Thermal and Electrical Behaviors of Selected Geomaterials

Geomaterials can be often classified into two groups: virgin geomaterials such as soil and rock, and by-product materials such as mine tailings, coal fly/bottom ash, foundry sand, kiln dust, blast furnace/steel slag, reclaimed concrete and asphalt. Studies on these materials and their mixtures have been carried out extensively for geoengineering applications, including the characterization of mechanical properties such as the strength, compressibility, compactivity and permeability, as well as mineralogical and geochemical properties. The goal of this study is to investigate the thermal and electrical properties of selected geomaterials and their mixtures for enhancement of knowledge and engineering applications. The thesis consists of three parts as follows: The first part presents the electrical conductivity measured on compacted kaolin clay using a circular two-electrode cell in conjunction with a specially designed compaction apparatus, which has the advantage of reducing errors owing to sample handling. The experimental results are analyzed to observe the influencing factors on the soil electrical conductivity. The performance of existing analytical models for predicting the soil electrical conductivity is evaluated by calculating empirical constants in these models. The second part investigates the thermal and packing behaviors of mine tailings and tire crumbs mixtures in dry and wet states, which are important in engineering applications for utilizing recycled tire particles as lightweight fill materials with improved thermal insulation. The thermal and packing properties measurements of the mine tailings and tire crumbs mixtures with different mixing ratios are presented, which are then analyzed to establish the thermal properties relationships with respect to the mixing ratio of tire crumbs, porosity, bulk density, water content, compactive effort and tire crumbs size. The multiple linear regression analysis shows that the thermal conductivity of the dry and wet mixtures can be estimated using a general model consisting of the factors affecting the thermal conductivity. The third part evaluates the thermal conductivity, compressive strength, elastic modulus and temperature changes of compacted mine tailings and fly ash mixtures during the curing period as functions of the fly ash ratio, molding water content and compaction energy. The microporosity structure of the fly ash treated mine tailings is also examined

Free Vibration of Axially Functionally Graded Timoshenko Circular Arch

Functionally graded materials are innovative composites of hybrid ceramics and metals that exhibit excellent mechanical performance in harsh temperature environments and under various external loads. In this study, the free vibrations of Timoshenko circular arches, made of functionally graded materials in the axial direction, are investigated. The material properties of Young's modulus and mass density of the arch vary according to a symmetric quadratic function along the arch axis. Differential equations governing the free vibration of the arch including the rotatory inertia and shear deformation, called the Timoshenko arch, are derived. A novel numerical solution method is developed to calculate the natural frequencies and mode shapes of the arch. Parametric studies of the modular ratio, shear correction factor, shear modulus ratio, and slenderness ratio on the natural frequencies are conducted, and the results are reported in the tables and figures

Guards and Culprits in the Endoplasmic Reticulum: Glucolipotoxicity and β-Cell Failure in Type II Diabetes

The endoplasmic reticulum (ER) is a cellular organelle responsible for multiple important cellular functions including the biosynthesis and folding of newly synthesized proteins destined for secretion, such as insulin. The ER participates in all branches of metabolism, linking nutrient sensing to cellular signaling. Many pathological and physiological factors perturb ER function and induce ER stress. ER stress triggers an adaptive signaling cascade, called the unfolded protein response (UPR), to relieve the stress. The failure of the UPR to resolve ER stress leads to pathological conditions such as β-cell dysfunction and death, and type II diabetes. However, much less is known about the fine details of the control and regulation of the ER response to hyperglycemia (glucotoxicity), hyperlipidemia (lipotoxicity), and the combination of both (glucolipotoxicity). This paper considers recent insights into how the response is regulated, which may provide clues into the mechanism of ER stress-mediated β-cell dysfunction and death during the progression of glucolipotoxicity-induced type II diabetes

Distribution and Conservation of Long-billed Plovers Charadrius placidus in Korea

AbstractThe Long-billed Plover Charadrius placidus of distribution was surveyed from 2002 to 2005, on rivers, streams and coasts of 38 areas within Korea. The Sum of highest numbers (sum of peak counts) of Long-billed Plovers at 24 sites was 198 individuals. Number of observed individuals during breeding period was 88 individuals, 129 individuals during the migration period, and 56 individuals during the wintering period. The Long-billed Plover breeds and migrates throughout Korea. They spend winter south of 37° latitude. Highest numbers (73 individuals) were observed at Daejeon. Therefore, streams and rivers of Korea are considered as an important habitat for the Long-billed Plover