• Title/Summary/Keyword: Asymmetric damage

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X-ray and Plasma Process Induced Damages to PLZT Capacitor Characteristics for DRAM Applications

  • Kim, Jiyoung
    • The Korean Journal of Ceramics
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    • v.3 no.3
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    • pp.213-217
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    • 1997
  • In this paper, the imparct of X-ray and plasma process-induced-damages to La doped Lead Zirconate Titanate (PLZT, (Pb1-xLa)(Zr0.5Ti0.5)O3) capacitor characteristics have been investigated from the viewpoint of gigabit scale dynamic random access memory (DRAM) applications. Plamsa damage causes asymmetric degradation on hysteresis characteristics of PLZT films. On the other hand, X-ray damage results in a symmetrical reduction of charge storage densities (Qc's) for both polarities. As La concentration increases in the films, the radiation hardness of PLZT films on X-ray and plasma exposures is improved. It is observed that the damaged devices are fully recovered by thermal annealing under oxygen ambient.

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Study on Section Properties of Asymmetric-Sectioned Vessels (선박의 비대칭 단면 특성에 대한 연구)

  • Choung, Joon-Mo;Kim, Young-Hun
    • Journal of the Society of Naval Architects of Korea
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    • v.47 no.6
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    • pp.843-849
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    • 2010
  • This paper presents definition of symmetry of a ship section where three symmetries are proposed: material, geometric, and load symmetries. Precise terminologies of centroid, moment plane, and neutral axis plane are also defined. It is suggested that force vector equilibrium as well as force equilibrium are necessary condition to determine new position of neutral axis due to translational and rotational mobility. It is also stated that new reference datum of ENMP(elastic neutral moment plane), PNMP(fully plastic moment plane), ENAP(elastic neutral axis plane), and INAP(inelastic neutral moment plane) are required to define asymmetric section properties such as second moment of area, elastic section modulus, yield moment, fully plastic moment, and ultimate moment. Since collision-induced damage and flooding-induced biaxial bending moment produce typical asymmetry of section, the section properties are calculated for a typical VLCC. Geometry asymmetry is determined from ABS and DNV rules and two moment planes of 0/30 degs are assumed for load asymmetry. It is proved that the property reduction ratios directly calculated from second moment of area are usually larger than area reduction ratio. Reduction ratio of ultimate moment capacity shows almost linearly proportional to area reduction ratio. Mobility of elastic and inelastic neutral axis planes is visually provided.

The impact of successive earthquakes on the seismic damage of multistorey 3D R/C buildings

  • Kostinakis, Konstantinos;Morfidis, Konstantinos
    • Earthquakes and Structures
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    • v.12 no.1
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    • pp.1-12
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    • 2017
  • Historical earthquakes have shown that successive seismic events may occur in regions of high seismicity. Such a sequence of earthquakes has the potential to increase the damage level of the structures, since any rehabilitation between the successive ground motions is practically impossible due to lack of time. Few studies about this issue can be found in literature, most of which focused their attention on the seismic response of SDOF systems or planar frame structures. The aim of the present study is to examine the impact of seismic sequences on the damage level of 3D multistorey R/C buildings with various structural systems. For the purposes of the above investigation a comprehensive assessment is conducted using three double-symmetric and three asymmetric in plan medium-rise R/C buildings, which are designed on the basis of the current seismic codes. The buildings are analyzed by nonlinear time response analysis using 80 bidirectional seismic sequences. In order to account for the variable orientation of the seismic motion, the two horizontal accelerograms of each earthquake record are applied along horizontal orthogonal axes forming 12 different angles with the structural axes. The assessment of the results revealed that successive ground motions can lead to significant increase of the structural damage compared to the damage caused by the corresponding single seismic events. Furthermore, the incident angle can radically alter the successive earthquake phenomenon depending on the special characteristics of the structure, the number of the sequential earthquakes, as well as the distance of the record from the fault.

A Study on the Possibility of Damage by Anti-aircraft Debris between the Response of Unmanned Aircraft (무인기 대응 간 대공무기 파편에 의한 피해 가능성 연구)

  • Kim, Sea Ill;Shin, Jin
    • Journal of the Korea Society for Simulation
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    • v.29 no.3
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    • pp.1-8
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    • 2020
  • When enemy drones infiltrate large urban areas, various forms of great republics are deployed in large areas to respond. Due to the characteristics of a large number of government-run aircraft, the residual coal, other than the hit bullet, falls into various sizes of debris after its own explosion. The damage rate was analyzed by dividing the debris into anti-aircraft guns and guided weapons by deriving four factors: critical speed, fragmentation mass, initial speed of debris, and object collision speed, which can cause damage to human life as the debris falls to the ground. In the future, the North is expected to infiltrate the capital city of Seoul by operating unmanned aerial vehicles, which are asymmetric forces, and the damage could be minimized by setting up pre-fatal and fire-restricted zones to minimize casualties between responses.

X-ray diffraction analysis of the effect of ball milling time on crystallinity of milled polyacrylonitrile-based carbon fiber

  • Lee, Sang-Hye;Kang, Dong-Su;Lee, Sang-Min;Roh, Jae-Seung
    • Carbon letters
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    • v.26
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    • pp.11-17
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    • 2018
  • Milled carbon fiber (mCF) was prepared by a ball milling process, and X-ray diffraction (XRD) diffractograms were obtained by a $2{\theta}$ continuous scanning analysis to study mCF crystallinity as a function of milling time. The raw material for the mCF was polyacrylonitrile-based carbon fiber (T700). As the milling time increased, the mean particle size of the mCF consistently decreased, reaching $1.826{\mu}m$ at a milling time of 18 h. The XRD analysis showed that, as the milling time increased, the fraction of the crystalline carbon decreased, while the fraction of the amorphous carbon increased. The (002) peak became asymmetric before and after milling as the left side of the peak showed an increasingly gentle slope. For analysis, the asymmetric (002) peak was deconvoluted into two peaks, less-developed crystalline carbon (LDCC) and more-developed crystalline carbon. In both peaks, Lc decreased and $d_{002}$ increased, but no significant change was observed after 6 h of milling time. In addition, the fraction of LDCC increased. As the milling continued, the mCF became more amorphous, possibly due to damage to the crystal lattices by the milling.

The Effect of Visual Feedback on Postural Control During Sit-to-Stand Movements of Brain-Damaged Patients Under Different Support Conditions (지지조건에 따른 시각되먹임이 뇌손상환자의 일어서기 과정 동안 자세조절에 미치는 영향)

  • Shin, Jun-Beom;Lee, Jae-Sik
    • Physical Therapy Korea
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    • v.19 no.3
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    • pp.40-50
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    • 2012
  • The purpose of this study was to investigate the effect of visual feedback on the postural control of stroke patients, by systematically varying conditions of visual feedback [eye-open condition (EO) vs. eye-closed condition (EC)], and base-support (both-side support, affected-side support, and unaffected-side support). In this study, we allocated 41 stroke patients with no damage in the cerebellum and visual cortex who can walk at least 10 meters independently, and 35 normal adults who have no experience of stroke to the control group. Both groups were asked to perform a "sit-to-stand" task three to five times, and their postural control ability was measured and compared in terms of asymmetric dependence (AD) instead of the traditional symmetric index (SI) in the literature. The results showed that although both subject groups maintained better postural control in the EO condition than in the EC condition, the patient group appeared to be more stable in EC than in EO when they were required to perform the task of the support condition given on the affected side. These results implied that visual feedback can impair stroke patients' postural control when it is combined with a specific support condition.

Experimental Study on Cavitation Instability of a Solution Pump Inducer in an Absorption Chiller-Heater (흡수식 냉온수기내 용액펌프 Inducer의 Cavitation 불안정성에 대한 실험적 연구)

  • Seo, Min;Lee, Kyung-Hoon;Kang, Shin-Hyung
    • Proceedings of the KSME Conference
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    • 2008.11b
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    • pp.2434-2439
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    • 2008
  • This paper was studied on the cavitation instability of a Solution Pump Inducer in an absorption chiller-heater. Inlet pressure of LiBr and rotational speed at nominal mode are 2,800 Pa and 3,500 rpm respectively. Due to the marginal operation of available NPSH, the cavitation performance of the inducer is critical for the stable operation without the deterioration of head performance. In the study, cavitation performance and its mode of instability was investigated experimentally. Water was used as the working fluid and the test inducer was scaled up as 1.75 times for detail measurements and flow visualization. Inlet pressure was controlled by a vacuum pump. This research focused on types of cavitation instability and phenomena to investigate the possibility of harmful damage due to cavitation instability. Casing wall pressure and instantaneous inlet pressure was measured to observe the unsteady flow characteristics. Through the visualization and spectrum analysis of pressure, the occurrence region and intensity of asymmetric cavitation and cavitation surge are analyzed in the test inducer.

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Response of steel pipeline crossing strike-slip fault in clayey soils by nonlinear analysis method

  • Hadi Khanbabazadeh;Ahmet Can Mert
    • Geomechanics and Engineering
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    • v.34 no.4
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    • pp.409-424
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    • 2023
  • Response of the pipeline crossing fault is considered as the large strain problem. Proper estimation of the pipeline response plays important role in mitigation studies. In this study, an advanced continuum modeling including material non-linearity in large strain deformations, hardening/softening soil behavior and soil-pipeline interaction is applied. Through the application of a fully nonlinear analysis based on an explicit finite difference method, the mechanics of the pipeline behavior and its interaction with soil under large strains is presented in more detail. To make the results useful in oil and gas engineering works, a continuous pipeline of two steel grades buried in two clayey soil types with four different crossing angles of 30°, 45°, 70° and 90° with respect to the pipeline axis have been considered. The results are presented as the fault movement corresponding to different damage limit states. It was seen that the maximum affected pipeline length is about 20 meters for the studied conditions. Also, the affected length around the fault cutting plane is asymmetric with about 35% and 65% at the fault moving and stationary block, respectively. Local buckling is the dominant damage state for greater crossing angle of 90° with the fault displacement varying from 0.4 m to 0.55 m. While the tensile strain limit is the main damage state at the crossing angles of 70° and 45°, the cross-sectional flattening limit becomes the main damage state at the smaller 30° crossing angles. Compared to the stiff clayey soil, the fault movement resulting 3% tensile strain limit reach up to 40% in soft clayey soil. Also, it was seen that the effect of the pipeline internal pressure reaches up to about 40% compared to non-pressurized condition for some cases.

A baseline free method for locating imperfect bolted joints

  • Soleimanpour, Reza;Soleimani, Sayed Mohamad;Salem, Mariam Naser Sulaiman
    • Structural Monitoring and Maintenance
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    • v.9 no.3
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    • pp.237-258
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    • 2022
  • This paper studies detecting and locating loose bolts using nonlinear guided waves. The 3D Finite Element (FE) simulation is used for the prediction of guided waves' interactions with loose bolted joints. The numerical results are verified by experimentally obtained data. The study considers bolted joints consisting of two bolts. It is shown that the guided waves' interaction with surfaces of a loose bolted joint generates Contact Acoustic Nonlinearity (CAN). The study uses CAN for detecting and locating loose bolts. The processed experimentally obtained data show that the CAN is able to successfully detect and locate loose bolted joints. A 3D FE simulation scheme is developed and validated by experimentally obtained data. It is shown that FE can predict the propagation of guided waves in loose bolts and is also able to detect and locate them. Several numerical case studies with various bolt sizes are created and studied using the validated 3D FE simulation approach. It is shown that the FE simulation modeling approach and the signal processing scheme used in the current study are able to detect and locate the loose bolts in imperfect bolted joints. The outcomes of this research can provide better insights into understanding the interaction of guided waves with loose bolts. The results can also enhance the maintenance and repair of imperfect joints using the nonlinear guided waves technique.

Fault Detections of Ring Structures using Vibration Modes (진동모드를 이용한 링 구조물의 결함 탐지)

  • Kim, Seock-Hyun;Jang, Ho-Sik
    • Journal of Industrial Technology
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    • v.22 no.A
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    • pp.29-36
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    • 2002
  • A damage detection algorithm using vibration modes is applied to the ring structures and the modal behaviors of the slightly asymmetric rings are examined. Mode shape change, MSER(modal strain energy ratio) and MCR(modal curvature ratio) are investigated to identify the locations of faults or damages The above fault detection parameters are calculated and compared by the finite element analysis on rings with designed local damages. Damages are modeled as a reduced stiffness in the analysis The results show that MSER and MCR can be proper parameters to detect local damages in the ring structures.

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