Future Research Directions
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Xiaogang Wu ◽  
Jiulong Wang ◽  
Yun Zhang ◽  
Jiuyu Du ◽  
Zhengxin Liu ◽  

AbstractThe development of fuel cell vehicles (FCVs) has a major impact on improving air quality and reducing other fossil-fuel-related problems. DC-DC boost converters with wide input voltage ranges and high gains are essential to fuel cells and DC buses in the powertrains of FCVs, helping to improve the low voltage of fuel cells and “soft” output characteristics. To build DC-DC converters with the desired performance, their topologies have been widely investigated and optimized. Aiming to obtain the optimal design of wide input range and high-gain DC-DC boost converter topologies for FCVs, a review of the research status of DC-DC boost converters based on an impedance network is presented. Additionally, an evaluation system for DC-DC topologies for FCVs is constructed, providing a reference for designing wide input range and high-gain boost converters. The evaluation system uses eight indexes to comprehensively evaluate the performance of DC-DC boost converters for FCVs. On this basis, issues about DC-DC converters for FCVs are discussed, and future research directions are proposed. The main future research directions of DC-DC converter for FCVs include utilizing a DC-DC converter to realize online monitoring of the water content in FCs and designing buck-boost DC-DC converters suitable for high-power commercial FCVs.

Land ◽  
2021 ◽  
Vol 10 (10) ◽  
pp. 1101
Bahram Saeidian ◽  
Abbas Rajabifard ◽  
Behnam Atazadeh ◽  
Mohsen Kalantari

The development and use of underground space is a necessity for most cities in response to rapid urbanisation. Effective underground land administration is critical for sustainable urban development. From a land administration perspective, the ownership extent of underground assets is essential for planning and managing underground areas. In some jurisdictions, physical structures (e.g., walls, ceilings, and utilities) are also necessary to delineate the ownership extent of underground assets. The current practice of underground land administration focuses on the ownership of underground space and mostly relies on 2D survey plans. This inefficient and fragmented 2D-based underground data management and communication results in several issues including boundary disputes, underground strikes, delays and disruptions in projects, economic losses, and urban planning issues. This study provides a review of underground land administration from three common aspects: legal, institutional, and technical. A range of important challenges have been identified based on the current research and practice. To address these challenges, the authors of this study propose a new framework for 3D underground land administration. The proposed framework outlines the future research directions to upgrade underground land administration using integrated 3D digital approaches.

2022 ◽  
Vol 54 (8) ◽  
pp. 1-41
Rafael Belchior ◽  
André Vasconcelos ◽  
Sérgio Guerreiro ◽  
Miguel Correia

Blockchain interoperability is emerging as one of the crucial features of blockchain technology, but the knowledge necessary for achieving it is fragmented. This fact makes it challenging for academics and the industry to achieve interoperability among blockchains seamlessly. Given this new domain’s novelty and potential, we conduct a literature review on blockchain interoperability by collecting 284 papers and 120 grey literature documents, constituting a corpus of 404 documents. From those 404 documents, we systematically analyzed and discussed 102 documents, including peer-reviewed papers and grey literature. Our review classifies studies in three categories: Public Connectors, Blockchain of Blockchains, and Hybrid Connectors. Each category is further divided into sub-categories based on defined criteria. We classify 67 existing solutions in one sub-category using the Blockchain Interoperability Framework, providing a holistic overview of blockchain interoperability. Our findings show that blockchain interoperability has a much broader spectrum than cryptocurrencies and cross-chain asset transfers. Finally, this article discusses supporting technologies, standards, use cases, open challenges, and future research directions, paving the way for research in the area.

2021 ◽  
Vol 11 (10) ◽  
pp. 1345
Yael Skversky-Blocq ◽  
Jan Haaker ◽  
Tomer Shechner

Vicarious threat learning is an important pathway in learning about safety and danger in the environment and is therefore critical for survival. It involves learning by observing another person’s (the demonstrator) fearful responses to threat and begins as early as infancy. The review discusses the literature on vicarious threat learning and infers how this learning pathway may evolve over human development. We begin by discussing the methods currently being used to study observational threat learning in the laboratory. Next, we focus on the social factors influencing vicarious threat learning; this is followed by a review of vicarious threat learning among children and adolescents. Finally, we examine the neural mechanisms underpinning vicarious threat learning across human development. To conclude, we encourage future research directions that will help elucidate how vicarious threat learning emerges and how it relates to the development of normative fear and pathological anxiety.

Within the last few decades, wireless connectivity has experienced an exponential growth. With far more features than 4G communications, next-generation (5G) will soon be available worldwide. In the year 2027 to 2030, the sixth- generation (6G) wireless system, fully supported by artificial intelligence, will become the dominant paradigm for wireless communication. Beyond 5G, the main factors to consider are higher system capacity, greater data rates, reduced latency, enhanced security, and improved quality of service (QoS) compared to current 5G systems. In this paper, we describe the strategy for future 6G wireless networks, emerging technologies and the architecture within which they will operate. This paper focuses on key performance indicators, applications, new services, and key technologies that could enable 6G networks. By presenting a new perspective on future research directions, this article will make a significant contribution to future research directions.

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