1,645 research outputs found
On the BER of Multiple-Input Multiple-Output Underwater Wireless Optical Communication Systems
In this paper we analyze and investigate the bit error rate (BER) performance
of multiple-input multiple-output underwater wireless optical communication
(MIMO-UWOC) systems. In addition to exact BER expressions, we also obtain an
upper bound on the system BER. To effectively estimate the BER expressions, we
use Gauss-Hermite quadrature formula as well as approximation to the sum of
log-normal random variables. We confirm the accuracy of our analytical
expressions by evaluating the BER through photon-counting approach. Our
simulation results show that MIMO technique can mitigate the channel
turbulence-induced fading and consequently, can partially extend the viable
communication range, especially for channels with stronger turbulence
MIMO Underwater Visible Light Communications: Comprehensive Channel Study, Performance Analysis, and Multiple-Symbol Detection
In this paper, we analytically study the bit error rate (BER) performance of
underwater visible light communication (UVLC) systems with binary pulse
position modulation (BPPM). We simulate the channel fading-free impulse
response (FFIR) based on Monte Carlo numerical method to take into account the
absorption and scattering effects. Additionally, to characterize turbulence
effects, we multiply the aforementioned FFIR by a fading coefficient which for
weak oceanic turbulence can be modeled as a lognormal random variable (RV).
Moreover, to mitigate turbulence effects, we employ multiple transmitters
and/or receivers, i.e., spatial diversity technique over UVLC links.
Closed-form expressions for the system BER are provided, when equal gain
combiner (EGC) is employed at the receiver side, thanks to Gauss-Hermite
quadrature formula and approximation to the sum of lognormal RVs. We further
apply saddle-point approximation, an accurate photon-counting-based method, to
evaluate the system BER in the presence of shot noise. Both laser-based
collimated and light emitting diode (LED)-based diffusive links are
investigated. Since multiple-scattering effect of UVLC channels on the
propagating photons causes considerable inter-symbol interference (ISI),
especially for diffusive channels, we also obtain the optimum multiple-symbol
detection (MSD) algorithm to significantly alleviate ISI effects and improve
the system performance. Our numerical analysis indicates good matches between
the analytical and photon-counting results implying the negligibility of
signal-dependent shot noise, and also between analytical results and numerical
simulations confirming the accuracy of our derived closed-form expressions for
the system BER. Besides, our results show that spatial diversity significantly
mitigates fading impairments while MSD considerably alleviates ISI
deteriorations
Mathew S. Hull, Government of Paper: The Materiality of Bureaucracy in Urban Pakistan
The civilian bureaucracy has been central to everyday life and the imagination of ordinary citizens in Pakistan in a way that is almost unique in South Asia. Pakistani public discourse and scholarly debates on the country’s politics, internal security, foreign policy, and its overall direction inevitably return to the role of the ‘bureaucracy’ and the ‘establishment’ in charting the course of people’s individual and collective lives. These terms are used in the singular in conversations, indi..
Intelligent PID Controller of Flexible Link Manipulator with Payload
This paper presents the experimental study of intelligent PID controller with the present of payload. The controllers were constructed to optimally track the desired hub angle and vibration suppression of DLFRM. The hub angle and end-point vibration models were identified based on NNARX structure. The results of all developed controllers were analyzed in terms of trajectory tracking and vibration suppression of DLFRM subjected to disturbance. The simulation studies showed that the intelligent PID controllers have provided good performance. Further investigation via experimental studies was carried out. The results revealed that the intelligent PID control structure able to show similar performance up to 20 g of payload hold by the system. Once the payload increased more than 20 g, the performance of the controller degrades. Thus, it can be concluded that, the controllers can be applied in real application, provided the tuning process were carried out with the existence of the maximum payload which will be subjected in the system. The 20 g payload value can act as uncertainty for the controller performance
Superconductor Insulator Transition in Long MoGe Nanowires
Properties of one-dimensional superconducting wires depend on physical
processes with different characteristic lengths. To identify the process
dominant in the critical regime we have studied trans- port properties of very
narrow (9-20 nm) MoGe wires fabricated by advanced electron-beam lithography in
wide range of lengths, 1-25 microns. We observed that the wires undergo a
superconductor -insulator transition that is controlled by cross sectional area
of a wire and possibly also by the thickness-to-width ratio. Mean-field
critical temperature decreases exponentially with the inverse of the wire cross
section. We observed that qualitatively similar superconductor{insulator
transition can be induced by external magnetic field. Some of our long
superconducting MoGe nanowires can be identified as localized superconductors,
namely in these wires one-electron localization length is much shorter than the
length of a wire
The upper normal limit of serum alanine aminotransferase in Golestan Province, Northeast Iran
Background: The objective of this study was to determine the upper normal limit of serum alanine aminotransferase level in a population-based study in Golestan Province, northeast Iran. Methods: From the randomly invited individuals (2,292), 698 out of the 916 males and 1,351 out of the 1,376 females participated in the study (participation rate: 76.2 and 98.1, respectively). One hundred and twenty-one participants were excluded due to positive hepatitis B surface antigen or hepatitis C virus antibody and/or drinking more than 20 grams of alcohol per day. A total of 1,928 participants (1300 females) were included. The upper normal limit of serum alanine aminotransferase level was defined as the 95th percentile. Results: The upper normal limit of serum alanine aminotransferase level in normal weight and nondiabetics was significantly lower than the total study group (36 versus 45 U/L). Serum alanine aminotransferase level was independently associated with male gender, body mass index, and diabetes mellitus (OR=2.05; 95Cl: 1.44 - 2.94, OR=2.76; 95Cl: 1.84 - 4.13, and OR=2.96; 95Cl: 1.56-5.61, respectively). Conclusion: Considering the lower calculated upper normal limit in normal weight nondiabetic participants in this study, we recommend setting new upper normal limit for serum alanine aminotransferase level, It seems reasonable to set upper normal limit for serum alanine aminotransferase level in males and females separately
The upper normal limit of serum alanine aminotransferase in Golestan Province, Northeast Iran
Background: The objective of this study was to determine the upper normal limit of serum alanine aminotransferase level in a population-based study in Golestan Province, northeast Iran. Methods: From the randomly invited individuals (2,292), 698 out of the 916 males and 1,351 out of the 1,376 females participated in the study (participation rate: 76.2 and 98.1, respectively). One hundred and twenty-one participants were excluded due to positive hepatitis B surface antigen or hepatitis C virus antibody and/or drinking more than 20 grams of alcohol per day. A total of 1,928 participants (1300 females) were included. The upper normal limit of serum alanine aminotransferase level was defined as the 95th percentile. Results: The upper normal limit of serum alanine aminotransferase level in normal weight and nondiabetics was significantly lower than the total study group (36 versus 45 U/L). Serum alanine aminotransferase level was independently associated with male gender, body mass index, and diabetes mellitus (OR=2.05; 95Cl: 1.44 - 2.94, OR=2.76; 95Cl: 1.84 - 4.13, and OR=2.96; 95Cl: 1.56-5.61, respectively). Conclusion: Considering the lower calculated upper normal limit in normal weight nondiabetic participants in this study, we recommend setting new upper normal limit for serum alanine aminotransferase level, It seems reasonable to set upper normal limit for serum alanine aminotransferase level in males and females separately
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