• Structural Engineering and Mechanics
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• 제25권2호
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• pp.219-237
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• 2007

The effect of cable loosening on the nonlinear parametric vibrations of inclined cables is discussed in this paper. In order to overcome the small-sag limitation in calculating loosening for inclined cables, it is necessary to first derive equations of motion for an inclined cable. Using these equations and the finite difference method, the effect of cable loosening on the nonlinear parametric response of inclined cables under periodic support excitation is evaluated. A new technique that takes into account flexural rigidity and damping is proposed as a solution to solve the problem of divergence. The regions of inclined cables that undergo compression are also indicated.

• 식물분류학회지
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• 제41권3호
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• pp.242-245
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• 2011

In this study, we described and illustrated an unrecorded species from the Korean flora, Sciaphila nana Blume, which is included in the order Pandanales and the family Triuridaceae. This taxon was found at Mul Oreum in Namwon-eup, Seogwipo-si, Jeju Special Self-Governing Province for the first time in Korea. The order Pandanales can be distinguished from the order Liliales by the anomocytic or tetracytic stomata and syncarpous or apocarpous gynoecia of the Pandanales. The family Triuridaceae and the other four taxa in the Pandanales, Cyclanthaceae, Pandanaceae, Stemonaceae, and Velloziaceae, are easily distinguished because the Triuridaceae are microtrophic herbs with scaly leaves. S. nana has a subulate style with a glabrous apex, ovate to narrow ovate leaves and bracts, male perianth segments with a knob-like structure at the apex, and a dimorphic perianth. Therefore, it is easily distinguished from S. tenella, S. multiflora, S. secundiflora, S. thaidanica, S. ramosa, and S. arfakiana.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2004년도 Proceedings of ISRS 2004
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• pp.541-544
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• 2004

Recently, the heat island phenomenon in which the temperature of a city part rises from the circumference ground has developed into a big problem. In this study, we aimed at examining the impact of increasing vegetation in urban areas to reduce the heat island phenomenon by taking the Fukuoka City of Japan as a case. In order to discuss the relation between vegetation environment and the heat island phenomenon, we have calculated Normalized Difference Vegetation Index (NDVI) and mapped the spatial vegetation distribution. These are then compared with the heat island phenomenon investigations in Fukuoka City. The results of the study revealed that the areas showing comparatively lesser heat island phenomenon are those having increased vegetation.

• 한국고분자학회:학술대회논문집
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• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
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• pp.247-247
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• 2006

Chemical and physical synthesis routes were combined to prepare macroporous thin films of semiconducting metal-oxides such as $CaCu_{3}Ti_{4}O_{12}\;and\;TiO_{2}$ by sputtering onto (PMMA) microsphere templated substrates. Subsequently, the colloidal templates were removed by thermal decomposition. The remaining inorganic films comprised a monolayer of hollow hemispheres with diameter commensurate with that of the microspheres. This unique morphology increases the surface area and reduces the interfacial area between film and substrate. Consequently, the surface activity is markedly enhanced while deleterious interfacial effects between film and substrate are significantly reduced. Both effects are highly advantageous for gas sensing applications.

• Structural Engineering and Mechanics
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• 제23권6호
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• pp.691-711
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• 2006

This paper uses the finite element method to simultaneously consider the coupled cable-deck vibrations and the parametric vibrations of stay cables in dynamic analysis of a cable-stayed bridge. The stay cables are represented by some cable finite elements, which can consider the parametric vibration of the cables. In addition to modeling stay cables using multiple link cable elements, a procedure for removing the self-weight term of cable element is proposed. A eigenvalue analysis process using dynamic condensation method for sorting out the natural modes of the girder-tower vibrations and the Rayleigh damping considering element damping for damping matrix are also proposed for dynamic analyses of cable-stayed bridges. The possibilities of using cable elements and of using global and local vibrations to evaluate the parametric vibrations of stay cables in a cable-stayed bridge are confirmed, respectively.

• Journal of Power Electronics
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• 제10권3호
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• pp.228-234
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• 2010

This paper investigates the conducted-noise characteristics of a digitally-controlled randomly-switched dc-dc converter. In order to investigate the effect of the suggested digital controller on the conducted-noise characteristics of a dc-dc converter, three factors have been studied: the field-programmable gate array (FPGA) clock speed, the randomization ratio percentage, and the effect of using a closed loop feedback controller. A field-programmable gate array is much more flexible than analog control circuits, has a lower cost, and can be used for power supply applications. A novel FPGA-based implementation has been suggested for obtaining the experimental validations and realizing the studied concepts. Furthermore, the experimental results have been discussed and design guidelines have been included.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.89.2-89
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• 2001

Wheel chair bound persons need assistance since there are many steps or curbs or other obstacles blocking their path in the roadways and walkways. Although a step may be small, it may be very difficult for such a person to climb over it. Therefore, we are proposing a power assist wheel chair robot that enables a wheel chair bound person to climb over steps up to about 10 centimeters in height without assistance from others. By using the proposed wheel chair robot, a user can maintain inverse pendulum control after raising its front wheels Then, a user can move forward to the step maintaining the inverse pendulum control, and can climb over the step using motor force of a rear wheel shaft ...

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1990년도 한국자동제어학술회의논문집(국제학술편); KOEX, Seoul; 26-27 Oct. 1990
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• pp.1032-1036
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• 1990

This paper describes a system which enables a real-time measurement of 2-D water flow field. One distinctive feature of our system is that velocity vectors of water flow are obtained from the movement of tracer particles at video rate. In order to enable a fast measurement a real time video processor and two Digital Signal Processor(TMS32OC25) are employed. The real-time video processor extracts contours of tracer particles in order to reduce the amount of image data to be processed. And two DSP(Digital Signal Processor) analyse the correlation of every tracer paticle in the consecutive two images to obtain the velocity distribution of water flow.

• 한국양식학회지
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• 제10권3호
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• pp.321-326
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• 1997

The random amplified polymorphic DNA (RAPD) technique was used to anlayze six isolates of two species of Porphyra, P. yezoensis and P. tenera. Four 21-mer prrmers were combined randomly into six groups of double primers and screened for DNA amplification using nuclear and chloroplast tempate DNA. The RAPD patterns resulting from RnRc and CnCc primers provided evidence for both genetically homo-and heterogeneous populations of P. yezoensis and P. tenera. Similarity values obtained by RnRc primer analysis of nuclear DNA varied from 0.364 to 0.714 and those of chloroplast DNA were high, ranging from 0.727 to 1.000, except for P. yezoensis (Enoura).

• Structural Engineering and Mechanics
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• 제30권5호
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• pp.513-534
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• 2008

This paper examines local vibrations in the stay cables of a cable-stayed bridge subjected to wind gusts. The wind loads, including the self-excited load and the buffeting load, are converted into time-domain values using the rational function approximation and the multidimensional autoregressive process, respectively. The global motion of the girder, which is generated by the wind gusts, is analyzed using the modal analysis method. The local vibration of stay cables is calculated using a model in which an inclined cable is subjected to time-varying displacement at one support under global vibration. This model can consider both forced vibration and parametric vibration. The response characteristics of the local vibrations in the stay cables under wind gusts are described using an existing cable-stayed bridge. The results of the numerical analysis show a significant difference between the combined parametric and forced vibrations and the forced vibration.