Showing papers by "Cranfield University published in 2017"

Recent progress in cellulose nanocrystals: sources and production

Abstract: Cellulose nanocrystals, a class of fascinating bio-based nanoscale materials, have received a tremendous amount of interest both in industry and academia owing to its unique structural features and impressive physicochemical properties such as biocompatibility, biodegradability, renewability, low density, adaptable surface chemistry, optical transparency, and improved mechanical properties. This nanomaterial is a promising candidate for applications in fields such as biomedical, pharmaceuticals, electronics, barrier films, nanocomposites, membranes, supercapacitors, etc. New resources, new extraction procedures, and new treatments are currently under development to satisfy the increasing demand of manufacturing new types of cellulose nanocrystals-based materials on an industrial scale. Therefore, this review addresses the recent progress in the production methodologies of cellulose nanocrystals, covering principal cellulose resources and the main processes used for its isolation. A critical and analytical examination of the shortcomings of various approaches employed so far is made. Additionally, structural organization of cellulose and nomenclature of cellulose nanomaterials have also been discussed for beginners in this field.

Energy Management in Plug-in Hybrid Electric Vehicles: Recent Progress and a Connected Vehicles Perspective

Abstract: Plug-in hybrid electric vehicles (PHEVs) offer an immediate solution for emissions reduction and fuel displacement within the current infrastructure. Targeting PHEV powertrain optimization, a plethora of energy management strategies (EMSs) have been proposed. Although these algorithms present various levels of complexity and accuracy, they find a limitation in terms of availability of future trip information, which generally prevents exploitation of the full PHEV potential in real-life cycles. This paper presents a comprehensive analysis of EMS evolution toward blended mode (BM) and optimal control, providing a thorough survey of the latest progress in optimization-based algorithms. This is performed in the context of connected vehicles and highlights certain contributions that intelligent transportation systems (ITSs), traffic information, and cloud computing can provide to enhance PHEV energy management. The study is culminated with an analysis of future trends in terms of optimization algorithm development, optimization criteria, PHEV integration in the smart grid, and vehicles as part of the fleet.

Shades of Grey: guidelines for working with the grey literature in systematic reviews for management and organizational studies

Abstract: This paper suggests how the ‘grey literature’, the diverse and heterogeneous body of material that is made public outside, and not subject to, traditional academic peer-review processes, can be used to increase the relevance and impact of management and organization studies (MOS). The authors clarify the possibilities by reviewing 140 systematic reviews published in academic and practitioner outlets to answer the following three questions: (i) Why is grey literature excluded from/included in systematic reviews in MOS? (ii) What types of grey material have been included in systematic reviews since guidelines for practice were first established in this discipline? (iii) How is the grey literature treated currently to advance management and organization scholarship and knowledge? This investigation updates previous guidelines for more inclusive systematic reviews that respond to criticisms of current review practices and the needs of evidence-based management.

Reinforcement Learning Optimized Look-Ahead Energy Management of a Parallel Hybrid Electric Vehicle

Abstract: This paper presents a predictive energy management strategy for a parallel hybrid electric vehicle (HEV) based on velocity prediction and reinforcement learning (RL). The design procedure starts with modeling the parallel HEV as a systematic control-oriented model and defining a cost function. Fuzzy encoding and nearest neighbor approaches are proposed to achieve velocity prediction, and a finite-state Markov chain is exploited to learn transition probabilities of power demand. To determine the optimal control behaviors and power distribution between two energy sources, a novel RL-based energy management strategy is introduced. For comparison purposes, the two velocity prediction processes are examined by RL using the same realistic driving cycle. The look-ahead energy management strategy is contrasted with shortsighted and dynamic programming based counterparts, and further validated by hardware-in-the-loop test. The results demonstrate that the RL-optimized control is able to significantly reduce fuel consumption and computational time.

Experimental studies of nanofluid thermal conductivity enhancement and applications: A review

Abstract: In many applications, there is a critical need for enhancing the poor thermal conductivity of conventional fluids in order to develop efficient heat transfer fluids. This requirement can be met through dispersing nanometric particles in a given base fluid such as water, ethylene glycol, oil or air. The resulting nanofluids enhanced thermal conductivity of the base fluids. In order to evaluate this enhancement, nanofluid thermal conductivity is required to be measured. Several methods and techniques are covered in the present contribution. In addition, enhancements recorded experimentally are reviewed and summarized. Different parameters affecting on such enhancement are covered, including: nanoparticle concentration, size, shape and thermal conductivity. In addition, base fluid type, nanofluid bulk temperature and dispersion techniques are also covered parameters. However, nanofluids have the potential to contribute in several practical applications including solar thermal, transportation, electronic cooling, medical, detergency and military applications. In the present work, a brief overview of evolution in the use of nanofluids in some applications has been presented. According to this contribution, there is a critical need for further fundamental and applications of nanofluids studies in order to understand the physical mechanisms of using nanofluids as well as explore different aspects of applications of nanofluids.

Simulation of metallic powder bed additive manufacturing processes with the finite element method: A critical review

Abstract: This article provides a literature review of finite element simulation studies for metallic powder bed additive manufacturing processes. The various approaches in the numerical modeling of the processes and the selection of materials properties are presented in detail. Simulation results are categorized according to three major findings’ groups (i.e. temperature field, residual stresses and melt pool characteristics). Moreover, the means used for the experimental validation of the simulation findings are described. Looking deeper into the studies reviewed, a number of future directions are identified in the context of transforming simulation into a powerful tool for the industrial application of additive manufacturing. Smart modeling approaches should be developed, materials and their properties should be further characterized and standardized, commercial packages specialized in additive manufacturing simulation have to be developed and simulation needs to become part of the modern digital production chai...

A restatement of the natural science evidence concerning catchment-based 'natural' flood management in the UK.

Abstract: Flooding is a very costly natural hazard in the UK and is expected to increase further under future climate change scenarios. Flood defences are commonly deployed to protect communities and property from flooding, but in recent years flood management policy has looked towards solutions that seek to mitigate flood risk at flood-prone sites through targeted interventions throughout the catchment, sometimes using techniques which involve working with natural processes. This paper describes a project to provide a succinct summary of the natural science evidence base concerning the effectiveness of catchment-based ‘natural’ flood management in the UK. The evidence summary is designed to be read by an informed but not technically specialist audience. Each evidence statement is placed into one of four categories describing the nature of the underlying information. The evidence summary forms the appendix to this paper and an annotated bibliography is provided in the electronic supplementary material.

Parallel driving in CPSS: a unified approach for transport automation and vehicle intelligence

Abstract: The emerging development of connected and automated vehicles imposes a significant challenge on current vehicle control and transportation systems. This paper proposes a novel unified approach, Parallel Driving, a cloud-based cyberphysical-social systems U+0028 CPSS U+0029 framework aiming at synergizing connected automated driving. This study first introduces the CPSS and ACP-based intelligent machine systems. Then the parallel driving is proposed in the cyber-physical-social space, considering interactions among vehicles, human drivers, and information. Within the framework, parallel testing, parallel learning and parallel reinforcement learning are developed and concisely reviewed. Development on intelligent horizon U+0028 iHorizon U+0028 and its applications are also presented towards parallel horizon. The proposed parallel driving offers an ample solution for achieving a smooth, safe and efficient cooperation among connected automated vehicles with different levels of automation in future road transportation systems.

Electronic HRM : four decades of research on adoption and consequences

Abstract: Despite the existence of a number of recent reviews of e-HRM research, we still lack a comprehensive understanding of the factors affecting the adoption and consequences of e-HRM. This paper therefore provides a review of four decades of research in this area with the aim to provide a summary and integrative framework as a basis for future research. We found that the factors affecting the adoption of e-HRM can be divided into three areas: technology; organization; and people – we refer to this as the ‘TOP’ framework. In line with we divide consequences into those that are operational, relational and transformational. We also found that there has been a shift both in the goals for e-HRM, from efficiency to improved HR service provision and the strategic reorientation of HR departments; but also that the type of consequences that the literature focuses on has also changed from operational effects, to relational and then transformational outcomes. The paper discussed these shifts in some detail, along with the implications for future research and practice.

Detecting recovery of the stratospheric ozone layer

Abstract: As a result of the 1987 Montreal Protocol and its amendments, the atmospheric loading of anthropogenic ozone-depleting substances is decreasing. Accordingly, the stratospheric ozone layer is expected to recover. However, short data records and atmospheric variability confound the search for early signs of recovery, and climate change is masking ozone recovery from ozone-depleting substances in some regions and will increasingly affect the extent of recovery. Here we discuss the nature and timescales of ozone recovery, and explore the extent to which it can be currently detected in different atmospheric regions.

Delineation of Soil Management Zones for Variable-Rate Fertilization: A Review

Abstract: Different methods of management zone (MZ) delineation have been established over the past 2 decades based on approaches, which have been largely constrained by the available data collection methods that are often time consuming and expensive. This situation is being changed by recent advances in sensor technology, making a huge amount of data available. Advances in computing power make it possible to analyze and utilize this large amount of data. These current advances in technology are gradually turning MZ maps into commercially viable agricultural products for large-scale adoption. The aim of this paper is to provide a critical overview of MZ delineation approaches for precision agriculture applications, and to compare and contrast traditional with advanced sensing technologies for delineating MZs. This review illustrates how recent development in sensing technologies, geostatistical analysis, data fusion, and interpolation techniques have improved precision and reliability of MZ delineation, making it a viable strategy in commercial agriculture. Studies from the last decade showed that when MZ delineation techniques are used for variable-rate nutrient application, farm efficiency increased when this is compared to traditional uniform-rate application methods. This improved farm production efficiency is accompanied by a reduction in environmental impacts. Implementation of MZ therefore often provides financial and environmental benefits, and we can foresee an increase in the diffusion and application of precision agriculture techniques in the near future.

Key themes and research opportunities in sustainable supply chain management – identification and evaluation

Abstract: Supply chains play an integral role in today׳s globalised economy. Hence, in order to truly pursue sustainable business development, the underlying dynamics and influential themes for sustainability in supply chains have to be understood. However, this area remains characterized by limited theoretical knowledge and practical application. A literature review was conducted first in order to gain an overview of available theory and to develop initial categorisations. In the next step, the insights of supply chain and sustainability experts were gathered via an exploratory Delphi study conducted online over three rounds. A set of key themes (planning, execution, coordination, and collaboration) and associated research opportunities (within the categories of governance, risk, compliance, performance management, and the sustainability dimensions) were synthesised and evaluated according to their relative importance based on the experts׳ opinions. By relating these results to existing literature, this study confirms, questions and extends knowledge on sustainable supply chain management. The identified themes are integral for the management and performance of sustainable supply chains. They provide structure to the field and offer a prioritisation of sustainability initiatives that can be applied prescriptively by the practitioner. The future research opportunities are further enfolded in a categorised research agenda, driving the theoretical as well as practical development of the field.

Optoelectronic and spectroscopic characterization of vapour-transport grown Cu2ZnSnS4 single crystals

Abstract: Single crystals of Cu2ZnSnS4 (CZTS) have been grown by iodine vapor transport with and without addition of NaI. Crystals with tin-rich copper-poor and with zinc-rich copper-poor stoichiometries were obtained. The crystals were characterized by single crystal X-ray diffraction, energy-dispersive X-ray spectroscopy, photocurrent spectroscopy and electroreflectance spectroscopy using electrolyte contacts as well as by spectroscopic ellipsometry, Raman spectroscopy and photoluminescence spectroscopy (PL)/decay. Near-resonance Raman spectra indicate that the CZTS crystals adopt the kesterite structure with near-equilibrium residual disorder. The corrected external quantum efficiency of the p-type crystals measured by photocurrent spectroscopy approaches 100% close to the bandgap energy, indicating efficient carrier collection. The bandgap of the CZTS crystals estimated from the external quantum efficiency spectrum measured using an electrolyte contact was found to be 1.64–1.68 eV. An additional sub-bandgap photocurrent response (Urbach tail) was attributed to sub bandgap defect states. The room temperature PL of the crystals was attributed to radiative recombination via tail states, with lifetimes in the nanosecond range. At high excitation intensities, the PL spectrum also showed evidence of direct band to band transitions at ∼1.6 eV with a shorter decay time. Electrolyte electroreflectance spectra and spectra of the third derivative of the optical dielectric constant in the bandgap region were fitted to two optical transitions at 1.71 and 1.81 eV suggesting a larger valence band splitting than predicted theoretically. The high values of the EER broadening parameters (192 meV) indicate residual disorder consistent with the existence of tail states.

Perovskite and Organic Solar Cells Fabricated by Inkjet Printing: Progress and Prospects

Abstract: Inkjet printing (IJP) technology, adapted from home and office printing, has proven to be an essential research tool and industrial manufacturing technique in a wide range of printed electronic technologies, including optoelectronics. Its primary advantage over other deposition methods is the low-cost and maskless on-demand patterning, which offers unmatched freedom-of-design. Additional benefits include the efficient use of materials, contactless high-resolution deposition, and scalability, enabling rapid translation of learning from small-scale, laboratory-based research into large-scale industrial roll-to-roll manufacturing. In the development of organic solar cells (OSCs), IJP has enabled the printing of many of the multiple functional layers which comprise the complete cell as part of an additive printing scheme. Although IJP is only recently employed in perovskite solar cell (PeSC) fabrication, it is already showing great promise and is anticipated to find broader application with this class of materials. As OSCs and PeSCs share many common functional materials and device architectures, this review presents a progress report on the IJP of OSCs and PeSCs in order to facilitate knowledge transfer between the two technologies, with critical analyses of the challenges and opportunities also presented.

Vision Based Autonomous Landing of Multirotor UAV on Moving Platform

Abstract: This paper investigates solutions for the fundamental yet challenging problem of autonomous landing of multirotor Unammaned Aerial Vehicles UAVs. In addition to landing on static targets, tracking and landing on a moving platform is addressed, as a solution to facilitate the deployment of the UAV. The paper presents the design of a new landing pad and its relative pose estimation. The fusion of inertial measurement with the estimated pose is considered to ensure a high sampling rate, and to increase the manoeuvrability of the vehicle. Two filters are designed to conduct the fusion, an Extended Kalman Filter (EKF) and an Extended Hź (EHź). The extensive simulation and practical tests permitted identification of the challenges of the landing task. Adequate solutions to these challenges are proposed to lessen their impact on landing precision.