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Appl. Sci., Volume 9, Issue 11 (June-1 2019)

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Cover Story (view full-size image) The Paulownia genus is currently very interesting for growers. An increasing number of Paulownia [...] Read more.
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Open AccessArticle
Heating, Ventilation, and Air Conditioning System Optimization Control Strategy Involving Fan Coil Unit Temperature Control
Appl. Sci. 2019, 9(11), 2391; https://doi.org/10.3390/app9112391
Received: 2 May 2019 / Revised: 31 May 2019 / Accepted: 7 June 2019 / Published: 11 June 2019
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Abstract
The objective of this study was to develop a heating, ventilation, and air conditioning (HVAC) system optimization control strategy involving fan coil unit (FCU) temperature control for energy conservation in chilled water systems to enhance the operating efficiency of HVAC systems. The proposed [...] Read more.
The objective of this study was to develop a heating, ventilation, and air conditioning (HVAC) system optimization control strategy involving fan coil unit (FCU) temperature control for energy conservation in chilled water systems to enhance the operating efficiency of HVAC systems. The proposed control strategy involves three techniques, which are described as follows. The first technique is an algorithm for dynamic FCU temperature setting, which enables the FCU temperature to be set in accordance with changes in the outdoor temperature to satisfy the indoor thermal comfort for occupants. The second technique is an approach for determining the indoor cold air demand, which collects the set FCU temperature and converts it to the refrigeration ton required for the chilled water system; this serves as the control target for ensuring optimal HVAC operation. The third technique is a genetic algorithm for calculating the minimum energy consumption for an HVAC system. The genetic algorithm determines the pump operating frequency associated with minimum energy consumption per refrigeration ton to control energy conservation. To demonstrate the effectiveness of the proposed HVAC system optimization control strategy combining FCU temperature control, this study conducted a field experiment. The results revealed that the proposed strategy enabled an HVAC system to achieve 39.71% energy conservation compared with an HVAC system operating at full load. Full article
(This article belongs to the Special Issue Selected Papers from IEEE ICASI 2019)
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Open AccessReview
Review on the Electrical Resistance/Conductivity of Carbon Fiber Reinforced Polymer
Appl. Sci. 2019, 9(11), 2390; https://doi.org/10.3390/app9112390
Received: 9 May 2019 / Revised: 5 June 2019 / Accepted: 7 June 2019 / Published: 11 June 2019
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Abstract
Carbon fiber reinforced polymer (CFRP) plays an important role in many fields, especially in aviation and civil industries. The electrical conductivity of CFRP is critical for its electrical behavior, such as its lightning strike vulnerability, electromagnetic shielding ability, and potential uses for self-sensing. [...] Read more.
Carbon fiber reinforced polymer (CFRP) plays an important role in many fields, especially in aviation and civil industries. The electrical conductivity of CFRP is critical for its electrical behavior, such as its lightning strike vulnerability, electromagnetic shielding ability, and potential uses for self-sensing. In addition, the electrical conductivity is related to the mechanical integrity. Therefore, electrical properties can be measured as an indication when detecting delamination and other defects in CFRP. This review provides a comprehensive basis for readers to grasp recent research progresses on electrical behaviors of CFRP. Full article
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Open AccessArticle
Estimating Maize-Leaf Coverage in Field Conditions by Applying a Machine Learning Algorithm to UAV Remote Sensing Images
Appl. Sci. 2019, 9(11), 2389; https://doi.org/10.3390/app9112389
Received: 13 May 2019 / Revised: 5 June 2019 / Accepted: 6 June 2019 / Published: 11 June 2019
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Abstract
Leaf coverage is an indicator of plant growth rate and predicted yield, and thus it is crucial to plant-breeding research. Robust image segmentation of leaf coverage from remote-sensing images acquired by unmanned aerial vehicles (UAVs) in varying environments can be directly used for [...] Read more.
Leaf coverage is an indicator of plant growth rate and predicted yield, and thus it is crucial to plant-breeding research. Robust image segmentation of leaf coverage from remote-sensing images acquired by unmanned aerial vehicles (UAVs) in varying environments can be directly used for large-scale coverage estimation, and is a key component of high-throughput field phenotyping. We thus propose an image-segmentation method based on machine learning to extract relatively accurate coverage information from the orthophoto generated after preprocessing. The image analysis pipeline, including dataset augmenting, removing background, classifier training and noise reduction, generates a set of binary masks to obtain leaf coverage from the image. We compare the proposed method with three conventional methods (Hue-Saturation-Value, edge-detection-based algorithm, random forest) and a frontier deep-learning method called DeepLabv3+. The proposed method improves indicators such as Qseg, Sr, Es and mIOU by 15% to 30%. The experimental results show that this approach is less limited by radiation conditions, and that the protocol can easily be implemented for extensive sampling at low cost. As a result, with the proposed method, we recommend using red-green-blue (RGB)-based technology in addition to conventional equipment for acquiring the leaf coverage of agricultural crops. Full article
(This article belongs to the Section Optics and Lasers)
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Open AccessReview
Atomic Layer Deposition (ALD) of Metal Gates for CMOS
Appl. Sci. 2019, 9(11), 2388; https://doi.org/10.3390/app9112388
Received: 29 April 2019 / Revised: 17 May 2019 / Accepted: 22 May 2019 / Published: 11 June 2019
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Abstract
The continuous down-scaling of complementary metal oxide semiconductor (CMOS) field effect transistors (FETs) had been suffering two fateful technical issues, one relative to the thinning of gate dielectric and the other to the aggressive shortening of channel in last 20 years. To solve [...] Read more.
The continuous down-scaling of complementary metal oxide semiconductor (CMOS) field effect transistors (FETs) had been suffering two fateful technical issues, one relative to the thinning of gate dielectric and the other to the aggressive shortening of channel in last 20 years. To solve the first issue, the high-κ dielectric and metal gate technology had been induced to replace the conventional gate stack of silicon dioxide layer and poly-silicon. To suppress the short channel effects, device architecture had changed from planar bulk Si device to fully depleted silicon on insulator (FDSOI) and FinFETs, and will transit to gate all-around FETs (GAA-FETs). Different from the planar devices, the FinFETs and GAA-FETs have a 3D channel. The conventional high-κ/metal gate process using sputtering faces conformality difficulty, and all atomic layer deposition (ALD) of gate stack become necessary. This review covers both scientific and technological parts related to the ALD of metal gates including the concept of effect work function, the material selection, the precursors for the deposition, the threshold voltage (Vt) tuning of the metal gate in contact with HfO2/SiO2/Si. The ALD of n-type metal gate will be detailed systematically, based mainly on the authors’ works in last five years, and the all ALD gate stacks will be proposed for the future generations based on the learning. Full article
(This article belongs to the Special Issue Atomic Layer Deposition for the Synthesis of Thin Films)
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Open AccessFeature PaperArticle
Holographic Silicon Metasurfaces for Total Angular Momentum Demultiplexing Applications in Telecom
Appl. Sci. 2019, 9(11), 2387; https://doi.org/10.3390/app9112387
Received: 20 May 2019 / Revised: 4 June 2019 / Accepted: 6 June 2019 / Published: 11 June 2019
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Abstract
The simultaneous processing of orbital angular momentum (OAM) and polarization has recently acquired particular importance and interest in a wide range of fields ranging from telecommunications to high-dimensional quantum cryptography. Due to their inherently polarization-sensitive optical behavior, Pancharatnam–Berry optical elements (PBOEs), acting on [...] Read more.
The simultaneous processing of orbital angular momentum (OAM) and polarization has recently acquired particular importance and interest in a wide range of fields ranging from telecommunications to high-dimensional quantum cryptography. Due to their inherently polarization-sensitive optical behavior, Pancharatnam–Berry optical elements (PBOEs), acting on the geometric phase, have proven to be useful for the manipulation of complex light beams with orthogonal polarization states using a single optical element. In this work, different PBOEs have been computed, realized, and optically analyzed for the sorting of beams with orthogonal OAM and polarization states at the telecom wavelength of 1310 nm. The geometric-phase control is obtained by inducing a spatially-dependent form birefringence on a silicon substrate, patterned with properly-oriented subwavelength gratings. The digital grating structure is generated with high-resolution electron beam lithography on a resist mask and transferred to the silicon substrate using inductively coupled plasma-reactive ion etching. The optical characterization of the fabricated samples confirms the expected capability to detect circularly-polarized optical vortices with different handedness and orbital angular momentum. Full article
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Open AccessFeature PaperArticle
Conversion of Stearic Acid into Bio-Gasoline over Pd/ZSM-5 Catalysts with Enhanced Accessibility
Appl. Sci. 2019, 9(11), 2386; https://doi.org/10.3390/app9112386
Received: 29 April 2019 / Revised: 5 June 2019 / Accepted: 6 June 2019 / Published: 11 June 2019
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Abstract
Palladium supported on nanocrystalline ZSM-5 (n-ZSM-5, Si/Al = 32) and hierarchical ZSM-5 (h-ZSM-5) with different acidity (Si/Al = 33, 51, 122) were tested in the liquid-phase conversion of stearic acid under nitrogen atmosphere (6 bar). The incorporation of Pd into ZSM-5 zeolite increased [...] Read more.
Palladium supported on nanocrystalline ZSM-5 (n-ZSM-5, Si/Al = 32) and hierarchical ZSM-5 (h-ZSM-5) with different acidity (Si/Al = 33, 51, 122) were tested in the liquid-phase conversion of stearic acid under nitrogen atmosphere (6 bar). The incorporation of Pd into ZSM-5 zeolite increased significantly the share of gasoline in the reaction products due to the promotion by this metal of both decarboxylation and hydrogen transfer reactions. Likewise, the Pd nanoparticles dispersed over the zeolitic support favored the conversion of light olefins formed by end-chain cracking reactions into gasoline-range hydrocarbons according to an oligomerization/cyclization/aromatization pathway. Additionally, Pd/h-ZSM-5 gave rise to higher conversion and selectivity towards gasoline than Pd/n-ZSM-5, due mainly to the enhanced accessibility and improved Pd dispersion achieved when using the hierarchical zeolite. The decrease in the Si/Al atomic ratio in Pd/h-ZSM-5 samples resulted in a rise in the stearic acid conversion, although it was lower than expected. This finding denotes that, for supports with high acid sites concentration, the Pd availability became the limiting factor as the metal was loaded in similar amounts in all catalysts. Finally, the increase of the reaction temperature with the Pd/h-ZSM-5 (122) catalyst augmented both stearic acid conversion and gasoline selectivity, since it enhanced the conversion of the light olefins, formed as primary cracking products, into liquid hydrocarbons. Therefore, it can be concluded that Pd supported on hierarchical ZSM-5 zeolite is a convenient catalyst for obtaining bio-gasoline from oleaginous feedstock. Full article
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Open AccessEditorial
Special Issue on Sciences in Heat Pump and Refrigeration
Appl. Sci. 2019, 9(11), 2385; https://doi.org/10.3390/app9112385
Received: 30 May 2019 / Accepted: 4 June 2019 / Published: 11 June 2019
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Abstract
The history of heat pump and refrigeration is very long, and ever since mankind acquired mechanical refrigeration more than a century ago, heat pump and refrigeration technologies have made remarkable progress [...] Full article
(This article belongs to the Section Energy)
Open AccessArticle
Estimating Vocal Fold Contact Pressure from Raw Laryngeal High-Speed Videoendoscopy Using a Hertz Contact Model
Appl. Sci. 2019, 9(11), 2384; https://doi.org/10.3390/app9112384
Received: 30 April 2019 / Revised: 31 May 2019 / Accepted: 4 June 2019 / Published: 11 June 2019
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Abstract
The development of trauma-induced lesions of the vocal folds (VFs) has been linked to a high collision pressure on the VF surface. However, there are no direct methods for the clinical assessment of VF collision, thus limiting the objective assessment of these disorders. [...] Read more.
The development of trauma-induced lesions of the vocal folds (VFs) has been linked to a high collision pressure on the VF surface. However, there are no direct methods for the clinical assessment of VF collision, thus limiting the objective assessment of these disorders. In this study, we develop a video processing technique to directly quantify the mechanical impact of the VFs using solely laryngeal kinematic data. The technique is based on an edge tracking framework that estimates the kinematic sequence of each VF edge with a Kalman filter approach and a Hertzian impact model to predict the contact force during the collision. The proposed formulation overcomes several limitations of prior efforts since it uses a more relevant VF contact geometry, it does not require calibrated physical dimensions, it is normalized by the tissue properties, and it applies a correction factor for using a superior view only. The proposed approach is validated against numerical models, silicone vocal fold models, and prior studies. A case study with high-speed videoendoscopy recordings provides initial insights between the sound pressure level and contact pressure. Thus, the proposed method has a high potential in clinical practice and could also be adapted to operate with laryngeal stroboscopic systems. Full article
(This article belongs to the Special Issue Computational Methods and Engineering Solutions to Voice)
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Open AccessArticle
Auto-Generation System Based on Fractal Geometry for Batik Pattern Design
Appl. Sci. 2019, 9(11), 2383; https://doi.org/10.3390/app9112383
Received: 7 May 2019 / Revised: 29 May 2019 / Accepted: 6 June 2019 / Published: 11 June 2019
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Abstract
In order to obtain the automatic simulation generation of traditional handmade batik patterns in a computer, this paper proposes the automatic generation method of batik flower patterns based on fractal geometry. Firstly, we analyze the fractal characteristics of batik flowers and design an [...] Read more.
In order to obtain the automatic simulation generation of traditional handmade batik patterns in a computer, this paper proposes the automatic generation method of batik flower patterns based on fractal geometry. Firstly, we analyze the fractal characteristics of batik flowers and design an automatic flower generation algorithm based on a two-dimensional iterated function system (IFS) and a curve function. The algorithm forms a complete flower pattern. Secondly, a nonlinear function is defined and the flower pattern is introduced into the nonlinear function to iterate and change. On this basis, we present an automatic generation method of different distribution patterns for flower patterns which obtains the most effective range of each parameter value for each function. Finally, in order to verify the feasibility of the automatic generation method of batik flower patterns, we develop an automatic generation experiment system for batik patterns via an interactive way of working. The results show that the user or designer can quickly and automatically simulate a series of flower patterns by changing the relevant parameter values, realizing the digitization and innovative design of the pattern and enriching the batik pattern base. Full article
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Open AccessArticle
A Novel Ranging Technique Based on Optical Camera Communications and Time Difference of Arrival
Appl. Sci. 2019, 9(11), 2382; https://doi.org/10.3390/app9112382
Received: 3 May 2019 / Revised: 3 June 2019 / Accepted: 5 June 2019 / Published: 11 June 2019
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Abstract
In this work, a new Time Difference of Arrival (TDoA) scheme for distance measurement based on Optical Camera Communication (OCC) systems is proposed. It relies on the use of optical pulses instead of radio-frequency signals as the time reference triggers, and the introduction [...] Read more.
In this work, a new Time Difference of Arrival (TDoA) scheme for distance measurement based on Optical Camera Communication (OCC) systems is proposed. It relies on the use of optical pulses instead of radio-frequency signals as the time reference triggers, and the introduction of a rolling shutter camera, whose characteristics allows substituting the timer modules used in conventional TDoA techniques by image processing of the illuminated area in the picture. This processing on the camera’s images provides time measurements and implies and specific analysis, which is presented in this work. The system performance and properties, such as resolution and range, mainly depends on the camera characteristics, such as the frames capture rate and the image quality. This new technique is suitable to be implemented in smartphones or other Commercial Off-The-Shelf (COTS) devices equipped with a camera and speakers. Full article
(This article belongs to the Section Electrical, Electronics and Communications Engineering)
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Open AccessArticle
Scaffolds with a High Surface Area-to-Volume Ratio and Cultured Under Fast Flow Perfusion Result in Optimal O2 Delivery to the Cells in Artificial Bone Tissues
Appl. Sci. 2019, 9(11), 2381; https://doi.org/10.3390/app9112381
Received: 1 May 2019 / Revised: 1 June 2019 / Accepted: 7 June 2019 / Published: 11 June 2019
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Abstract
Tissue engineering has the potential for repairing large bone defects, which impose a heavy financial burden on the public health. However, difficulties with O2 delivery to the cells residing in the interior of tissue engineering scaffolds make it challenging to grow artificial [...] Read more.
Tissue engineering has the potential for repairing large bone defects, which impose a heavy financial burden on the public health. However, difficulties with O2 delivery to the cells residing in the interior of tissue engineering scaffolds make it challenging to grow artificial tissues of clinically-relevant sizes. This study uses image-based simulation in order to provide insight into how to better optimize the scaffold manufacturing parameters, and the culturing conditions, in order to resolve the O2 bottleneck. To do this, high resolution 3D X-ray images of two common scaffold types (salt leached foam and non-woven fiber mesh) are fed into Lattice Boltzmann Method fluid dynamics and reactive Lagrangian Scalar Tracking mass transfer solvers. The obtained findings indicate that the scaffolds should have maximal surface area-to-solid volume ratios for higher chances of the molecular collisions with the cells. Furthermore, the cell culture media should be flown through the scaffold pores as fast as practically possible (without detaching or killing the cells). Finally, we have provided a parametric sweep that maps how the molecular transport within the scaffolds is affected by variations in rates of O2 consumption by the cells. Ultimately, the results of this study are expected to benefit the computer-assisted design of tissue engineering scaffolds and culturing experiments. Full article
(This article belongs to the Special Issue Biomaterials for Bone Tissue Engineering)
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Open AccessEditorial
Preface for the Special Issue on Dynamical Models of Biology and Medicine
Appl. Sci. 2019, 9(11), 2380; https://doi.org/10.3390/app9112380
Received: 5 June 2019 / Accepted: 10 June 2019 / Published: 11 June 2019
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Abstract
Mathematical and computational modeling approaches in biological and medical research are experiencing rapid growth globally [...] Full article
(This article belongs to the Special Issue Dynamical Models of Biology and Medicine)
Open AccessArticle
Building Wireless Control Applications with XBee and LabVIEW
Appl. Sci. 2019, 9(11), 2379; https://doi.org/10.3390/app9112379
Received: 10 May 2019 / Revised: 5 June 2019 / Accepted: 6 June 2019 / Published: 11 June 2019
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Abstract
This study analyzed the application of the XBee technology for control applications embedded in big machinery. In particular, it presented the control layout, topology, design of frames, and error control mechanisms that are required for implementing wireless control networked applications. This study was [...] Read more.
This study analyzed the application of the XBee technology for control applications embedded in big machinery. In particular, it presented the control layout, topology, design of frames, and error control mechanisms that are required for implementing wireless control networked applications. This study was devoted to presenting experimental use cases of wireless control systems that help the scientific community to design and implement new control systems. Experimental tests were carried out over a Single Input Single Output (SISO) control application to evaluate its use in close loop applications. The results of these tests have been discussed in detail. In order to clarify the use of XBee in control applications, a high precision positioning application has been presented. It involved a piezoelectric actuator that was remotely controlled by means of a Proportional Integral (PI) controller, which was implemented in LabVIEW over a NI myRIO platform. Both the sensor and the actuators were connected with the NI myRIO by means of the XBee anthenae. The results showed that even though XBee technologies present some drawbacks, such as a lower performance when compared to wired connections and the influence of interferences, they have the potential to be used in some scenarios for non-critical control applications. Full article
(This article belongs to the Section Electrical, Electronics and Communications Engineering)
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Open AccessEditorial
Special Issue on “Micro/Nano Manufacturing”
Appl. Sci. 2019, 9(11), 2378; https://doi.org/10.3390/app9112378
Received: 5 June 2019 / Accepted: 10 June 2019 / Published: 11 June 2019
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Abstract
Micro manufacturing is dealing with the fabrication of structures in the order of 0 [...] Full article
(This article belongs to the Special Issue Micro/Nano Manufacturing)
Open AccessReview
A Review on the Use of Microalgae for Sustainable Aquaculture
Appl. Sci. 2019, 9(11), 2377; https://doi.org/10.3390/app9112377
Received: 24 April 2019 / Revised: 5 June 2019 / Accepted: 5 June 2019 / Published: 11 June 2019
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Abstract
Traditional aquaculture provides food for humans, but produces a large amount of wastewater, threatening global sustainability. The antibiotics abuse and the water replacement or treatment causes safety problems and increases the aquaculture cost. To overcome environmental and economic problems in the aquaculture industry, [...] Read more.
Traditional aquaculture provides food for humans, but produces a large amount of wastewater, threatening global sustainability. The antibiotics abuse and the water replacement or treatment causes safety problems and increases the aquaculture cost. To overcome environmental and economic problems in the aquaculture industry, a lot of efforts have been devoted into the application of microalgae for wastewater remediation, biomass production, and water quality control. In this review, the systematic description of the technologies required for microalgae-assisted aquaculture and the recent progress were discussed. It deeply reviews the problems caused by the discharge of aquaculture wastewater and introduces the principles of microalgae-assisted aquaculture. Some interesting aspects, including nutrients assimilation mechanisms, algae cultivation systems (raceway pond and revolving algal biofilm), wastewater pretreatment, algal-bacterial cooperation, harvesting technologies (fungi-assisted harvesting and flotation), selection of algal species, and exploitation of value-added microalgae as aquaculture feed, were reviewed in this work. In view of the limitations of recent studies, to further reduce the negative effects of aquaculture wastewater on global sustainability, the future directions of microalgae-assisted aquaculture for industrial applications were suggested. Full article
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Open AccessArticle
Dynamic Responses of Liquid Storage Tanks Caused by Wind and Earthquake in Special Environment
Appl. Sci. 2019, 9(11), 2376; https://doi.org/10.3390/app9112376
Received: 24 April 2019 / Revised: 26 May 2019 / Accepted: 3 June 2019 / Published: 11 June 2019
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Abstract
Based on potential flow theory and arbitrary Lagrangian–Eulerian method, shell–liquid and shell–wind interactions are solved respectively. Considering the nonlinearity of tank material and liquid sloshing, a refined 3-D wind–shell–liquid interaction calculation model for liquid storage tanks is established. A comparative study of dynamic [...] Read more.
Based on potential flow theory and arbitrary Lagrangian–Eulerian method, shell–liquid and shell–wind interactions are solved respectively. Considering the nonlinearity of tank material and liquid sloshing, a refined 3-D wind–shell–liquid interaction calculation model for liquid storage tanks is established. A comparative study of dynamic responses of liquid storage tanks under wind, earthquake, and wind and earthquake is carried out, and the influences of wind speed and wind interference effect on dynamic responses of liquid storage tank are discussed. The results show that when the wind is strong, the dynamic responses of the liquid storage tank under wind load alone are likely to be larger than that under earthquake, and the dynamic responses under wind–earthquake interaction are obviously larger than that under wind and earthquake alone. The maximum responses of the tank wall under wind and earthquake are located in the unfilled area at the upper part of the tank and the filled area at the lower part of the tank respectively, while the location of maximum responses of the tank wall under wind–earthquake interaction is related to the relative magnitude of the wind and earthquake. Wind speed has a great influence on the responses of liquid storage tanks, when the wind speed increases to a certain extent, the storage tank is prone to damage. Wind interference effect has a significant effect on liquid storage tanks and wind fields. For liquid storage tanks in special environments, wind and earthquake effects should be considered reasonably, and wind interference effects cannot be ignored. Full article
(This article belongs to the Special Issue Buildings and Structures under Extreme Loads)
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Open AccessArticle
An Adaptive Multi-Layer Botnet Detection Technique Using Machine Learning Classifiers
Appl. Sci. 2019, 9(11), 2375; https://doi.org/10.3390/app9112375
Received: 19 March 2019 / Revised: 22 April 2019 / Accepted: 24 April 2019 / Published: 11 June 2019
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Abstract
In recent years, the botnets have been the most common threats to network security since it exploits multiple malicious codes like a worm, Trojans, Rootkit, etc. The botnets have been used to carry phishing links, to perform attacks and provide malicious services on [...] Read more.
In recent years, the botnets have been the most common threats to network security since it exploits multiple malicious codes like a worm, Trojans, Rootkit, etc. The botnets have been used to carry phishing links, to perform attacks and provide malicious services on the internet. It is challenging to identify Peer-to-peer (P2P) botnets as compared to Internet Relay Chat (IRC), Hypertext Transfer Protocol (HTTP) and other types of botnets because P2P traffic has typical features of the centralization and distribution. To resolve the issues of P2P botnet identification, we propose an effective multi-layer traffic classification method by applying machine learning classifiers on features of network traffic. Our work presents a framework based on decision trees which effectively detects P2P botnets. A decision tree algorithm is applied for feature selection to extract the most relevant features and ignore the irrelevant features. At the first layer, we filter non-P2P packets to reduce the amount of network traffic through well-known ports, Domain Name System (DNS). query, and flow counting. The second layer further characterized the captured network traffic into non-P2P and P2P. At the third layer of our model, we reduced the features which may marginally affect the classification. At the final layer, we successfully detected P2P botnets using decision tree Classifier by extracting network communication features. Furthermore, our experimental evaluations show the significance of the proposed method in P2P botnets detection and demonstrate an average accuracy of 98.7%. Full article
(This article belongs to the Section Computing and Artificial Intelligence)
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Open AccessArticle
Intensity-Modulated PM-PCF Sagnac Loop in a DWDM Setup for Strain Measurement
Appl. Sci. 2019, 9(11), 2374; https://doi.org/10.3390/app9112374
Received: 9 April 2019 / Revised: 22 May 2019 / Accepted: 1 June 2019 / Published: 11 June 2019
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Abstract
A novel intensity-modulated Sagnac loop sensor based on polarization-maintaining photonic crystal fiber (PM-PCF) in a setup with a dense wavelength division multiplexer (DWDM) for strain measurement is presented. The sensor head is made of PM-PCF spliced to single-mode fibers. The interferometer spectrum shifts [...] Read more.
A novel intensity-modulated Sagnac loop sensor based on polarization-maintaining photonic crystal fiber (PM-PCF) in a setup with a dense wavelength division multiplexer (DWDM) for strain measurement is presented. The sensor head is made of PM-PCF spliced to single-mode fibers. The interferometer spectrum shifts in response to the longitudinal strain experienced by the PM-PCF. After passing the Sagnac loop, light is transmitted by a selected DWDM channel, resulting in a change in the output optical power due to the elongation of PM-PCF. Hence, appropriate adjustment of spectral characteristics of the DWDM channel and the PM-PCF Sagnac interferometer is required. However, the proposed setup utilizes an optical power measurement scheme, simultaneously omitting expensive and complex optical spectrum analyzers. An additional feature is the possibility of multiplexing of the PM-PCF Sagnac loop in order to create a fiber optic sensor network. Full article
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Open AccessArticle
Impact of Silicon Substrate with Low Resistivity on Vertical Leakage Current in AlGaN/GaN HEMTs
Appl. Sci. 2019, 9(11), 2373; https://doi.org/10.3390/app9112373
Received: 25 April 2019 / Revised: 26 May 2019 / Accepted: 29 May 2019 / Published: 11 June 2019
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Abstract
The role of low-resistivity substrate on vertical leakage current (VLC) of AlGaN/GaN-on-Si epitaxial layers has been investigated. AlGaN/GaN high-electron-mobility transistors (HEMTs) grown on both p-type and n-type Si substrates with low resistivity are applied to analyze the vertical leakage mechanisms. The activation energy [...] Read more.
The role of low-resistivity substrate on vertical leakage current (VLC) of AlGaN/GaN-on-Si epitaxial layers has been investigated. AlGaN/GaN high-electron-mobility transistors (HEMTs) grown on both p-type and n-type Si substrates with low resistivity are applied to analyze the vertical leakage mechanisms. The activation energy (Ea) for p-type case is higher than that for n-type at 0–600 V obtained by temperature-dependent current-voltage measurements. An additional depletion region in the region of 0–400 V forms at the AlN/p-Si interface but not for AlN/n-Si. That depletion region leads to a decrease of electron injection and hence effectively reduces the VLC. While in the region of 400–600 V, the electron injection from p-Si substrate increases quickly compared to n-Si substrate, due to the occurrence of impact ionization in the p-Si substrate depletion region. The comparative results indicate that the doping type of low-resistivity substrate plays a key role for VLC. Full article
(This article belongs to the Special Issue III-V Nitride: Materials, Physics and Devices)
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Open AccessArticle
Numerical–Experimental Correlation of Impact-Induced Damages in CFRP Laminates
Appl. Sci. 2019, 9(11), 2372; https://doi.org/10.3390/app9112372
Received: 8 April 2019 / Revised: 4 June 2019 / Accepted: 5 June 2019 / Published: 11 June 2019
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Abstract
Composite laminates are characterized by high mechanical in-plane properties and poor out-of-plane characteristics. This issue becomes even more relevant when dealing with impact phenomena occurring in the transverse direction. In aeronautics, Low Velocity Impacts (LVIs) may occur during the service life of the [...] Read more.
Composite laminates are characterized by high mechanical in-plane properties and poor out-of-plane characteristics. This issue becomes even more relevant when dealing with impact phenomena occurring in the transverse direction. In aeronautics, Low Velocity Impacts (LVIs) may occur during the service life of the aircraft. LVI may produce damage inside the laminate, which are not easily detectable and can seriously degrade the mechanical properties of the structure. In this paper, a numerical-experimental investigation is carried out, in order to study the mechanical behavior of rectangular laminated specimens subjected to low velocity impacts. The numerical model that best represents the impact phenomenon has been chosen by numerical–analytical investigations. A user defined material model (VUMAT) has been developed in Abaqus/Explicit environment to simulate the composite intra-laminar damage behavior in solid elements. The analyses results were compared to experimental test data on a laminated specimen, performed according to ASTM D7136 standard, in order to verify the robustness of the adopted numerical model and the influence of modeling parameters on the accuracy of numerical results. Full article
(This article belongs to the Special Issue Fatigue and Fracture of Non-metallic Materials and Structures)
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Open AccessArticle
A Compact Quad-Element UWB-MIMO Antenna System with Parasitic Decoupling Mechanism
Appl. Sci. 2019, 9(11), 2371; https://doi.org/10.3390/app9112371
Received: 30 April 2019 / Revised: 16 May 2019 / Accepted: 5 June 2019 / Published: 11 June 2019
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Abstract
This research work proposes a compact four-port multiple-input multiple-output (MIMO) antenna that operates in the whole license free ultra-wideband (UWB) spectrum of 3.1–10.6 GHz. Spatial diversity has been introduced by arranging these antennas in close proximity without developing a strong mutual coupling. Antenna [...] Read more.
This research work proposes a compact four-port multiple-input multiple-output (MIMO) antenna that operates in the whole license free ultra-wideband (UWB) spectrum of 3.1–10.6 GHz. Spatial diversity has been introduced by arranging these antennas in close proximity without developing a strong mutual coupling. Antenna elements are evolved from a conventional rectangular patch antenna whereas a customized decoupling structure is introduced on the back side of the substrate to achieve the desired isolation level. The parasitic decoupling structure consists of different features which are resonant at different frequencies offering a whole UWB coverage. In addition to the decoupling structure a dumbbell shaped stub has also been introduced to the partial ground plane to suppress the mutual coupling. The overall measured isolation among elements is more than 20 dB. Different MIMO performance parameters have also been investigated from the measured results. Whole MIMO system measures 0.41 λo × 0.44 λo at 3.1 GHz. The MIMO system is intended for high data rate and short-range communication devices used in wireless personal area networks. Full article
(This article belongs to the Special Issue Substrate Integrated Waveguide (SIW) and its Applications)
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Open AccessArticle
Large-Aperture Real-Time Compensated Collimating Wavefront Error Detection Method
Appl. Sci. 2019, 9(11), 2370; https://doi.org/10.3390/app9112370
Received: 30 April 2019 / Revised: 30 May 2019 / Accepted: 4 June 2019 / Published: 11 June 2019
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Abstract
This paper proposes a real-time compensated pentaprism scanning wavefront detection method to achieve real-time compensation for scanning errors occurring during prism movement along a guide rail. The method is based on existing pentaprism scanning wavefront detection technology and it is realized by applying [...] Read more.
This paper proposes a real-time compensated pentaprism scanning wavefront detection method to achieve real-time compensation for scanning errors occurring during prism movement along a guide rail. The method is based on existing pentaprism scanning wavefront detection technology and it is realized by applying self-collimation-based three-dimensional error compensation. Using theoretical and data analyses of a detection experiment, the reliability of the optimized pentaprism scanning detection method is verified, thus effectively ensuring the reasonable estimation of the interferometry surface measurement uncertainty. Full article
(This article belongs to the Section Applied Industrial Technologies)
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Open AccessArticle
Effect of Cement Content on the Deformation Properties of Cemented Sand and Gravel Material
Appl. Sci. 2019, 9(11), 2369; https://doi.org/10.3390/app9112369
Received: 31 March 2019 / Revised: 3 June 2019 / Accepted: 5 June 2019 / Published: 10 June 2019
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Abstract
Knowing the deformation properties of cemented sand and gravel (CSG) material can help construct reasonable constitutive models for the material, which can be used to simulate the structural performance of various practical projects including CSG dams. In this study, to investigate the effect [...] Read more.
Knowing the deformation properties of cemented sand and gravel (CSG) material can help construct reasonable constitutive models for the material, which can be used to simulate the structural performance of various practical projects including CSG dams. In this study, to investigate the effect of cement content on the deformation properties of CSG material, we employ triaxial compressive tests for cement contents of 20, 40, 60, 80, and 100 kg/m3 with a confining pressure range of 0.3–1.2 MPa, and theoretically analyze the results by the regression analysis prediction method. Here, we show that both cement content and confining pressure influence the deformation properties of CSG material: for an increase in cement content, the failure strain decreases and brittleness of CSG material increases; the initial modulus of the CSG material increased exponentially with increasing cement content or confining pressure; the peak volumetric strain and its corresponding axial strain increase linearly with increasing confining pressures, which decrease with increasing cement content; the initial tangent volumetric ratio can also be determined by the peak volumetric strain and its corresponding axial strain. Full article
(This article belongs to the Section Civil Engineering)
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Open AccessArticle
An Experimental Analytics on Discovering Work Transference Networks from Workflow Enactment Event Logs
Appl. Sci. 2019, 9(11), 2368; https://doi.org/10.3390/app9112368
Received: 21 May 2019 / Revised: 3 June 2019 / Accepted: 5 June 2019 / Published: 10 June 2019
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Abstract
Work transference network is a type of enterprise social network centered on the interactions among performers participating in the workflow processes. It is thought that the work transference networks hidden in workflow enactment histories are able to denote not only the structure of [...] Read more.
Work transference network is a type of enterprise social network centered on the interactions among performers participating in the workflow processes. It is thought that the work transference networks hidden in workflow enactment histories are able to denote not only the structure of the enterprise social network among performers but also imply the degrees of relevancy and intensity between them. The purpose of this paper is to devise a framework that can discover and analyze work transference networks from workflow enactment event logs. The framework includes a series of conceptual definitions to formally describe the overall procedure of the network discovery. To support this conceptual framework, we implement a system that provides functionalities for the discovery, analysis and visualization steps. As a sanity check for the framework, we carry out a mining experiment on a dataset of real-life event logs by using the implemented system. The experiment results show that the framework is valid in discovering transference networks correctly and providing primitive knowledge pertaining to the discovered networks. Finally, we expect that the analytics of the work transference network facilitates assessing the workflow fidelity in human resource planning and its observed performance, and eventually enhances the workflow process from the organizational aspect. Full article
(This article belongs to the Special Issue Applied Sciences Based on and Related to Computer and Control)
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Open AccessFeature PaperArticle
Fabrication and Luminescent Properties of Zn–Cu–In–S/ZnS Quantum Dot Films under UV Excitation
Appl. Sci. 2019, 9(11), 2367; https://doi.org/10.3390/app9112367
Received: 24 April 2019 / Revised: 24 May 2019 / Accepted: 5 June 2019 / Published: 10 June 2019
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Abstract
Quantum dots (QDs) are quite interesting materials due to their unique chemical and physical properties. ZnCuInS/ZnS QDs can be produced either in hydrophobic or hydrophilic form, are non-toxic, and thus favorable for studies in the area of biology. Poly(methyl methacrylate) (PMMA) is a [...] Read more.
Quantum dots (QDs) are quite interesting materials due to their unique chemical and physical properties. ZnCuInS/ZnS QDs can be produced either in hydrophobic or hydrophilic form, are non-toxic, and thus favorable for studies in the area of biology. Poly(methyl methacrylate) (PMMA) is a well-known biocompatible resin which is widely used in dentistry, ophthalmology, and orthopedic surgery. Four composite PMMA films of ZnCuInS/ZnS nanocrystals with maximum emission at 530 nm and concentrations of 1.0, 4.0, 6.0, and 10.0 %w/v, were prepared. X-ray irradiation was used to evaluate the volume homogeneity of the final samples, as a measure of QD dispersion. The luminescent efficiency was evaluated, under ultraviolet (UV) irradiation. The process of UV irradiation involved the experimental measurement of the forward luminescent light, as well as the backward luminescent light, in order to accurately calculate the energy quantum efficiency (EQE) of ZnCuInS/ZnS QDs. Reflected UV radiation was also measured, and results showed that it ranges from 2% to 6% approximately as the QD concentration rises from 1.0 %w/v to 10.0 %w/v. Beyond 6.0 %w/v, the reflected UV radiation remains essentially unchanged. Additionally, the reflected UV radiation remained unaffected as the power of the incident UV increased. Approximately 9% of incident UV radiation passed through the 1.0 %w/v sample, whereas for the samples with higher ZnCuInS/ZnS concentration, 0% UV radiation passed through. The EQE reached a maximum of about 45% with the 10.0 %w/v sample, while it remained practically unaffected relative to the increase of the emitted UV power. The homogeneity measurements revealed that the coefficient of variation (CV) increased with increasing concentration, for the 1.0, 4.0, and 6.0 %w/v samples. The minimum CV was obtained for the sample of 10.0 %w/v due to the incorporation of sonication in the final product, during the fabrication process. Full article
(This article belongs to the Section Chemistry)
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Open AccessArticle
A Versatile Setup for Time-Resolved Functional Near Infrared Spectroscopy Based on Fast-Gated Single-Photon Avalanche Diode and on Four-Wave Mixing Laser
Appl. Sci. 2019, 9(11), 2366; https://doi.org/10.3390/app9112366
Received: 15 April 2019 / Revised: 1 June 2019 / Accepted: 4 June 2019 / Published: 10 June 2019
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Abstract
In this paper, a time-domain fast gated near-infrared spectroscopy system is presented. The system is composed of a fiber-based laser providing two pulsed sources and two fast gated detectors. The system is characterized on phantoms and was tested in vivo, showing how the [...] Read more.
In this paper, a time-domain fast gated near-infrared spectroscopy system is presented. The system is composed of a fiber-based laser providing two pulsed sources and two fast gated detectors. The system is characterized on phantoms and was tested in vivo, showing how the gating approach can improve the contrast and contrast-to-noise-ratio for detection of absorption perturbation inside a diffusive medium, regardless of source-detector separation. Full article
(This article belongs to the Special Issue New Horizons in Time-Domain Diffuse Optical Spectroscopy and Imaging)
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Open AccessArticle
Reconstruction of the Microstructure of Cyanate Ester Resin by Using Prepared Cyanate Ester Resin Nanoparticles and Analysis of the Curing Kinetics Using the Avrami Equation of Phase Change
Appl. Sci. 2019, 9(11), 2365; https://doi.org/10.3390/app9112365
Received: 4 May 2019 / Revised: 4 June 2019 / Accepted: 5 June 2019 / Published: 10 June 2019
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Abstract
Bisphenol A dicyanate (BADCy) resin nanoparticles were synthesized by precipitation polymerization and used to modulate the microstructure of the BADCy resin matrix. A microscopic mechanism model was used to characterize the curing process of BADCy resin systems with different contents of the prepared [...] Read more.
Bisphenol A dicyanate (BADCy) resin nanoparticles were synthesized by precipitation polymerization and used to modulate the microstructure of the BADCy resin matrix. A microscopic mechanism model was used to characterize the curing process of BADCy resin systems with different contents of the prepared nanoparticles. Due to the curing process of the thermosetting resin being analogous to the crystallization process of the polymer, the Avrami equation was used to analyze the microscopic mechanism of the curing process. The reactive functional groups, structure, and size of the prepared BADCy resin nanoparticles were characterized by FT-IR, SEM, and TEM, respectively. The kinetic parameters of different systems were then obtained using the Avrami equation, and they adequately explained the microscopic mechanism of the curing process. The results showed that the Avrami equation effectively described the formation and growth of gel particles during the curing process of the BADCy resins. The addition of nanoparticles can affect the curing behavior and curing rate. Since the reaction between the BADCy resin nanoparticles and the matrix is dominant, the formation process of the gel particles was neglected. This phenomenon can be understood as the added BADCy resin nanoparticles replacing the formation of gel particles. The reasons for accelerated curing were analyzed from the perspective of thermodynamics and kinetics. Besides this, the Arrhenius equation for non-isothermal conditions correctly accounted for the change in the cross-linked mechanism in the late-stage curing process. A comparison of the theoretical prediction with the experimental data shows that the Avrami theory of phase change can simulate the curing kinetics of different BADCy resin systems well and explain the effects of BADCy resin nanoparticles on the formation of the microstructure. Full article
(This article belongs to the Special Issue Phase Transitions in Polymer and Polymer-Based (Nano)Composites)
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Open AccessReview
Recent Development of Aptamer Sensors for the Quantification of Aflatoxin B1
Appl. Sci. 2019, 9(11), 2364; https://doi.org/10.3390/app9112364
Received: 29 April 2019 / Revised: 29 May 2019 / Accepted: 31 May 2019 / Published: 10 June 2019
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Abstract
Aflatoxin B1 (AFB1) is one of the most frequently-found mycotoxins in contaminated food. As the content of mycotoxins is particularly low in food, the development of probes to detect AFB1 in foods with high sensitivity and selectivity is an urgent social need for [...] Read more.
Aflatoxin B1 (AFB1) is one of the most frequently-found mycotoxins in contaminated food. As the content of mycotoxins is particularly low in food, the development of probes to detect AFB1 in foods with high sensitivity and selectivity is an urgent social need for the evaluation of food quality. Numerous techniques have been developed to monitor AFB1. Nevertheless, most of them require cumbersome, labor-consuming, and sophisticated instruments, which have limited their application. An aptamer is a single, short nucleic acid sequence that is capable of recognizing different targets. Owing to their unique properties, aptamers have been considered as alternatives to antibodies. Aptasensors are considered to be an emerging strategy for the quantification of aflatoxin B1 with high selectivity and sensitivity. In this review, we summarize recent developments in colormetric, electrochemical, SERS, and fluorescent aptasensors for the quantification of AFB1. Finally, the perspectives and current challenges of aptasensors for AFB1 are outlined. Full article
(This article belongs to the Section Chemistry)
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Open AccessArticle
The Impacts of Random Distributed Vacancy Defects in Steady-State Thermal Conduction of Graphene
Appl. Sci. 2019, 9(11), 2363; https://doi.org/10.3390/app9112363
Received: 21 April 2019 / Revised: 3 June 2019 / Accepted: 3 June 2019 / Published: 10 June 2019
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Abstract
The unavoidable vacancy defects dispersed throughout the entire pristine graphene tailor to the integrity of the lattice structure and thereby have complicated impacts on the mechanical and thermal properties of graphene. In order to analyze the influence of vacancy defects on the extraordinary [...] Read more.
The unavoidable vacancy defects dispersed throughout the entire pristine graphene tailor to the integrity of the lattice structure and thereby have complicated impacts on the mechanical and thermal properties of graphene. In order to analyze the influence of vacancy defects on the extraordinary thermal conductivity of graphene, three typical kinds of vacancy defects—namely center concentrated, periodic, and random distributed vacancy defects—are compared and discussed. In the steady-state thermal conduction, the finite element method (FEM) is performed to calculate the total thermal energy and temperature field. The equivalent coefficient of thermal conductivity is derived from thermal energy, amount of vacancy defects, and boundary condition. The chirality in graphene is discussed by the location of its heat source. Moreover, the Monte Carlo simulation is applied to propagate the uncertainty of random vacancy defects in the finite element model of pristine graphene. In this paper, we provide the robustness to defend the impacts of vacancy defects on thermal conduction and the fluctuation and divergence caused by a certain number of random vacancy defects. Full article
(This article belongs to the Section Nanotechnology and Applied Nanosciences)
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Open AccessArticle
Volatile Secondary Metabolites with Potent Antidiabetic Activity from the Roots of Prangos pabularia Lindl.—Computational and Experimental Investigations
Appl. Sci. 2019, 9(11), 2362; https://doi.org/10.3390/app9112362
Received: 14 May 2019 / Revised: 30 May 2019 / Accepted: 31 May 2019 / Published: 10 June 2019
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Abstract
(1) Background: Almost 500 million people worldwide are suffering from diabetes. Since ancient times, humans have used medicinal plants for the treatment of diabetes. Medicinal plants continue to serve as natural sources for the discovery of antidiabetic compounds. Prangos pabularia Lindl. is a [...] Read more.
(1) Background: Almost 500 million people worldwide are suffering from diabetes. Since ancient times, humans have used medicinal plants for the treatment of diabetes. Medicinal plants continue to serve as natural sources for the discovery of antidiabetic compounds. Prangos pabularia Lindl. is a widely distributed herb with large reserves in Tajikistan. Its roots and fruits have been used in Tajik traditional medicine. To our best knowledge, there are no previously published reports concerning the antidiabetic activity and the chemical composition of the essential oil obtained from roots of P. pabularia. (2) Methods: The volatile secondary metabolites were obtained by hydrodistillation from the underground parts of P. pabularia growing wild in Tajikistan and were analyzed by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). Protein tyrosine phosphatase 1B (PTP-1B) inhibition assay and molecular docking analysis were carried out to evaluate the potential antidiabetic activity of the P. pabularia essential oil. (3) Results: The main constituents of the volatile oil of P. pabularia were 5-pentylcyclohexa-1,3-diene (44.6%), menthone (12.6%), 1-tridecyne (10.9%), and osthole (6.0%). PTP-1B inhibition assay of the essential oil and osthole resulted in significant inhibitory activity with an IC50 value of 0.06 ± 0.01 and 0.93 ± 0.1 μg/mL. Molecular docking analysis suggests volatile compounds such as osthole inhibit PTP-1B, and the results are also in agreement with experimental investigations. (4) Conclusions: Volatile secondary metabolites and the pure isolated compound (osthole) from the roots of P. pabularia exhibited potent antidiabetic activity, twenty-five and nearly two times more than the positive control (3-(3,5-dibromo-4-hydroxybenzoyl)-2-ethylbenzofuran-6-sulfonic acid-(4-(thiazol-2-ylsulfamyl)-phenyl)-amide)) with an IC50 value of 1.46 ± 0.4 μg/mL, respectively. Full article
(This article belongs to the Special Issue Biological Activity and Applications of Natural Compounds)
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