bluuebunny/crossref_metadata_2025 huggingface dataset:
Outdoor Performance Characterization of Grid-Connected Inverters
Authors: Lynn Kevin
Published: December 2008

Between April 2001 and September 2002, the Florida Solar Energy Center conducted research to evaluate the performance of several utility-interactive inverters. The major issues to be identified were the efficiency of the inverters and their ability to follow the maximum power point of the photovoltaic (PV) array. Existing PV testing facilities at FSEC were modified to carry out this analysis. This facility, called the Photovoltaic Inverter Test Facility, is capable of providing approximately four kWp of array power to the inverter. Data on inverter performance were collected using a Campbell 10X datalogger. The parameters collected included the following: irradiance, PV array temperature, inverter temperature, PV voltage, PV current, AC voltage, AC current, and AC Power. Because of the voltage windows and power requirements of the different inverters, the array was designed to be easily reconfigured to meet those requirements. Each of the inverters was installed and allowed to run for several weeks under both clear and cloudy conditions. At the end of the test period, inverter efficiencies were calculated from the collected data. The ability of the inverter to follow the maximum power point of the array was evaluated in two ways. In the first method, DC voltage and current were measured while the inverter was operating, then the array was disconnected from the inverter and the maximum power point of the array was immediately taken. By comparing the measured DC voltage and current to the maximum power point of the array, one could determine the effectiveness of the inverter algorithm. Unfortunately this method requires steady-state conditions and does not show the effectiveness of the algorithm in cloudy conditions. To determine its effectiveness in cloudy conditions, DC voltage and current were compared to the expected maximum power. The expected array maximum power point was calculated from IV curves of the array, irradiance measurements, and array temperature measurements. DC to AC efficiency curves were derived from the data as well. Results from the inverters were mixed, but several showed room for improvement.
Design of a Flat Plate Solar Collector for Absorption-Cooling Applications in the Caribbean
Authors: Alva Solari Luis H. , Gonza´lez Cruz Jorge E. , Yei Ming
Published: December 2008

The present work deals with the design methodology of a high efficiency flat plate solar collector to be used in absorption cooling system and for climates like Puerto Rico and the Caribbean. Specialized software was used to simulate the thermal behavior of the solar collector and the mechanical stresses. Results such as the optimum thickness of insulation and spacing between the glass and the absorbing surface are given.
Lifetime of Imidazolium Salts at Elevated Temperatures
Authors: Blake Daniel M. , Moens Luc , Rudnicki Daniel , Pilath Heidi
Published: December 2008

This report summarizes progress to date on the thermal stability of imidazolium salts being considered for application as heat transfer and thermal storage fluids in solar parabolic trough power systems. Imidazolium salts are a subset of the general class of molten salts. They are termed ionic liquids because many have freezing points at or below room temperature. This class of salts was selected for initial study because there were many examples that were reported to be stable at high temperatures. These reports were usually based on the results of standard thermal gravimetric analysis (TGA) methods. Work by our subcontractor at the University of Alabama and at NREL showed that slow heating rates or when the temperature is held constant for long times resulted in decomposition temperatures that are much lower than found with the usual TGA methods. We have used a TGA technique that allows calculation of the rates of thermal decomposition as a function of temperature. The results lead us to the conclusion that the imidazolium salts known to be the most thermally stable would not have useful lifetimes above about 200°C. At present this determination is based on the rough approximation that the fluid in a solar trough system experiences a constant, high temperature. Better estimates of the useful lifetime will require a system model that takes into account the time at temperature distribution of a fluid moving through the different components in a solar plant.
Feasibility of Usage Possibility in Turkey of Solar Driven Ejector-Absorption Cooling System
Authors: So¨zen Adnan , Yu¨cesu H. Serdar
Published: December 2008

It appears that solar assisted refrigeration systems are a promising alternative to the conventional electrical driven units. Their main advantages are the reduction of peak loads for electricity utilities, the use of zero ozone depletion impact refrigerants, the decreased primary energy consumption, and decreased global warming impact. In this study, we have investigated the possibility of using ejector-absorption cooling systems (EACS) in Turkey. In addition, this study determines whether or not required heat for generator of EACS can be obtained from solar energy in Turkey. There are two important reasons to explain the use of EACS in Turkey. One is that the production and use of the CFCs and HCFCs will be phased out according to Montreal Protocol. The second is that, in Turkey, solar energy potential is very high due to its location in the northern hemisphere with latitudes 36–42°N and longitudes 26–45°E, the yearly average solar radiation is 3.6 kWh/m2 day, and the total yearly radiation period is ∼2610 h. The radiation data and sunshine duration information collected since 2000 for 17 cities are used for analysis in different regions of Turkey. For maximum coefficient of performance (COPmax) conditions of EACSs operated with aqua-ammonia, it is found that required optimum collector surface area was defined by using the meteorological data. In addition since the system can be used throughout the year, required minimum energy for auxiliary heater was also calculated. It is shown that the heat gain factor (HGF) varies in the range from 0.5 to 2.68 for the all the seasons in the selected cities. The maximum HGF is 2.68 for Van in July. This study shows that there is a great potential for utilisation of solar cooling system for domestic heating/cooling applications in Turkey.
Generation of Monthly Average Hourly Ambient Temperatures From Monthly Average Daily Temperature
Authors: Ravikumar P.
Published: December 2008

A method to generate monthly average hourly ambient temperature values, Tah,n, in terms of the monthly average daily ambient temperature, Ta and latitude, φ is presented here. The present correlations do not require the additional information needed in applying the correlations available in [1,2,3]. The predicted monthly average hourly ambient temperature, Tah,n values have been found to be in agreement with data values within a % rms difference of 0.43 (when Tah,n is in K) and the standard deviation has been found to be 1.243 K, for 56 primary locations of TMY2, comparable to the prediction of Erbs, Klein and Beckman [1].
Sustainability Assessment of Solar Energy Systems
Authors: Afgan Naim H. , Jovanovic Marina , Carvalho Maria G.
Published: December 2008

Solar energy systems are becoming potential option for numerous applications. It has been shown that the application of solar energy system is strongly dependent on criteria’s used in their evaluation. Single criteria evaluation of solar energy systems has shown its deficiency due to limited possibility to compare them with other potential options. In particular, present economic system is based on the econometric analysis with priority given to the optimum obtained by the economically justified optimization function. For this reason, it has become needed to introduce multi-criteria evaluation procedure in the assessment of solar energy system and its comparison with other potential options. This paper presents evaluation of the solar photovoltaic system and its comparison with other renewable energy system options for stand-alone application. In this evaluation following energy systems will be taking into a consideration: grid electric energy supply, wind energy system, gas turbine with cogeneration, small hydro energy system and solar photo-voltaic energy system. In the evaluation of these systems the multi-criteria evaluation procedure is used. The multi-criteria evaluation procedure will comprise a following criteria’s: economic, environmental, technological and social indicators. Each of indicators will be based on the sub-criteria which are defined in the paper. The sustainability index as the agglomeration function indicators will be used in the determination of the rating among the options under consideration. Special emphasize in evaluation is given to to the conditional priority of indicators leading to the investigation of the effect of the indicator priority to the finale rating among options.
Testing of Thermocline Filler Materials and Molten-Salt Heat Transfer Fluids for Thermal Energy Storage Systems in Parabolic Trough Power Plants
Authors: Brosseau Doug , Edgar Mike , Kelton John W. , Chisman Kye , Ray Daniel , Emms Blaine
Published: December 2008

Parabolic trough power systems that utilize concentrated solar energy to generate electricity are a proven technology. Industry and laboratory research efforts are now focusing on integration of thermal energy storage as a viable means to enhance dispatchability of concentrated solar energy. One option to significantly reduce costs is to use thermocline storage systems, low-cost filler materials as the primary thermal storage medium, and molten nitrate salts as the direct heat transfer fluid. Prior thermocline evaluations and thermal cycling tests at the Sandia National Laboratories’ National Solar Thermal Test Facility identified quartzite rock and silica sand as potential filler materials. An expanded series of isothermal and thermal cycling experiments were planned and implemented to extend those studies in order to demonstrate the durability of these filler materials in molten nitrate salts over a range of operating temperatures for extended timeframes. Upon test completion, careful analyses of filler material samples, as well as the molten salt, were conducted to assess long-term durability and degradation mechanisms in these test conditions. Analysis results demonstrate that the quartzite rock and silica sand appear able to withstand the molten salt environment quite well. No significant deterioration that would impact the performance or operability of a thermocline thermal energy storage system was evident. Therefore, additional studies of the thermocline concept can continue armed with confidence that appropriate filler materials have been identified for the intended application.
Two-Dimensional Axi-Symmetric Model of a Solar-Thermal Fluid-Wall Aerosol Flow Reactor
Authors: Dahl Jaimee K. , Weimer Alan W. , Z’Graggen Andreas , Steinfeld Aldo
Published: December 2008

A solar-thermal fluid-wall reactor consisting of three concentric vertical tubes is constructed to dissociate methane to hydrogen and carbon black using concentrated solar power. Several aspects of the design are modeled for scaling the system up: the heat transfer and its effect on the integrity of the materials, and the fluid flow of all gas streams within the reactor. It is determined that the inlet gas temperatures, mass flow rates, and permeability of the porous wall affect the gas flow profile through the porous tube wall. By increasing the inlet gas temperature and/or the tube permeability in the hot zone section of the reactor, a more uniform flow profile can be obtained along the length of the tube.
Solar Radiation Over the Caribbean Island of Puerto Rico
Authors: Rivera Ramiro L. , Altaii Karim
Published: December 2008

Solar radiation was measured and recorded on a 5-minute, hourly and daily basis at a number of sites on the Caribbean island of Puerto Rico (located from 18° to 18° 30’N latitude and from 65° 30’ to 67° 15’W longitude) over a 24 calendar month time frame. The global solar radiation was measured at four sites (namely: Aguadilla, Ponce, Gurabo, and San Juan). The global solar radiation data was measured by an Eppley Precision Spectral Pyranometer (model PSP) mounted on a horizontal surface. This pyranometer is sensitive to solar radiation in the range of 0.285 ≤ λ ≤ 2.8 μm wavelengths. Statistical analysis such as the daily average, monthly average hourly, monthly average daily, and annual average daily global radiation are presented in this paper. Despite its small size, a 13 percent variation in the global solar radiation has been observed within the island. Reasonable solar radiation values, for solar energy conversion system installation, seem to exist at and possibly around Aguadilla.
Generalized A/C and H/P Transcritical R744 Compressor Performance in Wet and Dry Regions
Authors: Abdel-Rahim Yousef M.
Published: December 2008

Performance of the compression process of Carbon Dioxide (R744) in (A/C) and (H/P) systems depends on many factors related to fluid properties, equipment design and process parameters. Diversity of these factors represents a difficulty to have an overall-view of the hidden capabilities and limitations of the compression process. Thus, it is hard to apply any appropriate design optimization methods for the compressors, specifically for two reasons: (1) when the compression starts from the wet or saturation region and commences through the transcritical dry region of the fluid and (2) when the compressor works at off-design operating point during its working life-time. In an answer to these two points, the present paper utilizes the first and second laws of thermodynamics augmented by Monte-Carlo method to investigate, expose and discuss the compression performance (e.g. final temperature and pressure, work and size of compressor and second law efficiency) starting randomly from the wet/saturation region to the transcritical dry region of R744. The study shows that initial temperature has a greatly decreasing effect on compressor specific displacement volume per unit work and to a less extent on size of compressor, while its effects on all other parameters are insignificant. Initial pressure has similar expected trends as those of the initial temperature due to their linear relationship in the wet region. Final to initial temperature ratio has increasing effects on both final pressure and work of compressor and decreasing effects on both second law efficiency and specific displacement volume per unit work. The method presented here could open many ways for further theoretical design optimization applications of the compressor and hence greatly limits the trade-off methods that are usually adopted in the selection of such units.
Effect of Design Parameters on the Performance of Thermal Energy Storage Systems
Authors: Henze Gregor P.
Published: December 2008

This paper describes simulation-based results of a large-scale investigation of a commercial cooling plant including a thermal energy storage system. A cooling plant with an ice-on-coil system with external melt and a reciprocating compressor operating in a large office building was analyzed under four different control strategies. Optimal control as the strategy that minimizes the total operating cost (demand and energy charges) served as a benchmark to assess the performance of the three conventional controls. However, all control strategies depend on properly selected design parameters. The storage and chiller capacities as the primary design parameters were varied over a wide range and the dependence of the system’s cost saving performance on these parameters was evaluated.
Improving Discharge Characteristics of Indirect Integral Collector Storage Systems With Multi-Element Storage
Authors: Boies A. M. , Homan K. O.
Published: December 2008

Desired performance of unpressurized integral collector storage systems hinges on the appropriate selection of storage volume and the immersed heat exchanger. This paper presents analytical results expressing the relation between storage volume, number of heat exchanger transfer units and temperature limited performance. For a system composed of a single storage element, the limiting behavior of a perfectly stratified storage element is shown to be superior to a fully-mixed storage element, consistent with more general analysis of thermal storage. Since, however, only the fully-mixed limit is readily obtainable in a physical system, the present paper also examines a division of the storage volume into separate compartments. This multi-element storage system shows significantly improved discharge characteristics as a result of improved elemental area utilization and temperature variation between elements, comparable in many cases to a single perfectly-stratified storage element. In addition, the multi-element system shows increased robustness with respect to variations in heat exchanger effectiveness and initial storage temperature.
SUWIC Innovations in Thermal Waste to Energy Technologies
Authors: Swithenbank Jim
Published: December 2008

Sustainable cities require the generation of electrical energy from those fractions of wastes that cannot be economically reused or recycled, including the “carbon dioxide neutral” biomass components. The energy content of these solid materials can be recovered by burning directly or after processing into refuse-derived fuel (RDF). Alternatively, the combustion process can be staged by the production of intermediate fuels using either pyrolysis or gasification. Co-processing of the material with coal generally increases plant utilisation and thus reduces costs.
Practical Applications for Ash Reuse
Authors: Hauser Robert
Published: December 2008

This panel session reviews a topic of long-standing interest and importance to the municipal waste combustion industry; how can some or all of the ten percent (10%) by volume of incoming material that remains after municipal solid waste is combusted be productively reused? This panel will address various reuse related topics, including but not limited to the following: • Pinellas County, Florida hosts a regional program where recovered ferrous metals from municipal waste combustors are shredded and recycled; an overview of experiences, economics, and logistics will be presented. • The Pennsylvania Department of Environmental Protection (PADEP) will discuss the technical and regulatory background behind a September 2003 Consent Decree entered with American Ash Recycling for removal of residual materials in York County, Pennsylvania. • The City of Tampa has short-listed two (2) companies for what promises to be a precedent-setting ash reuse program; a status report will be given. • SUNY Stony Brook’s Waste Reduction and Management Institute’s work on two demonstration programs using processed MWC ash (using processed MSW combustor ash in both cold mix asphalt and construction quality cement blocks as well as a concrete block demonstration program) will be discussed. • Florida Department of Environmental Protection’s (FDEP’s) multifaceted program to address municipal combustion ash residue beneficial use determinations, ash regulation changes, and its analysis of statewide total metals data will be reviewed.
Accrediting Greenhouse Gas Credits for Marketing: The Saugus Experience
Authors: Ferraro Francis
Published: December 2008

The potential for global climate change due to the release of greenhouse gas (GHG) emissions is being debated both nationally and internationally. While many options for reducing GHG emissions are being evaluated, MSW management presents potential options for reductions and has links to other sectors (e.g., energy, industrial processes, forestry, transportation) with further GHG reduction opportunities.
Replacement Operator for the Savannah Waste-to-Energy Facility
Authors: Howell Jay
Published: December 2008

The Savannah Waste-to-Energy Facility (the Facility) is a mass burn waste-to-energy facility with a processing capacity of 624 tons per day. The Facility commenced commercial operation in 1987, as a public-private partnership with the Resource Recovery Development Authority for the City of Savannah, Georgia. In April 2002, Montenay took over operation of the Facility from Katy-Seghers, continuing the established partnership Katy-Seghers had with the City of Savannah. This paper presents a case study of a successful change in operator for a waste-to-energy facility, detailing the hurdles crossed transitioning operation of the Facility to Montenay.
Simulation and Validation of a Mass Burn WTE Boiler Using CFD Modeling
Authors: Epelbaum Greg
Published: December 2008

American Ref-Fuel Company (ARC) spends millions of dollars each year on corrosion related costs in the boilers. The corrosion is caused by chloride salts in the slag that deposit on the boiler tubes, coupled with the high temperatures of flue gas going through the boiler. Corrosion rates are known to be very sensitive to the flue gas temperature and velocity, surface temperature and heat flux through the slag, oxygen in flue gas distribution, etc. These parameters are primarily determined by the firing rate of the boiler, and they are also affected by combustion control and air distribution in the boiler. Some design parameters, such as surface area of refractory, tile, and inconel overlay, also affect the flue gas temperature throughout the boiler, and thereby impact corrosion.
Closure of the City of Key West, Southernmost Waste to Energy Facility
Authors: Shabat Dan
Published: December 2008

The Southernmost Waste-to-Energy Facility, is a 150 ton per day, stoker fired, mass burn facility located on Stock Island in the City of Key West, Florida. The facility is owned and operated by the City of Key West and is categorized as a Small MWC, Class II facility under the Emission Guidelines for Existing Small Municipal Waste Combustors, 40 CFR 60 subpart BBBB. In order to reliably comply with the requirements of the small MWC regulations, the facility air pollution control trains were required to be retrofitted to include acid gas control and improved particulate control through the installation of scrubbers and baghouses. Additional controls for metals including mercury may have been added in order to assure compliance with these regulations. Other facility upgrades including combustion enhancements may have been required to assure compliance with allowable carbon monoxide limitations of the Small MWC regulations. The need for the air pollution control retrofit project represented a major expenditure for the City of Key West. Faced with a decision regarding its long term future waste handling and disposal methods, the City examined various options for future solid waste handling and disposal including the option to proceed with retrofitting the waste-to-energy facility and relying on waste-to-energy as a long-term major component of Key West’s solid waste handling and disposal plans. Alternatively, the City explored the option of building a transfer station, either privately or publicly operated, and contracting the hauling and disposal of the City’s waste to a private firm. The transfer station option would require a conversion of the waste-to-energy facility to a transfer station through a major demolition and reconstruction project. The City also considered available alternative technologies such as gasification for example. In order to help the City sort through the many issues associated with the solid waste handling and disposal options, a Technical Advisory Committee was formed consisting of engineering and legal consultants, City commission members, and other City representatives. Dvirka and Bartilucci Consulting Engineers, as a member of the Technical Advisory Committee, was responsible for estimating the costs associated with the design, construction and operation of a waste-to-energy facility air pollution control retrofit project. This paper describes the facility and discusses the decision making process of the technical advisory committee and the ultimate decision of the City Commission to close the Southernmost Waste to Energy Facility. The paper includes the requirements for closure of the facility and discusses how the City arrived at its final decision.
Making Lemonade From Lemons: Lessons Learned in Reducing the Economic and Environmental Impact and Negotiating the Post-2005 Service Agreements on Behalf of the 23 NESWC Communities
Authors: Worster Shawn , Brydges Andrew
Published: December 2008

The twenty-three communities that comprise the North East Solid Waste Committee have labored under what may well be the worst municipal solid waste service agreement in the country. In FY 2004, the disposal fee is $140 per ton. Over the past eighteen years, the communities have paid more for disposal, as much as two to three times what the neighboring communities have paid. The NESWC Board of Directors has, over the course of the past ten years, implemented a multifaceted program to reduce the environmental and economic burden associated with managing the municipal solid wastes generated in the 23 member communities. The program has included a series of innovative approaches to obtaining negotiating leverage and support from diverse stakeholders to reduce the cost and implementing innovative programs to help reduce the amount and toxicity of waste requiring disposal. What makes this particularly significant is that it was done on a regional basis, involved interaction with a broad, diverse group of stakeholders at the local, state and federal level and required the use of a wide array of change inducing tools, including arbitration and litigation, to achieve the results. Most recently, the communities and the vendor, Wheelabrator North Andover, completed negotiations regarding service post termination of the existing Service Agreement in September, 2005. This paper updates key lessons learned over the past decade.
Ash Recycling: Just a Dream?
Authors: Zwahr Heiner
Published: December 2008

Waste to energy is only one way of handling waste, material recovery is another aspect of sustainable waste management. This is actually nothing new and has always been part of the operation of WTE (Waste to Energy) plants in Hamburg. In descriptions of the first waste incineration plant in Hamburg, which started operation in 1896, it was stated that “the fly ash” collected in the ash chambers was used as filler material for the insulation of ceiling cavities. Its use in the sandwich walls of money safes was expressly recommended by the members of the urban refuse collection authority. Another lucrative trade was the sorting of scrap iron. It was separated from the incineration slag with magnets. The slag itself was said to be as sterile as lava, as hard as glass, as useful as bricks, and it was a profitable side product of waste incineration. The crushed incinerator slag was evidently so much in demand in road construction and as an aggregate in concrete production that demand could often not be met in the building season, even though it was stored through the winter, [1,2,3].
Effects of Feed Composition on Boiler Corrosion in Waste-to-Energy Plants
Authors: Albina Dionel O. , Millrath Karsten , Themelis N. J.
Published: December 2008

Municipal solid wastes (MSW) typically contain plastic materials, leather, textiles, batteries, food waste and alkalis. These materials are sources of chlorine, sulfur, potassium, zinc, lead and other heavy metals that can form corrosive media during combustion of the MSW in waste-to-energy (WTE) facilities. Chlorides and sulfates, along with fly ash particles, condense or deposit on the waterwall surfaces in the combustion chamber and on other heat exchanger surfaces in the convection path of the process gas, such as screens and superheater tubes. The resulting high corrosion spots necessitate shutdowns and tube replacements, which represent major operating costs. The aim of ongoing research at Columbia University is to gain a better understanding of the effects of fuel composition, products of combustion, and chemical reactions that lead to the corrosion of metal surfaces in WTE boilers. The potential chemical reactions and their chance of occurrence were determined by means of thermochemical calculations of the respective equilibrium constants as a function of temperature and gas phase composition.
Superheater Life With Stainless, Inconel, and Carbon Steel Alloys at the Maine Energy Recovery Company
Authors: Robbins Ken , Huard Ken , King John
Published: December 2008

The Maine Energy Recovery Company is a refuse derived fuel (RDF) waste to energy facility that began commercial operation in 1987. The facility consists of an RDF production operation, two B&W boilers which produce 210,000 lb/hr of steam at 650 psig/750F with a design Furnace Exit Gas Temperature of 1700 F, and a 22 MW steam turbine generator. Since startup, the facility has suffered fireside erosion/corrosion of the waterwalls, superheater, and generator bank hot side sections. Through the years, Maine Energy has made various operational and design changes in order to improve combustion and overall boiler availability. While combustion has improved as evidenced by improved emissions, reduced supplemental fuel usage, and lower ash production, superheater availability has suffered. At the same time reliability of the waterwall and generating bank components have improved. This paper will present a history of Maine Energy’s efforts to improve its superheater availability including a summary of the tube wastage rates for various superheater alloys, as well as Maine Energy’s plans for its superheaters.
Refractory Tile Installation: Mortar or No Mortar?
Authors: Stephan Patrick M. , His Christian , Monchalin Nathalie
Published: December 2008

Some domestic waste incinerators [1] have operated successfully with refractory tile systems for tube protection without using mortar to bond the tiles to the tube walls. Most tile protection systems installed around the world employ a paste of mortar behind the tiles to develop a rigid fixing system, with the presumption that the mortar provides another layer of tube protection behind the tiles. This paper examines the issues behind these approaches to tube wall protection and propose some guidelines for the use of refractories in these systems.
An Energy Audit That Saved Real Energy and Money
Authors: Bases Gary J.
Published: December 2008

An energy audit can mean many things to many different people. For some, an energy audit or assessment means focusing on processes, operations, or equipment. This particular audit was directed toward the brick, refractory, and insulation, and its direct effect on the boiler’s efficiency, reliability, and energy fuel savings. Compared to most components found on a steam-generating boiler the cost of the materials and the installation of the refractory or brick are very small (less than 1% of the total cost of a new boiler). Yet, when properly designed, specified, stored, installed, cured or dried, refractory will save as much as five to seven percent in annual fuel cost (oil, gas, coal, refuse). Refractory and brick problems are found on most steam-generating boilers. These problems directly affected the amount of fuel used to meet heat and steam requirements. A boiler will always use more fuel if the brick and refractory are not installed correctly. After all the changes and corrections were made it was estimated that there will be an annual fuel savings of approximately $100,000 per year. This is why experts say, “Brick and refractory installed to save energy also saves money at a rate that is essential for efficient plant operation.”
Combining Anaerobic Digestion and Waste-to-Energy
Authors: Ostrem Karena M. , Millrath Karsten , Themelis Nickolas J.
Published: December 2008

A large fraction of the municipal solid wastes (MSW) stream in the U.S. comprises of natural organic compounds (i.e., food and plant wastes) with high moisture content and low heating value. While these properties are undesirable during the combustion of MSW in waste-to-energy (WTE) plants, they are required for anaerobic digestion (AD). During AD, methane gas is produced that can be captured and used for energy generation. The required long residence times limit the throughput of an AD plant but further development may result in increasing the rates of bioreactions. This paper introduces current AD practices and identifies possible synergies between AD and WTE. It is suggested that co-siting of WTE and AD facilities may result in mutual benefits.
Modeling of Solid Waste Flow and Mixing on the Traveling Grate of a Waste-to-Energy Combustion Chamber
Authors: Nakamura Masato , Themelis N. J.
Published: December 2008

Mixing of the highly non-homogeneous municipal solid wastes (MSW) on the traveling grate of mass-burn combustion chambers assists the combustion process in waste-to-energy (WTE) facilities. A matrix-based Markov chain model was developed to simulate particle flow and mixing as the solid waste particles travel over a reverse acting Martin grate. The model was used to project the pathway of a solid waste particle over a time series, in the bottom layer of the bed that is in contact with the bars of the grate. Further analytical and experimental work is planned in order to develop this model to a useful tool for designing future moving grate systems and increasing the combustion efficiency of existing WTEs.
Electricity: From Tabletop to Power Plant
Authors: Moran Timothy
Published: December 2008

While electricity is central to our daily lives, it remains “black box” technology to most students. They know that electricity is produced somewhere and that it costs money, but they do not have personal experience with the operation and scale of the machines that provide it. Fortunately, electricity generation can be added to the more basic circuit topics (series, parallel, current, voltage, etc.) with only a small investment in equipment. Providing students with hands-on experience with small power sources will help them make wise decisions about electricity.
Comments on “Speed of Sound in Metal Pipes: An Inexpensive Lab”
Authors: Blodgett Earl D.
Published: December 2008

In a recent article Huggins1 outlines a very simple method of measuring the speed of sound in metal pipes by striking one end with a hammer and recording the transit time as the resultant pulse echoes back and forth. We immediately adapted this for use in an introductory laboratory where we are familiarizing students with the measurement of time-dependent signals, especially how to set trigger levels for transient capture. As we prepared to implement this in our situation, we made a few observations that others may find of value.
The Critical Angle Can Override the Brewster Angle
Authors: Froehle Peter H.
Published: December 2008

As a culminating activity in their study of optics, my students investigate polarized light and the Brewster angle. In this exercise they encounter a situation in which it is impossible to measure the Brewster angle for light reflecting from a particular surface. This paper describes the activity and explains the students' observations.
Nils Gustav Dalén, the Unknown Nobel Prize Winner
Authors: Greenslade Thomas B.
Published: December 2008

Hanging on the wall of my museum is a large “Map of Physics” published by the Central Scientific Company in 1938. On it is a list of the Nobel Prizes in physics, starting with Roentgen in 1901 and ending with Fermi in 1938. I can recognize every name except the one for 1912: Nils Gustav Dalén. Perhaps you have had the same experience when looking through the updated list.
Develop Your Questioning Techniques
Authors: Blanton Patricia
Published: December 2008

How much thought have you given to what you want your students to gain from your class? Far too often the emphasis on factual content overshadows the development of conceptual understanding, and accountability issues force us to present a wide-ranging curriculum in a short time period. As a beginning teacher, you are probably being directed to “cover” the curriculum, and your focus has been on making sure you understand the concepts you are presenting. You spend hours studying the content until you are sure you know every aspect and can work every problem in the textbook dealing with the given topic. You prepare a very detailed lesson plan and deliver a brilliant lecture only to find that your students did not “receive” the information you thought you transmitted. You know the content much better because you had to present your understanding of the concepts to others. You can provide your students the same opportunity to test their understanding by developing questioning techniques to engage them in effective dialogue.
A Glucosinolate Metabolism Pathway in Living Plant Cells Mediates Broad-Spectrum Antifungal Defense
Authors: Bednarek Paweł , Piślewska-Bednarek Mariola , Svatoš Aleš , Schneider Bernd , Doubský Jan , Mansurova Madina , Humphry Matt , Consonni Chiara , Panstruga Ralph , Sanchez-Vallet Andrea , Molina Antonio , Schulze-Lefert Paul
Published: December 2008

Selection pressure exerted by insects and microorganisms shapes the diversity of plant secondary metabolites. We identified a metabolic pathway for glucosinolates, known insect deterrents, that differs from the pathway activated by chewing insects. This pathway is active in living plant cells, may contribute to glucosinolate turnover, and has been recruited for broad-spectrum antifungal defense responses. The
Arabidopsis CYP81F2
gene encodes a P450 monooxygenase that is essential for the pathogen-induced accumulation of 4-methoxyindol-3-ylmethylglucosinolate, which in turn is activated by the atypical PEN2 myrosinase (a type of β-thioglucoside glucohydrolase) for antifungal defense. We propose that reiterated enzymatic cycles, controlling the generation of toxic molecules and their detoxification, enable the recruitment of glucosinolates in defense responses.
Comparison of two fine sands under torsional loading
Authors: Georgiannou V. N. , Tsomokos A.
Published: December 2008

In this paper the behaviour of two “standard research sands”, widely used for experimental purposes, is compared in a torsional hollow cylinder apparatus under monotonic and cyclic loading conditions. Both sands are fine and uniform with D50= 0.22 and 0.29 mm, respectively. However, their response to undrained monotonic loading at similar void ratios is dramatically different, with the finer sand showing strength reduction after peak and the coarser sand showing continuous increase in strength with torsional shear. The difference in response is mainly attributed to grain angularity and to a lesser degree to their grading. The results of drained torsional hollow cylinder tests show initial contraction followed by dilation. The stress ratio at phase transformation is uniquely defined by both drained and undrained tests for each sand. Cyclic loading instability is manifested by a sudden increase in shear strain and excess pore-water pressure leading to initial liquefaction. The instability initiates across the instability line for the sand showing strength reduction and across the phase transformation line for the sand showing continuous increase in strength with shearing. Both lines are defined under monotonic loading conditions. The liquefaction, stiffness, and damping characteristics of the sands are given in this paper.
Performance of soil nails in Dublin glacial till
Authors: Menkiti Christopher O. , Long Michael
Published: December 2008

Soil nailing is being used in many projects in glacial tills in Ireland, particularly to provide temporary support to steep slopes. Little design guidance is available for such materials, and it is known that the application of design procedures developed for other material is conservative. Detailed nail instrumentation and field monitoring has been undertaken during large-scale soil nailing works for the Dublin Port Tunnel project. It was found that the short-term behaviour of nails was the reverse of that assumed in current design methods. Most of the load was induced as a results of drilling and nailing the lift immediately below the nail being monitored rather than due to excavation-induced stress relief. The highest forces were developed in the upper nails where the largest ground movements occurred. This is the reverse of most current design methods where the highest soil–nail bond is assigned to the deepest nails. It seems that the observed short-term, prefailure behaviour of nailed slopes is governed more by the deformation pattern of the slope than by large-scale development of failed wedges. Current design procedures should be reviewed. Despite this, the trial confirmed that the currently used procedures are highly conservative for Dublin glacial till.
Relationships between size and velocity for particles within debris flows
Authors: Prochaska Adam B. , Santi Paul M. , Higgins Jerry D.
Published: December 2008

Estimation of the impact forces from boulders within a debris flow is important for the design of structural mitigation elements. Boulder impact force equations are most sensitive to the inputs of particle size and particle velocity. Current guidelines recommend that a design boulder should have a size equal to the depth of flow and a velocity equal to that of the flow. This study used video analysis software to investigate the velocities of different sized particles within debris flows. Particle velocity generally decreased with increasing particle size, but the rate of decrease was found to be dependent on the abilities of particles to rearrange within debris flows.
Effect of footing width onNγ
Authors: Kumar Jyant , Khatri V. N.
Published: December 2008

By incorporating the dependency of soil friction angle (ϕ) on mean principal stress (σm), the effect of footing width (B) on bearing capacity factor (Nγ) is examined for a rough strip footing. The analysis is performed by means of a numerical lower bound limit analysis in conjunction with triangular finite elements and linear programming. To account for the variation of ϕ with σm, a solution is obtained by using an iterative procedure. Two well defined ϕ–σmcurves from the literature, associated with Hoston and Toyoura sands that correspond to relative densities of 18% and 74.5%, respectively, are used. The magnitude of Nγis computed for different footing widths. It is noted that for B greater than about 0.2 m, the magnitude of Nγvaries almost linearly with B on a log–log scale. For different footing widths, a good comparison is seen between the obtained rigorous solution and that obtained by using a constant value of ϕ, which corresponds to the equivalent mean normal stress level as defined by De Beer.
Fluid Dynamic Mechanism Responsible for Breaking the Left-Right Symmetry of the Human Body: The Nodal Flow
Authors: Hirokawa Nobutaka , Okada Yasushi , Tanaka Yosuke
Published: December 2008

A left-right (LR) asymmetric body plan is crucial for the development of the human body. The past decade has seen rapid progress in our understanding of the LR symmetry-breaking process in vertebrate development. A series of experimental studies has demonstrated that leftward movement of fluid at the ventral node, designated nodal flow, is the central process in symmetry breaking. Nodal flow is autonomously generated by the posteriorly tilted rotation of cilia. The underlying fluid dynamic mechanism, especially the importance of viscous interactions between the cilia and the cell surface, has been clarified by theoretical analyses. Recent experiments have suggested how this leftward nodal flow can be interpreted to create LR asymmetry. Specifically, leftward transport of lipoprotein particles, called nodal vesicular parcels (NVPs), was uncovered. Nodal flow thus triggers left-specific signaling pathways by transporting signaling molecules to the left side using NVPs.
The 3D Navier-Stokes Problem
Authors: Doering Charles R.
Published: December 2008

It is not known whether the three-dimensional (3D) incompressible Navier-Stokes equations possess unique smooth (continuously differentiable) solutions at high Reynolds numbers. This problem is quite important for basic science, practical applications, and numerical computations. This review presents a selective survey of the current state of the mathematical theory, focusing on the technical source of difficulties encountered with the construction of smooth solutions. It also highlights physical phenomena behind the mathematical challenges.
Dietary glutamine and oral antibiotics each improve indexes of gut barrier function in rat short bowel syndrome
Authors: Tian Junqiang , Hao Li , Chandra Prakash , Jones Dean P. , Willams Ifor R. , Gewirtz Andrew T. , Ziegler Thomas R.
Published: December 2008

Short bowel syndrome (SBS) is associated with gut barrier dysfunction. We examined effects of dietary glutamine (GLN) or oral antibiotics (ABX) on indexes of gut barrier function in a rat model of SBS. Adult rats underwent a 60% distal small bowel + proximal colonic resection (RX) or bowel transection (TX; control). Rats were pair fed diets with or without l-GLN for 20 days after operation. Oral ABX (neomycin, metronidazole, and polymyxin B) were given in some RX rats fed control diet. Stool secretory immunoglobulin A (sIgA) was measured serially. On day 21, mesenteric lymph nodes (MLN) were cultured for gram-negative bacteria. IgA-positive plasma cells in jejunum, stool levels of flagellin- and lipopolysaccharide (LPS)-specific sIgA, and serum total, anti-flagellin- and anti-LPS IgG levels were determined. RX caused gram-negative bacterial translocation to MLN, increased serum total and anti-LPS IgG and increased stool total sIgA. After RX, dietary GLN tended to blunt bacterial translocation to MLN (−29%, P = NS) and significantly decreased anti-LPS IgG levels in serum, increased both stool and jejunal mucosal sIgA and increased stool anti-LPS-specific IgA. Oral ABX eliminated RX-induced bacterial translocation, significantly decreased total and anti-LPS IgG levels in serum, significantly decreased stool total IgA and increased stool LPS-specific IgA. Partial small bowel-colonic resection in rats is associated with gram-negative bacterial translocation from the gut and a concomitant adaptive immune response to LPS. These indexes of gut barrier dysfunction are ameliorated or blunted by administration of dietary GLN or oral ABX, respectively. Dietary GLN upregulates small bowel sIgA in this model.
Every slow-wave impulse is associated with motor activity of the human stomach
Authors: Hocke Michael , Schöne Ulrike , Richert Hendryk , Görnert Peter , Keller Jutta , Layer Peter , Stallmach Andreas
Published: December 2008

Using a newly developed high-resolution three-dimensional magnetic detector system (3D-MAGMA), we observed periodical movements of a small magnetic marker in the human stomach at the typical gastric slow-wave frequency, that is 3 min−1. Thus we hypothesized that each gastric slow wave induces a motor response that is not strong enough to be detected by conventional methods. Electrogastrographies (EGG, Medtronic, Minneapolis, MN) for measurement of gastric slow waves and 3D-MAGMA (Innovent, Jena, Germany) measurements were simultaneously performed in 21 healthy volunteers (10 men, 40.4 ± 13.6 yr; 11 women, 35.8 ± 11.6 yr). The 3D-MAGMA system contains 27 highly sensitive magnetic field sensors that are able to locate a magnetic pill inside a human body with an accuracy of ±5 mm or less in position and ±2° in orientation at a frequency of 50 Hz. Gastric transit time of the magnetic marker ranged from 19 to 154 min. The mean dominant EGG frequency while the marker was in the stomach was 2.87 ± 0.15 cpm. The mean dominant 3D-MAGMA frequency during this interval was nearly identical; that is, 2.85 ± 0.15 movements per minute. We observed a strong linear correlation between individual dominant EGG and 3D-MAGMA frequency ( R = 0.66, P = 0.0011). Our findings suggest that each gastric slow wave induces a minute contraction that is too small to be detected by conventional motility investigations but can be recorded by the 3D-MAGMA system. The present slow-wave theory that assumes that the slow wave is a pure electrical signal should be reconsidered.