• Structural Engineering and Mechanics
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• v.6 no.6
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• pp.693-710
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• 1998

This paper concerns studies on the shape formation of post-tensioned and shaped steel domes. The post-tensioned and shaped steel domes, assembled initially at ground level in an essentially flat condition, are shaped to a curved space form and erected into the final position by means of a post-tensioning technique. Based on previous studies on this shape formation principle, three post-tensioned and shaped steel domes have been constructed. The results of the shape formation tests and finite element analyses are reported in this paper. It is found that the first two test domes did not furnish a part-spherical shape as predicted by finite element analyses, because the movements of some mechanisms were not controlled sufficiently. With a revised post-tensioning method, the third dome obtained the theoretical prediction. The test results of the three post-tensioned and shaped domes have shown that a necessary condition to form a desired space shape from a planar layout with low joint stiffnesses is that the movements of all the existing mechanisms must be effectively controlled as indicated by the finite element analysis. The extent of the maximum elastic deformation of a post-tensioned and shaped steel structure is determined by the strength of the top chords and their joints. However, due to the semi-rigid characteristic of the top chord joints, the finite element analyses cannot give a close prediction for the maximum elastic deformations of the post-tensioned and shaped steel domes. The results of the current studies can be helpful for the design and construction of this type of structure.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.356-363
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• 2004

In this research, the shear behavior of four different interfaces consisting of 4 types of geosynthetics was examined, and both static and dynamic tests for the geosynthetic interface were conducted. The monotonic shear experiments were performed by using an inclined board apparatus and large direct shear device. The interface shear strength obtained from the inclined board tests were compared with those calculated from large direct shear tests. The comparison results indicated that direct shear tests are likely to overestimate the shear strength in low normal stress range where direct shear tests were not performed. Curved failure envelopes were also obtained for interface cases where two static shear tests were conducted. By comparing the friction angles measured from three tests, i.e. direct shear, inclined board, and shaking table tests, it was found that the friction angle might be different depending on the test method and normal stresses applied in this research. Therefore, it was concluded that the testing method should be determined carefully by considering the type of loads and the normal stress expected in the field.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.4
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• pp.18-24
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• 1999

The design method of a wave absorber for a perfectly conducting sphere is presented. The backscattered field from a coated sphere can be represented as the sum of the reflected field and the creeping wave. The wave absorber for a curved surface has been designed from that the reflection coefficient of the reflected field is zero. For the design of wave absorber for a small sized conducting sphere, the creeping wave should be considered as well as the reflected field. The perfect absorbing conditions are numerically searched using the Newton-Raphson method from the backscattered field of the eigenfunction series solution from a coated sphere. The wave absorber designed by this method exhibits a superior performance of absorption to that designed from the plate type absorbing condition.

• Journal of Mechanical Science and Technology
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• v.20 no.7
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• pp.1012-1018
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• 2006

Diagnosis and treatment using the conventional flexible endoscope in gastro-intestinal tract are very common since advanced and instrumented endoscopes allow diagnosis and treatment by introducing the human body through natural orifices. However, the operation of endoscope is very labor intensive work and gives patients some pains. As an alternative, therefore, the capsule endoscope is developed for the diagnosis of digestive organs. Although the capsule endoscope has conveniences for diagnosis, it is passively moved by the peristaltic waves of gastro-intestinal tract and thus has some limitations for doctor to get the image of the organ and to diagnose more thoroughly. As a solution of these problems, various locomotive mechanisms for capsule endoscopes are introduced. In our proposed mechanism, the capsule-type microrobot has synchronized multiple legs that are actuated by a linear actuator and two mobile cylinders inside of the capsule. For the feasibility test of the proposed microrobot, a series of in-vitro experiments using small intestine without incision were carried out. From the experimental results, our proposed microrobot can advance along the 3D curved and sloped path with the velocity of about $3.29\sim6.26mm/sec$ and $35.1\sim66.7%$ of theoretical velocity. Finally, the proposed locomotive mechanism can be not only applicable to micro capsule endoscopes but also effective to advance inside of gastro-intestinal tract.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.26 no.3
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• pp.328-336
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• 2017

The exit surface of a lens is designed using a three-dimensional free-form expression in order to easily modify a curved surface. This enables the design of numerical values and mathematical things using three-dimensional free-form expression, and enhances precision because it can be fine-tuned via numerical control. The standard of "Classification of Luminaire Light Distribution" for outdoor lighting fixtures by IESNA is adopted in order to examine the correlation between three-dimensional free-form surface expression and lighting performance. The variation of light distribution type and range is analyzed using the values of maximum light intensity and 50% light intensity. The actual tolerance occurs owing to parameters such as the thickness of the lens, the distance between LEDs, and the movement of the center of the incident surface; the effects of changes in these parameters on the performance are compared and analyzed.

• Bulletin of the Korean Chemical Society
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• v.35 no.7
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• pp.2130-2134
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• 2014

A kinetic study is reported on nucleophilic substitution reactions of 4-nitrophenyl isonicotinate (7) with a series of cyclic secondary amines in MeCN. The plots of $k_{obsd}$ vs. [amine] curve upward for the reactions with weakly basic amines (e.g., morpholine, 1-(2-hydroxyethyl)piperazine, and piperazine) but are linear for those with strongly basic amines (e.g., piperidine and 3-methylpiperidine). The curved plots for the reactions with the weakly basic amines are typical for reactions reported previously to proceed through uncatalyzed and catalyzed routes with two intermediates (e.g., a zwitterionic tetrahedral intermediate $T^{\pm}$ and its deprotonated form $T^-$). In contrast, the linear plots for the reactions with the strongly basic amines indicate that the catalytic route (i.e., the deprotonation process to yield $T^-$ from $T^{\pm}$ by a second amine molecule) is absent. The Br${\o}$nsted-type plots for $Kk_2$ and $Kk_3$ (i.e., the rate constants for the uncatalyzed and catalyzed routes, respectively) exhibit excellent linear correlations with ${\beta}_{nuc}$ = 0.99 and 0.69, respectively. The effect of amine basicity on the reaction mechanism is discussed in detail.

• Journal of Fisheries and Marine Sciences Education
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• v.29 no.1
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• pp.234-241
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• 2017

Morphological and molecular information about two microfilamentous endophytic algae of the Grateloupia lanceolata or Bryopsis sp. from Korea is given. Of two endophytes, Phaeophila dendroides is endophytic in Grateloupia lanceolata. It is green in color and composed of uniseriate branched filaments with long setae. Each cell had several pyrenoids. Undulate or twisted Phaeophila-type hair developed from vegetative cells. Dilabifilum arthropyreniae is endophytic in Bryopsis sp. The frond of this species consists of frequently irregular, branching uniseriate filaments. Each cell had a single pyrenoid without hairs. Sporangia were not observed. The ends of the filaments were curved. In the phylogenetic tree, based on tufA and ITS sequences, these two species are nested in the same clade as Phaeophila dendroides and Dilabifilum arthropyreniae, respectively. In this study, these two species are newly recorded in the Korean marine algal flora, based on the morphological and molecular data.

• Journal of the Korean Society of Costume
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• v.52 no.7
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• pp.1-11
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• 2002

The shape of floral Pattern in the Period of Baroque could be divided single. bunch and vine. The style of representation was stylized, abstract and realistic. the most of style was stylized. The type of composition was fullness, independent and scattered. Floral patterns were shaped simple and complex and components of design could be classified into flower and leaf. flower and fruit. flower and band. bunch of flower, flower and geometry. flower and pot, flower and animal. flower and crest. Kinds of flower were tulip. common marigold, lily, carnation, small bel]flower. lotus, acandus leaf, pomegranate, strawberry. pine cone and abstract anonymous flower which were unfolded by repeat. Characters of floral Pattern were classical elegance, taste of royalty and lively and damask, velvet, brocade which made with gold and silver so, those were a very brilliant and gorgeous. Characters of design were illustrated plane style and stylization where developed arranged on front by repeat or repeat symmetric of vertical. Art, costumes and textiles in this era were a very rich and colorful. The result of study on Baroque's floral pattern will be used to develope a various textile design and chance to be adopted classical pattern into aesthetic value in our time.

• Journal of Hydrospace Technology
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• v.2 no.1
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• pp.41-54
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• 1996

Sculptured surface structures such as ship hulls are traditionally formed up to the required double curved shape by line heating method. The nature of the line heating process is a transient thermal process, followed by a thermo-elastic-plastic stress field. The permanant shape is dependent on many factors involved in the process, Among them are torch speed and path, supplied heat type and amount , and plate size. Thus, the work is essentially leaded by experts with lots of experiences. However, in order to effectively improve productivity through automation, each factor should be clearly examined how much it affects the final shape. This can not be done only by experiments, but can be achieved by a mechanics-based approach. In this paper, we propose a conceptual configuration for plate forming system, and then present simulations of the line heating process with numerical data in practices and suggest a computerized process of the line heating for practical applications. The modeling of heating torch, water cooling, and the plate to be formed is proposed for the finite element analysis after the mechanics of line heating is studied. Parametric studies are given and discussed for the effects of plate thickness, torch speed and initial curvature in forming a saddle typed surface.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.667-672
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• 2009

In case of high-levelled platform in the urban railway system, a certain width of gap is inevitably formed between the train and the platform, and the gap gets wider when it is concerned with curved portion of the tracks at platform. This gap greatly contributes to decrease of passengers' safety while boarding and alighting a train. In particular, it endangers children's safety. Gap filler system is often fitted out to minimize gap and to overcome this safety problem at platform. However, as existing gap fillers are in most case structurally complex and organized to be powered from separate supply unit, there are a range of non-favorable points from the viewpoint of cost, installation and maintenance. In addition, existing gap fillers are due to cause disruptions in operation of train, with failures such as malfunctioning of control system. In this study, the authors will review on the gap filler applicable to the platforms of various height types, which neither requires any modifications of the train nor causes any operational disruptions. The proposed gap filler system here is a by-stage retractile type and based on the idea of interlocking it with train doors open-close mechanism, without any additional power supply unit or control system.