• Title/Summary/Keyword: load cycling

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Microleakage of Class V cavity restored with flowable and microfill composite resins after load cycling.

  • Kang, Suk-Ho;Son, Ho-Hyun
    • Proceedings of the KACD Conference
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    • 2001.11a
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    • pp.569.2-569
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    • 2001
  • Flowable and microfill composites have been recommended for Class V cavities. But the use of flowable composites is controversial because of its physical properties. Objectives: The aim of this study was to evaluate the microleakage of 6 composites (2 hybrids, 2 microfills, and 2 flowable composites) with/without load cycling. Methods: Notch-shaped Class V cavities were prepared on buccal surfaces of 180 extracted human upper premolars and then divided into non-load cycling group(G1) and load cycling group(G2).(omitted)

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Cyling Load Test of Architectural Glass Fiber Membrane (건축용 유리섬유 막재의 반복하중 시험)

  • Park, Kang-Geun;Yoon, Sung-Kee;Lee, Jang-Bok;Jun, Woo-Hong
    • Proceeding of KASS Symposium
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    • 2008.05a
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    • pp.31-36
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    • 2008
  • Architectural membrane are now used in the roof of large span structures throughout the world with the merits of free shape and lightness. Some membrane have some problems of structural capacity by the wind or snow load conditions, large span structures was shown to the tearing of the membrane. This paper is the experimental test on the stress strain curve of cycling load for the glass fiber membrane. In the result of stress strain relationship curve by the cycling load, glass fiber membrane was reduced the tensile strength, the polyester membrane was shown to occur the increase of displacement without load reduction in each load step.

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The nanoleakage patterns of experimental hydrophobic adhesives after load cycling (Load cycling에 따른 소수성 실험용 상아질 접착제의 nanoleakage 양상)

  • Sohn, Suh-Jin;Chang, Ju-Hae;Kang, Suk-Ho;Yoo, Hyun-Mi;Cho, Byeong-Hoon;Son, Ho-Hyun
    • Restorative Dentistry and Endodontics
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    • v.33 no.1
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    • pp.9-19
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    • 2008
  • The purpose of this study was: (1) to compare nanoleakage patterns of a conventional 3-step etch and rinse adhesive system and two experimental hydrophobic adhesive systems and (2) to investigate the change of the nanoleakage patterns after load cycling. Two kinds of hydrophobic experimental adhesives, ethanol containing adhesive (EA) and methanol containing adhesive (MA), were prepared. Thirty extracted human molars were embedded in resin blocks and occlusal thirds of the crowns were removed. The polished dentin surfaces were etched with a 35 % phosphoric acid etching gel and rinsed with water. Scotchbond Multi-Purpose (MP), EA and MA were used for bonding procedure. Z-250 composite resin was built-up on the adhesive-treated surfaces. Five teeth of each dentin adhesive group were subjected to mechanical load cycling. The teeth were sectioned into 2 mm thick slabs and then stained with 50 % ammoniacal silver nitrate. Ten specimens for each group were examined under scanning electron microscope in backscattering electron mode. All photographs were analyzed using image analysis software. Three regions of each specimen were used for evaluation of the silver uptake within the hybrid layer. The area of silver deposition was calculated and expressed in gray value. Data were statistically analyzed by two-way ANOVA and post-hoc testing of multiple comparisons was done with the Scheffe's test. Silver particles were observed in all the groups. However, silver particles were more sparsely distributed in the EA group and the MA group than in the MP group (p < .0001). There were no changes in nanoleakage patterns after load cycling.

Development of Reliability Design Technique and Life Prediction Model for Electronic Components (취성/연성 파괴에 대한 수명예측 모델 및 신뢰성 설계)

  • Kim, Il-Ho;Lee, Soon-Bok
    • Proceedings of the KSME Conference
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    • 2007.05a
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    • pp.1740-1743
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    • 2007
  • In this study, two types of fatigue tests were conducted. First, cyclic bending tests were performed using the micro-bending tester. A four-point bending test method was adopted, because it induces uniform stress fields within a loading span. Second, thermal fatigue tests were conducted using a pseudo power cycling machine which was newly developed for a realistic testing condition. The pseudo-power cycling method makes up for the weak points in a power cycling and a chamber cycling method. Two compositions of solder are tested in all test condition, one is lead-free solder (95.5Sn4.0Ag0.5Cu) and the other is eutectic lead-contained solder (63Sn37Pb). In the cyclic bending test, the solder that exhibits a good reliability can be reversed depending on the load conditions. The lead-contained solders have a longer fatigue life in the region where the applied load is high. On the contrary, the lead-free solder sustained more cyclic loads in the small load region. A similar trend was detected at the thermal cycling test. A three-dimensional finite element analysis model was constructed. A finite element analysis using ABAQUS was performed to extract the applied stress and strain in the solder joints. A constitutive model which includes both creep and plasticity was employed. Thermal fatigue was occurred due to the creep. And plastic deformation is main damage for bending failure. From the inelastic energy dissipation per cycle versus fatigue life curve, it can be found that the bending fatigue life is longer than the thermal fatigue life.

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MICROLEAKAGE OF MICROFILL AND FLOWABLE COMPOSITE RESINS IN CLASS V CAVITY AFTER LOAD CYCLING (Flowable 및 microfill 복합레진으로 충전된 제 5급와동에서 load cycling 전,후의 미세변연누출 비교)

  • Kang, Suk-Ho;Kim, Oh-Young;Oh, Myung-Hwan;Cho, Byeong-Hoon;Um, Chung-Moon;Kwon, Hyuk-Choon;Son, Ho-Hyun
    • Restorative Dentistry and Endodontics
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    • v.27 no.2
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    • pp.142-149
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    • 2002
  • Low-viscosity composite resins may produce better sealed margins than stiffer compositions (KempScholte and Davidson, 1988: Crim, 1989). Plowable composites have been recommended for use in Class V cavities but it is also controversial because of its high rates of shrinkage. On the other hand, in the study comparing elastic moduli and leakage, the microfill had the least leakage (Rundle et at. 1997) Furthermore, in the 1996 survey of the Reality Editorial Team, microfills were the clear choice for abfraction lesions. The purpose of this study was to evaluate the microleakage of 6 compostite resins (2 hybrids, 2 microfills, and 2 flowable composites) with and without load cycling. Notch-shaped Class V cavities were prepared on buccal surface of 180 extracted human upper premolars on cementum margin. The teeth were randomly divided into non-load cycling group (group 1) and load cycling group (group 2) of 90 teeth each. The experimental teeth of each group were randomly divided into 6 subgroups of 15 samples. All preparations were etched, and Single bond was applied. Preparations were restored with the following materials (n=15) : hybrid composite resin [Z250(3M Dental Products Inc. St. Paul, USA), Denfil(Vericom, Ahnyang, Korea)], microfill [Heliomolar RO(Vivadent, Schaan, Liechtenstein), Micronew(Bisco Inc. Schaumburg, IL, USA)], and flowable composite[AeliteFlo(Bisco Inc. Schaumburg, IL, USA), Revolution(Kerr Corp. Orange, CA, USA)]. Teeth of group 2 were subjected to occlusal load (100N for 50,000 cycles) using chewing simulator(MTS 858 Mini Bionix II system, MTS Systems Corp. Minn. USA). All samples were coated with nail polish 1mm short of the restoration, placed in 2% methylene blue for 24 hours, and sectioned with a diamond wheel. Enamel and dentin/cementum margins were analyzed for microleakage on a sclale of 0 (no leakage) to 3 (3/3 of wall). Results were statistically analyzed by Kruscal-Wallis One way analysis, Mann-Whitney U-test, and Student-Newmann-Keuls method. (p = 0.05) Results : 1. There was significantly less microleage in enamel margins than dentinal margins of all groups (p<0.05) 2. There was no significant between six composite resin in enamel margin of group 1. 3. In dentin margin of group 1, flowable composite had more microleakage than others but not of significant differences. 4. there was no significant difference between six composite resin in enamel margin of group 2. 5. In dentin margin of group 2, the microleakage were R>A =H=M>D>Z. But there was no significant differences. 6. In enamel margins, load cycling did not affect the marginal microleakage in significant degree. 7. In enamel margins, load cycling did affect the marginal microleakage only in Revolution. (p<0.05).

CCDC: A Congestion Control Technique for Duty Cycling WSN MAC Protocols

  • Jang, Beakcheol;Yoon, Wonyong
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.11 no.8
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    • pp.3809-3822
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    • 2017
  • Wireless Sensor Networks hold the limelight because of significant potential for distributed sensing of large geographical areas. The radio duty cycling mechanism that turns off the radio periodically is necessary for the energy conservation, but it deteriorates the network congestion when the traffic load is high, which increases the packet loss and the delay too. Although many papers for WSNs have tried to mitigate network congestion, none of them has mentioned the congestion problem caused by the radio duty cycling of MAC protocols. In this paper, we present a simple and efficient congestion control technique that operates on the radio duty cycling MAC protocol. It detects the congestion by checking the current queue size. If it detects the congestion, it extends the network capacity by adding supplementary wakeup times. Simulation results show that our proposed scheme highly reduces the packet loss and the delay.

The analysis of electrical characteristics with Micro-crack in PV module (Micro-cracks에 의한 PV 모듈의 전기적 특성 분석)

  • Song, Young-Hun;Ji, Yand-Geun;Kim, Kyung-Soo;Kang, Gi-Hwan;Yu, Gwon-Jong;Ahn, Hyung-Gun;Han, Deuk-Young
    • 한국태양에너지학회:학술대회논문집
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    • 2011.04a
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    • pp.25-30
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    • 2011
  • In this paper, we analyzed the electrical characteristics with Micro-cracks in Photovoltaic module. Micro cracks are increasing the breakage risk over the whole value chine from the wafer to the finished module, because the wafer or cell is exposed to mechanical stress. And The solar cells have to with stand the stress under out door operation in the finished module. Here the mechanical stress is induced by temperature changes and mechanical loads from wind and snow. So, we experimentally analyze the direct impact of micro-cracks on the module power and the consequences after artificial aging. The first step, we made micro-cracks in PV module by mechanical load test according to IEC 61215. Next, PV modules applied the thermal cycling test, because micro-cracks accelerated aging by thermal cycling test, according to IEC61215. Before every test, we checked output and EL image of PV module. As the result of first step, we detected little power loss(0.9%). But after thermal cycling test increased power loss about 3.2%.

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THE EFFECT OF REBONDING IN MICROLEAKAGE OF CLASS V RESTORATIONS UNDER LOAD CYCLING (부하순환 하에서 제V급 복합레진 수복물의 미세변연누출에 대한 재접착제의 효과에 관한 연구)

  • Youn, Yeon-Hee;Kim, Young-Jae;Kim, Jung-Wook;Jang, Ki-Taeg;Lee, Sang-Hoon;Kim, Chong-Chul;Hahn, Se-Hyun
    • Journal of the korean academy of Pediatric Dentistry
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    • v.31 no.3
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    • pp.527-533
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    • 2004
  • One clinical technique recommended for improving marginal integrity is "rebonding" or application of unfilled resins to the surface of composite restoration. But continuously the restorations are affected with occlusal load. There is room for doubt that the rebonding agent has the positive effect on microleakage in spite of the stress generated by the occlusal load. This study determined the effect of rebonding on microleakage of Class V resin composite restorations under load cycling. Class V cavities were prepared on the buccal surface of 40 sound extracted premolars and restored with a hybrid light-cured resin composite according to manufacturers' directions. They were randomly divided into two groups consisting of 20 samples: a control(group I), without surface sealing, and the other group(group II) in which margins were etched and rebonded. After thermocycling, each of groups was divided into subgroups(group A, B), and load cycling(total 100,000 cycles with 4-100N load at a rate of 1 Hz) were applied on the group B. Assessment of microleakage utilized methylene blue dye penetration. The following results were obtained: 1. In the occlusal region, no significant difference was noted in the scores regardless of whether or not the rebonding agent was used(group TA-IIA, IB-IIB)(p>0.05). 2. In the cervical region, the control group with rebonding(group IIA) showed the better result than the group without rebonding(group IA)(p<0.05). 3. In the cervical region, the rebonded group with load cycling(group IIB) showed similar results to the group without rebonding(group IB) and no significant difference was noted(p>0.05).

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CRYOGENIC AND ELEVATED TEMPERATURE CYCLING OF CARBON/POLYMER COMPOSITES (탄소/고분자 복합재료의 극저온-고온 싸이클링)

  • Yeh, Byung-Hahn;Won, Yong-Gu
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 2002.10a
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    • pp.38-42
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    • 2002
  • An apparatus was developed to repetitively apply a $-196^{\circ}C$ thermal load to coupon-sized mechanical test specimens. Using this device, IM7/5250-4 (carbon / bismaleimide) cross-ply and quasi-isotropic laminates were submerged in liquid nitrogen ($LN_2$) 400 times. Ply-by-ply micro-crack density, laminate modulus, and laminate strength were measured as a function of thermal cycles. Quasi-isotropic samples of IM7/977-3 (carbon / epoxy) composite were also manually cycled between liquid nitrogen and an oven set at $120^{\circ}C$ for 130 cycles to determine whether including elevated temperature in the thermal cycle significantly altered the degree or location of micro-cracking. In response to thermal cycling, both materials micro-cracked extensively in the surface plies fellowed by sparse cracking of the inner plies. The tensile modulus of the IM7/5250-4 specimens was unaffected by thermal cycling, but the tensile strength of two of the lay-ups decreased by as much as 8.5%.

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CRYOGENIC AND ELEVATED TEMPERATURE CYCLING OF CARBON / POLYMER COMPOSITES FOR RESUABLE LAUNCH VEHICLE CRYOGENIC TANKS (왕복선 연료탱크 적용을 위한 탄소/고분자 복합재료의 극저온-고온 싸이클링)

  • 예병한;원용구
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2003.05a
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    • pp.151-155
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    • 2003
  • An apparatus was developed to repetitively apply a -196 $^{\circ}C$ thermal load to coupon-sized mechanical test specimens. Using this device, IM7/5250-4 (carbon / bismaleimide) cross-ply and quasi-isotropic laminates were submerged in liquid nitrogen (L$N_2$) 400 times. Ply-by-Ply micro-crack density, laminate modulus, and laminate strength were measured as a function of thermal cycles. Quasi-isotropic samples of IM7/977-3 (carbon / epoxy) composite were also manually cycled between liquid nitrogen and an oven set at 120 $^{\circ}C$ for 130 cycles to determine whether including elevated temperature in the thermal cycle significantly altered the degree or location of micro-cracking. In response to thermal cycling, both materials micro-cracked extensively in the surface plies followed by sparse cracking of the inner plies. The tensile modulus of the IM7/5250-4 specimens was unaffected by thermal cycling, but the tensile strength of two of the lay-ups decreased by as much as 8.5 %.

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