• 한국지반환경공학회 논문집
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• 제15권11호
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• pp.5-12
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• 2014

사면은 건설된 후에도 집중강우나 지진, 풍화 등 외부요인으로 인해 파괴가 발생할 수 있기 때문에, 사면의 안정적 유지관리를 위해서는 사면 붕괴의 가능성을 파악하는 것이 필요하다. 특히 암반사면은 암석의 취성적인 특성으로 인해 변위 계측 등과 같은 일반적인 방법으로는 파괴발생이전에 사전징후를 감지하기 매우 어렵다. 그러나 AE 기법을 사면에 적용한다면 변위가 발생하기 전에 파괴 시 발생된 AE 신호를 분석함으로써 일반적인 계측 방법보다 초기에 상태파악이 가능할 것이다. 본 논문에서는 한국의 암반사면 중 붕괴 이력을 가지고 있는 사면에 AE 기법을 적용하여 사면붕괴 가능성을 파악하였다. 그 결과 붕괴위험이 있는 사면에 AE 기법을 적용하면 사면의 위치별 붕괴 가능성을 가능할 것으로 판단된다.

• 한국지반공학회지:지반
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• 제13권3호
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• pp.21-32
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• 1997

본 연구에서는 암반의 국부파괴 현상을 현실적으로 모형 화하기 위하여 혼합체기법을 적용한 새로운 유한요소를 제안하였다. 이를 위하여 각 유한요소의 적분점에서 재료의 안정성을 검토하고 필요시 국부파괴 요소와 인접한 암반 물성을 이용한 혼합체 물성을 도출하였으며 국부파괴 후의 재료 거동을 추적하였다. 제시한 모형을 사용하면 변형율 연화 모형을 사용하더라도 유한요소망의 객관성을 유지할 수 있으며 국부파괴 이후 재료의 거동을 현실적으로 모형화 할 수 있다. 또한 유한요소 갯수가 비교적 작더라도 수치해석 결과와 실험 결과가 잘 일치하고 있음을 알 수 있다.

• The Korean Journal of Physiology and Pharmacology
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• 제12권4호
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• pp.149-153
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• 2008

Endothelin-1 (ET-1) is unequivocally elevated in the kidney with ischemic acute renal failure (ARF), whereas ET receptors ($ET_AR$ and $ET_BR$) are variably expressed. Although renal functional and structural changes are similar between ischemic and nephrotoxic ARF, there are few reports on the alteration in the ET system in nephrotoxic ARF. This study was, therefore, undertaken to investigate changes in renal expression of ET-l and its receptors in nephrotoxic ARF induced by cisplatin. Mice were intraperitoneally injected with 16 mg of cisplatin/kg at a single dose, and the expression of mRNA and protein was then quantified by real-time RT-PCR and Western blot, respectively. Immunohistochemistry was conducted for localization. Three days after treatment, ET-1 transcript in cisplatin-treated mice was thirteen times higher than that in controls, whereas ET-1 peptide was increased by 1.5-fold. Cisplatin caused a 2-fold increase in the levels of ETAR mRNA and protein. Most of the increased immunoreactive ET-1 and ETAR were localized in damaged tubules. Neither the expression of ETBR mRNA nor the abundance and immunoreactive level of ETBR protein were changed. The findings suggest that the individual components of the renal ET system are differentially regulated in cisplatin-induced nephrotoxic ARF.

• Asian Pacific Journal of Cancer Prevention
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• 제14권7호
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• pp.4061-4066
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• 2013

The extranodal natural killer/T-cell lymphoma (ENKTL) shows high local or systemic failure rates when radiotherapy (RT) is taken as the primary treatment, suggesting a role for chemotherapy (CT) added to RT for this disease. However, the appropriate mode of combined modality therapy (CMT) has not been fully defined. A total of one hundred and twenty-one patients with ENKTL receiving sandwich CT with RT were reviewed between January 2003 and August 2012. The primary endpoints were the response rate, progression-free survival (PFS), overall survival (OS), and the relapse rate. After the initial CT, there were 84 (69.4%) patients in CR, 22 (18.2%) patients in PR, 9 (7.4%) patients in SD, and 6 (5%) patients in PD, respectively. At the end of RT, the CR, PR, SD, and PD rates for all patients were 90.9% (n=110), 1.7% (n=2), 4.1% (n=5), and 3.3% (n=4), respectively. After a median follow-up of 42.3 months (3.5~112.3 months), the 5-year PFS was 74.7% (95% CI 70.4%~79.0%), and 5-year OS was 77.3% (95% CI 67.9%~86.7%). Disease progression was documented in 25 (20.7%) patients. The rates of systemic failure, local failure, and regional failure were 18.2%, 5.8%, 1.7%, respectively. Twenty death events (16.5%) were observed for the entire group of patients (18 deaths related to PD). Furthermore, CR to the initial CT and low Korean Prognostic Index (KPI) can independently predict long PFS and OS. The sandwich CMT achieved an excellent outcome for localized ENKTL with acceptable toxicity. We recommend it can be applied as the optimal choice for localized ENKTL.

• Advances in pediatric surgery
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• 제15권2호
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• pp.132-140
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• 2009

The purpose of this study was to determine the success rate of air reduction as the primary treatment of intussusception and whether the success of air reduction could be predicted by plain x-ray. The authors reviewed the medical records of 54 consecutive patients diagnosed with intussusception from Jan 2005 to Dec 2007 at the Department of Surgery, Masan Samsung Hospital. The natures of symptoms and findings of plain abdominal radiography performed in the emergency department (ED) were reviewed. Air reduction failed more frequently (26.3 %) in patients who visited ED more than 24 hours after symptom onset (p=0.009). The mean duration of symptom for operated patients was longer than air reduction group (p=0.01). Also, 3/4 of patients having localized distension of small bowel in the left upper quadrant abdomen had unsuccessful air reduction (p=0.002). In conclusion, the time interval from symptom onset to arrival at ED and localized distension of small bowel in the left upper quadrant abdomen significantly increased the failure rate of air reduction.

• International Journal of Aeronautical and Space Sciences
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• 제18권2호
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• pp.236-244
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• 2017

In this study, the high-velocity impact penetration behavior of $[45/0/-45/90]_{ns}$ carbon/epoxy composite laminates was studied. The considered configuration includes a spherical steel ball impacting clamped circular laminates with various thicknesses and diameters. First, the impact experiment was performed to measure residual velocity and extent of damage. Next, the impact experiment was numerically simulated through finite element analysis using LS-dyna. Three-dimensional solid elements were used to model each ply of the laminates discretely, and progressive material failure was modeled using MAT162. The result indicated that the finite element simulation yielded residual velocities and damage modes well-matched with those obtained from the experiment. It was found that fiber damage was localized near the impactor penetration path, while matrix and delamination damage were much more spread out with the damage mode showing a dependency on the orientation angles and ply locations. The ballistic-limit velocities obtained by fitting the residual velocities increased almost linearly versus the laminate diameter, but the amount of increase was small, showing that the impact energy was absorbed mostly by the localized impact damage and that the influence of the laminate size was not significant at high-velocity impact.

• 소성∙가공
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• 제21권5호
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• pp.285-290
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• 2012

In spite of progress in predicting ductile failure, the development of a macroscopic yield criterion to describe damage evolution in HCP (hexagonal close-packed) materials remains a challenge. HCP materials display strength differential effects (i.e., different behavior in tension versus compression) in their plastic response due to twinning. Cazacu and Stewart(2009) developed an analytical yield criterion for porous material containing randomly distributed spherical voids in an isotropic, incompressible matrix that shows tension-compression asymmetry. The goal of the calculations in this paper is to investigate the effect of the tension-compression asymmetry on necking induced by void nucleation, evolution and consolidation. In order to investigate the effect of the tension-compression asymmetry of the matrix on necking and fracture initiation, three isotropic materials A, B, and C were examined with different ratios of tension-compression asymmetry. The various types of material had BCC, FCC, and HCP crystal structures, respectively. The ratio between tension and compression in plastic flow significantly influences the fracture shape produced by damage propagation as well as affecting the localized neck.

• Journal of Mechanical Science and Technology
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• 제19권7호
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• pp.1432-1440
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• 2005

High-temperature rupture behavior of 5083-Al alloy was tested for failure at 548K under multiaxial stress conditions: uniaxial tension using smooth bar specimens, biaxial shearing using double shear bar specimens, and triaxial tension using notched bar specimens. Rupture times were compared for uniaxial, biaxial, and triaxial stress conditions with respect to the maximum principal stress, the von Mises effective stress, and the principal facet stress. The results indicate that the von Mises effective and principal facet stresses give good correlation for the material investigated, and these parameters can predict creep life data under the multiaxial stress states with the rupture data obtained from specimens under the uniaxial stress. The results suggest that the creep rupture of this alloy under the testing condition is controlled by cavitation coupled with highly localized deformation process, such as grain boundary sliding. It is also conceivable that strain softening controls the highly localized deformation modes which result in cavitation damage in controlling rupture time of this alloy.

• Steel and Composite Structures
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• 제39권2호
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• pp.171-188
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• 2021

Plastic deformation of link beams in eccentrically braced frames is the primary dissipating source of seismic energy. Despite the excellent compatibility with the architectural designs, previous researches indicate the deficiency of flexural yielding links compared to the shear yielding ones because of their localized plastic deformation. Previous investigations have shown that implementing web openings in beams could be an efficient method to improve the seismic performance of moment-resisting connections. Accordingly, this research investigates the use of flexural links with stiffened and un-stiffened web openings to eliminate localized plasticity at the ends of the link. For this purpose, the numerical models are generated in finite element software "Abaqus" and verified against experimental data gathered from other studies. Models are subjected to cyclic displacement history to evaluate their behavior. Failure of the numerical models under cyclic loading is simulated using a micromechanical based damage model known as Cyclic Void Growth Model (CVGM). The elastic stiffness and the strength-based and CVGM-based inelastic rotation capacity of the links are compared to evaluate the studied models' seismic response. The results of this investigation indicate that some of the flexural links with edge stiffened web openings show increased inelastic rotation capacity compared to an un-perforated link.

• Steel and Composite Structures
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• 제44권2호
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• pp.183-198
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• 2022

Plastic deformation of link beams in eccentrically braced frames is the primary dissipating source of seismic energy. Despite the excellent compatibility with the architectural designs, previous researches indicate the deficiency of flexural yielding links compared to the shear yielding ones because of their localized plastic deformation. Previous investigations have shown that implementing web openings in beams could be an efficient method to improve the seismic performance of moment-resisting connections. Accordingly, this research investigates the use of flexural links with stiffened and un-stiffened web openings to eliminate localized plasticity at the ends of the link. For this purpose, the numerical models are generated in finite element software "Abaqus" and verified against experimental data gathered from other studies. Models are subjected to cyclic displacement history to evaluate their behavior. Failure of the numerical models under cyclic loading is simulated using a micromechanical based damage model known as Cyclic Void Growth Model (CVGM). The elastic stiffness and the strength-based and CVGM-based inelastic rotation capacity of the links are compared to evaluate the studied models' seismic response. The results of this investigation indicate that some of the flexural links with edge stiffened web openings show increased inelastic rotation capacity compared to an un-perforated link.