Sharif Digital Repository

In this research, Linear Amplitude Sweep (LAS) test was conducted on several asphalt binders modified by different percentages of gilsonite and Styrene-Butadiene-Styrene (SBS) polymer. Asphalt mixtures were also made from some of the study binders and tested for fatigue resistance using Four-point Bending Beam (FBB) fatigue test. The results showed that a strong correlation exists between LAS and FBB rankings at all the tested strain levels. Also, SHRP binder fatigue index (G∗sinδ), as a traditional binder fatigue index, was evaluated which did not show a strong correlation with either LAS or FBB tests. It was concluded that LAS test seems to be an effective binder fatigue test in predicting... 

JML is a behavioral interface specification language which has Java as its target implementation language. It combines the idea of using Java expressions from Eiffel language with the model-based approach to specify a program. Refinement calculus is a framework to produce executable code from a specification by preserving the correctness of programs. In this paper some constructs of JML concerning object creation, feature call, exceptional behavior and concurrency constructs are studied and some refinement rules are proposed to obtain an object oriented code in Java from a JML specification containig these constructs. The correctness of these rules is proved by weakest precondition predicate... 

In this study, SiC/Ti–Cu nanocomposite was fabricated by mechanical alloying and sintering process. Effects of SiC nano-reinforcement on phase transformation, microstructure and tribological and antibacterial properties Ti–Cu intermetallic alloy were studied. The microstructure of the powders and sintered materials was investigated using X-ray diffraction, and scanning/transmission electron microscopy. The results exhibited the formation of major TiCu and TiCu 4 , and minor Ti 2 Cu and Ti 2 Cu 3 nanocrystalline phases in the sintered Ti–Cu and SiC/Ti–Cu samples. With the addition of the nanoparticles, the amount of TiCu 4 phase increased. Reinforcing Ti–Cu intermetallic alloy by SiC... 

The demands for high-performance biomaterials are driving the development of new metallic alloys with improved mechanical and biological responses. In this study, a nanocrystalline Ti-Cu intermetallic alloy was prepared by a powder metallurgy route, and its application as an orthopedic material was evaluated by the microstructural, mechanical, corrosion, antibacterial, cytotoxicity and osseointegration examinations. Microstructural characterization revealed the formation of TiCu and Ti2Cu3 as major phases with 23 nm grain size in the structure of the alloy. The synthesized alloy exhibited ultra-high hardness of 10 GPa, acceptable toughness of 8.14 MPam1/2, a ∼98 % anti-bacterial rate against... 

Effects of SiC nanoparticles addition on synthesis and antibacterial properties of TiCu nanocrystalline powder prepared through high energy mechanical milling were studied. The results showed that the synthesis of TiCu powder in the presence of the nanoparticles was accelerated and after mechanical alloying for 20 h, a TiCu/SiC nanocrystalline powder with the crystallite size <5 nm, and 3.3% lattice micro-strain obtained. Further milling resulted in fully amorphous TiCu intermetallic alloy with more uniform distribution of SiC nanoparticles. The antibacterial activity of the synthesized powders was investigated by disk diffusion test. The TiCu/SiC nanocomposites showed enhanced antibacterial... 

This paper considers the Gaussian multichannel binary detection problem. A multichannel generalized likelihood ratio (GLR) is presented using a model-based approach where the signal and its amplitude are known and additive noise is characterized by autoregressive (AR) vector processes which can be a suitable model for ground clutter in most scenarios involving airborne surveillance phased array radar. The detector can use secondary vectors to improve its performance. Although, in our model, the amplitude of signal must be known, but according to its excellent performance, an approximation of GLR on the amplitude is also presented. The detector performance in various conditions and the result... 

An on-line extraction/determination set up was designed for micro solid-phase extraction of clodinafop propargyl from water, soil and wheat samples using electrospun polyamide nanofiber mats. The prepared mats were packed in a stainless steel tube which conveniently acted as a high-performance liquid chromatography injection loop. Influential parameters affecting the extraction efficiency were optimized using a distilled water sample fortified with 25 μg L-1 of clodinafop propargyl. An enrichment factor of 440 was achieved for clodinafop propargyl indicating the ability of the whole procedure. Under the optimum conditions, the linearity for the analyte was in the range of 6-700 μg L-1, while... 

The present work deals with a novel approach for grafting a sol-gel based sorbent, using diazonium salts for preparation of an unbreakable capillary microextraction (CME) device in on-line combination with high performance liquid chromatography (HPLC). The use of diazonium salts modifier allowed all types of metallic and non-metallic substrates to be used without any limitation. Substrates including copper, brass, stainless steel and polytetrafluoroethylene (PTFE) were chosen to be functionalized by chemical or electrochemical reduction of 4-amino phenyl acetic acid. Then, 3-(trimethoxysilyl)propylamine (3TMSPA) was selected as the precursor and the only reagent for preparation of the... 

HF radar systems are widely used for the measurement of ocean surface currents and wave parameters. Theoretical analysis of high frequency radio wave backscattering from the sea has been derived in the past. Also, the relationship between Bragg frequencies and surface currents is determined and has been proved by HF radars. It is known that when surface currents are present, the Bragg frequencies move to new frequencies. Their movement is proportional to the surface current in the direction toward radar. In addition, it is observed that sea surface current changes the second order part of the spectrum of radar reflection from the sea surface. In this paper, a theoretical analysis of... 

In this paper, ultra-small CuO nanoparticles (NPs) were synthesized through a mechanochemical method using two different Cu-containing precursors (i.e. CuSO4·5H2O and CuCl2·2H2O), and their structure and antibacterial activity were studied. From the microstructural studies, it was observed that CuO NPs have a spherical morphology and a narrow size distribution with 7 and 14 nm median particle sizes for CuCl2·2H2O and CuSO4.5H2O precursors, respectively. The CuCl2·2H2O derived nanoparticles showed more antibacterial activity than CuSO4.5H2O derived nanoparticles. The minimum inhibitory concentration (MIC) of the synthesized nanoparticles (derived from both precursors) against E. coli and... 

In this study, organic aerogels were synthesized by the sol-gel polycondensation of mixed cresol with formaldehyde in a slightly basic aqueous solution. Carbon aerogels and xerogels are generated by pyrolysis of organic aerogels. The novel sol-gel-based micro-solid-phase extraction sorbent, resorcinol-formaldehyde xerogel, was employed for preconcentration of some selected herbicides. Three herbicides of the aryloxyphenoxypropionate group, clodinafop-propargyl, haloxyfop-etotyl, and fenoxaprop-P-ethyl, were extracted from aqueous samples by micro-solid-phase extraction and subsequently determined by gas chromatography with mass spectrometry. The effect of different parameters influencing the... 

An attempt was made to combine μ-solid phase extraction and headspace single drop microextraction techniques and use their advantages for trace determination of some volatile organic compounds in aqueous samples. After performing the two-step preconcentration approach, the desired analytes were determined by gas chromatography-mass spectrometry. A resorcinol-formaldehyde-based xerogel was used as the extraction medium in the μ-solid phase extraction (μ-SPE) method. Then, the extracted BTEX was eluted with a rather large amount of methanol. To remove the laborious process including solvent evaporation and further reconstitution, which is usually accompanied by loss of analytes and accuracy,...