4 resultados para LINEAR STRUCTURAL RELATIONSHIPS
em Digital Commons - Michigan Tech
Resumo:
Aku Päiviö was one of the most influential voices of the Finnish labor movement in North America—a poet who also wrote plays and novels, and an editor who worked for a variety of newspapers across the United States and Canada. During the height of the Finnish socialist movement from around 1904-1916, Päiviö published a number of poems that identified with the actions and ideologies of the working-class. He also edited for newspapers such as Kansan Lehti and Raivaaja, further extending his literary reach. Despite his prodigious publications and influence, however, little of Päiviö’s writing has been translated into English. This paper celebrates Päiviö’s legacy with some English translations of his poems, specifically those commemorating the 1913-14 Michigan Copper Strike, and illuminates how various thematic and structural relationships in these poems relate to the ideologies and movements of the time.
Resumo:
Metal-organic frameworks (MOFs) obtained much attention because of their unusual structures and properties as well as their potential applications. This dissertation research was focused on (1) the effects of synthesis conditions on the structures of MOFs, (2) the thermal stability of MOFs, (3) pressure-induced amorphization, and (4) the effect of high-valent ions on the structure of a MOF. This research demonstrated that the crystal structure of MOF-5 could be controlled by drying solvents. If the vacuum solvent is dimethylformamide (DMF), the crystal structure of MOF-5 is tetragonal. In contrast, if the DMF is displaced by CH2Cl2 before the vacuum, the obtained MOF-5 occupies a cubic structure. Furthermore, it was found that the tetragonal MOF-5 exhibited a mediate surface area (300-1000 m2/g). The surface area of tetragonal MOF-5 is also dependent on Zn(NO3)2/H2BDC (H2BDC: terephthalic acid) molar ratios used for its synthesis. The optimum ratio is 1.38, at which synthesized tetragonal MOF-5 exhibits the highest crystallinity and surface area (1297 m2/g). The thermal stability and decomposition of MOF-5 were systematically investigated. The thermal decomposition of cubic and tetragonal MOF-5s resulted in the same products: CO2, benzene, amorphous carbon, and crystal ZnO. The thermal decomposition is due to breaking carboxylic bridges between benzene rings and Zn4O clusters. Identifying structural relationships between crystalline and noncrystalline states is of fundamental interest in materials research. Currently, amorphization of solid materials at ambient temperature requires an ultra-high pressure (several GPa). However, this research demonstrated that MOF-5 and IRMOF-8 can be irreversibly amorphized at ambient temperature by employing a low compressing pressure of 3.5 MPa, which is 100 times lower than that required for amorphization of other solids. Furthermore, the pressure-induced amorphization (PIA) of MOFs is strongly dependent on the changeability of bond angles. If the geometric structure of a MOF can allow bond angles to be changed without breaking bonds, it can easily be amorphized by compression. This can explain why MOF-5 and IRMOF-8 can easily be amorphized via compression than Cu-BTC. It is generally recognized that zeolitic imidazolate frameworks (ZIFs) occupy much higher stability than other types of MOFs. The representative of ZIFs is Zn(2-methylimidazole)2 (ZIF-8) exhibiting high-decomposition temperature and high chemical resistance to various solvents. However, so far, it is still unknown whether the high stability of ZIF-8 can be challenged by ions, which is important for its modification by doping ions. In this research, we performed aqueous salt solution treatment on ZIF-8, and the results showed that anions (Cl¯ and NO3¯) in a solution exhibited no effect on the crystal structure of ZIF-8. However, the effect of cations (in a solution) on structure of ZIF-8 strongly depends on the cation valences. The univalent metal cations showed no effect on the structure of ZIF-8, whereas the bivalent or higher-valent metal cations caused the collapse of ZIF-8 crystal structure. Therefore, structure stability of ZIF-8 is considered when it is subjected to the application, in which high-valent metal cations are involved.
Resumo:
Isolated water-soluble analytes extracted from fog water collected during a radiation fog event near Fresno, CA were analyzed using collision induced dissociation and ultrahigh-resolution mass spectrometry. Tandem mass analysis was performed on scan ranges between 100-400 u to characterize the structures of nitrogen and/or sulfur containing species. CHNO, CHOS, and CHNOS compounds were targeted specifically because of the high number of oxygen atoms contained in their molecular formulas. The presence of 22 neutral losses corresponding to fragment ions was evaluated for each of the 1308 precursors. Priority neutral losses represent specific polar functional groups (H2O, CO2, CH3OH, HNO3, SO3, etc., and several combinations of these). Additional neutral losses represent non-specific functional groups (CO, CH2O, C3H8, etc.) Five distinct monoterpene derived organonitrates, organosulfates, and nitroxy-organosulfates were observed in this study, including C10H16O7S, C10H17NO7S, C10H17 NO8S, C10H17NO9S, and C10H17NO10S. Nitrophenols and linear alkyl benzene sulfonates were present in high abundance. Liquid chromatography/mass spectrometery methodology was developed to isolate and quantify nitrophenols based on their fragmentation behavior.
Resumo:
The need for a stronger and more durable building material is becoming more important as the structural engineering field expands and challenges the behavioral limits of current materials. One of the demands for stronger material is rooted in the effects that dynamic loading has on a structure. High strain rates on the order of 101 s-1 to 103 s-1, though a small part of the overall types of loading that occur anywhere between 10-8 s-1 to 104 s-1 and at any point in a structures life, have very important effects when considering dynamic loading on a structure. High strain rates such as these can cause the material and structure to behave differently than at slower strain rates, which necessitates the need for the testing of materials under such loading to understand its behavior. Ultra high performance concrete (UHPC), a relatively new material in the U.S. construction industry, exhibits many enhanced strength and durability properties compared to the standard normal strength concrete. However, the use of this material for high strain rate applications requires an understanding of UHPC’s dynamic properties under corresponding loads. One such dynamic property is the increase in compressive strength under high strain rate load conditions, quantified as the dynamic increase factor (DIF). This factor allows a designer to relate the dynamic compressive strength back to the static compressive strength, which generally is a well-established property. Previous research establishes the relationships for the concept of DIF in design. The generally accepted methodology for obtaining high strain rates to study the enhanced behavior of compressive material strength is the split Hopkinson pressure bar (SHPB). In this research, 83 Cor-Tuf UHPC specimens were tested in dynamic compression using a SHPB at Michigan Technological University. The specimens were separated into two categories: ambient cured and thermally treated, with aspect ratios of 0.5:1, 1:1, and 2:1 within each category. There was statistically no significant difference in mean DIF for the aspect ratios and cure regimes that were considered in this study. DIF’s ranged from 1.85 to 2.09. Failure modes were observed to be mostly Type 2, Type 4, or combinations thereof for all specimen aspect ratios when classified according to ASTM C39 fracture pattern guidelines. The Comite Euro-International du Beton (CEB) model for DIF versus strain rate does not accurately predict the DIF for UHPC data gathered in this study. Additionally, a measurement system analysis was conducted to observe variance within the measurement system and a general linear model analysis was performed to examine the interaction and main effects that aspect ratio, cannon pressure, and cure method have on the maximum dynamic stress.