• 비파괴검사학회지
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• 제25권3호
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• pp.178-188
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• 2005

This paper introduces a structural damage identification method to identify 4he multiple directional damages generated within a cylindrical shell by using the measured frequency response function (FRF). The equations of motion for a damaged cylindrical shell are derived. by using a theory of continuum damage mechanics in which a small material volume containing a directional damage is represented by the effective orthotropic elastic stiffness. In contrast with most existing vibration-based structural damage identification methods which require the modal Parameters measured in both intact and damaged states, the present method requires only the FRF-data measured at damaged state. Numerically simulated damage identification tests are conducted to verify the feasibility of the Proposed structural damage identification method.

• 생명과학회지
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• 제17권7호통권87호
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• pp.956-963
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• 2007

본 연구의 목적은 골프 숙련도에 따른 아이언 샷 연습량이 혈중 근 손상 지표물질과 피로물질 농도 변화에 미치는 영향을 분석하는데 있었으며, 남자골프선수 24명을 대상으로 초급(8명), 중급(8명), 고급(8명)으로 나누어 각각 다른 연습량(100,200, 300타)으로 연습하는 동안 채혈시기별로 혈중근손상 지표물질인 CK(creatine kinase), LDH(lactate dehydrogenaset-혈중 피로물질인 무기인산, 젖산, 암모니아, 그리고 IGF- I (insulin like growth factor-I)과 크레아티닌의 수준차이를 비교하였다. 그 결과, 운동하는 동안 피로물질과 근손상 지표, 크레아티닌은 숙련도가 높을수록 낮은 수준을 보였으며, 연습량이 증가됨에 따라 높은 수준을 나타내었다. 회복시 피로물질과 크레아티닌은 운동종료 후 빠르게 회복되었으나, 근손상 지표, 특히 CK는 24시간이 지난 후에도 회복되지 못한 결과를 보였다. 따라서, 골프연습도 격렬한 운동과 마찬가지로 근손상과 상해를 예방하기 위해서는 개인의 숙련도와 연습량에 따라 차별화된 훈련과 회복방법을 고려해야 할 것으로 사료된다.

• Computers and Concrete
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• 제24권6호
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• pp.513-525
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• 2019

In this work, an experimental research has been performed on Steel Fiber-Steel Reinforced Concrete (SFSRC)specimens subjected to four-point bending tests to evaluate the feasibility of mutual replacement of steel fibers and conventional reinforcement through studying failure modes, load-deflection curves, stiffness of characteristic points, stiffness degradation curves and damage analysis. The variables considered in this experiment included steel fiber volume percentage with and without conventional reinforcements (stirrups or steel fibers) with shear span depth ratios of S/D=2.5 and 3.5. Experimental results revealed that increasing the volume percentage of steel fiber decreased the creation and propagation of shear and bond cracks, just like shortening the stirrups spacing. Higher crack resistance and suturing ability of steel fiber can improve the stability of its bearing capacity. Both steel fibers and stirrups improved the stiffness and damage resistance of specimens where stirrups played an essential role and therefore, the influence of steel fibers was greatly weakened. Increasing S/D ratio also weakened the effect of steel fibers. An equation was derived to calculate the bending stiffness of SFSRC specimens, which was used to determine mid span deflection; the accuracy of the proposed equation was proved by comparing predicted and experimental results.

• 대한본초학회지
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• 제35권1호
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• pp.19-25
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• 2020

Objects : The daily dose of Pinelliae Tuber in ≪Treatise on Cold Damage Diseases≫ is half seung in volume, two and half ryang in weight, and fifteen in total number. But the daily dose should be a whole number. So I found out the background of this setting and correct solution. Methods : I searched Classics of Traditional Medicine, found out the background of the daily dose setting, solution. Results : The daily dose of Pinelliae tuber in ≪Hangdi's Internal Classic Miraculous Pivot≫, ≪Bohenggyuljangbuyongyakbeobyo≫ is half seung. ≪Treatise on Cold Dameage Diseases≫ followed the same daily dose of that because it referred to these books. In ≪Synopsis of Prescription of the Golden Chamber≫, the daily dose of that is half seung, one or two seung. The half seung of the Pinelliae Tuber is thirty three mL, but the diameter is 1~1.5 cm that accurate measurement by volume is difficult. The daily dose by weight is correct considering the unity of marking of the daily dose, accuracy of measurement, the fact that Pinelliae Tuber is currently distributed by cutting. So, two ryang is correct which is thirteen gram. Conclusions : Considering the traditionality, the convenience of measurement, the daily dose of Pinelliae Tuber in the ≪Treatise on Cold Damage Diseases≫ is half seung, but considering the unity, accuracy, current state of distribution, it is correct that the daily dose of it is two ryang. It corresponds to thirteen gram.

• Steel and Composite Structures
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• 제47권1호
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• pp.121-134
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• 2023

This paper tested 11 concrete-encased concrete-filled steel tube (CFST) composite columns and one reinforced concrete column under combined axial compression and lateral loads. The primary parameters, including the loading system, axial compression ratio, volume stirrup ratio, diameter-to-thickness ratio of the steel tube, and stirrup form, were varied. The influence of the parameters on the failure mode, strength, ductility, energy dissipation, strength degradation, and damage evolution of the composite columns were revealed. Moreover, a two-parameter nonlinear seismic damage model for composite columns was established, which can reflect the degree and development process of the seismic damage. In addition, the relationships among the inter-story drift ratio, damage index and seismic performance level of composite columns were established to provide a theoretical basis for seismic performance design and damage assessments.

• 대한기계학회논문집A
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• 제25권4호
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• pp.564-573
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• 2001

The mechanical properties of short carbon/glass fiber reinforced polypropylene are experimentally measured as functions of fiber content and nozzle diameter. Also, these properties are compared with the survival rate of reinforced fibers and fiber volume fraction using image analysis after pyrolytic decomposition. The survival rate of fiber aspect ratio as well as fiber volume fraction is influenced by injection processing condition, the used materials and mold conditions such as diameter of nozzle, etc. In this study, the survival rate of fiber aspect ratio is investigated by nozzle size variations in injection/mold sides. It is found that the survival rate of glass fiber is higher that the survival rate of glass fiber is higher than that of carbon fiber. Both tensile modulus and strength of short-fiber reinforced polypropylene are improved s the fiber volume fraction and nozzle diameter are increased.

• Interaction and multiscale mechanics
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• 제1권2호
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• pp.279-301
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• 2008

This paper develops a 3D homogenization based continuum damage mechanics (HCDM) model for fiber reinforced composites undergoing micromechanical damage under monotonic and cyclic loading. Micromechanical damage in a representative volume element (RVE) of the material occurs by fiber-matrix interfacial debonding, which is incorporated in the model through a hysteretic bilinear cohesive zone model. The proposed model expresses a damage evolution surface in the strain space in the principal damage coordinate system or PDCS. PDCS enables the model to account for the effect of non-proportional load history. The loading/unloading criterion during cyclic loading is based on the scalar product of the strain increment and the normal to the damage surface in strain space. The material constitutive law involves a fourth order orthotropic tensor with stiffness characterized as a macroscopic internal variable. Three dimensional damage in composites is accounted for through functional forms of the fourth order damage tensor in terms of components of macroscopic strain and elastic stiffness tensors. The HCDM model parameters are calibrated from homogenization of micromechanical solutions of the RVE for a few representative strain histories. The proposed model is validated by comparing results of the HCDM model with pure micromechanical analysis results followed by homogenization. Finally, the potential of HCDM model as a design tool is demonstrated through macro-micro analysis of monotonic and cyclic damage progression in composite structures.

• 한국건설순환자원학회논문집
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• 제6권3호
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• pp.79-87
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• 2011

고로슬래그를 다량으로 혼입한 콘크리트를 동절기에 시공할 경우에는 배합에 따라서 응결과 경화가 현저히 지연되어 초기동해를 받을 위험성이 높다. 따라서 이 연구에서는 동절기에 고로슬래그를 다량으로 혼입한 콘크리트가 재령 초기에 동결을 받은 경우를 상정하여 초기동해가 콘크리트의 압축강도와 동결융해 저항성에 미치는 영향을 검토하였다. 그 결과, 고로슬래그를 다량으로 혼입한 콘크리트는 초기동해를 받음으로써 압축강도와 동결융해 저항성 모두가 현저히 저하되고, 고로슬래그를 혼입하지 않은 일반콘크리트에 비해서 특히 동결융해 저항성이 크게 저하되는 것으로 나타났다.

• 대한핵의학회지
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• 제3권2호
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• pp.1-16
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• 1969

The double tracer study on erythrokinetics was carried out experimentally with radioactive iron ($^{59}Fe$) and chromium ($^{51}Cr$) in rabbits. The 0.1% canthalidin solution and 1% pot. perchlomate solution was given subcutaneously to 20 rabbits respectively. 3 and 6 days after injection, the blood chemistry, urine examination, ferrokinetics and apparent half survival time of RBC were ($^{51}Cr\;T\frac{1}{2}$)determined. Following were the results: 1) Red blood cell hematocrit and hemoglobin values were moderately reduced and B.U.N. and serum creatinine values were slight]y inercased in the canthalidin group, while B.U.N. and serum creatinine values were within normal limits in the pot. perchlomate group. Reticulocyte values were slight]y increased in the canthalidin group, while was normal range in the pot. perchlomate group. 2) Blood chemistry finding was not significant statistically in both experimental groups, but serum iron value was moderately reduced in both group. 3) Plasma volume was unchanged in both group, but red cell volume and whole blood volume were slightly reduced in both groups. 4) Results of ferrokinetics were as follows: i) The plasma iron disappearance rate was delayed in both groups. Plasma iron turnover rate, red cell iron utilization and red cell iron turnover rate were decreased in both groups, and then red cell iron turnover rate was more decreased than plasma iron turnover rate in both groups. Circulating red cell iron was slight]y increased in canthalidin group and red cell iron concentration was within normal range in both groups. ii) P.I.T.R.-R.C.I.T. value was moderately increased in the canthalidin group and slightly increased in the pot. perchlomate group. Reticulocyte index, red cell iron turnover index, plasma iron turnover index and effective erythropoiesis index were whole]y reduced in both groups. iii) The red cell life span was slightly shortened in the canthalidin group while was within normal range in pot. perchlomate group. The pathologic finding of renal biopsy of the canthalidin group shows a selective damage in glomerulus, while shows almost normal range or slight damage in tubules. And that of the pot. perchlomate group shows a selective damage in tubules with slight damage of glomerulus.

• 대한예방한의학회지
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• 제13권1호
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• pp.13-27
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• 2009

This study aimed to validate neuroprotective effect of Chungpaesagan-tang on the early stage of cerebral ischemic damage. Cerebral ischemic damage was induced by the middle cerebral artery occlusion (MCAO) for 2 hours in the Sprague-Dawley rats. Water extract of Chungpaesagan-tang(8.7g/kg) was administered orally twice at 1 and 4 hours after the MCAO. Neurological score was tested at 3 and 24 hours after the MCAO and Chungpaesagan-tang administration. At 24 hours after the MCAO, infarct volume and edema ratio was evaluated with the TTC staining. Apoptotic cell death in cerebral cortex and caudate putamen was observed with cresyl violet staining and TUNEL labeling. Bax expression in the MCAO rat brain was stained with immunohistochemistry. Chungpaesagan-tang improved neurological and behavioral impairment of the MCAO rats and reduced infarct area, infarct volume and brain edema formation. Chungpaesagan-tang attenuated cell death percentage in cortex penumbra and reduced TUNEL positive cells in cortex penumbra and in caudate putamen of the MCAO rats. Chungpaesagan-tang reduced Bax positive neurons in caudate putamen and reduced c-Fos positive neurons in cortex penumbra of the MCAO rats. Chungpaesagan-tang intensified neuronal HSP72 expression in cortex penumbra of the MCAO rats. In results, Chunpaesagan-tang reduces infarct volume and edema formation through anti-apoptotic effect. This result suggests that Chunapaesagan-tang has an adequate neuroprotective effect on the early stage of cerebral ischemic damage.