• Journal of Korean Society of Forest Science
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• v.96 no.4
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• pp.455-461
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• 2007

This research was processed on morphological and physical characteristics of 'Yongdong' cultivar nuts. (1)Morphological properties of 'Yongdong' cultivar nuts were significantly different from the control, native species, in respect of all properties. (2) 'Yongdong' cultivar nuts showed higher figures than the native species on 9 items of morphological properties (kernel weight, size, length and width of pad on suture and etc.), whereas other 6 items (height of pad on suture, thickness of shell and septem, fragment numbers of isolated kernel, roundness index, and etc.) showed lower figures than those of the control. (3) In physical properties of the nut shells, 'Yongdong' cultivar was superior to the control at all items with the exception of compressive prove distance. Accordingly, it was also verified as effective cultivar of shelled walnut with suture line direction applied the minimum strength. (4) 'Yongdong' cultivar, 21.9 kg, was approximately twice lower than the control, 42.6 kg, on maximum compressive weight. It was demonstrated that the 'Yongdong' cultivar characterized by easily crushing shell by small strength was great in cracking properties. (5) On the study of yield strength, the native species being twice higher than 'Yongdong' cultivar showed the properties of the small elasticity and the shell hardness. While, the suture line of 'Yongdong' cultivar having the lowest yield strength 15.6 kg and 16.0 kg was identified the shell crushed easily. (6) The movement distance of the compressive prove of 'Yongdong' cultivar, 4.2 mm, was longer than that of the control, 2.7 mm. Subsequently, it means that the amount of loss possibly occurring to distribution process was not great, whereby productive value was high. (7) The compressive strength of the suture line of 'Yongdong' cultivar, $9.1kg/cm^2$, was much lower than total average of that $12.4kg/cm^2$. It was also statistically different with other properties. (8)The hardness examination by the compressive position revealed that the suture line of 'Yongdong' cultivar, $149.8kg/cm^2$, was lowest in contrast with the control, $300.9kg/cm^2$.

• Journal of the Korea Concrete Institute
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• v.27 no.3
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• pp.229-236
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• 2015

This paper describes the effect of aggregate size on compressive behavior of high-strength steel fiber reinforced concrete. The Specified compression strength is 60 MPa and the range of fiber volume fraction is 0~2%. The main variable is the aggregate size, which was used for the aggregate size of 8 and 20 mm. So, ten concrete mixtures were prepared and tested to evaluate the fresh and hardened properties of SFRC at curing ages (7, 14, 28, 56 and 91 days), respectively. Items estimated in this study are the fresh properties (air contents, slump), hardened properties (compressive strength, modulus of elasticity, post-peak response and compressive toughness). As a result, the aggregate size has little effect on the compressive strength and modulus of elasticity. On the other hand, the ductile behavior was shown after post peak and the compressive toughness was increasing as decreasing the aggregate size. These effects are clearly represented in the fiber volume fraction 2%, which are the point appeared fiber ball. It is considered that the decreasing the aggregate size has effect on the fiber dispersibility.

• Journal of Navigation and Port Research
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• v.29 no.6 s.102
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• pp.561-566
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• 2005

This study was carried out to amlyze and compare the stability of a 50ton container crane according to various wind load design codes. The wind load was evaluated according to 'The Specification of Port Facilities and Equipments / Specification for the design of crane structures (KS A 1627)' and 'Load Criteria of Building Structures' effected by the ministry of construction & transportation And the uplift forces qf a container crane under this wind load were estimated by amlyzing reaction forces at each supporting point and compared each other. From this study, we noticed that the design wind velocity criteria need to be defined specifically when the wind load is evaluated to design a container crane. And we verified the necessity of the estimation of the uplift forces at each supporting point to analyze a structural stability of a container crane and the maximum compressive force in order to consider the stability of the ground foundation of the berth.

• Composites Research
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• v.33 no.3
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• pp.108-114
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• 2020

Piecewise Integrated Composite (PIC) beam is composed of different stacking against loading type depending upon location. The aim of current study is to assign robust stacking sequences against external loading to every corresponding part of the PIC beam based on the value of stress triaxiality at generated reference points using the k-NN (k-Nearest Neighbor) classification, which is one of representative machine learning techniques, in order to excellent superior bending characteristics. The stress triaxiality at reference points is obtained by three-point bending analysis of the Al beam with training data categorizing the type of external loading, i.e., tension, compression or shear. Loading types of each plane of the beam were classified by independent plane scheme as well as total beam scheme. Also, loading fidelities were calibrated for each case with the variation of hyper-parameters. Most effective stacking sequences were mapped into the PIC beam based on the k-NN classification model with the highest loading fidelity. FE analysis result shows the PIC beam has superior external loading resistance and energy absorption compared to conventional beam.

• The Journal of Korean Academy of Prosthodontics
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• v.50 no.3
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• pp.156-161
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• 2012

Purpose: This study was conducted to obtain difference in fracture strength according to the diameter of one-body O-ring-type of mini implant fixture, to determine the resistance of mini implant to masticatory pressure, and to examine whether overdenture using O-ring type mini implant is clinically usable to maxillary and mandibular edentulous patients. Materials and methods: For this study, 13 mm long one body O-ring-type mini implants of different diameters (2.0 mm, 2.5 mm and 3.0 mm) (Dentis, Daegu, Korea) were prepared, 5 for each diameter. The sample was placed at $30^{\circ}$ from the horizontal surface on the universal testing machine, and off-axis loading was applied until permanent deformation occurred and the load was taken as maximum compressive strength. The mean value of the 5 samples was calculated, and the compressive strength of implant fixture was compared according to diameter. In addition, we prepared 3 samples for each diameter, and applied loading equal to 80%, 60% and 40% of the compressive strength until fracture occurred. Then, we measured the cycle number on fracture and analyzed fatigue fracture for each diameter. Additionally, we measured the cycle number on fracture that occurred when a load of 43 N, which is the average masticatory force of complete denture, was applied. The difference on compressive strength between each group was tested statistically using one-way ANOVA test. Results: Compressive strength according to the diameter of mini implant was $101.5{\pm}14.6N$, $149{\pm}6.1N$ and $276.0{\pm}13.4N$, respectively, for diameters 2.0 mm, 2.5 mm and 3.0 mm. In the results of fatigue fracture test at 43 N, fracture did not occur until $2{\times}10^6$ cycles at diameter 2.0 mm, and until $5{\times}10^6$ cycles at 2.5 mm and 3.0 mm. Conclusion: Compressive strength increased significantly with increasing diameter of mini implant. In the results of fatigue fracture test conducted under the average masticatory force of complete denture, fracture did not occur at any of the three diameters. All of the three diameters are usable for supporting overdenture in maxillary and mandibular edentulous patients, but considering that the highest masticatory force of complete denture is 157 N, caution should be used in case diameter 2.0 mm or 2.5 mm is used.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.6
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• pp.617-622
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• 2012

Structures are often subjected to various types of loading such as static, dynamic, or impact loading. Therefore, experimental and numerical methods have been employed to find adequate material properties according to the conditions. The Split-Hopkinson pressure bar (SHPB) test has frequently been used to test engineering materials, particularly those used under high strain rates. In this study, the compressive deformation behaviors of aluminum alloy under impact conditions have been investigated by means of the SHPB test. The experimental results were then compared with those of finite element analyses. It was shown that reasonably good agreement with the true stress-strain curves was obtained at strain rates ranging from 1000 $s^{-1}$ to 2000 $s^{-1}$. When the strain rate increased by 30%, the peak stress in particular increased by 17%, and the strain also increased by 20%.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.442-445
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• 2009

지진에 대한 건축물의 확률적 성능평가에 대해서는 지진하중에 대한 건축물의 손상확률 또는 파괴확률을 나타내는 지진취약도 함수를 작성하여 대상 건축물에 대한 지진위험도를 평가하는 방법을 이용하고 있으며 이에 대한 많은 연구가 이루어지고 있다. 본 연구에서는 지진하중과 구조물 재료특성의 불확실성을 고려하고 대상 건축물의 지진취약도 해석을 통하여 비내력벽의 유무에 따른 건축물의 지진거동 및 내진성능을 평가하였다. 비내력벽을 보편화된 모형화 방법인 등가의 대각 압축 스트럿으로 고려하여 비내력벽의 유무에 따른 저층 철근콘크리트 건축물을 모형화하였으며 지진하중의 강도는 유효최대지반가속도를 이용하여 각 건축물에 대하여 지진취약도를 작성하였다. 취약도해석 결과로 연약층을 가지고 있는 건축물의 경우는 손상확률이 골조만 있는 경우보다 크며 동일한 해석모델의 경우에도 해석방법에 따라서 취약도 곡선의 형태가 다름을 알 수 있었다.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.225-228
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• 2008

In case of nonlinear analysis for reinforced concrete structure, the characteristics of the failure, which are depend on loading conditions, such as tension splitting, compression crushing and shear distortion should be considered. On the analytical evaluation for the failure behavior of these, the finite element techniques is the most widely used. After the maximum load, however, an analytical results by finite element technique are depending on the size of the element. In this study, integral nonlocal model which is one of those study for overcoming the element sensitivity and dependancy, used for the failure analysis of box culvert specimen. Comparing on the experimental and analytical results, validity and reliability of integral nonlocal model are investigate.

• Magazine of the Korea Concrete Institute
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• v.8 no.3
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• pp.187-195
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• 1996

A finite element formulation based on the CFT(Compression Field Theory), considering the effect of compression softening in cracked concrete, and macro-scopic and rotating crack models etc., was presented for the nonlinear behaviour of structural concrete. Considering the computational efficency and the ability of modelling the post-ultimate behaviour as major concerns, the Incremental displacement solution algorithm involving initial material stiffnesses and the relaxation procedure for fast convergence was adopted and formulated in a type of 8-noded quadrilateral isoparametric elements. The analysis program NASCOM(Non1inear Analysis of Structural Concrete by FEM : Monotonic Loading) developed in this way enables the predictions of strength and deformation capacities in a full range, crack patterns and their corresponding widths, and yield extents of reinforcement. As the verification purpose of NASCOM, the predictions were made for Bhide's Panel(PB21) and Leonhardt's deep beam tests. The predicted results shows somewhat stiff behaviour for the panel test, and vice versa for deep beam tests. More refining process would be necessary hereafter in terms of more accurately simulating the effects of tension-stiffening and compression softening in concrete.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.4
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• pp.514-522
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• 2022

In this study, as part of a study to improve the self-healing performance of concrete structures by applying self-healing capsules made of cementitious materials to cement composite materials, the engineering characteristics of mortars according to PCC(Powder Compacted Capsule) size and mixing ratio were compared and analyzed. For this, fluidity, compressive strength, reload test, carbonation, ultrasonic velocity, and water permeability characteristics were measured according to PCC size and mixing ratio of mortar. As a result of the measurement, the fluidity and compressive strength increased as the mixing ratio of PCC increased, and in the case of the load reload test, the healing ratio increased as the mixing ratio of PCC increased in the 03PC formulation. In the case of water permeability test, it was found that when PCC was used, the reduction ratio of water flow was up to 35 % higher than that of Plain, and when PCC with a size of 0.3 to 0.6 mm was mixed with 15 %, it was found to be effective in improving the crack healing ratio of the mortar.