Sharif Digital Repository

A 2×2 pile group with one of its piles acting as an energy pile is modeled using a 1g test setup. The model piles are closed-end aluminum pipes with 2cm diameter and 60cm length. The energy pile goes under several heating and cooling cycles which in return induces unsymmetrical loading on the pile group. A single steel U-tube through which water with a desired temperature is to be circulated is placed inside the initially water-filled energy pile to control its temperature during thermal cycling. A plastic tilt of the pile cap is observed with each thermal cycle having a gradually decreasing rate as the number of cycles increased. Readings from the horizontally oriented total pressure cells... 

According to available information and references, water leakage and internal erosion in bodies and foundations of embankment dams are the main reasons of many problems and failures. To reduce this risk in foundation, plastic cut off walls is one of the most reliable solutions. In this research the effect of specimen's age on the mechanical properties of plastic concrete was studied. This paper summarizes the test results which were conducted in unconfined and triaxial state. Plastic concrete specimens were prepared in the laboratory condition using the materials provided from the Silve dam site. Test results have shown that the time and confining pressure extremely affect the mechanical... 

The desired milling process with high material removal rate (MRR) and low surface roughness of the product can be achieved only if machining chatter is absent. Incorporating chatter into the optimal selection of the machining parameters leads to a complex problem. Therefore, the approach of selecting conservative intervals for the machining parameters is usually employed instead. In this paper, a practical approach is proposed to specify the optimal machining parameters (depth of cut and spindle speed) in order to maximize MRR and minimize forced vibrations by considering machining chatter. Firstly, the worst-case scenario-based optimization problem in terms of the surface quality is solved... 

In this paper, a low energy yet reliable communication scheme for network-on-chip is suggested. To reduce the communication energy consumption, we invoke low-swing signals for transmitting data, as well as data encoding techniques, for minimizing both self and coupling switching capacitance activity factors. To maintain the communication reliability of communication at low-voltage swing, an error control coding (ECC) technique is exploited. The decision about end-To-end or hop-To-hop ECC schemes and the proper number of detectable errors are determined through high-level mathematical analysis on the energy and reliability characteristics of the techniques. Based on the analysis, the extended... 

Landslides have disastrous influence on buried pipeline operation. In order to overcome this phenomenon, many retrofitting solutions have been proposed in literature and practice. This paper concentrates on the solutions which deal with pipe thickness change and rerouting method. As an answer to this,ABAQUS FE program has been used for numerical modeling. Soil-pipe interaction was modeled as hard and frictional contact in normal and tangential directions respectively. Typical geotechnical parameters of Tehran soil and predicted acceleration time history, compatible with Tehran geological condition, have been introduced to program for numerical calculations. Usefulness of two basic proposed... 

Chatter vibration is a major obstacle in achieveing increased machining performance. In this research, a finite element model of chip formation in a 2D milling process is used to predict the occurrence of chatter vibrations, and to investigate the effects of various machining parameters on this phenomenon. The dynamic properties of the machine tool at the tool tip are obtained based on experimental modal analysis, and are used in the model as the cutter dynamics. The model allows for the natural development of vibration as the result of the chip-tool engagement, and accounts for various phenomena that occur at the chip-tool interface ultimately leading to stable or unstable cutting. The... 

In this paper, physical modeling tests are conducted to study some aspects of the dynamic compaction method. The loose models are prepared with dry sand. Four cylindrical tampers with different weight and cross section areas are used for compaction of the models and dropped from various heights. Strain gage type total stress measuring sensors are placed at different levels inside the model to measure the transferred vertical stresses due to collision of the tamper with the surface of the models. The typical stress time histories are presented. Improvement depth and crater depth and diameter created on the model surface are studied, among the various parameters affecting the phenomena. Using... 

Surface waves generated during vibration of machine foundations are sometimes troublemaking and cause some damages to the nearby sensitive structures or people. Considering the function of the machines located on the foundations the dynamic loading could be harmonic or impact type. The main part of the generated energy is transferred to the ground by Rayleigh surface waves. One of the most reliable and economic methods for reduction of the effects of these generated waves is using open trenches around the dynamic sources, so called active isolation in literature. In this paper applicability and affecting parameters of the open trenches around the impact dynamic source is studied using... 

It is estimated that 20% of couples are infertile, and half of these infertility cases are linked to men. One of conditions that can affect male fertility is asthenozoospermia. We applied Raman spectroscopy to the analysis of the metabolome of the human seminal plasma, and used chemometrics on the patterns of Raman spectra obtained. Significant changes were observed in the metabolome of the human seminal plasma of asthenozoospermic patients  

Hot corrosion is a serious problem in gas turbines due to poor quality fuels which contain Na, V, S and Cl. To resolve the problem, Cr-aluminide was coated on IN-738LC superalloy with a two steps pack cementation process. Oxidation behavior and near-surface microstructure of the coating showed consecutive increase in destruction by exposition to Na2SO4, 75Na2SO4 + 25 V2O5 and 70Na2SO4 + 25 V2O5 + 5NaCl (wt.%). Kinetic studies indicated parabolic corrosion rate in salt-less samples due to diffusion. Similar expression for salt-covered samples was assessed for oxide dissolution. Plate-like, broken-plate-like and cauliflower-like morphologies attributed to the corrosion products were observed... 

This work describes coating of NiCoCrAlY on IN-738LC superalloy by high-velocity oxygen fuel (HVOF) process. Properties of the coatings are significantly influenced by oxygen/fuel ratio and other spraying parameters. The effect of oxygen/fuel ratio on the oxidation behavior, bond strength, hardness, roughness and microstructure including porosity, inclusion formation and unmelted particles are discussed here. The porosity and inclusion in C1 coating are maximal. C2 coating with oxygen/fuel ratio of 2 has the highest bond strength and the lowest unmelted particles. C3 coating with the lowest total porosity and inclusion has the minimal roughness and the highest oxidation resistance and... 

The seismic response of soil depends on proper evaluation and use of soil dynamic properties, including shear modulus and damping ratio at various strain levels. Despite extensive studies on the shear modulus and damping ratio of saturated soils, research on the dynamic properties of unsaturated fine-grained soils — especially at high suction — is limited. This study aims to investigate the dynamic properties of loess at a variety of initial states resulting from different specimen preparation techniques (reconstituted, recompacted, and intact) and their evolutions due to suction-induced desiccation. Results of resonant column tests show that at initial states, the specimen preparation... 

Abstract: This work describes coating of NiCoCrAlY on IN-738LC superalloy by high-velocity oxygen fuel (HVOF) process. Properties of the coatings are significantly influenced by oxygen/fuel ratio and other spraying parameters. The effect of oxygen/fuel ratio on the oxidation behavior, bond strength, hardness, roughness and microstructure including porosity, inclusion formation and unmelted particles are discussed here. The porosity and inclusion in C1 coating are maximal. C2 coating with oxygen/fuel ratio of 2 has the highest bond strength and the lowest unmelted particles. C3 coating with the lowest total porosity and inclusion has the minimal roughness and the highest oxidation resistance...