• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.7
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• pp.567-575
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• 2014

This paper suggests an installation procedure of a smart skin prototype into an aircraft, flight demonstration test procedures and test results. Four communication and navigation antennas are embedded into one Conformal Load-bearing Antenna Structure(CLAS). Log periodic patch type antenna was designed as a multi-band antenna to cover four antenna frequency bands. The requirements of CLAS were verified by ground tests before aircraft installation. A CLAS speed-brake was installed into KT-1 aircraft and performances of dual antennas were verified as multi-antenna tests on the ground. Electromagnetic compatibility tests were conducted to check compatibility between the CLAS and all existing equipments. Flight demonstration tests were conducted by one sortie of flight test for one antenna. The activeness and continuity of communication and navigation signal during the flight, null area of antenna signal along the circling flight were monitored. The embedded antennas worked better than expected during four sorties of flight tests.

• 한국지구물리탐사학회:학술대회논문집
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• 2008.10a
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• pp.41-46
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• 2008

After choosing twenty sluice culverts located at national rivers by detailed appearance evaluation, hydraulic response test and acoustic televiewer in addition to surface geophysical explorations were carried out to investigate the cavities which exist at the boundary of sluice culvert and ground. Tapping, GPR, 3-D resistivity surveys and acoustic televiewer imagery obtained successful results in limited conditions according to characteristics of the sites. On the other hand, hydraulic response test successfully detected cavity existing at the lower part of sluice culvert and its continuity. However, hydraulic response test can not supply the quantitative informations on the scale and the shape of cavity. Thus it is very important for accurate investigation to make comprehensive interpretation after supplying various surveys proper to site characteristics.

• Journal of the Korea Convergence Society
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• v.12 no.2
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• pp.135-146
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• 2021

In this study, in order to provide an app with improved usability to users in the trend of gradually increasing the number of users of music streaming services, usability tests were conducted by conducting interviews before and after the execution of the screen test technique and the performance measurement method and contextual. Usability test was conducted using the Inquiry method. Usability tests were conducted by one user each from their teens to their 50s, and were conducted on Melon, YouTube Music, Genie, and FLO apps with many service users. As a result of the usability test, the icon does not sufficiently represent the function and is not recognized as an interactive button, which is overlooked by the user, the problem that the user does not recognize due to lack of visual effect when the function is activated, The problem was derived. In this regard, suggestions for improving the user screen, such as intuitively changing the icon for each app, adding a visual effect of the screen when the function is activated, and adjusting the position so that the function has continuity, were presented along with the visual data.

• Journal of Korean Academy of Nursing
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• v.45 no.2
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• pp.251-261
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• 2015

Purpose: The purpose of this study was to develop an integrated internet addiction prevention program and test its effects on the self-regulation and internet addiction of elementary students who are at risk for internet addiction. Methods: A quasi-experimental study with a non-equivalent control group pretest-posttest design was used. Participants were assigned to the experimental group (n=28) or control group (n=28). Contents of the program developed in this study included provision of information about internet addiction, interventions for empowerment and methods of behavioral modification. A pre-test and two post-tests were done to identify the effects of the program and their continuity. Effects were testified using Repeated measures ANOVA, simple effect analysis, and Time Contrast. Results: The self-regulation of the experimental group after the program was significantly higher than the control group. The score for internet addiction self-diagnosis and the internet use time in the experimental group were significantly lower than the control group. Conclusion: The effects of the integrated internet addiction prevention program for preventing internet addiction in elementary students at risk for internet addiction were validated.

• Structural Engineering and Mechanics
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• v.21 no.5
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• pp.539-551
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• 2005

Finite elements based on isoparametric formulation are known to suffer spurious stiffness properties and corresponding stress oscillations, even when care is taken to ensure that completeness and continuity requirements are enforced. This occurs frequently when the physics of the problem requires multiple strain components to be defined. This kind of error, commonly known as locking, can be circumvented by using reduced integration techniques to evaluate the element stiffness matrices instead of the full integration that is mathematically prescribed. However, the reduced integration technique itself can have a further drawback - rank deficiency, which physically implies that spurious energy modes (e.g., hourglass modes) are introduced because of reduced integration. Such instability in an existing stiffness matrix is generally detected by means of an eigenvalue test. In this paper we show that a knowledge of the dimension of the solution space spanned by the column vectors of the strain-displacement matrix can be used to identify the instabilities arising in an element due to reduced/selective integration techniques a priori, without having to complete the element stiffness matrix formulation and then test for zero eigenvalues.

• Transactions of the Korean hydrogen and new energy society
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• v.26 no.4
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• pp.386-392
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• 2015

Flow characteristics inside a 10 inch ball valve have been analyzed using three-dimensional numerical analysis and experiments. Continuity and three-dimensional Reynolds-averaged Navier-Stokes equations have been used as governing equations for the numerical analysis. The numerical model has been constructed through the grid dependency test and validation with the results of experiments to ensure reliability and numerical effectiveness. The shear stress transport (SST) model has been used as the turbulence closure. The experimental test-rig has been constructed to measure pressure, temperature and flow rate along the pipeline. Some valve opening angles have been tested to evaluate the flow characteristics inside the ball valve and pipeline. The results show that the rapid pressure variations is observed while the valve opening angle decreases, which caused by flow separation at the downstream of the ball valve.

• Journal of Ocean Engineering and Technology
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• v.20 no.2 s.69
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• pp.66-71
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• 2006

To develope a hull form of catamaran type dredging vessel, resistance characteristics is investigated to find the interaction effect of waves between the two hulls. Re fore body shape is simplified as two dimensional wedge shape for the maintenance and disassembly/assembly. Based on MAC method, numerical simulation is performed in staggered variable mesh system. Re conservation form of Euler equations and continuity equation are applied as governing equations. To verify numerical methods, the wive patterns along the hull surface are compared with the results of model tests. This study is performed as varying wedge shape of the bow and the distance between the two hulls. The wave interaction between two hulls are observed to investigate the relation the resistance performance and the flow characteristics. Suitable hull form and distance between two hulls are discussed.

• International Journal of Highway Engineering
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• v.18 no.2
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• pp.51-60
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• 2016

PURPOSES : The applicability of the mechanics-based similarity concept (suggested by Feng et al.) for determining scaled variables, including length and load, via laboratory-scale tests and discrete element analysis, was evaluated. METHODS: Several studies on the similarity concept were reviewed. The exact scaling approach, a similarity concept described by Feng, was applied in order to determine an analytical solution of a free-falling ball. This solution can be considered one of the simplest conditions for discrete element analysis. RESULTS : The results revealed that 1) the exact scaling approach can be used to determine the scale of variables in laboratory tests and numerical analysis, 2) applying only a scale factor, via the exact scaling approach, is inadequate for the error-free replacement of small particles by large ones during discrete element analysis, 3) the level of continuity of flowable materials such as SCC and cement mortar seems to be an important criterion for evaluating the applicability of the similarity concept, and 4) additional conditions, such as the kinetics of particle, contact model, and geometry, must be taken into consideration to achieve the maximum radius of replacement particles during discrete element analysis. CONCLUSIONS : The concept of similarity is a convenient tool to evaluate the correspondence of scaled laboratory test or numerical analysis to physical condition. However, to achieve excellent correspondence, additional factors, such as the kinetics of particles, contact model, and geometry, must be taken into consideration.

• Archives of Craniofacial Surgery
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• v.20 no.3
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• pp.164-169
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• 2019

Background: The conventional surgical method for reconstructing orbital floor fractures involves restoration of orbital continuity by covering an onlay with a thin material under the periorbital region. However, in large orbital floor fractures, the implant after inserting is often dislocated, leading to malposition. This study aimed to propose a novel implanting method and compare it with existing methods. Methods: Among patients who underwent surgery for large orbital floor fractures, 24 who underwent the conventional onlay implanting method were compared with 21 who underwent the novel ${\gamma}$ implanting method that two implant sheets were stacked and bent to resemble the shape of the Greek alphabet ${\gamma}$. When inserting a ${\gamma}$-shaped implant, the posterior ledge of the orbital floor was placed between the two sheets and the bottom sheet was impacted onto the posterior wall of the maxilla to play a fixative role while the top sheet was placed above the residual orbital floor to support orbital contents. Wilcoxon signed-rank test and Mann-Whitney U test were used for data analyses. Results: Compared to the conventional onlay method, the gamma method resulted in better restoration of orbital contents, better improvement of enophthalmos, and fewer revision surgeries. Conclusion: Achieving good surgical outcomes for extended orbital floor fractures is known to be difficult. However, better surgical outcomes could be obtained by using the novel implantation method of impacting a ${\gamma}$-shaped porous polyethylene posteriorly.

• The Korean Journal of Nuclear Medicine Technology
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• v.27 no.1
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• pp.55-61
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• 2023

Purpose In this study, the monthly population distribution was calculated for statistical verification of 10 tests (CA19-9, CA15-3, testosterone, PTH, calcitonin, AFP, CEA, CA72-4, PSA, estradiol) with changed reagents, and the trend of change By comparing and analyzing the results, we want to verify the accuracy of the results and improve the reliability of the test. Materials and Methods From June 2021 to February 2023, for the 10 items in which the reagent was changed, the monthly percentage and standard deviation index before and after the reagent change were compared, respectively. At this time, the reference value was arbitrarily set for the comparison group in consideration of the reference value of the test item, and the groups were subdivided and compared, and the standard deviation index allowed range was -2.0 or more and 2.0 or less. Results For CA19-9, CA15-3, AFP, CEA, and calcitonin 5 test items, the change in monthly ratio in all test sections before and after the reagent change was kept constant. On the other hand, for CA72-4, PSA, testosterone, PTH, and estradiol items, the standard deviation index exceeded the acceptable standard after changing the reagent. CA72-4 test items showed an increasing trend in standard deviation index in the test section exceeding the reference value. In the case of the PSA test item, the maintenance ratio of 0.04 ng/mL was significantly decreased after changing the reagent. The testosterone test item had a standard deviation index of -2.5 in the test section exceeding 10.1 ng/mL after changing the reagent, and the standard deviation index of the PTH test item was out of the acceptable range in all test sections. It was confirmed that the estradiol test item showed an overall increase in the result value. Conclusion Through this study, the continuity and accuracy of the test results could be verified. It is considered that the stability of the test can be secured by analyzing the factors affecting the test result and solving the cause for the test item whose standard deviation index is out of the acceptable standard.