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Appl. Sci., Volume 10, Issue 7 (April-1 2020) – 436 articles

Cover Story (view full-size image): In recent years, the technique of encapsulation or inclusion of medicine/active principle in polymer functional matrices has been employed to obtain textile materials with controlled drug release properties. In this study, a sol–gel-based coating was developed and used as an entrapping polymeric cross-linked network to deliver a molecule with anti-inflammatory and antioxidant properties. The combination of the functionality and transparency provided by the developed hybrid coating with its easy processability could represent an innovative method to fabricate smart textiles for healthcare and biomedical applications. View this paper.
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14 pages, 600 KiB  
Review
Mechanical Properties of Sandwich Composites Reinforced by Nanoclays: An Overview
by João Parente, Paulo N. B. Reis, M. Neto and A. M. Amaro
Appl. Sci. 2020, 10(7), 2637; https://doi.org/10.3390/app10072637 - 10 Apr 2020
Cited by 8 | Viewed by 3483
Abstract
Structural sandwich composites have been widely used in many engineering applications, and this trend continues due to their superior mechanical properties, thermal insulation and acoustic damping. However, to further improve their mechanical properties, literature reports significant benefits obtained with nano-reinforcements. In this context, [...] Read more.
Structural sandwich composites have been widely used in many engineering applications, and this trend continues due to their superior mechanical properties, thermal insulation and acoustic damping. However, to further improve their mechanical properties, literature reports significant benefits obtained with nano-reinforcements. In this context, nanoclays are the most popular nano-reinforcements for polymeric nanocomposites, due to their relatively high ion exchange capacity, high aspect ratio and economic advantages. In order to stablish a systematic understanding for design criteria, this work intends to summarize all studies present in the open literature about this topic. It was possible to conclude that using nanoclays improves the mechanical properties of structural sandwich composites, especially in terms of impact strength. Nevertheless, the benefits obtained regarding fatigue performance are not adequately reported in the literature, revealing the need to develop these studies. Full article
(This article belongs to the Special Issue Polymeric Composites Reinforced with Nanoparticles)
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16 pages, 3439 KiB  
Article
Characterization of Nano-Mechanical, Surface and Thermal Properties of Hemp Fiber-Reinforced Polycaprolactone (HF/PCL) Biocomposites
by Hom Nath Dhakal, Sikiru Oluwarotimi Ismail, Johnny Beaugrand, Zhongyi Zhang and Jurgita Zekonyte
Appl. Sci. 2020, 10(7), 2636; https://doi.org/10.3390/app10072636 - 10 Apr 2020
Cited by 10 | Viewed by 3710
Abstract
The quest for sustainable, low-cost and environmental friendly engineering materials has increased the application of natural fiber-reinforced polymer (FRP) composite. This paper experimentally investigates the effects of variable mean hemp fiber (HF) aspect ratios (ARs) of 00 (neat), aspect ratios AR_19, AR_26, AR_30 [...] Read more.
The quest for sustainable, low-cost and environmental friendly engineering materials has increased the application of natural fiber-reinforced polymer (FRP) composite. This paper experimentally investigates the effects of variable mean hemp fiber (HF) aspect ratios (ARs) of 00 (neat), aspect ratios AR_19, AR_26, AR_30 and AR_38 on nano-mechanical (hardness, modulus, elasticity and plasticity), surface and thermal properties of hemp fiber/polycaprolactone (HF/PCL) biocomposites. These biocomposites were characterized by nanoindentation, contact angle, surface energy, thermogravimetric analysis (TGA), thermal conductivity and differential scanning calorimetry (DSC) techniques. After nanoindentation and thermal conductivity tests, the results obtained evidently show that the HF/PCL sample with aspect ratio (AR_26) recorded optimal values. These values include maximum hardness of approximately 0.107 GPa, elastic modulus of 1.094 GPa, and plastic and elastic works of 1.580 and 1.210 nJ, respectively as well as maximum thermal conductivity of 0.2957 W/mK, when compared with other samples. Similarly, the optimal sample exhibits highest main degradable temperature and degree of crystallinity of 432 ℃ and 60.6%, respectively. Further results obtained for the total surface energies and contact angles of these samples with glycerol and distilled water are significant for their materials selection, design, manufacturing and various applications. Full article
(This article belongs to the Special Issue Tribological and Mechanical Properties Studies of Smart Materials at Micro–Nano Scale)
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23 pages, 3447 KiB  
Article
Predictive Voltage Control: Empowering Domestic Customers With a Key Role in the Active Management of LV Networks
by Micael Simões and André G. Madureira
Appl. Sci. 2020, 10(7), 2635; https://doi.org/10.3390/app10072635 - 10 Apr 2020
Cited by 4 | Viewed by 2583
Abstract
In order to avoid voltage problems derived from the connection of large amounts of renewable-based generation to the electrical distribution system, new advanced tools need to be developed that are able to exploit the presence of Distributed Energy Resources (DER). This paper describes [...] Read more.
In order to avoid voltage problems derived from the connection of large amounts of renewable-based generation to the electrical distribution system, new advanced tools need to be developed that are able to exploit the presence of Distributed Energy Resources (DER). This paper describes the approach proposed for a predictive voltage control algorithm to be used in Low Voltage (LV) distribution networks in order to make use of available flexibilities from domestic consumers via their Home Energy Management System (HEMS) and more traditional resources from the Distribution System Operator (DSO), such as transformers with On-Load Tap Changer (OLTC) and storage devices. The proposed algorithm—the Low Voltage Control (LVC)—is detailed in this paper. The algorithm was tested through simulation using a real Portuguese LV network and real consumption and generation data, in order to evaluate its performance in preparation for a field-trial validation in a Portuguese smart grids pilot. Full article
(This article belongs to the Special Issue Towards a Seamless Integration of DER in Power Systems: Future Prospects, Challenges and Solutions)
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14 pages, 4120 KiB  
Article
Log Analysis-Based Resource and Execution Time Improvement in HPC: A Case Study
by JunWeon Yoon, TaeYoung Hong, ChanYeol Park, Seo-Young Noh and HeonChang Yu
Appl. Sci. 2020, 10(7), 2634; https://doi.org/10.3390/app10072634 - 10 Apr 2020
Cited by 4 | Viewed by 3237
Abstract
High-performance computing (HPC) uses many distributed computing resources to solve large computational science problems through parallel computation. Such an approach can reduce overall job execution time and increase the capacity of solving large-scale and complex problems. In the supercomputer, the job scheduler, the [...] Read more.
High-performance computing (HPC) uses many distributed computing resources to solve large computational science problems through parallel computation. Such an approach can reduce overall job execution time and increase the capacity of solving large-scale and complex problems. In the supercomputer, the job scheduler, the HPC’s flagship tool, is responsible for distributing and managing the resources of large systems. In this paper, we analyze the execution log of the job scheduler for a certain period of time and propose an optimization approach to reduce the idle time of jobs. In our experiment, it has been found that the main root cause of delayed job is highly related to resource waiting. The execution time of the entire job is affected and significantly delayed due to the increase in idle resources that must be ready when submitting the large-scale job. The backfilling algorithm can optimize the inefficiency of these idle resources and help to reduce the execution time of the job. Therefore, we propose the backfilling algorithm, which can be applied to the supercomputer. This experimental result shows that the overall execution time is reduced. Full article
(This article belongs to the Special Issue Big Data Analysis and Visualization)
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21 pages, 4227 KiB  
Article
Guidelines for Impact Echo Test Signal Interpretation Based on Wavelet Packet Transform for the Detection of Pile Defects
by Hyeong-Joo Kim, Jose Leo Mission, Peter Rey Dinoy, Hyeong-Soo Kim and Tae-Woong Park
Appl. Sci. 2020, 10(7), 2633; https://doi.org/10.3390/app10072633 - 10 Apr 2020
Cited by 10 | Viewed by 4913
Abstract
Nonlinear amplification is typically done on velocity signals from low-strain pile integrity tests to enhance weak echoes and superimpose any peak reflections. This conventional method may sometimes fail to untangle the hidden information within the signal that is obscured by the presence of [...] Read more.
Nonlinear amplification is typically done on velocity signals from low-strain pile integrity tests to enhance weak echoes and superimpose any peak reflections. This conventional method may sometimes fail to untangle the hidden information within the signal that is obscured by the presence of noise. In this study, a pile defect identification system based on the conventional nonlinear amplification method and the wavelet packet transform (WPT) was proposed to easily detect the presence of any geometric or material defects by identifying feature parameters. Diagnostic rules, which have been lacking in the literature, were presented to serve as a guide in interpreting decomposed signals and in analyzing various characteristics of peak waveforms that are associated with certain types of defects. In this study, the finite element method was used to simulate the impact echo test of nine cases of defective piles. To verify the proposed scheme, six data sets of the nine cases of defective piles were made, in which a total of 54 piles were analyzed. The results of the study showed that the identification method based on WPT could detect defects 87.04% of the time compared to the conventional method, which only detected defects 64.81% of the time. Full article
(This article belongs to the Section Acoustics and Vibrations)
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15 pages, 1479 KiB  
Review
Update on TB Vaccine Pipeline
by Carlos Martin, Nacho Aguilo, Dessislava Marinova and Jesus Gonzalo-Asensio
Appl. Sci. 2020, 10(7), 2632; https://doi.org/10.3390/app10072632 - 10 Apr 2020
Cited by 36 | Viewed by 10500
Abstract
In addition to antibiotics, vaccination is considered among the most efficacious methods in the control and the potential eradication of infectious diseases. New safe and effective vaccines against tuberculosis (TB) could be a very important tool and are called to play a significant [...] Read more.
In addition to antibiotics, vaccination is considered among the most efficacious methods in the control and the potential eradication of infectious diseases. New safe and effective vaccines against tuberculosis (TB) could be a very important tool and are called to play a significant role in the fight against TB resistant to antimicrobials. Despite the extended use of the current TB vaccine Bacillus Calmette-Guérin (BCG), TB continues to be transmitted actively and continues to be one of the 10 most important causes of death in the world. In the last 20 years, different TB vaccines have entered clinical trials. In this paper, we review the current use of BCG and the diversity of vaccines in clinical trials and their possible indications. New TB vaccines capable of protecting against respiratory forms of the disease caused by sensitive or resistant Mycobacterium tuberculosis strains would be extremely useful tools helping to prevent the emergence of multi-drug resistance. Full article
(This article belongs to the Special Issue Tuberculosis Drug Discovery and Development 2019)
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18 pages, 4738 KiB  
Article
Study on New Bolted T-Stub Connection with Inserted Plates under Axial and Cyclic Loads
by Xiaoming Zhu and Zhaoqi Wu
Appl. Sci. 2020, 10(7), 2631; https://doi.org/10.3390/app10072631 - 10 Apr 2020
Cited by 6 | Viewed by 3849
Abstract
The bolted T-stub connection joining beam with column is being widely applied. To enhance the energy dissipation capacity of conventional T-stub connections, two rectangular plates are proposed to be inserted between the T-stub and column, so that the T-stub flange can yield both [...] Read more.
The bolted T-stub connection joining beam with column is being widely applied. To enhance the energy dissipation capacity of conventional T-stub connections, two rectangular plates are proposed to be inserted between the T-stub and column, so that the T-stub flange can yield both under tensile and compressive loads. This study put forward a mechanical model of a new T-stub connection with inserted plates and investigated important factors that could affect its mechanical behavior through experimental tests. Thirty specimens were designed with different configurations that differed according to the existence or absence of inserted plates, the fabrication method and the width of inserted plates. These configurations were tested under axial and cyclic loading conditions, and results showed that the proposal aiming to improve the energy dissipation capacity was feasible. The mechanical model presented coincided with the test observation and data. The advent of two inserted plates elevated the load bearing capacity, stiffness and ductility of connections under compression, whereas in tension the properties were not substantially enhanced. The welded T-stub connections outperformed those cut from standard section steel. The energy dissipated by connections with inserted plates was about 150% of that by traditional connections without inserted plates. Only within a reasonable range can the increment of plate width promote the energy dissipation capacity of T-stub connections. The optimum width of plates in terms of energy consumption accounted for around 31% of the overall width of connections. Full article
(This article belongs to the Special Issue Mechanics of Structural Joints)
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16 pages, 7384 KiB  
Article
Stability of Multiple Seasonal Holt-Winters Models Applied to Hourly Electricity Demand in Spain
by Óscar Trull, J. Carlos García-Díaz and Alicia Troncoso
Appl. Sci. 2020, 10(7), 2630; https://doi.org/10.3390/app10072630 - 10 Apr 2020
Cited by 17 | Viewed by 3467
Abstract
Electricity management and production depend heavily on demand forecasts made. Any mismatch between the energy demanded with respect to that produced supposes enormous losses for the consumer. Transmission System Operators use time series-based tools to forecast accurately the future demand and set the [...] Read more.
Electricity management and production depend heavily on demand forecasts made. Any mismatch between the energy demanded with respect to that produced supposes enormous losses for the consumer. Transmission System Operators use time series-based tools to forecast accurately the future demand and set the production program. One of the most effective and highly used methods are Holt-Winters. Recently, the incorporation of the multiple seasonal Holt-Winters methods has improved the accuracy of the predictions. These forecasts, depend greatly on the parameters with which the model is constructed. The forecasters need to deal with these parameters values when operating the model. In this article, the parameters space of the multiple seasonal Holt-Winters models applied to electricity demand in Spain is analysed and discussed. The parameters stability analysis leads to forecasters better understanding the behaviour of the predictions and managing their exploitation efficiently. The analysis addresses different time windows, depending on the period of the year as well as different training set sizes. The results show the influence of the calendar effect on these parameters and if it is necessary or not to update them in order to obtain a good accuracy over time. Full article
(This article belongs to the Special Issue Advanced Optimization Methods and Big Data Applications in Energy Demand Forecast)
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10 pages, 3636 KiB  
Article
Numerical and Experimental Analysis of Torsion Springs Using NURBS Curves
by Young Shin Kim, Yu Jun Song and Euy Sik Jeon
Appl. Sci. 2020, 10(7), 2629; https://doi.org/10.3390/app10072629 - 10 Apr 2020
Cited by 4 | Viewed by 3488
Abstract
Torsion springs, which transfer power through the twisting of their coil, provide advantages such as module simplification and efficient use of space. The design of a torsion spring has been formulated, but it is difficult to determine the local behaviors of torsion springs [...] Read more.
Torsion springs, which transfer power through the twisting of their coil, provide advantages such as module simplification and efficient use of space. The design of a torsion spring has been formulated, but it is difficult to determine the local behaviors of torsion springs according to actual load conditions. This study proposes a torsion-spring design method through finite element analysis (FEA) using nonuniform-rational-basis-spline (NURBS) curves. Through experimentation, the angle and displacement values for the actual spring load were converted into useable data. Torsion-spring displacement values were obtained via experimentation and converted into coordinates that may be expressed using NURBS curves. The results of these experiments were then compared to those obtained via FEA, and the validity of this method was thereby verified. Full article
(This article belongs to the Special Issue Applications of Finite Element Modeling for Mechanical and Mechatronic Systems)
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19 pages, 4505 KiB  
Article
Visual and Quantitative Evaluation of Amyloid Brain PET Image Synthesis with Generative Adversarial Network
by Hyeon Kang, Jang-Sik Park, Kook Cho and Do-Young Kang
Appl. Sci. 2020, 10(7), 2628; https://doi.org/10.3390/app10072628 - 10 Apr 2020
Cited by 20 | Viewed by 3162
Abstract
Conventional data augmentation (DA) techniques, which have been used to improve the performance of predictive models with a lack of balanced training data sets, entail an effort to define the proper repeating operation (e.g., rotation and mirroring) according to the target class distribution. [...] Read more.
Conventional data augmentation (DA) techniques, which have been used to improve the performance of predictive models with a lack of balanced training data sets, entail an effort to define the proper repeating operation (e.g., rotation and mirroring) according to the target class distribution. Although DA using generative adversarial network (GAN) has the potential to overcome the disadvantages of conventional DA, there are not enough cases where this technique has been applied to medical images, and in particular, not enough cases where quantitative evaluation was used to determine whether the generated images had enough realism and diversity to be used for DA. In this study, we synthesized 18F-Florbetaben (FBB) images using CGAN. The generated images were evaluated using various measures, and we presented the state of the images and the similarity value of quantitative measurement that can be expected to successfully augment data from generated images for DA. The method includes (1) conditional WGAN-GP to learn the axial image distribution extracted from pre-processed 3D FBB images, (2) pre-trained DenseNet121 and model-agnostic metrics for visual and quantitative measurements of generated image distribution, and (3) a machine learning model for observing improvement in generalization performance by generated dataset. The Visual Turing test showed similarity in the descriptions of typical patterns of amyloid deposition for each of the generated images. However, differences in similarity and classification performance per axial level were observed, which did not agree with the visual evaluation. Experimental results demonstrated that quantitative measurements were able to detect the similarity between two distributions and observe mode collapse better than the Visual Turing test and t-SNE. Full article
(This article belongs to the Special Issue Machine Learning in Medical Image Processing)
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12 pages, 4536 KiB  
Article
Optical Design of a Miniaturized Airborne Push-Broom Spectrometer
by Yang Wang, Zhiyuan Gu, Xiangyue Meng, Lei Zhang and Yuegang Fu
Appl. Sci. 2020, 10(7), 2627; https://doi.org/10.3390/app10072627 - 10 Apr 2020
Cited by 6 | Viewed by 3429
Abstract
Combining the requirements of spectrometers for unmanned aerial vehicle platforms, a miniaturized airborne wide-angle push-broom imaging spectrometer with an Offner configuration is designed. The system comprises an objective lens and an Offner-type spectrometer with a spectral range of 400~1000 nm and a spectral [...] Read more.
Combining the requirements of spectrometers for unmanned aerial vehicle platforms, a miniaturized airborne wide-angle push-broom imaging spectrometer with an Offner configuration is designed. The system comprises an objective lens and an Offner-type spectrometer with a spectral range of 400~1000 nm and a spectral resolution of 15 nm. The objective lens and Offner spectrometer are designed in isolation before integration. The front objective lens is an inverted telephoto with a focal length of 13 mm, a relative aperture of 1/4.5, and a field of view of 54°. The frequency of the convex grating in the Offner configuration is 102 LP/mm, and the dispersion width is 2.6 mm. The modulation transfer function of the integrated system is greater than 0.4 at the Nyquist frequency in all spectral bands. To estimate the volume and weight of the system, a preliminary optical–mechanical design scheme is given in this paper. The entire spectrometer has a volume of 130 × 80 × 120 mm and is less than 3 kg, which realizes the miniaturization design of the imaging spectrometer with a wide field of view for unmanned aerial vehicle platforms. Full article
(This article belongs to the Collection Optical Design and Engineering)
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20 pages, 6471 KiB  
Article
A Steering-Following Dynamic Model with Driver’s NMS Characteristic for Human-Vehicle Shared Control
by Hanbing Wei, Yanhong Wu, Xing Chen and Jin Xu
Appl. Sci. 2020, 10(7), 2626; https://doi.org/10.3390/app10072626 - 10 Apr 2020
Cited by 5 | Viewed by 2890
Abstract
For investigating driver characteristic as well as control authority allocation during the process of human–vehicle shared control (HVSC) for an autonomous vehicle (AV), a HVSC dynamic mode with a driver’s neuromuscular (NMS) state parameters was proposed in this paper. It takes into account [...] Read more.
For investigating driver characteristic as well as control authority allocation during the process of human–vehicle shared control (HVSC) for an autonomous vehicle (AV), a HVSC dynamic mode with a driver’s neuromuscular (NMS) state parameters was proposed in this paper. It takes into account the driver’s NMS characteristics such as stretch reflection and reflex stiffness. By designing a model predictive control (MPC) controller, the vehicle’s state feedback and driver’s state are incorporated to construct the HVSC dynamic model. For the validation of the model, a field experiment was conducted. The vehicle state signals are collected by V-BOX, and the driver’s state signals are obtained with the electromyography instrument. Subsequently, the hierarchical least square (HLS) parameter identification algorithm was implemented to identify the parameters of the model based on the experimental results. Moreover, the Unscented Kalman Filter (UKF) was utilized to estimate the important NMS parameters which cannot be measured directly. The experimental results showed that the model we proposed has excellent accuracy in characterizing the vehicle’s dynamic state and estimating the driver’s NMS parameter. This paper will serve as a theoretical basis for the new control strategy allocation between human and vehicle for L3 class AVs. Full article
(This article belongs to the Special Issue Artificial Intelligence for Connected and Automated Vehicles)
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25 pages, 9866 KiB  
Article
Investigation of Phase-Locked Loop Statistics via Numerical Implementation of the Fokker–Planck Equation
by Dah-Jing Jwo
Appl. Sci. 2020, 10(7), 2625; https://doi.org/10.3390/app10072625 - 10 Apr 2020
Cited by 1 | Viewed by 3336
Abstract
The goal of this paper is to explore the effect of various parameters on the information geometric structure of the phase-locked loop (PLL) statistics, both transient and stationary. Comprehensive treatment on the behavior of PLL statistics will be given. The behavior of the [...] Read more.
The goal of this paper is to explore the effect of various parameters on the information geometric structure of the phase-locked loop (PLL) statistics, both transient and stationary. Comprehensive treatment on the behavior of PLL statistics will be given. The behavior of the phase-error statistics of the first-order PLL, in the presence of additive white Gaussian noise (WGN) is investigated through solving the differential equations known as the Fokker–Planck (FP) equation using the implicit Crank–Nicolson finite-difference method. The PLL is one of the most commonly used circuits in electrical engineering. A full knowledge of probability density functions (PDFs) of the phase-error statistics becomes essential in understanding the PLLs. Several illustrative examples are presented to provide profound insights on understanding the PLL statistics both qualitatively and quantitatively. Results covered include the transient and stationary statistics for the nonmodulo-2π probability density function, modulo-2π probability density function, and cycle slipping density function, of the phase error. Various numerical settings of PLL parameters are involved, including the detuning factor and signal-to-noise ratio (SNR). The results presented in this paper elucidate the link between various parameters and the information geometry of the phase-error statistics and form a basis for future investigation on PLL designs. Full article
(This article belongs to the Section Electrical, Electronics and Communications Engineering)
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16 pages, 1399 KiB  
Article
Evaluating Earthworms’ Potential for Remediating Soils Contaminated with Olive Mill Waste Sediments
by Juan C. Sanchez-Hernandez, Jose A. Sáez, Alberto Vico, Joaquín Moreno and Raúl Moral
Appl. Sci. 2020, 10(7), 2624; https://doi.org/10.3390/app10072624 - 10 Apr 2020
Cited by 7 | Viewed by 3178
Abstract
The olive-oil industry generates large amounts of residues that, in the past, were accumulated in evaporating ponds in many Mediterranean countries. Currently, these open-air ponds pose a serious environmental hazard because of toxic chemicals that concentrate in their sediments. Bioremediation of olive mill [...] Read more.
The olive-oil industry generates large amounts of residues that, in the past, were accumulated in evaporating ponds in many Mediterranean countries. Currently, these open-air ponds pose a serious environmental hazard because of toxic chemicals that concentrate in their sediments. Bioremediation of olive mill waste (OMW) sediments has emerged as a viable option for managing this environmentally problematic residue. Here, we postulate that inoculation of an OMW-soil mixture with earthworms may be a complementary bioremediation strategy to that using native microorganisms only. A laboratory study assessed the ecotoxicity of OMW-amended soils (10%, 20%, 40% and 80% w/w) combining earthworm biomarker responses and soil enzyme activities. The doses of 40% and 80% were toxic to earthworms, as evidenced by the high mortality rate, loss of body weight and signs of oxidative stress after 30 d of soil incubation. Conversely, doses ≤ 20% w/w were compatible with earthworm activity, as indicated by the significant increase of soil enzyme activities. Total concentrations of phenolic compounds decreased by more than 70% respect to initial concentrations in 10% and 20% OMW treatments. These results suggest that OMW sediments intentionally mixed with soils in an up to 20% proportion is a workable bioremediation strategy, where earthworms can be inoculated to facilitate the OMW degradation. Full article
(This article belongs to the Special Issue Advances in Bioremediation Strategies: Solving Current Application Limitations and Expanding Their Use to Emerging Organic Contaminants)
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11 pages, 2915 KiB  
Article
An Evidence Basis for Future Equestrian Helmet Lateral Crush Certification Tests
by Thomas A. Connor, J. Michio Clark, Pieter Brama, Matt Stewart, Aisling Ní Annaidh and Michael D. Gilchrist
Appl. Sci. 2020, 10(7), 2623; https://doi.org/10.3390/app10072623 - 10 Apr 2020
Cited by 1 | Viewed by 3306
Abstract
The aim of this study is to determine what loads are likely to be applied to the head in the event of a horse falling onto it and to determine by how much a typical equestrian helmet reduces these loads. An instrumented headform [...] Read more.
The aim of this study is to determine what loads are likely to be applied to the head in the event of a horse falling onto it and to determine by how much a typical equestrian helmet reduces these loads. An instrumented headform was designed and built to measure applied dynamic loads from a falling horse. Two differently weighted equine cadavers were then dropped repeatedly from a height of 1 m (theoretical impact velocity of 4.43 m/s) onto both the un-helmeted and helmeted instrumented headforms to collect primary force–time history data. The highest mean peak loads applied to the headform by the lighter horse were measured at the bony sacral impact location (15.57 kN ± 1.11 SD). The lowest mean peak loads were measured at the relatively fleshier right hind quarter (7.91 kN ± 1.84 SD). For the heavier horse, highest mean peak loads applied to the headform were measured at the same bony sacral impact location (16.02 kN ± 0.83 SD), whilst lowest mean peak loads were measured at the more compliant left hind quarter (10.47 kN ± 1.08 SD). When compared with the un-helmeted mean values, a reduction of 29.7% was recorded for the sacral impact location and a reduction of 43.3% for the lumbosacral junction location for helmeted tests. Notably, all measured loads were within or exceeded the range of published data for the fracture of the adult lateral skull bone. Current helmet certification tests are not biofidelic and inadequately represent the loading conditions of real-world “lateral crush” accidents sustained in equestrian sports. This work presents the first ever evidence basis upon which any future changes to a certification standards test method might be established, thereby ensuring that such a test would be both useful, biofidelic, and could ensure the desired safety outcome. Full article
(This article belongs to the Special Issue Applied Biomechanics in Sport, Rehabilitation and Ergonomy)
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19 pages, 9394 KiB  
Article
Scenario-Based Pyroclastic Density Current Invasion Maps at Poorly Known Volcanoes: A Case Study from Changbaishan (China/North Korea)
by Anna Maria Lombardi, Pierdomenico Del Gaudio, Zhengfu Guo, Maoliang Zhang, Guoming Liu, Vincenzo Sepe, Jiaqi Liu and Guido Ventura
Appl. Sci. 2020, 10(7), 2622; https://doi.org/10.3390/app10072622 - 10 Apr 2020
Cited by 1 | Viewed by 3860
Abstract
Changbaishan volcano (China/North Korea; last eruption in 1903 AD) was responsible for a Volcanic Explosivity Index (VEI) 7 eruption in 946 AD. Approximately 186,000 people live around Changbaishan and 2,000,000 tourists/year visit the volcano. An unrest occurred between 2002 and 2006. Despite the [...] Read more.
Changbaishan volcano (China/North Korea; last eruption in 1903 AD) was responsible for a Volcanic Explosivity Index (VEI) 7 eruption in 946 AD. Approximately 186,000 people live around Changbaishan and 2,000,000 tourists/year visit the volcano. An unrest occurred between 2002 and 2006. Despite the relevant hazard, the eruptive history is poorly known, a condition common to many volcanoes worldwide. Here, we investigate the extension of the areas potentially affected by pyroclastic density currents (PDCs) in case of future eruptions following a scenario-based approach. We perform energy cone runs referred to four scenarios from columns of height 3, 10, 20 and 30 km at different vents. By using global datasets on PDCs, we produce spatial probability maps of PDCs invasion. Empirical laws between covered areas, PDC travelled distances, and heights of collapse are provided. In scenarios 3 and 4, PDCs expand at distances up to 42 km and 85 km, respectively. In scenarios 1 and 2, PDCs invade the touristic area and few main roads. Severe effects emerge from scenarios 3 and 4 with the interruption of the China–North Korea land and aerial connections and PDC. Our approach may serve as guide for the rapid evaluation of the PDC-related hazard at poorly known volcanoes. Full article
(This article belongs to the Special Issue Advances in Multihazard Science)
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18 pages, 8306 KiB  
Article
Blockchain Implementation to Verify Archives Integrity on Cilegon E-Archive
by Intan Permatasari, Meryam Essaid, Hyeonwoo Kim and Hongtaek Ju
Appl. Sci. 2020, 10(7), 2621; https://doi.org/10.3390/app10072621 - 10 Apr 2020
Cited by 9 | Viewed by 4398
Abstract
A good archive management system must consider information security aspects, such as availability, confidentiality, and integrity. The Cilegon E-Archive (CEA) system is a centralized system for managing the lifecycle of archives. The existing CEA system has several problems, including a single point of [...] Read more.
A good archive management system must consider information security aspects, such as availability, confidentiality, and integrity. The Cilegon E-Archive (CEA) system is a centralized system for managing the lifecycle of archives. The existing CEA system has several problems, including a single point of failure, low data availability, and difficulty in proving the originality of files. This paper introduces a prototype for a new CEA system that integrates IPFS and the Ethereum private network. In addition, CEA DApp is developed as an interface for users in interacting with CEA system, and its functionality is managed by a smart contract. The results show that the conducted improvements into the CEA system highly improved the system security in terms of preventing archival forgeries. Full article
(This article belongs to the Section Computing and Artificial Intelligence)
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20 pages, 2394 KiB  
Article
Enhancement of Computational Efficiency in Seeking Liveness-Enforcing Supervisors for Advanced Flexible Manufacturing Systems with Deadlock States
by Yen-Liang Pan, Chun-Wang Tai, Ching-Yun Tseng and Jong-Ching Huang
Appl. Sci. 2020, 10(7), 2620; https://doi.org/10.3390/app10072620 - 10 Apr 2020
Cited by 8 | Viewed by 2218
Abstract
In industry 4.0, all kinds of intelligent workstations are designed for use in manufacturing industries. Among them, flexible manufacturing systems (FMSs) use smart robots to achieve their production capacity under the condition of a high degree of resources sharing. As a result, deadlock [...] Read more.
In industry 4.0, all kinds of intelligent workstations are designed for use in manufacturing industries. Among them, flexible manufacturing systems (FMSs) use smart robots to achieve their production capacity under the condition of a high degree of resources sharing. As a result, deadlock states usually appear unexpectedly. For solving the damage deadlock problem, many pioneers have proposed new policies. However, it is very difficult to make systems maximally permissive even if their policies can solve the deadlock problem of FMSs. According to our survey, the Maximal number of Forbidding First Bad Marking (FBM) Problems (MFFP) seems to be the best technology to obtain systems’ maximally permissive states in the existing literature. More importantly, the number of added control places (CP) is the smallest among the existing research works. However, when the complexity of a flexible manufacturing system increases, the computational burden rises rapidly. To reduce computational cost, we define a new concept named Pre Idle Places (PIP) to enhance the computational efficiency in Seeking Liveness-Enforcing Supervisors. We can bypass all PIP once they can be identified from a deadlock system under the process of solving MFFP. According to the data showed in three classical examples, our proposed Improved MFFP is better than conventional MFFP in terms of computational efficiency with the same controllers. Full article
(This article belongs to the Special Issue Computational and Mathematical Methods in Engineering and Information Science)
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23 pages, 7597 KiB  
Article
Design of a Two-DOFs Driving Mechanism for a Motion-Assisted Finger Exoskeleton
by Giuseppe Carbone, Eike Christian Gerding, Burkard Corves, Daniele Cafolla, Matteo Russo and Marco Ceccarelli
Appl. Sci. 2020, 10(7), 2619; https://doi.org/10.3390/app10072619 - 10 Apr 2020
Cited by 34 | Viewed by 5689
Abstract
This paper presents a novel exoskeleton mechanism for finger motion assistance. The exoskeleton is designed as a serial 2-degrees-of-freedom wearable mechanism that is able to guide human finger motion. The design process starts by analyzing the motion of healthy human fingers by video [...] Read more.
This paper presents a novel exoskeleton mechanism for finger motion assistance. The exoskeleton is designed as a serial 2-degrees-of-freedom wearable mechanism that is able to guide human finger motion. The design process starts by analyzing the motion of healthy human fingers by video motion tracking. The experimental data are used to obtain the kinematics of a human finger. Then, a graphic/geometric synthesis procedure is implemented for achieving the dimensional synthesis of the proposed novel 2 degrees of freedom linkage mechanism for the finger exoskeleton. The proposed linkage mechanism can drive the three finger phalanxes by using two independent actuators that are both installed on the back of the hand palm. A prototype is designed based on the proposed design by using additive manufacturing. Results of numerical simulations and experimental tests are reported and discussed to prove the feasibility and the operational effectiveness of the proposed design solution that can assist a wide range of finger motions with proper adaptability to a variety of human fingers. Full article
(This article belongs to the Special Issue Modelling and Control of Mechatronic and Robotic Systems)
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28 pages, 17876 KiB  
Article
Behavior of Airport Concrete Pavement Slabs Exposed to Environmental Loadings
by Hae-Won Park, Dong-Hyuk Kim, Cha-Sang Shim and Jin-Hoon Jeong
Appl. Sci. 2020, 10(7), 2618; https://doi.org/10.3390/app10072618 - 10 Apr 2020
Cited by 6 | Viewed by 3016
Abstract
The behavior of pavement slabs was measured over a two-year period from the placement of concrete at a construction site in Incheon International Airport using temperature sensors and strain gauges. The influence of various environmental factors on the slab behavior was investigated by [...] Read more.
The behavior of pavement slabs was measured over a two-year period from the placement of concrete at a construction site in Incheon International Airport using temperature sensors and strain gauges. The influence of various environmental factors on the slab behavior was investigated by collecting weather data. Laboratory tests were conducted to obtain the material properties of the concrete slab, such as the elastic modulus, Poisson’s ratio, and modulus of rupture. The time of final setting of the concrete slab at the zero point of the strain gauges was determined according to the position and depth of the slab using the maturity of concrete obtained by a mortar penetration test. The real and shrinkage strains were calculated according to the position and depth of the slab using the coefficient of thermal expansion of the concrete, strain gauges, and correction factors of the strain gauges. The effects of environmental factors, such as temperature and moisture variations, were analyzed with respect to the strain in the concrete slab for the first seven days and two years after the placement of the concrete slab. The results obtained by the study shall be used to quantify the environmental effects on slabs for developing a method of designing airport concrete pavements. Full article
(This article belongs to the Section Civil Engineering)
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11 pages, 1667 KiB  
Case Report
Analysis of Salt Mixture Contamination on Insulators via Laser-Induced Breakdown Spectroscopy
by Shan Lu, Xinwei Wang, Tianzheng Wang, Xinran Qin, Xilin Wang and Zhidong Jia
Appl. Sci. 2020, 10(7), 2617; https://doi.org/10.3390/app10072617 - 10 Apr 2020
Cited by 10 | Viewed by 2341
Abstract
The composition of contamination deposited on transmission line insulators can affect their surface flashover voltage. Currently, there is no rapid on-line method to detect this contamination composition in power grids. In this paper, we applied laser-induced breakdown spectroscopy (LIBS) to analyze contamination on [...] Read more.
The composition of contamination deposited on transmission line insulators can affect their surface flashover voltage. Currently, there is no rapid on-line method to detect this contamination composition in power grids. In this paper, we applied laser-induced breakdown spectroscopy (LIBS) to analyze contamination on insulator surfaces. Usually, Na and Ca salts are found in contamination along with various sulfate, carbonate, and chloride compounds. As an element’s detection method, LIBS can only measure a certain element content, for example, Ca. The mixture of various compounds with the same cations can influence the LIBS signal. The influence of mixing ratios on the calibration curves and relative spectral intensity was studied via LIBS. Na2CO3, NaHCO3, CaSO4, and CaCO3 samples containing different proportions of Na and Ca were prepared. The linear correlation coefficients (R2) for the Na and Ca calibration curves generated using various mixing ratios were analyzed. The results showed that the mixture ratio did not dramatically affect the linear calibration curves for mixtures containing the same cations. This finding may significantly reduce the difficulty of applying LIBS analysis for complex contamination on insulators. The laser energy density had effects on the spectral characteristics of the measured elements. The partial least-square regression (PLSR) model can improve the accuracy of Na and Ca prediction. Full article
(This article belongs to the Special Issue Advances and Technologies in High Voltage Power Systems Operation, Control, Protection and Security)
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8 pages, 371 KiB  
Article
Effects of tDCS on Muscle Stiffness in Children with Cerebral Palsy Measured by Myotonometry: A Preliminary Study
by Małgorzata Smoter, Beata Jędrzejczyk-Góral, Aiguo Chen, Bogdan Ciszek and Zofia Ignasiak
Appl. Sci. 2020, 10(7), 2616; https://doi.org/10.3390/app10072616 - 10 Apr 2020
Cited by 4 | Viewed by 2977
Abstract
Background: The aim of this study was to investigate the influence of transcranial direct current stimulation (tDCS) on the biceps brachii and flexor carpi radialis stiffness in children with cerebral palsy (CP). The authors also aimed to verify the relationship between spasticity [...] Read more.
Background: The aim of this study was to investigate the influence of transcranial direct current stimulation (tDCS) on the biceps brachii and flexor carpi radialis stiffness in children with cerebral palsy (CP). The authors also aimed to verify the relationship between spasticity and muscle stiffness. Methods: Twelve children with CP (mean ± SD; age, 8 ± 1.3 years; height, 118.7 ± 4.1 cm; weight, 23.0 ± 2.2 kg) were involved in the study. Muscle stiffness was estimated using a MyotonPRO device in a MultiScan pattern of five measurements. Simultaneously, the tDCS stimulation was performed. Spasticity was assessed by a neurologist using the Ashworth Scale. Results: Stiffness of the flexor carpi radialis muscle decreased significantly after tDCS therapy (p = 0.04). There was no significant change in stiffness of the biceps brachii. For all participants, the Spearman rank correlation showed statistically significant and positive relationships between muscle stiffness and the Ashworth Scale (p = 0.04). Conclusions: Transcranial direct current stimulation has a decreasing effect on stiffness and spasticity of the flexor carpi radialis in children with CP. The MyotonPRO device provides objective data and correlates with spasticity measurements. Full article
(This article belongs to the Special Issue Human Skeletal Muscle and Tendon Characteristics in Sport and Rehabilitation)
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30 pages, 13085 KiB  
Review
Planar Microwave Resonant Sensors: A Review and Recent Developments
by Jonathan Muñoz-Enano, Paris Vélez, Marta Gil and Ferran Martín
Appl. Sci. 2020, 10(7), 2615; https://doi.org/10.3390/app10072615 - 10 Apr 2020
Cited by 87 | Viewed by 7572
Abstract
Microwave sensors based on electrically small planar resonant elements are reviewed in this paper. By virtue of the high sensitivity of such resonators to the properties of their surrounding medium, particularly the dielectric constant and the loss factor, these sensors are of special [...] Read more.
Microwave sensors based on electrically small planar resonant elements are reviewed in this paper. By virtue of the high sensitivity of such resonators to the properties of their surrounding medium, particularly the dielectric constant and the loss factor, these sensors are of special interest (although not exclusive) for dielectric characterization of solids and liquids, and for the measurement of material composition. Several sensing strategies are presented, with special emphasis on differential-mode sensors. The main advantages and limitations of such techniques are discussed, and several prototype examples are reported, mainly including sensors for measuring the dielectric properties of solids, and sensors based on microfluidics (useful for liquid characterization and liquid composition). The proposed sensors have high potential for application in real scenarios (including industrial processes and characterization of biosamples). Full article
(This article belongs to the Special Issue Passive Planar Microwave Devices )
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19 pages, 1712 KiB  
Article
Fuzzy Based Risk Assessment for Decommissioning Concrete Bioshield Structures in Nuclear Power Plants: Structural Risks and Worker Safety
by Byeol Kim, Joo sung Lee and Yong han Ahn
Appl. Sci. 2020, 10(7), 2614; https://doi.org/10.3390/app10072614 - 10 Apr 2020
Cited by 7 | Viewed by 3387
Abstract
Few studies have assessed the safety issues involved in decommissioning nuclear facilities, especially from a structural and job perspective; in most developed countries, the focus is generally on the radiological risks. This study highlights the inadequacy of existing deterministic risk assessment methods, which [...] Read more.
Few studies have assessed the safety issues involved in decommissioning nuclear facilities, especially from a structural and job perspective; in most developed countries, the focus is generally on the radiological risks. This study highlights the inadequacy of existing deterministic risk assessment methods, which cannot account for the uncertainty and complexity of hazards that workers are exposed to. We instead propose a fuzzy logic based safety assessment model that can analyze and compare alternatives utilizing a step-by-step risk quantification and multidimensional approach. This enables personnel to assess the various risks involved when decontaminating and decommissioning nuclear power plant structures that cannot be quantitatively assessed owing to a lack of data. Our proposed fuzzy based risk assessment model can also be applied to risk assessment in other engineering fields that depend on the judgment of experts supported by little or no statistical data. Full article
(This article belongs to the Special Issue Advances on Structural Engineering)
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27 pages, 2018 KiB  
Article
Modeling the Measurements of the Determinants of ICT Fluency and Evolution of Digital Divide Among Students in Developing Countries—East Africa Case Study
by Jean-Pierre Niyigena, Qingshan Jiang, Djemel Ziou, Ruey-Shiang Shaw and A S M Touhidul Hasan
Appl. Sci. 2020, 10(7), 2613; https://doi.org/10.3390/app10072613 - 10 Apr 2020
Cited by 6 | Viewed by 3626
Abstract
During the last decade, information and communication technology has brought remarkable changes to the education style of developed countries, especially in the context of online learning materials accessibility. However, in developing nations such as the East African (EA) countries, university students may lack [...] Read more.
During the last decade, information and communication technology has brought remarkable changes to the education style of developed countries, especially in the context of online learning materials accessibility. However, in developing nations such as the East African (EA) countries, university students may lack the necessary ICT training to take advantage of e-learning resources productively. Therefore, the comprehension of the key factors behind ICT fluency is a significant concern for this region and all the developing countries in general. This paper applies the Concentration Index and proposes a Logistic Regression based model to discover the key determinants of ICT fluency and to explore the evolution of the digital divide among EA students within the four years of undergraduate studies. To identify the principal determinants, data composing of 1237 participants is collected from three different universities in EA within a one year period. The experimental results indicate that the digital divide among students decreases quite fast from the first year to the fourth year. Regression computational findings show that the key determinants of ICT fluency are the student urban/rural origin, computer ownership, computer experience, class year, and major. The findings provide heuristic implications for developers, practitioners, and policy makers for an improved ICT environment implementation in EA and the developing nations in general. Full article
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11 pages, 11620 KiB  
Article
Surface Functionalization of Polyethylene by Silicon Nitride Laser Cladding
by Matteo Zanocco, Elia Marin, Francesco Boschetto, Tetsuya Adachi, Toshiro Yamamoto, Narisato Kanamura, Wenliang Zhu, Bryan J. McEntire, B. Sonny Bal, Ryutaro Ashida, Osam Mazda and Giuseppe Pezzotti
Appl. Sci. 2020, 10(7), 2612; https://doi.org/10.3390/app10072612 - 10 Apr 2020
Cited by 16 | Viewed by 4080
Abstract
Functional coatings are commonly applied to biomaterials in order to improve their properties. In this work, polyethylene was coated with a silicon nitride (Si3N4) powder using a pulsed laser source in a nitrogen gas atmosphere. Several analytical techniques were [...] Read more.
Functional coatings are commonly applied to biomaterials in order to improve their properties. In this work, polyethylene was coated with a silicon nitride (Si3N4) powder using a pulsed laser source in a nitrogen gas atmosphere. Several analytical techniques were used to characterize the functionalized surface of the polymer, including Raman spectroscopy, laser microscopy, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). Antibacterial properties were tested in vitro against Staphylococcus epidermidis. The Si3N4 coating sensibly reduced the amount of living bacteria when compared to the uncoated polymer. Osteoconductivity was also tested in vitro using SaOS-2 osteosarcoma cells. The presence of Si3N4 coating resulted in an increased amount of hydroxyapatite. Coating of polyethylene with silicon nitride may lead to improved performance of indwelling orthopaedic or less invasive medical devices. Full article
(This article belongs to the Section Materials Science and Engineering)
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8 pages, 1185 KiB  
Article
Nanofocusing Optics for an X-Ray Free-Electron Laser Generating an Extreme Intensity of 100 EW/cm2 Using Total Reflection Mirrors
by Hirokatsu Yumoto, Yuichi Inubushi, Taito Osaka, Ichiro Inoue, Takahisa Koyama, Kensuke Tono, Makina Yabashi and Haruhiko Ohashi
Appl. Sci. 2020, 10(7), 2611; https://doi.org/10.3390/app10072611 - 10 Apr 2020
Cited by 18 | Viewed by 3041
Abstract
A nanofocusing optical system—referred to as 100 exa—for an X-ray free-electron laser (XFEL) was developed to generate an extremely high intensity of 100 EW/cm2 (1020 W/cm2) using total reflection mirrors. The system is based on Kirkpatrick-Baez geometry, with [...] Read more.
A nanofocusing optical system—referred to as 100 exa—for an X-ray free-electron laser (XFEL) was developed to generate an extremely high intensity of 100 EW/cm2 (1020 W/cm2) using total reflection mirrors. The system is based on Kirkpatrick-Baez geometry, with 250-mm-long elliptically figured mirrors optimized for the SPring-8 Angstrom Compact Free-Electron Laser (SACLA) XFEL facility. The nano-precision surface employed is coated with rhodium and offers a high reflectivity of 80%, with a photon energy of up to 12 keV, under total reflection conditions. Incident X-rays on the optics are reflected with a large spatial acceptance of over 900 μm. The focused beam is 210 nm × 120 nm (full width at half maximum) and was evaluated at a photon energy of 10 keV. The optics developed for 100 exa efficiently achieved an intensity of 1 × 1020 W/cm2 with a pulse duration of 7 fs and a pulse energy of 150 μJ (25% of the pulse energy generated at the light source). The experimental chamber, which can provide different stage arrangements and sample conditions, including vacuum environments and atmospheric-pressure helium, was set up with the focusing optics to meet the experimental requirements. Full article
(This article belongs to the Special Issue Science at X-ray Free Electron Lasers)
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15 pages, 4778 KiB  
Article
Experimental Study on the Micromorphology and Strength Formation Mechanism of Epoxy Asphalt During the Curing Reaction
by Wei Xu, Guoyi Zhuang, Zhengxiong Chen and Jintao Wei
Appl. Sci. 2020, 10(7), 2610; https://doi.org/10.3390/app10072610 - 10 Apr 2020
Cited by 17 | Viewed by 2786
Abstract
The micromorphological changes and the strength formation mechanism of the curing of epoxy asphalt, which is mostly used for steel bridge deck pavements, were investigated. A tensile test was used to analyze the mechanical properties of epoxy asphalt, and Fourier transform infrared spectroscopy [...] Read more.
The micromorphological changes and the strength formation mechanism of the curing of epoxy asphalt, which is mostly used for steel bridge deck pavements, were investigated. A tensile test was used to analyze the mechanical properties of epoxy asphalt, and Fourier transform infrared spectroscopy (FTIR) was used to determine the change in the epoxy peak area. Laser scanning confocal microscopy (LSCM) and scanning electron microscopy (SEM) were used to observe two-dimensional and three-dimensional micromorphological changes, respectively, during the curing reaction of epoxy asphalt. The results of the tensile and FTIR tests on epoxy asphalt showed that the tensile strength and epoxy conversion rate both increased with the curing time and exhibited similar trends, indicating that the network formed by the crosslinking and polymerization of epoxy groups causes the increased strength of epoxy asphalt. The curing degree of epoxy asphalt during the curing reaction can be indirectly evaluated from the conversion rate of epoxy groups. The asphalt tended to evenly be dispersed in the continuous phase of the epoxy resin during the formation of the epoxy resin network, and the network structure increased the deformation of the epoxy resin. The epoxy asphalt curing reaction process was classified into three stages based on the degree of curing. Full article
(This article belongs to the Special Issue Asphalt Materials II)
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15 pages, 4760 KiB  
Article
Seismic Behavior of Concrete-Filled Circular Steel Tubular Column–Reinforced Concrete Beam Frames with Recycled Aggregate Concrete
by Zongping Chen, Ji Zhou, Zhibin Li, Xinyue Wang and Xingyu Zhou
Appl. Sci. 2020, 10(7), 2609; https://doi.org/10.3390/app10072609 - 10 Apr 2020
Cited by 12 | Viewed by 4032
Abstract
The application of recycled aggregate concrete (RAC) in concrete filled steel tubular (CFST) structures can eliminate the deterioration of concrete performance caused by the original defects of the recycled aggregate, which also provides an effective way for the recycling of waste concrete. In [...] Read more.
The application of recycled aggregate concrete (RAC) in concrete filled steel tubular (CFST) structures can eliminate the deterioration of concrete performance caused by the original defects of the recycled aggregate, which also provides an effective way for the recycling of waste concrete. In this paper, a test of a small scale model of a circular CFST column-reinforced concrete (RC) beam frame with RACs under low cyclic loading was presented in order to investigate its seismic behavior. The failure modes, plastic hinges sequence, hysteresis curve, skeleton curve, energy dissipation capacity, ductility and stiffness degeneration of the frame were presented and analyzed in detail. The test results show that the design method of the recycled aggregate concrete filled circular steel tube (RACFCST) frame complies with the seismic design requirements of a stronger joint followed by the stronger column and the weaker beam. The hysteresis curve of the frame is symmetrical, showing a relatively full shuttle shape; at the same time, the ductility coefficient of the frame is greater than 2.5, showing good deformation performance. In addition, when the frame is damaged, the displacement angle is greater than 1/38, and the equivalent damping ratios coefficient is 0.243, which indicates that the frame has excellent anti-collapse and energy dissipation abilities. In summary, the RACFCST frame has good seismic behavior, which can be applied to high-rise buildings in high-intensity seismic fortification areas. Full article
(This article belongs to the Special Issue Structural Reliability of RC Frame Buildings)
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7 pages, 1423 KiB  
Technical Note
A Clay-Based Geopolymer in Loess Soil Stabilization
by Nadav Hanegbi and Itzhak Katra
Appl. Sci. 2020, 10(7), 2608; https://doi.org/10.3390/app10072608 - 10 Apr 2020
Cited by 25 | Viewed by 3174
Abstract
Soil erosion has environmental and socioeconomic significances. Loess soils cover about 10% of the global land area. Most of these soils are subjected to increased land uses such as unpaved roads, which increase soil destruction and dust emission to the atmosphere. There is [...] Read more.
Soil erosion has environmental and socioeconomic significances. Loess soils cover about 10% of the global land area. Most of these soils are subjected to increased land uses such as unpaved roads, which increase soil destruction and dust emission to the atmosphere. There is a significant interest in applications for dust control and soil stabilization. Application of geopolymers may significantly reduce environmental impacts. This study examines the use of a metakaolin-based geopolymer for dust control and soil stabilization in a semi-arid loess soil. The application of the geopolymer for dust control in comparison with common products (brine, bitumen, polyvinyl acetate-PVA) resulted in no dust emission. As a soil stabilizer, the geopolymer tested in this study provides remarkably good results in the tensile test. The most successful composition of the geopolymer, which is activation solution of sodium silicate and sodium hydroxide (NaOH) together with an addition of 30% metakaolin, obtained soil strength of 23,900 N after 28 days. The attempt to replace NaOH with lime (CaO) in the activation solution was far inferior to the original composition. There is a strong potential to develop natural soil stabilizers from a mineral base that even surpass their capabilities over existing synthetic stabilizers. Full article
(This article belongs to the Special Issue Soil Erosion: Dust Control and Sand Stabilization)
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