• Journal of the Optical Society of Korea
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• v.17 no.4
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• pp.336-343
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• 2013

Recently various types of driver assistance systems have been used for automobiles. In 2008, the U.S Congress passed a law which required that most cars be equipped with devices to warn objects behind the vehicle. Because of that, market of rear view cameras is expected to rise dramatically. Therefore many suppliers try to provide a wide angle camera for car makers. But a high distortion is caused by the wide angle might result in lower image quality. In order to improve the image quality, normally we use an algorithm to correct a distortion. Though we can improve the distorted image by correction algorithm, we must pay more cost to use it. In this paper, we propose a new optical system reducing a distortion in contrast to a conventional lens without cost. In other words, we can see only an area of interest. That is similar to reducing a field of view. Using a new optical system, we can get a less distorted image. In order to view an area of interest, we introduce an off axis optical system having refractive surfaces and reflective surfaces. In this paper, we describe the results of design and, evaluation of an off axis wide angle compact imaging system. In comparison to conventional wide angle lens, we can get the improvement of MTF, distortion, and lateral color aberrations. And we also can reduce a total cost because we don't need the outer apparatus or bracket to mount on the car.

• Journal of Digital Convergence
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• v.19 no.10
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• pp.133-141
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• 2021

Recently, the elderly who actively use the Internet and digital devices are increasing. This study aims to investigate the effect of the willingness to use technology, digital alienation and experience of assistant who help technology use on life satisfactions of elderly consumers who are considered to be the vulnerable in the use of information technology. A total of 311 elderly consumers over 60 who can utilize information technology were selected as a research sample and data were collected through an online survey. As a result, it was found that elderly consumers have a strong will to utilize information technology independently, perceive a low sense of digital alienation, and receive help from others when using technology. In addition, the lower the perceived digital alienation, the greater the experience of help from others in the use of technology, the higher the elderly consumers' life satisfaction significantly increased. This study is valuable in that it reveals the factors affecting the improvement of life satisfaction of elderly consumers in the high-tech environment and suggests political and practical implications.

• Convergence Security Journal
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• v.21 no.1
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• pp.55-62
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• 2021

Recently, the use of sensor devices is gradually increasing. As various sensor device emerge and the related technologies advance, there has been a dramatic increase in the interest in heterogeneous wireless sensor networks (WSNs). While sensor device provide us many valuable benefits, automatically and remotely supported services offered and accessed remotely through WSNs also exposes us to many different types of security threats. Most security threats were just related to information leakage and the loss of authentication among the involved parties: users, sensors and gateways. An user authentication protocol for wireless sensor networks is designed to restrict access to the sensor data only to user. In 2019, Chen et al. proposed an efficient user authentication protocol. However, Ryu et al. show that it's scheme still unstable and inefficient. It cannot resist offline password guessing attack and session key attack. In this paper, we propose an improved protocol to overcome these security weaknesses by storing secret data in device. In addition, security properties like session-key security, perfect forward secrecy, known-key security and resistance against offline password attacks are implied by our protocol.

• Journal of Periodontal and Implant Science
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• v.51 no.4
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• pp.276-284
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• 2021

Purpose: The aim of this randomized clinical trial was to assess whether chemical cleansing using a sulfonic/sulfuric acid gel solution (HBX) as an adjunct to scaling and root planing (SRP) resulted in a decrease in residual plaque and calculus in deep periodontal pockets compared to SRP alone. Methods: Fifty-six patients with 56 hopeless posterior teeth, scheduled for extraction due to severe periodontitis, were enrolled in this study. Each tooth was randomly assigned to 1 of the 2 experimental procedures. The test teeth were subjected to the irrigation of the subgingival area with HBX for 2 minutes, followed by SRP with hand and ultrasonic instruments for 14 minutes, and then extracted. The control teeth received only mechanical instrumentation before extraction. Residual biofilm was evaluated on photographs and measured as total area and percentage of root surface covered by remaining plaque (RP) or calculus (RC) after treatment. Results: The initial pocket depth (PD) and total subgingival root surface area were similar between the 2 treatment groups. After treatment, the total subgingival root area covered by RP and RC was statistically significantly larger (P<0.001) in the control group than in the test group. The test teeth showed a lower percentage of RP, but a higher percentage of RC than the control teeth (both P<0.001). Complete calculus removal was achieved in 42% of the control teeth surfaces and in 25% of the test teeth surfaces for a PD of 4 mm. Conclusions: The additional chemical cleansing with HBX resulted in a statistically significant improvement in bacterial plaque removal during SRP of deep pockets, but it was not effective in reducing calculus deposits.

• Journal of the Korea Convergence Society
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• v.12 no.5
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• pp.31-38
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• 2021

Recently, devices that help the general public's urination activity have been developed, but products that take into account the user's urination habits, device functions, and user accessibility are still insufficient. This study conducted a usability evaluation to find user satisfaction and improvement points of products based on smart automatic urine disposer that have convergence and complex functions such as automatic suction functions. There are 21 indicators used in usability evaluation, and were developed based on safety, operability, and satisfaction. As a result, functional satisfaction was high, but in terms of design, problems to be improved such as handles were presented. Therefore, through this study, it was found that the satisfaction of the automatic urine disposer in terms of performance cannot be representative of the product, and the importance of developing usability evaluation index to find product problems.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.21 no.6
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• pp.141-145
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• 2021

Various types of memory architectures have been developed, and various compiler optimization techniques have been studied to efficiently use them. In particular, since a memory is a major component that determines performance in mobile computing devices, various optimization techniques have been developed to support them. Recently, a lot of research on hybrid type memory architecture is being conducted, so various compiler techniques are being studied to support it. Existing compiler optimization techniques can be used to achieve the required minimum performance and constraint on low power according to market requirements. References for determining the low-power effect and the degree of performance improvement using these optimization techniques are not properly provided yet. This study was conducted to provide the experimental results of the existing compiler technique as a reference for the development of multibank memory architecture.

• Journal of the Society of Naval Architects of Korea
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• v.55 no.6
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• pp.474-481
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• 2018

This paper is to compare by numerical analysis the flow characteristics and propulsion performance of stern with the shape change of K-duct, a pre-swirl duct developed by Korea Research Institute of Ships & Ocean Engineering (KRISO). First, the characteristics of the propeller and the resistance and self-propulsion before and after the attachment of the K-duct to the ship were verified and the validity of the calculation method was confirmed by comparing this result with the model test results. After that, resistance and self-propulsion calculations were performed by the same numerical method when the K-duct was changed into five different shapes. The efficiency of the other five cases was compared using the delivery horsepower in the model scale and the flow characteristics of the stern were analyzed as the velocity and pressure distributions in the area between the duct end and the propeller plane. For the computation, STAR-CCM +, a general-purpose flow analysis program, was used and the Reynolds Averaged Navier-Stokes (RANS) equations were applied. Rigid Body Motion (RBM) method was used for the propeller rotating motion and SST $k-{\omega}$ turbulence model was applied for the turbulence model. As a result, the tangential velocity of the propeller inflow changed according to the position angle change of the stator, and the pressure of the propeller hub and the cap changes. This regulated the propeller hub vortex. It was confirmed that the vortex of the portion where the fixed blade and the duct meet was reduced by blunt change.

• Journal of Convergence for Information Technology
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• v.8 no.6
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• pp.149-157
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• 2018

In this paper, we propose an attack detection technology using SDN Controller to study security threats in IoT environment. The research methodology has been developed by applying IoT security threat management technology to the IoT layer and analyzing the research trend of applied security technology. The study results show that the effectiveness of the detection method using the sampling method is studied by adding OpenFlow based SDN Controller to the network switch equipment of the existing IoT network. This method can detect the monitoring and attack of the whole network by interworking with IDS and IPS without affecting the performance of existing IoT devices. By applying such improved security threat countermeasure technology, we expect to be able to relieve anxiety of IoT security threat and increase service reliability.

• The Journal of the Korea Contents Association
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• v.19 no.7
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• pp.650-658
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• 2019

This study sought to examine and revise the 'Multicultural Family Support Act' for domestic multicultural families. To this end, we looked at the Multicultural Family Support Act along with the current status and support policies of multicultural families. First, as in Article 1 of the Act, it proposed to reflect Article 3 of the Article 5(basic ideas) to realize the purpose of the law contributing to 'improvement of quality of life' and 'social integration'. Second, the current law stipulates that support and related policies should be implemented every five years, and by conducting planning and due diligence surveys every three years, it suggested the necessity of consensus on the disagreement between the support policy and the planning period. Third, the government proposed a revision to the mandatory regulation (that is, it should be done) under the provisions set by law. Finally, we proposed a plan to designate 'Multicultural Family Day' or to designate it with other family days. As the globalization of the members of each country, which has been rapidly continuing in the 21st century, it is expected that Korea will be able to welcome them and review the act and institutional devices that can be together more than ever.

• Korean Journal of Materials Research
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• v.28 no.11
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• pp.680-684
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• 2018

We investigate the effect of light intensity and wavelength of a solar cell device using photoconductive atomic force microscopy(PC-AFM). A $POCl_3$ diffusion doping process is used to produce a p-n junction solar cell device based on a polySi wafer, and the electrical properties of prepared solar cells are measured using a solar cell simulator system. The measured open circuit voltage($V_{oc}$) is 0.59 V and the short circuit current($I_{sc}$) is 48.5 mA. Moreover, the values of the fill factors and efficiencies of the devices are 0.7 and approximately 13.6 %, respectively. In addition, PC-AFM, a recent notable method for nano-scale characterization of photovoltaic elements, is used for direct measurements of photoelectric characteristics in limited areas instead of large areas. The effects of changes in the intensity and wavelength of light shining on the element on the photoelectric characteristics are observed. Results obtained through PC-AFM are compared with the electric/optical characteristics data obtained through a solar simulator. The voltage($V_{PC-AFM}$) at which the current is 0 A in the I-V characteristic curves increases sharply up to $18W/m^2$, peaking and slowly falling as light intensity increases. Here, $V_{PC-AFM}$ at $18W/m^2$ is 0.29 V, which corresponds to 59 % of the average $V_{oc}$ value, as measured with the solar simulator. Furthermore, while the light wavelength increases from 300 nm to 1,100 nm, the external quantum efficiency(EQE) and results from PC-AFM show similar trends at the macro scale but reveal different results in several sections, indicating the need for detailed analysis and improvement in the future.