Mitigation of Side-Effect Modulation in Optical OFDM VLC Systems

Side-effect modulation (SEM) has the potential to be a significant source of interference in future visible light communication (VLC) systems. SEM is a variation in the intensity of the light emitted by a luminaire and is usually a side-effect caused by the power supply used to drive the luminaires. For LED luminaires powered by a switched mode power supply, the SEM can be at much higher frequencies than that emitted by conventional incandescent or fluorescent lighting. It has been shown that the SEM caused by commercially available LED luminaires is often periodic and of low power. In this paper, we investigate the impact of typical forms of SEM on the performance of optical OFDM VLC systems; both ACO-OFDM and DCO-OFDM are considered. Our results show that even low levels of SEM power can significantly degrade the bit-error-rate performance. To solve this problem, an SEM mitigation scheme is described. The mitigation scheme is decision-directed and is based on estimating and subtracting the fundamental component of the SEM from the received signal. We describe two forms of the algorithm; one uses blind estimation while the other uses pilot-assisted estimation based on a training sequence. Decision errors, resulting in decision noise, limit the performance of the blind estimator even when estimation is based on very long signals. However, the pilot system can achieve more accurate estimations, thus better performance. Results are first presented for typical SEM waveforms for the case where the fundamental frequency of the SEM is known. The algorithms are then extended to include a frequency estimation step and the mitigation algorithm is shown also to be effective in this case

Epizootiološko istraživanje slinavke i šapa u Sudanu: stanje nakon dva desetljeća

In order to update information on the situation regarding foot and mouth disease (FMD) in the Sudan, a serosurvey and disease survey were conducted. Recently collected data on FMD in the Sudan showed that FMD is a major constraint to animal production in the country. It presents no threat nor does it cause mild disease in sheep and goats. The disease, with obvious clinical signs, has been detected in cattle only, and is caused by serotype O and SAT 2. Seasonal occurrence of the disease in the cold, dry season has been observed and animal movement seems to play a major role in virus dissemination. A total of 1,069 sera were collected from cattle, sheep, goats, and camel, from seven states in the Sudan, for the detection of antibodies to FMDV. Application of liquid phase blocking (LPB) ELISA revealed that antibodies to four serotypes were present in ruminants; namely O, A, SAT 1 and SAT 2. No antibodies to FMDV were detected in camel sera. The results differed from early reports regarding the prevalence of serotype specifi c antibodies in different species; for instance, in cattle, the antibodies to type A (78.13%) surpassed that of type O (69.39%) and the antibodies to type SAT 2 (44%) surpassed that of type SAT 1 (20.2%). This work elucidates the current epidemiology of FMD in some parts of the Sudan.Radi pružanja informacija o sadašnjem stanju slinavke i šapa u Sudanu provedena su serološka istraživanja te je prikazana njezina pojavnost. Svježe prikupljeni podatci o pojavi slinavke i šapa u Sudanu pokazali su da ona predstavlja veliku prepreku životinjskoj proizvodnji u toj zemlji. U ovaca i koza javlja se kao blaga bolest i ne predstavlja veliku prijetnju, dok se u goveda javlja s očitim kliničkim znakovima, a uzrokovana je serotipovima O i SAT 2. Bolest se javlja sezonski u hladnoj i suhoj sezoni, a promet životinjama ima glavnu ulogu u širenju virusa. Ukupno je bilo prikupljeno 1069 uzoraka seruma goveda, ovaca, koza i deva podrijetlom iz sedam država u Sudanu radi pretrage na prisutnost protutijela za virus slinavke i šapa. Blokirajućim imunonenzimnim testom dokazana su protutijela za četiri serotipa virusa: O, A, SAT 1 i SAT 2. Protutijela za virus slinavke i šapa nisu bila dokazana u uzorcima seruma deva. Rezultati se razlikuju od ranijih izvješća s obzirom na prevalenciju specifi čnih protutijela u različitih vrsta. Npr., specifi čna protutijela za serotip A dokazana su u 78,13% goveda, za serotip O u 69,39%, serotip SAT 2 u 44% te serotip SAT 1 u 20,2% goveda. U radu je prikazano sadašnje epizootiološko stanje slinavke i šapa u nekim dijelovima Sudana

A Model of an E-Learning Web Site for Teaching and Evaluating Online

This research is endeavoring to design an e-learning web site on the internet having the course name as "Object Oriented Programming" (OOP) for the students of level four at Computer Science Department (CSD). This course is to be taught online (through web) and then a programme is to be designed to evaluate students performance electronically while introducing a comparison between online teaching , e-evaluation and traditional methods of evaluation. The research seeks to lay out a futuristic perception that how the future online teaching and e-electronic evaluation should be the matter which highlights the importance of this research