• Title/Summary/Keyword: Mode of failure

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Cyclic Seismic Testing of Cruciform Concrete-Filled U-Shape Steel Beam-to-H Column Composite Connections (콘크리트채움 U형합성보-H형강기둥 십자형 합성접합부의 내진성능)

  • Park, Chang-Hee;Lee, Cheol-Ho;Park, Hong-Gun;Hwang, Hyeon-Jong;Lee, Chang-Nam;Kim, Hyoung-Seop;Kim, Sung-Bae
    • Journal of Korean Society of Steel Construction
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    • v.23 no.4
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    • pp.503-514
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    • 2011
  • In this research, the seismic connection details for two concrete-filled U-shape steel beam-to-H columns were proposed and cyclically tested under a full-scale cruciform configuration. The key connecting components included the U-shape steel section (450 and 550 mm deep for specimens A and B, respectively), a concrete floor slab with a ribbed deck (165 mm deep for both specimens), welded couplers and rebars for negative moment transfer, and shear studs for full composite action and strengthening plates. Considering the unique constructional nature of the proposed connection, the critical limit states, such as the weld fracture, anchorage failure of the welded coupler, local buckling, concrete crushing, and rebar buckling, were carefully addressed in the specimen design. The test results showed that the connection details and design methods proposed in this study can well control the critical limit states mentioned above. Especially, the proposed connection according to the strengthening strategy successfully pushed the plastic hinge to the tip of the strengthened zone, as intended in the design, and was very effective in protecting the more vulnerable beam-to-column welded joint. The maximum story drift capacities of 6.0 and 6.8% radians were achieved in specimens A and B, respectively, thus far exceeding the minimumlimit of 4% radians required of special moment frames. Low-cycle fatigue fracture across the beam bottom flange at a 6% drift level was the final failure mode of specimen A. Specimen B failed through the fracture of the top splice plate of the bolted splice at a very high drift ratio of 8.0% radian.

Effects of primers on the microtensile bond strength of resin cements to cobalt-chromium alloy (레진 시멘트와 코발트 크롬 합금의 미세인장결합강도에 다양한 프라이머들이 미치는 영향)

  • Jung, Hong-Taek;Campana, Shiela A.;Park, Jin-Hong;Shin, Joo-Hee;Lee, Jeong-Yol
    • The Journal of Korean Academy of Prosthodontics
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    • v.57 no.2
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    • pp.95-101
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    • 2019
  • Purpose: The aim of this study is to evaluate the effects of various primers on the microtensile bond strength (${\mu}TBS$) of resin cements to cobalt-chromium (Co-Cr) dental casting alloy. Materials and methods: Four adhesive primers (Universal primer, Metal primer II, Alloy primer, and Metal/Zirconia primer) and two resin cements (Panavia F2.0, G-CEM LinkAce) were tested. One hundred fifty Co-Cr beams were prepared from Co-Cr ingots via casting ($6mm\;ength{\times}1mm\;width{\times}1mm\;thick$). The metal beams were randomly divided into ten groups according to the adhesive primers and resin cements used; the no-primer groups served as the control (n = 15). After sandblasting with aluminum oxide ($125{\mu}m$ grain), the metal and resin cements were bonded together using a silicone mold. Prior to testing, all metal-resin beams were examined under stereomicroscope, and subjected to the ${\mu}TBS$ test. The mean value of each group was analyzed via one-way ANOVA with Tukey's test as post hoc (${\alpha}=.05$) using SPSS software. Results: The mean ${\mu}TBS$ of all groups was ranged from 20 to 28 MPa. There is no statistically significant difference between groups (P > .05). Mixed failure, which is the combination of adhesive and cohesive failures, is the most prevalent failure mode in both the Panavia F2.0 and G-Cem LinkAce groups. Conclusion: The ${\mu}TBS$ of all tested groups are relatively high; however, the primers used in this study result in no favorable effect in the ${\mu}TBS$ of Panavia F2.0 and G-Cem LinkAce resin cement to Co-Cr alloy.

Behavior Analysis of Concrete Structure under Blast Loading : (II) Blast Loading Response of Ultra High Strength Concrete and Reactive Powder Concrete Slabs (폭발하중을 받는 콘크리트 구조물의 실험적 거동분석 : (II) 초고강도 콘크리트 및 RPC 슬래브의 실험결과)

  • Yi, Na Hyun;Kim, Sung Bae;Kim, Jang-Ho Jay;Cho, Yun Gu
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.29 no.5A
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    • pp.565-575
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    • 2009
  • In recent years, there have been numerous explosion-related accidents due to military and terrorist activities. Such incidents caused not only damages to structures but also human casualties, especially in urban areas. To protect structures and save human lives against explosion accidents, better understanding of the explosion effect on structures is needed. In an explosion, the blast load is applied to concrete structures as an impulsive load of extremely short duration with very high pressure and heat. Generally, concrete is known to have a relatively high blast resistance compared to other construction materials. However, normal strength concrete structures require higher strength to improve their resistance against impact and blast loads. Therefore, a new material with high-energy absorption capacity and high resistance to damage is needed for blast resistance design. Recently, Ultra High Strength Concrete(UHSC) and Reactive Powder Concrete(RPC) have been actively developed to significantly improve concrete strength. UHSC and RPC, can improve concrete strength, reduce member size and weight, and improve workability. High strength concrete are used to improve earthquake resistance and increase height and bridge span. Also, UHSC and RPC, can be implemented for blast resistance design of infrastructure susceptible to terror or impact such as 9.11 terror attack. Therefore, in this study, the blast tests are performed to investigate the behavior of UHSC and RPC slabs under blast loading. Blast wave characteristics including incident and reflected pressures as well as maximum and residual displacements and strains in steel and concrete surface are measured. Also, blast damages and failure modes were recorded for each specimen. From these tests, UHSC and RPC have shown to better blast explosions resistance compare to normal strength concrete.

A comparative study of three therapeutic modalities in loculated tuberculous pleural effusions (소방이 형성된 결핵성 흉막 질환에서 배액 방법에 따른 치료효과)

  • Lee, Sang Hwa;Lee, So Ra;Lee, Sang Youb;Park, Sang Muyn;Suh, Jung Kyung;Cho, Jae Youn;Shim, Jae Jeong;In, Kwang Ho;Yoo, Se Hwa;Kang, Kyung Ho
    • Tuberculosis and Respiratory Diseases
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    • v.43 no.5
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    • pp.683-692
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    • 1996
  • Background: Although most of the patients with tuberculous pleural effusions completely reabsorbed their effusions and became asymptomatic within 2 to 4 months, later surgical procedures such as decortication is needed in some patients because of dyspnea caused by pleural loculations and thickening despite anti-tuberculous chemotherapy. It is obligatory to secure adequate drainage to prevent the development of complications. But, the best methods for treating loculated tuberculous pleural effusions remain debatable. Recent several reports revealed that intrapleural instillation of fibrinolytic agents is an effective adjunct in the management of complicated empyema and may reduce the need of surgery. Purpose : The effects of catheterization with intrapleural urokinase instillation were prospectively evaluated in the patients with septated tuberculous pleural effusion, and compared with other therapeutic effects of different modalities of therapy such as repeated thoracentesis and small-bored catheterization. Methods : Forty-eight patients diagnosed with tuberculous pleurisy were randomly separated into three groups; control group(n=13), catheter group(n=12), urokinase group(n=22). In urokinase group, dose of 100.000U urokinase was instilled into the pleural cavity via a percutaneous drainage catheter for complete drainage or total dose of 700,000U of urokinase. After two hours clamping, the catheter was opened and intermittently irrigated. The early and late effectiveness of therapies was assessed by radiographically and by measuring the volume of fluid drained from the catheter. Results : There was statistically significantly better result in the urokinase group in respect of frequency of catheterization, frequency of catheter obstruction and the duration of catheterization in early effectiveness(p < 0.05). There were no difference in radiologic improvement of follow-up in later phase chest X-ray between urokinase group and catheter group in later phase(p > 0.05). But there were more failure rates in control group especially honeycomb septa in pleural effusion sonographically than former two groups. And there were no complications of urokinase such as fever or hemorrhage. Conclusion : In the treatment of septated tuberculous pleurisy, there were better results in urokinase than those of catheterization alone in early effectiveness. And there was no difference in radiographic improvement between urokinase group and catheter group. Intrapleural instillation of urokinase is an effective and safe mode of treatment for septated tuberculous pleural effusions and alleviates the need for thoracotomy.

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, the Cinema of Attractions (<디 워>, 매혹의 영화)

  • Ryu, Jae Hyung
    • Cartoon and Animation Studies
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    • s.29
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    • pp.209-241
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    • 2012
  • Is a failed blockbuster film? Is there no room for reconsideration of the value of the film in terms of its contents and forms? The purpose of this study is to answer these questions. In 2007, SHIM Hyung-rae's was in the limelight due to the nationalist discourse around the film rather than evaluation of the film itself. In terms of its narrative and formal properties, the film showed the difference from the Korean nationalist blockbuster films. It led to the disaccord and hard-to-understand results of having somewhat disappointed box-office success of 8,500,000 audiences in comparison to the input, of receiving well by a generous part of the audiences absorbed by nationalism, and of getting the critics' cynic criticism of the film's cinematic value. Eventually only provided the cultural battlefield of nationalism, was left as an unnoticed film in the realm of industry and criticism. However, it was interesting that there was a common ground between the film's supporters and the cynic critics. Both sides were being acknowledged that the spectacle of was way out of proportion to the degree that the spectacle was unbalanced with the story unfolding, achieved more than expected. Its spectacle overwhelming the narrative enfever a few audiences, and at the same time, it provided some reasons making critics face away from the film. In this context, the purpose of this study is to examine 's aesthetics that 'the spectacle dominating narrative' or 'the narrative as a pretext for showing spectacle,' leading to discussion of artistic/theoretical/critical value and to find out cinematic value of the film being regarded as a failure. In addition, this study is significant in that it suggests that is a new kind of moving image that it cannot be analyzed with existed critical methods of narrative film criticism; as a result, this study provides the chance to be evaluated through a new conceptual frame of the film. In order to grasp the narratological aesthetics, this study focuses on the concept of trickality that Andre Gaudreault suggests, and Tom Gunning's 'the cinema of attractions,' referring to the spectacle-oriented narrativity or the mode of production displaying the spectacle more than the narrative.

Influence of application methods of one-step self-etching adhesives on microtensile bond strength (한 단계 자가 산부식 접착제의 적용 방식이 미세인장 결합강도에 미치는 효과)

  • Choi, Chul-Kyu;Son, Sung-Ae;Ha, Jin-Hee;Hur, Bock;Kim, Hyeon-Cheol;Kwon, Yong-Hun;Park, Jeong-Kil
    • Restorative Dentistry and Endodontics
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    • v.36 no.3
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    • pp.203-210
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    • 2011
  • Objectives: The purpose of this study was to evaluate the effect of various application methods of one-step self-etch adhesives to microtensile resin-dentin bond strength. Materials and Methods: Thirty-six extracted human molars were used. The teeth were assigned randomly to twelve groups (n = 15), according to the three different adhesive systems (Clearfil Tri-S Bond, Adper Prompt L-Pop, G-Bond) and application methods. The adhesive systems were applied on the dentin as follows: 1) The single coating, 2) The double coating, 3) Manual agitation, 4) Ultrasonic agitation. Following the adhesive application, light-cure composite resin was constructed. The restored teeth were stored in distilled water at room temperature for 24 hours, and prepared 15 specimens per groups. Then microtensile bond strength was measured and the failure mode was examined. Results: Manual agitation and ultrasonic agitation of adhesive significantly increased the microtensile bond strength than single coating and double coating did. Double coating of adhesive significantly increased the microtensile bond strength than single coating did and there was no significant difference between the manual agitation and ultrasonic agitation group. There was significant difference in microtensile bonding strength among all adhesives and Clearfil Tri-S Bond showed the highest bond strength. Conclusions: In one-step self-etching adhesives, there was significant difference according to application methods and type of adhesives. No matter of the material, the manual or ultrasonic agitation of the adhesive showed significantly higher microtensile bond strength.

The Surgical Treatment of Atrial Fibrillation in Patients Undergoing Simultaneous Open Heart Surgery (심장세동의 수술요법)

  • Kim, Gi-Bong;Lee, Chang-Ha;Son, Dae-Won
    • Journal of Chest Surgery
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    • v.30 no.3
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    • pp.287-292
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    • 1997
  • .Itrial fibrillation is one of the most common cardiac arrhythmias requiring treatment. About 60% of patients with mitral valvular disease have atrial fibrillation and one third of patients with atrial fibrillation may have the past history of thromboembolic events. Between April 1994 and June 1995, 20 patients with organic heart diseases combined with atrial fibrillation underwent open heart surgery including Cox-maze 111 procedure. There were 6 men and 14 women with an average age of 48 years (range, 31 to 66 years). Nineteen patients had valvular heart diseases and 1 ventricular septal defEct (VSD). Mean duration of atrial fibrillation was 36 months (:42 months) (range, 1 to 132 months). T e past medical history of thromboembolic events was positive in 7 patients (35%) and left atrial thrombus was detected in 9 patients (45%). The concomitant procedures were mitral valve replacement (MVR) and aortic valve replacement (AVR) in 5 patients, MVR in 4, MVd and tricuspid annuloplasty(TAP) in 4, mitral valvuloplasty(Mln) in 3, Mln and Tln in 1, MIW and coronary artery bypass surgery in 1, AVR in 1, and patch closure of VSD in 1. Mean aortic cross-clamping time was 175 minutes (range, 116 to 270 minutes). Atrial fibrillation recurred in 16 patients (80%) during the early postoperative period, but, recurrent atrial fibrillation was converted to regular rhythm at postoperative forty-first day in average. There was no early or late death in this series of 20 patients and postoperative complications were inappropriate tachycardia in 5 patients (25%), low cardiac output syndrome in 3 (15%), aggravated hemiplegic in 1, and acute renal failure in 1. Mean follow-up interval of patient was 16.5 months (range, 10.5 to 24 months) and all patients are currently in regular rhythm. Seventeen patients (85%) are in sinus rhythm and 3 (15%) in junctional rhythm. Right atrial contraction was detected in 95% of patients and left atrial contraction in 63% on postoperative transthoracic echocardiogram. The surgical treatment of atrial fibrillation concomitant with open heart surgery is warranted in the recent clinical setting of improved myocardial protection technique, considering the untoward side-effects of atrial fibrillation.

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Influence of Implant Fixture-Abutment Connection and Abutment Design on Mechanical Strength (임플란트 고정체-지대주 연결부 및 지대주 디자인이 기계적 강도에 미치는 영향)

  • Chun, Mi-Hyun;Jeong, Chang-Mo;Jeon, Young-Chan;Eom, Tae-Gwan;Yoon, Ji-Hoon
    • Journal of Dental Rehabilitation and Applied Science
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    • v.24 no.3
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    • pp.269-281
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    • 2008
  • Fatigue or overload can result in mechanical problems of implant components. The mechanical strength in the implant system is dependent on several factors, such as screw and fixture diameters, material, and design of the fixture-abutment connection and abutment. In these factors, the last rules the strength and stability of the fixture-abutment assembly. There have been some previous reports on the mechanical strength of the fixture-abutment assembly with the compressive bending test or short-term cyclic loading test. However, it is restrictive to predict the long-term stability of the implant system with them. The purpose of this study was to evaluate the influence of the design of the fixture-abutment connection and abutment on the mechanical strength and failure mode by conducting the endurance limit test as well as the compressive bending strength test. Tests were performed according to a specified test(ISO/FDIS 14801) in 4 fixture-abutment assemblies of the Osstem implant system: an external butt joint with Cemented abutment (group BJT), an external butt joint with Safe abutment (group BJS), an internal conical joint with Solid abutment (group CJO), and an internal conical joint with ComOcta abutment (group CJT). The following conclusions were drawn within the limitation of this study. Compressive bending strengths were decreased in order of group BJS(1392.0N), group CJO(1261.8N), group BJT(1153.2N), and group CJT(1110.2N). There were no significant differences in compressive bending strengths between group BJT and group CJT(P>.05). Endurance limits were decreased in order of group CJO(600N), group CJT(453N), group BJS(360N), and group BJT(300N). 3. Compressive bending strengths were influenced by the connection and abutment design of the implant system, however endurance limits were affected more considerably by the connection design.

Bond strength of fiber reinforced composite after repair (섬유 강화 컴포지트의 수리 후 접합 강도)

  • Kim, Min-Jung;Kim, Kyung-Ho;Choy, Kwang-Chul
    • The korean journal of orthodontics
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    • v.36 no.3 s.116
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    • pp.188-197
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    • 2006
  • Fiber reinforced composite (FRC) is usually used as a connector joining a few teeth into one unit in orthodontics. However, fracture often occurs during the two to three years of the orthodontic treatment period due to repeated occlusal loading or water sorption in the oral environment. We simulated the repair by overlapping and attaching portions of two FRC strips in the middle and performed a three-point bending test to investigate the changes of the repair strength among the different FRC groups. The specimens were grouped according to the overlapping lengths of the two FRC strips, which were 1, 2, 3 and 4 mm (group E1, E2, E3 and E4, respectively) and the control group consisted of unrepaired, intact FRC strips. Each group consisted of 6 specimens and were cured with a light emitting diode curing unit. Group E4 showed the highest maximum loads of 2.67 N, then the control group (2.39 N), group E3 (2.35 N), E2 (2.10 N), and E1 (1.75 N) in decreasing order. Group E4 also showed the highest stiffness, which was 2.32 N/mm, however, the stiffness of group E3 (2.06N/mm) was higher than that of the control group (1.88 N/mm). According to the visual examination, the specimens tended to be bent rather than being fractured into two pieces with an increased length of overlapping portions. The above results suggest that a minimum overlapping length of 3 mm was necessary to obtain an adequate repair of a 10 mm length of FRC connector. In addition, the critical section adjacent to the joint area, where the thickness decreased abruptly, should be reinforced with flowable resin to minimize the bending tendency.

Experimental Study for Confirmation of Relaxation Zone in the Underground Cavity Expansion (지중 내 공동 확장에 따른 이완영역 확인을 위한 실험적 연구)

  • Kim, Youngho;Kim, Hoyeon;Kim, Yeonsam;You, Seung-Kyong;Han, Jung-Geun
    • Journal of the Korean Geosynthetics Society
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    • v.16 no.4
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    • pp.231-240
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    • 2017
  • Recently, there have been frequent occurrences of ground sink in the urban area, which have resulted in human and material damage and are accompanied by economic losses. This is caused by artificial factors such as soil loss, poor compaction, horizontal excavation due to the breakage of the aged sewage pipe, and lack of water proof at vertical excavation. The ground sink can be prevented by preliminary restoration and reinforcement through exploration, but it can be considered that it is not suitable for urgent restoration by the existing method. In this study, a model experiment was carried out to simulate the in-ground cavities caused by groundwater flow for developing non-excavation urgent restoration in underground cavity and the range of the relaxation zone was estimated by detecting the around the cavity using a relaxation zone detector. In addition, disturbance region and relaxation region were separated by injecting gypsum into cavity formed in simulated ground. The shape of the underground cavity due to the groundwater flow was similar to that of the failure mode III formed in the dense relative density ground due to water pipe breakage in the previous study. It was confirmed that the relaxed region detected using the relaxation zone detector is formed in an arch shape in the cavity top. The length ratio of the relaxation region to the disturbance region in the upper part of the cavity center is 2: 1, and it can be distinguished by the difference in the decrease of the shear resistance against the external force. In other words, it was confirmed that the secondary damage should not occur in consideration of the expandability of the material used as the injecting material in the pre-repair and reinforcement, and various ground deformation states will be additionally performed through additional experiments.