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Ammonia, as a hydrogen-derived fuel, primarily emits N 2 O and NO x when burned in an engine. The emissions originate from ammonia fuel and nitrogen in the air. In this paper, the N of N 2 was labeled by isotope labeling method, so that the nitrogen element in the formation path of the thermal N 2 O and NO x was labeled, and the chemical reaction path of the formation and evolution of the fuel and thermal nitrogen oxide was defined. In addition, the spatiotemporal distribution characteristics, generation and evolution rules of fuel and thermal nitrogen oxide in ammonia-diesel dual-fuel engine, as well as the influence of different ammonia energy ratios on the generation ratio of two types of N 2 O and NO x were studied by combining experiment and simulation. The ammonia energy ratio is defined as the proportion of energy provided by ammonia in a constant total lower calorific value. The results showed that when the ammonia energy ratio increased from 20 % to 60 %, the emissions of NO and NO 2 decreased, but the proportion of fuel NO and NO 2 increased. The proportion of N 2 O in nitrogen oxide emission increased from 7.3 % to 20 %. Fuel N 2 O accounts for about 90 % of N 2 O emission. Fuel N 2 O and NO x were mainly generated in ammonia-rich, low-temperature regions and thermal N 2 O and NO x were mainly generated in the high-temperature regions. Temperature significantly affected N 2 O generation. • The N in ammonia-diesel mechanism was labeled by isotope labeling method. • The chemical reaction paths of fuel and thermal nitrogen oxide were analyzed. • The nitrogen oxide emission characteristics were studied by engine experiments. • The content and generate features of fuel and thermal nitrogen oxides were studied. [ABSTRACT FROM AUTHOR]

Abstract: We prepare large areas of graphene on carbon paper from graphite powder and anionic surfactant, assisted electrochemical exfoliation as previous work. Using a four-point probe technique, we found the conductivity of graphene on carbon paper to be 66 mS cm−1, which is approximately 1.2 and 1.65 times better than that of graphite coated carbon paper and carbon paper. Then palladium is electro-reduced onto the carbon paper based electrodes (with or without graphene) in absence or presence of different concentrations of sodium dodecyl sulfate (SDS), that are used in oxygen reduction reaction (ORR) for direct methanol fuel cells. The electrochemically reduced Pd is carefully characterized by scanning electron microscopy (SEM). Their electrochemical properties are investigated with cyclic voltammetry, linear sweep voltammetry, and electrochemical impedance spectroscopy. Particularly, SEM images show that the size of the nanoparticles decreases from 1000 to 70 nm as SDS concentration increases from 0 to 14 mM. The catalytic activities of graphene-supported Pd nanoparticles and Pd–carbon paper electro-catalysts for ORR are 112 and 2 Ag−1 Pd, which can reveal the particular properties of the exfoliated graphene supports and SDS media. [Copyright &y& Elsevier]

Abstract: The thermodynamic inefficiencies associated with any energy conversion process are expressed by the exergy destruction and the exergy losses associated with the process. Combustion processes exhibit very high thermodynamic inefficiencies caused by chemical reaction, heat transfer, friction, and mixing. In this paper, we discuss how to estimate the thermodynamic inefficiencies resulting from each one of these sources. The thermodynamic evaluation can be conducted with the aid of either a conventional exergetic analysis or an advanced one. The latter allows estimation of the potential for improvement of the process being considered and demonstrates the interactions among the components of the system in which combustion takes place. The paper discusses how advanced exergy-based evaluations can be used to reduce the thermodynamic inefficiencies, costs, and environmental impacts associated with energy conversion systems including combustion processes. [Copyright &y& Elsevier]

This paper presents the effect of nozzle assembly design on the performance of a partial combustion unit (PCU) using the scale-adaptive simulation (SAS) and non-intrusive laser measurement techniques. Four different configurations were tested, namely, nozzle without wing and three nozzles with wing, i.e., flat surface wing, semi-sphere hollow wing and bent wingtip. The syngas-oxygen reaction chemistry was calculated using non-premixed flame model incorporated with GRI-MECH 3.0 mechanism. The radiative heat transfer was modelled using the discrete ordinates (DO) model. The simulation was compared with the particle image velocimetry (PIV) and a two-dimensional laser doppler anemometry (LDA) measurement on a scaled-down PCU model. A good agreement between the SAS prediction and experimental measurement was obtained. It was found that the modified nozzle assembly design with a semi-sphere hollow wing yielded the highest combustion temperature owing to the intense turbulence-induced recirculation mixing of oxy-fuel. The modified nozzle assembly design introduced in this work increased the peak outlet combustion temperature up to 18% higher compared to the original design. The finding in this work may useful for design retrofits of a combustion system. • Stereoscopic PIV provides a better agreement with CFD simulation. • Winged nozzle design induces flow recirculation that enhances combustion. • Winged nozzle design produces a bigger combustion flame. • Winged nozzle design increased the peak outlet temperature up to 18%. [ABSTRACT FROM AUTHOR]

This paper analyses the improved energy and environmental performance of the biomethanation of a mixture of sheep manure (20% by weight) and cheese whey (80% by weight) in a reactor of 2 L capacity containing 2 g of charcoal in the form of a fixed bed with respect to the same process but without the charcoal in the reactor (control experiment). The results show an increased methane production of 27.05% and a reduction of the H 2 S content in the biogas of 34.7%, over those obtained in the control experiment. These marked improvements of the biomethanation process are attributable to the content of highly electropositive metals such as K and Ca in the charcoal which, because chemical reactions, can increase the pH of the medium and thus favour the processes of methanogenesis and sulphate reduction. Charcoal would act as a bacteriological adherent promoting the biomethanation of the organic waste materials used in the study. • The biomethanation of sheep manure and cheese whey is studied. • Charcoal is used as a bacteriological adherent in the biomethanation. • Bioreactions are carried out for 168 days without inhibition. • The production of CH 4 increases by 27.05%. • The content of H 2 S in the biogas is reduced by 34.7%. [ABSTRACT FROM AUTHOR]

Abstract As the initial step in coal combustion and gasification, pyrolysis plays an important role in chemical reactions. The influencing mechanism of superfine particle on gas phase products during rapid pyrolysis remains problematic. In this paper, the formation and dissipation mechanism of the gas phase products especially CO, light hydrocarbons and NO X precursors of superfine pulverized coal pyrolyzed in an entrained flow reactor is focused. Pyrolysis experiments are taken out in Ar and N 2 respectively. The influence of particle size, coal rank, pyrolysis atmosphere and the final pyrolysis temperature on the formation and dissipation are analyzed. In addition, pore structures of raw coal and chars are also characterized by synchrotron radiation facility to better reveal the pyrolysis mechanism. Our results indicate that as the particle size decreases, the content of CO, light hydrocarbons and NO X precursors all show a trend of first increase and then decrease. Lower rank coal has larger release concentration of gas phase products. Additionally, with the increment of the final pyrolysis temperature, there is a decrease trend of light hydrocarbons and NO X precursors but an increase trend of CO. The fractal dimension (D SAXS) increases with the increase of the final pyrolysis temperature. Highlights • The release characteristics of gas phase products are affected by particle size. • Lower rank coal has larger release concentration of gas phase products. • Temperature has different effects on the release of gas phase products. • The fractal dimensions of chars increase with the increase of the temperature. [ABSTRACT FROM AUTHOR]

Abstract: Steam methane reforming (SMR) is one of the most promising processes for hydrogen production. Several studies have demonstrated its advantages from the economic viewpoint. Nowadays process development is based on technical and economical aspects; however, in the near future, the environmental impact will play a significant role in the design of such processes. In this paper, an SMR process is studied from the viewpoint of overall environmental impact, using an exergoenvironmental analysis. This analysis presents the combination of exergy analysis and life cycle assessment. Components where chemical reactions occur are the most important plant components from the exergoenvironmental point of view, because, in general, there is a high environmental impact associated with these components. This is mainly caused by the exergy destruction within the components, and this in turn is mainly due to the chemical reactions. The obtained results show that the largest potential for reducing the overall environmental impact is associated with the combustion reactor, the steam reformer, the hydrogen separation unit and the major heat exchangers. The environmental impact in these components can mainly be reduced by improving their exergetic efficiency. A sensitivity analysis for some important exergoenvironmental variables is also presented in the paper. [Copyright &y& Elsevier]

In this paper a novel approach is proposed for optimization of electrically serial two-stage thermoelectric refrigeration systems using a chemical reaction optimization algorithm (CRO). In order to investigate the performance of the proposed method, a full computer code was developed and two different test cases with different situations were solved by it to show the accuracy and efficiency of the method. Cooling capacity and coefficient of performance of the thermoelectric refrigeration system are considered as objective functions of the optimization process. The results of the research are compared to those obtained by literature approaches, including analytical and optimization algorithms. The effects of the joint thermal resistance at the interface of the two stages on objective functions in all of the case studies also were studied and sensitivity analysis of COP and cooling capacity of the system to this parameter is conducted. The obtained results showed improvement of the objective functions using the CRO method in comparison to the methods used previously for optimization of the considered refrigeration system. The outlined results revealed that the CRO algorithm can be successfully employed for optimal design of new systems and performance optimization of existence two-stage thermoelectric refrigeration system. [ABSTRACT FROM AUTHOR]

A preliminary experimental study on combustion in a nozzle of solid rocket motor is conducted using a division multiplexing scanning wavelength TDLAS system to accurately investigate the combustion characteristics in the nozzle of a solid rocket motor and provide a reference for improving the accuracy of the performance prediction model and design level of the solid rocket motor. In addition, the chemical reaction mechanisms in the nozzle are compared with results from numerical simulations, and the flow characteristics in the nozzle are analyzed. Results demonstrate that (1) the TDLAS system built for this study achieves real-time measurement of temperature and H 2 O concentration in the nozzle of a solid rocket motor; (2) The relative error among the three chemical reaction mechanisms is small, which indicates that the three chemical reaction mechanisms constructed in this paper are substantially equivalent; (3) The numerical calculation error of the H 2 O mole fraction of the three chemical reaction mechanisms is controlled within 13% at measuring points 1 and 2; (4) For bipropellant with low energy such as AP (80%)/HTPB (20%), the flow in the nozzle tends to a frozen flow. • The real-time parameters measurement in the solid rocket motor nozzle is realized. • The chemical reaction mechanisms are compared with results from numerical simulations. • The flow characteristics of AP(80%)/HTPB(20%) bipropellant in nozzle are evaluated. [ABSTRACT FROM AUTHOR]

The present work is to investigate the MILD (moderate and intense low-oxygen dilution) combustion of a premixed methane jet in hot coflow against its conventional counterpart, i.e., a typical bluff-body flame, under identical inlet and boundary conditions. This paper demonstrates that the MILD combustion develops as a stable 'flame' lifting far downstream from the nozzle while the conventional flame evolves immediately behind the bluff body. More specifically, all chemical reactions are found to occur far more slowly over a greatly larger reaction zone for the MILD combustion than for the conventional one. Also, for the MILD combustion, the laminar flame speed (S L) is very small, far below the local flow speed (U x), whereas chemical and mixing times are compatible so that the Damköhler number Da ∼1.0. In contrast, the conventional combustion takes place with S L ≥ U x and Da = 10–1000. Moreover, the MILD combustion eventually emits little NOx, only less than 3% of the emission from the conventional counterpart. Fundamentally, the MILD combustion produces the NOx emission mainly through the N 2 O-intermediate and NNH routes while the thermal NOx mechanism dominates the conventional flame. In addition, this paper provides a comprehensive explanation to each of the above differences. • Characterizing MILD combustion versus traditional bluff-body flame. • MILD/traditional combustion being established by auto-ignition/pilot flame. • Flamelets in eddies/flame sheets forming MILD/traditional combustion. • NOx emission of MILD combustion <3% of that from traditional one. • Revealing different NOx routes for MILD and traditional combustion. [ABSTRACT FROM AUTHOR]

Over recent years there has been a significant increase in the amount of technology contributing to lower emissions of carbon dioxide. The aim of this paper is to provide a comparison between two technologies for methanol production, both of which use carbon dioxide and hydrogen as initial raw materials. The first methanol production technology includes direct synthesis of methanol from CO 2 , and the second has two steps. During the first step CO 2 is converted into CO via RWGS (reverse water gas shift) reaction, and methanol is produced during the second step. A comparison between these two methods was achieved in terms of economical and energy-efficiency bases. The price of electricity had the greatest impact from the economical point of view as hydrogen is produced via the electrolysis of water. Furthermore, both the cost of CO 2 capture and the amounts of carbon taxes were taken into consideration. Energy-efficiency comparison is based on cold gas efficiency, while economic feasibility is compared using net present value. Even though the mentioned processes are similar, it was shown that direct methanol synthesis has higher energy and economic efficiency. [ABSTRACT FROM AUTHOR]

Abstract: The circulating fluidized bed is of increasing importance for gas–solid and gas–catalytic reactions, for drying, and recently its use in solar energy capture and storage has been advocated. In all applications, the supply or withdrawal of heat is a major issue, and the heat transfer coefficient from the gas–solid suspension to the heat transfer surface needs to be determined as design parameter. The present paper investigates the heat transfer coefficient for different operating gas velocity and solids circulation flux, whilst covering the different hydrodynamic solid flow regimes of dilute, core–annulus or dense mode. Measured values of the wall-to-bed heat transfer coefficients are compared with empirical predictions of both Molodstof and Muzyka, and Golriz and Grace. The application of a packet renewal mechanism at the wall is also investigated, and introducing the predicted solid contact time at the wall provides a very fair estimate of the heat transfer coefficient. [Copyright &y& Elsevier]

Abstract: This paper explores the use of molten alkali-carbonate salts as a reaction and heat transfer medium for steam gasification of plant biomass with the objectives of enhanced heat transfer, faster kinetics, and increased thermal capacitance compared to gasification in an inert gas. The intended application is a solar process in which concentrated solar radiation is the sole source of heat to drive the endothermic production of synthesis gas. The benefits of gasification in a molten ternary blend of lithium, potassium, and sodium carbonate salts is demonstrated for cellulose, switchgrass, a blend of perennial plants, and corn stover through measurements of reaction rate and product composition in an electrically heated reactor. The feedstocks are gasified with steam at 1200 K in argon and in the molten salt. The use of molten salt increases the total useful syngas production by up to 25%, and increases the reactivity index by as much as 490%. Secondary products, in the form of condensable tar, are reduced by 77%. [Copyright &y& Elsevier]

Abstract: This paper focuses on the characterization and modeling of a solid/gas thermochemical reaction between a porous reactive bed and moist air flowing through it. The aim is the optimization of both energy density and permeability of the reactive bed, in order to realize a high density thermochemical system for seasonal thermal storage for house heating application. Several samples with different implementation parameters (density, binder, diffuser, porous bed texture) have been tested. Promising results have been reached: energy densities about 430–460 kWh m−3 and specific powers between 1.93 and 2.88 W/kg of salt. A model based on the assumption of a sharp reaction front moving through the bed during the reaction was developed. It has been validated by a comparison with experimental results for several reactive bed samples and operating conditions. [Copyright &y& Elsevier]

Abstract: The cement industry is one of the leading producers of anthropogenic greenhouse gases, of which CO2 is the most significant. Recently, researchers have invested a considerable amount of time studying ways to improve energy consumption and pollutant formation in the overall cement manufacturing process. One idea involves dividing the calcination and clinkering processes into two separate furnaces. The calcination process is performed in a calciner while the clinkering process takes place in a rotary kiln. As this is new technology in the cement manufacturing process, calciners are still in the research and development phase. The purpose of this paper is to demonstrate the potential of CFD to support the design and optimization of calciners, whose use appears to be essential in reduction of CO2 emission during cement production. The mathematical model of the calcination process was developed, validated and implemented into a commercial CFD code, which was then used for the analysis. From the results obtained by these simulations, researchers will gain an in-depth understanding of all thermo-chemical reactions in a calciner. This understanding can be used to optimize the calciner''s geometry, to make production more efficient, to lower pollutant formation and to subsequently reduce greenhouse gas emissions. [Copyright &y& Elsevier]

Abstract: This work describes the application and the performance of a new radiation model in CFD calculations for the simulation of thermal radiation transfer effects on a fire scenario. A 3D Cartesian coordinates radiative heat transfer procedure based on coupling of the FTn finite volume method (FTnFVM) with the bounded high-order resolution CLAM scheme is developed. The narrow-band based weighted-sum-of-gray-gases (NB-WSGG) model is applied to take account of nongray effects by CO2, H2O and soot. To treat irregular boundaries, the present model used the blocked-off-region procedure. This radiation code is implemented in the Fire Dynamics Simulator (FDS), a Computational-Fluid-Dynamics-based fire model, where a the combustion is represented by means of the mixture fraction with a single step chemical reaction model and the Large Eddy Simulation (LES) is used to model the dissipative processes. Computational results with and without radiation effects are compared against available experimental data and quasi-steady state law correlations of in-rack storage fire, which consists a complex configuration of double tri-wall corrugated paper cartons placed onto a wood pallet. Sensibility analyses of spatial and angular grids demonstrate the improvements due to the FTnFVM and to the CLAM scheme in the configuration studied. Results show that the simulations of the flame height, the gas temperature and the gas velocity are strongly influenced by thermal radiation. Overall, simulations predicted closer profiles to the experimental results only when the nongray-sooting radiation model was incorporated and an over-prediction of the gas temperature and the flame height is found when radiation is neglected. A sensibility analysis has shown that the flame characteristics are strongly affected by the soot yield. [Copyright &y& Elsevier]

Abstract: Entropy generation during chemical reactions can cause significant irreversibility in chemical engines. These irreversibilities reduce the exergy of the fuel resource preventing potential work production. Understanding the cause of these irreversibilities and developing strategies for reducing them is critical for increasing engine efficiency. All chemical engines can be separated into two categories depending on how they manage the chemical reaction: restrained and unrestrained. A fuel cell with an electric motor is an example of a restrained engine design. Restrained engines have the potential to operate near the reversible limit, with no entropy generation from the chemical reaction. Combustion engines are unrestrained engines, which means the engine design has a built-in irreversibility due to the way it conducts the chemical reaction. This paper defines the requirements necessary to build restrained chemical engines, which helps to identify fundamental strategies for increasing efficiency in both engine designs as well as trade-offs between the two options. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, parameters affecting castor oil transesterification reaction were investigated. Applying four basic catalysts including NaOCH3, NaOH, KOCH3 and KOH the best one with maximum biodiesel yield was identified. Using Taguchi method consisting four parameters and three levels, the best experimental conditions were determined. Reaction temperature (25, 65 and 80°C), mixing intensity (250, 400 and 600rpm), alcohol/oil ratio (4:1, 6:1 and 8:1) and catalyst concentration (0.25, 0.35 and 0.5%) were selected as experimental parameters. It was concluded that reaction temperature and mixing intensity can be optimized. Using the optimum results, we proposed a kinetic model which resulted in establishing an equation for the beginning rate of transesterification reaction. Furthermore, applying ASTM D 976 correlation, minimum cetane number of produced biodiesel was determined as 37.1. [ABSTRACT FROM AUTHOR]

Abstract: While the use of a high level of platinum (Pt) loading in proton exchange membrane fuel cells (PEMFCs) can amplify the trade off towards higher performance and longer lifespan for these PEMFCs, the development of PEMFC electrocatalysts with low-Pt-loadings and high-Pt-utilization is critical and the limited supply and high cost of the Pt used in PEMFC electrocatalysts necessitate a reduction in the Pt level. In order to make such electrocatalysts commercially feasible, cost-effective and innovative, catalyst synthesis methods are needed for Pt loading reduction and performance optimization. Since a Pt-deposited carbon nanotube (CNT) shows higher performance than a commercial Pt-deposited carbon black (CB) with reducing 60% Pt load per electrode area in PEMFCs, use of CNTs in preparing electrocatalysts becomes considerable. This paper reviews the literature on the synthesis methods of carbon-supported Pt electrocatalysts for PEMFC catalyst loading reduction through the improvement of catalyst utilization and activity. The features of electroless deposition (ED) method, deposition on sonochemically treated CNTs, polyol process, electrodeposition method, sputter-deposition technique, γ-irradiation method, microemulsion method, aerosol assisted deposition (AAD) method, Pechini method, supercritical deposition technique, hydrothermal method and colloid method are discussed and characteristics of each one are considered. [ABSTRACT FROM AUTHOR]

Abstract: The aim of the paper is to investigate possible improvements in the geometry design of a monolithic solid oxide fuel cells (SOFCs) through analysis of the entropy generation terms. The different contributions to the local rate of entropy generation are calculated using a computational fluid dynamic (CFD) model of the fuel cell, accounting for energy transfer, fluid dynamics, current transfer, chemical reactions and electrochemistry. The fuel cell geometry is then modified to reduce the main sources of irreversibility and increase its efficiency. [Copyright &y& Elsevier]

Abstract: Fuel cells have great application potential as stationary power plants, as power sources in transportation, and as portable power generators for electronic devices. Most fuel cells currently being developed for use in vehicles and as portable power generators require hydrogen as a fuel. Chemical storage of hydrogen in liquid fuels is considered to be one of the most advantageous options for supplying hydrogen to the cell. In this case a fuel processor is needed to convert the liquid fuel into a hydrogen-rich stream. This paper presents a second-law analysis of an integrated fuel processor and fuel cell system. The following primary fuels are considered: methanol, ethanol, octane, ammonia, and methane. The maximum amount of electrical work and corresponding heat effects produced from these fuels are evaluated. An exergy analysis is performed for a methanol processor integrated with a proton exchange membrane fuel cell, for use as a portable power generator. The integrated FP–FC system, which can produce 100W of electricity, is simulated with a computer model using the flow-sheeting program Aspen Plus. The influence of various operating conditions on the system efficiency is investigated, such as the methanol concentration in the feed, the temperature in the reformer and in the fuel cell, as well as the fuel cell efficiency. Finally, it is shown that the calculated overall exergetic efficiency of the FP–FC system is higher than that of typical combustion engines and rechargeable batteries. [Copyright &y& Elsevier]

Hydrogen is recognized as an energy carrier and has substantial potential to fulfill future energy demands. This paper conducted energy and exergy analyses on a hydrogen production process that utilized the chemical reaction between aluminum and water. Various aspects of the system's performance, such as energetic efficiency, exergetic efficiency, sustainability index, and other methods to evaluate the system's performance were examined. The factors such as the lower heating value (LHV) of hydrogen, the reactant molecules' enthalpy of formation, and their respective chemical exergy were considered. The energy input from the heater was substantial enough to be taken into consideration; however, the energy input from the pump was considered negligible in the overall process efficiency. The standard reaction efficiency equation displayed the most favourable results at the higher water temperatures. Therefore, the variation in the water medium and NaOH concentration experiments used 70 °C as its water temperature. The variation in water medium test identified tap water as an effective water medium due to its higher energy efficiency, and its ability to achieve the maximum theoretical yield. However, seawater was identified as a viable option for future testing, as it was able to achieve standard energetic and exergetic efficiencies up to 32.40% and 54.35% for the 3-g samples. Additional parametric studies were conducted and compared throughout this study to provide a comprehensive analysis of the system's performance. • The significant findings from this research study are as follows: • 70 °C and 40 °C, has standard energy efficiency of 20.17% and 12.24% respectively. • Seawater achieved a standard energy and exergy efficiency of 32.40% and 54.35%. • Reaction is most efficient at a stoichiometric mole ratio. [ABSTRACT FROM AUTHOR]

In this paper, a novel solar thermochemical volumetric receiver/reactor with nanofluid is proposed. Thermal and chemical performance analyses of the volumetric receiver/reactor are numerically investigated and compared with those of the conventional surface receiver/reactor. A two-dimensional axisymmetric heat and mass transfer model coupled with reaction kinetics is developed to predict the temperature distribution and reactant conversion ratio. The effects of particle characteristics including size and volume fraction and solar irradiation intensity are discussed. The results indicate that for the nanofluid with a volume fraction greater than 0.005, an optical path depth of 0.015 m is sufficient to absorb almost 100% of the incident solar energy. The volume weighted average temperature of the volumetric receiver/reactor with a volume fraction of 0.05 and particle diameter of 10 nm can reach 506.0 K which is about 8.8 K higher than that of the surface receiver/reactor leading to a 5.2% increase of the outlet methanol conversion ratio from 56.9% to 62.1% under a typical operating condition. The methanol conversion ratio increases with the reduction of nanoparticle size and the increment of the volume fraction and solar irradiation intensity. The thermochemical efficiency has a maximum value of 48.9% when solar irradiation intensity is 600 W/m2. • A novel solar thermochemical volumetric receiver/reactor with nanofluid is proposed. • The effects of particle characteristics and solar irradiation intensity are discussed. • The volumetric receiver/reactor with nanofluid gains favorable temperature distribution. • The volumetric receiver/reactor with nanofluid can realize high thermochemical efficiency. [ABSTRACT FROM AUTHOR]