Optimizing the processing parameters of mechanical and hydraulic conductivity of geotextile liner

Glass geotextile reinforcement and needle-punch bonding are applied to compensate for the low mechanical strength of a geotextile clay liner (GCL) and reduce damage under complicated service conditions. Moreover, the effects of glass fibers embedded in the bentonite on hydraulic conductivity are investigated. A hybrid-structure glass geogrid-reinforced GCL (GGCL) is constructed by needle punching the bentonite laminated by a glass geogrid layer and separated by a 0.3 mm thick meltblown nonwoven layer. The central composite design (CCD) is proposed to discuss the effects of needle punch density (ND) and depth of punch (DP) on the tensile properties, quasi-static and dynamic puncture resistances, and hydraulic conductivity of the GGCL, and an empirical regression model of these properties is established. Results show that ND and DP significantly affect tensile the properties and puncture resistances while DP insignificantly affects the hydraulic conductivity of the GGCL. Glass fibers embedded into the bentonite improve the hydraulic conductivity of the material. At the 95% confidence interval, the process parameters can be optimized by the empirical regression model. The proposed regression model is consistent with experimental results and can thus be used to predict the mechanical properties and hydraulic conductivity of GGCL.     

Permeameter for investigating the hydraulic characteristics of geotextiles

The institute has developped and constructed a special permeameter to study the hydraulic properties of geotextiles. This apparatus has been designed for: the determination of reproducible results for the permeability for flow both normal to the plane and in the plane of geotextiles both alone and embedded in soil materials; the samples of geotextile are loaded statically and the deformations are obtained. The permeameter is described here in some detail. Some initial results for flow normal to the plane have already been obtained. In general, they show that the coefficient of permeability is dependent upon hydraulic gradient. It is also considerably influenced by the stress applied normal to the geotextile.     

Active control of cryogenic propellants in space

A new era of space exploration is being planned. Exploration architectures under consideration require the long term storage of cryogenic propellants in space. This requires development of active control systems to mitigate the effect of heat leak. This work summarizes current state of the art, proposes operational design strategies and presents options for future architectures. Scaling and integration of active systems will be estimated. Ideal long range spacecraft systems will be proposed with exploration architecture benefits considered.     

A High‐Performance Self‐Regenerating Solar Evaporator for Continuous Water Desalination

Emerging solar desalination by interfacial evaporation shows great potential in response to global water scarcity because of its high solar‐to‐vapor efficiency, low environmental impact, and off‐grid capability. However, solute accumulation at the heating interface has severely impacted the performance and long‐term stability of current solar evaporation systems. Here, a self‐regenerating solar evaporator featuring excellent antifouling properties using a rationally designed artificial channel‐array in a natural wood substrate is reported. Upon solar evaporation, salt concentration gradients are formed between the millimeter‐sized drilled channels (with a low salt concentration) and the microsized natural wood channels (with a high salt concentration) due to their different hydraulic conductivities. The concentration gradients allow spontaneous interchannel salt exchange through the 1–2 µm pits, leading to the dilution of salt in the microsized wood channels. The drilled channels with high hydraulic conductivities thus function as salt‐rejection pathways, which can rapidly exchange the salt with the bulk solution, enabling the real‐time self‐regeneration of the evaporator. Compared to other salt‐rejection designs, the solar evaporator exhibits the highest efficiency (≈75%) in a highly concentrated salt solution (20 wt% NaCl) under 1 sun irradiation, as well as long‐term stability (over 100 h of continuous operation).     

Hydraulic conductivity change of bio-barrier formed in the subsurface by the adverse conditions including freeze–thaw cycles

Bio-barrier is an emerging technology to control subsurface contaminant plum by making microorganisms clog soil pore to form a subsurface barrier. Extracellular polymeric substances (EPS) of microorganisms play an important role to maintain decreased hydraulic conductivity. In this research, the hydraulic conductivity changes of biomass–soil mixtures by the adverse conditions were studied to evaluate the applicability to the field condition as an alternative barrier material. The microorganisms used in this research were bacterium, Azotobacter chroococcum, and fungus, Aureobasidium pullulans, respectively. The hydraulic conductivity decreased to 1–10% of the initial hydraulic conductivity of residual soil, 1×10⁻⁴ cm/s, and stayed constant while substrate was provided. Under adverse conditions such as no substrate available, chemical solution permeation and freeze–thaw cycles, the hydraulic conductivity increased by 30–50% compared to the lowest value. The decrease of hydraulic conductivity in a fungus–soil mixture was faster than that of a bacterium–soil mixture. The fungus–soil mixture, however, was more sensitive to the adverse conditions. After the adverse conditions, hydraulic conductivity shows even lower value compare to that of before the adverse conditions.     

Liners for waste containment constructed with class F and C fly ashes

Hydraulic conductivity of a Class F fly ash containing residual organic carbon was evaluated in this study using laboratory and field tests. Compacted specimens of the Class F fly ash mixed with various materials (sand, Class C fly ash, and bottom ash) were prepared in the laboratory at various water contents and different compactive efforts. Hydraulic conductivity of the compacted specimens was measured using flexible-wall permeameters. A test pad was constructed to determine whether a low hydraulic conductivity liner could be constructed with Class F fly ash mixtures. Sealed double-ring infiltrometers and two-stage borehole permeameters were used to measure the field hydraulic conductivity of the test pad. Specimens were also removed from the test pad for hydraulic conductivity testing in the laboratory. Results of the study showed that mixtures of Class F and Class C fly ashes along with coarse aggregate can be compacted to hydraulic conductivities needed for landfill liners provided compaction is wet of optimum water content. The field tests showed that constructing a fly ash liner with hydraulic conductivities similar to those found in the laboratory is challenging, and requires careful attention to factors that result in cracks and permeable interlift regions that result in high field hydraulic conductivity. Leachate collected from the base of the test pad also showed that metal leaching must be considered when designing a liner with fly ash.     

An analytical solution for hydraulic conductivity of concrete considering properties of the Interfacial Transition Zone (ITZ)

As a composite material, hydraulic conductivity of concrete depends on conductivity of its components that are the mortar, aggregates and the Interfacial Transition Zone (ITZ). Since hydraulic conduction is analogous to heat and electrical conduction, analytical models from these analogous areas relating effective conductivity of composite to conductivity of its components can be used to find the effective hydraulic conductivity of concrete as a function of properties of its components, i.e., aggregate, mortar and the ITZ. However, effect of the conduction in the ITZ has not been considered in these models. This paper presents an analytical solution for the hydraulic conductivity of concrete as a three-phase composite material. The solution is an extension to the model originally proposed for conduction of composite media with randomly suspended spheres. Results of the proposed model compare well against the experimental results and those obtained from rigorous numerical analysis using the Finite Element (FE) method. The principal significance of this study lies in the development of a versatile analytical model that can be employed as a quick tool for assessment of hydraulic conductivity of concrete without the need for sophisticated FE models at the meso-scale level. It offers more insight into effect of different components of concrete on its overall conductivity.     

A literature survey on planning and control of warehousing systems

We present a literature survey on methods and techniques for the planning and control of warehousing systems. Planning refers to management decisions that affect the intermediate term (one or multiple months), such as inventory management and storage location assignment. Control refers to the operational decisions that affect the short term (hours, day), such as routing, sequencing, scheduling and order-batching. Prior to the literature survey, we give an introduction into warehousing systems and a classification of warehouse management problems     

Propagation of tides in the Mandovi and Zuari estuaries

The Mandovi and the Zuari are two shallow estuaries that are located in Goa and join the Arabian Sea. The main channel of each is about 50 km long, has its cross-sectional area decreasing rapidly in the upstream direction, and receives large amounts of riverine freshwater during the southwest Monsoon and little during the rest of the year. Tides in the channels exhibit the following characteristics: (a) The speed of propagation is about 6.5 m s⁻¹; (b) tidal amplitude remains unchanged over a distance of about 40 km from the mouth; (c) mean water level near the head increases with increase in runoff; (d) tidal amplitude decays rapidly over ≈ 10 km near the head, the decay is more rapid during periods of higher runoff. A nonlinear numerical model based on the equations for conservation of momentum and mass reproduces all the observed features. The model fields show that momentum balance in the channels is primarily between pressure gradient and friction. Assuming such a balance, we formulate a linear analytic model for tidal propagation in a channel whose cross-sectional area decreases exponentially with distance from the mouth and has influx of riverine freshwater at its head. The model solution mimics the observed features (a)–(c) cited above but not (d). Our conjecture is that the quadratic friction term in the momentum balance and the nonlinear term in the continuity equation are essential to simulate the decay of tidal amplitude at the upstream end.     

Using soil freezing characteristic curve to estimate the hydraulic conductivity function of partially frozen soils

We propose using the soil freezing characteristic curve (SFCC), instead of the soil water characteristic curve (SWCC), to estimate the hydraulic conductivity of partially frozen soils. Shortcomings associated with the use of the SWCC to estimate the hydraulic conductivity function of partially frozen soils are discussed. The hydraulic conductivity function for partially frozen Devon Silt is derived using the SFCC and the empirical relationships for hydraulic conductivity estimation method developed by Fredlund et al. (1994). The SFCC for Devon Silt is determined from unfrozen water content measurement using time domain reflectometry and temperature measurements inside the soil sample. The results using this novel approach compare well with results presented by others that use different methods to determine the hydraulic conductivity function of partially frozen soils.     

Plant-level maintenance decision support system for throughput improvement

In the current global scenario of extreme competition, factors such as productivity, availability, quality and cost of operations play a vital role in the success of a company. A critical component relating to all of the above is maintenance. The conventional maintenance decision support systems have primarily focused on maximising the gains of a single machine system. However, a real life application usually consists of multiple machines, and the operational level decisions are more complex. In this paper, an on line plant-level maintenance decision support system (PMDSS) is developed by combining the short term and long term decision making process to improve the overall system performance while continuously attempting to maximise immediate profits in the short term. The PMDSS works towards two basic aims: (1) unplanned downtime reduction by predicting the remaining useful life of the machines, and (2) efficient utilisation of the finite maintenance and production resources through identifying the throughput-critical machines. The benefits of this approach are presented by considering an industrial case study of an automotive assembly line. The results obtained using this PMDSS approach shows a big throughput improvement as compared to the conventional maintenance policies.     

An investigation of the potential of ethylene vinyl acetate/polyethylene blends for use in recyclable high voltage cable insulation systems

Ethylene vinyl acetate (EVA) co-polymers can potentially provide novel materials for inclusion into extruded high voltage cable systems, providing a degree of electrical conductivity whilst avoiding the dispersion problems associated with conventional particulate fillers or conducting polymers. Although a degree of conductivity can decrease the electrical breakdown performance, it can help to suppress the development of space charge and increase the tree initiation voltage leading to enhanced dielectric properties. In addition, novel two phase morphologies can be formulated leading to the ability to control key thermal and mechanical properties and the ability to tailor these to suit the application. In addition, one of the problems with conventional cross-linked polyethylene (XLPE) is that it cannot easily be recycled; therefore, in this time of increasing environmental awareness, it is prudent to begin investigations into alternative recyclable materials to replace XLPE in extruded cables for the medium to long term. The current article focuses on the crystallisation behaviour, morphology, mechanical and dielectric properties of a range of polymeric insulation systems based on an EVA co-polymer together with a high density polyethylene (HDPE) component. The morphology was controlled by choosing co-polymers containing different vinyl acetate contents together with appropriate crystallisation routes. The relationships between the morphology and the mechanical and dielectric properties were explored. Blends containing a low vinyl acetate content co-polymer combined with HDPE have significant potential to replace XLPE in cable systems and have the advantage of being easily recycled at the end of their service life.     

Asymmetric Supercapacitor Electrodes and Devices

The world is recently witnessing an explosive development of novel electronic and optoelectronic devices that demand more‐reliable power sources that combine higher energy density and longer‐term durability. Supercapacitors have become one of the most promising energy‐storage systems, as they present multifold advantages of high power density, fast charging–discharging, and long cyclic stability. However, the intrinsically low energy density inherent to traditional supercapacitors severely limits their widespread applications, triggering researchers to explore new types of supercapacitors with improved performance. Asymmetric supercapacitors (ASCs) assembled using two dissimilar electrode materials offer a distinct advantage of wide operational voltage window, and thereby significantly enhance the energy density. Recent progress made in the field of ASCs is critically reviewed, with the main focus on an extensive survey of the materials developed for ASC electrodes, as well as covering the progress made in the fabrication of ASC devices over the last few decades. Current challenges and a future outlook of the field of ASCs are also discussed.     

Developing a quality measurement tool and reporting format for long- term care

BACKGROUND: Quality measurement in long term care (LTC) presents many challenges: the lack of a uniform definition of quality, the existence of multiple domains for measurement, a multitude of potential perspectives, and regulatory influences that emphasize measurement only of poor quality. Research efforts have yet to solve the issues of measurement; however, operators of long term care facilities must use the current state of the art in quality measurement as the basis for their quality improvement efforts. A project was commissioned by management of a large integrated delivery system with a robust network of LTC facilities who wished to implement a continuous quality improvement process on the basis of a measurement tool that provides a comprehensive resident-centered assessment of quality. The objectives of this project, therefore, were to identify domains of quality, to select and adapt validated instruments for measurement within each domain, to pilot test a data collection process, and to develop an operational quality profiling report format for LTC facilities. DESIGN AND METHODS: Using an expert panel and the LTC research literature, an operational measurement tool was developed, consisting of four domains of quality: organizational, clinical, environmental, and social. DISCUSSION: A pilot study conducted in two nursing facilities demonstrated that the data collection process could be operationalized within tight resource and budgetary constraints. The development of an operational quality assessment tool enables management to take a consistent view of diverse institutions, focusing in detail on quality of care as it is perceived by residents. The tool allows evaluation of trends over time and comparison to external norms.     

X-ray technique for observation of ice lens growth in partially frozen,saturated soil

This paper reports observations on ice lens growth in partially frozen, saturated soil, and applications for the measurement of hydraulic conductivity in the frozen zone. The authors developed an experimental apparatus using an X-ray technique to observe the ice lens growth and measure the amount of dilatation due to the ice segregation in the sample (Yoneyama et al., 1983). The water flow rate was determined with the displacement of the lead spheres embedded in the sample under several overburden pressures and temperature gradients. The hydraulic conductivity in the frozen zone of the sample was calculated from the water flow rates in the frozen zone under the assumptions that (1) the water flow in the frozen zone could be described by the Darcy flow equation, (2) the generalized Clapeyron equation could be used to describe temperature-pressure relations and (3) ice pressure was equal to the overburden pressure behind the final ice lens. With decreases within a wider range of lower temperatures (?1 to ?10°C) than has ever been reported, the calculated hydraulic conductivities were found to decrease rapidly from 10^?11 to 10^?13 cm/s. It was also observed that the hydraulic conductivity did not depend greatly on the applied load.     

The CLOCK trial,a double‐blinded randomized controlled trial: Trisodium citrate 30% and minocycline 3 mg/mL plus EDTA 30 mg/mL are effective and safe for catheter patency maintenance among CKD 5D patients on hemodialysis

Introduction: Poor blood flow rate (PF) is highly prevalent among CKD 5D patients with long‐term central venous catheters. Heparin catheter lock solutions are commonly used to maintain catheter patency, however the incidence of PF remains high. The purpose of the CLOCK Trial was to evaluate two catheter lock solutions on reduction of PF incidence. Methods: Seventy‐five CKD 5D patients on high‐efficiency hemodialysis at the Integrated Centre of Nephrology (Guarulhos, Brazil) were randomized 1:1:1 to receive a lock solution combining minocycline 3 mg/mL with the anticoagulant/chelation agent EDTA 30 mg/mL (M‐EDTA) or heparin 1000 IU/mL (H) or trisodium citrate 30% (TSC) vs. Hfor 15 weeks. A total of 68 patients completed the trial in which both investigators and patients were blinded to treatment allocation. The primary end‐point was the occurrence of hydraulic resistance and secondary safety end‐point was adverse drug reactions related to the lock solutions. Findings: At the beginning of the trial, 7 patients were excluded from this trial due to their poor catheter care. The incidence of hydraulic resistance was significantly higher among patients on H (18/23) compared to TSC (4/22) and M‐EDTA (2/23) lock solutions, (P < 0.001). Discussion: The CLOCK Trial suggests TSC and M‐EDTA may preserve catheter patency better than H. TSC may be a better option due the lack of association with long‐term antimicrobial resistance.     

Uncertainty in analyses of one-dimensional steady-state seepage through random porous media

The aim of this paper is to assess the propagation of uncertainty in analyses of one-dimensional steady-state flow through random porous media. It is considered that uncertainty originates from lack of precise knowledge of soil hydraulic conductivity. This uncertainty is modelled by means of random variables. Taking into account experimental evidences, it is accepted that hydraulic conductivity has a log-normal probability distribution. The paper focuses on propagation of uncertainty from hydraulic conductivity to the computed flow rate through homogeneous and stratified random materials. The most common techniques available to evaluate propagation of uncertainty are briefly reviewed. The applicability and limitations of these techniques are assessed. Parametric studies to gauge the effect of uncertainty on soil hydraulic conductivity on the output statistics of flow rate are performed. Attenuation of uncertainty on flow rate as the number of materials in stratified soils increases is evaluated. Conclusions are presented regarding this attenuation and the usefulness of the different stochastic techniques employed, which proved to be more complementary than antagonistic.     

An artificial compressibility ensemble algorithm for a stochastic Stokes-Darcy model with random hydraulic conductivity and interface conditions

We propose and analyze an efficient ensemble algorithm with artificial compressibility (AC) for fast decoupled computation of multiple realizations of the stochastic Stokes-Darcy model with random hydraulic conductivity (including the one in the interface conditions), source terms, and initial conditions. The solutions are found by solving three smaller decoupled subproblems with two common time-independent coefficient matrices for all realizations, which significantly improves the efficiency for both assembling and solving the matrix systems. The fully coupled Stokes-Darcy system can be first decoupled into two smaller subphysics problems by the idea of the partitioned time stepping, which reduces the size of the linear systems and allows parallel computing for each subphysics problem. The AC further decouples the velocity and pressure which further reduces storage requirements and improves computational efficiency. We prove the long time stability and the convergence for this new ensemble method. Three numerical examples are presented to support the theoretical results and illustrate the features of the algorithm, including the convergence, stability, efficiency, and applicability.     

大尺度土工织物充填袋受力特性分析

建立了充填粉土泥浆重度成线性增加情况下土工织物充填袋袋体的力学特性方程,并给出它的数值分析方法。利用该方法研究了大尺度土工织物充填袋的受力特性,并通过实际工程验证了该方法的正确性。计算结果表明:充填压应力相同时,大尺度充填袋袋体的周向拉力远大于小尺度袋体。因此,为保证袋体的强度要求,大尺度土工织物充填袋的充填压应力应控制在比较小的范围。在此小充填压应力下,计算得到的大尺度土工充填袋的水平向尺寸远大于竖向尺寸,为扁平状态,与管状的小尺度土工织物充填袋的形状明显不同。     

1998 ASEM Conference Information and Registration Form

Abstract:

Highly capital-intensive systems in domains such as transportation, infrastructure, defense and aerospace, and telecom have long operational life cycles and their stakeholders expect them to exhibit the necessary operational and performance characteristics during these long operational life spans. Often the results have been less than satisfactory, which has led many to envision alternative approaches to effectively sustaining such systems. Among the alternative approaches is Performance Based Logistics (PBL), whose essence is to define key system readiness and effectiveness criteria and to contract for threshold values of these criteria. The emphasis is in contracting for results, and not for resources as traditionally done.

This article is based on a literature survey conducted on the papers published in connection with this topic since the advent of the PBL initiative, as well as on numerous personal interviews entertained in programs in which the authors have been involved, and briefly surveys current practices in PBL-based contracting, highlighting the lessons learned and outlining the primary drawbacks observed. Finally this article proposes a framework for formulating more efficient and effective PBL contractual agreements and identifies the main topics or aspects of a successful PBL initiative. Experience shows that in order for a PBL contract to yield the desired results it is essential to have a thorough agreement on the metrics to be used to represent system effectiveness, as well as an agreed reward scheme that links reward to achieved effectiveness.