bluuebunny/crossref_metadata_2025 huggingface dataset:
Incidence and 1‐Year Outcomes of Perioperative Atrial Arrhythmia in Elderly Adults After Hip Fracture Surgery
Authors: Gupta Bhanu P. , Steckelberg Rachel C. , Gullerud Rachel E. , Huddleston Paul M. , Kirkland Lisa L. , Wright R. Scott , Huddleston Jeanne M.
Published: October 2015

Objectives

To determine the incidence and 1‐year outcomes of an elderly population with perioperative atrial arrhythmia (PAA) within 7 days of hip fracture surgery.

Design

Retrospective cohort study.

Setting

The Rochester Epidemiology Project (REP).

Participants

Elderly adults consecutive undergoing hip fracture repair from 1988 to 2002 in Olmsted County, Minnesota (N = 1,088, mean age 84.0 ± 7.4, 80.2% female).

Measurements

Baseline clinical variables were analyzed in relation to survival using Cox proportional hazards methods for comparison.

Results

Sixty‐one participants (5.6%) developed PAA within the first 7 days. During 1 year of follow‐up, 239 (22%) participants died. PAA was associated with greater mortality (45% vs 21%; hazard ratio (HR) = 2.8, 95% confidence interval (CI) = 1.9–4.2). Other mortality risk factors were male sex (HR = 2.0, 95% CI = 1.5–2.6), congestive heart failure (HR = 2.1, 95% CI = 1.7–2.8), chronic renal insufficiency (HR = 2.0, 95% CI = 1.5–2.8), dementia (HR = 2.9, 95% CI = 2.2–3.7), and American Society of Anesthesiologists risk Class III, IV, or V (HR = 3.3, 95% CI = 1.9–5.9).

Conclusion

Elderly adults undergoing hip fracture surgery who develop PAA within 7 days have significantly higher 1‐year mortality than those who do not. Further studies are indicated to determine whether prevention of PAA will reduce mortality in this population.
Civil Society Organizations and International Cooperation Agencies in the Coproduction of a National Agenda for Afro‐Descendants in Argentina: Reflections on a SAICD Project
Authors: Rodriguez Pablo Gustavo , Surasky Javier , Maffia Marta M.
Published: October 2015

Se analiza un proyecto de cooperación internacional denominado “Apoyo a la población afro‐argentina y sus organizaciones de base” financiado por la Agencia Española de Cooperación Internacional al Desarrollo (AECID). Desarrollado entre los años 2008 y 2010 y liderado por la Sociedad de Socorros Mutuos Unión Caboverdeana de Dock Sud, localidad cercana a Buenos Aires, Argentina. La estructura de oportunidades creada por este proyecto permitió a los líderes de las organizaciones argentinas canalizar recursos para beneficiar a su propia gente y fortalecer de ese modo sus respectivos liderazgos. Las organizaciones afroargentinas adoptaron la jerga de la cooperación internacional y aprendieron a enmarcar sus intereses bajo las categorías de acciones estratégicas aceptadas por la AECID. Al apoyar el proyecto esta última cumplió su misión, justificó su existencia y ofreció a sus donantes evidencia del correcto uso de sus fondos de acuerdo a las directivas establecidas en su Plan Estratégico.
In situ electronic probing of semiconducting nanowires in an electron microscope
Authors: FAUSKE V.T. , ERLBECK M.B. , HUH J. , KIM D.C. , MUNSHI A.M. , DHEERAJ D.L. , WEMAN H. , FIMLAND B.O. , VAN HELVOORT A.T.J.
Published: October 2015

For the development of electronic nanoscale structures, feedback on its electronic properties is crucial, but challenging. Here, we present a comparison of various in situ methods for electronically probing single, p‐doped GaAs nanowires inside a scanning electron microscope. The methods used include (i) directly probing individual as‐grown nanowires with a sharp nano‐manipulator, (ii) contacting dispersed nanowires with two metal contacts and (iii) contacting dispersed nanowires with four metal contacts. For the last two cases, we compare the results obtained using conventional ex situ litho‐graphy contacting techniques and by in situ, direct‐write electron beam induced deposition of a metal (Pt). The comparison shows that 2‐probe measurements gives consistent results also with contacts made by electron beam induced deposition, but that for 4‐probe, stray deposition can be a problem for shorter nanowires. This comparative study demonstrates that the preferred in situ method depends on the required throughput and reliability.
Fish oil supplementation does not lower C‐reactive protein or interleukin‐6 levels in healthy adults
Authors: Muldoon M. F. , Laderian B. , Kuan D. C. H. , Sereika S. M. , Marsland A. L. , Manuck S. B.
Published: October 2015

Background

The n‐3 polyunsaturated fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) may prevent a range of chronic conditions through anti‐inflammatory actions. However, as clinical trials using these fatty acids for primary prevention are yet unavailable, their putative role in disease prevention rests, in part, on evidence of anti‐inflammatory actions in healthy individuals.

Objective

To investigate in a double‐blind, placebo‐controlled clinical trial whether supplementation with a moderate dose of EPA+DHA reduces common biomarkers of chronic, systemic inflammation in healthy individuals.

Methods

A total of 261 healthy individuals aged 30–54 years who were free of inflammatory conditions and consumed ≤300 mg per day EPA+DHA were included in the study. Participants were randomly assigned to 18 weeks of either fish oil supplementation providing 1400 mg per day EPA+DHA or matching placebo. Outcome measures were serum levels of C‐reactive protein (CRP) and interleukin (IL)‐6. In a substudy, ex vivo cytokine production was measured. Missing data for CRP and IL‐6 were estimated using regression imputation. Data analyses conformed to intention‐to‐treat principles.

Results

Participant blinding was verified. Red blood cell EPA+DHA increased by 64% in the active treatment group, but serum CRP and IL‐6 were not affected by supplementation (P ≥ 0.20). Findings were consistent with and without imputed values and across subgroups. Similarly, EPA+DHA supplementation did not alter ex vivo production of four pro‐inflammatory cytokines (P ≥ 0.20).

Conclusions

Supplementation with 1400 mg EPA+DHA did not reduce common markers of systemic inflammation in healthy adults. Whether this or a higher dose affects other measures of inflammation, oxidative stress or immune function warrants examination.
Recovery from Cucumber Mosaic Virus Infection for ‘Calwonder’ Bell Pepper Plants Does not Counter Negative Impacts on Plant Growth
Authors: Murphy John F. , Masiri Jongkit , Hadi Buyung A. R. , Dute Roland R.
Published: October 2015

Cucumber mosaic virus (CMV) accumulation in leaves and stems of infected bell pepper plants at specific symptom stages was evaluated with an emphasis on the transition from full infection to recovery from Cucumber mosaic disease. Four symptom phases occurred in successive order, designated chlorosis (leaves 6–8), mosaic (leaves 9–11/12), leaf distortion (first series of leaves on secondary and tertiary branches) and recovery (progressive recovery with newly emerging leaves in tertiary and younger branches). In situ detection of CMV in leaf tissues revealed widespread occurrence in leaves expressing chlorosis and mosaic symptoms but reduced, localized occurrence in leaves in the recovery phase. Similarly, CMV accumulated to high levels throughout stems expressing chlorosis and mosaic symptoms but with dramatically reduced levels for plants in the recovery symptom phase. Stunting of internodes occurred at all locations above the inoculated leaves by the first expression of systemic symptoms, suggesting an impact on stem growth in response to initial virus invasion of young developing tissues of the stem. Despite the recovery from CMV infection, plant growth was negatively impacted early in the infection process and remained so through the course of the experiment.
Short‐term manipulation of precipitation in Mongolian steppe shows vegetation influenced more by timing than amount of rainfall
Authors: Spence Laura A. , Liancourt Pierre , Boldgiv Bazartseren , Petraitis Peter S. , Casper Brenda B.
Published: October 2015

Questions

How does plant productivity and community composition in the mountain steppe of northern Mongolia respond to increased precipitation? Do these changes differ with the timing of precipitation?

Location

Mountain steppe at ecotone between steppe and taiga, Dalbay Valley, Lake Hövsgöl International Long Term Ecological Research Site (ILTER), northern Mongolia (51°01.405′ N 100°45.600′ E).

Methods

We experimentally applied water, representing a 25% increase in growing season precipitation, to plots at the drier end of a topographic moisture gradient in mountain steppe vegetation. In one treatment, supplemental water was applied weekly for four growing seasons. A second treatment started in year 2, in which three times the weekly supplement of water was applied once every 3 wk for three growing seasons. Vascular plant species presence and percentage cover were used to assess water treatment effects on forb and graminoid composition. Plant species biomass and percentage cover in year 4 was used to determine treatment effects on total productivity, and on the abundances of legumes, non‐leguminous forbs and graminoids, separately. Lichen, litter and root biomass, plant available N, P and K, and seedling demography were also examined in year 4.

Results

Weekly watering changed the relative abundances of forbs and increased the total abundance of legumes and non‐leguminous forbs measured either as percentage cover or biomass. The 3‐wk watering treatment did not induce the same changes in forb composition or abundance of functional groups but produced less compositional change in graminoids compared to controls. Neither treatment increased total productivity. Three‐week watering increased plant available P and decreased litter. Seedling emergence, survival and size increased with one or both watering treatments.

Conclusion

In mountain steppe, precipitation increases will produce immediate changes in composition and abundance of forbs, including legumes, but not in graminoids or total productivity. The steppe is more responsive to regular incremental increases in precipitation than to less frequent, larger storms whose effect would be timing‐dependent within the short, temperature‐limited growing season. Longer term investigations need to be conducted to explore if further lagged responses to water addition occur.
Post‐ablation des‐gamma‐carboxy prothrombin level predicts prognosis in hepatitis B‐related hepatocellular carcinoma
Authors: Lee Sunyoung , Rhim Hyunchul , Kim Young‐sun , Kang Tae Wook , Song Kyoung Doo
Published: October 2015

Background & Aims

We investigated whether pre‐ or post‐ablation serum alpha‐foetoprotein (AFP) and des‐gamma‐carboxy prothrombin (DCP) levels can predict prognosis in patients with curative radiofrequency ablation (RFA) for hepatitis B virus (HBV)‐related hepatocellular carcinoma (HCC).

Methods

We retrospectively analysed 412 patients with HBV‐related single HCC treated with percutaneous RFA between January 2004 and December 2013. AFP and DCP levels were measured before (pre‐ablation) and 1 month after treatment (post‐ablation). We assessed predictive factors for overall and recurrence‐free survival.

Results

On univariate analysis, Child‐Pugh score, Model for End‐Stage Liver Disease (MELD) score, platelet count, tumour size, Barcelona Clinic Liver Cancer (BCLC) stage, and pre‐ and post‐ablation DCP were significant for overall survival; and age, Child‐Pugh score, MELD score, platelet count, tumour size, Cancer of the Liver Italian Program (CLIP) score, BCLC stage, and pre‐ and post‐ablation AFP and DCP were significant for recurrence‐free survival. Multivariate analysis revealed significant differences in overall survival by MELD score and tumour size and in recurrence‐free survival by BCLC stage. Among the tumour markers, post‐ablation DCP was an independent prognostic factor for overall and recurrence‐free survival [hazard ratio (HR), 3.438; 95% confidence interval (CI), 1.331–8.877; P = 0.011 and HR, 4.934; 95% CI, 2.761–8.816; P < 0.001 respectively]. Post‐ablation AFP was associated with recurrence‐free survival (HR, 1.995; 95% CI, 1.476–2.697; P < 0.001) but not overall survival.

Conclusions

In patients with HBV‐related HCC, post‐ablation serum DCP is a useful biomarker for predicting survival and recurrence after curative RFA.
Seventeen years of subcutaneous infection by Aspergillus flavus; eumycetoma confirmed by immunohistochemistry
Authors: Ahmed Sarah A. , Abbas Manal A. , Jouvion Gregory , Al‐Hatmi Abdullah M. S. , de Hoog G. Sybren , Kolecka Anna , Mahgoub El Sheikh
Published: October 2015

Chronic subcutaneous infections caused by Aspergillus species are considered to be extremely rare. Because these fungi are among the most common laboratory contaminants, their role as eumycetoma causative agents is difficult to ascertain. Here, we report the first case of A. flavus eumycetoma confirmed by isolation, molecular identification and immunohistochemical analysis. Patient was a 55‐year‐old male from Sudan suffering from eumycetoma on his left foot for a period of 17 years. He developed swelling, sinuses and white grain discharge was observed. He has been operated nine times and was treated with several regimens of ketoconazole and itraconazole without improvement. Initial diagnosis based on histology and radiology was Scedosporium eumycetoma. However, examination of the biopsy revealed A. flavus, which was identified by molecular analysis and MALDI‐TOF MS. Immunohistochemistry using antibody directed against Aspergillus species was positive. Because of the earlier treatment failures with ketoconazole and itraconazole, therapy with voriconazole was initiated. However, in vitro susceptibility testing yielded a lower Minimum Inhibitory Concentration (MIC) value for itraconazole (0.25 μg ml−1) than for voriconazole (1 μg ml−1). Based on the presented results, A. flavus can be considered as one of the agents of white‐grain eumycetoma.
Physiological and transcriptional regulation in poplar roots and leaves during acclimation to high temperature and drought
Authors: Jia Jingbo , Li Shaojun , Cao Xu , Li Hong , Shi Wenguang , Polle Andrea , Liu Tong‐Xian , Peng Changhui , Luo Zhi‐Bin
Published: October 2015

To elucidate the physiological and transcriptional regulatory mechanisms that underlie the responses of poplars to high temperature (HT) and/or drought in woody plants, we exposed Populus alba × Populus tremula var. glandulosa saplings to ambient temperature (AT) or HT under 80 or 40% field capacities (FC), or no watering. HT increased the foliar total carbon (C) concentrations, and foliar δ13C and δ18O. HT triggered heat stress signaling via increasing levels of abscisic acid (ABA) and indole‐3‐acetic acid (IAA) in poplar roots and leaves. After perception of HT, poplars initiated osmotic adjustment by increasing foliar sucrose and root galactose levels. In agreement with the HT‐induced heat stress and the changes in the levels of ABA and carbohydrates, we detected increased transcript levels of HSP18 and HSP21, as well as NCED3 in the roots and leaves, and the sugar transporter gene STP14 in the roots. Compared with AT, drought induced greater enhancement of foliar δ13C and δ18O in poplars at HT. Similarly, drought caused greater stimulation of the ABA and foliar glucose levels in poplars at HT than at AT. Correspondingly, desiccation led to greater increases in the mRNA levels of HSP18, HSP21, NCED3, STP14 and INT1 in poplar roots at HT than at AT. These results suggest that HT has detrimental effects on physiological processes and it induces the transcriptional regulation of key genes involved in heat stress responses, ABA biosynthesis and sugar transport and HT can cause greater changes in drought‐induced physiological and transcriptional responses in poplar roots and leaves.
The Headmaster Ritual: The Importance of Management for School Outcomes
Authors: Böhlmark Anders , Grönqvist Erik , Vlachos Jonas
Published: October 2015

We estimate the impact of individual principals on school outcomes by using panel data that allow us to track principals over time. We find that individual principals have a substantive impact on school policies, working conditions, and student outcomes. In particular, students who attend a school that has a one standard deviation better principal improve their achievement by between 0.05 and 0.1 standard deviations. Despite rich background information on principals, it is difficult to characterize successful management, suggesting that innate skills are central. We find that the scope for discretion is larger among voucher schools and in areas with school competition.
Signaling Corporate Social Responsibility: Third‐Party Certification versus Brands
Authors: Etilé Fabrice , Teyssier Sabrina
Published: October 2015

Corporate social responsibility (CSR) is a credence attribute of products, which can be signaled either through a label certified by a third party, or via unsubstantiated claims used as part of a brand‐building strategy. We use an experimental posted‐offer market with sellers and buyers to compare the impact of these signaling strategies on market efficiency. Only third‐party certification gives rise to a separating equilibrium and an increase in CSR investments. Unsubstantiated claims can generate a halo effect on consumers, whereby the latter are nudged into paying more for the same level of CSR investments by firms.
Modes of Supply for US Exports of Services
Authors: Christen Elisabeth , Francois Joseph
Published: October 2015

We examine the choice of modes of delivery in services based on US data, including both cross‐border exports and sales through foreign affiliates. We focus on characteristics of destination markets and how this impacts on mode choice. We find that market size, distance and policy all play a role in where firms establish, and in how many markets firms enter. The importance of sales through affiliates relative to total foreign sales also depends on factors like market size, geographic and economic distance and the policy regime in place. Precisely, how important these factors are depends on the sector in question.
The ‘intrusive as’‐construction in South Asian varieties of English
Authors: LANGE CLAUDIA
Published: October 2015

It has been observed (Nihalani et al. 1979; Yadurajan 2001) that Indian English differs from other varieties of English in that it allows ‘intrusive as’ in complex‐transitive constructions, especially with the verbs call, name and term. However, the construction is not restricted to Indian English, but represents a pan‐South Asian feature that is gaining ground in the written language across South Asian varieties of English. This paper will provide a corpus‐based analysis of the forms, functions and distribution of ‘intrusive as’‐constructions in South Asian Englishes, and consider possible motivations for this innovation in verb complementation patterns.
Multiphase Flow Large-Eddy Simulation Study of the Fuel Split Effects on Combustion Instabilities in an Ultra-Low-NOx Annular Combustor
Authors: Bauerheim M. , Jaravel T. , Esclapez L. , Riber E. , Gicquel L. Y. M. , Cuenot B. , Cazalens M. , Bourgois S. , Rullaud M.
Published: October 2015

This paper describes the application of a coupled acoustic model/large-eddy simulation approach to assess the effect of fuel split on combustion instabilities in an industrial ultra-low-NOx annular combustor. Multiphase flow LES and an analytical model (analytical tool to analyze and control azimuthal modes in annular chambers (ATACAMAC)) to predict thermoacoustic modes are combined to reveal and compare two mechanisms leading to thermoacoustic instabilities: (1) a gaseous type in the multipoint zone (MPZ) where acoustics generates vortex shedding, which then wrinkle the flame front, and (2) a multiphase flow type in the pilot zone (PZ) where acoustics can modify the liquid fuel transport and the evaporation process leading to gaseous fuel oscillations. The aim of this paper is to investigate these mechanisms by changing the fuel split (from 5% to 20%, mainly affecting the PZ and mechanism 2) to assess which mechanism controls the flame dynamics. First, the eigenmodes of the annular chamber are investigated using an analytical model validated by 3D Helmholtz simulations. Then, multiphase flow LES are forced at the eigenfrequencies of the chamber for three different fuel split values. Key features of the flow and flame dynamics are investigated. Results show that acoustic forcing generates gaseous fuel oscillations in the PZ, which strongly depend on the fuel split parameter. However, the correlation between acoustics and the global (pilot + multipoint) heat release fluctuations highlights no dependency on the fuel split staging. It suggests that vortex shedding in the MPZ, almost not depending on the fuel split, is the main feature controlling the flame dynamics for this engine.
Energy Consumption Prediction of University Buildings in China and Strategies for Energy Efficiency Management
Authors: Qu Li-juan , Lei Li-nan , Chen Wei , Qian Jin-yuan
Published: October 2015

In 2007, Chinese Ministry of Education (MOE) and Ministry of Housing & Urban-Rural Development (MOHURD) carried out the Campus Resource Conservation Actions, in order to take full use of resources and to improve the energy efficiency. However, due to the large amounts of universities, the total energy consumption and the energy efficiency situation have no objective statistics. Taking modeling the energy consumption of university buildings as the starting point, this paper analyzes the characteristics of university buildings in China. Then, we do the prediction, trend and potential analysis of the total energy consumption in 2020. In addition, four strategies for energy efficiency management are carried out, which might be helpful for all the university managers and related departments.
A Computational Study of In-Cylinder NOx Reduction Strategies for a Compression-Ignition Engine Fueled With Diesel/Hydrogen Mixtures
Authors: Khairallah Hassan A. , Koylu Umit O.
Published: October 2015

Considerable efforts have been made to introduce alternative fuels for use in conventional diesel and gasoline engines. There is significant interest in adding hydrogen to a diesel engine to reduce emissions and improve efficiency. However, the main challenge associated with the use of hydrogen in diesel engines is high nitrogen oxide (NOX) emissions. In the present study, a reduced chemical kinetics mechanism, consisting of 52 reactions and 29 chemical species for n-heptane fuel combustion, was incorporated with detailed chemical kinetics consisting of 29 reactions for hydrogen as well as additional nitrogen oxidation. This reaction mechanism was coupled with 3-D advanced CFD software to investigate the performance and emission characteristics of a diesel-hydrogen dual-fuel engine. Computational results showed good agreements with the experimental results for brake thermal efficiency, CO2, CO, and NOX emissions. The model was then employed to examine the effects of exhaust gas recirculation (EGR) and N2 dilution on NOX emissions. The computational results quantified the reduction in NOX emissions with EGR and N2 dilution, and a more remarkable reduction was found with 30% N2 dilution. However, in terms of the N2 dilution, a general decreasing trend was observed for both NOX and CO2 emissions, while CO emissions increased. In relation to the EGR, the NOX emissions decreased while CO2 and CO emissions significantly increased. Additionally, the results showed that the indicated mean effective pressure (IMEP) and indicated power decreased as the N2 dilution increased. The same trend was observed for the EGR but the reduction was less compared to that of the N2 dilution.
Heat Transfer Coefficient and Pressure Drop of R410A During Evaporation Inside Aluminum Multiport Minichannels
Authors: Nguyen Chien , Pham Vu , Kwang-Il Choi , Jong-Taek Oh
Published: October 2015

Micro and minichannel are progressively used in heat exchangers nowadays. The application of these heat exchanger types in refrigeration and air conditioning fields show various advantages such as high efficiency, low air side pressure, reducing refrigerant charge and the compactness size. The aim of this study is to investigate the two phase flow heat transfer coefficient and pressure drop of R410A during evaporation.

The experimental data were observed in aluminum channel with the hydraulic diameters of 1.14 and 1.16 mm, mass fluxes of 50–150 kW/m2s heat fluxes of 3–6 kW/m2, saturation temperature of 6°C and vapor quality from 0.1 to 0.9. The effect of mass flux, heat flux, and hydraulic diameter on heat transfer coefficient and pressure drop were analyzed. The database was compared with numerous well-known heat transfer coefficient and pressure drop correlations. Finally, a modify heat transfer coefficient correlation was developed that showed a good prediction against the database.
Parametric Investigation of Concentrating PV/T System With Spectral Filtering Utilizing a 2-D Model
Authors: Brekke Nick , Otanicar Todd , DeJarnette Drew , Harikumar Parameswar
Published: October 2015

Hybrid photovoltaic/thermal (PV/T) systems are continually being investigated, in particular the use of such systems in concentrating collectors as part of the ARPA-E FOCUS program. While many combined thermal and electrical models exist, most are limited to 0-D energy balance approaches or 1-D approaches where temperature variations through insulation, glazing and substrates are considered. Here, we develop a 2-D model for a concentrating PV/T system where the model accounts for temperature variations along the length of the collector. The proposed configuration consists of a GaAs cell laminated to an aluminum extrusion. The working fluid, a transparent high temperature heat transfer fluid with suspended nanoparticles, flows through the extrusion where it actively cools the PV cell before passing in front of the cell acting as an optical filter. The model includes PV cell efficiency, temperature, and bandgap dependence, a detail often neglected in prior works. This paper focuses on PV efficiency along the length of the system and outlet fluid temperature for both counter and parallel flow arrangements. Of particular interest here is the wavelength used in the design of the fluid filter and how changing the design impacts the exergetic efficiency and percent of exergy created as heat.
Solar Load Ratio Parameters for a Passive Solar Heat Pipe System
Authors: Poteat Logan S. , Sharp M. Keith
Published: October 2015

The Solar Load Ratio (SLR) method is a performance prediction algorithm for passive solar space heating systems developed at Los Alamos National Laboratory. Based on curve fits of detailed thermal simulations of buildings, the algorithm provides fast estimation of monthly solar savings fraction for direct gain, indirect gain (water wall and concrete wall) and sunspace systems of a range of designs. Parameters are not available for passive solar heat pipe systems, which are of the isolated gain type. While modern computers have increased the speed with which detailed simulations can be performed, the quick estimates generated by the SLR method are still useful for early building design comparisons and for educational purposes. With this in mind, the objective of this project was to develop SLR predictions for heat pipe systems, which use heat pipes for one-way transport of heat into the building. A previous thermal network was used to simulate the heat pipe system with Typical Meteorological Year (TMY3) weather data for 13 locations across the US, representing ranges of winter temperature and available sunshine. A range of (nonsolar) load-to-collector ratio LCR = 1–15 W/m2K was tested for each location. The thermal network, along with TMY3 data, provided monthly-average-daily absorbed solar radiation and building load to calculate SLR. Losses from the solar aperture in a heat pipe system are very low compared to conventional passive solar systems, thus the load-to-collector ratio of the solar aperture was neglected in these preliminary calculations. Likewise, nighttime insulation is unnecessary for a heat pipe system, and was not considered. An optimization routine was used to determine an exponential fit (the heart of the SLR method) to simulated monthly solar savings fraction (SSF) across all locations and LCR values. Accuracy of SSF predicted by SLR compared to the thermal network results was evaluated. The largest errors (up to 50%) occurred for months with small heating loads (< 80 K days), which inflated SSF. Limiting the optimization to the heating season (October to March), reduced the error in SSF to an average of 4.24% and a standard deviation of 5.87%. These results expand the applications of the SLR method to heat pipe systems, and allow building designers to use this method to estimate the thermal benefits of heat pipe systems along with conventional direct gain, indirect gain and sunspace systems.
Exergetic Efficiency: A Detailed Reaction Mechanism Analysis of Hydrogen Combustion With Singlet Oxygen
Authors: Washington DeVon A. , Shapiro Howard N.
Published: October 2015

In previous work the authors have demonstrated that when hydrogen is combusted in stoichiometric proportions at 1 atm and 1200 K, and singlet oxygen comprises 0–20% of the oxidizer, an optimal range of exergetic efficiency exists. The maximum exergetic efficiency occurs at approximately 10%. Over this range, roughly 60% of the total exergy destruction occurs prior to ignition. This is a significant result because it suggests that the exergetic efficiency of combustion might be improved at a fundamental level by chemical means, thereby inherently increasing the efficiency of fuel use for a desired energy application.

The objective of the study presented in this paper is to analyze the reaction mechanisms for combustion with varying percentages of singlet oxygen, to determine which reaction pathways most influence the observed trends in exergy destruction and exergetic efficiency. This was accomplished by performing both sensitivity and rate-of-production analyses of the hydrogen-oxygen combustion mechanism. The results of the analysis show that the presence of singlet oxygen governs the rate of production of hydroxyl and other key radicals. These key radicals directly affect the phenomenological processes associated with chemical induction and thermal induction during ignition. Therefore, the observed optimum exergetic efficiency correlates to the quantity of singlet oxygen in the inlet charge that minimizes exergy destruction by fostering chemical reactions due to radical formation to a greater extent than thermal heat release. The results of this analysis are noteworthy and provide new insight regarding how the exergetic efficiency of combustion may be optimized by introducing singlet oxygen, thereby altering the reaction pathways to enhance energy conversion in a fundamental way that could have important implications for improved fuel use.
Maximizing Energy Output of a Wind Farm Using Teaching–Learning-Based Optimization
Authors: Patel Jaydeep , Savsani Vimal , Patel Rajesh
Published: October 2015

World is facing a big problems for fossil fuel as it deals with the issues like availability, environmental effect like global warming etc, which forces us to explore new renewable sources of energy like solar, tidal, geothermal, wind etc. Among all the energies wind energy is the effective form of energy. As evaluated from the research, main cause for reduction of energy output in wind farm is the positioning of the wind turbine, as it is a function of wake loss. Present paper investigates an effective meta-heuristics optimization method known as Teaching–Learning-Based Optimization (TLBO), to optimize the positioning of the wind turbine in a wind farm. Two different scenarios of wind speed and its direction distribution across the wind site is considered like, (a) uniform wind speed of 12 m/s with uniform direction and (b) uniform wind speed of 12 m/s with variable wind direction. The results show that the implementation of TLBO is effective then other existing strategy, in terms of maximized expected power output and minimum wake effect of turbines by each other.
Design of a Secondary Concentrator for a Small Particle Heat Exchange Receiver
Authors: Berchtold Olivier , Miller Fletcher
Published: October 2015

The design of a secondary concentrator for the Small Particle Heat Exchange Receiver (SPHER) using a Monte Carlo Ray Tracing (MCRT) method is discussed in this paper. Applying basic MCRT rules, a modular solver logic for secondary concentrators is established. The logic is coded into FORTRAN subroutines to be compatible with MIRVAL, a ray trace code for heliostat fields created by Sandia National Laboratories. Based on a 3D Compound Parabolic Concentrator (3D-CPC) example the power of the simulation based on the Sandia heliostat field calculations is demonstrated.

The results of the simulations are used to calculate the solar flux distributions in the ideal 3D CPC inlet and outlet planes as well as the incident ray distribution hitting the secondary concentrator. Code modifications to account for surface irregularities and spectral reflectivity are implemented in the appropriate FORTRAN subroutine. Using the automated simulation routines first the optimal receiver tilt angle and secondly the secondary concentrator acceptance angle are determined. These parameters combined with the fixed secondary concentrator outlet radius — which is determined by the SPHER window diameter — fully constrain the 3D CPC geometry. The flux maps generated using MATLAB post processing on the derived concentrator results clearly indicate the strengths and weaknesses of the specific concentrator and heliostat field combination.

The influence of the secondary concentrator on the window incident flux distribution and window transmission, absorption and reflection properties is evaluated. Early findings using the code suggest higher yearly average power entering the receiver when compared to a non-secondary case. The reason for this effect is found in increased heliostat efficiency towards the edges of the heliostat field. At the same time the peak power hitting the window is found to increase very slightly only. This means the maximum window design specifications do not need to be adjusted dramatically to be able to accommodate the average power increase. First indications using the MCRT output in preliminary receiver simulations suggest increased receiver efficiency and a boost in receiver outlet gas temperature. The combined effect of these improvements is expected to raise overall power generation efficiency by improving the gas- / steam turbine combined cycle efficiency.
Hybrid Sensible/Thermochemical Storage of Solar Energy in Cascades of Redox-Oxide-Pair-Based Porous Ceramics
Authors: Agrafiotis Christos , Becker Andreas , Roeb Martin , Sattler Christian
Published: October 2015

The current work is a follow-up of the idea described in previous publications, namely of combining active thermochemical redox oxide pairs like Co3O4/CoO, Mn2O3/Mn3O4 or CuO/Cu2O with porous ceramic structures in order to effectively store solar heat in air-operated Solar Tower Power Plants. In this configuration the storage concept is rendered from “purely” sensible to a “hybrid” sensible/thermochemical one and the current heat storage recuperators to integrated thermochemical reactors/heat exchangers. In addition, the construction modularity of the current state-of-the-art sensible storage systems provides for the implementation of concepts like spatial variation of redox oxide materials chemistry and solid materials porosity along the reactor/heat exchanger, to enhance the utilization of the heat transfer fluid and the storage of its enthalpy. In this perspective the idea of employing cascades of various porous structures, incorporating different redox oxide materials and distributed in a certain rational pattern in space tailored to their thermochemical characteristics and to the local temperature of the heat transfer medium has been set forth and tested.

Thermogravimetric analysis (TGA) studies described in previous works have shown that the Co3O4/CoO redox pair with a reduction onset temperature ≈ 885–905°C is capable of stoichiometric, long-term, cyclic reduction-oxidation under a variety of heatup/cooldown rates. Further such studies with the other two powder systems above, described herein, have demonstrated that the Mn3O4/Mn2O3 redox pair is characterized by a large temperature gap between reduction (≈ 950°C) and oxidation (≈ 780–690°C) temperature, whereas the CuO/Cu2O pair cannot work reproducibly and quantitatively since its redox temperature range is narrow and very close to the melting point of Cu2O. Thus, a combination of two such systems, namely Co3O4/CoO and Mn2O3/Mn3O4 has been further explored. Thermal cycling tests with these two powders together under the conditions required for complete oxidation of the less “robust” one, namely Mn3O4/Mn2O3, demonstrated in principle the proof-of-concept of the cascaded configuration, i.e. that both powders can be reduced and oxidized in complementary temperature ranges, extending thus the temperature operation window of the whole storage cascade. A suitably designed test rig where similar experiments in the form of cascades of coated honeycombs and foams can be performed has been built and further such tests are under way.
Experimental and Numerical Investigation of Melting Process in PCM Storage
Authors: Shibahara Makoto
Published: October 2015

Thermal energy storage (TES) technologies have been developed using Phase Change Materials (PCM) at various power plants to utilize waste heat sources. The melting process of PCM has been investigated experimentally and numerically to construct a fundamental database of TES systems. D-Mannitol was selected as a PCM for medium TES systems in this study. The experimental apparatus consisted of the cartridge heater, thermocouples, test tube, acryl tube, vacuum pump, pressure indicator, volt slider and shunt resistance. The temperatures near the cartridge heater were measured by K-type thermocouples. The heat inputs were ranged from 10W to 15W. As a result, temperature of D-mannitol increased with time linearly under the solid state until the fusion temperature. When D-mannitol changed from the solid phase to the liquid phase, temperatures remained constantly due to the latent heat. Moreover, the numerical simulation was conducted using the commercial CFD code, ANSYS FLUENT. As a result of the numerical simulation, it was understood that the melting process was affected by the natural convection at the inner wall. As the heat flux of the cartridge heater input from the inner wall, the liquid fraction increased from the inner wall to the outer wall. The numerical result was compared with the experimental data. It was understood that the temperature of numerical simulation was approximately consistent with that of the experiment during the phase change process.
Numerical Simulation of Heat Transfer in a 3D Cavity-Receiver
Authors: Pandi Parthasarathy , Le Clercq Patrick
Published: October 2015

The unsteady 3D fluid flow coupled to radiative, convective, and conductive heat transfers are computed within a cavity-receiver that was successfully tested experimentally. A Monte-Carlo radiation model is used in the fluid regions of the reactor with source terms outside the cavity’s window to account for the concentrated radiative power input. Darcy’s law for the viscous regime and the Forchheimer’s term for the inertial regime are used in the momentum equation to account for the pressure drop within the porous region (RPC).

Two separate energy equations for the solid and for the fluid regions of the porous domain are solved in order to capture the non-equilibrium effects in that region. Rosseland diffusion approximation is used in the solid regions of the RPC domain. The material properties and boundary conditions were taken from published experimental measurements. The simulation results are compared to the measurement data collected during the pre-heating and the ceria reduction phases, which sum up to four different radiative power inputs. Results of the comparison are very good and constitute the verification that the numerical methods, physical sub-process models and material properties are adequately selected and implemented. An analysis regarding the heat balance, the recirculating flow and, the effect of dual-scale porosity is also presented.
Piston Expanders Technology as a Way to Recover Energy From the Expansion of Highly Wet Organic Refrigerants
Authors: Fiaschi Daniele , Secchi Riccardo , Galoppi Giovanni , Tempesti Duccio , Ferrara Giovanni , Ferrari Lorenzo , Karellas Sotirios
Published: October 2015

The design of expanders for organic fluids is gaining an increasing attention due to the large opportunities opened by the ORC as a way to recover low grade heat. The possibility of recovering at least a fraction of the energy related to throttling in inverse cycles could have interesting relapses on the market of heating (heat pumps) and refrigeration machines. The main challenge to be faced is the management of a highly wet fluid (typical quality is in the 0–0.6 range), which puts off side dynamic expanders like turbines. For this reason, piston technology is proposed and analyzed. The potential recovery from the throttling of a 20 kW target domestic heat pump cycle is determined by modeling the real expansion cycle with two different codes, a commercial one (largely widespread and very easy to use) and a purposely developed one, which is much more customizable and may include different approaches to the physical behavior of the two–phase expansion.

The results show interesting possibility of energy recovery from this generally wasted source, which opens the way to improvements of the heat pump COP from 4% to about 7%, depending on the working (i.e. seasonal) conditions. The analysis also points out the agreement in the results of two different adopted simulation tools (commercial AMESim® and self-made customizable EES®), which can be thus considered valuable in the design, analysis and optimization of the proposed expander.

Due to the biphasic nature of the working fluid, the performance of the expander is strongly influenced by the inlet conditions of the fluid from the condenser of the heat pump to the cylinders, such as throttling of the inlet/outlet valves and friction through the ducts.

On the whole, this expander technology has very interesting chances to effectively manage fluids under highly wet conditions, like those related to the throttling from upper to lower pressure of inverse cycles.
Economic Performance of Thermal Energy Storage Integrated With Natural Gas Combined Cycle Power Plants
Authors: Osterman-Burgess Barry E. , Goswami D. Yogi , Stefanakos Elias K.
Published: October 2015

This paper focuses on the economics of integrating thermal energy storage into natural gas combined cycle power plants for improved operational and economic performance of the utility grid. Costs and fuel consumption are modeled based on a Florida electric utility’s hour-by-hour load data under two scenarios: 1) no storage, and 2) thermal storage attached to intermediate load, NGCC plants, displacing energy production from older, less efficient NGCT peaking units. Due to the nature of the power grid, several of the older units feature abnormally high fuel costs and abnormally low thermal efficiencies. By shifting load from the most expensive peaking units to more cost-effective combined cycles with a 204 MWhth storage system costing about $4 million, savings of more than $1 million per year can be realized while also reducing CO2 emissions by about 5000 metric tons per year. These savings represent an internal rate of returns of up to 23% over a 30-year lifetime, depending on the initial cost of the storage system.
Emergency Energy Management Model for Durham Region
Authors: Sarvendran Vajran , Harvel Glenn , McKellar Jennifer , Samuel Jeffrey
Published: October 2015

In the last 50 years, the province of Ontario has lost electrical power at various times, which has challenged Ontario’s emergency-response capabilities. In addition to the loss of electricity supply, there were concerns regarding access to diesel fuels and gasoline due to loss of electrical power to pump the fuel. However, natural gas and propane are a viable alternative energy supply in an emergency scenario.

The purpose of this project is to assess the role of natural gas in an emergency scenario and potential areas for further optimization to meet energy needs within the region of Durham, Ontario. An energy management model for the region of Durham has been developed for both electricity and natural gas. This model can be used to assess the impact of an emergency scenario on energy supply. This was achieved by researching different types of critical facilities such as hospitals, emergency services, schools, water/sewage facilities, community centers, shopping centers and gas stations and their reliance upon electricity and natural gas. Major shopping centers were included within this project as they provide communities with medical, grocery and basic needs.

Data gathered for 415 facilities was incorporated into a Visual Basic model. The data was based on floor space, population, fleet size, water consumption, fuel types and energy use behavior. Facilities were divided into categories based on sizes of less than 5,000 m2, between 5,000 m2 and 15,000 m2, and greater than 15,000 m2 for the purposes of the model. Unique facilities such as the six water treatment facilities and the ten E.M.S stations were assessed individually. The data was then used to create a model that related the available electricity and natural gas to the various types of facilities in the Durham Region.

The results show that natural gas infrastructure is already in place in the Region of Durham and many critical facilities currently use natural gas to supply heat energy. Hence, modest changes (cogeneration plants/ micro gas turbines) in the current infrastructure could be implemented to ensure emergency power is available from natural gas in a loss of electricity scenario and further improve the resiliency of the region of Durham in an emergency scenario.
Coupled Optical-Thermal-Fluid Modeling of a Directly Heated Tubular Solar Receiver for Supercritical CO2 Brayton Cycle
Authors: Ortega Jesus D. , Khivsara Sagar D. , Christian Joshua M. , Yellowhair Julius E. , Ho Clifford K.
Published: October 2015

Recent studies have evaluated closed-loop supercritical carbon dioxide (s-CO2) Brayton cycles to be a higher energy-density system in comparison to conventional superheated steam Rankine systems. At turbine inlet conditions of 923K and 25 MPa, high thermal efficiency (∼50%) can be achieved. Achieving these high efficiencies will make concentrating solar power (CSP) technologies a competitive alternative to current power generation methods. To incorporate a s-CO2 Brayton power cycle in a solar power tower system, the development of a solar receiver capable of providing an outlet temperature of 923 K (at 25 MPa) is necessary. The s-CO2 will need to increase in temperature by ∼200 K as it passes through the solar receiver to satisfy the temperature requirements of a s-CO2 Brayton cycle with recuperation and recompression. In this study, an optical-thermal-fluid model was developed to design and evaluate a tubular receiver that will receive a heat input ∼2 MWth from a heliostat field. The ray-tracing tool SolTrace was used to obtain the heat-flux distribution on the surfaces of the receiver. Computational fluid dynamics (CFD) modeling using the Discrete Ordinates (DO) radiation model was used to predict the temperature distribution and the resulting receiver efficiency. The effect of flow parameters, receiver geometry and radiation absorption by s-CO2 were studied. The receiver surface temperatures were found to be within the safe operational limit while exhibiting a receiver efficiency of ∼85%.