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Appl. Sci., Volume 10, Issue 14 (July-2 2020) – 336 articles

Cover Story (view full-size image): Microparticles (MPs) are vesicular-like structures composed by a phospholipid bilayer containing molecules of their cell of origin such as surface proteins, enzymes, growth factors, RNA, and miRNAs. Released by diverse cell types in response to numerous stimuli, MPs act as cell–cell communicators and are involved in the control of several homeostatic processes, including angiogenesis.
Cardiovascular endurance training is the strongest stimulus for exercise-induced angiogenesis that, increasing the vascular bed, improves the blood flow and oxygen delivery to the exercising muscles. Thus, MPs released by platelets and endothelial cells in response to the mechanical and chemical stimuli provided by exercise, may play a pivotal role in the regulation of the angiogenic process. View this paper
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Open AccessArticle
Flat Cross-Shaped Piezoelectric Rotary Motor
Appl. Sci. 2020, 10(14), 5022; https://doi.org/10.3390/app10145022 - 21 Jul 2020
Cited by 1 | Viewed by 680
Abstract
A numerical and experimental investigation of a flat, cross-shaped piezoelectric rotary motor is presented. The design and configuration of the motor allow it to be mounted directly to the printed circuit board or integrated into the other system where mounting space is limited. [...] Read more.
A numerical and experimental investigation of a flat, cross-shaped piezoelectric rotary motor is presented. The design and configuration of the motor allow it to be mounted directly to the printed circuit board or integrated into the other system where mounting space is limited. The design of the motor is based on the cross-shaped stator with 16 piezo ceramic plates, which are glued on it. The rotor is placed at the center of the stator and consists of two hemispheres, a shaft, and a preloading spring. Special clamping of the stator was developed as well. It consists of four V-shaped beam structures that allow it to rigidly clamp the stator with reduced damping effect to vibrations. The operation principle of the motor is based on the first in-plane bending mode of the cross-shaped stator. The motor excitation is performed through four harmonic signals, which have a phase difference of π/2. A numerical investigation of the motor was conducted to optimize the geometrical parameters of the stator and to analyze the displacement characteristics of the contacting point. The prototype of the motor was made, and the electrical, as well as rotation speed characteristics of the motor, were measured. The results of the experimental investigation showed that the motor is able to provide a maximum rotation speed of 972.62 RPM at 200 Vp-p when the preload force of 22.65 mN was applied. Full article
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Open AccessArticle
The Impact of Thermal Treatment on Structural Changes of Teak and Iroko Wood Lignins
Appl. Sci. 2020, 10(14), 5021; https://doi.org/10.3390/app10145021 - 21 Jul 2020
Cited by 3 | Viewed by 686
Abstract
Thermal modification is an environmentally friendly method to improve dimensional stability, durability, and aesthetic properties of wood. Changes in lignin as one of the main wood components markedly influence wood product properties and recycling possibilities of thermowood at the end of its life [...] Read more.
Thermal modification is an environmentally friendly method to improve dimensional stability, durability, and aesthetic properties of wood. Changes in lignin as one of the main wood components markedly influence wood product properties and recycling possibilities of thermowood at the end of its life cycle. Teak and iroko wood samples were thermally treated at the temperatures of 160 °C, 180 °C and 210 °C following the Thermowood process. Dioxane lignin was isolated from treated and untreated wood and analysed by nitrobenzene oxidation (NBO), size exclusion chromatography (SEC) and Fourier transform infrared spectroscopy (FTIR). The yields of both acid-insoluble and dioxane lignins increased with an increasing treatment temperature. Dioxane lignins are GS-types containing more guaiacyl units compared to syringyl ones with S/G ratios of 0.91 and 0.84, respectively. In the process of thermal modification, several degradation and condensation reactions were observed. The cleavage of methoxyl groups and side chains, oxidation reactions, cleavage of the β-O-4 ether linkage and cross-linking radicals arising at higher temperatures were all confirmed. However, during the thermal treatment, teak lignin changed in a different way than iroko lignin, e.g., the molecular weight of iroko lignin decreased at all applied temperatures while it increased at 180 °C and 210 °C in teak lignin, and the change in S/G ratio and the cleavage of alkyl-aryl bonds are different in both wood species. Full article
(This article belongs to the Special Issue Advanced Technologies in Wood Science)
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Open AccessArticle
Missing Value Imputation in Stature Estimation by Learning Algorithms Using Anthropometric Data: A Comparative Study
Appl. Sci. 2020, 10(14), 5020; https://doi.org/10.3390/app10145020 - 21 Jul 2020
Viewed by 619
Abstract
Estimating stature is essential in the process of personal identification. Because it is difficult to find human remains intact at crime scenes and disaster sites, for instance, methods are needed for estimating stature based on different body parts. For instance, the upper and [...] Read more.
Estimating stature is essential in the process of personal identification. Because it is difficult to find human remains intact at crime scenes and disaster sites, for instance, methods are needed for estimating stature based on different body parts. For instance, the upper and lower limbs may vary depending on ancestry and sex, and it is of great importance to design adequate methodology for incorporating these in estimating stature. In addition, it is necessary to use machine learning rather than simple linear regression to improve the accuracy of stature estimation. In this study, the accuracy of statures estimated based on anthropometric data was compared using three imputation methods. In addition, by comparing the accuracy among linear and nonlinear classification methods, the best method was derived for estimating stature based on anthropometric data. For both sexes, multiple imputation was superior when the missing data ratio was low, and mean imputation performed well when the ratio was high. The support vector machine recorded the highest accuracy in all ratios of missing data. The findings of this study showed appropriate imputation methods for estimating stature with missing anthropometric data. In particular, the machine learning algorithms can be effectively used for estimating stature in humans. Full article
(This article belongs to the Special Issue Advances in Deep Learning Ⅱ)
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Open AccessArticle
Simultaneous Smoothing and Untangling of 2D Meshes Based on Explicit Element Geometric Transformation and Element Stitching
Appl. Sci. 2020, 10(14), 5019; https://doi.org/10.3390/app10145019 - 21 Jul 2020
Cited by 1 | Viewed by 543
Abstract
Mesh quality can affect both the accuracy and efficiency of numerical solutions. This paper first proposes a geometry-based smoothing and untangling method for 2D meshes based on explicit element geometric transformation and element stitching. A new explicit element geometric transformation (EEGT) operation for [...] Read more.
Mesh quality can affect both the accuracy and efficiency of numerical solutions. This paper first proposes a geometry-based smoothing and untangling method for 2D meshes based on explicit element geometric transformation and element stitching. A new explicit element geometric transformation (EEGT) operation for polygonal elements is firstly presented. The transformation, if applied iteratively to an arbitrary polygon (even inverted), will improve its regularity and quality. Then a well-designed element stitching scheme is introduced, which is achieved by carefully choosing appropriate element weights to average the temporary nodes obtained by the above individual element transformation. Based on the explicit element geometric transformation and element stitching, a new mesh smoothing and untangling approach for 2D meshes is proposed. The proper choice of averaging weights for element stitching ensures that the elements can be transitioned smoothly and uniformly throughout the calculation domain. Numerical results show that the proposed method is able to produce high-quality meshes with no inverted elements for highly tangled meshes. Besides, the inherent regularity and fine-grained parallelism make it suitable for implementation on Graphic Processor Unit (GPU). Full article
(This article belongs to the Section Mechanical Engineering)
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Open AccessReview
Applications of the Open-Source Hardware Arduino Platform in the Mining Industry: A Review
Appl. Sci. 2020, 10(14), 5018; https://doi.org/10.3390/app10145018 - 21 Jul 2020
Cited by 4 | Viewed by 799
Abstract
In this study, applications of the Arduino platform in the mining industry were reviewed. Arduino, a representative and popular open-source hardware, can acquire information from various sensors, transmit data using communication technology, and control devices through actuators. The review was conducted by classifying [...] Read more.
In this study, applications of the Arduino platform in the mining industry were reviewed. Arduino, a representative and popular open-source hardware, can acquire information from various sensors, transmit data using communication technology, and control devices through actuators. The review was conducted by classifying previous studies into three types of Arduino applications: field monitoring systems, wearable systems, and autonomous systems. With regard to field monitoring systems, most studies in mines were classified as atmospheric or geotechnical monitoring. In wearable systems, the health status of the miner was an important consideration, in addition to the environmental conditions of the mine. Arduino can be a useful tool as an initial prototype for autonomous mine systems. Arduino has advantages in that it can be combined with various electronic products and is cost-effective. Therefore, although many studies have been conducted in the laboratory (as opposed to field tests), Arduino applications can be further expanded in the mining field in the future. Full article
(This article belongs to the Special Issue Recent Advances in Smart Mining Technology)
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Open AccessArticle
Modeling the Long-Term Deformation of a Geodesic Spherical Frame Structure Made from Wood Plastic Composite Lumber
Appl. Sci. 2020, 10(14), 5017; https://doi.org/10.3390/app10145017 - 21 Jul 2020
Cited by 1 | Viewed by 487
Abstract
The long-term deformation of a geodesic spherical frame structure with a diameter of 20 m made from wood plastic composite (WPC) lumber (struts) is described using the Norton-Bailey power law model to predict the service life creep behavior (the creep strain ( ε c r )) of the WPC. The Norton-Bailey power law model parameters, A the power law multiplier, n the stress order, and m the time order, were obtained from experimental four-point bending flexural creep measurements of WPC lumber subjected to three levels of flexural stress: 7, 14, and 29% of the ultimate flexural strength for 200 days. The parameters obtained from the experiments showed good agreement to the model of the WPC lumber in flexure. The Norton-Bailey power law parameters were then implemented to describe the long-term deformation of the spherical frame structure. The limit of failure was considered when the WPC creep strain reaches the value of 1%. However, the FEA predicted the maximum creep strain to be 20% of the failure strain. This modeling approach is considered useful to describe and predict the long-term deformation of aquacultural structures made from viscoelastic materials during the envisioned service life (10 years) based on experimental creep data for the members that form the structure. Full article
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Open AccessArticle
Study on Reverse Logistics Focused on Developing the Collection Signal Algorithm Based on the Sensor Data and the Concept of Industry 4.0
Appl. Sci. 2020, 10(14), 5016; https://doi.org/10.3390/app10145016 - 21 Jul 2020
Cited by 1 | Viewed by 600
Abstract
Reverse logistics include all operations related to the reuse of products and materials. In this study, we focus on collection, which is the first operation of reverse logistics, and on the strength of using the sensor data and the concept of Industry 4.0. [...] Read more.
Reverse logistics include all operations related to the reuse of products and materials. In this study, we focus on collection, which is the first operation of reverse logistics, and on the strength of using the sensor data and the concept of Industry 4.0. Previously, the collection activities of electronic wastes (e-wastes) was conducted by a fixed schedule without consideration of the fulfillment level of the collection boxes. However, due to the progress of IoT(internet of things) technology and sensor technology, it is possible to consider the fulfillment level of the collection boxes in order to make the collection schedule. To utilize the sensor data and IoT technology in reverse logistics, a collection signal algorithm is required to treat the rate of fulfilment of collection boxes. However, the collection signal algorithm for the disposal of small and medium (S&M)-sized e-wastes have not yet been developed in South Korea. This study uses a collection box to develop the collection algorithm based on an experimental design method with multiple sensors. The proposed algorithm can be utilized to solve the current collection problems and to save logistics costs. Furthermore, proper collection of e-wastes will lead to more recycling activities, which can further create and sustain a safer environment on Earth. Full article
(This article belongs to the Special Issue Big Data and AI for Process Innovation in the Industry 4.0 Era)
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Open AccessArticle
Zinc Oxide Nanorod Surface-Enhanced Raman Scattering Substrates without and with Gold Nanoparticles Fabricated through Pulsed-Laser-Induced Photolysis
Appl. Sci. 2020, 10(14), 5015; https://doi.org/10.3390/app10145015 - 21 Jul 2020
Viewed by 588
Abstract
We fabricated surface-enhanced Raman scattering (SERS) substrates using gold nanoparticle (AuNP)-decorated zinc oxide (ZnO) nanorods (NRs). Prior to decoration with AuNPs, ZnO NRs on the glass substrate fabricated using the sol–gel method could enhance the SERS signal for detecting 10−5 M rhodamine [...] Read more.
We fabricated surface-enhanced Raman scattering (SERS) substrates using gold nanoparticle (AuNP)-decorated zinc oxide (ZnO) nanorods (NRs). Prior to decoration with AuNPs, ZnO NRs on the glass substrate fabricated using the sol–gel method could enhance the SERS signal for detecting 10−5 M rhodamine 6G (R6G). Microscopic analysis revealed that the thermal-annealing process for fabricating the seed layers of ZnO facilitated the growth of ZnO NRs with the highly preferred c-axis (002) orientation. A decrease in the diameter of ZnO NRs occurred because of the use of annealed seek layers further increased the surface-to-volume ratio of ZnO NRs, resulting in an increase in the SERS signal for R6G of 10−5 M. To combine the localized surface plasmon resonance (LSPR) mode with the charge transfer (CT) mode, ZnO NRs were decorated with AuNPs through pulsed-laser-induced photolysis (PLIP). However, the preferred vertical (002) orientation of ZnO NRs was prone to the aggregation of AuNPs, which hindered the SERS signal. The experimental results revealed that ZnO NRs with the crystalline structure of horizontal (100) and (101) orientations facilitated the growth of homogeneous, independent and isolated AuNPs which serves as “hot spots” for SERS signal of detecting R6G at a low concentration of 10−9 M. Comparing to previous fabrication of SERS substrate, our method has advantage to fabricate AuNP-decorated ZnO NR in a short time. Moreover, the optimization of the SERS behaviors for different fabrication conditions of AuNPs using the PLIP method was investigated in detail. Full article
(This article belongs to the Special Issue Nano-Biophotonics in Sensing Using Nanostructures)
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Open AccessReview
Measurement of Head-Related Transfer Functions: A Review
Appl. Sci. 2020, 10(14), 5014; https://doi.org/10.3390/app10145014 - 21 Jul 2020
Cited by 1 | Viewed by 1082
Abstract
A head-related transfer function (HRTF) describes an acoustic transfer function between a point sound source in the free-field and a defined position in the listener’s ear canal, and plays an essential role in creating immersive virtual acoustic environments (VAEs) reproduced over headphones or [...] Read more.
A head-related transfer function (HRTF) describes an acoustic transfer function between a point sound source in the free-field and a defined position in the listener’s ear canal, and plays an essential role in creating immersive virtual acoustic environments (VAEs) reproduced over headphones or loudspeakers. HRTFs are highly individual, and depend on directions and distances (near-field HRTFs). However, the measurement of high-density HRTF datasets is usually time-consuming, especially for human subjects. Over the years, various novel measurement setups and methods have been proposed for the fast acquisition of individual HRTFs while maintaining high measurement accuracy. This review paper provides an overview of various HRTF measurement systems and some insights into trends in individual HRTF measurements. Full article
(This article belongs to the Section Acoustics and Vibrations)
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Open AccessArticle
Development Cycle Modeling: Resource Estimation
Appl. Sci. 2020, 10(14), 5013; https://doi.org/10.3390/app10145013 - 21 Jul 2020
Viewed by 434
Abstract
This paper presents results produced by a domain-independent system development model that enables objective and quantitative calculation of certain development cycle characteristics. The presentation recounts the model’s motivation and includes an outline of the model’s structure. The outline shows that the model is [...] Read more.
This paper presents results produced by a domain-independent system development model that enables objective and quantitative calculation of certain development cycle characteristics. The presentation recounts the model’s motivation and includes an outline of the model’s structure. The outline shows that the model is constructive. As such, it provides an explanatory mechanism for the results that it produces, not just a representation of qualitative observations or measured data. The model is a Statistical Agent-based Model of Development and Evaluation (SAbMDE); and it appears to be novel with respect to previous design theory and methodology work. This paper focuses on one development cycle characteristic: resource utilization. The model’s resource estimation capability is compared to Boehm’s long-used software development estimation techniques. His Cone of Uncertainty (COU) captures project estimation accuracy empirically at project start but intuitively over a project’s duration. SAbMDE calculates estimation accuracy at start up and over project duration; and SAbMDE duplicates the COU’s empirical values. Additionally, SAbMDE produces results very similar to the Constructive Cost Model (COCOMO) effort estimation for a wide range of input values. Full article
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Open AccessEditorial
Food Chains and Food Webs in Aquatic Ecosystems
Appl. Sci. 2020, 10(14), 5012; https://doi.org/10.3390/app10145012 - 21 Jul 2020
Viewed by 578
Abstract
Food chains and food webs describe the structure of communities and their energy flows, and they present interactions between species. Recently, diverse methods have been developed for both experimental studies and theoretical/computational studies on food webs as well as species interactions. They are [...] Read more.
Food chains and food webs describe the structure of communities and their energy flows, and they present interactions between species. Recently, diverse methods have been developed for both experimental studies and theoretical/computational studies on food webs as well as species interactions. They are effectively used for various applications, including the monitoring and assessment of ecosystems. This Special Issue includes six empirical studies on food chains and food webs as well as effects of environmental factors on organisms in aquatic ecosystems. They confirmed the usefulness of their methods including isotope, DNA-barcoding with gut contents, and environmental DNA for biological monitoring and ecosystem assessment. Full article
(This article belongs to the Special Issue Food Chains and Food Webs in Aquatic Ecosystems)
Open AccessArticle
A Discrete Hidden Markov Model for SMS Spam Detection
Appl. Sci. 2020, 10(14), 5011; https://doi.org/10.3390/app10145011 - 21 Jul 2020
Cited by 6 | Viewed by 873
Abstract
Many machine learning methods have been applied for short messaging service (SMS) spam detection, including traditional methods such as naïve Bayes (NB), vector space model (VSM), and support vector machine (SVM), and novel methods such as long short-term memory (LSTM) and the convolutional [...] Read more.
Many machine learning methods have been applied for short messaging service (SMS) spam detection, including traditional methods such as naïve Bayes (NB), vector space model (VSM), and support vector machine (SVM), and novel methods such as long short-term memory (LSTM) and the convolutional neural network (CNN). These methods are based on the well-known bag of words (BoW) model, which assumes documents are unordered collection of words. This assumption overlooks an important piece of information, i.e., word order. Moreover, the term frequency, which counts the number of occurrences of each word in SMS, is unable to distinguish the importance of words, due to the length limitation of SMS. This paper proposes a new method based on the discrete hidden Markov model (HMM) to use the word order information and to solve the low term frequency issue in SMS spam detection. The popularly adopted SMS spam dataset from the UCI machine learning repository is used for performance analysis of the proposed HMM method. The overall performance is compatible with deep learning by employing CNN and LSTM models. A Chinese SMS spam dataset with 2000 messages is used for further performance evaluation. Experiments show that the proposed HMM method is not language-sensitive and can identify spam with high accuracy on both datasets. Full article
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Open AccessArticle
Micro-Structured Patches for Dermal Regeneration Obtained via Electrophoretic Replica Deposition
Appl. Sci. 2020, 10(14), 5010; https://doi.org/10.3390/app10145010 - 21 Jul 2020
Viewed by 579
Abstract
Artificial substrates supporting the healing of skin wounds require specific structural and chemical architectures that promote a recapitulation of the complexity of the native organ. Bottom-up fabrication technologies are emerging as effective strategies to fine tune biochemical, morphological, and structural features intended for [...] Read more.
Artificial substrates supporting the healing of skin wounds require specific structural and chemical architectures that promote a recapitulation of the complexity of the native organ. Bottom-up fabrication technologies are emerging as effective strategies to fine tune biochemical, morphological, and structural features intended for regenerative applications. Here, we proposed an electrophoretic replica deposition (EPrD) approach to realize chitosan three-dimensional structures specifically designed to treat patients with serious cutaneous damages or losses. The EPrD process has been optimized to consistently obtain random porosity vs. hierarchical lattice structures, showing mechanical properties in the range of skin tissue (E = 0.2–20 MPa). The obtained patches were tested in vivo via a one-stage grafting procedure in a full thickness skin wound rat model. Chitosan patches showed no adverse reactions throughout the experimental period (14 days). Hair follicles and sebaceous glands were observed in histological sections, indicating the regeneration of a thin epidermal layer with more skin appendages. Immunohistochemistry results demonstrated that keratin 10 was mostly expressed in basal and suprabasal layers, like normal skin, in structures with random porosity and with smaller lattice structures. The obtained results show the potential of EPrD to innovate the design of artificial substrates in skin healing therapies. Full article
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Open AccessArticle
Analysis of Mobile Phone Data to Compare Mobility Flows and Hotspots Before and After the Opening of High-Speed Railway: Case Study of Honam KTX in Korea
Appl. Sci. 2020, 10(14), 5009; https://doi.org/10.3390/app10145009 - 21 Jul 2020
Viewed by 473
Abstract
Mobile phone data provides information, such as the home (origin) and current locations of people. The data can be used to analyze the impact of new high-speed railway (HSR) openings. This study examined the population observed in stations and cities of the Honam [...] Read more.
Mobile phone data provides information, such as the home (origin) and current locations of people. The data can be used to analyze the impact of new high-speed railway (HSR) openings. This study examined the population observed in stations and cities of the Honam HSR line in Korea, based on mobile phone data recorded one year before and after its opening. We analyzed the volume of the population observed at each railway station, density of the distance between home and station, and activity hotspots in a city. The results show that the number of people and travel distance increased after the opening of the HSR. The distance to access railway stations increased, as the HSR saves travel time. Moreover, the activity hotspots in a city increased after the opening of the HSR, as more people gathered near the station area. The findings show that the mobility measures enhanced after the opening of the HSR for regional travel and local activities. These measures can help transit agencies and planners in providing better intercity travel. Full article
(This article belongs to the Section Civil Engineering)
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Open AccessArticle
BactericidalActivity of Crevicular Polymorphonuclear Neutrophils in Chronic Periodontitis Patients and Healthy Subjects under the Influence of Areca Nut Extract: An In Vitro Study
Appl. Sci. 2020, 10(14), 5008; https://doi.org/10.3390/app10145008 - 21 Jul 2020
Cited by 5 | Viewed by 502
Abstract
Arecanutchewing is an established risk factor for oral submucous fibrosis (OSMF), but its role in periodontal disease has not yet been defined. Thisstudy aimed to assess the effect of areca nut extracts (ANE) on the bactericidal activity of crevicular polymorphonuclear neutrophils (cPMNs) in [...] Read more.
Arecanutchewing is an established risk factor for oral submucous fibrosis (OSMF), but its role in periodontal disease has not yet been defined. Thisstudy aimed to assess the effect of areca nut extracts (ANE) on the bactericidal activity of crevicular polymorphonuclear neutrophils (cPMNs) in healthy subjects and chronic periodontitis (CP) patients. An in vitro study was designed with an equal number of (n = 30) gingival crevicular fluid (GCF) samples collected from CP patients and healthy subjects. Bactericidal activity and hydrogen peroxide (H2O2) assays were performed with the GCF samples pre-treated with extracts of two varieties of areca nut: ripe and tender. Simultaneously, controls were also carried out with Hank’s balanced salt solution (HBSS) and catechin. Independent t-test and one-way analysis of variance (ANOVA), along with post-hoc analysis, were employed for statistical analysis. In both study groups, a significant reduction (p < 0.01)in the bactericidal activity was noted when the samples treated with the ripe areca nut (rANE) were compared with the tender variant (tANE). Similarly, H2O2 levels were significantly reduced (p < 0.001) in the rANE in contrast to tANE for both study groups. The above results were significant within the group but were found to be non-significant between the study groups, except when it was treated with HBSS (p < 0.001). In the present study, it was found that there was a reduction in the bactericidal activity and H2O2 production of cPMNs in both healthy subjects and CP patients in the presence of areca nut extract. Moreover, the effect of rANE on cPMNs was more detrimental than tANE. Full article
(This article belongs to the Section Applied Biosciences and Bioengineering)
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Open AccessArticle
Layer-by-Layer Deposition of Copper and Phosphorus Compounds to Develop Flame-Retardant Polyamide 6/Montmorillonite Hybrid Composites
Appl. Sci. 2020, 10(14), 5007; https://doi.org/10.3390/app10145007 - 21 Jul 2020
Cited by 2 | Viewed by 677
Abstract
Nowadays, increasing attention is devoted to the search for polymeric composite materials that are characterized by reduced flammability. In this work, the layer-by-layer (LbL) technique was applied to form multilayered protective coatings for polyamide 6/montmorillonite (PA6/MMT) hybrid nanocomposites. This time, the double layers [...] Read more.
Nowadays, increasing attention is devoted to the search for polymeric composite materials that are characterized by reduced flammability. In this work, the layer-by-layer (LbL) technique was applied to form multilayered protective coatings for polyamide 6/montmorillonite (PA6/MMT) hybrid nanocomposites. This time, the double layers LbL deposition was used in order to improve the thermal properties or flammability of PA6 materials. Our goal was to check how five, 10, and 15 triple-layer deposition onto the surface of PA6 and PA6/MMT composites influenced these relevant properties. For this reason, disodium H-phosphonate, sodium montmorillonite, and iodo-bis(triphenylphosphino)copper were used for polyelectrolyte solution preparation. It was found that the LbL method could be successfully used to improve the flammability characteristics of polyamide 6-based composites. Nevertheless, the deposition of the copper complex should be combined with other flame retardants—preferentially containing phosphorus—which enable synergistic effects to occur. Moreover, microscopic observations confirmed that the surfaces on which the formation of interwoven fibrous crystal structures was observed had a tendency to protect the entire material against the destructive effects of heat, contributing, among other things, to reduce the maximum point of heat release rate (PHRR). Full article
(This article belongs to the Special Issue Synthesis, Characterization and Application of Hybrid Composites)
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Open AccessArticle
Identifying Groundwater Fluoride Source in a Weathered Basement Aquifer in Central Malawi: Human Health and Policy Implications
Appl. Sci. 2020, 10(14), 5006; https://doi.org/10.3390/app10145006 - 21 Jul 2020
Cited by 1 | Viewed by 618
Abstract
Consumption of groundwater containing fluoride exceeding World Health Organization (WHO) 1.5 mg/L standard leaves people vulnerable to fluorosis: a vulnerability not well characterised in Malawi. To evaluate geogenic fluoride source and concentration, groundwater fluoride and geology was documented in central Malawi where groundwater [...] Read more.
Consumption of groundwater containing fluoride exceeding World Health Organization (WHO) 1.5 mg/L standard leaves people vulnerable to fluorosis: a vulnerability not well characterised in Malawi. To evaluate geogenic fluoride source and concentration, groundwater fluoride and geology was documented in central Malawi where groundwater supplies are mainly sourced from the weathered basement aquifer. Lithological composition was shown as the main control on fluoride occurrence. Augen gneiss of granitic composition posed the greatest geological fluoride risk. The weathered basement aquifer profile was the main factor controlling fluoride distributions. These results and fluoride-lithology statistical analysis allowed the development of a graded map of geological fluoride risk. A direct link to human health risk (dental fluorosis) from geological fluoride was quantified to support science-led policy change for fluoride in rural drinking water in Malawi. Hazard quotient (HQ) values were calculated and assigned to specific water points, depending on user age group; in this case, 74% of children under six were shown to be vulnerable to dental fluorosis. Results are contrary to current standard for fluoride in Malawi groundwater of 6 mg/L, highlighting the need for policy change. Detailed policy recommendations are presented based on the results of this study. Full article
(This article belongs to the Special Issue Effects of Mineral Elements on the Environment)
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Open AccessArticle
Effect of Strain Hardening on Increase in Collapse Pressure during the Manufacture of ERW Pipe
Appl. Sci. 2020, 10(14), 5005; https://doi.org/10.3390/app10145005 - 21 Jul 2020
Cited by 1 | Viewed by 543
Abstract
Plastic deformation during the manufacture process of electric resistance welded (ERW) pipe determines the stress–strain relationship of the steel pipe, which affects the collapse pressure of offshore pipelines. To track the deformation history of the pipe, the entire process was simulated via finite [...] Read more.
Plastic deformation during the manufacture process of electric resistance welded (ERW) pipe determines the stress–strain relationship of the steel pipe, which affects the collapse pressure of offshore pipelines. To track the deformation history of the pipe, the entire process was simulated via finite element analysis using a solid element. A material model that considered both the Bauschinger effect and strain hardening was adopted. Various sizes of pipe cross-sections were simulated. As greater compression was applied during the sizing process, the strain hardening effect became more significant, so that the compressive yield strength was increased in the circumferential direction. The strain hardening effect was most prominent for a smaller diameter-to-thickness ratio (D/t), so that an increase in the collapse pressure could be obtained with a larger sizing ratio. Therefore, current design criteria for the collapse pressure recommended by Det Norske Verita (DNV) and API could be enhanced for a smaller D/t to consider the strain hardening effect during the sizing process. Full article
(This article belongs to the Special Issue Advances on Structural Engineering)
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Open AccessArticle
Tracking of Multiple Closely Spaced Extended Targets Based on Prediction-Driven Measurement Sub-Partitioning Algorithm
Appl. Sci. 2020, 10(14), 5004; https://doi.org/10.3390/app10145004 - 21 Jul 2020
Viewed by 409
Abstract
For multiple extended target tracking, the accuracy of measurement partitioning directly affects the target tracking performance, so the existing partitioning algorithms tend to use as many partitions as possible to obtain accurate estimates of target number and states. Unfortunately, this may create an [...] Read more.
For multiple extended target tracking, the accuracy of measurement partitioning directly affects the target tracking performance, so the existing partitioning algorithms tend to use as many partitions as possible to obtain accurate estimates of target number and states. Unfortunately, this may create an intolerable computational burden. What is worse is that the measurement partitioning problem of closely spaced targets is still challenging and difficult to solve well. In view of this, a prediction-driven measurement sub-partitioning (PMS) algorithm is first proposed, in which target predictions are fully utilized to determine the clustering centers for obtaining accurate partitioning results. Due to its concise mathematical forms and favorable properties, redundant measurement partitions can be eliminated so that the computational burden is largely reduced. More importantly, the unreasonable target predictions may be marked and replaced by PMS for solving the so-called cardinality underestimation problem without adding extra measurement partitions. PMS is simple to implement, and based on it, an effective multiple closely spaced extended target tracking approach is easily obtained. Simulation results verify the benefit of what we proposed—it has a much faster tracking speed without degrading the performance compared with other approaches, especially in a closely spaced target tracking scenario. Full article
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Open AccessArticle
Corridor Detection from Large GPS Trajectories Datasets
Appl. Sci. 2020, 10(14), 5003; https://doi.org/10.3390/app10145003 - 21 Jul 2020
Cited by 1 | Viewed by 660
Abstract
Given the widespread use of mobile devices that track their geographical location, it has become increasingly easy to acquire information related to users’ trips in real time. This availability has triggered several studies based on user’s position, such as the analysis of flows [...] Read more.
Given the widespread use of mobile devices that track their geographical location, it has become increasingly easy to acquire information related to users’ trips in real time. This availability has triggered several studies based on user’s position, such as the analysis of flows of people in cities, and also new applications, such as route recommendation systems. Given a dataset of geographical trajectories in an urban metropolitan area, we propose a new algorithm to detect corridors. Corridors can be defined as geographical paths, with a minimum length, that are commonly traversed by a minimum number of different users. We propose an efficient strategy based on the Apriori algorithm to extract frequent trajectory patterns from the geo-spatial dataset. By discretizing the data and adapting the roles of itemsets and baskets of this algorithm to our context, we find the longest corridors formed by cells shared by a minimum number of trajectories. After that, we refine the results obtained with a subsequent filtering step, by using a Radius Neighbors Graph. To illustrate the algorithm, the GeoLife dataset is analyzed by following the proposed method. Our approach is relevant for transportation analytics because it is the base to detect lacking lines in public transportation systems and also to recommend to private users which route to take when moving from one part of the city to another on the basis of behavior of the users who provided their logs. Full article
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Open AccessArticle
Spatial Variability of Grouting Layer of Shield Tunnel and Its Effect on Ground Settlement
Appl. Sci. 2020, 10(14), 5002; https://doi.org/10.3390/app10145002 - 21 Jul 2020
Viewed by 455
Abstract
This study aims to investigate the effect of the spatial variability of grouting-layer thickness on ground-surface settlement caused by shield tunneling and to provide a rational prediction method. The spatial characteristics of grouting layers were obtained based on statistical analysis. The random finite [...] Read more.
This study aims to investigate the effect of the spatial variability of grouting-layer thickness on ground-surface settlement caused by shield tunneling and to provide a rational prediction method. The spatial characteristics of grouting layers were obtained based on statistical analysis. The random finite element method was used to study the effect of spatial variability of different parameters on ground-surface settlement. Simulation results indicate that the spatial variability of the grouting layer has a negative impact on ground settlement. The surface settlement will be underestimated without considering the spatial characteristics of the grouting layer. Thus, a reliable prediction approach of the maximum ground settlement was proposed to control the construction quality. Full article
(This article belongs to the Section Civil Engineering)
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Open AccessArticle
The Effectiveness of Nafion-Coated Stainless Steel Surfaces for Inhibiting Bacillus Subtilis Biofilm Formation
Appl. Sci. 2020, 10(14), 5001; https://doi.org/10.3390/app10145001 - 21 Jul 2020
Cited by 1 | Viewed by 441
Abstract
Stainless steel is one of most commonly used materials in the world; however, biofilms on the surfaces of stainless steel cause many serious problems. In order to find effective methods of reducing bacterial adhesion to stainless steel, and to investigate the role of [...] Read more.
Stainless steel is one of most commonly used materials in the world; however, biofilms on the surfaces of stainless steel cause many serious problems. In order to find effective methods of reducing bacterial adhesion to stainless steel, and to investigate the role of electrostatic effects during the formation of biofilms, this study used a stainless steel surface that was negatively charged by being coated with Nafion which was terminated by sulfonic groups. The results showed that the roughness of stainless steel discs coated with 1% Nafion was similar to an uncoated surface; however the hydrophobicity increased, and the Nafion-coated surface reduced the adhesion of Bacillus subtilis by 75% compared with uncoated surfaces. Therefore, a facile way to acquire antibacterial stainless steel was found, and it is proved that electrostatic effects have a significant influence on the formation of biofilms. Full article
(This article belongs to the Section Chemistry)
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Open AccessArticle
Task Planning of Space-Robot Clusters Based on Modified Differential Evolution Algorithm
Appl. Sci. 2020, 10(14), 5000; https://doi.org/10.3390/app10145000 - 21 Jul 2020
Cited by 1 | Viewed by 475
Abstract
This study studies the problem of on-orbit maintenance task planning for space-robot clusters. Aiming at the problem of low maintenance efficiency of space-robot cluster task-planning, this study proposes a cluster-task-planning method based on energy and path optimization. First, by introducing the penalty-function method, [...] Read more.
This study studies the problem of on-orbit maintenance task planning for space-robot clusters. Aiming at the problem of low maintenance efficiency of space-robot cluster task-planning, this study proposes a cluster-task-planning method based on energy and path optimization. First, by introducing the penalty-function method, the task planning problem of the space-robot cluster under limited energy is analyzed, and the optimal-path model for task planning with comprehensive optimization of revenue and energy consumption are constructed; then, the maintenance task points are clustered to reduce the scale of the problem, thus reducing the difficulty of solving the problem; finally, a modified differential evolution algorithm is proposed to solve the problem of space-robot cluster task-planning, improve the performance of space-robot cluster task-assignment and path planning. Simulation results show that the proposed optimal-path model of space-robot cluster and the modified differential evolution algorithm can effectively solve the task-planning problem of spatial robot clusters. Full article
(This article belongs to the Section Aerospace Science and Engineering)
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Open AccessArticle
Off-Design Performance Prediction of a S-CO2 Turbine Based on Field Reconstruction Using Deep-Learning Approach
Appl. Sci. 2020, 10(14), 4999; https://doi.org/10.3390/app10144999 - 21 Jul 2020
Cited by 1 | Viewed by 490
Abstract
The reliable design of the supercritical carbon dioxide (S-CO2) turbine is the core of the advanced S-CO2 power generation technology. However, the traditional computational fluid dynamics (CFD) method is usually applied in the S-CO2 turbine design-optimization, which is a [...] Read more.
The reliable design of the supercritical carbon dioxide (S-CO2) turbine is the core of the advanced S-CO2 power generation technology. However, the traditional computational fluid dynamics (CFD) method is usually applied in the S-CO2 turbine design-optimization, which is a high computational cost, high memory requirement, and long time-consuming solver. In this research, a flexible end-to-end deep learning approach is presented for the off-design performance prediction of the S-CO2 turbine based on physical fields reconstruction. Our approach consists of three steps: firstly, an optimal design of a 60,000 rpm S-CO2 turbine is established. Secondly, five design variables for off-design analysis are selected to reconstruct the temperature and pressure fields on the blade surface through a deconvolutional neural network. Finally, the power and efficiency of the turbine is predicted by a convolutional neural network according to reconstruction fields. The results show that the prediction approach not only outperforms five classical machine learning models but also focused on the physical mechanism of turbine design. In addition, once the deep model is well-trained, the calculation with graphics processing unit (GPU)-accelerated can quickly predict the physical fields and performance. This prediction approach requires less human intervention and has the advantages of being universal, flexible, and easy to implement. Full article
(This article belongs to the Section Energy)
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Open AccessFeature PaperArticle
Comparison between Design Formulations and Numerical Results for In-Plane FRCM-Strengthened Masonry Walls
Appl. Sci. 2020, 10(14), 4998; https://doi.org/10.3390/app10144998 - 21 Jul 2020
Cited by 2 | Viewed by 776
Abstract
Strengthening strategies and structural rehabilitation of existing buildings with innovative materials and techniques are today one of the main activities in the field of structural engineering. Externally bonded Fiber Reinforced Cementitious Matrix (FRCM), materials are spreading as an alternative strengthening technique to the [...] Read more.
Strengthening strategies and structural rehabilitation of existing buildings with innovative materials and techniques are today one of the main activities in the field of structural engineering. Externally bonded Fiber Reinforced Cementitious Matrix (FRCM), materials are spreading as an alternative strengthening technique to the more traditional Fiber Reinforced Polymer (FRP) ones, especially for masonry elements. This research focuses on the assessment of the shear strength of in-plane FRCM-strengthened masonry walls by means of code predictions and numerical results, with particular attention on the interpretation of diagonal compression tests simulated by means of Finite Element (FE) models. Firstly, the various approaches commonly adopted for the interpretation of diagonal compression tests in terms of shear strength were examined, since codes give generally provisions in terms of maximum shear force, while several experimental and numerical results of diagonal compression tests are available in literature. Then, the numerical simulations of diagonal compression tests obtained by several FE analyses in a previous work were examined in light of these different approaches; the corresponding predictions of the shear force are compared with code indications in order to individuate the most reliable approach both for the un-strengthened and the FRCM-strengthened walls. For the latter ones, a detailed analysis of the actual strain levels in the reinforcement was carried out, too, by means of FE analysis. Full article
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Open AccessArticle
Evolutions of CO2 Adsorption and Nanopore Development Characteristics during Coal Structure Deformation
Appl. Sci. 2020, 10(14), 4997; https://doi.org/10.3390/app10144997 - 21 Jul 2020
Cited by 1 | Viewed by 423
Abstract
The coal structure deformation attributed to actions of tectonic stresses can change characteristics of nanopore structure of coals, affecting their CO2 adsorption. Three tectonically deformed coals and one undeformed coal were chosen as the research objects. The isotherm adsorption experiments of four [...] Read more.
The coal structure deformation attributed to actions of tectonic stresses can change characteristics of nanopore structure of coals, affecting their CO2 adsorption. Three tectonically deformed coals and one undeformed coal were chosen as the research objects. The isotherm adsorption experiments of four coal specimens were carried out at the temperature of 35 °C and the pressure of 0 to 7 MPa. Nanopore structures were characterized using the liquid nitrogen adsorption method. The results show that there exist maximum values of excess and absolute adsorption capacity, which increase with increasing coal deformation degree. As the degree of coal deformation increases, the pore volume and specific surface area present an obvious increasing trend in the case of micropores, exhibiting an increase at first (cataclastic coal and ganulitic coal) and then stabilization (crumple coal), in the case of mesopores, and showing a gradual decrease in the case of macropores. The mesopores are the key factor of CO2 adsorption of tectonically deformed coals, followed by the micropores and the limited effect of macropores at the strong coal deformation stage. Full article
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Open AccessReview
What Can Complex Dietary Supplements Do for Hair Loss and How Can It Be Validly Measured—A Review
Appl. Sci. 2020, 10(14), 4996; https://doi.org/10.3390/app10144996 - 21 Jul 2020
Viewed by 926
Abstract
Hair plays a major role in perception within a society. It provides information about gender, age, health, and social status. It is therefore not surprising that those affected are exposed to great suffering due to the widespread occurrence of hair loss. As a [...] Read more.
Hair plays a major role in perception within a society. It provides information about gender, age, health, and social status. It is therefore not surprising that those affected are exposed to great suffering due to the widespread occurrence of hair loss. As a result, the demand for new products to remedy this problem is not diminishing. Hair grows in cycles, and a hair follicle goes through several phases called the hair cycle. The active growth phase (anagen phase) lasts 2–6 years. In this state a hair follicle shows a growth of about 1 cm per month. In order to improve the existing hair status, hair should be kept in the active anagen phase as long as possible, or the transition to anagen should be stimulated. A number of reviews already describe the influence of individual active ingredients on hair growth. However, the following review describes existing studies of complex dietary supplements with their experimental weaknesses and strengths and their influence on hair loss. Also, for the determination of hair loss, it is important to use a valid method with high acceptance by the test persons. In this context, the TrichoScale® is a validated and non-invasive tool for quantifying hair loss/hair growth. Thus, it is an ideal measuring instrument to objectively quantify the effectiveness of a hair loss treatment. Full article
(This article belongs to the Special Issue Recent Advances in Hair Science)
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Open AccessArticle
Cytotoxicity and UV Light Absorption in Biopolymeric Membranes from Native Vegetation of Mexico
Appl. Sci. 2020, 10(14), 4995; https://doi.org/10.3390/app10144995 - 21 Jul 2020
Viewed by 612
Abstract
Sustainable processing from native vegetation such as agave, nopal and aloe, is mainly centered on the components of lignin, cellulose, and hemicellulose, defined generally as lignocellulosic. Cytotoxicity of lignocellulosic biopolymer membranes (LBMs) of mucilages of Opuntia ficus-indica, Aloe barbadensis Miller, fructans, [...] Read more.
Sustainable processing from native vegetation such as agave, nopal and aloe, is mainly centered on the components of lignin, cellulose, and hemicellulose, defined generally as lignocellulosic. Cytotoxicity of lignocellulosic biopolymer membranes (LBMs) of mucilages of Opuntia ficus-indica, Aloe barbadensis Miller, fructans, and residual Agave tequilana Weber fibers at different concentrations (30, 50 and 70%), was evaluated in contact with human fibroblast cells (ATCC® PCS-201-010), cultured in vitro. Long and short LMBs were formed from the fibrous material. The interaction showed mild cytotoxicity according to ISO 10993-5: 2009. Cytotoxic activity demonstrated in the presence of fibroblasts implied a maximum cytotoxicity of close to 46% and a minimum of 7% in LBMs. UV light absorption results of the large fiber LMBs showed the highest prevention of passage of light, having a protective effect mechanism of delaying the response of hypersensitivity as a result of exposure to UV radiation. The morphology and structure were characterized using SEM, FT-IR, and image texture analysis. According to the LBMs reactivity measured, the feasible uses of these membranes can be suggested as materials for biomedical applications over a short period of time, with feasibility as a support to provide some beneficial solutions. Full article
(This article belongs to the Special Issue New Frontiers of Natural Fibers and Their Composites)
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Open AccessArticle
The Value and Optimal Sizes of Energy Storage Units in Solar-Assist Cogeneration Energy Hubs
Appl. Sci. 2020, 10(14), 4994; https://doi.org/10.3390/app10144994 - 21 Jul 2020
Cited by 3 | Viewed by 535
Abstract
Cogeneration is becoming increasingly popular in building and community energy systems with demands on electricity and heat, which is suitable for residential and industrial use in remote areas. This paper considers a stand-alone cogeneration energy hub. The electrical and thermal energies are produced [...] Read more.
Cogeneration is becoming increasingly popular in building and community energy systems with demands on electricity and heat, which is suitable for residential and industrial use in remote areas. This paper considers a stand-alone cogeneration energy hub. The electrical and thermal energies are produced by a combined heat and power (CHP) unit, photovoltaic panels, and a solar thermal collector. Since solar units generate no electricity and heat during the night, energy storage units which shift demands over time can promote the usage of solar energy and reduce the fuel cost of the CHP unit. This paper proposes a method to retrieve the optimal operation cost as an explicit function in the capacity parameters of electric and thermal energy storage units, reflecting the value of energy storage in the cogeneration energy hub. The capacity parameter set is divided into a collection of polyhedrons; on each polyhedron, the optimal value is an affine function in the capacity parameters. Furthermore, the optimal sizes of system components are discussed. The capacity of the CHP unit is determined from a linear program, ensuring supply adequacy; the capacities of solar generation and energy storage units are calculated based on the cost reduction and the budget. Case studies demonstrate the effectiveness of the proposed method. Full article
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Open AccessArticle
Effect of Acoustic Shock on Submarine
Appl. Sci. 2020, 10(14), 4993; https://doi.org/10.3390/app10144993 - 20 Jul 2020
Viewed by 610
Abstract
The carried-out analysis of the dynamics of a submarine body’s translational motion affected by an acoustic shock in the ideal medium provides for the possibility to evaluate the physical properties of the medium and elastic properties of the external body of the submarine [...] Read more.
The carried-out analysis of the dynamics of a submarine body’s translational motion affected by an acoustic shock in the ideal medium provides for the possibility to evaluate the physical properties of the medium and elastic properties of the external body of the submarine to the value of limited motion of a submersible vehicle. The results of analysis provide for the possibility to conduct a comparative analysis of the submersible vehicle’s translational motion affected by an acoustic shock, taking into account the peculiarities of the motion medium, or rather taking into account the viscosity of the real medium. In this work, evaluative measurements of the features of moving the layout of the submarine were carried out. The limiting values of the displacement of the layout of the submarine are established for the case of the presence of an external artificial diffuse disturbance. A fluid with air bubbles from a compressed air cylinder was used to create an artificial diffuse perturbation. Such conditions are possible with intensive local bombardment or the presence of other high-speed underwater vehicles involved in local underwater operations. Full article
(This article belongs to the Section Acoustics and Vibrations)
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