Squeeze Flow of Highly Concentrated Suspensions

In this thesis we investigated through experiment and model, the anomalous normal stress distribution during constant-force squeeze flow of highly concentrated suspensions. Using pressure-sensitive films the normal stress distribution is measured in suspensions of glass spheres in a Newtonian liquid undergoing constant-force squeeze flow. At volume fractions of solids up to 0.55, the normal stress distribution is independent of volume fraction and almost identical to the parabolic pressure distribution expected for Newtonian fluids. However, at higher volume fractions, the normal stresses become an order of magnitude larger near the center and very low beyond that region. At these high volume fractions, the normal stresses decrease in the outer regions and increase in the inner regions as the squeezing proceeds. The normal stress distribution that results when the glass spheres without any fluid are subjected to squeeze flow is very similar to that for suspensions with volume fractions above 0.55, suggesting that the cause for the drastic changes in the normal stress distribution is the jamming of the particles in the suspension. The drastic changes in the normal stress distribution are explained in terms of the radial flow migration of the liquid phase away from the center of the sample and of the jamming that results from it. Experimental measurements show that changes in the volume fraction of solids due to liquid-phase migration are found to depend on the initial volume fraction of solids, the viscosity of the suspending fluid, and the size of the particles. Under some conditions, the volume fraction of solids remains essentially constant during the squeeze test, indicating that liquid-phase migration does not take place to any significant degree; however, under other conditions, the volume fraction of solids increases throughout the sample as the squeezing proceeds and liquid is expelled from the test region in preference to the solids. In these latter cases the concentration increases are largest toward the center of the samples. Criteria for the occurrence of liquid-phase migration in suspensions undergoing squeeze flow are discussed in terms of dimensionless groups. Liquid-phase migration is modeled numerically by taking into account the time and position dependence of the rheological properties of the material due to the change in the volume fraction of solids. This is done by coupling the equation of motion for a non-Newtonian material that approximates a Bingham plastic with a continuity equation that includes diffusive flux. The developed model is first validated with experimental data and then used to study the effect of various parameters on pressure-induced phase separation. Changes in the volume fraction of solids within the squeezed suspensions due to liquid-phase migration were found to depend on the degree of slip at the surfaces and on the applied force as well as on the material properties

Resonance of a rectangular plate influenced by sequential moving masses

In this work, an improved semi-analytical technique is adopted to track the dynamic response of thin rectangular plates excited by sequential traveling masses. This technique exploits a so-called indirect definition of inertial interaction between the moving masses and the plate and leads to a reduction, in the equations of motion, of the number of time-varying coefficients linked to the changing position of the masses. By employing this optimized method, the resonance of the plate can be obtained according to a parametric study of relevant maximum dynamic amplification factor. For the case of evenly spaced, equal masses travelling along a straight line, the resonance velocity of the masses themselves is also approximately predicted via a fast methodology based on the fundamental frequency of the system only

Favorable association between Mediterranean diet (MeD) and DASH with NAFLD among Iranian adults of the Amol Cohort Study (AmolCS)

Nonalcoholic fatty liver disease (NAFLD) is an emerging cause of chronic liver diseases and a major health problem worldwide. Dietary patterns may play a critical role in controlling and preventing this disease, but the available evidence is scarce. The current study aims to ascertain the association of adherence to the Dietary Approach to Stop Hypertension (DASH) diet and Mediterranean diet (MeD) with nonalcoholic fatty liver disease (NAFLD) among Iranian adults of the Amol Cohort Study (AmolCS). In a cross-sectional analysis among 3220 adults (55.3% men), age ≥ 18 years (46.96 ± 14.67), we measured usual dietary intake with a validated food frequency questionnaire (FFQ) and then calculated dietary pattern scores for DASH and MeD. Sociodemographic and lifestyle factors were collected by a structured questionnaire. The presence and degree of NAFLD were also determined by abdominal sonography. Multiple regression models were used to estimate NAFLD odds across tertiles of DASH and Mediterranean dietary scores. Dietary DASH and Mediterranean components were adjusted for total energy intake, based on the residual methods. After adjusting for multiple potential confounders, we found an inverse association of DASH and MeD with NAFLD (Ptrend = 0.02, and Ptrend = 0.002, respectively). Those in the highest tertiles of adherence to the DASH and MeD had the lowest risk for NAFLD (OR = 0.80, 95%CI = 0.66–0.96, OR = 0.64, 95%CI = 0.52–0.78, respectively). The results of logistic analysis of MeD, stratified by gender and abdominal obesity, revealed the favorable association was more pronounced in women (OR = 0.42, 95%CI = 0.29–0.61, Ptrend = 0.004), and in participants with or without abdominal obesity (OR = 0.62, 95% CI = 0.47–0.81, Ptrend = 0.03, OR = 0.64, 95%CI = 0.475–0.91, Ptrend = 0.04, respectively). Similar results were obtained for the adherence to DASH diet score with the prevalence of NAFLD patients with abdominal obesity (OR = 0.75, 95% CI = 0.57–0.97, Ptrend = 0.04). The findings suggested the favorable association between DASH and MeD with NAFLD in Iranian adults, especially women and subjects with or without abdominal obesity. Further prospective investigations are needed to confirm the integrity of our findings

Evaluation and Foresight of PhD Courses; Pllot Case in an Engineering Department

Universities train PhD graduates for themselves and industries of the knowledge-based economies of the future. This paper studies an engineering PhD course from graduates, faculty and the job market view points. Foresight methods for such courses is then introduced and applied to an engineering department. A discussion of the results show the need for stronger industrial contacts for PhD student

Simplified modeling of beam vibrations induced by a moving mass by regression analysis

In this paper, we propose a fast computation of beam-type dynamic response to a moving mass. Dynamics of a single-span beam is first accurately computed with a semi-analytical procedure based on characteristic orthogonal polynomials (COPs), in the case of a force or a mass traveling across. A regression analysis is then adopted to automatically define the effects of the moving mass once the effects of the moving force are known. Best-fitting multivariable correlation splines, with strictly given coefficients, are obtained. The provided correlation splines conveniently interpolate the maximum design parameters of the base beam over a wide range of load inertia and velocity. Results provided are valid for any geometry and elastic stiffness of the beam, thanks to a properly set normalization factor here defined. Hence, practitioners are provided with an effortless and highly simplified direct prediction of design parameters when inertial interactions are taken into consideration

Innovation and University

Public and private institutions today use organized innovation to achieve their development targets. Design of an innovation plan is the prime step to reach innovation at any university. This paper presents Amirkabir University of Technology innovation plan. This plan includes some specific features that are new to Iranian universities. First, it explains the innovation concept and management and their key components. Then it explores the role of universities in local, national and international innovation and growth. Finally it introduces the methodology, and elements of Amikabir University of technology innovation plan. The unique point in this article is that it utilizes group dynamic techniques at university level in order to devise an innovation plan that reflects the characteristics of Amirkabir University of Technology in particular and Iranian universities in general