• 디지털융복합연구
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• 제18권1호
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• pp.357-368
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• 2020

이 연구는 K3 리그 축구선수들의 시즌 중 체력 상태를 점검하기 위한 목적으로 종목 특이적인 체력측정을 시즌 초반과 후반에 실시하였다. 평가항목은 신체구성, 순발력, 민첩성, 지구력 및 등속성 하지근력 등으로 구성하였다. 측정 결과 시즌 초반과 비교하여 시즌 후반에 향상된 기능을 보여준 항목은 골격근량, 순발력, 민첩성 등이며, 신체조성, 지구력 및 등속성 하지근력은 차이점이 발견되지 못하였다. 시즌 후반부에 향상도를 보여준 항목은 시즌 중 반복적인 훈련과 시합 참여에 의한 학습효과 및 다양한 생리학적 기전에 의한 것으로 생각된다. 마지막으로 지구력과 하지근력은 별도의 특이적인 훈련을 시즌 중에 실시하지 못한 이유로 인하여 시즌 후반에 향상도를 보여주지 못한 것으로 판단된다. 이상의 결과를 종합한 결과, 선수들의 체력상태를 주기적으로 점검하는 연구를 통하여 시합기, 전이기 및 준비기에 적합한 체력 훈련프로그램의 개발 및 적용이 필요한 것으로 생각된다.

• 한국건설순환자원학회논문집
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• 제3권3호
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• pp.199-205
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• 2015

이 연구에서는 고온의 축열재료로 사용하기 위한 알루미나 시멘트 복합재료의 역학적 및 열적 특성을 파악하고자 하였다. 알루미나 시멘트를 기본 바인더로 하고 플라이애시, 실리카퓸, CSA (calcium sulfo-aluminate) 및 그라파이트의 치환에 따른 고온에서의 물성을 파악하였다. 알루미나 시멘트 기반 복합재료의 역학적 특성으로서 열사이클 전과 후의 압축강도 및 인장강도를 측정하였다. 또한, 복합재료의 열적 특성으로서 열전도율과 비열을 측정하였다. 열사이클링 적용 이후의 잔류압축강도 측정결과, 알루미나 시멘트만을 사용한 배합과 알루미나 시멘트를 실리카퓸으로 치환한 배합의 압축강도가 크게 나타나며, 이 두 배합의 잔류강도 비는 65%를 상회한다. 그라파이트를 혼합한 복합재료의 비열이 가장 크고 이는 그라파이트의 비열이 크기 때문이다. 연구결과는 콘크리트를 고온조건에서의 축열매체로 활용하기 위한 실제적인 기초실험 자료로 활용될 수 있을 것으로 사료된다.

• 한국구조물진단유지관리공학회 논문집
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• 제20권4호
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• pp.9-18
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• 2016

이 연구에서는 태양열 에너지 저장용도로 사용하기 위한 시멘트 기반 복합재료의 열적 및 역학적 특성을 파악하였다. 다양한 시멘트 재료의 배합이 섬유보강 시멘트 기반 복합재료의 열적 및 역학적 특성에 미치는 영향을 파악하기 위한 실험연구를 수행하였다. 시멘트 기반 복합재료의 역학적 특성으로써 열싸이클 전과 후의 압축강도 및 인장강도를 측정하였다. 또한, 섬유보강 시멘트 기반 복합재료의 열적 특성으로써 열전도율과 비열을 측정하였다. OPC와 슬래그를 포함한 배합의 잔류압축강도가 가장 크게 나타난다. 그라파이트를 혼합한 배합의 열전도율이 크게 나타나며, 이는 그라파이트가 열저장 시스템의 효율적인 축열과 방열에 유리함을 의미한다. 또한, CSA 또는 지르코늄의 첨가는 섬유보강 복합재료의 비열을 증가시킨다. 실험연구결과는 잡광형 태양열 발전소에서 고성능 복합재료를 사용하는 열저장 시스템 설계에 기초자료로 활용될 수 있다.

• 한국가금학회지
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• 제23권1호
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• pp.39-46
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• 1996

산란계에 대한 오전사료와 오후사료의 별도 급여가 계란의 난각질에 미치는 영향을 조사하고, 난각질 조사항목 상호간의 관계를 조사하기 위해 ISA Brown 갈색산란계 480수를 공시하여 32~36주령과 52~56주령 및 72~76주령에 각각 4주간 사양시험을 실시하였다. 각 산란기별로 처리당 60개씩 모두 1,080개의 계란을 수집하여 난각질을 조사하고 난각질 조사항목 상호간의 관계를 연구한 결과는 다음과 같다. 1. 계란의 비중, 난각 강도, 난각 후도 및 난각 비율등은 모두 오전사료 와 오후사료를 별도급여한 시험구들(T$_1$-T$_{5}$)이 대조구(C)에 비해 향상되었으며(P<0.05), 오후사료의 Ca 수준이 증가할수록 향상되는 경향이었다(P<0.05). 2. 난각질 조사항목간의 상관계수(r)는 0.79~0.90 으로 모두 고도의 유의적인 상관관계가 있었다(P<0.01). 3. 난각질 조사방법간의 관계를 조사하기 위해 단순회귀방정식과 다중회귀방정식을 구하였다.

• Geomechanics and Engineering
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• 제23권2호
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• pp.165-178
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• 2020

This paper investigates the effect of the jaw's curvature, also known by contact angle and jaw arc central angle (2α), of the Brazilian test apparatus on indirect tensile strength of various rock types. That's why, ten rock samples including limestone, marble, skarn, granite, diorite, and granodiorite were collected from some quarries in different provinces of Iran. Petrographic, mineralogical and textural investigations were performed using thin section analyses. Physical properties of the selected rock samples namely dry and saturated unit weights, porosity, water absorption, and specific gravity were determined for the rock samples. In addition, Brazilian tensile strength at different 2α angles (i.e., 2α = 0°, 10°, 15°, 20°, 45°, and 60°) were determined for the rocks in the laboratory. Results show that the parameter for the rocks is between 3.81 MPa at 2α=0° and 54.76 MPa at 2α=60°. This means that Brazilian tensile strength increased with increasing 2α angle from 0° to 60°. Also, it was found that the highest change rate of the Brazilian tensile strength occurs in range of 2α=15°-30° for most studied rock samples. In some tested samples, the parameter is decreased only at 2α = 60°. The values of Brazilian tensile strength of the rocks tested by flat and standard jaws are near to each other.

• Earthquakes and Structures
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• 제8권2호
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• pp.379-399
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• 2015

Existing building structures can easily present material mechanical properties which can largely vary even within a single structure. The current European Technical Code, Eurocode 8, does not provide specific instructions to account for high variability in mechanical properties. As a consequence of the high strength variability, at the occurrence of seismic events, the structure may evidence unexpected phenomena, like torsional effects, with larger experienced deformations and, in turn, with reduced seismic performance. This work is focused on the torsional effects related to the irregular stiffness and strength distribution due to the concrete strength variability. The analysis has been performed on a case-study, i.e., a 3D RC framed 4 storey building. A Normal distribution, compatible to a large available database, has been taken to represent the concrete strength domain. Different plan layouts, representative of realistic stiffness distributions, have been considered, and a statistical analysis has been performed on the induced torsional effects. The obtained results have been compared to the standard analysis as provided by Eurocode 8 for existing buildings, showing that the Eurocode 8 provisions, despite not allowing explicitly for material strength variability, are conservative as regards the estimation of structural demand.

• 콘크리트학회논문집
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• 제18권1호
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• pp.135-145
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• 2006

In high multistory reinforced concrete buildings, coupled shear walls can provide an efficient structural system to resist horizontal force due to wind and seismic effects. Coupled shear walls are usually built over the whole height of the building and re laid out either as a series of walls coupled by beams and/or slabs or a central core structure with openings to accommodate doors, elevators walls, windows and corridors. A number of recent studies have focused on examining the seismic response of concrete, steel, and composite coupling beams. However, since no specific equations are available for computing the bearing strength of steel coupling beam-wall connections, it is necessary to develop such strength equations. There were carried out analytical and experimental studies to develop the strength equations of steel coupling beam-connections. Experiments were conducted to determine the factors influencing the bearing strength of the steel coupling beam-wall connection. The results of the proposed equations were in good agreement with both test results and other test data from the literature. Finally, this paper provides background for design guidelines that include a design model to calculate the bearing strength of steel coupling beam-wall connections.

• 한국운동역학회지
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• 제22권2호
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• pp.237-242
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• 2012

The purpose of this study was (a) to develop carbon nanotube-based shock absorbers for reducing potentially harmful impact forces and excessive foot pronation, and (b) to briefly determine how the effects of carbon nanotube-based shock absorbers on biomechanical variance during drop landing. A university student(age: 24.0 yrs, height: 176.2 cm, weight: 679.5 N) who has no musculoskeletal disorder was recruited as the subject. Hardness, specific gravity, tensile strength, elongation, 100% modulus, tear strength, split tear strength, compression set, resilience, vertical GRF, and loading rate were determined for each material. For each dependent variable, a descriptive statistics was used for different conditions. The property test results showed that tensile strength, tear strength, split tear strength, compression set, and resilience in carbon nanotube-based shock absorbers were greater than general Ethylene Vinyl Acetate(EVA). These indicated that resistance against variable strength in developed carbon nanotube-based shock absorbers were greater than general EVA. In vertical GRF of CNTC was less than those of EVA during drop landing and loading rate of CNTC was greater than EVA. It seems that the use of CNT can be a effective way of reducing and controlling shock from impact.

• Structural Engineering and Mechanics
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• 제52권4호
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• pp.701-721
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• 2014

In the assessment of existing RC buildings, the reliable appraisal of the compressive strength of in-situ concrete is a fundamental step. Unfortunately, the data that can be obtained by the available testing methods are typically affected by a high level of uncertainty. Moreover, in order to derive indications about the degradation and ageing of the materials by on site tests, it is necessary to have the proper terms of comparison, that is to say, to know the reference data measured during the construction phases, that are often unavailable when the building is old. In the cases when such a comparison can be done, the in situ strength values typically turn out to be lower than the reference strength values (tests performed on taken samples during the construction). At this point, it is crucial to discern and quantify the specific effect induced by different factors: ageing of the materials; poor quality of the placement, consolidation or cure of the concrete during the construction phases; damage due to drilling. This paper presents a procedure for correlating the destructive compressive tests and non-destructive tests (ultrasonic pulse velocity tests) with the data documenting the compressive strength tested during the construction phases. The research work is aimed at identifying the factors that induce the difference between the in-situ strength and cubes taken from the concrete casting, and providing, so, useful information for the assessment procedure of the building.

• 한국정밀공학회지
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• 제27권2호
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• pp.94-101
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• 2010

Composite materials have a higher specific strength and modulus than traditional metallic materials. Additionally, these materials offer new design flexibilities, corrosion and wear resistance, low thermal conductivity and increased fatigue life. These, however, are susceptible to impact damage due to their lack of through-thickness reinforcement and it causes large drops in the load-carrying capacity of a structure. Therefore, the impact damage behavior and subsequently load-carrying capacity of impacted composite materials deserve careful investigation. In this study, the residual strength and impact characteristics of plain-woven CFRP composites with impact damage are investigated under axial tensile test. Impact test was performed using drop weight impact tester. And residual strength behavior by impact was evaluated using the caprino model. Also we evaluated behavior of residual strength by change of mass and size of impactor. Examined change of residual strength by impact energy change through this research and consider impactor diameter in caprino model.