bluuebunny/crossref_metadata_2025 huggingface dataset:
Phonon transport at interfaces between different phases of silicon and germanium
Authors: Gordiz Kiarash , Henry Asegun
Published: January 2017

Current knowledge and understanding of phonon transport at interfaces are wholly based on the phonon gas model (PGM). However, it is difficult to rationalize the usage of the PGM for disordered materials, such as amorphous materials. Thus, there is essentially no intuition regarding interfaces with amorphous materials. Given this gap in understanding, herein we investigated heat conduction at different crystalline and amorphous Si/Ge interfaces using the recently developed interface conductance modal analysis method, which does not rely on the PGM and can therefore treat an interface with a disordered material. The results show that contrary to arguments based on lower mean free paths in amorphous materials, the interface conductances are quite high. The results also show that the interfacial modes of vibration in the frequency region of 12–13 THz are so important that perturbing the natural vibrations with velocity rescaling heat baths (i.e., in non-equilibrium molecular dynamics simulations) affects the conductance even when the heat baths are >60 nm away from the interface. The results suggest that it may be possible to affect interfacial heat transfer by perturbations very far away from the interface, which is an effect that cannot be explained or even rationalized by the traditional paradigm that stems from the Landauer formalism.
Magnetoelectric tuning of the inverse spin-Hall effect
Authors: Vargas José M. , Gómez Javier E. , Avilés-Félix Luis , Butera Alejandro
Published: January 2017

We demonstrate in this article that the magnetoelectric (ME) mechanism can be exploited to control the spin current emitted in a spin pumping experiment using moderate electric fields. Spin currents were generated at the interface of a ferromagnet/metal bilayer by driving the system to the ferromagnetic resonance condition at X-Band (9.78 GHz) with an incident power of 200 mW. The ME structure, a thin (20 nm) FePt film grown on top of a polished 011-cut single crystal lead magnesium niobate-lead titanate (PMN-PT) slab, was prepared by dc magnetron sputtering. The PMN-PT/FePt was operated in the L-T mode (longitudinal magnetized-transverse polarized). This hybrid composite showed a large ME coefficient of 140 Oe cm/kV, allowing to easily tune the ferromagnetic resonance condition with electric field strengths below 4 kV/cm. A thin layer of Pt (10 nm) was grown on top of the PMN-PT/FePt structure and was used to generate and detect the spin current by taking advantage of its large spin-orbit coupling that produces a measurable signal via the inverse spin-Hall effect. These results proved an alternative way to tune the magnetic field at which the spin current is established and consequently the inverse spin-Hall effect signal, which can promote advances in hybrid spintronic devices.
Assessment of the physicochemical characteristics of surface waterbodies in a region earmarked for shale gas exploration (Eastern Cape Karoo, South Africa)
Authors: Mabidi Annah , Bird Matthew S. , Perissinotto Renzo
Published: January 2017

The proposed drilling for shale gas resources in the Eastern Cape Karoo region of South Africa has triggered much debate over the potential effects of hydraulic fracturing on water resources. Herein we present results on some limnological aspects of surface waterbodies in this water-scarce region before shale gas exploration. Thirty-three waterbodies (nine dams, 13 depression wetlands and 11 rivers) were sampled in November 2014 and April 2015. Principal component analysis revealed that depression wetlands and rivers had distinct physicochemical signatures, whereas dams were highly variable in their physicochemical attributes and exhibited characteristics similar to those of either rivers or depression wetlands. Non-parametric multivariate regressions and permutational multivariate analysis of variance (MANOVA) indicated that landscape variables such as underlying geology, altitude and land use poorly explained the physicochemical characteristics of the sampled waterbodies. Waterbody type was the only factor that explained a significant amount of the variation in physicochemistry during both sampling events. These data need to be supplemented by water quality information from additional sites and over longer time periods, as well as supporting data relating to other aspects, such as algae and invertebrates, before they can be used as a baseline for the long-term monitoring of freshwater ecosystems in the region.
Cattle landscape selectivity is influenced by ecological and management factors in a heterogeneous mountain rangeland
Authors: von Müller A. R. , Renison D. , Cingolani A. M.
Published: January 2017

Few studies addressing drivers of cattle selectivity focus on the combination of ecological (biotic and abiotic) and management factors such as rotational systems, paddock sizes and paddock shapes. As a consequence, it is difficult to prioritise management practices integrating information of different driving factors. In a heterogeneous mountain rangeland in Central Argentina we established a total of 419 square study plots of 1 ha located in 18 paddocks with differing sizes, shapes and cattle grazing management. Plots were small samples of landscapes, covering all existing variability in vegetation and physiography. For each plot we estimated the annual cattle use, average seasonal cattle density, forage types and abiotic characteristics. We used general linear models to show that selectivity was mainly driven by biotic variables. Cattle selected landscapes dominated by short palatable plants, but the strength of this influence differed among paddocks. Selectivity was strongest in paddocks with low abundance of lawns dominated by short palatable plants and low annual stocking rate. As stocking rate and the availability of lawns increased, selectivity strength decreased. Abiotic variables had far less influence than biotic variables, showing that cattle tended to avoid rough landscapes with steep terrain in the wet-warm season; and to be attracted by permanent water sources during the dry-cold season. Seasonal stocking density and paddock size had no detectable influence on cattle selectivity and distribution. Paddock shape influenced distribution but not the strength of forage selectivity. We conclude that in our system, cattle selectivity is mainly driven by biotic factors, and the most effective methods of changing the consequent distribution pattern is by manipulating forage types and paddock shape. The role of stocking rate remains controversial as it was correlated with the proportion of lawns in the paddock.
Impacts of fire radiative flux on mature Pinus ponderosa growth and vulnerability to secondary mortality agents
Authors: Sparks Aaron M. , Smith Alistair M. S. , Talhelm Alan F. , Kolden Crystal A. , Yedinak Kara M. , Johnson Daniel M.
Published: January 2017

Recent studies have highlighted the potential of linking fire behaviour to plant ecophysiology as an improved route to characterising severity, but research to date has been limited to laboratory-scale investigations. Fine-scale fire behaviour during prescribed fires has been identified as a strong predictor of post-fire tree recovery and growth, but most studies report these metrics averaged over the entire fire. Previous research has found inconsistent effects of low-intensity fire on mature Pinus ponderosa growth. In this study, fire behaviour was quantified at the tree scale and compared with post-fire radial growth and axial resin duct defences. Results show a clear dose–response relationship between peak fire radiative power per unit area (W m–2) and post-fire Pinus ponderosa radial growth. Unlike in previous laboratory research on seedlings, there was no dose–response relationship observed between fire radiative energy per unit area (J m–2) and post-fire mature tree growth in the surviving trees. These results may suggest that post-fire impacts on growth of surviving seedlings and mature trees require other modes of heat transfer to impact plant canopies. This study demonstrates that increased resin duct defence is induced regardless of fire intensity, which may decrease Pinus ponderosa vulnerability to secondary mortality agents.
Nation-building projects through new capitals: from St. Petersburg to Yerevan and Astana
Authors: Mkrtchyan Narek
Published: January 2017

The aim of this article is to provide a comprehensive explanation for the reasons behind governments' decisions to relocate and build new capital cities. The process of capital-building is not a mere phenomenon of urbanization; rather it is a process of “text inventing” for nation-building projects. To emphasize implications for identity behind city constructions, the paper will discuss urbanization practices of Soviet Yerevan and post-Soviet Astana. However, to verify the validity and generalizability of the proposed argument, the article will also briefly provide historical analysis of relocation of capitals from Moscow to St. Petersburg, and from Istanbul to Ankara. The reconstruction of the capital of Soviet Armenia, Yerevan, in the 1920s is important in understanding the role of Utopias in initiating identity transformations. The central conceptual premise of the article is Samuel Huntington's theoretical concept of a “torn country” and the redefinition of civilizational identity. One reason capitals have been relocated and new capitals have been built throughout history is a need to initiate a long-term transformation of identity.
The preparation of Al/Fe composite powders by electroless plating
Authors: Liu Huichao , Zhang Jingde , Gou Jinyan , Ding Changku
Published: January 2017

The core–shell Al/Fe composite powders were synthesised by electroless plating. The effects of concentration of FeSO4·7H2O, pre-treatment method of aluminium powders, and secondary plating on the preparation of core–shell Al/Fe composite powders were studied. The composite powders were analysed by the X-ray diffraction, a scanning electron microscope, and an energy-dispersive spectrometer. The results indicate that the content of iron in the composite powders could be effectively controlled by adjusting the concentration of FeSO4·7H2O in the plating solution. The pre-treatment of the raw aluminium powders is also a key factor to form a uniform iron layer on the surface of aluminium particles. Furthermore, the density and iron content of the composite powders prepared by secondary plating have been improved.
Novel bioflocculant produced by salt-tolerant, alkaliphilic strainOceanobacillus polygoniHG6 and its application in tannery wastewater treatment
Authors: Li Jing , Yun Yue-qing , Xing Li , Song Lei
Published: January 2017

The optimized production of MBF-HG6, which is a novel salt-tolerant alkaliphilic bioflocculant produced by Oceanobacillus polygoni with its application in tannery wastewater treatment was investigated in this study. It was found the optimal carbon source, nitrogen source, cation, and initial pH of the medium for bioflocculant production were starch, urea, Fe2+, and pH 9.0, respectively. The best stability in the temperature range was from 0 to 80°C and the purified MBF-HG6 contained polysaccharides of 81.53% and proteins of 9.98%. The carboxyl, hydroxyl, and amino groups were determined in bioflocculants, while the optimized bioflocculating activity was observed as 90.25% for the dosages of 6.96mL MBF-HG6, 4.77mL CaCl2 (1%, m/v), and 19.24g/L NaCl using response surface methodology. In addition, SS and turbidity removal rates of the tannery wastewater (4g/L MBF-HG6) could, respectively, reach 46.49% and 91.08%, indicating that the great potential was emerged in enhancement of tannery wastewater treatment by MBF-HG6.
Improving the accuracy of likelihood-based inference in meta-analysis and meta-regression
Authors: Kosmidis I. , Guolo A. , Varin C.
Published: January 2017

Random-effects models are frequently used to synthesize information from different studies in meta-analysis. While likelihood-based inference is attractive both in terms of limiting properties and of implementation, its application in random-effects meta-analysis may result in misleading conclusions, especially when the number of studies is small to moderate. The current paper shows how methodology that reduces the asymptotic bias of the maximum likelihood estimator of the variance component can also substantially improve inference about the mean effect size. The results are derived for the more general framework of random-effects meta-regression, which allows the mean effect size to vary with study-specific covariates.
Potential Inoculum Sources and Incidence of Strawberry Soilborne Pathogens in Spain
Authors: Pastrana Ana María , Basallote-Ureba María José , Aguado Ana , Capote Nieves
Published: January 2017

The decline and death of strawberry plants in Spanish fruit production fields have mainly been attributed to the soilborne pathogens Macrophomina phaseolina, Phytophthora cactorum, and Fusarium spp. Inoculum sources of M. phaseolina and P. cactorum, and the incidence all three genera, were investigated in nurseries and fruit production fields over three consecutive seasons. M. phaseolina inoculum sources consisted of fumigated preplant fruit production soils (50%) and fumigated nursery soils (47%), although the pathogen could not be detected in nursery mother and runner plants. P. cactorum inoculum sources included nursery (20%) and preplant fruit production (17%) fumigated soils, and nursery runner plants (up to 15%). In fruit production plants, the average incidence of M. phaseolina and P. cactorum were 4.2 and 3.7%, respectively. Fusarium spp. inoculum sources could not be accessed extensively due to the lack of effective quantitative real-time PCR assays. Limited testing of nursery plants showed that Fusarium oxysporum f. sp. fragariae (Fof) was absent. In field production plants and soil, F. solani was the main pathogenic Fusarium spp., with Fof only identified once in a fruit production plant. Ineffectively fumigated soils in nurseries and production fields, along with infected runner plants, can be inoculum sources of soilborne strawberry pathogens in Spain.
Clozapine Treatment of Olanzapine-induced Tardive Dyskinesia: A Case Report
Authors: SANGROULA DINESH , VIRK INDERPREET , MOHAMMAD WALI , KAHN DAVID A.
Published: January 2017

Tardive dyskinesias (TD) are serious, often irreversible side effects of dopamine blocking agents, most commonly first-generation antipsychotics. No definitive treatment exists, with different interventions showing inconsistent results. We report a case of TD presenting after 12 years of olanzapine therapy in a 66-year-old Hispanic male with paranoid schizophrenia. The TD symptoms were successfully treated within a few weeks by switching to clozapine. Two cases of olanzapine-induced TD treated with clozapine have previously been reported, but in those cases, the symptom onset was quicker, ranging from a few months to a few years after initiation of olanzapine therapy, and the treatment response was relatively slower. Clinicians should carefully monitor for symptoms of TD after prolonged treatment with olanzapine and other antipsychotics. If otherwise indicated for psychiatric treatment, clozapine can be considered a good choice for patients with TD in preventing or reversing the debilitating consequences of this condition.
Acute Neuropsychiatric Symptoms Associated With Antibiotic Treatment of Helicobacter Pylori Infections: A Review
Authors: NEUFELD NICHOLAS H. , MOHAMED NOURHAN S. , GRUJICH NIKOLA , SHULMAN KENNETH
Published: January 2017

Helicobacter pylori infects half the global population. Because serious complications can result from this infection, a so-called “triple therapy” is recommended: treatment with a proton-pump inhibitor and clarithromycin, along with amoxicillin or metronidazole. Although these antibiotics have been associated with neuropsychiatric symptoms, it is difficult to disentangle the effects of antibiotics from the effects of acute infections that may precipitate acute neuropsychiatric symptoms. Study of patients with chronic H. pylori infections who undergo antibiotic treatment may provide a clearer view of the associations between acute neuropsychiatric symptoms and antibiotics. The literature concerning this association in patients with H. pylori has not been reviewed. We therefore undertook a review of MEDLINE and postmarket surveillance data concerning this issue and identified 25 cases. Postmarket data indicated that gastrointestinal symptoms were the most commonly reported adverse reactions, followed by neurological adverse reactions; neuropsychiatric symptoms were less commonly reported, with variable and nonspecific terminology used to describe them. More specific, yet still variable terminology was found in the literature. Anxiety, delirium, dissociation, mania, and psychosis were reported, with approximately half of these neuropsychiatric symptoms occurring without symptoms of delirium. The use of standardized neuropsychiatric symptom rating scales and the Confusion Assessment Method for monitoring adverse reactions may improve our knowledge of neuropsychiatric symptoms and their association with antibiotics and thus mitigate underreporting. Physicians should remain alert to the possibility that neuropsychiatric symptoms may occur during antibiotic treatment of H. pylori and recognize that rapid resolution typically occurs with discontinuation of the antibiotics.
Whole genome sequencing and assembly of aCaenorhabditis elegansgenome with complex genomic rearrangements using the MinION sequencing device
Authors: Tyson JR , O’Neil NJ , Jain M , Olsen HE , Hieter P , Snutch TP
Published: January 2017

Advances in 3rdgeneration sequencing have opened new possibilities for ‘benchtop’ whole genome sequencing. The MinION is a portable device that uses nanopore technology and can sequence long DNA molecules. MinION long reads are well suited for sequencing andde novoassembly of complex genomes with large repetitive elements. Long reads also facilitate the identification of complex genomic rearrangements such as those observed in tumor genomes. To assess the feasibility of thede novoassembly of large complex genomes using both MinION and Illumina platforms, we sequenced the genome of aCaenorhabditis elegansstrain that contains a complex acetaldehyde-induced rearrangement and a biolistic bombardment-mediated insertion of a GFP containing plasmid. Using ∼5.8 gigabases of MinION sequence data, we were able to assemble aC. elegansgenome containing 145 contigs (N50 contig length = 1.22 Mb) that covered >99% of the 100,286,401 bp reference genome. In contrast, using ∼8.04 gigabases of Illumina sequence data, we were able to assemble aC. elegansgenome in 38,645 contigs (N50 contig length = ∼26 kb) containing 117 Mb. From the MinION genome assembly we identified the complex structures of both the acetaldehyde-induced mutation and the biolistic-mediated insertion. To date, this is the largest genome to be assembled exclusively from MinION data and is the first demonstration that the long reads of MinION sequencing can be used for whole genome assembly of large (100 Mb) genomes and the elucidation of complex genomic rearrangements.
Effect of polyaniline/montmorillonite content on the corrosion protection of epoxy coating
Authors: Zhang Yingjun , Shao Yawei , Shi Qiumei , Wang Yanqiu , Meng Guozhe , Li Ping
Published: January 2017

Purpose

The purpose of this paper was to research the influence of polyaniline/montmorillonite (PANI/OMMT) composite powder content on the corrosion protection of epoxy (EP) coating.

Design/methodology/approach

The polyaniline/montmorillonite/epoxy (PANI/OMMT/EP) coatings containing different contents of PANI/OMMT composite powder were prepared on steel. The corrosion protection performances of PANI/OMMT/EP coatings in 3.5 per cent NaCl solutions were investigated by electrochemical impedance spectroscopy. The barrier property of coatings was examined using water absorption analysis. The structure and crosslink density of coatings were examined using scanning electron microscopy and differential scanning calorimetry, respectively.

Findings

The PANI/OMMT composite powder could enhance the barrier properties of the EP coating and reduce the corrosion rate of the steel beneath the coating. The coating showed the best corrosion protection performance when 3 per cent PANI/OMMT powder was added to the coating.

Originality/value

The research clarified the influence of PANI/OMMT content on the corrosion protection of coating from two aspects: one is the barrier performance of the coating; the other is the corrosion inhibitors for metal substrate.
Effects of laser remelting on surface-interface morphologies, bonding modes and corrosion performances of arc-sprayed Al coating
Authors: Wenming Liu , Tianyuan Sheng , Dejun Kong
Published: January 2017

Purpose

The purpose of this paper is to provide an experimental basis for studying the effects of laser remelting on the surface modification of arc-sprayed Al coating.

Design/methodology/approach

A layer of arc-sprayed Al coating on S355 steel was remelted with a CO2 laser, and the surface-interface morphologies, compositions of chemical elements and phases of Al coating were analyzed with scanning electron microscopy, energy disperse spectroscopy and X-ray diffraction, respectively. The effects of laser remelting on compositions of chemical elements and bonding performance of Al coatings were discussed.

Findings

The result shows that there are some pores existing on the Al coating surface after arc spraying, and the combination mode of coating interface is primarily composed of mechanical bonding. The pores on the Al coating reduce after laser remelting, which improves the compact performance, and the mechanical binding mode by arc spraying is changed into metallurgical bonding. The Fe and Al atoms at the coating interface are distributed with gradient, and the stratified enrichment is evident, which improves binding performance of the Al coating. The Al coating exhibits general corrosion before laser remelting and local corrosion after laser remelting, which improves the corrosion resistance of Al coating.

Originality/value

The arc-sprayed Al coating is remelted by CO2 laser, improving its microstructures and bonding mode with the substrate.
In pursuit of innovation value in building projects
Authors: Maghsoudi Soroush , Duffield Colin , Wilson David
Published: January 2017

Purpose

Although the construction industry is known for its low level of innovation and slow pace of change, some of its characteristics not only make this sector unique but also provide some opportunities to innovate. Innovation evaluation has become one of the priorities for building practitioners. This study aims to develop a practical methodology to evaluate the outcomes of innovation in small building and construction projects.

Design/methodology/approach

The research used three real case projects and information along with what was found in the literature. A framework was developed based on an extensive literature review of innovation outcomes evaluation.

Findings

The outcomes of the building projects were categorized into six categories of economic, quality, social, environmental, satisfaction and soft and organizational impacts. It was found that the outcomes of innovative practices in construction projects could be evaluated if subjective assessment is tolerated. The findings of this research are limited to the domestic and medium-density building projects, thus the outcomes might be generalized with appropriate care. The proposed practical framework would assist practitioners in the field of building and construction to realize the impacts of innovation introduced in their projects. The project owners and developers could be the main users of this framework.

Originality/value

Previously developed models or frameworks have mainly remained at the abstract level that could be used as guidelines, but the proposed framework in this study is practical and applicable to real building projects.
Investor reaction to R&D investment
Authors: Li Xin , Wang Tienan
Published: January 2017

Purpose

This paper aims to examine the impact of research and development (R&D) investment on firms’ stock price from the perspective of investors.

Design/methodology/approach

Building on signaling theory, the authors propose that R&D investment sends important signals to the investment community regarding future growth, which in turn impacts investor reaction to such investment.

Findings

Using a sample of listed pharmaceutical firms in China from 2007 to 2011, the authors find that R&D investment has a positive effect on firms’ stock price, indicating that investors have a positive reaction to R&D investment signals. Further, the authors find that the signaling role of new product announcements mediates this relationship between R&D investment and investor reaction.

Originality/value

The authors also find that the signaling role of development capacity (DC) has a moderating effect on the relationship between innovation activities (i.e. R&D investment and new product announcements) and investor reaction, such that DC strengthens the positive effect of R&D and new product announcements on investors.
Increasing innovation through engagement
Authors: Walton Abram L.J. , Glassman Brian , Sandall Darrel L.
Published: January 2017

Purpose

This paper aims to investigate the phenomenology behind how an idea stock market created employee engagement of 80 per cent+ within the largest telecom company in Portugal. More importantly, this case study investigates the results created using this system, and whether the “investment/betting” process yielded successful and replicable results.

Design/methodology/approach

This critical review took the form of an exploratory-grounded theory study. Initial conversations led to creation of questionnaires regarding the internal workings of Sonaecom’s idea market, implementation methods, incentive structures, necessary cultural adjustments, system outcomes and topics related to idea screening, types of users, herd behavior, idea storage, diffusion, implementation and perceptions of the idea market and its success.

Findings

The idea market produced engagement outcomes nearly twice that of standard industry engagement methodologies and showed promise for increasing corporate innovation outcomes.

Research limitations/implications

This study was limited to a single idea market within one company. As such, the conclusions from the study are limited in their generalizability to other companies implementing idea markets.

Practical implications

Because the challenges faced by Sonaecom are the same challenges faced by any company implementing an idea market, the findings from the study have important practical implications for any organization implementing an idea market.

Social implications

There are behavioral, psychological and leadership implications for organizations implementing an idea market.

Originality/value

Based on a thorough literature review, no other study has been made of Sonaecom’s Idea Market system, nor has a study of this depth and breadth been completed with any idea market system. The findings of the study have broad implications for any organization seeking to implement an idea management system.
Determinants of bank profitability in Tunisia: does corruption matter?
Authors: Bougatef Khemaies
Published: January 2017

Purpose

In this paper, the author aims to examine the effect of perceived level of corruption on bank profitability.

Design/methodology/approach

The analysis is based on a balanced panel of ten commercial banks in Tunisia over the period 2003-2014. The author uses the generalized method of moments estimator technique described by Arellano and Bover (1995).

Findings

The author finds a positive relationship between the bank profitability and the corruption level. This surprising result suggests that Tunisian commercial banks take advantage from the high level of corruption. Regarding the others determinants, the findings reveal that bank profitability is positively related to capitalization level and liquidity. By contrast, a low asset quality is associated with low profitability.

Originality/value

The novelty of this study consists in the inclusion of the corruption level as a determinant of bank profitability.
Results and analysis of a large-scale fire test on a multi-bay composite steel-frame floor system
Authors: Proe David J.
Published: January 2017

Purpose

This paper aims to facilitate verification of computer modelling techniques for complex structures exposed to fire and to test the effect of some steel beams being left unprotected.

Design/methodology/approach

This paper describes a fire test conducted on a large-scale structure representing four corner bays of a typical multi-storey steel-frame office building.

Findings

A new and unexpected mode of damage occurred.

Originality/value

The test results indicate that an alternate reinforcement detail should be used in combination with unprotected beams.
Experimental study of post-fire performance of high-strength bolts under combined tension and shear
Authors: Kawohl Anne , Lange Jörg
Published: January 2017

Purpose

This study aims to verify whether the reduction factors for the post-fire performance of Grade 10.9 bolts stated in an earlier study at the TU Darmstadt are also valid for shear and combined tension and shear.

Design/methodology/approach

Tests on Grade 10.9 bolt sets under combined tension and shear were carried out. The tested bolts were heated and cooled without being stressed by an additional mechanical load before being tested.

Findings

The test results show that the reduction factors can also be adopted for bolts under combined tension and shear, but the tension-shear-ratio has an influence on the load bearing capacity.

Originality/value

The post-fire performance of high-strength bolts is of special interest when a building structure is evaluated after an event of fire. In contrast to conventional structural steel, high-strength bolts do not recover their original strength and material properties.
Composite beams under fire loading: numerical modeling of behavior
Authors: Selden Kristi L. , Varma Amit H.
Published: January 2017

Purpose

The purpose of this study was to develop a three-dimensional (3D) finite element modeling (FEM) technique using the commercially available program ABAQUS to predict the thermal and structural behavior of composite beams under fire loading.

Design/methodology/approach

The model was benchmarked using experimental test data, and it accounts for temperature-dependent material properties, force-slip-temperature relationship for the shear studs and concrete cracking.

Findings

It was determined that composite beams can be modeled with this sequentially coupled thermal-structural 3D FEM to predict the displacement versus bottom flange temperature response and associated composite beam failure modes, including compression failure in the concrete slab, runaway deflection because of yielding of the steel beam or fracture of the shear studs.

Originality/value

The Eurocode stress-strain-temperature (σ-ε-T) material model for structural steel and concrete conservatively predict the composite beam deflections at temperatures above 500°C. Models that use the National Institute of Standards and Technology (NIST) stress-strain-temperature (σ-ε-T) material model more closely match the measured deflection response, as compared to the results using the Eurocode model. However, in some cases, the NIST model underestimates the composite beam deflections at temperatures above 500°C.
Thermal properties of jute fiber concrete at high temperature
Authors: Ozawa Mitsuo , Kim Gyu-Yong , Choe Gyeong-Choel , Yoon Min-Ho , Sato Ryoichi , Rokugo Keitetsu
Published: January 2017

Purpose

The behavior of high-performance concrete (HPC) at high temperatures is very complex and also affects the global behavior of heated HPC-based structures. Researchers have also reported how various types of fibers affected the mechanical properties of cement-based materials at high temperatures. This study aims to discuss the effects of high temperatures on the compressive strength and elastic modulus of HPC with polypropylene (PP) and jute fiber.

Design/methodology/approach

Adding synthetic fiber (especially the PP type) to HPC is a widely used and effective method of preventing explosive spalling. Although researchers have experimentally determined the permeability of heated PP-fiber-reinforced HPC, few studies have investigated how adding natural fiber such as jute to this type of concrete might prevent spalling. In this study, the effects of high temperatures on the compressive strength and elastic modulus of HPC with PP and jute fiber (jute fiber addition ratio: 0.075 vol.%; length: 12 mm; PP fiber addition ratio: 0.075 vol.%; length: 12 mm) were experimentally investigated.

Findings

The work was intended to clarify the influence of elevated temperatures ranging from 20°C to 500°C on the material mechanical properties of HPC at 80 MPa. HSC with jute fiber showed a compressive strength loss of about 40 per cent at 100°C before recovering to full strength between 200°C and 300°C.

Originality/value

The elastic modulus of high-strength concrete decreased by 10-40 per cent between 100°C and 300°C. At 500°C, the elastic modulus was only 30 per cent of the room temperature value. The thermal expansion strain of all specimens was 0.006 at 500°C.
Fire performance of single plate shear connections in a composite floor
Authors: Selamet Serdar , Bolukbas Caner
Published: January 2017

Purpose

This paper aims to present a numerical investigation on the fire performance of a single plate shear connection in a steel-framed composite floor. Large-scale fire experiments show that the tensile membrane action of the concrete slab enhances the fire performance of composite floors. The enhancement in the performance is contributed to large slab deflections. However, these deflections cause significant rotations and tensile force in the single plate connection.

Design/methodology/approach

A finite element model is constructed, which consists of a secondary steel beam, concrete slab and shear connection components. The interaction between the connection components such as bolts and single plate is defined by contact surfaces. The analysis is conducted in two uncoupled phases: thermal analysis by creating fire boundaries on the composite floor model with convective and radiative heat transfer, and mechanical analysis by considering thermal expansion and changes in the material stiffness and strength due to temperature.

Findings

The thermo-mechanical analysis of the composite floor finite element model shows that the structure survives the 2-h Standard fire, but the connection fails by bolt shear and buckling of the connection plate.

Originality/value

This paper investigates the fire performance of a shear connection in a steel-framed concrete slab. Previous work generally focused on the concrete slab behavior only. The originality of the research is that the connection is considered as part of a sub-assembly and is subjected to forces due to concrete and steel beam interaction.
Fire performance, including the cooling phase, of structural glued laminated timber beams
Authors: Kinjo H. , Hirashima T. , Yusa S. , Horio T. , Matsumoto T.
Published: January 2017

Purpose

Based on heating tests and load-bearing fire tests, this paper aims to discuss the charring rate, the temperature distribution in the section and the load-bearing capacity of structural glued laminated timber beams not only during the heating phase during a 1-h standard fire in accordance with ISO 834-1 but also during the cooling phase.

Design/methodology/approach

Heating tests were carried out to confirm the charring rate and the temperature distribution in the cross-section of the beams. Loading tests under fire conditions were carried out to obtain the load-deformation behavior (i.e. the stiffness, maximum load and ductility) of the beam.

Findings

The temperature at the centroid reached approximately 30°C after 1 h and then increased gradually until reaching 110-200°C after 4 h, during the cooling phase. The maximum load of the specimen exposed to a 1-h standard fire was reduced to approximately 30 per cent of that of the specimen at ambient temperature. The maximum load of the specimen exposed to a 1-h standard fire and 3 h of natural cooling in the furnace was reduced to approximately 14 per cent. In case of taking into consideration of the strength reduction at elevated temperature, the reduction ratio of the calculated bending resistance agreed with that of the test results during not only heating phase but also cooling phase.

Originality/value

The results of this study state that it is possible to study on strength reduction in cooling phase for end of heating, timber structural which has not been clarified. It is believed that it is possible to appropriately evaluate the fire performance, including the cooling phase of the timber structural.
New algorithm for behaviour-based mobile robot navigation in cluttered environment using neural network architecture
Authors: Pandey Anish , Parhi Dayal R.
Published: January 2017

Purpose

This study concerns an on-line path planning technique for a behaviour-based wheeled mobile robot local navigation in an unknown environment with hurdles, using the feedforward back-propagation neural network sensor-actuator control technique. The purpose of this study is to find the non-collision path for the mobile robot moving towards the goal in a cluttered environment.

Design/methodology/approach

Neural network architecture input layers are the different hurdle distance information, which are acquired by an array of equipped sensors, and the output layer is the turning angle (motor control). In this way, the mobile robot is effectively being trained to move autonomously in the environment.

Findings

Computer simulation and real-time experimental results show that the proposed neural network controller can improve navigation performance in cluttered and unknown environments.

Originality/value

The proposed neural network controller gives better results (in terms of path length) as compared to previously developed models, which verifies the effectiveness of the proposed architecture.
Effects of organophosphorus and mineral based flame retardants on combustibility and mechanical performances of natural fiber reinforced composites
Authors: Khalili Pooria , Tshai Kim Yeow , Kong Ing
Published: January 2017

Purpose

The study aimed to investigate epoxy composites reinforced with mechanical performances, thermal decomposition and ignitibility of natural fiber (NF) and doped with 5 wt.% of varying flame-retardant (FR) compounds. The incorporation of ammonium polyphosphate (APP) and zinc borate (ZB) showed improvement in modulus and elongation to break compared to the empty fruit bunch-filled epoxy (control). However, slightly lower tensile and impact strengths were recorded in all FR-containing composites.

Design/methodology/approach

Among the FR-loaded specimens, enhancement in flexural property was observed in composites with APP, whereas the addition of ZB and alumina trihydrate (ATH) resulted in the reduction of flexural strength. Thermogravimetric analysis results indicated that the introduction of APP and ATH negatively impacted the thermal degradation temperature (Td) of the NF-filled composites. Greater mass residue with FR-filled composites, where increment was in the range from 32-80 per cent compared to the control, was observed, with the greatest being the ZB-containing formulation. Vertical Bunsen burner experiment revealed that the addition of ZB and APP led to a zero dripping flame system, whereas such a phenomenon was absent in both the control and NF composites loaded with ATH. The bomb calorimeter results revealed that addition of NF into neat epoxy significantly enhanced the FR behavior of the composite, and the gross heat of combustion was greatly reduced when FRs were incorporated into the control sample.

Findings

Results from the current study concluded that non-halogenated FRs including APP, ZB and ATH were able to enhance the fire retardancy of EFB epoxy composite without significantly deteriorate the mechanical behaviors.

Originality/value

It can be shown from scanning electron microscopy micrographs that the fabrication technique produced composites with good interfacial adhesion between NF and epoxy matrix, and homogenous distribution of FRs were achieved.
Nanotechnology: new hope of efficiency enhancement for solar evacuated tube collector
Authors: Ramani Rupeshkumar V. , Ramani Bharat M. , Saparia Anjana D. , Shah Nikesh A. , Kacha Pinank , Markna J.H.
Published: January 2017

Purpose

In the twenty-first century, the use of fossil fuels has increased drastically because the necessity of energy is increasing day by day which affects the world’s economy. The solar energy (photo-thermal energy conversion) system is the most economical and eco-friendly alternative source. To increase the use of domestic as well as commercialization purpose, the authors have reviewed this paper on the solar water heater along with its structural mechanism for energy enhancement and to create easier stair steps for climbing on the green world dream.

Design/methodology/approach

In this study, nanotechnology has remarkably built its own use for extending thermal efficiency by using some gradual experiments. It is a phenomenon, like nanofluid (as a working fluid for a direct solar collector), nanocoating (on the surface of a solar-evacuated tube by using the chemical vapor deposition/physical vacuum deposition/sol–gel technique) and nanorod-based solar collector tube.

Findings

This invention gives greater efficiency rather than the conventional systems, but also this advancement is not too much supported in a low- temperature environment also, we can consider the poor light absorption characteristics of the pure water (Bencic, et al., 2000).

Originality/value

The basic idea and understanding of this phenomenon to improve solar collecting performance for obtaining a high working-fluid temperature are discussed in this paper.
Experimental investigations of a solar dryer with and without multiple phase change materials (PCM’s)
Authors: Sreerag T.S. , Jithish K.S.
Published: January 2017

Purpose

This paper aims to present a comparative study of a solar dryer with and without multiple phase change materials (PCMs). It also involves designing and fabricating the experimental model of an indirect solar dryer which uses PCMs for thermal energy storage.

Design/methodology/approach

A corrugated aluminium sheet is used as an absorber plate. Aluminium pipes of 0.75 inch are welded under the corrugated sheet to store the PCM. Here, multiple PCMs are used – one with a high melting point and the other with a low melting point for the purpose of improving efficiency. A single air pass model in which air moves over the absorber plate is used for the study. Air is heated in an air heater section which also contains thermal energy storage. The energy obtained in the air heater section is first used to heat and melt the PCM.

Findings

Thus, heat energy is stored into the PCM and then the heated air moves into the drying chamber in which drying take place. When the sun’s insolation reduces, discharging from the PCM takes place. Thus, it reduces the fluctuation in the energy and provides continuous energy to the system. Glass wool is used as an insulation material. Different parameters for this air heater-dryer have been calculated.

Originality/value

The current study enhances the understanding of solar drying process and the developed model with and without multiple phase change materials can be used for optimising the drying process.
Experimental investigation of sensible thermal energy storage in small sized, different shaped concrete material packed bed
Authors: Warkhade Ganesh S. , Babu A. Veeresh , Mane Santosh , Ganesh Babu Katam
Published: January 2017

Purpose

Solar energy varies with time, intermittent; an accumulator unit is required to attach with collectors to collect energy for use when the sunshine is not available. This paper aims to design a system for storing the solar sensible heat thermal energy.

Design/methodology/approach

This paper presents the design and experimental evaluation of sensible heat thermal energy storage (TES) system for its energy storage performance by varying the air flow rate and packing material shape. Heat transfer fluid as air and solid concrete material of high density of different shapes were used for storage.

Findings

This paper presents the evaluation of data of number of experimental observations on the system. It was found that charging/discharging was based on the shape of the material and void fraction.

Originality/value

This paper provides the data for designing the TES, considering the concrete as storage material and shape of material for optimizing the system.
Effect of geometrical and temperature-dependence parameters on forced convection of a nanofluid in a micro-channel heat sink
Authors: Nebbati Rabah , Kadja Mahfoud
Published: January 2017

Purpose

The purpose of this study is the numerical prediction of the thermal and hydraulic characteristics (Nusselt number and shear stress) of a forced convection laminar flow through a rectangular micro-channel heat sink, using constant and temperature-dependent thermo-physical properties. The effects of the solids volume fraction and the size of the micro-channel on heat transfer enhancement have also been investigated.

Design/methodology/approach

The authors use the flow of a water-Al2O3 nanofluid and a single-phase approach. The equations are solved using the commercial code Fluent Version 6.3. This code uses the finite volume approach to solve the equations subject to the boundary conditions, which govern three-dimensional conjugate convection-conduction heat transfer model. The physical domain was meshed using the code GAMBIT. The mesh used is non-uniform and was obtained by sweeping in the Z direction an X-Y surface meshed with QUAD/pave type cells.

Findings

The results clearly show that the inclusion of nanoparticles produces a considerable increase in the heat transfer. Also, the temperature-dependent models present higher values of local and average Nusselt number than in the case of constant thermo-physical properties, and an increase in the channel dimensions leads to an important increase in heat transfer. Consequently, we ensure a better cooling of the base of the micro-channel heat sink.

Research limitations/implications

Because of the settling of nanoparticles, the research results may not be generalized to high values of solids volume fraction. Therefore, researchers are encouraged to find other techniques of cooling when the heat loads exceed values that cannot be dissipated using nanonofluids.

Practical implications

The paper includes implications for the miniaturization of electronic devices such as in microprocessors or those used in robotics and automotive industries, where continually increasing power densities are requiring more innovative techniques of heat dissipation from a small area and small coolant requirements.

Originality/value

This paper shows the implementation of variable property nanofluid models in CFD commercial codes.