Applied Sciences

Research

12 pages, 1290 KiB

Open AccessArticle

Data-Driven Model for Identifying Factors Influencing Electric Vehicle Charging Demand: A Comparative Analysis of Early- and Maturity-Phases of Electric Vehicle Programs in Korea

by Daejin Kim, Doyun Kwon, Jihoon Han, Seongkwan Mark Lee, Sabeur Elkosantini and Wonho Suh

Appl. Sci. 2023, 13(6), 3760; https://doi.org/10.3390/app13063760 - 15 Mar 2023

Cited by 6 | Viewed by 2709

Abstract

With increasing concerns about urban pollution, electric vehicles (EVs) have offered an alternative mode of transportation that reduces urban pollution levels. Previous studies have sought to identify the various factors influencing EV charging patterns to deploy an appropriate charging infrastructure. However, limited attention [...] Read more.

With increasing concerns about urban pollution, electric vehicles (EVs) have offered an alternative mode of transportation that reduces urban pollution levels. Previous studies have sought to identify the various factors influencing EV charging patterns to deploy an appropriate charging infrastructure. However, limited attention has been paid to the investigation of different charging patterns identified in different regions at different phases of the EV program. This study aims to fill this research gap in the literature by developing binary logistic models that account for the factors influencing charging demands in different regions of Korea, i.e., Jeju-do and Gangneung-si. To this end, we collected historical data on EV charging transactions in these study regions and analyzed them to evaluate the difference in charging demands. The developed models suggest that the charging demand varies with charger characteristics and charging time. Moreover, different charging patterns in different regions can be explained by the different travel behaviors of those who use EVs for different trip purposes. These findings provide an important implication suggesting that policymakers should consider a stepwise strategy to construct charging infrastructure at the appropriate scale and configuration, depending on the phase of the EV program. Full article

(This article belongs to the Special Issue Selected Papers from IMETI 2021)

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21 pages, 7001 KiB

Open AccessArticle

Voice Interaction Recognition Design in Real-Life Scenario Mobile Robot Applications

by Shih-An Li, Yu-Ying Liu, Yun-Chien Chen, Hsuan-Ming Feng, Pi-Kang Shen and Yu-Che Wu

Appl. Sci. 2023, 13(5), 3359; https://doi.org/10.3390/app13053359 - 6 Mar 2023

Cited by 14 | Viewed by 4572

Abstract

This paper designed a voice interactive robot system that can conveniently execute assigned service tasks in real-life scenarios. It is equipped without a microphone where users can control the robot with spoken commands; the voice commands are then recognized by a well-trained deep [...] Read more.

This paper designed a voice interactive robot system that can conveniently execute assigned service tasks in real-life scenarios. It is equipped without a microphone where users can control the robot with spoken commands; the voice commands are then recognized by a well-trained deep neural network model of automatic speech recognition (ASR), which enables the robot to execute and complete the command based on the navigation of a real-time simultaneous localization and mapping (SLAM) algorithm. The voice interaction recognition model is divided into two parts: (1) speaker separation and (2) ASR. The speaker separation is applied by a deep-learning system consisting of eight convolution layers, one LSTM layer, and two fully connected (FC) layers to separate the speaker’s voice. This model recognizes the speaker’s voice as a referrer that separates and holds the required voiceprint and removes noises from other people’s voiceprints. Its automatic speech recognition uses the novel sandwich-type conformer model with a stack of three layers, and combines convolution and self-attention to capture short-term and long-term interactions. Specifically, it contains a multi-head self-attention module to directly convert the voice data into text for command realization. The RGB-D vision-based camera uses a real-time appearance-based mapping algorithm to create the environment map and replace the localization with a visional odometer to allow the robot to navigate itself. Finally, the proposed ASR model was tested to check if the desired results will be obtained. Performance analysis was applied to determine the robot’s environment isolation and voice recognition abilities. The results showed that the practical robot system successfully completed the interactive service tasks in a real environment. This experiment demonstrates the outstanding performance with other ASR methods and voice control mobile robot systems. It also verified that the designed voice interaction recognition system enables the mobile robot to execute tasks in real-time, showing that it is a convenient way to complete the assigned service applications. Full article

(This article belongs to the Special Issue Selected Papers from IMETI 2021)

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17 pages, 2862 KiB

Open AccessArticle

A Research on Fault Diagnosis of a USV Thruster Based on PCA and Entropy

by Ki-Beom Choo, Hyunjoon Cho, Jung-Hyeun Park, Jiafeng Huang, Dongwook Jung, Jihyeong Lee, Sang-Ki Jeong, Jongsu Yoon, Jinhun Choo and Hyeung-Sik Choi

Appl. Sci. 2023, 13(5), 3344; https://doi.org/10.3390/app13053344 - 6 Mar 2023

Cited by 6 | Viewed by 1884

Abstract

This study focuses on faults in the thrusters of unmanned surface vehicles, which are fatal to the integrity of their missions. As for the fault conditions, the breakage of the thruster blade and the entanglement of floating objects were selected, and a data-driven [...] Read more.

This study focuses on faults in the thrusters of unmanned surface vehicles, which are fatal to the integrity of their missions. As for the fault conditions, the breakage of the thruster blade and the entanglement of floating objects were selected, and a data-driven method was used to diagnose the faults. In the data-driven method, it is important to select the sensitive fault feature. In this study, vibration, current consumption, rotational speed and input voltage were selected as fault features. An experiment was conducted in an engineering water tank to obtain and analyze data on fault conditions to verify the validity of the selected features. In addition, a new fault diagnosis algorithm combining principal component analysis and Shannon entropy was applied for analyzing the correlations among fault features. This algorithm reduces the dimensionality of data while preserving their structure and characteristics, and diagnoses faults by quantifying entropy values. A fault is detected by comparing the entropy value and a predetermined threshold value, and is diagnosed by analyzing the entropy value and visualized 2D or 3D principal component results. Moreover, the fault diagnosis performance of the unmanned surface vehicle’s thruster was verified by analyzing the results for each fault condition. Full article

(This article belongs to the Special Issue Selected Papers from IMETI 2021)

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23 pages, 9847 KiB

Open AccessArticle

Unmanned Surface Vehicle Using a Leader–Follower Swarm Control Algorithm

by Ji-Hyeong Lee, Sang-Ki Jeong, Dae-Hyeong Ji, Hae-Yong Park, Do-Young Kim, Ki-Beom Choo, Dong-Wook Jung, Myung-Jun Kim, Myoung-Hak Oh and Hyeung-Sik Choi

Appl. Sci. 2023, 13(5), 3120; https://doi.org/10.3390/app13053120 - 28 Feb 2023

Cited by 8 | Viewed by 2362

Abstract

To overcome the limitations of a single unmanned surface vehicle (USV), this study investigated the swarm control algorithms of USVs. Among various swarm control methods, a leader–follower swarm control method was selected and studied. The performance of the swarm algorithm proposed in this [...] Read more.

To overcome the limitations of a single unmanned surface vehicle (USV), this study investigated the swarm control algorithms of USVs. Among various swarm control methods, a leader–follower swarm control method was selected and studied. The performance of the swarm algorithm proposed in this study was verified through an actual sea area test. A USV was designed and manufactured by dividing the power and communication parts. The power system was equipped with a coulometer to monitor the battery state in real time to protect the system through a switch linked to the coulometer in the case of abnormalities in the battery and to prevent accidents. In addition, a communication system was established to process the sensor data and camera image data of the USV in real time. Consequently, the desired swarm formation was achieved through the separately constructed swarm control algorithm. Before the actual sea area test, individual performance tests of each sensor were conducted. Finally, the performance of the swarm algorithm was verified by conducting a sea area test. The performance of the controllers was confirmed to be good, and the swarm formation was confirmed to be successful. Full article

(This article belongs to the Special Issue Selected Papers from IMETI 2021)

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14 pages, 2805 KiB

Open AccessArticle

A Novel Measurement Method for Determining Geometric Errors of Rotary Tables by Using LaserTRACER and Reflectors

by Chi-Hua Hsu, Jr-Rung Chen, Fan-Hsi Hsu and Yu-Ta Chen

Appl. Sci. 2023, 13(4), 2419; https://doi.org/10.3390/app13042419 - 13 Feb 2023

Cited by 3 | Viewed by 2024

Abstract

In this paper, a novel and robust measurement method is proposed for obtaining the geometric errors of rotary tables by using LaserTRACER and the reflectors mounted on the reflector standard fixture. For the machining accuracy, the six-degree-of-freedom (6-DOF) geometric errors of the rotary [...] Read more.

In this paper, a novel and robust measurement method is proposed for obtaining the geometric errors of rotary tables by using LaserTRACER and the reflectors mounted on the reflector standard fixture. For the machining accuracy, the six-degree-of-freedom (6-DOF) geometric errors of the rotary axes interactively influence the manufacturing quality of the precise workpieces. Therefore, this paper mainly aims to develop a measurement method for identifying the 6-DOF geometric errors of rotary tables without using the external linear axis. Furthermore, the set-up errors of the reflector standard fixture are also considered and identified to reduce the influence of the 6-DOF geometric error measurements. For each rotary table geometric error measurement, the positions of the LaserTRACER as well as the relative distance between the reflectors and the LaserTRACER are measured and obtained for determining the 6-DOF geometric errors of the rotary tables. In addition, the homogeneous transformation matrix (HTM), multilateration method, and least squares method are used for building the mathematical measurement algorithm. Moreover, the experimental verifications are implemented to demonstrate the accuracy of the proposed measurement method. Conclusively, the experiment and simulation verification results clearly delineate that the maximal relative differences in the linear errors and the angular errors of the 6-DOF geometric errors are, at most, 3.25% and 2.30%, respectively. Full article

(This article belongs to the Special Issue Selected Papers from IMETI 2021)

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12 pages, 2465 KiB

Open AccessArticle

Calibration of a Rotary Encoder and a Polygon Using a Two-Autocollimator Method

by Tsung-Han Hsieh, Ming-Xian Lin, Kuan-Ting Yeh and Tsukasa Watanabe

Appl. Sci. 2023, 13(3), 1865; https://doi.org/10.3390/app13031865 - 31 Jan 2023

Cited by 6 | Viewed by 2263

Abstract

In this work, we propose a two-autocollimator method in which all pitch angle deviations of a polygon and angle errors of a rotary encoder can be calibrated simultaneously. A polygon with any number of faces can be calibrated. Any face of the polygon [...] Read more.

In this work, we propose a two-autocollimator method in which all pitch angle deviations of a polygon and angle errors of a rotary encoder can be calibrated simultaneously. A polygon with any number of faces can be calibrated. Any face of the polygon is a measurement cycle of one. Compared to a traditional method, cross-calibration calibrates a rotary encoder and a polygon. This method can simultaneously calibrate all pitch angle deviations of the polygon and angle errors of the rotary encoder. The measurement cycle depends on how many faces the polygon has. There are 24 measurement cycles for a 24-faced polygon. In the experiment, we use two autocollimators to calibrate a 24-faced polygon and the SelfA rotary encoder to conduct the proposed two-autocollimator method. According to the uncertainty evaluation, the expanded uncertainty is 0.46”. For a 95% confidence level, the coverage factor is 2.00. To verify all pitch angle deviations, the shift-angle method, based on cross-calibration, uses one autocollimator to measure the same polygon. The difference in pitch angle deviations is smaller than ±0.28”. The maximum En-value is 0.58. The SelfA rotary encoder comprises 12 read heads and calibrates using self-calibration. The difference in angle errors is smaller than ±0.27”. The maximum En-value is 0.59. The two En-values mean that the proposed two-autocollimator method is practical. Full article

(This article belongs to the Special Issue Selected Papers from IMETI 2021)

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24 pages, 17683 KiB

Open AccessArticle

Monitoring of Possible Activities of Yangsan Fault Zone Using GNSS

by Hee-Un Kim and Tae-Suk Bae

Appl. Sci. 2023, 13(3), 1862; https://doi.org/10.3390/app13031862 - 31 Jan 2023

Cited by 1 | Viewed by 1599

Abstract

After the Gyeongju earthquake in 2016 and the subsequent one in Pohang the following year, there is an imminent necessity to evaluate the risk of earthquakes accurately as well as respond to the risks on the Korean peninsula. For this purpose, the existence [...] Read more.

After the Gyeongju earthquake in 2016 and the subsequent one in Pohang the following year, there is an imminent necessity to evaluate the risk of earthquakes accurately as well as respond to the risks on the Korean peninsula. For this purpose, the existence and movement of a fault should be investigated in the area. In this study, we calculated the displacement of the crust around the mass production fault using GNSS (Global Navigation Satellite System) data and analyzed the deformation characteristics by applying the method of stress calculation. The Yangsan Fault Zone has been analyzed with a total of 24 GNSS stations between 2018 and 2021. Data processing was conducted with Bernese GNSS Software, which requires high-precision orbit, satellite clock, ionosphere information for high-precision position estimation. By accumulating daily solutions over the three years to produce the final solution with the velocity of the stations, the Yangsan Fault Zone moved about 32 mm per year southeast on average. Based on the results, the movements of the stations on either side of the Faults are almost the same. Stress analysis of the Yangsan Fault Zone showed a large east–west expansion during 2018–2019 but decreased in stress afterwards, thus it is evaluated to be relatively stable compared to the past. However, due to the nature of crustal variation continuous monitoring research with long-term data processing should be followed, which will be discussed in further research. Full article

(This article belongs to the Special Issue Selected Papers from IMETI 2021)

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16 pages, 5731 KiB

Open AccessArticle

Analysis of a New Twin Hybrid Autonomous Underwater Vehicle

by Jiafeng Huang, Hyeung-Sik Choi, Dong-Wook Jung, Ki-Beom Choo, Hyunjoon Cho, Phan Huy Nam Anh, Ruochen Zhang, Joon-Young Kim, Daehyeong Ji and Jung-Hyeun Park

Appl. Sci. 2023, 13(3), 1551; https://doi.org/10.3390/app13031551 - 25 Jan 2023

Cited by 1 | Viewed by 2219

Abstract

The twin hybrid autonomous underwater vehicle (THAUV) is a novel type of unmanned underwater platform that consists of a twin torpedo-shaped hull and is actuated by two buoyancy engines and two thrusters proposed in this paper. The THAUV was designed to have faster [...] Read more.

The twin hybrid autonomous underwater vehicle (THAUV) is a novel type of unmanned underwater platform that consists of a twin torpedo-shaped hull and is actuated by two buoyancy engines and two thrusters proposed in this paper. The THAUV was designed to have faster speed generated by the two buoyancy engines and two thrusters. The two buoyancy engines on each hull and the airfoil are mainly responsible for the diving and surfacing motion, and the thrusters drive the THAUV along the horizontal plane. The THAUV is capable of carrying more instrumentation and energy than a conventional hybrid autonomous underwater vehicle (HAUV) with a single buoyancy engine such that the THAUV can perform more exploration tasks and operate for a longer period in a one-time operation. Different from other unmanned underwater vehicles (UUVs) with two airfoils or wings, the THAUV has a single airfoil connecting the twin hull such that it does not require connecting bars and additional airfoils. For this reason, the structure of THAUV is more compact and simpler. In this paper, a new compact THAUV is designed and CFD simulation is used to obtain the hydrodynamic parameters of THAUV operation in water. The motion model of the THAUV is also established and the operating parameters of the THAUV are obtained by simulation. Full article

(This article belongs to the Special Issue Selected Papers from IMETI 2021)

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12 pages, 1094 KiB

Open AccessArticle

Fusion Swarm-Intelligence-Based Decision Optimization for Energy-Efficient Train-Stopping Schemes

by Xianguang Jia, Xinbo Zhou, Jing Bao, Guangyi Zhai and Rong Yan

Appl. Sci. 2023, 13(3), 1497; https://doi.org/10.3390/app13031497 - 23 Jan 2023

Cited by 5 | Viewed by 1668

Abstract

To solve the decision problem of train stopping schemes, this paper introduces the static game into the optimal configuration of stopping time to realize the rational decision of train operation. First, a train energy consumption model is constructed with the lowest energy consumption [...] Read more.

To solve the decision problem of train stopping schemes, this paper introduces the static game into the optimal configuration of stopping time to realize the rational decision of train operation. First, a train energy consumption model is constructed with the lowest energy consumption of train operation as the optimization objective. In addition, a Mustang optimization algorithm based on cubic chaos mapping, the population hierarchy mechanism, the golden sine strategy, and the Levy flight strategy was designed for solving the problem of it being easy for the traditional population intelligence algorithm to fall into a local optimum when solving complex problems. Lastly, simulation experiments were conducted to compare the designed algorithm with PSO, GA, WOA, GWO, and other cutting-edge optimization algorithms in cross-sectional simulations, and the results show that the algorithm had excellent global optimization finding and convergence capabilities. The simulation results show that the research in this paper can provide effective decisions for the dwell time of trains at multiple stations, and promote the intelligent operation of the train system. Full article

(This article belongs to the Special Issue Selected Papers from IMETI 2021)

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18 pages, 5053 KiB

Open AccessArticle

Sound Activity Monitor Circuit for Low Power Consumption of Always-On Microphone Applications

by Jong Pal Kim

Appl. Sci. 2022, 12(23), 11947; https://doi.org/10.3390/app122311947 - 23 Nov 2022

Cited by 1 | Viewed by 2232

Abstract

A novel sound activity monitor (SAM) circuit for low power consumption of always-on microphone applications is presented. To reduce average power consumption, the ultra-low-power SAM is essential and operates a readout integrated circuit (ROIC) in low power mode with silent input or in [...] Read more.

A novel sound activity monitor (SAM) circuit for low power consumption of always-on microphone applications is presented. To reduce average power consumption, the ultra-low-power SAM is essential and operates a readout integrated circuit (ROIC) in low power mode with silent input or in normal power mode with voice input. A novel SAM with an architecture that does not include an envelope detector is proposed to achieve low power consumption. A new architecture is also proposed to improve MEMS sensitivity by connecting the SAM input to the source follower (SF) output instead of connecting the SAM input to the MEMS port already connected to the SF. In addition, in order to prevent inefficient frequent operation mode conversion, a feature of delaying the transition to the low-power mode after the sound is silenced is implemented. The proposed architecture is designed and verified based on the standard 0.18 µm CMOS process. The SAM, which consists of two-stage amplifiers (OA, AMP2), comparators, and a logic circuit, consumes a 1 µA current. The analog path consisting of SF, OA, and AMP2 in low power mode has a maximum amplification gain of 63 dB and a noise of 72 nV_rms/√Hz at 1 kHz. Full article

(This article belongs to the Special Issue Selected Papers from IMETI 2021)

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13 pages, 1750 KiB

Open AccessArticle

Auxiliary Decision-Making System for Steel Plate Cold Straightening Based on Multi-Machine Learning Competition Strategies

by Zhen-Hu Dai, Rui-Hua Wang and Ji-Hong Guan

Appl. Sci. 2022, 12(22), 11473; https://doi.org/10.3390/app122211473 - 11 Nov 2022

Cited by 2 | Viewed by 1395

Abstract

In the process of steel plate production, whether cold straightening is required is significant to reduce costs and improve product qualification rates. It is not effective by adopting classic machine learning judgment algorithms. Concerning the effectiveness of ensemble learning methods on improving traditional [...] Read more.

In the process of steel plate production, whether cold straightening is required is significant to reduce costs and improve product qualification rates. It is not effective by adopting classic machine learning judgment algorithms. Concerning the effectiveness of ensemble learning methods on improving traditional machine learning methods, a steel plate cold straightening auxiliary decision-making algorithm based on multiple machine learning competition strategies is proposed in this paper. The algorithm firstly adopts the rough set method to simplify the attributes of the conditional factors for affecting whether the steel plate cold straightening is required, and reduce the attribute dimensions of the steel plate cold straightening auxiliary decision-making data set. Secondly, the competition of training multiple different learners on the data set produces the optimal base classifier. Finally, the final classifier is generated by training weights on the optimal base classifier and combining it with a centralized strategy. While the hit rate of good products of the final classifier is 97.9%, the hit rate of defective products is 90.9%. As such, the accuracy rate is better than the single kind of simple machine learning algorithms, which effectively improves the product quality of steel plates in practical production applications. Full article

(This article belongs to the Special Issue Selected Papers from IMETI 2021)

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19 pages, 6894 KiB

Open AccessArticle

The Cross-Zone Navigation and Signage Systems for Combatting Cybersickness and Disorientation in Middle-Aged and Older People within a 3D Virtual Store

by Cheng-Li Liu and Shiaw-Tsyr Uang

Appl. Sci. 2022, 12(19), 9821; https://doi.org/10.3390/app12199821 - 29 Sep 2022

Cited by 1 | Viewed by 1593

Abstract

With the maturation and popularization of 3D virtual reality (3D VR) technology, various corporations have employed 3D VR animations to enrich the experience of visiting a store and change how products are presented. Because middle-aged and older adults have weaker mobility and perception [...] Read more.

With the maturation and popularization of 3D virtual reality (3D VR) technology, various corporations have employed 3D VR animations to enrich the experience of visiting a store and change how products are presented. Because middle-aged and older adults have weaker mobility and perception abilities, their behaviors in 3D virtual stores may differ entirely from those of younger age groups. This study aimed to develop a cross-zone navigation system and a signage system for 3D virtual retail stores to provide middle-aged and older consumers with high-efficiency navigation for finding products quickly. Additionally, the effect of the systems on combating perceptual conflict was assessed to confirm the practicability of 3D virtual retail shopping. The results revealed that the cross-zone navigation system effectively assisted participants in searching for their desired products. Additionally, the cybersickness score (SSQ) of the cross-zone navigation system group was significantly lower than that of the map-based navigation system group. The participants who used both the cross-zone navigation system and the signage system exhibited the lowest perceptual conflict scores. Therefore, this study provides references for developing a novel navigation system for 3D virtual retail stores (i.e., a cross-zone navigation system with signage). Full article

(This article belongs to the Special Issue Selected Papers from IMETI 2021)

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16 pages, 5618 KiB

Open AccessArticle

Autonomous Driving Assistance with Dynamic Objects Using Traffic Surveillance Cameras

by Kuk Cho and Dooyong Cho

Appl. Sci. 2022, 12(12), 6247; https://doi.org/10.3390/app12126247 - 20 Jun 2022

Cited by 8 | Viewed by 2497

Abstract

This paper describes a method that precisely estimates the position of images of traffic surveillance camera objects. We suggest a projection method with multiple traffic surveillance cameras through a local coordinate system into a global coordinate system. The transformation of coordinates uses detected [...] Read more.

This paper describes a method that precisely estimates the position of images of traffic surveillance camera objects. We suggest a projection method with multiple traffic surveillance cameras through a local coordinate system into a global coordinate system. The transformation of coordinates uses detected objects, parameters of the camera and the geometric information of high- definition (HD) maps. Traffic surveillance cameras that pursue traffic safety and convenience use various sensors to generate traffic information. We suggest a transformation method with images of the camera and HD maps and an evaluation method. Therefore, it is necessary to improve the sensor-related technology to increase the efficiency and reliability of the traffic information. Recently, the role of the camera in collecting video information has become more important due to advances in artificial intelligence (AI) technology. The objects projected from the traffic surveillance camera domain to the HD domain are helpful to identify imperceptible zones, such as blind spots, on roads for autonomous driving assistance. In this study, we proposed to identify and track dynamic objects (vehicles, pedestrian, etc.) with traffic surveillance cameras, and to analyze and provide information about them in various environments. To this end, we conducted the identification of dynamic objects using the Yolov4 and DeepSort algorithms, established real-time multi-user support servers based on Kafka, defined transformation matrices between images and spatial coordinate systems, and implemented map-based dynamic object visualization. In addition, a positional consistency evaluation was performed to confirm its usefulness. Through the proposed scheme, we confirmed that multiple traffic surveillance cameras can serve as important sensors to provide relevant information by analyzing road conditions in real-time in terms of road infrastructure beyond a simple monitoring role. Full article

(This article belongs to the Special Issue Selected Papers from IMETI 2021)

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12 pages, 45627 KiB

Open AccessArticle

Geospatial Simulation System of Mountain Area Black Ice Accidents

by Jae-Kang Lee, Yong Huh and Jisoo Park

Appl. Sci. 2022, 12(11), 5709; https://doi.org/10.3390/app12115709 - 3 Jun 2022

Cited by 3 | Viewed by 2598

Abstract

As the development of mountain areas has recently increased in Korea, existing roads are being renovated, and new highways are being constructed, which increases driving speeds in mountainous areas. However, the mountainous region in northeastern Korea is more likely to form black ice [...] Read more.

As the development of mountain areas has recently increased in Korea, existing roads are being renovated, and new highways are being constructed, which increases driving speeds in mountainous areas. However, the mountainous region in northeastern Korea is more likely to form black ice due to higher humidity, frequent fog, and hillshade, depending on the terrain, which can cause serious traffic pileups. In this study, therefore, we present a method to build a more effective black ice prediction and warning system by linking spatial information to the existing road management system that estimates the road surface temperature based on real-time weather information. The spatial information enabled a prediction to be made of the risk level of black ice formation for each time zone by simulating changes in the shadow area based on precise 3D terrain information. Moreover, this information also presented slope and curvature information of the road to estimate the risk zone. The spatial information was integrated with weather data to predict road surface temperature. The proposed system was tested in two mountainous regions with weather data accumulated from 2017 to 2018. As a result, the proposed system anticipated 71% of traffic accidents caused by black ice during the testing period. The results show that the system can contribute significantly to preventing black-ice-related traffic accidents by providing reasonable predictions. Full article

(This article belongs to the Special Issue Selected Papers from IMETI 2021)

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13 pages, 1640 KiB

Open AccessArticle

Automated Detection of Greenhouse Structures Using Cascade Mask R-CNN

by Haeng Yeol Oh, Muhammad Sarfraz Khan, Seung Bae Jeon and Myeong-Hun Jeong

Appl. Sci. 2022, 12(11), 5553; https://doi.org/10.3390/app12115553 - 30 May 2022

Cited by 5 | Viewed by 2392

Abstract

Automated detection of the content of images remains a challenging problem in artificial intelligence. Hence, continuous manual monitoring of restricted development zones is critical to maintaining territorial integrity and national security. In this regard, local governments of the Republic of Korea conduct four [...] Read more.

Automated detection of the content of images remains a challenging problem in artificial intelligence. Hence, continuous manual monitoring of restricted development zones is critical to maintaining territorial integrity and national security. In this regard, local governments of the Republic of Korea conduct four periodic inspections per year to preserve national territories from illegal encroachments and unauthorized developments in restricted zones. The considerable expense makes responding to illegal developments difficult for local governments. To address this challenge, we propose a deep-learning-based Cascade Mask region-based convolutional neural network (R-CNN) algorithm designed to perform automated detection of greenhouses in aerial photographs for efficient and continuous monitoring of restricted development zones in the Republic of Korea. Our proposed model is regional-based because it was optimized for the Republic of Korea via transfer learning and hyperparameter tuning, which improved the efficiency of the automated detection of greenhouse facilities. The experimental results demonstrated that the mAP value of the proposed Cascade Mask R-CNN model was 83.6, which was 12.83 higher than baseline mask R-CNN, and 0.9 higher than Mask R-CNN with hyperparameter tuning and transfer learning considered. Similarly, the F1-score of the proposed Cascade Mask R-CNN model was 62.07, which outperformed those of the baseline mask R-CNN and the Mask R-CNN with hyperparameter tuning and transfer learning considered (i.e., the F1-score 52.33 and 59.13, respectively). The proposed improved Cascade Mask R-CNN model is expected to facilitate efficient and continuous monitoring of restricted development zones through routine screening procedures. Moreover, this work provides a baseline for developing an integrated management system for national-scale land-use planning and development infrastructure by synergizing geographical information systems, remote sensing, and deep learning models. Full article

(This article belongs to the Special Issue Selected Papers from IMETI 2021)

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13 pages, 1809 KiB

Open AccessArticle

Impact of Lowering Speed Limit on Urban Transportation Network

by Sunhee Jang, Seungkook Wu, Daejin Kim, Ki-Han Song, Seongkwan Mark Lee and Wonho Suh

Appl. Sci. 2022, 12(11), 5296; https://doi.org/10.3390/app12115296 - 24 May 2022

Cited by 6 | Viewed by 3770

Abstract

The purpose of this study is to analyze the impact of lowering speed limit on an urban transportation network. A microscopic traffic simulation model, Vissim was utilized to measure the impact. Also, various traffic inputs were tested with different signal coordination scenarios to [...] Read more.

The purpose of this study is to analyze the impact of lowering speed limit on an urban transportation network. A microscopic traffic simulation model, Vissim was utilized to measure the impact. Also, various traffic inputs were tested with different signal coordination scenarios to investigate the impact in different traffic conditions. It was found that during early morning hours with very light traffic, the impact of lowering speed limit was significant. During congested time periods, including level of service E and F, the travel speed reduction from lowering speed limit was not significant. As suggested in other studies, the results demonstrated that lowering the speed limit does not have a significant impact on average travel speed in congested traffic networks. Also, different signal coordination was tested. As expected, signal coordination based on the lowered speed limit performed better than the case with signal coordination based on the previous higher speed limit. The results of this study are expected to provide insights when considering lowering speed limit for existing traffic networks. Full article

(This article belongs to the Special Issue Selected Papers from IMETI 2021)

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11 pages, 2400 KiB

Open AccessArticle

Machine Learning-Based Automatic Utterance Collection Model for Language Development Screening of Children

by Jeong-Myeong Choi, Yoon-Kyoung Lee, Jong-Dae Kim, Chan-Young Park and Yu-Seop Kim

Appl. Sci. 2022, 12(9), 4747; https://doi.org/10.3390/app12094747 - 9 May 2022

Viewed by 1814

Abstract

To assess a child’s language development, utterance data are required. The approach of recording and transcribing the conversation between the expert and the child is mostly utilized to obtain utterance data. Because data are obtained through one-on-one interactions, this approach is costly. In [...] Read more.

To assess a child’s language development, utterance data are required. The approach of recording and transcribing the conversation between the expert and the child is mostly utilized to obtain utterance data. Because data are obtained through one-on-one interactions, this approach is costly. In addition, depending on the expert, subjective dialogue situations may be incorporated. To acquire speech data, we present a machine learning-based phrase generating model. It has the benefit of being able to cope with several children, which reduces costs and allows for the collection of objectified utterance data through consistent conversation settings. Children’s utterances are initially categorized as topic maintenance or topic change, with rule-based replies based on scenarios being formed in the instance of a topic change. When it comes to topic maintenance, it encourages the child to say more by answering with imitative phrases. The strategy we suggest has the potential to reduce the cost of collecting data for evaluating children’s language development while maintaining data collection impartiality. Full article

(This article belongs to the Special Issue Selected Papers from IMETI 2021)

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13 pages, 1301 KiB

Open AccessArticle

Deep Learning-Based End-to-End Language Development Screening for Children Using Linguistic Knowledge

by Byoung-Doo Oh, Yoon-Kyoung Lee, Jong-Dae Kim, Chan-Young Park and Yu-Seop Kim

Appl. Sci. 2022, 12(9), 4651; https://doi.org/10.3390/app12094651 - 6 May 2022

Cited by 1 | Viewed by 2254

Abstract

Language development is inextricably linked to the development of fundamental human abilities. A language problem can result from abnormal language development in childhood, which has a severe impact on other elements of life. As a result, early treatment of language impairments in children [...] Read more.

Language development is inextricably linked to the development of fundamental human abilities. A language problem can result from abnormal language development in childhood, which has a severe impact on other elements of life. As a result, early treatment of language impairments in children is critical. However, because it is difficult for parents to identify atypical language development in their children, optimal diagnosis and treatment periods are frequently missed. Furthermore, the diagnosis process necessitates a significant amount of time and work. As a consequence, in this study, we present a deep learning-based language development screening model based on word and part-of-speech and investigate the effectiveness of a large-scale language model. For the experiment, we collected data from Korean children by transcribing the utterances of children aged 2, 4, and 6 years. Convolutional neural networks and the notion of Siamese networks, as well as word and part-of-speech information, were used to determine the language development level of children. We also investigated the effectiveness of employing KoBERT and KR-BERT among Korean-specific large-scale language models. In 5-fold cross-validation study, the proposed model has an average accuracy of 78.0%. Furthermore, contrary to predictions, the large-scale language models were shown to be ineffective for representing children’s utterances. Full article

(This article belongs to the Special Issue Selected Papers from IMETI 2021)

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14 pages, 1016 KiB

Open AccessArticle

Perceptions on Regional Benefit of Airport Development and Operation

by Ki-Han Song and Wonho Suh

Appl. Sci. 2022, 12(9), 4340; https://doi.org/10.3390/app12094340 - 25 Apr 2022

Cited by 3 | Viewed by 2914

Abstract

Airport development and operation has a significant impact on local economy. However, the impact is assessed differently from different perspectives. In this paper, the authors investigated how the public think on the benefit of airport development and operation from a regional perspective. More [...] Read more.

Airport development and operation has a significant impact on local economy. However, the impact is assessed differently from different perspectives. In this paper, the authors investigated how the public think on the benefit of airport development and operation from a regional perspective. More specifically, the paper focuses on what the main factors are in public perceptions on the regional benefit of airport development and operation. The authors analyzed a survey collected in South Korea using structural equation models. The authors assigned five categories of perception factors and examined these factor relationships regarding the ripple effects caused by airport development and operation on each region. The five factors were “increased use in air transportation”, “increased exchange with other regions”, “regional economic benefit”, “regional development”, and “dis-benefit to the region”. The model was verified with structural equations and path analysis results for each factor. It was revealed that people perceive the increased use in air transportation and the increased exchange with other regions as bringing about the most significant ripple effects, followed by regional development and regional economic benefit in this order, according to the order of path groups. The results of this paper are expected to provide stakeholders’ perspectives and insights when planning airport development and operation. Full article

(This article belongs to the Special Issue Selected Papers from IMETI 2021)

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20 pages, 80594 KiB

Open AccessArticle

Development of a Dual-Input Magnetic Gear Train for the Transmission System of Small-Scale Wind Turbines

by Yi-Chang Wu, Feng-Ming Ou, Mi-Ching Tsai and Saian Nur Fajri

Appl. Sci. 2022, 12(7), 3685; https://doi.org/10.3390/app12073685 - 6 Apr 2022

Cited by 2 | Viewed by 2905

Abstract

Magnetic gear mechanisms have advanced to have a promising future in transmission technology. Previous research indicates that magnetic gear mechanisms might replace mechanical gear mechanisms in some applications. Small-scale wind turbines (SWT) with counter-rotating rotors that were initially fitted by bevel gears are [...] Read more.

Magnetic gear mechanisms have advanced to have a promising future in transmission technology. Previous research indicates that magnetic gear mechanisms might replace mechanical gear mechanisms in some applications. Small-scale wind turbines (SWT) with counter-rotating rotors that were initially fitted by bevel gears are proposed to be replaced by a coaxial magnetic gear train (CMGT). The CMGT is intended for use as a speed multiplier in order to obtain maximum power at low wind speeds, due to its beneficial transmission of power without physical contact. The primary objective of this study is to build a dual-input CMGT that will be employed in the transmission system of small-scale counter-rotating wind turbines. A dual-input CMGT is built through the analytical modeling of an equivalent magnetic circuit (EMC), which aims to predict the magnetic flux density in the air-gaps of CMGT. Several models within design constraints were compared to obtain the optimum design parameters of the preliminary CMGT design resulting from an EMC analysis. The optimized critical design parameters were then selected and analyzed using finite-element analysis (FEA) to depict the performance of the proposed SWT design. According to the findings, the developed design can generate an inner air-gap flux density of 0.8314 T and an outer air-gap flux density of 1.0200 T. The model likewise produces promising simulation results with an output transmitted torque in the inner rotor (output link) of 8.7 Nm, 56.9 Nm in the outer rotor, and 48.0 Nm in the carrier with pole-pieces. Thus, this design can generate higher torque than a bevel-geared wind turbine. The speed characteristics are also compromised in order to raise the generator’s rotating speed to generate more power. Finally, this study demonstrates the performance and embodiment design of the proposed SWT using CMGT. Full article

(This article belongs to the Special Issue Selected Papers from IMETI 2021)

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15 pages, 27370 KiB

Open AccessArticle

Development of an On-Line Defect Detection System for EDM Process

by Yu-Ting Lyu, Chia-Ming Jan, Herchang Ay, Chiu-Feng Lin, Haw-Ching Yang, Min-Chun Chuang, Heng-Sheng Lin and Tsung-Pin Hung

Appl. Sci. 2022, 12(4), 2230; https://doi.org/10.3390/app12042230 - 21 Feb 2022

Cited by 1 | Viewed by 1860

Abstract

In the electrical discharge machining process, preliminary research has been able to effectively estimate machining accuracy in response to its long machining history and high discharge frequency characteristics. However, when processing abnormalities occur, it is difficult to identify them since the electrical discharge [...] Read more.

In the electrical discharge machining process, preliminary research has been able to effectively estimate machining accuracy in response to its long machining history and high discharge frequency characteristics. However, when processing abnormalities occur, it is difficult to identify them since the electrical discharge process contains multiple processing parameters, which increases the cost of repair or loss afterwards. Therefore, the question concerning how to monitor the abnormality of the discharge process in real time represents the main purpose of this research. This research develops an EDM process abnormal diagnosis system. First, the data are stored in a circular array to speed up the processing time, and the coefficient of variation feature is added, which has effectively extracted the abnormal characteristics. In terms of diagnostic methods, the composite voting model established by neural networks, random forests, and XGB-RF (extreme gradient boosting applying RF) can provide robust diagnostic results. Finally, through the Node-RED webpage and MQTT agreement, it can provide the ability to monitor machine abnormalities in real time. Through refinement and optimization of the previous research results, this study took the electrical discharge machining diamond grinding wheel as an example, and developed a warning that can be issued within 3 min when abnormalities (abnormal patterns such as polycrystalline diamond high protrusions) occur, with an accuracy of 93% and a false positive rate. The abnormal diagnosis ability is less than 0.2%. Therefore, the online abnormality monitoring system developed by this research institute will be able to provide online abnormality diagnosis for electrical discharge machining. Full article

(This article belongs to the Special Issue Selected Papers from IMETI 2021)

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18 pages, 5404 KiB

Open AccessArticle

An Investigation to Reduce the Effect of Moisture on Injection-Molded Parts through Optimization of Plasticization Parameters

by Shia-Chung Chen, Han Su, Jibin Jose Mathew, Hariyanto Gunawan, Chun-Wei Huang and Ching-Te Feng

Appl. Sci. 2022, 12(3), 1410; https://doi.org/10.3390/app12031410 - 28 Jan 2022

Cited by 4 | Viewed by 3548

Abstract

Plastic materials can absorb moisture from the atmosphere even after drying. This absorbed moisture can cause many defects in the molding process. Conventionally, a dryer is used to reduce the moisture content. However, the use of a drying unit involves huge daily power [...] Read more.

Plastic materials can absorb moisture from the atmosphere even after drying. This absorbed moisture can cause many defects in the molding process. Conventionally, a dryer is used to reduce the moisture content. However, the use of a drying unit involves huge daily power consumption and is also time-consuming. Therefore, this study proposed a new method to reduce the impact of moisture on molded product part quality through the optimization of plasticization parameters while reducing drying time. Two plastic materials, polyurethane (TPU) and polycarbonate (PC), were used for the experimental verification. Key plasticization parameters, including back pressure, screw rotation speed, and barrel temperature were chosen; their influence was investigated by the design of experiments (DOE). Moisture-induced defects, such as air bubble area, part surface gloss, and appearance were measured and correlated with the plasticization parameters. It was found, after optimization via a three-level DOE and factorial design multivariate statistical analysis using TPU, that the gloss (GU) of the PC part without drying was very close to that (98.4 GU) of the fully dried PC. The proposed methodology may help molders to improve production efficiency and achieve cost savings. Full article

(This article belongs to the Special Issue Selected Papers from IMETI 2021)

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17 pages, 492 KiB

Open AccessArticle

Controllability of Fractional-Order Particle Swarm Optimizer and Its Application in the Classification of Heart Disease

by Fu-I Chou, Tian-Hsiang Huang, Po-Yuan Yang, Chin-Hsuan Lin, Tzu-Chao Lin, Wen-Hsien Ho and Jyh-Horng Chou

Appl. Sci. 2021, 11(23), 11517; https://doi.org/10.3390/app112311517 - 5 Dec 2021

Cited by 7 | Viewed by 2058

Abstract

This study proposes a method to improve fractional-order particle swarm optimizer to overcome the shortcomings of traditional swarm algorithms, such as low search accuracy in a high-dimensional space, falling into local minimums, and nonrobust results. In natural phenomena, our controllable fractional-order particle swarm [...] Read more.

This study proposes a method to improve fractional-order particle swarm optimizer to overcome the shortcomings of traditional swarm algorithms, such as low search accuracy in a high-dimensional space, falling into local minimums, and nonrobust results. In natural phenomena, our controllable fractional-order particle swarm optimizer can explore search spaces in detail to obtain high resolutions. Moreover, the proposed algorithm is memorable, i.e., position updates focus on the particle position of previous and last generations, rendering it conservative when updating the position, and obtained results are robust. For verifying the algorithm’s effectiveness, 11 test functions compare the average value, overall best value, and standard deviation of the controllable fractional-order particle swarm optimizer and controllable particle swarm optimizer; experimental results show that the stability of the former is better than the latter. Furthermore, the solution position found by the controllable fractional-order particle swarm optimizer is more reliable. Therefore, the improved method proposed herein is effective. Moreover, this research describes how a heart disease prediction application uses the optimizer we proposed to optimize XGBoost hyperparameters with custom target values. The final verification of the obtained prediction model is effective and reliable, which shows the controllability of our proposed fractional-order particle swarm optimizer. Full article

(This article belongs to the Special Issue Selected Papers from IMETI 2021)

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20 pages, 5792 KiB

Open AccessArticle

Estimating Critical Latency Affecting Ship’s Collision in Re-Mote Maneuvering of Autonomous Ships

by Jeong-Bin Yim and Deuk-Jin Park

Appl. Sci. 2021, 11(22), 10987; https://doi.org/10.3390/app112210987 - 19 Nov 2021

Cited by 4 | Viewed by 2195

Abstract

Estimation of the critical latency that can cause collision in remote maneuvering of autonomous ships can provide a clue to avoid collisions. The concept of estimating the critical latency was established using the turning circle formed by the turning maneuver of the own [...] Read more.

Estimation of the critical latency that can cause collision in remote maneuvering of autonomous ships can provide a clue to avoid collisions. The concept of estimating the critical latency was established using the turning circle formed by the turning maneuver of the own ship, and critical latency was estimated using the radius of the turning circle with the turning time ratio. The turning circle was observed using the turning trajectory of the give-way vessel measured in the ship maneuvering simulation experiment. Experimental results demonstrated that the proposed method is capable of identifying both the location and time of the collision due to critical latency. As a result, a clue to avoid possible collision in remote maneuvering caused by critical latency was deduced. Full article

(This article belongs to the Special Issue Selected Papers from IMETI 2021)

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16 pages, 5250 KiB

Open AccessArticle

Assessing the Effects of Gamification on Enhancing Information Security Awareness Knowledge

by Tienhua Wu, Kuang-You Tien, Wei-Chih Hsu and Fu-Hsiang Wen

Appl. Sci. 2021, 11(19), 9266; https://doi.org/10.3390/app11199266 - 8 Oct 2021

Cited by 13 | Viewed by 5673

Abstract

Information security awareness (ISA) has become a vital issue, as security breaches often attributed to humans lead to losses for individuals and organizations. Information security (IS) education may be an effective strategy to improve students’ ISA; however, studies associated with the relationships between [...] Read more.

Information security awareness (ISA) has become a vital issue, as security breaches often attributed to humans lead to losses for individuals and organizations. Information security (IS) education may be an effective strategy to improve students’ ISA; however, studies associated with the relationships between teaching effects and information security learning are few. This study adopted gamification practice and examined its effect on students’ ISA knowledge enhancement, attitude and intention of security compliance, and willingness for continuous IS education. This study also examined the gender difference in a gamified learning system. One hundred ten undergraduates participated in a quasi-experimental study. The results indicated that students within a gamified class performed better than students within a lecture-based instructional group. We found significant gamification effects on the three security focus areas of password management, Internet use, and information handling. Gamification did not significantly impact the attitude and intention of participants’ security compliance and students’ willingness for continuous IS learning. Gender difference in the effect of gamification on ISA knowledge enhancement was not observed as well. The research provides theoretical and practical contributions by incorporating gamification into IS learning and suggests gamification as an effective means to enhance students’ knowledge acquisition in an engaging, timely, economical, and repeated manner. Full article

(This article belongs to the Special Issue Selected Papers from IMETI 2021)

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12 pages, 9068 KiB

Open AccessArticle

A Potentiostat Readout Circuit with a Low-Noise and Mismatch-Tolerant Current Mirror Using Chopper Stabilization and Dynamic Element Matching for Electrochemical Sensors

by Kyeongsik Nam, Gyuri Choi, Hyungseup Kim, Mookyoung Yoo and Hyoungho Ko

Appl. Sci. 2021, 11(18), 8287; https://doi.org/10.3390/app11188287 - 7 Sep 2021

Cited by 7 | Viewed by 5132

Abstract

This paper presents a potentiostat readout circuit with low-noise and mismatch-tolerant current mirror using chopper stabilization and dynamic element matching (DEM) for electrochemical sensors. Current-mode electrochemical sensors are widely used to detect the blood glucose and viruses in the diagnosis of various diseases [...] Read more.

This paper presents a potentiostat readout circuit with low-noise and mismatch-tolerant current mirror using chopper stabilization and dynamic element matching (DEM) for electrochemical sensors. Current-mode electrochemical sensors are widely used to detect the blood glucose and viruses in the diagnosis of various diseases such as diabetes, hyperlipidemia, and the H5N1 avian influenza virus (AIV). Low-noise and mismatch-tolerant characteristics are essential for sensing applications that require high reliability and high sensitivity. To achieve these characteristics, a proposed potentiostat readout circuit is implemented using the chopper stabilization scheme and the DEM technique. The proposed potentiostat readout circuit consists of a chopper-stabilized programmable gain transimpedance amplifier (TIA), gain-boosted cascode current mirror, and a control amplifier (CA). The chopper scheme, which is implemented in the TIA and CA, can reduce low frequency noise components, such as 1/f noise, and can obtain low-noise levels. The mismatch offsets of the cascode current mirror can be reduced by the DEM operation. The proposed current-mirror-based potentiostat readout circuit is designed using a standard 0.18 μm CMOS process and can measure the sensor current from 350 nA to 2.8 μA. The input-referred noise integrated from 0.1 Hz to 1 kHz is 21.7 pA_RMS, and the power consumption was 287.9 μW with a 1.8 V power supply. Full article

(This article belongs to the Special Issue Selected Papers from IMETI 2021)

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22 pages, 120992 KiB

Open AccessArticle

Deep Learning Model for the Inspection of Coffee Bean Defects

by Shyang-Jye Chang and Chien-Yu Huang

Appl. Sci. 2021, 11(17), 8226; https://doi.org/10.3390/app11178226 - 4 Sep 2021

Cited by 18 | Viewed by 6119

Abstract

The detection of coffee bean defects is the most crucial step prior to bean roasting. Existing defect detection methods used in the specialty coffee bean industry entail manual screening and sorting, require substantial human resources, and are not standardized. To solve these problems, [...] Read more.

The detection of coffee bean defects is the most crucial step prior to bean roasting. Existing defect detection methods used in the specialty coffee bean industry entail manual screening and sorting, require substantial human resources, and are not standardized. To solve these problems, this study developed a deep learning algorithm to detect defects in coffee beans. The results reveal that when the pooling layer was used to enhance features and reduce neural dimensionality, some of the coffee been features were lost or misclassified. Therefore, a novel dimensionality reduction method was adopted to increase the ability of feature extraction. The developed model also overcame the drawbacks of padding causing blurred image boundaries and the dead neurons causing impeding feature propagation. Images of eight types of coffee beans were used to train and test the proposed detection model. The proposed method was verified to reduce the bias when classifying defects in coffee beans. The detection accuracy rate of the proposed model was 95.2%. When the model was only used to detect the presence of defects, the accuracy rate increased to 100%. Thus, the proposed model is highly accurate in coffee bean defect detection in the classification of eight types of coffee beans. Full article

(This article belongs to the Special Issue Selected Papers from IMETI 2021)

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21 pages, 6967 KiB

Open AccessArticle

Design and Motion Simulation of an Underwater Glider in the Vertical Plane

by Jiafeng Huang, Hyeung-Sik Choi, Dong-Wook Jung, Ji-Hyeong Lee, Myung-Jun Kim, Ki-Beom Choo, Hyun-Joon Cho and Han-Sol Jin

Appl. Sci. 2021, 11(17), 8212; https://doi.org/10.3390/app11178212 - 4 Sep 2021

Cited by 5 | Viewed by 3405

Abstract

Net buoyancy, as the main power source for the motion of an underwater glider, is affected by the pump or bladder that the glider adopts to change its buoyancy force in water. In this study, a new underwater glider that can dive to [...] Read more.

Net buoyancy, as the main power source for the motion of an underwater glider, is affected by the pump or bladder that the glider adopts to change its buoyancy force in water. In this study, a new underwater glider that can dive to a depth of 400 m at a cruising speed of 2 knots, which is faster than conventional underwater gliders and is less affected by sea currents, is investigated. The UG resisting 400 m pressure on the buoyancy engine and achieving 2 knots’ speed was designed and constructed. For this UG, its steady-state attitude was studied according to the variance of the buoyancy center and the center of gravity with the buoyancy engine influenced by the displacement of the movable mass block. In motion simulation of the UG, the attitude of the UG under different displacement conditions was simulated in Simulink according to the displacements of the piston and the movable mass block. To validate the simulation performance, a UG was constructed and experiments were conducted. The simulation and experimental results were compared to show the reliability of the simulation results under limited conditions. Full article

(This article belongs to the Special Issue Selected Papers from IMETI 2021)

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10 pages, 1201 KiB

Open AccessArticle

Differences in Gait Cycle and Biomechanical Lower-Limb Joint Function between Elderly People with and without Cognitive Decline

by Kiyoung Kwak, Emilija Kostic and Dongwook Kim

Appl. Sci. 2021, 11(17), 8016; https://doi.org/10.3390/app11178016 - 30 Aug 2021

Viewed by 1716

Abstract

Because dementia is difficult to treat, the best way is to detect the prodromal stage; this can identify those at high risk of dementia and help to delay its onset. It is a well-known fact that gait has a high correlation with cognitive [...] Read more.

Because dementia is difficult to treat, the best way is to detect the prodromal stage; this can identify those at high risk of dementia and help to delay its onset. It is a well-known fact that gait has a high correlation with cognitive function. Considering that dementia starts with cognitive decline, investigating the association between cognitive decline and gait may contribute to the detection of elderly individuals at high risk of dementia and even the prevention of dementia. The purpose of the present study was to investigate the gait cycle and biomechanics of elderly people with and without cognitive decline. A three-dimensional motion analysis system was used, and older adults over 65 participated in this study. K-MoCA was used to assess cognitive function and, according to the results of a cognition function assessment, they were classified into two groups. Spatiotemporal variables, subdivisions of the gait cycle, joint angle, joint moment, joint power, and support moment were investigated. Significant differences between both groups appeared in the subdivisions of the gait cycle, and parameters of gait biomechanics were established. These results provide insight into the mechanism dictating the gait of elderly individuals with cognitive decline. Full article

(This article belongs to the Special Issue Selected Papers from IMETI 2021)

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13 pages, 4895 KiB

Open AccessArticle

A Low-Power, Low-Noise, Resistive-Bridge Microsensor Readout Circuit with Chopper-Stabilized Recycling Folded Cascode Instrumentation Amplifier

by Gyuri Choi, Hyunwoo Heo, Donggeun You, Hyungseup Kim, Kyeongsik Nam, Mookyoung Yoo, Sangmin Lee and Hyoungho Ko

Appl. Sci. 2021, 11(17), 7982; https://doi.org/10.3390/app11177982 - 28 Aug 2021

Cited by 9 | Viewed by 5514

Abstract

In this paper, a low-power and low-noise readout circuit for resistive-bridge microsensors is presented. The chopper-stabilized, recycling folded cascode current-feedback instrumentation amplifier (IA) is proposed to achieve the low-power, low-noise, and high-input impedance. The chopper-stabilized, recycling folded cascode topology (with a Monticelli-style, class-AB [...] Read more.

In this paper, a low-power and low-noise readout circuit for resistive-bridge microsensors is presented. The chopper-stabilized, recycling folded cascode current-feedback instrumentation amplifier (IA) is proposed to achieve the low-power, low-noise, and high-input impedance. The chopper-stabilized, recycling folded cascode topology (with a Monticelli-style, class-AB output stage) can enhance the overall noise characteristic, gain, and slew rate. The readout circuit consists of a chopper-stabilized, recycling folded cascode IA, low-pass filter (LPF), ADC driving buffer, and 12-bit successive-approximation-register (SAR) analog-to-digital converter (ADC). The prototype readout circuit is implemented in a standard 0.18 µm CMOS process, with an active area of 12.5 mm². The measured input-referred noise at 1 Hz is 86.6 nV/√Hz and the noise efficiency factor (NEF) is 4.94, respectively. The total current consumption is 2.23 μA, with a 1.8 V power supply. Full article

(This article belongs to the Special Issue Selected Papers from IMETI 2021)

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15 pages, 4687 KiB

Open AccessArticle

Carbon Dioxide Adsorption on Carbon Nanofibers with Different Porous Structures

by Yu-Chun Chiang, Chih-Cheng Huang and Wei-Ting Chin

Appl. Sci. 2021, 11(16), 7724; https://doi.org/10.3390/app11167724 - 22 Aug 2021

Cited by 14 | Viewed by 3328

Abstract

Electrospinning techniques have become an efficient way to produce continuous and porous carbon nanofibers. In view of CO₂ capture as one of the important works for alleviating global warming, this study intended to synthesize polyacrylonitrile (PAN)-based activated carbon nanofibers (ACNFs) using electrospinning [...] Read more.

Electrospinning techniques have become an efficient way to produce continuous and porous carbon nanofibers. In view of CO₂ capture as one of the important works for alleviating global warming, this study intended to synthesize polyacrylonitrile (PAN)-based activated carbon nanofibers (ACNFs) using electrospinning processes for CO₂ capture. Different structures of PAN-based ACNFs were prepared, including solid, hollow, and porous nanofibers, where poly(methyl methacrylate) (PMMA) was selected as the sacrificing core or pore generator. The results showed that the PMMA could be removed successfully at a carbonization temperature of 900 °C, forming the hollow or porous ACNFs. The diameters of the ACNFs ranged from 500 to 900 nm, and the shell thickness of the hollow ACNFs was approximately 70–110 nm. The solid ACNFs and hollow ACNFs were microporous materials, while the porous ACNFs were characterized by hierarchical pore structures. The hollow ACNFs and porous ACNFs possessed higher specific surface areas than that of the solid ACNFs, while the solid ACNFs exhibited the highest microporosity (94%). The CO₂ adsorption capacity on the ACNFs was highly dependent on the ratio of V_{<0.7 nm} to V_t, the ratio of V_mi to V_t, and the N-containing functional groups. The CO₂ adsorption breakthrough curves could be curve-fitted well with the Yoon and Nelson model. Furthermore, the 10 cyclic tests demonstrated that the ACNFs are promising adsorbents. Full article

(This article belongs to the Special Issue Selected Papers from IMETI 2021)

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29 pages, 98559 KiB

Open AccessArticle

Isomorphic Circuits of Independent Amplitude Tunable Voltage-Mode Bandpass Filters and Quadrature Sinusoidal Oscillators

by San-Fu Wang, Hua-Pin Chen, Yitsen Ku and Wei-Yuan Chen

Appl. Sci. 2021, 11(16), 7431; https://doi.org/10.3390/app11167431 - 12 Aug 2021

Cited by 3 | Viewed by 2085

Abstract

This paper presents isomorphic circuits of voltage-mode (VM) non-inverting bandpass filters (NBPFs) and VM quadrature sinusoidal oscillators (QSOs) with independent amplitude control functionality. The proposed VM NBPFs and VM QSOs exhibit low-output impedance and independent amplitude control, which are important for easily cascading [...] Read more.

This paper presents isomorphic circuits of voltage-mode (VM) non-inverting bandpass filters (NBPFs) and VM quadrature sinusoidal oscillators (QSOs) with independent amplitude control functionality. The proposed VM NBPFs and VM QSOs exhibit low-output impedance and independent amplitude control, which are important for easily cascading the VM operation and independent control of the amplitude gain. The proposed isomorphic circuits employ three LT1228 commercial integrated circuits (ICs), two grounded capacitors, two grounded resistors and one floating resistor. The use of grounded capacitors is beneficial for the implementation of the IC. Both NBPFs have a high-input impedance and have a wide range of independent amplitude tunable passband gain without affecting the quality factor (Q) and center frequency (f_o). The Q and f_o parameters of the proposed NBPFs are orthogonal tunability. By feeding back each input signal to the output response of the NBPF, two VM fully uncoupled QSOs are also proposed. The proposed VM fully uncoupled QSOs have two quadrature sinusoidal waveforms with two low-output impedances and one independent amplitude tunable sinusoidal waveform. The frequency of oscillation (FO) and the condition of oscillation (CO) are fully uncoupled and controlled electronically. The performances of the proposed isomorphic circuits have been tested with a ±5 volt power supply and are demonstrated by experimental measurements which confirm the theoretical assumptions. Full article

(This article belongs to the Special Issue Selected Papers from IMETI 2021)

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20 pages, 8270 KiB

Open AccessArticle

Design and Experiment of Electronically Tunable Voltage-Mode Biquad and Output Current Amplitude Oscillator

by San-Fu Wang, Hua-Pin Chen, Yitsen Ku and Fang-Yu Liu

Appl. Sci. 2021, 11(16), 7357; https://doi.org/10.3390/app11167357 - 10 Aug 2021

Cited by 3 | Viewed by 1899

Abstract

This study presents an electronically tunable configuration for the design of a voltage-mode (VM) biquad with four input terminals and three output terminals. The proposed circuit employs four operational transconductance amplifiers (OTAs) and two grounded capacitors. Depending on the selections of the four [...] Read more.

This study presents an electronically tunable configuration for the design of a voltage-mode (VM) biquad with four input terminals and three output terminals. The proposed circuit employs four operational transconductance amplifiers (OTAs) and two grounded capacitors. Depending on the selections of the four input voltage signals, all the standard filtering functions can be realized. The proposed configuration simultaneously provides VM inverting band-pass, non-inverting low-pass, and non-inverting band-reject filtering functions without any component-matching choices. It offers the features of a resistorless structure, high-input impedance, electronic control of the pole frequency and quality factor, and low active and passive sensitivities. The measured power dissipation of the biquad is 0.96 W under 32 mA constant output current. The measured 1 dB power gain compression point of the output inverting band-pass filter is −7 dBm. The measured value of the third-order intercept point is 5.136 dBm, and the measured value of the third-order intermodulation distortion is −50.83 dBc. Moreover, the measured value of the spurious-free dynamic range is 53.49 dB, and the figure-of-merit of the biquad is 268.75 × 10³. In addition, an electronically controllable quadrature oscillator (QO) with amplitude of output current can be realized using the proposed biquad. The proposed electronically controllable QO can provide an amplitude modulation signal or an amplitude shift keying signal, and is widely applied in signal processing systems and electronic communication systems. PSpice simulations and experimental results are accomplished. Full article

(This article belongs to the Special Issue Selected Papers from IMETI 2021)

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