• Proceedings of the KSME Conference
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• 2000.04a
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• pp.254-260
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• 2000

The spacer grid is one of the main structural components in fuel assembly, which supports the fuel rods, guides cooling water, and protects the fuel assembly from the external impact load such as earthquakes. The nonlinear dynamic impact analysis is conducted by using the finite element code ABAQUS/Explicit. Boundary condition for dynamic analysis is well applied to the test condition. Simulation results also similarly predict the local buckling phenomena. In addition to the buckling parameter, the local buckling cause is examined by both simulation and test method. It is found to correspond well with the test results. Impact tests are also carried out for some specimens of the spacer grid in order to compare the results between the test and the simulation. This test is accomplished by a free fall dummy weight onto the specimen. From this test, only the uppermost and lowermost layers of the multi-cell are buckled, which implies the local buckling at the weakest point of the grid structure.

• Korean Journal of Organic Agriculture
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• v.14 no.2
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• pp.159-177
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• 2006

Governance systems are basically an autonomous cooperation type among the government, civil society and market, also a new paradigm for efficient and democratic administration of policies. The governance mainly consists of the central operating body, institutions, operating principles and so on. The constituents are the nation(government), civil society(NGO) and market(firm). Institutional conditions are a legitimate base, financial stability and independency. And as a operating principle, governance systems have common goals and issues from a national and social point of view. This governance has been recently emerged due to financial risk of government, diffusion of new liberalism going with the globalization, localization-decentralization, and development of civil society and information-oriented society. We have to grope fur the framework of participatory agri- policy confronting globalization and localization as well as developing our agriculture and rural village. This agri-policy governance should be theoretically focused on policy network or self-organizing network or multi-lateral governance (MLG) based on NPM. Also, it is proper to have connection of nation-central type and civil society-central type. And it is necessary to have a MLG type with local governance corresponding to localization and decentralization. Governance should have the type whose participants have authority and responsibility as well. Basic directions of environmentally friendly agri-policy governance are as follows : first, its purposes are constructing the democratic and efficient framework of participatory environmentally friendly agri-policy based on consensus of all the related groups, embodying environmentally friendly agri-policy adjusted to local field, raising farmer's real interest, and improving their position. Second, its form should have a council or an agreement system, not an advisory or a consultation organ. Thus, public sector(eg. government) and voluntary sector(eg. farmers' organization) jointly execute agricultural policy and are responsible together. Environmentally friendly agri-policy governance is mainly made up of farmers' organization, cooperative and civil society(NGO). And secondary bodies are agribusinesses and academic groups. Government interacts with the main bodies on administrative execution. And environmentally friendly agri-policy governance has MLG type with a central unit, province and county units. Environmentally friendly agri-policy governance has several main functions such as agri-policy partnership, speaking for farmer's rights and interests, investigation and research on domestic and foreign agricultural streams, and etc. Especially, local unit will play roles in activation for regional agriculture, consulting on technique and management, education and training services, services entrusted by government, and so on.

• Korean Journal of Optics and Photonics
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• v.12 no.4
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• pp.312-319
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• 2001

We proposed a B-RWG LD (Buried-ridge waveguide laser diode) having more merits than a conventional RWG-LD. It's ridge width is controlled easily, it has the advantage of being more planar than the RWG-LD and it is possible to control refractive index with growth layer thickness. Before fabricating the device, we designed the optimal device for single mode, high efficiency and high power operation. From theoretical analysis, we have to control the $d_2, d_3$ layer thicknesses for lateral effective index difference, $\Delta_{nL}$ to be higher than critical value, and simultaneously consider the ridge width for single mode and low threshold current operation. As a result, it is possible to make a single mode LD having the ridge width of $6~9{\mu}m$ if the lateral effective index difference was controlled properly. perly.

• Earthquakes and Structures
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• v.15 no.5
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• pp.487-498
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• 2018

Buckling-restrained braces are passive control devices with high level of energy dissipation ability. However, they suffer from low post-yield stiffness which makes them vulnerable to severe ground motions, especially near-field earthquakes. Among the several methods proposed to improve resistance of BRB frames, mega-brace configuration can be a solution to increase frame lateral strength and stiffness and improve distribution of forces to prevent large displacement in braces. Due to the limited number of research regarding the performance of such systems, the current paper aims to assess seismic performance of BRB frames with mega-bracing arrangement under near-field earthquakes via a detailed probabilistic framework. For this purpose, a group of multi-story mega-BRB frames were modelled by OpenSEES software platform. In the first part of the paper, simplified procedures including nonlinear pushover and Incremental Dynamic Analysis were conducted for performance evaluation. Two groups of near-fault seismic ground motions (Non-pulse and Pulse-like records) were considered for analyses to take into account the effects of record-to-record uncertainties, as well as forward directivity on the results. In the second part, seismic reliability analyses are conducted in the context of performance based earthquake engineering. Two widely-known EDP-based and IM-based probabilistic frameworks are employed to estimate collapse potential of the structures. Results show that all the structures can successfully tolerate near-field earthquakes with a high level of confidence level. Therefore, mega-bracing configuration can be an effective alternative to conventional BRB bracing to withstand near-field earthquakes.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.402.1-402.1
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• 2014

Photonic force microscopy (PFM) is an optical tweezers-based scanning probe microscopy, which measures the forces in the range of fN to pN. The low stiffness leads proper to measure single molecular interaction. We introduce a novel photonic force microscopy to stably map various chemical properties as well as topographic information, utilizing weak molecular bond between probe and object's surface. First, we installed stable optical tweezers instrument, where an IR laser with 1064 nm wavelength was used as trapping source to reduce damage to biological sample. To manipulate trapped material, electric driven two-axis mirrors were used for x, y directional probe scanning and a piezo stage for z directional probe scanning. For resolution test, probe scans with vertical direction repeatedly at the same lateral position, where the vertical resolution is ~25 nm. To obtain the topography of surface which is etched glass, trapped bead scans 3-dimensionally and measures the contact position in each cycle. To acquire the chemical mapping, we design the DNA oligonucleotide pairs combining as a zipping structure, where one is attached at the surface of bead and other is arranged on surface. We measured the rupture force of molecular bonding to investigate chemical properties on the surface with various loading rate. We expect this system can realize a high-resolution multi-functional imaging technique able to acquire topographic map of objects and to distinguish difference of chemical properties between these objects simultaneously.

• International Journal of Concrete Structures and Materials
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• v.11 no.1
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• pp.161-169
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• 2017

Flat slab systems are vastly used in multi-story buildings because of their savings in story height and construction time, as well as for their flexibility in architectural remodeling. However, they frequently suffer brittle punching-shear failure around columns, especially when subjected to lateral loads. Therefore, seismic codes labeled flat slabs as non-ductile systems. This research goal is investigating some construction alternatives to enhance flat slab ductility and deformability. The alternatives are: adding different types of punching-shear reinforcement, using discreet fibers in concrete mixes, and increasing thickness of slab around columns. The experimental study included preparation and testing of seven half-scale interior slab-column connections up to failure. The first specimen is considered a reference, the second two specimens made of concrete mixes with different volumetric ratios of polymer fibers. Another three specimens reinforced with different types of punching-shear reinforcement, and the last specimen constructed with drop panel of inverted pyramidal shape. It is found that using the inverted pyramid-shape drop panel of specimen, increases the punching-shear capacity, and the initial and the post-cracking stiffnesses. The initial elastic stiffnesses are different for all specimens especially for the slab with closed stirrups where it is experienced the highest initial stiffness compared to the reference slab.

• Earthquakes and Structures
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• v.10 no.1
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• pp.1-23
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• 2016

Steel plate shear walls (SPSWs) have been shown to be efficient lateral force-resisting systems, which are increasingly used in new and retrofit construction. These structural systems are designed with either stiffened and stocky or unstiffened and slender web plates based on disparate structural and economical considerations. Based on some limited reported studies, on the other hand, employment of low yield point (LYP) steel infill plates with extremely low yield strength, and high ductility as well as elongation properties is found to facilitate the design and improve the structural behavior and seismic performance of the SPSW systems. On this basis, this paper reports system-level investigations on the seismic response assessment of multi-story SPSW frames under the action of earthquake ground motions. The effectiveness of the strip model in representing the behaviors of SPSWs with different buckling and yielding properties is primarily verified. Subsequently, the structural and seismic performances of several code-designed and retrofitted SPSW frames with conventional and LYP steel infill plates are investigated through detailed modal and nonlinear time-history analyses. Evaluation of various seismic response parameters including drift, acceleration, base shear and moment, column axial load, and web-plate ductility demands, demonstrates the capabilities of SPSW systems in improving the seismic performance of structures and reveals various advantages of use of LYP steel material in seismic design and retrofit of SPSW systems, in particular, application of LYP steel infill plates of double thickness in seismic retrofit of conventional steel and code-designed SPSW frames.

• The Journal of Engineering Geology
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• v.25 no.2
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• pp.291-298
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• 2015

For hydrogeological studies, it is of importance to observe hydraulic head in order to interpret groundwater flow, characterize aquifers, and calibrate groundwater flow model. This study analyzed the zonal variation of hydraulic heads at the eight monitoring wells (GM-1~GM-8) installed with multi-packers in a coastal area and verified vertical and lateral trends of the hydraulic gradients. Hydraulic heads were expressed as the depth of water because the monitoring wells have different depths. The hydraulic gradient at the nearest well (GM-5) shows 0.0142 with increasing trend of hydraulic gradient along depth. This fact indicates typical phenomenon of the discharge area. On the other hand, GM-1 and GM-2 wells in coastal area demonstrate constant hydraulic gradient down to the depth of 100 meters while at the zone of deeper than 100 m the hydraulic gradients illustrate 0.0196 and 0.0735, respectively. This indicates that horizontal flow is dominant at shallower zone than 100 m whereas upward flow is dominant at the zone deeper than 100 m. GM-3 well located farther than the other wells from the coast shows a small hydraulic gradient of 0.0046 that evidences a prevalent horizontal flow between the recharge area and the discharge area.

• Korean journal of communication and information
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• v.56
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• pp.219-236
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• 2011

Since the end of the $19^{th}$ century, Korean English-language newspapers have been published in Korea to inform readers about Korea and Korean people's point of view concerning world problems. Among them was the Korean Republic (KR), the former name of the Korea Herald, founded on August $15^{th}$, 1953 (Korean Liberation Day from Japanese colonial rule). This newspaper was started especially to report on international affairs, just after the Armistice agreement was signed on July $27^{th}$, 1953, at the initiative of the first president of the Republic of Korea, Syngman Rhee. He vehemently expressed his and the Korean people's opinion about Korean problems in world politics where big powers were dominating and deciding small countries' destinies. This paper is written to show that Korean English-language newspapers were used as tool of public diplomacy not only for the readers of target countries but also for Korean readers, well before the media diplomacy theory became popular several decades later. In the deplorable world situation where Korea was colonized and divided into halves by the wills of the super powers, the Korean media participated actively via dialogue in English to solve the Korean problem. This paper studies the editorials of the KR for one year, the year just after its foundation. Vis-a-vis the United States, the KR defended its political system of free democracy by insisting on the Korean people's hopes, the reunification of the peninsula and acquiring American assistance in economic and military areas. Regarding Japan, Korea had doubt about its expansionist policy by way of rearmament. First, the Korean government tried to defend its territorial waters, including Dokdo Island. As for multi-lateral relationships, Korea was concerned about the spread of communism to its territory in the world where socialism was dominating.

• Korean Journal of Optics and Photonics
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• v.6 no.4
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• pp.379-384
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• 1995

In order to construct B-ISDN, it is inevitable to introduce optical fiber of low loss and wide bandwidth. Coincidently, high count optical fiber cable is solely important to form optical subscriber network. The best structure of high count optical fiber cable to achieve multi-splicing as well as high density at the same time is the one of taking optical ribbon as a unit of accomodation. However, since optical ribbon has its own width. optical loss due to length difference during the bending of ribbon cable unit occurs in relatively easy way. Therefore, care should be taken during its manufacturing and storage. In t\1::; paper, strain, bending radius and lateral pressure of each fiber in ribbon due to the bending of ribbon cable unit are caculated theoretically. Hence, we have measured optical loss of each fiber as function of unit bending radius, when we bent the ribbon cable unit on the various reel. We found that the result accords well with the theoretical analysis. The result shows the importance to determine proper radius of reel used in ribbon cable manufacturing and storage. orage.