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Appl. Sci., Volume 10, Issue 6 (March-2 2020) – 302 articles

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Cover Story (view full-size image) Copper and zinc mine tailings can become the next generation of aggregates for most civil [...] Read more.
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Open AccessArticle
Topology and Response Surface Optimization of a Bicycle Crank Arm with Multiple Load Cases
Appl. Sci. 2020, 10(6), 2201; https://doi.org/10.3390/app10062201 - 24 Mar 2020
Viewed by 357
Abstract
This paper presents an application of topology optimization and response surface method to optimize the geometry of a bicycle crank arm and the experimental validation of it. This is purposely to reduce the crank arm mass and create a preliminary design of a [...] Read more.
This paper presents an application of topology optimization and response surface method to optimize the geometry of a bicycle crank arm and the experimental validation of it. This is purposely to reduce the crank arm mass and create a preliminary design of a lightweight structure necessary for the high-performance bicycle development. A three-dimensional bike crank arm model was made in the SpaceClaim software followed by a static finite element analysis using ANSYS Workbench 2019 R1. A multiple cycling load was applied simultaneously in seven crank angles of 30, 45, 60, 90, 120, 135, and 150° relative to the horizontal position to create the multiple loads to the crank. From there, topology optimization was then conducted to investigate the effect of mass constraint, stress constraint, angle of cycling, and crank materials on the topological pattern result. To minimize stress concentration at corners, a shape optimization using the response surface method was conducted and obtained the final geometry. From the result, it is shown that both optimization methods not only successfully reduce the crank arm mass and provide several optimum design options but also are able to reduce the maximum stress in the crank arm up to 20% after the optimization process. The experimental validation using a newly developed wireless measurement system shows a considerable agreement to the numerical results. Full article
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Open AccessArticle
Influence of Exposure to Elevated Temperatures on the Physical and Mechanical Properties of Cementitious Thermal Mortars
Appl. Sci. 2020, 10(6), 2200; https://doi.org/10.3390/app10062200 - 24 Mar 2020
Viewed by 268
Abstract
Thermal mortars incorporating insulating aggregates are a possible solution to ensure good thermal performance and thermal comfort in buildings due to their low thermal conductivity coefficient. Under some circumstances, namely for particular in-service conditions in industrial applications and/or accidental actions (such as fire), [...] Read more.
Thermal mortars incorporating insulating aggregates are a possible solution to ensure good thermal performance and thermal comfort in buildings due to their low thermal conductivity coefficient. Under some circumstances, namely for particular in-service conditions in industrial applications and/or accidental actions (such as fire), it is important to quantify the retention of their properties after exposure to elevated temperatures, however this information is not yet available in the literature. This study aims to characterize the physical and mechanical behavior of thermal mortars incorporating expanded clay, granulated expanded cork and silica aerogel as aggregates after exposure to elevated temperatures. To this end, five types of mortars were produced in laboratory conditions—three thermal mortars, one reference sand mortar and one sand mortar with admixtures—and then exposed to different elevated temperatures (from 20 °C to 250 °C) in a thermal chamber. After thermal exposure, the following properties were assessed: bulk density; ultrasonic pulse velocity; dynamic elasticity modulus; dynamic shear modulus; Poisson coefficient; compressive strength; and thermal conductivity. The results obtained show that residual properties present a very high dependence on the reactions that take place in the cement paste when the mortars are exposed to elevated temperatures. After such exposure, all mortars with thermal insulating aggregates were able to maintain their insulating characteristics, but experienced internal damage and degradation of their mechanical properties. Results obtained also showed that insulating aggregates allowed to produce mortars with higher aggregate-cement paste compatibility at elevated temperatures compared to conventional mortars, resulting in less micro-cracking of the mortar, and leading to lower reductions in thermal conductivity with increasing temperature. Full article
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Open AccessArticle
Behavior and Performance of BIM Users in a Collaborative Work Environment
Appl. Sci. 2020, 10(6), 2199; https://doi.org/10.3390/app10062199 - 24 Mar 2020
Viewed by 245
Abstract
Collaborative work in Building Information Modeling (BIM) projects is frequently understood as the interaction of modelers in an asynchronous way through modification requests or via e-mail/telephone. However, alternative work methodologies based on creating a common and synchronous environment allow solving issues instantaneously during [...] Read more.
Collaborative work in Building Information Modeling (BIM) projects is frequently understood as the interaction of modelers in an asynchronous way through modification requests or via e-mail/telephone. However, alternative work methodologies based on creating a common and synchronous environment allow solving issues instantaneously during the design process. This study aimed to analyze the behavior and performance of BIM users with different specialties who were subjected to an experimental exercise in a collaborative environment. For this purpose, a process was devised to collect, sort, and select the data from the log files generated by the BIM software. A timeline of the experiment was populated with data on the intensity and types of commands used by each specialist, which allowed determining behavioral patterns, preferred commands, indicators of their experience, further training needs, and possible strategies for improving the team’s performance. In the experiment, the mechanical designer’s performance was 49% and the rest approximately 64%, with respect to that of the architect. An average rate of 1.66 necessary or auxiliary commands for each contributory command was detected. The average performance was 200–400 commands per hour, which intensified by the end of the experiment. Further training needs were detected for the plumbing designer to reduce the use of backwards commands. Conversely, the electrical designer showed a positive evolution regarding this aspect during the experiment. The analysis methods here described become useful for the aforementioned purposes. Nevertheless, combinations with methods from existing research might improve the outcomes and therefore the specificity of recommendations. Full article
(This article belongs to the Special Issue BIM in the Construction Industry)
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Open AccessArticle
Instance Hard Triplet Loss for In-video Person Re-identification
Appl. Sci. 2020, 10(6), 2198; https://doi.org/10.3390/app10062198 - 24 Mar 2020
Viewed by 264
Abstract
Traditional Person Re-identification (ReID) methods mainly focus on cross-camera scenarios, while identifying a person in the same video/camera from adjacent subsequent frames is also an important question, for example, in human tracking and pose tracking. We try to address this unexplored in-video ReID [...] Read more.
Traditional Person Re-identification (ReID) methods mainly focus on cross-camera scenarios, while identifying a person in the same video/camera from adjacent subsequent frames is also an important question, for example, in human tracking and pose tracking. We try to address this unexplored in-video ReID problem with a new large-scale video-based ReID dataset called PoseTrack-ReID with full images available and a new network structure called ReID-Head, which can extract multi-person features efficiently in real time and can be integrated with both one-stage and two-stage human or pose detectors. A new loss function is also required to solve this new in-video problem. Hence, a triplet-based loss function with an online hard example mining designed to distinguish persons in the same video/group is proposed, called instance hard triplet loss, which can be applied in both cross-camera ReID and in-video ReID. Compared with the widely-used batch hard triplet loss, our proposed loss achieves competitive performance and saves more than 30% of the training time. We also propose an automatic reciprocal identity association method, so we can train our model in an unsupervised way, which further extends the potential applications of in-video ReID. The PoseTrack-ReID dataset and code will be publicly released. Full article
(This article belongs to the Special Issue Advanced Intelligent Imaging Technology 2020)
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Open AccessArticle
A Corrected Adaptive Balancing Approach of Motorized Spindle Considering Air Gap Unbalance
Appl. Sci. 2020, 10(6), 2197; https://doi.org/10.3390/app10062197 - 24 Mar 2020
Viewed by 197
Abstract
Motorized spindles widely used for high-speed precision machine tools are very sensitive to the mass unbalance of rotors; thus, their balancing problem is always a research hotspot. Although many significant studies were done regarding the theory and application of various rotor balancing technologies [...] Read more.
Motorized spindles widely used for high-speed precision machine tools are very sensitive to the mass unbalance of rotors; thus, their balancing problem is always a research hotspot. Although many significant studies were done regarding the theory and application of various rotor balancing technologies for motorized spindles, the particularity of motorized spindles is not carefully considered in the existing balancing approaches. When the rotor unbalance of a motorized spindle occurs in operation, it is subject to both the mass unbalance-induced inertia force and air gap unbalance-induced electromagnetic force, which is an important feature that distinguishes the motorized spindle from a mechanical spindle. This paper describes an investigation into the corrected adaptive balancing approach of a motorized spindle by newly introducing a coefficient representing the removing effect of the air gap unbalance of the motor on the balancing capacity into the balancing formula. The determination of the newly defined coefficient refers to the calculation of electromagnetic force caused by the dynamic air gap eccentricity of motor; thus, much attention is paid to the analytical derivation of the unbalanced magnetic pull (UMP). Finally, a motorized spindle with an electromagnetic ring balancer was developed; then, the balancing tests and vibration signal analysis were done to validate the effectiveness of the newly proposed balancing approach in residual vibration reduction. It can be seen from the test results under different cases that the proposed balancing approach is effective. Full article
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Open AccessFeature PaperReview
Optics Based Label-Free Techniques and Applications in Brain Monitoring
Appl. Sci. 2020, 10(6), 2196; https://doi.org/10.3390/app10062196 - 24 Mar 2020
Viewed by 290
Abstract
Functional near-infrared spectroscopy (fNIRS) has been utilized already around three decades for monitoring the brain, in particular, oxygenation changes in the cerebral cortex. In addition, other optical techniques are currently developed for in vivo imaging and in the near future can be potentially [...] Read more.
Functional near-infrared spectroscopy (fNIRS) has been utilized already around three decades for monitoring the brain, in particular, oxygenation changes in the cerebral cortex. In addition, other optical techniques are currently developed for in vivo imaging and in the near future can be potentially used more in human brain research. This paper reviews the most common label-free optical technologies exploited in brain monitoring and their current and potential clinical applications. Label-free tissue monitoring techniques do not require the addition of dyes or molecular contrast agents. The following optical techniques are considered: fNIRS, diffuse correlations spectroscopy (DCS), photoacoustic imaging (PAI) and optical coherence tomography (OCT). Furthermore, wearable optical brain monitoring with the most common applications is discussed. Full article
(This article belongs to the Special Issue Optics and the Brain)
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Open AccessArticle
Parallel Compact Differential Evolution for Optimization Applied to Image Segmentation
Appl. Sci. 2020, 10(6), 2195; https://doi.org/10.3390/app10062195 - 24 Mar 2020
Viewed by 205
Abstract
A parallel compact Differential Evolution (pcDE) algorithm is proposed in this paper. The population is separated into multiple groups and the individual is run by using the method of compact Differential Evolution. The communication is implemented after predefined iterations. Two communication strategies are [...] Read more.
A parallel compact Differential Evolution (pcDE) algorithm is proposed in this paper. The population is separated into multiple groups and the individual is run by using the method of compact Differential Evolution. The communication is implemented after predefined iterations. Two communication strategies are proposed in this paper. The first one is to replace the local optimal solution by global optimal solution in all groups, which is called optimal elite strategy (oe); the second one is to replace the local optimal solution by mean value of the local optimal solution in all groups, which is called mean elite strategy (me). Considering that the pcDE algorithm does not need to store a large number of solutions, the algorithm can adapt to the environment with weak computing power. In order to prove the feasibility of pcDE, several groups of comparative experiments are carried out. Simulation results based on the 25 test functions demonstrate the efficacy of the proposed two communication strategies for the pcDE. Finally, the proposed pcDE is applied to image segmentation and experimental results also demonstrate the superior quality of the pcDE compared with some existing methods. Full article
(This article belongs to the Section Computing and Artificial Intelligence)
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Open AccessFeature PaperArticle
Estimation of Hand Motion from Piezoelectric Soft Sensor Using Deep Recurrent Network
Appl. Sci. 2020, 10(6), 2194; https://doi.org/10.3390/app10062194 - 24 Mar 2020
Viewed by 216
Abstract
Soft sensors are attracting significant attention in human–machine interaction due to their high flexibility and adaptability. However, estimating motion state from these sensors is difficult due to their nonlinearity and noise. In this paper, we propose a deep learning network for a smart [...] Read more.
Soft sensors are attracting significant attention in human–machine interaction due to their high flexibility and adaptability. However, estimating motion state from these sensors is difficult due to their nonlinearity and noise. In this paper, we propose a deep learning network for a smart glove system to predict the moving state of a piezoelectric soft sensor. We implemented the network using Long-Short Term Memory (LSTM) units and demonstrated its performance in a real-time system based on two experiments. The sensor’s moving state was estimated and the joint angles were calculated. Since we use moving state in the sensor offset calculation and the offset value is used to estimate the angle value, the accurate moving state estimation results in good performance for angle value estimation. The proposed network performed better than the conventional heuristic method in estimating the moving state. It was also confirmed that the calculated values successfully mimic the joint angles measured using a leap motion controller. Full article
(This article belongs to the Special Issue Flexible Piezoelectric Materials)
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Open AccessArticle
Surface Radiation Balance of Urban Materials and Their Impact on Air Temperature of an Urban Canyon in Lisbon, Portugal
Appl. Sci. 2020, 10(6), 2193; https://doi.org/10.3390/app10062193 - 24 Mar 2020
Viewed by 330
Abstract
Urban climate results from the modifications caused by the characteristics of cities, which modifies the regional climatic conditions of a city. When urban areas are warmer than the surrounding areas, the urban heat island (UHI) phenomenon occurs. Being a major phenomenon and a [...] Read more.
Urban climate results from the modifications caused by the characteristics of cities, which modifies the regional climatic conditions of a city. When urban areas are warmer than the surrounding areas, the urban heat island (UHI) phenomenon occurs. Being a major phenomenon and a global topic of interest for all affected cities, there are already numerous studies that address this subject. However, most studies are only focused on the macro and mesoscales. This study looks at the micrometeorological scale in a neighborhood of Lisbon (Telheiras). Having as a main objective to evaluate how the radiation balance of urban materials influences air temperature in an urban canyon, thermal images of different urban materials were obtained using infrared thermography, a technique that allowed understanding how the temperatures registered in the facades and other urban surfaces can affect the air temperature of the urban canyon. The components of the radiation budget were obtained by using a pyranometer and a pyrgeometer. Moreover, a microclimatic network to monitor air temperature and relative humidity was installed in the study area. The results show that, when the streets are less exposed to the prevailing wind direction in Lisbon (north and northwest), air temperatures are slightly higher than those found in opposite conditions. Both the temperature and the radiative balance of the facades and other surfaces (asphalt, light Portuguese sidewalk, and tile floor) respond directly to incident solar radiation. As expected, it was found that south facades have the highest temperatures of the four exposures under study (>4 °C when compared to the opposite facade), and the highest radiative balance was always registered on asphalt when compared to the sidewalk (at 9:00 a.m. + 30 W∙m−2, at 1:00 p.m. + 149 W∙m−2, and at 7:00 p.m. + 66 W∙m−2). Full article
(This article belongs to the Special Issue Solar Applications in the Public Space)
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Open AccessArticle
Throughput Analysis of IEEE 802.11 WLANs with Inter-Network Interference
Appl. Sci. 2020, 10(6), 2192; https://doi.org/10.3390/app10062192 - 24 Mar 2020
Viewed by 187
Abstract
Recently, we often see the environment where many one-to-one Wireless Local Area Networks (WLANs) exist in a small area. In this environment, the network throughput of certain WLAN reduces significantly because of the interference from other networks (i.e., inter-network interference). The inter-network interference [...] Read more.
Recently, we often see the environment where many one-to-one Wireless Local Area Networks (WLANs) exist in a small area. In this environment, the network throughput of certain WLAN reduces significantly because of the interference from other networks (i.e., inter-network interference). The inter-network interference is the effect of carrier-sensing activities when there are ongoing transmissions in neighbor networks. This paper presents analytical expressions using airtime concept, which newly take into account the inter-network interference, for network throughputs of WLANs. There are existing works that similarly address the WLAN’s carrier-sensing duration. However, they either consider a simple interference model or assume the simultaneous transmission time is negligible. Different from them, we consider the significant impact of simultaneous transmission. As a result, our analytical model can precisely express each network carrier-sensing duration by subtracting the simultaneous transmission time. More specifically, we have successfully obtained each network throughput by expressing frame-existence probabilities concerning each network’s End Device (ED). We also confirm the validity of the analysis by comparison with simulation. The analytical results and the simulation results agree well. Full article
(This article belongs to the Section Electrical, Electronics and Communications Engineering)
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Open AccessArticle
Microseismic Signal Denoising via Empirical Mode Decomposition, Compressed Sensing, and Soft-thresholding
Appl. Sci. 2020, 10(6), 2191; https://doi.org/10.3390/app10062191 - 24 Mar 2020
Viewed by 197
Abstract
Microseismic signal denoising is of great significance for P wave, S wave first arrival picking, source localization, and focal mechanism inversion. Therefore, an Empirical Mode Decomposition (EMD), Compressed Sensing (CS), and Soft-thresholding (ST) combined EMD_CS_ST denoising method is proposed. First, through EMD decomposition [...] Read more.
Microseismic signal denoising is of great significance for P wave, S wave first arrival picking, source localization, and focal mechanism inversion. Therefore, an Empirical Mode Decomposition (EMD), Compressed Sensing (CS), and Soft-thresholding (ST) combined EMD_CS_ST denoising method is proposed. First, through EMD decomposition of the noise signal, a series of Intrinsic Mode Functions (IMF) from high frequency to low frequency are obtained. By calculating the correlation coefficient between each IMF and the original signal, the boundary component between the signal and the noise was identified, and the boundary component and its previous components were sparsely processed in the discrete wavelet transform domain to obtain the original sparse coefficient θ. Second, θ is filtered by ST to get the reconstruction coefficient θnew after denoising. Then, CS was used to recover and reconstruct θnew to get the denoised IMFnew component and then recombined with the remaining IMF components to get the signal after denoising. In the simulation experiment, the denoising process of EMD_CS_ST method is introduced in detail, and the denoising ability of EMD_CS_ST, DWT, EEMD, and VMD_DWT under 10 different noise levels is discussed. The signal-to-noise ratio, signal standard deviation, correlation coefficient, waveform diagram, and spectrogram before and after denoising are compared and analyzed. Moreover, the signals obtained from the underground cavern of the Shuangjiangkou hydropower station were denoised by the EMD_CS_ST method, and the signals before and after denoising were analyzed by time-frequency spectrum. These results show that the proposed method has better denoising ability. Full article
(This article belongs to the Section Civil Engineering)
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Open AccessArticle
User Friendliness of a Wearable Visual Behavior Monitor for Cataract and Refractive Surgery
Appl. Sci. 2020, 10(6), 2190; https://doi.org/10.3390/app10062190 - 24 Mar 2020
Viewed by 249
Abstract
A prospective feasibility study was conducted to determine whether a new wearable device, the Visual Behavior Monitor (VBM), was easy to use and did not present any difficulties with the daily activities of patients. Patients for cataract surgery and refractive lens exchange were [...] Read more.
A prospective feasibility study was conducted to determine whether a new wearable device, the Visual Behavior Monitor (VBM), was easy to use and did not present any difficulties with the daily activities of patients. Patients for cataract surgery and refractive lens exchange were randomly selected and screened for inclusion in the study. A total of 129 patients were included in the study as part of a multicenter study. All measurements were performed before surgery. Upon inclusion, patients were trained to wear the device, instructed to wear it for a minimum of 36 h, and were scheduled to return in one week. The VBM measures the distance at which patients’ visual activities are performed, the level of illumination, and head translational and rotational movements along the three axes. On the follow-up visit, patients completed a questionnaire about their experience in wearing the device. All patients underwent standard diagnostic testing, with their cataract grade determined by the Lens Opacities Classification System (LOCS) classification. Results indicate that 87% of patients felt comfortable using the wearable device while 8% of patients responded as not feeling comfortable (5% of patients did not respond to the question). In addition, 91% of patients found it easy to attach the wearable to the magnetic clip while 4% of patients did not find it easy, and 5% of patients did not respond. Overall, patients found the device easy to use, with most reporting that the device was not intrusive. Full article
(This article belongs to the Special Issue Engineering for Surgery)
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Open AccessArticle
Investigation of Ytterbium Incorporation in Lithium Niobate for Active Waveguide Devices
Appl. Sci. 2020, 10(6), 2189; https://doi.org/10.3390/app10062189 - 24 Mar 2020
Viewed by 217
Abstract
In this work, we report on an investigation of the ytterbium diffusion characteristics in lithium niobate. Ytterbium-doped substrates were prepared by in-diffusion of thin metallic layers coated onto x- and z-cut congruent substrates at different temperatures. The ytterbium profiles were investigated in detail [...] Read more.
In this work, we report on an investigation of the ytterbium diffusion characteristics in lithium niobate. Ytterbium-doped substrates were prepared by in-diffusion of thin metallic layers coated onto x- and z-cut congruent substrates at different temperatures. The ytterbium profiles were investigated in detail by means of secondary neutral mass spectroscopy, optical microscopy, and optical spectroscopy. Diffusion from an infinite source was used to determine the solubility limit of ytterbium in lithium niobate as a function of temperature. The derived diffusion parameters are of importance for the development of active waveguide devices in ytterbium-doped lithium niobate. Full article
(This article belongs to the Special Issue Ion-exchange in Glasses and Crystals: from Theory to Applications )
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Open AccessArticle
A Hidden Fingerprint Device on an Opaque Display Panel
Appl. Sci. 2020, 10(6), 2188; https://doi.org/10.3390/app10062188 - 23 Mar 2020
Viewed by 266
Abstract
In recent years, fingerprint recognition has become more and more widely used in mobile phones. A fingerprint recognition device hidden under an opaque display panel designed based on a waveguide and frustrated total internal reflection (FTIR) is proposed and demonstrated herein. In order [...] Read more.
In recent years, fingerprint recognition has become more and more widely used in mobile phones. A fingerprint recognition device hidden under an opaque display panel designed based on a waveguide and frustrated total internal reflection (FTIR) is proposed and demonstrated herein. In order to meet the demand for a high screen ratio for mobile phone displays, we use a symmetrical zoom-in and zoom-out coupler design. With this comprehensive coupler and waveguide design, not only can fingerprint recognition be achieved using an opaque display panel, but it also meets the appearance requirements for a mobile phone with a high screen ratio. Full article
(This article belongs to the Special Issue Joint Special Issue With OPTIC 2019)
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Open AccessArticle
Cryptanalysis of a New Color Image Encryption Using Combination of the 1D Chaotic Map
Appl. Sci. 2020, 10(6), 2187; https://doi.org/10.3390/app10062187 - 23 Mar 2020
Viewed by 267
Abstract
Security of image communication is more and more important in many applications such as the transmission of military and medical images. To meet the requirement, a new color image encryption algorithm using a new one-dimension (1D) chaotic map was proposed recently, which can [...] Read more.
Security of image communication is more and more important in many applications such as the transmission of military and medical images. To meet the requirement, a new color image encryption algorithm using a new one-dimension (1D) chaotic map was proposed recently, which can resist various attacks because the range of the new chaotic map is larger than that of the previous ones. In our study, the security of the new original method is analyzed and a novel attack method is proposed. It is demonstrated that the scheme is not secure under chosen-plaintext attack, by which the encrypted image can be successfully converted into the corresponding plaintext image without any error. Full article
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Open AccessArticle
Multi-Pooled Inception Features for No-Reference Image Quality Assessment
Appl. Sci. 2020, 10(6), 2186; https://doi.org/10.3390/app10062186 - 23 Mar 2020
Viewed by 279
Abstract
Image quality assessment (IQA) is an important element of a broad spectrum of applications ranging from automatic video streaming to display technology. Furthermore, the measurement of image quality requires a balanced investigation of image content and features. Our proposed approach extracts visual features [...] Read more.
Image quality assessment (IQA) is an important element of a broad spectrum of applications ranging from automatic video streaming to display technology. Furthermore, the measurement of image quality requires a balanced investigation of image content and features. Our proposed approach extracts visual features by attaching global average pooling (GAP) layers to multiple Inception modules of on an ImageNet database pretrained convolutional neural network (CNN). In contrast to previous methods, we do not take patches from the input image. Instead, the input image is treated as a whole and is run through a pretrained CNN body to extract resolution-independent, multi-level deep features. As a consequence, our method can be easily generalized to any input image size and pretrained CNNs. Thus, we present a detailed parameter study with respect to the CNN base architectures and the effectiveness of different deep features. We demonstrate that our best proposal—called MultiGAP-NRIQA—is able to outperform the state-of-the-art on three benchmark IQA databases. Furthermore, these results were also confirmed in a cross database test using the LIVE In the Wild Image Quality Challenge database. Full article
(This article belongs to the Section Electrical, Electronics and Communications Engineering)
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Open AccessArticle
Remediation of Copper Contaminated Soils Using Water Containing Hydrogen Nanobubbles
Appl. Sci. 2020, 10(6), 2185; https://doi.org/10.3390/app10062185 - 23 Mar 2020
Viewed by 264
Abstract
This basic research study was undertaken to use ecofriendly nanobubbles that can improve the electrokinetic remediation of copper-contaminated soil, as well as to determine that remediation efficiency. The nanobubbles were generated by using pressurized hydrogen gas, and the quantity of hydrogen gas bubble [...] Read more.
This basic research study was undertaken to use ecofriendly nanobubbles that can improve the electrokinetic remediation of copper-contaminated soil, as well as to determine that remediation efficiency. The nanobubbles were generated by using pressurized hydrogen gas, and the quantity of hydrogen gas bubble that remained over 14 days was measured. The generated nanobubbles were used as an enhancer to remove a heavy metal on contaminated soil, and their applicability was confirmed. A batch test was used to compare the remediation effects of nanobubbles and distilled water on copper-contaminated soil. The results proved that the nanobubbles are a proper desorption agent for copper-contaminated sand and clay specimens. The solid–liquid ratio and the contact time for desorption of the sand and clay were then respectively determined. A large amount of effluent was obtained from electrokinetic remediation of the sand sample after applying the nanobubbles as an enhancer. The remediation efficiency demonstrated with sand proved to be higher than that for clay. This greater efficiency was attributed to a wider specific surface area, demonstrating the potential use of the nanobubbles as an enhancer for soil contaminated by copper with a large amount of effluent outflow. It was also assumed to be affected by the moving capability of the nanobubbles in the soil layer. Thus, the nanobubbled water can be used to improve the removal of heavy metals from contaminated soils. An ecofriendly enhancer for electrokinetic remediation with a relatively large void ratio and fast flowrate was confirmed by the nanobubbles. Full article
(This article belongs to the Special Issue Sustainable Environmental Solutions)
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Open AccessFeature PaperArticle
Ag-Sensitized NIR-Emitting Yb3+-Doped Glass-Ceramics
Appl. Sci. 2020, 10(6), 2184; https://doi.org/10.3390/app10062184 - 23 Mar 2020
Viewed by 213
Abstract
The optical photoluminescent (PL) emission of Yb3+ ions in the near infrared (NIR) spectral region at about 950–1100 nm has many potential applications, from photovoltaics to lasers and visual devices. However, due to their simple energy-level structure, Yb3+ ions cannot directly [...] Read more.
The optical photoluminescent (PL) emission of Yb3+ ions in the near infrared (NIR) spectral region at about 950–1100 nm has many potential applications, from photovoltaics to lasers and visual devices. However, due to their simple energy-level structure, Yb3+ ions cannot directly absorb UV or visible light, putting serious limits on their use as light emitters. In this paper we describe a broadband and efficient strategy for sensitizing Yb3+ ions by Ag codoping, resulting in a strong 980 nm PL emission under UV and violet-blue light excitation. Yb-doped silica–zirconia–soda glass–ceramic films were synthesized by sol-gel and dip-coating, followed by annealing at 1000 °C. Ag was then introduced by ion-exchange in a molten salt bath for 1 h at 350 °C. Different post-exchange annealing temperatures for 1 h in air at 380 °C and 430 °C were compared to investigate the possibility of migration/aggregation of the metal ions. Studies of composition showed about 1–2 wt% Ag in the exchanged samples, not modified by annealing. Structural analysis reported the stabilization of cubic zirconia by Yb-doping. Optical measurements showed that, in particular for the highest annealing temperature of 430 °C, the potential improvement of the material’s quality, which would increase the PL emission, is less relevant than Ag-aggregation, which decreases the sensitizers number, resulting in a net reduction of the PL intensity. However, all the Ag-exchanged samples showed a broadband Yb3+ sensitization by energy transfer from Ag aggregates, clearly attested by a broad photoluminescence excitation spectra after Ag-exchange, paving the way for applications in various fields, such as solar cells and NIR-emitting devices. Full article
(This article belongs to the Special Issue Photonic Glass-Ceramics: Fabrication, Properties and Applications)
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Open AccessFeature PaperCommunication
A Broadband Active Microwave Monolithically Integrated Circuit Balun in Graphene Technology
Appl. Sci. 2020, 10(6), 2183; https://doi.org/10.3390/app10062183 - 23 Mar 2020
Viewed by 308
Abstract
This paper presents the first graphene radiofrequency (RF) monolithic integrated balun circuit. It is composed of four integrated graphene field effect transistors (GFETs). This innovative active balun concept takes advantage of the GFET ambipolar behavior. It is realized using an advanced silicon carbide [...] Read more.
This paper presents the first graphene radiofrequency (RF) monolithic integrated balun circuit. It is composed of four integrated graphene field effect transistors (GFETs). This innovative active balun concept takes advantage of the GFET ambipolar behavior. It is realized using an advanced silicon carbide (SiC) based bilayer graphene FET technology having RF performances of about 20 GHz. Balun circuit measurement demonstrates its high frequency capability. An upper limit of 6 GHz has been achieved when considering a phase difference lower than 10° and a magnitude of amplitude imbalance less than 0.5 dB. Hence, this circuit topology shows excellent performance with large broadband performance and a functionality of up to one-third of the transit frequency of the transistor. Full article
(This article belongs to the Special Issue Graphene and Graphene-Based Composites for Electronics)
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Open AccessArticle
Microscopic Mechanism of the Macroscopic Mechanical Properties of Cement Modified Subgrade Silty Soil Subjected to Freeze-Thaw Cycles
Appl. Sci. 2020, 10(6), 2182; https://doi.org/10.3390/app10062182 - 23 Mar 2020
Viewed by 233
Abstract
In order to study the effects of the microstructure parameters of cement modified subgrade silty soil (CMSS) in a frozen area under freeze-thaw (F-T) cycles on the macroscopic mechanical properties, the static triaxial test, scanning electron microscopy (SEM), and grey relation analysis (GRA) [...] Read more.
In order to study the effects of the microstructure parameters of cement modified subgrade silty soil (CMSS) in a frozen area under freeze-thaw (F-T) cycles on the macroscopic mechanical properties, the static triaxial test, scanning electron microscopy (SEM), and grey relation analysis (GRA) were implemented on silty soil modified with 0% and 2% cement at optimum moisture content from the northwest in Jilin Province in China. The results showed that the shear strength, the cohesion of 0% and 2% CMSS, decreased with the increase of F-T cycles, while the internal friction angle was not obviously changed. The shear strength and its parameters of 2% CMSS doubled compared to that of 0% CMSS. The micro-parameters, representing the particle morphological characteristics, particle arrangement, and pore characteristics of CMSS, changed differently under F-T cycles. If the cement was not added, the cohesion and the internal friction angle were most sensitive to the average particle diameter (Dp) and the average particle abundance (C), respectively. When the cement content was 2%, the cohesion was chiefly affected by the particle size fractal dimension (Dps), while the internal friction angle was mainly related to the average pore diameter (Dh). The main principle of cement improvement was to decrease Dh of soil under F-T cycles. Full article
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Open AccessArticle
Web Objects Based Contextual Data Quality Assessment Model for Semantic Data Application
Appl. Sci. 2020, 10(6), 2181; https://doi.org/10.3390/app10062181 - 23 Mar 2020
Viewed by 382
Abstract
Due to the convergence of advanced technologies such as the Internet of Things, Artificial Intelligence, and Big Data, a healthcare platform accumulates data in a huge quantity from several heterogeneous sources. The adequate usage of this data may increase the impact of and [...] Read more.
Due to the convergence of advanced technologies such as the Internet of Things, Artificial Intelligence, and Big Data, a healthcare platform accumulates data in a huge quantity from several heterogeneous sources. The adequate usage of this data may increase the impact of and improve the healthcare service quality; however, the quality of the data may be questionable. Assessing the quality of the data for the task in hand may reduce the associated risks, and increase the confidence of the data usability. To overcome the aforementioned challenges, this paper presents the web objects based contextual data quality assessment model with enhanced classification metric parameters. A semantic ontology of virtual objects, composite virtual objects, and services is also proposed for the parameterization of contextual data quality assessment of web objects data. The novelty of this article is the provision of contextual data quality assessment mechanisms at the data acquisition, assessment, and service level for the web objects enabled semantic data applications. To evaluate the proposed data quality assessment mechanism, web objects enabled affective stress and teens’ mood care semantic data applications are designed, and a deep data quality learning model is developed. The findings of the proposed approach reveal that, once a data quality assessment model is trained on web objects enabled healthcare semantic data, it could be used to classify the incoming data quality in various contextual data quality metric parameters. Moreover, the data quality assessment mechanism presented in this paper can be used to other application domains by incorporating data quality analysis requirements ontology. Full article
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Open AccessArticle
Stress Corrosion Cracking Threshold for Dissimilar Capacitive Discharge Welding Joint with Varied Surface Geometry
Appl. Sci. 2020, 10(6), 2180; https://doi.org/10.3390/app10062180 - 23 Mar 2020
Viewed by 317
Abstract
Stress corrosion cracking (SCC) is known as a major factor that should be considered in the assessment of welding joint structure integrity. Despite the promising and wide application of dissimilar metal joints, the currently available SCC mitigation technique of dissimilar metal joints is [...] Read more.
Stress corrosion cracking (SCC) is known as a major factor that should be considered in the assessment of welding joint structure integrity. Despite the promising and wide application of dissimilar metal joints, the currently available SCC mitigation technique of dissimilar metal joints is not adequate. The challenge is to obtain a good joint while different melting points exist. This article reports a novel SCC mitigation method on a brass–steel dissimilar metal joint by modifying the geometry of the surface. It is evidenced that the sharpened steel (α1 specimen) significantly improves the SCC resilience of the joint. The evaluation of SEM/EDS photos reveals that the α1 geometry induces a smaller pore area around brass–steel micro-joint interfaces which in turn produces stronger joints. Full article
(This article belongs to the Section Nanotechnology and Applied Nanosciences)
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Open AccessArticle
Droplet Size Distribution Characteristics of Aerial Nozzles by Bell206L4 Helicopter under Medium and Low Airflow Velocity Wind Tunnel Conditions and Field Verification Test
Appl. Sci. 2020, 10(6), 2179; https://doi.org/10.3390/app10062179 - 23 Mar 2020
Viewed by 210
Abstract
To investigate the spray atomization characteristics of aerial nozzles adapted to manned agricultural helicopters under medium-low airflow velocity (0 to 27.8 m/s) conditions, the droplet size test was carried out in both wind tunnel and field tests. In the wind tunnel test, the [...] Read more.
To investigate the spray atomization characteristics of aerial nozzles adapted to manned agricultural helicopters under medium-low airflow velocity (0 to 27.8 m/s) conditions, the droplet size test was carried out in both wind tunnel and field tests. In the wind tunnel test, the laser diffraction device (LDD) was used to test the spray droplet size of CP02, CP03, and CP04 aerial nozzles. A Bell206L4 helicopter was used in the field test. The results in the wind tunnel test showed that due to the nozzles had been used for a long time and the cause of wear, the spray stability of individual nozzles was affected during the test. The limitation of droplet size measurement by using LDD was also found. The field test results showed that the main distribution range of the droplet size measured in the field test was consistent with the results of the wind tunnel test, but the droplet size value was significantly higher and the uniformity of droplet size distribution was poorer than the wind tunnel test value due to the influence of the actual environment. However, the results of field test and wind tunnel test can still be used as a reference for each other. Full article
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Open AccessArticle
Multifocus Image Fusion Using a Sparse and Low-Rank Matrix Decomposition for Aviator’s Night Vision Goggle
Appl. Sci. 2020, 10(6), 2178; https://doi.org/10.3390/app10062178 - 23 Mar 2020
Viewed by 228
Abstract
This study proposed the concept of sparse and low-rank matrix decomposition to address the need for aviator’s night vision goggles (NVG) automated inspection processes when inspecting equipment availability. First, the automation requirements include machinery and motor-driven focus knob of NVGs and image capture [...] Read more.
This study proposed the concept of sparse and low-rank matrix decomposition to address the need for aviator’s night vision goggles (NVG) automated inspection processes when inspecting equipment availability. First, the automation requirements include machinery and motor-driven focus knob of NVGs and image capture using cameras to achieve autofocus. Traditionally, passive autofocus involves first computing of sharpness of each frame and then use of a search algorithm to quickly find the sharpest focus. In this study, the concept of sparse and low-rank matrix decomposition was adopted to achieve autofocus calculation and image fusion. Image fusion can solve the multifocus problem caused by mechanism errors. Experimental results showed that the sharpest image frame and its nearby frame can be image-fused to resolve minor errors possibly arising from the image-capture mechanism. In this study, seven samples and 12 image-fusing indicators were employed to verify the image fusion based on variance calculated in a discrete cosine transform domain without consistency verification, with consistency verification, structure-aware image fusion, and the proposed image fusion method. Experimental results showed that the proposed method was superior to other methods and compared the autofocus put forth in this paper and the normalized gray-level variance sharpness results in the documents to verify accuracy. Full article
(This article belongs to the Special Issue Intelligent Processing on Image and Optical Information)
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Open AccessArticle
Image Quality Improvement and Memory-Saving in a Permanent-Magnet-Array-Based MRI System
Appl. Sci. 2020, 10(6), 2177; https://doi.org/10.3390/app10062177 - 23 Mar 2020
Viewed by 228
Abstract
Point-of-care magnetic resonance imaging (MRI) requires clear images within a short scanning time, a small footprint of the scanner, and relatively low memory required for image reconstruction. A permanent magnet array (PMA)-based MRI system is a good candidate to supply a magnetic field [...] Read more.
Point-of-care magnetic resonance imaging (MRI) requires clear images within a short scanning time, a small footprint of the scanner, and relatively low memory required for image reconstruction. A permanent magnet array (PMA)-based MRI system is a good candidate to supply a magnetic field due to its compactness and low power consumption. However, it has relatively inhomogeneous magnetic field and thus non-linear gradients, which results in location-dependent k-spaces (so called local k-spaces) and uneven signal point populations in the local k-spaces, compromising the image quality. Moreover, owing to the non-linearity, imaging reconstruction using Fourier transform does not work, which leads to an increase in the required computation memory. In this study, in order to improve the image quality, the approaches of compensating the uneven signal point population by increasing the numbers of sampling points or rotation angles are investigated in terms of their impacts on image quality improvement, acquisition time, image reconstruction time, and memory consumption. Both methods give a significant improvement on image image quality although they result in a large and dense encoding matrix and thus a large memory consumption. To lower the memory consumption, it is further proposed to transform such a matrix to frequency domain where the matrix could be sparse. Moreover, a row-wise truncation to the transformed encoding matrix is applied to further reduce the memory consumption. Through the results of numerical experiments, it is shown that the required memory for calculation can effectively be reduced by 71.6% while the image becomes clearer by increasing the number of sampling point and/or the number of rotation angles. With the successful demonstration where improved image quality and a lowered memory required can be obtained simultaneously, the proposed study is one step forward for a PMA-based MRI system towards its targeted point-of-care application scenario. Full article
(This article belongs to the Special Issue Applications of Low Field Magnetic Resonance)
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Open AccessArticle
Positioning Accuracy of the Shearer Based on a Strapdown Inertial Navigation System in Underground Coal Mining
Appl. Sci. 2020, 10(6), 2176; https://doi.org/10.3390/app10062176 - 23 Mar 2020
Viewed by 300
Abstract
Automation and intelligent coal mining comprise the most important fields in coal mining technology research. The key to automation and intelligent coal mining is the automated mining of the working face, and accurate positioning of the shearer is one of the most important [...] Read more.
Automation and intelligent coal mining comprise the most important fields in coal mining technology research. The key to automation and intelligent coal mining is the automated mining of the working face, and accurate positioning of the shearer is one of the most important technologies in the automated mining process. However, significant defects in non-inertial navigation system (INS)-based methods have led to low positioning accuracy. In this paper, we propose a new shearer positioning technology to further improve the positioning accuracy of the shearer and monitor the shearer position in real time. The shearer positioning system proposed is based on the strapdown inertial navigation system (SINS). We conducted shearer positioning experiments with gyroscopes, accelerometers, and other inertial navigation instruments. The experimental results are thoroughly studied on the basis of error compensation techniques such as inertial instrument zero bias compensation and Kalman filter compensation. Compared with traditional shearer positioning technology, the experimental results show that the shearer positioning system based on SINS can achieve more accurate positioning of the shearer and can accurately reflect the running characteristics of the shearer working the mining face. Full article
(This article belongs to the Section Mechanical Engineering)
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Open AccessArticle
Experimental Study on Stress Corrosion Index Governing Time-Dependent Degradation of Rock Strength
Appl. Sci. 2020, 10(6), 2175; https://doi.org/10.3390/app10062175 - 23 Mar 2020
Viewed by 201
Abstract
Rock fractures in geological conditions are caused not only by applied stress, but also by stress corrosion. Stress corrosion is an environmentally activated chemical process, associated with the fluid-assisted crack growth. Crack growth due to stress corrosion is related to the time-dependent behaviours [...] Read more.
Rock fractures in geological conditions are caused not only by applied stress, but also by stress corrosion. Stress corrosion is an environmentally activated chemical process, associated with the fluid-assisted crack growth. Crack growth due to stress corrosion is related to the time-dependent behaviours of rocks and is a crucial factor in determining the stability of underground structures over the long period of time. In this study, constant stress-rate tests including Brazilian tension and three-point flexural tests for the tensile strength, short-beam compression and single-shear tests for the in-plane shear strength, and a torsion test of rectangular section specimens and a circumferentially notched cylindrical specimen test for the out-of-plane shear strength were conducted at a different loading rate from 0.01 to 10 MPa/s using Coconino sandstone. The results show that the rock strength was proportional to the 1/(n+1)th power of the loading rate, where the parameter n indicates the stress corrosion index. The stress corrosion index (n) ranged from 34 to 38, with an average value of 36. The stress corrosion indices (n) were similar, irrespective of the loading configuration and specimen geometry. The stress corrosion index (n) can, therefore, be regarded as a material constant of rocks. Full article
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Open AccessArticle
Security Assessment of Urban Areas through a GIS-Based Analysis of Lighting Data Generated by IoT Sensors
Appl. Sci. 2020, 10(6), 2174; https://doi.org/10.3390/app10062174 - 23 Mar 2020
Viewed by 369
Abstract
The current perspective about urban development expects 70% of energy consumption will be concentrated in the cities in 2050. In addition, a growing density of people in the urban context leads to the need for increased security and safety for citizens, which imply [...] Read more.
The current perspective about urban development expects 70% of energy consumption will be concentrated in the cities in 2050. In addition, a growing density of people in the urban context leads to the need for increased security and safety for citizens, which imply a better lighting infrastructure. Smart solutions are required to optimize the corresponding energy effort. In developing countries, the cities’ lighting is limited and the lighting world map is strongly significant about the urban density of the different areas. Nevertheless, in territories where the illumination level is particularly high, such as urban contexts, the conditions are not homogenous at the microscale level and the perceived security is affected by artificial urban lighting. As an example, 27.2% of the families living in the city of Milan, ombardy Region, Italy, consider critical the conditions of lighting in the city during the night, although the region has diffused infrastructure. The paper aims to provide a local illuminance geographic information system (GIS) mapping at the neighborhood level that can be extended to the urban context. Such an approach could unveil the need to increase lighting to enhance the perceived safety and security for the citizens and promote a higher quality of life in the smart city. Lighting mapping can be matched with car accident mapping of cities and could be extended to perceived security among pedestrians in urban roads and green areas, also related to degradation signs of the built environment. In addition, such an approach could open new scenarios to the adaptive street lighting control used to reduce the energy consumption in a smart city: the perceived security of an area could be used as an additional index to be considered during the modulation of the level of the luminosity of street lighting. An example of a measurement set-up is described and tested at the district level to define how to implement an extensive monitoring campaign based on an extended research schema. Full article
(This article belongs to the Special Issue Smart Urban Lighting Systems)
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Open AccessArticle
Reliable OFDM Data Transmission with Pilot Tones and Error-Correction Coding in Shallow Underwater Acoustic Channel
Appl. Sci. 2020, 10(6), 2173; https://doi.org/10.3390/app10062173 - 23 Mar 2020
Viewed by 219
Abstract
The performance of Underwater Acoustic Communication (UAC) systems are strongly related to the specific propagation conditions of the underwater channel. Horizontal, shallow-water channels are characterised by extremely disadvantageous transmission properties, due to strong multipath propagation and refraction phenomena. The paper presents the results [...] Read more.
The performance of Underwater Acoustic Communication (UAC) systems are strongly related to the specific propagation conditions of the underwater channel. Horizontal, shallow-water channels are characterised by extremely disadvantageous transmission properties, due to strong multipath propagation and refraction phenomena. The paper presents the results of communication tests performed during a shallow, inland-water experiment with the use of a laboratory model of a UAC system implementing the Orthogonal Frequency-Division Multiplexing (OFDM) technique. The physical layer of data transmission is partially configurable, enabling adaptation of the modulation and channel coding parameters to the specific propagation conditions. The communication tests were preceded by measurement of the UAC channel transmission properties. Based on the estimated transmission parameters, four configurations of OFDM modulation parameters were selected, and for each of them, communication tests were performed with the use of two Error-Correction Coding (ECC) techniques. In each case, the minimum coding rate was determined for which reliable data transmission with a Bit Error Rate (BER) of less than 10 4 is possible. Full article
(This article belongs to the Special Issue Underwater Acoustic Communications and Networks)
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Open AccessArticle
Study of Interfacial Adhesion between Nickel-Titanium Shape Memory Alloy and a Polymer Matrix by Laser Surface Pattern
Appl. Sci. 2020, 10(6), 2172; https://doi.org/10.3390/app10062172 - 23 Mar 2020
Viewed by 213
Abstract
The aim of this article is to investigate the interfacial adhesion of Ni-Ti shape memory alloy with a polymer matrix of Poly (methyl methacrylate) (PMMA). The surface pattern on Ni-Ti plates was channeled by a solid state laser machine. The laser machine allows [...] Read more.
The aim of this article is to investigate the interfacial adhesion of Ni-Ti shape memory alloy with a polymer matrix of Poly (methyl methacrylate) (PMMA). The surface pattern on Ni-Ti plates was channeled by a solid state laser machine. The laser machine allows for creating channels on the Ni-Ti surface for infiltration of the PMMA matrix, which could be attached as an intra-surface locking pattern to the Ni-Ti surface. The influence of the PMMA matrix on the surface of the NiTi plate was evaluated by thermomechanical analysis (TMA) and dynamic mechanical analysis (DMA). The surface characterization was carried out by an optical microscope on the PMMA/NiTi composite after mechanical testing. During mechanical testing, the polymer displays the multiple cracks in the longitudinal direction that result in slipping and fracture. TMA and DMA analyses were performed on the Ni-Ti- and PMMA-coated Ni-Ti ribbon to observe elasticity and the storage modulus for both samples. Better adhesion than 80 % was observed in the Ni-Ti surface, in the laser surface pattern, in comparison to the free plain surface. However, the polymer acts as mechanical backing that caused a reduction in the shape-memory properties of the composite material. Full article
(This article belongs to the Special Issue Synthesis, Characterization and Application of Hybrid Composites)
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