bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Scanning Strategy and Printing Temperature on the Compressive Behaviors of 3D Printed Polyamide-Based Composites
Authors: Wang Jin , Xiang Jiangyang , Lin Hao , Wang Kui , Yao Song , Peng Yong , Rao Yanni
Published: August 2020

In this work, the effects of scanning strategies and printing temperature on mechanical properties and crush behaviors of columns manufactured using the fused deposition modeling (FDM) technique were studied. The results showed that scanning strategy and printing temperature had significant influences on mechanical response and deformation mode of the columns. The columns printed in different scanning strategies showed significant anisotropy due to the preferred orientation of short fibers during the printing process. The columns printed in a circular direction presented the highest compressive force response. The columns printed with carbon fiber-reinforced polyamide in a circular direction showed the final oblique fracture failure mode, in which there were fiber pull-out and matrix pull-apart on fracture surfaces. Different indicators were also used to evaluate the mechanical properties and crushing characteristics of the columns. The carbon fiber reinforcement columns presented the highest energy absorption, and the glass fiber reinforcement columns showed the highest elastic modulus and yield strength. The results indicated that the scanning strategy and printing temperature not only influenced the elastic modulus and yield strength, but also affected the energy absorption performances of the columns.
Clinical Effectiveness of Bulk-Fill and Conventional Resin Composite Restorations: Systematic Review and Meta-Analysis
Authors: Arbildo-Vega Heber Isac , Lapinska Barbara , Panda Saurav , Lamas-Lara César , Khan Abdul Samad , Lukomska-Szymanska Monika
Published: August 2020

The objective of this systematic review and meta-analysis was to determine the clinical effectiveness of bulk-fill and conventional resin in composite restorations. A bibliographic search was carried out until May 2020, in the biomedical databases Pubmed/MEDLINE, EMBASE, Scopus, CENTRAL and Web of Science. The study selection criteria were: randomized clinical trials, in English, with no time limit, with a follow-up greater than or equal to 6 months and that reported the clinical effects (absence of fractures, absence of discoloration or marginal staining, adequate adaptation marginal, absence of post-operative sensitivity, absence of secondary caries, adequate color stability and translucency, proper surface texture, proper anatomical form, adequate tooth integrity without wear, adequate restoration integrity, proper occlusion, absence of inflammation and adequate point of contact) of restorations made with conventional and bulk resins. The risk of bias of the study was analyzed using the Cochrane Manual of Systematic Reviews of Interventions. Sixteen articles were eligible and included in the study. The results indicated that there is no difference between restorations with conventional and bulk resins for the type of restoration, type of tooth restored and restoration technique used. However, further properly designed clinical studies are required in order to reach a better conclusion.
A Novel Approach for Predicting the Height of Water-Conducting Fracture Zone under the High Overburden Caving Strength Based on Optimized Processes
Authors: Hu Tao , Hou Gongyu , Bu Su , Zhu Zhen , Wang Yan , Hu Ziyi , Li Zixiang
Published: August 2020

The height of water-conducting fracture zones (WCFZs) is vital for the prevention of water, gas, and roof accidents in coal mines. However, its dynamic evolution law and maximum height are difficult to be obtained by traditional prediction methods, especially for conditions in which there is high overburden caving strength and a thick coal seam. Therefore, taking the 150,313 fully mechanized caving working face in Yingying Coal Mine as a background, according to the principle of optimized processes, a new predicting approach based on the Brillouin optical time-domain reflectometry (BOTDR) is proposed. Firstly, we estimated the height through empirical formula calculation, theoretical analysis, and similar model simulation tests. Secondly, we studied the optimized layout of optical cables in the overburden in detail for predicting the maximum height of the WCFZ and keeping the cables in good performance during field prediction. Thirdly, we researched and optimized the borehole parameters, optical fiber selection, and the special protection measures. Finally, we applied the aforementioned optimized outcomes in the field experiment to dynamically predict the height of the WCFZ. As a result of the field experiment, the distribution characteristics of optical fiber strain, the maximum height, and the evolution law of the WCFZ were obtained through the regular monitoring of fiber strain using BOTDR. The experiment demonstrated that its maximum height is consistent with the results studied indoors. The validation and feasibility of the approach proposed in this paper were verified via the aforementioned studies. The research in this paper has good reference value and important significance for predicting the height of the WCFZ using BOTDR in coal mines with similar geological and productive conditions.
Assessing the Potential of Enhanced Resolution Gridded Passive Microwave Brightness Temperatures for Retrieval of Sea Ice Parameters
Authors: Meier Walter N. , Stewart J. Scott
Published: August 2020

A new enhanced resolution gridded passive microwave brightness temperature (TB) product is used to estimate sea ice concentration and motion. The effective resolution of the TBs is found to be roughly twice that of the standard 25 km resolution, though the gridded resolution of the distributed product is higher. Enhanced resolution sea ice concentrations from the Bootstrap algorithm show more detail in the sea ice, including relatively small open water regions within the ice pack. Sea ice motion estimates from the enhanced resolution TBs using a maximum cross-correlation method show a smoother motion circulation pattern; in comparison to buoys, RMS errors are 15–20% lower than motion estimates from the standard resolution fields and the magnitude of the bias is smaller as well. The enhanced resolution product includes other potentially beneficial characteristics, including twice-daily grids based on local time of day and a complete timeseries of data from nearly all multi-channel passive microwave radiometers since 1978. These enhanced resolution TBs are potential new source for long-term records of sea ice concentration, motion, age, melt, as well as salinity and ocean-atmosphere fluxes.
Improved Estimation of Regional Surface Mass Variations from GRACE Intersatellite Geopotential Differences Using a Priori Constraints
Authors: Zhong Bo , Li Qiong , Chen Jianli , Luo Zhicai , Zhou Hao
Published: August 2020

We presented an improved method for estimation of regional surface mass variations from the Gravity Recovery and Climate Experiment (GRACE)-derived precise intersatellite geopotential differences using a priori constraints. An alternative analytic formula was proposed to incorporate the K-band ranging (KBR) range rate into the improved energy balance equation, and precise geopotential differences were estimated from GRACE Level-1B data based on the remove-compute-restore (RCR) technique, which avoids the long-wavelength gravity signals being absorbed by empirical parameters. To reduce the ill condition for inversion of regional mass variations from geopotential differences, a priori information from hydrological models was used to construct the constraint equations, and the optimal regularization parameters were adaptively determined based on iterative least-squares estimation. To assess our improved method, a case study of regional mass variations’ inversion was carried out over South America on 2° × 2° grids at monthly intervals from January 2005 to December 2010. The results show that regional mascon solutions inverted from geopotential differences estimated by the RCR technique using hydrological models as a priori constraints can retain more signal energy and enhance regional mass variation inversion. The spatial distributions and annual amplitudes of geopotential difference-based regional mascon solutions agree well with the official GRACE mascon solutions, although notable differences exist in spatial patterns and trends, especially in small basins. In addition, our improved method can robustly estimate the mascon solutions, which are less affected by the a priori information. The results from the case study have clearly demonstrated the feasibility and effectiveness of the proposed method.
Adjusting for Desert-Dust-Related Biases in a Climate Data Record of Sea Surface Temperature
Authors: Merchant Christopher , Embury Owen
Published: August 2020

Atmospheric desert-dust aerosol, primarily from north Africa, causes negative biases in remotely sensed climate data records of sea surface temperature (SST). Here, large-scale bias adjustments are deduced and applied to the v2 climate data record of SST from the European Space Agency Climate Change Initiative (CCI). Unlike SST from infrared sensors, SST measured in situ is not prone to desert-dust bias. An in-situ-based SST analysis is combined with column dust mass from the Modern-Era Retrospective analysis for Research and Applications, Version 2 to deduce a monthly, large-scale adjustment to CCI analysis SSTs. Having reduced the dust-related biases, a further correction for some periods of anomalous satellite calibration is also derived. The corrections will increase the usability of the v2 CCI SST record for oceanographic and climate applications, such as understanding the role of Arabian Sea SSTs in the Indian monsoon. The corrections will also pave the way for a v3 climate data record with improved error characteristics with respect to atmospheric dust aerosol.
Extended Geometry and Probability Model for GNSS+ Constellation Performance Evaluation
Authors: Meng Lingdong , Wang Jiexian , Chen Junping , Wang Bin , Zhang Yize
Published: August 2020

We proposed an extended geometry and probability model (EGAPM) to analyze the performance of various kinds of (Global Navigation Satellite System) GNSS+ constellation design scenarios in terms of satellite visibility and dilution of precision (DOP) et al. on global and regional scales. Different from conventional methods, requiring real or simulated satellite ephemerides, this new model only uses some basic parameters of one satellite constellation. Verified by the reference values derived from precise satellite ephemerides, the accuracy of visible satellite visibility estimation using EGAPM gets an accuracy better than 0.11 on average. Applying the EGAPM to evaluate the geometry distribution quality of the hybrid GNSS+ constellation, where highly eccentric orbits (HEO), quasi-zenith orbit (QZO), inclined geosynchronous orbit (IGSO), geostationary earth orbit (GEO), medium earth orbit (MEO), and also low earth orbit (LEO) satellites included, we analyze the overall performance quantities of different constellation configurations. Results show that QZO satellites perform slightly better in the Northern Hemisphere than IGSO satellites. HEO satellites can significantly improve constellation geometry distribution quality in the high latitude regions. With 5 HEO satellites included in the third-generation BeiDou navigation satellite system (BDS-3), the average VDOP (vertical DOP) of the 30° N–90° N region can be decreased by 16.65%, meanwhile satellite visibility can be increased by 38.76%. What is more, the inclusion of the polar LEO constellation can significantly improve GNSS service performance. When including with 288 LEO satellites, the overall DOPs (GDOP (geometric DOP), HDOP (horizontal DOP), PDOP (position DOP), TDOP (time DOP), and VDOP) are decreased by about 40%, and the satellite visibility can be increased by 183.99% relative to the Global Positioning System (GPS) constellation.
Geophysical and Sedimentological Investigations Integrate Remote-Sensing Data to Depict Geometry of Fluvial Sedimentary Bodies: An Example from Holocene Point-Bar Deposits of the Venetian Plain (Italy)
Authors: Cassiani Giorgio , Bellizia Elena , Fontana Alessandro , Boaga Jacopo , D’Alpaos Andrea , Ghinassi Massimiliano
Published: August 2020

Over the past few millennia, meandering fluvial channels drained coastal landscapes accumulating sedimentary successions that today are permeable pathways. Propagation of pollutants, agricultural exploitation and sand liquefaction are the main processes of environmental interest affecting these sedimentary bodies. The characterization of these bodies is thus of utmost general interest. In this study, we particularly highlight the contribution of noninvasive (remote and ground-based) investigation techniques, and the case study focuses on a late Holocene meander bend of the southern Venetian Plain (Northeast Italy). Electromagnetic induction (EMI) investigations, conducted with great care in terms of sonde stability and positioning, allowed the reconstruction of the electrical conductivity 3D structure of the shallow subsurface, revealing that the paleochannel ranges in depth between 0.8 and 5.4 m, and defines an almost 260 m-wide point bar. The electrical conductivity maps derived from EMI at different depths define an arcuate morphology indicating that bar accretion started from an already sinuous channel. Sedimentary cores ensure local ground-truth and help define the evolution of the channel bend. This paper shows that the combination of well-conceived and carefully performed inverted geophysical surveys, remote sensing and direct investigations provides evidence of the evolution of recent shallow sedimentary structures with unprecedented detail.
How Does the Location of Transfer Affect Travellers and Their Choice of Travel Mode?—A Smart Spatial Analysis Approach
Authors: Chia Jason , Lee Jinwoo (Brian) , Han Hoon
Published: August 2020

This study explores the relationship between the spatial distribution of relative transfer location (i.e., the location of the transfer point in relation to the trip origin and destination points) and the attractiveness of the transit service using smart card data. Transfer is an essential component of the transit trip that allows people to reach more destinations, but it is also the main factor that deters the smartness of the public transit. The literature quantifies the inconvenience of transfer in terms of extra travel time or cost incurred during transfer. Unlike this conventional approach, the new “transfer location” variable is formulated by mapping the spatial distribution of relative transfer locations on a homogeneous geocoordinate system. The clustering of transfer points is then quantified using grid-based hierarchical clustering. The transfer location factor is formulated as a new explanatory variable for mode choice modelling. This new variable is found to be statistically significant, and no correlation is observed with other explanatory variables, including transit travel time. These results imply that smart transit users may perceive the travel direction (to transfer) as important, in addition to the travel time factor, which would influence their mode choice. Travellers may disfavour even adjacent transfer locations depending on their relative location. The findings of this study will contribute to improving the understanding of transit user behaviour and impact of the smartness of transfer, assist smart transport planning and designing of new transit routes and services to enhance the transfer performance.
Focus on the Visible Regions: Semantic-Guided Alignment Model for Occluded Person Re-Identification
Authors: Yang Qin , Wang Peizhi , Fang Zihan , Lu Qiyong
Published: August 2020

The occlusion problem is very common in pedestrian retrieval scenarios. When persons are occluded by various obstacles, the noise caused by the occluded area greatly affects the retrieval results. However, many previous pedestrian re-identification (Re-ID) methods ignore this problem. To solve it, we propose a semantic-guided alignment model that uses image semantic information to separate useful information from occlusion noise. In the image preprocessing phase, we use a human semantic parsing network to generate probability maps. These maps show which regions of images are occluded, and the model automatically crops images to preserve the visible parts. In the construction phase, we fuse the probability maps with the global features of the image, and semantic information guides the model to focus on visible human regions and extract local features. During the matching process, we propose a measurement strategy that only calculates the distance of public areas (visible human areas on both images) between images, thereby suppressing the spatial misalignment caused by non-public areas. Experimental results on a series of public datasets confirm that our method outperforms previous occluded Re-ID methods, and it achieves top performance in the holistic Re-ID problem.
Uncertainty Analysis of Fluorescence-Based Oil-In-Water Monitors for Oil and Gas Produced Water
Authors: Severin Hansen Dennis , Jespersen Stefan , Bram Mads Valentin , Yang Zhenyu
Published: August 2020

Offshore oil and gas facilities are currently measuring the oil-in-water (OiW) concentration in the produced water manually before discharging it into the ocean, which in most cases fulfills the government regulations. However, as stricter regulations and environmental concerns are increasing over time, the importance of measuring OiW in real-time intensifies. The significant amount of uncertainties associated with manual samplings, that is currently not taken into consideration, could potentially affect the acceptance of OiW monitors and lower the reputation of all online OiW measurement techniques. This work presents the performance of four fluorescence-based monitors on an in-house testing facility. Previous studies of a fluorescence-based monitor have raised concerns about the measurement of OiW concentration being flow-dependent. The proposed results show that the measurements from the fluorescence-based monitors are not or insignificantly flow-dependent. However, other parameters, such as gas bubbles and droplet sizes, do affect the measurement. Testing the monitors’ calibration method revealed that the weighted least square is preferred to achieve high reproducibility. Due to the high sensitivity to different compositions of atomic structures, other than aromatic hydrocarbons, the fluorescence-based monitor might not be feasible for measuring OiW concentrations in dynamic separation facilities with consistent changes. Nevertheless, they are still of interest for measuring the separation efficiency of a deoiling hydrocyclone to enhance its deoiling performance, as the separation efficiency is not dependent on OiW trueness but rather the OiW concentration before and after the hydrocyclone.
Energy-Efficient UAVs Deployment for QoS-Guaranteed VoWiFi Service
Authors: Mayor Vicente , Estepa Rafael , Estepa Antonio , Madinabeitia Germán
Published: August 2020

This paper formulates a new problem for the optimal placement of Unmanned Aerial Vehicles (UAVs) geared towards wireless coverage provision for Voice over WiFi (VoWiFi) service to a set of ground users confined in an open area. Our objective function is constrained by coverage and by VoIP speech quality and minimizes the ratio between the number of UAVs deployed and energy efficiency in UAVs, hence providing the layout that requires fewer UAVs per hour of service. Solutions provide the number and position of UAVs to be deployed, and are found using well-known heuristic search methods such as genetic algorithms (used for the initial deployment of UAVs), or particle swarm optimization (used for the periodical update of the positions). We examine two communication services: (a) one bidirectional VoWiFi channel per user; (b) single broadcast VoWiFi channel for announcements. For these services, we study the results obtained for an increasing number of users confined in a small area of 100 m2 as well as in a large area of 10,000 m2. Results show that the drone turnover rate is related to both users’ sparsity and the number of users served by each UAV. For the unicast service, the ratio of UAVs per hour of service tends to increase with user sparsity and the power of radio communication represents 14–16% of the total UAV energy consumption depending on ground user density. In large areas, solutions tend to locate UAVs at higher altitudes seeking increased coverage, which increases energy consumption due to hovering. However, in the VoWiFi broadcast communication service, the traffic is scarce, and solutions are mostly constrained only by coverage. This results in fewer UAVs deployed, less total power consumption (between 20% and 75%), and less sensitivity to the number of served users.
A Hyperspectral Bidirectional Reflectance Model for Land Surface
Authors: Yang Qiguang , Liu Xu , Wu Wan
Published: August 2020

A hyperspectral bidirectional reflectance (HSBR) model for land surface has been developed in this work. The HSBR model includes a very diverse land surface bidirectional reflectance distribution function (BRDF) database with ~40,000 spectra. The BRDF database is saved as Ross-Li parameters, which can generate hyperspectral reflectance spectra at different sensor and solar observation geometries. The HSBR model also provides an improved method for generating hyperspectral surface reflectance using multiband satellite measurements. It is shown that the land surface reflective spectrum can be easily simulated using BRDF parameters or reflectance at few preselected wavelengths. The HSBR model is validated using the U.S. Geological Survey (USGS) vegetation database and the AVIRIS reflectance product. The simulated reflective spectra fit the measurements very well with standard deviations normally smaller than 0.01 in the unit of reflectivity. The HSBR model could be used to significantly improve the quality of the reflectance products of satellite and airborne sensors. It also plays important role for intercalibration among space-based instruments and other land surface related applications.
Underwater TDOA Acoustical Location Based on Majorization-Minimization Optimization
Authors: Li Shuangshuang , Sun Haixin , Esmaiel Hamada
Published: August 2020

Underwater acoustic localization is a useful technique applied to any military and civilian applications. Among the range-based underwater acoustic localization methods, the time difference of arrival (TDOA) has received much attention because it is easy to implement and relatively less affected by the underwater environment. This paper proposes a TDOA-based localization algorithm for an underwater acoustic sensor network using the maximum-likelihood (ML) ratio criterion. To relax the complexity of the proposed localization complexity, we construct an auxiliary function, and use the majorization-minimization (MM) algorithm to solve it. The proposed localization algorithm proposed in this paper is called a T-MM algorithm. T-MM is applying the MM algorithm to the TDOA acoustic-localization technique. As the MM algorithm iterations are sensitive to the initial points, a gradient-based initial point algorithm is used to set the initial points of the T-MM scheme. The proposed T-MM localization scheme is evaluated based on squared position error bound (SPEB), and through calculation, we get the SPEB expression by the equivalent Fisher information matrix (EFIM). The simulation results show how the proposed T-MM algorithm has better performance and outperforms the state-of-the-art localization algorithms in terms of accuracy and computation complexity even under a high presence of underwater noise.
Demosaicing of RGBW Color Filter Array Based on Rank Minimization with Colorization Constraint
Authors: Kim Hansol , Lee Sukho , Kang Moon Gi
Published: August 2020

Recently, the white (w) channel has been incorporated in various forms into color filter arrays (CFAs). The advantage of using theWchannel is thatWpixels have less noise than red (R), green (G), or blue (B) (RGB) pixels; therefore, under low-light conditions, pixels with high fidelity can be obtained. However, RGBW CFAs normally suffer from spatial resolution degradation due to a smaller number of color pixels than in RGB CFAs. Therefore, even though the reconstructed colors have higher sensitivity, which results in larger Color Peak Signal-to-Noise Ratio (CPSNR) values, there are some color aliasing artifacts due to a low resolution. In this paper, we propose a rank minimization-based color interpolation method with a colorization constraint for the RGBW format with a large number ofWpixels. The rank minimization can achieve a broad interpolation and preserve the structure in the image, and it thereby eliminates the color artifacts. However, the colors fade from this global process. Therefore, we further incorporate a colorization constraint into the rank minimization process for the better reproduction of the colors. The experimental results show that the images can be reconstructed well, even from noisy pattern images obtained under low-light conditions.
Sensing Exposure Time to Oxygen by Applying a Percolation-Induced Principle
Authors: Afik Noa , Yadgar Omri , Volison-Klimentiev Anastasiya , Peretz-Damari Sivan , Ohayon-Lavi Avia , Alatawna Amr , Yosefi Gal , Bitton Ronit , Fuchs Naomi , Regev Oren
Published: August 2020

The determination of food freshness along manufacturer-to-consumer transportation lines is a challenging problem that calls for cheap, simple, reliable, and nontoxic sensors inside food packaging. We present a novel approach for oxygen sensing in which the exposure time to oxygen—rather than the oxygen concentration per se—is monitored. We developed a nontoxic hybrid composite-based sensor consisting of graphite powder (conductive filler), clay (viscosity control filler) and linseed oil (the matrix). Upon exposure to oxygen, the insulating linseed oil is oxidized, leading to polymerization and shrinkage of the matrix and hence to an increase in the concentration of the electrically conductive graphite powder up to percolation, which serves as an indicator of food spoilage. In the developed sensor, the exposure time to oxygen (days to weeks) is obtained by measuring the electrical conductivity though the sensor. The sensor functionality could be tuned by changing the oil viscosity, the aspect ratio of the conductive filler, and/or the concentration of the clay, thereby adapting the sensor to monitoring the quality of food products with different sensitivities to oxygen exposure time (e.g., fish vs grain).
Automatic Detection of Dynamic and Static Activities of the Older Adults Using a Wearable Sensor and Support Vector Machines
Authors: Zhang Jian , Soangra Rahul , E. Lockhart Thurmon
Published: August 2020

Although Support Vector Machines (SVM) are widely used for classifying human motion patterns, their application in the automatic recognition of dynamic and static activities of daily life in the healthy older adults is limited. Using a body mounted wireless inertial measurement unit (IMU), this paper explores the use of SVM approach for classifying dynamic (walking) and static (sitting, standing and lying) activities of the older adults. Specifically, data formatting and feature extraction methods associated with IMU signals are discussed. To evaluate the performance of the SVM algorithm, the effects of two parameters involved in SVM algorithm—the soft margin constant C and the kernel function parameter γ—are investigated. The changes associated with adding white-noise and pink-noise on these two parameters along with adding different sources of movement variations (i.e., localized muscle fatigue and mixed activities) are further discussed. The results indicate that the SVM algorithm is capable of keeping high overall accuracy by adjusting the two parameters for dynamic as well as static activities, and may be applied as a tool for automatically identifying dynamic and static activities of daily life in the older adults.
Water-Soluble Fiber from Bengkoang (Pachyrhizus erosus (L.) Urban) Tuber Modulates Immune System Activity in Male Mice
Authors: Baroroh Hanif Nasiatul , Nugroho Agung Endro , Lukitaningsih Endang , Nurrochmad Arief
Published: August 2020

Our previous study showed that water-soluble fiber from bengkoang (Pachyrizus erosus (L.) Urban) fiber extract (BFE) and bengkoang fiber fraction B (BFE-B) have phagocytic activity and modulation of cytokine production in vitro. The present study evaluates the immunomodulatory effects of water-soluble fibers BFE and BFE-B on male mice induced by hepatitis B vaccine. Thirty mice were divided into six groups and induced by hepatitis B vaccine intraperitoneally on days 7 and 14. The mice were then treated with BFE, BFE-B, levamisole, or sodium carboxymethyl cellulose for 18 days. At the end of the treatments (day 19), phagocytic activity, lymphocyte proliferation, spleen index, cytokine, and immunoglobulin G (IgG) production were determined. The results showed that the water-soluble fiber treatment could significantly increase phagocytic capacity, nitric oxide production, and spleen index. However, BFE-B could modulate tumor necrosis factor (TNF)-α and interleukin (IL)-10 secretion, BFE demonstrated no such effect on cytokine production. Lymphocyte proliferation assay revealed that treatment with 50 mg/kg body weight (BW) BFE and 50 mg/kg BW BFE-B could significantly enhance lymphocyte proliferation. Treatment with 25 and 50 mg/kg BW BFE-B stimulated IgG production. In conclusion, BFE and BFE-B similarly have immunomodulatory effects on innate immune responses. BFE-B further demonstrated immunomodulatory effects on adaptive immune responses.
Testing the Obligations of Presence in Academia in the COVID-19 Era
Authors: Shelley-Egan Clare
Published: August 2020

The COVID-19 crisis has given us a new, unprecedented impetus for thinking about the imperative of mobility in research. Travel and co-presence are widely accepted as being essential to career progression and promotion in academic life. Academics with fewer opportunities to travel find themselves at a significant disadvantage. COVID-19 and related public health measures have significantly limited the ability to be physically co-present in academia. Addressing obligations of co-presence in a less mobile world allows us to think concretely—and empathetically—about how to improve and extend virtual networking opportunities to those who have been marginalised with respect to research mobility. It also allows us to reflect on the role of reduced mobility and locality in how we think about and enact research. This article is informed and inspired by insights from research addressing academic mobility. I describe and discuss two prospects to productively work towards a new academic modus operandi characterised by limited opportunities for mobility. Furthermore, I highlight those issues and components that will require capacity building and a greater allocation of resources within the research system. In addition, I sketch out some pressing issues and questions for research mobility studies in a less mobile age going forward.
Gob-Side Entry Retaining Involving Bag Filling Material for Support Wall Construction
Authors: Du Zhaowen , Chen Shaojie , Ma Junbiao , Guo Zhongping , Yin Dawei
Published: August 2020

Gob-side entry retaining, also termed as non-pillar mining, plays an important role in saving coal resources, high production and efficiency, extending the service life of mine and improving the investment benefit. Herein, a gob-side entry retaining method involving the use of bag filling material for wall construction is proposed based on the thin seam mining characteristics. First, a gob-side entry retaining mechanical model is established, and the side support resistance of the 8101 working face is calculated. The mechanical properties of the bag material are investigated through experiments, and the construction technology of the gob-side entry retaining approach involving the use of bag filling material for wall construction is introduced. The deformation on the two sides, the roof and floor of the roadway, are simulated via numerical methods and monitored during field tests. The results show a small control range for the deformations and a good roadway retention effect, thereby proving the feasibility of the bag filling material for wall construction. This study provides a reference for the development of gob-side entry retaining mining for thin coal seams.
A Bibliometric Diagnosis and Analysis about Smart Cities
Authors: Pérez Luis Miguel , Oltra-Badenes Raul , Oltra Gutiérrez Juan Vicente , Gil-Gómez Hermenegildo
Published: August 2020

This article aims to present a bibliometric analysis of Smart Cities. The study analyzes the most important journals during the period between 1991 and 2019. It provides helpful insights into the document types, the distribution of countries/territories, the distribution of institutions, the authors’ geographical distribution, the most active authors and their research interests or fields, the relationships between principal authors and more relevant publications, and the most cited articles. This paper also provides important information about the core and historical references and the most cited papers. The analysis used the keywords and thematic noun-phrases in the titles and abstracts of the sample papers to explore the hot research topics in the top journals (e.g., ‘Smart Cities’, ‘Intelligent Cities’, ‘Sustainable Cities’, ‘e-Government’, ‘Digital Transformation’, ‘Knowledge-Based City’, etc.). The main objective is to have a quantitative description of the published literature about Smart Cities; this description will be the basis for the development of a methodology for the diagnosis of the maturity of a Smart City. The results presented here help to define the scientific concept of Smart Cities and to measure the importance that the term has gained through the years. The study has allowed us to know the main indicators of the published literature in depth, from the date of publication of the first articles and the evolution of these indicators to the present day. From the main indicators in the literature, some were selected to be applied: The most influential journals on Smart Cities according to the general citation structure in Smart Cities, Global Impact Factor of Smart Cities, number of publications, publications on Smart Cities around the world, and their correlation.
Understanding the Rural Livelihood Stability System: The Eco-Migration in Huanjiang County, China
Authors: Li Xiang , Xu Shuang , Hu Yecui
Published: August 2020

Immigrants are a special group whose livelihood stability is crucial to local sustainable development. To understand the positive effect of eco-migration policy on the immigrants, we innovatively selected the perspective of stability and quantified immigrants’ livelihood stability with relevant concepts, including livelihood capitals and strategies, response capacity, and land-use efficiency, which helped identify the problems and put forward suggestions to enhance livelihood sustainability, achieve better social integration, and promote the sustainable development of the rural resettlement areas. Huanjiang County was used as a study case as it is the largest and most representative eco-migrant resettlement county of the southwestern karst region, China. Aided by participatory rural appraisal (PRA), this paper explores the livelihood stability of immigrants and takes natives as the reference group. The results show that the livelihood stability values of immigrants were less than that of natives, but the gap was smaller than ten years ago; the natural, social, and other capitals owned by immigrants were almost the same as those of natives, demonstrating that the Chinese government’s poverty alleviation policies have benefitted immigrants. However, both immigrants and natives were found to have less natural and social capitals; high income dependency and an unbalanced proportion of income sources in addition to low land-use efficiency. Therefore, there are several suggestions put forward to achieve stable livelihood and rural sustainable development, and these items should be given increased consideration by both the government and households in resettlement areas.
A Spatial–Temporal Analysis of Cultural and Creative Industries with Micro-Geographic Disaggregation
Authors: Boal-San Miguel Iván , Herrero-Prieto Luis César
Published: August 2020

Recent years have witnessed growing interest in studying the spatial distribution of cultural and creative industries (CCI), both for their contribution to economic development and for their impact on spatial planning and remodeling of urban structure. However, spatial interdependence and diffusion of agglomeration economies have not been explained enough so far, due to the use of aggregate spatial units. This paper examines CCI sector location patterns in Spain from a spatial–temporal perspective, using micro-geographic data and considering a new and hitherto unused territorial unit, districts, an intermediate demarcation between municipalities and provinces or regions. We used a geographic information system (GIS) analysis and spatial econometric techniques to study territorial distribution and spatial dependences. Results show that CCI are mainly concentrated in metropolitan areas, with spillover effects in adjacent districts, reflecting a non-contemporary spatial dependence process, whilst large territories are devoid of these effects. This reveals a new source of regional disparities, as CCI seems to follow technology gap models, triggering greater and more intense spatial imbalances wherever it appears. Policy implications regarding accountability resources and institutional coordination must be deduced.
Scenario-Based Allocation of Emergency Resources in Metro Emergencies: A Model Development and a Case Study of Nanjing Metro
Authors: Lu Ying , Sun Shuqi
Published: August 2020

As metro systems are becoming more and more widely used, all kinds of emergencies happen from time to time. A series of cases indicate that inefficient emergency response is a dominating cause of tremendous casualties and losses. The fast and valid allocation of emergency resources after the occurrence of metro emergencies has become a key point in improving the sustainability of metro operations. However, few studies have attempted to determine the allocation of emergency resources in metro emergencies. In this study, considering the unpredictability of different emergency scenarios in the metro system, the scenario-response mode was applied in the resource allocation decision. In this mode, a metro emergency scenario framework was first constructed through the identification of metro emergency elements. Next, a multi-objective model was established for the allocation of emergency resources in the metro emergency rescue process using a scenario-based analysis. The model aims to minimize both the penalty costs due to delays and the sum of allocation costs. The particle swarm optimization algorithm was adopted to solve the model. Eventually, a fire accident scenario at Nanjing Metro was applied to verify the feasibility and validity of the presented model and algorithm. The research results not only enrich and improve metro emergency management theoretically, but also enhance metro emergency rescue ability in practice.
Institutional Design and Performance of Markets for Watershed Ecosystem Services: A Systematic Literature Review
Authors: Wang Hao , Meijerink Sander , van der Krabben Erwin
Published: August 2020

Markets for watershed ecosystem services have been developed as a tool in integrated water resources management. The development of vast markets for watershed ecosystem services has raised attention for the performance of these markets, their institutional design, and how their institutional design influences market performance. The main research questions guiding this systematic literature review are: Which types of markets can be distinguished; how is market performance operationalized; which institutional design characteristics are distinguished in the literature; and which of these characteristics are crucial to understanding performance? A systematic review of 224 journal articles from Web of Science leads to several main findings regarding these questions. Market performance is usually equated with effectiveness in the reviewed articles. Discussions in these articles include whether the market contributes to the preservation of ecosystem services, what the distributional impacts are, and what the participation rate is. The reviewed articles have illustrated specific institutional design features as well. The key features include the security of property rights, role of governments, bundling of ecosystem services (ES), and role of trust. In those articles addressing the relationship between institutional design and performance, the relevance of monitoring and enforcement, clearly defined property rights, and geographical market scope have been pointed out.
Constructability Criteria for Farmland Reclamation and Vegetable Cultivation Using Micro-Dam Sediments in Tigray, Ethiopia
Authors: Koda Kazuhisa , Girmay Gebreyohannes , Berihu Tesfay
Published: August 2020

The Ethiopian agriculture sector is characterized by rain-fed smallholder systems. The Ethiopian Government has promoted micro-dam construction in micro-watershed in Tigray for the past two decades. The lack of proper conservation measures to control severe soil erosion at the micro-watershed level, however, has often filled downstream micro-dams in with sediments. Sedimentation has affected the irrigation performance of micro-dams due to their bottom pipes becoming clogged with nutrient-rich soils eroded from upstream farmlands. While there is a growing need for adequate resource management to mitigate severe soil erosion at the watershed-level, it is urgent that methods to make use of the sediments deposited in micro-dam reservoirs to facilitate rural agricultural development are discovered. One practical solution is to use sediments to rehabilitate the bare land excavated for micro-dam embankment construction and turn it into reclaimed farmland. The purpose of this paper is to relate the constructability criteria to the farmland reclamation to solve sedimentation problems. This case study reports the yield of vegetable cultivation on farmland reclaimed using sediments from a micro-dam reservoir in Tigray. This case study highlights the practical potential of such a method to contribute to the livelihoods of farmers through the production of vegetable cash crops. The future research needs cost reduction factors on durability, safety or other related aspects to improve our “Constructability Criteria” approach.
The Effects of the Selective Enlargement of Fare-Free Public Transport
Authors: Grzelec Krzysztof , Jagiełło Aleksander
Published: August 2020

In recent years fare-free public transport (FFPT) found itself at the centre of attention of various groups, such as economists, transport engineers and local authorities, as well as those responsible for the organisation of urban transport. The FFPT is hoped to be the answer to contemporary transport-related problems within cities, problems which largely result from insensible proportions between trips carried out via personal mode of transportation and those completed by the means of public transport. This article reviews the motives and effects connected with the introduction to date of fare-free transport zones across the globe. It also presents, using data obtained in market research, the actual impact of a selective extension of the entitlement to free fares on the demand for urban transport services. The effects observed in other urban transport systems were then compared against those observed in relation to one, examined system. Analyses of observed FFPT implementation effects were then used to establish good and bad practices in the introduction of FFPT. The article also contains forecasts on the effect of the extension of entitlement to free fares and an increase in the public transport offer may have on the volume of demand for such services. The analyses have shown that an increase in the public transport offer (understood as an increase in the volume of vehicle-kilometres) would increase the demand for urban transport services more than the selective implementation of FFPT (assuming that the costs incurred by the local authorities remain unchanged).
Exploring Efficiencies: Examining the Possibility of Decreasing the Size of the Briquettes Used as the Batch in the Electric Arc Furnace Dust Processing Line
Authors: Bembenek Michał
Published: August 2020

Sintering of well-prepared briquetted mixtures in a shaft furnace is one of the possible methods of electric arc furnace dust (EAFD) utilization. Simultaneously, some metal oxides from exhaust gases can be separated. In this way, various metals are recovered, particularly zinc. As a result, zinc-free briquettes are produced with a high iron content, which can be used in the steelmaking process. This method is still being developed. In Ostrowiec Świetokrzyski, Poland, a prototype line of a new method for the reduction of zinc oxide in a shaft furnace with simultaneous sintering of briquettes was installed. The batch for the shaft furnace was actually briquetted in the roller press, which produces briquettes with a volume of 13 cm3. It may prove beneficial to reduce the size of the resulting briquettes, as a smaller size could prove more efficient in reducing zinc in the furnace. Decreasing the volume of the briquettes causes an increase in the power consumption in the drive system and brings an increase in the briquetting force, which occurred in the compaction zone. It could be harmful to the roller press construction. The aim of this article was to prove that decreasing the volume of briquettes of the EAFD mixtures had no negative effects on the roller press which was installed in the prototype line.
Determination of the Optimal Operative Conditions for the Torrefaction of Olive Waste Biomass
Authors: Martín-Pascual Jaime , Jódar Joaquín , Rodríguez Miguel L. , Zamorano Montserrat
Published: August 2020

The need for new energy sources and the problems associated with waste in the agroforestry industry are an opportunity for the recovery of this waste. For the use of this agricultural waste as energy, different pretreatments, such as torrefaction, can be carried out. Torrefaction is a thermochemical treatment involving energetic densification of biomass at temperatures ranging from 200 to 300 °C under an inert and anaerobic environment. This study developed a numerical model to evaluate the effect of temperature and residence time of torrefaction on biomass from olive tree waste to determine optimum operative conditions for the process. Four temperatures and four residence times, in the operation range of the process, were tested to determine the weight loss and the higher heating values (HHVs) of the torrefied sample. From these data, a numerical model was developed to infer the complete behavior of the process in the temperature range between 200 and 300 °C and in the residence time range of a few minutes to 2 h. The HHV of the torrefied sample increased at a temperature between 200 and 275 °C. However, from 275 to 300 °C, there was an HHV decrease. The effect of the residence time depended on the torrefaction temperature. At low temperatures, there were no statistically significant differences, although an increase of HHV was detected under 120 min. However, at 250 °C this effect was reversed, and statistically significant differences were not observed between 30 and 120 min. Overall, the increase of temperature in the torrefaction process reduces the residence time needed to achieve the maximum HHV. As a result, the optimum conditions of torrefaction for this biomass were, approximately, 275 °C and 30 min of residence time. This reaction yielded an optimum 5830 cal/g HHV.