Leachate Recirculation in Bioreactor Landfills Using Geocomposite Drainage Material

The key purpose of this study was to test the use of a permeable blanket made up of a geocomposite drainage layer (GDL) for leachate recirculation in municipal solid waste (MSW) landfills and to predict the observed leachate travel in the blanket using a numerical model. A 34?m long by 12?m wide permeable blanket made up of GDL was constructed at an active MSW landfill located in Michigan. Leachate was injected in the GDL using a perforated pipe placed centrally above the GDL along its length. Moisture content sensors, pressure transducers, thermistors, thermocouple sensors, and a vertical load sensor were embedded immediately below the GDL blanket to monitor the flow of injected leachate. After the blanket was covered with waste, leachate was injected into the blanket at rates ranging from 0.9 to 2.6?m3/h per meter length of the blanket. Data collected from the embedded sensors indicated that the injected leachate traveled at rates ranging from 5 to 18?m/h through the blanket depending upon the leachate injection rate. Only pressure transducers and thermistors were consistently able to detect migration of injected leachate once the blanket got saturated. Moisture content sensors could not register any change in readings once the blanket became saturated. Leachate injection pressure monitored over a period of about 12 months indicated no signs of clogging of the blanket. The leachate pressures measured immediately below the blanket were less than the net leachate injection pressure indicting that there was a head loss in the GDL blanket. Numerical modeling of liquid flow in the blanket indicated that predicted leachate travel in the blanket was consistent with the field data for assumed values of the waste hydraulic conductivity. In the absence of measured representative hydraulic properties of the waste, absolute verification of the field data was not possible.     

Performance Characteristics of Alpha-Particle Corona-Streamer Counter

Alpha-particle wire-plate corona counters in air can be operated either in the spark or in the corona-streamer modes. The streamer mode is preferred over the spark mode since it has the advantages of low dead time and the absence of electrode corrosion by sparking. An analysis of the alpha-particle corona-streamer counter is described. The alpha-particle triggered corona pulse characteristics (e.g., pulse shape, amplitude, repetition rate, etc.) are calculated. Not only the pulse characteristics but also the inception voltages of the corona-mode regime are determined. For each wire diameter, a transition gap length between corona and spark modes exists, which is termed ``critical gap length.' The counting rate characteristics have been obtained for wire diameters 0.05-0.1 mm. All the theoretical findings are confirmed by experiment.     

Load Tests on Prestressed Precast Concrete and Timber Piles

This paper presents the results of six pile-load tests performed on timber and prestressed concrete piles. Five axial compressive pile-load tests and one lateral-load test are presented. Comparisons are made between the results of these tests and predictions made using available geotechnical computer software. These comparisons provide an insight into using the Brinch-Hansen method of pile-load test evaluation along with wave equation and other computer analyses to evaluate pile capacities from load test data. This paper demonstrates how wave equation analyses can be used to anticipate and mitigate excess driving stresses during the installation of prestressed concrete piles. This paper also demonstrates that the use of well-established analytical methods can adequately predict the vertical and lateral behavior of timber and prestressed concrete piles. However, the bending rigidity of concrete piles under lateral loading should be carefully selected to obtain a good prediction to the measured data.     

EFFECT OF REDUCTION CONDITIONS ON THE ACTIVITY OF Ni/γAl2O3 CATALYST FOR METHANATION REACTION

The effect of reduction conditions, mainly reduction temperature and duration time on the activity of Ni/γAl₂O₃ catalyst were studied for a methanation reaction in a gradientless Berty reactor. The methanation reaction was investigated using a feed containing CO (6.7 mole%), H₂ (26 mole%) and the balance being nitrogen at a pressure of 30 psig and a fixed temperature of 350°C. The reduction temperature was varying from 250 to 500°C, in order to investigate its effect on the methanation reaction. The methanation activity of the catalyst increased to a maximum by increasing the reduction temperature up to a maximum at 300-350°C and showed a slight negative decline afterward. The second parameter investigated was reduction duration time which was varied from 2 to 16 hours. It was observed that the methanation reaction activity increased by increasing the reduction duration time up to 6 hours. After six hours, there was no increase in activity. Based on the finding of this investigation, a recommended set of reduction conditions is given: reduction temperature of 300°C and a duration time of six hours.     

Determination of Sensory Thresholds of Selected Calcium Salts and Formulation of Calcium-fortified Pocket-type Flat Bread

Pita bread loaves were prepared from flours fortified with calcium carbonate, calcium sulfate, and tricalcium dicitrate at 8 ascending levels to provide ranges of 800 to 2500, 700 to 1500, and 400 to 2000 mg of added Ca/100 g flour, respectively. The detection thresholds of calcium salts in pita bread were determined by the 3‐alter‐native forced choice (3‐AFC) test and construction of dose‐response curves. Detection thresholds determined by calculating geometric mean of individual best estimate thresholds, using criterion of 50%‐above‐chance and probit analysis of 3‐AFC data, were in the middle region of calcium concentrations. Analysis of dose‐response curves yielded values for thresholds outside the range of surveyed calcium concentrations. The detection threshold of CaSO₄ (2724 mg/100 g) in pita bread was significantly higher (P < 0.01) than those of calcium carbonate (1984 mg/100 g) and tricalcium dicitrate (2132 mg/100 g). Calcium‐fortified pita bread was similar (P < 0.01) to its regular counterpart when formulated to contain 1254.6, 1772.5, or 1155 mg/100 g of CaCO₃, CaSO₄, or tricalcium dicitrate, respectively. At the indicated levels of fortification, calcium‐fortified pita bread is expected to provide between 61% and 126.5% of the recommended daily intake for calcium for Middle Eastern populations.     

Verbundverhalten von Vollgewindeschrauben in Brettschichtholzbauteilen

Bond behaviour of self‐tapping screws being used as reinforcement in glue‐laminated timber elements – Part 2: Analytical and numerical investigations as well bond model derivation for the calculation of anchorage length In favor of the investigation of bond behaviour, force transfer and anchorage length of self‐tapping screws, several tests have been realized at the Chair of Structures and Structural Design in cooperation with the Institute for Building Material Research of the RWTH Aachen University. The experimental investigations comprise more than 160 pull‐out tests of screws with long embedment length and over 84 load distributions tests. Additionally, several tests displaying the effect of longitudinal cracks in the surrounding wood as well as the effect of the screw tip have been conducted. Through various analyses of the bond behaviour, the experimental investigations form the basis for the calibration and evaluation of the numerical models and allow a prediction of the force transfer of the screws in glue‐laminated elements. Design rules that enable the application of the self‐tapping screws as reinforcement in timber elements have been derived from the knowledge obtained in the experimental and numerical investigations. This paper, which results from a research project funded by the German Research Foundation [1], presents the results of investigations on the bond behavior of self‐tapping screws in glue‐laminated timber elements. Part 1 elaborates on the experimental investigations [2] whereas part 2 illustrates the numerical analyses and presents a bond model, which enables the design of the anchorage length and the safe application of the screws as reinforcement in timber elements.     

Synaptic plasticity based model for epileptic seizures

In this paper, a new dynamic model describing the epileptic seizure initiation through transition from interictal to ictal state in a brain predisposed to epilepsy is suggested. The model follows Freeman’s approach where the brain is viewed as a network of interconnected oscillators. The proposed nonlinear model is experimentally motivated and relies on changes in synaptic strength in response to excitatory spikes. This model exhibits a threshold beyond which a bifurcation toward a short-term plasticity state occurs leading to seizure onset. A resulting explanatory assumption is that when considering epilepsy, brain regions are characterized by abnormally low thresholds toward short-term synaptic plasticity. It is shown by simulation that the proposed model enables some experimentally observed qualitative features to be reproduced. Moreover, a preliminary discussion on the impact of the underlying assumptions on the fundamental issue of seizure control is proposed through an EEG based feedback control scheme.     

Recent advances in nuclear power: A review

The rise in oil prices and the increased concern about environmental protection from CO₂ emissions have promoted the attention to the use of nuclear power as a viable energy source for power generation. This review presents the recent advances in the field of nuclear power and addresses the aspects of nuclear economics, safety, nuclear reactor design and spent fuel processing and waste management.     

Toward a better understanding of multifunctional cement-based materials: The impact of graphite nanoplatelets (GNPs)

The impact of graphite nanoplatelets (GNPs) on the physical and mechanical properties of cementitious nanocomposites was investigated. A market-available premixed mortar was modified with 0.01% by weight of cement of commercial GNPs characterized by two distinctively different aspect ratios.The rheological behavior of the GNP-modified fresh admixtures was thoroughly evaluated. Hardened cementitious nanocomposites were investigated in terms of density, microstructure (Scanning Electron Microscopy, SEM and micro–Computed Tomography, μ-CT), mechanical properties (three-point bending and compression tests), and physical properties (electrochemical impedance spectroscopy, EIS and thermal conductivity measurements). At 28 days, all GNP-modified mortars showed about 12% increased density. Mortars reinforced with high aspect ratio GNPs exhibited the highest compressive and flexural strength: about 14% and 4% improvements compared to control sample, respectively. Conversely, low aspect ratio GNPs led to cementitious nanocomposites characterized by 36% decreased electrical resistivity combined with 60% increased thermal conductivity with respect to the control sample.