sensing, and access techniques indulging in artificial intelligence (AI). This will lead to fine-tuning the PU and SU channel mapping without being hindered by predefined policies. We identify the cognitive radio transmitter and receiver parameters, and resort to the same in a proposed channel adaption algorithm. We also analyze the white spaces offered by spectrum ranges of VHF, GSM-900, and GSM-1800 by a real-time survey with a spectrum analyzer. The identified parameters and white spaces are mapped with the help of a swotting algorithm. A sample policy has been stated for ISM band 2.4 GHz where such policies can be excited in a policy server. The policy engine is suggested to be configured over the 5G CORE spectrum management function.
Abstract
The development of new methods for the study of agricultural products is an actual task. A large number of studies on the electrical properties of biological objects are performed today for ...scientific and industrial purposes. Distortions of electric signals are considered conventionally as harmful. The authors performed test-bench analysis of harmonic distortion, produced by different agricultural products. Apple, banana, tomato, tangerine were tested. The digital source of sinusoidal signals and a computed spectrum analyzer were main components of the test-bench circuit. Results of measurements of harmonics, from first to tenth, were presented in a graphic form. Each kind of agricultural products created harmonic distortion with an authentic set and a level of harmonics. So, the authors have shown the ability of analyzing harmonic distortions to determine properties of agricultural products.
•The measurement range is enlarged from 25 °C to −195 °C by using TiN-coated FBG.•The results showed that temperature sensitivity of 10.713 pm/ °C and R2 is 0.995.•The sensors have highly responsive ...when used at cryogenic temperature sensing.
In this study, single metal-coated Fiber Bragg grating (FBG) sensors and bare FBG sensors were placed in an aluminum alloy mold, which were in turn packaged in a thermal insulation container to monitor the temperature response, and used as cryogenic temperature sensors. Specifically, the performance of titanium nitride (TiN)-coated FBG sensors in cryogenic temperature environments was evaluated. Using an optical spectrum analyzer (OSA), the reflection spectra of the TiN-coated FBG sensors were measured and compared with those of bare FBG for temperatures ranging from 25 to −195 °C. The results showed that the TiN-coated FBG exhibited a temperature sensitivity of 10.713 pm/°C and R-squared value of 0.995. The TiN-coated on the FBG altered the non-linear characteristics of the thermo-optic and thermal expansion coefficients of the FBG. Through this research to get thermo-optic coefficient (ξ = 5.12 × 10−6) and thermal expansion coefficient (α = 1.81 × 10−6) and resulted in more precise measurements at cryogenic temperature.
Space division multiplexing, in conjunction with wavelength division multiplexing, is a powerful mechanism that increases spatial channels significantly in a single optical fiber. Spiral ...Phased-Laguerre-Gaussian (SP-LG) modes indicate that they effectively reduce mode coupling, thereby increasing the channel response and performance positively. However, mode-coupling influence optical fiber system leads to inter-symbol interference (ISI) between the channels and reduces both capacity and distance. In this paper, we apply the SP-LG modes in a space wavelength division multiplexing over a few-mode fiber system. The results demonstrate significant improvements in reducing channels effects and ISI. The performance evaluations are based on the bit-error-rate (BER), eye diagram and spectrum analyzer.
A novel compact device with spectrum analyzer characteristics has been designed, which allows the measuring of the maximum power received in multiple narrow frequency bands of 300 kHz, recording the ...entire spectrum from 78 MHz to 6 GHz; the device is capable of measuring the entire communications spectrum and detecting multiple sources of electromagnetic fields using the same communications band. The proposed device permits the evaluation of the cross-talk effect that, in conventional exposimeters, generates a mistake estimation of electromagnetic fields. The device was calibrated in an anechoic chamber for far-fields and was validated against a portable spectrum analyzer in a residential area. A strong correlation between the two devices with a confidence higher than 95% was obtained; indicating that the device could be considered as an important tool for electromagnetic field studies.
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•An optical fiber thermometer for continuous temperature measurement inside molten steel.•A robust cladding material for sapphire fiber at high temperature.•Precise temperature ...determination using convolutional neural network.
This paper demonstrates a robust optical fiber thermometer (OFT) for temperature measurement under extreme environments. To date, the development of sensors for continuous temperature measurement in environments with temperatures over 1000 °C, severe electromagnetic interferences, and strong oxidizing agents has been very challenging. The proposed nano-OFT system consists of a ceramic tube, a nanorod coated sapphire fiber, and a near-infrared (NIR) spectrum analyzer for continuous measurement of molten steel temperature in furnaces. The nanorod layer functions as an effective cladding material for the sapphire fiber to sustain a reliable transmission of NIR thermal emissions. The thermal radiation from the ceramic tube's tip was coupled out of the nano-OFT probe via the sapphire fiber and measured using the NIR spectrometer. The NIR emissions were analyzed using a convolution neural network to determine the probe temperature. Our results show that the nano-OFT probe can measure furnace temperature in the temperature range from 1,000–1,650 °C, with the error percentage as low as 0.5 %. The nano-OFT system can be employed by the steel industry to monitor steel temperature continuously, and thus enhance steel production efficiency and reduce energy consumption.
With the advantages of low power consumption and high stability, chirp transform spectrometer (CTS) has become a powerful tool widely used in spectrum analysis today. In recent years, compared with ...other spectrum analyzers, CTS is limited by the lack of bandwidth, which severely restricts its application and development. In this article, a CTS system with a wide bandwidth is proposed. The chirp signal with 2 GHz bandwidth is generated by DAC and multiplier, and its dispersion characteristics are matched with a 1 GHz bandwidth surface acoustic wave (SAW) filter to build a spectrum analyzer with an analysis bandwidth of 1 GHz. Experimental results show that the system frequency resolution can reach up to 102 kHz, which is very close to the theoretical value (100 kHz).
One of the major challenges of diagnosing rotor symmetry faults in induction machines (IMs) is severe modulation of fault and supply frequency components. In particular, existing techniques are not ...able to identify fault components in the case of low slips. In this article, this problem is tackled by proposing a novel approach. First, a new use of singular spectrum analysis (SSA), as a powerful spectrum analyzer, is introduced for fault detection. Our idea is to treat the stator current signature of the wound rotor IM as a time series. In this approach, the current signature is decomposed into several eigenvalue spectra (rather than frequency spectra) to find a subspace where the fault component is recognizable. Subsequently, the fault component is detected using some data-driven filters constructed with the knowledge about characteristics of supply and fault components. Then, an inexpensive peak localization procedure is applied to the power spectrum of the fault component to identify the exact frequency of the fault. The fault detection and localization methods are then combined in a recursive regime to further improve the diagnosis' performance particularly at high rotor speeds and small rotor faults. The proposed approach is data-driven and is directly applied to the raw signal with no suppression or filtration of the frequency harmonics with a low computational complexity. The numerical results obtained with real data at several rotation speeds and fault severities unveil the effectiveness and real-time feature of the proposed approach.
Cartilage is an important tissue contributing to the structure and function of support and protection in the human body. There are many challenges for tissue cartilage repair. However, 3D ...bio-printing of osteochondral scaffolds provides a promising solution. This study involved preparing bio-inks with different proportions of chitosan (Cs), Gelatin (Gel), and Hyaluronic acid (HA). The rheological properties of each bio-ink was used to identify the optimal bio-ink for printing. To improve the mechanical properties of the bio-scaffold, Graphene (GR) with a mass ratio of 0.024, 0.06, and 0.1% was doped in the bio-ink. Bio-scaffolds were prepared using 3D printing technology. The mechanical strength, water absorption rate, porosity, and degradation rate of the bio-scaffolds were compared to select the most suitable scaffold to support the proliferation and differentiation of cells. P3 Bone mesenchymal stem cells (BMSCs) were inoculated onto the bio-scaffolds to study the biocompatibility of the scaffolds. The results of SEM showed that the Cs/Gel/HA scaffolds with a GR content of 0, 0.024, 0.06, and 0.1% had a good three-dimensional porous structure and interpenetrating pores, and a porosity of more than 80%. GR was evenly distributed on the scaffold as observed by energy spectrum analyzer and polarizing microscope. With increasing GR content, the mechanical strength of the scaffold was enhanced, and pore walls became thicker and smoother. BMSCs were inoculated on the different scaffolds. The cells distributed and extended well on Cs/Gel/HA/GR scaffolds. Compared to traditional methods in tissue-engineering, this technique displays important advantages in simulating natural cartilage with the ability to finely control the mechanical and chemical properties of the scaffold to support cell distribution and proliferation for tissue repair.
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