Two-way multiple relays channel: achievable rate region and optimal resources

This paper considers a communication model containing two users that exchange their information with the help of multiple parallel relay nodes. To avoid interference at these common nodes, two users are required to transmit over the different frequency bands. Based on this scenario, the achievable rate region is initially derived. Next, an optimization scheme is described to choose the best relays that can be used by each user. Then, two power allocation optimization schemes are investigated to allocate the proper average power value to each node. Finally, comparisons between these two optimization schemes are carried out through some numerical examples

Capacity of Gaussian Relay Channel with Orthogonal Components and Non-causal Interference at the Source

In this work, we consider a relay channel model, with an out-of-band relay, in which the interference signal is available non-causally only at the source. The case in which the relay operates over different frequency bands with respect to the direct link is investigated. In particular, the source-destination (S-D), the source-relay (S-R) and the relay-destination (R-D) links are designed to be pairwise orthogonal. This may model a communication scenario in which the direct link (S-D) is parallel to the multihop channel (S-R-D). For this channel model, we establish the capacity of the Gaussian relay channel by showing that the developed upper and lower bounds are equal. In particular, the capacity results are obtained in which the relay may operate in either a full-duplex mode or a half-duplex mode. Keywords: Relay Channel, Decode and Forward, Orthogonal Transmission Bands, Gaussian Channel

RFID-Based Inventory and Security System

During the last decades, the technology of Radio Frequency Identification (hereafter RFID) has been widely used for practical functions in different disciples including; air industry, military, library services, health services, sports, security and many other fields. Within the industry, RFID has been utilized for various functions such as: storing security, personnel and vehicle access/tracking, production and inventory tracking, bagging, delivery and logistics. In this research, a prototype of inventory and security system for the devices and equipment in university labs is implemented. The system uses RFID technology, which is a form of wireless communication that is used to identify tagged objects by a reader. Both hardware and software implementation of the system are described in this paper. Keywords: RFID, Inventory system, RFID Implementation

Few-mode optical fiber surface plasmon resonance sensor with controllable range of measured refractive index

A few-mode optical fiber surface plasmon resonance sensor with graphene layer is investigated, firstly, with the aim of studying the behavior of the guided modes and, secondly, with the aim of determining the range of the measured refractive index for some selected few-mode fibers. The results show that as the number of modes propagated in the fiber increases, the maximum sensitivity of a particular mode decreases while the range of the measured refractive index of that mode increases. Also, it is shown that the range can be easily tuned with sensitivity consideration by only adjusting the operating wavelength without any modification of the sensor, which is desirable from practical point of view. In addition, it is shown that the core diameter of the fiber should be chosen according to sensitivity and range needing, where a compromise between them must be found. The study presented in this paper can significantly help in developing new sensing techniques, such as multi-parameter sensing, by monitoring the various responses of the modes. Also, it can be used to customize the sensor for specific sensing applications in various fields, especially to measure refractive indices in subranges of 1.38 to 1.46

On Optimal Power Allocation for Gaussian Broadcast Channel

We derive the optimal power allocation for Gaussian two users broadcast channel. To find the optimal power allocation between the two users, two optimization schemes are considered. In each optimization scheme, an analytical expression for the optimal power allocation between the two users is derived. The first optimization criterion finds the optimal power allocation between the two users such that they have equal rates. Then, the optimal power allocation that maximizes the sum rate capacity is studied. In addition, numerical examples are provided to verify the optimality of the derived schemes. Keywords: Gaussian Broadcast Channel, Capacity Region, Optimization

Burnout among surgeons before and during the SARS-CoV-2 pandemic: an international survey

Background: SARS-CoV-2 pandemic has had many significant impacts within the surgical realm, and surgeons have been obligated to reconsider almost every aspect of daily clinical practice. Methods: This is a cross-sectional study reported in compliance with the CHERRIES guidelines and conducted through an online platform from June 14th to July 15th, 2020. The primary outcome was the burden of burnout during the pandemic indicated by the validated Shirom-Melamed Burnout Measure. Results: Nine hundred fifty-four surgeons completed the survey. The median length of practice was 10 years; 78.2% included were male with a median age of 37 years old, 39.5% were consultants, 68.9% were general surgeons, and 55.7% were affiliated with an academic institution. Overall, there was a significant increase in the mean burnout score during the pandemic; longer years of practice and older age were significantly associated with less burnout. There were significant reductions in the median number of outpatient visits, operated cases, on-call hours, emergency visits, and research work, so, 48.2% of respondents felt that the training resources were insufficient. The majority (81.3%) of respondents reported that their hospitals were included in the management of COVID-19, 66.5% felt their roles had been minimized; 41% were asked to assist in non-surgical medical practices, and 37.6% of respondents were included in COVID-19 management. Conclusions: There was a significant burnout among trainees. Almost all aspects of clinical and research activities were affected with a significant reduction in the volume of research, outpatient clinic visits, surgical procedures, on-call hours, and emergency cases hindering the training. Trial registration: The study was registered on clicaltrials.gov "NCT04433286" on 16/06/2020

Vliv ohybu na rozložení intenzity světla v málovidovém optickém vlákně

Prezenční výpůjčkaVŠB - Technická univerzita Ostrava. Fakulta elektrotechniky a informatiky. Katedra (454) elektroniky a telekomunikační technik

Studium vlivu periodických ohybů na přenos signálu optickým vláknem

Import 20/04/2006Prezenční výpůjčkaVŠB - Technická univerzita Ostrava. Fakulta elektrotechniky a informatiky. Katedra (454) elektroniky a telekomunikační technik

Lightning protection for power transformers of Aqaba Thermal Power Station

In this paper, a study of the lightning phenomenon and its harmful effect on Aqaba Thermal Power Station (ATPS), located in the south-western border of Jordan, is presented using the Electromagnetic Transients Program – Alternative Transients Program (EMTPATP). This study has been arisen due to an installation need of appropriate lightning arresters (LAs) for the 15/410 kV step-up transformers of the ATPS to eliminate the destructive effect of lightning. The simulation is carried out for two cases, once without using LAs and once more with using them. Two scenarios are applied for each of these cases, once when lightning strikes the primary side of the transformer and once more when it strikes the secondary side. The results obtained by the simulation indicate the necessity of LAs installation. This study, with using the EMTP-ATP program, is done for the first time with additional details that help researchers, designers, and engineers to get a broad overview of the ATPS in order to protect it against lightning

Few-mode optical fiber surface plasmon resonance sensor with controllable range of measured refractive index

A few-mode optical fiber surface plasmon resonance sensor with graphene layer is investigated, firstly, with the aim of studying the behavior of the guided modes and, secondly, with the aim of determining the range of the measured refractive index for some selected few-mode fibers. The results show that as the number of modes propagated in the fiber increases, the maximum sensitivity of a particular mode decreases while the range of the measured refractive index of that mode increases. Also, it is shown that the range can be easily tuned with sensitivity consideration by only adjusting the operating wavelength without any modification of the sensor, which is desirable from practical point of view. In addition, it is shown that the core diameter of the fiber should be chosen according to sensitivity and range needing, where a compromise between them must be found. The study presented in this paper can significantly help in developing new sensing techniques, such as multi-parameter sensing, by monitoring the various responses of the modes. Also, it can be used to customize the sensor for specific sensing applications in various fields, especially to measure refractive indices in subranges of 1.38 to 1.46