bluuebunny/crossref_metadata_2025 huggingface dataset:
The uncertain role of diversity dependence in species diversification and the need to incorporate time-varying carrying capacities
Authors: Marshall Charles R. , Quental Tiago B.
Published: March 2016

There is no agreement among palaeobiologists or biologists as to whether, or to what extent, there are limits on diversification and species numbers. Here, we posit that part of the disagreement stems from: (i) the lack of explicit criteria for defining the relevant species pools, which may be defined phylogenetically, ecologically or geographically; (ii) assumptions that must be made when extrapolating from population-level logistic growth to macro-evolutionary diversification; and (iii) too much emphasis being placed on fixed carrying capacities, rather than taking into account the opportunities for increased species richness on evolutionary timescales, for example, owing to increased biologically available energy, increased habitat complexity and the ability of many clades to better extract resources from the environment, or to broaden their resource base. Thus, we argue that a more effective way of assessing the evidence for and against the ideas of bound versus unbound diversification is through appropriate definition of the relevant species pools, and through explicit modelling of diversity-dependent diversification with time-varying carrying capacities. Here, we show that time-varying carrying capacities, either increases or decreases, can be accommodated through changing intrinsic diversification rates (diversity-independent effects), or changing the effects of crowding (diversity-dependent effects).
Ecogeochemistry potential in deep time biodiversity illustrated using a modern deep-water case study
Authors: Trueman Clive N. , Chung Ming-Tsung , Shores Diana
Published: March 2016

The fossil record provides the only direct evidence of temporal trends in biodiversity over evolutionary timescales. Studies of biodiversity using the fossil record are, however, largely limited to discussions of taxonomic and/or morphological diversity. Behavioural and physiological traits that are likely to be under strong selection are largely obscured from the body fossil record. Similar problems exist in modern ecosystems where animals are difficult to access. In this review, we illustrate some of the common conceptual and methodological ground shared between those studying behavioural ecology in deep time and in inaccessible modern ecosystems. We discuss emerging ecogeochemical methods used to explore population connectivity and genetic drift, life-history traits and field metabolic rate and discuss some of the additional problems associated with applying these methods in deep time.
Stepwise and dynamic assembly of the earliest precursors of small ribosomal subunits in yeast
Authors: Zhang Liman , Wu Chen , Cai Gaihong , Chen She , Ye Keqiong
Published: March 2016

The eukaryotic ribosomal RNA (rRNA) is associated cotranscriptionally with numerous factors into an enormous 90S preribosomal particle that conducts early processing of small ribosomal subunits. The assembly pathway and structure of the 90S particle is poorly understood. Here, we affinity-purified and analyzed the constituents of yeast 90S particles that were assembled on a series of plasmid-encoded 3′-truncated pre-18S RNAs. We determined the assembly point of 65 proteins and the U3, U14, and snR30 small nucleolar RNAs (snoRNAs), revealing a stepwise and dynamic assembly map. The 5′ external transcribed spacer (ETS) alone can nucleate a large complex. When the 18S rRNA is nearly complete, the 90S structure undergoes a dramatic reorganization, releasing U14, snR30, and 14 protein factors that bind earlier. We also identified a reference state of 90S that is fully assembled yet has not undergone 5′ETS processing. The assembly map present here provides a new framework to understand small subunit biogenesis.
7-Iodo-1H-indole-2,3-dione
Authors: Golen James A. , Manke David R.
Published: March 2016

The title compound, C8H4INO2, has a single planar molecule in the asymmetric unit, with the non-H atoms possessing a mean deviation from planarity of 0.058 Å. The molecules dimerize in the solid state through N—H...O hydrogen bonds. There are intermolecular I...O close contacts of 3.193 (4) Å that link the molecules into infinite chains along [20-1]. No π–π interactions were observed in the structure.
Understanding gender, creativity, and entrepreneurial intentions
Authors: Smith Ronda Marie , Sardeshmukh Shruti R , Combs Gwendolyn M
Published: March 2016

Purpose

– The purpose of this paper is to explore the complex relationships between gender and entrepreneurial intentions.

Design/methodology/approach

– This paper uses a two study design where the second study is a constructive replication of the first study. The first study uses a cross-sectional design, while the second uses a design where data collection of variables were temporally separated. The analysis is conducted using Hayes (2014) process macro using 1,000 bootstrapped draws to understand the interaction between gender and creativity and the potential mediation involving life roles and goals.

Findings

– The empirical results are threefold. First, the results show that creativity has a direct and positive effect on entrepreneurial intentions. Second, gender did not have a direct effect on entrepreneurial intentions, and finally, gender showed an interaction with creativity such that in both the samples, creativity had a stronger relationship with intentions among women.

Practical implications

– The results point to the inclusion of creativity exercises in the entrepreneurship curriculum as well as to create and tailor programs to enhance women’s entrepreneurial intentions.

Originality/value

– Using a two study constructive replication approach, this study demonstrates the complex effect of gender on entrepreneurial intentions. Traditionally, women are argued to have lower entrepreneurial intentions, but this study finds that creative women were more likely to have entrepreneurial intentions in the sample. The results also show that the women’s family salience (life roles and goals) did not mediate the relationship between gender and entrepreneurial intentions.
Feminine men and masculine women: in/exclusion in the academy
Authors: Atkins Liz , Vicars Mark
Published: March 2016

Purpose

– The purpose of this paper is to draw on concepts of “female masculinity” to interrogate how hegemonic gendering discourses, forms and performances are inscribed in neoliberal narratives of competency in higher education in the Western Hemisphere.

Design/methodology/approach

– Drawing on individual examples, the authors consider how these narratives are omnipresent in the sector, and systematically act to exclude those who do not conform. In doing so, the authors draw extensively on bodies of literature exploring gender/identity, and neo-liberalism. In particular, the paper draws on the work of Halberstam (1998, 2011), and of Drake (2015).

Findings

– There are comparatively few women in senior positions in Higher Education and the authors argue that as gendering institutions they reproduce hegemonic gendering discourses. The authors find that hegemonic gendering discourses are instrumental in maintaining and privileging specific forms and perceptions of masculinity and femininity as inscribed within and reproduced by perceptions of professional competency.

Originality/value

– This paper examines neo-liberal practices from a more nuanced perspective than some traditional polarised critiques which regard gender as a binary. In doing so, it contributes to debates on masculinity, but more importantly, opens discussions about the implications of gendering discourses for the role of the few women in senior positions in higher education institutions globally.
Developing a reverse logistics competency
Authors: Morgan Tyler R. , Richey Jr Robert Glenn , Autry Chad W.
Published: March 2016

Purpose

– The purpose of this paper is to explore the influence of collaboration and information technology (IT) on the reverse logistics competency of firms. Through collaboration firms can improve their ability to handle returns, but this research introduces IT as providing a moderating influence over the impact of collaboration in the advancement of a reverse logistics competency.

Design/methodology/approach

– A survey was administered to employees involved with supply chain relationships. Empirical evidence from 267 respondents is analyzed with structural equation modeling.

Findings

– Support is found for the positive moderating influence of an IT competency on the relationship between collaboration and a reverse logistics competency. Additional benefits for logistics performance are also realized.

Research limitations/implications

– This research provides theoretical implications for the development of a reverse logistics competency through an application of resource-based theory/resource-based view of the firm. The study is limited to the selected research questions and sample of predominantly US firms.

Practical implications

– This research assists managers as they attempt to develop a reverse logistics competency to address the growing problem of returns through collaboration with supply chain members and the development of an IT competency.

Originality/value

– The framework developed in this research provides insights regarding the handling of product returns. Specifically, the moderating influence of an IT competency is addressed as it enhances the impact of collaboration on the development of a reverse logistics competency.
The effect of information technology on the agility of the supply chain in the Iranian power plant industry
Authors: Bargshady Ghazal , Zahraee Seyed Mojib , Ahmadi Mohammad , Parto Ali
Published: March 2016

Purpose

– An agile supply chain (ASC) includes companies that are operationally linked to each other, such as supply, design, manufacturing and distribution centers that respond and react quickly and effectively to change markets. Information systems and technology have a main role in achieving this objective. Therefore, the purpose of this paper is to examine the relationship between information integration, information infrastructure flexibility and the ASC in the Iranian power plant industry (IPPI).

Design/methodology/approach

– The quantitative method was employed in this study. Survey questionnaires were sent to 87 managers in the IPPI to examine the relationship between information integration, information infrastructure flexibility, and the ASC.

Findings

– The final results indicated that information sharing and responsibility were strongly related with the ASC; accessibility and connectivity had important relations with the ASC; while the relationships between compatibility and adaptableness as IT flexibility variables and ASC were positive but not significant.

Research limitations/implications

– This study focussed on the impact of IT on the IPPI specifically companies that manufacture boilers, electronic control tools, turbines, turbine blades, generators and other power plant-related components.

Practical implications

– A new research model was developed to assess the impact of the interrelationships among IT capabilities and the ASC and results should assist managers as well as academicians.

Originality/value

– An investigation was carried out through this study based on the current situation in IPPI to empirically examine and evaluate the effect of IT integration and flexibility on ASC. Besides, a very limited number of studies have been done on the implementation of information technology in the IPPI.
Can tourism confidence index improve tourism demand forecasts?
Authors: Croce Valeria
Published: March 2016

Purpose

The link between confidence and economic decisions has been widely covered in the economic literature, yet it is still an unexplored field in tourism. The purpose of this paper is to address this gap, and investigate benefits in forecast accuracy that can be achieved by combining the UNWTO Tourism Confidence Index (TCI) with statistical forecasts.

Design/methodology/approach

Research is conducted in a real-life setting, using UNWTO unique data sets of tourism indicators. UNWTO TCI is pooled with statistical forecasts using three distinct approaches. Forecasts efficiency is assessed in terms of accuracy gains and capability to predict turning points in alternative scenarios, including one of the hardest crises the tourism sector ever experienced.

Findings

Results suggest that the TCI provides meaningful indications about the sign of future growth in international tourist arrivals, and point to an improvement of forecast accuracy, when the index is used in combination with statistical forecasts. Still, accuracy gains vary greatly across regions and can hardly be generalised. Findings provide meaningful directions to tourism practitioners on the use opportunity cost to produce short-term forecasts using both approaches.

Practical implications

Empirical evidence suggests that a confidence index should not be collected as input to improve their forecasts. It remains a valuable instrument to supplement official statistics, over which it has the advantage of being more frequently compiled and more rapidly accessible. It is also of particular importance to predict changes in the business climate and capture turning points in a timely fashion, which makes it an extremely valuable input for operational and strategic decisions.

Originality/value

The use of sentiment indexes as input to forecasting is an unexplored field in the tourism literature.
Value chain supply procurement strategies in international construction
Authors: Martek Igor , Chen Chuan
Published: March 2016

Purpose

– Firms compete using a variety of strategies. Typically they aim to provide something different, to be better, or simply cheaper. In the construction industry, the performance characteristics, quality and cost of the final delivered project will be the outcome of the interplay of capabilities of all the firms involved in the project. Consequently, in order to improve competitiveness, firms must pay attention to not only their own competitive advantage but to those of the firms, both up-stream and down-stream, on whom they depend in delivering their projects. For foreign constructors in China, those competitive considerations will be informed by circumstances different from home. How then do foreign constructors adapt themselves to the problem of sourcing competitively when located within a China-based supply chain? The paper aims to discuss these issues.

Design/methodology/approach

– In this study 60 foreign enterprises operating within the Chinese construction sector were investigated by using a comparative case study approach.

Findings

– Four generic procurement strategies were identified. First, firms adapt themselves in the search for optimal supply sources by replicating home-based suppliers, controlling local suppliers, or by remaining agile and non-aligned. Second, firms develop niche supply monopolies through market dominance, uniquely differentiated offerings, or by integration with down-stream providers. Third, firms find opportunities to bring in off-shore technology intensive procurements, where that technology is either protected, improved upon, or sold. Finally, firms also seek to transit to China as a procurement base in order to reduce local supply cost, service world-wide operations, or as part of a total strategy of China relocation.

Originality/value

– The identification of this rich range of procurement approaches will be of interest to internationalization strategists, as well as to industry practitioners looking to find appropriate business models for off-shore operations.
Developing sustainable management theory: goal-setting theory based in virtue
Authors: Neubert Mitchell J. , Dyck Bruno
Published: March 2016

Purpose

– This paper responds to ongoing calls to develop alternative management theory to guide management practice. In particular, the purpose of the paper is to demonstrate the merit of developing sustainable management theory and organizational practices that parallel conventional management theory and practices. Sustainable theory is based on a variation of virtue theory that seeks to achieve multiple forms of well-being for multiple stakeholders in the immediate as well as distant future. To illustrate the approach, the authors develop a sustainable variation of goal setting theory.

Design/methodology/approach

– The paper includes three parts. First, the authors establish the need for developing sustainable management theory (based on virtue theory) that parallels conventional management theory. Second, the authors identify and briefly review the main tenets of goal setting theory and then describe a Sustainable variation of this theory. Finally, the authors discuss the implications of the paper for management and organization theory and practice.

Findings

– The conceptual arguments for a sustainable version of goal setting theory based in virtue are supported by research and practitioner examples.

Originality/value

– Although there is growing concern regarding the shortcomings of management theory and practice based on a materialist-individualist moral-point-of-view, few alternatives have been discussed in detail. This paper presents an alternative based in virtue theory and illustrates how it relates to goal setting theory and practice.
Understanding the challenges and strategic actions of social entrepreneurship at base of the pyramid
Authors: Goyal Sandeep , Sergi Bruno S. , Jaiswal Mahadeo P.
Published: March 2016

Purpose

– The purpose of this paper is to examine the social entrepreneurship focussed organizations in the context of challenges faced and strategic actions adopted by them during the different stages of self-sustainable business model design and implementation.

Design/methodology/approach

– The empirical context involves the use of qualitative multi-case-based research methodology for data collection and analysis. The sampling involves undertaking the field study of social entrepreneurship oriented organizations, which have made the perceptible socio-economic difference in the lives of the rural and semi-urban population lying at the base of the pyramid (BoP) in India.

Findings

– The findings of this study are presented in two complementary stages. The first stage involves presenting the narrative incorporating the emergent themes and key characteristics of the social entrepreneurship focussed organizations based on the field-research based data collection and analysis. The second stage involves mapping the challenges with the strategic actions thereby formulating a challenge-action framework.

Research limitations/implications

– The paper strengthens the belief in social entrepreneurship as a viable alternative for creating a market-based ecosystem at the BoP. This paper highlights the conception of social entrepreneurship in terms of challenges and corresponding strategic actions.

Practical implications

– The derived challenge-action framework will enable the social entrepreneurs to learn, understand, design and implement a better informed and transparent market-based business models at the BoP resulting in reduced market risks and uncertainty.

Social implications

– The government needs to recognize the social entrepreneurs as partners having a separate legal entity as well as consider their inputs and on-field experiences while framing the policies in favor of the BoP. In addition, the government needs to facilitate the social entrepreneurs in leveraging the government network and institutions for reaching the BoP segment.

Originality/value

– This study is an original contribution to the field of social entrepreneurship in number of ways. The first contribution lies in reviewing the research literature from the definition perspective. The second contribution lies in reviewing the research literature to determine the key challenges faced by the social entrepreneurs at the BoP. The third contribution lies in identifying the propositions and conceptualizing the challenge-action framework depicting the challenges faced and strategic actions required by the social entrepreneurs for successful and sustainable social intervention at the BoP.
On the Dynamic Collapse of Cylindrical Shells Under Impulsive Pressure Loadings
Authors: da Silva Monteiro Luciana Loureiro , Netto Theodoro Antoun , da Camara Monteiro Paulo Cesar
Published: March 2016

The dynamic collapse of submerged cylindrical shells subjected to lateral impulsive pressure loads caused by underwater explosions is studied via coupled experimental and numerical work. Two sets of experiments were performed. Initially, 50.8 mm outside diameter aluminum tubes with diameter-to-thickness ratio of 32.3 were tested inside a pressure vessel. Hydrostatic pressure was applied quasi-statically up to the onset of collapse in order to obtain the collapse pressure of the tubes tested. Subsequently, similar tubes were tested in a 5 m × 5 m × 1.6 m deep water tank under various explosive charges placed at different distances. Explosive charges and standoff distances were combined so as to eventually cause collapse of the specimens. Dynamic pressures were recorded using a fit-for-purpose data acquisition system with sampling rates of up to 1 mega samples/s/channel. In parallel, finite element models were developed using commercially available software to simulate underwater explosion, pressure wave propagation, its interaction with a cylindrical shell, and the subsequent onset of dynamic collapse. The surrounding fluid was modeled as an acoustic medium, the shells as J2 flow theory based materials with isotropic hardening, and proper fluid–structure interaction elements accounting for relatively small displacements of the boundary between fluid and structure were used. Subsequently, the physical explosion experiments were numerically reproduced with good correlation between results. Finally, a parametric study was carried out to examine the effect on the pipe under different impulsive pressure loads.
Experimental Characterization of Inward Freezing and Melting of Additive-Enhanced Phase-Change Materials Within Millimeter-Scale Cylindrical Enclosures
Authors: Mahamudur Rahman Md , Hu Han , Shabgard Hamidreza , Boettcher Philipp , Sun Ying , McCarthy Matthew
Published: March 2016

The inward melting and solidification of phase-change materials (PCM) within millimeter-scale cylindrical enclosures have been experimentally characterized in this work. The effects of cylinder size, thermal loading, and concentration of high-conductivity additives were investigated under constant temperature boundary conditions. Using a custom-built apparatus with fast response, freezing and melting have been measured for time periods as short as 15 s and 33 s, respectively. The enhancement of PCM thermal conductivity using exfoliated graphene nanoplatelets (xGnPs) has also been measured, showing a greater than 3× increase for a concentration of 6 wt.%. Reductions in the total melting and freezing times of up to 66% and 55%, respectively, have been achieved using xGnP concentrations of only 4.5 wt.%. It is shown that the phase-change dynamics of pure and enhanced PCM are well predicted using a simple conduction-only model, demonstrating the validity of approximating enhanced PCM with low additive loadings as homogenous materials with isotropic properties. While general consistency between the measurements and model is seen, the effect of additives on heat transfer rate during the initial stages of freezing and melting is lower than expected, particularly for the smaller cylinder sizes of 6 mm. These results suggest that the thermal resistance of the PCM is not the limiting factor dictating the speed of the solid–liquid interface during these initial stages.
Heat and Mass Transfer Analysis of a Pot-in-Pot Refrigerator Using Reynolds Flow Model
Authors: Pandey Ramendra , Pesala Bala
Published: March 2016

Heat and mass transfer analysis of evaporative cooling process in a pot-in-pot cooling system is done based on Reynolds flow hypotheses. The model proposed herein assumes that the heat transfer due to natural convection is coupled with an imaginary ambient air mass flow rate (gAo) which is an essential assumption in order to arrive at the solution for the rate of water evaporation. Effect of several parameters on the pot-in-pot system performance has been studied. The equations are iteratively solved and detailed results are presented to evaluate the cooling performance with respect to various parameters: ambient temperature, relative humidity (RH), pot height, pot radius, total heat load, thermal and hydraulic conductivity, and radiation heat transfer. It was found that pot height, pot radius, total heat load, and radiation heat transfer play a critical role in the performance of the system. The model predicts that at an ambient temperature of 50 °C and RH of 40%, the system achieves a maximum efficiency of 73.44% resulting in a temperature difference of nearly 20 °C. Similarly, for a temperature of 30 °C and RH of 80%, the system efficiency was minimum at 14.79%, thereby verifying the usual concept that the pot-in-pot system is best suited for hot and dry ambient conditions.
In Vitro Investigation of a New Thin Film Nitinol-Based Neurovascular Flow Diverter
Authors: Babiker M. H. , Chun Y. , Roszelle B. , Hafner W. , Farsani H. Y. , Gonzalez L. F. , Albuquerque F. , Kealey C. , Levi D. S. , Carman G. P. , Frakes D. H.
Published: March 2016

Fusiform and wide-neck cerebral aneurysms (CAs) can be challenging to treat with conventional endovascular or surgical approaches. Recently, flow diverters have been developed to treat these cases by diverting flow away from the aneurysm rather than occluding it. The pipeline embolization device (PED), which embodies a single-layer braided design, is best known among available flow diverters. While the device has demonstrated success in recent trials, late aneurysmal rupture after PED treatment has been a concern. More recently, a new generation of dual-layer devices has emerged that includes a novel hyperelastic thin film nitinol (HE-TFN)-covered design. In this study, we compare fluid dynamic performance between the PED and HE-TFN devices using particle image velocimetry (PIV). The PED has a pore density of 12.5–20 pores/mm2 and a porosity of 65–70%. The two HE-TFN flow diverters have pore densities of 14.75 pores/mm2 and 40 pores/mm2, and porosities of 82% and 77%, respectively. Conventional wisdom suggests that the lower porosity PED would decrease intra-aneurysmal flow to the greatest degree. However, under physiologically realistic pulsatile flow conditions, average drops in root-mean-square (RMS) velocity (VRMS) within the aneurysm of an idealized physical flow model were 42.8–73.7% for the PED and 68.9–82.7% for the HE-TFN device with the highest pore density. Interestingly, examination of collateral vessel flows in the same model also showed that the HE-TFN design allowed for greater collateral perfusion than the PED. Similar trends were observed under steady flow conditions in the idealized model. In a more clinically realistic scenario wherein an anatomical aneurysm model was investigated, the PED affected intra-aneurysmal VRMS reductions of 64.3% and 56.3% under steady and pulsatile flow conditions, respectively. In comparison, the high pore density HE-TFN device reduced intra-aneurysmal VRMS by 88% and 71.3% under steady and pulsatile flow conditions, respectively. We attribute the superior performance of the HE-TFN device to higher pore density, which may play a more important role in modifying aneurysmal fluid dynamics than the conventional flow diverter design parameter of greatest general interest, absolute porosity. Finally, the PED led to more elevated intra-aneurysmal pressures after deployment, which provides insight into a potential mechanism for late rupture following treatment with the device.
Derivation for Electric Current Regulation Equation of a Gradient Magnetic Field to Control Suspending Magnetic Particles Inside Dialysate Solution
Authors: Lu Junfeng , Lu Wen-qiang
Published: March 2016

To allow a better adsorption performance inside a novel magnetic adsorption device designed in the process of hemodialysis, the mechanical properties of magnetic absorbents trapped inside a two-phase system are studied in this paper. A gradient magnetic coil field was assumed to produce the magnetic driving force that balances other hydraulic forces for the adsorbents. Applying this field, a complement practical form of winding equation for the solenoid coil is obtained. The case studies are also made in this paper to explore the design of the field.
A Design of a Multiple-Level Magnetic Field Used for Driving Micro Magnetic Particles During a Dialysate Adsorption Process
Authors: Lu Junfeng , Lu Wen-qiang
Published: March 2016

Recently in our research studies, ferroferric oxide magnetic micro particles were used as magnetic seeds combining with adsorbent materials during post hemodialysis (HD) nutrition recovery process. The combined particles were designed as magnetic adsorbents to selectively take back nutritional substances from waste dialysate solution, and then, these substances can be further chemically released to blood. To allow a better adsorption performance, these particles should be trapped inside their working area. So, a gradient magnetic field was designed accordingly. Instead to use a permanent magnet which could accumulate magnetic particles, the field was produced by multiple-level magnetic solenoid coils. This paper outlined the design method for the multiple-level solenoid field. And then, the measurement results for the magnetic intensity at different axis locations inside the solenoid field were compared with the numerical computation results. The computation results also showed that, near the axis area of the multiple-level solenoid, the magnetic intensity is smoothly developed. This feature allows the easy movement of magnetic particles since an abrupt gradient tends to accumulate the particles.
Performance Comparison of Nanofluids Through Plain Channel Considering the Effects of Uncertainties in Thermophysical Properties
Authors: Zhao Ningbo , Wang Qiang , Li Shuying
Published: March 2016

To compare and understand the laminar thermal-hydraulic performance of plate-fin channel with rectangle plain fin by using variable thermophysical properties of the most commonly used nanofluids (Al2O3-water), a three-dimensional numerical study is investigated by using the single-phase approach at a constant wall temperature boundary condition. Different models published in literatures are considered for the thermal conductivity and viscosity. On this basis, a parametric analysis is conducted to evaluate the effects of various pertinent parameters including nanoparticle volume fraction (0%–4%), Brownian motion of nanoparticle and Reynolds number (800–1500) on the heat transfer and flow characteristics of plain fin channel in detail. All the numerical results demonstrate that the addition of Al2O3 nanoparticle can enhance the heat transfer and flow pressure loss of base fluid because of the higher thermal conductivity and viscosity for nanofluids. And these enhancements are more obvious by increasing the volume fraction of nanoparticle, increasing Reynolds number, and considering the effects of nanoparticle Brownian motion. In addition, there are significantly differences in the thermal and flow fields for different nanofluids models at a fixed Reynolds number, which means that the effective theoretical formulas and empiric corrections for the nanofluids thrmophysical properties need to be studied extensively in the future.
Light-Harvesting and Photon Management in GaAs Solar Cells for Photovoltaic-Thermoelectric Hybrid Systems
Authors: Yuanpei Xu , Yimin Xuan
Published: March 2016

The utilization of solar energy in photovoltaics is limited due to the band gap of the materials. Hence, photovoltaic–thermoelectric hybrid system was proposed to utilize solar energy in the full spectrum of AM1.5G. On this basis, a novel design of GaAs solar cell is proposed in this paper for the full spectrum absorption in the cell structure, which consists of an ultra-thin GaAs layer with nanocones on the surface and a nanogrid–AZO–Ag back contact. The Finite Difference Time Domain method is used to analyze the full spectrum absorption features for TE and TM polarizations over the incident angles varying from 0° to 60°. The designed structure shows high absorption in the full spectrum. For GaAs layer, it is shown that the solar usable energy for GaAs solar cells in 300–900nm is absorbed by GaAs almost perfectly due to the anti–reflection property of the nanocone array. The absorbed energy in the back contact in the longer wavelengths over 900nm is due to the Fabry-Perot and the localized plasmonic resonances. The structure can collect full-spectrum incident photons efficiently in GaAs solar cells for the application of photovoltaic–thermoelectric hybrid system.
Graphene Nanoplatelets/Epoxy Resin Composites With High Thermal Conductivity
Authors: Qi Yu , Yu Wei , Chen Li-Fei , Xie Hua-qing , Wang Ming-Zhu
Published: March 2016

Graphene nanoplatelets (GNPs) are a kind of material with excellent thermal conductivity. It can significantly improve the heat-conducting property of epoxy resin (EP) matrix. In this study, GNPs/EP composites were prepared by ultrasonication and the cast molding method. The effect of optimization in the preparation process on the thermal transfer performance of the composites was discussed. The pulverizing time of GNPs and three-roll grinder grinding of composites were considered. The results indicated that when the mass fraction of GNPs was 4.3%, in its pulverizing time of 2s, the thermal conductivity of GNPs/EP composites was up to 0.99 W/m·K, and it was increased by 9% compared with non-pulverization treatment. However, after pulverizing two seconds and grinding three times, the thermal conductivity of the composite reached the maximum (1.06 W/m·K) when the mass fraction of GNPs was 4.3%, and it was finally increased by 307.7% compared with epoxy resin matrix.
Effect of Temperature on Rheology and Nanoparticle Movements of Water Based Nanofluids by Molecular Dynamics Simulation
Authors: Cui Wenzheng , Shen Zhaojie , Yang Jianguo , Wu Shaohua
Published: March 2016

Employing nanofluids is an innovative way to enhance heat transfer in cooling system of internal combustion engine. the reasons for the significantly enhanced heat transfer properties of nanofluids are various. On one hand, the markedly increased thermal conductivity is the most apparent reason; on the other hand, the changed rheology properties of base fluid due to the disordered movements of countless nanoparticles is even more important. Because the size scale of nanoparticles is too small, in some cases of computational simulations nanofluids is simplified as single-phase fluids. However, the influence of nanoparticles for flow behaviors of base fluids distinctly should not be ignored. By means of molecular dynamics method, a nano-scale simulation on the rheology of nanofluids could be conducted, therefore the movements of nanoparticles could be directly observed, which is conducive to reveal the influence of movements of nanoparticles for rheology of nanofluids. The present work is intended to perform a molecular dynamic simulation on the rheology of water based nanofluids. By applying temperature difference, the velocity and temperature distribution of fluid zone are calculated to evaluate heat transfer through nanofluids. Moreover, the influence of temperature for the movements of nanoparticle is discussed.
Effect of Nanoparticle Concentration on Thermal Damage in Nanoparticle-Assisted Thermal Therapy
Authors: Soni Sanjeev , Tyagi Himanshu , Taylor Robert A. , Kumar Amod
Published: March 2016

Photothermal therapy involving nanoparticles is evolving as a promising targeted treatment for cancer. This paper presents the results for the effect of nanoparticle concentration, within a tumor, to control the thermal damage during nanoparticle assisted thermal therapy.

A surface tumor embedded with gold nanoparticles (distributed uniformly) is considered. The thermal damage is evaluated for various nanoparticle concentrations (within the tumor) to identify an optimal concentration of the nanoparticles so as to achieve spatial confinement of the damage to the tumor region. Optical interaction is coupled to the biological heat transfer through Pennes’ bioheat model and Beer’s law. Spatiotemporal thermal damage is simulated through the Arrhenius method. The finite difference implicit method is used to solve the coupled phenomenon.

Results show that there is a specific value of nanoparticle concentration at which it is possible to confine thermal damage to the tumor within a spatial scale of less than 1 mm. This way the healthy tissues surrounding a tumor are safe. This optimum value of nanoparticle concentration (irrespective of tumor diameters) is 0.00001%. This concentration along with irradiation intensity of 1 W/cm2 for irradiation duration of 110 seconds is sufficient to thermally ablate the considered tumors. Novelty of this study is that it presents a combination of the controlling parameters for achieving a high (<1 mm) spatial confinement of the thermal damage. This finding is very much significant from clinical point of view. Clinically it is always desired to attain the therapeutic efficacy with minimal delivery of external agents (nanoparticles in this case) to a patient.
Mixing Enhancement in Spiral Microchannels
Authors: Balasubramaniam Lakshmi , Arayanarakool Rerngchai , Marshall Samuel D. , Li Bing , Lee Poh Seng , Chen Peter C. Y.
Published: March 2016

Advancements in the field of microfluidics has led to an increasing interest to study laminar flow in microchannel and its potential applications. Understanding mixing at a microscale can be useful in various biological, heating and industrial applications due to the space and time reduction that micro mixing permits. This work aims to study mixing enhancement due to curved microchannel and the influence of varying microchannel cross sectional shape through numerical and experimental investigations. Unlike prior studies which use channel dimensions in the lower microscale range, this work has been conducted on channels with dimensions in the higher end of micrometer range. Using a cross sectional hydraulic diameter of 600 μm enables introduction of flow into the curved channel at a Reynolds Number ranging from 0.15 to 75, the findings of which show considerable improvement in the mixing performance as compared to that of equivalent straight channels, due to the development of secondary flows known as Dean Vortices.
Theoretical and DSMC Study on Heat Conduction of Gas in Nanoscale Pores
Authors: Zhu Chuan-Yong , Li Zeng-Yao
Published: March 2016

This article presents a theoretical and numerical study on the heat conduction of gas confined in a nanoscale cube. An effective thermal conductivity model of confined gas using a modified mean free path is proposed for the heat conduction in transition regime inside a closure. Excellent agreement of the present model with the results from our simulations by the method of direct simulation Monte Carlo (DSMC) has been achieved for different boundary conditions of side walls. The temperature jumps and the reduction of local heat flux near the side walls are observed from the DSMC results.
Separation of Water Vapor From Methane by Nanoporous Graphene Membrane
Authors: Sun Chengzhen , Bai Bofeng
Published: March 2016

We study the separation process of gaseous H2O/CH4 mixtures using nanoporous graphene membranes via molecular dynamics simulations. We run the simulation in an equilibrium system 10 times with different initial atomic velocities to overcome the inefficiency brought by the low pressure of the system. The results show that the H2O molecules can permeate the graphene membrane with a linearly time-dependent crossing number. The permeance of the H2O molecules reaches to 9.5×10−4 mol/m2sPa, far exceeding that of the polymer gas separation membranes. High selectivity of H2O over CH4 is also observed. In summary, this study demonstrates that the specific NPG cloud be adopted as an efficient membrane in natural gas dehydration.
Molecular Dynamics Simulation on the Effect of Micro-Motions of Nanoparticles in Heat Transfer Enhancement of Nanofluids
Authors: Hu Chengzhi , Bai Minli , Lv Jizu , Wang Yuyan
Published: March 2016

The flow and heat transfer characteristics of nanofluids in the near-wall region were studied by non-equilibrium molecular dynamics simulation. The nanofluid model consisted of one spherical copper nanoparticle and argon atoms as base liquid. The effective thermal conductivity (ETC) of nanofluids and base fluid in shear flow fields were obtained. The ETC was increased with the increasing of shear velocity for both base fluid and nanofluids. The heat transfer enhancement of nanofluids in the shear flow field (v≠0) is better than that in the zero-shear flow field (v=0). By analyzing the flow characteristics we proved that the micro-motions of nanoparticles were another mechanism responsible for the heat transfer enhancement of nanofluids in the flow field. Based on the model built in the paper, we found that the thermal properties accounted for 52%–65% heat transfer enhancement and the contribution of micro-motions is 35%–48%.
Influence of Reynolds Numbers on the Flow and Heat Transfer Around Row of Magnetic Obstacles
Authors: Zhang Xidong , Zhu Guiping , Zhang Yin , Wang Hongyan , Huang Hulin
Published: March 2016

An incompressible electrically conducting viscous fluid flow influenced by a local external magnetic field may develop vortical structures and eventually instabilities similar to those observed in flows around bluff bodies (such as circular cylinder), denominated magnetic obstacle. The present investigation analyses numerically the three-dimensional flow and heat transfer around row of magnetic obstacles. The vortex structures of magnetic obstacles, heat transfer behaviors in the wake of magnetic obstacles and flow resistance are analyzed at different Reynolds numbers. It shows that the flow behind magnetic obstacles contains four different regimes: (1) one pair of magnetic vortices, (2) three pairs namely, magnetic, connecting, and attached vortices, (3) smaller vortex shedding from the in-between magnetic obstacles, i.e. quasi-static and (4) regular vortex shedding from the row of magnetic obstacles. Furthermore, downstream cross-stream mixing induced by the unstable wakes can enhance wall-heat transfer, and the maximum value of percentage heat transfer increment (HI) is equal to about 35%. In this case, the thermal performance factor is more than one.
Nanoparticle Motion and Deposition Pattern From Evaporating Binary Droplets
Authors: Zhong Xin , Duan Fei
Published: March 2016

The effect of ethanol in the binary solution sessile droplet is investigated on the flow field, nanoparticle motion and nanoparticle deposition pattern. It is found that the droplets with ethanol exhibited three distinct flow regimes through the Particle Image Velocimetry (PIV) analysis on the flow field of droplets suspended with fluorescent microspheres. Regime I features furious flows and vortices which transport particles to the liquid-vapor interface and make them aggregate. In regime II, the aggregates of particles move towards the central area of the droplet dominated by Marangoni flow led by non-uniformity of ethanol along the droplet surface. As the droplet enters regime III, most ethanol has evaporated and it is dominated by the drying of the remaining water. The loading of ethanol in the solution prolongs the relative durations of regimes I and II, resulting in the variety of the final drying pattern of nanoparticles.
Channel Size Optimization for 3D-IC Integrated Interlayer Microchannel Liquid Cooling
Authors: Ma D. D. , Xia G. D. , Wang W. , Li X. F. , Jia Y. T.
Published: March 2016

3D-IC is getting increasingly attractive, as it improves speed and frequency, and reduces power consumption, noise and latency. However, three dimension (3D) integration technologies bring a new serious challenge to chip thermal management with the power density increased exponentially. Interlayer microchannel liquid cooling is thought as a promising and scalable solution for cooling high heat flux 3D-IC. In this paper, firstly channel number, channel width and height parameters of rectangular channel are optimized by the method of multi-objective parameter optimization under given overall size of 5mm in length and 5mm in width. The results show the total thermal resistances can reach very small under individual constraint condition of volume flow rates, but the pressure drop is too larger to accept. The minimum thermal resistance structure can be got by multi-objective optimization at various constraint conditions. It is found that the channel height and width increase with increasing of flow rates at pumping power less than 0.1W and pressure drop less than 20kPa. Secondly, the zigzag channels are designed on the basis of the optimized rectangular channel structure. The expansion and contraction ratio as an important parameter is optimized by numerical simulation. The thermal enhancement factor and Nusselt number measure the comprehensive performances of heat transfer. The results show heat transfer characteristic is enhanced with the decreasing of expansion and contraction ratio. Besides, the maximum junction temperature and maximum temperature difference are also reduced. 3D-IC with wave channel of β=3/7 is more promising for interlayer cooling.
Enhancing the Thermal Conductivity of Randomly Oriented CNT Networks via Welded Junctions
Authors: Yang Xueming , Cao Bingyang
Published: March 2016

The thermal conductivity of bulk CNT materials based on three-dimensional randomly oriented CNT networks is rather low comparing with that of the individual carbon nanotube, and one of the important reasons has been considered to be the huge intertube thermal resistance. Though intertube thermal resistance can be reduced via welded junctions between the tubes, it is still unknown whether the formation of the welded junctions can enhance the thermal conductivity of random SWCNTs network. In this approach, the calculations of the average number of thermal contacts per SWCNT are compared by two different methods, and influencing factors of the thermal conductivity of random SWCNTs network are discussed; a hybrid macroscopic analytical model is proposed to predict the overall thermal conductivity of the partially sintered randomly oriented carbon nanotube (CNT) networks. Results show that choosing proper fraction of welded contacts can enhance the thermal conductivity of randomly oriented CNT networks effectively.
Thermal Management in Silicene Nanosheets With Designed Cavities by Molecular Dynamic Simulations
Authors: Yuan Feng , Liang Xingang
Published: March 2016

Silicene, the silicon-based two-dimensional structure with honeycomb lattice, has been discovered to have tremendous application potential in fundamental industries. However, the thermal transport mechanism and thermal properties of silicene has not been fully explained. We report a possible way to control the thermal transport and thermal rectification in silicene nanosheets by designing distributions of a series of triangular cavities in this paper with the nonequilibrium molecular dynamic simulations. The cavities are arranged in a staggered way. The reflection of phonon at the vertex and the base of the triangular cavities are quite different. This difference is used to control the phonon transport in opposite directions and such an arrangement is expected to have very significant thermal rectification effect. The size of cavities, the distance between the triangular cavities and the distribution of cavities are investigated to observe the thermal rectification, which would benefit the design of an experiment that can clearly demonstrate thermal rectification.