bluuebunny/crossref_metadata_2025 huggingface dataset:
Understanding the Effect of Cementitious Grouting Pressure on Micro-Fracture Permeability for Rock Reinforcement Underground: A Lab Study
Authors: Wang Kai , Wang Lianguo , Ren Bo , Fan Hao
Published: August 2020

In grouting support projects, due to the small concealment of micro-fractures, the support effect often fails to meet design requirements. The percolation effect is a common factor that causes grouting failure, and the influence of grouting pressure on the percolation effect is very obvious. In this article, a design of a micro-fracture grouting experimental system is presented that can realize high-pressure grouting and then uses a variety of ultrafine cements to carry out high- and low-pressure grouting tests under different fracture opening conditions, thereby obtaining the grouting pressure and accumulated grouting weight during the grouting process. The results show that a combination of the grouting pressure curve and the cumulative grouting weight curve can determine whether the ultrafine cement will have a percolation effect. Increasing the grouting pressure can reduce the critical fracture opening value and also reduce the occurrence of the percolation effect. The research results provide a theoretical basis for the high-pressure grouting of micro-fracture rock masses and offer certain guiding significance for the design of high-pressure grouting support schemes.
Real-Time Control of Plug-in Electric Vehicles for Congestion Management of Radial LV Networks: A Comparison of Implementations
Authors: García Veloso César , Rauma Kalle , Fernández Julián , Rehtanz Christian
Published: August 2020

The global proliferation of plug-in electric vehicles (PEVs) poses a major challenge for current and future distribution systems. If uncoordinated, their charging process may cause congestion on both network transformers and feeders, resulting in overheating, deterioration, protection triggering and eventual risk of failure, seriously compromising the stability and reliability of the grid. To mitigate such impacts and increase their hosting capacity in radial distribution systems, the present study compares the levels of effectiveness and performances of three alternative centralized thermal management formulations for a real-time agent-based charge control algorithm that aims to minimize the total impact upon car owners. A linear formulation and a convex formulation of the optimization problem are presented and solved respectively by means of integer linear programming and a genetic algorithm. The obtained results are then compared, in terms of their total impact on the end-users and overall performance, with those of the current heuristic implementation of the algorithm. All implementations were tested using a simulation environment considering multiple vehicle penetration and base load levels, and equipment modeled after commercially available charging stations and vehicles. Results show how faster resolution times are achieved by the heuristic implementation, but no significant differences between formulations exist in terms of network management and end-user impact. Every vehicle reached its maximum charge level while all thermal impacts were mitigated for all considered scenarios. The most demanding scenario showcased over a 30% reduction in the peak load for all thermal variants.
A Review of Approaches for the Detection and Treatment of Outliers in Processing Wind Turbine and Wind Farm Measurements
Authors: Zou Mingzhe , Djokic Sasa Z.
Published: August 2020

Due to the significant increase of the number of wind-based electricity generation systems, it is important to have accurate information on their operational characteristics, which are typically obtained by processing large amounts of measurements from the individual wind turbines (WTs) and from the whole wind farms (WFs). For further processing of these measurements, it is important to identify and remove bad quality or abnormal data, as otherwise obtained WT and WF models may be biased, or even inaccurate. There are wide ranges of both causes and manifestations of these bad/abnormal data, which are often denoted with the common general term “outlier”. This paper reviews approaches for the detection and treatment of outliers in processing WT and WF measurements, starting from the discussion of the commonly measured parameters, variables and resolutions, as well as the corresponding requirements and recommendations in related standards. Afterwards, characteristics and causes of outliers reported in existing literature are discussed and illustrated, as well as the requirements for the data rejection in related standard. Next, outlier identification methods are reviewed, followed by a review of approaches for testing the success of outlier removal procedures, with a discussion of their potential negative effects and impact on the WT and WF models. Finally, the paper indicates some issues and concerns that could be of interests for the further research on the detection and treatment of outliers in processing WT and WF measurements.
Modeling, Control and Power Management of Six-Phase PMSM Based Shipboard MVDC Distribution System
Authors: Lamichhane Anil , Zhou Lidan , Yao Gang , Luqman Muhammad
Published: August 2020

In the modern shipboard power system, there is a growing concern about reduced fuel economy, efficiency improvement, and minimized emission in recent years. Besides, considering the islanded nature of the shipboard power system, ensuring the system reliability at both generation and load side is crucial. In this context, a hybrid medium voltage DC (MVDC) distribution system concept with diesel engine, PV system, and battery energy storage system (BESS) as the generators for the shipboard power system is proposed. Variable speed operation of a diesel engine is considered for the benefit of minimal specific fuel oil consumption (SFOC). Regarding the fault-tolerant characteristics of six-phase permanent magnet synchronous machine (PMSM), it is used for both generating and motoring application, thus maintaining system reliability at any time. A hierarchical control system is designed and implemented to ensure proper load power-sharing among the generators and to regulate the dc-link voltage of the proposed MVDC distribution system. To bolster the intent of minimal SFOC zone operation of diesel engines and coordination between the generators and load, a deterministic rule-based power management system is proposed and implemented. The simulation is carried out for potential operational modes of a cruise ship in the MATLAB/Simulink environment. Simulation results show that the proposed topological and control structure has satisfactory performance in terms of power delivery, stable dc-link dynamics, and overall system stability.
Approximation Framework of Embodied Energy of Safety: Insights and Analysis
Authors: Zhong Zijia , Zhu Lei , Young Stanley
Published: August 2020

Transportation safety, as a critical component of an efficient and reliable transportation system, has been extensively studied with respect to societal economic impacts by transportation agencies and policy officials. However, the embodied energy impact of safety, other than induced congestion, is lacking in studies. This research proposes an energy equivalence of safety (EES) framework to provide a holistic view of the long-term energy and fuel consequences of motor vehicle crashes, incorporating both induced congestion and impacts from lost human productivity resulting from injury and fatal accidents and the energy content resulting from all consequences and activities from a crash. The method utilizes a ratio of gross domestic product (GDP) to national energy consumed in a framework that bridges the gap between safety and energy, leveraging extensive studies of the economic impact of motor vehicle crashes. The energy costs per fatal, injury, and property-damage-only (PDO) crashes in gasoline gallon equivalent (GGE) in 2017 were found to be 200,259, 4442, and 439, respectively, which are significantly greater than impacts from induced congestion alone. The results from the motor vehicle crash data show a decreasing trend of EES per crash type from 2010 and 2017, due primarily in part to a decreasing ratio of total energy consumed to GDP over those years. In addition to the temporal analysis, we conducted a spatial analysis addressing national-, state-, and local-level EES comparisons by using the proposed framework, illustrating its applicability.
Energy Internet, the Future Electricity System: Overview, Concept, Model Structure, and Mechanism
Authors: Joseph Akhil , Balachandra Patil
Published: August 2020

Energy Internet, a futuristic evolution of electricity system, is conceptualized as an energy sharing network. Its features, such as plug-and-play mechanism, real-time bidirectional flow of energy, information, and money can lead to significant benefits and innovation in electricity production and utilization. Energy Internet integrates small-scale renewable energy systems, electric loads, storage devices, and electric vehicles for effective transaction of power backed by emerging technologies such as Internet of Things, vehicle-to-grid, and blockchain. At present, there is no scaled-up working model of Energy Internet, and literature is scarce, which makes the research in this domain significant, novel, and timely. Given this, an attempt is made to develop the conceptual model of an Energy Internet, elaborate its structure and components, and discuss its operational principles. First, a comprehensive overview of Energy Internet is presented along with its aptness as a future evolution of electricity system. Second, concepts, architectures, and features that underpin Energy Internet are outlined. Third, concept of ‘Energy Intranet’ is introduced to denote the scaled-down version of Energy Internet, which embodies energy prosumers and local energy markets to form a local energy cluster. Finally, discussion is presented on the network structure of Energy Internet, relevance of emerging technologies and innovative operational mechanisms.
Analytical Modeling of the Cyclic ES-SAGD Process
Authors: Manfre Jaimes Diego , Clarke Matthew
Published: August 2020

Approximately half of the daily oil production from the Canadian oil sands comes from the application of steam assisted gravity drainage (SAGD). Due to the high steam requirements of SAGD, many studies have focused on solvent injection as a means of reducing the steam consumption. One of the multiple variations of the steam-solvent injection process consists on the intermittent co-injection of solvent with steam, also known as a cyclic expanding-solvent (ES)-SAGD process. The current study represents a first attempt to create an analytical model that can describe a cyclic ES-SAGD process. The proposed analytical model uses previous SAGD and ES-SAGD models to describe the steam plus solvent stages of the process. The results obtained from the analytical model were contrasted against numerical simulation results for cases in which the solvent was hexane, pentane, and butane, as well as for cases in which hexane is a solvent and the injection cycle length is variable. In all cases, it was seen that the cumulative oil production computed by the analytical model and the numerical model are in good agreement. Over the range of conditions that were tested the absolute relative difference in the cumulative oil production, after a period of 10 years, ranged from 8.6% to 9.4%, with a median value of 9%. However, compared to the numerical simulations, the analytical model did not fully match the oil rate and the steam chamber shape. This difference was attributed to the analytical model’s simplified description of heat and mass transfer during the process. Thus, it is recommended that further studies be conducted, and recommendations for further investigations are given.
The Effect of Contact-Drying on Physical Properties of European Beech (Fagus sylvatica L.)
Authors: Klement Ivan , Vilkovský Peter , Vilkovská Tatiana
Published: August 2020

Beech wood is mainly used for furniture, plywood, decorative veneer manufacturing or packaging. Timber or lumber is traditionally dried in kilns by processes often taking several weeks. This research deals with more rapid process called contact-drying process. Drying was performed using the heating plates with a temperature of 160 °C and pressures of 1.0 MPa, 1.4 MPa and 1.8 MPa. The results were compared to conventional warm-air drying. The warm-air drying mode was divided into two phases, with and without free water and bound water in the dried wood. The density of the samples increased remarkably during the contact-drying. The effect of the pressure of the heating plates was substantial. The difference in the average density between the pressure of 1.0 MPa and 1.8 MPa was more than 22 kg·m−3. The pressure of the heating plates affected the process and the resulting change in the sample thickness. The change in the sample thickness was more considerable in the case of the tangential samples. The thickness did not increase significantly after air conditioning. During contact-drying, the hygroscopicity and absorptivity of wood reduced on average by 21.24% and 25%, respectively, compared to warm-air drying.
Progressive Teaching Improvement For Small Scale Learning: A Case Study in China
Authors: Jiang Bo , He Yanbai , Chen Rui , Hao Chuanyan , Liu Sijiang , Zhang Gangyao
Published: August 2020

Learning data feedback and analysis have been widely investigated in all aspects of education, especially for large scale remote learning scenario like Massive Open Online Courses (MOOCs) data analysis. On-site teaching and learning still remains the mainstream form for most teachers and students, and learning data analysis for such small scale scenario is rarely studied. In this work, we first develop a novel user interface to progressively collect students’ feedback after each class of a course with WeChat mini program inspired by the evaluation mechanism of most popular shopping website. Collected data are then visualized to teachers and pre-processed. We also propose a novel artificial neural network model to conduct a progressive study performance prediction. These prediction results are reported to teachers for next-class and further teaching improvement. Experimental results show that the proposed neural network model outperforms other state-of-the-art machine learning methods and reaches a precision value of 74.05% on a 3-class classifying task at the end of the term.
Mode and Tempo of Microsatellite Evolution across 300 Million Years of Insect Evolution
Authors: Jonika Michelle , Lo Johnathan , Blackmon Heath
Published: August 2020

Microsatellites are short, repetitive DNA sequences that can rapidly expand and contract due to slippage during DNA replication. Despite their impacts on transcription, genome structure, and disease, relatively little is known about the evolutionary dynamics of these short sequences across long evolutionary periods. To address this gap in our knowledge, we performed comparative analyses of 304 available insect genomes. We investigated the impact of sequence assembly methods and assembly quality on the inference of microsatellite content, and we explored the influence of chromosome type and number on the tempo and mode of microsatellite evolution across one of the most speciose clades on the planet. Diploid chromosome number had no impact on the rate of microsatellite evolution or the amount of microsatellite content in genomes. We found that centromere type (holocentric or monocentric) is not associated with a difference in the amount of microsatellite content; however, in those species with monocentric chromosomes, microsatellite content tends to evolve faster than in species with holocentric chromosomes.
Assembling Reads Improves Taxonomic Classification of Species
Authors: Tran Quang , Phan Vinhthuy
Published: August 2020

Most current approach to metagenomic classification employ short next generation sequencing (NGS) reads that are present in metagenomic samples to identify unique genomic regions. NGS reads, however, might not be long enough to differentiate similar genomes. This suggests a potential for using longer reads to improve classification performance. Presently, longer reads tend to have a higher rate of sequencing errors. Thus, given the pros and cons, it remains unclear which types of reads is better for metagenomic classification. We compared two taxonomic classification protocols: a traditional assembly-free protocol and a novel assembly-based protocol. The novel assembly-based protocol consists of assembling short-reads into longer reads, which will be subsequently classified by a traditional taxonomic classifier. We discovered that most classifiers made fewer predictions with longer reads and that they achieved higher classification performance on synthetic metagenomic data. Generally, we observed a significant increase in precision, while having similar recall rates. On real data, we observed similar characteristics that suggest that the classifiers might have similar performance of higher precision with similar recall with longer reads. We have shown a noticeable difference in performance between assembly-based and assembly-free taxonomic classification. This finding strongly suggests that classifying species in metagenomic environments can be achieved with higher overall performance simply by assembling short reads. Further, it also suggests that long-read technologies might be better for species classification.
Probabilistic-Based Assessment of Liquefaction-Induced Damage with Analytical Fragility Curves
Authors: Forcellini Davide
Published: August 2020

Soil liquefaction may cause severe damages to structures mainly in terms of lateral spread and settlements, as documented during historical earthquakes. Liquefaction-potential (LP) estimation has become an important issue in seismic assessment, and this paper aims to propose a new methodology based on fragility curves. LP curves were developed and applied to two case studies performed with 3D numerical models applying Opensees. Nonlinear hysteretic materials and advanced plasticity models were used to reproduce the high nonlinear mechanisms of liquefaction, such as strong dilation tendency and cyclic shear behaviour. LP curves were applied to compare the results of the performed free field (FF) and soil–structure interaction (SSI) case studies.
Vegetation and Fluvial Geomorphology Dynamics after an Urban Fire
Authors: Mathews Lauren E. H. , Kinoshita Alicia M.
Published: August 2020

The goal of this research was to characterize the impact of invasive riparian vegetation on burn severity patterns and fluvial topographic change in an urban Mediterranean riverine system (Med-sys) after fire in San Diego, California. We assessed standard post-fire metrics under urban conditions with non-native vegetation and utilized field observations to quantify vegetation and fluvial geomorphic processes. Field observations noted both high vegetation loss in the riparian area and rapidly resprouting invasive grass species such as Arundo donax (Giant Reed) after fire. Satellite-based metrics that represent vegetation biomass underestimated the initial green canopy loss, as did volumetric data derived from three-dimensional terrestrial laser scanning data. Field measurements were limited to a small sample size but demonstrated that the absolute maximum topographic changes were highest in stands of Arundo donax (0.18 to 0.67 m). This work is the first quantification of geomorphic alterations promoted by non-native vegetation after fire and highlights potential grass–fire feedbacks that can contribute to geomorphic disruption. Our results support the need for ground-truthing or higher resolution when using standard satellite-based indices to assess post-fire conditions in urban open spaces, especially when productive invasive vegetation are present, and they also emphasize restoring urban waterways to native vegetation conditions.
Automated Land Cover Change Detection and Forest Succession Monitoring Using LiDAR Point Clouds and GIS Analyses
Authors: Szostak Marta
Published: August 2020

This paper investigates the possibility of applying light detection and ranging (LiDAR) point clouds and geographic information system (GIS) analyses for land use and land cover (LULC) change detection, mainly with a view to monitoring uncontrolled forest succession occurring on postagricultural lands. The research was conducted in a part of the administrative district of Milicz (in the central-west area of Poland). The areas of interest were parcels in which agricultural use has been abandoned and forest succession processes have progressed. The airborne laser scanning (ALS) data (acquired in 2007, 2012, and 2015) revealed detailed changes in land cover as a result of the progression in the forest succession process. Using the ALS data, the LULC changes and the progress of secondary forest succession are shown, and the vegetation parameters (LiDAR metrics) are presented.
The Soul of the Phonograph: Media-Technologies, Auditory Experience, and Literary Modernism in the Age of COVID-19
Authors: Goebel Rolf J.
Published: August 2020

The unpredictable duration of the COVID-19 pandemic necessitates renewed reflection on our collective reliance on video platforms such as Zoom and YouTube for telecommunication and music listening purposes, which have virtually filled the gap left by widely cancelled live performances. The affectively close relationship we forge with these services today echoes a recurrent theme in literary modernism: the tendency to endow early mechanical sound reproduction machines such as the phonograph and the record player with quasi-human subjectivity, emotions, and agency. This historical topos, in turn, anticipates posthumanism’s fascination with the seamless interface between machine-intelligence and its human users. Thinking about these cultural continuities may help the Humanities articulate the crucial role of media technologies and literary discourses under exceptional circumstances.
The Upshot on Princess Merida in Disney/Pixar’s Brave: Why the Tomboy Trajectory Is Off Target
Authors: Dundes Lauren
Published: August 2020

Princess Merida, the “tomboy” princess in Disney/Pixar’s Brave, won praise for escaping the strictures of femininity and maternal demands for feminine propriety. In addition to her overt defiance of gender roles and demand for agency, Merida also enacts hegemonic masculinity by mocking her suitors during an archery contest in which she is the prize. The ridicule is the prelude to her dramatic, winning bullseye that feminizes the men, in a scene rich in symbolism about gender and power. In enacting the final phase of the tomboy paradigm, however, Merida reverses her trajectory as her rebellion against femininity ebbs. She then resolves conflict by displaying vulnerability rather than performing brave deeds. This marked shift to a more traditional gender role raises questions about her stature as a model of autonomy able to withstand the pressure to conform.
Artificial Intelligence and Suicide Prevention: A Systematic Review of Machine Learning Investigations
Authors: Bernert Rebecca A. , Hilberg Amanda M. , Melia Ruth , Kim Jane Paik , Shah Nigam H. , Abnousi Freddy
Published: August 2020

Suicide is a leading cause of death that defies prediction and challenges prevention efforts worldwide. Artificial intelligence (AI) and machine learning (ML) have emerged as a means of investigating large datasets to enhance risk detection. A systematic review of ML investigations evaluating suicidal behaviors was conducted using PubMed/MEDLINE, PsychInfo, Web-of-Science, and EMBASE, employing search strings and MeSH terms relevant to suicide and AI. Databases were supplemented by hand-search techniques and Google Scholar. Inclusion criteria: (1) journal article, available in English, (2) original investigation, (3) employment of AI/ML, (4) evaluation of a suicide risk outcome. N = 594 records were identified based on abstract search, and 25 hand-searched reports. N = 461 reports remained after duplicates were removed, n = 316 were excluded after abstract screening. Of n = 149 full-text articles assessed for eligibility, n = 87 were included for quantitative synthesis, grouped according to suicide behavior outcome. Reports varied widely in methodology and outcomes. Results suggest high levels of risk classification accuracy (>90%) and Area Under the Curve (AUC) in the prediction of suicidal behaviors. We report key findings and central limitations in the use of AI/ML frameworks to guide additional research, which hold the potential to impact suicide on broad scale.
Performance of Five Postharvest Storage Methods for Maize Preservation in Northern Benin
Authors: Baributsa Dieudonne , Bakoye Ousmane Nouhou , Ibrahim Baoua , Murdock Larry L.
Published: August 2020

Several postharvest technologies are currently being commercialized to help smallholder farmers in sub-Saharan Africa reduce grain storage losses. We carried out a study in Northern Benin to compare the effectiveness of five technologies being sold to protect stored grain. Maize that had been naturally infested by insects was stored in four hermetic storage technologies (SuperGrainbag™, AgroZ® bag, EVAL™, and Purdue Improved Crop Storage-PICS™ bags), an insecticide impregnated bag (ZeroFly®), and a regular polypropylene (PP) woven bag as control. Oxygen levels in hermetic bags fluctuated between 0.5 ± 0.0 (v/v) and 1.0 ± 0.3 (v/v) percent during the seven months of storage. No weight loss or insect damage was observed in grain stored in any of the hermetic storage bags after seven months. However, grain stored in ZeroFly® and PP woven bags had weight losses of 6.3% and 10.3%, respectively. These results will help farmers and development agencies when making decisions to use and/or promote storage technologies to reduce postharvest grain losses.
Environmental Influence on the Spatiotemporal Variability of Spawning Grounds in the Western Guangdong Waters, South China Sea
Authors: Lu Yao , Yu Jing , Lin Zhaojin , Chen Pimao
Published: August 2020

Spawning grounds occupy an important position in the supplementary population of fishery resources, especially in Western Guangdong waters (WGWs) in the northern South China Sea (SCS), where fishery resources are being depleted. This study investigated the environmental effects on the spatiotemporal variability of spawning grounds in WGWs, on the basis of generalized additive models (GAMs) and central spawning-ground gravity (CoSGG) by using satellite and in situ observations. Results showed that 57.2% of the total variation in fish-egg density in WGWs was explained. On the basis of stepwise GAMs, the most important factor was sea surface salinity (SSS), with a contribution of 32.1%, followed by sea surface temperature (SST), water depth, month, and chlorophyll a concentration (Chl-a), with contributions of 10.7%, 8.8%, 2.6%, and 2.6%, respectively. Offshore distance had slight influence on the model, explaining approximately 0.4% of the variation in fish-egg density. In summary, fish eggs in WGWs were mainly distributed in the area with SSS of 32.0–34.0 Practical Salinity Unit (PSU), SST of 24–27 °C, and depth of 0–18 m. CoSGG shifted eastwards by 0.38° N and northwards by 0.26° E from April to June. The distribution of spawning grounds in the WGW was affected by the Western Guangdong coastal current (WGCC), cyclonic circulation, the SCS warm current (SCSWC), and changes in the habitat environment (such as SST). Fish in WGWs tend to spawn in areas with a high seabed slope and steep terrain (near the Qiongzhou Strait).
Changes in the Diversity of Human Skin Microbiota to Cosmetic Serum Containing Prebiotics: Results from a Randomized Controlled Trial
Authors: Hong Ki-Bae , Hong Yang Hee , Jung Eun Young , Jo Kyungae , Suh Hyung Joo
Published: August 2020

Prebiotic treatment may rebalance the skin microbiota by regulating the growth of harmful and beneficial microorganisms. In this randomized, double-blind, placebo-controlled clinical trial (N = 60), we evaluated the effects of a cosmetic serum containing galacto-oligosaccharides (GOS) on the balance of the skin microbiota by measuring various skin parameters. The skin water-holding capacity between the control (ND) and experimental (NF) groups was significantly different after 8 weeks of serum treatment (p < 0.05). Similarly, changes in transepidermal water loss (TEWL) and the erythema index in the ND and NF groups were significantly different (p < 0.05). Furthermore, the wrinkle depth and Staphylococcus aureus population decreased in the NF group compared with those in the ND group (p < 0.05). The mean form factor, Shannon index, and Pediococcus population were significantly increased in the post-NF group compared with those in the post-ND group (p < 0.05). Finally, in the ND group, water-holding capacity was positively correlated with Enhydrobacter, whereas Enterobacteriaceae was negatively correlated with TEWL in the NF group. These results suggest that GOS inhibit the growth of harmful skin microbes and increase the population of beneficial microbes.
Temporal Aggregation and Long Memory for Asset Price Volatility
Authors: Perron Pierre , Shi Wendong
Published: August 2020

The effects of temporal aggregation and choice of sampling frequency are of great interest in modeling the dynamics of asset price volatility. We show how the squared low-frequency returns can be expressed in terms of the temporal aggregation of a high-frequency series. Based on the theory of temporal aggregation, we provide the link between the spectral density function of the squared low-frequency returns and that of the squared high-frequency returns. Furthermore, we analyze the properties of the spectral density function of realized volatility series, constructed from squared returns with different frequencies under temporal aggregation. Our theoretical results allow us to explain some findings reported recently and uncover new features of volatility in financial market indices. The theoretical findings are illustrated via the analysis of both low-frequency daily Standard and Poor’s 500 (S&P 500) returns from 1928 to 2011 and high-frequency 1-min S&P 500 returns from 1986 to 2007.
Risk-Sharing and the Creation of Systemic Risk
Authors: Acharya Viral V. , Iyer Aaditya M. , Sundaram Rangarajan K.
Published: August 2020

We address the paradox that financial innovations aimed at risk-sharing appear to have made the world riskier. Financial innovations facilitate hedging idiosyncratic risks among agents; however, aggregate risks can be hedged only with liquid assets. When risk-sharing is primitive, agents self-hedge and hold more liquid assets; this buffers aggregate risks, resulting in few correlated failures compared to when there is greater risk sharing. We apply this insight to build a model of a clearinghouse to show that as risk-sharing improves, aggregate liquidity falls but correlated failures rise. Public liquidity injections, for example, in the form of a lender-of-last-resort can reduce this systemic risk ex post, but induce lower ex-ante levels of private liquidity, which can in turn aggravate welfare costs from such injections.
Experimental Assessment of Thermal Performance and Bridging Effects of Low-Cost Sandwich Panels under a High-Temperature Impinging Jet
Authors: Ye Wei , Cai Jian , Huang Yixiang , Zhi Chengqiang , Zhang Xu
Published: August 2020

Sandwich panels are commonly used across industries for their ability to bear structural and thermal loads. In this paper, a panel chamber matching apparatus was designed to investigate the thermal performance of eight steel-based panels by exposing them to an impinging jet at approximately 550 °C for 30 min. Three types of low-cost materials (polycrystalline filaments, silica aerogel, and aluminum silicate) were used as the insulation core. The temperature of the panel surfaces was measured, as well as the metallic fasteners, including bolts, nails, battens, seams, and angle iron, to examine their thermal bridge effects. Major conclusions include the following: first, the maximum temperature on the impinged surface was consistent among all 20 cases, whereas that of the surface under free convection varied, ranging from 41 to 120 °C, depending on the core and thermal bridges. Second, most of the highest temperatures on opposite surfaces were caused by a section of bare angle iron, and this bridging effect could be significantly reduced by up to 50 °C using a few layers of cloth, although the improvement could be temporary. Bolts and nails were less effective as thermal bridges, while the battens could be more effective. Third, the estimated heat flux of all specimens ranged from 167 to 331 W·m−2.
Effect of Reclaimed Asphalt Pavement Heating Temperature on the Compactability of Recycled Hot Mix Asphalt
Authors: Ma Xiang , Leng Zhen , Wang Lili , Zhou Peisheng
Published: August 2020

The compactability of an asphalt mixture is related to the heating temperature of the materials, but the heating temperature of reclaimed asphalt pavement (RAP) is limited by the production process of hot-in-plant recycled mixtures. To choose a reasonable heating temperature for RAP according to the compactability, the compaction energy ratio (CER) obtained from the Superpave gyratory compactor compaction curve was developed. The CERs of fourteen kinds of asphalt mixtures made with different RAPs were compared, all of which were different in type, content, and heating temperature. The results indicated that CER is an effective energy index to evaluate the workability of a bituminous mixture, and it considers both the accumulated energy after each gyration and the number of gyrations. It was also found that increasing the heating temperature of the RAP cannot always improve the workability of the recycled mixture, because the higher heating temperature caused more hard-aged bitumen to be blended with soft virgin bitumen during the mixing process. At the same RAP heating temperature, increasing the RAP content made it more difficult to compact the mixture, especially for RAPs with styrene–butadiene–styrene (SBS) modified bitumen, and the recycled mixtures with SBS-modified bitumen were more difficult to compact than those with nonmodified bitumen.
Superhard Boron-Rich Boron Carbide with Controlled Degree of Crystallinity
Authors: Chakrabarty Kallol , Chen Wei-Chih , Baker Paul A. , Vijayan Vineeth M. , Chen Cheng-Chien , Catledge Shane A.
Published: August 2020

Superhard boron-rich boron carbide coatings were deposited on silicon substrates by microwave plasma chemical vapor deposition (MPCVD) under controlled conditions, which led to either a disordered or crystalline structure, as measured by X-ray diffraction. The control of either disordered or crystalline structures was achieved solely by the choice of the sample being placed either directly on top of the sample holder or within an inset of the sample holder, respectively. The carbon content in the B-C bonded disordered and crystalline coatings was 6.1 at.% and 4.5 at.%, respectively, as measured by X-ray photoelectron spectroscopy. X-ray diffraction analysis of the crystalline coating provided a good match with a B50C2-type structure in which two carbon atoms replaced boron in the α-tetragonal B52 structure, or in which the carbon atoms occupied different interstitial sites. Density functional theory predictions were used to evaluate the dynamical stability of the potential B50C2 structural forms and were consistent with the measurements. The measured nanoindentation hardness of the coatings was as high as 64 GPa, well above the 40 GPa threshold for superhardness.
Dynamics Studies of Nitrogen Interstitial in GaN from Ab Initio Calculations
Authors: He Huan , Liu Wenbo , Zhang Pengbo , Liao Wenlong , Tong Dayin , Yang Lin , He Chaohui , Zang Hang , Zong Hongxiang
Published: August 2020

Understanding the properties of defects is crucial to design higher performance semiconductor materials because they influence the electronic and optical properties significantly. Using ab initio calculations, the dynamics properties of nitrogen interstitial in GaN material, including the configuration, migration, and interaction with vacancy were systematically investigated in the present work. By introducing different sites of foreign nitrogen atom, the most stable configuration of nitrogen interstitial was calculated to show a threefold symmetry in each layer and different charge states were characterized, respectively. In the researches of migration, two migration paths, in-plane and out-of-plane, were considered. With regards to the in-plane migration, an intermediated rotation process was observed first time. Due to this rotation behavior, two different barriers were demonstrated to reveal that the migration is an anisotropic behavior. Additionally, charged nitrogen Frenkel pair was found to be a relatively stable defect complex and its well separation distance was about 3.9 Å. Part of our results are in good agreement with the experimental results, and our work provides underlying insights of the identification and dynamics of nitrogen interstitial in GaN material. This study of defects in GaN material is useful to establish a more complete theory and improve the performance of GaN-based devices.
Dissolution of Metals in Different Bromide-Based Systems: Electrochemical Measurements and Spectroscopic Investigations
Authors: Varvara Simona , Dorneanu Sorin-Aurel , Okos Alexandru , Muresan Liana Maria , Bostan Roxana , Popa Maria , Marconi Daniel , Ilea Petru
Published: August 2020

The dissolution of the main metals (Cu, Zn, Sn, Pb and Fe) found in waste printed circuit boards (WPCBs) was investigated by electrochemical corrosion measurements (potentiodynamic polarization and electrochemical impedance spectroscopy (EIS)) in different bromide-based systems that could be used as lixiviants in hydrometallurgical route of metals recovery. The analysis of the corrosion products was carried out by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurements. All measurements showed that the addition of bromine in the electrolyte favors to great extents the dissolution process of all studied metals as compared to bromine-free electrolytes. In the investigated experimental conditions, the highest dissolution rates of the metals were obtained in acidic KBr solution containing 0.01 mol/L bromine and they decreased in the following order: Zn >> Sn > Pb > Fe > Cu. The XRD and XPS chemical assessment allowed the identification of the dissolution products formed on the metallic surfaces after exposure to the electrolytes. They consisted mainly of oxides in the case of Cu, Zn, Sn and Fe, while the presence of PbBr2 was also noticed on the lead surface. Based on the results of EIS and surface investigations, several models explaining the corrosion behavior of the metals were proposed and discussed. The obtained results demonstrate that all studied metals could be successfully leached using brominated solutions, providing a viable alternative for the selective and efficient recovery of the base metals from WPCBs through a multi-step hydrometallurgical processing route.
Implication of Hemodynamic Assessment during Durable Left Ventricular Assist Device Support
Authors: Imamura Teruhiko , Narang Nikhil
Published: August 2020

Durable left ventricular assist device therapy has improved survival in patients with advanced heart failure refractory to conventional medical therapy, although the readmission rates due to device-related comorbidities remain high. Left ventricular assist devices are designed to support a failing left ventricle through relief of congestion and improvement of cardiac output. However, many patients still have abnormal hemodynamics even though they may appear to be clinically stable. Furthermore, such abnormal hemodynamics are associated with an increased risk of future adverse events including recurrent heart failure, gastrointestinal bleeding, stroke, and pump thrombosis. Correction of residual hemodynamic derangements post-implantation may be a target in improving longitudinal clinical outcomes during left ventricular assist device support. Automatic and timely device speed adjustments considering a patients’ hemodynamic status (i.e., with a smart pump) are potential improvements in forthcoming devices.
Factors Influencing Nursing Students’ Person-Centered Care
Authors: Kim Myoungsuk
Published: August 2020

Background and objectives: Numerous theoretical and clinical advances have been made through research on person-centered care (PCC). Nevertheless, care is still focused on the medical aspects of treating patients’ diseases in Korea, and thus providing individualized PCC to patients tends to be neglected. This study aimed to investigate the relationship between PCC competence, empathic competence, interpersonal competence, and perceived stress to identify the factors that impact PCC competence for developing programs that foster PCC competence in nursing students. Materials and Methods: Data were collected from 149 participants, which comprised third- and fourth-year nursing students from two universities in Korea who have experienced clinical training. PCC competence, empathic competence, interpersonal competence, and perceived stress were measured using structured self-reported questionnaires. Results: PCC competence was positively correlated with empathic competence (p < 0.001) and interpersonal competence (p < 0.001), and negatively correlated with perceived stress (p < 0.001). Empathic competence, perceived stress, interpersonal competence, and satisfaction with the participants’ nursing major were identified as factors that influenced the PCC competence (adjusted R2 = 0.570). Conclusions: To enhance PCC competence in nursing students, empathic competence, interpersonal competence, and satisfaction with the participants’ nursing major need to be improved and perceived stress needs to be reduced.
Spectrum of MEFV Variants and Genotypes among Clinically Diagnosed FMF Patients from Southern Lebanon
Authors: El Roz Ali , Ghssein Ghassan , Khalaf Batoul , Fardoun Taher , Ibrahim José-Noel
Published: August 2020

Background: Familial Mediterranean Fever (FMF) is an autosomal recessive auto-inflammatory disease characterized by pathogenic variants in the MEFV gene, with allele frequencies greatly varying between countries, populations and ethnic groups. Materials and methods: In order to analyze the spectrum of MEFV variants and genotypes among clinically diagnosed FMF patients from South Lebanon, data were collected from 332 participants and 23 MEFV variants were screened using a Real-Time PCR Kit. Results: The mean age at symptom onset was 17.31 ± 13.82 years. The most prevalent symptoms were abdominal pain, fever and myalgia. MEFV molecular analysis showed that 111 patients (63.79%) were heterozygous, 16 (9.20%) were homozygous, and 47 (27.01%) carried two variants or more. E148Q was the most encountered variant among heterozygous subjects. E148Q/M694V was the most frequent in the compound heterozygous/complex genotype group, while M694I was the most common among homozygous patients. Regarding allele frequencies, M694V was the most common variant (20.7%), followed by E148Q (17.1%), V726A (15.7%) and M694I (13.2%). Conclusion: The high percentage of heterozygous patients clinically diagnosed as FMF highlights the pseudo-dominant transmission of the disease in Lebanon and emphasizes the importance of molecular testing for a more accurate diagnosis and better management and treatment of FMF.
Pebax® 2533/Graphene Oxide Nanocomposite Membranes for Carbon Capture
Authors: Casadei Riccardo , Giacinti Baschetti Marco , Yoo Myung Jin , Park Ho Bum , Giorgini Loris
Published: August 2020

In this work, the behavior of new GO-based mixed matrix membranes was tested in view of their use as CO2-selective membrane in post combustion carbon capture applications. In particular, the new materials were obtained by mixing of Pebax® 2533 copolymer with different types of graphene oxide (GO). Pebax® 2533 has indeed lower selectivity, but higher permeability than Pebax® 1657, which is more commonly used for membranes, and it could therefore benefit from the addition of GO, which is endowed with very high selectivity of CO2 with respect to nitrogen. The mixed matrix membranes were obtained by adding different amounts of GO, from 0.02 to 1% by weight, to the commercial block copolymers. Porous graphene oxide (PGO) and GO functionalized with polyetheramine (PEAGO) were also considered in composites produced with similar procedure, with a loading of 0.02%wt. The obtained films were then characterized by using SEM, DSC, XPS analysis and permeability experiments. In particular, permeation tests with pure CO2 and N2 at 35°C and 1 bar of upstream pressure were conducted for the different materials to evaluate their separation performance. It has been discovered that adding these GO-based nanofillers to Pebax® 2533 matrix does not improve the ideal selectivity of the material, but it allows to increase CO2 permeability when a low filler content, not higher than 0.02 wt%, is considered. Among the different types of GO, then, porous GO seems the most promising as it shows CO2 permeability in the order of 400 barrer (with an increase of about 10% with respect to the unloaded block copolymer), obtained without reducing the CO2/N2 selectivity of the materials, which remained in the order of 25.
Design and Analysis of a Slot Photonic Crystal Waveguide for Highly Sensitive Evanescent Field Absorption Sensing in Fluids
Authors: Jannesari Reyhaneh , Pühringer Gerald , Grille Thomas , Jakoby Bernhard
Published: August 2020

The design and modeling of a highly sensitive sensor based on a slot photonic crystal waveguide (slot-PCWG) is presented. The structure consists of cylindrical air rods drilled in a dielectric slab on a triangular lattice, which are filled with SiO2. The waveguide is formed by removing elements from the regular photonic crystal grid in a row, and embedding a slot in the center position. This concept allows for a vast enhancement of the evanescent field ratio, leading to a strong overlap between the field of the waveguide mode and the analyte. In the present work, we show that the sensitivity at the constant slab thickness of the slot-PCWG modes is greatly enhanced, up to a factor of 7.6 compared with the corresponding PCWG modes or Si-slab WGs. The finite-difference time-domain (FDTD) technique and plane wave expansion (PWE) methods were used to study the dispersion and profile of the PCWG mode. The simulation results show the potential of this design, which will be fabricated and tested in the following steps of the project.