Abstract:
The reconstruction of an unknown continuously defined function from the samples of the responses of linear time-invariant (LTI) systems sampled by the th Nyquist rate is the aim of the generalized sampling. Papoulis (1977) provided an elegant solution for the case where is a band-limited function with finite energy and the sampling rate is equal to times cutoff frequency. In this paper, the scope of the Papoulis theory is extended to the case of bandpass signals. In the first part, a generalized sampling theorem (GST) for bandpass signals is presented. The second part deals with utilizing this theorem for signal recovery from nonuniform samples, and an efficient way of computing images of reconstructing functions for signal recovery is discussed.

Abstract:
In the paper, the influence of temperature variation on the sensitivity of an avalanche-photodiode-based optical receiver applied in the free space optical communication link is discussed. Communication systems of this type are exposed to a wide range of operating temperatures, which markedly affect many photodiode and preamplifier parameters. The paper presents a receiver sensitivity calculation, taking into consideration the temperature dependence of avalanche photodiode gain, excess noise factor, dark current and thermal noise of preamplifier resistances, and describes the compensation of temperature effects on photodiode gain based on a corresponding change in the reverse voltage applied to the diode. The calculations are demonstrated on the connection of a small-area silicon APD operating in the wavelength range from 820 to 1150 nm with a transimpedance preamplifier using a bipolar junction transistor.

Abstract:
This paper deals with design of wideband low-noise preamplifier of atmospheric optical link receiver. Sources of noise and the noise models for the PIN photodiode coupled to a transimpedance amplifier are described here. This paper presents the way of optimization the signal to noise ratio at the required frequency range.

Abstract:
Atmospheric turbulence results in many effects causing fluctuation in the received optical power. Terrestrial laser beam communication is affected above all by scintillations. The paper deals with modeling the influence of scintillation on link performance, using the modified Rytov theory. The probability of correct signal detection in direct detection system in dependence on many parameters such as link distance, power link margin, refractive-index structure parameter, etc. is discussed and different approaches to the evaluation of scintillation effect are compared. The simulations are performed for a horizontal-path propagation of the Gaussian-beam wave.

Abstract:
Bandpass time-continuos signals are shown being able to be uniquely expressed in terms of the samples gi(nTv) of the impulse responses gi(t) of m linear time-invariant systems with input f(t) sampled at 1/m Nyquist rate. Various known extensions of the sampling theorem can be regarded as special cases of the resulting generalized sampling expansion of f(t).

Abstract:
In this paper, a velocity measurement method using the spatialfilter is presented. Luminous emitance of the surface passing throughthe moving spatial filter and optical set is projected to the activearea of photo-detector. The velocity determination is based on thefrequency spectrum evaluation of the photo-detector output signal. Theformula for velocity computing is derived first. Then, correctness ofvelocity evaluation in dependence on the surface and measuring systemproperties is discussed.

Abstract:
The quantum treatment of gravity has been researched for more than fifty years. The focus of the efforts was the investigation of the “gravitational quantum field” concept. This article paves the way to solving this puzzle. Gravity is a phenomenon that emerges from the undulating nature of the universe. To support this claim, I deduce a more generalized expression than that of Newton’s gravity from simple considerations relating to the wave function, the probability density function, and a hypothesis of how all particles in the universe are related. This expression uncovers the true nature of the gravitational phenomenon, dark matter, and dark energy. This true nature of the gravitational field allows its renormalization and the definition of its elementary charge. The result obtained considers the Mach’s principle and deduces the origin of the inertial force. Finally, it is concluded that a new model of the universe is necessary.

Abstract:
This paper analyzes the effect
of foreign direct investment (FDI) on agricultural sector in Tanzania. The
paper also examines the declining contribution of agriculture to real GDP
growth despite the fact that the sector employs more than 70 percent of the
total labour force. Annual time series data spanning from 1990 to 2015 are used
to test the significance of the relationship between FDI inflow and agriculture
value added-to-GDP ratio on one hand and FDI inflows and economic growth on the
other hand. Also, the relationship between agriculture value added and economic
growth rate is empirically examined. Variables such as gross fixed capital
formation, inflation rate, trade liberalization, real exchange rate and population
are considered as control variables. For the purpose of inference, the paper
employs classical linear regression model. Ordinary least squares methods are
used for estimation. The diagnostic tests including RESET regression errors specification
test, Breusch-Godfrey serial correlation LM test, Jacque-Bera-normality test
and white heteroskedasticity test reveal that the models have no signs of misspecification
and that, the residuals are serially uncorrelated, normally distributed and
homoskedastic. Interestingly, empirical results suggest that there is no significant
effect of FDI inflows on agriculture value added-to-GDP ratio in Tanzania
despite the fact that FDI inflows in economy have been outstanding particularly
in past two decades. Unsurprisingly, the results show that FDI inflows-to-GDP
ratio and real GDP growth rate are positively correlated. Notwithstanding,
agriculture sector, which constitutes the largest proportion of the total
labour force, contributes, on average, less than 30 percent, to total GDP. This
suggests that the sector is inefficient and therefore, effort towards
attracting more FDI aiming at improving productivity in agriculture sector,
which in turn may reduce poverty, is much needed.

Abstract:
We present a novel new approach to study quark-hadron duality using truncated moments of structure functions, and determine the degree to which individual resonance regions are dominated by leading twist.