bluuebunny/crossref_metadata_2025_split huggingface dataset:
Glaciers and Land‐to‐Ocean Flux of Carbon
Authors: Paulsen Maria L. , Robson Benjamin A. 
Published: December 2019

Abstract
Glaciers, ice caps, and ice sheets currently cover 12% of the Earth's land surface. The vast majority of glaciers worldwide are now in a state of retreat at unprecedented rates, with the most substantial mass loss originating from Greenland (37% of the global). The mass of ice‐locked organic matter is substantial and represents a hitherto poorly understood reservoir of organic carbon. In this article, we aim to summarize the current data on the concentrations of organic carbon across glacial systems and its origin and fate. Further, we aim to discuss the land‐to‐ocean flux of organic carbon and the effect on downstream environments. Several studies have suggested the glacial dissolved organic carbon (DOC) to have a pronounced impact on the coastal ecosystems because glacial DOC is highly bioavailable, i.e. has a high potential to feed downstream heterotrophic organisms. These studies, however, do not consider that the bioavailable carbon of coastal systems is in fact higher than in the glacial runoff. Contrary to previous studies, we, therefore, stress that glaciers are not a major source of neither DOC or bioavailable DOC and instead identify new focus areas in the field, such as the influence of the catchment area and the role of particulate organic carbon.
Microplastics: A Global Water Pollution Problem
Authors: Weinstein John E. , Viado Hildehardo F. , Leads Rachel R. , Deloughry Emma , Schandera Louisa , Liddy Karlee , Scott Geoffrey I. 
Published: December 2019

Abstract
Microscopic particles of plastic, known as microplastics, have become a ubiquitous contaminant in the environment. Their presence in the marine environment has been correlated to the exponential increase in global plastic production over the past 70 years and the subsequent increased abundance of plastic litter in the oceans. Other sources of microplastics include synthetic microfibers associated with the washing of textiles and tire particles associated with the abrasion and wear of the tread on automobile tires. Microplastics are recognized as contaminants of emerging concern because they occupy the same size fraction as plankton and sediment, making them bioavailable to a wide range of organisms, and they have the potential to adversely impact environmental health. Ingestion of microplastics by humans is likely, but confounding any assessment of health impacts is the lack of estimates on the total human exposure to these particles. This article will review the magnitude of plastic production and waste, provide an overview of the major sources of microplastics in the aquatic environment and the hazards they pose to both environmental and human health, and present a case study of ongoing efforts to characterize the sources and fate of microplastic contamination in Charleston Harbor, SC, USA.
Lead in Groundwater: Chemical Behavior and Treatment
Authors: Jacobs James A. 
Published: December 2019

AbstractLead (Pb) is the most abundant of the heavy metals on Earth, with the average Pb content of the crust ranging from 13 to 16 parts per million (ppm). Although Pb is widely used in many applications, it can pose substantial health risks, including Pb poisoning. This article discusses the occurrence and properties of Pb, along with controls on fate and transport and common methods of Pb remediation.
Mercury in Groundwater: Chemical Behavior and Treatment
Authors: Jacobs James A. 
Published: December 2019

Abstract
Mercury is highly toxic and is rarely found as a pure metal. It is the only metal element that is a liquid at room temperature. There are three forms of mercury in the environment: elemental, inorganic, and organic mercury. All forms of mercury are toxic. This article discusses the forms and occurrence of mercury, along with health risks, controls on fate and transport, and potential methods of remediation. Specific regulatory guidelines in the United States are also discussed.
Remediation and Case Closure Policy for Petroleum Hydrocarbons
Authors: Vance David B. , Jacobs James A. 
Published: December 2019

Abstract
This article discusses regulatory changes regarding more realistic enforcement and achievable cleanup standards for petroleum hydrocarbons. Advantages of a risk‐based and future‐use approach to managing subsurface contamination are described in detail. Regulatory environmental goul evolve over time related to improvements in assessments of ecosystem impacts, human health exposure and remedial experience.
In SituAeration and Volatilization of Petroleum Hydrocarbons in Groundwater
Authors: Vance David B. , Jacobs James A. 
Published: December 2019

AbstractThere are a variety of groundwater remediation processes for petroleum hydrocarbons that usein situaeration and volatilization as a part of their technology. Some of these technologies have a bioremediation component to them as well. This article discusses groundwater remediation technologies including soil venting, soil vapor extraction, air sparging, bioventing, and biosparging. A case study of biosparging is described in detail.
Soil Vapor Data: Groundwater Applications
Authors: Hartman Blayne , Jacobs James A. 
Published: December 2019

AbstractSoil vapor data analysis can be applied to enhance groundwater investigations and subsurface interpretations. Collecting reproducible and representative soil vapor data in a subsurface sampling project is critical in the soil vapor sampling planning phase. Soil vapor data can be collected using active or passive methods. Specific vapor sampling protocols have been developed by regulatory agencies and others over the past three decades. Once the soil vapor samples have been collected and analyzed in a laboratory, interpretation of the data is critical in understanding vapor migration as well as the potential for soil vapor intrusion into subsurface conduits and into structures. This article begins with an overview of the various applications of soil vapor surveys, a brief discussion of the various soil vapor methods, and then focuses on a number of specific issues relating to soil vapor surveys for groundwater investigations. The intent of this article is to guide professionals on when, why, and how soil vapor data can be useful for groundwater‐related investigations and how to interpret the results.
Lead in Water and Soil: Speciation, Toxicity, and Treatment Technologies
Authors: Manecki Maciej 
Published: December 2019

AbstractLead (Pb) is widely distributed in the environment and its negative health effects, especially to children, have been well documented. The aqueous species of Pb, in their form and concentration, strongly depend on mineral–water interaction processes in the environment. Lead exists in the environment mostly in the form of solid particles but bioavailable toxic Pb is absorbed by living organisms through solution. Therefore, our understanding of formation, transformation, dissolution, and precipitation of Pb‐bearing phases in aqueous solutions is critical for successful strategies to minimize Pb in drinking water or food and to prevent exposure and poisoning. This article summarizes our current understanding of processes governing the presence of Pb in waters and soils, briefly discusses Pb toxicity, and reviews some key technologies for immobilizing Pb and making it less bioavailable. Finally, the article ends with some suggestions for further research.
Hydrodynamics of Lakes
Authors: Boegman Leon 
Published: December 2019

AbstractLake hydrodynamics change seasonally in response to the net heat flux through the free surface. Heating during summer causes seasonal stratification to develop, where basin‐scale hydrodynamics occur under a balance between the surface wind force, which displaces the stratification, and the restoring gravitational force, which acts to bring isotherms back to the horizontal. As a result of wind forcing, turbulent mixing may be strong within the surface layer and the boundary layers at the lake perimeter, with the lake interior remaining comparatively quiescent due to the stabilizing effect of the thermocline. Ice and snow cover, in winter, shelter the lake from wind stress and reduce convective motions, resulting in a “reverse” winter stratification. During spring and fall, net heat flux through the free surface, erodes the strength of the stratification, allowing penetrative convection and wind‐driven mixing to turnover the water column. These brief mixing periods, therefore, have profound implications for vertical biogeochemical fluxes. The lake response to wind forcing can be classified according to an energy balance or the dimensionless Wedderburn (or Lake) Number, both of which show strong seasonal dependence in accordance with changes in the net surface heat flux.
Massively Parallel and Flexible Processing forMIMOSystems
Authors: Nikitopoulos Konstantinos 
Published: December 2019

Abstract5G mobile systems and beyond are envisaged to provide very high throughput, to meet very strict requirements in terms of latency, and to support a very large number of devices in a very small area. Multiple‐input, multiple‐output (MIMO) systems can contribute to meeting these targets by enabling the concurrent transmission of a large number of information streams. In such MIMO systems, the choice of the corresponding required beamforming/precoding (in the downlink) and detection (in the uplink) algorithms can determine how much of the overall MIMO channel capacity and how much of MIMO's inherent capability to support multiple users we can exploit in practice. Linear beamforming and detection approaches are practical, but they highly underutilize the MIMO channel. Nonlinear methods can provide substantial gains, both in terms of throughput and connectivity, but their complexity increases exponentially with the number of concurrently transmitted information streams. This complexity, together with the soon‐to‐be‐reached plateau in the speed of processors, urges a paradigm shift toward massively parallel signal processing for wireless communications systems. Ideal parallelization methods should be scalable to any number of available processing elements, generic, adjustable to the transmission conditions, and transparent to the choice of the implementation platform. Promising parallelization algorithms in this direction enable up to 70% throughput gains without changing the number of base‐station antennas and RF chains, and can substantially increase the number of connected devices, with processing latency requirements similar to those of linear approaches.
Random Access for Machine‐Type Communications
Authors: Leyva‐Mayorga Israel , Stefanovic Cedomir , Popovski Petar , Pla Vicent , Martinez‐Bauset Jorge 
Published: December 2019

AbstractThe success of 5G wireless networks (5G) substantially relies on efficiently embracing machine‐type communications (MTC), intended to support autonomous exchange of data between devices. Typical MTC applications include smart metering, e‐health care, environmental and structural monitoring, and asset tracking. Therefore, MTC is an essential component of smart cities and the Internet of Things (IoT). However, cellular networks have traditionally been designed to efficiently handle human‐to‐human (H2H) traffic, whose characteristics greatly differ from those of MTC traffic. Only recently the cellular networks started to be optimized for MTC and, in that sense, a special focus has been put on the random access (RA), which occurs whenever a device requests initial access to a base station (BS). Specifically, the RA mechanism of cellular networks is based on the slotted ALOHA protocol, whose efficiency degrades rapidly as the number of users increases, also presenting a large signaling overhead when short packets are transmitted. The RA channels are further challenged by massive machine‐type communications (mMTC) applications, where a great number of MTC devices attempt to access the BS, while the class of MTC applications with strict latency requirements is challenged by the signaling overhead. These problems have been inherited from the H2H‐oriented cellular systems and, while numerous solutions have been proposed, there is still no consensus on the MTC enhancements for the second phase of 5G standardization.
Full‐Duplex in Small‐Cell Networks
Authors: Hong Jun‐Pyo 
Published: December 2019

AbstractBased on recent advances in analog/digital circuits for self‐interference cancellation, the use of full duplex (FD) in small‐cell networks has been receiving increasing attention as a promising solution to cope with explosive demand for wireless communications. FD operation has the potential to double the spectral efficiency of point‐to‐point communications by enabling concurrent transmission and reception over the same frequency band. However, the spectral efficiency gain of FD can be significantly limited in small‐cell networks if traditional strategies developed for half duplex (HD) are reused without careful consideration of cross‐mode interference. In this article, we look at some major issues in developing FD communication strategies for small‐cell networks and introduce recent results on spectral efficiency gains of FD over HD in various networks.First, we focus on single‐antenna systems. To improve mitigate the cross‐mode interference, selection diversity is exploited by allocating the same channel to widely separated uplink/downlink users, opportunistically scheduling uplink/downlink user pair, and selecting FD/HD mode. In particular, the spectral efficiency gain of FD over HD can be at most about 20% in randomly deployed large networks. This low gain comes from the limited interference avoidance capability of single‐antenna systems. Second, we shift our focus to multi‐antenna systems. By means of multi‐antenna techniques, multi‐antenna system can effectively mitigate the aggregated network interference. In particular, the FD operation can asymptotically double the spectral in randomly deployed large networks with massive MIMO. Finally, we present challenges and opportunities in developing FD strategies for future small‐cell networks.
MassiveMIMO
Authors: Zhang Ticao , Mao Shiwen 
Published: December 2019

AbstractMassive MIMO has been regarded as a promising technique for 5G wireless communication networks. It equips the base station (BS) with a large number of antennas to serve a set of user equipment (UEs) simultaneously. Due to channel hardening, the uncorrelated noise and the small‐scale fading can be eliminated. As a result, the transmitted signal can be directed into very focused areas, which brings orders‐of‐magnitude improvements in both spectral efficiency and energy efficiency with simple (linear) processing. In this chapter, we present a comprehensive overview of the state‐of‐the‐art research on massive MIMO. We begin with an information theoretic analysis to illustrate the advantages of massive MIMO. Then, we introduce both the physical layer and networking issues of massive MIMO. The integration of other 5G technologies with massive MIMO is also reviewed. Finally, we conclude this article with a discussion of challenges and future research topics.
Energy‐Efficient Offloading for Mobile Edge Computing
Authors: You Changsheng , Mao Yuyi , Zhang Jun , Huang Kaibin 
Published: December 2019

AbstractThe visions of Internet of Things and 5G communications have driven the evolution of mobile computing paradigm, shifting from the centralized mobile cloud computing toward mobile edge computing (MEC). By pushing mobile computing, network control, and storage to the network edges (e.g. base stations and wireless access points), MEC is expected to enable computation‐intensive and latency‐critical applications at the resource‐limited mobile devices. MEC promises dramatic reduction in mobile energy consumption and latency, tackling the key challenges for realizing the 5G visions. The promised gains of MEC have motivated extensive research efforts in both academia and industry. A main thrust of MEC research is to seamlessly integrate the two disciplines of wireless communications and mobile computing, leading to a wide range of new designs ranging from techniques for energy‐efficient computation offloading to network architectures. This article first introduces the basic principles of computation offloading in MEC, and then provides a comprehensive survey of the state‐of‐the‐art MEC research with emphasis on energy‐efficient computation offloading and joint radio‐and‐computational resource management. Last, we introduce recent 5G standardization efforts on MEC as well as typical use scenarios.
An Introduction on Millimeter Wave Communications
Authors: He Shiwen , Huang Yongming 
Published: December 2019

AbstractIn the past few years, millimeter wave (mmWave) communication has attracted significant attention both from industry and academia, due to the large available spectrum at mmWave frequency bands. With the significantly increased communication bandwidth, mmWave communication is able to achieve tremendous data rate (e.g. on the order of dozens of Gbps) to satisfy the ever‐increasing traffic demand in 5G‐and‐beyond wireless networks. This article aims to give an introductory overview on the fundamentals of mmWave communication, including the general background of mmWave systems, the propagation characteristics of mmWave channels, followed by the design of hybrid antenna architecture to balance the trade‐off between the hardware cost and the system performance. The state of the art for the design of hybrid precoding/combining and channel acquisition for mmWave systems will be highlighted.
Network Economics of Spectrum Management
Authors: Jiang1 Changkun , Duan2 Lingjie 
Published: December 2019

AbstractProviding economic incentives is essential for the success of sustainable spectrum management. There are two promising spectrum management schemes, namely, database‐assisted and cooperative spectrum sharing. In the former one, a spectrum database centrally identifies idle spectrum from primary users (PUs), and exclusively allocates the spectrum to secondary users (SUs). In the latter one, users trade spectrum in a distributed manner and SUs relay PU traffics in exchange for their own spectrum access. In this article, we present the economic design and analysis for (i) spectrum database management via centralized pricing and admission control, and (ii) cooperative peer‐to‐peer spectrum sharing via contract mechanism design. In part (i), we study how to maximize a database operator's revenue through joint pricing and admission control. We formulate the revenue maximization problem, considering the stochastic and heterogeneous SU demands. We study the optimal solutions under both static and dynamic pricing, showing that dynamic pricing can improve revenue by 30%. In part (ii), we study cooperative spectrum sharing under incomplete information, where SUs' wireless characteristics are private information and not known by PUs. We model the PU–SU interaction as a labor market using contract theory. We study the optimal contract design for both weakly and strongly incomplete information scenarios. In the former one, we show that the PU will optimally hire the most efficient SUs and the PU achieves the same maximum utility as in the complete information benchmark. In the latter one, however, the PU may conservatively hire less‐efficient SUs as well.
Aerial Networks
Authors: Kim Minsu , Kim Dongsun , Lee Jemin 
Published: December 2019

AbstractOn unmanned aerial vehicle (UAV) communications, we can obtain better communication performance due to line‐of‐sight (LoS) environments and flexible mobility. It also means that received signal power of the interference link increases as the interference link is in the LoS environment. Hence, we analyze the successful transmission probability (STP) of the aerial network in the presence of the interfering node by considering channel fadings and channel components, which are affected by the elevation angle of the communication link. We present the STP for noise‐limited environments and interference‐limited environments in closed‐form expressions. We also show the non‐line‐of‐sight (NLoS) environments for both main and interference links can be better than the LoS environments for both main and interference links if the effect of the interfering signal is more dominant than that of the transmitting signal. Furthermore, we present the aerial network with multiple interfering nodes and the multi‐layer aerial network, where various types of UAVs form aerial networks in different heights with different densities and transmission power, and show the existence of optimal height and density of the UAV that maximize the STP.
AI‐Enabled Radio Access Network
Authors: Jang Han Seung , Lee Hoon 
Published: December 2019

Abstract
Initialization and performance optimization of wireless networks are key enablers for the fifth‐generation (5G) radio access network (RAN) design. However, heterogeneity of wireless devices and massive connectivity requirements on 5G systems result in intractable end‐to‐end communication models where traditional model‐based wireless protocols cannot be straightforwardly applied. To tackle this issue, a new 5G RAN design paradigm is addressed based on artificial intelligence (AI) techniques, which lead to data‐driven optimization solutions for nontrivial implementation problems of 5G systems. Still, however, it has not been adequately investigated how to include AI technologies into 5G RAN architecture. To answer this fundamental question, this article illustrates the possibility and the feasibility of using AI for handling implementation difficulties occurring in 5G communication systems. The way to replace traditional model‐based communication solutions with AIs is investigated, especially focused on massive random access and nonconvex resource management applications. Several examples of reinforcement learning, supervised learning, and unsupervised learning techniques applied to 5G RAN are visited. Recent successes of AI‐defined 5G RAN verify that AIs can effectively identify unknown and optimal communication rules in various networking scenarios including initial accessing protocols for massive connectivity and wireless resource control strategies for network performance optimization.
Slicing Across Multiple Operators and Domains
Authors: Vaishnavi Ishan 
Published: December 2019

AbstractThis article presents the background, current status, and the possible future directions on multidomain telecommunication networks, with particular focus on multioperator networks. The article starts by giving a short background on development virtualization and programmable networks that led to the need of creating multidomain telecommunication networks. The solutions present in the industry today are typically in technology silos, which seldom had the need to interact among those silos. As this article will show deployed telecom networks often consist of a criss‐cross of innumerable technology silos resulting in a very large operational expenditure (OPEX) for the operator. Multiple efforts with the aim of reducing operational expenditure (OPEX) for the operator have been proposed and concluded finally resulting in a standards organization that has the objective of integrating those silos into a common architectural technology independent framework and extending itself to the case where the different technologies may also be operated by different operators. This article is a story of the developments that lead to where we are today, in particular focusing on the final status in multidomain and multioperator networks.