Performance of BPSK subcarrier intensity modulation free-space optical communications using a log-normal atmospheric turbulence model

In this paper, we present simulation results for the bit error rate (BER) performance and the fading penalty of a BPSK - subcarrier intensity modulation (BPSK-SIM) free-space optical (FSO) communication link in a log-normal atmospheric turbulence model. The results obtained are based on the Monte-Carlo simulation. Multiple subcarrier modulation schemes offer increased system throughput and require no knowledge of the channel fading in deciding what symbol has been received. In an atmospheric channel with a fading strength 2 l ? of 0.1 obtaining a BER of 10-6 using a 2-subcarrier system will require a signal-tonoise (SNR) of 23.1 dB. The required SNR increases with the fading strength and at a BER of 10-9 the fading penalty due to the atmospheric turbulence is ~ 41 dB for 9 . 0 2 = l ? . The comparative studies of the OOK and BPSK-SIM schemes showed that for similar electrical SNR, BPSK-SIM offered improved performance across all range of turbulence variance

Free-space optical communication employing subcarrier modulation and spatial diversity in atmospheric turbulence channel

An expression for the bit error rate of a multiple subcarrier intensity-modulated atmospheric optical communication system employing spatial diversity is derived. Spatial diversity is used to mitigate scintillation caused by atmospheric turbulence, which is assumed to obey lognormal distribution. Optimal but complex maximum ratio, equal gain combining (EGC) and relatively simple selection combining spatial diversity techniques in a clear atmosphere are considered. Each subcarrier is modulated using binary phase shift keying. Laser irradiance is subsequently modulated by a subcarrier signal, and a direct detection PIN receiver is employed (i.e. intensity modulation/direction detection). At a subcarrier level, coherent demodulation is used to extract the transmitted data/information. The performance of on–off-keying is also presented and compared with the subcarrier intensity modulation under the same atmospheric conditions

Optical coherence tomography and scanning laser ophthalmoscopy: Approaches to dual-channel retinal tissue imaging

We report a Talbot bands-based optical coherence tomography (OCT) system capable of producing longitudinal B-scan OCT images and en-face scanning laser ophthalmoscopy (SLO) images of the human retina in-vivo, with various degrees of simultaneity

Reichenbach, Russell and the Metaphysics of Induction

Hans Reichenbach’s pragmatic treatment of the problem of induction in his later works on inductive inference was, and still is, of great interest. However, it has been dismissed as a pseudo-solution and it has been regarded as problematically obscure. This is, in large part, due to the difficulty in understanding exactly what Reichenbach’s solution is supposed to amount to, especially as it appears to offer no response to the inductive skeptic. For entirely different reasons, the significance of Bertrand Russell’s classic attempt to solve Hume’s problem is also both obscure and controversial. Russell accepted that Hume’s reasoning about induction was basically correct, but he argued that given the centrality of induction in our cognitive endeavors something must be wrong with Hume’s basic assumptions. What Russell effectively identified as Hume’s (and Reichenbach’s) failure was the commitment to a purely extensional empiricism. So, Russell’s solution to the problem of induction was to concede extensional empiricism and to accept that induction is grounded by accepting both a robust essentialism and a form of rationalism that allowed for a priori knowledge of universals. So, neither of those doctrines is without its critics. On the one hand, Reichenbach’s solution faces the charges of obscurity and of offering no response to the inductive skeptic. On the other hand, Russell’s solution looks to be objectionably ad hoc absent some non-controversial and independent argument that the universals that are necessary to ground the uniformity of nature actually exist and are knowable. This particular charge is especially likely to arise from those inclined towards purely extensional forms of empiricism. In this paper the significance of Reichenbach’s solution to the problem of induction will be made clearer via the comparison of these two historically important views about the problem of induction. The modest but important contention that will be made here is that the comparison of Reichenbach’s and Russell’s solutions calls attention to the opposition between extensional and intensional metaphysical presuppositions in the context of attempts to solve the problem of induction. It will be show that, in effect, what Reichenbach does is to establish an important epistemic limitation of extensional empiricism. So, it will be argued here that there is nothing really obscure about Reichenbach’s thoughts on induction at all. He was simply working out the limits of extensional empiricism with respect to inductive inference in opposition to the sort of metaphysics favored by Russell and like-minded thinkers

A non-pragmatic dominance argument for conditionalization

In this paper, I provide an accuracy-based argument for conditionalization (via reflection) that does not rely on norms of maximizing expected accuracy. (This is a draft of a paper that I wrote in 2013. It stalled for no very good reason. I still believe the content is right)

A master\u27s recital in horn

Casey Chlapek performed his graduate horn recital on November 9, 2017 at 6:00 pm in Davis Hall of the Gallagher Bluedorn Performing Arts Center on the campus of the University of Northern Iowa. He was assisted by pianist Natia Shioshvili. This recital represents the partial fulfillment of obtaining a Master of Music degree in Horn Performance. The program included works by Wolfgang Amadeus Mozart, Jan Koetsier Sigurd Berge, Carl Nielsen, and Jean Françaix. This abstract examines each piece in the context of its composer’s total musical output, explores the purpose and circumstances of composition, and provides brief comments regarding the music for both listeners and performers

The correlation of choroidal thickness and ocular pulse amplitude in non-exudatıve age-related macular degeneration

Introduction: The choroid is involved in the pathogenesis of various retinal diseases, including age-related macular degeneration (AMD). The ocular pulse amplitude (OPA) gives useful information about intraocular blood flow and is an indirect indicator of choroidal perfusion. In this study, we aimed to assess the correlation between the OPA and choroidal thickness (CT) in the eyes of healthy individuals and of individuals with non-exudative early stage AMD. Materials and Method: Fourty-four eyes of 44 non-exudative AMD patients and 41 age-matched eyes of 41 healthy individuals were included in the study. All eyes underwent a detailed ophthalmic evaluation, including axial length (AL) and ocular pulse amplitude (OPA) measurements. The CT was measured using optical coherence tomography. Parameters were compared between the two groups and correlation between OPA and CT was assessed. Results: The mean subfoveal, foveal, and parafoveal CT were 245.82 +/- 24.29 mu m, 230.66 +/- 23.44 mu m, 219.55 +/- 25.39 mu m in AMD group, respectively. The corresponding values were 278.44 +/- 34.18 mu m, 263.76 +/- 32.45 mu m, and 253.79 +/- 34.81 mu m in control group, respectively. The mean ages of groups were 69.6 +/- 8.97 years, and 65.0 +/- 5.89 years, respectively. The mean OPA was 3.43 +/- 1.14mmHg and 3.49 +/- 1.12mmHg, respectively. The average CT in AMD patients were significantly lower than the control group in all three regions (subfoveal- foveal- parafoveal) (all p<0,001). In controls, there was a moderate positive correlation between the OPA and CT in the three segments (p=0.002, 0.009, and 0.003; respectively). However only the foveal CT showed significant positive correlation with the OPA in AMD group (p=0.047). Conclusion: Our results showed a considerable correlation between ocular pulse amplitude and choroidal thickness in healthy subject. In non-exudative AMD group, there was a weak correlation between them. It can be hypothesized that; in patients with AMD, degeneration and/or thinning of choroidal pattern is a reason for this result

Βιβλιοκρισία του: EIRINI AFENTOULIDOU-LEITGEB, Die Hymnen des Theoktistos Studites auf Athanasios I. von Konstantinopel. Einleitung, Edition, Kommentar [Öst. Akad. d. Wissenschaften]. WBS XXVII, Wien 2008

Βιβλιοκρισία: Eirini Afentoulidou-Leitgeb, Die Hymnen des Theoktistos Studites auf Athanasios I. von Konstantinopel. Einleitung, Edition, Kommentar  [Österreichische Akademie der Wissenschaften. Institut für Byzanzforschung. Institut für Byzantinistik und Neogräzistik der Universität Wien, WBS XXVII], Wien 2008, σσ. 246+7 πίν. ISBN 978-3-7001-6043-4.Βιβλιοκρισία: Eirini Afentoulidou-Leitgeb, Die Hymnen des Theoktistos Studites auf Athanasios I. von Konstantinopel. Einleitung, Edition, Kommentar  [Österreichische Akademie der Wissenschaften. Institut für Byzanzforschung. Institut für Byzantinistik und Neogräzistik der Universität Wien, WBS XXVII], Wien 2008, σσ. 246+7 πίν. ISBN 978-3-7001-6043-4