• The Journal of Korean Academy of Prosthodontics
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• v.9 no.1
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• pp.29-34
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• 1969

Occlusal force is a critical factor affecting the condition and structure of the periodontium. When the occlusal forces exceed the physiologic adaptive capacity of the tissues, tissue damage ensues. Such damage is referred to as trauma from occlusion. Excessive pressure causes compression, degeneration and realignment of the periodontal ligament fibers so that they are paralleled perpendicular to the tooth and bone. By inducing excessive occlusal forces with a high amalgam filling on rat's molar, the author observed histologic alterations of the periodontal ligament fibers by means of Hematoxylin-eosin, Van Gieson and Aldenyde fuchsin stainings. The results of the study were observed as follows: 1) The excessive occlusal forces altered arrangement of the collagenous fibers. 2) The arrangement of the oblique fibers showed appreciable differences between the control group and the group subjected to 10 days experimental trauma from occlusion. 3) The realignment of the transseptal fibers was not found. 4) The arrangement of the oblique fibers after 15 days of trauma from occusion was similar to that of 10 days experimental group. 5) The oxytalan fibers were more abundant at the cementum rather than at the alveolar bone. 6) The excessive occlusal forces produced funnel-shaped widening of the oxytalan fibers, which followed wavy course. 7) The oxytalan fibers appeared to be distributed mainly around the middle third of the root rather than that of the apical third of the root during the experimental trauma from occlusion.

• Journal of Applied Reliability
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• v.14 no.2
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• pp.97-102
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• 2014

Radar is an object-detection system that uses radio waves to determine the range, altitude, direction, or speed of objects. High power amplifier Module is the most critical part of the high-power radar transmitter systems. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. Research related to radar has been conducted in various fields according to improvement of the communication technology. But only performance-originated technology development has been dashed; study concerning environment duality and safety concerning reliability are still insufficient. In general, radar module is exposed to the outside, on the means of moving or fixed in a certain place. It should be guaranteed sufficient immunity for a variety of environmental stresses that can occur in the outdoor. HALT is a great process used for quickly finding failure mechanisms in a hardware design and product. By applying various kinds and extreme level of stresses, we can find the operating limits of products. In thesis, we conducted HALT test of the high power amplifier modules which used in military and automotive radar. After the test, we analyzed environmental weaknesses of high power amplifier modules using conventional construction data.

• Journal of the Korea Society of Computer and Information
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• v.10 no.5 s.37
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• pp.251-258
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• 2005

In this paper, we investigate the strategy for the promotion of IT industry in Yongin region and suggest some directions for operations strategy of them. we divide the strategy into centralization of supporting facilities , construction of supporting network, development of lesion based firm, and modernization of marketing/logistics based on the result of the Previous study on the 19 critical success factors. The strategy foactors are analyzed by AHP and evaluated by the three groups(IT firms, local government official worker, professor) which have an influence on IT policy. This research contribute to assist planners and policy-makers in supporting IT industry by providing useful information about the suggested strategy, and by suggesting the effective means to assist the IT industry.

• Journal of the Korea Institute of Building Construction
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• v.12 no.6
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• pp.636-647
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• 2012

Construction projects have become so large, complicated and incredibly high-tech that process management is currently considered one of the most important issues. Unlike typical manufacturing industries, most major construction activities are performed in the open air and thus are exposed to various environmental factors. Many studies have been conducted with the goal of establishing efficient techniques and tools for overcoming these limitations. Productivity analysis and prediction, one of the related research subjects, must be considered when evaluating approaches to reducing construction duration and costs. The aim of this research is to present a quantified impact analysis of construction delay factors on construction productivity of a steel staircase system, which has been widely applied to high rise building construction. It is also expected to improve the process by managing the factors, ultimately achieving an improvement in construction productivity. To achieve the research objectives, this paper analyzed different delay factors affecting construction duration by means of multiple regression analysis focusing on steel staircase systems, which have critical effects on the preceding and subsequent processes in structure construction. Statistical analysis on the multiple linear regression model indicated that the environment, labor and material delay factors were statistically significant, with 0.293, 0.491, and 0.203 as the respective quantified impacts on productivity.

• International Journal of Fluid Machinery and Systems
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• v.8 no.2
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• pp.94-101
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• 2015

To investigate the influence of blade profiles on cavitation behavior in impeller of centrifugal pump, a centrifugal pump with five different blade profiles impellers are studied numerically. The impellers with five different blade profiles (single arc, double arcs, triple arcs, logarithmic spiral and linear-variable angle spiral) were designed by the in-house hydraulic design code using geometric parameters of IS 150-125-125 centrifugal pump. The experiments of the centrifugal pump have been conducted to verify numerical simulation model. The numerical results show that the blade profile lines has a weak effect on cavitation inception near blade inlet edge position, however it has the key effect on the development of sheet cavitation in impeller, and also influences the distribution of sheet cavitation in impeller channels. A slight changing of blade setting angle will induce significant difference of cavitation in impeller. The sharp changing of impeller blade setting angle causes obvious cavitation region separation near the impeller inlet close to blade suction surface and much more flow loss. The centrifugal pump with blade profile of setting angle gently changing (logarithmic spiral) has the super cavitation performance, which means smaller critical cavitation number and lower vapor cavity volume fraction at the same conditions.

• The Journal of Information Systems
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• v.18 no.3
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• pp.111-134
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• 2009

Today many owners of Web sites are looking to user's satisfaction survey as a key means of measuring the usability of a Web site. While it is preferred for it simplicity and ease of use, this survey method is not without potential risks. This paper focuses on showing that the existing practice of questionnaire-based usability measurement is subject to human recall errors, and that such flaws can be reduced when the questionnaire survey is followed by the users hands-on experience of the site. An empirical study was conducted, and the results indicate that the above speculation holds true. Even if respondents felt highly confident about their responses on a recall survey, a hands-on experience with a focal Web site increased the extent to which the respondents were satisfied with the shopping mall site. This indicates that a user's perception of the quality of a Web site may be distorted or lost as time goes by. In addition, the findings have shown that the use of the verbal protocol analysis method can reveal critical information that can help track the root causes of Web site usability problems, thereby helping to develop site enhancement strategies. The paper concludes with directions for future research.

• The Journal of Korean Association of Computer Education
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• v.7 no.3
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• pp.23-33
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• 2004

In the knowledge-based society, ICT should take an integral part in K-12 curriculum. The purpose of this paper was to investigate the means to integrate ICT into K-12 curriculum. For the purpose, we reviewed the current national curriculum in light of ICT use. From the review, we identified that the recently revised 7th national curriculum reflected the necessity of using ICT in the view point of knowledge-based society, but it did not include the ICT specifically as a critical element of the curriculum. We discussed the meaning of ICT integrated curriculum, and also the role of ICT as a component of the curriculum. Finally, we suggested the direction of restructuring the curriculum as we consider integrating ICT into it.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.05a
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• pp.639-642
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• 2015

As attack to routing function on MANET(Mobile Ad-Hoc Network), hole attack make cause some critical effects. MANET is easily influenced with hole attack and can be critically effected on transmission performance, because it is configured with terminal device as temporary network and dose not have effective means for malicious attack. In this paper, effects of grayhole attack to network performance on MANTE is analyzed with computer simulation. Voice traffic is used in simulation, effects of grayhole attack is compaerd with blackhole attack. The method and result of this paper can be used for data to study grayhoke attack.

• Journal of the Korean Institute of Educational Facilities
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• v.25 no.3
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• pp.13-24
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• 2018

Unlike other educational spaces in school facilities, restrooms have remained unpleasant spaces without reflecting the change in social awareness and students' lifestyle. In the process of the 'School Restroom Environment Remodeling Project in Seoul' by means of "user participatory design method", this study aimed to suggest a design of the school restroom environment responding to the different needs of actual users, who are students and school staffs. By surveying them, it was revealed that they have a variety of respective behavioral patterns and spatial needs according to their status, gender, age and working period. Implications of this study are as follows; First, it is necessary to establish a separate restroom facility standards that respond to the characteristics of elementary school students. Second, there should be an expansive approach to widely accommodate with the users' needs that were found out through 'user participation', more than just repairing pre-existing space. Third, it needs to have critical review of the maintenance and operation system itself as well as the improvement of the school restroom environment.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.2
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• pp.111-114
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• 2017

In this research, the development of fabrication technique of bulk YBaCuO superconductors for application was studied. In fluence of $BaZrO_3$ addition on magnetization characteristics of thermal pyrolysis textured YBaCuO superconductor was investigated. Fine $BaZrO_3$ particle were dispersed within the textured YBaCuO matrix by means of the thermal pyrolysis processing. Magnetic levitation force for YBaCuO superconductors were obtained using Nd-B-Fe permanent magnet, at 77 K and at the magnetic field from 0 to 5.3 K gauss. In the unadded superconductor and 5 wt% $BaZrO_3$ addition, anomalous magnetization behavior, which is characterized by the intermediate magnetic field, was observed at 77 K. Critical current density was about few hundreds $A/cm^2$ and the magnetic characteristics increased slightly by addition of $BaZrO_3$ powder. Maximum magnetic force was obtained in the YBaCuO superconducting bulk with 3 wt.% $BaZrO_3$ addition.