Response of piles due to lateral slope movement[taliem.ir]

Response of piles due to lateral slope movement

A displacement method using the FLAC3D program is used to evaluate the response of piles caused by an embankment slope in a translational failure mode, induced by a weak soil layer or a liquefied layer beneath the embankment. The analyses include the kinematic loading acting on the bridge piles caused by lateral soil movements, and the effects of spatial variation of soil displacement on the response of piles and pile groups (2 · 2). The analysis demonstrates that the proposed displacement method can be applied to design of pile foundations undergoing lateral soil movement or for use in pile–slope stability analysis. Sensitivity studies varying soil and pile parameters are also presented. The results bring out the important effects of relative stiffness between pile and soil on the piles failure modes. Published case histories are examined and used as a basis for verifying the proposed methodology
An investigation of microstructureproperty relationships[taliem.ir]

An investigation of microstructure/property relationships in dissimilar welds between martensitic and austenitic stainless steels

The metallurgical characteristics, tensile, hardness, toughness and corrosion resistance of dissimilar welds between X5CrNi18-10 grade austenitic and X20CrMo13 grade martensitic stainless steel have been evaluated. Both austenitic and duplex stainless steel electrodes were used to join this combination, using multipass manual metal arc welding process. Defect free welds were made with each welding consumable. It was found that the tensile strength of weldment, which was produced by duplex electrode (E2209-17), was slightly lower than that of austenitic electrode (E308L-16). The toughness of the both E2209-17 and E308L-16 deposits was acceptable even at low temperature regardless of heat input. Hardness was increased in both welds made with E2209-17 duplex and E308L-16 austenitic electrode along the X20CrMo13/weld metal fusion boundary due to heat annealing and then following high cooling rate. The pitting corrosion resistance of the weld metal made with E308L-16 and E2209-17 filler metal was found acceptable. Although, heat affected zone in the weldment and X20CrMo13 base metal were affected by electrolytic corrosion. This investigation has shown that both filler metals can be used to join austenitic stainless steel to the martensitic stainless steel
Exploring the Mechanical Properties of[taliem.ir]

Exploring the Mechanical Properties of Spot Welded Dissimilar Joints for Stainless and Galvanized Steels

Spot weldability of dissimilar metal joints between stainless steels and nonstainless steels was investigated. The aim was to determine the spot welding parameters for the dissimilar metal joints and to characterize the mechanical properties of the joints. Metallographical investigations, microhardness measurements, peel tests, lap shear tests, cross-tension tests, corrosion fatigue tests, and stress corrosion cracking tests were performed. It was found that in the dissimilar metal joints between stainless steel and nonstainless steel, the failure load of the cross-tension specimens was around 72–78% of that of the lap shear specimens. The weld nugget of the dissimilar metal joints was fully martensitic, but it was ductile enough so that the failure type was plug failure in both lap shear and cross-tension tests. In the case of the corrosion fatigue testing of the spot welded joints, different strength levels of the base materials did not have an effect on the corrosion fatigue strength, but the sheet thickness had a significant effect. The fatigue strength of a spot welded specimen increased with the increasing sheet thickness. Electro-coating of the test specimens did not have an effect on the corrosion fatigue properties of the spot welded joints
استفاده از رادیوهاي هوشمند در کنترل بهینه پهناي باند[taliem.ir]

استفاده از رادیوهاي هوشمند در کنترل بهینه پهناي باند

امروزه با توجه به پیشرفت هاي روز دنیا بخصوص در صنعت مخابرات استفاده از سیستم هاي بی سیم ، جهت برقراري ارتباطات صوتی ، تصویري و دیتا بسیار شده است . این امر موجب شده که انتخاب و استفاده بهینه از پهناي باند امري مهم و یکی از مشکلات این صنعت گردد .با توجه به این مسئله روش هاي متعددي جهت استفادة بهینه از پهناي باند ارائه گردیده است در این مقاله به یکی از این روش ها که به کارگیري تکنیک هاي دسترسی به طیف به صورت دینامیک است می پردازیم . این تکنیک توسط سیستمی تحت عنوان رادیوي هوشمند صورت می گیرد . شبکه هاي متشکل از رادیوهاي هوشمند ، در برابر چالش هاي خاصی که ناشی از تغییرات شدید طیف در دسترس و همچنین کیفیت سرویس هاي مختلفی که کاربردهاي متنوع از آن ها انتظار دارند ، قرار دارند . در این مقاله ، ابتدا رادیوي هوشمند معرفی می شود ، سپس به بررسی چالش هاي موجود در ارتباط با مدیریت طیف در شبکه هاي متشکل از رادیوهاي هوشمند پرداخته خواهد شد
Optimizing the durability and service life of self-consolidating concrete[taliem.ir]

Optimizing the durability and service life of self-consolidating concrete containing metakaolin using statistical analysis

This paper utilizes the statistical design of experiments approach to optimize the mixture design of selfconsolidating concrete (SCC) incorporating metakaolin (MK). The factors studied were total binder content, percentage of MK, water-to-binder ratio, and curing conditions. The results obtained from the developed statistical models were exploited to determine the most significant factors affecting the chloride permeability and the expected service life (calculated using Fick’s second law of diffusion) of the tested mixtures. The developed models were also used to optimize the level of each response variable to minimize the chloride permeability, and to maximize the expected service life of the developed high performance SCC mixture. The results yielded an optimum SCC mixture with MK which achieved the lowest chloride permeability compared to counterpart SCC mixtures containing fly ash, slag, and silica fume. The results also showed that MK replacement proved to be the most significant variable affecting the chloride permeability, decline of permeability over time, and the service life of the tested mixtures
A simplified Nonlinear Sway-Rocking model for evaluation of seismic[taliem.ir]

A simplified Nonlinear Sway-Rocking model for evaluation of seismic response of structures on shallow foundations

This paper presents a simplified Nonlinear Sway-Rocking model as a preliminary design tool for seismic soil-structure interaction analysis. The proposed model is intended to capture the nonlinear loaddisplacement response of shallow foundations during strong earthquake events where foundation bearing capacity is fully mobilised. Emphasis is given to heavily-loaded structures resting on a saturated clay half-space. The variation of soil stiffness and strength with depth, referred to as soil non-homogeneity, is considered in the model. Although independent springs are utilised for each of the swaying and rocking motions, coupling between these motions is taken into account by expressing the loaddisplacement relations as functions of the factor of safety against vertical bearing capacity failure (FSv) and the moment-to-shear ratio (M/H). The simplified model has been calibrated and validated against results from a series of static push-over and dynamic analyses performed using a more rigorous finitedifference numerical model. Despite some limitations of the current implementation, the concept of this model gives engineers more degrees of freedom in defining their own model components, providing a good balance between simplicity, flexibility and accuracy.
Corrosion resistance of sintered[taliem.ir]

Corrosion resistance of sintered duplex stainless steel evaluated by electrochemical method

Purpose: of this paper was to examine the corrosion resistance of duplex stainless steels using electrochemical methods in 1M NaCl solution. The influence of powder mixes preparation and cooling cycle after sintering on corrosion properties was evaluated. Design/methodology/approach: In presented study duplex stainless steels were obtained through powder metallurgy starting from austenitic, martensitic base powders by controlled addition of alloying elements, such as Cr, Ni, Mo and Cu. In the studies behind the preparation of mixes, Schaeffler’s diagram was taken into consideration. Prepared mixes have been compacted at 800 MPa and sintered in a vacuum furnace with argon backfilling at 1260°C for 1 h. After sintering two different cooling cycles were applied: rapid cooling with an average cooling rate of 245 °C/min and slow cooling of 5 °C/min in argon atmosphere. Produced duplex stainless steels have been studied by scanning and optical microscopy and EDS chemical analysis of microstructure components. Corrosion properties have been studied through electrochemical methods in 1M NaCl water solution Findings: According to achieved results, it was affirmed that applied sintering method as well as powder mixes preparation allows for manufacturing the sintered duplex steels with good corrosion properties which depends on austenite/ferrite ratio in the microstructure and elements partitioning between phases. Corrosion resistance of sintered stainless steels is strictly connected with the density and the pore morphology present in the microstructure too. The highest resistance to pitting corrosion in 1M NaCl solution was achieved for composition with approximate balance of ferrite and austenite in the microstructure. Research limitations/implications: According to the powders characteristic, the applied fast cooling rate seems to be a good compromise for corrosion properties and microstructures, nevertheless further tests should be carried out in order to examine different cooling rates
Electrical discharge machining of ceramiccarbon nanostructure[taliem.ir]

Electrical discharge machining of ceramic/carbon nanostructure composites

The miniaturization of mechanical components with complex shapes is a great challenge in emerging applications. Silicon nitride (Si3N4) ceramics are excellent candidates for such applications due to their outstanding mechanical, thermal, and tribological properties. However, they are difficult to machine using normal mechanical machining methods. If the material were electrically conductive, electrical discharge machining (EDM) could be applied to produce precise and complex shapes. In this paper, in order to investigate the effects of electrical conductivity on the EDM characteristics, several carbon nanostructure composite materials are fabricated and EDMed using the assisting electrode method proposed by the current authors. The performance of the process is evaluated as a function of the carbon nanostructure content and type. The former is separately selected to be close to the electrical percolation threshold (0.9 vol.% and 5.3 vol.% for carbon nanotube (CNT) and graphene Nano platelet (GNP) composites, respectively), and well above that limit (5.3 vol.% and 20.6 vol.%), where electrical conductivities on the order of 10 and 100 S·m-1 are attained for CNTs and GNPs-based nanocomposites, respectively. In addition, bare Si3N4 specimens are also tested. Material removal rate, electrode wear ratio, and surface roughness of the machined pieces are analyzed for all testing conditions
A fuzzy control system of diesel generator speed[taliem.ir]

A fuzzy control system of diesel generator speed

Diesel generator, in which the generator is driven by the diesel engine to generate alternating current which frequency should keep stable and constant, is broadly used as mobile, urgent or field power sourc. The alternating current frequency is determined by the diesel speed. So the diesel speed should keep stable and constant too. This paper introduces two analogue control systems: rigid feedback and constant-speed feedback control system, and constructs a fuzzy control system of the diesel speed. Comparison of their control performances and practical applications indicate that the fuzzy control method is feasible and better than the others
Effects of Exercise Training on Outcomes[taliem.ir]

Effects of Exercise Training on Outcomes in Women With Heart Failure

The authors hypothesized that the women enrolled in the HF-ACTION (Heart Failure–A Controlled Trial Investigating Outcomes of Exercise TraiNing) trial and randomly assigned to exercise training (ET) would improve functional capacity as measured by peak oxygen uptake (VO2) compared with those in the usual care group