Sharif Digital Repository

This paper presents a novel DLL-based frequency synthesizer architecture to generate fractional multiples of reference frequency and reduce the power consumption of the frequency synthesis block. The architecture is adopted for French VHF application as an example. The DLL architecture allows for minimal area, while consuming low power. The proposed circuit can operate at a substantially low supply voltage. The circuit level and system level designs are presented. It was shown that for the mentioned standard, a mere 27 delay stages for VCDL are sufficient to cover French VHF band. Simulation results confirm the analytical predictions. The proposed DLL-based frequency synthesizer is... 

In this study, the effect of the geometrical parameters of the Lateral Flow Immunoassay (LFI) membrane on the performance of the pregnancy kits is investigated. Consequently, a new geometry for LFI membrane is proposed based on some theoretical, numerical and experimental observations in order to improve the performance of the related kits. A pregnancy kit (for the detection of hCG in urine samples) is developed and the effect of the relocation of the test and the control lines over the membrane was studied based on the variation of the sample fluid velocity. Using Lattice-Boltzmann simulation of the lateral flow within the porous media and the experimental results, the fluid flow within the... 

The Model Driven Architecture (MDA) is meant to facilitate system development by using models for representing both the "problem" and its "solution". In its ideal form, software development based on MDA would follow a development process that begins by producing models of the problem domain at a high level of abstraction, and then proceeds by gradually and automatically transforming them into executable code with the help of tools. However, MDA-based development has encountered several setbacks, the mitigation of which requires detailed scrutiny and analysis. In this research, MDA-based development is analyzed through applying SWOT (Strengths, Weaknesses, Opportunities, and Threats) analysis... 

The gas-phase kinetics of diallyl sulfide pyrolysis were studied experimentally and theoretically in a static system over the temperature range 433-463 K and a total pressure of 80 Torr in a glass vessel with the free radical inhibitor cyclohexene. The experimental results show that this reaction is homogeneous, unimolecular and follows a first-order rate law. Theoretical studies at the B3LYP/6-31G* computational level indicate that the elimination reaction proceeds through a six-centered cyclic transition state and the reaction mechanism is concerted and non-synchronous. Copyright © 2003 John Wiley & Sons, Ltd  

A combined theoretical and experimental kinetic and mechanism of diallyl disulfide pyrolysis reaction in the gas phase was studied in a static system over the temperature range of 586.7-621.2 K and a total pressure of 72 Torr in the presence of cyclohexene as radicals inhibitor. The experimental results show that the reaction is homogeneous, unimolecular and proceeds through a radical mechanism. Theoretical calculations at the B3LYP level using the 6-31G*, 6-31++G* and 6-311++G* basis sets confirm the radical mechanism for the diallyl disulfide pyrolysis. The calculated kinetic and activation parameters especially at the B3LYP/6-31G* level are in good agreement with the experimental data. ©... 

Structural and kinetic aspects of the retro-cheletropic ene reactions of 2,2-dimethyl but-3-enal, 1-methyl-6-methylenecyclohexa-2,4-diene-1-carbaldehyde and their deuterated derivatives were investigated using a variety of computational methods. Theoretical calculations were carried out with ab initio and DFT methods at the RHF, MP2 and B3LYP levels of the theory, using the 6-31G* basis set. Vibrational frequency analysis confirmed the stationary states including the transition state (TSs) structures. Intrinsic reaction coordinate calculations show the localized TSs connect with the corresponding minima associated with the reactants and the products. The mechanistic studies on the... 

In the band structure analysis of photonic crystals it is normally assumed that the full photonic gaps could be found by scanning high-symmetry paths along the edges of Irreducible Brillouin Zones (IBZ). We have recently shown [1] that this assumption is wrong in general for sufficiently symmetry breaking geometries, so that the IBZ is exactly half of the complete BZ. That minimal required symmetry arises from the requirement on time-reversal symmetry. In this paper we show that even that requirement might be broken by using gyro-magnetic materials in the composition of photonic structures we can observe that the IBZ extends fully to the boundaries of the complete BZ, that is IBZ must be as... 

This paper presents a new architecture for a DLL based frequency synthesizer for wireless transceivers. Owing to its DLL based nature, the synthesizer generates the target frequencies with minimum phase noise and jitter. To cover the desired frequency proposed architecture consists of mixer and divider. As an example, VHF frequency band of IRAN is covered. The circuit level design guidelines and power consumption trade-offs are presented. It was shown that for the mentioned standard a 40 delay cell and 9 switches for switching channels is sufficient. Simulation results confirm the analytical predictions