• International Journal of Precision Engineering and Manufacturing
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• 제3권2호
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• pp.61-71
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• 2002

This paper presents the dynamic analysis of indeterminate rotor systems with angular contact ball bearings subject to axial and radial loads. The reaction forces against applied radial loads significantly influence the dynamic characteristics of angular contact ball bearings. However, the reaction forces are hard to determine in the case of indeterminate rotor-bearing systems. To this end, this paper proposes a finite element model for indeterminate rotor systems with angular contact ball bearings. An improved bearing model is adopted which is originated from the Harris's bearing dynamic model. The bearing model is also extended to include centrifugal forces due to the ball and inner ring. This paper utilizes a new iterative algorithm for general, indeterminate rotor systems with angular contact ball bearings. This examples are provided to illustrate the dynamic characteristics of rotor systems with angular contact ball bearings subject to axial and radial loads. The experimental and numerical results prove that the proposed method is useful for the dynamic analysis of indeterminate rotor systems with angular contact ball bearings.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집A
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• pp.67-72
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• 2001

The LBB behavior and the crack opening displacement after a crack penetrated wall thickness of statically indeterminate piping system were investigated in this study, compared with statically determinate piping system. The reduction of ultimate strength caused by a crack was relatively small in the statically indeterminate piping system. The statically indeterminate piping system has more safety margin for LBB behavior than the statically determinate piping system. The crack opening displacement could be evaluated by using the plastic rotation angle proposed to evaluate the crack opening displacement after crack penetration in pipe with a non-penetrating crack.

• Tribology and Lubricants
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• 제10권1호
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• pp.62-68
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• 1994

The analysis of statically indeterminate bearing-shaft system was investigated. The moment loads and misalignment angles which were induced in the ball bearings were determined, and the influence of span length of this system on the moment loads and fatigue lives was identified. The sliding and spinning speeds between balls and raceways which affected the performance of ball bearing evaluated. The equation to estimate the cage speed of ball bearing under moment loads was proposed. This equation had been verified by the test results of measuring of cage speed, which was useful to the prediction of ball bearing under moment loads.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1993년도 제18회 학술대회 초록집
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• pp.70-76
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• 1993

From the analysis of shaft-bearing indeterminate system, moment and misalingment angle which was generated in bearing were determined. And the influence of span length between bearings on the fatigue life was established. The equation to estimate the cage rotational speed was proposed, and this equation was verified by the measuring of cage speed and shaft speed. And accoding to quasi-static analysis, the spinning speed of ball was determined.

• 대한기계학회논문집A
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• 제34권6호
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• pp.725-730
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• 2010

부정정계 배관의 두께 관통 후 파단전누설 거동과 균열개구변위는 정정계 배관과 비교하여 연구 하였다. 부정정 배관은 균열 발생으로 인한 최대 강도의 감소가 비교적 적었다. 부정정 배관계의 파단 전누설 거동은 정정계 배관보다 더 안전 하였다. 균열개구변위는 미관통균열을 가지는 배관에서 균열 관통 후 평가하기 위하여 제안된 소성힌지를 사용하여 평가하였다.

• Architectural research
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• 제3권1호
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• pp.71-80
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• 2001

It is quite difficult to calculate the collapse probability of a system such as statically indeterminate structure that has many possible modes or paths to complete failure and the problem has remained essentially unsolved. A structure is synthesized by several components or elements and its capacity to resist the given loads is a function of the capacity of the individual element. Thus it is reasonable to assess the probability of failure of the system based upon those of its elements. This paper proposes an efficient technique to directly assess the reliability of a complex structural system from the reliabilities of its components or elements. The theory for the calculation of the probability of a structural system is presented. The target requirements of the method and the fundamental assumptions governing the method are clearly stated. A portal frame and two trusses are selected to demonstrate the efficiency of the method by comparing the results obtained from the proposed method to those from the existing methods in the literature.

• Korean Journal of Radiology
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• 제24권9호
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• pp.912-923
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• 2023

Objective: This study aimed to validate the risk stratification system (RSS) and biopsy criteria for cervical lymph nodes (LNs) proposed by the Korean Society of Thyroid Radiology (KSThR). Materials and Methods: This retrospective study included a consecutive series of preoperative patients with thyroid cancer who underwent LN biopsy, ultrasound (US), and computed tomography (CT) between December 2006 and June 2015. LNs were categorized as probably benign, indeterminate, or suspicious according to the current US- and CT-based RSS and the size thresholds for cervical LN biopsy as suggested by the KSThR. The diagnostic performance and unnecessary biopsy rates were calculated. Results: A total of 277 LNs (53.1% metastatic) in 228 patients (mean age ± standard deviation, 47.4 years ± 14) were analyzed. In US, the malignancy risks were significantly different among the three categories (all P < 0.001); however, CT-detected probably benign and indeterminate LNs showed similarly low malignancy risks (P = 0.468). The combined US + CT criteria stratified the malignancy risks among the three categories (all P < 0.001) and reduced the proportion of indeterminate LNs (from 20.6% to 14.4%) and the malignancy risk in the indeterminate LNs (from 31.6% to 12.5%) compared with US alone. In all image-based classifications, nodal size did not affect the malignancy risks (short diameter [SD] ≤ 5 mm LNs vs. SD > 5 mm LNs, P ≥ 0.177). The criteria covering only suspicious LNs showed higher specificity and lower unnecessary biopsy rates than the current criteria, while maintaining sensitivity in all imaging modalities. Conclusion: Integrative evaluation of US and CT helps in reducing the proportion of indeterminate LNs and the malignancy risk among them. Nodal size did not affect the malignancy risk of LNs, and the addition of indeterminate LNs to biopsy candidates did not have an advantage in detecting LN metastases in all imaging modalities.

• 대한기계학회논문집
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• 제12권4호
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• pp.675-681
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• 1988

본 연구에서는 표면감쇠처리되지 않은 구조물의 모우드특성을 아는 경우에 표 면감쇠처리에 의해서 결정되는 새로운 오무드변수를 계산하는 한 방법을 제시하고자 한다.즉, 실험적으로 측정된 점탄성물질의 동특성으로부터 표면감쇠처리되기 전의 모우드를 이용하여 표면감쇠처리된 구조물의 모우드감쇠와 고유진동수 및 주파수응답 함수를 계산한다. 이 과정을 Fig.1에 보여진, 표면감쇠처리된 네 개의 보와 하나의 집중질량으로 구성된 부정정계 구조물에 적용 서술하고자 한다.

• 대한치과교정학회지
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• 제26권3호
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• pp.281-290
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• 1996

Edgewise bracket에 continuous straight archwire를 장착 했을 때 각 bracket에 발생 하는 force system은 statically indeterminate system이기 때문에 임상적으로 측정이 어렵다. 이에 본 연구는 linear beam theory를 도입하여 full arch에 straight wire가 장착된 경우 geometry(a/b), 재질, 단면의 모양, interbracket distance에 관계없이 발생 가능한 모든 상태를 설명할 수 있는 식을 유도하고 일례의 분석을 통하여 다음과 같은 결과를 얻었다. 1. Bilateral fixed beam의 양끝에서 발생하는 force system을 알 수 있는 계산식을 얻었다. 2. 이를 이용하여 continuous straight archwire가 장착된 경우 각 치아에 발생하는 force system을 알 수 있다. 3. Continuous straight archwire장착시 영구변형의 발생여부와 발생위치를 예측 할 수 있다.

• 한국농공학회논문집
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• 제57권6호
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• pp.59-68
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• 2015

Traditional structure analysis method is based on numerical matrix analysis to use the geometries consisting of the structure. The characteristics require a lot of computer memories and computational time. To avoid these weaknesses, new approach to analyze truss structure was suggested by adopting topological load redistribution method. The axial forces to be not structurely analyzed yet against outside loads were redistributed by using nodal equation of equilibrium randomly at each node without constructing global matrix. However, this method could not calculate the axial forces if structure is statically indeterminate due to degree of many indeterminacies. Therefore, to apply the method suggested in this research, all redundancies of truss structure were replaced by unit loads. Each unit load could make the deformation of a whole structure, and a superposition method was finally adopted to solve the simultaneous equations. The axial forces and deflections agreed with the result of commercial software within the relative error of 1 %, whereas in the case that the axial forces are relatively very smaller than others, the relative errors were increased to 2 %. However, as the values were small enough not to be considered, it was practically useful as a structural analysis model. This model will be used for structural analysis of truss type of large structure such as agricultural farming facility.