• 대한물리치료과학회지
• /
• 제29권3호
• /
• pp.29-47
• /
• 2022

Purpose: This study was conducted to find out the mediated effects of smartphone overindulgence in the relationship between attention and spinal health of adolescents and to find out how cognitive strength moderates these relationships. Design: Cross-sectional study. Methods: All subjects measured attention, cognition strength, spinal angle, and smartphone overindulgence by measuring the ratio of SMR and mid-beta power to the power of the brain wave, amplitude variation of Cognitive Gamma-Peak, forward slope angle of the cervical spine, and the scale of diagnosis of smartphone addiction. Results: As a result, it shows a significant correlation between Attention, spinal angle, cognitive strength, and smartphone overindulgence(p<.05). In addition, attention was significantly mediated on the spinal angle through smartphone overindulgence(p<.001), and cognitive strength was significantly mediated in relation to smartphone overindulgence and spinal angle(p<.05). Conclusion: This result indicates that the mediation effect of overindulgence of a Smartphone is mediated according to its cognitive strength in relation to its effect of attention on the spine angle.

• Journal of the Korean Wood Science and Technology
• /
• 제50권4호
• /
• pp.237-245
• /
• 2022

This study examined the structural performance of experimental parallel strand lumber (PSL) from a Larch veneer strand. The prototype of PSL from a Larch veneer strand was manufactured in the experimental laboratory and tested. The bending and dowel bearing strength were determined from the modulus of elasticity (MOE), modulus of rupture (MOR), and dowel bearing strength based on a 5% offset yield load. The test results indicated that the average MOR of PSL was higher than that of 2 × 4 dimension lumber, and the average MOE of PSL was lower than that of 2 × 4 dimension lumber. A linear relationship was observed between the MOR and MOE. The allowable bending stress of PSL was derived as specified in ASTM D2915 and compared with other research. The dowel bearing strength of PSL in parallel to the grain was approximately double that perpendicular to the grain of PSL. A comparison of several theoretical calculations based on each national code for the dowel bearing strength was conducted, and some theoretical equations produced results closer to the experimental results when it was parallel to the grain, but the difference was higher in the case perpendicular to the grain. The test results showed that PSL made with Japanese larch veneer strands appeared to be suitable for a raw material of structural composite lumber (SCL) appeared to be used as a raw material for SCL.

• 센서학회지
• /
• 제33권2호
• /
• pp.86-92
• /
• 2024

Flexible electronic devices are exposed to repeated mechanical deformation; therefore, electrode performance is an important element. Recently, a new technology has been developed to improve the adhesion strength between polymer substrates and metal thin films through the cross-linking reaction of bovine serum albumin (BSA) bioconjugation proteins; however, additional performance evaluation as an electrode is necessary. Therefore, in this study, we investigated the effect of adhesive strength between a flexible substrate and a metal thin film on the performance of a flexible electrode. Cracks and changes in the electrical resistance of the electrode surface were observed through outer bending fatigue tests and tensile tests. As a result of a bending fatigue test of 50,000 cycles and a tensile test at 10% strain, the change in the electrical resistance of the flexible electrode with a high adhesion strength was less than 40%, and only a few microcracks were formed on the surface; thus, the electrical performance did not significantly deteriorate. Through this study, the relationship between the adhesion strength and electrical performance was identified. This study will provide useful information for analyzing the performance of flexible electrodes in the commercialization of flexible electronic devices in the future.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(I)
• /
• pp.395-398
• /
• 2005

To understand an influence of rectangular openings on the structural behavior in reinforced concrete deep beams, results of 52 specimens were analyzed. The structural behavior such as load-deflection relationship, load-maximum crack width relationship, and maximum strength was significantly affected by inclination of concrete strut beneath opening.

• Advances in concrete construction
• /
• 제10권1호
• /
• pp.81-92
• /
• 2020

Flexural and splitting strength behavior of conventional concrete can significantly be improved by incorporating the fibers in it. A significant number of research studies have been conducted on various types of fibers and their influence on the tensile capacity of concrete. However, as an important property, tensile capacity of fiber reinforced concrete (FRC) is not modelled properly. Therefore, this paper intends to formulate a model based on experiments that show the relationship between the fiber properties such as the aspect ratio (length/diameter), fiber content, compressive strength, flexural strength and splitting strength of FRC. For the purpose of modeling, various FRC mixes only with steel fiber are adopted from the existing research papers. Automated neural network search (ANS) is then developed and used to investigate the effect of input parameters such as fiber content, aspect ratio and compressive strength to the output parameters of flexural and splitting strength of FRC. It is found that the ANS model can be used to predict the flexural and splitting strength of FRC in a sensible precision.

• 한국건축시공학회지
• /
• 제2권2호
• /
• pp.129-134
• /
• 2002

The strength and durability of concrete are affected by various factors such as the quality of material, mixing ratio, construction, the method of cure, time elapsed. the condition of test and etc., it is very difficult to pre-estimate the strength of concrete with the use of experimental specimen. The domestic standard of specimen cylindrical type and its sizes are both l0cm$\times$20cm and 15cm$\times$30cm, which are prescribed in KS F2405, and the loading speed is prescribed to test with 2~3kgf/$\textrm{cm}^2$ per second. The loading speed should have great effect on the compressive strength, but in reality in the construction site sometimes the loading speed is applied so dubiously that the value of the compressive strength can be unreliable. And the cross sectional area of a specimen should be level and smooth, otherwise it can be broken at a lower stress than the real strength through the eccentric or intensive working of the load. Capping should be carried out in order to measure the strength correctly. And used for capping are various materials such as capping compound, cement glue, plaster, mechanical grinding and etc. In this study, therefore, I have carried out an experiment on the relationship among the loading speed, the ratio of height to diameter of specimen, the method of capping, and the compressive strength, for the efficient quality control of concrete structures. So this study has been purposed to provide some basic data that can be used effectively at construction sites.

• 한국구조물진단유지관리공학회 논문집
• /
• 제12권3호
• /
• pp.101-109
• /
• 2008

본 연구에서는 마이크로 입자들로 구성된 매트릭스의 강섬유 보강 시멘트 복합체에서 강섬유가 압축강도에 미치는 영향을 규명하고자 하였으며, 강섬유의 섬유혼입률과 섬유형상비에 따른 영향을 파악하고 혼입률과 형상비를 동시에 고려한 변수인 섬유보강지수(RI)에 따른 압축강도의 변화를 살펴보았다. 실험결과에 따르면 마이크로 입자로 구성된 매트릭스의 강섬유보강 복합체에서는 섬유보강지수가 증가에 따라 압축강도가 선형적으로 증가하였다. 이와 같은 결과로부터 섬유보강지수와 압축강도와의 관계를 나타내는 모델식을 제안하였다.

• 대한물리의학회지
• /
• 제16권1호
• /
• pp.103-109
• /
• 2021

PURPOSE: This study examined the effects of the Visual Analog Scale (VAS) and knee function index on the knee strength and endurance in the national male field-hockey athletes. METHODS: Twenty-four male field-hockey athletes with a painful knee who trained at the national training center in 2019 were enrolled. The VAS and knee function index questionnaire were used to evaluate the degree of pain and functional state of the knee. The muscle strength and endurance of the knee were measured by Biodex (System 4, USA). The Pearson product moment correlation was performed to examine the effects of the VAS and knee function index the of knee on the strength and endurance. In addition, the VAS and knee function index and muscle strength and muscle endurance were examined to determine the relationship using Simple Linear Regression. The statistical significance level was α=.05. RESULTS: An analysis of the correlation between VAS and knee function index and muscle strength and muscle endurance revealed the VAS and knee function index to be statistically significant (r = .700). In addition, the extensor muscle strength, knee VAS (r = -.457), and knee function index (r = -.414) were also statistically significant. A 1-point increase in the VAS and knee function index was associated with an approximately 9.881 and 1.006 extensor muscle strength. CONCLUSION: The VAS and knee function index of field-hockey athletes are related to the strength of the knee extensors. Therefore, field-hockey athletes should develop a program to strengthen the extensor muscle strength of the knee.

• 한국지반공학회논문집
• /
• 제24권11호
• /
• pp.91-100
• /
• 2008

본 연구에서는 Mohr-Coulomb 파괴기준에 따라 고결모래의 전단강도를 유도하고, 삼축 및 일축압축시험으로 검증하였다. 모래의 마찰각은 고결의 영향을 받지 않으며, 일정구속압 이하에서 고결모래의 점착력은 고결정도에 따라 일정하다. 따라서 고결모래의 전단강도는 미고결 모래의 전단강도와 고결모래의 일축압축강도의 합으로 표현되며, 고결모래의 점착력은 마찰각과 일축압축강도의 함수로 표현되었다. 또한 고결결합 파괴구속압 이후인 전이구간에서 고결모래의 전단강도는 비교적 일정하게 유지된다고 가정하여 전이구간에서 고결모래의 전단강도와 점착력을 유도하였다. 추정된 고결모래의 전단강도와 점착력은 실험결과와 잘 일치하였다. 실험 결과는 또한 고결모래의 점착력 변화에 큰 영향을 미치는 고결결합 파괴구속압이 일축압축강도와 선형비례관계임을 보여준다.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2003년도 봄 학술발표회 논문집
• /
• pp.853-860
• /
• 2003

Relationship between axial strain and volumetric strain of Light-Weighted Foam Soil (LWFS) are investigated. LWFS is composed of the dredged soil from offshore, cement and foam to reduce the unit weight and also increase compressive strength. For this purpose. the triaxial compression tests are carried out on the prepared specimens of LWFS with various conditions such as initial water contents, cement contents, and curing stresses, The test results of LWFS Indicated that the axial strain - volumetric strain relationship is almost linearity with increase cement contents and the unit weight but the relationship is non-linearity with decrease cement contents and the unit weight. In this study, it is found that assuming no change of cross section area of LWFS, axial strain occurring the poisson's ratio of zero, that the axial strain same to volumetric strain, steeply increases with decrease the unit weight, initial water content, and cement contents.