• 한국산학기술학회논문지
• /
• 제16권6호
• /
• pp.4098-4107
• /
• 2015

이 연구는 특발성 척추측만증 청소년을 대상으로, Schroth 3차원 운동처치와 볼 슬링운동을 수행하는 재활운동프로그램의 처치가 콥스각의 변화와 근력 및 유연성, 평형성에 어떠한 영향을 미치는지를 구명하고자 수행되었다. 특발성 척추측만증을 진단받은 청소년 30명을 대상으로, Schroth 3차원 운동처치집단(n=15)과 볼과 슬링을 수행하는 재활운동 처치집단(n=15)으로 무선배정 하였으며 운동 프로그램은 8주간, 주 3회, 90분으로 구성하여 실시하였다. 이 연구의 결과에서, 8주간의 운동 후 Schroth 3차원 운동처치집단에서 콥스각이 유의하게 감소되었으며(p<.001), 복부근지구력(p<.05) 및 유연성(p<.001)과 평형성(p<.001) 모두 운동 후에 유의한 개선의 효과가 있는 것으로 나타났다. 또한 8주간의 운동 전 후 Schroth 3차원 운동 처치집단에서의 콥스각 변화율이 재활운동 처치집단의 콥스각 변화율보다 유의하게 높은 것으로 나타났다(p<.05). 이상의 결과에서 Schroth 처치집단과 재활운동 처치집단 모두 8주간의 처치 후, 특발성 척추측만증이 있는 청소년에게 유의한 개선의 효과가 있었으며, 그러나 Schroth 3차원 운동처치가 콥스각 교정에 보다 더 효과적인 것으로 나타났다. 따라서 청소년들의 특발성 척추측만증 예방과 운동치료에 Schroth 3차원 운동처치가 보다 효과적인 것으로 사료된다.

• Advances in concrete construction
• /
• 제7권2호
• /
• pp.117-126
• /
• 2019

When designing reinforced concrete (RC) members, the rebar is assumed to resist all tensile forces, but the resistance of the concrete in the tension area is neglected. However, concrete can also resist tensile forces and increase the tensile stiffness of RC members, which is called the tension stiffening effect (TSE). Therefore, this study assessed the TSE, particularly after yielding of the steel bars and the effects of the steel ratio on the TSE. For this purpose, RC member specimens with steel ratios of 2.87%, 0.99%, and 0.59% were fabricated for uniaxial tensile tests. A vision-based non-contact measurement system was used to measure the behavior of the specimens. The cracks on the specimen at the stabilized cracking stage and the fracture stage were measured with the image analysis method. The results show that the number of cracks increases as the steel ratio increases. The reductions of the limit state and fracture strains were dependent on the ratio of the rebar. As the steel ratio decreased, the strain after yielding of the RC members significantly decreased. Therefore, the overall ductility of the RC member is reduced with decreasing steel ratio. The yielding plateau and ultimate load of the RC members obtained from the proposed equations showed very good agreement with those of the experiments. Finally, the image analysis method was possible to allow flexibility in expand the measurement points and targets to determine the strains and crack widths of the specimens.

• 한국공간구조학회논문집
• /
• 제16권3호
• /
• pp.47-58
• /
• 2016

Cable network system is a flexible lightweight structure which curved cables can transmit only tensile forces. The weight of cable roof dramatically can reduce when the length becomes large. The cable network system is too flexible, most cable systems are stabilized by pretension forces. The tensile force of cable system is greatly influenced by the sag ratio and pretension forces. Determining initial sag ratio of cable roof system is essential in a design process of cable structures. Final sag ratio and pretension depends on initial installed sag and on proper handling during installation. The design shape of cable system has an affect on the sag and pretension, and must be determined using well-defined design philosophy. This paper is carried out the comparative data of the deflection and tensile forces on the geometric non-linear analysis of cable network systems according to sag ratio. The study of cable network system is provided to technical informations for the design of a large span cable roof, analytical results are compared with the results of other researchers. Structural nonlinear analysis of systems having cable elements is relatively complex than other rigid structural systems because displacements are large as a reason of flexibility, initial prestress is applied to cables in order to increase the rigidity, and then divergence of nonlinear analysis occurs rather frequently. Therefore, cable network systems do not exhibit a typical nonlinear behavior, iterative method that can handle geometric nonlinearities are necessary.

• Structural Engineering and Mechanics
• /
• 제90권6호
• /
• pp.543-549
• /
• 2024

The utilization of the fabric materials for lightweight building structures has attracted considerable attention due to the multiple functions and high strength-to-weight ratio. The mechanical properties of the fabric materials evolve with the loading cycle, especially for the Poisson's ratio that requires the full cyclic strain to determine the accurate values. The digital image correlation method has been justified but needs to meet the flexibility and complexity requirements of the fabric materials. This paper thus proposes a modified digital image correlation method to quantify the Poisson's ratio of fabric materials. To obtain the accurate Poisson's ratio of fabric materials in the cyclic experiments using non-contact measuring method, a speckle generation of the digital image correlation method is implemented to obtain the strain distribution and strain characteristics. The uniaxial cyclic experiments for the fabric materials are carried out in the warp, weft and 45° directions. The digital image correlation photos are taken when the material properties become stable in the cyclic loading. The results show that the strain distributions are non-uniform and dependent on the specimen directions. The reliable Poisson's ratios of the fabric materials in the warp, weft and 45° directions are 0.016, 1.2 and 2.6. The strain asymmetry at the maximum strain position is related with the weaving architecture. These observations and results are indispensable to understand the Poisson's ratios of fabric materials and to guide the proper analysis of the large-span membrane structures.

• 한국실내디자인학회:학술대회논문집
• /
• 한국실내디자인학회 2003년도 춘계학술발표대회 논문집
• /
• pp.74-77
• /
• 2003

After the Enforcement of Price Deregulation of Apartment, Apartment house get down to originality goods, The Housing Market have reorganized the nucleus by a user, have demanding the development for discriminative unit plan. The purpose of this study is that before and after the Price Decontrol of Apartment take part a variety of unit plan, search for transformation factor and analyze into the tendency of the distinction plan of Housing Goods. Before and after the Price Decontrol of Apartment, Apartment unit have analyzed from 85 $m^2$ till 152 $m^2$ private area; ten corporations of civil construction' unit in Seoul and The national capital region supply apartment, will supply apartment. For selected examples, first, unit plan is normalized from the ratio of front to side wall, bay, a Room' organization and a kind of Room, number, and for examples of unit plan of apartment, the examples were analyzed with respect to change of a Room' organization and the number of a room and the ratio of front wall to side wall for item investigated. Finally, I search out course of transformation tendency of an apartment unit plan after Enforcement of Price Deregulation and analyzed a factor. The results of the study are follows, after Enforcement of Price Deregulation, unit plan of apartment lead to change lay out, to secure each family's privacy, to secure feeling for open hearted, tendency of flexibility.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
• /
• pp.583-586
• /
• 2005

Strength of concrete is very important factor in design and quality management and may represent overall quality of concrete. Such strength of concrete may differ depending on amount of cement mixed, water and fine aggregate ratio. Classic concrete products have been produced mainly with ordinary portland cement(hereinafter 'cement'), water and fine aggregate as shown above, but various additives and mixture materials have been used for concrete manufacturing, along with development of high functional concrete and diversification of structures. Various kinds of chemical mixtures agents and mixture materials have been used as it requires concretes with other features which cannot be solved with existing materials only, such as high strength, high flexibility and no-separation in the water. Such addition of various mixture agents may cause change in cement hydrate, affecting strength. Hydration of cement is the process of producing potassium hydroxide, C-S-H, C-A-H and Ettringite, while causing heat generation reaction after it is mixed with water, and generation amounts of such hydrates play lots of roles in condensation and hardening. This study aims to analyze its strength and features with hydrates by making specimen according to curing temperature, types of mixture agent, mixing ratio and ages and by analyzing such hydrates in order to analyze role of cement hydrate on early strength of concrete.

• 한국정밀공학회지
• /
• 제24권7호
• /
• pp.98-105
• /
• 2007

In modern industries, materials are required that possess multi-functional properties and at the same time flexibility in their shapes with structural stability. The major technology realizing this requirement consists of thinning metal wires and laying them with stable contact nodes. This research has dealt with a new method to manufacture thin wires by drawing without applying dies, but with introducing enforced necking, which enables to process multi-ends. Based on the new method, the process dynamics was modelled and its steady-state characteristics were analyzed. Results showed that the profiles of the material velocity in the drawing zone increased with a downward convex shape, while the cross-sectional area decreased with the shape of upward convex. The microwave heating turned out to be effective in wire drawing, but dependent on the input feeding direction. The variation in the diameters of the drawn wires was negatively affected by increasing the drawing ratio.

• Earthquakes and Structures
• /
• 제18권5호
• /
• pp.625-635
• /
• 2020

Suspension bridges have the extended in plan configuration which makes them prone to dynamic events like earthquake. The longer span lead to more flexibility and slender of them. So, control systems seem to be essential in order to protect them against ground motion excitation. Tuned mass damper or in brief TMD is a passive control system that its efficiency is practically proven. Moreover, its parameters i.e. mass ratio, tuning frequency and damping ratio can be optimized in a manner providing the best performance. Meta-heuristic optimization algorithm is a powerful tool to gain this aim. In this study, TMD parameters are optimized in different-length suspension bridges in three distinct cases including 3, 4 and 5 TMDs by observer-teacher-learner based algorithm under a complete set of ground motions formed from both near-field and far-field instances. The Vincent Thomas, Tacoma Narrows and Golden Gate suspension bridges are selected for case studies as short, mean and long span ones, respectively. The results indicate that All cases of used TMDs result in response reduction and case 4TMD can be more suitable for bridges in near and far-field conditions.

• 대한치과기공학회지
• /
• 제24권1호
• /
• pp.127-138
• /
• 2002

There are some cases that dental prosthesis does not operate as properly as expected in oral mouth. The reasons are such as a distortion of the mandibular, a fault of impression taking system or an extrusion of remaining teeth. One of dental prostheses to consider in the situations is the attachment which connects segment bridge. Active discussions are managed on theoretical side of this field but few on clinical side of it, which must be considered first. Accordingly I'd like to suggest a theoretical background for connect attachment of fixed segmented bridge. 1. As a bridge gets longer, burden on dental ligament is increased and the hardness of a bridge is lessened. 2. The flexibility of a bridge increases in ratio to 3 multiplication of the length and decreases in ratio to 3 multiplication of the width of occlusal surface and base of pontic. 3. Precision rest is needed to cope with the shake of teeth and the difference of axis direction among abutments. 4. Female part of the precision rest should be on middle abutment distal and male one on mesial of pontic. 5. Segmented attachment can be efficiently used to cope with long span bridgework and also in case that one piece casting can't be done because of slant of abutment.

• 한국응용과학기술학회지
• /
• 제32권4호
• /
• pp.623-630
• /
• 2015

Buffalo leather 표면 코팅에 사용된 폴리우레탄 수지에 glycerol의 함유를 mole % 비로 달리하면서 첨가 하였다. 합성된 폴리우레탄 수지의 기계적 특성은 SEM, FT-IR, UTM 등을 이용하여 측정하였다. 친환경적인 고분자 수지의 관심이 고조됨에 따라 용제의 사용을 최소화한 buffalo leather 코팅에 사용되는 수분산 수지를 합성하였다. 지방족 3가 알콜인 glycerol의 mole % 비가 증가함에 따라 내마모도, 인장강도가 감소함을 알 수 있었다. 반대로 연신율, 내굴곡 물성은 증가함을 알 수 있었다. Toluene을 이용한 내용제성 물성측정 결과에는 glycerol의 mole % 증가에 따른 물성 증감 효과는 없었다.