Digital Spectrum Research Articles

A TDLAS gas detection method based on digital signal modulation

This research presents a novel TDLAS gas concentration detection method based on digital modulation. The method inherits the advantage of a simple system structure from Direct Absorption Spectroscopy, as well as the excellent sensitivity of Wavelength Modulation Spectroscopy. A low-frequency sawtooth wave is employed to drive the laser, resulting in a digital direct absorption spectrum signal. By constructing a cosine modulation sequence in the time domain and performing linear interpolation on the direct absorption spectrum, it successfully converts to a wavelength-modulated absorption spectrum and simultaneously generates a digital reference signal at double the frequency. Ultimately, phase-locked amplification technology can be used to calculate the amplitude of the second harmonic. Since both the modulation and reference signals are generated digitally, they ensure a strict frequency-doubling relationship and phase correlation, which not only reduces the complexity of the hardware system but also effectively minimizes system errors. Because digital technology generates both the modulation and reference signals, it ensures that they have the same phase and a strict frequency-doubling relationship. Experimental results demonstrate that, when fitted by a cubic polynomial, the second harmonic amplitude and the gas concentration have a correlation coefficient (R2) as high as 0.99999 and a root mean square error as low as 0.0011. This proves the method's great accuracy and reliability in practical applications.

A Framework for the Analysis of Personal Learning Networks

This paper reports on research undertaken to map and analyse Personal Learning Networks (PLNs). PLNs are the total preferred connections to the different people, technological devices, services, and information resources an individual uses for learning activities and learning goals in all learning contexts. Drawing from Education, Web Science, Digital Sociology and Network Science, a Framework was developed which conceptualises PLNs as egocentric interaction networks involving a mode, purpose and endpoint. The Framework introduces the idea of measuring the frequency of interaction along paths consisting of pre-determined, generalised nodes (and node sets). This eliminate network differences at the micro level and allows meaningful comparison and aggregation of individual PLNs into groups or whole samples. Quantitative survey data was collected as part of a FutureLearn MOOC and in real-time converted by a bespoke mapping and visualisation tool into an online PLN map. Analysis indicates that regardless of any contextual factors, individuals interact nearly three quarters of the time via digital devices, and just a quarter of the time face-to-face or non-digitally. One third of those interactions are with smartphones, most often for the purpose of gathering information from web searches. Individuals also interact more frequently with non-humans than they do with humans. Chi-square significance testing to examine the effect of a range of external shaping factors found that the PLNs of apparently diverse groups display a considerable homogeneity. Gender, country of residence and position on the Digital Resident-Digital Visitor spectrum have no effect on the size and use of a PLN. Age and being a UK HE student have the most effect. There may also be evidence of a Network Lifecycle, with a critical period of PLN growth occurring during the age of 18-25. This means that universities are ideally placed, indeed may even have a duty of care, to foster PLN development in educationally and personally productive ways. If HE institutions are to respond to the networked student, living, working and learning in a network age, then no longer can the learner be considered separately from the network of people, devices, services and information resources they use for daily life. Transitioning towards a PLN-centred, networked learning HE pedagogy and learning design may arguably be the most suitable response to a study body which is increasingly and inextricably embedded in a sociotechnical reality.

High-resolution wide-swath SAR imaging with multifrequency pulse diversity mode in azimuth multichannel system

ABSTRACT High-resolution wide-swath (HRWS) imaging has emerged as a focal point in synthetic aperture radar (SAR) research. However, conventional SAR systems face challenges in achieving both high azimuth resolution and wide swath simultaneously due to the minimum antenna area constraint. In this paper, we propose a HRWS imaging method based on multifrequency pulse diversity (MFPD) and azimuth multichannel (AMC) technique, capable of resolving range and Doppler ambiguities concurrently. In MFPD mode, range ambiguous echoes can be separated by matched filters in the range frequency domain, as multifrequency pulses are transmitted by a single channel in the transmitter. To further enhance the ambiguity resolution ability of the system and address azimuth incoherence, a novel scheme applying the MFPD to AMC system is proposed, categorized into two distinct scenarios. 1) Uniform Sampling: This scenario satisfies the displaced phase centre antenna condition. Under this condition, high range resolution imaging can be achieved through spectrum splicing in range frequency domain, simultaneously resolving Doppler ambiguity. 2) Non-uniform Sampling: In this scenario, the ambiguous echoes are processed by spatial digital beamforming and spectrum splicing in two-dimensional frequency domain. Finally, the HRWS imaging can be obtained by performing the traditional SAR algorithm. Furthermore, the proposed method can synthesize a wideband signal from multifrequency signals, thereby enhancing the feasibility of super-high-resolution imaging. Simulation results demonstrate the effectiveness of the proposed method.

Data acquisition system for a newly-built hard x-ray/soft gamma-ray spectrometer imaging system on experimental advanced superconducting tokamak

A portable hard X-ray and soft gamma-ray spectrometer imaging system (HXS) has been constructed to gather physical information about fast electrons confined in the Experimental Advanced Superconducting Tokamak (EAST). The system is installed on the low field side of the mid-plane and provides a viewing field tangential to the toroidal field. The system utilizes a two-dimensional Cadmium Zinc Telluride (CdZnTe) semiconductor detector with 128 channels, and a data acquisition (DAQ) system has been designed for it. The DAQ system features a highly integrated signal processing system with the capability of high-speed processing and digital transmission of signals from 128 channels. In addition, a related DAQ software has been developed using a modular design approach, facilitating tasks such as data reception, storage, and preliminary processing. HXS, which has been applied during the recent EAST campaign, directly obtains the digital energy spectrum of incident photons. The DAQ system is described in detail in this paper. The hardware components and energy calibration have also been described. Experimental data have been successfully obtained and briefly discussed. More physical research will be reported in future publications.

Digital Spectrum Twins for Enhanced Spectrum Sharing and Other Radio Applications

Digital Spectrum Twins for Enhanced Spectrum Sharing and Other Radio Applications

The use and effective analysis of vocal spectrum analysis method in vocal music teaching

Abstract As computer science and technology continue to evolve and become more pervasive, their application in analyzing the audio spectrum of vocalizations offers valuable insights for vocal music education. This study introduces a method utilizing Fourier transform analysis to examine time-frequency domain signals in vocal teaching. Initially, voice frequencies are collected during vocal music instruction. Subsequently, these frequencies are processed to extract characteristic sequences, which are then reduced in scale to develop a model for voice spectrum recognition tailored to vocal music education. This model facilitates detailed spectral analysis, enabling the investigation of its auxiliary benefits in vocal music teaching, particularly in identifying prevalent instructional challenges. Our findings indicate that during training on vowels “a” and “i,” professional singers’ pitch at 4kHz declined to between −15 and −18 dB, whereas students’ pitch varied around ±6dB, trending upwards. In cases of air leakage, significant gaps were observed at frequencies of 5500Hz, 10500Hz, and 14500Hz. At the same time, students exhibited missing frequencies at 7kHz, 12kHz, and 14kHz during glottal tone production, with pronounced, abrupt peaks occurring when vocal folds were tightly constricted and devoid of excessive links. This research substantiates the theoretical and practical benefits of digital spectrum technology in enhancing vocal music education, thereby providing a scientific and supportive role.

A revised digital media–arena framework guiding strategic communication in digital environments

PurposeThis paper refines the Digital Media–Arena (DMA) framework to address the diversity of stakeholders contributing to the production, (re)appropriation and (re)distribution of organisational messages in digital environments. It also presents a case analysis for the purpose of demonstrating the applicability of the revised conceptual framework to a critical situation.Design/methodology/approachGrounded in key public relations, corporate communication and strategic communication research, this study first extends the DMA framework by introducing six new forms of media-arenas. Next, the study takes a public sector perspective to analyse the revised framework against a critical situation involving the Finnish prime minister in summer 2022.FindingsThe application of the revised DMA framework to analyse the critical situation shows the importance of mapping and understanding diverse discourses across multi-arenas and their communication role in a rapidly unfolding scandal surrounding the prime minister of Finland. Findings also reveal the diversity of stakeholder voices forming their own versions of organisational messages and sometimes converging organisational messages within and across DMAs.Practical implicationsThe DMA framework can offer practical suggestions to guide communicators to make strategic choices in what, where, how and with whom they can communicate.Originality/valueThe revised DMA framework contributes expanding the field's knowledge of the strategic communicative use of the digital environment in typically highly volatile and multi-vocal situations by offering instrumental understanding of the conflicting challenge between subjugating and liberating organisational messages across the digital spectrum.

Hybrid digital-analog FSO fronthaul system with channel-adaptive insertion of analog bandwidth.

With the arrival of the 5th generation mobile network, the number of user devices is increasing exponentially, and thus it is necessary to expand the capacity of transmission systems. In order to further improve the system spectral efficiency on the basis of existing mobile fronthaul devices, we propose a hybrid digital-analog fronthaul transmission system with adaptive insertion of analog bandwidth, which can dynamically change the position of inserted analog bandwidth based on the state information of free space optical (FSO) channel. We consider the effects of atmospheric attenuation and turbulence on the FSO channel and derive an analytical expression for the maximum analog signal bandwidth that can be inserted into the first null of the digital signal spectrum to meet BER requirement of 3.8 × 10-3. Through a comprehensive simulation, it is verified that the analog bandwidth is obtained by this expression can exactly represent the lower bound of the simulation results under weak turbulence condition. The obtained results show that the maximum insertable analog bandwidth beyond the spectral null of the digital signal can reach 10% of the digital signal bandwidth, even in the FSO link with a transmission distance of 0.5 km and attenuation factor of 8 dB/km.

Digital Advocacy for Punitive Justice and Vigilantism: Analyzing Citizen Dissatisfaction with the Klitih Prevention Policy

This study aims to investigate how the digital advocacy process in responding to the Klitih occurrence in Yogyakarta, Indonesia, was executed in expressing public dissatisfaction on social media (particularly Twitter), who are the actors, and how it will contribute to future social problem resolution. This study seeks the public response on Twitter regarding the Klitih accident that occurred in early April 2022 in Yogyakarta, Indonesia, by using the Twitter API executed in Python programming language. The analysis tools use qualitative content analysis through statistical analysis, sentiment analysis, emotional classification analysis, and social network analysis. We found that collective public responses on Twitter have successfully formed digital communities. This study observes two advocacy fibers; vigilantism and punitive law enforcement. Massive negative sentiments, colossal anger, and fear over how the Klitih issues are being resolved have a dissatisfaction impact through advocacy. The study's findings contended that the next step for digital advocacy lies in the presence of popular government opinion leaders in welcoming the advocacy and how strategies may be advanced by the dissatisfied party in lifting the advocacy to a greater stage. Future scholars can broaden it by applying the same methodology to the non- digital advocacy spectrum

Digital Residual Spectrum-Based Generalized Soft Failure Detection and Identification in Optical Networks

Machine learning is regarded as an attractive solution for soft failure management in optical networks; however, the performance of trained models working on unseen data is of growing concern, due to scarce historical data and high training costs. Hence, the issues of reducing training data and improving generalization have received considerable attention. In this paper, a soft failure detection (SFD) and identification scheme is proposed based on digital residual spectrum that leverages auto-encoder (AE) and support vector machine. The digital residual spectrum acquired by the coherent receiver is computed by subtracting the averaged spectrum of multiple normal digital spectra from the digital spectrum. The scheme features: (i) high generalization, i.e., a model trained for a specific transmission setup performs well in other setups with different fiber lengths; (ii) low cost, i.e., the digital residual spectrum is easily obtained from a coherent receiver without additional hardware; and (iii) easy training, i.e., only normal samples are needed to train the SFD model (less pressure on the collection of rare soft-failure data). Using the model trained for any specific setup, we demonstrated an area under the curve and identification accuracy above 99.24% and 96.45%, respectively, for five experimental setups.

Dissent Art in the Digital Age: Insights into the Culture of Artivism on Instagram in India

The introduction of the Citizenship Amendment Act (CAA) in 2019 marked a discernible change in the landscape of online protest art. As protests against the act gathered momentum, a surge in the art endorsing the movement dominated Indian social media and increased during the COVID-19 pandemic. This wave was propelled by a cohort of “artivists” with social and cultural influence who were positioned favorably on the digital spectrum. They used platforms such as Instagram to craft and share protest art, leveraging social media to express their dissent. The intensification of the online protests subsequently led to instances of individual and organized abuse directed at the artists, including mob attacks and threats of First Information Reports. This paper explores this phenomenon through extensive interactions with online “artivists” in India in order to understand the cultural shift and emphasize the similarities and differences between virtual dissent art and traditional forms of art activism. Adopting a qualitative methodology that combines digital ethnography and semi-structured interviews, the author—who also found her artistic voice amidst this movement—seeks to capture the artists’ approaches and subjectivity. The paper further delves into the limitations and constraints posed by social media platforms, addressing the issue of online harassment faced by artivists on Instagram. Lastly, it engages in a discourse on how social media commodifies dissent within the landscape of digital capitalism.

Mobile and online consumer tools to screen for autism do not promote equity.

Many parents wonder if their child might have autism. Many parents use their smartphones to answer health questions. We asked, "How easy or hard is it for parents to use their smartphones to find 'tools' to test their child for signs of autism?" After doing pretend parent searches, we found that only one in 10 search results were tools to test children for autism. These tools were not designed for parents who have low income or other challenges such as low literacy skills, low English proficiency, or not being tech-savvy.

Compact automatic modulation recognition using over-the-air signals and FOS features

The recent deployment of automatic modulation recognition (AMR) for cognitive radio (CR) systems has significantly enhanced spectrum sensing capabilities. The utilization of real-time over-the-air digital radio frequency (RF) data for the development of a digital spectrum sensing model based on the automatic modulation classification (AMC) is presented in this study as a step for incorporating opportunistic spectrum sensing onto the NomadicBTS architecture. Some digital modulation techniques were studied for second-generation (2G) through fourth-generation (4G) technology. The raw RF signal dataset was digitized and curated, while non-complex first-order statistical (FOS) features were used with algorithms based on the Scaled conjugate gradient (SCG) and Levenberg-Marquardt (LM) to find the best learning algorithm for the generated AMR model. The results show that the developed AMR model has a very high likelihood of correctly classifying signals, with distinct patterns for each of the features of FOS. The results are compared to reveal a least mean square error (MSE) of 0.0131 with a maximum accuracy of 93.5 percent when the model was trained with seventy (70) neurons in the hidden layer using the LM method. The best model's accuracy will allow for the most precise identification of spectrum holes in the bands under consideration.

The influence of regions of interest on tractography virtual dissection protocols: general principles to learn and to follow.

Efficient communication across fields of research is challenging, especially when they are at opposite ends of the physical and digital spectrum. Neuroanatomy and neuroimaging may seem close to each other. When neuroimaging studies try to isolate structures of interest, according to a specific anatomical definition, a variety of challenges emerge. It is a non-trivial task to convert the neuroanatomical knowledge to instructions and rules to be executed in neuroimaging software. In the process called "virtual dissection" used to isolate coherent white matter structure in tractography, each white matter pathway has its own set of landmarks (regions of interest) used as inclusion and exclusion criteria. The ability to segment and study these pathways is critical for scientific progress, yet, variability may depend on region placement, and be influenced by the person positioning the region (i.e., a rater). When raters' variability is taken into account, the impact made by each region of interest becomes even more difficult to interpret. A delicate balance between anatomical validity, impact on the virtual dissection and raters' reproducibility emerge. In this work, we investigate this balance by leveraging manual delineation data of a group of raters from a previous study to quantify which set of landmarks and criteria contribute most to variability in virtual dissection. To supplement our analysis, the variability of each pathway with a region-by-region exploration was performed. We present a detailed exploration and description of each region, the causes of variability and its impacts. Finally, we provide a brief overview of the lessons learned from our previous virtual dissection projects and propose recommendations for future virtual dissection protocols as well as perspectives to reach better community agreement when it comes to anatomical definitions of white matter pathways.

Spatial distribution of frequency modulated signals in Uyo, Nigeria

The kernel of this study is to x-ray the extent of radio coverage of two Frequency Modulated (FM) radio stations (AKBC 90.5MHz and Passion FM 94.5MHz), both located in Uyo, Nigeria. Measurement of signal strengths were carried out across 14 locations using a digital spectrum analyzer. A GPS app was used to take measurements of distance, elevation, longitude and latitude. The collected data was analyzed in the form of scattered plot, contour plots, bar charts, graphs and correlation analysis. For AKBC, good reception was received by users at locations N, C, L, and F. For Passion FM, excellent reception was obtained at locations N, F, A and B. For both stations under investigation, location N had the best reception while location E had poor reception. To establish the effects of Line of Sight (LOS) distance on signal strength, correlation values of – 0.84 and - 0.67 were obtained for AKBC and Passion FM. For signal strength against elevation, 0.71 and 0.55 were the correlation values obtained for AKBC and Passion FM. This shows that an increase in distance from the transmitting antenna led to a decrease in reception while an increase in elevation led to an increase in reception. Existing and intending radio stations in Uyo, are advised to increase the height of their transmitter and transmitting power for better reception and coverage.

Indicative findings from a study of information behaviour in digital business ideation: insights from the developing world

nt="Indicative findings from a study of information behaviour in digital business ideationr" /> <meta name="description" content="Though a wealth of information behaviour research has been undertaken in various contexts over the years, less has been done on entrepreneurship. In particular, there is a lack of literature around the ideation component in the early stages of business formation. This study seeks to address the theoretical and empirical gap within this research stream, bringing together information, innovation, and creativity theory, as lenses through which to explore the phenomenon. Twelve semi-structured interviews were conducted with business founders. Participants operated in a variety of segments of the digital technology spectrum. Critical Realism and Grounded Theory were used as theoretical and practical data techniques, using abduction in the theoretical redescription of concepts (codes) identified in the empirical data, and retroduction to identify the necessary contextual conditions for a particular causal mechanism to take effect and result in the observed empirical trends. Indicative results show several societal and personal factors play a role in shaping the information behaviour of digital entrepreneurs. These factors include but are not limited to poverty, parenting, and unequal power between mentors and mentees. While this research project is ongoing, early findings emerge in previously unexplored aspects of information behaviour such as the importance of reading passion and early exposure to digital devices amongst digital entrepreneurs.

Design of a digital tunable stellar spectrum calibration source based on a digital micromirror device

A design method of spectral tunable radiation source with supercontinuum laser as the radiation source and digital micro-mirror device (DMD) as the spectral modulation device is proposed. Adopt the design idea of reducing the relative aperture of the spectral imaging system to improve the imaging quality, use cylindrical collimating beam expanding system to replace the collimating objective in the traditional spectral imaging system, and the relative aperture of the system is reduced in the dispersion direction. According to the test results, in narrow-band mode, the maximum full width at half maximum (FWHM) of monochromatic light bandwidth in the spectrum range of 450–1000 nm is 3.86 nm. In the broad-band mode, four typical stellar color temperature of T = 2600 K, 3500 K, 7000 K, 11,000 K are simulated, and the simulation results show that the accuracy of the star spectrum is better than 3.1% at 2600 K, 4.2% at 3500 K, 2.8% at 7000 K and 5.1% at 11,000 K.

Unified description of compressive modulus revealing multiscale mechanics of living cells

How to accurately characterize the modulus of living cells at the whole-cell level with a well-defined measurement geometry and precise mathematical modeling of viscoelastic relaxation is an ongoing challenge in biophysics and mechanobiology. Here, we report combined atomic-force-microscopy (AFM) measurements of stress relaxation and indentation force for 10 cell types ranging from epithelial, muscle, and neuronal cells to blood and stem cells, from which we obtain a unified quantitative description of the compressive modulus $E(t)$ of individual living cells. The cell modulus $E(t)$ is found to have an initial exponential decay at short times $t$ followed by a long-time power-law decay together with a persistent modulus. The three components of $E(t)$ at different timescales thus provide a digital spectrum of mechanical readouts that are closely linked to the hierarchical structure and active stress of living cells. This work provides a reliable experimental framework that can be utilized to characterize the mechanical state of living cells and investigate their physiological functions and diseased states.

МІЖЗОРЯНЕ СЕРЕДОВИЩЕ ТА ДЕКАМЕТРОВА РАДІОСПЕКТРОСКОПІЯ

Purpose: The analytical review of the main results of research in the new direction of the low-frequency radio astronomy, the interstellar medium radio spectroscopy at decameter waves, which had led to astrophysical discovery, recording of the radio recombination lines in absorption for highly excited states of interstellar carbon atoms (more than 600). Design/methodology/approach: The UTR-2 world-largest broadband radio telescope of decameter waves optimally connected with the digital correlation spectrum analyzers has been used. Continuous modernization of antenna system and devices allowed increasing the analysis band from 100 kHzto 24 MHz and a number of channels from 32 to 8192. The radio telescope and receiving equipment with appropriate software allowed to have a long efficient integration time enough for a large line series simultaneously with high resolution, noise immunity and relative sensitivity. Findings: A new type of interstellar spectral lines has been discovered and studied, the interstellar carbon radio recombination lines in absorption for the record high excited atoms with principal quantum numbers greater than 1000. The line parameters (intensity, shape, width, radial velocity) and their relation ship with the interstellar medium physical parameters have been determined. The temperature of line forming regions is about 100 K, the electron concentration up to 0.1 cm–3 and the size of a line forming region is about 10 pc. For the first time, radio recombination lines were observed in absorption. They have significant broadening and are amplified by the dielectronic-like recombination mechanism and are also the lowest frequency lines in atomic spectroscopy. Conclusions: The detected low-frequency carbon radio recombination lines and their observations have become a new highly effective tool for the cold partially ionized interstellar plasma diagnostics. Using them allows obtaining the information which is not available with the other astrophysical methods. For almost half a century of their research, a large amount of hardware-methodical and astrophysical results have been obtained including a record number of Galaxy objects, where there levant lines have been recorded. The domestic achievements have stimulated many theoretical and experimental studies in other countries, but the scientific achievements of Ukrainian scientists prove the best prospects for further development of this very important area of astronomical science. Key words: low-frequency radio astronomy; radio telescope; interstellar medium; radio recombination lines; carbon; hydrogen; spectral analyzer

Some advantages of non-binary Galois fields for digital signal processing

It is shown that the convenient processing facilities of digital signals that varying in a finite range of amplitudes are non-binary Galois fields, the numbers of which elements are equal to prime numbers. Within choosing a sampling interval which corresponding to such a Galois field, it becomes possible to construct a Galois field Fourier transform, a distinctive feature of which is the exact correspondence with the ranges of variation of the amplitudes of the original signal and its digital spectrum. This favorably distinguishes the Galois Field Fourier Transform of the proposed type from the spectra, which calculated using, for example, the Walsh basis. It is also shown, that Galois Field Fourier Transforms of the proposed type have the same properties as the Fourier transform associated with the expansion in terms of the basis of harmonic functions. In particular, an analogue of the classical correlation, which connected the signal spectrum and its derivative, was obtained. On this basis proved, that the using of the proposed type of Galois fields makes it possible to develop a complete analogue of the transfer function apparatus, but only for signals presented in digital form.