Sharif Digital Repository

This Regular evaluation and analysis of river quality helps accurate management to reach acceptable quality. In this study, water quality indices (WQI) method applied to evaluate quality of Jajrood River which is one of the main sources of Tehran drinking water. It helps to subsidize management actions in Jajrood watershed. Sampling carried out for 9 years during 2001-2010 in 10 stations along the river in wet and dry stations to identify water quality and the main source of pollution. Results show water quality in all stations classifies as medium according to National Sanitation Foundation (NSF) and water quality index in wet season is better than the corresponding value in dry seasons.... 

Attitude determination for underwater vehicles in control and navigation applications has been always an important issue. MEMS-based accelerometer and gyroscope data can be usually used to determine the underwater vehicle attitude. However, the gyroscope sensors suffer from bias problem and the accelerometer data is not reliable in the presence of the external acceleration for the attitude determination. Therefore, data fusion for these two sensors is used to determine the attitude. But it should be noted that the common fusion algorithm does not perceive some special maneuvering accelerated motions and the use of accelerometer data causes a mistake in determining the Euler angles in these... 

KMnO4 oxidation combined with polyelectrolyte (K530CF) flocculation was investigated to mitigate membrane fouling in a membrane bioreactor. The optimum dosages of chemical additives in order to enhance the removal of soluble microbial products (SMPs) were determined. This method was able to reduce the concentration of COD in the effluent to 57.1% and 51.1% lower than those in the experiments in the absence of chemical flocculants and in the presence of polyelectrolyte, respectively. NH3-N removal was improved by combining KMnO4 and K530CF. When KMnO4 was used along with polyelectrolyte, the zeta potential was neutralized to a greater extent which resulted in an improvement in the... 

Wettability is a key parameter affecting petrophysical properties of reservoir rocks. Mirzaei-Paiaman et al. (Energy Fuels 27:7360–7368, 2013) presented an index (referred to as MPMS) for laboratory characterization of wettability of native- or restored-state reservoir rock samples. To use this index two counter-current spontaneous imbibition (COUCSI) experiments are needed, one on the native- or restored-state core sample and another on the strongly water-wet (SWW) reference system. Slope analysis of recovery data in these two systems gives inputs for determination of MPMS index. The two systems must have the same pore structure, initial water saturation, and viscosity ratio. The case of... 

High mixing efficiency that is of great importance in various industrial processes is a significant feature of spinning disk reactors. This work was focused on the characterization of mixing in a new reactor called Double Spinning Disk Reactor (DSDR) by adopting a competitive parallel reaction system known as iodide–iodate test reaction. The proposed DSDR consists of two coaxial rotating disks that the feeds are introduced into the gap between them. The mixing improves with an increase in the rotational speed of the disk, the radial distance of the feed introduced through the lower disk, and its number of feed points, while an increase in each of the feed flow rate and the distance between... 

High mixing efficiency that is of great importance in various industrial processes is a significant feature of spinning disk reactors. This work was focused on the characterization of mixing in a new reactor called Double Spinning Disk Reactor (DSDR) by adopting a competitive parallel reaction system known as iodide–iodate test reaction. The proposed DSDR consists of two coaxial rotating disks that the feeds are introduced into the gap between them. The mixing improves with an increase in the rotational speed of the disk, the radial distance of the feed introduced through the lower disk, and its number of feed points, while an increase in each of the feed flow rate and the distance between... 

A series of UiO-66/polyaniline (UiO-66/PANI) nanohybrids with various UiO-66 to aniline weight ratios ranging from 0.01 to 0.1 was synthesized using an in situ polymerization technique. The adsorption behavior of the neat PANI nanofiber network and the synthesized nanohybrids was examined toward anionic methyl orange (MO) dye from aqueous media. It was realized that the maximum adsorption capacity of PANI (229 mg/g) increases steadily by increasing the UiO-66 content in the nanohybrid up to 7 wt % at 426 mg/g, and then, it approximately levels off at 432 mg/g for the nanohybrid sample containing 10 wt % UiO-66, that is, UP10. Based on a thorough characterization, it was shown that UiO-66 is... 

Injection locked frequency dividers (ILFD) are used for frequency division to reduce the overall power consumption. By injecting a high frequency signal to an LC oscillator, injecting signal gets synchronous with oscillator output. All ILFDs analysis reports are based on steady state solution when locking is reached. At the same time, it is important to consider transient analysis too. In this paper a simple model is developed to study phase transient analysis when injecting signal is small in amplitude. This model can be used for large signal injection as a good approximation  

A very low power CMOS, 1.5V, 2.5GHz prescaler was designed. Implemented in 0.25u standard CMOS technology, this prescaler can operate up to 3GHz range. The prescaler consists of three delay flip flops (DFF) that work synchronously with RF sinusoidal clock and divides by 4 or 5 according to control signal  

A 5GHz, 1.5 Volt and low power CMOS frequency synthesizer with LC-tuned VCO (voltage controlled oscillator) is presented. The synthesizer consists of an LC-tuned VCO, an injection-lock frequency divider, a very low power prescaler which brings 2.5GHz range frequency to 11 MHz, a phase-frequency detector and charge-pump with improved architecture. Spiral inductors with Q-factor of 9 are used for the LC-tuned 5 GHz VCO. A fixed 2 frequency divider based on injection-locking phenomenon is used to bring 5 GHz VCO frequency to 2.5GHz. Both VCO and injection-locked divider's oscillators are tuned with NMOS varactors with their bodies are grounded, resulting in about 700 MHz tuning range.... 

We use concepts to make distinctions. Blurring these distinctions results in conflations. So, they are commonly seen as vicious. The claim here is that, by contrast, conflations are virtuous because they can do cognitive work. They enrich our conceptual resources. It is not conflation per se that is destructive but the lack of evaluation. Committing a conflation requires two cognitive acts at once. First, keeping things together and, second, appreciating the gap between them. Conflation thus has a family resemblance with notions like analogy and metaphor. Despite their apparent difference, a shared trait is recognizable in this family: the simultaneous maintenance of similarity and... 

Introduction: Water is consumed in almost all industries. Consequently the used water is turning to a waste that usually should be treated to meet the regulated standard level prior to reuse or discharge into the environment. Cutting oil wastewater is an emulsion normally comprised ofl-10% oil and the remainder water. The main functions of this oil in industry are lubrication, friction reduction, and cooling of instrument s parts. This wastewater is classified as a toxic waste according to the existence of some additive material to prevent corrosion and bacterial growth. Breakage of the emulsion and separation of the water and the oil can alone reduce more than about 90% of the aqueous phase... 

In this experimental study, a kinetic model has been developed for Fischer-Tropsch synthesis reactions by using sol-gel technique and Fe/Ni/Al 2O 3 as the catalyst (40% Fe/60% Ni/40 wt.%Al 2O 3) in a differential fixed-bed micro reactor assuming no internal or external diffusion. Operating conditions of the reactor were as follows: total pressure 1-12 atm; Temperature 220-260 °C; H 2/CO feed ratio 1.5-2; gas hourly space velocity 2100-7000 cm 3(STP)/h/ g cat and conversions of 6-37% of hydrogen and 7-21% of carbon monoxide. Mass transfer limitations were investigated by changing synthesis gas velocity in reactors which differ in size. Based on the hypothesis that water inhibits the intrinsic... 

Fiber optic sensors have emerged as a promising technology for precise measurements in various applications. In this study, we propose an integrated all-fiber Cascade Fabry–Perot (CFP) sensor that uses the harmonic Vernier effect to enhance its sensitivity. The sensor consists of a Silica Capillary Tube (SCT) fusion spliced to a Single-Mode Fiber (SMF), and its cavity length is optimized to locate Vernier's internal envelopes for three different Vernier harmonic orders within the spectral range of 1500 nm–1600 nm. Three CFPs were fabricated and utilized as strain and temperature sensors. By analyzing and tracing Vernier's internal envelopes, we experimentally demonstrated that sensitivity... 

In software programs, most of the time, there is a chance of error, even though they are tested carefully. Finding error-related pieces of code is one of the most complicated tasks and it can make incorrect results if done manually. Semi-automated and fully-automated methods have been introduced to overcome this issue. The rapid growth of developing Smart Mobile Applications (SMAs) in recent years, competition among the development teams and many other factors have increased the chance of errors, and hence, the quality of these applications have reduced. There are two approaches to test SMAs in order to reach a high degree of quality: (i) using existing traditional methods and adapting them... 

In software programs, most of the time, there is a chance for occurrence of faults in general, and exception faults in particular. Localizing those pieces of code that are responsible for a particular fault is one of the most complicated tasks, and it can produce incorrect results if done manually. Semi-automated and fully-automated techniques have been introduced to overcome this issue. However, despite recent advances in fault localization techniques, they are not necessarily applicable to Android applications because of their special characteristics such as context-awareness, use of sensors, being executable on various mobile devices, limited hardware resources, etc. To this aim, in this... 

In software programs, most of the time, there is a chance for occurrence of faults in general, and exception faults in particular. Localizing those pieces of code that are responsible for a particular fault is one of the most complicated tasks, and it can produce incorrect results if done manually. Semi-automated and fully-automated techniques have been introduced to overcome this issue. However, despite recent advances in fault localization techniques, they are not necessarily applicable to Android applications because of their special characteristics such as context-awareness, use of sensors, being executable on various mobile devices, limited hardware resources, etc. To this aim, in this... 

Abstract: Transient liquid phase (TLP) bonding of 304L austenitic stainless steel was carried out using MBF-20 interlayer at 1070 °C with different holding times. The effect of bonding time on the microstructure and corrosion resistance of the TLP bonded samples was investigated aiming to obtain the optimal bonding time. The results showed that isothermal solidification was completed within 45 min at 1070 °C and shorter holding times gave rise to the formation of intermetallic compounds at the joint centerline. It was found that the solidification sequence in the joint region is as follows: (1) isothermal solidification of γ solid solution, (2) formation of ternary eutectic of γ + Ni boride...