bluuebunny/crossref_metadata_2025 huggingface dataset:
Classroom Dynamic Assessment: A Critical Examination of Constructs and Practices
Authors: DAVIN KRISTIN J.
Published: November 2016

This article explores the implementation of dynamic assessment (DA) in an elementary school foreign language classroom by considering its theoretical basis and its applicability to second language (L2) teaching, learning, and development. In existing applications of L2 classroom DA, errors serve as a window into learners’ instructional needs and provide opportunities for the teacher to mediate, prompting learners to reformulate their utterance. The investigation presented here draws on data from a combination of classroom DA and small‐group work in a unit focused on Spanish interrogatives. Extending earlier studies (Davin,; Davin & Donato,), it critically evaluates the extent to which the teacher's DA records, the heart of DA assessment, provide sufficiently robust evidence for central claims in DA for the dynamic link between assessment and teaching in order to advance learner development. It does so by contextualizing the teacher's record with transcripts from small‐group work that alternated with DA, and with a microgenetic analysis of two learners across both DA and small‐group work. It concludes that whole classroom applications of DA will require considerable expertise on the part of teachers that would have to become part of teacher education programs. Equally importantly, it will benefit from being anchored in an explicitly meaning‐oriented theory of language.
Plastic responses of invasive Bidens frondosa to water and nitrogen addition
Authors: Wei Chunqiang , Tang Saichun , Pan Yumei , Li Xiangqin
Published: November 2016

Invasive species are hypothesized to be more plastic than co‐occurring native congeners, and variation in plasticity among invasive populations is predicted to facilitate invasion of new habitats. To explore the invasive ability of Bidens frondosa, we compared the plastic responses to water and nitrogen addition of the invasive B. frondosa in China with the co‐occurring native congener B. tripartita, as well as among B. frondosa populations. The invasive plant performed better and showed higher phenotypic plasticity to water and nitrogen addition than the native. In addition, variations in performance and phenotypic plasticity were observed among the invasive populations. The biomass of the HN (Henan province) population increased more than that of other populations in response to nitrogen addition. The specific leaf area (SLA) of the GX (Guangxi province) population increased, while the SLA of the HN population decreased, and the HB (Hebei province) and EZ (Hubei province) populations showed no change in response to nitrogen addition. The observed higher phenotypic plasticity of B. frondosa relative to B. tripartita, and the observed variation in plasticity among B. frondosa populations may explain the invasiveness of this species. Predicted future increases in precipitation and atmospheric N deposition may further increase the invasiveness of B. frondosa.
Shifting from priming of salicylic acid‐ to jasmonic acid‐regulated defences by Trichoderma protects tomato against the root knot nematode Meloidogyne incognita
Authors: Martínez‐Medina Ainhoa , Fernandez Ivan , Lok Gerrit B. , Pozo María J. , Pieterse Corné M. J. , Van Wees Saskia C. M.
Published: November 2016

Beneficial root endophytes such as Trichoderma spp. can reduce infections by parasitic nematodes through triggering host defences. Little is currently known about the complex hormone signalling underlying the induction of resistance. In this study, we investigated whether Trichoderma modulates the hormone signalling network in the host to induce resistance to nematodes.

We investigated the role and the timing of the jasmonic acid (JA)‐ and salicylic acid (SA)‐regulated defensive pathways in Trichoderma‐induced resistance to the root knot nematode Meloidogyne incognita. A split‐root system of tomato (Solanum lycopersicum) was used to study local and systemic induced defences by analysing nematode performance, defence gene expression, responsiveness to exogenous hormone application, and dependence on SA and JA signalling of Trichoderma‐induced resistance.

Root colonization by Trichoderma impeded nematode performance both locally and systemically at multiple stages of the parasitism, that is, invasion, galling and reproduction. First, Trichoderma primed SA‐regulated defences, which limited nematode root invasion. Then, Trichoderma enhanced JA‐regulated defences, thereby antagonizing the deregulation of JA‐dependent immunity by the nematodes, which compromised galling and fecundity.

Our results show that Trichoderma primes SA‐ and JA‐dependent defences in roots, and that the priming of responsiveness to these hormones upon nematode attack is plastic and adaptive to the parasitism stage.
Microtubule‐dependent targeting of the exocyst complex is necessary for xylem development in Arabidopsis
Authors: Vukašinović Nemanja , Oda Yoshihisa , Pejchar Přemysl , Synek Lukáš , Pečenková Tamara , Rawat Anamika , Sekereš Juraj , Potocký Martin , Žárský Viktor
Published: November 2016

Cortical microtubules (MTs) play a major role in the patterning of secondary cell wall (SCW) thickenings in tracheary elements (TEs) by determining the sites of SCW deposition. The EXO70A1 subunit of the exocyst secretory vesicle tethering complex was implicated to be important for TE development via the MT interaction. We investigated the subcellular localization of several exocyst subunits in the xylem of Arabidopsis thaliana and analyzed the functional significance of exocyst‐mediated trafficking in TE development.

Live cell imaging of fluorescently tagged exocyst subunits in TE using confocal microscopy and protein–protein interaction assays were performed to describe the role of the exocyst and its partners in TE development.

In TEs, exocyst subunits were localized to the sites of SCW deposition in an MT‐dependent manner. We propose that the mechanism of exocyst targeting to MTs involves the direct interaction of exocyst subunits with the COG2 protein. We demonstrated the importance of a functional exocyst subunit EXO84b for normal TE development and showed that the deposition of SCW constituents is partially compromised, possibly as a result of the mislocalization of secondary cellulose synthase in exocyst mutants.

We conclude that the exocyst complex is an important factor bridging the pattern defined by cortical MTs with localized secretion of the SCW in developing TEs.
Metabolic engineering of micronutrients in crop plants
Authors: Blancquaert Dieter , De Steur Hans , Gellynck Xavier , Van Der Straeten Dominique
Published: November 2016

Micronutrient deficiency is a widespread phenomenon, most prevalent in developing countries. Being causally linked to the occurrence of a range of diseases, it affects billions of people worldwide. Enhancing the content of micronutrients in crop products through biotechnology is a promising technique to fight micronutrient malnutrition worldwide. Micronutrient fortification of food products has been implemented in a number of Western countries, but remains inaccessible for poor rural populations in a major part of the developing world. Moreover, evidence of the negative impacts of this practice on human health, at least for some vitamins, is accumulating. Biofortification of crop plants—the enhancement of vitamins and minerals through plant biotechnology—is a promising alternative or complement in the battle against micronutrient deficiencies. Owing to a growing knowledge about vitamin metabolism, as well as mineral uptake and reallocation in plants, it is today possible to enhance micronutrient levels in crop plants, offering a sustainable solution to populations with a suboptimal micronutrient intake.
Neurocognitive Function and Suicide in U.S. Army Soldiers
Authors: Naifeh James A. , Nock Matthew K. , Ursano Robert J. , Vegella Patti L. , Aliaga Pablo A. , Fullerton Carol S. , Kessler Ronald C. , Wryter Christina L. , Heeringa Steven G. , Stein Murray B. ,   the Army STARRS Collaborators
Published: November 2016

This prospective cohort study used administrative data from the Army Study to Assess Risk and Resilience in Servicemembers to examine associations between neurocognitive functioning and subsequent suicidal events among Regular Army enlisted soldiers during the years 2004–2009. Cases were all soldiers who completed the Army's Automated Neuropsychological Assessment Metrics (ANAM) computerized testing battery prior to documented suicide attempt (n = 607), ideation (n = 955), or death (n = 57). Controls were an equal‐probability sample of 9,893 person‐months from other soldiers. Exploratory factor analysis of five ANAM tests identified a general neurocognitive factor that excluded the mathematic processing test (MTH). When examined separately in logistic regression analyses that controlled for sociodemographics and prior mental health diagnosis, both the general neurocognitive factor (logit [β] = −.197 to −.521; p < .01) and MTH (β = −.024 to −.064; p < .05) were associated with all outcomes. When both predictors were examined simultaneously, the general neurocognitive factor continued to be associated with all outcomes (β = −.164 to −.417; p < .05) and MTH continued to be associated with suicide attempt (β = −.015; p = .046) and ideation (β = −.014; p = .018). These small but robust associations suggest that future research must continue to examine the extent to which objective neurocognitive tests may enhance understanding and prediction of suicide risk.
Effect of aging on breast skin thickness and elasticity: implications for breast support
Authors: Coltman C. E. , Steele J. R. , McGhee D. E.
Published: November 2016

Background/purpose

The skin overlying a woman's breast acts as an anatomical support structure to the breast. Although aging is known to affect the thickness and elasticity of human skin, limited research has examined age‐related changes to skin covering the breast or related these changes to breast support requirements. The purpose of this study was to determine the effect of age on female breast skin thickness and elasticity.

Methods

The left breast of 339 women (18–84 years), classified into four age groups (18–24 years, 25–44 years, 45–64 years, and 65 + years), was divided into four quadrants. Skin thickness (dermal layer; 20 MHz ultrasound probe) and skin elasticity (Cutometer® MPA 580) were measured for each breast quadrant and then compared to determine whether there was any significant (P < 0.05) effect of aging on breast skin.

Results

Breast skin thickness significantly decreased from 45 years of age onwards. A significant decline in breast skin elasticity was evident from the mid 20's.

Conclusion

Aging is associated with a significant decline in breast skin thickness and elasticity, which is likely to reduce anatomical breast support. Women might therefore benefit from increased external breast support (i.e. a more supportive bra) with increasing age.
Reactive oxygen species, abiotic stress and stress combination
Authors: Choudhury Feroza K. , Rivero Rosa M. , Blumwald Eduardo , Mittler Ron
Published: November 2016

Reactive oxygen species (ROS) play a key role in the acclimation process of plants to abiotic stress. They primarily function as signal transduction molecules that regulate different pathways during plant acclimation to stress, but are also toxic byproducts of stress metabolism. Because each subcellular compartment in plants contains its own set of ROS‐producing and ROS‐scavenging pathways, the steady‐state level of ROS, as well as the redox state of each compartment, is different at any given time giving rise to a distinct signature of ROS levels at the different compartments of the cell. Here we review recent studies on the role of ROS in abiotic stress in plants, and propose that different abiotic stresses, such as drought, heat, salinity and high light, result in different ROS signatures that determine the specificity of the acclimation response and help tailor it to the exact stress the plant encounters. We further address the role of ROS in the acclimation of plants to stress combination as well as the role of ROS in mediating rapid systemic signaling during abiotic stress. We conclude that as long as cells maintain high enough energy reserves to detoxify ROS, ROS is beneficial to plants during abiotic stress enabling them to adjust their metabolism and mount a proper acclimation response.
Pricing in M/M/1 queues when cost of waiting in queue differs from cost of waiting in service
Authors: Sarıyer Görkem
Published: November 2016

Service providers can adjust the entrance price to the state of the demand in real life service systems where the customers' decision to receive the service, is based on this price, state of demand and other system parameters. We analyzed service provider's short and long term pricing problems in unobservable M/M/1 queues having the rational customers, where, for customers, the unit cost of waiting in the queue is higher than unit cost of waiting in the service. We showed that waiting in the queue has a clear negative effect on customers’ utilities, hence the service provider's price values. We also showed that, in the short term, monopolistic pricing is optimal for congested systems with high server utilization levels, whereas in the long term, market capturing pricing is more profitable.
A New Method of Designing the Tooth Surfaces of Spiral Bevel Gears With Ruled Surface for Their Accurate Five-Axis Flank Milling
Authors: Zhou Yuansheng , Chen Zezhong C. , Tang Jinyuan
Published: November 2016

The advantages of the five-axis flank milling of (developable) ruled surfaces include that (1) the machined surfaces could be very accurate and smooth and (2) the machining efficiency is high. Currently, spiral bevel gears are machined on the machine tools specially used for gear manufacturing. The disadvantages are that the cost is high for small batch, prototype, or repair. If a small group of spiral bevel gears are needed, the current methods are not valid. Thus, it is expected to machine the gears on five-axis computer numerical control (CNC) milling centers. Unfortunately, when tooth surfaces are designed based on the conventional gear manufacturing methods, they cannot be accurately machined in five-axis flank milling. This work is to develop the new technique for the five-axis flank milling of spiral bevel gears. First, a new method of designing the tooth surface of spiral bevel gears with ruled surface is proposed. Second, the cutter locations and orientations are calculated for five-axis flank milling the tooth surfaces. Third, the actual tooth surfaces are accurately represented with the cutter envelope surface in five-axis flank milling. It is confirmed that the difference of the actual tooth surface and the designed tooth surface is within the tolerance. Then, a pinion is generated to mesh with the gear, and the tooth contact analysis (TCA) is conducted. The good result demonstrates that the proposed method is valid, thus it can be used in industry.
Design of Reverse Materials Resurfacing Implants for Mild–Moderate Medial Osteoarthritis of the Knee
Authors: Chan Hao Yang , Walker Peter S. , Lerner Aaron , Chaudhary Miriam , Bosco Joseph A.
Published: November 2016

The areas of the most frequent cartilage loss in mild–moderate medial osteoarthritis (OA) were reviewed from previous studies. Implant components were designed to resurface these areas. The surface geometries of the components were based on an average femur and tibia produced from 20 magnetic resonance imaging (MRI) models of normal knees. Accuracy of fit of the components was determined on these 20 individual knees. The femoral surface was toroidal, covering a band on the distal end of the femur, angled inward anteriorly. For a five-size system, the average deviations between the implant surfaces and the intact cartilage surfaces of 20 femurs were only 0.3 mm. For the tibia, the deviations were 0.5–0.7 mm, but the errors were mainly around the tibial spine, with smaller deviations in the central bearing region. Hence, these small implant components would accurately restore the original bearing surfaces and allow for preservation of all the knee structures. Using a thin metal component for the tibia would preserve the strong cancellous bone near the surface, an advantage for fixation. In this case, the femoral component would have a plastic bearing surface, but still be less than 10 mm thickness. Such a design could have a useful place in the early treatment of medial OA of the knee.
Structure, Design, and Modeling of an Origami-Inspired Pneumatic Solar Tracking System for the NPU-Phonesat
Authors: Qiao Qiao , Yuan Jianping , Shi Yong , Ning Xin , Wang Fei
Published: November 2016

Various plants have the ability to follow the sun with their flowers or leaves via a mechanism known as heliotropism, which is powered by pressure gradients between neighboring motor cells. Adapting this bio-inspired mechanism, in this paper we present a novel origami-inspired pneumatic solar tracking system for a picosatellite named NPU-PhoneSat that is capable of solar tracking without altering the attitude of the NPU-PhoneSat. We give an overview of the system design and address the theoretical problem of modeling the origami-inspired pneumatic solar tracking system. The theoretical results are compared with the experimental data, demonstrating the validity of the proposed analytical model. Such understanding of soft solar trackers will allow their performance to be predicted, thus enabling their wide utilization in enhancing energy supply.
Time Series Forecasting With Orthogonal Endocrine Neural Network Based on Postsynaptic Potentials
Authors: Milovanović Miroslav , Antić Dragan , Milojković Marko , Nikolić Saša S. , Spasić Miodrag , Perić Staniša
Published: November 2016

This paper presents a new type of endocrine neural network (ENN). ENN utilizes artificial glands which enable the network to be adaptive to external disturbances. Sensitivity is controlled by the hormone decay rate and the value of the sensitivity parameter. The network presented in this paper is improved by making the sensitivity parameter self-tuning and implementing orthogonal activation functions inside the network structure. Automatic tuning is performed on the basis of the biological principle of postsynaptic potentials by implementing inhibitory and excitatory glands inside the standard backpropagation learning algorithm of developed orthogonal ENN. These additional network functionalities enable extra sensitivity to external conditions and an additional network feature of activation sharpening. The network was tested on real-time series of experimental data with a purpose to forecast exchange rate of the three widely used international currencies.
Design and Analysis of Adaptive Control Systems Over Wireless Networks
Authors: Albattat Ali , Gruenwald Benjamin , Yucelen Tansel
Published: November 2016

In this paper, we study the design and analysis of adaptive control systems over wireless networks using event-triggering control theory. The proposed event-triggered adaptive control methodology schedules the data exchange dependent upon errors exceeding user-defined thresholds to reduce wireless network utilization and guarantees system stability and command following performance in the presence of system uncertainties. Specifically, we analyze stability and boundedness of the overall closed-loop dynamical system, characterize the effect of user-defined thresholds and adaptive controller design parameters to the system performance, and discuss conditions to make the resulting command following performance error sufficiently small. An illustrative numerical example is provided to demonstrate the efficacy of the proposed approach.
Application of Sol-Gel Method as a Protective Layer on a Specular Reflective Surface for Secondary Reflector in a Solar Receiver
Authors: Afrin Samia , Dagdelen John , Ma Zhiwen , Kumar Vinod
Published: November 2016

Highly-specular reflective surfaces that can withstand elevated-temperatures are desirable for many applications including reflective heat shielding in solar receivers and secondary reflectors, which can be used between primary concentrators and heat collectors. A high-efficiency, high-temperature solar receiver design based on arrays of cavities needs a highly-specular reflective surface on its front section to help sunlight penetrate into the absorber tubes for effective flux spreading. Since this application is for high-temperature solar receivers, this surface needs to be durable and to maintain its optical properties through the usable life. Degradation mechanisms associated with elevated temperatures and thermal cycling, which include cracking, delamination, corrosion/oxidation, and environmental effects, could cause the optical properties of surfaces to degrade rapidly in these conditions. Protected mirror surfaces for these applications have been tested by depositing a thin layer of SiO2 on top of electrodeposited silver by means of the sol-gel method. To obtain an effective thin film structure, this sol-gel procedure has been investigated extensively by varying process parameters that affect film porosity and thickness. Endurance tests have been performed in a furnace at 150°C for thousands of hours. This paper presents the sol-gel process for intermediate-temperature specular reflective coatings and provides the long-term reliability test results of sol-gel protected silver-coated surfaces.
A Process Simulation of Guayule Biorefining, Including an Exergy Analysis
Authors: Larkin John , Macken Nelson , Schaffer Mark , Elkasabi Yaseen , Mullen Charles A. , Boateng Akwasi A. , Bjornebo Lars , Spatari Sabrina
Published: November 2016

The guayule (Parthenium argentatum) plant is a source of natural rubber and a possible high-energy biofuel. Herein guayule bagasse, the residual biomass after latex extraction, which accounts for 90% of the processed plant material, is modeled in a fast pyrolysis biorefining process. The simulation uses PRO/II® software and is based on data and processes used successfully in a bench scale facility. The unique 200-ton per day plant includes fast pyrolysis utilizing the tail gas reactive process followed by atmospheric separation, hydrodeoxygenation and final product separation, resulting in products similar to traditional fuels, i.e., gasoline, jet fuel and diesel. Approximately 10% of the biomass is converted to liquid fuels with 10% of this converted to gasoline, 34% jet fuel and 56 % diesel. These yields are compared to alternative feedstock and methods. The simulation results are utilized in an exergetic assessment. The depletion of exergy from its natural state (cumulative exergy demand, CExD) is considered as a measure of sustainability of the refining process. Breeding factors, measures of exergy production (the ratio of chemical exergy of the output products to the process exergy inputs), are determined. Results show, for the entire biorefining process, favorable breeding factors can possibly exceed 10, thus suggesting a favorable method of exergy production.
Optimization of Solar (Thermal) Powered Membrane Based Multi-Effect Regenerator
Authors: Ja M. Kum , Dubey Swapnil , Hoong Choo Fook , Mohan Das E. T.
Published: November 2016

Membrane based liquid desiccant dehumidifier and regenerator system have recently gained much attention in liquid desiccant air-conditioning (LDAC) system due to their merit of zero contamination or carryover and resistance to corrosion. A typical system for the LDAC application will consist of a number of stages depending on the capacity of the LDAC system. The multi-effect design allows energy recovery to be achieved to reduce the overall thermal energy consumption. The objective of this study was to test and evaluate the effectiveness and performance of solar powered multi-effect distillation system with desiccant salt solution.

Design Expert was used to characterize the output of regenerator system and optimize overall design using sets of experiment test data. The optimized working zone for performance ratio for different feed flow rate and hot water temperature has been derived. It was found that the optimized zone for LiCl inlet concentration 31.71% was representing performance ratio of 0.5 if operated at feed flow rate range of 32 L/min to 60 L/min and hot water temperature of 54°C to 67°C and optimized zone for LiCl inlet concentration 37.74% was representing performance ratio of 0.5 if operated at feed flow rate range of 40 L/min to 50 L/min and hot water temperature of 59°C to 67°C.
The Effect of Yaw Error on the Reliability of Wind Turbine Blades
Authors: Bakhshi Roozbeh , Sandborn Peter
Published: November 2016

The rise of energy prices, concerns over climate change and geopolitical issues have brought special attention to renewable sources of energy and wind energy in particular. Based on NREL projections, the United States has more than 32,000 TWh of onshore and 17,000 TWh of offshore potential for wind power generation, which is far beyond its 11,000 TWh of current annual electricity consumption. However, there are a number of efficiency challenges that must be overcome in order to turn this potential into actual production. One area that can potentially improve the energy production of wind turbines is the correction of yaw error. Yaw error (also referred to as yaw angle or yaw misalignment) is the angle between the turbine’s rotor and the wind direction. A yaw error reduces turbine’s power production at wind speeds below the rated speed.

Besides impacting the power producing ability of a turbine, yaw error also affects the reliability of critical subsystems in wind turbines. Variation in yaw error (at any wind speed and not only below the rated speed) affects the loads on the components and the subsequent mechanical stresses. These mechanical stresses change the damage accumulation for components and sub-assemblies, which ultimately affects their reliability. About 17 to 28% of wind project costs attribute to O&M costs, which are directly affected by the reliability.

In this study, we investigate the effects of yaw error on the reliability of blades by performing load and stress analysis for various yaw errors. We then use the results of these analyses to adjust the Weibull parameters used for predicting the failure time of blades. Finally, we will use a stochastic cost model to show how correcting the yaw error can avoid maintenance costs in wind farms.
Design of a Modular Solid-Based Thermal Energy Storage for a Hybrid Compressed Air Energy Storage System
Authors: Baghaei Lakeh Reza , Villazana Ian C. , Houssainy Sammy , Anderson Kevin R. , Kavehpour H. Pirouz
Published: November 2016

The share of renewable energy sources in the power grid is showing an increasing trend world-wide. Most of the renewable energy sources are intermittent and have generation peaks that do not correlate with peak demand. The stability of the power grid is highly dependent on the balance between power generation and demand. Compressed Air Energy Storage (CAES) systems have been utilized to receive and store the electrical energy from the grid during off-peak hours and play the role of an auxiliary power plant during peak hours. Using Thermal Energy Storage (TES) systems with CAES technology is shown to increase the efficiency and reduce the cost of generated power. In this study, a modular solid-based TES system is designed to store thermal energy converted from grid power. The TES system stores the energy in the form of internal energy of the storage medium up to 900 K. A three-dimensional computational study using commercial software (ANSYS Fluent) was completed to test the performance of the modular design of the TES. It was shown that solid-state TES, using conventional concrete and an array of circular fins with embedded heaters, can be used for storing heat for a high temperature hybrid CAES (HTH-CAES) system.
Experimental Study on Emissions of Hydrogen Enriched Diesel Engine With Varied Combustion Chamber Geometry
Authors: Us Jyothi , Vijaya Kumar Reddy K.
Published: November 2016

The depletion of fossil fuels and its emissions promoted the researchers to search for substitute fuels and their controlled combustion. Hydrogen is considered as one of the best fuels for internal combustion engines because of its unique combustion properties. Currently, there are very few commercial devices that utilize hydrogen combustion for the production of heat, which is mainly due to the limited availability of hydrogen fuel. As the accompanying environmental legislation will clearly favour clean technologies, the emergence of hydrogen as an energy carrier will modify this situation. To achieve controlled combustion, an attempt was made at investigating the effect of change of piston geometry on the emission characteristics of diesel engine enriched with hydrogen at optimum flow rate. Experiments were conducted to study the effect of varied piston bowl geometry on the emission characteristics of diesel engine enriched with hydrogen at a flow rate of 6 lpm on four stroke single cylinder diesel engine at constant speed of 1500 rpm for different loads. For flow rates above 6 lpm knocking tendency was observed due to raise in temperature and peak pressures with addition of hydrogen. The experiments were conducted with standard hemispherical, toroidal and re-entrant toroidal piston bowl geometry at 6 lpm flow rate of hydrogen duly ensuring the same compression ratio in all three cases. The emissions for diesel engine enriched with hydrogen in hemispherical combustion chamber at 6 lpm flow rate were reduced by 27.1%, 37.5% and 10.8% of unburnt hydrocarbons (UHC), Carbon monoxide (CO) and smoke density respectively when compared to diesel fuel alone operation at rated load. This is mainly due to high combustion temperatures which lead to complete burning of fuel and reduction in carbon content with addition of hydrogen. However, there was a 14% increase in oxides of Nitrogen (NOx) emission due to high combustion temperatures by hydrogen induction. With toroidal and reentrant geometry of the combustion chambers at 6 lpm flow rate of hydrogen, the emission parameters were further reduced notably. Further there is an increase in NOx emission was observed in dual fuel mode compared to standard piston due to high cylinder temperatures and pressures. The obtained results show that at part load conditions with enriched hydrogen, the percentage reduction of NOx emission was engine load dependent, being least increase at low loads and high increase at high loads. The reduction in emission particulates with varied combustion chamber bowl geometry was due to improved swirl motion of high turbulence of air in the combustion.
Upscaling, Manufacturing and Test of a Centrifugal Particle Receiver
Authors: Ebert Miriam , Amsbeck Lars , Jensch Andrea , Hertel Johannes , Rheinländer Jens , Trebing David , Uhlig Ralf , Buck Reiner
Published: November 2016

Previous successful tests and promising results of a Centrifugal Particle Receiver (CentRec) for high temperature solar applications has been achieved in a lab scale prototype with 7.5 kWth [1, 2, 3]. In a next step this receiver technology is scaled up to higher thermal power for a future pilot plant.

This paper presents the optimization methodology of the design and technical solutions. It describes the manufacturing and assembly of the prototype and first tests and results of the commissioning including cold particle tests and prototype costs. Finally the paper gives an outlook on the planned further steps regarding hot lab tests and solar tests.
Rechargeable Personal Air Conditioning Device
Authors: Du Yilin , Muehlbauer Jan , Ling Jiazhen , Aute Vikrant , Hwang Yunho , Radermacher Reinhard
Published: November 2016

A rechargeable personal air-conditioning (RPAC) device was developed to provide an improved thermal comfort level for individuals in inadequately cooled environments. This device is a battery powered air-conditioning system with the phase change material (PCM) for heat storage. The condenser heat is stored in the PCM during the cooling operation and is discharged while the battery is charged by using the vapor compression cycle as a thermosiphon loop. The conditioned air is discharged towards a single person through adjustable nozzle. The main focus of the current research was on the development of the cooling system. A 100 W cooling capacity prototype was designed, built, and tested. The cooling capacity of the vapor compression cycle measured was 165.6 W. The PCM was recharged in nearly 8 hours under thermosiphon mode. When this device is used in the controlled built environment, the thermostat setting can be increased so that building air conditioning energy can be saved by about 5–10%.
Design and Analysis of a High Temperature Particulate Hoist for Proposed Particle Heating Concentrator Solar Power Systems
Authors: Repole Kenzo K. D. , Jeter Sheldon M.
Published: November 2016

The central receiver power tower (CRPT) with a particle heating receiver (PHR) is a form of concentrating solar power (CSP) system with strong potential to achieve high efficiency at low cost and to readily incorporate cost-effective thermal energy storage (TES). In such a system, particulates are released into the PHR, and are heated to high temperature by concentrated solar radiation from the associated heliostat field. After being heated, the particles will then typically flow into the hot bin of the TES. Particulates accumulated in the hot bin can flow through a heat exchanger to energize a power generation system or be held in the hot TES storage bin for later use such as meeting a late afternoon peak demand or even overnight generation. Particles leaving the heat exchanger are held in the low temperature bin of the TES.

A critical component in such a PHR system is the particle lift system, which must transport the particulate from the lower temperature TES bin back to the PHR. In our baseline 60 MW-thermal (MW-th) design, the particulate must be lifted around 70 m at the rate of 128 kg/s. For the eventual commercial scale system of a 460 MW-th design the particulate must be lifted around 138 m at the rate of 978 kg/s. The obvious demands on this subsystem require the selection and specification of a highly efficient, economical, and reliable lift design.

After an apparently exhaustive search of feasible alternatives, the skip hoist was selected as the most suitable general design concept. While other designs have not been dismissed, our currently preferred somewhat more specific preliminary design employs a Kimberly Skip (KS) in a two-skip counterbalanced configuration. This design appears to be feasible to fabricate and integrate with existing technology at an acceptably low cost per MW-th and to promise high overall energy use efficiency, long service life, and low maintenance cost. A cost and performance model has been developed to allow optimization of our design and the results of that study are also presented. Our developed design meets the relevant criteria to promote cost effective CSP electricity production.
Part Load Behavior of Molten Salt Cavity Receiver Solar Tower Plants Under Storage Mode Operational Mode
Authors: Mostafavi Tehrani S. Saeed , Taylor Robert A. , Shafiei Ghazani Ardalan , Saberi Pouya
Published: November 2016

The performance of the tower based concentrated solar thermal (CST-tower) plant is very sensitive to the operation strategy of the plant and the incident heat flux on the receiver. To date, most studies have been examined only the design mode characteristics of the cavity receivers, but this paper significantly expands the literature by considering non-design operating conditions of this important sub-component of the CST-tower plants. A feasible non-design operating conditions of the cavity receivers that was considered in this study is the storage mode of operation. Two practical dynamic control strategies were examined then to find the most efficient approach: fixed solar field mass flowrate (Approach “A”) and fixed outlet temperature at receiver (Approach “B”). To evaluate the performance of the cavity receiver, a thermal model is developed to be used for design and non-design analysis. The thermal model has been then validated against available data from the Gemasolar operating solar Tower plant. In non-design conditions, the effects of heat transfer fluid (solar salt) temperature and flowrate are mainly evaluated in terms of the non-dimensional receiver thermal output, non-dimensional power output, receiver energetic efficiency, receiver surface temperature, receiver outlet temperature, and the fraction of solar field usage. The results of this study (e.g. off design receiver efficiency correlations) assist researchers to evaluate cavity receivers without performing detail simulations. They also help investigators to choose an appropriate control strategy and to analyze the viability of other CST-tower subcomponents that have thermal interactions with the receiver (e.g. dynamic control of the phase change storage unit or its boundary conditions).
An Optimal Predictive Control of 0.75 kW PEM Fuel Cell Cogeneration With Home Appliances for Efficient PV Utilization
Authors: Yoshida Akira , Yoshikawa Jun , Fujimoto Yu , Amano Yoshiharu
Published: November 2016

This paper proposes an optimal predictive control of 0.75 kW PEM fuel-cell cogeneration with home appliances. This paper also models fuel cell system for design and operation evaluation of building equipment based on actual measurement of residential fuel cell system on sale. As one application of constructed model and proposed control method, this paper discusses concerning home EMS for efficient PV utilization.
Testing and Preliminary Modelling of a 2.5 kW Micro-CHP SOFC Unit
Authors: Mastropasqua Luca , Campanari Stefano , Valenti Gianluca , Guariniello Anna , Modena Stefano , Ghigliazza Francesco
Published: November 2016

The experimental activities, carried out at the Laboratory of Micro-Cogeneration (LMC) of the Department of Energy at Politecnico di Milano are hereby outlined in relation to the testing of four 2.5 kWel AC SOFC-based micro-CHP units developed by SOLIDpower S.p.a.

The novelty of the work consists in carrying out a complete thermodynamic and environmental performance characterisation of the studied commercial system in a third-party laboratory.

The main objectives of the experimental campaign have been the investigation and assessment of the electric and heat recovery performances in different cogeneration thermal power demand loads.

The generator has been tested in five different thermal loads, whilst operated at full electric load, in order to simulate the coupling with thermal appliances of diverse nature. The cogeneration water inlet temperature has been varied from 20°C (as in more complex cogeneration systems which may envisage a thermal storage and additional pre-heating section) to 50°C (as for district heating purposes or heating of sanitary water).

Each measurement has been acquired with a redundant approach for statistical purposes aiming to the reduction of uncertainty and to guarantee procedure robustness.

Moreover, the design point experimental characterisation has been supported by an overall process calibration and simulation performed by means of an in-house software (GS), developed at the Department of Energy. Each component has been modelled using a 0D approach, such that the required mass and energy balances of the plant can be compared with those obtained from the experimental activity.

In conclusion, the overall performances have met the expectations, being characterised by a net electric efficiency of approximately 39% and a total efficiency which may overcome 95%.
Design Space Assessment of Hydrogen Storage Onboard Medium and Heavy Duty Fuel Cell Electric Trucks
Authors: Gangloff John , Kast James , Morrison Geoffrey , Marcinkoski Jason
Published: November 2016

Hydrogen fuel cells are an important part of a portfolio of strategies for reducing petroleum use and emissions from medium and heavy duty (MD and HD) vehicles; however, their deployment is very limited compared to other powertrains. This paper addresses gaseous hydrogen storage tank design and location on representative MD and HD vehicles. Storage design is based on vehicle size and occupation. The available storage space on representative vehicles is assessed and is used to estimate the weight and capacity of composite material-based compressed gaseous storage at 350 and 700 bar. Results demonstrate the technical feasibility of using hydrogen storage for Fuel Cell Electric Trucks (FCETs) across a wide range of the MD and HD vehicle market. This analysis is part of a longer-term project to understand which market segments provide the maximum economic impact and greenhouse gas reduction opportunities for FCETs.
Simulation of Model Predictive Control for a Fuel Cell/Gas Turbine Power System Based on Experimental Data and the Recursive Identification Method
Authors: Restrepo Bernardo , Banta Larry E. , Tucker David
Published: November 2016

A Model Predictive Control (MPC) strategy has been suggested and simulated with the empirical dynamic data collected on the Hybrid Performance (HyPer) project facility installed at the National Energy Technology Laboratory (NETL), U.S. Department of Energy, in Morgantown, WV. The HyPer facility is able to simulate gasifier/fuel cell power systems and uses hardware-based simulation approach that couples a modified recuperated gas turbine cycle with hardware driven by a solid oxide fuel cell model. Dynamic data was collected by operating the HyPer facility continuously during five days. Bypass valves along with electric load of the system were manipulated and variables such as mass flow, turbine speed, temperature, pressure, among others were recorded for analysis. This work was developed by focusing on a multivariable recursive system identification structure fitting measured transient data. The results showed that real-time or online data is a viable means to provide a dynamic model for controller design.

The excursion dynamic data collected between the setup changes of the experiments was processed off-line to determine the feasibility of applying an adaptive Model Predictive Control strategy. One of the strengths of MPC is that it can allow the designer to impose strict limits on inputs and outputs in order to keep the system within known safe bounds. Two identification structures, ARX and a State-Space model, were used to fit the measured data to dynamic models of the HyPer facility. The State-Space identification was very accurate with a second order model. Visual inspection of the tracking accuracy shows that the ARX approach was approximately as accurate as the State-Space structure in its ability to reproduce measured data. However, by comparing the Loss Function and the FPE parameters, the State-Space approach gives better results.

The MPC proved to be a good strategy to control the HyPer facility. The airflow valves and the electric load were used to control the turbine speed and the cathode airflow. For the ARX/State Space models, the MPC was very robust in tracking set-point variations. The anticipation feature of the MPC was revealed to be a good tool to compensate time delays in the output variables of the facility or to anticipate eventual set-point moves in order to achieve the objectives very quickly. The MPC also displayed good disturbance rejection on the output variables when the fuel flow was set to simulate FC heat effluent disturbances. Different off-design scenarios of operation have been tested to confirm the estimated implementation behavior of the plant-controller dynamics.
Investigation of Water Transport Within a Proton Exchange Membrane Fuel Cell by Diffusion Layer Saturation Analysis
Authors: Battrell Logan , Trunkle Aubree , Eggleton Erica , Zhang Lifeng , Anderson Ryan
Published: November 2016

Diffusion layer saturation analysis (DLSA) is introduced in order to further investigate water transport within the cell. The analysis relies on two separate experimental processes. First, an ex-situ investigation of the relative humidity of the gas streams and their resulting pressure drop is performed. Next, multiple variables of the cathode and anode gas streams are manipulated in-situ to create an evaporative driving force to remove water out of the porous layers. Multiple gas stream settings are investigated as well as the temperature set point of the cell. The ex-situ pressure drop data is used to infer how much water is being removed from the system and to begin to estimate an overall water balance. Multiple cathode and anode GDL configurations are tested in order to further investigate initial saturation conditions of the GDLs. By coupling the voltage results to the calculated water removed from the system, it can be seen which configurations had low initial voltage due to GDL oversaturation. The potential for DLSA both as a diagnostic tool and an investigative technique into multiphase flow in the porous layer is demonstrated.
Design, Energy Modeling and Performance of an Integrated Industrial Size Biogas SOFC System in a Wastewater Treatment Plant
Authors: Gandiglio Marta , Saberi Mehr Ali , Lanzini Andrea , Santarelli Massimo
Published: November 2016

DEMOSOFC [1] is a Fuel Cell & Hydrogen Joint Undertaking (FCH-JU) funded project which foresees the installation of the largest biogas fed Solid Oxide Fuel Cell (SOFC) in Europe. The SOFC will be the sole combined heat & power (CHP) generator within a medium size wastewater treatment plant (WWTP) located in Torino (IT). Three SOFC modules, each rated 58 kWe, will supply around 30% of the internal electrical loads and a variable share of the thermal load depending on the season. The key objective of the project is to demonstrate the industrial readiness of SOFC systems, which are able to guarantee better performance both in terms of electrical efficiency and emission of pollutants with respect to conventional internal combustion engines.

SOFC systems have a high potential for integration with local renewable fuels as biogas and/or bio-syngas from waste sources. Looking at the biogas potential in EU, the most common plant size lies in the sub-MW scale.

This work aims to describe the DEMOSOFC concept, the approach followed for the design of the integrated system. Energy performance, environmental benefits, underlining advantages and barriers of this integration are presented and discussed.
Fuel Property Effects on the Fate of Volume Distributed Combustion
Authors: Khalil Ahmed E. E. , Gupta Ashwani K.
Published: November 2016

Colorless Distributed Combustion (CDC) has been shown to provide singular benefits on ultra-low pollutants emission, enhanced stability and thermal field uniformity. To achieve CDC conditions, fuel-air mixture must be properly prepared and mixed with hot reactive gases from within the combustor prior to the mixture ignition. Hot reactive gases reduce the oxygen concentration in the mixture while increasing its temperature. In this paper, the impact of fuel type (methane, propane, and hydrogen enriched methane) on achieving distributed combustion is investigated. A mixture of nitrogen and carbon dioxide was mixed to simulate the hot recirculated gases at different temperatures using normal air upstream of the combustor. Increasing the amounts of nitrogen and carbon dioxide reduced the oxygen concentration within the combustor. Distributed combustion was identified through OH* chemiluminescence distribution across the combustor. For methane, this oxygen concentration varied between 13.8% and 11.2% (depending on the mixture temperature) with some 85% reduction in NO emissions as compared to that without entrainment. Similar behavior was demonstrated with propane and hydrogen enriched methane, albeit at a lower oxygen concentration (13.7%–11.6% and 12.2%–10.5%), to result in 94% and 92% reduction in NO emission, respectively. The inlet gas temperature was varied between 300K and 750K. Experimental data using a variety of fuels showed NO emissions of 1 PPM or less. Analysis and extrapolation of obtained data suggest that distributed combustion can be achieved at an oxygen concentration of 9.5% for hot reactive entrained gases having a temperature of 1800K. This value may be used as a guideline to achieve distributed combustion with ultra-low emission.