• The korean journal of orthodontics
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• v.42 no.5
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• pp.255-262
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• 2012

Objective: We aimed to compare the retention characteristics of Essix and Hawley retainers. Methods: Adolescents undergoing fixed appliance treatment at 2 centers were recruited for this study. Twenty-two patients (16 women and 6 men) wore Essix retainers (Essix group) while 20 (14 women and 6 men) wore Hawley retainers (Hawley group). The mean retention time was 1 year, and the mean follow-up recall time for both groups was 2 years. Two qualified dental examiners evaluated the blind patient data. Maxillary and mandibular dental casts and lateral cephalograms were analyzed at 4 stages: pretreatment (T1), post-treatment (T2), post-retention (T3), and follow-up (T4). Results: The results revealed that Essix appliances were more efficient in retaining the anterior teeth in the mandible during a 1-year retention period. The irregularity index increased in both arches in both groups after a 2-year post-retention period. The mandibular arch lengths increased during treatment and tended to return to their original value after retention in both groups; however, these changes were statistically significant only in the Hawley group. Cephalometric variables did not show any significant differences. Conclusions: The retention characteristics of both Essix and Hawley retainers are similar.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.521-532
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• 2008

Supporting system design and construction management for the soft and hard rock layers with fractured zones are very important theme for the safety of temporary retaining wall, surrounding ground and structures in the urban deep excavation for the construction of subway, railway, building etc. The prevailing design method of supporting system for the soft and hard rock layers in the deep excavation is mostly carrying out by simplification without proper consideration for the characteristic of rock discontinuities. Therefore the behaviors of rock discontinuities and fractured zones dominate the whole safety of excavation work in the real construction stage, serious disaster due to the failure of temporary retaining wall can be induced in the case of developing large deformations in the ground and large axial forces in the supporting system. This paper introduces examples of deep excavation where the soft and hard rock layers with fractured zones were designed to be supported by shotcrete and rock bolt, deformations of corresponding ground and supporting systems in the construction period and increments of axial force in the upper earth anchors and strut due to the these deformations were investigated through detailed analysis of measurement data, the results were so used for the management of consecutive construction that led to the safe and economical completion of excavation work. The effort of this article aims to improve and develop the technique of design and construction in the coming projects having similar ground condition and supporting method.

• Journal of the Institute of Convergence Signal Processing
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• v.3 no.4
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• pp.23-28
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• 2002

In this paper, we have proposed the hardware architecture which implements the algorithm for retaining the connectivity which prevents the disconnection in the gray-scale image thinning. To extract the skeleton from the image in a real time, it is necessary to examine the connectivity of the skeleton in a real time. The proposed architecture finds the connectivity number in the 4-clock period. The architecture consists of three blocks, PS(Parallel to Serial) Converter and Stare Generator and Ridge Checker. The PS Converter changes the 3$\times$3 gray level image to four sets of image pixels. The State Generator examines the connectivity of the central pixel by searching the data from the PS Converter. The Ridge Checker determines whether the central pixel is on the skeleton or not. The proposed architecture finds the connectivity of the central pixel in a 3$\times$3 gray level image in the 4-clocks. The total circuits are verified by the design tools and operate correctly.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.4C
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• pp.239-245
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• 2006

The steep slopes have been increased of new roads, industrial site development and large scale residential development. The preservation administration and steep slope construction are currently investigated by many researchers in Korea. However, concrete retaining wall or reinforced soil (i.e. Block or Pannel) are being applied for the steep slope, which results in the front face form of the structure being limited. This research investigates the method that can make up afforestation environment-friendly circumstances during the construction of steep slope structure. It is considered that steep slope reinforced structure would be possible based on the monitoring results about earth pressure, horizontal displacement and consolidation quality generated during the construction of whole constructing reinforced structure. Also, there no problems in grassy surface, drainage, and deformation in spite of rainy season after construction period and until now. So that the seeding soil layer surface reinforced soil method could be adopt for steep slope reinforced structure and others.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.457-464
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• 2010

Ever since the introduction of high strength steel pipe strut(POSTRUT) in 2008, there has been over 50 applications domestically. The merits of construction period reduction and cost savings have been well reported abroad in countries such as America, Europe and China but ever in domestic projects or ground condidtions. 25 actual construction projects were investigated and statistically analyzed to evaluate the quantitative effects of POSTRUT. Also the construction projects along with the cautions that should be taken and the structural behavior differences between POSTRUT and H-section struts are briefly described in this paper.

• Journal of Ocean Engineering and Technology
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• v.4 no.1
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• pp.35-42
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• 1990

The area where age dating of the seafloor and interpretation of geomagnetic basic structure are conducted is also important in the aspect of geophysics. Near the sea mount (water depth to the top is 3900m and 6500m to the bottom), there are Mesozoic magnetic lineations at the sea-side flank along the trench axis. A two dimensional model analysis of Talwani and Heirtzler(1964) and a three dimensional model analysis of Talwani are performed by using data obtained from the marine proton magnetometer. Distribution, direction of the lineation, amplitude and period of magnetic anomaly are correlated and analysed with speed of the plate movement and lineation of the sea mount. In the west and north-west Pacific there are lots of huge sea mounts retaining the history of oceanic crust. This indicates that geomagnetic basis subsided into the oceanic crust and has interest in the aspects of the isostasy theory of the gravity.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.251-258
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• 2008

The use of reinforced earth walls in permanent structures is getting it's popularity. Despite a number of advantages of reinforced earth walls over conventional concrete retaining walls, there exit concerns over long-term residual deformation when subjected to repeated and/or cyclic loads, during their service period. In this investigation, the effect of preloading in reducing long term residiual deformation of back-to-back reinforced soil wall under sustained and/or repeated loading enviormentment using a series of reduced-scale model tests. It is found that the preloading technique can be an effective means of controlling residual deformations of reinforced soils under varisous loading conditions.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.870-877
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• 2005

This study examined a case of collapse and reinforcement of the colluvial deposit slope in Kyeongnam Geoje Area. The reason for the collapse was found first in the reduction of the resistant force due to slope-cut for constructing retaining walls. This decreased the resistant force against sliding, which enabled precipitation during the rainy period to seep into the ground in the upper colluvium, resulting in increase in porewater pressure. This leads to decreased shear strength and increased sliding force, which ultimately caused the collapse of the slope. For the long-term stability, methods attained for stability reinforcement are summarized in the following table.

• Proceedings of the IEEK Conference
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• 2002.07b
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• pp.860-863
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• 2002

Realizations of multirate converters are proposed using periodically time-varying (PTV) structures. By exploiting the computational redundancy of the filtering operation in a multirate filter, it is possible to implement the filter with much less hardware. In the proposed implementations, several coefficients time-share in a periodic fashion the hardware of one multiply-and-add. Therefore, each multiply-and-add circuit performs different coefficient scalings at different time instants within a period. Compared to the direct form realization, the proposed realizations reduce the hardware of an interpolator and a decimator by a factor of approximately U and M, respectively, while retaining the same processing speed, where U and M are the upsampling and downsampling factors, respectively. The approach can be used to obtain realizations for sampling rate conversion by a rational factor of U/M, where U and M are relatively prime, in which case hardware reduction by a factor of approximately UM can be achieved.

• Tunnel and Underground Space
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• v.4 no.1
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• pp.63-76
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• 1994

This paper discusses contents of the existing design, the behaviours prediction on the strut and retaining wall around subsurfaces, and also evaluates the measured results in comparison with the management criterion during excavation period of ventilation shaft at Pusan-Subway 220. Field measurements showed that maximum displacement 23.74 mm at boundary site of multistratification and the weathered rock to be formed at 0.2~0.6 H of total excavating depth(H), 68 ton of maximum axial force and 4.4X102 kg/cm2 of stress on strut. The measured axial force exceeds prediction levels by up to 50 percent at the weathered soil & rock, and the others come under the category of their levels. The great gap of both field measurements and prediction on behaviour makes a difference of the site situation at the design stage and the practical working. This measured value is greatly safety in comparison with that of the safety criterion, but axial force at 4~5 strut of ventilation shaft l is higher than the prediction.