• The Journal of the Korea Contents Association
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• v.8 no.4
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• pp.92-99
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• 2008

Most of existing Ceramic bottle has a problem because of the entrance facing the upper, and then having the entrance exposed in the outside. This study has made up for this problem and manufactured a bottle having dual structure. This bottle contains the contents being poured, has the containing part having the entrance in the lower part, multiple connecting passage hole connected with the water containing part in the upper, and the storage part, keeping contents, located in the circumference of the water containing part. The tail end of the entrance of the water containing part is located more upper than the lower part of a storage part, being at the bottom. This bottle has a dual structure of which the entrance faces the lower part. So, because of checking a foreign substance to be inflowed, restraining the diffusion of an alcohol ingredient, it is possible to have the custody of products, having alcohol element, and other contents for a long time. And then, the water containing part, through the connecting hole, always can pour the contents of a certain level in a cup or bowl. Accordingly, the purpose of this study is to make a convenient, a practicable bottle with having settled problems of customary know-how explained previously.

• Journal of the Korean GEO-environmental Society
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• v.17 no.9
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• pp.13-20
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• 2016

This study carried out field measurements of rock drilling where two PRD (Percussion Rotary Drilling) methods, T-4 drilling method and dual drilling method, were considered and the study examined the characteristics of vibration level, noise level, drilling speed, and drillig verticality of the two method. The results of field measurements were compared and analyzed in details to provide the drilling information so that the problems due to rock drilling is minimized and the drilling efficiency is improved in the future. The limited measurements in the field indicated that the dual drilling method showed lower vibration and noise levels and better drilling speed and verticality.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.9
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• pp.34-40
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• 2005

In present study, a two dimensional unsteady Navier-Stokes solver has been developed using the Diagonalized ADI (DADI) method and implicit dual time stepping method. The jacobian matrices in steady state Navier-Stokes equations are introduced from inviscid flux terms. The implicit treatment of artificial dissipation terms results in a block penta-diagonal matrix system and it becomes a scalar penta-diagonal matrix by diagonalization. In steady state equations about fictitious time, a new residual including a real time derivative term is introduced. From a converged solution about fictitious time, a real time unsteady solution can be obtained, which is called 'implicit dual time stepping method'. For code validation, an oscillating flat plate, a regular Karman vortices past a circular cylinder and shock buffeting around a bicircular airfoil problems are numerically solved. And they are compared with a theoretical solution, experiments and other researcher's computations.

• Archives of Craniofacial Surgery
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• v.15 no.2
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• pp.82-88
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• 2014

Background: The chin shape and position is important in determining the general shape of the face, and augmentation genioplasty is performed alone or in combination with other aesthetic procedures. However, augmentation genioplasty using osteotomy is an invasive and complex procedure with the potential to damage mentalis muscle and mental nerve, to affect chin growth, and prolonged recovery. Our aim was to present our experience with a modified augmentation genioplasty procedure for hypoplastic chins using a Gore-Tex implant. Methods: Two vertical slit incisions were made at the canine level to create a supra-periosteal pocket between the incisions, preserving the periosteum and mentalis muscle. Minimal sub-periosteal dissection was performed lateral to the incisions along the mandibular border. The both wings of implant were inserted under the periosteum to achieve a stable dual plane implantation. Results: In total, 47 patients underwent dual plane chin augmentation using a Gore- Tex implant between January 2008 and May 2013. The mean age at operation was 25.77 years (range, 15-55 years). There were 3 cases of infection; one patient was treated with antibiotics, the others underwent implant removal. Additionally, two patients complained of postoperative parasthesia that spontaneously improved without any additional treatment. Most patients were satisfied with the postoperative outcomes, and no chin growth problems were observed among the younger patients. Conclusion: Dual plane Gore-Tex chin augmentation is a minimally-invasive operation that is simple and safe. All implants yielded satisfactory results with no significant complications such as mental nerve injury, lower lip incompetence, or chin growth limitation.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.29 no.2
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• pp.417-429
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• 2019

WPA2-PSK uses a 4-way handshake protocol based on a shared secret to establish a secure session between a client and an AP. It has various security problems such as eavesdropping attacks and the secure session establishment process is inefficient because it requires multiple interactions between client and AP. The WPA3 standard has recently been proposed to solve the security problem of WPA2, but it is a small improvement using the same 4-way handshake methodology. OAuth 2.0 token authentication is widely used on the web, which can be used to keep an authenticated state of a client for a long time by using tokens issued to an authenticated client. In this paper, we apply the dual-token based randomized token authentication technology to the Wi-Fi security protocol to achieve an efficient Wi-Fi security protocol by dividing initial authentication and secure session establishment. Once a client is authenticated and equipped with dual tokens issued by AP, it can establish secure session using them quickly with one message exchange over a non-secure channel.

• Journal of Engineering Education Research
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• v.23 no.6
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• pp.17-26
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• 2020

In this paper, the effect of daily creativity of engineering students on problem-solving ability is addressed through the dual mediating effect of teamwork competency and self-directed learning ability. To this end, a regression-based statistical mediation analysis has been performed on the dual mediation model in which daily creativity and problem solving ability were treated as independent and dependent variables respectively, and teamwork competence and self-directed learning ability were included as mediation variables. The analysis result confirmed that the daily creativity has direct effect on the problem-solving ability, as well as indirect effects through teamwork competence and self-directed learning ability. In particular, the serial mediating effect of teamwork competency and self-directed learning ability was also confirmed to be statistically significant in the relationship between daily creativity and problem-solving ability. This verifies that problem-solving ability can be improved not only directly by improving daily creativity but also indirectly by improving teamwork competence and self-directed learning ability. In addition, teamwork competency showed greater indirect effect on problem-solving ability than self-directed learning ability, so increasing teamwork competency has a more significant effect on improving problem-solving ability than increasing self-directed learning ability. Therefore, in order to develop better problem-solving ability, it is necessary to identify and improve the learners' teamwork competency first and to strive to create an environment where learners can solve problems based on mutual trust with their teammates.

• Korean Journal of Childcare and Education
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• v.10 no.6
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• pp.265-289
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• 2014

This study analyzed the change of after-school guardians' absence types during the first 3 school years, and the relations of after-school care, family environment(family income, parental monitoring) to self-regulatory learning ability and emotional-behavioral problems in each gender of early school-age children from dual income families. The data from 526 boys and 483 girls among 3rd graders of Korean Child and Youth Panel Survey(KCYPS) were statistically analyzed by Friedman's test, t-test, correlational coefficient analysis, regression analysis. The results showed that 45% of boys and 50% of girls were with a guardian for their after-school care in each of the first 3 school years and after-school care had changed gradually into the types of temporal or contingent absence of a guardian. Family income and children's self-regulatory learning ability were different from adult-care and self-care in each gender, but there were differences in the parental monitoring of girls and emotional-behavioral problems of boys according to the care types. Both of boys and girls showed that family environment meaningfully related with the ability and the problems, and also showed the relatively different effects of after-school care and family environment on those ability and problems variables. The results suggested some implications for after-school care.

• Journal of Electrical Engineering and Technology
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• v.12 no.1
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• pp.45-52
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• 2017

This paper deals with the operation strategy of reactive power in a multi-infeed HVDC (MIHVDC) system, in which several converters are connected to the same or nearby separate AC buses. The potential problems concerning a MIHVDC system when feeding a weak AC network are as follows: the need for coordination of the recovery control, the possibility of voltage instability or low quality of the area connected to the MIHVDC system, and the risk of mutual commutation failures. These problems in MIHVDC systems are similar to those in single-infeed HVDC (SIHVDC) systems, but the differences with the phenomenon of the SIHVDC system are the interactions between converters. The main reason for the potential problems of HVDC systems (MIHVDC or SIHVDC) is voltage variation; therefore, to mitigate the voltage variations, the performances of the HVDC system should be enhanced. Consequently, to mitigate the potential problems of MIHVDC systems, several solutions are suggested in this study, including installing STATCOM and installing a line arrester on the tower. The study results will be applied to a multi-infeed HVDC system in Korea.

• Journal of Advanced Navigation Technology
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• v.15 no.5
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• pp.781-788
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• 2011

A sphere-packing problem is to find an arrangement of the spheres to fill as large area of the given space as possible, and covering problems are optimization problems which are dual problems to the packing problems. We generalize the concepts of the weight and the Hamming distance for a binary code to those of Boolean algebra. In this paper, we define a weight and a distance on a Boolean algebra and research some properties of the weight and the distance. Also, we prove the notions of the sphere-packing bound and the Gilbert-Varshamov bound on Boolean algebra.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.678-681
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• 2003

In conventional optical data storage numerical aperture (NA) cannot be over 1 because of diffraction limit. To overcome this limitation. solid immersion lens(SIL) have produced a great interest in near-field optical data storage. In conventional optical recording method, the dual lens system using object lens and SIL had been studied generally. But the conventional SIL system has some critical problems that must be solved. The problems are heat, contamination. alignment of optical components and so on. To solve these problems. this work proposes enhanced SIL which has several advantages for mechanical and optical issues. This new SIL system named elliptic SIL(ESIL) can use evanescent energy in near-field more effectively. In addition. because of applying the inside recording unlike previous surface recording, ESIL can clear up the problems. The design and analysis of ESIL art executed by using CODE V. Also, in this paper we composed actual data recording system and achieved recording experiment by applying ESIL to magneto-optical recording. In conclusion. we analyze the improvement of aerial density and the reasonability of application to real data storage system.