• 대한치과보철학회지
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• 제20권1호
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• pp.25-32
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• 1982

An in vitro study was conducted to compare the bond strength of cements between Verabond coping and various cores. Fifty-four idential cores simulating maxillary central incisor prepared for PFM crowns were made. Eighteen samples were made with 20K cast gold, eighteen with Verabond, and eighteen with Adaptic. Samples were randomly divided into three groups, each consisting of six 20K cast gold, six verabond, and six Adaptic samples. The first group was cemented with zinc phosphate cement, the second group with poly-carboxylate cement, and the third group with glass ionomer cement. Constant finger pressure was applied for cementation. The sample were then stored at $37^{\circ}C$ in distilled water bath for 24 hours. The tensile strength test was performed on an Instron Universal test machine with crosshead speed of 0.05cm/min and the results compared statistically. Results of the study showed that: 1. A significant difference of bond strength was observed with different types of dental cements and core materials. 2. With gold core, zinc phosphate cement was stronger than both the polycarboxylate cement and glass ionomer cement, which did not differ in bond strength. 3. With base-metal core, zinc phosphate cement showed the highest bond strength and was followed by polycarboxylate cement and glass ionomer cement. 4. With composite resin core, zinc phosphate cement showed the highest bond strength and was followed by glass ionomer cement and polycarboxylate cement. 5. The base-metal core (Verabond core) privided the highest retention of all core materials.

• 펄프종이기술
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• 제31권2호
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• pp.70-76
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• 1999

This study was to measure the potential of nonwoody fibrous material, kenaf. Whole stalk of kenaf, Hibiscus cannabinus was separated by two parts of bast and core portion, and cooked separately by alkaline method. Morphological characteristic was evaluated using confocal laser scanning microscope (CLSM) and fiber quality analyzer(FQA). The strength properties of handsheets, made by different mixing ration between kenaf base and core fibers, were measured. Cross-sectional area of bast fibers was smaller than that of core fibers, but the bast fibers had a thick cell wall and narrow lumen area. Bast fibers were longer in length than core fibers. Core fibers had thin cell walls, broad lumen areas, and short lengths, and they had collapsed shape even in water. These characteristics of core fibers affected strength properties of handsheet positively. When the amount of core fibers increased, the strength properties of handsheet were increased. When the amount of bast fibers increased, the handsheet had rougher surface and higher air permeability.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2016년도 춘계 학술논문 발표대회
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• pp.143-144
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• 2016

The core drilling method is considered to be the most effective and common method of assessing the compressive strength of concrete in existing reinforced concrete buildings for structural repair and retrofit. In general, core specimens within reinforcing bars are not permitted in the regulations with regard to assessing concrete strength even if the core specimens can contain the bars in some cases. The purpose of this study is to investigate the effects of the reinforcement arrangement on the concrete compressive strength as a basic research to propose the quantitative criteria of strength for core specimens containing reinforcements. To complete the basic research, cylinder specimens inserted in a variety of reinforcement arrangements were prepared and tested.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 봄 학술발표회 논문집
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• pp.973-978
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• 2002

This study was performed to verify the effect of various testing conditions affecting measured compressive strength of concrete core and to compute the correction coefficients for it. Conditions of specimens affecting test results include size(diameter), height-diameter ratio, humidity of specimen, amount and arrangement of bar, core direction from structure and method of end preparation. In testing core strength of concrete, special cares should be taken on various testing conditions whose effects have been latent in conventional concrete.

• Interaction and multiscale mechanics
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• 제1권2호
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• pp.231-250
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• 2008

The statistical two-order and two-scale method is developed for predicting the mechanics parameters, such as stiffness and strength of core-shell particle-filled polymer composites. The representation and simulation on meso-configuration of random particle-filled polymers are stated. And the major statistical two-order and two-scale analysis formulation is briefly given. The two-order and two-scale expressions for the strains and stresses of conventionally strength experimental components, including the tensional or compressive column, the twist bar and the bending beam, are developed by means of their classical solutions with orthogonal-anisotropic coefficients. Then a new effective mesh generation algorithm is presented. The mechanics parameters of core-shell particle-filled polymer composites, including the expected stiffness parameters, minimum stiffness parameters, and the expected elasticity limit strength and the minimum elasticity limit strength, are defined by means of the stiffness coefficients and elasticity strength criterions for core, shell and matrix. Finally, the numerical results for predicting both stiffness and elasticity limit strength parameters are compared with the experimental data.

• 한국운동역학회지
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• 제26권2호
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• pp.229-236
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• 2016

Objective: This study aimed, first, to develop core strength training equipment with elderly-friendly, easy-to-use features and, second, to investigate the effect of core strength training using the equipment on the performance and stability of the elderly in activities of daily living. Method: In this study, we developed training equipment with a stability ball that can be used for performing core strength exercises in the elderly. Twenty-three elderly subjects (age: $77.87{\pm}6.95years$, height: $149.78{\pm}6.95cm$, and weight: $60.57{\pm}7.21kg$) participated in this study. The subjects performed the core strength training exercise with 16 repetitions for 8 weeks (2 repetitions per week). Performance in activities of daily living was assessed by using the Short Physical Performance Battery (SPPB), a test of going up and down 4 stairs, and one-leg static balance test. Stability was quantified as changes in the center of pressure (COP) and C90 area. Results: With the core strength equipment, trunk core strength exercise could be performed by pulling or pushing a rope with 2 hands on the stability ball. During the task, the tension in the rope was manipulated by a motor connected to the rope and the COP of the subject was measured by 4 load cells mounted in the equipment. Our results showed that the SPPB score was significantly higher (p < .05), the time to complete the "going up and down 4 stairs" test was significantly shorter (p < .05), and one-leg static balance statistically improved under an eyes-open condition (p < .05) after as compared with before the core strength training. The changes in the COP in the anteroposterior and mediolateral directions, and C90 area were significantly lower in the posttest (p <. 05) than in the pretest. Conclusion: The core strength training exercise using the equipment developed in the present study improved the performance and stability of the elderly in activities of daily living.

• 한국전문물리치료학회지
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• 제28권1호
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• pp.59-64
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• 2021

Background: Hip flexor muscles are very important in the hip joint structure as a mover and stabilizer. In addition, isometric hip flexor strength in the supine position needs to be considered with isometric core strength (WICS) to measure a precise strength in a clinical way. Objects: We compared isometric hip flexor strength in the supine position in subjects with and without WICS (between factors) and conditions with and without an external support (within factors). Methods: A total of 34 subjects (16 with WICS, 18 without WICS) participated in this study. We used the double-bent leg-lowering test to divide the subjects in two groups according to the presence of WICS. Isometric hip flexor strength was evaluated in the supine position both with and without an external support condition. The two-way mixed analysis of variance was applied to identify significant differences between groups (with vs. without WICS: between factors) and conditions (with vs. without an external support: within factors). Statistical significance was set at α = 0.05. Results: In subjects with WICS, isometric hip flexor strength was greater with an external support than without it (p = 0.0064). In subjects without WICS, there were no significant differences in isometric hip flexor strength in the presence or absence of an external support (p = 0.075). The isometric hip flexor strength was significantly greater with an external support condition in particular in subjects with WICS. Conclusion: The findings of this study reported that an external support condition in individuals with WICS may contribute to the improvement of isometric hip flexion strength in the supine position. Therefore, isometric core strength should be evaluated to distinguish the weakness between core region and hip flexors.

• Restorative Dentistry and Endodontics
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• 제30권2호
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• pp.86-94
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• 2005

비금속 지대치 재료의 구강 내 환경변화에 따른 물리적 성질을 구명하기 위하여 4종의 지대치 재료를 다양한 환경에 보관한 후 굴곡강도 및 표면경도의 변화를 관찰하여 조건에 따른 영향을 구명하고자 이 연구를 시행하였다. Bisfil Core, Core Max, Fuji IX GP, Miracle Mix를 사용하여 굴곡강도 측정을 위한 시편을 제작한 후 최대하중을 측정하여 굴곡강도와 굴곡탄성계수를 계산하였다. 표면경도 측정을 위하여 아크릴릭 레진블럭에 상기 4종의 재료를 충전하여 중합시킨 후 순차 연마하여 경도측정을 위한 시편을 제작하고 Vickers hardness를 계산하였다. 1. 굴곡강도는 Core Max에서 가장 높고 Miracle Mix에서 가장 낮았다. 2. $37^{\circ}C$ 증류수에 24시간 보관한 군에서 Bisfil Core가 경도가 가장 높았다. 3. 30일 저장군에서는 Core Max가 경도가 가장 높았다. 4. 모든 군에서 Miracle Mix가 가장 낮은 경도를 나타냈다. 5. $2\%$ NaF용액과 0.02N lactic acid용액은 증류수보다 지대치 재료의 굴곡강도와 표면경도를 저하시켰다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(II)
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• pp.133-136
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• 2005

Compressive strength of recycled aggregate concrete was tested by the core and by the non-destructive testing. A prediction model of compressive strength considering the replacement level of recycled aggregate was suggested by multi-regression analysis and was compared with test results. Also, Test results showed that the ratio of compressive strength by core and non-destructive testing to actual was somewhat affected by the replacement level of recycled aggregate.

• 한국주조공학회지
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• 제28권4호
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• pp.166-169
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• 2008

This study deals about the development of fusible core with low melting temperature by addition of ceramic particles. A new concept of salt core was introduced to produce an integrated casting part having a complicated inner shape or requiring under-cut in high pressure die casting or squeeze casting process. The mechanical properties of fusible core were improved due to the addition of ceramic particles which helped to produce fine microstructure. The new technology for the preparation of new fusible core materials which possess high compression strength was established. Addition of ceramics particles increased the mechanical properties of fusible core materials. There was an increasing relationship between percentage of ceramic particles and mechanical strength was existed up to 60%.