Signal Reception Research Articles

Improving a method for non-coherent processing of signals by a network of two small-sized radars for detecting a stealth unmanned aerial vehicle

The object of this study is the process of detecting stealth unmanned aerial vehicles by a network of two small-sized radars with incoherent signal processing. The main hypothesis of the study assumed that combining two small-sized radars into a network could improve the quality of detection of stealth unmanned aerial vehicles with incoherent signal processing. The improved method for detecting a stealth unmanned aerial vehicle by a network of two small-sized radars with incoherent signal processing, unlike the known ones, provides for the following: – synchronous inspection of the airspace by small-sized radars; – sounding signal emission by each small-sized radar; – reception of echo signals from a stealth unmanned aerial vehicle by two small-sized radars; – coordinated filtering of incoming echo signals (separation of echo signals); – quadratic detection of signals at the outputs of matched filters; – summation of the detected signals at the outputs of the matched filters; – summation of the outputs of adders of two small-sized radars. The scheme of a stealth unmanned aerial vehicle detector is presented, optimal according to the Neumann-Pearson criterion, with incoherent signal processing. The quality of detection of a stealth unmanned aerial vehicle by a network of two small-sized radars with incoherent signal processing was evaluated. It was found that with incoherent processing, the gain in the value of the conditional probability of correct detection is on average from 19 % to 26 %, depending on the value of the signal-to-noise ratio. The gain in the value of the conditional probability of correct detection is greater at low values of the signal-to-noise ratio. At the same time, the gain in signal-to-noise value is more significant with coherent signal processing than with non-coherent signal processing by a network of two small-sized radars

Optimal Incoherent Reception Noise Immunity of Binary Signals with Differential Phase Manipulation in the Presence of Several Harmonic Interferences

This article proposes the calculation of the probabilities of incoherent reception of signals with binary relative phase manipulation (OFM–2) in the presence of several harmonic interference. Examples of calculating the error probability per bit of receiving signals from OFM – 2 according to the presented method in the presence of several harmonic interference are shown. The obtained graphs depend on the magnitude of the signal at different values of interference and the same magnitude of the frequency shift, as well as on the frequency shift of interference at different levels of signals and interference. The results of the study using this technique allow us to calculate with high accuracy and reliable forecasting the reliability of transmitted information in radio communication channels under the influence of several harmonic interference during processing on two clock cycles. And also to predict the maximum damage to the process of transmitting information in a radio communication channel under various conditions: the coincidence of interference frequencies with the signal frequency, the offset of interference frequencies relative to the signal frequency and the spread of interference frequencies with the signal frequency.

Primary cilia promote the differentiation of human neurons through the WNT signaling pathway.

Primary cilia emanate from most human cell types, including neurons. Cilia are important for communicating with the cell's immediate environment: signal reception and transduction to/from the ciliated cell. Deregulation of ciliary signaling can lead to ciliopathies and certain neurodevelopmental disorders. In the developing brain cilia play well-documented roles for the expansion of the neural progenitor cell pool, while information about the roles of cilia during post-mitotic neuron differentiation and maturation is scarce. We employed ciliated Lund Human Mesencephalic (LUHMES) cells in time course experiments to assess the impact of ciliary signaling on neuron differentiation. By comparing ciliated and non-ciliated neuronal precursor cells and neurons in wild type and in RFX2 -/- mutant neurons with altered cilia, we discovered an early-differentiation "ciliary time window" during which transient cilia promote axon outgrowth, branching and arborization. Experiments in neurons with IFT88 and IFT172 ciliary gene knockdowns, leading to shorter cilia, confirm these results. Cilia promote neuron differentiation by tipping WNT signaling toward the non-canonical pathway, in turn activating WNT pathway output genes implicated in cyto-architectural changes. We provide a mechanistic entry point into when and how ciliary signaling coordinates, promotes and translates into anatomical changes. We hypothesize that ciliary alterations causing neuron differentiation defects may result in "mild" impairments of brain development, possibly underpinning certain aspects of neurodevelopmental disorders.

An optimization NPUSCH uplink scheduling approach for NB-IoT application via the feasible combinations of link adaptation, Resource assignment and energy efficiency

Low-power wide area (LPWA) technology, specifically Narrowband Internet of Things (NB-IoT), has emerged as a pivotal sixth-generation (6G) network technology, catering to the demands of massive-type communications (m-MTC), extended battery life, wide range coverage, and high reliability. Despite its advancements, existing studies often fall short in simultaneously addressing energy efficiency, latency, link adaptation, and resource allocation in the bandwidth-constrained environments typical of NB-IoT. The complexity of finding a comprehensive optimal solution for resource allocation is compounded by its non-convex and NP-hard combinatorial nature. This research addresses these challenges by introducing a Hybrid-Optimizer approach, which integrates link adaptation, resource allocation, and scheduling algorithms. This approach aims to identify the optimal feasible combination for each device (UE), focusing on energy conservation and improved signal reception. Applied to the Narrow Physical Uplink Shared Channel (NPUSCH) uplink scheduling in NB-IoT, this method is benchmarked against the conventional Round-Robin scheduling algorithm. Simulation results demonstrate that the Hybrid-Optimizer approach significantly outperforms the Round-Robin algorithm in terms of scheduling processing time and energy efficiency. Furthermore, the proposed algorithm is capable of generating candidate combinations that enhance signal reception in UEs and meet the required subframe criteria, adhering to system modeling assumptions for scheduling optimization.

Novel Modification of Integrated Optimization Method for Sensor's Communication in Wi-Fi Public Networks.

A novel modification of IP networks integrated optimization method for heterogeneous networks, for example, the seamless Wi-Fi network serving simultaneously mobile users and wireless sensors, has been developed in this article. The mutual influence of signal reception, frequency-territorial planning, and routing procedures in heterogeneous networks have been analyzed in the case of simultaneous data transmission by both mobile users and wireless sensors. New principles for the listed procedures interaction and the basic functions for their describing are formulated. A novel modification of the integrated optimization method and its algorithm have been developed. The developed method's effectiveness has been analyzed for the IEEE 802.11ax network segment. Its result showed that the network load was decreased by an average of 20%, the data rate over the network as a whole increased for users and sensors by an average of 25% and 40%, respectively, and the sensors' lifetime increased by an average of 20% compared to the novel modification of the Collective Dynamic Routing method.

Real-time high-precision baseline measurement of satellite formation flying based on GNSS

With the establishment of the Chinese space station, a series of space science missions will be conducted in its vicinity. One of the extended tasks for the in-orbit service of space station is the formation flying of small satellites centered around the space station. Satellite formations can perform simultaneous three-dimensional observations of the space station, generating three-dimensional images and monitoring and assessing the status of critical components of the space station. The real-time and accurate relative position measurement is one of the key issues in formation flying. It is a fundamental prerequisite for maintaining and reconfiguring formation configurations, collision avoidance and safety assurance. GNSS-based relative positioning is a low-cost and high-precision measurement method, which is not constrained by light, weather, or relative attitude of satellites. This study introduces a novel approach to determine the relative position of satellites based on single-epoch Global Navigation Satellite System (GNSS) carrier phase difference measurements. Unlike traditional methods, the proposed technique eliminates the need for precise ephemeris and clock bias files and does not require historical observation data. The algorithm avoids the complexity associated with full cycle ambiguity jumps, facilitating real-time, high-precision calculations of relative position baseline vectors. Special attention is given to the influence of Geostationary Earth Orbit (GEO) satellites in the BeiDou Navigation Satellite System (BDS), and measures are taken to mitigate their impact on measurement accuracy by adjusting their observation weights. Our newly developed GNSS-based real-time measurement module, designed for high-quality GNSS signal reception and data communication, was tested on terrestrial and simulated low-orbit platforms. Remarkably, over baselines ranging from 10 m to 9.3 km, while traditional pseudorange differential measurements showed errors up to 1.5571 m, our proposed method consistently held errors under 5 cm and ensured computational speeds within 0.1 s per epoch. High-dynamic zero-baseline tests further validated its potential, with errors less than 1 cm. The innovations encapsulated in this work, resonating with the evolving trends of miniaturized and scalable satellites, present a cost-efficient and real-time solution for inter-satellite relative position measurement. This promises a new horizon in satellite formation technology, with future endeavors focusing on on-orbit experiments.

Pied tamarins change their vocal behavior in response to noise levels in the largest city in the Amazon.

Many animal species depend on sound to communicate with conspecifics. However, human-generated (anthropogenic) noise may mask acoustic signals and so disrupt behavior. Animals may use various strategies to circumvent this, including shifts in the timing of vocal activity and changes to the acoustic parameters of their calls. We tested whether pied tamarins (Saguinus bicolor) adjust their vocal behavior in response to city noise. We predicted that both the probability of occurrence and the number of long calls would increase in response to anthropogenic noise and that pied tamarins would temporally shift their vocal activity to avoid noisier periods. At a finer scale, we anticipated that the temporal parameters of tamarin calls (e.g., call duration and syllable repetition rate) would increase with noise amplitude. We collected information on the acoustic environment and the emission of long calls in nine wild pied tamarin groups in Manaus, Brazil. We found that the probability of long-call occurrence increased with higher levels of anthropogenic noise, though the number of long calls did not. The number of long calls was related to the time of day and the distance from home range borders-a proxy for the distance to neighboring groups. Neither long-call occurrence nor call rate was related to noise levels at different times of day. We found that pied tamarins decreased their syllable repetition rate in response to anthropogenic noise. Long calls are important for group cohesion and intergroup communication. Thus, it is possible that the tamarins emit one long call with lower syllable repetition, which might facilitate signal reception. The occurrence and quantity of pied tamarin' long calls, as well as their acoustic proprieties, seem to be governed by anthropogenic noise, time of the day, and social mechanisms such as proximity to neighboring groups.

Design and Analysis of a Quad-Band Antenna for IoT and Wearable RFID Applications

The role of antennas in wireless communication is critical for enabling efficient signal transmission and reception across various frequency bands, including those associated with IoT (Internet of Things), X-band, S-band, and RFID (radio-frequency identification) systems. This paper presents a small quadruple-band antenna with 25 × 40 × 1.5 mm3 dimensions designed for diverse wireless applications. It is adept at operating in the S-band (2.2 GHz), wireless local area network (WLAN) (5.7 GHz), microwave RFID frequency band (5.8 GHz), and X-band (7.7 GHz and 8.3 GHz). While the majority of existing research focuses on antennas covering two or three bands, our work stands out by achieving quad-band operation in the proposed antenna design. This antenna is constructed on a semiflexible Rogers RT5880 substrate, making it well-suited for wearable applications. Computer Simulation Technology (CST) Microwave studio (2019) simulation package software is chosen for design and analysis. The antenna design features a comb-shaped radiating structure, where each “tooth” is responsible for resonating at a distinct frequency with an appropriate bandwidth. The antenna retains stability in both free space and on-body wearability scenarios. It achieves a low specific absorption rate (SAR), meeting wearable criteria with SAR values below 1.6 W/Kg for all resonating frequencies. The proposed antenna demonstrates suitable radiation efficiency, reaching a maximum of 82.6% and a peak gain of 6.3 dBi. It exhibits a bidirectional pattern in the elevation plane and omnidirectional behavior in the azimuth plane. The antenna finds applications across multiple frequencies and shows close agreement between simulated and measured results, validating its effectiveness.

Two-stage look-up-table-based 16QAM vector millimeter-wave signal generation and reception.

We propose a two-stage look-up table (LUT) scheme for a photonic 16 quadrature-amplitude-modulation (QAM) millimeter-wave (MMW) communication system. The first-stage LUT is used at the transmitter, which can eliminate complex computational processes and adaptively adjust the precoded amplitude values to achieve optimal performance without being affected by half-wave voltage variations. We have completed a signal transmission below the hard-decision forward error correction (HD-FEC) threshold of 3.8 × 10-3 at the baud rate of 2/4 GBaud for weak turbulence and 2 GBaud for medium turbulence free-space optics (FSO) channel transmission. The second-stage LUT is used for post-compensation at the receiver as a nonlinear scheme that records the average pattern-related distortion of the channel and mitigates transmission impairment through nonlinear post-compensation. With the help of the second-stage LUT, the sensitivity of the optical receiver is improved by 0.15 dB at a baud rate of 2 GBaud for medium turbulence FSO channel transmission. As the baud rate increases to 4 GBaud, the system's bit error ratio (BER) can reach the soft-decision forward error correction (SD-FEC) threshold of 4.2 × 10-2 only after applying the second-stage LUT.

The applications of sonar and radar systems in underwater detection

The development of sonar and radar systems utilizing sound and radio waves, respectively, has evolved significantly over the past two centuries. Recent decades have witnessed remarkable progress in remote sensing using high-frequency Doppler radars for marine surface parameter analysis. Understanding animal behavior around sustainable ocean energy sources is crucial for mitigating potential risks linked to such installations. Increasing the Signal-to-Noise Ratio (SNR) enhances signal reception. A technique estimating noise in the detection coil's first half determines the transfer function between the reference and detection coils. This enables separation of the Ultra-Nuclear Magnetic Resonance signal from noise, preserving it using non-linear fitting. Sonar systems, using sound waves, detect underwater objects, map surfaces, and track marine life. Sound waves emitted by the transmitter are reflected back to calculate distances. Challenges in sonar systems include a blind zone caused by submerged transducers in shallow water. To improve, SNR enhancement is critical. Sonar's future may rely on AI-assisted signal processing. Radar systems, operating with radio waves, share features with sonar, focusing on object detection and ranging. Improvement avenues include 3D imaging and AI-enhanced signal processing. In conclusion, sonar and radar systems are crucial tools for underwater exploration and object detection. While challenges persist, innovative solutions and AI advancements promise enhanced capabilities for both systems.

Cilia Provide a Platform for the Generation, Regulated Secretion, and Reception of Peptidergic Signals.

Cilia are microtubule-based cellular projections that act as motile, sensory, and secretory organelles. These structures receive information from the environment and transmit downstream signals to the cell body. Cilia also release vesicular ectosomes that bud from the ciliary membrane and carry an array of bioactive enzymes and peptide products. Peptidergic signals represent an ancient mode of intercellular communication, and in metazoans are involved in the maintenance of cellular homeostasis and various other physiological processes and responses. Numerous peptide receptors, subtilisin-like proteases, the peptide-amidating enzyme, and bioactive amidated peptide products have been localized to these organelles. In this review, we detail how cilia serve as specialized signaling organelles and act as a platform for the regulated processing and secretion of peptidergic signals. We especially focus on the processing and trafficking pathways by which a peptide precursor from the green alga Chlamydomonas reinhardtii is converted into an amidated bioactive product-a chemotactic modulator-and released from cilia in ectosomes. Biochemical dissection of this complex ciliary secretory pathway provides a paradigm for understanding cilia-based peptidergic signaling in mammals and other eukaryotes.

A Preliminary Investigation about the Influence of WIMU PROTM Location on Heart Rate Accuracy: A Comparative Study in Cycle Ergometer.

Technological development has boosted the use of multi-sensor devices to monitor athletes' performance, but the location and connectivity between devices have been shown to affect data reliability. This preliminary study aimed to determine whether the placement of a multi-sensor device (WIMU PROTM) could affect the heart rate signal reception (GARMINTM chest strap) and, therefore, data accuracy. Thirty-two physical education students (20 men and 12 women) performed 20 min of exercise in a cycle ergometer based on the warm-up of the Function Threshold Power 20 test in laboratory conditions, carrying two WIMU PROTM devices (Back: inter-scapula; Bicycle: bicycle's handlebar-20 cm from the chest) and two GARMINTM chest straps. A one-dimensional statistical parametric mapping test found full agreement between the two situations (inter-scapula vs. bicycle's handlebar). Excellent intra-class correlation values were obtained during the warm-up (ICC = 0.99, [1.00-1.00], p < 0.001), the time trial test (ICC = 0.99, [1.00-1.00], p < 0.001) and the cool-down (ICC = 0.99, [1.00-1.00], p < 0.001). The Bland-Altman plots confirmed the total agreement with a bias value of 0.00 ± 0.1 bpm. The interscapular back placement of the WIMU PROTM device does not affect heart rate measurement accuracy with a GARMINTM chest strap during cycling exercise in laboratory conditions.

Unmanned aerial vehicle location systems. Antenna Arrays

Radars remain the only all–weather location systems, which is especially important in difficult conditions of their use. Antenna array technologies remain critical for the development of dynamic areas of technology and, first of all, UAVs location systems. The development of location systems and antenna arrays for UAVs has been going on for a long time. Radars and antenna arrays installed on medium– and large–class UAVs differ little from airplane and helicopter systems. Among UAVs, the maximum number of UAVs used are UAVs of minimal size, weight and cost. Due to their high maneuverability, minimal visibility and a large number of tasks to be solved. Therefore, radars are subject to minimum size, weight, dimensions and consumption requirements at maximum range. The widespread use of small UAVs has led to the fact that their radars and antenna arrays are on a par with automotive ones, when the possibilities for their placement are significantly limited, even more so than in cars. For the latter, the problem of miniaturization appeared earlier, but not as severely as in UAVs. Antenna arrays are subject to requirements for minimizing dimensions, weight and consumption. Nanotechnology provides this. It's safe to say that the time has come for large–scale solutions to complex problems in antenna systems. Depending on the type of a UAV, it is possible to use a number of methods for constructing antenna arrays: known and proven – linear and fractal; the most modern – metastructures; widely used – tiled; new: flexible and three–dimensional printed; a combination of several methods. Currently, the most attractive areas for the development of antenna arrays for UAVs are: scaling – growing a large number of similar structures to create large apertures; spacing antenna arrays across the surface of the carrier for viewing both forward, sideways and backward, as well as down and up. The development of silicon tiled antenna arrays has led to the realization of very high operating frequencies (90–100 GHz) on the most affordable process technologies (130–180 nm), and the antenna array is fabricated as a chip. The optimal option for constructing antenna arrays is to ensure the reception, conversion and preprocessing of input signals directly in the antenna system in real time, unloading the radar for solving problems that require powerful processing. Post–processing allows you to obtain a more accurate solution to the problem. The combination of pre–processing and post–processing, supported by advanced software and powerful artificial intelligence, expands the capabilities and improves the parameters of the location system. It is important that artificial intelligence ensures the autonomous movement of a UAV, although its use requires large consumption and memory resources. The integrated location system absorbed for the most part the capabilities of a large stationary radar. At the same time, minimum dimensions, weight and consumption are ensured to solve the necessary modern problems. Several radars with their own antenna arrays can be installed on a UAV, which operate in the internal network, complementing each other.

Influence of quadrature transformation imbalance on the noise immunity of signal reception with amplitude-phase shift keying

Objectives. At the present time, amplitude-phase shift keyed (APSK) signals are actively used in satellite communication systems. In particular, they are applied in systems which operate in a limited radio frequency spectrum with increased data transmission quality requirements. Such systems use multi-channel type receivers with maximum likelihood decision on the received symbol (correlation receiver) or quadrature type receivers. The noise immunity of these receivers is directly dependent on the quality of the formation of reference oscillations. These oscillations are reference signals for correlation receivers and in-phase and quadrature components for quadrature receivers. The aim of the work is to analyze the influence of the amplitude and phase parameter spread of the in-phase and quadrature channels on the noise immunity of receiving APSK signals with a circular shape of the signal constellation.Methods. Methods of statistical radio engineering, theory of optimal signal reception, and computer simulation are used.Results. The study established the characteristics of noise immunity of the APSK signal reception depending on the spread of parameters of the quadrature converter. The theoretical calculations were confirmed by the results of modeling the transmission of APSK signals in a Gaussian communication channel. A comparison with systems using quadrature amplitude modulation (QAM) was carried out, in order to assess system stability in the presence of spread parameters among other similar systems.Conclusions. The studies enabled us to conclude that an imbalance of the quadrature reference oscillations can lead to a significant decrease in the noise immunity of radio systems using APSK signals. The minimum energy loss due to imbalance of quadrature reference oscillations is achieved when the imbalance value is less than 10% in amplitude and 2°–3° in phase. The amplitude imbalance of quadrature reference oscillations when receiving QAM signals is more pronounced than in the case of APSK signals. The phase imbalance affects approximately the same.

Feasibility of Passive Sounding of Uranian Moons Using Uranian Kilometric Radiation

AbstractWe present a feasibility study for passive sounding of Uranian icy moons using Uranian Kilometric Radio (UKR) emissions in the 100–900 kHz band. We provide a summary description of the observation geometry, the UKR characteristics, and estimate the sensitivity for an instrument analogous to the Cassini Radio Plasma Wave Science (RPWS) but with a modified receiver digitizer and signal processing chain. We show that the concept has the potential to directly and unambiguously detect cold oceans within Uranian satellites and provide strong constraints on the interior structure in the presence of warm or no oceans. As part of a geophysical payload, the concept could therefore have a key role in the detection of oceans within the Uranian satellites. The main limitation of the concept is coherence losses attributed to the extended source size of the UKR and dependence on the illumination geometry. These factors represent constraints on the tour design of a future Uranus mission in terms of flyby altitudes and encounter timing.

MiR-6881-3p contributes to diminished ovarian reserve by regulating granulosa cell apoptosis by targeting SMAD4

BackgroundIn our previous investigation, we revealed a significant increase in the expression of microRNA-6881-3p (miR-6881-3p) in follicular fluid granulosa cells (GCs) from women with diminished ovarian reserve (DOR) compared to those with normal ovarian reserve (NOR). However, the role of miR-6881-3p in the development of DOR remains poorly understood.ObjectiveThis study aimed to elucidate the involvement of miR-6881-3p in the regulation of granulosa cells (GCs) function and the pathogenesis of DOR.Materials and methodsInitially, we assessed the expression levels of miR-6881-3p in GCs obtained from human follicular fluid in both NOR and DOR cases and explored the correlation between miR-6881-3p expression and clinical outcomes in assisted reproduction technology (ART). Bioinformatic predictions and dual-luciferase reporter assays were employed to identify the target gene of miR-6881-3p. Manipulation of miR-6881-3p expression was achieved through the transfection of KGN cells with miR-6881-3p mimics, inhibitor, and miRNA negative control (NC). Following transfection, we assessed granulosa cell apoptosis and cell cycle progression via flow cytometry and quantified target gene expression through quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot (WB) analysis. Finally, we examined the correlation between target gene expression levels in GCs from NOR and DOR patients and their association with ART outcomes.ResultsOur findings revealed elevated miR-6881-3p levels in GCs from DOR patients, which negatively correlated with ovarian reserve function and ART outcomes. We identified a direct binding interaction between miR-6881-3p and the 3’-untranslated region of the SMAD4. Transfection with miR-6881-3p mimics induced apoptosis in KGN cell. Furthermore, miR-6881-3p expression negatively correlated with both mRNA and protein levels of the SMAD4. The mRNA and protein levels of SMAD4 were notably reduced in GCs from DOR patients, and SMAD4 mRNA expression positively correlated with ART outcomes. In addition, the mRNA levels of FSHR, CYP11A1 were notably reduced after transfection with miR-6881-3p mimics in KGN cell, while LHCGR notably increased. The mRNA and protein levels of FSHR, CYP11A1 were notably reduced in GCs from DOR patients, while LHCGR notably increased.ConclusionThis study underscores the role of miR-6881-3p in directly targeting SMAD4 mRNA, subsequently diminishing granulosa cell viability and promoting apoptosis, and may affect steroid hormone regulation and gonadotropin signal reception in GCs. These findings contribute to our understanding of the pathogenesis of DOR.

A Borehole Acoustic Calculation Approach with Gas Hydrate Saturation Inversion in Gas Hydrate-Bearing Sediments

The inversion of gas hydrate saturation is a critical procedure in the evaluation of hydrate reservoirs. In this paper, a theoretical model for a borehole acoustic wavefield excited by multipole sources is established for the first time. On this basis, the attenuation of the dipole flexural waves is obtained, and in combination with the results of sensitivity analysis, an approach for inverting natural gas hydrates using the attenuation characteristics of the dipole flexural wave is proposed. The results of the sensitivity analysis demonstrate that the attenuation of the dipole flexural wave is sensitive to gas hydrate saturation. Numerical results derived from synthetic logging data are provided to illustrate the viability of the inversion of gas hydrate saturation. Even when significant noise is introduced into the receiver signal arrays, the inversion method remains stable and accurately assesses gas hydrate saturation. The correctness and effectiveness of the proposed approach are substantiated through the processing of numerical simulation data. This work provides a potent processing approach for evaluating reservoir hydrate saturation utilizing acoustic well-logging information.

Effectiveness of Modes of Radio Broadcasting in Gain and Retention of Knowledge About Child Care Message

Abstract: India is dominantly a country of villages. There is a great necessity for transmitting latest scientific knowledge about agriculture and related fields among the farming communities. Today we have many problems- high rate of illiteracy, accelerating population growth which eats into any gain that educational expansion may bring, increasing pressures on admissions at all stages, explosion in knowledge necessitating change and review of curricula and teaching method, urban – rural imbalance, wastage in education need for raising standards and the criterion of an environment favourable to social change and capable of softening its harsher incidences. The mass media are supremly adapted to adult education. Radio is the transmission and reception of signals by means of electric waves without the use of connection wires. Therefore, this study was undertaken with a view to find out relative effectiveness of three mode of presentation

On the imaging depth limit of photoacoustic tomography in the visible and first near-infrared windows.

It is well known that photoacoustic tomography (PAT) can circumvent the photon scattering problem in optical imaging and achieve high-contrast and high-resolution imaging at centimeter depths. However, after two decades of development, the long-standing question of the imaging depth limit of PAT in biological tissues remains unclear. Here we propose a numerical framework for evaluating the imaging depth limit of PAT in the visible and the first near-infrared windows. The established framework simulates the physical process of PAT and consists of seven modules, including tissue modelling, photon transportation, photon to ultrasound conversion, sound field propagation, signal reception, image reconstruction, and imaging depth evaluation. The framework can simulate the imaging depth limits in general tissues, such as the human breast, the human abdomen-liver tissues, and the rodent whole body and provide accurate evaluation results. The study elucidates the fundamental imaging depth limit of PAT in biological tissues and can provide useful guidance for practical experiments.

Damage Monitoring and Localization Imaging of Aluminum Alloy Thin-Walled Structure Based on Remote Bonding Fiber Bragg Gratings Sensing.

In this paper, the damage monitoring investigation based on the remote bonding fiber Bragg grating sensing is performed on the aerospace aluminum alloy thin-walled structure with prefabricated damage. Firstly, an ultrasonic excitation-fiber Bragg gratings (UE-FBGs) sensing experimental platform is established for the simulation of defects monitoring, in which the sensors are placed at a certain distance from the bonding area. Secondly, different arrangements of exciters and receivers are utilized for the original signals and the damage signals. Subsequently, the raw signals are processed by filter and feature extraction in order to denoise the signals and acquire the parameters sensitive to the damage. Finally, an improved Reconstruction for Image Defects (RAPID) algorithm is used to locate and reconstruct the pre-existing damage. The results show that the proposed system improves the sensitivity of the FBG receiver signal and the accuracy of the damage imaging.