• Smart Structures and Systems
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• v.13 no.3
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• pp.453-471
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• 2014

The fault diagnosis of rolling element bearings has drawn considerable research attention in recent years because these fundamental elements frequently suffer failures that could result in unexpected machine breakdowns. Artificial intelligence algorithms such as artificial neural networks (ANNs) and support vector machines (SVMs) have been widely investigated to identify various faults. However, as the useful life of a bearing deteriorates, identifying early bearing faults and evaluating their sizes of development are necessary for timely maintenance actions to prevent accidents. This study proposes a new two-layer structure consisting of support vector regression machines (SVRMs) to recognize bearing fault patterns and track the fault sizes. The statistical parameters used to track the fault evolutions are first extracted to condense original vibration signals into a few compact features. The extracted features are then used to train the proposed two-layer SVRMs structure. Once these parameters of the proposed two-layer SVRMs structure are determined, the features extracted from other vibration signals can be used to predict the unknown bearing health conditions. The effectiveness of the proposed method is validated by experimental datasets collected from a test rig. The results demonstrate that the proposed method is highly accurate in differentiating between fault patterns and determining their fault severities. Further, comparisons are performed to show that the proposed method is better than some existing methods.

• The Korean Journal of Ecology
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• v.24 no.2
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• pp.111-115
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• 2001

Vegetational changes along elevational and topographical gradients were studied in Mt. Jumbong which is located at the core area of the Mt. Sorak Biosphere Reserve in Kangwon-do Province in central Korea. Two 500 m north-south transects crossing two valleys and a small ridge were laid out, and fifty-one 10 m$\times$10 m permanent quadrats were systematically set up. All trees bigger than 2.5 cm DBH were marked with numbered aluminum tags, and their DBH measured and the species identified. Coverage of plant species in the herb layer were determined in two 2 m $\times$ 2 m subquadrats in each of the permanent quadrats. Thirty-two species of woody plants occurred in the tree layer in the permanent quadrats studied. Quercus mongolica was the dominant species across the study site, and Acer pseudosieboldianum and Carpinus cordata were also important. Quercus mongolica occurred on the ridges and south-facing slopes, and Acer pseudosieboldianum occurred extensively except for valleys. In contrast, Fraxinus mandshurica, Acer mono, Acer triflorum, and Ulmus laciniata were common in valleys. At the herbaceous layer, 112 species were identified. Dominant species were Ainsliaea acerifolia and Sasa borealis on the ridges, Meehania urticifolia on north-facing slopes, and Deutzia glabrata on valleys. Soil environmental factors were compared among the quadrats. pH was lower in the quadrats located on ridges and south-facing slopes, and organic matter was lowest on south-facing slopes. Quadrats located on valleys were generally higher in pH, organic matter, N, P, K, Ca and Mg. DCA ordinations for tree layer and herb layer were carried out in order to identify the dominant environmental factors affecting the distribution of plant species along the environmental gradients. Correlation analysis between ordination axis scores and environmental factors showed that axis one was negatively correlated with elevation and positively correlated with soil organic matter, pH, Ca, Mg, and P, but that axis two was positively correlated with elevation. These results indicate that vegetation responds very sensitively to elevational and topographical gradients although the study area is relatively small with about 100 m in elevational variation.

• Journal of Plant Biology
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• v.15 no.1
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• pp.33-41
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• 1972

Nine shrub layer communities under two relatively well conserved natural summer green forests in the central region of Korean Peninsula were studied for the pattern of stem distribution in terms of Greig-Smith's multiple split-plot experiment and for the association between the population of the two main species in terms of Kershaw's covariance analysis respectively. Four contiguous belt transects, $4{\times}64m size with 1{\times}1m$ basic unit, were set in each shrub layer communities. Significant primary clumps with $1{\times}1m or 1{\times}2m$ dimension wer observed consistently throughout the nine study sites. The primary clumps themselves were significantly distributed either regularly or at random. The association between the two principal species of each shrub layer is highly significantly either positive or negative in $1{\times}1m or 1{\times}2m$ dimension. As the plot size increases from $1{\times}1m to 8{\times}8m$ the associational trends were changed from negative to positive direction in one forests. But the change from positive to negative direction and the consistent negative association were also observed from the other forest. All of the association trends were observed only from $1{\times}1m to 4{\times}4m$ dimension. These results are suggestive that the distributional pattern of the shrub layer species under the summer green forest is simple mosaic fashioned with $1{\times}1m or 1{\times}2m$ dimension. The rest of the principal species are located in that matrix. The simple mosaic pattern of two principal species are located in that matrix. The simple mosaic pattern of two principal species seems to be controlled by change in micro-environmental pattern. Differences between the primary random group and clumped group among sites also suggest that competition exists for light or/and soil between primary clumped groups.

• Journal of Welding and Joining
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• v.21 no.1
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• pp.107-113
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• 2003

Joining of $Si_3N_4$ to $Si_3N_4$ with crystallized glass solder was studied. $SiO_2-Al_2O_3-MgO$ glass with $P_2O_5$ as a crystallizing reagent was used as a solder. To improve the hish temperature toughness of joined specimen, two stage heat treatment was applied to Joined sample for the crystallization of joined layer, Two factors, i.e. thickness of soldered layer and crystallization were taken and thier effects on joining strength were investigated by a SEM-EDX observation of joined interface and bending strength both at room and elevated temperatures. Obtained results are summarized as follows: (1) Nitrogen diffused from $Si_3N_4$ to solder during the Joining process. Average amount of nitrogen in soldered layer depended on the thickness of the soldered layer and increased with decrease of the thickness. (2) Joining strength of the specimen having a thinner soldered layer was stronger than that of thicker layer. This can be mainly attributed to the difference of the nitrogen content in the soldered layer. (3) Higher content of nitrogen in solder brought forth higher viscosity of the solder. Hence the crystallization of the solder become more difficult in thinner layer of the solder than thicker one. (4) Thus, the effect of crystallization was evaluated mostly by the thicker layer specimen. Crystallization of soldered layer improved markedly the fracure strength of joining at higher temperatures than the softening temperature of glass solder.

• Journal of the Korean Society of Food Science and Nutrition
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• v.25 no.3
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• pp.497-503
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• 1996

In order to obtain basic data for the preparation of rice flour, chemical properties of grain layers were compared using Chucheongbyeo and Samgangbyeo, which are Japonica and Tongil type rice, respectively. The amylose contents of L6(center) layer in two different type of rice were the highest among 6 layers of rice grain tested. Reduction in amylose content was observed as the layer reached the surface, resulting in the lowest amylose content in the L0 layer. Amylose contents of L6 layer of Chucheongbyeo and Sangangbyeo were 3 and 2.2 times higher than those of L1 layer, respectively. Crude protein content of the L2 layer was the highest among 6 layers of rice grain tested and 2.2~2.5 times higher than that of whole milled rice. Crude fat content of grain layer was reduced as reaching the center layer. The crude fat contents of L6 layer of grain were 0.21% and 0.25% in Chucheongbyeo and Samgangbyeo, respectively. Most of free and bound lipids in L0 layer of two different rices were 69 : 31 and 79.5 : 20.5, respectively. Bound lipid content of grain layers increased as reaching the center layer. Major fatty acids in free lipids of both cultivars were linoleic acid, oleic acid, and palmitic acid. Linoleic acid content was higher than oleic acid in Chucheongbyeo, but oleic acid content was higher in Samgangbyeo. Palmitic and myristic acid contents of Chucheongbyeo were higher than those of Samgangbyeo, but stearic and linolenic acid contents were lower than those of Samgangbyeo.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.413-414
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• 2008

We have studied an organic layer thickness dependent optical properties and microcavity effects for top-emission organic light-emitting diodes. Manufactured top emission device, structure is Al(100nm)ITPD(xnm)/$Alq_3$(ynm)/LiF(0.5nm)/Al(23nm). While a thickness of hole-transport layer of TPD was varied from 35 to 65nm, an emissive layer thickness of $Alq_3$ was varied from 50 to 100nm for two devices. A ratio of those two layers was kept to about 2:3. Variation of the layer thickness changes a traverse time of injected carriers across the organic layer, so that it may affect on the chance of probability of exciton formation. View-angle dependent emission spectra were measured for the optical measurements. Top-emission devices show that the emission peak wavelength shifts to longer wavelength as the organic layer thickness increases. For instance, it shifts from 490 to 555nm in the thickness range that we used. View-angle dependent emission spectra show that the emission intensity decreases as the view-angle increases. The organic layer thickness-dependent emission spectra show that the full width at half maximum decreases as the organic layer thickness increases. Top emission devices show that the full width at half maximum changes from 90 to 35nm as the organic layer thickness increases. In top-emission device, the microcavity effect is more vivid as the organic layer thickness increases.

• Journal of the korean society of oceanography
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• v.31 no.2
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• pp.75-88
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• 1996

The analytic and numerical solution of the 1$\frac{1}{2}$-layer and 2$\frac{1}{2}$-layer models are derived. The large coastal-sea level drop and the fast westward speed of the anticyclonic gyre due to strong offshore winds using two ocean models are investigated. The models are forced by wind stress fields similar in structure to the intense mountain-pass jets(${\sim}$20 dyne/$cm^{2}$) that appear in the Gulfs of Tehuantepec and Papagayo in the Central America for periods of 3${\sim}$7 days. Analytic and numerical solutions compare favorably with observations, the large sea-level drop (${\sim}$30 cm) at the coast and the fast westward propagation speeds (${\sim}$13 km/day) of the gyres. The coastal sea-level drop is enhanced by several factors: horizontal mixing, enhanced forcing, coastal geometry, and the existence of a second active layer in the 2$\frac{1}{2}$-layer model. Horizontal mixing enhances the sea-level drop because the coastal boundary layer is actually narrower with mixing. The forcing ${\tau}$/h is enhanced near the coast where h is thin. Especially, in analytic solutions to the 2$\frac{1}{2}$-layer model the presence of two baroclinic modes increases the sea-level drop to some degree. Of theses factors the strengthened forcing ${\tau}$/h has the largest effect on the magnitude of the drop, and when all of them are included the resulting maximum drop is -30.0 cm, close to observed values. To investigate the processes that influence the propagation speeds of anticyclonic gyre, several test wind-forced calculations were carried out. Solutions to dynamically simpler versions of the 1$\frac{1}{2}$-layer model show that the speed is increased both by ${\beta}$-induced self-advection and by larger h at the center ofthe gyres. Solutions to the 2$\frac{1}{2}$-layer model indicate that the lower-layer flow field advects the gyre westward and southward, significantly increasing their propagation speed. The Papagayo gyre propagates westward at a speed of 12.8 km/day, close to observed speeds.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.10
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• pp.118-128
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• 2015

Compressive sensing (CS) has to face with two challenges of computational complexity reconstruction and low coding efficiency. As a solution, this paper presents a novel spatially scalable Kronecker two layer compressive sensing framework which facilitates reconstruction up to three spatial resolutions as well as much improved CS coding performance. We propose a dual-resolution sensing matrix based on the quincunx sampling grid which is applied to the base layer. This sensing matrix can provide a fast-preview of low resolution image at encoder side which is utilized for predictive coding. The enhancement layer is encoded as the residual measurement between the acquired measurement and predicted measurement data. The low resolution reconstruction is obtained from the base layer only while the high resolution image is jointly reconstructed using both two layers. Experimental results validate that the proposed scheme outperforms both conventional single layer and previous multi-resolution schemes especially at high bitrate like 2.0 bpp by 5.75dB and 5.05dB PSNR gain on average, respectively.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.4 no.1
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• pp.10-17
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• 1999

The purpose of this study is to investigate the baroclinic response of the upper-layer of two-layered fluid when the lower-layer motion is driven by pumping an external fluid into the lower-layer or by pumping out the lower-layer fluid. Recent observations of the barotropic nature of deep water movements in the East Sea (fakematsu et al., 1994; KORDI, 1997) may suggest a possibility of interaction between the upper and lower layer via interface tilting. For homogeneous fluid, steady and axisymmetric source or sink causes axisymmetric geostrophic flow, and the lower-layer motion in two-layered fluid was similar to homogeneous flow. But as Rossby number (${\varepsilon}$) or internal Froude number ($f_2$) increases, the lower-layer motion was affected by the interface tilting. The interface tilting calculated based on the observed azimuthal velocities of upper- and lower-layers becomes greater as $f_2$ increases. In other words, the increase of the $f_2$ changes the barotropic system to baroclinic system.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.10a
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• pp.206-213
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• 2013

Transient response of a crack in a functionally graded piezoelectric material (FGPM) interface layer between two dissimilar homogeneous piezoelectric layers under anti-plane shear is analyzed using integral transform approaches. The properties of the FGPM layer vary continuously along the thickness. Laplace and Fourier transforms are used to reduce the problem to two sets of dual integral equations, which are then expressed to the Fredholm integral equations of the second kind. Numerical values on the dynamic energy release rate (DERR) are presented for the FGPM to show the effects on electric loading, gradient of the material properties, and thickness of the layers. Computed results yield following conclusions: (a) the DERR increases with the increase of the gradient of the material properties of the FGPM layer; (b) certain direction and magnitude of the electric impact loading impedes crack extension; (c) increase of the thickness of the FGPM layer and the homogeneous piezoelectric layer which has larger material properties than those of the crack plane are beneficial to increase of the resistance of transient fracture of the FGPM layer.