Nanotechnology Formulations and Modeling of Hydraulic Permeability Improvement for Nonwoven Geotextiles

First, the general concept of nanotechnology formulations used to manufacture geotextiles (GT) is introduced. Separation and filtration functions using geotextiles from nanoclay formulations are introduced as important concepts. Yellow clay was added as nanoparticles to make a polyester formulation in turn to make nonwoven geotextiles to improve the removal effects of toxic and organic components of leachate solutions. Engineering behavior was evaluated to confirm the effects of adding yellow clay. There is a possibility of nanocomposite formulations for geosynthetics in the future. Second, sustainable laminar geotextile composites with different fiber-packing densities were made, and the effects of laminar structures were examined on water permeability. To fabricate these materials, the fiber-packing densities of laminar geotextile composites were discriminated correspondingly. The experimental values of water permeability by permittivity test were smaller than those of the theoretical values due to the loss of hydraulic pressure at the interface between geotextiles. To interpret the water permeability behaviors, structural model of tubes with different fiber-packing densities was applied. Finally, the inlet forms – bell mouth and soft tube structures – of laminar geotextile composite pores were estimated from the loss rates of hydraulic pressure

Review of Long-Term Durable Creep Performance of Geosynthetics by Constitutive Equations of Reduction Factors

In an elastic solid the strain stays constant with time and is constant and the stress decays slowly with time. The increase in strain is not linear, and the curve becomes steeper with time and also as the stress-rate is increased. The slope of the curve tends to decrease with time, but it is steeper for higher strain rates. The variation of both strain and stress with time is linear for constant stress- and strain-rate tests upon elastic materials. The final comment about the compressive creep test and data interpretation is as follows: (1) Description of the creep mechanism of the geosynthetics (exactly not compression but perpendicular compression) is very important because the creep mechanism of tension and compression is quite deferent. (2) To reduce the specimen-to-specimen, many ramp-and-hold (in the case of tension creep: 1 h) tests are recommended. (3) Loading rate is also important because it make initial strain value. To check the nonaffected loading rate, prior to the main creep test, some kind of short-term test is needed. (4) The method to assess the reduction factor by creep also will be reviewed because the value will be changed according to the applied load

Analysis of Porous Behaviors by Water Flow Property of Geonets by Theoretical Simulation

The relationship of compressive behavior according to manufacturing process parameters of geonet was investigated. We analyzed the drainage behavior of the bi- and tri-plane geonet used for the planar drainage and investigated the changes of the drainage behavior due to the restraining load. The data showed that there is no critical manufacturing factor to affect the compressive strength of the bi-planar geonet. All of these parameters can affect in a very complicated way. And the strand inclination can mainly affect to the after compressive strength, i.e., roll-over behavior. The results considering site-specific conditions of the landfill system explained the temperature has influence on the compressive behavior of the geonet. The compressive strength was reduced and the strain at yield increase gradually with the temperature for both of bi- and tri-planar geonet. Significant reductions in flow capacity were observed for the traditional bi-planar and cylindrical type geonet and this value was consistent to the compressive strength. These decreases were anticipated due to the abrupt thickness decrease of the geonet caused by roll-over. In the other hand, there was no significant decrease of transmissivity for the tri-planar geonet which has no roll-over phenomena

Polymeric Synthetic Fabrics to Improve Stability of Ground Structure in Civil Engineering Circumstance

Polymeric synthetic fabrics are continuous sheets of woven, nonwoven, knitted, or stitch-bonded fibers and yarns. The sheets are flexible and permeable and generally have the appearance of a fabric. Among polymeric synthetic fabrics, geosynthetics including geotextiles have special functions of separation, filtration, drainage, reinforcement, and erosion control in civil engineering applications. Also, geosynthetics such as geotextiles and geogrids are used in asphalt pavement reinforcement. An important function of these geotextiles is as cushion layers to prevent puncture of geomembranes (by reducing point contact stresses) from stones in the adjacent soil, waste, or drainage aggregate. Geotextiles, however, are made from a combination of two or more polymeric synthetic fabrics. In this chapter, geotextiles as polymeric synthetic fabrics are introduced not only for improvement but also maintaining stability of ground structure in civil engineering circumstance with their related technologies

Review of Sustainable Geosynthetic Development Trend with Environmental Adaptive and Eco-Environmental Performances Point of View

Most of the geosynthetics contribute to the long-term stability of the soil structure, so products with little change in long-term performance are mainly used. To this end, demand for biodegradable products emphasizing planting and environmental compatibility is increasing. Sustainable geosynthetics can be categorized as “Usual Geosynthetics” and “Green Geosynthetics” on the basis of required performance, and it can be said that it is meaning to expand the use of geosynthetics in the fusion level. In here, “Usual Geosynthetics” refer to functional long-term maintenance and environmental adaptive products, and “Green Geosynthetics” refer to eco-environmental products that are decomposable geosynthetic fibers whose functions are extinguished after a required period of time. In this paper, we introduce sustainable geosynthetics, which are differentiated from raw materials to applicability

Dynamical mean-field theory of Hubbard-Holstein model at half-filling: Zero temperature metal-insulator and insulator-insulator transitions

We study the Hubbard-Holstein model, which includes both the electron-electron and electron-phonon interactions characterized by $U$ and $g$, respectively, employing the dynamical mean-field theory combined with Wilson's numerical renormalization group technique. A zero temperature phase diagram of metal-insulator and insulator-insulator transitions at half-filling is mapped out which exhibits the interplay between $U$ and $g$. As $U$ ($g$) is increased, a metal to Mott-Hubbard insulator (bipolaron insulator) transition occurs, and the two insulating states are distinct and can not be adiabatically connected. The nature of and transitions between the three states are discussed.Comment: 5 pages, 4 figures. Submitted to Physical Review Letter

Monoclinic and Correlated Metal Phase in VO_2 as Evidence of the Mott Transition: Coherent Phonon Analysis

In femtosecond pump-probe measurements, the appearance of coherent phonon oscillations at 4.5 THz and 6.0 THz indicating the rutile metal phase of VO_2 does not occur simultaneously with the first-order metal-insulator transition (MIT) near 68^oC. The monoclinic and correlated metal(MCM) phase between the MIT and the structural phase transition (SPT) is generated by a photo-assisted hole excitation which is evidence of the Mott transition. The SPT between the MCM phase and the rutile metal phase occurs due to subsequent Joule heating. The MCM phase can be regarded as an intermediate non-equilibrium state.Comment: 4 pages, 2 figure

Association between Workplace Risk Factor Exposure and Sleep Disturbance: Analysis of the 2nd Korean Working Conditions Survey

OBJECTIVES: Sleep is essential for human beings to live and work properly. This study was conducted to investigate the relationship between occupational exposures to workplace risk factors and sleep disturbance in Korean workers. METHODS: The data were drawn from the second Korean Working Conditions Survey (KWCS); a total of 7,112 paid workers were analyzed. The independent variables were occupational exposures such as physical, chemical, biological, and psychosocial risk factor in the workplace, and psychosocial risk factor was divided into five categories (job demand, job control, social support, job insecurity, lack of reward). We estimated the relationship between various occupational exposures and sleep disturbance using multivariate logistic regression analysis. RESULTS: The results showed that people who exposed to physical, chemical, biological, and psychosocial (high job demand, inadequate social support, lack of reward) risk factors were more likely to increase the risk of sleep disturbance. Furthermore, after adjusting for general and occupational characteristics, we found significant positive associations between exposures to physical (odds ratios [OR] 1.47, 95% confidence interval [CI] 1.05-2.07) and psychosocial (high job demand (OR 2.93, 95% CI 2.16-3.98), inadequate social support (OR 1.57, 95% CI 1.14-2.15), lack of reward (OR 1.45, 95% CI 1.08-1.96)) risk factors and sleep disturbance. CONCLUSION: These results suggest that occupational exposures to physical and psychosocial workplace risk factors are significantly related to sleep disturbance

Properties of Central Caustics in Planetary Microlensing

To maximize the number of planet detections, current microlensing follow-up observations are focusing on high-magnification events which have a higher chance of being perturbed by central caustics. In this paper, we investigate the properties of central caustics and the perturbations induced by them. We derive analytic expressions of the location, size, and shape of the central caustic as a function of the star-planet separation, $s$, and the planet/star mass ratio, $q$, under the planetary perturbative approximation and compare the results with those based on numerical computations. While it has been known that the size of the planetary caustic is \propto \sqrt{q}, we find from this work that the dependence of the size of the central caustic on $q$ is linear, i.e., \propto q, implying that the central caustic shrinks much more rapidly with the decrease of $q$ compared to the planetary caustic. The central-caustic size depends also on the star-planet separation. If the size of the caustic is defined as the separation between the two cusps on the star-planet axis (horizontal width), we find that the dependence of the central-caustic size on the separation is \propto (s+1/s). While the size of the central caustic depends both on $s$ and q, its shape defined as the vertical/horizontal width ratio, R_c, is solely dependent on the planetary separation and we derive an analytic relation between R_c and s. Due to the smaller size of the central caustic combined with much more rapid decrease of its size with the decrease of q, the effect of finite source size on the perturbation induced by the central caustic is much more severe than the effect on the perturbation induced by the planetary caustic. Abridged.Comment: 5 pages, 4 figures, ApJ accepte