Electrohydrodynamic Enhancement of Heat Transfer and Mass Transport in Gaseous Media, Bulk Dielectric Liquids and Dielectric Thin Liquid Films

Controlling transport phenomena in liquid and gaseous media through electrostatic forces has brought new important scientific and industrial applications. Although numerous EHD applications have been explored and extensively studied so far, the fast-growing technologies, mainly in the semiconductor industry, introduce new challenges and demands. These challenges require enhancement of heat transfer and mass transport in small scales (sometimes in molecular scales) to remove highly concentrated heat fluxes from reduced size devices. Electric field induced flows, or electrohydrodynamics (EHD), have shown promise in both macro and micro-scale devices. Several existing problems in EHD heat transfer enhancements were investigated in this thesis. Enhancement of natural convection heat transfer through corona discharge from an isothermal horizontal cylindrical tube at low Rayleigh numbers was studied experimentally and numerically. Due to the lack of knowledge about local heat transfer enhancements, Mach-Zehnder Interferometer (MZI) was used for thermal boundary layer visualization. For the first time, local Nusselt numbers were extracted from the interferograms at different applied voltages by mapping the hydrodynamic and thermal field results from numerical analysis into the thermal boundary layer visualizations and local heat transfer results. A novel EHD conduction micropump with electrode separations less than 300 µm was fabricated and investigated experimentally. By scaling down the pump, the operating voltage was reduced one order of magnitude with respect to macro-scale pumps. The pumping mechanism in small-scales was explored through a numerical analysis. The measured static pressure generations at different applied voltages were predicted numerically. A new electrostatically-assisted technique for spreading of a dielectric liquid film over a metallic substrate was proposed. The mechanism of the spreading was explained through several systematic experiments and a simplified theoretical model. The theoretical model was based on an analogy between the Stefan’s problem and current problem. The spreading law was predicted by the theoretical approach and compared with the experimental results. Since the charge transport mechanism across the film depends on the thickness of the film, by continuing the corona discharge exposure, the liquid film becomes thinner and thinner and both hydrodynamic and charge transport mechanisms show a cross-over and causes different regimes of spreading. Four different regimes of spreading were identified. For the first time, an electrostatically accelerated molecular film (precursor film) was reported. The concept of spreading and interfacial pressure produced by a corona discharge was applied to control an impacting dielectric droplet on non-wetting substrate. For the first time, the retraction phase of the impact process was actively suppressed at moderate corona discharge voltages. At higher corona discharge strengths, not only was the retraction inhibited but also the spreading phase continued as if the surface was a wetting surface

High pressure injection technique for hypochlorite treatment of polysulfone hollow fibre membranes

High pressure injection technique for hypochlorite treatment of polysulfone hollow fibre membranes has been developed. This technique allows injection of the hypochlorite solution into the channel of the fibres at a high pressure. The effect of this treatment on water flux of the membranes is studied. The results are compared with the water flux of identical membranes subjected to traditional hypochlorite treatment. Concentrated polymer solution containing polysulfone (PSf) /poly-vinyl pyrrolidone (PVP-K90)/N-Methyl-2-pyrrolidone (NMP) in weight ratio of 15/5/80 together with two types of bore fluids have been used for the production of two types of hollow fibre membranes via dry-wet-spinning process. Distilled water and mixture of NMP/ distilled water are used as bore fluids. Atomic force microscopic analysis and image processing technique (SEM microphotographs) have been employed to investigate performance of PSf hollow fibres treated with the traditional and high pressure injection techniques in relation to the composition of bore fluid. It is observed that in general both treatment methods result in the increase in water flux of the hollow fibres due to elimination of PVP (poly-vinyl pyrrolidone) swelling and alteration in pore size and pore distribution. The rate of increase in water flux in the membranes treated by high pressure injection technique is found to be higher in comparison to traditionally treated membranes. It is also found that the membranes produced using a mixture of NMP/ distilled water as bore fluid exhibit a higher rate of flux increase than those produced using distilled water. High pressure injection technique yields to production of highly permeable membranes. In addition, it is found that the composition of bore fluid controls the performance of the membranes subjected to hypochlorite treatment

Torque Ripple Minimization for a Permanent Magnet Synchronous Motor Using a Modified Quasi-Z-Source Inverter

This paper presents a torque ripple minimization method for a permanent magnet synchronous motor (PMSM) drive system that utilizes a modified quasi-Z-source (qZS) inverter. The proposed modified qZS network is designed by adding an extra switching device to the conventional qZS topology and provides a wider range of capabilities for inverter input voltage control, e.g., both step-up and step-down operations. It also allows for modification of the traditional switching sequence selection scheme when using the space vector modulation (SVM) for switching. The provided flexibilities are leveraged to develop a control system that minimizes the torque ripples during PMSM operation while satisfying conventional control objectives such as shaft speed control. The control system is comprised of an input voltage optimization subsystem with the goal of torque ripple minimization, which provides the reference for a cascaded modulated model predictive control subsystem for the modified qZS network control, and a motor side predictive control subsystem. The control system employs a new switching sequence selection scheme for SVM modulation to further reduce PMSM torque ripples. Experimental results are provided to validate the theoretical outcomes

A study on the role of relational information processes and technology usage in customer relationship management(CRM) in the State Tax Organization (Case study: Tehran office of VAT)

This study deals with the role of relational information processes and technology usage in customer relationship management CRM in The State Tax Organization. It is based on the applied design and for the nature of the data collection, it is descriptive. The population of this study consists of experts in General Dept. of VAT in Tehran. Random sampling was used for selecting the data after considering Morgan – Kerjesi table. For data analysis, the structural equation model and path analysis was used in particular.The results showed that customer orientation is associated with the use of technology of CRM and customer management system based on relational data processing, environment technology of environment, and using the customer contact technologies. CRM has a significant positive impact on customer relationship performance. Also, there is no meaningful effects by the orientation of customer relationship on relational data processing, and Customer Management System CRM on the usage, CRM technology, the environment dynamics, the information processing relational and relational data processing, and the performance of customer relationships

A study on the role of relational information processes and technology usage in customer relationship management(CRM) in the State Tax Organization (Case study: Tehran office of VAT)

This study deals with the role of relational information processes and technology usage in customer relationship management CRM in The State Tax Organization. It is based on the applied design and for the nature of the data collection, it is descriptive. The population of this study consists of experts in General Dept. of VAT in Tehran. Random sampling was used for selecting the data after considering Morgan – Kerjesi table. For data analysis, the structural equation model and path analysis was used in particular.The results showed that customer orientation is associated with the use of technology of CRM and customer management system based on relational data processing, environment technology of environment, and using the customer contact technologies. CRM has a significant positive impact on customer relationship performance. Also, there is no meaningful effects by the orientation of customer relationship on relational data processing, and Customer Management System CRM on the usage, CRM technology, the environment dynamics, the information processing relational and relational data processing, and the performance of customer relationships

The Efficacy of the Ketogenic Diet in Improving Seizures and EEG Findings in Patients with Refractory Infantile Spasms

Abstract ObjectivesInfantile spasm is an epileptic disorder of early childhood and infancy and is characterized by cluster epileptic spasms and abnormal EEG findings. Developmental delay is prevalent. Some studies haveindicated the significant effect of the Ketogenic Diet (KD) on intractable spasms in children who are unresponsive to first-line treatments. It has been used successfully as a first-line treatment withfewer side effects than ACTH.Materials & MethodsThis was an interventional study in which the effectiveness of KD over a six-month period was evaluated in patients with infantile spasms. Those who fulfilled the inclusion criteria and were willing touse the diet received free cans of the 4:1 ketogenic formula. The diet was prescribed based on the Johns Hopkins protocol in the outpatient setting. All patients used a full formula diet for one month. After a month, the patients were examined by a neurologist and a dietitian, and an EEG was obtained to compare pre- and post-KD findings. In order to compare pre- and post-KD seizures, the maximum number of seizures was multiplied by the longest duration of seizures ResultsTen patients were assessed for one month. Using the KD led to significant changes in seizures/clusters and EEG findings. Nine parents reported improvement in their children’s social interactionsafter using the KD. ConclusionBased on the findings of this study, the KD can control seizures in patients suffering from infantile spasms by reducing seizure frequency & duration and improving EEG finding

RF Receiver front end for 28.5 GHz applications on a 70 GHz F-T SiGe BiCMOS process

This article presents the design and test of a receiver front end aimed at LMDS applications at 28.5 GHz. It presents a system-level design after which the receiver was designed. The receiver comprises an LNA, quadrature mixer and quadrature local oscillator. Experimental results at 24 GHz center frequency show a conversion voltage gain of 15 dB and conversion noise figure of 14 5 dB. The receiver operates from a 2 5 V power supply with a total current consumption of 31 mA

Assessment of genetic diversity in late flowering almond varieties using ISSR molecular markers aimed to select genotypes tolerant to early spring frost in Yazd province

The genetic diversity of 19 late flowering almond genotypes in Yazd province were assessed using ISSR markers. 10 selected ISSR primers revealed 101 polymorphic bands among which the 5`-G(AG)7ASG-3` with 17 and 5`-A(GA)7GSC-3` with 3 bands had the most and the least polymorphic bands respectively. In principal component analysis the explanation of a minor part of the total diversity by few prior components as well as the distribution of total variance among different components, indicate the relevant scattering of the ISSR primers through the genome and the validity of ISSR data for the genetic analysis in almond germplasm. The most genetic similarity in cluster analysis was observed between the genotypes 88 and 191. The high genetic similarity between some genotypes may be caused by their common origin or the geographical similarity between their regions of cultivation and improvement. The transfer and translocation of these genotypes among different studied regions have been carried out frequently. The results of molecular analysis showed that almond varieties and genotypes that are collected from close geographical regions all over the Yazd province are of large genetic homogeneity and the overall polymorphism content in studied genomes is rather low. Considering the self-incompatible nature of the almond plants, it may be concluded that the domesticated genotypes and those cultivated in studied regions, have had little mixture with alien almond germplas