• Land and Housing Review
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• v.2 no.4
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• pp.509-516
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• 2011

Compared with the traditional RC system, precast stairs can save construction time, reduce the cost of concrete casting, etc. This paper focuses on an investigation of improved continuous longitudinal joint details for PC stair systems. The performance of the precast concrete stair connections subjected to displacement control cyclic loading is compared with that of the monolithic connection. The developed connection is composed of U-rods and clamp joint metals. This paper proposes precast stair connection with improved structural performance and experimentally evaluates the structural performance of the proposed joints in terms of maximum load, displacement ductiliy, strain, crack and failure modes.

• 제어로봇시스템학회:학술대회논문집
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• 1987.10b
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• pp.613-618
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• 1987

Rod consolidation is a method of increasing spent nuclear fuel storage capacity by disassembling fuel assemblies thus storing the fuel rods in a tighter array. It involves some basic operations which closely resemble to the material handling of a manufacturing process. But all the operations must be controlled remotely in shielded environment from outside due to the highly radioactive nature of the workpiece. In this study the status of the rod consolidation technology in other countries has been surveyed and a feasibility study for the conceptual design of this process have been made.

• Journal of Periodontal and Implant Science
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• v.29 no.4
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• pp.737-749
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• 1999

Recently many researches on plaque removal effect and therapeutic effect of toothpaste containing natural medicines are being studied in early periodontal diseases. The purpose of this study is to examine the clinical and microbiological effect of toothpaste containing natural medicines such as camomile, rhatany, myrrh，sage oil, glycyrrhetinic acid and vitamin E. Sixty three subjects with gingivitis were divided into an experimental group which performed normal oral hygiene procedure with toothpaste containing natural medicines and vitamine E and a control group which also performed normal oral hygiene procedure with Syrinmed? toothpaste without containing herbal extracts and vitamine E. At the baseline, 2 weeks, and 4 weeks, subjects were analyzed for clinical study and microbiological study. After 2 weeks and 4 weeks use of their respective toothpastes, statistically significant decreases of gingival index, plaque index, and bleeding index were shown in both the control and the experimental group. The degree of decrease was more significant in the experimental group than the control group. A statistically significant decrease of pocket depth, and gingival crevicular fluid were shown in both the control and lie experimental group. A statistically significant increase of cocci was shown in both the control and the experimental group, the degree of increase was more significant in the experimental group than control group. A statistically significant decrease ofnon-motile rods, and motile rods were shown in both the control and the experimental group, the degree of decrease was more significant in the experimental group than the control group. Spirochetes increased weakly in both the control and the experimental group but a statistic significance was not shown. A statistically significant decrease of anaerobic bacteria, aerobic bacteria, and black pigmented Bacteroides were shown in both the control and the experimental group. These results indicate that the use of toothpaste containing natural medicines is effective in the prevention and the treatment of periodontal diseases.

• Proceedings of the KIEE Conference
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• 2003.11c
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• pp.559-562
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• 2003

In this paper, we introduce a new method detecting thyristor faults of the power converter module in Control Rod Control System. When we control the currents in each coil of Control Rod Drive Mechanism by using the current control method, the current value can follow the current reference despite the faults like the missing phase or the diode acting. Comparing the fault current values with the normal current values, the bad transient characteristics of the abnormal current can make the operations of control rods incorrect. In this case, the information from the current trends cannot be enough to detect the fault occurrence in thyristors. Instead of the coil currents, the state of thyristors can be watched by measuring the coil voltages. In the existing system of Westinghouse type, the ripple detector takes charge of this task. But this detector has some shortcomings in the point of time for fault detection, we come to devise a new fault detection method solving the problems which belong to the ripple detector.

• Nuclear Engineering and Technology
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• v.55 no.5
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• pp.1665-1670
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• 2023

It is shown that in the IBR-2M reactor by the end of the reactor cycle, changes in dynamics are observed associated with a strong weakening of the fast power feedback (PF), as a result of which the reactor becomes oscillatorily unstable. After each week of zero-power operation the negative changes in reactor dynamics disappear and the stability of the reactor is restored. Thus, the reactor undergoes cyclic changes in the oscillatory instability. The correlation between of a fast PF and a slow PF is experimentally observed, which makes it possible to almost completely eliminate the cyclic component of instability by changing the control mode of rods of the control system.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.732-737
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• 2005

Distal 3D Real Object Duplication System(RODS) consists of 3D Scanner and Solid Freeform Fabrication System(SFFS). It is a device to make three-dimensional objects directly from the drawing or the scanning data. In this research, we developed an office type SFFS based on Three Dimensional Printing Process and a industrial SFFS using Dual Laser. An office type SFFS applied sliding mode control with sliding perturbation observer(SMCSPO) algorithm for control of this system. And we measured process variables about droplet diameter measurement and powder bed formation etc. through experiments. Also, in order to develop more elaborate and speedy system for large objects than existing SLS process, this study applies a new Selective Multi-Laser Sintering(SMLS) process and 3-axis dynamic Focusing Scanner for scanning large area instead of the existing $f\theta$ lens. In this process, the temperature has a great influence on sintering of the polymer. Also the laser parameters are considered like that laser beam power, scan speed, scan spacing. Now, this study is in progress to eveluate the effect of experimental parameters on the sintering process.

• Nuclear Engineering and Technology
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• v.56 no.2
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• pp.552-557
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• 2024

The actual swelling of AgInCd absorber might exceed the predicted swelling value after years of service in pressurized water reactors, and the chemical and microstructural changes of AgInCd absorber induced by transmutation reactions are the main reason for the swelling acceleration of AgInCd absorber. In the present study, a model for calculating the irradiation swelling of AgInCd absorber in nuclear control rods is developed according to chemical and microstructural changes of AgInCd absorber. In this model, the chemical compositions of AgInCd absorber as a function of the thermal neutron fluence are firstly calculated, and then the volume of AgInCd absorber after irradiation is obtained on the basis of the crystallographic parameters of phases in the AgInCd absorber, and the irradiation swelling of AgInCd absorber is finally calculated. The crystallographic parameters can be obtained by preparing the simulated AgInCd alloys and fitting the experimental data. The model calculating results of irradiation swelling are in good agreement with the actual swelling data in literature. More importantly, the present model can well explain the EPRI results of the acceleration in the diametral swelling rate above 6-8 × 10²⁰ n/cm² and the decrease in the diametral swelling rate above about 2 × 10²¹ n/cm².

• Nuclear Engineering and Technology
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• v.50 no.5
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• pp.648-653
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• 2018

Elimination of soluble boron from reactor design eliminates boron-induced reactivity accidents and leads to a more negative moderator temperature coefficient. However, a large negative moderator temperature coefficient can lead to large reactivity feedback that could allow the reactor to return to power when it cools down from hot full power to cold zero power. In soluble boron-free small modular reactor (SMR) design, only control rods are available to control such rapid core transient. The purpose of this study is to investigate whether an SMR would have enough control rod worth to compensate for large reactivity feedback. The investigation begins with classification of reactivity and completes an analysis of the reactivity balance in each reactor state for the SMR model. The control rod worth requirement obtained from the reactivity balance is a minimum control rod worth to maintain the reactor critical during the whole cycle. The minimum available rod worth must be larger than the control rod worth requirement to manipulate the reactor safely in each reactor state. It is found that the SMR does have enough control rod worth available during rapid transient to maintain the SMR at subcritical below k-effectives of 0.99 for both hot zero power and cold zero power.

• Journal of Periodontal and Implant Science
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• v.23 no.3
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• pp.411-421
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• 1993

The purpose of this study was to assess the effect of polycaprolactone strip with minocycline on the periodontal pocket in humans and the various clinical parameters in rapidly progressive periodontitis. Nine patients with rapidly progressive periodontitis were selected for the study. They had not taken antibiotics for 6 months and had no history of dental treatment for 6 months before the study. They were in good general health. By the split-mouth method, patients received a supragingival scaling, experimental group (9sites) were subjected to subgingival placement of polycaprolactone strips(1 strip) containg 30% minocyclne and control group (9 site) were subjected to subgingival placement of not polycaprolactone strips(1 strip) containing 30 A Minocycline. Strips were replaced with freshly filled ones at 1 week and 2 week. All strips were removed from pockets at 3 week Clinical examination (plaque index, gingival index, probing pocket depth) and distribution on the bacteria morphology of subgingival plaque were monitored on baseline (0 week), 1, week, 2 week, 4 week and 8 week. The result were as follows : 1. Plaque index in experimental group was not significantly reduced during all weeks(P<0.05), but slightly reduced at 2, 4 and 8 weeks and that in control group was not significantly reduced during monitoring period. 2. Probing pocket depth was significantly reduced at 2, 4 and 8 weeks(P<0.05) in experimental group, but that in control group was not siginificantly changed during monitoring period. 3. Gingival index was significantly improved at 2, 4 and 8 weeks(P<0.05) in experimental group but that in control group was not significantly changed. 4. Percentage of cocci was significantly increased at 2, 4 and 8 weeks in experimental group but that in control group was not significantly changed. 5. Percentage of non-motile rods in both group were not significantly changed when compared with those of baseline(0 week) (P<0.05). 6. Percentage of motile rods was siginificantly reduced at 1, 2 and 4 weeks in experimental group (p<0.05) but that in control group was not significantly changed. 7. Percentage of spirochetes was siginificantly reduced during all weeks(P<0.05) but that in control group was not significantly changed. The result showed that polycaprolactone containing 30% minocycline effect the clinical index and bacterial morphotype.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.4
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• pp.402-407
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• 2014

In this paper, residual sway control of objects that are moved underwater is investigated. The fuel transfer system in a nuclear power plant transfers the nuclear fuel rods underwater. The research on the dynamics of the loads transferred in different mediums (water and air) and their control methods have not been fully developed yet. The attenuation characteristics of the fuel transfer system have been studied to minimize its residual vibration by considering the effects of hydrodynamic forces acting on the fuel rod. First, a mathematical model is derived for the underwater fuel transfer system, and then experiments have been conducted to study the dynamic behavior of the rod while it travels underwater. Lastly, the residual vibration at the end point is minimized using the input shaping technique.