scholarly journals Terminal fall velocity: the legacy of Stokes from the perspective of fluvial hydraulics

Author(s):  
Subhasish Dey ◽  
Sk Zeeshan Ali ◽  
Ellora Padhi

This review article, dedicated to the bicentenary celebration of Sir George Gabriel Stokes' birthday, presents the state-of-the-science of terminal fall velocity, highlighting his rich legacy from the perspective of fluvial hydraulics. It summarizes the fluid drag on a particle and the current status of the drag coefficient from both the theoretical and empirical formulations, highlighting the three major realms—Stokesian, transitional and Newtonian realms. The force system that drives the particle motion falling through a fluid is described. The response of terminal fall velocity to key factors, which include particle shape, hindered settling and turbulence (nonlinear drag, vortex trapping, fast tracking and effects of loitering), is delineated. The article puts into focus the impact of terminal fall velocity on fluvial hydraulics, discussing the salient role that the terminal fall velocity plays in governing the hydrodynamics of the sediment threshold, bedload transport and suspended load transport. Finally, an innovative perspective is presented on the subject's future research track, emphasizing open questions.

2021 ◽  
pp. 135481662199996
Author(s):  
Ali Salman Saleh ◽  
Charbel Bassil ◽  
Arsalan Safari

Tourism in the Gulf Cooperation Council (GCC) countries has recently been considered by policymakers as a new avenue for economic diversification. Despite the considerable literature concerning the impact of tourism worldwide, only a limited number of studies have looked at the tourism sector in the GCC region or analyzed its economic, sociocultural, and environmental impacts. This article therefore conducts a systematic review of the state of the literature related to tourism in the GCC region. It provides effective insights about the current status, gaps, and challenges and proposes future research directions in this area for academics, practitioners, and policymakers with an interest in regional tourism development. The preferred reporting items for systematic reviews and meta-analyses approach was used to identify and select the papers. Some 23 papers were identified and analyzed. The majority of these studies focused on the United Arab Emirates, specifically the Dubai emirate. We found the most dominant research theme to be tourism planning.


2021 ◽  
Vol 13 (11) ◽  
pp. 6503
Author(s):  
Yu Peng ◽  
Hubert Hirwa ◽  
Qiuying Zhang ◽  
Guoqin Wang ◽  
Fadong Li

Given the impact of COVID-19 and the desert locust plague, the Ethiopian food security issue has once again received widespread attention. Its food crisis requires comprehensive and systematic research to achieve the United Nations Sustainable Development Goal of zero hunger. This review discusses the current situation and the causes of food security in Ethiopia. We focus on the challenges in the food security assessment field. The article lists seven typical causes of food insecurity and three roots of food security in Ethiopia. Long-term food security assessment and a comprehensive understanding and manageability for food security causes are considered as the main existing research challenges. Climate-resilient management, water management, and long-term ecosystem network monitoring and data mining are suggested as potential roadmap for future research.


2016 ◽  
Vol 22 (4) ◽  
pp. 556-583 ◽  
Author(s):  
Cristina Dai Prá Martens ◽  
Fabrício Martins Lacerda ◽  
Ana Claudia Belfort ◽  
Henrique Mello Rodrigues de Freitas

Purpose – Research on entrepreneurial orientation (EO) has attracted researchers’ attention for over 30 years. The purpose of this paper is to comprehensively analyze the body of literature resulting from 30 years of research in EO, and to answer the following questions: what are the major themes that have emerged? What areas are missing? What degree of convergence do we see in the field of EO, and what concepts/topics has the field converged around? Design/methodology/approach – A bibliometric study with a sample of 405 articles published from January 1987 to July 2014 was developed. Techniques of bibliometric, lexical, and content analysis were used. The analysis involved: the evolution of published articles; the main authors, their nationalities, and institutional affiliations; citation and co-citations analysis; the journals that have published the most articles; and the most frequently-searched topics. Opting for bibliometric techniques permit an analysis of a larger number of articles and a greater variety of articles than other methodologies such as meta-analyses and systematic review studies. Accordingly, a more comprehensive look at the field of EO can be taken. Findings – Two distinct but complementary classifications are proposed to characterize the body of the literature resulting from 30 years of research in EO. The first one demonstrates that the field presents a convergence of the themes in four axis which together comprise studies on EO: performance, strategy, entrepreneurial attitude, and management. The second one presents the frequency of occurrence of the themes in the field: high-frequency themes or classical themes, frequently in the literature; moderate-frequency themes or emerging issues have not been sufficiently explored; low-frequency themes or potential opportunities related to understudied issues and contexts less frequently surveyed. A future research agenda is proposed for emerging themes and specific contexts. Practical implications – The identification of key themes in the field of EO contributes to assess the research evolution in order to recognize emerging themes and contexts, and the research gaps. With this, it is possible to lead new studies to cover a lack of research and advance knowledge in the field. The themes most studied also show the contribution for EO to organizational practice, especially in relation to the impact on the performance, the stimulus to the development of innovations, and the effects on organizational growth. Additionally, the identification of the authors most cited, most productive on the theme and the identification of the core journals for publishing of the area is recommended as a general reference for researchers interested in the topic of EO. Social implications – Although EO literature has been widely developed in Anglo regions (especially in the USA and UK) and Germanic Europe (especially Spain), there are others lacking these studies, especially Latin America, sub-Saharan Africa, Eastern Europe, and Middle East, with rare articles published internationally. The results can guide the advancement of research in these different contexts and realities where even issues more widely treated in the literature have been unexplored. The lack of studies in certain contexts can lead to new studies for inserting new insights into EO, such as potential differences between developed regions and in development. For regions where the studies on EO are more developed, the results of this paper contribute to signaling issues and contexts little explored that may be the focus of attention. Originality/value – The generation of literature indicators of EO through bibliometric fills a research gap on the theme, providing a more comprehensive view of the field and of the current status of the research on EO. Identifying the most frequent topics in EO literature, and little-explored themes and contexts makes it possible to propose an agenda for future research and knowledge generation on EO. Thus, it is suggested the development of studies focus on emerging themes like growth, learning, knowledge, resources, and capabilities; also in specific contexts with potential for aggregating new knowledges in the EO field such as family firms, non-profit organizations, social contexts, the public sector, university, spin-off, firms in emerging and developing economies.


Author(s):  
Mengxiang Zhuang ◽  
Qixin Zhu

Objective: In order to better understand the research results of AC load prediction and carry out new research, the Air Conditioning (AC) load forecasting method plays an important role in the energy consumption of AC. Method: This paper summarizes the methods of building AC load prediction, mainly from the impact factors of AC operating load and the methods of AC system operating load forecasting to introduce the current status of load prediction. This paper describes some studies on load influencing factors, compares the advantages and disadvantages of modeling methods for AC operation load prediction and points out the research direction of AC load forecasting. Results: The current research methods are summarized and analyzed. Traditional forecasting methods are no longer applicable to air conditioning systems. From the current research, combinatorial prediction has become a hot research object. This method combines two or more methods to reduce the prediction error and shorten the prediction time. Conclusion: This paper points out some shortcomings of the present research and the future research suggestions are given in the three aspects of sharing AC operation data, selecting the key factors of AC, and exploring the new methods.


2019 ◽  
Vol 38 (1) ◽  
pp. 121-135 ◽  
Author(s):  
Chinmoy Bandyopadhyay ◽  
Subhasis Ray

Purpose The purpose of this paper is to review existing literature on marketing in social enterprises (SEs). It identifies major trends and issues and highlights gaps in the existing knowledge base on social enterprise marketing (SEM). Design/methodology/approach Relevant articles on SEM were searched, following the PRISMA framework, in online databases using keywords and phrases like “marketing in social enterprises,” “marketing strategy/practice in social enterprises,” “social enterprise marketing” and “business practices in social enterprises.” After screening and checking for eligibility, 47 significant articles published in 21 peer-reviewed journals during 1995–2018 were selected for review. Findings The findings suggest that marketing in SEs has different issues and challenges when compared to marketing practices adopted by conventional business organizations. They are forced to address the varied expectations of the stakeholders in a resource-constrained situation, which creates problems for them. The review also highlights the fact that resource constraints, legacy mindset, and lack of marketing skills limit the impact of marketing practices in SEs. To address these issues, many social entrepreneurs survive through cost-effective marketing techniques. Originality/value To the authors’ knowledge, this is the first effort to identify and analyze extant literature in SEM. The resultant themes and research gaps highlight the current status of SEM literature. The paper can help SEs to understand and plan their marketing activities for better impact and profitability. Future research can draw on the findings of this review.


Computers ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 73
Author(s):  
Daniel Zielasko ◽  
Bernhard E. Riecke

Virtual Reality (VR) users typically either sit or stand/walk when using VR; however, the impact of this is little researched, and there is a lack of any broad or systematic analysis of how this difference in physical posture might affect user experience and behavior. To address this gap, we propose such a systematic analysis that was refined through discussions and iterations during a dedicated workshop with VR experts. This analysis was complemented by an online survey to integrate the perspectives of a larger and more diverse group of VR experts, including developers and power users. The result is a validated expert assessment of the impact of posture and degree of embodiment on the most relevant aspects of VR experience and behavior. In particular, we posit potential strong effects of posture on user comfort, safety, self-motion perception, engagement, and accessibility. We further argue that the degree of embodiment can strongly impact cybersickness, locomotion precision, safety, self-motion perception, engagement, technical complexity, and accessibility. We provide a compact visualization of key findings and discuss areas where posture and embodiment do or do not have a known influence, as well as highlight open questions that could guide future research and VR design efforts.


2018 ◽  
Vol 58 (8) ◽  
pp. 1538 ◽  
Author(s):  
J. E. Kelly ◽  
J. C. Quinn ◽  
P. Loukopoulos ◽  
J. C. Broster ◽  
K. Behrendt ◽  
...  

Seed contamination significantly affects production capacity and animal welfare in Australian sheep flocks and causes considerable financial loss to producers and processors across sheepmeat value chains. Seven grass-weed species contribute to seed contamination in Australia, with barley grass (Hordeum spp.) identified as a key perpetrator. Herbicide resistance and variable dormancy emerging in southern Australian barley grass populations are thought to enhance its capacity for successful pasture invasion, further exacerbating the potential for seed contamination in sheep. The present article reviews the current literature regarding the impact and incidence of seed contamination on sheepmeat production, with particular reference to key grass-weed species prevalence across Australia. Data are presented on a recent incidence of carcass contamination across years, where incidence varied between 11% and 80% from 2009 to 2013, contracting to between 2% and 60% during 2014 and 2015. Key areas requiring future research are defined. Understanding the biology of key grass weeds, historical influences and economic consequences associated with seed contamination in sheep may assist in defining future risks to sheep production and improve weed management. Furthermore, examining more recent data describing the current status of seed contamination across Australia and the associations with causal weed species may aid the development of critical weed-management strategies in highly infested regions, subsequently limiting the extent of future seed contamination.


Author(s):  
Anastasios Anastasiadis ◽  
David Lario ◽  
Athanasios Papaioannou ◽  
Athanasios Kouloumvakos ◽  
Angelos Vourlidas

Solar energetic particle (SEP) events are related to both solar flares and coronal mass ejections (CMEs) and they present energy spectra that span from a few keV up to several GeV. A wealth of observations from widely distributed spacecraft have revealed that SEPs fill very broad regions of the heliosphere, often all around the Sun. High-energy SEPs can sometimes be energetic enough to penetrate all the way down to the surface of the Earth and thus be recorded on the ground as ground level enhancements (GLEs). The conditions of the radiation environment are currently unpredictable due to an as-yet incomplete understanding of solar eruptions and their corresponding relation to SEP events. This is because the complex nature and the interplay of the injection, acceleration and transport processes undergone by the SEPs in the solar corona and the interplanetary space prevent us from establishing an accurate understanding (based on observations and modelling). In this work, we review the current status of knowledge on SEPs, focusing on GLEs and multi-spacecraft events. We extensively discuss the forecasting and nowcasting efforts of SEPs, dividing these into three categories. Finally, we report on the current open questions and the possible direction of future research efforts. This article is part of the theme issue ‘Solar eruptions and their space weather impact’.


2013 ◽  
Vol 68 (2) ◽  
pp. 448-461 ◽  
Author(s):  
Ludiwine Clouzot ◽  
Jean-Marc Choubert ◽  
Frédéric Cloutier ◽  
Rajeev Goel ◽  
Nancy G. Love ◽  
...  

Models for predicting the fate of micropollutants (MPs) in wastewater treatment plants (WWTPs) have been developed to provide engineers and decision-makers with tools that they can use to improve their understanding of, and evaluate how to optimize, the removal of MPs and determine their impact on the receiving waters. This paper provides an overview of such models, and discusses the impact of regulation, engineering practice and research on model development. A review of the current status of MP models reveals that a single model cannot represent the wide range of MPs that are present in wastewaters today, and that it is important to start considering classes of MPs based on their chemical structure or ecotoxicological effect, rather than the individual molecules. This paper identifies potential future research areas that comprise (i) considering transformation products in MP removal analysis, (ii) addressing advancements in WWTP treatment technologies, (iii) making use of common approaches to data acquisition for model calibration and (iv) integrating ecotoxicological effects of MPs in receiving waters.


Author(s):  
Van Ky Long Nguyen ◽  
Thi My Hanh Le ◽  
Thi Minh Chau Tran ◽  
Thi Thu Hien Le ◽  
Thi Ngoc Mai Duong ◽  
...  

The pandemic has caused several health issues and deaths and numerous severe devastations to the global economy. Due to the extreme impacts of the epidemics, it is crucial to investigate the pandemics and their pessimistically hidden influences to devise proper strategies. However, although this topic gains enormous recognition from scholars and researchers, there is still an inadequacy of a comprehensive literature review on the issues, and in-depth research on individual aspects of the world economy. Accordingly, the objective of this paper is to contribute a literature review that synthesises and evaluates prior research, to examine the current state of the pandemic impacts on the global economy, as well as become the requisite foundation for the practitioners to perceive how to respond to a pandemic in the future. A literature review is conducted, with 254 most relevant articles are analysed and classified based on the proposed framework. Thus, the findings of this study contribute diverse theoretical and practical insights concerning pandemics and the global economy. The results of this paper indicate the current status of the literature review and discover future research directions. Additionally, this paper proposes an integrated framework of the most influenced industries, followed by some emerging solutions to the most suffering sectors. Future research directions are further suggested based on the identified research gaps and the analysis results.


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