Current Induced Vortex Wall Dynamics in Helical Magnetic Systems

Nontrivial topology of interfaces separating anti-chiral phases in helical magnets result in new effects as they interact with spin polarized current. These interfces or vortex walls consist of a one dimensional array of vortex lines. Topological Hall effect comes as a natural expectation. Also Lenz's law will result in a new damping mechanism in these systems. We study the dynamics of these wall interacting with electric current and use fundamental electromagntic laws to calculate this effect. On the other hand discrete nature of these walls affects their pinning and result in low depinning current density. We predict the value of this currnt using collective pinnng theory. Finally throughout this study we propose possible standard experiments that may distinguish our theoretical findings

Interaction-driven capacitance in Graphene electron-hole double layer in the quantum Hall regime

Fabrication of devices made by isolated Graphene or Graphene-like single layers (such as h-BN) has opened up possibility of examining highly correlated states of electron systems in parts of their phase diagram that is impossible to access in their counterpart devices such as semiconductor heterostructures. An example of such states are Graphene (or Graphene like) double layer electron-hole systems under strong magnetic fields where the separation between layers can be of the order of one magnetic length with interlayer tunneling still suppressed. In those separations correlations between electrons and holes are of crucial importance and must be included in determination of observable quantities. Here we report a thorough mean-field study of the coherent and crystalline ground states of the interacting balanced electron-hole Graphene systems in small and intermediate separations with each layer occupying up to four lowest lying Landau levels. We calculate the capacitance of such states as a function of layer separation and filling factor. Our calculations show significant enhancement of the capacitance compared to geometrical value due to quantum mechanical corrections.Comment: To be published in Physical Review

Integrated Strategies For Sustainable Wastewater-Based Algal Biofuel Production And Environmental Mitigation In The Us

Integration of algae cultivation with wastewater treatment has received increasing interest as a cost-effective strategy for biofuel production. However, there has been no full assessment of algal biofuel production with wastewater on macro-scale by taking into account wastewater resources, land availability, CO2 emission resources, and geographic variation. This research addressed and evaluated the use of wastewater for algae cultivation, in terms of modeling and laboratory experiments. The first goal of this research was to develop a spatially explicit lifecycle model, by integrating life cycle assessment (LCA), and Geographic Information Systems (GIS) analysis, for the evaluation of the environmental and economic performance of algal biofuel production with wastewater across the whole U.S. (total 12,455 WWTPs are evaluated). Results indicate that growing algae in wastewater for biofuel production would be both environmentally and economically sustainable. The potential production of algal crude oil is 0.98 billion gallons/yr. As the second goal, we performed laboratory experiments for a better understanding of the potential of using the heterotrophic and mixotrophic methods (mixotrophic uses both light and carbon sources for energy), in addition to biofilm attached growth in algal wastewater. Because one of the main issues in algae cultivation is the harvesting process which is energy intensive, the attached growth can help reduce the cost. In this research, we evaluated the results of growing attached algae in different material and surface roughness. This novel algae cultivation strategy, mixotrophic microalgae biofilm, can help improve the productivity and cost-efficiency of algal biofuel production. In contrast to previous methods, this improved approach can achieve high productivity at low cost by harnessing the benefits of mixotrophic growth’s high efficiency, i.e., capable of subsisting on inorganic and organic carbons thus unaffected by limited light, and microalgae biofilm’s low harvesting cost. Our results, as one of the first studies of this type, proved that microalgae biofilms under mixotrophic condition exhibited significantly higher productivity and quality of biofuel feedstock: 2-3 times higher of biomass yield, 2-10 times higher of lipid accumulation, and 40 – 60 % lower of ash content when compared to microalgae biofilms under autotrophic condition. Finally, for the third goal, we have evaluated the potential of using life cycle optimization (LCO) and Machine Learning in the sustainability analysis. Availability of CO2 emission from coal and natural gas power plants has been evaluated to be used in HRAP in an LCO model. We considered a hypothetical model of providing CO2 gases to the nearby HRAP system. Environmental effects have been optimized based on the following minimizing function 1) energy needed for pumping wastewater and CO2 function 2) water needed to produce pipes, and finally, function 3) eutrophication potential. The primary results indicate that an HRAP close to the WWTP is the optimized condition in a distributed system on the CO2 pipe. The second challenge that we have evaluated in our research is the application of machine learning. We collected some of those independent parameters that affect the normalized CO2 generation. The results indicate that for different accuracy scenarios the model can predict very well. For example, considering the 75% accuracy (the absolute error between prediction and actual data is less than 25%), our machine learning model can accurately predict in 1,822 out of 2491 WWTPs. Besides that, our work resulted in some additional applications and award in the area of Internet of Things, community engagement, and data mining

STUDYING OF SAFETY CLIMATE ASSESSMENT: A CASE STUDY AT STEEL INDUSTRY

Evolution of safety climate used as a practical means has determined and assessed potential problems relevant to safety issues in an organization and can be used in individuals’ performance and work efficiency and decreasing rate of incidents ;as well as; guidance to provide safety organization policy and comparison of safety performance in different organizations. The study wants to determine and prepare safety climate profile and application of its results in improving safety situation. In this study, applied tools presented by Loughborough University are used to evaluate safety climate in one of steel industries and data is collected through questionnaire, group discussions or purposeful interviews and observations, and safety climate score was obtained in 17 scopes. Calculating the score of each safety climate domain and preparing the profile indicated there is the average rate (4.89 2) in the safety climate of the industry.safety climate, safety evaluation,safety culture, steel industry, Iran

Novel phenomena in confined electronic systems.

Modern experimental methods have made it possible for physicists to investigate matter in extreme conditions. Two of the most extreme conditions are low temperature and low dimensionality. Fabricated semiconductor or metal nano-ring arrays and narrow quantum wells in semiconductor heterostructures at low temperatures provide such an extreme environments for electrons. I will explain these systems in this dissertation. Quantum Wells. In a closely spaced double quantum well (DQW), electrons are thought to form an interlayer coherent state when a perpendicular magnetic field is applied such that the total Landau level filling factor one. The low energy topological excitations of the electron gas in these structures includes charged pseudo-spin vortices and anti-vortices. By calculating the energy per electron and the electron densities in the Hartree-Fock approximation, we show that there are new excited states with interwoven spin and pseudo-spin and that their presence in the system can explain new experimental results. The excitations of DQW's (called merons) also have important effects on transport in these systems. These objects carry charge, vorticity, and electric dipole moment. Disorder is likely to unbind them and allow them to diffuse through the system independently. Due to their different dipole moments, the various types of merons may then in principle be distinguished in transport activation energies by an interlayer bias potential. We explore the dynamics of merons using Chern-Simon theory for quantum Hall systems. We numerically estimate their energies in various circumstances and compare them to the recent experiments. Nano-rings. In this dissertation we also fully analyze the possible phases of a model of singly charged one and two dimensional arrays of rings each having a diameter " 100 nm. Using the Hartree approximation and Monte-Carlo simulations we demonstrate that the electrostatic polarization of these arrays undergoes a quantum phase transition due to quantum mechanical fluctuations. Using a complete finite size scaling analysis for a one dimensional array we show that this phase transition is in the universality class of the transverse field Ising model. Also we will show that an external magnetic field changes the polarization behavior from anti-ferroelectric to ferroelectric due to the Aharanov-Bohm effect

Spatially Explicit Life Cycle Assessment: Opportunities and challenges of wastewater-based algal biofuels in the United States

This work presented a Spatially-Explicit-High-Resolution Life Cycle Assessment (SEHR-LCA) model for wastewater-based algal biofuel production, by integrating life cycle assessment, GIS analysis, and site-specific Wastewater Treatment Plants (WWTPs) data analysis. Wastewater resources, land availability, and meteorological variation were analyzed for algae cultivation. Three pathways, Microwave Pyrolysis, hydrothermal liquefaction, and lipid extraction were modeled for bio-oil conversion. This model enables the assessment of seasonal and site-specific variations in productivity and environmental impacts of wastewater-based algal bio-oil across the whole U.S. Model results indicate that wastewater-based algal bio-oil can provide an opportunity to increase national biofuel output. The potential production of algal bio-oil can reach to 0.98 billion gallon/yr, nearly 20% of advanced biofuel projection as outlined in the U.S. Energy Independence and Security Act (EISA) of 2007. LCA results shows significant variations among different locations, WWTPs, and operational seasons. Although not competitive to conventional fossil fuel in energy efficiency, wastewater-based algal biofuel could offer significant benefit in controlling GHG emissions. However, spatial analysis shows that only 61% of the total wastewater could be used, based on current land use efficiency for algae cultivation and land availability around each WWTP in a radius where algal biofuel production is energy positive (energy output N energy input). These results indicate that land availability could be a significant challenge for wastewater-based algal biofuels that have not been considered in previous studies. They also suggest that improvement should be made in technological development and system design to increase energy and land use efficiency for full potential of wastewater as a promising resource for algal biofuel production. Although focusing on the U.S. as the case study, the developed methodology could be used for spatially explicit analysis of algal biofuel integrated with wastewater on macro-scale in other regions as well

AN INVESTIGATION ON RELATION AND PREDICTION OF PERCEIVED ORGANIZATIONAL SUPPORT (POS) ACCORDING TO 15 FOLD ORGANIZATIONAL VARIABLES

The aim of this article is to study the relation between perceived organizational support(POS) with 15 fold variables including cooperation in decision making, servicing the public, job vision, trust to supervisor, satisfaction with salary, promotion opportunity, inner provocation, quality of supervising, desire to remain, leaving the job, organizational trust, job interest, satisfaction with supervisor and satisfaction with colleagues. In order to achieve the foregoing aim, there were 198 people selected from all employed personnel in Rahpooyan Company and answered the questionnaires. The document related to validity and reliability of this investigation means were in an acceptable level. The data collected from these questionnaires was analysed via coefficient of Pierson correlation, analysis of step by step regression, analysis of structural equation (path analysis). The results indicate there was a significant correlation between perceived organizational support and including cooperation in decision making, servicing the public, job vision, trust to supervisor, satisfaction with salary, promotion opportunity, quality of supervising, desire to remain, leaving the job, organizational trust, satisfaction with supervisor and satisfaction with colleagues. But there was no significant correlation between inner provocation and job interest with perceived organizational support. In analysis of step by step regression, it was also indicated that cooperation in decision making, promotion opportunity, trust to supervisor, job interest and organizational trust can specify about 56% of the perceived organizational support variance. The results of the path analysis also indicated that cooperation in decision making, promotion opportunity, trust to supervisor, job interest have a coefficient of direct path on perceived organizational support

Evaluation of computer networks with administrative structure at Islamic Azad University

The purpose of this study is to evaluate and compare the dependency between administrative structure and design and implementation of computer networks in Islamic Azad University. So, a collection of data shows the administrative structure and network administration is needed. The major of the proposed hypotheses is that there is a significant relationship between administrative structure variables, computer network administration and distributing variables. In this study, more than 150 questionnaires have been distributed among the participants. 100 questionnaires were answered, and then the required information test hypotheses were extracted. For testing the research hypotheses, chi-square test displayed the relationship between variables. Correlation coefficients were positive and in order to evaluate the reliability of questionnaire, Cronbach's alpha test was used. The results of examination of the relationship between variables showed that there is a meaningful relationship among all variables. Thus, all the proposed hypotheses were proved