Applied Sciences

15 pages, 2398 KiB

Open AccessArticle

Analytical Model for Predicting the UCS from P-Wave Velocity, Density, and Porosity on Saturated Limestone

by Javier González, Manuel Saldaña and Javier Arzúa

Appl. Sci. 2019, 9(23), 5265; https://doi.org/10.3390/app9235265 - 3 Dec 2019

Cited by 27 | Viewed by 5748

Rock mechanics and rock engineering projects require determining, among other parameters, the uniaxial compressive strength (UCS) of rock. For such a purpose, it is not uncommon to perform ultrasonic pulse laboratory tests. Many researchers have found experimental relationships between strength and P-wave velocity, [...] Read more.

Rock mechanics and rock engineering projects require determining, among other parameters, the uniaxial compressive strength (UCS) of rock. For such a purpose, it is not uncommon to perform ultrasonic pulse laboratory tests. Many researchers have found experimental relationships between strength and P-wave velocity, but these relationships are based mainly on dry conditions and without considering any other physical or chemical characteristics of the studied rock. Specifically, for limestone, there are 11 correlations reported in the literature, eight of which are simple and the remaining three are multiple, and, among the latter, only two of them consider the saturation. In order to evaluate the combined effect of P-wave velocity, density, and porosity on the UCS of saturated limestone, simple and multiple regression analyses were carried out on the test results of 13 saturated limestone specimens to determine the parameters of both previously mentioned predictive models. The results showed that density is not correlated with strength. Full article

(This article belongs to the Section Civil Engineering)

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16 pages, 3244 KiB

Open AccessArticle

Neural Computing Improvement Using Four Metaheuristic Optimizers in Bearing Capacity Analysis of Footings Settled on Two-Layer Soils

by Hossein Moayedi, Dieu Tien Bui and Phuong Thao Thi Ngo

Appl. Sci. 2019, 9(23), 5264; https://doi.org/10.3390/app9235264 - 3 Dec 2019

Cited by 22 | Viewed by 3669

Abstract

This study outlines the applicability of four metaheuristic algorithms, namely, whale optimization algorithm (WOA), league champion optimization (LCA), moth–flame optimization (MFO), and ant colony optimization (ACO), for performance improvement of an artificial neural network (ANN) in analyzing the bearing capacity of footings settled [...] Read more.

This study outlines the applicability of four metaheuristic algorithms, namely, whale optimization algorithm (WOA), league champion optimization (LCA), moth–flame optimization (MFO), and ant colony optimization (ACO), for performance improvement of an artificial neural network (ANN) in analyzing the bearing capacity of footings settled on two-layered soils. To this end, the models estimate the stability/failure of the system by taking into consideration soil key factors. The complexity of each network is optimized through a sensitivity analysis process. The performance of the ensembles is compared with a typical ANN to evaluate the efficiency of the applied optimizers. It was shown that the incorporation of the WOA, LCA, MFO, and ACO algorithms resulted in 14.49%, 13.41%, 18.30%, and 35.75% reductions in the prediction error of the ANN, respectively. Moreover, a ranking system is developed to compare the efficiency of the used models. The results revealed that the ACO–ANN performs most accurately, followed by the MFO–ANN, WOA–ANN, and LCA–ANN. Lastly, the outcomes demonstrated that the ACO–ANN can be a promising alternative to traditional methods used for analyzing the bearing capacity of two-layered soils. Full article

(This article belongs to the Special Issue Artificial Intelligence in Smart Buildings)

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11 pages, 2107 KiB

Open AccessArticle

Receptance-Based Dominant Eigenvalues Computation of Controlled Vibrating Systems with Multiple Time-Delays Using a Contour Integral Method

by Jun-Shen Yang, Huajiang Ouyang, Jia-Fan Zhang, Ke-Wei Zhang, Zhi-Gang Hu and Hai-Min Liu

Appl. Sci. 2019, 9(23), 5263; https://doi.org/10.3390/app9235263 - 3 Dec 2019

Cited by 1 | Viewed by 2313

Abstract

The computation of dominant eigenvalues of second-order linear control systems with multiple time-delays is tackled by using a contour integral method. The proposed approach depends on a reduced characteristic function and the associated characteristic matrix comprised of measured open-loop receptances. This reduced characteristic [...] Read more.

The computation of dominant eigenvalues of second-order linear control systems with multiple time-delays is tackled by using a contour integral method. The proposed approach depends on a reduced characteristic function and the associated characteristic matrix comprised of measured open-loop receptances. This reduced characteristic function is derived from the original characteristic function of the second-order time delayed systems based on the reasonable assumption that eigenvalues of the closed-loop system are distinct from those of the open-loop system, and has the same eigenvalues as those of the original. Then, the eigenvalues computation is equivalent to solve a nonlinear eigenvalue problem of the associated characteristic matrix by using a contour integral method. The proposed approach also utilizes the spectrum distribution features of the retarded time-delay systems. Finally, numerical examples are given to illustrate the effectiveness of the proposed approach. Full article

(This article belongs to the Section Acoustics and Vibrations)

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15 pages, 3758 KiB

Open AccessArticle

A Novel Design of Fractional PI/PID Controllers for Two-Input-Two-Output Processes

by Vo Lam Chuong, Truong Nguyen Luan Vu, Nguyen Tam Nguyen Truong and Jae Hak Jung

Appl. Sci. 2019, 9(23), 5262; https://doi.org/10.3390/app9235262 - 3 Dec 2019

Cited by 6 | Viewed by 3022

Abstract

In this paper, a new formulation of fractional order proportional integral (PI)/ proportional integral derivative (PID) controller is proposed. The proposed controller will be justified for some well-known two-input-two-output (TITO) processes. In order to deal with interactions between process variables in a multivariable [...] Read more.

In this paper, a new formulation of fractional order proportional integral (PI)/ proportional integral derivative (PID) controller is proposed. The proposed controller will be justified for some well-known two-input-two-output (TITO) processes. In order to deal with interactions between process variables in a multivariable system, as well as multiple delay times in process transfer functions, the simplified decoupling Smith predictor (SDSP) structure is also used. The issue of decoupling realizability is solved by the PSO algorithm and fractional order processes are also suggested for model reduction. The tuning rules of the controller are derived in analytical terms based on the internal model control (IMC) structure. The effectiveness and robust stability of the proposed approach are illustrated by comparing it with other methods. To have a fair comparison, the robustness criterion using the M-Δ structure with μ-synthesis is adopted and the μ value of the proposed method is always kept smaller than the value of the others. Full article

(This article belongs to the Section Mechanical Engineering)

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4 pages, 174 KiB

Open AccessEditorial

Special Issue on Modelling, Simulation and Data Analysis in Acoustical Problems

by Claudio Guarnaccia, Lamberto Tronchin and Massimo Viscardi

Appl. Sci. 2019, 9(23), 5261; https://doi.org/10.3390/app9235261 - 3 Dec 2019

Cited by 3 | Viewed by 2252

Abstract

Modelling and simulation in acoustics is gathering more and more importance nowadays [...] Full article

(This article belongs to the Special Issue Modelling, Simulation and Data Analysis in Acoustical Problems)

14 pages, 8176 KiB

Open AccessArticle

Research and Development of a Novel TIG Welding Torch for Joining Thin Sheets

by Ngo Huu Manh, Nguyen Van Anh, Nguyen Van Tuan, Bin Xu and Murata Akihisa

Appl. Sci. 2019, 9(23), 5260; https://doi.org/10.3390/app9235260 - 3 Dec 2019

Cited by 7 | Viewed by 5487

Abstract

This paper aims to develop a novel tungsten inner gas (TIG) welding torch in order to join thin sheets efficiently. Using a narrowing nozzle (constricted nozzle) inside a conventional TIG torch can critically improve the position accuracy of the tungsten electrode and also [...] Read more.

This paper aims to develop a novel tungsten inner gas (TIG) welding torch in order to join thin sheets efficiently. Using a narrowing nozzle (constricted nozzle) inside a conventional TIG torch can critically improve the position accuracy of the tungsten electrode and also the arc plasma characteristics and heat input density. In order to evaluate the efficiency of this new torch, weld bead appearance and cross-section images were examined by an optical microscope, scanning electron microscope (SEM), and electron back scatter diffraction patterns (EBSD). The results showed that in all cases, the weld bead profile was stable without undercut and burn-through. Full penetration weld was seen. The width of weld bead on the bottom surface was increased much in comparison to conventional TIG welding. However, the results from SEM and EBSD images indicated that in the case of low welding current, the blowholes were found out on the side of the thinner material (SS400). The penetration of SUS430 material to SS400 material was not good. It seems that no fusion of SUS430 material to SS400 at the bottom surface can be seen. Meanwhile, no blowholes were seen in the case of high welding current. The penetration was better, and the fusion was reached on the bottom surface. Full article

(This article belongs to the Section Mechanical Engineering)

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14 pages, 2145 KiB

Open AccessArticle

Thermo-Optical and Particle Number Size Distribution Characteristics of Smoldering Smoke from Biomass Burning

by Feng Wang, Qixing Zhang, Xuezhe Xu, Weixiong Zhao, Yongming Zhang and Weijun Zhang

Appl. Sci. 2019, 9(23), 5259; https://doi.org/10.3390/app9235259 - 3 Dec 2019

Cited by 3 | Viewed by 2849

Abstract

Controlled laboratory combustion experiments were conducted in the fire test room to mimic freshly emitted smoldering smoke of biomass burning in China. The biomass components were determined by ultimate analysis and proximate analysis before experiments. The particle number size distribution (PNSD) between 5 [...] Read more.

Controlled laboratory combustion experiments were conducted in the fire test room to mimic freshly emitted smoldering smoke of biomass burning in China. The biomass components were determined by ultimate analysis and proximate analysis before experiments. The particle number size distribution (PNSD) between 5 and 1000 nm of smoke was measured by a high sampling frequency size spectrometer. A cavity-enhanced aerosol albedometer with wavelength of 532 nm was used to measure scattering coefficients, extinction coefficients, and single scattering albedo (SSA) of smoldering smoke. The PNSDs of smoldering smoke from the burning of agricultural straw could be fitted with a bimodal lognormal distribution as modes around 10 nm (nucleation mode) and 60 nm (Aitken mode). The PNSDs of wood sawdust could be fitted with a trimodal lognormal distribution, while the two modes were in nucleation mode, and one was in Aitken mode. The bulk optical properties (scattering and extinction coefficients) of smoldering smoke had strong correlations with particle number concentrations of sizes bigger than 100 nm. The correlation between SSA and fixed carbon (FC) was strong (the correlation coefficient is 0.89), while the correlation between SSA and volatile matter (VM) or ash was weak. The relationship between SSA and N (or S) showed a positive correlation, while that of SSA and C showed a negative correlation. The relationship between SSA and VM/FC (or N) showed a strong linear relationship (r² > 0.8). This paper could improve understanding of the relationship between the optical and particle size distribution properties of smoke from biomass burning and the components of biomass materials under similar combustion conditions. Full article

(This article belongs to the Special Issue Combustion Aerosol)

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15 pages, 6848 KiB

Open AccessArticle

Failure Analysis on a Collapsed Flat Cover of an Adjustable Ballast Tank Used in Deep-Sea Submersibles

by Fang Wang, Mian Wu, Genqi Tian, Zhe Jiang, Shun Zhang, Jian Zhang and Weicheng Cui

Appl. Sci. 2019, 9(23), 5258; https://doi.org/10.3390/app9235258 - 3 Dec 2019

Cited by 1 | Viewed by 3372

Abstract

A flat cover of an adjustable ballast tank made of high-strength maraging steel used in deep-sea submersibles collapsed during the loading process of external pressure in the high-pressure chamber. The pressure was high, which was the trigger of the collapse, but still considerably [...] Read more.

A flat cover of an adjustable ballast tank made of high-strength maraging steel used in deep-sea submersibles collapsed during the loading process of external pressure in the high-pressure chamber. The pressure was high, which was the trigger of the collapse, but still considerably below the design limit of the adjustable ballast tank. The failure may have been caused by material properties that may be defective, the possible stress concentration resulting from design/processing, or inappropriate installation method. The present paper focuses on the visual inspections of the material inhomogeneity, ultimate cause of the collapse of the flat cover in pressure testing, and finite element analysis. Special attention is paid to the toughness characteristics of the material. The present study demonstrates the importance of material selection for engineering components based on the comprehensive properties of the materials. Full article

(This article belongs to the Special Issue Recent Trends in Advanced High-Strength Steels)

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17 pages, 4601 KiB

Open AccessArticle

A Study on a Mechanism of Lateral Pedestrian-Footbridge Interaction

by Zhou Chen, Siyuan Chen, Xijun Ye and Yunlai Zhou

Appl. Sci. 2019, 9(23), 5257; https://doi.org/10.3390/app9235257 - 3 Dec 2019

Cited by 6 | Viewed by 2454

Abstract

Based on the pedestrian lateral force hybrid Van der Pol/Rayleigh model, this study investigates the interaction dynamic model of a pedestrian-flexible footbridge lateral coupling system. A multi scale method is adopted to decouple the equation. The paper also studies the nonlinear dynamic response [...] Read more.

Based on the pedestrian lateral force hybrid Van der Pol/Rayleigh model, this study investigates the interaction dynamic model of a pedestrian-flexible footbridge lateral coupling system. A multi scale method is adopted to decouple the equation. The paper also studies the nonlinear dynamic response of the pedestrian-footbridge coupling system as well as the relationship between the lateral displacement of pedestrians and flexible footbridges, and the lateral interaction of the two variables. The results show that with the same frequency tuning parameters, when the mass ratio of pedestrians and footbridges is very small, the larger the mass ratio is, the larger the lateral response amplitude of pedestrians becomes. Conversely, when the mass ratio of pedestrians and footbridges is much larger, the larger the mass ratio is, the smaller the response amplitude becomes. When the natural frequency of a footbridge is larger, its Phase Angle becomes larger. As the lateral amplitude of pedestrians increases, the Phase Angle approaches zero. Moreover, regarding the variation of the Phase Angle between the interaction force and footbridge lateral vibration speed based on the lateral relative displacement of pedestrians, of which the variation range is (0,

π

), as the pedestrians’ lateral amplitude increases, the Phase Angle approaches −

π / 2

. The dynamic load coefficient varies linearly with the lateral amplitude of pedestrian vibrations. Full article

(This article belongs to the Special Issue Bridge Dynamics)

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Graphical abstract

12 pages, 1882 KiB

Open AccessArticle

Architecture and Viability of the Biofilms Formed by Nine Listeria Strains on Various Hydrophobic and Hydrophilic Materials

by Cristina Rodríguez-Melcón, Carlos Alonso-Calleja and Rosa Capita

Appl. Sci. 2019, 9(23), 5256; https://doi.org/10.3390/app9235256 - 3 Dec 2019

Cited by 12 | Viewed by 4531

Abstract

Biofilms are a key factor in the persistence of Listeria in food processing plants, representing a potential source of foodstuff contamination. Nine Listeria strains (eight Listeria monocytogenes and one Listeria ivanovii) were studied by confocal laser scanning microscopy (CLSM) for their ability [...] Read more.

Biofilms are a key factor in the persistence of Listeria in food processing plants, representing a potential source of foodstuff contamination. Nine Listeria strains (eight Listeria monocytogenes and one Listeria ivanovii) were studied by confocal laser scanning microscopy (CLSM) for their ability to form biofilm on glass, polystyrene, graphene and resin after 120 h of incubation at 12 °C. The relationship between cell surface hydrophobicity and biofilm formation was also investigated. On comparing the data for all the strains, similar (P > 0.05) biovolume values were obtained on glass (average 3.39 ± 1.69 µm³/µm²) and graphene (2.93 ± 1.14 µm³/µm²), while higher (P < 0.05) values were observed for polystyrene (4.39 ± 4.14 µm³/µm²). The highest (P < 0.01) biovolume levels were found in the biofilms formed on resin (7.35 ± 1.45 µm³/µm²), which also had the smallest biomass of inactivated cells (0.38 ± 0.37 µm³/µm² vs. 1.20 ± 1.12 µm³/µm² on the remaining surfaces; P < 0.001). No relationship was noted between cell surface hydrophobicity and biofilm-forming ability. Full article

(This article belongs to the Special Issue Biofilms in Focus: A Threat to Foods)

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Graphical abstract

15 pages, 7262 KiB

Open AccessArticle

Seismic Behavior of Steel Plate-Concrete Shear Walls with Holes

by Zhihua Chen, Jingshu Wu and Hongbo Liu

Appl. Sci. 2019, 9(23), 5255; https://doi.org/10.3390/app9235255 - 3 Dec 2019

Cited by 4 | Viewed by 3461

Abstract

Steel plate-concrete shear walls (SPSW) are used as the containment in nuclear power stations. However, the influence of holes and axial loading on the behavior of steel plate-concrete shear walls is neglected in most studies. Thus, it is necessary to understand the seismic [...] Read more.

Steel plate-concrete shear walls (SPSW) are used as the containment in nuclear power stations. However, the influence of holes and axial loading on the behavior of steel plate-concrete shear walls is neglected in most studies. Thus, it is necessary to understand the seismic behavior of SPSW members with holes in order to avoid the potential risks for nuclear power stations. In this study, a series of specimens were tested by low-cycle reciprocal loading. The specimens were designed with different holes to simulate real members in nuclear power stations. A hysteretic curve of specimens was obtained from a low-cycle reciprocal test to discuss the seismic behavior of steel plate-concrete shear walls (SPSW). Moreover, effects of axial compression ratio, hole size, thickness of the steel plate, and hole position on the hysteretic performance of SPSW were analyzed. The horizontal ultimate bearing capacity of SPSW specimens was estimated using the norms of the Architecture Institute of Japan and the calculation method of Ono reduction rate. Results provide theoretical references for the design and application of SPSW with holes. Full article

(This article belongs to the Special Issue Advanced Methods for Seismic Performance Evaluation of Building Structures)

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17 pages, 3282 KiB

Open AccessArticle

Modeling and Solution of the Routing Problem in Vehicular Delay-Tolerant Networks: A Dual, Deep Learning Perspective

by Roberto Hernández-Jiménez, Cesar Cardenas and David Muñoz Rodríguez

Appl. Sci. 2019, 9(23), 5254; https://doi.org/10.3390/app9235254 - 3 Dec 2019

Cited by 9 | Viewed by 2973

Abstract

The exponential growth of cities has brought important challenges such as waste management, pollution and overpopulation, and the administration of transportation. To mitigate these problems, the idea of the smart city was born, seeking to provide robust solutions integrating sensors and electronics, information [...] Read more.

The exponential growth of cities has brought important challenges such as waste management, pollution and overpopulation, and the administration of transportation. To mitigate these problems, the idea of the smart city was born, seeking to provide robust solutions integrating sensors and electronics, information technologies, and communication networks. More particularly, to face transportation challenges, intelligent transportation systems are a vital component in this quest, helped by vehicular communication networks, which offer a communication framework for vehicles, road infrastructure, and pedestrians. The extreme conditions of vehicular environments, nonetheless, make communication between nodes that may be moving at very high speeds very difficult to achieve, so non-deterministic approaches are necessary to maximize the chances of packet delivery. In this paper, we address this problem using artificial intelligence from a hybrid perspective, focusing on both the best next message to replicate and the best next hop in its path. Furthermore, we propose a deep learning–based router (DLR+), a router with a prioritized type of message scheduler and a routing algorithm based on deep learning. Simulations done to assess the router performance show important gains in terms of network overhead and hop count, while maintaining an acceptable packet delivery ratio and delivery delays, with respect to other popular routing protocols in vehicular networks. Full article

(This article belongs to the Special Issue Artificial Intelligence Applications to Smart City and Smart Enterprise)

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18 pages, 2549 KiB

Open AccessArticle

Supplier Selection and Performance Evaluation for High-Voltage Power Film Capacitors in a Fuzzy Environment

by Chun-Ming Yang, Kuen-Suan Chen, Ting-Hsin Hsu and Chang-Hsien Hsu

Appl. Sci. 2019, 9(23), 5253; https://doi.org/10.3390/app9235253 - 3 Dec 2019

Cited by 8 | Viewed by 3423

Abstract

Rapid advances in technology have shortened the upgrade and replacement cycles in industries such as electronics, household appliances, and communication technologies. Within these industries, high-voltage power film capacitors have become indispensable electrical components due to their good electrical performance and high reliability. The [...] Read more.

Rapid advances in technology have shortened the upgrade and replacement cycles in industries such as electronics, household appliances, and communication technologies. Within these industries, high-voltage power film capacitors have become indispensable electrical components due to their good electrical performance and high reliability. The selection and evaluation of suppliers of these capacitors is therefore increasingly important. Suppliers play a crucial role in the electronics industry; the quality of their products determines the degree to which the quality of the final product can be guaranteed. Supplier quality also affects the ability of all the members in a supply chain to control costs. Evaluation by decision-makers is highly significant in the supplier selection process. However, when the opinions of multiple decision-makers are combined, issues such as cognitive differences, fuzzy linguistics, and uncertainty are common. This study presents a supplier performance index S_PL and derives the estimates of the index S_PL and its statistical properties. The proposed index is not only helpful for the accurate measurement of supplier performance; it can also reduce cognitive differences among evaluators in the decision-making process (that is, the sample variability associated with the Likert scale). Evaluation scores for each criterion for the linguistic labels are converted to triangular fuzzy numbers in order to reduce ambiguity. Subsequently, integrated crisp values are obtained by defuzzification in a fuzzy inference system. A real-world case study of the supplier selection of high-voltage power film capacitors is provided to illustrate the efficacy of the proposed method. Full article

(This article belongs to the Special Issue Industrial Engineering and Management: Current Issues and Trends)

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12 pages, 864 KiB

Open AccessArticle

Potential of Advanced Consolidants for the Application on Sandstone

by Monika Remzova, Radek Zouzelka, Jaroslav Lukes and Jiri Rathousky

Appl. Sci. 2019, 9(23), 5252; https://doi.org/10.3390/app9235252 - 3 Dec 2019

Cited by 13 | Viewed by 2460

Abstract

Alkoxy-based consolidants are widely used for conservation of cultural heritage objects made from sandstones. Even if such consolidants were introduced into practice already in the 19th century, their performance has been enhanced by several modifications to their composition only recently. To obtain a [...] Read more.

Alkoxy-based consolidants are widely used for conservation of cultural heritage objects made from sandstones. Even if such consolidants were introduced into practice already in the 19th century, their performance has been enhanced by several modifications to their composition only recently. To obtain a relevant comparison of their application potential, both commercial (Remmers KSE OH and SurfaPore FX SB) and a self-developed particle-modified ethyl silicate consolidant supplemented with two phosphate-based ones, were assessed. Importantly, the potential toxicity of our novel consolidants was considered. Since the stone substrate should mimic the properties of naturally weathered stone, sandstone from the Msene quarry in Central Bohemia, characterized by a high porosity and relatively low mechanical strength, is selected. From practical point of view, the long-term durability of the consolidation effect is crucial compared to the initial level of consolidation. Regarding the determination of durability of the sandstone consolidation according to an American Society for Testing and Materials (ASTM) accelerated weathering test, we performed mechanical tests in micro- (nanoindentation) and macroscale (drilling resistance measurements). The cohesion of the consolidant xerogels in the pores were determined by sorption experiments in gas phase. The durability of our TiO₂ and ZnO particle-modified consolidants is superior to that of the commercial products. The aqueous diammonium hydrogen phosphate-based consolidant, which also shows exceptional durability, reveals itself to be a promising product for not only carbonate but also sandstone materials. Full article

(This article belongs to the Section Civil Engineering)

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15 pages, 8959 KiB

Open AccessArticle

Multiscale Damage Evolution Analysis of Aluminum Alloy Based on Defect Visualization

by Yuquan Bao, Yali Yang, Hao Chen, Yongfang Li, Jie Shen and Shuwei Yang

Appl. Sci. 2019, 9(23), 5251; https://doi.org/10.3390/app9235251 - 3 Dec 2019

Cited by 7 | Viewed by 2656

Abstract

The evaluation of fatigue life through the mechanism of fatigue damage accumulation is still a challenging task in engineering structure failure analysis. A multiscale fatigue damage evolution model was proposed for describing both the mesoscopic voids propagation in the mesoscopic-scale and fatigue damage [...] Read more.

The evaluation of fatigue life through the mechanism of fatigue damage accumulation is still a challenging task in engineering structure failure analysis. A multiscale fatigue damage evolution model was proposed for describing both the mesoscopic voids propagation in the mesoscopic-scale and fatigue damage evolution process, reflecting the progressive degradation of metal components in the macro-scale. An effective method of defect classification was used to implement 3D reconstruction technology based on the MCT (micro-computed tomography) scanning damage data with ABAQUS subroutine. The effectiveness was validated through the comparison with the experimental data of fatigue damage accumulation. Our results indicated that the multiscale fatigue damage evolution model built a bridge between mesoscopic damage and macroscopic fracture, which not only used the damage variable in the macro-scale to characterize the mesoscopic damage evolution indirectly but also understood macroscopic material degradation behavior from mesoscale with sufficient precision. Furthermore, the multiscale fatigue damage evolution model could offer a new reasonable explanation of the effect of load sequence on fatigue life, and also could predict the fatigue life based on damage data by nondestructive testing techniques. Full article

(This article belongs to the Special Issue Fracture and Fatigue Assessments of Structural Components)

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15 pages, 4308 KiB

Open AccessArticle

Calculation Model of High-Pressure Water Jet Slotting Depth for Coalbed Methane Development in Underground Coal Mine

by Jianguo Zhang, Yingwei Wang, Zhaolong Ge, Songqiang Xiao, Hanyun Zhao and Xiaobo Huang

Appl. Sci. 2019, 9(23), 5250; https://doi.org/10.3390/app9235250 - 3 Dec 2019

Cited by 7 | Viewed by 2655

Abstract

In underground coal mines, high-pressure water jet slotting is effective at improving coal seams’ permeability. The slotting depth determines the effect of pressure relief and permeability enhancement in coal seams. However, there is no effective and feasible way of determining the slotting depth; [...] Read more.

In underground coal mines, high-pressure water jet slotting is effective at improving coal seams’ permeability. The slotting depth determines the effect of pressure relief and permeability enhancement in coal seams. However, there is no effective and feasible way of determining the slotting depth; thus, the operational parameters and borehole layout are unknown. This study determined the effects of key parameters, including the nozzle diameter, jet pressure, rotation speed, and slotting time, on the slotting depth. A water jet slotting depth calculation model was established and verified according to the slotting experiments under different operational conditions. The slotting depths were investigated based on the results of field slotting experiments. The results revealed that there exists an optimal nozzle diameter for a higher jet impact velocity. The slotting depth linearly increased with the jet pressure and decreased as a power function with the increase of the jet translation speed. The slotting depth increased with the slotting time, but the growth rate gradually decreased and tended to be stable. As the rotation speed increased, the slotting depth became greater at the initial period and the limit depth was reached faster. Laboratory and field slotting experiments were conducted to verify the model, and the experimental results are approximately in agreement with the theoretical predictions. The results of this study can be useful as guidelines for the hydraulic parameter selection of water jet slotting and for optimizing the layout of coal gas drainage boreholes. Full article

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16 pages, 4559 KiB

Open AccessArticle

Adsorption of Ammonium Nitrogen from Aqueous Solution on Chemically Activated Biochar Prepared from Sorghum Distillers Grain

by Derlin Hsu, Changyi Lu, Tairan Pang, Yuanpeng Wang and Guanhua Wang

Appl. Sci. 2019, 9(23), 5249; https://doi.org/10.3390/app9235249 - 3 Dec 2019

Cited by 45 | Viewed by 4776

Abstract

Chemically activated biochars prepared from sorghum distillers grain using two base activators (NaOH and KOH) were investigated for their adsorption properties with respect to ammonium nitrogen from aqueous solution. Detailed characterizations, including scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction [...] Read more.

Chemically activated biochars prepared from sorghum distillers grain using two base activators (NaOH and KOH) were investigated for their adsorption properties with respect to ammonium nitrogen from aqueous solution. Detailed characterizations, including scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetry (TG), and specific surface area analyses, were carried out to offer a broad evaluation of the prepared biochars. The results showed that the NaOH- and KOH-activated biochars exhibited significantly enhanced adsorption capacity, by 2.93 and 4.74 times, respectively, in comparison with the pristine biochar. Although the NaOH-activated biochar possessed larger specific surface area (132.8 and 117.7 m²/g for the NaOH- and KOH-activated biochars, respectively), the KOH-activated biochar had higher adsorption capacity owing to its much higher content of functional groups. The adsorption kinetics and isotherms of the KOH-activated biochar at different temperatures were further studied. The biochar had a maximum adsorption capacity of 14.34 mg/g at 45 °C, which was satisfactory compared with other biochars prepared using different feedstocks. The adsorption process followed pseudo-second-order kinetics, and chemical adsorption was the rate-controlling step. The equilibrium data were consistent with the Freundlich isotherm, and the thermodynamic parameters suggested that the adsorption process was endothermic and spontaneous. Consequently, this work demonstrates that chemically activated biochar from sorghum distillers grain is effective for ammonium nitrogen removal. Full article

(This article belongs to the Special Issue Advanced or Conventional Materials as Sorbent)

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13 pages, 5032 KiB

Open AccessArticle

Diesel Spray Macroscopic Parameter Estimation Using a Synthetic Shapes Database

by Andrea Bottega and Claudio Dongiovanni

Appl. Sci. 2019, 9(23), 5248; https://doi.org/10.3390/app9235248 - 2 Dec 2019

Cited by 1 | Viewed by 2096

Abstract

The paper presents a method for the macroscopic characterization of diesel sprays starting from digital images. Macroscopic spray characterization mainly consists in the definition of two parameters, namely penetration and cone angle. The latter can be evaluated according to many possible definitions, all [...] Read more.

The paper presents a method for the macroscopic characterization of diesel sprays starting from digital images. Macroscopic spray characterization mainly consists in the definition of two parameters, namely penetration and cone angle. The latter can be evaluated according to many possible definitions, all based on the spray contour that is obtained by means of image thresholding. Therefore, the obtained cone angle value depends on the adopted angle definition and on the used thresholding algorithm. In order to avoid this double dependence, an alternative method has hence been proposed. The algorithm does not require the image thresholding and has an intrinsic cone angle definition. The algorithm takes advantage of principal component analysis technique and allows for a direct estimation of spray penetration and cone angle by comparing the original image with a database made of artificial spray images. In the present work, images coming from two different experiments are analyzed with the proposed method and results are compared with those obtained with a traditional procedure based on the Otsu’s image thresholding and four cone angle definitions. Full article

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

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11 pages, 2088 KiB

Open AccessArticle

A High Peak Power and High Beam Quality Sub-Nanosecond Nd:YVO₄ Laser System at 1 kHz Repetition Rate without SRS Process

by Yutao Huang, Hongbo Zhang, Xiaochao Yan, Zhijun Kang, Fuqiang Lian and Zhongwei Fan

Appl. Sci. 2019, 9(23), 5247; https://doi.org/10.3390/app9235247 - 2 Dec 2019

Cited by 7 | Viewed by 3943

Abstract

We present a compact sub-nanosecond diode-end-pumped Nd:YVO₄ laser system running at 1 kHz. A maximum output energy of 65.4 mJ without significant stimulated Raman scattering (SRS) process was obtained with a pulse duration of 600 ps, corresponding to a pulse peak power [...] Read more.

We present a compact sub-nanosecond diode-end-pumped Nd:YVO₄ laser system running at 1 kHz. A maximum output energy of 65.4 mJ without significant stimulated Raman scattering (SRS) process was obtained with a pulse duration of 600 ps, corresponding to a pulse peak power of 109 MW. Laser pulses from this system had good beam quality, where M² < 1.6, and the excellent signal to noise ratio was more than 42 dB. By frequency doubling with an LBO crystal, 532 nm green light with an average power of 40.5 W and a power stability of 0.28% was achieved. The diode-end-pumped pump power limitation on a high peak power amplifier caused by the SRS process and thermal fracture in bulk Nd:YVO₄ crystal is also analyzed. Full article

(This article belongs to the Special Issue Modern Applications in Optics and Photonics: From Sensing and Analytics to Communication)

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11 pages, 1331 KiB

Open AccessArticle

Respiration Monitoring for Premature Neonates in NICU

by Yue Sun, Wenjin Wang, Xi Long, Mohammed Meftah, Tao Tan, Caifeng Shan, Ronald M. Aarts and Peter H. N. de With

Appl. Sci. 2019, 9(23), 5246; https://doi.org/10.3390/app9235246 - 2 Dec 2019

Cited by 15 | Viewed by 4645

Abstract

In this paper, we investigate an automated pipeline to estimate respiration signals from videos for premature infants in neonatal intensive care units (NICUs). Two flow estimation methods, namely the conventional optical flow- and deep learning-based flow estimation methods, were employed and compared to [...] Read more.

In this paper, we investigate an automated pipeline to estimate respiration signals from videos for premature infants in neonatal intensive care units (NICUs). Two flow estimation methods, namely the conventional optical flow- and deep learning-based flow estimation methods, were employed and compared to estimate pixel motion vectors between adjacent video frames. The respiratory signal is further extracted via motion factorization. The proposed methods were evaluated by comparing our automated extracted respiration signals to that extracted from chest impedance on videos of five premature infants. The overall average cross-correlation coefficients are 0.70 for the optical flow-based method and 0.74 for the deep flow-based method. The average root mean-squared errors are 6.10 and 4.55 for the optical flow- and the deep flow-based methods, respectively. The experimental results are promising for further investigation and clinical application of the video-based respiration monitoring method for infants in NICUs. Full article

(This article belongs to the Section Applied Physics General)

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22 pages, 8774 KiB

Open AccessArticle

Effects of Toe-Out and Toe-In Gaits on Lower-Extremity Kinematics, Dynamics, and Electromyography

by Weiling Cui, Changjiang Wang, Weiyi Chen, Yuan Guo, Yi Jia, Weijin Du and Chenyan Wang

Appl. Sci. 2019, 9(23), 5245; https://doi.org/10.3390/app9235245 - 2 Dec 2019

Cited by 15 | Viewed by 9313

Abstract

Toe-in and toe-out gait modifications have received increasing attention as an effective, conservative treatment for individuals without severe osteoarthritis because of its potential for improving knee adduction moment (KAM) and knee flexion moment (KFM). Although toe-in and toe-out gaits have positive effects on [...] Read more.

Toe-in and toe-out gait modifications have received increasing attention as an effective, conservative treatment for individuals without severe osteoarthritis because of its potential for improving knee adduction moment (KAM) and knee flexion moment (KFM). Although toe-in and toe-out gaits have positive effects on tibiofemoral (TF) joint pain in the short term, negative impacts on other joints of the lower extremity may arise. The main purpose of this study was to quantitatively compare the effects of foot progression angle (FPA) gait modification with normal walking speeds in healthy individuals on lower-extremity joint, ground reaction force (GRF), muscle electromyography, joint moment, and TF contact force. Experimental measurements using the Vicon system and multi-body dynamics musculoskeletal modelling using OpenSim were conducted in this study. Gait analysis of 12 subjects (n = 12) was conducted with natural gait, toe-in gait, and toe-out gait. One-way repeated measures of ANOVA (p < 0.05) with Tukey’s test was used for statistical analysis. Results showed that the toe-in and toe-out gait modifications decreased the max angle of knee flexion by 8.8 and 12.18 degrees respectively (p < 0.05) and the max angle of hip adduction by 1.28 and 0.99 degrees respectively (p < 0.05) compared to the natural gait. Changes of TF contact forces caused by FPA gait modifications were not statistically significant; however, the effect on KAM and KFM were significant (p < 0.05). KAM or combination of KAM and KFM can be used as surrogate measures for TF medial contact force. Toe-in and toe-out gait modifications could relieve knee joint pain probably due to redistribution of TF contact forces on medial and lateral condylar through changing lateral contact centers and shifting bilateral contact locations. Full article

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

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15 pages, 6582 KiB

Open AccessArticle

Numerical Simulation of the Tip Leakage Vortex Characteristics in a Semi-Open Centrifugal Pump

by Like Wang, Jinling Lu, Weili Liao, Yaping Zhao and Wei Wang

Appl. Sci. 2019, 9(23), 5244; https://doi.org/10.3390/app9235244 - 2 Dec 2019

Cited by 33 | Viewed by 3246

Abstract

Tip leakage vortex has an important influence on the performance of semi-open centrifugal pumps. Simulations based on the three-dimensional Reynolds-Averaged Navier–Stokes were conducted to study the structural characteristics of tip leakage vortex and its effects on the internal flow field, and the Shear [...] Read more.

Tip leakage vortex has an important influence on the performance of semi-open centrifugal pumps. Simulations based on the three-dimensional Reynolds-Averaged Navier–Stokes were conducted to study the structural characteristics of tip leakage vortex and its effects on the internal flow field, and the Shear Stress Transport k-ω turbulence model was used to simulate the whole flow passage of centrifugal pumps with tip clearances of 0 mm and 1 mm. Then, the tip leakage vortex was analyzed using the relative vorticity transport equation. The numerical data and experimental results agreed well. The leakage vortex formed in the tip clearance led to 18.7% and 14.4% decrease in head and efficiency under design condition, respectively, and the bigger the flow rate, the fast the performance decreased. Tip leakage vortex formed at the leading edge of the blade moved along the suction surface. Whereas the tip leakage vortex formed near the middle of the blade extended to the pressure surface of the adjacent blade. This phenomenon deteriorated the flow field and induced passage vortex, thereby reducing the static pressure and blade load and changing the static pressure distribution law. The formation and development of leakage vortex could be attributed to the relative vortex stretching the term. The Coriolis force term could reflect the change of vorticity caused by leakage flow, and the viscous diffusion term served as the vorticity source. Full article

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

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16 pages, 3257 KiB

Open AccessArticle

Integrated Design of Aerodynamic Performance and Structural Characteristics for Medium Thickness Wind Turbine Airfoil

by Quan Wang, Pan Huang, Di Gan and Jun Wang

Appl. Sci. 2019, 9(23), 5243; https://doi.org/10.3390/app9235243 - 2 Dec 2019

Cited by 6 | Viewed by 3323

Abstract

The currently geometric and aerodynamic characteristics for wind turbine airfoils with the medium thickness are studied to pursue maximum aerodynamic performance, while the interaction between blade stiffness and aerodynamic performance is neglected. Combining the airfoil functional integration theory and the mathematical model of [...] Read more.

The currently geometric and aerodynamic characteristics for wind turbine airfoils with the medium thickness are studied to pursue maximum aerodynamic performance, while the interaction between blade stiffness and aerodynamic performance is neglected. Combining the airfoil functional integration theory and the mathematical model of the blade cross-section stiffness matrix, an integrated design method of aerodynamic performance and structural stiffness characteristics for the medium thickness airfoils is presented. The aerodynamic and structural comparison of the optimized WQ-A300 airfoil, WQ-B300 airfoil, and the classic DU97-W-300 airfoil were analyzed. The results show that the aerodynamic performance of the WQ-A300 and WQ-B300 airfoils are better than that of the DU97-W-300 airfoil. Though the aerodynamic performance of the WQ-B300 airfoil is slightly reduced compared to the WQ-A300 airfoil, its blade cross-sectional stiffness properties are improved as the flapwise and edgewise stiffness are increased by 6.2% and 8.4%, respectively. This study verifies the feasibility for the novel design method. Moreover, it also provides a good design idea for the wind turbine airfoils and blade structural properties with medium or large thickness. Full article

(This article belongs to the Special Issue Wind Power Technologies)

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16 pages, 6759 KiB

Open AccessArticle

Forecasting Landslides via Three-Dimensional Discrete Element Modeling: Helong Landslide Case Study

by Wei Peng, Shengyuan Song, Chongjia Yu, Yiding Bao, Jiaxuan Sui and Ying Hu

Appl. Sci. 2019, 9(23), 5242; https://doi.org/10.3390/app9235242 - 2 Dec 2019

Cited by 7 | Viewed by 3478

Abstract

Forecasting the occurrence potential of landslides is important but challenging. We aimed to forecast the failure potential of the Helong landslide, which is temporarily stable but has clearly deformed in recent years. To achieve the goal, we used reconnaissance, remote sensing, drilling, laboratory [...] Read more.

Forecasting the occurrence potential of landslides is important but challenging. We aimed to forecast the failure potential of the Helong landslide, which is temporarily stable but has clearly deformed in recent years. To achieve the goal, we used reconnaissance, remote sensing, drilling, laboratory tests, topographical analysis, and electrical resistivity tomography (ERT). The factor of safety (FOS) of the slope was first calculated using a limit equilibrium method. The results show the FOS of the slope was 1.856 under natural conditions, 1.506 under the earthquake conditions, 1.318 under light rainfall, 0.986 under heavy rainfall, 1.075 under light rainfall and earthquake, and 0.832 under simultaneous heavy rainfall and earthquake. When the FOS is less than 1.35, the slope is considered metastable according to the Technical Code for Building Slope Engineering (GB50330-2013) published by the Chinese Ministry of Housing and Urban-Rural Development. Based on the drilling data and digital elevation data, a three-dimensional discrete element method (DEM) model was used to simulate potential landslides. The simulation was used to examine catastrophic slope failure under heavy rainfall conditions within a range of friction coefficients and the corresponding affected areas were determined. Then, we analyzed a typical run-out process. The dynamic information of the run-out behavior, including velocity, run-out distance, and depth, were obtained, which is useful for decision support and future landslide hazard assessment. Full article

(This article belongs to the Section Earth Sciences)

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15 pages, 2347 KiB

Open AccessArticle

Mixed Convective Flow of Micropolar Nanofluid across a Horizontal Cylinder in Saturated Porous Medium

by Ahmed M. Rashad, Waqar A. Khan, Saber M. M. EL-Kabeir and Amal M. A. EL-Hakiem

Appl. Sci. 2019, 9(23), 5241; https://doi.org/10.3390/app9235241 - 2 Dec 2019

Cited by 39 | Viewed by 2822

Abstract

The micropolar nanofluids are the potential liquids that enhance the thermophysical features and ability of heat transportation instead of base liquids. Alumina and Titania nanoparticles are mixed in a micropolar fluid. The impact of convective boundary condition is also examined with assisting and [...] Read more.

The micropolar nanofluids are the potential liquids that enhance the thermophysical features and ability of heat transportation instead of base liquids. Alumina and Titania nanoparticles are mixed in a micropolar fluid. The impact of convective boundary condition is also examined with assisting and opposing flows of both nanofluids. The main objective of this study is to investigate mixed convective flow and heat transfer of micropolar nanofluids across a cylinder in a saturated porous medium. Non-similar variables are used to make the governing equations dimensionless. The local similar and non-similar solutions are obtained by using the Runge-Kutta-Fehlberg method of seventh order. The impacts of various embedded variables on the flow and heat transfer of micropolar nanofluids are investigated and interpreted graphically. It is demonstrated that the skin friction and heat transfer rates depend on solid volume fraction of nanoparticles, Biot number, mixed convection, and material parameters. Full article

(This article belongs to the Section Mechanical Engineering)

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22 pages, 8738 KiB

Open AccessArticle

Availability and Fade Margin Calculations for 5G Microwave and Millimeter-Wave Anyhaul Links

by Attila Hilt

Appl. Sci. 2019, 9(23), 5240; https://doi.org/10.3390/app9235240 - 2 Dec 2019

Cited by 35 | Viewed by 16754

Abstract

The deployment of new radio access technologies always provides a good opportunity and timing to optimize the existing mobile front- and backhaul (commonly called “anyhaul”). The legacy systems (Long-Term Evolution (LTE), High-Speed Packet Access (HSPA), third-generation mobile (3G), second-generation mobile (2G)) already extensively [...] Read more.

The deployment of new radio access technologies always provides a good opportunity and timing to optimize the existing mobile front- and backhaul (commonly called “anyhaul”). The legacy systems (Long-Term Evolution (LTE), High-Speed Packet Access (HSPA), third-generation mobile (3G), second-generation mobile (2G)) already extensively utilize the transmission and transport capacities of the mobile anyhaul. With the current launch of 5G (fifth-generation mobile) and recent LTE-A (Advanced Long-Term Evolution), additional new transmission capacities are required again. Depending on the traffic and network topology, additional cell sites are built, and even more locations are connected with fiber optics. The existing microwave and millimeter-wave links are rotated toward those aggregation points that already have optical-fiber access. Due to the increased cell-site density, the average distance of the radio access links can be reduced by network and topology optimization. The reduced hop lengths combined with adaptive modulation and automatic power control bring an opportunity for capacity increase in shortened radio links. Links newly deployed for 5G find a wide spectrum in the millimetric V, E, W, and D frequency bands. This paper discusses the availability and hop-length targets of the anyhaul links that should be carefully kept by proper planning and monitoring. Full article

(This article belongs to the Special Issue Selected Papers from the 2019 42nd International Conference on Telecommunications and Signal Processing (TSP))

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14 pages, 7666 KiB

Open AccessArticle

Uncertainty Analysis of Two Methods in Hydrocarbon Prediction under Different Water Saturation and Noise Conditions

by Changcheng Liu, Deva Ghosh and Ahmed Mohamed Ahmed Salim

Appl. Sci. 2019, 9(23), 5239; https://doi.org/10.3390/app9235239 - 2 Dec 2019

Viewed by 2216

Abstract

The uncertainty of two recently proposed methods, “new fluid factor” and “delta K”, is analyzed under different water saturation and noise conditions through Monte Carlo modelling. The new fluid factor performs reliably (all metric parameters are above 0.9) when the water saturation is [...] Read more.

The uncertainty of two recently proposed methods, “new fluid factor” and “delta K”, is analyzed under different water saturation and noise conditions through Monte Carlo modelling. The new fluid factor performs reliably (all metric parameters are above 0.9) when the water saturation is up to 95%. The delta K has better performance (all metric parameters are close to 1) such that it is able to distinguish hydrocarbon from brine without the interference of high water saturation. The results prove the performances of the two methods are stable in a high water-saturation scenario. The analysis of noise indicates the methods are sensitive to noise in the input data in that the performance is excellent when the noise is relatively low (−20 dB) and decreases with increasing noise energy. The new fluid factor, which is in the interface domain, is more sensitive than delta K in the impedance domain. The metric parameters of the new fluid factor and delta K are in the range of 0.5 to 0.8 when the noise is high (−7 dB). High-quality input data and integration with other geophysical methods can effectively reduce these risks. In addition, two widely used traditional methods (fluid factor and Lambda-Rho) are analyzed as comparisons. It turns out the new fluid factor and delta K have better performance than traditional methods in both high water saturation and noise conditions. Full article

(This article belongs to the Section Earth Sciences)

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20 pages, 5446 KiB

Open AccessArticle

A Comparative Evaluation of Cement and By-Product Petrit T in Soil Stabilization

by Wathiq Al-Jabban, Jan Laue, Sven Knutsson and Nadhir Al-Ansari

Appl. Sci. 2019, 9(23), 5238; https://doi.org/10.3390/app9235238 - 2 Dec 2019

Cited by 13 | Viewed by 3865

Abstract

This study presents a comparison between the effectiveness of adding low binder amounts of industrial by-product Petrit T as well as cement to modify and improve fine-grained soil. Binder amount was added by soil dry weight; cement at 1%, 2%, 4% and 7% [...] Read more.

This study presents a comparison between the effectiveness of adding low binder amounts of industrial by-product Petrit T as well as cement to modify and improve fine-grained soil. Binder amount was added by soil dry weight; cement at 1%, 2%, 4% and 7% and Petrit T at 2%, 4% and 7%. The unconfined compressive strength (UCS) was used as an indicator of soil strength. In addition, the consistency limits, laser particle size analysis, and pH tests were also conducted on the treated soil. The samples were cured at 20 °C for different periods from 7 to 90 days before testing. Results indicate that cement is more effective at improving the physical and engineering properties of the treated soil. Soil plasticity index decreases after treatment and with time. Liquidity index and the water content to plastic limit ratio are introduced as new indices to define the improvement in the workability of treated soil. Soil particle size distribution is changed by reducing the clay size fraction and increasing the silt size fraction after treatment. The findings confirm that adding small binder contents improve soil properties, which subsequently reduce the environmental threats and costs that are associated with using a high amount of binder. Full article

(This article belongs to the Section Civil Engineering)

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12 pages, 4337 KiB

Open AccessArticle

Facile Fabrication of Micro/Nano Hierarchical SERS Sensor via Anisotropic Etching and Electrochemical Treatment for Malachite Green Detection

by Chu-Yu Huang and Chih-Hung Chien

Appl. Sci. 2019, 9(23), 5237; https://doi.org/10.3390/app9235237 - 2 Dec 2019

Cited by 10 | Viewed by 4365

Abstract

We propose a facile method to produce micro/nano hierarchical surface-enhanced Raman scattering (SERS) active substrates using simple steps and inexpensive costs. The proposed SERS substrate is a silicon pyramid array covered by a nanostructured gold film (AuNS @ SiPA). Through finite element method [...] Read more.

We propose a facile method to produce micro/nano hierarchical surface-enhanced Raman scattering (SERS) active substrates using simple steps and inexpensive costs. The proposed SERS substrate is a silicon pyramid array covered by a nanostructured gold film (AuNS @ SiPA). Through finite element method (FEM) simulation, we showed that many strong local electric field enhancements (hot spots) were formed between the nano-gap of gold nanostructures. In addition, the micron-scale pyramid structure not only increases the sensing surface area of the sensor, but also helps trap light. By combining these micro and nano structures, the proposed micro/nano hierarchical SERS sensor exhibited high sensitivity. Experimental results confirmed that the AuNS @ SiPA substrate has high sensitivity. The SERS signal enhancement factor obtained from the Rhodamine 6G (R6G) probe molecules was as high as 1 × 10⁷ and the SERS substrates were found to be able to detect a very low concentration of 0.01 nM malachite green (MG) solution. Therefore, this study provides a novel and practical method for fabricating SERS substrates that can facilitate the use of SERS in medicine, food safety, and biotechnology. Full article

(This article belongs to the Special Issue Bottom-up Approach and Self-Assembled Nano-Structures for Plasmonics and Nano-Optics Applications)

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16 pages, 5736 KiB

Open AccessArticle

Directed Silica Co-Deposition by Highly Oxidized Silver: Enhanced Stability and Versatility of Silver Oxynitrate

by Carla J. Spina, Roohee Ladhani, Carlie Goodall, Michelle Hay and Rod Precht

Appl. Sci. 2019, 9(23), 5236; https://doi.org/10.3390/app9235236 - 2 Dec 2019

Cited by 5 | Viewed by 3493

Abstract

Novel silver compounds in higher oxidation states, Ag (II) and Ag (III), have emerged as desirable alternatives to existing forms of antimicrobial silver compounds. Offering enhanced efficacy without sacrificing biocompatibility. Unique physiochemical characteristics associated with higher oxidation state silver confer desirable therapeutic traits. [...] Read more.

Novel silver compounds in higher oxidation states, Ag (II) and Ag (III), have emerged as desirable alternatives to existing forms of antimicrobial silver compounds. Offering enhanced efficacy without sacrificing biocompatibility. Unique physiochemical characteristics associated with higher oxidation state silver confer desirable therapeutic traits. However, these same characteristics create challenges in terms of long-term stability and chemical compatibility with conventional biomedical materials. Core-shell methodologies, utilizing silica as a mesoporous or amorphous shell, have been adopted to enhance the stability of reactive active ingredients or cores. These methodologies commonly utilize controlled condensation of silicic acids in non-aqueous media by way of hydrolyzing alkyl silicates: the Stöber process or modified processes thereof. However, these strategies are not conducive to cores of higher oxidation state silver wherein hydroxyl organic precursors and by-products are incompatible with strong oxidizing agents. Addressing these challenges, we present a strategy herein for the preparation of a self-directed silver oxynitrate-silica, Ag₇NO₁₁:SiO₂, framework. The method described utilizes pH gradients generated from the oxidation reaction of soluble silver, Ag (I), with a strong oxidizing agent/alkaline silicate media to facilitate spatial control over the protonation and subsequent condensation of silicic acid from aqueous solution. The resulting Ag₇NO₁₁:SiO₂ framework confers enhanced long term and thermal stability to silver oxynitrate without impairing aqueous degradation profiles or subsequent antimicrobial and antibiofilm activities. Full article

(This article belongs to the Special Issue The Design, Synthesis, and Biological Evaluation of Compounds with Medicinal Value)

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Appl. Sci., Volume 9, Issue 23 (December-1 2019) – 287 articles

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