Sharif Digital Repository

An inconsistency between the circular symmetric geometry of conventional optical imagers and the geometry of long linear sensors used in today's line-scan cameras results in suboptimal separate design of optics and electronics of scanner systems. Based on the method of foveated optical imaging, a technique named foveated scanning (FS) is proposed in this paper. The FS technique is employed to enlarge the one-dimensional resolved field of view (RFOV) of conventional lenses and permits optimized performance on a line-of-interest in the image plane where the optoelectronic sensor is located. The achieved enlargement of RFOV is verified on a proof-of-concept basic telephoto lens. Both modulation... 

The geometry of the sensed and thus optically relevant area in the image plane of line scan cameras suggests that improvement of the overall system is possible, by joint design of optics and electronics. By a technique named Linear Fovea (LF) proposed in this paper, the optical contrast along the Line-of-Interest (LOI) in the image plane i.e. the location of the opto-electronic sensor, is optimized at the expense of contrast elsewhere. In the LF method, employing a single doubly symmetric surface, the resolved field of view (RFOV) as the merit function, is maximized, by finding appropriate Zernike coefficients describing that surface. The technique is applied on a proof-of-concept single... 

In this paper we study the performance of spectrally-encoded spread-time (SE/ST) technique when applied to ultrawideband (UWB) signals in the context of wireless code-division multiple-access (CDMA) communication. In this technique UWB pulses are spectrally encoded with pseudorandom codes that are assigned uniquely to each user. We shall show that the SE/ST ultrawideband system provides an appropriate multi-user capacity in realistic UWB channels, along with the ability of narrowband interference (NBI) suppression. To this end, after obtaining a suitable statistical model for spectrally encoded spread-time signals, we investigate the performance of the system in the presence of... 

Detection of ultrashort light pulses with conventional bandlimited photodetectors can lead to substantial performance degradation in digital lightwave communication systems. All-optical nonlinear processing of the received field prior to the optical to electrical conversion can greatly overcome this problem. In this letter, through a decision-theoretic framework and using a basic invariance property of the photodetector, we obtain the optimal zero-memory nonlinear element and evaluate its performance. Possible suboptimum nonlinearities are also investigated and their performance is examined. The results in this letter strongly justify the intuitive use of power-law devices, such as those... 

Autocorrelation receiver (AcR) is usually used as the general receiver for transmitted reference (TR) communication systems on a quite intuitive basis. In this paper, we apply the principle of statistical invariance to obtain the optimum TR receiver on a decision-theoretic basis, and it is shown that the autocorrelation receiver is optimal only in a special case. Performance of the optimum receiver and the suboptimum AcR for some important modulation schemes is also evaluated. The results imply that allocating a part of the transmitted energy and bandwidth to reference pulses would not help improve the performance of the system and the optimal performance might be achieved via much simpler... 

Autocorrelation receiver (AcR) is usually used as the general receiver for transmitted reference (TR) communication systems on a quite intuitive basis. In this paper, we apply the principle of statistical invariance to obtain the optimum TR receiver on a decision-theoretic basis, and it is shown that the autocorrelation receiver is optimal only in a special case. Performance of the optimum receiver and the suboptimum AcR for some important modulation schemes is also evaluated. The results imply that allocating a part of the transmitted energy and bandwidth to reference pulses would not help improve the performance of the system and the optimal performance might be achieved via much simpler... 

The main objective of the current study is to investigate the impacts of environmental evolutions at global scale on Iran's environmental planning. Thereby, all political movements towards solving environmental issues in Iran were accurately reviewed to find out the impressibility of the events by the global environmental evolutions. The findings indicated that Iran has joined the conventions and protocols with a time lag. During the period 1948-1993, the mean time lag between holding an international convention until its approval in Iran was eleven years while from 1994 to 2007, the average lag time was shortened to four years. As the results show, attention to environmental issues was... 

Detection of ultrashort light pulses with conventional bandlimited photodetectors can lead to substantial performance degradation in digital lightwave communication systems. All-optical nonlinear processing of the received field prior to the optical to electrical conversion can greatly overcome this problem. In this letter, through a decision-theoretic framework and using a basic invariance property of the photodetector, we obtain the optimal zero-memory nonlinear element and evaluate its performance. Possible suboptimum nonlinearities are also investigated and their performance is examined. The results in this letter strongly justify the intuitive use of power-law devices, such as those... 

In this paper we study the performance of Spectrally-Encoded Spread-Time (SE/ST) technique when applied to ultrawideband (UWB) signals in the context of wireless code-division multiple-access (CDMA) communication. In this technique UWB pulses are spectrally encoded with pseudorandom codes that are assigned uniquely to each user. We shall show that the SE/ST ultrawideband system provides an appropriate multi-user capacity in realistic UWB channels, along with the ability of narrowband interference (NBI) suppression. To this end, after obtaining a suitable statistical model for spectrallyencoded spread-time signals, we investigate the performance of the system in the presence of... 

The use of Spread-Time CDMA for ultrawideband (UWB) wireless communication is proposed and its capability for supporting many high data rate users is investigated. Furthermore we will study a hybrid technique, namely, Spread-Time/Time-Hopping to increase the capacity of the above mentioned technique and simultaneously minimizing the effect of near-far in a typical CDMA system  

Textbooks provide the most serious source of knowledge construction and transmission for children at schools. This paper used a discursive and qualitative content analysis approach to extract the dominant values, ideologies and identities in four social studies textbooks taught nationwide to children in primary schools in Iran. Textual and visual analysis were applied on these textbooks and the results showed the saliency of four dominant discourses and values including pre-Islamic ethos and Iranian-Islamic identity, war and peace, social and traditional values in Iranian culture, and respect for diversity. Each of these discourses are discussed and some recommendations are made at the end... 

Textbooks provide the most serious source of knowledge construction and transmission for children at schools. This paper used a discursive and qualitative content analysis approach to extract the dominant values, ideologies and identities in four social studies textbooks taught nationwide to children in primary schools in Iran. Textual and visual analysis were applied on these textbooks and the results showed the saliency of four dominant discourses and values including pre-Islamic ethos and Iranian-Islamic identity, war and peace, social and traditional values in Iranian culture, and respect for diversity. Each of these discourses are discussed and some recommendations are made at the end... 

Integrated seismic attributes, coherency, acoustic impedance (AI), lambda-rho (λρ) and mu-rho (μρ), were used to delineate and to characterize a complex regional channel deposition system in a carbonate reservoir interval in the upper part of the Sarvak Formation. The study area incorporates three adjacent oil fields in SW Iran (Khuzestan Province) covered by three individual 3D seismic surveys having a total area of about 2800 km 2. We generated a regional horizon-based coherency cube using these three seismic surveys. This revealed a carbonate clastic deposition channelling system over the entire study area. We characterized this channel deposition system in agreement with regional...