• Computers and Concrete
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• 제12권6호
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• pp.831-850
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• 2013

The high strength materials have been more widely used in reinforced concrete structures because of the benefits of the mechanical and durable properties. Generally, it is known that the ductility decreases with an increase in the strength of the materials. In the design of a reinforced concrete beam, both the flexural strength and ductility need to be considered. Especially, when a reinforced concrete structure may be subjected an earthquake, the members need to have a sufficient ductility. So, each design code has specified to provide a consistent level of minimum flexural ductility in seismic design of concrete structures. Therefore, it is necessary to assess accurately the ductility of the beam sections with high strength materials in order to ensure the ductility requirement in design. In this study, the effects of concrete strength, yield strength of reinforcement steel and amount of reinforcement including compression reinforcement on the complete moment-curvature behavior and the curvature ductility factor of doubly reinforcement concrete beam sections have been evaluated and a newly prediction formula for curvature ductility factor of doubly RC beam sections has been developed considering the stress of compression reinforcement at ultimate state. Based on the numerical analysis results, the proposed predictions for the curvature ductility factor are verified by comparisons with other prediction formulas. The proposed formula offers fairly accurate and consistent predictions for curvature ductility factor of doubly reinforced concrete beam sections.

• 설비공학논문집
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• 제27권6호
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• pp.328-336
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• 2015

Currently, 22% of the total energy consumption of buildings in Korea is used for lighting. Light-shelves have garnered attention as a way to reduce consumption, but there are few studies on the types of curve and curvature, which limits the improvement of light-shelf performance and its design. This study constructed a test bed of actual residential types to evaluate the performance. Outcomes of light usage, according to variables of light-shelves, were used as indicators of performance evaluation. The results are as follows:1) Performance evaluation was conducted on flat-type light-shelves to verify performance of curvature-shelves, which are movable with a width of 200 mm, and the most ideal angle and specification per solar term are calculated. 2) The (-) shaped curvature contributed to a reduction in energy consumption and an improvement of evenness. 3) In case of light-shelves with (-) shaped curvature, an increased angle not exceeding $80^{\circ}$ of the arc contributed to an improvement of light penetration. 4) Appropriate specifications of curved light-shelves include movable types with widths of 200 mm, and angle ranges of $20^{\circ}{\sim}60^{\circ}$. 5) Light energy consumption of a movable light-shelf with curvature and width of 200 mm were reduced by 17% and 7.8% compared to a $0^{\circ}$ fixed and a movable light-shelf, respectively.

• 한국의류학회지
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• 제32권9호
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• pp.1478-1486
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• 2008

The human body composed of concave and convex curvatures, and the current 3D scanning technology which involves inherent measurement errors make it difficult to extract distinct curvature plot directly. In this study, a method of extracting the clear curvature plot and its application to the cycling pants design were proposed. We have developed the ergonomic pattern from the 3D human body reflecting cycling posture. For the ergonomic design line on the 3D human body, the 3D information on the lower part of four male bodies with flexed posture was analyzed. The 3D scan data of four subjects were obtained using Cyberware. As results, the iteration of the tessellated shell was executed 100 times to obtain optimized curvature plots of the muscles on the body surface, and the boundaries of the curvature plots were applied to the design lines. Maximum(Max-pattern) and mean curvature plots(Mean-pattern) were adopted in the design line of the cycling pants, and performance of those lines was compared with that of conventional princess line(Con-pattern). The average error of total area and length in the 2D pattern developed from the 3D flexed body surface in this study were very minimal($4.58cm^2$(0.19%) and 0.15mm(0.46%)), which was within the range of tolerable limits in clothing production. The pattern obtained from the flexed body reflecting cycling posture already included the contraction and extension of the cycling skin, so that the extra ease for movement and good fit was not need to be considered.

• Computers and Concrete
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• 제16권2호
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• pp.191-207
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• 2015

It is generally accepted that, in the interest of safety, it is essential to provide a minimum level of flexural ductility, which will allow energy dissipation and moment redistribution as required. If one wishes to be uniformly conservative across all of the design variables, curvature ductility and moment redistribution factor should be calculated using a probabilistic method, as is the case for other design parameters in reinforced concrete mechanics. In this study, simple expressions are derived for the evaluation of curvature ductility and moment redistribution factor, based on the concept of demand and capacity rotation. Probabilistic models are then derived for both the curvature ductility and the moment redistribution factor, by means of central limit theorem and through taking advantage of the specific behaviour of moment redistribution factor as a function of curvature ductility and plastic hinge length. The Monte Carlo Simulation (MCS) method is used to check and verify the results of the proposed method. Although some minor simplifications are made in the proposed method, there is a very good agreement between the MCS and the proposed method. The proposed method could be used in any future probabilistic evaluation of curvature ductility and moment redistribution factors.

• Tribology and Lubricants
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• 제28권1호
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• pp.27-32
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• 2012

Oval gears are typical kinds of non-circular gears and are widely used in flow meters. This paper presents a tooth profile design of an oval gear according to the curvature of the pitch curve. The length of the pitch oval is divided by the number of teeth and the curvature of the divided points is obtained. The tooth profile is designed on the circle of the curvature as if it is the pitch circle of a gear. The teeth of the oval gear have the same module and pressure angle, but the pitch circle of each tooth differs in size. Thus, the teeth on the divided points of the pitch oval are different in shape. This type of oval gear will improve the meshing properties.

• 한국의류학회지
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• 제14권3호
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• pp.183-195
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• 1990

The author has studied the effect of clothes design to mask the dorsal curvature that is one of the commonest changes in elderly women. Body measurements including the body type and the status of dorsal curvature were perfor-med on 153 women of over 60 years of age, and then a body form to fit to the mean measure-ments was made to evaluate the effects of various designs to it. With 31 pattern designs modified by changing in their slash lines and gathers using darts, the diminishing effect of the rounded back were evaluated by means of sensory test. The results of this study can be summarized as follows: I . Results from the body measurements 1) The mean body type in elderly women was that of obesity. 2) With the advancement of age, the angle to indicate the degree of dorsal curvature as well as the angle to indicate the posture are increased. II . Concerning to the clothes design to diminish the shape of dorsal curvature 1) Among the designs by the position of darts, the basic pattern (Fig. 5-1-(1)) showed the best effect to mask the shape of dorsal curvature. 2) Out of the applied designs of princess lines, that in which the slash line is pointing toward the shoulder point (Fig. 5-2-(1)) seemed to be most effective. 3) What has angled princess line (Fig. 5-3-(1)) had the most diminishing effect among the waist darts and armhole princess lines. 4) Among the V-shaped designs, the slashed at the shoulder point (Fig. 5-4-(1)) had the best effect to lessen the shape of the dorsal cuuature. 5) Wider angle yoke had better effect to the narrow angle one among the designs with straight yoke, and that with downward direction (Fig. 5-5-(1)) showed the best effect. 6) Between straight wide angle yoke and curved yoke, that of curved one with downward direction (Fig. 5-6-(1)) had better effect as far as the masking effect of dorsal curvature is concerned. 7) Gathers around the neck showed better effect to those around the shoulder, and the more amount of gathers (Fig. 5-7-(1)), there was better effect. 8) The design with midline gathers at the level of horizontal slash line of armhole (Fig. 5-8-(1)) showed better effect to that with seperated gathers. 9) In case of design with gathers at the horizontal line of armhole, it showed the better effect with less amount of gathers in midline ones, but with more amount in the side ones. 10) Considering all 7 different designs with better effect in covering the shape of dorsal curvature, it was evident that the design with gathers was far better than the design with application of slash lines.

• International Journal of Concrete Structures and Materials
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• 제10권3호
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• pp.393-406
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• 2016

Axially loaded reinforced concrete columns are hardly exist in practice due to the development of some bending moments. These moments could be produced by gravity loads or the lateral loads. First, the current paper presents a detailed analysis on the overall structural behavior of 15 eccentrically loaded columns as well as one concentrically loaded control one. Columns bent in either single curvature or double curvature modes are tested experimentally up to failure under the effect of different end eccentricities combinations. Three end eccentricities ratio were studied, namely, 0.1b, 0.3b and 0.5b, where b is the column width. Second, an expression correlated the decay in the normalized axial capacity of the column and the acting end eccentricities was developed based on the experimental results and then verified against the available formula. Third, based on the equivalent column concept, the equivalent pin-ended columns were obtained for columns bent in either single or double curvature modes. And then, the effect of end eccentricity ratio was correlated to the equivalent column length. Finally, a simplified design procedure was proposed for eccentrically loaded braced column by transferring it to an equivalent axially loaded pin-ended slender column. The results of the proposed design procedure showed comparable results against the results of the ACI 318-14 code.

• 대한기계학회논문집
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• 제19권9호
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• pp.2223-2236
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• 1995

0The fields of turbomachinery and electrical generators provide many examples of flow through rotating internal passages. At the practicing Reynolds number, most of the flow motion is three dimensional and highly turbulent. The proper understanding for the characteristics of these turbulent flow is necessary for the design of thermo-fluid machinery of a good efficiency. The flow characteristics in the rotating duct with curvature are very complex in practice due to the curvature and rotational effect of the duct. The understanding of the effect of the curvature on the structure and rotational effect of the duct. The understanding of the effect of the curvature on the structure of turbulence in the curved passage and the characteristics of the flow in a rotating radial straight channel have been well studied separately by many workers. But the combined effects of curvature and rotation on the flow have not been well understood inspite of the importance of the phenomena in the practical design process. In this study, the characteristics of a developing turbulent flow in a square sectioned 90.deg. bend rotating at a constant angular velocity are measured by using hot-wire anemometer to seize the rotational effects on the flow characteristics. As the results of this study, centrifugal forces associated with the curvature of the bend and Coriolis forces and centripetal forces associated with the rotational affect directly both the mean motion and the turbulent fluctuations.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2005년도 추계학술발표대회 논문집
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• pp.35-38
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• 2005

The Objective of this work was to design Composite Antenna Structures (CAS) and investigate impact behavior of CAS which was various curvature. This term, CAS, indicates that structural surface becomes antenna. Constituent materials were selected considering electrical properties, dielectric constants and tangent loss as well as mechanical properties. For the antenna performance, microstrip antenna layers inserted into structural layers were designed for satellite communication at the resonant frequency of 12.5 GHz and final demonstration article was. After making five kinds of curved CAS, which radii of curvature are flat, 200, 150, 100, 50 mm. The antenna performance changed in accordance with variation of curvature. The Reflection coefficient was independent of curvature but the gain decreased with the radius of curvature. The impact test equipment was Dyna-8250 drop weight tester. The impact characteristic in accordance with curvature is maximum absorb energy is same each other. The impact energy was 8.5 J. For various Impact energy test, five energy levels 3 J, 5 J, 7 J, 10 J, 20 J were used. The performance of impact damaged antenna was estimated by measuring the return loss and the radiation pattern. It was revealed that the performance of antenna was not related to the impact damage. Because the impactor did not damage the patch directly. CAS have good impact stability for the antenna performance.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.377-378
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• 2006

The knuckle crane mainly consists of six parts such as swing, main boom, outer boom, extension boom, hydraulic rotor and knuckle. And the hydraulic rotor is connected at the end of extension boom has rotor block, rotor body, rotor vane. In this study, we carried out kinematics analysis of the hydraulic rotor block curvature for a knuckle crane. Then, we showed the formula to establish the radius of a circumscribed circle to form the rotor block curvature. Third, we analyzed the stress at each point of the rotor block curvature according to the contact angle. From the result of this study, we designed the rotor block curvature with a proper contact angle for a knuckle crane to guarantee the stability of hydraulic rotor.