یعقوب خراسانی

In this paper, the Aluminum-doped graphene has been investigated and simulated based on the electron density functional theory as a sensor for nitrogen dioxide and hydrogen sulfide gases. The simulation results using SIESTA software demonstrate that the optimum doping is substitutional and occurs when a carbon atom in graphene is replaced with an Al atom. The dopant Al atom at the minimum relaxation energy is placed 1.85 Å higher than the graphene sheet and creates a bulge on the graphene surface. The different probable adsorption states of each NO2 and H2S gas were simulated and the results showed that the optimum adsorption occurred around the placement of dopant where the electron density is higher. Finally, the adsorption energy of NO2 and H2S molecules were obtained -3.45 eV and -0.87 eV, respectively. The resulting adsorption enthalpies, which demonstrate the formation of strong bonds, illustrate that doped graphene could serve as a suitable substrate for the fabrication of NO2 and H2S sensors.

In this paper, a second order discrete-time quadrature delta sigma modulator for GSM / EDGE receivers is designed. By reducing the OSR in the designed modulator, its operating frequency is decreased. This frequency reduction has led to the use of smaller bandwidth-based op-amps in this modulator that work at lower frequencies with less power consumption. A three-bit quantizer is used to achieve the desired signal to noise ratio (SNR). A 3-bit quantizer is used To achieve the desired SNR, and consequently it has a 3-bit DAC at the feedback paths of modulator. The mismatch of its cells is one of the problems of multi bit modulators. Another problem with quadrature modulators is the mismatch between paths I and Q. A complex DEM block is designed to correct the DAC cells error mismatch in each path and between I and Q paths. The designed modulator is implemented in CMOS-180nm technology. The designed modulator is implemented in CMOS-180nm technology. The SNR of the output spectrum of this modulator is obtained 86dB with a sampling rate of 50 and a power consumption of 5.58mw.

Today, the security of information in communication channels is of great importance, and the higher the classification of information, the higher the importance of security. From a long time ago, various encryption algorithms were proposed to ensure communication security, and different organizations use different encryption algorithms based on the sensitivity of the information. Information can be classified into different types, textual information is one of the most diverse types of information, which becomes more important if there is a classification. In this article, based on the 28-character alphabet, a new encryption method is presented, which has high security and speed, and is resistant to attacks based on the frequency of letters. Laboratory results show a very high resistance of this method against a comprehensive attack. The attacker's need for a lot of memory, which is practically inaccessible, that is another reason for the robustness of this algorithm. Given the key generation algorithm in this method, it can be ensured that this algorithm is also very resistant to attack in the middle.