Predicting water flow in fully and partially saturated porous media: a new fractal-based permeability model

Hydrogeology Journal - Predicting the permeability of porous media in saturated and partially saturated conditions is of crucial importance in many geo-engineering areas, from water resources to...     

Geochemical Appraisal of Groundwater Quality in Ottapidaram Taluk,Thoothukudi District,Tamil Nadu using Graphical and Numerical Method

Groundwater qualities of coastal aquifers in the Ottapidaram taluk of Thoothukudi district, Tamil Nadu have been extensively monitored in post monsoon seasons in 2014 to assess its suitability in relation to domestic and drinking uses in four regions (N-S-EW). 34 groundwater samples were analyzed for various physicochemical attributes like pH, electrical conductivity (EC), Total dissolved solid (TDS), Na, K, Ca, Mg, Cl, HCO₃, CO₃, SO₄, NO₃, PO₄. Most of these parameters fall under not permissible limits. The western part of the study area is highly polluted from K, Cl, HCO₃ due to industrial/agriculture activity. The southern part is less polluted compared to other region. Hydrogeochemical processes controlling the water chemistry (Gibbs) indicates that most of groundwater samples fall at rock-weathering supremacy zone. Geochemical processes and temporal variation in the groundwater in this area are influenced by evaporation processes, ion exchange and dissolution of minerals. Major cation and anion ionic interaction indicate that weathering reactions have an inconsequential role in the hydrochemical processes of the shallow groundwater system. As a result of the hydrogeochemical analysis, seawater intrusion, aquifer rock weathering, sewer leakage are the overriding factors that determine the major ionic composition. The appropriate management plan is necessary to preserve precious groundwater resources.     

A petrologic, geochemical and Sr–Nd isotopic study on contact metamorphism and degassing of Devonian evaporites in the Norilsk aureoles, Siberia

Devonian evaporites and associated sedimentary rocks in the Norilsk region were contact metamorphosed during emplacement of mafic sills that form part of the end-Permian (~252 Ma) Siberian Traps. We present mineralogical, geochemical and Sr–Nd isotopic data on sedimentary rocks unaffected by metamorphism, and meta-sedimentary rocks from selected contact aureoles at Norilsk, to examine the mechanisms responsible for magma-evaporite interaction and its relation to the end-Permian environmental crisis. The sedimentary rocks include massive anhydrite, rock salt, dolostone, calcareous siltstones and shale, and the meta-sedimentary rocks comprise calcareous hornfels, siliceous hornfels and minor meta-anhydrite and meta-sandstone. Contact metamorphism took place at low pressure and at maximum temperatures corresponding to the phlogopite-diopside stability field. Calcareous hornfels have high CaO, MgO, CΟ₂, SΟ₃, low SiO₂ and initial Sr isotopic ratios of 0.7079–0.7092, features indicative of calcareous siltstone protoliths. Siliceous hornfels, in contrast, have high SiO₂, Al₂O₃, Na₂O, low in other major element oxides and initial Sr isotopic ratios of 0.7083–0.7152, consistent with pelitic or shaley protoliths. Loss of CO₂ in a subset of calcareous hornfels can be explained by decarbonation reactions during metamorphism, but release of SO₂ from evaporites cannot be accounted for by a similar mechanism. Occurrences of wollastonite and a variety of hydrous minerals in the calcareous hornfels are consistent with equilibration with hydrous fluid, which was capable of leaching large quantities of anhydrite in the presence of dissolved NaCl. In this way, substantial sediment-derived sulfur could have been mobilized, incorporated into the magmatic system and released to the atmosphere. The release of CO₂ and SO₂ from Siberian evaporites added to the variety of toxic gases generated during metamorphism of organic matter, coal and rock salt, contributing to the end-Permian environmental crisis.     

Reduced-order modeling for thermal recovery processes

Thermal recovery can entail considerably higher costs than conventional oil recovery, so the use of computational optimization techniques in designing and operating these processes may be beneficial. Optimization, however, requires many simulations, which results in substantial computational cost. Here, we implement a model-order reduction technique that aims at large reductions in computational requirements. The technique considered, trajectory piecewise linearization (TPWL), entails the representation of new solutions in terms of linearizations around previously simulated (and saved) training solutions. The linearized representation is projected into a low-dimensional space, with the projection matrix constructed through proper orthogonal decomposition of solution “snapshots” generated in the training step. Two idealized problems are considered here: primary production of oil driven by downhole heaters and a simplified model for steam-assisted gravity drainage, where water and steam are treated as a single “effective” phase. The strong temperature dependence of oil viscosity is included in both cases. TPWL results for these systems demonstrate that the method can provide accurate predictions relative to full-order reference solutions. Observed runtime speedups are very substantial, over 2 orders of magnitude for the cases considered. The overhead associated with TPWL model construction is equivalent to the computation time for several full-order simulations (the precise overhead depends on the number of training runs), so the method is only applicable if many simulations are to be performed.     

Housing Foreclosure as A Geographically Contingent Event: Columbus Ohio 2003–2007

This article seeks to better understand geographic manifestations of housing foreclosure, moving beyond the usual portrayal that highlights, e.g., race/ethnicity and income. We depart from the usual analytical strategy which centers on factors that subsume high proportions of variance. Instead, this is the starting point for considering constellations and idiosyncratic but formative characteristics—contingencies—that further understanding of, e.g., why two households with identical attributes experience different outcomes. Empirical focus is on Columbus Ohio, 2003–2007. Regression analysis identifies central tendencies, followed by regression tree procedures that reveal variable combinations which alter correlational expectations. Unique areas are examined by neighborhood reconnaissance, exploratory data analysis, interviews, and archival research. Relevant factors include race/ethnicity and socio-economic characteristics. Beyond that, differing variable combinations lead to different outcomes, as do processes such as neighborhood life cycle, institutional actions/involvement, and year of home purchase/construction relative to housing de/inflation and mortgage market characteristics.     

Storm surge prediction with management information systems: A case study of estimating value and observations system

A natural disaster is a major adverse event resulting from the earth’s natural forces. We can now take advantage of information technology (IT) devices to make migration decisions and hazard analysis. The range of IT applications is very wide, and could include robot manufacturing, remote exploration, fuzzy Lyapunov techniques, artificial intelligence, intelligent devices, tension leg platform design, consumer and service quality, and management information systems. Management information systems are especially helpful to medical personnel when carrying out the treatment and medication of patients. Sometimes, though, hospital staff might not have immediate access to a patient’s records such as response to treatments, medication status, or examination results because the computer equipment is not easily portable. In such situations, it is only possible to keep written records, with the data being cataloged or referred to only after returning to the nursing station or office. If the hospital could implement a computerized medical service cart for use in the wards, the above problems would be solved. These computers could use a wireless network system, linked with the central server to access information. The technology now exists and the era of the smart phone has now been entered. Smart phones/tablet PCs could be applied for clinical medical care. For the elderly and patients with chronic diseases, smart health devices designed for home care service are necessary and should be applied as soon as possible. This study designs a wireless physiology signal monitoring system that uses a smart phone with a wireless network apparatus to provide convenient monitoring for patients in the home care service system. The wireless care system is designed for patients who need long-term home care services or assistance with chronic diseases. This paper provides important suggestions to develop ways to connect patients to medical care institutions through the internet.     

Adjusting Chlorine Dosage and to Prevent Bio‐Growth and Minimize Trihalomethanes in Reverse Osmosis Filtrate in a Wastewater Reclamation Process

Feasibility of effluent reclamation for the Futian municipal WWTP in Taichung Taiwan was evaluated using an “SF‐UF‐RO” pilot plant. The optimal parameters of each unit were obtained during the pilot plant test. The pilot plant started the operation in late October 2008 and operated until January 2011. The reverse osmosis (RO) system produces 75 m³ water daily, and the produced water quality was comparable to the city water in Taichung. Chlorine dosed in the sand filtration (SF) inlet and ultrafiltration (UF) backwash had the most significant effect on the stability of system performance. When the chlorine was underdosed, biofilm clogged the bag filter (prefilter of UF) and led to the flow rate decay of the UF. The prefilter needed replacement every 1 or 2 weeks resulting in increased process cost. On the other hand, when the chlorine dosage was increased to mitigate the biofilm growth, the residual chlorine not only reacted with TOC and derived trihalomethanes (THMs) in the RO product water (more than 20 µg/L), but it also damaged the RO membrane. After trial and error, the chlorine concentration was optimized as 0.7 mg/L in SF inlet to prevent growth of biofilm as well as to control the residual chlorine in the RO inlet and THMs in the RO product water. It is suggested that cautiously adjusting chlorine dosage is essential for stably operating such a hybrid membrane system to reclaim the municipal wastewater.     

Seismic capacity of retrofitted beam–column connections in high‐rise steel frames when subjected to long‐period ground motions

The seismic capacity of beam‐to‐column connections in steel high‐rise frames is a matter of concern, particularly when they are subjected to long‐period ground motions. A previous full‐scale shaking table test conducted at the E‐Defense National Research Institute for Earth Science and Disaster Prevention in Japan disclosed cracks and fractures in such beam‐to‐column connections. This paper examines the effects of three types of beam‐to‐column connection retrofit: supplemental welds, wing plates, and a haunch. Quasi‐static member tests and a series of shaking table tests applied to a full‐scale specimen are conducted to quantify the respective performances of the retrofit schemes. The performance of a total of 28 connections tested by the member and shaking table tests is evaluated together with that of an additional 12 unretrofitted connections tested in the previous test. When the supplemental welds are applied only to the shear tab to the web, the connection fractures at the same instant as the connection without retrofit. The corresponding cumulative plastic rotation is not improved. When the supplement welds are further applied to the web‐to‐column connection, strain concentration at the bottom flange, primarily promoted by the presence of the RC floor slab, is significantly reduced, and the cumulative plastic rotation capacity is increased to eight times that of the connection without retrofit. For the wing plate connection and haunch connection, the critical section is moved from the beam end to the beam cross‐section corresponding to the tip of the wing plates or haunch, resulting in an improvement of ductility by eight times that of the unretrofitted connection. Copyright © 2011 John Wiley & Sons, Ltd.     

Undrained Shear Strength from Field Vane Test on Busan Clay

An unusually thick and soft clay, which is called Busan clay, has been deposited throughout the Nakdong River estuary, South Korea. Although many reclamation works have been carried out in the area since early 1990s, large- and small-scale slope failures have taken place mostly during the soil placement on the clay. A case history briefly describes failure of a breakwater resulting from overestimation of the undrained strength, obtained from laboratory testing. An attempt has been made to examine the methods for determining the undrained strength from field vane testing. For this, the undrained strengths from field vane testing were obtained using different correction factors and compared with each other at five sites in the area. An alternative correction method applicable especially for Busan clay was found, using a range of corrected strength ratios. Further, relationships between the depositional environment and the undrained strength of the clay have also been investigated.