Browsing by Subject "Response surface methodology"

Now showing 1 - 4 of 4

Open Access
Cost-effective production of biological materials for food applications
(2012) Han, Diren
This thesis consists of two chapters; in the first chapter response surface optimization of the production of a potential probiotic strain was studied by using bioreactors and in the second chapter screening of biosurfactant producing microorganisms was carried out followed by the purification and characterization of the biosurfactant produced. Probiotics are live microorganisms that when administered in adequate amounts are favorable to their host. They are used on livestock to enhance the growth of animals, improve the efficiency of feed conversion and to decrease mortality rate. Therefore, it is important to produce these microorganisms in high amounts. However, process economics is a problem in large scale production of the microorganisms. Main factors that affect the process economics are the growth medium of the organism and the process conditions. Therefore, optimizing the composition of the growth media and cultivation conditions are of crucial importance in large scale production. In this study, optimization of growth media composition and cultivation conditions of a novel probiotic strain, Bacillus pumilus STF26, was done. Factors optimized were temperature, pH and the concentrations of dextrose as carbon source, yeast extract as nitrogen source, KH2PO4 and MgSO4.7H2O. Response surface methodology was used to optimize the parameter and the optimum values are found to be 30.9 °C, 6.9, 20 % (w/v), 1.526 % (w/v), 0.1 % (w/v) and 0.5 % (w/v) for temperature, pH and the concentrations of dextrose, yeast extract, KH2PO4 and MgSO4.7H2O, respectively. Maximum biomass at optimum conditions was 10.42 g/L which is nearly 2.5 times higher when compared to the one obtained by using LB medium at optimized temperature and pH values. In the second chapter, production and characterization of a biosurfactant produced by a novel strain of Staphylococcus xylosus, STF1, was studied. Biosurfactants are surface active agents that have a broad range of applications in different industries and they have several advantages over their chemically synthesized counterparts. However, they cannot compete economically with synthetic surfactants due to their high production cost, the difficulties in downstream processing and the lack of overproducing strains. In this study a novel strain that produces biosurfactant, STF1, was isolated and the biosurfactant was characterized by using mass spectrometry and Fourier transform infrared (FTIR) spectroscopy. FTIR results indicated the lipopeptide nature of the biosurfactant produced by this strain. Moreover, the mass of the purified biosurfactant was 931.9550 (m/z).
Open Access
Experimental and finite element analysis of EDM process and investigation of material removal rate by response surface methodology
(2013) Hosseini Kalajahi, M.; Rash Ahmadi, S.; Nadimi Bavil Oliaei, S.
In this study, thermal modeling and finite element simulation of electrical discharge machining (EDM) has been done, taking into account several important aspects such as temperature-dependent material properties, shape and size of the heated zone (Gaussian heat distribution), energy distribution factor, plasma flushing efficiency, and phase change to predict thermal behavior and material removal mechanism in EDM process. Temperature distribution on the cathode has been calculated using ANSYS finite element code, and the effect of EDM parameters on heat distribution along the radius and depth of the workpiece has been obtained. Temperature profiles have been used to calculate theoretical material removal rate (MRR) from the cathode. Theoretically calculated MRRs are compared with the experimental results, making it possible to precisely determine the portion of energy that enters the cathode for AISI H13 tool steel. Also in this paper, the effect of EDM parameters on MRR has been investigated by using the technique of design of experiments and response surface methodology. Finally, a quadratic polynomial regression model has been proposed for MRR, and the accuracy of this model has been checked by means of analysis of residuals. © 2013 Springer-Verlag London.
Open Access
Response of surface acoustic wave imaging systems to cylindrical inhomogeneities
(IEEE, 1988-10) Gunalp, N.; Baygun, B.; Surucu, F.; Atalar, Abdullah
The authors present a theory to predict the response of a SAW (surface acoustic wave) imaging system. In particular, they calculate the response to cylindrical cavities as a function of cavity position with respect to the focus point. The calculations indicated a high leak rate material will result in a better resolution in the y-direction. The theory also predicts an enhancement in the received signal level when the cylinder circumference equals the SAW wavelength. The images of cylinders obtained with such systems will indicate the size of the cylinders correctly at 20 dB below peak value as long as the cylinder diameter is larger than about a Rayleigh wavelength. For small cylinders the received peak amplitude can be used to determine the size of the cylinder.
Embargo
Systematic investigation of power enhancement of vertical axis wind turbines using bio-inspired leading edge tubercles
(Elsevier, 2023-02-17) Saddam ul Hassan, S.; Javaid, M.T.; Rauf, Umar.; Nasir, S.; Shahzad, A.; Salamat, S.
Wind energy is employed as an effective source for catering to the increasing energy demands and depleting fossil fuels, while also counteracting their adverse environmental effects. VAWTs have numerous advantages over HAWTs. But, the relatively low power coefficient of VAWTs in comparison to HAWTs restricts their utili zation. Bio-inspired leading-edge tubercles appear to be one of the potential design changes for enhancing the power performance of VAWTs. This study systematically investigated the relative influence of tubercle design variables and their geometrical trend subjected to power performance by employing a hybrid Design of Exper iments (DoE) approach and Response Surface Methodology (RSM) rather than choosing random values of tu bercle variables. Furthermore, the conflict existing in the literature about the improved or degraded power performance of VAWTS with tubercles is resolved by evaluating the power performance of VAWT at on-design and off-design conditions. For the computation of aerodynamic forces, unsteady Computational Fluid Dynamics (CFD) was utilized with a 4-equation transition SST turbulence model. Tubercle amplitude influences the aerodynamic efficiency of VAWTs relatively more than its wavelength. It is evident from the results that energy is harnessed efficiently at on-design conditions considering lower tubercle amplitude and higher wavelength. However, the reverse trend of variables is observed under off-design conditions. At on-design conditions, tu bercles degraded the VAWTs performance in comparison to baseline VAWT configuration by a minimum of 13.55% among the 14 hybrid DoE generated cases, while the performance was enhanced by a maximum of 55% at off-design conditions of VAWT