Sharif Digital Repository

Xanthan gum is a water-soluble exo-polysaccharide. It is produced industrially from carbon sources by fermentation using the gram-negative bacterium Xanthomonas campestris. There have been various attempts to produce xanthan gum by fermentation method using bacteria and yeast by using various cheap raw materials. In this study the cultural conditions for xanthan gum production by Xanthomonas campestris were investigated and optimized by response surface methodology, to maximize cell and xanthan production in batch experiments using YM broth without pH control. The individual and interactive effects of three independent variables (carbon source concentration (40-80 g/l), nitrogen source... 

Constructing bespoke software development processes according to the specifications of the project at hand has become a crucial issue, giving rise to a new branch of engineering known as Situational Method Engineering (SME). Compared with Software Engineering, Situational Method Engineering has not suitably matured, in that many of its deficiencies have not been properly addressed yet; SME approaches are especially deficient in support for modeling, portability, and automation.Model-Driven Development (MDD) has been effectively used for enhancing portability and automation in Software Engineering, and it is also considered as a promising approach for resolving the same issues in SME.... 

The present thesis has provided more fundamental understanding of granulation rate processes (such as coalescence, attrition and breakage) by investigating the effects of operating parameters on product properties. The studied process was wet granulation carried out in two high shear mixer granulators. Granulation duration, binder mass and impeller speed were considered as operating parameters and granule size distribution (measured by sieving) and granule binder distribution (measured by thermogravimetery method) were regarded as product properties. Experiments were conducted in two analogous cylindrical and conical high shear granulators. The obtained experimental and theoretical results... 

Selection of development methodologies according to the specifications of software development projects continues to be an important challenge for the software industry. Despite the growth of software methodologies, this problem has not been fully resolved yet. Software engineers have realized, however, that there is no general-purpose methodology which is suitable for all situations. Therefore, the necessity of Situational Method Engineering (SME) has become apparent, and engineers have started to use different methods for engineering software processes to fit the project situation at hand. Assembly-based, Extension-based and Paradigm-based approaches are the SME methods prevalently used... 

Software engineers have long realized that they cannot use existing methodologies for all project situations, as every software development project has its own specific characteristics. Therefore, a branch of software engineering–known as Situational Method Engineering (SME)–has emerged which helps develop bespoke methodologies to fit the specific characteristics of each and every project situation. As in software development, SME too involves rigorous Requirements Engineering (RE), so much so that if requirements elicitation and definition is botched in any way, methodology development will most likely fail as a result. In software engineering, requirements engineering has long been the... 

In this project, the feasibility of hydrocarbon waste water treatment with low concentration by physical- chemical treatment methods will be discussed. The purpose of this thesis is to investigate the feasibility of reusing the water outlet of the oil and gas refineries, in the region of ASALUYEH where there is an urgent need for water. By using activated carbon and wooden absorbent (absorption method) efficiency of this method was determined. Both coagulation and flocculation methods were investigated. To design and optimize various operating conditions on the adsorption process the RSM method was used. Temperature, residence time, feed concentration, amount of adsorbent, and adsorbent ... 

In order to increase the life-cycle of membrane filtration systems, energy efficient membranes are being developed in membrane bioreactor systems. Technology has been introduced which allows the power required to aerate the membrane for cleaning to be reduced whilst still maintaining a high flux level. Mechanical cleaning processes have also been adopted using granulates as an alternative to conventional forms of cleaning; this reduces energy consumption and also reduces the area required for filtration tanks.Membrane properties have also been enhanced to reduce fouling tendencies by modifying surface properties. This can be noted in the biotechnology industry where membrane surfaces have... 

In this study, the response surface methodology (RSM) based on the central composite design (CCD) were used to prepare a polypropylene grafted maleic anhydride (PP-g-MA) microporous flat sheet membrane via thermally induced phase separation (TIPS) method. Mixture of dibutyl phthalate (DBP) and dioctyl phthalate (DOP) were used as diluent. The effect of the polymer composition and coagulation bath temperature on the morphology and performance of the fabricated microporous membranes in a bioreactor (MBR) were investigated. Analysis of variance (ANOVA) was used to determine which variables and interactions between variables have a significant effect on our responses. The ANOVA revealed that the... 

Polychlorinated Biphenyls are a class of organic compounds that are composed of two biphenyl rings attached by 1-10 chlorine atoms. Due to their specific properties, such as physical and chemical stability, flame resistance, and dielectric properties, these compounds are used as dielectric liquids, heat-exchange fluids, hydraulic liquids, plastifiers, and especially as Askarel oil in power plant transformer. Because of their high persistency in the environment, high toxicity, and bioaccumulation in the adipose tissue of humans and animals, their production is banned in most countries, and their use has been limited. There are different methods for detoxification of these compounds, and in... 

Natural Boron consists of two stable isotopes, 10B (19.3%) and 11B (80.7%). 10B isotope has a large thermal neutron absorption and therefore, use widely in such aspects as modern industry, atomic energy industry (as control rods, chemical shim and etc.), Medical science and applications in disclosing neutrons to measure neutron reactors fluxes. Boron trifluoride is most importantly used as a reagent in organic synthesis, typically as a Lewis acid. In this study, we designed and built the related setup for preparation of high purity BF3 gas. And then we tried to optimize the efficiency with process design tools such as response surface methodology (RSM). At the end of this study, we were able... 

Environmental regulations with respect to the marine diesel emissions have become stricter during recent years, thereby imposing traffic limitations on Iranian ships preventing them to enter emission control areas. Nitrogen oxides (NOx), as one of most important air pollutants, have adverse impacts on public health and ecosystem, so as the ships are the primary source of NOx internationally, the after-treatment system finds more urge to be developed. In this study, a NOx reduction system using non-thermal plasma technology is studied in order to determine its application and efficiency for NOx removal from the exhaust gas of Iranian marine diesel engines. Meanwhile, important factors were... 

In the recent years, the world has been faced with a spectacular increase in variety and usage of electronic and electric devices. Unfortunately, the highly increasing march of technology reduces the time of their usage, causing a high degree of electric and electronic waste. Nonetheless, these E-waste enjoys a high percentage in precious metals such as Cadmium, Copper, Nickle, Zinc, Barium, Beryllium, Aluminum, Gold, Silver, Platinum, and so forth. With this in mind, they can be named as “secondary mines”, enjoying higher in degree of these metals even than natural mines. Therefore, extraction and recovery of the very metals are of great importance. Nowadays, using microorganisms in order... 

The aim of this thesis is experimentally and numerically investigation of annular flow between the inner rotating smooth surface and the outer stationary grooved surface with or without axial fluid flow. Mounting grooves on the surfaces is important in cooling of rotating machineries such as electric generators and rotating heat pipes. The effect of different parameters such as the air gap between the surfaces, the geometry of the grooves, axial flow and rotation speed are numerically and experimentally investigated. The experimental results with axial grooves show that the entrance length decreases up to 17% with increasing the grooves depth. The reason is enhancement of the mixing and the... 

In this study, lyophilized advance platelet rich fibrin (A-PRF) was used in combination with collagen membrane for the first time to accelerate bone regeneration as a result of growth factor release. Firstly, collagen was extracted from calf skin and analyzed using SDS-PAGE. FTIR has shown that EDC/NHS were chemically crosslinked collagen to collagen and collagen to chitosan. The morphology of collagen, collagen/chitosan composite membrane with different chitosan content, lyophilized A-PRF attached to membrane were showed using SEM images. The pore sizes were varied from 100 to 300 µm. Response surface methodology (RSM) was used to design experimental condition and to correlate the effect... 

This study aims to investigate the influence of important operational parameters on membrane fouling with the approach of fouling layers and to model these influences in the membrane bioreactor (MBR) for municipal wastewater treatment. At the first phase, 11 operational scenarios were executed using a pilot setup for identifying the system behavior and the optimal scenario. Protein and carbohydrate as the fouling components (SMP) and the transmembrane pressure (TMP) as the fouling criteria were measured in the tests. By studying the influence of operational parameters (sludge retention time (SRT), aeration rate and filtration mode), some useful results obtained for the next phase, including... 

Accumulation of electronic wastes in the environment is one of the recent ecological problems. This type of wastes contain metallic and non-metallic elements which can contaminate the environment. On the other hand due to the high volume of precious and basic metals within e-waste, it could be considered as a secondary resource. Bioleaching is a suitable method for the recovery of metals from e-waste which, on the contrary to the conventional recycling methods in the industry, is both economically and ecologically efficient. The aim of this research is the isolation of native micro-organism and evaluating its ability in recovering copper from a mixture of computer, cellphone, fax and copy... 

In this study, we investigate the effect of adding potassium persulfate (PDS) (K2S2O8) and hydrogen peroxide (H2O2) to E.coli (as a model microorganism) photocatalytic removal system in the presence of the TiO2-P25 as photocatalyst and UV irradiation. In this regard, the PDS and H2O2 oxidants were added separately in the different levels of pH and photocatalyst loading under UV irradiation. The experimental points were determined based on the central composite design (CCD) and in order to study the main and the interactive effects of the photocatalyst concentration (mg/L), oxidant concentration (mg/L) and the pH on the final concentration of E.coli (cfu/mL), a response surface model (RSM)... 

Vitamin C is one of the essential ingredients for the survival of human beings, animals and plants. This vitamin is an ester that in its structure there is a cyclic ester, an alkene Factor (C = C) and four hydroxyl factor (OH). This vitamin is a white solid, water-soluble and non-toxic that exists in many fruits, especially citrus. Its presence in the diet of human resistance them against infections increases. The main factor causing acidic property in vitamin C is the presence of OH groups attached to the alkene. Various forms of vitamin C exists in pharmaceutical collection of European countries. Since the tablet form because of the many advantages including being economical compared with... 

Software Reuse, the use of (pre)existing artifacts to create new systems, can reduce development costs and improve software quality and productivity. With a primary investment, Software Product Line facilitates a systematic reuse of the common parts of an specific domain in developing similar systems of that domain. On the Contrary, Agile Methods who value working software over comprehensive documentations and such investments is not done, lack reuse in developing similar systems. Here the question arises: why do we completely or almost miss such reuse when the only focus is on creating working software? When such investments or additional works like documentation are not done? Is there any... 

The term “scientific naturalism” is the invention of Thomas H. Huxley. He used it to describe a philosophical outlook that shunned the supernatural and adopted empirical science as the only reliable basis of knowledge about the physical, social, and moral worlds. Recent decades have witnessed a flurry of philosophical activity in the name of naturalism. Most contemporary philosophers identify themselves as naturalist, and much recent work in philosophy can be seen as part of general trend toward conducting philosophical inquiry under the umbrella of naturalistic assumptions. Today the label “naturalism” refers to a particular worldview. Nevertheless, naturalism is not a clearly defined...