Sharif Digital Repository

In this paper, heat effects due to powerful pump beam in the lens duct delivery system is investigated and subsequent thermal effects are described. Temperature raise in the device, thermal loading, and material considerations for the lens ducts fabrication are reported. For an absorbed intensity of 10 W/cm2 in a 4 cm-long lens duct, the temperature difference between the midpoint and its faces, for a lens duct made from borosilicate is 7.05°C, for sapphire 4.01°C, and for synthetic fused silica is the smallest value of 0.54°C. For a typical absorbed intensity of 1.4 W/cm2 in a 4 cm-long lens duct, with a steady-state time constant of 120 s, the fractional thermal loading is 1.98% for BK-7,... 

Results of an investigation on the evolution of microstructure during simple compression testing of two face-centered-cubic (fcc) polycrystals, IN625 superalloy and 316L stainless steel, are reported and a review on the existing data related to the uniaxial deformation of fcc polycrystals is presented. It is found that while a number of fcc polycrystals show linear hardening behavior, the evolution of the underlying microstructure may be quite different. It is argued that, in contrast to the current belief, deformation twinning may not be the sole cause of linear hardening in low stacking fault energy (SFE) fcc polycrystals. It is suggested that, due to the requirement of slip system change... 

This paper proposes a software framework for dynamic-reconfigurable protocol stack. The framework presents mechanisms andan algorithm/or all required phases for reconfiguration of a running protocol component that include freezing the component in a safe state, changing the component, and state transfer to a new component. Considering that every running protocol component communicates with at least one peer component in another system, we perform the reconfiguration with respect to the peer component. © 2007 IEEE  

Future communication and computation devices require mechanisms for on-the-fly reconfiguration in their protocol stack to operate in different situations and networks. This paper proposes a component-based framework for dynamic-reconfigurable protocol stack. Considering that every running protocol component communicates with at least one peer component, unlike related work our framework supports synchronous reconfiguration of two peer protocol components in two communicating protocol stacks. © Springer-Verlag Berlin Heidelberg 2007  

Recent investigations have shown that the steady state grain size of severely deformed materials is dependent on the stacking fault energy. In this paper, a model is presented to investigate such a dependency which uses thermodynamics based calculations. The present model shows that the relationship between the steady state grain size and the stacking fault energy of material is in power law form, directly. Furthermore, the model shows that the steady state grain size has an exponential relationship with the self-diffusion activation energy and a decrease in the self-diffusion activation energy increases the steady state grain size. The model predictions are in good agreement with the... 

A new method for forecasting the trend of time series, based on mixture of MLP experts, is presented. In this paper, three neural network combining methods and an Adaptive Network-Based Fuzzy Inference System (ANFIS) are applied to trend forecasting in the Tehran stock exchange. There are two experiments in this study. In experiment I, the time series data are the Kharg petrochemical company's daily closing prices on the Tehran stock exchange. In this case study, which considers different schemes for forecasting the trend of the time series, the recognition rates are 75.97%, 77.13% and 81.64% for stacked generalization, modified stacked generalization and ANFIS, respectively. Using the... 

Forthcoming networked systems require mechanisms for on-the-fiy reconfiguration in their protocol stacks to be able to operate in different situations and networks. Since every protocol in a protocol stack has at least one peer protocol in another system, dynamic reconfiguration of a protocol raises the need for reconfiguration in the peer stack. For an assured dynamic (run-time) reconfiguration, executions of two peer protocols are stopped in a safe state, new protocols are initialized, and stacks switch to the new protocols at the same time. This paper proposes a software framework for dynamic reconfiguration of two communicating protocol stacks. A distributed algorithm is implemented in... 

Thermoacoustics describes energy conversion processes, activated by interaction temperature oscillation, accompanying the pressure oscillation in a sound wave, with solid boundaries. In ordinary experience this interaction of sound and heat cannot be observed, because of the very low temperature differences, but under suitable conditions, it can be emphasized and amplified to create remarkable thermodynamic effects such as, steep thermal gradients, powerful convective heat fluxes, and strong sound fields. We designed and constructed a simple thermoacoustic refrigerator with an adjustable mechanical resonator, coupled with the acoustic resonator. Our experimental data showed about % 10... 

In this paper, results of an investigation on strain hardening mechanisms of aged AEREX350 alloy during room temperature compression testing are reported. TEM studies were conducted on commercial samples aged at 850 °C both before and after deformation in a strain range of 0.15-0.27. It was found that only coherent γ′ precipitates with L12 structure formed in these samples prior to deformation. TEM studies also showed twin intersections in the deformed samples. Based on these observations, it is suggested that the high strain hardening rate of the aged material in this strain range is mainly related to the formation of intersecting deformation twins. This is attributed to the decrease in the... 

True stress vs. true strain responses of Cu-6 wt.% Al and Cu-12 wt.% Mn alloys are presented. While Cu-6 wt.% Al alloy shows the typical mechanical response of low stacking fault energy alloys, the Cu-12 wt.% Mn alloy behaved similarly to medium to high stacking fault energy alloys. These findings clearly show that while short-range ordering triggers slip planarity, it has a minor effect on total dynamic recovery of these copper alloys