• Title, Summary, Keyword: CWR

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Discomfort caused by the circumferential comfortable retainer (CCR) as a removable maxillary retainer (상악 가철식 보정장치인 circumferential comfortable retainer (CCR)에 대한 불편감 평가)

  • Choi, Jin-Hugh;Moon, Cheol-Hyun
    • The korean journal of orthodontics
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    • v.40 no.5
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    • pp.325-333
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    • 2010
  • Objective: The aim of this study was to illustrate the circumferential comfortable retainer (CCR) as a removable maxillary retainer with good potential patient compliance and to evaluate the discomfort of the retainers including distorted speech, gagging sensation and appliance discomfort. Methods: Sixty-six orthodontic patients (male, 23; female, 43; mean age, $23.42{\pm}10.19$ years) who received orthodontic treatment with fixed orthodontic appliances were randomly assigned to two groups after debonding, a conventional wraparound retainer (CWR) group that fully covers the palate with an acrylic plate and a highly polished surface, and a circumferential comfortable retainer (CCR) group which has a horseshoe shaped base plate with three folds on the anterior region. A questionnaire that had a visual analog scale (VAS) which consists of a 100-mm horizontal line with 2 end-points labeled "no discomfort" on the left and "worst discomfort" on the right, with regard to distorted speech, gagging sensation and discomfort, was administered to patients after 4 weeks of retainer wear. The Mann-Whitney test was used to test the hypothesis that there was no difference between the two retainers. Results: Comparing distorted speech and discomfort, the CCR group significantly had lower values than the CWR group ($p$ < 0.05). Comparing gagging sensation, the CCR group had lower values than the CWR group but there were no statistically significant differences between groups ($p$ = 0.146). Conclusions: In conclusion, the results suggest that the circumferential comfortable retainer (CCR) might facilitate patient compliance and thereby improve the maintenance of the fixed orthodontic treatment outcome.

Thermal Buckling Analysis of Continuous Welded Rail Track (장대 레일의 온도 좌굴 해석)

  • 신정렬;임남형;양재성;강영종
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.433-440
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    • 1998
  • For many decades, railroad technology was used to set up tracks with jointed rails and lengths in accordance with rolling and handling technology. The joints lead to drawbacks in the track and in controlling rising maintenance costs. So, railroad engineers became interested in eliminating joints to increase loads, speeds and improvements in rolling, welding, and fastening technology. Continuous welded rail(CWR) track has many advantages over the conventional jointed-rail track. In the case of the elimination of rail joints, it may cause the track to be suddenly and laterally buckled by thermal forces and vehicle load. Thermal forces are caused by an increase in the temperature of railway track. For many years, many analytical and experimental investigations have been conducted to improve the safety of CWR track by various research center in many country. In this paper, CWR track model and CWRB program is developed for buckling analysis using finite element method(FEM). The finite element discretization is used for a rail element with a total of 14 degrees of freedom. The stiffness of the fasteners, tie, and ballast bed is included by a set of spring elements. The investigation on the buckling modes and temperature of CWR track is presented in this paper

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Seismic Response of CWR on HSR Bridge Considering Derailment Inducing Factors (탈선취약요소를 고려한 고속철도교량 장대레일 지진응답 평가)

  • Yi, Jang-Seok;Kim, Dae-Sang
    • Journal of the Earthquake Engineering Society of Korea
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    • v.13 no.3
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    • pp.29-38
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    • 2009
  • n the event of an earthquake, additional stresses can occur in the continuous welded rails (CWR) of High-speed railway (HSR) bridges due to relative displacements at expansion joints, and this stress can cause derailment. The amplification of ground motion occurs as a result of site effects, and this is pronounced at the site of a soft surface soil layer and of a rigid surface soil layer over a soft one. As a result, the amplified ground motion leads to an amplified seismic response in HSR bridges. A change in bridge pier height affects the seismic behavior of the bridge. A HSR bridge with gravel ballast tracks will show different dynamic behavior during an earthquake than one with concrete ballast tracks. The seismic responses of HSR bridges and their CWR are analyzed considering the derailment-inducing factors.

Parametric Study on Rail and Bridge Interaction (레일과 교량의 상호작용 매개변수 분석 연구)

  • Kim, Jong-Min;Han, Sang-Yun;Lim, Nam-Hyoung;Kim, Jung-Hun;Kang, Young-Jong
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.445-450
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    • 2007
  • CWR(Continuous Welded Rail) and bridge interaction produce rail force, bridge displacement and rail/bridge relative displacement. Each of these has limitation by many codes. In this paper, analysis of interaction has been carried out by using foreign codes(UIC 774-3 R code of Europe etc.) because there is no code about interaction between rail and bridge in Korea. Recently, railway bridges with CWR has been constructed for structural and economical reasons. When designer plans railway bridges, design a bridge model first and then investigate railway forces and displacement by interaction analysis. If these results go out bounds from limitation, designer plans railway bridges again and again. In this paper, using the parametric study on CWR and railway bridge interaction, railway bridge parameters such as length of bridge span, area of bridge, moment of inertia, stiffness of pier, etc. are presented. It helps preliminary design of railway bridges.

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Sensitivity of the ballast resistance and track irregularity on the track stability (궤도 안정성에 대한 도상저항력과 궤도틀림의 민감도)

  • Lim, Nam Hyoung;Choi, Sang Hyun;Lee, Chin Ok;Sung, Ik Hyun
    • Journal of Korean Society of Steel Construction
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    • v.17 no.5
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    • pp.519-526
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    • 2005
  • During summer, very high compressive force occurs on the continuous welded rail (CWR) track because of the increase of rail temperature (max. $60^{\circ}C$). This extreme temperature stress can cause the CWR track to buckle. Among many CWR parameters affecting the track buckling, the influence of the lateral and longitudinal ballast resistance was investigated on the stability of the CWR track in this study. Also, the sensitivity of the track irregularity such as the alignment defect and the gauge irregularity was investigated.

The Growth friend Analysis of Rail Surface Irregularity according to the Types of Track (궤도구조별 레일두부 표면요철의 성장 경향 분석)

  • Sung, Deok-Yong;Kong, Sun-Yong;Kim, Bag-Jin;Shin, Hyo-Jeong;Park, Yong-Gul
    • Proceedings of the KSR Conference
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    • pp.369-375
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    • 2009
  • The Periodic replacements criterion of rail is calculated on the basis of the research result of RTRI in Japan. It is suggested that the service life of the continuous welded rail(CWR) is estimated by the relationship between the rail surface irregularity according to the accumulated passing tonnage and bending fatigue of welded part in CWR. In order to establish the periodic replacements criterion of CWR, this study measured the rail surface irregularity according to the accumulated passing tonnage, the types of track system and welding. Therefore, it is analyzed that the gas pressure welding is the worst one of the others. In addition, it is analyzed that the rail surface irregularity growth rate in ballast track is about $0.02{\sim}0.03mm$/100MGT and its in concrete track is about $0.005{\sim}0.02mm$/100MGT Finally, the result of this study is able to use the basis data to establishing the periodic replacements criterion of CWR considering rail grinding.

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The Fatigue Life Evaluation of CWR based on the Rail Grinding (레일연마를 고려한 장대레일의 피로수명 평가)

  • Kong, Sun-Young;Sung, Deok-Yong;Park, Yong-Gul
    • Journal of The Korean Society of Civil Engineers
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    • v.35 no.5
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    • pp.1191-1198
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    • 2015
  • In this study, vehicle/track interaction analysis by the Saemaul powered vehicle was carried out. The prediction equation for the bending stress of rail was estimated using the rail bending stress by the rail surface irregularities at welds. Also, the fatigue analysis using a S-N curve of welds in the conventional railway was carried out. We estimated the fatigue life of CWR by the fracture probability. By the rail grinding, the fatigue life of CWR was evaluated in consideration to reduce the rail bending stress through removing the rail surface irregularities. Therefore, it presented the fatigue life of CWR according to the rail grinding execution plan in the conventional railway.

Effects of Aspergillus Oryzae Culture and 2-Hydroxy-4-(Methylthio)-Butanoic Acid on In vitro Rumen Fermentation and Microbial Populations between Different Roughage Sources

  • Sun, H.;Wu, Y.M.;Wang, Y.M.;Liu, J.X.;Myung, K.H.
    • Asian-Australasian Journal of Animal Sciences
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    • v.27 no.9
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    • pp.1285-1292
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    • 2014
  • An in vitro experiment was conducted to evaluate the effects of Aspergillus oryzae culture (AOC) and 2-hydroxy-4-(methylthio)-butanoic acid (HMB) on rumen fermentation and microbial populations between different roughage sources. Two roughage sources (Chinese wild rye [CWR] vs corn silage [CS]) were assigned in a $2{\times}3$ factorial arrangement with HMB (0 or 15 mg) and AOC (0, 3, or 6 mg). Gas production (GP), microbial protein (MCP) and total volatile fatty acid (VFA) were increased in response to addition of HMB and AOC (p<0.01) for the two roughages. The HMB and AOC showed inconsistent effects on ammonia-N with different substrates. For CWR, neither HMB nor AOC had significant effect on molar proportion of individual VFA. For CS, acetate was increased (p = 0.02) and butyrate was decreased (p<0.01) by adding HMB and AOC. Increase of propionate was only occurred with AOC (p<0.01). Populations of protozoa ($p{\leq}0.03$) and fungi ($p{\leq}0.02$) of CWR were differently influenced by HMB and AOC. Percentages of F. succinogenes, R. albus, and R. flavefaciens (p<0.01) increased when AOC was added to CWR. For CS, HMB decreased the protozoa population (p = 0.01) and increased the populations of F. succinogenes and R. albus ($p{\leq}0.03$). Populations of fungi, F. succinogenes (p = 0.02) and R. flavefacien (p = 0.03) were increased by adding AOC. The HMB${\times}$AOC interactions were noted in MCP, fungi and R. flavefacien for CWR and GP, ammonia-N, MCP, total VFA, propionate, acetate/propionate (A/P) and R. albus for CS. It is inferred that addition of HMB and AOC could influence rumen fermentation of forages by increasing the number of rumen microbes.

Estimation of the Roadbed Settlement and Bearing Capacity According to Radius of Curve and Cant in Railroad (철도의 곡선반경 및 캔트에 따른 노반의 침하 및 지지력 산정)

  • Jeon, Sang-Soo;Eum, Gi-Young;Kim, Jae-Min
    • Journal of Korean Society of Hazard Mitigation
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    • v.7 no.1
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    • pp.29-38
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    • 2007
  • The research on the track performance and stability of the tilting-train was performed and the settlement of the roadbed was estimated as the tilting train was being operated on the rail joint under the allowable velocity subjected to the track performance and the stability of the tilting-train. Since the impact on the continuous welded rail (CWR) induced by the tilting-train loading is different from the impact on the rail joint, it needs to investigate the settlement of the roadbed beneath the CWR. In this study, when the tilting-train is being operated on the CWR under the allowable velocity subjected to the track performance and the stability of the tilting-train, the settlement and bearing capacity of the roadbed beneath the CWR have been evaluated using numerical analysis and compared with those beneath the rail joint. The numerical results show that the settlements of the roadbed beneath CWR and rail joint are amount to 71.2% and 88.8% of the allowable settlement, respectively. And the stresses are amount to 10.4% and 12.1% of the allowable bearing capacity, respectively.