• Smart Structures and Systems
• /
• v.26 no.4
• /
• pp.419-433
• /
• 2020

Investigation of structural integrity has been a critical issue in the field of civil engineering for years. Visual inspection is one of the most available methods to explore deteriorative components in structures. Still, this method is not applicable to invisible damage of structures. Alternatively, system identification methods are capable of tracking modal properties of structures over time. The deviation of these dynamic properties can serve as indicators to access structural integrity. In this study, a modal tracking technique using frequency-domain system identification from seismic responses of structures is proposed. The method first segments the measured signals into overlapped sequential portions and then establishes multiple Hankel matrices. Each Hankel matrix is then converted to the frequency domain, and a temporal-average frequency-domain Hankel matrix can be calculated. This study also proposes the frequency band selection that can divide the frequency-domain Hankel matrix into several portions in accordance with referenced natural frequencies. Once these referenced natural frequencies are unavailable, the first few right singular vectors by the singular value decomposition can offer these references. Finally, the frequency-domain stochastic subspace identification tracks the natural frequencies and mode shapes of structures through quick stabilization diagrams. To evaluate performance of the proposed method, a numerical study is carried out. Moreover, the long-term monitoring strong motion records at a specific site are exploited to assess the tracking performance. As seen in results, the proposed method is capable of tracking modal properties through seismic responses of structures.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.23 no.2
• /
• pp.230-238
• /
• 2015

The main purpose of this paper is to suggest opportunities for reducing $CO_2$ emission in energy conversion of a vehicle, focused on auxiliary energy improvement in the automotive field. As part of worldwide efforts to curb global warming and to protect the domestic industry as trade barriers, many countries have set goals to regulate greenhouse gas emissions. As an example, new $CO_2$ emission regulation in EU was expected to go into effect strictly in 2020. Therefore, global car-makers need to establish strategic responsiveness of the regulations. This paper shows $CO_2$ economic value by using the correct interpretation of the relevant laws and regulations. The $CO_2$ value analyzed using quantitative figures leads to the possibility of auxiliary(accessories, HVAC, electric apparatus etc.) technology for improving fuel economy. As a result, this study generalizes the meaning of electric power saving for each driving mode by auxiliary energy improvement.

• Applied Chemistry for Engineering
• /
• v.31 no.5
• /
• pp.552-559
• /
• 2020

Activated carbon-nickel (II) oxide (AC-NiO) electrodes were studied as materials for the capacitive deionization (CDI) of aqueous sodium chloride solution. AC-NiO electrodes were fabricated through physical mixing and low-temperature heating of precursor materials. The amount of NiO in the electrodes was varied and its effect on the deionization performance was investigated using a single-pass mode CDI setup. The pure activated carbon electrode showed the highest specific surface area among the electrodes. However, the AC-NiO electrode with approximately 10 and 20% of NiO displayed better deionization performance. The addition of a dielectric material like NiO to the carbon material resulted in the enhancement of the electric field, which eventually led to an improved deionization performance. Among all as-prepared electrodes, the AC-NiO electrode with approximately 10% of NiO gave the highest salt adsorption capacity and charge efficiency, which are equal to 7.46 mg/g and 90.1%, respectively. This finding can be attributed to the optimum enhancement of the physical and chemical characteristics of the electrode brought by the addition of the appropriate amount of NiO.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
• /
• 2003.02a
• /
• pp.123-125
• /
• 2003

We joined 19-multifilamentary (Bi, Pb)$_2$Sr$_2$Ca$_2$Cu$_3$O$_{x}$ Superconducting tapes and fabricated double-pancake coils by using resistive- and superconducting-joint methods. The joint resistance of the coils were characterized by the field decay technique and standard four-probe method. It was evaluated that joint resistance was 3.21$\times$10$^{-11}$ $\Omega$ in the superconducting-joint coil, which is approximately 4 orders of magnitude smaller than that in the resistive-joint coil (107$\times$10$^{-9}$ $\Omega$). The low value of joint resistance obtained by superconducting-joint is expected to be suitable for the practical applications in the persistent current mode.e.

• Journal of the Korean Home Economics Association
• /
• v.50 no.5
• /
• pp.39-49
• /
• 2012

This study looked into the trend of expression of animal motifs that appears in modern fashion, and the values embedded in them. As to the research method, empirical analysis was performed on the works presented at the four global collections of Paris, Milan, New York and London from 2001S/S to 2010F/W, as well as a literature review. As a result, animal motifs applied in modern fashion appeared in material groups, such as leather or feather. The first group shows a realistic material feel, with artificial leather or fur, expressed in a transformed complex animal motif, with process skill or various methods of expression. The second group is the case of a single motif or reality, mode, and ion pattern. Printing is a generic expression, but patchwork, collage or bead ornament are also used, and expressed in the various forms of pattern: pattern in a single animal, pattern in different animals, and pattern combining both animal and other shape. The third group is a small decorative ornament, including headset or accessory and makeup, which is transformed in an animal-characterized motif into part of clothing components for expression, or to set the real animal to the stage for a performance. The embedded values were also categorized as natural beauty, sensual female beauty, pleasure, and ornamentation, which could be an endless spiritual source, and a breakthrough that enables us to show a creative and new aesthetic for the modern fashion field.

• Journal of The Korean Astronomical Society
• /
• v.37 no.4
• /
• pp.249-255
• /
• 2004

Here we present a linear stability analysis and an MHD 2D model for the Parker-Jeans instability in the Galactic gaseous disk. The magnetic field is assumed parallel to a Galactic spiral arm, and the gaseous disk is modelled as a multi-component, magnetized, and isothermal gas layer. The model employs the observed vertical stratifications for the gas density and the gravitational acceleration in the Solar neighborhood, and the self-gravity of the gas is also included. By solving Poisson's equation for the gas density stratification, we determine the vertical acceleration due to self-gravity as a function of z. Subtracting it from the observed gravitational acceleration, we separate the total acceleration into self and external gravities. The linear stability analysis provides the corresponding dispersion relations. The time and length scales of the fastest growing mode of the Parker-Jeans instability are about 40 Myr and 3.3 kpc, respectively. In order to confirm the linear stability analysis, we have performed two-dimensional MHD simulations. These show that the Parker-Jeans instability under the self and external gravities evolves into a quasi-equilibrium state, creating condensations on the northern and southern sides of the plane, in an alternate manner.

• Journal of the Korean Institute of Telematics and Electronics A
• /
• v.28A no.9
• /
• pp.721-728
• /
• 1991

In this paper, a magneto-optic modulator has been designed by using single crystal BSO and polycrystal ZnSe as Faraday cells. And practical core-type optical current sensors using pure iron and permalloy have been prepared and experimented. In order to obtain efficient magnetic field detection, LED(NEC OD08358, 0.87 $\mu$m) was used as optical source, PIN-PD(OD-8454)as optical receiver and multi-mode optical fiber (100/140$\mu$m) as transmission line. The characteristics matrix of the optical element was calculated by Stokes parameter, and optic modulation characteristics equations were derived by Muller matrix. Electromagnetic analysis program (FLUX 2D, micro VAX 3600) by finite element method was used to find the magnetic flux density around the core. The measuring error of the output voltage to input current has been masured below 5% in the range of 50A to 1000A. As the temperature was changed from -20$^{\circ}C$ to 60$^{\circ}C$, the maximum measurement error of the optical output has been found to be 0.5% at 60$^{\circ}C$. These experimental results show good temperature and linearity characteristics. The SNR of the overall system was 47dB in case of 600A (250.2 Oe) conductor current and the system has good noise immunity.

• Journal of Applied Reliability
• /
• v.13 no.1
• /
• pp.45-53
• /
• 2013

In this paper, we analyze the failure mechanism of the washer pump to find what is the failure cause in the road environment. The statistics show the field common failure mode is inner corrosion. The failure mechanism is assumed that the inner part of washer pump is corroded due to inflow of moisture through vent hole. To prevent the failure, we can think a method that is covering the vent hole. In general, the vent hole is designed to play an important role in an automobile parts. So, we need to prove the vent hole is not necessary. The first purpose of this paper is to make sure that the vent hole does not affect the durability of washer pump using the analysis of operating condition. The second purpose is to compare the durability properties if the vent hole is covered.

• Proceedings of the KSR Conference
• /
• 2008.06a
• /
• pp.2455-2462
• /
• 2008

Global warming has become one of the most important social responsibilities. After Kyoto protocol for greenhouse gas reduction by climatic change convention came into effect, developed countries are presenting various policies to reduce greenhouse gas that is produced in transport field. One of those policies is modal shift that change from road freight to sea, inland waterway and railway transportation that is eco-friendly. Because increase of road freight brings about road congestion and accident, logistics cost, air pollution and green house gases. Railways are superior to all other modes of transport in mass transportability, high speed, timeliness, safety and environmental-friendliness, but the railway industry has been pushed behind in competition. In developed country's government actively promoted relevant legislation, policies, and countermeasures known as modal shift policies to shift freight transport from road to large volume mode such as railway and ship. In this paper, we discuss the current situation in modal shift, compare it with cases in other countries EU and Japan, identify problems in Korea, and propose the following ways to enhance competitiveness of rail freight.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.13 no.2
• /
• pp.209-220
• /
• 2000

For non-linear analysis of stiffened shell structures, the total Lagrangian formulation is presented based upon the degenerated shell element. Geometrically correct formulation is developed by updating the direction of normal vectors and taking into account second order rotational terms in the incremental displacement field. Assumed strain concept is adopted in order to overcome shear locking phenomena and to eliminate spurious zero energy mode. The post-buckling behaviors of stiffened shell structures are traced by modeling the stiffener as a shell element and considering general transformation between the main structure and the stiffener at the connection node. Numerical examples to demonstrate the accuracy and the effectiveness of the proposed shell element are presented and compared with references' results.