Advances in technology make it easier for users to post content on social media. People can post different types of content in digital environments. Sometimes, they post such content in risky ...situations. Accordingly, this study aims to determine the sociological and psychological reasons why people record dangerous occurrences where they or other people are under risk or threat and post these recordings on social media.
This study aimed to answer five research questions. a) Why do individuals use social media? b) Why do people post on social media? c) What types of posts do people share on social media? d) What are the possible psychological reasons that push people to share such occurrences on social media? e) Why do individuals feel the need to record and share dangerous occurrences while under risk or danger? This study was conducted on the basis of a case study design, and interviews were conducted with two psychiatrists, two specialist clinical psychologists, and two sociologists.
After the interviews, the reasons why individuals use social media platforms and post on the said platforms were laid out. It can be argued that the most prominent reason behind individuals' tendency to post while under risk or threat is isolation and inability to help.
Generalized mutual information (GMI) has been comprehensively studied in multidimensional constellation and probabilistic-shaped (PS) constellation together with different forward error correction ...(FEC) coding schemes. The simulation results confirm that GMI is an efficient and accurate tool to compare their post-FEC performance. In particular for uniformly geometric-shaped constellation, the pre-FEC Q-factor is highly correlated with GMI though the correlation is reduced at lower FEC coding rate. Furthermore, GMI can be used to design optimized constellation together with generalized pairwise optimization algorithm to mitigate the GMI loss in non-Gray-mapped constellation. The GMI-optimized 32QAM (opt32) shows <inline-formula><tex-math notation="LaTeX">\sim</tex-math></inline-formula> 0.5 dB signal-to-noise ratio improvement between 3 and 4 b/s GMI in both simulated and experimental results. Optimized two-dimensional 8 QAM is also designed to show the consistent GMI improvement over multi-dimensional 8 QAM-equivalent formats. In simulations, PS-64 QAM outperforms opt32 when a long sequence block is used in the distribution matcher.
Fiber nonlinearity is one of the major limitations to the achievable capacity in long distance fiber optic transmission systems. Nonlinear impairments are determined by the signal pattern and the ...transmission system parameters. Deterministic algorithms based on approximating the nonlinear Schrodinger equation through digital back propagation, or a single step approach based on perturbation methods have been demonstrated, however, their implementation demands excessive signal processing resources, and accurate knowledge of the transmission system. A completely different approach uses machine learning algorithms to learn from the received data itself to figure out the nonlinear impairment. In this work, a single-step, system agnostic nonlinearity compensation algorithm based on a neural network is proposed to pre-distort symbols at transmitter side to demonstrate ~0.6 dB Q improvement after 2800 km standard single-mode fiber transmission using 32 Gbaud signal. Without prior knowledge of the transmission system, the neural network tensor weights are constructed from training data thanks to the intra-channel cross-phase modulation and intra-channel four-wave mixing triplets used as input features.
Using multimode fibers for long-haul transmission is proposed and demonstrated experimentally. In particular few-mode fibers (FMFs) are demonstrated as a good compromise since they are sufficiently ...resistant to mode coupling compared to standard multimode fibers but they still can have large core diameters compared to single-mode fibers. As a result these fibers can have significantly less nonlinearity and at the same time they can have the same performance as single-mode fibers in terms of dispersion and loss. In the absence of mode coupling it is possible to use these fibers in the single-mode operation where all the data is carried in only one of the spatial modes throughout the fiber. It is shown experimentally that the single-mode operation is achieved simply by splicing single-mode fibers to both ends of a 35-km-long dual-mode fiber at 1310 nm. After 35 km of transmission, no modal dispersion or excess loss was observed. Finally the same fiber is placed in a recirculating loop and 3 WDM channels each carrying 6 Gb/s BPSK data were transmitted through 1050 km of the few-mode fiber without modal dispersion.
A universal post-compensation scheme for fiber impairments in wavelength-division multiplexing (WDM) systems is proposed based on coherent detection and digital signal processing (DSP). Transmission ...of 10 x 10 Gbit/s binary-phase-shift-keying (BPSK) signals at a channel spacing of 20 GHz over 800 km dispersion shifted fiber (DSF) has been demonstrated numerically.
An advanced split-step method is employed for the digital backward-propagation (DBP) method using the coupled nonlinear Schrodinger equations for the compensation of inter-channel nonlinearities. ...Compared to the conventional DBP, cross-phase modulation (XPM) can be efficiently compensated by including the effect of the inter-channel walk-off in the nonlinear step of the split-step method (SSM). While self-phase modulation (SPM) compensation is inefficient in WDM systems, XPM compensation is able to increase the transmission reach by a factor of 2.5 for 16-QAM-modulated signals. The advanced SSM significantly relaxes the step size requirements resulting in a factor of 4 reduction in computational load.
The global COVID-19 outbreak has caused an anxious situation in every part of society and forced many countries to implement distance education programs without even knowing the fundamental ...components involved in the processes and the consequences of their decisions. Likewise, in Turkey, it is still uncertain as to what will be taught, what instructional technologies will be employed, how infrastructural inequalities will be addressed, and how assessment and evaluation activities will be conducted. In this context, the purpose of this study was (a) to examine the experiences and opinions of academics, Distance Education Center managers, students, and parents and (b) offer solutions to emerging issues. In doing so, a qualitative research approach was employed, and the study was designed as a phenomenology. The data were collected from 175 individuals from 20 universities through Google Forms. The second cycle coding methods were employed in the analysis. The results indicated that COVID-19 had mostly psychological effects on individuals, and it affected every level of education at varying degrees. The pandemic reminded us how hopelessly we are dependent on traditional means of instruction by rendering us unable to use them. Since the beginning of the outbreak, many higher education institutions have been trying to implement distance education; however, the quality of instruction is rather questionable. This situation threatens the quality of learning outcomes and if not approached with due diligence, results could be catastrophic. Also, this mandatory transition to distance education has made the difference between the experienced and inexperienced academics more apparent. In light of the results, recommendations were provided for national and international policymakers. As long as the recommendations were implemented, all higher education stakeholders could attain the required knowledge and skills, and, in return, the adverse effects of the COVID-19 pandemic could be alleviated.
A comprehensive treatment of digital backward propagation (DBP) accounting for the vectorial nature of optical transmission is presented. Experimental results show that self-phase and cross-phase ...modulation are the major sources of nonlinear impairments, even for small channel spacings and for transmission in low dispersion fibers. It is verified that compensating only the incoherent nonlinear impairments not only has the advantage of requiring lower computational load but also removes the necessity of using phase-locked carriers for the signal or phase-locked local oscillators. Simulation results show that polarization-mode dispersion has to be taken into account for practical wavelength division multiplexing systems for DBP to work properly. It is found that to compensate interchannel nonlinear impairments, the changes in the polarization states of channels have to be followed at every span.
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