Applied Sciences

19 pages, 18916 KiB

Open AccessArticle

Optical Coherence Tomography Angiography Monitors Cutaneous Wound Healing under Angiogenesis-Promoting Treatment in Diabetic and Non-Diabetic Mice

by Martin Pfister, Kornelia Schützenberger, Bhavapriya J. Schäfer, Stefan Puchner, Hannes Stegmann, Christine Hohenadl, Michael Mildner, Gerhard Garhöfer, Leopold Schmetterer and René M. Werkmeister

Appl. Sci. 2021, 11(5), 2447; https://doi.org/10.3390/app11052447 - 9 Mar 2021

Cited by 5 | Viewed by 3511

Abstract

During wound healing, the rapid re-establishment of a functional microcirculation in the wounded tissue is of utmost importance. We applied optical coherence tomography (OCT) angiography to evaluate vascular remodeling in an excisional wound model in the pinnae of C57BL/6 and db/db mice receiving [...] Read more.

During wound healing, the rapid re-establishment of a functional microcirculation in the wounded tissue is of utmost importance. We applied optical coherence tomography (OCT) angiography to evaluate vascular remodeling in an excisional wound model in the pinnae of C57BL/6 and db/db mice receiving different proangiogenic topical treatments. Analysis of the high-resolution OCT angiograms, including the four quantitative parameters vessel density, vessel length, number of bifurcations, and vessel tortuosity, revealed changes of the microvasculature and allowed identification of the overlapping wound healing phases hemostasis, inflammation, proliferation, and remodeling. Angiograms acquired in the inflammatory phase in the first days showed a dilation of vessels and recruitment of pre-existing capillaries. In the proliferative phase, angiogenesis with the sprouting of new capillaries into the wound tissue led to an increase of the OCT angiography parameters vessel density, normalized vessel length, number of bifurcations, and vessel tortuosity by 28–47%, 39–52%, 33–48%, and 3–8% versus baseline, respectively. After the peak observed on study days four to seven, the parameters slowly decreased but remained still elevated 18 days after wounding, indicating a continuing remodeling phase. Our study suggests that OCT angiography has the potential to serve as a valuable preclinical research tool in studies investigating impaired vascular remodeling during wound healing and potential new treatment strategies. Full article

(This article belongs to the Special Issue Applications of Advanced Imaging Technology in Biomedical Engineering)

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12 pages, 3620 KiB

Open AccessFeature PaperArticle

Steel Reinforcing Bar and Steel Fibers Content Effect on Tensile and Electrical Behaviors of Strain-Hardening Cement Composite (SHCC) with MWCNTs in Direct Tension

by Dong-Hui Kim, Wan-Shin Park, Sun-Woo Kim, Moon-Sung Lee, Soo-Yeon Seo and Hyun-Do Yun

Appl. Sci. 2021, 11(5), 2446; https://doi.org/10.3390/app11052446 - 9 Mar 2021

Cited by 2 | Viewed by 2713

Abstract

This research examines the influence of an embedded steel reinforcing bar and micro steel fibers on the tensile and electrical properties of polyethylene (PE) fibers reinforced cement composite dumbbell-shaped specimens with multi-walled carbon nanotubes (MWCNTs) in direct tension. The cement composites are reinforced [...] Read more.

This research examines the influence of an embedded steel reinforcing bar and micro steel fibers on the tensile and electrical properties of polyethylene (PE) fibers reinforced cement composite dumbbell-shaped specimens with multi-walled carbon nanotubes (MWCNTs) in direct tension. The cement composites are reinforced with 0.75 vol.% PE fibers to achieve a strain-hardening performance in direct tension and 1.0 wt % MWCNTs are incorporated to give the electrical conductivity into the cement composites. To investigate the steel bar and steel fibers effect on the electrical behavior of synthetic PE fiber reinforced strain-hardening cement composites (PE-SHCCs), a round bar with a diameter of 4 or 7 mm is placed at the center of specimen’s cross-section. Additionally, steel fibers’ content of 0, 0.5 and 1.0 vol.% are added into the PE-SHCC mixtures. The test result indicates that the addition of steel fibers improves the tensile strength and electrical behavior of synthetic PE fiber reinforced SHCC. The self-sensing ability of PE-SHCC with 1.0% steel fibers is improved by the presence of the embedded steel bar before an initial crack while the reinforced PE-SHCC specimens were less sensitive as the tensile strain increased after the initial crack. The optimal linear regressions between fractional changes in resistivity (FCR) and tensile strain were achieved for PE-SHCC containing 1.0% steel fibers. Full article

(This article belongs to the Special Issue Advanced Fiber-Reinforced Cementitious Composites)

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19 pages, 569 KiB

Open AccessSystematic Review

The Alterations in CD14 Expression in Periodontitis: A Systematic Review

by Vivian Hirsch, Alice Blufstein, Christian Behm and Oleh Andrukhov

Appl. Sci. 2021, 11(5), 2444; https://doi.org/10.3390/app11052444 - 9 Mar 2021

Cited by 4 | Viewed by 2333

Abstract

Objective: Cluster of differentiation (CD14) is an important protein involved in activating toll-like receptors by bacterial components. It exists as either a transmembrane or soluble protein, called mCD14 or sCD14, respectively. Several studies show that CD14 regulates the inflammatory response to periodontal pathogens, [...] Read more.

Objective: Cluster of differentiation (CD14) is an important protein involved in activating toll-like receptors by bacterial components. It exists as either a transmembrane or soluble protein, called mCD14 or sCD14, respectively. Several studies show that CD14 regulates the inflammatory response to periodontal pathogens, and its expression is altered in periodontitis, an inflammatory disease of tooth-supporting tissues. It is the intent of this review to investigate the levels of expression of mCD14 and sCD14 in peripheral blood monocytes, saliva, gingival crevicular fluid, and gingival tissue biopsies in periodontitis patients. Methods: PubMed, Scopus, Ovid/Medline, Embase, and the Cochrane Library were consulted for the online literature search. To ensure methodical quality, titles and abstracts were reviewed in accordance to the PRISMA guidelines. Data extraction and evaluation of the full texts were executed in agreement with the GRADE approach. Results: This systematic review shows that mCD14 levels are decreased in peripheral blood monocytes of periodontitis patients in comparison to healthy patients, while sCD14 levels in sera, gingival crevicular fluid (GCF), and biopsies of periodontitis patients have a tendency to be increased in comparison to healthy controls. The evaluation of CD14 in gingival biopsies and periodontal tissues elucidated the fact that interpretation of the data obtained with qPCR, ELISA, and flow cytometry is questionable. Full article

(This article belongs to the Special Issue Cellular and Molecular Mechanism in Periodontal Diseases)

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15 pages, 2205 KiB

Open AccessFeature PaperArticle

Concentrate Apple Juice Industry: Aroma and Pomace Valuation as Food Ingredients

by Elisabete Coelho, Mariana Pinto, Rita Bastos, Marco Cruz, Cláudia Nunes, Sílvia M. Rocha and Manuel A. Coimbra

Appl. Sci. 2021, 11(5), 2443; https://doi.org/10.3390/app11052443 - 9 Mar 2021

Cited by 8 | Viewed by 5321

Abstract

Apple concentrate juice industry generates a flavored coproduct (apple aroma) recovered in the evaporation process, which is poorly valuated due to the lack of chemical characterization and standardization. In this study, industry apple aroma was characterized, allowing for the identification of 37 compounds, [...] Read more.

Apple concentrate juice industry generates a flavored coproduct (apple aroma) recovered in the evaporation process, which is poorly valuated due to the lack of chemical characterization and standardization. In this study, industry apple aroma was characterized, allowing for the identification of 37 compounds, the majority esters (20), alcohols (7), and aldehydes (4). The storage temperature did not affect its volatile composition. Five key compounds were selected and monitored for 10 months of storage, and also compared with other three productions of another season allowing for observation of the same Aroma Index. Apple pomace was also used to produce a hydrodistillate. Contrary to the apple aroma, apple pomace hydrodistillate was unpleasant, reflected in a different volatile composition. Although no additional aroma fraction could be obtained from this wet byproduct, when dried, apple pomace presented 15 volatile compounds with toasted, caramel, sweet, and green notes. The infusions prepared with the dried apple pomace exhibited 25 volatile compounds with a very pleasant (fruity, apple-like, citrus, and spicy notes) and intense aroma. The addition of sugar changed the volatile profile, providing a less intense flavor, with almond, caramel, and sweet notes. These results show that apple aroma and pomace are high-quality flavoring agents with high potential of valuation as food ingredients. Full article

(This article belongs to the Special Issue Evaluation of Chemical Characteristics of Biowaste and By-Products from Food Systems)

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25 pages, 2858 KiB

Open AccessArticle

Thermo-Economic Comparisons of Environmentally Friendly Solar Assisted Absorption Air Conditioning Systems

by Adil Al-Falahi, Falah Alobaid and Bernd Epple

Appl. Sci. 2021, 11(5), 2442; https://doi.org/10.3390/app11052442 - 9 Mar 2021

Cited by 7 | Viewed by 2641

Abstract

Absorption refrigeration cycle is considered a vital option for thermal cooling processes. Designing new systems is needed to meet the increasing communities’ demands of space cooling. This should be given more attention especially with the increasing conventional fossil fuel energy costs and CO [...] Read more.

Absorption refrigeration cycle is considered a vital option for thermal cooling processes. Designing new systems is needed to meet the increasing communities’ demands of space cooling. This should be given more attention especially with the increasing conventional fossil fuel energy costs and CO₂ emission. This work presents the thermo-economic analysis to compare between different solar absorption cooling system configurations. The proposed system combines a solar field, flashing tank and absorption chiller: two types of absorption cycle H₂O-LiBr and NH₃-H₂O have been compared to each other by parabolic trough collectors and evacuated tube collectors under the same operating conditions. A case study of 200 TR total cooling load is also presented. Results reveal that parabolic trough collector combined with H₂O-LiBr (PTC/H₂O-LiBr) gives lower design aspects and minimum rates of hourly costs (5.2 $/h) followed by ETC/H₂O-LiBr configuration (5.6 $/h). H₂O-LiBr gives lower thermo-economic product cost (0.14 $/GJ) compared to the NH₃-H₂O (0.16 $/GJ). The absorption refrigeration cycle coefficient of performance ranged between 0.5 and 0.9. Full article

(This article belongs to the Special Issue Thermochemical Conversion Processes for Solid Fuels and Renewable Energies: Volume II)

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13 pages, 12315 KiB

Open AccessArticle

A Study on the Microstructure and Corrosion Characteristics of Early Iron Age Bronze Mirrors Excavated from the Korean Peninsula

by Nam Chul Cho, Min Kyeong Jang and Il Kwon Huh

Appl. Sci. 2021, 11(5), 2441; https://doi.org/10.3390/app11052441 - 9 Mar 2021

Cited by 2 | Viewed by 2862

Abstract

Bronze mirrors, considered important grave goods, were widely used before glass mirrors in ancient times. Most excavated bronze artifacts are covered with corrosive materials and lose their original colors. More importantly, identifying corrosion characteristics and the manufacturing techniques used for these artifacts are [...] Read more.

Bronze mirrors, considered important grave goods, were widely used before glass mirrors in ancient times. Most excavated bronze artifacts are covered with corrosive materials and lose their original colors. More importantly, identifying corrosion characteristics and the manufacturing techniques used for these artifacts are essential for proper artifact preservation. In this study, Early Iron Age bronze mirrors excavated from the Korean Peninsula were examined to determine their microstructures, corrosion characteristics, and production techniques using various analytical methods, such as Micro-Raman spectroscopy and field emission electron probe microanalysis. As a result, sulfides containing iron suggested chalcopyrite use during production or that the sulfides originated from copper, iron, and sulfur residual matte. The analysis also detected corrosion layers with high tin oxide (SnO₂) levels and selective corrosion in the α + δ eutectoid phase on the artifact’s surface. In the corrosive layer, cuprite, malachite, and cassiterite corrosion products were detected, and nanocrystalline SnO₂ was identified as a characteristic of long-term soil erosion. Identifying these artifacts’ corrosion characteristics and manufacturing techniques is essential and can greatly contribute to proper artifact preservation. Full article

(This article belongs to the Special Issue Scientific Methods for Cultural Heritage)

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Graphical abstract

22 pages, 8545 KiB

Open AccessArticle

Numerical Optimization of a Microchannel Geometry for Nanofluid Flow and Heat Dissipation Assessment

by Inês M. Gonçalves, César Rocha, Reinaldo R. Souza, Gonçalo Coutinho, Jose E. Pereira, Ana S. Moita, António L. N. Moreira, Rui Lima and João M. Miranda

Appl. Sci. 2021, 11(5), 2440; https://doi.org/10.3390/app11052440 - 9 Mar 2021

Cited by 9 | Viewed by 3187

Abstract

In this study, a numerical approach was carried out to analyze the effects of different geometries of microchannel heat sinks on the forced convective heat transfer in single-phase flow. The simulations were performed using the commercially available software COMSOLMultiphysics 5.6^® (Burlington, MA, [...] Read more.

In this study, a numerical approach was carried out to analyze the effects of different geometries of microchannel heat sinks on the forced convective heat transfer in single-phase flow. The simulations were performed using the commercially available software COMSOLMultiphysics 5.6^® (Burlington, MA, USA) and its results were compared with those obtained from experimental tests performed in microchannel heat sinks of polydimethylsiloxane (PDMS). Distilled water was used as the working fluid under the laminar fluid flow regime, with a maximum Reynolds number of 293. Three sets of geometries were investigated: rectangular, triangular and circular. The different configurations were characterized based on the flow orientation, type of collector and number of parallel channels. The main results show that the rectangular shaped collector was the one that led to a greater uniformity in the distribution of the heat transfer in the microchannels. Similar results were also obtained for the circular shape. For the triangular geometry, however, a disturbance in the jet impingement was observed, leading to the least uniformity. The increase in the number of channels also enhanced the uniformity of the flow distribution and, consequently, improved the heat transfer performance, which must be considered to optimize new microchannel heat sink designs. The achieved optimized design for a heat sink, with microchannels for nanofluid flow and a higher heat dissipation rate, comprised a rectangular collector with eight microchannels and vertical placement of the inlet and outlet. Full article

(This article belongs to the Special Issue Flow and Heat Transfer in Micro and Millifluidic Devices)

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27 pages, 31615 KiB

Open AccessArticle

Integrated Design of a Morphing Winglet for Active Load Control and Alleviation of Turboprop Regional Aircraft

by Ignazio Dimino, Giovanni Andreutti, Frédéric Moens, Federico Fonte, Rosario Pecora and Antonio Concilio

Appl. Sci. 2021, 11(5), 2439; https://doi.org/10.3390/app11052439 - 9 Mar 2021

Cited by 27 | Viewed by 5428

Abstract

Aircraft winglets are well-established devices that improve aircraft fuel efficiency by enabling a higher lift over drag ratios and lower induced drag. Retrofitting winglets to existing aircraft also increases aircraft payload/range by the same order of the fuel burn savings, although the additional [...] Read more.

Aircraft winglets are well-established devices that improve aircraft fuel efficiency by enabling a higher lift over drag ratios and lower induced drag. Retrofitting winglets to existing aircraft also increases aircraft payload/range by the same order of the fuel burn savings, although the additional loads and moments imparted to the wing may impact structural interfaces, adding more weight to the wing. Winglet installation on aircraft wing influences numerous design parameters and requires a proper balance between aerodynamics and weight efficiency. Advanced dynamic aeroelastic analyses of the wing/winglet structure are also crucial for this assessment. Within the scope of the Clean Sky 2 REG IADP Airgreen 2 project, targeting novel technologies for next-generation regional aircraft, this paper deals with the integrated design of a full-scale morphing winglet for the purpose of improving aircraft aerodynamic efficiency in off-design flight conditions, lowering wing-bending moments due to maneuvers and increasing aircraft flight stability through morphing technology. A fault-tolerant morphing winglet architecture, based on two independent and asynchronous control surfaces with variable camber and differential settings, is presented. The system is designed to face different flight situations by a proper action on the movable control tabs. The potential for reducing wing and winglet loads by means of the winglet control surfaces is numerically assessed, along with the expected aerodynamic performance and the actuation systems’ integration in the winglet surface geometry. Such a device was designed by CIRA for regional aircraft installation, whereas the aerodynamic benefits and performance were estimated by ONERA on the natural laminar flow wing. An active load controller was developed by PoliMI and UniNA performed aeroelastic trade-offs and flutter calculations due to the coupling of winglet movable harmonics and aircraft wing bending and torsion. Full article

(This article belongs to the Special Issue Smart Aircraft Morphing Technologies)

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12 pages, 646 KiB

Open AccessReview

Histological and Histomorphometric Effectiveness of the Barrier Membranes for Jawbone Regeneration: An Overview of More Than 30 Years’ Experience of Research Results of the Italian Implant Retrieval Center (1988–2020)

by Margherita Tumedei, Carlos Fernando Mourão, Silvia D’Agostino, Marco Dolci, Michele Di Cosola, Adriano Piattelli and Alessandra Lucchese

Appl. Sci. 2021, 11(5), 2438; https://doi.org/10.3390/app11052438 - 9 Mar 2021

Cited by 6 | Viewed by 2261

Abstract

With the advent of implant dentistry, height and width of the bone site are fundamental to perform implant placements. There are several techniques to restore the amount of bone loss and one of them is guided bone regeneration, which is based on the [...] Read more.

With the advent of implant dentistry, height and width of the bone site are fundamental to perform implant placements. There are several techniques to restore the amount of bone loss and one of them is guided bone regeneration, which is based on the employment of a membrane in order to bypass non-osteogenic cell invasion in the bone healing area, dispersing every interference with bone regeneration. Two expert reviewers performed a retrospective evaluation of all scientific papers published by the Implant Retrieval Center Laboratory of University “G. D’Annunzio” of Chieti-Pescara in the last three decades, and they implemented it by also similar conducting research on the main scientific databases, i.e., PubMed, Scopus, and EMBASE. The search was conducted up to December 2020, and a total of 843 articles published by the Implant Retrieval Center Laboratory of University “G.D’Annunzio” of Chieti-Pescara were identified and evaluated. After the application of inclusion and exclusion criteria, a total of 27 manuscripts were included for the qualitative synthesis: 8 animal studies, 17 human studies, and 2 in vitro articles. The present overview shows the importance of translational research for barrier membranes for bone regeneration, and additionally, the need for experts in different fields and research centers to produce high quality data in future research. Full article

(This article belongs to the Special Issue Materials and Technologies in Oral Research)

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14 pages, 7418 KiB

Open AccessArticle

Investigation of Thermal Effects of Radiofrequency Ablation Mediated with Iron Oxide Nanoparticles Dispersed in Agarose and Chitosan Solvents

by Zhannat Ashikbayeva, Arman Aitkulov, Alexey Wolf, Alexander Dostovalov, Aida Amantayeva, Aliya Kurbanova, Vassilis J. Inglezakis and Daniele Tosi

Appl. Sci. 2021, 11(5), 2437; https://doi.org/10.3390/app11052437 - 9 Mar 2021

Cited by 5 | Viewed by 2445

Abstract

Thermal ablation (TA) is known as an alternative therapy to surgery to treat tumors. However, TA-based therapy requires advanced approaches in order to prevent causing damage to healthy tissue around the tumor and selectively target the desired area. Nanoparticles are considered as a [...] Read more.

Thermal ablation (TA) is known as an alternative therapy to surgery to treat tumors. However, TA-based therapy requires advanced approaches in order to prevent causing damage to healthy tissue around the tumor and selectively target the desired area. Nanoparticles are considered as a promising tool in biomedicine to fulfill these requirements. This study was carried out in order to analyze the effect of iron oxide nanoparticles on the temperature increment during radiofrequency ablation therapy of porcine liver. In addition, this research aimed to experimentally evaluate the impact of two solvents such as agarose and chitosan on the temperature change, when magnetic nanoparticles were dispersed in them. The iron oxide nanoparticles were synthesized by the solvothermal method demonstrating the magnetic properties by acting to the external magnetic field. To increase the local heat superparamagnetic nanoparticles (iron oxide magnetic nanoparticle (IONPs)) of the average size of 20 nm in size and the concentrations from 1 to 10 mg/mL of MNPs with a step size of 1 mg/mL were tested in 10 replicates for each concentration and solvent. Moreover, the temperature changes for dry liver, and 0 mg/mL concentration was checked for calibration and reference purposes. As a sensing system, advanced 16-FBG optical fiber sensors connected to an interrogator were employed allowing the temperature change to be monitored accurately in real time. A maximum temperature of about 142 °C was recorded by a 5 mg/mL concentration of iron oxide nanoparticles dispersed in the agarose solvent. Full article

(This article belongs to the Section Applied Biosciences and Bioengineering)

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Graphical abstract

13 pages, 20486 KiB

Open AccessArticle

Statistical Analysis of Nanofiber Mat AFM Images by Gray-Scale-Resolved Hurst Exponent Distributions

by Tomasz Blachowicz, Krzysztof Domino, Michał Koruszowic, Jacek Grzybowski, Tobias Böhm and Andrea Ehrmann

Appl. Sci. 2021, 11(5), 2436; https://doi.org/10.3390/app11052436 - 9 Mar 2021

Cited by 9 | Viewed by 3243

Abstract

Two-dimensional structures, either periodic or random, can be classified by diverse mathematical methods. Quantitative descriptions of such surfaces, however, are scarce since bijective definitions must be found to measure unique dependency between described structures and the chosen quantitative parameters. To solve this problem, [...] Read more.

Two-dimensional structures, either periodic or random, can be classified by diverse mathematical methods. Quantitative descriptions of such surfaces, however, are scarce since bijective definitions must be found to measure unique dependency between described structures and the chosen quantitative parameters. To solve this problem, we use statistical analysis of periodic fibrous structures by Hurst exponent distributions. Although such a Hurst exponent approach was suggested some years ago, the quantitative analysis of atomic force microscopy (AFM) images of nanofiber mats in such a way was described only recently. In this paper, we discuss the influence of typical AFM image post-processing steps on the gray-scale-resolved Hurst exponent distribution. Examples of these steps are polynomial background subtraction, aligning rows, deleting horizontal errors and sharpening. Our results show that while characteristic features of these false-color images may be shifted in terms of gray-channel and Hurst exponent, they can still be used to identify AFM images and, in the next step, to quantitatively describe AFM images of nanofibrous surfaces. Such a gray-channel approach can be regarded as a simple way to include some information about the 3D structure of the image. Full article

(This article belongs to the Special Issue Characterizations of Three-Dimensional Surfaces at Micro/Nanoscale)

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11 pages, 681 KiB

Open AccessArticle

Facial Paralysis Detection on Images Using Key Point Analysis

by Gemma S. Parra-Dominguez, Raul E. Sanchez-Yanez and Carlos H. Garcia-Capulin

Appl. Sci. 2021, 11(5), 2435; https://doi.org/10.3390/app11052435 - 9 Mar 2021

Cited by 35 | Viewed by 6460

Abstract

The inability to move the muscles of the face on one or both sides is known as facial paralysis, which may affect the ability of the patient to speak, blink, swallow saliva, eat, or communicate through natural facial expressions. The well-being of the [...] Read more.

The inability to move the muscles of the face on one or both sides is known as facial paralysis, which may affect the ability of the patient to speak, blink, swallow saliva, eat, or communicate through natural facial expressions. The well-being of the patient could also be negatively affected. Computer-based systems as a means to detect facial paralysis are important in the development of standardized tools for medical assessment, treatment, and monitoring; additionally, they are expected to provide user-friendly tools for patient monitoring at home. In this work, a methodology to detect facial paralysis in a face photograph is proposed. A system consisting of three modules—facial landmark extraction, facial measure computation, and facial paralysis classification—was designed. Our facial measures aim to identify asymmetry levels within the face elements using facial landmarks, and a binary classifier based on a multi-layer perceptron approach provides an output label. The Weka suite was selected to design the classifier and implement the learning algorithm. Tests on publicly available databases reveal outstanding classification results on images, showing that our methodology that was used to design a binary classifier can be expanded to other databases with great results, even if the participants do not execute similar facial expressions. Full article

(This article belongs to the Special Issue Computational Intelligence in Bioinformatics)

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19 pages, 1434 KiB

Open AccessArticle

AraSenCorpus: A Semi-Supervised Approach for Sentiment Annotation of a Large Arabic Text Corpus

by Ali Al-Laith, Muhammad Shahbaz, Hind F. Alaskar and Asim Rehmat

Appl. Sci. 2021, 11(5), 2434; https://doi.org/10.3390/app11052434 - 9 Mar 2021

Cited by 37 | Viewed by 5039

Abstract

At a time when research in the field of sentiment analysis tends to study advanced topics in languages, such as English, other languages such as Arabic still suffer from basic problems and challenges, most notably the availability of large corpora. Furthermore, manual annotation [...] Read more.

At a time when research in the field of sentiment analysis tends to study advanced topics in languages, such as English, other languages such as Arabic still suffer from basic problems and challenges, most notably the availability of large corpora. Furthermore, manual annotation is time-consuming and difficult when the corpus is too large. This paper presents a semi-supervised self-learning technique, to extend an Arabic sentiment annotated corpus with unlabeled data, named AraSenCorpus. We use a neural network to train a set of models on a manually labeled dataset containing 15,000 tweets. We used these models to extend the corpus to a large Arabic sentiment corpus called “AraSenCorpus”. AraSenCorpus contains 4.5 million tweets and covers both modern standard Arabic and some of the Arabic dialects. The long-short term memory (LSTM) deep learning classifier is used to train and test the final corpus. We evaluate our proposed framework on two external benchmark datasets to ensure the improvement of the Arabic sentiment classification. The experimental results show that our corpus outperforms the existing state-of-the-art systems. Full article

(This article belongs to the Special Issue Sentiment Analysis for Social Media Ⅱ)

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21 pages, 7681 KiB

Open AccessArticle

Research on Real-Time Joint Stiffness Configuration of a Series Parallel Hybrid 7-DOF Humanoid Manipulator in Continuous Motion

by Yang Yu, Shimin Wei, Haiyan Sheng and Yingkun Zhang

Appl. Sci. 2021, 11(5), 2433; https://doi.org/10.3390/app11052433 - 9 Mar 2021

Viewed by 1942

Abstract

In this paper, the real-time joint stiffness configuration strategy of a series parallel hybrid 7-DOF (degree of freedom) humanoid manipulator with flexible joints in continuous motion is studied. Firstly, considering the potential human robot accidental collision, combined with the manipulator safety index (MSI) [...] Read more.

In this paper, the real-time joint stiffness configuration strategy of a series parallel hybrid 7-DOF (degree of freedom) humanoid manipulator with flexible joints in continuous motion is studied. Firstly, considering the potential human robot accidental collision, combined with the manipulator safety index (MSI) and human body injury thresholds, the motion speed and joint stiffness of the robot are optimized in advance. Secondly, using hyperbolic tangent function for reference, the relationship between joint torques and passive joint deflection angles of the robot is given, which is beneficial for the real-time calculation of joint stiffness and obtain reasonable joint stiffness. Then, the structural model of the selected humanoid manipulator is described, on this basis, the relationship between the joint space stiffness and the Cartesian space stiffness of the humanoid manipulator is analyzed through Jacobian matrix, and the results show that the posture and joint space stiffness of the humanoid manipulator directly affect the Cartesian space stiffness of the humanoid manipulator. Finally, according to whether the humanoid manipulator works in the human-robot interaction environment, the real-time joint stiffness configuration of the humanoid manipulator in continuous motion is simulated and analyzed. The research shows that the humanoid manipulator with flexible joints can adjust the joint stiffness in real-time during continuous motion, and the joint stiffness configuration strategy can effectively improve the safety of human body in human-robot collision. In addition, in application, when the joint space stiffness of the robot is lower, the position accuracy can be improved by trajectory compensation. Full article

(This article belongs to the Section Mechanical Engineering)

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14 pages, 2264 KiB

Open AccessArticle

Anti-Inflammatory and Antioxidant Properties of Ethanol Extracts of Raw, Blanched, Steamed, and Sous-Vide Cooked Okra (Abelmoschus esculentus L.) in LPS or H₂O₂-Treated RAW264.7 Cells

by Taenam Lee and Nami Joo

Appl. Sci. 2021, 11(5), 2432; https://doi.org/10.3390/app11052432 - 9 Mar 2021

Cited by 7 | Viewed by 3815

Abstract

Okra (Abelmoschus esculentus L.) is a plant belonging to the Malvaceae family. All parts of okra, including the pod, leaf, and branch, are edible, with the pod being especially enriched with sugars, dietary fibers, minerals, vitamins, and antioxidants. It has beneficial effect [...] Read more.

Okra (Abelmoschus esculentus L.) is a plant belonging to the Malvaceae family. All parts of okra, including the pod, leaf, and branch, are edible, with the pod being especially enriched with sugars, dietary fibers, minerals, vitamins, and antioxidants. It has beneficial effect against colitis, hepatitis, and gastric ulcer. However, studies on okra’s anti-inflammatory effects remain limited. It is known that cooking methods change nutrition and functional compounds in foods. In this study, we prepared ethanolic extracts of okra using four different cooking methods (raw, blanching, steaming, and sous-vide), and analyzed anti-inflammatory and antioxidant effects on lipopolysaccharide- (LPS) or hydrogen peroxide (H₂O₂)-treated RAW264.7 macrophages. Cell viability was similar between all four cooking methods, confirming that okra extracts (≤200 μg/mL) were not cytotoxic. All cooking methods inhibited nitric oxide production (indicator of inflammatory responses). Sous-vide cooking showed low inhibitory effect at 100–200 μg/mL of okra extract. Moreover, examining the mRNA expression of inducible cycloxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS) and inflammatory cytokines (tumor necrosis factor alpha (TNF-α), interleukin 6 (IL-6), and interleukin 1-beta (IL-1β)) showed inhibitory effects by all cooking methods. Reactive oxygen species (ROS) levels were also reduced for all cooking methods, with sous-vide cooking showing the highest rate of reduction. These results confirm the anti-inflammatory and antioxidant effects of raw and multimethod cooked okra. Notably, sous-vide cooking showed the greatest potential to improve okra’s therapeutic effects. Full article

(This article belongs to the Section Food Science and Technology)

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11 pages, 31477 KiB

Open AccessArticle

Drivers’ Psychomotor Reaction Times Tested with a Test Station Method

by Tomasz Szydłowski, Krzysztof Surmiński and Damian Batory

Appl. Sci. 2021, 11(5), 2431; https://doi.org/10.3390/app11052431 - 9 Mar 2021

Cited by 8 | Viewed by 4362

Abstract

The article presents the standard method of the evaluation of car drivers’ psychomotor reaction times. A characteristic feature of this method is the ability to conduct tests using real vehicles equipped with mobile measuring apparatus. Measurements are carried out on people whose task [...] Read more.

The article presents the standard method of the evaluation of car drivers’ psychomotor reaction times. A characteristic feature of this method is the ability to conduct tests using real vehicles equipped with mobile measuring apparatus. Measurements are carried out on people whose task is to initiate specific maneuvers (such as: a braking or turning maneuver, a combined braking and turning maneuver, as well as e.g., the use of an audio signal) in response to external stimuli coming from different directions. The sources of the stimuli are light signals emitted by variable message signs placed around the vehicle. The developed control and measurement equipment allows us to realize various and complex test scenarios. It generates stimulus sequences, assesses the correctness of the driver’s response and measures its time. This method allows us to obtain sets of results from tests carried out under different conditions and variable test durations. The possibility of testing a large number of participants in a relatively short time and in repetitive conditions allows for reliable statistical inference. The paper presents examples of research results obtained on the basis of few thousand tests carried out on a large group of respondents. The registered data was statistically processed and referred to the literature. A high degree of correlation between the analyzed results and the literature reports proves that the presented method may be a source of data for the analysis of phenomena related to the time of the driver’s response, especially the influence of various factors affecting its values. Full article

(This article belongs to the Special Issue Human Factors in Transportation Systems)

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10 pages, 2100 KiB

Open AccessArticle

Heart Diseases Diagnose via Mobile Application

by Mesut Güven, Fırat Hardalaç, Kanat Özışık and Funda Tuna

Appl. Sci. 2021, 11(5), 2430; https://doi.org/10.3390/app11052430 - 9 Mar 2021

Cited by 2 | Viewed by 3088

Abstract

One of the oldest and most common methods of diagnosing heart abnormalities is auscultation. Even for experienced medical doctors, it is not an easy task to detect abnormal patterns in the heart sounds. Most digital stethoscopes are now capable of recording and transferring [...] Read more.

One of the oldest and most common methods of diagnosing heart abnormalities is auscultation. Even for experienced medical doctors, it is not an easy task to detect abnormal patterns in the heart sounds. Most digital stethoscopes are now capable of recording and transferring heart sounds. Moreover, it is proven that auscultation records can be classified as healthy or unhealthy via artificial intelligence techniques. In this work, an artificial intelligence-powered mobile application that works in a connectionless fashion is presented. According to the clinical experiments, the mobile application can detect heart abnormalities with approximately 92% accuracy, which is comparable to if not better than humans since only a small number of well-trained cardiologists can analyze auscultation records better than artificial intelligence. Using the diagnostic ability of artificial intelligence in a mobile application would change the classical way of auscultation for heart disease diagnosis. Full article

(This article belongs to the Section Computing and Artificial Intelligence)

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18 pages, 7879 KiB

Open AccessArticle

Method for Select Best AIS Data in Prediction Vessel Movements and Route Estimation

by Rogelio Bautista-Sánchez, Liliana Ibeth Barbosa-Santillan and Juan Jaime Sánchez-Escobar

Appl. Sci. 2021, 11(5), 2429; https://doi.org/10.3390/app11052429 - 9 Mar 2021

Cited by 7 | Viewed by 3074

Abstract

The prediction of vessel maritime navigation has become an exciting topic in the last years, especially considering economics, commercial exchange, and security. In addition, vessel monitoring requires better systems and techniques that help enterprises and governments to protect their interests. Specifically, the prediction [...] Read more.

The prediction of vessel maritime navigation has become an exciting topic in the last years, especially considering economics, commercial exchange, and security. In addition, vessel monitoring requires better systems and techniques that help enterprises and governments to protect their interests. Specifically, the prediction of vessel movements is essential for safety and tracking. However, the applications of prediction techniques have a high cost related to computational efficiency and low resource saving. This article presents a sample method to select historical data on vessel-specific routes to optimize the computational performance of the prediction of vessel positions and route estimation in real-time. These historical navigation data can help to estimate a complete path and perform vessel position predictions through time. This Select Best AIS Data in Prediction Vessel Movements and Route Estimation (PreMovEst) method works in a Vessel Traffic Service database to save computational resources when predictions or route estimations are executed. This article discusses AIS data and the artificial neural network. This work aims to present a prediction model that correctly predicts the physical movement in the route. It supports path planning for the Vessel Traffic Service. After testing the method, the results obtained for route estimation have a precision of 76.15%, and those for vessel position predictions through time have an accuracy of 81.043%. Full article

(This article belongs to the Special Issue Interdisciplinary Artificial Intelligence: Methods and Applications of Nature-Inspired Computing)

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21 pages, 1567 KiB

Open AccessArticle

A Complete and Fast Analysis Procedure for Three-Phase Induction Motors Using Finite Element, Considering Skewing and Iron Losses

by Matteo Carbonieri and Nicola Bianchi

Appl. Sci. 2021, 11(5), 2428; https://doi.org/10.3390/app11052428 - 9 Mar 2021

Cited by 7 | Viewed by 4444

Abstract

This paper deals with a complete finite-element analysis procedure for squirrel cage induction motors, including the presence of skewing and the iron losses evaluation. The machine is analyzed performing only magneto-static finite element analyses. Saturation phenomena are carefully considered in any operating condition, [...] Read more.

This paper deals with a complete finite-element analysis procedure for squirrel cage induction motors, including the presence of skewing and the iron losses evaluation. The machine is analyzed performing only magneto-static finite element analyses. Saturation phenomena are carefully considered in any operating condition, avoiding long time-stepping analyses. The synergy between analytical and finite element model leads to a rapid and precise estimation of the rotor induced current, saving computational time. Furthermore, the procedure proposed in this paper allows the motor performance to be directly derived, without the preliminary knowledge of the machine equivalent circuit. In order to complete the analysis, skewing effect is included, using the 2-D multi-slice technique, based on static simulations. Experimental tests are carried out and reported in order to verify analysis results. Full article

(This article belongs to the Special Issue Modeling, Design and Control of Electric Machines)

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19 pages, 6499 KiB

Open AccessArticle

Modeling the Evolution of Construction Solutions in Residential Buildings’ Thermal Comfort

by Inês F. G. Reis, António Figueiredo and António Samagaio

Appl. Sci. 2021, 11(5), 2427; https://doi.org/10.3390/app11052427 - 9 Mar 2021

Cited by 7 | Viewed by 2689

Abstract

The evolution of the construction sector over the years has been marked by the replacement of high thermal inertia mass constructions by increasingly lighter solutions that are subject to greater thermal fluctuations and, consequently, thermal discomfort. To minimize these effects, energy demanding space [...] Read more.

The evolution of the construction sector over the years has been marked by the replacement of high thermal inertia mass constructions by increasingly lighter solutions that are subject to greater thermal fluctuations and, consequently, thermal discomfort. To minimize these effects, energy demanding space conditioning technologies are implemented, contributing significantly to the sector’s share of global energy consumption. Enhanced constructive solutions involving phase-change materials have been developed to respond to the constructive thermal inertia loss, influencing buildings’ thermal and energy performance. This work aims to model the evolution of the construction over the last decades to understand to what extent constructive characteristics influence the occupants’ thermal comfort. For this purpose, typical and enhanced solutions representing distinct constructive periods were simulated using the EnergyPlus^® software through its graphical interface DesignBuilder^® and the thermal comfort of the different solutions was evaluated using the adaptive model for thermal comfort EN16798-1. The main results reveal that more restraining regulatory requirements are indeed mitigating thermal discomfort situations. However, overheating phenomena can rise, creating worrying consequences in the short-medium term. Thus, countries with mild climates such as Portugal, must pay special attention to these effects, which may be aggravated by climate change. Full article

(This article belongs to the Special Issue Advances in Thermal Energy Storage in Buildings Incorporating Phase-Change Materials)

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10 pages, 2292 KiB

Open AccessArticle

High-Temperature Synthesis of Metal–Matrix Composites (Ni-Ti)-TiB2

by Vladimir Promakhov, Alexey Matveev, Nikita Schulz, Mikhail Grigoriev, Andrey Olisov, Alexander Vorozhtsov, Alexander Zhukov and Victor Klimenko

Appl. Sci. 2021, 11(5), 2426; https://doi.org/10.3390/app11052426 - 9 Mar 2021

Cited by 10 | Viewed by 2679

Abstract

Currently, metal–matrix composite materials are some of the most promising types of materials, and they combine the advantages of a metal matrix and reinforcing particles/fibres. Within the framework of this article, the high-temperature synthesis of metal–matrix composite materials based on the (Ni-Ti)-TiB2 system [...] Read more.

Currently, metal–matrix composite materials are some of the most promising types of materials, and they combine the advantages of a metal matrix and reinforcing particles/fibres. Within the framework of this article, the high-temperature synthesis of metal–matrix composite materials based on the (Ni-Ti)-TiB2 system was studied. The selected approaches make it possible to obtain composite materials of various compositions without contamination and with a high degree of energy efficiency during production processes. Combustion processes in the samples of a 63.5 wt.% NiB + 36.5 wt.% Ti mixture and the phase composition and structure of the synthesis products were researched. It has been established that the synthesis process in the samples proceeds via the spin combustion mechanism. It has been shown that self-propagating high-temperature synthesis (SHS) powder particles have a composite structure and consist of a Ni-Ti matrix and TiB2 reinforcement inclusions that are uniformly distributed inside it. The inclusion size lies in the range between 0.1 and 4 µm, and the average particle size is 0.57 µm. The obtained metal-matrix composite materials can be used in additive manufacturing technologies as ligatures for heat-resistant alloys, as well as for the synthesis of composites using traditional methods of powder metallurgy. Full article

(This article belongs to the Special Issue Development of the New Alloys and Metallic Composites for Strategic Applications through Additive Manufacturing)

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15 pages, 1096 KiB

Open AccessArticle

Modeling of Railway Stations Based on Queuing Networks

by Igor Bychkov, Alexander Kazakov, Anna Lempert and Maxim Zharkov

Appl. Sci. 2021, 11(5), 2425; https://doi.org/10.3390/app11052425 - 9 Mar 2021

Cited by 21 | Viewed by 4590

Abstract

Among the micro-logistic transport systems, railway stations should be highlighted, such as one of the most important transport infrastructure elements. The efficiency of the transport industry as a whole depends on the quality of their operation. Such systems have a complex multi-level structure, [...] Read more.

Among the micro-logistic transport systems, railway stations should be highlighted, such as one of the most important transport infrastructure elements. The efficiency of the transport industry as a whole depends on the quality of their operation. Such systems have a complex multi-level structure, and the incoming traffic flow often has a stochastic character. It is known that the most effective approach to study the operation of such systems is mathematical modeling. Earlier, we proposed an approach to transport hub modeling using multiphase queuing systems with a batch Markovian arrival process (BMAP) as an incoming flow. In this paper, we develop the method by applying more complex models based on queuing networks that allow us to describe in detail the route of requests within an object with a non-linear hierarchical structure. This allows us to increase the adequacy of modeling and explore a new class of objects—freight railway stations and marshalling yards. Here we present mathematical models of two railway stations, one of which is a freight railway station located in Russia, and the other is a marshalling yard in the USA. The models have the form of queuing networks with BMAP flow. They are implemented as simulation software, and a numerical experiment is carried out. Based on the numerical results, some “bottlenecks” in the structure of the studied stations are determined. Moreover, the risk of switching to an irregular mode of operation is assessed. The proposed method is suitable for describing a wide range of cargo and passenger transport systems, including river ports, seaports, airports, and multimodal transport hubs. It allows a primary analysis of the hub operation and does not need large statistical information for parametric identification. Full article

(This article belongs to the Special Issue Risk Assessment in Traffic and Transportation)

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25 pages, 4585 KiB

Open AccessArticle

Optimal Planning Method for Large-Scale Historical Exhibits in the Taiwan Railway Museum

by Lin Pey Fan and Tzu How Chu

Appl. Sci. 2021, 11(5), 2424; https://doi.org/10.3390/app11052424 - 9 Mar 2021

Cited by 2 | Viewed by 6587

Abstract

The curation design of cultural heritage sites, such as museums, influence the level of visitor satisfaction and the possibility of revisitation; therefore, an efficient exhibit layout is critical. The difficulty of determining the behavior of visitors and the layout of galleries means that [...] Read more.

The curation design of cultural heritage sites, such as museums, influence the level of visitor satisfaction and the possibility of revisitation; therefore, an efficient exhibit layout is critical. The difficulty of determining the behavior of visitors and the layout of galleries means that exhibition layout is a knowledge-intensive, time-consuming process. The progressive development of machine learning provides a low-cost and highly flexible workflow in the management of museums, compared to traditional curation design. For example, the facility’s optimal layout, floor, and furniture arrangement can be obtained through the repeated adjustment of artificial intelligence algorithms within a relatively short time. In particular, an optimal planning method is indispensable for the immense and heavy trains in the railway museum. In this study, we created an innovative strategy to integrate the domain knowledge of exhibit displaying, spatial planning, and machine learning to establish a customized recommendation scheme. Guided by an interactive experience model and the morphology of point–line–plane–stereo, we obtained three aspects (visitors, objects, and space), 12 dimensions (orientation, visiting time, visual distance, centrality, main path, district, capacity, etc.), 30 physical principles, 24 suggestions, and five main procedures to implement layout patterns and templates to create an exhibit layout guide for the National Railway Museum of Taiwan, which is currently being transferred from the railway workshop for the sake of preserving the rail culture heritage. Our results are suitable and extendible to different museums by adjusting the criteria used to establish a new recommendation scheme. Full article

(This article belongs to the Special Issue AI and HCI Methods and Techniques for Cultural Heritage Curation, Exploration and Fruition)

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11 pages, 15480 KiB

Open AccessArticle

Biomechanical Consequences of Tibial Insert Thickness after Total Knee Arthroplasty: A Musculoskeletal Simulation Study

by Periklis Tzanetis, Marco A. Marra, René Fluit, Bart Koopman and Nico Verdonschot

Appl. Sci. 2021, 11(5), 2423; https://doi.org/10.3390/app11052423 - 9 Mar 2021

Cited by 10 | Viewed by 5695

Abstract

The thickness of the tibial polyethylene (PE) insert is a critical parameter to ensure optimal soft-tissue balancing in the intraoperative decision-making procedure of total knee arthroplasty (TKA). However, there is a paucity of information about the kinetic response to PE insert thickness variations [...] Read more.

The thickness of the tibial polyethylene (PE) insert is a critical parameter to ensure optimal soft-tissue balancing in the intraoperative decision-making procedure of total knee arthroplasty (TKA). However, there is a paucity of information about the kinetic response to PE insert thickness variations in the tibiofemoral (TF) joint, and subsequently, the secondary effects on the patellofemoral (PF) biomechanics. Therefore, the purpose of this study was to investigate the influence of varying PE insert thickness on the ligament and TF compressive forces, as well as on the PF forces and kinematics, after a cruciate-retaining TKA. A previous patient-specific musculoskeletal model of TKA was adapted to simulate a chair-rising motion in which PE insert thickness was varied with 2 mm increments or decrements compared to the reference case (9 mm), from 5 mm up to 13 mm. Greater PE insert thickness resulted in higher ligament forces and concurrently increased the TF compressive force by 21% (13 mm), but slightly unloaded the PF joint with 7% (13 mm) while shifting the patella distally in the trochlear groove, compared to the reference case. Thinner PE inserts showed an opposite trend. Our findings suggest that the optimal PE insert thickness selection is a trade-off between the kinetic outcomes of the TF and PF joints. Full article

(This article belongs to the Special Issue Musculoskeletal Models in a Clinical Perspective)

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16 pages, 4864 KiB

Open AccessFeature PaperArticle

Improvement on Flux Weakening Control Strategy for Electric Vehicle Applications

by Claudio Bianchini, Giovanni Franceschini and Ambra Torreggiani

Appl. Sci. 2021, 11(5), 2422; https://doi.org/10.3390/app11052422 - 9 Mar 2021

Cited by 7 | Viewed by 3967

Abstract

This paper proposes an optimized flux weakening (FW) control strategy for interior permanent-magnet synchronous electric motor to address the critical issues that could occur under torque setpoint transition in flux weakening region, due, for example, to an emergency braking. This situation is typical [...] Read more.

This paper proposes an optimized flux weakening (FW) control strategy for interior permanent-magnet synchronous electric motor to address the critical issues that could occur under torque setpoint transition in flux weakening region, due, for example, to an emergency braking. This situation is typical in electric vehicles where the electrical machines operate over a wide speed range to reach high power density and avoid gearboxes. Two modified traditional flux weakening strategies are proposed in this paper to improve torque control quality during high speed torque transition. The proposed modified control strategies were validated both by Matlab/Simulink simulations, modeling the power train of a light vehicle application, and extensive experimental tests on a dedicated test bench. Full article

(This article belongs to the Special Issue Electric Powertrain Design for High Efficiency and High Speed Operation Range)

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21 pages, 355 KiB

Open AccessArticle

Phenolic Profiling of Five Different Australian Grown Apples

by Heng Li, Vigasini Subbiah, Colin J. Barrow, Frank R. Dunshea and Hafiz A. R. Suleria

Appl. Sci. 2021, 11(5), 2421; https://doi.org/10.3390/app11052421 - 9 Mar 2021

Cited by 28 | Viewed by 5251

Abstract

Apples (Malus domestica) are one of the most widely grown and consumed fruits in the world that contain abundant phenolic compounds that possess remarkable antioxidant potential. The current study characterised phenolic compounds from five different varieties of Australian grown apples (Royal [...] Read more.

Apples (Malus domestica) are one of the most widely grown and consumed fruits in the world that contain abundant phenolic compounds that possess remarkable antioxidant potential. The current study characterised phenolic compounds from five different varieties of Australian grown apples (Royal Gala, Pink Lady, Red Delicious, Fuji and Smitten) using LC-ESI-QTOF-MS/MS and quantified through HPLC-PDA. The phenolic content and antioxidant potential were determined using various assays. Red Delicious had the highest total phenolic (121.78 ± 3.45 mg/g fw) and total flavonoid content (101.23 ± 3.75 mg/g fw) among the five apple samples. In LC-ESI-QTOF-MS/MS analysis, a total of 97 different phenolic compounds were characterised in five apple samples, including Royal Gala (37), Pink Lady (54), Red Delicious (17), Fuji (67) and Smitten (46). In the HPLC quantification, phenolic acid (chlorogenic acid, 15.69 ± 0.09 mg/g fw) and flavonoid (quercetin, 18.96 ± 0.08 mg/g fw) were most abundant in Royal Gala. The obtained results highlight the importance of Australian apple varieties as a rich source of functional compounds with potential bioactivity. Full article

(This article belongs to the Special Issue Potential Health Benefits of Fruits and Vegetables)

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20 pages, 3343 KiB

Open AccessArticle

A Layered KNN-SVM Approach to Predict Missing Values of Functional Requirements in Product Customization

by Ye Gu, Shuyou Zhang, Lemiao Qiu, Zili Wang and Lichun Zhang

Appl. Sci. 2021, 11(5), 2420; https://doi.org/10.3390/app11052420 - 9 Mar 2021

Cited by 5 | Viewed by 2569

Abstract

The conversion from functional requirements (FRs) to design parameters is the foundation of product customization. However, original customer needs usually result in incomplete FRs, limited by customers’ incomprehension on the design requirements of these products. As the incomplete FRs may undermine the design [...] Read more.

The conversion from functional requirements (FRs) to design parameters is the foundation of product customization. However, original customer needs usually result in incomplete FRs, limited by customers’ incomprehension on the design requirements of these products. As the incomplete FRs may undermine the design activities afterwards, managers need to develop an effective approach to predict the missing values of the FR. This study proposes an integrative approach to obtain the complete FR. The k nearest neighbor (KNN) algorithm is employed to predict the missing continuous variables in FR, using the improved distance formula for two incomplete FRs. Support vector machine (SVM) classifiers are adopted to classify the missing categorical variables in FR, combined with directed acyclic graph for multi-class classification. KNN and SVM are then integrated into a multi-layer framework to predict the missing values of FR, where categorical and continuous variables both exist. A case study on the elevator customization is conducted to verify that KNN-SVM is feasible in accurate prediction of elevator FR values. Furthermore, KNN-SVM outperforms other five single and five composite methods, with average reduction in root mean squared error (RMSE) of 39% and 21% against KNN and KNN-Tree, respectively. Full article

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29 pages, 7757 KiB

Open AccessArticle

Optimization of a Faraday Cup Collimator for Electric Propulsion Device Beam Study: Case of a Hall Thruster

by Hugonnaud Valentin and Mazouffre Stéphane

Appl. Sci. 2021, 11(5), 2419; https://doi.org/10.3390/app11052419 - 9 Mar 2021

Cited by 5 | Viewed by 6420

Abstract

A Faraday cup (FC) is an instrument dedicated to current measurement in beams, jets and plasmas. It consists of a set of polarized electrodes mounted in such a way plasma sheath effect can be neglected, yielding accurate and reliable results. A FC is [...] Read more.

A Faraday cup (FC) is an instrument dedicated to current measurement in beams, jets and plasmas. It consists of a set of polarized electrodes mounted in such a way plasma sheath effect can be neglected, yielding accurate and reliable results. A FC is composed of three main parts, namely a collector or cup, which collects the current, a collimator, which defines the collection area and can contribute to limit electrons from entering the cup and a housing which protects the instrument from perturbation caused by the surrounding medium. In this paper, we provide experimental results of the effect of the collimator upon the measured ion current within the beam of a low-power Hall thruster. Different collimator materials, aperture diameters and polarization voltages are studied to determine the optimum design. Minimum dimension as well as appropriate materials are given as a conclusion in the case of low-power Hall thruster beam investigation. Full article

(This article belongs to the Special Issue Plasmas for Space Propulsion)

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11 pages, 3816 KiB

Open AccessArticle

A Study of Correction to the Point Cloud Distortion Based on MEMS LiDAR System

by Dongbing Guo, Chunhui Wang, Baoling Qi, Yu Zhang and Qingyan Li

Appl. Sci. 2021, 11(5), 2418; https://doi.org/10.3390/app11052418 - 9 Mar 2021

Cited by 3 | Viewed by 3188

Abstract

Active imaging technology can perceive the surrounding environment and obtain three-dimensional information of the target. Among them, light detection and ranging (LiDAR) imaging systems are one of the hottest topics in the field of photoelectric active imaging. Due to the small size, fast [...] Read more.

Active imaging technology can perceive the surrounding environment and obtain three-dimensional information of the target. Among them, light detection and ranging (LiDAR) imaging systems are one of the hottest topics in the field of photoelectric active imaging. Due to the small size, fast scanning speed, low power consumption, low price and strong anti-interference, a micro-electro-mechanical system (MEMS) based micro-scanning LiDAR is widely used in LiDAR imaging systems. However, the imaging point cloud will be distorted, which affects the accurate acquisition of target information. Therefore, in this article, we analyzed the causes of distortion initially, and then introduced a novel coordinate correction method, which can correct the point cloud distortion of the micro-scanning LiDAR system based on MEMS. We implemented our coordinate correction method in a two-dimensional MEMS LiDAR system to verify the feasibility. Experiments show that the point cloud distortion is basically corrected and the distortion is reduced by almost 72.5%. This method can provide an effective reference for the correction of point cloud distortion. Full article

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18 pages, 3871 KiB

Open AccessArticle

Mixed Reality: A Reconsideration Based on Mixed Objects and Geospatial Modalities

by Konstantinos Evangelidis, Theofilos Papadopoulos and Stella Sylaiou

Appl. Sci. 2021, 11(5), 2417; https://doi.org/10.3390/app11052417 - 9 Mar 2021

Cited by 8 | Viewed by 4325

Abstract

We put forward a conceptualization of Mixed Reality as a blend of digital objects with real ones that coexist and interact with each other and they are also spatially referenced so that they are properly perceived in space by an observer that could [...] Read more.

We put forward a conceptualization of Mixed Reality as a blend of digital objects with real ones that coexist and interact with each other and they are also spatially referenced so that they are properly perceived in space by an observer that could potentially be at any position any time. In accordance with this statement, we have adopted the concept of a Mixed Object which is composed of a set of physical properties linked with a set of digital ones. In our case, the physical properties are acquired by employing geospatial technologies such as photogrammetry, laser scanning, unmanned aerial vehicles and positioning systems and are further processed in order to be visually displayed by utilizing Geographical Information Systems and Geovisualization frameworks in combination with traditional image processing techniques. We show that the Mixed Object approach is in conformance with Microsoft’s approach on Mixed Reality as the common space between humans, computers, and the environment and we further incorporate in these the Geospatial Linking Modalities. We finally provide an affordable MR experience as a proof of concept, by utilizing a smartphone for capturing and visualizing the environment, a visual tag for positioning purposes and freely available photogrammetrically mapped content and virtual objects to form a digital scene blended with the real environment. Full article

(This article belongs to the Special Issue Extended Reality: From Theory to Applications)

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