• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.10
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• pp.1004-1010
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• 2003

In this paper, the 1/4 wavelength backward-wave directional coupler using coupled lines with finite metallization thickness is described. A mode-matching method, simple and fast approach to the quasi-static analysis, has been used to analyse this structure. The numerical results show that it is possible to overcome the disadvantages of weakly coupling, low directivity, and narrow strip distance non-realizable in the case of 1/4 wavelength backward-wave directional coupler with zero thickness conductor. It is also revealed that thicker metallization causes longer coupler length in the case of backward-wave symmetrical parallel coupled line directional coupler. The finite metallization thickness can be a new parameter for tight coupling in the design of backward-wave directional couplers, which enables us to design more accurate properties of monolithic microwave integrated circuits.

• Steel and Composite Structures
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• v.22 no.5
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• pp.1019-1038
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• 2016

The use of high-strength concrete (HSC) in precast concrete segmental bridges (PCSBs) can minimize the superstructure geometry and reduce beam weight, which can accelerate the construction speed. Dry joints between the segments in PCSBs introduce discontinuity and require special attention in design and construction. Cracks in dry joints initiate more easily than those in epoxy joints in construction period or in service. Due to the higher rupture strength of HSC, the higher cracking resistance can be achieved. In this study, shear behavior of dry joints in PCSBs was investigated by experiments, especially focusing on cracking resistance and shear strength of HSC dry joints. It can be concluded that the use of HSC can improve the cracking resistance, shear strength, and ductility of monolithic, single-keyed and three-keyed specimens. The experimental results obtained from tests were compared with the AASHTO 2003 design provisions. The AASHTO 2003 provision underestimates the shear capacity of single-keyed dry joint C50 and C70 HSC specimens, underestimates the shear strength of three-keyed dry joint C70 HSC specimens, and overestimates the shear capacity of three-keyed dry joint C50 HSC specimens.

• Korean Institute of Interior Design Journal
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• v.19 no.3
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• pp.172-179
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• 2010

The Sydney Opera House is built on a peninsula of rock that juts out into Sydney Harbor. The site was once a landing place for ships. Utzon, Architect, designed the theatres for the Opera House to fit the shape. The two theatres were placed side by side so that they both had extensive harbor views. The Sydney Opera House is designed the foyers to take full advantage of these sights. Because the building would be seen from all sides, even from above, it was to be a piece of sculpture. The outside was as important as the inside. The audience enters from behind the stage and walks around to the foyers overlooking the harbour. The wing and backstage areas are small because of the way the foyers wrap around the theatre. The stage is made up of large platform lifts which provide the vertical movement for changing scenery. The sets come up from the workshops below stage. The flytower fits under the largest roof shell and doesn't break the skyline. The important elements are the podium, the shells and the reminders. The podium, the huge monolithic concrete structure, contains hundreds of rooms and nearly all the technical equipment. The podium is clad with pink granite slabs and seen from the water. This design eliminated a maze of fire escape stairs and, at the same time, gave people a wonderful view of the harbour. The egg shell is remarkably strong and express the form as the symbol of the site.

• Korean Journal of Social Welfare
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• v.56 no.2
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• pp.53-70
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• 2004

This study is about family discourses of social workers in Korea. The purpose of this study is to gain suggestions of relatedness between discourse and practice by grasping the contents and meaning of discourses in social workers. 10 social workers in various fields were interviewed for this study. The results are followed: First, social workers understand family as a private space which have a meaning of shelter and refuge. Second, there are gaps between consciousness and practice of division of gender role in family. But social workers generally are inclined toward receiving division of gender role in family and applied to their family practice. Third, monolithic family image have a tendency of versatility in family structure, is inclined toward the division of gender role and myth of motherhood. Fourth, social workers perceived emotional tie as important nature of family solidarity and family as natural institution. Also these discourses of social workers were applied to their family practice. The results of this study reveals possibility that social work practice can be discoursive practice or interpretive practice.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.17-20
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• 2008

As a part of a research program to study the shear reinforcement of flat plate system, this investigation aimed to determine the effect of shear reinforcement type on punching shear strength of monolithic slab-column connection. A total of 5 specimens were fabrication and tested. The dimension of the slab were $2.63{\ast}2.725{\ast}0.18m$, with a centrally located column $0.6{\ast}0.8m$ in cross section. Experimental results showed that the CFS shear reinforcement was not effective because of lack of proper bond with concrete. 3 shear reinforcement except of CFS showed high effectiveness, which resulted in a considerable increment of the punching shear resistance of the connection.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.7 s.361
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• pp.24-30
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• 2007

Latching optical switches and optical logic gates with AND or OR, and the INVERT functionality are demonstrated, for the first time, by the monolithic integration of a differential typed vertical cavity laser with depleted optical thyristor (VCL-DOT) structure with a low threshold current of 0.65 mA, a high slope efficiency of 0.38 mW/mA, and high sensitivity to input optical light. Many kinds of logic functions (AND, OR, NAND, NOR, and INVERT) are experimentally demonstrated using a differential switching operation scheme changing the intensity of a reference input beam without any changes of electrical circuits.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.1
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• pp.44-50
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• 2004

In this paper, a DBM(Doubly Balanced Mixer) of 2 GHz is implemented on FR4 substrate. The structure of doubly balanced mixer requires, in general, two batons and a quad diode. For balun, a novel planar balun using microstrip to CPS is suggested and designed. The suggested balun shows the phase imbalance of 180$^{\circ}$${\pm}$ 1.5$^{\circ}$and the amplitude imbalance of ${\pm}$ 0.2 ㏈ for 1.5 to 2.5 GHz. Using the balun, DBM is succesfully implemented, and the measured conversion loss of up/down converter show about 6 ㏈ over the bandwidth. The balun may be applicable for MMIC DBM with the process supporting backside via thourgh more study.

• Journal of the Korean Ceramic Society
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• v.43 no.11 s.294
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• pp.715-723
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• 2006

Perovskite oxide materials are very important for the electronics industry, because they exhibit promising properties. With an interest in the obvious applications, significant effort has been invested in the growth of highly crystalline epitaxial perovskite oxide thin films in our laboratory. And the desired structure of films was formed to achieve excellent properties. $Y_1Ba_2Cu_3O_{7-x}$ (YBCO) superconducting thin films were simultaneously deposited on both sides of 3 inch wafer by inverted cylindrical sputtering. Values of microwave surface resistance R$_2$ (75 K, 145 GHz, 0 T) smaller than 100 m$\Omega$ were reached over the whole area of YBCO thin films by pre-seeded a self-template layer. For implementation of voltage tunable high-quality varactor, A tri-layer structured SrTiO$_3$ (STO) thin films with different tetragonal distortion degree was prepared in order to simultaneously achieve a large relative capacitance change and a small dielectric loss. Highly a-axis textured $Ba_{0.65}Sr_{0.35}TiO_3$ (BST65/35) thin films was grown on Pt/Ti/SiO$_2$/Si substrate for monolithic bolometers by introducing $Ba_{0.65}Sr_{0.35}RuO_3$ (BSR65/35) thin films as buffer layer. With the buffer layer, the leakage current density of BST65/35 thin films were greatly reduced, and the pyroelectric coefficient of $7.6\times10_{-7}$ C $cm^{-2}$ $K^{-1}$ was achieved at 6 V/$\mu$m bias and room temperature.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.1
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• pp.148-155
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• 2010

The purpose of this study is to propose and evaluate the continuous joint constructed with MRS system which is utilized for floor system in the parking structures or commercial retail buildings. Four specimens were fabricated and tested to examine the structural performance of the continuous joint with different joint detailing. Structural test for the specimens was undertaken to simulate the actual stress condition of the negative moment resisting connection in the prestressed precast concrete parking structures with 8m span. Based on the experimental results, the MRS system could be designed as the ductile continuous joint governed by flexural behavior. Therefore the MRS system developed in this study would provide a superior joint behavior to conventional double-tee system when constructing monolithic joint composed of simply supported precast members.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.33 no.12
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• pp.45-52
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• 2017

The precast concrete (PC) method has many advantages in fast construction, quality control, etc. In domestic construction market, however, its application has been quite limited because of the concerns about structural integrity and seismic performances due to the discrete connections between precast concrete members. By applying the post-tensioning method, the precast beam-column connection can be well tightened, allowing improved structural integrity, and proper seismic performances can be also achieved. In this study, reversed cyclic tests have been conducted on the beam-column connection specimens, where the test variables included the compressive strength of grouting mortar and the tensile strengths of prestressing strands, based on which their seismic performances have been examined in detail. The post-tensioned PC beam-column connections showed good seismic performances comparable to that of the monolithic reinforced concrete connection specimen. When 2400 MPa prestressing strands are applied to the beam-column connection, it is preferable to adjust the prestress level similar to that applied for the 1860 MPa prestressing strands to avoid premature local crushing failures at the beam-column connections.