• 대한기계학회논문집A
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• 제24권1호
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• pp.38-51
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• 2000

The study on the mechanical behavior of a spot-welded specimen is largely divided into the quasi-static overload failure analysis and the fatigue failure prediction. The main issue in an overload analysis is to examine the critical loads, thereby providing a generalized overload failure criterion. As the welding spot forms a singular geometry of an external crack type, fatigue failure of spot-welded specimens can be evaluated by means of a fracture parameter. In this study, we first present the limit loads of 4 representative types of single spot-welded specimens in terms of the base metal yield strength and specimen geometries. Recasting the load vs. fatigue life relationships experimentally, obtained here, we then predict the fatigue life of spot-weld specimens with a single parameter denoted the equivalent stress intensity factor. This crack driving parameter is demonstrated to successfully describe the effects of specimen geometry and loading type in a comprehensive manner. The suggested fatigue life formula for a single spot weld can play a key, role in the design and assessment of spot-welded panel structures, in that the fatigue strength of multi-spots is eventually determined by the fatigue strength of each single spot.

• Clinical and Experimental Pediatrics
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• 제50권11호
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• pp.1041-1048
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• 2007

Not a few patients in children and adolescents are suffering from right ventricular (RV) dysfunction resulting from various conditions such as chronic lung disease, left ventricular dysfunction, pulmonary hypertension, or congenital heart defect. The RV is different from the left ventricle in terms of ventricular morphology, myocardial contractile pattern and special vulnerability to the pressure overload. Right ventricular failure (RVF) can be evaluated in terms of decreased RV contractility, RV volume overload, and/or RV pressure overload. The management for RVF starts from clear understanding of the pathophysiology of RVF. In addition to correction of the underlying disease, management of RVF per se is very important. Meticulous control of volume status, inotropic agents, vasopressors, and pulmonary selective vasodilators are the main tools in the management of RVF. The relative importance of each tool depends on the individual clinical status. Medical assist device and surgery can be considered selectively in case of refractory RVF to optimal medical treatment.

• Steel and Composite Structures
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• 제12권3호
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• pp.231-248
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• 2012

This research aims to investigate the structural behavior of concentrically braced frames after element loss by performing nonlinear static and dynamic analyses such as Time History Analysis (THA), Pushdown Analysis (PDA), Vertical Incremental Dynamic Analyses (VIDA) and Performance-Based Analysis (PBA). Such analyses are to assess the potential and capacity of this structural system for occurrence of progressive collapse. Besides, by determining the Failure Overload Factors (FOFs) and associated failure modes, it is possible to relate the results of various types of analysis in order to save the analysis time and effort. Analysis results showed that while VIDA and PBA according to FEMA 356 are mostly similar in detecting failure mode and FOFs, the Pushdown Overload Factors (PDOFs) differ from others at most to the rate of 23%. Furthermore, by sensitivity analysis it was observed that among the investigated structures, the eight-story frame had the most FOF. Finally, in this research the trend of FOF and the FOF to critical member capacity ratio for the plane split-X braced frames were introduced as a function of the number of frame stories.

• Clinical and Experimental Pediatrics
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• 제56권3호
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• pp.101-106
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• 2013

Despite developments in surgical techniques and other interventions, right ventricular (RV) failure remains an important clinical problem in several congenital heart diseases (CHD). RV function is one of the most important predictors of mortality and morbidity in patients with CHD. RV failure is a progressive disorder that begins with myocardial injury or stress, neurohormonal activation, cytokine activation, altered gene expression, and ventricular remodeling. Pressure-overload RV failure caused by RV outflow tract obstruction after total correction of tetralogy of Fallot, pulmonary stenosis, atrial switch operation for transposition of the great arteries, congenitally corrected transposition of the great arteries, and systemic RV failure after the Fontan operation. Volume-overload RV failure may be caused by atrial septal defect, pulmonary regurgitation, or tricuspid regurgitation. Although the measurement of RV function is difficult because of many reasons, the right ventricle can be evaluated using both imaging and functional modalities. In clinical practice, echocardiography is the primary mode for the evaluation of RV structure and function. Cardiac magnetic resonance imaging is increasingly used for evaluating RV structure and function. A comprehensive evaluation of RV function may lead to early and optimal management of RV failure in patients with CHD.

• 항공우주기술
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• 제3권2호
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• pp.208-216
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• 2004

항공기 전기체 구조시험에 사용되는 기존의 과하중 방지모듈의 성능을 개량하여 고성능의 과하중방지 모듈을 개발하였다. 항공기 전기체 구조시험 수행시에는 예기치 않은 오류(자연재해로 인한 정전사고, 시험체의 파손, 설계강도 미달로 인한 시험정지 등)로 인해 시험하중보다 큰 하중이 시험체에 가해질 수 있다. 이 때 발생한 과하중을 해소하여 시험체를 파손으로부터 보호하는 과하중 방지기능이 필요하다. 본 논문에서는 상용의 기존 과하중 방지모듈에 대해 구성요소별로 기능을 살펴보고, 기존 제품을 이용하여 구조시험을 수행하는 도중 나타난 문제점을 분석하였다. 또한, 기존 과하중 방지모듈이 갖고 있는 문제점을 개선한 고성능 과하중 방지모듈의 개발에 대해 기술하였다.

• 대한치과보철학회지
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• 제39권1호
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• pp.25-36
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• 2001

Among the numerous factors contributing to implant failure, the most common are infection, failure of proper healing and overload. These factors may occur combined. Implant fractures are one of the complications resulting from overload. Implant fracture is not a common feature, but once it occurs it causes very unpleasant circumstances for the patient as well as for the practitioner. Only few studies have been reported regarding this subject. Thus, little is known about its solutions. It is important that analyzing reasons for implant fracture and finding appropriate solutions. Factors leading to implant fracture are design, material defects, nonpassive fit of prosthetic framework and biomechanical overload. Previous studies have reported that implant fractures ares associated with marginal bone loss and occur mostly in the posterior regions and that most patients showing parafunctional habits also have implant fracture. Abutment and gold screw loosening or fracture were also observed in some of the cases previous to implant fracture. Similar observations were seen in our hospital as well. The following cases will present implant fracture cases which have been successfully treated regarding function and biomechanics. This was achieved by means of using increased number of futures, increasing fixture diameter and establishing proper occlusion.

• 구강회복응용과학지
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• 제19권2호
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• pp.105-108
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• 2003

After stage-two surgery, the highest incidence of failure has been attributed to implant overload. However, the biomechanical factors cited inthe literature that contribute to implant overload, such as bone type, cuspal inclination, horizontal offset, maxillary compared to mandibular arch, the inclusion of natural teeth within the prosthesis, and occlusal harmony are superimposed on physiologic variations. Following two cases, including reduction of cuspal inclination and usage of modified incisal pin, showed a method of contouring occlusal surface for reduction of unpreditable implant overload.

• Clinical and Experimental Pediatrics
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• 제50권10호
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• pp.938-947
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• 2007

Many dialysis modalities such as peritoneal dialysis (PD), hemodialysis (HD) and continuous hemofiltration or hemodialysis (CRRT) are available for the management of pediatric patients with acute renal failure (ARF). PD is a relatively simple, inexpensive modality and can be used in hemodynamically unstable patients. But, it may not be the optimal therapy for patients with severe volume overload or life threatening hyperkalemia. HD is the preferred modality for the treatment of severe volume overload, severe hyperkalemia, but it needs vascular access. Improvements in the HD equipment have allowed HD to be performend in small children. Recents technological improvements in CRRT therapies have enabled pediatric patients who are less stable to be treated. CRRT is becoming the preferred method of acute therapy in pediatric intensive care units. A sound knowledge of the underlying principles of dialysis and awareness of recent technological advancements in differnet dialysis modalities will hopefully result in improved management of children with ARF.

• Clinical and Experimental Pediatrics
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• 제50권10호
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• pp.948-953
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• 2007

Acute renal failure is the generic term for an abrupt and sustained decrease in renal function resulting in retention of nitrogenous and non nitrogenous waste product. This may results in life threatening consequences including volume overload, hyperkalemia, and metabolic acidosis. Acute renal failure is both common and carries high mortality rate, but as it is often preventable, identification of patients at risk and and appropriate management are crucial. This review summarized the most recent information on definition, epidemiology, clinical causes and management of acute renal failure in pediatric patients.

• 대한한방내과학회지
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• 제38권6호
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• pp.877-890
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• 2017

Objectives: Lonicerae flos (LF), a dried flower part of Lonicera japonica Thunb., has been widely used in Korean medicine as anti-inflammatory and antioxidative agent. The purpose of this study was to determine the cardioprotective effects of LF, through potential antioxidant effects, on the pressure overload (PO)-induced heart failure (HF) in C57BL/6 mice after transverse aortic constriction (TAC) surgery. Methods: Resveratrol (10 mg/kg body weight) or LF (125, 250 or 500 mg/kg body weight) was orally administered, once daily for 14 days, starting 14 days after TAC surgery. Changes in the mortality, body weights, heart weights, histopathology of the heart, and antioxidant defense systems of the heart were analyzed. Results: Marked and noticeable increases of heart weights, mortalities, and hypertrophic, focal, and lytic fibrotic histological changes in the LVs were observed, with destruction of heart antioxidant defense systems after surgery. However, HF signs, induced by TAC surgery through PO, and destruction of heart antioxidant defense systems were significantly and dose-dependently inhibited by 14 days of maintained oral treatment with LF 500, 250 or 125 mg/kg. Treatment with 250 mg/kg LF was comparable to treatment with 10 mg/kg resveratrol. Conclusions: The results in this study suggest that oral administration of LF favorably relieves PO-induced HF following TAC, through increase of heart antioxidant defense systems. The overall effects of 250 mg/kg LF were similar to those of 10 mg/kg resveratrol. More detailed mechanistic studies should be conducted in the future, with screening of the biologically active compounds in LF.