Car-less Cities

The rapid growth of world population along with the sprawl growth of towns and suburbanization, has affected the human life and its surrounding nature dramatically. The fact is this level of growth is not sustainable with the current patterns of development. Most cities all around the world are designed in a way that encourages car dependency which is harming the environment and human health. During the past decade, urban planners formulate new principles of land use development to preserve the environment and protect public health, safety and general welfare of the citizens. These concepts are characterized by some movements such as sustainable communities, new urbanism, green urbanism, and livable places, pedestrian and transit-oriented development, healthy communities, retrofitting suburbia, brownfield redevelopment, community revitalization, and smart growth. The goal of most these movements is to reduce the amount of reliance on motor vehicles to have a sustainable community. One of the newly developed ideologies which decreases the reliance on motor vehicles, is a Car-less city. A car-less city is a city that is designed to remove cars from the streets. This may sound unrealistic in the beginning, but in fact, many cities all around the world, are shifting their mobility solution away from automobile toward more environmentally friendly methods. The intent of this thesis is to study ways to minimize the use of motor vehicles and their negative effects on societies and propose different means of transportation that are environmentally friendly. The materials were gathered from secondary sources and by reviewing similar cases in Iran, Europe and United States to analyze how these cities could help us to preserve the environment

Development of a Radiopaque Infiltration Resin for Early Enamel Carious Lesion

PhDA white spot lesion (WSL) is defined as enamel porosity, which could be due to an enamel defect or an initial carious lesion. ICON® resin is a resin infiltrant that penetrates into the enamel porosity and seals the lesion, thus inhibiting the progression of caries. This method is micro-invasive; however, the resin is radiolucent and the clinician cannot detect the material using radiographs. In order to develop a radiopaque resin, understanding the pore size and pore structure in WSLs is helpful. Therefore, the aim of this study was to characterise: (1) the pore size and structure, (2) the incorporation of radiopaque agents into ICON® resin. Brunauer–Emmett–Teller (BET) and focused ion beam-scanning electron microscopy (FIB-SEM) were used to characterise the porosity in WSLs. The data showed the enamel prisms become more pronounced in the advanced areas of the WSLs and demineralisation occurs within or/and between the enamel prisms. The pore size could be as small as an enamel crystallite, 28x48nm. Nano-strontium hydroxyapatite (non-coated and coated) and strontium bioglass were made as radiopaque fillers and characterised using different techniques including fourier transform infrared spectroscopy (FTIR), BET, transmission electron microscopy (TEM), X-ray diffraction (XRD) and particle size measurements. The radiopaque fillers had micron-sized particles, which made them unsuitable for infiltration into WSLs despite their possible ability to remineralise the WSLs. Radiopaque monomers including bromine-methacrylate and tin-methacrylate were able to make ICON® resin radiopaque and they showed a similar viscosity, wettability and biocompatibility compared to ICON® resin. The X-ray microtomography (XMT) showed that the experimental radiopaque resins were able to infiltrate into the WSLs, artificial and natural lesions, and they could be detected using image subtraction. Backscattered electron (BSE) imaging after each step of application of materials showed that the etching pattern and etchant gel could be barriers for a successful infiltration of the resins into WSLs

Design and implementation of a proper modulation and control scheme for a single and three phases Dual Active Bridge Converter

In this master thesis, the aim is to implement the single and three phase Dual Active Bridge converter both with simulation and experimentally. In the first phase of the thesis, as a case study, the single and three phase DAB converter are simulated in the PLECS software. The phase shift method has been implemented in order to control the converter. The operation frequency of the simulation is 5 KHz and the input and output voltage of the converters are 3KV and 6KV respectively. The transmitted power is 2MW. In the second phase of the project, the single phase dual active bridge has been implemented in the laboratory by using the dSPACE controller. The DAB converter has been tested for the frequencies of 50, 500 Hz and 1 KHz and for the maximum power of 0.5 KW. The maximum input and output voltage is 80 and 144 volts respectively. All tests for different voltage levels and frequencies have been done by simulation as well and the simulation results have been verified by the experimental results. The same tests also have been done for the three phase DAB converter which is implemented in the laboratory. These tests have been done for the frequency of 55 and 555 Hz and for the maximum power of 1.5 KW. The simulation results are also verified by the experimental results. In the last phase of the thesis, soft switching has been implemented by using snubber capacitors on both the single and three phase DAB converter and the results have been compared with the previous results. The highest possible frequency for the Single phase dual active bridge used in this thesis is 1 KHz and the highest possible frequency for the three phase case is 555 KHz by using the digital implementation of the dSPACE controller. The accuracy of the phase shift for the single phase DAB converter for the frequency of 1 KHz is 3.6 degrees and for the three phase DAB converter for the frequency of 555 Hz is 2 degrees. Loss calculation also has been done theoretically, for the simulation and also for the experimental tests. The results show that the implemented DAB converter has higher losses for higher frequencies. The implemented three phase DAB converter also has higher losses than the single phase one in this thesis due to the higher cabling and switchin

Contamination-assisted rather than metal catalyst-free bottom-up growth of silicon nanowires

Well-established metal-catalyzed vapor-liquid-solid (VLS) growth represents still undoubtedly the key technology for bottom-up synthesis of single-crystalline silicon nanowires (SiNWs). Although various SiNW applications are demonstrated, electrical and optical properties are exposed to the inherent risk of electronic deep trap state formation by metal impurities. Therefore, metal catalyst-free growth strategies are intriguing. The oxid-assisted SiNW synthesis is explored and it is shown that contamination control is absolutely crucial. Slightest metal impurities, such as iron, are sufficient to trigger SiNW growth, calling into question true metal catalyst-free SiNW synthesis. Therefore, the term contamination-assisted is rather introduced and it is shown that contamination-assisted SiNW growth is determined by the chemical surface treatment (e.g., with KOH solution), but also by the crystal orientation of a silicon substrate. SiNWs are grown in this regards in a reproducible manner, but so far with a distinct tapering, using a conventional gas-phase reactor system at temperatures of about 680 °C and monosilane (SiH4) as the precursor gas. The synthesized SiNWs show convincing electrical properties compared to Au-catalyzed SiNWs. Nevertheless, contamination-assisted growth of SiNWs appears to be an important step toward bottom-up synthesis of high-quality SiNWs with a lower risk of metal poisoning, such as those needed for CMOS and other technologies

Effects of pH, particle size and porosity of raw rice husk and its silica on removing lead and hexavalent chromium from aqueous solution

Adsorbent properties and aqueous characteristics are very important parameters in the removal efficiency (RE) of environmental pollutants. The main goal of this study was to investigate the effects of pH, particle size and porosity of raw rice husk and its silica on removing lead and hexavalent chromium (Cr+6) from aqueous solution. The raw rice husk was collected from north of Iran and the rice husk silica was prepared at 800ºC after acid leaching. The effects of the adsorbent particle sizes (0.07-0.1, 0.1-0.5, 0.5-1.0 and 1.0-1.5 mm), porosity and pH from 2 to 8 were investigated by varying any of the process variables while keeping the other variables constant (adsorbent dosage= 1.5 g.l-1, contact time = 60 min, chromium and lead initial concentration = 5 mg.l -1). The results of this study showed that the RE of Cr+6 is intensively pH - dependent. Using 1.5 g.l-1 adsorbents, particle size = 0.5 - 1.0 mm, 5.0 mg.l-1 initial concentration of Cr+6 and 60 min contact time, the maximum RE obtained by raw rice husk and its silica at pH 2 were up to 98.8 and 88.4%, respectively. However, at the same condition with changing pH (pH 7),the maximum RE decreased up to 69.4 and 60.4%, respectively. Moreover, a positive strong significant correlation was detected between decreasing the adsorbents particle sizes and lead removal efficiency in the two adsorbents (P < 0.01). The scanning electron microscope images of the two adsorbents showed that silica derived from raw rice husk has more porosity. In conclusion, the acidic condition of aqueous for Cr+6 and neutral condition for lead, increases the adsorbents porosity, while decreased adsorbent particle sizes causes an elevation in the RE of the two pollutants

Economic Contribution of a Proposed Veterans Home in Fillmore County, Minnesota

This archival publication may not reflect current scientific knowledge or recommendations. Current information available from the University of Minnesota Extension: https://www.extension.umn.edu

Water Defluoridation Using Modify Zeolite by Al+3 Ions and Nanoscale Zero-Valent Iron (nZVI) in a Fixed Bed Column

Removal of the fluoride ion of drinking water requires an effective technique. In study zeolite clinoptilolite by Al+3ions and nanoscale iron (nZVI) modify was used to remove fluoride from water. Contact was done by a fixed bed absorbent column. In this column, experiments were carried out using aqueous solutions and drinking water with mass. The dynamics of the adsorption process were fitted to Langmuir and Freundlich models. The results showed that highest uptake capacities 1.14 and 2.4mg/g for the modified zeolitic Al and nanoscale iron (nZVI) respectively, were obtained with a 5g mass column, an inlet 10 mg/L fluoride solution, and a flow rate of 3mL/min, but the sorption capacities decreased when drinking water used. Experimental data were fitted to both models Langmuir and Freundlich, and the methods indicated that these materials are suitable for the removal of fluoride from water in fix bed systems. In general, it can be concluded that modified zeolite clinoptilolite with fixed bed an effective and economical method to remove fluoride from groundwater

Economic Contribution of Federal Funding for Small Business Innovation Research (SBIR) and Small Business Technology Transfer (STTR) Programs

This archival publication may not reflect current scientific knowledge or recommendations. Current information available from the University of Minnesota Extension: https://www.extension.umn.edu.Minnesota, Fiscal Years 1983-201

Effect of the pillar ligand on preventing agglomeration of ZnO nanoparticles prepared from Zn(II) metal-organic frameworks

Metal-Organic Frameworks (MOFs) represent a new class of highly porous materials. On this regard,  two nano porous metal-organic frameworks of [Zn2(1,4-bdc)2(H2O)2∙(DMF)2]n (1) and [Zn2(1,4-bdc)2(dabco)]·4DMF·1⁄2H2O (2), (1,4-bdc = benzene-1,4-dicarboxylate, dabco = 1,4-diazabicyclo[2.2.2]octane and DMF = N,N-dimethylformamide) were synthesized and characterized. They were used for preparation of ZnO nanomaterials. With calcination of 1, agglomerated ZnO nanoparticles could be fabricated, but by the same process on 2, the tendency of ZnO nanoparticles to agglomeration was decreased. In addition, the ZnO nanoparticles prepared from compound 2 had smaller diameter than those obtained from compound 1. In fact, the role of organic dabco ligands in 2 is similar to the role of polymeric stabilizers in formation of nanoparticles. Finally, considering the various applications of ZnO nanomaterials such as light-emitting diodes, photodetectors, photodiodes, gas sensors and dye-sensitized solar cells (DSSCs), it seems that preparation of ZnO nanomaterials from their MOFs could be one of the simple and effective methods which may be applied for preparation of them

Economic Futures Workshop: Madelia, Minnesota

This archival publication may not reflect current scientific knowledge or recommendations. Current information available from the University of Minnesota Extension: https://www.extension.umn.edu