Estimation of thermal properties of randomly packed bed of silicagel particles using IHTP method

Accurate values of thermophysical transport properties of particle beds are necessary to accurately model heat and mass transfer processes in particle beds that under-go preferred processes and changes. The objective of this study is to use a proven analytical/numerical methodology to estimate the unknown transport properties within test cells filled with silicagel particles and compare the results with the previously published data. An experimental test cell was designed and constructed to carry out transient heat transfer tests for both step change conduction and convection heat transfer within a packed bed of silicagel particles. For a known step change in the test cell temperature boundary condition, the temporal temperature distribution within the bed during heat conduction depends only on the effective heat conduction coefficient and the thermal capacity of the particle bed. The central problem is to, using only the boundary conditions and a few time-varying temperature sensors in the test cell of particles, determine the effective thermal conductivity of the test bed and specify the resulting measurement uncertainty. A similar problem occurs when the heat convection coefficient is sought after a step change in the airflow inlet temperature for the test cell. These types of problems are known as inverse heat transfer problems (IHTP). In this thesis, IHTP method was used to estimate the convective heat transfer coefficient. Good agreement was seen in experimental and numerical temperature profiles, which were modeled by using the estimated convective heat transfer coefficient. The same methodology was used to estimate the effective thermal conductivity of the particle bed. Comparison between the experimental temperature distribution and numerical temperature distribution, which was modeled by using the estimated effective conductivity, illustrated good agreement. On the other side, applying the effective thermal conductivity, obtained from a direct steady state measurement, in the numerical simulation could not present agreement between the numerical and experimental results. It was concluded that the IHTP methodology was a successful approach to find the thermophysical properties of the particle beds, which were hard to measure directly

Evaluating delay factors in the construction and operation of port operational areas (case study: Shahid Rajaee port complex)

A significant part of the annual budget of developing countries is allocated to civil projects and the construction industry. In Iran, between 30% and 40% of the total budget of the country `is allocated to this industry. However, the implementation of these projects is often faced with several problems that cause delays and increase costs. The main objective of this research is to identify, analyze, and prioritize factors effective in delays in the construction of port operational area and to offer suggestions for preventing or reducing these delays. The statistical population of the study consists of employers,investors, consultants and contractors involved in the construction of port operational areas in Iran. Data were collected through a questionnaire and were then analyzed using structural equation modeling in VPLS software. Results showed the most effective factors of the delay in the construction of port operational areas to be inadequate monitoring(11%), poor planning and time scheduling (19%), improper allocation of resources (24%), cash flows changes(28%), failure to fund the projects on time (16%)and other factors (27%). These results can assist companies and legal authorities involved in the construction of port operational areas in Iran in making the right decisions based on the importance and effectiveness of each delay factor.Keywords: Delay Factors, Port Construction Projects, Project Management

Three dimensional image analysis for prediction of vinyl triethoxysilane concentration and porosity percent of methyl methacrylate/ethylene glycol dimethacrylate copolymers using scanning electron microscopy

In this work, scanning electron micrographs of copolymer beads based on methyl methacrylate (MMA), ethylene glycol dimethacrylate (EGDM) and vinyl triethoxysilane (VTES) were used to construct multivariate image regression models. Scanning electron microscopy (SEM) and swelling measurements indicated that increasing the silicone concentration (VTES) of the copolymers enhances the amount of pores and porosity percent. Scanning electron micrographs of the synthesized copolymers with different VTES concentrations were used to construct two soft models, which were able to relate the VTES concentration and the porosity percent of the copolymers with their SEM images. The constructed models were the three-way partial least squares analysis (N-PLS) and unfolded principal component regression (unfold-PCR). The predictive ability of the constructed models were evaluated by a test set. The results showed the models were able to effectively predict the VTES concentration and the porosity percent of the copolymers using their corresponding SEM images

Modeling of Free Radical Styrene/Divinylbenzene Copolymerization with the Numerical Fractionation Technique

The modeling approach called “numerical fractionation” has been incorporated into a PREDICI model to simulate crosslinking copolymerization. To take into account inhomogeneities of the considered copolymerization, the kinetic parameters of the model are proposed to be different for each generation of the numerical fractionation. Using this approach the chain-length dependence of termination has been incorporated into the model so that even the method of moments could be applied to study crosslinking copolymerization. The styrene/m-divinylbenzene crosslinking copolymerization at low content of crosslinker has been simulated. The chain-length dependence of termination has been found to accelerate the gel point in monovinyl/divinyl copolymerization and must be taken into account for correct description of the gel points

Large-Scale Mitochondrial DNA Analysis of the Domestic Goat Reveals Six Haplogroups with High Diversity

Background. From the beginning of domestication, the transportation of domestic animals resulted in genetic and demographic processes that explain their present distribution and genetic structure. Thus studying the present genetic diversity helps to better understand the history of domestic species. Methodology/Principal Findings. The genetic diversity of domestic goats has been characterized with 2430 individuals from all over the old world, including 946 new individuals from regions poorly studied until now (mainly the Fertile Crescent). These individuals represented 1540 haplotypes for the HVI segment of the mitochondrial DNA (mtDNA) control region. This large-scale study allowed the establishment of a clear nomenclature of the goat maternal haplogroups. Only five of the six previously defined groups of haplotypes were divergent enough to be considered as different haplogroups. Moreover a new mitochondrial group has been localized around the Fertile Crescent. All groups showed very high haplotype diversity. Most of this diversity was distributed among groups and within geographic regions. The weak geographic structure may result from the worldwide distribution of the dominant A haplogroup (more than 90% of the individuals). The large-scale distribution of other haplogroups (except one), may be related to human migration. The recent fragmentation of local goat populations into discrete breeds is not detectable with mitochondrial markers. The estimation of demographic parameters from mismatch analyses showed that all groups had a recent demographic expansion corresponding roughly to the period when domestication took place. But even with a large data set it remains difficult to give relative dates of expansion for different haplogroups because of large confidence intervals. Conclusions/Significance. We propose standard criteria for the definition of the different haplogroups based on the result of mismatch analysis and on the use of sequences of reference. Such a method could be also applied for clarifying the nomenclature of mitochondrial haplogroups in other domestic species

Numerical Modeling of Contrail Formation

In this study, I developed a numerical module to model contrail formation