• 소음진동
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• 제8권1호
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• pp.57-74
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• 1998

구조체의 연결부위에서 미지의 결합강성으로 인하여, 실험과 유한 요소법으로 구한 모달 매개변수들은 종종 일치하지 않는다. 본 논문은 실험으로 추출된 동특성 데이타에 근거하여, 해석적인 방법을 통해 새로운 모델링 방법을 제시하고 있다. 대표적인 연결방법으로 리벳을 이용한 Lap이음보에서 동강성을 측정하기 위한 비선형 진동실험이 제안 되었으며, 이를 Lap 이음판에 적용하기 위하여 동강성에 해당하는 설계변수로서 빔요소를 도입하였다. 이 유한요소 모델링은 범용 패키지인 PATRAN과 ABAQUS를 사용하였으며, 빔요소의 직경을 실험치의 고유진동수와 일치하도록 조절함으로써 직경의 최적치 경향을 관찰하였다. 제시된 모델링 기법과 기존의 모델링 기법으로 얻은 결과치들을 실험치와 비교하였다.

• 한국식품조리과학회지
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• 제4권1호
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• pp.17-26
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• 1988

The polysaccharide produced by pseudomonas elodea, Gellan gum, was rheologically characterized, compared with agar. Rheological properties were determined from the change in the value of intrinsic viscosity with the pH and salt concentration. At the range of pH 2∼ll and salt 0∼0.16M KC1, the intrinsic viscosity of Gellan gum ranged from 8.8 to 21.2dl/g and agar ranged from 1.97 to 11.46d1/g. In the absence of salt, the intrinsic viscosity of Gellan gum increased as the pH of solution increased up to neutral pH then decreased slightly at alkaline pH, whearas the intrinsic viscosity of agar increased as the pH of solution increased up to pH 9 then decreased slightly. Intrinsic viscosity of Gellan gum and agar decreased with an increase in salt concentration. The chain stiffness parameter for the Gellan gum was 0.033. The overlap parameter of Gellan gum and agar were 0.047g/dl and 0.087g/dl, respectively. Gellan gum and agar were shear rate dependent or pseudoplastic. The yield stress and proportionality constant of Gellan gum increased slightly as the concentration increase, on the other hand, the shear index of Gellan gum showed a maximum at 0.75g/dl and gradually decreased as the concentration increase. The apparent viscosity of Gellan gum and agar decreased as the temperature increase. A lower concentration of the divalent cations calcium and magnesium is required to obtain maximum gel strength than for the monovalent cations sodium and potassium.

• Smart Structures and Systems
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• 제26권1호
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• pp.103-115
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• 2020

The cold-formed steel storage racks are extensively employed in various industries applications such as storing products in reliable places and storehouses before distribution to the market. Racking systems lose their stability under lateral loads, such as seismic actions due to the slenderness of elements and low ductility. This justifies a need for more investigation on methods to improve their behavior and increase their capacity to survive medium to severe loads. A standardized connection could be obtained through investigation on the moment resistance, value of original rotational stiffness, ductility, and failure mode of the connection. A total of six monotonic tests were carried out to determine the behavior of the connection of straight 2.0 mm, and 2.6 mm thickness connects to 5 lug end connectors. Then, the obtained results are benched mark as the original data. Furthermore, an extreme learning machine (ELM) technique has been employed to verify and predict both moment and rotation results. Out of 4 connections, increase the ultimate moment resistance of connection by 13% and 18% for 2.0 mm and 2.6 mm upright connection, respectively.

• Asian Pacific Journal of Cancer Prevention
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• 제13권4호
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• pp.1447-1452
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• 2012

Aim: To evaluate the differential diagnostic potential of lesion stiffness assessed by the sonoelastographic strain index ratio (SR) and elastographic color scoring system (UE) for breast lesions. Materials and Methods: Three hundred and forty two breast masses (158 benign and 184 malignant) from 325 consecutive patients (mean age 44.2 years; range 16-81)who had been scheduled for a sonographically guided core biopsy were examined proposed by Itoh et al, with scoring 1-3=benign and 4-5=malignant. Strain and area ratios of each lesion were calculated within the same machine. Histological diagnosis was used as the reference standard. The area under the curve (AUC) and cut-off point were obtained by receiver operating curve and the cross table Fischer Test was carried out for assessing diagnostic value. Sensitivity, specificity, PPV, NPV, accuracy and false-discovery rates were compared. Results: The mean strain ratios for benign and malignant lesions were 1.87 and 7.9 respectively. (P<0.0001). When a cutoff point of 3.54 was used, SR had a sensitivity of 94.6%, a specificity 94.3%, a PPV of 95.1%, an NPV of 93.7% and an accuracy of 94.4%. The AUC values were 0.90 for the 5 point scoring system (UE) and 0.96 for the strain index ratio. The overall diagnostic performance was SR method was better (P<0.05). Conclusions: Strain ratio measurement could be another effective predictor in elastography imaging besides 5 the point scoring system for differential diagnosis of breast lesions.

• 전기전자학회논문지
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• 제11권3호
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• pp.108-116
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• 2007

This paper proposed an analyzable parameter and its analytic method to provide more accurate information than currently employed 4 channels system which uses pulse wave velocity (PWV) information of the volume pulse wave measured from 4 arterial channels for the characterization of arterial vessel. In order to verify the volume pulse waves on 4 sites were simultaneously acquired subjects aged from 12 to 81 years old. and the proposed parameters were extracted from time (UT) was then compared with blood pressure. Then, the regression analyses were done relationships among the proposed parameter and others, such as aging, pulse transit time pressure (BP). The followings are the results of linear regression analysis of the proposed parameter for total 50 normal subjects. We selected any two subjects (58 years and 27 years) and measured PPG (photoplethysmogram) and BP of before and after exercise. The coefficient of correlations between BP and UT observed was -0.928 for 50 years subject, and -0.922 for 20 years subject. For total 50 normal subjects, in case of correlation between the pulse transit time and BP, the result showed -0.170 on left side and -0.233 on right side, and the coefficient value of correlation between the pulse transit time and UT was -0.607 on left side and -0.510 on right side. UI is strongly correlated with the pulse transit time than BP. Hence, we believe that the proposed parameter is related with the index of arterial stiffness.

• 한국지진공학회논문집
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• 제14권1호
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• pp.43-50
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• 2010

철근의 부식을 해결하기 위해 철근의 대체 재료로 적용 가능한 FRP에 대한 연구의 적용성이 대두되었다. 그러나 취성적인 성질과 탄성계수가 낮은 단점을 가지고 있어, FRP rebar로 보강된 휨 부재의 사용성 평가 즉 처짐에 대한 연구가 필요하다. 본 연구에서는 보강비를 변수로 한, CFRP rebar로 보강된 콘크리트 보의 휨 실험을 수행하였다. 실험 결과, CFRP rebar로 보강된 실험체는 보강비가 증가함에 따라 내력 및 강성이 증가하는 양상을 보였으며, 철근 실험체와 동일한 단면성능을 발휘하기 위해서는 약 1.3배의 보강비가 요구되는 것으로 나타났다. 또한 유효단면2차모멘트에 대한 기존 제안식의 비교 결과, Bischoff & Scanlon이 제안한 식이 가장 정밀해에 가까운 처짐을 예측하였다.

• 한국멀티미디어학회논문지
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• 제11권8호
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• pp.1146-1159
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• 2008

본 연구에서는 복셀(voxel) 단위로 물체의 햅틱 거동을 모사하는 햅틱 모델에 물리적 속성을 결정하기 위한 방법과 이를 이용한 햅틱 렌더링 구조(framework)를 제안한다. 또한 본 연구에서는 햅틱 모델에 물리적 속성을 결정하기 위해 탄성영상을 이용한다. 제안하는 방법과 기존 방법의 가장 큰 차이점은 제안하는 방법을 이용하면 원하는 물체의 물리적 속성을 쉽게 햅틱 모델에 적용하여 실제적인 햅틱 거동을 모사할 수 있다는 것이다. 본 연구에서는 또한 제안하는 방법을 평가하기 위하여 간단한 실시간 촉진 훈련 시뮬레이터를 구축한다. 구축한 시뮬레이터에서, 사용자에게 되돌려지는 힘은 제안한 방법으로 적용된 대상 물체의 물리적 속성과 상호작용 양에 따라 계산된다. 본 연구에서, 시뮬레이션 대상으로는 사람의 간을 선택하였고 간 모델은 실시간 햅틱 렌더링을 위하여 Shape-retaining Chain Linked Model(S-chain 모델)로 모델링하였다. 또한, 제안한 방법과 구축된 시스템을 이용하여 사용자가 물체를 촉진할 때 이상부분을 손쉽게 찾을 수 있는지에 대한 실험을 수행하였다. 본 연구의 실험 결과로부터, 제안하는 방법은 사용자에게 실시간으로 구별 가능한 힘을 전달해 줌을 알 수 있었다.

• 한국전산유체공학회지
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• 제10권2호
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• pp.38-47
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• 2005

Substructuring methods are often used in finite element structural analyses. In this study a multi-level substructuring(MLSS) algorithm is developed and proposed as a possible candidate for finite element fluid solvers. The present algorithm consists of four stages such as a gathering, a condensing, a solving and a scattering stage. At each level, a predetermined number of elements are gathered and condensed to form an element of higher level. At the highest level, each sub-domain consists of only one super-element. Thus, the inversion process of a stiffness matrix associated with internal degrees of freedom of each sub-domain has been replaced by a sequential static condensation of gathered element matrices. The global algebraic system arising from the assembly of each sub-domain matrices is solved using a well-known iterative solver such as the conjugare gradient(CG) or the conjugate gradient squared(CGS) method. A time comparison with CG has been performed on a 2-D Poisson problem. With one domain the computing time by MLSS is comparable with that by CG up to about 260,000 d.o.f. For 263,169 d.o.f using 8 x 8 sub-domains, the time by MLSS is reduced to a value less than $30\%$ of that by CG. The lid-driven cavity problem has been solved for Re = 3200 using the element interpolation degree(Deg.) up to cubic. in this case, preconditioning techniques usually accompanied by iterative solvers are not needed. Finite element formulation for the incompressible flow has been stabilized by a modified residual procedure proposed by Ilinca et al.[9].

• 한국구조물진단유지관리공학회 논문집
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• 제17권1호
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• pp.1-9
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• 2013

철골구조에서 지진력 저항시스템으로 많이 사용되고 있는 가새골조시스템은 중심가새골조(Concentrically Braced Frames, CBF)와 편심가새골조(Eccentrically Braced Frames, EBF)로 구분하여 KBC2009 건축구조기준에서는 서로 다른 반응수정계수를 적용하여 설계하도록 되어있다. 현행 내진설계기준에서 편심가새골조에 대하여 링크 타단 접합부의 종류에 따라 모멘트 저항접합일 경우 반응수정계수는 R=8, 비모멘트 저항접합일 경우 반응수정계수 R=7로 적용하여 설계하도록 규정하고 있을 뿐 편심길이의 영향을 고려하지 않고 있다. 본 연구에서는 편심가새골조 중에서 역V형가새골조를 대상으로 비탄성 거동을 파악한 다음 편심길이에 따른 반응수정계수를 산정하여 내진설계 기준에서 제시한 값과 비교한 결과 편심가새골조에 대하여 동일한 반응수정계수를 적용하는 것은 적절하지 않음을 확인하였다.

• 대한한방소아과학회지
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• 제17권2호
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• pp.173-198
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• 2003

Back ground : Cerebral palsy(CP) is a static encephalopathy caused by an insult to the brain during the prenatal, perinatal, or postnatal period (ie, up to 2 years). CP can lead to global dysfunction but always includes motor problems Objective : The purpose of this study is to investigate the current tendency of oriental approach to the CP and promote oriental treatment of CP in Korea Method : Investigation of current literature and clinical paper in Korea and Chinese Result and Conclusion : 1) CP fall under the category of wu-chi(five kinds of retardations : 五遲), wu-ruan(five kinds of flaccidity : 五軟), wu-ying(five kinds of Stiffness : 五硬) in oriental medicine and correspond to naoxing-tanhuan in current chinese medicine. 2) CP is mainly caused by weakness of the liver and kidney(肝腎不足), weakness of the spleen and stomach(脾胃虛弱), and the method of treatment is tonify the liver and kidney(補益肝腎), tonify the spleen and replenish qi(補脾益氣), but yu-chi(the faculty of speech : 語遲) is caused by deficiency of the heart(心虛) so that treated with method of invigorating the heart and nourishing blood(補心養血). Recently blood stagnancy the stagnation of qi(氣滯血瘀) is considered as the cause of CP, promoting qi circulation to invigorate blood(行氣活血) is mentioned the treatment of method. 3) In addtion to a herbal medication and acupuncture, the various treatments of scalp acupuncture(頭鍼), acupoint injection(穴位注射), catgut embedding therapy(埋鍼) etc. had been applicated to CP and for the objective evaluation of remedial value, TCD, EEG, BMD have been used.