• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.5
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• pp.445-451
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• 2022

Ultrasonic sensor is suitable as a next-generation autonomous driving assist device because its lower price compared to that of other sensors and its sensing stability in the external environment. Although Pb(Zr, Ti)O₃ (PZT)-relaxor ferroelectric system has excellent piezoelectric properties, the change in capacitance is large in the daily operating temperature range due to the low phase transition temperature. Recently, many studies have been conducted to improve the temperature stability of ferroelectric ceramics by controlling the grain size and crystal structure, so it is necessary to study the effect of the grain size on the piezoelectric properties and the temperature stability of PZT-relaxor ferroelectric system. In this study, the piezoelectric properties, phase transition temperature, and temperature coefficient of capacitance (TCC) of 0.9 Pb(Zr_1-xTi_x)O₃-0.1 Pb(Zn_1/3Nb_2/3)O₃ (PZT_x-PZN) ceramics with various grain sizes were investigated. PZT_x-PZN ceramics with larger grain size showed higher piezoelectric properties and temperature stability, and are expected to be suitable for ultrasonic devices in the future.

• Journal of the Korea Society of Computer and Information
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• v.27 no.2
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• pp.9-14
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• 2022

In this study, we propose a method for moving a device such as a flexible air sculpture while stably maintaining the user's desired posture. To accomplish this, a robot system with a structure of a mobile robot capable of running according to a given trajectory was studied by applying the PI algorithm and horizontal maintenance posture control using IMU. The air sculptures used in this study often use thin strings in a fixed posture. Another method is to put a load on the center of gravity to maintain the posture, and it is a system with flexibility because it uses air pressure. It is expected that these structures can achieve various results by combining flexible structures and mobile robots through the convergence process of digital sensor technology. In this study, posture control was performed by fusion of the driving technology of AGV(Automatic Guided Vehicle),, a field of robot, and technologies applying various sensors. For verification, the given performance evaluation was performed through an accredited certification test, and its validity was verified through an experiment.

• Journal of the Korean Society of Industry Convergence
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• v.25 no.6_3
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• pp.1147-1154
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• 2022

Now that the development of autonomous driving is progressing, LiDAR has become an indispensable element. However, LiDAR is a device that uses lasers, and laser side effects may occur. One of them is the much-talked-about eye-safety, and developers have been satisfying this through laser characteristics and operation methods. But eye-safety is just one of the problems lasers pose. For example, irradiating a laser with a specific energy level or higher in a dusty environment can cause deterioration of the dust particles, leading to a sudden explosion. For this reason, the dust ignition proof regulations clearly state that "a source with a pulse period of less than 5 seconds is considered a continuous light source, and the average energy does not exceed 5 mJ/mm 2 or 35 mW" [2]. Energy of output optical power is limited by the law. In this way, the manufacturer cannot define the usage environment of the LiDAR, and the development of a LiDAR that can be used in such an environment can increase the ripple effect in terms of use in application fields using the LiDAR. In this paper, we develop a LiDAR with low optical power that can be used in environments where high power lasers can cause problems, evaluate its performance. Also, we discuss and present one of the directions for the development of LiDAR with laser power limited by dust ignition proof regulations.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.4
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• pp.723-730
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• 2023

Due to the recent development of battery technology, various types of means of transportation such as electric kickboards, Segways, and electric bicycles have emerged, which can be defined as Personal Mobility. In this paper, as the incidence of safety accidents increases due to the increase in the number of users of Personal Mobility, safety helmet devices that strengthen safety capabilities and peripheral recognition functions were studied. In order for the helmet to send a safety signal, Arduino was used as a base to set the value of the sensor according to changes in distance and angle using the ultrasonic sensor to minimize errors and ensure smooth recognition. In addition, a gyro sensor was used to turn on the direction indicator according to each slope. Using a CDS sensor, the LED is designed to turn on when it goes below 150 lux at night. Finally, it is possible to check whether a helmet is worn within 5cm, and when driving at an average speed, the direction indicator light is turned on at 10 degrees, and the LED is turned on at less than 150 lux.

• The Korean Journal of Emergency Medical Services
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• v.27 no.2
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• pp.7-17
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• 2023

Purpose: This study aimed to identify the factors that contribute to head injuries among drivers of personal mobility devices and provide insights into safety perceptions. Methods: This retrospective study analyzed data of 221 trauma patients obtained from electronic medical records and the National Emergency Department Information System (NEDIS) over one year, from August 1, 2021, to July 31, 2022. The patients, all in their 20s and 30s, presented to a single emergency medical center following personal mobility device accidents (motorcycles, electric scooters, and bicycles). Results: Among motorcycle riders, 18.2% were not wearing helmets, while the percentage of e-scooter riders not wearing helmets was 87.5%. Wearing a helmet was associated with a 71.2% lower likelihood of head injuries (OR=0.288, CI=0.163 to 0.509, p=0.000). Of the personal mobility devices, motorcycles had a 0.431 times lower odds ratio for head injury compared to e-scooters (p=0.009), and there was no significant difference between e-scooters and bicycles (p=0.776). Conclusion: It is imperative to strengthen safety regulations by mandating helmet use for riders of personal mobility devices. A system to enhance driving enforcement for electric scooters, which are increasingly popular among young adults, should also be established.

• Journal of the Microelectronics and Packaging Society
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• v.30 no.3
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• pp.88-93
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• 2023

As the demand for High Bandwidth Memory (HBM) increases and the handling capability of larger wafers expands, ensuring reliable Total Thickness Variation (TTV) measurement for stacked wafers becomes essential. This study presents the design of a measurement module capable of measuring TTV across the entire area of a 300mm wafer, along with estimating potential mechanical measurement errors. The module enables full-area measurement by utilizing a center chuck and lift pin for wafer support. Modal analysis verifies the structural stability of the module, confirming that both the driving and measuring parts were designed with stiffness exceeding 100 Hz. The mechanical measurement error of the designed module was estimated, resulting in a predicted measurement error of 1.34 nm when measuring the thickness of a bonding wafer with a thickness of 1,500 ㎛.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.5
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• pp.911-918
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• 2023

This paper analyzed technologies related to video and sound device manufacturing closely related to media images, divided applicants into companies, research institutes, universities, individuals and the public, and conducted technical statistical analysis, collective intelligence analysis, and open innovation analysis. It is necessary to express innovative ideas through technology in research institutes or universities, and efforts are needed to expand technologies in the media field in universities. Looking at the contents of patents actually filed, patents filed by companies or individuals were mostly related to media technology, and patents filed by universities and research institutes were mostly related to media content. This means that hardware technology patents should be developed extensively and in-depth in an inseparable relationship between media technology and content, and should be a driving force for software content to play a more diverse and creative role.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.22 no.6
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• pp.157-167
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• 2023

The use of big data for transportation often involves using data that includes personal information, such as the driver's driving routes and coordinates. This study explores the creation of a route choice prediction model using a large dataset from mobile navigation apps using federated learning. This privacy-focused method used distributed computing and individual device usage. This study established preprocessing and analysis methods for driver data that can be used in route choice modeling and compared the performance and characteristics of widely used learning methods with federated learning methods. The performance of the model through federated learning did not show significantly superior results compared to previous models, but there was no substantial difference in the prediction accuracy. In conclusion, federated learning-based prediction models can be utilized appropriately in areas sensitive to privacy without requiring relatively high predictive accuracy, such as a driver's preferred route choice.

• The Critical Review of Religion and Culture
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• no.25
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• pp.195-241
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• 2014

When the objective of a modern state focuses on securing basic human right of an individual and realizing public good in a state community, the direction of policy on religion of a state can not deviate far away from such objective. Meanwhile, the policy on religion of modern states today mostly takes the church and state separation principle as its basis. The states secure religious freedom and enforce the separation of church and state by differentiating religion and the mundane world and establishing the relation between the two. This study examined the church and state separation principle, which is an important system device of recent age nation-states, and explored the possibility of more active policy on religion. First, the relationship among religion, state and politics was examined from more structural and functional viewpoint. Next, how the separation of church and state principle has become recent age political principle and what was the settlement process of church and state separation in other countries are summarized. At last, the actual situation of church and state separation in Korea, the structural limitation of it and the direction of policy on religion are examined. The application experience of church and state separation principle is quite short in Korean society. In addition, when there is a religious issue, there is the trend of evading the issue unconditionally or responding to it passively. However, the religious culture in Korean society is one of the biggest cultural resources and social assets. Since it has big potential as driving force for the advance of state, it is regretful to leave religion alone as it is. Therefore, this study explored the original limitations of church and state separation principle which are limiting the religious policy of of state and searched for a theoretical basis for the utilization of resources in religious culture as driving force of state by overcoming the limitations. This study examined the situation in Korea by paying attention to how differently the church and state separation principle is being applied in other states, The separation of church and state, which is the basis of policy on religion in Korea, belongs to 'similar separation type' like in Japan; therefore, there is a trend of doctrinaire interpretation or arbitrary interpretation. This study suggests that it is required to overcome this limping state and settle down the church and state separation principle, which fits to Korean society, as a social and cultural practice. It is also suggested that more active policy on religion would be enforced by wider interpretation of church and state separation.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.6C
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• pp.295-304
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• 2012

In this study, a resonant column testing system which is the largest in Korea has been developed to evaluate the dynamic deformation characteristics of coarse granular geomaterials, and the performance and the applicability of the testing system have been verified. The system has been developed as a typical Stokoe type device whose boundary conditions are fixed bottom and free top with additional mass, and can adopt a large specimen with 200 mm in diameter and 400 mm in height. The driving and measurement instruments are configured as high performance and precision systems, hence the automated testing system is appropriate to drive enough stress and to measure the behavior precisely for the test in practical manner. The dynamic response of the mechanical components and the applicability of the system have been evaluated using metal specimens as well as polyurethane specimens, and its precision was verified by comparing its results with those from other equipment and/or methods. To confirm the applicability of the large system for coarse geomaterials, the resonant column test results from both large and normal scale apparatus for the same material were compared and it was found that the result can be partially affected by scale. Finally, the dynamic deformation characteristics of coarse geomaterial which is used for construction of large dam was evaluated using the large system and its practicality could be confirmed.