People of the Lakes

Publisher PD

Numerical Solution Of Subsidence Mound Problems In Porous Media

From the macroscopic equations of flow through a porous medium, a model is developed for the subsidence or decay of a mound of fluid over a horizontal impervious barrier. Three finite difference approaches are used to investigate the resulting moving boundary problem. In the first method, a coordinate transformation is used that fixes the toe or leading edge of the fluid location. The resulting problem is solved on a regular grid with interpolation near the moving boundary. In the second method, a coordinate transformation is employed that fixes the location of the entire boundary while in the third method, a transformed polar coordinate formulation is employed that maps the domain onto a quarter circle. For the latter two methods the resulting equations are solved using a regular grid. It is demonstrated that for all three methods, a predictor-corrector scheme gives satisfactory results for the boundary position without iteration. It was found that the first two methods were more accurate than the third for a given spatial discretization. A new similarity solution to the Bousinesq approximation to the problem for an initially parabolic mound is presented and is found to compare favourably to the numerical solution to the full problem for mounds with large initial aspect ratios.;The model is refined so that the effect on the mobility of the fluid of heating along the interface is incorporated. The fluid viscosity and density are assumed to be dependent on temperature. The problem is investigated using the latter two fully transformed finite difference grids above. The backwards Euler method is used for the temporal derivatives of both the temperature and boundary position equation and a successive substitution scheme with relaxation is used to iterate between the various coupled equations. Again it is found that the scheme based on rectangular coordinates is more accurate for a given spacial discretization than the scheme based on polar coordinates. Depending upon the choice of parameters in the problem the mound takes on a \u27kinked\u27 appearance with the quickly heated toe area spreading out with a linear like profile and the central body of the fluid dropping slowly

ANWB automates and improves repair men dispatching

ANWB, the Dutch automobile association, provides assistance, car repair andreplacement services to its nearly 4 million members. ANWB services around 1.3 millionrequests per year in The Netherlands. Historically, the operational planning process ofassigning requests to service men was regionally organized, and human planners solvedthe sometimes large and hectic planning situations in real time. At a national level, some50 planners were required to do the job, and the quality of the planning and operationswere largely unknown. In a large business process reengineering project, ANWBredesigned the planning processes, leveraging state of the art IT and operations researchtechniques. As a result, the 24/7 planning processes are smoothened, can be executed byas few as 14 planners who work at a national level, and the operational planning andperformance have improved. As new competitors entered the market, ANWB has beenable to sustain its extraordinary high customer ratings and market share, while adaptingits proposition to the competitive prices dictated by the market.Economics (Jel: A)

"Walking Threads, Threading Walk": Weaving and Entangling Deleuze and Ingold with Threads

In this paper, I explore theoretical discussions that have emrged through the Walking Threads exercise, correspondences with Lembo, philosophical treatises by Deleuze and Guattari, and anthropological works by Ingold. The subsequent theoretical exploration has been an attempt in weaving together all these different correspondences by walking in the theoretical imaginations of Ingold and Deleuze. Walking Threads, I conclude, can be considered as an exercise or way of incorporating theory into practice

Electronic dispersion precompensation of direct-detected NRZ using analog filtering

We demonstrate (in real-time) electrical dispersion compensation in direct detection links using analog transmit side filtering techniques. By this means, we extend the fiber reach using a low complexity solution while avoiding digital preprocessing and digital-to-analog converters (DACs) which are commonly used nowadays. Modulation is done using an IQ MachZehnder modulator (MZM) which allows straightforward compensation of the complex impulse response caused by chromatic dispersion in the fiber. A SiGe BiCMOS 5-tap analog complex finite impulse response (FIR) filter chip and/or a delay between both driving signals of the MZMs is proposed for the filter implementation. Several link experiments are conducted in C-band where transmission up to 60 km of standard single-mode fiber (SSMF) of direct detected 28Gb/s NRZ/OOK is demonstrated. The presented technique can be used in applications where low power consumption is critical

Electrochemically induced precipitation enables fresh urine stabilization and facilitates source separation

Source separation of urine can enable nutrient recycling, facilitate wastewater management, and conserve water. Without stabilization of the urine, urea is quickly hydrolyzed into ammonia and (bi)carbonate, causing nutrient loss, clogging of collection systems, ammonia volatilization, and odor nuisance. In this study, electrochemically induced precipitation and stabilization of fresh urine was successfully demonstrated. By recirculating the urine over the cathodic compartment of an electrochemical cell, the pH was increased due to the production of hydroxyl ions at the cathode. The pH increased to 11-12, decreasing calcium and magnesium concentrations by >80%, and minimizing scaling and clogging during downstream processing. At pH 11, urine could be stabilized for one week, while an increase to pH 12 allowed urine storage without urea hydrolysis for >18 months. By a smart selection of membranes [anion exchange membrane (AEM) with a cation exchange membrane (CEM) or a bipolar membrane (BPM)], no chemical input was required in the electrochemical cell and an acidic stream was produced that can be used to periodically rinse the electrochemical cell and toilet. On-site electrochemical treatment, close to the toilet, is a promising new concept to minimize clogging in collection systems by forcing controlled precipitation and to inhibit urea hydrolysis during storage until further treatment in more centralized nutrient recovery plants

Understanding the Impact of Brand Delistings on Assortment Evaluations and Store Switching and Complaining Intentions

Recently, retailers have begun considering which brands they can delist without reducing customer satisfaction, losing category sales, or increasing store switching behavior. Although several studies have considered assortment reductions, none has explicitly investigated the impact of total brand delistings. Therefore, the authors study the impact of brand delistings on assortment evaluations and store switching and complaining intentions. They execute both a controlled experiment and a survey and find that brand delisting mainly has negative consequences when the delisted brands have high equity, assortment size is limited, the assortment consists of a low proportion of high-equity brands, and the brand delistings take place in categories with high hedonic levels. The authors discuss the theoretical and managerial implications of these findings

Congenital radial head dislocation with a progressive cubitus valgus: a case report

Congenital dislocation of the radial head is rare, although it is the most common congenital anomaly of the elbow. A concomitant progressive cubitus valgus of the elbow has not previously been described in literature. We describe a case of an 8-year-old girl with an unilateral congenital radial head dislocation with a progressive cubitus valgus of 35°, caused by a prematurely closing physis of the lateral humeral condyle. This might be caused by an increased pressure on the lateral physis by the anteriorly dislocated radial head. As no complaints or limitations were present, treatment was non-operative with clinical observation, with satisfactory results after a follow-up of 18 months. A concomitant progressive cubitus valgus can be present in patients with a congenital radial head dislocation. Non-operative treatment can provide satisfactory results

Introducing the Walking Threads Project

The following collections of essays and creative interventions of Paola Esposito, Ragnhild Freng Dale, Jan Peter Laurens Loovers, and Brian Schultis are the result of individual attempts to recall, reflect, and make sense of an exercise called "Walking threads". It also expressed a commitment to allow experiences to grow within and between the authors in an exercise of attunement